JP2006078541A - Liquid crystal display device and electronic appliance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transflective and reflective liquid crystal display device with which desired transmissive display quality is realized. <P>SOLUTION: The liquid crystal display device has a transmissive display region T and a reflective display region R, wherein layer thickness dr of a liquid crystal layer 50 in the reflective display region R is larger than layer thickness dt of the liquid crystal layer 50 in the transmissive display region T. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device and an electronic apparatus, and more particularly to a transflective liquid crystal display device that performs both transmissive display and reflective display.

  A so-called transflective liquid crystal display device that combines two display methods, a reflective display and a transmissive display, consumes power by switching to either the reflective mode or the transmissive mode depending on the ambient brightness. It is possible to perform clear display even when the surroundings are dark while reducing the above. As this type of transflective liquid crystal display device, a liquid crystal display device has been proposed in which a reflective film having a light transmissive portion is provided on the inner surface of a lower substrate, and this reflective film functions as a transflective film. In this case, in the reflection mode, external light incident from the upper substrate side is reflected by the reflective film on the inner surface of the lower substrate after passing through the liquid crystal layer, and is emitted again from the upper substrate side after passing through the liquid crystal layer, thereby contributing to display. On the other hand, in the transmission mode, light from the backlight incident from the lower substrate side is transmitted through the liquid crystal layer from the light transmission portion of the reflective film and then emitted to the outside from the upper substrate side, contributing to display. In this case, the region where the light transmission part of the reflective film is formed becomes the transmissive display region, and the other region becomes the reflective display region.

  In a transflective liquid crystal display device, the change in the polarization state is a function of the product (retardation Δn · d) of the refractive index anisotropy Δn of the liquid crystal and the layer thickness d of the liquid crystal layer, so this value is optimized. By doing so, a display with good visibility can be obtained. However, since the transmissive display light passes through the liquid crystal layer only once while the reflective display light passes back and forth through the liquid crystal layer twice, the retardation Δn · It is difficult to optimize d. Therefore, if the liquid crystal layer thickness is set so that the visibility of the reflective display is improved, the transmissive display is sacrificed. Conversely, when the liquid crystal layer thickness is set so that the visibility of the transmissive display is improved, the reflective display is sacrificed.

Therefore, Patent Document 1 below discloses a configuration in which the liquid crystal layer thickness in the reflective display region is smaller than the liquid crystal layer thickness in the transmissive display region. Such a configuration is called a multi-gap method. For example, a liquid crystal layer thickness adjusting layer having an opening corresponding to a transmissive display region is provided on the lower layer side of the transparent electrode on the lower substrate and the upper layer side of the reflective film. Can be realized. That is, in the transmissive display area, the thickness of the liquid crystal layer is increased by the thickness of the liquid crystal layer thickness adjusting layer as compared with the reflective display area. Therefore, the retardation Δn · d is set for both the transmissive display light and the reflective display light. Can be optimized. For example, specifically, if the thickness of the liquid crystal layer in the transmissive display area is approximately twice the thickness of the liquid crystal layer in the reflective display area, the retardation of the transmissive display area and the reflective display area can be matched. As a result, display with high contrast can be obtained for both transmissive display and reflective display.
Japanese Patent Laid-Open No. 11-242226

  In the recent market for transflective liquid crystal display devices, display quality at the time of transmission tends to be more important than display quality at the time of reflection. However, in the conventional liquid crystal display device adopting the multi-gap method, the liquid crystal layer thickness in the reflective display region is thinner than the liquid crystal layer thickness in the transmissive display region. Due to this limitation, the thickness of the liquid crystal layer in the transmissive display region cannot be made very thin. For this reason, it is difficult to obtain a desired transmissive display quality even though it is desired to emphasize the display quality during transmission. For example, even if it is found that the liquid crystal layer thickness in the transmissive display region is preferably 2 μm in device design, in that case, the liquid crystal layer thickness in the reflective display region must be 1 μm, and the liquid crystal layer thickness is 1 μm. Since it is difficult to actually form the liquid crystal cell in the liquid crystal cell, there is a problem that the liquid crystal layer thickness of 2 μm in the transmissive display region cannot be realized.

  Further, as described in the above-mentioned conventional Patent Document 1, in order to adjust the thickness of the liquid crystal layer using the liquid crystal layer thickness adjusting layer, it is necessary to form the liquid crystal layer thickness adjusting layer to be considerably thick. For example, a photosensitive resin is suitably used for forming the thick layer. However, if such a configuration is to be realized in a liquid crystal cell, it is difficult to form a stepped step, and a slope portion (inclined portion) of a photosensitive resin is formed at the boundary portion between the transmissive display area and the reflective display area. It is inevitable that it will be made. Therefore, there is a problem that the liquid crystal is aligned obliquely with respect to the substrate surface in the slope portion while this is a vertical alignment mode, and this portion causes a decrease in display contrast.

  The present invention has been made to solve the above-described problems, and provides a transflective liquid crystal display device capable of realizing a desired transmissive display quality, and an electronic apparatus including the same. With the goal.

  In order to achieve the above object, a liquid crystal display device of the present invention is a liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of substrates, and is incident from the outer surface of one of the pair of substrates. A liquid crystal layer in the reflective display area, and a transmissive display area that transmits transmissive light and performs transmissive display; and a reflective display area that reflects light incident from the outer surface of the other substrate and performs reflective display. The layer thickness of the liquid crystal layer is larger than the layer thickness of the liquid crystal layer in the transmissive display region.

  In the configuration of the present invention, the liquid crystal layer thickness in the reflective display region is larger than the liquid crystal layer thickness in the transmissive display region, contrary to the conventional multi-gap liquid crystal display device. The liquid crystal layer thickness in the transmissive display area can be set appropriately without being restricted on the reflective display area side. As a result, it is possible to obtain a desired transmissive display quality while maintaining the reflective display, and it is possible to provide a technique suitable for a liquid crystal display device that emphasizes transmissive display.

In the above-described liquid crystal display device of the present invention, the liquid crystal layer thickness adjustment is made such that the thickness of the liquid crystal layer in the reflective display region is larger than the thickness of the liquid crystal layer in the transmissive display region on the inner surface of at least one of the pair of substrates. It is desirable to provide a layer.
According to this configuration, a liquid crystal display having a difference in liquid crystal layer thickness between the reflective display region and the transmissive display region as described above, for example, by forming a liquid crystal layer thickness adjusting layer using a photosensitive resin or the like on the substrate. The apparatus can be easily realized.

In addition, it is desirable that the thickness of the liquid crystal layer in the reflective display region is approximately 1.5 times the thickness of the liquid crystal layer in the transmissive display region.
Generally, the transmittance-voltage characteristics (TV characteristics) are different between the reflective display area and the transmissive display area. However, when the layer thickness relationship is set as described above, a location where the peak positions of the reflective display and transmissive display TV curves coincide with each other occurs, so that the reflective display region and the transmissive display region are formed in the liquid crystal layer. By applying the same voltage, bright and dark display is possible in both reflective display and transmissive display. Regarding the TV curve of the reflective display and the transmissive display when the thickness of the liquid crystal layer in the reflective display area is 1.5 times the liquid crystal layer thickness of the transmissive display area, the section of [Best Mode for Carrying Out the Invention] This will be shown in detail. In addition, the conventional multi-gap structure has a liquid crystal layer thickness of the transmissive display region twice that of the reflective display region, whereas the multi-gap structure of the present invention has a liquid crystal layer thickness of the reflective display region of transmissive display. Since the thickness of the liquid crystal layer in the region is 1.5 times, the liquid crystal layer thickness adjusting layer formed using a photosensitive resin or the like can be thin. Therefore, it is possible to suppress a decrease in contrast due to the slope portion (inclined portion) of the liquid crystal layer thickness adjusting layer. In addition, the liquid crystal layer thickness adjusting layer can be manufactured easily by reducing the layer thickness.

Alternatively, it is desirable that the voltage applied to the liquid crystal layer is different between the reflective display region and the transmissive display region.
As described above, since the TV characteristics are different between the reflective display area and the transmissive display area, if the liquid crystal layer thickness of the reflective display area is not 1.5 times the liquid crystal layer thickness of the transmissive display area, The positions of the peaks of the TV curves in the display and the transmission display do not match. In that case, if the voltage applied to the liquid crystal layer is different between the reflective display area and the transmissive display area, that is, if different voltages corresponding to the peak positions of the TV curves of the reflective display and transmissive display are applied, Bright and dark display is possible for both display and transmissive display.

  Further, when considering color display, that is, when having a plurality of sub-pixel regions that perform different color display of red (R), green (G), and blue (B), the layer thickness of the liquid crystal layer in the reflective display region is It is desirable to set so that the blue subpixel region, the green subpixel region, and the red subpixel region increase in this order. Alternatively, it is desirable that the voltage applied to the liquid crystal layer in the reflective display region is set to increase in the order of the blue subpixel region, the green subpixel region, and the red subpixel region.

  Considering the color light of different colors (wavelengths), the retardation is different for each color (wavelength) due to the wavelength dispersion of the refractive index, and the TV characteristics are different. Specifically, the retardation increases in the order of blue light, green light, and red light, and the TV curve of the reflective display shifts to the higher voltage side in the order of blue light, green light, and red light. Therefore, the contrast of the reflective display can be optimized for each color by setting the liquid crystal layer thickness or the applied voltage in the blue subpixel region, the green subpixel region, and the red subpixel region as described above. .

The liquid crystal layer is preferably made of a liquid crystal having an initial alignment state substantially perpendicular to the substrate surface and a negative dielectric anisotropy.
The present invention is suitable for a vertical alignment mode liquid crystal display device, and according to this configuration, a liquid crystal display device having a high contrast and a wide viewing angle can be realized.

An electronic apparatus according to the present invention includes the liquid crystal display device according to the present invention.
According to this configuration, it is possible to realize an electronic apparatus including a transflective liquid crystal display unit that is particularly excellent in transmissive display quality.

[First Embodiment]
A first embodiment of the present invention will be described below with reference to FIGS.
In this embodiment, an example of an active matrix transflective liquid crystal display device will be described. FIG. 1 is a plan view of the liquid crystal display device according to the present embodiment as viewed from the counter substrate side together with each component, and FIG. 2 is a cross-sectional view taken along the line HH ′ of FIG. FIG. 3 is an equivalent circuit diagram of various elements and wirings in a plurality of pixels formed in a matrix in the image display region of the electro-optical device (liquid crystal display device). In each drawing used in the following description, the scale is different for each layer and each member so that each layer and each member can be recognized on the drawing.

[Overall configuration of liquid crystal display]
As shown in FIGS. 1 and 2, in the liquid crystal display device 100 of the present embodiment, the TFT array substrate 10 and the counter substrate 20 are bonded together by a sealing material 52, and the liquid crystal is in a region partitioned by the sealing material 52. Layer 50 is encapsulated. A light shielding film (peripheral parting) 53 made of a light shielding material is formed in a region inside the region where the sealing material 52 is formed. A data line driving circuit 201 and an external circuit mounting terminal 202 are formed along one side of the TFT array substrate 10 in a region outside the sealing material 52, and the scanning line driving circuit is formed along two sides adjacent to the one side. 204 is formed. On the remaining side of the TFT array substrate 10, a plurality of wirings 205 are provided for connecting between the scanning line driving circuits 204 provided on both sides of the image display area. In addition, an inter-substrate conductive material 206 for providing electrical continuity between the TFT array substrate 10 and the counter substrate 20 is disposed at a corner portion of the counter substrate 20.

  Instead of forming the data line driving circuit 201 and the scanning line driving circuit 204 on the TFT array substrate 10, for example, a TAB (Tape Automated Bonding) substrate on which a driving LSI is mounted and terminals on the TFT array substrate 10 are used. The groups may be connected via an anisotropic conductive film. In the liquid crystal display device 100, depending on the type of liquid crystal to be used, that is, depending on the operation mode such as TN (Twisted Nematic) mode, STN (Super Twisted Nematic) mode, and normally white mode / normally black mode. Although a phase difference plate, a polarizing plate, and the like are arranged in a predetermined direction, illustration is omitted here.

  In the image display area of the liquid crystal display device 100 having such a structure, as shown in FIG. 3, a plurality of dots (sub-pixels) 100a are configured in a matrix, and each of these dots 100a has , A pixel switching TFT 30 is formed, and a data line 6 a for supplying pixel signals S 1, S 2,..., Sn is electrically connected to the source of the TFT 30. Pixel signals S1, S2,..., Sn to be written to the data lines 6a may be supplied line-sequentially in this order, or may be supplied for each group to a plurality of adjacent data lines 6a. . Further, the scanning line 3a is electrically connected to the gate of the TFT 30, and the scanning signals G1, G2,..., Gm are applied to the scanning line 3a in a pulse-sequential manner in this order at a predetermined timing. It is configured. The pixel electrode 9 is electrically connected to the drain of the TFT 30, and the pixel signal S1, S2,..., Sn supplied from the data line 6a is obtained by turning on the TFT 30 as a switching element for a certain period. Write to each pixel at a predetermined timing. The pixel signals S1, S2,..., Sn written in the liquid crystal via the pixel electrode 9 in this way are held for a certain period with the counter electrode 21 of the counter substrate 20 shown in FIG. Further, in order to prevent the held pixel signals S1, S2,..., Sn from leaking, a storage capacitor 60 is added in parallel with the liquid crystal capacitor formed between the pixel electrode 9 and the counter electrode 21. Reference numeral 3 b denotes a capacity line constituting the storage capacity 60.

[Detailed configuration of one sub-pixel]
FIG. 4 is a plan view showing a schematic configuration of one sub pixel 100a constituting an image of the liquid crystal display device 100 of the present embodiment. FIG. 5 is a cross-sectional view taken along line AA ′ of FIG. Note that wiring such as data lines 6a and scanning lines 3a and TFTs 30 are actually formed on the TFT array substrate 10, but illustration of these wirings and TFTs is omitted in FIG. The liquid crystal display device 100 of the present embodiment performs color display, and one pixel is composed of three adjacent sub-pixels of R (red), G (green), and B (blue).

  As shown in FIG. 4, an area defined by a light shielding film 40 (black matrix) provided in a grid pattern on a counter substrate described later constitutes one sub-pixel 100a. A reflective film 42 is provided on the counter substrate. An opening 42 a is provided at the center of the reflective film 42. With this configuration, the opening 42a of the reflective film 42 allows the transmissive display region T that performs transmissive display using light emitted from a backlight, which will be described later, and external light that is incident on the portion where the reflective film 42 is present from the upper substrate side. The reflective display region R is used for reflective display. The reflective display region R is configured to scatter and emit reflected light as will be described later.

  As shown in FIG. 5, the liquid crystal display device 100 according to the present embodiment has a basic structure in which a liquid crystal layer 50 is sandwiched between a TFT array substrate 10 made of transparent glass or the like and arranged opposite to each other and a counter substrate 20. It has. The liquid crystal layer 50 is composed of a liquid crystal having a negative dielectric anisotropy whose initial alignment state is vertical alignment. A liquid crystal having a refractive index anisotropy Δn of 0.1, a dielectric constant (vertical) εv of 9, a dielectric constant (parallel) εp of 4, and an elastic coefficient of K11 = 10, K22 = 5, K33 = 15 is used. .

  The counter substrate 20 is composed of a substrate body 1a made of transparent glass, quartz or the like. On the outer surface side of the counter substrate 20, a backlight 60 including a light source 61, a light guide plate 62, and the like is provided. The phase difference plate 12 and the polarizing plate 13 are disposed on the outer surface side (observer side) of the TFT array substrate 10, and the phase difference plate 14 and the polarizing plate are also disposed on the outer surface side (backlight 60 side) of the counter substrate 20. 15 are arranged. The polarizing plates 13 and 15 transmit only linearly polarized light in one direction with respect to external light incident from the upper side and backlight light incident from the lower side. The retardation plates 12 and 14 convert linearly polarized light transmitted through the polarizing plates 13 and 15 into substantially circularly polarized light (including elliptically polarized light). Therefore, the polarizing plates 13 and 15 and the retardation plates 12 and 14 function as circularly polarized light incident means. The transmission axes of the two polarizing plates 13 and 15 are arranged orthogonally (crossed Nicols).

  On the inner surface side of the counter substrate 20, a reflective film 42 made of a metal material having a high light reflectance such as aluminum or silver is formed. As described above, the opening 42 a constituting the transmissive display region T is provided at the center of the reflective film 42. On the surface of the reflective film 42, irregularities reflecting the surface shape of the base insulating layer 25 made of, for example, acrylic resin are formed. Reflected light is scattered by the unevenness, and the visibility of the reflective display is improved. On the reflective film 42 including the inside of the opening 42 a on the inner surface side of the counter substrate 20, a color filter 45 having R, G, and B colored layers is provided.

  In the present embodiment, the uniform color filter 45 is provided in the transmissive display region T and the reflective display region R. Instead of this configuration, a color filter is provided in the transmissive display region T and the reflective display region R. Differently, spectral characteristics are different between the color filter for transmissive display and the color filter for reflective display, and the color purity of the color filter for transmissive display may be higher than that of the color filter for reflective display. With this configuration, it is possible to adjust the balance of color density in the transmissive display area T and the reflective display area R.

  On the color filter 45, a liquid crystal layer thickness adjusting layer (insulating layer) 46 for forming a thick layer region and a thin layer region in the liquid crystal layer 50 is formed corresponding to the transmissive display region T. Yes. Specifically, by forming the liquid crystal layer thickness adjusting layer 46, the layer thickness of the liquid crystal layer 50 in the reflective display region R is larger than the layer thickness of the liquid crystal layer 50 in the transmissive display region T. In the present embodiment, the liquid crystal layer thickness dr of the reflective display region R is 7.2 μm, the liquid crystal layer thickness dt of the transmissive display region T is 4.8 μm, and the liquid crystal layer thickness dr of the reflective display region R is transmissive display region T. The liquid crystal layer thickness dt is 1.5 times. Although not shown, the boundary region between the reflective display region R and the transmissive display region T at the edge of the liquid crystal layer thickness adjusting layer 46 is actually an inclined surface inclined at a predetermined angle from the substrate surface. . For the liquid crystal layer thickness adjusting layer 46, an insulating material having translucency such as a photosensitive acrylic resin is used.

  The counter electrode 21 made of a transparent conductive film such as indium tin oxide (hereinafter abbreviated as ITO) covers the color filter 45 and the liquid crystal layer thickness adjusting layer 46 on the inner surface of the counter substrate 20. In addition, a vertical alignment film 22 made of a polymer material film such as polyimide is formed on the counter electrode 21.

  On the other hand, the TFT array substrate 10 is composed of a substrate body 2a made of transparent glass, quartz or the like. A pixel electrode 9 made of a transparent conductive film such as ITO is provided on the inner surface side of the TFT array substrate 10. On the pixel electrode 9, as in the counter substrate 20 side, a vertical alignment film 23 made of a polymer material film such as polyimide is formed. Both the alignment films of the TFT array substrate 10 and the counter substrate 20 have been subjected to a vertical alignment process, but a pretilt may be imparted to the liquid crystal molecules by a rubbing process or the like.

  According to the liquid crystal display device 100 of the present embodiment, the liquid crystal layer thickness dr of the reflective display region R is larger than the liquid crystal layer thickness dt of the transmissive display region T, contrary to the conventional multi-gap type liquid crystal display device. The upper liquid crystal layer thickness is not restricted on the reflective display region side, and the liquid crystal layer thickness in the transmissive display region can be set appropriately. As a result, it is possible to obtain a desired transmissive display quality while maintaining the reflective display, and it is possible to provide a technique suitable for a liquid crystal display device that emphasizes transmissive display. Further, since the liquid crystal layer thickness dr of the reflective display region R is set to 1.5 times the liquid crystal layer thickness dt of the transmissive display region T, the same voltage is applied to the liquid crystal layers in the reflective display region R and the transmissive display region T. When applied, bright and dark display is possible in both reflective display and transmissive display. The grounds are explained below.

  FIG. 6 shows a simulation result performed by the present inventor, and shows transmittance-voltage characteristics (TV curve) in reflective display and transmissive display in the liquid crystal display device 100 of the present embodiment. . In this embodiment, Δn of the liquid crystal layer 50 is 0.1, the liquid crystal layer thickness dr of the reflective display region R is 7.2 μm, and the liquid crystal layer thickness dt of the transmissive display region T is 4.8 μm. The retardation of the transparent display area T is 0.72, and the retardation of the transmissive display area T is 0.48. The TV curve of reflection display with retardation 0.72 is indicated by a solid line, and the TV curve of transmission display with retardation 0.48 is indicated by a one-dot chain line. On the other hand, as a comparative example of reflective display, a conventional multi-gap structure, that is, when the liquid crystal layer thickness of the reflective display region is ½ of the transmissive display region (the liquid crystal layer thickness of the reflective display region is 2.4 μm and the retardation is 0). .24) is shown by a broken line.

  As can be seen from FIG. 6, the transmission curve TV curve (dotted line) having a retardation of 0.48 and the reflection curve TV curve (dashed line) having a retardation of 0.24 substantially coincide with each other. It can be seen that a good contrast can be obtained for both transmissive display and reflective display with this multi-gap structure. However, the conventional multi-gap structure has a disadvantage that the liquid crystal layer thickness is restricted on the reflective display region side, which is disadvantageous for the design of transmissive display. On the other hand, when the transmission curved TV curve with a retardation of 0.48 (one-dot chain line) and the reflective curved TV curve with a retardation of 0.72 (solid line) are compared, the shape of the curve is completely different. The peak positions of the curves match at the voltage V = 3.1V. Therefore, for example, when the liquid crystal is driven at a voltage V = 0 V (no voltage applied state) and a voltage V = 3.1 V, both the reflective display and the transmissive display are dark display with the voltage V = 0 V (the orthogonality of the two polarizing plates). Bright display (transmittance of transmissive display: 48%, transmissivity of reflective display: 42%) can be performed at a voltage V = 3.1V.

  Further, in the case of the present embodiment, since the liquid crystal layer thickness dr of the reflective display region R is set to 1.5 times the liquid crystal layer thickness dt of the transmissive display region T, liquid crystal formed using a photosensitive acrylic resin or the like. The layer thickness of the layer thickness adjusting layer 46 may be thinner than that of the conventional multi-gap structure (twice). Therefore, the area of the slope portion (inclined portion) of the liquid crystal layer thickness adjusting layer 46 is reduced, and a reduction in contrast due to the slope portion can be suppressed. Further, the liquid crystal layer thickness adjusting layer 46 can be manufactured easily by reducing the layer thickness.

  In this embodiment, the liquid crystal layer thickness dr of the reflective display region R is set to 1.5 times the liquid crystal layer thickness dt of the transmissive display region T, and the reflective display and the transmissive display are driven with the same applied voltage. Although shown, the applied voltage to the liquid crystal layer 50 is different between the reflective display region R and the transmissive display region T without changing the liquid crystal layer thickness of the reflective display region R to 1.5 times the liquid crystal layer thickness of the transmissive display region T. It is good also as a structure to make.

  Unlike the case of FIG. 6, when the liquid crystal layer thickness of the reflective display region R is not 1.5 times the liquid crystal layer thickness of the transmissive display region T, the peak positions of the TV curves of the reflective display and the transmissive display match. do not do. Therefore, in this case, different voltages are used in the reflective display region R and the transmissive display region T, that is, voltages in which the TV curve has a peak in the reflective display region R, and voltages in which the TV curve has a peak in the transmissive display region T. When applied to each region, bright and dark display is possible in both reflective display and transmissive display. Specific means for differentiating the voltage applied to the liquid crystal layer 50 between the reflective display region R and the transmissive display region T are as follows: (1) The reflective display region R and the transmissive display region T are separated into separate TFTs (switching elements). (2) Dielectric films having different film thicknesses on the pixel electrode 9 in the reflective display region R and the transmissive display region T even when driven by the same TFT (switching element) and pixel electrode A method of changing the voltage that is effectively applied to the liquid crystal layer 50 by arranging the liquid crystal layer 50 can be considered.

[Second Embodiment]
The second embodiment of the present invention will be described below with reference to FIG.
The basic configuration of the liquid crystal display device of this embodiment is exactly the same as that of the first embodiment, and is different from the first embodiment only in that the configuration is changed for each sub-pixel of a different color. Therefore, the description of the basic components of the liquid crystal display device is omitted.

  In the liquid crystal display device of this embodiment, the liquid crystal layer thickness dr of the reflective display region R is 1.5 times the liquid crystal layer thickness dt of the transmissive display region T, as in the first embodiment. However, when viewed between sub-pixels of different colors, the applied voltages to the liquid crystal layer 50 in the transmissive display region T are the same, but the applied voltages to the liquid crystal layer 50 in the reflective display region R are the blue sub-pixel region, The size is set to increase in the order of the green sub-pixel region and the red sub-pixel region. For example, the blue subpixel region is set to 2.7V, the green subpixel region is set to 3.1V, and the red subpixel region is set to 3.9V. The applied voltage to the liquid crystal layer 50 in the transmissive display region T is 3.1V.

  The TV characteristics shown in FIG. 6 shown in the first embodiment do not consider the difference in color (wavelength) and are indicated by the Y value (brightness) of transmitted light and reflected light. Here, when considered for each color light of different colors (wavelengths), the retardation is different for each color (wavelength) due to the wavelength dispersion of the refractive index, and the TV curve is different.

  FIG. 7 shows the result of a simulation performed by the present inventor, and shows the transmittance-voltage characteristic (TV curve) of the reflective display for each color. Various conditions such as Δn of the liquid crystal layer 50 and the liquid crystal layer thickness dr are the same as those in the first embodiment. The retardation of the reflective display area is 0.72. In FIG. 7, the TV curve of blue light (wavelength: 450 nm) is a broken line, the TV curve of green light (wavelength: 550 nm) is a solid line, and the TV curve of red light (wavelength: 650 nm) is a one-dot chain line. It showed in.

  As shown in FIG. 7, the retardation increases in the order of blue light, green light, and red light, and the TV curve is shifted to the higher voltage side in the order of blue light, green light, and red light. The voltage at the peak position of each TV curve (the higher of the two peaks) is 2.7 V for blue light, 3.1 V for the green sub-pixel region, and 3.9 V for the red sub-pixel region. . Therefore, if the voltage applied to the liquid crystal layer 50 in the reflective display region R is set to the above value for each sub-pixel of each color, the transmittance for each color becomes the highest, so that a bright overall display with high contrast is obtained. It is done.

  In the present embodiment, an example in which the voltage applied to the liquid crystal layer 50 in the reflective display region R is increased in the order of the blue sub-pixel region, the green sub-pixel region, and the red sub-pixel region is shown. The layer thickness of the liquid crystal layer 50 in the display region R may be set so as to increase in the order of the blue subpixel region, the green subpixel region, and the red subpixel region. With this configuration, the same effect as described above can be obtained.

[Electronics]
Examples of electronic devices provided with the liquid crystal display device of the above embodiment will be described.
FIG. 8 is a perspective view showing an example of a mobile phone. In FIG. 8, reference numeral 1000 denotes a mobile phone body, and reference numeral 1001 denotes a liquid crystal display unit using the liquid crystal display device.
Since the electronic device illustrated in FIG. 8 includes the liquid crystal display portion using the liquid crystal display device of the above embodiment, an electronic device having a display portion particularly excellent in transmissive display quality can be realized.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, an example in which a vertically aligned liquid crystal is used for the liquid crystal layer has been described. However, a homogeneously aligned liquid crystal that is not twisted can also be used. As a means for making the liquid crystal layer thickness in the reflective display area larger than the liquid crystal layer thickness in the transmissive display area, other means other than providing the liquid crystal layer thickness adjusting layer in the transmissive display area may be used. The present invention can also be applied to an active matrix liquid crystal display device using a thin film diode (TFD) as a switching element.

It is a top view which shows the whole structure of the liquid crystal display device of 1st Embodiment of this invention. It is sectional drawing which follows the H-H 'line | wire of FIG. 2 is an equivalent circuit diagram of a display unit of the liquid crystal display device. FIG. 2 is a plan view showing one sub-pixel of the liquid crystal display device. FIG. FIG. 5 is a cross-sectional view taken along line A-A ′ of FIG. 4. It is a figure which shows the TV curve of a liquid crystal display device equally. It is a figure which shows the TV curve of the liquid crystal display device of 2nd Embodiment of this invention. It is a perspective view which shows an example of the electronic device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 ... Pixel electrode, 10 ... TFT array substrate, 20 ... Counter substrate, 21 ... Counter electrode, 46 ... Liquid crystal layer thickness adjustment layer, 50 ... Liquid crystal layer, 100 ... Liquid crystal display device, R ... Reflection display area, T ... Transmission display Region, dr ... liquid crystal layer thickness in reflective display region, dt ... liquid crystal layer thickness in transmissive display region

Claims (8)

A liquid crystal display device in which a liquid crystal layer is sandwiched between a pair of substrates,
A transmissive display region that transmits light incident from the outer surface of one of the pair of substrates and performs transmissive display, and a reflective display that reflects light incident from the outer surface of the other substrate and performs reflective display A liquid crystal display device, wherein a layer thickness of the liquid crystal layer in the reflective display region is larger than a layer thickness of the liquid crystal layer in the transmissive display region.   A liquid crystal layer thickness adjusting layer is provided on an inner surface of at least one of the pair of substrates so that a layer thickness of the liquid crystal layer in the reflective display region is larger than a layer thickness of the liquid crystal layer in the transmissive display region. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device.   3. The liquid crystal display device according to claim 1, wherein the thickness of the liquid crystal layer in the reflective display region is approximately 1.5 times the thickness of the liquid crystal layer in the transmissive display region.   4. The liquid crystal display device according to claim 1, wherein a voltage applied to the liquid crystal layer is different between the reflective display region and the transmissive display region. 5.   It has a plurality of sub-pixel areas that display different colors of red, green, and blue, and the thickness of the liquid crystal layer in the reflective display area increases in the order of the blue sub-pixel area, the green sub-pixel area, and the red sub-pixel area. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device.   It has a plurality of sub-pixel areas that display different colors of red, green, and blue, and the voltage applied to the liquid crystal layer in the reflective display area is in the order of the blue sub-pixel area, the green sub-pixel area, and the red sub-pixel area. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is large.   The liquid crystal display according to claim 1, wherein the liquid crystal layer is made of a liquid crystal having an initial alignment state substantially perpendicular to the substrate surface and having a negative dielectric anisotropy. apparatus. An electronic apparatus comprising the liquid crystal display device according to claim 1.

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