JP5421154B2 - Reflective liquid crystal display device, driving method thereof and electronic apparatus - Google Patents

Description

  The present invention relates to a technique for suppressing color misregistration in a reflective liquid crystal display device.

  Color misregistration is a phenomenon in which the color (saturation and hue) differs between the color to be displayed and the actual display color. In a conventional reflective liquid crystal display device for monochrome display, a chromatic color is displayed during white display (when white, which is the highest gradation, should be displayed) due to wavelength dispersion of optical characteristics of an optical member such as a liquid crystal layer. End up. As a technique for suppressing color shift at the time of white display, there is a technique in which another liquid crystal layer is disposed between a polarizing plate and a liquid crystal layer to cancel wavelength dispersion of the liquid crystal layer (Patent Document 1). .

JP-A-11-231305

However, this technique does not consider wavelength dispersion of optical characteristics of optical members other than the liquid crystal layer, such as polarizing plates and optical films. Therefore, it is insufficient for suppressing color misregistration when displaying the highest gradation. Although it is conceivable to arrange another optical member so as to cancel the wavelength dispersion of the optical characteristics of the optical member other than the liquid crystal layer, it is unrealistic because the reflectance of the reflective liquid crystal display device is significantly reduced. .
In view of the above-described circumstances, an object of the present invention is to suppress a shift in the color tone of the display color of the highest gradation in a reflective liquid crystal display device.

  The present invention solves the above problem by controlling the reflectance. Specifically, a reflective liquid crystal display device, a driving method of the reflective liquid crystal display device, and an electronic device described below are provided. In the following description, “color” means an attribute identified by lightness, saturation, and hue, and includes an achromatic color. In addition, “single” for the color means that the color is the same. “Monochrome” means an achromatic color having a plurality of gradations. In monochrome, the highest gradation color is white, the lowest gradation color is black, and the halftone color between the highest gradation and the lowest gradation is darker than white and lighter than black. is there. “Monocolor” means a plurality of colors composed of a single chromatic color having a plurality of gradations and black. In mono color, the color of the lowest gradation is black, and the color of the other gradation is a single chromatic color.

The first reflective liquid crystal display device of the present invention includes pixels that reflect light and display colors on a display surface, and each of the pixels reflects a plurality of light that reflects light and displays colors on the display surface. Each of the plurality of sub-pixels includes a reflection surface that reflects light, and a liquid crystal layer disposed between the reflection surface and the display surface, and the plurality of sub-pixels include: A non-colored achromatic sub-pixel and one or more chromatic sub-pixels of a single chromatic color are included, and the one or more chromatic sub-pixels include a blue chromatic sub-pixel.
The first reflective liquid crystal display device is a so-called monochrome display reflective liquid crystal display device. In the first reflective liquid crystal display device, in each sub-pixel, part or all of the reflected light from the reflective surface is emitted from the display surface, whereby the color of the emitted light is displayed. An achromatic color is expected as the display color of the non-colored achromatic sub-pixel. However, since there is wavelength dispersion in the optical characteristics of the internal optical member, it is actually a chromatic color. For example, in the case of adopting a general structure, the achromatic sub-pixel displays yellowish green that is close to yellow when displaying white. Therefore, in the first reflective liquid crystal display device, one or more chromatic color sub-pixels include a blue chromatic color sub-pixel. The blue chromatic color sub-pixel is a chromatic color sub-pixel capable of displaying blue, for example, a chromatic color sub-pixel in which a part or all of the internal optical member is colored in blue. That is, the first reflective liquid crystal display device can display blue in part of the pixels. Therefore, the difference in color between the display color of the pixel and the achromatic color can be made smaller than the difference in color between the display color of the achromatic color sub-pixel and the achromatic color. That is, according to the first reflective liquid crystal display device, it is possible to suppress the color shift of the display color of the highest gradation.

  In the first reflective liquid crystal display device, the one or more chromatic color sub-pixels preferably include a red chromatic color sub-pixel. The red chromatic color sub-pixel is a chromatic color sub-pixel capable of displaying red, for example, a chromatic color sub-pixel in which a part or all of the internal optical member is colored in red. In other words, the reflective liquid crystal display device of this aspect can display not only blue but also red on a part of the pixels. As described above, when the general structure is adopted, the display color of the achromatic sub-pixel is not yellow but yellowish green close to yellow. According to the reflective liquid crystal display device of this aspect, It is possible to further suppress the color shift of the gradation display color.

  Furthermore, in the reflective liquid crystal display device of this aspect, the one or more chromatic color sub-pixels may include a green chromatic color sub-pixel. The green chromatic color sub-pixel is a chromatic color sub-pixel capable of displaying green, for example, a chromatic color sub-pixel in which a part of the internal optical member is colored in green. That is, the reflective liquid crystal display device according to this aspect can display blue, red, and green on a part of the pixels. Therefore, according to the reflection type liquid crystal display device of this aspect, it is possible to suppress a color shift of the display color of the highest gradation, regardless of the chromatic color of the display color of the achromatic sub-pixel.

  In each of the reflection type liquid crystal display devices, at least one chromatic color sub-pixel of the one or more chromatic color sub-pixels includes a color filter of the color, and the color filter includes the liquid crystal layer and the display. It may be arranged between the display surface and the reflective surface in a direction orthogonal to the display surface. For example, a blue chromatic subpixel is provided with a blue color filter. The color filter is a thin film having a high transmittance in a specific wavelength band and a low transmittance in other wavelength bands, and is formed of a pigment, for example.

  Furthermore, in the reflective liquid crystal display device according to this aspect, in each of the at least one chromatic color sub-pixel, the reflective surface may have a portion that does not overlap the color filter in the direction. In other words, in the chromatic sub-pixel provided with the color filter, a part of the reflected light of the reflection surface reaches the display surface through the color filter, and the other part does not pass through the color filter on the display surface. To reach. According to the reflective liquid crystal display device of this aspect, even if it is difficult to make the color filter sufficiently thin, it is possible to suppress a decrease in the reflectance of the pixel.

  Incidentally, the wavelength dispersion of the optical characteristics of the optical member inside the sub-pixel depends on the gradation. For this reason, a phenomenon in which the color of the display color of the pixel is different for each gradation, that is, a color shift between gradations may occur. Therefore, each of the reflection type liquid crystal display devices includes a first driving unit that drives the pixel based on a gradation signal that specifies any one of a plurality of gradations, and the plurality of gradations Each of the first gradation according to the voltage applied to the achromatic sub-pixel and the second gradation according to the voltage applied to a specific chromatic sub-pixel among the one or more chromatic sub-pixels. The first driving unit applies a voltage corresponding to the first gradation corresponding to the gradation specified by the gradation signal to the achromatic sub-pixel. A voltage corresponding to the second gradation corresponding to the gradation specified by the gradation signal is applied to the specific chromatic color sub-pixel, and the plurality of gradations are the first gradation It is preferable that the second gradation ratio includes two gradations different from each other. According to the reflective liquid crystal display device of this aspect, the ratio of the second gradation to the first gradation based on the gradation designated for the pixel, that is, the gradation between the achromatic subpixel and the specific chromatic subpixel. Since the ratio can be varied, the color shift between gradations can be suppressed.

  In the reflective liquid crystal display device according to this aspect, the specific chromatic color sub-pixel is a blue chromatic color sub-pixel, and the two gradations are a low gradation and a high gradation, and are designated by the gradation signal. It is preferable that the ratio when the gradation is the low gradation is smaller than the ratio when the gradation specified by the gradation signal is the high gradation. This is because, in a general structure, the lower the display color gradation of the achromatic sub-pixel, the greater the proportion of blue light in the reflected light of the achromatic sub-pixel.

  Similarly, the specific chromatic color sub-pixel is a red chromatic color sub-pixel, the two gradations are a low gradation and a high gradation, and the gradation specified by the gradation signal is It is preferable that the ratio in the case of the low gradation is larger than the ratio in the case where the gradation specified by the gradation signal is the high gradation. This is because, in a general structure, the lower the gradation of the display color of the achromatic sub-pixel, the smaller the proportion of red light in the reflected light of the achromatic sub-pixel.

A second reflective liquid crystal display device of the present invention includes a pixel that reflects light and displays a color on a display surface, and the pixel includes a reflective surface that reflects light, the reflective surface, and the display surface. A liquid crystal layer disposed between the liquid crystal layer and the display surface, and a polarizing plate having a higher transmittance for a specific wavelength band in a visible light wavelength band than a transmittance for other wavelength bands It is characterized by providing.
In the second reflective liquid crystal display device, in the pixel, part or all of the reflected light on the reflective surface passes through the liquid crystal layer and the polarizing plate and is emitted from the display surface, whereby the color of the emitted light is displayed. Since there is wavelength dispersion in the optical characteristics of the optical member inside the pixel, when the general structure is adopted, the display color of the highest gradation of the pixel is different from the intended color. However, in the second reflective liquid crystal display device, the transmittance (average value) for a specific wavelength band in the visible light wavelength band is transmitted through the polarizing plate higher than the transmittance (average value) for other wavelength bands. Since light is emitted, it is possible to suppress a color shift of the display color of the highest gradation. For example, when the second reflective liquid crystal display device is used for monochrome display, the wavelength band of blue light is set to a specific wavelength band, or the wavelength band of blue light and the wavelength band of red light are set to specific wavelength bands. By doing so, it is possible to suppress a shift in the color of the display color during white display in a general structure.

The third reflective liquid crystal display device of the present invention is based on a pixel that reflects light and displays a color on a display surface, and a gradation signal that specifies any one gradation among a plurality of gradations. A second driving unit that drives the pixels, and each of the pixels includes a plurality of sub-pixels that reflect light and display a color on the display surface, and each of the plurality of sub-pixels emits light. A reflective surface that reflects, and a liquid crystal layer disposed between the reflective surface and the display surface, wherein the plurality of sub-pixels are a first sub-pixel of a first color and a color of the first color A second sub-pixel of a second color having a different taste, and each of the plurality of gradations includes a third gradation corresponding to a voltage applied to the first sub-pixel and the second sub-pixel. A fourth gradation corresponding to the applied voltage is associated in advance, and the second driving unit applies a front to each of the plurality of sub-pixels. A voltage corresponding to a gradation corresponding to a gradation specified by a gradation signal is applied, and the plurality of gradations are two gradations having different ratios of the fourth gradation to the third gradation. It is characterized by including.
The third reflective liquid crystal display device is a so-called monocolor display reflective liquid crystal display device. In the third reflective liquid crystal display device, as in the first reflective liquid crystal display device, in each sub-pixel, a part or all of the reflected light of the reflective surface is emitted from the display surface, whereby the color of the emitted light is obtained. Is displayed. As described above, the optical characteristic of the optical member inside the sub-pixel has chromatic dispersion, and this chromatic dispersion depends on the gradation, and therefore color misregistration between gradations may occur. However, according to the third reflective liquid crystal display device, the ratio of the fourth gradation to the third gradation, that is, the level of the first subpixel and the second subpixel, based on the gradation designated for the pixel. Since the tone ratios can be made different, color misregistration between gradations can be suppressed. Therefore, according to the third reflective liquid crystal display device, it is possible to suppress the color shift of the display color of the highest gradation by appropriately determining the first color and the second color.

  A driving method of a reflective liquid crystal display device according to the present invention includes pixels that reflect light to display a color on a display surface, and each of the pixels includes a plurality of pixels that reflect light and display a color on the display surface. Driving a reflective liquid crystal display device comprising a sub-pixel, each of the plurality of sub-pixels including a reflective surface that reflects light, and a liquid crystal layer disposed between the reflective surface and the display surface Determining a gradation to be designated for the sub-pixel based on a gradation signal for designating any one of the plurality of gradations for each of the plurality of sub-pixels; An application process of applying a voltage corresponding to the determined gradation to the subpixel is sequentially performed, and in the determination process, the plurality of gradations are determined for two subpixels of the plurality of subpixels. In order to include two gradations with different gradation ratios, And determining the. According to this driving method, the same effect as that of the reflective liquid crystal display device including the first driving unit or the second driving unit can be obtained.

  An electronic apparatus according to the present invention includes each of the reflection type liquid crystal display devices described above, and has the same effect as the provided reflection type liquid crystal display device.

1 is a diagram illustrating an overall configuration of a reflective liquid crystal display device 100 according to a first embodiment of the present invention. 3 is a plan view of a pixel P1 provided in the reflective liquid crystal display device 100. FIG. FIG. 3 is a cross-sectional view taken along line AA ′, line BB ′, and line CC ′ of FIG. 2. It is a figure which shows the whole structure of the reflection type liquid crystal display device 300 which concerns on a comparative example. 3 is a cross-sectional view of a pixel P3 provided in the reflective liquid crystal display device 300. FIG. It is a figure which shows the wavelength dispersion of the reflectance of the pixel P3 for every gradation. It is xy chromaticity diagram which shows the color of the display color of the pixel P3 for every gradation. It is a figure which shows the correspondence of the designated gradation of the pixel P1, and the designated gradation of the subpixels W, B, and R which comprise the pixel P1. It is xy chromaticity diagram which shows the color of the display color of the pixel P1 in the case of white display, and the pixel P3. It is xy chromaticity diagram which shows the color tone of the display color of the pixel P1 and the pixel P3 for every gradation. It is a top view of pixel P4 with which a reflective liquid crystal display device concerning modification 1 of a 1st embodiment is provided. It is a top view of pixel P5 with which the reflective liquid crystal display device concerning modification 2 of a 1st embodiment is provided. It is a figure which shows the whole structure of the reflection type liquid crystal display device 200 which concerns on 2nd Embodiment of this invention. It is sectional drawing of the pixel P2 with which the reflection type liquid crystal display device 200 is provided. It is a figure which shows the wavelength dispersion of the transmittance | permeability of the polarizing plate 56 with which the reflection type liquid crystal display device 300 is provided. It is a figure which shows the wavelength dispersion of the transmittance | permeability of the polarizing plate 58 with which the reflection type liquid crystal display device 200 is provided. It is a figure which shows the wavelength dispersion of the reflectance of the pixel P2 in the case of white display, and the pixel P3. It is xy chromaticity diagram which shows the color of the display color of the pixel P2 in the case of white display, and the pixel P3. 1 is a perspective view illustrating a configuration of a portable personal computer that employs a reflective liquid crystal display device 100 or 200. FIG. 1 is a perspective view illustrating a configuration of a mobile phone to which a reflective liquid crystal display device 100 or 200 is applied. It is a perspective view which shows the structure of the portable information terminal to which the reflective liquid crystal display device 100 or 200 is applied.

<A: First Embodiment>
FIG. 1 is a diagram showing an overall configuration of a reflective liquid crystal display device (first reflective liquid crystal display device) 100 according to the first embodiment of the present invention. The reflective liquid crystal display device 100 is a monochrome display reflective liquid crystal display device, as shown in FIG. 1, including a plurality of pixels P1 arranged in a matrix, and a display surface constituted by these pixels P1. 10 The pixel P1 reflects light and displays a color on the display surface 10. The reflective liquid crystal display device 100 controls the display color of all the pixels P1, and displays an image indicated by the image data IM supplied from a host device (not shown) on the display surface 10.

  The pixel P1 is composed of three subpixels. The sub-pixel reflects light and displays a color on the display surface 10 and includes a reflective electrode 52 that reflects light, which will be described in detail later. Specifically, the three sub-pixels constituting the pixel P1 are an uncolored sub-pixel W, a blue sub-pixel B, and a red sub-pixel R. The sub-pixel B is a sub-pixel that can display blue, and the sub-pixel R is a sub-pixel that can display red.

  In addition, the reflective liquid crystal display device 100 includes a plurality of scanning lines 11 extending in the X direction and a plurality of data lines 12 extending in the Y direction orthogonal to the X direction. Each of the plurality of scanning lines 11 and each of the plurality of data lines 12 intersect with each other behind the display surface 10, and a pixel P1 is disposed corresponding to each intersection. The data line 12 is composed of three sub data lines. Specifically, these sub-data lines are the sub-data line 12W connected to the reflection electrode 52 of the sub-pixel W, the sub-data line 12B connected to the reflection electrode 52 of the sub-pixel B, and the reflection of the sub-pixel R. This is the sub data line 12 </ b> R connected to the electrode 52.

  In addition, the reflective liquid crystal display device 100 includes a driver IC 20 that drives all the pixels P1. The driver IC 20 includes a scanning line driving circuit 21, a data line driving circuit (first driving unit) 22, and a control circuit 23. The control circuit 23 controls the scanning line driving circuit 21 and the data line driving circuit 22 based on the image data IM. In the control of the data line driving circuit 22, the gradation signal g is supplied from the control circuit 23 to the data line driving circuit 22. The gradation signal g is a signal indicating the gradation designated for each of all the pixels P1, and the gradation designated for each pixel P1 is a plurality of gradations from the highest gradation to the lowest gradation. , Any one gradation.

  The scanning line driving circuit 21 is a circuit that drives the plurality of scanning lines 11 and sequentially selects them, and drives the plurality of scanning lines 11 by supplying a selection signal. The selection signal is a signal that becomes a predetermined level only for a certain period, and is determined so that a period in which the selection signal becomes a predetermined level does not overlap between the scanning lines 11.

  The data line driving circuit 22 is a circuit for designating gradations to the plurality of pixels P1 corresponding to the selected scanning line 11 by driving the plurality of data lines 12 based on the gradation signal g. The plurality of data lines 12 are driven by the supply of. When attention is paid to one sub-pixel constituting one pixel P1, the data line driving circuit 22 determines the gradation designated for the sub-pixel based on the gradation designated for the pixel P1 by the gradation signal g. And a data signal having a level corresponding to the gradation determined in the determination process is connected to the reflective electrode 52 of the sub-pixel in a period in which the scanning line 11 corresponding to the pixel P1 is selected. By supplying to the sub data line, an application process of applying a voltage corresponding to the gradation determined in the determination process to the pixel P1 is sequentially performed.

  FIG. 2 is a plan view of the pixel P1 when the pixel P1 is viewed from the display surface 10 side. As shown in FIG. 2, the pixel P <b> 1 occupies one rectangular area in the display surface 10. This rectangular area is the display area of the pixel P1. Of the four sides surrounding the display area of the pixel P1, two sides extend in the X direction, and the other two sides extend in the Y direction. The display area of the pixel P1 is equally divided into three rectangular areas in the X direction. Among these rectangular areas, one is a display area of the sub-pixel W, another one is a display area of the sub-pixel B, and another one is a display area of the sub-pixel R. The area of the display area of the pixel P1 is S, and the areas of the display areas of the sub-pixels W, B, and R are both S / 3.

  The display area of the sub-pixel B is divided into two rectangular areas in the Y direction. Of these rectangular areas, the narrower is the display area of the blue part B1, and the wider is the display area of the transparent part B2. That is, in the Y direction, the sub-pixel B is divided into a blue portion B1 that reflects blue light and displays blue, and a transparent portion B2 that reflects light and displays color. Similarly, the sub-pixel R is divided in the Y direction into a red portion R1 that reflects red light and displays red, and a transparent portion R2 that reflects light and displays color. In the Y direction, the lengths of the blue part B1 and the red part R1 are both L1, the lengths of the transparent parts B2 and R2 are both L2, and L1: L2 = 1: 3. That is, the areas of the blue part B1 and the red part R1 are both S / 12.

  3 is a cross-sectional view taken along line AA ′, line BB ′, and line CC ′ of FIG. As shown in FIG. 3, the reflective liquid crystal display device 100 includes an array substrate 51, a plurality of reflective electrodes 52 arranged on the array substrate 51, a plurality of liquid crystal layers 53 disposed thereon, and a liquid crystal layer 53 disposed thereon. A transparent electrode 54 disposed thereon, a counter substrate 55 disposed thereon, a polarizing plate 56 disposed thereon, and color filters 57B and 57R disposed between the transparent electrode 54 and the counter substrate 55. Prepare. Of the widest surface of the polarizing plate 56, the surface opposite to the reflective electrode 52 is the display surface 10.

  In each subpixel, the reflective electrode 52, the liquid crystal layer 53, and the transmissive electrode 54 constitute a liquid crystal element. That is, the same number of liquid crystal elements as sub-pixels are arranged on the array substrate 51. Although the liquid crystal layer 53 is formed of normally black liquid crystal, the liquid crystal layer 53 may be formed of normally white liquid crystal. Moreover, in this embodiment, although the reflective electrode 52 serves as a reflective surface and an electrode, a reflective surface and an electrode are separately comprised, ie, a reflective surface is formed with a metal layer, and a transparent electrode is formed on it. It is good also as a structure. In this embodiment, a structure in which a liquid crystal layer is sandwiched between two electrodes (vertical electric field) is adopted as the structure of the liquid crystal element. However, a so-called lateral electric field structure, that is, an insulating layer on the reflective electrode 52 is used. A structure in which the transmissive electrode 54 is formed in a comb shape or a shape having a slit may be employed.

  The color filter 57B is a blue color filter. Specifically, the color filter 57B is a thin film having high transmittance in the wavelength band of blue light and low transmittance in other wavelength bands in the visible light wavelength band. The color filter 57R is a red color filter. Specifically, the color filter 57R is a thin film having a high transmittance in the wavelength band of red light and a low transmittance in the other wavelength bands in the visible light wavelength band. Each of the color filters 57B and 57R has a film thickness of 0.5 μm, and is formed of a dye on the reflective electrode 52 side of the widest surface of the counter substrate 55.

  Optical characteristics (reflectance, transmittance, etc.) of optical members (reflection electrode 52, liquid crystal layer 53, transmission electrode 54, counter substrate 55, polarizing plate 56, alignment film (not shown), etc.) other than color filters 57B and 57R Is the same as that of a general reflective liquid crystal display device. The color filters 57B and 57R may be formed on the opposite side of the widest surface of the counter substrate 55 from the reflective electrode 52, and the film thickness of the color filters 57B and 57R may be other than 0.5 μm. The thickness may be different, or the thicknesses of the two may be different from each other.

  Each of the sub-pixels W, B, and R is configured to partially include each of the array substrate 51, the transmissive electrode 54, the counter substrate 55, and the polarizing plate 56, and includes a reflective electrode 52 and a liquid crystal layer 53. The sub-pixel W, the transparent part B2, and the transparent part R2 do not include a color filter, whereas the blue part B1 includes a color filter 57B and the red part R1 includes a color filter 57R. The reflective electrode 52 of the subpixel B includes a portion that overlaps with the color filter 57B, and the reflective electrode 52 of the subpixel R includes a portion that overlaps with the color filter 57R. Of the sub-pixel B, a portion (including the color filter 57B) that overlaps the color filter 57B in the Z direction orthogonal to the display surface 10 is the blue portion B1, and among the sub-pixels R, a portion that overlaps the color filter 57R in the Z direction. (Including the color filter 57R) is the red portion R1.

  In the sub-pixel W, the transparent part B2, and the transparent part R2, a part or all of incident light from the display region (display surface 10) is not polarized by the liquid crystal element, but the polarizing plate 56, the counter substrate 55, and the transmissive electrode. 54, the liquid crystal layer 53, and the reflective electrode 52 are sequentially transmitted to reach the reflective electrode 52, and part or all of the reflected light of the reflective electrode 52 passes through the liquid crystal layer 53, the transmissive electrode 54, the counter substrate 55, and the polarizing plate 56. The light is transmitted in order and emitted from the display area. This emitted light is reflected light from the sub-pixel W, the transparent portion B2, and the transparent portion R2.

  The optical path described above is the same for the blue portion B1 and the red portion R1. However, in the blue part B1, light that has passed through the color filter 57B twice becomes reflected light, and in the red part R1, light that has passed through the color filter 57R twice becomes reflected light. Therefore, the display color of the blue part B1 is blue or black, and the display color of the red part R1 is red or black.

<A-1: Comparative example>
Here, the comparative example compared with this embodiment is demonstrated.
FIG. 4 is a diagram illustrating an overall configuration of a reflective liquid crystal display device 300 according to a comparative example. The reflective liquid crystal display device 300 is a monochrome-type reflective liquid crystal display device. The pixel P3 having no sub-pixel is substituted for the pixel P1, and the data line 13 which is one signal line is substituted for the data line 12. The driver IC 30 includes a data line driving circuit 24 instead of the driver IC 20. The data line driving circuit 24 is different from the data line driving circuit 22 in that the data signal supplied to the data line is a signal having a level corresponding to the gradation designated for the pixel P3 by the gradation signal g.

  FIG. 5 is a cross-sectional view of the pixel P3. As shown in FIG. 5, the pixel P <b> 3 has the same structure as the sub-pixel W. That is, the pixel P3 is uncolored. Therefore, the display color of the pixel P3 is ideally an achromatic color. However, actually, a chromatic color is displayed due to the wavelength dispersion of the optical characteristics of the optical member in the pixel P3. For example, when displaying white, yellowish green that is close to yellow is displayed.

  FIG. 6 is a diagram illustrating the wavelength dispersion of the reflectance of the pixel P3 for each gradation. As shown in FIG. 6, the reflectance of the pixel P3 depends on the wavelength of incident light. For example, the reflectance for the wavelength band of red light (620 to 750 nm) is lower than the reflectance for the wavelength band of green light (495 to 570 nm). The reason why the reflectance of the pixel P3 depends on the wavelength of incident light is that there is wavelength dispersion in the optical characteristics of the optical member in the pixel P3.

  Further, the reflectance distribution of the pixel P3 with respect to the wavelength of the incident light depends on the gradation specified for the pixel P3. For example, when the specified gradation is 100% (maximum gradation), the reflectance for the blue light wavelength region (450 to 495 nm) is lower than the reflectance for the wavelength bands of green light and red light. When the gradation is 80%, the reflectance for the wavelength region of blue light is higher than the reflectance for the wavelength bands of green light and red light. The above distribution depends on the designated gradation because the wavelength dispersion of the optical characteristics of the optical member in the pixel P3 depends on the designated gradation.

  FIG. 7 is an xy chromaticity diagram showing the tone of the display color of the pixel P3 for each gradation. Since the reflective liquid crystal display device 300 is a monochrome display reflective liquid crystal display device, an achromatic color (x = 0.3113, y = 0.318) is displayed as the color of the display color of the pixel P3. preferable. However, as shown in FIG. 7, the color of the display color of the pixel P3 is far from the achromatic color. Further, as shown in FIG. 7, the designated gradation in which the distance between the display color and the achromatic color is the longest in the xy chromaticity diagram is 100%. That is, the color shift is maximized during white display.

<A-2: Comparison>
As described above, since the sub-pixel W of the reflective liquid crystal display device 100 has the same structure as the pixel P3 of the reflective liquid crystal display device 300, the display color and achromatic color of the sub-pixel W A gap similar to that in FIG. Therefore, in the reflective liquid crystal display device 100, the data line driving circuit 22 specifies the specified gradations of the sub-pixels W, B, and R constituting the pixel P1 so as to cancel out this shift in the determination process related to each pixel P1. To decide.

  FIG. 8 is a diagram illustrating a correspondence relationship between the designated gradation (%) of the pixel P1 and the designated gradations (%) of the sub-pixels W, B, and R constituting the pixel P1. As is clear from FIG. 8, a plurality of gradations (100%, 80%, 60%, 40%, 20%, and 0%) are prepared as gradations that can be designated for the pixel P1. Each of the gradations includes a designated gradation (first gradation) of the sub-pixel W, a designated gradation (second gradation) of the sub-pixel B, and a designated gradation (second gradation) of the sub-pixel R. Are associated in advance. Note that the illustration of the case where the designated gradation of the pixel P1 is 0% is omitted because the liquid crystal layer 53 is formed of normally black liquid crystal.

  The correspondence relationship shown in FIG. 8 is determined in advance, and the data line driving circuit 22 applies the voltage corresponding to the designated gradation previously associated with the designated gradation of the pixel P1 to the sub-pixel W constituting the pixel P1. , B, and R, the determination process and the application process related to the pixel P1 are executed, and the pixel P1 is driven. Note that “driving” a subpixel means driving the liquid crystal element by applying a voltage to the liquid crystal element included in the subpixel.

  The correspondence relationship shown in FIG. 8 is determined so that the plurality of prepared gradations include two gradations relating to blue. Between the two gradations relating to blue, the designated gradation of the sub-pixel W corresponding to the designated gradation of the pixel P1 is the first gradation, and the designated gradation of the sub-pixel B corresponding to the designated gradation of the pixel P1 is When the second gradation is set, the ratio of the second gradation to the first gradation is different from each other. For example, the ratio of the second gradation to the first gradation is 100/100 = 1 when the designated gradation of a certain pixel P1 is 100%, and when the designated gradation of the pixel P1 is 80%. 100/60 = 5/3.

  Further, the correspondence relationship shown in FIG. 8 is determined so that the plurality of prepared gradations include two gradations relating to red. Between the two gradations related to red, the designated gradation of the sub-pixel W corresponding to the designated gradation of the pixel P1 is the first gradation, and the designated gradation of the sub-pixel R corresponding to the designated gradation of the pixel P1 is When the second gradation is set, the ratio of the second gradation to the first gradation is different from each other. For example, the ratio of the second gradation to the first gradation is 100/60 = 5/3 when the designated gradation of a certain pixel P1 is 60%, and when the designated gradation of the pixel P1 is 40%. Is 80/40 = 2.

Here, how to determine the correspondence shown in FIG. 8 will be described.
First, the designated gradations of the sub-pixels W, B, and R when the designated gradation of the pixel P1 is 100% are determined. Specifically, the designated gradations of the sub-pixels W, B, and R are all 100%. In other words, the reflective liquid crystal display device 100 is designed to display a color close to white when the designated gradations of the sub-pixels W, B, and R are all 100%.

  As shown in FIG. 6, when the designated gradation of the sub-pixels W, B and R is 100%, the reflectance of the non-colored portion (sub-pixel W, transparent portion B2 and transparent portion R2) is about red light. 0.32, about 0.33 for green light, and about 0.28 for blue light. Therefore, the reflectance of the blue portion B1 is about 0.28, and the reflectance of the red portion R1 is about 0.32. Actually, the reflectance of the blue portion B1 is weaker than the reflectance of the blue light in the non-colored portion due to the presence of the color filter, but here, it is assumed that both are equal. The same applies to the red portion R1.

  As shown in FIG. 2, the area ratio of the non-colored portion, the blue portion B1, and the red portion R1 in the display region of the pixel P1 is 10: 1: 1. Therefore, when the designated gradations of the sub-pixels W, B, and R are all set to 100%, the light amount ratio of red light, green light, and blue light in the reflected light of the pixel P1 is approximately 0.32 × 10 + 0. .32 × 1: 0.33 × 10: 0.28 × 10 + 0.28 × 1 = 3.62: 3.3: 3.08.

  Since the ratio of the amount of red light to the amount of green light is 3.62 / 3.3 = about 1.1, the ratio of the amount of red light to the amount of green light (0.32) in the reflected light of the pixel P3. /0.33=about 0.96). Similarly, since the ratio of the blue light amount to the green light amount is 3.08 / 3.3 = about 0.93, the blue light amount relative to the green light amount in the reflected light of the pixel P3. Greater than the ratio (0.28 / 0.33 = about 0.85). Therefore, as shown in FIG. 9, the difference between the color of the display color of the pixel P1 and the color of the achromatic color (x = 0.113, y = 0.318) is different from the color of the display color of the pixel P3. It becomes smaller than the difference from the achromatic color.

  Next, the designated gradations of the sub-pixels W, B, and R when the designated gradation of the pixel P1 is 80% are determined. Assuming that the designated gradations of the sub-pixels W, B and R are both 80%, the reflectance of the non-colored portion (sub-pixel W, transparent portion B2 and transparent portion R2) is red light as shown in FIG. Is about 0.22, green light is about 0.29, and blue light is about 0.31. Therefore, the ratio of the light amount of red light, the light amount of green light, and the light amount of blue light in the reflected light of the pixel P1 is approximately 0.22 × 10 + 0.22 × 1: 0.29 × 10: 0.31 ×. 10 + 0.31 × 1 = 2.42: 2.9: 3.41. Therefore, the ratio of the amount of red light to the amount of green light is 2.42 / 2.9 = about 0.83, and the ratio of the amount of blue light to the amount of green light is 3.41 / 2.9 = about 1. .18.

  Since 0.83 is significantly smaller than 1.1 and 1.18 is significantly larger than 0.93, the difference in color between the display color of the pixel P1 and the achromatic color is the designated floor of the pixel P1. It becomes larger than the difference when the key is 100%. Therefore, the designated gradations of the sub-pixels B and R are determined so that the color of the display color of the pixel P1 with the designated gradation of 80% approaches the color of the display color of the pixel P1 with the designated gradation of 100%. . That is, the designated gradations of the sub-pixels B and R are determined so that the ratio of red light increases and the ratio of blue light decreases in the reflected light of the pixel P1.

  As the designated gradation of the sub-pixel R decreases, the ratio of the reflected light of the sub-pixel R to the reflected light of the pixel P1 decreases. Further, as apparent from FIG. 6, the lower the gradation of the display color of the non-colored portion, the smaller the proportion of red light in the reflected light of the non-colored portion. Therefore, if the designated gradation of the sub-pixel R is increased, the proportion of red light in the reflected light of the pixel P1 can be increased. Therefore, the designated gradation of the sub-pixel R when the designated gradation of the pixel P1 is 80% is set to 100% instead of 80%.

  On the other hand, the ratio of the reflected light of the sub-pixel B to the reflected light of the pixel P1 decreases as the designated gradation of the sub-pixel B decreases. Therefore, in order to reduce the proportion of blue light in the reflected light of the pixel P1, it is natural to lower the designated gradation of the sub-pixel B. However, as is clear from FIG. 6, for this reason, when the designated gradation of the sub-pixel B is reduced from 100% to 80% to 60%, the reflectance of blue light in the reflected light of the non-colored portion is high. It becomes low after becoming. That is, as a method of sufficiently reducing the ratio of blue light in the reflected light of the pixel P1 having a designated gradation of 80%, in addition to the method of reducing the designated gradation of the sub-pixel B from 80% to 60%, 80% There is a way to increase to 100%.

  In the former method, the ratio of blue light in the reflected light of the sub-pixel B is increased, whereas in the latter method, the ratio of blue light in the reflected light of the sub-pixel B is decreased. Since the purpose here is to reduce the proportion of blue light, the latter is preferred. Therefore, the latter is adopted, and the designated gradation of the sub-pixel B when the designated gradation of the pixel P1 is 80% is set to 100% instead of 80%.

  Then, in order to set the gradation of the display color of the pixel P1 to about 80%, the designated gradation of the sub-pixel is set to 60%. As shown in FIG. 6, when the designated gradation is 60%, the reflectance of the non-colored portion is about 0.15 for red light, about 0.17 for green light, and about 0.24 for blue light. Therefore, when the designated gradation of the subpixel W is 60% and the designated gradations of the subpixels B and R are both 100%, the light amounts of red light, green light, and blue light in the reflected light of the pixel P1. The ratio is approximately 0.15 × 4 + 0.32 × 6 + 0.32 × 1: 0.17 × 4 + 0.33 × 6: 0.24 × 4 + 0.28 × 6 + 0.28 × 1 = 2.84: 2.66 2.92, the light quantity ratio of red light to green light is 2.84 / 2.66 = about 1.07, and the light quantity ratio of blue light to green light is 2.92 / 2.66 = about 1.1. It becomes.

  1.1-1.07 = 0.03 <1.1-0.83 = 0.27, 1.1-0.93 = 0.17 <1.18-0.93 = 0.25 Therefore, by setting the designated gradations of the sub-pixels B and R to 100% and the designated gradation of the sub-pixel W to 60%, the light quantity ratio of the red light to the green light is 1 in the reflected light of the pixel P1. .1 and the light quantity ratio of blue light to green light approaches 0.93.

  Next, the designated gradations of the sub-pixels W, B, and R when the designated gradation of the pixel P1 is 60% are determined. Assuming that the designated gradations of the sub-pixels W, B, and R are both 60%, the reflectance of the non-colored portion is about 0.15 for red light and about 0 for green light, as shown in FIG. .22, about 0.24 for blue light. The ratio of the amount of red light, the amount of green light, and the amount of blue light in the reflected light of the pixel P1 is approximately 0.15 × 10 + 0.15 × 1: 0.22 × 10: 0.24 ×. 10 + 0.24 × 1 = 1.65: 2.2: 2.64 Therefore, the ratio of the amount of red light to the amount of green light is 1.65 / 2.2 = about 0.75, and the ratio of the amount of blue light to the amount of green light is 2.64 / 2.2 = about 1. .2.

  Since 0.75 is significantly smaller than 1.1 and 1.2 is significantly larger than 0.93, the designated gradations of the sub-pixels B and R are determined as in the case of 80%. Specifically, the designated gradation of the subpixel B is 20%, and the designated gradation of the subpixel R is 100%. When the designated gradation of the sub-pixel B is 20%, as shown in FIG. 6, the reflectance of the transparent portion B2 is about 0.05 for red light, about 0.075 for green light, and blue light. Is about 0.09.

  Therefore, when the designated gradation of the subpixel W is 60%, the designated gradation of the subpixel B is 20%, and the designated gradation of the subpixel R is 100%, red light and green light in the reflected light of the pixel P1. The ratio of light quantity to blue light is approximately 0.15 × 4 + 0.32 × 3 + 0.05 × 3 + 0.32 × 1: 0.17 × 4 + 0.33 × 3 + 0.075 × 3: 0.24 × 4 + 0.28 × 3 + 0.09 × 3 + 0.09 × 1 = 2.03: 1.895: 2.16 The ratio of the amount of red light to green light is 2.03 / 1.895 = 1.07, which is about 1.07. The light quantity ratio of blue light is 2.16 / 1.895 = 1.14.

1.1-1.07 = 0.03 <1.1-0.75 = 0.35, 1.14-0.93 = 0.21 <1.2-0.93 = 0.27 Therefore, by setting the designated gradation of the sub-pixel B to 20%, the designated gradation of the sub-pixel R to 100%, and the designated gradation of the sub-pixel W to 60%, green light is reflected in the reflected light of the pixel P1. The light quantity ratio of red light to light approaches 1.1, and the light quantity ratio of blue light to green light approaches 0.93.
In this way, the designated gradations of the sub-pixels W, B, and R are determined even when the designated gradation of the pixel P1 is 40% and 20%.

  FIG. 10 is an xy chromaticity diagram illustrating the display colors of the pixels P1 and P3 for each gradation. In the present embodiment, since the designated gradation of the pixel P1 and the designated gradations of the sub-pixels W, B, and R are associated as described above, a plurality of prepared gradations are provided as shown in FIG. , The difference between the color of the display color of the pixel P1 and the color of the achromatic color (x = 0.3113, y = 0.318) is the difference between the color of the display color of the pixel P3 and the color of the achromatic color. And smaller than the difference. As a result, the color variation range of the display color of the pixel P1 over a plurality of prepared gradations is narrower than the color variation range of the display color of the pixel P3 with respect to the prepared plurality of gradations.

  That is, according to the reflective liquid crystal display device 100, the pixel P1 including a plurality of subpixels is provided, and the plurality of subpixels include an uncolored subpixel W, a blue subpixel B, and a red subpixel R. Therefore, since the sub pixel B can display blue and the sub pixel R can display red, it is possible to suppress the color shift between the display color and the achromatic color.

<B: Modification 1>
FIG. 11 is a plan view of a pixel P4 included in the reflective liquid crystal display device according to the first modification obtained by modifying the first embodiment. As illustrated in FIG. 11, the pixel P4 includes subpixels W and B, but does not include the subpixel R. Further, the display area of the sub-pixel B and the color filter 57B included in the sub-pixel B are completely overlapped with each other in the vertical direction (Z direction) in FIG. As described above, the color displayed in the non-colored portion at the time of white display is yellowish green that is close to yellow. Therefore, even if the subpixel R is not provided, the designated gradation of the pixel P4 and the subpixels W and B By appropriately associating with the designated gradation, the color shift can be suppressed to some extent. Note that, similarly to the first embodiment, the sub-pixel B may include an uncolored transparent portion.

<C: Modification 2>
FIG. 12 is a plan view of a pixel P5 included in the reflective liquid crystal display device according to the second modification obtained by modifying the first embodiment. As shown in FIG. 12, the pixel P5 includes a sub-pixel G in addition to the sub-pixels W, B, and R. The sub-pixel G includes a color filter that has a high transmittance in the wavelength band of green light in the visible light wavelength band and a low transmittance in other wavelength bands. In each of the sub-pixels B, R, and G, the display area and the color filter completely overlap in the direction perpendicular to the paper surface (Z direction) in FIG. According to this reflection type liquid crystal display device, even if the display color of the sub-pixel W is any chromatic color, the color shift of the display color of the pixel P5 can be suppressed. Note that at least one of the sub-pixels B, R, and G may include a non-colored transparent portion as in the first embodiment.

<D: Modification 3>
In the first embodiment, the sub-pixels B and R are provided with a transparent portion to suppress the decrease in the reflectance of the pixels. However, this is modified and the color filters 57B and 57R are thinned to reflect the pixels. You may make it suppress the fall of a rate. This modification is also possible for Modifications 1 and 2. Moreover, you may employ | adopt an optical film as a color filter.

<E: Second Embodiment>
FIG. 13 is a diagram showing an overall configuration of a reflective liquid crystal display device (second reflective liquid crystal display device) 200 according to the second embodiment of the present invention. The reflective liquid crystal display device 200 is a monochrome display reflective liquid crystal display device, and is obtained by modifying the reflective liquid crystal display device 300. The reflective liquid crystal display device 200 includes a pixel P2 instead of the pixel P3.

  FIG. 14 is a cross-sectional view of the pixel P2. As shown in FIG. 14, the pixel P <b> 2 is different from the pixel P <b> 3 only in that a polarizing plate 58 is provided instead of the polarizing plate 56. FIG. 15 is a diagram illustrating the wavelength dispersion of the transmittance of the polarizing plate 56, and FIG. 16 is a diagram illustrating the wavelength dispersion of the transmittance of the polarizing plate 58. As is clear from both figures, the polarizing plate 58 is different from the polarizing plate 56 in that the transmittance for the wavelength band of blue light in the wavelength band of visible light is higher than the transmittance for other wavelength bands. In other words, the polarizing plate 58 differs from the polarizing plate 56 in that the degree of polarization with respect to the wavelength band of blue light in the wavelength band of visible light is lower than the degree of polarization with respect to other wavelength bands.

  FIG. 17 is a diagram illustrating the wavelength dispersion of the reflectance of the pixel P2 and the pixel P3 in the case of white display. As shown in FIG. 17, in the pixel P3 according to the comparative example, the reflectance is reduced particularly in the wavelength band of blue light in the wavelength band of visible light, but in the pixel P2 of the reflective liquid crystal display device 200, The decrease is suppressed. As a result, as shown in the xy chromaticity diagram of FIG. 18, the deviation between the display color tone and the achromatic color tone in the reflective liquid crystal display device 200 in the case of white display is smaller than the deviation in the comparative example. Become.

<F: Modification 4>
The second embodiment may be modified, and instead of the polarizing plate 58, a polarizing plate in which the transmittance for the wavelength band of red light in the visible light wavelength band is higher than the transmittance for the other wavelength bands may be used. A polarizing plate in which the transmittance with respect to the wavelength band of blue and red light in the wavelength band of visible light is higher than the transmittance with respect to other wavelength bands may be used. In addition, mono color display may be performed. Even in the case of monocolor display, it is beneficial to suppress color misregistration of the display color of the highest gradation.

<G: Modification 5>
The first embodiment may be modified to perform monocolor display. In this case, a data line driving circuit (second driving unit) different from the data line driving circuit 22 is required. Each pixel includes a first sub-pixel having a single chromatic color (first color) and a second sub-pixel having a second color different from the first color. Further, each of a plurality of gradations from the highest gradation to the lowest gradation includes a designated gradation (third gradation) of the first sub-pixel and a designated gradation (fourth gradation) of the second sub-pixel. Are associated with each other in advance, and the second driving unit applies a voltage corresponding to the gray level corresponding to the gray level specified by the gray level signal g to each of the sub-pixels. According to the reflection type liquid crystal display device (third reflection type liquid crystal display device) of this embodiment, even in the case of monocolor display, it is possible to suppress the color shift of the display color of the highest gradation and the color shift between gradations. it can. Note that the pixel may further include one or more sub-pixels having colors different in both the first color and the second color.

<H: Application example>
Next, an electronic apparatus using the reflective liquid crystal display device 100 or 200 according to each of the above aspects will be described. 19 to 21 exemplify forms of electronic devices that employ the reflective liquid crystal display device 100 or 200 as a display device.

  FIG. 19 is a perspective view showing the configuration of a portable personal computer that employs the reflective liquid crystal display device 100 or 200. The personal computer 2000 includes a reflective liquid crystal display device 100 or 200 that displays various images, and a main body 2010 on which a power switch 2001 and a keyboard 2002 are installed.

  FIG. 20 is a perspective view showing a configuration of a mobile phone to which the reflective liquid crystal display device 100 or 200 is applied. The cellular phone 3000 includes a plurality of operation buttons 3001, scroll buttons 3002, and a reflective liquid crystal display device 100 or 200 that displays various images. By operating the scroll button 3002, the screen displayed on the reflective liquid crystal display device 100 or 200 is scrolled.

  FIG. 21 is a perspective view showing a configuration of a personal digital assistant (PDA) to which the reflective liquid crystal display device 100 or 200 is applied. The portable information terminal 4000 includes a plurality of operation buttons 4001, a power switch 4002, and the reflective liquid crystal display device 100 or 200 that displays various images. When the power switch 4002 is operated, various information such as an address book and a schedule book are displayed on the reflective liquid crystal display device 100 or 200.

DESCRIPTION OF SYMBOLS 10 ... Display surface, 20, 30 ... Driver IC, 22, 24 ... Data line drive circuit, 52 ... Reflection electrode, 53 ... Liquid crystal layer, 56, 58 ... Polarizing plate, 57B, 57R ... Color Filter, 100, 200, 300... Reflective liquid crystal display device, P1 to P5... Pixel, W, R, B.

Claims (9)

A pixel that reflects light and displays a color on a display surface; and a first drive unit that drives the pixel based on a gradation signal that specifies any one of a plurality of gradations ;
The pixel is composed of a plurality of sub-pixels each reflecting light and displaying a color on the display surface,
Each of the plurality of sub-pixels includes a reflective surface that reflects light, and a liquid crystal layer disposed between the reflective surface and the display surface,
The plurality of sub-pixels include a non-colored achromatic sub-pixel and one or more chromatic sub-pixels of a single chromatic color,
The one or more chromatic color subpixel look containing a chromatic color sub-pixels of the blue,
Each of the plurality of gradations includes a first gradation of the achromatic sub-pixel and a second gradation of a specific chromatic sub-pixel among the one or more chromatic sub-pixels with respect to the gradation. Are associated in advance,
The first driving unit applies a voltage corresponding to the first gradation corresponding to the gradation specified by the gradation signal to the achromatic color sub-pixel, and applies the voltage to the specific chromatic color sub-pixel. On the other hand, a voltage corresponding to the second gradation corresponding to the gradation specified by the gradation signal is applied,
The plurality of gradations include gradations in which the ratio of the second gradation to the first gradation is different from each other.
Reflective liquid crystal display device. The one or more chromatic color sub-pixels include a red chromatic color sub-pixel ,
The reflective liquid crystal display device according to claim 1. The one or more chromatic color sub-pixels include a green chromatic color sub-pixel ,
The reflective liquid crystal display device according to claim 1. Each of at least one chromatic color sub-pixel among the one or more chromatic color sub-pixels includes a color filter of the color,
The color filter is disposed between the liquid crystal layer and the display surface and overlaps the reflection surface in a direction orthogonal to the display surface .
The reflective liquid crystal display device according to claim 1. In each of the at least one chromatic subpixel,
The reflective surface has a portion that does not overlap the color filter in the direction .
The reflective liquid crystal display device according to claim 4.   The specific chromatic color sub-pixel is a blue chromatic color sub-pixel,
  The plurality of gradations are a high gradation and a lower gradation in which the gradation is lower than the high gradation and the ratio is smaller than the ratio when the gradation specified by the gradation signal is the high gradation. Including key,
  The reflective liquid crystal display device according to claim 1.   The plurality of gradations are lower in gradation than the high gradation and higher in gradation than the low gradation, and more than the ratio when the gradation specified by the gradation signal is the high gradation. Including medium tones where the ratio increases,
  The reflective liquid crystal display device according to claim 6.   The specific chromatic color sub-pixel is a red chromatic color sub-pixel,
  The plurality of gradations are a high gradation and a lower gradation in which the gradation is lower than the high gradation, and the ratio is larger than the ratio when the gradation specified by the gradation signal is the high gradation. Including key,
  The reflective liquid crystal display device according to claim 1. An electronic apparatus comprising the reflective liquid crystal display device according to claim 1.

Images