JP2002317013A - Material for optical alignment film, the optical alignment film, and method for producing the film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a material for an optical alignment film, capable of giving the optical alignment film having good characteristics for a liquid crystal display device, such as high alignment stability and sufficient durability to the light and heat while keeping voltage retention, and to prepare the optical alignment film. SOLUTION: The material for the optical alignment film comprises a polymerizable monomer having at least one optical alignment group which exhibits an optical alignment function through a photo-dimerization reaction and at least two polymerizable maleimide groups in its molecule. The optical alignment film on which liquid crystal molecules can be aligned without rubbing is formed by using the material. A method for producing the film is carried out by using the material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical alignment film used for a liquid crystal display device, and more particularly, to an optical alignment film capable of aligning liquid crystal molecules by irradiating light without rubbing. The present invention relates to a forming material, a photo-alignment film made of the material, a method for manufacturing the same, and a liquid crystal display device using the photo-alignment film.

[0002]

2. Description of the Related Art In a liquid crystal display device, the state of the molecular arrangement of liquid crystal is changed by the action of an electric field or the like, and a change in optical characteristics accompanying the change is used for display. In many cases, the liquid crystal is used in a state of being sandwiched between two substrates, but here, in order to arrange the liquid crystal molecules in a specific direction,
An alignment process is performed inside the substrate.

Usually, the orientation treatment is performed by a method called rubbing, in which a polymer film such as polyimide is provided on a substrate such as glass, and the film is rubbed in one direction with a cloth or the like. As a result, the liquid crystal molecules in contact with the substrate are arranged so that their major axes (directors) are parallel to the rubbing direction. For example, in a twisted nematic (TN) cell, two substrates having an alignment film applied inside are opposed to each other between two orthogonal polarizing plates, and the rubbing directions thereof are arranged so as to be orthogonal to each other. Display by change is enabled.

However, although the rubbing method has an advantage that the manufacturing apparatus is simple, static electricity and dust are generated in the manufacturing process, so that a cleaning step is required after the alignment treatment, and especially a TFT which has been widely used in recent years.
In the liquid crystal cell of the system, the TFT element provided in advance on the substrate is destroyed by static electricity, and this also causes a reduction in the production yield. On the other hand, in the liquid crystal display device, since the inclination of the liquid crystal molecules included in the liquid crystal display device has directionality, the viewing angle dependency such as a change in display color or contrast depending on the direction in which the display device is viewed is a problem.

As one method of improving this, one pixel is divided, and the pretilt angle of liquid crystal molecules (JP-A-62-159119) and the alignment direction (JP-A-6-159119) are divided for each area.
An orientation division method has been devised which changes the above method. Such an orientation for each divided region is not suitable for practical use because the process is complicated in the conventional rubbing method.

In order to solve such a problem, attention has been paid to a liquid crystal alignment control technique which does not perform rubbing in recent years. Such rubbingless orientation techniques include oblique deposition,
An LB (Langmuir-Blodgett) film method, a photolithography method, a photo-alignment method and the like have been studied. In particular, a photo-alignment method for irradiating a coating film provided on a substrate with polarized light to generate liquid crystal alignment is simple, does not require a washing step after the alignment treatment, and further requires a photomask or the like. Since the above-mentioned orientation division can be easily performed by using the compound, research has been actively conducted. This photo-alignment method is based on photo-alignment groups that exhibit a photo-alignment function in organic molecules, for example, by photoisomerization of azo groups, etc., by photodimerization of cinnamoyl groups, coumarin groups, chalcone groups, etc., benzophenone groups, etc. And those resulting from photodecomposition of polyimide resin and the like.

As a photo-alignment film material utilizing photoisomerization, photodimerization or photocrosslinking, a polymer material is often used so that a uniform film can be obtained when applied to a substrate such as glass. In many cases, the photo-alignment group as described above is introduced into a side chain or a main chain of the polymer material. In some cases, a molecule having photo-alignment property is used as a guest molecule and dispersed in a host compound including a high molecular compound.

[0008] However, in the case of the photoisomerization type, cis-trans (cis-trans)
s) Since the isomerization is used, there is a problem in light stability after the photo-alignment treatment. Further, in the case of the photodecomposition type, since the liquid crystal may be contaminated by decomposition products generated when performing the photoalignment treatment, it is necessary to wash the substrate after the treatment,
Features such as unnecessary cleaning of the photo-alignment film are lost. In addition, many photo-alignment materials using a polymer material have a low solubility in a solvent, and there is a problem in that the types of solvents that can be used when applying to a substrate are limited.

For example, see WO9637807 (US Pat. No. 6,001,277, JP-A-8-32800).
No. 5) discloses a liquid crystal alignment film using a resin having a photoisomerizable and dichroic structural unit and a reactive functional group, but this material is a polymer compound. The types of solvents that can be used for coating the substrate are limited, and a high-boiling polar solvent such as N, N-dimethylacetamide or N-methyl-2-pyrrolidone is generally used. In this case, it takes a long time to volatilize the solvent after the application, and the productivity is reduced. In addition, this material
Since the ratio of the reactive functional groups in the resin is low, the crosslink density is low, and as a result, the heat resistance of the alignment film made of this material is not always sufficient.

As an example of a method for solving these problems and for stably obtaining the liquid crystal alignment ability of the photo-alignment film for a long period of time, a polymerizable polymer having a photo-alignment group having an alignment property by irradiation with polarized light is added. There is a method in which a monomer is thermally or photopolymerized and is photo-aligned by irradiation with polarized light. However, in many cases, thermal or photopolymerization of the monomer requires the addition of a polymerization initiator. Since this polymerization initiator is a low-molecular compound, even after curing of the photo-alignment film, after a long period of time, the polymerization initiator diffuses into the liquid crystal layer in the cell, and characteristics as a liquid crystal display element, for example, The voltage holding ratio may be degraded.

The unnecessary photopolymerizable group of the polymerization initiator includes:
There is a polymerizable maleimide group. A photo-alignment film using the compound having a polymerizable maleimide group is disclosed in JP-A-2000-537.
No. 66 (US Pat. No. 6,218,501) and Japanese Patent No. 2962473 (JP-A No. 11-2815, US Pat. No. 6,489,928). These photo-alignment films are obtained by adding a functional group that expresses photo-alignment as a side chain to the main chain of polymaleimide.However, these photo-alignment films still have long-term stability of heat resistance and liquid crystal alignment ability. Not enough.

[0012]

The problem to be solved by the present invention is to provide good liquid crystal display device characteristics, for example, a voltage holding ratio, a good alignment stability, and a sufficient durability against light and heat. Another object of the present invention is to provide a photo-alignment film for a liquid crystal display device having the same.

[0013]

According to the present invention, in order to solve the above-mentioned problems, at least one photo-alignment group capable of expressing a photo-alignment function by a photo-dimerization reaction in one molecule is provided.
Provided is a material for a photo-alignment film, comprising a polymerizable monomer having two polymerizable maleimide groups.

Further, in order to solve the above-mentioned problems, the present invention provides a polymer having at least one photo-alignment group exhibiting a photo-alignment function by a photodimerization reaction and at least two polymerizable maleimide groups in one molecule. A photo-alignment film comprising a polymer of a polymerizable monomer and having a photo-alignment function developed by photodimerization of the photo-alignable group and a cross-linked structure generated by polymerization of the polymerizable maleimide group. I do.

In order to solve the above-mentioned problems, the present invention provides a polymer having at least one photo-alignment group exhibiting a photo-alignment function by a photodimerization reaction and at least two polymerizable maleimide groups in one molecule. A polymerizable monomer is applied on a substrate, and the coating film is irradiated with light to cause a photodimerization reaction of the structural unit and a photopolymerization reaction of the polymerizable maleimide group to form a crosslinked polymer film. In addition, the present invention provides a method for producing a photo-alignment film, wherein the polymer film exhibits a photo-alignment function.

Further, in order to solve the above-mentioned problems, the present invention provides a polymer having at least one photo-alignment group exhibiting a photo-alignment function by a photodimerization reaction and at least two polymerizable maleimide groups in one molecule. A polymerizable monomer is coated on a substrate, and a thermal polymerization reaction of the polymerizable maleimide group is caused by heating the coating film to form a crosslinked polymer film, and the polymer film is irradiated with light. Thus, a photo-dimerization reaction of the structural unit is caused to cause the polymer film to exhibit a photo-alignment function.

In order to solve the above problems, the present invention provides a liquid crystal display device having a structure in which a liquid crystal is sandwiched between two substrates having an alignment film inside, wherein the alignment film has at least one molecule in one molecule. Consisting of a polymer of a polymerizable monomer having a photo-alignment group that exhibits a photo-alignment function by one photo-dimerization reaction and at least two polymerizable maleimide groups,
Provided is a liquid crystal display device, characterized by being a photo-alignment film having a photo-alignment function developed by photodimerization of the photo-alignable group and a crosslinked structure generated by polymerization of the polymerizable maleimide group.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In one molecule used in the material for a photo-alignment film of the present invention, at least one photo-dimerization group exhibiting a photo-alignment function by a photo-dimerization reaction and at least two polymerizable maleimide groups are contained. In the polymerizable monomer having a photo-alignment group that expresses a photo-alignment function by a photo-dimerization reaction, if it is a functional group that causes a photo-reaction such that the dimer orientation can be obtained by irradiating polarized light. Although it is not particularly limited, at least one double bond represented by C = C and C = O (excluding a double bond forming an aromatic ring)
A structural unit having the following formula is particularly preferably used.

The basic structure of a photo-alignment group that exhibits a photo-alignment function by the photo-dimerization reaction includes the following. Examples of the photo-alignment group that expresses a photo-alignment function by a photodimerization reaction having a C ＝ C bond include, for example,
Polyene group, stilbene group, stilbazole group, stilbazolium group, cinnamoyl group, hemithioindigo group,
Groups having a structure such as a chalcone group are exemplified. Examples of the photo-alignment group that exhibits a photo-alignment function by a photodimerization reaction having a C ＝ O bond include groups having a structure such as a benzophenone group and a coumarin group.

Specific examples include groups having the following structures. Of course, these structures may have a substituent such as an alkyl group, an alkoxy group, an aryl group, an allyloxy group, a cyano group, an alkoxycarbonyl group, a hydroxyl group, a sulfonic acid group, and a halogenated alkyl group.

[0021]

Embedded image

Specifically, a polymerizable monomer having at least one photo-alignment group capable of exhibiting a photo-alignment function by a photo-dimerization reaction and at least two polymerizable maleimide groups in one molecule is represented by the general formula: (1)

Embedded image The compounds represented by the following formulas are preferable, and among these, the general formula (2)

Embedded image The compound represented by is preferred.

In the general formulas (1) and (2), R
₁ represents at least one group selected from the group consisting of a linear or branched alkylene group having 1 to 30 carbon atoms, a cycloalkylene group having 3 to 12 carbon atoms, an arylalkylene group and a cycloalkylalkylene group. .

Specific examples of the organic group represented by R ₁ include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group,
Linear alkylene groups such as heptamethylene group, octamethylene group, nonamethylene group, decamethylene group, undecamethylene group, dodecamethylene group; 1-methylethylene group, 1-methyl-trimethylene group, 2-methyl-trimethylene group, 1-methyl-tetramethylene group, 2-methyl-tetramethylene group, 1-methyl-pentamethylene group,
An alkylene group having a branched alkyl group such as a 2-methyl-pentamethylene group, a 3-methylpentamethylene group or a neopentyl group;

Cycloalkylene groups such as cyclopentylene group and cyclohexylene group; main or side chains such as benzylene group, 2,2-diphenyl-trimethylene group, 1-phenyl-ethylene group and 1-phenyl-tetraethylene group And a cycloalkyl-alkylene group having a cycloalkyl group in a main chain or a side chain such as a cyclohexylmethylene group, a 1-cyclohexyl-ethylene group, or a 1-cyclohexyl-tetraethylene group. Among these, an alkylene group having 1 to 30 carbon atoms or a carbon atom having 3 to 1 carbon atoms
Two cycloalkylene groups are preferred.

R ₁ is a group of the above-mentioned groups.
Up to 5 may be groups linked by a single bond, an ester bond, an ether bond or a urethane bond.

Examples of such a linked group include, for example, a group composed of (poly) ether in which at least two alkylene groups are linked by an ether bond, and at least two alkylene groups linked by an ester bond. A group composed of a (poly) ester, a group composed of a (poly) urethane in which at least two alkylene groups are bonded by a urethane bond, and a (poly) ether in which at least two alkylene groups are bonded by an ether bond ( (Poly) carboxylic acid obtained by esterifying (poly) ol and (poly) carboxylic acid 酸 (poly) ether (poly)
Examples include groups composed of all diesters.

In the above general formulas (1) and (2), R
₂ represents the above-mentioned photo-alignment group which expresses a photo-alignment function by the above-mentioned photo-dimerization reaction.

Among the photo-alignment groups exhibiting a photo-alignment function by the photodimerization reaction described above, a photo-alignment material using a maleimide derivative having a photo-alignment group having a benzophenone structure and exhibiting a photo-alignment function is a photo-alignment material. It is particularly preferable because the amount of irradiation of polarized light necessary for exhibiting the function is small and the obtained photo-alignment film has excellent thermal stability and stability over time.

In the compounds represented by the general formulas (1) and (2), the photo-alignment group which exhibits a photo-alignment function by the photo-dimerization reaction represented by R ₂ comprises a group represented by R ₁ and a single bond , An ester bond or a urethane bond. The number of bonds of a photo-alignment group that expresses a photo-alignment function by a photodimerization reaction is the same as the number of polymerizable maleimide groups in one molecule, but the maleimide derivative used in the present invention includes a plurality of polymerizable maleimides. Since it has a group, the number is preferably in the range of 2 to 4. Among them, the polymerization of the polymerizable maleimide group easily proceeds to form a stable maleimide polymer, and the amount of light energy required to express the photo-alignment of the photo-alignment group that expresses the photo-alignment function is relatively large. Since the number is small, it is preferable that the number of bonds of the photo-alignment group that expresses the photo-alignment function by the photodimerization reaction is two.

In the above general formulas (1) and (2), R
₃ and R ₄ each independently represent a hydrogen atom, a carbon atom 1
And represents an alkyl group, a phenyl group or a halogen atom.

In the above general formula (1), n represents an integer from 2 to 4. Among them, the polymerization of the polymerizable maleimide group proceeds easily, a stable maleimide polymer is formed, and the amount of light energy required for expressing the photo-alignment function of the photo-alignment group is relatively small. Is particularly preferably a compound represented by the general formula (2).

In the photo-alignment material of the present invention, the introduction density of a photo-alignment group exhibiting a photo-alignment function by a photo-dimerization reaction is adjusted to improve the alignment state of the liquid crystal, or to improve the solubility in a solvent, A maleimide compound represented by the following general formula (3) may be appropriately mixed for the purpose of improving applicability to a substrate and the like. In order to obtain good sensitivity to irradiation light for photo-alignment, a maleimide derivative containing a photo-alignment group that exhibits a photo-alignment function by a photodimerization reaction represented by the general formula (2) and a general formula (3) )

[0034]

Embedded image

A maleimide derivative which does not contain a photo-alignment group which exhibits a photo-alignment function by a photo-dimerization reaction represented by the formula (1) may be copolymerized. The mixing ratio of the maleimide derivative that does not contain a photo-alignment group that exhibits a photo-alignment function by this photodimerization reaction is preferably in the range of 0 to 80% by weight, particularly preferably 0 to 50% by weight, based on the whole. Range.

In the above general formula (3), R ₇ is a linear alkylene group having 1 to 30 carbon atoms, a branched alkylene group having 1 to 30 carbon atoms, and 3 to 12 carbon atoms.
Represents at least one group selected from the group consisting of a cycloalkylene group, an arylalkylene group and a cycloalkylalkylene group. R ₅ and R ₆ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group or a halogen atom.

Specific examples of R ₇ in the general formula (3) include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, a nonamethylene group,
Linear alkylene groups such as decamethylene group, undecamethylene group and dodecamethylene group; 1-methylethylene group,
1-methyl-trimethylene group, 2-methyl-trimethylene group, 1-methyl-tetramethylene group, 2-methyl-tetramethylene group, 1-methyl-pentamethylene group, 2-
An alkylene group having a branched alkyl group such as a methyl-pentamethylene group, a 3-methylpentamethylene group or a neopentyl group;

Cycloalkylene groups such as cyclopentylene and cyclohexylene; main or side chains such as benzylene, 2,2-diphenyl-trimethylene, 1-phenyl-ethylene and 1-phenyl-tetraethylene; And a cycloalkyl-alkylene group having a cycloalkyl group in a main chain or a side chain such as a cyclohexylmethylene group, a 1-cyclohexyl-ethylene group, or a 1-cyclohexyl-tetraethylene group.

In the general formula (3), R ₇ represents a group consisting of a single bond, an ester bond,
It may be a group linked by an ether bond or a urethane bond.

Examples of such a linked group include a group composed of a (poly) ether in which at least two alkylene groups are linked by an ether bond, and a group in which at least two alkylene groups are linked by an ester bond. A group composed of a (poly) ester, a group composed of a (poly) urethane bonded by a (poly) urethane bond in which at least two alkylene groups are bonded by a urethane bond, and at least two alkylene groups bonded by an ether bond (Poly) ether (poly) ol and (poly) linked by
And a group composed of (poly) carboxylic acid {(poly) ether (poly) ol} ester obtained by esterifying carboxylic acid.

Next, using the material for a photo-alignment film of the present invention,
An example of a method for manufacturing a photo-alignment film and a liquid crystal display device having the same will be described.

First, the photo-alignment material of the present invention is used after being dissolved in a suitable solvent. At this time, the solvent is not particularly limited,
N-methylpyrrolidone, dimethylformamide, butyl cellosolve, γ-butyrolactone, chlorobenzene, dimethylsulfoxide, dimethylacetamide, tetrahydrofuran and the like are generally used. Among them, butyl cellosolve and γ-butyrolactone are particularly preferable because they have good coatability and can provide a uniform film. These solvents can be used as a mixture of two or more types in consideration of applicability and volatilization of the solvent in a short time after application.

The solution of the photo-alignment material is applied on a substrate by a method such as spin coating or printing, and after drying, polymerization of a polymerizable maleimide group and photo-alignment operation are performed.

The substrate used in the present invention is a substrate usually used for a photo-alignment film and has heat resistance enough to withstand thermosetting. Such a substrate includes a glass substrate.

The polymerization operation of the polymerizable maleimide group by light or heat is more preferably performed prior to the alignment operation, because the photodimerization reaction may affect the structural units mixed with light.

The polymerization of the polymerizable maleimide group is performed by irradiation with light such as ultraviolet rays or heating. When using light irradiation,
It is preferable to use light having a wavelength at which the photo-alignment group does not exhibit the photo-alignment function. On the other hand, it is more preferable that the polymerization by heating is performed before the photo-alignment operation, because it can also serve as drying of the solvent used for application to the substrate. Further, in order to completely polymerize the polymerizable maleimide group, first, polymerization is performed by light irradiation or heating, and then an operation of expressing photo-alignment by light irradiation is performed. Irradiation of non-polarized light suitable for polymerization may be performed.

On the other hand, when the wavelength of the light at which the polymerizable maleimide group is polymerized is close to the wavelength of the light at which the photo-alignment function is developed, the operation of polymerizing the polymerizable maleimide group and developing the photo-alignment function is performed once. It can be performed simultaneously by light irradiation.
Irradiation light used for photopolymerization of such a polymerizable maleimide group is not particularly limited, but ultraviolet light can be preferably used. The irradiation method is not particularly limited, and non-polarized light or polarized light such as linearly polarized light or elliptically polarized light can be used.

The operation of developing photo-alignment by the photodimerization reaction is performed by irradiating polarized light. The wavelength of the polarized light is selected to be a wavelength at which the photo-alignment group efficiently dimerizes, and includes visible light, ultraviolet light, and the like, with ultraviolet light being preferred. As the polarized light, linearly polarized light or elliptically polarized light is often used. At this time, in order to obtain the pretilt of the liquid crystal molecules,
A method of irradiating the substrate with polarized light in an oblique direction or a method of irradiating unpolarized light in an oblique direction after irradiating polarized light may be used.

According to the present invention, a material for a photo-alignment film containing a photo-alignable group exhibiting a photo-alignment function by a photo-dimerization reaction in one molecule and a polymerizable monomer having a plurality of polymerizable maleimide groups. Is applied to the substrate, the polymerizable maleimide group is polymerized, and a photo-dimerization reaction of the photo-alignment group exhibiting a photo-alignment function is caused to obtain a photo-alignment film.
Since the maleimide compound used in the present invention is a low-molecular compound, it has high solvent solubility and is easy to apply. Further, according to the present invention, a photo-alignment film having high stability to light and heat because a cross-linked structure is formed by polymerization of a polymerizable maleimide group and photo-alignment is realized by a photo-dimerization reaction of the photo-alignable group. Is obtained.

Further, since the polymerization by the maleimide group does not require a polymerization initiator, the polymerization initiator does not elute into the liquid crystal after the liquid crystal cell is manufactured, and the voltage holding ratio is lowered.
The cause of the performance degradation of the liquid crystal display element can be eliminated.

[0051]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Synthesis Examples, Examples and Comparative Examples, but the present invention is not limited to the scope of these Examples.

[Synthesis Example 1] Synthesis of a maleimide-based photo-alignment film material having a benzophenone structure a. Synthesis of Maleimide Acetic Acid In a 500 ml four-necked flask equipped with a stirrer, thermometer, dropping funnel, Dean-Stark fractionator and condenser, 140 g of toluene, 5.2 g of p-toluenesulfonic acid monohydrate and After 2.8 g of triethylamine was sequentially charged, 30 g of maleic anhydride was added with stirring, and then dissolved while heating to 30 ° C. After further adding 23 g of glycine, the mixture was reacted at 70 ° C. for 3 hours with stirring. 50 g of toluene and 60 g of triethylamine were added, and the mixture was reacted for 1 hour while heating and refluxing the solvent to remove generated water. The residue obtained by evaporating the solvent from the reaction mixture was adjusted to pH 2 by adding hydrochloric acid of 4 mol / dm ³ and then heated and recrystallized to obtain 7.3 g of a pale yellow solid of maleimide acetic acid. Was.

B. Synthesis of 4,4'-bis (2-hydroxyethoxy) benzophenone Capacity 3 with stirrer, thermometer, dropping funnel and condenser
62.5 g of 2-bromoethanol was placed in a 00 ml four-necked flask, and 100 g of N-methylpyrrolidone was added thereto while stirring under cooling with an ice bath. This is p-
Toluenesulfonic acid monohydrate (10 mg) was added, and dihydropyran (42.1 g) was added dropwise over about 10 minutes. 2 under ice cooling
After stirring for an additional 2 hours at room temperature,
-42.8 g of dihydroxybenzophenone and 69.1 g of potassium carbonate were added and reacted at 120 ° C for 3 hours.
After cooling, the reaction mixture was added to 400 ml of water, extracted twice with 400 ml of toluene, the obtained toluene layer was dried over anhydrous sodium sulfate, and the solvent was distilled off with an evaporator.
450 g of methanol, 70 g of water and 1.0 g of concentrated hydrochloric acid were added to the obtained residue, and the mixture was stirred at room temperature overnight. The resulting precipitate was filtered, washed well with methanol, and dried.
52 g of 4'-bis (2-hydroxyethoxy) benzophenone was obtained.

C. Synthesis of Maleimide Photoalignment Film Material In a 500 ml three-necked flask equipped with a stirrer, a thermometer, a Dean-Stark fractionator, and a condenser, 8.8 g of the maleimide acetic acid obtained in a of Synthesis Example 1 was added. 6.1 g of 4,4'-bis (2-hydroxyethoxy) benzophenone obtained in b of Synthesis Example 1, 0.4 g of p-toluenesulfonic acid monohydrate, 20 mg of hydroquinone and 150 ml of toluene
Were sequentially heated, and the mixture was heated at 90 ° C. under reduced pressure to react for 15 hours while refluxing the solvent to remove generated water.
After completion of the reaction, the reaction mixture was filtered while hot, and the obtained solid was thoroughly washed with methanol and dried to obtain the compound of the formula (4).

[0055]

Embedded image The material for a bifunctional maleimide-based photo-alignment film represented by the formula 8.6
g was obtained.

¹ H-NMR (300 MHz, (CD ₃ )
₂ SO) δ = 4.37-4.50 (m, 12H), 7.03-
7.15 (m, 8H), 7.65 to 7.76 (d, 4
H)

[Synthesis Example 2] Synthesis of a maleimide derivative having no benzophenone structure In a 500 ml three-necked flask equipped with a stirrer, a thermometer, a Dean-Stark fractionator and a condenser, 8.8 g of the obtained maleimide acetic acid, 5.0 g of polypropylene glycol having a number average molecular weight of 400, 0.4 g of p-toluenesulfonic acid monohydrate, hydroquinone 20
mg and 150 ml of toluene were successively charged, and the pressure was reduced to 90 ° C.
The mixture was reacted for 15 hours while the solvent was refluxed to remove generated water. After completion of the reaction, the reaction mixture was washed twice with dilute sodium hydroxide solution and then three times with pure water,
Toluene is distilled off and the formula (5)

[0058]

Embedded image 7.7 g of a bifunctional maleimide derivative represented by the following formula was obtained.

Synthesis Example 3 Synthesis of Maleimide Derivative Having Cinnamoyl Group a. Synthesis of 4- (2-hydroxyethoxy) cinnamic acid-2-hydroxyethyl ester Sodium hydroxide was added to a 500 ml autoclave.
80 g of 0.0 g (1.0 mol) of ethanol and 100 of water
Then, 4-hydroxycinnamic acid was added.
1 g (0.5 mol) was added and dissolved. While cooling with ice, 132.2 g (3.0 mol) of oxirane was added thereto, and the mixture was sealed and reacted at 80 ° C. for 6 hours. The mixture was diluted with 200 ml of water and extracted twice with 100 ml of ethyl acetate. After the extract was purified by silica gel chromatography, ethyl acetate was distilled off under reduced pressure, dried and recrystallized from butanol.
(2-hydroxyethoxy) cinnamic acid-2
90.8 g (72%) of hydroxyethyl ester were obtained.

B. Synthesis of Maleimide Derivative Having Cinnamoyl Group In a 500 ml three-necked flask equipped with a stirrer, thermometer, Dean-Stark fractionator, and a condenser, 8.8 g of the maleimide acetic acid obtained in a of Synthesis Example 1 was synthesized. Example 3a
5.1 g of 4- (2-hydroxyethoxy) cinnamic acid-2-hydroxyethyl ester obtained in
0.4 g of toluenesulfonic acid monohydrate, hydroquinone 2
0 mg and 150 ml of toluene were sequentially charged, and 90
The reaction was carried out for 15 hours while heating to 0 ° C. and refluxing the solvent to remove generated water. After completion of the reaction, the reaction mixture was filtered while hot, and the obtained solid was thoroughly washed with methanol and dried to obtain the compound of the formula (6).

[0061]

Embedded image 7.8 g of a bifunctional maleimide derivative represented by the following formula was obtained.

1H-NMR (300 MHz, (CD3)
2SO) [delta] = 3.75-4.47 (m, 12H), 6.84-
7.15 (m, 8H), 7.63 to 8.18 (m, 6
H)

[Comparative Synthesis Example 1] Synthesis of bifunctional acrylate having benzophenone structure c. In the synthesis of a maleimide derivative, acrylic acid is used in place of maleimide acetic acid to obtain a compound of formula (7)

[0064]

Embedded image The bifunctional acrylate represented by was obtained.

[Comparative Synthesis Example 2] Synthesis of material for photo-alignment film having polymaleimide in the main chain and parafluorobenzoylcinnamoyl group in the side chain a. Synthesis of polyhydroxyphenylmaleimide In a three-necked round bottom flask filled with nitrogen, Polyscience Co., USA, USA
A. 5 g of maleic anhydride polymer and 3 g of aminophenol in 100 ml of xylene were stirred at room temperature for 30 minutes, 2.9 g of isoquinoline was further added, the temperature was gradually raised to 150 ° C., and the mixture was formed during the reaction. The reaction was continued for about 3 hours while continuously removing water. After confirming that water was no longer generated, the reaction was terminated, the temperature was lowered to room temperature, and the product was poured into 500 ml of methanol to precipitate the product.
After vacuum filtration, vacuum drying was performed at 100 ° C. to obtain polyhydroxyphenylmaleimide.

B. Synthesis of parafluorobenzoylcinnamoyl chloride 16.42 g (0.1 mol) of parahydroxycinnamic acid and 8 g of sodium hydroxide were dissolved in 100 ml of water and 100 ml of dimethyl sulfoxide (DMSO), and the mixture was stirred vigorously at 0 ° C. Fluorobenzoyl chloride 15.8
6 g (0.1 mol) was gradually added dropwise. After reacting at room temperature for about 2 hours, the mixture was neutralized to pH = 6-7 with dilute hydrochloric acid. The resulting solid intermediate was filtered and washed thoroughly with water. After being completely dried under vacuum, it was recrystallized in ethanol to give parafluorobenzoyloxycinnamic acid in a yield of 90%.
I got it. This was added with 1.2 equivalents of thionyl chloride and about 50 ml of methylene chloride, and reacted at room temperature until a clear solution was obtained. After the reaction, the solvent and thionyl chloride were removed under vacuum and dried completely to obtain parafluorobenzoylcinnamoyl chloride.

C. Synthesis of Photoalignment Film Material Having Polymaleimide in Main Chain and Parafluorobenzoylcinnamoyl Group in Side Chain a. 1.7 g of the polyhydroxyphenylmaleimide obtained in (1) above was added to N-methylpyrrolidone (NMP).
After dissolving in 50 ml, 1.0 g of triethylamine was added and stirred for 30 minutes. The reaction temperature was lowered to 5 ° C. and the mixture was stirred vigorously to obtain b. 2.13 g of parafluorobenzoylcinnamoyl chloride obtained in the above was slowly added dropwise. After dropping all of parafluorobenzoylcinnamoyl chloride, the mixture was continuously stirred for about one hour to complete the reaction. The reaction solution was poured into a beaker containing 200 ml of water and methanol to precipitate the product, followed by thorough washing with excess water and methanol, followed by filtration under reduced pressure and vacuum drying to finally give the main product. A material for a photo-alignment film having a polymaleimide in the chain and a parafluorobenzoylcinnamoyl group in the side chain was obtained.

A photo-alignment film was prepared using the photo-alignment film materials obtained in the above synthesis examples and comparative synthesis examples, and physical properties were evaluated. The method for preparing the photo-alignment film and the method for evaluating physical properties
It carried out according to the following method.

[Method of Forming Photo-Alignment Film] a. Preparation of Photo-Alignment Material Solution The maleimide derivative obtained in the synthesis example was dissolved in a mixed solvent of N-methylpyrrolidone / butyl cellosolve = 1/1 to form a 5% nonvolatile content solution, which was filtered through a 0.1 μm filter. Thus, a photo-alignment film material solution was obtained.

B-1. Preparation of photo-alignment film (thermosetting method) a. The material solution for a photo-alignment film obtained by the above method was uniformly applied on a glass substrate with an ITO electrode by a spin coater, and dried and cured at 190 ° C. for 1 hour. next,
The surface of the obtained coating film was irradiated with a linearly polarized ultraviolet light near 365 nm at an integrated light intensity of 30 J / cm ² from an ultra-high pressure mercury lamp to form a photo-alignment film.

B-2. Preparation of photo-alignment film (photo-curing method) a. The material solution for a photo-alignment film obtained by the above method is uniformly coated on a glass substrate with an ITO electrode by a spin coater, dried at 100 ° C. for 15 minutes, and integrated on the surface of the coating film from an ultra-high pressure mercury lamp. wavelength of 2J / cm ² in quantity 313nm
The surrounding area was irradiated with ultraviolet light. Next, a super-high pressure mercury lamp was applied to the surface of the obtained coating film at an integrated light intensity of 30 J / cm ² at 365.
Irradiation with linearly polarized ultraviolet light near nm was performed to form a photo-alignment film.

C. Preparation of Liquid Crystal Cell An epoxy adhesive containing styrene beads having a diameter of 8 μm is applied around the photo-alignment film substrate obtained in b-1 or 2 above, leaving a liquid crystal injection port, so that the alignment surfaces face each other. ,
In addition, the adhesive was overlaid in a direction orthogonal to the direction of the polarized light and pressed, and the adhesive was cured at 150 ° C. for 90 minutes. Next, a nematic liquid crystal (5CB) was vacuum-injected and filled with an isotropic phase from the liquid crystal injection port, and then the liquid crystal injection port was sealed with an epoxy-based adhesive.

[Evaluation Method of Photo Alignment Film] a. Evaluation of liquid crystal alignment property The above c. The liquid crystal cell obtained by the method described above is sandwiched between two polarizing plates whose polarization directions are orthogonal to each other, and a voltage of 5 V is applied between the electrodes to turn on / off and switch between light and dark, thereby changing the orientation of the liquid crystal. evaluated.

B. Measurement of voltage holding ratio c. A DC voltage of 5 V was applied to the liquid crystal cell obtained by the above method for 64 microseconds, and subsequently, the voltage was retained for 16.6 milliseconds, and the voltage holding ratio with respect to the initial applied voltage was measured.

C. Measurement of durability The orientation of this liquid crystal cell after being held at 80 ° C. for 1000 hours was visually evaluated.

D. Evaluation of heat resistance The photo-alignment film obtained by the above method b-1 or b-2 was
After heating at 80 ° C. for 60 minutes, the above c. A liquid crystal cell was prepared by the method described above, and the liquid crystal alignment was visually evaluated.

Example 1 A material solution for a photo-alignment film was prepared from the maleimide derivative (4) obtained in Synthesis Example 1 according to the method for preparing a material solution for a photo-alignment film, and then b-1.
A photo-alignment film was prepared according to the method for preparing a thermosetting photo-alignment film described above. A liquid crystal cell was prepared using the obtained photo-alignment film, and physical properties were evaluated according to the above evaluation methods. As a result, the voltage holding ratio was 99%, and the liquid crystal alignment, durability, and heat resistance were all good.

Example 2 A material solution for a photo-alignment film was prepared from the maleimide derivative (4) obtained in Synthesis Example 1 according to the method for preparing a material solution for a photo-alignment film, and then b-2.
A photo-alignment film was prepared according to the photo-curing method for photo-alignment film of No. 1. A liquid crystal cell was prepared using the obtained photo-alignment film, and physical properties were evaluated according to the above evaluation methods. As a result, the voltage holding ratio was 99%, and the liquid crystal alignment, durability, and heat resistance were all good.

[Example 3] The maleimide derivative (4) obtained in Synthesis Example 1 was mixed with the maleimide derivative (4) obtained in Synthesis Example 1 and the maleimide derivative (5) obtained in Synthesis Example 2 by weight. Evaluation was performed in the same manner as in Example 1 except that the mixture was 1/1. As a result, the voltage holding ratio is 99
% As well as good liquid crystal alignment, durability and heat resistance.

Example 4 Evaluation was performed in the same manner as in Example 1 except that the maleimide derivative (4) obtained in Synthesis Example 1 was replaced with the maleimide derivative (6) obtained in Synthesis Example 3. went. As a result, the voltage holding ratio was as good as 99%, and the liquid crystal alignment, durability, and heat resistance were all good.

Comparative Example 1 The maleimide derivative (4) obtained in Synthetic Example 1 was replaced with an acrylic acid derivative (7) synthesized in Comparative Synthetic Example 1 and 2,2′-azobisisobutyronitrile. Was evaluated in the same manner as in Example 1 except that 0.1% was added. As a result, the liquid crystal alignment, durability and heat resistance were good, but the voltage holding ratio was as low as 89%.

[Comparative Example 2] The maleimide derivative (4) obtained in Synthetic Example 1 was synthesized from Comparative Example 2 having a polymaleimide in the main chain and a parafluorobenzoylcinnamoyl group in the side chain. Evaluation was performed in the same manner as in Example 1 except that the material for the alignment film was replaced. As a result, the voltage holding ratio was good at 98%, and the liquid crystal alignment was good. However, after the durability or heat resistance test, the switching between light and dark was unclear and the alignment was low.

[0083]

By using the material for a photo-alignment film comprising the maleimide derivative of the present invention, it has good liquid crystal display element characteristics, for example, a voltage holding ratio, good alignment stability and sufficient light and heat resistance. A photo-alignment film having durability can be obtained.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Hayakawa 4510-4 Murakami, Yachiyo-shi, Chiba Prefecture (72) Inventor Hirokazu Takada 2-21-13 Osakidai, Sakura-shi, Chiba F-term (reference) 2H090 HB08Y HC02 JB02 KA05 KA06 LA04 MB01 MB12 4F073 AA14 AA32 BA34 CA45 4J100 AM55P AM59P BA11P BA12P BA15P BC43P BC53P CA01 CA23 HA49 HE22 JA32

Claims (9)

[Claims] 1. A polymerizable monomer having at least one photo-alignment group that exhibits a photo-alignment function by a photo-dimerization reaction in one molecule and at least two polymerizable maleimide groups. Photo alignment film material. 2. The polymerizable monomer having a maleimide group is represented by the following general formula (1). (In the formula, R ₁ is an alkylene group having 1 to 30 carbon atoms or a cycloalkylene group having 3 to 12 carbon atoms, or 2 to 5 of these groups are a single bond, an ester bond, an ether bond, or a urethane. R ₂ represents a photo-aligning group selected from the group consisting of a benzophenone group, a cinnamoyl group, a chalcone group and a coumarin group, and R ₃ and R ₄ each independently represent a hydrogen atom , Which represents an alkyl group having 1 to 8 carbon atoms, a phenyl group or a halogen atom, and n represents an integer of 2 to 4). 3. A polymer comprising a polymerizable monomer having at least one photo-dimerization reaction in one molecule and exhibiting a photo-alignment function by a photo-dimerization reaction and at least two polymerizable maleimide groups, A photo-alignment film having a photo-alignment function developed by photo-dimerization of a photo-alignable group and a cross-linked structure generated by polymerization of the polymerizable maleimide group. 4. The polymerizable monomer having a maleimide group is represented by the following general formula (1): (In the formula, R ₁ is an alkylene group having 1 to 30 carbon atoms or a cycloalkylene group having 3 to 12 carbon atoms, or 2 to 5 of these groups are a single bond, an ester bond, an ether bond, or a urethane. Represents a group linked by a bond.
R ₂ represents a photo-aligning group selected from the group consisting of a benzophenone group, a cinnamoyl group, a chalcone group and a coumarin group, and R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms. , A phenyl group or a halogen atom. 4. The photo-alignment film according to claim 3, which is a compound represented by the formula: 5. A polymerizable monomer having at least one photo-dimerization reaction in one molecule and exhibiting a photo-alignment function by a photo-dimerization reaction and having at least two polymerizable maleimide groups on a substrate, By irradiating the coating film with light, a photodimerization reaction of the structural unit and a photopolymerization reaction of the polymerizable maleimide group are caused to form a crosslinked polymer film, and the polymer film exhibits a photo-alignment function. A method for producing a photo-alignment film. 6. A polymerizable monomer having at least one photo-dimerization reaction in one molecule and exhibiting a photo-alignment function by a photo-dimerization reaction and having at least two polymerizable maleimide groups on a substrate, Heating the coating film causes a thermal polymerization reaction of the polymerizable maleimide group to form a crosslinked polymer film, and irradiating the polymer film with light to cause a photodimerization reaction of the structural unit. Causing the polymer film to exhibit a photo-alignment function. 7. The maleimide compound represented by the general formula (1): (In the formula, R ₁ is an alkylene group having 1 to 30 carbon atoms or a cycloalkylene group having 3 to 12 carbon atoms, or 2 to 5 of these groups are a single bond, an ester bond, an ether bond, or a urethane. Represents a group linked by a bond.
R ₂ represents a photo-aligning group selected from the group consisting of a benzophenone group, a cinnamoyl group, a chalcone group and a coumarin group, and R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms. , A phenyl group or a halogen atom. 7. The method for producing a photo-alignment film according to claim 5, which is a compound represented by the formula: 8. A liquid crystal display device having a structure in which a liquid crystal is sandwiched between two substrates having an alignment film inside, wherein the alignment film expresses a photo alignment function by at least one photodimerization reaction in one molecule. It comprises a polymer of a polymerizable monomer having a photo-alignable group and at least two polymerizable maleimide groups, and a photo-alignment function developed by photodimerization of the photo-alignable group and polymerization of the polymerizable maleimide group. A liquid crystal display device comprising a photo-alignment film having a crosslinked structure. 9. The maleimide compound represented by the general formula (1): (In the formula, R ₁ is an alkylene group having 1 to 30 carbon atoms or a cycloalkylene group having 3 to 12 carbon atoms, or 2 to 5 of these groups are a single bond, an ester bond, an ether bond, or a urethane. Represents a group linked by a bond.
R ₂ represents a photo-aligning group selected from the group consisting of a benzophenone group, a cinnamoyl group, a chalcone group and a coumarin group, and R ₃ and R ₄ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms. , A phenyl group or a halogen atom. The liquid crystal display device according to claim 8, which is a compound represented by the formula: