JPS619620A - Manufacture of liquid crystal orientation film - Google Patents

Abstract

PURPOSE:To enable low temp. hardening and to obtain good orientation performance by coating a transparent base with a resin soln. made of a spedified polyimide type resin and a specified solvent mixture, and subjecting it to heat treatment and orientation treatment. CONSTITUTION:The transparent base is coated with the resin soln. composed of a polyimide type resin having the imide structure of which all the rings are closed in the molecule, and its org. solvent composed of an amide compd. represented by formula I or II, R1-R5 being H or <=1C alkyl, and another org. solvent having a m.p. of <=150 deg.C, and undergoes heat and orientation treatments. Since all the imide rings are closed in the molecule, and it is not necessary to heat it to high temp., and the resin is soluble in said amide compd. of formula I or II, a uniform coat film can be obtained by coating with a soln., and the use of the solvent of <=150 deg.C m.p. permits the solvent of the polyimide type resin to be evaporated perfectly by the heat treatment at temps. of <=150 deg.C. The orientation treatment is executed after that time, thus premitting this film to be used for a liquid crystal orientation film using an org. film as the base.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a liquid crystal alignment film using a polyimide resin composition that can be cured at low temperatures.

[Prior art]

Conventionally, a method is known in which an inorganic material such as 8i0x is deposited as an alignment layer of a liquid crystal display.

However, this method is extremely expensive and not suitable for mass production.

Also known is a method of using an organic polymer resin such as polyvinyl alcohol or polyimide as an alignment film.

In particular, polyimide has the function of aligning various liquid crystals,
It is widely used because of its excellent thermal stability.

In order to form polyimide, polyamide Cal having the structure of general C=α which is its precursor is dissolved in a polar organic solvent, coated on a transparent substrate, and then heat-treated. In this heat treatment step, the organic solvent is removed while the resin is ring-closed and imidized, yielding a polyimide having the structure of formula 2).

In order to completely imidize (= = 3 at a high temperature of 350℃ or higher)
It is necessary to process for 0 minutes or more.

Therefore, it is necessary to use a glass substrate with high heat resistance as the transparent substrate, and organic films (polyester, polyethersulfone, etc.) cannot withstand this heat treatment.

Such an organic film has a heat resistance of about 1 hour at 150° C., and no resin has been known that can be completely imidized under such conditions.

[Purpose of the invention]

As a result of various researches aimed at obtaining a polyimide resin composition that can be cured at low temperatures, the present invention uses a resin having a complete (two-closed ring imidized structure) as a polyimide resin, and uses a resin with a high boiling point that dissolves the polyimide as a solvent. In addition to polar solvents, they were able to complete the process by combining a low-boiling point solvent to create a two-distribution boiling point (:), which makes it easier for the solvent to evaporate.

As a method for obtaining a polyimide resin having all ring-closed imide groups, there is a method such as heat treatment of a polyamide carboxylic acid having a structure of the formula α] (=therefore, a method of converting it into a polyimide having a structure of the formula (2), polyimide is treated with an organic solvent (-
It was found to be insoluble and unsuitable for practical use.

After conducting various studies using organic solvents (= soluble polyimide), we found that the objective could be achieved by introducing polar groups such as amide groups, ester groups, and ether groups.

In the polyamideimide, polyesterimide, and polyetherimide resins obtained in this manner, all imide groups are ring-closed and are soluble in organic solvents.

Furthermore, N-methyl-2-pyrrolidone (hereinafter referred to as NMP), N-methyl-2-pyrrolidone (hereinafter referred to as NMP), and
, N'-dimethylacetamide (hereinafter DMAc)
That's what it means. ), N,N'-dimethylformamide (hereinafter referred to as D
It's called MF. ) is required.

By applying a resin solution obtained by using these solvents (2) to a transparent substrate and removing the solvent by heat treatment, a polyimide resin film can be obtained.

In order to completely evaporate the solvent (secondly, a temperature higher than the boiling point of these solvents is required; for example, NMP (boiling point 202℃)
) requires heating at a temperature of 200° C. or higher for several hours.

Therefore, an organic solvent with a boiling point of 1501: or less was added and the boiling point (
This objective was achieved by providing two distributions (=Therefore, we obtained the knowledge that the solvent can be removed even at temperatures below the boiling point of NMP, etc.).

[Structure of the invention]

The present invention uses a polyimide resin having a completely ring-closed imide structure in its molecule and an amide compound (3) generally represented by (R, -R-, is a hydrogen atom or an alkyl group containing one or more carbon atoms) as an organic solvent 11. The compound and (Bl boiling point is 1
This method of producing a liquid crystal alignment film is characterized in that a resin solution containing an organic solvent at 50° C. or lower is applied to a transparent substrate, and then heat treatment and alignment treatment are performed.

The polyimide resin used in the present invention (=polyimide resin having a completely ring-closed imide structure in the molecule) is represented by the following general formula.

(R+-melon is an alkyl group or aromatic group, X is -n is 2
- 100) Among these, those showing particularly good effects as a two-component ('+) crystal orientation orientation film include polyamide, polyesterimide, polyetherimide, and the like.

All of the imide rings in the molecule are closed, so there is no need to heat them at high temperatures for imidization, and since they are soluble in polar organic solvents (= soluble), they can be applied as a solution and form a uniform coating film. have sex.

Among the organic solvents used in the present invention, (A) the amide compound of the general formula is a polar organic solvent necessary for dissolving the above-mentioned polyimide resin.

These polar organic solvents include, for example, N,N-dimethylformamide, N,N-dimethylacetamide, and N.

N-diethylacetamide, N,N-dimethylpropylamide, N,N-diethylbenzamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and the like.

In addition, the present invention (CB among the organic solvents used in binary) has a boiling point of 15
The solvent for polyimide resin solution is 150°C or lower.
It is necessary to completely volatilize it by heat treatment below ℃.

These organic solvents include, for example, aliphatic hydrocarbons such as hexane and cyclohexine, aromatic hydrocarbons such as benzene, toluene, and quinolene, alcohols such as alcohol, ether alcohol, butyl alcohol, and ketones. Acetone, methyl ethyl ketone, methyl isobutyl ketone, etc., and ethyl acetate as esters.

Butyl acetate, etc., tetrahydrofuran as ethers,
Dioxane etc.

At least one of each of the solvents and (Bl) is used, but several types may be used in combination.

In addition, in order to smoothly volatilize the solvent, it is necessary to have two distributions of the boiling point of the solvent, and for this reason, it is preferable to use two or more of each solvent in combination.

The amount of the polyimide resin solution used in the present invention is 5 parts by weight of the polar organic solvent (A) per 100 parts by weight of the polyimide resin.
The amount is 0 to 5000 parts by weight, preferably 100 to 1000 parts by weight.

The organic solvent CB+ exhibits excellent effects when the total amount of the polyamide resin and the polar organic solvent (A) is 10 to 1000 parts by weight, preferably 50 to 500 parts by weight, based on 100 parts by weight.

If the amount of polar organic solvent (A) is less than 50 parts by weight, the polyimide resin will not dissolve completely, and if it is more than 5,000 parts by weight, the viscosity of the resin solution will become too low and coating will be difficult.

In addition, when the organic solvent (Bl) is 10 parts by weight or less, it is difficult to volatilize the polar organic solvent at a temperature of 150°C (secondary, 100 parts by weight).
If the amount is 0 parts by weight or more, the polyimide resin will not dissolve.

As the transparent substrate, a glass substrate, a glass substrate, a film such as a polyester film, a polyether sulfone film, etc. are used. In particular, the polyimide resin composition obtained in the present invention can be cured at a temperature of 150° C. or lower, and is therefore suitable for applications where an organic film is used as a substrate.

The method of manufacturing a liquid crystal alignment film on a transparent substrate using this polyimide resin is to prepare a solution in which the resin composition is uniformly dissolved to a concentration of 1 to 50% on the surface of the transparent substrate (double casting, Apply it to a uniform thickness in the range of 0.01 to 10μ, and then heat it in a dryer at a temperature of 50 to 350℃ (heat-treated in two or more steps for 3 minutes to 30 hours). Forms a resin film.

A wheeler is used as a device to cast the resin solution.

Spinner, roll coater, Vri 9-7' rate.

A flow coater or the like can be used.

Drying (2) can use electric heat, infrared rays, steam, high frequency, or a combination of these, but is common (2) can use a circulating air oven.

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

〔Example〕

The present invention will be explained below with reference to Examples.

Example 1 1 mole of trimellitic anhydride and 1 mole of diphenylmethane diisocyanate were reacted in N-methyl-2-pyrrolidone at 80 to 100°C for 2 hours and at 125 to 160°C for 3 hours to obtain an intrinsic viscosity of 0.8. A polyamideimide resin was obtained.

When the product was examined by infrared absorption spectrum, it was confirmed that the imide group was completely ring-closed.

100 parts by weight of this polyamideimide resin was added to N-methyl-
A uniform resin solution with a resin concentration of 10% and a viscosity of 200 cps obtained by dissolving 400 parts by weight of 2-pyrrolidone (2-pyrrolidone) and adding 100 parts by weight of m-xylene and 400 parts by weight of toluene and stirring for half a time is formed by the electrode. Coated on the transparent polyester film using a roll coater,
A film with a thickness of 0.1 μm was formed by heat treatment at 0° C. for 1 hour.

The surface of the film was rubbed with a brush in a certain direction (twice) to form an alignment layer, then a liquid crystal cell was assembled, biphenyl liquid crystal was injected, and the alignment of the liquid crystal was examined. As a result, good alignment was confirmed.

In addition, the humidity resistance test (80℃, 90%RH) of the liquid crystal panel was 10.
After treatment for 00 hours, no deterioration in alignment properties was observed.

Comparative Example 1 In place of the polyamideimide resin used in Example 1, a polyamic acid resin obtained by reacting 1 mole of pyromellitic dianhydride with 1 mole of diaminodiphenyl ether was used, and the same operation as in the example was carried out. went.

When the orientation of the liquid crystal was examined, there was almost no orientation.

After heat treatment at 150° C. for 1 hour, the imidization rate in the infrared absorption spectrum was about 30%, which is thought to affect the orientation of the liquid crystal.

Comparative Example 2 Using a resin solution in which 100 parts by weight of the polyamideimide resin obtained in Example 1 was dissolved only in 1000 parts by weight of N-methyl-2-pyrrolidone, the same operation as in Example 1 was carried out to prepare a liquid crystal. The orientation was investigated.

As a result, although some orientation was exhibited at the initial stage, a significant decrease in orientation was observed in the humidity test (SO°C, 90% RJi) after 100 hours of treatment.

Example 2 1 mole of dinitrobisphthalimide having the structure of the following formula was reacted with 1 mole of 0 0 bisphenol A sodium salt to obtain a polyetherimide resin of the following formula.

100 parts by weight of this resin was dissolved in 900 parts by weight of N,N'-dimethylacetamide (=200 parts by weight of (2m-xylene)
parts by weight and 800 parts by weight of toluene to give a resin concentration of 5%.
A solution with a viscosity of 5 Qcps was applied using a spinner at 4000 revolutions onto a transparent polyethersulfone film in which a box/pole was formed, and heat treated at 130°C for 5 hours to form a film with a thickness of 0.05μ. .

A liquid crystal cell was assembled in the same manner as in Example 1, and the alignment of the liquid crystal was examined. It showed good alignment and passed the moisture resistance test (8
At 0° C. and 90% RH), there was no change in the alignment properties after treatment for 1000 hours.

Example 3 One mole of cyphthalic anhydride having the structure of the following formula was reacted with diphenylmethane diisocyanate to obtain a polyesterimide resin of the following formula.

100 parts by weight of this resin were mixed with 500 parts by weight of N,N'-dimethylacetamide and 4 parts by weight of N,N'-dimethylformamide.
A solution with a resin concentration of 5% and a viscosity of 4 Q cps obtained by dissolving 00 parts by weight of dioxane and adding 500 parts by weight of dioxane and 500 parts by weight of methyl isobutyl ketone was applied using a transparent glass plate with electrodes formed with a loss spinner. ℃
A film with a thickness of 0.1 μm was formed by heat treatment for 3 hours.

A liquid crystal cell was assembled in the same manner as in Example 1, and the alignment of the liquid crystal was examined. It showed good alignment and passed the moisture resistance test (8
At 0° C. and 90% RH), there was no change in the alignment properties after treatment for 100 hours.

As described above, the polyimide resin obtained by the present invention is characterized by having low-temperature curing while maintaining the excellent liquid crystal orientation of conventional polyimide resins. (2) This makes it possible to use organic film substrates that were previously impossible (
This is a method for manufacturing a liquid crystal alignment film.

Claims (1)

[Scope of Claims] A polyimide resin having a completely ring-closed imide structure in the molecule and an organic solvent for the resin (A) The general formula is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ Numerical formulas, chemical formulas, tables, etc. ▼ A resin solution containing an amide compound represented by (R_1 to R_5 are hydrogen atoms or alkyl groups containing one or more carbon atoms) and (B) an organic solvent with a boiling point of 150°C or less is applied to a transparent substrate. and then heat treatment and alignment treatment.