JP2007052268A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device with which reflective and transmissive displays with high display quality are available without increasing the number of steps in manufacture and without complication. <P>SOLUTION: The liquid crystal display device is equipped with: an array substrate 101 and an opposite substrate 102; a liquid crystal layer 190 interposed between the array substrate 101 and the opposite substrate 102 and including a transmissive display region A1 and a reflective display region A2; and a transparent resin layer 35 arranged on the array substrate 101 according to the reflective display region A2 and making thickness of the liquid crystal layer 190 mutually different between the reflective display region A2 and the transmissive display region A1. In the liquid crystal display device, the transparent resin layer 35 contains a transparent member 35A arranged on the array substrate 101 according to a part of the transmissive display region A1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a transflective liquid crystal display device.

  Since a display device using a liquid crystal display panel does not emit light itself, unlike a CRT (cathode tube) or EL (electroluminescence), a transmissive liquid crystal display device that illuminates with a backlight installed on the back of the liquid crystal display panel is used. It has been. However, since the backlight generally consumes 50% or more of the total power consumption of the liquid crystal display device, a portable information device that is frequently used outdoors or always has a reflector instead of the backlight. Also, a reflection type liquid crystal display device that performs display only with ambient light has been realized.

  The reflective liquid crystal display device has a problem that the reflected light used for display is lowered when the ambient light is dark, and the visibility is extremely lowered. On the other hand, the transmissive liquid crystal display device has a problem in that visibility under a clear sky or the like in which ambient light is very bright is lowered. In order to solve this problem, a transflective liquid crystal display device in which a reflective display area and a transmissive display area are arranged in one pixel has been proposed.

  In the transflective liquid crystal display device, reflective display and transmissive display are realized such that the thickness of the liquid crystal layer in the reflective display region is approximately half the thickness of the liquid crystal layer in the transmissive display region (Patent Document 1). reference).

  As a liquid crystal display method used for a liquid crystal display device, a method using a change in the orientation of liquid crystal for display is generally used. For example, a TN (twisted nematic) mode used in a reflective liquid crystal display device, STN (super) In addition to a type using a polarizing plate such as a twisted nematic mode, a phase transition type guest-host mode capable of realizing bright display because a polarizing plate is not used has been actively developed in recent years (Patent Document 2 and Patent Document 3). reference).

  However, the phase transition type guest-host mode is a type that uses a polarizing plate such as a TN mode or an STN mode because the liquid crystal layer in which liquid crystal molecules and the dye are dispersed performs display using light absorption of the dye and does not have sufficient contrast. The display quality is significantly worse than

  In the case of a liquid crystal display system of horizontal alignment or twist alignment, the liquid crystal molecules near the center of the liquid crystal layer are tilted in the vertical direction with respect to the substrate surface when a voltage is applied, but the liquid crystal molecules near the alignment film surface apply a voltage. Even if it is not perpendicular to the substrate, the birefringence of the liquid crystal layer is far from 0, and in the display mode that displays black when a voltage is applied, sufficient black cannot be displayed due to the birefringence of the liquid crystal layer. A sufficient contrast could not be obtained. TN mode and STN mode liquid crystal display devices are also difficult to say at present with sufficient display quality in terms of brightness and contrast, and further improvements in display quality such as higher brightness and improved contrast are required.

  On the other hand, in the multi-domain type VAN (MVA) mode, the liquid crystal molecules near the surface of the alignment film are perpendicular to the substrate and the birefringence of the liquid crystal layer is almost 0 by adopting the vertical alignment treatment, so that sufficient black can be displayed. High contrast can be obtained. In addition, it has been attracting attention in recent years because the viewing angle compensation design is relatively easy and a wide viewing angle can be realized, and the rubbing alignment treatment process that has been concerned about the occurrence of defects such as electrostatic breakdown can be eliminated. It is a liquid crystal display mode.

  However, in the conventional liquid crystal display, the thickness of the liquid crystal layer is approximately equal for red, green, and blue pixels. In this case, since the effective phase difference of the liquid crystal layer for each wavelength is different, the γ characteristic is different for each color. For this reason, there is a problem that the balance of the transmittance of each color changes depending on the applied voltage, and the display color deviates from the target color as the applied voltage is increased.

In particular, this phenomenon is more noticeable when observed from an oblique direction. As a means for solving this problem, a multi-gap method has been proposed in which the liquid crystal layer thickness is changed for each color so that the balance of the transmittance of each color is not disturbed by the applied voltage (see Patent Document 4).
JP 2003-114419 A JP-A-4-75022 Japanese Patent Application No. 7-228365 Japanese Patent Laid-Open No. 7-120746

  However, in order to change the thickness of the liquid crystal layer for each color, the thickness of the color filter and the thickness of the insulating layer must be changed for each color, which causes problems such as an increase in the formation process and complexity. appear.

  The present invention has been made in view of the above problems, and provides a liquid crystal display device capable of high-quality reflective display and transmissive display without increasing and complicating the number of manufacturing steps. With the goal.

  A liquid crystal display device according to an aspect of the present invention includes a first and second electrode substrate, a liquid crystal layer sandwiched between the first and second electrode substrates and including a transmissive display region and a reflective display region, and the reflective display region. And a resin layer disposed on the first electrode substrate and different in thickness between the reflective display region and the transmissive display region. The resin layer is formed on the transmissive display region. A transparent member disposed on the first electrode substrate corresponding to a part is included.

  According to the present invention, it is possible to provide a liquid crystal display device capable of high-quality reflective display and transmissive display without increasing and complicating the number of manufacturing steps.

  Hereinafter, a liquid crystal display device according to the present invention will be described with reference to the drawings. The liquid crystal display device according to the first embodiment of the present invention has a liquid crystal display panel 100. The liquid crystal display panel 100 is, for example, an active matrix type liquid crystal display panel.

  As shown in FIGS. 1 and 2, a liquid crystal display panel 100 includes an array substrate 101, a counter substrate 102 disposed to face the array substrate 101, and a liquid crystal composition having negative dielectric anisotropy. 101 and a liquid crystal layer 190 sandwiched between the counter substrate 102 and the counter substrate 102.

  In the liquid crystal display panel 100, a display area 103 for displaying an image is disposed in an area surrounded by an outer edge seal member 106 that bonds the array substrate 101 and the counter substrate 102 together. The display area 103 includes a plurality of display pixels PX arranged in a matrix. The peripheral region 104 arranged along the outer periphery of the display region 103 is formed in a region outside the outer edge seal member 106 and has a light shielding region 141 formed in a frame shape.

  The array substrate 101 includes m × n pixel electrodes 151 arranged for each display pixel PX in the display region 103, and m scanning lines Y (Y1 to Ym) formed along the row direction of the pixel electrodes 151. The n signal lines X (X1 to Xn) formed along the column direction of the pixel electrodes 151, and the switching elements in the vicinity of the intersections of the scanning lines Y and the signal lines X corresponding to the pixel electrodes 151. M × n thin film transistors (hereinafter referred to as pixel TFTs) 121. In the peripheral region 104, the array substrate 101 includes a scanning line driving circuit 118 that drives the scanning lines Y, a signal line driving circuit 119 that drives the signal lines X, and the like.

  As shown in FIG. 3, each pixel electrode 151 is provided with a slit portion 15. In addition, a hook-shaped protrusion 18 is disposed on the counter substrate 102. In the liquid crystal display panel 100, the hook-shaped protrusions 18 and the slits 15 correspond to the pixel electrodes 151 of the liquid crystal layer 190 by forming a plurality of regions having different directions of electric lines of force in the liquid crystal layer 190. A plurality of domains in which the alignment directions of the liquid crystal molecules 190A are different from each other are formed in the portion.

  In the liquid crystal display panel 100 shown in FIG. 3, the region on each pixel electrode 151 is composed of a plurality of domains 22a to 22d in which the alignment directions of the liquid crystal molecules 190A are different from each other. As a result, the viewing angle is compensated, so that a wide viewing angle characteristic can be obtained.

  As shown in FIG. 4, the array substrate 101 of the liquid crystal display panel 100 is a switching element formed on the transparent insulating substrate 111 such as a glass substrate in the display region 103 corresponding to each of the plurality of display pixels PX. The pixel TFT 121, the insulating layer 123 formed so as to cover the display region 103 including the pixel TFT 121, the pixel electrode 151 disposed for each display pixel PX on the insulating layer 123, and the plurality of columnar spacers 131 formed on the insulating layer 123. And an alignment film 113A formed so as to cover the entire plurality of pixel electrodes 151.

  Further, the array substrate 101 includes a light shielding layer SP disposed in the light shielding region 141 of the transparent substrate surrounding the outer periphery of the display region 103 in the peripheral region 104.

  The pixel electrode 151 is formed of a transparent conductive member such as ITO on the insulating layer 123, and is connected to the pixel TFT 121 through a through hole 126 that penetrates the insulating layer 123. Each pixel TFT 121 is connected to a scanning line Y formed along a row of pixel electrodes 151 and a signal line X formed along a column of pixel electrodes 151, and is made conductive by a driving voltage from the scanning line Y. A signal voltage is applied to the pixel electrode 151.

  In addition, the liquid crystal display panel 100 includes a columnar spacer 131 for forming a predetermined gap between the array substrate 101 and the counter substrate 102.

  The counter substrate 102 includes a color filter 124 (124R, 124G, 124B) formed on a transparent insulating substrate 111 such as a glass substrate, a counter electrode 153, and an alignment film 113B that covers the counter electrode 153. .

  The color filter 124 includes a plurality of red coloring layers 124R, a green coloring layer 124G, and a blue coloring layer 124B that divide the liquid crystal layer 190 into a plurality of red pixels PXR, green pixels PXG, and blue pixels PXB. The transmissive display area A1 and the reflective display area A2 are provided for each of the plurality of red pixels PXR, green pixels PXG, and blue pixels PXB.

  The counter electrode 153 is formed of a light-transmitting conductive member such as ITO arranged so as to face the entire plurality of pixel electrodes 151 on the array substrate 101 side. The alignment film 113A and the alignment film 113B align the liquid crystal molecules 190A included in the liquid crystal layer 190 in a direction substantially perpendicular to the array substrate 101 and the counter substrate 102.

  As shown in FIGS. 5 and 6, the liquid crystal display panel 100 has a transmissive display area A1 for transmissive display and a reflective display area A2 for reflective display. The insulating layer 123 disposed on the array substrate 101 has a concavo-convex surface in the reflective display area A2. On the insulating layer 123, the reflective electrode 40 is disposed along the uneven shape of the reflective display region A2. The reflective electrode 40 is formed of a metal having light reflectivity such as aluminum, and reflects the light incident on the reflective display area A2 from the counter substrate 102 side to the counter substrate 102 side.

  That is, in the transmissive display area A1, for example, an image is displayed by light that is illuminated by a backlight (not shown) disposed on the back side (array substrate 101 side) of the liquid crystal display panel 100 and passes through the array substrate 101 and the counter substrate 102. Display. In the reflective display area A2, light incident from the front surface side (counter substrate 102 side) of the liquid crystal display panel 100 is reflected again by the reflective electrode 40 to the front surface side to display an image.

  The counter substrate 102 has a transparent resin layer 35 for changing the thickness of the liquid crystal layer 190 in the transmissive display area A1 and the liquid crystal layer 190 in the reflective display area A2 below the counter electrode 153. The transparent resin layer 35 includes a transparent member 35A that is disposed in the reflective display area A2 and extends to the phase correction area A3 that is a part of the transmissive display area A1. That is, the transparent member is a single layer that extends from the reflective display area A2 to a part of the transmissive display area A1 in the counter substrate 102.

  As described above, by disposing the transparent resin layer 35 on the counter electrode 153 in the reflective display area A2, there is a difference between the liquid crystal layer thickness G2 in the reflective display area A2 and the liquid crystal layer thickness G1 in the transmissive display area A1. . At this time, the transparent resin layer 35 is desirably arranged so that the liquid crystal layer thickness G2 of the reflective display area A2 is about half of the liquid crystal layer thickness G1 of the transmissive display area A1.

  Further, since the transparent member 35A is arranged in the phase correction region A3, the liquid crystal layer thickness of the phase correction region A3 becomes equal to the liquid crystal layer thickness G2 of the reflective display region A2. At this time, the area of the phase correction area A3 is arranged so that the ratio of the area of the entire transmissive display area A1 to the red pixel PXR, the green pixel PXG, and the blue pixel PXB is different. In the present embodiment, as shown in FIG. 7, the ratio of the area of the phase correction region A3 to the transmissive display region A1 is 0% for the red pixel PXR, 17% for the green pixel PXG, and 25% for the blue pixel PXB. A transparent member 35A was disposed on the surface.

For the transparent resin layer 35, for example, an inorganic thin film such as SiO ₂ , SiN _x , or Al ₂ O ₃ , an organic thin film such as polyimide, photoresist resin, or polymer liquid crystal can be used. When the insulating film is an inorganic thin film, it can be formed by vapor deposition, sputtering, CVD (Chemical Vapor Deposition), or solution coating. When the insulating film is an organic thin film, it is applied by a spinner coating method, a screen printing coating method, a roll coating method or the like using a solution in which an organic substance is dissolved or a precursor solution thereof, and a predetermined curing condition ( It can also be formed by a method of curing by heating, light irradiation or the like, or a vapor deposition method, a sputtering method, a CVD method, an LB (Langumuir-Blodgett) method, or the like.

  Further, in this embodiment, the thickness of the transparent resin layer 35 is 1.8 μm, the height of the hook-shaped protrusion 18 on the counter electrode 153 is 1.2 μm, and the height of the columnar spacer 131 is 3.8 μm. On the counter substrate 102 facing the array substrate 101, a vertical alignment film 113B was applied to a thickness of 70 nm to configure the liquid crystal display panel 100. A liquid crystal material having a negative dielectric anisotropy was filled between the array substrate 101 and the counter substrate 102 to enable reflective display and transmissive display.

  With respect to the liquid crystal display panel 100 of the present embodiment, the VT characteristics of the red pixel PXR, the green pixel PXG, and the blue pixel PXB in the transmissive display area A1 were measured, and the results are shown in FIG. Further, the transmittance when white was displayed and the color difference (Δu′v ′) from the front of the viewing angle in the direction of 50 ° in the vertical and horizontal directions were evaluated. The result is shown in FIG.

  Next, a liquid crystal display device according to a second embodiment of the present invention will be described. The height of the columnar spacer 131 of the liquid crystal display panel 100 shown in FIGS. 4 and 5 was 3.5 μm, and the ratio of the area of the phase correction region A3 of the transparent resin layer 35 was as shown in FIG. That is, as shown in FIG. 9, the area ratio of the phase correction area A3 to the transmissive display area A1 is set to 0% for the red pixel PXR and the green pixel PXG, and to 17% for the blue pixel PXB.

  Since points other than the above are the same as those in the first embodiment, the same reference numerals are given and description thereof is omitted. For the liquid crystal display panel of this embodiment, the VT characteristics of the red pixel PXR, the green pixel PXG, and the blue pixel PXB in the transmissive display area were measured, and the results are shown in FIG. Further, the transmittance when white was displayed and the color difference (Δu′v ′) from the front of the viewing angle in the direction of 50 ° in the vertical and horizontal directions were evaluated. The result is shown in FIG.

  As a comparative example with respect to the first and second embodiments described above, a liquid crystal display panel 100 that prevents the transparent resin layer 35 from covering the transmissive display area A1 was used as shown in FIG. That is, the liquid crystal display panel 100 in which the area ratio of the phase correction region A3 to the transmissive display region A1 is 0% for the red pixel PXR, the green pixel PXG, and the blue pixel PXB was used as a comparative example.

  The liquid crystal display panel 100 of the comparative example has the same configuration as that of the second embodiment except for the above. With respect to the above comparative example, the voltage-transmittance characteristics of the red pixel PXR, the green pixel PXG, and the blue pixel PXB in the transmissive display area A1 were measured. The result is shown in FIG. Further, the transmittance when white was displayed and the color difference from the front of the viewing angle in the direction of 50 ° in the vertical and horizontal directions were evaluated. The result is shown in FIG.

  As shown in FIG. 8, the liquid crystal according to the first and second embodiments is also obtained from the measurement results and subjective evaluation results of the transmissive display area A1 obtained from the first embodiment, the second embodiment, and the comparative example. The display panel 100 has higher white display brightness and a smaller color difference from the front than the comparative example, that is, a small color shift.

  From the above results, the liquid crystal display panel 100 according to the first and second embodiments can cope with the phase of each color by changing the area of the transparent resin layer 35 formed in the transmissive display area A1 for each color display pixel PX. Thus, the same effect as when the gap between the array substrate 101 and the counter substrate 102 is changed is obtained, and the shape (γ characteristic) of the VT curve changes. That is, when the ratio of the area of the transparent resin layer 35 is increased, the shape of the VT curve is inclined to the high voltage side as in the case where the gap between the array substrate 101 and the counter substrate 102 is decreased, and conversely the transparent resin layer If the area of 35 is reduced, the slope can be changed to the low voltage side as in the case of increasing the cell gap.

  When the cell thickness is the same for each color display pixel PX, the γ characteristic is also different, so that the intensity ratio of light of R, G, and B changes depending on the applied voltage, resulting in a color shift. However, as described above, by changing the area of the phase correction region A3 in which the transparent resin layer 35 is arranged in the display pixels PX of each color and adjusting the γ characteristics by R, G, and B, the front and oblique directions can be obtained. Color shift can be reduced. Accordingly, it is possible to provide the liquid crystal display panel 100 capable of high-quality display and reflection display.

  In the first and second embodiments, the transparent resin layer 35 disposed on the counter substrate 102 is used in order to make the thickness of the liquid crystal layer 190 different between the transmissive display area A1 and the reflective display area A2. The same effect as when the thickness of the liquid crystal layer 190 is changed for each of the red pixel PXR, the green pixel PXG, and the blue pixel PXB is obtained. Therefore, according to the present invention, it is possible to provide a liquid crystal display device capable of high-quality reflective display and transmissive display without increasing and complicating the number of manufacturing steps.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage.

  For example, in the first and second embodiments described above, the transparent resin layer 35 is disposed on the counter substrate 102, and the thickness of the liquid crystal layer 190 in the transmissive display area A1 and the thickness of the liquid crystal layer 190 in the reflective display area A2 are determined. However, the thickness of the liquid crystal layer 190 in the transmissive display area A1 and the reflective display area A2 may be different by increasing the thickness of the insulating layer 123 disposed on the array substrate 101 in the reflective display area A2. .

  In that case, the same effect as the above-described embodiment can be obtained by disposing the thickened portion of the insulating layer 123 in a part of the transmissive display region A1.

  In the first and second embodiments described above, the transparent resin layer 35 disposed in the phase correction region A3 is integrated with the transparent resin layer 35 disposed in the reflective display region A2. It may be the body. Even if they are separate bodies, the liquid crystal display panel 100 can be formed without increasing the number of manufacturing steps by being formed of the same material, and the same effects as those of the first and second embodiments can be obtained. Can do.

  In the above embodiment, the liquid crystal display panel 100 adopting the MVA display mode has been described, but any mode may be used as the display method. However, it is desirable to use the MVA mode using a liquid crystal material having a negative dielectric anisotropy, and a liquid crystal display device having a high contrast ratio of 500: 1 or more in the transmissive display portion and 100: 1 or more in the reflective display portion. Can be produced.

  In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

1 is a perspective view schematically showing an example of a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a plan view illustrating a configuration example of a liquid crystal display device illustrated in FIG. 1. FIG. 3 is a diagram illustrating an example of arrangement of a display pixel inclination correction unit of the liquid crystal display device illustrated in FIG. 1. FIG. 2 is a cross-sectional view illustrating a configuration example of a liquid crystal display device illustrated in FIG. 1. The figure which shows an example of the cross section which cut | disconnected the pixel shown in FIG. 5 by AA '. FIG. 3 is a diagram illustrating a configuration example of a pixel of the liquid crystal display device according to the first embodiment of the present invention. The figure which shows the result of having evaluated the transmittance | permeability of the liquid crystal display device shown in FIG. The figure explaining the evaluation result of the liquid crystal display device which concerns on 1st Embodiment of this invention, 2nd Embodiment, and a comparative example. FIG. 6 is a diagram illustrating a configuration example of a pixel of a liquid crystal display device according to a second embodiment of the present invention. The figure which shows the result of having evaluated the transmittance | permeability of the liquid crystal display device shown in FIG. FIG. 10 is a diagram illustrating a configuration example of a pixel of a liquid crystal display device according to a third embodiment of the present invention. The figure which shows the result of having evaluated the transmittance | permeability of the liquid crystal display device shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Liquid crystal display panel, 101 ... Array substrate, 102 ... Opposite substrate, 103 ... Display area, 151 ... Pixel electrode, 190 ... Liquid crystal layer, 190A ... Liquid crystal molecule, X (X1-Xn) ... Signal line, Y (Y1- Ym) ... scanning line, 121 ... pixel TFT, 123 ... insulating layer, 124 ... color filter, 15 ... electrode slit, 18 ... bowl-like structure, 35 ... transparent resin layer, 35A ... transparent member, 40 ... reflective electrode, A1 ... transmissive display area, A2 ... reflective display area, A3 ... phase correction area, PXR ... red pixel, PXG ... green pixel, PXB ... blue pixel, G1, G2 ... gap

Claims (9)

First and second electrode substrates;
A liquid crystal layer sandwiched between the first and second electrode substrates and including a transmissive display area and a reflective display area;
A resin layer disposed on the first electrode substrate corresponding to the reflective display region and different in thickness between the reflective display region and the transmissive display region.
The liquid crystal display device, wherein the resin layer includes a transparent member disposed on the first electrode substrate corresponding to a part of the transmissive display region. 2. The liquid crystal display device according to claim 1, wherein the transparent member is a single layer extending from the reflective display area to a part of the transmissive display area on the first electrode substrate. A color filter including a plurality of red colored layers, a green colored layer, and a blue colored layer that divides the liquid crystal layer into a plurality of red pixels, green pixels, and blue pixels; and The liquid crystal device according to claim 1, provided for each of a plurality of red pixels, green pixels, and blue pixels. The liquid crystal display device according to claim 3, wherein the transparent member is provided for each of the blue pixel, the red pixel, and the green pixel, and has a larger area in the blue pixel than in the red pixel and the green pixel. The liquid crystal display device according to claim 3, wherein the transparent member is provided for each of the blue pixel, the red pixel, and the green pixel, and has a large area in the order of the blue pixel, the green pixel, and the red pixel. The liquid crystal display device according to claim 3, wherein the transparent member is provided only for the blue pixel. The second electrode substrate further includes a reflective electrode disposed corresponding to the reflective region and an insulating layer disposed under the reflective electrode, and the transparent member is made of a material equal to the insulating layer. Item 2. A liquid crystal display device according to item 1. The liquid crystal display device according to claim 1, wherein the liquid crystal layer has negative dielectric anisotropy. 2. The liquid crystal display device according to claim 1, wherein the liquid crystal molecules in the liquid crystal layer are aligned substantially vertically by a pair of alignment films formed on the first and second electrode substrates.

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