WO2022210082A1

WO2022210082A1 - Display device

Info

Publication number: WO2022210082A1
Application number: PCT/JP2022/013095
Authority: WO
Inventors: 則博荒井; 朋子尾崎; 歩佐藤
Original assignee: 凸版印刷株式会社
Priority date: 2021-03-30
Filing date: 2022-03-22
Publication date: 2022-10-06
Also published as: TW202247136A; CN117043841A; JP2022154077A; TWI817417B

Abstract

This display device comprises a pixel array having a plurality of pixels. The plurality of pixels each have first to third sub pixels. The first sub pixels can display a first color other than white or black. The second and third sub pixels can display white.

Description

Display device

The present invention relates to display devices.

Conventionally, there is a full-color reflective display in which red/green/blue sub-pixels are used to drive gradations. In addition, 8-color (white/black/red/green/blue/cyan/magenta/yellow) display in which each pixel is binary-driven (on/off) using three sub-pixels of red/green/blue. It has a reflective display. There is also a black-and-white reflective display in which one white pixel is binary-driven.

In the case of the full-color reflective display described above, since red/green/blue color filters are used, the reflectance of the panel is lowered, and each of the three sub-pixels performs gradation display. Power consumption will increase.

Even in the case of the above-mentioned 8-color reflective display, the reflectance of the panel decreases because red/green/blue color filters are used.

In the case of the black-and-white reflective display mentioned above, the reflectance is high and it is possible to reduce power consumption. However, only two colors, white and black, can be displayed, and not only color display but also halftone display cannot be performed.

Japanese Patent Application Laid-Open No. 1998-339871 Japanese Patent Application Laid-Open No. 2003-241178

The present invention provides a display device capable of reducing power consumption while performing color display.

According to a first aspect of the present invention, there is provided a pixel array having a plurality of pixels, each of said plurality of pixels having first to third sub-pixels, said first sub-pixels being other than white and black. , and the second and third sub-pixels are capable of displaying white.

A second aspect of the present invention provides the display device according to the first aspect, further comprising a control circuit for binary driving the first to third sub-pixels.

According to the third aspect of the present invention, the display device according to the second aspect, wherein the control circuit turns off the first sub-pixel and turns on the second and third sub-pixels to perform white display. is provided.

According to the fourth aspect of the present invention, the second aspect, wherein the control circuit turns on the first sub-pixel and turns off the second and third sub-pixels to display the first color. A display device according to the above is provided.

According to the fifth aspect of the present invention, the control circuit turns off the first sub-pixel, turns on one of the second and third sub-pixels, and turns on the other of the second and third sub-pixels. A display device according to a second aspect is provided that performs halftone display in an off state.

According to the sixth aspect of the present invention, the control circuit turns on the first sub-pixel, turns on one of the second and third sub-pixels, and turns on the other of the second and third sub-pixels. A display device according to a second aspect is provided, which is turned off to display a second color having a lower density than the first color.

According to a seventh aspect of the present invention, the display according to the sixth aspect, wherein the control circuit turns on the first to third sub-pixels to display a third color having a lower density than the second color. An apparatus is provided.

An eighth aspect of the present invention provides the display device according to the first aspect, wherein the first to third sub-pixels have the same area.

A ninth aspect of the present invention provides the display device according to the first aspect, wherein the first and second sub-pixels have different areas.

A tenth aspect of the present invention provides the display device according to the first aspect, wherein the second and third sub-pixels have different areas.

An eleventh aspect of the present invention provides the display device according to the first aspect, wherein each of the first to third sub-pixels includes a reflective layer that reflects light.

A twelfth aspect of the present invention provides the display device according to the first aspect, wherein the second and third sub-pixels do not have color filters.

According to the present invention, it is possible to provide a display device capable of reducing power consumption while performing color display.

FIG. 1 is a block diagram of the liquid crystal display device according to the first embodiment. FIG. 2 is a circuit diagram of a pixel array included in the liquid crystal display panel. FIG. 3 is a schematic plan view of a pixel. FIG. 4 is a cross-sectional view of the liquid crystal display panel. FIG. 5 is a diagram for explaining the operation of the liquid crystal display device. FIG. 6 is a schematic plan view of a pixel according to the second embodiment. FIG. 7 is a schematic plan view of a pixel according to the third embodiment. FIG. 8 is a diagram for explaining the operation of the liquid crystal display device according to the third embodiment. FIG. 9 is a block diagram of a liquid crystal display device according to the fourth embodiment. FIG. 10 is a cross-sectional view of a liquid crystal display panel according to the fourth embodiment.

Hereinafter, embodiments will be described with reference to the drawings. However, the drawings are schematic or conceptual, and the dimensions and proportions of each drawing are not necessarily the same as the actual ones. Also, even when the same parts are shown in the drawings, there are cases in which the dimensional relationships and ratios are shown differently. In particular, several embodiments shown below are examples of apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention can be is not specified. In the following description, elements having the same functions and configurations are denoted by the same reference numerals, and overlapping descriptions are omitted.

[1] First Embodiment [1-1] Configuration of Liquid Crystal Display Device 1 FIG. 1 is a block diagram of a liquid crystal display device 1 according to a first embodiment of the present invention. The liquid crystal display device 1 according to this embodiment is a reflective liquid crystal display device that uses external light for display.

The liquid crystal display device 1 includes a liquid crystal display panel 2, a scanning line drive circuit 3, a signal line drive circuit 4, a common electrode drive circuit 5, a voltage generation circuit 6, and a control circuit 7.

The liquid crystal display panel 2 has a pixel array in which a plurality of sub-pixels SP are arranged in a matrix. Three sub-pixels SP arranged in the row direction form a pixel PX. The liquid crystal display panel 2 is provided with a plurality of scanning lines GL each extending in the row direction and a plurality of signal lines SL each extending in the column direction. Sub-pixels SP are arranged in intersection regions between the scanning lines GL and the signal lines SL.

The scanning line driving circuit 3 is electrically connected to a plurality of scanning lines GL. The scanning line driving circuit 3 sends scanning signals for turning on/off the switching elements included in the sub-pixels SP to the liquid crystal display panel 2 based on control signals sent from the control circuit 7 .

The signal line drive circuit 4 is electrically connected to a plurality of signal lines SL. The signal line drive circuit 4 receives control signals and display data from the control circuit 7 . The signal line driving circuit 4 sends a plurality of signals (driving voltages) corresponding to display data to the liquid crystal display panel 2 based on the control signal.

The common electrode drive circuit 5 generates a common voltage Vcom and supplies it to the common electrodes within the liquid crystal display panel 2 . The voltage generation circuit 6 generates various voltages necessary for the operation of the liquid crystal display device 1 and supplies them to corresponding circuits.

The control circuit 7 comprehensively controls the operation of the liquid crystal display device 1 . The control circuit 7 receives image data DT and a control signal CNT from the outside. The control circuit 7 generates various control signals based on the image data DT and sends these control signals to the corresponding circuits.

FIG. 2 is a circuit diagram of the pixel array 2A included in the liquid crystal display panel 2. FIG. The X direction in FIG. 2 is the row direction in which scanning lines extend, and the Y direction is the column direction in which signal lines extend.

A plurality of scanning lines GL1 to GLm and a plurality of signal lines SL1 to SLn are arranged in the pixel array 2A. "m" and "n" are each an integer of 2 or more.

The sub-pixel SP includes a switching element (active element) 13, a liquid crystal capacitor (liquid crystal element) Clc, and a storage capacitor Cs. As the switching element 13, for example, a TFT (Thin Film Transistor) is used, or an n-channel TFT is used. Note that although the source and drain of a transistor change depending on the direction of current flowing through the transistor, an example of the connection state of the transistor will be described below. However, it goes without saying that the source and drain are not fixed as the name suggests.

The source of the TFT 13 is connected to the signal line SL, its gate is connected to the scanning line GL, and its drain is connected to one electrode of the liquid crystal capacitor Clc. A liquid crystal capacitor Clc as a liquid crystal element is composed of a pixel electrode, a common electrode, and a liquid crystal layer sandwiched therebetween. A common electrode driving circuit 5 applies a common voltage Vcom to the other electrode of the liquid crystal capacitor Clc.

One electrode of the storage capacitor Cs is connected to one electrode of the liquid crystal capacitor Clc. A common electrode drive circuit 5 applies a common voltage Vcom to the other electrode of the storage capacitor Cs. The storage capacitor Cs has a function of suppressing the potential fluctuation occurring in the pixel electrode and holding the drive voltage applied to the pixel electrode until the drive voltage corresponding to the next signal is applied. The storage capacitor Cs is composed of a pixel electrode, a storage capacitor line, and an insulating layer sandwiched therebetween. A storage capacitor voltage different from the common voltage Vcom may be applied to the other electrode (storage capacitor line) of the storage capacitor Cs.

[1-2] Configuration of Liquid Crystal Display Panel 2 Next, the configuration of the liquid crystal display panel 2 will be described.

FIG. 3 is a schematic plan view of the pixel PX. The pixel PX is composed of three sub-pixels SP-R, SP-W1 and SP-W2.

The size of the pixel PX is, for example, square, and each of the sub-pixels SP-R, SP-W1, and SP-W2 is a rectangle extending in the Y direction. Although not shown, a light shielding layer (black matrix) is arranged on the boundary between the plurality of sub-pixels SP.

The sub-pixel SP-R can display colors other than white and black. In this embodiment, as an example, the sub-pixel SP-R can display red. A red filter is provided for the sub-pixel SP-R. The sub-pixel SP-R may have a color other than red.

The sub-pixels SP-W1 and SP-W2 are capable of displaying white. White display is achieved by transmitting reflected light of external light without passing through a color filter (that is, by transmitting the reflected light as it is). The sub-pixels SP-W1 and SP-W2 are not provided with color filters.

4 is a cross-sectional view of the liquid crystal display panel 2. FIG. FIG. 4 extracts and shows three sub-pixels SP (sub-pixels SP-R, SP-W1, and SP-W2 shown in FIG. 3) included in one pixel PX. , a plurality of pixels in FIG. 4 are arranged in a matrix.

The liquid crystal display panel 2 includes a TFT substrate 10 on which switching elements (TFTs) and pixel electrodes are formed, and a color filter substrate (referred to as a CF substrate) 11 arranged opposite to the TFT substrate 10 and on which color filters and the like are formed. Prepare. Each of the TFT substrate 10 and the CF substrate 11 is composed of a transparent and insulating substrate (for example, a glass substrate or a plastic substrate).

The liquid crystal layer 12 is sandwiched and filled between the TFT substrate 10 and the CF substrate 11 . Specifically, the liquid crystal layer 12 is enclosed within a display area surrounded by the TFT substrate 10, the CF substrate 11, and a sealing material (not shown). The sealing material is made of, for example, an ultraviolet curable resin, a thermosetting resin, or an ultraviolet/heat combination type curable resin. Let me.

The liquid crystal material that constitutes the liquid crystal layer 12 changes its optical properties by manipulating the orientation of the liquid crystal molecules according to the applied electric field. The liquid crystal display panel 2 of this embodiment is, for example, a VA mode using vertical alignment (VA) type liquid crystal. Negative (N-type) nematic liquid crystal having negative dielectric anisotropy is used as the liquid crystal layer 12 . The liquid crystal layer 12 is vertically aligned in the initial state. Liquid crystal molecules are oriented substantially perpendicularly to the main surface of the substrate when no voltage (no electric field) is present. When voltage is applied (electric field is applied), the directors of the liquid crystal molecules are tilted in the horizontal direction (direction parallel to the main surface of the substrate).

First, the configuration on the TFT substrate 10 side will be described. A switching element 13 is provided for each sub-pixel on the liquid crystal layer 12 side of the TFT substrate 10 . As the switching element 13, for example, a TFT (Thin Film Transistor) is used, or an n-channel TFT is used. FIG. 4 shows the TFT 13 in a simplified manner. The TFT 13 includes a gate electrode functioning as a scanning line, a gate insulating film provided on the gate electrode, a semiconductor layer provided on the gate insulating film, a source electrode and a semiconductor layer provided separately on the semiconductor layer. and a drain electrode.

A reflective layer 14 is provided on the TFT substrate 10 . The reflective layer 14 is provided over substantially the entire sub-pixel area. The reflective layer 14 has a function of reflecting external light incident from the CF substrate 11 . As the reflective layer 14, for example, aluminum (Al), silver (Ag), or an alloy containing one or more of these is used.

A pixel electrode 15 is provided above the reflective layer 14 and the TFT 13 via an insulating layer (not shown). The pixel electrode 15 is provided over substantially the entire sub-pixel region. The pixel electrode 15 is composed of a transparent electrode, and for example, ITO (indium tin oxide) is used.

An alignment film 16 for controlling the alignment of the liquid crystal layer 12 is provided on the pixel electrode 15 . The alignment film 16 vertically aligns the liquid crystal molecules in the initial state of the liquid crystal layer 12 .

Next, the configuration on the CF substrate 11 side will be described. A color filter 17 is provided on the liquid crystal layer 12 side of the CF substrate 11 . In this embodiment, the color filter 17 is composed of a red filter. The red filter 17 transmits red light. The red filter 17 is arranged in the sub-pixel SP-R area shown in FIG.

On the side of the CF substrate 11 facing the liquid crystal layer 12, transparent members 18-1 and 18-2 are provided. The transparent members 18-1 and 18-2 are made of a photosensitive transparent resin (also called a resist) that does not contain pigment as a coloring material. The transparent members 18-1 and 18-2 transmit light without coloring it. That is, the light transmitted through the transparent members 18-1 and 18-2 is viewed as white light. The transparent member 18-1 is arranged in the sub-pixel SP-W1 area, and the transparent member 18-2 is arranged in the sub-pixel SP-W2 area.

A light shielding layer (also called black matrix or black mask) 19 is provided on the CF substrate 11 on the side of the liquid crystal layer 12 . A black matrix 19 is arranged at the boundaries of the sub-pixels. The black matrix 19 is formed, for example, in a mesh shape so as to surround the sub-pixels. The black matrix 19 has a function of shielding unnecessary light generated at the boundaries of sub-pixels and improving contrast. Although the contrast is slightly lowered, the black matrix may not be arranged between the red filter 17, the transparent member 18-1, and the transparent member 18-2 in order to further improve the reflectance.

A common electrode 20 is provided on the red filter 17, the transparent members 18-1 and 18-2, and the black matrix 19. The common electrode 20 is planarly formed over the entire display area of the liquid crystal display panel 2 . The common electrode 20 is composed of a transparent electrode, such as ITO. A structure such as a protrusion may be formed on the common electrode 20 in order to control the orientation of the liquid crystal layer 12 when a voltage is applied.

An alignment film 21 for controlling the alignment of the liquid crystal layer 12 is provided on the common electrode 20 . The alignment film 21 vertically aligns the liquid crystal molecules in the initial state of the liquid crystal layer 12 .

On the side of the CF substrate 11 opposite to the liquid crystal layer 12, a diffusing member 22, a retardation plate 23, and a polarizing plate 24 are laminated in this order. The retardation plate 23 and the polarizing plate 24 constitute a circularly polarizing plate.

The polarizing plate (linear polarizer) 24 has a transmission axis and an absorption axis that are orthogonal to each other in a plane orthogonal to the traveling direction of light. The polarizing plate 24 transmits linearly polarized light (linearly polarized light component) having a plane of vibration parallel to the transmission axis among light having planes of vibration in random directions, and transmits linearly polarized light having a plane of vibration parallel to the absorption axis. (linearly polarized light component).

The retardation plate 23 has refractive index anisotropy, and has a slow axis and a fast axis that are orthogonal to each other in a plane orthogonal to the traveling direction of light. The retardation plate 23 has a function of providing a predetermined retardation (a phase difference of λ/4, where λ is the wavelength of light) between lights of a predetermined wavelength that pass through the slow axis and the fast axis. . That is, the retardation plate 23 is composed of a quarter-wave plate (λ/4 plate). The slow axis of the retardation plate 23 is set to form an angle of approximately 45° with respect to the transmission axis of the polarizing plate 24 .

It should be noted that the angles that define the polarizing plate and the retardation plate described above include errors that allow desired operations to be realized and errors that result from the manufacturing process. For example, the approximate 45° mentioned above includes the range of 45°±5°. For example, the aforementioned orthogonal shall include a range of 90°±5°.

The diffusing member 22 has a function of diffusing (scattering) the transmitted light in random directions to make the transmitted light uniform. The diffusion member 22 is made of a diffusion adhesive material, a diffusion film, a diffusion plate, or the like. When the diffusion adhesive material is used as the diffusion member 22, the diffusion adhesive material has the function of adhering the members on both sides in addition to the function of diffusing the transmitted light. The stacking order of the diffusion member 22 and the retardation plate 23 may be reversed.

The diffusion member 22 diffuses the reflected light reflected by the reflective layer 14, and the diffused reflected light is observed by the observer. By using the diffusion member 22, the viewing angle can be improved.

[1-3] Operation The operation of the liquid crystal display device 1 configured as described above will be described. The liquid crystal display device 1 is normally black mode.

First, the driving of the sub-pixel SP will be described. A common voltage Vcom is applied to the common electrode 20 by the common electrode driving circuit 5 . The common voltage Vcom is, for example, the ground voltage (0V). The OFF state is a state in which no electric field is applied to the liquid crystal layer 12 , and the same common voltage Vcom as the common electrode 20 is applied to the pixel electrode 15 . The ON state is a state in which an electric field is applied to the liquid crystal layer 12 and a positive voltage is applied to the pixel electrode 15 . A positive voltage is a voltage equal to or higher than the threshold voltage of the liquid crystal layer. Note that in practice, inversion driving (AC driving) is performed in which the polarity of the electric field between the pixel electrode 15 and the common electrode 20 is reversed at predetermined intervals. By performing inversion driving, deterioration of the liquid crystal can be suppressed. The cycle of inversion drive can be set arbitrarily.

In the off state, the liquid crystal molecules are set to the initial state, ie the long axes of the liquid crystal molecules are oriented vertically. External light incident on the display surface of the liquid crystal display panel 2 is circularly polarized after passing through the polarizing plate 24 and the retardation plate 23 and enters the liquid crystal layer 12 . The light incident on the liquid crystal layer 12 is hardly affected by birefringence in the liquid crystal layer 12, and passes through the liquid crystal layer 12 while maintaining, for example, a right-handed circularly polarized state. Light transmitted through the liquid crystal layer 12 is reflected by the reflective layer 14 . When the light is reflected by the reflective layer 14, it becomes circularly polarized light in the opposite direction (eg counterclockwise direction). After passing through the retardation plate 23 , this reflected light becomes linearly polarized light perpendicular to the transmission axis of the polarizing plate 24 . Therefore, reflected light of external light cannot pass through the polarizing plate 24, resulting in black display (that is, normally black mode). A sub-pixel being in an off state means the same as a sub-pixel being in a light-blocking state (a state in which light is not emitted from the sub-pixel).

In the ON state, the liquid crystal molecules are horizontally aligned, that is, the long axes of the liquid crystal molecules are oriented horizontally with respect to the substrate surface (main surface of the substrate). External light incident on the display surface of the liquid crystal display panel 2 is circularly polarized after passing through the polarizing plate 24 and the retardation plate 23 and enters the liquid crystal layer 12 . The polarization state of the light incident on the liquid crystal layer 12 changes due to the birefringence of the liquid crystal layer 12 . Therefore, part of the reflected light reflected by the reflective layer 14 is transmitted through the polarizing plate 24 . Therefore, the reflected light of the external light is transmitted through the polarizing plate 24, resulting in white display or color display. A sub-pixel being in an ON state means the same as a sub-pixel being in a transmissive state (a state in which light is emitted from the sub-pixel).

In this embodiment, each sub-pixel SP is binary-driven. Binary driving means driving the sub-pixel SP using two states (binary values) of an OFF state and an ON state. In binary driving, two types of voltages (eg, ground voltage and positive voltage) are used to drive the sub-pixel SP. In the present embodiment, it is possible to perform color display of a plurality of colors by performing binary driving on each sub-pixel SP without performing gray-scale driving on each sub-pixel SP. Grayscale driving is a method of driving pixels by changing a voltage level for each of a plurality of grayscales.

FIG. 5 is a diagram for explaining the operation of the liquid crystal display device 1. FIG. FIG. 5 shows the operations of sub-pixels SP-R, SP-W1, and SP-W2 included in one pixel PX. The sub-pixel SP-R is a red sub-pixel, the sub-pixel SP-W1 is a white sub-pixel (denoted as white 1), and the sub-pixel SP-W2 is a white sub-pixel (denoted as white 2).

The liquid crystal display device 1 uses one pixel PX as a display unit, and displays six display colors, specifically, white, black, red, halftone (50% gray), "light red-2", and " It is possible to display a light red-4″ display color. A halftone means a color intermediate between white and black, and is called "50% gray" in this embodiment. The gradation levels of the display color of red are "red>"light red-1">"light red-2">"light red-3">"light red-4"". The larger the subscript number for light red, the lighter the color density. “Light Red-1” and “Light Red-3” will be described later.

Since it is normally black mode, the display is off (dark display, black display) when the sub-pixel is off, and the display is on (bright display, white display) when the sub-pixel is on.

When displaying white in the pixel PX, the control circuit 7 turns off the sub-pixel SP-R and turns on the sub-pixels SP-W1 and SP-W2. That is, when displaying white in the pixel PX, two white sub-pixels are turned on.

When displaying black in the pixel PX, the control circuit 7 turns off the sub-pixel SP-R, the sub-pixel SP-W1, and the sub-pixel SP-W2. That is, when displaying black, all sub-pixels are turned off.

When displaying red in the pixel PX, the control circuit 7 turns on the sub-pixel SP-R and turns off the sub-pixels SP-W1 and SP-W2. That is, when displaying red in the pixel PX, only the red sub-pixel is turned on.

When displaying "50% gray" on the pixel PX, the control circuit 7 turns off the sub-pixel SP-R, turns on the sub-pixel SP-W1, and turns off the sub-pixel SP-W2. For "50% gray", the sub-pixel SP-W1 may be turned off and the sub-pixel SP-W2 may be turned on. That is, when displaying "50% gray" in the pixel PX, only one white sub-pixel is turned on.

When displaying "light red-2" on the pixel PX, the control circuit 7 turns on the sub-pixel SP-R and the sub-pixel SP-W1, and turns off the sub-pixel SP-W2. For “light red-2”, the sub-pixel SP-W1 may be turned off and the sub-pixel SP-W2 may be turned on.

When displaying "light red-4" in the pixel PX, the control circuit 7 turns on the sub-pixel SP-R, the sub-pixel SP-W1, and the sub-pixel SP-W2. That is, when displaying "light red-4", all sub-pixels are turned on.

With the above operation, the liquid crystal display device 1 can display six display colors (white, black, red, “50% gray”, “light red-2”, and “light red” with one pixel PX as a display unit). -4") can be displayed.

[1-4] Effect of First Embodiment In the first embodiment, the liquid crystal display device 1 is composed of a reflective liquid crystal display device. The liquid crystal display device 1 includes a pixel array 2A having a plurality of pixels PX. Each pixel PX is composed of three sub-pixels SP-R, SP-W1 and SP-W2. The sub-pixel SP-R is capable of displaying a first color (eg, red) other than white and black. The sub-pixels SP-W1 and SP-W2 are capable of white display. The control circuit 7 drives the sub-pixels SP-R, SP-W1, and SP-W2 in binary.

Therefore, according to the first embodiment, it is possible to display in a predetermined color in addition to black and white display, despite the binary drive. In addition, power consumption can be reduced as compared with the case of grayscale driving.

Also, by turning on one of the two white sub-pixels, it is possible to display a halftone (50% gray) regardless of the binary drive.

Also, for white display, two white sub-pixels without color filters are turned on. Thereby, the reflectance can be improved. That is, the liquid crystal display device 1 can realize a brighter display.

By switching the remaining two white sub-pixels between the on-state and off-state while turning on the red sub-pixel, in addition to the primary color red, two types of red with different densities (excluding the red primary color) can be obtained. ) can be displayed.

In addition, since color display can be realized by binary driving, display control can be simplified while performing color display.

Also, since the liquid crystal display device 1 does not use a backlight, power consumption can be further reduced.

[2] Second Embodiment In the second embodiment, among the three sub-pixels SP forming the pixel PX, the area ratios of the red sub-pixel and the two white sub-pixels are changed.

FIG. 6 is a schematic plan view of a pixel PX according to the second embodiment of the invention. The pixel PX is composed of three sub-pixels SP-R, SP-W1 and SP-W2.

The area of the sub-pixel SP-R is smaller than the area of each of the sub-pixels SP-W1 and SP-W2. For example, the area of sub-pixel SP-W1 is the same as the area of sub-pixel SP-W2. The area ratio of the sub-pixels SP-R, SP-W1, SP-W2 is, for example, "2:5:5".

The driving of the sub-pixels SP-R, SP-W1, and SP-W2 is the same as in the first embodiment.

In the second embodiment, the area ratio of each of the two white sub-pixels is increased with respect to the red sub-pixel. Thereby, the reflectance can be further improved. Also, the brightness of the white display can be made brighter.

[3] Third Embodiment In the third embodiment, the area ratio of two white sub-pixels among the three sub-pixels SP forming the pixel PX is changed.

FIG. 7 is a schematic plan view of a pixel PX according to the third embodiment of the invention. The pixel PX is composed of three sub-pixels SP-R, SP-W1 and SP-W2.

The area of the sub-pixel SP-W1 and the area of the sub-pixel SP-W2 are different. For example, the area of sub-pixel SP-W2 is smaller than the area of sub-pixel SP-W1. The area ratio of the sub-pixels SP-W1 and SP-W2 is, for example, "3:1". The area ratio of the sub-pixels SP-R, SP-W1, SP-W2 is, for example, "2:3:1". In this embodiment, halftone display other than "50% gray" is possible by changing the area ratio of the two white sub-pixels.

FIG. 8 is a diagram for explaining the operation of the liquid crystal display device 1 according to the third embodiment. The liquid crystal display device 1 uses one pixel PX as a display unit, and displays eight display colors, specifically, white, black, red, first halftone (dark gray), second halftone (light gray), " It is possible to display display colors of "light red-2" and "light red-4". In this embodiment, the area ratio of the sub-pixels SP-W1 and SP-W2 is "3:1". In this example, the first halftone is "75% gray" and the second halftone is "25% gray".

The white display, black display, and red display operations are the same as in the first embodiment.

When displaying "75% gray" on the pixel PX, the control circuit 7 turns off the sub-pixel SP-R, turns on the sub-pixel SP-W1, and turns off the sub-pixel SP-W2. That is, when displaying "75% gray" in the pixel PX, the one with the larger area of the two white sub-pixels is turned on.

When displaying "25% gray" on the pixel PX, the control circuit 7 turns off the sub-pixel SP-R and the sub-pixel SP-W1, and turns on the sub-pixel SP-W2. That is, when displaying "25% gray" in the pixel PX, the one with the smaller area of the two white sub-pixels is turned on.

When displaying "light red-1" on the pixel PX, the control circuit 7 turns on the sub-pixel SP-R, turns off the sub-pixel SP-W1, and turns on the sub-pixel SP-W2. That is, when displaying "light red - 1", the one of the two white sub-pixels with the smaller area is turned on.

When displaying "light red-3" on the pixel PX, the control circuit 7 turns on the sub-pixel SP-R and the sub-pixel SP-W1, and turns off the sub-pixel SP-W2. That is, when displaying "light red-3", the one with the larger area of the two white sub-pixels is turned on.

According to the third embodiment, two types of halftones (for example, "75% gray" and "25% gray") can be displayed. Also, by controlling the ON and OFF states of two white sub-pixels while turning on the red sub-pixel, it is possible to display three types of red with different shades (excluding the primary color of red).

[4] Fourth Embodiment A fourth embodiment is a configuration example of a transflective liquid crystal display device capable of both reflective display and transmissive display.

FIG. 9 is a block diagram of the liquid crystal display device 1 according to the fourth embodiment of the invention. The liquid crystal display device 1 further includes an illumination device (also called a backlight) 8 .

The backlight 8 is composed of a surface light source and irradiates the back surface of the liquid crystal display panel 2 with light. As the backlight 8, for example, a direct type or sidelight type (edge light type) LED backlight is used.

The voltage generation circuit 6 supplies a predetermined voltage to the backlight 8. A control circuit 7 controls the on/off operation of the backlight 8 .

FIG. 10 is a cross-sectional view of the liquid crystal display panel 2 according to the fourth embodiment.

The backlight 8 is arranged on the back side (surface opposite to the display surface) of the liquid crystal display panel 2 . The backlight 8 includes a light source section 8A that emits illumination light. The backlight 8 illuminates the back surface of the liquid crystal display panel 2 with illumination light.

A reflective layer 14 is provided on the TFT substrate 10 . A reflective layer 14 is provided in a portion of the sub-pixel region. A pixel electrode 15 is provided above the reflective layer 14 and the TFT 13 via an insulating layer (not shown). The pixel electrode 15 is provided over substantially the entire sub-pixel region.

The sub-pixel SP has a reflective area RA and a transmissive area TA. A region in which the reflective layer 14 is provided in the sub-pixel region is the reflective region RA, and a region in which the reflective layer 14 is not provided is the transmissive region TA.

A retardation plate 25 and a polarizing plate 26 are laminated in this order on the side of the TFT substrate 10 opposite to the liquid crystal layer 12 . The retardation plate 25 and the polarizing plate 26 constitute a circularly polarizing plate.

A polarizing plate (linear polarizer) 26 has a transmission axis and an absorption axis that are perpendicular to each other. The transmission axis of the polarizing plate 26 is set orthogonal to the transmission axis of the polarizing plate 24 . That is, the

polarizers

24 and 26 are arranged in crossed Nicols.

The retardation plate 25 is composed of a quarter-wave plate (λ/4 plate). The slow axis of the retardation plate 25 is set to form an angle of approximately 45° with respect to the transmission axis of the polarizing plate 26 .

The configuration of the pixel PX is the same as in the first embodiment. That is, the pixel PX has three sub-pixels SP-R, SP-W1 and SP-W2. The sub-pixel SP-R has a red filter and constitutes a red sub-pixel. Each of the sub-pixels SP-W1 and SP-W2 does not have a color filter and constitutes a white sub-pixel.

The liquid crystal display device 1 can use the backlight 8. The operation of performing color display in the liquid crystal display device 1 is the same as in the first embodiment.

The same effects as in the first embodiment can be obtained in the fourth embodiment as well. It is also possible to apply the second and third embodiments to the fourth embodiment.

In each of the above embodiments, the VA mode is taken as an example of the liquid crystal mode. The liquid crystal mode may be TN (Twisted Nematic) mode, ECB (Electrically Controlled Birefringence) mode, or STN (Super Twisted Nematic) mode.

In each of the above embodiments, an active matrix system using active elements is taken as an example of the drive system. The driving method is not limited to the active matrix method, and may be a passive matrix method.

In each of the above embodiments, a liquid crystal display device is used as an example of the display. The present embodiment need not be a liquid crystal display device, and may be applied to an organic EL (electroluminescence) display device, an electrophoretic display device, or the like. Also, the display device according to the present embodiment may be applied to electronic paper.

In each of the above embodiments, a reflective liquid crystal display device and a semi-transmissive liquid crystal display device are shown, but it is also possible to apply to a transmissive liquid crystal display device. A transmissive liquid crystal display device includes a backlight and has a structure in which sub-pixels do not have a reflective region.

The present invention is not limited to the above embodiments, and can be modified in various ways without departing from the gist of the present invention. Further, each embodiment may be implemented in combination as appropriate, in which case the combined effect can be obtained. Furthermore, various inventions are included in the above embodiments, and various inventions can be extracted by combinations selected from a plurality of disclosed constituent elements. For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiments, if the problem can be solved and effects can be obtained, the configuration with the constituent elements deleted can be extracted as an invention.

DESCRIPTION OF SYMBOLS 1... Liquid crystal display device 2... Liquid crystal display panel 2A... Pixel array 3... Scanning line drive circuit 4... Signal line drive circuit 5... Common electrode drive circuit 6... Voltage generation circuit 7... Control circuit 8 Illuminating device 8A Light source unit 10 TFT substrate 11 CF substrate 12 Liquid crystal layer 13 Switching element 14 Reflective layer 15

Pixel electrode

16, 21 Alignment film 17 Color filter , 18-1, 18-2... transparent member, 19... light shielding layer, 20... common electrode, 22... diffusion member, 23, 25... retardation plate, 24, 26... polarizing plate.

Claims

a pixel array having a plurality of pixels;
each of the plurality of pixels has first to third sub-pixels,
the first sub-pixel is capable of displaying a first color other than white and black;
The display device, wherein the second and third sub-pixels are capable of displaying white.
2. The display device according to claim 1, further comprising a control circuit for binary driving the first to third sub-pixels.
3. The display device according to claim 2, wherein the control circuit turns off the first sub-pixel and turns on the second and third sub-pixels to perform white display.
3. The display device according to claim 2, wherein the control circuit turns on the first sub-pixel and turns off the second and third sub-pixels to display the first color.
The control circuit turns off the first sub-pixel, turns on one of the second and third sub-pixels, and turns off the other of the second and third sub-pixels to perform halftone display. The display device according to claim 2.
The control circuit turns on the first sub-pixel, turns on one of the second and third sub-pixels, turns off the other of the second and third sub-pixels, and turns off the first color. 3. The display device according to claim 2, wherein display is performed in a second color having a lower density.
7. The display device according to claim 6, wherein the control circuit turns on the first to third sub-pixels to display a third color whose density is lighter than that of the second color.
The display device according to claim 1, wherein the first to third sub-pixels have the same area.
2. The display device of claim 1, wherein the first and second sub-pixels have different areas.
The display device of claim 1, wherein the second and third sub-pixels have different areas.
The display device according to claim 1, wherein each of the first to third sub-pixels includes a reflective layer that reflects light.
2. The display device of claim 1, wherein the second and third sub-pixels do not have color filters.