JP2007108249A - Display device and its driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of correcting variance in color tone appearing by panels. <P>SOLUTION: The display device includes a color correcting circuit 5 which corrects colors of an externally input RGB video signal and then outputs the RGB video signal to a panel 1. The color correcting circuit 5 previously measures a saturation color and white characteristic of the panel in the form of XYZ chromaticity and finds a first conversion matrix for converting RGB chromaticity of the input RGB video signal into XYZ chromaticity, based upon measurement results. Further, the color correcting circuit 5 finds a second conversion matrix for converting XYZ chromaticity of a saturation color previously set depending upon specifications of the panel into RGB chromaticity, and then converts the input RGB video signal into an output RGB video signal by using those first and second conversion matrixes to correct variances in saturation color and white appearing by panels according to specifications of the panels. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an active matrix color display device and a driving method thereof. More specifically, the present invention relates to a chromaticity adjustment technique for a color display device using a light emitting element represented by an organic electroluminescence (EL) element as a pixel.

  In recent years, interest in organic EL display devices as flat panel displays (hereinafter abbreviated as “FPD”) has increased. Currently, liquid crystal display devices (hereinafter abbreviated as “LCD”) are the mainstream in FPD, but this is not a self-luminous device, but requires a member such as a backlight or a polarizing plate. This is disadvantageous in reducing the thickness and brightness.

  On the other hand, the organic EL display device is a self-luminous type device, and a member such as a backlight is not necessary in principle. Therefore, the organic EL display device is advantageous in reducing the thickness and brightness of the device as compared with the LCD. . In particular, in an active matrix organic EL display device in which a switching element is formed in each pixel, current consumption can be kept low by lighting each pixel in a hold manner, and a large screen and high definition can be made relatively easily. . Due to these advantages, active matrix organic EL display devices are being actively developed and are expected to become the mainstream of next-generation FPDs.

  In recent years, personal photographing devices such as digital still cameras and digital camcorders have been developed. As these finder display elements, LCOS (Liquid Crystal on Silicon) in which a pixel circuit and a drive circuit are formed on a crystalline silicon substrate, or a high temperature or low temperature polycrystalline silicon LCD is used. In a finder element using an LCD, a transmissive type requires a backlight, and a reflective type requires a front light. Therefore, the module thickness is inevitably increased, which is disadvantageous for making the device thinner. In addition, with the miniaturization of personal photographing devices, the viewfinder itself is also miniaturized, and the pixels themselves are being reduced accordingly. For this reason, the transmissive LCD cannot sufficiently secure the aperture ratio of the display unit, and is approaching the performance limit. In addition, although LCOS is becoming mainstream in reflective LCDs, an illumination system is still necessary, which is disadvantageous in reducing the thickness of equipment.

  On the other hand, when an organic EL is used as a viewfinder display element, since it is a self-luminous type, it does not require an illumination system such as an LCD, which can contribute to thinning of the device. In addition, by using a top-emitting element as the organic EL element structure, the aperture ratio of the display portion can be sufficiently secured.

  As an element structure suitable for color display using RGB three primary color light emission, an optical resonance type organic EL element has been proposed. (For example, see Patent Document 1 and Patent Document 2). In the optical resonance type organic EL element, a reflective film that reflects light with a predetermined reflectance is formed on each of the upper and lower layers of the organic EL layer, and the light emitted from the organic EL layer is transmitted between the upper and lower reflective films. By resonating and amplifying the light intensity, light of a specific wavelength (color) component is extracted through one reflection film.

  In an organic EL display device including such an optical resonant organic EL element, an organic EL layer is sandwiched between R (red), G (green), and B (blue) pixels (subpixels) arranged in a matrix. By individually setting (adjusting) the facing distance between the upper and lower reflective films, light of each color can be extracted in pixel units (sub-pixel units). This is because the characteristics of the optical resonator are determined by the reflectance and the opposing distance of each reflective film.

JP 2004-127588 A JP 2005-108644 A

  In an optical resonance type organic EL element, white light emitted from a white organic EL layer is filtered by an optical resonator composed of a pair of reflective electrodes to obtain RGB colors, and only a specific wavelength component is output. ing. By changing the optical distance between the pair of electrodes, only the wavelength components corresponding to the RGB colors can be selectively extracted. Therefore, in principle, RGB color light can be obtained without using a color filter, so that a low-cost color organic EL display device can be obtained. However, it is difficult to accurately set the optical distance between the electrodes facing each other according to the respective RGB wavelengths, and variations occur between panels. Therefore, when viewed at the product level, the color tone differs from panel to panel, which is a problem to be solved.

  FIG. 13 is a graph showing variations in chromaticity appearing on individual panels. This graph is an xy chromaticity diagram of the CIE-XYZ color system, and the chromaticities actually measured for three panels are listed on the graph. As is apparent from the graph, the chromaticity of individual panels varies greatly during the manufacturing process.

  Here, as background of the present invention, RGB chromaticity and XYZ chromaticity will be briefly described. If the intensity of RGB color light, which is human's sensory three primary colors, is used as it is to represent colors, three numerical values are required to represent one color. However, since the color itself is determined by the mixing ratio of RGB light, if the relative ratio of R and G light is used with the sum of the intensity of all RGB light as 1, the relative ratio of the remaining B is automatically determined. The color can be determined by two numerical values. Actually, there are colors that cannot be expressed only by the sensuous three primary colors RGB. Therefore, tristimulus values XYZ, which are the colorimetric and colorimetric characteristics of the machine and the wavelength sensitivity characteristics of the eyes, which are quantified (three primary colors on the color), are expressed. use. Then, based on the tristimulus values XYZ and expressing the color in the xy coordinate space using the two numerical values (x, y) according to the above concept, it is called an xy chromaticity diagram. The color system based on the tristimulus values XYZ is an international display method created by the International Lighting Commission CIE and is referred to as the CIE-XYZ color system. The xy chromaticity diagram based on this color system is called a CIE system or CIE chromaticity diagram. All colors are represented in the chromaticity diagram. The central point corresponds to white (achromatic color), the vividness increases toward the periphery, and monochromatic light (pure color or saturated color) is formed at the boundary around the chromaticity diagram.

  The sensory three primary colors RGB when viewing the colored light and the three primary colors XYZ on the color specification based on the tristimulus values do not correspond one-to-one. The human eye or RGB sensitivity curve is a curve having a single peak at a characteristic wavelength (red, green, and blue). The human eye mainly captures brightness at the center of the sensitivity region (green light) and determines the hue at both ends (blue and red) of the sensitivity region. On the other hand, since the XYZ color system is a system that also expresses colors that cannot be reproduced by RGB, the sensitivity curves of the three colors in the XYZ color system have different shapes from the RGB sensitivity curves.

When the tristimulus values are XYZ, the CIE system determines the respective stimulus values for RGB light and white light as shown in FIG. Using these tristimulus values XYZ,
The relative ratio x of x is x = X / (X + Y + Z)
The relative ratio y of Y is y = Y / (X + Y + Z)
The relative ratio Z of Z is z = Z / (X + Y + Z) = 1−xy.
Also, as a relational expression between RGB value and xy value,
x = 0.6R-0.28G-0.32B
y = 0.2R−0.52G + 0.31B.

  In view of the above-described problems of the conventional technology, an object of the present invention is to provide a display device capable of correcting variations in color tone appearing for each panel. In order to achieve this purpose, the following measures were taken. That is, the present invention includes a panel in which pixels including light emitting elements are arranged in a matrix, a row driving circuit that sequentially selects rows of pixels, and a column driving circuit that supplies a video signal to the selected pixels. A display device that emits light emitting elements included in a pixel at a luminance corresponding to the video signal, wherein the panel is configured by RGB pixels including any of the light emitting elements that emit light in three colors of RGB. The column driving circuit supplies RGB video signals divided into three colors corresponding to RGB pixels, and outputs color to the column driving circuit after correcting the RGB video signals input from the outside. The color correction circuit measures the saturation color and white color specific to the panel in XYZ chromaticity in advance, and converts the RGB chromaticity of the input RGB video signal into XYZ chromaticity based on the result. 1 conversion Tricks are obtained, and a second conversion matrix for converting XYZ chromaticities of saturated colors set in advance according to the panel specifications into RGB chromaticities is obtained, and these first conversion matrix and second conversion matrix are used. An input RGB video signal is converted into an output RGB video signal, and thus variations in saturated color and white color appearing for each panel are corrected in accordance with panel specifications.

  Preferably, the color correction circuit includes a plurality of multipliers and adders for performing the conversion by the first conversion matrix and the second conversion matrix, and using these multipliers and adders, The input RGB video signal is digitally processed and converted into a digital output RGB video signal. Alternatively, the color correction circuit includes a plurality of volumes and amplifiers for performing conversion by the first conversion matrix and the second conversion matrix, and an analog input RGB video signal is converted using these volumes and amplifiers. It is processed in an analog manner and converted into an analog output RGB video signal. In some cases, the color correction circuit performs conversion processing on an input video signal having a large variation among the input video signals of three colors of RGB to generate an output video signal of a corresponding color, and a remaining color having a small variation. For the input video signal, the conversion is omitted and the output video signal is used as it is, thereby reducing the load required for the conversion process. The light emitting elements that emit light in three colors of RGB are each composed of an organic EL element having an anode electrode, a cathode electrode, and an organic electroluminescence layer, and a first metal reflective film, a first insulating film, and a second metal reflective film are formed on the substrate. The third insulating film has a structure in which a three-layer metal reflecting film is embedded as an optical resonance mirror in the insulating film by sequentially laminating a film, a second insulating film, a third metal reflecting film, and a third insulating film. An anode electrode is formed on each of the RGB light emitting elements so as to face the first, second, and third metal reflecting films, and the common reflection of each color is formed on these anode electrodes via an organic electroluminescence layer. A cathode electrode also serving as a film is formed. Each pixel includes a plurality of MOS transistors that drive light emitting elements of the respective colors. The MOS transistor, the first, second, and third metal reflecting films, and the first, second, and third insulating films are formed on a silicon substrate. Are formed using a MOS process.

  The present invention also includes a panel in which pixels including light-emitting elements are arranged in a matrix, a row driving circuit that sequentially selects rows of pixels, and a column driving circuit that supplies a video signal to the selected pixels, The panel is composed of RGB pixels each including one of light emitting elements that emit light in RGB three colors, and the column driving circuit supplies RGB video signals divided into RGB three colors corresponding to the RGB pixels, Accordingly, a driving method of a display device for causing a light emitting element included in each pixel to emit light with a luminance corresponding to the video signal, which is color-corrected from an externally input RGB video signal and then output to the column driving circuit Therefore, a procedure for obtaining a first conversion matrix for converting the RGB chromaticity of the input RGB video signal into the XYZ chromaticity based on the result of measuring the saturation color and white color specific to the panel in advance with the XYZ chromaticity and the result, The procedure for obtaining the second conversion matrix for converting the XYZ chromaticity of the saturated color set according to the specifications of the RGB into the RGB chromaticity, and the output RGB video using the first conversion matrix and the second conversion matrix And a variation of saturation color and white color appearing for each panel is corrected according to the specifications of the panel.

  According to the present invention, a specific saturated color and white color that are different for each panel are measured in XYZ chromaticity. Based on this measurement result, a first conversion matrix for converting the RGB chromaticity of the input RGB video signal into XYZ chromaticity is obtained. Further, a second conversion matrix for converting the XYZ chromaticity of the saturated color set uniformly according to the panel design specifications into the RGB chromaticity is obtained. Using these first conversion matrix and second conversion matrix obtained in advance, an input RGB video signal supplied from the outside is converted into an output RGB video signal, which is supplied to the panel. With such a configuration, it is possible to correct a variation in saturated color and white color that appears for each panel in each manufacturing process according to the product specifications of the panel.

  For example, in an organic EL display device, particularly an optical resonant organic EL display device having a buried mirror structure formed by a MOS process, a digital input video signal is converted into saturation color and white chromaticity coordinates to be output from the panel. By performing conversion using a multiplier and an adder, a high-quality and low-cost display device with corrected chromaticity can be obtained.

  Further, according to the present invention, for example, in an organic EL display device having an optical resonance type embedded mirror structure, an analog input video signal is corrected by an analog conversion circuit including a volume and an amplifier, and is determined in advance according to product specifications. Therefore, an organic EL display device with high image quality and low cost is realized.

  In some cases, there may be a difference in the degree of chromaticity deviation between the three primary colors of RGB. For example, when the chromaticity deviation of the G saturated color is large and the chromaticity deviation of the other saturated colors is small, the conversion process using the first conversion matrix and the second conversion matrix is applied only to color components having a large chromaticity deviation. Thus, it is possible to remarkably improve the color tone of the entire panel practically.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a display device according to the present invention. As shown in the figure, this display device basically includes a panel 1, a row drive circuit (2), a column drive circuit (3, 4), and a color correction circuit 5. The panel 1 is composed of row-like scanning lines WS and column-like signal lines SIG, and pixels 100 arranged at a portion where they intersect. The pixel 100 includes a light emitting element. The row driving circuit includes the V scanner 2 and sequentially selects the rows of the pixels 100 via the scanning line WS. The column drive circuit includes an H scanner 3 and a sampling switch 4. A video signal supplied from the outside is distributed to each signal line SIG via the sampling switch 4. The H scanner 3 supplies the video signal to each signal line SIG by controlling the opening and closing of the sampling switch 4. In this display device, a V scanner 2, an H scanner 3, and a sampling switch 4 are arranged outside the panel 1. However, the present invention is not limited to this, and at least a part of these peripheral drive circuits can be built in the panel 1.

  This display device can perform color display. For this reason, the panel 1 is composed of RGB pixels each of which includes one of the light emitting elements that emit light in RGB three colors. The column drive circuits (3, 4) supply RGB video signals divided into RGB three colors corresponding to the RGB pixels 100. A color correction circuit 5 is provided as a feature of the present invention, and an RGB video signal input from the outside is color-corrected and output to the column drive circuit (3, 4). The color correction circuit 5 previously measures a saturated color and white color specific to the panel 1 with XYZ chromaticity, and obtains a first conversion matrix for converting the RGB chromaticity of the input RGB video signal into XYZ chromaticity based on the result. In addition, a second conversion matrix for converting the XYZ chromaticity of the saturated color set in advance according to the specifications of the panel 1 into RGB chromaticity is obtained, and the input RGB using the first conversion matrix and the second conversion matrix is obtained. The video signal is converted into an output RGB video signal, so that saturation and white color variations appearing for each panel are corrected in accordance with the panel specifications.

  In one aspect, the color correction circuit 5 includes a plurality of multipliers and adders in order to perform conversion by the first conversion matrix and the second conversion matrix, and using these multipliers and adders, The input RGB video signal is digitally processed and converted into a digital output RGB video signal. In another aspect, the color correction circuit 5 includes a plurality of volumes (variable resistors) and amplifiers (amplifiers) in order to perform conversion using the first conversion matrix and the second conversion matrix. Is used to process the analog input RGB video signal in an analog manner and convert it into an analog output RGB video signal. In yet another aspect, the color correction circuit 5 performs a conversion process on an input video signal having a large variation (for example, R) from among RGB three-color input video signals to generate an output video signal of a corresponding color, The remaining input video signals with small variations (for example, B and R) are converted into output video signals as they are, thereby reducing the load required for the conversion process.

  FIG. 2 is a schematic cross-sectional view showing a specific example of a light-emitting element that emits light in any of the three colors RGB included in each pixel 100 shown in FIG. This cross-sectional view represents three sets of light emitting elements in three colors of RGB for easy understanding. These light emitting elements are of an optical resonance type and have a buried mirror structure in which a metal reflective film is buried. In the figure, the substrate 6 is made of, for example, a semiconductor substrate such as a silicon substrate or a glass substrate. On one surface of the substrate 6, a first metal reflective film 7, a first insulating film 8, a second metal reflective film 9, a second insulating film 10, a third metal reflective film 11, a third insulating film 12, an anode The electrode 13, the organic EL layer 14, and the cathode electrode 15 are formed in this order. Here, the electrode closer to the substrate 6 (lower electrode) is the anode electrode 13, and the electrode farther away (upper electrode) is the cathode electrode 15. However, the positional relationship between these electrodes may be upside down. Absent.

  Each of the metal reflection films 7, 9, and 11 is formed of a metal material having a high light reflectance such as a single metal such as aluminum or silver or an alloy containing them. The first metal reflection film 7 is formed at a pixel position from which G light is extracted. The second metal reflection film 9 is formed at a pixel position from which B light is extracted, and the third metal reflection film 11 is formed at a pixel position from which R light is extracted. Each of the metal reflection films 7, 9, and 11 is opposed to the cathode electrode 15 at the corresponding RGB pixel position, and constitutes an optical resonator with the cathode electrode 15 as one reflection film (mirror). . For this reason, the film thickness of each of the metal reflective films 7, 9, and 11 is within a range of, for example, 5 to 50 nm so that a desired reflectance (generally set within a range of 80 to 90%) is obtained. Is set to

Each of the insulating films 8, 10, and 12 has optical transparency, and is formed of, for example, silicon oxide (SiO ² ). The first insulating film 8 is formed on the substrate 6 so as to cover the first metal reflective film 7. The second insulating film 10 is formed on the first insulating film 8 so as to cover the second metal reflective film 9, and the third insulating film 12 is formed on the second insulating film so as to cover the third metal reflective film 11. 10 is formed. Thereby, in the thickness direction (stacking direction) of the substrate 6, the first insulating film 8 is interposed between the first metal reflective film 7 and the second metal reflective film 9, and the second insulating film 10 is the second metal. It is in a state of being interposed between the reflective film 9 and the third metal reflective film 11.

  The film thickness of each of the insulating films 8, 10, and 12 is such that the opposing distance L1 between the first metal reflecting film 7 and the cathode electrode 15 constituting the optical resonator at the G pixel position, and the B pixel position. The distance L2 between the second metal reflective film 9 constituting the optical resonator and the cathode electrode 15 and between the third metal reflective film 12 constituting the optical resonator and the cathode electrode 15 at the R pixel position. Is set so as to be a value suitable for the wavelength of the corresponding color light. That is, the facing distance L1 is set to a value suitable for resonating G light, the facing distance L2 is set to a value suitable for resonating B light, and the facing distance L3 is set to R light. Is set to a value suitable for resonating. Incidentally, the relative magnitude relationship between the facing distances L1, L2, and L3 is L1> L2> L3. Further, the end portions of the respective metal reflective films 7, 9, 11 in the surface direction of the substrate 6 are shifted by, for example, 50 nm or more in each layer in consideration of the coverage property of the cathode electrode 15 film formation, and each end step difference. It is desirable to suppress this to about one metal reflective film.

  The anode electrode 13 is formed using a transparent conductive material such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide). One anode electrode 13 is provided for each RGB pixel (sub-pixel) in the surface direction of the substrate 6.

  The organic EL layer 14 constitutes a light source body including at least a light emitting layer (organic material). For example, in the case of a three-layer type, a hole transport layer, a light emitting layer, and an electron transport layer are sequentially stacked. In the case of a layer type, a hole injection layer, a hole transport layer, a light emitting layer, and an electron injection layer are laminated in this order. The light emitting layer of the organic EL layer 14 emits white light.

  The cathode electrode 15 is formed of a metal material having a high light reflectivity, such as a single metal such as aluminum or silver, or an alloy containing them, like the metal reflective films 7, 9, and 11. The cathode electrode 15 is formed with a uniform film thickness over the entire display portion of the panel 1 as an electrode common to each color of RGB. Further, the cathode electrode 15 constitutes an optical resonator using each of the metal reflection films 7, 9, and 11 formed for each RGB pixel as the other reflection film (mirror). For this reason, the film thickness of the cathode electrode 15 is set within a range of, for example, 5 to 50 nm so as to obtain a reflectance equivalent to that of each of the metal reflecting films 7, 9, and 11 (strictly, a slightly lower reflectance). Has been.

  In such a configuration of the organic EL element, when a predetermined voltage is applied between the anode electrode 13 and the cathode electrode 15, holes from the anode electrode 13 side and electrons from the cathode electrode 15 side to the organic EL layer 14 respectively. The organic EL layer 14 is brought into a light emitting state by being sent and coupled (recombined) in the light emitting layer. At this time, the organic EL layer 14 emits white light.

  When the organic EL layer 14 emits light in this way, the G light resonates between the first metal reflective film 7 and the cathode electrode 15, and the G light whose light intensity is amplified by this resonance is reflected in the first metal reflective film 7. It is taken out from the cathode electrode 15 side (the side opposite to the substrate 6) in a direction away from the cathode. Further, the B light resonates between the second metal reflective film 9 and the cathode electrode 15, and the B light whose light intensity is amplified by this resonance moves away from the second metal reflective film 9 in the direction of the cathode electrode 15. Taken from the side. Similarly, R light resonates between the third metal reflecting film 11 and the cathode electrode 15, and the R light whose light intensity is amplified by this resonance moves away from the third metal reflecting film 11 in the cathode electrode. 15 is taken out from the side. Thereby, in the display unit of the organic EL display panel 1, desired light is selectively extracted at each RGB pixel position in accordance with the “upper surface emission method” in which light is extracted from the upper electrode.

  FIG. 3 is a schematic circuit diagram showing a configuration example of the pixel 100 included in the display device of FIG. The figure shows a circuit configuration of a red pixel 100R, a blue pixel 100B, and a green pixel 100G that are one set in RGB. The red pixel 100R is arranged at a portion where the scanning line WS and the signal line SIG-R for supplying the R video signal intersect. Similarly, the blue pixel 100B is arranged at a portion where the scanning line WS and the signal line SIG-B for supplying the B video signal intersect. The green pixel 100G is arranged at a portion where the scanning line WS and the signal line SIG-G for supplying the G video signal intersect. Each of the pixels 100R, 100B, and 100G has the same configuration, and the corresponding light emitting elements ELR, ELB, and ELG are driven by the sampling transistor T1, the drive transistor T2, and the pixel capacitor Cs, respectively. For example, when focusing on the red pixel 100R, the gate of the sampling transistor T1 is connected to the scanning line WS, one of the source / drain is connected to the signal line SIG-R, and the other is connected to one end of the pixel capacitor Cs. The other end of the pixel capacitor Cs is connected to the ground potential Vss. The gate of the drive transistor T2 is connected to one end of the pixel capacitor Cs, one of the source / drain is connected to the power supply potential Vcc, and the other end is connected to the anode of the light emitting element ELR. The cathode of the light emitting element ELR is connected to a predetermined cathode potential Vk.

  In such a configuration, when the sampling transistor T1 is selected by the scanning line WS, the sampling transistor T1 samples the R video signal supplied from the signal line SIG-R and holds it in the pixel capacitor Cs. The drive transistor T2 operates in response to the R video signal held in the pixel capacitor Cs, and supplies the drain current IR to the light emitting element ELR. As a result, the light emitting element ELR emits red light with a luminance corresponding to the R video signal.

  Here, the sampling transistor T1 and the drive transistor T2 are integrally formed on the substrate 6 made of, for example, a silicon wafer by using a MOS process. The pixel capacitor Cs can also be formed and integrated by the MOS process at the same time. Further, the light-emitting element EL can be formed on the transistors T and T2 and the pixel capacitor Cs by a technique using a MOS process. The anode of the upper light emitting element EL is connected to the lower drive transistor T2 through a contact. Note that the circuit configuration shown in FIG. 3 is merely an example, and does not limit the technical scope of the present invention.

  FIG. 4 is a flowchart schematically showing the driving method of the display device according to the present invention. An algorithm for color correction performed mainly in connection with the color correction circuit 5 is shown. First, in step S1, the saturation color and white chromaticity coordinates specific to the panel corresponding to the input video RGB data (Ri, Gi, Bi) are measured. In step S2, a color conversion matrix (RGB → XYZ) Mc is determined from the measurement result. Subsequently, in step S3, RGB data actually output on the panel is obtained from the color conversion matrix (XYZ → RGB) Mp of the chromaticity coordinates to be output. Finally, in step S4, the converted RGB signal is output to the panel to perform color display.

  FIG. 5 is a block diagram of the algorithm in the flowchart format shown in FIG. First, since the saturation chromaticity displayed by each panel varies depending on the manufacturing process, the saturation color and white chromaticity (XYZ) specific to the panel are measured. A conversion matrix Mc is obtained from the measured XYZ and input RGB data. This conversion matrix is a 3 × 3 matrix. This conversion matrix is stored in the memory in advance. Further, the conversion matrix Mp is obtained from the saturated chromaticity that is actually output from the panel. This conversion matrix Mp is also a 3 × 3 matrix, and converts from XYZ to RGB. The conversion matrix Mp is determined in advance according to product specifications and is constant regardless of individual panels. Therefore, with the RGB signal converted by this algorithm, the saturation color and the white chromaticity can be made constant in each panel regardless of the input RGB signal. In the actual conversion operation, first, a product of the first conversion matrix Mc and the second conversion matrix Mp is obtained to obtain a combined conversion matrix Mt. This composite conversion matrix is also a 3 × 3 matrix. This 3 × 3 matrix Mt is applied to input RGB data (Ri, Gi, Bi) to obtain output RGB data (Ro, Go, Bo). This output RGB data (Ro, Go, Bo) is supplied to the panel side.

  FIG. 6 is a graph showing the conversion result. Changes in chromaticity distribution appearing on individual panels before and after conversion are shown in the xy chromaticity diagram. As is apparent from the figure, the saturation chromaticity of each color varies depending on the manufacturing process before conversion, and a color having a different chromaticity is output for the same input. On the other hand, by converting the video signal with the color correction circuit, the same color can be output with the same input RGB data regardless of the individual panels, and chromaticity variations caused by the manufacturing process can be corrected. . As is apparent from the graph, after conversion, every panel has a chromaticity distribution in the hatched area in the center.

  FIG. 7 is a block diagram showing a specific configuration example of the color correction circuit 5 shown in FIG. The color correction circuit of the present embodiment performs a conversion operation from input video data (Ri, Gi, Bi) shown in FIG. 5 to output video data (Ro, Go, Bo) in a digital manner. As shown in the figure, the digital color correction circuit is composed of 18 digital multipliers and 6 digital adders. The input N-bit RGB signal is first multiplied by panel conversion coefficient data obtained from the panel specific saturation color and white chromaticity coordinates in the first multiplier group, and the output is passed to the first adder group. It is. The signal calculated and output by the first adder group becomes the panel chromaticity XYZ corresponding to the input RGB data. This XYZ signal is passed to the second multiplier group. In the second multiplier group, the specification conversion coefficient obtained from the saturated color and white chromaticity data desired to be output from the panel is multiplied by the chromaticity XYZ. This output is passed to the second adder group, and the output is supplied to the panel side. The final output is converted from XYZ chromaticity data to RGB data. In the above description, the panel conversion coefficient is obtained from the matrix Mc shown in FIG. 5, and the specification conversion coefficient is also obtained from the matrix Mp. Through the above digital calculation, digital input data (Ri, Gi, Bi) is also converted into digital output video data (Ro, Go, Bo) and supplied to the panel side.

  FIG. 8 is a schematic circuit diagram showing another embodiment of the color correction circuit shown in FIG. This embodiment includes a volume (variable resistor) and an operational amplifier (operational amplifier), and analog input RGB video signals (Ri, Gi, Bi) are processed in an analog manner by using these, and an analog output is provided. Conversion into RGB video signals (Ro, Go, Bo). In the illustrated example, the color correction circuit is composed of three operational amplifiers and twelve resistors, of which nine are variable resistors. By multiplying the input RGB signals (Ri, Gi, Bi) by the coefficients determined by the variable resistors and taking the sum, an output video signal (Ro, Go, Bo) is obtained. The value of the variable resistor is given based on the maximum color reproduction range unique to the panel and the color reproduction range determined by the panel specifications. Specifically, the coefficients set in these variable resistors are determined by 3 × 3 matrix coefficients of a conversion matrix Mt obtained by combining the first conversion matrix Mc and the second conversion matrix Mp.

  By the way, in the light-emitting element of the optical resonance type mirror embedded structure shown in FIG. 2, the optical path lengths L1, L2, and L3 corresponding to GBR are determined by the thickness of the oxide film covering the embedded metal reflection film. Since the oxide film thickness fluctuates due to variations in the manufacturing process, the optical path lengths L1, L2, and L3 are not constant, and as a result, the color tone varies from panel to panel. In some cases, the chromaticity shift inherent to the panel may occur strongly only in a specific color. For example, in the example shown in FIG. 9, on the xy chromaticity coordinates, the G chromaticity shift is particularly large due to manufacturing variations. Compared with this, the variation of other B chromaticity and R chromaticity is small.

  In such a case, conversion processing is performed on an input video signal having a large variation among the input video signals of RGB three colors to generate an output video signal having a corresponding color, and the remaining input video signal having a small variation is input. Thus, the conversion is omitted and the output video signal is used as it is, so that the load required for the conversion process can be reduced. A color correction circuit configured for this purpose is shown in FIG. This color correction circuit is formed by one digital multiplier. This color correction circuit is applied particularly to a panel in which a green chromaticity shift is remarkable. Of the input N-bit RGB signal, only G data is multiplied by conversion coefficient data obtained from the panel's original G saturated color, and the output is passed to the panel side. Input data Ri and Bi of other colors are passed to the panel side as output video signals Ro and Bo as they are.

  The operation principle of the color correction circuit shown in FIG. 10 will be described with reference to FIG. FIG. 11 shows the algorithm of this method. First, since the saturation color chromaticity inherent to each panel varies depending on the manufacturing process or the like, the saturation color and white chromaticity (XYZ) inherent to the panel are measured. A conversion matrix Mc is obtained from the measured XYZ chromaticity and input RGB data. This conversion matrix is a 3 × 3 matrix and is stored in a memory. Further, a conversion matrix Mp is obtained from the saturated chromaticity that is originally desired to be output from the panel. Mp is also a 3 × 3 matrix and converts from XYZ to RGB. This conversion matrix Mp is determined by the product specifications of the panel and is constant regardless of the individual panels. Here, the first conversion matrix Mc and the second conversion matrix Mp are multiplied to obtain a composite matrix Mt used for input / output conversion. This composite conversion matrix Mt = Mc × Mp is also a 3 × 3 matrix. Here, since G chromaticity having a particularly large variation is to be corrected, Ri and Bi in the input data are set to 0.

  Here, a conversion operation (Ri, Gi, Bi) × Mt = (Ro, Go, Bo) is executed. Since Ri = Bi = 0, Ro = K12 · Gi, Go = K22 · Gi, Bo = K32 · Gi. It becomes. Here, Kij is an element of i rows and j columns of the composite conversion matrix Mt. The chromaticity shifts of the B and R colors other than the G color are small between the individual panels, and the values of the matrix elements K12 and K32 are negligibly low. Therefore, the calculation result of (Ri, Gi, Bi) × Mt = (Ro, Go, Bo) can be expressed by Go = K22 · Gi using only the green component. The color correction circuit shown in FIG. 10 performs this calculation.

  The result of correcting the green color by the correction circuit shown in FIG. 10 is shown in the graph of FIG. Before conversion, the saturation chromaticity of each color varies depending on the manufacturing process, and even with the same video input, a color with a different chromaticity is displayed for each panel. On the other hand, by converting the digital RGB video signal by the color correction circuit shown in FIG. 10, the G color component having particularly large variation can be made constant. In this way, the G color having a large chromaticity deviation can be output uniformly regardless of the panel with the same input RGB data, and the difference in color tone caused by the manufacturing process variation can be corrected.

1 is a block diagram showing an overall configuration of a display device according to the present invention. It is typical sectional drawing which shows the structural example of the RGB light emitting element contained in the panel shown in FIG. FIG. 2 is a circuit diagram showing a circuit configuration of RGB pixels included in the panel shown in FIG. 1. 3 is a flowchart showing a color correction algorithm executed by the display device shown in FIG. 1. It is a block diagram which similarly shows a color correction algorithm. It is a graph which shows a color correction result. FIG. 2 is a block diagram illustrating an embodiment of a color correction circuit illustrated in FIG. 1. It is a circuit diagram which similarly shows other embodiment. It is a graph which shows the dispersion | variation in the chromaticity of a panel. FIG. 5 is a schematic diagram illustrating another embodiment of the color correction circuit illustrated in FIG. 1. It is a block diagram which shows the color correction algorithm performed in embodiment shown in FIG. FIG. 11 is a chromaticity diagram showing a result corrected by the color correction circuit shown in FIG. 10. It is the graph which showed the dispersion | variation in the color tone of each panel. It is a chart showing the relationship between the RGB color system and the XYZ color system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Panel, 2 ... V scanner, 3 ... H scanner, 4 ... Sampling switch, 5 ... Color correction circuit, 100 ... Pixel

Claims (7)

A panel in which pixels including light-emitting elements are arranged in a matrix, a row driving circuit that sequentially selects rows of pixels, and a column driving circuit that supplies a video signal to the selected pixels, and light emission included in each pixel A display device that emits light at a luminance according to the video signal,
The panel is composed of RGB pixels each including one of light emitting elements that emit light in RGB three colors,
The column drive circuit supplies RGB video signals divided into three colors corresponding to RGB pixels,
A color correction circuit that corrects the color of an externally input RGB video signal and outputs the signal to the column drive circuit is provided.
The color correction circuit measures a saturated color and white color specific to the panel in XYZ chromaticity in advance, and obtains a first conversion matrix for converting the RGB chromaticity of the input RGB video signal into XYZ chromaticity based on the result. ,
Further, a second conversion matrix for converting XYZ chromaticities of saturated colors set in advance according to the panel specifications into RGB chromaticities is obtained,
The input RGB video signal is converted into the output RGB video signal using the first conversion matrix and the second conversion matrix, and the variations in saturated color and white color appearing for each panel are corrected according to the specifications of the panel. Characteristic display device.   The color correction circuit includes a plurality of multipliers and adders for performing conversion by the first conversion matrix and the second conversion matrix, and the digital input RGB image is obtained by using these multipliers and adders. 2. The display device according to claim 1, wherein the signal is digitally processed and converted into a digital output RGB video signal.   The color correction circuit includes a plurality of volumes and amplifiers for performing conversion by the first conversion matrix and the second conversion matrix, and an analog input RGB video signal is converted into an analog signal using these volumes and amplifiers. 2. The display device according to claim 1, wherein the display device is converted into an analog output RGB video signal.   The color correction circuit performs a conversion process on an input video signal with a large variation among the input video signals of RGB three colors to generate an output video signal with a corresponding color, and a remaining input video signal with a small variation The display device according to claim 1, wherein the conversion is omitted and the output video signal is used as it is, thereby reducing the load required for the conversion process. The light emitting elements that emit light in RGB three colors are each composed of an organic EL element having an anode electrode, a cathode electrode, and an organic electroluminescence layer,
By laminating the first metal reflective film, the first insulating film, the second metal reflective film, the second insulating film, the third metal reflective film and the third insulating film in this order on the substrate, three layers are formed in the insulating film. With a structure in which a metal reflective film is embedded as a mirror for optical resonance,
An anode electrode is formed on the third insulating film so as to face the first, second and third metal reflecting films for each of the RGB light emitting elements, and an organic electroluminescence layer is formed on these anode electrodes through the organic electroluminescence layer. 2. A display device according to claim 1, wherein a cathode electrode which also serves as a reflective film common to each color is formed.   Each pixel includes a plurality of MOS transistors that drive light emitting elements of the respective colors. The MOS transistor, the first, second, and third metal reflecting films, and the first, second, and third insulating films are formed on a silicon substrate. 6. The display device according to claim 5, wherein the display device is formed using a MOS process. A panel in which pixels including light emitting elements are arranged in a matrix; a row driving circuit that sequentially selects rows of pixels; and a column driving circuit that supplies a video signal to the selected pixels. It is composed of RGB pixels including any of light emitting elements that emit light in RGB three colors, and the column driving circuit supplies RGB video signals divided into three colors corresponding to the RGB pixels, and thereby each pixel A display device driving method for causing the light emitting element included in the light emitting element to emit light at a luminance corresponding to the video signal,
In order to output the RGB video signal input from the outside to the column driving circuit after color correction,
A procedure for obtaining a first conversion matrix for measuring the RGB saturation of the input RGB video signal into XYZ chromaticity based on the result of measuring the saturation color and white color specific to the panel in advance with XYZ chromaticity,
A procedure for obtaining a second conversion matrix for converting XYZ chromaticities of saturated colors set in advance according to panel specifications into RGB chromaticities;
Performing a procedure of converting an input RGB video signal into an output RGB video signal using the first conversion matrix and the second conversion matrix;
Therefore, a display device driving method, wherein variations in saturated color and white color appearing for each panel are corrected in accordance with panel specifications.

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