JPS6378130A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain the titled device capable of obtaining high tilt angle with ease, and reducing a production cost and having good productivity by using a polyimide film obtd. by effecting dehydration and ring-closure of a polyamidic acid which is obtd. by reacting diamines contg. a specific diamine and tetracarboxylic acid dianhydride to the titled device as the orientation film. CONSTITUTION:The titled device is produced by sealing the environs of a pair of the substrates which are formed the orientation film on one side of the substrates with a sealing material to form a cell, followed by enclosing a liquid crystal in said cell. THe orientation film is composed of the polyimide film obtd. by reacting tetracarboxylic acid dianhydride and diamines contg. the diamine shown by the formula (wherein R is 7-25C a straight chain alkylene group, a methine group contd. in said group may be substd. with oxygen atom, oxygen-oxygen atoms are not adjacent directly or through a methine group with each other) to form polyamidic acid, followed by effecting the dehydration- ring closure of the obtd. amidic acid. In this case, to obtain the titled device having the high tilt angle, the diamine shown by the formula is incorporated to the used diamines in an amount of >=20mol%, especially, 20-95mol%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a liquid crystal display element having a polyimide alignment film having a large tilt angle.

[Prior Art] Conventionally, in twisted nematic (TN) type axillary crystal display elements, in order to horizontally align the liquid crystal, organic materials such as polyimide, polyimide-isoindoroquinazoline, polyimide benzimidazene, etc. have been used as the material for the alignment film. Polymer membranes have been proposed. In particular, in order to perform high-density display, a small tilt angle is suitable for this purpose, so various alignment films with a small tilt angle have been developed, and they have almost the same properties in terms of uniform alignment of liquid crystals, heat resistance, and insulation resistance. It had achieved its purpose.

For this purpose, a diamine represented by the following general formula (11) and a tetracarboxylic dianhydride represented by the following general formula (m) are used as raw materials, and these are reacted to form a polyamic acid, which is then dehydrated. Polyimide was synthesized by ring closure.

H2N-R'-NH2(II) In this diamine, R' is phenylene.

However, in recent years, super twisted nematic (STN) liquid crystal display elements, which are suitable for higher-density displays and proposed by Type 2 (%p, 120-123 (1995)), have been developed. requires a large tilt angle.

For this reason, an oblique vapor deposition method that can easily obtain a high tilt angle has been adopted. However, the oblique deposition method is expensive and requires a vacuum system.

It has poor productivity and is not suitable for mass production of large liquid crystal display elements.

[Problems to be solved by the invention] Therefore, a high tilt angle of 4" or more was achieved by rubbing a polyimide film, which has been used in ordinary TN type liquid crystal display elements and has high reliability and good productivity. It was hoped to obtain.

However, polyimide used in conventional TN-type liquid crystal display elements is required to have a low tilt angle within a range that does not cause reverse tilt in order to increase display contrast, so rubbing conditions are Even after making various changes, only a low tilt angle could be obtained.

Therefore, it was necessary to improve the polyimide material and obtain a polyimide material that itself can obtain a high tilt angle. By finding rubbing conditions suitable for the polyimide material that can obtain this high tilt angle, a higher tilt angle can be obtained.

[Means for Solving the Problems] The present invention has been made to solve these problems, and includes sealing the periphery of a pair of substrates, at least one of which has an alignment film formed thereon, with a sealing material. In a liquid crystal display element in which a cell is formed and a liquid crystal is sealed inside, the alignment film is represented by the general formula (I) (wherein R represents an alkylene group having a chain length of 7 to 25,
The methylene groups therein may be substituted with oxygen atoms, but the oxygen atoms are not adjacent directly or through one methylene group) and tetracarboxylic dianhydrides. The present invention provides a liquid crystal display element characterized in that it uses a polyimide film formed by dehydrating and ring-closing polyamic acid reacted with a substance.

The diamine used in the polyimide alignment film of the present invention includes a diamine represented by the following general formula (I). In order to obtain a high tilt angle, the diamine preferably contains 20 mol% or more of the diamine represented by general formula (I), particularly 20 to 95 mol%.
Diamines containing are preferred.

However, R in general formula (I) represents a fullkylene group having a chain length of 7 to 25, and the methylene group therein may be substituted with an oxygen atom, but the oxygen atom and the oxygen atom may be substituted directly or with one oxygen atom. are not adjacent via methylene groups.

In the present invention, diamines containing diamines represented by general formula (I) are used. The diamine represented by the general formula (I) is preferably contained in an amount of 20 mol% or more in order to obtain a high tilt angle.

In addition to the diamine represented by the general formula (I), the following diamines can be used in combination.

In particular, there are diaminosiloxanes as diamines that improve adhesion to glass substrates, such as those shown below. % and diaminosiloxane in an amount of 5 to 80 mol %, it is possible to obtain a poimide alignment film that has a high tilt angle and has good adhesion to a glass substrate.

(However, ph represents a phenyl group or a substituted phenyl group, and n is an integer of 2 to 10.) In particular, the general formula (I
) It is preferable to use a mixture of 20 to 95 mol % of the diamine represented by the formula and 5 to 80 mol % of diaminosiloxane from the viewpoint of adhesion to the glass substrate.

Various known tetracarboxylic dianhydrides can be used as the tetracarboxylic dianhydride which is the reaction partner of the diamine. Aromatic tetracarboxylic dianhydrides such as chloride, diphenyl ether, and benzophenone, and alicyclic tetracarboxylic dianhydrides such as cyclopentane and cyclohexane are used.

More specifically, there are the following.

The reaction between this diamine and the tetracarboxylic dianhydride to form a polyamic acid is carried out under various known conditions. As the solvent, for example, N,N-dimethylacetamide, N-methylpyrrolidone, etc. are used. The reaction temperature in this case is preferably 0 to 100°C, especially 5
~60°C is preferred.

200-350 to dehydrate and ring-close polyamic acid
It may be heated to ℃, but a catalyst such as quinoline may also be present.

When forming an alignment film for a liquid crystal display element, a mixture of the above-mentioned diamine and tetracarboxylic dianhydride, or a polyamic acid obtained by reacting them, is prepared by dipping, transfer, or dipping.
It can be applied onto a substrate by a method such as a roll coating method, and heated to dehydrate and close the ring. After that, it is rubbed with a cloth such as nylon fiber, cotton fiber, or a brush made of carbon fiber, etc., that is, in a certain direction. Rub to form a horizontal alignment film.

In the present invention, it is sufficient to form this polyimide alignment film on at least one of the substrates of the liquid crystal display element; however, in most cases, both substrates are often made of the same polyimide alignment film. Of course, one of the substrates may be diagonally thinly coated, an alignment film made of other resin or inorganic material may be applied, or a vertical alignment film may be formed by applying a vertical alignment agent, as long as it is determined according to the purpose of the liquid crystal display element.

In addition, this substrate usually has an electrode on the substrate, specifically an I
Transparent electrodes made of TO (indium oxide-tin oxide) or tin oxide, opaque electrodes made of chromium, aluminum, etc. are formed. Furthermore, an undercoat film such as an insulating film, a polarizing film, a color filter film, etc. for the purpose of preventing elution of alkali from the substrate may be formed under this electrode, and an insulating film, a color filter film, etc. may be formed on the electrode. , an overcoat film such as a light transmission prevention film may be formed, these electrodes may have a two-layer structure with an insulating film interposed therebetween, or an emotional element such as TPT or a non-linear resistance element may be formed. However, for these electrodes, undercoat, overcoat, and other structures inside the cell, conventional structures of liquid crystal display elements can be used.

The substrate thus formed is used to form a cell, liquid crystal is injected into the cell, and the injection port is sealed. As the liquid crystal to be sealed, various liquid crystals such as ordinary nematic liquid crystal, liquid crystal added with dichroic dye, and ferroelectric liquid crystal (SmC liquid crystal) can be used.

In addition, on the outer surface of the liquid crystal cell manufactured in this way, characters, figures, light-opaque layers, color filters, etc. may be printed, a non-reflective layer may be formed, or a polarizing film may be applied as necessary. Laminate them and arrange reflectors, light guide plates, and lighting.

In addition, in the present invention, since a high tilt angle can be obtained, it is suitable for applications where the liquid crystal is largely twisted. Therefore, it is suitable for a liquid crystal display element in which the alignment processing directions of the alignment films of a pair of substrates are twisted by 160 to 360 degrees.

Furthermore, a pair of polarizing films are arranged on both outer surfaces of this substrate,
Each polarization axis is 20~
Spur twisted nematic (ST
N) Suitable for use in LCDs.

That is, by setting the twist angle of the liquid crystal to 180 to 360 degrees and using the high tilt angle alignment film of the present invention, it is possible to easily obtain a liquid crystal display element that does not cause alignment abnormalities and has high contrast. The liquid crystal used in this 5TN LCD is a liquid crystal with positive dielectric anisotropy.
It may be created by mixing various liquid crystals.

[Function] By using the substrate on which the polyimide alignment film of the present invention is formed as at least one substrate, a high tilt angle can be obtained and the twist angle of the liquid crystal can be increased, so that a high contrast liquid crystal display element can be obtained. can be obtained.

The reason why this high tilt angle is obtained is not clear, but it is thought that it is because the alkylene chain R, which is a soft segment in the diamine, is relatively likely to become concave during rubbing.

[Example code] Examples and comparative examples will be described below.

In these Examples and Comparative Examples, the tilt angle was measured by the Hc-θ method when the tilt angle was 5° or less;
When the angle was 5° or more, the magnetic null method was used.

Example 1 25 g of p-hydroxyacetanilide (0,188++
+ol) in ethanol 150+s(2), water 20+s
11.8 g of potassium hydroxide dissolved in IIQ was added dropwise,
Subsequently, 27.3 g (0,091 mol) of 1,10-dibromodecane dissolved in 80 ml of ethanol was added dropwise and heated under reflux for 6 hours to produce a white precipitate. 500 IIQ of water was added to the reaction mixture, and the resulting white precipitate was collected, washed with acetone, and recrystallized from dimethyl sulfoxide to obtain 1.10-bis-(4'-acetaminophenoxy)decane28. Obtained Og.

Melting point: 182.11°C, yield: 88.8% 1. 28.0 g of IO-bis-(4'-acetaminophenoxy)decane, 40 g of potassium hydroxide, 300 Q of diethylene glycol, and 3 Q of water were mixed under reflux. heated for an hour. 200ml of water was added to this and extracted with dichloromethane. The organic layer was washed with water, dried over anhydrous magnesium sulfate, and then the solvent was distilled off. The obtained crude product was recrystallized from ethanol to give 1.10-bis-(4'-7
Minophenoxy) deca 71B, Og was obtained.

Melting point 121.2°C, 70.8% The NMR spectrum of this compound was as follows: (CDC+23 solvent solvent TMS internal standard) δ 8.8~
6.5 complex m 8Hδ3.
88 t J=7Hz 4Hδ 3
．． 23 br-s 4H62,0-
1,2C0IIP11! ! ts 1 [IH diamine The following compound was used as the tetracarboxylic dianhydride.

Diamine ■1.1O: bis-(4'-7 minophenoxy) deca7
95 mol% tetracarboxylic dianhydride 3.3',4.4'-benzophenonetetracarboxylic dianhydride 100 mol% Using the above mixture and using N-methylpyrrolidone as a solvent,
By stirring at room temperature for 5 hours, a 13.5 wt % copolymer solution with a viscosity of 1790 cP at 25° C. was obtained. This solution was diluted 4 times and I
It was applied to a thickness of approximately 700 mm on a glass substrate equipped with a TO electrode. After baking at 150℃ for 30 minutes and then at 300℃ for 30 minutes, rubbing and scattering 10gm spacers,
Created a cell. This Selnymerk liquid crystal rZLI-
2293J was sealed and the tilt angle was measured.5.
Example 2 Instead of 1.10-dibromodecane in Example 1, 1.2
-Bis(chloroethoxy)ethane 1? , Og(0,0
91 mol) was used to react in the same manner.

The obtained crude product was recrystallized from ethanol to give 1.2-
7.4 g of bis[2'-(4''-7cetaminophenoxy)ethoxyconitane was obtained.

Melting point 190.0°C, yield 19.5% 1.2-bis[2'-(4''-7cetaminophenoxy)ethoxyconitane 7.0g, potassium hydroxide 10g,
100 Q of ethylene glycol and 3 mQ of water were reacted in the same manner as in Example 1 to obtain 3.7 g of 1,2-bis[2'-(4''-aminophenoxy)ethoxy]ethane.

Melting point: 83.0°C, yield: 66.2%. The NMR spectrum of this compound was as follows.

(CDCQ3 solvent solvent TMS internal standard) 67.0-8.
5 coa + plex m 8)! 64.
3-3.6 complex ra 12)
The following compounds were used as 163.4s 4H diamine and tetracarboxylic dianhydride.

Diamine ■1. 2-bis[2'-(4"-aminophenoxy)ethoxyconitane 95 mol% Tetracarboxylic dianhydride 3.3", 4.4'-benzophenone Tetracarboxylic dianhydride 100 mol% Using the above mixture and using N-methylpyrrolidone as a solvent,
By stirring at room temperature for 5 hours, a 13.5 wt % copolymer solution with a viscosity of 535 cP at 25° C. was obtained.

This solution was diluted 4 times and applied in the same manner as in Example 1,
It became a cell. When I measured the tilt angle of this cell, it was 4
．． It was 7°.

Examples 3 to 5 Cells were formed in the same manner as in Example 1, except that the mixing ratio of diamine in Example 1 was changed in mol% as follows.

Table 1 Examples ■ ■ 5 80 mol% 40 mol% Tilt angle is ■
There was a tendency for the value to decrease as the amount of 1.10-bis-(4'-7minophenoxy)decane decreased, but in all cases it was 4° or more.

Moreover, in Example 3, ■ is 100 mol%.

Compared to other materials, the adhesion to the glass substrate was slightly inferior, and depending on the rubbing conditions, part of the alignment film sometimes peeled off.

Comparative Example In Example 1, 1. The same treatment was performed using 95 mol% of bis(4-aminophenyl) ether instead of lO-bis-(4'-aminophenoxy)decane, and the tilt angle was measured. As a result, the tilt angle is 2.
The tilt angle was 8°, which was considerably lower than the tilt angle obtained in Examples 1 to 5.

[Effects of the Invention] In the present invention, the alignment film has the general formula (I) (wherein R represents an alkylene group having a chain length of 7 to 25, and the methylene group therein may be substituted with an oxygen atom). , oxygen atoms are not adjacent to each other directly or through one methylene group) A polyimide obtained by dehydrating and ring-closing a polyamic acid obtained by reacting a diamine with a tetracarboxylic dianhydride. By rubbing this with a film-like material, a high tilt angle can be easily obtained.
Since there is no need to use manufacturing methods with poor productivity such as oblique vapor deposition, productivity is high and costs are reduced.

In particular, by using diaminosiloxane as the diamine in combination with 20 to 95 mol% of the diamine of the present invention and 5 to 80 mol% of diaminosiloxane, it has a high tilt angle and is compatible with glass substrates. A poimide alignment film with good adhesiveness can be obtained.

Further, by using the substrate having a high tilt angle alignment film of the present invention, the alignment treatment direction of the alignment film of a pair of substrates is 18
A cell was formed by arranging the cells so that they were twisted by 0 to 360 degrees, and a pair of polarizing films was placed on both outer surfaces of this cell so that each polarization axis was shifted by 20 to 70' with respect to the adjacent alignment direction. Spur twisted nematic (STN) LC
By using D, it is possible to easily obtain a liquid crystal display element that is less likely to cause alignment abnormalities and has a high contrast.

The present invention can be applied in various ways, such as adding a third component or coexisting with other film-like materials within a range that does not impair the effects of the present invention.

Claims (6)

[Claims] (1) In a liquid crystal display element in which a pair of substrates, at least one of which has an alignment film formed thereon, are sealed with a sealing material around the substrate to form a cell, and a liquid crystal is sealed inside, the alignment film is General formula (I) ▲Mathematical formulas, chemical formulas, tables, etc.▼(I) (However, R represents an alkylene group with a chain length of 7 to 25,
The methylene groups therein may be substituted with oxygen atoms, but the oxygen atoms are not adjacent directly or through one methylene group) and tetracarboxylic dianhydrides. 1. A liquid crystal display element characterized by using a polyimide film-like material obtained by dehydrating and ring-closing polyamic acid reacted with a substance. (2) The liquid crystal display element according to claim 1, which uses a diamine containing 20 mol% or more of the diamine of general formula (I). (3) 20 to 95 mol% of diamine of general formula (I),
3. The liquid crystal display element according to claim 2, which uses a diamine containing 5 to 80 mol% of diaminosiloxane. (4) The liquid crystal display element according to any one of claims 1 to 3, wherein the alignment film is obtained by rubbing a polyimide film. (5) The alignment treatment direction of the alignment film of the pair of substrates is 160 to 3
The liquid crystal display element according to claim 4, which is twisted by 60 degrees. (6) A pair of polarizing films are arranged on both outer surfaces of the substrate, and each polarizing axis is oriented at 20 to 70 degrees with respect to the adjacent alignment direction.
The liquid crystal display element according to claim 5, which is shifted.