JPH0219836A - Production of orientation film for liquid crystal - Google Patents

Abstract

PURPOSE:To obtain a resin film for the orientation of liquid crystal molecules by irradiating the surface of a substrate or a resin utilizing primarily alpha-rays, namely atomic nuclei of He, and changing thus the surface of the substrate or the resin. CONSTITUTION:alpha-Rays, namely atomic nuclei of He, from an alpha-ray source which primarily undergoes the alpha-decay are used. In some cases, an angle of incidence to the substrate surface or the resin film surface on the substrate is restricted with a metallic slit. Thus, fine unevennesses are formed on the surface of the substrate or the resin, and liquid crystals are oriented along the fine unevennesses. By this method, liquid crystal molecules are erected from the surface by the adjustment of the angle of incidence of the alpha-rays, and an orientation film for liquid crystal is 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.

Generally, the rubbing method is widely used in industry, but in a mode in which liquid crystal molecules have a large twist angle, 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.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a method for producing an alignment film for liquid crystal, which is characterized by mainly irradiating alpha rays onto the substrate surface to change the substrate surface. It is something to do.

Further, in order to solve the above-mentioned problems, the present invention provides a method for producing an alignment film for liquid crystal, which is characterized by mainly irradiating the resin surface with alpha rays to change the resin surface.

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 a certain order is required on the surface of the alignment film. 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 considered that the present invention places some emphasis on the latter orientation mechanism.

The method according to the invention does not require high vacuum and, in this respect, the equipment costs are low. Even if it is necessary, it is about 10-'' Torr.

Furthermore, in conventional rubbing of the resin film by maintenance, etc., if the pre-tilt of the nematic liquid crystal molecules is to be raised slightly from the horizontal level, very delicate condition settings and selection of the resin film material are required. The present invention utilizes alpha radiation from an alpha source that primarily undergoes alpha decay, ie He nuclei.

In some cases, a metal slit defines the angle of incidence of the alpha rays onto the substrate surface or the resin film on the substrate. By doing so, fine irregularities are formed on the substrate surface or resin surface, and liquid crystal molecules are thought to be aligned along these irregularities. By adjusting the incident angle, the liquid crystal molecules can be raised higher than the surface. Further, it is more efficient to perform this irradiation using a rotary pump in an atmosphere of about 10-' Torr.

As the resin, polyimide or the like is preferable from the viewpoint of reliability.

Alpha sources include radium (Rd), beryllium (Be), thorium (Th) sources,
Uranium (U) Source, Plutonium (Pu)
- Sources are appropriate, but there are laws and regulations regarding handling, so care must be taken.

Example An embodiment of the present invention will be described below.

In this example, polyimide resin (solvent type) was used as the resin.
PX5400, manufactured by Hitachi Chemical Co., Ltd., was applied onto a glass substrate and thermally cured to form a resin film. A separately cleaned glass substrate was also obtained.

The resin film was irradiated with alpha rays in a vacuum chamber drawn by a rotary pump. A radium-beryllium source was used as the alpha ray source, and the direction of irradiation of the glass substrate itself or the resin film was regulated by a metal slit. Irradiation was carried out for about 10 minutes.

In a normal method, the glass substrates that have been irradiated with alpha rays, the glass substrates that have the resin films that have been irradiated with alpha rays, or the unirradiated glass substrates themselves for comparison, and the resin films that have not been irradiated with each other. The glass substrates were bonded together in a predetermined direction so as to maintain a predetermined gap. In this case, the irradiation surface was directed towards the void.

When this gap was filled with nematic liquid crystal, the glass substrate wall had a gap in the direction of alpha ray irradiation.
It was confirmed that the liquid crystal molecules were oriented. No alignment of liquid crystal molecules was observed between unirradiated glass substrates or between unirradiated glass substrates with resin films.

Note that from other observations, it is estimated that liquid crystal molecules have a blur/tilt that is approximately the same as the direction of incidence of alpha rays.

Furthermore, the alignment of liquid crystal molecules is more stable if alpha rays are applied to the glass substrate itself, then immersed in diluted hydrofluoric acid, washed with water, dried, and then bonded together.

In addition to the effects of the invention, the present invention provides a method for obtaining a resin film for aligning liquid crystal molecules, and can be used for applications other than liquid crystal display devices, and has great industrial value.

Claims (2)

[Claims] (1) A method for producing an alignment film for liquid crystal, which is characterized by irradiating the substrate surface with alpha rays to change the substrate surface. (2) A method for producing an alignment film for liquid crystal, which is characterized by irradiating the resin surface with alpha rays to change the resin surface.