JPH11174462A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the image quality of a liquid crystal display element in a transverse electric field drive system capable of realizing an excellent multi-level display over a wide visual angle. SOLUTION: Optical characteristic of this element is controlled by sticking a 1st glass substrate 1 where pillar-shaped insulating films 11 are provided at the intersections of plural electrode wiring arranged in a matrix shape and where an oriented film layer for controlling the direction of the orientation of liquid crystal molecules is provided and a 2nd glass substrate 9 where an oriented film layer for controlling the direction of the liquid crystal molecules is formed on the surface by holding a space through the pillar-shaped insulating film 11, arranging a liquid crystal layer 8 inside and generating an almost parallel electric field in the principal plane of the 1st glass substrate 1 between the picture element electrode wiring 6 of the plural electrode wiring common electrode wiring 3. At this time, the cross-section form of the pillar-shaped insulating film 11 provided at each of the intersections of the plural electrode wiring arranged in a matrix shape is formed to have a side face 11a in parallel to the direction of rubbing (the direction of an arrow).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an active matrix array substrate of 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 a liquid crystal are 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.

In particular, an active matrix type TN (Twisted Nematic) liquid crystal display 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. PCs and laptops,
Furthermore, it is being actively developed as a large, large-capacity full-color display for engineering workstations.

In such an active matrix type liquid crystal display device, there is a TN (twisted nematic) type as a widely used liquid crystal display mode. In the TN mode, a panel having a structure in which liquid crystal molecules are twisted by 90 ° between electrode substrates sandwiching a liquid crystal layer is sandwiched between two polarizing plates.

The two polarizing plates are arranged such that their polarization axes are orthogonal to each other, and one of the polarizing plates is arranged such that its polarization axis is parallel or perpendicular to the long axis direction of the liquid crystal molecules in contact with one substrate. When no voltage is applied, white display is performed. However, when a voltage is applied between two substrates, that is, in a direction perpendicular to the liquid crystal panel, the light transmittance gradually decreases, and black display is performed.

[0006] Such display characteristics can be obtained because, when a voltage is applied to the liquid crystal panel, the liquid crystal molecules try to align in the direction of the electric field while untwisting the twisted structure. This is because the state changes and the light transmittance is modulated.

However, even in the same molecular arrangement state, the polarization state of the transmitted light changes depending on the incident direction of the light incident on the liquid crystal panel, so that the light transmittance varies according to the incident direction. . That is, the liquid crystal panel has a viewing angle dependency.

The viewing angle characteristic is such that when the viewpoint is inclined obliquely with respect to the main viewing angle direction (the major axis direction of the liquid crystal molecules in the intermediate layer of the liquid crystal layer), the phenomenon of reversal of luminance is caused and the image quality is changed. This is an important issue.

Conventionally, various methods have been proposed and developed to solve this problem. Among them, a method that has been particularly noticed in recent years is that, instead of applying an electric field in a direction perpendicular to the substrate as in the TN type liquid crystal display method, the direction in which the liquid crystal is applied is substantially parallel to the glass substrate. There is an IPS (in-plane switching) system for controlling the direction of arrangement on a plane parallel to the glass substrate, and is proposed in, for example, Japanese Patent Publication No. 63-21907 and Japanese Patent Application Laid-Open No. 6-160878.

FIG. 5 shows a basic sectional configuration diagram of a general IPS mode liquid crystal display device. In FIG. 5, reference numeral 1 denotes a first glass substrate, and 2 denotes a scanning electrode wiring. Reference numeral 3 denotes a common electrode wiring formed in the same layer as the scanning electrode wiring 2 at the same time as the formation of the scanning electrode wiring 2, and reference numeral 4 denotes an insulating layer which is generally used and has a laminated structure containing SiNx or SiNx.

Reference numeral 5 denotes a signal electrode wiring, and reference numeral 6 denotes a pixel electrode wiring formed simultaneously with the signal electrode wiring 5. Reference numeral 7 denotes a switching element portion, which mainly uses a-Si as a semiconductor layer. Reference numeral 8 denotes a liquid crystal layer, and 9 denotes an opposing second glass substrate, a part of which is shown to prevent congestion in the figure.

In the above method, the liquid crystal molecules of the liquid crystal layer 8 are connected to the voltage applied to the common electrode wiring 3 and the switching element 7.
Is controlled by an electric field generated substantially in parallel with the substrate 1 between the pixel electrode wiring 6 and the pixel voltage supplied from the signal electrode wiring 5 to the pixel electrode wiring 6.

[0013]

The IPS mode is a mode in which linearly polarized light is controlled by a change in birefringence caused by the movement of liquid crystal molecules in a plane, and the IPS mode has a smaller liquid crystal panel than the conventional TN mode. The dependence of the change in optical characteristics on the gap is large, and it is necessary to control the gap with an accuracy of about 0.1 μm or less.

At present, a method widely used as a gap forming process for a liquid crystal panel is a method in which small spherical spacers are dispersed on a glass substrate and bonded to an opposing glass substrate.

The gap of the liquid crystal panel is determined by the material, dispersion density, pressure and the like of the spacer. To increase the gap accuracy, it is necessary to increase the dispersion density of the spacer.

However, as the number of spacers in the panel increases, minute light leakage caused by disorder in the alignment of the liquid crystal molecules around the spacers cannot be ignored, which causes a deterioration in image quality, particularly in contrast.

As a method for removing the influence of such spacers, for example, as shown in FIG. 6, each intersection P of various wirings PX and PY formed on one glass substrate 1 is used.
A method has been proposed in which an insulating resin block is formed in a columnar shape on P and is used as a spacer 10 to realize a panel having no spacer in a pixel (for example, JP-A-3-89320).

However, according to this method, the height of the spacer 10 provided on one substrate is set to about 4 to 5 μm, which is the gap of a general liquid crystal panel, and the cross-sectional shape is a characteristic of the electrode wiring. During the rubbing process for controlling the alignment direction of the liquid crystal molecules, it must be a square or a rectangle as shown in the figure, aligned with PX and PY.
Dislocation of the orientation of the liquid crystal due to the influence of the protrusions of the spacer 10 and display unevenness caused by the deviation cause problems.

That is, as shown in FIG. 7, the rubbing direction may be declination θ with respect to the substrate. When rubbing is performed under such conditions, the fluffed fibers of the rubbing cloth are distributed at the corner 10A of the spacer 10. Is divided into widths of asin θ + b / cos θ = β (> b) with respect to the vertical and horizontal widths a and b, so that the alignment direction is disturbed as indicated by the arrow, and the width β is wider than the width b. There has been a problem that the aforementioned minute light leakage cannot be effectively prevented.

Particularly, in the IPS system, as described above, since the optical characteristics are controlled by the birefringence, there is a problem that the optical characteristics change greatly depends on a slight deviation of the orientation and the display is easily affected. is there.

A main object of the present invention is to provide a new structure of a liquid crystal panel which can improve the above-mentioned problems with respect to gap formation and alignment in the IPS display system.

[0022]

According to a first aspect of the present invention, there is provided a liquid crystal display device comprising: a columnar insulating film provided at an intersection of a plurality of electrode wirings arranged in a matrix; A first glass substrate provided with an alignment film layer for controlling the direction and a second glass substrate provided with an alignment film layer for controlling the alignment direction of the liquid crystal molecules on the surface are separated by the columnar insulating film. By holding a liquid crystal layer inside and generating an electric field substantially parallel to the main plane of the first glass substrate between the pixel electrode and the common electrode wiring among the plurality of electrode wirings. In a liquid crystal display element having controlled characteristics, a cross-sectional shape of a columnar insulating film provided at each intersection of a plurality of electrode wirings arranged in a matrix is formed to have a side surface parallel to a rubbing direction. It is an feature.

Accordingly, the fluffed fibers of the rubbing cloth move parallel to the rubbing direction along the side surfaces of the columnar insulating film, so that the rubbing disturbance is extremely reduced, and the liquid crystal around the spacer generated in the pixel by the spacer. This can eliminate minute light leakage due to the disorder in the orientation of the image, and can realize image quality with high contrast and excellent display uniformity.

The liquid crystal display element according to the second aspect is the first aspect.
In the liquid crystal display device of the above, the planar shape of the columnar insulating film is
The first glass substrate has a rectangular shape having sides coincident with the orientation direction of the liquid crystal layer.

Therefore, the fluffed fibers heading toward the front of the insulating film pass over the insulating film without being separated by the insulating film, so that the fluff of the rubbing cloth due to the columnar insulating layer is disturbed and the orientation caused thereby. The misalignment of the azimuth can be greatly improved.

According to a third aspect of the present invention, there is provided a liquid crystal display device, wherein the insulating film has a shape in which a plurality of small cylindrical projections are arranged in a line at regular intervals and substantially perpendicular to the rubbing direction. It is a feature.

In this case, since the fluffed fibers of the rubbing cloth move in such a relationship as to scoop the hair with a comb, turbulence of the rubbing can be extremely reduced. A liquid crystal display element according to a fourth aspect is characterized in that the columnar insulating film according to the first, second or third aspect is formed of a photosensitive acrylic resin.

Since the columnar insulating film can be formed by the photo-etching method, the columnar insulating film having a shape regulated in the rubbing direction can be formed easily and accurately.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the liquid crystal display device according to the present invention will be described in detail with reference to the drawings. (Embodiment 1) FIGS. 1 and 2 show a schematic plan view of a thin film transistor array substrate of a liquid crystal display device according to a first embodiment of the present invention, and a schematic view of a cross sectional structure thereof.

In the figure, reference numerals 2 and 3 denote first glass substrates 1 respectively.
The scanning electrode wiring and the common electrode wiring formed above are shown. In the present embodiment, the two electrode wirings 2 and 3 are formed by depositing a metal thin film containing aluminum as a main component on the same plane. The shape shown in the figure was formed by photolithography.

The metal material to be used is desirably a metal material having a low wiring resistance. However, it is not particularly limited to an aluminum-based metal, and a single-layer film or a multilayer film may be used. Next, as the insulating film 4, after stacking the anodic oxide layer of the aluminum film and silicon nitride (SiNx) and amorphous silicon as the semiconductor layer, the anodic oxide layer on the first common electrode wiring 3 and the silicon nitride are stacked. After removing part of the layer and then depositing two layers of aluminum / titanium (Al / Ti) deposited by sputtering,
The signal electrode wiring 5 and the pixel electrode wiring 6 were pattern-formed by dry etching.

Reference numeral 7 denotes a thin film transistor which is a switching element. In this embodiment, the line width of the pixel electrode wiring 6 is 5 μm. Further, an additional capacitance 10 (FIG. 2) was formed between the pixel electrode wiring 6 and the scanning electrode wiring 2. Although the additional capacitance 10 is formed between the scanning electrode wiring and the common electrode wiring 3 one line after the corresponding scanning electrode wiring, the additional capacitance 10 is not limited. It does not do.

Thereafter, silicon nitride is deposited as an insulating layer 4 (FIG. 2), and two columnar insulating films 11 are formed on the additional capacitor 10 in a rectangular shape as shown in FIG. Was formed so as to coincide with the rubbing direction of the liquid crystal panel as shown by the dotted arrow.

The columnar insulating film 11 is formed by applying a photosensitive acrylic resin so as to have a predetermined thickness corresponding to the panel gap, and then processing it into the shape of the present invention by photolithography and etching. Formed.

In this embodiment, the thickness of the insulating film 11 is set to 3 (μ
m). Next, the thin film transistor array substrate of the present invention is rubbed at an angle of θ = 10 ° with respect to the longitudinal direction of the pixel electrode wiring 6 and the common electrode wiring 3 as shown in FIG. Matrix), red,
A second glass substrate 9 on which green and blue color filters were formed was similarly aligned and bonded, and then liquid crystal 8 was injected to form a panel.

As a result of measuring the in-plane gap distribution of the liquid crystal panel, it was 3.2 (μm) ± 0.05 (μm), and a panel with extremely excellent uniformity was realized. This is because, as indicated by the arrow in FIG. 3, the fluffed fibers of the rubbing cloth pass from right in front of the columnar insulating film 11 and pass over the front side 11b of the columnar insulating film 11 as it is. This is because the fiber on the side surface 11a passes while maintaining the posture in the rubbing direction without receiving side pressure from the fiber on the front side.

Therefore, display unevenness and a decrease in contrast due to disordered orientation near the pillar-shaped insulating layer, which have conventionally been problems with the pillar-shaped spacer, do not occur. Over the entire panel,
An excellent contrast ratio of> 300: 1 was realized. (Embodiment 2) Next, a liquid crystal display device according to a second embodiment of the present invention will be described in detail.

FIG. 4 is a schematic diagram showing a plan configuration of a thin film transistor array substrate of a liquid crystal display device according to a second embodiment of the present invention. The scanning electrode wiring, the signal electrode wiring, the common electrode wiring, the pixel electrode, and the thin film transistor are the same as in the first embodiment.

In the present embodiment, as shown in the figure, a columnar insulating film is formed on a plurality of small cylinder-shaped protrusions 1 on an additional capacitance 10.
1A... 11A were arranged in a line at equal intervals. The formation method is
In the same manner as in Example 1, a photosensitive acrylic resin was applied to a predetermined thickness corresponding to the panel gap, and then processed into the shape of the present invention by photolithography and etching.

As a result of measuring the in-plane distribution of the gap of the liquid crystal panel thus produced, the variation was less than ± 0.05 (μm) as in Example 1, and a panel with good uniformity could be realized. Was. Also, the contrast ratio was confirmed to be> 300: 1 over the entire panel.

This is because the projection area of the columnar insulating film in the rubbing direction is extremely small with respect to the fluffed fibers of the rubbing cloth, and the rubbing cloth has a relationship similar to that of a comb tooth with respect to the hair, so that the disturbance of the rubbing cloth is rather suppressed. This is because

[0042]

As described above, in the liquid crystal display device of the present invention, in the horizontal electric field display system capable of realizing a wide viewing angle characteristic, the uniformity of the gap and the securing of the orientation, which are problems in the conventional structure, can be simultaneously realized. . As a result, a high-quality liquid crystal display device having a wide visual field and excellent display uniformity can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a thin film transistor substrate of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a thin film transistor substrate of the liquid crystal display device according to the first embodiment of the present invention.

FIG. 3 is a main part plan view showing a state at the time of rubbing.

FIG. 4 is a plan view showing a configuration of a thin film transistor substrate of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 5 is a perspective view showing the concept of the configuration of a conventional in-plane switching (IPS) liquid crystal display device.

FIG. 6 is a plan view of a conventional liquid crystal display device using a columnar insulating film.

FIG. 7 is a plan view showing a conventional rubbing process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 First glass substrate 2 Scanning electrode wiring 3 Common electrode wiring 4 Insulating layer (SiNx) 5 Signal electrode wiring 6 Pixel electrode wiring 7 Thin film transistor element 8 Liquid crystal layer 9 Second glass substrate 10 Additional capacitance 11 Columnar insulating film 11A Columnar Insulation film

Claims (4)

[Claims] A first glass substrate provided with a columnar insulating film at an intersection of a plurality of electrode wirings arranged in a matrix, and an alignment film layer for controlling an alignment direction of liquid crystal molecules; A second glass substrate on which an alignment film layer for controlling the alignment direction of liquid crystal molecules is bonded to the second glass substrate while maintaining a gap by the columnar insulating film, and a liquid crystal layer is disposed inside,
In a liquid crystal display element in which an optical property is controlled by generating an electric field substantially parallel to a main plane of the first glass substrate between a pixel electrode of the plurality of electrode wirings and a common electrode wiring, the liquid crystal display elements are arranged in a matrix. A liquid crystal display device, characterized in that a cross-sectional shape of a columnar insulating film provided at each intersection of a plurality of electrode wirings has side surfaces parallel to a rubbing direction. 2. The liquid crystal display device according to claim 1, wherein the planar shape of the columnar insulating film is a quadrangle having sides coinciding with the orientation direction of the liquid crystal layer of the first glass substrate. 3. The insulating film according to claim 1, wherein the insulating film has a shape in which a plurality of small cylindrical protrusions are arranged at regular intervals in a row at a right angle to the rubbing direction. Liquid crystal display element. 4. The liquid crystal display device according to claim 1, wherein the columnar insulating film is formed of a photosensitive acrylic resin.