JP2565061B2 - Liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art In a conventional liquid crystal display element, for example, in a twisted nematic (TN) type liquid crystal display element in which the liquid crystal orientation is twisted by 90 ° between upper and lower substrates, the viewing angle direction from the substrate vertical direction of the display element is When tilted, the viewing angle dependence of the display appeared. This TN structure will be described with reference to FIG. As shown in FIG. 6A, in the TN structure, the alignment direction of liquid crystal molecules on the upper and lower substrates forms an angle of 90 °. However, this TN structure has a viewing angle dependency. In particular, the viewing angle dependency is remarkable in the AA ′ direction shown in FIG. 6A, and the viewing angle dependency is relatively weak in the BB ′ direction shown in FIG. 6A. Therefore, the BB 'direction is usually used as the horizontal direction of the display surface, and the AA' direction is used as the vertical direction of the display surface.

Therefore, in order to reduce the vertical viewing angle dependence, one pixel is divided into a plurality of regions as shown in FIG. 6 (b).
The method shown in has been performed. In FIG. 6B, TN structures having different 180 ° orientation directions are set, and the viewing angle dependences in the upper and lower directions are averaged and the viewing angle dependences are relaxed (Japanese Patent Laid-Open No. 63-106624). . FIG. 4 shows a schematic diagram of the rubbing direction that determines the orientation direction.

[0004]

However, although the conventional example improves the vertical viewing angle dependency, it has a problem in its manufacturing process. The alignment process in this conventional example will be described with reference to FIG. Region I of glass substrate 701
An appropriate shield is placed on I to perform the orientation process of the region I. Next, a shield is placed on the region I and the alignment treatment of the region II is performed. Similar steps are performed for the glass substrate 702. Therefore, it is necessary to perform the alignment process and the photolithography process four times on the upper and lower substrates, respectively. Therefore, there is a problem in that the manufacturing process becomes extremely long. In addition, as the number of photolithography steps is large, there are problems that the peeling failure of the photoresist increases, the alignment film is easily damaged by the photoresist developing solution, and the alignment state of the liquid crystal is disturbed. It was

As described above, it can be said that the conventional example is not put to practical use. The present invention provides a liquid crystal display device having good vertical viewing angle characteristics which can be manufactured by a short manufacturing process without causing the disorder of the liquid crystal alignment as described above.

[0006]

According to the liquid crystal display device of the present invention, liquid crystal molecules have a constant pretilt angle direction and a single in-plane orientation direction (A direction) on one substrate surface, and the other substrate surface. The upper part is divided into two regions (B, C) smaller than one pixel , and the pretilt angle direction of the B region is a direction in which the pretilt angle direction of the C region is rotated by about 180 ° about the substrate surface normal line, The in-plane orientation directions of the B and C regions (B and C directions) form an angle of approximately 45 ° with the boundary between the B and C regions, and the A direction and the B or C direction form approximately 90 °. Composed of.

[0007]

The present invention will be described with reference to FIG. In the present invention, two liquid crystal regions (A, B) having different alignment directions are alternately arranged on the liquid crystal display substrate. As shown in FIGS. 1A and 1B, these regions may be either vertical strips or horizontal strips. Further, it may be divided into rectangles as shown in FIG. In either case, the liquid crystal display substrate is divided into either A or B areas. In these regions A and B, the pretilt angle directions on the upper and lower substrates are different from each other, and each has a TN structure having a specific orientation direction. First, the alignment direction perpendicular to the surface of the liquid crystal display substrate of the present invention will be described with reference to FIG. For the sake of clarity, FIG. 2 is shown without the twist of the upper and lower substrates. In FIG. 2A, the pretilt angle directions of the liquid crystal molecules on the upper and lower substrates are aligned. On the other hand, in FIG. 2B, the pretilt angle directions of the liquid crystal molecules on the upper and lower substrates are not aligned. The region A of the present invention has a liquid crystal alignment structure in which the upper substrate is twisted as shown in FIG. This twist direction is
It may be leftward or rightward, and the twisting direction is determined according to the chiral dopant in the nematic liquid crystal. The area B of the present invention is shown in FIG.
It has a liquid crystal alignment structure in which the upper substrate as shown in (b) is twisted in the same direction as the region A. As a result, the area A,
B has a TN structure having the same twist direction but different pretilt angle directions on the upper and lower substrates. Plan views are mainly used for the subsequent drawings showing the orientation directions. Therefore, as shown in FIG. 2, the pretilt direction is distinguished by writing a black circle for the liquid crystal alignment direction on the substrate.

Next, the orientation directions of the regions A and B in the plane of the substrate will be described with reference to FIGS. 3 and 4. In the present invention, the liquid crystal alignment direction on each of the upper and lower substrates and the alignment boundary line are approximately four.
Make an angle of 5 °. In this case, the orientation direction in the plane of the substrate is as shown in FIG. 3 or 4. In any of these four types of orientation directions, the orientation directions of the regions A and B in the lower substrate are different by 180 °. Therefore, the alignment treatment of the lower substrate must be performed twice. The upper substrate has the same orientation direction regardless of the regions A and B. Therefore, the alignment treatment of the upper substrate only needs to be performed once.

As described above, by adopting the region B in which the number of times of the alignment treatment of the upper substrate is one, it is possible to reduce the number of alignment treatments during the manufacturing process.

Further, if the alignment direction on each of the upper and lower substrates and the alignment boundary line form an angle of about 45 °, each region can be stably present when a voltage is applied. In the extreme case of FIG. 5 where the angle is 90 °, the region B becomes unstable when a voltage is applied and is absorbed by the region A, and the desired effect of compensating for the viewing angle dependency cannot be obtained. As described above, when the liquid crystal display device having the alignment direction of the present invention is used,
It is possible to obtain a stable effect of compensating the viewing angle dependency with a small number of manufacturing steps.

[0011]

EXAMPLE A first example of the present invention will be described with reference to FIG. As shown in FIG. 8A, the glass substrate (A, B) 80
An indium tin oxide (ITO) film 801 having a thickness of 0 or more was formed by a sputtering method. Thereafter, as shown in FIG. 8B, a polyimide solution was applied to the glass substrate (A, B) and baked at 200 ° C. to form a polyimide film 802. After this, as shown in FIG. 8C, both glass substrates (A, B)
Was subjected to rubbing treatment. Next, as shown in FIG. 8D, a photoresist 803 was applied to only one substrate (A) and exposed and developed. If the baking temperature of the polyimide solution is low, the polyimide alignment film is damaged during this development, resulting in poor alignment of the liquid crystal. In order to avoid this, it is necessary to bake the polyimide alignment film at 200 ° C. or higher. And
As shown in FIG. 8E, the glass substrate (A) is
Rubbing treatment was performed in the opposite direction to (c). After that, the photoresist was peeled off, and both glass substrates (A, B) were bonded together using an ultraviolet curable resin 804 via a silica spacer (diameter 5 μm) as shown in FIG. 8 (f). After that, nematic liquid crystal was injected in a vacuum and sealed. FIG.
In, the rubbing direction experienced by the polyimide film surface is shown, but the twist direction in the substrate surface is ignored for simplicity.

The relationship between the rubbing direction and the exposure shape of the photoresist in the above process is shown in FIGS. 9 (a), 9 (b) and 9 (c). Thus, in this example, three types of liquid crystal cells were prepared. A rectangular voltage waveform was applied and observed with a polarizing microscope.
As a result, stable disclination occurred in FIGS. 9A and 9B. This disclination did not move or disappear even when a rectangular voltage waveform was applied for a long time. That is, since the disclination is stably generated, it can be seen that the state in which the orientation direction is different in each region is maintained even if a voltage is applied. Therefore, it was confirmed that these two regions compensate each other for the viewing angle dependency, and the compensation effect can be stably realized.

On the other hand, in FIG. 9 (c), disclination did not occur. From this, it can be seen that the divided regions are not always stable when the rubbing direction and the region boundary line do not form an angle of 45 ° as in the present invention. Therefore, in this case, the effect of compensating for the viewing angle dependency cannot always be obtained.

FIG. 10A shows the result of measuring the viewing angle dependence of FIG. 9A corresponding to the present invention. For comparison, the measurement result of the viewing angle dependence of a normal TN cell is shown in FIG. These results are shown in the vertical direction (A-A 'in FIG. 3).
Direction) depending on the viewing angle. From now on, conventional TN
It can be seen that the viewing angle characteristic is better than that of the cell.

A liquid crystal display device using an amorphous silicon TFT array substrate could be obtained by the same manufacturing method as above. Also in this case, the viewing angle characteristics similar to those in FIG. 10A could be obtained.

[0016]

As described above, the liquid crystal display device of the present invention can be manufactured in a shorter process than the conventional one, and each region operates stably, and good viewing angle characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view of a liquid crystal display device of the present invention.

FIG. 2 is a cross-sectional view for explaining a pretilt angle direction of the present invention, omitting a twist angle.

FIG. 3 is a plan view for explaining an orientation direction within a substrate plane of the present invention.

FIG. 4 is a plan view for explaining an orientation direction in a substrate surface of the present invention.

FIG. 5 is a plan view for explaining an unstable alignment direction.

FIG. 6 is a plan view for explaining a conventional technique.

FIG. 7 is a diagram for explaining an orientation direction of a conventional technique.

FIG. 8 is a process drawing for explaining the embodiment of the present invention.

FIG. 9 is a diagram for explaining the orientation direction of the example of the present invention.

FIG. 10 is a diagram showing measurement results of viewing angle characteristics according to an example of the present invention.

[Explanation of symbols]

 701, 702, 800 Glass substrate 800a Glass substrate A 800b Glass substrate B 801 ITO film 802 Polyimide film 803 Photoresist 804 UV curable resin

Claims (1)

(57) [Claims] 1. A liquid crystal display device having a plurality of alignment directions on a substrate, wherein liquid crystal molecules have a constant pretilt angle direction and a single in-plane alignment direction (A direction) on one substrate surface, and the other The surface of the substrate is divided into two regions (B, C) smaller than one pixel , and the pretilt angle direction of the region B is a direction obtained by rotating the pretilt angle direction of the region C by about 180 ° about the substrate surface normal. None, the in-plane orientation directions of the B region and the C region (the B direction and the C direction) form an angle of approximately 45 ° with the boundary between the B region and the C region, and the A direction and the B direction or the C direction form approximately 90 °. A liquid crystal display device characterized by being made.