JPS6366534A - Production of liquid crystal display element - Google Patents

Abstract

PURPOSE:To perform uniform orientation throughout a large area without frequently replacing a rubbing material by rubbing a substrate while shifting relative positions of the rubbing material and the substrate in the direction orthogonal to the rubbing direction. CONSTITUTION:A substrate 3 on which a transparent electrode and an overcoat layer are formed is placed on a table 4 and is rubbed with a rubbing roll 1 around which a rubbing material 2 is wound. For example, the rubbing roll is moved by an extent 2d after the first rubbing and is moved by an extent -d after the second rubbing and is moved by the extent 2d after the third rubbing. By this method, the rubbing material 2 is prevented from being damaged only in a specific position and a wide area is uniformly rubbed without replacing the rubbing material for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a liquid crystal display element in which a 2Ji plate is aligned by a rubbing method.

[Prior Art] Ever since twisted nematic liquid crystal display devices (TNLCDs) were put into practical use, the rubbing method has been widely used as an alignment treatment method with excellent mass productivity and reproducibility.

Recently, liquid crystal displays other than the conventional TNLCD have begun to be put into practical use.

Specifically, it is a liquid crystal display element that uses birefringence, uses neptic liquid crystal, and has a twist angle of 1[10~
360°, and the alignment direction of liquid crystal molecules and 20~
It has a configuration in which polarizing films having polarization axes in directions shifted by 70° are arranged.

In liquid crystal display elements that utilize such birefringence, unlike conventional TNLCDs, it has become important to control the pretilt angle by a rubbing method.

That is, in the conventional TNLCD, this pretilt angle is usually 1.
It was said that a low angle of about 2 degrees is preferable within a range that does not cause reverse tilt. Moreover, since the pretilt angle is low, there is little variation in the pretilt angle.
Even if the rubbing conditions varied slightly, there was almost no deterioration in display quality.

On the other hand, in liquid crystal display devices that utilize birefringence as described above, the twist angle is large, ranging from 160 to 3,600 degrees, so in order to obtain stable display, the pretilt angle must be 5° or more with little variation. It is hoped that this will be done.

If the pretilt angle due to this rubbing varies within the cell plane, the threshold voltage, which is the voltage at which liquid crystal molecules rise, will fluctuate, resulting in display unevenness when a certain voltage is applied, reducing display quality. It was the cause.

For this reason, it has become necessary to strictly control the rubbing conditions.

The rubbing conditions related to this pretilt angle include, for example, the rotation speed of the rubbing roll, the pressure with which the roll is pressed against the substrate, and the like. Therefore, in order to keep these conditions constant, in addition to the accuracy of the table on which the substrate is placed during rubbing, the accuracy of the mechanical equipment such as the positional accuracy of the rubbing roll, the uniformity of the thickness of the rubbing material, and the accuracy of the flocking. Uniformity, etc. will also be required.

Among these, the accuracy of mechanical devices can be achieved relatively easily. However, even if the rubbing material is fairly uniform when new, it must be used repeatedly as it processes a large number of substrates, and during use, the edges of the substrate may When a specific location of the rubbing material continuously comes into contact with a corner, an edge of an electrode, etc., damage progresses only at that contact portion, making uniform rubbing difficult.

When the substrate with this uneven orientation is made into cells.

The pretilt angle varies, resulting in a liquid crystal display element with poor display quality, resulting in a decrease in manufacturing yield.

Therefore, the rubbing material must be replaced after a short period of time.

Although rubbing materials were frequently replaced with new ones, this had the disadvantage of reducing productivity.

In addition, the same situation exists in ferroelectric liquid crystal display elements that use a ferroelectric liquid crystal with a smectinic C phase as the liquid crystal and have polarizing films arranged on both sides. The characteristics are significantly influenced by the rubbing conditions.

Therefore, a similar method was necessary in order to provide good display performance over the large [r1 eyes J1.

[Problems to be solved by the invention] As mentioned above, replacing the rubbing material in a short period of time and frequently replacing it with a new rubbing material is useful for preventing deterioration in display quality caused by uneven orientation. However, this frequent replacement has the drawbacks of increased manufacturing costs due to the use of a large number of rubbing materials and production stoppage during replacement, resulting in a decrease in productivity.

For this reason, there is a need for a rubbing method that can achieve uniform alignment over a large area without frequent replacement of rubbing materials, and the present invention aims to provide such a rubbing method. There is.

[Means for Solving the Problems] The present invention has been made to solve these problems, and includes a method for manufacturing a liquid crystal display element in which alignment treatment is performed by rubbing the surface of a substrate with a rubbing material.
The present invention provides a method for manufacturing a liquid crystal display element, characterized in that rubbing is performed while shifting the relative positions of the rubbing material and the substrate in a direction perpendicular to the rubbing direction.

The method for manufacturing a liquid crystal display element of the present invention includes using a nematic liquid crystal as a liquid crystal, having a twist angle of 160 to 360'', and forming polarizing films on both sides of the liquid crystal having polarization axes in a direction deviated from the alignment direction of liquid crystal molecules by 20 to 70'. When applied to a liquid crystal display element that utilizes birefringence, or a ferroelectric liquid crystal display element that uses a ferroelectric liquid crystal with a smectic C phase and has polarizing films on both sides, the effect is large and the display A liquid crystal display element with less unevenness can be easily obtained.

Of course, the devices are not limited to these, but include conventional TNLCDs and guest-host liquid crystal display devices (GH) using dichroic dyes.
LCD), etc.

In the present invention, the substrate is made of glass, plastic, etc.
, ITO (indium oxide-tin oxide) in necessary parts,
A material with a transparent electrode formed of tin oxide or the like is used. In addition, this substrate may be coated with silicon oxide, aluminum oxide, titanium oxide, resin, etc. coating layers, color filters, polarizing films, and light shielding layers between the substrate and electrodes to prevent alkali elution and improve adhesion. A coat layer of silicon oxide, aluminum oxide-titanium oxide, resin, etc., a color filter, a polarizing film, a light-shielding layer, etc. may be formed on the electrode to improve insulation and orientation. A metal electrode may be formed in place of the electrode or in parallel with the transparent electrode. Furthermore, an active element such as a transistor, a diode, or a nonlinear resistance element may be incorporated on the substrate, or an electrode may be formed on only one of the two substrates. It may be formed into a comb-tooth shape, and a known substrate structure of a liquid crystal display element can be adopted.

This board is rubbed with a rubbing material.

In the present invention, when rubbing with this rubbing material, the rubbing is performed while shifting the relative positions of the rubbing material and the substrate in a direction perpendicular to the rubbing direction.

FIG. 1 is a side view showing a typical example of the rubbing method, and FIG. 2 is a plan view of i.

In FIGS. 1 and 2, 1 is a rubbing roll around which a rubbing material 2 is wound, 3 is a substrate, and 4 is a table for holding the substrate.

In this example, the rubbing roll 1 and the table 4 move relatively in the rubbing direction, that is, in the horizontal direction in FIG. 1, and in the vertical direction in FIG. 2, to perform rubbing.

In the present invention, in addition to the movement in the rubbing direction, the relative positions of the rubbing roll l and the table 4 are moved in a direction perpendicular to the rubbing direction between rubbings. This movement is in the front-rear direction in FIG. 1, and in the left-right direction in FIG. 2.

This movement in the direction perpendicular to the rubbing direction may be performed by moving the rubbing roll side or by moving the table side. However, if the substrate is movable on the table, the relative position between the rubbing roll and the substrate may be changed.

As the rubbing material of the present invention, conventionally used rubbing materials can be used, such as cloth-like materials, fiber-flocked materials,
There are brush-like items.

In addition, although we have described a roll as a typical example of conventionally used methods for attaching this rubbing material, it does not necessarily have to be a roll, but can be applied by attaching the rubbing material and pressing it against the substrate. Good to have.

FIGS. 3A to 3D are diagrams showing changes in the relative positions of the rubbing roll and the substrate when the same substrate is rubbed four times.

Figure 3 (A) shows a constant distance ftel each time the back and forth rubbing is performed.
This is an example in which the object is moved in a direction perpendicular to the rubbing direction.

(B) moves by 2d after rubbing once, moves by -d after rubbing for the second time, and 3 moves by J
This is an example of rubbing by tA and then moving by HH2a again.

(C) is an example of rubbing in only one direction, not reciprocating rubbing, and is an example in which the rubbing is performed by d each time, similar to (A).

(D) is an example of reciprocating rubbing in which the position is not changed during one reciprocation, and after one reciprocation, the position is moved by 2d and reciprocating rubbing is performed.

Among these examples, from the viewpoint of uniformity, it is preferable to move in a direction perpendicular to the rubbing direction each time rubbing is performed.

In this example, the same substrate is rubbed four times, but if one rubbing is sufficient as in the case of a conventional TNLCD substrate, one rubbing may be performed. However, in the case of a liquid crystal display using birefringence; (in the case of substrates for g-conductor or ferroelectric liquid crystal display elements, it is preferable to rub multiple times because it is easier to obtain a more uniform alignment by rubbing multiple times. .

Furthermore, it is preferable to move and rub the substrate even when the substrate is replaced.

The distance of movement in the direction perpendicular to the rubbing direction may be approximately 3 to 100 mm at a time, and may be appropriately selected depending on the sizes of the rubbing material and the substrate. This movement is
From the point of view of uniformity, it is preferable to perform rubbing every time, but it is also possible to move every two times.In addition, if you only want to rub 1@ on one substrate, you can do it more than once. You can rub at the same position continuously.Also, this position can be moved, for example, by 20 mm at 5 positions, and then returned to the initial position after 5 movements.20 times at 20 positions at 5 cm intervals Return to the first place after the movement of 2
After 0 movements, it may be moved back by -5 mm and returned to the initial position after 20 movements.

By performing rubbing while shifting the relative positions of the rubbing material and the substrate in this manner, a fixed position of the rubbing material does not always come into contact with the edge portions of the substrate or electrode, and damage to the rubbing material is reduced. This reduces the frequency of replacing the rubbing material and improves productivity.

In particular, more uniform rubbing is possible by performing rubbing multiple times on the same substrate while shifting the relative (θ) position between the position of the rubbing material and the position of the substrate.

The pair of substrates rubbed in this way are sealed around the periphery, liquid crystal is injected into the inside, and the injection port is closed by -1 to complete a liquid crystal cell.

In addition to the above, various techniques used in known liquid crystal display elements can be applied to the present invention within a range that does not impair the effects of the present invention.

[Operation] In the conventional rubbing direction, rubbing was performed while shifting the relative positions of the rubbing material and the substrate in the rubbing direction, but the position of the rubbing material in the direction perpendicular to the rubbing direction; The heavy position of I0 Yu and I1 Yu was rubbed in the same position. The rubbing material used for this rubbing is usually the same rubbing material for a large number of substrates k g j ;! Since it is l f 6, it will be used red and red. However, the board to be rubbed has
There are uneven parts such as the edges and corners of the substrate, the edges of the electrodes, etc., and if a specific place of the rubbing material comes into continuous contact with these parts, damage may progress to only those contact areas, or the bristles may become high. This made it difficult to rub uniformly over a wide area.

On the other hand, if the rubbing direction of the present invention is adopted, the rubbing is performed while shifting the relative position between the position of the rubbing material, the position of the substrate, and the position U in the direction orthogonal to the rubbing direction.

Therefore, a specific location of the rubbing material does not continuously come into contact with the uneven part of the board, and only a specific location of the rubbing material is not significantly damaged. This allows for thorough rubbing.

[Example: After forming a transparent electrode of ITO (indium Mide-tin butyride) on a glass substrate and patterning it into a stripe shape, poly-Rmide is applied to this "-1" and cured to form an ONO. - A coating layer was formed.

A roll with a diameter of 10 cm wrapped around a cloth as a rubbing material was prepared as a rubbing roll, and after contacting the substrate, it was pressed 0.1 mi+ and rubbed twice back and forth. At this time, the table was moved so that d=51 and the rubbing process was performed using the method shown in FIG. 3(B).

This substrate was used to form a cell with a twist angle of 160°, and a pair of polarizing films were placed on both sides to manufacture a liquid crystal display device utilizing birefringence.

This liquid crystal display element had a uniform display state even when voltage was applied, and had good display quality.

On the other hand, as a comparative example, a similar cell was constructed using a substrate that was rubbed twice back and forth without moving the table.

This liquid crystal display element had no problems when a new rubbing cloth was used, as in the example, but it was at a stage where almost no problems occurred in the example after repeated use of the rubbing cloth. However, in this comparative example, there was a sudden increase in the number of poor results, and there were many cases in which unevenness occurred along the rubbing direction when voltage was applied, and the display quality deteriorated significantly.

[Effects of the Invention] According to the rubbing method of the present invention, since rubbing is performed while shifting the relative positions of the rubbing material and the substrate in the direction orthogonal to the rubbing direction, There is no continuous contact with irregularities around the substrate or electrodes, and specific parts of the rubbing material are not significantly damaged, allowing uniform rubbing of a wide area over a long period of time without replacing the rubbing material. It becomes possible.

This eliminates the need for frequent replacement of rubbing materials.
Productivity is high and production costs are low.

[Brief explanation of drawings]

FIG. 1 is a side view showing a typical example of the rubbing method of the present invention. FIG. 2 is a plan view of the example shown in FIG. 1. FIGS. 3A to 3D are explanatory diagrams showing the relative positions of the rubbing roll and the substrate during rubbing. Rubbing roll: l Rubbing material: 2 Substrate: 3 Table: 4 Notebook 1 drawing Ren 2L71 藷 3 Nagi (ha) (B)
(c) CD) 11

Claims (5)

[Claims] (1) In a method for manufacturing a liquid crystal display element in which alignment treatment is performed by rubbing the surface of a substrate with a rubbing material, rubbing is performed while shifting the relative position of the rubbing material and the substrate in a direction perpendicular to the rubbing direction. A method for manufacturing a liquid crystal display element, characterized by: (2) The method for manufacturing a liquid crystal display element according to claim 1, wherein rubbing is performed on the same substrate multiple times while shifting the relative positions of the rubbing material and the substrate. (3) The method for manufacturing a liquid crystal display element according to claim 1 or 2, wherein rubbing is performed on different substrates while shifting the relative positions of the rubbing material and the substrate. (4) The liquid crystal is a nematic liquid crystal, and its twist angle is 16
0 to 360°, and the alignment direction of liquid crystal molecules and 2
Manufacture of a liquid crystal display element according to any one of claims 1 to 3, which is a liquid crystal display element using birefringence in which a polarizing film having a polarization axis in a direction shifted by 0 to 70 degrees is arranged. Method. (5) The liquid crystal display element according to any one of claims 1 to 3, which is a liquid crystal display element in which the liquid crystal is a ferroelectric liquid crystal having a smectic C phase, and polarizing films are arranged on both sides of the liquid crystal. manufacturing method.