JP2000284293A - Liquid crystal alignment agent and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal alignment agent which exhibits a stable alignment property irrespectively of processes and use environment. SOLUTION: This liquid crystal alignment agent contains two kinds of resins whose surface tensions of resin coating films formed by casting the resin solution dissolved in a solvent system being a homogeneous solution at <=10% resin concentration on a solid substrate and subsequently reducing the solvent concentration to <=10% by pressure decrease or heating are different by >=2 dyne/cm different from each other. These two kinds of resins are optionally polyamide acid and polyimide respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a liquid crystal aligning agent. More specifically, the present invention relates to a liquid crystal aligning agent which can be suitably used for providing a liquid crystal alignment film of a TN type, STN type or ferroelectric liquid crystal type liquid crystal display device, and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art Conventionally, there has been known a method of using an organic polymer film such as polyvinyl alcohol, polyamide resin, polyamideimide resin, or polyimide resin as an alignment film of a liquid crystal display. Among them, polyimide resin and polyamide resin are particularly widely used as liquid crystal alignment films because they have a function of aligning various liquid crystals and have relatively excellent heat resistance and the like.

However, with the recent improvement in the characteristics of liquid crystal displays, it has been required that alignment layer materials have better characteristics than ever before. Specifically, in the properties of the liquid crystal alignment film, the liquid crystal alignment under various conditions, showing a stable pretilt angle, and having a good electro-optical characteristics, and that in the process, it is uniform There are coating film forming properties, good adhesion to substrates, rubbing resistance, baking at low temperatures, etc., but there is no liquid crystal alignment agent or alignment film that satisfies all of these properties, and there is no better liquid crystal. There is a need for an alignment film material.

[0004]

The present invention provides a stable liquid crystal alignment and a pretilt angle irrespective of the process conditions of a liquid crystal display element assembling and the use environment, and provides a good electric power, as compared with the conventional liquid crystal alignment film material. An object of the present invention is to provide a liquid crystal aligning agent for providing a liquid crystal alignment film having optical characteristics and a liquid crystal display device using the same.

[0005]

SUMMARY OF THE INVENTION According to the present invention, the resin concentration is reduced.
After casting a resin solution dissolved in a solvent system that becomes a homogeneous solution at 10% or less on a solid substrate, the surface tension of a resin film formed by reducing the pressure or heating to a solvent concentration of 10% or less differs by 2 dyne / cm or more. A liquid crystal alignment agent characterized by containing two kinds of resins and a liquid crystal display device using the same.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a resin concentration of 10
%, A resin solution dissolved in a solvent system that becomes a homogeneous solution is cast on a solid substrate, and then the surface tension of the resin film formed by reducing the pressure or heating to a solvent concentration of 10% or less differs by 2 dyne / cm or more. The two types of resins are not particularly limited, but the heat resistance of the resin as the alignment film,
Considering the compatibility and the like in the solution state, polyamic acid,
It is preferable to be selected from polyamide and polyimide.
Further, the resin contained in the liquid crystal alignment agent of the present invention is the above-mentioned 2)
It is sufficient that a seed is contained as an essential component, and it is possible to contain other than the two kinds, and the kind of the resin is not particularly limited.

[0007] The liquid crystal aligning agent of the present invention is characterized by the fact that it is difficult to express various characteristics required for a liquid crystal alignment film with a single resin, and the required characteristics are mutually controlled by a plurality of resins. It is intended to complement.

The liquid crystal alignment film is generally a thin film having a thickness of 0.1 μm or less, and comprehensively analyzes various interactions at the interface between the alignment film and the liquid crystal, characteristics of the inside of the film (bulk), characteristics of the interface between the alignment film and the substrate, and the like. This is called the so-called alignment film characteristic.
Among them, characteristics related to the orientation of liquid crystal (uniaxial orientation of liquid crystal, pretilt angle, etc.) mainly depend on the structure and properties of the surface of the alignment film. In addition to the interface between the alignment film and the liquid crystal, the electrical characteristics inside the film (bulk) and the electrical characteristics of the interface between the alignment film and the substrate greatly contribute.
At that time, an alignment film showing good alignment characteristics has poor electro-optical characteristics, and conversely, an alignment film having good electro-optical characteristics has poor liquid crystal alignment characteristics or only a low pretilt angle. Most do not give.

Therefore, we focused on the property that when a resin coating film was formed from a mixed solution of two or more components, components having relatively low surface tension tended to segregate spontaneously on the film surface. Of the various properties and functions required for, especially the properties related to liquid crystal alignment and electro-optical properties, the surface tension of the resin showing good liquid crystal alignment properties expresses good electrical properties By making it 2 dyne / cm or more smaller than the resin, a resin showing good liquid crystal alignment characteristics is formed on the surface of the alignment film, and the bulk is made of an alignment film having a structure mainly composed of a resin component exhibiting good electric characteristics. We have found that we have completed the present invention.

The method for preparing the liquid crystal aligning agent of the present invention is not particularly limited, and the above-mentioned two kinds of resins whose surface tension of the coating film differs by 2 dyne / cm or more, and other resins as required, are prescribed. To obtain a homogeneous solution. In this case, homogeneity means that the solution is not in a state where a precipitate is formed or suspended.

The liquid crystal alignment film obtained by using the liquid crystal alignment agent of the present invention can be applied to a liquid crystal display device by, for example, the following method. First, a liquid crystal aligning agent of the present invention is applied to a transparent conductive film side of a substrate such as glass or plastic provided with a transparent conductive film by a method such as a roll coater method, a spinner method, or a printing method, and is heated to 100 ° C. to 300 ° C. Baking at a temperature of 5 ° C. to form a coating film. Thereafter, a rubbing process is performed to form a liquid crystal alignment film. The substrate on which the liquid crystal alignment film is formed is bonded at a predetermined interval with the alignment film inside, and a liquid crystal is injected to obtain a liquid crystal display element.

[0012]

The present invention will now be described in detail with reference to Examples.
The present invention is not limited by these examples.

(Synthesis Example 1) 500 ml equipped with a thermometer, a stirrer, a raw material charging port, a reflux condenser, and a dry nitrogen gas inlet.
In a four-necked separable flask, 13.78 g of 1,4-cyclohexanedicarboxylic acid and 2,2-bis (4- (4-aminophenoxy)
(Phenyl) propane 32.84 g, triphenyl phosphite 49.6
5 g, 17.8 g of lithium chloride, 200 g of NMP, and 150 g of pyridine were added and reacted at 100 ° C. for 3 hours to obtain a viscous solution. After reprecipitating this solution in methanol, the polymer was isolated and reprecipitated in pure water three times to dry sufficiently.

(Synthesis Example 2) 1,4-cyclohexanedicarboxylic acid was used as the dicarboxylic acid under the same reaction conditions as in Synthesis Example 1.
A polyamide was synthesized using 13.78 g of diaminodiphenylmethane as a diamine raw material and 15.86 g of diaminodiphenylmethane.

(Synthesis Example 3) 1,4-cyclohexanedicarboxylic acid was used as the dicarboxylic acid under the same reaction conditions as in Synthesis Example 1.
A polyamide was synthesized using 13.78 g and 41.48 g of 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane as a diamine raw material.

(Synthesis Example 4) 1,4-cyclohexanedicarboxylic acid was used as the dicarboxylic acid under the same reaction conditions as in Synthesis Example 1.
A polyamide was synthesized using 13.78 g of the diamine and 16.2 g of 4,4′-diaminodiphenyl ether as the diamine raw material.

(Synthesis Example 5) Under the same reaction conditions as in Synthesis Example 1, a polyamide was synthesized using 9.45 g of succinic acid as a dicarboxylic acid and 15.86 g of diaminodiphenylmethane as a diamine raw material.

(Synthesis Example 6) Under the same reaction conditions as in Synthesis Example 1, 9.45 g of succinic acid was used as a dicarboxylic acid, and 32.84 g of 2,2-bis (4- (4-aminophenoxy) phenyl) propane was used as a diamine raw material. A polyamide was synthesized.

(Synthesis Example 7) Under the same reaction conditions as in Synthesis Example 1, a polyamide was synthesized using 11.69 g of adipic acid as a dicarboxylic acid and 15.86 g of diaminodiphenylmethane as a diamine raw material.

(Synthesis Example 8) Under the same reaction conditions as in Synthesis Example 1, 11.69 g of adipic acid was used as a dicarboxylic acid, and 32.84 g of 2,2-bis (4- (4-aminophenoxy) phenyl) propane was used as a diamine raw material. A polyamide was synthesized.

(Synthesis Example 9) 1,4-cyclohexanedicarboxylic acid was used as the dicarboxylic acid under the same reaction conditions as in Synthesis Example 1.
A polyamide was synthesized using 6.89 g, 6.64 g of terephthalic acid, and 15.86 g of diaminodiphenylmethane as a diamine raw material.

(Synthesis Example 10) 1,4-cyclohexanedicarboxylic acid was used as the dicarboxylic acid under the same reaction conditions as in Synthesis Example 1.
6.89 g and terephthalic acid 6.64 g, 2,2
A polyamide was synthesized using 41.48 g of 2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane.

(Synthesis Example 11) Under the same reaction conditions as in Synthesis Example 1, 4,4'-biphenyldicarboxylic acid as a dicarboxylic acid 19.
Polyamide was synthesized using 38 g and 41.48 g of 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane as a diamine raw material.

(Synthesis Example 12) Under the same reaction conditions as in Synthesis Example 1, 2,6-naphthalenedicarboxylic acid 17.3 was used as the dicarboxylic acid.
Polyamide was synthesized using 0 g and 41.48 g of 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane as a diamine raw material.

(Synthesis Example 13) 1,4-cyclohexanedicarboxylic acid 1 was used as the carboxylic acid under the same reaction conditions as in Synthesis Example 1.
3.78g, stearic acid 1.14g, 4,4 'as diamine raw material
A polyamide was synthesized using 16.26 g of -diaminodiphenylmethane.

(Synthesis Example 14) In a 500 ml four-neck separable flask equipped with a thermometer, a stirrer, a raw material charging port and a nitrogen gas inlet, 21.81 g of pyromellitic dianhydride, dehydrated NMP250
g and stirred under a stream of dry nitrogen. Reduce the temperature of the reaction system to 20.
9.94 g of bisaminopropyltetramethyldisiloxane was added while maintaining the temperature at + 2 ° C., and then a further 2,2-bis (4- (4-
Aminophenoxy) phenyl) propane (24.63 g) was added, and the mixture was stirred and reacted for 5 hours to obtain a pale yellow viscous solution.

(Synthesis Example 15) Pyromellitic dianhydride 21.81 was used as a raw material by the same apparatus and reaction method as in Synthesis Example 14.
g, bisaminopropyltetramethyldisiloxane 9.94
g, 12.4 g of 4,4'-diaminodiphenyl ether to obtain a pale yellow viscous solution.

(Synthesis Example 16) Pyromellitic dianhydride 21.81 was used as a raw material by the same apparatus and reaction method as in Synthesis Example 14.
g, bisaminopropyltetramethyldisiloxane 9.94
g, 31.11 g of 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane was used to obtain a pale yellow viscous solution.

(Synthesis Example 17) Pyromellitic dianhydride 21.81 was used as a raw material by the same apparatus and reaction method as in Synthesis Example 14.
g, bisaminopropyltetramethyldisiloxane 9.94
g, 11.90 g of diaminodiphenylmethane to obtain a pale yellow viscous solution.

(Synthesis Example 18) Butanetetracarboxylic dianhydride was used as a raw material by the same apparatus and reaction method as in Synthesis Example 14.
Using 11.89 g and 11.90 g of diaminodiphenylmethane, a pale yellow viscous solution was obtained.

(Synthesis Example 19) Butanetetracarboxylic dianhydride was used as a starting material by the same apparatus and reaction method as in Synthesis Example 14.
A pale yellow viscous solution was obtained using 11.89 g and diaminodiphenyl ether 12.01 g.

(Synthesis Example 20) Butanetetracarboxylic dianhydride was used as a raw material by the same apparatus and reaction method as in Synthesis Example 14.
11.89 g, 2,2-bis (4- (4-aminophenoxy) phenyl)
A pale yellow viscous solution was obtained using 24.63 g of propane.

(Synthesis Example 21) 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride was used as a starting material by the same apparatus and reaction method as in Synthesis Example 14. Using 15.85 g and 11.90 g of diaminodiphenylmethane, a light brown viscous solution was obtained.

(Synthesis Example 22) 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride was used as a starting material in the same apparatus and reaction method as in Synthesis Example 14. Using 15.85 g and 12.01 g of diaminodiphenyl ether, a light brown viscous solution was obtained.

(Synthesis Example 23) 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride was used as a starting material by the same apparatus and reaction method as in Synthesis Example 14. Using 15.85 g and 24.63 g of 2,2-bis (4- (4-aminophenoxy) phenyl) propane, a light brown viscous solution was obtained.

(Synthesis Example 24) In a 500 ml four-neck separable flask equipped with a thermometer, a stirrer, a raw material charging port and a nitrogen gas inlet, 11.90 g of diaminodiphenylmethane was placed, and NMP was added.
200 g was added and dissolved. To this, add 15.85 g of 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride and react at 20 ° C. for 6 hours to obtain a viscous polyamide. An acid solution was obtained. 20 g of toluene was added thereto, the internal temperature was raised to about 190 ° C. in an oil bath, and water generated along with imidization was removed from the system by a Dean-Stark trap. After refluxing for about 5 hours,
The system was cooled to room temperature, the obtained polyimide solution was reprecipitated in methanol, and the obtained resin was dried at 80 ° C. under reduced pressure to obtain a polyimide.

(Synthesis Example 25) 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride was used as a starting material by the same apparatus and reaction method as in Synthesis Example 24. Using 15.85 g and 12.01 g of diaminodiphenyl ether, a polyimide was obtained.

(Synthesis Example 26) 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride was used as a starting material by the same apparatus and reaction method as in Synthesis Example 24. Using 15.85 g and 6.49 g of p-phenylenediamine, a polyimide was obtained.

(Synthesis Example 27) 7.57 g of p-phenylenediamine was placed in a 500 ml four-neck separable flask equipped with a thermometer, a stirrer, a raw material charging port and a nitrogen gas inlet, and 200 g of NMP was prepared.
And dissolved. To this, add 15.85 g of 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride and react at 20 ° C. for 6 hours to obtain a viscous polyamide. An acid solution was obtained. 20 g of toluene was added thereto, the internal temperature was raised to about 190 ° C. in an oil bath, and water generated along with imidization was removed from the system by a Dean-Stark trap. After refluxing imidization for about 5 hours, the system was cooled to room temperature and further cooled with ice, and triethylamine (2.53 g) was added thereto, and stearic acid chloride (6.06 g) was added.
Was added dropwise to a 50 g solution of NMP. The obtained reaction solution was reprecipitated in methanol, and the obtained resin was dried at 80 ° C. under reduced pressure to obtain a terminal alkylamide polyimide.

(Measurement of Coating Surface Tension) The measurement of the surfaces of the resin coating films of Synthesis Examples 1 to 27 was performed as follows. Each was dissolved in NMP so as to have a resin content of about 6%, applied on a glass substrate by a spinner, and then baked at 180 ° C. for 1 hour to obtain a coating film. From the weight change before and after the firing, the solvent concentration was 5% or less in all the coating films. The surface tension of the coating film surface was measured by measuring the contact angle of water, ethylene glycol, and methylene iodide droplets on the coating film. Table 1 shows the results.

[0041]

[Table 1]

Example 1 The polyamide containing the aliphatic dicarboxylic acid obtained in Synthesis Example 1 as an essential component and the polyamide acid containing the aromatic tetracarboxylic acid obtained in Synthesis Example 14 as an essential component were separated into resin components. Was dissolved in NMP so as to have a weight ratio of 70 to 30 to prepare a total resin concentration of 6%, and then filtered through a membrane filter having a pore size of 0.5 micron 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 800 Å. Subsequently, the coating film surface was rubbed with a rubbing machine, the two substrates were bonded together with a gap of 5 μm, and a liquid crystal (ZLI-5081, manufactured by Merck) was injected to form a TN liquid crystal cell. When the orientation of the liquid crystal was evaluated using a microscope, the orientation was uniform over the entire surface, and the orientation of the liquid crystal was not disturbed at all even after treatment at 120 ° C. for 500 hours. The voltage holding ratio was evaluated as 99.1% as an electrical property of the cell, and was 98.5% even after being treated at 120 ° C. for 500 hours.
Further, the evaluation of the pretilt angle by the anti-parallel cell was 4.2 degrees, and the degree after the treatment at 120 ° C. for 50 hours was 5.1 degrees.

(Examples 2-38) An NMP solution was prepared in the same manner as in Example 1 by using two kinds of resins having different surface tensions of the coating film by 2 dyne / cm or more from the resins of Synthesis Examples 1 to 27 to prepare a liquid crystal cell. The evaluation was performed. Table 2 shows the results. or,
In each case, the pretilt angle was 3 degrees or more before and after the treatment at 120 ° C. for 500 hours.

[0044]

[Table 2]

The mixing ratio in the table is the weight ratio of a polyamide containing an aliphatic dicarboxylic acid as an essential component and a polyamide acid containing an aromatic tetracarboxylic dianhydride as an essential component. Also, after the heat treatment of the items of orientation and voltage holding ratio, it is after the treatment at 120 ° C./500 hours.

Comparative Example 1 A liquid crystal cell was prepared in the same manner as in Example 1 using only the polyamic acid containing the aliphatic dicarboxylic acid obtained in Synthesis Example 2 as an essential component. However, the pretilt angle was as low as 1.1 degrees.

Comparative Example 2 Using only the polyamic acid obtained in Synthesis Example 16, a liquid crystal cell was prepared and evaluated in the same manner as in Example 1. The liquid crystal orientation is good and the pretilt angle is
5.5 degree after 500 hours treatment at 120 ° C, but 1 of voltage holding ratio
The value after treatment at 20 ° C. for 5 hours was as low as 90.2%.

Comparative Example 3 A liquid crystal cell was prepared and evaluated in the same manner as in Example 1 using only the polyamic acid obtained in Synthesis Example 20, and disclination was observed in the orientation of the liquid crystal.

Comparative Example 4 A liquid crystal cell was prepared and evaluated in the same manner as in Example 1 using only the polyimide obtained in Synthesis Example 25. The orientation of the liquid crystal was good, but the pretilt angle was as low as 1.0 degree.

[0050]

The liquid crystal aligning agent of the present invention has excellent properties as a liquid crystal aligning film, and is therefore suitably used for various liquid crystal display devices.

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Claims (8)

[Claims] 1. A resin film formed by casting a resin solution dissolved in a solvent system that becomes a homogeneous solution when the resin component concentration is 10% or less on a solid substrate, and then reducing the pressure or heating to a solvent concentration of 10% or less. Has a surface tension of 2 dyne / c
A liquid crystal aligning agent characterized by containing two types of resins differing by at least m. 2. The liquid crystal aligning agent according to claim 1, wherein the two kinds of resins are polyamic acid and polyimide, respectively. 3. The liquid crystal aligning agent according to claim 1, wherein the two kinds of resins are polyamide and polyimide, respectively. 4. The liquid crystal aligning agent according to claim 1, wherein the two kinds of resins are polyamic acid and polyamide, respectively. 5. The liquid crystal aligning agent according to claim 1, wherein the two kinds of resins are both polyamic acids. 6. The liquid crystal aligning agent according to claim 1, wherein the two kinds of resins are both polyamides. 7. The liquid crystal aligning agent according to claim 1, wherein the two kinds of resins are both polyimide. 8. A liquid crystal display device using the liquid crystal alignment agent according to claim 1. Description: Detailed description