JP4490650B2 - EL display device driving method and EL display device - Google Patents

EL display device driving method and EL display device Download PDF

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JP4490650B2
JP4490650B2 JP2003121475A JP2003121475A JP4490650B2 JP 4490650 B2 JP4490650 B2 JP 4490650B2 JP 2003121475 A JP2003121475 A JP 2003121475A JP 2003121475 A JP2003121475 A JP 2003121475A JP 4490650 B2 JP4490650 B2 JP 4490650B2
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current
voltage
transistor
pixel
signal line
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JP2004029755A5 (en
JP2004029755A (en
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博司 高原
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東芝モバイルディスプレイ株式会社
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Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a self-luminous display panel such as an EL display panel using an organic or inorganic electroluminescence (EL) element. The present invention also relates to a drive circuit (IC) for these display panels. The present invention relates to a driving method and a driving circuit of an EL display panel, an information display device using them, and the like.
[0002]
[Prior art]
In general, in an active matrix display device, an image is displayed by arranging a large number of pixels in a matrix and controlling the light intensity for each pixel in accordance with a given video signal (see, for example, Patent Document 1). For example, when liquid crystal is used as the electro-optical material, the transmittance of the pixel changes according to the voltage written to each pixel. In an active matrix image display device using an organic electroluminescence (EL) material as an electro-optic conversion substance, light emission luminance changes according to a current written to a pixel.
[0003]
In the liquid crystal display panel, each pixel operates as a shutter, and an image is displayed by turning on and off light from a backlight with a shutter that is a pixel. The organic EL display panel is a self-luminous type having a light emitting element in each pixel. Therefore, the organic EL display panel has advantages such as higher image visibility than the liquid crystal display panel, no backlight, and high response speed.
[0004]
In the organic EL display panel, the luminance of each light emitting element (pixel) is controlled by the amount of current. That is, it is greatly different from the liquid crystal display panel in that the light emitting element is a current drive type or a current control type.
[0005]
The organic EL display panel can also be configured in a simple matrix system and an active matrix system. Although the former has a simple structure, it is difficult to realize a large and high-definition display panel. However, it is cheap. The latter can realize a large, high-definition display panel. However, there is a problem that the control method is technically difficult and relatively expensive. At present, active matrix systems are actively developed. In the active matrix system, a current flowing through a light emitting element provided in each pixel is controlled by a thin film transistor (transistor) provided in the pixel.
[0006]
  This active matrix organic EL display panel isPatent Document 2Is disclosed. An equivalent circuit for one pixel of this display panel is shown in FIG. The pixel 16 includes an EL element 15 that is a light emitting element, a first transistor 11 a, a second transistor 11 b, and a storage capacitor 19. Reference numeral 15 denotes an organic electroluminescence (EL) element. In the present invention, the transistor 11 a that supplies (controls) current to the EL element 15 is referred to as a driving transistor 11. A transistor that operates as a switch, such as the transistor 11b in FIG. 46, is referred to as a switching transistor 11.EIn many cases, the L element 15 has a rectifying property and is therefore called an OLED (organic light emitting diode). In FIG. 46 and the like, a diode symbol is used as the EL element 15.
[0007]
However, the light-emitting element in the present invention is not limited to the OLED, and may be any element whose luminance is controlled by the amount of current flowing through the element 15. For example, an inorganic EL element is illustrated. In addition, a white light emitting diode made of a semiconductor is exemplified. Moreover, a common light emitting diode is illustrated. In addition, a light emitting transistor may be used. In addition, the light emitting element is not necessarily required to have rectification. A bidirectional diode may also be used. Any of these may be sufficient as the EL element 15 of this invention.
[0008]
  In the example of FIG. 46, the source terminal (S) of the P-channel transistor 11a is set to Vdd (power supply potential), and the cathode (cathode) of the EL element 15 is connected to the ground potential (Vss). On the other hand, the anode (anode) is the transistor 11.aConnected to the drain terminal (D). On the other hand, a P-channel type transistor 11bThe gate terminal is connected to the gate signal line 17a, the source terminal is connected to the source signal line 18,DoThe rain terminal is connected to the storage capacitor 19 and the gate terminal (G) of the transistor 11a.
[0009]
  In order to operate the pixel 16, first, the gate signal line 17 a is selected, and a video signal representing luminance information is applied to the source signal line 18. Then, the transistor 11bBecomes conductive, the storage capacitor 19 is charged or discharged, and the transistor 11aThe gate potential is equal to the potential of the video signal. When the gate signal line 17a is not selected, the transistor 11a is turned off and the transistor 11b is electrically disconnected from the source signal line 18. However, the gate potential of the transistor 11 a is stably held by the storage capacitor (capacitor) 19. The current flowing through the EL element 15 via the transistor 11a has a value corresponding to the gate / source terminal voltage Vgs of the transistor 11a.dThe light continues to be emitted with a luminance corresponding to the amount of current supplied through the light.
[0010]
[Patent Document 1]
JP 2001-147659 A
[Patent Document 2]
JP-A-8-234683
[0011]
[Problems to be solved by the invention]
  However, conventionalLCD panelInIsHigh image quality, good video display performance, low power consumption, low cost, high brightness, etc.There was a problem.
An object of the present invention is to provide a high-quality EL display device and a driving method thereof in consideration of the above-described conventional problems.
[0014]
[Means for Solving the Problems]
  The first aspect of the present invention for solving the above problems is as follows.
  Pixels with EL elements in a matrixIn the display screen areaArrangedA display unit; a gate driver circuit that applies an on / off signal to a gate signal line connected to the pixel; and a source driver circuit that applies a video signal to a source signal line connected to the pixel;HaveIn the pixel, a driving transistor for supplying a current to the EL element and a switching transistor formed in the current path are formed.A method for driving an EL display device, comprising:
  From image data for generating a signal to be applied to the pixel of the EL display deviceThe EL element isIn one frame periodDisplay areaAsk for display period,
The image data is subjected to gradation conversion by a gamma curve,
  The gamma curve of the output gradation with respect to the input gradation when the obtained display period is shorter than when the obtained display period is longIncrease the x multiplier of
By applying the on / off signal to the gate signal line by the gate driver circuit, the switch transistor is turned on and off to control the current,
The gate driver circuit generates a strip-shaped non-display area and the display area on the display screen by controlling the current.This is a method for driving an EL display device.
  The second aspect of the present invention
  The EL display device further includes detection means for detecting the brightness of external light,
  According to the driving method of the EL display device of the first aspect of the present invention, the ratio between the non-display area and the display area is changed or the ratio between the non-display area and the display area is adjusted according to an output value of the detection means. is there.
  The third aspect of the present invention
  The EL display device further includes a time means for grasping the elapsed time,
  The EL display device driving method according to the first aspect of the present invention is characterized in that the ratio of the non-display area on the display screen is increased after a predetermined time has elapsed.
  The fourth aspect of the present invention is
  The EL display device driving method according to the first aspect of the present invention is characterized in that the ratio between the non-display area and the display area can be changed or adjusted to a predetermined ratio by a user operation.
  The fifth aspect of the present invention provides
  The EL display device includes a source driver circuit that supplies a signal to a source signal line connected to a pixel arranged in a region of the display screen, a substrate on which the pixel is formed, and the source driver circuit A selection circuit disposed between the output terminal and the source signal line;
  The selection circuit applies the output signal of the source driver circuit by selecting one source signal line from the plurality of source signal lines, and driving the EL display device according to the first aspect of the present invention. is there.
  In addition, the sixth aspect of the present invention,
A display unit in which pixels having EL elements are arranged in a region of a display screen in a matrix,
  A gate driver circuit for applying an on / off signal to a gate signal line connected to the pixel;
  A source driver circuit for applying a video signal to a source signal line connected to the pixel,
  In the pixel, a driving transistor for supplying current to the EL element and a switching transistor formed in the current path are formed,
  From image data that generates a signal to be applied to the pixelThe EL element isIn one frame periodDisplay areaAsk for the display period,
The image data is subjected to gradation conversion by a gamma curve,
  The gamma curve of the output gradation with respect to the input gradation when the obtained display period is shorter than when the obtained display period is longIncrease x multiplierAnd
  The gate driver circuit controls the current by turning on and off the switch transistor by applying the on / off signal to the gate signal line,
  The gate driver circuit has a strip-shaped non-display area and a display area on the display screen under the control of the current.SaidAn EL display device that generates a display area.
  Also,7thThe present invention is
  The EL display device further includes detection means for detecting the brightness of external light,
  The ratio between the non-display area and the display area is changed or the ratio between the non-display area and the display area is adjusted according to an output value of the detection means.6thThe EL display device of the present invention.
  Also,8thThe present invention is
  The EL display device further includes a time means for grasping the elapsed time,
  After a certain period of time, the display brightness of the EL display device is lowered by increasing the ratio of the non-display area on the display screen.6thThe EL display device of the present invention.
  Also,9thThe present invention is
  The control signal to the gate driver circuit is supplied from the source driver circuit.6thThe EL display device of the present invention.
  Also,10thThe present invention is
  The EL display device further includes a selection circuit,
  The source driver circuit is an IC chip made of a semiconductor,
  The selection circuit is formed by polysilicon technology on a substrate on which the display area is formed,
  The selection circuit has one input terminal and a plurality of output terminals,
  The input terminal of the selection circuit is connected to the output terminal of the source driver circuit,
  The source signal line is connected to each output terminal of the selection circuit.6thThe EL display device of the present invention.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
In the present specification, each drawing is omitted or / and enlarged or reduced for easy understanding and / or drawing. For example, in the cross-sectional view of the display panel shown in FIG. 11, the thin film sealing film 111 and the like are shown to be sufficiently thick. On the other hand, in FIG. 10, the sealing lid 85 is shown thinly. Also, there are some omitted parts. For example, in the display panel of the present invention, a phase film such as a circularly polarizing plate is necessary for preventing reflection. However, it is omitted in each drawing of this specification. The same applies to the following drawings. Moreover, the part which attached | subjected the same number or the symbol etc. has the same or similar form, material, function, or operation | movement.
[0017]
Note that the contents described in the drawings and the like can be combined with other embodiments and the like without particular notice. For example, a touch panel or the like is added to the display panel of FIG. 8, and the information display device illustrated in FIGS. 157 and 159 to 161 can be obtained. Further, a viewfinder (see FIG. 58) used for a video camera (see FIG. 159, etc.) can be configured by attaching a magnifying lens 1582. Also, the driving method of the present invention described in FIGS. 4, 15, 18, 21, 23, 29, 30, 30, 35, 36, 40, 41, 44, 100, etc. The present invention can be applied to any display device or display panel of the present invention.
[0018]
Note that in this specification, the driving transistor 11 and the switching transistor 11 are described as thin film transistors, but the present invention is not limited thereto. A thin film diode (TFD), a ring diode, or the like can also be used. The transistor is not limited to a thin film element, and may be a transistor formed on a silicon wafer. The substrate 71 may be formed of a silicon wafer. Of course, an FET, a MOS-FET, a MOS transistor, or a bipolar transistor may be used. These are also basically thin film transistors. In addition, it goes without saying that varistors, thyristors, ring diodes, photodiodes, phototransistors, PLZT elements may be used. That is, any of these can be used for the transistor element 11, the gate driver circuit 12, the source driver circuit 14, and the like of the present invention.
[0019]
Hereinafter, the EL panel of the present invention will be described with reference to the drawings. As shown in FIG. 10, the organic EL display panel includes at least one of an electron transport layer, a light emitting layer, a hole transport layer, and the like on a glass plate 71 (array substrate) on which a transparent electrode 105 as a pixel electrode is formed. An organic functional layer (EL layer) 15 and a metal electrode (reflection film) (cathode) 106 are laminated. A positive voltage is applied to the anode (anode), which is the transparent electrode (pixel electrode) 105, and a negative voltage is applied to the cathode (cathode) of the metal electrode (reflection electrode) 106, that is, a direct current is applied between the transparent electrode 105 and the metal electrode 106. As a result, the organic functional layer (EL layer) 15 emits light.
[0020]
The metal electrode 106 is preferably made of a material having a small work function such as lithium, silver, aluminum, magnesium, indium, copper, or an alloy thereof. In particular, for example, an Al—Li alloy is preferably used. The transparent electrode 105 can be made of a conductive material having a high work function such as ITO or gold. In addition, when gold is used as an electrode material, the electrode is in a translucent state. ITO may be other materials such as IZO. The same applies to the other pixel electrodes 105.
[0021]
A desiccant 107 is disposed in the space between the sealing lid 85 and the array substrate 71. This is because the EL film 15 is vulnerable to humidity. The desiccant 107 absorbs moisture penetrating the sealant and prevents the EL film 15 from deteriorating.
[0022]
  FIG. 10 shows a configuration in which sealing is performed using a glass lid 85, but sealing may be performed using a film (which may be a thin film, that is, a thin film sealing film) 111 as illustrated in FIG. For example, as the sealing film (thin film sealing film) 111, it is exemplified to use a film of an electrolytic capacitor obtained by vapor-depositing DLC (diamond-like carbon). This film has extremely poor moisture permeability (high moisture resistance). This film is used as the sealing film 111. In addition, a structure in which a DLC (diamond-like carbon) film or the like is directly deposited on the surface of the electrode 106ButNeedless to say, it is good. In addition, a thin film sealing film may be configured by laminating a resin thin film and a metal thin film in multiple layers.
[0023]
  The thickness of the thin film is n · d (where n is the refractive index of the thin film, and if a plurality of thin films are stacked, the refractive indexes of them are combined (calculate n · d for each thin film))ShiTo calculate. d is the thickness of the thin film, and if multiple thin films are stacked,With multiple thin filmsCalculate the total refractive index. ) May be less than or equal to the emission main wavelength λ of the EL element 15. By satisfying this condition, the light extraction efficiency from the EL element 15 becomes twice or more as compared with the case of sealing with a glass substrate. Further, an alloy or a mixture or a laminate of aluminum and silver may be formed.
[0024]
A configuration in which sealing is performed with the sealing film 111 without using the lid 85 as described above is referred to as thin film sealing. Thin film sealing in the case of “lower extraction (see FIG. 10, the light extraction direction is the arrow direction in FIG. 10)” for extracting light from the substrate 71 side becomes a cathode on the EL film after the EL film is formed. An aluminum electrode is formed. Next, a resin layer as a buffer layer is formed on the aluminum film. Examples of the buffer layer include organic materials such as acrylic and epoxy. Further, the film thickness is suitably 1 μm or more and 10 μm or less. More preferably, the film thickness is 2 μm or more and 6 μm or less. A sealing film 74 on the buffer film is formed. Without the buffer film, the structure of the EL film collapses due to the stress, and a line-like defect occurs. As described above, the sealing film 111 is exemplified by DLC (Diamond Like Carbon) or a layer structure of an electric field capacitor (a structure in which dielectric thin films and aluminum thin films are alternately deposited).
[0025]
In the case of extracting light from the EL layer 15 side, see “Upper extraction see FIG. 11, the light extraction direction is the arrow direction in FIG. 11”, thin film sealing is performed by forming a cathode (on the EL film 15 after forming the EL film 15. An Ag—Mg film to be an anode is formed with a film thickness of 20 Å or more and 300 Å. A transparent electrode such as ITO is formed thereon to reduce the resistance. Next, a resin layer as a buffer layer is formed on the electrode film. A sealing film 111 is formed on the buffer film.
[0026]
Half of the light generated from the EL layer 15 is reflected by the reflective film 106 and transmitted through the array substrate 71 to be emitted. However, external light is reflected on the reflective film 106 and a reflection occurs to reduce the display contrast. For this measure, a λ / 4 plate 108 and a polarizing plate (polarizing film) 109 are arranged on the array substrate 71. These are generally called circularly polarizing plates (circularly polarizing sheets).
[0027]
When the pixel is a reflective electrode, the light generated from the EL layer 15 is emitted upward. Therefore, it goes without saying that the phase plate 108 and the polarizing plate 109 are arranged on the light emitting side. The reflective pixel is obtained by forming the pixel electrode 105 with aluminum, chromium, silver, or the like. Further, by providing a convex portion (or a concave and convex portion) on the surface of the pixel electrode 105, the interface with the EL layer 15 is widened, the light emitting area is increased, and the luminous efficiency is improved. Note that the circularly polarizing plate is not necessary when the reflective film to be the cathode 106 (anode 105) is formed on the transparent electrode or when the reflectance can be reduced to 30% or less. This is because the reflection is greatly reduced. It is also desirable to reduce light interference.
[0028]
Since the light emitted from the EL element 15 of the EL display panel has no directivity, this light is emitted to an external space through the substrate 71 on which the EL element 15 is formed. Therefore, when light is emitted into a space (refractive index 1.0) from a substrate with a high refractive index (refractive index is about 1.5), 2/3 of the light is above the critical angle based on Snell's law, It is not emitted into the space (that is, 2/3 of the light generated by the EL element 15 cannot be emitted from the substrate 71). The light confined in the substrate 71 is irregularly reflected in the substrate 71 and becomes halation (see FIG. 420. The light 4093 is irregularly reflected in the substrate 71), and the display contrast of the EL display panel is lowered. In addition, it is not preferable because it causes heat generation.
[0029]
In order to solve this problem, in the present invention, as shown in FIG. 410, a light absorbing material is used as the bank (rib) 101 material. Hereinafter, the bank formed of the light absorbing material is referred to as a light absorbing bank 4101. By using the light absorbing bank 4101, it is possible to prevent the occurrence of halation occurring on the substrate 71 and the like, and to significantly improve the display contrast.
[0030]
That is, as illustrated in FIG. 420, light 4093 that is irregularly reflected in the substrate 71 is absorbed by the light absorption film 4101 (4102). As shown in FIG. 421, the light absorption film 4102 (4101) is an ineffective area (an area other than the effective area A (screen 50 through which light effective for image display passes) (area where light effective for image display is emitted). Preferably, the light absorbing film 4102 (4101) is also formed or disposed on the sealing lid 85, as shown in FIG. It is also effective to form 85 with a black material or the like.
[0031]
Substances that make up the light absorption film include organic materials such as acrylic resins containing carbon, black pigments or pigments dispersed in organic resins, and gelatin or casein as a color filter. What was dye | stained with the acid dye is illustrated. In addition, a single black fluoran dye may be used, and a color scheme black obtained by mixing a green dye and a red dye may also be used. Examples thereof include a PrMnO3 film formed by sputtering and a phthalocyanine film formed by plasma polymerization.
[0032]
The above materials are all black materials, but as the light absorption film, a material having a complementary color with respect to the light color generated by the display element may be used. For example, a light-absorbing material for a color filter may be used so as to obtain desired light absorption characteristics. Basically, a material obtained by dyeing a natural resin with a pigment may be used in the same manner as the black absorbing material described above. Further, a material in which a pigment is dispersed in a synthetic resin can be used. The selection range of the pigment is wider than the black pigment, and may be one suitable from azo dye, anthraquinone dye, phthalocyanine dye, triphenylmethane dye, or a combination of two or more thereof.
[0033]
Further, a metal material may be used as the light absorption film. For example, hexavalent chromium is exemplified. Hexavalent chromium is black and functions as a light absorbing film. In addition, light scattering materials such as opal glass and titanium oxide may be used. This is because scattering the light is equivalent to absorbing the light as a result.
[0034]
In addition, as illustrated in FIG. 411, it is preferable to form or dispose a light absorption film 4102 also in a region of the transistor 11 (transistor formation region 4111) included in the pixel 16. This is because when light is incident on the transistor 11, a photoconductor phenomenon occurs and the off-characteristic of the transistor is deteriorated.
[0035]
The light absorption film 4102 is also formed on the back surface of the gate driver circuit 12 so that light confined in the substrate 71 does not enter the driver circuit 12. Similarly, it is preferably formed on the back surface of the source driver circuit (IC) 14. This is for the same reason as that for forming the base anode line 2631 in FIG.
[0036]
In the EL display panel, the sealing lid 85 and the substrate 71 are bonded together in order to prevent external moisture from entering the EL element 15 part. At that time, in order to realize a narrow frame, the joining portion is placed on the gate driver circuit 12. However, when pressure is applied to the bonding portion, the gate driver circuit 12 may be destroyed due to this pressure. In particular, in order to make the adhesive layer 4123 at the bonding portion uniform, beads 4121 are mixed into the adhesive constituting the adhesive layer 4123 (see FIG. 412). This bead 4121 may be pressurized to sink into the gate driver circuit 12 and destroy the gate driver circuit 12. The configuration of the gate driver circuit 12 and the like will be described later.
[0037]
In order to solve this problem, in the present invention, the interlayer insulating film 102 is formed on the gate driver circuit 12. The thickness of the interlayer insulating film 102 is preferably 0.5 μm or more and 2.0 μm or less. In particular, the thickness is preferably 0.8 μm or more and 1.6 μm or less. Further, a light absorbing bank 4101 (bank material 4124) formed simultaneously with the formation of the bank 101 is formed on the interlayer insulating film 102. For the sake of convenience, the light absorption bank 4101 is described. However, the bank formed on the gate driver circuit 12 does not function as a bank, and prevents the gate driver circuit 12 from being broken by the bead 4121. This is the main purpose.
[0038]
The light absorbing bank 4101 also exhibits an effect of shielding light incident on the gate driver circuit 12. The film thickness of the light absorbing bank 4101 is the same as the height of the bank 101 of the pixel 16. The film thickness of the light absorption bank 4101 is preferably 0.5 μm or more and 2.0 μm or less. In particular, the thickness is preferably 0.8 μm or more and 1.6 μm or less. Note that an acrylic resin material is preferably used as the main material of the light absorbing bank 4101.
[0039]
Further, an aluminum thin film 106 serving as a cathode electrode is formed on the light absorbing bank 4101. The aluminum thin film 106 is formed simultaneously with the cathode electrode of the pixel 16. By forming the aluminum thin film 106, the moisture-proof performance is remarkably improved. The film thickness of the aluminum thin film 106 is preferably 0.1 μm or more and 1.5 μm or less. In particular, the thickness is preferably 0.2 μm or more and 1.0 μm or less. This thin film is not limited to aluminum, but may be formed of a material constituting the cathode electrode.
[0040]
As described above, by forming the interlayer insulating film 102, the light absorption bank 4101, and the aluminum thin film 106 on the gate driver circuit 12, the gate driver circuit 12 is not destroyed due to the attachment of the sealing lid 85. Moreover, sufficient moisture resistance can be obtained.
[0041]
In particular, in FIG. 412, as indicated by arrows, the aluminum thin film 106 covers the light absorption bank 4101 and the side surfaces of the interlayer insulating film 102. This coating can completely prevent moisture from entering. More preferably, a thin film made of an inorganic material is formed on the aluminum thin film 106. Examples of the thin film made of an inorganic material include SiO2 and SiNx. Needless to say, Al2O3, Ta2O3, or the like may be used. The thin film made of an inorganic material is preferably formed to have a thickness of 0.1 μm or more. It is also formed on the side surface shown in FIG. In addition, you may use what vapor-deposited DLC (diamond like carbon) for a thin film.
[0042]
The diameter of the beads 4121 is preferably 5 μm or more and 30 μm or less, and more preferably 8 m or more and 15 μm or less. Moreover, it is preferable that the width | variety of the contact bonding layer 4123 shall be 0.8 mm or more and 2 mm or less. Moreover, it is preferable to use resin beads as the material of the beads.
[0043]
In the embodiment of FIG. 412, the adhesive layer 4123 of the sealing lid 85 is disposed on the gate driver circuit 12. However, the present invention is not limited to this. As illustrated in FIG. 413, the adhesive layer 4123 may be disposed avoiding the gate driver circuit 12. With the configuration as shown in FIG. 413, the gate driver circuit 12 is not destroyed by the beads 4121 or the like.
[0044]
In FIG. 413, the adhesive layer 4123 is formed on the power supply wiring 4131 of the gate driver circuit 12. This is because even if pressure is applied to the power supply wiring 4131, the power supply wiring 4131 is not destroyed. A range indicated by B in FIG. 414 is a range where the adhesive layer 4123 that adheres to the sealing lid 85 is applied (adhesion range). A voltage is supplied to the gate driver circuit 12 from a power supply wiring 4131 through a voltage supply line 4141.
[0045]
In order to make the film thickness of the adhesive layer 4123 uniform without using the beads 4121, a convex portion 4151 may be formed on the sealing lid 85 as shown in FIG. 415 (shown by a dotted line in FIG. 415). . The protrusion 4151 can be easily formed by pressing. The convex portion 4151 is not limited to being formed on the sealing lid 85, and may be formed on the substrate 71 side.
[0046]
As shown in FIG. 415, it is preferable not to arrange the gate driver circuit 12 below the convex portion 4151. Further, when the source driver circuit 14 is also formed directly on the substrate 71 as shown in FIG. 416, it is preferable to avoid the source driver 14 as well. However, when the convex portion 4151 is formed in a linear shape (4151a, 4151b) as shown in FIG. 416, there is no escape space for the applied adhesive (becomes the adhesive layer 4123). Therefore, as shown in FIG. 417, the convex portion 4151 is preferably formed or arranged in a dot shape. The dot shape means a state other than a linear shape that is not completely interrupted as shown in FIG. Even if it is the linear convex part 4151, if the part has interrupted, it will become the escape place of an adhesive agent. Therefore, the dot shape may be a linear shape. Other configurations are the same as or similar to those in FIG.
[0047]
FIG. 412 shows a configuration for sealing with a sealing lid 85. However, the present invention is not limited to this, and may be sealed with a thin film 111 (thin film sealing film 111) as shown in FIG. Other configurations are the same as those in FIG. As described above, the thin film sealing film 111 is exemplified by using a film of an electrolytic capacitor obtained by vapor-depositing DLC (diamond-like carbon). Moisture resistance is very good. This film is used as the sealing film 111. Needless to say, a structure in which a DLC film or the like is directly deposited on the surface of the electrode 106 is preferable.
[0048]
When the source driver IC is COG-mounted (chip-on-glass mounting method) as the source driver circuit 14, it is necessary to pay attention to the mounting. This is because the EL material constituting the EL element 15 has a low glass transition temperature and may be deteriorated by heating during COG mounting. In general, an organic EL material causes deterioration of its characteristics when a temperature of 100 degrees (Celsius) or higher is applied for 1 minute.
[0049]
In order to cope with this problem, the distance between the driver IC to be COG-mounted and the portion where the EL film is formed (display screen 50) may be increased by a certain distance. According to the experiment, when the maximum heating temperature applied during COG mounting is C and the distance from the terminal position end of the IC to be mounted to the nearest EL element forming portion is K, K (mm)> C / It is preferable to satisfy the relationship of 120 (mm). More preferably, it is preferable to satisfy the relationship of K (mm)> C / 100 (mm).
[0050]
If this condition cannot be satisfied, a heat radiating plate 4191 (heat radiating means) is disposed between the IC chip and the display screen 50 during COG mounting as shown in FIG. The heat radiating plate 4191 can prevent the heat at the time of COG mounting from being transmitted to the display screen 50. The heat radiating plate 4191 may be any configuration or material as long as it has better thermal conductivity than the material constituting the substrate 71 such as metal.
[0051]
As shown in FIG. 418, when a thin film sealing configuration is adopted, it is also effective to dispose or attach a metal plate 4231 or the like to the sealing thin film 111 and dissipate heat (FIG. 423). An adhesive made of a silicon material is applied on the sealing thin film 111, and a metal plate 4231 having a heat dissipation effect is disposed. Of course, the material is not limited to the metal plate (metal sheet) 4231, and any material may be used as long as it has a heat dissipation effect. For example, organic materials such as diamond thin film and carbon are exemplified. Note that the adhesive layer 4123 is not necessarily required, and the metal plate 4231 may be in close contact with the sealing thin film 111.
[0052]
In order to further improve the heat dissipation effect, the surface of the metal plate 4231 may be uneven as shown in FIG.
[0053]
As shown in FIG. 423, when the adhesive layer 4123 is applied to the entire surface of the sealing thin film 111, the sealing thin film 111 may be broken due to shrinkage when the adhesive layer is cured. In order to cope with this problem, as shown in FIG. 424, the adhesive 4123 may be applied in the form of dots (dotted state). Of course, the adhesive 4123 may be applied linearly.
[0054]
In order to suppress reflection at the cathode 106, the configuration illustrated in FIG. 425 may be employed. In FIG. 425, the cathode electrode 106 (4251 in FIG. 425) is formed very thin. Therefore, the cathode electrode 4251 is used in FIG. The thickness of the cathode electrode 4251 is 100 angstroms or more and 1000 angstroms or less. More preferably, it is 200 angstroms or more and 500 angstroms or less. By forming the cathode electrode 4251 thin, the cathode electrode becomes a semi-transmissive state, so that reflection is reduced. However, if the cathode electrode 4251 is thin, the resistance value becomes high.
[0055]
As a countermeasure, as shown in FIG. 425, a conductor film 4253 made of a transparent material is formed on the cathode electrode 4251. Examples of the conductor film 4253 include ITO or IZO. The transparent conductor film 4253 may be a light-absorbing conductor film such as carbon. This is because the reflection is suppressed by carbon or the like.
[0056]
The sealing thin film 111 is further formed on the transparent conductor film 4253, or fine beads 4252 are dispersed directly on the transparent conductor film 4253. The diameter of the beads is preferably 1 μm or more and 10 μm or less. On this, a fixing material 4254 for fixing the beads 4252 is formed by coating or vapor deposition. An inorganic material such as the fixing material 4254, SiO2, or SiOx, or an organic material such as polyvinyl alcohol or polyimide can be used. In addition to the acrylic resin, an epoxy adhesive or a polyester adhesive can be used. Note that the thickness of the fixing material 4254 is 100 μm or less.
[0057]
Note that when a thin film is deposited on the pixel electrode 105 or the like, the EL film 15 may be formed in an argon atmosphere. Further, by forming a carbon film with a thickness of 20 to 50 nm on ITO as the pixel electrode 105, the stability of the interface is improved, and the light emission luminance and the light emission efficiency are also improved. Moreover, it is needless to say that the EL film 15 is not limited to being formed by vapor deposition, and may be formed by inkjet. This inkjet method is particularly effective for polymer organic EL materials. In this case, it is preferable to form a hydrophilic film at a location where the polymer organic EL material is applied.
[0058]
Since the polymer EL material is formed by the ink jet method, it is necessary to satisfactorily apply to the substrate 71. Basically, as shown in FIG. 429 (a), the periphery is surrounded by a bank 101, and a polymer EL material 4291 is applied into the bank 101. However, as illustrated in FIG. 429 (a), when the periphery is surrounded by the bank 101, a portion where the polymer EL material 4291 is not applied to the peripheral portion as indicated by C occurs.
[0059]
In response to this problem, the present invention removes the portion D of the bank 101 as shown in FIG. 429 (b) (the bank 101 is interrupted). In this way, by removing the four corners of the bank 101 in particular, the polymer EL material 4291 can be satisfactorily applied to the periphery of the pixel.
FIG. 428 illustrates the shape and arrangement of the bank 101 of the present invention. The bank 101 includes banks 101a dotted in the vertical direction and dots 101b dotted in the horizontal direction.
[0060]
As shown in FIG. 430, even when the region to which the polymer EL material 4291 is applied is a circle (other than a rectangle), as shown in the figure, the structure where the bank 101 is removed is shown. It is good to adopt.
[0061]
Hereinafter, in order to facilitate understanding of the EL display panel structure of the present invention, a method for manufacturing the organic EL display panel of the present invention will be described first.
[0062]
In order to improve the heat dissipation of the sealing lid 85 and the substrate 71, the substrate may be formed of sapphire glass. Further, a thin film or a thick film having good thermal conductivity may be formed. For example, the use of a substrate on which a diamond thin film (such as DLC) is formed is exemplified. Of course, a quartz glass substrate or a soda glass substrate may be used. In addition, a ceramic substrate such as alumina may be used, a metal plate made of copper or the like, or an insulating film coated with a metal film or a carbon film by vapor deposition or coating may be used. When the pixel electrode 105 is of a reflective type, light is emitted from the surface direction of the substrate as the substrate material. Therefore, non-transparent materials such as stainless steel can be used in addition to transparent or translucent materials such as glass, quartz and resin.
[0063]
Further, a microlens may be formed or disposed outside or inside the sealing lid 85 and the substrate 71 corresponding to the pixel shape. By configuring the microlens, the directivity of light emitted from the EL film is narrowed, and high luminance can be realized.
[0064]
In the embodiment of the present invention, the cathode electrode 106 and the like are formed of a metal film. However, the present invention is not limited to this, and may be formed of a transparent film such as ITO or IZO. Thus, by making both the anode and cathode electrodes of the EL element 15 transparent, a transparent EL display panel can be formed (of course, one of them may be formed of a light-transmitting metal film, or An extremely thin metal film may be used as a cathode electrode, and a transparent conductor material such as ITO may be laminated on the cathode electrode). By increasing the transmittance to about 80% without using a metal film, it is possible to make the other side of the display panel almost transparent while displaying characters and pictures.
[0065]
Needless to say, a plastic substrate may be used for the sealing lids 85 and 71. Plastic substrates are difficult to break and are lightweight, making them ideal as display panel substrates for mobile phones. The plastic substrate is preferably used as a laminated substrate by attaching an auxiliary substrate to one surface of a base substrate serving as a core material with an adhesive. Of course, these substrates are not limited to plates, and may be films having a thickness of 0.05 mm or more and 0.3 mm or less.
[0066]
As the base substrate, an alicyclic polyolefin resin is preferably used. As such alicyclic polyolefin resin, a single plate of 200 μm in thickness of ARTON manufactured by Nippon Synthetic Rubber Co., Ltd. is exemplified. From polyester resin, polyethylene resin or polyethersulfone resin, etc., on which one side of the base substrate is formed with a hard coat layer with heat resistance, solvent resistance or moisture permeability function, and a gas barrier layer with air permeability resistance function An auxiliary substrate (or film or membrane) is placed.
[0067]
As described above, when the substrate 71 and the like are formed of plastic, the substrate 71 and the like are formed of a base substrate and an auxiliary substrate. On the other surface of the base substrate, an auxiliary substrate (or film or film) made of a polyethersulfone resin or the like on which a hard coat layer and a gas barrier layer are formed is disposed in the same manner as described above. It is preferable that the angle formed by the optical slow axis of the auxiliary substrate and the optical slow axis of the auxiliary substrate is 90 degrees. Note that the base substrate and the auxiliary substrate are attached to each other with an adhesive or a pressure-sensitive adhesive to form a laminated substrate.
[0068]
As the adhesive, it is preferable to use a UV (ultraviolet) curable adhesive made of an acrylic resin. The acrylic resin preferably has a fluorine group. In addition, an epoxy adhesive or pressure-sensitive adhesive may be used. The refractive index of the adhesive or pressure-sensitive adhesive is preferably 1.47 or more and 1.54 or less. Moreover, it is preferable that the difference in refractive index with the refractive index of the substrate is 0.03 or less. In particular, the adhesive is preferably added with a light diffusing material such as titanium oxide as described above to function as a light scattering layer.
[0069]
When the auxiliary substrate and the auxiliary substrate are bonded to the base substrate, the angle formed by the optical slow axis of the auxiliary substrate and the optical slow axis of the auxiliary substrate is preferably set to 45 degrees or more and 120 degrees or less. More preferably, it is 80 degrees or more and 100 degrees or less. By setting it within this range, the retardation generated in the auxiliary substrate and the polyethersulfone resin as the auxiliary substrate can be completely canceled in the laminated substrate. Therefore, the plastic substrate for display panel can be handled as an isotropic substrate having no phase difference. Therefore, the structure using a circularly polarizing plate does not cause unevenness of the display panel due to different phase states. Needless to say, the matter regarding the circularly polarizing plate is not limited to a plastic substrate, but is also effective for a glass substrate. This is because a reduction in contrast due to external light reflected on the substrate surface can be effectively suppressed.
[0070]
With this configuration, versatility is significantly increased as compared with a film substrate or a film laminated substrate having a phase difference. That is, by combining the retardation film, linearly polarized light can be converted into elliptically polarized light as designed. If the substrate has a phase difference, an error from the design value occurs due to this phase difference.
[0071]
Here, as the hard coat layer, a polyester resin, an epoxy resin, a urethane resin, an acrylic resin, or the like can be used, and a stripe electrode (simple matrix EL display panel) or a pixel electrode (active matrix display panel). ) Also serves as the first undercoat layer of the transparent conductive film.
[0072]
As the gas barrier layer, an inorganic material such as SiO 2 or SiO x, or an organic material such as polyvinyl alcohol or polyimide can be used. As an adhesive, an adhesive, etc., an epoxy adhesive or a polyester adhesive can be used in addition to the acrylic described above. The adhesive layer has a thickness of 100 μm or less. However, it is preferably 10 μm or more in order to smooth the surface irregularities such as the substrate.
[0073]
The transistor 11 preferably employs an LDD (lightly doped drain) structure. In this specification, an EL element (described with various abbreviations such as OEL, PEL, PLED, and OLED) 15 is described as an example of the EL element, but the present invention is not limited to this. It goes without saying that also applies.
[0074]
First, the active matrix method used for organic EL display panels is:
A specific pixel can be selected and given display information can be given.
Two conditions must be satisfied that current can flow through the EL element throughout one frame period.
[0075]
In order to satisfy these two conditions, in the conventional organic EL pixel configuration shown in FIG. 46, the first transistor 11b is a switching transistor for selecting a pixel, and the second transistor 11a is an EL element (EL film). ) A driving transistor for supplying current to 15.
[0076]
In the case of displaying gradation using this configuration, it is necessary to apply a voltage corresponding to the gradation as the gate voltage of the driving transistor 11a. Therefore, the variation in the on-state current of the driving transistor 11a appears in the display as it is.
[0077]
The on-current of a transistor is very uniform if it is a transistor formed of a single crystal, but in a low-temperature polycrystalline transistor formed by low-temperature polysilicon technology that can be formed on an inexpensive glass substrate with a formation temperature of 450 degrees or less. The threshold value varies in the range of ± 0.2V to 0.5V. For this reason, the on-current flowing through the driving transistor 11a varies correspondingly, and the display is uneven. These irregularities are caused not only by variations in threshold voltage, but also by transistor mobility, gate insulating film thickness, and the like. The characteristics also change due to deterioration of the transistor 11.
[0078]
This phenomenon is not limited to low-temperature polysilicon technology, and transistors and the like are formed using solid-phase (CGS) grown semiconductor films even in high-temperature polysilicon technology with a process temperature of 450 degrees Celsius or higher. Even things can occur. In addition, it occurs in organic transistors. It also occurs in amorphous silicon transistors.
[0079]
The present invention described below is a configuration or method that can cope with these techniques. In this specification, a transistor formed by low-temperature polysilicon technology will be mainly described.
[0080]
Therefore, as shown in FIG. 46, in the method of displaying gradation by writing a voltage, it is necessary to strictly control the device characteristics in order to obtain a uniform display. However, the current low-temperature polycrystalline polysilicon transistor and the like cannot satisfy the specification of suppressing this variation within a predetermined range.
[0081]
Specifically, the pixel structure of the EL display device of the present invention is formed by a plurality of transistors 11 and EL elements each having at least four unit pixels as shown in FIG. The pixel electrode is configured to overlap the source signal line. That is, an insulating film or a planarizing film made of an acrylic material is formed on the source signal line 18 for insulation, and the pixel electrode 105 is formed on the insulating film. Such a configuration in which the pixel electrode is overlaid on at least a part on the source signal line 18 is called a high aperture (HA) structure. Unnecessary interference light and the like are reduced, and a good light emission state can be expected.
[0082]
By activating the gate signal line (first scanning line) 17a (applying an ON voltage), the current value to be passed through the EL element 15 through the driving transistor 11a and the switching transistor 11c of the EL element 15 is sourced. It flows from the driver circuit 14. In addition, the transistor 11b opens when the gate signal line 17a becomes active (applies an ON voltage) so as to short-circuit between the gate and drain of the transistor 11a, and a capacitor (capacitor, capacitor) connected between the gate and source of the transistor 11a. The gate voltage (or drain voltage) of the transistor 11a is stored in the storage capacitor (additional capacitor) 19 (see (a) of FIG. 3).
[0083]
  Note that the size of the capacitor (storage capacitor) 19 is preferably 0.2 pF or more and 2 pF or less, and in particular, the size of the capacitor (storage capacitor) 19 is preferably 0.4 pF or more and 1.2 pF or less. . The capacitance of the capacitor 19 is determined in consideration of the pixel size. If the capacity required for one pixel is Cs (pF) and the area occupied by one pixel (not the aperture ratio) is Sp (square μm), 500 /Sp  ≦ Cs ≦ 20000 /SpMore preferably, 1000 / Sp ≦ Cs ≦ 10000 / Sp. Note that the gate capacitance of the transistor is small, so hereCsIs the capacity of the storage capacitor (capacitor) 19 alone.
[0084]
The gate signal line 17a is inactive (OFF voltage is applied), the gate signal line 17b is active, and the current flow path includes the transistor 11d and the EL element 15 connected to the first transistor 11a and the EL element 15. It switches to a path | route, and it operate | moves so that the memorize | stored electric current may be sent through the said EL element 15 (refer FIG.3 (b)).
[0085]
This circuit has four transistors 11 in one pixel, and the gate of the transistor 11a is connected to the source of the transistor 11b. The gates of the transistors 11b and 11c are connected to the gate signal line 17a. The drain of the transistor 11 b is connected to the source of the transistor 11 c and the source of the transistor 11 d, and the drain of the transistor 11 c is connected to the source signal line 18. The gate of the transistor 11d is connected to the gate signal line 17b, and the drain of the transistor 11d is connected to the anode electrode of the EL element 15.
[0086]
In FIG. 1, all the transistors are P-channel. The P channel has a lower mobility than an N channel transistor, but is preferable because it has a high breakdown voltage and is less likely to deteriorate. However, the present invention is not limited to the configuration of the EL element with the P channel. You may comprise only N channel. Moreover, you may comprise using both N channel and P channel.
[0087]
Optimally, it is preferable that all the transistors 11 constituting the pixel are formed by P-channel, and the built-in gate driver circuit 12 is also formed by P-channel. By forming the array with only P-channel transistors in this way, the number of masks becomes five, and cost reduction and high yield can be realized.
[0088]
Hereinafter, in order to facilitate the understanding of the present invention, the EL element configuration of the present invention will be described with reference to FIG. The EL device configuration of the present invention is controlled by two timings. The first timing is a timing for storing a necessary current value. When the transistor 11b and the transistor 11c are turned on at this timing, an equivalent circuit is obtained as shown in FIG. Here, a predetermined current Iw is written from the signal line. As a result, the gate and drain of the transistor 11a are connected, and a current Iw flows through the transistor 11a and the transistor 11c. Therefore, the gate-source voltage of the transistor 11a is a voltage at which I1 flows.
[0089]
  The second timing is the transistor 11bThe transistor 11c is closed and the transistor 11d is opened, and the equivalent circuit at that time is shown in FIG. The voltage between the source and gate of the transistor 11a remains held. In this case, since the transistor 11a always operates in the saturation region, the current Iw is constant.
[0090]
When operated in this way, it is as shown in FIG. That is, 51a in FIG. 5A indicates a pixel (row) (write pixel row) on the display screen 50 that is current-programmed at a certain time. This pixel (row) 51a is not lit (non-display pixel (row)) as shown in FIG. The other pixel (row) is a display pixel (row) 53 (current flows through the EL element 15 of the pixel 16 in the display area 53, and the EL element 15 emits light).
[0091]
In the case of the pixel configuration of FIG. 1, as shown in FIG. 3A, the program current Iw flows through the source signal line 18 during current programming. The voltage is set (programmed) in the capacitor 19 so that the current Iw flows through the transistor 11a and the current flowing through Iw is maintained. At this time, the transistor 11d is in an open state (off state).
[0092]
Next, during a period in which a current flows through the EL element 15, the transistors 11c and 11b are turned off and the transistor 11d operates as shown in FIG. That is, the off voltage (Vgh) is applied to the gate signal line 17a, and the transistors 11b and 11c are turned off. On the other hand, an on voltage (Vgl) is applied to the gate signal line 17b, and the transistor 11d is turned on.
[0093]
This timing chart is shown in FIG. In FIG. 4 and the like, subscripts in parentheses (for example, (1) and the like) indicate pixel row numbers. That is, the gate signal line 17a (1) indicates the gate signal line 17a of the pixel row (1). Also, * H in the upper part of FIG. 4 (an arbitrary symbol or numerical value is applied to “*” and indicates a horizontal scanning line number) indicates a horizontal scanning period. That is, 1H is the first horizontal scanning period. The above items are for ease of explanation and are not limited (1H number, 1H cycle, order of pixel row numbers, etc.).
[0094]
As can be seen from FIG. 4, when a turn-on voltage is applied to the gate signal line 17a in each selected pixel row (selection period is 1H), a turn-off voltage is applied to the gate signal line 17b. Yes. During this period, no current flows through the EL element 15 (non-lighting state). In an unselected pixel row, an off voltage is applied to the gate signal line 17a, and an on voltage is applied to the gate signal line 17b. Further, during this period, a current flows through the EL element 15 (lighting state).
[0095]
Note that the gate of the transistor 11a and the gate of the transistor 11c are connected to the same gate signal line 17a. However, the gate of the transistor 11a and the gate of the transistor 11c may be connected to different gate signal lines 17 (see FIG. 32). One pixel has three gate signal lines (the configuration in FIG. 1 is two). By individually controlling the ON / OFF timing of the gate of the transistor 11b and the ON / OFF timing of the gate of the transistor 11c, variation in the current value of the EL element 15 due to variations in the transistor 11a can be further reduced.
[0096]
When the gate signal line 17a and the gate signal line 17b are made common and the transistors 11c and 11d have different conductivity types (N channel and P channel), the drive circuit can be simplified and the aperture ratio of the pixel can be improved. .
[0097]
With this configuration, the write path from the signal line is turned off as the operation timing of the present invention. That is, when a predetermined current is stored, if there is a branch in the current flow path, an accurate current value is not stored in the capacitance (capacitor) between the source (S) and the gate (G) of the transistor 11a. By making the transistors 11c and 11d have different conductivity types, the transistor 11d can be turned on after the transistor 11c is always turned off at the timing of switching of the scanning lines by controlling the threshold values of the transistors 11c and 11d.
[0098]
In this case, however, it is necessary to carefully control each other's thresholds, so care must be taken in the process. Although the circuit described above can be realized with at least four transistors, the transistor 11e is cascade-connected as shown in FIG. 2 to control the timing more accurately or to reduce the mirror effect as described later. The operation principle is the same even when the total number of transistors is 4 or more. With the configuration in which the transistor 11e is added as described above, the current programmed through the transistor 11c can be supplied to the EL element 15 with higher accuracy.
[0099]
Note that the pixel configuration of the present invention is not limited to the configurations of FIGS. For example, it may be configured as shown in FIG. 113 does not have the switching transistor 11d as compared with the configuration of FIG. Instead, a changeover switch 1131 is formed or arranged. The switch 11d in FIG. 1 has a function of controlling on / off (flow or not flow) of a current flowing from the driving transistor 11a to the EL element 15. As will be described in the following embodiments, the on / off control function of the transistor 11d is an important component of the present invention. The configuration in FIG. 113 realizes an on / off function without forming the transistor 11d.
[0100]
In FIG. 113, the terminal a of the changeover switch 1131 is connected to the anode voltage Vdd. The voltage applied to the terminal a is not limited to the anode voltage Vdd, and any voltage that can turn off the current flowing through the EL element 15 may be used.
[0101]
The b terminal of the changeover switch 1131 is connected to the cathode voltage (shown as ground in FIG. 113). The voltage applied to the b terminal is not limited to the cathode voltage, and any voltage that can turn on the current flowing through the EL element 15 may be used.
[0102]
The cathode terminal of the EL element 15 is connected to the c terminal of the changeover switch 1131. Note that the change-over switch 1131 may be any as long as it has a function of turning on and off the current flowing through the EL element 15. Therefore, it is not limited to the formation position in FIG. 113, and any path may be used as long as the current of the EL element 15 flows. Further, the function of the switch is not limited, and any function may be used as long as the current flowing through the EL element 15 can be turned on and off. In other words, in the present invention, any pixel configuration may be used as long as switching means capable of turning on and off the current flowing through the EL element 15 is provided in the current path of the EL element 15.
[0103]
Further, “off” does not mean a state in which no current flows completely. Any current can be used as long as the current flowing through the EL element 15 can be reduced more than usual. The above matters are the same in other configurations of the present invention.
[0104]
Since the change-over switch 1131 can be easily realized by combining a P-channel transistor and an N-channel transistor, description thereof will not be required. For example, two analog switches may be formed. Of course, since the switch 1131 only turns on and off the current flowing through the EL element 15, it is needless to say that the switch 1131 can be formed of a P-channel transistor or an N-channel transistor.
[0105]
When the switch 1131 is connected to the a terminal, the Vdd voltage is applied to the cathode terminal of the EL element 15. Therefore, no current flows through the EL element 15 regardless of the voltage holding state of the gate terminal G of the driving transistor 11a. Therefore, the EL element 15 is not turned on.
[0106]
When the switch 1131 is connected to the b terminal, the GND voltage is applied to the cathode terminal of the EL element 15. Therefore, a current flows through the EL element 15 in accordance with the voltage state held at the gate terminal G of the driving transistor 11a. Therefore, the EL element 15 is turned on.
[0107]
From the above, in the pixel configuration of FIG. 113, the switching transistor 11 d is not formed between the driving transistor 11 a and the EL element 15. However, the lighting control of the EL element 15 can be performed by controlling the switch 1131.
[0108]
In the pixel configuration shown in FIGS. 1 and 2, the number of driving transistors 11a is one per pixel. The present invention is not limited to this, and a plurality of driving transistors 11a may be formed or arranged in one pixel. FIG. 116 shows an example. In FIG. 116, two driving transistors 11 a 1 and 11 a 2 are formed in one pixel, and the gate terminals of the two driving transistors 11 a 1 and 11 a 2 are connected to a common capacitor 19. By forming a plurality of driving transistors 11a, there is an effect that variation in programmed current is reduced. Other configurations are the same as those in FIG.
[0109]
1 and 2, the current output from the driving transistor 11a is supplied to the EL element 15, and the current is controlled to be turned on and off by the switching transistor 11d disposed between the driving transistor 11a and the EL element 15. However, the present invention is not limited to this. For example, the configuration of FIG. 117 is illustrated.
[0110]
In the embodiment of FIG. 117, the current flowing through the EL element 15 is controlled by the driving transistor 11a. The switching transistor 11 d disposed between the Vdd terminal and the EL element 15 is controlled to turn on and off the current flowing through the EL element 15. Therefore, in the present invention, the switch transistor 11d may be arranged anywhere, and any arrangement can be used as long as the current flowing through the EL element 15 can be controlled.
[0111]
The variation in the characteristics of the transistor 11a has a correlation with the transistor size. In order to reduce the characteristic variation, the channel length of the first transistor 11a is preferably 5 μm or more and 100 μm or less. More preferably, the channel length of the first transistor 11a is 10 μm or more and 50 μm or less. This is considered to be because when the channel length L is increased, the grain boundary included in the channel increases, the electric field is relaxed, and the kink effect is suppressed to a low level.
[0112]
As described above, the present invention controls the current flowing through the EL element 15 in the path through which current flows into the EL element 15 or the path through which current flows from the EL element 15 (that is, the current path of the EL element 15). The circuit means is configured, formed or arranged.
[0113]
Even in the current mirror system which is one of current programming systems, as shown in FIG. 114, an EL element is formed by arranging or arranging a transistor 11g as a switching element between the driving transistor 11b and the EL element 15. The current flowing through 15 can be turned on and off (can be controlled). Of course, the transistor 11g may be replaced with the switch 1131 in FIG.
[0114]
114 are connected to one gate signal line 17a. However, as shown in FIG. 115, the transistor 11c is controlled by the gate signal line 17a1, and the transistor 11d has a gate signal. You may comprise so that it may control by the line 17a2. 115 is more versatile in controlling the pixel 16.
[0115]
Further, as illustrated in FIG. 42A, the transistors 11b and 11c may be formed of N-channel transistors. Further, as illustrated in FIG. 42B, the transistors 11c and 11d may be formed of P-channel transistors.
[0116]
The object of the invention of this patent is to propose a circuit configuration in which variations in transistor characteristics do not affect display, and for that purpose four or more transistors are required. When circuit constants are determined based on these transistor characteristics, it is difficult to obtain appropriate circuit constants if the characteristics of the four transistors do not match. When the channel direction is horizontal and vertical with respect to the major axis direction of laser irradiation, the threshold value and mobility of transistor characteristics are different. In both cases, the degree of variation is the same. The average value of mobility and threshold value differs between the horizontal direction and the vertical direction. Therefore, it is desirable that the channel directions of all the transistors constituting the pixel are the same.
[0117]
  The capacitance value of the storage capacitor 19 is set to Cs.(PF), The off-state current value of the second transistor 11b is set to Ioff(PA)In this case, it is preferable to satisfy the following formula.
[0118]
3 <Cs / Ioff <24
More preferably, it is preferable to satisfy the following formula.
[0119]
  6 <Cs / Ioff <18
  Off-state current of transistor 11bIoffBy setting the current to 5 pA or less, the change in the current value flowing through the EL can be suppressed to 2% or less. This is because when the leakage current increases, the electric charge stored between the gate and the source (both ends of the capacitor) cannot be held for one field in the voltage non-writing state. Therefore, if the storage capacity of the capacitor 19 is large, the allowable amount of off-current is also large. By satisfying the above equation, the fluctuation of the current value between adjacent pixels can be suppressed to 2% or less.
[0120]
In addition, it is preferable to adopt a multi-gate structure in which the transistors constituting the active matrix are configured as p-channel polysilicon thin film transistors and the transistor 11b is a dual gate or higher. Since the transistor 11b functions as a switch between the source and drain of the transistor 11a, the transistor 11b is required to have as high a ON / OFF ratio as possible. By setting the gate structure of the transistor 11b to a multi-gate structure that is equal to or higher than the dual gate structure, a characteristic with a high ON / OFF ratio can be realized.
[0121]
The semiconductor film constituting the transistor 11 of the pixel 16 is generally formed by laser annealing in the low temperature polysilicon technology. Variations in the laser annealing conditions result in variations in transistor 11 characteristics. However, if the characteristics of the transistors 11 in one pixel 16 match, the current programming method shown in FIG. 1 can be driven so that a predetermined current flows through the EL element 15. This is an advantage not found in voltage programming. An excimer laser is preferably used as the laser.
[0122]
In the present invention, the formation of the semiconductor film is not limited to the laser annealing method, but may be a thermal annealing method or a method by solid phase (CGS) growth. In addition, the present invention is not limited to the low temperature polysilicon technology, and it goes without saying that the high temperature polysilicon technology may be used. Further, it may be a semiconductor film formed using amorphous silicon technology.
[0123]
To deal with this problem, in the present invention, as shown in FIG. 7, a laser irradiation spot (laser irradiation range) 72 at the time of annealing is irradiated in parallel to the source signal line 18. Further, the laser irradiation spot 72 is moved so as to coincide with one pixel column. Of course, the present invention is not limited to one pixel column. For example, RGB in FIG. 55 may be irradiated with laser in units of one pixel 16 (in this case, it is a three pixel column). In addition, a plurality of pixels may be irradiated simultaneously. It goes without saying that the movement of the laser irradiation range may overlap (usually, the irradiation range of the moving laser light is usually overlapped).
[0124]
The pixels are made of three pixels of RGB and have a square shape. Accordingly, each of the R, G, and B pixels has a vertically long pixel shape. Therefore, by annealing the laser irradiation spot 72 in a vertically long shape, the characteristic variation of the transistor 11 can be prevented from occurring within one pixel. Further, the characteristics (mobility, Vt, S value, etc.) of the transistor 11 connected to one source signal line 18 can be made uniform (that is, the characteristics are different from those of the transistor 11 of the adjacent source signal line 18). However, the characteristics of the transistor 11 connected to one source signal line can be made substantially equal).
[0125]
In the configuration of FIG. 7, three panels are formed vertically within the range of the length of the laser irradiation spot 72. The annealing apparatus that irradiates the laser irradiation spot 72 recognizes the positioning markers 73a and 73b of the glass substrate 74 (automatic positioning by pattern recognition) and moves the laser irradiation spot 72. The positioning marker 73 is recognized by a pattern recognition device. An annealing apparatus (not shown) recognizes the positioning marker 73 and extracts the position of the pixel column (makes the laser irradiation range 72 parallel to the source signal line 18). The laser irradiation spot 72 is irradiated so as to overlap the pixel column position, and annealing is sequentially performed.
[0126]
The laser annealing method described in FIG. 7 (method of irradiating a line-shaped laser spot in parallel with the source signal line 18) is preferably employed particularly in the current programming method of the organic EL display panel. This is because the characteristics of the transistor 11 match in the direction parallel to the source signal line (the characteristics of the pixel transistors adjacent in the vertical direction are approximate). Therefore, there is little change in the voltage level of the source signal line at the time of current driving, and current writing shortage hardly occurs.
[0127]
For example, in the case of white raster display, the current flowing through the transistor 11a of each adjacent pixel is almost the same, so the change in the current amplitude output from the source driver IC 14 is small. If the characteristics of the transistor 11a in FIG. 1 are the same and the current values to be programmed in each pixel are the same in the pixel columns, the potential of the source signal line 18 at the time of current programming is constant. Therefore, the potential fluctuation of the source signal line 18 does not occur. If the characteristics of the transistors 11a connected to one source signal line 18 are almost the same, the potential fluctuation of the source signal line 18 is small. This is the same for other current-programmed pixel configurations such as FIG. 38 (that is, it is preferable to apply the manufacturing method of FIG. 7).
[0128]
In addition, uniform image display (since display unevenness due to variations in transistor characteristics is unlikely to occur) can be realized by a method of simultaneously writing a plurality of pixel rows described with reference to FIGS. In FIG. 27 and the like, a plurality of pixel rows are selected simultaneously. Therefore, if the transistors in adjacent pixel rows are uniform, the transistor characteristic unevenness in the vertical direction can be absorbed by the source driver circuit 14.
[0129]
In FIG. 7, the source driver circuit 14 is illustrated as having an IC chip mounted thereon; however, the present invention is not limited to this, and the source driver circuit 14 may be formed in the same process as the pixel 16. Needless to say.
[0130]
In the present invention, in particular, the threshold voltage Vth2 of the driving transistor 11b is set not to be lower than the threshold voltage Vth1 of the corresponding driving transistor 11a in the pixel. For example, the gate length L2 of the transistor 11b is made longer than the gate length L1 of the transistor 11a so that Vth2 does not become lower than Vth1 even if the process parameters of these thin film transistors vary. Thereby, a minute current leak can be suppressed.
[0131]
The above items can also be applied to the pixel configuration of the current mirror shown in FIG. In FIG. 38, the pixel circuit and the data line data are controlled by controlling the gate signal line 17a1 in addition to the driving transistor 11b for controlling the driving current flowing in the light emitting element including the driving transistor 11a and the EL element 15 through which the signal current flows. The switching transistor 11d that short-circuits the gate and drain of the transistor 11a during the writing period and the gate-source voltage of the transistor 11a are held even after the writing is finished, by controlling the take-in transistor 11c to be connected or cut off and the gate signal line 17a2. For example, a capacitor C19 and an EL element 15 as a light emitting element.
[0132]
In FIG. 38, the transistors 11c and 11d are N-channel transistors, and the other transistors are P-channel transistors. However, this is an example, and this is not necessarily the case. The capacitor Cs has one terminal connected to the gate of the transistor 11a and the other terminal connected to Vdd (power supply potential). However, the capacitor Cs is not limited to Vdd, and may be any constant potential. The cathode (cathode) of the EL element 15 is connected to the ground potential.
[0133]
Next, the EL display panel or EL display device of the present invention will be described. FIG. 6 is an explanatory diagram focusing on the circuit of the EL display device. Pixels 16 are arranged or formed in a matrix. Each pixel 16 is connected to a source driver circuit 14 that outputs a current for current programming of each pixel. A current mirror circuit corresponding to the number of bits of the video signal is formed at the output stage of the source driver circuit 14 (described later). For example, in the case of 64 gradations, 63 current mirror circuits are formed in each source signal line, and a desired current can be applied to the source signal line 18 by selecting the number of these current mirror circuits. (See FIG. 48).
[0134]
The minimum output current of one current mirror circuit is 10 nA or more and 50 nA. In particular, the minimum output current of the current mirror circuit is preferably 15 nA or more and 35 nA. This is to ensure the accuracy of the transistors constituting the current mirror circuit in the source driver IC 14.
[0135]
A precharge or discharge circuit for forcibly releasing or charging the source signal line 18 is incorporated. The voltage (current) output value of the precharge or discharge circuit that forcibly releases or charges the source signal line 18 is preferably configured to be set independently by R, G, and B. This is because the threshold value of the EL element 15 is different between RGB (refer to FIGS. 65 and 67 and the description of the precharge circuit).
[0136]
It is known that the EL element has a large temperature dependency characteristic (temperature characteristic). In order to adjust the light emission luminance change due to the temperature characteristics, a non-linear element such as a thermistor or a posistor that changes the output current is added to the current mirror circuit, and the temperature characteristics change is adjusted by the thermistor as an analog reference. Adjust (change) the current.
[0137]
  In the present invention, the source driver 14 is formed of a semiconductor silicon chip,Chip on glassIt is connected to the terminal of the source signal line 18 of the substrate 71 by (COG) technology. The mounting of the source driver 14 is not limited to the COG technology, and the source driver IC 14 described above may be mounted on the chip on film (COF) technology and connected to the signal line of the display panel. Further, the drive IC may have a three-chip configuration by separately producing a power supply IC 82.
[0138]
On the other hand, the gate driver circuit 12 is formed by low-temperature polysilicon technology. That is, it is formed by the same process as the pixel transistor. This is because the internal structure is easier and the operating frequency is lower than that of the source driver circuit 14. Therefore, it can be formed easily even if it is formed by a low temperature polysilicon technique, and a narrow frame can be realized. Of course, it goes without saying that the gate driver circuit 12 may be formed of a silicon chip and mounted on the substrate 71 using COG technology or the like. In addition, switching elements such as pixel transistors, gate drivers, and the like may be formed by high-temperature polysilicon technology or organic materials (organic transistors).
[0139]
The gate driver circuit 12 includes a shift register circuit 61a for the gate signal line 17a and a shift register circuit 61b for the gate signal line 17b. Each shift register circuit 61 is controlled by positive-phase and negative-phase clock signals (CLKxP, CLKxN) and a start pulse (STx) (see FIG. 6). In addition, it is preferable to add an enable (ENABL) signal for controlling the output and non-output of the gate signal line and an up / down (UPDWM) signal for reversing the shift direction up and down. In addition, it is preferable to provide an output terminal for confirming that the start pulse is shifted to the shift register and output. Note that the shift timing of the shift register is controlled by a control signal from the control IC 81. A level shift circuit for shifting the level of external data is incorporated.
[0140]
Since the buffer capacity of the shift register circuit 61 is small, the gate signal line 17 cannot be driven directly. For this reason, at least two or more inverter circuits 62 are formed between the output of the shift register circuit 61 and the output gate 63 that drives the gate signal line 17.
[0141]
  The same applies to the case where the source driver 14 is directly formed on the substrate 71 by a polysilicon technique such as low-temperature polysilicon. Between the gate of an analog switch such as a transfer gate that drives the source signal line 18 and the shift register of the source driver circuit 14. A plurality of inverter circuits are formed. The following items (outputs of shift registers and output stages for driving signal lines (related to inverter circuits arranged between output stages such as output gates or transfer gates)))Is common to the source drive and gate drive circuits.
[0142]
For example, FIG. 6 shows that the output of the source driver 14 is directly connected to the source signal line 18, but actually, the output of the shift register of the source driver is connected to a multi-stage inverter circuit, The output is connected to the gate of an analog switch such as a transfer gate.
The inverter circuit 62 includes a P-channel MOS transistor and an N-channel MOS transistor. As described above, the inverter circuit 62 is connected in multiple stages to the output terminal of the shift register circuit 61 of the gate driver circuit 12, and its final output is connected to the output gate circuit 63. Note that the inverter circuit 62 may be composed of only the P channel. However, in this case, it may be configured as a simple gate circuit instead of an inverter.
[0143]
FIG. 8 is a configuration diagram of signal and voltage supply of the display device of the present invention or a configuration diagram of the display device. Signals (power supply wiring, data wiring, etc.) supplied from the control IC 81 to the source driver circuit 14 a are supplied via the flexible substrate 84.
[0144]
In FIG. 8, the control signal of the gate driver circuit 12 is generated by the control IC, and after the level shift is performed by the source driver 14, it is applied to the gate driver circuit 12. Since the drive voltage of the source driver 14 is 4 to 8 (V), the 3.3 (V) amplitude control signal output from the control IC 81 is converted to 5 (V) amplitude that the gate driver circuit 12 can receive. Can do.
[0145]
8 is described as a source driver in FIG. 8 and the like, but not only a driver, but also a power supply circuit, a buffer circuit (including a circuit such as a shift register), a data conversion circuit, a latch circuit, a command decoder, a shift circuit, an address A conversion circuit, an image memory, or the like may be incorporated. Needless to say, the three-side free configuration or configuration described in FIG. 9 or the like, the driving method, or the like can be applied to the configuration described in FIG. 8 or the like.
[0146]
When the display panel is used for an information display device such as a mobile phone, as shown in FIG. 9, the source driver IC (circuit) 14 and the gate driver IC (circuit) 12 are mounted (formed) on one side of the display panel. (A configuration in which the driver IC (circuit) is mounted (formed) on one side in this way is called a three-side free configuration (structure). Conventionally, the gate driver IC 12 is mounted on the X side of the display area, and Y The source driver IC 14 was mounted on the side). This is because it is easy to design the center line of the screen 50 to be the center of the display device, and it is easy to mount the driver IC. Note that the gate driver circuit may be fabricated with a three-side free configuration using high-temperature polysilicon or low-temperature polysilicon technology (that is, at least one of the source driver circuit 14 and the gate driver circuit 12 in FIG. 9 is polysilicon). Directly formed on the substrate 71 by technology).
[0147]
The three-side free configuration is not only a configuration in which an IC is directly stacked or formed on the substrate 71, but also a film (TCP, TAB technology, etc.) on which a source driver IC (circuit) 14, a gate driver IC (circuit) 12, etc. are attached. ) Is attached to one side (or almost one side) of the substrate 71. In other words, this means a configuration, arrangement, or all similar to that where no IC is mounted or attached to two sides.
[0148]
When the gate driver circuit 12 is arranged beside the source driver circuit 14 as shown in FIG. 9, the gate signal line 17 needs to be formed along the side C.
[0149]
In FIG. 9 and the like, a portion indicated by a thick solid line indicates a portion where the gate signal lines 17 are formed in parallel. Therefore, the gate signal lines 17 corresponding to the number of scanning signal lines are formed in parallel in the portion b (lower screen), and one gate signal line 17 is formed in the portion a (upper screen).
[0150]
  The pitch of the gate signal lines 17 formed on the C side is 5 μm or more and 12 μm or less. If it is less than 5 μm, noise will be applied to the adjacent gate signal line due to the influence of parasitic capacitance. According to the experiment, the influence of the parasitic capacitance is remarkably generated at 7 μm or less. Furthermore, if it is less than 5 μm, image noise such as a beat is generated violently on the display screen. In particular, noise generation differs between the left and right sides of the screen, and it is difficult to reduce image noise such as a beat. Also,PitchIf it exceeds 12 μm, the frame width D of the display panel becomes too large and is not practical.
[0151]
  In order to reduce the above-mentioned image noise, the ground signal layer 17 is formed on the lower layer or upper layer of the portion where the gate signal line 17 is formed.DoIt can be reduced by arranging a pattern (a conductive pattern fixed to a constant voltage or set to a stable potential as a whole). Further, a separately provided shield plate (shield foil (conductive pattern fixed to a constant voltage or set to a stable potential as a whole)) may be disposed on the gate signal line 17.
[0152]
Although the gate signal line 17 on the C side in FIG. 9 may be formed of an ITO electrode, it is preferably formed by laminating ITO and a metal thin film in order to reduce resistance. Moreover, it is preferable to form with a metal film. When laminating with ITO, a titanium film is formed on ITO, and an aluminum or aluminum / molybdenum alloy thin film is formed thereon. Alternatively, a chromium film is formed on ITO. In the case of a metal film, it is formed of an aluminum thin film or a chromium thin film. The above matters are the same in other embodiments of the present invention.
[0153]
In FIG. 9 and the like, the gate signal lines 17 and the like are arranged on one side of the display area. However, the present invention is not limited to this and may be arranged on both sides. For example, the gate signal line 17 a may be arranged (formed) on the right side of the screen 50 display screen 50, and the gate signal line 17 b may be arranged (formed) on the left side of the display screen 50. The above matters are the same in other embodiments.
[0154]
Further, the source driver IC 14 and the gate driver IC 12 may be integrated into one chip. If one chip is used, only one IC chip needs to be mounted on the display panel. Therefore, the mounting cost can be reduced. Various voltages used in the one-chip driver IC can be generated simultaneously.
[0155]
The source driver IC 14 and the gate driver IC 12 are made of a semiconductor wafer such as silicon and mounted on the display panel. However, the present invention is not limited to this, and the source driver IC 14 and the gate driver IC 12 are directly formed on the display panel 82 by low-temperature polysilicon technology or high-temperature polysilicon technology. Needless to say.
[0156]
The pixels are R, G, and B primary colors. However, the present invention is not limited to this, and may be cyan, yellow, and magenta. Also, two colors of B and yellow may be used. Of course, it may be a single color. Also, six colors of R, G, B, cyan, yellow, and magenta may be used. Five colors of R, G, B, cyan, and magenta may be used. These are natural colors, and the color reproduction range is expanded to achieve a good display. As described above, the EL display device of the present invention is not limited to one that performs color display with the three primary colors RGB.
[0157]
There are mainly three methods for colorizing an organic EL display panel, and one of them is a color conversion method. It is only necessary to form a blue-only single layer as the light emitting layer, and the remaining green and red colors necessary for full color are generated from blue light by color conversion. Therefore, there is an advantage that it is not necessary to separately coat each layer of RGB, and it is not necessary to prepare organic EL materials of each color of RGB. The color conversion method does not cause a decrease in yield unlike the color separation method. The EL display panel of the present invention can be applied to any of these methods.
[0158]
In addition to the three primary colors, white light emitting pixels may be formed. A white light emitting pixel can be realized by forming (forming or configuring) by stacking R, G, and B light emitting structures. One set of pixels includes three primary colors of RGB and a pixel 16W that emits white light. By forming a pixel emitting white light, white peak luminance can be easily expressed. Accordingly, it is possible to realize a bright image display.
[0159]
Even in the case of forming a set of pixels for three primary colors such as RGB, it is preferable that the areas of the pixel electrodes of the respective colors are different. Of course, if the luminous efficiency of each color is well balanced and the color purity is well balanced, the same area may be used. However, if the balance of one or more colors is bad, it is preferable to adjust the pixel electrode (light emitting area). The electrode area of each color may be determined based on the current density. That is, when the white balance is adjusted within a color temperature range of 7000 K (Kelvin) to 12000 K, the difference in current density of each color is within ± 30%. More preferably, it is within ± 15%. For example, if the current density is 100 A / square meter, the three primary colors are all set to 70 A / square meter or more and 130 A / square meter or less. More preferably, the three primary colors are all set to 85 A / square meter or more and 115 A / square meter or less.
[0160]
The EL element 15 is a self-luminous element. When light emitted by this light emission enters a transistor as a switching element, a photoconductor phenomenon (photoconversion) occurs. “Photocon” refers to a phenomenon in which leakage (off leak) increases when a switching element such as a transistor is turned off by photoexcitation.
[0161]
In order to cope with this problem, in the present invention, a light shielding film below the gate driver circuit 12 (or the source driver 14 in some cases) and below the pixel transistor 11 is formed. The light shielding film is formed of a metal thin film such as chromium, and the film thickness is set to 50 nm or more and 150 nm or less. If the film thickness is thin, the light shielding effect is poor, and if it is thick, irregularities are generated, making it difficult to pattern the upper transistor 11A1.
[0162]
The gate driver circuit 12 and the like should prevent light from entering not only from the back surface but also from the front surface. This is because malfunction occurs due to the influence of the photocon. Therefore, in the present invention, when the cathode electrode is a metal film, the cathode electrode is also formed on the surface of the driver 12 and the like, and this electrode is used as a light shielding film.
[0163]
However, when a cathode electrode is formed on the driver 12, there is a possibility that a malfunction of the driver due to an electric field from the cathode electrode or an electrical contact between the cathode electrode and the driver circuit may occur. In order to cope with this problem, in the present invention, at least one layer, preferably a plurality of layers of EL films are formed on the gate driver circuit 12 and the like simultaneously with the formation of the EL film on the pixel electrode.
[0164]
When the terminals of one or more transistors 11 of the pixel or the transistor 11 and the signal line are short-circuited, the EL element 15 may be a bright spot that is always lit. This bright spot is visually conspicuous and needs to be turned into black (not lit). For the bright spot, the corresponding pixel 16 is detected, and the capacitor 19 is irradiated with laser light to short-circuit the terminals of the capacitor. Therefore, since the capacitor 19 cannot hold the electric charge, the transistor 11a can be prevented from flowing current. It is desirable to remove the cathode film corresponding to the position where the laser beam is irradiated. This is to prevent the terminal electrode of the capacitor 19 and the cathode film from being short-circuited by laser irradiation.
[0165]
The defect of the transistor 11 of the pixel 16 also affects the source driver IC 14 and the like. For example, in FIG. 45, when a source-drain (SD) short 452 is generated in the driving transistor 11a, the Vdd voltage of the panel is applied to the source driver IC. Therefore, the power supply voltage of the source driver IC 14 is preferably the same as or higher than the power supply voltage Vdd of the panel. It should be noted that the reference current used in the source driver IC is preferably configured so that it can be adjusted by the electronic volume 451.
[0166]
When the SD short 452 is generated in the transistor 11a, an excessive current flows in the EL element 15. That is, the EL element 15 is always lit (bright spot). Bright spots are easily noticeable as defects. For example, in FIG. 45, when the source-drain (SD) short of the transistor 11a occurs, a current always flows from the Vdd voltage to the EL element 15 regardless of the gate (G) terminal potential of the transistor 11a ( When the transistor 11d is on). Therefore, it becomes a bright spot.
[0167]
On the other hand, when an SD short occurs in the transistor 11a, the Vdd voltage is applied to the source signal line 18 and the Vdd voltage is applied to the source driver 14 when the transistor 11c is in the on state. If the power supply voltage of the source driver 14 is equal to or lower than Vdd, the source driver 14 may be destroyed beyond the breakdown voltage. Therefore, it is preferable that the power supply voltage of the source driver 14 be equal to or higher than the Vdd voltage (the higher voltage of the panel).
[0168]
The SD short of the transistor 11a is not limited to a point defect, and may cause destruction of the source driver circuit of the panel. Further, since the bright spot is conspicuous, the panel becomes defective. Therefore, it is necessary to cut the wiring connecting the transistor 11a and the EL element 15 to make the bright spot a black spot defect. For this cutting, it is preferable to use an optical means such as a laser beam.
[0169]
Hereinafter, the driving method of the present invention will be described. As shown in FIG. 1, the gate signal line 17a becomes conductive during the row selection period (here, since the transistor 11 of FIG. 1 is a p-channel transistor, it becomes conductive at a low level), and the gate signal line 17b remains in the non-selection period. Sometimes conductive.
[0170]
The source signal line 18 has a parasitic capacitance (not shown). The parasitic capacitance is generated by the capacitance of the cross portion between the source signal line 18 and the gate signal line 17, the channel capacitance of the transistors 11b and 11c, and the like.
[0171]
The time t required to change the current value of the source signal line 18 is t = C · V / I, where C is the size of the stray capacitance, V is the voltage of the source signal line, and I is the current flowing through the source signal line. The fact that the value can be increased 10 times can shorten the time required for the current value change to nearly 1/10. Or, it shows that even if the parasitic capacitance of the source signal line 18 is increased 10 times, it can be changed to a predetermined current value. Therefore, it is effective to increase the current value in order to write a predetermined current value within a short horizontal scanning period.
[0172]
  When the input current is increased 10 times, the output current is also increased 10 times, and the EL brightness is increased 10 times.11dThe predetermined luminance is displayed by setting the conduction period of 1/10 of the conventional and the light emission period of 1/10. Note that the explanation is given by exemplifying 10 times for easy understanding. Needless to say, it is not limited to 10 times.
[0173]
That is, it is necessary to output a relatively large current from the source driver 14 in order to sufficiently charge and discharge the parasitic capacitance of the source signal line 18 and to program a predetermined current value in the transistor 11 a of the pixel 16. However, when such a large current flows through the source signal line 18, this current value is programmed in the pixel, and a large current flows through the EL element 15 with respect to a predetermined current. For example, if programming is performed with 10 times the current, naturally, 10 times the current flows through the EL element 15, and the EL element 15 emits light with 10 times the luminance. In order to obtain a predetermined light emission luminance, the time required to flow through the EL element 15 may be reduced to 1/10. By driving in this way, the parasitic capacitance of the source signal line 18 can be sufficiently charged and discharged, and a predetermined light emission luminance can be obtained.
[0174]
It should be noted that although 10 times the current value is written in the pixel transistor 11a (more precisely, the terminal voltage of the capacitor 19 is set) and the on-time of the EL element 15 is reduced to 1/10, this is merely an example. In some cases, a 10 times larger current value may be written in the pixel transistor 11a, and the on-time of the EL element 15 may be reduced to 1/5. On the contrary, there may be a case where a 10 times larger current value is written in the pixel transistor 11a and the on-time of the EL element 15 is halved.
[0175]
The present invention is characterized in that the pixel write current is set to a value other than a predetermined value and the current flowing through the EL element 15 is driven intermittently. In this specification, for ease of explanation, it is assumed that N times the current value is written in the transistor 11 of the pixel and the on-time of the EL element 15 is 1 / N times. However, the present invention is not limited to this, and it goes without saying that a current value of N1 times is written in the transistor 11 of the pixel, and the ON time of the EL element 15 may be 1 / (N2) times (different from N1 and N2). .
[0176]
  In the white raster display, it is assumed that the average luminance in one field (frame) period of the display screen 50 is B0. At this time, the current (voltage) program is performed so that the luminance B1 of each pixel 16 is higher than the average luminance B0. And in at least one field (frame) period, a non-display area52This is a driving method for generating the above. Therefore, in the driving method of the present invention, the average luminance in one field (frame) period is lower than B1.
[0177]
The intermittent interval (non-display area 52 / display area 53) is not limited to an equal interval. For example, it may be random (as a whole, the display period or the non-display period may be a predetermined value (a constant ratio)). Also, it may be different for RGB. That is, the driving method of the present invention may be adjusted (set) so that the R, G, B display period or the non-display period becomes a predetermined value (a constant ratio) so that the white balance is optimal. 1 / N is described assuming that 1F is set to 1 / N on the basis of 1F (one field or one frame). However, there is a time during which one pixel row is selected and the current value is programmed (usually, one horizontal scanning period (1H)), and it goes without saying that an error may occur depending on the scanning state.
[0178]
For example, the pixel 16 may be current-programmed with a current N = 10 times, and the EL element 15 may be turned on for a period of 1/5. The EL element 15 is lit with 10/5 = 2 times the luminance. The pixel 16 may be current-programmed with N = 2 times the current, and the EL element 15 may be turned on for a quarter period. The EL element 15 is lit with a brightness of 2/4 = 0.5 times. In other words, the present invention performs programming with a current that is not N = 1 times and performs a display other than the always-on (1/1, ie, not intermittent display) state. Further, this is a driving method in which the current supplied to the EL element 15 is turned off at least once in one frame (or one field) period. Further, it is a driving method in which the pixel 16 is programmed with a current larger than a predetermined value and at least intermittent display is performed.
[0179]
The organic (inorganic) EL display device also has a problem in that the display method is basically different from a display that displays an image as a set of line displays with an electron gun, such as a CRT. That is, in the EL display device, the current (voltage) written to the pixel is held for a period of 1F (1 field or 1 frame). For this reason, when a moving image is displayed, there is a problem that the outline of the display image is blurred.
[0180]
In the present invention, a current is passed through the EL element 15 only during the period of 1F / N, and no current is passed during the other period (1F (N-1) / N). Consider the case where this driving method is implemented and one point on the screen is observed. In this display state, image data display and black display (non-lighting) are repeatedly displayed every 1F. That is, the image data display state is intermittently displayed over time. When the moving image data display is viewed in the intermittent display state, the outline of the image is not blurred and a good display state can be realized. That is, a moving image display close to a CRT can be realized.
[0181]
In the driving method of the present invention, intermittent display is realized. However, the intermittent display only needs to be turned on / off for the transistor 11d in a cycle of 1H. Therefore, the main clock of the circuit is not different from the conventional one, and the power consumption of the circuit does not increase. In the liquid crystal display panel, an image memory is necessary to realize intermittent display. In the present invention, image data is held in each pixel 16. Therefore, an image memory for performing intermittent display is unnecessary.
[0182]
In the present invention, the current supplied to the EL element 15 is controlled only by turning on or off the switching transistor 11d or the transistor 11e. That is, even when the current Iw flowing through the EL element 15 is turned off, the image data is held in the capacitor 19 as it is. Therefore, if the switching transistor 11d and the like are turned on at the next timing and a current flows through the EL element 15, the flowing current is the same as the previously flowing current value. In the present invention, it is not necessary to increase the main clock of the circuit even when black insertion (intermittent display such as black display) is realized. Further, there is no need for an image memory because it is not necessary to perform time axis expansion. Further, the EL element 15 has a short time from application of current to light emission, and responds at high speed. Therefore, it is suitable for moving image display and can solve the problem of moving image display, which is a problem of conventional data retention type display panels (liquid crystal display panel, EL display panel, etc.) by performing intermittent display.
[0183]
Further, when the wiring length of the source signal line 18 is increased and the parasitic capacitance of the source signal line 18 is increased in a large display device, it is possible to cope with the problem by increasing the N value. When the program current value applied to the source signal line 18 is increased N times, the conduction period of the gate signal line 17b (transistor 11d) may be set to 1 F / N. Accordingly, the present invention can be applied to large display devices such as televisions and monitors.
[0184]
Hereinafter, the driving method of the present invention will be described in more detail with reference to the drawings. The parasitic capacitance of the source signal line 18 is generated by a coupling capacitance between adjacent source signal lines 18, a buffer output capacitance of the source drive IC (circuit) 14, a cross capacitance between the gate signal line 17 and the source signal line 18, and the like. This parasitic capacitance is usually 10 pF or more. In the case of voltage driving, a voltage is applied to the source signal line 18 with a low impedance from the source driver IC 14, so that there is no problem in driving even if the parasitic capacitance is somewhat large.
[0185]
However, current driving requires that the pixel capacitor 19 be programmed with a very small current of 20 nA or less, particularly for black level image display. Accordingly, when the parasitic capacitance is generated with a magnitude greater than or equal to a predetermined value, the time for programming to one pixel row (usually within 1H, however, it is not limited to within 1H because two pixel rows may be written simultaneously. ) Can not charge and discharge the parasitic capacitance. If charging / discharging is not possible in the 1H period, writing into the pixel is insufficient and the resolution is not high.
[0186]
In the case of the pixel configuration of FIG. 1, as shown in FIG. 3A, the program current Iw flows through the source signal line 18 during current programming. The voltage is set (programmed) in the capacitor 19 so that the current Iw flows through the transistor 11a and the current flowing through Iw is maintained. At this time, the transistor 11d is in an open state (off state).
[0187]
Next, during a period in which a current flows through the EL element 15, the transistors 11c and 11b are turned off and the transistor 11d operates as shown in FIG. That is, the off voltage (Vgh) is applied to the gate signal line 17a, and the transistors 11b and 11c are turned off. On the other hand, an on voltage (Vgl) is applied to the gate signal line 17b, and the transistor 11d is turned on.
[0188]
Assuming that the current I1 is N times the current (predetermined value) that flows originally, the current flowing through the EL element 15 in FIG. 3B is also Iw. Therefore, the EL element 15 emits light with a luminance 10 times the predetermined value. That is, as shown in FIG. 12, the display brightness B of the pixel 16 increases as the magnification N increases. Therefore, the magnification and the luminance of the pixel 16 are in a proportional relationship.
[0189]
Therefore, if the transistor 11d is turned on only for a period of 1 / N of the time for which the transistor 11d is originally turned on (about 1F) and is turned off for the other periods (N-1) / N, the average brightness of the entire 1F becomes a predetermined brightness. Become. This display state approximates that the CRT is scanning the screen with an electron gun. The difference is that the range in which the image is displayed is 1 / N of the entire screen (the whole screen is 1) is lit (in CRT, the lit range is one pixel row (strictly Is one pixel).
[0190]
In the present invention, the 1F / N image display area 53 moves from the top to the bottom of the screen 50 as shown in FIG. In the present invention, current flows through the EL element 15 only during the period of 1F / N, and no current flows during the other period (1F · (N−1) / N). Accordingly, each pixel 16 is intermittently displayed. However, since the image is retained by the afterimage to the human eye, the entire screen appears to be displayed uniformly.
[0191]
As shown in FIG. 13, the writing pixel row 51a is a non-lighting display 52a. However, this is the case of the pixel configuration shown in FIGS. In the pixel configuration of the current mirror illustrated in FIG. 38 and the like, the writing pixel row 51a may be lit. However, in this specification, for ease of explanation, the pixel configuration in FIG. A driving method in which programming is performed with a current larger than the predetermined driving current Iw, such as FIGS. 13 and 16, and intermittent driving is referred to as N-fold pulse driving.
[0192]
In this display state, image data display and black display (non-lighting) are repeatedly displayed every 1F. That is, the image data display state is a temporal display (intermittent display) state. In a liquid crystal display panel (an EL display panel other than the present invention), since data is held in pixels for a period of 1F, even if image data changes in the case of moving image display, the change cannot be followed. The video was blurred (outline blur in the image). However, since the image is intermittently displayed in the present invention, the outline of the image is not blurred and a good display state can be realized. That is, a moving image display close to a CRT can be realized.
[0193]
As shown in FIG. 13, in order to drive, the current program period of the pixel 16 (in the pixel configuration of FIG. 1, the period during which the ON voltage Vgl of the gate signal line 17a is applied), the EL element It is necessary to be able to control independently the period during which 15 is turned off or on (in the pixel configuration of FIG. 1, the period during which the on voltage Vgl or the off voltage Vgh of the gate signal line 17b is applied). Therefore, the gate signal line 17a and the gate signal line 17b need to be separated.
[0194]
For example, when there is one gate signal line 17 wired from the gate driver circuit 12 to the pixel 16, the logic (Vgh or Vgl) applied to the gate signal line 17 is applied to the transistor 11 b, and the gate signal line 17 is applied. The driving method of the present invention cannot be implemented in a configuration in which the applied logic is converted (Vgl or Vgh) by an inverter and applied to the transistor 11d. Therefore, the present invention requires the gate driver circuit 12a for operating the gate signal line 17a and the gate driver circuit 12b for operating the gate signal line 17b.
[0195]
In addition, the driving method of the present invention is a driving method for non-lighting display in the pixel configuration of FIG. 1 and in a period other than the current program period (1H).
[0196]
FIG. 14 shows a timing chart of the driving method of FIG. In the present invention and the like, the pixel configuration when there is no particular notice is assumed to be FIG. As can be seen from FIG. 14, when the ON voltage (Vgl) is applied to the gate signal line 17a in each selected pixel row (the selection period is 1H) (see FIG. 14A). In addition, an off voltage (Vgh) is applied to the gate signal line 17b (see FIG. 14B). During this period, no current flows through the EL element 15 (non-lighting state). In an unselected pixel row, an off voltage (Vgh) is applied to the gate signal line 17a, and an on voltage (Vgl) is applied to the gate signal line 17b. Further, during this period, a current flows through the EL element 15 (lighting state). In the lighting state, the EL element 15 is lit with a predetermined N times luminance (N · B), and the lighting period is 1 F / N. Therefore, the display luminance of the display panel that averages 1F is (N · B) × (1 / N) = B (predetermined luminance).
[0197]
FIG. 15 shows an embodiment in which the operation of FIG. 14 is applied to each pixel row. A voltage waveform applied to the gate signal line 17 is shown. In the voltage waveform, the off voltage is Vgh (H level) and the on voltage is Vgl (L level). Subscripts such as (1) and (2) indicate the selected pixel row number.
[0198]
In FIG. 15, the gate signal line 17 a (1) is selected (Vgl voltage), and a program current flows through the source signal line 18 from the transistor 11 a of the selected pixel row toward the source driver 14. This program current is N times a predetermined value (for ease of explanation, it is assumed that N = 10. Of course, since the predetermined value is a data current for displaying an image, it is not a fixed value unless it is a white raster display or the like. .) Therefore, the capacitor 19 is programmed so that 10 times the current flows through the transistor 11a. When the pixel row (1) is selected, in the pixel configuration of FIG. 1, the gate signal line 17b (1) is applied with the off voltage (Vgh), and no current flows through the EL element 15.
[0199]
After 1H, the gate signal line 17a (2) is selected (Vgl voltage), and a program current flows through the source signal line 18 from the transistor 11a in the selected pixel row toward the source driver. This program current is N times a predetermined value (in order to facilitate explanation, explanation will be made assuming that N = 10). Therefore, the capacitor 19 is programmed so that 10 times the current flows through the transistor 11a. When the pixel row (2) is selected, the gate signal line 17b (2) is applied with the off voltage (Vgh) in the pixel configuration of FIG. 1, and no current flows through the EL element 15. However, the off voltage (Vgh) is applied to the gate signal line 17a (1) of the previous pixel row (1), and the on voltage (Vgl) is applied to the gate signal line 17b (1). It has become.
[0200]
After the next 1H, the gate signal line 17a (3) is selected, the off voltage (Vgh) is applied to the gate signal line 17b (3), and no current flows through the EL elements 15 in the pixel row (3). However, the off voltage (Vgh) is applied to the gate signal lines 17a (1) (2) of the previous pixel rows (1) (2), and the on voltage (Vgl) is applied to the gate signal lines 17b (1) (2). ) Is applied, and is in a lighting state.
[0201]
The above operation is displayed in synchronization with the 1H synchronization signal. However, in the driving method of FIG. 15, 10 times of current flows through the EL element 15. Therefore, the display screen 50 is displayed with about 10 times the luminance. Of course, in order to perform a predetermined luminance display in this state, it goes without saying that the program current may be set to 1/10. However, if the current is 1/10, insufficient writing occurs due to parasitic capacitance or the like. Therefore, programming at a high current and obtaining a predetermined luminance by inserting the black screen 52 is the basic gist of the present invention.
[0202]
In the driving method of the present invention, the concept is that a current higher than a predetermined current flows in the EL element 15 and the parasitic capacitance of the source signal line 18 is sufficiently charged and discharged. That is, it is not necessary to flow N times the current through the EL element 15. For example, a current path is formed in parallel with the EL element 15 (a dummy EL element is formed, a light shielding film is not formed on the EL element to emit light, etc.), and the current is shunted between the dummy EL element and the EL element 15. May be flushed. For example, when the signal current is 0.2 μA, the program current is set to 2.2 μA, and 2.2 μA is passed through the transistor 11a. Of these currents, a system is exemplified in which a signal current of 0.2 μA is passed through the EL element 15 and 2 μA is passed through a dummy EL element. That is, the dummy pixel row 271 in FIG. 27 is always selected. Note that the dummy pixel rows are configured not to emit light or to form a light-shielding film or the like so that they cannot be visually seen even if they emit light.
[0203]
With the above configuration, by increasing the current flowing through the source signal line 18 by N times, it is possible to program the driving transistor 11a so that N times the current flows, and the current EL element 15 Therefore, a current sufficiently smaller than N times can be achieved. In the above method, the entire display screen 50 can be used as the image display area 53 without providing the non-display area 52 as shown in FIG.
[0204]
FIG. 13A illustrates a writing state on the display screen 50. In FIG. 13A, reference numeral 51a denotes a writing pixel row. A program current is supplied from the source driver IC 14 to each source signal line 18. In FIG. 13 and the like, one pixel row is written in the 1H period. However, it is not limited to 1H at all, and it may be 0.5H period or 2H period. In addition, although the program current is written to the source signal line 18, the present invention is not limited to the current program method, and a voltage program method (such as FIG. 46) in which the voltage is written to the source signal line 18 may be used. .
[0205]
In FIG. 13A, when the gate signal line 17a is selected, the current flowing through the source signal line 18 is programmed into the transistor 11a. At this time, an off voltage is applied to the gate signal line 17 b and no current flows through the EL element 15. This is because, when the transistor 11d is in the ON state on the EL element 15 side, the capacitance component of the EL element 15 can be seen from the source signal line 18, and the capacitor 19 cannot be sufficiently accurately programmed due to the capacitance. It is. Therefore, taking the configuration of FIG. 1 as an example, a pixel row in which a current is written becomes a non-display area 52 as shown in FIG.
[0206]
Now, if the current is programmed with N times (N = 10 as described above), the screen brightness will be 10 times. Accordingly, a 90% range of the display screen 50 may be set as the non-display area 52. Therefore, if the horizontal scanning lines of the image display area are 220 QCIF (S = 220), 22 lines and the display area 53 may be used, and 220-22 = 198 may be the non-display area 52. Generally speaking, if the horizontal scanning line (number of pixel rows) is S, the S / N area is set as the display area 53, and the display area 53 is caused to emit light with N times the luminance. Then, the display area 53 is scanned in the vertical direction of the screen. Therefore, the area of S (N−1) / N is a non-display area 52. This non-display area is black display (non-light emission). The non-light emitting portion 52 is realized by turning off the transistor 11d. Although it is assumed that the light is lit at N times the luminance, it goes without saying that the value is adjusted to N times by brightness adjustment and gamma adjustment.
[0207]
Further, in the previous embodiment, if programming was performed with 10 times the current, the brightness of the screen would be 10 times, and the 90% range of the display screen 50 should be the non-display area 52. However, this is not limited to the common use of the RGB pixels as the non-display area 52. For example, 1/8 of the R pixel is the non-display area 52, 1/6 is the non-display area 52 of the G pixel, and 1/10 of the non-display area 52 is the color of the B pixel. You may change by. Further, the non-display area 52 (or the display area 53) may be individually adjusted with RGB colors. In order to realize these, separate gate signal lines 17b are required for R, G, and B. However, by allowing individual adjustment of RGB as described above, it is possible to adjust white balance, and color balance adjustment is facilitated at each gradation (see FIG. 41).
[0208]
As shown in FIG. 13B, the pixel row including the writing pixel row 51a is a non-display area 52, and the S / N (1F / N in terms of time) range of the upper screen from the writing pixel row 51a. Is the display area 53 (if the writing scan is from the top to the bottom of the screen, the opposite is true when the screen is scanned from the bottom to the top). In the image display state, the display area 53 is strip-shaped and moves from the top to the bottom of the screen.
[0209]
In the display of FIG. 13, one display area 53 moves downward from the top of the screen. When the frame rate is low, it is visually recognized that the display area 53 moves. In particular, it becomes easier to recognize when the eyelid is closed or when the face is moved up and down.
[0210]
For this problem, the display area 53 may be divided into a plurality of parts as shown in FIG. If the divided sum is an area of S (N-1) / N, it is equivalent to the brightness of FIG. The divided display areas 53 do not have to be equal (equally divided). Further, the divided non-display areas 52 need not be equal.
[0211]
As described above, screen flickering is reduced by dividing display area 53 into a plurality of parts. Therefore, no flicker occurs and a good image display can be realized. The division may be made finer. However, the moving image display performance decreases as it is divided.
[0212]
FIG. 17 shows the voltage waveform of the gate signal line 17 and the light emission luminance of EL. As is apparent from FIG. 17, the period (1F / N) during which the gate signal line 17b is set to Vgl is divided into a plurality of numbers (the number of divisions K). That is, a period of 1 gl / (K · N) is performed K times for the period of Vgl. By controlling in this way, the occurrence of flicker can be suppressed and an image display with a low frame rate can be realized. Further, it is preferable that the number of divisions of the image is variable. For example, this change may be detected and the value of K may be changed by the user pressing a brightness adjustment switch or turning the brightness adjustment volume. Moreover, you may comprise so that a user may adjust a brightness | luminance. You may comprise so that it may change manually or automatically by the content and data of the image to display.
[0213]
In FIG. 17 and the like, the period (1F / N) for setting the gate signal line 17b to Vgl is divided into a plurality (number of divisions K), and the period for setting the Vgl is 1F / (K · N) K times. However, this is not a limitation. The period of 1F / (K · N) may be performed L (L ≠ K) times. In other words, the present invention displays the screen 50 by controlling the period (time) flowing through the EL element 15. Therefore, it is included in the technical idea of the present invention to execute the period of 1F / (K · N) L (L ≠ K) times. Further, the brightness of the screen 50 can be changed digitally by changing the value of L. For example, when L = 2 and L = 3, the luminance (contrast) changes by 50%. Further, when the image display area 53 is divided, the period during which the gate signal line 17b is set to Vgl is not limited to the same period.
[0214]
In the above embodiment, the current flowing through the EL element 15 is cut off, and the current flowing through the EL element is connected to turn on and off the display screen 50 (lighting or non-lighting). That is, substantially the same current is caused to flow through the transistor 11a a plurality of times by the charge held in the capacitor 19. The present invention is not limited to this. For example, the display screen 50 may be turned on / off (lighted or not lighted) by charging / discharging the charge held in the capacitor 19.
[0215]
FIG. 18 shows voltage waveforms applied to the gate signal line 17 for realizing the image display state of FIG. The difference between FIG. 18 and FIG. 15 is the operation of the gate signal line 17b. The gate signal lines 17b are turned on / off (Vgl and Vgh) corresponding to the number of divided screens. The other points are the same as in FIG.
[0216]
In the EL display device, since the black display is completely unlit, there is no reduction in contrast as in the case where the liquid crystal display panel is intermittently displayed. In the configurations of FIGS. 1, 2, 32, 43, and 117, intermittent display can be realized only by turning on and off the transistor 11d. In the configurations of FIGS. 38, 51, and 115, intermittent display can be realized simply by turning on and off the transistor element 11e. In FIG. 113, intermittent display can be realized by controlling the switching circuit 1131. In FIG. 114, intermittent display can be realized by on / off controlling the transistor 11g. This is because the image data is stored in the capacitor 19 (the number of gradations is infinite because it is an analog value). That is, the image data is held in each pixel 16 during the period of 1F. Whether or not a current corresponding to the stored image data is supplied to the EL element 15 is realized by controlling the transistors 11d and 11e.
[0217]
Therefore, the above driving method is not limited to the current driving method, but can also be applied to the voltage driving method. That is, in the configuration in which the current flowing through the EL element 15 is stored in each pixel, the driving transistor 11 is intermittently driven by turning on and off the current path between the EL elements 15.
[0218]
  Maintaining the terminal voltage of the capacitor 19 is important for reducing flicker and reducing power consumption. When the terminal voltage of the capacitor 19 changes (charges / discharges) in one field (frame) period, the screen brightness changes.To do. When screen brightness changesThis is because flickering (such as flicker) occurs when the frame rate decreases. It is necessary that the current that the transistor 11a passes through the EL element 15 in one frame (one field) period does not decrease to at least 65% or less. This 65% means that when the current written to the pixel 16 and the current flowing to the EL element 15 is 100%, the current flowing to the EL element 15 immediately before writing to the pixel 16 in the next frame (field) is 65% or more. It is to do.
[0219]
In the pixel configuration of FIG. 1, there is no change in the number of transistors 11 constituting one pixel in the case where intermittent display is realized or not. That is, the current configuration is realized by removing the influence of the parasitic capacitance of the source signal line 18 without changing the pixel configuration. In addition, a moving image display close to a CRT is realized.
[0220]
Further, since the operation clock of the gate driver circuit 12 is sufficiently slower than the operation clock of the source driver circuit 14, the main clock of the circuit does not increase. Further, it is easy to change the value of N.
[0221]
The image display direction (image writing direction) may be from the top to the bottom in the first field (one frame) and from the bottom to the top in the second field (frame). In other words, the top-to-bottom direction and the bottom-to-top direction are alternately repeated.
[0222]
In the first field (one frame), the screen is displayed from the top to the bottom. Once the entire screen is displayed in black (not displayed), the second field (frame) is displayed from the bottom to the top. Also good. Alternatively, the entire screen may be displayed black (not displayed) once.
[0223]
In the above description of the driving method, the screen writing method is set from the top to the bottom or from the bottom to the top, but the present invention is not limited to this. The screen writing direction is constantly fixed from top to bottom or from bottom to top, and the non-display area 52 operation direction is from top to bottom in the first field, and from the bottom in the second field. It is good also as an upward direction. Further, one frame may be divided into three fields, and R is formed in the first field, G is formed in the second field, and B is formed in the third field. Further, R, G, and B may be switched and displayed for each horizontal scanning period (1H) (see FIGS. 125 to 132 and the description thereof). The above matters are the same in other embodiments of the present invention.
[0224]
The non-display area 52 does not have to be completely unlit. Even if there is weak light emission or low luminance image display, there is no practical problem. That is, it should be interpreted as an area having a lower display luminance than the image display area 53. Further, the non-display area 52 includes a case where only one or two colors of the R, G, and B image displays are in a non-display state. In addition, the case where only one or two colors of the R, G, and B image displays are in a low luminance image display state is also included.
[0225]
Basically, when the brightness (brightness) of the display area 53 is maintained at a predetermined value, the brightness of the screen 50 increases as the area of the display area 53 increases. For example, when the luminance of the display area 53 is 100 (nt), if the ratio of the display area 53 to the display screen 50 is changed from 10% to 20%, the luminance of the screen is doubled. Therefore, the display brightness of the screen can be changed by changing the area of the display area 53 occupying the display screen 50. The display brightness of the screen 50 is proportional to the ratio of the display area 53 occupying the screen 50.
[0226]
The area of the display area 53 can be arbitrarily set by controlling the data pulse (ST2) to the shift register 61. Also, the display state of FIG. 16 and the display state of FIG. 13 can be switched by changing the input timing and period of the data pulse. If the number of data pulses in the 1F cycle is increased, the screen 50 becomes brighter, and if it is decreased, the screen 50 becomes darker. If the data pulse is continuously applied, the display state shown in FIG. 13 is obtained, and if the data pulse is input intermittently, the display state shown in FIG. 16 is obtained.
[0227]
FIG. 19A shows a brightness adjustment method when the display area 53 is continuous as shown in FIG. The display brightness of the screen 50 of (a1) in FIG. 19 is the brightest. The display brightness of the screen 50 in (a2) of FIG. 19 is the next brightest, and the display brightness of the screen 50 of (a3) in FIG. 19 is the darkest. FIG. 19A is most suitable for moving image display.
[0228]
The change from (a1) in FIG. 19 to (a3) in FIG. 19 (or vice versa) can be easily realized by controlling the shift register circuit 61 of the gate driver circuit 12 as described above. At this time, it is not necessary to change the Vdd voltage in FIG. That is, it is possible to change the luminance of the display screen 50 without changing the power supply voltage. Further, the gamma characteristic of the screen does not change at all in the case of the change from (a1) in FIG. 19 to (a3) in FIG. Therefore, the contrast and gradation characteristics of the display image are maintained regardless of the brightness of the screen 50. This is an effective feature of the present invention.
[0229]
In the conventional screen brightness adjustment, when the brightness of the screen 50 is low, the gradation performance deteriorates. That is, even when 64 gradation display can be realized during high brightness display, only half or less of the number of gradations can be displayed during low brightness display. Compared to this, the driving method of the present invention can realize the highest 64 gradation display without depending on the display brightness of the screen.
[0230]
FIG. 19B shows a brightness adjustment method when the display area 53 is dispersed as shown in FIG. The display brightness of the screen 50 in FIG. 19B1 is the brightest. The display brightness of the screen 50 in FIG. 19B2 is the next brightest, and the display brightness of the screen 50 in FIG. 19B3 is the darkest. The change from (b1) in FIG. 19 to (b3) in FIG. 19 (or vice versa) can be easily realized by controlling the shift register circuit 61 of the gate driver circuit 12 as described above. If the display area 53 is dispersed as shown in FIG. 19B, flicker does not occur even at a low frame rate.
[0231]
In order to prevent flicker from occurring even at a lower frame rate, the display area 53 may be finely dispersed as shown in FIG. However, the display performance of moving images decreases. Therefore, the driving method shown in FIG. 19A is suitable for displaying a moving image. When a still image is displayed and low power consumption is desired, the driving method shown in FIG. 19C is suitable. Switching of the driving method from (a) in FIG. 19 to (c) in FIG. 19 can be easily realized by controlling the shift register 61.
[0232]
The above embodiments are mainly embodiments in which N = 2 times, 4 times, and the like. However, it goes without saying that the present invention is not limited to integer multiples. Moreover, it is not limited to N = 2 or more. For example, an area less than half of the display screen 50 at a certain time may be set as the non-display area 52. If the current is programmed with a current Iw that is 5/4 times the predetermined value and the light is turned on for 4/5 of 1F, a predetermined luminance can be realized.
[0233]
The present invention is not limited to this. As an example, there is a method in which current programming is performed with a current Iw that is 10/4 times, and lighting is performed for a 4/5 period of 1F. In this case, it is lit at twice the predetermined luminance. There is also a method in which current programming is performed with a current Iw that is 5/4 times, and lighting is performed for a period of 2/5 of 1F. In this case, the light is lit at half the predetermined luminance. There is also a method in which current programming is performed with a current Iw that is 5/4 times, and lighting is performed for a 1/1 period of 1F. In this case, it is lit at 5/4 times the predetermined luminance.
[0234]
That is, the present invention is a method for controlling the luminance of the display screen by controlling the magnitude of the program current and the lighting period of 1F. Further, by turning on the light for a period shorter than the 1F period, the black screen 52 can be inserted, and the moving image display performance can be improved. A bright screen can be displayed by always lighting it for the period of 1F.
[0235]
When the pixel size is A square mm and the white raster display predetermined luminance is B (nt), the current written into the pixel (program current output from the source driver circuit 14) is:
(A * B) / 20 <= I <= (A * B)
It is preferable to set it as the range. Luminous efficiency is improved and insufficient current writing is eliminated.
[0236]
Further preferably, the program current I (μA) is
(A * B) / 10 <= I <= (A * B)
It is preferable to set it as the range.
[0237]
FIG. 20 is an explanatory diagram of another embodiment in which the current flowing through the source signal line 18 is increased. Basically, a plurality of pixel rows are selected simultaneously, and a parasitic capacitance of the source signal line 18 is charged / discharged with a current obtained by combining the plurality of pixel rows, thereby greatly improving current writing shortage. However, since a plurality of pixel rows are selected at the same time, the driving current per pixel can be reduced. Therefore, the current flowing through the EL element 15 can be reduced. Here, for ease of explanation, as an example, N = 10 will be described (the current flowing through the source signal line 18 is multiplied by 10).
[0238]
The present invention described with reference to FIG. 20 selects M pixel rows at the same time as the pixel rows. From the source driver IC 14, a current N times the predetermined current is applied to the source signal line 18. Each pixel is programmed with a current N / M times the current flowing through the EL element 15. As an example, in order to set the EL element 15 to a predetermined light emission luminance, the time flowing through the EL element 15 is set to M / N time of one frame (one field) (however, it is not limited to M / N). / N is for ease of understanding, as described above, needless to say, it can be set freely depending on the brightness of the screen 50 to be displayed.) By driving in this way, the parasitic capacitance of the source signal line 18 can be sufficiently charged and discharged, and a predetermined light emission luminance can be obtained with good resolution.
[0239]
Display is performed so that current flows through the EL element 15 only during the M / N period of one frame (one field) and no current flows during the other period (1F (N−1) M / N). In this display state, image data display and black display (non-lighting) are repeatedly displayed every 1F. That is, the image data display state is a temporal display (intermittent display) state. Accordingly, the outline blurring of the image is eliminated and a good moving image display can be realized. Further, since the source signal line 18 is driven with N times the current, it is not affected by the parasitic capacitance and can be applied to a high-definition display panel.
[0240]
FIG. 21 is an explanatory diagram of drive waveforms for realizing the drive method of FIG. The signal waveform has an off voltage of Vgh (H level) and an on voltage of Vgl (L level). The subscript of each signal line describes the number of the pixel row ((1) (2) (3) etc.). The number of rows is 220 for the QCIF display panel and 480 for the VGA panel.
[0241]
In FIG. 21, the gate signal line 17 a (1) is selected (Vgl voltage), and a program current flows through the source signal line 18 from the transistor 11 a of the selected pixel row toward the source driver 14. Here, for ease of explanation, first, it is assumed that the writing pixel row 51a is the pixel row (1) -th.
[0242]
The program current flowing through the source signal line 18 is N times a predetermined value (for ease of explanation, N = 10 will be described. Of course, since the predetermined value is a data current for displaying an image, white raster display is performed. It is not a fixed value unless it is). Further, description will be made assuming that five pixel rows are selected simultaneously (M = 5). Therefore, ideally, the capacitor 19 of one pixel is programmed so that the current flows through the transistor 11a twice (N / M = 10/5 = 2).
[0243]
When the writing pixel row is the (1) pixel row, as shown in FIG. 21, (1), (2), (3), (4), and (5) are selected for the gate signal line 17a. That is, the switching transistors 11b and the transistors 11c in the pixel rows (1), (2), (3), (4), and (5) are on. Further, the gate signal line 17b has an opposite phase to the gate signal line 17a. Therefore, the switching transistors 11d in the pixel rows (1), (2), (3), (4), and (5) are in the OFF state, and no current flows through the EL elements 15 in the corresponding pixel rows. That is, it is a non-lighting state 52.
[0244]
Ideally, each of the five-pixel transistors 11a passes an Iw × 2 current to the source signal line 18 (that is, Iw × 2 × N = Iw × 2 × 5 = Iw × 10 in the source signal line 18). Therefore, when the N-times pulse driving according to the present invention is not performed and the predetermined current Iw is used, a current 10 times as large as Iw flows in the source signal line 18).
[0245]
With the above operation (driving method), a double current is programmed in the capacitor 19 of each pixel 16. Here, in order to facilitate understanding, description will be made assuming that the characteristics (Vt, S value) of the transistors 11a are the same.
[0246]
Since five pixel rows (M = 5) are selected at the same time, the five driving transistors 11a operate. That is, 10/5 = 2 times the current flows through the transistor 11a per pixel. A current obtained by adding the program currents of the five transistors 11a flows through the source signal line 18. For example, the write current Iw is originally set to the write pixel row 51a, and a current of Iw × 10 is supplied to the source signal line 18. This is a pixel row used as an auxiliary to increase the amount of current to the writing pixel row 51b to which the image data is written after the writing pixel row (1). However, there is no problem in the writing pixel row 51b because normal image data is written later.
[0247]
Accordingly, the same display as 51a is performed in the four pixel row 51b during the 1H period. Therefore, at least the non-display state 52 is set for the writing pixel row 51a and the pixel row 51b selected to increase the current. However, in the current mirror pixel configuration as shown in FIG. 38 and other voltage programming pixel configurations, the display state may be used.
[0248]
After 1H, the gate signal line 17a (1) is not selected, and an ON voltage (Vgl) is applied to the gate signal line 17b. At the same time, the gate signal line 17a (6) is selected (Vgl voltage), and a program current flows from the transistor 11a of the selected pixel row (6) to the source driver 14 to the source signal line 18. By operating in this way, regular image data is held in the pixel row (1).
[0249]
After the next 1H, the gate signal line 17a (2) is not selected, and the ON voltage (Vgl) is applied to the gate signal line 17b. At the same time, the gate signal line 17 a (7) is selected (Vgl voltage), and a program current flows from the transistor 11 a of the selected pixel row (7) toward the source driver 14 through the source signal line 18. By operating in this way, regular image data is held in the pixel row (2). One screen is rewritten by performing the above operation and scanning while shifting one pixel row at a time.
[0250]
In the driving method of FIG. 20, since each pixel is programmed with twice the current (voltage), the light emission luminance of the EL element 15 of each pixel is ideally doubled. Therefore, the brightness of the display screen is twice the predetermined value. In order to obtain a predetermined luminance, as shown in FIG. 16, a non-display area 52 may be included that includes the write pixel row 51 and that is ½ of the display screen 50.
[0251]
As in FIG. 13, when one display area 53 moves downward from the top of the screen as shown in FIG. 20, it is visually recognized that the display area 53 moves when the frame rate is low. In particular, it becomes easier to recognize when the eyelid is closed or when the face is moved up and down.
[0252]
For this problem, the display area 53 may be divided into a plurality of parts as shown in FIG. When the divided non-display area 52 is added to have an area of S (N-1) / N, it is the same as when not divided.
[0253]
FIG. 23 shows voltage waveforms applied to the gate signal line 17. The difference between FIG. 21 and FIG. 23 is basically the operation of the gate signal line 17b. The gate signal lines 17b are turned on / off (Vgl and Vgh) corresponding to the number of divided screens. The other points are almost the same as those in FIG.
[0254]
As described above, screen flickering is reduced by dividing display area 53 into a plurality of parts. Therefore, no flicker occurs and a good image display can be realized. The division may be made finer. However, the more divided, the less flicker. In particular, since the responsiveness of the EL element 15 is fast, even if it is turned on / off in a time shorter than 5 μsec, the display luminance does not decrease.
[0255]
In the driving method of the present invention, ON / OFF of the EL element 15 can be controlled by ON / OFF of a signal applied to the gate signal line 17b. Therefore, in the driving method of the present invention, control is possible at a low frequency on the order of KHz. Further, an image memory or the like is not required to realize black screen insertion (non-display area 52 insertion). Therefore, the drive circuit or method of the present invention can be realized at low cost.
[0256]
FIG. 24 shows a case where two pixel rows are selected simultaneously. According to the examination result, in the display panel formed by the low-temperature polysilicon technology, the method of selecting two pixel rows at the same time has practical display uniformity. This is presumably because the characteristics of the driving transistors 11a of the adjacent pixels are very consistent. In addition, when laser annealing was performed, a good result was obtained by irradiating the stripe laser beam in parallel with the source signal line 18.
[0257]
This is because the characteristics of the semiconductor film that is annealed in the same time are uniform. That is, the semiconductor film is uniformly formed within the stripe-shaped laser irradiation range, and the Vt and mobility of the transistor using the semiconductor film are almost equal. Therefore, by irradiating a striped laser shot parallel to the formation direction of the source signal line 18 and moving the irradiation position, pixels (pixel columns, pixels in the vertical direction of the screen) along the source signal line 18 are moved. The characteristics are made approximately equal. Therefore, when current programming is performed with multiple pixel rows turned on at the same time, the program current is selected at the same time, and the current obtained by dividing the program current by the number of selected pixels is the same current program. Is done. Therefore, a current program close to the target value can be implemented, and uniform display can be realized. Therefore, there is a synergistic effect between the laser shot direction and the driving method described in FIG.
[0258]
As described above, by making the direction of the laser shot substantially coincide with the formation direction of the source signal line 18 (see FIG. 7), the characteristics of the transistor 11a in the vertical direction of the pixel become substantially the same, and a good current can be obtained. The program can be executed (even if the characteristics of the transistors 11a in the horizontal direction of the pixel do not match). The above operation is performed by shifting the position of the selected pixel row by one pixel row or a plurality of pixel rows in synchronization with 1H (one horizontal scanning period).
[0259]
As described with reference to FIG. 8, the laser shot direction is made parallel to the source signal line 18, but it is not necessarily parallel. This is because even if the source signal line 18 is irradiated with a laser shot in an oblique direction, the characteristics of the transistors 11a in the vertical direction of the pixels along one source signal line 18 are formed substantially coincident with each other. Therefore, irradiating a laser shot in parallel with the source signal line means that adjacent pixels above or below an arbitrary pixel along the source signal line 18 are formed so as to fall within one laser irradiation range. . The source signal line 18 is generally a wiring for transmitting a program current or voltage that becomes a video signal.
[0260]
In the embodiment of the present invention, the writing pixel row position is shifted every 1H. However, the present invention is not limited to this, and the writing pixel row position may be shifted every 2H (every 2 pixel rows). The pixel rows may be shifted one by one. Moreover, you may shift by arbitrary time units. Further, it may be shifted by one pixel row.
[0261]
  Depending on the screen position, the shift time may be changed. For example, the shift time at the center of the screen may be shortened and the shift time may be lengthened at the top and bottom of the screen. For example, the center portion of the screen 50 shifts one pixel row every 200 μsec, and the upper and lower portions of the screen 50 shift one pixel row every 100 μsec. By shifting in this way, the light emission luminance at the center of the screen 50 is increased, and the periphery (upper and lower portions of the screen 50) can be decreased.TheNeedless to say, the shift time between the central portion of the screen 50 and the upper portion of the screen, and the shift time between the central portion of the screen 50 and the lower portion of the screen are changed smoothly so as not to have a luminance contour.
[0262]
  Note that the reference current of the source driver circuit 14 may be changed corresponding to the scanning position of the screen 50 (see FIG. 146 and the like). For example, the reference current at the center of the screen 50 is 10 μA, and the reference current at the top and bottom of the screen 50 is 5 μA. Thus, by changing the reference current corresponding to the position of the screen 50, the light emission luminance at the center of the screen 50 is increased, and the periphery (the upper and lower portions of the screen 50) can be decreased.TheThe values of the reference current between the center portion of the screen 50 and the upper portion of the screen and the reference current values between the center portion of the screen 50 and the lower portion of the screen are changed with time so that the luminance contour is not present. Needless to say, control.
[0263]
It goes without saying that image display may be performed by combining a driving method for controlling the time for shifting the pixel rows in accordance with the screen position and a driving method for changing the reference current in accordance with the position of the screen 50.
[0264]
The shift time may be changed for each frame. Further, the present invention is not limited to selecting a plurality of continuous pixel rows. For example, a pixel row extending to one pixel row may be selected.
[0265]
That is, the first pixel row and the third pixel row are selected in the first horizontal scanning period, and the second pixel row and the fourth pixel row are selected in the second horizontal scanning period. The third pixel row and the fifth pixel row are selected during the third horizontal scanning period, and the fourth pixel row and the sixth pixel row are selected during the fourth horizontal scanning period. This is a driving method. Of course, a driving method of selecting the first pixel row, the third pixel row, and the fifth pixel row in the first horizontal scanning period is also a technical category. Of course, even if a pixel row position extending to a plurality of pixel rows is selected.
[0266]
Note that the combination of the laser shot direction and the selection of a plurality of pixel rows at the same time is not limited to the pixel configurations of FIGS. 1, 2, and 32, and is a pixel configuration of a current mirror. Needless to say, the present invention can be applied to other current-driven pixel configurations such as 38, 42, and 50. The present invention can also be applied to voltage-driven pixel configurations such as those shown in FIGS. 43, 51, 54, and 46. That is, if the characteristics of the transistors on the upper and lower sides of the pixel match, the voltage program can be satisfactorily performed with the voltage value applied to the same source signal line 18.
[0267]
In FIG. 24, when the writing pixel row is (1) pixel row, (1) and (2) are selected for the gate signal line 17a (see FIG. 25). That is, the switching transistors 11b and 11c in the pixel rows (1) and (2) are in the on state. Accordingly, at least the switching transistors 11d in the pixel rows (1) and (2) are in the OFF state, and no current flows through the EL elements 15 in the corresponding pixel rows. That is, it is a non-lighting state 52. In FIG. 24, the display area 53 is divided into five parts in order to reduce the occurrence of flicker.
[0268]
Ideally, the transistors 11a of two pixels (rows) each have Iw × 5 (N = 10. That is, since K = 2, the current flowing through the source signal line 18 is Iw × K × 5 = Iw. A current of × 10) is passed through the source signal line 18. Then, the capacitor 19 of each pixel 16 is programmed with 5 times the current.
[0269]
Since two pixel rows (K = 2) are selected at the same time, the two driving transistors 11a operate. That is, a current of 10/2 = 5 times flows through the transistor 11a per pixel. A current obtained by adding the program currents of the two transistors 11a flows through the source signal line 18.
[0270]
For example, the write current Id is originally written in the write pixel row 51 a, and a current of Iw × 10 is passed through the source signal line 18. There is no problem in the writing pixel row 51b because normal image data is written later. The pixel row 51b has the same display as 51a during the 1H period. Therefore, at least the non-display state 52 is set for the writing pixel row 51a and the pixel row 51b selected to increase the current.
[0271]
After the next 1H, the gate signal line 17a (1) is not selected, and the ON voltage (Vgl) is applied to the gate signal line 17b. At the same time, the gate signal line 17 a (3) is selected (Vgl voltage), and a program current flows from the transistor 11 a of the selected pixel row (3) toward the source driver 14 through the source signal line 18. By operating in this way, regular image data is held in the pixel row (1).
[0272]
After the next 1H, the gate signal line 17a (2) is not selected, and the ON voltage (Vgl) is applied to the gate signal line 17b. At the same time, the gate signal line 17 a (4) is selected (Vgl voltage), and a program current flows from the transistor 11 a of the selected pixel row (4) toward the source driver 14 through the source signal line 18. By operating in this way, regular image data is held in the pixel row (2). The above operation and shift by one pixel row (of course, multiple pixel rows may be shifted. For example, if pseudo-interlace driving is used, the shift will be performed by two rows. One screen is rewritten by scanning while the same image may be written in the pixel row.
[0273]
Although it is the same as FIG. 16, in the driving method of FIG. 24, since each pixel is programmed with a current (voltage) 5 times, the emission luminance of the EL element 15 of each pixel is ideally 5 times. . Therefore, the luminance of the display area 53 is five times higher than the predetermined value. In order to obtain a predetermined luminance, as shown in FIG. 16 and the like, a non-display area 52 may be included that includes a writing pixel row 51 and that is 1/5 of the display screen 1.
[0274]
As shown in FIG. 27, two write pixel rows 51 (51a, 51b) are selected and sequentially selected from the upper side to the lower side of the screen 50 (see also FIG. 26. In FIG. 26, the pixel row 16a). And 16b are selected). However, as shown in FIG. 27B, when the pixel reaches the lower side of the screen, the writing pixel row 51a exists, but the 51b disappears. That is, only one pixel row is selected. Therefore, all the current applied to the source signal line 18 is written to the pixel row 51a. Therefore, twice as much current is programmed in the pixel as compared with the pixel row 51a.
[0275]
In response to this problem, the present invention forms (places) a dummy pixel row 271 on the lower side of the screen 50 as shown in FIG. Therefore, when the selected pixel row is selected up to the lower side of the screen 50, the last pixel row and the dummy pixel row 271 on the screen 50 are selected. Therefore, a prescribed current is written into the write pixel row in FIG.
[0276]
Although the dummy pixel row 271 is illustrated as being formed adjacent to the upper end or the lower end of the display screen 50, the present invention is not limited to this. It may be formed at a position away from the display screen 50. Further, it is not necessary to form the switching transistor 11d, the EL element 15 and the like in FIG. By not forming, the size of the dummy pixel row 271 is reduced.
[0277]
FIG. 28 shows the state shown in FIG. As is apparent from FIG. 28, when the selected pixel rows are selected up to the pixel 16c row on the lower side of the screen 50, the last pixel row (dummy pixel row) 271 of the screen 50 is selected. The dummy pixel row 271 is arranged outside the display screen 50. That is, the dummy pixel row (dummy pixel) 271 is configured not to be lit, not to be lit, or not to be seen as a display even when lit. For example, the contact hole between the pixel electrode 105 and the transistor 11 is eliminated, or the EL film 15 is not formed in the dummy pixel row 271. Further, a configuration in which an insulating film is formed over the pixel electrode 105 in the dummy pixel row is exemplified.
[0278]
In FIG. 27, the dummy pixels (rows) 271 are provided (formed or arranged) on the lower side of the screen 50, but the present invention is not limited to this. For example, as shown in FIG. 29A, when scanning from the lower side to the upper side of the screen (upside down scanning), dummy pixels are also formed on the upper side of the screen 50 as shown in FIG. Row 271 should be formed. That is, the dummy pixel rows 271 are formed (arranged) on the upper side and the lower side of the screen 50, respectively. With the configuration described above, it is possible to cope with upside down scanning of the screen. In the above embodiment, two pixel rows are selected simultaneously.
[0279]
The present invention is not limited to this. For example, a method of simultaneously selecting five pixel rows (see FIG. 23) may be used. That is, in the case of simultaneous driving of five pixel rows, the dummy pixel rows 271 may be formed for four rows. Therefore, the dummy pixel rows 271 may be formed by the number of pixels of the pixel row-1 selected simultaneously. However, this is a case where pixel rows to be selected are shifted one pixel row at a time. In the case of shifting by a plurality of pixel rows, it is sufficient to form (M-1) × L pixel rows, where M is the number of selected pixels and L is the number of pixel rows to be shifted.
[0280]
The dummy pixel row configuration or dummy pixel row driving according to the present invention is a method using at least one dummy pixel row. Of course, it is preferable to use a combination of the dummy pixel row driving method and N-times pulse driving.
[0281]
In the driving method of selecting a plurality of pixel rows at the same time, it becomes more difficult to absorb the characteristic variation of the transistor 11a as the number of pixel rows to be selected simultaneously increases. However, when the number M of simultaneously selected pixel rows decreases, the current programmed to one pixel increases, and a large current flows through the EL element 15. If the current passed through the EL element 15 is large, the EL element 15 is likely to deteriorate.
[0282]
FIG. 30 solves this problem. The basic concept of FIG. 30 is a method of simultaneously selecting a plurality of pixel rows in 1 / 2H (1/2 of the horizontal scanning period) as described in FIGS. Subsequent (1/2) H (1/2 of the horizontal scanning period) is a combination of methods for selecting one pixel row as described with reference to FIGS. By combining in this way, it is possible to absorb the characteristic variation of the transistor 11a, and to improve the in-plane uniformity at a higher speed. In addition, in order to make an understanding easy, although it demonstrates as operating by (1/2) H, it is not limited to this. The first period may be (1/4) H and the latter period may be (3/4) H.
[0283]
In FIG. 30, for ease of explanation, it is assumed that five pixel rows are simultaneously selected in the first period and one pixel row is selected in the second period. First, in the first period (1 / 2H in the first half), as shown in (a1) of FIG. 30, five pixel rows are simultaneously selected. Since this operation has been described with reference to FIG. As an example, the current flowing through the source signal line 18 is 25 times the predetermined value. Accordingly, the transistor 11a of each pixel 16 (in the case of the pixel configuration in FIG. 1) is programmed with a current that is five times (25/5 pixel row = 5). Since the current is 25 times, the parasitic capacitance generated in the source signal line 18 and the like is charged and discharged in a very short time. Therefore, the potential of the source signal line 18 becomes the target potential in a short time, and the terminal voltage of the capacitor 19 of each pixel 16 is also programmed to flow 5 times the current. The application time of the 25 times current is set to 1 / 2H in the first half (1/2 of one horizontal scanning period).
[0284]
As a matter of course, since the same image data is written in the five pixel rows of the writing pixel row, the transistors 11d in the five pixel rows are turned off so as not to be displayed. Therefore, the display state is (a2) in FIG.
[0285]
In the next ½H period of the second half, one pixel row is selected and current (voltage) programming is performed. This state is illustrated in (b1) of FIG. The write pixel row 51a is programmed with a current (voltage) so as to pass a current that is five times the current as before. 30 (a1) and FIG. 30 (b1) make the current passed through each pixel the same, the change in the terminal voltage of the programmed capacitor 19 can be reduced, and the target current can be passed at a higher speed. It is for doing so.
[0286]
That is, in (a1) of FIG. 30, current is supplied to a plurality of pixels, and the value is approximated to a value at which an approximate current flows at high speed. In this first stage, since programming is performed by the plurality of transistors 11a, an error due to transistor variation occurs with respect to the target value. In the next second stage, only a pixel row in which data is written and held is selected, and a complete program is executed from a rough target value to a predetermined target value.
[0287]
Since the non-display area 52 is scanned from the top to the bottom of the screen and the writing pixel row 51a is scanned from the top to the bottom of the screen as well, the description is omitted. .
[0288]
FIG. 31 shows drive waveforms for realizing the drive method of FIG. As can be seen in FIG. 31, 1H (one horizontal scanning period) is composed of two phases. These two phases are switched by the ISEL signal. The ISEL signal is illustrated in FIG.
[0289]
First, the ISEL signal will be described. The source driver circuit 14 that implements FIG. 30 includes a current output circuit A and a current output circuit B. Each current output circuit includes a DA circuit for DA-converting 8-bit gradation data, an operational amplifier, and the like. In the embodiment of FIG. 30, the current output circuit A is configured to output a current 25 times larger. On the other hand, the current output circuit B is configured to output five times the current. The outputs of the current output circuit A and the current output circuit B are applied to the source signal line 18 by controlling the switch circuit formed (arranged) in the current output unit by the ISEL signal. This current output circuit is disposed on each source signal line.
[0290]
When the ISEL signal is at the L level, the current output circuit A that outputs a current 25 times larger is selected, and the current from the source signal line 18 is absorbed by the source driver IC 14 (more suitably, formed in the source driver circuit 14). Absorbed by the current output circuit A). It is easy to adjust the magnitude of the current output circuit current such as 25 times or 5 times. This is because it can be easily configured with a plurality of resistors and analog switches.
[0291]
  As shown in FIG. 30, when the writing pixel row is (1) pixel row (FIG. 3).1(1), (1), (2), (3), (4), and (5) are selected for the gate signal line 17a (in the case of the pixel configuration in FIG. 1). That is, the switching transistors 11b and the transistors 11c in the pixel rows (1), (2), (3), (4), and (5) are on. Further, since ISEL is at the L level, the current output circuit A that outputs a 25-fold current is selected and connected to the source signal line 18. Further, an off voltage (Vgh) is applied to the gate signal line 17b. Therefore, the switching transistors 11d in the pixel rows (1), (2), (3), (4), and (5) are in the OFF state, and no current flows through the EL elements 15 in the corresponding pixel rows. That is, it is a non-lighting state 52.
[0292]
Ideally, each of the five-pixel transistors 11 a allows a current of Iw × 2 to flow through the source signal line 18. Then, the capacitor 19 of each pixel 16 is programmed with 5 times the current. Here, in order to facilitate understanding, description will be made assuming that the characteristics (Vt, S value) of the transistors 11a are the same.
[0293]
Since five pixel rows (K = 5) are selected at the same time, the five driving transistors 11a operate. That is, a current of 25/5 = 5 times flows to the transistor 11a per pixel. A current obtained by adding the program currents of the five transistors 11a flows through the source signal line 18. For example, when the current Iw to be written to the pixel by the conventional driving method is set in the write pixel row 51a, a current of Iw × 25 is passed through the source signal line 18. This is a pixel row used as an auxiliary to increase the amount of current to the writing pixel row 51b to which the image data is written after the writing pixel row (1). However, there is no problem in the writing pixel row 51b because normal image data is written later.
[0294]
Therefore, the pixel row 51b has the same display as 51a during the 1H period. Therefore, at least the non-display state 52 is set for the writing pixel row 51a and the pixel row 51b selected to increase the current.
[0295]
In the next 1 / 2H (1/2 of the horizontal scanning period), only the writing pixel row 51a is selected. That is, (1) only the pixel row is selected. As apparent from FIG. 31, only the gate signal line 17a (1) is applied with the ON voltage (Vgl), and the gate signal lines 17a (2), (3), (4), and (5) are applied with OFF (Vgh). Has been. Therefore, the transistor 11a in the pixel row (1) is in an operating state (a state in which current is supplied to the source signal line 18), but the switching transistor 11b in the pixel rows (2), (3), (4), and (5). The transistor 11c is off. That is, it is a non-selection state.
[0296]
Further, since ISEL is at the H level, the current output circuit B that outputs a 5-fold current is selected, and the current output circuit B and the source signal line 18 are connected. Further, the state of the gate signal line 17b is not changed from the previous state of 1 / 2H, and an off voltage (Vgh) is applied. Therefore, the switching transistors 11d in the pixel rows (1), (2), (3), (4), and (5) are in the OFF state, and no current flows through the EL elements 15 in the corresponding pixel rows. That is, it is a non-lighting state 52.
[0297]
  From the above, the transistors 11a in the pixel row (1) flow Iw × 5 current to the source signal line 18, respectively. And, PaintingThe capacitor 19 of the elemental row (1) is programmed with 5 times the current.
[0298]
In the next horizontal scanning period, one pixel row and a writing pixel row are shifted. That is, the writing pixel row is (2) this time. In the first ½H period, when the writing pixel row is the (2) pixel row as shown in FIG. 31, the gate signal line 17a is (2) (3) (4) (5) (6). Is selected. That is, the switching transistors 11b and the transistors 11c in the pixel rows (2), (3), (4), (5), and (6) are on. Further, since ISEL is at the L level, the current output circuit A that outputs a 25-fold current is selected and connected to the source signal line 18. Further, an off voltage (Vgh) is applied to the gate signal line 17b.
[0299]
Therefore, the switching transistors 11d in the pixel rows (2), (3), (4), (5), and (6) are in the off state, and no current flows through the EL elements 15 in the corresponding pixel rows. That is, it is a non-lighting state 52. On the other hand, since the Vgl voltage is applied to the gate signal line 17b (1) of the pixel row (1), the transistor 11d is on, and the EL element 15 of the pixel row (1) is lit.
[0300]
Since five pixel rows (K = 5) are selected at the same time, the five driving transistors 11a operate. That is, a current of 25/5 = 5 times flows to the transistor 11a per pixel. A current obtained by adding the program currents of the five transistors 11a flows through the source signal line 18.
[0301]
In the next 1 / 2H (1/2 of the horizontal scanning period), only the writing pixel row 51a is selected. That is, (2) only the pixel row is selected. As apparent from FIG. 31, only the gate signal line 17a (2) is applied with the ON voltage (Vgl), and the gate signal lines 17a (3), (4), (5), and (6) are applied with OFF (Vgh). Has been.
[0302]
Therefore, the transistors 11a in the pixel rows (1) and (2) are in an operating state (the pixel row (1) supplies current to the EL element 15 and the pixel row (2) supplies current to the source signal line 18). However, the switching transistors 11b and 11c in the pixel rows (3), (4), (5), and (6) are off. That is, it is a non-selection state.
[0303]
  In addition, since ISEL is at the H level, the current output circuit B that outputs a 5 times current is selected, and this current output circuitBAnd the source signal line 18 are connected. Further, the state of the gate signal line 17b is not changed from the previous state of 1 / 2H, and an off voltage (Vgh) is applied. Therefore, the switching transistors 11d in the pixel rows (2), (3), (4), (5), and (6) are in the off state, and no current flows through the EL elements 15 in the corresponding pixel rows. That is, it is a non-lighting state 52.
[0304]
From the above, the transistors 11 a in the pixel row (2) flow a current of Iw × 5 to the source signal line 18. Then, the capacitor 19 in each pixel row (2) is programmed with 5 times the current. One screen can be displayed by sequentially performing the above operations.
[0305]
The driving method described with reference to FIG. 30 selects G pixel rows (G is 2 or more) in the first period, and performs programming so that N times the current flows in each pixel row. In the second period after the first period, a B pixel row (B is smaller than G and 1 or more) is selected, and the pixel is programmed to flow N times as much current.
[0306]
However, there are other strategies. In the first period, G pixel rows (G is 2 or more) are selected and programmed so that the total current of each pixel row is N times the current. In the second period after the first period, a B pixel row (B is smaller than G and is 1 or more) is selected, and the total current of the selected pixel rows (however, when the selected pixel row is 1, In this method, the current of one pixel row is programmed to be N times. For example, in (a1) of FIG. 30, five pixel rows are selected at the same time, and a double current is passed through the transistor 11a of each pixel. Therefore, the current of 5 × 2 = 10 times flows through the source signal line 18. In the next second period, one pixel row is selected in (b1) of FIG. A 10-fold current flows through the transistor 11a of one pixel.
[0307]
In FIG. 31, the period for simultaneously selecting a plurality of pixel rows is set to 1 / 2H and the period for selecting one pixel row is set to 1 / 2H. However, the present invention is not limited to this. The period for selecting a plurality of pixel rows at the same time may be 1 / 4H, and the period for selecting one pixel row may be 3 / 4H. In addition, the period including the period for simultaneously selecting a plurality of pixel rows and the period for selecting one pixel row is set to 1H, but the present invention is not limited to this. For example, it may be a 2H period or a 1.5H period.
[0308]
In FIG. 30, the period for simultaneously selecting five pixel rows may be set to 1 / 2H, and two pixel rows may be simultaneously selected in the next second period. Even in this case, it is possible to realize an image display that is practically satisfactory.
[0309]
In FIG. 30, the first period for selecting five pixel rows at the same time is ½H, and the second period for selecting one pixel row is ½H. However, the present invention is not limited to this. Absent. For example, the first stage may select three pixel rows at the same time, the second period may select three pixel rows among the five pixel rows, and finally select one pixel row. . That is, the image data may be written in the pixel row at a plurality of stages.
[0310]
In the above-described embodiments, one pixel row is sequentially selected and current programming is performed on the pixels, or a plurality of pixel rows are sequentially selected and current programming is performed on the pixels. However, the present invention is not limited to this. A method in which one pixel row is sequentially selected according to image data and current programming is performed on the pixel may be combined with a method in which a plurality of pixel rows are sequentially selected and current programming is performed on the pixel.
[0311]
Hereinafter, the interlace drive of the present invention will be described. FIG. 133 shows the structure of the display panel of the present invention which performs interlace driving. In FIG. 133, the gate signal lines 17a in the odd-numbered pixel rows are connected to the gate driver circuit 12a1. The gate signal lines 17a in the even pixel rows are connected to the gate driver circuit 12a2. On the other hand, the gate signal lines 17b in the odd-numbered pixel rows are connected to the gate driver circuit 12b1. The gate signal lines 17b in the even pixel rows are connected to the gate driver circuit 12b2.
[0312]
Therefore, the image data of the odd-numbered pixel rows is sequentially rewritten by the operation (control) of the gate driver circuit 12a1. In the odd-numbered pixel row, lighting / non-lighting control of the EL element is performed by the operation (control) of the gate driver circuit 12b1. In addition, the image data of the even pixel rows is sequentially rewritten by the operation (control) of the gate driver circuit 12a2. In the even-numbered pixel row, lighting / non-lighting control of the EL element is performed by the operation (control) of the gate driver circuit 12b2.
[0313]
FIG. 134 (a) shows the operation state of the display panel in the first field. FIG. 134 (b) shows the operating state of the display panel in the second field. For ease of explanation, it is assumed that one frame is composed of two fields. In FIG. 134, the hatched gate driver circuit 12 indicates that no data scanning operation is performed. That is, in the first field of FIG. 134A, the gate driver circuit 12a1 operates as program current write control, and the gate driver circuit 12b2 operates as lighting control of the EL element 15. In the second field of FIG. 134 (b), the gate driver circuit 12a2 operates as program current write control, and the gate driver circuit 12b1 operates as lighting control of the EL element 15. The above operation is repeated in the frame.
[0314]
  FIG. 135 shows an image display state in the first field. FIG. 135A shows a write pixel row (odd pixel row position where current (voltage) programming is performed.)Is illustrated. The write pixel row position is sequentially shifted in the order of (a1) → (a2) → (a3) in FIG. In the first field, the odd-numbered pixel rows are sequentially rewritten (the image data of the even-numbered pixel rows are retained). FIG. 135 (b) illustrates a display state of odd-numbered pixel rows. Note that FIG. 135 (b) illustrates only odd-numbered pixel rows. Even-numbered pixel rows are illustrated in FIG. As is clear from FIG. 135 (b), the EL elements 15 of the pixels corresponding to the odd-numbered pixel rows are in a non-lighting state. On the other hand, the even-numbered pixel row scans the display area 53 and the non-display area 52 as shown in FIG. 135 (c) (N-fold pulse drive).
[0315]
  FIG. 136 shows the image display state in the second field. 136 (a) shows a write pixel row (odd pixel row position where current (voltage) programming is performed.)Is illustrated. The write pixel row position is sequentially shifted in the order of (a1) → (a2) → (a3) in FIG. In the second field, even-numbered pixel rows are sequentially rewritten (image data of odd-numbered pixel rows is retained). FIG. 136 (b) illustrates a display state of odd-numbered pixel rows. Note that FIG. 136 (b) illustrates only odd-numbered pixel rows. The even pixel rows are illustrated in FIG. 136 (c). As is clear from FIG. 136 (b), the EL elements 15 of the pixels corresponding to the even-numbered pixel rows are in a non-lighting state. On the other hand, the odd-numbered pixel rows scan the display area 53 and the non-display area 52 as shown in FIG. 136 (c) (N-fold pulse drive).
[0316]
By driving as described above, interlaced driving can be easily realized with an EL display panel. In addition, by performing N-fold pulse driving, writing shortage does not occur and moving image blur does not occur. In addition, the control of the current (voltage) program and the lighting control of the EL element 15 are easy, and the circuit can be easily realized.
[0317]
Note that the driving method of the present invention is not limited to the driving method shown in FIGS. 135 and 136. For example, the driving method of FIG. 137 is also exemplified. 135 and 136, the odd-numbered pixel row or the even-numbered pixel row for which the current (voltage) program is performed is the non-display area 52 (non-lit, black display). In the embodiment of FIG. 137, both the gate driver circuits 12b1 and 12b2 for controlling the lighting of the EL element 15 are operated in synchronization. However, it goes without saying that the pixel row 51 on which current (voltage) programming is performed is controlled to be a non-display area (the current mirror pixel configuration in FIG. 38 does not need to do so). In FIG. 137, since the lighting control of the odd-numbered pixel row and the even-numbered pixel row is the same, it is not necessary to provide two gate driver circuits 12b1 and 12b2. One gate driver circuit 12b can be controlled for lighting.
[0318]
FIG. 137 shows a driving method in which the lighting control is the same for odd-numbered pixel rows and even-numbered pixel rows. However, the present invention is not limited to this. FIG. 138 shows an embodiment in which the lighting control for odd-numbered pixel rows and even-numbered pixel rows is different. In particular, FIG. 138 is an example in which the reverse pattern of the lighting state of the odd-numbered pixel rows (display area 53, non-display area 52) is changed to the lighting state of even-numbered pixel rows. Therefore, the area of the display area 53 and the area of the non-display area 52 are made the same. Of course, the area of the display area 53 and the area of the non-display area 52 are not limited to be the same.
[0319]
In FIG. 136 and FIG. 135, the pixel rows are not limited to the non-lighting state in the odd pixel rows or the even pixel rows.
[0320]
The above embodiment is a driving method for executing a current (voltage) program for each pixel row. However, the driving method of the present invention is not limited to this, and it goes without saying that two pixel rows (multiple pixel rows) may be simultaneously programmed with current (voltage) as shown in FIG. 139 (FIG. 27). And its description). FIG. 139 (a) shows an example of an odd field, and FIG. 139 (b) shows an example of an even field. In the odd field, (1,2) pixel rows, (3,4) pixel rows, (5,6) pixel rows, (7,8) pixel rows, (9,10) pixel rows, (11,12) pixels ... (N, n + 1) Two pixel rows are sequentially selected from a set of (n, n + 1) pixel rows (n is an integer of 1 or more), and current programming is performed. In the even field, (2, 3) pixel rows, (4, 5) pixel rows, (6, 7) pixel rows, (8, 9) pixel rows, (10, 11) pixel rows, (12, 13) pixels ... (N + 1, n + 2) Two pixel rows are sequentially selected from a set of (n + 1, n + 2) pixel rows (n is an integer of 1 or more), and current programming is performed.
[0321]
As described above, by selecting a plurality of pixel rows in each field and performing current programming, the current flowing through the source signal line 18 can be increased, and black writing can be improved. Further, the resolution of the image can be improved by shifting a set of a plurality of pixel rows selected in the odd field and the even field by at least one pixel row.
[0322]
In the embodiment of FIG. 139, the pixel rows selected in each field are two pixel rows. However, the pixel row is not limited to this, and may be three pixel rows. In this case, it is possible to select two methods, ie, a method of shifting one pixel and a method of shifting two pixels by a set of three pixel rows selected in the odd field and the even field. The pixel rows selected in each field may be four or more pixel rows. Further, as shown in FIGS. 125 to 132, one frame may be composed of three or more fields.
[0323]
In the embodiment of FIG. 139, two pixel rows are selected at the same time. However, the present invention is not limited to this, and 1H is set to the first half 1 / 2H and the second half 1 / 2H, and in the odd field, the first half of the first H period. In the 1 / 2H period, the first pixel row is selected and current programming is performed, and in the latter half of the 1 / 2H period, the second pixel row is selected and current programming is performed. In the first half of the next 2H period, the third pixel row is selected and current programming is performed, and in the second half of the H period, the fourth pixel row is selected and current programming is performed. The fifth pixel row is selected and current programming is performed in the first 1 / 2H period of the first H period of the next 3H period, and the sixth pixel row is selected and current programming is performed in the second 1 / 2H period. Do.・ ・ ・ ・ It may be driven.
[0324]
In the even field, the second pixel row is selected and current programming is performed in the first 1 / 2H period of the first H period, and the third pixel row is selected and current programming is performed in the second half of the H period. In the first half of the next 2H period, the fourth pixel row is selected for current programming, and in the second half of the H period, the fifth pixel row is selected for current programming. Further, the sixth pixel row is selected and current programming is performed in the first 1 / 2H period of the first H period of the next 3H period, and the seventh pixel row is selected and current programming is performed in the second half of the H period. Do.・ ・ ・ ・ It may be driven.
[0325]
Also in the above embodiment, the pixel rows selected in each field are two pixel rows. However, the pixel rows are not limited to this and may be three pixel rows. In this case, it is possible to select two methods, ie, a method of shifting one pixel and a method of shifting two pixels by a set of three pixel rows selected in the odd field and the even field. The pixel rows selected in each field may be four or more pixel rows.
[0326]
In the N-fold pulse driving method of the present invention, the waveform of the gate signal line 17b is made the same in each pixel row, and the application is performed by shifting at an interval of 1H. By scanning in this way, it is possible to sequentially shift the pixel rows to be lit while prescribing the time during which the EL element 15 is lit to 1 F / N. Thus, it is easy to realize that the waveform of the gate signal line 17b is the same and shifted in each pixel row. This is because it is only necessary to control ST1 and ST2 which are data applied to the shift register circuits 61a and 61b in FIG. For example, if Vgl is output to the gate signal line 17b when the input ST2 is L level, and Vgh is output to the gate signal line 17b when the input ST2 is H level, ST2 applied to the shift register 61b is output. Input is made at the L level only for the period of 1F / N, and is set to the H level for the other periods. The input ST2 is simply shifted by the clock CLK2 synchronized with 1H.
[0327]
  Note that the cycle of turning on and off the EL element 15 needs to be 0.5 msec or more. When this period is short, the image is not completely displayed due to the afterimage characteristics of the human eye, and the image becomes blurred, as if the resolution is lowered. Further, the display state of the data holding type display panel is set. However, when the on / off cycle is 100 msec or more, it appears to blink. Therefore, the on / off period of the EL element is 0.5.mIt should be not less than sec and not more than 100 msec. More preferably, the on / off cycle should be 2 msec or more and 30 msec or less. More preferably, the on / off cycle should be 3 msec or more and 20 msec or less.
[0328]
As described above, if the number of divisions of the black screen 52 is one, a satisfactory moving image display can be realized, but the flickering of the screen can be easily seen. Therefore, it is preferable to divide the black insertion portion into a plurality. However, if the number of divisions is too large, motion blur will occur. The number of divisions should be between 1 and 8. More preferably, it is 1 or more and 5 or less.
[0329]
  It should be noted that the number of divisions of the black screen is preferably configured so that it can be changed between a still image and a moving image. With N = 4, 75% is a black screen and 25% is an image display. At this time, the division number is 1 to scan the 75% black display portion in the vertical direction of the screen in the 75% black belt state. The number of divisions is 3 for scanning with 3 blocks of a 25% black screen and a 25/3% display screen. Increase the number of divisions for still images. Reduce the number of divisions for movies. Switching may be performed automatically (moving image detection or the like) according to the input image, or may be performed manually by the user. In addition, video of the display deviceofInput controlTenzWhat is necessary is just to comprise so that it can switch corresponding to.
[0330]
For example, in a mobile phone or the like, the number of divisions is set to 10 or more on the wallpaper display and input screen (extremely, it may be turned on / off every 1H). When displaying NTSC moving images, the number of divisions is set to 1 or more and 5 or less. It should be noted that the number of divisions is preferably configured so that it can be switched to multiple stages of 3 or more. For example, no division number, 2, 4, 8, etc.
[0331]
The ratio of the black screen to the total display screen is preferably 0.2 or more and 0.9 or less (1.2 or more and 9 or less if displayed in N) when the area of the entire screen is 1. In particular, it is preferably 0.25 or more and 0.6 or less (1.25 to 6 if expressed in N). If it is 0.20 or less, the improvement effect in moving image display is low. If it is 0.9 or more, the luminance of the display portion increases, and it is easy to visually recognize that the display portion moves up and down.
[0332]
The number of frames per second is preferably 10 or more and 100 or less (10 Hz or more and 100 Hz or less). Furthermore, 12 or more and 65 or less (12 Hz or more and 65 Hz or less) are preferable. If the number of frames is small, the flickering of the screen becomes conspicuous. If the number of frames is too large, writing from the source driver circuit 14 becomes difficult and the resolution is deteriorated.
[0333]
Needless to say, the above items can be applied to the pixel configuration of the current program shown in FIG. 38 and the pixel configuration of the voltage program shown in FIGS. 43, 51, and 54. In FIG. 38, the transistor 11d, the transistor 11d in FIG. 43, and the transistor 11e in FIG. In this way, by turning on and off the wiring for supplying current to the EL element 15, the N-fold pulse driving of the present invention can be easily realized.
[0334]
Further, the time to set Vgl only during the period of 1F / N of the gate signal line 17b may be any time in the period of 1F (not limited to 1F; it may be a unit period). This is because a predetermined average luminance is obtained by turning on the EL element 15 for a predetermined period of time in the unit time. However, it is better to set the gate signal line 17b to Vgl immediately after the current program period (1H) and cause the EL element 15 to emit light. This is because it is less susceptible to the retention characteristics of the capacitor 19 of FIG.
[0335]
Further, it is preferable that the number of divisions of the image is variable. For example, when the user presses the brightness adjustment switch or turns the brightness adjustment volume, this change is detected and the value of K is changed. You may comprise so that it may change manually or automatically by the content and data of the image to display.
[0336]
In this way, it is possible to easily change the value of K (the number of divisions of the image display unit 53). This is because the timing of data to be applied to ST in FIG. 6 (when it is set to L level at 1F) can be adjusted or varied.
[0337]
In FIG. 16 and the like, the period (1F / N) in which the gate signal line 17b is set to Vgl is divided into a plurality (number of divisions M), and the period of 1F / (K · N) is performed K times for the period to set Vgl. However, this is not a limitation. The period of 1F / (K · N) may be performed L (L ≠ K) times. In other words, the present invention displays the screen 50 by controlling the period (time) flowing through the EL element 15. Therefore, it is included in the technical idea of the present invention to execute the period of 1F / (K · N) L (L ≠ K) times. Further, the brightness of the screen 50 can be changed digitally by changing the value of L. For example, when L = 2 and L = 3, the luminance (contrast) change is 50%. It goes without saying that these controls can also be applied to other embodiments of the present invention (of course, the present invention described later can also be applied). These are also the N-fold pulse drive of the present invention.
[0338]
In the above embodiment, the transistor 11d as a switching element is disposed (formed) between the EL element 15 and the driving transistor 11a, and the screen 11 is displayed on and off by controlling the transistor 11d. . By this driving method, current writing shortage in the black display state of the current programming method is eliminated, and a good resolution or black display is realized. That is, in the current program method, it is important to realize a good black display. The driving method described below is to reset the driving transistor 11a to realize good black display. Hereinafter, the embodiment will be described with reference to FIG.
[0339]
FIG. 32 basically shows the pixel configuration of FIG. In the pixel configuration of FIG. 32, the programmed Iw current flows through the EL element 15, and the EL element 15 emits light. That is, the driving transistor 11a retains the ability to flow current by being programmed. A method of resetting (turning off) the transistor 11a using this current flowing capability is the driving method of FIG. Hereinafter, this driving method is referred to as reset driving.
[0340]
In order to realize reset driving with the pixel configuration of FIG. 1, it is necessary to configure the transistor 11b and the transistor 11c so that they can be controlled on and off independently. That is, as shown in FIG. 32, the gate signal line 17a (gate signal line WR) for controlling on / off of the transistor 11b and the gate signal line 17c (gate signal line EL) for controlling on / off of the transistor 11c can be controlled independently. To do. The gate signal line 17a and the gate signal line 17c may be controlled by two independent shift registers 61 as shown in FIG.
[0341]
The drive voltage of the gate signal line 17a for driving the transistor 11b and the gate signal line 17b for driving the transistor 11d may be changed (in the case of the pixel configuration in FIG. 1). The amplitude value of the gate signal line 17a (difference between the on voltage and the off voltage) is made smaller than the amplitude value of the gate signal line 17b.
[0342]
If the amplitude value of the gate signal line 17 is large, the punch-through voltage between the gate signal line 17 and the pixel 16 increases, and black floating occurs. The amplitude of the gate signal line 17a may be controlled so that the potential of the source signal line 18 is not applied to the pixel 16 (applied (when selected)). Since the potential fluctuation of the source signal line 18 is small, the amplitude value of the gate signal line 17a can be reduced.
[0343]
On the other hand, the gate signal line 17b needs to perform EL on / off control. Therefore, the amplitude value becomes large. In order to cope with this, the output voltages of the shift registers 61a and 61b are changed. When the pixel is formed of a P-channel transistor, the Vgh (off voltage) of the shift registers 61a and 61b is substantially the same, and the Vgl (on voltage) of the shift register 61a is greater than the Vgl (on voltage) of the shift register 61b. make low.
[0344]
Hereinafter, the reset driving method will be described with reference to FIG. FIG. 33 is a diagram for explaining the principle of reset driving. First, as illustrated in FIG. 33A, the transistors 11c and 11d are turned off and the transistor 11b is turned on. Then, the drain (D) terminal and the gate (G) terminal of the driving transistor 11a are short-circuited, and an Ib current flows. Generally, the transistor 11a is current-programmed in the previous field (frame). In this state, when the transistor 11d is turned off and the transistor 11b is turned on, the drive current Ib flows to the gate (G) terminal of the transistor 11a. Therefore, the gate (G) terminal and the drain (D) terminal of the transistor 11a have the same potential, and the transistor 11a is reset (a state in which no current flows).
[0345]
Note that before the operation in FIG. 33A, it is preferable to perform an operation in which the transistor 11b and the transistor 11c are turned off, the transistor 11d is turned on, and a current is supplied to the driving transistor 11a. This operation is preferably completed in as short a time as possible. This is because a current flows through the EL element 15 and the EL element 15 is lit, which may reduce the display contrast. This operation time is preferably 0.1% or more and 10% or less of 1H (one horizontal scanning period). More preferably, it is preferably 0.2% or more and 2% or less. Alternatively, it is preferable to be 0.2 μsec or more and 5 μsec or less. Further, the above-described operation (operation performed before (a) in FIG. 33) may be performed collectively on the pixels 16 of the entire screen. By performing the above operation, the drain (D) terminal voltage of the driving transistor 11a is lowered, and a smooth Ib current can be passed in the state of FIG. The above matters also apply to other reset driving methods of the present invention.
[0346]
As the execution time of FIG. 33A is increased, the Ib current flows and the terminal voltage of the capacitor 19 tends to decrease. Therefore, the execution time of FIG. 33A needs to be a fixed value. According to experiments and examinations, it is preferable that the execution time of FIG. 33 (a) is 1H or more and 5H or less.
[0347]
Note that this period is preferably different for R, G, and B pixels. This is because the EL material is different for each color pixel, and the rising voltage of the EL material is different. For each pixel of RGB, the most optimal period is set according to the EL material. In the embodiment, this period is set to 1H or more and 5H or less, but it goes without saying that it may be 5H or more in a driving method mainly for black insertion (writing a black screen). Note that the longer the period, the better the black display state of the pixel.
[0348]
After implementing (a) of FIG. 33, it is set to the state of (b) of FIG. 33 in the period of 1H or more and 5H or less. FIG. 33B shows a state in which the transistors 11c and 11b are turned on and the transistor 11d is turned off. The state shown in FIG. 33 (b) is a state where current programming is performed as described above. That is, the program current Iw is output (or absorbed) from the source driver circuit 14, and this program current Iw is supplied to the driving transistor 11a. The potential of the gate (G) terminal of the driving transistor 11a is set so that the program current Iw flows (the set potential is held in the capacitor 19).
[0349]
If the program current Iw is 0 (A), the transistor 11a remains in a state where no current flows as shown in FIG. 33A, so that a good black display can be realized. In addition, even when white display current programming is performed in FIG. 33B, even if there is a variation in the characteristics of the driving transistors of each pixel, the current programming is completely performed from the offset voltage in the black display state. Do. Therefore, the time programmed to the target current value becomes equal according to the gradation. Therefore, there is no gradation error due to the characteristic variation of the transistor 11a, and a good image display can be realized.
[0350]
After the current programming in FIG. 33B, as shown in FIG. 33C, the transistors 11b and 11c are turned off, the transistor 11d is turned on, and the program current Iw (= Ie) is caused to flow through the EL element 15 to cause the EL element 15 to emit light. 33 (c) has already been described with reference to FIG.
[0351]
That is, in the driving method (reset driving) described in FIG. 33, the driving transistor 11a and the EL element 15 are disconnected (the current does not flow), and the drain (D) terminal and the gate (G) ) Terminal (or source (S) terminal and gate (G) terminal, more generally, two terminals including the gate (G) terminal of the driving transistor), Thereafter, a second operation of performing current (voltage) programming on the driving transistor is performed. In addition, at least the second operation is performed after the first operation. In order to perform reset driving, the transistor 11b and the transistor 11c must be configured to be independently controlled as in the configuration of FIG.
[0352]
The image display state (if an instantaneous change can be observed), first, the pixel row for which current programming is performed is in the reset state (black display state), and current programming is performed after 1H (at this time) Is also in a black display state because the transistor 11d is off.) Next, a current is supplied to the EL element 15, and the pixel row emits light with a predetermined luminance (programmed current). That is, it should appear that the black pixel line moves from the top to the bottom of the screen, and the image is rewritten at the position where the pixel line passes.
[0353]
Although current programming is performed 1H after reset, this period may be within about 5H. This is because a relatively long time is required for the reset of FIG. If this period is 5H, 5 pixel rows should be displayed in black (6 pixel rows if a current program pixel row is included).
[0354]
In addition, the reset state is not limited to performing one pixel row at a time, and the reset state may be simultaneously performed for a plurality of pixel rows. Alternatively, the scanning may be performed while simultaneously resetting and overlapping each pixel row. For example, if four pixel rows are simultaneously reset, the pixel rows (1), (2), (3), and (4) are reset in the first horizontal scanning period (one unit), and the next second horizontal scan is performed. In the scanning period, the pixel rows (3), (4), (5), and (6) are reset, and in the next third horizontal scanning period, the pixel rows (5), (6), (7), and (8) are reset. Put it in a state. In addition, a driving state in which the pixel rows (7), (8), (9), and (10) are reset in the next fourth horizontal scanning period is exemplified. Of course, the driving states of FIGS. 33B and 33C are also performed in synchronization with the driving state of FIG.
[0355]
Further, it goes without saying that the driving shown in FIGS. 33B and 33C may be carried out after all the pixels of one screen are reset at the same time or in the scanning state. Needless to say, the interlace drive state (interlaced scanning of one pixel row or a plurality of pixel rows) may be set to the reset state (interlace of one pixel row or a plurality of pixel rows). Moreover, you may implement a random reset state. Further, the description of the reset driving according to the present invention is a method of operating a pixel row (that is, controlling the vertical direction of the screen). However, the concept of reset driving does not limit the control direction to pixel rows. For example, it goes without saying that reset driving may be performed in the pixel column direction.
[0356]
Note that the reset driving in FIG. 33 can be combined with the N-fold pulse driving of the present invention or with interlaced driving to realize better image display. In particular, the configuration of FIG. 22 is an intermittent N / K-fold pulse drive (a drive method in which a plurality of lighting regions are provided on one screen. This drive method is easy by controlling the gate signal line 17b and turning on / off the transistor 11d. (This has been described before.) Can be easily realized, so that a good image display can be realized without occurrence of flicker.
[0357]
It goes without saying that a better image display can be realized by combining with other driving methods, for example, a precharge driving method described below. As described above, it is needless to say that reset driving can be performed in combination with other embodiments of the present specification as in the present invention.
[0358]
FIG. 34 is a configuration diagram of a display device that realizes reset driving. The gate driver circuit 12a controls the gate signal line 17a and the gate signal line 17b in FIG. The transistor 11b is on / off controlled by applying an on / off voltage to the gate signal line 17a. Further, the transistor 11d is on / off controlled by applying an on / off voltage to the gate signal line 17b. The gate driver circuit 12b controls the gate signal line 17c in FIG. The transistor 11c is on / off controlled by applying an on / off voltage to the gate signal line 17c.
[0359]
  Therefore, the gate signal line 17a is operated by the gate driver circuit 12a, and the gate signal line 17c is operated by the gate driver circuit 12b. Therefore, the timing for turning on the transistor 11b and resetting the driving transistor 11a, and the transistor11cCan be freely set to the timing for performing current programming on the driving transistor 11a. Other configurations are the same as or similar to those previously described, and thus description thereof is omitted.
[0360]
FIG. 35 is a timing chart of reset driving. When a turn-on voltage is applied to the gate signal line 17a to turn on the transistor 11b and the driving transistor 11a is reset, a turn-off voltage is applied to the gate signal line 17b and the transistor 11d is turned off. Therefore, the state shown in FIG. During this period, an Ib current flows.
[0361]
In the timing chart of FIG. 35, the reset time is 2H (the on-voltage is applied to the gate signal line 17a and the transistor 11b is turned on), but the invention is not limited to this. It may be 2H or more. If the reset can be performed at a very high speed, the reset time may be less than 1H.
[0362]
The number of reset periods can be easily changed by the DATA (ST) pulse period input to the gate driver circuit 12. For example, if DATA input to the ST terminal is set to H level for 2H period, the reset period output from each gate signal line 17a becomes 2H period. Similarly, if DATA input to the ST terminal is set to the H level during the 5H period, the reset period output from each gate signal line 17a becomes the 5H period.
[0363]
After the reset of the 1H period, the ON voltage is applied to the gate signal line 17c (1) of the pixel row (1). When the transistor 11c is turned on, the program current Iw applied to the source signal line 18 is written to the driving transistor 11a via the transistor 11c.
[0364]
After current programming, a turn-off voltage is applied to the gate signal line 17c of the pixel (1), the transistor 11c is turned off, and the pixel is disconnected from the source signal line. At the same time, a turn-off voltage is applied to the gate signal line 17a, and the reset state of the driving transistor 11a is canceled (in this period, it is more appropriate to express the current program state than the reset state). is there). Further, an on-voltage is applied to the gate signal line 17b, the transistor 11d is turned on, and a current programmed in the driving transistor 11a flows through the EL element 15. The pixel row (2) and subsequent pixels are the same as the pixel row (1), and the operation is obvious from FIG.
[0365]
In FIG. 35, the reset period is a 1H period. FIG. 36 shows an embodiment in which the reset period is 5H. The number of reset periods can be easily changed by the DATA (ST) pulse period input to the gate driver circuit 12. FIG. 36 shows an embodiment in which DATA input to the ST1 terminal of the gate driver circuit 12a is set to H level for 5H periods, and the reset period output from each gate signal line 17a is 5H periods. The longer the reset period, the more complete the reset and the better black display can be realized. However, the display luminance is reduced for the ratio of the reset period.
[0366]
FIG. 36 shows an example in which the reset period is 5H. Moreover, this reset state was a continuous state. However, the reset state is not limited to being performed continuously. For example, the signal output from each gate signal line 17a may be turned on / off every 1H. Such an on / off operation can be easily realized by operating an enable circuit (not shown) formed in the output stage of the shift register. Further, it can be easily realized by controlling the DATA (ST) pulse input to the gate driver circuit 12.
[0367]
In the circuit configuration of FIG. 34, the gate driver circuit 12a requires at least two shift register circuits (one for controlling the gate signal line 17a and the other for controlling the gate signal line 17b). Therefore, there is a problem that the circuit scale of the gate driver circuit 12a is increased. FIG. 37 shows an embodiment in which the gate driver circuit 12a has one shift register. A timing chart of an output signal obtained by operating the circuit of FIG. 37 is as shown in FIG. Note that FIG. 35 and FIG. 37 are different in the symbol of the gate signal line 17 output from the gate driver circuits 12a and 12b.
[0368]
As is apparent from the addition of the OR circuit 371 in FIG. 37, the output of each gate signal line 17a is ORed with the preceding stage output of the shift register circuit 61a. That is, the ON voltage is output from the gate signal line 17a during the 2H period. On the other hand, the output of the shift register circuit 61a is output as it is to the gate signal line 17c. Therefore, the on-voltage is applied during the 1H period.
[0369]
For example, when the second H level signal is output from the shift register circuit 61a, an ON voltage is output to the gate signal line 17c of the pixel 16 (1), and the pixel 16 (1) is in a current (voltage) program state. It is. At the same time, an on-voltage is output to the gate signal line 17a of the pixel 16 (2), the transistor 11b of the pixel 16 (2) is turned on, and the driving transistor 11a of the pixel 16 (2) is reset.
[0370]
  Similarly, when the third H level signal is output from the shift register circuit 61a, an on-voltage is output to the gate signal line 17c of the pixel 16 (2), and the pixel 16 (2) is subjected to the current (voltage) program. State. At the same time, pixel 16 (3)The ON voltage is also output to the gate signal line 17a, the pixel 16 (3) transistor 11b is turned on, and the pixel 16 (3) driving transistor 11a is reset. That is, an on-voltage is output from the gate signal line 17a during the 2H period, and an on-voltage is output to the gate signal line 17c during the 1H period.
[0371]
In the programmed state, when the transistor 11b and the transistor 11c are simultaneously turned on (FIG. 33B), the transistor 11c is more than the transistor 11b when shifting to the non-programmed state (FIG. 33C). If the switch is turned off first, the reset state shown in FIG. In order to prevent this, the transistor 11c needs to be turned off after the transistor 11b. For this purpose, it is necessary to control the gate signal line 17a so that the ON voltage is applied before the gate signal line 17c.
[0372]
The above example is an example related to the pixel configuration of FIG. 32 (basically, FIG. 1). However, the present invention is not limited to this. For example, the pixel configuration of a current mirror as shown in FIG. 38 can be implemented. In FIG. 38, the N-fold pulse driving illustrated in FIGS. 13 and 15 can be realized by on / off controlling the transistor 11e. FIG. 39 is an explanatory diagram of an embodiment in the pixel configuration of the current mirror of FIG. Hereinafter, the reset driving method in the pixel configuration of the current mirror will be described with reference to FIG.
[0373]
  As illustrated in FIG. 39A, the transistors 11c and 11e are turned off and the transistor 11d is turned on. Then, the current programming transistor11aThe drain (D) terminal and the gate (G) terminal are short-circuited, and an Ib current flows as shown in the figure. In general, the transistor 11b is current-programmed in the previous field (frame) and has a capability of flowing current (the gate potential is held in the capacitor 19 for 1F period and is naturally displayed. , Current does not flow when a complete black display is performed). In this state, when the transistor 11e is turned off and the transistor 11d is turned on, the drive current Ib flows in the direction of the gate (G) terminal of the transistor 11a (the gate (G) terminal and the drain (D) terminal are short-circuited). ) Therefore, the gate (G) terminal and the drain (D) terminal of the transistor 11a have the same potential, and the transistor 11a is reset (a state in which no current flows). Further, since the gate (G) terminal of the driving transistor 11b is common with the gate (G) terminal of the current programming transistor 11a, the driving transistor 11b is also reset.
[0374]
The reset state (state in which no current flows) of the transistors 11a and 11b is equivalent to the state in which the offset voltage of the voltage offset canceller system described in FIG. That is, in the state of FIG. 39A, an offset voltage (starting voltage at which current starts to flow) is applied between the terminals of the capacitor 19. By applying a voltage higher than the absolute value of this voltage, current flows through the transistor 11. ) Is held. This offset voltage has a different voltage value depending on the characteristics of the transistors 11a and 11b. Therefore, by carrying out the operation shown in FIG. 39A, the transistor 19a and the transistor 11b do not pass current through the capacitor 19 of each pixel (that is, the black display current (almost equal to 0)) is maintained. (Reset to the starting voltage at which current begins to flow).
[0375]
39 (a), as in FIG. 33 (a), the Ib current flows and the terminal voltage of the capacitor 19 tends to decrease as the reset execution time increases. Therefore, the implementation time of FIG. 39A needs to be a fixed value. According to experiments and examinations, it is preferable that the execution time of FIG. 39A is 1H or more and 10H (10 horizontal scanning periods) or less. Furthermore, it is preferable to set it to 1H or more and 5H or less. Alternatively, it is preferably 20 μsec or more and 2 msec or less. The same applies to the driving method shown in FIG.
[0376]
  The same applies to (a) of FIG. 33, but when the reset state of (a) of FIG. 39 and the current program state of (b) of FIG. There is no problem because the period from the reset state to the current program state shown in FIG. 39B is a fixed value (constant value). That is, the period from the reset state in FIG. 33A or 39A to the current program state in FIG. 33B or 39B is 1H or more and 10H (10 horizontal scanning periods). ) The following is preferable. Furthermore, it is preferable to set it to 1H or more and 5H or less. Alternatively, it is preferably 20 μsec or more and 2 msec or less. If this period is short, the driving transistor11aIs not reset completely. If it is too long, the driving transistor 11 is completely turned off, and this time, it takes a long time to program the current. In addition, the brightness of the screen 50 also decreases.
[0377]
After implementing (a) of FIG. 39, the state shown in (b) of FIG. 39 is obtained. FIG. 39B shows a state in which the transistors 11c and 11d are turned on and the transistor 11e is turned off. The state of (b) in FIG. 39 is a state where current programming is performed. That is, the program current Iw is output (or absorbed) from the source driver circuit 14, and this program current Iw is supplied to the current programming transistor 11a. The potential of the gate (G) terminal of the driving transistor 11b is set in the capacitor 19 so that the program current Iw flows.
[0378]
  If the program current Iw is 0 (A) (black display), the transistor 11b displays the current.39Since the state in which the current of (a) does not flow is maintained, good black display can be realized. Further, when white display current programming is performed in FIG. 39B, even if there is a variation in the characteristics of the driving transistors in each pixel, the offset voltage in the completely black display state (characteristics of each driving transistor). The current program is started from the starting voltage at which the current set according to the current flows. Therefore, the time programmed to the target current value becomes equal according to the gradation. Therefore, there is no gradation error due to the characteristic variation of the transistor 11a or the transistor 11b, and a good image display can be realized.
[0379]
After the current programming of FIG. 39B, as shown in FIG. 39C, the transistors 11c and 11d are turned off, the transistor 11e is turned on, and the program current Iw (= Ie) is caused to flow through the EL element 15 to cause the EL element 15 to emit light. Since (c) in FIG. 39 has been described before, the details are omitted.
[0380]
In the driving method (reset driving) described with reference to FIGS. 33 and 39, the driving transistor 11a or 11b and the EL element 15 are disconnected (the current does not flow. Performed by the transistor 11e or the transistor 11d) and the driving is performed. Between a drain (D) terminal and a gate (G) terminal of a transistor for driving (or a source (S) terminal and a gate (G) terminal, more generally two terminals including a gate (G) terminal of a driving transistor)) A first operation for short-circuiting and a second operation for performing a current (voltage) program on the driving transistor after the operation are performed.
[0381]
At least the second operation is performed after the first operation. Note that the operation of disconnecting the driving transistor 11a or the transistor 11b and the EL element 15 in the first operation is not necessarily an essential condition. If the driving transistor 11a or the transistor 11b and the EL element 15 in the first operation are not disconnected, the first operation of shorting between the drain (D) terminal and the gate (G) terminal of the driving transistor is performed. This is because there may be a case where a slight variation in the reset state may occur. This is determined by examining the transistor characteristics of the fabricated array.
[0382]
The pixel configuration of the current mirror in FIG. 39 is a driving method in which the current transistor transistor 11b is reset as a result by resetting the current program transistor 11a.
[0383]
In the pixel configuration of the current mirror in FIG. 39, it is not always necessary to disconnect the driving transistor 11b and the EL element 15 in the reset state. Accordingly, the drain (D) terminal and the gate (G) terminal (or the source (S) terminal and the gate (G) terminal) of the current programming transistor a, or more generally, the gate (G) terminal of the current programming transistor. A first operation for short-circuiting between the two terminals including the first terminal and the second terminal including the gate (G) terminal of the driving transistor), and a second program for performing current (voltage) programming on the current programming transistor after the first operation. Operation. At least the second operation is performed after the first operation.
[0384]
In the image display state (if an instantaneous change can be observed), first, the pixel row to be subjected to the current program is in a reset state (black display state), and the current program is performed after a predetermined H. From the top of the screen to the bottom, the black pixel row should move, and the image should appear to be rewritten at the position where this pixel row has passed.
[0385]
Although the above embodiments have been described with a focus on the pixel configuration of the current program, the reset driving of the present invention can also be applied to the pixel configuration of the voltage program. FIG. 43 is an explanatory diagram of the pixel configuration (panel configuration) of the present invention for performing reset driving in the pixel configuration of the voltage program.
[0386]
In the pixel configuration of FIG. 43, a transistor 11e for resetting the driving transistor 11a is formed. When a turn-on voltage is applied to the gate signal line 17e, the transistor 11e is turned on, and the gate (G) terminal and the drain (D) terminal of the driving transistor 11a are short-circuited. In addition, a transistor 11d that cuts off a current path between the EL element 15 and the driving transistor 11a is formed. Hereinafter, the reset driving method of the present invention in the pixel configuration of the voltage program will be described with reference to FIG.
[0387]
As shown in FIG. 44A, the transistors 11b and 11d are turned off and the transistor 11e is turned on. The drain (D) terminal and the gate (G) terminal of the driving transistor 11a are short-circuited, and an Ib current flows as shown in the figure. Therefore, the gate (G) terminal and the drain (D) terminal of the transistor 11a have the same potential, and the driving transistor 11a is reset (a state in which no current flows). Before resetting the transistor 11a, as described in FIG. 33 or FIG. 39, in synchronization with the HD synchronization signal, the transistor 11d is first turned on, the transistor 11e is turned off, and a current flows through the transistor 11a. Keep it. Thereafter, the operation of FIG. 44A is performed.
[0388]
In the voltage-programmed pixel configuration, like the current-programmed pixel configuration, the Ib current flows and the terminal voltage of the capacitor 19 tends to decrease as the reset execution time in FIG. is there. Therefore, the execution time of FIG. 44 (a) needs to be a fixed value. The implementation time is preferably 0.2H or more and 5H (5 horizontal scanning periods) or less. Furthermore, it is preferable to set it to 0.5H or more and 4H or less. Or it is preferable to set it as 2 to 400 microseconds.
[0389]
The gate signal line 17e is preferably shared with the gate signal line 17a in the previous pixel row. That is, the gate signal line 17e and the gate signal line 17a of the previous pixel row are formed in a short state. This configuration is called a pre-stage gate control system. Note that the pre-stage gate control method uses a gate signal line waveform of a pixel row selected at least 1H before the target pixel row. Therefore, it is not limited to one pixel row before. For example, the driving transistor 11a of the pixel of interest may be reset using the signal waveform of the gate signal line two rows before.
[0390]
A more specific description of the pre-stage gate control method is as follows. A pixel row of interest is an (N) pixel row, and its gate signal lines are a gate signal line 17e (N) and a gate signal line 17a (N). The pixel row in the previous stage selected 1H before is the (N-1) pixel row, and the gate signal lines are the gate signal line 17e (N-1) and the gate signal line 17a (N-1). . A pixel row selected after 1H after the pixel row of interest is an (N + 1) pixel row, and its gate signal lines are a gate signal line 17e (N + 1) and a gate signal line 17a (N + 1).
[0390]
In the (N−1) H period, when the ON voltage is applied to the gate signal line 17a (N−1) of the (N−1) th pixel row, the gate signal line 17e (N) of the (N) th pixel row. ) Is also applied with an ON voltage. This is because the gate signal line 17e (N) and the gate signal line 17a (N-1) in the previous pixel row are formed in a short state. Therefore, the transistor 11b (N-1) of the pixel in the (N-1) th pixel row is turned on, and the voltage of the source signal line 18 is written to the gate (G) terminal of the driving transistor 11a (N-1). At the same time, the transistors 11e (N) of the pixels in the (N) th pixel row are turned on, the gate (G) terminal and the drain (D) terminal of the driving transistor 11a (N) are short-circuited, and the driving transistor 11a (N ) Is reset.
[0392]
In the (N) period following the (N−1) H period, when the ON voltage is applied to the gate signal line 17a (N) of the (N) pixel row, the gate signal of the (N + 1) pixel row. The on-voltage is also applied to the line 17e (N + 1). Accordingly, the transistor 11b (N) of the pixel in the (N) th pixel row is turned on, and the voltage applied to the source signal line 18 is written to the gate (G) terminal of the driving transistor 11a (N). At the same time, the transistor 11e (N + 1) of the pixel in the (N + 1) th pixel row is turned on, the gate (G) terminal and the drain (D) terminal of the driving transistor 11a (N + 1) are short-circuited, and the driving transistor 11a (N + 1) ) Is reset.
[0393]
Similarly, in the (N + 1) period subsequent to the (N) H period, when the ON voltage is applied to the gate signal line 17a (N + 1) in the (N + 1) th pixel row, the (N + 2) th pixel row. The on-voltage is also applied to the gate signal line 17e (N + 2). Accordingly, the transistor 11b (N + 1) of the pixel in the (N + 1) th pixel row is turned on, and the voltage applied to the source signal line 18 is written to the gate (G) terminal of the driving transistor 11a (N + 1). At the same time, the transistor 11e (N + 2) of the pixel in the (N + 2) th pixel row is turned on, the gate (G) terminal and the drain (D) terminal of the driving transistor 11a (N + 2) are short-circuited, and the driving transistor 11a (N + 2) ) Is reset.
[0394]
In the above-described pre-stage gate control system of the present invention, the driving transistor 11a is reset for 1H period, and then the voltage (current) program is executed.
[0395]
  The same applies to (a) of FIG. 33, but when the reset state of FIG. 44 (a) and the voltage program state of (b) of FIG. There is no problem because the period from the reset state to the current program state shown in FIG. 44B is a fixed value (constant value). If this period is short, the driving transistor 11 is not completely reset. If it is too long, the driving transistor 11a is completely turned off, and this time, it takes a long time to program the current. Also screen50The brightness is also reduced.
[0396]
After implementing (a) of FIG. 44, the state of (b) of FIG. 44 is obtained. FIG. 44B shows a state in which the transistor 11b is turned on and the transistors 11e and 11d are turned off. The state shown in FIG. 44B is a state where voltage programming is being performed. That is, a program voltage is output from the source driver circuit 14, and this program voltage is written to the gate (G) terminal of the driving transistor 11a (the potential of the gate (G) terminal of the driving transistor 11a is set in the capacitor 19). In the case of the voltage programming method, it is not always necessary to turn off the transistor 11d during voltage programming. Further, it is a combination of the N-fold pulse drive shown in FIGS. 13 and 15 or the like, or the intermittent N / K-fold pulse drive as described above (a drive method in which a plurality of lighting regions are provided on one screen. The transistor 11e is not necessary if it is not necessary to implement (by easily turning on and off the transistor 11e). Since this has been described before, the description is omitted.
[0397]
When the voltage program for white display is performed by the configuration of FIG. 43 or the driving method of FIG. 44, the offset voltage of each black display state (each driving transistor is completely different even if the characteristics of the driving transistor for each pixel vary. The voltage program is performed from the starting voltage at which a current set according to the characteristics of the current flows. Therefore, the time programmed to the target current value becomes equal according to the gradation. Therefore, there is no gradation error due to the characteristic variation of the transistor 11a, and a good image display can be realized.
[0398]
  44 (b)PressureAfter programming, as shown in FIG. 44C, the transistor 11b is turned off, the transistor 11d is turned on, the program current from the driving transistor 11a is supplied to the EL element 15, and the EL element 15 is caused to emit light.
[0399]
As described above, in the reset driving of the present invention in the voltage program of FIG. 43, first, in synchronization with the HD synchronization signal, the transistor 11d is first turned on, the transistor 11e is turned off, and the current flows through the transistor 11a. 1, the transistor 11 a and the EL element 15 are disconnected, and the drain (D) terminal and the gate (G) terminal (or the source (S) terminal and the gate (G) terminal of the driving transistor 11 a, In other words, a second operation for short-circuiting between the gate (G) terminals of the driving transistor) and a third operation for performing voltage programming on the driving transistor 11a after the above operation are performed. Is.
[0400]
In the above embodiment, the transistor 11d is turned on / off to control the current flowing from the driving transistor 11a (in the pixel configuration of FIG. 1) to the EL element 15. In order to turn on and off the transistor 11d, it is necessary to scan the gate signal line 17b, and the shift register 61 (gate driver circuit 12) is necessary for scanning. However, the shift register 61 is large in scale and cannot be narrowed by using the shift register 61 for controlling the gate signal line 17b. The method described in FIG. 40 solves this problem.
[0401]
Although the present invention will be described mainly by exemplifying the pixel configuration of the current program illustrated in FIG. 1 and the like, the present invention is not limited to this, and other current program configurations described in FIG. Needless to say, the present invention can be applied to a pixel configuration. Needless to say, the technical concept of turning on / off in a block can be applied to the pixel configuration of the voltage program shown in FIG.
[0402]
FIG. 40 shows an embodiment of the block drive system. First, for ease of explanation, the description will be made assuming that the gate driver circuit 12 is formed directly on the substrate 71 or the gate driver IC 12 of a silicon chip is mounted on the substrate 71. Further, the source driver 14 and the source signal line 18 are omitted because the drawing becomes complicated.
[0403]
In FIG. 40, the gate signal line 17a is connected to the gate driver circuit 12. On the other hand, the gate signal line 17 b of each pixel is connected to the lighting control line 401. In FIG. 40, four gate signal lines 17b are connected to one lighting control line 401.
[0404]
Needless to say, blocking with the four gate signal lines 17b is not limited to this, and may be more than that. In general, the display screen 50 is preferably divided into at least five or more. More preferably, it is preferably divided into 10 or more. Furthermore, it is preferable to divide into 20 or more. When the number of divisions is small, flicker is easy to see. If the number of divisions is too large, the number of lighting control lines 401 increases, and the layout of the control lines 401 becomes difficult.
[0405]
  Therefore, in the case of a QCIF display panel, since the number of vertical scanning lines is 220, it is necessary to block at least 220/5 = 44, preferably 220/10 =22It is necessary to make a block by the above. However, when two blocks are formed on the odd and even lines, the occurrence of flicker is relatively small even at a low frame rate, and thus two blocks may be sufficient.
[0406]
In the embodiment of FIG. 40, an ON voltage (Vgl) or an OFF voltage (Vgh) is sequentially applied to the lighting control lines 401a, 401b, 401c, 401d. The current that flows is turned on and off.
[0407]
  In the embodiment of FIG. 40, the gate signal line 17b and the lighting control line 401 do not cross each other. Therefore, a short defect between the gate signal line 17b and the lighting control line 401 does not occur. Further, since the gate signal line 17b and the lighting control line 401 are not capacitively coupled, the capacitance when the gate signal line 17b side is viewed from the lighting control line 401.loadIs extremely small. Therefore, it is easy to drive the lighting control line 401.
[0408]
A gate signal line 17 a is connected to the gate driver circuit 12. By applying an on voltage to the gate signal line 17a, a pixel row is selected, the transistors 11b and 11c of each selected pixel are turned on, and the current (voltage) applied to the source signal line 18 is supplied to each pixel. Program the capacitor 19. On the other hand, the gate signal line 17b is connected to the gate (G) terminal of the transistor 11d of each pixel. Therefore, when a turn-on voltage (Vgl) is applied to the lighting control line 401, a current path is formed between the driving transistor 11a and the EL element 15, and conversely, when a turn-off voltage (Vgh) is applied, the EL element Fifteen anode terminals are opened.
[0409]
Note that the control timing of the on / off voltage applied to the lighting control line 401 and the timing of the pixel row selection voltage (Vgl) output from the gate driver circuit 12 to the gate signal line 17a are synchronized with one horizontal scanning clock (1H). It is preferable. However, the present invention is not limited to this.
[0410]
The signal applied to the lighting control line 401 simply turns on and off the current to the EL element 15. Further, it is not necessary to be synchronized with the image data output from the source driver 14. This is because the signal applied to the lighting control line 401 controls the current programmed in the capacitor 19 of each pixel 16. Therefore, it is not necessarily required to be synchronized with the pixel row selection signal. Even in the case of synchronization, the clock is not limited to the 1H signal, and may be 1 / 2H or 1 / 4H.
[0411]
Even in the pixel configuration of the current mirror shown in FIG. 38, the transistor 11e can be controlled to be turned on / off by connecting the gate signal line 17b to the lighting control line 401. Therefore, block driving can be realized.
[0412]
In FIG. 32, if the gate signal line 17a is connected to the lighting control line 401 and resetting is performed, the block driving can be realized. That is, the block driving of the present invention is a driving method in which a plurality of pixel rows are simultaneously not lit (or black display) with one control line.
[0413]
  In the above embodiment, one selection per pixel rowGate signal lineIt is the structure which arrange | positions (forms). The present invention is not limited to this, and one selection gate signal line may be arranged (formed) in a plurality of pixel rows.
[0414]
FIG. 41 shows an example. In order to facilitate the description, the pixel configuration will be described mainly using the case of FIG. In FIG. 41, the pixel row selection gate signal line 17a simultaneously selects three pixels (16R, 16G, 16B). The symbol “R” means a red pixel relationship, the symbol “G” means a green pixel relationship, and the symbol “B” means a blue pixel relationship.
[0415]
Therefore, by selecting the gate signal line 17a, the pixel 16R, the pixel 16G, and the pixel 16B are simultaneously selected to enter a data writing state. The pixel 16R writes data from the source signal line 18R to the capacitor 19R, and the pixel 16G writes data from the source signal line 18G to the capacitor 19G. The pixel 16B writes data from the source signal line 18B to the capacitor 19B.
[0416]
The transistor 11d of the pixel 16R is connected to the gate signal line 17bR. The transistor 11d of the pixel 16G is connected to the gate signal line 17bG, and the transistor 11d of the pixel 16B is connected to the gate signal line 17bB. Accordingly, the EL element 15R of the pixel 16R, the EL element 15G of the pixel 16G, and the EL element 15B of the pixel 16B can be separately controlled on and off. That is, the EL element 15R, the EL element 15G, and the EL element 15B can individually control the lighting time and the lighting cycle by controlling the gate signal lines 17bR, 17bG, and 17bB.
[0417]
In order to realize this operation, in the configuration of FIG. 6, the shift register circuit 61 that scans the gate signal line 17a, the shift register circuit 61 that scans the gate signal line 17bR, and the shift register that scans the gate signal line 17bG. It is appropriate to form (place) four circuits 61 and shift register circuit 61 that scans gate signal line 17bB.
[0418]
Although a current N times the predetermined current is supplied to the source signal line 18 and a current N times the predetermined current is supplied to the EL element 15 for a period of 1 / N, this cannot be realized in practice. This is because the signal pulse applied to the gate signal line 17 actually penetrates the capacitor 19 and a desired voltage value (current value) cannot be set in the capacitor 19. Generally, a voltage value (current value) lower than a desired voltage value (current value) is set for the capacitor 19. For example, even if it is driven to set a current value 10 times, only about 5 times the current is set in the capacitor 19. For example, even when N = 10, the current that actually flows through the EL element 15 is the same as when N = 5. Therefore, the present invention is a method of setting the current value N times and driving the EL element 15 so that a current proportional to or corresponding to the N times flows through the EL element 15. Alternatively, it is a driving method in which a current larger than a desired value is applied to the EL element 15 in a pulse shape.
[0419]
Further, a current (voltage) program is applied to the driving transistor 11a (in the case of FIG. 1) by supplying a current (a current that is higher than the desired luminance when a current is continuously passed through the EL element 15 as it is) from a desired value. In this way, the light emission luminance of the desired EL element is obtained by making the current flowing through the EL element 15 intermittent.
[0420]
Further, the switching transistors 11b, 11c and the like shown in FIG. 1 are preferably formed of an N channel. This is because the penetration voltage to the capacitor 19 is reduced. Further, since the off-leakage of the capacitor 19 is also reduced, it can be applied to a low frame rate of 10 Hz or less.
[0421]
Further, depending on the pixel configuration, when the punch-through voltage acts in the direction of increasing the current flowing through the EL element 15, the white peak current increases and the contrast of the image display increases. Therefore, a good image display can be realized.
[0422]
On the other hand, it is also effective to make the black display better by causing the penetration transistors of the switching transistors 11b and 11c of FIG. When the P-channel transistor 11b is turned off, the voltage becomes Vgh. Therefore, the terminal voltage of the capacitor 19 is slightly shifted to the Vdd side. For this reason, the gate (G) terminal voltage of the transistor 11a rises, resulting in a black display. In addition, since the current value for the first gradation display can be increased (a constant base current can be made to flow until gradation 1), a shortage of write current can be reduced by the current programming method.
[0423]
The transistor 11b in FIG. 1 operates to hold the current flowing in the driving transistor 11a in the capacitor 19. That is, it has a function of shorting between the gate terminal (G) and the drain terminal (D) or the source terminal (S) of the driving transistor 11a at the time of programming. A switching transistor having a function like the transistor 11b is referred to as a short-circuit transistor. The short-circuit transistor has a source terminal or drain terminal connected to the holding capacitor 19. The short-circuit transistor is on / off controlled by the voltage applied to the gate signal line 17a. The problem is that the voltage of the gate signal line 17a penetrates the capacitor 19 when the off-voltage is applied. Due to this punch-through voltage, the potential of the capacitor 19 (= the potential of the gate terminal (G) of the driving transistor 11a) fluctuates, and a good current program cannot be performed, causing laser shot unevenness and the like. Therefore, it is necessary to reduce the punch-through voltage.
[0424]
In order to reduce the punch-through voltage, it is preferable to reduce the size of the short-circuit transistor 11b. Now, the size Scc of the short-circuit transistor is defined as channel width W (μm) and channel length L (μm), and Scc = W · L (square μm). When a plurality of short-circuit transistors are connected in series, Scc is the sum of the connected transistor sizes. For example, if W = 5 (μm) and L = 6 (μm) of one short-circuit transistor and the number (n = 4) is connected, Scc = 5 × 6 × 4 = 120 (square μm) ).
[0425]
There is a correlation between the size of the short-circuit transistor and the punch-through voltage. This relationship is shown in FIG. Note that the short-circuit transistor is a P-channel transistor. However, even an N-channel transistor can be applied.
[0426]
In FIG. 194, the horizontal axis is Scc / n. As described above, Scc is the sum of the sizes of the short-circuit transistors. n is the number of connected short-circuit transistors. In FIG. 194, the horizontal axis represents n pieces of Scc. That is, the size of one short-circuit transistor is one.
[0427]
In the first embodiment, when the size Scc of the short-circuit transistor is the channel width W (μm) and the channel length L (μm), and the number of short-circuit transistors is n = 4, Scc / n = 5 × 6 × 4/4 = 30 (square μm). In FIG. 194, the vertical axis represents the penetration voltage (V).
[0428]
If the punch-through voltage is not within 0.3 (V), laser shot unevenness occurs and is not visually acceptable. Therefore, the size of one short-circuited transistor needs to be 25 (square μm) or less. On the other hand, unless the short-circuit transistor is set to 5 (square μm) or more, the processing accuracy of the transistor cannot be achieved and the variation becomes large. There is also a problem with drive capability. From the above, the short-circuit transistor 11b needs to be 5 (square μm) or more and 25 (square μm) or less. More preferably, the short-circuit transistor 11b needs to be 5 (square μm) or more and 20 (square μm) or less.
[0429]
The punch-through voltage due to the short-circuit transistor is also correlated with the amplitude value (Vgh−Vgl) of the voltage (Vgh, Vgl) for driving the short-circuit transistor. The larger the amplitude value, the larger the punch-through voltage. This relationship is illustrated in FIG. In FIG. 196, the horizontal axis represents the amplitude value (Vgh−Vhl) (V). The vertical axis represents the penetration voltage. As described with reference to FIG. 194, the punch-through voltage needs to be 0.3 (V) or less.
[0430]
In other words, the permissible voltage 0.3 (V) of the penetration voltage is 1/5 or less (20% or less) of the amplitude value of the source signal line 18. The source signal line 18 is 1.5 (V) when the program current is white, and 3.0 (V) when the program current is black. Therefore, (3.0−1.5) /5=0.3 (V).
[0431]
On the other hand, if the amplitude value (Vgh−Vhl) of the gate signal line is 4 (V) or more, the pixel 16 cannot be sufficiently written. From the above, the amplitude value (Vgh−Vgl) of the gate signal line needs to satisfy the condition of 4 (V) or more and 15 (V) or less. More preferably, the amplitude value (Vgh−Vgl) of the gate signal line needs to satisfy the condition of 5 (V) or more and 12 (V) or less.
[0432]
In the EL element 15, electrons are injected from the cathode (cathode) into the electron transport layer and simultaneously holes are also injected from the anode (anode) into the hole transport layer. The injected electrons and holes move to the counter electrode by the applied electric field. At that time, carriers are trapped in the organic layer or carriers are accumulated due to a difference in energy level at the interface of the light emitting layer.
[0433]
When space charge is accumulated in the organic layer, the molecule is oxidized or reduced, and the generated radical anion molecule or radical cation molecule is unstable. It is known that this causes an increase in driving voltage. In order to prevent this, the device structure is changed as an example, and a reverse voltage is applied.
[0434]
When a reverse bias voltage is applied, a reverse current is applied, so that injected electrons and holes are extracted to the cathode and the anode, respectively. Thereby, it becomes possible to extend the lifetime by eliminating the formation of space charge in the organic layer and suppressing the electrochemical degradation of the molecules.
[0435]
Note that the reverse bias driving of the present invention described below is performed during a period in which no image is displayed. That is, reverse bias driving is performed for a certain period after the display panel of the present invention is turned on. Alternatively, reverse bias driving is performed for a certain period before the display panel is turned on.
[0436]
FIG. 340 is an explanatory diagram for explaining the reverse bias drive system of the present invention. The power supply circuit (IC) 82 has two terminals. One terminal A is connected to the base anode line 2631 and applies the anode voltage Vdd to the anode line of the pixel 16. On the other hand, the other terminal B is connected to the base cathode line 2671 and supplies the Vss voltage to the cathode of the pixel 16.
[0437]
For ease of explanation, it is assumed that the anode voltage Vdd is higher than the cathode voltage Vss. Further, the pixel configuration will be described by exemplifying the configuration of FIG. 1, but is not limited to this pixel configuration. This is because the reverse bias drive system of the present invention described below applies a reverse bias voltage to the EL element 15 by changing the voltage applied to at least one of the cathode and the anode. More preferably, the source driver circuit 14 writes a predetermined voltage to the pixel, and a reverse bias voltage is applied by this voltage and the voltage applied to the changed EL element 15. Therefore, the pixel configuration is not limited.
[0438]
For easier understanding, as an example, voltage values and the like are specified for the drive voltages and signal amplitudes of the respective units. First, the source driver circuit 14 operates with a power supply voltage of GND (0 (V)) and 5.5 (V), and the output video signal is a maximum of 5.5 (V) and a minimum of 0.5 (V). (Since the operation of the unit transistor 634 in FIG. 71 requires about 0.5 (V), GND + 0.5 (V) is the minimum output amplitude). Therefore, a video signal having a potential of 5.5 (V) to 0.5 (V) is output to the source signal line 18. The precharge voltage output from the source driver circuit 14 is set to 5.5 (V) to 0 (V).
[0439]
On the other hand, the anode voltage Vdd of the pixel is set to 5.5 (V) which is the power supply voltage of the source driver circuit 14. Therefore, when the driving TFT 11a of the pixel 16 passes the maximum current Imax necessary for image display, the voltage drop in the channel (between S and D) in the diode connection state is set to 5.0 (V) or less. This is important. That is, when the voltage Vic (in this case, 5.5 (V))-0.5 (V) used by the source driver circuit 14 is set, the driving transistor of the pixel 16 is diode-connected (the GD short state of the TFT 11a). When the maximum current (white display) necessary for image display is passed, the pixel voltage is set so that the channel voltage (SD voltage) is smaller than Vic-0.5 (V). Design. That is, in the above embodiment, the voltage of the video signal output from the source driver circuit 14 to the source signal line 18 is 5.0 (V). At this time, the S-D voltage of the diode-connected TFT 11a is set to 5.0 (V) or less at the maximum. The diode characteristics can be freely varied by designing the channel width (W) and channel length (L) of the transistor to predetermined values.
[0440]
The cathode voltage Vss is -8 (V). The on voltage Vgl applied to the gate signal line 17 is −8 + (− 2) = − 10 (V), and the off voltage Vgh applied to the gate signal line 17 is + 5.5 + 1.5 = + 7 (V). . The precharge voltage Vp output from the source driver circuit 14 is 5 (V), and Vm is 0 (V).
[0441]
FIG. 340 shows an image display state. From the power supply circuit (IC) 82, the Vdd voltage is applied to the anode of the pixel 16, and the Vss voltage is applied to the anode. A video signal is applied from the source driver circuit 14 to the source signal line 18 based on the video signal displayed on the display panel. Further, as described with reference to FIGS. 65, 66, 67, 232, 233, etc., the precharge voltage Vp is applied to the source signal line 18 as necessary. The gate driver circuit 12 synchronizes with the horizontal synchronization signal, sequentially selects the gate signal lines 17, and applies an ON voltage to the selected gate signal lines 17.
[0442]
Through the above operation, the program current Iw corresponding to the video signal is written into the pixel 16, the current corresponding to the program current Iw is applied from the drive TFT 11a to the EL element 15, and the EL element 15 emits light. The above is the operation in the image display state.
[0443]
When the user turns off the power switch, the controller 81 (see FIG. 8 and the like) detects that the power switch is turned off, and controls the power circuit 82 and the source driver circuit 14 to start reverse bias driving. FIG. 341 is an explanatory diagram of the reverse bias drive state.
[0444]
At the time of reverse bias driving, first, the EL side gate driver circuit 12b is controlled to apply the off voltage Vgh to the gate signal line 17b so that no current flows through the EL element 15. Next, the precharge voltage Vm is output from the source driver circuit 14 to the source signal line 18. In addition, the selection-side gate driver circuit 12a is operated sequentially or simultaneously, the selection TFTs 11b and 11c are operated, and the Vm voltage is written to the gate terminal of the TFT 11a (in other words, the pixel electrode 105 is written. This is the anode side terminal of the EL element 15). For the relationship between the EL element 15 and the pixel electrode, see FIG. 10 and the description thereof.
[0445]
Next, an off voltage is applied to the gate signal line 17a to turn off the selection side TFT 11b and TFT 11c. Note that in the case where the source driver circuit 14 can fix the potential of the source signal line 18 to the Vm voltage without variation, the TFT 11b and the TFT 11c may remain in the on state.
[0446]
Next or simultaneously with the previous operation, the power supply circuit 82 is controlled so that the voltage V2 = Vdd is applied to the base cathode line 2671 and the voltage V1 = Vm−2 (V) is applied to the base anode line 2631. To do. The reason why the voltage V1 is set to Vm−2 (V) is to completely turn off the TFT 11a so that no current flows. Therefore, the V1 voltage may be any voltage as long as the TFT 11a can be set to a current value equal to or lower than the leakage state in relation to the Vm voltage.
[0447]
In this state, the EL side gate driver circuit 12a is operated to turn on the TFT 11d. When the TFT 11d is turned on, the Vm voltage is applied to the anode side of the EL element 15 (applied to the pixel electrode 105), and the V2 voltage is applied to the cathode side (reflection electrode) of the EL element 15. Therefore, a reverse bias voltage is applied to the EL element 15.
[0448]
Although the TFT 11d is turned on after applying the Vm voltage to the pixel electrode 105, the present invention is not limited to this. The Vm voltage may be applied with the TFT 11d turned on. However, if the V2 voltage is applied to the cathode terminal while the TFTs 11d and 11c are on, the potential of the source signal line 18 is lowered and the source driver circuit 14 may be destroyed. It is necessary to consider (consider) the control timing.
[0449]
Further, although the V2 voltage is the Vdd voltage, it is not limited to this. Since the Vdd voltage is a voltage generated by the power supply circuit 82, the use of the Vdd voltage has an effect of reducing the circuit scale of the power supply circuit 82. However, the higher the voltage applied to the cathode of the EL element 15, the higher the effect of reverse bias, and the lower the terminal voltage increase of the EL element 15 due to deterioration often decreases. Therefore, it may be another voltage (may be Vdd voltage or more and Vdd voltage or less). That is, the effect of applying the reverse bias voltage needs to be determined by experiment. Here, in order to facilitate the description, the description will be made assuming that V2 = Vdd. In addition, the Vm voltage can be set to Vm = 0 (V) or less (for example, −5 (V)).
[0450]
Further, the reverse bias voltage Vs (the absolute value of Vs = (V2−Vm)) applied to the EL element 15 is required to be 3 (V) or more when the EL element 15 is made of a polymer EL material. Preferably, 5 (V) or more is necessary. Note that the maximum value Vs needs to be 15 (V) or less (if the reverse bias voltage is higher than a predetermined value, the application of the reverse bias voltage causes a short circuit between the anode electrode and the cathode electrode of the EL element 15). appear). When the EL element 15 is made of a low molecular EL material, the Vs voltage needs to be 5 (V) or more, and preferably 10 (V) or more. Note that the maximum value Vs needs to be 20 (V) or less (if the reverse bias voltage is higher than a predetermined value, the application of the reverse bias voltage causes a short circuit between the anode electrode and the cathode electrode of the EL element 15). appear).
[0451]
FIG. 344 illustrates the effect of the reverse bias drive method of FIG. 341 (the same applies to other embodiments described later). In FIG. 344, the vertical axis indicates the change voltage ratio. The change voltage ratio is the ratio of the voltage change when the reverse bias voltage is applied and when it is not applied. For example, when the constant terminal current of 1 (μA) is passed through the EL element 15, the initial terminal voltage is 10 (V), and the reverse bias voltage driving of the present invention is not performed, the power failure of 1 (μA) If the terminal voltage of the EL element 15 at the time of the dragon is 13 (V), the change voltage ratio is 13 (V) / 10 (V) = 1.3.
[0452]
When reverse bias voltage driving is performed, the terminal voltage increase of the EL element 15 due to deterioration is reduced. For example, if the initial terminal voltage when a constant current of 1 (μA) is passed through the EL element 15 is 10 (V) and the reverse bias voltage driving of the present invention is performed, the EL during a power outage dragon of 1 (μA) The terminal voltage of the element 15 becomes 11 (V) or less, and a significant improvement effect is seen. In this case, the change voltage ratio is 11 (V) / 10 (V) = 1.1.
[0453]
In FIG. 344, the horizontal axis indicates the application time of the reverse bias voltage to be applied after the display panel is used. Note that the reverse bias voltage Vs needs to be 3 (V) or more, preferably 5 (V) or more when the EL element 15 is made of a polymer EL material. The maximum value Vs needs to be 15 (V) or less. When the EL element 15 is made of a low molecular EL material, the Vs voltage needs to be 5 (V) or more, and preferably 10 (V) or more. Note that the maximum value Vs needs to be 20 (V) or less. Note that the solid line in FIG. 344 indicates the case where the EL element 15 is a low molecular material, and the dotted line indicates the case where the EL element 15 is a high molecular material. In FIG. 344, when G color is displayed at 200 (nt), continuous lighting is performed for 10 minutes, and then a reverse bias voltage is applied to the EL element 15, and the total lighting time is 2000 hours. The voltage change ratio is shown. However, the tendency of R and B is the same or similar.
[0454]
As can be seen from FIG. 344, when no reverse bias voltage is applied, the terminal voltage of the EL element 15 is increased by 30%. However, the change voltage ratio is reduced by performing the reverse bias voltage driving of the present invention. When a reverse bias voltage is applied for 2 seconds after the EL display element is continuously turned on, the change voltage ratio changes by about 5% (1.05). Therefore, the reverse bias voltage is preferably applied for 2 seconds (sec) or longer. In particular, when a reverse bias voltage is applied for 5 seconds after the EL display element is continuously turned on, the change voltage ratio changes by about 2% (1.02). Therefore, the reverse bias voltage is more preferably applied for a time of 5 seconds (sec) or more. The maximum period during which the reverse bias voltage is applied is a limitation in the use of the system. When a reverse bias voltage is applied for a long time, the controller 81 or the like needs to be operated during the period in which the reverse bias voltage is applied. Therefore, the power consumption of the system (display device) increases. Therefore, the period during which the reverse bias voltage is applied needs to be within 60 seconds (60 seconds) at the maximum.
[0455]
Note that FIG. 344 shows an example in which the reverse bias voltage driving of the present invention is performed after using the display panel. However, the display panel is used after the reverse bias voltage driving of the present invention is performed before using the display panel. However, the characteristics of FIG. 344 are the same. FIG. 344 shows an example in which the reverse bias voltage driving of the present invention is performed after the display panel is used for 10 minutes. There is no difference in the effect of reverse bias voltage driving depending on the usage time of the display panel. That is, whether the display panel is used continuously for 3 minutes or continuously for 60 minutes, the terminal voltage of the EL element 15 is increased by applying a reverse bias voltage for 2 seconds or more. Can be suppressed. This is presumably because the charge charged in the EL element 15 can be discharged by applying a voltage of a certain level or more regardless of the period of use.
[0456]
FIG. 342 illustrates a connection state between the power supply circuit 82 and the source driver circuit 14 of the present invention. Voltages (Vp, Vm) are applied to the source signal line 18 from the precharge circuit. During normal display, the analog switch 561b2 applies the Vp voltage to the source signal line 18. When the reverse bias voltage is driven, the Vm voltage is applied to the source signal line 18 in synchronization with the power supply circuit 82 (synchronization is controlled by the controller 81). When the Vm voltage is applied, the analog switch 561 disposed or formed between the output terminal of the current output circuit 654 and the connection terminal 2633 is turned off (opened). This is because the current output circuit 654 is protected from the Vm voltage or the voltage output from the pixel 16 to the source signal line 18 and is prevented from being destroyed.
[0457]
Although the Vm voltage is applied to the source signal line 18 from the source driver circuit 14, the application of the Vm voltage is not limited to being applied from the source driver circuit 14. For example, as described with reference to FIG. 92, the array substrate may be configured to generate the precharge voltage PV, and this PV voltage may be changed to the Vm voltage and applied to the source signal line 18. Further, as shown in FIG. 103, the probe may be directly brought into contact with the connection terminal 971, and the Vm voltage may be applied from the probe.
[0458]
FIG. 343 is a block diagram of the power supply circuit (IC) 82 of the present invention. The power supply circuit 82 of the present invention includes two booster circuits 3433. The booster circuit 3433 is applied with a reference voltage or a DC voltage Vd supplied from a battery. This DC voltage Vd is converted into a rectangular wave (AC) by a switching circuit (not shown). The converted rectangular wave is boosted to a specified value (desired value) by a transformer 1121 formed of a single-winding coil. The boosted rectangular wave is again converted to a DC voltage by a smoothing circuit formed or arranged in the booster circuit 3433. This DC voltage can be easily varied by the switching cycle or timing of the switching circuit. Further, the polarity of the generated DC voltage can be freely set according to the winding direction of the coil of the transformer 1121.
[0459]
As described above, two voltages (Va and Vb) are generated by the two boosting circuits, and these two voltages are applied to the a terminal and the b terminal of the switching circuit 481 (481c, 481d).
[0460]
The switching circuit 481c controls whether to output the Va voltage or the Vb voltage to the base anode line 2631 under the control of the controller 81. Similarly to the switching circuit 481d, the controller 81 controls whether to output the Va voltage or the Vb voltage to the base cathode line 2671.
[0461]
Reference numeral 3431 denotes an output buffer circuit, which has a function of holding the Va voltage or Vb voltage at a constant voltage value regardless of the magnitude of the output current. Further, as shown in FIG. 351, the switches 561c and 561d are switches for setting the voltage output to the base anode line 2631 or the base cathode line 2671 to a high impedance state.
[0462]
FIG. 345 is a timing chart of reverse bias voltage driving according to the present invention. When the display control signal is at the H level, the power is on (a state in which an image is displayed on the display panel), and when the display control signal is at the L level, the power is off (a state in which no image is displayed on the display panel). Therefore, the controller 81 detects when the display control signal becomes L level and enters the reverse bias voltage drive mode.
[0463]
The voltage (V1 applied voltage) applied to the base anode line 2631 after t1 (point c) after the display control signal becomes L level (point b) is changed from the VH1 voltage (Vdd voltage) to the VL1 voltage (Vm). -2 (V)) (see FIG. 341). Further, the voltage (V2 applied voltage) applied to the base cathode line 2671 changes from the VL2 voltage (Vss voltage) to the VH2 voltage (Vdd voltage) (see FIG. 341). In this way, preparation for applying a reverse bias voltage to the EL element 15 is completed. The Vm voltage need not be a constant value, and may be changed.
[0464]
The time (t1) between the points c and b needs to be 1 msec or more. This is to ensure a period for changing the selection state of the gate signal line 17. Further, the time between the point d and the point c (t2: t2 is a period from when the first gate signal line 17a is selected and the Vm voltage is applied to the pixel electrode 105. Basically, in order to perform reverse bias driving, the pixel electrode 105 It is necessary to secure a period of at least 1 msec at the time until the potential is set to 1). More preferably, it must be 4 msec or more. This is because the cathode electrode has a capacity of 0.01 μF or more, so that it takes a relatively long time for the voltages (V1, V2) output from the power supply circuit 82 to reach a predetermined voltage.
[0465]
On the other hand, the gate signal line 17 a is sequentially scanned, and the Vm voltage applied to the source signal line 18 is applied to the pixel electrode 105. At this time, the TFT 11d is not turned on when the Vm voltage is applied (written) to the pixel electrode 105 in synchronization with the on / off of the EL-side TFT 11d. Since the period during which the TFT 11c and TFT 11b are on is the selection period (basically one horizontal scanning period) of the one gate signal line 17a, the TFT 11d is turned off and a reverse bias voltage is applied to the EL element 15. The period when it is not negligible.
[0466]
As described above, the reverse bias voltage can be applied to the EL element 15 by sequentially selecting the gate signal lines 17a, applying the Vm voltage to the anode side of the EL element 15, and applying the + voltage to the cathode side. Therefore, there is no increase in the terminal voltage of the EL element 15, and the life of the EL display panel can be extended.
[0467]
In the embodiment of FIG. 345, the period for selecting each gate signal line 17a for applying a reverse bias voltage is set to one horizontal scanning period (1H) which is the same as that for normal image display. It is not limited. For example, as illustrated in FIG. 346, a period (T1) longer than 1H may be used. That is, since an image is not displayed, it is not necessary to limit to 1H. By setting T1> 1H, the stability when the reverse bias voltage is applied is improved.
[0468]
In the embodiment of FIG. 345, the gate signal line 17a is selected by scanning. However, the present invention is not limited to this. For example, as shown in FIG. 347, an ON voltage may be applied to all the gate signal lines 17a, and a Vm voltage may be applied to the anode of the EL element 15 of each pixel 16.
[0469]
Similarly, as shown in FIG. 348, the period (T2) in which the on-voltage is applied to all the gate signal lines 17a and the period (T3) in which the off-voltage is applied may be alternately repeated. Further, as shown in FIG. 349, an on-voltage is applied to the even-numbered gate signal line 17a, and in this case, an off-voltage is applied to the odd-numbered gate signal line 17a. A state in which an on-voltage is applied to the gate signal line 17a and an off-voltage is applied to the even-numbered gate signal line 17a may be alternately repeated.
[0470]
In FIG. 341, a voltage of V1 = Vm−2 (V) is applied to the base anode line 2631. The reason why the voltage V1 = Vm−2 (V) is applied is to turn off the TFT 11a so that no current flows into the pixel electrode 105. To prevent current from flowing, the source (S) terminal of the driving TFT 11a may be opened as shown in FIG. By opening the source terminal, no current flows between the channels of the TFT 11a. Opening can be easily realized by opening the switch 561 (see FIG. 343). Alternatively, the connection point between the power supply circuit 82 and the base anode line 2631 may be removed.
[0471]
350, the voltage Vm applied from the source driver circuit 14 to the source signal line 18 can be applied to the pixel electrode 105 (Vm voltage can be applied to the anode side of the EL element 15). Further, a Vdd voltage can be applied from the power supply circuit 82 to the cathode side of the EL element 15, and a reverse bias voltage can be applied to the EL element 15.
[0472]
In the above-described embodiment, the Vm voltage is written on the anode side of the EL element 15 by sequentially selecting the gate signal line 17a, selecting the gate signal line 17a, or selecting the gate signal line 17a at a predetermined cycle. By writing the Vm voltage, the potential is accurately determined on the anode side of the EL element 15. However, if the purpose is to apply a reverse bias voltage to the EL element 15, the anode potential of the EL element 15 need not be accurate (predetermined value). For example, there may be an error of about ± 2 (V) from the Vm voltage.
[0473]
Therefore, unlike the embodiment of FIG. 351, the on / off state of the gate signal lines 17a and 17b is not timing-controlled, the off voltage is applied to the gate signal line 17a, and the TFT 11b and TFT 11c are maintained in the off state. An on voltage may be applied to the signal line 17b to keep the TFT 11d on. In this state, the V1 voltage is applied to the base anode line 2631 and the V2 voltage is applied to the base cathode line 2671 as shown in FIG. In this case, the potential Vc of the pixel electrode 105 is divided by the inter-channel voltage of the TFT 11a and the inter-terminal voltage of the EL element 15 (basically determined by the impedance of both elements). Accordingly, the Vc voltage is not an accurate value, but at least the relationship of Vc> V1 and Vc <V2 is satisfied, and therefore a reverse bias voltage is applied to the EL element 15.
[0474]
The above embodiment has been described by exemplifying the pixel configuration of FIG. However, the present invention is not limited to this. For example, as shown in FIG. 352, the reverse bias voltage drive of the present invention can be implemented even with a current mirror pixel configuration. Further, as shown in FIG. 353, it is needless to say that the reverse bias voltage driving of the present invention can also be implemented by a voltage driving pixel configuration. Even in the pixel configurations of FIG. 352 and FIG. 353, the reverse bias voltage driving method is the same as or similar to the method or configuration described above, and thus description thereof is omitted.
[0475]
As described above, deterioration of the EL element 15 can be prevented by the reverse bias voltage driving of the present invention. However, measures using only the drive system are not perfect. This is because the EL element 15 causes burn-in when the luminance decreases by 1 to 5%. The burn-in in the case of the liquid crystal display panel disappears by driving for 1 to 2 hours. However, the burn-in of the EL display panel is a deterioration of the EL element 15 and therefore does not disappear once.
[0476]
In order to counter this problem, the EL display panel (device) of the present invention has a display area for one character in both the vertical and horizontal directions with respect to the display screen 50 of horizontal M characters and vertical N characters as shown in FIG. . As shown in FIG. 355, if one character is expressed by horizontal D1 dots × vertical D2 dots, the number of dots is larger than the number of display dots originally required by the horizontal D1 dots and vertical D2 dots. have.
[0477]
The burn-in occurs because the fixed pattern is displayed at the same position. Therefore, if the fixed pattern (character or wallpaper) is moved at a constant cycle or interval, the occurrence of image sticking is reduced. The movement cycle (timing, that is, the time interval for moving from one display location state to another display location) is preferably 10 seconds or more and 120 seconds or less. If it is 10 seconds or less, the screen (characters, etc.) moves while the user is gazing at the screen, which is visually unacceptable. On the other hand, if it is displayed at the same position for an excessively long time, printing will occur.
[0478]
The movement interval is preferably within 3 dots. More preferably, it is preferably within 1 dot. If it is 4 dots or more, it is recognized as a large fluctuation state when the screen (characters, etc.) moves while the user is gazing at the screen, which is visually unacceptable. Further, when the power is turned off and the next power is turned on, the previous image display position may be stored in the flash memory.
[0479]
In FIG. 355, the movement from (a) in FIG. 355 to (b) in 355 shows a state in which one dot is moved both vertically and horizontally. However, as shown in FIG. 356, the movement is preferably performed little by little in the vertical direction or the horizontal direction. In FIG. 355, first, the character display position is moved downward (upper left in FIG. 356), then moved one dot left and right, and this time the character display position is moved upward. ing. When it moves to the end (upper right of FIG. 356), it moves in the reverse order of the arrows. This operation is repeated.
[0480]
As described above, by moving the display position, it is possible to significantly reduce the fixed pattern from being burned on the EL display panel.
[0481]
Hereinafter, another driving method of the present invention will be described with reference to the drawings. FIG. 125 is an explanatory diagram of a display panel for carrying out the sequence driving of the present invention. The source driver circuit 14 switches the R, G, B data to the connection terminal 681 and outputs it. Therefore, the number of output terminals of the source driver circuit 14 can be reduced to 1/3 as compared with the case of FIG.
[0482]
A signal output from the source driver circuit 14 to the connection terminal 681 is distributed to the source signal lines 18R, 18G, and 18B by the output switching circuit 1251. The output switching circuit 1251 is directly formed on the substrate 71 by polysilicon technology or amorphous silicon technology. The output switching circuit 1251 may be formed of a silicon chip and mounted on the substrate 71 by COG technology, TAB technology, or COF technology. Further, the output switching circuit 1251 may incorporate the changeover switch 1251 in the source driver circuit 14 as a circuit of the source driver circuit 14.
[0483]
When the changeover switch 1252 is connected to the R terminal, the output signal from the source driver circuit 14 is applied to the source signal line 18R. When the changeover switch 1252 is connected to the G terminal, the output signal from the source driver circuit 14 is applied to the source signal line 18G. When the changeover switch 1252 is connected to the B terminal, the output signal from the source driver circuit 14 is applied to the source signal line 18B.
[0484]
In the configuration of FIG. 126, when the changeover switch 1252 is connected to the R terminal, the G terminal and B terminal of the changeover switch are open. Therefore, the current input to the source signal lines 18G and 18B is 0A. Therefore, the pixels 16 connected to the source signal lines 18G and 18B display black.
[0485]
When the changeover switch 1252 is connected to the G terminal, the R terminal and the B terminal of the changeover switch are open. Therefore, the current input to the source signal lines 18R and 18B is 0A. Therefore, the pixels 16 connected to the source signal lines 18R and 18B display black.
[0486]
In the configuration of FIG. 126, when the changeover switch 1252 is connected to the B terminal, the R terminal and the G terminal of the changeover switch are open. Therefore, the current input to the source signal lines 18R and 18G is 0A. Therefore, the pixels 16 connected to the source signal lines 18R and 18G display black.
[0487]
Basically, when one frame is composed of three fields, R image data is sequentially written in the pixels 16 of the display screen 50 in the first field. In the second field, G image data is sequentially written to the pixels 16 of the display screen 50. In the third field, B images are sequentially written in the pixels 16 of the display screen 50.
[0488]
As described above, R data → G data → B data → R data → G data → B data → R data →. As described with reference to FIGS. 5, 13, and 16, the switching transistor 11 d is turned on / off as shown in FIG. 1 to realize N-fold pulse driving. Needless to say, these driving methods can be combined with sequence driving. Of course, it goes without saying that other driving methods of the present invention and sequence driving can be combined.
[0489]
In the embodiment described above, when image data is written to the R pixel 16, black data is written to the G pixel and the B pixel. When image data is written to the G pixel 16, black data is written to the R pixel and the B pixel. When image data is written to the B pixel 16, black data is written to the R pixel and the G pixel. The present invention is not limited to this.
[0490]
For example, when image data is written to the R pixel 16, the image data of the G pixel and the B pixel may hold the image data rewritten in the previous field. By driving in this way, the brightness of the screen 50 can be increased. When the image data is written to the G pixel 16, the image data of the R pixel and the B pixel is retained as the image data rewritten in the previous field. When writing image data to the B pixel 16, the image data of the G pixel and the R pixel holds the image data rewritten in the previous field.
[0491]
As described above, in order to hold image data of pixels other than the color pixel being rewritten, the gate signal line 17a may be controlled independently by RGB pixels. For example, as shown in FIG. 125, the gate signal line 17aR is a signal line for controlling on / off of the transistors 11b and 11c of the R pixel. The gate signal line 17aG is a signal line for controlling on / off of the transistors 11b and 11c of the G pixel. The gate signal line 17aB is a signal line for controlling on / off of the transistors 11b and 11c of the B pixel. On the other hand, the gate signal line 17b is a signal line that turns on and off the transistors 11d of the R pixel, the G pixel, and the B pixel in common.
[0492]
With the above configuration, when the source driver circuit 14 outputs R image data and the switch 1252 is switched to the R contact, an ON voltage is applied to the gate signal line 17aR, and the gate signal line aG and the gate An off voltage can be applied to the signal line aB. Accordingly, R image data can be written to the R pixel 16, and the G pixel 16 and the B pixel 16 can retain the image data of the field before.
[0493]
In the second field, when the source driver circuit 14 outputs G image data and the switch 1252 is switched to the G contact, an ON voltage is applied to the gate signal line 17aG, and the gate signal line aR, the gate signal line aB, An off-voltage can be applied to. Therefore, the G image data can be written into the G pixel 16, and the R pixel 16 and the B pixel 16 can retain the image data of the field before.
[0494]
When the source driver circuit 14 outputs B image data and the switch 1252 is switched to the B contact in the third field, an ON voltage is applied to the gate signal line 17aB, and the gate signal line aR, the gate signal line aG, An off-voltage can be applied to. Therefore, the B image data can be written to the B pixel 16, and the R pixel 16 and the G pixel 16 can retain the image data of the field before.
[0495]
In the embodiment of FIG. 125, the gate signal line 17a for turning on and off the transistor 11b of the pixel 16 is formed or arranged for each of RGB. However, the present invention is not limited to this. For example, as shown in FIG. 126, a configuration in which a gate signal line 17a common to the RGB pixels 16 is formed or arranged may be employed.
[0496]
In the configuration of FIG. 125 and the like, it has been described that the G source signal line and the B source signal line are opened when the changeover switch 1252 selects the R source signal line. However, the open state is an electrically floating state, which is not preferable.
[0497]
FIG. 126 shows a configuration in which measures are taken to eliminate this floating state. The a terminal of the switch 1252 of the output switching circuit 1251 is connected to the Vaa voltage (voltage for black display). The b terminal is connected to the output terminal of the source driver circuit 14. The switch 1252 is provided for each of RGB.
[0498]
In the state of FIG. 126, the switch 1252R is connected to the Vaa terminal. Therefore, Vaa voltage (black voltage) is applied to the source signal line 18R. The switch 1252G is connected to the Vaa terminal. Therefore, Vaa voltage (black voltage) is applied to the source signal line 18G. The switch 1252B is connected to the output terminal of the source driver circuit 14. Therefore, the B video signal is applied to the source signal line 18B.
[0499]
In the above state, the B pixel is rewritten, and the black display voltage is applied to the R pixel and the G pixel. By controlling the switch 1252 as described above, the image of the pixel 16 is rewritten. Note that the control of the gate signal line 17b and the like are the same as those in the previously described embodiment, and thus the description thereof is omitted.
[0500]
In the above embodiment, the R pixel 16 is rewritten in the first field, the G pixel 16 is rewritten in the second field, and the B pixel 16 is rewritten in the third field. That is, the color of the pixel that is rewritten for each field changes. The present invention is not limited to this. The color of the pixel to be rewritten may be changed every horizontal scanning period (1H). For example, the R pixel is rewritten in the 1H, the G pixel is rewritten in the 2Hth, the B pixel is rewritten in the 3Hth, the R pixel is rewritten in the 4Hth, and so on. Of course, the color of the pixel to be rewritten may be changed every 2H or more horizontal scanning periods, or the color of the pixel to be rewritten may be changed every 1/3 field.
[0501]
FIG. 127 shows an embodiment in which the color of the pixel to be rewritten is changed every 1H. In FIG. 127 to FIG. 129, the pixel 16 shown by hatching indicates that the image data of the previous field is held without rewriting the pixel, or is displayed in black. Of course, it may be repeatedly performed such that the pixel is displayed in black or the data of the previous field is retained.
[0502]
Needless to say, in the driving methods shown in FIGS. 125 to 129, N-fold pulse driving or M-row simultaneous driving as shown in FIG. 125 to 129 and the like illustrate the writing state of the pixel 16. Although the lighting control of the EL element 15 will not be described, it goes without saying that the embodiments described before or after can be combined. Of course, the configuration in which the dummy pixel row 271 described in FIG. 27 is formed and the driving method using the dummy pixel row may be combined.
[0503]
Further, one frame is not limited to being composed of three fields. Two fields or four or more fields may be used. In the case where one frame has two fields and the three primary colors of RGB, an example in which R and G pixels are rewritten in the first field and B pixels are rewritten in the second field is exemplified. In addition, when one frame has four fields and three primary colors of RGB, the R pixel is rewritten in the first field, the G pixel is rewritten in the second field, and the B pixel is rewritten in the third field and the fourth field. An example is illustrated. These sequences can achieve white balance more efficiently by considering the light emission efficiency of the RGB EL elements 15.
[0504]
In the above embodiment, the R pixel 16 is rewritten in the first field, the G pixel 16 is rewritten in the second field, and the B pixel 16 is rewritten in the third field. That is, the color of the pixel that is rewritten for each field changes.
[0505]
In the embodiment of FIG. 127, the R pixel is rewritten in the 1H of the first field, the G pixel is rewritten in the 2Hth, the B pixel is rewritten in the 3Hth, the R pixel is rewritten in the 4Hth, and so on. It is a method of driving. Of course, the color of the pixel to be rewritten may be changed every 2H or more horizontal scanning periods, or the color of the pixel to be rewritten may be changed every 1/3 field.
[0506]
In the embodiment of FIG. 127, the R pixel is rewritten in the 1H of the first field, the G pixel is rewritten in the 2Hth, the B pixel is rewritten in the 3Hth, and the R pixel is rewritten in the 4Hth. The G pixel is rewritten in the 1H of the second field, the B pixel is rewritten in the 2Hth, the R pixel is rewritten in the 3Hth, and the G pixel is rewritten in the 4Hth. The B pixel is rewritten in 1H of the third field, the R pixel is rewritten in the 2Hth, the G pixel is rewritten in the 3Hth, and the B pixel is rewritten in the 4Hth.
[0507]
As described above, R, G, and B color separation can be prevented by rewriting R, G, and B pixels arbitrarily or with a predetermined regularity in each field. In addition, occurrence of flicker can be suppressed.
[0508]
In FIG. 128, the number of colors of pixels 16 rewritten every 1H is plural. In FIG. 127, in the first field, the 1H-th pixel 16 to be rewritten is an R pixel, and the 2H-th pixel 16 to be rewritten is a G pixel. Further, the 3H-th pixel 16 to be rewritten is a B pixel, and the 4H-th pixel 16 to be rewritten is an R pixel.
[0509]
In FIG. 128, the color position of the pixel to be rewritten is different for each 1H. R, G, and B color separation can be prevented by making R, G, and B pixels different in each field (it goes without saying that they may have a predetermined regularity) and sequentially rewriting them. In addition, occurrence of flicker can be suppressed.
[0510]
In the embodiment of FIG. 128 as well, each pixel (a set of RGB pixels) has the same RGB lighting time or light emission intensity. Needless to say, this is also implemented in the embodiments of FIG. 126, FIG. 127, and the like. This is because the color becomes uneven.
[0511]
As shown in FIG. 128, the number of pixels to be rewritten every 1H (in the 1H field of FIG. 128, the three colors R, G, and B are rewritten) is plural in FIG. The source driver circuit 14 is configured to output a video signal of any color (may have a certain regularity) to each output terminal, and the switch 1252 can arbitrarily connect the contacts R, G, and B (a certain rule) It may be configured so that it can be connected.
[0512]
The display panel of the embodiment of FIG. 129 has W (white) pixels 16W in addition to the three primary colors RGB. By forming or arranging the pixel 16W, the color peak luminance can be satisfactorily realized. In addition, high luminance display can be realized. FIG. 129 (a) shows an embodiment in which R, G, B, and W pixels 16 are formed in one pixel row. FIG. 129 (b) shows a configuration in which RGBW pixels 16 are arranged for each pixel row.
[0513]
It goes without saying that the driving method shown in FIGS. 127 and 128 can also be implemented in the driving method shown in FIG. It goes without saying that N-fold pulse driving, M pixel row simultaneous driving, and the like can be performed. Those matters can be easily realized by those skilled in the art according to the present specification, and the description thereof will be omitted.
[0514]
In order to facilitate the description of the present invention, the display panel of the present invention is described as having three primary colors of RGB, but the present invention is not limited to this. In addition to RGB, cyan, yellow, and magenta may be added, or a display panel using any one of R, G, and B, and any two colors of R, G, and B may be used.
[0515]
In the above sequence driving method, although RGB is operated for each field, it goes without saying that the present invention is not limited to this. Further, the embodiments of FIGS. 125 to 129 describe a method of writing image data to the pixels 16. It does not describe a method of operating the transistor 11d in FIG. 1 or the like and causing an electric current to flow through the EL element 15 to display an image (which is of course relevant). The current flowing through the EL element 15 is controlled by controlling the transistor 11d in the pixel configuration of FIG.
[0516]
In the driving method shown in FIGS. 127 and 128, RGB images can be sequentially displayed by controlling the transistor 11d (in the case of FIG. 1). For example, FIG. 130 (a) scans the R display area 53R, the G display area 53G, and the B display area 53B from the top to the bottom of the screen (or from the bottom to the top) in one frame (one field) period. . An area other than the RGB display area is a non-display area 52. That is, intermittent driving is performed.
[0517]
FIG. 130 (b) shows an example in which a plurality of RGB display areas 53 are generated in one field (one frame) period. This driving method is similar to the driving method of FIG. Therefore, no explanation will be required. By dividing the display area 53 into a plurality of parts in FIG. 130B, flicker is eliminated even at a lower frame rate.
[0518]
FIG. 131A shows an RGB display area 53 in which the area of the display area 53 is different (it goes without saying that the area of the display area 53 is proportional to the lighting period). In FIG. 131A, the R display area 53R and the G display area 53G have the same area. The area of the B display area 53B is larger than that of the G display area 53G. In the organic EL display panel, the light emission efficiency of B is often poor. As shown in FIG. 131 (a), the B display area 53B is made larger than the display area 53 of other colors, thereby effectively achieving white balance. Will be able to.
[0519]
FIG. 131 (b) shows an example in which the B display period 53B is plural (53B1, 53B2) in one field (frame) period. FIG. 131 (a) shows a method of changing one B display area 53B. By changing it, the white balance can be adjusted well. FIG. 131 (b) improves white balance by displaying a plurality of B display regions 53B having the same area.
[0520]
The drive system of the present invention is not limited to either FIG. 131 (a) or FIG. 131 (b). An object is to generate display areas 53 for R, G, and B, and to intermittently display them, thereby preventing motion blur and improving insufficient writing to the pixels 16. In the driving method of FIG. 16, the display area 53 in which R, G, and B are independent does not occur. RGB is displayed at the same time (should be expressed when the W display area 53 is displayed). Of course, (a) in FIG. 131 and (b) in FIG. 131 may be combined. For example, the driving method for changing the RGB display area 53 in FIG. 131A and generating a plurality of RGB display areas 53 in FIG. 131B is shown.
[0521]
130 to 131 is not limited to the drive system of the present invention shown in FIGS. 125 to 129. As shown in FIG. 41, if the current flowing through the EL element 15 (EL element 15R, EL element 15G, EL element 15B) can be controlled for each of RGB, the driving method shown in FIGS. 130 and 131 can be easily implemented. But not. By applying an on / off voltage to the gate signal line 17bR, the R pixel 16R can be on / off controlled. By applying an on / off voltage to the gate signal line 17bG, the G pixel 16G can be on / off controlled. By applying an on / off voltage to the gate signal line 17bB, the B pixel 16B can be on / off controlled.
[0522]
In order to realize the above driving, as shown in FIG. 132, the gate driver circuit 12bR for controlling the gate signal line 17bR, the gate driver circuit 12bG for controlling the gate signal line 17bG, and the gate signal line 17bB are controlled. The gate driver circuit 12bB to be formed may be formed or arranged. The gate driver circuits 12bR, 12bG, and 12bB in FIG. 132 are driven by the method described with reference to FIG. 6 and the like, whereby the driving method in FIGS. 130 and 131 can be realized. Of course, it is needless to say that the driving method of FIG. 16 can be realized with the configuration of the display panel of FIG.
[0523]
If the black image data is rewritten to the pixels 16 other than the pixel 16 whose image data is to be rewritten with the configuration shown in FIGS. 125 to 128, the gate signal line 17bR for controlling the EL element 15R and the EL element 15G are controlled. Needless to say, the gate signal line 17bG and the gate signal line bB for controlling the EL element 15B are not separated, and the drive system shown in FIGS. 130 and 131 can be realized even if the gate signal line 17b is common to the RGB pixels. .
[0524]
In FIG. 15, FIG. 18, FIG. 21, etc., it is assumed that the gate signal line 17b (EL-side selection signal line) applies ON voltage (Vgl) and OFF voltage (Vgh) in units of one horizontal scanning period (1H). Did. However, the light emission amount of the EL element 15 is proportional to the flow time when the flow current is a constant current. Therefore, it is not necessary to limit the flowing time to 1H unit.
In order to introduce the concept of output enable (OEV), it is defined as follows. By performing the OEV control, an on / off voltage (Vgl voltage, Vgh voltage) can be applied to the pixel 16 to the gate signal lines 17a and 17b within one horizontal scanning period (1H).
For ease of explanation, the display panel of the present invention will be described on the assumption that it is the gate signal line 17a (in the case of FIG. 1) for selecting a pixel row for current programming. The output of the gate driver circuit 12a that controls the gate signal line 17a is called a WR-side selection signal line. The description will be made assuming that the gate signal line 17b (in the case of FIG. 1) for selecting the EL element 15 is used. The output of the gate driver circuit 12b that controls the gate signal line 17b is called an EL-side selection signal line.
[0525]
The gate driver circuit 12 receives a start pulse, and the input start pulse sequentially shifts in the shift register as retained data. Data held in the shift register of the gate driver circuit 12a determines whether the voltage output to the WR side selection signal line is the on voltage (Vgl) or the off voltage (Vgh). Further, an OEV1 circuit (not shown) that forcibly turns off the output is formed or arranged at the output stage of the gate driver circuit 12a. When the OEV1 circuit is at the L level, the WR side selection signal that is the output of the gate driver circuit 12a is output to the gate signal line 17a as it is. If the above relationship is logically illustrated, the relationship shown in FIG. 224 (a) is obtained (an OR circuit). The on-voltage is a logic level L (0), and the off-voltage is a logic voltage H (1).
[0526]
That is, when the gate driver circuit 12a outputs an off voltage, the off voltage is applied to the gate signal line 17a. When the gate driver circuit 12a outputs an on-voltage (logic L level), the OR circuit takes an OR with the output of the OEV1 circuit and outputs it to the gate signal line 17a. That is, when the OEV1 circuit is at the H level, the voltage output to the gate driver signal line 17a is set to the off voltage (Vgh) (see the timing chart example in FIG. 176).
[0527]
Data held in the shift register of the gate driver circuit 12b determines whether the voltage output to the gate signal line 17b (EL-side selection signal line) is the on voltage (Vgl) or the off voltage (Vgh). Further, an OEV2 circuit (not shown) for forcibly turning off the output is formed or arranged at the output stage of the gate driver circuit 12b. When the OEV2 circuit is at L level, the output of the gate driver circuit 12b is output as it is to the gate signal line 17b. If the above relationship is illustrated logically, the relationship shown in FIG. The on-voltage is a logic level L (0), and the off-voltage is a logic voltage H (1).
[0528]
  That is, when the gate driver circuit 12b outputs the off voltage (the EL side selection signal is the off voltage), the off voltage is applied to the gate signal line 17b. When the gate driver circuit 12b outputs an ON voltage (logic L level), the OR circuit takes an OR with the output of the OEV2 circuit and outputs it to the gate signal line 17b. In other words, when the input signal is at the H level, the OEV2 circuitGate signal lineThe voltage output to 17b is turned off (Vgh). Therefore, even if the EL side selection signal of the OEV2 circuit is in the ON voltage output state, the signal forcibly output to the gate signal line 17b becomes the OFF voltage (Vgh). If the input of the OEV2 circuit is L, the EL side selection signal is output through to the gate signal line 17b (see the timing chart example in FIG. 176).
[0529]
  The screen brightness is adjusted by the control of OEV2. There is a permissible range of brightness that can change depending on the screen brightness. FIG. 175 illustrates the relationship between the allowable change (%) and the screen brightness (nt). As can be seen from FIG. 175, the allowable change amount is relatively small in a relatively dark image. Therefore, the brightness adjustment of the screen 50 by the control by the OEV2 or the duty ratio control is controlled in consideration of the screen 50 brightness. Allowable change due to control is when the screen is darker than bright.smallTo do.
[0530]
FIG. 140 shows the 1/4 duty ratio drive. During the 1H period in the 4H period, the ON voltage is applied to the gate signal line 17b (EL-side selection signal line), and the position where the ON voltage is applied in synchronization with the horizontal synchronizing signal (HD) is scanned. Therefore, the on-time is 1H unit.
[0531]
  However, the present invention is not limited to this, and as shown in FIG.more than(FIG. 143 may be 1 / 2H), or may be 1H or less. That is, it is not limited to 1H units, and generation other than 1H units is easy. An OEV2 circuit formed or arranged at the output stage of the gate driver circuit 12b (a circuit for controlling the gate signal line 17b) may be used. Since the OEV2 circuit is the same as the OEV1 circuit described above, description thereof is omitted.
[0532]
In FIG. 141, the ON time of the gate signal line 17b (EL-side selection signal line) does not have 1H as a unit. The on-voltage is applied to the gate signal line 17b (EL-side selection signal line) in the odd pixel row for a period of less than 1H. The on-voltage is applied to the gate signal line 17b (EL-side selection signal line) in the even pixel row for an extremely short period. Further, an on-voltage time T1 applied to the gate signal line 17b (EL-side selection signal line) of the odd-numbered pixel row and an on-voltage time T2 applied to the gate signal line 17b (EL-side selection signal line) of the even-numbered pixel row. The added time is set to be 1H period. FIG. 141 shows the state of the first field.
[0533]
In the second field next to the first field, the ON voltage is applied to the gate signal line 17b (EL-side selection signal line) of the even-numbered pixel row for a period of less than 1H. The ON voltage is applied to the gate signal line 17b (EL-side selection signal line) in the odd-numbered pixel row for an extremely short period. Further, an on-voltage time T1 applied to the gate signal line 17b (EL-side selection signal line) of the even-numbered pixel row and an on-voltage time T2 applied to the gate signal line 17b (EL-side selection signal line) of the odd-numbered pixel row. The added time is set to be 1H period.
[0534]
As described above, the sum of the ON times applied to the gate signal lines 17b (EL-side selection signal lines) in a plurality of pixel rows is made constant, and the lighting time of the EL elements 15 in each pixel row in a plurality of fields. May be constant.
[0535]
  142 shows the ON time of the gate signal line 17b (EL-side selection signal line).But1.5HIndicates the caseis doing. Further, the rising and falling of the gate signal line 17b (EL-side selection signal line) at the point A overlap each other. The gate signal line 17b (EL-side selection signal line) and the source signal line 18 are coupled. Therefore, when the waveform of the gate signal line 17b (EL-side selection signal line) changes, the change in waveform penetrates to the source signal line 18. When potential fluctuation occurs in the source signal line 18 due to this penetration, the accuracy of current (voltage) programming is lowered, and the characteristic unevenness of the driving transistor 11a is displayed.
[0536]
142, at point A, the gate signal line 17B (EL-side selection signal line) (1) changes from the on-voltage (Vgl) application state to the off-voltage (Vgh) application state. The gate signal line 17B (EL-side selection signal line) (2) changes from the off voltage (Vgh) application state to the on voltage (Vgl) application state. Therefore, at point A, the signal waveform of the gate signal line 17B (EL-side selection signal line) (1) and the signal waveform of the gate signal line 17B (EL-side selection signal line) (2) cancel each other. Therefore, even if the source signal line 18 and the gate signal line 17B (EL-side selection signal line) are coupled, the waveform change of the gate signal line 17B (EL-side selection signal line) does not penetrate into the source signal line 18. Absent. Therefore, good current (voltage) programming accuracy can be obtained, and uniform image display can be realized.
[0537]
FIG. 142 shows an example in which the on-time is 1.5H. However, the present invention is not limited to this, and it goes without saying that the ON voltage application time may be 1H or less as shown in FIG.
[0538]
The brightness of the display screen 50 can be linearly adjusted by adjusting the period during which the ON voltage is applied to the gate signal line 17B (EL-side selection signal line). This can be easily realized by controlling the OEV2 circuit. For example, in FIG. 145, the display luminance is lower in FIG. 145 (b) than in FIG. 145 (a). In addition, the display luminance is lower in (c) of FIG. 145 than in (b) of FIG.
[0539]
FIG. 109 illustrates the relationship between the signal waveforms of OEV2 and the gate signal line 17b. In FIG. 109, (a) in FIG. 109 has the shortest period during which OEV2 is at the L level. Therefore, since the period during which the on-voltage is applied to the gate signal line 17b is short, the current period flowing through the EL element 15 is shortened. This state is a state where the duty ratio is small as a result. In FIG. 109 (b), the period during which OEV2 becomes L level next is long. Further, FIG. 109 (c) has a longer period during which OEV2 is at the L level than FIG. 109 (b). For this reason, the duty ratio in FIG. 109 (c) is larger than the duty ratio in FIG. 109 (b).
[0540]
Note that the embodiments of FIGS. 109A, 109B, and 109C perform duty ratio control in a period shorter than 1H. However, the present invention is not limited to this, and the duty ratio control may be performed in units of 1H as illustrated in FIG. FIG. 109 (d) shows an example with a duty ratio of 1/2.
In FIG. 109A, the period during which OEV2 is at the L level is the shortest. Therefore, since the period during which the on-voltage is applied to the gate signal line 17b is short, the current period flowing through the EL element 15 is shortened. This state is a state where the duty ratio is small as a result. In FIG. 109A, the period during which OEV2 is at the L level is the shortest. Therefore, since the period during which the on-voltage is applied to the gate signal line 17b is short, the current period flowing through the EL element 15 is shortened. This state is a state where the duty ratio is small as a result.
In addition, as illustrated in FIG. 146, a set of a period in which the on-voltage is applied and a period in which the off-voltage is applied in the 1H period may be provided a plurality of times. FIG. 146 (a) shows an embodiment provided six times. FIG. 146 (b) shows an embodiment provided three times. FIG. 146 (c) shows an embodiment provided once. In FIG. 146, the display brightness is lower in FIG. 146 (b) than in FIG. 146 (a). In addition, the display brightness is lower in (c) of FIG. 146 than in (b) of FIG. Therefore, the display luminance can be easily adjusted (controlled) by controlling the number of ON periods.
[0541]
Hereinafter, the current driver type source driver IC (circuit) 14 of the present invention will be described. The source driver IC of the present invention is used to realize the driving method and driving circuit of the present invention described above. Further, it is used in combination with the driving method, driving circuit, and display device of the present invention. Although the description will be made with reference to an IC chip, the present invention is not limited to this, and it goes without saying that it may be produced on the substrate 71 of the display panel using a low-temperature polysilicon technique, an amorphous silicon technique, or the like.
[0542]
First, FIG. 55 shows an example of a conventional current-driven driver circuit. However, FIG. 55 is a principle for explaining the current driver type source driver IC (source driver circuit) 14 of the present invention.
[0543]
In FIG. 55, reference numeral 551 denotes a D / A converter. An n-bit data signal is input to the D / A converter 551, and an analog signal is output from the D / A converter based on the input data. This analog signal is input to the operational amplifier 552. The operational amplifier 552 is input to the N-channel transistor 471a, and the current flowing through the transistor 471a flows through the resistor 531. The terminal voltage of the resistor R becomes the negative input of the operational amplifier 552, and the negative terminal voltage and the positive terminal of the operational amplifier 552 become the same voltage. Therefore, the output voltage of the D / A converter 551 becomes the terminal voltage of the resistor 531.
[0544]
If the resistance value of the resistor 531 is 1 MΩ and the output of the D / A converter 551 is 1 (V), a current of 1 (V) / 1 MΩ = 1 (μA) flows through the resistor 531. This is a constant current circuit. Therefore, the analog output of the D / A converter 551 changes according to the value of the data signal, and a predetermined current flows through the resistor 531 based on the value of the analog output, and becomes the program current Iw.
[0545]
However, the circuit scale of the DA conversion circuit 551 is large. The circuit scale of the operational amplifier 552 is also large. If the DA converter circuit 551 and the operational amplifier 552 are formed in one output circuit, the size of the source driver IC 14 becomes enormous. Therefore, it is impossible to produce practically.
[0546]
The present invention has been made in view of this point. The source driver circuit 14 of the present invention has a circuit configuration and a layout configuration for reducing the scale of the current output circuit and minimizing variations in output current between the current output terminals as much as possible.
[0547]
FIG. 47 shows a configuration diagram of one embodiment of the current-driven source driver IC (circuit) 14 of the present invention. FIG. 47 shows a multistage current mirror circuit when the current source has a three-stage configuration (471, 472, 473) as an example.
[0548]
In FIG. 47, the current value of the first-stage current source 471 is copied to N (where N is an arbitrary integer) second-stage current sources 472 by a current mirror circuit. Further, the current value of the second stage current source 472 is copied to M (where M is an arbitrary integer) third stage current sources 473 by a current mirror circuit. With this configuration, as a result, the current value of the first stage current source 471 is copied to N × M third stage current sources 473.
[0549]
For example, when the source signal line 18 of the QCIF display panel is driven by one source driver IC 14, the output is 176 (because the source signal line needs 176 outputs for each RGB). In this case, N is 16 and M = 11. Therefore, 16 × 11 = 176, which corresponds to 176 outputs. In this way, by setting one of N or M to 8 or 16, or a multiple thereof, the layout design of the current source of the driver IC is facilitated.
[0550]
In the current driver type source driver IC (circuit) 14 using the multistage current mirror circuit of the present invention, the current value of the first stage current source 471 is directly applied to the N × M third stage current sources 473 as described above. Instead of copying with the current mirror circuit, the second-stage current source 472 is provided in the middle, so that variations in transistor characteristics can be absorbed there.
[0551]
  In particular, the present invention is characterized in that the first stage current mirror circuit (current source 471) and the second stage current mirror circuit (current source 472) are closely arranged. The first-stage current source 471 to the third-stage current source 473 (that is, the two-stage configuration of the current mirror circuit) are connected to the first-stage current source.3The number of stage current sources 473 is large, and the first stage current source 471 and the third stage current source 473 cannot be disposed closely.
[0552]
Like the source driver circuit 14 of the present invention, the current of the first stage current mirror circuit (current source 471) is copied to the second stage current mirror circuit (current source 472), and the second stage current mirror circuit ( In this configuration, the current of the current source 472) is copied to the current mirror circuit (current source 472) in the third stage. In this configuration, the number of second-stage current mirror circuits (current sources 472) connected to the first-stage current mirror circuits (current sources 471) is small. Therefore, the first-stage current mirror circuit (current source 471) and the second-stage current mirror circuit (current source 472) can be closely arranged.
[0553]
If the transistors constituting the current mirror circuit can be arranged in close proximity, naturally, the variation of the transistors is reduced, so that the variation in the copied current value is also reduced. Further, the number of third-stage current mirror circuits (current sources 473) connected to the second-stage current mirror circuits (current sources 472) is also reduced. Therefore, the second-stage current mirror circuit (current source 472) and the third-stage current mirror circuit (current source 473) can be closely arranged.
[0554]
That is, as a whole, the transistors in the current receiving section of the first-stage current mirror circuit (current source 471), the second-stage current mirror circuit (current source 472), and the third-stage current mirror circuit (current source 473) Can be placed closely. Accordingly, since the transistors constituting the current mirror circuit can be closely arranged, the variation of the transistors is reduced, and the variation of the current signal from the output terminal is extremely reduced (high accuracy).
[0555]
  In the present invention, they are expressed as current sources 471, 472, and 473, or as current mirror circuits. These are used synonymously. That is, the current source is a basic configuration concept of the present invention, and when the current source is specifically configured, it becomes a current mirror circuit. Therefore, the current source is not limited to the current mirror circuit, but the operational amplifier 552 and the transistor.471aAnd a constant current circuit composed of a combination of resistors R.
[0556]
FIG. 48 is a structural diagram of a more specific source driver IC (circuit) 14. FIG. 48 illustrates a portion of the third current source 473. That is, the output unit is connected to one source signal line 18. As a final stage current mirror configuration, a plurality of current mirror circuits of the same size (unit transistors 484 (one unit)) are configured, and the number of bits is weighted corresponding to the bits of the image data.
[0557]
The transistors constituting the source driver IC (circuit) 14 of the present invention are not limited to the MOS type but may be a bipolar type. Moreover, it is not limited to a silicon semiconductor, and a gallium arsenide semiconductor may be used. Further, a germanium semiconductor may be used. Further, the substrate may be formed directly by polysilicon technology such as low-temperature polysilicon or amorphous silicon technology.
[0558]
As is apparent from FIG. 48, a case of 6-bit digital input is shown as one embodiment of the present invention. That is, since it is 2 6, it is a 64 gradation display. By mounting the source driver IC 14 on the array substrate, red (R), green (G), and blue (B) have 64 gradations, so that 64 × 64 × 64 = about 260,000 colors can be displayed. Become.
[0559]
In the case of 64 gradations, there are one D0 bit unit transistor 484, two D1 bit unit transistors 484, four D2 bit unit transistors 484, eight D3 bit unit transistors 484, and D4 bit units. Since there are 16 unit transistors 484 and 32 D5-bit unit transistors 484, the total number of unit transistors 484 is 63. In other words, the present invention configures (forms) one unit transistor 484 with one output number of gradations (in this example, 64 gradations) minus one unit transistor 484. Even when one unit transistor is divided into a plurality of sub-unit transistors, the unit transistor is simply divided into sub-unit transistors. Therefore, there is no difference (synonymous) in that the present invention is composed of unit transistors with the number of grayscale representations minus one.
[0560]
In FIG. 48, D0 indicates the LSB input, and D5 indicates the MSB input. When the D0 input terminal is at the H level (positive logic), the switch 481a (on / off means. Of course, it may be constituted by a single transistor or an analog switch in which a P channel transistor and an N channel transistor are combined). ) Turns on. Then, a current flows toward a current source (1 unit) 484 constituting the current mirror. This current flows through the internal wiring 483 in the source driver IC 14. Since the internal wiring 483 is connected to the source signal line 18 via the terminal electrode of the source driver IC 14, the current flowing through the internal wiring 483 becomes the program current of the pixel 16.
[0561]
For example, when the D1 input terminal is at the H level (positive logic), the switch 481b is turned on. Then, current flows toward the two current sources (1 unit) 484 constituting the current mirror. This current flows through the internal wiring 483 in the source driver IC 14. Since the internal wiring 483 is connected to the source signal line 18 via the terminal electrode of the source driver IC 14, the current flowing through the internal wiring 483 becomes the program current of the pixel 16.
[0562]
The same applies to the other switches 481. When the D2 input terminal is at the H level (positive logic), the switch 481c is turned on. Then, current flows toward the four current sources (1 unit) 484 constituting the current mirror. When the D5 input terminal is at the H level (positive logic), the switch 481f is turned on. Then, current flows toward 32 current sources (1 unit) 484 constituting the current mirror.
[0563]
As described above, according to data (D0 to D5) from the outside, a current flows toward the corresponding current source (1 unit). Therefore, the current flows from 0 to 63 current sources (one unit) according to the data.
[0564]
  In the present invention, for ease of explanation, the number of current sources is 63, which is 6 bits. However, the present invention is not limited to this. In the case of 8 bits, 255 unit transistors 484 may be formed (arranged). In the case of 4 bits, 15 unit transistors 484 may be formed (arranged). The transistors 484 constituting the unit current source have the same channel width W and channel.LongLet L be. By configuring with the same transistor in this way, an output stage with little variation can be configured.
[0565]
Further, all the unit transistors 484 are not limited to flowing the same current. For example, each unit transistor 484 may be weighted. For example, the current output circuit may be configured by mixing one unit unit transistor 484, a double unit transistor 484, a quadruple unit transistor 484, and the like. However, if the unit transistors 484 are weighted, the weighted current sources do not have a weighted ratio, and there is a possibility of variation. Therefore, even in the case of weighting, each current source is preferably configured by forming a plurality of transistors serving as one unit of current source.
[0566]
The size of the transistor constituting the unit transistor 484 needs to be a certain size or more. The smaller the transistor size, the greater the variation in output current. The size of the transistor 484 is a size obtained by multiplying the channel length L by the channel width W. For example, if W = 3 μm and L = 4 μm, the size of the transistor 484 constituting one unit current source is W × L = 12 square μm. The reason why the variation increases as the transistor size decreases is considered to be due to the influence of the crystal interface state of the silicon wafer. Therefore, when one transistor is formed across a plurality of crystal interfaces, the output current variation of the transistor is reduced.
[0567]
FIG. 119 shows the relationship between transistor size and output current variation. The horizontal axis of the graph in FIG. 119 is the transistor size (square μm). The vertical axis shows the variation in output current in%. However, the variation% of the output current is that the unit current source (one unit transistor) 484 is formed of 63 groups (63 units are formed), and a large number of these groups are formed on the wafer, and the variation of the output current is reduced. I have found it. Therefore, although the horizontal axis of the graph is shown as the size of a transistor constituting one unit current source (the size of the unit transistor 484), the area is 63 times because there are 63 actual transistors in parallel. However, in FIG. 119, the size of the unit transistor 484 is considered as a unit. Therefore, in FIG. 119, when 63 unit transistors 484 of 30 square μm are formed, the variation in output current at that time is 0.5%.
[0568]
In the case of 64 gradations, 100/64 = 1.5%. Therefore, the output current variation needs to be within 1.5%. In order to make it 1.5% or less from FIG. 119, the size of the unit transistor needs to be 2 square μm or more (63 unit transistors of 2 square μm operate in 64 gradations). On the other hand, the transistor size is limited. This is because the IC chip size increases and the lateral width per output is limited. From this point, the upper limit of the size of the unit transistor 484 is 300 square μm. Therefore, in the 64 gradation display, the size of the unit transistor 484 needs to be 2 square μm or more and 300 square μm or less.
[0569]
In the case of 128 gradations, 100/128 = 1%. Therefore, the output current variation needs to be within 1%. In order to obtain 1% or less from FIG. 119, the size of the unit transistor needs to be 8 square μm or more. Therefore, in 128 gradation display, the size of the unit transistor 484 needs to be 8 square μm or more and 300 square μm or less.
[0570]
Generally, when the number of gradations is K and the size of the unit transistor 484 is St (square μm),
The relationship of 40 ≦ K / √ (St) and St ≦ 300 is satisfied.
More preferably, it is preferable to satisfy the relationship of 120 ≦ K / √ (St) and St ≦ 300.
[0571]
The above example is a case where 63 transistors are formed with 64 gradations. In the case of configuring 64 gradations with 127 unit transistors 484, the size of the unit transistor 484 is a size obtained by adding two unit transistors 484. For example, if there are 64 gradations, the size of the unit transistor 484 is 10 square μm, and 127 are formed, the size of the unit transistor needs to be in the column of 10 × 2 = 20 in FIG. Similarly, in 64 gradations, if the size of the unit transistor 484 is 10 square μm and 255 are formed, it is necessary to see the column of 10 × 4 = 40 for the size of the unit transistor in FIG.
[0572]
The unit transistor 484 needs to consider not only the size but also the shape. This is to reduce the influence of kink. Kink is a phenomenon in which the current flowing through the unit transistor 484 changes when the source (S) -drain (D) voltage of the unit transistor 484 is changed while the gate voltage of the unit transistor 484 is kept constant. To tell. When there is no kink effect (ideal state), the current flowing through the unit transistor 484 does not change even when the voltage applied between the source (S) and the drain (D) is changed.
[0573]
  The influence of the kink occurs because of the variation in Vt of the driving transistor 11a shown in FIG.PotentialIs different. The source driver circuit 14 supplies a program current to the source signal line 18 so that the program current flows to the pixel driving transistor 11a. With this program current, the gate terminal voltage of the drive transistor 11a changes, and the program current flows through the drive transistor 11a. As can be seen from FIG. 3, when the selected pixel 16 is in the programmed state, the gate terminal voltage of the driving transistor 11a is equal to the potential of the source signal line 18.
[0574]
Therefore, the potential of the source signal line 18 varies depending on the Vt variation of the driving transistor 11a of each pixel 16. The potential of the source signal line 18 becomes the source-drain voltage of the unit transistor 484 of the source driver circuit 14. That is, the source-drain voltage applied to the unit transistor 484 varies depending on the Vt variation of the driving transistor 11a of the pixel 16, and the source-drain voltage causes variation in the output current due to the kink in the unit transistor 484.
[0575]
FIG. 123 is a graph of deviation (variation) from the unit transistor L / W and the target value. When the L / W ratio of the unit transistor is 2 or less, the deviation from the target value is large (the slope of the straight line is large). However, as L / W increases, the deviation of the target value tends to decrease. When the unit transistor L / W is 2 or more, the change in deviation from the target value is small. The deviation (variation) from the target value is L / W = 2 or more and 0.5% or less. Therefore, it can be adopted in the source driver circuit 14 as transistor accuracy. Note that L is the channel length of the unit transistor 484, and W is the channel width of the unit transistor.
[0576]
However, the channel length L of the unit transistor 484 cannot be increased as much as possible. This is because the longer L is, the larger the source driver IC 14 is. Further, the gate terminal voltage of the unit transistor 484 increases, and the power supply voltage required for the source driver IC 14 increases. When the power supply voltage increases, it is necessary to adopt a high breakdown voltage IC process. The source driver IC 14 formed by the high breakdown voltage IC process has a large output variation of the unit transistor 484 (see FIG. 121 and its description). According to the results of the study, L / W is preferably set to 100 or less. More preferably, L / W is preferably 50 or less.
[0577]
From the above, the unit transistor L / W is preferably set to 2 or more. L / W is preferably 100 or less. More preferably, L / W is preferably 40 or less.
[0578]
The magnitude of L / W also depends on the number of gradations. When the number of gradations is small, there is no problem even if the output current of the unit transistor 484 varies due to the kink because the difference between the gradations is large. However, in a display panel with a large number of gradations, the difference between the gradations is small, so that the number of gradations is reduced if the output current of the unit transistor 484 varies even slightly due to the influence of kink.
[0579]
In consideration of the above, the source driver circuit 14 of the present invention sets the number of gradations to K and L / W of the unit transistor 484 (L is the channel length of the unit transistor 484 and W is the channel width of the unit transistor). Time,
(√ (K / 16)) ≦ L / W ≦ and (√ (K / 16)) × 20
It is configured (formed) to satisfy this relationship. This relationship is illustrated in FIG. The upper side of the straight line in FIG. 120 is an implementation range of the present invention.
[0580]
The variation in the output current of the unit transistor 484 also depends on the withstand voltage of the source driver IC 14. The breakdown voltage of the source driver IC generally means the power supply voltage of the IC. For example, with a 5 (V) breakdown voltage, the power supply voltage is used at a standard voltage of 5 (V). The IC withstand voltage may be read as the maximum usable voltage. These breakdown voltages are standardized and held by semiconductor IC manufacturers as a 5 (V) breakdown voltage process and a 10 (V) breakdown voltage process.
[0581]
It is considered that the IC withstand voltage affects the output variation of the unit transistor 484 due to the film quality and film thickness of the gate insulating film of the transistor 484. A transistor 484 manufactured by a process with high IC breakdown voltage has a thick gate insulating film. This is to prevent dielectric breakdown even when a high voltage is applied. When the insulating film is thick, it becomes difficult to control the gate insulating film thickness, and the film quality variation of the gate insulating film also increases. As a result, the variation of the transistors increases. In addition, the mobility of a transistor manufactured by a high breakdown voltage process is low. If the mobility is low, the characteristics differ only by a small change in the electrons injected into the gate of the transistor. Therefore, the variation of the transistors increases. Therefore, in order to reduce the variation of the unit transistors 484, it is preferable to employ an IC process having a low IC withstand voltage.
[0582]
FIG. 121 illustrates the relationship between the IC breakdown voltage and the output variation of the unit transistor 484. With respect to the variation ratio of the vertical axis, the variation of the unit transistor 484 is set to 1 by the 1.8 (V) breakdown voltage process. FIG. 121 shows the output variation of the unit transistor 484 manufactured by each withstand voltage process when the shape L / W of the unit transistor 484 is 12 (μm) / 6 (μm). In addition, a plurality of unit transistors are formed in each IC withstand voltage process, and output current variation is obtained. However, the breakdown voltage process is 1.8 (V) breakdown voltage, 2.5 (V) breakdown voltage, 3.3 (V) breakdown voltage, 5 (V) breakdown voltage, 8 (V) breakdown voltage, 10 (V) breakdown voltage, 15 ( V) A discrete value such as a withstand voltage. However, for ease of explanation, the variation of the transistors formed at each breakdown voltage is entered in a graph and connected by a straight line.
[0583]
As can be seen from FIG. 121, the increase rate of the variation ratio (the output current variation of the unit transistor 484) with respect to the IC process is small until the IC breakdown voltage is about 9 (V). However, when the IC withstand voltage is 10 (V) or more, the slope of the variation ratio with respect to the IC withstand voltage increases.
[0584]
In FIG. 121, the variation ratio within 3 is a variation allowable range in 64 gradation to 256 gradation display. However, this variation ratio varies depending on the area of the unit transistor 484 and L / W. However, even if the shape of the unit transistor 484 is changed, there is almost no difference in the variation tendency of the variation ratio with respect to the IC breakdown voltage. When the IC withstand voltage is 9 to 10 (V) or more, the variation ratio tends to increase.
[0585]
On the other hand, the potential of the output terminal 681 in FIG. 48 changes depending on the program current of the driving transistor 11 a of the pixel 16. The gate terminal voltage of the driving transistor 11a is almost equal to the potential of the source signal line 18. Further, the potential of the source signal line 18 becomes the potential of the output terminal 681 of the source driver IC (circuit) 14. The gate terminal potential Vw when the driving transistor 11a of the pixel 16 passes white raster (maximum white display) current is used. A gate terminal potential Vb when the driving transistor 11a of the pixel 16 passes a black raster (full black display) current is used. The absolute value of Vw−Vb needs to be 2 (V) or more. Further, when the Vw voltage is applied to the terminal 681, the channel-to-channel voltage of the unit transistor 484 needs to be 0.5 (V).
[0586]
Therefore, the output terminal 681 (the terminal 681 is connected to the source signal line 18 and the gate terminal voltage of the driving transistor 11a of the pixel 16 is applied during current programming) from 0.5 (V) to ((Vw A voltage of −Vb) +0.5) (V) is applied. Since Vw−Vb is 2 (V), a maximum of 2 (V) +0.5 (V) = 2.5 (V) is applied to the terminal 681. Therefore, even if the output voltage (current) of the source driver IC 14 has a rail-to-rail circuit configuration (a circuit configuration capable of outputting a voltage up to the IC power supply potential), an IC withstand voltage of 2.5 (V) is required. . The required amplitude range of the terminal 741 is 2.5 (V) or more.
[0587]
From the above, it is preferable to use a process with a withstand voltage of the source driver IC 14 of 2.5 (V) or more and 10 (V) or less. More preferably, the source driver IC 14 has a withstand voltage of 3 (V) or more and 9 (V) or less.
[0588]
  In addition, the above description is a source driver IC.14As for the withstand voltage process, a process of 2.5 (V) to 10 (V) is used. However, this withstand voltage is also applied to an embodiment in which the source driver circuit 14 is formed directly on the substrate 71 (low temperature polysilicon process or the like). The use withstand voltage of the source driver circuit 14 formed on the substrate 71 may be as high as 15 (V) or more. In this case, the power supply voltage used for the source driver circuit 14 may be replaced with the IC withstand voltage shown in FIG. Even in the source driver IC 14, the IC withstand voltage may be replaced with the power supply voltage to be used.
[0589]
  The area of the unit transistor 484 is correlated with variations in output current. FIG. 122 is a graph when the area of the unit transistor 484 is constant and the transistor width W of the unit transistor 484 is changed. Figure122The unit transistor 484 has a channel width W = 2 (μm) variation of 1. The vertical axis of the graph is when the variation of channel width W = 2 (μm) is 1.Variation ratioIt is.
[0590]
As shown in FIG. 122, the variation ratio of the unit transistor gradually increases from 2 (μm) to 9 to 10 (μm), and the variation ratio tends to increase when the unit transistor exceeds 10 (μm). Also, the variation ratio tends to increase when the channel width W = 2 (μm) or less.
[0591]
  In FIG. 122, the variation ratio within 3 is a variation allowable range in 64 gradation to 256 gradation display. However, this variation ratio is the same as that of the unit transistor 484.shapeVaries by However, the unit transistor 484shapeEven if you changeChannel width WThere is almost no difference in the variation tendency of the variation ratio.
[0592]
From the above, the channel width W of the unit transistor 484 is preferably 2 (μm) or more and 10 (μm) or less. More preferably, the channel width W of the unit transistor 484 is preferably 2 (μm) or more and 9 (μm) or less. However, when the number of gradations is 64, there is no practical problem even if the channel width W is 2 (μm) or more and 15 (μm) or less.
[0593]
As shown in FIG. 52, the current flowing through the second-stage transistor 472b is copied to the transistor 473a constituting the third-stage current mirror circuit. When the current mirror magnification is 1, this current is transferred to the transistor 473b. Flowing into. This current is copied to the unit transistor 484 in the final stage.
[0594]
Since the portion corresponding to D0 is composed of one unit transistor 484, it is a current value flowing through the unit transistor 473 of the final stage current source. Since the portion corresponding to D1 is composed of two unit transistors 484, the current value is twice that of the final stage current source. Since D2 is composed of four unit transistors 484, the current value is four times that of the final stage current source, and the portion corresponding to D5 is composed of 32 transistors. The current value is 32 times that of the stage current source. However, this is a case where the mirror ratio of the last stage current mirror circuit is 1.
[0595]
  The program current Iw is output to the source signal line through the switch controlled by the 6-bit image data D0, D1, D2,..., D5 (current is drawn). Therefore, according to the ON / OFF of the 6-bit image data D0, D1, D2,..., D5, the output line is 1 time, 2 times, 4 times,. A current of 32 times is added and output. That is, a current value 0 to 63 times that of the final stage current source 473 is output from the output line by 6-bit image data D0, D1, D2,..., D5 (current is drawn from the source signal line 18).).
[0596]
  actually,77As shown in the figure, the source driver IC 14 is configured such that reference currents (IaR, IaG, IaB) for R, G, and B can be adjusted by a resistor 491 (491R, 491G, 491B) or the like. The white balance can be easily adjusted by adjusting the reference current Ia.
  In order to realize full color display on an EL display panel, it is necessary to form (create) a reference current for each of RGB. White balance can be adjusted by the ratio of RGB reference currents. In the case of the current driving method, the present invention also determines the current value that the unit transistor 484 flows from one reference current. Therefore, if the magnitude of the reference current is determined, the current that the unit transistor 484 flows can be determined. For this reason, if R, G, and B reference currents are set, white balance can be obtained in all gradations. The above items are the effects that are exhibited because the source driver circuit 14 has a current step output (current drive). Therefore, the point is how the reference current can be set for each RGB.
  The luminous efficiency of the EL element is determined by the thickness of the EL material deposited or applied. Or it is the dominant factor. The film thickness is almost constant from lot to lot. Therefore, if the formed film thickness of the EL element 15 is managed as a lot, the relationship between the current passed through the EL element 15 and the light emission luminance is determined. That is, the current value for white balance is fixed for each lot.
[0597]
FIG. 49 shows an example of a circuit diagram of 176 outputs (N × M = 176) by a three-stage current mirror circuit. 49, the current source 471 based on the first stage current mirror circuit is referred to as a parent current source, the current source 472 based on the second stage current mirror circuit is referred to as a child current source, and the current source 473 based on the third stage current mirror circuit is referred to as a grandchild current source. ing. With a configuration of an integral multiple of the current source by the third stage current mirror circuit which is the final stage current mirror circuit, variation in 176 outputs is suppressed as much as possible, and highly accurate current output is possible.
[0598]
Note that the dense arrangement means that the first current source 471 and the second current source 472 are arranged at a distance of at least 8 mm (current or voltage output side and current or voltage input side). . Furthermore, it is preferable to arrange within 5 mm. This is because, if it is within this range, it is arranged in the silicon chip by examination, and the difference in transistor characteristics (Vt, mobility (μ)) hardly occurs. Similarly, the second current source 472 and the third current source 473 (current output side and current input side) are also arranged at a distance of at least 8 mm. More preferably, it is preferable to arrange at a position within 5 mm. Needless to say, the above matters also apply to other embodiments of the present invention.
[0599]
The current or voltage output side and the current or voltage input side mean the following relationship. In the case of the voltage delivery in FIG. 50, the relation is that the transistors 471 (output side) of the (I) -th current source and the transistors 472a (input side) of the (I + 1) -th current source are closely arranged. In the case of the current delivery in FIG. 51, the relationship is that the transistors 471a (output side) of the (I) -th current source and the transistors 472b (input side) of the (I + 1) -th current source are closely arranged.
[0600]
Note that although the number of transistors 471 is one in FIGS. 49 and 50, the present invention is not limited to this. For example, the unit transistor 484 may be configured by forming a plurality of small sub-transistors 471 and connecting the source or drain terminals of the plurality of sub-transistors to the resistor 491. By connecting a plurality of small sub-transistors in parallel, variations in the unit transistors 484 can be reduced.
[0601]
Similarly, although the number of transistors 472a is one, it is not limited to this. For example, a plurality of small transistors 472a may be formed, and a plurality of gate terminals of the transistor 472a may be connected to a gate terminal of the transistor 471. By connecting a plurality of small transistors 472a in parallel, variation in the transistors 472a can be reduced.
[0602]
Therefore, the structure of the present invention includes a structure in which one transistor 471 and a plurality of transistors 472a are connected, a structure in which a plurality of transistors 471 and one transistor 472a are connected, and a plurality of transistors 471 and a plurality of transistors. A configuration in which the transistor 472a is connected is exemplified. The above embodiment will be described in detail later.
[0603]
The above items also apply to the structures of the transistor 473a and the transistor 473b in FIG. A configuration in which one transistor 473a and a plurality of transistors 473ba are connected, a configuration in which a plurality of transistors 473a and one transistor 473b are connected, and a configuration in which a plurality of transistors 473a and a plurality of transistors 473b are connected Illustrated. This is because variation of the transistors 473 can be reduced by connecting a plurality of small transistors 473 in parallel.
[0604]
The above items can also be applied to the relationship with the transistors 472a and 472b in FIG. In addition, the transistor 473b in FIG. 48 is preferably formed using a plurality of transistors. Similarly, the transistor 473 in FIGS. 56 and 57 is preferably formed using a plurality of transistors.
[0605]
Here, the source driver IC 14 is described as being formed of a silicon chip, but the present invention is not limited to this. The source driver IC 14 may be another semiconductor chip formed such as a gallium substrate or a germanium substrate. The unit transistor 484 may be a bipolar transistor, a CMOS transistor, an FET, a bi-CMOS transistor, or a DMOS transistor. However, from the viewpoint of reducing the output variation of the unit transistor 484, the unit transistor 484 is preferably composed of a CMOS transistor.
[0606]
The unit transistor 484 is preferably composed of an N channel. The unit transistor composed of P-channel transistors has an output variation of 1.5 times that of a unit transistor composed of N-channel transistors.
[0607]
Since the unit transistor 484 of the source driver IC 14 is preferably composed of an N-channel transistor, the program current of the source driver IC 14 is a drawing current from the pixel 16 to the source driver IC. Therefore, the driving transistor 11a of the pixel 16 is formed of a P channel. The switching transistor 11d shown in FIG. 1 is also a P-channel transistor.
[0608]
From the above, the configuration in which the unit transistor 484 in the output stage of the source driver IC (circuit) 14 is configured by an N-channel transistor, and the driving transistor 11a of the pixel 16 is configured by a P-channel transistor is characteristic of the present invention. It is a configuration. Note that all of the transistors 11 (transistors 11a, 11b, 11c, and 11d) included in the pixel 16 may be formed as a P channel. Since the process for forming the N-channel transistor can be eliminated, cost reduction and high yield can be realized.
[0609]
Although the unit transistor 484 is formed in the source driver IC 14, it is not limited to this. The source driver circuit 14 may be formed by low-temperature polysilicon technology. Also in this case, the unit transistor 484 in the source driver circuit 14 is preferably composed of an N-channel transistor.
[0610]
FIG. 51 shows an embodiment of a current delivery configuration. FIG. 50 shows an example of a voltage delivery configuration. 50 and 51 are the same as the circuit diagrams, and the layout configuration, that is, the way of wiring is different. In FIG. 50, 471 is a first-stage current source N-channel transistor, 472a is a second-stage current source N-channel transistor, and 472b is a second-stage current source P-channel transistor.
[0611]
In FIG. 51, 471a is a first-stage current source N-channel transistor, 472a is a second-stage current source N-channel transistor, and 472b is a second-stage current source P-channel transistor.
[0612]
In FIG. 50, the gate voltage of the first-stage current source composed of the variable resistor 491 (used to change the current) and the N-channel transistor 471 is the gate voltage of the N-channel transistor 472a of the second-stage current source. Therefore, the layout configuration is a voltage delivery system.
[0613]
On the other hand, in FIG. 51, the gate voltage of the first-stage current source composed of the variable resistor 491 and the N-channel transistor 471a is applied to the gate of the N-channel transistor 472a of the adjacent second-stage current source, and as a result, Since the flowing current value is transferred to the P-channel transistor 472b of the second-stage current source, the layout configuration is a current transfer method.
[0614]
In the embodiment of the present invention, the relationship between the first current source and the second current source is mainly described for the sake of easy explanation or easy understanding. However, the present invention is not limited to this. Needless to say, the present invention can also be applied (applicable) in the relationship between the second current source and the third current source, or in the relationship with other current sources.
[0615]
In the layout configuration of the voltage transfer type current mirror circuit shown in FIG. 50, the N-channel transistor 471 of the first-stage current source and the N-channel transistor 472a of the second-stage current source that constitute the current mirror circuit are separated from each other. (It should be easy to get away from each other.) Therefore, the transistor characteristics of the two are likely to be different. Therefore, the current value of the first stage current source is not accurately transmitted to the second stage current source, and variations tend to occur.
[0616]
On the other hand, in the layout configuration of the current transfer type current mirror circuit shown in FIG. 51, the N-channel transistor 471a of the first-stage current source and the N-channel transistor 472a of the second-stage current source that constitute the current mirror circuit are adjacent to each other. Therefore, the transistor characteristics of the two are hardly different, the current value of the first stage current source is accurately transmitted to the second stage current source, and variations are less likely to occur.
[0617]
From the above, the circuit configuration of the multi-stage current mirror circuit of the present invention (the current-driven source driver IC (circuit) 14 of the present invention has a layout configuration that does not pass voltage but passes current). Of course, the above embodiments can be applied to other embodiments of the present invention.
[0618]
For convenience of explanation, the case of the first stage current source to the second stage current source is shown, but the second stage current source to the third stage current source, the third stage current source to the fourth stage current source,. Needless to say, the same applies to multi-stages such as. In addition, it goes without saying that the present invention may adopt a one-stage current source configuration (see FIGS. 48, 164, 165, 166, etc.).
FIG. 52 shows an example in which the current mirror circuit (three-stage current source) having the three-stage configuration shown in FIG. 49 is configured as a current delivery system (therefore, FIG. 49 shows a circuit configuration of the voltage delivery system). ).
[0619]
In FIG. 52, first, a reference current is created by the variable resistor 491 and the N-channel transistor 471. Although the reference current is adjusted by the variable resistor 491, the source voltage of the transistor 471 is actually set by an electronic volume circuit formed (or arranged) in the source driver IC (circuit) 14. Configured to be adjusted. Alternatively, the reference current is adjusted by supplying the current output from the current-type electronic volume composed of a large number of current sources (one unit) 484 as shown in FIG. 48 directly to the source terminal of the transistor 471. (See FIG. 53).
[0620]
The gate voltage of the first-stage current source by the transistor 471 is applied to the gate of the N-channel transistor 472a of the adjacent second-stage current source, and as a result, the current value flowing through the transistor is the P-channel transistor 472b of the second-stage current source. Is passed on. In addition, the gate voltage of the second current source transistor 472b is applied to the gate of the N-channel transistor 473a of the adjacent third-stage current source, and as a result, the current value flowing through the transistor is the N-channel of the third-stage current source. Passed to the transistor 473b. A large number of unit transistors 484 shown in FIG. 48 are formed (arranged) on the gate of the N-channel transistor 473b of the third stage current source according to the required number of bits.
[0621]
In FIG. 53, the first-stage current source 471 of the multistage current mirror circuit includes a current value adjusting element. With this configuration, the output current can be controlled by changing the current value of the first stage current source 471.
[0622]
The Vt variation (characteristic variation) of the transistors varies about 100 (mV) within one wafer. However, the Vt variation of transistors formed close to each other within 100 μm is at least 10 (mV) or less (actual measurement). That is, by forming transistors in close proximity to form a current mirror circuit, output current variation of the current mirror circuit can be reduced. Therefore, variations in output current at each terminal of the source driver IC can be reduced.
[0623]
Note that the transistor variation is described as Vt, but the transistor variation is not limited to Vt. However, since Vt variation is a main factor of transistor characteristic variation, Vt variation = transistor variation will be described for easy understanding.
[0624]
FIG. 118 shows measurement results of the transistor formation area (square millimeters) and the output current variation of the single transistor 484. The output current variation is a current variation at the Vt voltage. Black spots are transistor output current variations of evaluation samples (10 to 200) produced within a predetermined formation area. The transistor formed in the region A (formation area within 0.5 square millimeter) in FIG. 118 has almost no output current variation (almost only an output current variation in an error range. That is, a constant output current is Output). Conversely, in the C region (formation area of 2.4 square millimeters or more), the variation in output current with respect to the formation area tends to increase rapidly. In the region B (formation area of 0.5 square millimeters or greater and 2.4 square millimeters or less), the variation in output current with respect to the formation area is in a substantially proportional relationship.
[0625]
However, the absolute value of the output current varies from wafer to wafer. However, this problem can be addressed by adjusting the reference current or setting it to a predetermined value in the source driver IC (circuit) 14 of the present invention. Moreover, it can respond (solve) by circuit devices, such as a current mirror circuit.
[0626]
The present invention changes (controls) the amount of current flowing through the source signal line 18 by switching the number of currents flowing through the unit transistor 484 according to the input digital data (D). If the number of gradations is 64 gradations or more, 1/64 = 0.015, so theoretically, it is necessary to make the output current variation within 1-2%. In addition, it is difficult to visually discriminate output variations within 1%, and it is almost impossible to discriminate below 0.5% (appears uniform).
[0627]
In order to make the output current variation (%) within 1%, it is necessary to make the formation area of the transistor group (transistor for which the occurrence of variation is suppressed) within 2 square millimeters as shown in the result of FIG. . More preferably, output current variation (that is, transistor Vt variation) is preferably within 0.5%. As shown in the result of FIG. 118, the formation area of the transistor group 521 may be set within 1.2 square millimeters. The formation area is an area of length × width. For example, as an example, 1.2 mm2 is 1 mm × 1.2 mm.
[0628]
The same applies to the set of unit transistors 484 (for 64 gradations, a set of 63 transistors 484 (see FIG. 48, etc.). The formation area of the set of unit transistors 484 is within 2 square millimeters. More preferably, the formation area of the unit transistor set 484 should be within 1.2 square millimeters.
[0629]
The above is particularly the case of 8 bits (256 gradations) or more. In the case of 256 gradations or less, for example, in the case of 6 bits (64 gradations), the variation in output current may be about 2% (the actual state is not problematic in image display). In this case, the transistor group 521 may be formed within 5 square millimeters. Further, both of the transistor groups 521 (two transistor groups 521a and 521b are illustrated in FIG. 52) do not need to satisfy this condition. If at least one (one or more transistor groups 521 when there are three or more) is configured to satisfy this condition, the effect of the present invention is exhibited. In particular, it is preferable to satisfy this condition with respect to the lower-order transistor group 521 (the relationship in which 521a is the higher order and 521b is the lower order). This is because a problem in image display is less likely to occur.
[0630]
In the source driver IC (circuit) 14 of the present invention, as shown in FIG. 52, a plurality of current sources such as a parent, a child, and a grandchild are connected in multiple stages, and the current sources are arranged densely (of course, A two-stage connection of a parent and a child may be used). In addition, current is passed between the current sources (between the transistor groups 521). Specifically, a range (transistor group 521) surrounded by a dotted line in FIG. 52 is densely arranged. The transistor group 521 is in a voltage transfer relationship. Further, the parent current source 471 and the child current source 472a are formed or arranged at substantially the center of the source driver IC 14 chip. This is because the distance between the transistor 472a constituting the child current source arranged on the left and right of the chip and the transistor 472b constituting the child current source can be made relatively short. That is, the uppermost transistor group 521a is arranged at the substantially central portion of the IC chip. Then, lower transistor groups 521b are arranged on the left and right of the source driver IC. Preferably, the lower transistor group 521b is arranged, formed, or manufactured so that the number of the lower transistor groups 521b is substantially equal on the left and right of the IC chip. The above items are not limited to the source driver IC 14, but also apply to the source driver circuit 14 formed directly on the substrate 71 by the low temperature polysilicon technique or the high temperature polysilicon technique. The same applies to other matters.
[0631]
In the present invention, one transistor group 521a is configured, arranged, formed, or manufactured at a substantially central portion of the source driver IC 14, and eight transistor groups 521b are formed on the left and right sides of the chip (N = 8 + 8, FIG. 47). The child transistor group 521b is equal to the left and right of the chip, or the number of transistor groups 521b formed or arranged on the left side and the position formed or arranged on the right side of the chip with respect to the position where the parent at the center of the chip is formed. It is preferable that the difference between the number of the transistor groups 521b formed is 4 or less. Furthermore, it is preferable that the difference between the number of transistor groups 521b formed or arranged on the left side of the chip and the number of transistor groups 521b formed or arranged on the right side of the chip be within one. . The above matters are the same for the transistor group (not shown in FIG. 52) as a grandchild.
[0632]
Voltage transfer (voltage connection) is performed between the parent current source 471 and the transistor 472a. Therefore, it is easily affected by the Vt variation of the transistor. Therefore, the transistor group 521a is densely arranged. The formation area of the transistor group 521a is formed within an area of 2 square millimeters as shown in FIG. More preferably, it is formed within 1.2 mm 2. Of course, when the number of gradations is 64 gradations or less, it may be within 5 square millimeters.
[0633]
Since data is transferred (current transfer) between the transistor group 521a and the child transistor 472b, a distance may flow. This distance range (for example, the distance from the output terminal of the upper transistor group 521a to the input terminal of the lower transistor 521b) is the same as that of the transistor 472a constituting the second current source (child) as described above. The transistor 472b constituting the second current source (child) is arranged at a distance of at least 10 mm. This is preferably arranged or formed within 8 mm. Furthermore, it is preferable to arrange within 5 mm.
[0634]
This is because the difference in the characteristics (Vt, mobility (μ)) of the transistors arranged in the silicon chip by examination will hardly affect the current delivery. In particular, this relationship is preferably implemented by a lower-order transistor group. For example, if the transistor group 521a is higher, the lower is the transistor group 521b, and the lower is the transistor group 521c, the current transfer between the transistor group 521b and the transistor group 521c is satisfied. Therefore, the present invention is not limited to all the transistor groups 521 satisfying this relationship. It is only necessary that at least one transistor group 521 satisfies this relationship. This is because the number of transistor groups 521 increases especially in the lower order.
[0635]
The same applies to the transistor 473a constituting the third current source (grandchild) and the transistor 473b constituting the third current source. Needless to say, the present invention can also be applied to voltage transfer.
[0636]
The transistor group 521b is formed, fabricated, or arranged in the left-right direction of the chip (longitudinal direction, that is, at a position facing the output terminal 681). The transistor group 521b is formed, fabricated, or arranged in the left-right direction of the chip (longitudinal direction, that is, at a position facing the output terminal 681). The number M of the transistor groups 521b is 11 in the present invention (see FIG. 47).
[0637]
A voltage is passed (voltage connected) between the transistor 472b and the grandchild current source 473a. Therefore, as in the transistor group 521a, the transistor group 521b is densely arranged. The formation area of this transistor group 521b is formed within an area of 2 square millimeters as shown in FIG. More preferably, it is formed within 1.2 mm 2. However, if the Vt of the transistor group 521b varies slightly, it is easily recognized as an image. Therefore, it is preferable that the formation area be an A region (within 0.5 square millimeters) in FIG. 118 so that the variation hardly occurs.
[0638]
Since data is exchanged (current exchange) between the grandchild transistor 473a and the transistor 473b in the transistor group 521b, a slight distance may flow. This distance range is the same as described above. The transistor 473a constituting the third current source (grandchild) and the transistor 473b constituting the second current source (grandchild) are arranged at a distance of at least 8 mm. Furthermore, it is preferable to arrange within 5 mm.
[0639]
FIG. 53 shows a case where the current value control element is composed of an electronic regulator. The electronic volume includes a resistor 531 (which generates a current limit and each reference voltage. The resistor 531 is formed of polysilicon), a decoder 532, a level shifter 533, and the like. The electronic volume outputs a current. The transistor 481 functions as an analog switch circuit.
[0640]
In the source driver IC (circuit) 14, the transistor may be described as a current source. This is because a current mirror circuit composed of transistors functions as a current source.
[0641]
The electronic volume circuit is formed (or arranged) according to the number of colors of the EL display panel. For example, in the case of three primary colors of RGB, it is preferable to form (or arrange) three electronic volume circuits corresponding to each color so that each color can be adjusted independently. However, when one color is used as a reference (fixed), an electronic volume circuit of −1 number of colors is formed (or arranged).
[0642]
  FIG. 68 shows a configuration in which a resistance element 491 that controls the reference current independently for the three primary colors RGB is formed (arranged). Of course, it goes without saying that the resistance element 491 may be replaced with an electronic regulator. The resistance element 491 may be built in the source driver IC (circuit) 14. A basic current source such as a current source 471 and a current source 472 such as a parent current source and a child current source is provided in a region shown in FIG.WhenArrange closely. By arranging them densely, output variations from the source signal lines 18 are reduced. As shown in FIG. 68, a current output circuit is provided at the center of the IC chip (circuit) 14.691(It is not limited to the current output circuit. It may be a reference current generating circuit unit or a controller unit.691Is an area in which no output circuit is formed), it becomes easy to evenly distribute current from the current sources 471 and 472 to the left and right of the IC chip (circuit) 14. Therefore, left and right output variations are unlikely to occur.
[0643]
However, the present invention is not limited to being arranged in the current output circuit 654 at the center. You may form in the one end or both ends of an IC chip. Further, it may be formed or arranged in parallel with the output current circuit 654.
[0644]
Forming the controller or the output current circuit 654 in the center of the source driver IC 14 is not preferable because it is easily affected by the Vt distribution of the unit transistor 484 of the source driver IC 14 (the Vt of the wafer is smooth in the wafer). This is because a random distribution occurs).
[0645]
In the circuit configuration of FIG. 52, one transistor 473a and one transistor 473b are connected in a one-to-one relationship. Also in FIG. 51, one transistor 472a and one transistor 472b are connected in a one-to-one completion. The same applies to FIG. 49 and the like.
[0646]
  However, if one transistor and one transistor are connected in a one-to-one relationship, the characteristics of the corresponding transistor (Vt, etc.)ButVariation occurs in the output of the transistor connected to the transistor.
[0647]
An example of a configuration for solving this problem is the configuration of FIG. In the configuration of FIG. 58, for example, a transmission transistor group 521b (521b1, 521b2, 521b3) including four transistors 473a and a transmission transistor group 521c (521c1, 521c2, 521c3) including four transistors 473b are connected. However, although the transfer transistor group 521b and the transfer transistor group 521c are each configured by four transistors 473, the present invention is not limited to this, and it goes without saying that it may be 3 or less or 5 or more. That is, the reference current Ib flowing through the transistor 473a is output by the plurality of transistors 473 that form a current mirror circuit with the transistor 473a, and the output current is received by the plurality of transistors 473b.
[0648]
It is preferable that the plurality of transistors 473a and the plurality of transistors 473b have substantially the same size and the same number. Further, the number of unit transistors 484 constituting one output (63 in the case of 64 gradations as shown in FIG. 48) and the number of unit transistors 484 and transistors 473b constituting the current mirror are substantially the same size and the same. It is preferable to use a number. Specifically, the difference between the size of the unit transistor 484 and the size of the transistor 473b is preferably within ± 25%. With the above configuration, the current magnification can be set with high accuracy, and variations in output current are reduced. Note that the area of the transistor is an area obtained by multiplying the channel length L of the transistor by the channel width W of the transistor.
[0649]
Note that the current Ib flowing through the transistor 473b is preferably set so that the current Ib flowing through the transistor 473b is five times or more. This is because the gate potential of the transistor 473a is stabilized and the occurrence of a transient phenomenon due to the output current can be suppressed.
[0650]
In addition, four transistors 473a are arranged adjacent to the transfer transistor group 521b1, the transfer transistor group 521b2 is arranged adjacent to the transfer transistor group 521b1, and the four transistors 473a are adjacent to the transfer transistor group 521b2. However, the present invention is not limited to this. For example, the transistor 473a of the transfer transistor group 521b1 and the transistor 473a of the transfer transistor group 521b2 may be arranged or formed so that their positional relationships are interlaced with each other. By varying the positional relationship (the arrangement of the transistors 473 is exchanged between the transmission transistor groups 521), the variation in output current (program current) at each terminal can be further reduced.
[0651]
By configuring the current passing transistor with a plurality of transistors in this way, variations in output current as a whole transistor group are reduced, and variations in output current (program current) at each terminal can be further reduced.
[0652]
The total formation area of the transistors 473 constituting the transmission transistor group 521 is an important item. Basically, the larger the total formation area of the transistors 473, the smaller the variation of the output current (program current flowing from the source signal line 18). That is, the variation decreases as the formation area of the transfer transistor group 521 (the total formation area of the transistors 473) increases. However, if the formation area of the transistor 473 increases, the chip area increases and the price of the source driver IC 14 increases.
[0653]
Note that the formation area of the transfer transistor group 521 is the total area of the transistors 473 constituting the transfer transistor group 521. The area of the transistor 473 is an area obtained by multiplying the channel length L of the transistor 473 and the channel width W of the transistor 473. Therefore, if the transistor 521 is composed of 10 transistors 473, the channel length L of the transistor 473 is 10 μm, and the channel width W of the transistor 473 is 5 μm, the formation area Tm (square μm) of the transfer transistor group 521 is 10 μm × 5 μm × 10 = 500 (square μm).
[0654]
  The formation area of the transmission transistor group 521 is the unit transistor 484.WhereIt is necessary to maintain a certain relationship. Further, it is necessary to maintain a predetermined relationship between the transfer transistor group 521a and the transfer transistor group 521b.
[0655]
  The relation between the formation area of the transistor group 521 and the unit transistor 484 will be described. Figure48However, as shown, a plurality of unit transistors 484 are connected corresponding to one transistor 473b. In the case of 64 gradations, there are 63 unit transistors 484 corresponding to one transistor 473b (in the case of the configuration in FIG. 48). The formation area Ts (square μm) of this unit transistor group (in this example, 63 unit transistors 484) is the unit transistor.484If the channel length L is 10 μm and the channel width W of the transistor 473 is 10 μm, then 10 μm × 10 μm × 63 = 6300 square μm.
[0656]
The transistor 473b in FIG. 48 corresponds to the transfer transistor group 521c in FIG. The formation area Ts of the unit transistor group and the formation area Tm of the transfer transistor group 521c are set as follows.
[0657]
1/4 ≦ Tm / Ts ≦ 6
More preferably, the formation area Ts of the unit transistor group and the formation area Tm of the transmission transistor group 521c have the following relationship.
[0658]
1/2 ≦ Tm / Ts ≦ 4
By satisfying the above relationship, variations in output current (program current) at each terminal can be reduced.
[0659]
  BiographyThe formation area Tmm of the transmission transistor group 521b is set to have the following relationship with the formation area Tms of the transmission transistor group 521c.
[0660]
1/2 ≦ Tmm / Tms ≦ 8
More preferably, the formation area Ts of the unit transistor group and the formation area Tm of the transmission transistor group 521c have the following relationship.
[0661]
1 ≦ Tmm / Tms ≦ 4
By satisfying the above relationship, variations in output current (program current) at each terminal can be reduced.
[0662]
When the output current Ic1 from the transistor group 521b1, the output current Ic2 from the transistor group 521b2, and the output current Ic3 from the transistor group 521b2, it is necessary to match the output current Ic1, the output current Ic2, and the output current Ic3. In the present invention, since the transistor group 521 includes a plurality of transistors 473, even if the individual transistors 473 vary, the transistor group 521 does not vary in output current Ic.
[0663]
  The above embodiment is not limited to the configuration of the three-stage current mirror connection (multi-stage current mirror connection) as shown in FIG. Needless to say, this can also be applied to a one-stage current mirror connection. 52, the transistor group 521b (521b1, 521b2, 521b3,...) Composed of a plurality of transistors 473a and the transistor group 521c (521c1, 521c2, 521c3,...) Composed of a plurality of transistors 473b. ..)). However, the present invention is not limited to this, and a transistor group 521c (521c1, 521c2, 521c3,...) Including one transistor 473a and a plurality of transistors 473b may be connected. In addition, a transistor group 521b (521b1, 521b2, 521b3,...) Including a plurality of transistors 473a and one transistor473b may be connected.
[0664]
48, switch 481a corresponds to the 0th bit, switch 481b corresponds to the 1st bit, switch 481c corresponds to the 2nd bit,... Switch 481f corresponds to the 5th bit. The 0th bit is composed of one unit transistor, the 1st bit is composed of 2 unit transistors, the 2nd bit is composed of 4 unit transistors, the 5th bit is composed of 32 unit transistors. . For ease of explanation, the source driver circuit 14 is assumed to be 64-bit display and 6 bits.
[0665]
In the configuration of the source driver IC (circuit) 14 of the present invention, the first bit outputs a program current twice as large as the 0th bit. The second bit outputs a program current twice that of the first bit. The third bit outputs a program current twice that of the second bit. The fourth bit outputs a program current twice that of the third bit. The fifth bit outputs a program current twice that of the fourth bit. Conversely, each adjacent bit needs to be configured to output exactly twice the program current.
[0666]
The configuration of FIG. 58 reduces the variation in output current at each terminal by receiving the output currents of the plurality of transistors 473a by the plurality of transistors 473b. FIG. 60 shows a configuration in which variations in output current are reduced by supplying a reference current from both sides of a transistor group. That is, a plurality of current Ib supply sources are provided. In the present invention, the current Ib1 and the current Ib2 have the same current value, and a transistor that generates the current Ib1, a transistor that generates the current Ib2, and a pair of transistors constitute a current mirror circuit.
[0667]
Therefore, the present invention has a configuration in which a plurality of transistors (current generating means) for generating a reference current that defines the output current of the unit transistor 484 are formed or arranged. More preferably, the output current from the plurality of transistors is connected to a current receiving circuit such as a transistor constituting a current mirror circuit, and the output current of the unit transistor 484 is controlled by the gate voltage generated by the plurality of transistors. is there. That is, the present invention has a configuration in which a plurality of unit transistors 484 and a plurality of transistors 473b forming a current mirror circuit are formed. In FIG. 58, five transistors 473b forming a current mirror circuit are arranged (formed) for a transistor group in which 63 unit transistors 484 are formed.
[0668]
When the IC chip is a silicon chip, the gate terminal voltage of the unit transistor 484 is preferably set in the range of 0.52 to 0.68 (V). Within this range, the variation in the output current of the unit transistor 484 is reduced. The above matters also apply to other embodiments of the present invention such as FIGS. 163, 164, and 165.
[0669]
In FIG. 60, if the reference current Ib1 and the reference current Ib2 can be individually adjusted, the voltage at the point a and the voltage at the point b of the gate terminal 581 can be freely set. By adjusting the reference currents Ib1 and Ib2, the unit transistors Vt are different on the left and right sides of the source driver IC 14, so that it is possible to correct even when the output current is tilted.
[0670]
The current generated by the transistors constituting the current mirror circuit is preferably transferred by a plurality of transistors. Variations in characteristics occur in the transistors formed in the source driver IC 14. In order to suppress variations in transistor characteristics, there is a method of increasing the transistor size. However, even if the transistor size is increased, the current mirror magnification of the current mirror circuit may be greatly shifted. In order to solve this problem, it is preferable to use a plurality of transistors to exchange current or voltage. If a plurality of transistors are used, even if the characteristics of the transistors vary, the overall characteristic variation becomes small. Also, the accuracy of the current mirror magnification is improved. In total, the IC chip area is also reduced.
[0671]
  In FIG. 58, a transistor group 521a and a transistor group 521b constitute a current mirror circuit. Transistorgroup521a includes a plurality of transistors 472b. On the other hand, the transistor group 521b includes a transistor 473a. Similarly, the transistor group 521c includes a plurality of transistors 473b.
[0672]
The transistor groups 521b1, transistor groups 521b2, transistor groups 521b3, transistor groups 521b4,... Are formed in the same number. Further, the total area of the transistors 473a in each transistor group 521b (WL size of the transistors 473a in the transistor group 521b × number of transistors 473a) is formed to be (substantially) equal. The same applies to the transistor group 521c.
[0673]
The total area of the transistor 473b of the transistor 521c (WL size of the transistor 473b in the transistor group 521c × number of transistors 473b) is Sc. Further, the total area of the transistors 473a in the transistor 521b (WL size of the transistors 473a in the transistor group 521b × the number of transistors 473a) is defined as Sb. The total area of the transistors 472b in the transistor 521a (WL size of the transistors 472b in the transistor group 521a × number of transistors 472b) is Sa. Further, the total area of one output unit transistor 484 is Sd (in the embodiment of FIG. 48, WL area of unit transistor 484 × 63).
[0674]
The total area Sc and the total area Sb are preferably formed to be substantially equal. The number of transistors 473a included in the transistor group 521b is preferably the same as the number of transistors 473b in the transistor group 521c. However, the number of transistors 473a included in the transistor group 521b is smaller than the number of transistors 473b included in the transistor group 521c due to layout restrictions of the source driver IC 14, and the size of the transistor 473a included in the transistor group 521b is reduced to the transistor group. It may be larger than the size of the transistor 473b of 521c.
[0675]
  This embodiment is illustrated in FIG. The transistor group 521a includes a plurality of transistors 472b. The transistor group 521a and the transistor 473a constitute a current mirror circuit. Transistor 473a generates current Ic. One transistor 473a drives a plurality of transistors 473b in the transistor group 521c (current Ic from one transistor 473a is divided into a plurality of transistors 473b.)In general, the number of transistors 473a is arranged or formed by the number of output circuits. For example, in the case of the QCIF + panel, 176 transistors 473a are formed or arranged in the R, G, and B circuits.
[0676]
The relationship between the total area Sd and the total area Sc correlates with output variations. This relationship is illustrated in FIG. Refer to FIG. 121 for the variation ratio and the like. The variation ratio is 1 when the total area Sd: total area Sc = 2: 1 (Sc / Sd = 1/2). As can be seen from FIG. 124, when Sc / Sd is small, the variation ratio sharply deteriorates. In particular, there is a tendency for Sc / Sd = 1/2 or less to deteriorate. When Sc / Sd is ½ or more, output variation is reduced. The reduction effect is moderate. Further, when Sc / Sd = 1/2, the output variation is within the allowable range. In view of the above, it is preferable to form such that 1/2 <= Sc / Sd. However, as Sc increases, the IC chip size also increases. Therefore, the upper limit is preferably Sc / Sd = 4. That is, the relationship of 1/2 <= Sc / Sd <= 4 is satisfied.
[0677]
A> = B means that A is B or more. A> B means that A is larger than B. A << = B means A is B or less. A <B means that A is smaller than B.
[0678]
Furthermore, it is preferable that the total area Sd and the total area Sc are substantially equal. Furthermore, it is preferable that the number of unit transistors 484 with one output and the number of transistors 473b in the transistor group 521c be the same. That is, in the case of 64 gradation display, 63 unit transistors 484 of 1 output are formed. Accordingly, 63 transistors 473b are included in the transistor group 521c.
[0679]
Preferably, the transistor group 521a, the transistor group 521b, the transistor 521c, and the unit transistor 484 are each formed using a transistor having a WL area ratio of 4 times or less. More preferably, a transistor with a WL area ratio of 2 times or less is preferable. Furthermore, it is preferable that all the transistors be the same size. That is, it is preferable that the current mirror circuit and the output current circuit 654 are configured by transistors having substantially the same shape.
[0680]
The total area Sa is set to be larger than the total area Sb. Preferably, it is configured to satisfy the relationship of 200Sb> = Sa> = 4Sb. Further, the total area of the transistors 473a configuring all the transistor groups 521b and Sa are configured to be substantially equal.
[0681]
In FIG. 60 and the like, transistors or transistor groups are arranged at both ends of the gate wiring 581. Therefore, two transistors are arranged on both sides of the gate wiring 581 or two sets of transistors are included. However, the present invention is not limited to this. As shown in FIG. 61, a transistor or a transistor group may be arranged or formed in the central portion of the gate wiring 581 or the like. In FIG. 61, three transistor groups 521a are formed. The present invention is characterized in that a plurality of transistors or transistor groups 521 are formed in the gate wiring 581. By forming a plurality of gate wirings 581, the impedance of the gate wiring 581 can be reduced, and stability is improved.
[0682]
In order to further improve the stability, it is preferable to form or place a capacitor 661 on the gate wiring 581 as shown in FIG. The capacitor 661 may be formed in the source driver IC 14 or the source driver circuit 14, or may be arranged or stacked outside the chip as an external capacitor of the source driver IC 14. When the capacitor 661 is externally attached, a capacitor connection terminal is arranged on the terminal of the IC chip.
[0683]
In the above embodiment, a reference current is supplied, the reference current is copied by a current mirror circuit, and is transmitted to the unit transistor 484 at the final stage. When the image display is black display (complete black raster), no current flows through any of the unit transistors 484. This is because any switch 481 is open. Therefore, since the current flowing through the source signal line 18 is 0 (A), no power is consumed.
[0684]
However, the reference current flows even in black raster display. For example, the current Ib and the current Ic in FIG. This current becomes a reactive current. It is efficient if the reference current is configured to flow during current programming. Therefore, the reference current is restricted from flowing during the vertical blanking period and the horizontal blanking period of the image. Further, the flow of the reference current is also restricted during the wait period.
[0685]
To prevent the reference current from flowing, the sleep switch 631 may be opened as shown in FIG. The sleep switch 631 is an analog switch. The analog switch is formed in the source driver circuit or the source driver IC 14. Of course, the sleep switch 631 may be disposed outside the source driver IC 14 and the sleep switch 631 may be controlled.
[0686]
By turning off the sleep switch 631, the reference current Ib does not flow. Therefore, since no current flows through the transistor 473a in the transistor group 521a1, the reference current Ic is also 0 (A). Accordingly, no current flows through the transistor 473b of the transistor group 521c. Therefore, power efficiency is improved.
[0687]
FIG. 64 is a timing chart. A blanking signal is generated in synchronization with the horizontal synchronizing signal HD. When the blanking signal is at the H level, it is a blanking period, and when it is at the L level, it is a period during which the video signal is applied. The sleep switch 631 is off (open) when at the L level, and is on when at the H level.
[0688]
Therefore, during the blanking period A, the sleep switch 631 is off, so that the reference current does not flow. During the period D, the sleep switch 631 is on and a reference current is generated.
[0689]
Note that on / off control of the sleep switch 631 may be performed according to the image data. For example, when the image data of one pixel row is all black image data (the program current output to all the source signal lines 18 is 0 during the 1H period), the sleep switch 631 is turned off and the reference current (Ic , Ib, etc.). Further, a sleep switch may be formed or arranged so as to correspond to each source signal line, and on / off control may be performed. For example, when the odd-numbered source signal line 18 is displaying black (vertical black stripe display), the sleep switch corresponding to the odd-numbered source signal line 18 is turned off.
[0690]
52 and 77 are configuration diagrams of the source driver IC (circuit) 14 having a multi-stage connection current mirror configuration. The present invention is not limited to the multi-stage connection configuration shown in FIG. A one-stage source driver circuit 14 may be used. FIGS. 166 to 172, 190, 191, 208, 211, 213, and 214 are configuration diagrams of a one-stage connection source driver IC (circuit). The one-stage configuration has a simple circuit configuration and small output current variation. Also in this case, the unit transistor 484 is composed of an N-channel transistor. Therefore, the program current from the source signal line 18 becomes a sink current. The gate terminal of the unit transistor 484 and the gate terminal of the transistor 473b are connected by a common gate wiring 581. FIG. 166 shows the unit transistor group 521c. It is arranged or formed within a dotted line showing the unit transistor 521c in each drawing.
[0691]
Consider a case where a plurality of source driver ICs (14a, 14b) are arranged adjacent to each other as shown in FIGS. 207, 210, and 228. In the white raster display, it is preferable that the output currents of all the terminals (Iout) coincide with each other without variation. Even if the output current varies, if the output current difference between adjacent output terminals is small, it is not visually recognized as a variation. Note that the variation between adjacent output terminals needs to be within 1%.
[0692]
When the display screen 50 is driven by one source driver IC 14, it is sufficient that the variation between adjacent output terminals is small. However, as shown in FIG. 228, driving a single screen 50 with a plurality of source driver ICs 14 is a problem. This is because there is a difference between the absolute values of the output currents of the source driver IC 14a and the source driver IC 14b.
[0693]
This is because if the absolute value of the output current of Ioutn of the unit transistor group 521 of the source driver IC 14a and the output current of Iout (n + 1) of the unit transistor group 521 of the source driver IC 14b are different, a boundary occurs on the screen 50 due to the adjacent output difference. Hereinafter, a method for solving this problem will be described.
[0694]
In FIG. 167, the transistor 472b and the two transistors 473a constitute a current mirror circuit. The transistors 473a1 and 473a2 are the same size. Accordingly, the current Ic flowing through the transistor 473a1 and the current Ic flowing through the transistor 473a2 are the same.
[0695]
The transistor group 521c and the transistor 473b1 including the unit transistor 484 and the transistor group 521c and the transistor 473b2 including the unit transistor 484 form a current mirror circuit in FIG. Variations occur in the output current of the transistor group 521c. However, the current of the output of the transistor group 521 that forms a current mirror circuit in close proximity is accurately defined.
[0696]
In the source driver IC 14a, the transistor 473b1 and the transistor group 521c1 are arranged close to each other to form a current mirror circuit. In addition, the transistor 473b2 and the transistor group 521cn are arranged close to each other to form a current mirror circuit. Therefore, if the current flowing through the transistor 473b1 is equal to the current flowing through the transistor 473b2, the output current of the transistor group 521c1 and the output current of the transistor group 521cn become equal.
[0697]
Similarly, in the source driver IC 14b, the transistor 473b1 and the transistor group 521c (n + 1) are arranged close to each other to form a current mirror circuit. In addition, the transistor 473b2 and the transistor group 521c (2n) are also arranged close to each other to form a current mirror circuit. Therefore, if the current flowing through the transistor 473b1 is equal to the current flowing through the transistor 473b2, the output current of the transistor group 521c (n + 1) and the output current of the transistor group 521c (2n) are equal.
[0698]
In FIG. 228, the reference voltage Vs is applied to the positive terminal of the operational amplifier 522. An external resistor R1 is connected to the negative terminal of the operational amplifier 522. One terminal of the resistor R1 is connected to a stable voltage Vp. Therefore, the resistor R1, the operational amplifier 522, and the transistor 473 constitute a constant current circuit. The current Ic flowing through the transistor 473 is Ic = (Vs−Vp) / R1. The resistor R1 is an external resistor. However, the resistor R1 is not limited to this and may be incorporated in the source driver IC (circuit) 14. For example, diffused resistors and polysilicon resistors formed in the IC chip are exemplified. Of course, the resistor may be formed by low temperature polysilicon technology. Further, the reference voltages Vs, Vp, etc. may be shared with the power supply voltage Vcc of the source driver IC (circuit) 14. Further, it may be shared with the anode voltage Vdd of the panel.
[0699]
The same reference voltage Vs is applied to the source driver IC 14a and the source driver IC 14b, and a reference current Ic is generated by a constant current circuit including the operational amplifier 552 by the reference voltage Vs (see also FIG. 170 and the like). In the following, for ease of explanation, the resistor R1 is an external resistor of the source driver IC 14 and will be described assuming that one having an accuracy of 1% or less is used.
[0700]
With the above configuration, the current Ic flowing through the transistor 473b1 and the transistor 473b2 of the source driver IC 14a and the current Ic flowing through the transistor 473b1 and the transistor 473b2 of the source driver IC 14b can be made equal. Therefore, the current Ic flowing through the transistor 473b2 of the source driver IC 14a and the transistor 473b1 of the source driver IC 14b can be made equal.
[0701]
In the source driver IC 14a, the transistor 473b2 and the transistor group 521cn are arranged close to each other, so that a highly accurate current mirror circuit is configured. In the source driver IC 14b, the transistor 473b1 and the transistor group 521c (n + 1) are arranged close to each other, so that a highly accurate current mirror circuit is configured. From the above, the output current of the unit transistor group 521cn of the source driver IC 14a and the output current of the unit transistor 521c (n + 1) of the source driver IC 14b are substantially the same. Therefore, the boundary between the source driver IC 14a and the source driver IC 14b on the screen 50 does not occur.
[0702]
As described above, the source driver IC 14 of the present invention is characterized in that it includes the transistor 473b that allows the reference current to flow to the left and right of the chip. For example, as shown in FIG. 207, it is obvious when the source driver IC 14 includes the transistor 473b on only one side. In the configuration of FIG. 207, as shown in FIG. 208, the unit transistor group 521c1 is close to the transistor 473b, so that an accurate current mirror circuit is configured. However, the unit transistor group 521cn and the transistor 473b which are D distance away from the transistor 473b (D is a distance close to the lateral width of the IC chip size) do not have the accuracy of the current mirror circuit.
[0703]
When a plurality of source driver ICs 14 having the configuration of FIG. 208 are arranged as shown in FIG. 207, even when a plurality of transistors 4 of the source driver IC 14a are arranged as shown in FIG. 207, the transistors 473b of the source driver IC 14a and the source drivers are arranged. Even if the same reference current Ic is supplied to the transistor 473b of the IC 14b, as shown in FIG. 209, the output currents at the terminals 681a and 681n are inclined. Therefore, a boundary is generated between the screen 50a driven by the source driver IC 14a and the screen 50b driven by the source driver IC 14b.
[0704]
In the present invention, as shown in FIG. 210, the source driver IC 14 is formed or arranged with transistors 473b (473b1, 473b2) that flow a reference current to the left and right of the chip. A specific circuit configuration is shown in FIG.
[0705]
In the embodiment of FIG. 228, the currents Ic1 and Ic2 flowing through the transistors 473a and 473b of the source driver IC 14 can be made equal by increasing the degree of the external resistor and the accuracy of the reference voltage Vs. Therefore, the output currents in the same gradation of the transistor 473b and the transistor groups 521c1, 521cn, 521c (n + 1), and 521c (2n) that form the current mirror circuit can be made the same with high accuracy. Therefore, even when the screen 50 is driven by a plurality of source driver ICs (circuits) 14, the boundary between the source driver ICs (circuits) 14 is not visible. Needless to say, the currents Ic1 and Ic2 may be generated by a reference current circuit configured outside the IC chip and supplied to the transistor 473b.
[0706]
The resistors R11a and R12a are formed (designed) with a resistance value of a predetermined ratio or preferably with the same resistance value. Similarly, the resistor R21a and the resistor R22a are formed (designed) with a predetermined ratio of resistance values or preferably with the same resistance value. The same applies to the combination of the resistors R11b and R12b and the resistors R21b and R22b. Here, for ease of explanation, it is assumed that the resistors R11a, R12a, R21a, R22a, R11b, R12b, R21b, and R22b are designed (formed) to have the same resistance value. .
[0707]
The resistors R11a and R12a are formed or arranged close to each other. Similarly, the resistors R21a and R22a are formed or arranged close to each other, and the resistors R11b and R12b are formed or arranged close to each other. Similarly, the resistors R21b and R22b are formed or arranged close to each other. Each resistor is a polysilicon resistor or a diffused resistor. The value of the resistor formed (configured) in the IC chip has a characteristic that the relative ratio of the resistors arranged close to each other can be formed with high accuracy. However, absolute values often do not have accuracy.
[0708]
In many cases, the reference current source of the source driver IC 14 is formed at both ends of the IC chip. However, the distance between the two reference current sources is at most about 20 mm. Therefore, the resistance value difference between the resistor R11a and the resistor R21a of the source driver IC 14a is often small. However, the absolute values of the resistors R11a and R21a and the source driver IC14b resistors R11b and R21b of the source driver IC14a having different IC chips are often different. This is because even if the source driver ICs 14a and 14b are formed on the same wafer, the IC formation positions are often greatly different.
[0709]
In order to facilitate the explanation, the resistance value of the resistor 11Ra, the resistor R12a, the resistor R21a, and the resistor R22a of the source driver IC 14a is assumed to be equal and 50 (KΩ) as an example. Further, description will be made assuming that the resistance values of the resistor R11b, the resistor R12b, the resistor R21b, and the resistor R22b of the source driver IC 14b are equal to 75 (KΩ). That is, it is assumed that the built-in resistance of the source driver IC 14a and the built-in resistance of the source driver IC 14b have different absolute values, and the relative resistance value of the built-in resistance of each source driver IC is equal.
[0710]
In FIG. 229, one terminal of the resistor R11a, the resistor R21a, the resistor R11b, and the resistor R21b is connected to the voltage Vp. A reference voltage Vs is applied to the operational amplifier 522. In this respect, the configuration is the same as that of FIG. The difference between FIG. 229 and FIG. 228 is that in FIG. 228, the resistor R1 is an external resistor. In addition, the built-in resistors of adjacent source driver ICs in FIG. 229 are cascade-connected by the connection wiring 2291.
[0711]
The resistor R22a of the source driver IC 14a and the resistor R11b of the source driver IC 14b are electrically connected by a connection wiring 2291. The connection wiring 2291c is exemplified by a wiring pattern formed on the substrate 71. Therefore, the resistance connected to the operational amplifier 522b of the source driver IC 14a is R11b + R22a = 75 (KΩ) +50 (KΩ) = 125 (KΩ). The resistor R21a of the source driver IC 14a and the resistor R12b of the source driver IC 14b are electrically connected by a connection wiring 2291b. Therefore, the resistance connected to the operational amplifier 522a of the source driver IC 14b is R11b + R22a = 75 (KΩ) +50 (KΩ) = 125 (KΩ).
[0712]
The resistance connected to the operational amplifier 522b of the source driver IC 14a and the operational amplifier 522a of the source driver IC 14b is equal to 125 (KΩ), and the applied reference voltages Vs and Vp are also the same. Therefore, the current Ic2 flowing through the transistor 473b2 of the source driver IC 14a in FIG. 229 is equal to the current Ic1 flowing through the transistor 473b1 of the source driver IC 14b. Therefore, the program current flowing through the transistor group 521cn of the source driver IC 14a is equal to the program current flowing through the transistor group 521c (n + 1) of the source driver IC 14b.
[0713]
With the configuration of FIG. 229, the program output current between adjacent source driver ICs 14 can be made equal without an external resistor as shown in FIG. That is, even if the absolute value of the resistor R in the source driver IC 14 varies, the reference current can be made equal by self-alignment. Therefore, even when a plurality of source driver ICs 14 of the present invention are mounted on the substrate 71, there is no need for adjustment at all, and the cascade connection of the source driver ICs can be realized only by mounting.
[0714]
Note that the resistance R in the source driver IC 14 may be adjusted to a predetermined absolute value by trimming. Further, the relative resistance value of a set of resistors R11a and R12a, resistors R21a and R22a, etc. may be adjusted to be a predetermined relative value.
Further, as illustrated in FIG. 229, the internal resistor R11a and the resistor R12a at the end of the source driver 14a are short-circuited by a wiring 2291a. Further, the internal resistor R21b and the resistor R22b at the end of the source driver 14b are short-circuited by the wiring 2291d.
[0715]
The internal resistor R11a and the resistor R12a at the end of the source driver 14a are connected by a connection wiring 2291a. The resistance connected to the operational amplifier 522a of the source driver IC 14a is resistance R11a + resistance R12a = 50 (KΩ) +50 (KΩ) = 100 (KΩ). The resistance connected to the operational amplifier 522b of the source driver IC 14a is R21b + R22a = 75 (KΩ) +50 (KΩ) = 125 (KΩ). Therefore, the reference current Ic1 and the reference current Ic2 of the source driver IC 14a have different values. For this reason, the Iout1 program output current of the source driver IC 14a and the Ioutn program output current of the source driver IC 14a have different values. However, since Iout1 is located at the end of the screen 50, it is not visually recognized even if the brightness of the end of the screen 50 is different from the central portion of the screen 50. However, the brightness needs to change smoothly from the center to the end of the screen 50.
[0716]
Similarly, the internal resistor 21b and the resistor 22b at the end of the source driver 14b are connected by a connection wiring 2291d. The resistance connected to the operational amplifier 522b of the source driver IC 14b is resistance 21b + resistance 22b = 75 (KΩ) +75 (KΩ) = 150 (KΩ). The resistance connected to the operational amplifier 522a of the source driver IC 14b is R11b + R12b = 75 (KΩ) +50 (KΩ) = 125 (KΩ). Therefore, the reference current Ic1 and the reference current Ic2 of the source driver IC 14b have different values. Therefore, the program output current of Iout (n + 1) of the source driver IC 14b is different from the program output current of Iout (2n) of the source driver IC 14b. However, since Iout (2n) is located at the end of the screen 50, it is not visually recognized even if the brightness of the end of the screen 50 is different from the central portion of the screen 50.
[0717]
230, the program current from the transistor group 521c can be adjusted by connecting a volume 491a to the resistor R12a and by connecting the volume 491b to the resistor R22b. Good. Further, the resistor R12a, the resistor R22a, etc. may be an electronic volume. It goes without saying that the above matters may be applied to the resistor R22a and the resistor R12b.
[0718]
228, FIG. 229, and FIG. 230 have a configuration in which each source driver circuit 14 has a built-in resistor. The present invention is not limited to this. For example, as shown in FIG. 231, the same resistance value R (R1, R2, R3, R4) may be built in the source driver IC 14a. The resistors R (R1, R2, R3, R4) are arranged close to each other. By arranging them close to each other, the relative value of the resistance value can be accurately formed. The resistors (R1, R2, R3, R4) may be adjusted so that the absolute values are equal by performing laser trimming. Further, the relative values of the resistors may be adjusted to be equal by trimming.
[0719]
The resistors R3 and R4 of the source driver IC 14a are output via the terminals a2 and a4. This output is input to the source driver IC 14b from the terminals b2 and b3 of the source driver IV14b. With the above configuration, the resistor R3 in the source driver IC 14a is connected to the operational amplifier 522a of the source driver IC 14b, and a constant current circuit is configured. In addition, the resistor R4 in the source driver IC 14a is connected to the operational amplifier 522b of the source driver IC 14b to constitute a constant current circuit.
[0720]
The reference voltage Vs is also input to the source driver IC 14a, and is output to the source driver IC 14b via the terminal a1 of the source driver IC 14a. The output reference voltage Vs is input to the source driver IC 14b from the terminal b1 of the source driver IC 14b.
[0721]
In the previous embodiment, the currents flowing through the transistors 473b1 and 473b2 are the same. However, for ease of explanation in FIG. 211, the reference current Ic1 is passed through the transistor 473b1 and the reference current Ic2 is passed through the transistor 473b2. Explain.
[0722]
In the configuration of FIG. 210, since the unit transistor group 521cn of the source driver IC 14a is close to the transistor 473b2, a highly accurate current mirror circuit is configured. Further, since the unit transistor group 521c1 of the source driver IC 14b is close to the transistor 473b1, an accurate current mirror circuit is configured. Therefore, by adjusting the reference current Ic2 of the source driver IC 14a and the reference current Ic1 of the source driver IC 14b, the output current of the unit transistor group 521cn of the source driver IC 14a and the output current of the unit transistor group 521c1 of the source driver IC 14b are adjusted. be able to.
[0723]
Therefore, even when the output currents of the source driver IC 14a and the source driver IC 14b are inclined as shown in FIG. 209, by adjusting the reference current Ic2 of the source driver IC 14a and / or the reference current Ic1 of the source driver IC 14b, FIG. As shown, the output current can be adjusted to be continuous on the screens 50a and 50b. Of course, it goes without saying that the boundary between the screen 50a and the screen 50b can be prevented by making the reference current Ic1 and the reference current Ic2 the same.
[0724]
That is, in the present invention, by configuring so that the reference current Ic1 of the transistor 473b1 and the reference current Ic2 of the transistor 473b2 can be adjusted, the boundary between the screen 50a and the screen 50b can be further prevented.
[0725]
Note that in the above description, the number of transistors 473b is one. However, it is preferable that a plurality of transistors 473b be formed to form the transistor group 521b. The transistor 521b includes a plurality of transistors 473b. The transistor size and shape of the transistor 473b in the transistor group 521b are preferably the same shape and size as the unit transistor 484. The number of transistors 473b in the transistor group 521b is preferably the same as the number of unit transistors 484 in the transistor 521c. Further, it is preferable to form a plurality of blocks of the transistor group 521b.
[0726]
Alternatively, the total area of the transistors 473b in the transistor group 521b is preferably substantially equal to the total area of the unit transistors 484 included in the unit transistor group 521c. Further, it is preferable to form a plurality of blocks of the transistor group 521b.
[0727]
FIG. 215 shows an arrangement configuration of the transistor 483b of the transistor group 521b. In one transistor group 521b, 63 transistors 473b having the same number as the unit transistors 484 of the unit transistor group 521c are formed. Of course, the number of transistors 473b in one transistor group 521b is not limited to 63. When the number of unit transistors 484 in the unit transistor group 521c is configured with the number of gradations −1, the number of transistors 473b in the transistor group 521b is also the number of gradations −1 or the same or similar number. Further, the configuration is not limited to the configuration shown in FIG. 215, and may be formed or arranged in a matrix as shown in FIG.
[0728]
The above configuration is schematically shown in FIG. The unit transistor groups 521c are arranged in parallel by the number of output terminals. A plurality of transistor groups 521b are formed on both sides of the unit transistor group 521c. A gate wiring 581 connects the gate terminal of the transistor 473b of the transistor group 521b and the gate terminal of the unit transistor 484 of the unit transistor group 521c.
[0729]
In the above description, for the sake of simplicity, the description has been made as a single-color source driver IC 14, but it is originally configured as shown in FIG. 214. That is, in the transistor group 521b and the unit transistor group 521c, red (R), green (G), and blue (B) transistor groups are alternately arranged (in FIG. 214, the transistor group to which the subscript R is added is red. (R) is shown, the transistor group to which the subscript G is added indicates green (G), and the transistor group to which the subscript B is added indicates blue (B)). As described above, output variations between RGB are reduced by alternately arranging RGB transistor groups. This configuration is also an important requirement for the layout in the source driver IC 14.
[0730]
  In FIG. 228, the reference current Ic is generated by the operational amplifier 552 or the like, but is not limited to this. Instead of the volume, the reference current Ic may be adjusted by this volume. Similarly to FIG. 62, the transistor 473b is formed using a plurality of transistors, and includes a transistor group 521b1, a transistorgroupIt may be 521b2. Also, a fixed resistor may be used.
[0731]
The arrangement of the unit transistors 484 in the transistor group 521c is also considered. Note that the following matters regarding the arrangement and configuration of the unit transistors 484 and the like also apply to the transistors 473a of the transistor group 521a and the transistors 473b of the transistor group 521b.
[0732]
The unit transistor group 521c needs to be regularly arranged or formed. Further, the unit transistors 484 in the unit transistor group 521c need to be regularly formed or arranged. For example, if the unit transistor 484 is missing, the characteristics of the surrounding unit transistors 484 are different from the characteristics of the other unit transistors 484. Further, it is necessary to regularly form or arrange the layout on the gate line of the transistor.
[0733]
FIG. 217 schematically shows the arrangement of the unit transistors 484 in the unit transistor group 521c in the output stage. 63 unit transistors 484 expressing 64 gradations are regularly arranged in a matrix. However, 64 unit transistors 484 can be arranged in 4 columns × 16 rows. However, since there are 63 unit transistors 484, one portion is not formed (shaded portion). Then, the characteristics of the unit transistors 484a, 484b, and 484c in the vicinity of the shaded area are manufactured differently from those of the other unit transistors 484.
[0734]
In order to solve this problem, in the present invention, a dummy transistor 1341 is formed or arranged in the shaded portion. Then, the characteristics of the unit transistor 484a, the unit transistor 484b, and the unit transistor 484c become the same as those of the other unit transistors 484. That is, according to the present invention, the unit transistors 484 are configured in a matrix by forming the dummy transistors 1341. Further, the unit transistors 484 are arranged so as not to be covered in a matrix. Alternatively, the unit transistors 484 are arranged so as to have line symmetry.
[0735]
In order to express 64 gradations, 63 unit transistors 484 are arranged in the transistor group 521c, but the present invention is not limited to this. The unit transistor 484 may be composed of a plurality of sub-transistors.
[0736]
FIG. 218 (a) shows a unit transistor 484. FIG. FIG. 218 (b) shows a unit transistor 484 composed of four sub-transistors 12181. The output current obtained by adding the plurality of sub-transistors 2181 is set to be the same as that of the unit transistor 484. That is, the unit transistor 484 includes four sub-transistors 2181.
[0737]
Note that the present invention is not limited to the unit transistor 484 configured by the four sub-transistors 2181, and any configuration may be employed as long as the unit transistor 484 is configured by the plurality of sub-transistors 2181. However, the sub-transistors 2181 are configured to output the same size or the same output current.
[0738]
In FIG. 218, S represents a source terminal of the transistor, G represents a gate terminal of the transistor, and D represents a drain terminal of the transistor. In FIG. 218 (b), the sub-transistors 2181 are arranged in the same direction. In FIG. 218 (c), the sub-transistors 2181 are arranged in different directions in the row direction. In FIG. 218 (d), the sub-transistors 2181 are arranged in different directions in the column direction and arranged so as to be point-symmetric. All of FIG. 218 (b), FIG. 218 (c), and FIG. 218 (d) have regularity.
[0739]
218 (a), (b), (c), and (d) are layouts, the sub-transistor 2181 may be connected in series as shown in FIG. 218 (e) to form a unit transistor 484. Further, as shown in FIG. 218 (f), the unit transistors 484 may be connected in parallel.
[0740]
When the formation direction of the unit transistor 484 or the sub-transistor 2181 is changed, the characteristics are often different. For example, in FIG. 218 (c), the unit transistor 484a and the sub-transistor 2181b have different output currents even if the voltages applied to the gate terminals are the same. However, in FIG. 218 (c), the same number of sub-transistors 2181 having different characteristics are formed. Therefore, variations in the transistor (unit) are reduced. Further, by changing the direction of the unit transistor 484 or the sub-transistor 2181 in which the formation direction is different, the characteristic difference is interpolated and the variation of the transistor (one unit) is reduced. Needless to say, the above matters also apply to the arrangement shown in FIG.
[0741]
Therefore, as shown in FIG. 219 and the like, the direction of the unit transistor 484 is changed, and the characteristics of the unit transistor 484 formed in the vertical direction and the characteristics of the unit transistor 484 formed in the horizontal direction are interpolated as the transistor group 521c. Thus, variations in the transistor group 521c can be reduced.
[0741]
FIG. 219 shows an example in which the formation direction of the unit transistors 484 is changed for each column in the transistor group 521c. FIG. 220 shows an embodiment in which the formation direction of the unit transistors 484 is changed for each row in the transistor group 521c. FIG. 221 shows an embodiment in which the formation direction of the unit transistors 484 is changed for each row and column in the transistor group 521c. Note that the dummy transistor 1341 is also formed or arranged in accordance with this configuration requirement.
[0743]
In the above embodiment, unit transistors having the same size or the same current output are configured or formed in the transistor group 521c (see FIG. 222B). However, the present invention is not limited to this. As shown in FIG. 222A, the 0th bit (switch 641a) connects (forms) one unit of unit transistor 484a. The first bit (switch 641b) connects (forms) two units of unit transistors 484b. The second bit (switch 641c) connects (forms) four unit transistors 484c. The third bit (switch 641d) connects (forms) 8 unit transistors 484d. The fourth bit (not shown) connects (forms) 16 unit transistors 484a. The fifth bit (not shown) may connect (form) 32 unit transistors 484a. For example, a unit transistor of 16 units is a transistor that outputs a current corresponding to 16 units of the unit transistor 484.
[0744]
The unit transistor (* is an integer) can be easily formed by changing the channel width W proportionally (the channel length L is constant). However, in reality, even if the channel width W is doubled, the output current often does not double. In this case, the channel width W is determined by experiment by actually manufacturing a transistor. However, in the present invention, even if the channel width W deviates from the proportional condition, it is expressed as proportional.
[0745]
As shown in FIGS. 48, 166, etc., the present invention generates a program current Iw corresponding to video data by controlling the current flowing through the unit current source 484. The unit current source 484 is composed of a transistor. The transistors are densely formed or arranged as a transistor group 521 in the IC chip. Random variations occur in the transistor 484 constituting the unit current. This random variation is caused by IC process etching variation (processing accuracy) and transistor shape. Another variation in characteristics (especially output current) is caused by transistor position distribution in the IC chip.
[0746]
In FIG. 64, the transistor group 521f is formed (arranged) with 32 transistors densely arranged. The transistor group 521f tends to have different output currents depending on the position of the IC chip. When all the output currents of the 32 transistors are large (or small), the accuracy of the program current Iw is determined by the transistor group 521f. Therefore, even if the transistors 484 constituting each transistor group 521 vary individually, the total current (for example, the addition of 32 unit current sources 484) is consistent between the terminals. preferable.
[0747]
In FIGS. 48 and 166, the single transistor 484 is illustrated, and thus the drawings are complicated. For ease of understanding, the configuration of FIGS. 48 and 166 is illustrated as in FIG. The number written in each transistor group 521 is the number of transistors that allow a unit current to flow. For example, the transistor group 521a (in this case, since there is one transistor as the unit current source 484, it may not be appropriate to call it a group. However, in order to facilitate the explanation, it is intentionally called a transistor group) Each unit transistor is configured (formed).
[0748]
Similarly, the transistor group 521b includes (forms) two transistors. The transistor group 521c includes four transistors, the transistor group 521c includes four transistors, the transistor group 521d includes eight transistors, and the transistor group 521e includes sixteen transistors. The transistor group 521f includes 32 transistors.
[0749]
The analog switch 481 corresponds to the video (image) data corresponding to D0 as the switch 481a, and the analog switch 481 corresponds to D1 as the switch 481b. A switch corresponding to D2 is referred to as a switch 481c, and a switch corresponding to D3 is referred to as a switch 481d. Similarly, a switch corresponding to D4 is referred to as a switch 481e, and a switch corresponding to D5 is referred to as a switch 481f.
[0750]
As described above, when the switch 481 is turned on / off, the sum of the unit current sources corresponding to the image data flows to the internal wiring 483, which becomes the program current Iw. For ease of understanding, the drawings will be described assuming that the in-chip layout of each transistor group 521 is imaged. That is, in FIG. 299, the transistor group 521f is arranged at a position close to the output terminal 681 connected to the source signal line 18, and then the transistor group 521e, then the transistor group 521d, the transistor group 521c, and the transistor group 521b are laid out. The transistor group 521a is laid out at a position farthest from the output terminal 681 (see FIG. 322). However, the above is for easy understanding, and it goes without saying that the IC chip layout design is more complicated.
[0751]
The transistor group 521 in FIG. 299 is connected to one output terminal (in the present invention, there is a transistor group 521 that passes IwH in the high gradation region, IwL in the low gradation region, and IwK in the raised current. In order to facilitate the explanation, it is assumed that the configuration of FIG. 299 is connected to one output terminal), and the program current Iw. However, if the transistor groups 521 are arranged too regularly, an output terminal is generated in which the program current Iw is larger than specified.
[0752]
The configuration of the present invention that addresses this problem is the configuration of FIG. Specifically, there are two transistor groups 521f (521f1, 521f2) each including 32 unit transistors. In addition, two transistor groups 521e (521e1, 521e2) each including 16 unit transistors are provided. The transistor group 521 is arranged in order from the output terminal 681 as a transistor group 521f1, a transistor group 521e1, a transistor group 521d, a transistor group 521c, a transistor group 521b, a transistor group 521a, a transistor group 521f2, and a transistor group 521e2 (see FIG. 323). FIG. 323 is a conceptual diagram of the layout of the source driver IC 14).
[0753]
Further, as shown in FIG. 329, the R, G, and B transistor groups 521 may be regularly arranged. 330, the high gradation side transistor group 521H and the low gradation side transistor group 521L may be regularly arranged in RGB.
[0754]
Switching between the transistor group 521f1 and the transistor group 521f2 is performed by the selection switch 3001a. When the selection switch 3001a is set to the a side, the transistor group 521f1 is selected, and when the selection switch 3001a is set to the b side, the transistor group 521f2 is selected. When the selection switch 3001b is set to the a side, the transistor group 521e1 is selected, and when the selection switch 3001b is set to the b side, the transistor group 521e2 is selected.
In the above embodiment, two transistor groups 521f and transistor groups 521e are formed or arranged. However, the present invention is not limited to this, and three or more transistor groups may be formed or arranged. In this case, the selection switch 3001 is a three-input one selection switch. The plurality of transistor groups 521 to be formed or arranged is not limited to the transistor group 521f and the transistor group 521e, and a plurality of other transistor groups 521 may be formed. However, the larger the number of unit current sources 484, the greater the influence on the output variation due to the deviation in transistor characteristics. Therefore, it is preferable to form or arrange a plurality of transistor groups 521 having a large number of unit transistors. In addition, an image is easily noticeable if there is a variation in halftone display. Therefore, it is preferable to form or arrange a plurality of transistor groups 521 that contribute to halftone display. In the case of the 64-gradation display of FIG. 299 (the total number of transistors is 63 (1 + 2 + 4 + 8 + 16 + 32)), the transistor group 521e (the number of unit current sources is 16) and the transistor group 521f (the number of unit current sources is 32) Applicable. The transistor group 521e outputs current at gradation 16 or higher, and the transistor group 521f outputs current at gradation 32 or higher. This is because this range corresponds to halftone display. Therefore, when the number of gradations is Y, a plurality of at least one transistor group 521 among the transistor groups 521 that operate at Y / 5 or more (2Y) / 3 gradations or less may be formed or arranged.
[0755]
The selector switch 3001 is switched between the a side (selecting the transistor group 521f1 and the transistor group 521e1) and the b side (selecting the transistor group 521e1 and the transistor group 521f2) for each field (one frame) (represented as 1F). Switch. This conceptual diagram is illustrated in FIG. Note that FIG. 324 illustrates a switched display of the transistor group 521f1 and the transistor group 521f2 for ease of explanation. In the display screen 50, the transistor group 521f1 or the transistor group 521f2 indicates that the program current Iw from the transistor group 521f1 or the transistor group 521f2 is output to the source signal line 18 and written to the pixel 16 ing. Of course, the other transistor group 521 also operates in the image display of the natural image, so that it does not become as shown in FIG. For illustrative purposes, FIG. 324 assumes that the screen is a white raster display, and further, a white raster display of gradation such as the transistor group 521f is displayed. Note that the explanations of the above drawings are the same in other drawings (FIGS. 325 and 326).
[0756]
In FIG. 324, the transistor group 521f1 is selected in the first F, and the transistor group 521f2 is selected in the second F to display an image. In addition, the transistor group 521f1 is selected repeatedly after the third F, and the transistor group 521f2 is displayed in the fourth F. As described above, the variation in the output current can be averaged by alternately operating the plurality of transistor groups 521 and writing the program current Iw to the pixels, thereby realizing a uniform image display.
In the embodiment of FIG. 324, the image is displayed by the output current of the transistor group 521f1 in the first F and the transistor group 521f2 is displayed in the second F. However, the present invention is not limited to this. For example, the first F and the second F display an image with the output current of the transistor group 521f1, the third F and the fourth F display an image with the output current of the transistor group 521f2, and the fifth F and the sixth F output current of the transistor group 521f1. The image may be displayed with. That is, according to the present invention, the currents written to the pixels 16 are averaged by operating the plurality of transistor groups 521 alternately, thereby reducing variations in image display.
[0757]
In FIG. 324, uniform display is realized by selecting and switching the transistor group 521 to be written in the pixel 16 for each field (frame). However, the present invention is not limited to this. As illustrated in FIG. 325, the transistor group 521 that outputs the program current Iw to be written to the pixels may be switched for each pixel row (or a plurality of pixel rows). FIG. 325 (a) conceptually illustrates a writing state of the first F screen 50. FIG. In FIG. 325 (a), the output current of the transistor group 521f1 is written in the odd pixel row, and the output current of the transistor group 521f2 is written in the even pixel row. In the second F, as shown in FIG. 325 (b), the output current of the transistor group 521f1 is written in the even pixel row, and the output current of the transistor group 521f2 is written in the odd pixel row. This operation is repeated alternately in subsequent fields (frames).
[0758]
In FIG. 325, the transistor group 521 to be written to the pixel 16 is switched for each pixel row or a plurality of pixel rows, and the transistor group 521 to be written to the pixel 16 is switched for each frame (field) or a plurality of frames (fields). By operating as described above, the current written to the pixels 16 can be averaged, and variations in image display can be reduced. That is, in FIG. 325, the transistor group 521 written to the pixel row 16 is changed every horizontal scanning period (the transistor group 521 is changed in synchronization with the horizontal synchronization signal). Of course, the transistor group 521 may be changed for each of a plurality of pixel rows (a plurality of horizontal scanning periods) (that is, the cycle is two horizontal scanning periods). The above matters are the same in FIG.
[0759]
In FIG. 325, uniform display is realized by selecting and switching the transistor group 521 to be written to the pixel 16 for each pixel row and switching the transistor group 521 to be written to the pixel 16 for each frame (field). However, the present invention is not limited to this. As illustrated in FIG. 326, the transistor group 521 that outputs the program current Iw to be written to the pixels may be switched for each pixel column (or a plurality of pixel columns).
[0760]
FIG. 326 (a) conceptually illustrates the writing state of the first F screen 50. FIG. In FIG. 326 (a), the output current of the transistor group 521e1 is written in the odd pixel column, and the output current of the transistor group 521e2 is written in the even pixel column. In the second F, as shown in FIG. 326 (b), the output current of the transistor group 521e1 is written in the even pixel column, and the output current of the transistor group 521e2 is written in the odd pixel column. This operation is repeated alternately in subsequent fields (frames). In FIG. 326, the transistor group 521 written to the pixel row 16 is changed every vertical synchronization period (the transistor group 521 is changed in synchronization with the vertical synchronization signal). The period is two vertical scanning periods. Of course, the transistor group 521 may be changed every plural vertical scanning periods. The above matters are the same in FIG.
[0761]
In FIG. 326, the transistor group 521 to be written to the pixel 16 is switched for each pixel column or a plurality of pixel columns, and the transistor group 521 to be written to the pixel 16 is switched for each frame (field) or a plurality of frames (fields). By operating as described above, the current written to the pixels 16 can be averaged, and variations in image display can be reduced.
In FIG. 325, the transistor group 521 to be written to the pixel 16 is switched for each pixel row, and in FIG. 326, the transistor group 521 to be written to the pixel 16 is switched for each pixel column. However, the present invention is not limited to this. For example, FIG. 325 and FIG. 326 may be combined. That is, the transistor group 521 to be written to the adjacent pixel row is changed, and the transistor group 521 to be written to the adjacent pixel column is changed. Needless to say, the present invention is not limited to adjacent pixel rows or pixel columns, and the transistor group 521 to be written to the pixels 16 may be changed by combining a plurality of pixel rows or a plurality of pixel columns. Further, the transistor group 521 to be written to the pixel 16 by R, G, and B may be changed.
[0762]
Needless to say, the concept of switching the transistor group 521 in the field (frame), the pixel row, and the pixel column can be applied to other embodiments of the present invention.
[0763]
In the example of FIG. 300, the transistor group 521 including the unit current sources 484 having the number of gradations or more is formed or arranged (that is, a plurality of transistor groups 521 overlapping with gradation display are formed). The uneven output of the transistor group 521 occurs because the unit transistors constituting the transistor group 521 are arranged too densely in the chip. Of course, the characteristics of the unit transistors are made uniform by making them dense. However, there is a case where mobility is specifically formed at a position in the chip. In this case, if one transistor group 521 is disposed at this specific location, the gradation output current becomes abnormal. When the number of unit transistors constituting the transistor group 521 is small, the output current is small even when the transistor group 521 is arranged at this specific location, so that it does not stand out in natural image display. However, if the number of unit transistors 484 constituting the transistor group 521 is large (in FIG. 299, the transistor group 521f, the transistor group 521e, and the like), the output current is large, resulting in an unnatural image display.
[0764]
The embodiment of FIG. 301 is an embodiment in which a transistor group 521f having a large number of unit transistors 484 is divided into a plurality of parts. A conceptual diagram of the layout in the chip 14 is shown in FIG. That is, the transistor group 521 corresponding to the 1-bit gradation signal is divided into a plurality of sub-transistor groups 521. Note that the sub-transistor group 521 to be divided is not limited to being divided equally (in FIG. 301, the unit transistor 484 is divided into two pieces each having 16 pieces). For example, the transistor group 521f1 may be composed of 20 unit transistors, and the transistor group 521f2 may be composed of the remaining 12 unit transistors. It goes without saying that the above matters can be applied to other embodiments of the present invention.
[0765]
The transistor group 521f includes 32 unit transistors 484. In FIG. 301, the pixel group is divided into two, and is divided into a transistor group 521f1 and a transistor group 521f2 formed of 16 unit transistors. Further, the formation positions of the transistor group 521f1 and the transistor group 521f2 are separated from each other in the chip. Specifically, as illustrated in FIG. 327, a transistor group 521e is disposed between the transistor group 521f1 and the transistor group 521f2. The division is preferably performed by a multiple of 8. This is because layout becomes easy and gradation control becomes easy.
[0766]
The operation in FIG. 301 is the same as that in FIGS. When the switch 481f is turned on, the program current Iw flows through the transistor group 521f1 and the transistor group 521f2. When the switch 481e is turned on, the program current Iw flows through the transistor group 521e. As described above, the corresponding switch 481 is ON / OFF controlled according to the image data, and the program current Iw flows through the corresponding transistor group 521 and is applied to the source signal line 18.
The embodiment of FIG. 302 is an embodiment in which the transistor group 521 is further divided into a number of parts in comparison with FIG. The transistor group 521f includes 32 unit transistors 484. In FIG. 302, the pixel group is divided into four, and divided into a transistor group 521f1, a transistor group 521f2, a transistor group 521f3, and a transistor group 521f4, each including eight unit transistors. The transistor group 521e is also divided into a transistor group 521e1 and a transistor group 521e2. Further, the layout positions of the transistor group 521a, the transistor group 521b, the transistor group 521c, and the transistor group 521d are changed from those in FIG.
[0767]
The operation in FIG. 302 is the same as that in FIGS. When the switch 481f is turned on, the program current Iw flows through the transistor group 521f1, the transistor group 521f2, the transistor group 521f3, and the transistor group 521f4. When the switch 481e is turned on, the program current Iw flows through the transistor group 521e1 and the transistor group 521e2. As described above, the corresponding switch 481 is ON / OFF controlled according to the image data, and the program current Iw flows through the corresponding transistor group 521 and is applied to the source signal line 18.
[0768]
The above embodiment has been described by exemplifying the case of monochromatic display for easy explanation. In the following description, color display by R, G, and B is exemplified. The following embodiments exemplify the three primary colors of RGB. However, the present invention is not limited to this, and may be replaced with the three primary colors of cyan, yellow, and magenta. Needless to say, the present invention can also be applied to two-color display. Further, the present invention can be applied to six-color display such as R, G, B, cyan, yellow, and magenta.
The following embodiments exemplify the case of color display, but it goes without saying that the layout, driving method, configuration, operation, etc. described in FIGS. 299, 300, 301 and the like can be combined. In addition, although the R, G, and B layouts are used, this can be considered as a single color. For example, the neighbor of R in FIG. 303 is G and the neighbor is B. However, all of these may be considered as a single color transistor group 521. That is, according to the present invention, output variation is reduced by dispersing unit transistors constituting the transistor group 521 under certain conditions. Therefore, if it is considered that the output variation can be reduced by replacing the layout of the adjacent transistor group 521, the effect is exhibited even if they are not distinguished by RGB.
[0769]
FIG. 303 shows the arrangement of FIGS. 48 and 166 expressed in RGB. A conceptual diagram of the layout is shown in FIG. Note that the switch 481 and the like are omitted for ease of illustration. For ease of explanation, “a b c de f” is added to the layout position in the horizontal direction (short side direction of the chip), and “1 2 3” in the vertical direction (long side direction of the chip). 4 5 6 "and the symbol are added. The layout position for explanation is expressed as “a1”, “d3”, and the like.
[0770]
FIG. 304 shows an embodiment of the present invention. RGB transistor groups 521 are arranged at three positions 1, 2, and 3, and are repeatedly laid out. In red (R), the transistor group 521f is arranged at “f1”, the transistor group 521e is arranged at “e2”, the transistor group 521d is arranged at “d3”, the transistor group 521c is arranged at “c1”, The transistor group 521b is arranged at “b2”, and the transistor group 521a is arranged at “a3”. As described above, the layout position is changed.
[0771]
In green (G), the transistor group 521f is arranged at “f2”, the transistor group 521e is arranged at “e3”, the transistor group 521d is arranged at “d1”, the transistor group 521c is arranged at “c2”, The transistor group 521b is arranged at “b3”, and the transistor group 521a is arranged at “a1”. As described above, the layout position is changed.
[0772]
Similarly, in blue (B), the transistor group 521f is arranged at “f3”, the transistor group 521e is arranged at “e1”, the transistor group 521d is arranged at “d2”, and the transistor group 521c is arranged at “c3”. The transistor group 521b is arranged at “b1”, and the transistor group 521a is arranged at “a2”. As described above, the layout position is changed.
[0773]
As described above, instead of making the layout position of the transistor group 521 linear as shown in FIG. 303, the unit constituting the transistor group 521 is replaced by “1”, “2”, “3” positions. The characteristics of the transistor 484 are not biased, and variations in the program current Iw from each output terminal can be reduced. In addition, as illustrated in FIG. 300, a plurality of transistor groups 521 may be formed or arranged, and may be switched and selected in a 1F cycle or the like. Further, the transistor group 521 may be divided as shown in FIGS. 301 and 302. Needless to say, the arrangement of the transistor groups 521 may be interchanged. Needless to say, the above matters can be applied to other embodiments of the present invention.
[0774]
As described above, the effect of reducing the variation in the output current by changing the layout position is an effect that can be exhibited without using RGB as shown in FIG. Therefore, if it is considered that the output variation can be reduced by replacing the layout of the adjacent transistor group 521, the effect is exhibited even if they are not distinguished by RGB.
[0775]
FIG. 304 shows an example in which the transistor group 521 is replaced by a set of three layout lines “1 2 3”, “4, 5, 6”. FIG. 305 shows an embodiment in which the transistor group 521 to be selected line by line is changed.
[0776]
To illustrate red (R), the transistor group 521f is arranged in “f1”, the transistor group 521e is arranged in “e2”, the transistor group 521d is arranged in “d3”, and the transistor group 521c is “ The transistor group 521b is disposed at “b5”, and the transistor group 521a is disposed at “a6”. As described above, the layout position is changed.
[0777]
Similarly, when green (G) is described as an example, the transistor group 521f is arranged in “f2”, the transistor group 521e is arranged in “e3”, the transistor group 521d is arranged in “d4”, and the transistor group 521c. Is arranged at “c5”, the transistor group 521b is arranged at “b6”, and the transistor group 521a is arranged at “a7”. As described above, the layout position of the transistor group 521 selected for each row is changed.
[0778]
In the embodiment of FIG. 306, a transistor group 521L (unit transistor 484 controlled by the L0 to L4 terminals in FIG. 56) that operates mainly for low gradation display, and a transistor group 521H (H0 of FIG. 57) that operates in high gradation display. The layout position of the unit transistor 484) controlled by the .about.H5 terminals is changed.
[0779]
In FIG. 306, the red (R) transistor group 521L is arranged at the “a1” position, and the transistor group 521H is arranged at “b1”. The green (G) transistor group 521L is arranged at the “a2” position, and the transistor group 521H is arranged at the “b2” position. The blue (B) transistor group 521L is arranged at the “a3” position, and the transistor group 521H is arranged at the “b3” position.
[0780]
The next red (R) transistor group 521H is arranged at the “a4” position, and the transistor group 521L is arranged at “b4”. The green (G) transistor group 521H is arranged at the “a5” position, and the transistor group 521L is arranged at the “b5” position. The blue (B) transistor group 521H is arranged at the “a6” position, and the transistor group 521L is arranged at the “b6” position. The following is repeated.
[0781]
In the layout of FIG. 306, when attention is paid to R, it can be seen that the arrangement of the transistor group 521H and the transistor group 521L of the adjacent R output current circuit is alternately changed (replaced). As described above, the output variation can be reduced by replacing the layout of the adjacent transistor group 521.
[0782]
The above is the case of RGB. If it is considered as a single color (if it is considered simply to change the layout position), the transistor group 521L is disposed at the “a1” position, the transistor group 521H is disposed at the “b1” position, and the transistor group 521H is disposed at the “b1” position. The transistor group 521L may be arranged at the “b2” position, the transistor group 521L may be arranged at the “a3” position, and the transistor group 521H may be arranged at the “b3” position (FIG. 308 shows the case of RGB. This is a case where RGB is not considered in FIG. 308).
[0783]
FIG. 307 shows an example in which a plurality of transistor groups 521L and transistor groups 521H are laid out in one row (“1 2 3 4 5...”). The transistor group 521 at the “a1” position and the “b1” position serves as an output of the source signal line 18 of R1 (red 1). The transistor group 521 at the “c1” position and the “d1” position serves as an output of the source signal line 18 of R2 (red 2). The transistor group 521 at the “e1” position and the “f1” position serves as an output of the source signal line 18 of R3 (red 3).
[0784]
Similarly, the transistor group 521 at the “a2” position and the “b2” position becomes the output of the source signal line 18 of G1 (green 1). The transistor group 521 at the “c2” position and the “d2” position serves as an output of the source signal line 18 of G2 (green 2). The transistor group 521 at the “e2” position and the “f2” position is the output of the source signal line 18 of G3 (green 3).
[0785]
Further, the transistor group 521 at the “a3” position and the “b3” position serves as an output of the source signal line 18 of B1 (blue 1). The transistor group 521 at the “c3” position and the “d3” position becomes the output of the source signal line 18 of B2 (blue 2). The transistor group 521 at the “e3” position and the “f3” position becomes the output of the source signal line 18 of B3 (blue 3). The following is repeated in the same manner.
[0786]
The embodiment in FIG. 308 is an embodiment in which a transistor group 521L in a low gradation region and a transistor group 521H in a high gradation region are arranged as a set. In FIG. 309, unit transistors corresponding to each bit of the low gradation region transistor group 521L and unit transistors corresponding to each bit of the high gradation region transistor group 521H are alternately (distributed). This is an example. As described above, the arrangement and distribution of the transistor group 521 of the present invention has a wide variety of configurations. By implementing the configuration of the present invention, there is no variation in the output current Iw, and a uniform image display can be realized.
[0787]
As described above, by considering the arrangement of the transistor group 521 and the like, uniform image display can be realized. Furthermore, a more uniform image display can be realized by implementing the driving method described below. However, it goes without saying that the drive system described below is effective even when implemented alone.
[0788]
First, description will be made with reference to FIG. The program current Iw is output by the number of unit transistors 484 in the transistor group 521 that are in an operating state. The gradation is 0 when all the unit transistors 484 are off, and the gradation is 63 when the unit transistors of all the transistor groups 521 are on.
[0789]
In the gradation 32, the unit transistor 484 of the transistor group 521f is on (the switch 481f is on and the other switches 481 are off). In the gray scale 31, the unit transistor 484 of the transistor group 521a, transistor group 521b, transistor group 521c, transistor group 521d, and transistor group 521e is on (the switch 481f is off and the other switch 481 is on). ).
[0790]
Therefore, the unit transistor 484 that is turned on is completely different between the gradation 32 and the gradation 31. For this reason, if there is a characteristic difference between the unit transistors of the transistor group 521f and the unit transistors of the other transistor groups 521, gradation skip occurs. In addition, variations in the output current to each source signal line 18 are easily noticeable.
[0791]
In response to this problem, the present invention implements the driving method shown in FIG. In order to facilitate understanding, the gradation 32 is illustrated as an example. The indication “32” on the display screen 50 indicates a white raster display of gradation 32 (only the transistor group 521f is operating). The indication “31” on the display screen 50 indicates a white raster display of gradation 31 (other than the transistor group 521f is operating). That is, the gradation 32 is displayed in the first F, the gradation 31 is displayed in the second F, and the gradation display 32 and the gradation 31 are alternately repeated to display an image. That is, to perform gradation display, image display is performed by operating another transistor group 521 without being fixed to one transistor group 521. As described above, by operating a large number of unit transistors 484 using a plurality of fields (frames) to display an image, output variation does not occur and uniform image display can be realized.
[0792]
The above operation is generally expressed as follows. In the first F, the video signal data is converted into on / off data of the switch 481 as it is. In the next second F, after the video signal data is decremented by 1, it is converted into on / off data of the switch 481. In the next third F, the video signal data is converted into ON / OFF data of the switch 481 as it is. In the next 4F, the video signal data is decremented by 1, and then converted into on / off data of the switch 481. The above operation is repeated to display an image. That is, the transistor group 521 contributing to image display operates uniformly. In the gradation 32, the transistor group 521f operates, and in the gradation 31 reduced by 1, the elements other than the transistor group 521f operate. Therefore, the unit transistors 484 of all the transistor groups 521 operate, and the variation in output current in image display is greatly reduced. The driving method is also easy to implement because it only determines whether the video signal is decremented by -1 in synchronization with the 1F signal. However, the gradation 0 cannot be -1 (the unit transistors 484 of all the transistor groups 521 are in the off state). Therefore, the gradation 0 remains 0.
[0793]
The image display is an intermediate image display between the video signal and the -1 video signal. However, this difference is slight. Further, the image display is only in a state where the luminance is slightly lowered. As an effect, characteristic variations of the transistor group 521 are not displayed, and a very uniform image display can be realized.
[0794]
In the embodiment, the video signal is assumed to be -1, but the present invention is not limited to this. The video signal may be incremented by one. That is, in the first F, the video signal data is converted into on / off data of the switch 481 as it is. In the next second F, after the video signal data is incremented by 1, it is converted into on / off data of the switch 481. In the next third F, the video signal data is converted into ON / OFF data of the switch 481 as it is. In the next 4F, after the video signal data is incremented by 1, it is converted to on / off data of the switch 481. The above operation is repeated to display an image.
[0795]
Furthermore, -1 and +1 may be combined. That is, in the first F, the video signal data is converted into on / off data of the switch 481 as it is. In the next second F, after the video signal data is decremented by 1, it is converted into on / off data of the switch 481. In the next third F, the video signal data is converted into ON / OFF data of the switch 481 as it is. In the next 4F, after the video signal data is incremented by 1, it is converted to on / off data of the switch 481. The above operation is repeated at a cycle of 4F to display an image.
[0796]
Although the video signal is assumed to be -1, the present invention is not limited to this. It is good also as -2 or more or +2 or more. The present invention aims to achieve uniform image display by averaging unit fields (frames) by operating unit transistors 484 other than unit transistors 484 of transistor group 521 corresponding to video signals. is there. Therefore, the size is not limited to changing the original video signal.
[0797]
In FIG. 310, the transistor group 521f is selected in the first F, and the transistor group 521 other than the transistor group 521f is selected in the second F to display an image. In addition, the transistor group 521f is selected repeatedly after the third F and the transistor group 521 other than the transistor group 521 is operated in the fourth F. As described above, the variation in the output current can be averaged by alternately operating the plurality of transistor groups 521 and writing the program current Iw to the pixels, thereby realizing a uniform image display.
[0798]
In FIG. 310, it is more appropriate to change the unit transistor of the transistor group 521 to be turned on rather than to select and switch the transistor group 521 to be written to the pixel 16 for each field (frame). It is appropriate to operate 521 or add another transistor group 521. However, here, for the sake of explanation, the expression “switching” is adopted to facilitate uniform display. It was. However, the present invention is not limited to this. As illustrated in FIG. 311, the transistor group 521 that outputs the program current Iw to be written to the pixels may be switched for each pixel row (or a plurality of pixel rows). FIG. 311 (a) conceptually illustrates the writing state of the first F screen 50. In FIG. 311 (a), the output current of the transistor group 521f is written in the odd-numbered pixel row, and the output current of the transistor group 521 other than the transistor group 521f is written in the even-numbered pixel row. In the second F, as shown in FIG. 311B, the output current of the transistor group 521f is written in the even-numbered pixel row, and the output current of the transistor group 521 other than the transistor group 521f is written in the odd-numbered pixel row. This operation is repeated alternately in subsequent fields (frames).
In the above embodiment, only the gradation 32 is illustrated for easy understanding. In general, the video signal conversion described with reference to FIG. 310 is performed.
[0799]
In FIG. 311, the transistor group 521 to be written to the pixel 16 is switched for each pixel row or a plurality of pixel rows, and the transistor group 521 to be written to the pixel 16 is switched for each frame (field) or a plurality of frames (fields). By operating as described above, the current written to the pixels 16 can be averaged, and variations in image display can be reduced.
[0800]
In FIG. 311, uniform display is realized by selecting and switching the transistor group 521 to be written to the pixel 16 for each pixel row and switching the transistor group 521 to be written to the pixel 16 for each frame (field). However, the present invention is not limited to this. As illustrated in FIG. 312, the transistor group 521 that outputs the program current Iw written to the pixel may be switched for each pixel column (or a plurality of pixel columns). FIG. 311 (a) conceptually illustrates the writing state of the first F screen 50. In FIG. 311 (a), the output current of the transistor group 521f is written in the odd pixel column, and the output current of the transistor group 521 other than the transistor group 521f is written in the even pixel column. In the second F, as shown in FIG. 311 (b), the output current of the transistor group 521f is written in the even pixel column, and the output current of the transistor group 521 other than the transistor group 521f is written in the odd pixel column. This operation is repeated alternately in subsequent fields (frames).
[0801]
In FIG. 311, the transistor group 521 to be written to the pixel 16 is switched for each pixel column or a plurality of pixel columns, and the transistor group 521 to be written to the pixel 16 is switched for each frame (field) or a plurality of frames (fields). By operating as described above, the current written to the pixels 16 can be averaged, and variations in image display can be reduced.
In FIG. 311, the transistor group 521 to be written to the pixel 16 is changed for each pixel row, and in FIG. 326, the transistor group 521 to be written to the pixel 16 is changed for each pixel column. However, the present invention is not limited to this. For example, FIG. 311 and FIG. 312 may be combined. That is, the transistor group 521 to be written to the adjacent pixel row is changed, and the transistor group 521 to be written to the adjacent pixel column is changed. Needless to say, the present invention is not limited to adjacent pixel rows or pixel columns, and the transistor group 521 to be written to the pixels 16 may be changed by combining a plurality of pixel rows or a plurality of pixel columns. Further, the transistor group 521 to be written to the pixel 16 by R, G, and B may be changed.
[0802]
Needless to say, the concept of switching the transistor group 521 in the field (frame), the pixel row, and the pixel column can be applied to other embodiments of the present invention.
[0803]
In the above embodiment, the source driver IC 14 is expressed. However, the present invention is not limited to this. Needless to say, the present invention can also be applied to the source driver circuit 14 directly formed on the substrate 71 by the low temperature polysilicon technology, the high temperature polysilicon technology, the CGS technology, or the like.
[0804]
In the above embodiment, uniform display is realized by the source driver circuit (IC) 14 or by a driving method. The embodiment described below is a system that makes the characteristic variation unnoticeable mainly by considering the pixel arrangement of the display panel. Of course, a further characteristic effect can be exhibited by combining with the manufacturing method described in FIG. Further, by combining with the configuration and driving method described in FIGS. 299 to 312 and the like, a further characteristic effect can be exhibited. Further, by combining with other driving methods, configurations, specifications, and the like described in this specification, further characteristic effects can be exhibited.
[0805]
FIG. 313 is a pixel layout in the embodiment of the present invention. For ease of explanation, only one gate signal line 17a (G1, G2, G3,...) Is shown in the pixel 16. The source signal line 18 (S1, S2, S3, S4,...) Is used. The pixel 16 is described as P, and the pixel position is indicated by (m, n). Also, RGB is not represented.
[0806]
In FIG. 313, the source signal lines 18 and the gate signal lines 17a are linearly arranged in a matrix. The pixel P is connected to the gate signal line G3 with P (3,1), P (2,2), P (3,3), P (2,4), P (3,5). . Further, P (4,1), P (3,2), P (4,3), P (3,4), P (4,5),... Are connected to the gate signal line G4. FIG. 314 shows the pixel 16 into which the program current is written when the gate signal line 17a is selected in FIG. 313 for easy understanding.
[0807]
That is, in FIG. 314, when one gate signal line G is selected, the program current Iw is written to the pixels 16 at positions shifted by one pixel row alternately. Of course, the video current output from the source driver circuit 14 is controlled in accordance with the pixel position to be written.
[0808]
As shown in FIG. 313, since the pixel rows to be written are not linear (they are written at alternate vertical positions over two pixel rows), even if the program current Iw output from the source driver circuit 14 varies, In FIG. 314, since the writing is performed in a zigzag manner in two pixel rows, the variation is not conspicuous.
[0809]
FIG. 315 is a pixel layout in the second embodiment of the present invention. In FIG. 315, the source signal lines 18 and the gate signal lines 17a are linearly arranged in a matrix. The pixel P is connected to the gate signal line G3 by P (3,1), P (3,2), P (2,3), P (2,4), P (3,5), P (3,6).・ ・ Connected with Further, P (4,1), P (4,2), P (3,3), P (3,4), P (4,5), P (4,6),.・ It is connected to. FIG. 316 illustrates the pixel 16 into which the program current is written when the gate signal line 17a is selected in FIG.
[0810]
In other words, in FIG. 316, when one gate signal line G is selected, the program current Iw is written to the pixel 16 at a position shifted by one pixel row alternately every two pixel columns. Of course, the video current output from the source driver circuit 14 is controlled in accordance with the pixel position to be written.
[0811]
As shown in FIG. 315, since the pixel rows to be written are not linear (they are written at alternate vertical positions over two pixel rows), even if the program current Iw output from the source driver circuit 14 varies, In FIG. 316, since the writing is performed in a zigzag manner in two pixel rows, the variation is not conspicuous.
[0812]
In FIG. 317, the positions of the pixels 16 are delta arranged in the direction of the gate signal line 17a. In FIG. 317, the source signal line 18 is formed linearly. The gate signal line 17a is formed in a zigzag manner so as to be shifted by 1/2 pixel. The pixel P is connected to the gate signal line G2 by P (2,1), P (2,2), P (2,3), P (2,4), P (2,5), P (2,6).・ ・ Connected with Further, P (3,1), P (3,2), P (3,3), P (3,4), P (3,5), P (3,6),.・ It is connected to. FIG. 318 shows the pixel 16 into which the program current is written when the gate signal line 17a is selected in FIG.
[0813]
In other words, in FIG. 318, when one gate signal line G is selected, the program current Iw is written to the pixel 16 at a position shifted by half a pixel row alternately. Of course, the video current output from the source driver circuit 14 is controlled in accordance with the pixel position to be written.
[0814]
In FIG. 318, since the pixel rows to be written are not linear (the pixel rows are written alternately at the upper and lower positions), even if the program current Iw output from the source driver circuit 14 varies, the variation does not occur. Inconspicuous.
[0815]
In FIG. 319, the position of the pixel 16 is shifted by one pixel in the direction of the gate signal line 17a. In FIG. 319, the source signal line 18 is formed linearly. The gate signal line 17a is formed zigzag pixel by pixel. The pixel P is connected to the gate signal line G3 by P (3,1), P (2,2), P (3,3), P (2,4), P (3,5), P (2,6 ) ... and connected. The gate signal line G3 includes P (4,1), P (3,2), P (4,3), P (3,4), P (4,5), P (3,6). ... and connected.
[0816]
That is, in FIG. 319, when one gate signal line G is selected, the program current Iw is written to the pixels 16 at positions shifted by one pixel row alternately. Of course, the video current output from the source driver circuit 14 is controlled in accordance with the pixel position to be written. In FIG. 319, since the pixel rows to be written are not linear (written at alternate upper and lower positions), even if the program current Iw output from the source driver circuit 14 varies, the variation is not conspicuous.
[0817]
In FIG. 320, the pixel 16 position is delta-arranged in the direction of the source signal line 17a. In FIG. 320, the gate signal line 17a is formed linearly. The source signal line 18 is formed in a zigzag so as to be shifted by 1/2 pixel. The pixel P is connected to the source signal line S2 by P (1,2), P (2,2), P (3,2), P (4,2), P (5,2), P (6,3).・ ・ Connected with Further, P (1,3), P (2,3), P (3,3), P (4,3), P (5,3), P (6,3),.・ It is connected to.
[0818]
That is, in FIG. 320, when one gate signal line G is selected, the program current Iw is written to the pixel 16 at a position shifted by 1/2 pixel row alternately by one pixel row in the left-right direction. Of course, the video current output from the source driver circuit 14 is controlled in accordance with the pixel position to be written. In FIG. 320, since the pixel row to be written is not linear (the pixel pixel is written with a shift of 1/2 pixel in the horizontal direction over two pixel rows), even if the program current Iw output from the source driver circuit 14 varies, The variation is inconspicuous.
[0819]
FIG. 321 shows that the pixel 16 position is shifted by one pixel in the direction of the source signal line 18. In FIG. 321, the gate signal line 17a is formed linearly. The source signal line 18 is formed zigzag pixel by pixel. The pixel P is connected to the source signal line S3 by P (1,2), P (2,2), P (3,2), P (4,3), P (5,2), P (6,3 ) ... and connected. The source signal line S4 includes P (1,3), P (2,4), P (3,3), P (4,4), P (5,3), P (6,4). ... and connected.
[0820]
That is, in FIG. 321, when one gate signal line G is selected, the program current Iw is written to the pixels 16 at positions shifted by one pixel column alternately. Of course, the video current output from the source driver circuit 14 is controlled in accordance with the pixel position to be written. In FIG. 321, since the pixel columns to be written are not linear (written at alternate left and right positions), even if the program current Iw output from the source driver circuit 14 varies, the variation is not conspicuous.
[0821]
Needless to say, as shown in FIGS. 174 and 175, the transistor groups 521 may be interchanged.
[0822]
In FIGS. 167, 168, and 169, the current of the transistor 472b is defined by the resistor R1, but the current is not limited to this, and may be electronic volumes 451a and 451b as shown in FIG. 170, the electronic volume 451a and the electronic volume 451b can be operated independently. Therefore, the value of the current flowing through the transistor 472a1 and the transistor 472a2 can be changed. Therefore, it is possible to adjust the output current slope of the left and right output stages 521c of the chip. Note that one electronic volume 451 may be provided as shown in FIG. 171, and the two operational amplifiers 722 may be controlled. Also, the sleep switch 631 has been described with reference to FIG. Similarly, it goes without saying that a sleep switch may be arranged or formed as shown in FIG.
[0823]
Since the number of unit transistors 484 is very large in the one-stage configuration of the current mirror of FIGS. 166 to 172, the driver circuit output stage of the source driver IC (circuit) 14 will be described. For ease of explanation, FIGS. 168 and 169 will be described as an example. However, since the description relates to the number and total area of the transistors 473b and the number and total area of the unit transistors 484, it goes without saying that the description can be applied to other embodiments.
[0824]
In FIGS. 168 and 169, the total area of the transistors 473b in the transistor group 521b (WL size of the transistors 473b in the transistor group 521b × number of transistors 473b) is Sb. Note that in the case where the transistor group 521b is provided on the left and right of the gate wiring 581 as in FIGS. 168 and 169, the area is doubled. As shown in FIG. 167, the two cases are the area of the transistor 473b × 2. Needless to say, when the transistor group 521b includes one transistor 473b, the transistor group 521b has the size of one transistor 473b.
[0825]
The total area of the unit transistors 484 in the transistor group 521c (WL size of the transistors 484 in the transistor group 521c × number of transistors 484) is Sc. Let n be the number of transistor groups 521c. n is 176 in the case of the QCIF + panel (when a reference current circuit is formed for each RGB).
[0826]
  The horizontal axis of FIG. 165 is Sc × n / Sb. The vertical axis is the fluctuation ratio, and the fluctuation ratio is the mostgoodThe situation is 1. As shown in FIG. 165, as Sc × n / Sb increases, the fluctuation ratio becomes worse. An increase in Sc × n / Sb indicates that the total area of the unit transistors 484 in the transistor group 521c is larger than the total area of the transistors 473b in the transistor group 521b when the number of output terminals n is constant. In this case, the fluctuation ratio becomes worse.
[0827]
The smaller Sc × n / Sb indicates that the total area of the unit transistors 484 in the transistor group 521c is smaller than the total area of the transistors 473b in the transistor group 521b when the number of output terminals n is constant. In this case, the fluctuation ratio becomes small.
[0828]
As for the variation allowable range, Sc × n / Sb is 50 or less. If Sc × n / Sb is 50 or less, the variation ratio is within an allowable range, and the potential variation of the gate wiring 581 becomes extremely small. Therefore, there is no occurrence of lateral crosstalk, and output variation is within an allowable range, so that a good image display can be realized. If Sc × n / Sb is 50 or less, it is an acceptable range, but if Sc × n / Sb is 5 or less, there is almost no effect. Conversely, Sb increases and the chip area of the source driver IC 14 increases. Accordingly, Sc × n / Sb is preferably 5 or more and 50 or less.
[0829]
FIG. 185 illustrates the relationship between the IC breakdown voltage and the output variation of the unit transistors. With respect to the variation ratio of the vertical axis, the variation of the unit transistor 484 is set to 1 by the 1.8 (V) breakdown voltage process. Note that FIG. 185 shows the output variation of the unit transistor 484 manufactured by each withstand voltage process when the shape L / W of the unit transistor 484 is 12 (μm) / 6 (μm). In addition, a plurality of unit transistors are formed in each IC withstand voltage process, and output current variation is obtained. However, the breakdown voltage process is 1.8 (V) breakdown voltage, 2.5 (V) breakdown voltage, 3.3 (V) breakdown voltage, 5 (V) breakdown voltage, 8 (V) breakdown voltage, 10 (V) breakdown voltage, 15 ( V) Breakdown such as withstand voltage. However, for ease of explanation, the variation of the transistors formed at each breakdown voltage is entered in a graph and connected by a straight line.
[0830]
From FIG. 185, until the IC withstand voltage is about 9 (V), the increase rate of the variation ratio (output current variation of the unit transistor 484) with respect to the IC process is small. However, when the IC withstand voltage is 10 (V) or more, the slope of the variation ratio with respect to the IC withstand voltage increases.
[0831]
In FIG. 185, the variation ratio within 3 is the variation allowable range in the 64 gradation to 256 gradation display. However, this variation ratio varies depending on the area of the unit transistor 484 and L / W. However, even if the shape of the unit transistor 484 is changed, there is almost no difference in the variation tendency of the variation ratio with respect to the IC breakdown voltage. When the IC withstand voltage is 9 to 10 (V) or more, the variation ratio tends to increase.
[0832]
On the other hand, the potential of the output terminal 681 of the source driver IC (circuit) 14 changes depending on the program current of the driving transistor 11 a of the pixel 16. The gate terminal potential Vw when the driving transistor 11a of the pixel 16 passes white raster (maximum white display) current is used. A gate terminal potential Vb when the driving transistor 11a of the pixel 16 passes a black raster (full black display) current is used. The absolute value of Vw−Vb needs to be 2 (V) or more. Further, when the Vw voltage is applied to the output terminal 681, the channel-to-channel voltage of the unit transistor 484 needs to be 0.5 (V).
[0833]
Therefore, the output terminal 681 (the terminal 681 is connected to the source signal line 18 and the gate terminal voltage of the driving transistor 11a of the pixel 16 is applied during current programming) from 0.5 (V) to ((Vw A voltage of −Vb) +0.5) (V) is applied. Since Vw−Vb is 2 (V), a maximum of 2 (V) +0.5 (V) = 2.5 (V) is applied to the terminal 681. Therefore, even if the output voltage (current) of the source driver IC 14 is a rail-to-rail output, the IC withstand voltage needs to be 2.5 (V). The required amplitude range of the output terminal 681 is 2.5 (V) or more.
[0834]
From the above, it is preferable to use a process with a withstand voltage of the source driver IC 14 of 2.5 (V) or more and 10 (V) or less. More preferably, the source driver IC 14 has a withstand voltage of 3 (V) or more and 9 (V) or less. The IC withstand voltage is equivalent to the maximum power supply voltage that can be used. The power supply voltage that can be used is a voltage that can be used at all times and is not an instantaneous withstand voltage.
[0835]
In the above description, the withstand voltage process of the source driver IC 12 is assumed to be a process of 2.5 (V) or more and 10 (V) or less. However, this withstand voltage is also applied to an embodiment (such as a low-temperature polysilicon process) in which the source driver circuit 14 is formed directly on the array substrate 71. The use withstand voltage of the source driver circuit 14 formed on the array substrate 71 may be as high as 15 (V) or more. In this case, the power supply voltage used for the source driver circuit 14 may be replaced with the IC withstand voltage shown in FIG. Even in the source driver IC 14, the IC withstand voltage may be replaced with the power supply voltage to be used.
[0836]
The area of the unit transistor 484 is correlated with variations in output current. FIG. 186 is a graph when the area of the unit transistor 484 is constant and the transistor width W of the unit transistor 484 is changed. In FIG. 186, the variation of the channel width W = 2 (μm) of the unit transistor 484 is 1.
[0837]
As shown in FIG. 186, the variation ratio of the unit transistor gradually increases from 2 (μm) to 9 to 10 (μm), and the variation ratio tends to increase when the unit transistor is 10 (μm) or more. Also, the variation ratio tends to increase when the channel width W = 2 (μm) or less.
[0838]
In FIG. 186, the variation ratio within 3 is the variation allowable range in the 64 gradation to 256 gradation display. However, this variation ratio varies depending on the area of the unit transistor 484. However, even if the area of the unit transistor 484 is changed, there is almost no difference in the variation tendency of the variation ratio with respect to the IC breakdown voltage.
[0839]
From the above, the channel width W of the unit transistor 484 is preferably 2 (μm) or more and 10 (μm) or less. More preferably, the channel width W of the unit transistor 484 is preferably 2 (μm) or more and 9 (μm) or less. In addition, the channel width W of the unit transistor 484 is preferably formed in the above range in order to prevent linking of the gate wiring 581 in FIG.
[0840]
FIG. 187 is a graph of L / W of the unit transistor 484 and a deviation (variation) from the target value. When the L / W ratio of the unit transistor 484 is 2 or less, the deviation from the target value is large (the slope of the straight line is large). However, as L / W increases, the deviation of the target value tends to decrease. When the L / W of the unit transistor 484 is 2 or more, the change in deviation from the target value is small. The deviation (variation) from the target value is L / W = 2 or more and 0.5% or less. Therefore, it can be adopted in the source driver circuit 14 as transistor accuracy.
[0841]
From the above, the L / W of the unit transistor 484 is preferably 2 or more. However, large L / W means that L becomes long, so that the transistor size becomes large. Therefore, L / W is preferably 40 or less.
[0841]
The magnitude of L / W also depends on the number of gradations. When the number of gradations is small, there is no problem even if the output current of the unit transistor 484 varies due to the kink because the difference between the gradations is large. However, in a display panel with a large number of gradations, the difference between the gradations is small, so that the number of gradations is reduced if the output current of the unit transistor 484 varies even slightly due to the influence of kink.
[0843]
In consideration of the above, the source driver circuit 14 of the present invention sets the number of gradations to K and L / W of the unit transistor 484 (L is the channel length of the unit transistor 484 and W is the channel width of the unit transistor). Time,
It is configured (formed) so as to satisfy the relationship of (√ (K / 16)) ≦ L / W ≦ and (√ (K / 16)) × 20.
[0844]
In FIG. 169 and the like, when the total area Sa of the transistors 473a in the transistor group 521a is set as the total area Sb of the transistors 473b in the transistor group 521b, the relationship between the total area Sa and the total area Sb has a correlation with the output variation. This relationship is illustrated in FIG. Refer to FIG. 185 for the variation ratio and the like.
[0845]
The variation ratio is set to 1 when the total area Sb: total area Sa = 2: 1 (Sa / Sb = 1/2). As can be seen from FIG. 188, when Sa / Sb is small, the variation ratio suddenly deteriorates. In particular, when Sa / Sb = 1/2 or less, it tends to be worse. When Sa / Sb is 1/2 or more, output variation is reduced. The reduction effect is moderate. Further, the output variation is within an allowable range at about Sa / Sb = 1/2. In view of the above, it is preferable to form such that 1/2 <= Sa / Sb. However, as Sa increases, the IC chip size also increases. Therefore, the upper limit is preferably Sa / Sb = 4. That is, the relationship of 1/2 <= Sa / Sb <= 4 is satisfied.
[0846]
A> = B means that A is B or more. A> B means that A is larger than B. A <= B means A is B or less. A <B means that A is smaller than B.
[0847]
Furthermore, it is preferable that the total area Sb and the total area Sa are substantially equal. Further, it is preferable that the number of unit transistors 484 with one output and the number of transistors 633b in the transistor group 521c be the same. That is, in the case of 64 gradation display, 63 unit transistors 484 of 1 output are formed. Therefore, 63 transistors 633b constituting the transistor group 521c are formed.
[0848]
In addition, the transistor group 521a, the transistor group 521b, the unit transistor group 521c, and the unit transistor 484 are preferably formed using transistors having a WL area within four times. More preferably, the transistor is configured with a transistor having a WL area within twice. Furthermore, it is preferable that all the transistors be the same size. That is, it is preferable that the current mirror circuit and the output current circuit 704 are configured by transistors having substantially the same shape.
[0849]
The total area Sa is set to be larger than the total area Sb. Preferably, it is configured to satisfy the relationship of 200Sb> = Sa> = 4Sb. Further, the total area of the transistors 633a constituting all the transistor groups 521b is set to be substantially equal to Sa.
[0850]
In the one-stage source driver circuit as shown in FIG. 191, particularly when an image is displayed on the display panel, the source signal line potential varies depending on the current applied to the source signal line 18. There is a problem that the gate wiring 581 of the source driver IC 14 which is good against this potential fluctuation is fluctuated (see FIG. 184). As shown in FIG. 184, linking occurs in the gate wiring 581 at the point where the video signal applied to the source signal line 18 changes. Since the potential of the gate wiring 581 changes due to linking, the gate potential of the unit transistor 484 changes and the output current fluctuates. In particular, the potential fluctuation of the gate wiring 581 becomes crosstalk (lateral crosstalk) along the gate signal line 17.
[0851]
This fluctuation (linking of the gate wiring 581 (see FIG. 184)) is influenced by the power supply voltage of the source driver IC. This is because the peak value of linking increases as the power supply voltage increases. Worst, it swings to the power supply voltage. The voltage of the gate wiring 581 has a steady value of 0.55 to 0.65 (V). Therefore, even if slight linking occurs, the fluctuation value of the magnitude of the output current is large.
[0852]
FIG. 163 shows the potential variation ratio of the gate wiring with reference to the time when the power supply voltage of the source driver IC 14 is 1.8 (V). The variation ratio increases as the power supply voltage of the source driver IC 14 increases. The allowable range of the fluctuation ratio is about 3. If the fluctuation ratio is larger than this, lateral crosstalk occurs. The variation ratio tends to increase with respect to the power supply voltage when the IC power supply voltage is 10 to 12 (V) or higher. Therefore, the power supply voltage of the source driver IC 14 needs to be 12 (V) or less.
[0853]
On the other hand, in order for the driving transistor 11a to pass a current from white display to black display, the potential of the source signal line 18 needs to be changed by a constant amplitude. This required amplitude range is 2.5 (V) or more. The required amplitude range is below the power supply voltage. This is because the output voltage of the source signal line 18 cannot exceed the power supply voltage of the IC.
[0854]
From the above, the power supply voltage of the source driver IC 14 needs to be 2.5 (V) or more and 12 (V) or less. By setting it within this range, fluctuations in the gate wiring 581 are suppressed to the specified range, and horizontal crosstalk does not occur, and a good image display can be realized.
[0855]
The wiring resistance of the gate wiring 581 is also a problem. In FIG. 167, the wiring resistance R (Ω) of the gate wiring 581 is a resistance of the entire wiring length from the transistor 473b1 to the transistor 473b2. Alternatively, the resistance is the total length of the gate wiring. The magnitude of the transient phenomenon of the gate wiring 581 also depends on one horizontal scanning period (1H). This is because if the 1H period is short, the influence of the transient phenomenon is large. The higher the wiring resistance R (Ω), the more likely the transient phenomenon occurs. This phenomenon becomes a problem particularly in the configuration of the one-stage current mirror connection shown in FIGS. 166 to 172. This is because the gate wiring 581 is long and the number of unit transistors 484 connected to one gate wiring 581 is large. Of course, it goes without saying that the multistage connection of FIG. 162 is also a problem.
[0856]
FIG. 164 is a graph in which the wiring resistance R (Ω) of the gate wiring 581, the 1H period T (sec), and the multiplication (R · T) are plotted on the horizontal axis and the variation ratio is plotted on the vertical axis. The fluctuation ratio of 1 is based on R · T = 100. As can be seen from FIG. 164, when R · T is 5 or less, the variation ratio tends to increase. Further, when R · T is 1000 or more, the variation ratio tends to increase. Therefore, R · T is preferably 5 or more and 1000 or less.
[0857]
Duty ratio is also an issue. This is because the variation of the source signal line 18 also increases due to the duty ratio. Here, the total area of the unit transistors 484 in the transistor group 521c (WL size of the transistors 484 in the transistor group 521c × number of transistors 484) is Sc.
[0858]
In FIG. 189, the horizontal axis represents the Sc × Duty ratio, and the vertical axis represents the fluctuation ratio. As can be seen from FIG. 189, the fluctuation ratio tends to increase when the Sc × Duty ratio is 50 or more. Further, the fluctuation allowable range is when the fluctuation ratio is 3 or less. Therefore, it is preferable to control so that the Sc × Duty ratio can be driven at 50 or less.
[0859]
The variation allowable range is that the Sc × Duty ratio b is 50 or less. If the Sc × Duty ratio is 50 or less, the fluctuation ratio is within an allowable range, and the potential fluctuation of the gate wiring 581 becomes extremely small. Therefore, there is no occurrence of lateral crosstalk, and output variation is within an allowable range, so that a good image display can be realized. If the Sc × Duty ratio is 50 or less, it is acceptable, but if the Sc × Duty ratio is 5 or less, there is almost no effect. Conversely, the chip area of the source driver IC 14 increases. Therefore, the Sc × Duty ratio is preferably 5 or more and 50 or less.
[0860]
In FIG. 211, the reference current Ic1 that flows through the transistor 473b1 and the reference current Ic2 that flows through the transistor 473b2 are adjusted so that the cascade connection between the source driver ICs 14a and 14b can be satisfactorily performed as illustrated in FIG. did.
[0861]
In FIG. 211, the reference currents Ic1 and Ic2 are adjusted. However, if the gate wiring 581 has a resistance value greater than or equal to a predetermined value, even if the reference current Ic1 flowing through the transistor 473b1 and the reference current Ic2 flowing through the transistor 473b2 are the same, the output current of FIG. The tilt is corrected. This is because the correction current Id for correcting the inclination flows through the gate wiring 581 as shown in FIG.
[0862]
In order to facilitate understanding, specific numerical values will be described. Ic1 = Ic2 = 10 (μA). At this time, the gate terminal voltage V1 of the transistor 473b1 = 0.60 (V) and the gate terminal voltage V2 of the transistor 473b2 = 0.61 (V). Since the difference between the reference current flowing through the transistor 473b2 and the reference current flowing through the transistor 473b1 needs to be within 1%, 1% of the reference current = 10 (μA) is 0.1 (μA). Therefore, (V2−V1) /0.1 (μA) = (0.61−0.60) (V) /0.1 (μA) = 100 (KΩ). Therefore, by setting the resistance value of the gate wiring 581 to 100 (KΩ), the slope of the output current is adjusted, and the difference between the output currents of the adjacent source driver ICs 14 is within 1%.
[0863]
The higher the resistance of the gate wiring 581, the smaller the magnitude of the correction current Id. However, if the resistance value of the gate wiring 581 is too high, the peak value of linking in FIG. 184 also increases and the occurrence of lateral crosstalk becomes significant. Therefore, an appropriate range exists for the resistance value of the gate wiring 581.
[0864]
The present invention is characterized in that all of the gate wiring 581 or at least a part of the gate wiring 581 is formed of a wiring made of polysilicon. Preferably, polysilicon other than the contact portion with the gate terminal of unit transistor 484 or the vicinity thereof is formed. The gate wiring 581 is formed or configured to have a target resistance value by adjusting the wiring width or by meandering.
[0865]
Suppression of the linking of the gate wiring can be achieved by setting the gate wiring 581 to a resistance value equal to or lower than a predetermined value. Further, this can be achieved by increasing the total area Sb of the transistor 473b (total area Sb of the transistor group 521b). Further, this can be achieved by increasing the reference current Ic.
[0866]
When the area of one output unit transistor 484 (total area of unit transistors 484 in one transistor group 521c) is S0, the total area Sb of transistors 473b of the transistor group 521b (when there are a plurality of transistor groups 521b as shown in FIG. 213) Is the total area of the transistors 473b of the plurality of transistor groups 521b). FIG. 192 shows the relationship when Sb / S0 is on the horizontal axis and allowable gate wiring resistance (KΩ) is on the vertical axis. The range below the solid line in FIG. 192 is an allowable range (a range that is not affected by the occurrence of linking). In other words, lateral crosstalk is practically acceptable.
[0867]
The horizontal axis in FIG. 192 is the size S0 of the unit transistor 484 per output with respect to the size Sb of the total transistor group 521b (in the case of 64 gradations, 63 unit transistors 484). Assuming that S0 is a fixed value, the resistance value that the gate wiring 581 can tolerate increases as Sb increases. This is because as Sb increases, the impedance with respect to the gate wiring 581 decreases and the stability increases.
[0868]
Since S0 generates an output current (program current), and the output variation needs to be a certain value or less, the size of S0 has a narrow design change range. On the other hand, there are design restrictions in order to set the resistance value of the gate wiring 581 to a predetermined value. In order to increase the resistance of the gate wiring 581, there are a problem that the wiring becomes thin and disconnection occurs, and a problem of stability. Further, increasing Sb increases the chip area and the cost. Therefore, it is preferable to set Sb / S0 to 50 or less because of the problem of the chip size of the source driver IC 14, and Sb / S0 is set to 5 or more because of restrictions such as stable design of the gate wiring 581 and problems of linking. It is preferable. Therefore, it is necessary to satisfy the condition of 5 <= Sb / S0 <= 50.
[0869]
From the graph (solid line) in FIG. 192, the slope of the solid line curve becomes gentler as Sb / S0 becomes smaller. Further, when Sb / S0 is 15 or more, the inclination tends to be constant. Therefore, when Sb / S0 is 5 or more and 15 or less, the resistance value of the gate wiring 581 needs to be 400 (KΩ) or less. Further, when Sb / S0 is 15 or more and 50 or less, it is necessary to set Sb / S0 × 24 (KΩ) or less. For example, when Sb / S0 = 50, it is necessary to set it to 50 × 24 = 1200 (KΩ) or less.
[0870]
There is a correlation between the reference current Ic flowing through the transistor 473b and the allowable gate wiring resistance. This is because the larger the reference current Ic, the lower the impedance when the gate wiring 581 is viewed from the transistor 473b. FIG. 193 shows the relationship. In FIG. 193, the horizontal axis represents the reference current Ic (μA) flowing through the transistor 473b (or the transistor group 521b). The vertical axis represents allowable gate wiring resistance (KΩ). The range below the solid line in FIG. 193 is an allowable range (a range that is not affected by the occurrence of linking). In other words, lateral crosstalk is practically acceptable.
[0871]
When the reference current Ic is increased, the stability of the gate wiring 581 is improved. However, the reactive current consumed by the source driver IC 14 increases, and the potential of the gate wiring 581 also increases. For this reason, the reference current Ic needs to be 50 (μA) or less.
[0872]
If the reference current Ic is reduced, the stability of the gate wiring 581 decreases, so that the resistance value of the gate wiring 581 needs to be decreased. However, when the reference current is lowered below a certain value, the variation in the output current from the unit transistor 521c increases. That is, the stability of the output current is lost. Therefore, the reference current Ic needs to be 2 (μA) or more. From the above, the reference current Ic flowing through the transistor 473b needs to be 2 (μA) or more and 50 (μA) or less.
[0873]
The graph (solid line) in FIG. 193 can be approximated by two straight lines. When Ic is 2 (μA) or more and 15 (μA) or less, the resistance value (MΩ) of the gate wiring 581 needs to be 0.04 × Ic (MΩ) or less. For example, if Ic = 15 (μA), the resistance value of the gate wiring 581 needs to satisfy the condition of 0.04 × 15 = 0.6 (MΩ) or less.
[0874]
When Ic is 15 (μA) or more and 50 (μA) or less, the resistance value (MΩ) of the gate wiring 581 needs to be 0.025 × Ic (MΩ) or less. For example, if Ic = 50 (μA), the resistance value of the gate wiring 581 needs to satisfy the condition of 0.025 × 50 = 1.25 (MΩ) or less.
[0875]
There is also a correlation between a period in which one pixel row is selected (one horizontal scanning period (1H)) and the resistance R (KΩ) of the gate wiring 581 × the length D (m) of the gate wiring 581. This is because the shorter the period of 1H, the shorter the period required for the potential of the gate wiring 581 to return to the normal value. Further, as shown in FIG. 211, when the gate wiring 581 length D (= chip length of the driver IC) becomes longer, the potential fluctuation of the unit transistor group 521c farthest from the transistor 473b exceeds the allowable range. This phenomenon is presumed to be caused by the parasitic capacitance between the unit transistor 484 and the source signal line 18. That is, when the chip length D of the source driver IC 14 is increased, it is necessary to consider not only the simple resistance value of the gate wiring 581 but also the potential fluctuation of the gate wiring 581 due to parasitic capacitance.
[0876]
In FIG. 195, the horizontal axis represents one horizontal scanning period (μ seconds). The vertical axis represents the product of gate wiring resistance (KΩ) and chip length D (m). The range below the solid line in FIG. 195 is the allowable range. As for R · D, 9 (KΩ · m) is the production limit of the source driver IC. Above this, the cost increases and is not practical. On the other hand, when R · D is 0.05 or less, the current Id in FIG. 191 becomes too large, and the deviation of the adjacent output current becomes too large. Therefore, R · D (KΩ · m) needs to be 0.05 or more and 9 or less.
[0877]
When the transistor 11 constituting the pixel 16 is configured by a P channel, the program current flows in the direction from the pixel 16 to the source signal line 18. Therefore, the unit transistor 484 (see FIGS. 48 and 57) of the source driver circuit needs to be formed of an N-channel transistor. In other words, the source driver circuit 14 needs to be configured to draw the program current Iw.
[0878]
Therefore, when the driving transistor 11a of the pixel 16 (in the case of FIG. 1) is a P-channel transistor, the unit transistor 484 is configured with an N-channel transistor so that the source driver circuit 14 always draws the program current Iw. In order to form the source driver circuit 14 on the array substrate 71, it is necessary to use both an N channel mask (process) and a P channel mask (process). Describing conceptually, the display panel (display device) of the present invention comprises the pixel 16 and the gate driver circuit 12 by P-channel transistors, and the source current source transistor of the source driver by N-channel.
[0879]
Therefore, the transistor 11 of the pixel 16 is formed by a P-channel transistor, and the gate driver circuit 12 is formed by a P-channel transistor. Thus, by forming both the transistor 11 and the gate driver circuit 12 of the pixel 16 with P-channel transistors, the cost of the substrate 71 can be reduced. However, the source driver 14 needs to form the unit transistor 484 as an N-channel transistor. Therefore, the source driver circuit 14 cannot be formed directly on the substrate 71. Therefore, the source driver circuit 14 is manufactured separately using a silicon chip or the like and mounted on the substrate 71. That is, the present invention has a configuration in which a source driver IC 14 (means for outputting a program current as a video signal) is externally attached.
[0880]
Although the source driver circuit 14 is formed of a silicon chip, the present invention is not limited to this. For example, a large number of glass substrates may be simultaneously formed by low-temperature polysilicon technology, cut into chips, and loaded on the substrate 71. Although the description has been made assuming that the source driver circuit is loaded on the substrate 71, the present invention is not limited to loading. Any form may be used as long as the output terminal 681 of the source driver circuit 14 is connected to the source signal line 18 of the substrate 71. For example, a method of connecting the source driver circuit 14 to the source signal line 18 by TAB technology is exemplified. By separately forming the source driver circuit 14 on a silicon chip or the like, variation in output current can be reduced and a good image display can be realized. Moreover, cost reduction is possible.
[0881]
Further, the configuration in which the selection transistor of the pixel 16 is configured by a P channel and the gate driver circuit is configured by a P channel transistor is not limited to a self-luminous device (display panel or display device) such as an organic EL. For example, the present invention can be applied to a liquid crystal display device and FED (field emission display).
[0882]
When the switching transistors 11b and 11c of the pixel 16 are formed of P-channel transistors, the pixel 16 is selected by Vgh. The pixel 16 is in a non-selected state by Vgl. As described before, the voltage penetrates when the gate signal line 17a changes from on (Vgl) to off (Vgh) (penetration voltage). When the driving transistor 11a of the pixel 16 is formed of a P-channel transistor, the current does not flow through the transistor 11a due to the punch-through voltage in the black display state. Therefore, good black display can be realized. It is difficult to realize black display, which is a problem of the current driving method.
[0883]
In the present invention, the on-voltage is Vgh by configuring the gate driver circuit 12 with a P-channel transistor. Therefore, matching with the pixel 16 formed by the P channel transistor is good. Further, in order to exert the effect of improving the black display, the driving transistor 11a and the source signal are generated from the anode voltage Vdd as in the configuration of the pixel 16 in FIGS. 1, 2, 32, 113, and 116. It is important to configure the program current Iw to flow into the unit transistor 484 of the source driver circuit 14 via the line 18. Therefore, it is excellent synergistic effect that the gate driver circuit 12 and the pixel 16 are composed of P channel transistors, the source driver circuit 14 is mounted on the substrate, and the unit transistors 484 of the source driver circuit 14 are composed of N channel transistors. Demonstrate. Further, the unit transistor 484 formed by the N channel has a smaller variation in output current than the unit transistor 484 formed by the P channel. When compared with the transistor 484 having the same area (W · L), the variation in output current of the N-channel unit transistor 484 is 1 / 1.5 to 1/2 compared to the P-channel unit transistor 484. . For this reason, the unit transistor 484 of the source driver IC 14 is preferably formed of an N channel.
[0884]
The same applies to FIG. 42B. In FIG. 42B, current does not flow into the unit transistor 484 of the source driver circuit 14 via the driving transistor 11b. However, the configuration is such that the program current Iw flows from the anode voltage Vdd into the unit transistor 484 of the source driver circuit 14 via the programming transistor 11 a and the source signal line 18. Therefore, as in FIG. 1, the gate driver circuit 12 and the pixel 16 are configured by P-channel transistors, the source driver circuit 14 is mounted on the substrate, and the unit transistors 484 of the source driver circuit 14 are configured by N-channel transistors. Exerts an excellent synergistic effect.
[0885]
In the present invention, the driving transistor 11a of the pixel 16 is configured by the P channel, and the switching transistors 11b and 11c are configured by the P channel. Further, the unit transistor 484 in the output stage of the source driver IC 14 is configured with N channels. Preferably, the gate driver circuit 12 is composed of a P-channel transistor.
[0886]
Needless to say, the above-described reverse configuration is effective. The driving transistor 11a of the pixel 16 is configured with an N channel, and the switching transistors 11b and 11c are configured with an N channel. Further, the unit transistor 484 in the output stage of the source driver IC 14 is configured as a P channel. Preferably, the gate driver circuit 12 is composed of an N channel transistor. This configuration is also a configuration of the present invention.
[0887]
Hereinafter, the reference current circuit will be described. As shown in FIG. 68, the reference current circuit 691 is formed (arranged) for each of R, G, and B. Further, the reference current circuits 691R, 691G, and 691B are arranged close to each other.
[0888]
  R reference current circuit691In R, a volume (electronic volume) 491R for adjusting the reference current is arranged, and the G reference current circuit691In G, a volume (electronic volume) 491G for adjusting a reference current is arranged, and a reference current circuit for B is arranged.691In B, a volume (electronic volume) 491B for adjusting the reference current is arranged.
[0889]
Note that the volume 491 and the like are preferably configured to change with temperature so that the temperature characteristics of the EL element 15 can be compensated. 69, the reference current circuit 691 is controlled by a current control circuit 692. By controlling (adjusting) the reference current, the unit current output from the unit transistor 484 can be changed.
[0890]
In the current output method of the present invention described above (the source driver of the liquid crystal display panel is a voltage output method (a signal is a voltage step)), a plurality of unit currents proportional to the reference current are combined based on the reference current. The program current Iw is output. Therefore, it is important that the reference current can be accurately generated without variation between chips.
[0891]
FIG. 331 shows an example. 49 and 162, the reference current is created by the resistor 471. In FIG. 167, the reference current is created by the resistor R1. In FIG. 331, the resistor 471 in FIG. 68 is replaced with a transistor, and the current flowing through the transistor 3314 forming a current mirror circuit with this transistor is controlled by using an operational amplifier 722 or the like (see FIG. 170 and the like). The transistor 3314 and the transistor form a current mirror circuit. If the current mirror magnification is 1, the current flowing through the transistor 3313 becomes the reference current. Note that 654 described in FIG. 331 and the like is a circuit for generating a program current Iw.
[0892]
The output voltage of the operational amplifier 722 is input to the N-channel transistor 3313, and the current flowing through the transistor 3313 flows through the external resistor 531a. The resistor 531a is a fixed chip resistor. Basically, only the resistor 531a is required. The resistor 531b is a resistance element whose resistance value changes with temperature, such as a posistor or a thermistor. The resistor 531a is used to compensate for the temperature characteristics of the EL element 15. The resistor 531a is inserted or arranged in parallel or in series with the resistor 531b in accordance with the temperature of the EL element 15 particularly (to compensate). Also in FIG. 170 and the like, the resistor 531b may be formed or arranged in parallel or in series with the resistor R1. In the following description, the resistor 531a and the resistor 531b are regarded as one resistor 531 for ease of explanation.
[0893]
The resistor 531a is a chip resistor. Therefore, those with an accuracy of 1% or more can be easily obtained. If the resistor is configured in the IC using diffusion resistance technology or a polysilicon pattern, the resistance value accuracy is very poor. Therefore, it is preferable that the resistor 531a that determines the reference current is a highly accurate external resistor. The chip resistor 531a is attached to the input terminal 681a. In particular, in the EL display panel, the temperature characteristics of the EL element 15 are different for each RGB. Therefore, three external resistors 531a for each RGB are required.
[0894]
The terminal voltage of the resistor 531 is the negative input of the operational amplifier 722, and the negative terminal voltage and the positive terminal of the operational amplifier 722 are the same voltage. Therefore, if the + input voltage of the operational amplifier 722 is V1, the voltage divided by the resistor 531 is the current flowing through the transistor 3314. This current becomes the reference current.
[0895]
If the resistance value of the resistor 531 is 100 KΩ and the input voltage at the + terminal of the operational amplifier 722 is V1 = 1 (V), a reference current of 1 (V) / 100 KΩ = 10 (μA) flows through the resistor 531. . The magnitude of the reference current is preferably set to 2 μA or more and 30 μA or less. More preferably, it is set to 5 μA or more and 20 μA or less. If the reference current flowing through the parent transistor 63 is small, the accuracy of the unit current source 484 is deteriorated. If the reference current is too large, the current mirror magnification converted in the IC (in this case, the reduction direction) increases, the variation in the current mirror circuit increases, and the accuracy of the unit current source 484 deteriorates as before. Needless to say, the above matters also apply to other embodiments of the present invention. The same applies to the items described below.
[0896]
According to the above configuration, if the accuracy of the + input terminal of the operational amplifier 722 is good and the resistance value accuracy 531 is good, an extremely accurate reference current (size, variation accuracy) can be formed. The reference voltage Vref from the reference voltage circuit 3311 is applied to the + terminal of the operational amplifier 722. Many types of ICs for the reference voltage circuit 3311 for outputting the reference voltage are available from Maxim Corporation. The reference voltage Vref can also be formed in the source driver circuit 14 (incorporation of the reference voltage Vref). The range of the reference voltage Vref is preferably 1 (V) or more and 3 (V) or less.
[0897]
The reference voltage is input from the connection terminal 681a. Basically, this Vref voltage may be input to the + terminal of the operational amplifier 722. The reason why the electronic volume circuit 451 is disposed between the connection terminal 681a and the + terminal is that the EL elements 15 have different luminous efficiencies in RGB. In other words, this is for adjusting the current flowing through the RGB EL elements 15 to achieve white balance. Of course, when adjustment can be made with the resistor 531, adjustment with the electronic volume 451 is not necessary. The electronic volume 451 can be used for white balance adjustment again because the EL element 15 is RGB and the deterioration rate is different. In particular, B is easily deteriorated in the EL element 15. For this reason, when an EL display panel is used, the B EL element 15 becomes dark over many years, and the screen turns yellow. In this case, the white balance is implemented by adjusting the electronic volume 451 for B. Needless to say, the electronic volume 451 may be linked to the temperature sensor 781 (see FIG. 78 and the description thereof) to perform EL element luminance compensation or white balance compensation.
[0898]
The electronic volume 451 is built in the IC (circuit) 14 (formed directly on the substrate 71). A plurality of unit resistors (R1, R2, R3, R4,... Rn) are formed by patterning polysilicon and connected in series. Further, analog switches (S1, S2, S2,... Sn + 1) are arranged between the unit resistors, and the reference voltage Vref is divided to output a voltage.
[0899]
In FIG. 331, the transistor 3313 is illustrated as a bipolar transistor; however, the present invention is not limited to this. FIG. 332 (a) shows an embodiment in which the transistor 3313 is an FET. Needless to say, the transistor 3313 need not be built in the IC 14 and may be arranged outside the IC. In addition, a generation circuit such as a power source may be incorporated in the gate driver circuit 12, and a transistor 3313 may be incorporated.
[0900]
Further, instead of the reference voltage circuit 3311 as shown in FIG. 331, the reference voltage Vref may be generated by a Zener diode 3321 and a resistor 531 as shown in FIG. Of course, it is not necessary to use the operational amplifier 722 as shown in FIG. The Zener diode 3321 may be a variable type of reference voltage.
[0901]
When the number of pixels of the EL display panel is large, it is necessary to load a plurality of source driver ICs (circuits) 14 on one EL display panel. In this case, it is necessary to use the reference voltage so as to be common to a plurality of source driver ICs. Simply, a plurality of source driver ICs 14 using the reference voltage Vref from one reference voltage circuit 3311 may be input. A problem arises when the reference voltage input to the operational amplifier 722 is changed by operating (controlling) the electronic volume 451 in FIG. In order to facilitate the following description, the voltage input to the + terminal of the operational amplifier will be referred to as an adjustment reference voltage Vrs. Vrs is a voltage obtained by adjusting the reference voltage Vref to a voltage used in the source driver IC 14.
[0902]
As described above, according to the present invention, in a current output (source) driver circuit (IC), a reference voltage is generated internally or input from the outside, and a reference current is generated from the reference voltage. A plurality of unit current sources 484 are configured, and an output (absorbed) current is changed by switching the number of unit current sources 484 according to an external video (image) data signal.
[0903]
When the adjustment reference voltage Vrs is used, it is necessary to use this adjustment reference voltage Vrs in another source driver 14. FIG. 333 shows an example. The reference voltage Vref from the reference voltage circuit 3311 is voltage-adjusted by the electronic volume circuit 451a to become the adjusted reference voltage Vrs. This adjustment reference voltage Vrs is input to the buffer circuit 3332. The reason why the buffer circuit 3332 is arranged is to suppress fluctuations in the Vrs voltage due to the connection of another source driver 14 to the adjustment reference voltage output wiring 1453. The output Vrs of the buffer circuit 3332 is applied to the + terminal of the operational amplifier 722 and to the adjustment reference voltage output wiring 3333.
[0904]
The adjustment reference voltage output wiring 3333 is connected to the adjustment reference voltage output terminal 3341. A wiring 3331 is connected to the adjustment reference voltage output terminal 3341, and the adjustment reference voltage Vrs is supplied to the other source driver circuit 14 through the wiring 3331. In FIG. 333, an electronic volume 451 b is formed or arranged between the terminal 681 b and the emitter terminal of the transistor 3313. The configuration of the electronic volume 451b is the same as that of the electronic volume 451a. However, the electronic volume 451b changes the magnitude of the reference current according to the magnitude of the resistance value. That is, the electronic volume 451b changes the number of series resistors by turning on and off an internal switch. The magnitude of the reference current varies depending on the resistance value of the electronic volume 451b + the resistance 531 and the Vrs voltage. The maximum resistance of the electronic volume 451b is set to 1/5 or less of the resistance of the resistor 531. This is because variations in the resistance value of the electronic volume 451b result in variations in the reference current. The electronic volume 451b is mainly used for temperature characteristic compensation of the EL element 15.
[0905]
In order to realize full color display on an EL display panel, it is necessary to form (create) a reference current for each of RGB. White balance can be adjusted by the ratio of RGB reference currents. In the case of the current driving method, as shown in FIG. 251, the current I and the luminance B have a linear relationship. Further, the present invention determines the current value that the unit current source 484 flows from one reference current. Therefore, if the magnitude of the reference current is determined, the current that the unit current source 484 flows can be determined. For this reason, if R, G, and B reference currents are set, white balance can be obtained in all gradations. The above matter is a significant feature of the source driver circuit 14 being current step output (current drive). Therefore, the point is how to set the magnitude of the RGB reference current.
[0906]
The luminous efficiency of the EL element is determined (dominant) by the thickness of the deposited or applied EL material. The film thickness is almost constant from lot to lot. Therefore, if the formed film thickness of the EL element 15 is managed as a lot, the relationship between the current passed through the EL element 15 and the light emission luminance is determined. That is, the current value for white balance is fixed for each lot. For example, if the current flowing through the R EL element 15 is Ir (A), the current flowing through the G EL element 15 is Ig (A), and the current flowing through the B EL element 15 is Ib (A), then Ir: Ig : It can be seen that white balance can be obtained when Ib = 1: 2: 4. Therefore, the value of the fixed resistor 531 is determined so that this current flows. If the R circuit resistor 531R is Rr (Ω), the G circuit resistor 531G is Rg (Ω), the B circuit resistor 531B is Rb (Ω), and the adjustment reference voltage Vrs is common to RGB, then Rr: Rg: The resistance value 531 may be set so that Rb = 4: 2: 1. By simply setting in this way, the EL display panel of the present invention can achieve white balance over all gradations. This point is a very effective effect of the present invention.
[0907]
The adjustment reference voltage VrsR of the R circuit is connected to the adjustment reference voltage output terminal 3341R for cascade connection with the other source driver circuit 14. Similarly, the adjustment reference voltage VrsG of the G circuit is also connected to the adjustment reference voltage output terminal 3341G in order to cascade-connect with the other source driver circuit 14. Further, the adjustment reference voltage VrsB of the B circuit is also connected to the adjustment reference voltage output terminal 3341B for cascade connection with the other source driver circuits 14. The other points are the same as in FIG.
[0908]
In the embodiment of FIG. 334, the adjustment reference voltages (VrsR, VrsG, VrsB) are output from the adjustment reference voltage output 3341 for each of RGB, but the present invention is not limited to this. When adjustment is not necessary in the electronic volume circuit 451a (451Ra, 451Ga, 451Ba) for each RGB (for example, when white balance adjustment, temperature compensation, etc. can be performed with the fixed resistor 531 arranged or formed for each RGB) The output of the adjustment reference voltage Vrs for each RGB is not necessary. In addition, when the reference voltage Vref from the outside can be used as it is (when the + terminal input of the operational amplifier 722 is set to Vref), it goes without saying that the electronic volume circuits 451a (451Ra, 451Ga, 451Ba) for each RGB are not necessary. .
[0909]
The source driver circuit (IC) 14 needs to switch between using the reference voltage Vref or adjusting reference voltage Vrs for cascade connection. FIG. 335 shows an embodiment of the source driver circuit (IC) 14 of the present invention incorporating a reference voltage changeover switch 3352.
[0910]
In order to set whether to use the reference voltage Vref or the adjustment reference voltage Vrs, in the present invention, a switching terminal (not shown) of the switch 3352 is provided as an IC terminal, and a logic voltage applied to this terminal The switch 3352 can be switched. This is also used as a master / slave selector switch of the source driver IC 14. Since the master / slave function has been described with reference to FIG.
[0911]
The configuration described above is illustrated in FIG. The reference voltage Vref from one reference voltage circuit 3311 is input to the source driver circuit 14 from the terminal 681a. This voltage is adjusted by the RGB electronic volume circuits 451a (451Ra, 451Ga, 451Ba) as necessary, and the adjustment reference voltage Vrs (VrsR for the R circuit, VrsG for the G circuit, VrsB for the B circuit) is each RGB. To the operational amplifier 722.
[0912]
The reference voltage changeover switch 3352 determines whether the output voltage V2 of the electronic volume circuit 451 inside the source driver IC 14 is input to the operational amplifier 722 or the external reference voltage V1 applied to the terminal 3353 is input to the operational amplifier 722. Switch. When the V2 voltage is input to the operational amplifier 722, the IC (circuit) 14 is used in the master mode. In this case, the V2 voltage is output from the adjustment reference voltage output 3341, and the adjustment reference voltage input terminal 3353 of the source driver IC (circuit) 14 serving as the slave is connected to the wiring 3331 connected to the adjustment reference voltage output 3341. It will be. As described above, when the plurality of source driver circuits (ICs) 14 operate with the reference voltage Vref from one reference voltage circuit 3311 as an input without distinguishing between master and slave, the changeover switch 3352 is It is unnecessary. This is because the reference voltage Vref or the adjustment reference voltage Vrs generated inside the IC becomes the + terminal input of the operational amplifier 722 of each IC. In addition, since other matters have been described above, description thereof will be omitted.
[0913]
An important matter in FIG. 335 is that two adjustment reference voltage input terminals 3353 are provided. Within the source driver IC 14, terminals 3353a and 3353b are connected. This point will be described with reference to FIG.
[0914]
FIG. 336 conceptually illustrates a state in which a plurality of source driver circuits (ICs) 14 are mounted. The drawing shows a state observed through the back surface of the substrate 71 (observed from the back surface of the source driver IC 14). Note that items regarding the base anode wiring 2631, the common anode wiring 2642, and the like have been described with reference to FIGS. 263, 264, 267, and the like, and thus description thereof will be omitted. The above matters also apply to FIGS. 337 and 338.
[0915]
In FIG. 336, the adjustment reference voltage outputs 3341 and 3353 are arranged in the center of the source driver IC 14 chip, and are parallel to the formation direction of the source signal line 18 (parallel to the short side direction of the IC chip). Arranged (formed). As described above, the wiring is formed so that the wiring 3331 connected to the terminal does not intersect.
[0916]
The reference voltage Vref is applied to the source driver IC 14a from the reference voltage circuit 3311 to the terminal 681a by wiring. Therefore, the source driver IC 14a operates as a master. The changeover switch 3352 in the IC is in the input state of the V2 voltage (see FIG. 335). The source driver ICs 14b and 14c mounted adjacent to the source driver IC 14a operate as slaves. The changeover switch 3352 of the source driver IC 14b and the source driver IC 14c is in the V1 voltage input state (see FIG. 335).
[0917]
In FIG. 336, the adjustment voltage Vrs from the source driver IC 14a is output from each RGB adjustment reference voltage output terminal 3341 (3341R, 3341G, 3341B), and the adjustment of the source driver IC 14b and the source driver IC 14c is performed via the wiring 3331 or 3351. The voltage is input to the voltage input terminal 3353 (3353R, 3353G, 3353B). This voltage is the V2 voltage.
[0918]
If the adjustment reference voltage outputs 3341 and 3353 for each RGB are arranged as shown in FIG. 336, the wirings 3351 and 3331 do not cross each RGB. Therefore, the wiring layout is facilitated. Further, since only the reference current flows through the adjusted reference voltage outputs 3341 and 3351, there is no potential change as in the video signal line. Therefore, it can be used as a light shielding pattern as with the base anode line 2631. That is, even if it is arranged on the back surface of the source driver IC 14, noise or the like is generated and the source driver IC 14 is not affected. This effect can be applied as it is by replacing the base anode line 2631 with the adjustment reference voltage output 3341 (3351) in the matters described in FIG. 101, FIG. 102, FIG.
[0919]
FIG. 337 is an explanatory diagram of the effect of forming a plurality of adjustment reference voltage input terminals 3353 described in FIG. In FIG. 337, unlike FIG. 336, the adjusted reference voltage outputs 3341 and 3353 are formed at the edge of the source driver IC. That is, they are formed or arranged on the same side as the video signal input terminal and control terminal of the IC.
[0920]
In the source driver IC 14a, the reference voltage Vref from the reference voltage circuit 3311 is applied to the terminal 681a by wiring. Therefore, the source driver IC 14a operates as a master. The changeover switch 3352 in the IC is in the input state of the V2 voltage (see FIG. 335). The source driver ICs 14b and 14c mounted adjacent to the source driver IC 14a operate as slaves. The changeover switch 3352 of the source driver IC 14b and the source driver IC 14c is in the V1 voltage input state (see FIG. 335).
[0921]
In FIG. 337, the adjustment voltage Vrs from the source driver IC 14a is output from the adjustment reference voltage output terminal 3341. Although not shown in FIG. 335, one adjustment reference voltage output terminal 3341 is formed on each side of the reference voltage input terminal 681a (3341a, 3341b). The adjustment reference voltage Vrs is input to the adjustment voltage input terminal 3353 (3353a, 3353b) of the source driver IC 14b and the source driver IC 14c via the wiring 3331 or 3351. This voltage is the V2 voltage.
[0922]
The adjustment reference voltage input terminals 3353a and 3353b are electrically connected as shown in FIG. Therefore, the voltage Vrs output from the adjusted reference voltage output 3341a of the source driver IC 14a is applied to the terminal 3353b of the source driver IC 14b, and this voltage Vrs is output to the terminal 3353a via the IC 16b. The terminal 3353a is input to the terminal 3353 to the source driver IC 14 mounted adjacent to the other. Similarly, the voltage Vrs output from the adjusted reference voltage output 3341b of the source driver IC 14a is applied to the terminal 3353a of the source driver IC 14c, and this voltage Vrs is output to the terminal 3353b via the IC 16c. The terminal 3353b is input to the terminal 3353 to the source driver IC 14 mounted adjacent to the other. By arranging or connecting the terminals 3353 and 3341 as described above, ICs can be connected in cascade.
[0923]
If the adjustment reference voltage outputs 3341 and 3353 are arranged as shown in FIG. 337 and the wirings 3351 and 3331 are formed on the back surface of the IC, the wirings 3351 and 3331 do not cross each other. Therefore, the wiring layout is facilitated. Similarly to FIG. 336, the adjustment reference voltage outputs 3341 and 3351 only have a reference current flowing therethrough, and thus there is no potential change as in the video signal line. Therefore, it can be used as a light shielding pattern as well as the base anode line 2631. That is, even if it is arranged on the back surface of the source driver IC 14, noise or the like is generated and the source driver IC 14 is not affected. This effect can be applied as it is by replacing the base anode line 2631 with the adjusted reference voltage output 3341 (3351) in the matters described with reference to FIG.
[0924]
FIG. 337 shows the EL display device as a single color for ease of explanation. The EL display device is composed of three colors of RGB. Therefore, adjustment reference voltage outputs 3341 and 3353 are necessary for each RGB. FIG. 338 is a configuration diagram in which adjustment reference voltage outputs 3341 and 3353 are arranged for each RGB.
[0925]
The source driver IC 14a operates as a master, and the reference voltage Vref from the reference voltage circuit 3311 is applied to the terminal 681a in the source driver IC 14a. Adjusted reference voltage output terminals 3341 are arranged on the left and right sides of the reference voltage input terminal 681a. Each RGB adjustment reference voltage output terminal 3341 is arranged at a line-symmetrical position with respect to the reference voltage input terminal 681a. That is, the left and right terminals of the input terminal 681a are 3341Ra and 3341Rb, and 3341Ga and 3341Gb are arranged outside the terminals. Further, 3341Ba and 3341Bb are arranged outside thereof. The adjusted reference voltage outputs 3341Ra and 3341Rb are connected inside the source driver IC 14a. Similarly, the adjustment reference voltage outputs 3341Ga and 3341Gb are also connected inside the source driver IC 14a. Further, the adjustment reference voltage outputs 3341Ba and 3341Bb are also connected inside the source driver IC 14a.
[0926]
The source driver IC 14b operates as a slave, and the adjustment reference voltage Vrs from the source driver IC 14a is input to the source driver IC 14b. Adjustment reference voltage input terminals 3353 are arranged on the left and right sides of the reference voltage input terminal 681a. Each RGB adjustment reference voltage input terminal 3353 is arranged at a line-symmetrical position with respect to the reference voltage input terminal 681a. That is, the left and right terminals of the input terminal 681a are 3353Ra and 3353Rb, and 3353Ga and 3353Gb are arranged outside the terminals. Further, 3353Ba and 3353Bb are arranged outside thereof. The terminals 3353Ra and 3353Rb are connected inside the source driver IC 14a. Similarly, the terminals 3353Ga and 3353Gb are also connected inside the source driver IC 14a. Terminals 3353Ba and 3353Bb are also connected inside the source driver IC 14a (see FIG. 335).
[0927]
The voltage Vrs output from the adjustment reference voltage output 3341Bb of the source driver IC 14a is applied to the terminal 3353Ba of the source driver IC 14b, and this voltage Vrs is output to the terminal 3353Bb via the IC 16b. The terminal 3353Bb is input to the terminal 3353 in the source driver IC 14 mounted adjacent to the other. The voltage Vrs output from the adjustment reference voltage output 3341Gb of the source driver IC 14a is applied to the terminal 3353Ga of the source driver IC 14b, and this voltage Vrs is output to the terminal 3353Gb through the IC 16b. Further, the terminal 3353Gb is input to the terminal 3353 to the source driver IC 14 mounted adjacent to the other. Similarly, the voltage Vrs output from the adjustment reference voltage output 3341Rb of the source driver IC 14a is applied to the terminal 3353Ra of the source driver IC 14b, and this voltage Vrs is output to the terminal 3353Rb through the IC 16b. Further, the terminal 3353Rb is input to the terminal 3353 to the source driver IC 14 mounted adjacent to the other. By arranging or connecting the terminals 3353 and 3341 as described above, the IC can be easily connected to the cascade.
[0928]
If the adjustment reference voltage outputs 3341 and 3353 are arranged and the wirings 3351 and 3331 are formed on the back surface of the IC as shown in FIG. 338, the wirings 3351 and 3331 do not cross each other. Therefore, the wiring layout is facilitated. Similarly to FIG. 336, the adjustment reference voltage outputs 3341 and 3351 only have a reference current flowing therethrough, and thus there is no potential change as in the video signal line. Therefore, it can be used as a light shielding pattern as well as the base anode line 2631. That is, even if it is arranged on the back surface of the source driver IC 14, noise or the like is generated and the source driver IC 14 is not affected. This effect can be applied as it is by replacing the base anode line 2631 with the adjustment reference voltage output 3341 (3351) in the matters described in FIG. 101, FIG. 102, FIG.
[0929]
77, 78, 79, 80, 81, etc., the gamma current ratio has been described. 56 is the ratio of the current flowing through the unit current source 484 in the low gradation part of FIG. 56 to the current flowing through the unit current source 484 in the high gradation part of FIG. It is preferable to set the reference current of the high gradation part to INH and the reference current of the low gradation part to INL, and to set this ratio (gamma current ratio) within a predetermined range, while the reference current is basically Therefore, it is preferable to reduce the adjustment to one current as much as possible (if the reference current for the high gradation part is INH and the reference current for the low gradation part is INL, two reference currents for each RGB) Adjustment is required).
[0930]
FIG. 339 shows a configuration in which a single reference current Ib is used for each RGB. The upper circuit in FIG. 339 is a current source for high gradation, and the lower one is a current source for low gradation (more precisely, the current of the low gradation current source also flows in the high gradation portion). The left part of FIG. 339 is the circuit configuration of FIGS. 333 and 335.
[0931]
An original reference current Ib flows through the transistor 3313. At least one variable-magnification transistor 3392 is formed or arranged in parallel with the high-gradation parent transistor 471aH. The low gradation parent transistor 471aL forms a current mirror circuit with the transistor 3314 as it is. Therefore, the high gradation current mirror circuit includes the transistor 3314, the transistor 3392, and the transistor 471aH. A variable magnification switch 3391 is formed or arranged in series with the transistor 3392. The switch 3391 is exemplified by an analog switch or the like.
[0932]
By controlling on / off of the switch 3391, the current flowing through the transistor 471bH can be changed. When the switch 3391b is turned on, two transistors 3392 + current flowing through the transistor 471aH flows through the transistor 471bH. When the switch 3391a is turned on, one transistor 3392 plus a current flowing through the transistor 471aH flows through the transistor 471bH. When the switches 3391a and 3391b are turned on at the same time, three transistors 3392 + current flowing through the transistor 471aH flows through the transistor 471bH. The switch 3391 is switched by a command to the source driver IC 14. As described above, the gamma current ratio can be changed by the control of the switch 3391. Also, since the reference current is only Ib, the white balance can be adjusted very easily. Other configurations have been described with reference to FIGS. 48, 333, 335, 79, 80, 81, and the like, and thus description thereof will be omitted.
[0933]
An output pad 681 is formed or arranged at the output terminal of the IC chip. This output pad is connected to the source signal line 18 of the display panel. The output pad 681 has bumps (projections) formed by a plating technique or a nail head bonder technique. The height of the protrusion is set to be 10 μm or more and 40 μm or less.
[0934]
The bumps and the source signal lines 18 are electrically connected via a conductive bonding layer (not shown). Conductive bonding layer is mainly composed of epoxy, phenolic, etc. as adhesive and mixed with flakes such as silver (Ag), gold (Au), nickel (Ni), carbon (C), tin oxide (SnO2) Or an ultraviolet curable resin. The conductive bonding layer is formed on the bump by a technique such as transfer. The connection between the bump or output pad 681 and the source signal line 18 is not limited to the above method. Further, the film carrier technology may be used without mounting the source driver IC 14 on the array substrate. Further, the source signal line 18 or the like may be connected using a polyimide film or the like.
[0935]
In the present invention, since the reference current circuit 691 is separated into three systems for R, G, and B, the light emission characteristics and temperature characteristics can be adjusted by R, G, and B, respectively. White balance can be obtained (see FIG. 70).
[0936]
Next, the precharge circuit will be described. As described above, in the current driving method, the current written to the pixel is small during black display. For this reason, if the source signal line 18 or the like has a parasitic capacitance, there is a problem that a sufficient current cannot be written to the pixel 16 in one horizontal scanning period (1H). In general, a current-driven light-emitting element has a weak black level current value of about several nA, and thus it is difficult to drive a parasitic capacitance (wiring load capacitance) that seems to be about several tens of pF in its signal value. . In order to solve this problem, before writing image data to the source signal line 18, a precharge voltage is applied, and the potential level of the source signal line 18 is set to the black display current (basically the transistor 11a of the pixel). It is effective to set 11a to an off state. For the formation (creation) of the precharge voltage, it is effective to output a constant voltage at the black level by decoding the upper bits of the image data.
[0937]
FIG. 65 shows an example of a current output type source driver IC (circuit) 14 having a precharge function of the present invention. FIG. 65 shows a case where a precharge function is mounted in the output stage of a 6-bit constant current output circuit. In FIG. 65, the precharge control signal is a dot clock signal CLK that is decoded by the NOR circuit 652 when the upper 3 bits D3, D4, and D5 of the image data D0 to D5 are all 0 and has a reset function by the horizontal synchronization signal HD. The AND circuit 653 is connected to the output of the counter circuit 651 and outputs the black level voltage Vp for a certain period. In other cases, the output current from the current output stage 654 (specifically, the configuration of FIGS. 48, 56, 57, etc.) is applied to the source signal line 18 (from the source signal line 18 to the program current Iw). Absorbs). With this configuration, when the image data is in the 0th to 7th gradations close to the black level, a voltage corresponding to the black level is written only for a certain period at the beginning of one horizontal period, and the burden of current driving is reduced. It becomes possible to make up for insufficient writing. The complete black display is the 0th gradation, and the complete white display is the 63rd gradation (in the case of 64 gradation display).
[0938]
In FIG. 65, when the precharge voltage is applied, the precharge voltage is applied to the point B of the internal wiring 483. Therefore, the precharge voltage is also applied to the current output stage 654. However, since the current output stage 654 is a constant current circuit, it has a high impedance. Therefore, even if a precharge voltage is applied to the constant current circuit 654, no problem occurs in circuit operation. In order to prevent the precharge voltage from being applied to the current output stage 654, the switch 655 may be disposed by cutting at point A in FIG. 65 (see FIG. 66). The switch is interlocked with the precharge switch 481a and is controlled to be turned off when the precharge switch 481a is on.
[0939]
The precharge may be performed in the entire gradation range, but preferably, the gradation for precharging should be limited to the black display region. That is, the writing image data is determined, and the black region gradation (low luminance, that is, the writing current is small (small) in the current driving method) is selected and precharged (referred to as selective precharging). When pre-charging is performed on all gradation data, this time, a decrease in luminance (not reaching the target luminance) occurs in the white display area. Moreover, the subject that a vertical stripe is displayed on an image may generate | occur | produce.
[0940]
Preferably, selective precharge is performed in a gradation region from gradation 0 to 1/8 of all gradations of gradation data (for example, in the case of 64 gradations, the 0th to 7th gradations are performed). In the case of image data up to, after precharging, the image data is written). Further, it is preferable that selective precharge is performed with gradations in a region of gradations 0 to 1/16 of gradation data (for example, in the case of 64 gradations, images from the 0th gradation to the 3rd gradation are used. Data and time, precharge and then write image data).
[0941]
In particular, in order to increase the contrast in black display, it is also effective to detect only the gradation 0 and precharge. The black display is extremely good. The method of precharging only the gradation 0 has less adverse effects on image display. Therefore, it is preferable to adopt as the most precharge technology.
[0942]
  It is also effective to vary the precharge voltage and gradation range for R, G, and B. This is because the EL display element 15 has different emission start voltages and emission luminances for R, G, and B. For example, R performs selective precharge at the gradation in the range of gradation 0 to 1/8 of the gradation data (for example, at 64 gradations,0 floorAt the time of the image data from the gradation to the seventh gradation, the image data is written after precharging.) Other colors (G, B) are selectively precharged with gradations in the range of gradations 0 to 1/16 of gradation data (for example, in the case of 64 gradations, the 3rd floor from the 0th gradation) The image data up to the time of the adjustment and the control such as writing the image data after precharging are performed. As for the precharge voltage, if R is 7 (V), a voltage of 7.5 (V) is written to the source signal line 18 for the other colors (G, B). The optimum precharge voltage is often different depending on the production lot of the EL display panel. Therefore, it is preferable that the precharge voltage is configured to be adjustable with an external volume or the like. This adjustment circuit can also be easily realized by using an electronic volume circuit.
[0943]
  The precharge voltage is equal to or lower than the anode voltage Vdd-0.5 (V) in FIG. 1 and the anode voltage Vdd-2.5 (V).more thanIt is preferable to make it.
[0944]
Even in the method of precharging only gradation 0, a method of precharging by selecting one or two colors of R, G, B is also effective. Less harmful to image display. It is also effective to precharge when the screen brightness is less than or equal to a predetermined brightness. In particular, when the brightness of the screen 50 is low, black display is difficult. By performing precharge driving such as 0 gradation precharge when the luminance is low, the contrast of the image is improved.
[0945]
In addition, the 0th mode in which no precharge is performed, the first mode in which only the gradation 0 is precharged, the second mode in which the precharge is performed in the range from the gradation 0 to the gradation 3, and the precharging is performed in the range from the gradation 0 to the gradation 7. It is preferable that a third mode to be charged, a fourth mode to be precharged in a range of all gradations, and the like are set, and these are switched by a command. These can be easily realized by configuring (designing) a logic circuit in the source driver IC (circuit) 14.
[0946]
FIG. 66 is a specific configuration diagram of the selective precharge circuit section. PV is a precharge voltage input terminal. Individual precharge voltages are set for R, G, and B by an external input or an electronic volume circuit. Note that although individual precharge voltages are set for R, G, and B, the present invention is not limited to this. R, G, and B may be common. This is because the precharge voltage correlates with Vt of the driving transistor 11a of the pixel 16, and this pixel 16 is the same for the R, G, and B pixels. When the W / L ratio of the driving transistor 11a of the pixel 16 is different between R, G, and B (having different designs), the precharge voltage should be adjusted corresponding to the different designs. Is preferred. For example, if the channel length L of the driving transistor 11a is increased, the diode characteristics of the transistor 11a are deteriorated and the source-drain (SD) voltage is increased. Therefore, the precharge voltage needs to be set lower than the source potential (Vdd).
[0947]
The precharge voltage PV is input to the analog switch 561. The analog switch W (channel width) needs to be 10 μm or more in order to reduce the on-resistance. However, if W is too large, the parasitic capacitance increases, so the thickness is made 100 μm or less. More preferably, the channel width W is preferably 15 μm or more and 60 μm or less.
[0948]
Note that this selective precharge may be fixed by precharging only gradation 0 or precharging in the range of gradation 0 to gradation 7, but the low gradation basin (gradation 0 in FIG. 79). To gradation R1 or gradation (R1-1)) may be linked to the low gradation area. That is, the selective precharge is performed in this range when the low gradation region is from gradation 0 to gradation R1, and is performed in this range when the low gradation region is from gradation 0 to gradation R2. Implement in conjunction. Note that this control method has a smaller hardware scale than other methods.
[0949]
The switch 481a is controlled to be turned on / off by the application state of the above signal, and the precharge voltage PV is applied to the source signal line 18 when the switch 481a is turned on. The time for applying the precharge voltage PV is set by a separately formed counter (not shown). This counter is configured to be set by a command. The precharge voltage application time is preferably set to 1/100 or more and 1/5 or less of one horizontal scanning period (1H). For example, if 1H is 100 μsec, it is 1 μsec or more and 20 μsec (1/100 of 1H or more and 1/5 or less of 1H). More preferably, it is 2 μsec or more and 10 μsec (2/100 of 1H or more and 1/10 or less of 1H).
[0950]
FIG. 67 is a modification of FIG. 65 or FIG. FIG. 67 shows a precharge circuit that determines whether or not to precharge according to input image data and performs precharge control. For example, precharge is set when the image data is only gradation 0, setting is performed when the image data is only gradations 0 and 1, gradation 0 is always precharged, and gradation 1 is continuously greater than a predetermined value. In such a case, a precharge setting can be made.
[0951]
FIG. 67 shows an example of a current output type source driver IC (circuit) 14 having a precharge function of the present invention. FIG. 67 shows a case where a precharge function is mounted in the output stage of a 6-bit constant current output circuit. In FIG. 67, the coincidence circuit 671 decodes according to the image data D0 to D5, and determines whether or not to precharge by the REN terminal input having a reset function by the horizontal synchronization signal HD and the dot clock CLK terminal input. The coincidence circuit 671 has a memory, and holds a precharge output result based on image data of several H or several fields (frames). Based on the holding result, it has a function of determining whether or not to precharge and performing precharge control. For example, it is possible to perform setting so that the gradation 0 is always precharged and the gradation 1 is precharged when the gradation 1 is continuously generated for 6H (6 horizontal scanning periods) or more. In addition, it is possible to perform setting so that the gradations 0 and 1 are always precharged, and the gradation 2 is continuously precharged when the gradation 2 is continuously generated for 3F (three frame periods) or more.
[0952]
The output of the coincidence circuit 671 and the output of the counter circuit 651 are ANDed by an AND circuit 653, and the black level voltage Vp is output for a certain period. In other cases, the output current from the current output stage 654 described with reference to FIG. 52 and the like is applied to the source signal line 18 (the program current Iw is absorbed from the source signal line 18). Other configurations are the same as or similar to those shown in FIGS. In FIG. 67, the precharge voltage is applied to point A, but it goes without saying that it may be applied to point B (see also FIG. 66).
As described above, it is possible to obtain a good result by changing the precharge application time for R, G, and B. For example, the R precharge time is made longer than the G and B precharge times. This is because, in an organic EL or the like, the light emission start time is different for each RGB material. A good result can also be obtained by varying the precharge voltage PV application time according to the image data applied to the source signal line 18 next time. For example, the application time is lengthened in gradation 0 for full black display, and shorter than that in gradation 4. It is also possible to obtain a good result by setting the application time in consideration of the difference between the image data before 1H and the image data to be applied next. For example, when writing a current to display a pixel in white on the source signal line 1H before and writing a current to display a black in the pixel to the next 1H, the precharge time is lengthened. This is because the black display current is very small. On the other hand, when writing the current to make the pixel display black on the source signal line 1H before, and writing the current to make the black display on white next 1H, shorten the precharge time or precharge the current. Stop (do not do). This is because the white display write current is large.
[0953]
It is also effective to change the precharge voltage according to the image data to be applied. This is because the writing current for black display is very small and the writing current for white display is large. Therefore, the precharge voltage is increased as the low gradation region is reached (relative to Vdd. When the pixel TFT 11a is in the P channel), and the precharge voltage is decreased as the high gradation region is reached (the pixel TFT 11a). Is P channel).
[0954]
When the program current open terminal (PO terminal) is “0”, the switch 481b is turned off, and the IL terminal, the IH terminal, and the source signal line 18 are disconnected (the Iout terminal is connected to the source signal line 18). ) Therefore, the program current Iw does not flow through the source signal line 18. The PO terminal is set to “1” when the program current Iw is applied to the source signal line, turns on the switch 481b, and flows the program current Iw to the source signal line 18.
[0955]
The time when “0” is applied to the PO terminal and the switch 481b is opened is when no pixel row in the display area is selected. The current source 484 does not keep current based on the input data (D0 to D5), but is drawn from the source signal line 18. This current is a current that flows from the Vdd terminal of the selected pixel 16 to the source signal line 18 via the TFT 11a. Therefore, when no pixel row is selected, there is no path for current to flow from the pixel 16 to the source signal line 18. The time when no pixel row is selected occurs between the time when an arbitrary pixel row is selected and the next pixel row is selected. Note that a state in which no pixel (pixel row) is selected and there is no path for flowing into (flowing out) the source signal line 18 is referred to as an all non-selection period.
[0956]
In this state, when the IOUT terminal is connected to the source signal line 18, the unit current source 484 that is turned on (actually it is the switch 481 that is controlled by the data of the D0 to D5 terminals). Current). For this reason, the charge charged in the parasitic capacitance of the source signal line 18 is discharged, and the potential of the source signal line 18 rapidly decreases.
[0957]
As described above, when the potential of the source signal line 18 is lowered, it takes time to restore the original potential due to the current originally written in the source signal line 18.
[0958]
In order to solve this problem, the present invention applies “0” to the PO terminal during all non-selection periods, turns off the switch 481b in FIG. 66, and disconnects the IOUT terminal and the source signal line 18. By disconnecting, no current flows from the source signal line 18 to the current source 484, so that no potential change of the source signal line 18 occurs during the entire non-selection period. As described above, good current writing can be performed by controlling the PO terminal during the entire non-selection period and disconnecting the current source from the source signal line 18.
[0959]
In addition, the area of white display area (area with constant brightness) (white area) and the area of black display area (area with luminance below predetermined) (black area) are mixed on the screen. It is effective to add a function of stopping the precharge when the ratio is in a certain range (appropriate precharge). This is because vertical stripes occur in the image within this certain range. Of course, conversely, precharging may be performed within a certain range.
[0960]
Also, when the image moves, the image becomes noise-like. Appropriate precharging can be easily realized by counting (calculating) data of pixels corresponding to the white area and the black area with an arithmetic circuit. It is also effective to make the appropriate precharge different for R, G, and B. This is because the EL display element 15 has different emission start voltages and emission luminances for R, G, and B. For example, R is the ratio of the white area of the predetermined luminance: the black area of the predetermined luminance is stopped or started when the ratio of the black area of the predetermined luminance is 1:20 or more, and G and B are the ratio of the white area of the predetermined luminance: the black area of the predetermined luminance. Is a configuration in which precharge is stopped or started at 1:16 or more. According to the experiment and examination results, in the case of the organic EL panel, the precharge is performed when the ratio of the white area of the predetermined luminance to the black area of the predetermined luminance is 1: 100 or more (that is, the black area is 100 times or more of the white area). Is preferably stopped. Furthermore, it is preferable to stop the precharge when the ratio of the white area with the predetermined luminance to the black area with the predetermined luminance is 1: 200 or more (that is, the black area is 200 times or more of the white area).
[0961]
When the driving TFT 11a of the pixel 16 is a P-channel, the precharge voltage PV needs to be output from the source driver circuit (IC) 14 near Vdd (see FIG. 1). However, as the precharge voltage PV is closer to Vdd, the driver circuit (IC) 14 needs to use a semiconductor with a high breakdown voltage process (even if the high breakdown voltage is referred to, it is 5 (V) to 10 (V). However, when the breakdown voltage exceeds 5 (V), the problem is that the cost of the semiconductor process becomes high, so a higher-definition, low-cost process is used than that of adopting the process of 5 (V) breakdown voltage. be able to).
[0962]
When the diode characteristics of the driving TFT 11a of the pixel 16 are good and an on-current for white display is ensured, if it is 5 (V) or less, the source driver IC 14 can also use the 5 (V) process, so no problem occurs. However, when the diode characteristics exceed 5 (V), it becomes a problem. In particular, since it is necessary to apply a precharge voltage PV close to the source voltage Vdd of the TFT 11a, the precharge cannot be output from the source driver IC.
[0964]
FIG. 260 shows a panel configuration that solves this problem. In FIG. 260, a switch circuit 481 is formed on the array 71 side. The source driver IC 14 outputs an on / off signal for the switch 481. This on / off signal is boosted by a level shift circuit 2591 formed in the array 71 to turn on / off the switch 481. Note that the switch 481 and the level shift circuit 2591 are formed simultaneously or sequentially in the process of forming the pixel TFT. Of course, it may be formed separately by an external circuit (IC) and mounted on the array 71.
[0964]
The on / off signal is output from the terminal 761a of the source driver IC 14 based on the precharge condition described above. Therefore, it goes without saying that the precharge voltage application and driving method can be applied to the embodiment of FIG. The voltage (signal) output from the terminal 761a is as low as 5 (V) or less. The amplitude of this voltage (signal) is increased by the level shifter circuit 2591 to the on / off logic level of the switch 481.
[0965]
With the configuration described above, the source driver circuit (IC) 14 has a power supply voltage in the operating voltage range that can drive the program current Iw. The precharge voltage PV is eliminated by the array substrate 71 having a high operating voltage. Therefore, the precharge can be sufficiently applied up to the Vdd voltage.
[0966]
If the switch circuit 481a in FIG. 66 is also formed (arranged) in the source driver circuit (IC) 14, the breakdown voltage becomes a problem. For example, when the Vdd voltage of the pixel 16 is higher than the power supply voltage of the source driver IC 14, there is a danger that a voltage that destroys the source driver IC 14 is applied to the terminal 761 of the source driver IC 14.
[0967]
An embodiment that solves this problem is the configuration of FIG. A switch circuit 481 is formed (arranged) on the array substrate 71. The configuration and the like of the switch circuit 481 are the same as or similar to the configuration and specifications described in FIG.
[0968]
91 and 92, the switch 481 is arranged before the output of the source driver IC 14 and in the middle of the source signal line 18. When the switch 481 is turned on, a current Iw for programming the pixel 16 flows into the source driver circuit (IC) 14. When the switch 481 is turned off, the source driver circuit (IC) 14 is disconnected from the source signal line 18.
[0969]
Similarly to FIG. 260, the voltage (signal) output from the terminal 761a is as low as 5 (V) or less. The amplitude of this voltage (signal) is increased by the level shifter circuit 2591 to the on / off logic level of the switch 481.
[0970]
With the configuration described above, the source driver circuit (IC) 14 has a power supply voltage in the operating voltage range that can drive the program current Iw. Further, since the switch 481 also operates with the power supply voltage of the array 71, the switch 481 is not destroyed even when the Vdd voltage is applied from the pixel 16 to the source signal line 18, and the source driver circuit (IC) 14 is destroyed. It is never done.
[0971]
It goes without saying that both the switch 481 disposed (formed) in the middle of the source signal line 18 in FIG. 259 and the precharge voltage PV application switch 481 may be formed (arranged) on the array substrate 71 (FIG. 259 + configuration of FIG. 260).
[0972]
FIG. 223 shows an embodiment in which the precharge voltage can be changed according to the gradation in addition to FIG. In FIG. 223, it is possible to easily change the precharge voltage in accordance with the applied image data. The precharge voltage can be changed by the electronic volume 451 according to the image data (D3 to D0). In FIG. 223, since the D3 to D0 bits are connected to the electronic volume, it can be seen that the low gradation precharge voltage can be changed. This is because the black display write current is very small and the white display write current is large. Therefore, the precharge voltage is increased as the low gradation region is reached. Since the driving transistor 11a of the pixel 16 is a P channel, the anode voltage (Vdd) is a black display voltage. As the high gradation region is reached, the precharge voltage is lowered (when the pixel transistor 11a is in the P channel). That is, the voltage programming method is implemented in the low gradation display, and the current programming method is implemented in the high gradation display (white display).
[0973]
In the precharge circuit in FIG. 223, it is possible to select whether to precharge only the gradation 0 or to precharge in the range from the gradation 0 to the gradation 7. In addition, the precharge voltage for each gradation can also be changed by the electronic volume 451. Other configurations are the same as those shown in FIGS. 65, 66, and 67, and thus description thereof is omitted.
[0974]
Good results can also be obtained by varying the precharge voltage PV application time according to the image data applied to the source signal line 18. For example, the application time is lengthened in gradation 0 for full black display, and shorter than that in gradation 4. It is also possible to obtain a good result by setting the application time in consideration of the difference between the image data before 1H and the image data to be applied next. For example, when writing a current to display a pixel in white on the source signal line 1H before and writing a current to display a black in the pixel to the next 1H, the precharge time is lengthened. This is because the black display current is very small. On the other hand, when writing the current to make the pixel display black on the source signal line 1H before, and writing the current to make the black display on white next 1H, shorten the precharge time or precharge the current. Stop (do not do). This is because the white display write current is large.
[0975]
It is also effective to change the precharge voltage according to the image data to be applied. This is because the writing current for black display is very small and the writing current for white display is large. Therefore, the precharge voltage is increased (with respect to Vdd when the pixel transistor 11a is in the P channel) as the low gradation region is reached, and the precharge voltage is decreased (pixel) as the high gradation region is obtained. A control method in which the transistor 11a is in the P channel) is also effective.
[0976]
Hereinafter, for ease of understanding, description will be made with reference to FIG. Needless to say, the items described below can be applied to the precharge circuits shown in FIGS.
[0977]
When the program current open terminal (PO terminal) is “0”, the switch 655 is turned off, and the IL terminal, the IH terminal, and the source signal line 18 are disconnected (the Iout terminal is connected to the source signal line 18). ) Therefore, the program current Iw does not flow through the source signal line 18. The PO terminal is set to “1” when the program current Iw is applied to the source signal line, turns on the switch 655, and flows the program current Iw to the source signal line 18.
[0978]
When “0” is applied to the PO terminal and the switch 655 is opened, no pixel row in the display area is selected. The unit transistor 484 does not keep current based on the input data (D0 to D5) and is drawn from the source signal line 18. This current is a current that flows from the Vdd terminal of the selected pixel 16 to the source signal line 18 via the transistor 11a. Therefore, when no pixel row is selected, there is no path for current to flow from the pixel 16 to the source signal line 18. The time when no pixel row is selected occurs between the time when an arbitrary pixel row is selected and the next pixel row is selected. Note that a state in which no pixel (pixel row) is selected and there is no path for flowing into (flowing out) the source signal line 18 is referred to as an all non-selection period.
[0979]
When the output terminal 681 is connected to the source signal line 18 in this state, the unit transistor 484 that is turned on (actually, the switch 481 that is controlled by the data of the D0 to D5 terminals is used. Current). For this reason, the charge charged in the parasitic capacitance of the source signal line 18 is discharged, and the potential of the source signal line 18 rapidly decreases. As described above, when the potential of the source signal line 18 is lowered, it takes time to restore the original potential due to the current originally written in the source signal line 18.
[0980]
In order to solve this problem, the present invention applies “0” to the PO terminal during all non-selection periods, turns off the switch 655 in FIG. 66, and disconnects the output terminal 681 and the source signal line 18. By disconnecting, no current flows from the source signal line 18 to the unit transistor 484, and therefore no potential change of the source signal line 18 occurs during the entire non-selection period. As described above, good current writing can be performed by controlling the PO terminal during the entire non-selection period and disconnecting the current source from the source signal line 18.
[0981]
In addition, the area of white display area (area with constant brightness) (white area) and the area of black display area (area with luminance below predetermined) (black area) are mixed on the screen. It is effective to add a function of stopping the precharge when the ratio is in a certain range (appropriate precharge). This is because vertical stripes occur in the image within this certain range. Of course, conversely, precharging may be performed within a certain range. Also, when the image moves, the image becomes noise-like. Appropriate precharging can be easily realized by counting (calculating) data of pixels corresponding to the white area and the black area with an arithmetic circuit.
[0982]
It is also effective to make the precharge control different for R, G, and B. This is because the EL display element 15 has different emission start voltages and emission luminances for R, G, and B. For example, R is the ratio of the white area of the predetermined luminance: the black area of the predetermined luminance is stopped or started when the ratio of the black area of the predetermined luminance is 1:20 or more, and G and B are the ratio of the white area of the predetermined luminance: the black area of the predetermined luminance. Is a method of stopping or starting the precharge at 1:16 or more. According to the experiment and examination results, in the case of the organic EL panel, the precharge is performed when the ratio of the white area of the predetermined luminance to the black area of the predetermined luminance is 1: 100 or more (that is, the black area is 100 times or more of the white area). Is preferably stopped. Furthermore, it is preferable to stop the precharge when the ratio of the white area with the predetermined luminance to the black area with the predetermined luminance is 1: 200 or more (that is, the black area is 200 times or more of the white area).
[0983]
Further, precharge will be described. FIG. 232 shows another embodiment of the precharge circuit. The difference from the embodiment of FIG. 66 is that the precharge switch 481a is controlled by precharge enable (PEN), precharge select (PSL), and the like. The control switch is OPV. The switch 656 in the current output stage is controlled by the PO signal.
[0984]
In this embodiment of the present invention, whether or not to precharge is determined by the image data. As this control, the PSL signal and the PEN signal perform important functions.
[0985]
As described before, as shown in FIG. 235, RGB image data (RDATA, GDATA, BDATA) is 8 bits each. The RGB 8-bit image data is gamma-converted by the gamma circuit 834 to become a 10-bit signal. The signal subjected to gamma conversion is subjected to FRC processing by a frame rate control (FRC) circuit 835 and converted to 6-bit image data. A precharge control circuit (PC) 2351 generates a precharge control signal (set to H level when precharging and set to L level when not precharging) from the converted 6-bit image data. A method for generating this precharge will be described later.
[0986]
FIG. 236 is a block diagram centering on the precharge circuit 2363 of the source driver IC (circuit) 14. The precharge circuit 2363 corresponds to circuits such as FIGS. 66, 232, and 233. The precharge control circuit 2351 outputs a precharge control signal PC signal (red (RPC), green (GPC), blue (BPC)). The PC signal is generated by the precharge control circuit 2351 of the control IC 81 shown in FIG. 235, and the PC signal is input to the selector circuit 2362 of the source driver IC 14 shown in FIG.
[0987]
The selector circuit 2362 sequentially latches in the latch circuit 2361 corresponding to the output stage in synchronization with the main clock. The latch circuit 2361 has a two-stage structure of a latch circuit 2361a and a latch circuit 2361b. The latch circuit 2361b sends data to the precharge circuit 2363 in synchronization with the horizontal scanning clock (1H). That is, the selector sequentially latches the image data and PC data for one pixel row, and stores the data in the latch circuit 2361b in synchronization with the horizontal scanning clock (1H).
[0988]
In FIG. 236, R, G, and B of the latch circuit 2361 are RGB image data 6-bit latch circuits, and P is a latch circuit that latches 3 bits of the precharge signals (RPC, GPC, and BPC). .
[0989]
The precharge circuit 2363 turns on the switch 481a and outputs the precharge voltage to the source signal line 18 when the output of the latch circuit 2361b is at the H level. The current output circuit 654 outputs a program current to the source signal line 18 according to the image data.
[0990]
If the configurations of FIGS. 235 and 236 are schematically illustrated, the configuration of FIG. 237 is obtained. 237 and 238 show a configuration in which a plurality of source driver ICs (circuits) 14 are stacked on one display panel (cathode connection of source driver ICs) as shown in FIG. Also, CSEL1 and CSEL2 in FIGS. 237 and 238 are select signals for the IC chip. The IC chip is selected by the CSEL signal to determine which image data and PC signal are input.
[0991]
In the configurations of FIGS. 236 and 237, a PC signal is generated corresponding to each RGB image data. The precharge is preferably applied for each RGB as described above. However, in moving image display and natural image display, it is often unnecessary to determine whether or not to precharge for each RGB. That is, RGB may be converted (converted) into a luminance signal, and it may be determined whether or not to precharge based on the luminance. This is the configuration of FIG. 238. In the configuration of FIG. 237, the PC signal requires 3 bits (RPC, GPC, BPC), but in the configuration of FIG. 238, the PC signal may be 1 bit of RGBPC. Therefore, in the latch circuit 2361 in FIG. 236, P may be a 1-bit latch. In the following description, the description will be made without considering RGB from the viewpoint of facilitating the explanation and drawing.
[0992]
In the configuration of the present invention described above, the controller 81 generates a PC signal (precharge control signal) based on the image data, and the source driver IC 14 latches the PC signal and synchronizes with the 1H synchronization signal in the source signal line 18. It is characterized in that it is applied to. Further, as shown in FIG. 235, the controller 81 can easily change the generation of the precharge signal by a precharge mode (PMODE) signal. For example, PMODE is a mode in which only gradation 0 is precharged, a mode in which a certain gradation range such as gradation 0-7 is precharged, and precharge when image data changes from bright image data to dark image data. Examples include a mode for precharging when low gradation display is continuously performed in a certain frame.
[0993]
Note that the present invention is not limited to determining whether or not to precharge one pixel data. For example, the precharge determination may be performed based on the image data of a plurality of pixel rows. In addition, the precharge determination may be performed in consideration of the image data of the surrounding pixels to be precharged (for example, weighting processing). Further, a method of changing the precharge judgment between a moving image and a still image is also exemplified. The above matter is important in that good versatility is exhibited when the controller generates a precharge signal based on image data. Hereinafter, the precharge determination and the precharge mode will be mainly described.
[0994]
In the present invention, the precharge drive is described as outputting a precharge voltage, but the present invention is not limited to this. A method of writing a current shorter than one horizontal scanning period and larger than the program current to the source signal line 18 may be used. That is, a method of writing the precharge current to the source signal line 18 and then writing the program current to the source signal line 18 may be used. There is no difference in that the precharge current also physically causes a voltage change. A method of performing precharge with a precharge current is also within the category of precharge driving of the present invention. For example, in FIG. 223, the precharge voltage changes by switching the electronic volume 451. This electronic volume 451 may be changed to a current output electronic volume. The change can be easily realized by combining a plurality of current mirror circuits. In FIGS. 232 and 233, the precharge voltage Vp may be changed to a current output composed of a current mirror circuit. In the present invention, for ease of explanation, it is assumed that precharge driving is performed with a precharge voltage.
[0995]
The application of the precharge voltage (current) is not limited to the application of a constant precharge voltage (current). For example, a plurality of precharge voltages may be applied to the source signal line. For example, after applying the first precharge voltage 5 (V) for 5 (μsec), the second precharge voltage 4.5 (V) is applied for 5 (μsec). Thereafter, the program current Iw is applied to the source signal line 18. Alternatively, the precharge voltage may be changed in a sawtooth shape. A rectangular wave may be applied. Further, a precharge voltage (current) may be superimposed on a regular program current (voltage). Further, the magnitude of the precharge voltage (current) and the application period of the precharge voltage (current) may be changed according to the image data.
[0996]
Although the present invention is described as applying a precharge voltage (current) in the current drive method, the precharge drive is also effective in the voltage drive method. In the voltage driving method, the size of the driving transistor for driving the EL element 15 is large, so that the gate capacitance is large. Therefore, there is a problem that it is difficult to write a regular program voltage. In response to this problem, by performing precharge before applying the program voltage, the driving transistor can be reset, and good writing can be realized. Therefore, the precharge driving method of the present invention is not limited to current program driving. In the embodiments of the present invention, for ease of explanation, the current program driving pixel configuration (see FIG. 1 and the like) will be described as an example.
[0997]
In the embodiment of the present invention, the precharge driving method does not affect only the driving transistor 11a. For example, in the pixel configuration of FIG. 38, the transistor 11a constituting the current mirror circuit is also acted to exert the effect. The precharge drive system of the present invention is intended to charge and discharge the parasitic capacitance of the source signal line 18 as viewed from the source driver IC (circuit) 14, but of course, in the source driver IC (circuit) 14. The purpose is to charge and discharge the parasitic capacitance.
[0998]
The precharge voltage (current) is intended to improve black display, but is not limited thereto. If a white write precharge voltage (current) that makes white display easy to write is applied, good white display can be realized. In other words, the precharge driving of the present invention applies pre-charging by applying a predetermined voltage (current) for facilitating writing of the program current (program voltage) before writing the program current (program voltage). It is.
[0999]
Although the present invention is described as precharging with black display, this is basically a case where the current is sucked from the driving transistor 11a into the source driver IC (circuit) 14 by a sink current. When the driving transistor 11a or the like is an N-channel transistor, the source driver IC (circuit) 14 is programmed with a discharge current. In this case, a pixel configuration that is white and difficult to write may occur. Therefore, the precharge driving method of the present invention changes the source signal line 18 and the like to a predetermined potential, and precharging with white display or precharging with black display is merely an embodiment. Therefore, it is not limited to these.
[1000]
The application timing of the precharge voltage (current) is preferably written while the pixel row to which the program voltage (current) is written is selected. However, the precharge voltage (current) is not limited to this. In a selected state, a precharge voltage (current) may be applied to the source signal line 18 to perform precharge, and then a pixel row in which a program current (voltage) is written may be selected.
[1001]
Further, although the precharge voltage is applied to the source signal line 18, other methods are also exemplified. For example, the applied voltage (Vdd) to the anode terminal or the applied voltage (Vss) to the cathode terminal may be changed (a precharge voltage is applied). By changing the anode voltage or the cathode voltage, the writing capability of the driving transistor 11a is expanded. Therefore, the precharge effect is exhibited. In particular, the effect of implementing a method of changing the anode voltage (Vdd) in a pulse manner is high.
[1002]
FIG. 239 (a) is an explanatory diagram when only gradation 0 is precharged. Precharge with only gradation 0 is a preferable method because there is no gradation skip and good black display can be realized. In FIG. 239, the row number indicates the pixel row number. In the pixel row, image data is sequentially rewritten from the first pixel row to the n pixel row, and when current programming is performed up to the final pixel row n, current programming is started from the first pixel row.
[1003]
The image data is 64-gradation image data. The image data takes a value from 0 to 63. Of course, when the gradation is 256, values from 0 to 255 are taken. PSL is a precharge select signal, which permits the output of the precharge voltage when it is at the H level (symbol H). At the L level, no precharge voltage is output. PEN is a precharge enable signal. This PEN is a signal output by the determination of the controller 81. That is, the controller sets the PEN signal to the H or L level based on the image data. When PEN is at the H level, it is a determination signal for precharging, and when it is at the L level, it is a determination signal for not precharging. In FIG. 239, the PEN signal is at the H level only at gradation 0. The P output is an on / off state of the switch 481a (see FIGS. 232 and 233). In the table, ◯ indicates that the switch 481a is in an on state (a state in which the precharge voltage Vp is applied to the source signal line 18). X indicates that the switch 481a is in an off state (a state in which a precharge voltage is not applied to the source signal line 18).
[1004]
In FIG. 239 (a), the PEN signal is H at locations corresponding to pixel row number 3 and pixel row number 8. At the same time, in the pixel row number 3 and the pixel row number 8, since the PSL signal is also at the H level, the P output is ◯ (the precharge voltage Vp is output. In FIG. 239 (b), the PEN signal is Is the same as (a) of Fig. 239, but the PSL signal is at the L level, so that the P output is not maintained and the state is x (the precharge voltage Vp is not output). The PEN signal is also output from the controller 81. However, the PEN signal is preferably adjustable by the user.
[1005]
Further, the period during which the precharge voltage Vp is output can be set by the counter 651 in FIG. This counter is a programmable counter and operates based on a set value from a controller or a set value of a user. The counter 651 is configured to operate in synchronization with the main clock (CLK).
[1006]
FIG. 240A is an explanatory diagram when only the gradations 0 to 7 are precharged. The method of precharging only in the low gradation region is effective as a measure for solving the problem that current driving is difficult to write in the black display region. Note that the controller 81 can set which range is precharged.
[1007]
In FIG. 240, the PEN signal is at the H level only at the gradation 0-7. The P output is an on / off state of the switch 481a (see FIGS. 232, 233, etc.). In FIG. 240A, since the image data is 7 or less at the locations corresponding to the pixel row numbers 3, 5, 6, 7, 11, 12, and 13, the PEN signal is H. At the same time, since the PSL signal is also at the H level, the P output is ◯ (a state where the precharge voltage Vp is output). In (b) of FIG. 240, since the PSL signal is at the L level, all the P outputs are x (a state where no precharge voltage is applied).
[1008]
FIG. 241 is an explanatory diagram of a driving method for performing precharging when the luminance of the pixel 16 is lowered. In the current program method, the program current Iw when the luminance of the pixel 16 is increased (white display) is large. Therefore, even if the source signal line 18 has a parasitic capacitance, the parasitic capacitance can be charged and discharged sufficiently. However, when the pixel 16 is programmed to display black, the program current is small and the parasitic capacitance of the source signal line 18 cannot be sufficiently charged / discharged. Therefore, when the program current written to the pixel 16 becomes large, it is often unnecessary to precharge. Conversely, when the current written to the pixel 16 is small (when black display is performed), it is necessary to precharge.
[1009]
FIG. 241 is an explanatory diagram of a driving method for performing precharging when the luminance of the pixel 16 is lowered. The image data of the first pixel row is 39. Therefore, the source signal line 18 holds a potential for current-programming the pixel 16 to the image data 39. The image data of the second pixel row is 12. Therefore, the source signal line 18 needs to have a potential corresponding to the image data 12. However, the program current decreases from gradation 39 to gradation 12. Therefore, a state where the source signal line 18 cannot be sufficiently charged / discharged may occur. In order to cope with this problem, precharging is performed (PEN signal is at H level). Similar determination results are obtained for pixel rows 3, 5, 6, 8, 11, 12, 13, and 15.
[1010]
The image data in the third pixel row is zero. Therefore, the source signal line 18 holds a potential for current-programming the pixel 16 to the image data 0. The image data in the fourth pixel row is 21. Therefore, the source signal line 18 needs to have a potential corresponding to the image data 21. The program current increases from gradation 0 to gradation 21. Therefore, the source signal line 18 can be sufficiently charged / discharged. Therefore, it is not necessary to precharge the fourth pixel row.
[1011]
The above determination is performed by the controller 81. As a result of the implementation, the PEN signal becomes the H level in the pixel rows 2, 3, 5, 6, 8, 11, 12, 13, and 15 as illustrated in FIG. That is, the pixel row is precharged. In FIG. 241 (a), since the PSL signal is also at the H level, as can be seen from the P output column, the P output is in pixel rows 2, 3, 5, 6, 8, 11, 12, 13, and 15. ○ (Precharge). Note that precharge is not performed in other pixel rows.
[1012]
In (b) of FIG. 241, the PEN signal is the same as (a) of FIG. 241, but the PSL signal is at L level. Therefore, the P output is constantly maintained and the state is x (the precharge voltage Vp is not output). Basically, the PEN signal is also output from the controller 81. However, the PEN signal is preferably adjustable by the user.
[1013]
FIG. 242 shows a combination of the precharge methods of FIG. 240 and FIG. In this method, precharging is performed when the luminance of the pixel 16 is low, and precharging is performed when the program current of the pixel 16 has low luminance of 0-7 gradation. It can be changed by the set value of the controller IC 81 at which gradation or less the precharge is performed. Also, the user can change it. The change is made to the table inside the controller from the microcomputer via the serial interface.
[1014]
The image data is the same as in the embodiment of FIG. However, in FIG. 242, since the image data is 12 in the second pixel row and the image data is 12 in the 15th pixel row, the PEN signal is an L level determination result. As described above, the parasitic capacitance of the source signal line 18 can be charged / discharged if the program current Iw is larger than a certain level. Therefore, there is no need to precharge. Conversely, when precharged, the potential of the source signal line 18 changes to the black display potential, and it takes time to return to the halftone display potential.
[1015]
The above determination is performed by the controller 81. As a result of the implementation, the PEN signal becomes H level in the pixel rows 3, 5, 6, 8, 11, 12, and 13 as illustrated in FIG. That is, the pixel row is precharged. In (a) of FIG. 242, since the PSL signal is also at the H level, as can be seen from the P output column, the P output is ◯ (precharged) in the pixel rows 3, 5, 6, 8, 11, 12, and 13. Will be). Note that precharge is not performed in other pixel rows. In (b) of FIG. 242, the PEN signal is the same as (a) of FIG. 242, but the PSL signal is at the L level. Therefore, the P output is constantly maintained and the state is x (the precharge voltage Vp is not output).
[1016]
The above embodiment does not describe the precharge of each RGB, but it goes without saying that it is preferable to perform the precharge determination for each RGB as shown in FIG. This is because image data is different for each RGB. In particular, as shown in FIGS. 41, 125, and 126, good results can be obtained when RGB pixels are arranged in the column direction. This is because pixel data of the same color is continuously applied to each source signal line.
[1017]
FIG. 243 shows a driving method in which precharging is performed in the range of gradations 0-7 as in FIG. The controller 81 determines the precharge for each RGB. As a result of the implementation, as illustrated in FIG. 243, in the R image data, the PEN signal becomes H level in the pixel rows 3, 5, 6, 7, 8, 11, 12, and 13. That is, the pixel row is precharged. In the G image data, the PEN signal becomes H level in the pixel rows 3, 7, 9, 11, 12, 13, and 14. That is, the pixel row is precharged. In the B image data, the PEN signal becomes H level in the pixel rows 1, 2, 3, 6, 7, 8, 9, and 15. That is, the pixel row is precharged.
[1018]
In the above embodiment, it is determined whether or not to precharge corresponding to the pixel row. However, the present invention is not limited to this. It goes without saying that the size or change of image data applied to each pixel in units of frames (fields) may be determined to determine whether or not to precharge. FIG. 244 shows an example thereof.
[1019]
FIG. 244 shows changes in image data focusing on a certain pixel 16. The first row of the table in FIG. 244 indicates the frame number. The second row of the table shows changes in image data programmed in a certain pixel 16. FIG. 244 shows a modified example of the driving method in which precharging is performed at gradation 0 as in FIG. In FIG. 239, the precharge is always performed at gradation 0. FIG. 244 shows a method of precharging when gradation 0 continues for a certain frame. Continuation is indicated by a counter.
[1020]
In FIG. 244 (a), tone is 0 in frames 3, 4, 5, 6, 11, and 12. Therefore, the count value is sequentially counted from the third frame to the sixth frame. In addition, it is counted in frames 11 and 12. In FIG. 244 (a), precharge is controlled when gradation 0 continues for three frames. Accordingly, the P output becomes ◯ (a precharge voltage is output) in frames 5 and 6. In frames 11 and 12, gradation 0 is continuous for only two frames, so precharge is not performed.
[1021]
In FIG. 244 (b), the count control is performed by the PSL signal. When the PSL signal is at H level, the count value is increased. In FIG. 244 (b), since the PSL signal is at L level in frames 5 and 12, the count is not counted up. Therefore, the precharge voltage is output only in the frame 6.
[1022]
In FIG. 244, precharge is performed when gradation 0 continues for a certain number of frames. However, the present invention is not limited to this, and as described with reference to FIG. 240, a certain gradation range (for example, gradation 0). It may be controlled to precharge when −7) continues. Moreover, it is not limited to continuous frames, and may be discrete. Further, it may be controlled to precharge when a certain gradation range (for example, only gradation 0, gradation 0-7, etc.) continues in a continuous pixel row.
[1023]
As described above, in the precharge driving method of the present invention, it is determined whether or not to precharge based on the value of the image data or the change state of the image data or the image data value near the pixel to be precharged and its change, Apply precharge voltage (current). Information on whether or not to apply precharge is held in a source driver IC (circuit). Therefore, since the source driver IC (circuit) 14 only includes a latch circuit 2361 (holding circuit or storage means (memory)) for latching the precharge signal, the configuration is easy. In addition, any precharge method can be dealt with only by changing the program of the controller IC.
[1024]
In FIG. 232, the switch 481a is turned on / off to output the precharge voltage Vp from the terminal 681, and the switch 655 is turned on / off by the PO signal to apply the program current Iw from the terminal 681 to the source signal line 18. However, in the configuration of FIG. 232, when the switch 481a is closed and the precharge voltage Vp is applied to the terminal 681, the precharge voltage Vp is also applied to the current output circuit 654 (unit transistor group 521c). When a precharge voltage is applied to the current output circuit 654, an abnormal operation may occur in the current output circuit 654.
[1025]
As shown in FIG. 233, the switch 655 is disposed between the current output circuit 654 and the point A, and the switch 656 is controlled by inverting the logic of the OPV signal by the inverter 62. To do. That is, when the switch 481a is closed, the switch 656 is opened (open). With this configuration, when the precharge voltage Vp is applied to the terminal 681, the switch 655 is open, so that the precharge voltage is not applied to the current output circuit 654. This timing chart is shown in FIG. In FIG. 234 (a), the PO signal is L during the period t in which the OPV signal is H. More preferably, the switch 655 is turned off (open) before and after the period in which the switch 481a is closed. That is, as shown in FIG. 234 (b), the PO signal is set to the L level during the period t2 including before and after the period when the OPV signal is H. This is to prevent the adverse effect of the transient phenomenon due to the on / off of the switch 481a.
[1026]
As shown in FIG. 1, when the driving transistor 11a and the selection transistors (11b, 11c) of the pixel 16 are P-channel transistors, a punch-through voltage is generated. This is because the potential fluctuation of the gate signal line 17a penetrates to the terminal of the capacitor 19 through the GS capacitance (parasitic capacitance) of the selection transistors (11b, 11c). When the P-channel transistor 11b is turned off, the voltage becomes Vgh. Therefore, the terminal voltage of the capacitor 19 is slightly shifted to the Vdd side. For this reason, the gate (G) terminal voltage of the transistor 11a rises, resulting in a black display. Therefore, good black display can be realized.
[1027]
However, complete black display of the 0th gradation can be realized, but it is difficult to display the 1st gradation. Alternatively, a large gradation jump occurs from the 0th gradation to the first gradation, or blackout occurs in a specific gradation range.
[1028]
The configuration for solving this problem is the configuration of FIG. It has a function of raising the output current value. The main purpose of the raising circuit 541 is to compensate the punch-through voltage. Further, even when the image data has a black level of 0, a certain amount of current (several tens of nA) flows, and can be used for black level adjustment.
[1029]
Basically, FIG. 54 is obtained by adding a raising circuit (portion surrounded by a dotted line in FIG. 54) to the output stage of FIG. FIG. 54 assumes that the current value raising control signal is 3 bits (K0, K1, K2), and outputs a current value 0 to 7 times the current value of the grandchild current source by this 3-bit control signal. It is possible to add to the current.
[1030]
The above is the basic outline of the source driver IC (circuit) 14 of the present invention. Hereinafter, the source driver IC (circuit) 14 of the present invention will be described in more detail.
[1031]
There is a linear relationship between the current I (A) flowing through the EL element 15 and the light emission luminance B (nt). That is, the current I (A) flowing through the EL element 15 is proportional to the light emission luminance B (nt). In the current driving method, one step (gradation step) is a current (unit transistor 484 (one unit)).
[1032]
Human vision of brightness has a square characteristic. That is, when changing with a square curve, the brightness is recognized as changing linearly. However, in the relationship shown in FIG. 83, the current I (A) flowing through the EL element 15 and the light emission luminance B (nt) are proportional to each other in both the low luminance region and the high luminance region. Therefore, if the step is changed step by step (one gradation), the luminance change for one step is large (black skip occurs) in the low gradation portion (black region). Since the high gradation portion (white region) substantially coincides with the linear region of the square curve, the luminance change for one step is recognized as changing at equal intervals. From the above, in the current driving method (when one step is in increments of current) (in the current driving source driver IC (circuit) 14), the display of the black display region becomes a particular problem.
[1033]
To solve this problem, the slope of the current output in the low gradation region (gradation 0 (full black display) to gradation (R1)) is reduced, and the maximum gradation (R) from the high gradation region (gradation (R1)). )) Increase the current output slope. In other words, in the low gradation region, the current amount is increased with a small amount (one step) per gradation. In the high gradation region, the current amount increases with one gradation (one step). By making the amount of current changing per step different between the high gradation region and the low gradation region, the gradation characteristic becomes close to a square curve, and blackout does not occur in the low gradation region.
[1034]
In the above embodiment, the current gradient has two steps of the low gradation region and the high gradation region. However, the present invention is not limited to this. Needless to say, there may be three or more stages. However, it is needless to say that the case of two stages is preferable because the circuit configuration is simplified. Preferably, the gamma circuit is preferably configured so as to generate a gradient of five or more steps.
[1035]
The technical idea of the present invention is a circuit for performing gradation display by current output in a current-driven source driver IC (circuit), etc. Therefore, the display panel is limited to an active matrix type. (Instead, a simple matrix type is also included.) This means that a plurality of current increase amounts per gradation step exist.
[1036]
In a current-driven display panel such as an EL, display luminance changes in proportion to the amount of current applied. Therefore, in the source driver IC (circuit) 14 of the present invention, the luminance of the display panel can be easily adjusted by adjusting the reference current that causes the current to flow through one current source (one unit transistor) 484. .
[1037]
In the EL display panel, the luminous efficiency is different between R, G, and B, and the color purity with respect to the NTSC standard is shifted. Therefore, in order to optimize the white balance, it is necessary to appropriately adjust the RGB ratio. Adjustment is performed by adjusting the respective reference currents of RGB. For example, the R reference current is set to 2 μA, the G reference current is set to 1.5 μA, and the B reference current is set to 3.5 μA. As described above, it is preferable that at least one color reference current among at least a plurality of display color reference currents can be changed, adjusted, or controlled.
[1038]
In the current driving method, the relationship between the current I flowing through the EL and the luminance has a linear relationship. Therefore, the white balance adjustment by mixing RGB only needs to adjust the RGB reference current at one point of predetermined luminance. That is, if the RGB reference current is adjusted at one point with a predetermined luminance and the white balance is adjusted, the white balance is basically achieved over all gradations. Therefore, the present invention is characterized in that it includes an adjusting unit that can adjust the RGB reference currents, and includes a one-point bent or multi-point bent gamma curve generating circuit (generating unit). The above items are circuit systems peculiar to the current control EL display panel.
[1039]
In the gamma circuit of the present invention, as an example, the increase is 10 nA per gradation in the low gradation area (the slope of the gamma curve in the low gradation area). Further, it increases by 50 nA per gradation in the high gradation area (gamma curve inclination in the high gradation area).
[1040]
The increase in current per gradation in the high gradation area / the increase in current per gradation in the low gradation area is referred to as a gamma current ratio. In this embodiment, the gamma current ratio is 50 nA / 10 nA = 5. The RGB gamma current ratio is the same. That is, in RGB, the current (= program current) flowing in the EL element 15 is controlled with the gamma current ratio being the same.
[1041]
If the gamma current ratio is adjusted to be the same in RGB as described above, the circuit configuration is facilitated. For each color, a constant current circuit for generating a reference current to be applied to the low gradation part and a constant current circuit for generating a reference current to be applied to the high gradation part are manufactured, and a volume for adjusting the current flowing relatively to these is adjusted. This is because it is sufficient to produce (arrange).
[1042]
FIG. 56 is a configuration diagram of a constant current generating circuit unit in a low current region. FIG. 57 is a configuration diagram of the constant current circuit portion and the raised current circuit portion in the high current region. As shown in FIG. 56, a reference current INL is applied to the low current source circuit unit, which basically becomes a unit current, and the required number of unit transistors 484 are operated by the input data L0 to L4, and the sum thereof is obtained. The program current IwL of the low current part flows.
[1043]
  Further, as shown in FIG. 57, a reference current INH is applied to the high current source circuit unit, which basically becomes a unit current, and the input data H0 to H0.H5 causes the required number of unit transistors 484 to operate,HighA program current IwH of the current section flows.
[1044]
The raised current circuit section is the same, and a reference current INH is applied as shown in FIG. 57. This current basically becomes a unit current, and the necessary number of unit transistors 484 are operated by the input data AK0 to AK2. The current IwK corresponding to the raised current flows as the sum
The program current Iw flowing through the source signal line 18 is Iw = IwH + IwL + IwK. The ratio of IwH and IwL, that is, the gamma current ratio satisfies the first relationship described above.
[1045]
As shown in FIGS. 56 and 57, the on / off switch 481 includes an inverter 562, and an analog switch 561 composed of a P-channel transistor and an N-channel transistor. As described above, the switch 481 includes the inverter 562 and the analog switch 561 including the P-channel transistor and the N-channel transistor, so that the on-resistance can be reduced, and the voltage drop between the unit transistor 484 and the source signal line 18 is reduced. It can be made extremely small. Needless to say, this also applies to other embodiments of the present invention.
[1046]
The operation of the low current circuit unit in FIG. 56 and the high current circuit unit in FIG. 57 will be described. The source driver IC (circuit) 14 of the present invention is composed of 5 bits of low current circuit portions L0 to L4 and 6 bits of high current circuit portions H0 to H5. Note that data input from the outside of the circuit is 6 bits of D0 to D5 (64 gradations for each color). The 6-bit data is converted into 5 bits L0 to L4 and 6 bits of the high current circuit portions H0 to H5, and a program current Iw corresponding to the image data is applied to the source signal line. That is, the input 6-bit data is converted into 5 + 6 = 11-bit data. Therefore, a highly accurate gamma curve can be formed.
[1047]
As described above, the input 6-bit data is converted into 5 + 6 = 11-bit data. In the present invention, the number of bits (H) of the circuit in the high current region is the same as the number of bits of the input data (D), and the number of bits (L) of the circuit in the low current region is the number of bits of the input data (D). -1. Note that the bit number (L) of the circuit in the low current region may be the bit number −2 of the input data (D). With this configuration, the gamma curve in the low current region and the gamma curve in the high current region are optimal for image display on the EL display panel.
[1048]
In the current driving method, the relationship between the current I flowing through the EL and the luminance has a linear relationship. Therefore, the white balance adjustment by mixing RGB only needs to adjust the RGB reference current at one point of predetermined luminance. That is, if the RGB reference current is adjusted at one point with a predetermined luminance and the white balance is adjusted, the white balance is basically achieved over all gradations. This point is also a characteristic effect of the current drive system of the present invention.
[1049]
In the case of a gamma curve having a broken line (having a bent position) as shown in FIG. 247, a little care is required. First, in order to obtain RGB white balance, it is necessary to make the bending position of the gamma curve (gradation R1) the same in RGB. By making it the same, in the current driving method, the relative relationship of the gamma curve can be made the same in RGB. Further, it is necessary to make the ratio of the gradient of the low gradation region and the gradient of the high gradation region constant in RGB. By making it constant, in the current driving method, the relative relationship of the gamma curve can be made the same in RGB.
[1050]
For example, 10 nA per gradation is increased in the low gradation area (gamma curve inclination in the low gradation area), and 50 nA is increased per gradation in the high gradation area (gamma curve inclination in the high gradation area). The increase in current per gradation in the high gradation area / the increase in current per gradation in the low gradation area is referred to as a gamma current ratio. In this embodiment, the gamma current ratio is 50 nA / 10 nA = 5. In RGB, the current flowing through the EL element 15 is adjusted with the same gamma current ratio.
[1051]
FIG. 248 shows an example of the gamma curve. In FIG. 248 (a), the current increase per gradation is large in both the low gradation part and the high gradation part. In FIG. 248 (b), the increase in current per gradation is smaller in both the low gradation part and the high gradation part than in FIG. 248 (a). However, the gamma current ratio is the same in both FIG. 248 (a) and FIG. 248 (b). In this way, adjusting the gamma current ratio while maintaining the same value for RGB generates a constant current circuit for generating a reference current to be applied to the low gradation portion and a reference current to be applied to the high gradation portion for each color. This is because a constant current circuit is prepared, and a volume for adjusting the current flowing relatively to these is prepared (arranged).
[1052]
FIG. 245 shows a circuit configuration for varying the output current while maintaining the gamma current ratio. The current control circuit 692 changes the current flowing through the current sources 473L and 473H while maintaining the gamma current ratio between the reference current source 691L in the low current region and the reference current source 691H in the high current region.
[1053]
Further, as shown in FIG. 246, it is preferable to detect the relative temperature of the display panel with a temperature detection circuit 701 formed in the IC chip (circuit) 14. This is because EL elements have different temperature characteristics depending on the materials constituting RGB. This temperature detection utilizes the fact that the state of the junction of the bipolar transistor changes with temperature, and the output current changes with temperature. The detected temperature is fed back to the temperature control circuit 702 arranged (formed) for each color, and the current control circuit 692 performs temperature compensation.
[1054]
It is appropriate that the gamma ratio has a relationship of 3 to 10. More preferably, a relationship of 4 or more and 8 or less is appropriate. In particular, the gamma current ratio preferably satisfies the relationship of 5 or more and 7 or less. This is called the first relationship.
[1055]
Further, it is appropriate to set the change point (gradation R1 in FIG. 247) between the low gradation portion and the high gradation portion to 1/32 or more and 1/4 or less of the maximum gradation number K. For example, if the maximum number of gradations K is 6 bits and 64 gradations, 64/32 = 2 gradations or more and 64/4 = 16 gradations or less. More preferably, the change point (gradation R1 in FIG. 247) between the low gradation portion and the high gradation portion is appropriately set to 1/16 or more and 1/4 or less of the maximum gradation number K. For example, if the maximum number of gradations K is 6 bits and 64 gradations, 4816 = 4th gradation or more and 64/4 = 16th gradation or less. More preferably, it is set to 1/10 or more and 1/5 or less of the maximum number of gradations K. If the calculation results in a decimal point, round it down. For example, if the maximum number of gradations K is 6 bits and 64 gradations, 4810 = 6th gradation or more and 64/5 = 12th gradation or less. The above relationship is referred to as a second relationship.
[1056]
The above explanation is the relationship between the gamma current ratios of the two current regions. However, the second relationship described above is also applied when there are gamma current ratios of three or more current regions (that is, there are two or more bending points). In other words, for three or more inclinations, the relationship may be applied to any two inclinations.
[1057]
By satisfying both the first relationship and the second relationship at the same time, it is possible to realize a good image display without blackout.
[1058]
FIG. 250 shows an embodiment in which a plurality of current-driven source driver circuits (ICs) 14 of the present invention are used in one display panel. The source driver IC of the present invention includes a slave / master (S / M) terminal 2502 that is assumed to use a plurality of source driver ICs 14. The S / M terminal 2502 is set to H level to operate as a master chip, and a reference current is output from a reference current output terminal (not shown). This current becomes the current that flows through the INL and INH terminals in FIGS. 56 and 57 of the slave source driver IC 14 (14a, 14c). By setting the S / M terminal 2502 to the L level, the source driver IC 14 operates as a slave chip, and receives the reference current of the master chip from a reference current input terminal (not shown).
[1059]
The reference current passed between the reference current input terminal and the reference current output terminal is of two systems, a low gradation region and a high gradation region for each color. Note that the reference current is supplied by the reference current transfer wiring 2501. Therefore, with 3 colors of RGB, there are 6 systems of 3 × 2. In the above-described embodiment, each color has two systems. However, the present invention is not limited to this, and there may be three or more systems for each color.
[1060]
In the current driving method of the present invention, as shown in FIG. 249, the bending point (gradation R1, etc.) can be changed. In FIG. 249 (a), the low gradation part and the high gradation part are changed at gradation R1, and in FIG. 249 (b), the low gradation part and the high gradation part are changed at gradation R2. Yes. In this way, the bending position can be changed at a plurality of locations.
[1061]
Specifically, the present invention can realize 64-gradation display. The bending point (R1) is none, the second gradation, the fourth gradation, the eighth gradation, and the sixteenth gradation. Since the complete black display has gradation 0, the bending points are 2, 4, 8, and 16. If the complete black display gradation is gradation 1, the bending point is 3, 5, 9, 17, 33. As described above, it is possible to simplify the circuit configuration by configuring the bent position so that it can be performed at a location that is a multiple of 2 (or a location that is a multiple of 2 plus 1 when the complete black display is gradation 1). An effect occurs.
[1062]
FIG. 56 is a configuration diagram of a current source circuit section in a low current region. FIG. 57 is a configuration diagram of a current source section and a raised current circuit section in a high current region. As shown in FIG. 56, a reference current INL is applied to the low current source circuit unit. Basically, this current becomes a unit current, and the necessary number of current sources 484 are operated by the input data L0 to L4. The program current IwL of the low current part flows.
[1063]
Further, as shown in FIG. 57, the reference current INH is applied to the high current source circuit unit. Basically, this current becomes a unit current, and the necessary number of current sources 484 are operated by the input data H0 to L5. As a sum, the program current IwH of the high current portion flows.
[1064]
The raising current circuit unit is the same, and a reference current INH is applied as shown in FIG. 57. This current basically becomes a unit current, and the necessary number of current sources 484 are operated by the input data AK0 to AK2. The current IwK corresponding to the raised current flows as the sum
The program current Iw flowing through the source signal line 18 is Iw = IwH + IwL + IwK. It should be noted that the ratio of IwH and IwL, that is, the gamma current ratio satisfies the first relationship described above.
[1065]
As shown in FIGS. 56 and 57, the on / off switch 481 includes an inverter 562, and an analog switch 561 composed of a P-channel transistor and an N-channel transistor. As described above, the switch 481 includes the inverter 562 and the analog switch 561 including the P-channel transistor and the N-channel transistor, so that the on-resistance can be reduced, and the voltage drop between the current source 484 and the source signal line 18 is reduced. It can be made extremely small.
[1066]
The operation of the low current circuit unit in FIG. 56 and the high current circuit unit in FIG. 57 will be described. The source driver circuit (IC) 14 of the present invention is composed of 5 bits of low current circuit portions L0 to L4 and 6 bits of high current circuit portions H0 to H5. Note that data input from the outside of the circuit is 6 bits of D0 to D5 (64 gradations for each color). The 6-bit data is converted into 5 bits L0 to L4 and 6 bits of the high current circuit portions H0 to H5, and a program current Iw corresponding to the image data is applied to the source signal line. That is, the input 6-bit data is converted into 5 + 6 = 11-bit data. Therefore, a highly accurate gamma curve can be formed.
[1067]
As described above, the input 6-bit data is converted into 5 + 6 = 11-bit data. In the present invention, the number of bits (H) of the circuit in the high current region is the same as the number of bits of the input data (D), and the number of bits (L) of the circuit in the low current region is the number of bits of the input data (D). -1. Note that the bit number (L) of the circuit in the low current region may be the bit number −2 of the input data (D). With this configuration, the gamma curve in the low current region and the gamma curve in the high current region are optimal for image display on the EL display panel.
[1068]
Hereinafter, a method for controlling the circuit control data (L0 to L4) in the low current region and the circuit control data (H0 to H4) in the high current region will be described with reference to FIGS. 252 to 254.
[1069]
The present invention is characterized by the operation of the current source 484a connected to the L4 terminal of FIG. 56 of FIG. This 484a is composed of one transistor which becomes a current source of one unit. By turning this transistor on and off, the program current Iw can be easily controlled (on / off control).
[1070]
FIG. 252 is an applied signal to the low current side signal line (L) and the high current side signal line (H) when the low current region and the high current region are switched at gradation 4. In FIGS. 252 to 254, gradations 0 to 18 are shown, but there are actually up to the 63rd gradation. Therefore, the gradation 18 or higher is omitted in each drawing. In addition, the switch 481 is turned on when “1” in the table, the current source 484 and the source signal line 18 are connected, and the switch 481 is turned off when “0” in the table. The gradation is not limited to the 63rd gradation, and may be 255 gradations or more.
[1071]
In FIG. 252, in the case of gradation 0 of complete black display, (L0 to L4) = (0, 0, 0, 0, 0), and (H0 to H5) = (0, 0, 0, 0, 0). Accordingly, all the switches 481 are in the OFF state, and the program current Iw = 0 in the source signal line 18.
[1072]
In gradation 1, (L0 to L4) = (1, 0, 0, 0, 0) and (H0 to H5) = (0, 0, 0, 0, 0). Therefore, one unit current source 484 in the low current region is connected to the source signal line 18. The unit current source in the high current region is not connected to the source signal line 18.
[1073]
In gradation 2, (L0 to L4) = (0, 1, 0, 0, 0) and (H0 to H5) = (0, 0, 0, 0, 0). Therefore, the two unit current sources 484 in the low current region are connected to the source signal line 18. The unit current source in the high current region is not connected to the source signal line 18.
[1074]
In gradation 3, (L0 to L4) = (1, 1, 0, 0, 0) and (H0 to H5) = (0, 0, 0, 0, 0). Accordingly, the two switches 481La and 481Lb in the low current region are turned on, and the three unit current sources 484 are connected to the source signal line 18. The unit current source in the high current region is not connected to the source signal line 18.
[1075]
In gradation 4, (L0 to L4) = (1,2681) and (H0 to H5) = (0, 0, 0, 0, 0). Accordingly, the three switches 481La, 481Lb, 481Le in the low current region are turned on, and the four unit current sources 484 are connected to the source signal line 18. The unit current source in the high current region is not connected to the source signal line 18.
[1076]
At the gradation 5 or higher, the low current region (L0 to L4) = (1,2681) is not changed. However, in the high current region, (H0 to H5) = (1, 0, 0, 0, 0) in gradation 5, the switch 481Ha is turned on, and one unit current source 481 in the high current region is the source signal. Connected to line 18. In gradation 6, (H0 to H5) = (0, 1, 0, 0, 0), the switch 481Hb is turned on, and the two unit current sources 481 in the high current region are connected to the source signal line 18. The Similarly, in gradation 7, (H0 to H5) = (1, 1, 0, 0, 0), the two switches 481Ha switch 481Hb are turned on, and the three unit current sources 481 in the high current region are the source signals. Connected to line 18. Further, in gradation 8, (H0 to H5) = (0, 0, 1, 0, 0), one switch 481Hc is turned on, and four unit current sources 481 in the high current region are connected to the source signal line 18. Connected. Thereafter, as shown in FIG. 252, the switch 481 is sequentially turned on and off, and the program current Iw is applied to the source signal line 18.
[1077]
A characteristic of the above operation is an operation at a bending point. However, the bending point is a switching point between the low current region and the high current region. To be exact, since the low current IwL is added as the program current Iw in the case of gradation in the high current region, the switching point is changed. The expression point is not correct. That is, in the gradation of the high gradation portion, the current corresponding to the step (gradation) of the high gradation portion is added to the current of the low gradation portion, and becomes the program current Iw. This is a point where the control bit (L) in the low current region does not change with a gradation of one step (which should be called a point where the current changes or a point or a position). At this time, the L4 terminal in FIG. 56 becomes “1”, the switch 481e is turned on, and a current flows through the transistor 484a.
[1078]
Accordingly, in the gradation 4 in FIG. 252, four unit transistors (current sources) 484 in the low gradation portion are operating. In gradation 5, four unit transistors (current sources) 484 in the low gradation part operate, and one transistor (current source) 484 in the high gradation part operates. Thereafter, similarly, in the gradation 6, four unit transistors (current sources) 484 in the low gradation part operate, and two transistors (current sources) 484 in the high gradation part operate. Therefore, at the gradation level 5 or higher, which is the bending point, the current source 484 in the low gradation area below the bending point is turned on for the gradation level (in this case, four), and in addition to this, the current of the high gradation part is sequentially increased. A number of sources 484 are sequentially turned on according to the gradation.
[1079]
Therefore, it can be seen that one of the L4 terminal transistors 484a in FIG. Without this transistor 484a, after the gradation 3, one transistor 484 in the high gradation portion is turned on. Therefore, the switching point is not a multiplier of 2, such as 4, 8, and 16. The multiplier of 2 is a state in which only one signal is “1”.
[1080]
Therefore, it is easy to perform the condition determination that the weighting signal line of 2 is “1”. Therefore, the hardware scale for condition determination can be reduced. That is, the logic circuit of the IC chip is simplified, and as a result, an IC having a small chip area can be designed (cost reduction is possible).
[1081]
FIG. 253 is an explanatory diagram of signals applied to the low current side signal line (L) and the high current side signal line (H) when the low current region and the high current region are switched at gradation 8.
[1082]
In FIG. 253, in the case of gradation 0 for complete black display, it is the same as FIG. 252, (L0 to L4) = (0, 0, 0, 0, 0), and (H0 to H5) = (0 , 0, 0, 0, 0). Accordingly, all the switches 481 are in the OFF state, and the program current Iw = 0 in the source signal line 18.
[1083]
Similarly, in gradation 1, (L0 to L4) = (1, 0, 0, 0, 0) and (H0 to H5) = (0, 0, 0, 0, 0). Therefore, one unit current source 484 in the low current region is connected to the source signal line 18. The unit current source in the high current region is not connected to the source signal line 18.
[1084]
In gradation 2, (L0 to L4) = (0, 1, 0, 0, 0) and (H0 to H5) = (0, 0, 0, 0, 0). Therefore, the two unit current sources 484 in the low current region are connected to the source signal line 18. The unit current source in the high current region is not connected to the source signal line 18.
[1085]
In gradation 3, (L0 to L4) = (1, 1, 0, 0, 0) and (H0 to H5) = (0, 0, 0, 0, 0). Accordingly, the two switches 481La and 481Lb in the low current region are turned on, and the three unit current sources 484 are connected to the source signal line 18. The unit current source in the high current region is not connected to the source signal line 18.
[1086]
Similarly, in the gradation 4, (L0 to L4) = (0, 0, 1, 0, 0) and (H0 to H5) = (0, 0, 0, 0, 0). In gradation 5, (L0 to L4) = (1, 0, 1, 0, 0) and (H0 to H5) = (0, 0, 0, 0, 0). In gradation 6, (L0 to L4) = (0, 1, 1, 0, 0) and (H0 to H5) = (0, 0, 0, 0, 0). In gradation 7, (L0 to L4) = (1, 1, 1, 0, 0) and (H0 to H5) = (0, 0, 0, 0, 0).
[1087]
Gradation 8 is the switching point (folding position). In gradation 8, (L0 to L4) = (1, 1, 1, 0, 1) and (H0 to H5) = (0, 0, 0, 0, 0). Accordingly, the four switches 481La, 481Lb, 481Lc, 481Le in the low current region are turned on, and the eight unit current sources 484 are connected to the source signal line 18. The unit current source in the high current region is not connected to the source signal line 18.
[1088]
At the gradation 8 or higher, the low current region (L0 to L4) = (1, 1, 1, 0, 1) is not changed. However, in the high current region, in gradation 9, (H0 to H5) = (1, 0, 0, 0, 0), the switch 481Ha is turned on, and one unit current source 481 in the high current region is the source signal. Connected to line 18.
[1089]
Similarly, the number of transistors 484 in the high current region increases by one according to the gradation step. That is, at gradation 10, (H0 to H5) = (0, 1, 0, 0, 0), the switch 481Hb is turned on, and the two unit current sources 481 in the high current region are connected to the source signal line 18. The Similarly, in the gradation 11, (H0 to H5) = (1, 1, 0, 0, 0), the two switches 481Ha, the switch 481Hb are turned on, and the three unit current sources 481 in the high current region are the source signals. Connected to line 18. Further, in gradation 12, (H0 to H5) = (0, 0, 1, 0, 0), one switch 481Hc is turned on, and four unit current sources 481 in the high current region are connected to the source signal line 18. Connected. Thereafter, as shown in FIG. 252, the switch 481 is sequentially turned on and off, and the program current Iw is applied to the source signal line 18.
FIG. 254 is an explanatory diagram of signals applied to the low current side signal line (L) and the high current side signal line (H) when the low current region and the high current region are switched at gradation 16. In this case, the basic operation is the same as that in FIGS. 252 and 253.
[1090]
That is, in FIG. 254, in the case of gradation 0 for complete black display, it is the same as in FIG. 253, and (L0 to L4) = (0, 0, 0, 0, 0), and (H0 to H5) = (0, 0, 0, 0, 0). Accordingly, all the switches 481 are in the OFF state, and the program current Iw = 0 in the source signal line 18. Similarly, from gradation 1 to gradation 16, high gradation region (H0 to H5) = (0, 0, 0, 0, 0). Therefore, one unit current source 484 in the low current region is connected to the source signal line 18. The unit current source in the high current region is not connected to the source signal line 18. That is, only (L0 to L4) in the low gradation region changes.
[1091]
In other words, (L0 to L4) = (1, 0, 0, 0, 0) in gradation 1, and (L0 to L4) = (0, 1, 0, 0, 0) in gradation 2. Yes, in gradation 3, (L0-L4) = (1, 1, 0, 0, 0), and in gradation 2, (L0-L4) = (0, 0, 1, 0, 0) is there. Thereafter, the gradation is sequentially counted up to gradation 16. That is, in gradation 15, (L0 to L4) = (1, 1, 1, 1, 0), and in gradation 16, (L0 to L4) = (1, 1, 1, 1, 1). is there. In gradation 16, only one fifth bit (D4) of D0 to D5 indicating gradation is turned on, so that the content expressed by data D0 to D5 is 16, indicating that one data signal line ( It can be determined by the determination of D4). Therefore, the hardware scale of the logic circuit can be reduced.
[1092]
Gradation 16 is a switching point (bending position) (or gradation 17 may be a switching point). In gradation 16, (L0 to L4) = (1, 1, 1, 1, 1) and (H0 to H5) = (0, 0, 0, 0, 0). Accordingly, the four switches 481La, 481Lb, 481Lc, 481d, and 481Le in the low current region are turned on, and the 16 unit current sources 484 are connected to the source signal line 18. The unit current source in the high current region is not connected to the source signal line 18.
[1093]
At gradation 16 or higher, the low current region (L0 to L4) = (1, 1, 1, 0, 1) has no change. However, in the high current region, at gradation 17, (H0 to H5) = (1, 0, 0, 0, 0), the switch 481Ha is turned on, and one unit current source 481 in the high current region is the source signal. Connected to line 18. Similarly, the number of transistors 484 in the high current region increases by one according to the gradation step. That is, at gradation 18, (H0 to H5) = (0, 1, 0, 0, 0), the switch 481Hb is turned on, and the two unit current sources 481 in the high current region are connected to the source signal line 18. The Similarly, in gradation 19, (H0 to H5) = (1, 1, 0, 0, 0), the two switches 481Ha switch 481Hb are turned on, and the three unit current sources 481 in the high current region are the source signals. Connected to line 18. Further, in gradation 20, (H0 to H5) = (0, 0, 1, 0, 0), one switch 481Hc is turned on, and four unit current sources 481 in the high current region are connected to the source signal line 18. Connected.
[1094]
As described above, at the switching point (bending position), the current source (1 unit) 484 whose number is a multiplier of 2 is turned on or connected to the source signal line 18 (conversely, a configuration in which it is turned off is also conceivable). Logic processing is extremely easy. For example, as shown in FIG. 252, if the bending position is gradation 4 (4 is a multiplier of 2), the four current sources (one unit) 484 are configured to operate. Then, in the gradation beyond that, the current source (one unit) 484 in the high current region is added. Further, as shown in FIG. 253, when the bending position is gradation 8 (8 is a multiplier of 2), the eight current sources (one unit) 484 are configured to operate. Then, in the gradation beyond that, the current source (one unit) 484 in the high current region is added. If the configuration of the present invention is adopted, a gamma control circuit with a small hardware configuration can be configured with any gradation expression, not limited to 64 gradations (16 gradations: 4096 colors, 256 gradations: 16.7 million colors, etc.).
[1095]
In the embodiment described with reference to FIGS. 252, 253, and 254, the gradation of the switching point is a multiplier of 2. This is the case where the complete black gradation is gradation 0. When gradation 1 is to be displayed completely black, +1 is necessary. However, these are matters for convenience.
[1096]
What is important in the present invention is to have a plurality of current regions (low current region, high current region, etc.), and to make a determination (processing) with few signal inputs at the switching points. As an example thereof, the technical idea is that the hardware scale becomes extremely small because it is only necessary to detect one signal line if it is a multiplier of 2. In order to facilitate the processing, a current source 484a is added.
[1097]
Therefore, in the case of negative logic, the switching point may be set at the gradations 1, 3, 7, 15. Further, although gradation 0 is set to be completely black, the present invention is not limited to this. For example, in the case of 64-gradation display, gradation 63 may be in a completely black display state, and gradation 0 may be the maximum white display. In this case, the switching point may be processed in consideration of the reverse direction. Therefore, there may be a different configuration from the multiplier of 2.
[1098]
Further, the switching point (bending position) is not limited to one gamma curve. Even when there are a plurality of bent positions, the circuit of the present invention can be configured. For example, the folding position can be set to gradation 4 and gradation 16. It is also possible to set 3 points or more, such as gradation 4, gradation 16, and gradation 32.
[1099]
In the above embodiment, the gradation is set to a multiplier of 2. However, the present invention is not limited to this. For example, the bending points may be set with multipliers 2 and 8 (2 + 8 = 10th gradation, that is, two signal lines required for determination). Bending points may be set at 2 and 8 and 16 (2 + 8 + 16 = 26th gradation, that is, three signal lines required for determination), which are 2 multipliers beyond that. In this case, the hardware scale required for determination or processing is somewhat increased, but it can be adequately handled in terms of circuit configuration. Needless to say, the above-described matters are included in the technical category of the present invention.
[1100]
As shown in FIG. 255, the source driver circuit (IC) 14 of the present invention is composed of a current output circuit 654 of three parts. A high current region current output circuit 654a that operates in a high gradation region, a low current region current output circuit 654b that operates in a low current region and a high gradation region, and a current raising current output circuit 654b that outputs a raising current.
[1101]
The high current region current output circuit 654a and the current raising current output circuit 654c operate using the reference current source 691a that outputs a high current as a reference current, and the low current region current output circuit 654b uses the reference current source 691b that outputs a low current as a reference. Operates as a current.
[1102]
As described above, the current output circuit 654 is not limited to the high current region current output circuit 654a, the low current region current output circuit 654b, and the current raising current output circuit 654c. Two current output circuits 654a and a low current region current output circuit 654b may be used, or three or more current output circuits 654 may be used. Of course, the number of current output circuits 654 may be one. The reference current source 691 may be arranged or formed corresponding to each current region current output circuit 654, or may be common to all the current region current output circuits 654.
[1103]
The above-described current output circuit 654 corresponds to the gradation data, and the internal unit transistor 484 operates to absorb current from the source signal line 18. The unit transistor 484 operates in synchronization with one horizontal scanning period (1H) signal. That is, during the period of 1H, a current based on the corresponding gradation data is input (when the unit transistor 484 is an N channel).
[1104]
On the other hand, the gate driver circuit 12 basically selects one gate signal line 17a sequentially in synchronization with the 1H signal. That is, in synchronization with the 1H signal, the gate signal line 17a (1) is selected during the first H period, the gate signal line 17a (2) is selected during the second H period, and the gate signal line 17a is selected during the third H period. (3) is selected, and the gate signal line 17a (4) is selected in the fourth H period.
[1105]
However, after the first gate signal line 17a is selected, no gate signal line 17a is selected during the period in which the next second gate signal line 17a is selected (non-selection period, t1 in FIG. 256). To be provided). The non-selection period requires a rising period and a falling period of the gate signal line 17a, and is provided to ensure an on / off control period of the TFT 11d.
[1106]
If an on voltage is applied to any one of the gate signal lines 17a and the TFTs 11b and 11c of the pixel 16 are on, the program current Iw is applied to the source signal line 18 from the Vdd power supply (anode voltage) through the driving TFT 11a. Flowing. This program current Iw flows through the transistor 484 (period t2 in FIG. 256). A parasitic capacitance C is generated in the source signal line 18 (parasitic capacitance is generated due to a cross-point capacitance between the gate signal line and the source signal line).
[1107]
However, when none of the gate signal lines 17a is selected (non-selection period: period t1 in FIG. 256), there is no current path flowing through the TFT 11a. Since the transistor 484 conducts current, it absorbs charge from the parasitic capacitance of the source signal line 18. As a result, the potential of the source signal line 18 decreases (portion A in FIG. 256). When the potential of the source signal line 18 decreases, it takes time to write a current corresponding to the next image data.
[1108]
In order to solve this problem, a switch 481a is formed at the output terminal of the source terminal 681, as shown in FIG. Further, the switch 481b is formed or arranged at the output stage of the raised current output circuit 654c.
[1109]
In the non-selection period t1, a control signal is applied to the control terminal S1, and the switch 481a is turned off. In the selection period t2, the switch 481a is turned on (conductive state). In the on state, a program current Iw = IwH + IwL + IwK flows. When the switch 481a is turned off, no Iw current flows. Therefore, as shown in FIG. 258, the potential decreases as A in FIG. 256 (no change). Note that the channel width W of the analog switch 561 of the switch 481 is 10 μm or more and 100 μm or less. The analog switch W (channel width) needs to be 10 μm or more in order to reduce the on-resistance. However, if W is too large, the parasitic capacitance increases, so the thickness is made 100 μm or less. More preferably, the channel width W is preferably 15 μm or more and 60 μm or less.
[1110]
The switch 481b is a switch that controls only low gradation display. At the time of low gradation display (black display), the gate potential of the TFT 11a of the pixel 16 needs to be close to the anode voltage Vdd. Therefore, in the black display, the potential of the source signal line 18 needs to be close to the anode voltage Vdd. In the black display, the program current Iw is small, and once the potential drops as shown in FIG. 256A, it takes a long time to return to the normal potential.
[1111]
Therefore, in the case of low gradation display, it must be avoided that the non-selection period t1 occurs. On the contrary, in the high gradation display, since the program current Iw is large, there is often no problem even if the non-selection period t1 occurs. Therefore, in the present invention, in high gradation display image writing, both the switch 481a and the switch 481b are turned on even in the non-selection period. Further, the raising current IwK needs to be cut off. This is to achieve black display as much as possible. In the low gradation display image writing, the switch 481a is turned on during the non-selection period, and the switch 481b is turned off. The switch 481b is controlled by the terminal S2.
[1112]
Needless to say, in both the low gradation display and the high gradation display, driving may be performed in which the switch 481a is turned off (non-conducting state) and the switch 481b is kept on (conducting) in the non-selection period t1. Needless to say, in both the low gradation display and the high gradation display, driving in which both the switch 481a and the switch 481b are turned off (non-conduction) may be performed in the non-selection period t1.
[1113]
In any case, the switch 481 can be controlled by controlling the control terminals S1 and S2. The control terminals S1 and S2 are controlled by command control.
[1114]
For example, the control terminal S2 sets the t3 period to the “0” logic level so as to overlap the non-selection period t1. By controlling in this way, the state A in FIG. 256 does not occur. Further, when the gray level is a black display level above a certain level, the control terminal S1 is set to the “0” logic level. Then, the raising current IwK is stopped, and good black display can be realized.
[1115]
The above embodiment has been described as an embodiment on the assumption that one source driver IC 14 is mounted on the display panel. However, the present invention is not limited to this configuration. A plurality of source driver ICs 14 may be stacked on one display panel. For example, FIG. 261 shows an embodiment of a display panel on which three source driver ICs 14 are mounted.
[1116]
As described in FIG. 56, FIG. 57, FIG. 245, and the like, the source driver IC 14 of the present invention includes at least two systems of a reference current in a low gradation region and a reference current in a high gradation region.
[1117]
As described with reference to FIG. 250, the current-driven source driver circuit (IC) 14 of the present invention includes a slave / master (S / M) terminal 2502 that is assumed to use a plurality of source driver ICs 14. . The S / M terminal 2502 is set to H level to operate as a master chip, and a reference current is output from a reference current output terminal (not shown). Of course, the logic of the S / M terminal may have a reverse polarity. Further, it may be switched by a command to the source driver IC 14. The reference current is transmitted through the caskate current connection line 2611. By setting the S / M terminal 2502 to the L level, the source driver IC 14 operates as a slave chip, and receives the reference current of the master chip from a reference current input terminal (not shown). This current is the current flowing through the INL and INH terminals in FIGS.
[1118]
The reference current is generated by a reference current generation circuit 1691 at the center (middle part) of the source driver IC 14. The reference current of the master chip is adjusted and applied from the outside by an external resistor or a current step type electronic volume arranged or configured inside the IC.
[1119]
A control circuit (such as a command decoder) is also formed (arranged) at the center of the source driver IC 14. The reason why the reference current source is formed at the center of the chip is to shorten the distance between the reference current generating circuit and the program current output terminal as much as possible.
[1120]
In the configuration of FIG. 261, the reference current is transmitted from the master chip 14b to the two slave chips (14a, 14c). The slave chip receives a reference current, and generates a parent, a child, and a grandchild current based on this current. Note that the reference current transferred from the master chip 14b to the slave chip is performed by current transfer of the current mirror circuit. By performing the current transfer, there is no deviation in the reference current among the plurality of chips, and the dividing lines on the screen are not displayed.
[1121]
FIG. 262 conceptually illustrates the position of the reference current transfer terminal. A reference current signal line 2501 is connected to the signal input terminal 2621i disposed at the center of the IC chip. The current applied to the reference current signal line 2501 is compensated for the temperature characteristics of the EL material. Further, compensation is made due to deterioration of the life of the EL material.
[1122]
Based on the current (voltage) applied to the reference current signal line 2501, each current source (471, 472, 473, 484) is driven in the chip. This reference current is output as a reference current to the slave chip via the current mirror circuit. The reference current to the slave chip is output from the terminal 2621o. At least one terminal 2621o is arranged (formed) on the left and right sides of the reference current generating circuit 1691. In FIG. 262, two are arranged (formed) on the left and right. This reference current is transmitted to the slave chip 14 through the cascade signal lines 2611a1, 2611a2, 2611b1, and 2611b2. The circuit may be configured so that the reference current applied to the slave chip 14a is fed back to the master chip 14b to correct the shift amount.
[1123]
In the current-driven EL display panel, the program current in black display is very small, 100 nA or less. Therefore, if parasitic capacitance exists in the source signal line 18 or the like, charging / discharging of the parasitic capacitance cannot be performed in one horizontal scanning period (1H) (the influence of the parasitic capacitance cannot be sufficiently eliminated). Therefore, writing shortage occurs. Insufficient writing leads to lower display contrast and lower resolution.
[1124]
The parasitic capacitance includes a parasitic capacitance in the display area and a parasitic capacitance in the output circuit of the source driver IC 14. The parasitic capacitance of the output circuit is a parasitic capacitance 3751b due to a protection diode 3751a connected to the internal wiring 3752 in the output stage, as mainly shown in FIG. 375 (a). The protection diode 3751a is an important circuit as a countermeasure against static electricity of the source driver IC 14, but the protection diode 3751a is equivalent to a capacitor 3751b (parasitic capacitance) as shown in FIG. 375 (b). Note that parasitic capacitance due to a protection diode or the like is referred to as protection capacitance.
[1125]
When the source driver IC 14 is a voltage output, there is no influence because the output impedance of the source driver IC 14 is low even if the protection capacitance is relatively large. However, when the source driver IC 14 is a current output, since the output impedance of the source driver IC 14 is high, the size of the protective capacitor greatly affects the time constant. That is, the program current Iw cannot be written to the pixel 16 within one horizontal scanning period (1H). However, the protective diode cannot be deleted for countermeasures against static electricity.
[1126]
The present invention solves this problem. FIG. 376 shows an example. The protective diode 3751a as shown in FIG. 375 (a) is not formed. Instead, a switch 3761 (short circuit) for short-circuiting adjacent source signal lines 18 is formed in the source driver IC 14. The short circuit 3761 is a very small switch. Switching is exemplified by MOS transistors. In addition, it may be a bipolar transistor or an analog switch composed of P-channel and N-channel transistors. When the switch is in an open state, the W (channel width) and L (channel length) of the transistor are designed so as to exhibit a resistance value of 100 MΩ or more. The switch 3761 is configured to be in a closed state when the source driver IC 14 is formed (normally closed). A signal (voltage) applied to a control terminal (not shown) is opened as shown in FIG. The control terminal is connected to the gate terminal of the transistor constituting the switch 3761.
[1127]
The embodiment of FIG. 378 is an embodiment in which a short-circuit portion 3781 is formed between adjacent source signal lines 18. It is formed with high impedance wiring of 100 MΩ or more. Although a minute leak occurs between the adjacent source signal lines 18, the program current Iw is not affected due to the minute current. The short circuit part is formed of polysilicon.
[1128]
FIG. 379 (a) shows an example in which a complete short-circuit portion 3781 is formed between adjacent source signal lines 18. The short circuit part is formed by metal wiring or the like. Until the source driver IC 14 is mounted on the substrate 71, the short-circuit portion 3781 is left. After mounting, the substrate 71 and the source driver IC 14 are immersed in an etching solution or the like, and the short-circuit portion 3781 is etched away. In the above embodiment, the short-circuit portion 3781 is separated by etching. However, the short-circuit portion 3781 may be cut by irradiating a laser or the like.
[1129]
FIG. 382 shows an example. As described above, the base anode line 2631 is formed on the back surface of the source driver IC 14 in the present invention. In addition, the base anode line 2631 is formed on the substrate 71 so as to shield the circuit formation portion from light so as to prevent the IC from malfunctioning due to photoconversion (see FIG. 102 and its description).
[1130]
In FIG. 382, in the source driver IC 14, a slit 3821 is opened in the base anode line 2631 at a location where the short-circuit portion 3781 is formed. The slit 3821 is a portion through which light can pass. As shown in FIG. 383, laser light 3831 is incident from the slit 3821 to cut the short-circuit portion 3781. The wavelength of the laser beam is preferably around 1 μm. A YAG laser is exemplified as this wavelength laser. Of course, other lasers may be used. For example, carbon dioxide laser, excimer laser, neon helium laser, white laser, dye laser and the like are exemplified. In addition, a light collected by an argon lamp or a xenon lamp may be used. That is, any optical energy can be used as long as the wiring can be processed.
[1131]
The laser light 3831 is transmitted through the glass substrate 71 and irradiated to the short-circuit portion 3781 and the like. Laser light 3831 is incident from a slit 3821 formed in the base anode line 2631. Although the slit 3821 is formed, the present invention is not limited to this. What is important is that the cutting portion such as the short-circuit portion 3781 is configured so as to be processed by the laser beam 3831 or the like.
[1132]
FIG. 380 shows an embodiment in which a protective diode 3751 connected to the internal wiring 3752 is formed. A difference from (a) of FIG. 375 is that a short-circuit portion (that is, a cut portion) 3781b is formed so that the protection diode 3751 can be separated from the internal wiring 3751a. Further, a short-circuit portion 3781a is formed or arranged so that both the Vss voltage source and the Vdd voltage source can be disconnected. In FIG. 381, the cut portions are marked with x. Note that the cutting of the short-circuit portion 3781 has been described with reference to FIGS.
[1133]
When modularizing the organic EL display panel, there is a problem of the resistance value of the routing (arrangement) of the anode wiring 2631 and the cathode wiring as a problem. The organic EL display panel has a large current flowing through the EL element 15, although the drive voltage of the EL element 15 is relatively low. Therefore, it is necessary to thicken the anode wiring and cathode wiring for supplying current to the EL element 15. As an example, even in a 2-inch class EL display panel, in a polymer EL material, it is necessary to pass a current of 200 mA or more through the anode wiring 2631. Therefore, in order to prevent a voltage drop of the anode wiring 2631, it is necessary to reduce the resistance of the anode wiring to 1Ω or less. However, in the array substrate 71, since the wiring is formed by thin film deposition, it is difficult to reduce the resistance. Therefore, it is necessary to increase the pattern width. However, in order to transmit a current of 200 mA with almost no voltage drop, there is a problem that the wiring width becomes 2 mm or more.
[1134]
FIG. 273 shows the configuration of a conventional EL display panel. Built-in gate driver circuits 12 a and 12 b are formed (arranged) on the left and right of the display screen 50. The source driver circuit 14p is also formed by the same process as the TFT of the pixel 16 (built-in source driver circuit).
[1135]
The anode wiring 2631 is disposed on the right side of the panel. A Vdd voltage is applied to the anode wiring 2631. As an example, the width of the anode wiring 2631 is 2 mm or more. The anode wiring 2631 is branched from the lower end of the screen to the upper end of the screen. The number of branches is the number of pixel columns. For example, in the QCIF panel, 176 columns × RGB = 528 lines. On the other hand, the source signal line 18 is output from the built-in source driver 14p. The source signal line 18 is arranged (formed) from the upper end of the screen to the lower end of the screen. The power supply wiring 2731 of the built-in gate driver circuit 12 is also arranged on the left and right of the screen.
[1136]
Therefore, the frame on the right side of the display panel cannot be narrowed. At present, narrowing the frame is important for display panels used in mobile phones and the like. It is also important to make the left and right picture frames uniform. However, in the configuration of FIG. 273, it is difficult to narrow the frame.
[1137]
In order to solve this problem, in the display panel of the present invention, as shown in FIG. 274, the anode wiring 2631 is disposed (formed) at a position located on the back surface of the source driver IC 14 and on the surface of the array. The source driver circuit (IC) 14 is formed (manufactured) by a semiconductor chip and mounted on the substrate 71 by a COG (chip on glass) technique. The reason why the anode wiring 2631 can be arranged (formed) in the source driver IC 14 is that there is a space of 10 μm to 30 μm in the direction perpendicular to the substrate on the back surface of the chip 14.
[1138]
As shown in FIG. 273, when the source driver circuit 14p is formed directly on the array substrate 71, anode wiring (base anode line, anode) is formed below or above the source driver circuit 14p due to the problem of the number of masks, the problem of yield, and the problem of noise. It is difficult to form the voltage line (basic anode line) 2631.
[1139]
Further, as illustrated in FIG. 274, a common anode line 2642 is formed, and the base anode line 2631 and the common anode line 2642 are short-circuited by the connection anode line 2641. In particular, the point is that the connection anode line 2641 at the center of the IC chip is formed. By forming the connection anode line 2641, the potential difference between the base anode line 2631 and the common anode line 2642 is eliminated. The point is that the anode wiring 2632 branches off from the common anode line 2642. By adopting the above configuration, the anode wiring 2631 is not routed as shown in FIG. 273, and a narrow frame can be realized.
[1140]
The above items will be described in more detail with reference to other drawings. FIG. 263 is an explanatory diagram of part of the display panel of the present invention. In FIG. 263, a dotted line is a position where the source driver IC 14 is arranged. That is, the base anode line (anode voltage line, that is, the anode wiring before branching) is formed (arranged) on the back surface of the source driver IC 14 and on the array substrate 71. In the embodiment of the present invention, it is described that the anode wiring 2631 before branching is formed on the back surface of the IC chip (12, 14), but this is for ease of explanation. For example, a cathode wiring or cathode film before branching may be formed (arranged) instead of the anode wiring 2631 before branching. In addition, the power supply wiring 1051 of the gate driver circuit 12 may be arranged or formed.
[1141]
The source driver IC 14 is connected to a current output (current input) terminal and a connection terminal 2633 formed in the array 71 by COG technology. The connection terminal 2633 is formed at one end of the source signal line 18. The connection terminals 2633 are arranged in a staggered manner as 2633a and 2633b. Note that a connection terminal 2633 is formed at one end of the source signal line, and a check terminal electrode is also formed at the other end.
[1142]
In the present invention, the IC chip is a current-driven driver IC (a method for programming a pixel with a current), but the present invention is not limited to this. For example, the present invention can also be applied to an EL display panel (device) on which a voltage-driven driver IC for driving pixels of a voltage program shown in FIG. 43 is mounted.
[1143]
An anode wiring 2632 (branched anode wiring) is disposed between the connection terminals 2633a and 2633b. In other words, the anode wiring 2632 branched from the thick, low-resistance base anode line 2631 is formed between the connection terminals 2633 and arranged along the 16 columns of pixels. Therefore, the anode wiring 2632 and the source signal line 18 are formed (arranged) in parallel. With the configuration (formation) as described above, the Vdd voltage can be supplied to each pixel without drawing the base anode line 2631 to the side of the screen as shown in FIG.
[1144]
FIG. 264 further illustrates in detail. The difference from FIG. 263 is that the anode wiring is not arranged between the connection terminals 2633 but is branched from a separately formed common anode line 2642. The common anode line 2642 and the base anode line 2631 are connected by a connection anode line 2641.
[1145]
FIG. 264 shows the state of the back surface as seen through the source driver IC 14. The source driver IC 14 is provided with a current output circuit 654 that outputs a program current Iw to an output terminal 681. Basically, the output terminal 681 and the current output circuit 654 are regularly arranged. At the center of the source driver IC 14, a circuit for producing a basic current of the parent current source and a control circuit are formed. Therefore, the output terminal 681 is not formed at the center of the IC chip (because the current output circuit 654 cannot be formed at the center of the IC chip).
[1146]
In the present invention, the output terminal 681 is not formed on the IC chip in the central portion 654a of FIG. This is because there is no output circuit. In many cases, a control circuit or the like is formed at the center of an IC chip such as a source driver, and an output circuit is not formed. The IC chip of the present invention pays attention to this point, and the output terminal 681 is not formed (arranged) in the central portion of the IC chip. Even when a control circuit or the like is formed at the center of an IC chip such as a source driver and an output circuit is not formed, a dummy pad is formed at the center to form an output terminal 681 (pad). It is common that A common anode line 2641 is formed at this position (however, the common anode line 2641 is formed on the surface of the array substrate 71). The width of the connecting anode line 2641 is 50 μm or more and 1000 μm or less. The resistance (maximum resistance) value with respect to the length is set to 100Ω or less.
[1147]
By short-circuiting the base anode line 2631 and the common anode line 2642 with the connection anode line 2641, a voltage drop caused by a current flowing through the common anode line 2642 is suppressed as much as possible. That is, the connection anode line 2641 which is a constituent element of the present invention effectively uses the point that there is no output circuit in the central part of the IC chip. Conventionally, by removing the output terminal 681 formed as a dummy pad at the center of the IC chip, the IC chip is electrically affected by the contact between the dummy pad and the connection anode line 2641. To prevent that. However, if this dummy pad is electrically insulated from the base substrate (chip ground) of the IC chip and other components, there is no problem even if the dummy pad contacts the connection anode line 2641. Therefore, it goes without saying that the dummy pad may be formed at the center of the source driver IC 14.
[1148]
More specifically, the connection anode line 2641 and the common anode line 2642 are formed (arranged) as shown in FIG. First, the connection anode line 2641 has a thick part (2641a) and a thin part (2641b). The thick part (2641a) is for reducing the resistance value. The thin portion (2641b) is for forming a connection anode line 2641b between the output terminals 963 and connecting to the common anode line 2642.
[1149]
In addition, the connection between the base anode line 2631 and the common anode line 2642 is short-circuited not only in the central connection anode line 2641b but also in the left and right connection anode lines 2641c. Therefore, the common anode line 2642 and the base anode line 2631 are short-circuited by the three connection anode lines 2641. Therefore, even if a large current flows through the common anode line 2642, a voltage drop is unlikely to occur in the common anode line 2642. This is because the source driver IC 14 normally has a width of 2 mm or more, and the line width of the base anode line 2631 formed under the source driver IC 14 can be increased (impedance can be reduced). For this reason, since the low-impedance base anode line 2631 and the common anode line 2642 are short-circuited by the connection anode line 2641 at a plurality of locations, the voltage drop of the common anode line 2642 becomes small.
[1150]
As described above, the voltage drop in the common anode line 2642 can be reduced because the base anode line 2631 can be disposed (formed) under the source driver IC 14 and the left and right positions of the source driver IC 14 are used. The connection anode line 2641b can be disposed (formed) at the center of the source driver IC 14.
[1151]
In FIG. 267, a base anode line 2631 and a cathode power supply line (base cathode line) 2671 are stacked with an insulating film 2661 interposed therebetween. The laminated portion forms a capacitor (this configuration is referred to as an anode capacitor configuration). This capacitor functions as a power supply pass capacitor. Therefore, a rapid current change in the base anode line 2631 can be absorbed. Further, by applying the above configuration, it can be used as a power supply pass capacitor such as the source driver IC 14.
[1152]
The capacitance of the capacitor preferably satisfies a relationship of M / 200 ≦ C ≦ M / 10 or less, where the display area of the EL display device is S square millimeters and the capacitance of the capacitor is C (pF). Furthermore, it is preferable to satisfy the relationship of M / 100 ≦ C ≦ M / 20 or less. If C is small, it is difficult to absorb a change in current.
[1153]
In the embodiment such as FIG. 267, the base anode line 2631 is arranged (formed) under the source driver IC 14, but it goes without saying that the anode line may be a cathode line. In FIG. 267, the base cathode line 2671 and the base anode line 2631 may be interchanged. The technical idea of the present invention is that a driver is formed of a semiconductor chip, the semiconductor chip is mounted on an array substrate 71 or a flexible substrate, and a power source such as an EL element 15 or a ground potential (current) is supplied to the lower surface of the semiconductor chip. The point is to arrange (form) wiring and the like.
[1154]
Therefore, the semiconductor chip is not limited to the source driver 14 but may be the gate driver circuit 12 or the power supply IC 82. Also included is a configuration in which a semiconductor chip is mounted on a flexible substrate, and a power source or a ground pattern such as an EL element 15 is wired (formed) on the surface of the flexible substrate and the lower surface of the semiconductor chip. Of course, both the source driver IC 14 and the gate driver IC 12 may be configured by semiconductor chips, and COG mounting may occur on the substrate 71. A power supply or ground pattern may be formed on the lower surface of the chip. Further, although the power source or the grant pattern to the EL element 15 is used, the present invention is not limited to this, and a power source wiring to the source driver 14 and a power source wiring to the gate driver circuit 12 may be used. Further, the present invention is not limited to an EL display device, and can be applied to a liquid crystal display device. In addition, the present invention can be applied to display panels such as FED and PDP. The above matters are the same in other embodiments of the present invention.
[1155]
FIG. 265 shows another embodiment of the present invention. 263, FIG. 264, and FIG. 267 are different from FIG. 263 in that the anode wiring 2632 is arranged between the output terminals 2633, whereas in FIG. The connection anode line 2641d is branched and the common anode line 2642 is short-circuited. Further, the thin connection anode line 2641d and the source signal line 18 connected to the connection terminal 2633 are stacked with an insulating film 2661 interposed therebetween.
[1156]
The anode line 2641d is connected to the base anode line 2631 through a contact hole 2651a, and the anode wiring 2632 is connected to the common anode line 2642 through a contact hole 2651b. Other points (connection anode lines 2641a, 2641b, 2641c, anode capacitor configuration, and the like) are the same as those in FIGS.
[1157]
A cross-sectional view taken along line aa ′ of FIG. 267 is illustrated in FIG. 266. In FIG. 266 (a), the source signal line 18 having substantially the same width is laminated with the connecting anode line 2641d through the insulating film 2661a.
The thickness of the insulating film 2661a is set to be 500 Å or more and 3000 Å (3) or less. More preferably, it is 800 angstroms or more and 2000 angstroms (Å) or less. If the film thickness is small, the parasitic capacitance between the connection anode line 2641d and the source signal line 18 becomes large, and a short circuit between the connection anode line 2641d and the source signal line 18 is likely to occur, which is not preferable. If it is thick, it takes a long time to form the insulating film, resulting in a longer manufacturing time and higher cost. In addition, it is difficult to form the upper wiring.
The insulating film 2661 is exemplified by the same material as an organic material such as polybiphenyl alcohol (PVA) resin, epoxy resin, polypropylene resin, phenol resin, acrylic resin, and polyimide resin. In addition, other materials such as SiO 2 and SiNx are used. Inorganic materials are exemplified. Needless to say, Al2O3, Ta2O3, or the like may be used. Further, as shown in FIG. 266 (a), an insulating film 2661b is formed on the outermost surface to prevent corrosion and mechanical damage of the wiring 2641 and the like.
[1158]
In FIG. 266 (b), a connection anode line 2641d having a line width narrower than that of the source signal line 18 is stacked on the source signal line 18 with an insulating film 2661a interposed therebetween. With the configuration described above, it is possible to suppress a short circuit between the source signal line 18 and the connection anode line 2641d due to a step of the source signal line 18. In the configuration of FIG. 266 (b), it is preferable that the line width of the connection anode line 2641d is narrower by 0.5 μm or more than the line width of the source signal line 18. Furthermore, it is preferable that the line width of the connection anode line 2641d is narrower by 0.8 μm or more than the line width of the source signal line 18.
[1159]
In FIG. 266 (b), the connection anode line 2641d having a line width narrower than that of the source signal line 18 is stacked on the source signal line 18 via the insulating film 2661a. As shown, the source signal line 18 having a line width narrower than that of the connection anode signal line 2641d may be stacked on the connection anode line 2641d with an insulating film 2661a interposed therebetween. Since other matters are the same as those of the other embodiments, description thereof is omitted.
[1160]
FIG. 268 is a cross-sectional view of the source driver IC 14 part. The configuration shown in FIG. 267 is basically used as a reference, but the same applies to FIGS. 264 and 265. Or it can be applied similarly.
[1161]
FIG. 268 (b) is a sectional view taken along the line AA 'in FIG. As is clear from FIG. 268 (b), the output pad 681 is not formed (arranged) in the central portion of the IC chip 14. This output pad is connected to the source signal line 18 of the display panel. The output pad 681 has bumps (projections) formed by a plating technique or a nail head bonder technique. The height of the protrusion is set to be 10 μm or more and 40 μm or less. Of course, it goes without saying that the protrusions may be formed by a gold plating technique (electrolysis or electroless).
[1162]
The protrusions and the source signal lines 18 are electrically connected via a conductive bonding layer (not shown). Conductive bonding layer is mainly composed of epoxy, phenolic, etc. as adhesive and mixed with flakes such as silver (Ag), gold (Au), nickel (Ni), carbon (C), tin oxide (SnO2) Or an ultraviolet curable resin. The conductive bonding layer (connection resin) 2681 is formed on the bump by a technique such as transfer. Alternatively, the protrusion and the source signal line 18 are thermocompression bonded with the ACF resin 2681. The connection between the protrusion or output pad 681 and the source signal line 18 is not limited to the above method. Further, the film carrier technology may be used without mounting the source driver IC 14 on the array substrate. Further, the source signal line 18 or the like may be connected using a polyimide film or the like. FIG. 268 (a) is a cross-sectional view of a portion where the source signal line 18 and the common anode line 2642 overlap (see FIG. 266).
[1163]
An anode wiring 2632 branches from the common anode line 2642. In the case of the QCIF + panel, the anode wiring 2632 is 176 × RGB = 528. The Vdd voltage (anode voltage) illustrated in FIG. 1 and the like is supplied through the anode wiring 2632. When the EL element 15 is made of a low molecular material, a current of about 200 μA at the maximum flows through one anode wiring 2632. Therefore, a current of about 100 mA flows at 200 μA × 528 through the common anode wiring 2642.
[1164]
Therefore, in order to make the voltage drop in the common anode wiring 2642 within 0.2 (V), the resistance value of the maximum path through which the current flows needs to be 2Ω (assuming 100 mA flows) or less. In the present invention, as shown in FIG. 267, the connection anode lines 2641 are formed at three locations. Therefore, if the connection anode lines 2641 are replaced, the resistance value of the common anode lines 2642 can be easily designed to be extremely small. If a large number of connection anode lines 2641d are formed as shown in FIG. 265, the voltage drop in the common anode line 2642 is almost eliminated.
[1165]
The problem is the influence of parasitic capacitance (referred to as common anode parasitic capacitance) at the overlapping portion of the common anode line 2642 and the source signal line 18. Basically, in the current driving method, it is difficult to write the black display current if the source signal line 18 for writing current has a parasitic capacitance. Therefore, it is necessary to make the parasitic capacitance as small as possible.
[1166]
The common anode parasitic capacitance needs to be 1/10 or less of the parasitic capacitance (referred to as display parasitic capacitance) generated in at least one source signal line 18 in the display region. For example, if the display parasitic capacitance is 10 (pF), it must be 1 (pF) or less. More preferably, it should be 1/20 or less (referred to as display parasitic capacitance). If the display parasitic capacitance is 10 (pF), it must be 0.5 (pF) or less. Considering this point, the line width of the common anode line 2642 (M in FIG. 271) and the film thickness of the insulating film 2661 (see FIG. 269) are determined.
[1167]
The base anode line 2631 is formed (arranged) under the source driver IC 14. It goes without saying that the line width to be formed should be as thick as possible from the viewpoint of reducing resistance. In addition, the base anode wiring 2631 preferably has a light shielding function. This explanatory diagram is shown in FIG. Needless to say, if the base anode wiring 2631 is formed of a metal material with a predetermined film thickness, there is a light shielding effect. Further, when the base anode line 2631 cannot be thickened or is formed of a transparent material such as ITO, a light absorption film or a light reflection film is laminated under the source driver IC 14 on the base anode line 2631 or in multiple layers ( Basically, it is formed on the surface of the array 71. Further, the light shielding film (base anode line 2631) in FIG. 270 does not need to be a complete light shielding film. There may be an opening in the part. Moreover, what exhibits a diffraction effect and a scattering effect may be used. Further, a light shielding film made of an optical interference multilayer film may be formed or disposed by being laminated on the base anode line 2631.
[1168]
Of course, it goes without saying that a reflecting plate (sheet) made of metal foil, a plate or a sheet, and a light absorbing plate (sheet) may be arranged, inserted or formed in the space between the array substrate 71 and the source driver IC 14. Needless to say, the present invention is not limited to metal foil, and a reflecting plate (sheet) made of an organic material or an inorganic material, a plate or sheet, and a light absorbing plate (sheet) may be arranged, inserted, or formed.
[1169]
Further, a light absorbing material or a light reflecting material made of gel or liquid may be injected or disposed in the space between the array substrate 71 and the source driver IC 14. Furthermore, it is preferable to cure the light absorbing material and the light reflecting material made of the gel or liquid by heating or light irradiation. Here, for ease of explanation, it is assumed that the base anode line 2631 is a light shielding film (reflection film).
[1170]
As shown in FIG. 270, the base anode line 2631 is not limited to the surface of the array substrate 71 (note that it is not limited to the surface. In order to satisfy the idea of a light shielding film / reflective film, light is applied to the back surface of the source driver IC 14. Accordingly, it is needless to say that the base anode line 2631 or the like may be formed on the inner surface or the inner layer of the substrate 71. Further, the base anode line 2631 (reflection film, light) may be formed on the back surface of the substrate 71. The back surface of the array substrate 71 may be used as long as light can be prevented or suppressed from entering the source driver IC 14 by forming a structure or structure that functions as an absorption film.
[1171]
In FIG. 270 and the like, the light shielding film and the like are formed on the array substrate 71. However, the present invention is not limited to this, and the light shielding film and the like may be directly formed on the back surface of the source driver IC 14. In this case, an insulating film 2661 (not shown) is formed on the back surface of the source driver IC 14, and a light shielding film or a reflective film is formed on the insulating film. In the case of a configuration in which the source driver circuit 14 is formed directly on the array substrate 71 (a driver configuration using a low-temperature polysilicon technology, a high-temperature polysilicon technology, a solid phase growth technology, or an amorphous silicon technology), A reflective film may be formed on the substrate 71, and the source driver circuit 14 may be formed (arranged) thereon.
[1172]
In the source driver IC 14, many transistor elements such as a current source 484 through which a minute current flows are formed (circuit formation portion 2701 in FIG. 270). When light is incident on a transistor element through which a minute current flows, a photoconductor phenomenon occurs, and the output current (program current Iw), the parent current amount, the child current amount, and the like become abnormal values (such as variations). In particular, in a self-luminous element such as an organic EL, light generated from the EL element 15 within the substrate 71 is diffusely reflected, and therefore, strong light is emitted from locations other than the display screen 50. When this emitted light is incident on the circuit forming portion 1021 of the source driver IC 14, a photoconductor phenomenon occurs. Therefore, the countermeasure against the photoconductor phenomenon is a countermeasure specific to the EL display device.
[1173]
In order to deal with this problem, in the present invention, the base anode line 2631 is formed on the substrate 71 to shield it from light. The formation region of the base anode line 2631 covers the circuit forming portion 2701 as shown in FIG. As described above, the photoconductor phenomenon can be completely prevented by forming the light shielding film (base anode line 2631). In particular, in the EL power supply line such as the base anode wiring 2631, a current flows and a certain potential changes as the screen is rewritten. However, since the amount of potential change changes little by little at 1H timing, it can be regarded as a ground potential (meaning that the potential does not change). Therefore, the base anode line 2631 or the base cathode line exhibits not only a light shielding function but also a shielding effect.
[1174]
In a self-luminous element such as an organic EL, light generated from the EL element 15 in the substrate 71 is diffusely reflected, and therefore, strong light is emitted from locations other than the display screen 50. In order to prevent or suppress this irregularly reflected light, as shown in FIG. 269, a light absorbing film 2691 is formed in a place (ineffective area) where light effective for image display does not pass (in contrast, the effective area is a display screen. 50 in the vicinity thereof). The portions where the light absorption film is formed are the outer surface of the sealing lid 85 (light absorption film 2691a), the inner surface of the sealing lid 85 (light absorption film 2691c), the side surface of the substrate 71 (light absorption film 2691d), and the image display of the substrate. Other than the region (light absorption film 2691b) or the like. Note that the light absorption film 2691 is not limited, and a light absorption sheet may be attached or a light absorption wall may be used. The concept of light absorption includes a system or structure that diverges light by scattering light, and a system or structure that confines light by reflection in a broad sense.
[1175]
As a substance constituting the light absorption film 2691, an organic material such as an acrylic resin containing carbon, a black pigment or pigment dispersed in an organic resin, or gelatin or casein black as in a color filter is used. What was dye | stained with acid dye of this is illustrated. In addition, a single black fluoran dye may be used, and a color scheme black obtained by mixing a green dye and a red dye may also be used. Examples thereof include a PrMnO3 film formed by sputtering and a phthalocyanine film formed by plasma polymerization.
[1176]
The above materials are all black materials, but as the light absorption film 2691, a material having a complementary color with respect to the light color generated by the display element may be used. For example, a light-absorbing material for a color filter may be used so as to obtain desired light absorption characteristics. Basically, a material obtained by dyeing a natural resin with a pigment may be used in the same manner as the black absorbing material described above. Further, a material in which a pigment is dispersed in a synthetic resin can be used. The selection range of the pigment is wider than the black pigment, and may be one suitable from azo dye, anthraquinone dye, phthalocyanine dye, triphenylmethane dye, or a combination of two or more thereof.
[1177]
Further, a metal material may be used as the light absorption film. For example, hexavalent chromium is exemplified. Hexavalent chromium is black and functions as a light absorbing film. In addition, light scattering materials such as opal glass and titanium oxide may be used. This is because scattering the light is equivalent to absorbing the light as a result.
[1178]
In addition, the sealing lid 85 adheres the substrate 71 and the sealing lid 85 using a sealing resin 2693 containing resin beads 2692 having a size of 4 μm or more and 15 μm or less. The sealing lid 85 and the substrate 71 are attached with a sealing resin 2693 containing resin beads 2692. The lid 85 is arranged and fixed without applying pressure.
[1179]
In the embodiment of FIG. 267, the common anode line 2642 is illustrated as being formed (arranged) in the vicinity of the source driver IC 14, but the embodiment is not limited thereto. For example, it may be formed in the vicinity of the display screen 50 as shown in FIG. Moreover, it is preferable to form. This is because the portion where the source signal line 18 and the anode wiring 2632 are arranged in a short distance and in parallel (formed) is reduced. This is because parasitic capacitance is generated between the source signal line 18 and the anode wiring 2632 when the source signal line 18 and the anode wiring 2632 are arranged in a short distance and in parallel. If the common anode line 2642 is arranged in the vicinity of the display screen 50 as shown in FIG. 271, the problem is eliminated. The distance K (see FIG. 271) from the screen display screen 50 to the common anode line 2642 is preferably 1 mm or less.
[1180]
The common anode line 2642 is preferably formed of a metal material for forming the source signal line 18 in order to reduce the resistance as much as possible. In the present invention, a Cu thin film, an Al thin film, a laminated structure of Ti / Al / Ti, or a metal material (SD metal) made of an alloy or aman gum is used. Therefore, a portion where the source signal line 18 and the common anode line 2642 intersect is replaced with a metal material (GE metal) constituting the gate signal line 17 in order to prevent a short circuit. The gate signal line is formed of a metal material having a Mo / W laminated structure.
[1181]
In general, the sheet resistance of the gate signal line 17 is higher than the sheet resistance of the source signal line 18. This is common in liquid crystal display devices. However, in the organic EL display panel and the current driving method, the current flowing through the source signal line 18 is as small as 1 to 5 μA. Therefore, even if the wiring resistance of the source signal line 18 is high, a voltage drop hardly occurs and a good image display can be realized. In the liquid crystal display device, image data is written to the source signal line 18 with a voltage. Therefore, if the resistance value of the source signal line 18 is high, an image cannot be written in one horizontal scanning period.
[1182]
However, in the current driving method of the present invention, even if the resistance value of the source signal line 18 is high (that is, the sheet resistance value is high), there is no problem. Therefore, the sheet resistance of the source signal line 18 may be higher than the sheet resistance of the gate signal line 17. Therefore, in the EL display panel of the present invention (conceptually in a current-driven display panel or display device), as shown in FIG. 272, the source signal line 18 is formed (formed) with GE metal, and the gate The signal line 17 may be made (formed) with SD metal. This is a configuration opposite to that of the liquid crystal display panel.
[1183]
FIG. 275 shows a configuration in which a power supply wiring 2731 for driving the gate driver circuit 12 is arranged in addition to the configurations of FIGS. 267 and 271. The power supply wiring 2731 is routed from the right end of the display screen 50 of the panel to the bottom side to the left end of the display screen 50. That is, the power sources of the gate driver circuits 12a and 12b are the same.
[1184]
However, the gate driver circuit 12a for selecting the gate signal line 17a (the gate signal line 17a controls the TFT 11b and the TFT 11c) and the gate driver circuit 12b for selecting the gate signal line 17b (the gate signal line 17b controls the TFT 11d) The control of the current flowing through the EL element 15 is preferably different from the power supply voltage. In particular, the amplitude (on voltage-off voltage) of the gate signal line 17a is preferably small. This is because the penetration voltage to the capacitor 19 of the pixel 16 decreases as the amplitude of the gate signal line 17a decreases (see FIG. 1 and the like). On the other hand, since the gate signal line 17b needs to control the EL element 15, the amplitude cannot be reduced.
[1185]
Therefore, as shown in FIG. 276, the voltage applied to the gate driver circuit 12a is Vha (the off voltage of the gate signal line 17a) and Vla (the on voltage of the gate signal line 17a).
The applied voltages of the gate driver circuit 12a are Vhb (the off voltage of the gate signal line 17b) and Vla (the on voltage of the gate signal line 17b). Let Vla <Vlb. Note that Vha and Vhb may be substantially matched.
[1186]
The gate driver circuit 12 is normally composed of an N channel transistor and a P channel transistor. However, it is preferable to form the P channel transistor alone. This is because the number of masks required for manufacturing the array is reduced, and the manufacturing yield and throughput can be improved. Therefore, as illustrated in FIGS. 1 and 2 and the like, the transistor constituting the pixel 16 is a P-channel transistor, and the gate driver circuit 12 is also formed or constituted by a P-channel transistor. If the gate driver circuit is composed of an N-channel transistor and a P-channel transistor, the required number of masks is 10. However, if only a P-channel transistor is formed, the required number of masks is 5.
[1187]
However, if the gate driver circuit 12 or the like is composed of only P-channel transistors, a level shifter circuit cannot be formed on the array substrate 71. This is because the level shifter circuit is composed of an N channel transistor and a P channel transistor.
[1188]
In response to this problem, the present invention incorporates a level shifter circuit function in the power supply IC 82. FIG. 277 shows an example. The power supply IC 82 generates a drive voltage for the gate driver circuit 12, an anode / cathode voltage for the EL element 15, and a drive voltage for the source driver circuit 14.
[1189]
Since the power supply IC 82 generates the anode and cathode voltages of the EL elements 15 of the gate driver circuit 12, it is necessary to use a semiconductor process having a high breakdown voltage. With this withstand voltage, the level can be shifted to the signal voltage driven by the gate driver circuit 12.
[1190]
Therefore, the level shift and the drive of the gate driver circuit 12 are performed with the configuration of FIG. Input data (image data, command, control data) 2672 is input to the source driver IC 14. The input data includes control data for the gate driver circuit 12. The source driver IC 14 has a withstand voltage (operating voltage) of 5 (V). On the other hand, the gate driver circuit 12 has an operating voltage of 15 (V). The signal output from the source driver circuit 14 to the gate driver circuit 12 needs to be level-shifted from 5 (V) to 15 (V). This level shift is performed by a power supply circuit (IC) 82. In FIG. 277, a data signal for controlling the gate driver circuit 12 is also a power supply IC control signal 2772.
[1191]
The power supply circuit 82 shifts the level of the input data signal 2772 for controlling the gate driver circuit 12 by a built-in level shifter circuit and outputs it as a gate driver circuit control signal 2773 to control the gate driver circuit 12.
[1192]
Hereinafter, the gate driver circuit 12 of the present invention in which the gate driver circuit 12 built in the substrate 71 is composed of only P-channel transistors will be described. As described above, the pixel 16 and the gate driver circuit 12 are formed by only P-channel transistors (that is, all transistors formed on the substrate 71 are P-channel transistors. Conversely, N-channel transistors are formed. This is because the number of masks required for manufacturing the array is reduced, and the manufacturing yield and throughput are expected to be improved. Moreover, since it is possible to work on improving only the performance of the P-channel transistor, it is easy to improve characteristics as a result. For example, the Vt voltage can be reduced (for example, closer to 0 (V)) and the Vt variation can be reduced more easily than the CMOS structure (configuration using P-channel and N-channel transistors).
[1193]
As an example, as illustrated in FIG. 274, in the present invention, the gate driver circuit 12 is arranged, formed, or configured by one phase (shift register) on the left and right of the display screen 50. The gate driver circuit 12 and the like (including the transistor of the pixel 16) are described as being formed or configured by a low-temperature polysilicon technology having a process temperature of 450 degrees (Celsius) or lower, but are not limited thereto. A high-temperature polysilicon technique having a process temperature of 450 degrees Celsius or higher may be used, or a TFT formed with a semiconductor film grown by solid phase (CGS) may be used. In addition, you may form with organic TFT. Further, it may be a TFT formed or constituted by amorphous silicon technology.
[1194]
One is a gate driver circuit 12a on the selection side. An on / off voltage is applied to the gate signal line 17 a to control the pixel TFT 11. The other gate driver circuit 12b controls (turns on and off) the current flowing through the EL element 15.
[1195]
In the embodiment of the present invention, the pixel configuration of FIG. 1 will be mainly described as an example, but the present invention is not limited to this. Needless to say, the present invention can also be applied to other pixel configurations such as FIGS. 2, 42, 43, 115, 116, and 117. Further, the configuration of the gate driver circuit 12 of the present invention or the driving method thereof exhibits a more characteristic effect in combination with the display panel, display device or information display device of the present invention. However, it goes without saying that a characteristic effect can be exhibited in other configurations.
[1196]
  In the embodiment of the present invention, the pixel configuration in FIG. 1 will be mainly illustrated and described, but the present invention is not limited to this, and it goes without saying that other pixel configurations may be used. Further, the configuration or arrangement of the gate driver circuit 12 described below is not limited to a self-luminous device such as an organic EL display panel. LCD panel, electromagneticGuidanceIt can also be employed in a display panel or FED (field emission display). For example, in the liquid crystal display panel, the configuration or system of the gate driver circuit 12 of the present invention may be adopted as control of the pixel selection switching element. Further, when the gate driver circuit 12 is used in two phases, one phase may be used for selecting a switching element of the pixel, and the other may be connected to one terminal of the storage capacitor in the pixel. This method is called independent CC drive. Needless to say, the configuration described with reference to FIGS. 71 and 73 can be applied not only to the gate driver circuit 12 but also to the shift register circuit of the source driver circuit 14.
[1197]
FIG. 71 is a block diagram of the gate driver circuit 12 of the present invention. For ease of explanation, only four stages are shown, but basically, unit gate output circuits 711 corresponding to the number of gate signal lines 17 are formed or arranged.
[1198]
As shown in FIG. 71, in the gate driver circuit 12 (12a, 12b) of the present invention, four clock terminals (SCK0, SCK1, SCK2, SCK3), one start terminal (data signal (SSTA)), shift It is composed of signal terminals of two inverting terminals (DIRA and DIRB, which apply signals of opposite phases) that control the direction upside down. In addition, the power supply terminal includes an L power supply terminal (VBB) and an H power supply terminal (Vd).
[1199]
By configuring the pixel 16 with a P-channel transistor, matching with the gate driver circuit 12 formed with the P-channel transistor is improved. P-channel transistors (transistors 11b, 11c, and transistor 11d in the pixel configuration of FIG. 1) are turned on with an L voltage. On the other hand, the L voltage is also the selection voltage in the gate driver circuit 12. As can be seen from the configuration of FIG. 73, the P-channel gate driver has good matching when the L level is selected. This is because the L level cannot be maintained for a long time. On the other hand, the H voltage can be held for a long time.
[1200]
  By configuring the driving transistor (transistor 11a in FIG. 1) for supplying current to the EL element 15 with a P channel, the cathode of the EL element 15 can be configured as a solid electrode of a metal thin film. In addition, a current can flow through the EL element 15 in the forward direction from the anode potential Vdd. From the above, it is preferable that the transistor of the pixel 16 is a P channel and the transistor of the gate driver circuit 12 is also a P channel. From the above, the transistors constituting the pixel 16 of the present invention (driving transistors,TheThe matter that the transistor for switching) is formed by the P channel and the transistor of the gate driver circuit 12 is formed by the P channel is not a mere design matter.
[1201]
A level shifter (LS) circuit may be formed directly on the substrate 71. That is, a level shifter (LS) circuit is formed by N-channel and P-channel transistors. A logic signal from a controller (not shown) is boosted by a level shifter circuit formed directly on the substrate 71 so as to conform to the logic level of the gate driver circuit 12 formed of a P-channel transistor. The boosted logic voltage is applied to the gate driver circuit 12.
[1202]
Note that the level shifter circuit may be formed of a semiconductor chip and mounted on the substrate 71 by COG. The source driver circuit 14 is formed of a semiconductor chip and is mounted on the substrate 71 by COG. However, the source driver circuit 14 is not limited to being formed of a semiconductor chip, and may be formed directly on the substrate 71 using polysilicon technology.
[1203]
  When the transistor 11 constituting the pixel 16 is configured by a P channel, the program current flows in the direction from the pixel 16 to the source signal line 18. Therefore, the source driver circuitUnit transistor (Unit currentsource)484 (see FIG. 56, FIG. 57, etc.) needs to be composed of N-channel transistors. In other words, the source driver circuit 14 needs to be configured to draw the program current Iw.
[1204]
Therefore, when the driving transistor 11a of the pixel 16 (in the case of FIG. 1) is a P-channel transistor, the unit transistor 484 is configured with an N-channel transistor so that the source driver circuit 14 always draws the program current Iw. In order to form the source driver circuit 14 on the array substrate 71, it is necessary to use both an N channel mask (process) and a P channel mask (process). Describing conceptually, the display panel (display device) of the present invention comprises the pixel 16 and the gate driver circuit 12 by P-channel transistors, and the source current source transistor of the source driver by N-channel.
[1205]
Therefore, the transistor 11 of the pixel 16 is formed by a P-channel transistor, and the gate driver circuit 12 is formed by a P-channel transistor. Thus, by forming both the transistor 11 and the gate driver circuit 12 of the pixel 16 with P-channel transistors, the cost of the substrate 71 can be reduced. However, the source driver 14 needs to form the unit transistor 484 as an N-channel transistor. Therefore, the source driver circuit 14 cannot be formed directly on the substrate 71. Therefore, the source driver circuit 14 is manufactured separately using a silicon chip or the like and mounted on the substrate 71. Although the source driver circuit 14 is formed of a silicon chip, the present invention is not limited to this. For example, a large number of glass substrates may be simultaneously formed by low-temperature polysilicon technology, cut into chips, and loaded on the substrate 71. Although the description has been made assuming that the source driver circuit is loaded on the substrate 71, the present invention is not limited to loading. Any form may be used as long as the output terminal 681 of the source driver circuit 14 is connected to the source signal line 18 of the substrate 71. For example, a method of connecting the source driver circuit 14 to the source signal line 18 by TAB technology is exemplified. By separately forming the source driver circuit 14 on a silicon chip or the like, variation in output current can be reduced and a good image display can be realized. Moreover, cost reduction is possible.
[1206]
Further, the configuration in which the selection transistor of the pixel 16 is configured by a P channel and the gate driver circuit is configured by a P channel transistor is not limited to a self-luminous device (display panel or display device) such as an organic EL. For example, the present invention can be applied to a liquid crystal display device and FED (field emission display).
[1207]
A common signal is applied to each unit gate output circuit 711 at the inverting terminals (DIRA, DIRB). Incidentally, as can be understood from the equivalent circuit diagram of FIG. 73, voltage values having opposite polarities are input to the inverting terminals (DIRA and DIRB). When the scanning direction of the shift register is reversed, the polarity of the voltage applied to the inverting terminals (DIRA, DIRB) is reversed.
[1208]
In the circuit configuration of FIG. 71, the number of clock signal lines is four. Four is the optimum number in the present invention, but the present invention is not limited to this. Four or less may be sufficient.
[1209]
Inputs of clock signals (SCK 0, SCK 1, SCK 2, SCK 3) are different in adjacent unit gate output circuits 711. For example, in the unit gate output circuit 711a, the clock terminal SCK0 is input to OC and SCK2 is input to RST. The same applies to the unit gate output circuit 711c. In a unit gate output circuit 711b (next unit gate output circuit) adjacent to the unit gate output circuit 711a, the clock terminal SCK1 is input to OC and SCK3 is input to RST. Therefore, as for the clock terminal input to the unit gate output circuit 711, SCK0 is input to OC, SCK2 is input to RST, the next stage is SCK1 of the clock terminal input to OC, SCK3 is input to RST, and The clock terminals input to the unit gate output circuit 711 are alternately changed such that SCK0 is input to OC and SCK2 is input to RST.
[1210]
FIG. 73 shows a circuit configuration of the unit gate output circuit 711. The transistors to be configured are composed of only the P channel. FIG. 74 is a timing chart for explaining the circuit configuration of FIG. 72 shows a timing chart for a plurality of stages in FIG. Therefore, the overall operation can be understood by understanding FIG. The understanding of the operation is achieved by understanding the timing chart of FIG. 74 with reference to the equivalent circuit diagram of FIG. 73 rather than the description of the text. Therefore, detailed description of the operation of each transistor is omitted.
[1211]
If a driver circuit configuration is created using only the P channel, it is basically possible to maintain the gate signal line 17 at the H level (Vd voltage in FIG. 73). However, it is difficult to maintain the L level (VBB voltage in FIG. 73) for a long time. However, it can be sufficiently maintained for a short period of time, such as when a pixel row is selected.
[1212]
When the switching transistors 11b and 11c of the pixel 16 are formed of P-channel transistors, the pixel 16 is selected by Vgh. The pixel 16 is in a non-selected state by Vgl. As described before, the voltage penetrates when the gate signal line 17a changes from on (Vgl) to off (Vgh) (penetration voltage). When the driving transistor 11a of the pixel 16 is formed of a P-channel transistor, the current does not flow through the transistor 11a due to the punch-through voltage in the black display state. Therefore, good black display can be realized. It is difficult to realize black display, which is a problem of the current driving method. However, by configuring the gate driver circuit 12 with a P-channel transistor, the ON voltage becomes Vgh. Therefore, matching with the pixel 16 formed by the P channel transistor is good. Further, as in the pixel 16 configuration of FIGS. 1, 2, 32, 113, and 116, the unit transistor 484 of the source driver circuit 14 is programmed from the anode voltage Vdd through the driving transistor 11a and the source signal line 18. It is important to configure the current Iw to flow. Therefore, it is excellent synergistic effect that the gate driver circuit 12 and the pixel 16 are composed of P channel transistors, the source driver circuit 14 is mounted on the substrate, and the unit transistors 484 of the source driver circuit 14 are composed of N channel transistors. Demonstrate.
[1213]
The same applies to FIG. 42B. In FIG. 42B, current does not flow into the unit transistor 484 of the source driver circuit 14 via the driving transistor 11b. However, the configuration is such that the program current Iw flows from the anode voltage Vdd into the unit transistor 484 of the source driver circuit 14 via the programming transistor 11 a and the source signal line 18. Therefore, as in FIG. 1, the gate driver circuit 12 and the pixel 16 are configured by P-channel transistors, the source driver circuit 14 is mounted on the substrate, and the unit transistors 484 of the source driver circuit 14 are configured by N-channel transistors. Exerts an excellent synergistic effect.
[1214]
N1 changes depending on the signal input to the IN terminal and the SCK clock input to the RST terminal, and n2 becomes an inverted signal state of n1. Although the potential of n2 and the potential of n4 have the same polarity, the potential level of n4 is further lowered by the SCK clock input to the OC terminal. Corresponding to this lowering level, the Q terminal is maintained at the L level during that period (ON voltage is output from the gate signal line 17). The signal output to the SQ or Q terminal is transferred to the unit gate output circuit 711 in the next stage.
[1215]
In the circuit configuration shown in FIGS. 71 and 73, one gate signal line 17 is selected as shown in FIG. 75A by controlling the timing of the applied signals at the IN (INA, INB) and clock terminals. The state in which the two-gate signal line 17 is selected as shown in FIG. 75B can be realized using the same circuit configuration.
[1216]
In the selection-side gate driver circuit 12a, the state shown in FIG. 75A is a driving method in which one pixel row (51a) is simultaneously selected (normal driving). The selected pixel row is shifted one row at a time. FIG. 75B shows a configuration in which two pixel rows are selected. This driving method is the simultaneous selection driving (a method of forming a dummy pixel row) of a plurality of pixel rows (51a, 51b) described with reference to FIGS. The selected pixel row is shifted by one pixel row, and two adjacent pixel rows are selected simultaneously. In particular, in the driving method of FIG. 75B, the pixel row 51b is precharged with respect to the pixel row 51a holding the final video. Therefore, the pixel 16 can be easily written. In other words, the present invention can be realized by switching between the two driving methods by a signal applied to the terminal.
[1217]
75 (b) shows a method of selecting 16 adjacent rows of pixels, but as shown in FIG. 76, 16 rows of pixels other than adjacent pixels may be selected (FIG. 76 shows three pixels). This is an embodiment in which pixel rows at positions separated from each other are selected). Further, in the configuration of FIG. 73, control is performed with a set of four pixel rows. Of the four pixel rows, it is possible to control whether one pixel row is selected or two consecutive pixel rows are selected. This is a restriction that four clocks (SCK) are used. If eight clocks (SCK) are used, control can be performed with a set of eight pixel rows.
[1218]
The operation of the gate driver circuit 12a on the selection side is the operation of FIG. As shown in FIG. 75A, one pixel row is selected, and the selected position is shifted by one pixel row in synchronization with one horizontal synchronization signal. Also, as shown in FIG. 75B, two pixel rows are selected, and the selected position is shifted by one pixel row in synchronization with one horizontal synchronization signal.
In FIG. 279 (a), one pixel row can be selected as a set of four pixel rows (one pixel row is selected in a set of four pixel rows, but no selection is made in accordance with the IN data). Determined by input state and shift state). In FIG. 279 (b), it is possible to select two pixel rows that are consecutive in groups of four pixel rows (two pixel rows are selected in a set of four pixel rows, but not selected at all. Data input state and shift state). In the present invention, a pixel row equal to the number of clocks is taken as a set, and in this set of pixel rows, one pixel row or a number less than half of the set of pixel rows (for example, a set of 4 pixel rows) 4/2 = 2 pixel rows). Therefore, a non-selected pixel row is always generated in the pixel row group.
In the method of selecting one pixel row, the program current Iw flows to one pixel 16 as illustrated in FIG. The driving method for simultaneously selecting two pixel rows is the same as the driving method described with reference to FIGS. The program current Iw is divided into two pixel rows and written to the pixels 16 as shown in FIG. However, it is not limited to this. For example, as shown in FIG. 278 (b), a program current Iw × 2 may be applied, and the same current may be supplied to the two selected pixels (16a, 16b).
[1219]
The operation of the gate driver circuit 12a on the selection side is the operation of FIG. As shown in FIG. 75A, one pixel row is selected, and the selected position is shifted by one pixel row in synchronization with one horizontal synchronization signal. Also, as shown in FIG. 75B, two pixel rows are selected, and the selected position is shifted by one pixel row in synchronization with one horizontal synchronization signal.
[1220]
FIG. 279 is an explanatory diagram for explaining the operation of the gate driver circuit 12b for controlling the gate signal line 17b for turning the EL element 15 on and off. FIG. 279 (a) shows a state in which an ON voltage is applied to the gate signal line 17b of one pixel row in a set of four pixel rows (hereinafter, such a set of pixel rows is referred to as a pixel row set). The position of the display pixel row 53 is shifted by one pixel row in synchronization with the horizontal synchronization signal (HD). Of course, an on-voltage is applied to the gate signal line 17b corresponding to one pixel row in the four-pixel row set (an off-voltage is applied to the gate signal line 17b corresponding to the other three pixel rows) or four pixels. Whether the off voltage is applied to all of the row sets (the off voltage is applied to the gate signal lines 17b corresponding to the four pixel rows) can be arbitrarily selected. Since the shift register is configured, the set selection state is shifted in synchronization with the horizontal synchronization signal.
[1221]
FIG. 279 (b) shows a state in which an ON voltage is applied to the gate signal line 17b of the two pixel rows of the four pixel row group. The position of the display pixel row 53 is shifted by one pixel row in synchronization with the horizontal synchronization signal (HD). Of course, an on voltage is applied to the gate signal line 17b corresponding to the two pixel rows in the four pixel row group (an off voltage is applied to the gate signal line 17b corresponding to the other two pixel rows), or four pixels. Whether the off voltage is applied to all of the row sets (the off voltage is applied to the gate signal lines 17b corresponding to the four pixel rows) can be arbitrarily selected. Since the shift register is configured, the set selection state is shifted in synchronization with the horizontal synchronization signal.
[1222]
FIG. 279 (a) shows a state in which an ON voltage is applied to the gate signal line 17b of one pixel row in a group of four pixel rows. FIG. 279 (b) shows a state in which an ON voltage is applied to the gate signal line 17b of the two pixel rows of the four pixel row group. However, the present invention is not limited to this configuration (system). For example, a turn-on voltage may be applied to the gate signal line 17b of one pixel row in a group of six pixel rows.
[1223]
FIG. 280 shows the state of the voltage output to the gate signal line 17b in the driving state of FIG. 279 (a). As described above, the subscript indicated by () of the signal line 17b indicates a pixel row. For ease of explanation, the pixel rows are from (1). The numbers in the upper part of the table indicate the numbers of the horizontal scanning period.
[1224]
As shown in FIG. 280, the gate signal lines 17b (1) to 17b (4) and the gate signal lines 17b (5) to 17b (8) have the same waveform. That is, the same operation is performed in the 4-pixel row group.
FIG. 281 shows the state of the voltage output to the gate signal line 17b in the driving state of FIG. 279 (b). As shown in FIG. 281, the gate signal lines 17b (1) to 17b (4) and the gate signal lines 17b (5) to 17b (8) have the same waveform. That is, the same operation is performed in the 4-pixel row group.
[1225]
In the embodiment of FIG. 279, the brightness of the display screen 50 can be adjusted by increasing or decreasing the number of pixels in the display state at an arbitrary time. In the case of the QCIF + panel, the number of vertical pixels is 220 dots. Therefore, in FIG. 279 (a), 220/4 = 55 pixel rows can be displayed. That is, in white raster display, the maximum brightness is obtained when 55 pixel rows are displayed. The brightness of the screen is the number of display pixel lines 55 → 54 → 53 → 52 → 51 → ... 5 → 4 → 3 → 2 → 1 → 0 → By changing the above, the display screen can be darkened. Conversely, 0 → 1 → 2 → 3 → 4 → 5 → → 50 → 51 → 52 → 53 → 54 → 55 , Can brighten the screen. Therefore, multi-level brightness adjustment can be realized.
[1226]
In this brightness adjustment, the screen brightness is proportional to the number of display pixels, and the change is linear. In addition, there is no change in the gamma characteristic corresponding to the brightness (the number of gradations is maintained regardless of whether the screen is bright or dark).
[1227]
In the above embodiment, the change in the number of display pixel rows for adjusting the brightness of the display screen 50 is set to be one by one. However, the present invention is not limited to this. 54-> 52-> 50-> 48-> 46-> ... 6-> 4-> 2-> 2-> 0. Further, 55, 50, 45, 40, 35,..., 15, 10, 10, 5, and 0 may be changed.
[1228]
Similarly, in FIG. 279 (b), 220/2 = 110 pixel rows can be displayed in the QCIF + panel. That is, in white raster display, the maximum brightness is when 110 pixel rows are displayed. The brightness of the screen is 110 → 108 → 106 → 104 → 102 → ... 10 → 8 → 6 → 4 → 2 → 0 By changing the above, the display screen can be darkened. Conversely, 0 → 2 → 4 → 6 → 8 → 10 → → 100 → 102 → 104 → 106 → 108 → 110 , Can brighten the screen. Therefore, multi-level brightness adjustment can be realized. Note that although the change in the number of display pixel rows for adjusting the brightness of the display screen 50 is made every two, it is not limited to this. It may be every four or four or more. In order to adjust the brightness, the display pixel rows are thinned out so as to be dispersed as much as possible instead of concentrating at a single place. This is to suppress the occurrence of flicker.
[1229]
The brightness adjustment is not a unit of the number of pixel rows (a drive in which the pixel rows are turned on or off for substantially the entire period of one horizontal scanning period), and the lighting time per horizontal scanning period is also adjusted. Can do. That is, the brightness of the display screen is adjusted by turning on a part of one horizontal scanning period (for example, 1/8 period of 1H, 15/16 period of 1H).
[1230]
This adjustment (control) is performed using the main clock (MCLK) of the display panel. For the QCIF + panel, MCLK is about 2.5 MHz. That is, 176 clocks can be counted in one horizontal scanning period (1H). Therefore, by counting MCLK and controlling the period during which the ON voltage (Vgl) is applied to the gate signal line 17b based on this count value, the EL elements 15 in each pixel row can be turned on / off.
[1231]
Specifically, in the timing charts shown in FIGS. 72 and 74, this can be realized by controlling the position of the clock (SCK) at the L level and the period of the L level. The shorter the period during which SCK is at the L level, the shorter the period during which the output Q terminal is at the L level (Vgl).
[1232]
In the driving method of FIG. 279 (a), as shown in FIG. 282, the period during which Vgl (ON voltage) is symmetrically reduced in the period of 1H is shortened. (A) in FIG. 282 is a period in which all of the 1H period is outputting Vgl (ON voltage) (however, in the configuration of the P-channel gate driver circuit 12 in FIG. 73, L level output is performed in all of the 1H period. A period of Vgh voltage (off voltage) occurs between 1H and the next 1H, and FIG.282 is shown as (a) for ease of explanation. ing.
[1233]
Similarly, FIG. 282 (b) illustrates that the period during which Vgl is output to the gate signal line 17b is shortened by two clocks (compared to (a)). . Further, FIG. 282 (c) shows that the period during which Vgl is output to the gate signal line 17b is shortened by two clocks (compared to (b)). Hereinafter, since it is the same, description is abbreviate | omitted.
In the drive method of FIG. 279 (b), as shown in FIG. 283, the period of Vgl (ON voltage) symmetrically in the 2H period is shortened. In FIG. 283, (a) is a period in which all of the 1H period outputs Vgl (ON voltage) (however, in the configuration of the P-channel gate driver circuit 12 in FIG. 73, the L level output is output in all of the 2H period. A period of Vgh voltage (off voltage) is generated between 2H and the next 2H, which is the same as FIG.
[1234]
Similarly, in FIG. 283 (b), the period during which Vgl is output to the gate signal line 17b is 2H, and MCLK is shortened by two clocks (compared to (a)). Show. Further, FIG. 283 (c) shows that the period during which Vgl is output to the gate signal line 17b is shortened by two clocks (compared to (b)). Hereinafter, since it is the same, description is abbreviate | omitted.
[1235]
If the configuration of the gate driver circuit 12 is slightly changed and the clock is adjusted, as shown in FIG. 284, the application period of the gate signal line 17b in FIG. 282 can be continuously performed for 2H periods.
[1236]
In FIG. 13, FIG. 14, etc., the driving method for solving the moving image blur has been described. This is a method in which an image is intermittently displayed, so that the outline blur of the image is eliminated and a good display state can be realized. That is, a display state close to that of a CRT is realized, and an excellent moving image display is realized.
[1237]
Even with the driving method of FIG. 279, good moving image display can be realized. However, in FIG. 13, the display area 53 is continuous and the non-display area 52 is also continuous, whereas in FIG. 279, the display area 53 is not continuous. Whether the on-voltage is applied to one pixel row in the 4-pixel row set (FIG. 279 (a)) or the on-voltage is applied to two consecutive pixel rows in the 4-pixel row set (FIG. 279 (b)). It is because it will be in a display state. Needless to say, by changing or improving the circuit configuration illustrated in FIGS. 71 and 73, the display pixel row with respect to the clock (SCK) can be changed or changed. For example, it can be displayed by skipping one pixel line. It is also possible to light up by skipping 6 pixel rows. However, in a driver circuit (shift register) configured or formed with P-channel transistors, at least display pixel rows 52 that are not lit are arranged (inserted) between the display pixel rows 53.
[1238]
FIG. 285 shows a driving method for displaying moving images when the gate driver circuit 12 is formed of P-channel as shown in FIG. As previously described, in order to prevent image display deterioration due to moving image blur, it is necessary to perform intermittent display. That is, it is necessary to insert black (display a black or low-brightness display screen). Drive (display) like a CRT display. That is, when an image is displayed in an arbitrary pixel row, black (low luminance) display is performed after display for a predetermined period. This pixel row blinks (image display and non-display (black display or low luminance display) are repeated alternately). The black display period needs to be 4 msec or more. Alternatively, black display (low luminance display) is performed for a period of 1/4 or more of one frame (one field). Preferably, black display (low luminance display) is performed for a period of ½ or more of one frame (one field). This condition depends on the afterimage characteristics of the human eye. That is, an image that blinks faster than a predetermined period appears to be continuously lit due to the afterimage characteristics of human eyes. This leads to motion blur. However, although the image blinking later than the predetermined period seems to be continuous visually, the non-lighting (black display) state inserted between them can be recognized, and the display image is displayed. It will be in a state of flying (but it doesn't feel strange visually). For this reason, images are skipped in moving image display, and image blurring does not occur. That is, there is no moving image blur.
[1239]
In FIG. 285 (a), in the region A, one pixel row is displayed (lighted state) in four pixel rows. Therefore, it is turned on once in 4 horizontal scanning periods (4H) (lights up for 1H period in 4H period). This period (a period from when the pixel row is lit, when it is not lit, and when it is next lit) is 4 msec or less. Therefore, it seems to the human eye that the image is displayed completely continuously (arbitrary pixel rows do not persist and are not much different from being lit). In the area B of FIG. 285 (a), black is inserted (low luminance display) so as to be 4 msec or more, preferably 8 msec or more after the pixel row is displayed until the next display. Therefore, the image is skipped and a good moving image display can be realized.
[1240]
In addition, although it demonstrated as the area | region A or the area | region B in the above description, the above matter is for making description easy. In FIG. 285, the area A is sequentially scanned in the arrow direction (from the top to the bottom of the screen). It is like scanning an electron beam with a CRT. That is, the image is rewritten sequentially (refer to FIG. 286 for (a) in FIG. 285. Scanning (driving) is performed in the order of (a) → (b) → (c) → (a) in FIG. 286). (B) in Fig. 285 is referred to in Fig. 287. Scanning (driving is performed as shown in Fig. 287 (a)-> (b)-> (c)-> (a)).
[1241]
As described above, in the driving method of the present invention, in any pixel row, a period of 4 msec (preferably 8 msec) or more in one field (one frame) is displayed as a period of 1H in 4H in FIG. In other periods (the remaining period of one field (one frame)), the non-lighting state (black display (black insertion) or low luminance display) is continuously maintained. Therefore, in order to facilitate the explanation, it is expressed as the A region or the B region, but it is more appropriate to express the A period or the B period from the viewpoint of time. That is, the area A (period A) is a period in which images are continuously lit, and the area B (period B) is a period in which pixel rows (screen 50) are intermittently displayed. The above matters are the same in FIG. 285 (b) or other embodiments of the present invention.
[1242]
In FIG. 285 (b), the two pixel rows are continuously lit, and then the two pixel rows are not lit. That is, in the A region (A period), the light is turned on for a period of 2H and the light is not turned on for a period of 2H. In the B region (B period), the non-lighting state is continuously maintained for a predetermined period. Also in the driving method of FIG. 285 (b), the A area is apparently a continuous display state, and the B area is apparently intermittent display.
[1243]
As described above, when the display state is observed by paying attention to an arbitrary pixel row (pixel), the driving method of the present invention has a period of less than 4 msec (or a period of less than ¼ of one frame (one field)). In the first period in which image display and non-display (black display or low luminance display below a predetermined level) are repeated at least once, and the pixel row (pixel) is not displayed (black display or low below a predetermined level) from the display state. (Brightness display) state, and the second display period (or a period of 1/4 or more of one frame (one field)) in which the period of the next display state is 4 msec or more is performed. By implementing the above driving, it is possible to realize a favorable moving image display, and the configuration of the control circuit (gate driver circuit 12 and the like) is easy, so that the cost can be reduced.
[1244]
Also in FIG. 285, the brightness of the screen 50 can be adjusted (changed) by changing the number of lighting pixel rows (similar to FIG. 279, the number of display pixels 53 may be changed or adjusted). Further, by changing the ratio of the black insertion area (B area in FIG. 285), the optimum state can be obtained according to the image display state. For example, in a still image, it should be avoided that the B area becomes long. This is because flickering occurs. In the case of a still image, the display pixel rows 53 should be distributed and displayed (arranged in the screen 50). For example, in the case of a QCIF + panel, the number of pixel rows is 220. Among these, if 55 pixel rows are displayed as a still image, 220/44 = 4, and therefore, one pixel row may be displayed every four pixel rows. If 10 pixel rows of 220 pixel rows are displayed, one pixel row may be displayed on 220/10 = 22 pixel rows. In FIG. 285, the B region (B period) is one, but it is not limited to this, and it is needless to say that it may be divided or distributed into two or more (plural).
[1245]
However, in FIG. 285 (a), it is only possible to display whether or not one pixel row is lit in a 4-pixel row group. Therefore, one pixel row cannot be lit in 22 pixel rows. Therefore, 4 pixel row sets are displayed 5 times = one pixel row is displayed on 20 pixel rows (that is, one pixel row is displayed on 20 pixel rows. In other words, four of the four pixel row sets have no pixel rows at all. One pixel row of one pixel row group is set to a lighting state without being turned on). All of the remaining 20 pixel rows (220−4 × 5 = 200) are turned off. In other words, according to the present invention, the number of pixel row groups to be lit in this block within the combination (block) of the pixel row set, with the pixel row set being restricted (restricted or regulated) as one unit. Control whether or not. The above matters are also applied to FIG. 285 (b), and also to other embodiments of the present invention.
[1246]
In the case of moving image display, as described in FIG. 285, it is necessary to perform black insertion of at least 4 msec or more. Also, the moving image display state can be changed (adjusted to the optimum state) by changing the ratio of black insertion (black display continuous time, black display area with respect to the display screen). For very high-speed moving image display (such as when the movement of the image is intense), the black insertion area should be increased. At this time, a decrease in luminance due to a decrease in the number of pixels displaying an image is dealt with by increasing the emission luminance of one pixel row. Further, it is preferable to lengthen the period during which black display continues. When the ratio of the moving image display area to the entire screen is relatively small, or when the movement of the moving image is relatively slow, the ratio of black insertion may be reduced. In this case, the increase in display luminance due to the increase in the number of lit pixel rows 53 can be easily adjusted by reducing the light emission luminance per pixel row. This is because this adjustment can be changed by the program current Iw or the like. Alternatively, the black insertion period may be distributed over a plurality of times. Flicker is reduced and good image display can be realized.
[1247]
Even in moving image display as described above, a more optimal image display can be realized by changing or adjusting the black insertion state. Needless to say, the above matters also apply to the following embodiments.
Moving image detection (ID detection) of the input video signal is performed, and in the case of a moving image or an image with many moving images, the driving method shown in FIG. 285 (intermittent display by black insertion) is performed. In the case of a still image, the driving method shown in FIG. 279 (the lighting pixel row positions are dispersed as much as possible) is performed. Of course, switching may be performed according to the use of the display panel or display device of the present invention. For example, in the case of a still image such as a computer monitor, the driving method shown in FIG. 279 is adopted. In the case of AV use such as a television, the driving method shown in FIG. The switching of the driving method can be easily changed by the SSTA data of the gate driver circuit 12b. This is because only the TFT that turns on and off the current flowing through the EL element 15 shown in FIG. 1 is controlled. Switching between FIG. 285 and FIG. 279 (whether it is compatible with moving images or still images, or more compatible with moving images or more still images) may be performed by a changeover switch or the like that can be operated by the user depending on the situation. The manufacturer of the display panel of the present invention may implement it. Alternatively, the ambient environment state may be detected using a photo sensor or the like, and the switching may be performed automatically. In addition, a control signal (switching signal) may be put on the video signal received by the present invention in advance, and the display state (driving method) may be switched by detecting this control signal.
[1248]
FIG. 288 shows an output waveform of the gate signal line 17b in the case of the driving method shown in FIG. In the pixel configuration of FIG. 1, the TFT 11d is on / off controlled by an on / off signal (Vgh is an off voltage, Vgl is an on voltage) applied to the gate signal line 17b, and the current flowing through the EL element 15 is turned on / off. In FIG. 1, the upper part shows the horizontal scanning period, and the L symbol shows the number of pixel rows L (L = 220 in the case of QCIF + panel). In FIGS. 279 and 285, the driving method of the present invention is not limited to the pixel configuration of FIG. For example, it goes without saying that the present invention can be applied to other pixel configurations (FIG. 54 and the like).
[1249]
As can be seen from FIG. 288, in the A period (A region), the ON voltage (Vhl) is applied to each gate signal line 17b at a rate of 1H period in 4H period. In the B period (B region), the off voltage (Vgh) is continuously applied. Therefore, no current flows through the EL element 15 during this period. Then, the ON voltage position of each gate signal line 17b is scanned by one pixel row.
[1250]
In the above embodiment, scanning is performed for each pixel row, but the present invention is not limited to this. For example, in interlace scanning, scanning is performed by skipping one pixel line. That is, even pixel rows are scanned in the first frame. In the second frame, odd-numbered pixel rows are scanned. When the first frame is rewritten, the image written in the second frame is held as it is. However, the blinking operation is performed (not necessary). When the second frame is rewritten, the image written in the first frame is held as it is. Of course, the blinking operation may be performed as in the embodiment of FIG.
[1251]
Interlaced scanning is normally performed in 2 frames and 1 field in CRT. However, the present invention is not limited to this. For example, 4 frames = 1 field may be sufficient. In this case, in the first frame, an image of (4N + 1) pixel rows (where N is an integer greater than or equal to) is rewritten. In the second frame, the image of (4N + 2) pixel rows is rewritten. In the next third frame, the image of (4N + 3) pixel rows is rewritten. In the last fourth frame, the image of (4N + 4) pixel rows is rewritten. As described above, according to the present invention, writing to a pixel row is not limited to only sequential scanning. The above matters also apply to other embodiments. In the present invention, interlaced scanning means wide and general interlaced scanning, and is not limited to 2 frames = 1 field. That is, multiple frames = 1 field.
[1252]
288 and 289 also control the current flowing through the EL element 15 within one horizontal scanning period (1H) or a plurality of horizontal scanning periods as shown in FIGS. 282, 283, and 284 (the ON period is changed). It goes without saying that a driving method for adjusting the brightness of the display screen 50 can be used together by controlling the brightness.
[1253]
FIG. 289 shows the waveform applied to the gate signal line 17b in FIG. The difference from FIG. 288 is that each gate signal line 17b has an on-voltage (Vgl) for two horizontal scanning periods (2H) in the A period (A region, see FIG. 279 (b)). After that, an off voltage (Vgh) is applied for a period of 2H. The on-voltage and off-voltage are repeated alternately. In the B period (B region), the off voltage is continuously applied. The ON voltage application position of each gate signal line 17b is scanned every 1H.
[1254]
FIG. 288 shows an output waveform of the gate signal line 17b in the case of the driving method of FIG. In the pixel configuration of FIG. 1, the TFT 11d is on / off controlled by an on / off signal (Vgh is an off voltage, Vgl is an on voltage) applied to the gate signal line 17b, and the current flowing through the EL element 15 is turned on / off. In FIG. 1, the upper part shows the horizontal scanning period, and the L symbol shows the number of pixel rows L (L = 220 in the case of QCIF + panel). In FIGS. 279 and 285, the driving method of the present invention is not limited to the pixel configuration of FIG. For example, it goes without saying that the present invention can be applied to other pixel configurations (FIG. 54 and the like).
[1255]
As can be seen from FIG. 288, in the A period (A region), the ON voltage (Vhl) is applied to each gate signal line 17b at a rate of 1H period in 4H period. In the B period (B region), the off voltage (Vgh) is continuously applied. Therefore, no current flows through the EL element 15 during this period. Then, the ON voltage position of each gate signal line 17b is scanned by one pixel row.
[1256]
In the above embodiment, scanning is performed for each pixel row, but the present invention is not limited to this. For example, in interlace scanning, scanning is performed by skipping one pixel line. That is, even pixel rows are scanned in the first frame. In the second frame, odd-numbered pixel rows are scanned. When the first frame is rewritten, the image written in the second frame is held as it is. However, the blinking operation is performed (not necessary). When the second frame is rewritten, the image written in the first frame is held as it is. Of course, the blinking operation may be performed as in the embodiment of FIG.
[1257]
Interlaced scanning is normally performed in 2 frames and 1 field in CRT. However, the present invention is not limited to this. For example, 4 frames = 1 field may be sufficient. In this case, in the first frame, an image of (4N + 1) pixel rows (where N is an integer greater than or equal to) is rewritten. In the second frame, the image of (4N + 2) pixel rows is rewritten. In the next third frame, the image of (4N + 3) pixel rows is rewritten. In the last fourth frame, the image of (4N + 4) pixel rows is rewritten. As described above, according to the present invention, writing to a pixel row is not limited to only sequential scanning. The above matters also apply to other embodiments. In the present invention, interlaced scanning means wide and general interlaced scanning, and is not limited to 2 frames = 1 field. That is, multiple frames = 1 field.
[1258]
288 and 289 also control the current flowing through the EL element 15 within one horizontal scanning period (1H) or a plurality of horizontal scanning periods as shown in FIGS. 282, 283, and 284 (the ON period is changed). It goes without saying that a driving method for adjusting the brightness of the display screen 50 can be used together by controlling the brightness.
[1259]
FIG. 289 shows the waveform applied to the gate signal line 17b in FIG. The difference from FIG. 288 is that each gate signal line 17b has an on-voltage (Vgl) for two horizontal scanning periods (2H) in the A period (A region, see FIG. 279 (b)). After that, an off voltage (Vgh) is applied for a period of 2H. The on-voltage and off-voltage are repeated alternately. In the B period (B region), the off voltage is continuously applied. The ON voltage application position of each gate signal line 17b is scanned every 1H. Other items are the same as or similar to those in FIG.
[1260]
In the above embodiment, the driving method is such that the A region and the B region are mixed in the display screen 50. That is, in any period of the screen display state, the A area is always the B area (of course, the location of the A area is different). This means that there are an A period and a B period within one field (one frame, that is, a screen rewriting cycle). However, in order to improve the moving image display, black insertion (black display or low luminance display) may be performed. Therefore, the driving method is not limited to that shown in FIG.
[1261]
For example, the drive method of FIG. 290 is illustrated. In order to facilitate understanding, it is assumed that FIG. 290 includes four display periods ((a), (b), (c), and (d)). Further, 4 frames = 1 field, FIG. 290 (a) is the first frame, FIG. 290 (b) is the second frame, FIG. 290 (c) is the third frame, and FIG. 290 (d) is the first frame. 4 frames. The display is repeated in the order of (a) → (b) → (c) → (d) → (a) → (b) →...
[1262]
In the first frame, as shown in FIG. 290 (a), even-numbered pixel rows are sequentially selected and the image is rewritten. When the rewriting of the first frame is finished, as shown in FIG. 290 (b), black display is sequentially performed from the top of the screen 50 (FIG. 290 (b) is a state in which the black display writing is finished). In the next third frame, as shown in FIG. 290 (c), images are sequentially written in the odd-numbered pixel rows from the top of the screen 50. That is, odd-numbered images are sequentially displayed from the top of the screen. In the next fourth frame, the image is turned off (black display) from the top of the screen 50 ((d) in FIG. 290 also shows a state when the light is completely turned off).
[1263]
In FIG. 290, in (a) and (c), it is expressed that an image is written and an image is displayed. However, the present invention is basically characterized in a state of displaying (lighting) an image. . Therefore, writing an image (implementing a program) and displaying an image are not necessarily the same. In other words, in FIGS. 290 (a) and 290 (c), it may be considered that the current flowing through the EL element 15 is controlled by the control of the gate signal line 17b so as to be turned on or off. Therefore, switching between the state of FIG. 290 (a) and the state of FIG. 290 (b) can be performed in a lump (for example, in a 1H period). For example, it can be implemented by controlling the enable terminal (in the shift register of the gate driver circuit 12b, the on / off state (in FIG. 290 (a), the shift register corresponding to the even-numbered pixel row is on-data) is held and enabled. When the terminal is off, the states of (b) and (d) of FIG. 290 are displayed, and the enable terminal is turned on, resulting in the display state of (a) of FIG. Therefore, the display shown in FIGS. 290 (a) and (c) can be performed in the on / off state of the gate signal line 17b (image data is held in the capacitor 19 in advance in the pixel configuration shown in FIG. 1). In the above description, it is assumed that the states (a), (b), (c), and (d) in FIG. 290 are performed during each 1 l frame period.
[1264]
However, the present invention is not limited to this display state. This is because the black insertion state such as (b) and (d) in FIG. 290 may be performed for a period of 4 msec in order to improve or improve the moving image display state at least. Therefore, in the embodiment of the present invention, the use of the shift register circuit of the gate driver circuit 12b to scan the gate signal line 17b and to realize the display state of FIGS. 290 (a) and (c) is limited. is not. Odd-numbered gate signal lines 17b (referred to as odd-numbered gate signal line sets) are connected together, and even-numbered gate signal lines 17b (referred to as even-numbered gate signal line sets) are connected together and odd-numbered gates. The on / off voltage may be applied alternately between the signal line set and the even-numbered gate signal line set. When the on-voltage is applied to the odd-numbered gate signal line group and the off-voltage is applied to the even-numbered gate signal line group, the display state shown in FIG. 290 (c) is realized. When the on-voltage is applied to the even-numbered gate signal line group and the off-voltage is applied to the odd-numbered gate signal line group, the display state of FIG. 290 (a) is realized. If a turn-off voltage is applied to both the odd-numbered gate signal line group and the even-numbered gate signal line group, the display states of (b) and (d) in FIG. 290 are realized. Each state of (a), (b), (c), and (d) in FIG. 290 may be performed for a period of 4 msec or more (particularly, in (b) and (d) of FIG. 290).
[1265]
In the drive method of FIG. 290 described above, the screen display state ((a) and (c) in FIG. 290) and the black display state (black insertion, (b) and (d) in FIG. 290) are alternately repeated. Therefore, the image display becomes intermittent display, and the moving image display performance is improved (moving image blur does not occur).
[1266]
In the embodiment of FIG. 290, in the first frame and the third frame, an image is displayed in an odd pixel row or an even pixel row, and a black screen ((b) and (d) in FIG. 290) is inserted between the two screens. It was a driving system to do. However, the present invention is not limited to this, and the display state of FIG. 279 may be implemented in the first frame and the third frame, and a black display may be inserted between the two frames. A timing chart in the above embodiment is shown in FIG. FIG. 291 (a) shows the first frame, and FIG. 291 (b) shows the second frame in the black insertion state. FIG. 291 (c) shows the third frame. Note that the fourth frame is the same as (b) in FIG. 291, and is omitted. However, the fourth frame is not always necessary. The configuration may be 3 frames = 1 field. This is because the motion picture blur is greatly improved because the black screen is inserted in the second frame. That is, (a) → (b) → (c) → (a) →...
[1267]
291 (a) shows an image in FIG. 279 (a) for four horizontal scanning periods (4H) for a period of 1H (each gate signal line 17b has a Vgl voltage (ON voltage) every 4H for a period of 1H. In the next second frame, the off voltage (Vgh) is applied to all the gate signal lines 17b, which is controlled by controlling the enable terminal as in the previous embodiment. Therefore, the state shown in Fig. 291 (b) is not limited to the implementation of one frame period, and a period of 4 msec or more is required to improve the video display. However, if the images are rewritten sequentially from the top of the screen (although not limited to the top) in FIG. 291, the image will be skipped as described in FIG. As Of collectively connecting the gate signal line 17b, also, according to the controlling the enable terminal, can be easily performed.
[1268]
In FIG. 291, image display is regularly performed such that each pixel row is lit for 1H period in 4H period. However, each pixel row needs to have the same lighting (display) period in a unit period (for example, one frame, one field, etc.). That is, it is not necessary to regularly perform the lighting state and the non-lighting state.
[1269]
FIG. 292 shows an example of an irregular lighting state. The gate signal line 17b (1) is applied with an on-voltage to the first H, fifth H, sixth H, ninth H, thirteenth H, fourteenth H,. The off voltage is applied during other periods. Therefore, the on-voltage is not periodically applied (though it is periodic in the long term), it is random. The one frame period (unit period) plus the period during which the on-voltage is applied to each gate signal line 17b may be substantially matched with the other gate signal lines 17b. In this way, the lighting times of the respective pixel rows (the pixel rows are supposed to be lit (displayed) by applying the ON voltage to the gate signal line 17b) are substantially the same. In FIG. 292, the signal waveform applied to each gate signal line 17b is scanned 1H at a time. In this way, by scanning (applying) the basic pattern waveform by shifting the gate signal line 17b by 1H (predetermined clock or unit), the luminance of the display screen can be made uniform over the entire screen. In FIG. 292, it goes without saying that the brightness of the screen can be controlled (adjusted) by adjusting the application period of the on-voltage (Vgl).
[1270]
In the above embodiment, the same on / off voltage pattern is applied to the gate signal line 17b in each frame (unit period). However, according to the present invention, the period in which each pixel row (pixel) is lit (displayed) or not lit (not displayed) in a predetermined period is substantially equal. Therefore, in the driving method of 2 frames = 1 field, the signal waveforms of the gate signal lines 17b applied to the first frame and the second frame may be different. For example, an arbitrary pixel row may be driven such that an on-voltage is applied for a period of 10H in the first frame and an on-voltage is applied for a period of 20H in the second frame (referred to as two frames). In the unit period, an ON voltage is applied for a period of 10H + 20H). The on-voltage is applied to the other pixel rows for a period of 30H.
[1271]
This embodiment is illustrated in FIG. In FIG. 293 (a) (assumed to be the first frame), an on-voltage is applied to the gate signal line 17b corresponding to each pixel row in one horizontal scanning period (1H) with a period of four horizontal scanning periods (4H). . In FIG. 293 (b) (assumed to be the second frame), the ON voltage is applied to the gate signal line 17 corresponding to each pixel row for a period of 2H in a 4H cycle. That is, in 2 frames, an on-voltage is applied for a period of (1 + 2) H with a (4 + 4) H cycle. Even when driven in this way, in the unit period (2 frames in FIG. 293), the ON voltage is applied to each gate signal line 17b for the same period. Therefore, each pixel row is displayed with the same luminance (assuming white raster display).
[1272]
In FIG. 291, the on-voltage is applied for a period of 1H in a 4H cycle, but the present invention is not limited to this. For example, as shown in FIG. 294, an on-voltage may be applied for a period of 1H with a period of 8H. Further, the signal waveform applied to each gate signal line 17b in each frame may be completely randomized without giving periodicity. This is because the total period in which the ON voltage is applied in a unit cycle (unit period) only needs to be the same for all the gate signal lines 17b.
[1273]
However, in the above embodiment, the sum period for applying the ON voltage is made to coincide in the unit period in all the gate signal lines 17b, but this is not applied in the following cases. This is a case where a plurality of screens 50 having different luminances are provided within one screen 50 (that is, one display panel). The screen 50 is a case where the first screen 50a and the second screen 50b are configured, and the screens 50a and 50b have different luminances. Although the brightness of the two screens 50 can be changed by adjusting the program current Iw, the gate signal line 17b is scanned and each pixel row on the first screen 50a is turned on (displayed). ) It is easy to realize a method in which the period and the lighting (display) period of each pixel row on the second screen 50b are different. For example, each pixel row on the first screen 50a applies an ON voltage to the gate signal line 17b for a period of 1H to 4H. Each pixel row on the second screen 50b applies an ON voltage to the gate signal line 17b for a period of 1H to 8H. Thus, by changing the period during which the on-voltage is applied to each screen, the brightness of the screen can be adjusted, and the gamma curve at that time can be made similar.
[1274]
In the above embodiment, the current flowing through the EL element 15 is adjusted (turned on and off) by adjusting the gate signal line 17b, thereby adjusting the luminance of the display screen 50 or improving the moving image display. there were. FIG. 295 shows another embodiment of the present invention having the above-described effects.
[1275]
The pixel 16 in FIG. 295 is arranged or configured as shown in FIG. A difference from the pixel configuration of FIG. 1 is that one terminal of the storage capacitor 19 (capacitor 19) is connected to the capacitance control line 2951. One capacitance control line 2951 is common to one pixel row. The capacity control line 2951 is connected to the capacity control common line 2953.
[1276]
In FIG. 296, the capacitor 19 has one terminal connected to the capacitance control line 2951 and the other terminal connected to the gate terminal of the TFT 11a. Now, it is assumed that the Va voltage is applied to the gate terminal (G) of the TFT 11a. Further, it is assumed that a Vdd voltage is applied to the source terminal (S) of the TFT 11a. Also, Va <Vdd. Assume that a Vc voltage is applied to the capacitance control line 2951.
[1277]
In this state, when the Vc voltage of the capacitance control line 2951 is changed to the + side, the Va voltage is also shifted to the + side along with this change. Since the TFT 11a is a P-channel transistor, when the gate terminal of the TFT 11a is shifted to the + side (Vdd side), the TFT 11a is in a direction in which no current flows. Therefore, when the change to the + side of the Vc voltage is larger than a certain value, the TFT 11a is in a state where no current flows completely (cut-off state). That is, by controlling the potential applied to the capacitance control line 2951, the corresponding pixel row can be brought into a black display state. Conversely, when the Vc voltage of the capacitance control line 2951 is changed to the-side, the potential of the gate terminal (G) of the TFT 11a is also shifted to the-side. Therefore, more current flows through the TFT 11a. The above matter is the case where the driving TFT 11a is composed of a P-channel transistor. When the driving TFT 11a is an N channel, the opposite is true. That is, when the potential of the capacitance control line 2951 is shifted to the + side, the N-channel driving TFT 11a allows more current to flow through the EL element 15.
[1278]
By applying the above driving method to FIG. 296, the display screen 50 can be displayed in black. That is, the black insertion described with reference to FIG.
[1279]
In FIG. 295, a capacitance control common line 2953 (2953a, 2953b, 2953c, 2953d) is formed or arranged. The capacity control line 2951 in the (4N + 1) pixel row (where N is an integer greater than or equal to 0) is connected to the capacity control common line 2953a. Further, the capacitance control line 2951 of the (4N + 2) pixel row is connected to the capacitance control common line 2953b. The (4N + 3) pixel row is connected to the capacitance control common line 2953c, and the capacitance control line 2951 of the (4N + 4) pixel row is connected to the capacitance control common line 2953d.
[1280]
With the above configuration, if the voltage applied to the capacitance control common line 2953a is shifted to the + side, (4N + 1) pixel rows are not displayed (black display or low luminance display). Similarly, if the voltage applied to the capacitance control common line 2953b is shifted to the + side, the (4N + 2) pixel row is not displayed (black display or low luminance display). If the applied voltage of the capacitance control common line 2953c is shifted to the + side, the (4N + 3) pixel row is not displayed, and if the applied voltage of the capacitance control common line 2953d is shifted to the + side, (4N + 4) pixels. The line is hidden.
[1281]
By controlling the capacity control common line 2953 as described above, a predetermined pixel row can be displayed in black. Accordingly, the screen brightness can be adjusted by adjusting the control timing and control cycle of the capacity control common line 2953. Further, by setting the connection state of the capacitance control line 2951 and the capacitance control common line 2953, the number of connections, and the number of formation of the capacitance control common lines 2953 to a predetermined state, a concentrated black insertion portion is provided as shown in FIG. Can do. Therefore, the moving image display can be improved.
[1282]
In FIG. 296 (a), the odd-numbered pixel rows are connected to the capacitance control common line 2953a, and the even-numbered pixel rows are connected to the capacitance control common line 2953b. Accordingly, by alternately applying a voltage to the positive side to the capacitance control common lines 2953a and 2953b, the display screen 50 can be made into a non-display pixel row in a comb shape. In FIG. 296 (b), each of the three pixel rows is connected to a different capacitance control common line 2953. Therefore, lighting or non-lighting control can be performed in a cycle of three pixel rows.
[1283]
When the voltage applied to the capacitance control line 2951 and changed to the + side is relatively small, the voltage applied to the capacitance control line 2951 is shifted again to the-side, so that the current flowing through the TFT 11a is returned to the original current. (However, it is necessary to add a compensation voltage.) However, if the voltage shifted to the + side is larger than a predetermined value, the current flowing through the TFT 11a cannot be restored (the necessary compensation voltage increases and it becomes difficult to obtain the original current value).
[1284]
In order to perform black insertion with the configuration of FIG. 296, basically, it is better not to restore the image data held in the capacitor 19 (because it is difficult to completely restore the original holding voltage). is there). In other words, the image can be displayed in black.
[1285]
For example, as shown in FIG. 297, a positive voltage is applied to the capacitance control line 2951 at the R position before the image is written, so that the black display 52 is obtained. That is, a positive voltage is applied to the capacitance control line 2951 and the screen 50 is displayed in black. Next, after the elapse of a predetermined period, an image is written (the image writing position is the pixel writing line 51). In FIG. 297, writing is performed at a position where the pixel row is separated by K (K1 in the case of (a) in FIG. 297, K2 in the case of (b) in FIG. 297). K1 indicates the number of pixel rows. That is, the time from writing black at the R position to writing the image is the number of pixel rows × 1 horizontal scanning period. Therefore, as K is larger, the black writing period increases (K1 <K2), and the image display becomes darker. The larger the K value, the darker the screen, and the smaller the K value, the brighter the screen. The brightness of the image can be adjusted by adjusting the value of K. Also, the greater the value of K, the higher the effect of improving moving image blur.
[1286]
In the above embodiment, one source driver circuit (IC) 14 and one gate driver circuit (IC) 12 display an image on one screen 50. However, the present invention is not limited to this. For example, in the embodiment of FIG. 298, the screen 50 is composed of a screen 50a and a screen 50b. A source driver circuit 14a is connected to the source signal line 18a of the screen 50a. A source driver circuit 14b is connected to the source signal line 18b of the screen 50b. Gate signal lines (17a, 17b) to the screen 50a and the screen 50b are connected to one built-in gate driver circuit 12.
[1287]
In other words, in the embodiment of FIG. 298, the gate driver circuit (IC) 12 is common to the screens 50a and 50b, and the screen 50 is divided into two and driven by the two source driver circuits (14a and 14b). Yes. The writing of the image is not limited to the downward direction (A direction) from the top of the screen 50. As shown in FIG. 298, scanning may be performed from the bottom of the screen 50 upward (B direction). Further, the screen 50a may be scanned in the A direction, and the screen 50b may be scanned in the B direction. In FIG. 298, the screen 50 is divided into two, but it goes without saying that it may be divided into three or more. Further, the source driver circuit 14a is arranged or configured to drive even-numbered source signal lines 18 on one display screen 50, and the source driver circuit 14b drives odd-numbered source signal lines 18 on the display screen 50. May be. The same applies to the gate driver circuit 12. A plurality of gate driver circuits 12 may be used to drive each screen (50a, 50b). The gate driver circuit 12a is arranged or configured to drive even-numbered gate signal lines 18 in one display screen 50, and the gate driver circuit 12b drives odd-numbered gate signal lines 18 in the display screen 50. May be. Note that a protection diode is preferably formed on the source signal line 14 and the gate signal line 12 for electrostatic protection. It goes without saying that the above matters can be applied to other embodiments of the present invention.
[1288]
Hereinafter, a high-quality display method using a current driving method (current programming method) will be described with reference to the drawings. In the current programming method, a current signal is applied to the pixel 16 to cause the pixel 16 to hold the current signal. Then, a current held in the EL element 15 is applied.
[1289]
The EL element 15 emits light in proportion to the magnitude of the applied current. That is, the light emission luminance of the EL element 15 has a linear relationship with the value of the current to be programmed. On the other hand, in the voltage programming method, the applied voltage is converted into current by the pixel 16. This voltage-current conversion is non-linear. Non-linear conversion complicates the control method.
[1290]
In the current driving method, the value of video data is linearly converted into a program current as it is. As a simple example, in the case of 64 gradation display, 0 of the video data is set to the program current Iw = 0 μA, and the video data 63 is set to the program current Iw = 6.3 μA (having a proportional relationship). Similarly, the video data 32 has a program current Iw = 3.2 μA, and the video data 10 has a program current Iw = 1.0 μA. That is, the video data is directly converted into the program current Iw in a proportional relationship.
In order to facilitate understanding, description will be made assuming that the video data and the program current are converted in a proportional relationship. Actually, video data and program current can be converted more easily. This is because the unit current of the unit transistor 484 corresponds to 1 of video data as shown in FIG. Furthermore, the unit current can be easily adjusted to an arbitrary value by adjusting the reference current circuit. This is because the reference current is provided for each of the R, G, and B circuits, and white balance can be achieved over the entire gradation range by adjusting the reference current circuit to the RGB circuit. This is a synergistic effect of the current program method and the configuration of the source driver circuit 14 and the display panel of the present invention.
[1291]
The EL display panel is characterized in that the program current and the light emission luminance of the EL element 15 have a linear relationship. This is a major feature of the current programming method. That is, the emission luminance of the EL element 15 can be adjusted linearly by controlling the magnitude of the program current.
[1292]
In the driving transistor 11a, the voltage applied to the gate terminal and the current flowing through the driving transistor 11a are nonlinear (often a square curve). Therefore, in the voltage program method, the program voltage and the light emission luminance are in a non-linear relationship, and the light emission control is extremely difficult. Compared with the voltage program, the light emission control is extremely easy in the current program method. In particular, in the pixel configuration of FIG. 1, the program current and the current flowing through the EL element 15 are theoretically equal. Accordingly, the light emission control is very easy to understand and control. The N-fold pulse driving according to the present invention is also excellent in that it is easy to control light emission since the light emission luminance can be grasped by calculating with the program current set to 1 / N. When the pixel configuration in FIG. 38 or the like is a current mirror configuration, the driving transistor 11b and the programming transistor 11a are different from each other, causing a deviation in current mirror magnification, which causes an error factor in light emission luminance. However, the pixel configuration in FIG. 1 does not have this problem because the driving transistor and the programming transistor are the same.
[1293]
In the EL element 15, the light emission luminance changes in proportion to the input current amount. The voltage (anode voltage) applied to the EL element 15 is a fixed value. Therefore, the light emission luminance of the EL display panel is proportional to the power consumption.
[1294]
  From the above, the video data and the program current are proportional, the program current and the light emission luminance of the EL element 15 are proportional, and the light emission luminance and the power consumption of the EL element 15 are proportional. Therefore, if the video data is subjected to logic processing, the current consumption (power) of the EL display panel, the light emission luminance of the EL display panelTheYou can control it. That is, the luminance and power consumption of the EL display panel can be grasped by performing logic processing (addition or the like) on the video data. Therefore, processing such as preventing the peak current from exceeding the set value is extremely easy.
[1295]
In particular, the EL display panel of the present invention is a current drive system. In addition, image display control with a characteristic configuration is easier. There are two distinct image display control methods. One is control of the reference current. The other is duty ratio control. By combining the reference current control and the duty ratio control alone or in combination, a wide dynamic range, high image quality display, and high contrast can be realized.
[1296]
First, in the reference current control, as shown in FIG. 77, the source driver IC (circuit) 14 includes a circuit for adjusting the reference current of each RGB. Further, the program current Iw from the source driver circuit 14 is determined by how many unit transistors 484 are being output. The current output from one unit transistor 484 is proportional to the magnitude of the reference current. Therefore, by adjusting the reference current, the current output by one unit transistor 484 is determined, and the magnitude of the program current is determined. Since the reference current and the output current of the unit transistor 484 are in a linear relationship, and the program current and the luminance are in a linear relationship, if the white balance is adjusted by adjusting the reference current of each RGB in white raster display , White balance is maintained in all gradations.
[1297]
FIG. 77 shows a configuration in which current mirrors are connected in multiple stages, but the present invention is not limited to this. It goes without saying that even the single-stage source driver IC (circuit) 14 shown in FIGS. 166 to 170 can easily adjust the reference current and maintain the white balance in all gradations. Needless to say, the luminance of the EL display panel can be controlled by adjusting the reference current.
[1298]
FIG. 78 shows a duty ratio control method. FIG. 78A shows a method of continuously inserting the non-display area 52. Suitable for video display. Also, (a1) in FIG. 78 is the darkest image, and (a4) in FIG. 78 is the brightest. The duty ratio can be freely changed by controlling the gate signal line 17b. FIG. 78 (c) shows a method of inserting the non-display area 52 by dividing it into a large number. Particularly suitable for still image display. Also, (c1) in FIG. 78 is the darkest image, and FIG. 78 (c4) is the brightest. The duty ratio can be freely changed by controlling the gate signal line 17b. FIG. 78 (b) is an intermediate state between FIG. 78 (a) and FIG. 78 (c). Similarly in FIG. 78B, the duty ratio can be freely changed by controlling the gate signal line 17b.
[1299]
  The dispersion of the display area 53 is 220/4 = 55 when the number of pixel rows of the display panel is 220 and 1/4 duty, and is adjusted from 1 to 55 (brightness from 1 to 55 times the brightness). it can). Further, if the number of pixel rows of the display panel is 220 and 1/2 Duty, 220/2 = 110, so 1 to 110 (adjustable from 1 brightness to 110 times the brightness). Hence the screen50 brightnessThe brightness adjustment range is very wide (the dynamic range of image display is wide). Further, there is a feature that the number of gradations that can be expressed can be maintained regardless of the brightness. For example, in the case of 64-gradation display, 64-gradation display can be realized regardless of whether the screen 50 brightness in white raster is 300 nt or 3 nt.
[1300]
As described above, the duty can be easily changed by controlling the start pulse to the gate driver circuit 12b. Accordingly, it is possible to easily change various duties such as 1/2 Duty, 1/4 Duty, 3/4 Duty, and 3/8 Duty.
[1301]
In the duty ratio driving in units of one horizontal scanning period (1H), an on / off signal of the gate signal line 17b may be applied in synchronization with the horizontal synchronizing signal. Furthermore, the duty ratio can be controlled even in units of 1H or less. This is the driving method of FIGS. 145 and 146. By performing OEV2 control within the 1H period, it is possible to perform brightness control (duty ratio control) in a minute step (see also FIG. 109 and its description, and also refer to FIG. 175 and its description). .
[1302]
The duty ratio control within 1H is performed when the duty ratio is ¼ duty or less. If the number of pixel rows is 220 pixel rows, it is 55/220 Duty or less. That is, it is performed in the range of 1/220 to 55/220 Duty. This is performed when a change in one step changes from 1/20 (5%) or more after change to after change. More preferably, it is desirable to perform minute duty ratio drive control by performing OEV2 control even with a change of 1/50 (2%) or less. That is, in the duty ratio control by the gate signal line 17b, when the brightness change after the change from before the change becomes 5% or more, the change amount is gradually changed by the control by the OEV2 so that the change amount becomes 5% or less. Let For this change, it is preferable to introduce the Wait function described in FIG. The duty ratio control within 1H when the duty ratio is ¼ duty or less is due to the large amount of change per step, but since the image is halftone, even minute changes are visually recognized. It is also because it is easy. Human vision has a low ability to detect changes in brightness on dark screens above a certain level. In addition, even on a bright screen above a certain level, the detection capability for brightness change is low. This seems to be because human vision depends on the square characteristic.
[1303]
  FIG.5Is a graph of the detection function for screen changes. The horizontal axis represents screen brightness (nt). The vertical axis represents the allowable change (%). The permissible change (%) describes the limit point whether the change rate (%) of the brightness changed from the arbitrary duty to the next duty is permissible. However, the allowable change (%) has a large change rate depending on the content of the image (change rate, scene, etc.). Also, it tends to depend on personal video detection capabilities.
[1304]
As can be seen from FIG. 174, when the luminance of the screen 50 is high, the allowable change with respect to the duty change is large. Further, even when the brightness of the screen 50 is dark, the allowable change with respect to the duty change tends to be large. However, in the case of halftone display, the limit value (%) of the allowable change is small. This is because the image is halftone, and even a minute change is easily recognized visually.
[1305]
As an example, if there are 200 pixel rows on the panel, OEV2 control is performed at 50/200 duty or less (1/200 or more and 50/200 or less), and duty ratio control is performed for a period of 1H or less. When changing from 1/200 Duty to 2/200 Duty, the difference between 1/200 Duty and 2/200 Duty is 1/200, which is a change of 100%. This change is completely visually recognized as flicker. Therefore, OEV2 control (see FIG. 175 and the like) is performed, and current supply to the EL element 15 is controlled in a period of 1H (one horizontal scanning period) or less. Although the duty ratio control is performed in the 1H period or less (within 1H period), the present invention is not limited to this. As can be seen in FIG. 19, the non-display area 52 is continuous. That is, control such as the 10.5H period is also within the scope of the present invention. In other words, the present invention is not limited to the 1H period (a fractional part is generated) and performs duty ratio driving.
[1306]
When changing from 40/200 Duty to 41/200 Duty, the difference between 40/200 Duty and 41/200 Duty is 1/200, and the change is 2.5% at (1/200) / (40/200). Whether or not this change is visually recognized as flicker is likely to depend on the screen brightness 50. However, since 40/200 Duty is a halftone display, it is visually sensitive. Therefore, it is desirable to perform OEV2 control (see FIG. 175 etc.) and control the current supply to the EL element 15 in a period of 1H (one horizontal scanning period) or less.
[1307]
As described above, the driving method and the display device according to the present invention can store the current value flowing through the EL element 15 in the pixel 16 (corresponding to the capacitor 19 in FIG. 1), the driving transistor 11a, and the light emitting element (EL A display panel having a configuration capable of turning on and off a current path with respect to the element 15 (a pixel configuration shown in FIGS. 1, 43, 113, 114, 117, and the like corresponds), and at least displaying a display image 19 is generated in the state (depending on the brightness of the image, the screen 50 may become the display area 53 (Duty 1/1).))It is a driving method. And duty ratio drive (at least a part of the screen 50 is a non-display area)52If the driving method or driving state is equal to or less than a predetermined duty ratio, the luminance control of the display screen 50 is controlled by controlling the current flowing through the EL element 15 that is limited to one horizontal scanning period (1H period) or 1H period unit. Is to do. This control is performed by OEV2 control (refer to FIG. 175 and its description regarding OEV2).
[1308]
  The predetermined duty ratio for performing duty ratio control other than 1H unit is performed when the duty ratio is equal to or less than ¼ duty. Conversely, when the duty ratio is equal to or higher than the predetermined duty ratio, duty ratio control is performed in units of 1H. Or, OEV2 control is not performed. Further, duty ratio control other than the 1H period is performed when a change in one step changes from 1/20 (5%) or more after change to after change. More preferably, even when the change is less than 1/50 (2%), OEV2 control is performed and a small duty ratio is obtained.Control driveIt is desirable to do. Alternatively, it is carried out with a luminance of 1/4 or less of the maximum luminance of the white raster.
[1309]
According to the duty ratio control drive of the present invention, as shown in FIG. 79, if the number of gradation representations of the EL display panel is 64 gradations, the display brightness (nt) of the display screen 50 is any brightness. Even so, the 64 gradation display is maintained. For example, even when the number of pixel rows is 220 and only one pixel row is in the display area 53 (display state) (Duty ratio 1/220), 64-gradation display can be realized. This is because an image is sequentially written in each pixel row by the program current Iw of the source driver circuit 14, and this one pixel row is sequentially displayed by the gate signal line 17b.
[1310]
Of course, even when all of the 220 pixel rows are in the display area 53 (display state) (Duty ratio 220/220 = Duty ratio 1/1), 64-gradation display can be realized. This is because images are sequentially written to the pixel rows by the program current Iw of the source driver circuit 14, and all the pixel rows are simultaneously displayed by the gate signal lines 17b. Further, even when only 20 pixel rows are in the display region 53 (display state) (Duty 20/220 = Duty 1/11), 64-gradation display can be realized. This is because an image is sequentially written in each pixel row by the program current Iw of the source driver circuit 14, and the 20 pixel rows are sequentially scanned and displayed by the gate signal line 17b.
[1311]
Since the duty ratio control drive of the present invention is the control of the lighting time of the EL element 15, the brightness of the screen 50 with respect to the duty ratio has a linear relationship. Therefore, it is very easy to control the brightness of the image, the signal processing circuit is simple, and the cost can be reduced. As shown in FIG. 77, the RGB reference current is adjusted to achieve white balance. In the duty ratio control, white balance is maintained at any gradation and brightness of the screen 50 in order to simultaneously control the brightness of R, G, and B.
[1312]
In the duty ratio control, the luminance of the screen 50 is changed by changing the area of the display region 53 with respect to the display screen 50. Naturally, the current flowing through the EL display panel changes in proportion to the display area 53. Therefore, by calculating the sum total of the video data, the total current consumption flowing through the EL element 15 of the display screen 50 can be calculated. Since the anode voltage Vdd of the EL element 15 is a DC voltage and is a fixed value, if the total current consumption can be calculated, the total power consumption can be calculated in real time according to the image data. If the calculated total power consumption is predicted to exceed the prescribed maximum power, the reference current in FIG. 77 may be adjusted by an adjustment circuit such as an electronic volume, and the RGB reference current may be controlled to be suppressed.
[1313]
In addition, a predetermined luminance in white raster display is set, and this time is set so as to minimize the duty ratio. For example, the duty ratio is set to 1/8. For natural images, the duty ratio is increased. The maximum duty is 1/1. For example, a natural image in which an image is displayed only 1/100 of the screen 50 is set to Duty 1/1. The duty ratio 1/1 to the duty ratio 1/8 is smoothly changed depending on the display state of the natural image on the screen 50.
[1314]
As described above, as an example, in white raster display (all pixels are lit 100% in a natural image), the duty ratio is 1/8, and 1/100 pixels of the screen 50 are lit. The state is a duty ratio of 1/1. The approximate power consumption can be calculated by the number of pixels × the ratio of the number of lit pixels × Duty ratio.
[1315]
For ease of explanation, assuming that the number of pixels is 100, the power consumption in white raster display is 100 × 1 (100%) × Duty ratio 1/8 = 80. On the other hand, the power consumption of a natural image in which 1/100 is lit is 100 × (1/100) (1%) × Duty ratio 1/1 = 1. Duty 1/1 to Duty ratio 1/8 is a smooth duty ratio control so that flicker does not occur according to the number of lighting pixels of the image (actually, the total current of the lighting pixels = the sum of the program currents of one frame). Is done.
As described above, the power consumption ratio of white raster is 80, and the power consumption ratio of a natural image in which 1/100 is lit is 1. Therefore, the maximum current can be suppressed by setting a predetermined luminance in white raster display and setting this time so as to minimize the duty ratio.
[1316]
In the present invention, the sum of the program currents for one screen is S, the duty ratio is D, and drive control is performed with S × D. Also, the total program current in the white raster display is Sw, the maximum duty ratio is Dmax (usually, the duty ratio 1/1 is the maximum), the minimum duty ratio is Dmin, and any natural This is a drive method and a display device that realizes the drive method in which the relationship of Sw × Dmin> = Ss × Dmax is maintained when the total program current in the image is Ss.
[1317]
The maximum duty ratio is 1/1. The minimum is preferably a duty ratio of 1/16 or more. That is, the duty ratio is set to 1/8 or more and 1/1 or less. Needless to say, the use of 1/1 is not restricted. Preferably, the minimum duty ratio is 1/10 or more. This is because if the duty ratio is too small, the occurrence of flicker is conspicuous, and the luminance change of the screen due to the image content becomes too large, making it difficult to see the image.
[1318]
  As described above, the program current is proportional to the video data. Therefore,Video dataIs the same as the sum of program currents. Although the sum of program currents for one frame (one field) period is obtained, the present invention is not limited to this. Pixels to which program current is added at a predetermined interval or a predetermined period in one frame (one field) May be sampled to obtain the sum of program currents (video data). Further, sum data before and after a frame (field) to be controlled may be used, or duty ratio control may be performed using sum data obtained by estimation or prediction.
[1319]
In the above description, the control is performed with the duty ratio D. However, the duty ratio is a predetermined period (usually one field or one frame. In other words, in general, a cycle in which image data of an arbitrary pixel is rewritten. Or the time during which the EL element 15 is turned on. That is, a duty ratio of 1/8 means that the EL element 15 is lit during a 1/8 period (1F / 8) of one frame. Therefore, the duty ratio can be read as Duty ratio = Ta / Tf, where Tf is the period when the pixel 16 is rewritten and the lighting period Ta of the pixel.
[1320]
In addition, although the period time in which the pixel 16 is rewritten is Tf and is based on Tf, the present invention is not limited to this. The duty ratio control drive of the present invention does not need to be completed in one frame or one field. That is, the duty ratio control may be performed with several fields or several frame periods as one cycle (see FIG. 104 and the like). Therefore, Tf is not limited to the cycle of rewriting pixels, and may be one frame or one field or more. For example, if the lighting period Ta is different for each field or frame, the repetition period (period) may be Tf and the total lighting period Ta of this period may be employed. That is, Ta may be the average lighting time of several fields or several frame periods. The same applies to the duty ratio. When the duty differs for each frame (field), an average duty ratio of a plurality of frames (fields) may be calculated and used.
[1321]
Therefore, the sum of program currents in white raster display is Sw, the sum of program currents in an arbitrary natural image is Ss, the minimum lighting period is Tas, and the maximum lighting period is Tam (usually Tam = Tf). To Tam / Tf = 1), a driving method for maintaining the relationship of Sw × (Tas / Tf)> = Ss × (Tam / Tf) and a display device that realizes the driving method.
[1322]
As a method for controlling the brightness of the screen 50, there is the configuration described in FIG. That is, by adjusting the reference current, the screen current 50 is changed by changing the current flowing through the unit transistor 484 and adjusting the magnitude of the program current. The reference current adjustment method is described with reference to FIG.
[1323]
  491R in FIG. 77 is a volume for adjusting the reference current of red (R). However, the expression “volume” is for ease of explanation, and it is actually an electronic volume. The reference current IaR of the R circuit can be linearly adjusted in 64 steps by a 6-bit digital signal from the outside. It is configured as follows. By adjusting the reference current IaR, the current flowing through the transistor 471R and the transistor 472a forming the current mirror circuit can be linearly changed. Therefore, the transistor 472a of the transistor group 521a andFrom transistor 472aThe current flowing through the transistor 472b that has passed the current changesTo do.Transistor 473a of transistor group 521b that forms a current mirror circuit with transistor 472bCurrent flowing throughChanges,AlsoTransistor 473aFromThe transistor 473b to which the current is passed changes. Accordingly, since the drive current (unit current) of the unit transistor 484 changes, the program current can be changed. The same applies to the G reference current IaG and the B reference current IaB.
[1324]
  FIG. 77 shows a three-stage transistor connection of a parent and a descendant, but the present invention is not limited to this. For example, as shown in FIGS. 166 to 170, it goes without saying that the present invention can be applied to a single-stage configuration in which a circuit for generating a reference current and a unit transistor 484 are directly connected. That is, the present invention is a circuit configuration in which the program current or the program voltage can be changed by one reference current or reference voltage, and the brightness of the screen 50 is changed by the reference current or reference voltage.
  As shown in FIG. 77, the (electronic) volume 491 is formed in red (R), green (G), and B (blue) circuits, respectively. Therefore, by adjusting the volumes 491R, 491G, and 491B, the currents of the unit transistors 484 connected thereto can be changed (controlled or adjusted). Therefore, white (W) adjustment can be easily performed by adjusting the RGB ratio. Of course, if the RGB reference currents (currents flowing through the transistors 472R, 472G, and 472B) are adjusted in advance at the time of shipment, an RGB electronic volume (491R, 491G, 491B) can be changed at once. Thus, white (W) balance adjustment can also be performed. For example,170 and 171Then, the value of the resistor R1 is adjusted so that the white balance is obtained in each RGB circuit. In this state, if the switches S of the electronic volume 451 in FIGS. 169 and 170 are switched to the same RGB, the screen brightness can be adjusted while maintaining the white balance.
[1325]
As described above, the reference current driving method of the present invention adjusts the RGB reference current values so that white balance is achieved. With this state as the center, the RGB reference current is adjusted at the same ratio. White balance is maintained because adjustment is performed at the same ratio.
[1326]
As described above, the program current can be changed linearly by adjusting the electronic volume 491. For ease of explanation, the pixel configuration shown in FIG. 1 will be described as an example. However, the present invention is not limited to this, and it is needless to say that other pixel configurations may be used.
[1327]
As shown or described in FIG. 77, the program current can be linearly adjusted by controlling the reference current. This is because the output current of one unit transistor 484 changes. When the output current of the unit transistor 484 is changed, the program current Iw is also changed. The larger the current programmed in the pixel capacitor 19 (actually, the voltage corresponding to the program current) is, the larger the current flowing through the EL element 15 is. The current flowing through the EL element 15 and the light emission luminance are linearly proportional. Therefore, the light emission luminance of the EL element 15 can be linearly changed by changing the reference current.
[1328]
In the present invention, screen brightness and the like are controlled using at least one of the reference current control method described in FIG. 77 and the duty ratio control method described in FIG. Preferably, it is preferable to implement a combination of the methods shown in FIGS. 77 and 78.
[1329]
Hereinafter, the driving method using the method described in FIGS. 77 and 78 will be described in more detail. One object of the driving method of the present invention is to limit the upper limit of current consumption consumed by the EL display panel. In the EL display panel, the luminance is proportional to the current flowing through the EL element 15. Therefore, if the current flowing through the EL element 15 is increased, the luminance of the EL display panel can be increased. The current consumed (= power consumption) increases in proportion to the luminance.
[1330]
When used for a portable device, the capacity of a battery or the like is limited. Further, the scale of the power supply circuit increases as the current consumed increases. Therefore, it is necessary to provide a limit for the consumed current. Providing this limit (peak current suppression) is one object of the present invention.
[1331]
Further, the display is improved by increasing the contrast of the image. Display is improved by converting the image so that there is an edge and displaying the image. The second object of the present invention is to improve the image display as described above. The present invention that realizes the above two purposes (or one) will be referred to as AI driving.
[1332]
First, for ease of explanation, it is assumed that the source driver IC 14 of the present invention has a 64-gradation display. In order to realize AI driving, it is desirable to expand the gradation expression range. For ease of explanation, the source driver IC (circuit) 14 according to the present invention has 64 gradation display and the image data has 256 gradation. This image data is subjected to gamma conversion so as to match the gamma characteristic of the EL display device. The gamma conversion is performed by expanding the input 256 gradations to 1024 gradations. The gamma-converted image data is subjected to error diffusion processing or frame rate control (FRC) processing so as to conform to the 64 gradations of the source driver IC 14 and is applied to the source driver IC 14.
[1333]
FRC realizes high gradation display by superimposing image display for each field. In the error diffusion processing, as shown in FIG. 99 as an example, the image data of the pixel A is distributed to 7/16 on the right, 3/16 on the lower left, 5/16 on the lower, and 1/16 on the lower right. Is the method. High gradation display can be realized by distributed processing. It is a kind of area gradation.
[1334]
For ease of illustration, FIGS. 80 and 81 will be described assuming that 64 gradation display is converted to 512 gradation. The conversion is performed by an error diffusion processing method or frame rate control (FRC). However, in FIG. 80, it may be interpreted that the brightness of the image is converted rather than performing the gradation conversion.
[1335]
  FIG. 80 explains the image conversion processing by the driving method of the present invention. In FIG. 80, the horizontal axis represents gradation (number). The larger the gradation (number) is, the brighter the screen 50 is. Conversely, the smaller the gradation (number), the darker the image. The vertical axis is frequency.Vertical axisOf the pixels that make up the imageAppearance rate of luminanceIs shown. For example, A1 in FIG.32It indicates that the number of pixels having gradation level luminance is the largest.
[1336]
FIG. 80A shows an example in which the display brightness is changed while maintaining the number of gradation representations of the image. When A1 is an original image, the original image has an expression range of approximately 64 gradations. A2 is an example in which the center of brightness is converted to 256 gradations while maintaining the number of gradation representations. Similarly, A3 is an example in which the center of brightness is converted to 448 gradations while maintaining the number of gradation representations. Such conversion can be achieved by converting the image data by adding data of a predetermined size.
[1337]
However, the gradation conversion of FIG. 80A is difficult to realize with the driving method of the present invention. In the driving method of the present invention, gradation conversion shown in FIG. 80 (b) is performed.
[1338]
FIG. 80B is an example in which the frequency distribution of the original image is enlarged. When B1 is an original image, the original image has an expression range of approximately 64 gradations. B2 is an example in which the gradation expression range is expanded to 256 gradations. The brightness of the screen becomes brighter and the gradation expression range is expanded. B3 is an example in which the gradation expression range is further expanded to 512 gradations. The screen display brightness is further increased and the gradation expression range is expanded.
[1339]
The realization of (b) of FIG. 80 can be easily realized by the driving method of the present invention. This can be realized by changing the reference current described in FIG. Further, this can be realized by changing (controlling) the duty ratio of FIG. Alternatively, it can be realized by combining the methods of FIG. 77 and FIG. The brightness control of the image is easy by the reference current control or the duty ratio control. For example, if the duty ratio is 1/4 and the display state is B2 in FIG. 80B, if the duty ratio is 1/16, the display state is B1 in FIG. 80B. Further, when the duty ratio is halved, the display state of B3 in FIG. The same applies to the reference current control. By making the magnitude of the reference current double or 1/4, the image display of FIG. 80 (b) can be performed.
[1340]
The horizontal axis in FIG. 80B is the number of gradations. The driving method of the present invention does not increase the number of gradations. The driving method of the present invention is characterized in that the number of gradations is maintained even when the display luminance changes as described in FIG. That is, in FIG. 80B, it is assumed that the number of 64 gradations of B1 is converted to 256 gradations in B2. However, the gradation number of B2 is 64 gradations. One gradation range is expanded four times compared to B1. The conversion from B1 to B2 is nothing but the dynamic conversion of the image display. Therefore, it is equivalent to realizing high gradation display. Therefore, high quality display can be realized.
[1341]
Similarly, in FIG. 80B, it is assumed that the number of 64 gradations of B1 is converted to 512 gradations in B3. However, the number of gradations of B3 is 64 gradations. One gradation range is expanded eight times compared to B1. The conversion from B1 to B3 is nothing but the dynamic conversion of the image display.
[1342]
In FIG. 80A, the brightness of the screen 50 can be improved. However, the entire screen 50 becomes whitish (white floating). However, the increase in current consumption is relatively small (although the current consumption increases in proportion to the screen brightness). In FIG. 80B, the luminance of the screen 50 can be improved and the gradation display range is expanded, so that there is no deterioration in image quality. However, the increase in current consumption is large.
[1343]
If the number of gradations is proportional to the screen luminance, and the original image has 64 gradations, the increase in the number of gradations (expansion of dynamic range) = the increase in luminance. Therefore, power consumption (current consumption) increases. In order to solve this problem, the present invention combines either the reference current of FIG. 77 and the method of adjusting (controlling), the method of controlling the duty ratio of FIG. 78, or a combination of both.
[1344]
When the image data of one screen is large as a whole, the total sum of the image data becomes large. For example, since the white raster has 63 gradations as image data in the case of 64-gradation display, the number of pixels of the screen 50 × 63 is the total sum of the image data. In the white window display of 1/100 and the white display portion displaying white with the maximum luminance, the number of pixels of the screen 50 × (1/100) × 63 is the total sum of the image data.
[1345]
In the present invention, a value capable of predicting the total sum of image data or the amount of current consumption of the screen is obtained, and duty ratio control or reference current control is performed based on this sum or value.
Although the sum of the image data is obtained, the present invention is not limited to this. For example, an average level of one frame of image data may be obtained and used. In the case of an analog signal, the average level can be obtained by filtering the analog image signal with a capacitor. A direct current level may be extracted from an analog video signal through a filter, and the direct current level may be AD converted to be a sum of image data. In this case, the image data can also be referred to as an APL level.
Further, it is not necessary to add all the data of the image constituting the screen 50, and 1 / W (W is a value greater than 1) of the screen 50 may be picked up and extracted, and the sum of the picked up data may be obtained. .
[1346]
  In order to facilitate the description, the description will be made assuming that the sum of the image data is also obtained in the above case. In many cases, the sum of the image data coincides with the determination of the APL level of the image. The total sum of image data includes means for digital addition, but the sum of the above digital and analog image data.TheHereinafter, for ease of explanation, this is referred to as an APL level.
[1347]
  Since the APL level is 6 bits for each of RGB in the white raster, 63 (indicated as 63 as data representation because it is the 63rd gradation) × number of pixels (176 × in the case of the QCIF panel)3× 220). Therefore, the APL level is maximized. However, since the current consumed by the RGB EL elements 15 is different, it is preferable to calculate the image data separately for RGB.
[1348]
For this problem, the arithmetic circuit shown in FIG. 84 is used. In FIG. 84, reference numerals 841 and 842 are multipliers. Reference numeral 841 denotes a multiplier for weighting the emission luminance. R, G, and B have different visibility. The visibility in NTSC is R: G: B = 3: 6: 1. Accordingly, the R multiplier 841R performs a multiplication of 3 times on the R image data (Rdata). The G multiplier 841G multiplies G image data (Gdata) by 6 times. Further, the B multiplier 841B performs multiplication of 1 time on the B image data (Bdata).
[1349]
  The EL element 15 has different luminous efficiencies for RGB. Usually, the luminous efficiency of B is the worst. Next, G is bad. R has the best luminous efficiency. Therefore, the multiplier 842 weights the light emission efficiency. The R multiplier 842R multiplies the R image data (Rdata) by the R luminous efficiency. The G multiplier 842G multiplies the G image data (Gdata) by the G light emission efficiency. The B multiplier 842B multiplies the B image data (Bdata) by the B light emission efficiency.
  The results of multipliers 841 and 842 are added by adder 843 and accumulated in summation circuit 844. This sum circuit844Based on the result, the duty ratio control in FIG. 77 and the reference current control in FIG. 78 are performed.
[1350]
When the control is performed as shown in FIG. 84, the duty ratio control and the reference current control for the luminance signal (Y signal) can be performed. However, when a luminance signal (Y signal) is obtained and duty control or the like is performed, a problem may occur. For example, a blue back display. In the blue back display, the current consumed by the EL panel is relatively large. However, the display brightness is low. This is because the visibility of blue (B) is low. Therefore, the sum (APL level) of the luminance signal (Y signal) is calculated to be small, so that the duty control becomes high. Accordingly, flicker occurs.
[1351]
For this problem, the multiplier 841 may be used as through. This is because the sum (APL level) with respect to the current consumption is obtained. It is desirable to obtain the total APL level by taking both the sum (APL level) based on the luminance signal (Y signal) and the sum (APL level) based on the current consumption into consideration. Duty ratio control and reference current control are performed according to the total APL level.
[1352]
Since the black raster is the 0th gradation in the case of the 64 gradation display, the APL level is 0 and becomes the minimum value. In the driving method of FIG. 80, power consumption (current consumption) is proportional to image data. The image data does not need to count all the bits of the data constituting the screen 50. For example, when the image is expressed by 6 bits, only the upper bits (MSB) may be counted. In this case, the number of gradations is 32 or more and one count is made. Accordingly, the APL level changes depending on the image data constituting the screen 50.
[1353]
In the present invention, the reference current control of FIG. 78 or the duty ratio control of FIG. 77 is performed according to the magnitude of the obtained APL level.
In order to facilitate understanding, specific numerical values will be exemplified. However, this is virtual, and it is actually necessary to determine control data and a control method by experiment and image evaluation.
[1354]
The current that can flow maximum in the EL panel is 100 (mA). In the case of white raster display, the sum (APL level) is assumed to be 200 (no unit). When the APL level is 200, it is assumed that 200 (mA) flows through the EL panel when applied to the panel as it is. When the APL level is 0, the current flowing through the EL panel is 0 (mA). When the APL level is 100, the duty ratio is ½.
[1355]
Therefore, when the APL is 100 or more, it is necessary to make the limit 100 (mA) or less. Most simply, when the APL level is 200, the duty is (1/2) × (1/2) = 1/4, and when the APL level is 100, the duty is 1/2. When the APL level is 100 or more and 200 or less, the duty is controlled to be between 1/4 and 1/2. The duty ratio of 1/4 to 1/2 can be realized by controlling the number of gate signal lines 17b to be simultaneously selected by the gate driver circuit 12b on the EL selection side.
[1356]
  However, if only the APL level is considered and the duty ratio control is performed, the average brightness (APL) of the screen 50 according to the image.)ButChange and flicker occurs. In response to this problem, the APL level to be calculated is held for a period of at least 2 frames, preferably 10 frames, more preferably 60 frames or more, and calculation is performed during this period, and the duty ratio by duty ratio control is calculated by this APL level. calculate. In addition, it is preferable to perform duty ratio control by extracting image features such as the maximum luminance (MAX), minimum luminance (MIN), and luminance distribution state (SGM) of the screen 50. Needless to say, the above items also apply to the reference current control.
[1357]
It is also important to perform black stretching and white stretching by extracting image features. This may be performed in consideration of the maximum luminance (MAX), the minimum luminance (MIN), and the luminance distribution state (SGM). For example, in (a) of FIG. 81, the center data Kb of the image is distributed around 256 gradations, and the high luminance portion Kc is distributed around 320 gradations. Further, the low luminance portion Ka is distributed in the vicinity of 128 gradations.
[1358]
  FIG. 81B shows an example in which black extension and white extension are performed on the image shown in FIG. However, it is not necessary to perform black stretching and white stretching simultaneously, and only one of them may be performed. Further, the center portion of the image (Kb in FIG.)May be moved to a low gradation portion or a high gradation portion. Such appropriate movement information can be obtained from the APL level, the maximum luminance (MAX), the minimum luminance (MIN), and the luminance distribution state (SGM). However, it may be an empirical matter. This is because human visibility is affected. Therefore, it is necessary to repeat image evaluation and experiment. However, image processing such as black stretching or white stretching can be easily realized because a gamma curve can be obtained by calculation or from a lookup table. By performing the processing as shown in FIG. 81 (b), the image is sharpened and a good image display can be realized.
[1359]
Note that the brightness of the screen 50 is changed by duty ratio control as shown in FIG. FIG. 82A shows a driving method in which the display area 53 is continuously changed. The screen 50 brightness of (a2) of FIG. 82 is brighter than the screen 50 brightness of (a1) of FIG. The brightest is the state shown in FIG. The drive by duty ratio control in FIG. 82A is suitable for moving image display.
[1360]
FIG. 82B shows a driving method in which the display area 53 is divided and changed. In FIG. 82 (b1), display areas 53 are generated at two locations on the screen 50 as an example. 82 (b2) also generates display areas 53 at two locations on the screen 50 as in FIG. 82 (b1), but the number of pixel rows in the display area 53 increases at one of the two locations. (One pixel row is the display area 53 and the other is the two pixel row is the display area 53). 82 (b3) also generates display areas 53 at two locations on the screen 50 as in FIG. 82 (b2), but the pixel rows of the display area 53 increase at one of the two locations. (In both cases, two pixel rows are the display area 53). As described above, the duty ratio control may be performed by dispersing the display area 53. In general, FIG. 82 (b) is suitable for still image display.
[1361]
In FIG. 82 (b), the dispersion of the display area 53 is 2 dispersion. However, this is to facilitate drawing. Actually, the dispersion of the display area 53 is 3 dispersions or more.
[1362]
  FIG. 83 is a block diagram of the drive circuit of the present invention. Hereinafter, the drive circuit of the present invention will be described. In FIG. 83, a Y / UV video signal and a composite (COMP) video signal can be input from the outside. WhichofWhether to input a video signal is selected by the switch circuit 831.
[1363]
The video signal selected by the switch circuit 831 is decoded and AD converted by a decoder and an A / D circuit, and converted into digital RGB image data. RGB image data is 8 bits each. The RGB image data is subjected to gamma processing by a gamma circuit 834. At the same time, a luminance (Y) signal is obtained. The RGB image data is converted into 10-bit image data by gamma processing.
[1364]
After the gamma processing, the image data is subjected to FRC processing or error diffusion processing in the processing circuit 835. RGB image data is converted into 6 bits by FRC processing or error diffusion processing. This image data is subjected to AI processing or peak current processing in an AI processing circuit 836. In addition, the moving image detection circuit 837 performs moving image detection. At the same time, color management processing is performed by the color management circuit 838. The processing results of the AI processing circuit 836, the moving image detection circuit 837, and the color management circuit 838 are sent to the arithmetic circuit 839. The arithmetic processing circuit 839 converts the result into control arithmetic, duty ratio control, and reference current control data. The data is sent to the source driver circuit 14 and the gate driver circuit 12 as control data.
[1365]
The duty ratio control data is sent to the gate driver circuit 12b, and duty ratio control is performed. On the other hand, the reference current control data is sent to the source driver circuit 14 and the reference current control is performed. Image data that has been subjected to gamma correction and subjected to FRC or error diffusion processing is also sent to the source driver circuit 14.
[1366]
The image data conversion in (b) of FIG. 81 needs to be performed by gamma processing of the gamma circuit 834. The gamma circuit 834 performs gradation conversion using a multipoint broken gamma curve. The 256-gradation image data is converted to 1024 gradations by a multipoint broken gamma curve.
[1367]
The gamma circuit 834 performs gamma conversion with a multipoint broken gamma curve, but the present invention is not limited to this. As shown in FIG. 85, gamma conversion may be performed using a one-point broken gamma curve. Since the hardware scale constituting the one-point broken gamma curve is small, the cost of the control IC can be reduced.
[1368]
In FIG. 85, a is a polygonal line gamma conversion at the 32nd gradation. b is a polygonal line gamma conversion at the 64th gradation. c is a polygonal line gamma conversion at the 96th gradation. d is a polygonal line gamma conversion at the 128th gradation. If the image data is concentrated in high gradations, the gamma curve d in FIG. 85 is selected to increase the number of gradations in the high gradations. When the image data is concentrated in the low gradation, the gamma curve a in FIG. 85 is selected in order to increase the number of gradations in the low gradation. If the distribution of image data is dispersed, gamma curves such as b and c in FIG. 85 are selected. In the above embodiment, the gamma curve is selected. However, actually, the gamma curve is not selected because it is generated by calculation.
[1369]
The gamma curve is selected in consideration of the APL level, maximum luminance (MAX), minimum luminance (MIN), and luminance distribution state (SGM). Further, the duty ratio control and the reference current control are taken into consideration.
[1370]
  FIG. 86 shows an example of a multipoint broken gamma curve. If the image data is concentrated at high gradations, the number of gradations at high gradations is increased.86Select the n gamma curve. If the image data is concentrated in the low gradation, the number of gradations in the low gradation is increased.86Select the gamma curve of a. If the distribution of image data is distributed,86B-1 to n-1 gamma curves are selected. The gamma curve is selected in consideration of the APL level, maximum luminance (MAX), minimum luminance (MIN), and luminance distribution state (SGM). Further, the duty ratio control and the reference current control are taken into consideration.
[1371]
It is also effective to change the gamma curve selected in accordance with the environment used by the display panel (display device). In particular, in an EL display panel, a good image display can be realized indoors, but a low gradation portion cannot be seen outdoors. The EL display panel is for self light emission. Therefore, as shown in FIG. 87, the gamma curve may be changed. The gamma curve a is an indoor gamma curve. The gamma curve b is an outdoor gamma curve. The gamma curves a and b are switched by the user operating the switch. Alternatively, the brightness of outside light may be detected by a photo sensor and automatically switched. Although the gamma curve is switched, the present invention is not limited to this. It goes without saying that a gamma curve may be generated by calculation. In the case of the outdoors, the low gradation display portion cannot be seen due to the strong external light. Therefore, it is effective to select the gamma curve b that crushes the low gradation part.
[1372]
In the outdoors, it is also effective to generate a gamma curve as shown in FIG. In the gamma curve a, the output gradation is set to 0 until the 128th gradation. Gamma conversion is performed from 128 gradations. As described above, power consumption can be reduced by performing gamma conversion so that the low gradation portion is not displayed at all. Also, gamma conversion may be performed as in the gamma curve b in FIG. The gamma curve in FIG. 88 sets the output gradation to 0 up to the 128th gradation. For 128 or more, the output gradation is 512 or more. The gamma curve b in FIG. 88 has the effect of making the image display easier to see even outdoors by displaying a high gradation part and reducing the number of output gradations.
[1373]
In the drive system of the present invention, image brightness is controlled by duty ratio control and reference current control, and the dynamic range is expanded. In addition, high contrast display is realized.
[1374]
In the liquid crystal display panel, white display and black display are determined by the transmittance from the backlight. Even when the non-display area 52 is generated on the screen 50 as in the duty ratio drive of the present invention, the transmittance in black display is constant. On the contrary, when the non-display area 52 is generated, the white display luminance in one frame period is lowered, so that the display contrast is lowered.
[1375]
In the EL display panel, black display is a state in which the current flowing through the EL element 15 is zero. Therefore, even when the non-display area 52 is generated on the screen 50 as in the duty ratio driving of the present invention, the luminance of black display is zero. When the area of the non-display area 52 is increased, the white display luminance is lowered. However, since the luminance of black display is 0, the contrast is infinite. Therefore, the duty ratio driving is an optimal driving method for the EL display panel. The same applies to the reference current control. Even if the magnitude of the reference current is changed, the luminance of black display is zero. Increasing the reference current increases the white display luminance. Therefore, a good image display can be realized even in the reference current control.
[1376]
In the duty ratio control, the number of gradations is maintained in the entire gradation range, and the white balance is maintained in the entire gradation range. Further, the luminance change of the screen 50 can be changed by nearly 10 times by the duty ratio control. Further, since the change has a linear relationship with the duty ratio, it is easy to control. However, since the duty ratio control is N-times pulse driving, the magnitude of the current flowing through the EL element 15 is large, and the magnitude of the current flowing through the EL element is always large regardless of the brightness of the screen 50. There is a problem that the EL element 15 is easily deteriorated.
[1377]
  In the reference current control, when the screen brightness 50 is increased, the reference current amount is increased. Hence the screenBrightnessOnly when the current is high, the current flowing through the EL element 15 does not increase. Therefore, the EL element 15 is not easily deteriorated. The problem tends to be that it is difficult to maintain white balance when the reference current is changed.
[1378]
In the present invention, both reference current control and duty ratio control are used. When the screen 50 is close to white raster display, the reference current is fixed to a constant value, and only the duty ratio is controlled to change the display luminance or the like. When the screen 50 is close to black raster display, the duty ratio is fixed to a constant value, and only the reference current is controlled to change the display brightness.
[1379]
The duty ratio control is performed in a range where the data sum / maximum value is 1/10 or more and 1/1. More preferably, the data sum / maximum value is in the range of 1/100 to 1/1. In addition, the change in the reference current magnification (change in the output current of the unit transistor 484) is performed in a range where the data sum / maximum value is 1/10 to 1/1000. More preferably, the data sum / maximum value is in the range of 1/100 to 1/2000. It is preferable that the reference current control and the duty ratio control do not overlap. In FIG. 89, when the data sum / maximum value is 1/100 or less, the reference current magnification is changed, and when the data sum / maximum value is 1/100 or more, the duty ratio is changed. Therefore, there is no overlap.
[1380]
Here, for ease of explanation, the maximum duty ratio is assumed to be a duty ratio 1/1 and the minimum is assumed to be a duty ratio 1/8. The reference current is changed from 1 to 3 times. Further, the data sum means the sum of the data on the screen 50, and the maximum value (of the data sum) is assumed to be the sum of the image data in the white raster display at the maximum luminance. Needless to say, it is not necessary to use a duty ratio of 1/1. The duty ratio 1/1 is described as the maximum value. Needless to say, in the driving method of the present invention, the maximum duty ratio may be set to 210/220 or the like. 220 represents the number of pixel rows of the QCIF + display panel.
[1381]
The maximum duty ratio is preferably set to 1/1 and the minimum is preferably within 1/16. More preferably, the duty ratio is within 1/10. This is because the occurrence of flicker can be suppressed. The change range of the reference current is preferably within 4 times. More preferably, it is within 2.5 times. This is because if the multiple of the reference current is too large, the linearity of the reference current generating circuit is lost and white balance deviation occurs.
[1382]
Data sum / (maximum value of data sum) = 1/100 is, for example, 1/100 white window display. In a natural image, it means a state in which the data sum of pixels for image display can be converted to 1/100 of white raster display. Therefore, the display of one bright spot per 100 pixels also has a data sum / maximum value of 1/100.
[1383]
In the following description, the maximum value is an added value of white raster image data, but this is for ease of description. The maximum value is the maximum value generated in the image data addition processing or APL processing. Therefore, the data sum / maximum value is a ratio to the maximum value of the image data of the screen to be processed.
[1384]
Note that the data sum may be calculated based on current consumption or luminance. Here, for ease of explanation, it is assumed that luminance (image data) is added. In general, the method of adding luminance (image data) is easy to process, and the hardware scale of the controller IC can be reduced. Further, it is preferable because a flicker is not generated by duty ratio control and a wide dynamic range can be obtained.
[1385]
FIG. 89 shows an example in which the reference current control and the duty ratio control of the present invention are implemented. In FIG. 89, when the data sum / maximum value is 1/100 or less, the magnification of the reference current is changed to 3 times. The duty ratio is changed from 1/1 to 1/8 at 1/100 or more. Therefore, since the data sum / maximum value is 1/1 to 1/10000, the duty ratio control is 8 times, and the reference current control is 3 times, a change of 8 × 3 = 24 times is performed. Since both the reference current control and the duty ratio control change the screen brightness, a 24 times dynamic range is realized.
[1386]
When the data sum / maximum value is 1/1, the duty ratio is 1/8. Therefore, the display brightness is 1/8 of the maximum value. Since the data sum / maximum value is 1, it is a white raster display. That is, in white raster display, the display brightness is reduced to 1/8, the maximum. 1/8 of the screen 50 is the image display area 53, and the non-display area 52 occupies 7/8. In an image having a data sum / maximum value close to 1/1, most of the pixels 16 are in high gradation display. In terms of a histogram, the majority of data is distributed in the high gradation area of the histogram. In this image display, the image is crushed white and there is no sharpness. Therefore, a gamma curve n or a value close to n in FIG. 86 or the like is selected.
[1387]
When the data sum / maximum value is 1/100, the duty ratio is 1/1. The entire screen 50 is a display area 53. Therefore, N-fold pulse driving is not performed. The light emission luminance of the EL element 15 becomes the display luminance of the screen 50 as it is. Most of the image display is black display, and an image is partially displayed. In terms of an image, an image display with a data sum / maximum value of 1/100 is an image in which the moon appears in a dark night sky. Setting the duty ratio to 1/1 in this image means that the moon portion is displayed with a brightness 8 times the brightness of the white raster. Therefore, an image display with a wide dynamic range can be realized. Since the image is displayed in the 1/100 area, even if the luminance of the 1/100 area is increased by 8 times, the increase in power consumption is slight.
[1388]
In an image whose data sum / maximum value is close to 1/100, most of the pixels 16 are in low gradation display. In terms of a histogram, the majority of data is distributed in the low gradation area of the histogram. In this image display, the image is blacked out and there is no sharpness. For this reason, a gamma curve similar to b or b in FIG. 86 or the like is selected.
[1389]
  As described above, according to the driving method of the present invention, the duty ratio issmallAccordingly, the driving method increases the x multiplier of gamma. Duty ratio isbigAccordingly, this is a driving method for reducing the x multiplier of gamma.
[1390]
In FIG. 89, when the data sum / maximum value is 1/100 or less, the magnification of the reference current is changed to 3 times. When the data sum / maximum value is 1/100, the duty ratio is 1/1, and the screen brightness is increased by the duty ratio. As the data sum / maximum value becomes smaller than 1/100, the magnification of the reference current is increased. Therefore, the light emitting pixel 16 emits light with higher luminance. For example, a data sum / maximum value of 1/1000 is an image in which a star appears in a dark night sky when expressed as an image. Setting the duty ratio to 1/1 in this image means that the star portion is displayed with a brightness 8 × 2 = 16 times the brightness of the white raster. Therefore, an image display with a wide dynamic range can be realized. Since the image is displayed in the 1/1000 area, even if the luminance of the 1/1000 area is increased 16 times, the increase in power consumption is slight.
[1391]
The control of the reference current is that it is difficult to maintain white balance. However, in the image in which stars appear in the dark night sky, even if the white balance is shifted, the white balance shift is not visually recognized. From the above, the present invention in which the reference current control is performed in a range where the data sum / maximum value is very small is an appropriate driving method.
[1392]
When the data sum / maximum value is 1/1000, the duty ratio is 1/1. The entire screen 50 is a display area 53. Therefore, N-fold pulse driving is not performed. The light emission luminance of the EL element 15 becomes the display luminance of the screen 50 as it is. Most of the image display is black display, and an image is partially displayed.
[1393]
In an image having a data sum / maximum value close to 1/1000, most of the pixels 16 are in low gradation display. In terms of a histogram, the majority of data is distributed in the low gradation area of the histogram. In this image display, the image is blacked out and there is no sharpness. For this reason, a gamma curve similar to b or b in FIG. 86 or the like is selected.
[1394]
As described above, the driving method of the present invention is a driving method that increases the x multiplier of gamma as the reference current decreases. Further, this is a driving method in which the x multiplier of gamma is decreased as the reference current increases.
[1395]
In FIG. 89, the change in the reference current and the change in the duty ratio control are illustrated linearly. However, the present invention is not limited to this. As shown in FIG. 90, the reference current magnification control and duty ratio control may be curved. In FIGS. 89 and 90, since the data sum / maximum value on the horizontal axis is a logarithm, it is natural that the lines of the reference current control and the duty ratio control become curves. The relationship between the data sum / maximum value and the reference current magnification and the relationship between the data sum / maximum value and the duty ratio control are preferably set in accordance with the contents of the image data, the image display state, and the external environment.
[1396]
89 and 90 show an embodiment in which the RGB duty ratio control and the reference current control are made the same. The present invention is not limited to this. As shown in FIG. 91, the slope of the reference current magnification may be changed in RGB. In FIG. 91, the slope of the change in the reference current magnification for blue (B) is the largest, the slope of the change in the reference current magnification for green (G) is the next largest, and the change in the reference current magnification for red (R) is increased. The inclination is minimized. When the reference current is increased, the current flowing through the EL element 15 is also increased. The EL elements have different luminous efficiencies for RGB. Further, when the current flowing through the EL element 15 is increased, the light emission efficiency with respect to the applied current is degraded. In particular, the tendency is remarkable in B. Therefore, white balance cannot be achieved unless the reference current amount is adjusted in RGB. Therefore, as shown in FIG. 91, when the reference current magnification is increased (region where the current flowing through each RGB EL element 15 is large), it is effective to change the RGB reference current magnification so that white balance can be maintained. is there. The relationship between the data sum / maximum value and the reference current magnification and the relationship between the data sum / maximum value and the duty ratio control are preferably set in accordance with the contents of the image data, the image display state, and the external environment.
[1397]
FIG. 91 shows an example in which the reference current magnification is varied between RGB. In FIG. 92, the duty ratio control is also different. The sum of data / maximum value is 1/100 or more, B and G are the same, and the slope of R is reduced. G and R are 1/100 or less and the duty ratio is 1/1, while B is 1/100 or less and the duty ratio is 1/2. The above driving method can be implemented by the driving method described with reference to FIGS. If driven as described above, RGB white balance adjustment can be optimized. The relationship between the data sum / maximum value and the reference current magnification and the relationship between the data sum / maximum value and the duty ratio control are preferably set in accordance with the contents of the image data, the image display state, and the external environment. Further, it is preferable that the user can set or adjust freely.
[1398]
FIGS. 89 to 91 show a method of changing the reference current magnification and the duty ratio with the sum of data / maximum value being 1/100 as an example. The reference current magnification and the duty ratio are changed with the data sum / maximum value as a boundary, so that the region where the reference current magnification changes and the region where the duty ratio changes do not overlap. With this configuration, it is easy to maintain white balance. That is, the duty ratio is changed when the data sum / maximum value is 1/100 or more, and the reference current is changed when the data sum / maximum value is 1/100 or less. The region where the reference current magnification is changed is not overlapped with the region where the duty ratio is changed. This method is a characteristic method of the present invention.
[1399]
Although the duty ratio is changed when the data sum / maximum value is 1/100 or more and the reference current is changed when the data sum / maximum value is 1/100 or less, the reverse relationship may be used. That is, the duty ratio may be changed when the data sum / maximum value is 1/100 or less, and the reference current may be changed when the data sum / maximum value is 1/100 or more. Also, the duty ratio is changed when the data sum / maximum value is 1/10 or more, the reference current is changed when the data sum / maximum value is 1/100 or less, and the data sum / maximum value is 1/100 or more and 1/10 or less. Then, the reference current magnification and the duty ratio may be set to constant values.
[1400]
In some cases, the present invention is not limited to the above method. As shown in FIG. 93, the duty ratio may be changed when the data sum / maximum value is 1/100 or more, and the B reference current may be changed when the data sum / maximum value is 1/10 or less. The reference current change of B and the duty ratio of RGB are overlapped with each other.
[1401]
When a bright screen and a dark screen are alternately repeated at a high speed, flicker occurs when the duty ratio is changed according to the change. Therefore, when changing from a certain duty ratio to another duty ratio, it is preferable to provide a hysteresis (time delay). For example, assuming that the hysteresis period is 1 sec, the previous duty ratio is maintained even if the screen brightness is bright and dark but is repeated a plurality of times within the 1 sec period. That is, the duty ratio does not change.
[1402]
This hysteresis (time delay) time is called Wait time. Also, the duty ratio before the change is called the pre-change duty ratio, and the duty ratio after the change is called the post-change duty ratio.
[1403]
When the duty ratio before change is small and changes to another duty ratio, flicker is likely to occur due to the change. The state where the duty ratio before change is small is a state where the data sum of the screen 50 is small or a state where there are many black display portions on the screen 50. Therefore, it is considered that the screen 50 has a halftone display and high visibility. In addition, in a region where the duty ratio is small, the difference from the change duty tends to increase. Of course, when the duty ratio difference increases, control is performed using the OEV2 terminal. However, OEV2 control also has a limit. From the above, when the duty ratio before change is small, it is necessary to lengthen the wait time.
[1404]
When the pre-change duty ratio is changed to another duty ratio, flicker due to the change is less likely to occur. The state where the duty ratio before change is large is a state where the data sum of the screen 50 is large or a state where there are many white display portions on the screen 50. Therefore, it seems that the entire screen 50 is white and the visibility is low. From the above, when the duty ratio before change is large, the wait time may be short.
[1405]
The above relationship is illustrated in FIG. The horizontal axis is the duty ratio before change. The vertical axis represents the wait time (seconds). When the duty ratio is 1/16 or less, the wait time is increased to 3 seconds (sec). When the duty ratio is 1/16 or more and the duty ratio is 8/16 (= 1/2), the wait time is changed from 3 seconds to 2 seconds in accordance with the duty ratio. When the duty ratio is 8/16 or more and the duty ratio is 16/16 = 1/1, the duty ratio is changed from 2 seconds to 0 seconds according to the duty ratio.
[1406]
As described above, the duty ratio control of the present invention changes the wait time according to the duty ratio. When the duty ratio is small, the wait time is lengthened, and when the duty ratio is large, the wait time is shortened. That is, in the driving method in which at least the duty ratio is variable, the duty ratio before the first change is smaller than the duty ratio before the second change, and the wait time of the first before-change duty ratio is the second It is characterized in that it is set longer than the wait time of the duty ratio before change.
[1407]
In the above embodiment, the wait time is controlled or specified based on the duty ratio before change. However, the difference between the pre-change duty ratio and the post-change duty ratio is slight. Therefore, in the above-described embodiment, the pre-change duty ratio may be read as the post-change duty ratio.
[1408]
In the above embodiment, the pre-change duty ratio and the post-change duty ratio have been described. Needless to say, when the difference between the pre-change duty ratio and the post-change duty ratio is large, it is necessary to increase the wait time. Needless to say, when the difference in duty ratio is large, it is preferable to change to the duty ratio after change via the duty ratio in the intermediate state.
[1409]
The duty ratio control method of the present invention is a driving method that takes a longer wait time when the difference between the pre-change duty ratio and the post-change duty ratio is large. That is, this is a driving method in which the wait time is changed in accordance with the difference in duty ratio. Further, this is a driving method in which the wait time is increased when the difference in duty ratio is large.
[1410]
The duty ratio method of the present invention is a driving method characterized in that when the duty ratio difference is large, the duty ratio is changed to the changed duty ratio via the intermediate duty ratio.
[1411]
In the example of FIG. 94, the wait time with respect to the duty ratio is assumed to be the same for R (red), G (green), and B (blue). However, it goes without saying that the present invention may change the wait time in RGB as shown in FIG. This is because the visibility is different between RGB. By setting the wait time according to the visibility, a better image display can be realized.
[1412]
Data sum / (maximum value of data sum) = 1/100 is, for example, 1/100 white window display. In a natural image, it means a state in which the data sum of pixels for image display can be converted to 1/100 of white raster display. Therefore, the display of one bright spot per 100 pixels also has a data sum / maximum value of 1/100.
[1413]
In the following description, the maximum value is an added value of white raster image data, but this is for ease of description. The maximum value is the maximum value generated in the image data addition processing or APL processing. Therefore, the data sum / maximum value is a ratio to the maximum value of the image data of the screen to be processed.
[1414]
However, the sum of data does not require accurate addition of data for one screen. An addition value of one screen may be estimated (predicted) from an addition value of pixel data obtained by sampling one screen. The same applies to the maximum value. Also, predicted values or estimated values from a plurality of fields or a plurality of frames may be used. In addition to the addition of image data, the APL level of video data may be obtained by a low-pass filter circuit, and this APL level may be used as the data sum. The maximum value at this time is the maximum value of the APL level when video data having the maximum amplitude is input.
[1415]
Note that the data sum may be calculated based on the current consumption of the display panel or the luminance. Here, for ease of explanation, it is assumed that luminance (image data) is added. In general, the process of adding luminance (image data) is easy.
[1416]
In FIG. 197, the horizontal axis represents the data sum / maximum value. The maximum value is 1. The vertical axis represents the DUTY ratio. Data sum = maximum value (data sum / maximum value = 1) is the maximum white display state in all pixel rows. When the data sum / maximum value is small, the screen is dark or has a small image display area. At this time, the DUTY ratio is increased. Therefore, the luminance of the pixel displaying the image is high. For this reason, the dynamic range of the image is expanded and high-quality display is performed. When the data sum / maximum value is large (the maximum value is 1), the screen is a bright screen or a wide image display area. At this time, the DUTY ratio is reduced. Therefore, the luminance of the pixel displaying the image is low. Therefore, power consumption can be reduced. Since the amount of light emitted from the screen is large, the image does not feel dark.
[1417]
In FIG. 197, the DUTY ratio value reached when the data sum / maximum value is 1.0 is changed. For example, when the duty ratio is 1/2, 1/2 of the screen is in the image display state. Therefore, the image is bright. When DUTY ratio = 1/8, 1/8 of the screen is in the image display state. Therefore, the brightness is 1/4 compared with DUTY ratio = 1/2.
[1418]
In the driving method of the present invention, the image luminance is controlled by the data sum or the like, and the dynamic range is expanded. In addition, high contrast display is realized.
[1419]
In the liquid crystal display panel, white display and black display are determined by the transmittance from the backlight. Even when a non-display area is generated on the screen as in the driving method of the present invention, the transmittance in black display is constant. On the contrary, when the non-display area is generated, the white display luminance in one frame period is lowered, so that the display contrast is lowered.
[1420]
In the EL display panel, black display is a state in which the current flowing through the EL element is zero. Therefore, even when a non-display area is generated on the screen as in the driving method of the present invention, the luminance of black display is zero. When the area of the non-display area is increased, the white display luminance is lowered. However, since the luminance of black display is 0, the contrast is infinite. Therefore, a good image display can be realized.
[1422]
In the driving method of the present invention, the number of gradations is maintained over the entire gradation range, and white balance is maintained over the entire gradation range. Further, the luminance change of the screen can be changed nearly 10 times by the DUTY ratio control. Further, since the change has a linear relationship with the DUTY ratio, the control is easy. Further, R, G, and B can be changed at the same ratio. Therefore, the white balance is maintained at any duty ratio.
[1422]
The relationship between the data sum / maximum value and the DUTY ratio is preferably set according to the content of the image data, the image display state, and the external environment. Further, it is preferable that the user can set or adjust freely.
[1423]
The above switching operation displays the display screen very brightly when the power of a mobile phone, a monitor, etc. is turned on. After a certain period of time, the display brightness is reduced to save power. Use. It can also be used as a function for setting the brightness desired by the user. For example, when outdoors, the screen is very bright. This is because the surroundings are bright outdoors and the screen cannot be seen at all. In other words, the curve a in FIG. 197 is selected outdoors. However, if display is continued with high luminance, the EL element deteriorates rapidly. For this reason, when it is very bright, it is configured to return to normal luminance in a short time. For example, normally, the curve of c is selected. Furthermore, when displaying with high brightness, the display brightness can be increased by the user pressing the button.
[1424]
Therefore, it is preferable that the user can be switched with a button, can be automatically changed in a setting mode, or can be switched automatically by detecting the brightness of external light. Further, it is preferable that the display brightness is set to 50%, 60%, and 80% and can be set by the user. Further, it is preferable that the duty ratio curve, inclination, etc. are rewritten by an external microcomputer or the like. Further, it is preferable that one can be selected from a plurality of stored duty curves.
[1425]
Needless to say, it is preferable to select the DUTY ratio curve in consideration of the APL level, maximum luminance (MAX), minimum luminance (MIN), and luminance distribution state (SGM).
[1426]
As described above, for example, a is an outdoor curve. c is an indoor curve. b is a curve for an intermediate state between indoor and outdoor. Switching between the curves a, b, and c is performed by the user operating the switch. Alternatively, the brightness of outside light may be detected by a photo sensor and automatically switched. Although the gamma curve is switched, the present invention is not limited to this. It goes without saying that a gamma curve may be generated by calculation.
[1427]
The DUTY ratio in FIG. 197 is a straight line, but is not limited to this. As shown in FIG. 198, it may be a one-point folding curve.
[1428]
When the image data sum is small, the c curve in FIG. 198 is selected. The effect of reducing power consumption is exhibited. There is no degradation of image display. When the image data sum is large, the a curve is selected. The image display is not bright and the occurrence of flicker is reduced.
[1429]
In another embodiment of the present invention, the DUTY ratio is changed in a range where the data sum / maximum value is 1/10 or more (see FIG. 199). This is because an image whose data sum / maximum value is close to 1 is rarely generated, and when the data sum / maximum value is up to 1 and the DUTY ratio is changed as shown in FIG. More preferably, the change of the DUTY ratio is performed in a range where the data sum / maximum value is 8/10 or more.
[1430]
In FIG. 199, when the data sum / maximum value is 0.9 or less, the DUTY ratio is changed from 1 to 1/5. Therefore, a dynamic range of 5 times is realized.
[1431]
When the data sum / maximum value is 0.9 or more, it is 1/5. Therefore, the display brightness is 1/5 of the maximum value. Data sum / maximum value = 1 is white raster display. That is, in white raster display, the display brightness is reduced to 1/5, which is the maximum.
[1432]
When the data sum / maximum value is 0.1 or less, the DUTY ratio is 1/1. 1/10 of the screen is a display area. The light emission luminance of the EL element becomes the display luminance of the pixel as it is. Most of the image display is black display, and an image is partially displayed. In terms of an image, an image display with a data sum / maximum value of 0.1 or less is an image in which the moon appears in a dark night sky. Setting the DUTY ratio to 1/1 in this image means that the moon portion is displayed with a luminance five times that of the white raster. Therefore, an image display with a wide dynamic range can be realized. Since the image is displayed in the 1/10 area, even if the brightness of the 1/10 area is increased 5 times, the increase in power consumption is slight.
[1433]
In an image having a data sum / maximum value close to 0, most of the pixels are in low gradation display. In terms of a histogram, the majority of data is distributed in the low gradation area of the histogram. In this image display, the image is blacked out and there is no sharpness. Therefore, the dynamic range of the black display part is widened by controlling the gamma curve.
[1434]
In the above embodiment, when the data sum / maximum value is 0, the DUTY ratio is set to 1. However, the present invention is not limited to this. Needless to say, the DUTY ratio may be smaller than 1 as shown in FIG. Further, the curve of the DUTY ratio may be a curve as shown in FIG.
[1435]
As shown in FIG. 202, the DUTY ratio curve may be changed for red (R), green (G), and blue (B) pixels. In FIG. 202, the slope of the blue (B) DUTY ratio change is the largest, the slope of the green (G) DUTY ratio change is the next largest, and the slope of the red (R) DUTY ratio change is the largest. It is small. If driven as described above, RGB white balance adjustment can be optimized. The relationship between the data sum / maximum value and the DUTY ratio is preferably set according to the content of the image data, the image display state, and the external environment. Further, it is preferable that the user can set or adjust freely.
[1436]
When a bright screen and a dark screen are alternately repeated at a high speed, flicker occurs when the DUTY ratio is changed according to the change. Therefore, when changing from one DUTY ratio to another DUTY ratio, it is preferable to change by providing hysteresis (time delay) as shown in FIG. For example, assuming that the hysteresis period is 1 sec, the previous DUTY ratio is maintained even if the screen brightness is bright and dark but is repeated a plurality of times within the 1 sec period. That is, the DUTY ratio does not change.
This hysteresis (time delay) time is called Wait time. Further, the DUTY ratio before the change is called a pre-change DUTY ratio, and the DUTY ratio after the change is called a post-change DUTY ratio.
[1437]
When the pre-change DUTY ratio is changed to another DUTY ratio, flicker is likely to occur due to the change. The state where the DUTY ratio before change is small is a state where the data sum of the screen is small or a state where there are many black display portions on the screen.
[1438]
Therefore, it seems that the screen is halftone and the visibility is high. In addition, in a region where the DUTY ratio is small, the difference from the change DUTY ratio tends to increase. Of course, when the difference in DUTY ratio becomes large, control is performed using OEV. However, OEV control also has a limit. From the above, when the DUTY ratio before change is small, it is necessary to lengthen the wait time.
[1439]
When the pre-change DUTY ratio is changed to another DUTY ratio, flicker due to the change is less likely to occur. The state where the DUTY ratio before change is large is a state where the data sum of the screen is large or a state where there are many white display portions on the screen. Therefore, it seems that the entire screen is white and the visibility is low. From the above, when the DUTY ratio before change is large, the wait time may be short.
[1440]
The above relationship is illustrated in FIG. The horizontal axis is the pre-change DUTY ratio. The vertical axis represents the wait time (seconds). When the DUTY ratio is 1/16 or less, the wait time is increased to 3 seconds (sec). When the DUTY ratio is 1/16 or more and the DUTY ratio is 8/16 (= 1/2), the wait time is changed from 3 seconds to 2 seconds in accordance with the DUTY ratio. When the DUTY ratio is 8/16 or more and the DUTY ratio is 16/16 = 1/1, the DUTY ratio is changed from 2 seconds to 0 seconds in accordance with the DUTY ratio.
[1441]
As described above, the DUTY ratio control of the present invention changes the wait time according to the DUTY ratio. When the DUTY ratio is small, the wait time is lengthened, and when the DUTY ratio is large, the wait time is shortened. That is, in the driving method in which at least the DUTY ratio is variable, the DUTY ratio before the first change is smaller than the DUTY ratio before the second change, and the wait time of the first DUTY ratio before the second change is The DUTY ratio before change is set longer than the wait time.
[1442]
In the above embodiment, the wait time is controlled or specified based on the pre-change DUTY ratio. However, the difference between the pre-change DUTY ratio and the post-change DUTY ratio is slight. Therefore, the before-change DUTY ratio may be read as the after-change DUTY ratio in the above-described embodiment.
[1443]
Further, in the above embodiment, the description has been made based on the pre-change DUTY ratio and the post-change DUTY ratio. Needless to say, when the difference between the pre-change DUTY ratio and the post-change DUTY ratio is large, it is necessary to increase the wait time. Needless to say, when the difference in the DUTY ratio is large, it is preferable to change to the post-change DUTY ratio via the intermediate DUTY ratio.
[1444]
The DUTY ratio control method of the present invention is a driving method that takes a longer wait time when the difference between the pre-change DUTY ratio and the post-change DUTY ratio is large. That is, this is a driving method in which the wait time is changed in accordance with the difference in the DUTY ratio. Further, this is a driving method in which the wait time is lengthened when the difference in the DUTY ratio is large.
[1445]
The DUTY ratio method of the present invention is a driving method characterized in that when the difference in DUTY ratio is large, the DUTY ratio is changed to the post-change DUTY ratio via the intermediate DUTY ratio.
[1446]
In the above embodiments, the wait time for the DUTY ratio is described as being the same for R (red), G (green), and B (blue). However, needless to say, the present invention may change the wait time by R, G, and B. This is because the visibility is different between RGB. By setting the wait time according to the visibility, a better image display can be realized.
[1447]
The above embodiment is an embodiment related to duty ratio control. It is preferable to set the wait time for the reference current control. FIG. 96 shows an example.
[1448]
When the reference current is small, the screen 50 is dark, and when the reference current is large, the screen 50 is bright. That is, when the reference current magnification is small, it can be rephrased as a halftone display state. When the reference current magnification is high, the image display state is high brightness. Therefore, when the reference current magnification is low, the wait time needs to be increased because the visibility to changes is high. On the other hand, when the reference current magnification is high, the wait time may be short because the visibility to the change is low. Therefore, as shown in FIG. 96, the Wait time with respect to the reference current magnification may be set.
[1449]
It is desirable that the reference current magnification with respect to the data sum can be changed from the outside of the panel module. Changes from the outside may be written into the memory of the panel module control circuit 839 (see FIGS. 83 and 205 and the description thereof) using a microcomputer or the like.
[1450]
FIG. 224 is an explanatory diagram of a method of changing the reference current magnification. The horizontal axis of FIG. 224 is an address number. Address numbers are from 0 to 511, and are 9 bits. Further, although the horizontal axis is an address, it may be considered that it corresponds to the data sum / maximum value described with reference to FIGS. That is, when data sum = maximum value, data sum / maximum value = 1. It may be considered that this state corresponds to address 511. When data sum × 2 = maximum value, data sum / maximum value = ½. It may be considered that this state corresponds to address 255.
[1451]
Data (reference current magnification) for each address is sequentially rewritten by data values applied to the address bus and the data bus as shown in FIG.
[1452]
The reference current on the vertical axis varies depending on the memory state. A solid line a shows a case where the reference current magnification is not changed to 1 regardless of the address value. In the dotted line b, when the data sum is large (the entire screen 50 is close to white display), the reference current is not changed from 1, and when the data sum is small (whether the screen 50 is close to black display or display In a state where there are few pixels), the change in the reference current is increased. Therefore, the dynamic range of image display is expanded. In the d-dot chain line c-line, the change is made constant when the data sum is large to small.
[1453]
As described above, the applicability of the driving method of the present invention is expanded by rewriting the reference current magnification. In FIG. 224, the data for each address is rewritten so that the lines become a, b, and c. However, the present invention is not limited to this. ) May be stored and controlled to be selected and switched.
[1454]
FIG. 226 is an explanatory diagram of a method for changing the duty ratio. The horizontal axis in FIG. 226 is an address number. Address numbers range from 0 to 255, and are 8 bits. Further, although the horizontal axis is an address, it may be considered that it corresponds to the data sum / maximum value described with reference to FIGS. That is, when data sum = maximum value, data sum / maximum value = 1. It may be considered that this state corresponds to address 255. When data sum × 2 = maximum value, data sum / maximum value = ½. It may be considered that this state corresponds to address 127. The data (duty ratio) for each address is sequentially rewritten by data values applied to the address bus and the data bus as shown in FIG. The reference current on the vertical axis varies depending on the memory state. A solid line a shows a case where the duty ratio is not changed to 1 regardless of the address value. In the dotted line b, when the data sum is large (when the entire screen 50 is close to white display), the duty ratio is not changed from 0.2, and when the data sum is small (whether the screen 50 is close to black display) In the state where the number of displayed pixels is small), the change in the duty ratio is increased. Therefore, the dynamic range of image display is expanded. In the d-dot chain line c-line, the change is made constant when the data sum is large to small.
[1455]
As described above, the applicability of the driving method of the present invention is expanded by rewriting the duty ratio. In FIG. 226, the data for each address is rewritten so as to be the a, b, and c lines. However, the present invention is not limited to this. ) May be stored and controlled to be selected and switched. Needless to say, FIG. 224 and FIG. 226 may be implemented in combination with each other.
[1456]
In the present invention, data sum or APL is calculated (detected), and duty ratio control and reference current control are performed based on these values. FIG. 98 is a flowchart for obtaining the duty ratio and the reference current magnification.
[1457]
As shown in FIG. 98, a rough APL is calculated for the input image data (a temporary APL is calculated). The value of the reference current and the reference current magnification are determined from this APL. The determined reference current and reference current magnification are converted into electronic volume data and applied to the source driver circuit 14.
[1458]
  On the other hand, image data is input to a gamma processing circuit, and gamma characteristics are determined. APL is calculated from the image data processed with the gamma characteristic. The duty ratio is determined from the calculated APL. Next, the duty pattern is determined based on whether the image is a moving image or a still image. The duty pattern is a distribution state of the non-display area 52 and the display area 53. In the case of a moving image, the non-display area 52 is inserted at a time. In the case of a still image, the non-display area 52 is dispersed and inserted. Therefore, for still images, NonThe display area 52 is dispersed and converted into a duty pattern to be inserted. In the case of a moving image, the non-display area 52 is converted into a duty pattern to be inserted at once. The converted pattern is applied as a start pulse ST (see FIG. 6) of the gate driver circuit 12b.
[1459]
  94 and FIG. 95 explain that the wait time is controlled according to the duty ratio, and FIGS. 89 to 93 explain that the duty ratio control is performed according to the data sum. FIG. 103 further shows duty ratio control and wait time.controlIt is a detailed explanatory view for performing. However, for ease of explanation, the time factor and the like are reduced and expressed.
[1460]
In FIG. 103, the top row shows frame (field) numbers. The second row shows the APL level (data sum corresponds). The third row shows the corresponding duty ratio calculated from the APL level. The bottom row shows a duty ratio (processing duty ratio) obtained by correcting the wait time. That is, according to the APL level of each frame, the corresponding duty ratio (third stage) is 8/64 → 9/64 → 9/64 → 10/64 → 9/64 → 10/64 → 11/64 → 11/64 → 12 / 64 → 14/64 →...
[1461]
For the corresponding duty ratio, the processing duty ratio is 8/64 → 8/64 → 9/64 → 9/64 → 9/64 → 10/64 → 10/64 → 11/64 → considering the wait time. 12/64 → 12/64 →...
[1462]
In FIG. 103, the corresponding duty ratio is corrected based on the wait time. In addition, the processing duty ratio is an integer for the numerator (FIG. 107 compares the numerator with a decimal point). In FIG. 103, the driving is performed so that the change of the duty ratio is smooth and the flicker is hardly generated. In FIG. 103, the corresponding duty ratios are changed to 9/64, 10/64, and 9/64 in frames 3, 4, and 5, but the wait time control is performed, and the processing duty ratio is 9/64, 9 / 64 and 9/64 (corrected portions are indicated by dotted lines in frame 4). In FIG. 103, the corresponding duty ratios are changed to 12/64, 14/64, and 11/64 in frames 9, 10, and 11, but the wait time control is performed, and the processing duty ratio is 12/64. , 12/64, and 11/64 (corrected portions are indicated by dotted lines in the frame 10). By performing the wait time control as described above, the duty ratio control is provided with hysteresis (time delay or low-pass filter) so that the duty ratio does not change even if the APL level changes rapidly.
[1463]
The duty ratio control as described above need not be completed in one frame or one field. Duty ratio control may be performed in a period of several fields (several frames). In this case, the duty ratio is an average value of several fields (several frames) as the duty ratio. Even when the duty ratio control is performed in several fields (several frames), the period of several fields (several frames) is preferably 6 fields (six frames) or less. This is because flicker may occur when the value exceeds this value. Also, the number field (several frames) is not an integer, and may be 2.5 frames (2.5 fields). That is, it is not limited to a field (frame) unit.
[1464]
FIG. 104 shows an example in which the duty ratio control is performed in several fields (several frames). FIG. 104 illustrates the concept when several fields (several frames) are performed. M is a length for performing duty ratio control. If one field (one frame) has 256 pixel rows, M = 1024 corresponds to four fields (4 frames). That is, FIG. 104 shows an embodiment in which the duty ratio control is performed with 4 fields (4 frames).
[1465]
M indicates a data string held in the shift register 61b of the virtual gate driver circuit 12b (see FIG. 6). The retained data string retains data (on / off voltage) indicating whether the voltage applied to the gate signal line 17b is an off voltage or an on voltage. The average value of the retained data string indicates the duty ratio. In FIG. 104, it is needless to say that M = N. In addition, it goes without saying that the duty ratio control may be performed in a relationship of M <N in some cases.
[1466]
For example, in the retained data string of M = 1024, if the on-voltage data is 256 and the off-voltage is 768, the duty ratio is 256/1024 = 1/4. Note that the distribution state of the on-voltage data is held together when the display image is a moving image, and the distribution state of the on-voltage data is held dispersedly when the display image is a still image.
[1467]
  That is, the on / off voltage data string is virtually applied sequentially to the gate signal line 17b of the EL display panel. The EL display panel is controlled by the duty ratio by sequentially applying the on / off voltage, and at a predetermined brightness.displayIs done.
[1468]
FIG. 105 is a block diagram of a circuit configuration for realizing the duty ratio control of FIG. First, the video signal (image data) is converted into a luminance signal by the Y conversion circuit 1051. Next, the APL operation circuit 1052 determines the APL level (data sum or data sum / maximum value). Based on this APL level, the duty ratio is calculated in units of fields (frames), and the result is stored in the stack 1053. The stack circuit 1053 has a first in first out configuration. Note that the duty ratio is corrected by the wait time control and stored in the stack circuit 1053. The duty ratio data stored in the stack 1053 is applied as an ST pulse (see FIG. 6) of the shift register 61b by the parallel / serial conversion (P / S) circuit 1054, and depends on the order of the applied data. The gate driver circuit 12b outputs the on / off voltage of the gate signal line 17b.
[1469]
In the above embodiment, the duty ratio control is performed in the field or frame. However, the present invention is not limited to this. For example, one frame = 4 fields, and duty ratio control may be performed in units of a plurality of fields. By performing duty ratio control using a plurality of fields, it is possible to realize a smooth image display in which no flicker occurs.
[1470]
In FIG. 106, 1-1 indicates the first field of one frame, 1-2 indicates the second field of one frame, 1-3 indicates the third field of one frame, and 1-4 indicates This means the fourth field of one frame. 2-1 means the first field of two frames.
[1471]
When the duty ratio is changed from 128/1024 to 132/1024, it is 128/1024 for 1-1, 129/1024 for 1-2, 130/1024 for 1-3, 131/1024 for 1-4, 2- 1 is changed to 132/1024. Due to the above change, it gradually changes from 128/1024 to 132/1024.
[1472]
When the duty ratio is changed from 128/1024 to 130/1024, 128/1024 for 1-1, 128/1024 for 1-2, 129/1024 for 1-3, 129/1024 for 1-4, 2- 1 is changed to 130/1024. Due to the above changes, the speed gradually changes from 128/1024 to 130/1024.
[1473]
When the duty ratio is changed from 128/1024 to 136/1024, 128/1024 for 1-1, 130/1024 for 1-2, 132/1024 for 1-3, 134/1024 for 1-4, 2- 1 is changed to 136/1024. Due to the above changes, the speed gradually changes from 128/1024 to 136/1024.
[1474]
  The numerator of the duty ratio in the field (frame) duty ratio control need not be an integer. For example, as shown in FIG. 107, control may be performed so that the number is after the decimal point. The numerator can be easily achieved by controlling the OEV2 terminal. Further, by using the average duty ratio in a plurality of frames (fields), the duty ratio can be divided.ChildTheApparently,After the decimal pointIncan do. Conversely, a fractional part may be generated in the denominator of the duty ratio. In FIG. 107, the numerator is set to a decimal point such as 30.8 or 31.2. It should be noted that the decimal point can be eliminated by setting the denominator and numerator to a large integer greater than a certain value.
[1475]
The duty ratio pattern is changed between the moving image and the still image. If the duty ratio pattern is suddenly changed, an image change may be recognized. Also, flicker may occur. This problem occurs due to the difference between the duty ratio of the moving image and the duty ratio of the still image. In the moving image, a duty pattern for inserting the non-display area 52 at once is used. For a still image, a duty pattern in which the non-display area 52 is inserted in a distributed manner is used. The ratio of the area of the non-display area 52 / the screen area 50 is the duty ratio. However, even if the duty ratio is the same, human visibility varies depending on the dispersion state of the non-display area 52. This is thought to be due to the dependence on human video response.
[1476]
In the intermediate moving image, the non-display area 52 has a distribution state that is intermediate between the distribution state of the moving image and the distribution state of the still image. Note that a plurality of intermediate moving images may be prepared, and selected from a plurality of intermediate moving images corresponding to the moving image state or the still image state before the change. Examples of the plurality of intermediate moving image states include a configuration in which the non-display area is distributed in a manner close to that of the moving image display, and the non-display area 52 is divided into three parts. On the contrary, a state in which the non-display area is dispersed in a large number like a still image is illustrated.
[1477]
Some still images are bright and some are dark. The same applies to videos. Therefore, it is only necessary to determine which intermediate moving image state is to be changed according to the state before the change. In some cases, a moving image may be transferred to a still image without going through an intermediate moving image. You may transfer from a still image to a moving image without going through an intermediate moving image. For example, an image with low brightness on the screen 50 does not feel strange even if the moving image display and the still image display move directly. Further, the display state may be shifted via a plurality of intermediate moving image displays. For example, the state may be changed from the duty state of the moving image display to the duty ratio state of the intermediate moving image display 1 and further to the duty state of the intermediate moving image display 2 and then to the duty state of the still image display.
[1478]
As shown in FIG. 108, when moving from the moving image display to the still image display, the intermediate moving image state is passed. Also, the display is shifted from the still image display to the moving image display via the intermediate moving image display. It is preferable to set a wait time for the transition time of each state.
[1479]
FIG. 110 shows the duty ratio and the number of non-display area dispersions when moving a moving image, a still image, and an intermediate moving image. In FIG. 110, when the moving image still image level is 0, the image display is the moving image level, and when it is 1, the image display is in the quasi-moving image (intermediate moving image) state. In the case of 2, it indicates that the image display is in a still image state.
[1480]
The number of distributions is the number of divisions of the non-display area 52. 1 indicates that the non-display area 52 is collectively inserted into the screen. 30 indicates that the non-display area 52 is divided into 30 and inserted. Similarly, 50 indicates that the non-display area 52 is divided into 50 and inserted. As described before, the duty ratio shows the luminance reduction rate of white display. That is, a duty ratio of 1/2 indicates that the display state is 1/2 of the maximum white luminance.
[1481]
As illustrated in FIG. 110, the moving image still image level is changed through an intermediate moving image (quasi moving image) state when moving from a moving image to a still image and when moving from a still image to a moving image.
[1482]
  As shown in FIG. 111, it is preferable to provide a wait time for the time from the moving image to the still image. The wait time may be determined according to the moving image ratio. Figure111The number of different data on the horizontal axis indicates the ratio of moving images detected by moving image detection between a certain frame and the next frame. That is, the horizontal axis represents the ratio of pixels that are calculated between frames and that have different image data. Therefore, the larger the numerical value, the closer to the moving image display. Figure111Then, the closer to the moving image display, the longer the wait time is secured.
[1483]
Further, in order to describe the duty ratio control, the power supply circuit of the organic EL display device of the present invention will be described. FIG. 112 is a block diagram of the power supply circuit of the present invention. Reference numeral 1122 denotes a control circuit. The midpoint potential of the resistors 1125a and 1125b is controlled, and the gate signal of the transistor 1126 is output. The power source Vpc is applied to the primary side of the transformer 1121, and the primary side current is transmitted to the secondary side by the on / off control of the transistor 1126. 1123 is a rectifier diode, and 1124 is a smoothing capacitor.
[1484]
FIG. 201 is a block diagram of the power supply circuit of the present invention. Reference numeral 1122 denotes a control circuit. By applying on / off control to the transistor 1775, the current flowing through the coil 1771 and the drive waveform are changed, and the charge charged in the capacitor 1774 is controlled. The midpoint potential of the resistors 1125a and 1125b is controlled, and the gate signal of the transistor 1126 is output. The Vdd voltage (anode voltage) can be changed by changing the resistance value of the resistor. Since the voltage is generated by the coil (transformer) 1771, the cathode voltage (Vss) also changes due to the change in the anode voltage. That is, as the anode voltage (Vdd) increases, the cathode voltage (Vss) also shifts.
[1485]
For example, consider a case where the anode voltage (Vdd) is 6 (V) and the cathode voltage (Vss) is −6 (V). When the anode voltage (Vdd) is changed to 9 (V) by 3 (V), the cathode voltage (Vss) is shifted from −6 (V) to −3 (V). This is an effect that the input side and the output side of the transformer 1121 are insulated.
[1486]
The current-driven organic EL display panel has the following characteristics from the viewpoint of potential. In the pixel configuration of the present invention, as described in FIG. 1 and the like, the driving transistor 11a is a P-channel transistor. The unit transistor 484 of the source driver 14 that generates the program current is an N-channel transistor. With this configuration, the program current is a sink current (sink current) that flows from the pixel 16 toward the source driver IC (circuit) 14. Therefore, the potential operation is performed with the anode (Vdd) as the origin. That is, since the program to the pixel 16 is a current, the potential of the source driver IC (circuit) 14 may be any as long as a driving voltage margin is secured.
[1487]
The control circuit 1122 is controlled by a logic circuit such as a controller. Therefore, it is necessary to match the grounds of the control circuit 1122 and the logic circuit. However, the transformer 1121 is separated from the input side and the output side. The current program type source driver IC (circuit) 14 acts on the output side and operates based on the anode potential (Vdd). Therefore, the ground of the source driver IC (circuit) 14 does not need to match the ground of the control circuit 1122 and the logic circuit. At this point, the source driver IC 14 is of a current programming system, and generates an anode voltage (Vss) using the transformer 1122 (if further applied, generates a cathode voltage (Vss) based on the anode voltage (Vdd)). The combination that the driving transistor 11a of the pixel 16 is a P channel exhibits a synergistic effect.
[1488]
The organic EL display panel operates with absolute values of the anode (Vdd) and the cathode (Vss). For example, when Vdd = 6 (V) and Vss = −6 (V), the operation is performed at 6 − (− 6) = 12 (V). In the power supply circuit using the transformer 1121 of the present invention in FIG. 112, the cathode voltage (Vss) changes with the anode (Vdd) as a reference. The anode voltage (Vdd) is the reference position of the program current of the current-driven source driver IC (circuit) 14 of the present invention. That is, it operates with the anode voltage (Vdd) as the origin. Conversely, the potential or control of the cathode voltage (Vss) may be rough. Also for this reason, the power supply circuit of the present invention using the transformer of FIG. 112, the organic EL panel having the current-driven pixel 16 configuration, and the current-programmed source driver IC (circuit) 14 exhibit a synergistic effect. I understand that. It is also important that the cathode voltage shifts due to changes in the anode voltage.
[1489]
In the organic EL panel, the current Idd that flows from the anode Vdd into the driving transistor 11a and the current Iss that flows from the EL element 15 to the cathode Vss substantially match. That is, there is a relationship of Idd = Iss. Actually, Idd> Iss, but since this difference is the program current of the source driver IC (circuit) 14, it is negligible and can be ignored. 112 and 177, the current output from the anode Vdd and the current drawn from the cathode Vss are identical in configuration. Also in this respect, the synergistic effect of the combination of the organic EL panel and the power supply circuit using the transformer 1121 of the present invention is great.
[1490]
Needless to say, when the driving transistor 11a of the pixel 16 is an N-channel transistor, the same effect can be obtained if the unit transistor 484 of the source driver IC (circuit) 14 is a P-channel transistor.
[1491]
It is efficient to generate the Vgh voltage, Vgl voltage of the gate driver circuit 12, the power supply voltage of the source driver circuit, etc. from the cathode voltage (Vss) or (and) the anode voltage (Vdd). Further, the transformer 1121 may have a four-terminal configuration of two input terminals and two output terminals, or as shown in FIG. 112, it is desirable that the input two terminals and the output be a middle point and have three terminals. The transformer 1121 includes a single-winding transformer (coil).
[1492]
The power source Vpc is applied to the primary side of the transformer 1121, and the primary side current is transmitted to the secondary side by the on / off control of the transistor 1126. 1123 is a rectifier diode, and 1124 is a smoothing capacitor.
[1493]
The output voltage of the anode voltage Vdd is adjusted by the resistor 1125b. Vss is a cathode voltage. As shown in FIG. 178, the cathode voltage Vss is configured to select and output two voltages. Selection is performed with the switch 1781. The generation of two voltages (−9 (V) and −6 (V) in FIG. 178) as the cathode voltage can be easily generated by providing an intermediate tap on the output side of the transformer 1121. Further, two windings for −9 (V) and −6 (V) are formed on the output side of the transformer 1121, and it can be generated more easily by selecting one of these windings. This is also an excellent point of the present invention. In addition, FIG. 178 is characterized in that the cathode voltage (Vss) is switched. If the anode is changed as the potential origin, the circuit configuration becomes complicated and the cost increases. On the other hand, the cathode voltage (Vss) does not affect the image display even if a potential error of about 10% occurs (insensitive). Therefore, it is an excellent feature of the present invention that the cathode voltage is set based on the anode voltage and the cathode voltage (Vss) is changed in accordance with the temperature characteristics of the panel. In addition, the transformer 1121 has many advantages in that the cathode voltage and the anode voltage can be easily changed by changing the ratio between the number of input windings and the number of output windings. It is also advantageous to change the anode voltage (Vdd) by changing the switching state of the transistor 1776. In FIG. 178, −9 (V) is selected by the switch 1781.
[1494]
In FIG. 178, the cathode voltage Vss is selected from two voltages, but is not limited to this and may be two or more. The cathode voltage may be continuously changed using a variable regulator circuit.
[1495]
The selection of the switch 2021 is based on the output result from the temperature sensor 701. When the panel temperature is low, -9 (V) is selected as the Vss voltage. When the panel temperature is above a certain level, -6 (V) is selected. This is because the EL element 15 has a temperature characteristic, and the terminal voltage of the EL element 15 increases on the low temperature side. In FIG. 178, one voltage is selected from two voltages to be Vss (cathode voltage). However, the present invention is not limited to this, and the Vss voltage can be selected from three or more voltages. May be. The above matters are similarly applied to Vdd. The present invention is also characterized in that the cathode voltage (Vss) is lowered at low temperatures below a certain level.
[1496]
In FIG. 178, the cathode voltage is switched (changed) by the temperature sensor 701. However, the present invention is not limited to this. For example, as shown in FIG. 177, a variable resistor (posistor, thermistor, etc.) is formed or arranged in parallel or in series with a resistor 1775 that determines the output voltage, and the resistance value can be changed depending on the temperature as a whole. May be.
[1497]
As shown in FIG. 178, the power consumption of the panel can be reduced by configuring so that a plurality of voltages can be selected depending on the panel temperature. This is because the Vss voltage may be lowered when the temperature is below a certain temperature. Usually, Vss = −6 (V) having a low voltage can be used. Note that the switch 2021 may be configured as illustrated in FIG. The generation of a plurality of cathode voltages Vss can be easily realized by taking out an intermediate tap from the transformer 1121 in FIG. The same applies to the anode voltage Vdd. As an example, the configuration of FIG. 179 is illustrated. In FIG. 179, a plurality of cathode voltages are generated using an intermediate tap of a transformer 1771.
[1498]
FIG. 180 is an explanatory diagram of potential setting. In this example, for ease of explanation, the source driver IC 14 will be described on the basis of GND. The power source of the source driver IC 14 is Vcc. Vcc may match the anode voltage (Vdd). In the present invention, Vcc <Vdd is set from the viewpoint of power consumption. Preferably, the Vcc voltage of the source driver IC (circuit) preferably satisfies the relationship of Vdd−1.5 (V) <= Vcc <= Vdd. For example, if Vdd = 7 (V), Vcc preferably satisfies the condition of Vdd−1.5 = 5.5 (V) to 7 (V). The Vcc voltage is the maximum voltage for operating the switch 481 in FIGS. 48 and 166.
[1499]
The off voltage Vgh of the gate driver circuit 12 is set to be equal to or higher than the Vdd voltage. Preferably, the relationship of Vdd + 0.2 (V) <= Vgh <= Vdd + 2.5 (V) is satisfied. For example, if Vdd = 7 (V), Vgh satisfies the condition of 7 + 0.2 = 7.2 (V) or more and 7 + 2.5 = 9.5 (V) or less. The above conditions apply to both the pixel selection side (transistors 11b and 11c in the pixel configuration of FIG. 1) and the EL selection side (transistor 11d in the pixel configuration of FIG. 1).
[1500]
The on-voltage Vgl of the switching transistor that generates a program current path with the driving transistor 11a (corresponding to the transistors 11b and 11c in the pixel configuration of FIG. 1) is Vdd-Vdd or lower and Vdd-Vdd-4. It is preferable to satisfy the condition of (V) or substantially coincide with the cathode voltage Vss. Similarly, the ON voltage on the EL selection side (which corresponds to the transistor 11d in the pixel configuration of FIG. 1) is the same. That is, if the anode voltage is 7 (V) and the cathode voltage is -6 (V), the on-voltage Vgl is 7-7 (V) = 0 (V) or less. 7-7-4 = -4 (V) It is preferable to be in the range. Alternatively, the on voltage Vgl is preferably substantially equal to the cathode voltage and is set to −6 (V) or the vicinity thereof.
[1501]
Note that when the driving transistor 11a of the pixel 16 is an N-channel transistor, Vgh is an on-voltage. In this case, it goes without saying that the off voltage may be replaced with the on voltage.
[1502]
A problem of the power supply circuit of the present invention is that Vgh, Vgl voltage, etc. are generated from the anode voltage Vdd and / or the cathode voltage Vss. An anode voltage or the like is generated by the transformer 1121, and DCDC converter Vgh and Vgl voltages are applied from this voltage.
[1503]
However, Vgh and Vgl are control voltages for the gate driver circuit 12, and if these voltages are not