JP3197226B2 - Liquid crystal alignment agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal alignment agent used for manufacturing a liquid crystal display, and more particularly, to a liquid crystal alignment suitable for providing a liquid crystal alignment film for an STN type or active matrix TN type liquid crystal display. Agent.

[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 or a polyamide resin or 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 and a desired pretilt angle can be stably obtained under various conditions, and it has good electro-optical characteristics. In this case, uniform coating film forming properties, rubbing resistance and the like can be mentioned. In particular, in recent years, it has been demanded that the above-mentioned characteristics equal to or higher than those of the related art can be obtained even at a sintering temperature of less than 200 ° C. in order to cope with the lowering of the process temperature.

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 electrical characteristics such as voltage holding ratio and the like 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. As described above, currently used polyimide-based liquid crystal aligning agents are:
It cannot be said that various requirements are sufficiently satisfied, and a more excellent liquid crystal aligning agent is required.

On the other hand, we have disclosed in Japanese Patent Laid-Open No. 7-12076.
Patent Document 8 discloses a liquid crystal aligning agent containing a polyamic acid containing an aliphatic tetracarboxylic dianhydride as an essential component and a polyamic acid containing an aromatic tetracarboxylic dianhydride as an essential component. When the temperature is lower than 200 ° C., sufficient electrical characteristics may not be obtained.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and even when the firing temperature is lower than 200 ° C.
Shows excellent liquid crystal alignment, pretilt angle, and electrical characteristics.
An object of the present invention is to provide a liquid crystal aligning agent capable of producing a good liquid crystal display.

[0007]

The present invention provides: Polyamide acid obtained by reacting an aliphatic tetracarboxylic dianhydride with an aromatic diamine, an aromatic tetracarboxylic dianhydride, 1,4-bis (3-aminopropyldimethylsilyl) benzene and another diamine 1. A liquid crystal aligning agent containing a polyamic acid obtained by the reaction as an essential component. 2. The liquid crystal aligning agent according to item 1, wherein the aliphatic tetracarboxylic dianhydride has a structure selected from formulas (1) to (6).

[0008]

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[0009]

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[0010]

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[0011]

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[0012]

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[0013]

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3. 1,4-bis (3-aminopropyldimethylsilyl) used for polyamic acid obtained by reacting aromatic tetracarboxylic dianhydride with 1,4-bis (3-aminopropyldimethylsilyl) benzene and other diamines 2.) The liquid crystal alignment agent according to item 1, wherein the diamine other than benzene has a structure selected from formulas (7) to (12).

[0015]

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[0016]

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[0017]

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[0018]

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[0019]

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[0020]

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4. The aliphatic tetracarboxylic dianhydride used for the polyamic acid obtained by reacting the aliphatic tetracarboxylic dianhydride with the aromatic diamine has a structure selected from the formulas (1) to (6), Other than 1,4-bis (3-aminopropyldimethylsilyl) benzene used for polyamic acid obtained by reacting carboxylic dianhydride with 1,4-bis (3-aminopropyldimethylsilyl) benzene and other diamines 4. The liquid crystal aligning agent according to item 1, wherein the diamine has a structure selected from the formulas (7) to (12). 5. The liquid crystal aligning agent according to item 4, wherein the aromatic diamine to be reacted with the aliphatic tetracarboxylic dianhydride has a structure selected from the formulas (7) to (12). Among polyamic acids obtained by reacting aromatic tetracarboxylic dianhydride, 1,4-bis (3-aminopropyldimethylsilyl) benzene and other diamines, 1,4-bis (3-aminopropyldimethylsilyl) Benzene in an amount of from 30 mol% to less than 90 mol% and 1,4
Formula (11) and / or Formula (1) as a diamine other than -bis (3-aminopropyldimethylsilyl) benzene
Item 6. The liquid crystal aligning agent according to item 5, which contains the diamine represented by 2) in an amount of 10 mol% or more and less than 70 mol%.

The constituent materials of the polyamic acid obtained by reacting the aliphatic tetracarboxylic dianhydride and the aromatic diamine used in the present invention are not particularly limited. As the anhydride, those having the structures represented by the formulas (1) to (6) show particularly excellent properties.

Various aromatic diamines can be used as the diamine, and those having the structures represented by the formulas (7) to (12) show particularly excellent characteristics. Examples of diamines other than formulas (7) to (12) include 2,4-diaminotoluene, 2,5-diaminotoluene, 3,5-diaminotoluene, 2,5-diamino-p-xylene, o
-Tolidine, o-dianisidine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone, 1,4- (4-aminophenoxy) benzene,
4,4 '-(4-aminophenoxy) biphenyl and the like. Two or more of these can be used simultaneously.

Aromatic tetracarboxylic dianhydride can be used in combination as long as the function as a liquid crystal alignment film is not impaired. In this case, aromatic tetracarboxylic dianhydride is used in all tetracarboxylic dianhydrides. It is preferably at most 50 mol%.

The polyamic acid obtained by reacting an aromatic tetracarboxylic acid with a diamine in the present invention essentially uses 1,4-bis (3-aminopropyldimethylsilyl) benzene as a diamine component. It is more effective if 1,4-bis (3-aminopropyldimethylsilyl) benzene is at least 30 mol% based on all diamine components reacted with the aromatic tetracarboxylic acid.

As the diamine other than 1,4-bis (3-aminopropyldimethylsilyl) benzene, various aliphatic diamines and aromatic diamines can be used, and the structures represented by the formulas (7) to (12) can be used. Is particularly preferable, and among them, those having the structures represented by the formulas (11) and (12) are preferable, and the diamine represented by the formula (11) and / or More preferably, it is contained in an amount of at least 70 mol%. Equations (7) to (1)
Examples other than 2) include 2,4-diaminotoluene,
2,5-diaminotoluene, 3,5-diaminotoluene, 2,5-diamino-p-xylene, o-tolidine,
o-dianisidine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone, 1,4
-(4-aminophenoxy) benzene, 4,4 '-(4
-Aminophenoxy) biphenyl, ethylenediamine,
1,3-diaminopropane, 1,4-diaminobutane,
Examples include 1,5-diaminopentane, 1,6-diaminohexane, 1,8-diaminooctane, 1,4-diaminocyclohexane, and the like.

Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 3,3', 4
4'-benzophenonetetracarboxylic dianhydride and the like. Of these, it is particularly preferable to use pyromellitic dianhydride.

As a method for synthesizing a polyamic acid obtained by reacting an aliphatic tetracarboxylic dianhydride with an aromatic diamine used in the present invention and a polyamic acid obtained by reacting an aromatic tetracarboxylic acid with a diamine. Is not limited at all, but as a general synthesis method, N-methyl-2-pyrrolidone (NM
P), N, N-dimethylformamide (DMF), N,
A tetracarboxylic dianhydride is reacted with a diamine using a polar solvent such as N-dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), cresol, and γ-butyrolactone.

In preparing the liquid crystal aligning agent, a polyamic acid, an aromatic tetracarboxylic acid, and a diamine obtained by reacting the aliphatic tetracarboxylic dianhydride obtained by the above-described method with an aromatic diamine are used. The polyamic acid obtained by the reaction is mixed at a predetermined ratio according to the required characteristics of the liquid crystal alignment film. At this time, from the viewpoint of liquid crystal alignment and electrical characteristics, aliphatic tetracarboxylic dianhydride and aromatic The polyamic acid obtained by reacting the diamine is 30% by weight or more and 95% by weight of the total polyamic acid.
It is preferable to set the following.

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 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.

[0032]

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) 4,4'-Diaminodiphenylmethane (DDM) 1 was placed in a four-neck separable flask equipped with a thermometer, a stirrer, a raw material charging port, and a nitrogen inlet tube.
9.83 g (0.1 mol) and 150 g of N-methyl-2-pyrrolidone (NMP) were added and stirred while flowing dry nitrogen.
While maintaining the temperature of the system at 20 ° C, 3
4-dicarboxy-1,2,3,4-tetrahydro-1
30.03 g (0.1 mol) of naphthalene succinic dianhydride was added, and the mixture was stirred and reacted for 5 hours to obtain a pale yellow viscous liquid.

(Synthesis Example 2) In a four-neck separable flask equipped with a thermometer, a stirrer, a raw material charging port and a nitrogen inlet tube, 21.81 g (0.1 mol) of pyromellitic dianhydride and 250 g of NMP were put. The mixture was stirred while flowing dry nitrogen.
While maintaining the temperature of the system at 20 ° C., 18.52 g of 1,4-bis (3-aminopropyldimethylsilyl) benzene
(0.06 mol) was added followed by a further DDM 7.9.
3 g (0.04) mol was added, and the mixture was stirred and reacted for 5 hours to obtain a pale yellow viscous solution.

Example 1 A polyamic acid (abbreviated as R-PAA) obtained by reacting an aliphatic tetracarboxylic dianhydride and a diamine obtained in Synthesis Example 1 with an aromatic compound obtained in Synthesis Example 2 Polyamic acid (Si-Ar-) obtained by reacting aromatic tetracarboxylic dianhydride with 1,4-bis (3-aminopropyldimethylsilyl) benzene and other diamines
PAA) was added so that the weight ratio of the resin was 70:30, and NMP was added so that the total resin concentration was 6%.
The solution was filtered through a FE membrane filter 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 of about 600 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. When the orientation of the liquid crystal was observed with a polarizing microscope, it was uniform over the entire surface.
No change was observed even after treatment at 20 ° C. for 500 hours. When the voltage holding ratio was evaluated as an electrical characteristic of the cell, it was 99.2% before the heat treatment and 98.4% after the treatment at 120 ° C. for 500 hours.

(Example 2-9) Aliphatic acid dianhydride (a)
And R-PAA was synthesized in the same manner as in Synthesis Example 1 except that the diamine reacted with (a) was changed, and 1,4-bis () was reacted with aromatic dianhydrides (b) and (b). 3-Aminopropyldimethylsilyl) benzene (c) and other diamines (d), Si-Ar-PAA was synthesized in the same manner as in Synthesis Example 2 except that the ratio (mol%) of c in c + d was changed. , R-PAA and Si-Ar-PAA were mixed in the same manner as in Example 1 except that the weight ratio of the resin components was changed.
Observation of the coating film surface after rubbing, and evaluation of the orientation and voltage holding ratio of the liquid crystal before and after the treatment at 120 ° C. for 500 hours, the results shown in Table 1 were obtained.

[0037]

[Table 1]

The column of ASiB indicates the content (mol%) of 1,4-bis (3-aminopropyldimethylsilyl) benzene in all diamines in Si-Ar-PAA. The abbreviations in the table are as follows. THNDA: 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic dianhydride DDM: 4,4'-diaminodiphenylmethane ASiB: 1,4-bis (3-aminopropyldimethylsilyl ) Benzene BDA: butanetetracarboxylic dianhydride PMDA: pyromellitic dianhydride BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane BAPS: bis (4- (4-aminophenoxy) Phenyl)
Sulfone CBDA: cyclobutanetetracarboxylic dianhydride BPDA: biphenyltetracarboxylic dianhydride CHDA: 1,2,4,5-cyclohexanetetracarboxylic dianhydride PPD: p-phenylenediamine DDE: 4,4'-diamino Diphenyl ether BCODA: [2,2,2] bicyclooct-7-enetetracarboxylic dianhydride FMCHDA: 5- (2,5-dioxotetrahydro-3-furanyl) -3-methyl-3-cyclohexene-1, 2-
Dicarboxylic dianhydride DDMB: 4,4'-diamino-3,3'-dimethylbiphenyl DDMOB: 4,4'-diamino-3,3'-dimethoxybiphenyl HFBAPP: 2,2-bis [4- (4- Aminophenoxy)
Phenyl] hexafluoropropane *) Comparative Example 3 is a liquid crystal aligning agent which is a polyimide solution.

(Comparative Example 1) N-MP was added to the R-PAA obtained in Synthesis Example 1 so that the resin concentration became 6%, and the mixture was filtered through a PTFE membrane filter having a pore size of 0.5 μm to align the liquid crystal. 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 of about 600 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. 2
The 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 uniformity of the orientation of the liquid crystal was poor and that the contrast between light and dark was uneven.

(Comparative Example 2) Si-Ar- obtained in Synthesis Example 2
After NMP was added to PAA so that the total resin concentration was 6%, the solution 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 the glass substrate with a transparent electrode by a spinner, and baked at 180 ° C. for 1 hour,
An Angstrom coating 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 5 μm,
Liquid crystal (ZLI-5081 manufactured by Merck) was injected to prepare a TN liquid crystal cell. When the orientation of the liquid crystal was observed with a polarizing microscope, it was uniform over the entire surface.
There was no change even after treatment for 0 hours. When the voltage holding ratio was evaluated as an electrical characteristic of the cell, it was 98.9% before the heat treatment, which was good, but decreased to 87.4% after the treatment at 120 ° C. for 500 hours.

Comparative Example 3 In a four-neck separable flask equipped with a thermometer, a stirrer, a raw material charging port and a nitrogen inlet tube, 4,4′-diaminodiphenylmethane (DDM)
9.83 g (0.1 mol) and 150 g of N-methyl-2-pyrrolidone (NMP) were added and stirred while flowing dry nitrogen.
While maintaining the temperature of the system at 20 ° C, 3
4-dicarboxy-1,2,3,4-tetrahydro-1
30.03 g (0.1 mol) of naphthalene succinic dianhydride was added, and the mixture was stirred and reacted for 5 hours to obtain a pale yellow viscous liquid. 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 carry out 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. The solid content was dried with a vacuum drier for 24 hours, and then dissolved in γ-butyrolactone so that the concentration of the resin component became 5% 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 of about 600 Å.
Subsequently, the coating 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 12, good results were obtained. In Comparative Example 1, since only the polyamic acid obtained by reacting the aliphatic tetracarboxylic dianhydride with the aromatic diamine was used, good liquid crystal alignment was not obtained. In Comparative Example 2, since only the polyamic acid obtained by reacting the aromatic tetracarboxylic acid and the diamine,
The decrease in the voltage holding ratio due to high temperature storage was large and not good. In Comparative Example 3, when polyimide obtained by reacting aliphatic tetracarboxylic dianhydride with aromatic diamine and then performing imidization in a solution was used as a liquid crystal aligning agent, peeling occurred during rubbing. .

[0043]

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 (6)

(57) [Claims] 1. A polyamic acid obtained by reacting an aliphatic tetracarboxylic dianhydride with an aromatic diamine, an aromatic tetracarboxylic dianhydride and 1,4-bis (3-aminopropyldimethylsilyl) benzene And a liquid crystal aligning agent containing a polyamic acid obtained by reacting another diamine as an essential component. 2. The liquid crystal aligning agent according to claim 1, wherein the aliphatic tetracarboxylic dianhydride has a structure selected from the formulas (1) to (6). Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image 3. An aromatic tetracarboxylic dianhydride and 1,
Diamines other than 1,4-bis (3-aminopropyldimethylsilyl) benzene used for polyamic acid obtained by reacting 4-bis (3-aminopropyldimethylsilyl) benzene with other diamines are represented by formulas (7) to (7). (1
The liquid crystal aligning agent according to claim 1, which has a structure selected from 2). Embedded image Embedded image Embedded image Embedded image Embedded image Embedded image 4. An aliphatic tetracarboxylic dianhydride used for a polyamic acid obtained by reacting an aliphatic tetracarboxylic dianhydride with an aromatic diamine is represented by the formula (1) to the formula (6).
1,4-bis (used in polyamic acid obtained by reacting aromatic tetracarboxylic dianhydride, 1,4-bis (3-aminopropyldimethylsilyl) benzene and other diamines Diamines other than 3-aminopropyldimethylsilyl) benzene are represented by the formula (7)
The liquid crystal aligning agent according to claim 1, wherein the liquid crystal aligning agent has a structure selected from formulas (12) to (12). 5. The liquid crystal aligning agent according to claim 4, wherein the aromatic diamine reacted with the aliphatic tetracarboxylic dianhydride has a structure selected from the formulas (7) to (12). 6. An aromatic tetracarboxylic dianhydride and 1,
In a polyamic acid obtained by reacting 4-bis (3-aminopropyldimethylsilyl) benzene with another diamine, 1,4-bis (3-aminopropyldimethylsilyl) benzene is contained in an amount of 30 mol% or more and less than 90 mol%. The diamine other than 1,4-bis (3-aminopropyldimethylsilyl) benzene contains the diamine represented by the formula (11) and / or the formula (12) in an amount of 10 mol% or more and less than 70 mol%. Liquid crystal alignment agent.