JP6927050B2 - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element using it - Google Patents

Description

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

Liquid crystal display elements are widely used as display units for personal computers, mobile phones, smartphones, televisions, and the like. The liquid crystal display element includes, for example, a liquid crystal layer sandwiched between an element substrate and a color filter substrate, a pixel electrode and a common electrode that apply an electric field to the liquid crystal layer, and an alignment film that controls the orientation of liquid crystal molecules in the liquid crystal layer. It includes a thin film transistor (TFT) that switches the electrical signal supplied to the pixel electrodes. As the driving method of the liquid crystal molecule, a vertical electric field method such as a TN method and a VA method, and a horizontal electric field method such as an IPS method and an FFS method are known. The transverse electric field method in which electrodes are formed on only one side of the substrate and a voltage is applied in the direction parallel to the substrate is wider than the conventional longitudinal electric field method in which a voltage is applied to the electrodes formed on the upper and lower substrates to drive the liquid crystal display. It is known as a liquid crystal display element that has viewing angle characteristics and is capable of high-quality display.

Although the transverse electric field type liquid crystal cell is excellent in viewing angle characteristics, since there are few electrode portions formed in the substrate, if the voltage holding ratio is low, a sufficient voltage is not applied to the liquid crystal and the display contrast is lowered. Further, if the stability of the liquid crystal orientation is small, the liquid crystal does not return to the initial state when the liquid crystal is driven for a long time, which causes a decrease in contrast and an afterimage. Therefore, the stability of the liquid crystal orientation is important. Furthermore, static electricity is likely to be accumulated in the liquid crystal cell, and charges are accumulated in the liquid crystal cell even when a positive / negative asymmetric voltage generated by driving is applied, and these accumulated charges affect the display as a disorder of liquid crystal orientation or an afterimage. , The display quality of the liquid crystal element is significantly deteriorated. In addition, electric charges are accumulated by irradiating the liquid crystal cell with backlight light immediately after driving, afterimages are generated even after driving for a short time, and the magnitude of flicker (flicker) changes during driving. It causes problems.

Patent Document 1 contains a specific diamine and an aliphatic tetracarboxylic acid derivative as a liquid crystal aligning agent having excellent voltage retention and reduced charge accumulation when used in such a transverse electric field type liquid crystal display element. The liquid crystal alignment agent to be used is disclosed. However, as the performance of the liquid crystal display element is improved, the characteristics required for the liquid crystal alignment film are becoming stricter, and it is difficult to fully satisfy all the required characteristics with these conventional techniques.

International Publication WO2004 / 021076 Pamphlet

The present invention provides a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element capable of obtaining a liquid crystal alignment film having excellent voltage retention, quick relaxation of accumulated charges, and less flicker during driving. That is the issue.

As a result of diligent studies to solve the above problems, the present inventors have found that by introducing a specific structure into the polymer contained in the liquid crystal alignment agent, various properties can be improved at the same time. The present invention has been completed. The present invention is based on such findings, and the gist of the present invention is as follows.

（Ｒ_１は水素、フッ素原子、シアノ基、ヒドロキシ基、又は一価の有機基を表し、＊は他の基に結合する部位を表す。ベンゼン環の任意の水素原子を一価の有機基に置換されていてもよい。）
２．前記重合体が、前記式（１）で表される構造を有するジアミンとテトラカルボン酸二無水物との重縮合物であるポリイミド前駆体及びそのイミド化物であるポイミドからなる群から選ばれる少なくとも１種の重合体である前記１に記載の液晶配向剤。
３．前記ジアミンが、下記の式（２）で表される前記１又は２に記載の液晶配向剤。

（Ｒ_１の定義は、前記式（１）と同様であり、Ｒ_２はそれぞれ独立して単結合又は下記式（３）の構造を表し、ｎは１から３の整数を表す。ベンゼン環の任意の水素原子は一価の有機基で置換されていてもよい。）

（Ｒ_３は、単結合、−Ｏ−、−ＣＯＯ−、−ＯＣＯ−、−（ＣＨ_２）_ｌ−、−Ｏ（ＣＨ_２）_ｍＯ−、−ＣＯＮＨ−、及び−ＮＨＣＯ−から選ばれる２価の有機基を表し（ｌ、ｍは１〜５の整数を表す）、＊_１は式（２）中のベンゼン環と結合する部位を表し、＊_２は式（２）中のアミノ基と結合する部位を表す。）
４．前記ポリイミド前駆体が、下記式（６）で表される前記１〜３に記載の液晶配向剤。

（Ｘ_１はテトラカルボン酸誘導体に由来する４価の有機基であり、Ｙ_１は式（１）の構造を含むジアミンに由来する２価の有機基であり、Ｒ_４は水素原子又は炭素数１〜５のアルキル基である。）
５．前記式（６）中、Ｘ_１の構造が、後記する式（Ａ−１）〜式（Ａ−２１）の構造からなる群から選ばれる少なくとも１種である前記４に記載の液晶配向剤。
６．前記式（６）で表される構造単位を有する重合体が、液晶配向剤に含有される全重合体に対して１０モル％以上含有される前記４又は５に記載の液晶配向剤。
７．前記有機溶媒が４−ヒドロキシ−４−メチル−２−ペンタノン及びジエチレングリコールジエチルエーテルからなる群から選ばれる少なくとも１種を含有する、前記４〜６に記載の液晶配向剤。
８．前記１〜７のいずれかに記載の液晶配向剤を用いて得られる液晶配向膜。
９．前記８に記載の液晶配向膜を具備する液晶表示素子。
１０．液晶表示素子が横電界駆動方式である前記９に記載の液晶表示素子。
１１．下記式（１）で表される構造を有するジアミンとテトラカルボン酸二無水物との重縮合物であるポリイミド前駆体及びそのイミド化物であるポリイミドからなる群から選ばれる少なくとも１種の重合体。

（Ｒ_１及び＊は前記１にしたとおりである。）
１２．上記ジアミンが、以下の式（２）で表される前記１１に記載の重合体。

（Ｒ_１、Ｒ_２、及びｎは前記３に記載したとおりである。）
１３．前記ポリイミド前駆体が、下記式（６）で表される前記１１又は１２に記載の重合体。

（Ｘ_１、Ｙ_１及びＲ_４は前記４に記載したとおりである。）
１４．前記式（６）中、Ｘ_１の構造が、後記する式（Ａ−１）〜式（Ａ−２１）の構造からなる群から選ばれる少なくとも１種である前記１３に記載の重合体。1. 1. A liquid crystal alignment agent containing a polymer obtained from a diamine having a structure represented by the following formula (1) and an organic solvent.

(R ₁ represents a hydrogen, a fluorine atom, a cyano group, a hydroxy group, or a monovalent organic group, and * represents a site that binds to another group. Any hydrogen atom of the benzene ring can be used as a monovalent organic group. It may be replaced.)
2. At least one selected from the group consisting of a polyimide precursor which is a polycondensate of a diamine having a structure represented by the formula (1) and a tetracarboxylic dianhydride and a poimide which is an imide thereof. The liquid crystal alignment agent according to 1 above, which is a polymer of the species.
3. 3. The liquid crystal alignment agent according to 1 or 2 above, wherein the diamine is represented by the following formula (2).

( _{The definition of R 1} is the same as that of the above formula (1), R ₂ independently represents a single bond or the structure of the following formula (3), and n represents an integer of 1 to 3. Any hydrogen atom may be substituted with a monovalent organic group.)

(R ₃ is selected from single bond, -O- _{, -COO-, -OCO-,-(CH 2} ) _l- , -O (CH ₂ ) _m O-, -CONH-, and -NHCO- 2 Represents a valent organic group (l and m represent integers 1 to 5), * ₁ represents a site that binds to the benzene ring _{in formula (2), and * 2} represents an amino group in formula (2). Represents the site of binding.)
4. The liquid crystal alignment agent according to the above 1-3, wherein the polyimide precursor is represented by the following formula (6).

(X ₁ is a tetravalent organic group derived from a tetracarboxylic acid derivative, Y ₁ is a divalent organic group derived from a diamine containing the structure of the formula (1), and R ₄ is a hydrogen atom or the number of carbon atoms. 1 to 5 alkyl groups.)
5. In the formula (6), the structure of X ₁ is, the liquid crystal alignment agent according to the 4 is at least one selected from the group consisting of structures below Formula (A-1) ~ formula (A-21).
6. The liquid crystal alignment agent according to 4 or 5, wherein the polymer having the structural unit represented by the formula (6) is contained in an amount of 10 mol% or more based on the total polymer contained in the liquid crystal alignment agent.
7. 4. The liquid crystal alignment agent according to 4 to 6, wherein the organic solvent contains at least one selected from the group consisting of 4-hydroxy-4-methyl-2-pentanone and diethylene glycol diethyl ether.
8. A liquid crystal alignment film obtained by using the liquid crystal alignment agent according to any one of 1 to 7 above.
9. A liquid crystal display element including the liquid crystal alignment film according to 8.
10. 9. The liquid crystal display element according to 9, wherein the liquid crystal display element is a transverse electric field drive system.
11. At least one polymer selected from the group consisting of a polyimide precursor which is a polycondensate of a diamine having a structure represented by the following formula (1) and a tetracarboxylic dianhydride and a polyimide which is an imidized product thereof.

_{(R 1} and * are as in the above 1.)
12. The polymer according to 11 above, wherein the diamine is represented by the following formula (2).

(R ₁ , R ₂ , and n are as described in 3 above.)
13. The polymer according to 11 or 12 above, wherein the polyimide precursor is represented by the following formula (6).

(X ₁ , Y ₁ and R ₄ are as described in 4 above.)
14. In the formula (6), the structure of _{X 1} is The polymer according to the 13 is at least one selected from the group consisting of structures below Formula (A-1) ~ formula (A-21).

By using the liquid crystal alignment agent of the present invention, a liquid crystal alignment film in which accumulated charges are quickly relaxed and flicker is less likely to occur during driving, and a liquid crystal display element having excellent display characteristics are provided. It is not always clear why the above-mentioned problems can be solved by the invention of the present application, but it is generally considered as follows.
The structure (1) of the polymer contained in the liquid crystal alignment agent of the present invention has a conductive pyrrole structure and a conjugated structure, and thereby promotes charge transfer in, for example, a liquid crystal alignment film. It is considered that this can be achieved and the relaxation of accumulated charge can be promoted.

<Amine with a specific structure>
The liquid crystal alignment agent of the present invention is a polymer (also referred to as a specific polymer in the present invention) obtained from a diamine having the structure of the following formula (1) (also referred to as a specific diamine in the present invention) and an organic solvent. And contains.

In the above formula (1), R ₁ represents a hydrogen, a fluorine atom, a cyano group, a hydroxy group, or a monovalent organic group, and * represents a site that binds to another group. The hydrogen atom of the benzene ring may be optionally substituted with a monovalent organic group.
Examples of the monovalent organic group here include an alkyl group, an alkenyl group, an alkoxy group, a fluoroalkyl group, a fluoroalkoxy group, and a fluoroalkoxy group having 1 to 10 carbon atoms, preferably 1 to 3 carbon atoms. Of these, R ₁ is preferably a hydrogen atom or a methyl group.

In the structure of the above formula (1), the bond position of the benzene ring with respect to the pyrrole ring is the carbon atom next to the nitrogen atom on the pyrrole ring as shown in the following formula (1-1) from the point of charge transfer. Is preferable.

The specific diamine can be represented by, for example, the following formula (1-2), in particular, the diamine represented by the following formula (1-3) is preferable, and further, it is represented by the formula (1-4). Diamines are more preferred.

In formulas (1-2) to (1-4), _{the definition of R 1} is the same as in the case of formula (1), and Q ₁ and Q ₂ are independently single-bonded or divalent. an organic group, i.e., may have different structures each other as Q _1, Q _2. The two _{Q 2} 'in the formula (1-4) may have a different structure from each other. Further, any hydrogen atom of the benzene ring may be substituted with a monovalent organic group as in the case of the above formula (1).

As a preferable example of the specific diamine, a diamine represented by the following formula (2) can be mentioned, and a diamine represented by the formula (2-1) is more preferable.

_{The definition of R 1 in} the above formula (2) and the above formula (2-1) is the same as that of the above formula (1). Two R ₂ each independently represent a structure of a single bond or the following formula (3). As in the case of the above formula (1), any hydrogen atom of the benzene ring may be substituted with a monovalent organic group.

In the above formula (3), R ₃ is a single bond, -O- _{, -COO-, -OCO-,-(CH 2} ) _l- , -O (CH ₂ ) _m O-, -CONH-, and-. It represents a divalent organic group selected from the group consisting of NHCO−, where l and m represent integers 1-5. _{Among them, R 3} is preferably single-bonded, -O-, -COO-, -OCO-, -CONH-, or -NHCO- from the viewpoint of relaxation of accumulated charge. Further, * ₁ represents a site that binds to the benzene ring in the formula (2), and * ₂ represents a site that binds to the amino group in the formula (2).
N in the above equations (2) and (2-1) represents an integer of 1 to 3. It is preferably 1 or 2.

Specific examples of the diamine of the above formula (2) include, but are not limited to, the following. Among them, from the viewpoint of relaxation of accumulated charge, (2-1-1), (2-1-2), (2-1-3), (2-1-5), (2-1-8) , (2-1-9), (2-1-10), (2-1-11) or (2-1-12), preferably (2-1-1), (2-1-2). , (2-1-3), (2-1-11) or (2-1-12) are particularly preferred.

<Synthesis method of specific diamine>
The method for synthesizing the specific diamine is not particularly limited. For example, a method of using a dinitro compound represented by the following formula (4) and converting the nitro group contained therein into an amino group by a reduction reaction can be mentioned.

式（４）中、Ｒ_１の定義は、上記式（１）におけるのと同様である

In the formula (4), _{the definition of R 1} is the same as in the above formula (1).

The catalyst used in the reduction reaction is preferably an activated carbon-supported metal available as a commercially available product, and examples thereof include palladium-activated carbon, platinum-activated carbon, and rhodium-activated carbon. Further, palladium hydroxide, platinum oxide, Raney nickel and the like can also be used, and the catalyst does not necessarily have to be an activated carbon-supported metal catalyst. Palladium-activated carbon, which is generally widely used, is preferred because it gives good results.

In order to allow the reduction reaction to proceed more effectively, the reaction may be carried out in the presence of activated carbon. At this time, the amount of activated carbon used is not particularly limited, but is preferably 1 to 30% by mass, more preferably 10 to 20% by mass, based on the dinitro compound (4). For the same reason, the reaction may be carried out under pressure. In this case, in order to avoid reduction of benzene nuclei, the pressure range is up to 20 atm. The reaction is preferably carried out in the range of up to 10 atm.

The solvent can be used without limitation as long as it is a solvent that does not react with each raw material. For example, aprotonic polar organic solvents (dimethylformamide, dimethylshoxide, dimethylacetate, N-methyl-2-pyrrolidone, etc.); ethers (diethyl ether, diisopropyl ether, t-butylmethyl ether, cyclopentylmethyl ether, tetrahydrofuran, Dioxane, etc.); aliphatic hydrocarbons (pentane, hexane, heptane, petroleum ether, etc.); aromatic hydrocarbons (benzene, toluene, xylene, mesitylene, chlorobenzene, dichlorobenzene, nitrobenzene, tetralin, etc.); halogen-based hydrocarbons Hydrogens (chloroform, dichloromethane, carbon tetrachloride, dichloroethane, etc.); lower fatty acid esters (methyl acetate, ethyl acetate, butyl acetate, methyl propionate, etc.); nitriles (nitrile, propionitrile, butyronitrile, etc.); etc. Can be used. These solvents can be used alone or in combination of two or more. Further, the solvent can be dried with an appropriate dehydrating agent or desiccant and used as a non-aqueous solvent.

The amount of the solvent used (reaction concentration) is not particularly limited, but is 0.1 to 100 times by mass with respect to the dinitro compound (4). It is preferably 0.5 to 30 times by mass, and more preferably 1 to 10 times by mass.
The reaction temperature is not particularly limited, but is in the range from −100 ° C. to the boiling point of the solvent used, preferably −50 to 150 ° C. The reaction time is usually 0.05 to 350 hours, preferably 0.5 to 100 hours.

[Production method of compound of formula (4)]
There is no particular limitation on the method of synthesizing a compound of formula (4), for example, to synthesize a dinitro product represented by the following formula (5), and a method of further introducing a protecting group R ₁ to the NH group.

When _{introducing R 1} , any compound that can react with amines may be used. Examples thereof include acid halides, acid anhydrides, isocyanates, epoxy compounds, oxetans, aryl halides and alkyl halides. Further, alcohols in which the hydroxyl group of the alcohol is replaced with a leaving group such as OMs (mesyl group), OTf (triflate group), OTs (tosyl group) and the like can be used.

If is reacted with an acid halide to introduce the R _1, it is preferably carried out in the presence of a base. Examples of acid halides include acetyl chloride, chloride chloride, methyl chloroformate, ethyl chloroformate, n-propyl chloroformate, i-propyl chloroformate, n-butyl chloroformate, i-butyl chloroformate, t-chloroformate. Butyl, benzyl chloroformate, -9-fluorenyl chloroformic acid can be mentioned. The base is not particularly limited as long as it can be synthesized, but it is an inorganic base such as potassium carbonate, sodium carbonate, cesium carbonate, sodium alkoxide, potassium alkoxide, sodium hydroxide, potassium hydroxide, sodium hydride, etc., pyridine, dimethylamino, etc. Organic bases such as pyridine, trimethylamine, triethylamine and tributylamine can be used. The reaction solvent and reaction temperature are the same as in the reduction reaction of the nitro compound (4).

If is reacted with an acid anhydride to introduce R _1, examples of the acid anhydride are acetic anhydride, propionic anhydride, dimethyl dicarbonate, dicarbonate, diethyl dicarbonate - di - tertiary butyl, etc. dicarbonate dibenzyl Can be mentioned. Pyridine, colidine, N, N-dimethyl-4-aminopyridine and the like may be used as a catalyst to accelerate the reaction. The amount of catalyst is 0.0001 mol to 1 mol with respect to compound (5). The reaction solvent and reaction temperature are the same as those in the above acid halide.
When R ₁ is introduced by reacting isocyanates, examples of isocyanates include methyl isocyanate, ethyl isocyanate, n-propyl isocyanate, phenyl isocyanate and the like. The reaction solvent and reaction temperature are the same as in the case of the above acid halide.

When R ₁ is introduced by reacting an epoxy compound or an oxetane compound, examples of the epoxy compound or the oxetane include ethylene oxide, propylene oxide, 1,2-butylene oxide, and trimethylene oxide. The reaction solvent and reaction temperature are the same as those in the above acid halide.
OMs the hydroxyl group of alcohol, OTf, if by reacting alcohol substituted to a leaving group such as OTs introducing R _1, it is preferably carried out in the presence of a base. Examples of the above alcohols include methanol, ethanol, 1-propanol and the like. By reacting these alcohols with methanesulfonyl chloride, trifluoromethanesulfonyl chloride, paratoluenesulfonic acid chloride and the like, OMs, Alcohols substituted with leaving groups such as OTf and OTs can be obtained. The example of the base, the reaction solvent, and the reaction temperature are the same as in the case of the above acid halide.

If by reacting an alkyl halide to introduce the R _1, it is preferably carried out in the presence of a base. Examples of alkyl halides include methyl iodide, ethyl iodide, n-propyl iodide, methyl bromide, ethyl bromide, n-propyl bromide and the like. As an example of the base, in addition to the above-mentioned base, metal alkoxides such as potassium-tert-butoxide and sodium-tert-butoxide can be used. The reaction solvent and reaction temperature are the same as in the case of the above acid halide.

[Production method of compound of formula (5)]
The method for synthesizing the compound of the formula (5) is not particularly limited, but when the substitution positions on the pyrrole ring of the formula (5) are the 2-position and the 4-position, for example, as represented by the following reaction formula 1, It can be obtained by reacting an α-haloketone having a nitro group and a ketone having a nitro group, preferably in the presence of a base. In reaction equation 1, X represents Br, I or OTf.

As an example of the base used in the above reaction, the base exemplified in the above-mentioned acid halide can be used, and the reaction solvent and the reaction temperature are the same as those described above.
Zinc chloride, sodium iodide, potassium iodide, tetrabutylammonium iodide and the like can be used for the purpose of accelerating the rate in the above reaction.

反応式２中、ＸはＢｒ、I、又はＯＴｆを表す。Ｍは、Ｂ（ＯＨ）_２または４，４，５，５−テトラメチル−１，３，２−ジオキサボロラン−２−イルを表す。On the other hand, when the substitution of the compound of the formula (5) in the pyrrole ring is other than the 2-position and 4-position, it is obtained by subjecting the corresponding halogenated pyrrole and the organometallic reagent to a cross-coupling reaction preferably using a metal catalyst. be able to.

In reaction equation 2, X represents Br, I, or OTf. M represents B (OH) ₂ or 4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl.

The cross-coupling reaction (Suzuki-Miyaura reaction) preferably uses a metal complex and a ligand as catalysts, but the reaction proceeds without a catalyst. Examples of metal complexes include palladium acetate, palladium chloride, palladium chloride-acetonitrile complex, palladium-activated coal, bis (dibenzylideneacetone) palladium, tris (dibenzylideneacetone) dipalladium, bis (acetonitrile) dichloropalladium, bis (benzo). (Nitrile) Dichloropalladium, CuCl, CuBr, CuI, CuCN and the like can be mentioned. Examples of ligands are triphenylphosphine, tri-o-tolylphosphine, diphenylmethylphosphine, phenyldimethylphosphine, 1,2-bis (diphenylphosphine) ethane, 1,3-bis (diphenylphosphine) propane. , 1,4-Bis (diphenylphosphine) butane, 1,1'-bis (diphenylphosphino) ferrocene, trimethylphosphine, triethylphosphite, triphenylphosphine, tri-tert-butylphosphine and the like.
The amount of the metal complex used may be a so-called catalytic amount, and 20 mol% or less with respect to the substrate is sufficient, preferably 10 mol% or less.

<Polymer>
The liquid crystal alignment agent of the present invention is a polymer obtained by using a specific diamine. Specific examples of the polymer include polyamic acid, polyamic acid ester, polyimide, polyurea, and polyamide. Among them, a polymer which is at least one selected from the group consisting of a polyimide precursor having a structural unit represented by the following formula (6) and an imidized polyimide thereof is preferable.

In the above formula (6), X ₁ is a tetravalent organic group derived from a tetracarboxylic acid derivative. Y ₁ is a divalent organic group derived from a diamine containing the structure of the formula (1). R ₄ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ₄ is preferably a hydrogen atom, a methyl group or an ethyl group from the viewpoint of ease of imidization by heating.

In the above formula (6), X ₁ is a tetravalent organic group derived from a tetracarboxylic acid derivative. X ₁ depends on the degree of required characteristics such as the solubility of the polymer in the solvent, the coatability of the liquid crystal alignment agent, the orientation of the liquid crystal when it is used as a liquid crystal alignment film, the voltage retention rate, and the accumulated charge. It may be appropriately selected and may be one kind or two or more kinds in the same polymer.
Specific examples of X ₁ include the structures of the formulas (X-1) to (X-46) published on pages 13 to 14 of International Publication 2015/111968.

The following (A-1) to (A-21), which are _{preferable structures of X 1, are shown below.}

Of the above structures, (A-1) or (A-2) is particularly preferable from the viewpoint of further improving the rubbing resistance, and (A-4) is particularly preferable from the viewpoint of further improving the relaxation rate of the accumulated charge. , (A-15) to (A-17) are particularly preferable from the viewpoint of further improving the liquid crystal orientation and the relaxation rate of the accumulated charge.

In the formula (6), Y ₁ may have a structure obtained by removing two amino groups from the diamine of the formula (2). Among them, Y ₁ has the above formulas (2-1-1), (2-1-2), (2-1-3), (2-1-5), (2-1-8), (2). A structure in which two amino groups are removed from the structures of -1-9), (2-1-10), (2-1-11), and (2-1-12) is more preferable, and (2-1-1). ), (2-1-2), (2-1-3), (2-1-11), (2-1-12) with the two amino groups removed, which is particularly preferable.

<Other polymers (structural unit)>
The liquid crystal alignment agent of the present invention is made of a polyimide precursor having a structural unit represented by the following formula (7), a polyimide precursor having a structural unit represented by the following formula (7), and a polyimide which is an imidized product thereof, in addition to the polyimide precursor having the structural unit of the above formula (6). It may contain at least one polymer selected from the group.

In formula (7), X ₂ is a tetravalent organic group derived from a tetracarboxylic acid derivative. Y ₂ is a divalent organic group derived from a diamine that does not have the structure of the formula (1). R ₄ is as defined in the formula (6). R ₅ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Further, it is preferable that at least one of twofold R ₅ is a hydrogen atom.

Specific examples of X ₂ are the same as those illustrated by _{X 1} of the formula (6) including preferable examples. Further, Y ₂ is selected according to the characteristics such as the solubility of the polymer in the solvent, the coatability of the liquid crystal alignment agent, the orientation of the liquid crystal when it is used as a liquid crystal alignment film, the voltage retention rate, and the accumulated charge. However, two or more types may be used.

Specific examples of Y ₂ include the structure of the formula (2) published on page 4 of International Publication 2015/111968 and the formulas (Y-1) to (Y) published on pages 8 to 12. -97), Structures of (Y-101) to (Y-118); Divalent organic group obtained by removing two amino groups from formula (2), which is published on page 6 of International Publication 2013/008906; A divalent organic group obtained by removing two amino groups from the formula (1) published on page 8 of the International Publication 2015/122413; the structure of the formula (3) published on page 8 of the International Publication 2015/060360. A divalent organic group obtained by removing two amino groups from the formula (1) described on page 8 of Japanese Patent Publication 2012-173514; the formula (A) published on page 9 of International Publication 2010-050523. )-(F), a divalent organic group obtained by removing two amino groups, and the like can be mentioned.

The preferred _{structure of Y 2} is shown below, but the present invention is not limited thereto.

Of the above, (B-28), (B-29) and the like are particularly preferable from the viewpoint of further improving the rubbing resistance, and (B-1) to (B-3) and the like are further preferable in terms of liquid crystal orientation. Particularly preferable from the viewpoint of improvement, (B-14) to (B-18), (B-27) and the like are particularly preferable from the viewpoint of further improving the relaxation rate of the accumulated charge, and (B-26) and the like are particularly preferable. It is preferable from the viewpoint of further improving the voltage retention rate.
When the liquid crystal alignment agent of the present invention contains a polyimide precursor having the structural unit of the formula (6) and a polyimide precursor having the structural unit of the formula (7), the structural unit of the formula (6) is the structural unit of the formula (6). ) And the formula (7), 10 mol% or more is preferable, 20 mol% or more is more preferable, and 30 mol% or more is particularly preferable.

The molecular weight of the polyimide precursors of the above formulas (6) and (7) is preferably 2,000 to 500,000, more preferably 5,000 to 300,000, and further preferably 10 in terms of weight average molecular weight. It is 000 to 100,000.
Examples of the polyimide having a divalent group represented by the formula (1) in the main chain include a polyimide obtained by ring-closing the polyimide precursor. In this polyimide, the ring closure rate (also referred to as imidization rate) of the amic acid group does not necessarily have to be 100%, and can be arbitrarily adjusted according to the application and purpose.
Examples of the method for imidizing the polyimide precursor include thermal imidization in which the solution of the polyimide precursor is heated as it is, or catalytic imidization in which a catalyst is added to the solution of the polyimide precursor.

<Liquid crystal alignment agent>
The liquid crystal alignment agent of the present invention contains a polymer (specific polymer) obtained from a diamine having a structure represented by the formula (1), but may contain two or more specific polymers having different structures. good. Further, in addition to the specific polymer, other polymers, that is, polymers having no divalent group represented by the formula (1) may be contained. Other polymers include polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivative, polyacetal, polystyrene or its derivative, poly (styrene-phenylmaleimide) derivative, poly (meth) acrylate. And so on. When the liquid crystal alignment agent of the present invention contains other polymers, the ratio of the specific polymer to the total polymer components is preferably 5% by mass or more, and examples thereof include 5 to 95% by mass.

The liquid crystal alignment agent generally takes the form of a coating liquid from the viewpoint of forming a uniform thin film. The liquid crystal alignment agent of the present invention is also preferably a coating liquid containing the polymer component and an organic solvent that dissolves the polymer component. At that time, the concentration of the polymer in the liquid crystal alignment agent can be appropriately changed by setting the thickness of the coating film to be formed. From the viewpoint of forming a uniform and defect-free coating film, 1% by mass or more is preferable, and from the viewpoint of storage stability of the solution, 10% by mass or less is preferable. A particularly preferable concentration of the polymer is 2 to 8% by mass.

The organic solvent contained in the liquid crystal alignment agent is not particularly limited as long as the polymer component is uniformly dissolved. Specific examples thereof include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl. -Imidazoridinone, methylethylketone, cyclohexanone, cyclopentanone and the like can be mentioned. Of these, it is preferable to use N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ-butyrolactone.

Further, as the organic solvent contained in the liquid crystal alignment agent of the present invention, in addition to the above solvent, a solvent that improves the coatability when applying the liquid crystal alignment agent and the surface smoothness of the coating film can be used in combination. Specific examples of such organic solvents are given below, but they are not included.

For example, ethanol, isopropyl alcohol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, tert-Pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol , 2-Heptanol, 3-Heptanol, 1-Octanol, 2-Octanol, 2-Ethylene-1-hexanol, Cyclohexanol, 1-Methylcyclohexanol, 2-Methylcyclohexanol, 3-Methylcyclohexanol, 1,2- Ethylene diol, 1,2-propane diol, 1,3-propane diol, 1,2-butane diol, 1,3-butane diol, 1,4-butane diol, 2,3-butane diol, 1,5-pentane Diol, 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, dipropyl ether, dibutyl ether, dihexyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-Butoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 2-pentanone, 3-pentanone, 2-hexanone, 2-heptanone , 4-Heptanone, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetylate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, 2- (methoxymethoxy) ethanol, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, 2- (hexyloxy) ethanol, furfuryl alcohol, diethylene glycol, propylene glycol, propylene glycol monobutyl ether, 1-( Butoxyethoxy) propanol, propylene glycol monomethyl Ether acetate, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol mono Butyl ether acetate, ethylene glycol monoacetylate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2- (2-ethoxyethoxy) ethyl acetate, diethylene glycol acetate, triethylene glycol, tri Ethylene glycol monomethyl ether, triethylene glycol monoethyl ether, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate , Methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, methyl lactate ester, ethyl lactate ester, Examples thereof include lactic acid n-propyl ester, lactic acid n-butyl ester, lactic acid isoamyl ester, and solvents represented by the following formulas [D-1] to [D-3].

In the formula [D-1], D ¹ represents an alkyl group having 1 to 3 carbon atoms, and in the formula [D-2], D ² represents an alkyl group having 1 to 3 carbon atoms, and the formula [D-3]. Among them, D ³ represents an alkyl group having 1 to 4 carbon atoms.
Among them, 1-hexanol, cyclohexanol, 1,2-ethanediol, 1,2-propanediol, propylene glycol monobutyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monobutyl ether or It is preferable to use dipropylene glycol dimethyl ether. The type and content of such a solvent are appropriately selected according to the coating apparatus for the liquid crystal alignment agent, coating conditions, coating environment, and the like.

The liquid crystal alignment agent of the present invention may additionally contain components other than the polymer component and the organic solvent. Such additional components include an adhesion aid for increasing the adhesion between the liquid crystal alignment film and the substrate and the adhesion between the liquid crystal alignment film and the sealing material, a cross-linking agent for increasing the strength of the liquid crystal alignment film, and the liquid crystal alignment. Examples thereof include a dielectric and a conductive material for adjusting the dielectric constant and electric resistance of the film. Specific examples of these additional components include those disclosed in Paragraph 0115-55, Paragraph 0116 of International Publication No. 015/060357.

<Liquid crystal alignment film>
The liquid crystal alignment film of the present invention is obtained from the liquid crystal alignment agent. To give an example of a method for obtaining a liquid crystal alignment film, a liquid crystal alignment agent in the form of a coating liquid is applied to a substrate, dried, and fired to obtain a film that is oriented by a rubbing treatment method or a photoalignment treatment method. There is a method of applying.
The substrate to which the liquid crystal alignment agent is applied is not particularly limited as long as it is a highly transparent substrate, and a plastic substrate such as an acrylic substrate or a polycarbonate substrate can be used together with the glass substrate and the silicon nitride substrate. At that time, it is preferable to use a substrate on which an ITO electrode or the like for driving the liquid crystal is formed, from the viewpoint of simplifying the process. Further, in the reflective liquid crystal display element, if only one side of the substrate is used, an opaque object such as a silicon wafer can be used, and in this case, a material that reflects light such as aluminum can also be used for the electrode.

The method of applying the liquid crystal aligning agent is not particularly limited, but industrially, screen printing, offset printing, flexographic printing, inkjet method and the like are common. Other coating methods include a dip method, a roll coater method, a slit coater method, a spinner method, a spray method, and the like, and these may be used depending on the purpose.
After applying the liquid crystal aligning agent on the substrate, the solvent is evaporated and fired by a heating means such as a hot plate, a heat circulation type oven, or an IR (infrared) type oven. Any temperature and time can be selected for the drying and firing steps after applying the liquid crystal alignment agent. Usually, in order to sufficiently remove the contained solvent, the condition of firing at 50 to 120 ° C. for 1 to 10 minutes and then firing at 150 to 300 ° C. for 5 to 120 minutes can be mentioned.

If the thickness of the liquid crystal alignment film after firing is too thin, the reliability of the liquid crystal display element may decrease. Therefore, the thickness is preferably 5 to 300 nm, more preferably 10 to 200 nm.
The liquid crystal alignment film of the present invention is suitable for a horizontal electric field type liquid crystal display element such as an IPS type or an FFS type, and is particularly useful as a liquid crystal alignment film for an FFS type liquid crystal display element.

<Liquid crystal display element>
In the liquid crystal display element of the present invention, after obtaining a substrate with a liquid crystal alignment film obtained from the liquid crystal alignment agent, a liquid crystal cell is produced by a known method, and the liquid crystal cell is used as an element.
As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described as an example. An element having an active matrix structure in which a switching element such as a TFT (Thin Film Transistor) is provided in each pixel portion constituting the image display may be used.

Specifically, a transparent glass substrate is prepared, and a common electrode is provided on one substrate and a segment electrode is provided on the other substrate. These electrodes can be, for example, ITO electrodes and are patterned so as to display a desired image. Next, an insulating film is provided on each substrate so as to cover the common electrode and the segment electrode. The insulating film can be, for example, a film made of SiO _2- TiO ₂ formed by the sol-gel method. Next, a liquid crystal alignment film is formed on each substrate under the above conditions.

Next, for example, an ultraviolet curable sealing material was placed at a predetermined place on one of the two substrates on which the liquid crystal alignment film was formed, and liquid crystal was further placed at a predetermined number of places on the liquid crystal alignment film surface. After that, the other substrate is bonded and crimped so that the liquid crystal alignment film faces each other to spread the liquid crystal on the front surface of the liquid crystal alignment film, and then the entire surface of the substrate is irradiated with ultraviolet rays to cure the liquid crystal display. Get the cell.
Alternatively, after forming the liquid crystal alignment film on the substrate, when arranging the sealing material at a predetermined place on one of the substrates, an opening capable of filling the liquid crystal from the outside is provided and the substrates are bonded together. After that, the liquid crystal material is injected into the liquid crystal cell through the opening provided in the sealing material, and then the opening is sealed with an adhesive to obtain the liquid crystal cell. The liquid crystal material may be injected by a vacuum injection method or a method using a capillary phenomenon in the atmosphere.

In any of the above methods, in order to secure a space for filling the liquid crystal material in the liquid crystal cell, a columnar protrusion is provided on one substrate, a spacer is sprayed on one substrate, or a sealing material is provided. It is preferable to take measures such as mixing spacers in the liquid crystal display or combining them.

Examples of the liquid crystal material include nematic liquid crystal and smectic liquid crystal. Among them, nematic liquid crystal is preferable, and either positive liquid crystal material or negative liquid crystal material may be used. Next, the polarizing plate is installed. Specifically, it is preferable to attach a pair of polarizing plates to the surfaces of the two substrates opposite to the liquid crystal layer.
The liquid crystal alignment film and the liquid crystal display element of the present invention are not limited to the above description as long as the liquid crystal alignment agent of the present invention is used, and may be manufactured by other known methods. good. The process of obtaining the liquid crystal display element from the liquid crystal aligning agent is disclosed, for example, in paragraphs 0074 to 19 of paragraphs 0074 to 19 of Japanese Patent Application Laid-Open No. 2015-135393.

Hereinafter, the present invention will be specifically described with reference to Examples and the like. The present invention is not limited to these examples. The abbreviations of the compounds used below and the method for characterizing them are as follows.

In the above formula, Boc is a group represented by the following formula.

<Organic solvent>
NMP: N-methyl-2-pyrrolidone, GBL: γ-butyrolactone,
BCS: Butyl cellosolve <additive>
LS-4668: 3-glycidoxypropyltriethoxysilane

<Crosslinking agent>

( ¹ Measurement of 1 H-NMR)
Equipment: Varian NMR system 400NB (400MHz) (manufactured by Varian), and JMTC-500 / 54 / SS (500MHz) (manufactured by JEOL)
Measuring solvent: CDCl ₃ (deuterated chloroform), DMSO-d ₆ (deuterated dimethyl sulfoxide)
Reference substances: TMS (tetramethylsilane) (δ: 0.0 ppm, ¹ H) and CDCl ₃ (δ: 77.0 ppm, ¹³ C)

<Measurement of molecular weight of polyimide precursor and polyimide>
The measurement was carried out as follows using a room temperature gel permeation chromatography (GPC) apparatus (GPC-101) (manufactured by Showa Denko KK) and a column (KD-803, KD-805) (manufactured by Shodex).
Column temperature: 50 ° C
Eluent: N, N'-dimethylformamide (30 mmol / L (liter) of lithium bromide-hydrate (LiBr / H2O) and 30 mmol / L of phosphoric acid / anhydrous crystal (o-phosphoric acid) as additives) , Tetrahydrofuran (THF) is 10 ml / L)
Flow velocity: 1.0 ml / min Standard sample for preparing a calibration curve: TSK standard polyethylene oxide (molecular weight; about 900,000, 150,000, 100,000, and 30,000, manufactured by Tosoh Corporation) and polyethylene glycol (molecular weight; about) 12,000, 4,000, and 1,000, manufactured by Polymer Laboratory.

<Viscosity measurement>
The viscosity of the polyamic acid solution was measured using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25 ° C. with a sample volume of 1.1 mL and a cone rotor TE-1 (1 ° 34', R24). bottom.

<Synthesis of diamine compound (DA-1)>

Zinc chloride (120.3 g, 882 mmol) was added to a 3 L (liter) four-necked flask, the temperature was raised to 100 ° C., and the mixture was vacuum dried with an oil pump for 1 hour. Then, at room temperature under a nitrogen atmosphere, toluene (460 g), diethylamine (45.0 g, 615 mmol), t-butanol (46.4 g, 626 mmol), 2-bromo-4-nitroacetophenone (100.0 g, 410 mmol), And 4-Nitroacetophenone (104.2 g, 631 mmol) were sequentially added, and the mixture was stirred at room temperature for 3 days. After confirming the completion of the reaction by HPLC (High Performance Liquid Chromatography), a 5% aqueous sulfuric acid solution (400 g) was added for neutralization, and the mixture was stirred at room temperature for 1 hour. The precipitated crystals were filtered under reduced pressure, washed with toluene (200 g), pure water (300 g), and methanol (200 g), and then dried to obtain crude crystals. The obtained crude crystals were completely dissolved in tetrahydrofuran (1340 g) at 60 ° C., ethanol (1340 g) was added, and the mixture was stirred at 5 ° C. for 1 hour. The precipitated crystals were filtered under reduced pressure, washed with ethanol (200 g), and then dried to obtain powder crystals of compound (1) (yield 63 g, yield 45%).
1H-NMR (DMSO-d ₆ ): 8.40-8.36 (4H, m), 8.28-8.24 (4H, m), 3.53 (4H, s)

Compound (1) (65.8 g, 200 mmol), ammonium acetate (84.5 g, 1100 mmol), and acetic acid (855 g) were charged in a 2 L four-necked flask, heated to 120 ° C., and heated to 120 ° C. under reflux. Stirred for hours. After confirming the completion of the reaction by HPLC (High Performance Liquid Chromatography), the reaction solution was added to cold water (4000 g) and stirred for 1 hour. The precipitated crystals were filtered under reduced pressure, washed with acetonitrile (100 g), and then dried to obtain powdered crystals of compound (2) (yield 53 g, yield 78%).
1H-NMR (DMSO-d ₆ ): 11.8 (1H, br), 8.30-8.26 (4H, m), 8.11-8.07 (4H, m), 7.04 (2H) , S)

A mixture of powder crystals (22 g, 72.4 mmol) of compound (2), 5 mass% palladium carbon (Pd / C) (50% hydrous type), characteristic Shirasagi activated carbon (2.0 g), and dioxane (220 g). The mixture was stirred at 80 ° C. for 8 hours under hydrogen-pressurized conditions. After completion of the reaction, the catalyst was filtered, concentrated, 2-propanol (300 g) was added, and the mixture was stirred at 5 ° C. for 1 hour. The precipitated crystals were filtered under reduced pressure, washed with methanol (50 g), and dried to obtain powder crystals of DA-1 (yield 13 g, yield 69%).
1H-NMR (DMSO-d ₆ ): 10.6 (1H, s), 7.39-7.35 (4H, m), 6.57-6.53 (4H, m), 6.19 (2H) , S), 5.01 (4H, s)

[Synthesis Example 1]
After adding DA-1 (2.49 g, 10.0 mmol) to a 100 ml four-necked flask equipped with a stirrer and a nitrogen introduction tube, 29.0 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this solution, CA-2 (0.98 g, 5.0 mmol) and 3.6 g of NMP (additional amount 1 in Table 1) were added, and then the mixture was stirred under 25 ° C. conditions for 1 hour. .. Then, CA-1 (0.87 g, 4.0 mmol) was added, 3.6 g of NMP (additional amount 2 in Table 1) was added, and then the resin solid was further stirred under 50 ° C. conditions for 12 hours. A polyamic acid solution (PAA-A1) having a partial concentration of 12% by mass was obtained. The viscosity of this polyamic acid solution was 300 mPa · s.

[Synthesis Examples 2 to 16]
By using the tetracarboxylic dianhydride component, the diamine component, and the amount of NMP shown in Table 1 and setting them to the reaction temperatures shown in Table 1, the same procedure as in Synthesis Example 1 was carried out. Polyamic acid solutions (PAA-A2) to (PAA-A9) and polyamic acid solutions (PAA-B1) to ((PAA-B7) having the solid content concentration and viscosity shown in 1 were obtained.

[Synthesis Example 17]
DA-6 (4.03 g, 16.5 mmol), DA-7 (3.59 g, 9.0 mmol), and DA-8 (2) in a 200 ml four-necked flask with a stirrer and a nitrogen inlet tube. After adding .50 g, 4.5 ml), 102.1 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this solution, CA-4 (4.37 g, 19.5 mmol) and 12.8 g of NMP were added, and the mixture was stirred under 40 ° C. conditions for 3 hours. Then, under the condition of 25 ° C., CA-2 (1.71 g, 8.7 mmol) and 12.8 g of NMP were added, and then the mixture was further stirred for 12 hours to obtain a polyamic acid solution having a resin solid content concentration of 15% by mass. Got The viscosity of this polyamic acid solution was 820 mPa · s.
80.0 g of this polyamic acid solution was taken, 70.0 g of NMP was added, 6.8 g of acetic anhydride and 1.8 g of pyridine were added, and the mixture was reacted at 50 ° C. for 3 hours. The reaction solution was poured into 555.0 g of methanol and the resulting precipitate was filtered off. The precipitate was washed with methanol and dried under reduced pressure at 60 ° C. to obtain a polyimide powder. The imidization rate of this polyimide was 75%. A polyimide solution (SPI-B8) was obtained by adding NMP586.7 g to 80.0 g of the obtained polyimide powder and stirring at 50 ° C. for 20 hours to dissolve it.

[Synthesis Example 18]
DA-6 (2.20 g, 9.0 mmol), DA-13 (1.62 g, 15.0 mmol), and DA-14 (DA-14) in a 100 ml four-necked flask with a stirrer and a nitrogen inlet tube. After adding 2.45 g, 6.0 mmol), 81.8 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this solution, CA-4 (6.52 g, 29.10 mmol) was added, 9.1 g of NMP was added, and then the mixture was stirred under the condition of 40 ° C. for 24 hours to obtain a polyamic with a resin solid content concentration of 12% by mass. An acid solution (PAA-B9) was obtained. The viscosity of this polyamic acid solution was 386 mPa · s.

[Synthesis Example 19]
DA-1 (2.62 g, 10.5 mmol), DA-2 (1.39 g, 7.0 mmol), and DA-3 (3.49 g) in a 200 ml four-necked flask with a stirrer and a nitrogen inlet tube. , 17.5 mmol), then 70.0 g of NMP was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this solution, CA-2 (1.70 g, 8.7 mmol) and 9.5 g of NMP were added, and then the mixture was stirred under 25 ° C. conditions for 1 hour. Then, CA-3 (6.57 g, 26.3 mmol) was added, 9.5 g of NMP was added, and then the mixture was further stirred under the condition of 50 ° C. for 12 hours to obtain a polyamic acid solution having a resin solid content concentration of 12% by mass. (PAA-A10) was obtained. The viscosity of this polyamic acid solution was 375 mPa · s.

[Synthesis Example 20]
DA-1 (1.12 g, 4.5 mmol), DA-2 (0.59 g, 3.0 mmol), and DA-3 (1.49 g) in a 100 ml four-necked flask with a stirrer and a nitrogen inlet tube. , 7.5 mmol), then 31.0 g of NMP: GBL = 1: 1 mixed solvent was added, and the mixture was stirred and dissolved while feeding nitrogen. While stirring this solution, 10.0 g of CA-2 (1.15 g, 5.9 mmol) and NMP: GBL = 1: 1 mixed solvent were added, and then the mixture was stirred under 25 ° C. conditions for 1 hour. Then, CA-5 (2.60 g, 8.8 mmol) was added, 10.0 g of NMP: GBL = 1: 1 mixed solvent was added, and the mixture was further stirred under 50 ° C. conditions for 12 hours to obtain a resin solid content. A polyamic acid solution (PAA-A12) having a concentration of 12% by mass was obtained. The viscosity of this polyamic acid solution was 200 mPa · s.

[Examples 1 to 22] and [Comparative Examples 1 to 6]
The polyamic acid solutions obtained in Synthesis Examples 1 to 16 and 18 and the polyimide solutions obtained in Synthesis Example 17 were added to the ratio of polymer 1 to polymer 2 shown in Tables 2-1 and 2-2 below. Tables 2-1 and 2 show an NMP solution containing 1% by weight of NMP, GBL, BCS, and LS-4668 and an NMP solution containing 3% by weight of AD-1 with respect to the solution obtained by mixing in such a manner. The liquid crystal aligning agents of Examples 1 to 22 and Comparative Examples 1 to 6 were obtained by adding the mixture with stirring so as to have the composition shown in -2 and further stirring at room temperature for 2 hours.

<Manufacturing of liquid crystal display element by rubbing method>
A glass substrate with an electrode having a size of 30 mm × 35 mm and a thickness of 0.7 mm was prepared. An IZO electrode having a solid pattern, which constitutes a counter electrode as a first layer, is formed on the substrate. A SiN (silicon nitride) film formed by a CVD method is formed as a second layer on the counter electrode of the first layer. The thickness of the SiN film of the second layer is 500 nm, and it functions as an interlayer insulating film. A comb-shaped pixel electrode formed by patterning an IZO film as a third layer is arranged on the SiN film of the second layer to form two pixels, a first pixel and a second pixel. ing. The size of each pixel is 10 mm in length and about 5 mm in width. At this time, the counter electrode of the first layer and the pixel electrode of the third layer are electrically insulated by the action of the SiN film of the second layer.

The pixel electrode of the third layer is a comb formed by arranging a plurality of “dogleg” -shaped electrode elements having a bent central portion, as shown in FIG. 3 described in Japanese Patent Application Laid-Open No. 2014-77745. It has a tooth-like shape. The width of each electrode element in the lateral direction is 3 μm, and the distance between the electrode elements is 6 μm. Since the pixel electrodes forming each pixel are configured by arranging a plurality of bent "dogleg" shaped electrode elements in the central portion, the shape of each pixel is not rectangular, but is centered like the electrode elements. It has a shape similar to a bold "dogleg" that bends at a part. Each pixel is divided into upper and lower parts with a bent portion at the center as a boundary, and has a first region on the upper side and a second region on the lower side of the bent portion.

Comparing the first region and the second region of each pixel, the formation directions of the electrode elements of the pixel electrodes constituting them are different. That is, when the rubbing direction of the liquid crystal alignment film described later is used as a reference, the electrode elements of the pixel electrodes are formed so as to form an angle (clockwise) of + 10 ° in the first region of the pixel, and the pixel is formed in the second region of the pixel. The electrode elements of the electrodes are formed so as to form an angle of −10 ° (clockwise). Further, in the first region and the second region of each pixel, the directions of the rotation operation (inplane switching) of the liquid crystal in the substrate surface induced by the application of the voltage between the pixel electrode and the counter electrode are mutually different. It is configured to be in the opposite direction.

Next, after filtering the liquid crystal alignment agent with a filter having a pore size of 1.0 μm, an ITO film is formed on the back surface as a substrate facing the electrode-attached substrate, and a glass substrate having a columnar spacer having a height of 4 μm. Each was spin coated. Then, it was dried on a hot plate at 80 ° C. for 5 minutes and then fired at 230 ° C. for 20 minutes to obtain a polyimide film having a film thickness of 60 nm on each substrate. The polyimide film surface is rubbed with a rayon cloth under the conditions of a roll diameter of 120 mm, a roller rotation speed of 500 rpm, a stage moving speed of 30 mm / sec, and a rubbing cloth pushing pressure of 0.3 mm, and then in pure water for 1 minute. Ultrasonic irradiation was performed and the mixture was dried at 80 ° C. for 10 minutes.
Using the above two types of substrates with a liquid crystal alignment film, they were combined so that their rubbing directions were antiparallel, and the surroundings were sealed leaving the liquid crystal injection port to prepare an empty cell with a cell gap of 3.8 μm. .. A liquid crystal display (MLC-3019, manufactured by Merck & Co., Inc.) was vacuum-injected into this empty cell at room temperature, and then the injection port was sealed to obtain an antiparallel oriented liquid crystal cell. The obtained liquid crystal cell constituted an FFS mode liquid crystal display element. Then, the liquid crystal cell was heated at 120 ° C. for 1 hour, left overnight, and then used for each of the following evaluations.

<Evaluation of afterimage erasing time>
The afterimage was evaluated using the following optical system and the like. That is, the produced liquid crystal cell is installed between two polarizing plates arranged so that the polarization axes are orthogonal to each other, and the LED backlight is turned on in a state where no voltage is applied so that the brightness of the transmitted light is minimized. In addition, the arrangement angle of the liquid crystal cell was adjusted. Next, the VT curve (voltage-transmittance curve) was measured while applying an AC voltage having a frequency of 30 Hz to the liquid crystal cell, and the AC voltage having a relative transmittance of 23% was calculated as the drive voltage.
In the afterimage evaluation, an AC voltage having a frequency of 30 Hz having a relative transmittance of 23% was applied to drive the liquid crystal cell, and at the same time, a DC voltage of 1 V was applied to drive the liquid crystal cell for 30 minutes. After that, the applied DC voltage value was set to 0 V, only the application of the DC voltage was stopped, and the vehicle was driven for another 15 minutes in that state.

In the afterimage evaluation, the time during which the relative transmittance decreased to 30% or less was quantified from the time when the application of the DC voltage was started until 30 minutes passed. When the relative transmittance decreased to 30% or less within 5 minutes, it was defined as “◯”, and when it was within 6 to 30 minutes, it was defined as “Δ”. When it took 30 minutes or more for the relative transmittance to decrease to 30% or less, the afterimage could not be erased, and the evaluation was defined as “x”. Then, the afterimage evaluation according to the above-mentioned method was performed under the temperature condition in which the temperature of the liquid crystal cell was 23 ° C.

<Evaluation of flicker level immediately after driving>
The produced liquid crystal cell is placed between two polarizing plates arranged so that the polarization axes are orthogonal to each other, and the LED backlight is turned on in a state where no voltage is applied so that the brightness of the transmitted light is minimized. The arrangement angle of the liquid crystal cell was adjusted. Next, the VT curve (voltage-transmittance curve) was measured while applying an AC voltage having a frequency of 30 Hz to the liquid crystal cell, and the AC voltage having a relative transmittance of 23% was calculated as the drive voltage.

In the measurement of the flicker level, the LED backlight that has been turned on is turned off and left for 72 hours, then the LED backlight is turned on again, and the relative transmission rate becomes 23% at the same time as the backlight starts turning on. The AC voltage was applied to drive the liquid crystal cell for 60 minutes to track the flicker amplitude. The flicker amplitude is a data collection / data logger switch unit 34970A (Agilent technologies) in which the transmitted light of the LED backlight that has passed through the two polarizing plates and the liquid crystal cell between them is connected via a photodiode and an IV conversion amplifier. I read it with (manufactured by the company). The flicker level was calculated by the following formula.
Flicker level (%) = {flicker amplitude / (2 × z)} × 100

In the above formula, z is a value read by the data collection / data logger switch unit 34970A of the brightness when driven by an AC voltage having a frequency of 30 Hz at which the relative transmittance is 23%.
The flicker level was evaluated as "◯" when the flicker level was maintained at less than 3% from the time when the LED backlight was turned on and the application of the AC voltage was started to the time when 60 minutes had elapsed. When the flicker level reached 3% or more in 60 minutes, it was evaluated as "x".
Then, the evaluation of the flicker level according to the above-mentioned method was performed under the temperature condition in which the temperature of the liquid crystal cell was 23 ° C.

<Evaluation result>
Table 3 shows the results of the evaluation of the afterimage erasing time and the evaluation of the flicker level immediately after driving for the liquid crystal display elements using the liquid crystal alignment agents of Examples 1 to 22 and Comparative Examples 1 to 5. show.

<Manufacturing of liquid crystal display element by photo-alignment method>
After filtering the liquid crystal alignment agent with a filter having a pore size of 1.0 μm, an ITO film is formed on the back surface of the prepared substrate with electrodes as a facing substrate, and a glass substrate having a columnar spacer having a height of 4 μm. Each was spin coated. Then, after drying on a hot plate at 80 ° C. for 5 minutes, it was fired at 230 ° C. for 30 minutes to obtain a polyimide film on each substrate as a coating film having a film thickness of 100 nm. The coating film surface was irradiated with ultraviolet rays having a wavelength of 254 nm, which were linearly polarized with an extinction ratio of 26: 1, at 300 mJ / cm ^{2 via a polarizing plate.} This substrate was heated on a hot plate at 230 ° C. for 30 minutes to obtain a substrate with a liquid crystal alignment film. The above two substrates are made into a set, a sealant is printed on the substrate, and the other substrate is bonded so that the liquid crystal alignment film surfaces face each other and the orientation direction is 0 °, and then the sealant is applied. It was cured to prepare an empty cell. A negative liquid crystal display MLC-7026-100 (manufactured by Merck & Co., Inc.) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS-driven liquid crystal cell. Then, the obtained liquid crystal cell was heated at 110 ° C. for 1 hour, left overnight, and then used for each of the following evaluations.

<Evaluation of afterimage erasing time>
In the same manner as in the case of the liquid crystal display element by the rubbing method, the afterimage was evaluated using the optical system of the liquid crystal display element by the photoalignment method produced above.
In the afterimage evaluation, unlike the case of the liquid crystal display element by the rubbing method, the time during which the relative transmittance decreased to 23% was quantified from the time when the application of the DC voltage was started until 30 minutes passed. When the relative transmittance decreased to 23% within 5 minutes, it was defined as “◯”, and when it was within 6 to 30 minutes, it was defined as “Δ”. When it took 30 minutes or more for the relative transmittance to decrease to 23%, the afterimage could not be erased and was defined as "x".

<Evaluation of flicker level immediately after driving>
In the same manner as in the case of the liquid crystal display element by the rubbing method, the afterimage was evaluated using the optical system of the liquid crystal display element by the photoalignment method produced above.

<Evaluation result>
Table 4 shows the results of the evaluation of the afterimage erasing time and the evaluation of the flicker level immediately after driving for the liquid crystal display element using the liquid crystal alignment agent obtained in Example 19 and Comparative Example 6.

As can be seen in Tables 3 and 4, the liquid crystal display element using the liquid crystal alignment agent according to the embodiment of the present invention has a rapid relaxation of accumulated charges and is unlikely to cause a flicker shift that occurs immediately after the start of driving. I understand.

The liquid crystal aligning agent using the novel polymer of the present invention is widely used for a liquid crystal display element of a longitudinal electric field system such as a TN system or a VA system, particularly a transverse electric field system such as an IPS system or an FFS system.
The specification, scope of patent claims, and abstract of Japanese Patent Application No. 2016-010996 filed on January 22, 2016 and Japanese Patent Application No. 2016-10237 filed on June 1, 2016. The entire contents are cited herein and incorporated as a disclosure of the specification of the present invention.

Claims (10)

A liquid crystal alignment agent containing a polymer obtained from a diamine having a structure represented by the following formula (1) and an organic solvent.

(R ₁ represents a hydrogen, a fluorine atom, a cyano group, a hydroxy group, or a monovalent organic group, and * represents a site that binds to another group. Any hydrogen atom on the benzene ring is a monovalent organic group. It may be replaced.) At least one selected from the group consisting of a polyimide precursor which is a polycondensate of a diamine having a structure represented by the formula (1) and a tetracarboxylic dianhydride and a polyimide which is an imidized product thereof. The liquid crystal aligning agent according to claim 1, which is a polymer of the species. The liquid crystal alignment agent according to claim 1 or 2, wherein the diamine is represented by the following formula (2).

(The R ₁ definition is the formula (1) is the same as, the two R ₂ each represents a structure of a single bond or the following formula (3), n represents an integer of 1 to 3. Any hydrogen atom on the benzene ring may be substituted with a monovalent organic group.)

(R ₃ is selected from single bond, -O- _{, -COO-, -OCO-,-(CH 2} ) _l- , -O (CH ₂ ) _m O-, -CONH-, and -NHCO- 2 Represents a valent organic group (l and m represent integers from 1 to 5), * ₁ represents a site that binds to the benzene ring _{in formula (2), and * 2} represents an amino group in formula (2). Represents the site of binding.) The liquid crystal alignment agent according to claim 2 , wherein the polyimide precursor has a structural unit represented by the following formula (6).

(X ₁ is a tetravalent organic group derived from a tetracarboxylic acid derivative, Y ₁ is a divalent organic group derived from a diamine containing the structure of the formula (1), and R ₄ is a hydrogen atom or carbon. It is an alkyl group of number 1-5.)

The liquid crystal alignment agent according to claim 4, wherein in the formula (6), X ₁ is at least one selected from the group consisting of the structures of the following formulas (A-1) to (A-21).

The liquid crystal alignment agent according to claim 4 or 5, wherein the polymer having the structural unit represented by the formula (6) is contained in an amount of 10 mol% or more based on the total polymer contained in the liquid crystal alignment agent. The liquid crystal alignment agent according to any one of claims 1 to 6, wherein the organic solvent contains at least one selected from the group consisting of 4-hydroxy-4-methyl-2-pentanone and diethylene glycol diethyl ether. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of claims 1 to 7. A liquid crystal display element comprising the liquid crystal alignment film according to claim 8. The liquid crystal display element according to claim 9, wherein the liquid crystal display element is a transverse electric field drive system.