JP4250813B2 - Liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal display device with little coloring due to variation in a viewing angle direction and with excellent display quality by making a construction which cancels out respective coloring of a first and a second alignment layers. SOLUTION: An alignment layer 9A formed on a transparent substrate 1A comprises a first alignment layer 9Aa formed on right above common electrodes 3 and pixel electrodes 4 and a second alignment layer 9Ab formed on the parts except the first alignment layer 9Aa parts. Besides a direction forming 90 deg. angle with the initial alignment direction of the first alignment layer 9Aa is made to be the initial alignment direction of the second alignment layer 9Ab. With this kind of construction respective coloring of the first and the second alighment layers 9Aa and 9Ab is canceled out and a liquid crystal display device with little coloring due to variation in a viewing angle direction and with excellent display quantity is obtained.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device, and relates to a liquid crystal display device having a wide viewing angle and high brightness.
[0002]
[Prior art]
Hereinafter, an example of the liquid crystal display device will be described with reference to the drawings.
[0003]
FIG. 4 is a cross-sectional view showing a configuration of a pixel portion of a liquid crystal display device disclosed in Japanese Patent Laid-Open No. 10-307295.
[0004]
Conventionally, in the display method using the lateral electric field application method (IPS), a very wide viewing angle can be realized as compared with the vertical electric field application method (TN), but in the bright state display (voltage application), birefringence is achieved. There is a problem that the coloring changes depending on the viewing angle direction due to the change of the amount, that is, the coloring problem that it looks blue when viewed from the major axis direction of the liquid crystal and red when viewed from the minor axis direction.
[0005]
In order to solve this problem, in the liquid crystal display device disclosed in Japanese Patent Laid-Open No. 10-307295, as shown in FIG. 4, the initial orientation directions of the liquid crystal molecules 21 in the two subregions 1 and 2 are within each other in the pixel region. The liquid crystal molecules in each sub-region are configured to rotate in the same rotation direction while maintaining the alignment directions at 90 degrees with each other when a voltage is applied.
[0006]
Alternatively, the initial alignment directions of the liquid crystal molecules in the sub-region 1 and the sub-region 2 are the same, and when a voltage is applied, the liquid crystal molecules 21 in each sub-region are aligned with each other. It is configured to rotate in the reverse rotation direction while maintaining a symmetric relationship.
[0007]
According to such a configuration, the sub-region 1 and the sub-region 2 can compensate for each other's coloring characteristics, so that it is possible to obtain a liquid crystal display device with excellent image quality with little coloring due to a change in viewing angle direction.
[0008]
[Problems to be solved by the invention]
However, in the case of the liquid crystal display device as described above, the following problems remain.
[0009]
In other words, if the liquid crystal on the electrode is also modulated in order to improve the aperture ratio of the pixel portion, the modulation rate differs between the portion on the electrode and the other pixel aperture portions. Because it has a change characteristic, it can completely complement each other's colored characteristics by simply rotating the initial orientation direction by 90 degrees as in the conventional example, or by rotating the liquid crystal molecules in the opposite rotation direction while maintaining a symmetrical relationship. I can't do it.
[0010]
In order to obtain a high-definition display or to modulate the liquid crystal on the electrode, this problem is caused when the electrode gap is reduced and a transparent conductor is used for the electrode, and the opening on the electrode occupies the entire opening. The proportion becomes very high and becomes a more important issue.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the liquid crystal display device of the present application is
(1) A liquid crystal is sandwiched between at least a pair of substrates, a pixel electrode, a common electrode, and an alignment film are formed on at least one of the substrates, and a voltage is applied between the pixel electrode and the common electrode. In the liquid crystal display device, the alignment film is applied to change the alignment of liquid crystal molecules, and the alignment film is formed on the first alignment layer formed immediately above the pixel electrode and the common electrode and on portions other than the first alignment layer. The second alignment layer is formed.
[0012]
(2) The initial alignment direction of the first alignment layer is different from the initial alignment direction of the second alignment layer.
[0013]
(3) The initial alignment direction of the first alignment layer is different from the initial alignment direction of the second alignment layer by approximately 90 degrees.
[0014]
(4) The electrode gap between the common electrode and the pixel electrode is configured to be at least smaller than the electrode width and the substrate gap.
[0015]
(5) Each electrode gap is 6 μm or less.
[0016]
(6) The alignment film is made of a photoreactive material.
[0017]
(7) The pixel electrode and the common electrode are formed on a convex portion formed on the substrate.
[0018]
(8) Part or all of the pixel electrode and the common electrode are made of a transparent conductor.
[0019]
(9) Substantially the same alignment layer pattern corresponding to the first alignment layer and the second alignment layer is formed on the substrate facing the first substrate on which the first alignment layer and the second alignment layer are formed. The alignment film is formed.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
(Embodiment 1)
A first embodiment of the present invention will be described with reference to the drawings.
[0022]
FIG. 1 is a cross-sectional view showing a configuration of a liquid crystal display device according to a first embodiment of the present invention. FIG. 2 is a plan view showing the configuration of the liquid crystal display device according to the first embodiment of the present invention.
[0023]
1 and 2, 1A and 1B are transparent substrates, 2 is a liquid crystal, 3 is a common electrode, 4 is a pixel electrode, 5 is a video signal line connected to the pixel electrode 4 and gives a video signal, 6 is a scanning signal line, 7 is a semiconductor switch element, 8a is a red color filter material, 8b is a green color filter material, 8c is a blue color filter material, 9A is an alignment film formed on the inner surface of the transparent substrate 1A, and 9B is formed on the inner surface of the transparent substrate 1B. The alignment film 10 is a black matrix.
[0024]
Here, the alignment film 9A is composed of a first alignment layer 9Aa formed on the common electrode 3 and the pixel electrode 4, and a second alignment layer 9Ab formed on other portions.
[0025]
Hereinafter, the operation will be described with reference to FIGS.
[0026]
First, a scanning signal line 6 patterned with a conductive film made of Al or the like is formed on the transparent substrate 1A, and after further forming an insulating film, the semiconductor switch element 7 made of a-Si or the like, or made of Al or the like A video signal line 5 patterned with a conductive film is formed.
[0027]
In this embodiment, a lateral electric field application method is used, and the common electrode 3 and the pixel electrode 4 are formed in a comb shape by patterning with a transparent conductive ITO film or a conductive film made of Al or the like.
[0028]
Further, alignment films 9A and 9B made of polyimide or the like are formed on the transparent substrates 1A and 1B in order to align the molecular arrangement of the liquid crystal 2. The transparent substrate 1B is provided to face the transparent substrate 1A, and a red color filter material 8a, a green color filter material 8b, a blue color filter material 8c, and a black matrix 10 are formed in a predetermined pattern.
[0029]
The thus-prepared transparent substrates 1A and 1B each have an initial alignment orientation in a predetermined direction, and after adhering the peripheral portion with a sealant, the liquid crystal 2 is injected and sealed.
[0030]
The semiconductor switch element 7 is ON / OFF controlled by drive signals input from the video signal line 5 and the scanning signal line 6. Then, an electric field is generated by a voltage applied between the pixel electrode 4 connected to the semiconductor switch element 7 and the common electrode 3, and the luminance of each pixel is controlled by changing the orientation of the liquid crystal 2. indicate.
[0031]
However, since a sufficient electric field is not generated immediately above the common electrode 3 and the pixel electrode 4, light is not transmitted, which causes a reduction in aperture ratio.
[0032]
Therefore, as shown in FIG. 1, the electrode gap 1 between each of the common electrode 3 and the pixel electrode 4 is set to be smaller than at least the electrode width w and the cell gap d (l <d, l <w).
[0033]
For example, in this embodiment, the electrode gap l = 6 μm, the electrode width w = 4 μm, and the cell gap d = 5 μm. With such a configuration, not only a horizontal electric field but also a vertical electric field is generated, and the liquid crystal directly above the electrode can be modulated. Furthermore, by using a transparent conductor such as ITO for the electrode, the portion directly above the electrode can also transmit light, and the aperture ratio can be improved.
[0034]
However, since the modulation rate differs between the parallel electrode pair formed by the common electrode 3 and the pixel electrode 4 and the portion directly above the electrodes, the birefringence amount differs when the same voltage is applied. It will have unique color change characteristics.
[0035]
In the lateral electric field application method, it is known that the initial orientation direction also affects the threshold characteristics and response characteristics (“Liquid Crystal” Vol. 2, No. 4, 1998, page 313). Therefore, the alignment film 9A formed on the transparent substrate 1A includes a first alignment layer 9Aa formed immediately above the common electrode 3 and the pixel electrode 4, and a second alignment layer 9Ab formed in a portion other than the first alignment layer 9Aa. It is set as the structure which consists of. In addition, the first alignment layer 9Aa and the second alignment layer 9Ab may have different initial alignment directions.
[0036]
First, the initial alignment directions of the first alignment layer 9Aa and the second alignment layer 9Ab are determined as follows. An initial orientation direction in which the modulation factor is substantially the same in each portion is obtained and set as the initial orientation direction of the first alignment layer 9Aa. Then, an angle forming 90 degrees with the initial alignment direction of the first alignment layer 9Aa is defined as the initial alignment direction of the second alignment layer 9Ab.
[0037]
The method for forming the first alignment layer 9Aa and the second alignment layer 9Ab is as follows.
[0038]
For example, a polyimide photoreactive material is used for the alignment film, and a pattern corresponding to the electrode is formed by a mask method using a photoresist to form a first alignment layer 9Aa. Similarly, the pattern of the other part is set as the second alignment layer 9Ab. When irradiating polarized light, the initial alignment azimuth can be made different by changing the polarization angle between the first alignment layer 9Aa and the second alignment layer 9Ab.
[0039]
With such a configuration, the portion directly above the electrode and the other portion, that is, the first alignment layer 9Aa and the second alignment layer 9Ab can cancel each other's coloring, and the coloring is caused by the change in the viewing angle direction. It is possible to obtain a liquid crystal display device with less image quality and excellent image quality.
[0040]
(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to the drawings.
[0041]
FIG. 3 is a sectional view showing the configuration of the liquid crystal display device according to the second embodiment of the present invention.
[0042]
The operation of the liquid crystal display device according to the second embodiment of the present invention will be described below with reference to FIG.
[0043]
This example is different from (Embodiment 1) in that the common electrode 3 and the pixel electrode 4 are formed on a convex portion formed on the transparent substrate 1A.
[0044]
Even if the electrode is configured in such a tapered shape, the electric field intensity directly above the electrode can be increased to modulate the liquid crystal molecules. Therefore, if a transparent conductor such as ITO is used for the electrode, the portion directly above the electrode As a result, light can be transmitted and the aperture ratio can be improved.
[0045]
Other than the configuration of the electrodes, that is, the process of manufacturing the transparent substrates 1A and 1B, such as forming the first alignment layer 9Aa and the second alignment layer 9Ab, the process of manufacturing the panel, and the principle of operation for displaying an image are basically It may be the same as (Embodiment 1).
[0046]
In (Embodiment 1) and (Embodiment 2), an alignment pattern of first alignment layer 9Aa and second alignment layer 9Ab is formed only on transparent substrate 1A on which common electrode 3 and pixel electrode 4 are formed. In any of the embodiments, if the alignment film 9B having substantially the same alignment layer pattern corresponding to the first alignment layer 9Aa and the second alignment layer 9Ab is formed on the opposing second transparent substrate. A greater effect can be obtained.
[0047]
【The invention's effect】
As described above, in the liquid crystal display device according to the present invention, the alignment film is composed of the first alignment layer corresponding to the portion directly above the electrode and the second alignment layer corresponding to the other portion. A liquid crystal display with excellent image quality, in which the portion directly above and the other portion, that is, the first alignment layer and the second alignment layer can cancel each other's coloring, and there is little coloring due to a change in viewing angle direction. Since the device can be obtained, the industrial value is extremely large.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a liquid crystal display device according to a first embodiment of the present invention. FIG. 2 is a plan view showing a configuration of a liquid crystal display device according to the first embodiment of the present invention. Sectional drawing which shows the structure of the liquid crystal display device in 2nd Example of this FIG. 4 is a top view which shows the structure of the conventional liquid crystal display device
1A transparent substrate 1B transparent substrate 2 liquid crystal 3 common electrode 4 pixel electrode 5 video signal line 6 scanning signal line 7 semiconductor switch element 8a red color filter material 8b green color filter material 8c blue color filter material 9Aa first alignment layer 9Ab second alignment layer Layer 9B Alignment film 10 Black matrix

Claims (5)

A liquid crystal is sandwiched between at least a pair of substrates, a pixel electrode, a common electrode, and an alignment film are formed on at least one of the substrates, and a voltage is applied between the pixel electrode and the common electrode. A liquid crystal display device that changes the arrangement of liquid crystal molecules,
The alignment layer, the a first alignment layer formed right above the pixel electrode and the common electrode, Ri Do and a second alignment layer formed on the portion other than the first alignment layer, the first alignment layer The liquid crystal display device is characterized in that the initial alignment direction of the second alignment layer differs from the initial alignment direction of the second alignment layer by approximately 90 degrees. The liquid crystal display device according to claim 1, wherein the alignment film is made of a photoreactive material. The liquid crystal display device according to claim 1, wherein the pixel electrode and the common electrode are formed on a convex portion formed on the substrate. The liquid crystal display device according to claim 1, wherein a part or all of the pixel electrode and the common electrode are made of a transparent conductor. An alignment film having substantially the same alignment layer pattern corresponding to the first alignment layer and the second alignment layer on the substrate opposite to the first substrate on which the first alignment layer and the second alignment layer are formed. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is formed.

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