KR102708816B1 - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

(Q¹, Q² 는 (Q1-1) 등이고, Q¹, Q² 의 어느 것은 (Q1-1) 이다)
[화학식 2]

(q1, q2 는 0 또는 1 이고, R¹ 은 수소 원자 등이고, R², R³ 은, 에폭시 부위를 갖는 기 등이고, R², R³ 의 어느 것은 에폭시 부위를 갖는 기이다.)Provided are a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element capable of obtaining a liquid crystal alignment film having excellent voltage retention, rapid relaxation of accumulated charge, and good liquid crystal alignment property and transparency.
A liquid crystal alignment agent characterized by containing the following (A) component, (B) component, and an organic solvent.
(A) Component: At least one polymer selected from the group consisting of a polyimide precursor, an imidized polymer of the polyimide precursor, and a photosensitive side-chain acrylic polymer exhibiting liquid crystallinity in a temperature range of 100 to 300°C.
(B) Component: Compound represented by the following formula (1)
[Chemical Formula 1]

(Q ¹ , Q ² are (Q1-1) etc., and either Q ¹ or Q ² is (Q1-1))
[Chemical formula 2]

(q1, q2 are 0 or 1, R ¹ is a hydrogen atom, etc., R ² , R ³ are a group having an epoxy moiety, etc., and one of R ² and R ³ is a group having an epoxy moiety.)

Description

Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element

The present invention relates to a novel liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display device using the same.

Liquid crystal display elements are widely used as display units in PCs, mobile phones, smart phones, televisions, etc. A liquid crystal display element comprises, for example, a liquid crystal layer sandwiched between an element substrate and a color filter substrate, a pixel electrode and a common electrode that apply an electric field to the liquid crystal layer, an alignment film that controls the orientation of liquid crystal molecules in the liquid crystal layer, a thin film transistor (TFT) that switches an electric signal supplied to the pixel electrode, etc. As a method of driving the liquid crystal molecules, a vertical field method such as the TN method and the VA method, and a transverse field method such as the IPS method and the FFS method are known. In the transverse field method, in which electrodes are formed only on one side of the substrate and an electric field is applied in a direction parallel to the substrate, compared to the vertical field method in which a voltage is applied to electrodes formed on the conventional upper and lower substrates to drive the liquid crystal, it is known as a liquid crystal display element that has wide viewing angle characteristics and is capable of high-quality display.

Although the liquid crystal cell of the transverse electric field method has excellent viewing angle characteristics, since the electrode portion formed within the substrate is small, if the voltage retention ratio is low, sufficient voltage is not applied to the liquid crystal, which reduces the display contrast. In addition, if the stability of the liquid crystal orientation is low, the liquid crystal does not return to its initial state when driven for a long time, which causes a decrease in contrast or afterimages, so the stability of the liquid crystal orientation is important. In addition, since static electricity is easily accumulated within the liquid crystal cell, charges are accumulated within the liquid crystal cell by the application of positive and negative asymmetric voltages generated by driving, and these accumulated charges affect the display as liquid crystal alignment disorder or afterimages, which significantly reduces the display quality of the liquid crystal element.

When used in a liquid crystal display device of the transverse field type, a liquid crystal alignment agent having excellent voltage retention and reduced charge accumulation is disclosed in Patent Document 1, which contains a specific diamine and an aliphatic tetracarboxylic acid derivative. In addition, as a method for shortening the time until afterimage disappearance, a method of using an alignment film having a low volume resistivity, such as Patent Document 2, or an alignment film having a volume resistivity that does not change much even by the backlight of the liquid crystal display device, such as Patent Document 3, has been proposed. However, along with the improvement in the performance of liquid crystal display devices, the characteristics required for the liquid crystal alignment film are also becoming stricter, and it is difficult for these conventional technologies to sufficiently satisfy all the required characteristics.

International Publication (WO) 2004/021076 Pamphlet International Publication (WO) 2004/053583 Pamphlet International Publication (WO) 2013/008822 Pamphlet

The present invention aims to provide a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element capable of obtaining a liquid crystal alignment film having excellent voltage retention, rapid relaxation of accumulated charge, and good liquid crystal alignment properties and transparency.

The inventors of the present invention conducted thorough studies to solve the above problems and completed the present invention.

The present invention relates to a liquid crystal alignment agent, characterized by containing the following component (A), component (B), and an organic solvent.

(A) Component: Polymer

(B) Component: Compound represented by the following formula (1)

[Chemical Formula 1]

(In the formula, Q ¹ and Q ² are one selected from the following (Q1-1) and a single bond, and at least one of Q ¹ and Q ² is (Q1-1),

[Chemical formula 2]

q1 and q2 are each independently 0 or 1,

R ¹ is a hydrogen atom or a monovalent organic group,

R ² and R ³ are each independently a group having an epoxy moiety and a hydrogen atom, and at least one of R ² and R ³ is a group having an epoxy moiety.)

According to the liquid crystal alignment agent of the present invention, a liquid crystal alignment film having excellent voltage retention, rapid relaxation of accumulated charge, and good liquid crystal alignment properties and transparency, and a liquid crystal display element having excellent display characteristics are provided.

It is not clear why the above problem can be solved by the present invention, but it can be generally thought as follows. The structure of the compound represented by the above formula (1) contained in the liquid crystal alignment agent of the present invention has a conjugated structure. As a result, for example, in a liquid crystal alignment film, charge movement can be promoted, and relaxation of accumulated charge can be promoted.

＜(A) Component＞

The (A) component included in the liquid crystal alignment agent of the present invention is at least one kind of polymer selected from the group consisting of a polyimide precursor, an imidized polymer of the polyimide precursor, and a photosensitive side-chain type acrylic polymer that exhibits liquid crystal properties in a predetermined temperature range.

＜Polyimide precursor＞

(A) The polyimide precursor, which is a component, has a structural unit represented by the following formula (A1).

[Chemical Formula 3]

In formula (A1), X ₁ is a tetravalent organic group and Y ₁ is a divalent organic group.

R ₁ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and A ₁ and A ₂ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, an alkenyl group having 2 to 10 carbon atoms which may have a substituent, or an alkynyl group having 2 to 10 carbon atoms which may have a substituent.

Specific examples of the alkyl group for R ₁ include a methyl group, an ethyl group, a propyl group, an i-propyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group, an n-pentyl group, and the like. From the viewpoint of the ease of imidization by heating, R ₁ is preferably a hydrogen atom or a methyl group.

X ₁ is a tetravalent organic group derived from a tetracarboxylic acid derivative, and its structure is not particularly limited. Among the polyimide precursors, two or more types of X ₁ may be mixed.

As specific examples of X ₁ , structures of the following formulas (X-1) to (X-44) can be mentioned.

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical formula 6]

[Chemical formula 7]

In the above formula (X-1), R ₈ to R ₁₁ are each independently 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. When R ₈ to R ₁₁ have a bulky structure, there is a possibility of lowering the liquid crystal orientation, so a hydrogen atom, a methyl group, or an ethyl group is more preferable, and a hydrogen atom or a methyl group is particularly preferable.

For X ₁ , from the viewpoint of availability of the monomer, a structure selected from formulas (X-1) to (X-14) is preferable.

A preferable ratio of the structure selected from the above formulas (X-1) to (X-14) is 20 mol% or more of the total X ₁ , more preferably 60 mol% or more, and even more preferably 80 mol% or more.

A ₁ and A ₂ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, an alkenyl group having 2 to 10 carbon atoms which may have a substituent, or an alkynyl group having 2 to 10 carbon atoms which may have a substituent.

Specific examples of the above alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a t-butyl group, a hexyl group, an octyl group, a decyl group, a cyclopentyl group, a cyclohexyl group, a bicyclohexyl group, and the like.

As an alkenyl group, one or more CH ₂ -CH ₂ structures present in the above alkyl group can be substituted with a CH=CH structure. Specifically, examples thereof include a vinyl group, an allyl group, a 1-propenyl group, an isopropenyl group, a 2-butenyl group, a 1,3-butadienyl group, a 2-pentenyl group, a 2-hexenyl group, a cyclopropenyl group, a cyclopentenyl group, and a cyclohexenyl group.

As an alkynyl group, one may cite one in which one or more CH ₂ -CH ₂ structures present in the above alkyl group are substituted with a C≡C structure. Specifically, examples thereof include an ethynyl group, a 1-propynyl group, and a 2-propynyl group.

The above alkyl group, alkenyl group, and alkynyl group may have a substituent, and furthermore, may form a ring structure by the substituent. In addition, forming a ring structure by the substituent means that the substituents or the substituents and a part of the parent skeleton combine to form a ring structure.

Examples of the above substituents 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 ester group, an amide group, an alkyl group, an alkenyl group, an alkynyl group, and the like.

Halogen groups, which are substituents, include fluorine atoms, chlorine atoms, bromine atoms, or iodine atoms.

As an aryl group which is a substituent, a phenyl group can be mentioned. This aryl group may be additionally substituted with another substituent as mentioned above.

The organooxy group, which is a substituent, can have a structure represented by -O-R. This R may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These R's may be further substituted with the substituent described above. Specific examples of the organooxy group include a methoxy group, an ethoxy group, a propyloxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group.

The organothio group, which is a substituent, can have a structure represented by -S-R. As this R, the alkyl group, alkenyl group, alkynyl group, aryl group, etc. mentioned above can be exemplified. These R may be further substituted by the above-mentioned substituent. Specific examples of the organothio group include a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a pentylthio group, a hexylthio group, a heptylthio group, an octylthio group, etc.

The organosilyl group, which is a substituent, can have a structure represented by -Si-(R) _3. This R may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, aryl group, etc. described above. These R's may be further substituted with the substituents described above. Specific examples of the organosilyl group include a trimethylsilyl group, a triethylsilyl group, a tripropylsilyl group, a tributylsilyl group, a tripentylsilyl group, a trihexylsilyl group, a pentyldimethylsilyl group, a hexyldimethylsilyl group, etc.

The substituent acyl group can have a structure represented by -C(O)-R. As this R, the alkyl group, alkenyl group, aryl group, etc. mentioned above can be exemplified. These R may be further substituted with the above-mentioned substituent. Specific examples of the acyl group include a formyl group, an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, an isovaleryl group, a benzoyl group, etc.

The ester group, which is a substituent, can have a structure represented by -C(O)O-R or -OC(O)-R. As R, the alkyl group, alkenyl group, alkynyl group, aryl group, etc. mentioned above can be exemplified. These R may be additionally substituted with the substituent mentioned above.

The substituent thioester group can have a structure represented by -C(S)O-R or -OC(S)-R. As this R, the alkyl group, alkenyl group, alkynyl group, aryl group, etc. mentioned above can be exemplified. These R may be further substituted with the above mentioned substituent.

The phosphate ester group, which is a substituent, can have a structure represented by -OP(O)-(OR) _2. This R may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, aryl group, etc. described above. These R's may be additionally substituted with the substituent described above.

The substituent amide group can have a structure represented by -C(O)NH ₂ , or -C(O)NHR, -NHC(O)R, -C(O)N(R) ₂ , -NRC(O)R. This R may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, aryl group, etc. described above. These R may be further substituted with the substituent described above.

The aryl group as a substituent may be the same as the aryl group described above. This aryl group may be additionally substituted with another substituent described above.

The alkyl group which is a substituent may be the same as the alkyl group described above. This alkyl group may be further substituted with another substituent described above.

The substituent alkenyl group may be the same as the alkenyl group described above. This alkenyl group may be further substituted with another substituent described above.

The alkynyl group as a substituent may be the same as the alkynyl group described above. This alkynyl group may be further substituted with another substituent described above.

In general, since introducing a bulky structure may lower the reactivity or liquid crystal orientation of the amino group, as A ₁ and A ₂ , a hydrogen atom or an alkyl group having 1 to 5 carbon atoms that may have a substituent is more preferable, and a hydrogen atom, a methyl group or an ethyl group is particularly preferable.

Y ₁ is a divalent organic group derived from diamine, and its structure is not particularly limited. Specific examples of Y ₁ include the following formulae (Y-1) to (Y-119).

[Chemical formula 8]

[Chemical formula 9]

[Chemical Formula 10]

[Chemical Formula 11]

[Chemical Formula 12]

[Chemical Formula 13]

[Chemical Formula 14]

[Chemical Formula 15]

[Chemical Formula 16]

[Chemical Formula 17]

[Chemical Formula 18]

[Chemical Formula 19]

[Chemical formula 20]

[Chemical Formula 21]

[Chemical Formula 22]

[Chemical Formula 23]

In formula (Y-109), m and n are each an integer from 1 to 11, and m + n is an integer from 2 to 12.

In formula (Y-114), h is an integer from 1 to 3, and in formulas (Y-111) and (Y-117), j is an integer from 0 to 3.

As for Y ₁ , from the viewpoint of the liquid crystal alignment property or pretilt angle of the obtained liquid crystal alignment film, it is more preferable that it be at least one selected from the structures represented by the following formulas (5) and (6).

[Chemical Formula 24]

In formula (5), R ₁₂ is a single bond or a divalent organic group having 1 to 30 carbon atoms, R ₁₃ is a hydrogen atom, a halogen atom or a monovalent organic group having 1 to 30 carbon atoms, and a is an integer of 1 to 4. When a is 2 or more, R ₁₂ and R ₁₃ may be the same as or different from each other.

In formula (6), R ₁₄ is a single bond, -O-, -S-, -NR ₁₅ -, an amide bond, an ester bond, a urea bond, or a divalent organic group having 1 to 40 carbon atoms, and R ₁₅ is a hydrogen atom or a methyl group.

Specific examples of Y ₁ represented by formulas (5) and (6) include the following structures among formulas (Y-1) to (Y-119).

Since Y ₁ with a highly linear structure can improve the alignment of the liquid crystal when used as a liquid crystal alignment film, formula (Y-7), (Y-21), (Y-22), (Y-23), (Y-25), (Y-43), (Y-44), (Y-45), (Y-46), (Y-48), (Y-63), (Y-71), (Y-72), (Y-73), (Y-74), (Y-75), (Y-98), (Y-99), (Y-100), or (Y-118) is preferable.

The ratio of the structure of Y ₁ capable of increasing the orientation of the liquid crystal is preferably 20 mol% or more of the total Y ₁ , more preferably 60 mol% or more, and even more preferably 80 mol% or more.

When it is desired to increase the pretilt angle of the liquid crystal when used as a liquid crystal alignment film, it is preferable that Y ₁ has a structure in which a long-chain alkyl group, an aromatic ring, an aliphatic ring, a steroid skeleton, or a structure combining these in the side chain. As such Y ₁ , the formulas (Y-76) to (Y-97) are preferable. When it is desired to increase the pretilt angle, the ratio of the structure of Y ₁ is preferably 1 to 30 mol%, and more preferably 1 to 20 mol%, of the entire Y ₁ .

In addition, when a polyimide precursor or polyimide having a photo-orientable side chain is used as the polymer of component (A), it is preferable that the polyimide precursor or polyimide have the following photo-reactive side chain.

[Chemical Formula 25]

(In formula (c), R ⁶ represents -CH ₂ -, -O-, -COO-, -OCO-, -NHCO-, -CONH-, -NH-, -CH ₂ O-, -N(CH ₃ )-, -CON(CH ₃ )-, or -N(CH ₃ )CO-. R ⁷ represents a cyclic, unsubstituted or fluorine-substituted alkylene group having 1 to 20 carbon atoms (any -CH ₂ - of the alkylene group may be substituted with -CF ₂ - or -CH=CH-, and may be substituted by any of the groups exemplified below so as not to be adjacent to each other (groups are -O-, -COO-, -OCO-, -NHCO-, -CONH-, -NH-, a carbon ring, or a heterocyclic ring)). R ⁸ represents -CH ₂ -, -O-, -COO-, -OCO-, -NHCO-, -NH-, -N(CH ₃ )-, -CON(CH ₃ )-, -N(CH ₃ )CO-, a carbon ring, or a heterocyclic ring. R ⁹ represents a vinylphenyl group, -CR ¹⁰ =CH ₂ group, -CR ¹⁰ (OH)-CH ₃ group, a carbon ring, a heterocyclic ring, or a structure represented by the following formula, and R ¹⁰ represents a methyl group which may be substituted with a hydrogen atom or a fluorine atom.)

[Chemical Formula 26]

[Chemical formula 27]

[Chemical formula 28]

[Chemical Formula 29]

[Chemical formula 30]

[Chemical Formula 31]

[Chemical formula 32]

[Chemical formula 33]

[Chemical Formula 34]

[Chemical Formula 35]

When manufacturing the above polyimide precursor, it is convenient to use a diamine having a substituted side chain represented by the above formula (c) as the diamine.

In addition, a polyimide precursor having a photo-alignable group in the main chain may be used. In this case, it is convenient to use a diamine having a bond including a photo-alignable group between amines, as represented by the following formula (2).

[Chemical formula 36]

In formula (2), X ¹ is a single bond or an alkylene group having 1 to 5 carbon atoms, X ² is -OCO-CH=CH- or -CH=CH-COO-, X ³ is a single bond, an alkylene group having 1 to 10 carbon atoms or a divalent benzene ring, X ⁴ is a single bond, -OCO-CH=CH- or -CH=CH-COO-, and X ⁵ is a single bond or an alkylene group having 1 to 5 carbon atoms. However, it has at least one cinnamoyl group.

As diamines represented by formula (2), the following formulas (2-a) to (2-d) can be mentioned.

[Chemical Formula 37]

In the formula, X is a single bond or a bonding group selected from ether (-O-), ester (-COO- or OCO-), and amide (-CONH- or NHCO-), Y is a single bond or an alkylene group having 1 to 5 carbon atoms, and Z is an alkylene group or a phenylene group having 1 to 10 carbon atoms. The bonding position of the amino group on the benzene ring or the position of the bonding group with respect to the central benzene ring is not particularly limited.

In addition, specific examples of the diamine represented by formula (2) include the following diamines.

[Chemical formula 38]

[Chemical Formula 39]

A liquid crystal alignment film formed using a polyimide precursor such as a polyamic acid, a polyamic acid ester, or the like of the present invention, a liquid crystal alignment agent containing a polyimide or a polyamide, and using a diamine represented by the above formula (2) as a raw material, has reduced changes in liquid crystal alignment performance due to AC (alternating current) driving, for example, changes in the alignment direction of liquid crystals. Therefore, a liquid crystal display element having this liquid crystal alignment film hardly generates afterimages due to AC driving, since the liquid crystal alignment performance of the liquid crystal alignment film in AC driving is stable. In other words, it exhibits the effect of having very good afterimage characteristics due to AC driving.

In addition, the liquid crystal alignment film formed using the diamine represented by the above formula (2) has excellent liquid crystal alignment performance itself, and can be made to have substantially no alignment defects.

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

＜Manufacture of polyimide precursor (polyamic acid)＞

Polyamic acid, which is a polyimide precursor used in the present invention, is produced by the following method. Specifically, it can be synthesized by reacting tetracarboxylic dianhydride and diamine in the presence of an organic solvent at -20 to 150°C, preferably 0 to 50°C, for 30 minutes to 24 hours, preferably 1 to 12 hours.

The reaction of the diamine component and the tetracarboxylic acid component is usually carried out in an organic solvent. The organic solvent used at that time is not particularly limited as long as the produced polyimide precursor is soluble. Specific examples of the organic solvent used in the reaction are given below, but the organic solvent is not limited to these examples. For example, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, or 1,3-dimethyl-imidazolidinone can be given.

In addition, when the solubility of the polyimide precursor is high, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or an organic solvent represented by the following formulae [D-1] to [D-3] can be used.

[Chemical formula 40]

In formula [D-1], D ¹ represents an alkyl group having 1 to 3 carbon atoms, in formula [D-2], D ² represents an alkyl group having 1 to 3 carbon atoms, and in formula [D-3], D ³ represents an alkyl group having 1 to 4 carbon atoms.

These organic solvents may be used alone or in combination. In addition, even if they are solvents that do not dissolve the polyimide precursor, they may be mixed with the solvent and used within a range in which the produced polyimide precursor is not precipitated. In addition, since moisture in the organic solvent inhibits the polymerization reaction and further causes hydrolysis of the produced polyimide precursor, it is preferable to use an organic solvent that has been dehydrated and dried.

The concentration of the polyamic acid polymer in the reaction system is preferably 1 to 30 mass%, more preferably 5 to 20 mass%, from the viewpoint that precipitation of the polymer does not occur easily and it is easy to obtain a high molecular weight polymer.

The polyamic acid obtained as described above can be recovered by precipitating the polymer by injecting the reaction solution into a poor solvent while stirring it well. In addition, by performing precipitation several times, washing with a poor solvent, and drying at room temperature or by heating, a powder of purified polyamic acid can be obtained. The poor solvent is not particularly limited, but may include water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene, and the like.

＜Manufacture of polyimide precursor (polyamic acid ester)＞

The polyamic acid ester, which is a polyimide precursor used in the present invention, can be manufactured by the manufacturing method (1), (2), or (3) shown below.

(1) When manufactured from polyamic acid

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

As the esterifying agent, one that can be easily removed by purification is preferable, and examples thereof include N,N-dimethylformamidedimethylacetal, N,N-dimethylformamidediethylacetal, N,N-dimethylformamidedipropylacetal, N,N-dimethylformamidedineopentylbutylacetal, N,N-dimethylformamidedi-t-butylacetal, 1-methyl-3-p-tolyltriazene, 1-ethyl-3-p-tolyltriazene, 1-propyl-3-p-tolyltriazene, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride, and the like. The amount of the esterifying agent added is preferably 2 to 6 molar equivalents per 1 mol of the repeating unit of the polyamic acid.

Examples of the organic solvent include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone or γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide or 1,3-dimethylimidazolidinone. In addition, when the solvent solubility of the polyimide precursor is high, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, or organic solvents represented by the above formulae [D-1] to [D-3] can be used.

These organic solvents may be used alone or in combination. In addition, even if they are solvents that do not dissolve the polyimide precursor, they may be mixed with the solvent and used within a range in which the produced polyimide precursor is not precipitated. In addition, since moisture in the organic solvent inhibits the polymerization reaction and further causes hydrolysis of the produced polyimide precursor, it is preferable to use an organic solvent that 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 standpoint of the solubility of the polymer, and these may be used alone or in combination of two or more. The concentration during production is preferably 1 to 30 mass%, more preferably 5 to 20 mass%, from the viewpoint that polymer precipitation does not easily occur and a high molecular weight form is easily obtained.

(2) When manufactured by reaction of tetracarboxylic acid diester dichloride and diamine

Polyamic acid ester can be produced from tetracarboxylic acid diester dichloride and diamine. Specifically, it can be produced by reacting tetracarboxylic acid diester dichloride and diamine in the presence of a base and an organic solvent at -20 to 150°C, preferably 0 to 50°C, for 30 minutes to 24 hours, preferably 1 to 4 hours.

As the above base, pyridine, triethylamine, 4-dimethylaminopyridine, etc. can be used, but pyridine is preferred because the reaction proceeds mildly. The amount of base added is preferably 2 to 4 times molar with respect to tetracarboxylic acid diester dichloride because it is an amount that is easy to remove and also makes it easy to obtain a high molecular weight product.

As the organic solvent, N-methyl-2-pyrrolidone or γ-butyrolactone is preferable from the standpoint of solubility of the monomer and polymer, and these may be used alone or in combination of two or more.

The polymer concentration during manufacturing is preferably 1 to 30 mass%, more preferably 5 to 20 mass%, in that polymer precipitation does not occur easily and a high molecular weight form is easily obtained. In addition, in order to prevent hydrolysis of tetracarboxylic acid diester dichloride, the organic solvent used in the manufacturing of the polyamic acid ester is preferably dehydrated as much as possible, and it is preferable to prevent mixing of external air in a nitrogen atmosphere.

(3) When manufactured from tetracarboxylic acid diester and diamine

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

Examples of the condensing agent that can be used include triphenyl phosphite, dicyclohexyl carbodiimide, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride, N,N'-carbonyl diimidazole, dimethoxy-1,3,5-triazinyl methyl 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-thioxo-3-benzoxazolyl)phosphonic acid diphenyl, and the like. The amount of the condensing agent added is preferably 2 to 3 times molar with respect to the tetracarboxylic acid diester.

As the above base, a tertiary amine such as pyridine or triethylamine can be used. The amount of base added is preferably 2 to 4 times the mole with respect to the diamine component, because it is an amount that is easy to remove and also makes it easy to obtain a high molecular weight product.

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

Among the above three methods for producing polyamic acid esters, the method (1) or (2) is particularly preferable because a high molecular weight polyamic acid ester is obtained.

The solution of polyamic acid ester obtained as described above can be injected into a poor solvent while stirring well to precipitate a polymer. After performing precipitation several times, the solution can be washed with a poor solvent, and then dried at room temperature or by heating to obtain a powder of purified polyamic acid ester. The poor solvent is not particularly limited, but may include water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene, and the like.

＜Polyimide＞

The polyimide used in the present invention (imidized polymer in component (A)) can be produced by imidizing the above-mentioned polyamic acid ester or polyamic acid.

When producing a polyimide from a polyamic acid, chemical imidization is simple by adding a catalyst to a solution of the polyamic acid obtained by the reaction of a diamine component and tetracarboxylic dianhydride to cause a reaction. The chemical imidization is preferable because the imidization reaction proceeds at a relatively low temperature and the molecular weight of the polymer does not decrease easily during the imidization process.

Chemical imidization can be carried out 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, the organic solvent used in the polymerization reaction described above can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among them, pyridine is preferable because it has an appropriate basicity for promoting the reaction. In addition, examples of the acid anhydride include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. Among them, acetic anhydride is preferable because purification after the completion of the reaction is easy.

The temperature at which the above imidization reaction is performed is -20 to 140°C, preferably 0 to 100°C, and the reaction time can be performed for 0.5 to 100 hours, preferably 1 to 80 hours. The amount of the basic catalyst is 0.5 to 30 molar times that of the amic acid, preferably 2 to 20 molar times, and the amount of the acid anhydride is 1 to 50 molar times that of the amic acid, preferably 3 to 30 molar times. The imidization degree of the obtained polymer can be controlled by adjusting the amount of catalyst, temperature, and reaction time.

Since the solution after the imidization reaction of the polyamic acid ester or polyamic acid contains the added catalyst, it is preferable to recover the obtained imidized polymer by the means described below, re-dissolve it in an organic solvent, and use it as component (A) of the liquid crystal alignment agent of the present invention.

The polyimide solution obtained as described above can be injected into a poor solvent while stirring well to precipitate a polymer. After performing precipitation several times and washing with a poor solvent, a powder of purified polyimide can be obtained by drying at room temperature or by heating.

The above-mentioned poor solvents include, but are not particularly limited to, methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, etc.

＜Side chain acrylic polymer＞

The side chain type acrylic polymer, which is one aspect of component (A) of the present invention, exhibits liquid crystallinity and has photosensitivity in a certain temperature range.

The side-chain type acrylic polymer preferably reacts with light in a wavelength range of 200 to 450 nm and also preferably exhibits liquid crystallinity in a temperature range of 100 to 300°C.

As the side chain type acrylic polymer, it is preferable to have a photosensitive side chain that reacts to light in a wavelength range of preferably 200 to 450 nm, more preferably 250 to 400 nm.

As for the side chain type acrylic polymer, it is preferable that it has a mesogenic group for exhibiting liquid crystallinity in a temperature range of preferably 100 to 350°C, more preferably 120 to 300°C.

The side chain type acrylic polymer has a side chain having photosensitivity bonded to the main chain and can cause a crosslinking reaction, an isomerization reaction, or a photofree rearrangement in response to light. The structure of the side chain having photosensitivity is preferably such that it causes a crosslinking reaction or a photofree rearrangement in response to light, and more preferably such that it causes a crosslinking reaction. In this case, even if exposed to external stress such as heat, the realized orientation controllability can be stably maintained for a long period of time.

The structure of the photosensitive side chain type acrylic polymer film capable of expressing liquid crystallinity is not particularly limited as long as it satisfies such characteristics, but it is preferable to have a rigid mesogenic component in the side chain structure. In this case, when the side chain type acrylic polymer is used as a liquid crystal alignment film, stable liquid crystal alignment can be obtained.

As a structure of the side chain type acrylic polymer, for example, a structure is preferable in which the main chain and a side chain bonded thereto have a mesogenic component such as a biphenyl group, a terphenyl group, a phenylcyclohexyl group, a phenylbenzoate group, or an azobenzene group, and a photosensitive group bonded to a tip end that is sensitive to light and undergoes a crosslinking reaction or an isomerization reaction, or a structure in which the main chain and a side chain bonded thereto have a side chain that becomes a mesogenic component and further has a phenylbenzoate group that undergoes a photofree rearrangement reaction.

A specific example of the structure of the side chain type acrylic polymer is preferably a structure having a main chain derived from a radical polymerizable group of at least one compound selected from the group consisting of hydrocarbons, (meth)acrylates, itaconates, fumarates, maleates, α-methylene-γ-butyrolactone, styrene, vinyl, maleimides, and norbornene, and a side chain composed of at least one compound represented by the following formulae (i) to (v).

[Chemical Formula 41]

In the formula, Ar ₁ represents a divalent substituent having two hydrogen atoms removed from a benzene ring, a naphthalene ring, a pyrrole ring, a furan ring, a thiophene ring, or a pyridine ring.

Ar ₂ and Ar ₃ each independently represent a divalent substituent having two hydrogen atoms removed from a benzene ring, a naphthalene ring, a pyrrole ring, a furan ring, a thiophene ring, or a pyridine ring. One of q1 and q2 is 1 and the other is 0.

Ar ₄ and Ar ₅ each independently represent a divalent substituent having two hydrogen atoms removed from a benzene ring, a naphthalene ring, a pyrrole ring, a furan ring, a thiophene ring, or a pyridine ring. Y ₁ -Y ₂ represent -CH=CH-, -CH=N-, -N=CH-, or -C≡C-.

S ₁ , S ₂ and S ₃ each independently represent a single bond, a linear or branched alkylene group having 1 to 18 carbon atoms, a cycloalkylene group having 5 to 8 carbon atoms, a phenylene group or a biphenylene group, or represent one or more bonds selected from a single bond, an ether bond, an ester bond, an amide bond, a urea bond, a urethane bond, an amino bond, a carbonyl group or a combination thereof, or represent a structure in which 2 to 10 moieties selected from a linear or branched alkylene group having 1 to 18 carbon atoms, a cycloalkylene group having 5 to 8 carbon atoms, a phenylene group, a biphenylene group or a combination thereof are bonded via the bond. In addition, the divalent substituent may have a structure in which plural groups are each connected via the bond.

R ₁₁ represents a hydrogen atom, a hydroxyl group, a mercapto group, an amino group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylamino group having 1 to 8 carbon atoms, or a dialkylamino group having 2 to 16 carbon atoms.

The above benzene ring and/or naphthalene ring may be substituted by one or more identical or different groups selected from a halogen atom, a cyano group, a nitro group, a carboxyl group, and an alkoxycarbonyl group having 2 to 11 carbon atoms. At that time, the alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic, or may have a structure combining these, and may be substituted with a halogen atom.

It is preferable that the side chain type acrylic polymer of the present invention contains a liquid crystalline side chain.

The mesogenic group of the liquid crystalline side chain may be a group that forms a mesogenic structure by itself, such as biphenyl or phenyl benzoate, or a group that forms a mesogenic structure by hydrogen bonding between side chains, such as benzoic acid. The following structure is preferable as the mesogenic group of the side chain.

[Chemical formula 42]

＜Side chain acrylic polymer＞

The side chain type acrylic polymer of the present invention can be obtained by polymerizing a photoreactive side chain monomer having the above-mentioned photosensitive side chain and a liquid crystalline side chain monomer.

[Photoreactive side chain monomer]

A photoreactive side chain monomer is a monomer that, when formed into a polymer, can form a polymer having a photosensitive side chain at the side chain portion of the polymer.

As for the photoreactive group possessed by the side chain, the structures represented by the above formulas (i) to (v) are preferable.

A more specific example of the photoreactive side chain monomer is preferably a structure having a photosensitive side chain composed of a radical polymerizable group of at least one compound selected from the group consisting of hydrocarbons, (meth)acrylates, itaconates, fumarates, maleates, α-methylene-γ-butyrolactone, styrene, vinyl, maleimides, and norbornene, and at least one compound selected from the group consisting of formulae (i) to (v).

[Liquid crystal side chain monomer]

A liquid crystalline side chain monomer is a monomer in which a polymer derived from the monomer exhibits liquid crystalline properties and the polymer can form a mesogenic group at the side chain portion.

A more specific example of the liquid crystalline side chain monomer is preferably a structure having a liquid crystalline side chain having a radical polymerizable group of at least one compound selected from the group consisting of hydrocarbons, (meth)acrylates, itaconates, fumarates, maleates, α-methylene-γ-butyrolactone, styrene, vinyl, maleimides, and norbornene, and at least one compound selected from the group consisting of the above mesogenic groups.

The side chain type acrylic polymer of the present invention can be obtained by a polymerization reaction of the photoreactive side chain monomer that exhibits liquid crystallinity described above. In addition, it can also be obtained by copolymerization of a photoreactive side chain monomer that does not exhibit liquid crystallinity and a liquid crystal side chain monomer, or a copolymerization of a photoreactive side chain monomer that exhibits liquid crystallinity and a liquid crystal side chain monomer. In addition, it can be copolymerized with other monomers within a range that does not inhibit the ability to exhibit liquid crystallinity.

Other monomers include, for example, industrially available radical polymerization-capable monomers.

Specific examples of other monomers include unsaturated carboxylic acids, acrylic acid esters, methacrylic acid esters, maleimides, acrylonitriles, maleic anhydride, styrene compounds, vinyl compounds, etc.

Specific examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid.

Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, isopropyl acrylate, benzyl acrylate, naphthylacrylate, anthryl acrylate, anthryl methyl acrylate, phenyl acrylate, 2,2,2-trifluoroethyl acrylate, tert-butylacrylate, cyclohexylacrylate, isobornyl acrylate, 2-methoxyethyl acrylate, methoxytriethylene glycol acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, 3-methoxybutylacrylate, 2-methyl-2-adamantyl acrylate, 2-propyl-2-adamantyl acrylate, 8-methyl-8-tricyclodecylacrylate, 8-ethyl-8-tricyclodecylacrylate, etc. Can be.

As methacrylic acid esters, for example, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, benzyl methacrylate, naphthyl methacrylate, anthryl methacrylate, anthryl methyl methacrylate, phenyl methacrylate, 2,2,2-trifluoroethyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, 2-methoxyethyl methacrylate, methoxytriethylene glycol methacrylate, 2-ethoxyethyl methacrylate, tetrahydrofurfuryl methacrylate, 3-methoxybutyl methacrylate, 2-methyl-2-adamantyl methacrylate, 2-propyl-2-adamantyl methacrylate, Examples thereof include 8-methyl-8-tricyclodecyl methacrylate, 8-ethyl-8-tricyclodecyl methacrylate, and the like. In addition, (meth)acrylate compounds having a cyclic ether group, such as glycidyl (meth)acrylate, (3-methyl-3-oxetanyl)methyl (meth)acrylate, and (3-ethyl-3-oxetanyl)methyl (meth)acrylate, can also be used.

Examples of vinyl compounds include vinyl ether, methyl vinyl ether, benzyl vinyl ether, 2-hydroxyethyl vinyl ether, phenyl vinyl ether, and propyl vinyl ether.

Styrene compounds include, for example, styrene, methylstyrene, chlorostyrene, and bromostyrene.

Examples of maleimide compounds include maleimide, N-methylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide, etc.

The method for producing the side chain type acrylic polymer of the present invention is not particularly limited, and a general method handled industrially can be used. Specifically, it can be produced by cationic polymerization, radical polymerization, anionic polymerization, etc. using a vinyl group of a liquid crystal side chain monomer or a photoreactive side chain monomer. Among these, radical polymerization is particularly preferable from the viewpoint of ease of reaction control, etc.

The polymerization initiator for radical polymerization can be a known radical polymerization initiator such as azobisisobutyronitrile (AIBN), or a known compound such as a reversible addition-cleavage chain transfer (RAFT) polymerization reagent.

Radical polymerization is not particularly limited, and emulsion polymerization, suspension polymerization, dispersion polymerization, precipitation polymerization, bulk polymerization, solution polymerization, etc. can be used.

The organic solvent used in the polymerization reaction of the above side chain type acrylic polymer is not particularly limited as long as it dissolves the produced polymer. Specific examples thereof are given below.

N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methylcaprolactam, dimethyl sulfoxide, tetramethylurea, pyridine, dimethyl sulfone, hexamethyl sulfoxide, 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, 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, tetrahydrofuran, n-hexane, Examples thereof include n-pentane, n-octane, diethyl ether, cyclohexanone, ethylene carbonate, propylene carbonate, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl 3-ethoxypropionate ethyl, 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, etc. there is.

These organic solvents may be used alone or in combination. In addition, even if they are solvents that do not dissolve the polymer produced, they may be mixed with the organic solvents described above and used within a range in which the polymer produced is not precipitated.

In addition, in radical polymerization, since oxygen in the organic solvent inhibits the polymerization reaction, it is preferable to use an organic solvent that has been degassed to the extent possible.

The polymerization temperature during radical polymerization can be any temperature selected from 30 to 150°C, but is preferably in the range of 50 to 100°C.

In addition, the reaction can be carried out at an arbitrary 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 uniform stirring difficult. Therefore, the monomer concentration is preferably 1 to 50 mass%, more preferably 5 to 30 mass%. It is preferable to carry out the reaction at a high concentration at the beginning and then add an organic solvent.

In the above radical polymerization reaction, if the ratio of the radical polymerization initiator is large with respect to the monomer, the molecular weight of the obtained polymer becomes small, and if it is small, the molecular weight of the obtained polymer becomes large. Therefore, the ratio of the radical polymerization initiator is preferably 0.05 to 15 mol%, more preferably 0.1 to 10 mol% with respect to the monomer to be polymerized. In addition, various monomer components, organic solvents, radical polymerization initiators, etc. can be added during polymerization.

When recovering the produced polymer from the reaction solution containing the side-chain type acrylic polymer obtained by the above polymerization reaction, it is preferable to pour the reaction solution into a poor solvent and precipitate the produced polymer. Poor solvents used for precipitation include methanol, acetone, hexane, heptane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, diethyl ether, methyl ethyl ether, water, etc. It is preferable to dry the polymer precipitated by pouring it into a poor solvent, recover it by filtration, and then dry it at room temperature or by heating under normal pressure or reduced pressure. In addition, if the operation of redissolving the precipitated recovered polymer in an organic solvent and recovering it by reprecipitation is repeated 2 to 10 times, the amount of impurities in the polymer can be reduced. Examples of poor solvents for re-precipitation include alcohols, ketones, ethers, and hydrocarbons, and it is preferable to use three or more types of poor solvents selected from these because this further increases the efficiency of purification.

The molecular weight of the side-chain type acrylic polymer of the present invention is preferably 2,000 to 500,000, more preferably 5,000 to 100,000, as measured by the GPC (Gel Permeation Chromatography) method, when considering the strength of the obtained coating film, the workability during coating film formation, and the uniformity of the coating film.

The content of the polymer of component (A) in the liquid crystal alignment agent of the present invention can be appropriately changed depending on the setting of the thickness of the coating film to be formed, but is preferably 1 wt% or more from the viewpoint of forming a uniform and defect-free coating film, and is preferably 10 wt% or less from the viewpoint of the storage stability of the solution, and among these, 3 to 7 wt% is preferable.

＜(B) Component＞

The component (B) contained in the liquid crystal alignment agent of the present invention is a compound represented by the following formula (1).

[Chemical Formula 43]

(In the formula, Q ¹ and Q ² are one selected from the following formula (Q1-1) and a single bond, and at least one of Q ¹ and Q ² is formula (Q1-1). q1 and q2 are each independently 0 or 1. R ² and R ³ are each independently a group having an epoxy moiety and a hydrogen atom, and at least one of R ² and R ³ is a group having an epoxy moiety.)

[Chemical Formula 44]

(In formula (Q1-1), R ¹ is a hydrogen atom or a monovalent organic group. The monovalent organic group of R ¹ is more preferably a methyl group, a phenyl group, a group having an epoxy moiety, or a thermally decomposable leaving group.

A thermally decomposable leaving group is a substituent that is desorbed by heating and substituted with a hydrogen atom. This thermally decomposable leaving group is a protecting group of an amino group, and its structure is not particularly limited as long as it is a functional group that is substituted with a hydrogen atom by heat. In terms of the storage stability of the liquid crystal alignment agent, it is preferable that the protecting group D does not desorb at room temperature, and it is preferably a protecting group that desorbs with heat of 80° C. or higher, and more preferably a protecting group that desorbs with heat of 100° C. or higher. In terms of the desorbing temperature, it is particularly preferable that D is a tert-butoxycarbonyl group or a 9-fluorenylmethoxycarbonyl group.

Examples of groups having an epoxy moiety in the definitions of R ¹ , R ² , and R ³ include a glycidyl group, a 3,4-epoxycyclohexyl group, and the like, and a glycidyl group is preferable due to ease of synthesis.

Preferred examples of compounds represented by component (B) include, for example, compounds of (B-1) to (B-6) below.

(B-1): A compound in which, in the above formula (1), q1 and q2 are 0, Q ¹ is (Q1-1), and R ² and R ³ have an epoxy group,

(B-2): A compound in which, in the above formula (1), q1 and q2 are 0, Q ¹ is (Q1-1), R ² is a hydrogen atom, and R ³ has an epoxy group,

(B-3): A compound in which, in the above formula (1), q1 and q2 are 1, Q ¹ is a single bond or (Q1-1), Q ² is (Q1-1), and R ² and R ³ are epoxy groups.

(B-4): A compound in which, in the above formula (1), q1 and q2 are 1, Q ¹ is a single bond or (Q1-1), Q ² is (Q1-1), R ² is a hydrogen atom, and R ³ has an epoxy group.

(B-5): A compound in which, in the above formula (1), q1 and q2 are 1, Q ¹ is (Q1-1), Q ² is a single bond, and R ² and R ³ have an epoxy group.

(B-6): A compound in which, in the above formula (1), q1 and q2 are 1, Q ¹ is (Q1-1), Q ² is a single bond, R ² is a hydrogen atom, and R ³ has an epoxy group.

Among the above, preferred (B) components include, for example, compounds represented by any of the following formulae B-1-1 to B-5-1.

[Chemical Formula 45]

The compound of component (B) can be obtained by reacting a diamine represented by the following formula (0) with epihalohydrin, and then treating the resulting addition reactant with an alkali to cause a cyclization reaction.

[Chemical Formula 46]

As the diamine represented by equation (0), a known one may be used.

In formula (1), in order to produce a compound in which both R ² and R ³ have an epoxy moiety, epihalohydrin may be used in an amount of 4 equivalents or more, preferably 8 equivalents or more, relative to the diamine represented by formula (0), and then treated with alkali. However, in order to produce a compound in which R ¹ also has an epoxy moiety, an equivalent amount of epihalohydrin may be used. In a case where it is desired to produce a compound in which one of R ² and R ³ is a group having an epoxy moiety and the other is a hydrogen atom, epihalohydrin may be used in an amount of 2 to 2.2 equivalents relative to the diamine represented by formula (0), and then treated with alkali.

(B) If the component is too much, it affects the liquid crystal alignment, and if it is too little, the effect of the present invention cannot be sufficiently obtained. Therefore, the content of the component (B) in the liquid crystal alignment agent is preferably 0.1 to 20 mass%, and more preferably 1 to 10 mass%, with respect to the component (A) (100 mass%).

＜Liquid crystal orientation agent＞

The liquid crystal alignment agent used in the present invention has a form of a solution in which at least one kind of polymer (hereinafter referred to as a specific structural polymer) selected from the group consisting of the polyimide precursor and the imidized polymer of the polyimide precursor, which is the above-mentioned (A) component, and the compound of the (B) component are dissolved in an organic solvent. The molecular weight of the specific structural polymer is preferably 2,000 to 500,000, more preferably 5,000 to 300,000, and even more preferably 10,000 to 100,000, in terms of a weight average molecular weight. In addition, the number average molecular weight is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, and even more preferably 5,000 to 50,000.

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

The organic solvent (good solvent) contained in the liquid crystal alignment agent used in the present invention is not particularly limited as long as it uniformly dissolves a specific structural polymer.

Examples thereof include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, or 4-hydroxy-4-methyl-2-pentanone.

Among them, it is preferable to use N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and γ-butyrolactone.

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

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

The liquid crystal alignment agent of the present invention can use a solvent (also called a poor solvent) that improves the film properties or surface smoothness of a liquid crystal alignment film when the liquid crystal alignment agent is applied. Specific examples of poor solvents are given below, but the present invention is not limited to these examples.

For example, ethanol, isopropyl alcohol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, tert-pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-Ethanediol, 1,2-Propanediol, 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 Ether, Diethylene Glycol Dibutyl Ether, 2-Pentanone, 3-Pentanone, 2-Hexanone, 2-Heptanone, 4-Heptanone, 3-Ethoxybutylacetate, 1-Methylpentyl acetate, 2-ethylbutyl acetate, 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, propylene glycol monobutyl ether, 1-(butoxyethoxy)propanol, propylene glycol monomethyl ether acetate, dipropylene glycol, 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, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, 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 3-ethoxypropionate ethyl, 3-methoxypropionate ethyl, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, Examples thereof include lactic acid methyl ester, lactic acid ethyl ester, lactic acid n-propyl ester, lactic acid n-butyl ester, lactic acid isoamyl ester, or solvents represented by the above formulae [D-1] to [D-3].

Among these, it is preferable to use 1-hexanol, cyclohexanol, 1,2-ethanediol, 1,2-propanediol, propylene glycol monobutyl ether, ethylene glycol monobutyl ether or dipropylene glycol dimethyl ether.

These empty solvents are preferably 1 to 80 mass% of the total solvent contained in the liquid crystal alignment agent. Among them, 10 to 80 mass% is preferable. More preferably, 20 to 70 mass% is more preferable.

In addition to the above, the liquid crystal alignment agent of the present invention may further contain, in addition to the polymer described in the present invention, a dielectric or conductive material for changing electrical properties such as permittivity or conductivity of the liquid crystal alignment film, a silane coupling agent for improving adhesion between the liquid crystal alignment film and the substrate, a crosslinking compound for improving the hardness or density of the film when formed into a liquid crystal alignment film, and further, an imidization accelerator for efficiently promoting imidization of the polyimide precursor by heating when baking the coating film.

＜Liquid crystal alignment film＞

The liquid crystal alignment film of the present invention is a film obtained by applying the liquid crystal alignment agent to a substrate, drying, and baking. The substrate on which the liquid crystal alignment agent of the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, an acrylic substrate, a plastic substrate such as a polycarbonate substrate, etc. can be used, and it is preferable to use a substrate on which an ITO electrode for driving a liquid crystal is formed from the viewpoint of simplifying the process. Furthermore, in a reflective liquid crystal display element, an opaque material such as a silicon wafer can be used as long as it is only one-sided substrate, and in this case, a material that reflects light such as aluminum can also be used as the electrode.

Examples of methods for applying the liquid crystal alignment agent of the present invention include a spin coating method, a printing method, an inkjet method, and the like. The drying and baking processes after applying the liquid crystal alignment agent of the present invention can be performed at any temperature and time. Typically, drying is performed at 50°C to 120°C for 1 to 10 minutes to sufficiently remove the contained organic solvent, and then baking is performed at 150°C to 300°C for 5 to 120 minutes. The thickness of the coating film after baking is not particularly limited, but if it is too thin, the reliability of the liquid crystal display element may be lowered, and therefore, it is 5 to 300 nm, preferably 10 to 200 nm.

Methods for aligning the obtained liquid crystal alignment film include a rubbing method and a photoalignment method.

Rubbing treatment can be performed using an existing rubbing device. The rubbing cloth material at this time can include cotton, nylon, rayon, etc. The rubbing treatment conditions are generally a rotation speed of 300 to 2000 rpm, a feed speed of 5 to 100 mm/s, and a pressurization amount of 0.1 to 1.0 mm. After that, residues generated by rubbing are removed by ultrasonic cleaning using pure water or alcohol.

As a specific example of the light alignment treatment method, there can be mentioned a method of irradiating the surface of the coating film with radiation biased in a certain direction and, in some cases, additionally heat-treating at a temperature of 150 to 250°C to impart liquid crystal alignment ability. As the radiation, ultraviolet rays and visible light having a wavelength of 100 to 800 nm can be used. Among these, ultraviolet rays having a wavelength of 100 to 400 nm are preferable, and those having a wavelength of 200 to 400 nm are particularly preferable. Furthermore, in order to improve the liquid crystal alignment ability, radiation may be irradiated while heating the coating film substrate at 50 to 250°C. The dose of the radiation is preferably 1 to 10,000 mJ/cm2, and particularly preferably 100 to 5,000 mJ/cm2. The liquid crystal alignment film produced as described above can stably align liquid crystal molecules in a certain direction.

The higher the extinction ratio of polarized ultraviolet light, the higher the anisotropy can be imparted, which is desirable. Specifically, the extinction ratio of linearly polarized ultraviolet light is preferably 10:1 or higher, and more preferably 20:1 or higher.

In the above, the film irradiated with polarized radiation may then be contact-treated with a solvent containing at least one selected from water and an organic solvent.

The solvent used in the contact treatment is not particularly limited as long as it is a solvent that dissolves the decomposition product generated by light irradiation. Specific examples include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 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. Two or more of these solvents may be used in combination.

In terms of versatility and safety, at least one selected from the group consisting of water, 2-propanol, 1-methoxy-2-propanol, and ethyl lactate is more preferable. Water, 2-propanol, and a mixed solvent of water and 2-propanol are particularly preferable.

In the present invention, the contact treatment of the film irradiated with polarized radiation and the solution containing an organic solvent is preferably carried out by a treatment in which the film and the liquid are sufficiently brought into contact, such as an immersion treatment or a spray treatment. Among these, a method in which the film is immersed 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 heated, but is preferably carried out at 10 to 80°C, more preferably 20 to 50°C. In addition, a means for increasing contact, such as ultrasonic waves, may be carried out as necessary.

After the above contact treatment, for the purpose of removing the organic solvent in the solution used, either rinsing with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, or methyl ethyl ketone, or drying, or both, may be performed.

In addition, the film that has undergone contact treatment with a solvent as described above may be heated at 150°C 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°C. The higher the temperature, the more the reorientation of the molecular chains is promoted. However, if the temperature is too high, there is a risk of decomposition of the molecular chains. Therefore, the heating temperature is more preferably 180 to 250°C, and particularly preferably 200 to 230°C.

The heating time is preferably 10 seconds to 30 minutes, more preferably 1 to 10 minutes, because if it 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.

＜Liquid crystal display element＞

The liquid crystal display device of the present invention is characterized by having a liquid crystal alignment film obtained by the method for producing the liquid crystal alignment film.

The liquid crystal display element of the present invention is obtained by obtaining a substrate to which a liquid crystal alignment film is attached by the method for producing a liquid crystal alignment film from the liquid crystal alignment agent of the present invention, manufacturing a liquid crystal cell by a known method, and using the same to form a liquid crystal display element.

As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display element of a passive matrix structure will be described. In addition, a liquid crystal display element of an active matrix structure in which switching elements such as TFT (Thin Film Transistor) are formed in each pixel portion constituting an image display may also be used.

First, transparent glass substrates are prepared, and common electrodes are formed on one substrate and segment electrodes are formed on the other substrate. These electrodes can be, for example, ITO electrodes, and are patterned so as to enable a desired image display. Next, an insulating film is formed on each substrate so as to cover the common electrode and the segment electrode. The insulating film can be, for example, a film made of SiO ₂ -TiO ₂ formed by a sol-gel method.

Next, the liquid crystal alignment film of the present invention is formed on each substrate. Next, one substrate is polymerized with the other substrate so that their alignment film surfaces face each other, and the surrounding area is bonded with a sealant. In order to control the substrate gap, a spacer is usually mixed into the sealant. In addition, it is preferable to disperse a spacer for controlling the substrate gap even in a portion of the surface where the sealant is not formed. An opening capable of filling the liquid crystal from the outside is provided in a part of the sealant.

Next, through the opening formed in the sealant, the liquid crystal material is injected into the space surrounded by the two substrates and the sealant. Thereafter, the opening is sealed with an adhesive. For the injection, a vacuum injection method may be used, or a method utilizing a capillary phenomenon in the air may be used. Next, a polarizing plate is installed. Specifically, a pair of polarizing plates is attached to the surfaces of the two substrates opposite to the liquid crystal layers. By performing the above process, the liquid crystal display element of the present invention is obtained.

In the present invention, as a sealant, 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, an acetyl group, etc., and curing by ultraviolet irradiation or heating is used. In particular, it is preferable to use a curable resin system having both reactive groups of an epoxy group and a (meth)acryloyl group.

In order to improve adhesiveness and moisture resistance, an inorganic filler may be added to the sealant of the present invention. The inorganic filler that can be used is not particularly limited, but specifically, 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, asbestos, and the like can be mentioned, and preferably, 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, aluminum silicate. The above-mentioned inorganic fillers may be used in combination of two or more types.

Example

Hereinafter, the present invention will be specifically described with examples and the like, but the present invention is not limited to these examples. In addition, the meanings of the abbreviations of the compounds are as follows.

[Chemical formula 47]

[Chemical formula 48]

[Chemical Formula 49]

[Chemical formula 50]

NMP: N-methyl-2-pyrrolidone, BCS: butyl cellosolve

THF: Tetrahydrofuran

AIBN: 2,2'-Azobisisobutyronitrile

( ^1H -NMR measurement)

Devices: Varian NMR system 400NB (400 MHz) (manufactured by Varian), and JMTC-500/54/SS (500 MHz) (manufactured by JEOL)

Measuring solvent: CDCl ₃ (deuterated chloroform), DMSO-d ₆ (deuterated dimethyl sulfoxide)

Reference substances: TMS (tetramethylsilane) (δ: 0.0 ppm, ¹ H) and CDCl ₃ (δ: 77.0 ppm, ¹³ C)

＜Synthesis of Additive E1＞

[Chemical Formula 51]

To toluene (25 g) and purified water (2.5 g), epichlorohydrin (52.1 g) and 4,4'-diamino-N-methyldiphenylamine (10.0 g, 46.9 mmol) were added, and the mixture was stirred at 80°C for 4 hours. After cooling to room temperature, tetrabutylammonium hydrogen sulfate (0.48 g) and a 48% aqueous sodium hydroxide solution (23.5 g) were added, and the mixture was stirred at 35°C for 3 hours, and then at room temperature for 16 hours. Pure water (50 g) was added, and a separation operation was performed, and the oil layer was washed with pure water (50 g), dehydrated with magnesium sulfate, and the filtrate was concentrated, thereby obtaining a crude product. After dissolving the crude product in toluene (150 g), the resultant was filtered using a Kiriyama funnel with silica gel (20 g) placed on the filter surface. Further, after flowing toluene (50 g), the combined filtrates were concentrated to obtain compound [E1] (amount: 13.2 g, yield: 64%), brown viscous substance).

＜Synthesis of Additive E2＞

[Chemical formula 52]

To toluene (25 g) and purified water (2.5 g), epichlorohydrin (55.4 g) and 4,4'-diaminodiphenyl ether (10.0 g, 49.9 mmol) were added, and the mixture was stirred at 80°C for 23 hours. After cooling to room temperature, tetrabutylammonium hydrogen sulfate (0.51 g) and a 48% aqueous sodium hydroxide solution (25.0 g) were added, and the mixture was stirred at 35°C for 5 hours. Pure water (50 g) was added, and a separation operation was performed, and the oil layer was washed with purified water (50 g), dehydrated with magnesium sulfate, and the filtrate was concentrated to obtain a crude product. The crude product was dissolved in toluene (150 g), and then filtered using a Kiriyama funnel having silica gel (20 g) placed on the filter surface. In addition, by flowing toluene (50 g) and concentrating the combined filtrate, compound [E2] was obtained (amount: 15.3 g, yield: 72%), an orange-colored viscous substance).

＜Viscosity＞

In the synthesis example, the viscosity of the polymer solution was measured using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) with a sample amount of 1.1 mL, cone rotor TE-1 (1°34', R24), and a temperature of 25°C.

(Synthesis Example 1)

In a 5 ℓ four-necked flask equipped with a stirring device and a nitrogen introduction tube, 57.3 g (200 mmol) of DA-1 was weighed, 1147 g of NMP was added, and the mixture was dissolved by stirring while sending nitrogen. While stirring this diamine solution under water cooling, 29.4 g (150 mmol) of CA-1 and 191 g of NMP were added, and the mixture was stirred at 23°C for 1 hour under a nitrogen atmosphere. Thereafter, 119.3 g (400 mmol) of DA-2 and 60.1 g (400 mmol) of DA-3 were weighed, 1721 g of NMP was added, and the mixture was dissolved by stirring while sending nitrogen. While stirring this diamine solution under water cooling, 158.8 g (810 mmol) of CA-1 was added, 765 g of NMP was added, and the mixture was stirred for 6 hours at 23°C under a nitrogen atmosphere to obtain a polyamic acid solution (viscosity: 180 mPa·s).

(Synthesis Example 2)

MA1 (5.3 g) and MA2 (19.6 g) were dissolved in THF (102.6 g), and degassing was performed using a diaphragm pump, after which AIBN (0.39 g) was added and degassing was performed again. After this, the reaction was performed at 60°C for 8 hours to obtain a methacrylate polymer solution. This polymer solution was added dropwise to methanol (600 mL), and the obtained precipitate was filtered. The precipitate was washed with methanol and dried under reduced pressure in an oven at 40°C to obtain methacrylate polymer powder MP1.

[Example 1] and [Comparative Examples 1 and 2]

The polyamic acid solution obtained in Synthesis Example 1 was stirred so that the composition of the resulting liquid crystal alignment agent had the composition shown in Table 1, and a solvent and an additive were added thereto, and further stirred at room temperature for 2 hours to obtain a liquid crystal alignment agent.

※1: Indicates the content (weight parts) of each polymer relative to 100 weight parts of the total polymer in the liquid crystal alignment agent.

※2: Indicates the content (weight parts) of each additive relative to 100 weight parts of the total polymer in the liquid crystal alignment agent.

※3: Indicates the content (weight parts) of each solvent per 100 mass parts of liquid crystal alignment agent.

[Example 2] and [Comparative Examples 3 and 4]

NMP was added to the methacrylate powder obtained in Synthesis Example 2, and stirred for 30 minutes to obtain a methacrylate polymer solution. While stirring, a solvent and an additive were added, and further stirred at room temperature for 2 hours to obtain a liquid crystal alignment agent so that the composition of the resulting liquid crystal alignment agent was as shown in Table 2.

※1: Indicates the content (weight parts) of each polymer relative to 100 weight parts of the total polymer in the liquid crystal alignment agent.

※2: Indicates the content (weight parts) of each additive relative to 100 weight parts of the total polymer in the liquid crystal alignment agent.

※3: Indicates the content (weight parts) of each solvent per 100 mass parts of liquid crystal alignment agent.

Below, a method for manufacturing a liquid crystal cell for evaluating the relaxation characteristics of accumulated charge, flicker characteristics, and liquid crystal orientation is described.

A liquid crystal cell having a configuration of an FFS type liquid crystal display element is fabricated. First, a substrate to which electrodes are attached is prepared. The substrate is a glass substrate measuring 30 mm in length, 35 mm in width, and 0.7 mm in thickness. An IZO electrode, which constitutes a counter electrode as a first layer, is formed over the entire surface of the substrate. On the counter electrode of the first layer, a SiN (silicon nitride) film formed by the CVD method is formed as a second layer. The film thickness of the second SiN film is 500 nm, and functions as an interlayer insulating film. On the second SiN film, a comb-shaped pixel electrode formed by patterning an IZO film as a third layer is arranged, thereby forming two pixels, a first pixel and a second pixel. The size of each pixel is approximately 10 mm in length and 5 mm in width. At this time, the first layer counter electrode and the third layer pixel electrode are electrically insulated by the action of the second layer SiN film.

The third layer pixel electrode has a comb-shaped shape formed by arranging a plurality of "く" shaped electrode elements whose central portions are curved. The width in the width direction of each electrode element is 3 ㎛, and the interval between the electrode elements is 6 ㎛. Since the pixel electrode forming each pixel is formed by arranging a plurality of "く" shaped electrode elements whose central portions are curved, the shape of each pixel is not a rectangular shape, but has a shape similar to the bold "く" character that is curved in the central portion similarly to the electrode elements. Then, each pixel is divided upper and lower with the curved portion in the center as a boundary, and has a first region above the curved portion and a second region below the curved portion.

Comparing the first region and the second region of each pixel, the formation directions of the electrode elements of the pixel electrodes constituting them are different. That is, when the rubbing direction of the liquid crystal alignment film described later is used as a standard, in the first region of the pixel, the electrode elements of the pixel electrode are formed to form an angle of +10° (clockwise), and in the second region of the pixel, the electrode elements of the pixel electrode are formed to form an angle of -10° (clockwise). That is, in the first region and the second region of each pixel, the directions of the rotational operation (in-plane switching) of the liquid crystal within the substrate plane caused by the application of voltage between the pixel electrode and the opposing electrode are configured to be opposite to each other.

Next, the liquid crystal alignment agent obtained in the examples and comparative examples was filtered through a filter having a hole diameter of 1.0 ㎛, and then applied to the prepared substrate with the electrode attached by spin coating. After drying on a hot plate at 80° C. for 2 minutes, baking was performed in a hot air circulation oven at 230° C. for 20 minutes, thereby obtaining a polyimide film having a film thickness of 60 nm. This polyimide film was rubbed with rayon cloth (roller diameter: 120 mm, roller rotation speed: 500 rpm, moving speed: 30 mm/sec, pressing length: 0.3 mm, rubbing direction: 10° inclined direction with respect to the third-layer IZO comb-tooth electrode), and then cleaned by ultrasonic irradiation in pure water for 1 minute, and water droplets were removed by air blow. Thereafter, drying was performed at 80° C. for 15 minutes, thereby obtaining a substrate with a liquid crystal alignment film attached. In addition, a polyimide film was formed on a glass substrate having a 4 ㎛ high columnar spacer on the back surface of which an ITO electrode was formed as a counter substrate in the same manner as above, and a substrate having a liquid crystal alignment film attached thereto, which was subjected to alignment processing in the same manner as above, was obtained. These two substrates having a liquid crystal alignment film attached thereto were used as one set, and a sealant was printed on the substrate in a form in which a liquid crystal injection port was left, and another substrate was adhered so that the liquid crystal alignment film surfaces faced each other and the rubbing directions were opposite and parallel. Thereafter, the sealant was cured to produce an empty cell having a cell gap of 4 ㎛. The liquid crystal MLC-3019 (manufactured by Merck) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS type liquid crystal cell. Thereafter, the obtained liquid crystal cell was heated at 120 ° C. for 1 hour, left at 23 ° C. overnight, and then used for evaluating the liquid crystal alignment properties.

＜Relaxation characteristics of accumulated charge＞

The above liquid crystal cell was installed between two polarizing plates arranged so that their polarization axes are orthogonal, and while the pixel electrode and the opposing electrode were short-circuited to have the same potential, an LED backlight was irradiated from below the two polarizing plates, and the angle of the liquid crystal cell was adjusted so that the brightness of the LED backlight transmitted light measured on the two polarizing plates was minimized.

Next, while applying a square wave with a frequency of 30 Hz to the liquid crystal cell, the V-T characteristics (voltage-transmittance characteristics) at a temperature of 23°C were measured, and an AC voltage at which the relative transmittance was 23% was calculated. Since this AC voltage corresponds to a region in which the luminance changes significantly with respect to the voltage, it is appropriate for evaluating the accumulated charge through luminance.

Next, an AC voltage having a relative transmittance of 23% at a temperature of 23°C and a square wave having a frequency of 30 Hz was applied for 5 minutes, and then a DC voltage of +1.0 V was superimposed and driven for 30 minutes. Thereafter, the DC voltage was turned off, and only an AC voltage having a relative transmittance of 23% and a square wave having a frequency of 30 Hz was applied for 15 minutes.

The faster the relaxation of accumulated charge, the faster the charge accumulation in the liquid crystal cell when a DC voltage is superimposed. Therefore, the relaxation characteristics of accumulated charge were evaluated by the time required for the relative transmittance to decrease by 2% or more from the immediate aftermath of the DC voltage. That is, when the relative transmittance decreased by 2% or more within 30 minutes, it was defined as “good,” and when the relative transmittance did not decrease by 2% or more even after 30 minutes, it was defined as “poor.”

＜Evaluation of liquid crystal orientation＞

Using this liquid crystal cell, an AC voltage of 9 VPP at a frequency of 30 Hz was applied for 190 hours in a constant temperature environment of 60°C. After that, the pixel electrode and the counter electrode of the liquid crystal cell were short-circuited, and the cell was left at room temperature for one day.

After standing, the liquid crystal cell was installed between two polarizing plates arranged so that their polarization axes are orthogonal, the backlight was turned on without applying voltage, and the arrangement angle of the liquid crystal cell was adjusted so that the brightness of the transmitted light became the smallest. Then, the rotation angle when the liquid crystal cell was rotated from the angle at which the second area of the first pixel became the darkest to the angle at which the first area became the darkest was calculated as the angle Δ. Similarly, in the second pixel, the second area and the first area were compared to calculate the same angle Δ. Then, the average of the angle Δ values of the first pixel and the second pixel was calculated as the angle Δ of the liquid crystal cell. When the value of the angle Δ of the liquid crystal cell was less than 0.2 degrees, it was evaluated as “good”, and when the value of the angle Δ was 0.2 degrees or more, it was evaluated as “bad”.

＜Evaluation of voltage maintenance ratio (VHR)＞

A voltage of 1 V was applied to the obtained liquid crystal cell for 60 μs at a temperature of 60 °C, the voltage after 50 ms was measured, and the degree to which the voltage could be maintained was calculated as the voltage retention ratio. In addition, for the measurement of the voltage retention ratio, a voltage retention ratio measuring device VHR-1 manufactured by Toyo Technica Corporation was used.

＜Evaluation of optical properties (transparency)＞

A quartz substrate measuring 40 mm in length, 40 mm in width, and 1.0 mm in thickness was prepared. Next, a liquid crystal alignment agent was filtered through a 1.0 μm filter and spin-coated onto the quartz substrate. Subsequently, after drying on a hot plate at 80 ° C. for 2 minutes, it was baked at 230 ° C. for 20 minutes, and a polyimide film having a thickness of 100 nm was obtained on each substrate.

The evaluation of transparency was carried out by measuring the transmittance of the substrate obtained by the above method. Specifically, the transmittance was measured under the conditions of a temperature of 25°C and a scan wavelength of 300 to 800 nm using UV-3600 (manufactured by Shimadzu Corporation) as a measuring device. At that time, the evaluation was carried out using a quartz substrate on which nothing was coated as a reference (reference example). The evaluation was carried out by calculating the average transmittance at a wavelength of 400 to 800 nm, and the higher the transmittance, the better the transparency.

＜Evaluation Results＞

The results of the evaluation of the afterimage erasing time, the evaluation of the stability of the liquid crystal alignment, and the evaluation of the transparency of the liquid crystal display elements using the respective liquid crystal alignment agents of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 3.

※1: Indicates the content (weight parts) of each polymer relative to 100 weight parts of the total polymer in the liquid crystal alignment agent.

※2: Indicates the content (weight parts) of each additive relative to 100 weight parts of the total polymer in the liquid crystal alignment agent.

As shown in Table 3, it can be seen that the liquid crystal display element using the liquid crystal alignment agent of Example 1 has excellent voltage retention, fast relaxation of accumulated charge, and good liquid crystal alignment and transparency.

Industrial applicability

The liquid crystal alignment agent of the present invention is widely used in liquid crystal display elements of vertical field methods such as the TN method and the VA method, and particularly, horizontal field methods such as the IPS method and the FFS method.

Additionally, the entire disclosure of the specification, claims, and abstract of Japanese Patent Application No. 2018-51092, filed March 19, 2018, is incorporated herein by reference and is hereby incorporated by reference as disclosure of the specification of the present invention.

Claims (12)

A liquid crystal alignment agent characterized by containing the following (A) component, (B) component, and an organic solvent.
(A) Component: At least one polymer selected from the group consisting of a polyimide precursor, an imidized polymer of the polyimide precursor, and a photosensitive side-chain acrylic polymer exhibiting liquid crystallinity in a temperature range of 100 to 300°C.
(B) Component: At least one compound selected from the following formulas Q1-1-1, Q1-1-2, Q1-1-3, Q1-1-4 and Q1-1-6
In paragraph 1,
A liquid crystal alignment agent, wherein the polyimide precursor, which is the component (A), has a structural unit represented by the following formula (A1).

(In formula (A1), X ₁ is a tetravalent organic group. Y ₁ is a divalent organic group. R ₁ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and A ₁ and A ₂ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, an alkenyl group having 2 to 10 carbon atoms which may have a substituent, or an alkynyl group having 2 to 10 carbon atoms which may have a substituent.) In the second paragraph,
A liquid crystal alignment agent wherein, in the above formula (A1), Y ₁ is at least one selected from structures represented by the following formulas (5) and (6).

(In formula (5), R ₁₂ is a single bond or a divalent organic group having 1 to 30 carbon atoms. R ₁₃ is a hydrogen atom, a halogen atom, or a monovalent organic group having 1 to 30 carbon atoms. a is an integer of 1 to 4. When a is 2 or more, two or more R _12s and two or more R _13s may be the same or different. In formula (6), R ₁₄ is a single bond, -O-, -S-, -NR ₁₅ -, an amide bond, an ester bond, a urea bond, or a divalent organic group having 1 to 40 carbon atoms, and R ₁₅ is a hydrogen atom or a methyl group.) In paragraph 1,
A liquid crystal alignment agent having a side chain structure composed of at least one type of the following formulae (i) to (v), wherein the photosensitive side chain-type acrylic polymer exhibits liquid crystal properties in a temperature range of 100 to 300°C, which is the component (A).

(In formulas (i) to (v), Ar ₁ is a divalent substituent having two hydrogen atoms removed from a benzene ring, a naphthalene ring, a pyrrole ring, a furan ring, a thiophene ring, or a pyridine ring.
Ar ₂ and Ar ₃ are each independently a divalent substituent having two hydrogen atoms removed from a benzene ring, a naphthalene ring, a pyrrole ring, a furan ring, a thiophene ring or a pyridine ring. One of q1 and q2 is 1 and the other is 0. Ar ₄ and Ar ₅ each independently represent a divalent substituent having two hydrogen atoms removed from a benzene ring, a naphthalene ring, a pyrrole ring, a furan ring, a thiophene ring or a pyridine ring. Y ₁ and Y ₂ are each independently -CH=CH-, -CH=N-, -N=CH- or -C≡C-. S ₁ , S ₂ and S ₃ each independently represent a divalent substituent composed of a single bond, a linear or branched alkylene group having 1 to 18 carbon atoms, a cycloalkylene group having 5 to 8 carbon atoms, a phenylene group, a biphenylene group, or a combination of 2 to 10 thereof. In addition, the divalent substituents may have a structure in which plural of them are each connected via a single bond, an ether bond, an ester bond, an amide bond, a urea bond, a urethane bond, an amino bond, or a carbonyl bond. R ₁₁ is a hydrogen atom, a hydroxyl group, a mercapto group, an amino group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an alkylamino group having 1 to 8 carbon atoms, or a dialkylamino group having 2 to 16 carbon atoms.) In paragraph 1,
A liquid crystal alignment agent, wherein the organic solvent is N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, or 4-hydroxy-4-methyl-2-pentanone. In paragraph 5,
A liquid crystal alignment agent, wherein the organic solvent further comprises a solvent that improves the film properties or surface smoothness of the liquid crystal alignment film. In paragraph 1,
A liquid crystal alignment agent containing 1 to 10 mass% of a polymer including the above-mentioned (A) component among liquid crystal alignment agents. In paragraph 7,
A liquid crystal alignment agent containing 0.1 to 20 mass% of the above-mentioned (B) component with respect to the above-mentioned (A) component. A liquid crystal alignment film obtained from the liquid crystal alignment agent described in any one of claims 1 to 8. A liquid crystal display device having a liquid crystal alignment film as described in claim 9. delete delete