JP4419826B2 - Liquid crystal alignment film forming agent, liquid crystal alignment film, and liquid crystal element - Google Patents

Description

  The present invention relates to a liquid crystal alignment film capable of vertically aligning liquid crystal molecules without rubbing treatment, a forming agent for forming the liquid crystal alignment film, and a liquid crystal element including the liquid crystal alignment film.

As a liquid crystal display element, a sandwich structure cell in which a nematic liquid crystal layer having positive dielectric anisotropy is sandwiched between two substrates in which a liquid crystal alignment film made of polyamic acid or polyimide is formed on a transparent electrode substrate, and The so-called TN (Twisted Nematic) type liquid crystal display element having a structure in which the major axis of the liquid crystal molecules is twisted by 90 ° from one substrate to the other substrate, is superior in terms of contrast and viewing angle dependency than the TN type. An STN (Super Twisted Nematic) type liquid crystal display element is known. On the other hand, vertical alignment type liquid crystal display elements of MVA (Multi domain Vertical Alignment) method and PVA (Patterned Vertical Alignment) method having a structure in which the long axes of liquid crystal molecules are aligned in the normal direction of the substrate are also known.
These MVA-type and PVA-type liquid crystal display elements not only have excellent physical properties such as contrast and viewing angle dependency, but also require a rubbing treatment step that is usually performed in liquid crystal alignment films used in TN-type and STN-type liquid crystal display elements. It is excellent in terms of manufacturing process.
However, there are only limited forming agents that can form a liquid crystal alignment film in a vertical alignment type display element, induce a vertical alignment of liquid crystal molecules, and can impart industrially applicable heat resistance, transparency, and the like. It was not found.

Although the mechanism of the vertical alignment of the liquid crystal molecules is not necessarily clarified, in recent years, the introduction of a long-chain alkyl group as a polymer side chain or into the composition of a polymer mixture has led to It has been shown that the tilt angle increases, and based on this, a forming agent for a liquid crystal alignment film using such a long-chain alkyl group has been proposed.
For example, Patent Document 1 discloses an alignment film in which a forming agent containing polysiloxane having a hydrophobic long-chain alkyl side chain is applied on a substrate and thermally cured, and Patent Documents 2 to 4 include hydrophobic films. An alignment film obtained by applying a polyamic acid-containing forming agent having a long alkyl side chain with heat resistance on a substrate and thermally curing the same is disclosed in Patent Document 5, and an alignment film is formed using a long-chain alkyl dendrimer derivative. Each method of forming is proposed.
However, a method for obtaining a liquid crystal alignment film using a compound into which these long alkyl side chains are introduced has a problem that the alignment of liquid crystal molecules varies depending on the density of the side chains of the compound or the condition of the film thickness. In addition, by introducing a long alkyl side chain into the polymer, the tilt angle of the liquid crystal molecules does not necessarily appear, but also depends on the polymer main chain structure to be introduced, so limited materials such as polysiloxane and polyamic acid It is currently available only in
Such a material using polysiloxane or polyamic acid requires heat treatment at a high temperature to form a film for obtaining good liquid crystal orientation, and therefore can only be formed on a substrate surface having heat resistance. The material is limited. On the other hand, in the method using a long-chain alkyl dendrimer derivative, it is difficult to form an alignment film that ensures long-term stability by itself, and it is difficult to form a film unless the substrate surface has hydrophilicity.
JP-A-9-281502 Japanese Patent Laid-Open No. 9-21468 JP 2003-295194 A JP 2004-83810 A JP 2002-174724 A

An object of the present invention is to provide a liquid crystal alignment film that can satisfactorily align liquid crystal molecules and has excellent heat resistance and mechanical strength, and can easily form the liquid crystal alignment film on various substrates. An object of the present invention is to provide a liquid crystal alignment film forming agent.
Another object of the present invention is to provide a liquid crystal element that is capable of satisfactorily aligning liquid crystal molecules and has a liquid crystal alignment film having excellent heat resistance and mechanical strength, and is useful for MVA mode, PVA mode, etc. There is to do.

  As a result of diligent studies to solve the above problems, the present inventors have found that the use of a polymer having a specific substituted diphenylacetylene structural unit solves the above problems, and has completed the present invention. It was.

(式中、Ｘはトリメチルシリル基、ｔ−ブチル基、ジメチルアルキルシリル基又は１，１'−ジメチルアルキル基から選ばれる基を示す。Ｙはハロゲン原子又はメチル基を示し、ｍは０又は１を示す。またｎは任意の数を示す。)
また本発明によれば、上記液晶配向膜形成剤の塗液を基材に塗布・乾燥して得た液晶配向膜が提供される。
更に本発明によれば、対向する上記液晶配向膜の間隙に液晶層を有するセルを備えることを特徴とする液晶素子が提供される。 That is, according to the present invention, there is provided a liquid crystal alignment film forming agent comprising a polymer (A) containing 80% by mass or more of a substituted diphenylacetylene unit represented by the formula (1).

(In the formula, X represents a group selected from a trimethylsilyl group, a t-butyl group, a dimethylalkylsilyl group, or a 1,1′-dimethylalkyl group. Y represents a halogen atom or a methyl group, and m represents 0 or 1. And n is an arbitrary number.)
Moreover, according to this invention, the liquid crystal aligning film obtained by apply | coating and drying the coating liquid of the said liquid crystal aligning film forming agent to a base material is provided.
Furthermore, according to the present invention, there is provided a liquid crystal element comprising a cell having a liquid crystal layer in the gap between the liquid crystal alignment films facing each other.

The liquid crystal alignment film forming agent of the present invention contains the specific polymer (A), and the polymer (A) is solvent-soluble and can form a film without requiring heat treatment at a high temperature. Therefore, it is possible to easily form a liquid crystal alignment film in which liquid crystal molecules exhibit good vertical alignment properties and are excellent in heat resistance and mechanical strength.
Since the liquid crystal alignment film of the present invention is obtained by applying and drying the coating liquid of the forming agent of the present invention on a substrate, the liquid crystal molecules can be satisfactorily vertically aligned, and polyamics that are widely used at present are used. Excellent heat resistance and mechanical strength compared to liquid crystal alignment films using acid or polyimide.
Since the liquid crystal element of the present invention includes a cell having a liquid crystal layer in the gap between the liquid crystal alignment films of the present invention facing each other, the liquid crystal element is particularly useful for a liquid crystal element such as an MVA method or a PVA method that vertically aligns liquid crystal molecules.

Hereinafter, the present invention will be described in more detail.
The liquid crystal alignment film forming agent of the present invention contains a polymer (A) containing 80% by mass or more, preferably 90% by mass or more, particularly preferably 100% by mass of the substituted diphenylacetylene unit represented by the above formula (1). To do.
In the formula (1), X represents a group selected from a trimethylsilyl group, a t-butyl group, a dimethylalkylsilyl group, and a 1,1′-dimethylalkyl group. Here, the alkyl chain present in the dimethylalkylsilyl group and the 1,1′-dimethylalkyl group is preferably a straight chain from the viewpoint of obtaining good orientation characteristics, and the number of carbon atoms is about 10-20. preferable.
Examples of the dimethylalkylsilyl group include a dimethyl-n-dodecyl group and a dimethyl-n-octadecyl group. Examples of the 1,1′-dimethylalkyl group include 1,1′-dimethyl-n-dodecyl. Group, 1,1′-dimethyl-n-octadecyl group and the like.
X is preferably a trimethylsilyl group or a dimethylalkylsilyl group from the viewpoint of further improving the vertical alignment of liquid crystal molecules. In addition, a trimethylsilyl group is most preferable because the film thickness dependency on the liquid crystal orientation of the liquid crystal molecules is improved.

In the formula (1), Y represents a halogen atom or a methyl group, and m represents 0 or 1. Preferably, m is 0 or Y is a chlorine atom from the viewpoint of availability.
The combination of X and Y in the formula (1) is arbitrary and is not particularly limited, and examples thereof include the above preferred groups or combinations of atoms.
In the formula (1), n indicating the number of repeating structural units is arbitrary, and the content of the structural unit represented by the formula (1) in the polymer (A) described later and the weight average molecular weight of the polymer (A) are determined. The number can be satisfied. In addition, the structural units represented by the formula (1) in the polymer (A) are usually the same but may be different.

  The polymer (A) only needs to contain 80% by mass or more of the unit represented by the formula (1), in a range that does not hinder the liquid crystal orientation of the alignment film to be formed, and in a proportion of less than 20% by mass. If present, a unit having a chemical structure different from the formula (1) may exist. In order to obtain good liquid crystal alignment characteristics, it is composed only of the substituted diphenylacetylene unit represented by the above formula (1), or composed of the unit and a (substituted) diphenylacetylene unit other than the formula (1). In particular, a polymer composed only of a substituted diphenylacetylene unit represented by the formula (1) is preferable.

  Examples of the preferred polymer (A) include 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1-phenyl-2- (4- (t-butyl) phenyl) acetylene polymer, 1- (4-chlorophenyl) -2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1-phenyl-2- (4- (dimethyloctadecylsilyl) phenyl) acetylene polymer, 1-phenyl-2- (4 -(1,1'-dimethylnonadecyl) phenyl) acetylene polymer, 1-phenyl-2- (4- (dimethyloctadecylsilyl) phenyl) acetylene and 1- (4-methylphenyl) -2- (4'- And a copolymer of ethylphenyl) acetylene (copolymerization ratio 91: 9% by mass). Among them, from the viewpoint of excellent liquid crystal vertical alignment and heat resistance of the liquid crystal alignment film to be formed, 1-phenyl-2- (4- ( Trimethylsilyl) phenyl) acetylene polymer are mentioned most preferred.

The polymer (A) has a weight average molecular weight of usually 100,000 or more, preferably 500,000 to 2,000,000. If the weight average molecular weight is less than 100,000, the film-forming ability may be lowered, and if it is more than 2 million, the solubility in a solvent may be deteriorated.
Here, the weight average molecular weight means a value measured by gel permeation chromatography (GPC).

The polymer (A) is, for example, a blend of 80:20 to 100: 0 in terms of mass ratio of a monomer that is a raw material of the substituted diphenylacetylene unit represented by the formula (1) and other monomers. It can be obtained by a method such as polymerization in the presence of a catalyst or a cocatalyst.
Preferable examples of the catalyst include halides of Group V transition metals in the periodic table, such as niobium pentachloride, niobium pentabromide, tantalum pentachloride, and tantalum pentabromide.
The polymerization conditions can be appropriately selected according to the molecular weight of the polymer (A) to be obtained, but can be usually performed under conditions of a polymerization temperature of 0 to 80 ° C. and a polymerization time of 0.5 to 100 hours.

  Examples of the monomer used as a raw material for the substituted diphenylacetylene unit represented by the formula (1) include 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene, 1-phenyl-2- (4- (t-butyl) phenyl) acetylene, 1- (4-methyl) -2- (4- (trimethylsilyl) phenyl) acetylene, 1- (4-methyl) -2- (4- (dimethyloctadecylsilyl) phenyl) acetylene 1- (4-methyl) -2- (4- (1,1′-dimethyloctadecyl) phenyl) acetylene, 1- (4-chlorophenyl) -2- (4- (trimethylsilyl) phenyl) acetylene, 1-phenyl -2- (4- (dimethyloctadecylsilyl) phenyl) acetylene. Among them, 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene, 1-phenyl-2- (4- (t-butyl) phenyl) acetylene, 1- (4-chlorophenyl) -2- (4- (trimethylsilyl) ) Phenyl) acetylene and 1-phenyl-2- (4- (dimethyloctadecylsilyl) phenyl) acetylene are preferred, and 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene is preferred in terms of availability. Is most preferable.

  Examples of the monomer used as a raw material for the substituted diphenylacetylene unit different from the structural unit represented by the formula (1) among the other monomers include 1- (trimethylsilyl) -1-propynediphenylacetylene, 1- Phenyl-2- (4- (methyl) phenyl) acetylene, 1-phenyl-2- (4- (ethyl) phenyl) acetylene, 1- (4- (methyl) phenyl) -2- (4- (ethyl) phenyl ) Acetylene, 1-phenyl-2- (4- (isopropyl) phenyl) acetylene, 1-phenyl-2- (4- (triphenylsilyl) phenyl) acetylene, 1-phenyl-2- (4- (triisopropylsilyl) ) Phenyl) acetylene. Among them, 1- (4- (methyl) phenyl) -2- (4- (ethyl) phenyl) acetylene, 1-phenyl-2- (4- (isopropyl) is preferable because of the solubility and reactivity of the polymer (A). Preferred is phenyl) acetylene.

In addition to the polymer (A), the liquid crystal alignment film forming agent of the present invention is used within the range that does not impair the desired effects of the present invention, and additives for improving other effects and the film formation described later. A solvent may be included.
Examples of the additive include polymethyl methacrylate and polyfumarate. Although the ratio of an additive can be suitably determined according to the desired purpose, it is 0-20 mass parts normally with respect to 100 mass parts of polymers (A).

The liquid crystal alignment film of the present invention can be formed by applying and drying a coating liquid of the liquid crystal alignment film forming agent of the present invention on a substrate.
As said base material, a glass substrate, a plastic sheet, a plastic film is mentioned, for example, A commercial item etc. can be used. Preferably, a glass substrate with good heat resistance and dimensional stability is preferred, but the liquid crystal alignment film forming agent of the present invention can form a film without requiring high-temperature treatment, so that a plastic film or the like can be used depending on the purpose. Are also preferably used.
The thickness of the said plastic film is not specifically limited, According to the kind of liquid crystal element, it can select suitably, For example, it can be set as about 0.5 mm-3.0 mm.
The material of the plastic film is not particularly limited as long as it does not change with the temperature at which the liquid crystal molecules are aligned and is resistant to the solvent used in forming the liquid crystal alignment film. For example, polyethylene terephthalate, polyethylene Polyester polymers such as phthalate; Cellulosic polymers such as diacetyl cellulose; Polycarbonate polymers; Acrylic polymers; Transparent polymers such as imide polymers, and acrylic polymers are preferred from the viewpoint of transparency.

Examples of the coating liquid for the liquid crystal alignment film forming agent include a coating liquid in which the liquid crystal alignment film forming agent is dissolved in a volatile solvent, and the volatile solvent varies depending on the type of the base material, for example, benzene, toluene. Aromatic hydrocarbons such as xylene; halogenated hydrocarbons such as chloroform, carbon tetrachloride, dichloroethane, chlorobenzene, bromobenzene, etc., and toluene or xylene is preferred for the reason of solubility of the polymer (A).
The solid content concentration of the polymer (A) in the coating liquid is not particularly limited, but the solid content concentration is usually 0.1 to 5. considering the viscosity of the coating liquid, the film thickness of the target liquid crystal alignment film, and the like. It is 0 mass%, Preferably it is 0.5-2.0 mass%.

The coating liquid can be applied by various coating methods such as a dip coating method, a bar coating method, and a spin coating method, and the spin coating method is preferable because of the smoothness of the liquid crystal alignment film to be obtained.
Conditions for applying the coating solution by spin coating can be set as appropriate. For example, the volatile solvent is toluene, and the coating solution is applied onto a glass substrate using a coating solution having a solid content concentration of 0.5 mass%. In some cases, it can be performed under conditions of 3000 rpm and 30 seconds.
The drying after the application can be performed, for example, at 80 to 120 ° C. for 5 to 180 minutes.
The film thickness of the liquid crystal alignment film formed on the substrate after coating and drying is not particularly limited, but 0.01 μm to 1 μm is appropriate for practical reasons when used as a normal liquid crystal alignment film. is there.

The liquid crystal element of the present invention includes a sandwich type cell having a liquid crystal layer in the gap between the liquid crystal alignment films of the present invention facing vertically.
The liquid crystal constituting the liquid crystal layer can be freely selected according to desired optical characteristics such as a cholesteric liquid crystal, a smectic liquid crystal, a ferroelectric liquid crystal, and an antiferroelectric liquid crystal in addition to a nematic liquid crystal that is usually used. Particularly preferred liquid crystals are liquid crystals intended for production of vertical alignment type liquid crystal elements in practical use. For example, various nematic liquid crystals such as cyanobiphenyl-based such as 4-cyano-4′-pentylbiphenyl or fluorine-based or tolan-based liquid crystals. Is mentioned.

In the liquid crystal element of the present invention, a liquid crystal compound in an isotropic phase state is introduced into the gap between the opposing liquid crystal alignment films and brought into contact with the liquid crystal alignment film, so that the introduced liquid crystal molecules are perpendicular to the liquid crystal alignment film. Can be oriented. In order to confirm that the liquid crystal molecules are aligned perpendicularly to the liquid crystal alignment film, it can be performed, for example, by observing an optical image of the liquid crystal phase with a polarizing microscope in a crossed Nicol state. When the liquid crystal molecules are not aligned perpendicular to the liquid crystal alignment film, high-speed response and viewing angle dependency are reduced.
The liquid crystal element of the present invention can be made into, for example, a liquid crystal display element of an MVA system or the like by combining known liquid crystal element constituent members such as a thin film transistor, a polarizer, and a light source with the sandwich type cell.

Hereinafter, although an example and a comparative example explain the present invention still in detail, the present invention is not limited to these.
Example 1
A 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer having a weight average molecular weight of 500,000 was synthesized by the method described in J. Polym. Sci. A., 36, p2721-2725 (1998).
That is, 5 g of 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene and 0.304 g of tantalum pentachloride were dissolved in 170 ml of toluene in a polymerization vessel under a dry nitrogen atmosphere, and then 0.589 g of tetra-n-butyltin. And polymerized at 80 ° C. for 3 hours. Subsequently, the resulting polymer solution was precipitated in a large amount of methanol, and then filtered and dried to obtain the target 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer.

50 mg of a toluene solution containing 0.5% by mass of the obtained polymer was placed on a glass substrate having a thickness of 1.0 mm and a size of 25 mm × 20 mm using a spin coater (1H-D7, manufactured by MIKASA) at 3000 rpm for 30 seconds. The coating was performed by the spin coating method under the following conditions. Next, the coating film was dried at 120 ° C. for 2 hours under reduced pressure to form a liquid crystal alignment film having a thickness of about 0.5 μm.
Next, the two substrates on which the liquid crystal alignment film was formed were combined with the liquid crystal alignment film coating surface facing each other and a 50 μm spacer sandwiched therebetween, and then the isotropic temperature (40 ° C. in the gap). The liquid crystal cell which is a liquid crystal element model was produced by injecting 20 mg of a liquid crystal composed of 4-cyano-4′-pentylbiphenyl and slowly cooling it.
The alignment state of the liquid crystal molecules in this liquid crystal cell was observed from a direction perpendicular to the surface of the liquid crystal cell with a crossed Nicols polarization microscope (BH-2, manufactured by Olympus). Even if it was rotated, it was a dark field similarly. Further, the liquid crystal cell was tilted 45 degrees with respect to the light incident surface, and light was incident from an oblique direction. When observed under crossed Nicols, light transmission was observed. This confirmed that the injected liquid crystal molecules were vertically aligned.
If the liquid crystal is not vertically aligned, a random optical image such as a schlieren structure is observed, and the alignment state of the liquid crystal in the liquid crystal cell can be visually determined from the observation result.

Example 2
Example 1 except that a nematic liquid crystal (product name: MLC-6608, manufactured by Merck & Co., Inc.) having a nematic-isotropic phase transition temperature of 90.6 ° C. was used as the liquid crystal and heated to 100 ° C. and injected into the cell. A liquid crystal cell was prepared by the same procedure as described above. The alignment state of the liquid crystal molecules in the obtained cell was observed in the same manner as in Example 1. As a result, it was confirmed that the liquid crystal molecules were vertically aligned.

Example 3
Instead of 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1-phenyl-2- (4- (t--) having a weight average molecular weight of 500,000 synthesized by the method according to Example 1 was used. A liquid crystal cell was prepared in the same manner as in Example 1 except that the butyl) phenyl) acetylene polymer was used. The alignment state of the liquid crystal molecules in the obtained cell was observed in the same manner as in Example 1. As a result, it was confirmed that the liquid crystal molecules were vertically aligned.

Example 4
Instead of 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1- (4-chlorophenyl) -2- [4 having a weight average molecular weight of 500,000 synthesized by a method according to Example 1 was used. A liquid crystal cell was prepared in the same manner as in Example 1 except that-(trimethylsilyl) phenyl] acetylene polymer was used. The alignment state of the liquid crystal molecules in the obtained cell was observed in the same manner as in Example 1. As a result, it was confirmed that the liquid crystal molecules were vertically aligned.

Example 5
Instead of 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1-phenyl-2- (4- (dimethyloctadecyl) having a weight average molecular weight of 500,000 synthesized by the method according to Example 1 was used. A liquid crystal cell was prepared in the same manner as in Example 1 except that a silyl) phenyl) acetylene polymer was used. The alignment state of the liquid crystal molecules in the obtained cell was observed in the same manner as in Example 1. As a result, it was confirmed that the liquid crystal molecules were vertically aligned.

Example 6
Instead of 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1-phenyl-2- (4- (1,1) having a weight average molecular weight of 500,000 synthesized by the method according to Example 1 was used. A liquid crystal cell was prepared in the same manner as in Example 1 except that 1′-dimethylnonadecyl) phenyl) acetylene polymer was used. The alignment state of the liquid crystal molecules in the obtained cell was observed in the same manner as in Example 1. As a result, it was confirmed that the liquid crystal molecules were vertically aligned.

Example 7
Instead of 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1-phenyl-2- (4- (dimethyloctadecyl) having a weight average molecular weight of 500,000 synthesized by the method according to Example 1 was used. Example 1 except that a copolymer of (silyl) phenyl) acetylene and 1- (4-methylphenyl) -2- (4′-ethylphenyl) acetylene (copolymerization ratio 91: 9% by mass) was used. A liquid crystal cell was prepared by the procedure described above. The alignment state of the liquid crystal molecules in the obtained cell was observed in the same manner as in Example 1. As a result, it was confirmed that the liquid crystal molecules were vertically aligned.

Comparative Example 1
Instead of 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1-phenyl-2- (4- (triethylsilyl) having a weight average molecular weight of 500,000 synthesized by the method according to Example 1 was used. A liquid crystal cell was prepared in the same manner as in Example 1 except that a) phenyl) acetylene polymer was used. The alignment state of the liquid crystal molecules in the obtained cell was observed in the same manner as in Example 1. As a result, the vertical alignment of the liquid crystal molecules could not be confirmed.

Comparative Example 2
Instead of 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1-phenyl-2- (4- (dimethylisopropyl) having a weight average molecular weight of 500,000 synthesized by the method according to Example 1 was used. A liquid crystal cell was prepared in the same manner as in Example 1 except that the silyl) phenyl) acetylene polymer was used. The alignment state of the liquid crystal molecules in the obtained cell was observed in the same manner as in Example 1. As a result, the vertical alignment of the liquid crystal molecules could not be confirmed.

Comparative Example 3
Instead of 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1-phenyl-2- (4- (dimethylpina) having a weight average molecular weight of 500,000 synthesized by the method according to Example 1 was used. A liquid crystal cell was prepared in the same manner as in Example 1 except that the (nylsilyl) phenyl) acetylene polymer was used. The alignment state of the liquid crystal molecules in the obtained cell was observed in the same manner as in Example 1. As a result, the vertical alignment of the liquid crystal molecules could not be confirmed.

Comparative Example 4
Instead of 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1- (3,4,3′-trifluoro having a weight average molecular weight of 500,000 was synthesized by the method according to Example 1. A liquid crystal cell was prepared in the same manner as in Example 1 except that phenyl) -2- (4- (dimethylpinanylsilyl) phenyl) acetylene polymer was used. The alignment state of the liquid crystal molecules in the obtained cell was observed in the same manner as in Example 1. As a result, the vertical alignment of the liquid crystal molecules could not be confirmed.

Comparative Example 5
Instead of 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer, 1-phenyl-2- (4- (dimethyloctadecyl) having a weight average molecular weight of 500,000 synthesized by the method according to Example 1 was used. The same procedure as in Example 1 except that a copolymer of (silyl) phenyl) acetylene and 1- (4-methylphenyl) -2- (4-ethylphenyl) acetylene (copolymerization ratio 72: 28% by mass) was used. Thus, a liquid crystal cell was produced. The alignment state of the liquid crystal molecules in the obtained cell was observed in the same manner as in Example 1. As a result, the vertical alignment of the liquid crystal molecules could not be confirmed.

Example 8
The thermal decomposition temperature, the solubility in toluene, and the adhesion to the glass substrate of the liquid crystal alignment film forming agent comprising the 1-phenyl-2- (4- (trimethylsilyl) phenyl) acetylene polymer synthesized in Example 1 were as follows. The method was evaluated. For comparison, 50 g of N-methyl-2-pyrrolidone was added in the order of diamine and tetracarboxylic dianhydride in the order shown in Table 2 to obtain a solid content concentration of 10%, and reacted at room temperature for 6 hours from the polyamic acid solution. The polyimide compounds obtained by heat-treating the resulting polymers I to IV were similarly evaluated. The results are shown in Table 1.

The pyrolysis temperature is the 10% weight loss temperature when the sample polymer powder is heated and heated in the air at a heating rate of 10 ° C./min with a thermogravimetric analyzer (SSC5200, manufactured by Seiko Denshi Kogyo Co., Ltd.). evaluated. In addition, the powder samples of the polymers I to IV were prepared by drying a solid content obtained by dropping in methanol at 80 ° C. for 1 hour and then at 200 ° C. for 2 hours.
For solubility in toluene, the sample polymer powder was added to 100 times the mass of toluene and stirred at room temperature for a whole day and night. In addition, the powder samples of the polymers I to IV were prepared by drying a solid content obtained by dropping in methanol at 80 ° C. for 1 hour and then at 200 ° C. for 2 hours.
Adhesion to the glass substrate is achieved by making 25 squares of 2 mm x 2 mm squares on a sample polymer film prepared to a thickness of 0.5 μm by spin coating on the sample polymer glass substrate, and then applying an adhesive tape. This was done by measuring the number of squares remaining after peeling and pasting. The polymer I to IV film samples were prepared by applying a polyamic acid solution on a glass substrate by a spin coating method at 3000 rpm for 30 seconds using a spin coater. For 2 hours.

PMDA：ピロメリット酸無水物
DPDA：ジフェニルテトラカルボン酸無水物
PPD：ｐ−フェニレンジアミン
POP：４，４'−ジアミノジフェニルエーテル
PMP：４，４'−ジアミノジフェニルメタン

PMDA: pyromellitic anhydride
DPDA: Diphenyltetracarboxylic anhydride
PPD: p-phenylenediamine
POP: 4,4'-diaminodiphenyl ether
PMP: 4,4'-diaminodiphenylmethane

Claims (3)

A liquid crystal alignment film forming agent comprising a polymer (A) containing 80% by mass or more of a substituted diphenylacetylene unit represented by the formula (1).

(In the formula, X represents a group selected from a trimethylsilyl group, a t-butyl group, a dimethylalkylsilyl group, or a 1,1′-dimethylalkyl group. Y represents a halogen atom or a methyl group, and m represents 0 or 1. And n is an arbitrary number.)   The liquid crystal aligning film obtained by apply | coating and drying the coating liquid of the liquid crystal aligning film forming agent of Claim 1 to a base material.   3. A liquid crystal device comprising a cell having a liquid crystal layer in a gap between the liquid crystal alignment films facing each other.