Liquid crystal alignment agent, liquid crystal alignment film, manufacturing method thereof and liquid crystal element

Abstract

A liquid crystal alignment agent comprises a polyamic acid or a derivative thereof obtained by reacting a tetracarboxylic acid derivative with a diamine. The tetracarboxylic acid derivative includes a compound represented by the formula (I). The diamine comprises at least one selected from a group consisting of the formula (DI-13) and the formula (DI-17-1). The group of

Description

[Technical Field]

[0001] This invention relates to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal element using the liquid crystal alignment film. More specifically, it relates to a liquid crystal alignment agent for photoalignment used to form a photoaligned liquid crystal alignment film (hereinafter, sometimes abbreviated as photoalignment film), a photoaligned liquid crystal alignment film formed using the liquid crystal alignment agent, and a liquid crystal display element having the liquid crystal alignment film (hereinafter, sometimes abbreviated as liquid crystal element). [Previous Technology]

[0002] It is known that a liquid crystal element can produce optical phenomena such as refraction, scattering, and reflection of electromagnetic waves incident on the element by controlling or modulating the alignment state of the liquid crystal layer within the element. Specifically, in addition to the liquid crystal display element described below, liquid crystal antennas, dimming windows, optical compensation materials, and variable phase shifters are also known.

[0003] As liquid crystal display elements, there are known liquid crystal display elements with various driving methods, such as twisted nematic (TN) mode, super twisted nematic (STN) mode, in-plane switching (IPS) mode, fringe field switching (FFS) mode, and vertical alignment (VA) (multi-domain vertical alignment) mode. These liquid crystal display elements are used in image display devices of various electronic devices such as televisions and mobile phones, and are being developed with the goal of further improving display quality. Specifically, the performance improvement of liquid crystal display elements can be achieved not only through improvements in driving methods and element structure, but also through the structural components used in the element. Moreover, among the structural components used in liquid crystal display elements, the liquid crystal alignment film is one of the important materials related to display quality. In order to meet the requirements of high-quality liquid crystal display elements, research on the liquid crystal alignment film is also being actively carried out.

[0004] Here, the liquid crystal alignment film is disposed on a pair of substrates on both sides of the liquid crystal layer of the liquid crystal display element, in contact with the liquid crystal layer, and has the function of aligning the liquid crystal molecules constituting the liquid crystal layer with respect to the substrate in a certain regularity. By using a liquid crystal alignment film with high liquid crystal alignment, a liquid crystal display element with high contrast and improved image retention characteristics can be realized (for example, see Patent Document 1 and Patent Document 2).

[0005] Furthermore, in recent years, narrow bezels have been a trend in liquid crystal display elements, aiming to increase the display area by reducing the bezel size. To achieve this, a liquid crystal alignment film needs to be printed onto the end of the substrate, and a sealant is applied to the liquid crystal alignment film. Based on this, liquid crystal alignment films with high adhesion to the sealant have been developed (for example, Patent Documents 7 to 9).

[0006] In the formation of this type of liquid crystal alignment film, a solution (varnish) is currently mainly used, which is a solution obtained by dissolving polyamide, soluble polyimide, or polyamide ester in an organic solvent. When forming a liquid crystal alignment film using these varnishes, the varnish is applied to a substrate, and the coating is cured by heating or the like to form a polyimide-based liquid crystal alignment film. Alignment processing suitable for the display mode is then performed as needed. As alignment processing methods, known methods include: a friction method that adjusts the orientation of polymer molecules by rubbing the surface of the alignment film with a cloth or the like; and a photoalignment method that imparts anisotropy to the film by irradiating the alignment film with linearly polarized ultraviolet light, causing photodecomposition, photoisomerization, or dimerization in the polymer molecules. Among these, compared with the friction method, the photoalignment method has higher alignment uniformity and is a non-contact alignment processing method, thus having the following advantages: it does not damage the film and can reduce the causes of display defects in liquid crystal display elements such as dust or static electricity.

[0007] As for liquid crystal alignment films using this photoalignment method, Patent Documents 1 to 5 describe, for example, how a photoalignment film with high anchoring energy and good liquid crystal alignment is obtained by using diaminoazobenzene or the like as raw materials and applying photoisomerization technology. Patent Document 6 describes how a photoalignment film with high transparency and good liquid crystal alignment is obtained by applying a photodecomposition-type technology. [Prior Art Documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2010-197999 [Patent Document 2] International Publication No. 2013 / 157463 [Patent Document 3] Japanese Patent Application Publication No. 2005-275364 [Patent Document 4] Japanese Patent Application Publication No. 2007-248637 [Patent Document 5] International Publication No. 2015 / 016118 [Patent Document 6] Japanese Patent Application Publication No. 2012-155311 [Patent Document 7] Japanese Patent Application Publication No. 2017-198975 [Patent Document 8] International Publication No. 2016 / 043230 [Patent Document 9] Japanese Patent Application Publication No. 2018-106096 [Summary of the Invention]

[0009] [Problem to be Solved by the Invention] In recent years, the applications of liquid crystal display elements have expanded to various fields, including monitors for personal computers, LCD TVs, displays for mobile phones and smartphones, and medical monitors. Furthermore, there is a growing demand for superior display quality, with contrast ratio being a key characteristic affecting display quality. Additionally, in liquid crystal display elements using liquid crystal alignment films employing photoalignment, to improve the manufacturing efficiency of liquid crystal display elements, there is a requirement for liquid crystal alignment films that exhibit good contrast ratios even in short photoalignment processing times, i.e., photoalignment processing with low exposure energy.

[0010] Therefore, the inventors have made efforts to research a liquid crystal alignment film that can form a liquid crystal display element with good contrast and excellent display quality even when the exposure energy for photoalignment processing is lower than before, and a liquid crystal alignment agent for photoalignment that can form such a liquid crystal alignment film. [Technical Means for Solving the Problem]

[0011] The inventors have discovered that the aforementioned problem can be solved by using a liquid crystal alignment agent comprising a raw material composition including a compound represented by formula (I) and a compound with a specific structure, thereby completing the present invention. The present invention comprises the following structure.

[0012] [1] A liquid crystal alignment agent comprising polyacrylic acid or a derivative thereof obtained by reacting a tetracarboxylic acid derivative with a diamine, wherein the liquid crystal alignment agent comprises a compound represented by formula (I) as the tetracarboxylic acid derivative, and comprises at least one of the groups selected from formulas (DI-13) and (DI-17-1) as the diamine. In formula (I), *1, *1', *2 and *2' are bonding bonds, which are independently bonded to a hydroxyl group, a chlorine atom or an alkoxy group having 1 to 6 carbon atoms, and at least one of the groups of *1 and *1' and *2 and *2' can be bonded to the same oxygen atom; Rb1, Rb2, Rb3 and Rb4 are independently hydrogen atoms or methyl groups, and at least one is a methyl group. In formula (DI-13), R 23 is independently an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a chlorine atom, and p and q are independently integers from 0 to 4; in formula (DI-17-1), k is an integer from 1 to 6. [2] According to the liquid crystal alignment agent of [1], the compound represented by formula (DI-13) is the compound represented by formula (DI-13-1), and the compound represented by formula (DI-17-1) is the compound in formula (DI-17-1) where k is 2. [3] According to the liquid crystal alignment agent of [1] or [2], the compound represented by formula (DI-17-2) is included as a diamine. In formula (DI-17-2), e is an integer from 1 to 10, and Boc is a tertiary butoxycarbonyl group. [4] The liquid crystal alignment agent according to [3], wherein in formula (DI-17-2), e is an integer from 6 to 10. [5] The liquid crystal alignment agent according to [3], wherein in formula (DI-17-2), e is 6. [6] The liquid crystal alignment agent according to any one of [1] to [5], comprising polyacrylic acid or a derivative thereof obtained by reacting a tetracarboxylic acid derivative other than the compound represented by formula (I) with a diamine. [7] The liquid crystal alignment agent according to any one of [1] to [6], comprising an additive. [8] A liquid crystal alignment film formed from the liquid crystal alignment agent according to any one of [1] to [7]. [9] A liquid crystal element having the liquid crystal alignment film according to [8].

[10] A method for manufacturing a liquid crystal alignment film, comprising: a step of coating a substrate with the liquid crystal alignment agent according to any one of [1] to [7]; a step of calcining the substrate; and a step of irradiating the substrate with polarized ultraviolet light. [Effects of the Invention]

[0013] By using the liquid crystal alignment agent for photoalignment of the present invention, a liquid crystal alignment film with high liquid crystal alignment properties can be obtained even when the exposure energy of the photoalignment process is low. Moreover, by using the liquid crystal alignment film, liquid crystal display elements with good contrast and excellent display quality can be manufactured efficiently.

Implementation Method

[0015] Hereinafter, the present invention will be described in detail. The descriptions of structural elements described below are sometimes based on representative embodiments or specific examples, but the present invention is not limited to such embodiments. The "liquid crystal alignment agent" in the present invention is a liquid crystal alignment agent that can acquire anisotropy by irradiation with polarized ultraviolet light when a liquid crystal alignment agent film is formed on a substrate. In this specification, it is sometimes simply referred to as "liquid crystal alignment agent," and sometimes also as "liquid crystal alignment agent for photoalignment." Furthermore, the term "tetracarboxylic acid derivative" in the present invention refers to tetracarboxylic acid dianhydride, tetracarboxylic acid diester, or tetracarboxylic acid diester dihalide. Sometimes, tetracarboxylic acid diester and tetracarboxylic acid diester dihalide are collectively referred to as derivatives of tetracarboxylic acid dianhydride. In addition, in the present invention, diamines and diacetylhydrazine are sometimes referred to as "diamines." * in the chemical formulas of this specification indicates a bonding bond.

[0016] <The Photoaligning Liquid Crystal Alignment Agent of the Invention> The photoaligning liquid crystal alignment agent of the present invention comprises at least one polymer selected from the group consisting of polyamides and polyamide derivatives, formed by reacting a tetracarboxylic acid derivative with a diamine. The polymer is characterized in that, as a raw material, it comprises at least one compound represented by formula (I) and at least one compound selected from the group consisting of formulas (DI-13) and (DI-17-1). The polymer is sometimes referred to as the polymer of the present invention. In the present invention, polyamide derivatives refer to polyimides, partially polyimides, polyamide esters, polyamide-polyamide copolymers, and polyamide-polyimides.

[0017] <Types of Polymers> The following provides detailed information on polyamides and polyamide derivatives.

[0018] Here, polyamide is a polymer synthesized by polymerization of a tetracarboxylic acid dianhydride represented by formula (AN) and a diamine represented by formula (DI), and has a structural unit represented by formula (PAA). When the liquid crystal alignment agent containing polyamide is heated and calcined in the step of forming the liquid crystal alignment film, the polyamide is amide-iminated, and a polyimide liquid crystal alignment film having a structural unit represented by formula (PI) can be formed.

[0019] In formulas (AN), (PAA), and (PI), X1 is a tetravalent organogroup. In formulas (DI), (PAA), and (PI), X2 is a divalent organogroup. For preferred ranges and specific examples of the tetravalent organogroup in X1, refer to the structures corresponding to tetracarboxylic dianhydrides described in this specification. For preferred ranges and specific examples of the divalent organogroup in X2, refer to the descriptions related to the structures corresponding to diamines or diacetylhydrazines described in the diamines section of this specification.

[0020] Polyamide derivatives are compounds whose properties are altered by replacing a portion of polyamide with other atoms or groups of atoms. Polyamide derivatives with improved solubility in solvents used in liquid crystal alignment agents are particularly preferred. Specifically, examples of such polyamide derivatives include: 1) polyamides formed by dehydrating and cyclizing all amino groups and carboxyl groups of polyamide; 2) partially polyamides formed by partially dehydrating and cyclizing; 3) polyamide esters formed by converting the carboxyl groups of polyamide to esters; 4) polyamide-polyamide copolymers obtained by replacing a portion of the dianhydride contained in a tetracarboxylic acid dianhydride compound with an organic dicarboxylic acid and reacting the reaction; and 5) polyamide-polyamides formed by dehydrating and cyclizing a portion or all of the polyamide-polyamide copolymer. Among these derivatives, examples of polyimides include those having the structural unit represented by the formula (PI), and examples of polyamides include those having the structural unit represented by the formula (PAE). In formula (PAE), X1 is a tetravalent organogroup, X2 is a divalent organogroup, and Y is independently an alkyl group. For preferred ranges and specific examples of X1 and X2, refer to the descriptions related to X1 and X2 in formula (PAA). Y is preferably a straight-chain or branched alkyl group having 1 to 6 carbon atoms, more preferably methyl, ethyl, propyl, isopropyl, butyl, isobutyl, or tert-butyl.

[0021] The tetracarboxylic acid dianhydride and diamine used in the synthesis of polyamide can be one or more of the same.

[0022] When the polyamide of the present invention is configured as a polyamide derivative, the polyamide can be obtained by subjecting the obtained polyamide solution to a amide reaction at a temperature of 20°C to 150°C with an anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride as a dehydrating agent, and a tertiary amine such as triethylamine, pyridine, or trimethylpyridine as a dehydration ring-closing catalyst. Alternatively, polyamide can be obtained by using a large amount of unsuitable solvent (ethanol, isopropanol, or other alcohol-based or glycol-based solvents) to precipitate polyamide from the obtained polyamide solution, and then subjecting the precipitated polyamide to a amide reaction at a temperature of 20°C to 150°C with the dehydrating agent and the dehydration ring-closing catalyst in a solvent such as toluene or xylene.

[0023] In the amide oxidative reaction, the ratio of dehydrating agent to dehydration ring-closing catalyst is preferably 0.1 to 10 (molar ratio). The total amount of dehydrating agent and dehydration ring-closing catalyst used is preferably 1.5 to 10 molars relative to the total molar amount of tetracarboxylic dianhydride used in the synthesis of the polyamide. By adjusting the amount of dehydrating agent, catalyst, reaction temperature, and reaction time used in the amide oxidative reaction, the degree of amide oxidative oxidation can be controlled, thereby obtaining a partially amide formed by amide oxidizing only a portion of the polyamide. The obtained polyamide can also be separated from the solvent used in the reaction and redissolved in another solvent for use as a liquid crystal alignment agent, or it can be used as a liquid crystal alignment agent without separation from the solvent.

[0024] Polyamide esters can be obtained by reacting polyamide with hydroxyl-containing compounds, halides, epoxy-containing compounds, etc., or by reacting tetracarboxylic acid diesters or tetracarboxylic acid diester dichlorides derived from tetracarboxylic dianhydride with diamines. Tetracarboxylic acid diesters derived from tetracarboxylic dianhydride can be obtained, for example, by reacting tetracarboxylic acid dianhydride with 2 equivalents of an alcohol and opening the ring. Tetracarboxylic acid diester dichlorides can be obtained by reacting tetracarboxylic acid diesters with 2 equivalents of a chlorinating agent (e.g., thionyl chloride). Furthermore, polyamide esters may have only an amide structure, or they may be partially esterified products containing both amide and amide structures.

[0025] The polyamide or its derivatives of the present invention can be manufactured in the same manner as known polyamides or their derivatives used in the formation of polyimide films. The total amount of the tetracarboxylic acid derivative is preferably set to 0.9 to 1.1 mol relative to a total of 1 mol of diamines.

[0026] The liquid crystal alignment agent of the present invention may contain only one of these polyamides, polyamide esters and polyimides obtained by amide imidization of these, or may contain two or more.

[0027] The molecular weight of the polyacrylic acid or its derivatives of the present invention, expressed as the weight average molecular weight (Mw) converted from polystyrene, is preferably 5,000 to 500,000, more preferably 5,000 to 50,000. The molecular weight of the polyacrylic acid or its derivatives can be determined by gel permeation chromatography (GPC).

[0028] The polyamide or its derivatives of the present invention can be confirmed by analyzing the solid components obtained by precipitation in a large number of unsuitable solvents using infrared spectroscopy (IR) or nuclear magnetic resonance (NMR). Alternatively, the monomer used can be confirmed by analyzing the extract obtained from the decomposition products of the polyamide or its derivatives in an aqueous solution of a strong base such as KOH or NaOH using gas chromatography (GC), high performance liquid chromatography (HPLC), or gas chromatography-mass spectrometry (GC-MS).

[0029] <Tetracarboxylic Acid Derivatives> The polymer of the present invention includes the compound represented by formula (I) as a raw material, and may also include other tetracarboxylic acid derivatives. Specific examples of the compound represented by formula (I) and other tetracarboxylic acid derivatives are described below. <Compound represented by formula (I)> The compound represented by formula (I) used in the raw material of the polymer of the present invention will be described. In formula (I), *1, *1', *2 and *2' are bonding bonds, each independently bonded to a hydroxyl group, a chlorine atom or an alkoxy group having 1 to 6 carbon atoms, and at least one group of the groups of *1 and *1' and *2 and *2' may be bonded to the same oxygen atom; Rb1, Rb2, Rb3 and Rb4 are each independently a hydrogen atom or a methyl group, at least one of which is a methyl group.

[0030] Specific examples of alkoxy groups having 1 to 6 carbon atoms include: methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, or tert-butoxy. In terms of ease of imidization, methoxy is preferred.

[0031] Formula (I) includes: a configuration in which all four bonds are bonded to any one of the following: a hydroxyl group, a chlorine atom, or an alkoxy group having 1 to 6 carbon atoms; a configuration in which any one of the groups *1 and *1' and *2 and *2' is bonded to the same oxygen atom, and the other two bonds in the remaining groups are bonded to any one of the following: a hydroxyl group, a chlorine atom, or an alkoxy group having 1 to 6 carbon atoms; and a configuration in which both of the groups *1 and *1' and *2 and *2' are bonded to the same oxygen atom. Preferably, the configuration in which all four bonds are bonded to any one of the following: a hydroxyl group, a chlorine atom, or an alkoxy group having 1 to 6 carbon atoms; and a configuration in which both of the groups *1 and *1' and *2 and *2' are bonded to the same oxygen atom.

[0032] From the viewpoint of obtaining a liquid crystal alignment film with high sensitivity, it is preferable that Rb1 and Rb4 are methyl groups and Rb2 and Rb3 are hydrogen groups.

[0033] Preferred examples of compounds represented by formula (I) are listed below. In formulas (I-2) to (I-5), R 11 is independently an alkyl group having 1 to 6 carbon atoms. R 11 is preferably methyl.

[0034] By using the compound represented by formula (I), a liquid crystal alignment agent can be obtained that can form a liquid crystal alignment film with high liquid crystal alignment even when the exposure energy of the photoalignment process is low.

[0035] In the polymer of the present invention, the compound represented by formula (I) is preferably used in an amount of 50 mol% or more of the total amount of tetracarboxylic acid derivative used. Multiple compounds represented by formula (I) may also be used in combination.

[0036] <Tetracarboxylic acid derivatives other than formula (I)>

[0037] Hereinafter, tetracarboxylic acid dianhydrides represented by formulas (AN-1) to (AN-9), (AN-10-1), (AN-10-2), (AN-11), (AN-12), (AN-15), and (AN-16-1) to (AN-16-19) will be described as tetracarboxylic acid derivatives other than formula (I). These tetracarboxylic acid dianhydrides can also be derived into tetracarboxylic acid diesters or tetracarboxylic acid diester dichlorides and used as raw materials for polymers.

[0038] [Tetracarboxylic acid dianhydride represented by formula (AN-1)] In formula (AN-1), G 11 is a single bond, an alkylene group having 1 to 12 carbon atoms, 1,4-phenylene, 1,4-cyclohexylene, or formula (G11-1). R 11 is independently a hydrogen atom or a methyl group. In formula (G11-1), X is independently a single bond, -O-, -S-, or -NR 1-, R 1 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, n is independently an integer from 1 to 5, m is an integer from 1 to 3, and a group whose bonding position is not fixed on any carbon atom constituting the ring represents any carbon atom in the ring that can bond with it.

[0039] The following list includes examples of tetracarboxylic acid dianhydrides represented by formula (AN-1).

[0040] In formulas (AN-1-2) and (AN-1-5), m is independently an integer from 1 to 12. [Tetracarboxylic acid dianhydride represented by formula (AN-2)] In formula (AN-2), G 11 is a single bond, an alkylene group having 1 to 12 carbon atoms, a 1,4-phenylene group, or a 1,4-cyclohexylene group. X 11 is a single bond or -CH 2-. G 12 is independently any one of the following trivalent groups. When G 12 is >N-, G 11 is not a single bond and is not -CH 2-, and X 11 is not a single bond.

[0041] The following lists examples of tetracarboxylic acid dianhydrides represented by formula (AN-2). In formula (AN-2-1), m is an integer from 1 to 12.

[0042] [Tetracarboxylic acid dianhydride represented by formula (AN-3)] In formula (AN-3), ring A11 is a cyclohexane ring or a benzene ring.

[0043] Examples of tetracarboxylic acid dianhydrides represented by formula (AN-3) can be listed below as compounds represented by formula (AN-3-1) and formula (AN-3-2).

[0044] [Tetracarboxylic acid dianhydride represented by formula (AN-4)] In formula (AN-4), G13 is a single bond, -(CH2)m-, -O-, -S-, -C(CH3)2-, -SO2-, -CO-, -C(CF3)2-, or a divalent group represented by formula (G13-1) below, where m is an integer from 1 to 12. Ring A11 is independently a cyclohexane ring or a benzene ring. G13 can be bonded to any position on ring A11. In formula (G13-1), G13a and G13b are independently a single bond, -O-, -CONH-, or a divalent group represented by -NHCO-. The phenylene is preferably 1,4-phenylene or 1,3-phenylene.

[0045] As examples of tetracarboxylic acid dianhydrides represented by formula (AN-4), the compounds represented by formulas (AN-4-1) to (AN-4-31) can be listed below. In formula (AN-4-17)

[0046] , m is an integer from 1 to 12.

[0047] [Tetracarboxylic acid dianhydride represented by formula (AN-5)] In formula (AN-5), R 11 is independently a hydrogen atom or a methyl group. The R 11 bonds on the benzene ring of the two R 11 are bonded to either of the positions on the benzene ring that can be substituted.

[0048] As examples of tetracarboxylic acid dianhydrides represented by formula (AN-5), the compounds represented by formulas (AN-5-1) to (AN-5-3) can be listed below.

[0049] [Tetracarboxylic acid dianhydride represented by formula (AN-6)] In formula (AN-6), X11 is independently a single bond or -CH2-. X12 is -CH2-, -CH2CH2-, or -CH=CH-. n is 1 or 2. When n is 2, the two X12s can be the same or different.

[0050] As examples of tetracarboxylic acid dianhydrides represented by formula (AN-6), the compounds represented by formulas (AN-6-1) to (AN-6-12) can be listed below.

[0051] [Tetracarboxylic acid dianhydride represented by formula (AN-7)]

[0052] In formula (AN-7), X 11 is a single bond or -CH 2-. As examples of tetracarboxylic acid dianhydrides represented by formula (AN-7), compounds represented by formulas (AN-7-1) and (AN-7-2) can be listed below.

[0053] [Tetracarboxylic acid dianhydride represented by formula (AN-8)] In formula (AN-8), X 11 is a single bond or -CH 2-. R 12 is a hydrogen atom, methyl, ethyl, or phenyl. Ring A 12 is a cyclohexane ring or a cyclohexene ring.

[0054] Examples of tetracarboxylic acid dianhydrides represented by formula (AN-8) include compounds represented by formula (AN-8-1) and formula (AN-8-2) as described below.

[0055] [Tetracarboxylic acid dianhydride represented by formula (AN-9)] In formula (AN-9), r is 0 or 1 independently.

[0056] As examples of tetracarboxylic acid dianhydrides represented by formula (AN-9), the compounds represented by formulas (AN-9-1) to (AN-9-3) can be listed below.

[0057] [Tetracarboxylic acid dianhydrides represented by formulas (AN-10-1) and (AN-10-2)]

[0058] [Tetracarboxylic acid dianhydride represented by formula (AN-11)] In formula (AN-11), ring A11 is independently a cyclohexane ring or a benzene ring.

[0059] As examples of tetracarboxylic acid dianhydrides represented by formula (AN-11), the compounds represented by formulas (AN-11-1) to (AN-11-3) below can be listed.

[0060] [Tetracarboxylic acid dianhydride represented by formula (AN-12)]

[0061] In formula (AN-12), ring A11 is independently a cyclohexane ring or a benzene ring. As examples of tetracarboxylic acid dianhydrides represented by formula (AN-12), compounds represented by formulas (AN-12-1) to (AN-12-3) can be listed below.

[0062] [Tetracarboxylic acid dianhydride represented by formula (AN-15)] In formula (AN-15), w is an integer from 1 to 10.

[0063] As examples of tetracarboxylic acid dianhydrides represented by formula (AN-15), the compounds represented by formulas (AN-15-1) to (AN-15-3) below can be listed.

[0064] [Tetracarboxylic dianhydrides represented by formulas (AN-16-1) to (AN-16-19)] Other than the tetracarboxylic dianhydrides mentioned above, compounds represented by formulas (AN-16-1) to (AN-16-19) can be listed below.

[0065] Suitable materials for improving the various properties of the liquid crystal alignment film in the tetracarboxylic dianhydride will be described. When improving sealing performance is of paramount importance, compounds represented by formula (AN-2) are preferred. In formula (AN-2), compounds in which G 12 is > CH- are preferred. As specific examples, compounds represented by formulas (AN-2-1) to (AN-2-4) are preferred, and compounds represented by formula (AN-2-2) are more preferred.

[0066] <Diamines> The polymers of the present invention comprise at least one compound selected from the group consisting of formulas (DI-13) and (DI-17-1) as raw materials, and may also include diamines other than those listed thereto. Specific examples of compounds represented by formula (DI-13) or formula (DI-17-1) and diamines other than those listed below are described below.

[0067]

[0068] In formula (DI-1), G 20 is an alkylene group having 1 to 12 carbon atoms or a group represented by formula (DI-1-a). When G 20 is an alkylene group having 1 to 12 carbon atoms, at least one of -CH 2- may be substituted with -NH- or -O-, but they are not adjacent, and at least one hydrogen atom of -CH 2- may be substituted with a hydroxyl or methyl group. In formula (DI-1-a), v is independently an integer from 1 to 6.

[0069] In formulas (DI-3), (DI-6), and (DI-7), G 21 is independently a single bond, -NH-, -NCH 3-, -O-, -S-, -SS-, -SO 2-, -CO-, -COO-, -CONCH 3-, -CONH-, -C(CH 3) 2-, -C(CF 3) 2-, -(CH 2) m-, -O-(CH 2) mO-, -N(CH 3)-(CH 2) kN(CH 3)-, -(OC 2H 4) mO-, -O-CH 2-C(CF 3) 2-CH 2-O-, -O-CO-(CH 2) m-CO-O-, -CO-O-(CH 2) mO-CO-, -(CH 2) m-NH-(CH 2) m-, -CO-(CH 2) m-, - ... 2) k-NH-(CH 2) k-, -(NH-(CH 2) m) k-NH-, -CO-C 3H 6-(NH-C 3H 6) n-CO-, or -S-(CH 2) mS-, where m is an integer from 1 to 12, k is an integer from 1 to 5, and n is 1 or 2. In equation (DI-4)

[0070] , s is an integer from 0 to 2.

[0071] In the formula (DI-5), G 33 is a single bond, -NH-, -NCH 3-, -O-, -S-, -SS-, -SO 2-, -CO-, -COO-, -CONCH 3-, -CONH-, -C(CH 3) 2-, -C(CF 3) 2-, -(CH 2) m-, -O-(CH 2) mO-, -(OC 2H 4) mO-, -O-CH 2-C(CF 3) 2-CH 2-O-, -O-CO-(CH 2) m-CO-O-, -CO-O-(CH 2) mO-CO-, -(CH 2) m-NH-(CH 2) m-, -CO-(CH 2) k-NH-(CH 2) k-, -CO-C 3H 6-(NH-C 3H 6) The radical can be n-CO-, or -S-(CH 2) mS-, -N(Boc)-(CH 2) e-, -(CH 2) mN(Boc)-CONH-(CH 2) m-, -(CH 2) mN(Boc)-(CH 2) m-, or any radical represented by the following formula (DI-5-a) or the following formula (DI-5-b), where m is an integer from 1 to 12, k is an integer from 1 to 5, e is an integer from 2 to 10, and n is 1 or 2. Boc is a tert-butoxycarbonyl group.

[0072] In formula (DI-5-a), q is an integer from 0 to 6. R 44 is a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms.

[0073] In formulas (DI-6) and (DI-7), G 22 is independently a single bond, -O-, -S-, -CO-, -C(CH 3) 2-, -C(CF 3) 2-, or an alkylene group having 1 to 10 carbon atoms.

[0074] At least one hydrogen atom of the cyclohexane ring and benzene ring in formulas (DI-2) to (DI-7) may be substituted with a fluorine atom, a chlorine atom, an alkyl group having 1 to 3 carbon atoms, a methoxy group, a hydroxyl group, a trifluoromethyl group, a carboxyl group, an aminomethyl group, a phenylamino group, a phenyl group, or a benzyl group. In addition, in formula (DI-4), at least one hydrogen atom of the cyclohexane ring and benzene ring may be substituted with one of the groups of groups represented by any of the formulas (DI-4-a) to (DI-4-i) below. In formula (DI-5), when G 33 is a single bond, at least one hydrogen atom of the benzene ring may be substituted with NHBoc or N(Boc) 2.

[0075] In formulas (DI-4-a) and (DI-4-b), R 20 is independently a hydrogen atom or a methyl group. In formulas (DI-4-f) and (DI-4-g), m is independently an integer from 0 to 12, and Boc is a tert-butoxycarbonyl group.

[0076] In formulas (DI-2) to (DI-7), the bases whose bonding positions are not fixed on the carbon atoms constituting the ring indicate that the bonding positions in the ring are arbitrary.

[0077] In formula (DI-11), r is 0 or 1. In formulas (DI-8) to (DI-11), the amino groups bonded to the ring are at arbitrary positions.

[0078] In formula (DI-12), R 21 and R 22 are independently alkyl or phenyl with 1 to 3 carbon atoms, G 23 is independently alkylene, phenylene or alkyl-substituted phenylene with 1 to 6 carbon atoms, and w is an integer from 1 to 10.

[0079] In formula (DI-13), R 23 is independently an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a chlorine atom, and p and q are independently integers from 0 to 4.

[0080] In formula (DI-14), ring B is a monocyclic heterocyclic aromatic group, R 24 is a hydrogen atom, fluorine atom, chlorine atom, alkyl, alkoxy, alkenyl, or alkynyl group having 1 to 6 carbon atoms, and q is an independent integer from 0 to 4. When q is 2 or more, multiple R 24s may be the same or different. In formula (DI-15), ring C is a heterocyclic aromatic group or a heterocyclic aliphatic group. In formula (DI-16), G 24 is a single bond, an alkylene group having 2 to 6 carbon atoms, or a 1,4-phenylene group, and r is 0 or 1.

[0081] In formula (DI-17), R 23 is independently an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or a chlorine atom; p is independently an integer from 0 to 4; R 25 is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a tert-butoxycarbonyl group; and Z is a divalent group containing an alkylene group having 1 to 10 carbon atoms. In the alkylene group having 1 to 10 carbon atoms, any position and any number of CH 2 atoms can be substituted with NH, but the NH atoms are not adjacent.

[0082] A preferred example of an alkyl group having 1 to 4 carbon atoms in R 25 is methyl. Preferred examples of a divalent group containing an alkylene group having 1 to 10 carbon atoms in Z are -(CH 2) m- and -Ph-(CH 2) m-Ph-, where m is an integer from 1 to 10. Among these, -(CH 2) m- is preferred, and more preferably -(CH 2) 2-(ethylene). Here, Ph is 1,4-phenylene.

[0083] In formulas (DI-13) to (DI-17), the groups whose bonding positions are not fixed on the carbon atoms constituting the ring indicate that the bonding positions in the ring are arbitrary. The bonding positions of the amino groups on the two ends of the ring can be arbitrary, but are preferably para and meta, and more preferably para.

[0084] In formula (DIH-1), G 25 is a single bond, an alkylene group with 1 to 20 carbon atoms, -CO-, -O-, -S-, -SO 2-, -C(CH 3) 2-, or -C(CF 3) 2-.

[0085] In formula (DIH-2), ring D is cyclohexylene, phenylene, or naphthylene, and at least one hydrogen atom of the group may be substituted with methyl, ethyl, or phenyl.

[0086] In formula (DIH-3), ring E is independently cyclohexylene or phenylene, and at least one hydrogen atom of the group may be substituted with methyl, ethyl, or phenyl. The two ring E may be the same or different. Y is a single bond, an alkylene group having 1 to 20 carbon atoms, -CO-, -O-, -S-, -SO 2-, -C(CH 3) 2-, or -C(CF 3) 2-. In formulas (DIH-2) and (DIH-3), the bonding position of the -acehydrazine group with the ring bond is arbitrary.

[0087] Examples of diamines represented by formula (DI-1) are shown in the following formulas (DI-1-1) to (DI-1-9). In formulas (DI-1-7) and (DI-1-8), k is an integer from 1 to 3, respectively. In formula (DI-1-9), v is an integer from 1 to 6, respectively.

[0088] Examples of diamines represented by formulas (DI-2) to (DI-3) are shown in the following formulas (DI-2-1), (DI-2-2), (DI-3-1) to (DI-3-3).

[0089] Examples of diamines represented by formula (DI-4) are shown in the following formulas (DI-4-1) to (DI-4-27).

[0090] In formulas (DI-4-20) and (DI-4-21), m is an integer from 1 to 12, respectively.

[0091]

[0092] The following shows an example of a diamine represented by formula (DI-5). In formula (DI-5-1), m is an integer from 1 to 12.

[0093] In formulas (DI-5-12) and (DI-5-13), m is an integer from 1 to 12, respectively. In formula (DI-5-16)

[0094] , v is an integer from 1 to 6.

[0095]

[0096] In formulas (DI-5-35) to (DI-5-37), m is an integer from 1 to 12, respectively. In formula (DI-5-38), k is an integer from 1 to 5, respectively. In formula (DI-5-40), n is an integer of 1 or 2.

[0097] In formula (DI-5-44), e is an integer from 2 to 10, and in formula (DI-5-45), R 43 is a hydrogen atom, (tert-butoxycarbonyl)amino, or bis(tert-butoxycarbonyl)amino.

[0098]

[0099] Examples of diamines represented by formula (DI-6) are shown in the following formulas (DI-6-1) to (DI-6-7).

[0100] Examples of diamines represented by formula (DI-7) are shown in the following formulas (DI-7-1) to (DI-7-11). In formulas (DI-7-3) and (DI-7-4), m is an integer from 1 to 12, and n is 1 or 2, respectively.

[0101]

[0102] Examples of diamines represented by formula (DI-8) are shown in the following formulas (DI-8-1) to (DI-8-4).

[0103] Examples of diamines represented by formula (DI-9) are shown in the following formulas (DI-9-1) to (DI-9-3).

[0104] Examples of diamines represented by formula (DI-10) are shown in the following formulas (DI-10-1) and (DI-10-2).

[0105] Examples of diamines represented by formula (DI-11) are shown in the following formulas (DI-11-1) to (DI-11-3).

[0106] An example of a diamine represented by formula (DI-12) is shown in the following formula (DI-12-1).

[0107] Examples of diamines represented by formula (DI-13) are shown in the following formulas (DI-13-1) to (DI-13-13).

[0108] Examples of diamines represented by formula (DI-14) are shown in the following formulas (DI-14-1) to (DI-14-9).

[0109] Examples of diamines represented by formula (DI-15) are shown in the following formulas (DI-15-1) to (DI-15-12).

[0110] An example of a diamine represented by formula (DI-16) is shown in the following formula (DI-16-1).

[0111] The following shows examples of diamines represented by formula (DI-17). In formula (DI-17-1), k is an integer from 1 to 6. In formulas (DI-17-2) to (DI-17-3), e is an integer from 1 to 10, and Boc is tert-butoxycarbonyl. In formula (DI-17-4), m is 1 or 2, and k is 1 or 2.

[0112] Examples of compounds represented by any of the formulas (DIH-1) to (DIH-3) are shown in the following formulas (DIH-1-1), (DIH-1-2), (DIH-2-1) to (DIH-2-3), (DIH-3-1) to (DIH-3-6). In formula (DIH-1-2)

[0113] , m is an integer from 1 to 12.

[0114] By using compounds represented by formula (DI-13) or formula (DI-17-1), image retention characteristics can be improved. Among the compounds represented by formula (DI-13), compounds represented by formula (DI-13-1) are preferred. Among the compounds represented by formula (DI-17-1), k=2 is more preferred. In the polymer of the present invention, compounds represented by formula (DI-13) or formula (DI-17-1) are preferably used at 10 mol% or more of the total amount of diamines used. Multiple compounds represented by formula (DI-13) or formula (DI-17-1) may also be used in combination.

[0115] As a diamine other than that, when image retention characteristics are of greater importance, compounds represented by formula (DI-4-1), formula (DI-5-1), or formula (DI-17-2) are preferred. In formula (DI-5-1), m is more preferably 2 to 8, and even more preferably m = 4 to 8. The compound represented by formula (DI-17-2) is particularly preferred as a raw material for the polymer of the present invention in the form of a polymer other than the polymer of the present invention (the doped liquid crystal alignment agent described later). In formula (DI-17-2), e is more preferably 6 to 10, and even more preferably e = 6, 8, or 10, and particularly preferably e = 6.

[0116] In the polymer of the present invention, the compound represented by formula (DI-4-1), formula (DI-5-1), or formula (DI-17-2) is preferably used in a total amount of diamines of 5 moles or more.

[0117] In the raw material composition used as a raw material for the polymer of the present invention, a portion of the diamine may be substituted with at least one selected from the group consisting of monoamines and monohydrazides. Regarding the substitution ratio, it is preferably in the range of 40 mol% or less relative to the diamine, where at least one selected from the group consisting of monoamines and monohydrazides is present. This substitution can terminate the polymerization reaction during the formation of polyacrylic acid, and can inhibit further polymerization. Therefore, through this substitution, the molecular weight of the obtained polymer (polyacrylic acid or its derivatives) can be easily controlled, for example, improving the coating characteristics of the liquid crystal alignment agent without compromising the effects of the present invention. As long as the effects of the present invention are not compromised, the diamine that can be substituted with monoamines or monohydrazides may be one or more. Examples of such monoamines include: aniline, 4-hydroxyaniline, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, n-undecylamine, n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecanylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-eicosylamine, p-aminophenyltrimethoxysilane, and 3-aminopropyltriethoxysilane.

[0118] When the polymer of the present invention is polyamide or a derivative thereof, its raw material composition may also further include a monoisocyanate compound as a monomer. By including a monoisocyanate compound as a monomer, the ends of the obtained polyamide or its derivative are modified, and the molecular weight is adjusted. By using the end-modified polyamide or its derivative, for example, the coating characteristics of the liquid crystal alignment agent can be improved without compromising the effects of the present invention. From this point of view, the content of the monoisocyanate compound in the monomer is preferably 1 mol% to 10 mol% relative to the total amount of diamine and tetracarboxylic dianhydride in the monomer. Examples of the monoisocyanate compound include phenyl isocyanate and naphthyl isocyanate.

[0119] The liquid crystal alignment agent of the present invention may comprise one polymer of the present invention, or may be a mixture of the polymer of the present invention and polymers other than the polymer of the present invention. Furthermore, in this specification, a liquid crystal alignment agent comprising one of the polymers is sometimes referred to as a monolayer liquid crystal alignment agent. A liquid crystal alignment agent comprising two or more of the polymers is sometimes referred to as a blended liquid crystal alignment agent. Blended liquid crystal alignment agents are particularly useful in situations where voltage holding ratio (VHR) reliability or other electrical properties are of paramount importance.

[0120] The polymer other than the polymer of the present invention used as the doped liquid crystal alignment agent is preferably any one or more of polyamide and polyamide derivatives. Regarding the polymer other than the polymer of the present invention, polyamide and polyamide derivatives, except that they do not contain the compounds represented by formula (I) as raw material compositions, refer to the description of the polymer of the present invention.

[0121] The following describes tetracarboxylic acid derivatives preferred as raw materials for polymers other than the polymers of the present invention used as alignment agents for blended liquid crystals. When improving the transmittance of the liquid crystal display element is of paramount importance, compounds represented by formulas (AN-1-1), (AN-1-2), (AN-16-19), (AN-3-1), (AN-4-30), (AN-5-1), (AN-7-2), (AN-10-1), (AN-16-3), or (AN-16-4) are preferred, and compounds represented by formula (AN-1-1) are more preferred. Among the compounds represented by formula (AN-1-2), compounds with m=4 or 8 are particularly preferred.

[0122] When it is important to improve the VHR of the liquid crystal display element, the preferred compound is one represented by formula (AN-1-1), formula (AN-1-2), formula (AN-3-1), formula (AN-4-5), formula (AN-4-30), formula (AN-7-2), formula (AN-10-1), formula (AN-16-3), formula (AN-16-4), formula (AN-16-17), or formula (AN-16-19), wherein in formula (AN-1-2), m is preferably 4 or 8.

[0123] As one method to prevent burn-in, it is effective to increase the rate of mitigation of residual charge (residual direct current, DC) in the liquid crystal alignment film by reducing the volume resistivity of the liquid crystal alignment film. When the above objective is important, compounds represented by formulas (AN-2-10), (AN-3-2), (AN-4-21), (AN-4-29), or (AN-11-3) are preferred.

[0124] Among these, compounds represented by formula (AN-1-1), formula (AN-2-10), formula (AN-6-19), formula (AN-3-2), or formula (AN-4-21) are more preferred, and compounds represented by formula (AN-1-1), formula (AN-2-10), or formula (AN-3-2) are even more preferred.

[0125] The following describes diamines preferred as raw materials for polymers other than the polymers of the present invention used as doped liquid crystal alignment agents. When improving liquid crystal alignment is of paramount importance, compounds represented by formulas (DI-5-1), (DI-5-12), (DI-5-13), or (DI-7-3) are preferred. In formula (DI-5-1), m is preferably 2 to 8, more preferably m = 4 to 8. In formula (DI-5-12), m is preferably 2 to 6, more preferably m = 5. In formula (DI-5-13), m is preferably 1 or 2, more preferably m = 1.

[0126] When improving transmittance is of paramount importance, compounds represented by formulas (DI-1-3), (DI-2-1), (DI-5-1), (DI-5-5), (DI-5-24), or (DI-7-3) are preferred, and compounds represented by formula (DI-2-1) are more preferred. In formula (DI-5-1), m is preferably 2 to 8, and m is more preferably 8. In formula (DI-7-3), m is preferably 2 or 3, and m is more preferably 3 and n is 1.

[0127] When it is important to improve the VHR of the liquid crystal display element, it is preferable to use a compound represented by formula (DI-2-1), formula (DI-4-1), formula (DI-4-2), formula (DI-4-10), formula (DI-4-15), formula (DI-4-22), formula (DI-5-1), formula (DI-5-28), formula (DI-17-1), or formula (DI-13-1), and more preferably a compound represented by formula (DI-2-1), formula (DI-5-1), or formula (DI-13-1). In formula (DI-5-1), m is preferably 1. In formula (DI-17-1), k is preferably 2.

[0128] As one method to prevent burn marks, it is effective to increase the rate of mitigation of residual charge (residual DC) in the liquid crystal alignment film by reducing the volume resistivity of the liquid crystal alignment film. Where this objective is important, compounds represented by formulas (DI-4-1), (DI-4-2), (DI-4-10), (DI-4-15), (DI-5-1), (DI-5-12), (DI-5-13), (DI-5-28), (DI-4-20), (DI-4-21), or (DI-16-1) are preferred, and compounds represented by formulas (DI-4-1), (DI-5-1), or (DI-5-13) are even more preferred. In formula (DI-5-1), m is preferably 2 to 8, more preferably m = 4 to 8. In formula (DI-5-12), m is preferably 2 to 6, more preferably m = 5. In formula (DI-5-13), m is preferably 1 or 2, and more preferably m is 1.

[0129] Among these, compounds represented by formula (DI-4-1), formula (DI-4-2), formula (DI-4-10), formula (DI-4-18), formula (DI-4-19), formula (DI-5-1), formula (DI-5-9), formula (DI-5-28), formula (DI-13-1), or formula (DIH-1-2) are more preferred, wherein, in particular, compounds in formula (DI-4-1), formula (DI-4-18), formula (DI-4-19), formula (DI-5-1) where m=1 or 2, and compounds represented by formula (DI-5-9), formula (DI-13-1), or formula (DIH-1-2) are more preferred.

[0130] When using a two-component polymer, for example, the following form is adopted: one of the polymers is selected as having excellent performance in liquid crystal alignment capability, and the other of the polymer is selected as having excellent performance in improving the electrical characteristics of liquid crystal display elements, thus obtaining a liquid crystal alignment agent with a good balance between liquid crystal alignment and electrical characteristics.

[0131] In the aforementioned case, by controlling the structure or molecular weight of each polymer, during the process of forming a thin film by coating a liquid crystal alignment agent obtained by dissolving these polymers in a solvent onto a substrate and pre-drying it as described later, polymers with excellent liquid crystal alignment capabilities are segregated in the upper layer of the thin film, while polymers with excellent performance in improving the electrical characteristics of the liquid crystal display element are segregated in the lower layer of the thin film. Among the mixed polymers, the phenomenon that polymers with lower surface energy separate in the upper layer and polymers with higher surface energy separate in the lower layer can be observed. This layer separation can be confirmed by the following method: the surface energy of the formed liquid crystal alignment film is the same as or similar to the surface energy of a film formed from a liquid crystal alignment agent containing only the polymer intended to segregate in the upper layer.

[0132] As a method for separating the visible layer, reducing the molecular weight of the polymer that is to be segregated in the upper layer can also be listed.

[0133] In a liquid crystal alignment agent containing a mixture of polyamide and polyamide derivatives, the display layer can also be separated by setting the polymer to be segregated in the upper layer as a polyamide ester or a polyimide.

[0134] The polymer of the present invention can be used as a polymer segregated in the upper layer of the film, or as a polymer segregated in the lower layer of the film. In addition, it can be used as both polymers, but it is more preferable to use it as a polymer segregated in the upper layer of the film.

[0135] The polymer other than the polymer of the present invention used in the blended liquid crystal alignment agent is preferably a polymer used as the lower layer of the film.

[0136] The proportion of polyacrylic acid or its derivatives segregated in the upper layer of the film and polyacrylic acid or its derivatives segregated in the lower layer of the film is preferably 5% to 80% by weight, and more preferably 20% to 80% by weight, relative to the total amount of polyacrylic acid or its derivatives segregated in the upper layer of the film.

[0137] Furthermore, from the viewpoint of adjusting the coatability of the liquid crystal alignment agent or the concentration of the polyacrylic acid or its derivatives, the liquid crystal alignment agent of the present invention may also contain a solvent. The solvent can be used without particular limitation as long as it has the ability to dissolve polymeric components. The solvent broadly includes solvents commonly used in the manufacturing steps or applications of polymeric components such as polyacrylic acid and soluble polyimide, and can be appropriately selected according to the intended use. The solvent may be one type or a mixture of two or more solvents.

[0138] As a solvent, examples include solvents that are soluble in the polyamide or its derivatives, or other solvents intended to improve coatability.

[0139] Examples of aprotic polar organic solvents that are solubilizing relative to polyacrylic acid or its derivatives include: N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethylimidazolium ketone, N-methylcaprolactone, N-methylpropionic acid, N,N-dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, N,N-diethylformamide, diethylacetamide, N,N-dimethylisobutylamide, γ-butyrolactone, and γ-valerolactone. Among these solvents, N-methyl-2-pyrrolidone, dimethylimidazolium ketone, γ-butyrolactone, or γ-valerolactone are preferred.

[0140] Examples of other solvents used for improving coatability include: ethylene glycol monobutyl ether, ethylene glycol monotert-butyl ether and other ethylene glycol monoalkyl ethers, diethylene glycol monoethyl ether and other diethylene glycol monoalkyl ethers, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, diethylene glycol butyl methyl ether and other diethylene glycol dialkyl ethers. Additionally, examples include: propylene glycol monomethyl ether, 1-butoxy-2-propanol and other propylene glycol monoalkyl ethers, dipropylene glycol monomethyl ether and other dipropylene glycol monoalkyl ethers, triethylene glycol monoalkyl ethers, butyl cellosolve acetate, phenyl acetate, and ester compounds such as these acetates. Furthermore, examples include: dialkyl malonate such as diethyl malonate, alkyl lactate, diisobutyl ketone, diacetone alcohol, 3-methyl-3-methoxybutanol, 4-methyl-2-pentanol, diisobutylmethanol, tetrahydronaphthalene, and isophorone.

[0141] Among these solvents, diisobutyl ketone, 4-methyl-2-pentanol, diisobutylmethanol, ethylene glycol monobutyl ether, ethylene glycol monotert-butyl ether, diethylene glycol monoethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, diethylene glycol butyl methyl ether, 1-butoxy-2-propanol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, or butyl cellosolve acetate are preferred.

[0142] The concentration of the solid component in the liquid crystal alignment agent of the present invention is not particularly limited, and the most suitable value can be selected by combining the various coating methods described below. Generally, in order to suppress unevenness or pinholes during coating, the concentration is preferably 0.1% to 30% by weight, more preferably 1% to 10% by weight, relative to the weight of the varnish.

[0143] The viscosity of the liquid crystal alignment agent of the present invention varies depending on the coating method, the concentration of polyacrylic acid or its derivative, the type of polyacrylic acid or its derivative used, and the type and proportion of solvent. For example, when coating using a printing press, the viscosity is 5 mPa·s to 100 mPa·s (more preferably 10 mPa·s to 80 mPa·s). If the viscosity is 5 mPa·s or higher, it is easy to obtain a sufficient film thickness, and if it is 100 mPa·s or lower, it is easy to suppress printing unevenness. When coating using spin coating, the viscosity is suitable to be 5 mPa·s to 200 mPa·s (more preferably 10 mPa·s to 100 mPa·s). When coating using an inkjet coating apparatus, the viscosity is suitable to be 5 mPa·s to 50 mPa·s (more preferably 5 mPa·s to 20 mPa·s). The viscosity of liquid crystal alignment agents can be determined by rotational viscosity measurement, for example, using a rotational viscometer (TVE-20L type viscometer manufactured by Toki Sangyo Co., Ltd.) (measurement temperature: 25°C).

[0144] The liquid crystal alignment agent of the present invention may also contain various additives. Various additives may be selected and used according to their respective purposes in order to improve the various properties of the liquid crystal alignment film. Examples are shown below.

[0145] <Alkenyl-substituted nadimide compound> For example, for the purpose of stabilizing the electrical properties of the liquid crystal display element over a long period of time, the liquid crystal alignment agent of the present invention may also contain an alkenyl-substituted nadimide compound. One alkenyl-substituted nadimide compound may be used, or two or more may be used in combination. For the purpose stated therein, the content of the alkenyl-substituted nadimide compound relative to polyacrylic acid or its derivatives is preferably 1% to 50% by weight, more preferably 1% to 30% by weight, and even more preferably 1% to 20% by weight. The alkenyl-substituted nadimide compound is preferably a compound that can be dissolved in a solvent that dissolves the polyacrylic acid or its derivatives used in the present invention. Preferred alkenyl-substituted nadic nimodiimide compounds include those disclosed in Japanese Patent Application Publication Nos. 2008-096979, 2009-109987, and 2013-242526. Particularly preferred alkenyl-substituted nadic nimodiimide compounds include: bis{4-(allylbicyclo[2.2.1]hept-5-en-2,3-dicarboxylated nimodiimide)phenyl}methane, N,N'-m-phenylenedimethyl-bis(allylbicyclo[2.2.1]hept-5-en-2,3-dicarboxylated nimodiimide), or N,N'-hexamethylene-bis(allylbicyclo[2.2.1]hept-5-en-2,3-dicarboxylated nimodiimide).

[0146] <Compounds with free radical polymerizable unsaturated double bonds> For example, for the purpose of stabilizing the electrical properties of liquid crystal display elements over a long period of time, the liquid crystal alignment agent of the present invention may also contain compounds with free radical polymerizable unsaturated double bonds. The compound with free radical polymerizable unsaturated double bonds may be one compound or two or more compounds. Furthermore, the compound with free radical polymerizable unsaturated double bonds does not contain alkenyl-substituted nadicimines. Among compounds having free radical polymerizable unsaturated double bonds, preferred compounds include: N,N'-methylenebisacrylamide, N,N'-dihydroxyethylene-bisacrylamide, ethylene diacrylate, 4,4'-methylenebis(N,N-dihydroxyethylene acrylate aniline), triallyl cyanurate, and compounds having free radical polymerizable unsaturated double bonds disclosed in Japanese Patent Application Publication Nos. 2009-109987, 2013-242526, International Publication Nos. 2014 / 119682, and 2015 / 152014. For the stated purpose, the content of the compound having free radical polymerizable unsaturated double bonds is preferably 1% to 50% by weight, more preferably 1% to 30% by weight, relative to polyacrylic acid or its derivatives.

[0147] <Oxazine Compound> For example, for the purpose of stabilizing the electrical characteristics of the liquid crystal display element over a long period of time, the liquid crystal alignment agent of the present invention may also contain an oxazine compound. The oxazine compound may be one compound or two or more compounds. For the purpose stated, the content of the oxazine compound is preferably 0.1% to 50% by weight, more preferably 1% to 40% by weight, and even more preferably 1% to 20% by weight, relative to polyacrylic acid or its derivatives.

[0148] The oxazine compound is preferably an oxazine compound that is soluble in a solvent that dissolves polyacrylic acid or its derivatives and has ring-opening polymerization properties. Examples of preferred oxazine compounds include those represented by formulas (OX-3-1), (OX-3-9), and (OX-3-10), as well as those disclosed in Japanese Patent Application Publication Nos. 2007-286597 and 2013-242526.

[0149] <Oxazoline Compound> For example, for the purpose of stabilizing the electrical properties of the liquid crystal display element over a long period of time, the liquid crystal alignment agent of the present invention may also contain an oxazoline compound. The oxazoline compound is a compound having an oxazoline structure. The oxazoline compound may be one compound or two or more compounds. For the purpose stated, the content of the oxazoline compound relative to polyacrylic acid or its derivatives is preferably 0.1% to 50% by weight, more preferably 1% to 40% by weight, and even more preferably 1% to 20% by weight. Preferred oxazoline compounds include those disclosed in Japanese Patent Application Publication No. 2010-054872 and Japanese Patent Application Publication No. 2013-242526. More preferably, 1,3-bis(4,5-dihydro-2-oxazolyl)benzene is also mentioned.

[0150] <Epoxy Compound> For example, for the purpose of stabilizing the electrical properties of the liquid crystal display element over a long period, improving the hardness of the film, or improving adhesion to the sealant, the liquid crystal alignment agent of the present invention may also contain an epoxy compound. The epoxy compound may be one compound or two or more compounds. For the purposes stated, the content of the epoxy compound relative to polyacrylic acid or its derivatives is preferably 0.1% to 50% by weight, more preferably 1% to 20% by weight, and even more preferably 1% to 10% by weight.

[0151] As an epoxy compound, various compounds having one or more epoxy rings within the molecule can be used. For the purpose of improving the hardness of the film or improving the adhesion with the sealant, compounds having two or more epoxy rings within the molecule are preferred, and compounds having three or four epoxy rings within the molecule are more preferred.

[0152] Examples of epoxy compounds include those disclosed in Japanese Patent Application Publication No. 2009-175715, Japanese Patent Application Publication No. 2013-242526, Japanese Patent Application Publication No. 2016-170409, and International Publication No. 2017 / 217413. Preferred epoxy compounds include: N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, 3-glycidyloxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, (3,3',4,4'-diepoxy)bicyclohexyl, 1,4-butanediol glycidyl ether, tris(2,3-epoxypropyl) isocyanurate, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, or N,N,N',N'-tetraglycidyl-m-xylenediamine. More preferably, 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane may be added. In addition to the above-mentioned additions, oligomers or polymers having an epoxy ring may also be added. Oligomers or polymers having an epoxy ring may be those disclosed in Japanese Patent Application Publication No. 2013-242526.

[0153] <Silane Compound> For example, the liquid crystal alignment agent of the present invention may also contain a silane compound for the purpose of improving adhesion to the substrate and the sealant. For the purpose stated therein, the content of the silane compound is preferably 0.1% to 30% by weight, more preferably 0.5% to 20% by weight, and even more preferably 0.5% to 10% by weight, relative to polyamide or its derivatives.

[0154] As the silane compound, the silane coupling agents disclosed in Japanese Patent Application Publication No. 2013-242526, Japanese Patent Application Publication No. 2015-212807, Japanese Patent Application Publication No. 2018-173545, and International Publication No. 2018 / 181566 may be used. Preferred silane coupling agents include: 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, p-aminophenyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-isocyanate-propyltriethoxysilane, or 3-ureidopropyltriethoxysilane.

[0155] In addition to the additives described above, compounds having cyclic carbonate groups, hydroxyalkylamide sites, or hydroxyl groups may be added for the purpose of improving the strength of the liquid crystal alignment film or for ensuring long-term stability of the electrical characteristics of the liquid crystal display element. Examples of specific compounds include those disclosed in Japanese Patent Application Publication No. 2016-118753 and International Publication No. 2017 / 110976. Preferred compounds include those of formulas (HD-1) to (HD-4). These compounds are preferably added at amounts of 0.5% to 50% by weight, more preferably 1% to 30% by weight, and even more preferably 1% to 10% by weight, relative to polyamide or its derivatives.

[0156] In addition, when it is necessary to improve antistatic properties, an antistatic agent may be used, and when amide imidization is carried out at low temperature, an amide imidization catalyst may be used. As an amide imidization catalyst, the amide imidization catalyst disclosed in Japanese Patent Application Publication No. 2013-242526 can be cited as an example.

[0157] <Liquid crystal alignment film>

[0158] The liquid crystal alignment film of the present invention is formed by heating a coating of the liquid crystal alignment agent of the present invention. The liquid crystal alignment film of the present invention can be obtained by a conventional method for making a liquid crystal alignment film from a liquid crystal alignment agent. For example, the liquid crystal alignment film of the present invention can be obtained by a step of forming a coating of the liquid crystal alignment agent of the present invention, a step of heating and drying, and a step of heating and calcining. The liquid crystal alignment film of the present invention is subjected to a treatment to impart anisotropy. As a treatment, friction treatment can also be performed to impart anisotropy, but it is preferable to impart anisotropy by light irradiation.

[0159] Hereinafter, a method for forming a liquid crystal alignment film using the photoalignment liquid crystal alignment agent of the present invention will be described.

[0160] The coating can be formed in the same manner as the conventional liquid crystal alignment film by applying the liquid crystal alignment agent of the present invention onto the substrate of the liquid crystal display element. Examples of substrates include those made of glass, silicon nitride, acrylic, polycarbonate, polyimide, etc., which may be provided with electrodes such as indium tin oxide (ITO), indium zinc oxide (In2O3-ZnO, IZO), and indium gallium zinc oxide (In-Ga-ZnO4, IGZO) or color filters.

[0161] Commonly known methods for coating liquid crystal alignment agents onto a substrate include spinner method, printing method, dipping method, drop method, inkjet method, etc. These methods are also applicable to the present invention.

[0162] The heating and drying step is generally known to include methods such as heating in an oven or infrared furnace, or heating on a hot plate. The heating and drying step is preferably performed at a temperature within the range where the solvent can evaporate, and more preferably at a temperature relatively lower than that in the heating and calcining step. Specifically, the heating and drying temperature is preferably in the range of 30°C to 150°C, and more preferably in the range of 50°C to 120°C.

[0163] The heating and calcination step can be carried out under conditions required for the polyamide or its derivatives to undergo amide imidization. Methods for calcining the coating are generally known, such as heating in an oven or infrared furnace, or heating on a hot plate. These methods are also applicable to the present invention. It is generally preferred to carry out the process at a temperature of approximately 90°C to 300°C, more preferably 120°C to 280°C, and even more preferably 150°C to 250°C. The calcination time is not particularly limited, but is preferably 1 minute to 2 hours, more preferably 10 minutes to 40 minutes.

[0164] Heating can be performed in multiple stages, and the temperature can be changed during this process.

[0165] In order to align the liquid crystal in one direction with respect to the horizontal direction and / or the vertical direction, a known photoalignment method can be used as a method to impart anisotropy to the liquid crystal alignment film.

[0166] The light used in the photoirradiation step of the photoalignment method can be, for example, ultraviolet or visible light with wavelengths of 150 nm to 800 nm. There are no particular limitations on these lights as long as they can impart liquid crystal alignment capability to the thin film. If a strong alignment constraint force is desired to exhibit on the liquid crystal, polarized light is preferred, and linearly polarized light is even more preferred.

[0167] The wavelength of the polarized light in the light irradiation step is preferably 150 nm to 400 nm, more preferably 200 nm to 400 nm, and even more preferably 200 nm to 300 nm. The irradiation amount of the polarized light is preferably 0.001 J / cm² to 10 J / cm², more preferably 0.1 J / cm² to 5 J / cm². There is no particular limitation on the irradiation angle of the polarized light on the film surface. However, from the viewpoint of shortening the alignment processing time, it is preferable to make the angle as perpendicular as possible to the film surface when it is desired to exhibit a strong alignment constraint force on the liquid crystal. In addition, by irradiating the liquid crystal alignment film of the present invention with linearly polarized light, the liquid crystal can be aligned in a direction perpendicular to the polarization direction of the linearly polarized light.

[0168] Among the light sources used in the irradiation step, there may be no restriction on the use of ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, deep ultraviolet (Deep UV) lamps, halogen lamps, metal halide lamps, high-power metal halide lamps, xenon lamps, mercury xenon lamps, excimer lamps, KrF excimer lasers, fluorescent lamps, light emitting diode (LED) lamps, sodium lamps, microwave discharged electrodeless lamps, etc.

[0169] To improve the liquid crystal alignment capability of the liquid crystal alignment film, light irradiation can be performed simultaneously with heating the liquid crystal alignment film. In this case, the heating temperature is preferably in the range of 50°C to 250°C.

[0170] The light irradiation step can be performed after the heating and drying step or after the heating and calcining step, preferably after the heating and calcining step. Alternatively, it can be performed simultaneously with the heating and drying step.

[0171] The liquid crystal alignment film of the present invention is preferably subjected to additional heating after the light irradiation step. Regarding the heating temperature, it is performed at a temperature equal to or higher than the temperature of the heating and calcination step, preferably 150°C to 300°C, more preferably 150°C to 250°C, and even more preferably 200°C to 250°C. The additional heating time is preferably 5 minutes to 2 hours, more preferably 5 minutes to 60 minutes, and even more preferably 5 minutes to 30 minutes.

[0172] Alternatively, a cleaning step may be provided after the light irradiation step or after an additional heating step. Specifically, the liquid crystal alignment film is immersed in a solvent. The immersion temperature is preferably 10°C to 80°C, more preferably 20°C to 50°C. Ultrasonic treatment is also preferred. The treatment time is preferably 1 minute to 1 hour, more preferably 1 minute to 30 minutes. The solvent used is not particularly limited as long as it dissolves the decomposition products generated from the liquid crystal alignment film by ultraviolet irradiation, and 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, or cyclohexyl acetate, etc. Among these, water, 2-propanol, 1-methoxy-2-propanol, or ethyl lactate are preferred in terms of versatility and safety. After impregnation, heating or rinsing is preferred. Alternatively, both can be performed. The heating temperature is preferably 150°C to 300°C, more preferably 200°C to 230°C. The heating time is preferably 10 seconds to 30 minutes, more preferably 1 minute to 10 minutes. For rinsing, low-boiling-point solvents such as water, methanol, ethanol, 2-propanol, acetone, or methyl ethyl ketone are preferred.

[0173] The thickness of the liquid crystal alignment film of the present invention is not particularly limited, but is preferably 10 nm to 300 nm, more preferably 30 nm to 150 nm. The thickness of the liquid crystal alignment film of the present invention can be measured by a known film thickness measuring device such as a profilometer or an ellipsometer.

[0174] The liquid crystal alignment film of the present invention is suitable for alignment control of liquid crystal compositions in liquid crystal display elements. In addition to its application in alignment of liquid crystal compositions in liquid crystal display elements, it can also be used for alignment control of liquid crystal materials in all other liquid crystal elements such as liquid crystal antennas, dimming windows, optical compensation materials, and variable phase shifters.

[0175] <Liquid Crystal Display Element> Next, the liquid crystal display element of the present invention will be described. The liquid crystal display element of the present invention is characterized by having the liquid crystal alignment film of the present invention, which enables high display quality due to its excellent contrast ratio.

[0176] The liquid crystal display element of the present invention will be described in detail. In the present invention, in the following liquid crystal display element, the liquid crystal alignment film includes the liquid crystal alignment film of the present invention, the liquid crystal display element includes a pair of substrates arranged facing each other, an electrode formed on one or both of the opposing surfaces of the pair of substrates, the liquid crystal alignment film formed on the opposing surfaces of the pair of substrates, a liquid crystal layer formed between the pair of substrates, a pair of polarizing films disposed in a manner that clamps the opposing substrates, a backlight and a driving device.

[0177] There is no particular limitation as long as the electrode is formed on one side of the substrate. Examples of such electrodes include ITO or metal vapor-deposited films. Alternatively, the electrode can be formed on the entire surface of one side of the substrate, or it can be formed in a desired patterned shape. Examples of desired electrode shapes include comb-shaped or sawtooth structures. The electrode can be formed on one of a pair of substrates, or on both substrates. The electrode formation method varies depending on the type of liquid crystal display element. For example, in the case of an IPS type liquid crystal display element (lateral electric field type liquid crystal display element), the electrode is disposed on one of the pair of substrates; in the case of other liquid crystal display elements, the electrode is disposed on both of the pair of substrates. The liquid crystal alignment film is formed on the substrate or the electrode.

[0178] The liquid crystal layer is formed by sandwiching a liquid crystal composition between a pair of substrates with their surfaces facing each other and having liquid crystal alignment films formed thereon. During the formation of the liquid crystal layer, spacers such as microparticles or resin sheets may be used as needed to separate the pair of substrates and form appropriate intervals.

[0179] As methods for forming liquid crystal layers, vacuum injection and one drop fill (ODF) methods are known.

[0180] In the vacuum injection method, gaps (cell gaps) are set with the liquid crystal alignment film surfaces facing each other, and an injection port for the liquid crystal is left while a sealant is printed and the substrate is bonded. Liquid crystal is injected and filled into the cell gaps defined by the substrate surface and the sealant using a vacuum differential pressure, and then the injection port is sealed to manufacture a liquid crystal display element.

[0181] In the ODF method, a sealant is printed on the outer periphery of the liquid crystal alignment film surface of one of a pair of substrates, and liquid crystal is dropped into the area inside the sealant. Then, the other substrate is bonded together with the liquid crystal alignment film surfaces facing each other. Then, the liquid crystal is pressed and spread across the entire surface of the substrate, and then the entire surface of the substrate is irradiated with ultraviolet light to harden the sealant, thereby manufacturing a liquid crystal display element.

[0182] Regarding the sealant used in the bonding of the substrate, in addition to UV-curing types, thermosetting types are also known. The sealant can be printed, for example, by screen printing.

[0183] There are no particular limitations on the liquid crystal composition; various liquid crystal compositions with positive or negative dielectric anisotropy can be used. Preferred liquid crystal compositions with positive dielectric anisotropy include: Japanese Patent No. 3086228, Japanese Patent No. 2635435, Japanese Patent No. 5-501735, Japanese Patent No. 8-157826, Japanese Patent No. 8-231960, Japanese Patent No. 9-241644 (EP885272A1), Japanese Patent No. 9-302346 (EP806466A2), and Japanese Patent No. 8-199168 (EP7229). Liquid crystal compositions disclosed in Japanese Patent Application Publication No. 9-235552, Japanese Patent Application Publication No. 9-255956, Japanese Patent Application Publication No. 9-241643 (EP885271A1), Japanese Patent Application Publication No. 10-204016 (EP844229A1), Japanese Patent Application Publication No. 10-204436, Japanese Patent Application Publication No. 10-231482, Japanese Patent Application Publication No. 2000-087040, and Japanese Patent Application Publication No. 2001-48822, etc.

[0184] Examples of preferred liquid crystal compositions having negative dielectric constant anisotropy include: Japanese Patent Application Publication No. 57-114532, Japanese Patent Application Publication No. 2-4725, Japanese Patent Application Publication No. 4-224885, Japanese Patent Application Publication No. 8-40953, Japanese Patent Application Publication No. 8-104869, Japanese Patent Application Publication No. 10-168076, Japanese Patent Application Publication No. 10-168453, and Japanese Patent Application Publication No. 10-23. Japanese Patent Publication No. 6989, Japanese Patent Publication No. 10-236990, Japanese Patent Publication No. 10-236992, Japanese Patent Publication No. 10-236993, Japanese Patent Publication No. 10-236994, Japanese Patent Publication No. 10-237000, Japanese Patent Publication No. 10-237004, Japanese Patent Publication No. 10-237024, Japanese Patent Publication No. 10-237035, Japanese Patent Publication No. 10-237075 Japanese Patent Publication No. 10-237076, Japanese Patent Publication No. 10-237448 (EP967261A1), Japanese Patent Publication No. 10-287874, Japanese Patent Publication No. 10-287875, Japanese Patent Publication No. 10-291945, Japanese Patent Publication No. 11-029581, Japanese Patent Publication No. 11-080049, Japanese Patent Publication No. 2000-256307, Japanese Patent Publication No. 200 Liquid crystal compositions disclosed in Japanese Patent Publication No. 1-019965, Japanese Patent Application Publication No. 2001-072626, Japanese Patent Application Publication No. 2001-192657, Japanese Patent Application Publication No. 2010-037428, International Publication No. 2011 / 024666, International Publication No. 2010 / 072370, Japanese Patent Publication No. 2010-537010, Japanese Patent Application Publication No. 2012-077201, and Japanese Patent Application Publication No. 2009-084362.

[0185] Even if more than one optically active compound is added to a liquid crystal composition with positive or negative dielectric anisotropy, there is no effect.

[0186] Furthermore, from the viewpoint of improving alignment, additives may also be added to the liquid crystal composition used in the liquid crystal display element of the present invention. Such additives include photopolymerizable monomers, optically active compounds, antioxidants, ultraviolet absorbers, pigments, defoamers, polymerization initiators, polymerization inhibitors, etc. Preferred photopolymerizable monomers, optically active compounds, antioxidants, ultraviolet absorbers, pigments, defoamers, polymerization initiators, and polymerization inhibitors include compounds disclosed in International Publication No. 2015 / 146330, etc.

[0187] To suit liquid crystal display elements with polymer sustained alignment (PSA) mode, polymerizable compounds can be mixed into the liquid crystal composition. Preferred examples of polymerizable compounds are compounds having polymerizable groups such as acrylates, methacrylates, vinyl compounds, vinyloxy compounds, propylene ethers, epoxy compounds (oxetane, oxetane), and vinyl ketones. Preferred compounds include those disclosed in International Publication No. 2015 / 146330, etc. [Example]

[0188] Hereinafter, the present invention will be described by way of examples. Furthermore, the evaluation methods and compounds used in the examples are as follows.

[0189] Weight-average molecular weight (Mw) The weight-average molecular weight of polyacrylic acid was determined by GPC using a 2695 separation module ∙ 2414 differential refractometer (Waters Corporation), and polystyrene conversion was performed. The obtained polyacrylic acid was diluted to a concentration of approximately 2% by weight using a phosphate-dimethylformamide (DMF) mixture (phosphate / DMF = 0.6 / 100: weight ratio). The determination was performed using an HSPgel RT MB-M column (Waters Corporation), with the mixture as the developing solvent, at a column temperature of 50°C and a flow rate of 0.40 mL / min. Standard polystyrene was TSK standard polystyrene manufactured by Tosoh Corporation.

[0190] Tetracarboxylic dianhydride>

[0191] <Diamine>

[0192] <Solvent> NMP: N-methyl-2-pyrrolidone; BC: Butyl cellosolve (ethylene glycol monobutyl ether)

[0193] Preparation of Varnish

[0194] [Example 1 of Varnish Preparation] Varnish A1 was prepared by placing 2,016 g of the compound represented by formula (DI-17-1), k=2 and 0.804 g of the compound represented by formula (DI-4-1) into a 100 mL three-necked flask equipped with a stirrer and a nitrogen inlet tube, and adding 34.0 g of N-methyl-2-pyrrolidone (NMP) and stirring. Under nitrogen atmosphere, 3.178 g of the compound represented by formula (I-1) was added to the solution and stirred at room temperature for 12 hours. 30.0 g of NMP and 30.0 g of BC were added to the solution, and the solution was heated and stirred at 60°C until the weight average molecular weight of the polymer as the solute reached the desired weight average molecular weight, thereby obtaining varnish A1 with a solute weight average molecular weight of about 35,000 and a resin component concentration (solid component concentration) of 6% by weight.

[0195] [Preparation Examples 2 to 17] The preparation of varnishes A2 to A10, R1 to R3, and B1 to B4 were carried out as shown in Tables 1 and 2, with the compounds used as diamines and tetracarboxylic dianhydrides being modified. Otherwise, varnishes A2 to A10, R1 to R3, and B1 to B4 with a solid content concentration of 6% by weight were prepared in the same manner as in Preparation Example 1. Furthermore, in Tables 1 and 2, preparation examples showing two or more compounds as diamines refer to the combined use of all of the aforementioned compounds as diamines. The values ​​in square brackets indicate the mixing ratio (mol%), and empty columns indicate that the compound corresponding to the column was not used.

[0196] Table 1 varnish Tetracarboxylic acid dianhydride diamine molecular weight Preparation Example 1 A1 I-1

[95] DI-17-1 k=2

[50] DI-4-1

[50] 35,000 Preparation Example 2 A2 I-1

[95] DI-13-1

[50] DI-4-1

[50] 36,000 Preparation Example 3 A3 I-1

[95] DI-13-1

[40] DI-4-1

[20] DI-5-1 m=2

[40] 36,000 Preparation Example 4 A4 I-1

[95] DI-17-1 k=2

[50] DI-4-1

[25] DI-5-1 m=2

[25] 35,000 Preparation Example 5 A5 I-1

[95] DI-13-1

[10] DI-4-1

[20] DI-5-1 m=2

[40] DI-17-2 e=6

[30] 38,000 Preparation Example 6 A6 I-1

[95] DI-13-1

[30] DI-5-1 m=2

[40] DI-17-2 e=6

[30] 37,000 Preparation Example 7 A7 I-1

[95] DI-13-1

[40] DI-5-1 m=2

[30] DI-17-2 e=6

[30] 35,000 Preparation Example 8 A8 I-1

[95] DI-13-1

[50] DI-4-1

[25] DI-5-1 m=2

[25] 36,000 Preparation Example 9 A9 I-1

[95] DI-13-1

[40] DI-4-1

[20] DI-5-1 m=2

[20] DI-5-1 m=8

[20] 39,000 Preparation Example 10 A10 I-1

[80] AN-2-10

[15] DI-13-1

[40] DI-4-1

[20] DI-5-1 m=2

[40] 35,000 Preparation Example 11 R1 AN-16-19

[95] DI-17-1 k=2

[50] DI-4-1

[50] 35,000 Preparation Example 12 R2 AN-16-19

[95] DI-13-1

[50] DI-4-1

[50] 34,000 Preparation Example 13 R3 I-1

[95] DI-4-1

[50] DI-5-1 m=2

[50] 37,000

[0197] Table 2 varnish Tetracarboxylic acid dianhydride diamine molecular weight Preparation Example 14 B1 AN-1-1

[50] AN-4-5

[50] DI-13-1

[100] 90,000 Preparation Example 15 B2 AN-1-1

[100] DI-4-19

[100] 88,000 Preparation Example 16 B3 AN-1-1

[35] AN-4-5

[45] AN-16-19

[20] DI-4-19

[30] DI-13-1

[70] 92,000 Preparation Example 17 B4 AN-1-1

[50] AN-4-5

[50] DI-4-19

[30] DI-13-1

[70] 89,000

[0198] [Example 1] Liquid crystal alignment agent 1 was prepared by diluting and stirring varnish A1 to a solid content of 4% by weight using an NMP / BC mixed solution (NMP / BC = 7 / 3 by weight). The prepared liquid crystal alignment agent was coated onto a glass substrate with an FFS electrode and a glass substrate with column spacers using a spinner method. After coating, the substrate was heated at 60°C for 80 seconds to evaporate the solvent, and then calcined at 230°C for 30 minutes to form a liquid crystal alignment film. Linearly polarized ultraviolet light was irradiated by a polarizing plate with a polarization wavelength range of 230 nm to 310 nm perpendicular to the substrate using a Multi-Light ML-501C / B manufactured by Ushio Electric Machinery Co., Ltd. The exposure energy was measured using a UIT-150 ultraviolet cumulative photometer (photodetector: UVD-S254) manufactured by Ushio Electric Machinery Co., Ltd., and the exposure time of the linearly polarized light was adjusted to achieve a "standard exposure" of 0.5 J / cm² ± 0.05 J / cm² at a wavelength of 254 nm. Afterwards, an additional heating was performed at 230°C for 30 minutes. Then, two substrates with liquid crystal alignment films were bonded together with the surfaces having the liquid crystal alignment films facing each other, and gaps for injecting the liquid crystal composition were provided between the facing liquid crystal alignment films. At this time, the polarization direction of the linearly polarized light irradiating each liquid crystal alignment film was made parallel. A negative liquid crystal composition A was injected into the cell to fabricate a liquid crystal cell (liquid crystal display element) with a cell thickness of 5 μm.

[0199] <Negative Liquid Crystal Composition A> (Physical Properties) Phase transition temperature NI: 75.7℃, dielectric anisotropy Δε: -4.1, refractive index anisotropy Δn: 0.101, viscosity η: 14.5 mPa·s.

[0200] The luminance-voltage characteristic (BV characteristic) of the fabricated liquid crystal cell was measured, and the contrast ratio (CR) was calculated using the following formula. The result was a CR of 3600. CR = B max / B min Where B max represents the maximum luminance in the BV characteristic, and B min represents the minimum luminance in the BV characteristic. A higher CR value indicates more vivid dark displays and better contrast. A CR value above 3000 indicates good contrast, and a value above 3300 indicates excellent contrast.

[0201] Subsequently, the exposure time was adjusted so that the light intensity of the linearly polarized light was a "low exposure" of 0.3 J / cm² ± 0.03 J / cm², which was lower than the standard exposure. All other than this, liquid crystal cells were fabricated in the same manner, and the contrast ratio was calculated in the same way. As a result, the CR was 3600.

[0202] [Examples 2-10, Comparative Examples 1-3] Liquid crystal alignment agent 2 and comparative alignment agents 1-3 were prepared by diluting and stirring an NMP / BC mixed solution (NMP / BC = 7 / 3 weight ratio) with varnish A2 and varnishes R1-R3 at a solid component concentration of 4% by weight. Liquid crystal alignment agent 1 was replaced with the liquid crystal alignment agent shown in Table 3, and the contrast ratio was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3 together with those of Example 1.

[0203] Table 3 Varnish No. Contrast low exposure Standard exposure Example 1 Liquid crystal alignment agent 1 A1 3,600 3,600 Example 2 Liquid crystal alignment agent 2 A2 3,400 3,400 Comparative Example 1 Comparison of orientation agents 1 R1 2,500 2,800 Comparative Example 2 Comparison of orientation agent 2 R2 2,300 2,700 Comparative Example 3 Comparison of orientation agents 3 R3 2,800 3,200

[0204] In Examples 1 and 2, excellent contrast was observed not only at standard exposure levels but also at low exposure levels. On the other hand, in Comparative Examples 1 and 2, the CR values ​​were low at both standard and low exposure levels. Comparative Example 3 exhibited good contrast at standard exposure levels, but good contrast could not be obtained at low exposure levels.

[0205] [Examples 3] to [Examples 10] Liquid crystal alignment agents 2 to 10 were prepared by diluting and stirring varnishes A3 to A10 with a solid content concentration of 4% by weight using an NMP / BC mixed solution (NMP / BC = 7 / 3 by weight). Liquid crystal alignment agent 1 was replaced with the liquid crystal alignment agent shown in Table 3, and the exposure was set to "low exposure" (0.3 J / cm² ± 0.03 J / cm²). Otherwise, the contrast was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 4.

[0206] Table 4 Varnish No. Contrast Example 3 Liquid crystal alignment agent 3 A3 3,600 Example 4 Liquid crystal alignment agent 4 A4 3,500 Example 5 Liquid crystal alignment agent 5 A5 3,500 Example 6 Liquid crystal alignment agent 6 A6 3,500 Example 7 Liquid crystal alignment agent 7 A7 3,500 Example 8 Liquid crystal alignment agent 8 A8 3,500 Example 9 Liquid crystal alignment agent 9 A9 3,500 Example 10 Liquid crystal alignment agent 10 A10 3,500

[0207] [Example 11] Clear varnish A3 and clear varnish B1 were blended in a weight ratio of 6:4, and then diluted and stirred with an NMP / BC mixed solution (NMP / BC = 7 / 3 weight ratio) to obtain a solid component concentration of 3.7% by weight, in order to prepare liquid crystal alignment agent 11. The same operation as in Example 3 was performed using liquid crystal alignment agent 11, and the contrast ratio was measured.

[0208] [Examples 12] to [Examples 17], [Comparative Example 4] The varnishes shown in Table 5 were used instead of varnishes A3 and B1, and the mixing ratios were changed to those shown in Table 5. Otherwise, liquid crystal alignment agents 12 to 17 and comparative alignment agent 4 were prepared in the same manner as in Example 11. The contrast ratios were measured using the prepared liquid crystal alignment agents in the same manner as in Example 1. The varnishes used, the mixing ratios, and the results are shown in Table 5 together with those of Example 11.

[0209] Table 5 Varnish No. Contrast Example 11 Liquid crystal alignment agent 11 A3

[60] B1

[40] 3,300 Example 12 Liquid crystal alignment agent 12 A5

[60] B1

[40] 3,500 Example 13 Liquid crystal alignment agent 13 A6

[60] B1

[40] 3,500 Example 14 Liquid crystal alignment agent 14 A7

[60] B1

[40] 3,500 Example 15 Liquid crystal alignment agent 15 A5

[60] B2

[40] 3,400 Example 16 Liquid crystal alignment agent 16 A5

[60] B3

[40] 3,500 Example 17 Liquid crystal alignment agent 17 A5

[60] B4

[40] 3,400 Comparative Example 4 Comparison of orientation agents 4 R3

[60] B1

[40] 2,000

[0210] Regarding the contrast ratio in Examples 1 to 17, even with a low exposure amount of 0.3 J / cm² during photoalignment processing, an excellent CR value of 3,300 or higher was observed. It is understood that by combining the compound represented by formula (I) with at least one compound selected from the group consisting of formulas (DI-13) and (DI-17-1), a liquid crystal alignment film for a liquid crystal display element that achieves high contrast even with low exposure amounts can be obtained. [Industrial Applicability]

[0211] By using the photo-aligning liquid crystal alignment agent of the present invention, a liquid crystal alignment film for a liquid crystal display element that achieves high contrast even when the exposure energy of the photo-aligning process is low can be manufactured. The photo-aligning liquid crystal alignment agent of the present invention is suitable for use in lateral electric field type liquid crystal display elements. [Simplified Explanation of the Diagram]

[0014] None

Claims

1. A liquid crystal alignment agent comprising polyamide or a derivative thereof obtained by reacting a tetracarboxylic acid derivative with a diamine, wherein the liquid crystal alignment agent comprises a compound represented by formula (I) as the tetracarboxylic acid derivative, and comprises at least one of the groups selected from (DI-13) and (DI-17-1) as the diamine, wherein in formula (I), *1, *1', *2 and *2' are bonding bonds, each independently bonded to a hydroxyl group, a chlorine atom or an alkoxy group having 1 to 6 carbon atoms, and at least one of the groups of *1 and *1' and *2 and *2' can be bonded to the same oxygen atom; Rb1, Rb2, Rb3, and Rb4 are each independently hydrogen atoms or methyl groups, at least one of which is a methyl group; in formula (DI-13), R23 is independently an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms or a chlorine atom, and p and q are each independently integers from 0 to 4; In equation (DI-17-1), k is an integer from 1 to 6.

2. The liquid crystal alignment agent as claimed in claim 1, wherein the compound represented by formula (DI-13) is the compound represented by formula (DI-13-1), and the compound represented by formula (DI-17-1) is the compound in formula (DI-17-1) where k is 2.

3. The liquid crystal alignment agent as claimed in claim 1, comprising a compound represented by formula (DI-17-2) as a diamine, wherein e is an integer from 1 to 10 and Boc is tert-butoxycarbonyl.

4. The liquid crystal alignment agent as claimed in claim 3, wherein in formula (DI-17-2), e is an integer from 6 to 10.

5. The liquid crystal alignment agent as claimed in claim 3, wherein in formula (DI-17-2), e is 6.

6. The liquid crystal alignment agent according to any one of claims 1 to 5, comprising polyacrylic acid or a derivative thereof obtained by reacting a tetracarboxylic acid derivative other than the compound represented by formula (I) with a diamine.

7. The liquid crystal alignment agent as claimed in claim 1, comprising additives.

8. A liquid crystal alignment film formed from a liquid crystal alignment agent as described in any one of claims 1 to 7.

9. A liquid crystal element having a liquid crystal alignment film as described in claim 8.

10. A method for manufacturing a liquid crystal alignment film, including: The step of coating a liquid crystal alignment agent as described in any one of claims 1 to 7 onto a substrate; The step of calcining the substrate; The step of irradiating the substrate with polarized ultraviolet light.