JP2004206148A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device capable of excellently displaying various kinds of signals with a configuration wherein a plurality of display elements are wired in common, and to provide its driving method. <P>SOLUTION: The image display device has a row wire, a plurality of column wires, a modulating circuit, and a plurality of display elements; and the plurality of display elements are connected to the row wire in common, the plurality of column wires are connected to the plurality of display elements respectively, and the modulating circuit supplies a modulated signal to the column wires. The image display device has a plurality of display modes and has a potential setting circuit which sets the potential of a signal applied to the row wire according to a selected display mode. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an image display device and a driving method of the image display device. In particular, the present invention relates to an image display device in which a plurality of display elements are commonly wired and a driving method thereof. Further, the present invention relates to an image display device including a display panel in which a plurality of display elements are arranged in a matrix and a driving method thereof. In particular, the present invention relates to an image display device capable of displaying a television signal and a video signal of a computer with high quality and a driving method thereof.

  Conventionally, two types of electron-emitting devices, a hot cathode device and a cold cathode device, are known. Among them, the cold cathode device is, for example, a surface conduction type emission device, a field emission type device (hereinafter referred to as “FE type”), or a metal / insulating layer / metal type emission device (hereinafter referred to as “MIM type”). ) Are known.

  As the surface conduction type emission element, for example, Non-Patent Document 1 and other examples described later are known.

The surface conduction electron-emitting device utilizes a phenomenon in which electron emission occurs when a current flows in a small-area thin film formed on a substrate in parallel with the film surface. Examples of the surface conduction type emission element include an element using an Au thin film (Non-patent document 2) and an element using an In ₂ O ₃ / SnO ₂ thin film (Non-patent document 3) in addition to the element using the SnO ₂ thin film by Elinson et al. ) And those using a carbon thin film (Non-Patent Document 4).

  FIG. 11 shows a plan view of a device according to Non-Patent Document 3 as a typical example of the device configuration of these surface conduction electron-emitting devices. In the figure, reference numeral 3001 denotes a substrate; and 3004, a conductive thin film made of metal oxide formed by sputtering. The conductive thin film 3004 is formed in an H-shaped planar shape as shown. An electron emission portion 3005 is formed by performing an energization process called energization forming described later on the conductive thin film 3004. The interval L in the figure is set to 0.5 to 1 (mm), and W is set to 0.1 (mm). In addition, for convenience of illustration, the electron emitting portion 3005 is shown in a rectangular shape at the center of the conductive thin film 3004, but this is a schematic one, and the position and shape of the actual electron emitting portion are faithfully represented. It is not.

  In the surface conduction electron-emitting device described above, including the device according to Non-Patent Document 3, it is general to form an electron-emitting portion 3005 by subjecting the conductive thin film 3004 to an energization process called energization forming before performing electron emission. It was a target. That is, the energization forming means that a constant DC voltage or a DC voltage that increases at a very slow rate of, for example, about 1 V / min is applied to both ends of the conductive thin film 3004 to energize the conductive thin film 3004. Is locally destroyed, deformed or altered to form an electron emitting portion 3005 in a state of high electrical resistance. Note that a crack is generated in a part of the conductive thin film 3004 that is locally broken, deformed, or altered. When an appropriate voltage is applied to the conductive thin film 3004 after the energization forming, electron emission is performed in the vicinity of the crack.

  Non-Patent Document 5, Non-Patent Document 6, and the like are known as examples of the FE type.

  FIG. 12 shows a cross-sectional view of a device according to Patent Document 6 as a typical example of the FE-type device configuration. In the figure, 3010 is a substrate, 3011 is an emitter wiring made of a conductive material, 3012 is an emitter cone, 3013 is an insulating layer, and 3014 is a gate electrode. In this element, by applying an appropriate voltage between the emitter cone 3012 and the gate electrode 3014, field emission is caused from the tip of the emitter cone 3012.

  Further, as another element configuration of the FE type, there is an example in which an emitter and a gate electrode are arranged on a substrate almost in parallel with a substrate plane, instead of a laminated structure as shown in FIG.

  As an example of the MIM type, for example, Non-Patent Document 7 is known. FIG. 13 shows a typical example of the MIM element configuration. The figure is a sectional view, in which 3020 is a substrate, 3021 is a lower electrode made of a metal, 3022 is a thin insulating layer having a thickness of about 100 Å, and 3023 is an upper layer made of a metal having a thickness of about 80 to 300 Å. Electrodes. In the MIM type, an appropriate voltage is applied between the upper electrode 3023 and the lower electrode 3021 to cause electron emission from the surface of the upper electrode 3023.

  The above-described cold cathode device can obtain electron emission at a lower temperature than the hot cathode device, and thus does not require a heater for heating. Therefore, the structure is simpler than the hot cathode element, and a fine element can be produced. Further, even when a large number of elements are arranged on a substrate at a high density, problems such as thermal melting of the substrate hardly occur. In addition, unlike the hot cathode element, which operates by heating the heater, the response speed is slow, and the cold cathode element has an advantage that the response speed is fast.

  For this reason, research for applying the cold cathode device has been actively conducted.

  For example, the surface conduction electron-emitting device has the advantage of being able to form a large number of devices over a large area because it has a particularly simple structure and is easy to manufacture among cold cathode devices. Therefore, for example, as disclosed in Patent Document 1 by the present applicant, a method for arranging and driving a large number of elements has been studied.

  As for applications of the surface conduction electron-emitting device, for example, image forming devices such as image display devices and image recording devices, charged beam sources, and the like have been studied.

  In particular, as an application to an image display device, for example, as disclosed in Patent Document 2, Patent Document 3, or Patent Document 4 by the present applicant, a surface-conduction emission device and a phosphor that emits light by irradiation with an electron beam are disclosed. An image display device using a combination of the above has been studied. An image display device using a combination of a surface conduction electron-emitting device and a phosphor is expected to have better characteristics than other conventional image display devices. For example, compared to a liquid crystal display device that has become widespread in recent years, it can be said that it is excellent in that it does not require a backlight because it is a self-luminous type and that it has a wide viewing angle.

  A method of driving a large number of FE types in a row is disclosed, for example, in Patent Document 5 by the present applicant. As an example of applying the FE type to an image display device, for example, a flat panel display device reported by R. Meyer et al. Is known (Non-Patent Document 8).

An example in which a number of MIM types are arranged and applied to an image display device is disclosed in, for example, Patent Document 6 by the present applicant.
JP-A-64-31332 U.S. Pat. No. 5,066,883 JP-A-2-257551 JP-A-4-28137 U.S. Pat. No. 4,904,895 JP-A-3-55738 MI Elinson, Radio E-ng. Electron Phys., 10, 1290, (1965) G. Dittmer: “Thin Solid Films”, 9, 317 (1972) (M. Hartwell and CG Fonstad: “IEEE Trans. ED Conf.”, 519 (1975)) Hisashi Araki et al .: Vacuum, Vol. 26, No. 1, 22 (1983) WP Dyke & WW Dolan, “Field Emission”, Advance in Electron Physics, 8, 89 (1956) CA Spindt, “Physical Properties of Thin-Film Field Emission Cathodes with Molybdenum Cones, J. Appl. Phys., 47, 5248 (1976) CA Mead, “Operation of Tunnel-Emission Devices”, J. Appl. Phys., 32, 646 (1961) R. Meyer: “Recent Development on Microtips Display at LETI”, Tech.Digest of 4th Int. Vacuum Microelectronics Conf., Nagahama, pp. 6-9 (1991)

  It is an object of the present application to realize an image display device capable of favorably displaying various types of signals in a configuration in which a plurality of display elements are commonly wired, and a driving method thereof.

  One of the inventions of the image display device according to the present application is configured as follows.

A row wiring, a plurality of column wirings, a modulation circuit, and a plurality of display elements, wherein the plurality of display elements are commonly connected to the row wirings, and each of the plurality of column wirings is the plurality of column wirings. In the image display device connected to each of the display elements, the modulation circuit supplies a modulation signal to the column wiring,
An image display device having a plurality of display modes, and a potential setting circuit for setting a potential of a signal applied to the row wiring according to the selected display mode.

  This configuration is preferable because the control according to the type of the image signal to be displayed can be performed by the signal applied to the row wiring independently of the modulation control by the signal applied to the column wiring. Further, in the present invention, the modulation circuit may be configured to generate a pulse width modulation signal having a time width corresponding to a gradation of a signal to be displayed, or a peak value having a peak value according to a gradation of a signal to be displayed. Any of the configurations for generating a modulation signal can be employed. However, the configuration of pulse width modulation is more desirable in terms of gradation display.

  Also in the present invention, it is preferable that the column wiring is provided so that a longitudinal direction thereof intersects a longitudinal direction of the row wiring. Also, a plurality of display elements, each having a plurality of the row wirings, wherein the plurality of display elements are connected to each row wiring, and each of the plurality of display elements connected to each row wiring is connected to another row wiring. The present invention can be suitably applied to a configuration in which each of the column wirings and each of the column wirings are shared.

  Further, it is preferable that a scanning circuit for supplying a scanning signal for sequentially scanning the plurality of row wirings is further provided. Specifically, a configuration in which the scanning circuit applies a selected potential to the selected row wiring can be preferably employed. In this configuration, the selection potential may be set according to the type of the image signal to be displayed.

  Each of the above inventions can be particularly preferably applied when the display element is an element that consumes 80% or less of the current injected into the display element for display, and the display element is injected into the display element. The invention according to the present application can be more suitably applied to a case where the element consumes 50% or less of the generated current for display.

  In each of the inventions described above, the display element may be, for example, an electron-emitting element. It is preferable to use a combination of a light emitter (particularly, a phosphor) that emits light by irradiation with electrons emitted from the electron-emitting device. A cold cathode device can be suitably used as the electron-emitting device. In particular, the present invention can be suitably applied to a configuration employing a surface conduction electron-emitting device. In the case where the display element is an electron-emitting device, an image can be displayed suitably by providing a phosphor that emits light by electrons emitted from the electron-emitting device.

  Further, each of the above inventions can be suitably applied to a case where the display element is an electroluminescent element. It is preferable that the display element is an electroluminescent element because the element itself emits light.

  Further, one of the inventions of the driving method of the image display device according to the present application is configured as follows.

A row wiring, a plurality of column wirings, a modulation circuit, and a plurality of display elements, wherein the plurality of display elements are commonly connected to the row wirings, and each of the plurality of column wirings is the plurality of column wirings. The display device is connected to each of the display elements, the modulation circuit is a driving method of an image display device that supplies a modulation signal to the column wiring,
A method for driving an image display device, comprising: setting a potential of a signal to be applied to the row wiring according to a type of a signal to be displayed.

  In any of the inventions described above, when the modulation circuit outputs a signal whose potential is controlled as a control target (for example, a high-level potential), the modulation circuit outputs a signal whose current is controlled as a control target. Can also be suitably applied.

  A suitable display can be realized according to various signals according to the present invention.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  The inventors have tried electron-emitting devices having various materials, manufacturing methods, and structures, including those described in the above-mentioned prior art. Furthermore, research has been conducted on a multi-electron beam source in which a large number of electron-emitting devices are arranged, and on an image display device using the multi-electron source.

  The inventors have tried a multi-electron beam source by the electric wiring method shown in FIG. 9, for example. That is, it is a multi-electron beam source in which a large number of electron-emitting devices are arranged two-dimensionally and these devices are wired in a matrix as shown in the figure.

  In the figure, 4001 schematically shows an electron-emitting device, 4002 is a row wiring, and 4003 is a column wiring. Although the row wiring 4002 and the column wiring 4003 actually have a finite electric resistance, they are shown as wiring resistances 4004 and 4005 in the figure. The above-described wiring method is called simple matrix wiring.

  For convenience of illustration, the matrix is shown as a 6 × 6 matrix, but the size of the matrix is not limited to this. For example, in the case of a multi-electron beam source for an image display device, a desired image is displayed. Only enough elements are arranged and wired.

  In a multi-electron beam source in which electron-emitting devices are arranged in a simple matrix, an appropriate electric signal is applied to the row wiring 4002 and the column wiring 4003 in order to output a desired electron beam. For example, to drive one arbitrary row of electron-emitting devices in the matrix, the selection potential Vs is applied to the row wiring 4002 of the selected row, and at the same time, the non-selection potential is applied to the row wiring 4002 of the non-selected row. Vns is applied. In synchronization with this, a driving potential Ve for outputting an electron beam is applied to the column wiring 4003. According to this method, if the voltage drop due to the wiring resistances 4004 and 4005 is ignored, a voltage of Ve−Vs is applied to the electron-emitting devices in the selected row, and Ve−Vs is applied to the electron-emitting devices in the non-selected row. A voltage of -Vns is applied. If Ve, Vs, and Vns are set to potentials of appropriate magnitudes, an electron beam of a desired intensity is output only from the electron-emitting devices in the selected row, and if a different drive potential Ve is applied to each of the column wirings, the selection is made. Each of the elements in the row outputs an electron beam of a different intensity. Further, since the response speed of the cold cathode element is high, if the length of time for applying the driving potential Ve is changed, the length of time for outputting the electron beam can be changed.

  Therefore, various applications are considered for a multi-electron beam source in which electron-emitting devices are arranged in a simple matrix. For example, if a voltage signal corresponding to image information is appropriately applied, the multi-electron beam source can be applied as an electron source for an image display device. Is expected.

  However, when the voltage source is actually connected to the multi-electron beam source and driven by the above-described voltage application method, a voltage drop occurs due to wiring resistance, so that the voltage effectively applied to each electron-emitting device varies. The problem had occurred.

  First of all, as a cause of the variation in the voltage applied to each element, the simple matrix wiring has a different wiring length for each electron-emitting device (that is, a different wiring resistance for each element).

  Second, the magnitude of the voltage drop generated by the wiring resistance 4004 of each part of the row wiring is not uniform. This occurs because the current branches and flows from the row wiring of the selected row to each of the electron-emitting devices connected to the row, and the current flowing through each of the wiring resistances 4004 is not uniform. .

  Third, the magnitude of the voltage drop caused by the wiring resistance varies depending on the driving pattern (the image pattern to be displayed in the case of the image display device). This occurs because the current flowing through the wiring resistance changes depending on the driving pattern.

  If the voltage applied to each electron-emitting device varies due to the above reasons, the intensity of the electron beam output from each electron-emitting device deviates from a desired value, which is inconvenient in application. For example, when applied to an image display device, the luminance of a display image becomes non-uniform or the luminance fluctuates depending on the display image pattern.

  In particular, the effect of the luminance drop due to such a voltage drop is hardly noticeable in a natural image such as a normal television broadcast and is hardly subjective, but rather, a flat image represented by a computer output is displayed. In many cases, an image with a particularly uncomfortable feeling was often obtained.

  FIG. 10 is a diagram for explaining the problem of the present invention. FIG. 1 is an original image of a window screen often seen as an output image of a computer as an example of an image to be displayed.

  The screen of FIG. 10 has a single white color (R: 100%, R: 0%, G: 0%, B: 100%) as a background in the center with a single blue color (R: 0%, G: 0%, B: 100%). , G: 100%, B: 100%). When such an original image is displayed, comparing the blue with the line with the background and the window and the blue with the line with only the background, the voltage drop caused by the difference in the display pattern is the same even though the original image is the same blue. Due to the difference, the brightness of the blue was different. Therefore, when an image having such a pattern is displayed, there is a very inconvenience that a difference in luminance looks like a step on the horizontal line of the window.

  In particular, the decrease in luminance due to the effect of wiring resistance tends to increase at the center of the screen, and changes as a whole, but the human visual characteristics are very insensitive to such continuous changes. He was insensitive and didn't cause much discomfort.

  On the other hand, when there is a step-like luminance difference between adjacent rows, even a small change is very sensitive. It is very inconvenient that a luminance difference occurs along the horizontal line.

  On the other hand, in general, the output image of the computer is displayed with considerably lower brightness than the display of a normal TV due to the intended use.

  In the following embodiments, while considering such characteristics of computer images, it is possible to reduce uncomfortable patterns generated when displaying computer images and to display natural images represented by HDTV and other TV systems. Illustrates an image display device capable of displaying an image having a wide dynamic range as usual.

(Embodiment 1)
The first embodiment is an example in which a display device including a large number of surface conduction electron-emitting devices is modulated by a voltage pulse width modulation signal as a modulation signal in order to obtain a desired image.

  FIG. 4 is a perspective view of the display panel used in the embodiment, in which a part of the panel is cut away to show the internal structure. In the figure, reference numeral 1005 denotes a rear plate, 1006 denotes a side wall, 1007 denotes a face plate, and 1005 to 1007 form an airtight container for maintaining the inside of the display panel at a vacuum. When assembling an airtight container, it is necessary to seal the joints of each member to maintain sufficient strength and airtightness.For example, apply frit glass to the joints, Sealing was achieved by firing at 400 to 500 degrees for 10 minutes or more. A method for evacuating the inside of the airtight container will be described later.

  A substrate 1001 is fixed to the rear plate 1005, and N × M cold cathode elements 1002 are formed on the substrate. The N × M cold cathode devices are arranged in a simple matrix by M row wirings 1003 and N column wirings 1004. The portion constituted by 1001 to 1004 is referred to as a multi-electron source.

  A fluorescent film 1008 is formed on the lower surface of the face plate 1007. Since the present embodiment is a color display device, phosphors of three primary colors of red, green, and blue used in the field of CRT are separately applied to a portion of the fluorescent film 1008.

  In this embodiment, a surface conduction electron-emitting device was manufactured as a cold cathode device in a display panel having the above-described appearance.

  The surface conduction electron-emitting device has a characteristic of (emission current Ie) versus (device applied voltage Vf) and a characteristic of (device current If) versus (device applied voltage Vf) as shown in FIG. Note that the emission current Ie is significantly smaller than the device current If, and it is difficult to show them on the same scale. Therefore, the two graphs are shown on different scales.

  That is, the emission current Ie has the following three characteristics.

  First, when a voltage equal to or higher than a certain voltage (this is referred to as “threshold voltage Vth”) is applied to the element, the emission current Ie sharply increases. On the other hand, at a voltage lower than the threshold voltage Vth, the emission current Ie hardly increases. Not detected. In the case of FIG. 3, Vth is 8 volts.

  That is, it is a non-linear element having a clear threshold voltage Vth with respect to the emission current Ie. Second, since the emission current Ie changes depending on the voltage Vf applied to the element, the magnitude of the emission current Ie can be controlled by the voltage Vf.

  Third, since the response speed of the current Ie emitted from the element with respect to the voltage Vf applied to the element is high, the amount of charge of the electrons emitted from the element can be controlled by the length of time during which the voltage Vf is applied.

  Because of the above characteristics, the surface conduction electron-emitting device can be suitably used for a display device. For example, in a display device in which a large number of elements are provided corresponding to pixels of a display screen, display can be performed by sequentially scanning the display screen by using the first characteristic. That is, a voltage equal to or higher than the threshold voltage Vth is appropriately applied to the element being driven, and a voltage lower than the threshold voltage Vth is applied to the element in a non-selected state. By sequentially switching the elements to be driven, the display screen can be sequentially scanned and displayed.

  In addition, by using the second characteristic or the third characteristic, the light emission luminance can be controlled, so that gradation display can be performed.

  In this embodiment, an image is displayed using the first and third characteristics of the surface conduction electron-emitting device.

  FIG. 1 is a block diagram schematically showing the circuit configuration. In the figure, reference numeral 1 denotes a display panel having a built-in multi-electron source, Dx1 to DxM 'are row wiring terminals of the multi-electron source, Dy1 to DyN are column wiring terminals of the multi-electron source, and Hv is between the face plate and the rear plate. Is a high voltage power supply for applying an acceleration voltage, Va is a high voltage power supply, 2 and 2 'are scanning circuits, 3 is a synchronization signal separation circuit, 4 is a timing generation circuit, and 7 is a synchronization separation circuit for converting a YRB signal into RGB. A switching circuit 13 for switching between an RGB signal of HDTV (High Definition Television System standard) and a VGA (signal of VGA (Video Graphic Array) standard), and 5 for one line of image data. 6 is a line memory for one line of image data, 8 is a pulse width modulation circuit, 9 is amplitude setting means, 10 is a controller, and 11 is a remote control unit. Interface, 12 is a switch for controlling an image display device. In this embodiment, a surface conduction electron-emitting device is used as the electron-emitting device of the multi-electron source.

(Synchronous separation circuit, timing generation circuit)
The image display device of the present embodiment can display both an HDTV television signal and a VGA signal which is an output of a computer or the like. However, the present embodiment is one example, and is similarly applicable to other standards such as NTSC, PAL, and SECAM.

  The VGA signal is supplied to the signal switching unit 13 and supplies the synchronization signals Vsync and Hsync to the timing generation circuit 4. The HDTV television signal is first separated by a synchronization separation circuit 3 into a synchronization signal Tsync (including vertical synchronization and horizontal synchronization) and supplied to a timing generation circuit 4. Further, the video signal YRB is converted into a digital RGB signal by the RGB conversion circuit 7 and supplied to the signal switching unit 13. The signal switching unit 13 is a circuit for selecting between VGA and HDTV, and switches a video source according to a selection signal Tsel from the controller 10. When a video source to be selected is set by the remote controller 11, the switch 12, or the like, the controller 10 supplies a selection signal Tsel to each unit.

  The timing generation circuit 4 determines the operation timing of each unit in synchronization with the synchronization signal of the video source selected on the basis of the selection signal Tsel. That is, the timing generation circuit 4 generates signals such as Tsft for controlling Tsft for controlling the operation timing of the shift register 5, Tmry for controlling the operation timing of the line memory 6, and Tscan for controlling the operation of the scanning circuit 2.

(Scanning circuit)
The scanning circuits 2 and 2 'are circuits for outputting the selection potential Vs or the non-selection potential Vns to the connection terminals Dx1 to DxM' in order to sequentially scan the multi-electron source one row at a time. For example, as shown in FIG. Each have M 'switches. Note that these switches are preferably constituted by transistors or FETs.

  The values of the selection potential Vs and the non-selection potential Vns output from the scanning circuits 2 and 2 ′, and the value of the modulation signal described later are determined based on the (emission current Ie) versus (element applied voltage Vf) characteristics of the cold cathode element used. It may be determined based on (element current If) versus (element applied voltage Vf).

  In the surface conduction electron-emitting device of the present embodiment, a voltage of approximately +12 to +15 V is required as the device applied voltage Vf to display a desired image.

  For this reason, in this example, the selection potential is set to -7.5 V and the non-selection potential is set to 0 V, and a potential of +5 V to +7.5 V is applied from the modulation side for a time corresponding to image data to be displayed, as described later. As a result, electrons are emitted, and a desired image is obtained.

(Shift register, line memory, pulse width modulation circuit)
The image data separated by the synchronization signal separation circuit 3 is subjected to serial / parallel conversion by the shift register 5 and stored in the line memory 6 for one horizontal scanning period. The pulse width modulation circuit 8 outputs pulse width modulated voltage signals PW1 to PWN based on the image data I'D1 to I'DN stored in the line memory 6.

(Configuration of amplitude setting circuit)
The amplitude setting circuit 9, which is a potential setting circuit, is a circuit that changes the amplitude of the pulse width modulation signals PW1 to PWN according to the selected video source (see FIG. 5). During the period when the pulse width modulation signal PWi (i = 1, 2,... N) is HIGH, the pnp transistor in FIG. 5 is turned on and the npn transistor is turned off to supply the potential VX to each of the column wiring terminals Dy1 to DyN. When the signal is low, the pnp transistor is off and the npn transistor is on, and the column wiring terminals Dy1 to DyN are connected to the ground.

  The potential VX is an amount set according to the selection signal Tsel, and is connected to the power supply VX1 when the video signal is a natural image such as HD by the switch SW-A, and the video signal is output from a computer output such as VGA. In some cases, it is connected to the power supply VX2. In this embodiment, the potential of VX1 is set to + 7.5V, and the potential of VX2 is set to + 6V. As described in the problem, generally, when displaying an output image of a computer, it is general to display the image with reduced luminance as a whole, because the user looks directly at the monitor. In order to suppress the screen luminance as a whole, for example, the acceleration potential Va for accelerating the electrons emitted from the electron-emitting device is reduced, or the image data (corresponding to the pulse width of the pulse width modulation in the present embodiment) is changed. There are several ways, such as lowering or reducing the applied voltage.

  The inventors studied these methods, and as a result, it was optimal to reduce the drive voltage (drive voltage for driving the elements) applied to the display panel as the optimal control destination.

This is because if the driving voltage Vf supplied between the row wiring and the column wiring of the display panel is reduced, the current flowing through the row wiring and the column wiring is also reduced. If the current flowing through the wiring is reduced, the voltage drop in the wiring can be reduced, and the image with a sense of incongruity described in the subject can be reduced, which is very convenient.
(On the other hand, if the pulse width (application time) is reduced without reducing the drive voltage, the voltage drop due to the wiring resistance cannot be reduced. Can not.)
Also, when displaying a natural image typified by HDTV or another television system, driving with a driving voltage higher than that in the computer display mode makes it possible to display a realistic, high-luminance image. It was very convenient.

(Characteristics of display panel)
The display panel of the present embodiment has a so-called simple matrix structure in which cold cathode elements are arranged at intersections of M row wirings and N column wirings. In order to display an image with high quality, a desired number of row wirings and column wirings are required. In the present embodiment, an image display device having 480 row wirings and 2556 (852 × 3) column wirings was studied. In the image display device of the present embodiment, it is preferable to make the wiring resistance of the row wiring as low as possible because there is a concern about a voltage drop mainly due to the wiring resistance of the row wiring. From the process conditions, etc., the display panel considered in this embodiment is:
Resistance per row wiring = 0.5 (Ω)
Further, the surface conduction electron-emitting device which is the cold cathode device of the present embodiment was manufactured to have the characteristics shown in Table 1.

  For such a display panel, HDTV and VGA are selected as video sources, and all white (R: 100%, G: 100%, B: 100%, that is, the modulation signal of all columns is the maximum pulse). FIG. 6 shows the screen (when the width is the same) and the luminance of the display panel was measured. FIG. 6 is a diagram in which the horizontal axis represents the column number and the vertical axis represents the luminance, and the luminance of the display panel is cut out in the horizontal direction and graphed. Since the vertical axis changes depending on the characteristics of the phosphor and the characteristics of the metal back, the vertical axis is intentionally displayed as an arbitrary unit.

  As shown in the figure, in the VGA display mode than in the HD display mode, the driving is performed with the drive voltage lowered, so that the luminance is suppressed as a whole.

  FIG. 7 shows the rate of decrease in luminance over the entire screen when displaying all white. As shown in the figure, when the HD display mode is selected, the brightness is reduced by about 6.5% at the center of the screen as compared with both ends of the screen, whereas the brightness distribution in the VGA display mode is in-plane. Is suppressed to about 1.2% at the center and both ends of the screen.

  Since the voltage drop amount due to the wiring resistance is the largest when displaying all white, when displaying other patterns, the in-plane distribution of the luminance is at least the following value. Therefore, even when the window screen is displayed, the pattern with a sense of incongruity generated at the border of the horizontal line of the window can be reduced to 1.2% or less at the maximum.

  In fact, the present inventors have performed image display using such an image display device. When displaying an HDTV, the inventors can enjoy a realistic image with a wide dynamic range and display a VGA. In this case, it is hardly possible to confirm a pattern having a sense of incongruity caused by a voltage drop in the wiring, which is an issue of the present invention, and it is extremely excellent that sufficient characteristics can be obtained as an output monitor of a computer. Had an effect.

  In the present embodiment, the voltage on the modulation means side is set according to the selection state of the video source. However, the present invention is not limited to this. For example, the selection voltage source Vs on the scanning wiring side is a variable voltage source. Needless to say, the same effect can be obtained even if the value of Vs is varied depending on the selection state of the video source.

  Further, in the present embodiment, the amplitude is set by the two power supplies VX1 and VX2 in FIG. 1. However, the present invention is not limited to this, and the amplitude is similarly set even if the output of one variable voltage source is changed. It goes without saying that you can do it.

  In the present embodiment, the driving conditions of the former and the latter are changed by taking the output of a computer such as a VGA and a television signal such as an HDTV or an NTSC as an example, but the present invention is not limited to this. Alternatively, different drive voltages may be set according to various video formats.

  In the present embodiment, the driving conditions are changed according to the video format selected as described above, but the driving conditions may be changed according to the video content.

  For example, when displaying an image with a sense of reality such as sports, driving is performed at a high driving voltage, and when displaying a movie, driving is performed using a low driving voltage. Such a change allows the user to easily change the mode by giving a command to the controller using the remote controller described in FIG.

  As described above, when the display is performed by changing the driving voltage depending on the video content, there is a further effect that an image suitable for various video contents can be provided to the user.

Further, a circuit for determining the type of the image signal to be displayed may be provided, and the control circuit may be switched according to the determination result. As the determination circuit, a circuit that extracts the characteristics of the input signal (for example, the number of scanning lines, the number of synchronization signals, their timing, and the like) and determines based on the result can be used.
(Embodiment 2)
The second embodiment is an example in which a display device including a large number of surface conduction electron-emitting devices is modulated by a voltage amplitude modulation signal as a modulation signal in order to obtain a desired image.

  In this embodiment, an image is displayed using the first and second characteristics of the surface conduction electron-emitting device.

  FIG. 8 is a block diagram schematically showing the circuit configuration. In the present embodiment, an amplitude modulation circuit 8 'is provided instead of the pulse width modulation circuit 8 of the first embodiment for driving.

(Amplitude modulation circuit and amplitude setting circuit)
The image data separated by the synchronization signal separation circuit 3 is subjected to serial / parallel conversion by the shift register 5 and stored in the line memory 6 for one horizontal scanning period. The amplitude modulation circuit 21 D / A converts the image data stored in the line memory 6 and outputs the amplitude-modulated potential signals AM1 to AMN. The two outputs Vr1 and Vr2 of the amplitude setting circuit 22 are connected to the reference terminals of the D / A converter, and the amplitude-modulated potential signals AM1 to AMN are switched between the minimum Vr2 and the maximum Vr1 in accordance with the image data. The amplitude (potential value) is modulated and supplied to each column wiring.

  In the present embodiment, the output potentials Vr1 and Vr2 of the amplitude setting circuit 21 are set to two types of potentials according to the selected video source. For example, if the video signal is a natural image such as HDTV, Vr1 = 15 (V) and Vr2 = 10 (V), and if the video signal is an output of a computer such as VGA, Vr1 = 13. 5 (V) and Vr2 = 10 (V) were set.

  As described in the problem, generally, when displaying an output image of a computer, it is general to display the image with reduced luminance as a whole, because the user looks directly at the monitor. In order to suppress the luminance of the screen as a whole, there are several methods such as reducing the acceleration voltage Va, reducing the application time of the driving voltage, and reducing the applied voltage.

  The inventors studied these methods, and as a result, it was optimal to reduce the drive voltage (drive voltage for driving the elements) applied to the display panel as the optimal control destination.

  This is because if the driving voltage Vf supplied between the row wiring and the column wiring of the display panel is reduced, the current flowing through the row wiring and the column wiring is also reduced. If the current flowing through the wiring is reduced, the voltage drop in the wiring can be reduced, and the image with a sense of incongruity described in the subject can be reduced, which is very convenient.

  On the other hand, if the application time is reduced without reducing the drive voltage, the voltage drop due to the wiring resistance cannot be reduced, so that the unnatural image described in the problem cannot be reduced.

  Also, when displaying a natural image typified by HDTV or another television system, driving with a driving voltage higher than that in the computer display mode makes it possible to display a realistic, high-luminance image. It was very convenient.

  With such a drive circuit, HD and VGA are selected as video sources for the display panel described in the first embodiment, and all white (R: 100%, G: 100%, B: 100%, ie, FIG. 6 shows the screen when the modulation signals of all the columns have the maximum amplitude) and the luminance of the display panel is measured. FIG. 6 is a diagram in which the horizontal axis represents the column number and the vertical axis represents the luminance, and the luminance of the display panel is cut out in the horizontal direction and graphed. The vertical axis is intentionally displayed as an arbitrary unit because it changes depending on the characteristics of the phosphor and the characteristics of the metal back.

  As shown in the figure, in the VGA display mode rather than the HDTV display mode, the driving is performed with a lower driving voltage, so that the luminance is suppressed as a whole.

  FIG. 7 shows the rate of decrease in luminance over the entire screen when displaying all white. As shown in FIG. 7, when the HDTV display mode is selected, the brightness is reduced by about 6.5% at the center of the screen as compared with both ends of the screen, whereas the brightness is reduced in the VGA display mode. The error is suppressed to about 1.2% at the center and both ends of the screen. Even with the driving method according to the present embodiment, the voltage drop amount due to the wiring resistance becomes the largest when all white (R: 100%, G: 100%, B: 100%), so other patterns are displayed. In this case, the in-plane error of the luminance is at least the following value. Therefore, even when the window screen is displayed, the pattern with a sense of incongruity generated at the border of the horizontal line of the window can be reduced to 1.2% or less at the maximum.

  In fact, the present inventors have performed image display using such an image display device. When displaying an HDTV, the inventors can enjoy a realistic image with a wide dynamic range and display a VGA. In this case, it was almost impossible to confirm a pattern having a sense of incongruity caused by a voltage drop in the wiring, and there was an extremely excellent effect that sufficient characteristics could be obtained as an output monitor of a computer.

  The amplitude setting circuit (means) 21 of the present embodiment adjusts the amplitude of the amplitude modulation by adjusting the reference potential of the amplitude modulation circuit (means) 21, but is not limited to this. For example, the amplitude modulation circuit (means) 21 performs amplitude modulation using a fixed reference voltage D / A converter, and the amplitude setting circuit 22 adjusts the amplitude using an amplifier that can set two types of gains and offsets. A similar effect could be obtained.

  In the present embodiment, the driving conditions of the former and the latter are changed by taking the output of a computer such as a VGA and a television signal such as an HDTV or an NTSC as an example. However, the present invention is not limited to this. Different driving conditions may be set according to various video formats.

  In the present embodiment, the driving conditions are changed according to the video format selected as described above, but the driving conditions may be changed according to the video content.

  For example, when displaying an image with a sense of reality such as sports, driving is performed at a high driving voltage, and when displaying a movie, driving is performed using a low driving voltage. Such a change allows the user to easily change the mode by giving a command to the controller using the remote controller described in FIG. 7 and controlling the respective units by the controller.

In this way, a mode suitable for the video content that the user wants to display is provided, and for each mode, display is performed by changing the voltage for driving the display panel, and the user can display images suitable for various video content. There is a further effect that can be provided.
(Embodiment 3)
The image display device described above can enjoy a realistic image with a wide dynamic range when displaying a natural image typified by HDTV or another TV system as described above. At the same time, when a computer image represented by a VGA is displayed, it is almost impossible to confirm a pattern having a sense of incongruity due to a voltage drop in the wiring, and it is possible to obtain sufficient characteristics as an output monitor of the computer. There is a very good effect.

  On the other hand, the present inventors have studied the case where the present invention is applied to an image display device having a display panel in which electroluminescence (EL) is arranged in a simple matrix structure as an image display element of the display panel of the present invention. Effect was obtained.

  INDUSTRIAL APPLICATION This invention can be utilized for the image display apparatus which displays a television image, a computer image, etc.

FIG. 2 is a block diagram for explaining the image display device according to the first embodiment of the present invention. FIG. 3 is a diagram for explaining scanning circuits 2, 2 'of the image display device of the present invention. 4 is a graph showing typical characteristics of a surface conduction electron-emitting device used in an embodiment of the present invention. FIG. 1 is a perspective view of an image display device according to an embodiment of the present invention, in which a part of a display panel is cut away. FIG. 2 is a diagram for describing a configuration example of an amplitude setting circuit (means) 9 according to the first embodiment of the present invention. 5 is a graph showing a luminance distribution when the display circuit according to the first embodiment of the present invention displays all white (R: 100%, G: 100%, B: 100%). 4 is a graph showing a luminance reduction rate when displaying all white (R: 100%, G: 100%, B: 100%) by the display circuit according to the first embodiment of the present invention. It is a block diagram for explaining the image display device of Embodiment 2 of the present invention. FIG. 3 is a diagram for explaining electrical wiring of the display panel of the present invention. It is a figure for explaining a subject of the present invention. It is a top view which shows an example of the conventionally known surface conduction type | mold emission element. It is a side view which shows an example of FE conventionally known. It is sectional drawing which shows an example of the conventionally known MIM.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Display panel 2, 2 'scanning circuit 3 Synchronous signal separation circuit 4 Timing generation circuit 5 Shift register 6 Line memory 7 RGB conversion circuit 8 Pulse width modulation circuit 9 Amplitude setting circuit 10 Controller 11 Remote control 12 Switch 13 Signal switching section 21 Amplitude modulation Circuit 22 Amplitude setting circuit

Claims (11)

A row wiring, a plurality of column wirings, a modulation circuit, and a plurality of display elements, wherein the plurality of display elements are commonly connected to the row wirings, and each of the plurality of column wirings is the plurality of column wirings. In the image display device connected to each of the display elements, the modulation circuit supplies a modulation signal to the column wiring,
An image display device having a plurality of display modes, and a potential setting circuit for setting a potential of a signal applied to the row wiring according to the selected display mode.   The image display device according to claim 1, wherein the display element consumes only a part of a current injected into the display element for display.   It has a plurality of input units to which an image signal to be displayed is input, and further has a selection circuit for selecting any of the signals from the plurality of input units, and the potential setting circuit, 3. The image display device according to claim 1, wherein the setting of the potential is performed according to a selection state of the selection circuit.   The image display device according to claim 1, further comprising a determination circuit configured to determine a characteristic of an image signal to be displayed, wherein the setting of the potential is performed according to a result of the determination by the determination circuit.   3. The device according to claim 1, further comprising an external setting unit configured to set the potential according to an image to be displayed, wherein the potential setting circuit sets the potential according to the setting of the external setting unit. Image display device.   6. The image display device according to claim 1, wherein, when displaying an input image signal, the potential setting circuit sets a potential as a conflicting term between importance on luminance and reproducibility.   When displaying an input image signal, when the luminance is more important than the reproducibility, the potential set by the potential setting circuit is applied to the potential and the column wiring as compared with the case where the reproducibility is more important than the luminance. The image display device according to claim 1, wherein the potential difference from the applied potential is set to be large.   8. The image display device according to claim 1, wherein the amplitude setting circuit sets the potential according to whether a signal to be displayed is a computer image signal or a television image signal.   9. The image display device according to claim 1, wherein the display element consumes 80% or less of a current injected into the display element for display.   The image display device according to claim 1, wherein the display element is an electron emission element.   The image display device according to claim 1, wherein the display element is an electroluminescence element.

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