JP2005140918A - Display apparatus, driving method therefor, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display apparatus with reduced display unevenness caused by resistance of electrodes of light emitting elements, and variation in characteristics of the light emitting elements, and providing uniform display luminance within a display surface. <P>SOLUTION: An organic EL display apparatus is disclosed which is provided with light emitting elements 50 having EL layers 27 including light emitting layers in pixels 3 composing one display unit of the display apparatus, and a potential control part 51 electrically connected to the light emitting elements 50. The potential control part 51 controls the potential of common electrodes 28. The control part 51 may be disposed to control the potential of the common electrodes staddlingly formed over the plurality of light emitting elements 50. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a display device, a driving method thereof, and an electronic apparatus.

In recent years, attention has been paid to an EL display device including an electroluminescence (hereinafter referred to as EL) element as a display device including a self-luminous element that does not require a backlight or the like. An EL display device has a structure in which a plurality of light emitting elements each having an EL layer (light emitting layer) sandwiched between a pair of electrodes are provided in a substrate surface. In an active matrix display device, one electrode is placed on a substrate. Generally, a configuration is provided in which the other electrode is a solid common electrode. In this type of EL display device, since the EL layer emits light according to the supplied current value, when the amount of current decreases due to the resistance between the substrate and the electrode, the EL layer Has a problem in that the display luminance is reduced, and as a result, the display characteristics are deteriorated. Such display deterioration is likely to occur particularly due to a voltage drop due to the resistance of the common electrode formed in a solid shape. For example, in the case of a large EL display device having a screen size of 20 inches diagonal or more, a voltage drop due to the resistance of the common electrode becomes significant. In general, a conventional EL display device has a bottom emission structure that emits light downward through an organic EL element formed on a light-transmitting substrate and an organic EL element formed on the substrate. It can be classified as a top emission structure that emits light. In particular, since an EL display device having a top emission structure uses a transparent conductive material as a common electrode, the resistance increases as compared with a metal electrode that does not have optical transparency, and the voltage drop of the common electrode becomes significant.
In order to prevent such a voltage drop, a configuration has been proposed in which a rib that contacts the upper electrode is provided in the pixel boundary region and used as an auxiliary wiring (see, for example, Patent Document 1).
JP 2002-318556 A

  According to the technique described in the above document, the voltage drop due to the resistance of the upper electrode can surely be reduced, and the display unevenness due to the voltage drop is reduced, but it is considered that it cannot be fundamentally solved. Further, the display unevenness that occurs in this type of display device is not limited to that caused by the voltage drop, and there is also display unevenness that occurs due to, for example, variations among light emitting elements that constitute pixels. In particular, in an active matrix display device in which each light-emitting element is driven by a switching element such as a TFT (thin film transistor) element, luminance of the light-emitting element may change greatly due to variation in characteristics of the switching element, resulting in display unevenness.

  The present invention has been made in view of the above-described problems of the prior art, in which the display unevenness due to the resistance of the electrode of the light emitting element and the variation in characteristics of the light emitting element is reduced, and the display brightness is uniform within the display surface. It is an object to provide a display device capable of obtaining the above.

In order to solve the above-described problems, the present invention provides a display region in which a plurality of light-emitting elements each including a first electrode, a functional layer including a light-emitting layer, and a second electrode are sequentially stacked on a substrate. The display device includes a plurality of potential control units that control the potential of the second electrode in the display region.
According to this configuration, by providing a plurality of potential control units connected to the second electrode of the light emitting element, the potential of the second electrode can be controlled at a plurality of locations. Even when the electrode is made of a transparent conductive material having high resistance, it is possible to effectively prevent a voltage drop from occurring in the display region. In addition, since the second electrode can be held at an arbitrary potential, the voltage applied to the light-emitting element can be adjusted so as to alleviate luminance unevenness caused by variation in characteristics of the light-emitting element. It is possible to obtain a high-quality display with reduced image quality.

  In the display device of the present invention, a plurality of the second electrodes may be provided in the display area, and the potential control unit may be provided corresponding to each of the second electrodes. . According to this configuration, a plurality of second electrodes provided in the display region can be set to potentials independently of each other, and uneven luminance due to variation in characteristics of light emitting elements can be more effectively prevented. Can do.

  In the display device of the present invention, the second electrode may be formed across a plurality of the light emitting elements constituting one display unit of the display device. As such a configuration, one display unit is composed of light emitting elements of three colors of R (red), G (green), and B (blue), and the second electrode straddles the light emitting elements of these three colors. The structure formed in this way can be illustrated. According to this configuration, the luminance can be adjusted for each display unit, and uniform display luminance can be obtained within the display area.

  In the display device of the present invention, the second electrode may be provided for each of the light emitting elements, and the potential control unit may be provided corresponding to each of the second electrodes. . In this configuration, the potential of the second electrode can be controlled for each light emitting element constituting the minimum unit of display. Therefore, according to the display device of this configuration, it is possible to provide a display device in which the luminance of each light emitting element is controlled extremely highly and the display luminance is particularly excellent in uniformity.

In the display device of the present invention, the potential control section may include a potential control element that functions as a variable resistance element connected to the second electrode. Alternatively, in the display device of the present invention, the potential control unit may include a potential control element connected to the second electrode through a capacitor.
In any of these configurations, good potential controllability can be obtained, and improvement in display luminance uniformity can be achieved. One or a plurality of voltage control circuits can be added to the potential control element.

The display device of the present invention further includes a pixel driving switching element provided corresponding to the plurality of light emitting elements and conductively connected to the first electrode, the pixel driving switching element, and the potential The control element can be configured to have substantially the same configuration. According to this configuration, the potential control element and the pixel driving switching element can be formed at the same time in the same process, resulting in a significant process change and an increase in man-hours due to the provision of the potential control unit. There is no, and it can manufacture efficiently.
Furthermore, a current mirror circuit, a current program circuit, and a voltage program circuit, which may be mounted on the pixel driving circuit in order to control the current of the light emitting element, can be provided for the potential control unit. In this case, since the light emitting element and the potential control unit including these program circuits can have substantially the same configuration, an effect of improving the potential controllability by the potential control unit can be obtained while suppressing an increase in man-hours.

  In the display device of the present invention, the potential control element may be configured to be conductively connected to the second electrode through an electrode member made of the same material provided in the same layer as the first electrode. . With such a configuration, the potential control unit has a structure in which the first electrode and the second electrode are laminated in manufacturing, and therefore, the light emitting element and the potential control unit have a similar structure, and the manufacturing is easy. Can be increased.

  The display device of the present invention further includes voltage correction means connected to the plurality of potential control sections, and the voltage correction means uses the potential control to calculate voltage correction information calculated based on light emission characteristics of the plurality of light emitting elements. The structure which can be supplied with respect to a part may be sufficient. That is, since the voltage correction information calculated based on the optical / electrical circuit variation of the light emitting element can be applied to the second electrode, the light emitting element can be driven while highly controlling the applied voltage. become. Thereby, a display device excellent in luminance uniformity can be obtained.

  In the display device according to the aspect of the invention, the voltage correction unit includes a voltage value holding unit that holds a voltage value applied to each first electrode, and voltage correction information based on the voltage value held in the voltage value holding unit. It is good also as a structure provided with the correction information calculation means to calculate. According to this configuration, it is possible to estimate the variation in the light emission characteristics based on the voltage value applied to the light emitting element, and to correct the applied voltage to the light emitting element.

  In the display device according to the aspect of the invention, it is preferable that the correction information calculation unit includes a lookup table that associates the voltage value of the first electrode with the voltage correction information output to the potential control unit. . By using such a lookup table reference method, accurate voltage correction information can be obtained at high speed with a simple circuit, which is effective in reducing the size, power consumption, and speed of the display device. .

  The display device of the present invention may be configured such that voltage correction information set based on the luminance distribution of the display area can be supplied to the potential control unit. According to this configuration, a voltage can be applied to the second electrode in order to correct the luminance variation in the display area, and a display device with highly uniform display luminance can be obtained.

  In the display device according to the aspect of the invention, the pixel driving switching element is a thin film transistor element, and the voltage correction unit supplies voltage correction information set based on a threshold value or easy conductivity of each thin film transistor element to the potential control unit. It can also be set as the structure which can be supplied with respect to. Also with this configuration, it is possible to apply a voltage to the second electrode in order to correct the luminance variation in the display region, and a display device in which display luminance is highly uniformed can be obtained.

In the display device according to the aspect of the invention, the voltage correction unit may include a look-up table that associates the luminance distribution of the display area with the voltage correction information. According to this configuration, voltage correction information can be acquired at high speed with a simple circuit.
In the display device according to the aspect of the invention, the voltage correction unit may include a lookup table in which element characteristics of the pixel driving switching elements are associated with the voltage correction information.

Next, in order to solve the above-described problems, the present invention includes a plurality of light-emitting elements in which a first electrode, a functional layer including a light-emitting layer, and a second electrode are sequentially stacked on a substrate. There is provided a driving method of a display device including a display region, wherein display is performed while controlling the potential of the second electrode at a plurality of locations in the display region.
According to this driving method, by controlling the potential of the second electrode at a plurality of locations, not only the luminance variation of the light emitting element due to the voltage drop due to the resistance of the second electrode itself but also the characteristics of the light emitting element. Luminance variations caused by variations can also be reduced. Thereby, the display excellent in the uniformity of display luminance can be provided.

  In the display device driving method of the present invention, in the display device provided with a plurality of the second electrodes, the potential can be controlled for each of the plurality of second electrodes. According to this configuration, since the second electrode is divided into a plurality of regions and each potential can be controlled independently, the voltage of the light emitting element can be adjusted more precisely. As a result, it is possible to provide a display with further excellent luminance uniformity.

  In the display device driving method of the present invention, in the display device in which the second electrode is formed across a plurality of light emitting elements constituting one display unit, the potential of the second electrode is set for each display unit. It can also be controlled. In this configuration, since the variation in luminance is adjusted for each display unit that forms an image or the like in the display area, the uniformity of display luminance can be further improved.

  In the display device driving method of the present invention, in the display device in which the second electrode is provided for each light emitting element, the potential of the second electrode can be controlled for each light emitting element. According to this configuration, voltage control is performed for each light emitting element that constitutes the minimum display unit of the display area, and the brightness is precisely adjusted. Therefore, it is possible to provide a display with extremely excellent uniformity.

  In the display device driving method of the present invention, when the potential of the second electrode is controlled, voltage correction information set based on the light emission characteristics of the plurality of light emitting elements is applied to the second electrode. The voltage can be corrected. According to this driving method, the voltage is applied to the second electrode to correct the variation based on the optical / electrical circuit characteristics of the light emitting element, so that accurate luminance correction is possible and display luminance is uniform. Can be increased.

  In the display device driving method of the present invention, when controlling the potential of the second electrode, the voltage correction information calculated based on the voltage values applied to the first electrodes of the plurality of light emitting elements is used. The voltage applied to the second electrode can be corrected. According to this driving method, voltage correction information for performing luminance correction can be calculated based on the voltage value applied to the light emitting element, and accurate luminance correction becomes possible.

  In the driving method of the display device of the present invention, when correcting the voltage applied to the second electrode, a lookup table that associates the voltage value applied to the first electrode with the voltage correction information is referred to. Thus, the voltage correction information can be obtained. According to this driving method, the voltage correction information for correcting the luminance of the light emitting element can be acquired at high speed with a simple circuit.

In the driving method of the display device of the present invention, when the potential of the second electrode is controlled, the voltage applied to the second electrode is corrected using voltage correction information based on the luminance distribution of the display region. You can also. According to this driving method, since the luminance correction of the light emitting element is performed using the voltage correction information calculated from the luminance distribution of the entire display area, it is possible to obtain a uniform display in which the overall luminance correction is accurately performed. it can.
Alternatively, when the potential of the second electrode is controlled, voltage correction information set based on element characteristics (threshold value or easy conductivity) of the switching element provided in the light emitting element can be used.

  In the display device driving method of the present invention, when correcting the voltage applied to the second electrode, the voltage correction is performed by referring to a look-up table that associates the luminance distribution of the display area with the voltage correction information. You can also get information. Alternatively, the voltage correction information can be obtained by referring to a lookup table in which element characteristics of the pixel driving switching element are associated with the voltage correction information.

  Next, an electronic apparatus according to the present invention includes the display device according to the present invention described above. According to this configuration, it is possible to provide an electronic device including a display unit that has a uniform light emission intensity in the display region and can display with high luminance and high image quality.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In addition, about each drawing referred below, in order to make each element easy to see, dimensions, film thicknesses, and the like are appropriately changed and displayed.

(First embodiment)
<Organic EL display device>
FIG. 1 is a plan configuration diagram showing the overall configuration of an organic EL display device which is an example of the display device of the present invention, FIG. 2 is a circuit configuration diagram of one pixel provided in the device, and FIG. FIG. The organic EL display device of this embodiment is a top emission type organic EL display device that extracts display light from the upper surface side of the light emitting elements arrayed on the substrate, and a switching element is provided for each light emitting element. This is an active matrix type display device.

First, the overall configuration of the organic EL display device according to the present embodiment will be described with reference to FIG.
The organic EL display device 101 of this example is formed by arranging pixel electrodes connected to switching TFTs (not shown) in a matrix on a substrate 20 on an electrically insulating and translucent substrate 20. The pixel forming region 33 (within the one-dot chain line in FIG. 1) is provided. The pixel formation area 33 includes a display area 4 at the center (inside the two-dot chain line frame in FIG. 1) and a dummy area 5 (around the one-dot chain line frame and the two-dot chain line frame) arranged around the display area 4. Area). In the display area 4, pixels 3 of three colors (R, G, B) each having a pixel electrode are arranged in a matrix in such a manner as to be spaced apart from each other in the vertical direction and the horizontal direction on the paper surface. Further, scanning line driving circuits 80 are arranged on the left and right sides of the display area 4 in FIG. 1, while data line driving circuits 93 are arranged on the upper and lower sides of the display area 4 in FIG. The scanning line driving circuit 80 and the data line driving circuit 93 are arranged at the peripheral edge of the dummy region 5. In FIG. 1, the scanning lines and the data lines are not shown.

  Further, an inspection circuit 90 is arranged above the data line driving circuit 93 in FIG. The inspection circuit 90 is a circuit for inspecting the operating state of the organic EL display device 1, and includes, for example, inspection information output means (not shown) for outputting the inspection result to the outside. The quality and defects of the display device can be inspected. The inspection circuit 90 is also arranged below the dummy area 5. Further, a driving external substrate 95 is connected to the substrate 20, and the external driving circuit 100 is mounted on the driving external substrate 95.

Next, the circuit configuration of the pixel 3 will be described with reference to FIG. Referring to the circuit configuration diagram shown in FIG. 2, the pixel 3 according to the present embodiment is formed in a region partitioned by a plurality of wiring groups extending vertically and horizontally, and the light emitting element 50 provided in the region. , And a potential control unit 51 connected thereto.
The light emitting element 50 includes an EL layer 27 that includes a light emitting layer and forms a light emitting portion, and two transistors (the pixel driving TFT 12 and the pixel selecting TFT 43, and the pixel driving TFT 12 and the pixel selecting TFT 43 that are connected to the EL layer 27. The drain of the pixel driving TFT 12 is connected to the anode side of the EL layer 27, and the common electrode 28 is connected to the cathode side of the EL layer 27. A driving current is supplied to the EL layer 27. The power source line 45 is connected to the source of the pixel driving TFT 12 and the gate is connected to the drain of the pixel selecting TFT 43 and one electrode of the storage capacitor 70. The anode scanning line is connected to the source of the pixel selecting TFT 43. 46, and the gate is connected to the signal line 44. The other electrode of the storage capacitor 70 is connected to the capacitor line 71 extending along the signal line 44. There.

  The potential control unit 51 includes a potential control TFT (potential control element) 32 and a capacitor 49. The potential control TFT 32 is interposed between the voltage supply line 47 and the capacitor 49 and is connected to the gate thereof. Is connected to a cathode scanning line 34. The light emitting element 50 and the potential control unit 51 are connected to each other by sharing the common electrode 28.

Based on the above configuration, the organic EL display device 101 of this embodiment drives the pixel selection TFT 43 by inputting a signal to the signal line 44 and the anode scanning line 46 to select the light emitting element 50, and the power supply line 45. By driving the pixel driving TFT 12 connected to, and supplying a predetermined amount of current to the EL layer 27, the light emitting element 50 emits light with a predetermined luminance. The storage capacitor 70 connected to the pixel driving TFT 12 has a function of holding the output of the pixel selecting TFT 43 and maintaining the driving state of the pixel driving TFT 12 in the non-selected state.
In the pixel 3 according to this embodiment, a voltage can be applied to the common electrode 28 in conjunction with the operation of the light emitting element 50. That is, a scanning signal is input to the gate of the potential control TFT 32 via the cathode scanning line 34 to set the potential control unit 51 in a selected state, and an applied voltage is input via the voltage supply line 47, whereby the capacitor 49. The potential of the common electrode 28 is controlled by capacitive coupling.

As described above, the organic EL display device 101 according to the present embodiment is configured such that each pixel 3 includes the light emitting element 50 and the potential control unit 51 that controls the potential of the common electrode 28 of the light emitting element 50. Therefore, it is possible to control the voltage applied to the EL layer 27 for each pixel 3 which is the minimum display unit. This makes it possible to correct variations in the amount of current caused by variations in the characteristics of the pixel driving TFTs 12 that form the drive unit of the light emitting element 50, thereby enabling the light emitting element 50 to emit light with a target light emission luminance. is there. Therefore, according to the organic EL display device 101 of the present embodiment, uniform display luminance can be obtained over the entire surface of the display region 4, and high-quality display can be obtained.
In the case of the present embodiment, the pixel electrode 19 and the common electrode 28 arranged above and below the EL layer 27 are partitioned for each pixel 3, so that a voltage drop due to the resistance of the electrode itself hardly occurs.

  As a mode of controlling the potential of the common electrode 28, a voltage value supplied to the light emitting element 50 is observed in a voltage supply unit (or a constant current source) (not shown) connected to the light emitting element 50 via a power line 45. Then, a method of applying a voltage set based on the observed voltage value to the common electrode 28 of each pixel 3 (first method) and a variation in display luminance in the display region 4 are measured, and based on this luminance variation A method (second method) in which the set voltage is applied to the common electrode 28 of each pixel 3 can be exemplified.

As a configuration for controlling the potential of the common electrode 28 by the first method, voltage value holding means for observing and holding the applied voltage to the light emitting element 50, and applying the voltage from the potential control unit 51 to the common electrode 28. A configuration including correction information calculation means for calculating voltage correction information for correcting a voltage based on the held voltage value can be exemplified. That is, a method for estimating the luminance variation in the light emitting element 50 from the voltage / current characteristics of the light emitting element 50 and reducing the luminance variation among the plurality of light emitting elements 50 by changing the voltage applied to the common electrode 28 based on the estimation. It is.
In this case, the correction information calculation means may calculate the voltage correction information by performing a calculation using the held voltage value, and the voltage correction information is obtained by referring to a calculation result (lookup table) prepared in advance. The configuration may be such that it is acquired and output to the potential control unit 51. In the method of referring to the lookup table, the arithmetic circuit can be simplified, so that a high-speed operation of the circuit or the like and an effect of reducing the heat generation amount can be expected.

  Next, in the second method, the variation in the light emission characteristics of the light emitting element 50 is estimated from the light emission luminance actually obtained by the light emitting element 50, and a plurality of voltages are applied by changing the voltage applied to the common electrode 28 based on such estimation. This is a method of reducing the luminance variation between the light emitting elements 50. In this case, by measuring the luminance distribution in the display region 4, it is possible to obtain variations in threshold values or easy conductivities of the pixel driving TFTs 12 and the pixel selecting TFTs 43 that constitute the light emitting element 50, and voltage based on these can be obtained. What is necessary is just to comprise the correction information calculation means which calculates correction information and supplies it to the electric potential control part 51. The correction information calculation means may perform a calculation process based on variation information input from the outside and supply a calculation result to the potential control unit 51. A calculation result prepared in advance (from luminance variation) may be used. The voltage correction information acquired by referring to a lookup table holding the result of calculating the voltage correction information may be output. Alternatively, a luminance measuring means (for example, an optical sensor such as a photodiode or a phototransistor) for measuring display luminance is provided at one or more places in the display area 4, and the voltage is determined based on the luminance information output from the luminance measuring means. Correction information may be calculated.

<Other examples of pixel circuit configuration>
As the potential control unit 51, the configuration shown in the circuit configuration diagram of FIG. 3 can be applied. The potential control unit 51 provided in the pixel 3 shown in FIG. 3 is mainly composed of a potential control TFT (potential control element) 53. A voltage supply line 47 is connected to the gate of the potential control TFT 53, and a common electrode (com.) And a common electrode 28 are connected to the source and drain, respectively.
The potential control TFT 53 functions as a variable resistance element that divides a voltage applied to the common electrode 28 in accordance with a signal input via the voltage supply line 47. Even in such a configuration, it is possible to apply an arbitrary voltage to the common electrode 28, thereby suppressing variations in light emission luminance due to variations in characteristics of the TFTs 12 constituting the light emitting element 50, and reducing the variation in the display area. An organic EL display device capable of obtaining uniform display luminance can be provided. Further, in the potential control unit 51 shown in FIG. 3, no cathode scanning line is provided, and the potential of the common electrode 28 is controlled with respect to the common electrode that supplies the reference potential. There is an advantage that the configuration of the drive circuit for selectively driving the can be simplified.

  In the circuit configuration diagram shown in FIG. 3, the circuit configuration of the light emitting element 50 is also partially different from that shown in FIG. 2, and specifically, a connection is made between the pixel selection TFT 43 and the pixel driving TFT 12. One end of the storage capacitor 70 is connected to a power supply line 45 connected to the pixel driving TFT 12. In this configuration, the storage capacitor 70 holds the potential of the anode scanning line 46 when the pixel selection TFT 43 is turned on, and the switching operation of the pixel driving TFT 12 is selected according to the state of the storage capacitor 70. It is like that.

  Further, the circuit shown in FIG. 17 of Japanese Patent Application Laid-Open No. 2003-22049 or a current program circuit such as a current mirror circuit can be connected to each of the potential control TFTs 32 and 53 described above. Further, a part or the whole of the pixel driving circuit provided for each light emitting element 50 may be provided for the potential control unit 51. In other words, the pixel driving circuit of the light emitting element 50 is configured to change the resistance value of the pixel driving TFT 12 by controlling the voltage input to the gate of the pixel driving TFT 12 by the current mirror circuit, the current program circuit, and the voltage program circuit. It has been known. By connecting these voltage control circuits to the potential control TFTs 32 and 53 of the potential control unit 51, the voltage applied from the potential control unit 51 to the common electrode 28 can be controlled more accurately, and the light emitting element 50 can be controlled. And the potential control unit 51 can share a drive circuit. As a result, there is also an advantage that it is possible to shift from the conventional manufacturing process without accompanying a large-scale process change.

<Detailed configuration of pixel>
Next, a specific configuration of the pixel 3 will be described with reference to FIG. Looking at the cross-sectional configuration shown in FIG. 4, the organic EL display device 101 of this embodiment includes a light emitting element 50 and a potential control unit 51 provided adjacent thereto. A base insulating film 23 made of, for example, a silicon oxide film is formed on a light-transmitting substrate 20 such as glass. The pixel driving TFT 12 of the light emitting element 50 and the potential of the potential control unit 51 are formed on the base insulating film 23. A control TFT 32 is formed.

The pixel driving TFT 12 provided in the light emitting element 50 has an LDD (Lightly Doped Drain) structure. The semiconductor layer 13 includes a high concentration source region 13a, a low concentration source region 13b, a channel region 13c, and a low concentration drain region. 13d, a high concentration drain region 13e is formed. Then, a gate insulating film 24 is formed on the semiconductor layer 13, and the gate electrode 14 facing the channel region 13 c via the gate insulating film 24 is disposed. A first interlayer insulating film 25 is formed so as to cover the gate electrode 14, and a power supply line 45 and a relay conductive layer 17 are formed on the first interlayer insulating film 25.
The power supply line 45 is connected to the high concentration source region 13 a of the semiconductor layer 13 through a contact hole 15 that penetrates the first interlayer insulating film 25 and the gate insulating film 24. On the other hand, the relay conductive layer 17 is connected to the high concentration drain region 13 e of the semiconductor layer 13 through a contact hole 16 penetrating the first interlayer insulating film 25 and the gate insulating film 24.

A second interlayer insulating film 26 having a planarized surface is formed so as to cover the power supply line 45 and the relay conductive layer 17, and the pixel electrode 19 is formed on the second interlayer insulating film 26. The pixel electrode 19 is connected to the relay conductive layer 17 through a contact hole 18 penetrating the second interlayer insulating film 26. The pixel electrode 19 functions as an anode for injecting holes into an EL layer, which will be described later, and constitutes a first electrode constituting the light emitting element 50.
In the top emission type light emitting element 50, the pixel electrode 19 can be formed of a reflective metal film such as Al or silver or a non-light-transmitting conductive film. In some cases, the pixel electrode 19 is the same as the bottom emission type light emitting element. And transparent conductive materials such as ITO (indium tin oxide), IZO (indium zinc oxide (registered trademark)), ICO (indium cerium oxide), GZO (gallium zinc oxide), and ZnO (zinc oxide). It can also be formed.

  An inorganic material layer 22A and an organic material layer 22B are formed along the peripheral edge of the pixel electrode 19, and a bank 22 is constituted by the two layers of the inorganic material layer 22A and the organic material layer 22B. In the light emitting element 50, the EL layer 27 is formed in the center of the region on the pixel electrode 19 partitioned by the bank 22. In the present embodiment, the EL layer 27 is composed of two layers, for example, a hole injection (transport) layer 27A made of a thiophene-based conductive polymer and a light emitting layer 27B made of a light emitting polymer (LEP). As the structure of the EL layer 27, a structure in which a hole (electron) injection layer and a transport layer are separately provided, a structure including three layers of an electron injection layer, a hole injection layer, and a light emitting layer are applied. Also good.

A common electrode 28 is provided so as to cover the EL layer 27. The common electrode 28 can be formed of a transparent conductive material such as ITO, IZO, ICO, GZO, or ZnO. When the light emitting element 50 is of a bottom emission type, a metal film or a non-translucent conductive film is used. It may be formed. In the light emitting element 50, the common electrode 28 forms a cathode (second electrode) for injecting electrons into the EL layer 27. The common electrode 28 is formed across the light emitting element 50 and the potential control unit 51, and is a member that electrically connects them.
Further, a light-transmitting sealing layer 29 is provided to prevent moisture and the like from entering the EL layer 27.

  Next, the potential control unit 51 is provided with a potential control TFT 32. The potential control TFT 32 is also a transistor having an LDD structure. In the semiconductor layer 33, a high concentration source region 33a, a low concentration source region 33b, a channel region 33c, a low concentration drain region 33d, and a high concentration drain region 33e are formed. Yes. A gate insulating film 24 is formed on the semiconductor layer 33, and a gate electrode 42 facing the channel region 33c via the gate insulating film 24 is disposed. A first interlayer insulating film 25 is formed so as to cover the gate electrode 42, and the voltage supply line 47 and the relay conductive layer 37 are respectively connected to the semiconductor layer 33 through contact holes 35 and 36 provided in the first interlayer insulating film 25. The high concentration source region 33a and the high concentration drain region 33e are electrically connected. Similar to the above-described pixel driving TFT 12, the second interlayer insulating film 26 covering the voltage supply line 47 and the relay conductive layer 37 is formed, and the contact hole 38 provided in the second interlayer insulating film 26 is interposed. The pixel electrode 19 and the relay conductive layer 37 are electrically connected.

  A common electrode 28 extending from the light emitting element 50 side is formed in the bank 22 provided around the pixel electrode 19 of the potential control unit 51 and is electrically connected to the pixel electrode 19. That is, in the potential control unit 51, the pixel electrode 19 functions as an electrode member for conductively connecting the common electrode 28 and the potential control TFT 32. By adopting such a conductive connection structure, the potential control TFT 32 is used. And the contact resistance between the common electrode 28 can be reduced. In the present embodiment, the pixel electrode 19 and the common electrode 28 are directly connected to each other in the potential control unit 51. However, the conductive layer excluding the light emitting layer 27 </ b> B is included in the EL layer 27 on the pixel electrode 19. May be provided.

  Thin film transistors having substantially the same configuration can be used for the pixel driving TFT 12 provided in the light emitting element 50 and the potential control TFT 32 provided in the potential control unit 51. With such a configuration, it is possible to increase the efficiency of manufacturing, and it is effective in achieving reduction in manufacturing cost and improvement in yield. Further, the potential control TFT 32 may be a TFT having substantially the same configuration as the pixel selection TFT 43 shown in FIGS. 2 and 3. When the current program circuit or the like is mounted on the light emitting element 50, The same configuration as the TFT included in the circuit may be employed.

<Method for Manufacturing Organic EL Display Device>
Hereinafter, an example of a method for manufacturing the organic EL display device 101 of the present embodiment will be briefly described with reference to FIG.
First, after a base insulating film 23 made of a silicon oxide film having a thickness of about 200 to 500 nm is formed on one surface of the substrate 20 by a plasma CVD method or the like, amorphous silicon having a thickness of about 30 to 70 nm is formed on the base insulating film 23. A semiconductor layer made of a film is formed by a plasma CVD method or the like. Next, the semiconductor layer is crystallized by laser annealing or the like, so that the semiconductor layer is a polycrystalline silicon film. Next, after patterning the semiconductor layer to form island-shaped semiconductor layers 13 and 33, a gate insulating film 24 made of a silicon oxide film having a thickness of about 60 to 150 nm is formed by plasma CVD or the like. Next, after forming a light-transmitting material such as ITO by sputtering or the like, this is patterned to form scanning lines and gate electrodes 14 and 42. Then, source / drain regions are formed in the semiconductor layers 13 and 33 in a self-aligned manner by ion implantation using the gate electrodes 14 and 42 as a mask.

  Next, after forming the first interlayer insulating film 25 and forming the contact holes 15 and 16 reaching the source / drain regions of the semiconductor layer 13 and the contact holes 35 and 36 reaching the source / drain regions of the semiconductor layer 33, A light-transmitting material such as ITO is formed by sputtering or the like, and is patterned to form the power supply line 45, the voltage supply line 47, and the relay conductive layers 17 and 37. Next, after forming the second interlayer insulating film 26 and the contact holes 18 and 38 reaching the relay conductive layers 17 and 37, a metal film such as Al is formed by sputtering or the like, and this is patterned. Pixel electrodes 19 are formed. In the case of the bottom emission type, the pixel electrode 19 is formed of a light-transmitting conductive material such as ITO. The top emission type is not limited to the above metal film, and may be formed of a light-transmitting material or an opaque conductive material.

Next, an inorganic material layer 22A is formed by plasma CVD or the like and patterned. Thereafter, the organic material layer 22 </ b> B is formed in a predetermined pattern to form the bank 22. The organic material layer 22B can be formed by a photolithography method, a printing method, or the like. For example, silicon oxide or the like can be used for the inorganic material layer 22A, and acrylic or polyimide can be used for the organic material layer 22B, for example.
In the subsequent manufacturing process, when the EL layer 27 is formed using a droplet discharge method, it is preferable that at least the surface of the pixel electrode 19 has lyophilicity, and the hole injection transport layer forming material is an aqueous type. When using a solution, it is desirable to make it hydrophilic. Further, the bank 22 functions not only to isolate the pixel electrode 19 in a plane but also to assist the selective arrangement of the material by the droplet discharge method. That is, the surface of the bank 22 is subjected to a liquid repellency treatment, so that the material can be placed on the pixel electrode 19 more accurately and smoothly. Examples of the liquid repellency treatment of the bank 22 include a fluorine plasma treatment using a gas such as CF ₄ , SF ₆ , SiF ₄ , or BF ₃ . This fluorine-based plasma treatment may be performed collectively on the surface of the pixel electrode 19 and the bank 22, and in this case as well, the surface of the bank 22 is preferentially modified. Different surface characteristics (lyophilic / liquid repellent) can be obtained.

  Further, the method is not limited to the surface modification by plasma treatment, and the bank 22 itself can be provided with liquid repellency by forming the organic material layer 22B of the bank 22 with a material to which fluoride is added. If the organic material layer 22B formed on the upper side is made liquid repellent and the lower inorganic material layer 22A is made lyophilic, the patterning property of the material by the droplet discharge method is further improved.

Next, a solution containing a polymer organic compound is discharged onto the pixel electrode 19 in the region partitioned by the bank 22 using a droplet discharge method such as an ink jet method, and the EL layer 27 (hole injection transport layer 27A) is discharged. And a light emitting layer 27B) are selectively formed. In forming the EL layer 27, filling and drying of the solution containing the organic compound material are repeated for each layer.
As the hole injecting and transporting layer 27A, for example, a polythiophene derivative, a polypyrrole derivative or the like, or a doped body thereof is preferably used. Specifically, 3,4-polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT / PSS) dispersion, that is, polystyrene sulfonic acid as a dispersion medium is dispersed with 3,4-polyethylenedioxythiophene. A dispersion in which water is dispersed in water can be used.
As the light emitting layer 27B, a known light emitting material capable of emitting fluorescence or phosphorescence can be used. Specifically, (poly) fluorene derivative (PF), (poly) paraphenylene vinylene derivative (PPV), polyphenylene derivative (PP), polyparaphenylene derivative (PPP), polyvinyl carbazole (PVK), polythiophene derivative, polydialkyl Polysilanes such as fluorene (PDAF), polyfluorene benzodiazole (PFBT), polyalkylthiophene (PAT), and polymethylphenylsilane (PMPS) are preferably used. In addition, these polymer materials include polymer materials such as perylene dyes, coumarin dyes, rhodamine dyes, rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, and quinacridone. It can also be used by doping a low molecular weight material such as. The light emitting layer 27B may be a single color or may use multiple colors such as red, blue, and green. It is also possible to make four or more colors using an intermediate color.

When the EL layer 27 is formed, the common electrode 28 made of a transparent conductive material such as ITO is formed by sputtering or the like so as to straddle the formation region of the plurality of pixel electrodes 19. When the bottom emission type light emitting element 50 is manufactured, a film made of a single material such as Al, Mg, Li, or Ca or an alloy material such as Mg—Al (10: 1 alloy) may be formed as the cathode. good. Alternatively, a laminated film of Li ₂ O (thickness of about 0.5 nm) and Al, a laminated film of LiF (thickness of about 0.5 nm) and Al, a laminated film of MgF ₂ and Al, or the like may be used. it can.
Finally, the organic EL device 101 is completed by forming a sealing layer 29 made of a transparent resin or a thin layer.

  As described above, in the method for manufacturing the organic EL display device according to this embodiment, the pixel driving TFT 12 included in the light emitting element 50 and the potential control TFT 32 included in the potential control unit 51 are formed in the same layer. Even when compared with a conventional method of manufacturing an organic EL display device that does not include such a potential control unit 51, it can be manufactured without an increase in manufacturing steps. .

(Second Embodiment)
In the first embodiment, the configuration in which the light emitting element 50 and the potential control unit 51 are provided for each pixel 3 has been described. However, in the display device according to the present invention, the light emitting element 50 and the potential control unit 51 have It is not necessary to correspond to 1: 1, and a plurality of light emitting elements 50 may share the potential control unit 51. Hereinafter, the organic EL display device according to the second embodiment having such a configuration will be described with reference to FIGS. 5 and 6.

  FIG. 5 is a plan configuration diagram showing a display area including a plurality of pixels of the organic EL display device 102 of the present embodiment. In the display area shown in the figure, a plurality (30) of light emitting elements 50 are arranged in a matrix in a plan view. One potential control unit 51 is provided for the light emitting elements 50 of three colors (R, G, B) arranged in the horizontal direction in the figure, and straddles the three light emitting elements 50 and the potential control unit 51. A common electrode (second electrode) 28 having a rectangular shape in plan view is provided as a common electrode. That is, in the display device of the present embodiment, a pixel group Ps composed of the three-color light emitting elements 50 constituting the pixels and the potential control unit 51 provided in the vicinity thereof constitutes one display unit. Color display by a plurality of pixel groups Ps arranged in a matrix in plan view on the substrate 20 is possible.

  Each light emitting element 50 constitutes the minimum display unit (pixel) of the present display device. Each light emitting element 50 is provided with a pixel electrode (first electrode) 19, an EL layer (functional layer) 27 provided in a planar region of the pixel electrode 19, and a bank 22 surrounding the EL layer 27. ing. On the other hand, the bank 22 having the same planar shape as the light emitting element 50 is provided in the potential control unit 51, but the EL layer 27 is not provided. A common electrode (second electrode) 28 is provided across the light emitting element 50 and the potential control unit 51 constituting the pixel group Ps.

Next, FIG. 6 is a cross-sectional configuration diagram taken along the line AA ′ of FIG. In the cross-sectional structure shown in FIG. 6, an element forming layer 21 including a TFT and a plurality of insulating films, which will be described later, is provided on the substrate 20. Three light emitting elements 50, 1 A pixel group Ps composed of two conductive connection portions 51 is arranged. In the element formation layer 21, the pixel driving TFT 12 and the potential control TFT 32 as shown in FIG. 4 are formed. A bank 22 is erected on the peripheral edge of the pixel electrode 19 arranged on the element formation layer 21. In the present embodiment, the bank 22 includes an inorganic material layer 22A and an organic material layer 22B. It has a laminated structure.
Each light emitting element 50 has a configuration in which an EL layer 27 and a common 28 are stacked on the pixel electrode 19 in a region defined by the bank 22. The potential control unit 51 has a configuration in which the common electrode 28 shared by the three light emitting elements 50 and the pixel electrode 19 are conductively connected. Further, a sealing member 55 is mounted so as to cover the light emitting elements 50... And the potential control unit 51, and is hermetically bonded to the substrate 20.

  Further, as a circuit configuration in the organic EL display device 102 of the present embodiment, the pixel group Ps shown in FIGS. 5 and 6 includes three light emitting elements 50 including the circuit shown in FIG. 2 and one potential control unit 51. Are electrically connected to each other through the common electrode 28. That is, each light emitting element 50 is driven by a current supplied through the pixel driving TFT 12 and can control the voltage applied to the EL layer 27 by the potential control unit 51 connected through the common electrode 28. It has become.

The organic EL display device 102 of the present embodiment having the above-described configuration is a light emitting element 50 (pixel) of each color of R, G, B by lighting / non-lighting operation of each light emitting element 50 arranged in the display region 4. The display is performed with the pixel group Ps consisting of 1 as a display unit, and during the display operation, the common electrode 28 is held at an arbitrary potential by the potential control unit 51 provided corresponding to each pixel group Ps. It is possible to do. With this configuration, it is possible to apply a correction voltage to the common electrode 28 in order to reduce variations in light emission luminance due to variations in the characteristics of the pixel driving TFTs 12 of the light emitting element 50, and an organic display with excellent display luminance uniformity. It is an EL display device.
Further, even if a voltage drop occurs in each light emitting element 50 due to the resistance of the common electrode 28 itself, it can be corrected by the potential control unit 51, and it is possible to prevent the light emission luminance of the light emitting element 50 from being lowered. The light emitting element 50 can emit light with a predetermined luminance.

  In the organic EL display device 102, the potential control unit 51 provided on the substrate 20 adjacent to the light emitting element 50 does not function as a display pixel, so that the pixels in the display region are missing at a certain frequency. However, since the potential control unit 51 and the light emitting element 50 have fine dimensions of about several tens of μm to several mm, the region where the potential control unit 51 is provided is not visually recognized. In particular, in a large-sized high-definition display device, an observer appreciates a display image at a position about 1 to several meters away, so there is no problem at all.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 7 is a plan configuration diagram of a display area provided in the organic EL display device of the present embodiment, and corresponds to the plan configuration diagram shown in FIG. 5. The organic EL display device 103 of the present embodiment shown in FIG. 7 has the same basic configuration as the organic EL display device 102 of the second embodiment, and the potential control unit 151 having a different planar configuration is included in the pixel group Ps. It is characterized in that is included. Further, the cross-sectional structure taken along the line DD ′ shown in FIG. 7 is the same as the cross-sectional structure of the organic EL display device 102 shown in FIG.

  The potential controller 151 shown in FIG. 7 has a configuration in which a rectangular electrode 119 (electrode member) in plan view and a common electrode (second electrode) 28 shared by the three light emitting elements 50 are electrically connected. I have. In the potential control unit 151 according to the present embodiment, the shape of the opening of the bank 22 surrounding the electrode 119 is substantially circular in plan view. Although not shown, a potential control element similar to the potential control TFT 32 shown in FIGS. 2 and 4 is connected to the electrode 119 of the potential control unit 151, so that the potential of the common electrode 28 can be freely adjusted. Can be controlled.

  Also by the organic EL display device of the present embodiment including the potential control unit 151 having the above-described configuration, the potentials of the plurality of common electrodes 28 provided in the display region 4 can be favorably controlled. It is possible to suppress a variation in light emission intensity caused by a characteristic variation and obtain a high-quality display with excellent display luminance uniformity. In this embodiment, since the plane area of the potential control unit 151 is small, it is easy to increase the area ratio of the light emitting elements 50 (pixels) in the display region, and the potential control unit 151 is more visually recognized. It becomes difficult to be done.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in each of the above embodiments, the potential control unit 51 for controlling the potential of the common electrode 28 is provided for each pixel 3 or each pixel group Ps. The arrangement frequency of the potential control unit 51 can be arbitrarily determined. For example, the common electrode 28 may be divided for each scanning line, and the potential control unit 51 may be provided for each line. In addition, the common electrode 28 may be divided for each predetermined number of pixel drive circuits.
Alternatively, the common electrode 28 may be formed in a solid shape in the display region 4 and a plurality of potential control units 51 may be provided in the planar region. When the common electrode 28 is not divided, a voltage drop due to the resistance of the electrode tends to occur typically in the central portion of the display region 4. However, if the potential control units 51 are provided at a plurality of locations, the voltage drop Since a voltage for correcting the minute can be applied, uniform display luminance can be obtained in the display area. Also in this configuration, it is possible to suppress the luminance variation due to the characteristic variation of the light emitting element 50 to some extent. This is particularly effective in a top emission type display device using a transparent conductive material having a relatively high resistance as the common electrode 28.
The present invention can be applied not only to an organic EL display device but also to other display devices, and is particularly suitable for a display device including a current-driven light emitting element. In addition, specific descriptions of the material, film thickness, planar shape, and the like of each layer exemplified in the above embodiment can be changed as appropriate.

(Electronics)
FIG. 8 is a perspective configuration diagram showing an example of an electronic apparatus according to the present invention. A video monitor 1200 shown in the figure includes a display unit 1201 including the organic EL display device (display device) of the previous embodiment, a housing 1202, a speaker 1203, and the like. The video monitor 1200 can display uniform brightness on the organic EL display device. The present invention is effective in a large EL display device in which the voltage drop at the common electrode becomes significant, for example, the screen size is 20 inches diagonal or more.

FIG. 1 is an overall configuration diagram of an organic EL display device according to a first embodiment. FIG. 2 is a plan view showing the display area. FIG. 3 is a cross-sectional configuration diagram taken along the line A-A ′ of FIG. 2. FIG. 4 is a cross-sectional configuration diagram of a light emitting element and a potential control unit. FIG. 5 is a circuit configuration diagram including a light emitting element and a potential control unit. FIG. 6 is a diagram illustrating another circuit configuration example according to the embodiment. FIG. 7 is a plan configuration diagram of the organic EL display device according to the second embodiment. FIG. 8 is a perspective configuration diagram illustrating an example of an electronic apparatus.

Explanation of symbols

  101 to 103 Organic EL display device (display device), 3 pixels, 4 display area, 12 pixel driving TFT, 14 gate electrode, 17 relay conductive layer, 19 pixel electrode (first electrode), 20 substrate, 27 EL layer (Functional layer), 28 common electrode (second electrode), 32, 53 potential control TFT (potential control element), 34 cathode scanning line, 43 pixel selection TFT, 45 power supply line, 46 anode scanning line, 47 voltage Supply line, 49 capacitor, 50 light emitting element, 51 conductive connection portion, 70 storage capacitor, 119 electrode (electrode member), Ps pixel group

Claims (24)

A display device comprising a display region in which a plurality of light-emitting elements each including a first electrode, a functional layer including a light-emitting layer, and a second electrode are sequentially stacked on a substrate,
A display device, wherein a plurality of potential control units for controlling the potential of the second electrode are provided in the display region.   The display device according to claim 1, wherein a plurality of the second electrodes are provided in the display area, and the potential control unit is provided corresponding to each of the second electrodes. .   The display device according to claim 2, wherein the second electrode is formed across a plurality of the light-emitting elements constituting one display unit of the display device.   The display device according to claim 2, wherein the second electrode is provided for each of the light-emitting elements, and the potential control unit is provided corresponding to each of the second electrodes. .   5. The display device according to claim 1, wherein the potential control unit includes a potential control element that functions as a variable resistance element by being connected to the second electrode. 6.   The display device according to claim 1, wherein the potential control unit includes a potential control element connected to the second electrode via a capacitor. A pixel driving switching element provided corresponding to the plurality of light emitting elements and conductively connected to the first electrode;
The display device according to claim 5, wherein the pixel driving switching element and the potential control element have substantially the same configuration.   8. The potential control element according to claim 5, wherein the potential control element is conductively connected to the second electrode through an electrode member made of the same material provided in the same layer as the first electrode. Item 1. A display device according to item 1. Voltage correction means connected to the plurality of potential controllers;
The voltage correction means is capable of supplying voltage correction information calculated based on the light emission characteristics of the plurality of light emitting elements to the potential control unit. The display device according to item.   The voltage correction unit includes a voltage value holding unit that holds a voltage value applied to each first electrode, and a correction information calculation unit that calculates voltage correction information based on the voltage value held in the voltage value holding unit. The display device according to claim 9, further comprising:   The display device according to claim 10, wherein the correction information calculation unit includes a lookup table that associates the voltage value of the first electrode with the voltage correction information output to the potential control unit. .   The display device according to claim 9, wherein the voltage correction unit is capable of supplying voltage correction information set based on a luminance distribution of the display area to the potential control unit. The pixel driving switching element is a thin film transistor element,
13. The display according to claim 12, wherein the voltage correction means is capable of supplying voltage correction information set based on a threshold value or easy conductivity of each thin film transistor element to the potential control unit. apparatus.   The display device according to claim 12, wherein the voltage correction unit includes a lookup table in which a luminance distribution in the display area is associated with the voltage correction information. A driving method of a display device including a display region in which a plurality of light-emitting elements each including a first electrode, a functional layer including a light-emitting layer, and a second electrode are sequentially stacked on a substrate,
A display device driving method, wherein display is performed while controlling the potential of the second electrode at a plurality of locations in the display region.   16. The display device driving method according to claim 15, wherein a potential is controlled for each of the plurality of second electrodes in a display device provided with a plurality of the second electrodes.   The display device in which the second electrode is formed across a plurality of light emitting elements constituting one display unit, wherein the potential of the second electrode is controlled for each display unit. A driving method of the display device according to the above.   17. The display device according to claim 16, wherein in the display device in which the second electrode is provided for each of the light emitting elements, the potential of the second electrode is controlled for each of the light emitting elements. Driving method. In controlling the potential of the second electrode,
19. The voltage applied to the second electrode is corrected using voltage correction information set based on light emission characteristics of the plurality of light emitting elements. 19. A driving method of a display device. In controlling the potential of the second electrode,
The voltage applied to the second electrode is corrected using voltage correction information calculated based on a voltage value applied to the first electrode of the plurality of light emitting elements. A driving method of a display device. In correcting the voltage applied to the second electrode,
21. The display device driving method according to claim 20, wherein the voltage correction information is obtained by referring to a lookup table in which the voltage value applied to the first electrode is associated with the voltage correction information. . In controlling the potential of the second electrode,
The method for driving a display device according to claim 19, wherein the voltage applied to the second electrode is corrected using voltage correction information based on a luminance distribution of the display area. In correcting the voltage applied to the second electrode,
23. The method of driving a display device according to claim 22, wherein the voltage correction information is obtained by referring to a look-up table that associates the luminance distribution of the display area with the voltage correction information.   An electronic apparatus comprising the display device according to claim 1.

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