JPH06175134A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To produce an oriented film at low temp., to improve heat resistance, film strength and adhesion property to a substrate, to improve reliability, and to obtain a high-quality display without coloring, by incorporating a specified polyurea into the liquid crystal oriented film. CONSTITUTION:This liquid crystal display element has a liquid crystal oriented film on a substrate, and the liquid crystal oriented film contains polyurea having a repeating structural unit expressed by formula I and/or II. In fomrulae I and II, R<1> and R<2> are bivalent org. residual groups and may be same or different. R<3> and R<4> are hydrogen atoms or univalent org. residual groups and may be same or different. R<5> and R<6> are bivalent aliphatic residual groups and may be same or different, and n is 0 or 1. If necessary, a silane or titante coupling agent may be applied on the substrate to improve adhesion property to the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a liquid crystal alignment film containing a specific polymer compound.

[0002]

2. Description of the Related Art In a TN type liquid crystal display element, it is important to orient the liquid crystal in one direction, and therefore, a layer for orienting the liquid crystal uniformly on the substrate surface (liquid crystal orientation film). Is provided.

A method for forming a liquid crystal alignment film is SiO ₂
Typical methods include oblique vapor deposition of a thin film made of an inorganic compound such as, and a method of forming a film of an organic polymer and then rubbing it (rubbing in a certain direction with a cloth such as nylon or polyester). .

Of these, the method of depositing SiO ₂ requires batch processing, is high in manufacturing cost, and is not often used recently because it is not suitable for upsizing, and an organic polymer film is used. The method is commonly used. As the polymer compound for the alignment film, particularly aromatic polyimide,
It is widely used at present because of its excellent ability to align liquid crystals, high heat resistance, and excellent reliability.

[0005]

In the method using polyimide as the liquid crystal alignment film, the aromatic polyimide resin is generally insoluble in a solvent. A method of forming a film in the form of an acid and then heating and cyclizing it to convert it into a polyimide is used.
Since the high temperature of 300 ° C. or higher is required to complete the cyclization reaction, the heat resistance of the substrate is limited. Recently, a liquid crystal display element using a plastic substrate was developed,
Although attention has been paid to the advantages such as toughness and flexibility, it is difficult to form a liquid crystal alignment film using a polyimide resin because plastic has low heat resistance. At treatment temperatures below the heat-resistant temperature of plastics, cyclization to polyimide hardly occurs, and the resulting coating film is inferior in various properties such as strength, adhesion, and environmental resistance, and is difficult to use as a liquid crystal alignment film. Further, since the aromatic polyimide is generally colored brown, there is a problem that the display quality of the liquid crystal display device is deteriorated.
Further, polyamic acid, which is a precursor of polyimide, has poor storage stability, and has problems that insoluble matter is precipitated and viscosity is changed during storage.

In order to improve the above problems, an aliphatic or alicyclic acid anhydride such as 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4 -Polyimides using cyclopentanetetracarboxylic dianhydride as a raw material have been proposed. These are generally light-colored, and those having a ring-closed polyimide structure that are soluble in a solvent can be obtained. If they are used, high temperature treatment during film formation is not necessary, but the heat resistance is insufficient and the orientation There was a problem that the film was inferior in strength and adhesiveness to the substrate and the film was scratched during rubbing treatment.

Aromatic polyether amides (JP-A-58-37621) and aromatic polyether ester amides (JP-A-59-2002) are used as liquid crystal alignment film materials.
No. 15), aromatic polyether amide sulfone (JP-A-63-205639), aromatic polyamide (JP-A-1-219718), and other polymers have been proposed, but the heat resistance of the resin and the substrate The adhesiveness with the is not sufficient, and the reliability is not sufficiently satisfied.

The present invention solves the above-mentioned problems of the conventional alignment film material, and enables the alignment film to be formed even at a low temperature of about 150 ° C. or lower, but also has heat resistance, film strength, and a substrate. It is an object of the present invention to provide a liquid crystal display device which has various characteristics such as adhesion, has high reliability, and has high quality display quality with almost no coloring.

[0009]

The present invention relates to a liquid crystal display device having a liquid crystal alignment film on a substrate, wherein the liquid crystal alignment film comprises a repeating structural unit represented by the following general formula (I) and / or (II). The present invention relates to a liquid crystal display device containing the polyurea.

[0010] ^{-CONH-R 1 -NHCO-NR 3} - (R 2) n -NR 4 - (I)

[Chemical 2] (In the formula, R ¹ and R ² represent a divalent organic residue, and may be the same or different from each other. R ³ and R ⁴ represent a hydrogen atom or a monovalent organic residue, and R ⁵ and R ⁶ represent a divalent aliphatic residue, and may be the same or different from each other, n =
It is 0 or 1. ) The polyurea having a repeating structural unit represented by the general formula (I) includes a diisocyanate represented by the following general formula (III) and a monovalent or divalent represented by the following general formula (IV). It can be easily synthesized by subjecting a diamine to a polyaddition reaction. Similarly, the polyurea having the repeating structural unit represented by the general formula (II) is represented by the diisocyanate represented by the following general formula (III) and the diisocyanate represented by the following general formula (V). It can be easily synthesized by subjecting a divalent or divalent diamine to a polyaddition reaction.

OCN-R ¹ -NCO (III) R ³ NH- (R ² ) _n -NHR ⁴ (IV)

[Chemical 3] (In the formula, R ^{1 to} R ⁶ and n are represented by the general formulas (I) and (II)
Represents the same as in. ) Specific examples of the diisocyanate represented by the general formula (III) include 2,4-tolylene diisocyanate, phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate and 4,4′-diphenyl ether diisocyanate. Aromatic diisocyanates such as nato, 4,4′-diphenyl diisocyanate, tolidine diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate,
Aliphatic diisocyanates such as isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (isocyanatomethyl) cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, butanedi Aliphatic diisocyanates such as isocyanate, hexamethylene diisocyanate, octamethylene diisocyanate and lysine isocyanate can be mentioned. Particularly preferred among these diisocyanates are 2,4-tolylene diisocyanate and 4,4 ′.
-Diphenylmethane diisocyanate can be mentioned. These diisocyanates may be used alone or in combination of two or more kinds.

Examples of the diamine represented by the general formula (IV) include 4,4'-diaminodiphenyl ether and 3,4'-
Diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-
Diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, o-tolidine, 3,4'-diaminobenzanilide, 4,4'-diaminobenzophenone, 2,2-bis (4-
(4-aminophenoxy) phenyl) propane, bis (4- (4-aminophenoxy) phenyl) sulfone, 1,4-
Bis (4-aminophenoxy) benzene, 1,3-bis (4-
Aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, m-toluylenediamine, 2,2'-dihydroxybenzidine, 3 Aromatic diamines such as 2,5-diaminophenol, 3,5-diaminobenzoic acid, m-xylylenediamine and p-xylylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylenediamine, dodecamethylenediamine , 1,4-diaminocyclohexane, 4,4 '
-Aliphatic or alicyclic diamines such as bis (aminocyclohexyl) methane and isophoronediamine, the following formula

[Chemical 4] (In the formula, R ⁷ represents a divalent hydrocarbon group, R ⁸ represents a monovalent hydrocarbon, and m is an integer of 1 to 20), and hydrazine (an anhydride or an anhydride). Monohydrate) and the like. Of these, particularly preferred are 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, o-tolidine, 1,3-bis (4-aminophenoxy) benzene, 2,2-
Examples thereof include bis (4- (4-aminophenoxy) phenyl) propane. Examples of the diamine represented by the general formula (V) include piperazine and 2,5-dimethylpiperazine.

These diamines may be used alone or in admixture of two or more. That is, when the diamine having repeating structural units represented by the general formulas (IV) and (V) is used in combination for the polymerization, the polyurea obtained is represented by the general formulas (I) and (II). There will be repeating structural units. Also,
Two or more polyureas obtained from a single diamine may be blended and used.

The above diisocyanate and diamine each account for 30 mol% or more of the total amount, preferably 5 mol.
It is preferable to use an aromatic compound in an amount of 0 mol% or more. When the content of the aromatic component is less than the above range, the heat resistance of the produced polymer is lowered and the performance as an alignment film is deteriorated.

In the above reaction of the diisocyanate with the diamine, a part of the diamine has a reactivity with other isocyanate groups other than the diamine represented by the general formula (IV) or (V). It is also possible to substitute with a compound having two (in some cases three or more) groups. The functional group having reactivity with an isocyanate group includes a hydroxyl group, a hydrazide group, an oxime group, and the like, and examples of the compound having such a functional group include ethylene glycol, propylene glycol, trimethylene glycol, cyclohexanedimethanol, and xylylene. Glycol, isophthalic acid dihydrazide, terephthalic acid dihydrazide, sebacic acid dihydrazide, dimethylglyoxime, cyclohexanedione dioxime and the like can be mentioned.

When such a reaction component is used in combination, the resulting polymer contains structural units derived from other reaction components in addition to the structural unit represented by the general formula (I) or (II). In that case, the general formula (I) or (I
It is preferable that the structural unit represented by I) is contained in an amount of 30 mol% or more, preferably 50 mol% or more, based on the whole. When the content of the structural unit represented by the general formula (I) or (II) is less than the above, properties such as heat resistance will be insufficient.

The reaction between diisocyanate and diamine is carried out by dissolving or suspending both components in a suitable solvent, preferably -50.
The reaction can be carried out at a temperature of about 200 to 200 ° C., more preferably about 0 to 100 ° C. for about 0.5 to 24 hours. The molar ratio of the diisocyanate component to the diamine component is preferably 0.5 to 2, more preferably 0.9 to 1.1. The closer this ratio is to 1, the larger the molecular weight of the polymer produced, which is preferable.

The solvent used here is not particularly limited as long as it has substantially no reactivity with the raw material diisocyanate or diamine and dissolves the produced polyurea.
For example, organic solvents such as N-methyl-2-pyrrolidone, N, N'-dimethylacetamide, N, N'-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone are preferably used.

In addition to the above-mentioned solvents, other general solvents such as ethers, esters, ketones, hydrocarbons, halogenated hydrocarbons, etc., to the extent that polyurea does not precipitate It can be mixed and used. Examples of such solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, butyl acetate, diethyl oxalate, dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, methylene chloride, chloroform, 1,2. -Dichloroethane, 1,4-dichlorobutane, trichloroethane, chlorobenzene, o-dichlorobenzene, benzene, toluene, xylene, hexane, cyclohexane, etc.

The amount of the organic solvent is not particularly limited, but it is usually used in such an amount that the solid content concentration is about 0.2 to 50% by weight, preferably about 1 to 30% by weight.

The polyurea produced can be separated as a solid by adding a solvent in which the polyurea is not dissolved, such as water or alcohol, to the solution of the polyurea obtained above, but it is usually necessary to separate the polyurea. Alternatively, the obtained polyurea solution can be appropriately diluted with a solvent and used as a coating solution for a liquid crystal aligning agent. This coating solution
Usually, the solid content concentration is 0.5 to 30% by weight, preferably 1 to 2
It is used by adjusting to about 0% by weight. As the solvent for dilution here, other than the same organic solvent as the solvent used for the polyurea synthesis, a solvent having reactivity with an isocyanate group or an amino group, for example, alcohols or the like within a range that does not precipitate polyurea. Mixtures can be used.

In the present invention, the polymer used for forming the liquid crystal alignment film contains the above-mentioned polyurea as an essential component, but it is also possible to use other kinds of polymers in combination. In that case, the general formula (I) or (I
It is desirable that the structural unit represented by I) is 30 mol% or more, and more preferably 50 mol% or more of the whole polymer.

The polymer solution prepared as described above is applied onto a substrate having a transparent conductive film on its surface by a known means such as a spin coating method, a roll coating method or a printing method, and then preferably 80 To 300 ° C, more preferably 100 to 200 ° C, preferably 5-1
The liquid crystal alignment film is formed by heating and drying for 80 minutes, more preferably for 30 to 90 minutes. In the polyurea of the present invention, unlike the case of polyimide, there is no need to perform dehydration ring closure, and since it is only necessary to remove the solvent, a liquid crystal having good properties under mild drying conditions of about 150 ° C. or less. An alignment film can be formed.

The thickness of the liquid crystal alignment film is usually 0.0
It is about 1 to 10 μm, preferably about 0.1 to 2 μm.

If desired, a silane-based or titanate-based coupling agent may be coated on the substrate for the purpose of improving the adhesion to the substrate. It is also possible to use these coupling agents by adding them to the coating polymer solution.

The polyurea coating film obtained above is rubbed with a roller wound with a cloth such as nylon,
It is used as a liquid crystal alignment film. The two substrates having the alignment films thus prepared are arranged so as to face each other, and liquid crystal is injected between them to obtain the liquid crystal display device of the present invention.

[0027]

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 2.0 g of 4,4'-diaminodiphenyl ether (0.
01 mol) to N-methyl-2-pyrrolidone (NMP) 1
A solution prepared by dissolving 1.74 g (0.01 mol) of 2,4-tolylene diisocyanate in 5 g of NMP was dissolved in 0 g, and the solution was added dropwise with stirring at room temperature under a nitrogen atmosphere at room temperature for 2 hours. An exothermic reaction occurred and a viscous polyurea solution was obtained.

This solution was cast on a glass plate and
After drying for 2 hours at ℃ and evaporating the solvent, 5 hours in water
The coating could be peeled from the glass upon immersion. It was an almost colorless tough film.

The polyurea solution was diluted with N, N-dimethylacetamide so as to have a solid content concentration of 3%, and filtered through a filter having a pore size of 0.2 μm to prepare a coating solution.

The coating solution thus obtained was coated on a glass substrate having a transparent conductive film made of ITO with a spinner at 2000 rpm for 30 seconds and then at 140 ° C. for 1 hour.
After drying for an hour, the solvent was evaporated to form a liquid crystal alignment film. The film was rubbed three times at a roll speed of 800 rpm and a stage moving speed of 50 mm / sec by a rubbing device having a roll around which nylon felt was wound. No damage to the coating film due to rubbing was observed.

A pair of substrates having the liquid crystal alignment film obtained as described above are arranged so that the alignment films face each other so that the rubbing directions are antiparallel, and a polyethylene terephthalate film (thickness: 2 mm) cut into a strip with a width of 2 mm ( Toray Co., Ltd. “Lumirror” is sandwiched as a spacer, and epoxy sealant (“Structbond” ES-4500 manufactured by Mitsui Toatsu Chemicals, Inc.) is applied to the side surface of the substrate and cured at 110 ° C. for 30 minutes and sealed. I stopped. A liquid crystal (Merck Z
LI-2293) was injected in a vacuum, the injection port was closed with an epoxy sealant, and the liquid crystal was annealed by heating at 100 ° C. for 30 minutes.

When the test liquid crystal cell thus produced was observed between crossed Nicols of a polarizing microscope, it was confirmed that the liquid crystal was favorably and uniformly aligned. The cell was heat-treated at 180 ° C. for 1 hour and observed again. No change was observed in the alignment state of the liquid crystal, and it was found that the alignment film had good heat resistance and liquid crystal resistance.

Example 2 In Example 1, 1.9 g (0.95 mol) of 4,4'-diaminodiphenyl ether as a diamine component and 1,3-bis (3-aminopropyl) -tetramethyldisiloxane 0 Polyurea was synthesized in the same manner except that both .124 g (0.05 mol) were used. This solution was cast on a glass plate and dried at 140 ° C. for 1 hour to obtain an almost colorless tough coating film. Even if the glass plate having this coating film was immersed in water, the coating film could not be peeled off.
That is, the adhesion to glass is better than that of the polymer of Example 1.

Using this polymer, a liquid crystal alignment film was formed on a substrate in the same manner as in Example 1 to prepare a test liquid crystal cell. Similar to Example 1, the liquid crystal alignment and heat resistance were good.

Example 3 In Example 1, 4,4'-diaminodiphenylmethane was used in place of 4,4'-diaminodiphenyl ether.
A liquid crystal cell was prepared by synthesizing polyurea in the same manner except that 98 g (0.01 mol) was used. Similar to Example 1, the liquid crystal alignment and heat resistance were good.

Example 4 A polymer was synthesized in the same manner as in Example 1 except that 0.5 g (0.01 mol) of hydrazine monohydrate was used instead of 4,4'-diaminodiphenyl ether. A liquid crystal cell was prepared. The liquid crystal alignment is good,
No change occurred in the alignment state by heating at 160 ° C. for 1 hr.

Example 5 2.5 g (0.01 mol) of ground 4,4'-diphenylmethane diisocyanate was added to 15 g of NMP,
A solution of 4.1 g (0.01 mol) of 2,2-bis (4-aminophenoxyphenyl) propane dissolved in 15 g of NMP was added with stirring, and stirring was continued for 5 hours as it was. A liquid crystal cell was produced in the same manner as in Example 1 using the obtained polymer. The liquid crystal alignment was good, and no change was observed in the alignment even when the liquid crystal cell was heated to 150 ° C. for 1 hour.

Example 6 A liquid crystal cell was produced in the same manner as in Example 1 except that a polyethylene terephthalate film having a transparent conductive film was used as the substrate. Similar to Example 1, the liquid crystal alignment and heat resistance were good.

Comparative Example 2 g (0.01 g) of 4,4'-diaminodiphenyl ether
(18 mol) was dissolved in 16 g of NMP, 2.18 g (0.01 mol) of pyromellitic dianhydride was added with stirring, and stirring was continued for 4 hours at room temperature to obtain a polyamic acid. This polyamic acid was used to form a coating film for liquid crystal alignment film on a glass substrate in the same manner as in Example 1. When the obtained coating film was subjected to rubbing, the coating film was almost completely peeled off, and an alignment film could not be obtained.

[0041]

In the liquid crystal display device of the present invention, the polymer coating film containing polyurea as a liquid crystal alignment film as a main component,
Since high temperature heat treatment is not required at the time of manufacturing, it is possible to form a film sufficiently at a low temperature of about 150 ° C. or less, so that the manufacturing is easy and there is no fear of damaging other element materials. Alternatively, a plastic having low heat resistance can be used. Moreover, since the liquid crystal alignment film is excellent in various properties such as liquid crystal alignment ability, heat resistance, transparency, strength, and adhesion to a substrate, and provides highly reliable display characteristics, the liquid crystal display device of the present invention has a wide range of applications. Can be used very advantageously for

Claims (1)

[Claims] 1. A liquid crystal display device having a liquid crystal alignment film on a substrate, wherein the liquid crystal alignment film contains polyurea having a repeating structural unit represented by the following general formula (I) and / or (II). Characteristic liquid crystal display element. ^{-CONH-R 1 -NHCO-NR 3} - (R 2) n -NR 4 - (I) ## STR1 ## (In the formula, R ¹ and R ² represent a divalent organic residue, and may be the same or different from each other. R ³ and R ⁴ represent a hydrogen atom or a monovalent organic residue, and R ⁵ and R ⁶ represent a divalent aliphatic residue, and may be the same or different from each other, n =
It is 0 or 1. )