JP7191057B2 - Display device, image data conversion device and white balance adjustment method - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a display device, and more particularly to a display device with pixels composed of sub-pixels of four colors.

2. Description of the Related Art Conventionally, display devices such as liquid crystal displays and organic EL displays have been RGB type display devices that display images using three colors of R (red), G (green), and B (blue). In an RGB type display device, white light is composed of light that has passed through color filters of three colors of RGB, and is accompanied by a decrease in the amount of light due to the color filters. Therefore, the RGB type display device has a problem that it is difficult to increase the luminance.

As a technology for solving this problem, there is an RGBW type display device that displays an image using a total of four colors, that is, three colors of RGB plus W (white). Since the white light of the RGBW type display device can be composed of W light obtained through a transparent filter, the amount of light is not reduced by the color filter. Therefore, the RGBW type display device can easily achieve higher luminance than the RGB type display device. In addition, an RGBW type display device using a backlight, such as a liquid crystal display, can achieve the same brightness as that of an RGB type display device with a lower backlight brightness, so power can be saved.

However, the image data input to the display device is usually image data composed of RGB three-color data (hereinafter referred to as "RGB image data"). Therefore, in the RGBW type display device, by generating W data from the input RGB image data, the RGB image data is image data composed of RGBW four-color data (hereinafter referred to as "RGBW image data"). need to be converted to If this conversion is not properly performed, for example, W light is mixed with all display colors, causing problems such as the image becoming whitish and the image quality being degraded.

For example, Patent Document 1 below proposes a technique of converting RGB image data into RGBW image data by generating W data from the minimum data of three colors of RGB image data.

JP-A-2002-149116

In general, due to manufacturing variations of display devices, the chromaticity of white when displaying a white image (for example, the xy coordinates in the CIE1931 color space, hereinafter simply referred to as “xy coordinates”) is limited to the display device. variation occurs. For example, in a liquid crystal display, manufacturing variations in backlight LEDs, color filters, and the like cause variations in white chromaticity. For this reason, "white balance adjustment" for matching the xy coordinates of white (white coordinates) to desired xy coordinates is performed for each manufactured display device.

White balance adjustment of an RGBW type display device is performed in a state in which RGB image data before being converted into RGBW image data is input. In addition, the xy coordinates of white in an RGBW display device are determined by combining the xy coordinates of white generated by the RGB three-color sub-pixels and the xy coordinates of white generated by the W sub-pixels. Since the xy coordinates of the white of the W sub-pixel cannot be adjusted, the white balance adjustment of the RGBW type display device is performed by setting the luminance of the two sub-pixels of RGB to the maximum value (for example, 255 steps for 8-bit gradation). In other words, by setting an upper limit that is lower than the maximum value for two color data of the input RGB image data.

However, in the RGBW type display device, W data is generated from the minimum data of the input RGB image data. Pixel brightness is also reduced. As a result, there arises a problem that the brightness of the RGBW display device when white is displayed is greatly reduced, and the contrast ratio is also greatly reduced.

The present disclosure has been made to solve the above-described problems, and aims to suppress a decrease in luminance due to white balance adjustment in an RGBW type display device.

The image data conversion device according to the present disclosure converts RGB image data consisting of R (red), G (green), and B (blue) data into RGBW image data consisting of R, G, B, and W (white) data. , wherein the first storage unit stores the upper limit value of each of the R data, the G data and the B data of the RGBW image data, and the upper limit value of the W data of the RGBW image data is stored. and a second storage section for storing the R data, G data and B data of the RGB image data as the R data for the RGBW image data having the maximum value equal to the upper limit value stored in the first storage section. a first conversion unit for converting data, G data and B data; and based on the R data, G data and B data of the RGB image data, the upper limit value stored in the second storage unit is changed to the maximum value. and a second conversion unit that takes the upper limit value stored in the second storage unit regardless of the R data, G data, and B data of the RGB image data. an adjustment W data generation unit that generates W data; and an adjustment W data generated by the W data generated by the second conversion unit and the adjustment W data generated by the adjustment W data generation unit as the W data of the RGBW image data. and a W data switching unit for switching which of the above is used according to a switching signal input from the outside , wherein the R data, G data and B data generated by the first conversion unit and the W data switching The W data selected by the unit is output as the RGBW image data .

According to the image data conversion device according to the present disclosure, the upper limit value of the W data of the RGBW image data after the white balance adjustment is completed can be maintained at the same value as before the white balance adjustment. A decrease in luminance can be suppressed.

1 is a diagram showing a configuration of a liquid crystal display device according to Embodiment 1; FIG. 3 is a diagram showing a configuration example of an RGB-RGBW conversion circuit; FIG. FIG. 3 is a diagram showing a configuration example of a pixel of an RGBW type display device; FIG. 3 is a diagram showing a configuration example of a pixel of an RGBW type display device; 2 is a plan view showing the configuration of a color filter of the liquid crystal display device according to Embodiment 1; FIG. 2 is a cross-sectional view showing the configuration of a color filter of the liquid crystal display device according to Embodiment 1; FIG. 2 is a cross-sectional view showing the configuration of a color filter of the liquid crystal display device according to Embodiment 1; FIG. It is a figure for demonstrating the method of the white balance adjustment of a liquid crystal display device. FIG. 10 is a plan view showing the configuration of a color filter of a conventional liquid crystal display device; FIG. 10 is a cross-sectional view showing the configuration of a color filter of a conventional liquid crystal display device; FIG. 3 is a diagram showing an example of xy coordinates of a white image displayed by a conventional liquid crystal display device in an initial state; FIG. 10 is a diagram showing an example of xy coordinates of a white image displayed by a conventional liquid crystal display device after white balance adjustment is completed; 4 is a diagram showing an example of xy coordinates of a white image displayed by the liquid crystal display device according to Embodiment 1 in an initial state; FIG. FIG. 5 is a diagram showing an example of xy coordinates of a white image displayed by the liquid crystal display device according to Embodiment 1 after completion of white balance adjustment; 4 is a plan view showing a modification of the color filter of Embodiment 1; FIG. 4 is a cross-sectional view showing a modification of the color filter of Embodiment 1; FIG. 4 is a cross-sectional view showing a modification of the color filter of Embodiment 1; FIG. FIG. 10 is a plan view showing the configuration of a color filter of the liquid crystal display device according to Embodiment 2; 8 is a cross-sectional view showing the configuration of a color filter of the liquid crystal display device according to Embodiment 2; FIG. FIG. 10 is a diagram showing an example of xy coordinates of a white image displayed by the liquid crystal display device according to Embodiment 2 in the initial state; FIG. 10 is a diagram showing an example of xy coordinates of a white image displayed by the liquid crystal display device according to Embodiment 2 after completion of white balance adjustment; FIG. 10 is a diagram showing an RGB-RGBW conversion circuit of a liquid crystal display device according to Embodiment 3; FIG. 12 is a diagram showing an example of xy coordinates of a white image displayed by the liquid crystal display device according to Embodiment 3 in the initial state; FIG. 10 is a diagram showing an example of xy coordinates of a white image displayed by the liquid crystal display device according to Embodiment 3 after completion of white balance adjustment;

<Embodiment 1>
FIG. 1 is a diagram showing the configuration of a liquid crystal display device 200 according to Embodiment 1. As shown in FIG. The liquid crystal display device 200 is an RGBW type display device. As shown in FIG. 1 , the liquid crystal display device 200 includes a liquid crystal panel 100 , a display control section 103 and a signal conversion section 104 .

The liquid crystal panel 100 has a display area 100a in which a plurality of pixels are arranged. In the display area 100a, liquid crystal is sandwiched between a TFT substrate on which a TFT (Thin Film Transistor) for supplying a voltage corresponding to image data to each pixel and a CF substrate on which a color filter (CF) is formed. structure. In the area (frame area) outside the display area 100a in the liquid crystal panel 100, a source IC 101 for inputting image data to the source wiring connected to the source of the TFT in the display area 100a and the gate of the TFT in the display area 100a are connected. A gate IC 102 is provided for inputting a drive signal to the gate wiring.

RGB image data composed of data of three colors of RGB input from the outside is input to the signal conversion unit 104 , and is converted into RGBW image data composed of data of four colors of RGBW in the signal conversion unit 104 . The display control unit 103 controls the source IC 101 and gate IC 102 of the liquid crystal panel 100 based on the RGBW image data output from the signal conversion unit 104 .

For example, FIG. 2 shows the configuration of a conversion circuit 105 (hereinafter referred to as “RGB-RGBW conversion circuit 105”) which constitutes a part of the signal conversion unit 104 and is an image data conversion device for converting RGB image data into RGBW image data. FIG. 4 is a diagram showing an example; The RGB-RGBW conversion circuit 105 may be provided with a circuit for adjusting the hue, saturation, brightness, etc. of the image to be displayed. there is It is also assumed that each color of the RGB image data input to the RGB-RGBW conversion circuit 105 is 8-bit data. That is, the maximum value (maximum gradation) of each color of the RGB image data input to the RGB-RGBW conversion circuit 105 is 255.

As shown in FIG. 2, the RGB-RGBW conversion circuit 105 includes a minimum data detection circuit 1, a W function circuit 2, a register 3, data conversion circuits 4-7, and bit number conversion circuits 8-11.

The minimum data detection circuit 1 selects the minimum data among the RGB image data input to the RGB-RGBW conversion circuit 105 and outputs the selected value to the W function circuit 2 . That is, if the R data, G data and B data of the RGB image data are R _IN , G _IN and B _IN respectively, the output of the minimum data detection circuit 1 is Y _min =min(R _IN , G _IN , B _IN ) is represented.

The W function circuit 2 determines the mixing degree of W according to the preset W function F according to the output Y _min of the minimum data detection circuit 1 . The W function F is a linear or nonlinear function with Y _min as a variable, and is set as a function that takes a value of 0 when Y _min =0 and a value of 255 when Y _min =255, for example. In this case, when the RGB image data is black image data (all color data is 0), the output data of the W function circuit 2 is 0, and the RGB image data is white image data (all color data is 255). Then, the output data of the W function circuit 2 is 255, and the output data of the W function circuit 2 is a value between 0 and 255 when the RGB image data is color data other than black and white. In this embodiment, to simplify the explanation, the W function F is a linear function, and the output data of the W function circuit 2 is the same value (Y _min ) as the input data of the W function circuit 2. .

The register 3 stores the R data upper limit value R _W , the G data upper limit value G _W , the B data upper limit value B _W , and the W data upper limit value W _W of the converted RGBW image data. The R _W , G _W , B _W , and W _W stored in the register 3 are values of each color of the RGBW image data output by the RGB-RGBW conversion circuit 105 when the liquid crystal display device 200 displays a white image. These values are set by adjusting the white balance of the liquid crystal display device 200 . That is, if the R data, G data, B data and W data of the RGBW image data output from the RGB-RGBW conversion circuit 105 are R _OUT , G _OUT , B _OUT and W _OUT respectively, the input RGB image data is R When _IN /G _IN /B _IN =255/255/255, the output RGBW image data is R _OUT /G _OUT /B _OUT /W _OUT =R _W /G _W /B _W / _WW .

Among the data conversion circuits 4 to 7, the data conversion circuits 4 to 6, based on the R _W , G _W , and B _W stored in the register 3, convert the respective color data R _IN , G _IN of the input RGB image data. , B _IN are converted into R data, G data, and B data for RGBW image data having R _W , G _W , and B _W as maximum values. Based on the _WW stored in the register 3, the data conversion circuit 7 converts the output data (here, Y _min ) of the W function circuit 2 into W data for RGBW image data with _WW as the maximum value. Convert. The data conversion circuits 4 to 7 may include a gamma correction circuit that corrects the relationship between the gradation data and the display luminance for each RGBW color.

Here, when the number of output bits (the number of bits of output data) of the data conversion circuits 4 to 7 is the same as the number of input bits (the number of bits of input data), the input data representing different gradations are converted into so-called numerical data. "Rounding" may result in conversion to output data representing the same gradation. In order to prevent this problem from occurring, the number of output bits of the data conversion circuits 4 to 7 should be larger than the number of input bits. In the RGB-RGBW conversion circuit 105 of FIG. 2, the number of input bits of the data conversion circuits 4 to 7 is 8 bits, and the number of output bits is 10 bits.

However, since the source IC 101 mounted on the liquid crystal panel 100 of the liquid crystal display device 200 generally has an 8-bit input, the 10-bit image data output from the data conversion circuits 4 to 7 cannot be input to the source IC 101 . Therefore, in the RGB-RGBW conversion circuit 105, bit number conversion circuits 8-11 are provided at the respective output stages of the data conversion circuits 4-7. The bit number conversion circuits 8 to 11 use frame rate control technology to simulate a large number of gradations using image data with a small number of gradations by synthesizing the gradations of multiple frames. The 10-bit data output by the circuits 4 to 7 is assumed to be 8-bit data that can be input to the source IC 101 . The 8-bit R data, G data, B data and W data output from the bit number conversion circuits 8 to 11 are the RGBW image data output from the RGB-RGBW conversion circuit 105 (R _OUT /G _OUT /B _OUT / W _OUT ).

Returning to FIG. 1, in the display area 100a of the liquid crystal panel 100, M×N pixels are arranged in order to display an image with a resolution of M columns×N rows. Each pixel is, for example, a pixel 110 composed of a set of R, G, B, and W sub-pixels 111, 112, 113, and 114 of four RGBW colors, as shown in FIG. is. In the pixel 110 shown in FIG. 3, the R sub-pixel 111, the G sub-pixel 112, the B sub-pixel 113, and the W sub-pixel 114 are arranged in the horizontal direction. 111, G sub-pixels 112, B sub-pixels 113 and W sub-pixels 114 may be arranged in a 2×2 matrix. Also, the arrangement order of the R sub-pixels 111, G sub-pixels 112, B sub-pixels 113, and W sub-pixels 114 shown in FIGS.

Each of the sub-pixels 111-114 is connected to the source IC 101 and the gate IC 102, and the source IC 101 and the gate IC 102 apply voltages corresponding to the RGBW image data input to the display control unit 103 to the sub-pixels 111-114. do. By changing the transmittance of the sub-pixels 111 to 114 according to the applied voltage, the intensity of light from a backlight (not shown) arranged on the back surface of the liquid crystal panel 100 changes, thereby changing the display area. An image is displayed at 100a.

5, 6 and 7 are diagrams showing the configuration of color filter 120 provided in display region 100a of liquid crystal display device 200 according to the first embodiment. 5 is a plan view of a region corresponding to one pixel 110 in color filter 120, FIG. 6 is a cross-sectional view along line A1-A2 shown in FIG. 5, and FIG. It is a sectional view along B2 line.

As shown in FIGS. 5 and 6, the color filter 120 is formed on a transparent glass 125, a black mask 126 having openings formed over each sub-pixel, and a black mask 126 over each opening of the black mask 126. and a coloring material formed in the Specifically, in the region corresponding to one pixel 110, the black mask 126 has an opening 1261 formed over the R sub-pixel 111, an opening 1262 formed over the G sub-pixel 112, and an opening 1262 formed over the B sub-pixel. It has an opening 1263 formed over the pixel 113 and an opening 1264 formed over the W sub-pixel 114 . Then, as shown in FIG. 6, the R colorant 121 is formed in the opening 1261 on the R subpixel 111, and the G colorant 122 is formed in the opening 1262 on the G subpixel 112. A B colorant 123 is formed in the opening 1263 on the B sub-pixel 113 , and a transparent colorant 124 is formed in the opening 1264 on the W sub-pixel 114 .

However, as shown in FIGS. 5 and 7, the aperture 1264 above the W sub-pixel 114 contains not only the transparent colorant 124 but also any one of the R colorant, the G colorant, and the B colorant. A colored coloring material 124a is also formed. In the present embodiment, the opening 1264 above the W sub-pixel 114 has the colored coloring material 124a formed in a partial area and the transparent coloring material 124 formed in the remaining area in plan view. Further, in the present embodiment, the colored coloring material 124a is assumed to be a G coloring material, but may be an R coloring material or a B coloring material.

An overcoat 127 is formed on the R colorant 121, the G colorant 122, the B colorant 123, the transparent colorant 124, and the colored colorant 124a for the purpose of flattening the upper surface of the color filter 120. FIG.

The structure of the color filter 120 shown in FIGS. 5 to 7 is such that the liquid crystal panel 100 is of a lateral electric field drive type such as an IPS (In Plane Switching) type ("IPS" is a registered trademark) or an FFS type (Fringe Field Switching) type. This is an example of one case. When the liquid crystal panel 100 is of a longitudinal electric field driving type such as a TN (Twisted Nematic) type, a counter electrode made of a transparent conductive film such as ITO is formed on the overcoat 127 .

Next, a method for adjusting the white balance of the liquid crystal display device 200 will be described. When performing white balance adjustment, as shown in FIG. Color luminance meter 204 measures the luminance and chromaticity of an image displayed on liquid crystal display device 200 by computer 201 , and the measurement result of color luminance meter 204 is input to computer 201 through output wiring 205 . Here, it is assumed that the chromaticity measurement result by the color luminance meter 204 is expressed as xy coordinates in the CIE1931 color space.

First, the computer 201 controls the liquid crystal display device 200 in the initial state (the state in which all of the R _W , G _W , B _W , and W _W stored in the register 3 in FIG. 2 are set to the initial value, the maximum gradation 255). A white image is displayed on the liquid crystal display device 200 by inputting RGB image data in which three colors of RGB are set to the maximum gradation. When each of the R data (R _IN ), G data (G _IN ), and B data (B _IN ) of the RGB image data input to the liquid crystal display device 200 is 8-bit data, the RGB image data is R The data is _IN /G _IN /B _IN =255/255/255.

Next, color luminance meter 204 measures the luminance and xy coordinates of the white image displayed on liquid crystal display device 200 . Based on the luminance and xy coordinates measured by the color luminance meter 204, the computer 201 determines that the xy coordinates of the white image displayed on the liquid crystal display device 200 are the target values, i. ), the white balance is adjusted by adjusting the values of the R data, G data, and B data of the RGB image data input to the liquid crystal display device 200 . At this time, the computer 201 adjusts the gradation of two of the three colors of RGB, that is, two values of the R data, G data and B data of the RGB image data input to the liquid crystal display device 200 .

After that, the computer 201 causes the liquid crystal display device 200 to display a white image whose white balance has been adjusted (hereinafter referred to as "white adjusted image"), and the color luminance meter 204 measures the brightness and xy coordinates of the white adjusted image. At this time, if the distance between the xy coordinates of the white adjusted image and the target xy coordinates exceeds the allowable value, the computer 201 adjusts the white balance again based on the brightness and xy coordinates of the white adjusted image. When this is repeated and the distance between the xy coordinates of the white adjustment image and the target xy coordinates becomes equal to or less than the allowable value, the white balance adjustment is completed.

When the white adjusted image that achieves the target xy coordinates is obtained in this way, the computer 201 calculates the R data (R _IN ), G data (G _IN ) and B data of the RGB image data when the white balance adjustment is completed. (B _IN ) and W data calculated from the RGB image data by the same method as the minimum data detection circuit 1 and W function circuit 2 in FIG. The liquid crystal display device 200 stores these R data, G data, B data and W data received through the control wiring 203 in the register 3 of the RGB-RGBW conversion circuit 105 as R _W , G _W , B _W and W _W . Memorize.

Since the data of each color of the RGB image data cannot exceed its maximum value (here, 255), the R data (R _IN ) of the RGB image data input to the liquid crystal display device 200 when the white balance adjustment is completed. , G data (G _IN ) and B data (B _IN ) are, for example, R _IN /G _IN /B _IN =233/255/199. In this case, the register 3 of the RGB-RGBW conversion circuit 105 stores data of R _W /G _W /B _W /W _W =233/255/199/199.

The effects of the liquid crystal display device 200 of Embodiment 1 will be described below. As can be seen from the white balance adjustment method described above, the xy coordinates measured by the color luminance meter 204 during actual white balance adjustment are the xy coordinates of a white image obtained by synthesizing the four RGBW sub-pixels. For simplicity of explanation, the result of calculating the xy coordinates of the composite of the four RGBW sub-pixels, the xy coordinates of the composite of the three RGB sub-pixels, and the xy coordinates of the W sub-pixel by simulation. will be used for explanation. In the examples of xy coordinates shown below, cross marks are target xy coordinates, black squares are xy coordinates of synthesis of sub-pixels of four colors of RGBW, black circles are xy coordinates of synthesis of sub-pixels of three colors of RGB, The white circles indicate the xy coordinates of the W sub-pixels, respectively.

First, as a comparative example, a conventional liquid crystal display device will be described. 9 and 10 show a plan view and a sectional view of a color filter 120 of a conventional liquid crystal display device. FIG. 10 is a cross section along line A1-A2 of FIG. In the color filter 120 of the conventional liquid crystal display device, only the transparent coloring material 124 is formed in the opening 1264 above the W sub-pixel 114, and the colored coloring material 124a is not provided.

FIG. 11 is an example of xy coordinates of a white image displayed by a conventional liquid crystal display device in an initial state. In the initial state, all R _W , G _W , B _W , and W _W of the register 3 in FIG. The data is _OUT / _GOUT / _BOUT / _WOUT =255/255/255/255, and the sub-pixels 111 to 114 of the liquid crystal display device have the maximum luminance. In FIG. 11, there is a difference between the xy coordinates of the white image displayed by the liquid crystal display device and the target xy coordinates.

FIG. 12 is an example of xy coordinates of a white image displayed by a conventional liquid crystal display device when white balance adjustment is performed from the state of FIG. 11 and the white balance adjustment is completed. For example, if RGB image data of R _IN /G _IN /B _IN =233/255/199 is input when the white balance adjustment is completed, then the RGB-RGBW conversion circuit 105 outputs R _OUT /G _OUT /B RGBW image data of _OUT / _WOUT =233/255/199/199 is output, and the liquid crystal display device displays a white image (white adjusted image) with a corresponding transmittance. In this case, data of R _W /G _W /B _W /W _W =233/255/199/199 are stored in the register 3 of the RGB-RGBW conversion circuit 105 after the white balance adjustment is completed.

As can be seen from FIGS. 11 and 12, the xy coordinates of the composite of the four RGBW subpixels are located between the xy coordinates of the composite of the three RGB subpixels and the xy coordinates of the W subpixel. . Further, even if _WOUT changes due to white balance adjustment, the xy coordinates of the W sub-pixel do not change and are fixed at substantially constant xy coordinates. Therefore, in order to bring the combined xy coordinates of the four color sub-pixels of RGBW closer to the target xy coordinates, the xy coordinates of the combination of the three colors of RGB subpixels should be set to the target xy coordinates of the W subpixel. It is necessary to make a large movement to the opposite side of the xy coordinates. In order to move the composite xy coordinates of the sub-pixels of three colors of RGB to such a large extent, the RGB image data (R _IN /G _IN /B _IN =233/255/199) of the white adjustment image illustrated above , the gradation of one of the three colors of RGB must be greatly reduced, and along with this, the gradation of W generated by the RGB-RGBW conversion circuit 105 is also reduced.

As in the above example, when the RGB image data at the completion of the white balance adjustment is R _IN /G _IN /B _IN =233/255/199 data, the register 3 stores R _W /G _W /B Data of _W /W _W =233/255/199/199 are stored. Therefore, when white image data of R _IN /G _IN /B _IN =255/255/255 is input to the liquid crystal display device after the white balance adjustment is completed, the sub-pixels 111 to 114 have R _OUT /G _OUT /B _OUT / Display is performed with a transmittance corresponding to W _OUT =233/255/199/199. Therefore, the brightness of the liquid crystal display device after the white balance adjustment is completed is reduced to about 74% of the brightness in the initial state. Contrast is defined as the ratio of white luminance to black luminance (white luminance/black luminance), and since black luminance does not change due to white balance adjustment, contrast also decreases to about 74% of the initial contrast.

As described above, the xy coordinates of the composite of the four RGBW sub-pixels are located between the xy coordinates of the composite of the three RGB sub-pixels and the xy coordinates of the W sub-pixel. In order to suppress a decrease in luminance due to balance adjustment, it is effective to bring the xy coordinates of the W sub-pixel closer to the target xy coordinates of the white image. If the xy-coordinates of the W sub-pixel can be brought closer to the target xy-coordinates of the white image, the distance to move the xy-coordinates of the synthesis of the sub-pixels of three colors of RGB in the white balance adjustment can be reduced, and the decrease in luminance can be suppressed. .

FIG. 13 is an example of xy coordinates of a white image displayed in the initial state by the liquid crystal display device 200 including the color filter 120 shown in FIGS. In the color filter 120 of this liquid crystal display device 200, the G colorant is formed as the colored colorant 124a in 20% of the opening 1261 above the W sub-pixel 114. FIG. The liquid crystal panel 100, the backlight, and the like are exactly the same as those of the liquid crystal display device of the comparative example, except for the configuration of the color material provided in the opening 1264 on the W sub-pixel 114. FIG. As can be seen from the comparison between FIG. 13 and FIG. 11, in the liquid crystal display device 200 having the colored coloring material 124a in part of the openings above the W sub-pixels 114, the y-coordinates of the W sub-pixels are larger. , W are closer to the target xy coordinates than in the comparative example.

FIG. 14 is an example of xy coordinates of a white image displayed by the liquid crystal display device 200 when white balance adjustment is performed from the state of FIG. 13 and the white balance adjustment is completed. The RGB image data when the white balance adjustment was completed was R _IN /G _IN /B _IN =249/255/218 data, and had a higher gradation than the white adjusted image of the comparative example. As a result, data of R _W /G _W /B _W /W _W =249/255/218/218 are stored in the register 3 after the white balance adjustment is completed. Therefore, when white image data of R _IN /G _IN /B _IN =255/255/255 is input to the liquid crystal display device 200 after white balance adjustment is completed, the sub-pixels 111 to 114 are R _OUT /G _OUT /B _OUT Display is performed with a transmittance corresponding to /W _OUT =249/255/218/218. Therefore, the brightness of the liquid crystal display device 200 after completing the white balance adjustment is approximately 83% of the brightness in the initial state.

In the liquid crystal display device 200 of the present embodiment, since the colored coloring material 124a is partially provided on the W sub-pixel 114, the transmittance of the W sub-pixel 114 is reduced. Although the luminance is reduced to about 96% compared to the comparative example, the luminance of the white image after white balance adjustment is improved to about 108% compared to the comparative example even including this reduction in luminance. In addition, since the colored coloring material 124a is partially provided on the W sub-pixel 114, the black luminance is also lowered, so the decrease in contrast from the initial state is only about 83%. improved to 113%.

In the present embodiment, an example in which the colored coloring material 124a is arranged in 20% of the opening 1264 on the W sub-pixel 114 is shown. and the configuration of the backlight, etc. Therefore, the ratio of the colored colorant 124a to the aperture 1264 on the W sub-pixel 114 should be selected optimally according to the configuration used. However, since the brightness of the W sub-pixel 114 decreases as the proportion of the colored colorant 124a in the aperture 1264 on the W sub-pixel 114 increases, the proportion of the colored colorant 124a placed on the W sub-pixel 114 is approximately 50% or less of the opening 1264.

Further, in the present embodiment, an example of using a G colorant as the colored colorant 124a provided in the opening 1264 on the W sub-pixel 114 is shown. The material 124a may be the R colorant or the B colorant, and even in that case, by moving the xy coordinates of the W sub-pixel 114 closer to the target xy coordinates of the white image, the colored colorant 124a may be the G colorant. You can get the same effect as Note that the xy coordinates shown in FIGS. 13 and 14 are merely examples, and the xy coordinates of the white image on the liquid crystal display device 200 are not limited to the examples shown in FIGS.

The material of the colored coloring material 124a provided in the opening 1264 on the W subpixel 114 is formed in the openings 1261 to 1263 on the other subpixels 111 to 113 in order to suppress increases in manufacturing costs and the number of manufacturing processes. It is preferably the same as any of the R colorant 121 , G colorant 122 and B colorant 123 .

The color filter 120 can be formed, for example, by the following procedure. First, a black mask 126 is formed on a transparent glass 125 and patterned to form openings 1261 to 1264 in the black mask 126 . Then, a process of applying a coloring material to the entire surface of the transparent glass 125 and patterning the coloring material so as to leave the coloring material only in a desired area is performed by applying the R coloring material 121, the G coloring material 122, the B coloring material 123, and the transparent coloring material. 124 for each. At this time, the R colorant 121 is left on the opening 1261 arranged on the R subpixel 111 and the B colorant 123 is left on the opening 1263 arranged on the B subpixel 113 . The G colorant 122 is left on the opening 1262 arranged on the G sub-pixel 112 and left as a colored colorant 124 a on part of the opening 1264 arranged on the W sub-pixel 114 . In addition, the transparent coloring material 124 is left in the area above the opening 1264 excluding the formation area of the colored coloring material 124a. After that, the color filter 120 is completed by applying an overcoat 127 on the entire transparent glass 125 .

When the color filter 120 is formed by the above method, in the liquid crystal display device 200 , a sub-pixel having the same color as the colored coloring material 124 a is preferably arranged adjacent to the W sub-pixel 114 . For example, when the colored colorant 124a is a G colorant, the G sub-pixel 112 and the W sub-pixel 114 are preferably arranged adjacent to each other. The configuration of the color filter 120 is as shown in FIGS. 15 to 17, for example. 15 is a plan view of the color filter 120, FIG. 16 is a cross-sectional view along A1-A2 in FIG. 15, and FIG. 17 is a cross-sectional view along B1-B2 in FIG. Since the opening 1262 on the G colorant 122 and the opening 1264 on the W sub-pixel 114 are adjacent to each other, the colored colorant 124a can be integrally formed with the G colorant 122. Therefore, the film thickness of the colored colorant 124a Easy to control.

<Embodiment 2>
18 and 19 are diagrams showing the configuration of color filter 120 provided in display region 100a of liquid crystal display device 200 according to the second embodiment. 18 is a plan view of a region corresponding to one pixel 110 in color filter 120, and FIG. 19 is a cross-sectional view taken along line A1-A2 shown in FIG.

As in the first embodiment, the color filter 120 of the second embodiment is also formed on a transparent glass 125 and has a black mask 126 with openings 1261-1264 over each sub-pixel. The R colorant 121 is formed in the opening 1261 on the R subpixel 111, the G colorant 122 is formed in the opening 1262 on the G subpixel 112, and the opening on the B subpixel 113 is formed. A B color material 123 is formed in 1263 . However, in the color filter 120 of Embodiment 2, a layered structure of the transparent colorant 124 and the colored colorant 124a is formed in the opening 1264 above the W sub-pixel 114 . The colored colorant 124a is any one of an R colorant, a G colorant, and a B colorant, and the G colorant is used here.

The material of the colored coloring material 124a provided in the opening 1264 on the W subpixel 114 is formed in the openings 1261 to 1263 on the other subpixels 111 to 113 in order to suppress increases in manufacturing costs and the number of manufacturing processes. It is preferably the same as any of the R colorant 121 , G colorant 122 and B colorant 123 . In addition, the thickness of the colored coloring material 124a provided in the opening 1264 on the W sub-pixel 114 is different from the thickness of the R coloring material 121, G coloring material 122, or It is necessary to make it thinner than the thickness of the B colorant 123 . When the colored coloring material 124a is the G coloring material as shown in FIGS. thinned.

The color filter 120 of Embodiment 2 can be formed, for example, by the following procedure. First, a black mask 126 is formed on a transparent glass 125 and patterned to form openings 1261 to 1264 in the black mask 126 . Then, the process of applying the coloring material to the entire surface of the transparent glass 125 and patterning the coloring material so as to leave the coloring material only in a desired area is performed by applying the R coloring material 121, the G coloring material 122, the B coloring material 123, and the transparent coloring material. 124 for each. At this time, the step of forming the transparent colorant 124 is performed prior to the step of forming the G colorant 122, and the thickness of the transparent colorant 124 is made thinner than the thickness of the G colorant 122 formed thereafter. Specifically, the thickness of the transparent colorant 124 is a value (α -β). In addition, in the step of forming the G colorant 122, the G colorant 122 is left on the opening 1262 arranged on the G sub-pixel 112, and the colored color material 122 is left on the opening 1264 arranged on the W sub-pixel 114. It is left as material 124a. After that, the color filter 120 is completed by applying an overcoat 127 all over the transparent glass 125 .

When the color filter 120 is formed by the above method, in the liquid crystal display device 200 , a sub-pixel having the same color as the colored coloring material 124 a is preferably arranged adjacent to the W sub-pixel 114 . As shown in FIGS. 18 and 19, when the colored colorant 124a is a G colorant, the G sub-pixel 112 and the W sub-pixel 114 are preferably arranged adjacent to each other. Since the opening 1262 on the G colorant 122 and the opening 1264 on the W sub-pixel 114 are adjacent to each other, the colored colorant 124a can be integrally formed with the G colorant 122. Therefore, the film thickness of the colored colorant 124a Easy to control.

In the liquid crystal display device 200 of the second embodiment using the color filter 120 shown in FIGS. 18 and 19, the same effects as those of the first embodiment can be obtained.

FIG. 20 is an example of xy coordinates of a white image displayed in the initial state by liquid crystal display device 200 including color filter 120 shown in FIGS. Here, the thickness of the colored coloring material 124 a provided in the opening 1264 on the W sub-pixel 114 is 1/10 of the thickness of the G coloring material 122 provided in the opening 1262 on the G sub-pixel 112 . The configuration of the liquid crystal display device 200 is the same as that of the comparative example shown in the first embodiment except that the colored coloring material 124a is provided in the opening 1264 on the W sub-pixel 114. FIG. As can be seen from a comparison between FIGS. 20 and 11, in the liquid crystal display device 200 having the colored coloring material 124a in the openings above the W sub-pixels 114, the y-coordinates of the W sub-pixels are larger than the W sub-pixels. The xy coordinates of the sub-pixels are closer to the target xy coordinates than in the comparative example.

FIG. 21 is an example of xy coordinates of a white image displayed by the liquid crystal display device 200 when white balance adjustment is performed from the state of FIG. 20 and the white balance adjustment is completed. The RGB image data when the white balance adjustment is completed is R _IN /G _IN /B _IN =255/238/236 data, and has a higher gradation than the white adjusted image of the comparative example (FIG. 12). As a result, data of R _W /G _W /B _W /W _W =255/238/236/236 are stored in the register 3 after the white balance adjustment is completed. Therefore, when white image data of R _IN /G _IN /B _IN =255/255/255 is input to the liquid crystal display device 200 after white balance adjustment is completed, the sub-pixels 111 to 114 are R _OUT /G _OUT /B _OUT Display is performed with a transmittance corresponding to /W _OUT =255/238/236/236. Therefore, the luminance of the liquid crystal display device 200 after completing the white balance adjustment is approximately 87% of the luminance in the initial state.

In the liquid crystal display device 200 of the present embodiment, since the transmittance of the W sub-pixel 114 is reduced by providing the colored coloring material 124a on the W sub-pixel 114, the brightness of the liquid crystal display device 200 in the initial state is compared with that of the W sub-pixel 114. Although it is reduced to about 95% compared to the example, the luminance of the white image after white balance adjustment is improved to about 112% compared to the comparative example even if this decrease in luminance is included. In addition, since the colored coloring material 124a is partially provided on the W sub-pixel 114, the black luminance is also lowered, so the decrease in contrast from the initial state is only about 87%, and the contrast is about 87% compared to the comparative example. improved to 117%.

In this embodiment, the thickness of the transparent color material 124 provided in the opening 1264 on the W sub-pixel 114 is 1/10 of the thickness of the G color material 122 provided in the opening 1262 on the G sub-pixel 112. Although an example is shown, the preferable value of the colored coloring material 124a changes depending on the configuration of the liquid crystal panel 100, backlight, and the like. Therefore, the thickness of the colored coloring material 124a provided in the opening 1264 on the W sub-pixel 114 should be optimally selected according to the configuration used.

Further, in the present embodiment, an example of using a G colorant as the colored colorant 124a provided in the opening 1264 on the W sub-pixel 114 is shown. The material 124a may be the R colorant or the B colorant, and even in that case, by moving the xy coordinates of the W sub-pixel 114 closer to the target xy coordinates of the white image, the colored colorant 124a may be the G colorant. You can get the same effect as The xy coordinates shown in FIGS. 20 and 21 are merely examples, and the xy coordinates of the white image on the liquid crystal display device 200 are not limited to the examples shown in FIGS.

<Embodiment 3>
FIG. 22 shows a conversion circuit 106 (hereinafter referred to as “RGB -RGBW conversion circuit 106"). Elements in the RGB-RGBW conversion circuit 106 of FIG. 22 that have the same functions as those of the RGB-RGBW conversion circuit 105 of FIG. 2 are given the same reference numerals. Therefore, in the following description, the description of the portion similar to the RGB-RGBW conversion circuit 105 in FIG. 2 may be simplified.

The RGB-RGBW conversion circuit 106 may be provided with a circuit for adjusting the hue, saturation, brightness, etc. of the image to be displayed. there is It is also assumed that each color of the RGB image data input to the RGB-RGBW conversion circuit 106 is 8-bit data. That is, the maximum value (maximum gradation) of each color of the RGB image data input to the RGB-RGBW conversion circuit 106 is 255.

22, the configuration of the RGB-RGBW conversion circuit 106 in FIG. 22 replaces the register 3 with two registers 3a and 3b and replaces the data conversion circuit 7 with two data conversion circuits 7a. , 7b and the W data switching unit 12 are replaced.

The minimum data detection circuit 1 selects the minimum data among the RGB image data input to the RGB-RGBW conversion circuit 106 and outputs the selected value to the W function circuit 2 . That is, if the R data, G data and B data of the RGB image data are R _IN , G _IN and B _IN respectively, the output of the minimum data detection circuit 1 is Y _min =min(R _IN , G _IN , B _IN ) is represented.

The W function circuit 2 determines the mixing degree of W according to the preset W function F according to the output Y _min of the minimum data detection circuit 1 . Here, for simplicity of explanation, it is assumed that the W function F is a linear function and the output data of the W function circuit 2 is the same value (Y _min ) as the input data of the W function circuit 2 .

The register 3a is a first storage unit that stores an upper limit value _RW of R data, an upper limit value GW of _G data, and an upper limit value _BW of B data of RGBW image data after conversion. R _W , G _W , and B _W stored in the register 3a are the values of the RGB three-color data of the RGBW image data output by the RGB-RGBW conversion circuit 106 when the liquid crystal display device 200 displays a white image. These values are set by adjusting the white balance of the liquid crystal display device 200 .

The register 3b is a second storage unit that stores the upper limit value W _MAX of the W data of the converted RGBW image data. W _MAX stored in the register 3b defines the W data value of the RGBW image data output by the RGB-RGBW conversion circuit 106 when the liquid crystal display device 200 displays a white image. A constant value is set regardless of the white balance adjustment of the liquid crystal display device 200 .

Therefore, if the R data, G data, B data and W data of the RGBW image data output from the RGB-RGBW conversion circuit 106 are R _OUT , G _OUT , B _OUT and W _OUT respectively, the input RGB image data is R When _IN /G _IN /B _IN =255/255/255, the output RGBW image data is R _OUT /G _OUT /B _OUT /W _OUT =R _W /G _W /B _W /W _MAX .

Of the data conversion circuits 4, 5, 6, 7a, and 7b, the data conversion circuits 4 to 6 convert each color of the input RGB image data based on R _W , G _W , and B _W stored in the register 3a. Functions as a first conversion unit that converts each of the data R _IN , G _IN , and B _IN into R data, G data, and B data for RGBW image data having maximum values of R _W , G _W , and B _W .

Further, the data conversion circuit 7a converts the output data (here, Y _min ) of the W function circuit 2 to W data for RGBW image data having W _MAX as the maximum value, based on W _MAX stored in the register 3b. It functions as a second conversion unit that converts. The data conversion circuits 4, 5, 6, and 7a may include a gamma correction circuit that corrects the relationship between the gradation data and the display luminance for each RGBW color.

On the other hand, the data conversion circuit 7b generates W data for white balance adjustment (hereinafter referred to as "adjustment W data") that takes the value of W _MAX stored in the register 3b regardless of the output data of the W function circuit 2. It functions as a W data generation unit for adjustment.

The W data switching unit 12 is an exclusive switching circuit composed of logic circuits 12a and 12b, and is generated by the data conversion circuit 7a according to the CAL signal input from the outside (for example, the computer 201 in FIG. 8). It switches which of the W data and the adjustment W data generated by the data conversion circuit 7b is to be input to the bit number conversion circuit 11. FIG. That is, the W data switching unit 12 converts the W data of the RGBW image data output from the RGB-RGBW conversion circuit 106 into the W data generated by the data conversion circuit 7a, or the W data for adjustment generated by the data conversion circuit 7b. Data can be switched. The W data switching unit 12 shown in FIG. 22 outputs the W data generated by the data conversion circuit 7a when the CAL signal is at L (Low) level, and outputs the W data generated by the data conversion circuit 7b when the CAL signal is at H (High) level. operates to output the W data for adjustment generated by .

In the RGB-RGBW conversion circuit 106, the number of output bits of the data conversion circuits 4, 5, 6, 7a, and 7b is changed to the number of input bits ( 10 bits, which is larger than 8 bits). Therefore, the output stage of the RGB-RGBW conversion circuit 106 includes a bit number conversion circuit 8 that converts 10-bit RGBW image data into 8-bit data that can be input to the source IC 101 of the liquid crystal panel 100 using frame rate control technology. 11 are provided.

The 8-bit R data, G data, B data and W data output from the bit number conversion circuits 8 to 11 are the RGBW image data output from the RGB-RGBW conversion circuit 106 (R _OUT /G _OUT /B _OUT / W _OUT ). As can be seen from the above description, when the CAL signal is set to L level, the W data generated by the data conversion circuit 7a is input to the bit number conversion circuit 11, so that R _OUT , G _OUT , B _OUT and W _OUT all change according to the RGB image data input to the RGB-RGBW conversion circuit 106 . However, when the CAL signal is set to H level, the W data for adjustment generated by the data conversion circuit 7b is input to the bit number conversion circuit 11, so that one of R _OUT , G _OUT , B _OUT and W _OUT W _OUT is fixed at a constant value W _MAX regardless of the RGB image data input to the RGB-RGBW conversion circuit 106 .

In FIG. 22, the register 3a stores the upper limit values R _W , G _W and B _W of the R data, G data and B data of the converted RGBW image data, and the upper limit value W _MAX of the W data. Although the registers 3b and 3b are shown separately, the registers 3a and 3b may be configured as one register as long as R _W , G _W , B _W and W _MAX can be written at different timings.

Next, a method for white balance adjustment of the liquid crystal display device 200 of the third embodiment including the RGB-RGBW conversion circuit 106 of FIG. 22 will be described. Also in this embodiment, when performing white balance adjustment, the liquid crystal display device 200 is connected to the computer 201 through the image input wiring 202 and the control wiring 203 as in FIG. A luminance meter 204 is arranged. Here too, the chromaticity measurement result by the color luminance meter 204 is expressed as xy coordinates in the CIE1931 color space.

Prior to white balance adjustment, the computer 201 transmits the W _MAX value to the liquid crystal display device 200 through the control wiring 203 and stores the W _MAX value in the register 3b of the RGB-RGBW conversion circuit 106. FIG. For example, if it is desired to obtain the liquid crystal display device 200 with maximized brightness, W _MAX =255 is set. Since W _MAX is a constant value, W _MAX may be written in the register 3b at the manufacturing stage of the liquid crystal display device 200, in which case the procedure for setting the value of W _MAX by the computer 201 can be omitted.

Subsequently, the computer 201 sets the CAL signal set to H level to the liquid crystal display device 200 through the control wiring 203 . As a result, the W data (W _OUT ) of the RGBW image data output from the RGB-RGBW conversion circuit 106 is fixed at W _MAX which is a constant value.

In this state, white balance adjustment is performed in the same procedure as in the first embodiment. First, the computer 201 outputs the three colors of RGB to the liquid crystal display device 200 in the initial state (the state in which the R _W , G _W , and B _W stored in the register 3a are all set to the initial value, the maximum gradation 255). By inputting RGB image data (R _IN /G _IN /B _IN =255/255/255) with maximum gradation, the liquid crystal display device 200 is caused to display a white image.

Next, color luminance meter 204 measures the luminance and xy coordinates of the white image displayed on liquid crystal display device 200 . Then, the computer 201 adjusts the xy coordinates of the white image displayed on the liquid crystal display device 200 to the target xy coordinates of white (target xy coordinates) based on the luminance and the xy coordinates measured by the color luminance meter 204. , the white balance is adjusted by adjusting the values of the R data, G data and B data of the RGB image data input to the liquid crystal display device 200 . At this time, the computer 201 adjusts the gradation of two of the three colors of RGB, that is, two values of the R data, G data and B data of the RGB image data input to the liquid crystal display device 200 .

After that, the computer 201 causes the liquid crystal display device 200 to display a white image (white adjusted image) whose white balance has been adjusted, and the color luminance meter 204 measures the brightness and xy coordinates of the white adjusted image. At this time, if the distance between the xy coordinates of the white adjusted image and the target xy coordinates exceeds the allowable value, the computer 201 adjusts the white balance again based on the brightness and xy coordinates of the white adjusted image. When this is repeated and the distance between the xy coordinates of the white adjustment image and the target xy coordinates becomes equal to or less than the allowable value, the white balance adjustment is completed.

When the white adjusted image that achieves the target xy coordinates is obtained in this way, the computer 201 calculates the R data (R _IN ), G data (G _IN ) and B data of the RGB image data when the white balance adjustment is completed. (B _IN ) is transmitted to the liquid crystal display device 200 through the control wiring 203 . The liquid crystal display device 200 stores these R data, G data, B data and W data received through the control wiring 203 in the register 3a of the RGB-RGBW conversion circuit 106 as R _W , G _W and B _W . Note that W _MAX stored in the register 3b is maintained at the same value as before the white balance adjustment.

After completing the white balance adjustment, the CAL signal is fixed at L level. As a result, in the RGBW image data output from the RGB-RGBW conversion circuit 106, all of the R data (R _OUT ), G data (G _OUT ), B data (B _OUT ), and W data (W _OUT ) are RGB- The color changes according to the RGB image data input to the RGBW conversion circuit 106, and the liquid crystal display device 200 is ready to display a normal image according to the input RGB image data.

In the liquid crystal display device 200 of Embodiment 3, the upper limit value of the W data (W _OUT ) output from the RGB-RGBW conversion circuit 106 after the white balance adjustment is completed is maintained at W _MAX which is the same as before the white balance adjustment. In other words, the luminance of the W sub-pixel 114 is prevented from decreasing due to the white balance adjustment, so that the decrease in luminance due to the white balance adjustment is suppressed.

FIG. 23 is an example of xy coordinates of a white image displayed in the initial state by the liquid crystal display device 200 including the RGB-RGBW conversion circuit 106 of FIG. The color filter 120 of this liquid crystal display device 200 is the color filter of the conventional structure shown in FIGS. Since the operation of the RGB-RGBW conversion circuit 106 in the initial state is the same as the operation of the RGB-RGBW conversion circuit 105 in FIG. 2, FIG. 23 is the same as the example shown in FIG.

FIG. 24 is an example of xy coordinates of a white image displayed by the liquid crystal display device 200 when white balance adjustment is performed from the state of FIG. 23 and the white balance adjustment is completed. The RGB image data when the white balance adjustment is completed is R _IN /G _IN /B _IN =226/255/168 data. In FIG. 24, the composite xy coordinates of the sub-pixels of three colors of RGB are farther apart from the target xy coordinates than in the example shown in FIG. This is because the W data (W _OUT ) output by the RGB-RGBW conversion circuit 106 during white balance adjustment is fixed to W _MAX (255) regardless of the input RGB image data (R _IN , G _IN , B _IN ). This is because _RW / _GW / _BW =226/255/168 is stored in the register 3a after the completion of the RGB white balance adjustment. Therefore, when white image data of R _IN /G _IN /B _IN =255/255/255 is input to the liquid crystal display device 200 after white balance adjustment is completed, the sub-pixels 111 to 114 are R _OUT /G _OUT /B _OUT Display is performed with a transmittance corresponding to /W _OUT =226/255/168/255. Therefore, the brightness of the liquid crystal display device 200 after the white balance adjustment is completed is about 95% of the brightness in the initial state, and can be improved to about 129% compared with the conventional liquid crystal display device. The contrast is also about 95% of the contrast in the initial state, and can be improved to about 129% as compared with the conventional liquid crystal display device.

As described above, in the liquid crystal display device 200 of the third embodiment provided with the RGB-RGBW conversion circuit 106, the brightness and contrast after the white balance adjustment is completed are significantly higher than when the RGB-RGBW conversion circuit 105 in FIG. 2 is used. be improved. Note that the xy coordinates shown in FIGS. 23 and 24 are merely examples, and the xy coordinates of the white image on the liquid crystal display device 200 are not limited to the examples shown in FIGS.

In the above description, in order to maximize the luminance of the liquid crystal display device 200, the W _MAX stored in the register 3b was set to 255, which is the maximum gradation. . Reducing W _MAX below the maximum gradation of 255 can improve the saturation of intermediate colors, but reduces brightness and contrast. Another way to improve the saturation of midtones is to make the opening 1264 smaller in the black mask 126 above the W sub-pixel 114 . With this method, even if W _MAX is set to 255, which is the maximum gradation, the luminance of the W sub-pixel 114 is lowered, so that the saturation of intermediate colors is prevented from being lowered.

In particular, the value of W _MAX to be stored in the register 3b or the size of the opening 1264 on the W sub-pixel 114 is set to the R sub-pixel 111, G sub-pixel 112 and G sub-pixel 112 when the liquid crystal display device 200 displays a white image. When the total brightness of the B sub-pixel 113 and the brightness of the W sub-pixel 114 are adjusted to be equal, the decrease in brightness and contrast due to white balance adjustment is small, and the decrease in saturation in intermediate colors is prevented. , the liquid crystal display device 200 is obtained.

For example, in the color filter 120 having the conventional structure shown in FIGS. 9 and 10, if the size of the opening 1264 above the W sub-pixel 114 is vertically reduced to 87%, the W sub-pixel 114 before white balance adjustment is The luminance and the total luminance of the R sub-pixel 111, G sub-pixel 112 and B sub-pixel 113 are almost equal. In the liquid crystal display device 200 including the color filter 120 and the RGB-RGBW conversion circuit 106 of Embodiment 3, the brightness before the white balance adjustment is about 93% because the aperture 1264 on the W sub-pixel 114 is smaller. However, the luminance after the white balance adjustment is completed can be kept to about 95% of the luminance before the white balance adjustment. As a result, the brightness of the white image after completing the white balance adjustment can be improved to about 120% compared to the conventional liquid crystal display device. Further, the contrast after the white balance adjustment is completed remains at about 95% of the contrast in the initial state, and compared with the conventional liquid crystal display device, the contrast after the white balance adjustment is completed is improved to about 129%.

Furthermore, in order to suppress variations in chroma due to manufacturing variations, the sum of the luminance of the W sub-pixel 114, the R sub-pixel 111, the G sub-pixel 112, and the B sub-pixel 113 when a white image is displayed after the white balance adjustment is completed. If it is desired to equalize the luminance of the W sub-pixel 114 with the white image displayed on the liquid crystal display device 200 during white balance adjustment, the luminance of the W sub-pixel 114 is equal to that of the R sub-pixel 111, the G sub-pixel 112, and the B sub-pixel 113. Change the value of W _MAX so that it equals the total luminance.

In Embodiments 1 to 3, an example in which the RGBW type display device is a liquid crystal display device is shown, but for example, an organic EL display or the like may also be used. Embodiments 1 and 2 relate to the configuration of the color filter 120 of the RGBW type display device, and are widely applicable not only to liquid crystal displays but also to RGBW type display devices using the color filter 120 .

In Embodiment 3, an example in which the RGB-RGBW conversion circuit 106 is realized by hardware circuits is shown, but the RGB-RGBW conversion circuit 106 may be realized by cooperation between hardware resources and software. In other words, the functions of the RGB-RGBW conversion circuit 106 may be realized by a computer executing an image processing program. More specifically, the function of the RGB-RGBW conversion circuit 106 is such that an image processing program recorded in a recording medium (memory) such as a ROM is read into a main storage device and processed by a processor (eg, central processing unit (CPU)). It may be realized by being executed by

The image processing program may be recorded in a computer-readable recording medium such as a memory card and provided, or may be provided via a communication line such as the Internet. Therefore, the signal conversion method performed by the RGB-RGBW conversion circuit 106, the program for causing the computer to execute each process of the function of the RGB-RGBW conversion circuit 106 or the signal conversion method, and the recording medium on which the program is recorded It is also included in the third embodiment.

In addition, it is possible to combine each embodiment freely, and to modify|transform and abbreviate|omit each embodiment suitably.

1 minimum data detection circuit 2 W function circuit 3, 3a, 3b registers 4 to 7, 7a, 7b data conversion circuit 8 to 11 bit number conversion circuit 12 W data switching unit 12a, 12b logic circuit 100 Liquid crystal panel, 100a display area, 101 source IC, 102 gate IC, 103 display control unit, 104 signal conversion unit, 105, 106 RGB-RGBW conversion circuit, 110 pixel, 111 R sub-pixel, 112 G sub-pixel, 113 B sub-pixel pixel, 114 W sub-pixel, 120 color filter, 121 R colorant, 122 G colorant, 123 B colorant, 124 transparent colorant, 124a colored colorant, 125 transparent glass, 126 black mask, 1261 to 1264 openings, 127 overcoat, 200 liquid crystal display device, 201 computer, 202 image input wiring, 203 control wiring, 204 color luminance meter, 205 output wiring.

Claims (5)

An image data conversion device for converting RGB image data consisting of R (red), G (green), and B (blue) data into RGBW image data consisting of R, G, B, and W (white) data, ,
a first storage unit that stores upper limit values of R data, G data, and B data of the RGBW image data;
a second storage unit that stores an upper limit value of W data of the RGBW image data;
R data, G data, and B data of the RGB image data are converted into R data, G data, and B data of the RGBW image data, each of which has a maximum value equal to the upper limit value stored in the first storage unit. a first converter for converting;
a second conversion unit for generating W data having a maximum value equal to the upper limit value stored in the second storage unit, based on the R data, G data, and B data of the RGB image data;
an adjustment W data generation unit for generating adjustment W data having the upper limit value stored in the second storage unit regardless of the R data, G data and B data of the RGB image data;
a switch input from the outside to select which of the W data generated by the second conversion unit and the adjustment W data generated by the adjustment W data generation unit is used as the W data of the RGBW image data; a W data switching unit that switches according to a signal ;
with
outputting the R data, G data, and B data generated by the first conversion unit and the W data selected by the W data switching unit as the RGBW image data;
Image data converter. A display device comprising the image data conversion device according to claim 1 and displaying an image based on the RGBW image data. The upper limit value of the W data stored in the second storage unit is the sum of the luminance of the W sub-pixel and the total luminance of the R sub-pixel, the G sub-pixel and the B sub-pixel when the display device displays a white image. is set to a value that equals
3. The display device according to claim 2. A white balance adjustment method for a display device according to claim 2 or 3,
a step of displaying a white image on the display device using the adjustment W data generated by the adjustment W data generation unit as the W data of the RGBW image data;
measuring the chromaticity of the white image displayed on the display device;
adjusting the R data, G data and B data of the RGB image data to be input to the image data conversion device so that the chromaticity of the white image displayed on the display device approaches a predetermined target value; a step of adjusting the white balance with
A step of storing the values of the R data, the G data and the B data of the RGB image data after white balance adjustment in the first storage unit as the respective upper limit values of the R data, the G data and the B data of the RGBW image data. When,
A white balance adjustment method comprising: In a state where the white image is displayed on the display device, the second pixel is adjusted so that the luminance of the W sub-pixel and the total luminance of the R sub-pixel, the G sub-pixel and the B sub-pixel of the display device are equal to each other. further comprising the step of adjusting the upper limit of the W data to be stored in the storage unit;
The white balance adjustment method according to claim 4.

Images