阅读说明：本技术 二胺 (Diamines ) 是由 国见奈穂 永井健太郎 于 2016-03-23 设计创作，主要内容包括：提供一种下式所示的二胺,式中,R<Sub>1</Sub>及R<Sub>2</Sub>各自独立地为单键、-O-、-S-、-NR<Sub>12</Sub>-、酯键、酰胺键、硫酯键、脲键、碳酸酯键、或氨基甲酸酯键,R<Sub>12</Sub>为氢原子或甲基,A为碳数2～20的亚烷基。<Image he="94" wi="700" file="DDA0002581555910000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(A diamine represented by the formula wherein R is 1 And R 2 Each independently a single bond, -O-, -S-, -NR 12 -, ester bond, amide bond, thioester bond, urea bond, carbonate bond, or urethane bond, R 12 Is a hydrogen atom or a methyl group, and A is an alkylene group having 2 to 20 carbon atoms.)

1. A diamine represented by the formula,

in the formula, R₁And R₂Each independently a single bond, -O-, -S-, -NR₁₂-, ester bond, amide bond, thioester bond, urea bond, carbonate bond, or urethane bond, R₁₂Is a hydrogen atom or a methyl group, and A is an alkylene group having 2 to 20 carbon atoms.

Technical Field

The present invention relates to a liquid crystal aligning agent used for producing a liquid crystal display element having excellent afterimage characteristics, a liquid crystal alignment film obtained from the liquid crystal aligning agent, and a liquid crystal display element having the liquid crystal alignment film.

Background

The photo-alignment method is also a simple and industrially advantageous process as a rubbing-free alignment treatment method. In particular, In the liquid crystal display element of the IPS (In-Plane-Switching) driving method or the FFS (Fringe-field-Switching) driving method, by using the liquid crystal alignment film obtained by the above-described photo-alignment method, improvement In contrast and viewing angle characteristics of the liquid crystal display element can be expected as compared with the liquid crystal alignment film obtained by the rubbing treatment method. This can improve the performance of the liquid crystal display element, and has attracted attention as a promising method for liquid crystal alignment treatment.

However, the liquid crystal alignment film obtained by the photo-alignment method has a problem that anisotropy with respect to the alignment direction of the polymer film is smaller than that of the liquid crystal alignment film obtained by rubbing. If the anisotropy is small, sufficient liquid crystal alignment properties cannot be obtained, and there is a problem that image sticking occurs when a liquid crystal display element is manufactured.

On the other hand, as a method for improving the anisotropy of a liquid crystal alignment film obtained by a photo-alignment method, it has been proposed to remove low molecular weight components generated by cleaving the main chain of the polyimide by light irradiation after the light irradiation.

Disclosure of Invention

Problems to be solved by the invention

In the liquid crystal display device of the IPS driving method or the FFS driving method, a positive liquid crystal is used in the past, but by using a negative liquid crystal, a transmission loss at an upper portion of an electrode can be reduced, and contrast can be improved.

When a liquid crystal alignment film obtained by a photo-alignment method is used for a liquid crystal display device of an IPS driving method or an FFS driving method using a negative liquid crystal, it is expected to have higher display performance than a conventional liquid crystal display device. However, as a result of studies, the present inventors have found that when a liquid crystal display element is produced using a so-called photodegradable liquid crystal alignment film in which liquid crystal is aligned by anisotropy due to decomposition of a polymer by light irradiation and a negative liquid crystal, the occurrence rate of display defects (bright spots) due to decomposition products of the polymer constituting the liquid crystal alignment film caused by irradiation with polarized ultraviolet rays is high.

The present invention addresses the problem of providing a liquid crystal aligning agent for obtaining a liquid crystal alignment film for use in a photo-alignment method that can obtain good image sticking characteristics without producing bright spots even when a negative-type liquid crystal is used, a liquid crystal alignment film obtained from the liquid crystal aligning agent, and a liquid crystal display element provided with the liquid crystal alignment film.

Means for solving the problems

The present inventors have conducted extensive studies to solve the above problems, and as a result, the present invention has been completed. That is, the present invention is as follows.

1. A liquid crystal aligning agent contains at least 1 polymer selected from the group consisting of a polyimide precursor having a structure represented by the following formula (1) in the main chain and an imidized polymer of the polyimide precursor.

-B₁-R₁-A-R₂-B₂- (1)

(in the formula, R₁And R₂Each independently a single bond, -O-, -S-, -NR₁₂-, ester bond, amide bond, thioester bond, urea bond, carbonate bond, or urethane bond, R₁₂Is a hydrogen atom or a methyl group. A is an alkylene group having 2 to 20 carbon atoms. B is₁And B₂Each independently is a 2-valent organic radical selected from the following structures, B₁And B₂Not of the same structure. )

(in the formula, R₄Is an alkylene group having 1 to 5 carbon atoms. R₅Is hydrogen atom, methyl, hydroxyl or methoxyl. )

2. The liquid crystal aligning agent according to claim 1, wherein the polyimide precursor is a polymer containing a structural unit represented by the following formula (2).

(in the formula, X₁Is at least 1 selected from the group consisting of the structures represented by the following formulae (X1-1) and (X1-2). Y is₁Is a 2-valent organic group represented by the formula (1). R₃Is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Z₁And Z₂Each independently is a hydrogen atom, or an optionally substituted alkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms or C2 to E10 alkynyl group. )

3. The liquid crystal aligning agent according to claim 2, wherein the polyimide precursor has 20 to 100 mol% of the structural unit represented by the formula (2) with respect to the entire structural units.

4. The liquid crystal aligning agent for photo-alignment according to the above 2 or 3, wherein X₁Is represented by the following formula (X1-2).

5. The liquid crystal aligning agent according to any one of the above 1 to 4, wherein the structure of the formula (1) is as follows.

(in the formula, A, R₁And R₂As defined above. )

6. A liquid crystal alignment film obtained by applying and firing the liquid crystal alignment agent according to any one of the above 1 to 5, and irradiating polarized ultraviolet rays thereto.

7. A liquid crystal display element comprising the liquid crystal alignment film according to claim 6.

8. A diamine represented by the following formula.

(in the formula, R₁And R₂Each independently a single bond, -O-, -S-, -NR₁₂-, ester bond, amide bond, thioester bond, urea bond, carbonate bond, or urethane bond, R₁₂Is a hydrogen atom or a methyl group, and A is an alkylene group having 2 to 20 carbon atoms. )

ADVANTAGEOUS EFFECTS OF INVENTION

By using the liquid crystal aligning agent of the present invention, a liquid crystal alignment film which can suppress generation of a bright point due to a decomposition product derived from the liquid crystal alignment film at the time of photo-alignment treatment, has high irradiation sensitivity, and has excellent liquid crystal alignment properties can be obtained, and a liquid crystal display element having high reliability without display failure can be provided.

The reason why the above-mentioned effects are obtained by using the liquid crystal aligning agent of the present invention is not clear, and it is presumed that the solubility and crystallinity of the decomposition product produced by light irradiation are changed because the diamine used as a raw material of the polymer constituting the liquid crystal aligning agent has a specific asymmetric structure.

Detailed Description

< specific Structure >

The polymer constituting the liquid crystal aligning agent of the present invention contains a specific structure (hereinafter, also referred to as a specific structure) represented by the above formula (1) in the main chain.

-B₁-R₁-A-R₂-B₂- (1)

In the above formula (1), R₁And R₂Each independently a single bond, -O-, -S-, -NR₁₂-, ester bond, amide bond, thioester bond, urea bond, carbonate bond, or urethane bond, R₁₂Is a hydrogen atom or a methyl group. A is an alkylene group having 2 to 20 carbon atoms. B is₁And B₂Each independently is a 2-valent organic radical selected from the following structures, B₁And B₂Not of the same structure. In addition, B is prepared by₁And B₂Since the polymer is not of the same structure, the solubility and crystallinity of the decomposition product produced by light irradiation change, and bright spots derived from the decomposition component of the polymer can be suppressed.

In the above formula, R₄Is an alkylene group having 1 to 5 carbon atoms. R₅Is hydrogen atom, methyl, hydroxyl or methoxyl.

In the formula (1), R is₁、R₂From liquid crystalFrom the viewpoint of orientation, a single bond, -O-, -S-, -NR is preferable₁₂-, an ester bond or an amide bond, particularly preferably-O-. In addition, A is preferably an alkylene group having a carbon chain of 2 to 6, particularly preferably an alkylene group having a carbon chain of 2 to 4, from the viewpoint of liquid crystal alignment properties.

In the above formula, R₄The alkylene group having 1 to 3 carbon atoms is preferable from the viewpoint of liquid crystal alignment properties. R₅From the viewpoint of liquid crystal alignment properties, a hydrogen atom or a methyl group is preferable.

The above-mentioned specific structure is preferably contained in diamine which is a raw material of the polyimide precursor. Specific examples of the diamine having the above-mentioned specific structure include, but are not limited to, the following diamines.

(R₅As defined above. )

In the above formula, for R₅And R₁₂The same as defined above, including preferred examples thereof.

Among them, the diamine having the above-mentioned specific structure is preferably a diamine having the following structure from the viewpoint of the alignment and the reduction of a bright point when the liquid crystal display element is produced.

In the above formula, R₁、R₂And A are as described above including preferred examples thereof. As the diamine having the above-mentioned specific structure, the following diamines are particularly preferable.

< Synthesis of diamine >

The main synthesis method of the diamine is described in detail below. The method described below is an example, and is not limited to this.

The diamine of the present invention is obtained by reducing a dinitro compound to convert a nitro group into an amino group as shown in the following reaction formula. In the following reaction formula, diamines described in examples are described as 1 example.

The method for reducing the dinitro compound is not particularly limited, and the following methods can be exemplified: a method of using palladium-carbon, platinum oxide, raney nickel, platinum black, rhodium-alumina, platinum sulfide carbon, or the like as a catalyst, and reducing the catalyst in a solvent such as ethyl acetate, toluene, tetrahydrofuran, dioxane, alcohols, or the like with hydrogen gas, hydrazine, hydrogen chloride, or the like. If necessary, the reaction may be carried out under pressure using an autoclave or the like. On the other hand, when the structure of the substituent group substituted for the hydrogen atom of the benzene ring or the saturated hydrocarbon moiety contains an unsaturated bond site, if palladium carbon, platinum carbon or the like is used, the unsaturated bond site may be reduced to become a saturated bond. Therefore, it is preferable to use a reduction condition in which a transition metal such as reduced iron, tin chloride, or the like is used as a catalyst.

In the synthesis of a dinitro compound, a commercially available biphenyl derivative is reacted with nitrobenzene substituted with a leaving group X such as halogen, as shown in the following reaction formula, to obtain the dinitro compound. Preferred leaving groups X include: fluorine atom, chlorine atom, bromine atom, iodine atom, p-toluenesulfonate (-OTs), methanesulfonate (-OMs), etc.

The above reaction may be carried out in the presence of a base. The base to be used is not particularly limited as long as it can be synthesized, and examples thereof include inorganic bases such as potassium carbonate, sodium carbonate, cesium carbonate, sodium alkoxide, potassium alkoxide, sodium hydroxide, potassium hydroxide, and sodium hydride, and organic bases such as pyridine, dimethylaminopyridine, trimethylamine, triethylamine, and tributylamine. In addition, when a palladium catalyst such as palladium dibenzylideneacetone or palladium diphenylphosphinoferrocene, a copper catalyst, or the like is used in combination, the yield can be improved. The method using potassium carbonate is preferred from the viewpoint of ease of synthesis, but the synthesis method is not particularly limited since synthesis can be performed by a method other than this method.

< polymers >

The polyimide precursor constituting the liquid crystal aligning agent of the present invention contains a structural unit represented by the following formula (2).

X₁Is at least 1 selected from the group consisting of the structures represented by the following formulae (X1-1) and (X1-2). Among them, the following formula (X1-2) is preferable from the viewpoint of liquid crystal alignment properties.

Y₁Is a 2-valent organic group represented by the formula (1).

R₃Is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Specific examples thereof include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, and n-pentyl groups. From the viewpoint of easiness of imidation by heating, R₃Preferably a hydrogen atom or a methyl group.

Z₁And Z₂Each independently represents a hydrogen atom, or an optionally substituted alkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms or alkynyl group having 2 to 10 carbon atoms. Specific examples of the alkyl group include methyl, ethyl, propyl, butyl, tert-butyl, hexyl, octyl, decyl, cyclopentyl, cyclohexyl, dicyclohexyl, and the like. Examples of the alkenyl group include 1 or more CH groups present in the above alkyl group₂-CH₂Group having structure substituted by CH ═ CH structure. Specific examples thereof include vinyl, allyl, 1-propenyl, isopropenyl, 2-butenyl, 1, 3-butadienyl, 2-pentenyl, 2-hexenyl, cyclopropenyl, cyclopentenyl and cyclohexenyl. Examples of the alkynyl group include 1 or more CH groups present in the above-mentioned alkyl group₂-CH₂The structure is replaced by a group having a C ≡ C structure. Specific examples thereof include ethynyl, 1-propynyl and 2-propynyl.

The alkyl group, the alkenyl group, and the alkynyl group may have a substituent, and may further form a ring structure through the substituent. The ring structure formed by the substituents means that the substituents are bonded to each other or a part of the parent skeleton to form a ring structure.

Examples of the substituent include a halogen group, a hydroxyl group, a thiol group, a nitro group, an aryl group, an organooxy group, an organothio group, an organosilyl group, an acyl group, an ester group, a thioester group, a phosphate group, an amide group, an alkyl group, an alkenyl group, and an alkynyl group.

Examples of the halogen group include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

As the aryl group, a phenyl group is exemplified. The aryl group may be further substituted with the other substituents described above.

The organic oxy group may have a structure represented by O-R. The R is optionally the same or different, and may be exemplified by the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. These R may be further substituted with the aforementioned substituent. Specific examples thereof include: methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, and the like.

As the organic thio group, a structure represented by-S-R may be shown. Examples of the R include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. These R may be further substituted with the aforementioned substituents. Specific examples thereof include methylthio, ethylthio, propylthio, butylthio, pentylthio, hexylthio, heptylthio and octylthio.

As the organosilyl group, there may be mentioned-Si- (R)₃The structure shown. The R's are optionally the same or different and may be exemplifiedThe aforementioned alkyl, alkenyl, alkynyl, aryl, and the like are shown. These R may be further substituted with the aforementioned substituents. Specific examples thereof include trimethylsilyl, triethylsilyl, tripropylsilyl, tributylsilyl, tripentylsilyl, trihexylsilyl, pentyldimethylsilyl, and hexyldimethylsilyl groups.

The acyl group may have a structure represented by-C (O) -R. Examples of the R include the aforementioned alkyl group, alkenyl group, aryl group, and the like. These R may be further substituted with the aforementioned substituents. Specific examples thereof include formyl, acetyl, propionyl, butyryl, isobutyryl, valeryl, isovaleryl, benzoyl and the like.

The ester group may have a structure represented by-C (O) O-R or-OC (O) R. Examples of the R include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. These R may be further substituted with the aforementioned substituents.

The thioester group may have a structure represented by-C (S) O-R or-OC (S) -R. Examples of the R include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. These R may be further substituted with the aforementioned substituents.

As the phosphate group, there may be mentioned-OP (O) - (OR)₂The structure shown. The R is optionally the same or different, and may be exemplified by the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. These R may be further substituted with the aforementioned substituents.

As the amide group, there may be mentioned-C (O) NH₂or-C (O) NHR, -NHC (O) R, -C (O) N (R)₂-NRC (O) R. The R is optionally the same or different, and may be exemplified by the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. These R may be further substituted with the aforementioned substituents.

Examples of the aryl group include the same groups as those described above. The aryl group may be further substituted with the other substituents described above.

Examples of the alkyl group include the same groups as those mentioned above. The alkyl group may be further substituted with the other substituents described above.

Examples of the alkenyl group include the same groups as those described above. The alkenyl group may be further substituted with the aforementioned other substituents.

Examples of the alkynyl group include the same groups as those described above. The alkynyl group may be further substituted with the other substituents described above.

In general, when a bulky structure is introduced, the reactivity of amino groups and the liquid crystal alignment properties may be lowered, and therefore, Z is a structure₁And Z₂More preferred is a hydrogen atom or an optionally substituted alkyl group having 1 to 5 carbon atoms, and particularly preferred is a hydrogen atom, a methyl group or an ethyl group.

The structural unit represented by the formula (2) is preferably 20 to 100 mol% based on the total structural units, and particularly preferably 30 to 100 mol% from the viewpoint of liquid crystal alignment properties.

< other structural units >

When the polymer constituting the liquid crystal aligning agent of the present invention contains a structural unit other than the structural unit of the above formula (2), the structural unit is represented by the following formula (3).

R₃、Z₁And Z₂The definition of (3) is the same as that of the above formula (2).

X₂Is a 4-valent organic radical, Y₂Is a 2-valent organic group.

X₂The organic group having a valence of 4 derived from a tetracarboxylic acid derivative, and the structure thereof is not particularly limited. In the polyimide precursor, X₂More than 2 species may be present in combination. If X is shown₂Specific examples of (A) include the following formulae (X-1) to (X-44).

R in the above formula (X-1)₈～R₁₁Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms or a phenyl group. R₈～R₁₁In the case of a bulky structure, since there is a possibility that the liquid crystal alignment property is lowered, a hydrogen atom, a methyl group, or an ethyl group is more preferable, and a hydrogen atom or a methyl group is particularly preferable.

In the formula (3), Y₂The diamine-derived organic group has a valence of 2, and the structure thereof is not particularly limited. If it shows Y₂Specific examples of the structure of (A) include the following (Y-1) to (Y-118).

(in the formula (Y-109), m and n are each independently an integer of 1 to 11, m + n is an integer of 2 to 12, in the formula (Y-114), h is an integer of 1 to 3, and in the formulae (Y-111) and (Y-117), j is an integer of 0 to 3.)

The polyimide precursor used in the present invention is obtained by the reaction of a diamine component and a tetracarboxylic acid derivative, and examples thereof include polyamic acids and polyamic acid esters.

< polyimide precursor (Polyamic acid) >

The polyamic acid as a polyimide precursor used in the present invention is produced by the following method.

Specifically, the diamine can be synthesized by reacting tetracarboxylic dianhydride with diamine in the presence of an organic solvent at-20 to 150 ℃, preferably 0 to 50 ℃, for 30 minutes to 24 hours, preferably 1 to 12 hours.

The reaction of the diamine component with the tetracarboxylic acid component is usually carried out in an organic solvent. The organic solvent used in this case is not particularly limited as long as the polyimide precursor to be produced is dissolved. Specific examples of the organic solvent used in the reaction are given below, but the organic solvent is not limited to these examples. Examples thereof include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ -butyrolactone, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide and 1, 3-dimethylimidazolidinone.

When the polyimide precursor has high solubility, an organic solvent represented by methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or the following formulas [ D-1] to [ D-3] may be used.

Formula [ D-1]In (D)¹Represents an alkyl group having 1 to 3 carbon atoms of the formula [ D-2 ]]In (D)²Represents an alkyl group having 1 to 3 carbon atoms, formula [ D-3]]In (D)³Represents an alkyl group having 1 to 4 carbon atoms.

These solvents may be used alone or in combination. Further, even if the solvent does not dissolve the polyimide precursor, the solvent may be mixed with the polyimide precursor to be used in a range where the polyimide precursor to be produced does not precipitate. Further, since the moisture in the solvent inhibits the polymerization reaction and hydrolyzes the polyimide precursor produced, it is preferable to use a solvent which has been dehydrated and dried.

The concentration of the polyamic acid polymer in the reaction system is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, because precipitation of the polymer is not likely to occur and a high molecular weight product is easily obtained.

The polyamic acid obtained as described above can be recovered by pouring the reaction solution into a poor solvent while sufficiently stirring the reaction solution to precipitate a polymer. Further, the powder of the purified polyamic acid can be obtained by performing precipitation a plurality of times, washing with a poor solvent, and drying at normal temperature or under heating. The poor solvent is not particularly limited, and examples thereof include water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene, and the like.

< polyimide precursor (polyamic acid ester) >

The polyamic acid ester as a polyimide precursor used in the present invention can be produced by the following production method (1), (2) or (3).

(1) In the case of production from polyamic acid

The polyamic acid ester can be produced by esterifying the polyamic acid produced as described above. Specifically, the polyamic acid can be produced by reacting a polyamic acid with an esterifying agent in the presence of an organic solvent at-20 to 150 ℃ and preferably 0 to 50 ℃ for 30 minutes to 24 hours, preferably 1 to 4 hours.

As the esterification agent, preferred can be through purification easily removed esterification agent, can be cited, N-two methyl formamide two methyl acetal, N-two methyl formamide two ethyl acetal, N-two methyl formamide two propyl acetal, N-two methyl formamide two neopentyl butyl acetal, N-two methyl formamide two tert butyl acetal, 1-methyl-3-p-tolyl three nitrogen alkene, 1-ethyl-3-p-tolyl three nitrogen alkene, 1-propyl-3-p-tolyl three nitrogen alkene, chloride 4- (4, 6-two methoxy-1, 3, 5-three triazine-2-yl) -4-methyl morpholine. The amount of the esterifying agent added is preferably 2 to 6 molar equivalents based on 1 mole of the repeating unit of the polyamic acid.

Examples of the organic solvent include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ -butyrolactone, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, and 1, 3-dimethylimidazolidinone. When the polyimide precursor has high solubility in the solvent, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or the solvents represented by the formulae [ D-1] to [ D-3] may be used.

These solvents may be used alone or in combination. Further, even if the solvent does not dissolve the polyimide precursor, the solvent may be mixed with the polyimide precursor to be used in a range where the polyimide precursor to be produced does not precipitate. Further, since the moisture in the solvent inhibits the polymerization reaction and hydrolyzes the polyimide precursor produced, it is preferable to use a solvent which has been dehydrated and dried.

The solvent used in the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone or γ -butyrolactone from the viewpoint of the solubility of the polymer, and 1 kind or 2 or more kinds mixed may be used. The concentration in the production is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, because precipitation of the polymer hardly occurs and a high molecular weight product is easily obtained.

(2) In the case of production by reaction of a tetracarboxylic acid diester dichloride with a diamine

The polyamic acid ester can be made from a tetracarboxylic acid diester dichloride and a diamine.

Specifically, the reaction can be carried out by reacting a tetracarboxylic acid diester dichloride with a diamine in the presence of a base and an organic solvent at-20 to 150 ℃, preferably 0 to 50 ℃, for 30 minutes to 24 hours, preferably 1 to 4 hours.

As the base, pyridine, triethylamine, 4-dimethylaminopyridine and the like can be used, and pyridine is preferable in order to allow the reaction to proceed mildly. The amount of the base to be added is preferably 2 to 4 times by mol based on the tetracarboxylic acid diester dichloride, because the base is easily removed and a high molecular weight product is easily obtained.

The solvent used in the above reaction is preferably N-methyl-2-pyrrolidone or γ -butyrolactone, from the viewpoint of the solubility of the monomer and the polymer, and 1 kind or 2 or more kinds mixed may be used. The polymer concentration during production is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, because precipitation of the polymer is not likely to occur and a high molecular weight product is easily obtained. In order to prevent hydrolysis of the tetracarboxylic acid diester dichloride, the solvent used for producing the polyamic acid ester is preferably dehydrated as much as possible, and the mixing of the external gas is preferably prevented in a nitrogen atmosphere.

(3) In the case of a preparation from a tetracarboxylic diester and a diamine

The polyamic acid ester can be produced by polycondensing a tetracarboxylic acid diester and a diamine.

Specifically, the tetracarboxylic acid diester can be produced by reacting a tetracarboxylic acid diester with a diamine in the presence of a condensing agent, a base and an organic solvent at 0 to 150 ℃, preferably 0 to 100 ℃, for 30 minutes to 24 hours, preferably 3 to 15 hours.

As the condensing agent, triphenyl phosphite, dicyclohexylcarbodiimide, 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride, N, N ' -carbonyldiimidazole, dimethoxy-1, 3, 5-triazinylmethyl morpholinium, O- (benzotriazol-1-yl) -N, N, N ', N ' -tetramethyluronium tetrafluoroborate, O- (benzotriazol-1-yl) -N, N, N ', N ' -tetramethyluronium hexafluorophosphate, (2, 3-dihydro-2-thione-3-benzoxazolyl) diphenyl phosphonate, and the like can be used. The amount of the condensing agent to be added is preferably 2 to 3 times by mol based on the tetracarboxylic acid diester.

As the base, tertiary amines such as pyridine and triethylamine can be used. The amount of the base to be added is preferably 2 to 4 times by mole relative to the diamine component, from the viewpoint of easy removal and easy availability of a high molecular weight material.

In addition, in the above reaction, the reaction is efficiently performed by adding a lewis acid as an additive. As the lewis acid, lithium halide such as lithium chloride or lithium bromide is preferable. The amount of the Lewis acid added is preferably 0 to 1.0 mol per mol of the diamine component.

Among the above-mentioned 3 methods for producing polyamic acid esters, the above-mentioned method (1) or (2) is particularly preferable in order to obtain a polyamic acid ester having a high molecular weight.

The solution of the polyamic acid ester obtained as described above can be poured into a poor solvent while sufficiently stirring to precipitate a polymer. The polyamic acid ester is precipitated several times, washed with a poor solvent, and dried at room temperature or under heating to obtain a purified polyamic acid ester powder. The poor solvent is not particularly limited, and examples thereof include water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene, and the like.

< polyimide >

The polyimide used in the present invention can be produced by imidizing the polyamic acid ester or polyamic acid.

In the case of producing a polyimide from a polyamic acid ester, chemical imidization by adding a basic catalyst to a polyamic acid ester solution or a polyamic acid solution obtained by dissolving a polyamic acid ester resin powder in an organic solvent is simple. Chemical imidization is preferred because the imidization reaction proceeds at a relatively low temperature and the molecular weight of the polymer is not easily reduced during the imidization.

The chemical imidization can be carried out by stirring the polyamic acid ester to be imidized in an organic solvent in the presence of a basic catalyst. As the organic solvent, a solvent used in the above polymerization reaction can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among them, triethylamine is preferred because it has a basicity sufficient for the reaction to proceed.

The temperature for the imidization is-20 to 140 ℃ and preferably 0 to 100 ℃, and the reaction time is preferably 1 to 100 hours. The amount of the basic catalyst is 0.5 to 30 mol times, preferably 2 to 20 mol times, the amount of the amide ester group. The imidization ratio of the obtained polymer can be controlled by adjusting the amount of the catalyst, the temperature, the reaction time, and the like. Since the added catalyst and the like remain in the solution after the imidization reaction, it is preferable that the obtained imidized polymer is recovered by the following method and redissolved with an organic solvent to prepare the liquid crystal aligning agent of the present invention.

In the case of producing a polyimide from a polyamic acid, chemical imidization by adding a catalyst to a solution of a polyamic acid obtained by the reaction of a diamine component and a tetracarboxylic dianhydride is simple. Chemical imidization is preferred because the imidization reaction proceeds at a relatively low temperature and the molecular weight of the polymer is less likely to decrease during the imidization.

Chemical imidization can be performed by stirring the polyamic acid to be imidized in an organic solvent in the presence of a basic catalyst and an acid anhydride. As the organic solvent, a solvent used in the above polymerization reaction can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among them, pyridine is preferable because it has a suitable basicity for advancing the reaction. Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. Among these, acetic anhydride is preferred because purification after completion of the reaction is easy.

The temperature for the imidization is-20 to 140 ℃ and preferably 0 to 100 ℃, and the reaction time is preferably 1 to 100 hours. The amount of the basic catalyst is 0.5 to 30 times, preferably 2 to 20 times, the amount of the acid anhydride is 1 to 50 times, preferably 3 to 30 times, the amount of the acid amide group. The imidization ratio of the obtained polymer can be controlled by adjusting the amount of the catalyst, the temperature, the reaction time, and the like.

Since the catalyst to be added remains in the polyamic acid ester or the solution after the imidization of the polyamic acid, it is preferable to recover the obtained imidized polymer by the following method and redissolve it in an organic solvent to obtain the liquid crystal aligning agent of the present invention.

The solution of the polyimide obtained as described above can be poured into a poor solvent while sufficiently stirring the solution to precipitate a polymer. The polyimide is precipitated several times, washed with a poor solvent, and dried at room temperature or under heating to obtain a purified polyimide powder.

The poor solvent is not particularly limited, and examples thereof include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, and benzene.

< liquid Crystal alignment agent >

The liquid crystal aligning agent of the present invention contains at least 1 polymer selected from the group consisting of a polyimide precursor having a specific structure in the main chain and an imidized polymer of the polyimide precursor. The molecular weight of the polymer is preferably 2000 to 500000, more preferably 5000 to 300000, and further preferably 10000 to 100000 in terms of weight average molecular weight (Mw). The number average molecular weight (Mn) is preferably 1000 to 250000, more preferably 2500 to 150000, and further preferably 5000 to 50000.

The concentration of the polymer in the liquid crystal aligning agent of the present invention may be appropriately changed depending on the setting of the thickness of the coating film to be formed, and is preferably 1 mass% or more in terms of forming a uniform and defect-free coating film, and is preferably 10 mass% or less in terms of the storage stability of the solution. The concentration of the polymer is preferably 2 to 7 mass%.

The organic solvent (hereinafter, also referred to as a good solvent) for dissolving the polymer contained in the liquid crystal aligning agent used in the present invention is not particularly limited as long as the polymer is uniformly dissolved.

Examples thereof include N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ -butyrolactone, 1, 3-dimethylimidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, and 4-hydroxy-4-methyl-2-pentanone. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ -butyrolactone is preferably used.

Furthermore, when the polymer of the present invention has high solubility in a solvent, it is preferable to use solvents represented by the above-mentioned formulae [ D-1] to [ D-3 ].

The content of the good solvent in the liquid crystal aligning agent of the present invention is preferably 20 to 99% by mass of the total solvent contained in the liquid crystal aligning agent. Among them, 20 to 90% by mass is preferable. More preferably 30 to 80 mass%.

The liquid crystal aligning agent of the present invention may be a solvent (also referred to as a poor solvent) which improves the film coatability and surface smoothness of the liquid crystal alignment film when the liquid crystal aligning agent is applied, as long as the effects of the present invention are not impaired. Specific examples of the poor solvent are given below, but the poor solvent is not limited to these examples.

For example, ethanol, isopropanol, 1-butanol, 2-butanol, isobutanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentanol, t-pentanol, 3-methyl-2-butanol, neopentanol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-ethyl-1-hexanol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1, 2-ethanediol, 1, 2-propanediol, isobutanol, 2-pentanol, 2-methyl-1-pentanol, 2-methyl, 1, 3-propanediol, 1, 2-butanediol, 1, 3-butanediol, 1, 4-butanediol, 2, 3-butanediol, 1, 5-pentanediol, 2-methyl-2, 4-pentanediol, 2-ethyl-1, 3-hexanediol, dipropyl ether, dibutyl ether, dihexyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1, 2-butoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 2-pentanone, 3-pentanone, 2-hexanone, 2-heptanone, 4-heptanone, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethyl-2-ethylhexyl acetate, Ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, 2- (methoxymethoxy) ethanol, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, 2- (hexyloxy) ethanol, furfuryl alcohol, diethylene glycol, propylene glycol monobutyl ether, 1- (butoxyethoxy) propanol, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2- (2-ethoxyethoxy) ethyl acetate, diethylene glycol acetate, propylene glycol monobutyl ether acetate, propylene glycol mono-hexyl ether, 2- (hexyloxy) ethanol, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl 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, propyl 3-methoxypropionate, butyl 3-methoxypropionate, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate, and solvents represented by the formulae [ D-1] to [ D-3 ].

Of these, 1-hexanol, cyclohexanol, 1, 2-ethylene glycol, 1, 2-propylene glycol, propylene glycol monobutyl ether, ethylene glycol monobutyl ether, or dipropylene glycol dimethyl ether are preferable.

The content of the poor solvent is preferably 1 to 80% by mass of the total solvent contained in the liquid crystal aligning agent. Among them, the amount is preferably 10 to 80% by mass, more preferably 20 to 70% by mass.

In addition to the above components, the liquid crystal alignment agent of the present invention may further contain a polymer other than the polymer described in the present invention, a dielectric or conductive substance for changing electric characteristics such as dielectric constant, conductivity, and the like of the liquid crystal alignment film, a silane coupling agent for improving adhesion between the liquid crystal alignment film and a substrate, a crosslinkable compound for improving hardness and density of the film when the liquid crystal alignment film is formed, an imidization accelerator for efficiently imidizing a polyimide precursor by heating when the film is fired, and the like, within a range in which the effects of the present invention are not impaired.

< liquid Crystal alignment film >

The liquid crystal alignment film of the present invention is obtained by coating the liquid crystal alignment agent on a substrate, drying, and firing. The substrate to which the liquid crystal aligning agent of the present invention is applied is not particularly limited as long as it is a substrate having high transparency, and a plastic substrate such as a glass substrate, a silicon nitride substrate, an acrylic substrate, or a polycarbonate substrate can be used. In the case of the reflective liquid crystal display element, if the substrate is a single-sided substrate, an opaque material such as a silicon wafer may be used, and in this case, a material that reflects light such as aluminum may be used for the electrodes.

Examples of the method for applying the liquid crystal aligning agent of the present invention include spin coating, printing, and ink jet.

The drying and firing steps after the application of the liquid crystal aligning agent can be performed at any temperature and for any time. Generally, in order to sufficiently remove the organic solvent contained therein, the drying temperature is preferably 50 to 120 ℃, and the drying time is preferably 1 to 10 minutes. The firing temperature is preferably 150 to 300 ℃ and the firing time is preferably 5 to 120 minutes.

The thickness of the film after firing is not particularly limited, but if it is too thin, the reliability of the liquid crystal display element may be impaired, and therefore, it is preferably 5 to 300nm, more preferably 10 to 120 nm.

Examples of the method of photo-alignment treatment of the liquid crystal alignment film include the following methods: irradiating the surface of the coating film with a radiation beam deflected in a fixed direction, and optionally further heating the coating film at a temperature of 150 to 250 ℃ to impart liquid crystal alignment energy. As the radiation ray, ultraviolet rays and visible rays having a wavelength of 100 to 800nm can be used. Among them, ultraviolet rays having a wavelength of 100 to 400nm are preferable, and a wavelength of 200 to 400nm is particularly preferable. In addition, in order to improve the liquid crystal alignment, the coated substrate may be heated at 50 to 250 ℃ and irradiated with radiation. The irradiation dose of the radiation is preferably 1 to 10000mJ/cm²Particularly preferably 100 to 5000mJ/cm². The liquid crystal alignment film manufactured as described above can stably align liquid crystal molecules in a fixed direction.

In order to impart higher anisotropy, higher extinction ratio of polarized ultraviolet rays is more preferable. Specifically, the extinction ratio of ultraviolet rays polarized along a straight line is preferably 10: 1 or more, more preferably 20: 1 or more.

The film irradiated with polarized radiation may then be subjected to contact treatment with a solvent containing at least 1 selected from water and organic solvents.

The solvent used in the contact treatment is not particularly limited as long as it dissolves the decomposition product generated by the light irradiation. Specific examples thereof include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, and cyclohexyl acetate. These solvents may be used in combination of 2 or more. From the viewpoint of versatility and safety, at least 1 selected from the group consisting of water, 2-propanol, 1-methoxy-2-propanol, and ethyl lactate is more preferable. Water, 2-propanol, or a mixed solvent of water and 2-propanol is particularly preferable.

In the present invention, the contact treatment of the film irradiated with polarized radiation and the solution containing an organic solvent includes immersion treatment, spray (spray) treatment, and the like, and preferably such treatment that the film is brought into sufficient contact with a liquid. Among these, a method of immersing the film in a solution containing an organic solvent for preferably 10 seconds to 1 hour, more preferably 1 to 30 minutes is preferable. The contact treatment may be carried out at room temperature or by heating, and is preferably carried out at 10 to 80 ℃ and more preferably at 20 to 50 ℃. Further, if necessary, a method of improving the contact such as ultrasonic waves may be performed.

After the contact treatment, either washing (rinse) with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, or drying may be performed, or both may be performed, in order to remove the organic solvent in the solution used.

Further, the film subjected to the contact treatment with the solvent may be heated at 150 ℃ or higher for the purpose of drying the solvent and reorienting the molecular chains in the film. The heating temperature is preferably 150 to 300 ℃. Although the higher the temperature, the more the molecular chain is reoriented, the higher the temperature, the more the molecular chain is decomposed. Therefore, the heating temperature is more preferably 180 to 250 ℃, particularly preferably 200 to 230 ℃.

If the heating time is too short, the effect of reorienting the molecular chains may not be obtained, and if it is too long, the molecular chains may be decomposed, and therefore, it is preferably 10 seconds to 30 minutes, more preferably 1 to 10 minutes.

< liquid Crystal display element >

The liquid crystal display element of the present invention is produced by preparing a liquid crystal cell by a known method after obtaining a substrate having a liquid crystal alignment film formed from the liquid crystal aligning agent of the present invention, and using the cell.

As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described below as an example. Note that the liquid crystal display element may be an active matrix liquid crystal display element in which a switching element such as a TFT (Thin Film Transistor) is provided in each pixel portion constituting image display.

First, a transparent glass substrate is prepared, a common electrode is provided on one substrate, and segment electrodes are provided on the other substrate. These electrodes may be, for example, ITO electrodes and patterned in such a way as to form the desired image display. Next, an insulating film is provided on each substrate so as to cover the common electrode and the segment electrode. The insulating film may be, for example, SiO formed by a sol-gel method₂-TiO₂The film formed.

Next, the liquid crystal alignment film of the present invention is formed on each substrate. Next, one substrate and the other substrate are stacked so that the alignment film surfaces thereof face each other, and the periphery is bonded with a sealing material. In order to control the substrate gap, it is preferable to mix a spacer into the sealing material. Further, it is preferable that spacers for controlling the substrate gap are dispersed in advance also in the surface portion where the sealing material is not provided. In addition, an opening portion into which liquid crystal can be filled from the outside is usually provided in a part of the sealing material.

Next, a liquid crystal material was injected into the space surrounded by the 2 substrates and the sealing material through the opening provided in the sealing material. Then, the opening is sealed with an adhesive. For the injection, a vacuum injection method may be used, or a method using a capillary phenomenon in the atmosphere may be used. Next, a polarizing plate is provided. Specifically, a pair of polarizing plates was attached to the surfaces of the 2 substrates opposite to the liquid crystal layer. Through the above steps, the liquid crystal display element of the present invention is obtained.

In the present invention, as the sealing agent, for example, a resin having a reactive group such as an epoxy group, an acryloyl group, a methacryloyl group, a hydroxyl group, an allyl group, or an acetyl group, which is cured by ultraviolet irradiation or heating, is used. Particularly, curable resins having both reactive groups of an epoxy group and a (meth) acryloyl group are preferably used.

The sealant may contain an inorganic filler for the purpose of improving adhesiveness, moisture resistance, and the like. The inorganic filler to be used is not particularly limited, and specific examples thereof include spherical silica, fused silica, crystalline silica, titanium oxide, titanium black, silicon carbide, silicon nitride, boron nitride, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, magnesium oxide, zirconium oxide, aluminum hydroxide, calcium silicate, aluminum silicate, lithium aluminum silicate, zirconium silicate, barium titanate, glass fiber, carbon fiber, molybdenum disulfide, and asbestos. Preferred examples thereof include spherical silica, fused silica, crystalline silica, titanium oxide, titanium black, silicon nitride, boron nitride, calcium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, aluminum hydroxide, calcium silicate, and aluminum silicate. The inorganic filler may be used in a mixture of 2 or more.