JP6064997B2 - Polyimide-based liquid crystal alignment treatment agent, liquid crystal alignment film, and liquid crystal display element - Google Patents

Description

  The present invention relates to a polyimide-based liquid crystal alignment treatment agent, a liquid crystal alignment film using the same, and a liquid crystal display element.

The liquid crystal display element has a structure in which liquid crystal molecules are sandwiched between liquid crystal alignment films formed on a substrate, and is a display element utilizing the response of the liquid crystal molecules by voltage.
The liquid crystal alignment film has an important role of controlling the alignment direction and pretilt angle of the liquid crystal molecules in an arbitrary state.
The liquid crystal alignment film is generally produced by performing a so-called “rubbing process” in which the surface of a polyimide film formed on a substrate is rubbed against the surface with rayon, nylon cloth, or the like. The rubbing treatment determines the alignment direction of the liquid crystal molecules.
As means for increasing the pretilt angle of the liquid crystal, means for introducing a long-chain alkyl group into the structure of the polyimide forming the liquid crystal alignment film is known (for example, see Patent Document 1).

  As a means for forming a polyimide film on the substrate, there are a method of applying a solution such as polyamic acid and imidizing on the substrate, and a method of applying a soluble polyimide solution. Among them, the method using a soluble polyimide solution is capable of forming a polyimide film with good characteristics when used as a liquid crystal alignment film, even when firing at a relatively low temperature, but the formed film There is a problem that the strength of the film is low, and the rubbing treatment tends to cause scratches and peeling of the film surface.

In addition, flexographic printing is widely used industrially as a means for applying a polymer solution to a substrate when preparing a liquid crystal alignment film. However, since a solution of a soluble polyimide having a high imidization rate is inferior in printability such as causing a whitening phenomenon, it is necessary to devise such as using a mixture of soluble polyimides having a low imidization rate (for example, Patent Document 2). reference).
Furthermore, when a long-chain alkyl group is introduced into the structure of the soluble polyimide in order to give a large pretilt angle to the liquid crystal, this printability tends to deteriorate.
As means for improving the printability of a polymer solution on a substrate, a method of adding a solvent such as butyl cellosolve is known (for example, see Patent Document 3).
However, since soluble polyimide generally has lower solubility than polyamic acid and the like, a solvent such as butyl cellosolve cannot be used in a large amount.

Japanese Unexamined Patent Publication No. 2-282726 Japanese Unexamined Patent Publication No. 9-297312 Japanese Unexamined Patent Publication No. 2-037324

  The object of the present invention is to obtain a liquid crystal alignment film having good rubbing resistance, good printability even when the imidization ratio of soluble polyimide is high, voltage holding ratio (VHR), accumulated charge ( An object of the present invention is to provide a polyimide-based liquid crystal aligning agent containing soluble polyimide having excellent electrical characteristics such as (RDC).

The present inventor conducted research to improve the printing characteristics at the time of film formation without impairing the characteristics and electrical characteristics of the polyimide-based liquid crystal aligning agent containing the soluble polyimide. It discovered that the liquid-crystal aligning agent containing the polyamic acid ester which has a specific structure with the soluble polyimide which has can achieve this objective.
That is, the liquid crystal aligning agent containing a polyamic acid ester having a specific structure together with a soluble polyimide having a specific structure does not cause a whitening phenomenon at the time of coating film formation even if the imidization rate is high, and has good printability. In addition, it is possible to provide a liquid crystal alignment film having good coating film rubbing resistance. Further, the obtained liquid crystal alignment film was found to have excellent electrical characteristics, and in particular, has excellent characteristics that are not found in the past in terms of voltage holding ratio and accumulated charge (RDC).

（式（１）中、Ｘ_１は４価の有機基であり、Ｙ_１は２価の有機基である。式（２）中、Ｘ_２は４価の有機基であり、Ｙ_２は２価の有機基であり、Ｒ_１は、炭素数１〜５のアルキル基である。Ａ_１及びＡ_２は、それぞれ独立して、水素原子、又は置換基を有してもよい炭素数１〜１０のアルキル基、アルケニル基若しくはアルキニル基である。）
２．式（２）中のＲ_１がメチル基である上記１に記載の液晶配向処理剤。
３．式（１）、式（２）におけるＸ_１及びＸ_２が、それぞれ独立して、下記式で表される構造から選ばれる少なくとも１種である上記１又は２に記載の液晶配向処理剤。

４．式（２）において、Ｘ_２が芳香族環を有する以下の構造である上記１〜３のいずれかに記載の液晶配向処理剤。

５．式（１）において、Ｘ_１が脂肪族構造又は脂環式構造を有する上記１〜３のいずれかに記載の液晶配向処理剤。
６．前記ポリアミック酸エステルの重量平均分子量が、５，０００〜２００，０００ある上記１〜５のいずれかに記載の液晶配向処理剤。
７．前記可溶性ポリイミドが、イミド化率５０％以上を有し、かつ重量平均分子量が５，０００〜２００，０００である上記１〜６のいずれかに記載の液晶配向処理剤。
８．前記可溶性ポリイミドの含有量と前記ポリアミック酸エステルの含有量との比（可溶性ポリイミドの含有量／ポリアミック酸エステルの含有量）が、質量比率で１／９〜９／１である上記１〜７のいずれかに記載の液晶配向処理剤。That is, this invention is made | formed based on said knowledge, and has the following summary.
1. A liquid crystal aligning agent comprising a soluble polyimide represented by the following formula (1) and a polyamic acid ester represented by the following formula (2).

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

4). In the formula (2), a liquid crystal alignment treating agent according to any one of 1 to 3 X ₂ are the following structures having an aromatic ring.

5. In the formula (1), a liquid crystal alignment treating agent according to any one of the above 1 to 3 in which X ₁ having an aliphatic structure or alicyclic structure.
6). The liquid-crystal aligning agent in any one of said 1-5 whose weight average molecular weights of the said polyamic acid ester are 5,000-200,000.
7). 7. The liquid crystal aligning agent according to any one of 1 to 6, wherein the soluble polyimide has an imidization ratio of 50% or more and has a weight average molecular weight of 5,000 to 200,000.
8). The ratio of the content of the soluble polyimide and the content of the polyamic acid ester (the content of the soluble polyimide / the content of the polyamic acid ester) is 1/9 to 9/1 by mass ratio. The liquid-crystal aligning agent in any one.

9. The organic solvent which dissolves the soluble polyimide and the polyamic acid ester, and the total content of the soluble polyimide and the polyamic acid ester is 0.5 to 15% by mass with respect to 100% by mass of the organic solvent. The liquid-crystal aligning agent in any one of 1-8.
10. 10. The liquid crystal aligning agent according to 9 above, wherein the organic solvent contains at least one selected from the group consisting of N-methyl-pyrrolidone, N-ethyl-pyrrolidone, and γ-butyrolactone.
11. Furthermore, the liquid-crystal aligning agent in any one of said 1-10 containing a solvent.
12 12. The liquid crystal aligning agent according to 11 above, wherein the solvent is butyl cellosolve.
13. The liquid crystal aligning film obtained by apply | coating and baking the liquid-crystal aligning agent in any one of said 1-12.
14 14. The liquid crystal alignment film as described in 13 above, wherein the coating film obtained by applying and baking the liquid crystal alignment treatment agent has a thickness of 5 to 300 nm.
15. 15. A liquid crystal display device comprising the liquid crystal alignment film as described in 13 or 14 above.

According to the liquid crystal aligning agent of the present invention, even if the imidization ratio of the soluble polyimide is high, the liquid crystal has good printability without causing a whitening phenomenon at the time of coating film formation, and good rubbing resistance of the coating film. An alignment film is obtained. Further, the obtained liquid crystal alignment film has excellent electrical characteristics, and in particular, has excellent characteristics that are not present in terms of voltage holding ratio and accumulated charge (RDC).
In the present invention, by using a polyamic acid ester, the polarity and fat solubility are close to those of a soluble polyimide. Therefore, the polyamic acid ester does not have two layers as shown below, and the polyamic acid ester has a concentration at the interface in contact with the liquid crystal. It seems that it exists in.

On the other hand, when a polyamic acid is used instead of the polyamic acid ester contained in the liquid crystal aligning agent of the present invention, the whitening phenomenon at the time of coating film formation is improved, but the obtained liquid crystal alignment film has a voltage holding Results in unsatisfactory results in properties such as rate, stored charge (RDC), etc.
When polyamic acid is used instead of polyamic acid ester, the cause of deterioration in electrical characteristics is not always clear, but when polyamic acid is used, the polarity and fat solubility are different from soluble polyimide, so liquid crystal alignment This is probably due to a two-layer system in which a soluble polyimide component is located in the upper layer of the film and a polyamic acid component is located in the lower layer.

<Soluble polyimide>
The soluble polyimide used in the present invention has a structure represented by the following formula (1).

In the above formula (1), X ₁ is a tetravalent organic group.
If Specific preferred examples of X _1, include X-1 to X-46 shown below. Of the availability of monomers, _{X 1} is, X-1, X-2 , X-3, X-4, X-5, X-6, X-8, X-16, X-19, X-21, X-25, X-26, X-27, X-28 or X-32 is preferred.
Of these, X ₁ is, in a case having an aliphatic structure or alicyclic structure is preferable because the resulting liquid crystal alignment film has a high voltage holding ratio characteristics. X ₁ having a preferred aliphatic structure is preferably X-1, X-16, X-19, and particularly preferably X-1, X-19.

In Formula (1), Y ₁ is a divalent organic group and is not particularly limited. Preferable specific examples of Y ₁ include the following Y- ₁ to Y-97.
Among these, as _{Y 1, 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 and Y-98 are more preferred, and diamine compounds having these structures are preferred.

Y ₁ is Y-76, Y-77, Y-78, Y-79, Y-80, Y-81, Y-82, Y-83, Y-84, Y-85, Y-86, When Y-87, Y-88, Y-89, Y-90, Y-91, Y-92, Y-93, Y-94, Y-95, Y-96, or Y-97, The pretilt angle can be increased.

The soluble polyimide used in the present invention can be obtained by imidizing a polyimide precursor by a known method. A polyimide precursor means a polyamic acid or a polyamic acid ester.
In the case of using a polyamic acid in imidization, the polyamic acid is produced by dehydrating and ring-closing, and in the case of using a polyamic acid ester, the polyamic acid ester is produced by heating and ring-closing.
Among them, in the present invention, the method of dehydrating and ring-closing polyamic acid is more preferable because the imidization rate can be increased.
The imidation ratio of the soluble polyimide in the present invention can be controlled by adjusting the amount of catalyst, reaction temperature, reaction time, etc. in the imidization reaction. In the present invention, since a polyimide having a high imidization rate can be used, the imide rate is preferably 50% or more, more preferably 70% or more, and particularly preferably 80% or more. Especially, as for the imidation rate, 80 to 90% is more preferable.

A polyamic acid is obtained by a known method by the reaction of a diamine component and a tetracarboxylic acid dihydrate.
The polyamic acid ester can be reacted with a diamine component and a tetracarboxylic acid diester dichloride in the presence of a base or a tetracarboxylic acid diester and a diamine in the presence of an appropriate condensing agent or base according to a known method. Can be obtained.

上記式（２）において、Ｒ_１は炭素数１〜５のアルキル基である。
ポリアミック酸エステルは、アルキル基における炭素数が増えるに従ってイミド化が進行する温度が高くなる。そのため、Ｒ₁は、熱によるイミド化のしやすさの観点から、炭素数１又は２のアルキル基、特にメチル基が好ましい。
上記式（２）において、Ｘ_２は、上記式（１）におけるＸ_１と、上記式（２）のＹ_２は、上記式（１）におけるＹ_１と、それぞれ同じ定義を有する。なかでも、式（２）におけるＸ_２が、芳香族構造を有する場合は、得られる液晶配向膜が高い電圧保持率特性を有するために好ましい。芳香族構造を有する好ましいＸ_２としては、上記したＸ−２６〜Ｘ−４５が挙げられ、特には、Ｘ−２６が好ましい。<Polyamic acid ester>
The polyamic acid ester used in the present invention has a structure represented by the following formula (2).

In the above formula (2), R ₁ is an alkyl group having 1 to 5 carbon atoms.
In the polyamic acid ester, the temperature at which imidization proceeds increases as the number of carbon atoms in the alkyl group increases. Therefore, R ₁ is preferably an alkyl group having 1 or 2 carbon atoms, particularly a methyl group, from the viewpoint of ease of imidization by heat.
In the above formula (2), _{X 2} includes an _{X 1} in the formula (1), _{Y 2} in the formula (2), and _{Y 1} in the formula (1), the same definition, respectively. Among them, X ₂ in the formula (2) is, when having an aromatic structure is preferable because the resulting liquid crystal alignment film has a high voltage holding ratio characteristics. Preferred X ₂ having an aromatic structure includes X-26 to X-45 described above, and X-26 is particularly preferable.

In the above formula (2), A ₁ and A ₂ are each independently a hydrogen atom or a C 1-10 alkyl group, alkenyl group or alkynyl group which may have a substituent.
Specific examples of the alkyl group having 1 to 10 carbon atoms that may have a substituent 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, and a cyclopentyl group. , A cyclohexyl group, a bicyclohexyl group, and the like.
Examples of the alkenyl group having 1 to 10 carbon atoms that may have a substituent include those in which one or more CH ₂ —CH ₂ structures present in the above alkyl group are replaced with a CH═CH structure, More specifically, vinyl group, allyl group, 1-propenyl group, isopropenyl group, 2-butenyl group, 1,3-butadienyl group, 2-pentenyl group, 2-hexenyl group, cyclopropenyl group, cyclopentenyl group And cyclohexenyl group.
Examples of the alkynyl group having 1 to 10 carbon atoms which may have a substituent 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 Specific examples include an ethynyl group, a 1-propynyl group, and a 2-propynyl group.
A ₁ and A ₂ are each independently preferably a hydrogen atom, a methyl group, an ethyl group, a vinyl group or an allyl group, more preferably a hydrogen atom or a methyl group.

  The above alkyl group, alkenyl group, and alkynyl group may have a substituent as long as it has 1 to 10 carbon atoms 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.

（上記式中、Ｘ_２、Ｙ_２、Ｒ_１、Ａ_１及びＡ_２はそれぞれ上記で定義したとおりである。）The polyamic acid ester represented by the above formula (2) is obtained by a reaction between any of the tetracarboxylic acid derivatives represented by the following formulas (6) to (8) and the diamine compound represented by the formula (9). be able to.

(In the above formula, X ₂ , Y ₂ , R ₁ , A ₁ and A ₂ are as defined above.)

The polyamic acid ester represented by the above formula (2) can be synthesized by any of the methods (A) to (C) described below.
(A) When synthesizing from polyamic acid The polyamic acid ester can be synthesized by esterifying a polyamic acid obtained from tetracarboxylic dianhydride and diamine.

Specifically, it is synthesized by reacting a polyamic acid and an esterifying agent in the presence of an organic solvent at -20 to 150 ° C, preferably 0 to 50 ° C, for 30 minutes to 24 hours, preferably 1 to 4 hours. can do.
As the esterifying agent, those that can be easily removed by purification are preferred, and N, N-dimethylformamide dimethyl acetal, N, N-dimethylformamide diethyl acetal, N, N-dimethylformamide dipropyl acetal, N, N-dimethylformamide Dineopentyl butyl acetal, N, N-dimethylformamide di-t-butyl acetal, 1-methyl-3-p-tolyltriazene, 1-ethyl-3-p-tolyltriazene, 1-propyl-3-p -Tolyltriazene, 4- (4,6-dimethoxy-1,3,5-triazin-2-yl) -4-methylmorpholinium chloride and the like. Of these, N, N-dimethylformamide dimethyl acetal is preferable.
The addition amount of the esterifying agent is preferably 2 to 6 molar equivalents, more preferably 3 to 4 molar equivalents, per 1 mol of the polyamic acid repeating unit.

The organic solvent used in the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone from the viewpoint of the solubility of the polymer. These may be used alone or in combination. It may be used.
The concentration of the polymer at the time of synthesis is preferably 1 to 30% by mass and more preferably 5 to 20% by mass from the viewpoint that polymer precipitation is difficult to occur and a high molecular weight body is easily obtained.

(B) When synthesizing by reaction of tetracarboxylic acid diester dichloride and diamine The polyamic acid ester can be synthesized from tetracarboxylic acid diester dichloride and diamine.

Specifically, tetracarboxylic acid diester dichloride and diamine are -20 to 150 ° C., preferably 0 to 50 ° C., in the presence of a base and an organic solvent, for 30 minutes to 24 hours, preferably 1 to 4 hours. It can be synthesized by reacting.
As the base, pyridine, triethylamine, 4-dimethylaminopyridine and the like can be used, but pyridine is preferable because the reaction proceeds gently.
The addition amount of the base is preferably 2 to 4 times mol, more preferably 2 to 3 times mol with respect to the tetracarboxylic acid diester dichloride, from the viewpoint of easy removal and high molecular weight.

The organic solvent used in the above reaction is preferably N-methyl-2-pyrrolidone or γ-butyrolactone from the solubility of the monomer and polymer, and these may be used alone or in combination.
The polymer concentration at the time of synthesis is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass from the viewpoint that polymer precipitation hardly occurs and a high molecular weight body is easily obtained.
In order to prevent hydrolysis of the tetracarboxylic acid diester dichloride, the organic solvent used for the synthesis of the polyamic acid ester is preferably dehydrated as much as possible, and it is preferable to prevent mixing of outside air in a nitrogen atmosphere.

(C) When a polyamic acid is synthesized from a tetracarboxylic acid diester and a diamine The polyamic acid ester can be synthesized by polycondensation of a tetracarboxylic acid diester and a diamine.

Specifically, tetracarboxylic acid diester and diamine are added in the presence of a condensing agent, a base, and an organic solvent at 0 to 150 ° C., preferably at 0 to 100 ° C., for 30 minutes to 24 hours, preferably 3 to 15 hours. It can synthesize | combine by making it react for time.
Condensation agents include triphenyl phosphite, dicyclohexylcarbodiimide, 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride, N, N′-carbonyldiimidazole, dimethoxy-1,3,5-triazinyl Methylmorpholinium, O- (benzotriazol-1-yl) -N, N, N ′, N′-tetramethyluronium tetrafluoroborate, O- (benzotriazol-1-yl) -N, N, N ′, N′-tetramethyluronium hexafluorophosphate, (2,3-dihydro-2-thioxo-3-benzoxazolyl) phosphonate diphenyl, and the like can be used.
The amount of the condensing agent added is preferably 2 to 3 moles, more preferably 2 to 2.5 moles, relative to the tetracarboxylic acid diester.

As the base, tertiary amines such as pyridine and triethylamine can be used.
The addition amount of the base is preferably 2 to 4 times mol, more preferably 2 to 3 times mol with respect to the diamine component, from the viewpoint that it can be easily removed and a high molecular weight product can be easily obtained.
As the organic solvent used in the above reaction, N-methyl-2-pyrrolidone and γ-butyrolactone are preferable in view of the solubility of the monomer and the polymer, and these may be used alone or in combination.
In the above reaction, the reaction proceeds efficiently by adding Lewis acid as an additive. As the Lewis acid, lithium halides such as lithium chloride and lithium bromide are preferable. The addition amount of the Lewis acid is preferably 0 to 1.0-fold mol, more preferably 0.2 to 0.5-fold mol based on the diamine component.

Among the methods for synthesizing the three polyamic acid esters, a high molecular weight polyamic acid ester is obtained, and therefore the method (A) or the method (B) is particularly preferable.
The polyamic acid ester solution obtained as described above can be polymerized by pouring into a poor solvent while stirring well. Precipitation is performed several times, washed with a poor solvent, and then dried at room temperature or by heating to obtain a purified polyamic acid ester powder.
Although a poor solvent is not specifically limited, Water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene etc. are mentioned, Methanol and ethanol are preferable.

<Liquid crystal alignment agent>
The liquid-crystal aligning agent of this invention contains the soluble polyimide represented by above-described Formula (1), and the polyamic acid ester represented by Formula (2). Usually, the liquid-crystal aligning agent of this invention is a form of the solution which melt | dissolved the soluble polyimide and the polyamic acid ester (henceforth a polymer may be mentioned collectively) in the organic solvent. As long as it has such a solution form, for example, when a polyamic acid ester and / or polyamic acid is synthesized in an organic solvent, the resulting reaction solution itself may be used. It may be diluted. When the polyamic acid ester and / or polyamic acid is obtained as a powder, it may be dissolved in an organic solvent to form a solution.

The weight average molecular weight of the soluble polyimide is preferably from 5,000 to 200,000, more preferably from 10,000 to 100,000, in view of solubility in an organic solvent. The number average molecular weight is preferably 5,000 to 100,000, and more preferably 10,000 to 50,000.
On the other hand, the weight average molecular weight of the polyamic acid ester is preferably 5,000 to 200,000, and more preferably 10,000 to 100,000. The number average molecular weight is preferably 5,000 to 100,000, and more preferably 10,000 to 50,000.

  In the liquid crystal aligning agent of the present invention, the content of the polyimide and the content of the polyamic acid ester are preferably polyamic acid ester / polyamic acid (mass ratio), and preferably 1/9 to 9/1. Is 2/8 to 8/2, particularly preferably 3/7 to 7/3. By setting the ratio within this range, it is possible to provide a liquid crystal alignment treatment agent having both good liquid crystal alignment properties and electrical characteristics.

The content (concentration) of the polymer in the liquid crystal alignment treatment agent of the present invention can be appropriately changed depending on the thickness of the liquid crystal alignment film to be formed, but from the viewpoint of forming a uniform and defect-free coating film. The content of the polymer component is preferably 0.5% by mass or more with respect to 100% by mass of the organic solvent, and is preferably 15% by mass or less, more preferably 1 to 10% by mass from the viewpoint of storage stability of the solution. %.
In this case, a solution having a high concentration of polymer may be prepared in advance, and the concentrated solution may be diluted when used as a liquid crystal alignment treatment agent. The concentration of the concentrated solution of the polymer component is preferably 10 to 30% by mass, and more preferably 10 to 15% by mass.
Alternatively, the polymer component powder may be heated when dissolved in an organic solvent to prepare a solution. The heating temperature is preferably 20 to 150 ° C, particularly preferably 20 to 80 ° C.

The organic solvent contained in the liquid-crystal aligning agent of this invention will not be specifically limited if a polymer component melt | dissolves 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. Of these, those having high polarity such as N-methyl-pyrrolidone and N-ethyl-pyrrolidone are preferable from the viewpoint of solubility.
As an organic solvent, you may use 1 type or in mixture of 2 or more types. Moreover, even if it is an organic solvent in which a polymer component cannot be melt | dissolved uniformly by itself, if it is a range which a polymer does not precipitate, you may mix and use.

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, butyl cellosolve acetate, 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, 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. Of these, butyrocellosolve, ethyl carbitol and the like are preferably used. Two types of these solvents may be used in combination.
In the liquid crystal alignment treatment agent of the present invention, the above organic solvent for dissolving the polymer component and the solvent for improving the uniformity of the coating film may be used in combination, The volume ratio is 30/70 to 90/10, preferably 60/40 to 80/20.

  Moreover, the liquid-crystal aligning agent of this invention may contain various additives, such as a silane coupling agent and a crosslinking agent. The silane coupling agent is added for the purpose of improving the adhesion between the substrate on which the liquid crystal alignment treatment agent is applied and the liquid crystal alignment film formed thereon. Although the specific example of a silane coupling agent is given to the following, it is not limited to this.

  3-aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-phenylaminopropyltri Amine-based silane coupling agents such as methoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, 3-aminopropyldiethoxymethylsilane; vinyltrimethoxysilane, vinyltriethoxysilane, Vinyl-based silane couplings such as vinyltris (2-methoxyethoxy) silane, vinylmethyldimethoxysilane, vinyltriacetoxysilane, vinyltriisopropoxysilane, allyltrimethoxysilane, p-styryltrimethoxysilane Agents: 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4- Epoxy cyclohexyl) Epoxy silane coupling agent such as ethyltrimethoxysilane; 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltri Methacrylic silane coupling agents such as ethoxysilane; Acrylic silane coupling agents such as 3-acryloxypropyltrimethoxysilane; Ureido silane cups such as 3-ureidopropyltriethoxysilane Sulfide-based silane coupling agents such as bis (3- (triethoxysilyl) propyl) disulfide and bis (3- (triethoxysilyl) propyl) tetrasulfide; 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyl Mercapto silane coupling agents such as trimethoxysilane and 3-octanoylthio-1-propyltriethoxysilane; Isocyanate silane coupling agents such as 3-isocyanatopropyltriethoxysilane and 3-isocyanatopropyltrimethoxysilane; Aldehyde-based silane coupling agents such as butyraldehyde; carbamates such as triethoxysilylpropylmethylcarbamate and (3-triethoxysilylpropyl) -t-butylcarbamate Mate silane coupling agent.

If the amount of the silane coupling agent added is too large, unreacted ones may adversely affect the liquid crystal orientation, and if too small, the effect on adhesion will not appear, so the amount of the silane coupling agent is 0 with respect to the solid content of the polymer. 0.01 to 5.0% by weight is preferable, and 0.1 to 1.0% by weight is more preferable.
When adding the said silane coupling agent, in order to prevent precipitation of a polymer, it is preferable to add before adding the solvent for improving the above-mentioned coating-film uniformity. Also, when adding a silane coupling agent, add it to the polyamic acid ester solution, the polyamic acid solution, or both the polyamic acid ester solution and the polyamic acid solution before mixing the polyamic acid ester solution and the polyamic acid solution. Can do. Moreover, it can add to the mixed solution of polyamic acid ester and polyamic acid.
Since the silane coupling agent is added for the purpose of improving the adhesion between the polymer and the substrate, as a method for adding the silane coupling agent, the silane coupling agent is added to a polyamic acid solution that can be unevenly distributed in the film and the substrate interface, and the polymer is added. A method in which the silane coupling agent is sufficiently reacted with the polyamic acid ester solution is more preferable.
After applying the liquid crystal aligning agent of this invention to a board | substrate, in order to advance the imidation of polyamic acid ester efficiently, when baking a coating film, you may add an imidation promoter.
Although the specific example of the imidation promoter of polyamic acid ester is given to the following, it is not limited to this.

D in the above formulas (B-1) to (B-17) is each independently a tert-butoxycarbonyl group or a 9-fluorenylmethoxycarbonyl group. In (B-14) to (B-17), there are a plurality of Ds in one formula, but these may be the same or different.
The content of the imidization accelerator is not particularly limited as long as the effect of promoting thermal imidation of the polyamic acid ester is obtained, but the following formula contained in the polyamic acid ester in the liquid crystal aligning agent is not limited. Preferably it is 0.01 mol or more with respect to 1 mol of amic acid ester site | part of (12), More preferably, it is 0.05 mol or more, More preferably, it is 0.1 mol or more. In addition, since the imidization accelerator itself remaining in the film after baking minimizes adverse effects on various properties of the liquid crystal alignment film, the following formula (included in the polyamic acid ester in the liquid crystal alignment treatment agent ( The amount of the imidization accelerator is preferably 2 mol or less, more preferably 1 mol or less, and still more preferably 0.5 mol or less with respect to 1 mol of the amic acid ester moiety 12).

イミド化促進剤を添加する場合は、加熱することでイミド化が進行する可能性があるため、良溶媒及び貧溶媒で希釈した後に加えるのが好ましい。

When adding an imidization accelerator, since imidation may advance by heating, it is preferable to add after diluting with a good solvent and a poor solvent.

<Liquid crystal alignment film>
The liquid crystal alignment film of this invention is a film | membrane obtained by apply | coating the said liquid-crystal aligning agent to a board | substrate, drying, and baking.
The substrate to which the liquid crystal alignment treatment agent of the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, an acrylic substrate, a polycarbonate substrate such as a polycarbonate substrate, or the like can be used. It is preferable to use a substrate on which an ITO electrode or the like for driving is formed from the viewpoint of simplification of the process. In the reflective liquid crystal display element, an opaque material such as a silicon wafer can be used as long as only one substrate is used. In this case, a material that reflects light such as aluminum can be used as the electrode.

Examples of the method for applying the liquid crystal aligning agent of the present invention include spin coating, printing, and inkjet. Arbitrary temperature and time can be selected for the drying and baking process after apply | coating the liquid-crystal aligning agent of this invention. Usually, in order to sufficiently remove the organic solvent contained, it is dried at 50 to 120 ° C. for 1 minute to 10 minutes, preferably at 60 to 100 ° C. for 2 to 5 minutes, and then at 150 to 300 ° C. for 5 minutes to 120 minutes. Baked at a temperature of 180 to 230 ° C. for 10 to 60 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.

  Examples of a method for aligning the obtained liquid crystal alignment film include a rubbing method and a photo-alignment processing method. The liquid crystal aligning agent of the present invention is particularly useful when used in the rubbing method.

[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 in which liquid crystal is injected after reducing the pressure inside the manufactured liquid crystal cell, and a dropping method in which sealing is performed after dropping the liquid crystal.

Hereinafter, the present invention will be specifically described with reference to examples. However, it goes without saying that the present invention is not construed as being limited to these examples.
In addition, the symbol used by an Example and a comparative example and the measuring method of each characteristic are as follows.

(Tetracarboxylic dianhydride)
CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride PMDA: 2,5-bis (methoxycarbonyl) terephthalic acid TDA: 3,4-dicarboxy-1,2,3,4-tetrahydro-1 -Naphthalene succinic dianhydride (dicarboxylic acid diester)
CBDE: 2,4-bis (methoxycarbonyl) cyclobutane 1,3-dicarboxylic acid PMDE: 2,5-bis (methoxycarbonyl) terephthalic acid (diamine)
Me-DADPA: N1- (4-aminophenyl) -N1-methylbenzene-1,4-diamine DADPA: 4,4′-diaminodiphenylamine p-PDA: p-phenylenediamine DDM: 4,4′-diaminodiphenylmethane B76 : 2,4-diamino-N, N-diallylaniline 3-ABA: 3- (aminomethyl) aniline C16DAB: 4-hexadecyloxy-1,3-diaminobenzene C18DAB: 4-octadecyloxy-1,3-diamino benzene

(Condensing agent)
DMT-MM: 4- (4,6-dimethoxy-1,3,5-triazin-2-yl) -4-methylmorpholin-4-nium (organic solvent)
NMP: N-methyl-2-pyrrolidone BC: Butyl cellosolve γ-BL: γ-butyrolactone

Example 1
CBDA (70) PMDA / B76 (30) 3ABA (50) APC16
As tetracarboxylic dianhydride component, 13.53 g (0.069 mol) of CBDA, 6.54 g (0.030 mol) of PMDA, 6.10 g (0.030 mol) of B76 as diamine component, 3-ABA Using 6.11 g (0.050 mol) and 6.96 g (0.020 mol) of C18DAB, the reaction was performed in 222.39 g of NMP at room temperature for 24 hours to obtain a polyamic acid solution (PAA-1).

  To 20.00 g of polyamic acid solution (PAA-1), 30.00 g of NMP, 3.90 g of acetic anhydride, and 1.81 g of pyridine were added, stirred at room temperature for 30 minutes, and then stirred at 50 ° C. for 3 hours to react. I let you. After completion of the reaction, the mixture was slowly poured into 195 g of methanol to precipitate a polymer, stirred for 30 minutes, and a solid was collected by filtration. The obtained solid was sufficiently washed with methanol and then vacuum dried at 100 ° C. to obtain polyimide powder (SPI-1). The number average molecular weight of this polyimide was 13,600, the weight average molecular weight was 33,800, and the imidation ratio was 90%.

58.23 g of γ-BL was added to 6.47 g of polyimide powder (SPI-1) and dissolved by stirring at 50 ° C. for 24 hours to confirm that it was completely dissolved. Thereafter, 15.28 g of γ-BL and 19.73 g of BC were added, and the mixture was stirred at 50 ° C. for 24 minutes, so that polyimide was 6.0% by mass, γ-BL was 74% by mass, and BC was 20% by mass. A solution (SPI-1) was obtained. The obtained polyimide solution was used as a liquid crystal aligning agent (AL-1). Using this coating solution, rubbing resistance, whitening, and voltage holding ratio (VHR) were evaluated.
The evaluation results of rubbing resistance, whitening, and VHR obtained using the coating solution of Example 1 are shown in Table 1 together with the composition ratio (weight ratio) of the polymer solution.

(Example 2)
TDA / p-PDA (90) APC18
As a tetracarboxylic dianhydride component, 7.51 g (0.025 mol) of TDA, 2.43 g (0.023 mol) of p-PDA and 0.94 g (0.0025 mol) of C18DAB were used as a diamine component, The reaction was carried out at 50 ° C. for 24 hours in 61.66 g of NMP to obtain a polyamic acid solution (PAA-2).
30.67 g of NMP, 7.18 g of acetic anhydride, and 3.33 g of pyridine were added to 20.00 g of the polyamic acid solution (PAA-2), and the mixture was stirred at room temperature for 30 minutes and then stirred at 40 ° C. for 3 hours to be reacted. It was. After completion of the reaction, the mixture was slowly poured into 214 g of methanol to precipitate a polymer, stirred for 30 minutes, and a solid was collected by filtration. The obtained solid was sufficiently washed with methanol and then vacuum dried at 100 ° C. to obtain polyimide powder (SPI-2). The number average molecular weight of this polyimide was 12,400, the weight average molecular weight was 27,400, and the imidation ratio was 86%.

  29.90 g of γ-BL was added to 2.60 g of polyimide powder (SPI-2), and dissolved by stirring at 50 ° C. for 24 hours to confirm complete dissolution. Thereafter, 2.16 g of γ-BL and 8.67 g of BC were added and stirred at 50 ° C. for 24 minutes, so that polyimide was 6.0% by mass, γ-BL was 94% by mass, and BC was 20% by mass. A solution (SPI-2) was obtained. The obtained polyimide solution was used as a liquid crystal aligning agent (AL-2). Evaluation similar to Example 1 was performed using this coating liquid.

(Example 3)
CBDE (50) PMDE / DDM
As the dicarboxylic acid diester component, 11.97 g (0.046 mol) of CBDE, 14.12 g (0.050 mol) of PMDE, 19.83 g (0.10 mol) of DDM as the diamine component, and 5.3% of triethylamine as the base. 10 g (0.050 mol), 83.20 g (0.30 mol) of DMT-MM was used as a condensing agent, and the mixture was reacted in NMP 719.18 g at room temperature for 3 hours to obtain a polyamic acid ester solution (PAE-1).

This polyamic acid ester solution was put into 4692 g of methanol, and the precipitated solid was recovered. Further, the solid was washed several times with methanol and then dried under reduced pressure at 100 ° C. to obtain a white powder of polyamic acid ester (PAE-1). The number average molecular weight of this polyamic acid ester was 12,900, and the weight average molecular weight was 28,800.
NMP15.77g was added to 2.15g of obtained polyamic acid ester (PAE-1), and it stirred at room temperature for 4 hours. At the end of stirring, the polyamic acid ester was completely dissolved. Further, 5.47 g of NMP and 9.20 g of BC were added to this solution, and the mixture was stirred at room temperature for 2 hours to prepare a solution containing 6% by mass of polyamic acid ester, 74% by mass of NMP, and 20% by mass of BC. The polyamic acid ester solution obtained by the preparation was used as a liquid crystal aligning agent (AL-3). Evaluation similar to Example 1 was performed using this coating liquid.

Example 4
CBDE / Me-DADPA (50) DADPA (30) DDM
As the dicarboxylic acid diester component, 8.57 g (0.033 mol) of CBDE, as the diamine component, 3.73 g (0.018 mol) of Me-DADPA, 2.10 g (0.011 mol) of DADDA, and 1.39 g of DDM. (0.0070 mol), using 1.81 g (0.018 mol) of triethylamine as a base and 25.19 g (0.091 mol) of DMT-MM as a condensing agent, and reacting at room temperature in 247.11 g of NMP for 4 hours. A polyamic acid ester solution (PAE-2) was obtained.

This polyamic acid ester solution was put into 1594 g of methanol, and the precipitated solid was recovered. Further, the solid was washed several times with methanol and then dried under reduced pressure at 100 ° C. to obtain a white powder of polyamic acid ester (PAE-2). The number average molecular weight of this polyamic acid ester was 12,300, and the weight average molecular weight was 33,500.
NMP 19.62g was added to 2.18g of obtained polyamic acid ester (PAE-2), and it stirred at room temperature for 5 hours. At the end of stirring, the polyamic acid ester was completely dissolved. Further, 1.01 g of γ-BL and 6.54 g of BC were added to this solution and stirred at room temperature for 1 hour. The polyamic acid ester was 6% by mass, γ-BL was 57% by mass, NMP was 17% by mass, and BC was 20% by mass. % Solution was prepared. The polyamic acid ester solution obtained by the preparation was used as a liquid crystal aligning agent (AL-4). Evaluation similar to Example 1 was performed using this coating liquid.

(Example 5)
CBDA (50) PMDA / DDM
As the tetracarboxylic dianhydride component, 9.81 g (0.050 mol) of CBDA, 10.25 g (0.047 mol) of PMDA, and 19.83 g (0.0060 mol) of DDM as the diamine component were used. A polyamic acid solution (PAA-1) was obtained by reacting in BL 113.00 g and NMP 113.00 g at room temperature for 3 hours.
198.97 g of polyamic acid solution (PAA-1) was diluted with 204.23 g of γ-BL, 14.63 g of NMP, and 73.74 g of BC, and the solid content (polyamic acid) was 6% by mass, γ-BL 59% by mass, A solution containing 20% by mass of NMP and 15% by mass of BC was prepared. This polyamic acid had a number average molecular weight of 20,900 and a weight average molecular weight of 57,900.

(Example 6)
(Example 1) / (Example 3) = 3/7
The polyimide solution (SPI-1) prepared in Example 1 and the polyamic ester acid solution (PAE-1) prepared in Example 3 were mixed so that the weight ratio was 30:70. The mixture was stirred for a time to obtain a liquid crystal aligning agent (AL-5). Evaluation similar to Example 1 was performed using this coating liquid.

(Example 7)
(Example 2) / (Example 3) = 3/7
The polyimide solution (SPI-2) prepared in Example 1 and the polyamic ester acid solution (PAE-1) prepared in Example 3 were mixed so that the weight ratio was 30:70. The mixture was stirred for a time to obtain a liquid crystal aligning agent (AL-6). Evaluation similar to Example 1 was performed using this coating liquid.

(Example 8)
(Example 1) / (Example 4) = 3/7
The polyimide solution (SPI-1) prepared in Example 1 and the polyamic ester acid solution (PAE-2) prepared in Example 4 were mixed so that the weight ratio was 30:70. The mixture was stirred for a time to obtain a liquid crystal aligning agent (AL-7). Evaluation similar to Example 1 was performed using this coating liquid.

Example 9
(Example 2) / (Example 4) = 3/7
The polyimide solution (SPI-2) prepared in Example 2 and the polyamic ester acid solution (PAE-2) prepared in Example 4 were mixed so that the weight ratio was 30:70. The mixture was stirred for a time to obtain a liquid crystal aligning agent (AL-8). Evaluation similar to Example 1 was performed using this coating liquid.

(Comparative Example 1)
(Example 2) / (Example 5) = 3/7
The polyimide solution (SPI-2) prepared in Example 2 and the polyamic acid solution (PAA-1) prepared in Example 5 were mixed so that the weight ratio was 30:70, and then at room temperature for 1 hour. The liquid crystal aligning agent was obtained by stirring (AL-9). Evaluation similar to Example 1 was performed using this coating liquid.

<Measurement of molecular weight>
The molecular weight of the polyimide obtained by the polymerization reaction was measured with a GPC (normal temperature gel permeation chromatography) apparatus, and the number average molecular weight and weight average molecular weight were calculated as polyethylene glycol and polyethylene oxide equivalent values.
GPC device: manufactured by Shodex (GPC-101)
Column: manufactured by Shodex (series of KD803 and KD805)
Column temperature: 50 ° C
Eluent: N, N-dimethylformamide (as additives, lithium bromide-hydrate (LiBr · H 2 O) is 30 mmol / L (liter), phosphoric acid / anhydrous crystal (o-phosphoric acid) is 30 mmol / L, Tetrahydrofuran (THF) 10ml / L)
Flow rate: 1.0 ml / min Standard sample for preparing 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 molecular weight manufactured by Polymer Laboratories) 1,000).

<Production of liquid crystal cell>
About the liquid crystal aligning agent prepared in Examples 1-4 and 6-10, the liquid crystal cell was produced as follows.
A liquid crystal alignment treatment agent is spin-coated on a glass substrate with a transparent electrode, dried on a 70 ° C. hot plate for 70 seconds, and then baked on a 210 ° C. hot plate for 10 minutes to form a coating film having a thickness of 100 nm. I let you. This coating film surface was rubbed with a rubbing apparatus having a roll diameter of 120 mm using a rayon cloth under the conditions of a roll rotation speed of 1000 rpm, a roll traveling speed of 50 mm / sec, and an indentation amount of 0.3 mm to obtain a substrate with a liquid crystal alignment film.
Next, two substrates with a liquid crystal alignment film are prepared, and a spacer of 6 μm is sprayed on the surface of one liquid crystal alignment film, and then a sealing agent is printed thereon, and another substrate is mounted on the liquid crystal alignment film surface. Were stuck together so that the rubbing direction was orthogonal, and then the sealing agent was cured to produce an empty cell. Liquid crystal MLC-2003 (Merck Japan Co., Ltd.) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain a twisted nematic liquid crystal cell.
A method for measuring physical properties and evaluating characteristics of each liquid crystal cell produced was described below.
In addition, results such as composition of each liquid crystal alignment treatment agent in Examples 2 to 4, Examples 6 to 9, and Comparative Example 1, measurement of physical properties of each liquid crystal alignment film, and evaluation of characteristics are summarized in Table 1. Indicated.

<Measurement of voltage holding ratio (VHR)>
The voltage holding ratio of the manufactured twisted nematic liquid crystal cell is measured by applying a voltage of 4 V for 60 μs at a temperature of 90 ° C. and measuring the voltage after 166.7 ms to determine how much the voltage can be held. Calculated as retention.
The voltage holding ratio was measured using a voltage holding ratio measuring device (VHR-1) manufactured by Toyo Technica.

<Estimation of accumulated charge (RDC)>
A calibration curve was created by applying a DC voltage to the produced twisted nematic liquid crystal cell at a temperature of 23 ° C. from 0 V to 1.0 V at intervals of 0.1 V, and measuring the flicker amplitude level at each voltage. After grounding for 5 minutes, AC voltage 3.0V and DC voltage 5.0V were applied, the flicker amplitude level after 1 hour was measured, and RDC was estimated by comparing it with a calibration curve prepared in advance (this (The RDC estimation method is called the flicker reference method.)
Here, RDC (after OFF) shows the value immediately after applying AC voltage 3.0V and DC voltage 5.0V for 1 hour, and RDC (after 5 minutes) is the AC voltage immediately after OFF and 30 minutes after OFF. Indicates the value of the accumulated charge.

According to the liquid crystal aligning agent of the present invention, even if the imidization ratio of the soluble polyimide is high, the liquid crystal has good printability without causing a whitening phenomenon at the time of coating film formation, and good rubbing resistance of the coating film. An alignment film can be obtained, and electrical characteristics such as voltage holding ratio (VHR) and accumulated charge (RDC) of the obtained liquid crystal alignment film are excellent. A liquid crystal display element having the liquid crystal alignment film is a TN element, STN It is widely useful for devices, TFT liquid crystal devices, and vertical alignment type liquid crystal display devices.
The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2012-082729 filed on March 30, 2012 are incorporated herein as the disclosure of the specification of the present invention. Is.

Claims (15)

A liquid crystal aligning agent comprising a soluble polyimide represented by the following formula (1) and a polyamic acid ester represented by the following formula (2).

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

The liquid crystal aligning agent according to any one of claims 1 to 3, wherein in the formula (2), X ₂ has the following structure having an aromatic ring.

In the formula (1), a liquid crystal alignment treating agent according to claim 1 wherein X ₁ having an aliphatic structure or alicyclic structure.   The liquid-crystal aligning agent in any one of Claims 1-5 whose weight average molecular weights of the said polyamic acid ester are 5,000-200,000.   The liquid-crystal aligning agent according to any one of claims 1 to 6, wherein the soluble polyimide has an imidation ratio of 50% or more and has a weight average molecular weight of 5,000 to 200,000.   The ratio (content of soluble polyimide / content of polyamic acid ester) between the content of the soluble polyimide and the content of the polyamic acid ester is 1/9 to 9/1 in mass ratio. The liquid-crystal aligning agent in any one of.   The organic solvent which melt | dissolves the said soluble polyimide and the said polyamic acid ester is included, and the total amount of content of a soluble polyimide and polyamic acid ester is 0.5-15 mass%, Either of Claims 1-8. The liquid crystal aligning agent of description.   The liquid crystal aligning agent according to claim 9, wherein the organic solvent contains at least one selected from the group consisting of N-methyl-pyrrolidone, N-ethyl-pyrrolidone, and γ-butyrolactone.   Furthermore, the liquid-crystal aligning agent in any one of Claims 1-10 containing a solvent.   The liquid crystal aligning agent according to claim 11, wherein the solvent is butyl cellosolve.   The liquid crystal aligning film obtained by apply | coating and baking the liquid-crystal aligning agent in any one of Claims 1-12.   The liquid crystal alignment film according to claim 13, wherein the coating film obtained by applying and baking the liquid crystal alignment treatment agent has a thickness of 5 to 300 nm.   The liquid crystal display element which comprises the liquid crystal aligning film of Claim 13 or 14.