JPH0416927A - Method for controlling orientation of liquid crystalline polymers - Google Patents

Abstract

PURPOSE:To prevent the flawing of an orientation treated film at the time of rubbing and obtain a liquid crystalline high polymer layer which is free from defects and is uniformly oriented by applying the precursor material of a polyimide resin or the precursor material of the partially imidized polyimide resin on a substrate and subjecting the coating to a rubbing treatment before the complete imidization, then causing the imidization. CONSTITUTION:The soln. of the precursor material of the polyimide resin or the precursor material of the partially imidized polyimide resin is applied by printing or a spinner on a substrate 1. The coating is dried at such a relatively low temp. at which the imidization does not arise and is subjected to the rubbing treatment thereafter, the coating is subjected to such a high temp. treatment at which the imidization arises. The soln. of the liquid crystalline high polymer is then applied by printing or a spinner on the surface of the orientation treated film 2 and after the coating is dried, the coating is heated to the temp. range above the glass transition point of the liquid crystalling high polymer and below the transition point to an isotropic phase. The well oriented liquid crystalline high polymer layer 3 is then obtd. The liquid crystalline high polymer is oriented uniformly over a large area at a high degree in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling the orientation of liquid crystal polymers in compensating plates for liquid crystal display elements, optical recording media, and the like.

[Prior art and problems to be solved by the invention] The alignment state of liquid crystals changes depending on external fields such as electric fields, magnetic fields, and shear forces, and by utilizing the accompanying changes in optical properties, various optoelectronic devices can be used. used in the field.

Among these, liquid crystalline polymers have higher viscosity in the liquid crystal state than low-molecular liquid crystals, so after being oriented in the liquid crystal state, the liquid crystal orientation state is fixed by cooling below the glass transition point. It has a feature not found in low-molecular liquid crystals: the ability to Utilizing this, attempts are being made to apply it to optical electronics fields such as thermal writing optical memory and optical filters. In order to realize these, it is necessary to highly control the desired molecular orientation. For example, a color compensation plate for a super twisted nematic (STN) type liquid crystal display element, which is a type of optical retarder, is
It is inserted between the liquid crystal cell and the polarizing plate of a type liquid crystal display element, and it needs to function to return the light that has become elliptically polarized by the liquid crystal cell to linearly polarized light. Moreover, it can only be realized by orienting it in a certain direction with a high degree of order and uniformity.

In the case of low-molecular liquid crystals, alignment control methods are almost established, but in the case of liquid crystalline polymers (polymer liquid crystals), they are not fully established. Examples of orientation control of liquid crystalline polymers include:
Methods of applying an external force such as shear stress, and methods of applying an external field such as a magnetic field or electric field are known, but these methods either make it impossible to control the orientation over a large area, or are insufficient in terms of uniformity. I can't say that. If the method of injecting low-molecular-weight liquid crystal into the gap between substrates that has been subjected to alignment treatment is applied directly to liquid crystalline polymers, the liquid crystalline polymer will flow along the injection flow due to the high viscosity of liquid crystalline polymers. If the molecules become oriented and the desired orientation cannot be obtained, or if the area becomes large, even injection becomes difficult.

The present inventors have found that good alignment of liquid crystal polymers can be obtained by applying an alignment treatment film such as polyimide to a substrate and rubbing it. This is because the film may change in quality and lose its ability to align.

Significant restrictions are placed on the alignment treatment film material, the solvent, and even the liquid crystal polymer material itself.

Further, when an alignment film material having particularly strong solvent resistance is used, there is a problem that such a material is easily scratched by rubbing because such a material generally has high hardness.

The present invention has been made in view of the problems of the prior art as described above, and its purpose is to control the alignment of liquid crystalline polymers that can uniformly and highly align the liquid crystalline polymers over a large area. The purpose is to provide a method.

[Means and effects for solving the problem] In order to achieve the above object, according to the present invention, an alignment treatment film is formed on a transparent substrate, and a solution formed by dissolving a liquid crystalline polymer in an organic solvent is used. A method for controlling the alignment of a liquid crystalline polymer, in which the liquid crystalline polymer is coated on the alignment treatment film and the liquid crystalline polymer is aligned by heat treatment, the alignment treatment film comprising a precursor of a polyimide resin or a partially imidized resin. Provided is a method for controlling the alignment of a liquid crystalline polymer, which comprises using an alignment-treated film that is almost completely imidized by heating or the action of a catalyst after being subjected to a rubbing treatment in the state of a fringe material of a polyimide-based resin. be done.

In the method of the present invention, a precursor of a polyimide resin or a partially imidized precursor of a polyimide resin is applied onto a substrate, subjected to a rubbing treatment, and then imidization is proceeded by heating or a catalyst. During rubbing, the hardness of the alignment treatment film is not so high, and it can be rubbed without causing scratches, and the subsequent imidization dramatically increases its solvent resistance, so it does not change in quality when applying a liquid crystalline polymer solution. Therefore, good orientation can be maintained.

The present invention will be described in detail below with reference to FIG.

The substrate 1 is made of glass, plastic, or the like, and needs to be heat resistant if the alignment film is to be dried or imidized by heat treatment. A solution of a polyimide resin bang material or a partially imidized polyimide resin bang material is applied onto the substrate l by printing or a spinner. This is heated at a relatively low temperature (~150℃) where imidization does not occur.
'C or lower) and then subjected to rubbing treatment. After this,
A high temperature (~150°C or higher) treatment is performed to cause imidization. Imidization can also be promoted using a catalyst such as an acid anhydride, but unless high temperature treatment is performed, only the surface of the alignment film will be imidized, resulting in poor reliability, so high temperature treatment is preferable.

Next, a solution of a liquid crystalline polymer is applied onto the surface of the alignment treatment film 2 by printing or using a spinner. After drying, the liquid crystalline polymer layer 3 is heated to a temperature in the range above the glass transition point of the liquid crystalline polymer and below the transition point to the six-phase transition point to obtain a well-oriented liquid crystalline polymer layer 3.

The liquid crystalline polymer that can be used is a thermotropic liquid crystalline polymer, and the structure is not particularly limited, but for example, a main chain type having a liquid crystalline residue in the main chain such as polyester, polyesteramide, polycarbonate, polyether, etc. Liquid crystalline polymer: ÷"-X"←A"-X2) x", N-Ph-, -P
h-Ph-.

-Ph-Ph-COO-Ph-, -Ph-N=CH-P
h-etc A' knee (CH2, <o2co, OTh, -C
CHzα20) Fl.

CH3 M” Knee Ph-Ph-R', +Ph-Ph-R3,
-Ph-Coo-Ph-R3, +Ph-C0O-Ph-
R'.

CH3 CH.

represents a number. ) Or a side chain type liquid crystal polymer such as a vinyl polymer or polysiloxane having a liquid crystal residue in the side chain and having the following structure: (However, R3 is an alkyl group, an alkoxy group, a halogen atom, a nitro group, or a cyano group. and n represents an integer from 0 to 18.). Liquid crystalline polymers may be used alone or in combination. It is also possible to introduce an optically active group into the liquid crystalline polymer or add an optically active compound.

The solvent for the liquid crystalline polymer varies depending on the type of liquid crystalline polymer used, degree of polymerization, etc., but is usually selected from the following.

Chloroform, dichloroethane, tetrachloroethane,
Halogenated hydrocarbons such as trichlorethylene, tetrachlorethylene, and orthodichlorobenzene; phenolic solvents such as phenol, 0-chlorophenol, and cresol; aprotic polar solvents such as dimethylformamide, dimethylacetamide, and dimethylsulfoxide;
Ether solvents such as tetrahydrofuran and dioxane, and mixed solvents thereof.

Precursors for polyimide resins include polyamic acid, polyhydrazide acid, polyhydrazide amide, polyhydrazide siloxane, polyamic acid siloxane, and polyhydrazide acid produced from tetracarboxylic dianhydride and diamine compounds and dihydrazide compounds. Examples include siloxane and amic acid siloxane. After imidization, a liquid crystalline polymer solution is applied, so a material with high solvent resistance when imidized is preferable.

〔Example〕

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Example 1) Sunever 150, whose main component is a polyimide-based resin, was placed on a glass substrate patterned with a transparent conductive film.
(manufactured by Nissei Kagaku Co., Ltd.) was spin-coded.

The concentration was adjusted to 2 wt% using a solvent containing butyl cellosolve and N)IP as main ingredients. This was dried in an oven at 120° C. for 1 hour, allowed to cool to room temperature, and then rubbed with a nylon flocked cloth. Next, put it in the oven at 260℃ for 1
The mixture was heated for a period of time to complete imidization.

A polysiloxane-based liquid crystalline polymer was applied onto this substrate using a spinner. The concentration of the polymer was about 20%, and γ-butyrolactone was used as the main solvent. After drying in an oven at 90°C for 2 hours, increase the oven temperature to 120°C.
After 5 minutes had elapsed, the sample was taken out of the oven and allowed to cool to room temperature.

When this was observed using a crossed Nicol polarizing microscope, it was confirmed that a uniformly oriented layer having an extinction position in the rubbing direction and a direction perpendicular to the rubbing direction was obtained.

(Example 2) Polyimide resin precursor LQ5200 (manufactured by Hitachi Chemical Co., Ltd.) was diluted to 2 wt% with a solvent containing dimethyl formamide and butyl cellosolve as main ingredients, and an alignment film was placed on a glass substrate in the same manner as in Example 1. A film was formed.

Next, 5 wt% of a polyester-based liquid crystalline polymer was added to a solvent containing butyl cellosolve and N-methylpyrrolidone as main ingredients.
This solution was applied onto the alignment film using a spinner, followed by drying and heat treatment. When this was observed between two polarizing plates, uniform birefringence color was observed except for the edges of the substrate, indicating that the thickness of the liquid crystalline polymer layer was uniform.

〔Effect of the invention〕

In the method of the present invention, a polyimide resin bang material or a partially imidized polyimide resin precursor is applied to a substrate, and a rubbing treatment is performed before complete imidization, and then imidization is performed. Therefore, it is possible to prevent the alignment film from being scratched during rubbing, and it is possible to obtain a liquid crystalline polymer layer free from defects and aligned in a --like manner.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a substrate with a liquid crystalline polymer film produced by the method of the present invention. 1...Substrate 2...Alignment treatment film 3...Liquid crystal polymer layer Patent applicant Rico Co., Ltd.

Claims (1)

[Claims] (1) An alignment film is formed on a transparent substrate, a solution of a liquid crystalline polymer dissolved in an organic solvent is applied onto the alignment film, and the liquid crystalline polymer is aligned by heat treatment. A method for controlling the orientation of a polyimide polymer, wherein the orientation treatment film is subjected to a rubbing treatment in the state of a precursor of a polyimide resin or a precursor of a partially imidized polyimide resin, and then heated or treated with a catalyst. 1. A method for controlling the alignment of a liquid crystalline polymer, characterized by using an alignment treatment film that is almost completely imidized by an action.