Display device

Abstract

To provide a display device capable of reducing power consumption while performing color display.SOLUTION: A display device comprises a pixel array having a plurality of pixels. Each of the plurality of pixels has first to third sub-pixels. The first sub-pixel can display a first color other than white and black. The second and third sub-pixels can display white.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a display device. [Background technology]

[0002] Conventionally, there are full-color reflective displays that use three sub-pixels, red, green, and blue, for gradation driving. There are also reflective displays that use three sub-pixels, red, green, and blue, for eight-color (white / black / red / green / blue / cyan / magenta / yellow) driving each pixel with two values ​​(on / off). There are also reflective displays that use one white pixel for black-and-white driving.

[0003] In the case of the full-color reflective display mentioned above, red / green / blue color filters are used, which reduces the panel's reflectivity, and each of the three sub-pixels displays a different gray scale, resulting in high power consumption.

[0004] The aforementioned eight-color reflective display also uses red / green / blue color filters, which reduces the panel's reflectance.

[0005] The black and white reflective display mentioned above has a high reflectance and can reduce power consumption, but it can only display two colors, black and white, and cannot display color or grayscale. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 1998-339871 A [Patent Document 2] JP 2003-241178 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a display device capable of performing color display while reducing power consumption. [Means for solving the problem]

[0008] According to a first aspect of the present invention, there is provided a display device comprising a pixel array having a plurality of pixels, each of the plurality of pixels having first to third sub-pixels, the first sub-pixel being capable of displaying a first color other than white and black, and the second and third sub-pixels being capable of displaying white.

[0009] According to a second aspect of the present invention, there is provided the display device according to the first aspect, further comprising a control circuit for binary-driving the first to third sub-pixels.

[0010] According to a third aspect of the present invention, there is provided 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.

[0011] According to a fourth aspect of the present invention, there is provided a display device according to the second or third 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.

[0012] According to a fifth aspect of the present invention, there is provided a display device relating to any one of the second to fourth aspects, wherein the control circuit turns the first sub-pixel off, turns one of the second and third sub-pixels on, and turns the other of the second and third sub-pixels off, thereby performing half-tone display.

[0013] According to a sixth aspect of the present invention, there is provided a display device relating to any one of the second to fifth aspects, wherein the control circuit turns on 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, thereby displaying a second color that is lighter in density than the first color.

[0014] According to a seventh aspect of the present invention, there is provided the display device according to the sixth aspect, wherein the control circuit turns on the first to third sub-pixels to display a third color that is lighter in density than the second color.

[0015] According to an eighth aspect of the present invention, there is provided the display device according to any one of the first to seventh aspects, wherein the first to third sub-pixels have the same area.

[0016] According to a ninth aspect of the present invention, there is provided the display device according to the first or second aspect, wherein the first and second sub-pixels have different areas.

[0017] According to a tenth aspect of the present invention, there is provided the display device according to the first or second aspect, wherein the second and third sub-pixels have different areas.

[0018] According to an eleventh aspect of the present invention, there is provided the display device according to any one of the first to tenth aspects, wherein each of the first to third sub-pixels includes a reflective layer that reflects light.

[0019] According to a twelfth aspect of the present invention, there is provided the display device according to any one of the first to eleventh aspects, wherein the second and third sub-pixels do not have a color filter. Effect of the Invention

[0020] According to the present invention, it is possible to provide a display device capable of performing color display while reducing power consumption. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a block diagram of a liquid crystal display device according to the first embodiment. [Diagram 2] FIG. 2 is a circuit diagram of a pixel array included in a liquid crystal display panel. [Diagram 3] FIG. 3 is a schematic plan view of a pixel. [Figure 4] FIG. 4 is a cross-sectional view of a liquid crystal display panel. [Diagram 5]FIG. 5 is a diagram illustrating the operation of the liquid crystal display device. [Figure 6] FIG. 6 is a schematic plan view of a pixel according to the second embodiment. [Figure 7] FIG. 7 is a schematic plan view of a pixel according to the third embodiment. [Figure 8] FIG. 8 is a diagram illustrating the operation of the liquid crystal display device according to the third embodiment. [Figure 9] FIG. 9 is a block diagram of a liquid crystal display device according to the fourth embodiment. [Figure 10] FIG. 10 is a cross-sectional view of a liquid crystal display panel according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, the embodiments will be described with reference to the drawings. However, the drawings are schematic or conceptual, and the dimensions and ratios of each drawing are not necessarily the same as those in reality. In addition, even when the same parts are shown between the drawings, the dimensional relationships and ratios of each may be different. In particular, the following embodiments are examples of devices and methods for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not specified by the shape, structure, arrangement, etc. of the components. In the following description, elements having the same function and configuration are given the same reference numerals, and duplicated descriptions are omitted.

[0023] [1] First embodiment [1-1] Configuration of liquid crystal display device 1 1 is a block diagram of a liquid crystal display device 1 according to a first embodiment. The liquid crystal display device 1 according to this embodiment is a reflective liquid crystal display device that performs display by utilizing external light.

[0024] The liquid crystal display device 1 includes a liquid crystal display panel 2, a scanning line driving circuit 3, a signal line driving circuit 4, a common electrode driving circuit 5, a voltage generating circuit 6, and a control circuit .

[0025] The liquid crystal display panel 2 includes a pixel array in which a plurality of sub-pixels SP are arranged in a matrix. Three sub-pixels SP aligned in the row direction constitute 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. The sub-pixels SP are disposed in the intersections of the scanning lines GL and the signal lines SL.

[0026] The scanning line driving circuit 3 is electrically connected to the multiple scanning lines GL. The scanning line driving circuit 3 sends scanning signals to the liquid crystal display panel 2 to turn on / off switching elements included in the sub-pixels SP based on control signals sent from the control circuit 7.

[0027] The signal line driving circuit 4 is electrically connected to the multiple signal lines SL. The signal line driving circuit 4 receives a control signal and display data from the control circuit 7. The signal line driving circuit 4 sends a signal (driving voltage) corresponding to the display data to the liquid crystal display panel 2 based on the control signal.

[0028] The common electrode driving circuit 5 generates a common voltage Vcom and supplies it to the common electrode in the liquid crystal display panel 2. The voltage generating circuit 6 generates various voltages necessary for the operation of the liquid crystal display device 1 and supplies them to the corresponding circuits.

[0029] 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.

[0030] Fig. 2 is a circuit diagram of a pixel array 2A included in the liquid crystal display panel 2. 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.

[0031] The pixel array 2A includes a plurality of scanning lines GL1 to GLm and a plurality of signal lines SL1 to SLn, where "m" and "n" are each an integer of 2 or more.

[0032] The subpixel SP includes a switching element (active element) 13, a liquid crystal capacitance (liquid crystal element) Clc, and a storage capacitance Cs. For example, a TFT (Thin Film Transistor) is used as the switching element 13, and an n-channel TFT is used. Note that the source and drain of a transistor change depending on the direction of the current flowing through the transistor, but the following description will explain an example of the connection state of the transistor. However, it goes without saying that the source and drain are not fixed as their names suggest.

[0033] The source of the TFT 13 is connected to a signal line SL, its gate is connected to a scanning line GL, and its drain is connected to one electrode of a liquid crystal capacitance Clc. The liquid crystal capacitance Clc as a liquid crystal element is composed of a pixel electrode, a common electrode, and a liquid crystal layer sandwiched between them. A common voltage Vcom is applied to the other electrode of the liquid crystal capacitance Clc by a common electrode drive circuit 5.

[0034] One electrode of the storage capacitance Cs is connected to one electrode of the liquid crystal capacitance Clc. A common voltage Vcom is applied to the other electrode of the storage capacitance Cs by a common electrode drive circuit 5. The storage capacitance Cs has a function of suppressing potential fluctuations occurring in the pixel electrodes and holding the drive voltage applied to the pixel electrodes until a drive voltage corresponding to the next signal is applied. The storage capacitance Cs is composed of a pixel electrode, a storage capacitance line, and an insulating layer sandwiched between them. A storage capacitance voltage different from the common voltage Vcom may be applied to the other electrode (storage capacitance line) of the storage capacitance Cs.

[0035] [1-2] Configuration of LCD panel 2 Next, the configuration of the liquid crystal display panel 2 will be described.

[0036] 3 is a schematic plan view of a pixel PX. The pixel PX is composed of three sub-pixels SP-R, SP-W1, and SP-W2.

[0037] The size of the pixel PX is, for example, a 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 in the figure, a light-shielding layer (black matrix) is disposed at the boundaries between the multiple sub-SPs.

[0038] The sub-pixel SP-R can display a color other than white and black. In the present embodiment, as an example, the sub-pixel SP-R can display red. A red filter is provided in the sub-pixel SP-R. The sub-pixel SP-R may display a color other than red.

[0039] The sub-pixels SP-W1 and SP-W2 can display white. The white display is achieved by transmitting reflected light from outside without passing it through a color filter (i.e., the reflected light is transmitted as is). No color filter is provided for the sub-pixels SP-W1 and SP-W2.

[0040] Fig. 4 is a cross-sectional view of the liquid crystal display panel 2. Fig. 4 shows three sub-pixels SP (sub-pixels SP-R, SP-W1, and SP-W2 shown in Fig. 3) extracted from one pixel PX, and in reality, a plurality of the pixels shown in Fig. 4 are arranged in a matrix.

[0041] 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 on which color filters are formed and disposed opposite the TFT substrate 10. Each of the TFT substrate 10 and the CF substrate 11 is made of a transparent and insulating substrate (for example, a glass substrate or a plastic substrate).

[0042] 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 sealed in a display area surrounded by the TFT substrate 10, the CF substrate 11, and a sealant (not shown). The sealant is made of, for example, an ultraviolet curable resin, a thermosetting resin, or a combined ultraviolet and heat curable resin, and is applied to the TFT substrate 10 or the CF substrate 11 in the manufacturing process and then cured by ultraviolet irradiation, heating, or the like.

[0043] The liquid crystal material constituting the liquid crystal layer 12 has its optical characteristics changed as the orientation of the liquid crystal molecules is manipulated in response 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 type (N type) nematic liquid crystal having negative dielectric anisotropy is used for the liquid crystal layer 12. The liquid crystal layer 12 is vertically aligned in the initial state. When no voltage (no electric field) is applied, the liquid crystal molecules are aligned almost perpendicular to the main surface of the substrate. When a voltage (electric field) is applied, the director of the liquid crystal molecules is tilted toward the horizontal direction (parallel to the main surface of the substrate).

[0044] First, the configuration of the TFT substrate 10 side will be described. On the liquid crystal layer 12 side of the TFT substrate 10, a switching element 13 is provided for each sub-pixel. For example, a TFT (Thin Film Transistor) is used as the switching element 13, and an n-channel TFT is used. In Fig. 4, the TFT 13 is shown in a simplified form. The TFT 13 includes a gate electrode that functions as a scanning line, a gate insulating film provided on the gate electrode, a semiconductor layer provided on the gate insulating film, and a source electrode and a drain electrode provided on the semiconductor layer at a distance from each other.

[0045] The TFT substrate 10 is provided with a reflective layer 14. The reflective layer 14 is provided over substantially the entire sub-pixel region. The reflective layer 14 has a function of reflecting external light incident from the CF substrate 11. The reflective layer 14 is made of, for example, aluminum (Al).

[0046] 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 almost the entire sub-pixel region. The pixel electrode 15 is made of a transparent electrode, and for example, ITO (indium tin oxide) is used.

[0047] An alignment film 16 that controls the alignment of the liquid crystal layer 12 is provided on the pixel electrodes 15. In the initial state of the liquid crystal layer 12, the alignment film 16 aligns the liquid crystal molecules vertically.

[0048] 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 disposed in the sub-pixel SP-R region shown in FIG. 3.

[0049] Transparent members 18-1 and 18-2 are provided on the liquid crystal layer 12 side of the CF substrate 11. The transparent members 18-1 and 18-2 are made of a photosensitive transparent resin (also called a resist) that does not contain a pigment as a coloring material. The transparent members 18-1 and 18-2 transmit light without coloring it. In other words, light that transmits through the transparent members 18-1 and 18-2 is visually recognized as white light. The transparent member 18-1 is disposed in the sub-pixel SP-W1 region, and the transparent member 18-2 is disposed in the sub-pixel SP-W2 region.

[0050] A light-shielding layer (also called a black matrix or black mask) 19 is provided on the liquid crystal layer 12 side of the CF substrate 11. The black matrix 19 is disposed on 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 the function of blocking unnecessary light generated at the boundaries of the sub-pixels and improving contrast. Note that, although the contrast is slightly reduced, in order to further improve the reflectance, it is not necessary to dispose the black matrix between the red filter 17, the transparent member 18-1, and the transparent member 18-2.

[0051] 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 formed in a planar shape over the entire display area of ​​the liquid crystal display panel 2. The common electrode 20 is made of a transparent electrode, and for example, ITO is used. A structure such as a protrusion may be formed on the common electrode 20 in order to control the alignment of the liquid crystal layer 12 when a voltage is applied.

[0052] An alignment film 21 that controls the alignment of the liquid crystal layer 12 is provided on the common electrode 20. In the initial state of the liquid crystal layer 12, the alignment film 21 aligns the liquid crystal molecules vertically.

[0053] A diffusing member 22, a retardation plate 23, and a polarizing plate 24 are laminated in this order on the side of the CF substrate 11 opposite to the liquid crystal layer 12. The retardation plate 23 and the polarizing plate 24 form a circular polarizing plate.

[0054] The polarizing plate (linear polarizer) 24 has a transmission axis and an absorption axis that are perpendicular to each other in a plane perpendicular to the traveling direction of the light. The polarizing plate 24 transmits linearly polarized light (linearly polarized light component) having a vibration plane parallel to the transmission axis among light having a vibration plane in a random direction, and absorbs linearly polarized light (linearly polarized light component) having a vibration plane parallel to the absorption axis.

[0055] The retardation plate 23 has a refractive index anisotropy, and has a slow axis and a fast axis that are perpendicular to each other in a plane perpendicular to the traveling direction of the light. The retardation plate 23 has a function of giving a predetermined retardation (a phase difference of λ / 4, where λ is the wavelength of the light) between light of a predetermined wavelength that is transmitted through the slow axis and the fast axis, respectively. That is, the retardation plate 23 is composed of a 1 / 4 wavelength 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.

[0056] The angles that define the polarizing plate and the retardation plate described above include an error that allows the desired operation to be realized and an error that occurs in the manufacturing process. For example, the above-mentioned "approximately 45°" includes a range of 45°±5°. For example, the above-mentioned "orthogonal" includes a range of 90°±5°.

[0057] The diffusion member 22 has a function of homogenizing the transmitted light by diffusing (scattering) the transmitted light in random directions. The diffusion member 22 is composed of a diffusion adhesive, a diffusion film, a diffusion plate, or the like. When a diffusion adhesive is used as the diffusion member 22, the diffusion adhesive has a function of bonding 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.

[0058] The diffusing member 22 diffuses the light reflected by the reflective layer 14, and the diffused reflected light is observed by the viewer. By using the diffusing member 22, the viewing angle can be improved.

[0059] [1-3] Operation A description will be given of the operation of the liquid crystal display device 1 configured as above. The liquid crystal display device 1 operates in a normally black mode.

[0060] 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, 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 that of 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. The positive voltage is a voltage equal to or higher than the threshold voltage of the liquid crystal layer. 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 inverted at a predetermined period. By performing the inversion driving, it is possible to suppress the deterioration of the liquid crystal. The period of the inversion driving can be set arbitrarily.

[0061] In the off state, the liquid crystal molecules are set to the initial state, that is, the long axis of the liquid crystal molecules is oriented vertically. After passing through the polarizing plate 24 and the retardation plate 23, the external light incident on the display surface of the liquid crystal display panel 2 becomes circularly polarized light and enters the liquid crystal layer 12. The light incident on the liquid crystal layer 12 is hardly subjected to 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. The light that passes through the liquid crystal layer 12 is reflected by the reflective layer 14. When reflected by the reflective layer 14, the light becomes reversely (for example, left-handed) circularly polarized light. 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, the reflected light of the external light cannot pass through the polarizing plate 24, and a black display is displayed (i.e., normally black mode).

[0062] In the on state, the liquid crystal molecules are horizontally aligned, i.e., the long axes of the liquid crystal molecules are oriented horizontally. External light incident on the display surface of the liquid crystal display panel 2 passes through the polarizing plate 24 and the retardation plate 23, becomes circularly polarized light, 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, a part of the reflected light reflected by the reflective layer 14 passes through the polarizing plate 24. Therefore, the reflected external light passes through the polarizing plate 24, resulting in a white display or a color display.

[0063] In this embodiment, each sub-pixel SP is driven in two values. The two values ​​means that the sub-pixel SP is driven using two states (two values), an off state and an on state. In this embodiment, each sub-pixel SP is not driven in a gradation manner, but is driven in two values, thereby making it possible to display a plurality of colors. The gradation driving is a method of driving a pixel by changing the voltage level for each of a plurality of gradations.

[0064] Fig. 5 is a diagram illustrating the operation of the liquid crystal display device 1. Fig. 5 shows the operation of the subpixels SP-R, SP-W1, and SP-W2 included in one pixel PX. The subpixel SP-R is a red subpixel, the subpixel SP-W1 is a white subpixel (denoted as white 1), and the subpixel SP-W2 is a white subpixel (denoted as white 2).

[0065] The liquid crystal display device 1 is capable of displaying six colors, specifically, white, black, red, halftone (50% gray), light red-2, and light red-4, using one pixel PX as a display unit. Halftone means a color between white and black, and is called 50% gray in this embodiment. The shading levels of the red display color are "red > light red-1 > light red-2 > light red-3 > light red-4." The larger the number in the subscript of light red, the lighter the color density. Light red-1 and light red-3 will be described later.

[0066] Because of the normally black mode, when the sub-pixel is in the off state, the display is off (dark display, black display), and when the sub-pixel is in the on state, the display is on (light display, white display).

[0067] To display white in the pixel PX, the control circuit 7 turns off the subpixel SP-R and turns on the subpixels SP-W1 and SP-W2. That is, to display white in the pixel PX, the two white subpixels are turned on.

[0068] When displaying black in the pixel PX, the control circuit 7 turns off the subpixels SP-R, SP-W1, and SP-W2. That is, when displaying black, all the subpixels are turned off.

[0069] When displaying red in the pixel PX, the control circuit 7 turns on the subpixel SP-R and turns off the subpixels SP-W1 and SP-W2. That is, when displaying red in the pixel PX, only the red subpixel is turned on.

[0070] When displaying 50% gray in pixel PX, control circuit 7 sets subpixel SP-R to the off state, subpixel SP-W1 to the on state, and subpixel SP-W2 to the off state. For 50% gray, subpixel SP-W1 may be set to the off state and subpixel SP-W2 to the on state. That is, when displaying 50% gray in pixel PX, only one white subpixel is set to the on state.

[0071] To display light red-2 in the pixel PX, the control circuit 7 turns on the subpixels SP-R and SP-W1 and turns off the subpixel SP-W2. For light red-2, the subpixel SP-W1 may be turned off and the subpixel SP-W2 may be turned on.

[0072] When displaying a pale red-4 in the pixel PX, the control circuit 7 turns on the subpixels SP-R, SP-W1, and SP-W2. That is, when displaying a pale red-4, all the subpixels are turned on.

[0073] Through the above operations, the liquid crystal display device 1 can display six colors (white, black, red, 50% gray, light red-2, and light red-4) with one pixel PX as a display unit.

[0074] [1-4] Effects of the first embodiment In the first embodiment, the liquid crystal display device 1 is 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 other than white and black (e.g., red). The sub-pixels SP-W1 and SP-W2 are capable of displaying white. The control circuit 7 drives the sub-pixels SP-R, SP-W1, and SP-W2 in a binary manner.

[0075] Therefore, according to the first embodiment, it is possible to display a predetermined color in addition to black and white, despite the binary drive. Moreover, power consumption can be reduced compared to the case of gradation drive.

[0076] Moreover, by turning on one of the two white sub-pixels, it is possible to display a halftone (50% gray) despite the binary drive.

[0077] To display white, the two white sub-pixels that do not have color filters are turned on. This improves the reflectance, and the liquid crystal display device 1 can achieve a brighter display.

[0078] Furthermore, by turning on the red subpixel and switching the remaining two white subpixels between on and off, it is possible to display two different densities of red (excluding the primary color red) in addition to the primary color red.

[0079] Furthermore, since color display can be realized by binary driving, it is possible to simplify the display control while still providing a color display.

[0080] Furthermore, the liquid crystal display device 1 does not use a backlight, so that power consumption can be further reduced.

[0081] [2] Second embodiment In the second embodiment, among the three sub-pixels SP that configure a pixel PX, the area ratio between the red sub-pixel and the two white sub-pixels is changed.

[0082] 6 is a schematic plan view of a pixel PX according to embodiment 2. The pixel PX is made up of three sub-pixels SP-R, SP-W1, and SP-W2.

[0083] The area of ​​the subpixel SP-R is smaller than the areas of the subpixels SP-W1 and SP-W2. For example, the area of ​​the subpixel SP-W1 is the same as the area of ​​the subpixel SP-W2. The area ratio of the subpixels SP-R, SP-W1, and SP-W2 is, for example, "2:5:5."

[0084] The sub-pixels SP-R, SP-W1, and SP-W2 are driven in the same manner as in the first embodiment.

[0085] In the second embodiment, the area ratio of each of the two white sub-pixels to the red sub-pixel is increased, which can further improve the reflectance and also make the white display brighter.

[0086] [3] Third embodiment In the third embodiment, among the three sub-pixels SP that form a pixel PX, the area ratio of the two white sub-pixels is changed.

[0087] 7 is a schematic plan view of a pixel PX according to embodiment 3. The pixel PX is made up of three sub-pixels SP-R, SP-W1, and SP-W2.

[0088] The area of ​​the subpixel SP-W1 is different from the area of ​​the subpixel SP-W2. For example, the area of ​​the subpixel SP-W2 is smaller than the area of ​​the subpixel SP-W1. The area ratio of the subpixels SP-W1 and SP-W2 is, for example, "3:1." The area ratio of the subpixels SP-R, SP-W1 and SP-W2 is, for example, "2:3:1." In this embodiment, by changing the area ratio of the two white subpixels, it is possible to display intermediate tones other than 50% gray.

[0089] 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 is capable of displaying eight colors, specifically, white, black, red, a first halftone (dark gray), a second halftone (light gray), light red-2, and light red-4, with one pixel PX as a display unit. In this embodiment, the area ratio of the sub-pixels SP-W1 and SP-W2 is set to "3:1". In this example, the first halftone is 75% gray, and the second halftone is 25% gray.

[0090] The operations of white display, black display, and red display are the same as those in the first embodiment.

[0091] When displaying 75% gray in pixel PX, control circuit 7 turns subpixel SP-R off, subpixel SP-W1 on, and subpixel SP-W2 off. That is, when displaying 75% gray in pixel PX, the one with the larger area of ​​the two white subpixels is turned on.

[0092] When displaying 25% gray in pixel PX, control circuit 7 turns subpixels SP-R and SP-W1 off and turns subpixel SP-W2 on. That is, when displaying 25% gray in pixel PX, the smaller of the two white subpixels is turned on.

[0093] To display a pale red-1 in the pixel PX, the control circuit 7 turns on the subpixel SP-R, turns off the subpixel SP-W1, and turns on the subpixel SP-W2. That is, to display a pale red-1, the one of the two white subpixels with the smaller area is turned on.

[0094] To display pale red-3 in pixel PX, the control circuit 7 turns on subpixels SP-R and SP-W1 and turns off subpixel SP-W2. That is, to display pale red-3, the one of the two white subpixels with the larger area is turned on.

[0095] When displaying a pale red-4 in the pixel PX, the control circuit 7 turns on the subpixels SP-R, SP-W1, and SP-W2. That is, when displaying a pale red-4, all the subpixels are turned on.

[0096] According to the third embodiment, two intermediate tones (for example, 75% gray and 25% gray) can be displayed. In addition, by controlling the on and off states of the two white sub-pixels while keeping the red sub-pixel in the on state, three different shades of red (excluding the primary color red) can be displayed.

[0097] [4] Fourth embodiment The fourth embodiment is an example of the configuration of a semi-transmissive liquid crystal display device capable of both reflective display and transmissive display.

[0098] 9 is a block diagram of a liquid crystal display device 1 according to a fourth embodiment. The liquid crystal display device 1 further includes an illumination device 8 (also called a backlight).

[0099] The backlight 8 is formed of a surface light source, and irradiates light onto the back surface of the liquid crystal display panel 2. As the backlight 8, for example, a direct type or side light type (edge ​​light type) LED backlight is used.

[0100] The voltage generating circuit 6 supplies a predetermined voltage to the backlight 8. The control circuit 7 controls the on / off operation of the backlight 8.

[0101] FIG. 10 is a cross-sectional view of a liquid crystal display panel 2 according to the fourth embodiment.

[0102] The backlight 8 is disposed on the rear side (the side opposite to the display surface) of the liquid crystal display panel 2. The backlight 8 includes a light source unit 8A that emits illumination light. The backlight 8 irradiates the rear side of the liquid crystal display panel 2 with the illumination light.

[0103] A reflective layer 14 is provided on the TFT substrate 10. The reflective layer 14 is provided in a part 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 almost the entire sub-pixel region.

[0104] The sub-pixel SP has a reflective region RA and a transmissive region TA. Within the sub-pixel region, a region where the reflective layer 14 is provided is the reflective region RA, and a region where the reflective layer 14 is not provided is the transmissive region TA.

[0105] 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 form a circular polarizing plate.

[0106] The 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 to be perpendicular to the transmission axis of the polarizing plate 24. That is, the polarizing plate 24 and the polarizing plate 26 are arranged in a crossed Nicol state.

[0107] 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 .

[0108] The configuration of the pixel PX is the same as that of 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.

[0109] The liquid crystal display device 1 can use a backlight 8. The operation of the liquid crystal display device 1 for color display is the same as that of the first embodiment.

[0110] The fourth embodiment can also provide the same effects as the first embodiment. Moreover, the second and third embodiments can also be applied to the fourth embodiment.

[0111] In the above embodiments, the VA mode has been described as an example of the liquid crystal mode, but the liquid crystal mode may be a Twisted Nematic (TN) mode, an Electrically Controlled Birefringence (ECB) mode, a Super Twisted Nematic (STN) mode, or the like.

[0112] In the above-described embodiments, the active matrix type using active elements is taken as an example of the driving method, but the driving method is not limited to the active matrix type, and may be a passive matrix type.

[0113] In the above embodiments, a liquid crystal display device is used as an example of a display. The present embodiments may be applied to devices other than liquid crystal display devices, such as organic electroluminescence (EL) display devices or electrophoretic display devices. The display devices according to the present embodiments may also be applied to electronic paper.

[0114] In the above embodiments, a reflective liquid crystal display device and a semi-transmissive liquid crystal display device are described, but the present invention can also be applied to a transmissive liquid crystal display device. A transmissive liquid crystal display device includes a backlight and has a configuration in which the sub-pixels do not have a reflective region.

[0115] The present invention is not limited to the above-mentioned embodiment, and various modifications can be made in the implementation stage without departing from the gist of the invention. In addition, the embodiments may be implemented in appropriate combination, and in that case, the combined effect can be obtained. Furthermore, the above-mentioned embodiment includes various inventions, and various inventions can be extracted by combinations selected from the multiple components disclosed. For example, if the problem can be solved and the effect can be obtained even if some components are deleted from all the components shown in the embodiment, the configuration from which the components are deleted can be extracted as an invention. [Explanation of symbols]

[0116] 1...liquid crystal display device, 2...liquid crystal display panel, 2A...pixel array, 3...scanning line driving circuit, 4...signal line driving circuit, 5...common electrode driving circuit, 6...voltage generating circuit, 7...control circuit, 8...illumination 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...phase difference plate, 24, 26...polarizing plate.

Claims

1. a pixel array having a plurality of pixels; A control circuit for controlling an operation of the pixel array; Equipped with Each of the plurality of pixels is composed of first to third sub-pixels only, the first sub-pixel is capable of displaying a first color other than white and black; The second and third sub-pixels are capable of displaying white, The control circuit drives the first to third sub-pixels in a binary manner. Display device.

2. The control circuit turns the first sub-pixel off and turns the second and third sub-pixels on to perform white display. The display device according to claim 1 .

3. The control circuit turns on the first sub-pixel and turns off the second and third sub-pixels to display the first color. The display device according to claim 1 .

4. 4. The display device according to claim 1, wherein the control circuit performs gray scale display by turning off the first sub-pixel, turning on one of the second and third sub-pixels, and turning off the other of the second and third sub-pixels.

5. The control circuit turns on 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, thereby displaying a second color that is lighter in density than the first color. The display device according to claim 1 .

6. The control circuit turns on the first to third sub-pixels to display a third color that is lighter in density than the second color. The display device according to claim 5 .

7. The first to third sub-pixels have the same area. The display device according to claim 1 .

8. The first and second sub-pixels have different areas. The display device according to claim 1 .

9. The second and third sub-pixels have different areas. The display device according to claim 1 .

10. Each of the first to third sub-pixels includes a reflective layer that reflects light. The display device according to claim 1 .

11. The second and third sub-pixels do not have a color filter. The display device according to claim 1 .

Images