JPH11264984A - Liquid crystal aligning agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent liquid alignment characteristic and electrical characteristic and to suppress the occurrence of display defects even if a firing temp. is low by using specific two kinds of polyimide precursors as indispensable components. SOLUTION: The liquid crystal aligning agent consisting of the polyimide precursor having the repeating unit expressed by formula I and the polyimide precursor having the repeating unit expressed by formula II as the indispensable components is used. In the formula I, X denotes a quadrivalent org. group; R denotes H or alkyl group; (n) denotes a number of 4 to 16. In the formula II, Y denotes a quadrivalent aliphat. group; Z denotes a bivalent arom. group; R denotes H or alkyl group. In such a case, the reaction solvents used at the time of synthesizing the polyimide precursor to be used include N-methyl-2- pyrrolidone, (NMP), N-N-dimethylformamide (DMAc), dimethylsulfoxide(DMSO), cresol, γ-butyrolactone or the like but are not limited thereto.

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.

[0002]

2. Description of the Related Art Conventionally, there has been known a method of using an organic polymer film such as a polyimide resin, a polyamide resin, and a polyamideimide resin as an alignment film of a liquid crystal display. Among them, particularly, polyimide resin has a function of aligning various liquid crystals and is excellent in heat resistance and the like, so that it is widely used industrially.

On the other hand, with the recent improvement in the characteristics of liquid crystal displays, the alignment film material is required to have more characteristics than before. Specifically, in terms of the function of the liquid crystal alignment film, good alignment properties are stably obtained under various conditions, and it has good electro-optical characteristics. Formability, rubbing resistance and the like can be mentioned. Furthermore, in recent years, it has been required that the above-mentioned characteristics equal to or higher than those of the related art can be obtained even at a firing temperature of less than 200 ° C. in order to cope with the lowering of the process.

Conventional liquid crystal aligning agents include aromatic polyamic acids, aliphatic polyamic acids, and aliphatic soluble polyimides. However, aromatic polyamic acid-based aligning agents generally have poor electric characteristics such as voltage holding ratio as a liquid crystal display. Aliphatic polyamic acid-based aligning agents have poor liquid crystal alignment properties, and aliphatic soluble polyimides have poor adhesion to substrates and have the problem that the coating film tends to peel off during rubbing. Furthermore, in the case of conventional alignment agents, when used for recently developed low threshold voltage nematic liquid crystal, ferroelectric liquid crystal, and antiferroelectric liquid crystal, if used for a long time, display defects such as display unevenness and afterimages will occur. There is a problem that occurs.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and even when the firing temperature is lower than 200 ° C.
An object of the present invention is to provide a liquid crystal aligning agent capable of producing a liquid crystal display exhibiting excellent liquid crystal alignment properties and electric characteristics and having less display defects than before.

[0006]

The present invention provides: A liquid crystal aligning agent comprising, as essential components, a polyimide precursor having a repeating unit represented by the general formula (1) and a polyimide precursor having a repeating unit represented by the general formula (2)

[0007]

Embedded image (In the formula, X represents a tetravalent organic group, R represents H or an alkyl group, and n represents a number of 4 or more and 16 or less.)

[0008]

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(Wherein, Y represents a tetravalent aliphatic group, Z represents a divalent aromatic group, and R represents H or an alkyl group); The polyimide precursor composition described above, wherein X in the general formula (1) is the formula (3) and / or the formula (4)

[0010]

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[0011] 2. The above liquid crystal aligning agent wherein Y in the general formula (2) has a structure selected from the formulas (5) to (10).

[0012]

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[0013] 3. Z in the general formula (2) is the above liquid crystal aligning agent having a structure selected from the formulas (11) to (14).

[0014]

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[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The polyimide precursor composition represented by the general formula (1) of the present invention is prepared by adding a tetracarboxylic dianhydride or a half-alkyl ester thereof to a general formula (15) in a polar organic solvent. By reacting the resulting diamine.

[0016]

Embedded image (In the formula, n represents a number of 4 or more and 16 or less.)

In the general formula (15), n is 4 or more and 16
When n is 4 or less, good orientation may not be obtained, and when n exceeds 16, it becomes difficult to obtain good orientation.

Examples of preferred tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3 ',
4,4'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'
-Benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4'
-Diphenylsulfonetetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride , 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo [2,2,2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 5- (2 , 5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 3,4-dicarboxy-1,2 , 3,4-tetrahydro-1-naphthalenesuccinic dianhydride and the like, but are not limited thereto. Also, two or more of these may be used simultaneously. Of these, the use of pyromellitic dianhydride and / or cyclobutanetetracarboxylic dianhydride is particularly favorable.

When R in the general formula (1) is an alkyl group, methanol, ethanol, 1-propanol, 2-
It can be obtained by reacting an alcohol such as propanol with a tetracarboxylic dianhydride to form a tetracarboxylic diester and then dehydrating and condensing with a diamine, or by dehydrating and condensing an alcohol and a polyamic acid.

The polyimide precursor of the present invention having the structure represented by the general formula (1) may use another diamine as a raw material as long as the effect of the structure represented by the general formula (1) is not impaired. Absent. For example, p-phenylenediamine, m-
Phenylenediamine, 2,5-diaminotoluene, 3,5-diaminotoluene, 2,5-diamino-p-xylene, 3,3'-dimethylbenzidine, 3,4'-diaminodiphenyl ether, 4,
4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 1,3-
(3-aminophenoxy) benzene, 1,3- (4-aminophenoxy) benzene, 1,4- (3-aminophenoxy) benzene,
1,4- (4-aminophenoxy) benzene, 4,4 '-(4-aminophenoxy) biphenyl, 2,2-bis [4,4'-(4-aminophenoxy) phenyl] propane, 2,2- Bis [4,4 '-(4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis
[4,4 '-(4-aminophenoxy) phenyl] sulfone, 1,3-
Bis (4-aminophenoxy) propane, 1,4-bis (4-aminophenoxy) butane, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diamino Hexane, 1,7-diaminoheptane, 1,
8-diaminooctane, 1,10-diaminodecane, 1,12-diaminododecane 1,4-diaminocyclohexane, 4,4′-diaminodicyclohexylmethane, 1,3-bis (3-aminopropyl) tetramethyldisiloxane, Examples include, but are not limited to, 1,4-bis (3-aminopropyldimethylsilyl) benzene.

The polyimide precursor having a structure represented by the general formula (2) of the present invention is obtained by reacting an aliphatic tetracarboxylic dianhydride or a half alkyl ester thereof with an aromatic diamine in a polar organic solvent. Obtainable. Formulas (1) to (4) as aliphatic tetracarboxylic dianhydrides
The structure represented by the formula (6) shows particularly excellent characteristics. Other examples of the aliphatic tetracarboxylic dianhydride that can be used include 2,3,5-tricarboxycyclopentylacetic dianhydride, 3,4-dicarboxy-1,2,3,4
-Tetrahydro-1-naphthalene succinic dianhydride and the like, but is not limited thereto.

Various aromatic diamines can be used as the diamine for obtaining the polyimide precursor having the structure represented by the general formula (2) of the present invention, and p-phenylenediamine, 3,3'-dimethylbenzidine Those using 3,3'-dimethoxybenzidine and 4,4'-diaminodiphenylmethane show particularly excellent properties. Examples of diamines other than these include 2,4-diaminotoluene, 2,5-diaminotoluene, 3,5-diaminotoluene, 2,5-diamino-p-xylene, 4,4′-diaminodiphenyl ether, 4 , 4'-Diaminodiphenyl sulfone, 1,4- (3-aminophenoxy) benzene, 1,4- (4-aminophenoxy) benzene, 4,4 '-(4-aminophenoxy) biphenyl, 2,2-bis [4,4 '-(4-aminophenoxy) phenyl] propane, 2,2-bis [4,4'-(4-aminophenoxy) phenyl] hexafluoropropane, 2,2-
Bis [4,4 '-(4-aminophenoxy) phenyl] sulfone,
1,3-bis (4-aminophenoxy) propane and the like. It is also possible to use two or more of these at the same time.

As a reaction solvent used in synthesizing the polyimide precursor used in the present invention, N-methyl-2-
Pyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMA
c), dimethyl sulfoxide (DMSO), cresol, γ-butyrolactone, and the like, but are not limited thereto.

In preparing the liquid crystal aligning agent, a polyimide precursor containing the structure represented by the general formula (1) and a polyimide containing the structure represented by the general formula (2) obtained by the method described above are used. The precursor is mixed at a predetermined ratio according to the required characteristics as a liquid crystal alignment film. At this time, from the viewpoint of liquid crystal alignment and electrical characteristics, a polyimide precursor having a structure represented by the general formula (2) is used. Preferably, the total amount of the polyimide precursor is 30% by weight or more and 95% by weight or less.

The concentration of the resin component is preferably 1% or more and 10% or less. Examples of the solvent component include the polar solvents listed as the reaction solvent, and butyl cellosolve, ethyl carbitol, propylene glycol mono-n-butyl ether and propylene. Mixed solvents such as glycol diacetate and propylene glycol mono-n-butyl ether acetate can be used.

Examples of the method for forming an alignment film using the liquid crystal alignment agent of the present invention include the following examples. First,
The liquid crystal aligning agent of the present invention is applied to the transparent electrode side of the substrate provided with the transparent electrode by a method such as flexographic printing or spin coating, and is baked at a temperature of 130 to 250 ° C. to form a coating film. Thereafter, an alignment treatment such as rubbing is performed, and if necessary, washing and drying are performed to form an alignment film.

[0027]

The present invention will be described in detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Synthesis Example 1 27.23 g of 1,4-bis (4-aminophenoxy) butane in a four-neck separable flask equipped with a thermometer, a stirrer, a raw material inlet, and a dry nitrogen gas inlet tube.
(0.10 mol) to 300 g of N-methyl-2-pyrrolidone (NMP)
Dissolve in. After charging 21.81 g (0.10 mol) of pyromellitic dianhydride from the raw material inlet, stirring was continued for 5 hours while stirring under nitrogen inflow while maintaining the system temperature at 10 ° C.
The temperature of the system was returned to room temperature to obtain a polyamic acid NMP solution. This solution was treated with NMP and butyl cellosolve to achieve a resin component concentration of 5% and a ratio of NMP to butyl cellosolve.
The mixture was diluted to 8: 2 to obtain a solution of the polyimide precursor (1).

Synthesis Example 2 19.61 g of cyclobutanetetracarboxylic dianhydride in a four-neck separable flask equipped with a thermometer, a stirrer, a dropping funnel, and a dry nitrogen gas inlet tube.
(0.10 mol) is dispersed in 300 g of NMP. In a dropping funnel, 100 g of NMP and 12.62 g (0.05 mol) of 1,4-bis (3-aminopropyldimethylsilyl) benzene are uniformly dissolved. The whole amount of the solution in the dropping funnel was dropped while stirring under nitrogen inflow while maintaining the temperature of the system at 10 ° C., and stirring was continued for 3 hours. Subsequently, the dropping funnel was removed, and the 1,6-bis (4-
Aminophenoxy) hexane (15.02 g, 0.05 mol) was added, and stirring was continued for 5 hours while maintaining the system temperature at 10 ° C. The temperature of the system was returned to room temperature to obtain a polyamic acid NMP solution. This solution was treated with NMP and butyl cellosolve to achieve a resin component concentration of 5% and a ratio of NMP to butyl cellosolve.
The mixture was diluted to 8: 2 to obtain a solution of the polyimide precursor (2).

Synthesis Example 3 19.61 g of cyclobutanetetracarboxylic dianhydride in a four-neck separable flask equipped with a thermometer, a stirrer, a dropping funnel and a dry nitrogen gas inlet tube.
(0.10 mol) and 6.41 g (0.20 mol) of methanol in NMP2
Dissolve in 00g. 15.82 g of pyridine from the dropping funnel
(0.20 mol) was added dropwise, and the reaction was allowed to proceed at 25 ° C. for 16 hours. 41.27 g of dicyclohexylcarbodiimide in another dropping funnel
(0.20 mol) was dissolved in 100 g of NMP, and this was attached and dropped into the system. After the dropwise addition, 32.85 g (0.10 mol) of 1,8-bis (4-aminophenoxy) octane was added thereto, and stirring was continued at 25 ° C. for 5 hours. The obtained suspension was filtered to remove dicyclohexylcarbodiurea, thereby obtaining an NMP solution of polyamic acid methyl ester. This solution was diluted with NMP and butyl cellosolve such that the concentration of the resin component was 5% and the ratio of NMP to butyl cellosolve was 8: 2 to obtain a solution of the polyimide precursor (3).

Synthesis Example 4 Pyromellitic dianhydride 21.8
Synthesis Example 1 except that 1 g (0.10 mol) was changed to 29.42 g (0.10 mol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride
In the same manner as described above, a solution of the polyimide precursor (4) was obtained.

(Synthesis Example 5) In a four-neck separable flask equipped with a thermometer, a stirrer, a raw material charging port, and a nitrogen inlet tube, 20.02 g (0.10 mol) of 4,4'-diaminodiphenyl ether and 200 g of NMP were put, and dry nitrogen was added. The mixture was stirred while flowing. While maintaining the temperature of the system at 20 ° C., 30.03 g (0.10 mol) of 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride was charged from the raw material charging port, and 5 Stirring was continued for an hour. The temperature of the system is returned to room temperature,
An MP solution was obtained. This solution was diluted with NMP and butyl cellosolve such that the concentration of the resin component was 5% and the ratio of NMP to butyl cellosolve was 8: 2 to obtain a solution of the polyimide precursor (A).

Synthesis Example 6 20.02 g (0.10 mol) of 4,4'-diaminodiphenyl ether was added to 19.83 g (0.10 mol) of 4,4'-diaminodiphenylmethane and 3,4-dicarboxy-1,2,
3,4-tetrahydro-1-naphthalene succinic dianhydride 30.03
g (0.10 mol) butanetetracarboxylic dianhydride 19.81
Performed in the same manner as in Synthesis Example 5 except that g (0.10 mol) was used.
A solution of the polyimide precursor (B) was obtained.

(Synthesis Example 7) 20.02 g (0.10 mol) of 4,4'-diaminodiphenyl ether was added to 108.p-phenylenediamine.
To 14 g (0.10 mol), 30.03 g (0.10 mol) of 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride was added to 5- (2,5-dioxotetrahydrofuryl) ) -3-Methyl-
26.42 g of 3-cyclohexene-1,2-dicarboxylic anhydride (0.1
0 mol) to obtain a solution of the polyimide precursor (C).

Synthesis Example 8 Same as Synthesis Example 3 except that 32.85 g (0.10 mol) of 1,8-bis (4-aminophenoxy) octane was changed to 21.23 g (0.10 mol) of 3,3′-dimethylbenzidine. To obtain a solution of the polyimide precursor (D).

Synthesis Example 9 20.02 g (0.1 mol) of 4,4'-diaminodiphenyl ether was added to 3,3'-dimethoxybenzidine
To 24.43 g (0.10 mol) was added 30.03 g (0.10 g) of 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride.
0 mol) with 19.81 g of butanetetracarboxylic dianhydride (0.1
0 mol) to obtain a solution of the polyimide precursor (E).

Example 1 The solution of the polyimide precursor (1) obtained in Synthesis Example 1 and the solution of the polyimide precursor (A) obtained in Synthesis Example (4) were adjusted to have a weight ratio of 25:75. Mix,
The mixture was filtered through a PTFE membrane filter having a pore size of 0.5 μm to obtain a liquid crystal aligning agent. This liquid crystal aligning agent was applied to the transparent electrode surface of a glass substrate with a transparent electrode by a spinner and baked at 180 ° C. for 1 hour to form a coating film having a thickness of about 500 Å. Subsequently, the coating film surface was rubbed with a rubbing machine. When the coated surface after rubbing was observed with a microscope, no peeling was observed. The two substrates are bonded together with a gap of 5 μm, and the liquid crystal (Merck Z
LI-5081) was injected to produce a TN liquid crystal cell. Observation of the orientation of the liquid crystal with a polarizing microscope revealed that the orientation was uniform over the entire surface and did not change even after being left in a thermostat at 150 ° C. for 240 hours. When the voltage holding ratio was evaluated as an electrical characteristic of the cell, it was 99.4% before the heat treatment, and was 150%.
It was 98.8% even after treatment at 240 ° C for 240 hours.

(Examples 2 to 7) In the same manner as in Example 1 except that the polyimide precursor composition used was changed, observation of the coating surface after rubbing, orientation of the liquid crystal after standing at 150 ° C. for 240 hours, and The voltage holding ratio was evaluated, and the results shown in Table 1 were obtained.

[0039]

[Table 1]

Comparative Example 1 The polyimide precursor composition obtained in Synthesis Example 1 was filtered through a PTFE membrane filter having a pore size of 0.5 μm to obtain a liquid crystal aligning agent. This liquid crystal aligning agent was applied to the transparent electrode surface of a glass substrate with a transparent electrode by a spinner and baked at 180 ° C. for 1 hour to form a coating film having a thickness of about 500 Å. Subsequently, the coating film surface was rubbed with a rubbing machine. When the coated surface after rubbing was observed with a microscope, no peeling was observed. Two substrates were bonded together with a gap of 5 μm, and a liquid crystal (ZLI-5081 manufactured by Merck) was injected to produce a TN liquid crystal cell. Observation of the orientation of the liquid crystal with a polarizing microscope revealed that the orientation was uniform over the entire surface and did not change even after being treated at 150 ° C. for 240 hours. When the voltage holding ratio was evaluated as an electrical characteristic of the cell, it was 98.8% before the heat treatment, which was good, but decreased to 86.7% after the treatment at 150 ° C. for 240 hours.

Comparative Example 2 The polyimide precursor composition (A) obtained in Synthesis Example 4 was filtered through a PTFE membrane filter having a pore size of 0.5 μm to obtain a liquid crystal aligning agent. This liquid crystal aligning agent is applied to the transparent electrode surface of a glass substrate with a transparent electrode using a spinner, baked at 180 ° C. for 1 hour, and has a thickness of about 5
A coating of 00 Å was formed. Subsequently, the coating film surface was rubbed with a rubbing machine. When the coated surface after rubbing was observed with a microscope, no peeling was observed. Attach the two substrates with a gap of 5μm,
Liquid crystal (ZLI-5081 manufactured by Merck) was injected to prepare a TN liquid crystal cell. Observation of the orientation of the liquid crystal with a polarizing microscope revealed that the uniformity of the orientation of the liquid crystal was poor and that the contrast between light and dark was uneven.

Comparative Example 3 A 4-neck separable flask equipped with a thermometer, a stirrer, a raw material charging port and a nitrogen inlet tube was charged with 27.23 g (0.10 g) of 1,4-bis (4-aminophenoxy) butane.
Mol) and 150 g of NMP and stirred under flowing dry nitrogen. While maintaining the temperature of the system at 20 ° C,
30.03 g (0.1 mol) of 3-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride was added, and the mixture was stirred for 5 hours to continue the reaction. Subsequently, 60 g of toluene was added to the system, the dropping funnel was removed, and instead a Dean starch reflux condenser was attached to raise the temperature of the system. The toluene is refluxed to perform a dehydration / imidation reaction. When the generation of water is completed, the temperature of the system is returned to room temperature, and the solid content of the polyimide is recovered by dropping into 20 times the amount of methanol. Next, the solid content was dried with a vacuum dryer for 24 hours, and then dissolved in γ-butyrolactone so that the concentration of the resin component became 5%. This polyimide composition was filtered through a PTFE membrane filter having a pore size of 0.5 μm to obtain a liquid crystal aligning agent. This liquid crystal aligning agent is applied to the transparent electrode surface of a glass substrate with a transparent electrode using a spinner, baked at 180 ° C. for 1 hour, and has a thickness of about 5
A coating of 00 Å was formed. Subsequently, the coating film surface was rubbed with a rubbing machine. When the coating surface after rubbing was observed with a microscope, peeling due to rubbing was observed.

In Examples 1 to 7, good results were obtained.

In Comparative Example 1, only the polyimide precursor having the repeating unit represented by the general formula (1) was used.
The decrease in the voltage holding ratio due to high temperature storage was large and not good.

In Comparative Example 2, since only the polyimide precursor having the repeating unit represented by the general formula (2) was used, good liquid crystal orientation was not obtained.

In Comparative Example 3, a polyimide obtained by imidizing a polyimide precursor having a repeating unit represented by the general formula (1) in a solution was used as a liquid crystal aligning agent.
Peeling occurred during rubbing.

[0047]

The liquid crystal alignment agent of the present invention can provide a liquid crystal alignment film having good characteristics even at a low processing temperature, and is suitably used for various liquid crystal displays.

Claims (4)

[Claims] 1. A liquid crystal aligning agent comprising, as essential components, a polyimide precursor having a repeating unit represented by the general formula (1) and a polyimide precursor having a repeating unit represented by the general formula (2). Embedded image (In the formula, X represents a tetravalent organic group, R represents H or an alkyl group, and n represents a number of 4 or more and 16 or less.) (Wherein, Y represents a tetravalent aliphatic group, Z represents a divalent aromatic group, and R represents H or an alkyl group.) 2. In the general formula (1), X represents the formula (3) and / or
Or the liquid crystal aligning agent according to claim 1, which is represented by formula (4). Embedded image Embedded image 3. In the general formula (2), Y is represented by the formulas (5) to (1).
3. The liquid crystal aligning agent according to claim 1, which has a structure selected from 0). Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image 4. Z in the general formula (2) is represented by the formulas (11) to (1).
4. The liquid crystal aligning agent according to claim 1, wherein the liquid crystal aligning agent has a structure selected from 4). Embedded image Embedded image Embedded image Embedded image