JPH07159793A - Liquid crystal orienting agent and liquid crystal display element using the same - Google Patents

Abstract

PURPOSE:To provide a liquid crystal orienting agent capable of working it at low temp. such as 120 deg.C and obtaining a high pretilt angle by using a specific polyamide as a resin component. CONSTITUTION:The polyamide expressed by formula I or formula II is used as a liquid crystal orienting agent containing polyamide as a resin component. In the formula I and II, Ar denotes bivalent aromatic group, each of R1 and R2 denotes 4-30C alkyl group and may be the same or different. And Ar in the formula I and II is the liquid crystal orienting agent expressed by formula III. In the formula III, R3 denotes single bond, -O-, -CH2-, -C(CH3)2-, -C(CF3)2- or the like. A mixed solvent of N-methyl-2-pyrolidone (NMP) and butyl cellosolve, a mixed solvent of dimethyl acetoamide and butyl cellosolve or the like is exemplified as the solvent component of the liquid crystal orienting agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal aligning agent used for manufacturing a liquid crystal display device, and more particularly to a liquid crystal aligning agent which can be processed at a low temperature to obtain a high pretilt angle.

[0002]

2. Description of the Related Art At present, liquid crystal display devices have been widely used as thin displays. There are various types of liquid crystal display elements depending on the operation mode and driving method.
There is a Super Twisted Nematic (STN) type liquid crystal display element as a method that is low in cost and relatively excellent in display quality, and is widely used for portable word processors and computers. A liquid crystal aligning agent is used in a liquid crystal display device to form an alignment film on a substrate that uniformly aligns liquid crystals inside the liquid crystal display device. An item required for the liquid crystal aligning agent for STN is an alignment direction of liquid crystal molecules. The angle formed by the substrate, that is, the pretilt angle is 4 to 8 degrees, which is higher than that for the twisted nematic (TN) type.
Examples of the liquid crystal aligning agent capable of obtaining such a high pretilt angle include a polyimide precursor solution as described in JP-A-1-177514.

Generally, a substrate of a liquid crystal display device has a thickness of 0.3 m.
Glass with a thickness of about m to 1.0 mm is used. In recent years, in order to further reduce the thickness and weight of electronic devices equipped with liquid crystal display elements, substrates such as polyethylene terephthalate (hereinafter abbreviated as PET), polyether sulfone (hereinafter abbreviated as PES), and polyarylate are used. The use of a plastic substrate has been studied, and some have begun to put it into practical use. By using these plastic substrates, it is possible to make them thinner and lighter, and by taking advantage of the flexibility that is the characteristic of plastics,
It is also possible to manufacture a display having a curved display surface or a display having flexibility.

However, in manufacturing such a plastic liquid crystal display device, there arises a problem regarding a liquid crystal aligning agent used therein. That is, since a plastic substrate is used, about 120 ° C. for PET and about 150 ° C. for PES or polyarylate are the maximum allowable temperatures in the process, and the liquid crystal aligning agent for STN as described above, which has a firing temperature of 200 to 300 ° C. Is that you cannot use.

On the other hand, as a liquid crystal aligning agent which can be baked at 200 ° C. or lower, a liquid crystal aligning agent containing a soluble polyimide as a resin component, which is described in JP-A-61-205924,
A liquid crystal aligning agent containing a silicone-modified polyamic acid as a resin component described in JP-A-5-158047 has been proposed. The former is that the resin component is not a polyimide precursor but polyimide which has already been imidized, so that an alignment film can be obtained by evaporating the solvent. In the latter case, thermal imidization is more likely to proceed than a normal polyimide precursor, and therefore firing at low temperature is possible. However, although they exhibit sufficient performance when fired at 150 to 200 ° C, a sufficient pretilt angle cannot be obtained at a firing temperature of lower than 150 ° C, or the stability is insufficient and the pretilt angle is increased by an accelerated test. Phenomenon such as change may occur,
It has become a problem about yield and reliability of plastic liquid crystal display elements.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above problems of liquid crystal aligning agents and provides a liquid crystal aligning agent which can be processed at a low temperature of 150 ° C. or lower and can obtain a high pretilt angle. The present invention provides a liquid crystal display device using this, which can be processed at a low temperature and has excellent reliability.

[0007]

The present invention is based on the general formula (1)
Is a liquid crystal aligning agent containing polyamide as a resin component, and Ar in the general formula (1) is the liquid crystal aligning agent represented by the general formula (3). R ₃ is-
A liquid crystal aligning agent containing CH ₂ — as the above-mentioned liquid crystal aligning agent and a polyamide represented by the general formula (2) as a resin component, wherein Ar in the general formula (2) is represented by the general formula (3). And R ₃ in the general formula (3) is —CH ₂ —
And a liquid crystal display device using these aligning agents.

[0008]

[Chemical 5]

[0009]

[Chemical 6]

[0010]

[Chemical 7]

The liquid crystal aligning agent of the present invention is also one in which an alignment film can be obtained only by volatilizing a solvent as in the case of using the soluble polyimide as a resin component, but the following points are greatly different. That is, the polyamide containing the 1,4-cyclohexanedicarboxylic acid structure contained in the liquid crystal aligning agent of the present invention has stronger intermolecular interaction than the soluble polyimide described in JP-A-61-205924. Therefore, the orientation state of the molecular chains can be strongly maintained even when fired at a low temperature. Therefore, the liquid crystal aligning agent of the present invention can obtain a sufficient pretilt angle even at a firing temperature of less than 150 ° C. and has good stability, and the orientation test of the liquid crystal is lowered by the accelerated test, or the pretilt angle is greatly changed. Problem does not occur. This property is particularly exhibited when Ar in the general formulas (1) and (2) is represented by the general formula (3), and further when R ₃ in the general formula (3) is represented by —CH ₂ —. Excel. The wholly aromatic polyamide (aramid) has a strong intermolecular interaction, but this action is too strong to dissolve at all in the solvent, or even if it dissolves, it is a good film as an alignment film such as pure N-methyl-2-pyrrolidone. Only solvents that are difficult to obtain can be used. By using the aligning agent of the present invention, it is possible to produce a liquid crystal display device having excellent displayability and excellent reliability without causing these problems.

Of the structures of the polyamides represented by the general formulas (1) and (2) in the liquid crystal aligning agent of the present invention, the alkyl groups of R ₁ and R ₂ give a pretilt angle. R
The carbon number of ₁ and R ₂ is 4 or more and 30 or less. When the carbon number is 3 or less, the effect of giving the pretilt angle cannot be clearly obtained, and when the carbon number exceeds 30, the alignment property of the liquid crystal is deteriorated. However, good display cannot be obtained.

The polyamide represented by the general formulas (1) and (2) in the liquid crystal aligning agent of the present invention is 1,4-cyclohexanedicarboxylic acid, an alkylcarboxylic acid having a structure of R ₁ and R ₂ , an aromatic compound. Diamine is dehydrated in polar solvent or 1,4-
It can be obtained by reacting cyclohexanedicarboxylic acid chloride, an alkylcarboxylic acid chloride having a structure of R ₁ and R ₂ , and an aromatic diamine in a polar solvent.

In the present invention, a component other than the above-mentioned essential components can be copolymerized as the dicarboxylic acid component within a range not impairing the performance. Examples of the dicarboxylic acid component to be copolymerized include 1,2-cyclohexanedicarboxylic acid and 1,3-
Cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, 4,4'-oxydibenzoic acid, 4,4'-sulfonyldibenzoic acid, 2,2-bis (4-carboxyphenyl) propane, 2,2-bis (4- Examples include, but are not limited to, carboxyphenyl) hexafluoropropane. When an acid chloride is used, examples of the dicarboxylic acid chloride to be copolymerized include dicarboxylic acid chlorides corresponding to the above dicarboxylic acids, but the invention is not limited thereto. Also, two or more kinds can be used simultaneously.

The aromatic diamine used as a raw material for the polyamide in the present invention includes 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenyl sulfone. 1,3- (4-aminophenoxy)
Benzene, 2,2-bis [4,4 '-(4-aminophenoxy)
Phenyl] propane, 2,2-bis [4,4 '-(4-aminophenoxy) phenyl] hexafluoropropane and the like, but not limited thereto. Furthermore, 2,2-bis (4,4 ′-(4-aminophenoxy) phenyl) 4,4′-diamino, which is a diamine in which Ar in the general formulas (1) and (2) is the general formula (3), Diphenyl ether, 4,4'-
Diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, 2,2-bis [4,4 '-(4-aminophenoxy) phenyl] propane, 2,2-bis [4,4'-(4-aminophenoxy) Phenyl] hexafluoropropane and the like are preferable, and R ₃ in the general formula (3) is represented by the general formula —CH ₂ —
Particularly preferred is 4,4'-diaminodiphenylmethane. Further, in the present invention, it is possible to use two or more kinds of diamines. In this case, 1,4-diaminocyclohexane, 1,3-bis (aminomethyl) cyclohexane, 4,4'-diaminodicyclohexylmethane,
Aliphatic diamines such as ethylenediamine, hexamethylenediamine, 1,7-diaminopentane, and 1,8-diaminooctane may be used in combination.

Preferred examples of the solvent component of the liquid crystal aligning agent of the present invention include a mixed solvent of N-methyl-2-pyrrolidone (NMP) and butyl cellosolve, a mixed solvent of NMP and ethyl carbitol, dimethylacetamide and butyl cellosolve. There are mixed solvents and the like, but not limited to these.

When a liquid crystal display device is manufactured using the liquid crystal aligning agent of the present invention, the liquid crystal aligning agent is applied onto a substrate with a transparent electrode by flexographic printing, spin coating, dipping, etc., and 110 ° C. to 250 ° C. Preferably 120 ° C
Rub after firing at ~ 150 ° C. A cell in which a sealant is printed is made to face the periphery of this substrate to assemble a cell in which a gap is held by a spacer, a liquid crystal is injected, the injection port is sealed, and a polarizing plate is attached to form a liquid crystal display element. The alignment film develops an alignment regulating force by rubbing after firing, but its ability may be reduced if treated at a temperature higher than the firing temperature after rubbing. Therefore, it is preferable that the highest temperature process is the alignment film baking process.

As the substrate with a transparent electrode used in the liquid crystal display device of the present invention, a substrate with a color filter having a lower heat resistance than the most general glass / ITO substrate or a plastic substrate having a lower heat resistance can be used. it can. Examples of preferable plastic substrates include:
Polyethylene terephthalate (abbreviated as PET), polyether sulfone (PES), polycarbonate (PC),
There are polyarylate and the like, but the invention is not limited thereto.

[0019]

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

(Example 1) 19,83 g of 4,4'-diaminodiphenylmethane in a four-neck separable flask equipped with a thermometer, a stirrer, a raw material inlet, and a dry nitrogen gas inlet tube
(0.100 mol), triphenyl phosphite 62.06 g
Is dissolved in a mixed solvent of 300 g of N-methyl-2-pyrrolidone (NMP) and 75 g of pyridine. Into this system, feed the raw material from the inlet 1,4-cyclohexanedicarboxylic acid 16.3
6 g (0.095 mol) and 15.0 g of lithium chloride were added, and stirring was continued for 5 hours while maintaining the system temperature at 100 ° C. Then, from the raw material charging port, 2.003 g of lauric acid (0.00
(010 mol) was added and stirring was continued for 10 hours while maintaining the system temperature at 100 ° C. The temperature of the system was lowered to room temperature, the obtained suspension was added dropwise to 10 liters of methanol, and the solid content was filtered off. This solid content was dissolved / reprecipitated 3 times with an NMP / methanol system and then dried under reduced pressure at 80 ° C. for 24 hours. A solid content of 5 g after drying was dissolved in 95 g of a 7/3 mixed solvent of NMP and butyl cellosolve to obtain a liquid crystal aligning agent.

The above liquid crystal aligning agent was printed on a polyether sulfone substrate having an ITO electrode having an area of 1 cm ² by using a flexographic printing machine and heated in a dryer at 120 ° C. for 2 hours to form an alignment film on the substrate. Formed. Rubbing these two substrates upside down and making them parallel to each other
The spacer was sandwiched in between and sealed with an epoxy resin, and liquid crystal (ZLI-2293 manufactured by Merck & Co., Inc.) was injected to prepare a liquid crystal cell. The pretilt angle measured by the crystal rotation method was 7 degrees. Further, the liquid crystal cell was left in a constant temperature bath at 100 ° C. for 1 week, and then the pretilt angle was measured in the same manner.

An STN having a cell gap of 7 μm and a twist of 240 degrees is formed by using a substrate having an alignment film formed in the same manner as described above.
A display element was produced. At this time, the curing of the sealant is 120
Performed at ° C. The liquid crystal was used by adding a chiral agent to the above liquid crystal. When the display properties of this liquid crystal display element were visually confirmed, no unevenness or defects were found and it was good. The liquid crystal display device was allowed to stand in a constant temperature bath at 100 ° C. for 1 week, and the display property was confirmed.

Example 2 18.84 g of 4,4'-diaminodiphenylmethane in a four-neck separable flask equipped with a thermometer, a stirrer, a raw material inlet, and a dry nitrogen gas inlet tube.
(0.095 mol), laurylamine 1.854 g (0.0
10 mol) and 16.2 g of triethylamine in NMP37
Dissolve in 5 g. The temperature of the system was lowered to 5 ° C, and 1,4-cyclohexanedicarboxylic acid chloride 2 was fed from the raw material inlet.
Charge 0.91 g (0.100 mol) and raise the system temperature to 5 ° C.
Stirring was continued for 3 hours while maintaining the temperature. The system temperature was returned to room temperature and the resulting suspension was filtered. The filtrate was added dropwise to 10 liters of methanol, and the solid content was filtered off. This solid content was dissolved / reprecipitated 3 times with an NMP / methanol system and then dried under reduced pressure at 80 ° C. for 24 hours. Solid content after drying 5g
Was dissolved in 95 g of a 7/3 mixed solvent of NMP and butyl cellosolve to obtain a liquid crystal aligning agent.

Using this liquid crystal aligning agent, a liquid crystal cell was prepared in the same manner as in Example 1 and the pretilt angle was measured to be 6 degrees. Further, the liquid crystal cell was left in a constant temperature bath at 100 ° C. for 1 week, and then the pretilt angle was measured in the same manner. Further, when a liquid crystal display element was produced in the same manner as in Example 1 and the display property was visually confirmed, no unevenness or defects were found and it was good. This liquid crystal display device
When the display property was confirmed after leaving it in a constant temperature bath at 0 ° C. for 1 week, unevenness and defects were not found and it was good.

(Examples 3 to 6) The same procedure as in Example 1 was repeated except that the starting dicarboxylic acids, diamines and alkylcarboxylic acids were changed as shown in Table 1.

[0026]

[Table 1]

COMPARATIVE EXAMPLE 1 17.45 g (0.08) of pyromellitic dianhydride was placed in a four-neck separable flask equipped with a thermometer, a stirrer, a raw material inlet, and a dry nitrogen gas inlet tube.
Mol) in 200 g of NMP. To this system, using a dropping funnel, 9.94 g (0.04 mol) of 1,2-bis (aminopropyl) tetramethyldisiloxane was added dropwise and allowed to react for 1 hour after the addition while keeping the system temperature at 20 ° C. It was Subsequently, 16.42 g (0.04 mol) of 2,2-bis (4- (4-aminophenoxy) phenyl) propane was added all at once, and stirring was continued for 5 hours while maintaining the temperature at 20 ° C. to obtain a silicone-modified polyamic acid solution. Got This silicone-modified polyamic acid solution was diluted with a 6: 4 mixed solvent of NMP and butyl cellosolve so that the resin concentration was 5% to obtain a liquid crystal aligning agent.

Using this liquid crystal aligning agent, a liquid crystal cell was prepared in the same manner as in Example 1, and the pretilt angle was measured to be 1 degree. When the display properties of the liquid crystal display element produced in the same manner as in Example 1 were confirmed, the orientation was poor and display unevenness was observed.

Comparative Example 2 1,2,3,4-cyclopentanetetracarboxylic dianhydride in a four-neck separable flask equipped with a thermometer, a stirrer, a raw material inlet, and a dry nitrogen gas inlet tube. 21.01 g (0.100 mol) of NMP250
g. Then, 2,2-bis (4- (4-aminophenoxy) phenyl) propane 39.00 g (0.095
(Mole) was added all at once, and stirring was continued for 3 hours while maintaining the temperature at 20 ° C., 1.854 g (0.010 mole) of laurylamine was added, and the stirring was further continued for 3 hours. To this system, 25 g of toluene was added, the dry nitrogen gas introduction pipe was removed, and a Dean Starch reflux cooling pipe was attached instead, to raise the temperature of the system. Continue heating while removing water generated by imidization from the system by azeotropic distillation with toluene.
Water no longer formed due to imidization at ~ 170 ° C 5
The reaction was terminated after a lapse of time. The obtained polyimide varnish was added dropwise to 30 liters of methanol with stirring for 1 hour to precipitate the polymer, and the solid content was collected by filtration, followed by drying in a dryer at 80 ° C. for 8 hours. Let 5 g of this soluble polyimide resin was dissolved in 95 g of γ-butyrolactone to obtain a liquid crystal aligning agent.

Using this liquid crystal aligning agent, a liquid crystal cell was prepared in the same manner as in Example 1, and the pretilt angle was measured to be 7 degrees. The display properties of the liquid crystal display device produced in the same manner as in Example 1 were confirmed, and it was good. When these were left for 1 week in a thermostat at 100 ° C., a disclination line was observed, the pretilt angle could not be measured, and the displayability was poor.

In each of Examples 1 to 6, the pretilt angle was 4 degrees or more, which was a sufficient value, and the displayability of the liquid crystal display element was good. Further, even after a high temperature storage test of 110 ° C./one week, the deterioration of the performance such as the decrease of the pretilt angle and the display property hardly occurred, which was good.

In Comparative Example 1, when a liquid crystal aligning agent containing a silicone-modified polyamic acid as a resin component was used, the orientation was poor and good displayability was not obtained.

In Comparative Example 2, when a liquid crystal aligning agent containing a soluble polyimide as a resin component was used, good performance was exhibited before the high temperature storage test, but alignment failure occurred after the high temperature storage test, and the pretilt angle was measured. It was not possible and the displayability was poor.

[0034]

INDUSTRIAL APPLICABILITY The liquid crystal aligning agent of the present invention can be processed at a low temperature of 120 ° C. to obtain a high pretilt angle, is excellent in its stability, and requires a low temperature process STN-LCD. And color active matrix LC
D, which is suitable for manufacturing an organic film substrate LCD. Furthermore, the liquid crystal display element using the present aligning agent is a liquid crystal display element that can be processed at low temperatures and has excellent display properties and electrical characteristics.

Claims (7)

[Claims] 1. A liquid crystal aligning agent containing a polyamide represented by the general formula (1) as a resin component. [Chemical 1] (In the formula, Ar represents a divalent aromatic group, and R ₁ and R _{2 each} have 4 carbon atoms.
Representing an alkyl group of 30 or more and 30 or less, R ₁ and R ₂ may be the same or different. ) 2. A liquid crystal aligning agent containing a polyamide represented by the general formula (2) as a resin component. [Chemical 2] (In the formula, Ar represents a divalent aromatic group, and R ₁ and R _{2 each} have 4 carbon atoms.
Representing an alkyl group of 30 or more and 30 or less, R ₁ and R ₂ may be the same or different. ) 3. The liquid crystal aligning agent according to claim 1, wherein Ar is represented by the general formula (3). [Chemical 3] 4. The liquid crystal aligning agent according to claim 2, wherein Ar is represented by the general formula (3). [Chemical 4] 5. The liquid crystal aligning agent according to claim _{3, wherein} R ₃ is represented by —CH ₂ —. 6. The liquid crystal aligning agent according to claim 4, wherein R ₃ is represented by —CH ₂ —. 7. A liquid crystal display device using the liquid crystal aligning agent according to claim 1.