JP2000056336A - Active matrix type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to prevent the color formation dependent on the visual angle and to suppress the formation of pressed domain with a simple constitution. SOLUTION: In this liquid crystal display device, a pixel electrode 6 and a common electrode 5 are arranged in nearly parallel dogleg forms so that areas, wherein liquid crystal molecules 9 are allowed to orient to different directions (indicated by arrows, C), can be formed within a pixel area which is formed by the pixel electrode 6 and the common electrode 5 when an electric field is allowed to generate between the pixel electrode 6 and the common electrode 5, in nearly parallel to the main face of an array substrate. The angle θof the alignment direction of the liquid crystal molecule 9 with respect to the longitudinal direction of the pixel electrode 6 and the common electrode 5 is controlled to 10 deg.<=θ<=45 deg., preferably, 15 deg.<=θ<=45 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device having a liquid crystal display element which can be used as a flat display of AV / OA equipment.

[0002]

2. Description of the Related Art At present, display devices using liquid crystal have been applied in various fields such as a viewfinder of a video camera, a pocket TV, an information display terminal such as a high-definition projection TV, a personal computer, and a word processor. Development and commercialization are being actively conducted. In particular, an active matrix type liquid crystal display device using a thin film transistor (TFT) as a switching element has a great feature that a high contrast is maintained even when a large-capacity display is performed. The development and commercialization of large and large-capacity full-color displays for personal computers and notebook computers, as well as for engineering workstations, has been active.

[0003] The liquid crystal display modes used in such an active matrix type liquid crystal display device include IP.
There is an S (In-plane Switching) system, which is proposed in, for example, Japanese Patent Publication No. 63-21907 and Japanese Patent Application Laid-Open No. 6-160878. The IPS mode is a mode in which the direction in which an electric field is applied to the liquid crystal is substantially parallel to the main surface of the substrate. An interdigitated comb-shaped electrode is formed on one of the two substrates sandwiching the liquid crystal layer, and an electric field is applied between the comb-shaped electrodes to control the alignment direction of the liquid crystal molecules. As a result, the polarization state of light transmitted through the panel changes, and the light transmittance is modulated. This IPS type liquid crystal display device has excellent viewing angle characteristics, and does not cause a luminance inversion phenomenon, that is, a phenomenon in which when the viewpoint is inclined obliquely, the display luminance at a certain voltage becomes brighter than the luminance at a lower voltage. Therefore, development to large monitors is expected.

[0004] However, although the above-mentioned method is excellent in the viewing angle characteristic of the luminance inversion phenomenon, as shown in FIG. 2, the screen is viewed obliquely with respect to the comb-shaped electrode 18 in the directions of 45 ° and 135 °. However, there is a drawback that they are colored blue and yellow, respectively, which is a problem in image quality. As proposed in Japanese Patent Application No. Hei 7-312010 in order to solve the problem of coloring due to the viewing angle, a comb-shaped electrode 18 is formed in a V-shape to change the direction in which the arrangement of the liquid crystal molecules 9 changes. As shown in FIG. 3, the color change direction of yellow and the color change direction of blue overlap as shown in FIG. 3, and the color change with respect to the viewing angle is mutually compensated, so that an image without color change can be obtained.

[0005]

FIG. 4 shows a plan configuration of a pixel portion of an array substrate of a conventional IPS type liquid crystal display device. 4, a plurality of scanning wirings 11 and signal wirings 12 are formed so as to be orthogonal to each other, and a switching element T corresponding to each intersection between the scanning wirings 11 and the signal wirings 12 is provided.
An FT 13 is provided. A common wiring 14 is formed between two adjacent scanning wirings 11 in parallel with the scanning wirings 11,
Comb-shaped common electrode 15 electrically connected to common wiring 14
Are formed. Then, a comb-shaped pixel electrode 16 connected to the TFT 13 is formed so as to engage with the common electrode 15, and a storage capacitance portion 17 is formed on the scanning wiring 11 by being connected to the pixel electrode 16. 19 is a liquid crystal molecule.

[0006] Then, an alignment film is applied to an array substrate in which the common electrode 15 and the pixel electrode 16 are formed in a substantially U-shape substantially parallel to each other, rubbing is performed in the direction of arrow D, and the liquid crystal molecules 19 are formed in one direction. Is oriented. Here, when an electric field is generated between the common electrode 15 and the pixel electrode 16, in order to define the direction in which the arrangement of the liquid crystal molecules 19 changes, the common electrode 15 and the pixel Electrode 16
Must be angled, and the angle θ ′ may be 1 ° or more, and FIG. 4 shows the case where θ ′ = 5 °.
E indicates the polarization axis direction.

With this configuration, when an electric field is generated between the common electrode 15 and the pixel electrode 16, it is possible to have a region in which the direction in which the arrangement of the liquid crystal molecules 19 changes (the direction of arrow F) is different, and Compensate each other for color changes,
An image without color change can be obtained. Here, the area ratios of the regions in which the direction in which the arrangement of the liquid crystal molecules 19 changes are different are substantially equal.

However, since the regions where the arrangement of the liquid crystal molecules 19 are different are adjacent to each other, when the screen of the liquid crystal display device is pressed with a finger or the like, the area of the region where the arrangement of the liquid crystal molecules 19 changes easily is different. The balance of the ratio is lost, and a phenomenon in which the pressed portion is colored depending on the viewing angle (hereinafter referred to as a pressing domain) occurs, which is a display problem in the case where the color compensation is performed by the configuration of the V-shaped electrodes.

An object of the present invention is to provide a simple structure
It is an object of the present invention to provide an active matrix liquid crystal display device that can prevent coloring due to a viewing angle and can suppress generation of a pressing domain.

[0010]

In the active matrix type liquid crystal display device of the present invention, a plurality of signal wirings and scanning wirings are arranged in a matrix, and at least one switching element is provided corresponding to each intersection. An array substrate formed by connecting a comb-shaped pixel electrode to the switching element and engaging with the pixel electrode to form a comb-shaped common electrode;
A counter substrate disposed opposite the array substrate; a liquid crystal layer sandwiched between the array substrate and the counter substrate; and a pair of polarizing plates disposed on each outer surface of the array substrate and the counter substrate. In addition, the arrangement of the liquid crystal molecules is changed by generating an electric field substantially parallel to the main surface of the array substrate, and an electric field is generated between the pixel electrode and the common electrode substantially parallel to the main surface of the array substrate. When the pixel electrode and the common electrode are substantially parallel to each other so that the pixel region formed by the pixel electrode and the common electrode has a region in which the direction in which the arrangement of the liquid crystal molecules changes is different, Is 10 degrees with respect to the longitudinal direction of the pixel electrode and the common electrode.
゜ ≦ θ ≦ 45 °.

The angle θ formed by the alignment direction of the liquid crystal molecules with respect to the longitudinal direction of the pixel electrode and the common electrode is 10 ° ≦ θ ≦
15 ° ≦ θ ≦ 45 ° instead of 45 °. According to the active matrix type liquid crystal display device configured as described above, the pixel electrode and the common electrode are formed in a substantially rectangular shape in parallel with each other, and the orientation direction of the liquid crystal molecules is formed with respect to the longitudinal direction of the pixel electrode and the common electrode. Angle θ is 10 ° ≦ θ ≦ 45
{, Desirably 15 ° ≦ θ ≦ 45 °, by using a simple configuration and the same manufacturing process as in the related art, it is possible to prevent the occurrence of coloring and to suppress the generation of a pressing domain.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described in detail with reference to FIG. FIG. 1 shows a plan configuration of a TFT pixel portion of a thin film transistor array substrate used for a liquid crystal display device. In FIG. 1, a plurality of scanning lines 1
The signal lines 2 are formed so as to be orthogonal to each other, and a TFT 3 as a switching element is provided at each intersection of the scanning lines 1 and the signal lines 2. A common wiring 4 is formed between two adjacent scanning wirings 1 in parallel with the scanning wirings 1,
A comb-shaped common electrode 5 electrically connected to the common wiring 4 is formed. Then, a comb-shaped pixel electrode 6 connected to the TFT 3 is formed so as to engage with the common electrode 5, and a storage capacitance portion 7 is formed on the scanning wiring 1 by being connected to the pixel electrode 6. 9 is a liquid crystal molecule.

First, the scanning wiring 1 was formed in a pattern as shown in the figure on an array substrate by a photolithography method using chromium. At the same time, the common wiring 4,
The common electrode 5 was formed, and the common electrode 5 was formed in a letter shape as shown in the figure. Note that the width of the common electrode 5 is 4 μm, and a conductive single-layer film or a multilayer film such as aluminum or a metal containing aluminum as a main component may be used as a material in addition to chromium.

Next, as a first insulator layer acting as a gate insulating film of the TFT 3, silicon nitride (SiNx) is laminated thereon, and amorphous silicon (α-Si) which becomes a semiconductor layer which performs a switching function of the TFT 3 is formed. Plasma C
The layers are laminated by the VD method. Thereafter, two layers of titanium / aluminum (Ti / Al) are deposited by a sputtering method, and further, the signal wiring 2 is formed by dry etching.
Was formed into a pattern.

At the same time, the pixel electrode 6 is formed in a V-shape along the common electrode 5. The width of the pixel electrode 6 is 4 μm.
m, and the material is titanium / aluminum (Ti / A
In addition to l), a single-layer film or a multilayer film of a conductive metal may be used. At this time, the storage capacitor section 7 is formed by forming the pixel electrode 6 so as to overlap with the scanning wiring 1 with the first insulating film layer and the semiconductor layer interposed therebetween. The storage capacitor unit 7 is provided to hold the voltage supplied to the pixel. The distance between the common electrode 5 and the pixel electrode 6 is 12 μm.
m.

An alignment film was applied to the thin film transistor array substrate and the counter substrate completed as described above, and rubbing was performed in the direction of arrow A. Thereafter, a gap of 3 μm is formed and bonded, liquid crystal having a positive dielectric anisotropy is injected between the gaps, and the polarization axes are orthogonalized (in the direction of arrow B) on the outer surfaces of the array substrate and the counter substrate, respectively. The plates were arranged to produce a liquid crystal display device.

As shown in FIG. 1, since the common electrode 5 and the pixel electrode 6 are formed so as to be bent in a V-shape with respect to the alignment direction of the liquid crystal molecules 9, a voltage is applied between the common electrode 5 and the pixel electrode 6. Is applied, the direction in which the liquid crystal molecules 9 rotate (the direction of arrow C) is different, and the problem of coloring due to the viewing angle has been solved. FIG. 1 shows that the angle θ formed by the orientation direction of the liquid crystal molecules 9 with respect to the longitudinal direction of the common electrode 5 and the pixel electrode 6 is 12 °.
This is the case of ゜. Since the regions having different arrangements of the liquid crystal molecules 9 are adjacent to each other, once the screen is pressed with a finger, a pressing domain is generated once. However, the direction of each electric field is significantly different from 24 °, and the direction for controlling the arrangement of the liquid crystal molecules 9 is different. Are clearly separated, and the pressing domain disappears immediately.

As described above, a liquid crystal display device is manufactured using the thin film transistor array substrate in which the angle between the orientation direction of the liquid crystal molecules 9 and the longitudinal direction of the common electrode 5 and the pixel electrode 6 is changed, and the pressure domain is evaluated. Was. In practical use, the allowable time from the generation of the pressing domain to the disappearance of the pressing domain is 2 seconds. Therefore, the evaluation results show that the angle θ between the alignment direction of the liquid crystal molecules 9 and the longitudinal direction of the common electrode 5 and the pixel electrode 6 is 10 °. The above proved necessary. Further, assuming that the time until the disappearance is 0.5 seconds so that the generation of the pressing domain cannot be recognized at all, the angle θ between the orientation direction of the liquid crystal molecules 9 and the longitudinal direction of the common electrode 5 and the pixel electrode 6 becomes It turned out that 15 mm or more was necessary. That is, by setting the angle θ between the alignment direction of the liquid crystal molecules 9 and the longitudinal direction of the common electrode 5 and the pixel electrode 6 to 10 ° or more, preferably 15 ° or more, generation of a press domain can be suppressed. .
In the display mode, the liquid crystal molecules rotate on a 45 ° plane to display black and white, and the upper limit of the angle θ is four.
It becomes 5 ゜.

In the case of a liquid crystal having a negative dielectric anisotropy, the angle θ is 45 ° ≦ θ ≦ 80 °, preferably 45 ° ≦
θ ≦ 75 °, and the effect is effective in each range.

[0020]

According to the liquid crystal display device of the present invention, in an active matrix type liquid crystal display device of the IPS system capable of realizing good multi-gradation display with a wide viewing angle, a pixel electrode and a common electrode are formed in a substantially rectangular shape. And the angle θ formed by the orientation direction of the liquid crystal molecules with respect to the longitudinal direction of the pixel electrode and the common electrode is 10 ° ≦ θ ≦ 45 °, preferably 15 ° ≦ θ ≦
By setting the angle to 45 °, it is possible to prevent the occurrence of coloring and to suppress the generation of the pressing domain by a simple configuration and the same manufacturing process as that in the related art.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of an array substrate of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a plan view of a liquid crystal display device showing a colored direction of a conventional liquid crystal display device.

FIG. 3 is a plan view of a liquid crystal display device showing a principle of preventing a viewing angle-dependent coloring of a conventional liquid crystal display device.

FIG. 4 is a plan view showing a configuration of an array substrate of a conventional liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanning wiring 2 Signal wiring 3 TFT (switching element) 4 Common wiring 5 Common electrode 6 Pixel electrode 7 Storage capacity part 9 Liquid crystal molecule

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hirofumi Sekimoto 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (reference) 2H092 GA01 GA13 GA14 JA03 JA24 JB05 NA03 NA04 5C094 AA03 AA36 BA03 BA43 EA04 EA07 HA06 HA08 JA09

Claims (2)

[Claims] A plurality of signal wirings and scanning wirings are arranged in a matrix, at least one switching element is provided corresponding to each intersection thereof, and a comb-shaped pixel electrode is connected to the switching elements. An array substrate formed by interdigitating with a pixel electrode to form a comb-shaped common electrode; a counter substrate disposed to face the array substrate; a liquid crystal layer sandwiched between the array substrate and the counter substrate; A substrate and a pair of polarizers disposed on each outer surface of the counter substrate, and generating an electric field between the pixel electrode and the common electrode substantially in parallel with the main surface of the array substrate to thereby arrange the arrangement of the liquid crystal molecules. An active matrix type liquid crystal display device for changing, when an electric field is generated between the pixel electrode and the common electrode substantially in parallel with a main surface of the array substrate, the pixel electrode and the common electrode The pixel electrode and the common electrode are substantially parallel to each other so that the pixel region formed by the common electrode has a region in which the direction in which the arrangement of the liquid crystal molecules changes is different from each other. An active matrix type liquid crystal display device, wherein an angle θ formed between the pixel electrode and the common electrode in a longitudinal direction is 10 ° ≦ θ ≦ 45 °. 2. An active matrix type liquid crystal display device in which 15 ° ≦ θ ≦ 45 ° instead of 10 ° ≦ θ ≦ 45 ° according to claim 1.