JPH06100756B2 - Alignment treatment agent for liquid crystal cells - Google Patents

Description

The present invention relates to an alignment treatment agent for liquid crystal cells, and more specifically to alignment agents for liquid crystal cells in which liquid crystal molecules have an increased tilt alignment angle with respect to a substrate. It relates to a treating agent.

(B) Conventional technology As a substrate treating agent for orienting nematic liquid crystal molecules substantially parallel to a transparent substrate such as glass or a plastic film having a transparent electrode, organic resin films such as polyimide resin film have been conventionally used. Most commonly used.

In this case, by rubbing the organic resin film formed on the substrate with a cloth in a certain direction, liquid crystal molecules are aligned in the rubbing direction, and at the same time, a liquid crystal tilt alignment angle of about 1 to 3 ° is usually formed with respect to the substrate surface. Is known to cause

Further, as a method of largely orienting liquid crystal molecules, a method of depositing an inorganic film such as silicon oxide on a substrate has been conventionally performed.

(C) Problems to be Solved by the Invention However, it is difficult to largely orient the liquid crystal molecules by the method of rubbing the organic resin film formed on the substrate.

Further, the method of depositing an inorganic film on a substrate is more complicated than the rubbing method, and is not necessarily an appropriate method in actual industrial production.

(D) Means for Solving the Problems The inventors of the present invention have completed the present invention as a result of diligent studies to solve the above problems.

That is, the present invention is represented by diamine, tetracarboxylic dianhydride and general formula [I]. (In the formula, R ₁ is an alkyl group having 6 to 20 carbon atoms, R ₂ is an aliphatic group in which two carbonyl groups constituting a dicarboxylic acid anhydride are bonded to two different carbons, and a derivative or aromatic group thereof. And a derivative thereof.) An alignment treatment agent for a liquid crystal cell, which comprises a polyimide resin obtained from a dicarboxylic acid anhydride, and more specifically, a diamine a mole, a tetracarboxylic acid dianhydride b mole and a general formula [I].
The dicarboxylic acid anhydride (hereinafter, abbreviated as monoacid anhydride) c mol is represented by the following formula: a> b ≧ a / 2 (1) 2 (ab) ≧ c> 0 (2) The present invention relates to an alignment treatment agent for liquid crystal cells, which is made of a polyimide resin obtained by reacting and polymerizing.

The alignment treatment agent for liquid crystal cells of the present invention is used as an alignment treatment agent for liquid crystal cells by forming a polyimide resin film on a transparent substrate such as glass or a plastic film having a transparent electrode, and then subjecting it to a rubbing treatment. It is a thing.

Specific examples of the diamine used in the alignment treatment agent for liquid crystal cells of the present invention include p-phenylenediamine, m-phenylenediamine, diaminodiphenylmethane, diaminodiphenyl ether, 2,2-diaminodiphenylpropane, diaminodiphenylsulfone, diaminobenzophenone. , Diaminonaphthalene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-di (4-aminophenoxy) diphenyl sulfone, 2,2'- Examples thereof include aromatic diamines such as bis [4- (4-aminophenoxy) phenylpropane.

Other alicyclic diamines and aliphatic diamines may be used depending on the purpose.

Further, one kind or a mixture of two or more kinds of these diamines can be used.

Specific examples of the tetracarboxylic dianhydride used in the alignment treatment agent for liquid crystal cells of the present invention include aromatic compounds such as pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride and biphenyltetracarboxylic dianhydride. Alicyclic tetracarboxylic acid dianhydrides such as group tetracarboxylic acid dianhydride, cyclobutanetetracarboxylic acid dianhydride, cyclopentanetetracarboxylic acid dianhydride and cyclohexanetetracarboxylic acid dianhydride, butanetetracarboxylic acid dianhydride Aliphatic tetracarboxylic acid dianhydrides and the like.

These tetracarboxylic acid dianhydrides may be used alone or in combination of two or more.

The monoacid anhydride of the general formula [I] used in the alignment treatment agent for liquid crystal cells of the present invention is a dicarboxylic acid anhydride having an alkyl group having 6 to 20 carbon atoms.

Specific examples of monoacid anhydrides include n-hexyl succinic anhydride, n-octyl succinic anhydride, n-dodecyl succinic anhydride, n-tetradecyl succinic anhydride, n-hexadecyl succinic anhydride, and n-dodecyl glutaric anhydride. Acid, n-
Hexadecyl glutaric anhydride, n-octyl phthalic anhydride, n-dodecyl phthalic anhydride, n-hexadecyl phthalic anhydride, 3-hexadecyloxy phthalic anhydride, 3-
Dodecyloxycarbonyl phthalic anhydride, 3-tetradecyloxycarbonyl phthalic anhydride, 3-hexadecyloxycarbonyl phthalic anhydride, n-octylhexahydrophthalic anhydride, n-dodecylhexahydrophthalic anhydride and the like, It is not limited to these.

These monoacid anhydrides can be used alone or in admixture of two or more.

When the carbon number of R ₁ which is the alkyl group of the monoacid anhydride is 5 or less, the effect of increasing the tilt alignment angle of the liquid crystal molecules is not sufficient.

Further, when the carbon number of R ₁ exceeds 20, problems such as deterioration of coating property on the substrate are likely to occur.

The alignment treatment agent for a liquid crystal cell of the present invention comprises a mole of diamine, tetracarboxylic acid dianhydride b mole and monoacid anhydride c mole represented by the following formula: a> b ≧ a / 2 (1) 2 ( ab) ≧ c> 0 (2) It is necessary to use a polyimide resin obtained by reacting and polymerizing.

Here, when a ≦ b, the reaction and polymerization of the monoanhydride of the general formula [I] are not sufficient, so when used as an alignment treatment agent for liquid crystal cells, liquid crystal molecules cannot be largely tilted and aligned.

When b <a / 2, the degree of polymerization of the polyimide resin does not increase, so that a stable coating film cannot be formed as an alignment treatment agent for liquid crystal cells.

Further, when 2 (ab) <c, when used as an alignment treatment agent for a liquid crystal cell, a monoacid anhydride may be liberated in the liquid crystal cell, which may adversely affect the display characteristics of the liquid crystal cell.

The reaction and polymerization methods of the diamine, tetracarboxylic dianhydride and monoacid anhydride do not need to be particularly limited.

Generally, a method of reacting a diamine and a tetracarboxylic acid dianhydride and then reacting and polymerizing a monoacid anhydride, or a method of simultaneously reacting and polymerizing these three components is adopted.

Further, as a method of reacting a diamine, a tetracarboxylic dianhydride and a monoanhydride to form a polyimide resin film, a diamine, a tetracarboxylic dianhydride and a monoanhydride are reacted because of the ease of processing. After the polyamic acid intermediate is formed, the intermediate is preferably dehydrated and cyclized.

In this case, any one-step method of isolating the resulting polyamic acid intermediate into a polyimide resin without isolation or isolating the resulting polyamic acid intermediate followed by dehydration ring-closure polymerization into a polyimide resin is possible. Can be adopted.

The reaction and polymerization temperature of the diamine, tetracarboxylic dianhydride and monoacid anhydride may be any temperature from -20 to 400 ° C, but the range from -5 to 350 ° C is particularly preferable.

Further, the reaction temperature for producing the polyamic acid intermediate is −20.
Although any temperature of ˜150 ° C. can be selected, a range of −5 to 100 ° C. is particularly preferable.

Further, in order to convert the polyamic acid intermediate into a polyimide resin, a method of dehydration and ring closure by heating is usually adopted. The heat dehydration ring-closing temperature is 150 to 450 ° C., preferably
Any temperature between 170 and 350 ° C can be selected.

The time required for the dehydration ring closure is 30 seconds to 10 hours, preferably 5 minutes to 5 hours, depending on the reaction temperature.

As another method of converting the polyamic acid intermediate into a polyimide resin, a known dehydration ring-closing catalyst may be used to chemically perform ring closure.

The polyimide resin or polyamic acid intermediate solution obtained from the diamine, tetracarboxylic dianhydride and monoacid anhydride of the present invention is spin-coated or printed on a transparent substrate such as a glass or plastic film having a transparent electrode. After applying the coating solution, etc., cure at 150-250 ℃ for 1 minute-2 hours to form a polyimide resin film with a film thickness of 200-3000Å, and then rub the polyimide resin film layer to use it as an alignment treatment agent for liquid crystal cells. You can

(E) Effect of the Invention The alignment treatment agent for liquid crystal cells of the present invention can be used as an alignment treatment agent for liquid crystal cells having a large liquid crystal tilt alignment angle.

Also, diamine is used in a mole and tetracarboxylic acid dianhydride is used in b
If it is referred to as mol, c mol of monoacid anhydride is represented by the following formula.

a> b ≧ a / 2 (1) 2 (ab) ≧ c> 0 (2) As long as the relationship is satisfied, the liquid crystal tilt alignment angle can be arbitrarily adjusted.

(F) Examples The present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto.

Example 1 2,2-bis [4- (4-aminophenoxy) phenyl]
Propane 32.8 g (0.08 mol), n-tetradecyl succinic anhydride 4.73 g (0.016 mol) and cyclobutane tetracarboxylic dianhydride 14.11 g (0.072 mol) were added to N-methyl-2.
-In 465 g of pyrrolidone (hereinafter abbreviated as NMP), reaction was carried out at room temperature for 4 hours to prepare a polyamic acid intermediate solution.

The reduced viscosity η _{SP / C} of the obtained polyamic acid intermediate was 0.56.
It was dl / g (0.5 wt% NMP solution, 30 ° C.).

After diluting this solution with NMP to a total solid content of 2% by weight,
Spin on glass substrate with transparent electrode at 3500 rpm, 250
Heat treatment was performed at 30 ° C. for 30 minutes to form a polyimide resin film.

After rubbing this coating film with a cloth, it was assembled in parallel with the rubbing direction with a spacer of 50 μ interposed, and a liquid crystal (ZLI-2293, manufactured by Merck & Co., Inc.) was injected to prepare a homogeneously aligned cell.

When this cell was rotated in crossed Nicols, clear light and dark were seen, and it was confirmed that the cell was well oriented in the rubbing direction.

The liquid crystal tilt alignment angle of this cell was measured by the crystal rotation method and found to be 5.5 °.

Example 2 2,2-bis [4- (4-aminophenoxy) phenyl]
Propane 32.8 g (0.08 mol), n-hexadecyl succinic anhydride 5.18 g (0.016 mol) and cyclobutane tetracarboxylic dianhydride 14.11 g (0.072 mol) were reacted in NMP 465 g for 4 hours at room temperature to give a polyamic acid intermediate solution. Prepared.

The reduced viscosity η _{SP / C} of the obtained polyamic acid intermediate was 0.51.
It was dl / g (0.5 wt% NMP solution, 30 ° C.).

After diluting this solution with NMP to a total solid content of 2% by weight,
A cell was prepared in the same manner as in Example 1.

The liquid crystal tilt alignment angle was 7.6 ° and the alignment was good.

Comparative Example 1 2,2-bis [4- (4-aminophenoxy) phenyl]
Propane 32.8 g (0.08 mol) and cyclobutane tetracarboxylic acid dianhydride 14.11 g (0.072 mol) were reacted in NMP 465 g for 4 hours at room temperature to prepare a polyamic acid intermediate solution.

The reduced viscosity η _{SP / C} of the obtained polyamic acid intermediate was 0.41.
It was dl / g (0.5 wt% NMP solution, 30 ° C.).

After diluting this solution with NMP to a total solid content of 2% by weight,
A cell was prepared in the same manner as in Example 1.

The liquid crystal tilt alignment angle was 2.6 °.

Comparative Example 2 2,2-bis [4- (4-aminophenoxy) phenyl]
Propane 32.8g (0.08mol) and cyclobutanetetracarboxylic dianhydride 15.06g (0.0768mol) in NMP430g,
The reaction was carried out at room temperature for 4 hours to prepare a polyamic acid intermediate solution.

The reduced viscosity η _{SP / C} of the obtained polyamic acid intermediate was 0.58.
It was dl / g (0.5 wt% NMP solution, 30 ° C.).

After diluting this solution with NMP to a total solid content of 2% by weight,
A cell was prepared in the same manner as in Example 1.

The liquid crystal tilt alignment angle was 2.4 °.

Claims (1)

[Claims] 1. A mole of diamine, b mole of tetracarboxylic dianhydride, and general formula [I]. (In the formula, R ₁ is an alkyl group having 6 to 20 carbon atoms, R ₂ is an aliphatic group in which two carbonyl groups constituting a dicarboxylic acid anhydride are bonded to two different carbons, and a derivative or aromatic group thereof. And a derivative thereof.) C mol of dicarboxylic acid anhydride is represented by the following formula: a> b ≧ a / 2 (1) 2 (ab) ≧ c> 0 (2) An alignment treatment agent for liquid crystal cells, comprising a polyimide resin obtained as described above.