JP2019148774A - Liquid crystal display device - Google Patents

Abstract

To improve color reproducibility in a low gradation range in a liquid crystal display device constructed by overlapping a plurality of display panels.SOLUTION: A liquid crystal display device includes: a first display panel having at least two or more color filters with a plurality of colors different from each other; a second display panel which, on a back side of the first display panel, is arranged by being overlapped with the first display panel and does not have the color filter; and a backlight which is arranged on the back side of the second display panel and radiates a plurality of colored lights toward the second display panel at different timing respectively.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid crystal display device.

  Conventionally, as a technique for improving the contrast of a liquid crystal display device, a technique has been proposed in which two display panels are overlapped and an image is displayed on each display panel based on input image data. For example, in the following patent document, a first display panel arranged on the display surface side and having a color filter, and a second display panel arranged on the back side of the first display panel and not having a color filter, And a backlight that is disposed on the back side of the second display panel and irradiates white light from the back side of the second display panel toward the display surface side.

International Publication No. 2007/040139

  However, in the conventional liquid crystal display device, further improvement in color reproducibility in a low gradation range has been a problem. That is, in the above-described conventional configuration, when the total gamma value of both display panels is adjusted to a desired value, the transmittance of the first display panel in the low gradation range hardly changes. Therefore, it is difficult to display the colors, and improvement of color reproducibility in a low gradation range has been a problem.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to improve color reproducibility in a low gradation region in a liquid crystal display device configured by overlapping a plurality of display panels.

  In order to solve the above-described problem, a liquid crystal display device according to the present disclosure includes a first display panel having color filters of at least two or more different colors and a back side of the first display panel. The second display panel that is arranged so as to overlap with the first display panel and that does not have a color filter, and the second display panel that is arranged on the back side of the second display panel. And a backlight for irradiating the second display panel.

  According to the liquid crystal display device according to the present disclosure, an improvement in color reproducibility in a low gradation region can be realized in a liquid crystal display device configured by overlapping a plurality of display panels.

FIG. 1 is an exploded perspective view showing a schematic configuration of the liquid crystal display device according to the first embodiment. FIG. 2 is a diagram schematically showing a schematic configuration of the liquid crystal display device. FIG. 3A is a diagram for explaining a field sequential method in the liquid crystal display device. FIG. 3B is a diagram for explaining a field sequential method in the liquid crystal display device. FIG. 4 is a plan view showing a schematic configuration of the first display panel according to the first embodiment. FIG. 5 is a plan view showing a schematic configuration of the second display panel according to the first embodiment. 6 is a cross-sectional view corresponding to the line 6-6 ′ in FIGS. FIG. 7 is a graph showing transmittance characteristics (luminance characteristics) when the combined gamma value is 2.2. FIG. 8 is a block diagram illustrating a configuration of the image processing unit according to the first embodiment. FIG. 9 is a graph showing the first transmittance characteristic according to the first embodiment. FIG. 10 is a graph showing the second transmittance characteristic according to the first embodiment.

[First embodiment]
A first embodiment of the present disclosure will be described below with reference to the drawings. A liquid crystal display device according to each embodiment described below includes a plurality of display panels that display images, a plurality of drive circuits (a plurality of source drivers and a plurality of gate drivers) that drive the respective display panels, and respective drives. A plurality of timing controllers that control the circuit, an image processing unit that performs image processing on input video signals input from the outside, and outputs image data to each timing controller, and a plurality of display panels that emit light from the back side And a backlight for irradiating. The number of display panels is not limited and may be two or more. The plurality of display panels are arranged so as to overlap each other in the front-rear direction as viewed from the observer side, and each displays an image. Hereinafter, a liquid crystal display device LCD having two display panels will be described as an example.

  FIG. 1 is a perspective view showing a schematic configuration of a liquid crystal display device LCD according to the present embodiment. As shown in FIG. 1, the liquid crystal display device LCD includes a first display panel LCP1 arranged at a position close to the observer (display surface side), and a position farther from the observer than the first display panel LCP1 (rear side). ), The adhesive layer SEFIL that bonds the first display panel LCP1 and the second display panel LCP2, and the backlight BL disposed on the back side of the second display panel LCP2. And a front chassis FS that covers the first display panel LCP1 and the second display panel LCP2 from the display surface side.

  FIG. 2 is a diagram schematically showing a schematic configuration of the liquid crystal display device LCD according to the present embodiment. As shown in FIG. 2, the first display panel LCP1 includes a first source driver SD1 and a first gate driver GD1, and the second display panel LCP2 includes a second source driver SD2 and a second source driver SD2. And a gate driver GD2. The liquid crystal display device LCD also includes a first timing controller TCON1 that controls the first source driver SD1 and the first gate driver GD1, and a second timing that controls the second source driver SD2 and the second gate driver GD2. The timing controller TCON2 and an image processing unit IPU that outputs image data to the first timing controller TCON1 and the second timing controller TCON2. The first display panel LCP1 displays an image corresponding to the input video signal in the first image display area DISP1, and the second display panel LCP2 displays an image corresponding to the input video signal in the second image display area DISP2. To do. The image processing unit IPU receives an input video signal Data transmitted from an external system (not shown), performs image processing to be described later, and then outputs first image data DAT1 to the first timing controller TCON1. Then, the second image data DAT2 is output to the second timing controller TCON2. Further, the image processing unit IPU outputs a control signal (not shown in FIG. 2) such as a synchronization signal to the first timing controller TCON1 and the second timing controller TCON2.

  The liquid crystal display device LCD in the present embodiment displays a color image by so-called field sequential (FSC) driving. In the field sequential method, as shown in FIG. 3A, the backlight BL sequentially switches LEDs of a plurality of colors, for example, three colors (red (R), green (G), blue (B)) within one field. The color image is recognized by switching the screen of three colors of red, green and blue.

  In the present embodiment, as shown in FIG. 3B, the backlight BL emits light of a plurality of colors toward the second display panel LCP2 at different timings within one field. The second display panel LCP2 switches and displays images corresponding to a plurality of colors (three colors in the present embodiment) in accordance with the switching timing of the backlight BL in one field. More specifically, by switching the input timing of the data signal according to the switching timing for each pixel that is superimposed on the pixels of each color provided in the first display panel LCP1 in plan view, a plurality of colors are obtained. The corresponding image is switched and displayed. On the other hand, the first display panel LCP1 continues to input the data signal corresponding to the input image signal to the pixels corresponding to the color filters of a plurality of colors in one field regardless of the timing. In the first display panel LCP1, data signals are input for all the pixels. However, in the second display panel LCP2, as described above, the three color images are switched according to the switching timing. Therefore, the entire display device LCD is configured to sequentially display images corresponding to the three colors within one field.

  In the above embodiment, the second display panel LCP2 switches and displays images corresponding to a plurality of colors in accordance with the switching timing of the backlight BL in one field. However, the present invention is not limited to this. Not. That is, the timing of turning on and off the backlight BL may not be the same as the timing of starting input of the input image signal corresponding to each color or switching to a different color on the second display panel LCP2. For example, the red backlight BL may be turned on after a predetermined time has elapsed after the input of the input image signal corresponding to red is started on the second display panel LCP2. Further, the red backlight BL may be turned off before switching the input of the input image signal corresponding to green from red to the second display panel LCP2.

  FIG. 4 is a plan view showing a schematic configuration of the first display panel LCP1 according to the present embodiment, and FIG. 5 is a plan view showing a schematic configuration of the second display panel LCP2 according to the present embodiment. FIG. 6 is a cross-sectional view taken along the line 6-6 ′ of FIGS.

  A schematic configuration of the first display panel LCP1 will be described with reference to FIGS. As shown in FIG. 6, the first display panel LCP1 includes a first thin film transistor substrate TFT1 disposed on the backlight BL side and a first thin film transistor substrate TFT1 disposed on the viewer side and facing the first thin film transistor substrate TFT1. The counter substrate TIS1 and the first liquid crystal layer LC1 disposed between the first thin film transistor substrate TFT1 and the first counter substrate TIS1 are included. The second polarizing plate POL2 is disposed on the backlight BL side (back side) of the first display panel LCP1, and the first polarizing plate POL1 is disposed on the viewer side (display surface side). .

  As shown in FIG. 4, the first thin film transistor substrate TFT1 includes a plurality of source lines SL extending in a first direction (for example, the column direction) and a second direction (for example, a row) different from the first direction. A plurality of gate lines GL extending in the direction) are formed, and thin film transistors TFT are formed in the vicinity of the intersections of the plurality of source lines SL and the plurality of gate lines GL. A region surrounded by two adjacent source lines SL and two adjacent gate lines GL is defined as one subpixel SPIX when the first display panel LCP1 is viewed in plan, and the subpixel SPIX is defined as one subpixel SPIX. A plurality are arranged in a matrix (row direction and column direction). The plurality of source lines SL are arranged at equal intervals in the row direction, and the plurality of gate lines GL are arranged at equal intervals in the column direction. On the first thin film transistor substrate TFT1, a pixel electrode PX is formed for each subpixel SPIX, and one common electrode common to a plurality of subpixels SPIX is formed. The source electrode constituting the thin film transistor TFT is electrically connected to the source line SL, the drain electrode is electrically connected to the pixel electrode PX through the contact hole, and the gate electrode is electrically connected to the gate line GL. .

  As shown in FIG. 6, a plurality of color filters CL (colored layers) are formed on the first counter substrate TIS1 corresponding to each subpixel SPIX. Each color filter CL is surrounded by a first black matrix BM1 that blocks light transmission, and is formed in a rectangular shape, for example. The plurality of color filters CL are formed of a red material and are formed of a red color filter that transmits red light, a green color filter that is formed of green material and transmits green light, and a blue material. And a blue color filter that transmits blue light. As shown in FIG. 4, the red color filter, the green color filter, and the blue color filter in this embodiment are repeatedly arranged in this order in the row direction, and the color filters of the same color are arranged in the column direction. A first black matrix BM1 is formed at the boundary portion between the color filters CL adjacent in the direction. As shown in FIG. 2, the plurality of sub-pixels SPIX corresponding to each color filter CL include a red sub-pixel PIXR corresponding to the red color filter, a green sub-pixel PIXG corresponding to the green color filter, and a blue color filter. And a blue sub-pixel PIXB corresponding to. In the first display panel LCP1, one red subpixel PIXR, one green subpixel PIXG, and one blue subpixel PIXB are included to constitute one first pixel PIX1, and a plurality of first pixels PIX1 is arranged in a matrix. Note that the arrangement relationship of the red color filter, the green color filter, and the blue color filter is not limited to the above-described configuration.

  The first timing controller TCON1 is based on the first image data DAT1 output from the image processing unit IPU and the first control signal CS1 (clock signal, vertical synchronization signal, horizontal synchronization signal, etc.). Various timing signals (first data start pulse DSP1, first data clock DCK1, first gate start pulse) for controlling the image data DA1 and driving of the first source driver SD1 and the first gate driver GD1. GSP1 and first gate clock GCK1) are generated (see FIG. 4). The first timing controller TCON1 outputs the first image data DA1, the first data start pulse DSP1, and the first data clock DCK1 to the first source driver SD1, and the first gate start pulse GSP1. And the first gate clock GCK1 are output to the first gate driver GD1.

  The first source driver SD1 outputs a data signal (data voltage) corresponding to the first image data DA1 to the source line SL based on the first data start pulse DSP1 and the first data clock DCK1. The first gate driver GD1 outputs a gate signal (gate voltage) to the gate line GL based on the first gate start pulse GSP1 and the first gate clock GCK1.

  Each source line SL is supplied with a data voltage from the first source driver SD1, and each gate line GL is supplied with a gate voltage from the first gate driver GD1. A common voltage Vcom is supplied to the common electrode from a common driver (not shown). When the gate voltage (gate-on voltage) is supplied to the gate line GL, the thin film transistor TFT connected to the gate line GL is turned on, and the data voltage is supplied to the pixel electrode PX via the source line SL connected to the thin film transistor TFT. Is done. An electric field is generated by the difference between the data voltage supplied to the pixel electrode PX and the common voltage Vcom supplied to the common electrode. The liquid crystal is driven by this electric field to control the light transmittance of the backlight BL, thereby displaying an image. In the first display panel LCP1, by supplying a desired data voltage to the source line SL connected to the pixel electrodes PX of the red subpixel PIXR, the green subpixel PIXG, and the blue subpixel PIXB, color image display is performed. Done.

  Next, the configuration of the second display panel LCP2 will be described with reference to FIGS. As shown in FIG. 6, the second display panel LCP2 is arranged on the backlight BL side (back side) and the second thin film transistor substrate TFT2 and on the viewer side (display surface side). A second counter substrate TIS2 facing the thin film transistor substrate TFT2 and a second liquid crystal layer LC2 disposed between the second thin film transistor substrate TFT2 and the second counter substrate TIS2 are included. A fourth polarizing plate POL4 is disposed on the backlight BL side (back side) of the second display panel LCP2, and a third polarizing plate POL3 is disposed on the viewer side. An adhesive layer SEFIL is disposed between the second polarizing plate POL2 of the first display panel LCP1 and the third polarizing plate POL3 of the second display panel LCP2.

  As shown in FIG. 5, a plurality of source lines SL extending in the column direction and a plurality of gate lines GL extending in the row direction are formed on the second thin film transistor substrate TFT2, and the plurality of source lines SL are formed. A thin film transistor TFT is formed in the vicinity of each intersection of the gate line GL and the plurality of gate lines GL. When the second display panel LCP2 is viewed in plan, a region surrounded by two adjacent source lines SL and two adjacent gate lines GL is defined as one second pixel PIX2, and the second A plurality of pixels PIX2 are arranged in a matrix (row direction and column direction). The plurality of gate lines GL are arranged at equal intervals in the column direction. On the second thin film transistor substrate TFT2, a pixel electrode PX is formed for each second pixel PIX2, and one common electrode common to the plurality of second pixels PIX2 is formed. The source electrode constituting the thin film transistor TFT is electrically connected to the source line SL, the drain electrode is electrically connected to the pixel electrode PX through the contact hole, and the gate electrode is electrically connected to the gate line GL. . Each first pixel PIX1 of the first display panel LCP1 and each second pixel PIX2 of the second display panel LCP2 overlap each other in plan view. For example, one first pixel PIX1 including the red subpixel PIXR, the green subpixel PIXG, and the blue subpixel PIXB illustrated in FIG. 4 and the one second pixel PIX2 illustrated in FIG. They overlap each other in plan view. Note that the sub-pixels SPIX of the first display panel LCP1 and the second pixels PIX2 of the second display panel LCP2 may be arranged in a one-to-one relationship with each other, for example. And the correspondence relationship with each second pixel PIX2 is not limited to the above-described configuration.

  As shown in FIG. 6, the second black matrix BM2 is formed on the second counter substrate TIS2 at a position corresponding to the boundary portion of each second pixel PIX2, that is, a position overlapping the source line SL in plan view. Has been. In the region surrounded by the second black matrix BM2, no color filter layer (colored portion) is formed, and for example, an overcoat film OC is formed.

  Based on the second image data DAT2 output from the image processing unit IPU and the second control signal CS2 (clock signal, vertical synchronization signal, horizontal synchronization signal, etc.), the second timing controller TCON2 Various timing signals (second data start pulse DSP2, second data clock DCK2, second gate start pulse) for controlling the driving of the image data DA2, the second source driver SD2 and the second gate driver GD2. GSP2 and second gate clock GCK2) are generated (see FIG. 5). The second timing controller TCON2 outputs the second image data DA2, the second data start pulse DSP2, and the second data clock DCK2 to the second source driver SD2, and the second gate start pulse GSP2. And the second gate clock GCK2 are output to the second gate driver GD2.

  The second source driver SD2 outputs a data voltage corresponding to the second image data DA2 to the source line SL based on the second data start pulse DSP2 and the second data clock DCK2. The second gate driver GD2 outputs a gate voltage to the gate line GL based on the second gate start pulse GSP2 and the second gate clock GCK2.

  A data voltage is supplied from the second source driver SD2 to each source line SL, and a gate voltage is supplied from the second gate driver GD2 to each gate line GL. A common voltage Vcom is supplied to the common electrode from a common driver. When the gate voltage (gate-on voltage) is supplied to the gate line GL, the thin film transistor TFT connected to the gate line GL is turned on, and the data voltage is supplied to the pixel electrode PX via the source line SL connected to the thin film transistor TFT. Is done. An electric field is generated by the difference between the data voltage supplied to the pixel electrode PX and the common voltage Vcom supplied to the common electrode. The liquid crystal is driven by this electric field to control the light transmittance of the backlight BL, thereby displaying an image. On the second display panel LCP2, monochrome image display is performed.

  With the configuration described above, both improvement in contrast and improvement in color reproducibility in the low gradation range can be achieved. That is, in the liquid crystal display device LCD of the present disclosure, the first display panel LCP1 and the second display panel LCP2 are displayed in an overlapping manner, and the transmittance of the two display panels is adjusted, thereby improving the contrast. Can be planned. Further, since the backlight BL of the present disclosure is configured to light up by sequentially switching LED backlights of, for example, three colors (red (R), green (G), and blue (B)) within one field, even if the backlight BL is low Even in a case where the transmittance of the first display panel LCP1 in the gradation range hardly changes, a desired color can be reproduced by changing the transmittance of the second display panel LCP2. The color reproducibility in the gradation range can be improved.

  With the above-described configuration, the light of the backlight BL and the transmittance of the second display panel LCP2 are changed even when the transmittance of the first display panel LCP1 hardly changes in the low gradation range. Since a desired color can be reproduced, image processing described below can be employed. By adopting the following image processing, it becomes possible to further suppress parallax interference. For example, when the first display panel LCP1 and the second display panel CLP2 display the same single line, the parallax interference refers to the first display panel LCP1 and the first display panel LCP1 depending on the angle of the person who views the single line. Since the relative display positions of the second display panel LCP2 are different, it means that one line appears as two when the user views the display surface of the liquid crystal display device LCD from an oblique direction.

  As shown in FIG. 7, the liquid crystal display device LCD according to the present embodiment has a transmittance characteristic in which the combined gamma value (γ) of the first display panel LCP1 and the second display panel LCP2 is 2.2. Assume that each of the first display panel LCP1 and the second display panel LCP2 displays an image based on image data of n bits (in this embodiment, n = 10).

  FIG. 8 is a block diagram illustrating a configuration of the image processing unit IPU. The image processing unit IPU includes a first gradation determination unit 311, a first gradation lookup table (LUT) 312, a first image output unit 313, a monochrome image data generation unit 321, A gradation determination unit 322, a second gradation LUT 323, and a second image output unit 324 are included.

  The image processing unit IPU performs image processing to be described later on the basis of m-bit input image data Din (m = 10 in the present embodiment), for example, a 10-bit for the first display panel LCP1. First image data DAT1 of a color image and second image data DAT2 of a 10-bit monochrome image for the second display panel LCP2 are generated. In addition, the image processing unit IPU has a target gamma value (in this embodiment, γ = 2.2) of a display image (synthetic gradation) obtained by synthesizing a color image and a monochrome image. As described above, the gradation of the first image data DAT1 and the gradation of the second image data DAT2 are determined.

  Specifically, when the image processing unit IPU receives 10-bit input image data Din transmitted from an external system, the image processing unit IPU converts the input image data Din into the first gradation determination unit 311 and the monochrome image data generation unit 321. And forward to. Note that the input image data Din includes, for example, luminance information (gradation information) and color information. The color information is information for designating a color. For example, when the input image data Din is 10 bits, each of a plurality of colors including R color, G color, and B color is represented by a value of 0 to 1024. Can do. The plurality of colors include at least R, G, and B colors, and may further include W (white) color and / or Y (yellow) color. When the plurality of colors are R, G, and B colors, the color information of the input image data Din is represented by “RGB values” ([R value, G value, B value]). For example, when the color corresponding to the input image data Din is “white”, the “RGB value” is represented by [1024, 1024, 1024], and when the color corresponding to the input image data Din is “red”, “RGB” "Value" is represented by [1024, 0, 0], and when the color corresponding to the input image data Din is "black", "RGB value" is represented by [0, 0, 0].

  When the first gradation determination unit 311 acquires 10-bit input image data Din from an external system, the first gradation determination unit 311 refers to the first gradation LUT 312 and determines a gradation corresponding to the 10-bit color image data. . The first gradation LUT 312 is associated with a 10-bit output gradation based on the first gradation characteristic for the first display panel LCP1. The first gradation determination unit 311 determines a 10-bit output gradation corresponding to the 12-bit input image data Din (input gradation) based on the first gradation characteristic, and the determined output gradation 10-bit color image data corresponding to is output to the first image output unit 313.

  When the black-and-white image data generation unit 321 acquires the 10-bit input image data Din, it uses each color value (here, RGB value: [R value, G value, B value]) indicating the color information of the input image data Din. Thus, monochrome image data is generated for each subfield corresponding to each color. The monochrome image data generation unit 321 outputs the generated 10-bit monochrome image data to the second gradation determination unit 322.

  When the second gradation determination unit 322 acquires the 12-bit monochrome image data generated by the monochrome image data generation unit 321, the second gradation determination unit 322 corresponds to the 10-bit monochrome image data with reference to the second gradation LUT 323. Determine the gradation. Based on the second gradation characteristic for the display panel 200, the second gradation LUT 323 is associated with a 10-bit output gradation for a 12-bit input gradation. The second gradation determination unit 322 determines a 10-bit output gradation corresponding to 12-bit monochrome image data (input gradation) based on the second gradation characteristic, and sets the determined output gradation. Corresponding 10-bit monochrome image data is output to the second image output unit 324.

  The first image output unit 313 outputs 10-bit color image data as first image data DAT1 to the first timing controller TCON1, and the second image output unit 324 outputs 10-bit monochrome image data to the first image data DAT1. The second image data DAT2 is output to the second timing controller TCON2. Further, the image processing unit IPU outputs the first control signal CS1 to the first timing controller TCON1, and outputs the second control signal CS2 to the second timing controller 240 (FIGS. 4 and 5).

  FIG. 9 is a graph showing the first transmittance characteristic with respect to the input gradation of the first display panel LCP1, and FIG. 10 is a graph showing the second transmittance characteristic with respect to the input gradation of the second display panel LCP2. is there. In FIG. 9, the logarithm of the input gradation is displayed on the horizontal axis, and the logarithm of the transmittance of the first display panel LCP1 is displayed on the vertical axis. Note that the transmittance shown in FIG. 9 is a normalized transmittance obtained by normalizing the transmittance at the maximum gradation as 1. In FIG. 10, the logarithm of the input gradation is displayed on the horizontal axis, and the logarithm of the transmittance of the second display panel LCP2 is displayed on the vertical axis. Note that the transmittance shown in FIG. 10 is a normalized transmittance normalized by setting the transmittance at the maximum gradation to 1.

  When receiving the first image data DAT1 from the first image output unit 313, the first display panel LCP1 displays a color image having the first transmittance characteristic shown in FIG. As shown in FIG. 9, the first transmittance characteristic of the first display panel LCP1 has a first bending point A that is bent when the input gradation is 39 (first gradation). The slope below the first gradation is smaller than the slope above the first gradation. Further, when the input gradation is changed from 1 (lowest gradation) to 39 (first gradation), the amount of change in the transmittance of the first display panel LCP1 is such that the input gradation is changed from the lowest gradation to the maximum. When the gray level is changed to 1023, it is set to be within 10% of the change amount of the transmittance of the first display panel LCP1, more preferably within 1%. In the present embodiment, this value is 0.08%. Further, when the input gradation is changed from 39 (first gradation) to 1023 (maximum gradation), the change in the transmittance of the first display panel LCP1 causes the input gradation to be 1023 (maximum gradation). The transmittance of the first display panel LCP1 is 90% or more. In the present embodiment, the value of the first gradation is about 3.8% of the value of the maximum gradation, and the first gradation exists in a low gradation region that is 10% or less of the maximum gradation. To do.

  When the second display panel LCP2 receives the second image data DAT2 from the second image output unit 324, the second display panel LCP2 displays a monochrome image having the second transmittance characteristic shown in FIG. As shown in FIG. 10, the second transmittance characteristic of the second display panel LCP2 has a second bending point B that is bent when the input gradation is 37 (second gradation). The slope below the second gradation is larger than the slope above the second gradation. Further, when the input gradation is changed from 1 (lowest gradation) to 37 (second gradation), the amount of change in the transmittance of the second display panel LCP2 is such that the input gradation is changed from the lowest gradation to the maximum. When the gradation is changed to 1023, it is set to 90% or more of the change amount of the transmittance of the second display panel LCP2, more preferably 99% or more. In the present embodiment, this value is 99.4%. Further, when the input gradation is changed from 37 (second gradation) to 1023 (maximum gradation), the change in the transmittance of the second display panel CLP2 changes the input gradation to 1023 (maximum gradation). In this case, the transmittance of the second display panel LCP2 is within 10%. In the present embodiment, the value of the second gradation is about 3.6% of the value of the maximum gradation, and the second gradation exists in a low gradation region of 10% or less of the maximum gradation. To do.

  As shown in FIGS. 9 and 10, the first transmittance characteristic of the first display panel LCP1 is the first gradation having the first inflection point, and the second transmittance of the LCP2 of the second display panel. The difference between the characteristic and the second gradation having the second inflection point is set to be within 10% of the maximum gradation. Desirably, the difference between the first gradation and the second gradation is preferably within 5% of the maximum gradation, and more preferably within 1%. In this embodiment, since the first gradation is 39 and the second gradation is 37, the difference between the first gradation and the second gradation is 1023 which is the maximum gradation. About 0.2%.

  By adopting such image processing, it becomes possible to suppress parallax interference. That is, the transmittance of the first display panel LCP1 is lower than the second gradation in which the transmittance of the second display panel LCP2 changes greatly according to the change of the input gradation. It hardly changes according to the change of the key. On the other hand, the transmittance of the second display panel LCP2 is higher than the first gradation in which the transmittance of the first display panel LCP1 changes greatly according to the change of the input gradation. Almost no change in response to changes in Therefore, the transmittance of the plurality of panels does not change greatly at the same time according to the change of the input gradation, and as a result, it becomes possible to suppress the parallax interference.

  When the above-described image processing is employed, the transmittance of the first display panel LCP1 hardly changes in the low gradation range, but the liquid crystal display device LCD shown in the present disclosure adopts a so-called field sequential method. In addition, since the transmittance of the second display panel TCON2 can be largely changed in the constant gradation region, color reproducibility in the low gradation region can be ensured. Therefore, according to the configuration shown in the present disclosure, it is possible to achieve both suppression of parallax interference and improvement of color reproducibility in a low gradation range.

  Note that the above-described image processing is effective even when the field sequential method is not adopted. For example, if not only the first display panel LCP1 but also the second display panel LCP2 has a color filter, it is possible to achieve both suppression of parallax interference and improvement of color reproducibility in a low gradation range. It becomes.

  Note that the number of bits of the input image data Din and the number of bits of the color image data and the monochrome image data are not limited to the above-described number of bits.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to said each embodiment, The form suitably changed by those skilled in the art from said each embodiment within the range which does not deviate from the meaning of this invention. Needless to say, it is included in the technical scope of the present invention.

LCD liquid crystal display device, LCP1 first display panel, LCP2 second display panel, SEFIL adhesive layer, BL backlight, FS front chassis, TFT1 first thin film transistor substrate, TFT2 second thin film transistor substrate, TIS1 first facing Substrate, TIS2 second counter substrate, LC1 first liquid crystal layer, LC2 second liquid crystal layer, CL color filter, BM1 first black matrix, BM2 second black matrix, OC overcoat film, POL1 first Polarizing plate, POL2 second polarizing plate, POL3 third polarizing plate, POL4 fourth polarizing plate, Data input video signal, IPU image processing unit, DAT1 first image data, DAT2 second image data, TCON1 first 1 timing controller, TCON2 second timing controller , SD1 first source driver, GD1 first gate driver, SD2 second source driver, GD2 second gate driver, DISP1 first image display area, DISP2 second image display area, CS1 first Control signal, CS2 second control signal, DA1 first image data, DA2 second image data, DSP1 first data start pulse, DSP2 second data start pulse, DCK1 first second data clock DCK2 second data clock, GSP1 first gate start pulse, GSP2 second gate start pulse, GCK1 first gate clock, GCK2 second gate clock, SL source line, GL gate line, TFT thin film transistor, SPIX sub Pixel, PIXR red sub pixel, PIXG green sub image , PIXB blue sub-pixel, PIX1 first pixel, PIX2 second pixel, PX pixel electrode, 311 first gradation determination unit, 312 first gradation LUT, 313 first image output unit, 321 monochrome image Data generation unit, 322 second gradation determination unit, 323 second gradation LUT, 324 second image output unit.

Claims (12)

A first display panel having at least two or more different color filters of different colors;
A second display panel that is disposed on the back side of the first display panel so as to overlap the first display panel and does not have a color filter;
A backlight that is disposed on the back side of the second display panel and irradiates light of a plurality of colors toward the second display panel at different timings;
Including a liquid crystal display device. In one field period in which one image is displayed based on an input image signal, the backlight irradiates the light of the plurality of colors at different timings,
The second display panel switches and displays images corresponding to the plurality of colors at different timings.
The liquid crystal display device according to claim 1. In the one field period,
The first display panel continues to input a data signal corresponding to the input image signal to each pixel corresponding to each of the color filters of the plurality of colors.
The liquid crystal display device according to claim 2. An image processing unit that generates first image data corresponding to the first display panel and second image data corresponding to the second display panel based on an input video signal;
When the image processing unit changes the input gradation corresponding to the input video signal from the lowest gradation to the first gradation, the amount of change in the transmittance of the first display panel is the input gradation. Generating the first image data so that the amount of change in transmittance of the first display panel is within 10% when the minimum gradation is changed to the maximum gradation.
When the image processing unit changes the input gradation from the lowest gradation to the second gradation, the amount of change in the transmittance of the second display panel becomes the minimum gradation. Generating the second image data so that it is 90% or more of the amount of change in the transmittance of the second display panel when changing from the maximum gradation to the maximum gradation,
A difference between the first gradation and the second gradation is within 10% of the maximum gradation;
The liquid crystal display device according to claim 1. When the image processing unit changes the input gradation from the lowest gradation to the first gradation, the amount of change in the transmittance of the first display panel indicates that the input gradation is the lowest gradation. Generating the first image data so that it is within 1% of the amount of change in the transmittance of the first display panel when changing from the tone to the maximum gradation,
When the image processing unit changes the input gradation from the lowest gradation to the second gradation, the amount of change in the transmittance of the second display panel indicates that the input gradation is the lowest gradation. Generating the second image data so as to be 99% or more of the amount of change in the transmittance of the second display panel when changing from a tone to the maximum gradation;
The liquid crystal display device according to claim 4. An image processing unit that generates first image data corresponding to the first display panel and second image data corresponding to the second display panel based on an input video signal;
A graph displaying the logarithm of the input gradation corresponding to the input video signal on the horizontal axis, and displaying the logarithm of the transmittance of the first display panel on the vertical axis,
A first inflection point that bends at a first gradation, and an inclination equal to or lower than the first gradation is smaller than an inclination equal to or higher than the first gradation;
A second inflection point that bends at a second gradation, and the slope below the second gradation is greater than the slope above the second gradation;
A difference between the first gradation and the second gradation is within 10% of the maximum gradation;
The liquid crystal display device according to claim 1. A difference between the first gradation and the second gradation is within 5% of the maximum gradation;
The liquid crystal display device according to claim 4. A difference between the first gradation and the second gradation is within 1% of the maximum gradation;
The liquid crystal display device according to claim 4. An image processing unit that generates first image data corresponding to the first display panel and second image data corresponding to the second display panel based on an input video signal;
When the image processing unit changes the input gradation corresponding to the input video signal from the lowest gradation to the first gradation, the amount of change in the transmittance of the first display panel is the input gradation. Generating the first image data so that the amount of change in transmittance of the first display panel is within 10% when the minimum gradation is changed to the maximum gradation.
The first gradation is 10% or less of the maximum gradation.
The liquid crystal display device according to claim 1. When the image processing unit changes the input gradation corresponding to the input video signal from the lowest gradation to the first gradation, the amount of change in the transmittance of the first display panel is Generating the first image data so that the input gradation is within 1% of the amount of change in transmittance of the first display panel when the input gradation is changed from the lowest gradation to the maximum gradation;
The liquid crystal display device according to claim 9. An image processing unit that generates first image data corresponding to the first display panel and second image data corresponding to the second display panel based on an input video signal;
When the image processing unit changes the input gradation corresponding to the input video signal from the lowest gradation to the second gradation, the amount of change in the transmittance of the second display panel is the input gradation. Generating the second image data so as to be 90% or more of the amount of change in the transmittance of the second display panel when changing the minimum gradation to the maximum gradation,
The second gradation is 10% or less of the maximum gradation.
The liquid crystal display device according to claim 1. When the image processing unit changes the input gradation corresponding to the input video signal from the lowest gradation to the second gradation, the amount of change in the transmittance of the second display panel is, Generating the second image data so as to be 99% or more of the change amount of the transmittance of the second display panel when the input gradation is changed from the lowest gradation to the maximum gradation;
The liquid crystal display device according to claim 11.

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