JPH0255330A - Production of oriented film for liquid crystal - Google Patents

Abstract

PURPOSE:To produce the oriented film for liquid crystal molecules having high reproducibility and reliability at a low cost by irradiating a substrate having a resin layer on the main surface with collimated beams of UV light at a prescribed angle with the substrate. CONSTITUTION:Certain microorder is needed at about the molecular level on the surface of the oriented film at the boundary of a device wall in order to orient the liquid crystal molecules and this order is the case in which the groups interacting with the liquid crystal molecules are regularly arrayed or the recessed and projecting shapes are regular. The orientation control power is eventually considered to be imposed on the liquid crystal molecules by a decrease in the free energy by a volume expelling effect. The substrate 4 having the resin layer 3 is, thereupon, irradiated with the collimated beams of the UV light at the prescribed angle alpha. Ruggedness is effectively provided to the resin layer 3 on the substrate 4 by creating the fine spacial distributions of the collimated beams of the UV light in such a manner, by which the liquid crystals are effectively oriented. A mask is used in tight contact with the resin layer 3 and the resin layer is thereafter rubbed to obtain the better effect. The high pretilt orientation is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing an alignment film for liquid crystal molecules made of a polymer resin.

BACKGROUND OF THE INVENTION A liquid crystal molecule alignment film is essential for liquid crystal displays.

As the alignment film, an inorganic obliquely deposited film, a rubbed organic resin film, or the like is used (for example, Basics and Applications of Liquid Crystal Electronics, edited by Akio Sasaki).

Problems to be Solved by the Invention However, the problem with obliquely deposited inorganic films is that the equipment is relatively expensive and the process cost is high because it is a vacuum process.

The rubbing method is often used in industry for -a, but in a mode where the twist angle of liquid crystal molecules is large, that is, a super twisted nematic mode, a light rubbing pressure and high density rubbing are required. Strict management is required to achieve this condition.

Furthermore, in large-capacity displays using super twisted nematic mode, the pre-
It is necessary to increase the tilt angle.

There is no consensus at the moment, but I want a shake/tilt angle of 15° to 20°. Currently, when an organic resin is used as an alignment film material, the rubbing method has a maximum angle of about 10° in consideration of reproducibility and reliability.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides an alignment method for liquid crystal in which a substrate having a resin layer on its main surface is irradiated with parallel ultraviolet light and said resin layer is irradiated at a predetermined angle. The method for manufacturing the membrane will be submitted.

In order to solve the above-mentioned problems, the present invention provides a method for liquid crystal display in which a substrate having a resin layer on its main surface is irradiated with parallel ultraviolet light at a predetermined angle, and the resin layer is further rubbed. The present invention also provides a method for producing an alignment film.

Furthermore, in order to solve the above-mentioned problems, the present invention provides an alignment film for liquid crystal, characterized in that the spatial distribution of the irradiation intensity is modulated using a mask in the irradiation with the parallel ultraviolet light described above. It also provides a manufacturing method.

In addition, in order to solve the above-mentioned problems, the present invention provides a method for using the above-mentioned mask on the main surface of a substrate that is transparent to ultraviolet light.
Provided is a method for producing an alignment film for a liquid crystal as described above, characterized in that it is obtained by creating scratches on a thin film made of a substance that absorbs ultraviolet light by a sand blasting method, a liquid honing method, or a polishing method. It is.

In order to solve the above problems, the present invention provides a method for producing an alignment film for liquid crystal as described above, characterized in that the parallel ultraviolet light described above is obtained from an excimer laser.

In order to align the working liquid crystal molecules, it is necessary to align the liquid crystal molecules at the vessel wall interface. For this purpose, an alignment film is usually provided at the interface. It is understood that the surface of the alignment film requires a certain degree of microscopic order on the molecular level. This order may be caused by the groups that interact with liquid crystal molecules being regularly arranged, or by having a regular uneven shape, which results in a decrease in free energy due to the volume exclusion effect, which exerts an alignment regulating force on liquid crystal molecules. It is believed that there may be charges.

It is believed that the present invention is involved in these orientation mechanisms.

decomposition of the resin layer by the ultraviolet light itself or by excited oxygen atoms or ozone generated by the ultraviolet light;
Alternatively, the volume of the resin layer tends to change due to structural changes at the molecular level caused by ultraviolet light.

If the ultraviolet light itself is strong, it is assumed that it acts on the dipoles of the molecules in the resin layer, exerting a force that tends to cause a certain orientation.

The invention is based on these considerations. However, revealing this evidence is difficult. In experiments using an excimer laser, it is certain that the volume of the resin layer changes as a result of observation. This can be confirmed by observation using a microscope.

It is certain that by creating a fine spatial distribution of collimated ultraviolet light, the organic resin layer on the substrate, for example, will be more effectively textured.

At such times, the liquid crystal molecules were effectively aligned. In addition, by selecting the irradiation angle and the ultraviolet light source, and in some cases by performing rubbing after this, it was possible to achieve high shake/tilt alignment.

The fine spatial distribution of the parallel ultraviolet light may be achieved by utilizing the properties of the light source originating from the optical system itself, or more effectively by utilizing a mask that is in close contact with the organic resin layer on the substrate.

Masks with such fine patterns are difficult to make manually. Several or more white patterns are required in the 1 micron opening. This can be obtained, for example, as follows. A chromium layer with a thickness of approximately 500 angstroms is formed on a synthetic quartz blank, and countless scratches are removed by sand blasting using baking soda particles, liquid honing, or polishing using chromium oxide particles. generated in the chromium layer, resulting in a mask with countless white patterns. In sand blasting and liquid honing, changing the particle irradiation angle changes the shape of the average white pattern, which in turn affects the orientation and pre-tilt angle of liquid crystal molecules.

As a light source for ultraviolet light, it is possible to easily obtain light with a short wavelength of 0.2 microns or less, the irradiation energy is relatively large, it is easy to obtain parallel light, and it is possible to irradiate a large area at once. , excimer lasers are most preferred.

The method according to the invention does not require a vacuum and, in this respect, the equipment costs are low.

Furthermore, in conventional rubbing of a resin film with fibers, etc., if the pre-tilt of the nematic liquid crystal molecules is to be raised slightly from the horizontal level, it is necessary to set extremely delicate conditions and to select the resin film material. With the method according to the present invention, the pre-tilt angle can be made larger than before, the reproducibility is improved, and the degree of freedom in selecting the resin material is expanded.

In addition, in the present invention, the purpose of rubbing after irradiation with ultraviolet light is to strengthen the directionality of the arrangement of liquid crystal molecules near the substrate. The effects of the present invention are not impaired.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

In this example, polyimide resin (JIB-1, manufactured by Japan Synthetic Rubber Co., Ltd., solvent type) and polyamic acid resin (5E-4110, manufactured by Nissan Chemical Co., Ltd., solvent type) were used as the resins. The polyimide resin is used for low shake/tilt angles for nematic liquid crystals, and the resin originally contains polyimide oligomers. Even polyamic acid resins can be imidized by a predetermined heat treatment, and in this example, a heat treatment capable of imidization was performed.

First, the viscosity of polyimide resin and polyamic acid resin was adjusted using a solvent, and the mixture was spun and coated onto a glass substrate using a spinner. This was heat-treated at a predetermined temperature.

In this way, a glass substrate having a polyimide resin layer on the main surface was obtained.

We created a small ultraviolet irradiation device. FIG. 1 shows a schematic diagram of this device. In Fig. 1, 1 is an excimer laser (type, EMG 10) made by Lambda Physik.
1-104 MSC), which can extract parallel ultraviolet light of 0.193 microns by using an excimer of argon atoms and fluorine atoms. 2 is a mask in close contact with the substrate, 3 is a resin layer, and 4 is a substrate. In the figure, a is the angle between the normal line of the substrate and the ultraviolet light.

(Example 1) As shown in Fig. 1, a is Oo, mask 2 is omitted,
A glass substrate having a polyimide resin layer on its main surface, that is, the polyimide resin layer, was irradiated with linear ultraviolet light for 10 seconds. The frequency of laser pulse oscillation was 50 hertz.

Next, light rubbing was performed using a rayon cloth in the usual manner.

Two such substrates were bonded together so that the liquid crystal molecules were homogeneously aligned, and liquid crystal was injected to obtain a liquid crystal panel. As a result of pre-tilt measurement using the magnetic field method, it was 12 to 13 degrees.
A pre-tilt of Even in the actual panel,
The twisting stability of liquid crystal molecules has been improved compared to the conventional method.

(Example 2) As in Example 1, ultraviolet light was irradiated. However, in FIG. 1, a is set to 40°. In this case, no rubbing was performed.

As a result of the same pre-tilt measurement as in Example 1, it was found that the pre-tilt was 15° or more. In actual super twisted nematic panels (STN panels), the results of a simple study suggest that the properties are improved overall.

(Example 3) The mask was produced as follows. I obtained a polished synthetic quartz plate. First, a chromium film having a thickness of about 500 angstroms was formed on the synthetic quartz plate.

Numerous scratches were created on this chromium layer by sand blasting using baking soda particles. FIG. 2 shows a schematic diagram of an apparatus for performing sand blasting. 11 is a pipe for sending high-pressure air, 12 is a container containing baking soda particles, 13 is a particle outlet, 14 is a chromium layer, 15 is a substrate, and b is the relationship between the particle blowing direction and the normal to the substrate. It is a corner.

In this example, the angle in FIG. 2 was set to 0°.

Next, as in Example 1, the resin layer was irradiated with ultraviolet light using an excimer laser, but using a mask with the chrome surface of the mask in close contact with the resin layer. In FIG. 1, two conditions were tested for angle a: Oo and 30°.

Thereafter, the resin layer was subjected to normal rubbing at a low rubbing intensity.

When a liquid crystal panel was manufactured and the pre-tilt angle of the liquid crystal molecules was measured, the value was between 15° and 30°, and it depended on various conditions leading to this value. Reproducibility was sufficient and guaranteed.

The STN panel had excellent properties.

(Example 4) A mask was produced as in Example 3. However, the angle b of the baking soda particles was approximately 70° in FIG. 2 with respect to the chromium surface.

Next, as in Example 1, the resin layer was irradiated with ultraviolet light using an excimer laser, but using a mask with the chrome surface of the mask in close contact with the resin layer. In FIG. 1, two conditions were tested for angle a: Oo and 30'.

When a liquid crystal panel was manufactured and the pre-tilt angle of the liquid crystal molecules was measured, the value was between 15° and 30°, and it depended on various conditions leading to this value. Reproducibility was sufficient and guaranteed.

The STN panel had excellent properties.

(Example 5) A mask was produced as follows. As in Example 3, chromium was formed on a synthetic quartz plate, and numerous scratches were created on the chromium by liquid honing using alumina with a particle size of 1 micron or less or polishing using chromium oxide. At this time, in the case of liquid honing, consideration was given to the angle between the direction of the particles and the normal to the chromium surface. In addition, in the case of polishing, we investigated conditions in which the scratches have directionality and cases in which they do not.

Using this mask, attempts similar to those in Examples 3 and 4 were made.

Overall, the results were excellent.

Effects of the Invention The present invention provides a method for obtaining a resin film for aligning liquid crystal molecules, and has great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus for irradiating a resin layer with parallel ultraviolet rays, and FIG. 2 is a schematic diagram of an apparatus for performing sand blasting. 1...Excimer laser, 2...
Mask in close contact with the substrate, 3...Resin layer, 4...
... Substrate, 11 ... Pipe for sending high-pressure air, 12 ... Container containing baking soda particles, 13 ...
...Particle outlet, 14...Chromium layer,
15... Board.

Claims (5)

[Claims] (1) A method for producing an alignment film for a liquid crystal, which comprises irradiating a substrate having a resin layer on its main surface with parallel ultraviolet light at a predetermined angle. (2) A method for producing an alignment film for a liquid crystal, which comprises irradiating a substrate having a resin layer on its main surface with parallel ultraviolet light at a predetermined angle, and then rubbing the resin layer. (3) The method for producing an alignment film for a liquid crystal according to claim 1, wherein the spatial distribution of the irradiation intensity of the parallel ultraviolet light is modulated using a mask. (4) The mask is a thin film made of a substance that absorbs ultraviolet light on the main surface of a substrate that is transparent to ultraviolet light.
Claim (1) characterized in that the scratches are caused by a blasting method, a liquid honing method, or a polishing method.
) or (2), the method for producing an alignment film for liquid crystal. (5) The method for producing an alignment film for liquid crystal according to claim 1 or 2, wherein the parallel ultraviolet light is obtained from an excimer laser.