JP2913110B2 - Liquid crystal polymer alignment control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling the alignment of a liquid crystalline polymer in a compensator for a liquid crystal display device, an optical recording medium and the like.

[Problems to be solved by the prior art and the invention] The liquid crystal changes its alignment state due to an external field such as an electric field, a magnetic field, and a shear force. Used in the field. Of these, liquid crystalline polymers are more viscous in the liquid crystal state than low-molecular liquid crystals, so they can be aligned in the liquid crystal state and then cooled to below the glass transition point to fix the liquid crystal alignment state. Low-molecular liquid crystal. Utilizing this, applications in the field of optoelectronics such as an optical memory for thermal writing and an optical filter have been attempted. To achieve these, it is necessary to control the desired molecular orientation to a high degree.
For example, a color compensator for a super twisted nematic (STN) type liquid crystal display device, which is a kind of optical retarder, is S
Inserted between the liquid crystal cell of the TN type liquid crystal display element and the polarizing plate,
It is necessary to function to return the elliptically polarized light to linearly polarized light by the liquid crystal cell. Such a function has a high degree of order and uniformity in the liquid crystal polymer horizontally and in a certain direction. It can be expressed only by orientation.

In the case of a low-molecular liquid crystal, an alignment control method is almost established, but in the case of a liquid crystalline polymer (polymer liquid crystal), it is not sufficiently established. Examples of the method of controlling the alignment of the liquid crystalline polymer include a method of applying an external force such as shear stress and a method of applying an external field such as a magnetic field or an electric field. It is possible or not sufficient in terms of uniformity. When the method of injecting low-molecular liquid crystal into the gap between the substrates subjected to the alignment treatment is directly applied to the liquid crystalline polymer, the high viscosity of the liquid crystalline polymer causes the liquid crystalline polymer to follow the flow at the time of injection. Molecules are oriented, and the desired orientation cannot be obtained, or if the area is large, it becomes difficult even to implant.

The present inventors have found that a good alignment of a liquid crystalline polymer can be obtained after applying an alignment treatment film such as a polyimide-based film to a substrate and rubbing the film. Since the film may be deteriorated and lose the ability to align, a large restriction is imposed on the alignment film material, the solvent, and also the liquid crystal polymer material itself.

In addition, when an alignment treatment film material having a particularly strong solvent resistance is used, such a material generally has high hardness, so that there is a problem that rubbing is apt to cause scratches.

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

[Means and actions for solving the problem]

In order to achieve the above object, according to the present invention, an alignment treatment film is formed on a light-transmitting substrate, a solution obtained by dissolving a liquid crystalline polymer in an organic solvent is applied on the alignment treatment film, and heat treatment is performed. A method for controlling the alignment of a liquid crystalline polymer by which the liquid crystalline polymer is aligned, wherein the alignment treatment film is a precursor of a polyimide resin or a precursor of a partially imidized polyimide resin. After being rubbed
There is provided a method for controlling the alignment of a liquid crystalline polymer, which comprises using an alignment treatment film almost completely imidized by heating or the action of a catalyst.

In the method of the present invention, a polyimide-based resin precursor or a partially imidized polyimide-based resin precursor is applied on a substrate and subjected to a rubbing treatment. Sometimes the hardness of the alignment treatment film is not so high, it can be rubbed without scratching, and the imidization afterwards dramatically increases the solvent resistance, so it does not deteriorate even when applying the liquid crystalline polymer solution , Good orientation can be maintained.

 Hereinafter, the present invention will be described in detail with reference to FIG.

The substrate 1 is made of glass, plastic, or the like, and needs to have heat resistance if the alignment treatment film is dried or imidized by heat treatment. A solution of a polyimide resin precursor or a partially imidized polyimide resin precursor is applied onto the substrate 1 by printing or a spinner.
This is carried out at a relatively low temperature (~ 150
℃ or less), and rubbing treatment is performed. Thereafter, a high temperature treatment (up to 150 ° C. or more) is performed to cause imidization. The imidization can be promoted by a catalyst such as an acid anhydride. However, if the high-temperature treatment is not performed, only the surface of the alignment treatment film is imidized, so that the reliability is inferior and the high-temperature treatment is more preferable.

Next, a solution of a liquid crystalline polymer is applied on the surface of the alignment treatment film 2 by printing or spinner. After drying, the liquid crystalline polymer is heated to a temperature in the range from the glass transition point to the isotropic phase but not higher than the glass transition point.

The liquid crystal polymer that can be used is a thermotropic liquid crystal polymer, and the structure is not particularly limited.For example, a main chain type having a liquid crystal residue in a main chain of polyester, polyesteramide, polycarbonate, polyether, or the like. Liquid crystalline polymer: Alternatively, a side chain type liquid crystalline polymer having a liquid crystalline residue in a side chain such as a vinyl polymer or polysiloxane and having the following structure: (However, R ³ is an alkyl group, an alkoxy group, a halogen atom, a nitro group or a cyano group, and n represents an integer of 0 to 18.). The liquid crystalline polymer is used alone or as a mixture. An optically active group can be introduced into the liquid crystalline polymer, or an optically active compound can be added.

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

Chloroform, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, halogenated hydrocarbons such as orthodichlorobenzene, phenol, o-chlorophenol, phenolic solvents such as cresol, dimethylformamide, dimethylacetamide, aprotic polar solvents such as dimethylsulfoxide, Ether solvents such as tetrahydrofuran and dioxane and mixed solvents thereof.

As the precursor of the polyimide resin, polyamic acid, polyhydrazide acid, polyhydrazide amide, polyhydrazide siloxane, polyamic acid siloxane, polyamide siloxane, polyhydrazide generated from tetracarboxylic dianhydride and diamine compound or dihydrazide compound Siloxane,
Examples include amic acid siloxanes. After imidization,
Since a solution of a liquid crystalline polymer is applied, a material having high solvent resistance when imidized is preferable.

〔Example〕

Next, the present invention will be described in more detail with reference to examples.
The present invention is not limited to these examples.

(Example 1) On a glass substrate on which a transparent conductive film was patterned, a Sunever 150 mainly containing a precursor of a polyimide resin was used.
(Manufactured by Nissan Chemical Industries, Ltd.) was spin-coated. The concentration was adjusted to 2 wt% with a solvent mainly composed of butyl cellosolve and NMP. This was dried in an oven at 120 ° C. for 1 hour, allowed to cool to room temperature, and then rubbed with a nylon flocking cloth. Next, it was heated in an oven at 260 ° C. for 1 hour to complete imidization. On this substrate, a polysiloxane-based liquid crystalline polymer was applied by a spinner. Polymer concentration is about 20%
The solvent used was γ-butyrolactone as the main agent. 90
After drying for 2 hours in an oven at
The temperature was raised to 0 ° C., and after 5 minutes, the sample was taken out of the oven and allowed to cool to room temperature. When this was observed with a crossed Nicols polarizing microscope, it was confirmed that a uniform alignment layer having an extinction position in the rubbing direction and the direction perpendicular thereto was obtained.

(Example 2) LQ5200, a precursor of polyimide resin (manufactured by Hitachi Chemical Co., Ltd.)
Was diluted to 2 wt% with a solvent containing dimethylformamide and butyl cellosolve as main components, and an alignment treatment film was formed on a glass substrate in the same manner as in Example 1. Next, the polyester-based liquid crystalline polymer was dissolved up to 5 wt% in a solvent mainly composed of butyl cellosolve and N-methylpyrrolidone, and this solution was spin-coated on the alignment film, followed by drying and heat treatment. When this was observed between the two polarizing plates, a uniform birefringent color was observed except at the edge of the substrate, and it was found that the thickness of the liquid crystalline polymer layer was uniform.

〔The invention's effect〕

In the method of the present invention, a polyimide-based resin precursor or a partially imidized polyimide-based resin precursor is applied to a substrate, subjected to a rubbing treatment before being completely imidized, and then imidized. Therefore, it is possible to prevent the alignment treatment film from being damaged at the time of rubbing, and it is possible to obtain a liquid crystal polymer layer which is free from defects and uniformly aligned.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a substrate with a liquid crystalline polymer film produced by the method of the present invention. DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Alignment treatment film 3 ... Liquid crystalline polymer layer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02F 1/1337

Claims (1)

(57) [Claims] 1. An alignment treatment film is formed on a light-transmitting substrate, a solution obtained by dissolving a liquid crystalline polymer in an organic solvent is applied on the alignment treatment film, and the liquid crystal polymer is aligned by heat treatment. A method of controlling the alignment of a liquid crystalline polymer to be rubbed in a state of a precursor of a polyimide resin or a precursor of a partially imidized polyimide resin as the alignment treatment film, followed by heating or A method for controlling the alignment of a liquid crystalline polymer, comprising using an alignment treatment film almost completely imidized by the action of a catalyst.