JPS62150325A - Orientation substrate for liquid crystal display - Google Patents

Abstract

PURPOSE:To obtain the titled substrate having excellent responsibility for the liquid crystal and moisture resistance by using a composition contg. a fluorine contg. polymer having a low volume resistivity and a low absorption coefficient and a polyimide prepolymer having an excellent sticking property the titled substrate. CONSTITUTION:The titled substrate is formed by coating the composition composed of the fluorine contg. polymer shown by formula (1) and the polyimide prepolymer shown by formula (2) on a transparent substrate composed of a glass or a plastics, and then by thermally treating it to form a film followed by orientating the obtd. film. In formula (1), (x) and (y) are each 0-2. In formula (2), R1 and R2 are each a benzene ring or a condensed benzene ring. The used fluorine contg. polymer preferably comprises polyvinylidene fluoride. The used polyimide prepolymer is obtd. by reacting tetracarboxylic acid dianhydride and diamine in a polar org. solvent.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to the orientation of a composition comprising a fluorine-based cerimer with excellent moisture resistance and a limide predelimer with excellent adhesion to a substrate and heat resistance. The present invention relates to a liquid crystal alignment substrate made of a film.

[Prior art]

Is vinyl alcohol used as an alignment film for conventional liquid crystal displays? Methods using organic polymer films such as liimide and polyamide resins are known.

In particular, pyriimide resin is widely used because it has the function of aligning the liquid crystals in each cage and has excellent heat resistance.

In general, liquid crystal display Nominel is made by coating a transparent substrate on which electrodes are formed with imidosol polymer, and then performing heat treatment and alignment treatment to form an alignment layer and use these two sheets as a liquid crystal alignment substrate. It consists of a liquid crystal sealed between substrates, and by applying a voltage between the liquid crystal alignment substrates, an electric field is generated in the liquid crystal, and the liquid crystal molecules are arranged to display various patterns. .

Important performance requirements for liquid crystal displays include fast response when voltage is applied, and reliability such that alignment does not deteriorate even when exposed to high temperature and high humidity conditions.

However, seriimide alignment layers generally have the disadvantage of being superior in heat resistance or having poor moisture resistance. This is because the water absorption rate of the seriimide resin film is as high as 2 to 5 inches, so water easily enters the interface between the alignment layer and the substrate, reducing the adhesion between the alignment layer and the transparent substrate.

In addition, the volume resistivity of the pyriimide alignment layer is 1016 to 1017.
Since it is a highly insulating film of ohm-resistance, it has the disadvantage that when voltage is applied, a voltage drop occurs in the liquid crystal layer and the response is slow.

[Purpose of the invention]

The present invention was developed as a result of various studies aimed at obtaining an alignment layer that has a quick liquid crystal response, heat resistance, moisture resistance, and excellent adhesion to the substrate. It has been found that an excellent liquid crystal aligning substrate can be obtained by using a composition comprising a streamimide prepilimer having excellent adhesion.

[Structure of the invention]

The present invention is based on the general formula +CHxF 2-z CHy F 2-
A composition consisting of a fluorine-containing polymer represented by y-9 (X, y=Q, 1.2) and a polyimide prepolymer represented by the general formula is coated or painted on a transparent substrate made of plastic 1, and then heat treated. This is a liquid crystal alignment substrate, characterized in that it is obtained by forming a film using the above-mentioned method, and then subjecting the film to alignment treatment.

Examples of the fluorine-containing polymer used in the present invention include litetrafluoroethylene (-CF2-cvz), !rivinylidene fluoride (CF2-CH2J), and polyvinyl fluoride (-CHF-CH21).

Among these fluorine-containing telimers, polyvinylidene fluoride is particularly desirable. Polyvinylidene fluoride is easily soluble in organic solvents, easy to handle, and has a low volume resistivity when formed into a film, so when used as a liquid crystal aligning film, it is highly effective in preventing voltage drop.

Organic solvents for dissolving fluorine-containing pirimers include N, N
- Polar solvents such as dimethylformamide, N,N'-dimethylacetamide, N-methyl-2-pyrrolidone, ethers such as dioxane, ketones such as cyclohexanone, esters such as butyl acetate, or mixed solvents thereof. used.

Fluorine-containing pirimers have the disadvantage of poor adhesion to glass or plastic substrates. Therefore, by using a combination of NIJ imide prepolymer and fluorine-containing telimer, which have excellent adhesion to the substrate, we improved the adhesion to the substrate.

The NIJ imide prehiripiri used in the present invention is obtained by reacting a tetracarboxylic dianhydride and a diamine in a polar organic solvent.

Preprimers with various structures can be obtained by combining tetracarboxylic acid dianhydride and diamine, but when used as a liquid crystal alignment film, those that exhibit particularly good alignment properties include bilomeri, tetracarboxylic acid dianhydride, and diaminodiphenyl ether. or a combination of benzophenone tetracarboxylic dianhydride and diaminodiphenyl ether.

A method for manufacturing a liquid crystal alignment film using a composition consisting of a fluorine-containing pirimer and a polyimide preprimer is to apply the above solution onto the surface of a transparent substrate made of glass or plastic on which electrodes are formed to a thickness of 0.01 to 10 μm. The resin film is formed by applying or painting the resin uniformly over a range of 100 to 100° C., and then heat-treating in a drying oven at a temperature of 50 to 400°C for 3 minutes to 10 hours in two or more steps if necessary.

As the transparent substrate, a glass thin plate or a plastic film is used, and as the plastic film, a film of Hibari ester, pyriether sulfone, etc. is used.

Methods for casting resin include wheelers, spinners,
Use a roll coater, doctor blade, flow coater, etc.

A mixed composition of a fluorine-containing pyrimer and a pyriimide prepolymer can be obtained by mixing solutions of both.

The mixing ratio of the fluorine-containing pyrimer and the polyimide preprimer is preferably 10 to 1000 parts by weight of the fluorine-containing 2-rimer per 100 parts by weight of the polyimide prepyrimer in terms of solid content. If the amount is less than 10 parts by weight, the volume resistivity of the film will not be high and the response when assembling the liquid crystal will be slow. 10
If the amount exceeds 0.00 parts by weight, the adhesion to the substrate will decrease.

Although electric heat, infrared rays, steam, high frequency, or a combination of these can be used for the heat treatment, a circulating hot air oven is generally used.

Orientation treatment after film formation is generally carried out by rubbing the surface of the film with absorbent cotton, a brush, etc. to form grooves of about several λ in the same direction.

〔Effect of the invention〕

According to the present invention, a liquid crystal alignment substrate with excellent liquid crystal responsiveness and moisture resistance can be obtained without reducing the heat resistance and adhesion of the conventional yf IJ imide alignment layer.

〔Example〕

Example 1 5 parts by weight of polyvinylidene fluoride resin was dissolved in 95 parts by weight of N-methyl-2-pyrrolidone, and the viscosity was 100.
A solution of cps was obtained.

This solution and the d IJ imide prepolymer 〇N-methyl-2-pyrrolidone solution represented by the following formula were combined with a solid content of 25
After mixing at a rate of 75 °C and stirring for 2 hours, 100 ps
A composition was obtained.

This composition was applied onto a glass substrate on which electrodes were formed using a spinner, and heat-treated at 250° C. for 1 hour in a circulating hot air oven to form a film with a thickness of 0.1 μm.

This coating had excellent adhesion to the substrate, and the adhesion was examined using the substrate eye test method.

That is, a polyimide film of a predetermined thickness is coated and cured on the substrate to be measured, and then the polyimide film is coated with a cutter knife for 10 min.
Make a cut in the shape of a base so that there are 0 squares. This was peeled off with cellophane tape and expressed as the number of squares that were peeled off per 100 squares. The result of the base test was O/100 (number of peelings/total number).

The volume resistivity of this film was 6×10 14 Ω-, and the water absorption rate was 1.2%.

The surface of the coating was rubbed to form an alignment layer, and then a liquid crystal cell was assembled using this liquid crystal display alignment substrate, and a liquid crystal channel was created by injecting biphenyl liquid crystal.

As a result of examining the response characteristics of the liquid crystal, it was found that good alignment was achieved with an applied voltage of 3.

In addition, the moisture resistance test (80℃, 90iH) of the liquid crystal panel was 80.
Even after treatment for 0 hours, no deterioration of alignment properties occurred.

The properties of compositions in which the compositions of the fluorine-containing polymer and polyimide solenolymer were changed are shown in Table 1 together with Comparative Example 1.2.

Comparative Example 1 A film of 0.1 μm was formed in the same manner as in Example 1 using the ZIJ imide prepilimer used in Example 1.

The volume resistivity of this coating is 5 x 10” Ω.
The water absorption rate was 3.5 inches.

A liquid crystal ξ channel was prepared in the same manner as in Example 1, and the response characteristics of the liquid crystal were investigated. As a result, an applied voltage of 5 V was required.

Furthermore, when a moisture resistance test was conducted, poor orientation occurred after 20 hours.

Comparative Example 2 A film of 0.1 μm was formed using the polyvinylidene fluoride used in Example 1 in the same manner as in Example 1.

The volume resistivity of this film was 5 x 1012 Ω-1, and the water absorption rate was 0.2%. “The adhesion between this film and the base was examined and it was found to be 100/100 in the Gopan test.

As described above, according to the present invention, by using a liquid crystal display alignment substrate made of a composition consisting of a fluorine-containing polymer and a pyriimide prepolymer, it has excellent adhesion to the substrate, and A liquid crystal display and device with excellent response characteristics and good moisture resistance were obtained.
.

Claims (1)

[Claims] 1. Fluorine-containing polymer represented by the following general formula - [CH
xF_(_2_-_x_)-CHyF_(_2_-_y
＿)]-_n (x, y are natural numbers of 0, 1, 2) and a polyimide prepolymer represented by the general formula below. , R_2 is a benzene ring, a fused benzene ring, or ▲There is a mathematical formula, chemical formula, table, etc.▼, where X_1 is ▲There is a mathematical formula, chemical formula, table, etc.▼, -
O-, -SO_2-, -S-, -CH_2-, ▲ Formula,
There are chemical formulas, tables, etc. ▼] A liquid crystal alignment substrate characterized by being coated or painted on a transparent substrate made of plastic, then heat-treated to form a film, and then subjected to alignment treatment. 2. The liquid crystal alignment substrate according to claim 1, wherein the fluorine-containing polymer is polyvinylidene fluoride. 3. The liquid crystal alignment substrate according to claim 1 or 2, wherein the content of the fluorine-containing polymer is 10 to 1000 parts by weight based on 100 parts by weight of the polyimide prepolymer.