JPWO2013054858A1 - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element - Google Patents

Abstract

Disclosed are a liquid crystal alignment film that provides a highly reliable liquid crystal display element excellent in voltage holding ratio and ion density at high temperatures, and a liquid crystal alignment agent for obtaining the liquid crystal alignment film. A liquid crystal aligning agent comprising a polyamic acid obtained from tetracarboxylic dianhydride and diamine, at least one compound selected from the group consisting of a structure represented by the following formula (1), and an organic solvent. (In Formula (1), each D is independently a t-butoxycarbonyl group or a 9-fluorenylmethoxycarbonyl group.)

Description

  The present invention relates to a liquid crystal aligning agent for producing a liquid crystal aligning film, a liquid crystal aligning film obtained from the liquid crystal aligning agent, and a liquid crystal display element comprising the obtained liquid crystal aligning film.

In a liquid crystal display element used for a liquid crystal television, a liquid crystal display, and the like, a liquid crystal alignment film for controlling the alignment state of liquid crystals is usually provided in the element.
As a liquid crystal alignment film, a polyimide-based film obtained by applying a polyimide precursor such as polyamic acid (also referred to as polyamic acid) or a liquid crystal alignment agent having a soluble polyimide solution as a main component to a glass substrate or the like and baking it. A liquid crystal alignment film is mainly used.
As liquid crystal display elements have become higher in definition, liquid crystal alignment films have high liquid crystal alignment characteristics and stable pretilt angles in addition to the demands for suppressing the decrease in contrast and reducing the afterimage phenomenon. Characteristics such as a voltage holding ratio, suppression of an afterimage generated by AC driving, a small residual charge when a DC voltage is applied, and quick relaxation of a residual charge accumulated by the DC voltage are important.

In the polyimide-based liquid crystal aligning agent, various proposals have been made to meet the above requirements. For example, in addition to polyamic acid and imide group-containing polyamic acid, a liquid crystal aligning agent containing a tertiary amine having a specific structure (see Patent Document 1), a soluble polyimide using a specific diamine compound having a pyridine skeleton as a raw material A liquid crystal aligning agent (see Patent Document 2) has been proposed.
Further, in addition to polyamic acid and its imidized polymer, etc., a compound containing one carboxylic acid group in the molecule, a compound containing one carboxylic anhydride group in the molecule, and 1 in the molecule A liquid crystal aligning agent containing a very small amount of a compound selected from compounds containing three tertiary amino groups (see Patent Document 3), a tetracarboxylic dianhydride having a specific structure, and a tetracarboxylic dianhydride having cyclobutane, A liquid crystal aligning agent containing a polyamic acid obtained from a specific diamine compound or an imidized polymer thereof (see Patent Document 4) has been proposed.

Furthermore, at least 1 chosen from the liquid crystal aligning agent (refer patent document 5) containing the imide group containing monomer or amic acid site | part containing monomer which has a specific structure with a polyamic acid or a polyimide, polyamic acid, and the imidation polymer of a polyamic acid. A liquid crystal aligning agent (see Patent Document 6) containing a polymer of a kind and at least one compound selected from an amic acid compound and an imide compound has been proposed.
In recent years, as an alignment treatment method that replaces the rubbing treatment, a photo-alignment method that imparts liquid crystal alignment ability by irradiating polarized radiation has attracted attention, and the main chain has an alicyclic structure such as a cyclobutane ring. It has been proposed to use a polyimide film for the photo-alignment method (Patent Document 7).

The photo-alignment method as described above has not only the advantage that a film can be prepared by an industrially simple manufacturing process as a rubbing-less alignment treatment method, but also an IPS (In-Plane-Switching) driving method and fringe field switching. (Hereinafter referred to as FFS) drive type liquid crystal display element, by using the liquid crystal alignment film obtained by the above-mentioned photo-alignment method, the contrast and viewing angle of the liquid crystal display element compared to the liquid crystal alignment film obtained by the rubbing treatment method. Since it is possible to improve the performance of a liquid crystal display element such as an improvement in characteristics, it is attracting attention as a promising liquid crystal alignment treatment method.
The liquid crystal alignment film used in the liquid crystal display element of the IPS driving method or the FFS driving method is generated in the liquid crystal display element of the IPS driving method or the FFS driving method in addition to the basic characteristics such as excellent liquid crystal alignment property and electrical characteristics. It is necessary to suppress the afterimage by AC driving. However, the liquid crystal alignment film obtained by the photo-alignment method has insufficient liquid crystal alignment control ability and stability, and it has been difficult to satisfy the above characteristics.

Japanese Unexamined Patent Publication No. 9-316200 Japanese Unexamined Patent Publication No. 10-104633 Japanese Unexamined Patent Publication No. 8-76128 Japanese Unexamined Patent Publication No. 9-138414 Japanese Unexamined Patent Publication No. 6-110061 Japanese Unexamined Patent Publication No. 9-269491 Japanese Unexamined Patent Publication No. 9-297313

  Furthermore, in recent years, large-screen, high-definition liquid crystal televisions have become main components, and the demands for liquid crystal display elements have become more stringent. As a result, liquid crystal alignment films that are closely related to the characteristics of liquid crystal display elements have become even better. Characteristics are required. In particular, not only the initial characteristics are good, but also high reliability is required to maintain good characteristics even after being exposed to a high temperature for a long time.

  Polyamic acid, which is a polyimide precursor, has high solubility in organic solvents, good coatability, and can be used as a liquid crystal aligning agent as it is because it can be used as a liquid crystal aligning agent after being diluted with a polymerization solution. Yes. However, it is known that a liquid crystal alignment film obtained from a liquid crystal aligning agent made of polyamic acid has problems in reliability such as a decrease in voltage holding ratio and an increase in ion density at high temperatures when used as a liquid crystal display element. ing. With such a liquid crystal alignment film, it is difficult to achieve high reliability as a liquid crystal display element that has been required in recent years.

In addition, when polyamic acid is used as the polyimide precursor, the reverse reaction to diamine and acid dianhydride proceeds simultaneously with imidization during firing, and the resulting polyimide molecular weight is lower than the original polyamic acid Resulting in. The liquid crystal alignment film obtained by irradiating such a polyimide film with light is further deteriorated in the alignment regulating force of liquid crystal and its stability.
The present invention provides a liquid crystal alignment film from which a highly reliable liquid crystal alignment display element excellent in electrical characteristics such as voltage holding ratio and ion density at high temperatures can be obtained even when the liquid crystal alignment agent contains a polyamic acid, and Liquid crystal alignment agent for forming liquid crystal alignment film, liquid crystal alignment film capable of suppressing afterimages caused by alternating current drive generated in liquid crystal display elements of IPS driving method and FFS driving method, and liquid crystal alignment film for forming the liquid crystal alignment film The purpose is to provide an agent.

  The present inventor made extensive studies to achieve the above object. As a result, the liquid crystal aligning agent containing a polyamic acid and a compound having a specific structure represented by the following formula (1) achieves the above object. It has been found that it can be achieved, and the present invention has been completed.

（式（１）において、Ｄはそれぞれ独立に、ｔ−ブトキシカルボニル基又は９−フルオレニルメトキシカルボニル基である。）
２．前記ポリアミック酸の重量平均分子量が２，０００〜５００，０００であり、数平均分子量が１，０００〜２５０，０００である上記１に記載の液晶配向剤。
３．前記有機溶媒が、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジエチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ−メチル−２−ピロリドン、Ｎ−エチル−２−ピロリドン、Ｎ−メチルカプロラクタム、２−ピロリドン、Ｎ−ビニル−２−ピロリドン、ジメチルスルホキシド、ジメチルスルホン、γ−ブチロラクトン、１，３−ジメチル−イミダゾリジノン及び３−メトキシ−Ｎ，Ｎ−ジメチルプロパンアミドからなる群から選ばれる少なくとも１種類である上記１又は２に記載の液晶配向剤。
４．前記式（１）で表される化合物が、Ｎ−α−（９−フルオレニルメトキシカルボニル）−Ｎ−τ−ｔ−ブトキシカルボニル−Ｌ−ヒスチジンである上記１〜３のいずれかに記載の液晶配向剤。
５．上記式（１）で表される化合物の割合が、ポリアミック酸の構造単位１モルに対して０．０１〜０．５モル当量である上記１〜４のいずれかに記載の液晶配向剤。
６．ポリアミック酸の液晶配向剤中の濃度が、１質量％以上１０質量％以下である上記１〜５のいずれかに記載の液晶配向剤。Thus, the present invention has the following gist.
1. A liquid crystal aligning agent comprising a polyamic acid obtained from tetracarboxylic dianhydride and diamine, a compound represented by the following formula (1), and an organic solvent.

(In Formula (1), each D is independently a t-butoxycarbonyl group or a 9-fluorenylmethoxycarbonyl group.)
2. 2. The liquid crystal aligning agent according to 1, wherein the polyamic acid has a weight average molecular weight of 2,000 to 500,000 and a number average molecular weight of 1,000 to 250,000.
3. The organic solvent is N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone At least one selected from the group consisting of N-vinyl-2-pyrrolidone, dimethyl sulfoxide, dimethyl sulfone, γ-butyrolactone, 1,3-dimethyl-imidazolidinone and 3-methoxy-N, N-dimethylpropanamide 3. The liquid crystal aligning agent according to 1 or 2 above.
4). 4. The compound according to any one of 1 to 3 above, wherein the compound represented by the formula (1) is N-α- (9-fluorenylmethoxycarbonyl) -N-τ-t-butoxycarbonyl-L-histidine. Liquid crystal aligning agent.
5. The liquid crystal aligning agent in any one of said 1-4 whose ratio of the compound represented by the said Formula (1) is 0.01-0.5 molar equivalent with respect to 1 mol of structural units of a polyamic acid.
6). The liquid crystal aligning agent in any one of said 1-5 whose density | concentration in the liquid crystal aligning agent of a polyamic acid is 1 to 10 mass%.

（式（２）において、Ｘ_１は下記式（Ｘ−１）、（Ｘ−２）、（Ｘ−３）、（Ｘ−４）、（Ｘ−５）、（Ｘ−６）、（Ｘ−７）、（Ｘ−８）、（Ｘ−９）、（Ｘ−１０）、（Ｘ−１１）、（Ｘ−１２）、（Ｘ−１３）及び（Ｘ−１４）で表される構造からなる群から選ばれる少なくとも１種類である。）

（上記式において、Ｒ_１、Ｒ_２、Ｒ_３、及びＲ_４は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１〜６のアルキル基、炭素数２〜６のアルケニル基、アルキニル基、又はフェニル基である。）7). The polyamic acid is any one of the above 1 to 6, which is a polyamic acid obtained from a tetracarboxylic acid containing at least one tetracarboxylic acid selected from the group consisting of a structure represented by the following formula (2) and a diamine. Liquid crystal aligning agent.

(In the formula (2), X ₁ represents the following formulas (X-1), (X-2), (X-3), (X-4), (X-5), (X-6), (X -7), (X-8), (X-9), (X-10), (X-11), (X-12), (X-13) and (X-14) At least one selected from the group consisting of:

(In the above formula, R ₁ , R ₂ , R ₃ , and R ₄ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkynyl group. Or a phenyl group.)

8). Tetracarboxylic dianhydride containing the tetracarboxylic dianhydride represented by the above formula (2) in an amount of 0.6 to 1.0 mole equivalent to 1.0 mole of all tetracarboxylic dianhydrides The liquid crystal aligning agent in any one of said 1-7 which is.
9. X ₁ is, the liquid crystal alignment agent according to any one of the above 1 to 8 is at least one selected from the group consisting of structures represented by the following formula (X1-1) and (Xl-2).

（式（３）において、Y_１は下記式で表される構造からなる群から選ばれる少なくとも１種類である。）10. 10. The liquid crystal aligning agent according to any one of 1 to 9 above, wherein the diamine contains at least one diamine selected from the group consisting of a structure represented by the following formula (3).

(In Formula (3), Y ₁ is at least one selected from the group consisting of structures represented by the following formula.)

11. The liquid crystal aligning film obtained by apply | coating and baking the liquid crystal aligning agent in any one of said 1-10.
12 The liquid crystal aligning film obtained by apply | coating and baking the liquid crystal aligning agent in any one of said 1-10, and also irradiating the polarized radiation.
13. 13. The liquid crystal alignment film as described in 12 above, wherein the wavelength of radiation to be irradiated is 100 to 400 nm.
14 14. A liquid crystal display device comprising the liquid crystal alignment film according to any one of 11 to 13 above.

  A liquid crystal display device comprising a liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention has a high voltage holding ratio and a low ion density even at high temperatures. Furthermore, the liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention can suppress afterimages caused by alternating current drive generated in an IPS drive type or FFS drive type liquid crystal display element.

The reason why the problems of the present invention are solved in the liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention is not necessarily clear, but is considered as follows.
The specific compound used in the present invention is a thermal base generator that generates an imidazole and an amino group by heating, and is a compound that can promote imidization by heating of a polyamic acid (hereinafter also referred to as an imidization accelerator). .) By adding such an imidization accelerator, there is an advantage that the manufacturing process of the liquid crystal alignment film can be made efficient such that the baking temperature of the liquid crystal alignment film can be lowered and the baking time can be shortened. Moreover, a liquid crystal display element with high reliability is obtained, so that the imidation ratio of the liquid crystal aligning film obtained by coating and baking polyamic acid is high. However, when such an imidization accelerator is added, the added imidization accelerator may remain in the film, and the remaining compound elutes into the liquid crystal, reducing the reliability of the obtained liquid crystal display device. There is a possibility that problems such as reducing the orientation of the liquid crystal may occur.

The specific compound used in the present invention generates a highly reactive aliphatic amino group by heating. Since these functional groups react with the carboxyl group in the polyamic acid, the compound itself is taken into the polymer, and the elution of the imidization accelerator into the liquid crystal is suppressed. Moreover, since the specific compound described in the present invention has a carboxyl group, it has a high boiling point and is likely to remain in the film even at high temperatures, and thus has a high imidization promoting effect.
In the specific compound of the present invention, since the amino group and imidazole are protected in the liquid crystal aligning agent, the viscosity of the solution changes with time because it does not react with the carboxyl group of the polyamic acid or form a salt. A stable liquid crystal aligning agent that does not occur is obtained.
Furthermore, the specific compound used in the present invention promotes imidization of polyamic acid, but does not hinder liquid crystal alignment, and thus suppresses afterimages caused by AC driving in liquid crystal display elements of IPS driving method and FFS driving method. can do.

式（１）において、Ｄはそれぞれ独立にｔ−ブトキシカルボニル基又は９−フルオレニルメトキシカルボニル基である。
式（１）で表される構造の化合物の添加量は、特に制限されるものではないが、多すぎると液晶配向性を阻害してしまう可能性があり、少なすぎると本発明に記載の効果が得られない恐れがある。そのため、式（１）で表される構造の化合物の添加量は、ポリアミック酸の構造単位１．０モルに対して、０．０１〜０．５モル当量が好ましく、０．０５〜０．４モル当量がより好ましく、０．１〜０．３モル当量がさらに好ましい。ここで、ポリアミック酸の構造単位とは、下記式で表される構造を意味する。

<Specific compounds>
The liquid crystal aligning agent of this invention contains the compound of the structure represented by following formula (1), It is characterized by the above-mentioned.

In the formula (1), each D is independently a t-butoxycarbonyl group or a 9-fluorenylmethoxycarbonyl group.
The addition amount of the compound having the structure represented by the formula (1) is not particularly limited, but if it is too much, the liquid crystal orientation may be inhibited, and if it is too little, the effects described in the present invention. May not be obtained. Therefore, the amount of the compound having the structure represented by the formula (1) is preferably 0.01 to 0.5 molar equivalents relative to 1.0 mol of the structural unit of the polyamic acid, and 0.05 to 0.4 A molar equivalent is more preferable, and a 0.1-0.3 molar equivalent is still more preferable. Here, the structural unit of polyamic acid means a structure represented by the following formula.

  Specific examples of the compound having the structure represented by the formula (1) include N-α, im-di-t-butoxycarbonyl-L-histidine, N-α, im-di-t-butoxycarbonyl-D-histidine. N-α- (9-fluorenylmethoxycarbonyl) -N-τ-t-butoxycarbonyl-L-histidine, N-α- (9-fluorenylmethoxycarbonyl) -N-τ-t-butoxycarbonyl -D-histidine, N- [alpha], N- [tau] -di- (9-fluorenylmethoxycarbonyl) -L-histidine, N- [alpha], N- [tau] -di- (9-fluorenylmethoxycarbonyl) -D -Histidine, N-α- (9-fluorenylmethoxycarbonyl) -N-τ-t-butoxycarbonyl-L-histidine is particularly preferred.

<Polyamic acid>
The polyamic acid contained in the liquid crystal aligning agent of the present invention is a polymer obtained by polycondensation reaction of a tetracarboxylic dianhydride represented by the following formula (4) and a diamine represented by the following formula (5). It is.

式（４）において、Xは４価の有機基であり、その構造は特に限定されない。具体例としては、下記式（Ｘ−１）〜（Ｘ−４４）の構造が挙げられる。

In the formula (4), X is a tetravalent organic group, and its structure is not particularly limited. Specific examples include structures of the following formulas (X-1) to (X-44).

（式（Ｘ−１）中、Ｒ_１、Ｒ_２、Ｒ_３、及びＲ_４は、それぞれ独立して、水素原子、ハロゲン原子、炭素数１〜６のアルキル基、炭素数２〜６のアルケニル基、アルケニル基、又はフェニル基である。）

(In Formula (X-1), R ₁ , R ₂ , R ₃ , and R ₄ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkenyl having 2 to 6 carbon atoms. Group, alkenyl group, or phenyl group.)

（式（２）において、Ｘ_１は上記式（Ｘ−１）〜（Ｘ−１４）で表される構造からなる群から選ばれる少なくとも１種である。）
得られる液晶配向膜の信頼性をさらに高められることから、Ｘ_１の構造は、（Ｘ−１）〜（Ｘ−７）及び（Ｘ−１０）のような、脂肪族基のみからなる構造が好ましく、（Ｘ−１）で表される構造がより好ましい。更に、良好な液晶配向性を示すため、Ｘ_１の構造としては、下記式（Ｘ１−１）又は（Ｘ１−２）がさらに好ましい。From the viewpoint of availability of the compound, the tetracarboxylic dianhydride is preferably at least one tetracarboxylic acid selected from the group consisting of the structure represented by the following formula (2).

(In Formula (2), X ₁ is at least one selected from the group consisting of structures represented by Formulas (X-1) to (X-14) above.)
Since the reliability of the obtained liquid crystal alignment film can be further enhanced, the structure of X _{1 is} a structure consisting only of an aliphatic group such as (X-1) to (X-7) and (X-10). Preferably, the structure represented by (X-1) is more preferable. Furthermore, to show the good liquid crystal alignment property, the structure of _{X 1,} more preferably the following formula (X1-1) or (Xl-2).

式（２）で表される構造からなる群から選ばれる少なくとも1種のテトラカルボン酸二無水物の割合は、全テトラカルボン酸二無水物１モルに対して、４０〜１００モル％、より好ましくは、６０〜１００モル％である。

The proportion of at least one tetracarboxylic dianhydride selected from the group consisting of the structure represented by the formula (2) is preferably 40 to 100 mol% with respect to 1 mol of all tetracarboxylic dianhydrides. Is 60 to 100 mol%.

In the above formula (5), A ₁ and A ₂ are each independently a hydrogen atom, an alkyl group, an alkenyl group, or an alkynyl group having 1 to 10 carbon atoms that may have a substituent.
Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a t-butyl group, a hexyl group, an octyl group, a decyl group, a cyclopentyl group, and a cyclohexyl group.
Examples of the alkenyl group include those obtained by replacing one or more CH ₂ —CH ₂ structures present in the above alkyl group with a CH═CH structure, and more specifically, vinyl groups, allyl groups, 1- Examples include propenyl group, isopropenyl group, 2-butenyl group, 1,3-butadienyl group, 2-pentenyl group, 2-hexenyl group, cyclopropenyl group, cyclopentenyl group, and cyclohexenyl group.
Alkynyl groups include those in which one or more CH ₂ —CH ₂ structures present in the alkyl group are replaced with C≡C structures, and more specifically, ethynyl groups, 1-propynyl groups, 2 -A propynyl group etc. are mentioned.

The alkyl group, alkenyl group, and alkynyl group may have a substituent as long as the number of carbon atoms is 1 to 10 as a whole, and may further form a ring structure with the substituent. Note that forming a ring structure with a substituent means that the substituents or a substituent and a part of the mother skeleton are bonded to form a ring structure.
Examples of substituents are halogen groups, hydroxyl groups, thiol groups, nitro groups, aryl groups, organooxy groups, organothio groups, organosilyl groups, acyl groups, ester groups, thioester groups, phosphate ester groups, amide groups, alkyl groups. Alkenyl group, alkynyl group, and the like.

Examples of the halogen group as a substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
A phenyl group is mentioned as an aryl group which is a substituent. This aryl group may be further substituted with the substituent described above.
The organooxy group which is a substituent can have a structure represented by OR. When several organooxy groups are substituted, R may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These Rs may be further substituted with the substituent described above. Specific examples of the alkyloxy group include methoxy group, ethoxy group, propyloxy group, butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group and the like.
As the organothio group which is a substituent, the structure represented by -S-R can be shown. Examples of R include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. These Rs may be further substituted with the substituent described above. Specific examples of the alkylthio group include a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a pentylthio group, a hexylthio group, a heptylthio group, and an octylthio group.

As the organosilyl group which is a substituent, a structure represented by -Si- (R) ₃ can be shown. The R may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These Rs may be further substituted with the substituent described above. Specific examples of the alkylsilyl group include a trimethylsilyl group, a triethylsilyl group, a tripropylsilyl group, a tributylsilyl group, a tripentylsilyl group, a trihexylsilyl group, a pentyldimethylsilyl group, and a hexyldimethylsilyl group.
As an acyl group which is a substituent, the structure represented by -C (O) -R can be shown. Examples of R include the above-described alkyl group, alkenyl group, and aryl group. These Rs may be further substituted with the substituent described above. Specific examples of the acyl group include formyl group, acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group, isovaleryl group, benzoyl group and the like.

As an ester group which is a substituent, the structure represented by -C (O) O-R or -OC (O) -R can be shown. Examples of R include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. These Rs may be further substituted with the substituent described above.
As a thioester group which is a substituent, the structure represented by -C (S) O-R or -OC (S) -R can be shown. Examples of R include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. These Rs may be further substituted with the substituent described above.
As a phosphate group which is a substituent, the structure represented by -OP (O)-(OR) ₂ can be shown. The R may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These Rs may be further substituted with the substituent described above.

Examples of the amide group as a substituent include —C (O) NH ₂ , —C (O) NHR, —NHC (O) R, —C (O) N (R) ₂ , and —NRC (O) R. The structure represented can be shown. The R may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These Rs may be further substituted with the substituent described above.
Examples of the aryl group as a substituent include the same aryl groups as described above. This aryl group may be further substituted with the substituent described above.
Examples of the alkyl group as a substituent include the same alkyl groups as described above. This alkyl group may be further substituted with the substituent described above.
Examples of the alkenyl group as a substituent include the same alkenyl groups as described above. This alkenyl group may be further substituted with the substituent described above.
Examples of the alkynyl group that is a substituent include the same alkynyl groups as described above. This alkynyl group may be further substituted with the substituent described above.

In general, when a bulky structure is introduced, there is a possibility that the reactivity of the amino group and the liquid crystal orientation may be lowered. Therefore, as A ₁ and A ₂ , a hydrogen atom or a carbon atom that may have a substituent is 1 The alkyl group of ˜5 is more preferable, and a hydrogen atom, a methyl group or an ethyl group is particularly preferable.
In the formula (5), Y is a divalent organic group, and its structure is not particularly limited. If the specific example of Y is given, the structure of following formula (Y-1)-(Y-113) will be mentioned. Two or more diamines may be mixed and used.
Especially, in order to obtain favorable liquid crystal orientation, it is preferable to use diamine with high linearity, and as Y, Y-7, Y-10, Y-11, Y-12, Y-13, Y -21, Y-22, Y-23, Y-25, Y-26, Y-27, Y-41, Y-42, Y-43, Y-44, Y-45, Y-46, Y-48 Y-61, Y-63, Y-64, Y-71, Y-72, Y-73, Y-74, Y-75, Y-98 and the like.

As for the ratio of the said diamine, 40-100 mol% is preferable with respect to 1 mol of all diamines, More preferably, it is 60-100 mol%.
In order to increase the pretilt angle, it is preferable to introduce a diamine having a long chain alkyl group, aromatic ring, aliphatic ring, steroid skeleton, or a combination thereof in the side chain into the polyamic acid ester. Y-76, Y-77, Y-78, Y-79, Y-80, Y-81, Y-82, Y-83, Y-84, Y-85, Y-86, Y-87. Y-88, Y-89, Y-90, Y-91, Y-92, Y-93, Y-94, Y-95, Y-96, or Y-97.
Arbitrary pretilt angles can be expressed by adding 1 to 50 mol%, more preferably 5 to 20 mol% of these diamines with respect to 1 mol of all diamines.

式（３）において、Y_１は下記式で表される構造からなる群から選ばれる少なくとも１種類である。From the viewpoint of particularly excellent properties as a liquid crystal alignment film, the diamine used in the present invention is particularly preferably at least one diamine selected from the group consisting of a structure represented by the following formula (3).

In Formula (3), Y ₁ is at least one selected from the group consisting of structures represented by the following formulas.

上記式（３）で表されるジアミンの割合は、全ジアミン１．０モルに対して、０．６〜１．０モル当量が好ましく、より好ましくは、０．８〜１．０モル当量である。

The ratio of the diamine represented by the above formula (3) is preferably 0.6 to 1.0 molar equivalent, more preferably 0.8 to 1.0 molar equivalent, relative to 1.0 mole of the total diamine. is there.

<Method for producing polyamic acid>
The polyamic acid which is a polyimide precursor used in the present invention can be synthesized by the following method.
Specifically, tetracarboxylic dianhydride and diamine are reacted in the presence of an organic solvent at -20 to 150 ° C, preferably 0 to 50 ° C, for 30 minutes to 24 hours, preferably 1 to 12 hours. Can be synthesized.
The organic solvent used in the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, γ-butyrolactone, etc. in view of the solubility of the monomer and polymer, and these may be used alone or in combination of two or more. May be used.
The concentration of the polymer (polyamic acid) is preferably 1 to 30% by mass and more preferably 5 to 20% by mass from the viewpoint that the polymer is hardly precipitated and a high molecular weight body is easily obtained.

  The polyamic acid obtained as described above can be recovered by precipitating the polymer by pouring into the poor solvent while thoroughly stirring the reaction solution. In addition, by performing precipitation several times, washing with a poor solvent, and then drying at normal temperature or heat, a purified polyamic acid powder can be obtained. Although it does not specifically limit as a poor solvent, Water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene, etc. are mentioned.

<Liquid crystal aligning agent>
The liquid crystal aligning agent of the present invention has a form of a solution in which a polyamic acid and a compound represented by the formula (1) are dissolved in an organic solvent.
The molecular weight of the polyamic acid is preferably 2,000 to 500,000 in terms of weight average molecular weight, more preferably 5,000 to 300,000, and still more preferably 10,000 to 100,000. The number average molecular weight is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, and still more preferably 5,000 to 50,000.
The polymer concentration of the liquid crystal aligning agent of the present invention can be appropriately changed by setting the thickness of the coating film to be formed, but is 1% by mass or more from the viewpoint of forming a uniform and defect-free coating film. In view of storage stability of the solution, it is preferably 10% by mass or less. Particularly preferably, the polymer concentration is 2-8% by weight.

  The organic solvent contained in the liquid crystal aligning agent of this invention will not be specifically limited if a polyamic acid and the compound represented by Formula (1) melt | dissolve uniformly. Specific examples thereof include N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methylcaprolactam, Examples include 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethyl sulfoxide, dimethyl sulfone, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, 3-methoxy-N, N-dimethylpropanamide and the like. You may use these 1 type or in mixture of 2 or more types. Moreover, even if it is a solvent which cannot melt | dissolve a polymer component uniformly by itself, if it is a range which a polymer does not precipitate, you may mix with said organic solvent.

The liquid crystal aligning agent of this invention may contain the solvent for improving the coating-film uniformity at the time of apply | coating a liquid crystal aligning agent to a board | substrate other than the organic solvent for dissolving a polymer component. As such a solvent, a solvent having a surface tension lower than that of the organic solvent is generally used. Specific examples thereof include ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, ethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy-2 -Propanol, 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether-2-acetate, butyl cellosolve acetate, di Propylene glycol, 2- (2-ethoxypropoxy) propanol, lactate methyl ester, lactate ethyl ester, lactate n-propyl ester, lactate n-butyl ester, lactic acid Isoamyl ester, and the like. Two or more of these solvents may be used in combination.
In the liquid crystal aligning agent of the present invention, in addition to the above, as long as the effects of the present invention are not impaired, the polymer other than polyamic acid, the purpose of changing the electrical properties such as the dielectric constant and conductivity of the liquid crystal aligning film A dielectric or conductive material, a silane coupling agent for the purpose of improving the adhesion between the liquid crystal alignment film and the substrate, a crosslinkable compound for the purpose of increasing the hardness and density of the film when it is made into a liquid crystal alignment film, etc. May be.

<Liquid crystal alignment film>
The liquid crystal alignment film of the present invention is a coating film obtained by applying the liquid crystal aligning agent obtained as described above to a substrate, drying and baking, and this coating surface is subjected to rubbing treatment or radiation irradiation. It is obtained by performing an orientation treatment.
The substrate to which the liquid crystal aligning agent of the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, a plastic substrate such as an acrylic substrate or a polycarbonate substrate, or the like can be used. From the viewpoint of simplification of the process, it is preferable to use a substrate on which an ITO electrode or the like is formed. Further, in the reflection type liquid crystal display element, an opaque material such as a silicon wafer can be used as long as the substrate is only on one side, and in this case, a material that reflects light such as aluminum can be used.

Examples of the method for applying the liquid crystal aligning agent of the present invention include a spin coating method, a printing method, and an ink jet method.
Arbitrary temperature and time can be selected for the drying and baking steps after applying the liquid crystal aligning agent of the present invention. Usually, in order to fully remove the organic solvent contained, it is dried at 50 to 120 ° C. for 1 to 10 minutes and then baked at 150 to 300 ° C. for 5 to 120 minutes. Although the thickness of the coating film after baking is not specifically limited, Since the reliability of a liquid crystal display element may fall when too thin, it is 5-300 nm, Preferably it is 10-200 nm.

The liquid crystal aligning agent of this invention is especially useful when processing a film | membrane by the photo-alignment processing method.
As a specific example of the photo-alignment treatment method, the surface of the coating film is irradiated with radiation polarized in a certain direction, and in some cases, a heat treatment is further performed at a temperature of 150 to 250 ° C. to impart liquid crystal alignment ability. Is mentioned.
As the wavelength of radiation, ultraviolet rays and visible rays having a wavelength of 100 to 800 nm can be used. Among these, ultraviolet rays having a wavelength of 100 to 400 nm are preferable, and those having a wavelength of 200 to 400 nm are particularly preferable.
Moreover, in order to improve liquid crystal orientation, you may irradiate a radiation, heating a coating-film board | substrate at 50-250 degreeC.
Dose of the radiation is preferably in the range of 1~10,000mJ / cm ^2, and particularly preferably in the range of 100~5,000mJ / cm ^2.
The liquid crystal alignment film produced as described above can stably align liquid crystal molecules in a certain direction.

<Liquid crystal display element>
The liquid crystal display element of the present invention is a liquid crystal display element obtained by obtaining a substrate with a liquid crystal alignment film from the liquid crystal aligning agent of the present invention by the above-described method and performing alignment treatment, and then preparing a liquid crystal cell by a known method. Is.
The method for producing the liquid crystal cell is not particularly limited. For example, a pair of substrates on which the liquid crystal alignment film is formed is preferably 1 to 30 μm, more preferably 2 to 2 with the liquid crystal alignment film surface inside. A method is generally employed in which a 10 μm spacer is placed and then the periphery is fixed with a sealant, and liquid crystal is injected and sealed.
The method for enclosing the liquid crystal is not particularly limited, and examples thereof include a vacuum method of injecting liquid crystal after reducing the pressure inside the produced liquid crystal cell, and a dropping method of sealing after dropping the liquid crystal.

（式中、Ｂｏｃは、ｔｅｒｔーブトキシカルボニル基を意味する。）The present invention will be described in more detail with reference to the following examples, but the present invention should not be construed as being limited thereto.
The abbreviations of the compounds used in Examples and Comparative Examples are as follows.
NMP: N-methyl-2-pyrrolidone BCS: Butyl cellosolve DA-1: Formula (DA-1) below

(In the formula, Boc means a tert-butoxycarbonyl group.)

Evaluation methods for viscosity, voltage holding ratio, ion density, and AC drive image sticking characteristics of the FFS drive liquid crystal cell are as follows.
[viscosity]
The viscosity of the polyamic acid ester and the polyamic acid solution is an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.), sample volume 1.1 mL, cone rotor TE-1 (1 ° 34 ′, R24), temperature 25 Measured at ° C.

[Voltage holding ratio]
A liquid crystal aligning agent is spin-coated on a glass substrate with a transparent electrode, dried on a hot plate at a temperature of 80 ° C. for 5 minutes, and baked for 15 minutes in a hot air circulation oven at 230 ° C. to form an imidized film having a thickness of 100 nm. Got. This coating surface was subjected to alignment treatment by rubbing or polarized UV irradiation to obtain a substrate with a liquid crystal alignment film. Two substrates with such a liquid crystal alignment film are prepared, and a 6 μm spacer is sprayed on the liquid crystal alignment film surface of one of the substrates, and then the two substrates are combined so that the alignment is antiparallel. The periphery was sealed and the empty cell having a cell gap of 6 μm was produced. Liquid crystal (MLC-2041, manufactured by Merck & Co., Inc.) was vacuum-injected into this empty cell at room temperature, and the inlet was sealed to obtain a liquid crystal cell.
The voltage holding ratio of the liquid crystal cell was measured as follows.
By applying a voltage of 4 V for 60 μs and measuring the voltage after 16.67 ms, the fluctuation from the initial value was calculated as the voltage holding ratio. At the time of measurement, the temperature of the liquid crystal cell was set to 23 ° C., 60 ° C., and 90 ° C., and measurement was performed at each temperature to calculate.

[Ion density]
The measurement of the ion density of the liquid crystal cell was performed as follows.
Measurement was performed using a 6254 type liquid crystal property evaluation apparatus manufactured by Toyo Technica. A triangular wave of 10 V and 0.01 Hz was applied, and an area corresponding to the ion density of the obtained waveform was calculated by a triangle approximation method to obtain an ion density. During the measurement, the temperature of the liquid crystal cell was set to 23 ° C. and 60 ° C., and the measurement was performed at each temperature.

[AC drive image sticking characteristics of FFS drive liquid crystal cell (ΔV ₅₀ )]
The first layer is an electrode having a shape of 50 nm, the second layer is an insulating film, the shape is silicon nitride having a thickness of 500 nm, and the third layer is an electrode having a comb-like shape. Spin coating is applied to a glass substrate on which a fringe field switching (hereinafter referred to as FFS) driving electrode having electrodes (electrode width: 3 μm, electrode interval: 6 μm, electrode height: 50 nm) is formed. A liquid crystal aligning agent was applied. Subsequently, after drying on an 80 degreeC hotplate for 5 minutes, it baked for 15 minutes in 230 degreeC hot-air circulation type oven, and formed the coating film with a film thickness of 100 nm. The surface of the coating film was irradiated with ultraviolet rays of 254 nm through a polarizing plate and baked for 30 minutes in a hot air circulation oven at 230 ° C. to obtain a substrate with a liquid crystal alignment film. Further, a coating film was similarly formed on a glass substrate having a columnar spacer having a height of 4 μm on which no electrode was formed as a counter substrate, and an orientation treatment was performed.
The two substrates are combined as a set, a sealing agent is printed on the substrate, and the other substrate is bonded so that the liquid crystal alignment film surfaces face each other and the alignment direction becomes 0 °, and then the sealing agent Was cured to produce an empty cell. Liquid crystal MLC-2041 (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 drive liquid crystal cell.
After measuring the VT characteristic (voltage-transmittance characteristic) of this FFS drive liquid crystal cell at a temperature of 58 ° C., a rectangular wave of ± 4 V / 120 Hz was applied for 4 hours. After 4 hours, the voltage was turned off and left for 60 minutes at a temperature of 58 ° C., then the VT characteristics were measured again to calculate the voltage difference (ΔV ₅₀ ) that gave a transmittance of 50% before and after the rectangular wave application. The AC drive image sticking characteristics of the FFS drive liquid crystal cell were adopted.

(Synthesis Example 1)
In a 1000 ml four-necked flask equipped with a stirrer and a nitrogen introducing tube, 288 g of NMP was taken, and 35.30 g (0.180 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride was added. While stirring the slurry solution of tetracarboxylic dianhydride, 18.40 g (0.170 mol) of p-phenylenediamine was added, and NMP was further added so that the solid concentration was 10% by mass. The solution was stirred for a time to obtain a polyamic acid (PAA-1) solution. The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 175 mPa · s.

(Synthesis Example 2)
In a 2000 ml four-necked flask equipped with a stirrer and a nitrogen inlet tube, 58.39 g (0.540 mol) of p-phenylenediamine, 15.92 g (0.060 mol) of DA-1, and 1862 g of NMP were mixed and stirred. And dissolved. While stirring this diamine solution, 113.08 g (0.577 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and NMP was further added so that the solid content concentration was 10% by mass. The mixture was stirred at room temperature for 24 hours to obtain a solution of polyamic acid (PAA-2). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 186 mPa · s.
(Synthesis Example 3)
To a 500 ml four-necked flask equipped with a stirrer and a nitrogen inlet tube, 211.85 g (0.710 mol) of 1,3-bis (4-aminophenethyl) urea and 2007 g of NMP were added, stirred and dissolved. It was. While stirring this diamine solution, 193.25 g (0.657 mol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added, and NMP was further adjusted so that the solid content concentration became 10% by mass. And stirred at room temperature for 6 hours to obtain a solution of polyamic acid (PAA-3). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 83 mPa · s.

(Example 1)
In a 20 ml sample tube containing a stir bar, 6.00 g of the polyamic acid solution (PAA-1) obtained in Synthesis Example 1 was taken, 2.00 g of NMP, 2.00 g of BCS, and N-α- (9 -Fluorenylmethoxycarbonyl) -N-τ-t-butoxycarbonyl-L-histidine (0.084 g) was added, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (A1-1).

(Example 2)
In a 20 ml sample tube containing a stir bar, 6.00 g of the polyamic acid solution (PAA-1) obtained in Synthesis Example 2 was taken, 2.01 g of NMP, 2.00 g of BCS, and N-α- (9 -Fluorenylmethoxycarbonyl) -N-τ-t-butoxycarbonyl-L-histidine (0.084 g) was added, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (A1-2).

(Comparative Example 1)
Into a 20 ml sample tube containing a stir bar, 6.04 g of the polyamic acid solution (PAA-1) obtained in Synthesis Example 1 was added, 2.03 g of NMP and 2.01 g of BCS were added, and a magnetic stirrer was added. The mixture was stirred for 30 minutes to obtain a liquid crystal aligning agent (B1-1).

(Example 3)
After filtering the liquid crystal aligning agent (A1-1) obtained in Example 1 with a 1.0 μm filter, it was spin-coated on a glass substrate with a transparent electrode (width 30 mm, height 40 mm, thickness 1.1 mm), A polyimide film having a thickness of 100 nm was obtained through drying on a hot plate at a temperature of 80 ° C. for 5 minutes and baking at a temperature of 230 ° C. for 15 minutes. The surface of the coating film was irradiated with 1500 mJ / cm ^{2 of} 254 nm ultraviolet light through a polarizing plate, and baked for 30 minutes in a hot air circulation oven at 230 ° C. to obtain a substrate with a liquid crystal alignment film.
Two substrates with such a liquid crystal alignment film are prepared, and a 6 μm spacer is sprayed on the liquid crystal alignment film surface of one of the substrates, and then the two substrates are combined so that the alignment is antiparallel. The periphery was sealed and the empty cell having a cell gap of 6 μm was produced. Liquid crystal (MLC-2041, manufactured by Merck & Co., Inc.) was vacuum-injected into this empty cell at room temperature, and the inlet was sealed to obtain a liquid crystal cell. For this liquid crystal cell, the voltage holding ratio was measured, and then the ion density was measured. The voltage holding ratios at 23 ° C., 60 ° C., and 90 ° C. were 99.4%, 98.7%, and 97.3%, respectively. Each ion density at 23 ° C. and 60 ° C., was ^{23pC / cm 2, 92pC / cm} 2.

Example 4
A liquid crystal cell was produced in the same manner as in Example 4 except that the liquid crystal aligning agent (A1-2) obtained in Example 2 was used. For this liquid crystal cell, the voltage holding ratio was measured, and then the ion density was measured. The voltage holding ratios at 23 ° C., 60 ° C., and 90 ° C. were 99.4%, 99.0%, and 97.6%, respectively. Each ion density at 23 ° C. and 60 ° C., was ^{13pC / cm 2, 64pC / cm} 2.

(Comparative Example 2)
A liquid crystal cell was produced in the same manner as in Example 4 except that the liquid crystal aligning agent (B1-1) obtained in Comparative Example 1 was used. For this liquid crystal cell, the voltage holding ratio was measured, and then the ion density was measured. The voltage holding ratios at 23 ° C., 60 ° C., and 90 ° C. were 99.4%, 98.7%, and 96.8%, respectively. Each ion density at 23 ° C. and 60 ° C., was ^{87pC / cm 2, 183pC / cm} 2.

Table 1 summarizes the results of the voltage holding ratio and the ion density obtained in Examples 3 to 4 and Comparative Example 2.

(Example 5)
After the liquid crystal aligning agent (A1-1) obtained in Example 1 was filtered through a 1.0 μm filter, a 50 nm-thick ITO electrode was used as the first layer, and a second layer was used as the insulating film. On a glass substrate on which an FFS driving electrode having a comb-like ITO electrode (electrode width: 3 μm, electrode interval: 6 μm, electrode height: 50 nm) is formed by using silicon nitride having a thickness of 500 nm as a third layer. Then, it was applied by spin coating. Subsequently, after drying on an 80 degreeC hotplate for 5 minutes, it baked for 15 minutes in 230 degreeC hot-air circulation type oven, and formed the coating film with a film thickness of 100 nm. The surface of the coating film was irradiated with 1500 mJ / cm ^{2 of} 254 nm ultraviolet light through a polarizing plate, and baked for 30 minutes in a hot air circulation oven at 230 ° C. to obtain a substrate with a liquid crystal alignment film. In addition, a coating film was similarly formed on a glass substrate having a columnar spacer having a height of 4 μm on which no electrode was formed as the counter substrate, and an orientation treatment was performed.
The two substrates are combined as a set, a sealing agent is printed on the substrate, and the other substrate is bonded so that the liquid crystal alignment film surfaces face each other and the alignment direction becomes 0 °, and then the sealing agent Was cured to produce an empty cell. Liquid crystal MLC-2041 (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 drive liquid crystal cell.
As a result of evaluating the AC drive burn-in characteristics of this FFS drive liquid crystal cell, ΔV ₅₀ was 1.9 mV.

(Comparative Example 3)
An FFS drive liquid crystal cell was produced in the same manner as in Example 5 except that the liquid crystal aligning agent (B1-1) obtained in Comparative Example 1 was used. As a result of evaluating the AC drive burn-in characteristics of this FFS drive liquid crystal cell, ΔV ₅₀ was 5.0 mV.
(Example 6)
In a 3000 ml flask containing a stirrer, 1305.7 g of the polyamic acid solution (PAA-3) obtained in Synthesis Example 3 was taken, 467.9 g of NMP, 326.4 g of BCS, and N-α- (9- 12.6 g of fluorenylmethoxycarbonyl) -N-τ-t-butoxycarbonyl-L-histidine was added and stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (A2-1).
(Example 7)
In a 100 ml flask containing a stirring bar, 43.52 g of the polyamic acid solution (PAA-3) obtained in Synthesis Example 3 was taken, 15.60 g of NMP, 10.88 g of BCS, and N-α- (9- 0.21 g of fluorenylmethoxycarbonyl) -N-τ-t-butoxycarbonyl-L-histidine was added, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (A2-1).
(Comparative Example 4)
In a 100 ml flask containing a stirrer, 43.52 g of the polyamic acid solution (PAA-3) obtained in Synthesis Example ○ was taken, 15.60 g of NMP and 10.88 g of BCS were added, and 30 times with a magnetic stirrer. The liquid crystal aligning agent (B2-1) was obtained by stirring for minutes.
(Example 8)
After the liquid crystal aligning agent (A2-1) obtained in Example 6 was filtered through a 1.0 μm filter, it was spin-coated on a glass substrate with a transparent electrode (width 30 mm, height 40 mm, thickness 1.1 mm), A polyimide film having a thickness of 100 nm was obtained through drying on a hot plate at a temperature of 80 ° C. for 5 minutes and baking at a temperature of 230 ° C. for 15 minutes. This polyimide film was rubbed with a rayon cloth (roll diameter 120 mm, rotation speed 1000 rpm, moving speed 20 mm / sec, indentation amount 0.4 mm) to obtain a substrate with a liquid crystal alignment film.
Two substrates with such a liquid crystal alignment film are prepared, and a 6 μm spacer is sprayed on the liquid crystal alignment film surface of one of the substrates, and then the two substrates are combined so that the alignment is antiparallel. The periphery was sealed and the empty cell having a cell gap of 6 μm was produced. Liquid crystal (MLC-2041, manufactured by Merck & Co., Inc.) was vacuum-injected into this empty cell at room temperature, and the inlet was sealed to obtain a liquid crystal cell. For this liquid crystal cell, the voltage holding ratio was measured, and then the ion density was measured. The voltage holding ratios at 23 ° C., 60 ° C., and 90 ° C. were 99.4%, 98.5%, and 97.6%, respectively. Each ion density at 23 ° C. and 60 ° C., was ^{25pC / cm 2, 141pC / cm} 2.
Example 9
A liquid crystal cell was produced in the same manner as in Example 8, except that the liquid crystal aligning agent (A2-2) obtained in Example 7 was used. For this liquid crystal cell, the voltage holding ratio was measured, and then the ion density was measured. The voltage holding ratios at 23 ° C., 60 ° C., and 90 ° C. were 99.3%, 98.3%, and 97.5%, respectively. Each ion density at 23 ° C. and 60 ° C., was ^{31pC / cm 2, 152pC / cm} 2.
(Comparative Example 5)
A liquid crystal cell was produced in the same manner as in Example 8 except that the liquid crystal aligning agent (B2-1) obtained in Comparative Example 4 was used. For this liquid crystal cell, the voltage holding ratio was measured, and then the ion density was measured. The voltage holding ratios at 23 ° C., 60 ° C., and 90 ° C. were 98.8%, 97.1%, and 95.2%, respectively. Each ion density at 23 ° C. and 60 ° C., was ^{131pC / cm 2, 313pC / cm} 2.

When the liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention is used as a liquid crystal display device, it achieves a high voltage holding ratio and a low ion density even at high temperatures, has high reliability, and further has an IPS driving method. In the case of the liquid crystal display element of the FFS driving method, the residual image generated by the AC driving is reduced and the residual charge accumulated by the DC voltage is quickly relaxed, so that the afterimage characteristics are excellent, and the IPS driving method and the FFS driving method. It is useful as a liquid crystal alignment film for liquid crystal display elements and liquid crystal televisions.
The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2011-225275 filed on October 12, 2011 are incorporated herein as the disclosure of the specification of the present invention. Is.

Claims (14)

A liquid crystal aligning agent comprising a polyamic acid obtained from tetracarboxylic dianhydride and a diamine, a compound represented by the following formula (1), and an organic solvent.

(In Formula (1), each D is independently a t-butoxycarbonyl group or a 9-fluorenylmethoxycarbonyl group.)   The liquid crystal aligning agent according to claim 1, wherein the polyamic acid has a weight average molecular weight of 2,000 to 500,000 and a number average molecular weight of 1,000 to 250,000.   The organic solvent is N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone At least one selected from the group consisting of N-vinyl-2-pyrrolidone, dimethyl sulfoxide, dimethyl sulfone, γ-butyrolactone, 1,3-dimethyl-imidazolidinone and 3-methoxy-N, N-dimethylpropanamide The liquid crystal aligning agent of Claim 1 or 2.   The compound represented by the formula (1) is N-α- (9-fluorenylmethoxycarbonyl) -N-τ-t-butoxycarbonyl-L-histidine. Liquid crystal aligning agent.   The liquid crystal aligning agent in any one of Claims 1-4 whose ratio of the compound represented by the said Formula (1) is 0.01-0.5 molar equivalent with respect to 1 mol of structural units of a polyamic acid.   The liquid crystal aligning agent in any one of Claims 1-5 whose density | concentration in the liquid crystal aligning agent of a polyamic acid is 1 mass%-10 mass% or less. The polyamic acid is a polyamic acid obtained from a tetracarboxylic acid containing at least one tetracarboxylic acid selected from the group consisting of a structure represented by the following formula (2) and a diamine. The liquid crystal aligning agent of description.

(In the formula (2), X ₁ represents the following formulas (X-1), (X-2), (X-3), (X-4), (X-5), (X-6), ( X-7), (X-8), (X-9), (X-10), (X-11), (X-12), (X-13) and (X-14) (At least one selected from the group consisting of structures)

(In the above formula, R ₁ , R ₂ , R ₃ , and R ₄ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or an alkenyl group. Or a phenyl group.)   The tetracarboxylic dianhydride represented by the above formula (2) is contained in an amount of 0.6 to 1.0 mole equivalent based on 1.0 mole of all tetracarboxylic dianhydrides. The liquid crystal aligning agent of crab. X ₁ is, the liquid crystal alignment agent according to any one of claims 1 to 8 is at least one kind of Bareru independently from the group consisting of structures represented by the following formula (X1-1) and (Xl-2).

The liquid crystal aligning agent in any one of Claims 1-9 in which a diamine contains the at least 1 sort (s) of diamine chosen from the group which consists of a structure represented by following formula (3).

(In Formula (3), Y ₁ is at least one selected from the group consisting of structures represented by the following formula.)

  The liquid crystal aligning film obtained by apply | coating and baking the liquid crystal aligning agent in any one of Claims 1-10.   The liquid crystal aligning film obtained by apply | coating and baking the liquid crystal aligning agent in any one of Claims 1-10, and also irradiating the polarized radiation.   The liquid crystal alignment film according to claim 12, wherein the wavelength of radiation to be irradiated is 100 to 400 nm.   The liquid crystal display element which comprises the liquid crystal aligning film in any one of Claims 11-13.