JP7510119B2 - Polymer, liquid crystal alignment agent using same, liquid crystal alignment film, and liquid crystal display element using same - Google Patents

Description

The present invention relates to a polymer, a liquid crystal aligning agent using the polymer , a liquid crystal alignment film, and a liquid crystal display element using the polymer.

In liquid crystal display elements, the liquid crystal alignment film plays a role in orienting liquid crystals in a certain direction. Currently, the main liquid crystal alignment films used industrially are formed by applying a polyimide-based liquid crystal alignment agent made of polyamide acid (also called polyimide precursor or polyamic acid) or polyimide solution to a substrate and baking it. In addition, when aligning liquid crystals parallel to or at an angle to the substrate surface, a surface stretching process by rubbing (rubbing process) is performed after film formation. As an alternative to rubbing process, a method that utilizes anisotropic photochemical reactions by irradiation with polarized ultraviolet light, etc. has also been proposed.

Numerous techniques have been proposed to improve the display characteristics of liquid crystal display elements. For example, Patent Document 1 (JP Patent Publication No. 2-287324) proposes using a polyimide resin with a specific repeating structure to obtain a high voltage holding ratio (VHR). Also, Patent Document 2 (JP Patent Publication No. 10-104633) proposes using a soluble polyimide that has nitrogen atoms in addition to imide groups to shorten the time it takes for an afterimage to be erased.

Japanese Patent Application Laid-Open No. 2-287324 Japanese Patent Application Laid-Open No. 10-104633

In recent years, as liquid crystal displays (LCD panels) have become more multifunctional and diversified, development has progressed from displays using glass substrates to flexible displays using resin substrates (plastic substrates, i.e. film substrates). Accordingly, there is a growing need for liquid crystal alignment films that can be obtained by firing at low temperatures, and there is also a growing demand for the reliability of liquid crystal alignment films (high voltage retention rate, etc.).

Materials used for liquid crystal alignment films include polyimide precursors such as polyamic acid and polyamic acid esters, and polyimides obtained by dehydrating them through baking or chemical reaction. Of these, polyamic acid is easy to synthesize and has excellent solubility in solvents, making it possible to obtain a liquid crystal alignment agent that has excellent applicability to substrates and film formation properties. However, due to its structure, polyamic acid is easily decomposed by hydrolysis, etc., and it is difficult to ensure long-term reliability for liquid crystal alignment films obtained using it.

On the other hand, soluble polyimide (polyimide soluble in a solvent obtained by the dehydration reaction of polyamic acid) is pre-imidized, so there is no need for a heat curing process to heat it to imidize it, and therefore it can be baked at a relatively low temperature. In addition, because it has excellent chemical stability and heat resistance, it is easier to ensure long-term reliability in liquid crystal alignment films obtained using soluble polyimide. However, there are few options for solvents in which soluble polyimide can be dissolved, and therefore the solvents that can be used are limited. As a result, when soluble polyimide is used, precipitation occurs during application and film formation, and the coating film is prone to defects. In recent years, with the increase in size and resolution of LCD panels and the diversification of usage environments, there is a demand for methods that can solve each problem and improve various characteristics.

The present invention has been made in view of the above circumstances, and its object is to provide a liquid crystal alignment agent that can be baked at a low temperature and has good printability (solubility of the resulting polymer in an organic solvent). It also aims to provide a polymer from which the above liquid crystal alignment agent can be obtained. It also aims to provide a liquid crystal alignment film that has excellent rubbing resistance when a rubbing treatment is performed, has good liquid crystal alignment properties (i.e., can achieve a low pretilt angle), and has a high voltage retention rate. It also aims to provide a liquid crystal display element having the above liquid crystal alignment film.

As a result of intensive research, the inventors have found that a polymer having a specific structure and a liquid crystal alignment agent using the same are effective in achieving the above-mentioned objective, and have completed the present invention. The above-mentioned polymer is novel, and the monomer for obtaining the above-mentioned polymer also contains a novel compound.

That is, the present invention is summarized as follows: 1. to 9.
1. A liquid crystal aligning agent comprising a polymer that is a polyurea or a polyurea copolymer, having a structure represented by the following formula (1):

式中、Ｘはジイソシアネート誘導体に由来の二価の有機基を示し、Ｙはジアミン誘導体に由来の二価の有機基を示す。Ｒ_１は炭素数１～４のアルキル基を示し、分岐していてもよい。Ｒ_２は水素原子、炭素数１～４の脂肪族炭化水素基、又は下式（１－１）で表される有機基を示す。Ｒａ及びＲｂはそれぞれ独立して、水素原子、又は炭素数１～２の脂肪族炭化水素基を示す。

In the formula, X represents a divalent organic group derived from a diisocyanate derivative, and Y represents a divalent organic group derived from a diamine derivative. _R1 represents an alkyl group having 1 to 4 carbon atoms, which may be branched. _R2 represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms, or an organic group represented by the following formula (1-1). Ra and Rb each independently represent a hydrogen atom, or an aliphatic hydrocarbon group having 1 to 2 carbon atoms.

式中、黒点は窒素原子への結合箇所を意味し、Ｒ_１、Ｒａ及びＲｂは上記のＲ_１、Ｒａ及びＲｂと同義である。

In the formula, the black dot represents the bonding point to the nitrogen atom, and R ₁ , Ra, and Rb are the same as R ₁ , Ra, and Rb above.

2. The liquid crystal alignment agent according to 1., which contains a polymer that is a polyurea or polyurea copolymer obtained from a diamine derivative represented by the following formula (2) and a diisocyanate derivative.

式中、Ａは脂肪族炭化水素基又は芳香族炭化水素基の、二価の有機基を示し、Ｂ及びＣはそれぞれ独立して、単結合、又は炭素数１～５の脂肪族炭化水素基を示す。Ｒ_１、Ｒ_２、Ｒａ及びＲｂは上記のＲ_１、Ｒ_２、Ｒａ及びＲｂと同義である。

In the formula, A represents a divalent organic group such as an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and B and C each independently represent a single bond or an aliphatic hydrocarbon group having 1 to 5 carbon atoms. R ₁ , R ₂ , Ra, and Rb are the same as R ₁ , R ₂ , Ra, and Rb above.

3. The liquid crystal alignment agent according to 2., which contains a polymer that is a polyurea or a polyurea copolymer obtained from a diamino compound represented by the following formula (3) among the diamine derivatives and a diisocyanate derivative.

式中、Ａｒはアリーレン基を示し、Ｄは単結合、又は炭素数１～５の炭化水素基を示す。Ｒ_１、Ｒ_２、Ｒａ及びＲｂは上記のＲ_１、Ｒ_２、Ｒａ及びＲｂと同義である。

In the formula, Ar represents an arylene group , and D represents a single bond or a hydrocarbon group having 1 to 5 carbon atoms. R ₁ , R ₂ , Ra, and Rb are each synonymous with R ₁ , R ₂ , Ra, and Rb above.

4. The liquid crystal alignment agent according to 3., which contains a polymer that is a polyurea or a polyurea copolymer obtained from a diamino compound represented by the following formula (3-a) among the diamine derivatives and a diisocyanate derivative.

式中、Ｄ及びＲ_１は上記のＤ及びＲ_１と同義である。

In the formula, D and _R1 have the same meanings as D and _R1 above.

5. A polymer obtained from a diamino compound represented by the following formula (3-1) and a diisocyanate derivative.

式中、Ｒ_１は炭素数１～４のアルキル基を示し、分岐していてもよい。Ｂは単結合、又は炭素数１～５の脂肪族炭化水素基を示す。Ｒａ及びＲｂはそれぞれ独立して、水素原子、又は炭素数１～２の脂肪族炭化水素基を示す。

In the formula, _R1 represents an alkyl group having 1 to 4 carbon atoms, which may be branched. B represents a single bond or an aliphatic hydrocarbon group having 1 to 5 carbon atoms. Ra and Rb each independently represent a hydrogen atom or an aliphatic hydrocarbon group having 1 to 2 carbon atoms.

6. The polymer according to 5., obtained from the diamino compound and at least one of the diisocyanate derivatives represented by the following formulas (4-1) to (4-11) and (4-13).

7. A liquid crystal alignment agent using the polymer described in 5. or 6.

8. A liquid crystal alignment film obtained from the liquid crystal alignment agent described in any one of 1. to 4. and 7.

9. A liquid crystal display element using the liquid crystal alignment film described in 8.

According to the present invention, it is possible to provide a liquid crystal alignment agent that can be baked at a low temperature, can obtain a high-quality liquid crystal alignment film, and has excellent printability. Furthermore, according to the present invention, it is possible to provide a novel polymer for obtaining the above liquid crystal alignment agent. Furthermore, according to the present invention, it is possible to provide a liquid crystal alignment film that has excellent rubbing resistance when a rubbing treatment is performed, can achieve a low pretilt angle, and has a high voltage retention rate. Furthermore, according to the present invention, it is possible to provide a liquid crystal display element using the above liquid crystal alignment film.

The liquid crystal alignment agent, which is one aspect of the present invention, contains a polymer, which is one aspect of the present invention, obtained from a diamine derivative (hereinafter sometimes referred to as "diamine") represented by formula (2) and a diisocyanate derivative (hereinafter sometimes referred to as "diisocyanate").

<Diamine used in the present invention>
The diamine used in the present invention is represented by the formula (2).

式中、Ａは脂肪族炭化水素基又は芳香族炭化水素基の、二価の有機基を示し、Ｂ及びＣはそれぞれ独立して、単結合、又は炭素数１～５の脂肪族炭化水素基を示す。Ｒ_１は炭素数１～４のアルキル基を示し、分岐していてもよい。Ｒ_２は水素原子、炭素数１～４の脂肪族炭化水素基、又は式（１－１）で表される有機基を示す。Ｒａ及びＲｂはそれぞれ独立して、水素原子、又は炭素数１～２の脂肪族炭化水素基を示す。

In the formula, A represents a divalent organic group such as an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and B and C each independently represent a single bond or an aliphatic hydrocarbon group having 1 to 5 carbon atoms. _R1 represents an alkyl group having 1 to 4 carbon atoms, which may be branched. _R2 represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms, or an organic group represented by formula (1-1). Ra and Rb each independently represent a hydrogen atom, or an aliphatic hydrocarbon group having 1 to 2 carbon atoms.

From the viewpoints of obtaining a liquid crystal alignment film having excellent polymerization reactivity of the monomer, heat resistance, and liquid crystal alignment properties, etc., it is preferable that in formula (2), A is an aromatic hydrocarbon group, B is an aliphatic hydrocarbon group having 1 to 3 carbon atoms, and C is a single bond. Specific examples of formula (2) include the following structures.

式中、Ａｒはアリーレン基を示し、Ｄは単結合、又は炭素数１～５の炭化水素基を示す。Ｒ_１、Ｒ_２、Ｒａ及びＲｂは上記のＲ_１、Ｒ_２、Ｒａ及びＲｂと同義である。

In the formula, Ar represents an arylene group , and D represents a single bond or a hydrocarbon group having 1 to 5 carbon atoms. R ₁ , R ₂ , Ra, and Rb are each synonymous with R ₁ , R ₂ , Ra, and Rb above.

Considering the viewpoints that a reagent for synthesizing a diamine is easily available, that the reactivity with a diisocyanate is good, that the physical properties of the obtained polymer are good, etc., in formula (3), Ar is preferably a phenylene group , and _R2 is preferably a hydrogen atom. Therefore, formula (3) is preferably a structure represented by the following formula (3-a)'. In particular, in formula (3), it is preferable that Ra and Rb are each a hydrogen atom. Therefore, formula (3) is particularly preferably represented by formula (3-a).

式中、Ｄ及びＲ_１は上記のＤ及びＲ_１と同義である。

In the formula, D and _R1 have the same meanings as D and _R1 above.

From the viewpoints of being able to obtain the desired monomer in an efficient manner and being able to easily obtain all of the above-mentioned properties, the above formula (3-a)' is preferably represented by the following formula (3-1).

式中、Ｂ、Ｒ_１、Ｒａ及びＲｂは上記のＢ、Ｒ_１、Ｒａ及びＲｂと同義である。式（３－１）中、Ｂが炭素数１及び２であり、Ｒａ及びＲｂがそれぞれ水素原子であると、式（３－１）は、式（３－１ａ）及び式（３－１ｂ）で表される。

In the formula, B, R ₁ , Ra, and Rb have the same meanings as B, R ₁ , Ra, and Rb above. In formula (3-1), when B has 1 or 2 carbon atoms and Ra and Rb are each a hydrogen atom, formula (3-1) is represented by formula (3-1a) or formula (3-1b).

式中、Ｒ_１は上記のＲ_１と同義である。

In the formula, R ₁ has the same meaning as R ₁ above.

However, specific examples of the diamine represented by formula (2) are not limited to the diamine represented by formula (3). In synthesizing the above polymer, a part of the diamine represented by formula (2) or formula (3) may be replaced with the diamine represented by formula (5) described below, as long as the effects of the present invention (e.g., the ability to realize a low pretilt angle) are not impaired.

<Diisocyanate used in the present invention>
The diisocyanate used in the present invention is represented by the formula (4).

式中、Ｘは二価の有機基を示す。式（４）は、好ましくは式（４－１）～式（４－１１）及び式（４－１３）で表される。

In the formula, X represents a divalent organic group. Formula (4) is preferably represented by formulas (4-1) to (4-11) and (4-13).

When an aliphatic diisocyanate represented by formula (4-1) to formula (4-5) is used, the resulting polymer dissolves better in a solvent than when an aromatic diisocyanate represented by formula (4-6) to formula (4-13) is used. On the other hand, the aromatic diisocyanate reacts better with diamines than the aliphatic diisocyanates. For example, aromatic diisocyanates such as those represented by formula (4-6) and formula (4-7) react well with diamines, and can improve the heat resistance of the resulting liquid crystal alignment film.

From the viewpoints of being a compound with high versatility for obtaining the above polymer, and of obtaining good properties of the above polymer, etc., formula (4) is preferably formula (4-1), formula (4-7), formula (4-8), formula (4-9), or formula (4-10). Furthermore, from the viewpoint of obtaining good liquid crystal alignment properties of the obtained liquid crystal alignment film, formula (4) is preferably formula (4-13).

However, within the scope of the present invention, formula (4) is not limited to the above. Depending on the target properties of the resulting polymer, liquid crystal alignment agent, liquid crystal alignment film, etc., a diisocyanate that is easily available can be suitably used. Two or more diisocyanates may be used in combination.

<Diamine>
In obtaining the polymer, a part of the diamine represented by formula (2) may be replaced with other diamines (other diamines). In general, there are many kinds of diamines, and many compounds have organic groups with various functions. Therefore, by using other diamines in combination, it may be possible to impart further effects to the polymer or to further improve the effects of the diamine. The ratio of the number of moles of the other diamines to the number of moles of the diamine represented by formula (2) is arbitrary within a range in which the effects of the present invention (e.g., the ability to realize a low pretilt angle) are not impaired. For example, the ratio can be 0.5 or less. Of course, it is not necessary to use other diamines in combination. As such other diamines, for example, diamines represented by the following formula (5) can be mentioned.

式中、Ｙは二価の有機基を示す。Ｙの構造の例は、下式（Ｙ－１）～式（Ｙ－４９）及び式（Ｙ－５７）～式（Ｙ－１７５）のように列挙されるが、これらに限定されない。Ｒ_５はそれぞれ独立して、水素原子、メチル基、又はエチル基を示す。テトラカルボン酸二無水物と、ジアミンと、の反応ではポリアミド酸を与え、ジイソシアネートと、ジアミンと、の反応ではポリウレアを与える。

In the formula, Y represents a divalent organic group. Examples of the structure of Y are listed below as formulae (Y-1) to (Y-49) and formulae (Y-57) to (Y-175), but are not limited thereto. Each _R5 independently represents a hydrogen atom, a methyl group, or an ethyl group. The reaction of a tetracarboxylic dianhydride with a diamine gives a polyamic acid, and the reaction of a diisocyanate with a diamine gives a polyurea.

式中、特に断りのない限り、ｎは１から６の整数である。

In the formula, n is an integer from 1 to 6 unless otherwise specified.

<Polymer>
The term "polyurea and polyurea copolymer" refers to a polymer that is polyurea and/or a polyurea copolymer. Such a polymer is represented by the formula (1).

式中、Ｘはジイソシアネートに由来の二価の有機基を示し、Ｙはジアミンに由来の二価の有機基を示す。Ｒ_１は炭素数１～４のアルキル基を示し、分岐していてもよい。Ｒ_２は、水素原子、炭素数１～４の脂肪族炭化水素基、又は下式（１－１）で表される有機基を示す。Ｒａ及びＲｂはそれぞれ独立して、水素原子、又は炭素数１～２の脂肪族炭化水素基を示す。

In the formula, X represents a divalent organic group derived from a diisocyanate, and Y represents a divalent organic group derived from a diamine. _R1 represents an alkyl group having 1 to 4 carbon atoms, which may be branched. _R2 represents a hydrogen atom, an aliphatic hydrocarbon group having 1 to 4 carbon atoms, or an organic group represented by the following formula (1-1). Ra and Rb each independently represent a hydrogen atom, or an aliphatic hydrocarbon group having 1 to 2 carbon atoms.

式中、黒点は窒素原子への結合箇所を意味し、Ｒ_１、Ｒａ及びＲｂは上記のＲ_１、Ｒａ及びＲｂと同義である。

In the formula, the black dot represents the bonding point to the nitrogen atom, and R ₁ , Ra, and Rb are the same as R ₁ , Ra, and Rb above.

Polyurea forms strong hydrogen bonds due to the polarity of the urea bond sites, so the resulting film has excellent mechanical strength. On the other hand, the strong hydrogen bond strength can cause the polymer to aggregate, which can reduce the stability of the polymer solution (increased viscosity of the polymer solution, partial precipitation of the polymer, gelation of the polymer solution, etc.). Therefore, depending on the structure of the polyurea, the solvents that can be used are limited; for example, it may be necessary to use a solvent with high polarity and high boiling point.

The above polymer has a structure represented by formula (1), that is, a structure in which an organic group represented by formula (1-1) is substituted on the N atom of polyurea. The organic group represented by formula (1-1) inhibits the formation of hydrogen bonds, thereby preventing the aggregation of polymers. This greatly improves the stability of the polymer solution. Therefore, when obtaining a polyurea polymer solution, the range of solvents that can be used can be expanded, which in turn enables baking at low temperatures and greatly improves printability. Note that the urea bond site may form a hydantoin ring or an intermolecular crosslink, depending on the baking temperature during film formation.

<Reaction solution>
The reaction solution (organic solvent used in the reaction to obtain the polymer) is not particularly limited as long as it is a solution in which the polymer can be dissolved. Specific examples thereof include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methylcaprolactam, dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfone, hexamethylsulfoxide, γ-butyrolactone, isopropyl alcohol, methoxymethylpentanol, dipentene, ethyl amyl ketone, methyl nonyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, butyl carbitol, and ethyl carbitol. , ethylene glycol, ethylene glycol monoacetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, propylene glycol, propylene glycol monoacetate, propylene glycol monomethyl ether, propylene glycol-tert-butyl ether, dipropylene glycol monomethyl ether, diethylene glycol, diethylene glycol monoacetate, diethylene glycol dimethyl ether, dipropylene glycol monoacetate monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monoacetate monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoacetate monopropyl ether, 3-methyl-3-methoxybutyl acetate, tripropylene glycol methyl ether, 3-methyl-3-methoxybutanol, diisopropyl ether, ethyl isobutyl ether, diisobutylene, amyl acetate, butyl butyrate, butyl ether, diisobutyl ketone, methylcyclohexene, propyl ether, dihexyl ether, dioxane, n-hexane, n-pentane, n-octane, diethyl ether, cyclohexanone, ethylene carbonate, propylene carbonate Examples of the carboxylic acid include carboxylate, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, diglyme, 4-hydroxy-4-methyl-2-pentanone, 3-methoxy-N,N-dimethylpropanamide, 3-ethoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, and the like. These may be used alone or in combination of two or more. As long as the polymer does not precipitate, it can be mixed with the reaction solution and used even if the solution does not dissolve the polymer.

In addition, since moisture in the reaction solution inhibits the polymerization reaction and further causes hydrolysis of the produced polymer, it is preferable to use a dehydrated and dried reaction solution. When reacting diisocyanate and diamine in a reaction solution, any of the following methods may be used: a reaction solution in which the diamine is dispersed or dissolved is stirred, and the diisocyanate is added as is or dispersed or dissolved in the reaction solution; conversely, the diamine is added to the reaction solution in which the diisocyanate is dispersed or dissolved; or the diisocyanate and diamine are added alternately to the reaction solution.

In addition, when the diisocyanate or diamine is composed of a plurality of compounds, they may be reacted in a premixed state, or may be reacted individually in sequence, or the low molecular weight compounds that have been reacted individually may be mixed and reacted to form a high molecular weight compound. The polymerization temperature in this case can be selected from any temperature between -20°C and 150°C, but is preferably in the range of -5°C to 100°C. In addition, the reaction can be carried out at any concentration, but if the concentration is too low, it becomes difficult to obtain a high molecular weight polymer, and if the concentration is too high, the viscosity of the reaction solution becomes too high, making it difficult to stir uniformly. Therefore, the total concentration of the diisocyanate and diamine in the reaction solution is preferably 1% by mass to 50% by mass, more preferably 5% by mass to 30% by mass. The reaction can be carried out at a high concentration in the early stages, and then the reaction solution can be added.

In the polymerization reaction of polyurea, the ratio of the total number of moles of diisocyanate to the total number of moles of diamine is preferably 0.8 to 1.2. As in a normal polycondensation reaction, the closer this molar ratio is to 1.0, the higher the molecular weight of the polymer produced.

[Polymer recovery]
To recover the polymer produced from the reaction solution, the reaction solution may be poured into a poor solvent to precipitate the polymer. Examples of poor solvents include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, and water. The polymer precipitated by pouring into a poor solvent can be recovered by filtration, and then dried at room temperature or by heating under normal or reduced pressure. In addition, the recovered polymer can be redissolved in an organic solvent, and the reprecipitation and re-recovery operations can be repeated two to ten times to reduce impurities in the polymer. Examples of poor solvents in this case include alcohols, ketones, and hydrocarbons. It is preferable to use three or more poor solvents selected from these because the efficiency of purification is further improved.

The molecular weight of the polymer is preferably 5,000 to 1,000,000, more preferably 10,000 to 150,000, in terms of weight average molecular weight measured by GPC (Gel Permeation Chromatography), taking into consideration the strength of the coating film obtained from the polymer, the ease of work in forming the coating film, the uniformity of the coating film thickness, and the like.

<Liquid crystal alignment agent>
The liquid crystal alignment agent, which is one aspect of the present invention, is a coating liquid for forming a liquid crystal alignment film, and a resin component for forming a coating film (resin film) is dissolved in an organic solvent. The resin component contains at least one of the above polymers. The content of the resin component in the liquid crystal alignment agent is preferably 2% by mass to 20% by mass, more preferably 3% by mass to 15% by mass, and particularly preferably 3% by mass to 10% by mass. In the present invention, the polymers contained in the resin component may all be the above polymers, and may contain other polymers (other polymers) as long as they are within the scope of the purpose of the present invention. The content of the other polymers in the resin component is 0.5% by mass to 15% by mass, preferably 1% by mass to 10% by mass. Examples of such other polymers include acrylic polymers, methacrylic polymers, novolac resins, polyhydroxystyrene, polyimide precursors, polyimides, polyamides, polyesters, cellulose, polysiloxanes, and the like.

The organic solvent used in the liquid crystal alignment agent is not particularly limited as long as it is an organic solvent that dissolves the resin component. Specific examples include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfone, hexamethylsulfoxide, γ-butyrolactone, 3-methoxy-N,N-dimethylpropanamide, 3-ethoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, 1,3-dimethyl-imidazolidinone, ethyl amyl ketone, methyl nonyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, cyclohexanone, ethylene carbonate, propylene carbonate, diglyme, and 4-hydroxy-4-methyl-2-pentanone. These may be used alone or in combination of two or more.

The liquid crystal alignment agent may contain components other than those mentioned above. Examples of such components include solvents or compounds that improve the uniformity of the film thickness or the surface smoothness of the coating film formed by applying the liquid crystal alignment agent, or compounds that improve the adhesion between the liquid crystal alignment film and the substrate.

Solvents (poor solvents) that improve the uniformity of the film thickness and the smoothness of the surface include solvents with low surface tension, such as isopropyl alcohol, methoxymethyl pentanol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, butyl carbitol, ethyl carbitol, ethyl carbitol acetate, ethylene glycol, ethylene glycol monoacetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, propylene glycol, propylene glycol monoacetate, propylene glycol monomethyl ether, and propylene glycol. -tert-butyl ether, dipropylene glycol monomethyl ether, diethylene glycol, diethylene glycol monoacetate, diethylene glycol dimethyl ether, dipropylene glycol monoacetate monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monoacetate monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoacetate monopropyl ether, 3-methyl-3-methoxybutyl acetate, tripropylene glycol methyl ether, 3-methyl-3-methoxybutanol , diisopropyl ether, ethyl isobutyl ether, diisobutylene, amyl acetate, butyl butyrate, butyl ether, diisobutyl ketone, methylcyclohexene, propyl ether, dihexyl ether, 1-hexanol, n-hexane, n-pentane, n-octane, diethyl ether, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, 3- Examples of the poor solvent include propyl methoxypropionate, butyl 3-methoxypropionate, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol, 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether-2-acetate, dipropylene glycol, 2-(2-ethoxypropoxy)propanol, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, and isoamyl lactate. These poor solvents may be used alone or in combination. When the poor solvent is used, it is preferably 5% to 80% by mass, more preferably 20% to 60% by mass, of the total organic solvent contained in the liquid crystal alignment agent.

Compounds that improve the uniformity of the film thickness and the smoothness of the coating surface include fluorine-based surfactants, silicone-based surfactants, and nonionic surfactants. More specifically, for example, EFTOP EF301, EF303, and EF352 (manufactured by Tochem Products), Megafac F171, F173, and R-30 (manufactured by Dainippon Ink Co., Ltd.), Fluorard FC430 and FC431 (manufactured by Sumitomo 3M), Asahiguard AG710, Surflon S-382, SC101, SC102, SC103, SC104, SC105, and SC106 (manufactured by Asahi Glass Co., Ltd.) are included. The proportion of these surfactants used is preferably 0.01 to 2 parts by mass, more preferably 0.01 to 1 part by mass, per 100 parts by mass of the resin component contained in the liquid crystal alignment agent.

Specific examples of compounds that improve the adhesion between the liquid crystal alignment film and the substrate include the following functional silane-containing compounds and epoxy group-containing compounds. For example, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxy ... -aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl-1,4,7-triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate, N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxy Silane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-bis(oxyethylene)-3-aminopropyltrimethoxysilane, N-bis(oxyethylene)-3-aminopropyltriethoxysilane, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether , neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, 1,3,5,6-tetraglycidyl-2,4-hexanediol, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, etc.

Furthermore, in order to improve the adhesion between the substrate and the film and to prevent deterioration of electrical properties caused by irradiation with light from a backlight, the following phenoplast-based additives may be added. Specific phenoplast-based additives are shown below, but are not limited to these structures.

When a compound that improves adhesion between the substrate and the film is used, the amount of the compound used is preferably 0.1 to 30 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of the resin component contained in the liquid crystal alignment agent. If the amount used is less than the above value, it will be difficult to improve adhesion, and if the amount used is more than the above value, the liquid crystal alignment may deteriorate.

In addition to the above-mentioned solvents and compounds, the liquid crystal alignment agent may contain dielectric or conductive substances for the purpose of changing the electrical properties such as the dielectric constant and conductivity of the liquid crystal alignment film, and may also contain specific crosslinking compounds for the purpose of increasing the hardness and density of the film when made into a liquid crystal alignment film, as long as the effects of the present invention are not impaired.

<Liquid crystal alignment film/Liquid crystal display element>
The liquid crystal alignment agent is applied to a substrate and baked, and then an alignment treatment is performed by rubbing or light irradiation, thereby obtaining a liquid crystal alignment film, which is one embodiment of the present invention. As the substrate, a highly transparent glass substrate or a plastic substrate (for example, an acrylic substrate or a polycarbonate substrate) can be used. In addition, it is preferable to use a substrate on which an ITO electrode or the like for driving the liquid crystal is formed, from the viewpoint of simplifying the process of manufacturing a liquid crystal display element. In addition, in a reflective liquid crystal display element, an opaque material such as a silicon wafer can be used as the substrate on one side, and in this case, a material that reflects light such as aluminum can also be used as the electrode. The method of applying the liquid crystal alignment agent is not particularly limited, but in industry, spin coat printing, screen printing, offset printing, flexographic printing, inkjet printing, and the like are generally used. Other application methods include dipping, roll coater, slit coater, spinner, and the like, and these methods may be used depending on the purpose.

The baking can be carried out at 50°C to 300°C, preferably 80°C to 250°C, using a heating means such as a hot plate. A coating film can be formed by evaporating the organic solvent in the liquid crystal alignment agent. If the coating film is too thick, the power consumption of the liquid crystal display element is likely to increase, and if it is too thin, the reliability of the liquid crystal display element may decrease, so the thickness is preferably 5 nm to 300 nm, more preferably 10 nm to 150 nm. When aligning the liquid crystal horizontally or tilted, the coating film after baking is subjected to an alignment treatment such as rubbing or exposure to polarized ultraviolet light.

By the above-mentioned method, a substrate with a liquid crystal alignment film is obtained from the liquid crystal alignment agent, and then a liquid crystal cell is produced by a known method, thereby obtaining a liquid crystal display element, which is one embodiment of the present invention. One example of a method for producing a liquid crystal cell is a method in which a pair of substrates on which a liquid crystal alignment film has been formed are prepared, spacers are sprayed on the liquid crystal alignment film of one substrate, the other substrate is bonded so that the liquid crystal alignment film surface faces inward, and liquid crystal is injected under reduced pressure and sealed. Alternatively, a method in which liquid crystal is dropped onto the liquid crystal alignment film surface on which the spacers have been sprayed, and then the substrates are bonded together to perform sealing is exemplified. The thickness of the spacer in this case is preferably 1 μm to 30 μm, more preferably 2 μm to 10 μm. The liquid crystal display element produced using the liquid crystal alignment agent is highly reliable, and can be suitably used for large-screen, high-definition liquid crystal televisions, etc.

<Synthesis of diamine>
Example 1
Synthesis of ethyl(4-aminobenzyl)glycinate [NG4ABA]

Step 1: 1L 4-neck flask equipped with a nitrogen inlet tube and a reflux tube was charged with 105.6g (0.694mol) of ethyl glycine hydrochloride, 500g of THF, and 93.6g (0.925mol) of triethylamine. The mixture was stirred at room temperature for 1 hour using a mechanical stirrer, then heated at a temperature at which THF refluxes (set at 70°C). 50.0g (0.231mol) of 4-nitrobenzyl bromide was dissolved in 500.0g of THF and slowly dripped into the flask. After dripping, the mixture was allowed to react for another 24 hours. The reaction was terminated when 4-nitrobenzyl bromide disappeared, and the precipitated solid was removed by filtration. The THF was removed by a rotary evaporator, and the resulting crude product was redissolved in 300.0g of ethyl acetate. This solution was washed three times with 100 g of pure water, 300 g of 10% aqueous hydrochloric acid was added, and the mixture was stirred for one hour. The aqueous layer was collected, and the aqueous layer was washed three times with 100 g of ethyl acetate. 300 g of ethyl acetate was further added to the aqueous layer, potassium carbonate was slowly added, the pH was adjusted to about 10, and the mixture was stirred for one hour. The organic phase was collected, and the mixture was washed three times with 100 g of pure water. Anhydrous magnesium sulfate was added to the organic phase to dry it, and the mixture was filtered. Activated carbon was added and the mixture was stirred for a while, after which the activated carbon was removed by filtration, and the solvent was removed by a rotary evaporator to obtain 46.0 g (0.193 mol) of a pale yellow viscous body, which was the target product (nitro form). The fact that the target product was obtained was confirmed by ¹ H-NMR.
^1H NMR (500MHz, _CDCl3 ): δ 8.2(2H), 7.53(2H), 4.22(2H), 3.93(2H), 3.42(2H), 1.89(1H), 1.27(3H).

Step 2: 45.0 g (0.19 mol) of the nitro compound obtained above, 300.0 g of THF, and 4.5 g of iron-doped platinum carbon were added to a 500 ml four-neck flask equipped with a nitrogen inlet tube and a stirrer, and the inside of the container was carefully replaced with a hydrogen atmosphere and reacted at room temperature for 24 hours. The reaction was terminated when the raw material disappeared, the platinum carbon was removed with a membrane filter, activated carbon (Shirasagi) was added to the filtrate, and the mixture was stirred at 40°C for 30 minutes. After that, the mixture was filtered again, the solvent was removed with a rotary evaporator, and the mixture was dried with a high vacuum pump to obtain 35.4 g (0.17 mol: yield 89%) of the target pale yellow viscous material. The fact that the target product (NG4ABA) was obtained was confirmed by ¹ H-NMR.
^1H NMR (500MHz, _CDCl3 ): δ 6.99(2H), 6.63(2H), 4.15(2H), 3.70(2H), 3.38(2H), 3.00(2H), 1.24(3H).

Example 2
Synthesis of ethyl(3-aminobenzyl)glycinate [NG3ABA]

The synthesis was carried out in the same manner as in Example 1, except that the raw material 4-nitrobenzyl bromide was changed to 3-nitrobenzyl bromide. The target product (NG3ABA) was obtained as a pale yellow solid, with a yield of 37.4 g (0.18 mol: 94%). The fact that the target product had been obtained was confirmed by ¹ H-NMR.
^1H NMR (500MHz, _CDCl3 ): δ 7.10 (1H), 6.65 (1H), 6.57 (1H), 4.16 (2H), 3.70 (2H), 3.39 (2H), 3.09 (2H), 1.25 (3H).

Example 3
Synthesis of ethyl(4-aminophenethyl)glycinate [NG4APhA]

Step 1: 50 g (0.246 mol) of 4-nitrophenethylamine hydrochloride, 500 g of THF, and 62.1 g (0.604 mol) of triethylamine were added to a 1 L four-neck flask equipped with a nitrogen inlet tube and a reflux tube, and the mixture was stirred at room temperature for 1 hour using a mechanical stirrer, heated to a temperature at which THF refluxes (set at 70°C), and 25.1 g (0.205 mol) of ethyl 2-chloroacetate was dissolved in 300 g of THF and slowly dropped into the mixture, and after the dropwise addition was completed, the mixture was allowed to react for another 24 hours. The reaction was completed when ethyl 2-chloroacetate disappeared (confirmed by HPLC), the precipitated solid was removed by filtration, THF was removed by a rotary evaporator, and the obtained crude product was redissolved in 500 g of ethyl acetate. This solution was washed three times with 100 g of pure water, 500 g of 10% aqueous hydrochloric acid was added, and the mixture was stirred for one hour. The aqueous layer was collected, and the aqueous layer was washed three times with 100 g of ethyl acetate. 500 g of ethyl acetate was further added to the aqueous layer, potassium carbonate was slowly added, the pH was adjusted to about 10, and the mixture was stirred for one hour. The organic phase was collected, and the mixture was washed three times with 100 g of pure water. Anhydrous magnesium sulfate was added to the organic phase to dry it, and the mixture was filtered. Activated carbon was added and the mixture was stirred for a while, after which the activated carbon was removed by filtration, and the solvent was removed by a rotary evaporator to obtain 34.2 g (0.136 mol: yield 66%) of the target pale yellow viscous substance. It was confirmed by ¹ H-NMR that the target product (nitro body) was obtained.
^1H NMR (500MHz, _CDCl3 ): δ 8.14 (2H), 7.37 (2H), 4.16 (2H), 3.43 (2H), 2.95 (4H), 2.19 (1H), 1.25 (3H).

Step 2: 30.0 g of the nitro compound obtained above, 300 g of THF, and 3.0 g of iron-doped platinum carbon were added to a 500 ml four-neck flask equipped with a nitrogen inlet tube and a stirrer, and the inside of the container was carefully replaced with a hydrogen atmosphere and reacted at room temperature for 24 hours. The reaction was terminated when the raw material disappeared, the platinum carbon was removed with a membrane filter, activated carbon (Shirasagi) was added to the filtrate, and the mixture was stirred at 40°C for 30 minutes. After that, the mixture was filtered again, the solvent was removed with a rotary evaporator, and then dried with a high vacuum pump to obtain 25.1 g (0.113 mol: yield 95%) of a pale yellow viscous material, which is the target product (NG4APhA). The fact that the target product was obtained was confirmed by ¹ H-NMR.
^1H NMR (500MHz, _CDCl3 ): δ 6.99(2H), 6.60(2H), 4.18(2H), 3.42(2H), 2.89(2H), 2.86(2H), 2.75(2H), 1.24(3H).

<Abbreviations>
The abbreviations used in the preparation of the liquid crystal alignment agent are as follows.
(Diisocyanate)
IDI: Isophorone diisocyanate 4IBI: (isocyanatomethyl)phenyl isocyanate DI-3MG: 1,3-bis(4-isocyanatophenoxy)propane DI-2MG: 1,2-bis(4-isocyanatophenoxy)ethane

(Diamine)
NG4ABA: Ethyl (4-aminobenzyl) glycinate NG3ABA: Ethyl (3-aminobenzyl) glycinate NG4APhA: Ethyl (4-aminophenethyl) glycinate Me3ABA: N-methyl-3-aminobenzylamine Me4APhA: N-methyl-4-aminophenethylamine DA-3MG: 1,3-di(4-aminophenoxy)propane

(solvent)
NMP: N-methyl-2-pyrrolidone BCS: Butyl cellosolve GBL: γ-butyrolactone

The conditions for measuring the molecular weight of polyimide are as follows.
Apparatus: Senshu Scientific Co., Ltd. room temperature gel permeation chromatography (GPC) apparatus (SSC-7200)
Column: Shodex column (KD-803, KD-805)
Column temperature: 50 ° C.
Eluent: N,N'-dimethylformamide (additives: lithium bromide hydrate (LiBr.H ₂ O) 30 mmol/L, phosphoric acid anhydrous crystal (o-phosphoric acid) 30 mmol/L, THF 10 ml/L)
Flow rate: 1.0 ml/min. Standard samples for creating calibration curves: TSK standard polyethylene oxide (molecular weights: approximately 9,000,000, 150,000, 100,000, and 30,000) manufactured by Tosoh Corporation, and polyethylene glycol (molecular weights: approximately 12,000, 4,000, and 1,000) manufactured by Polymer Laboratory Co., Ltd.

<Synthesis of Polymer>
Example 4
DI-2MG/NG3ABA
1.00 g (4.80 mmol) of NG3ABA was weighed out into a 50 ml two-neck flask equipped with a nitrogen inlet tube and a stirrer, 13.43 g of NMP was added to dissolve it, 1.37 g (4.60 mmol) of DI-2MG was added, and the mixture was reacted for 24 hours at 40° C. under a nitrogen atmosphere. As a result, a polymer (polymer solution: P-1) with a concentration of 15% by mass and a viscosity of 420 mPas was obtained. The weight average molecular weight of the obtained polymer was Mw: 46,200.

Example 5
DI-2MG/NG4ABA
1.00 g (4.80 mmol) of NG4ABA was weighed out into a 50 ml two-neck flask equipped with a nitrogen inlet tube and a stirrer, 13.32 g of NMP was added to dissolve it, 1.35 g (4.56 mmol) of DI-2MG was added, and the mixture was reacted for 24 hours at 40° C. under a nitrogen atmosphere. As a result, a polymer (polymer solution: P-2) with a concentration of 15% by mass and a viscosity of 370 mPas was obtained. The weight average molecular weight of the obtained polymer was Mw: 39,800.

Example 6
DI-3MG/NG4APhA
1.00 g (4.50 mmol) of NG4APhA was weighed out into a 50 ml two-neck flask equipped with a nitrogen inlet tube and a stirrer, 13.20 g of NMP was added to dissolve it, 1.33 g (4.28 mmol) of DI-3MG was added, and the mixture was reacted for 24 hours at 40° C. under a nitrogen atmosphere. As a result, a polymer (polymer solution: P-3) with a concentration of 15% by mass and a viscosity of 440 mPas was obtained. The weight average molecular weight of the obtained polymer was Mw: 46,300.

Example 7
4IBI/NG4APhA, DA-3MG
NG4APhA 0.50g (2.25mmol) and DA-3MG 0.58g (2.25mmol) were weighed out into a 50ml two-neck flask equipped with a nitrogen inlet tube and a stirrer, NMP 10.48g was added to dissolve, 4IBI 0.77g (4.41mmol) was added, and the mixture was reacted at 40°C for 24 hours under a nitrogen atmosphere. As a result, a polymer (polymer solution: P-4) with a concentration of 15% by mass and a viscosity of 280mPas was obtained. The weight average molecular weight of the obtained polymer was Mw: 37300.

Example 8
IDI, DI-3MG/NG4ABA, DA-3MG
NG4ABA 0.50g (2.40mmol) and DA-3MG 0.62g (2.40mmol) were weighed out into a 50ml two-neck flask equipped with a nitrogen inlet tube and a stirrer, NMP 13.60g was added and dissolved, DI-3MG 0.74g (2.40mmol) and IDI 0.54g (2.42mmol) were added, and the mixture was reacted for 24 hours at 40°C under a nitrogen atmosphere. As a result, a polymer (polymer solution: P-5) with a concentration of 15% by mass and a viscosity of 330mPas was obtained. The weight average molecular weight of the obtained polymer was Mw: 41600.

Comparative Example 1
DI-2MG/Me3ABA
In a 50 ml two-neck flask equipped with a nitrogen inlet tube and a stirrer, 1.00 g (7.34 mmol) of Me3ABA was weighed out, 19.36 g of NMP was added and dissolved, 2.24 g (7.57 mmol) of DI-2MG was added, and the mixture was reacted for 24 hours at 40° C. under a nitrogen atmosphere. As a result, a polymer (polymer solution: PRef-1) with a concentration of 15% by mass and a viscosity of 530 mPas was obtained. The weight average molecular weight of the obtained polymer was Mw: 39,900.

Comparative Example 2
DI-2MG/Me4APhA
In a 50 ml two-neck flask equipped with a nitrogen inlet tube and a stirrer, 1.00 g (6.66 mmol) of Me4APhA was weighed out, 16.38 g of NMP was added and dissolved, 1.89 g (6.39 mmol) of DI-2MG was added, and the mixture was reacted for 24 hours at 40° C. under a nitrogen atmosphere. As a result, a polymer (polymer solution: PRef-2) with a concentration of 15% by mass and a viscosity of 490 mPas was obtained. The weight average molecular weight of the obtained polymer was Mw: 41,300.

<Preparation of Liquid Crystal Alignment Agent>
Example 9
In a 50 ml Erlenmeyer flask equipped with a stirrer, 10.0 g of the polymer (P-1) obtained in Example 4 was weighed out, 2.5 g of NMP, 5.0 g of GBL, and 7.5 g of BCS were added, and the mixture was stirred at room temperature for 30 minutes to obtain a liquid crystal alignment agent (AL-1) having a solid content of 6.0 mass%, NMP 44 mass%, GBL 20 mass%, and BCS 30 mass%.

Example 10
In a 50 ml Erlenmeyer flask equipped with a stirrer, 10.0 g of the polymer (P-2) obtained in Example 5 was weighed out, 2.5 g of NMP, 5.0 g of GBL, and 7.5 g of BCS were added, and the mixture was stirred at room temperature for 30 minutes to obtain a liquid crystal alignment agent (AL-2) having a solid content of 6.0 mass%, NMP 44 mass%, GBL 20 mass%, and BCS 30 mass%.

Example 11
In a 50 ml Erlenmeyer flask equipped with a stirrer, 10.0 g of the polymer (P-3) obtained in Example 6 was weighed out, 2.5 g of NMP, 5.0 g of GBL, and 7.5 g of BCS were added, and the mixture was stirred at room temperature for 30 minutes to obtain a liquid crystal alignment agent (AL-3) having a solid content of 6.0 mass%, NMP 44 mass%, GBL 20 mass%, and BCS 30 mass%.

Example 12
In a 50 ml Erlenmeyer flask equipped with a stirrer, 10.0 g of the polymer (P-4) obtained in Example 7 was weighed out, 2.5 g of NMP, 5.0 g of GBL, and 7.5 g of BCS were added, and the mixture was stirred at room temperature for 30 minutes to obtain a liquid crystal alignment agent (AL-4) having a solid content of 6.0 mass%, NMP 44 mass%, GBL 20 mass%, and BCS 30 mass%.

Example 13
In a 50 ml Erlenmeyer flask equipped with a stirrer, 10.0 g of the polymer (P-5) obtained in Example 8 was weighed out, 2.5 g of NMP, 5.0 g of GBL, and 7.5 g of BCS were added, and the mixture was stirred at room temperature for 30 minutes to obtain a liquid crystal alignment agent (AL-5) having a solid content of 6.0 mass%, NMP 44 mass%, GBL 20 mass%, and BCS 30 mass%.

Comparative Example 3
In a 50 ml Erlenmeyer flask equipped with a stirrer, 10.0 g of the polymer (PRef-1) obtained in Comparative Example 1 was weighed out, 2.5 g of NMP, 5.0 g of GBL, and 7.5 g of BCS were added, and the mixture was stirred at room temperature for 30 minutes to obtain a liquid crystal alignment agent (AL-6) having a solid content of 6.0 mass%, NMP 44 mass%, GBL 20 mass%, and BCS 30 mass%.

Comparative Example 4
In a 50 ml Erlenmeyer flask equipped with a stirrer, 10.0 g of the polymer (PRef-2) obtained in Comparative Example 2 was weighed out, 2.5 g of NMP, 5.0 g of GBL, and 7.5 g of BCS were added, and the mixture was stirred at room temperature for 30 minutes to obtain a liquid crystal alignment agent (AL-7) having a solid content of 6.0 mass%, NMP 44 mass%, GBL 20 mass%, and BCS 30 mass%.

Comparative Example 5
SE-6414 manufactured by Nissan Chemical Industries, Ltd. was used as a liquid crystal alignment agent (AL-8).

The liquid crystal alignment films were evaluated using the liquid crystal alignment agents of Examples 9 to 13 (AL-1 to AL-5) and the liquid crystal alignment agents of Comparative Examples 3 to 5 (AL-6 to AL-8) based on the following method.

<Evaluation of Whitening Resistance and Coatability (Printability)>
A drop of each of the obtained liquid crystal alignment agents was dropped onto a thoroughly washed Cr substrate, and the substrate was left at room temperature of 25° C. and humidity of 60% to measure the time until the substrate turned white (whitened). Based on the measured time, the whitening resistance was evaluated.

The liquid crystal alignment agent was filtered through a 1.0 μm filter, and then flexographic printing was performed on a cleaned Cr plate using an alignment film printer ("Angstromer" manufactured by Nissha Printing Co., Ltd.) to perform a coating test.

Approximately 1.0 ml of liquid crystal alignment agent was dropped onto the anilox roll, and after 10 idle runs, the printer was stopped for 10 minutes and the printing plate was dried. After that, printing was performed on one Cr substrate, and the printed substrate was left on a hot plate at 70°C for 5 minutes to pre-dry the coating film, and the film condition was observed. Film thickness unevenness and film thickness unevenness at edges were mainly observed visually and with an optical microscope (Nikon Corporation "Eclipse ME600") at a magnification of 50x.

<Evaluation of Liquid Crystal Alignment, Voltage Holding Ratio, and Pretilt Angle>
[Observation of Liquid Crystal Alignment and Preparation of Liquid Crystal Cell]
After filtering the liquid crystal alignment agent with a 1.0 μm filter, the liquid crystal alignment agent was applied by spin-coating to a substrate with electrodes (a glass substrate with a size of 30 mm wide x 40 mm long and a thickness of 1.1 mm. The electrodes were rectangular with a width of 10 mm and a length of 40 mm, and were ITO electrodes with a thickness of 35 nm). The substrate was dried on a hot plate at 50° C. for 5 minutes, and then baked in an IR oven at 180° C. for 20 minutes to form a coating film with a thickness of 100 nm. The film was rubbed with a rayon cloth (YA-20R manufactured by Yoshikawa Kako Co., Ltd.) (roller diameter: 120 mm, roller rotation speed: 1000 rpm, moving speed: 20 mm/sec, indentation length: 0.4 mm), and then washed by irradiating ultrasonic waves in pure water for 1 minute, and water droplets were removed by air blowing, and then dried at 80° C. for 15 minutes to obtain a substrate with a liquid crystal alignment film.

Two substrates with the above liquid crystal alignment film were prepared, 4 μm spacers were sprayed onto the liquid crystal alignment film surface of one of them, and then a sealant was printed on top of them. The other substrate was attached with the rubbing direction in the opposite direction and the film surfaces facing each other, and the sealant was cured to create an empty cell. MLC-2041 (manufactured by Merck Ltd.) was injected into this empty cell by the reduced pressure injection method, and the injection port was sealed to obtain a liquid crystal cell. After that, the liquid crystal alignment was observed, and the liquid crystal cell was heated at 110°C for 1 hour and left at 23°C overnight to obtain a liquid crystal cell for measuring the voltage holding ratio.

Using the liquid crystal cell for measuring the voltage retention rate obtained by the above procedure, a voltage of 1 V was applied for 60 μs at a temperature of 60°C, the voltage after 166.7 ms was measured, and the extent to which the voltage was retained was calculated as the voltage retention rate. Note that a VHR-1 voltage retention rate measuring device manufactured by Toyo Corporation was used to measure the voltage retention rate.

[Evaluation of pretilt angle]
The pretilt angle was measured using an Axo Scan Mueller matrix polarimeter manufactured by Optometrics.

[Evaluation of rubbing resistance]
After filtering the liquid crystal alignment agent with a 1.0 μm filter, it was applied by spin-coat printing to a substrate with electrodes (a glass substrate with a size of 30 mm wide x 40 mm long and a thickness of 1.1 mm. The electrode was a rectangle with a width of 10 mm and a length of 40 mm, and an ITO electrode with a thickness of 35 nm). After drying for 5 minutes on a hot plate at 50 ° C., it was baked for 20 minutes in an IR oven at 180 ° C. to form a coating film with a thickness of 100 nm. This film was rubbed with a rayon cloth (YA-20R manufactured by Yoshikawa Kako) (roller diameter: 120 mm, roller rotation speed: 1000 rpm, moving speed: 20 mm / sec, indentation length: 0.4 mm), and then the rubbing resistance was evaluated using a confocal laser microscope. If the film was peeled off, it was marked with ×, if many scrapes or scratches were found on the film, it was marked with △, and if it was good (no peeling of the film was observed and not many scrapes or scratches were observed on the film), it was marked with ○. The results of various evaluations are shown in Table 1.

The liquid crystal alignment agents of Examples 9 to 13 are significantly more resistant to whitening than the comparative examples, and also have good printability. Comparative Example 5 is a polyamic acid-based material, so it is a material system with good whitening resistance and printability. It is expected that Examples 9 to 13 will be able to obtain properties with whitening resistance and printability equal to or better than Comparative Example 5. The organic group represented by formula (1-1) is thought to be consumed in intramolecular reactions and intermolecular crosslinking, so Examples 9 to 13 have very good rubbing resistance compared to Comparative Examples 3 and 4. Comparative Example 5 is thought to have poor rubbing resistance because the imidization reaction does not proceed.

In addition, the liquid crystal cells obtained using the liquid crystal alignment agents of Examples 9 to 13 had a low pretilt angle and a high voltage retention rate. This is believed to be the result of the organic group represented by formula (1-1) being used in various reactions and not being accompanied by a decomposition reaction like polyamic acid. Therefore, the liquid crystal alignment film, which is one aspect of the present invention, is considered to be very promising as a liquid crystal alignment film that can be obtained by baking at a low temperature. It should be noted that, when any of the liquid crystal alignment agents of Examples 7 to 10 was used, a liquid crystal alignment film and a liquid crystal display element could be obtained suitably.

The liquid crystal display element produced using the liquid crystal aligning agent of the present invention can be a highly reliable liquid crystal display device, and can be suitably used as a display element of various types such as an IPS liquid crystal display element and an FFS liquid crystal display element.

Claims (5)

A polymer obtained from a diamino compound represented by the following formula (3-1) and a diisocyanate .

In the formula, _R1 represents an alkyl group having 1 to 4 carbon atoms, which may be branched. B represents a single bond or an aliphatic hydrocarbon group having 1 to 5 carbon atoms. Ra and Rb each independently represent a hydrogen atom or an aliphatic hydrocarbon group having 1 to 2 carbon atoms. The polymer according to claim 1, obtained from the diamino compound and at least one of diisocyanates represented by the following formulas (4-1) to (4-11) and (4-13).

A liquid crystal alignment agent using the polymer described in claim 1 or claim 2. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to claim 3. A liquid crystal display element using the liquid crystal alignment film according to claim 4.