TWI869411B - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

The invention relates to a liquid crystal alignment including a polymer (A) and a solvent (B). The polymer (A) includes a first polymer (A1) and a second polymer (A2). The first polymer (A1) is formed by reaction of a first mixture including a tetracarboxylic dianhydride component (a1) and a diamine component (b1). The diamine component (b1) includes at least one diamine compound (b1-1) represented as formula (I). The second polymer (A2) is formed by reaction of a first mixture including a tetracarboxylic dianhydride component (a2) and a diamine component (b2). The diamine component (b2) includes at least one diamine compound (b2-1) represented as formula (II). The invention further relates to a liquid crystal alignment film formed of the liquid crystal alignment agent, and a liquid crystal display element including the liquid crystal alignment film.

Description

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

The present disclosure relates to a liquid crystal alignment agent, a liquid crystal alignment film and a liquid crystal display element, and in particular to a liquid crystal alignment agent with good environmental resistance and not prone to afterimages, a liquid crystal alignment film formed by the aforementioned liquid crystal alignment agent and a liquid crystal display element having the aforementioned liquid crystal alignment film.

Liquid crystal display elements of liquid crystal televisions, liquid crystal displays, etc. usually have a liquid crystal alignment film inside the element to control the liquid crystal arrangement state. The most common method for forming a liquid crystal alignment film in the industry is to form a film of polyamide and/or imide-modified polyimide on an electrode substrate, and then rub it (i.e. rub the film surface in a single direction with cotton, nylon, polyester and other fabrics) to produce a liquid crystal alignment film.

In the process of aligning the liquid crystal alignment film, the method that is easier to produce in industry is to perform friction treatment on the film surface. However, with the increasing requirements for high performance, high precision, and large-scale liquid crystal display elements, during the friction treatment, the surface damage of the liquid crystal alignment film, dust, the influence caused by mechanical force and electrostatic force, and the unevenness on the alignment treatment surface have become more and more obvious.

As a method to replace the friction treatment, a photo-alignment method that uses polarized ultraviolet light to impart alignment energy to the liquid crystal is currently known. The liquid crystal alignment treatment of the photo-alignment method may include substances that utilize photoisomerization reactions, substances that utilize photocrosslink reactions, substances that utilize photodecomposition reactions, etc. in the reaction mechanism. Furthermore, the Japanese Patent Publication No. 9-297313 proposes that the photo-alignment method uses a polyimide film with an alicyclic structure such as cyclobutane in the main chain. When polyimide is used as an alignment film for photo-alignment, the applicability of this alignment film is highly anticipated because the heat resistance of this alignment film is higher than that of other types of alignment films.

The optical alignment method is a method that does not require rubbing alignment treatment. It not only has the advantage of simple process in industry, but also in the liquid crystal display elements of the In-Plane-Switching (IPS) driving method and the Fringe Field Switching (FFS) driving method, the liquid crystal alignment film obtained by the optical alignment method can improve the contrast and viewing angle characteristics of the liquid crystal display element compared to the liquid crystal alignment film obtained by the rubbing treatment method. Therefore, the optical alignment method is a promising and highly anticipated liquid crystal alignment treatment method.

However, when the liquid crystal alignment film produced by the photo-alignment method is applied to liquid crystal display elements, it still has problems such as poor environmental resistance and easy to produce afterimages. From the above, it can be seen that in order to meet the requirements of current photo-aligned IPS type liquid crystal display industry, providing a liquid crystal alignment agent that can form a liquid crystal display element with good environmental resistance and not easy to produce afterimages is the goal of the research efforts of the technical field.

The present invention uses the special composition and/or ratio of the liquid crystal alignment agent to enable the liquid crystal alignment film produced therefrom to have advantages such as good environmental resistance and/or less prone to afterimages when used in liquid crystal display devices.

Therefore, the present invention provides a liquid crystal alignment agent, comprising: a polymer (A); and a solvent (B); wherein the polymer (A) comprises a first polymer (A1) and a second polymer (A2), the first polymer (A1) being prepared by reacting a first mixture, the first mixture comprising a tetracarboxylic dianhydride component (a1) and a diamine component (b1), wherein the diamine component (b1) comprises at least one diamine compound (b1-1) represented by formula (I):

In formula (I), ^R1 to ^R10 are the same or different hydrogen atoms or monovalent organic groups, wherein ^R1 to ^R10 contain at least two primary amino groups; the second polymer (A2) is prepared by reacting a second mixture, wherein the second mixture comprises a tetracarboxylic dianhydride component (a2) and a diamine component (b2), wherein the diamine component (b2) comprises at least one diamine compound (b2-1) represented by formula (II):

In formula (II), _E1 and _E5 each independently represent a single bond or an alkylene group having 1 to 5 carbon atoms; _E2 and _E4 each independently represent an alkylene group having 1 to 5 carbon atoms; _E3 represents an alkylene group having 1 to 6 carbon atoms or a cycloalkylene group; _B1 and _B2 each independently represent a single bond, -O-, -NH-, _-NCH3- , -C(=O)-, -C(=O)O-, -C(=O) _NCH3- , -OC(=O)-, -NHC(=O)- or -N( _CH3 )C(=O)-; a represents 0 or 1; and _D1 has the structure represented by formula (II-1):

In formula (II-1), R is a linear, branched or cyclic monovalent hydrocarbon group with 1 to 20 carbon atoms, and * represents a linking group.

The present invention also provides a liquid crystal alignment film formed by the aforementioned liquid crystal alignment agent.

The present invention also provides a liquid crystal display element, comprising the aforementioned liquid crystal alignment film.

100: Liquid crystal display element

110: Unit 1

112: First substrate

114: First conductive film

116: First liquid crystal alignment film

120: Unit 2

122: Second substrate

126: Second liquid crystal alignment film

130: Liquid crystal unit

Figure 1 is a side view of a liquid crystal display element according to an embodiment of the present invention.

The present invention provides a liquid crystal alignment agent, comprising: a polymer (A); and a solvent (B); wherein the polymer (A) comprises a first polymer (A1) and a second polymer (A2), wherein the first polymer (A1) is prepared by reacting a first mixture, wherein the first mixture comprises a tetracarboxylic dianhydride component (a1) and a diamine component (b1), wherein the diamine component (b1) comprises at least one diamine compound (b1-1) represented by formula (I):

In formula (I), ^R1 to ^R10 are the same or different hydrogen atoms or monovalent organic groups, wherein ^R1 to ^R10 contain at least two primary amino groups; the second polymer (A2) is prepared by reacting a second mixture, wherein the second mixture comprises a tetracarboxylic dianhydride component (a2) and a diamine component (b2), wherein the diamine component (b2) comprises at least one diamine compound (b2-1) represented by formula (II):

In formula (II), _E1 and _E5 each independently represent a single bond or an alkylene group having 1 to 5 carbon atoms; _E2 and _E4 each independently represent an alkylene group having 1 to 5 carbon atoms; _E3 represents an alkylene group having 1 to 6 carbon atoms or a cycloalkylene group; _B1 and _B2 each independently represent a single bond, -O-, -NH-, _-NCH3- , -C(=O)-, -C(=O)O-, -C(=O) _NCH3- , -OC(=O)-, -NHC(=O)- or -N( _CH3 )C(=O)-; a represents 0 or 1; and _D1 has the structure represented by formula (II-1):

In formula (II-1), R is a linear, branched or cyclic monovalent hydrocarbon group with 1 to 20 carbon atoms, and * represents a linking group.

First polymer (A1)

The first polymer (A1) of the present invention is prepared by reacting the first mixture. Specifically, the first polymer (A1) can be selected from polyamic acid polymers, polyimide polymers, polyimide block copolymers or any combination of the above polymers. Among them, the polyimide block copolymer is selected from polyamic acid block copolymers, polyimide block copolymers, polyamic acid-polyimide block copolymers or any combination of the above polymers.

The first mixture comprises a tetracarboxylic dianhydride component (a1) and a diamine component (b1), wherein the tetracarboxylic dianhydride component (a1) is preferably (1) an aliphatic tetracarboxylic dianhydride compound, (2) an alicyclic tetracarboxylic dianhydride compound, (3) an aromatic tetracarboxylic dianhydride compound, or (4) a tetracarboxylic dianhydride compound represented by formula (a1-1) to formula (a1-6).

The (1) aliphatic tetracarboxylic dianhydride compound of the present invention includes but is not limited to aliphatic tetracarboxylic dianhydride compounds such as ethanetetracarboxylic dianhydride or butanetetracarboxylic dianhydride.

The (2) alicyclic tetracarboxylic dianhydride compounds of the present invention include but are not limited to 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dichloro-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, Alicyclic tetracarboxylic acid dianhydride compounds such as 2,3,4-cyclopentanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride, 3,3',4,4'-dicyclohexyltetracarboxylic acid dianhydride, cis-3,7-dibutylcycloheptyl-1,5-diene-1,2,5,6-tetracarboxylic acid dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride or dicyclo[2.2.2]-oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride.

Specific examples of the (3) aromatic tetracarboxylic dianhydride compounds of the present invention include, but are not limited to, 3,4-dicarboxy-1,2,3,4-tetrahydronaphthalene-1-succinic dianhydride, pyromellitic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydronaphthalene-1-succinic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,3,6,7-naphthalene ... ,3'-4,4'-diphenylethane tetracarboxylic dianhydride, 3,3',4,4'-dimethyldiphenylsilane tetracarboxylic dianhydride, 3,3',4,4'-tetraphenylsilane tetracarboxylic dianhydride, 1,2,3,4-furan tetracarboxylic dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfide dianhydride, 2,3,3',4'-diphenyl Sulfide tetracarboxylic dianhydride, 3,3',4,4'-diphenyl sulfide tetracarboxylic dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenylsulfone dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenylpropane dianhydride, 3,3',4,4'-perfluoroisopropylidene diphthalic acid dianhydride, 2,2',3,3'-diphenyltetracarboxylic dianhydride, 2,3,3',4'-diphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyltetracarboxylic dianhydride , bis(phthalic acid) phenylphosphine oxide dianhydride, p-phenylene-bis(triphenylphthalic acid) dianhydride, m-phenylene-bis(triphenylphthalic acid) dianhydride, bis(triphenylphthalic acid)-4,4'-diphenyl ether dianhydride, bis(triphenylphthalic acid)-4,4'-diphenylmethane dianhydride, ethylene glycol-bis(dehydrated trimellitate), propylene glycol-bis(dehydrated trimellitate), 1,4-butanediol-bis(dehydrated trimellitate), 1,6-hexanediol-bis( dehydrated trimellitate), 1,8-octanediol-bis(dehydrated trimellitate), 2,2-bis(4-hydroxyphenyl)propane-bis(dehydrated trimellitate), 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxy-3-furanyl)-naphtho[1,2-c]-furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro-5-methyl-5- (Tetrahydro-2,5-dioxo-3-furyl)-naphtho[1,2-c]-furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro-5-ethyl-5-(tetrahydro-2,5-dioxo-3-furyl)-naphtho[1,2-c]-furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro-7-methyl-5-(tetrahydro-2,5-dioxo-3-furyl)-naphtho[1,2-c ]-furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro-7-ethyl-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]-furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro-8-methyl-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]-furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro- -8-ethyl-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]-furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro-5,8-dimethyl-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-c]-furan-1,3-dione, 5-(2,5-dioxo-tetrahydrofuranyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, etc.

According to (4) of the present invention, the tetracarboxylic dianhydride compound has the following details:

In formula (a1-5), _A1 represents a divalent group containing an aromatic ring; r represents an integer from 1 to 2; _A2 and _A3 may be the same or different and may represent a hydrogen atom or an alkyl group, respectively. Preferably, the tetracarboxylic dianhydride compound represented by formula (a1-5) may be selected from the compounds represented by the following formulas (a1-5-1) to (a1-5-3).

In formula (a1-6), _A4 represents a divalent group containing an aromatic ring; _A5 and _A6 may be the same or different and represent a hydrogen atom or an alkyl group, respectively. Preferably, the tetracarboxylic dianhydride compound represented by formula (a1-6) can be selected from the compounds represented by the following formula (a1-6-1).

In the tetracarboxylic dianhydride component (a1), the above-mentioned tetracarboxylic dianhydride compounds can be used alone or in combination of multiple types.

Based on the usage of 100 mol of the diamine component (b1), the usage of the tetracarboxylic dianhydride component (a1) ranges from 20 mol to 200 mol; preferably, from 30 mol to 120 mol.

The diamine component (b1) of the first mixture comprises at least one diamine compound (b1-1) represented by formula (I):

In formula (I), ^R1 to ^R10 are the same or different hydrogen atoms or monovalent organic groups, wherein ^R1 to ^R10 contain at least two primary amino groups.

In one embodiment, two and only two of R ¹ to R ¹⁰ are primary amino groups.

Specific examples of the diamine compound (b1-1) include the following formula (I-1), wherein two primary amino groups among R ¹ to R ¹⁰ are linked to different benzene rings; or the following formula (I-2), wherein two primary amino groups among R ¹ to R ¹⁰ are linked to the same benzene ring.

The remaining ^R1 to ^R10 are the same or different hydrogen atoms or monovalent organic groups, and the monovalent organic group can be alkyl, alkenyl, cycloalkyl, phenyl, biphenyl, terphenyl, fluorine atom and combinations thereof having a carbon number of 1 to 20. Among the diamine compounds (b1-1), 4,4'-diaminodiphenylamine and 2,4-diaminodiphenylamine are preferred from the viewpoint of their reactivity with tetracarboxylic dianhydride and the liquid crystal alignment when forming a liquid crystal alignment film, and 2,4-diaminodiphenylamine is more preferred.

Based on the total usage of the diamine component (b1) being 100 mol, the usage of the diamine compound (b1-1) is 3 mol to 50 mol, preferably 5 mol to 50 mol, and more preferably 5 mol to 45 mol.

If the diamine component (b1) does not contain the diamine compound (b1-1), the resulting liquid crystal display element has the defect of poor environmental resistance.

The diamine component (b1) may also contain other diamine compounds (b1-2).

Other diamine compounds (b1-2) may include but are not limited to 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 4,4'-diaminoheptane, 1,3-diamino-2,2-dimethylpropane, 1,6-diamino-2,5-dimethylhexane, 1,7-diamino-2,5-dimethylheptane, 1,7-diamino-2,5-dimethylheptane, Amino-4,4-dimethylheptane, 1,7-diamino-3-methylheptane, 1,9-diamino-5-methylnonane, 2,11-diaminododecane, 1,12-diaminooctadecane, 2,6-diaminopyridine, 1,2-bis(3-aminopropoxy)ethane, 4,4'-diaminodicyclohexylmethane, 4,4'-diamino-3,3'-dimethyldicyclohexylamine, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, isophoronediamine, tetrahydrodicyclopentadienediamine, tricyclo[6.2.1.0 ^2,7 ]-undecene dimethyl diamine, 4,4'-methylenebis(cyclohexylamine), 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenylsulfone, 4,4'-diaminobenzanilide, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 5-amino-1-(4'-aminophenyl)-1,3,3-trimethylhydroindane, 6-amino-1-(4'-aminophenyl)- 1,3,3-trimethylhydroindene, hexahydro-4,7-methanedihydroindene dimethylenediamine, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]sulfone, 1,4 -Bis(4-aminophenoxy)cyclohexane, 1,5-bis(4-aminophenoxymethylene)adamantane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)-10-hydroanthracene, 9,10-bis(4-aminophenyl)anthracene, 2,7-diaminofluorene , 9,9-bis(4-aminophenyl)fluorene, 4,4'-methylene-bis(2-chloroaniline), 4,4'-(p-phenyleneisopropylidene)bisaniline, 4,4'-(m-phenyleneisopropylidene)bisaniline, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 4,4'-bis[(4-amino-2-trifluoromethyl)phenoxy]-octafluorobiphenyl, 5-[4-(4-n-pentylcyclohexyl)cyclohexyl]phenylmethylene -1,3-diaminobenzene {5-[4-(4-n-pentylcyclohexyl)cyclohexyl]phenylmethylene-1,3-diaminobenzene}, 1,1-bis[4-(4-aminophenoxy)phenyl]-4-(4-ethylphenyl)cyclohexane {1,1-bis[4-(4-aminophenoxy)phenyl]-4-(4-ethyl phenyl)cyclohexane} or other diamine compounds represented by the following formulas (3-1) to (3-31).

Formula (3-1) is as follows:

、

、

、

或

，且Z₂代表含甾基團、三氟甲基、氟基、碳數為2至30之烷基或衍生自吡啶、嘧啶、三嗪、哌啶及哌嗪等含 氮原子環狀結構的一價基團。 In formula (3-1), Z ₁ represents -O-,

,

,

,

or

, and Z ₂ represents a steryl group, a trifluoromethyl group, a fluoro group, an alkyl group having 2 to 30 carbon atoms, or a monovalent group derived from a nitrogen atom-containing cyclic structure such as pyridine, pyrimidine, triazine, piperidine and piperazine.

The other diamine compounds represented by the above formula (3-1) are preferably 2,4-diaminophenyl ethyl formate, 3,5-diaminophenyl ethyl formate, 2,4-diaminophenyl propyl formate, 3,5-diaminophenyl propyl formate, 1-dodecoxy-2,4-diamino-benzene, 1-hexadecoxy-2,4-diaminobenzene, 1-octadecoxy-2,4-diaminobenzene or other diamine compounds represented by the following formulas (3-1-1) to (3-1-6).

Formula (3-2) is as follows:

、

、

、

或

，Z₄及Z₅代表伸脂肪族環、伸芳香族環或伸雜環基團，且Z₆代表碳數為3至18之烷基、碳數為3至18之烷氧基、碳數為1至5之氟烷基、碳數為1至5之氟烷氧基、氰基或鹵素原子。 In formula (3-2), Z ₃ represents -O-,

,

,

,

or

, Z ₄ and Z ₅ represent an extended aliphatic ring, an extended aromatic ring or an extended heterocyclic group, and Z ₆ represents an alkyl group having 3 to 18 carbon atoms, an alkoxy group having 3 to 18 carbon atoms, a fluoroalkyl group having 1 to 5 carbon atoms, a fluoroalkoxy group having 1 to 5 carbon atoms, a cyano group or a halogen atom.

The other diamine compounds represented by the above formula (3-2) are preferably diamine compounds represented by the following formulas (3-2-1) to (3-2-13):

In formulas (3-2-10) to (3-2-13), s can represent an integer from 3 to 12.

Formula (3-3) is as follows:

In formula (3-3), _Z7 represents a hydrogen atom, an acyl group having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a halogen. P1 represents an integer from 1 to 3. When P1 is greater than 1, a plurality of _Z7 may be the same or different.

The diamine compound represented by the above formula (3-3) is preferably selected from (1) P1 is p-diaminobenzene, m-diaminobenzene, o-diaminobenzene or 2,5-diaminotoluene; (2) P1 is 4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 2,2'-dichloro-4,4'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl , 2,2',5,5'-tetrachloro-4,4'-diaminobiphenyl, 2,2'-dichloro-4,4'-diamino-5,5'-dimethoxybiphenyl or 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, etc.; (3) P1 is 1,4-bis(4'-aminophenyl)benzene, etc., and is more preferably selected from p-diaminobenzene, 2,5-diaminotoluene, 4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl or 1,4-bis(4'-aminophenyl)benzene.

Formula (3-4) is as follows:

In the above formula (3-4), P2 represents an integer from 1 to 5. The structure shown in formula (3-4) is preferably selected from 4,4'-diaminodiphenyl sulfide.

Formula (3-5) is as follows:

In formula (3-5), _Z8 and _Z10 may be the same or different and each represent a divalent organic group, and _Z9 represents a divalent group derived from a nitrogen atom-containing cyclic structure such as pyridine, pyrimidine, triazine, piperidine and piperazine.

Formula (3-6) is as follows:

In formula (3-6), Z ₁₁ , Z ₁₂ , Z ₁₃ and Z ₁₄ may be the same or different, and may represent a alkyl group having a carbon number of 1 to 12. P3 represents an integer of 1 to 3, and P4 represents an integer of 1 to 20.

In formula (3-7), Z ₁₅ represents -O- or a cyclohexylene group, Z ₁₆ represents -CH ₂ -, Z ₁₇ represents a phenylene group or a cyclohexylene group, and Z ₁₈ represents a hydrogen atom or a heptyl group.

The diamine compound represented by the above formula (3-7) is preferably selected from the diamine compounds represented by the following formulas (3-7-1) and (3-7-2).

Other diamine compounds represented by formula (3-8) to formula (3-31) are as follows:

In formula (3-16) to formula (3-19), Z ₁₉ is preferably an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms. In formula (3-20) to formula (3-24), Z ₂₀ is preferably a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms.

The other diamine compounds (b1-2) preferably include but are not limited to 1,2-diaminoethane, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 5-[4-(4-n-pentylcyclohexyl)cyclohexyl]phenylmethylene-1,3-diaminobenzene, 1,3-bis(3-aminophenoxy)benzene, 1,1-bis[4-(4 -aminophenoxy)phenyl]-4-(4-ethylphenyl)cyclohexane, ethyl 2,4-diaminophenylcarboxylate, p-diaminobenzene, m-diaminobenzene, o-diaminobenzene, compounds represented by formula (3-1-1), formula (3-1-2), formula (3-1-5), formula (3-2-1), formula (3-2-11), formula (3-7-1), formula (3-25) or formula (3-28).

The aforementioned other diamine compounds (b1-2) can be used alone or in combination of two or more.

Based on the total usage of the diamine component (b1) being 100 mol, the usage of the other diamine compounds (b1-2) is 80 mol to 99 mol, preferably 85 mol to 99 mol, and more preferably 90 mol to 99 mol.

Method for preparing the first polymer (A1)

The preparation of the polyamine polymer of the present invention can be a general method. Preferably, the preparation method of the polyamine polymer comprises the following steps: dissolving the first mixture comprising the tetracarboxylic dianhydride component (a1) and the diamine component (b1) in a solvent, carrying out a polycondensation reaction at a temperature of 0°C to 100°C for 1 hour to 24 hours, and then distilling the reaction solution under reduced pressure in an evaporator to obtain the polyamine polymer, or pouring the reaction solution into a large amount of a poor solvent to obtain a precipitate, and then drying the precipitate by reduced pressure drying to obtain the polyamine polymer.

The solvent used in the polymerization reaction may be the same as or different from the solvent in the liquid crystal alignment agent described below, and there is no particular limitation on the solvent used in the polymerization reaction, as long as it can dissolve the reactants and the products. Preferably, the solvent includes but is not limited to (1) aprotic polar solvents, such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, tetramethyl urea or hexamethylphosphoric acid triamide; (2) phenolic solvents, such as m-cresol, xylenol, phenol or halogenated phenols. Based on the usage of 100 parts by weight of the mixture, the usage of the solvent in the polymerization reaction is preferably 200 parts by weight to 2000 parts by weight, and more preferably 300 parts by weight to 1800 parts by weight.

In particular, in the polycondensation reaction, the solvent may be used together with an appropriate amount of a poor solvent, wherein the poor solvent does not cause the polyamine polymer to precipitate. The poor solvent may be used alone or in combination, and includes but is not limited to (1) alcohols, such as methanol, ethanol, isopropanol, cyclohexanol, ethylene glycol, propylene glycol, 1,4-butanediol or triethylene glycol; (2) ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; (3) esters, such as methyl acetate, ethyl acetate, butyl acetate, diethyl oxalate, diethyl malonate or ethylene glycol ethyl ether acetate; (4) ethers, For example: ethers such as diethyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol n-propyl ether, ethylene glycol isopropyl ether, ethylene glycol n-butyl ether, ethylene glycol dimethyl ether or diethylene glycol dimethyl ether; (5) halogenated hydrocarbons such as dichloromethane, 1,2-dichloroethane, 1,4-dichlorobutane, trichloroethane, chlorobenzene or o-dichlorobenzene; (6) hydrocarbons such as tetrahydrofuran, hexane, heptane, octane, benzene, toluene or xylene or any combination of the above solvents. Based on the usage of the diamine component (b1) being 100 parts by weight, the usage of the poor solvent is preferably 0 to 60 parts by weight, and more preferably 0 to 50 parts by weight.

The preparation of the polyimide polymer of the present invention can be a general method. Preferably, the preparation method of the polyimide polymer first dissolves the first mixture in a solution, wherein the first mixture contains a tetracarboxylic dianhydride component (a1) and a diamine component (b1), and performs a polymerization reaction to form a polyimide polymer. Then, in the presence of a dehydrating agent and a catalyst, further heating is performed and a dehydration ring-closing reaction is performed, so that the amide functional group in the polyimide polymer is converted into an imide functional group (i.e., imidization) through a dehydration ring-closing reaction, and a polyimide polymer is obtained.

The solvent used in the dehydration ring-closing reaction can be the same as the solvent in the liquid crystal alignment agent described below, so it is not described separately. Based on the usage of 100 parts by weight of the polyamine polymer, the usage of the solvent used in the dehydration ring-closing reaction is preferably 200 parts by weight to 2000 parts by weight, and more preferably 300 parts by weight to 1800 parts by weight.

In order to obtain a better degree of imidization of the polyamide polymer, the operating temperature of the dehydration ring-closing reaction is preferably 40°C to 200°C, and more preferably 40°C to 150°C. If the operating temperature of the dehydration ring-closing reaction is lower than 40°C, the imidization reaction is incomplete, thereby reducing the degree of imidization of the polyamide polymer. However, if the operating temperature of the dehydration ring-closing reaction is higher than 200°C, the weight average molecular weight of the obtained polyimide polymer is low.

The dehydrating agent used in the dehydration ring-closing reaction can be selected from anhydride compounds, such as acetic anhydride, propionic anhydride or trifluoroacetic anhydride. Based on 1 mol of polyamide polymer, the amount of the dehydrating agent used is 0.01 mol to 20 mol. The catalyst used in the dehydration ring-closing reaction can be selected from (1) pyridine compounds, such as pyridine, trimethylpyridine or dimethylpyridine; (2) tertiary amine compounds, such as triethylamine. Based on 1 mol of the dehydrating agent, the amount of the catalyst used is 0.5 mol to 10 mol.

Preferred examples of the polyimide block copolymers of the present invention are polyamic acid block copolymers, polyimide block copolymers, polyamic acid-polyimide block copolymers, or any combination thereof.

The preparation of the polyimide block copolymer of the present invention can be a general method. Preferably, the preparation method of the polyimide block copolymer first dissolves the starting material in a solvent and performs a polycondensation reaction, wherein the starting material comprises at least one polyamic acid polymer and/or at least one polyimide polymer as described above, and may further comprise a tetracarboxylic dianhydride component (a1) and a diamine component (b1).

The tetracarboxylic dianhydride component (a1) and diamine component (b1) in the aforementioned starting materials are the same as the tetracarboxylic dianhydride component (a1) and diamine component (b1) used in the preparation of the polyamide polymer, and the solvent used in the polycondensation reaction can be the same as the solvent in the liquid crystal alignment agent described below, which will not be described in detail here.

Based on the usage of 100 parts by weight of the aforementioned starting material, the usage of the solvent used in the polycondensation reaction is preferably 200 parts by weight to 2000 parts by weight, more preferably 300 parts by weight to 1800 parts by weight. The operating temperature of the polycondensation reaction is preferably 0°C to 200°C, and more preferably 0°C to 100°C.

Preferably, the starting materials include but are not limited to (1) two polyamic acid polymers with different terminal groups and different structures; (2) two polyimide polymers with different terminal groups and different structures; (3) polyamic acid polymers and polyimide polymers with different terminal groups and different structures; (4) polyamic acid polymers, tetracarboxylic dianhydride compounds and diamine compounds, wherein at least one of the tetracarboxylic dianhydride compounds and diamine compounds is combined with the polyamic acid polymer to form The tetracarboxylic dianhydride component (a1) and the diamine component (b1) used in the polyamic acid polymer have different structures; (5) a polyimide polymer, a tetracarboxylic dianhydride compound and a diamine compound, wherein at least one of the tetracarboxylic dianhydride compound and the diamine compound has a different structure from the tetracarboxylic dianhydride component (a1) and the diamine component (b1) used to form the polyimide polymer; (6) a polyamic acid polymer, a polyimide polymer (7) two kinds of polyamic acid polymers, tetracarboxylic acid dianhydride compounds and diamine compounds having different structures; (8) two kinds of polyimide polymers, tetracarboxylic acid dianhydride compounds and diamine compounds having different structures. Diamine compounds; (9) two polyamic acid polymers whose terminal groups are acid anhydride groups and have different structures, and diamine compounds; (10) two polyamic acid polymers whose terminal groups are amine groups and have different structures, and tetracarboxylic dianhydride compounds; (11) two polyimide polymers whose terminal groups are acid anhydride groups and have different structures, and diamine compounds; (12) two polyimide polymers whose terminal groups are amine groups and have different structures, and tetracarboxylic dianhydride compounds.

Without affecting the efficacy of the present invention, preferably, the aforementioned polyamic acid polymer, the aforementioned polyimide polymer and the aforementioned polyimide-based block copolymer can be terminal-modified polymers after molecular weight adjustment. By using terminal-modified polymers, the coating performance of the liquid crystal alignment agent can be improved. The method for preparing the aforementioned terminal-modified polymer can be prepared by adding a monofunctional compound to the polyamic acid polymer during the polycondensation reaction. The monofunctional compound includes but is not limited to (1) monobasic acid anhydrides, such as maleic anhydride, phthalic anhydride, itaconic anhydride, n-decylsuccinic anhydride, n-dodecylsuccinic anhydride, n-tetradecylsuccinic anhydride or n-hexadecylsuccinic anhydride; (2) monoamine Compounds, for example: monoamine compounds such as aniline, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, n-undecylamine, n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine or n-eicosylamine; (3) monoisocyanate compounds, for example: monoisocyanate compounds such as phenyl isocyanate or naphthyl isocyanate.

The first polymer (A1) of the present invention has a weight average molecular weight of 10,000 to 100,000, preferably 10,000 to 90,000, and more preferably 10,000 to 75,000, as measured by gel permeation chromatography and converted to polystyrene.

Second polymer (A2)

The second polymer (A2) of the present invention is prepared by reacting the second mixture. Specifically, the second polymer (A2) can be selected from polyamic acid polymers, polyimide polymers, polyimide block copolymers or any combination of the above polymers. Among them, the polyimide block copolymer is selected from polyamic acid block copolymers, polyimide block copolymers, polyamic acid-polyimide block copolymers or any combination of the above polymers.

The second mixture comprises a tetracarboxylic dianhydride component (a2) and a diamine component (b2), wherein the tetracarboxylic dianhydride component (a2) comprises at least one tetracarboxylic dianhydride compound (a2-1) represented by formula (III):

In formula (III), _R1 to _R4 each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom, or a phenyl group, _R1 to _R4 may be the same or different, and at least one of _R1 , _R2 , _R3 and _R4 is not a hydrogen atom.

When R ₁ , R ₂ , R ₃ and R ₄ have a stereo-hindering structure, the liquid crystal alignment of the liquid crystal alignment agent may be poor. Therefore, R ₁ , R ₂ , R ₃ and R ₄ are preferably hydrogen atoms, methyl groups or ethyl groups, with methyl groups being more preferred.

Specific examples of the tetracarboxylic dianhydride compound (a2-1) having a structure represented by formula (III) may be compounds represented by the following formulas (III-1) to (III-8). In terms of liquid crystal alignment, formula (III-1) is preferred.

The above-mentioned tetracarboxylic dianhydride compound (a2-1) can be used alone or in combination of two or more.

Based on the total usage of the tetracarboxylic dianhydride component (a2) being 100 mol, the usage of the tetracarboxylic dianhydride compound (a2-1) is 30 mol to 100 mol, preferably 40 mol to 100 mol, and more preferably 50 mol to 100 mol.

If the usage of the tetracarboxylic dianhydride compound (a2-1) falls within the above range, the resulting liquid crystal display element is less likely to produce afterimages.

The tetracarboxylic dianhydride component (a2) may further include other tetracarboxylic dianhydride compounds (a2-2). The types of the other tetracarboxylic dianhydride compounds (a2-2) may be the same as those listed for the tetracarboxylic dianhydride component (a1) in the first polymer (A1) above, so they will not be described in detail here.

Based on the total usage of the tetracarboxylic dianhydride component (a2) being 100 mol, the usage of other tetracarboxylic dianhydride compounds (a2-2) is 0 mol to 70 mol, preferably 0 mol to 60 mol, and more preferably 0 mol to 50 mol.

The diamine component (b2) comprises at least one diamine compound (b2-1) represented by formula (II):

In formula (II), _E1 and _E5 each independently represent a single bond or an alkylene group having 1 to 5 carbon atoms. In terms of the reactivity of the functional group in the sealant, a single bond or a methylene group is preferred. _E2 and _E4 each independently represent an alkylene group having 1 to 5 carbon atoms, preferably a methylene group or an ethylene group.

E ₃ represents an alkylene group or a cycloalkylene group having a carbon number of 1 to 6. In view of the reactivity of the functional group in the sealant, a is preferably a methylene group or an ethylene group. a represents 0 or 1.

_B1 and _B2 each independently represent a single bond, -O-, -NH-, _-NCH3- , -C(=O)-, -C(=O)O-, -C(=O) _NCH3- , -OC(=O)-, -NHC(=O)- or -N( _CH3 )C(=O)-. In terms of the liquid crystal alignment of the resulting liquid crystal aligner, a single bond or -O- is preferred.

D ₁ has a structure shown in formula (II-1):

In formula (II-1), R is a linear, branched or cyclic monovalent hydrocarbon group with 1 to 20 carbon atoms.

In terms of the convenience of obtaining raw materials, R is preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-hexyl, n-octyl, benzyl, n-hexadecyl or 9-fluorenylmethyl, and more preferably tert-butyl or 9-fluorenylmethyl.

Examples of _D1 include tert-butyloxycarbonyl, 9-fluorenylmethoxycarbonyl, dimethoxycarbonyl, ethoxycarbonyl, isopropyloxycarbonyl, benzyloxycarbonyl, hexyloxycarbonyl or octyloxycarbonyl. Among them, thermally dissociable groups such as tert-butyloxycarbonyl or 9-fluorenylmethoxycarbonyl are preferably used. If _D1 is a thermally dissociable group, the resulting liquid crystal display element is less likely to produce afterimages.

Examples of the diamine compound (b2-1) represented by formula (II) include the following formulas (II-2) to (II-47):

In formula (II-2) to formula (II-47), Me is a methyl group, Et is an ethyl group, iPr is an isopropyl group, Bn is a benzyl group, and Boc is a tert-butyloxycarbonyl group.

Based on the total usage of the diamine component (b2) being 100 mol, the usage of the diamine compound (b2-1) is 3 mol to 50 mol, preferably 5 mol to 50 mol, and more preferably 5 mol to 45 mol.

If the diamine component (b2) does not contain the diamine compound (b2-1), the resulting liquid crystal display element has the defect of easily generating afterimages.

The diamine component (b2) may further include other diamine compounds (b2-2). The types of the other diamine compounds (b2-2) may be the same as those listed for the other diamine compounds (b1-2) of the diamine component (b1) in the first polymer (A1) above, so they will not be described in detail here.

Based on the total usage of the diamine component (b2) being 100 mol, the usage of the other diamine compounds (b2-2) is 50 mol to 97 mol, preferably 50 mol to 95 mol, and more preferably 55 mol to 95 mol.

Preparation method of the second polymer (A2)

The preparation method of the second polymer (A2) of the present invention is the same as the preparation method of the first polymer (A1) described above. The difference is that the second polymer (A2) is prepared by reacting the aforementioned tetracarboxylic dianhydride component (a2) and diamine component (b2). Therefore, the preparation method of the second polymer (A2) is not described here separately.

The second polymer (A2) of the present invention has a weight average molecular weight of 10,000 to 90,000, preferably 12,000 to 75,000, and more preferably 15,000 to 60,000, as measured by gel permeation chromatography in terms of polystyrene.

Based on the total usage of polymer (A) being 100 parts by weight, the usage of the first polymer (A1) is 30 parts by weight to 90 parts by weight, preferably 40 parts by weight to 90 parts by weight; and the usage of the second polymer (A2) is 5 parts by weight to 70 parts by weight, preferably 10 parts by weight to 70 parts by weight, and more preferably 10 parts by weight to 60 parts by weight.

When the usage amount of the first polymer (A1) and the usage amount of the second polymer (A2) are within the aforementioned range, the formed liquid crystal display element has good environmental resistance.

Solvent (B)

There is no particular limitation on the solvent used in the liquid crystal alignment agent of the present invention, as long as it can dissolve the polymer (A) and any other components and does not react with them. It is preferably the same solvent used in the aforementioned synthesis of polyamine. At the same time, the poor solvent used in the synthesis of the aforementioned polyamine can also be used in combination.

Specific examples of the solvent (B) include, but are not limited to, N-methyl-2-pyrrolidone (NMP), γ-butyrolactone, γ-butyrolactamide, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether, butyl lactate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol n-propyl ether, ethylene glycol isopropyl ether, ethylene glycol n-butyl ether, ether), ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate or N,N-dimethylformamide or N,N-dimethylacetamide (N,N-dimethyl acetamide), etc.

The solvent (B) can be used alone or in combination of two or more.

Based on the usage of polymer (A) being 100 parts by weight, the usage of solvent (B) is 800 to 4000 parts by weight, preferably 900 to 3500 parts by weight, and more preferably 1000 to 3000 parts by weight.

Additive(C)

Within the scope that does not affect the efficacy of the present invention, the liquid crystal alignment agent of the present invention may optionally include an additive (C), and the additive (C) may be an epoxy compound or a silane compound with a functional group. The function of the additive (C) is to improve the adhesion between the aforementioned liquid crystal alignment film and the substrate surface. The additive (C) can be used alone or in combination.

The epoxy compound mentioned above may include but is not limited to ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerol diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, 1,3,5,6-tetraglycidyl-2,4-hexanediol, N,N, N',N'-tetracycloxypropyl-m-xylene diamine, 1,3-bis(N,N-dicycloxypropylaminomethyl)cyclohexane, N,N,N',N'-tetracycloxypropyl-4,4'-diaminodiphenylmethane, N,N-cycloxypropyl-p-cycloxypropyloxyaniline, 3-(N-allyl-N-cycloxypropyl)aminopropyltrimethoxysilane, 3-(N,N-dicycloxypropyl)aminopropyltrimethoxysilane, etc.

Based on the usage of polymer (A) being 100 parts by weight, the usage of epoxy compound is generally less than 40 parts by weight, and preferably 0.1 parts by weight to 30 parts by weight.

The silane compound having a functional group may include but is not limited to 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltrimethoxysilane, and the like. Triethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl-1,4,7-triazdecane, 10-triethoxysilyl-1,4,7-triazdecane, 9-trimethoxysilyl-3,6-diazononyl acetate, 9-triethoxysilyl-3,6-diazononyl acetate, N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-bis(ethylene oxide)-3-aminopropyltrimethoxysilane, N-bis(ethylene oxide)-3-aminopropyltriethoxysilane, etc.

Based on the usage of polymer (A) being 100 parts by weight, the usage of silane compound is generally less than 10 parts by weight, and preferably 0.5 parts by weight to 10 parts by weight.

Based on the usage of polymer (A) being 100 parts by weight, the usage of additive (C) can be 0.5 parts by weight to 50 parts by weight, and preferably 1 part by weight to 45 parts by weight.

Preparation method of liquid crystal alignment agent

The preparation method of the liquid crystal alignment agent of the present invention is not particularly limited, and a general mixing method can be adopted, for example, firstly mixing the first polymer (A1) and the first polymer (A2) to form a polymer (A), then adding a solvent (B) and an additive (C) to the polymer (A) at a temperature of 0°C to 200°C, and continuously stirring with a stirring device until the polymer (A) is dissolved. Preferably, the polymer (A) and the additive (C) are added to the solvent (B) at a temperature of 20°C to 60°C.

Method for forming liquid crystal alignment film

The present invention also provides a liquid crystal alignment film formed by the aforementioned liquid crystal alignment agent. In one embodiment, the liquid crystal alignment agent can be coated on a substrate and subjected to pre-baking, post-baking and photo-alignment treatment to form the liquid crystal alignment film.

The substrate on which the liquid crystal alignment agent of the present invention is applied is selected from transparent materials, wherein the transparent materials include but are not limited to alkali-free glass, sodium calcium glass, hard glass (Pyles glass), quartz glass, polyethylene terephthalate, polybutylene terephthalate, polyether sulfide, polycarbonate, etc. used in liquid crystal display devices. It is preferred to use the ITO electrode for liquid crystal driving that has been formed on the substrate to simplify the process. Furthermore, for a reflective liquid crystal display with only a single-sided substrate, the aforementioned substrate can use an opaque material such as a silicon wafer. In this case, the electrode can be formed using a material that reflects light such as aluminum. The coating method of the liquid crystal alignment agent of the present invention can be, for example, a spin coating method, a printing method, an inkjet method, etc.

The liquid crystal alignment agent of the present invention can be dried and baked at any temperature and time after coating. Generally speaking, in order to fully remove the organic solvent contained, it is necessary to dry at 50°C to 120°C for 1 minute to 10 minutes. After that, bake at 150°C to 300°C for 5 minutes to 120 minutes. There is no special restriction on the thickness of the coating after baking, but too thin a coating will cause the reliability of the liquid crystal display to deteriorate, so the above coating thickness is preferably 5nm to 300nm, and 10nm to 200nm is more preferred.

Although the liquid crystal alignment agent of the present invention can be subjected to the known rubbing alignment treatment, the effect is better when using the photoalignment treatment method.

A specific example of the photo-alignment treatment method may be, for example, irradiating the surface of the aforementioned coating with radiation polarized in a specific direction, and then heating it at a temperature of 150°C to 250°C as appropriate to give the aforementioned coating liquid crystal alignment ability. Among them, ultraviolet light or visible light with a wavelength of 100nm to 800nm can be used as the aforementioned radiation, and ultraviolet light with a wavelength of 100nm to 400nm is preferred, and ultraviolet light with a wavelength of 200nm to 400nm is more preferred. Furthermore, in order to improve the liquid crystal alignment, the coated substrate may be irradiated with radiation while heating the coated substrate at 150°C to 250°C. The radiation dose is preferably 1 mJ/cm ² to 10,000 mJ/cm ² , and more preferably 100 mJ/cm 2 to 5,000 mJ/cm ² . The liquid crystal alignment film prepared in the above manner can align liquid crystal molecules stably in a certain direction.

The liquid crystal alignment agent of the present invention is subjected to pre-baking, post-baking and photo-alignment treatment to form a liquid crystal alignment film, and the pre-tilt angle of the liquid crystal alignment film is 0° to 3°.

Method for manufacturing liquid crystal display element

The present invention also provides a liquid crystal display element, comprising the aforementioned liquid crystal alignment film.

The manufacturing method of liquid crystal display elements is well known to those in the art, so the following is only briefly described.

Referring to FIG. 1 , a preferred embodiment of the liquid crystal display element 100 of the present invention includes a first unit 110, a second unit 120, and a liquid crystal unit 130, wherein the second unit 120 is spaced opposite to the first unit 110, and the liquid crystal unit 130 is disposed between the first unit 110 and the second unit 120.

The first unit 110 includes a first substrate 112, an electrode 114 and a first liquid crystal alignment film 116, wherein the electrode 114 is formed on the surface of the first substrate 112 in a stylized pattern, and the first liquid crystal alignment film 116 is formed on the surface of the electrode 114.

The second unit 120 includes a second substrate 122 and a second liquid crystal alignment film 126, wherein the second liquid crystal alignment film 126 is formed on the surface of the second substrate 122.

The first substrate 112 and the second substrate 122 are selected from transparent materials, wherein the transparent materials include but are not limited to alkali-free glass, sodium calcium glass, hard glass (Pyles glass), quartz glass, polyethylene terephthalate, polybutylene terephthalate, polyether sulfide, polycarbonate, etc. used in liquid crystal display devices. The material of the electrode 114 is selected from transparent electrodes such as tin oxide (SnO ₂ ), indium oxide-tin oxide (In ₂ O ₃ -SnO ₂ ) or metal electrodes such as chromium.

The first liquid crystal alignment film 116 and the second liquid crystal alignment film 126 are the above-mentioned liquid crystal alignment films, which function to form a pre-tilt angle for the liquid crystal unit 130, and the liquid crystal unit 130 can be driven by the parallel electric field generated by the electrode 114.

The liquid crystal used in the liquid crystal unit 130 may be used alone or in combination of multiple types. The liquid crystal includes but is not limited to diaminobenzene liquid crystal, pyridazine liquid crystal, shiff base liquid crystal, azoxy liquid crystal, biphenyl liquid crystal, phenylcyclohexane liquid crystal, biphenyl liquid crystal, phenylcyclohexane liquid crystal, ester liquid crystal, terphenyl, biphenylcyclohexane liquid crystal, pyrimidine liquid crystal, dioxane liquid crystal, bicyclooctane liquid crystal, cubane liquid crystal, etc., and cholesterol chloride, cholesterol nonanoate, cholesterol carbonate, etc. may be added as needed. carbonate), or chiral agents such as "C-15" and "CB-15" (Merck), or ferroelectric liquid crystals such as p-decyloxybenzylidene-p-amino-2-methylbutylcinnamate.

The liquid crystal display element made by the liquid crystal alignment agent of the present invention is suitable for various nematic liquid crystals, such as TN, STN, TFT, VA, IPS and other liquid crystal display elements. In addition, according to the selected liquid crystal, it can also be used for different liquid crystal display elements such as strong induction or anti-strong induction. Among the above-mentioned liquid crystal display elements, it is particularly suitable for IPS type liquid crystal display elements.

The present invention is described in detail with the following examples, but it is not intended that the present invention is limited to the contents disclosed in these examples.

Synthetic polymer (A1) Synthesis Example A1-1

A 500 ml four-necked conical flask was equipped with a nitrogen inlet, a stirrer, a condenser and a thermometer, and nitrogen was introduced. Then, 0.0015 mol of 4,4'-diaminodiphenylamine (b1-1-1), 0.0235 mol of p-diaminobenzene (b1-2-1), 0.025 mol of 2,2'-dimethyl-4,4'-diaminobiphenyl (b1-2-2) and 80 g of N-methyl-2-pyrrolidone (hereinafter referred to as NMP) were added and stirred at room temperature until dissolved. Then, 0.005 mol of 2,3,5-tricarboxycyclopentylacetic dianhydride (a1-1) and 20 g of NMP were added and reacted at room temperature for 2 hours. After the reaction is completed, the reaction solution is poured into 1500 ml of water to precipitate the polymer. The obtained polymer is filtered and the steps of washing and filtering are repeated three times with methanol. Afterwards, the product is placed in a vacuum oven and dried at a temperature of 60°C to obtain polymer (A1-1), the formula of which is shown in Table 1.

Synthesis Examples A1-1 to A1-8 and Comparative Synthesis Examples A1'-1 to A1'-3

Synthesis Examples A1-1 to A1-8 and Synthesis Comparison Examples A1'-1 to A1'-3 use the same preparation method as the preparation method of the polymer (A1-1) of Synthesis Example A1-1. The difference is that Synthesis Examples A1-1 to A1-8 and Synthesis Comparison Examples A1'-1 to A1'-3 change the type and amount of raw materials in the polymer. The formula is shown in Table 1 and will not be further described here.

In Table 1:

a1-1 2,3,5-Tricarboxycyclopentyl acetic dianhydride

a1-2 1,2,3,4-cyclobutanetetracarboxylic dianhydride

a1-3 Benzene tetracarboxylic dianhydride

b1-1-1 4,4'-diaminodiphenylamine

b1-1-2 2,4-diaminodiphenylamine

b1-2-1 p-Diaminobenzene

b1-2-2 2,2'-dimethyl-4,4'-diaminobiphenyl

b1-2-3 4,4'-methylenebis(cyclohexylamine)

b1-2-4 1,4-Diaminocyclohexane

b1-2-5 2,6-diaminopyridine

b1-2-6

Synthetic polymer (A2) Synthesis Examples A2-1 to A2-11 and Comparative Synthesis Examples A2'-1 to A2'-3

Synthesis Examples A2-1 to A2-11 and Synthesis Comparison Examples A2'-1 to A2'-3 use the same preparation method as the preparation method of the polymer (A1-1) of Synthesis Example A1-1. The difference is that Synthesis Examples A2-1 to A2-11 and Synthesis Comparison Examples A2'-1 to A2'-3 change the type and amount of raw materials in the polymer. The formula is shown in Table 2 and will not be described here.

In Table 2:

a2-1-1 Formula (III-1)

a2-1-2 Formula (III-2)

a2-1-3 Formula (III-3)

a2-1-4 Formula (III-5)

a2-1-5 Formula (III-8)

a2-2-1 2,3,5-Tricarboxycyclopentyl acetic dianhydride

a2-2-2 1,2,3,4-cyclobutanetetracarboxylic dianhydride

a2-2-3 Benzene tetracarboxylic dianhydride

b2-1-1

b2-1-2

b2-1-3

b2-1-4

b2-1-5

b2-1-6

b2-1-7

b2-1-8

b2-2-1 p-Diaminobenzene

b2-2-2 2,2'-dimethyl-4,4'-diaminobiphenyl

b2-2-3 4,4'-methylenebis(cyclohexylamine)

b2-2-4 1,4-Diaminocyclohexane

b2-2-5

b2-2-6

Embodiment 1 Preparation of liquid crystal alignment agent

Weigh 30 parts by weight of the polymer (A1-1) of Synthesis Example A1-1, 70 parts by weight of the polymer (A2-1) of Synthesis Example A2-1, and 800 parts by weight of NMP, and stir and mix them at room temperature to prepare the liquid crystal alignment agent of Example 1.

Preparation of liquid crystal alignment film and liquid crystal display element

The prepared liquid crystal alignment agent is rotated and coated on a glass substrate, wherein a pixel electrode is formed on the glass substrate, wherein the pixel electrode is an IPS driving electrode having a pair of ITO electrodes (electrode width: 10μm, electrode spacing: 10μm, electrode height: 50nm), and the pair of ITO electrodes are respectively in a comb-shaped shape, and the comb-shaped parts of each other are configured in a separated and interlocking manner. After that, the glass substrate coated with the liquid crystal alignment agent is dried on a heating plate at 80°C for 5 minutes, and then baked in a hot air circulation oven at 250°C for 60 minutes to form a coating with a film thickness of 100nm.

Through a polarizing plate, the coated surface is irradiated with ultraviolet light of a wavelength of 254nm to produce a substrate with a liquid crystal alignment film. Next, similarly, a coating is formed on the opposite substrate and an alignment treatment is applied. The opposite substrate is a glass substrate without an electrode but with a columnar spacer with a height of 4μm.

The two substrates are a set, a sealant is printed on one of them, and the other is bonded in a way that it faces the liquid crystal alignment film and the alignment direction is 0°, and then the sealant is hardened to make an empty cell. This empty cell is injected with liquid crystal MLC-2041 (Merck) by the reduced pressure injection method, and the injection port is sealed, which is the liquid crystal display element of Example 1.

The liquid crystal display element of Example 1 was evaluated using the evaluation method described below, and the results are shown in Table 3.

Examples 2 to 15 and Comparative Examples 1 to 8

Examples 2 to 15 and Comparative Examples 1 to 8 use the same preparation method as the liquid crystal alignment agent in Example 1. The difference is that Examples 2 to 15 and Comparative Examples 1 to 8 change the type and amount of raw materials in the liquid crystal alignment agent. The formula and evaluation results are shown in Table 3-1, Table 3-2 and Table 4 respectively, which will not be described here.

In Table 3-1, Table 3-2 and Table 4:

B-1 N-methyl-2-pyrrolidone

B-2 Ethylene glycol n-butyl ether

B-3 N,N-dimethylacetamide

C-1 N,N,N',N'-Tetracyclyl-4,4'-diaminodiphenylmethane

C-2 N,N-glycidyl-p-glycidoxyaniline

Evaluation method Environmental resistance

The liquid crystal display elements of Examples 1 to 15 and Comparative Examples 1 to 8 were placed in an environment with a temperature of 65°C and a relative humidity of 85%. After 120 hours, the ion density of the liquid crystal display elements of Examples 1 to 16 and Comparative Examples 1 to 10 was measured using an electrical measuring machine (made by Dongyang Company, Model 6254). The test conditions are to apply a 1.7 volt voltage and a 0.01Hz triangle wave at a temperature of 60°C. In the current-voltage waveform, the peak area in the range of 0 to 1 volt can be calculated to measure the ion density (pC). The lower the ion density, the better the environmental resistance. The evaluation criteria for ion density are as follows.

◎: Ion density <20

○: 20≦ ion density <40

△: 40≦ ion density <50

×: 50≦ ion density

Afterimage test

The liquid crystal display elements of Examples 1 to 15 and Comparative Examples 1 to 8 were driven with an AC voltage of 10V for 30 hours, and then measured using a device with a polarizer and an analyzer between the light source and the light detector, and the minimum relative transmittance (%) was calculated using the following formula.

Minimum relative transmittance (%) = (β-B ₀ )/(B ₁₀₀ -B ₀ )×100

In the above formula, _B0 is blank and is the light transmittance under crossed nicols; _B100 is blank and is the light transmittance under parallel nicols; β is the light transmittance that becomes minimum when the liquid crystal unit is sandwiched between the polarizer and the analyzer under crossed nicols.

The black level in the dark state is represented by the minimum relative transmittance of the liquid crystal display element. The smaller the black level, the better the contrast, that is, the better the afterimage.

◎: Minimum relative transmittance ≦0.5%

○: 0.5%<minimum relative transmittance ≦1.0%

△: 1.0%<minimum relative transmittance ≦1.5%

×: Minimum relative transmittance>1.5%.

The above embodiments are only for illustrating the principle and effect of the present invention, but not for limiting the present invention. The modifications and changes made to the above embodiments by people familiar with this technology still do not violate the spirit of the present invention. The scope of rights of the present invention shall be as listed in the scope of the patent application described below.

100: Liquid crystal display element

110: Unit 1

112: first substrate

114: first conductive film

116: first liquid crystal alignment film

120: Unit 2

122: Second substrate

126: Second liquid crystal alignment film

130: Liquid crystal unit

Claims (12)

A liquid crystal alignment agent comprises: a polymer (A); and a solvent (B); wherein the polymer (A) comprises a first polymer (A1) and a second polymer (A2), wherein the first polymer (A1) is prepared by reacting a first mixture, wherein the first mixture comprises a tetracarboxylic dianhydride component (a1) and a diamine component (b1), wherein the diamine component (b1) comprises at least one diamine compound (b1-1) represented by formula (I):

In formula (I), ^R1 to ^R10 are the same or different hydrogen atoms or monovalent organic groups, wherein ^R1 to ^R10 contain at least two primary amino groups, and the two primary amino groups in ^R1 to ^R10 are linked to the same benzene ring; the second polymer (A2) is prepared by reacting a second mixture, wherein the second mixture comprises a tetracarboxylic dianhydride component (a2) and a diamine component (b2), wherein the diamine component (b2) comprises at least one diamine compound (b2-1) as shown in formula (II):

In formula (II), _E1 and _E5 each independently represent a single bond or an alkylene group having 1 to 5 carbon atoms; _E2 and _E4 each independently represent an alkylene group having 1 to 5 carbon atoms; _E3 represents an alkylene group having 1 to 6 carbon atoms or a cycloalkylene group; _B1 and _B2 each independently represent a single bond, -O-, -NH-, _-NCH3- , -C(=O)-, -C(=O)O-, -C(=O) _NCH3- , -OC(=O)-, -NHC(=O)- or -N( _CH3 )C(=O)-; a represents 0 or 1; and _D1 has a structure represented by formula (II-1):

In formula (II-1), R is a linear, branched or cyclic monovalent hydrocarbon group having 1 to 20 carbon atoms, and * represents a linking group. The liquid crystal alignment agent of claim 1, wherein in formula (II-1), R is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-hexyl, n-octyl, benzyl, n-hexadecyl or 9-fluorenylmethyl. As in claim 1, the liquid crystal alignment agent, wherein in formula (II-1), R is tert-butyl or 9-fluorenylmethyl. The liquid crystal alignment agent of claim 1, wherein the tetracarboxylic dianhydride component (a2) in the second mixture comprises at least one tetracarboxylic dianhydride compound (a2-1) represented by formula (III):

In formula (III), _R1 to _R4 each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms and containing a fluorine atom, or a phenyl group, _R1 to _R4 may be the same or different, and at least one of _R1 , _R2 , _R3 and _R4 is not a hydrogen atom. As claimed in claim 1, the liquid crystal alignment agent, wherein in the first mixture, based on the total usage of the diamine component (b1) being 100 mol, the usage of the diamine compound (b1-1) represented by the formula (I) is 3 mol to 50 mol. As claimed in claim 1, the liquid crystal alignment agent, wherein in the second mixture, based on the total usage of the diamine component (b2) being 100 mol, the usage of the diamine compound (b2-1) represented by the formula (II) is 3 mol to 50 mol. As claimed in claim 4, the liquid crystal alignment agent, wherein in the second mixture, based on the total usage of the tetracarboxylic dianhydride component (a2) being 100 mol, the usage of the tetracarboxylic dianhydride compound (a2-1) represented by the formula (III) is 30 mol to 100 mol. The liquid crystal alignment agent of claim 1, wherein the total usage of the polymer (A) is 100 parts by weight, the usage of the first polymer (A1) is 30 parts by weight to 95 parts by weight, and the usage of the second polymer (A2) is 5 parts by weight to 70 parts by weight. The liquid crystal alignment agent of claim 1, wherein the amount of the polymer (A) used is 100 parts by weight, and the amount of the solvent (B) used is 800 parts by weight to 3000 parts by weight. A liquid crystal alignment film is formed by a liquid crystal alignment agent as described in any one of claims 1 to 9. As in claim 10, the liquid crystal alignment film, wherein the liquid crystal alignment agent is subjected to pre-baking treatment, post-baking treatment and photo-alignment treatment to form the liquid crystal alignment film. A liquid crystal display element, comprising a liquid crystal alignment film as claimed in claim 11.