JP6638645B2 - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display device - Google Patents

Description

  The present invention relates to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display device.

  The liquid crystal alignment film is a film for controlling the alignment of liquid crystal molecules in a certain direction in a liquid crystal display element or a retardation plate using a polymerizable liquid crystal. For example, a liquid crystal display element has a structure in which liquid crystal molecules forming a liquid crystal layer are sandwiched between liquid crystal alignment films formed on respective surfaces of a pair of substrates. Then, in the liquid crystal display element, the liquid crystal molecules are aligned in a certain direction with a pretilt angle by the liquid crystal alignment film, and respond by applying a voltage to an electrode provided between the substrate and the liquid crystal alignment film. As a result, the liquid crystal display element displays a desired image using the change in alignment due to the response of the liquid crystal molecules. The liquid crystal alignment film is a main component in a liquid crystal display device and the like together with liquid crystal molecules and the like.

The liquid crystal alignment film can be formed by forming a polymer film on a substrate. As the polymer film, a polyimide film or the like having high heat resistance and high reliability can be used.
As a method of forming a polymer film to be a liquid crystal alignment film on a substrate, a liquid crystal alignment agent containing components for forming the polymer film is used, and a coating film is formed on the substrate to form a liquid crystal alignment film. Methods for obtaining molecular films are known.

  For example, when forming a polyimide film as a polymer film to be a liquid crystal alignment film on a substrate, as a method, using a liquid crystal alignment agent using a varnish prepared by containing a polyimide precursor such as polyamic acid, A method is known in which the coating film is prepared and imidized on a substrate. Further, as another method, a method in which a polyimide which has been imidized in advance is dissolved in a solvent to prepare a so-called solvent-soluble polyimide varnish, and a polyimide film is formed using a liquid crystal alignment agent using the polyimide varnish. There is.

  In recent years, in the field of liquid crystal display devices, which have been progressing more and more, liquid crystal alignment films have been developed so that liquid crystal display devices can exhibit high performance in addition to the performance of controlling the alignment of liquid crystal molecules (hereinafter, also referred to as liquid crystal alignment). Various characteristics are required. For example, as a characteristic relating to the improvement of the display quality of the liquid crystal display element, a characteristic relating to the improvement of the display defect and an improvement in the transmittance are required.

  The liquid crystal alignment film is required to have heat resistance, solvent resistance, and the like in consideration of applicability to a manufacturing process. At the same time, the liquid crystal alignment film is strongly required to have high resistance to rubbing treatment from the viewpoint of applicability to a liquid crystal display element manufacturing process. The rubbing treatment is known as a method for forming a liquid crystal alignment film from a polymer film formed on a substrate in a process of manufacturing a liquid crystal display element, and is still widely used industrially at present. In the rubbing process, an orientation process of rubbing the surface of a polymer film such as polyimide formed on a substrate with a cloth is performed.

  In such a rubbing treatment, there is a known problem that dust generated by scraping the liquid crystal alignment film and scratches on the liquid crystal alignment film deteriorate display quality. Therefore, resistance to rubbing treatment (hereinafter, also referred to as rubbing resistance) is required for the liquid crystal alignment film.

  As a method for forming a liquid crystal alignment film having high rubbing resistance, a method of adding various additives to a polyimide forming the liquid crystal alignment film or a polyimide precursor for forming the polyimide (Patent Documents 1 and 2) Further, a method of introducing a polyimide structure having good rubbing resistance has been proposed (Patent Documents 3 and 4). In addition, there has been reported a method of improving the rubbing resistance of a formed liquid crystal alignment film by adding a compound having a blocked isocyanate group to a polyimide-based liquid crystal alignment agent (Patent Document 5). By using these methods, generation of scraping of the liquid crystal alignment film during rubbing treatment (also referred to as rubbing scraping) and damage to the liquid crystal alignment film (also referred to as rubbing scratch) can be reduced.

Japanese Patent Application Laid-Open No. Hei 7-120767 JP-A-9-146100 Japanese Patent Application Laid-Open No. 2008-90297 JP-A-9-258229 International Publication No. WO / 2013/122062 pamphlet

As described above, in the liquid crystal display element, there is a demand for a liquid crystal alignment film which can prevent rubbing scraping and rubbing scratches even in strong rubbing treatment and can be applied to strong rubbing treatment. Therefore, a liquid crystal alignment agent capable of forming a liquid crystal alignment film having high rubbing resistance has been demanded.
When a liquid crystal aligning agent to which a compound having a blocked isocyanate group is added is used, it is known that three-dimensional crosslinking proceeds by heating, and the mechanical strength (rubbing resistance) of the liquid crystal alignment film is improved. However, it is generally said that as the three-dimensional cross-linking proceeds, the polymer stretchability during rubbing is reduced, and the alignment regulating force is reduced. Thus, a liquid crystal alignment film having both good alignment regulating force and high rubbing resistance. Is required.

Further, it is known that when the film is cleaned after the rubbing treatment, the optical anisotropy of the liquid crystal alignment film is reduced, and it is considered that the alignment regulating force is thereby reduced.
Therefore, a liquid crystal aligning agent which not only has a high rubbing resistance but also has a small degree of inhibition of polymer stretchability and a small decrease in optical anisotropy after film washing, and can form a liquid crystal alignment film having good liquid crystal alignment is required. Have been.

The present inventors have made intensive studies and found that the above-mentioned problems can be solved by adding a novel component which has not been known so far to the liquid crystal aligning agent, and reached the present invention.
Specifically, by including a compound having a blocked isocyanate group in a polyimide-based liquid crystal alignment agent, not only the rubbing resistance of the formed liquid crystal alignment film is improved, but also the liquid crystal alignment film excellent in alignment control force. Can be provided.

（但し、Ｚはそれぞれ独立して、炭素数１〜３のアルキル基、水酸基又は下記式（２）で表される有機基であり、Ｚの少なくとも１つは、下記式（２）で表される有機基である。）

The present invention has the following aspects 1 to 7.
1. A polyimide precursor and at least one polymer selected from the group consisting of a polyimide obtained by imidizing the polyimide precursor, and a compound having a blocked isocyanate group represented by the following formula (1): Liquid crystal aligning agent.

(However, Z is each independently an alkyl group having 1 to 3 carbon atoms, a hydroxyl group or an organic group represented by the following formula (2), and at least one of Z is represented by the following formula (2) Organic group.)

４．前記ポリイミド前駆体が、下記式（３）で表される構造単位を有する上記１〜３のいずれか１項に記載の液晶配向剤

（但し、Ｒ_１は、水素原子又は炭素数１〜５のアルキル基であり、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、炭素数２〜１０のアルケニル基若しくは炭素数２〜１０のアルキニル基である。Ｘ_１は、４価の有機基であり、Ｙ_１は、２価の有機基である。）2. 2. The liquid crystal aligning agent according to the above 1, wherein the block portion of the compound having a blocked isocyanate group represented by the formula (1) has a thermal dissociation temperature of 50 to 230 ° C.
3. The liquid crystal aligning agent according to the above 1 or 2, wherein the compound having a blocked isocyanate group represented by the formula (1) is represented by the following formula (X1).

4. The liquid crystal aligning agent according to any one of the above items 1 to 3, wherein the polyimide precursor has a structural unit represented by the following formula (3).

(However, R ₁ is a hydrogen atom or 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 5 carbon atoms which may have a substituent. An alkyl group, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms. X ₁ is a tetravalent organic group, and Y ₁ is a divalent organic group.

5. The liquid crystal aligning agent according to any one of the above items 1 to 4, wherein the compound having a blocked isocyanate group is contained in an amount of 0.1 to 10% by weight based on 100% by weight of the polymer.
6. The above-mentioned 1-5, wherein the polymer is at least one selected from the group consisting of a primary amine, a secondary amine, a polyimide precursor having a carboxylic acid or a urea group, and a polyimide obtained by imidizing the polyimide precursor. The liquid crystal alignment agent according to any one of the above.
7. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of the above 1 to 6.
8. 7. A liquid crystal alignment film obtained by applying the liquid crystal alignment agent according to any one of the above 1 to 6 to a substrate and baking it.
9. A liquid crystal display device having the liquid crystal alignment film according to the above item 7 or 8.

According to the liquid crystal alignment agent of the present invention, a liquid crystal alignment film having high rubbing resistance and good liquid crystal alignment can be provided. By having high rubbing resistance, it is possible to reduce the problem of dust generated by scraping of the liquid crystal alignment film by the rubbing treatment and the problem that the scratch on the liquid crystal alignment film deteriorates the display quality of the liquid crystal display element. .
Further, according to the present invention, it is possible to provide a liquid crystal display element exhibiting good afterimage characteristics.

Hereinafter, the present invention will be described in more detail.
The liquid crystal aligning agent of the present invention contains at least one polymer selected from the group consisting of a polyimide precursor obtained by reacting a tetracarboxylic acid derivative with a diamine component and a polyimide obtained by imidizing the polyimide precursor. Examples of the polyimide precursor include polyamic acid and polyamic acid ester. The liquid crystal alignment agent of the present invention contains a compound having a blocked isocyanate group (hereinafter, also simply referred to as a blocked isocyanate compound) together with at least one polymer selected from a polyimide precursor and a polyimide.

  Hereinafter, the polyimide precursor, the polyimide, and the compound having a blocked isocyanate group, which are components that can be contained in the liquid crystal alignment agent of the present invention, will be described. Further, the liquid crystal aligning agent of the present invention constituted by containing them will be described.

<Polyimide precursor>
The polyimide precursor contained in the liquid crystal alignment agent of the present invention refers to polyamic acid and polyamic acid ester, and has a structural unit represented by the following formula (3).

In the above formula (3), R ₁ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and A ₁ and A ₂ may each independently have a hydrogen atom or a substituent. An alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms or an alkynyl group having 2 to 10 carbon atoms.

In the above formula (3), R ₁ is a hydrogen atom or an alkyl group having 1 to 5, preferably 1 to 2 carbon atoms. In the polyamic acid ester, as the number of carbon atoms in the alkyl group increases, the temperature at which imidization proceeds increases. Therefore, R ₁ is particularly preferably a methyl group from the viewpoint of easy imidization by heat.

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

  The alkyl group having 1 to 10 carbon atoms, the alkenyl group having 2 to 10 carbon atoms and the alkynyl group having 2 to 10 carbon atoms may have a substituent, and further form a ring structure by the substituent. Is also good. Note that forming a ring structure with a substituent means that the substituents are bonded to each other or to a part of the parent skeleton to form a ring structure.

  Examples of the substituent include a halogen group, a hydroxyl group, a thiol group, a nitro group, an aryl group, an organooxy group, an organothio group, an organosilyl group, an acyl group, an ester group, a thioester group, a phosphoric ester group, an amide group, Examples thereof include an alkyl group, an alkenyl group, and an alkynyl group.

Examples of the halogen group as a substituent include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
Examples of the aryl group as a substituent include a phenyl group. This aryl group may be further substituted with the other substituents described above.

  As the organooxy group as a substituent, a structure represented by OR can be shown. R may be the same or different, and examples thereof include the aforementioned alkyl group, alkenyl group, alkynyl group, and aryl group. These R may be further substituted by the above-mentioned substituents. Specific examples of the organooxy group include a methoxy group, an ethoxy group, a propyloxy group, a butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group.

  As the organothio group as a substituent, a structure represented by -SR can be shown. Examples of R include the above-described alkyl group, alkenyl group, alkynyl group, and aryl group. These R may be further substituted by the above-mentioned substituents. Specific examples of the organothio 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 as a substituent, a structure represented by -Si- (R) ₃ can be shown. R may be the same or different, and examples thereof include the aforementioned alkyl group, alkenyl group, alkynyl group, and aryl group. These R may be further substituted by the above-mentioned substituents. Specific examples of the organosilyl 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 the acyl group which is a substituent, a structure represented by -C (O) -R can be shown. Examples of R include the above-described alkyl group, alkenyl group, and aryl group. These R may be further substituted by the above-mentioned substituents. Specific examples of the acyl group include a formyl group, an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, an isovaleryl group, and a benzoyl group.

As the ester group which is a substituent, a structure represented by -C (O) OR or -OC (O) -R can be shown. Examples of R include the above-described alkyl group, alkenyl group, alkynyl group, and aryl group. These R may be further substituted by the above-mentioned substituents.
As the thioester group which is a substituent, a structure represented by -C (S) OR or -OC (S) -R can be shown. Examples of R include the above-described alkyl group, alkenyl group, alkynyl group, and aryl group. These R may be further substituted by the above-mentioned substituents.

As the phosphate group which is a substituent, a structure represented by -OP (O)-(OR) ₂ can be shown. R may be the same or different, and examples thereof include the aforementioned alkyl group, alkenyl group, alkynyl group, and aryl group. These R may be further substituted by the above-mentioned substituents.
Examples of the amide group is a _{substituent, -C (O) NH 2,} -C (O) NHR, -NHC (O) R, -C (O) N (R) 2, or -NRC (O) R The structure represented can be shown. R may be the same or different, and examples thereof include the aforementioned alkyl group, alkenyl group, alkynyl group, and aryl group. These R may be further substituted by the above-mentioned substituents.

Examples of the aryl group as a substituent include the same aryl groups as those described above. This aryl group may be further substituted with the other substituents described above.
Examples of the alkyl group as a substituent include the same alkyl groups as those described above. This alkyl group may be further substituted with another substituent described above.
Examples of the alkenyl group as a substituent include the same alkenyl groups as those described above. This alkenyl group may be further substituted with the other substituents described above.
Examples of the alkynyl group as a substituent include the same alkynyl groups described above. This alkynyl group may be further substituted with the other substituents described above.

In general, when a bulky structure is introduced, the reactivity of the amino group and the liquid crystal alignment may be reduced. Therefore, as A ₁ and A ₂ , a hydrogen atom or a carbon atom having 1 carbon atom which may have a substituent is used. To 5 alkyl groups are more preferable, and a hydrogen atom, a methyl group or an ethyl group is particularly preferable.

In the above formula (3), as long as X ₁ is a tetravalent organic group, its structure is not particularly limited, and two or more kinds may be mixed. If Specific examples of X _1, include X-1 to X-47 shown below. Among them, from monomers of availability, _{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, X-32 or X-47 are preferred.

In the above formula (3), Y ₁ is a divalent organic group, and two or more kinds may be mixed. Specific examples of Y ₁ include, but are not limited to, the following Y-1 to Y-108. Among these, specific examples of Y ₁ include Y-7, Y-8, Y-13, Y-18, Y-19, Y-42, and Y-Y from the viewpoint of the reactivity of the diamine and the solubility of the polymer. -43, Y-45, Y-55, Y-59, Y-74, Y-78, Y-79, Y-80, Y-81, or Y-82 are preferable, and Y-19, Y-42, Y-43, Y-45, Y-74, Y-81 or Y-82 are more preferred.

  As the polyimide precursor contained in the liquid crystal alignment agent of the present invention, a polyimide precursor having a structure suitable for a crosslinking reaction to proceed with a compound having a blocked isocyanate group described later is preferable, and specifically, a primary A polyimide precursor having at least one of an amine, a secondary amine, a carboxylic acid and a urea group is preferred, and a polyimide precursor having at least one of a primary amine and a urea group is more preferred.

<Production method of polyimide precursor-production of polyamic acid>
Polyamic acid, which is a polyimide precursor having a structural unit represented by the above formula (3), is obtained by reacting a tetracarboxylic dianhydride, which is a tetracarboxylic acid derivative, with a diamine component.

  In order to obtain a polyamic acid by the reaction between the tetracarboxylic dianhydride and the diamine component, a known synthesis method can be used. The synthesis method is a method of reacting a tetracarboxylic dianhydride with a diamine component in an organic solvent. The reaction between the tetracarboxylic dianhydride and the diamine is advantageous in that it proceeds relatively easily in an organic solvent and does not generate by-products.

  The organic solvent used for the reaction between the tetracarboxylic dianhydride and the diamine component is not particularly limited as long as the generated polyamic acid can be dissolved. Specific examples are given below.

  N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methylcaprolactam, dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfone, hexamethylsulfoxide , Γ-butyrolactone, isopropyl alcohol, methoxymethylpentanol, dipentene, ethyl amyl ketone, methyl nonyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, butyl Carbitol, ethyl carbitol, ethylene glycol, ethylene glycol monoacetate, ethylene glycol monoisopropyl ether, ethylene Glycol monobutyl ether, propylene glycol, propylene glycol monoacetate, propylene glycol monomethyl ether, propylene glycol-tert-butyl ether, dipropylene glycol monomethyl ether, diethylene glycol, diethylene glycol monoacetate, diethylene glycol dimethyl ether, dipropylene glycol monoacetate monomethyl ether, dipropylene glycol Monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monoacetate monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoacetate monopropyl ether, 3-methyl-3-methoxybutyl acetate, trifluoropropyl Glycol methyl ether, 3-methyl-3-methoxybutanol, diisopropyl ether, ethyl isobutyl ether, diisobutylene, amyl acetate, butyl butyrate, butyl ether, diisobutyl ketone, methylcyclohexene, propyl ether, dihexyl ether, dioxane, n- Hexane, n-pentane, n-octane, diethyl ether, cyclohexanone, ethylene carbonate, propylene carbonate, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate, Ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropion , 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, diglyme, 4-hydroxy-4-methyl-2-pentanone, 3-methoxy-N, N-dimethylpropanamide, 3-ethoxy —N, N-dimethylpropanamide, 3-butoxy-N, N-dimethylpropanamide and the like.

  These exemplified solvents may be used alone or as a mixture. Furthermore, even if the solvent does not dissolve the polyamic acid, it may be used by mixing with the above solvent as long as the generated polyamic acid does not precipitate.

  Further, since water in the organic solvent inhibits the polymerization reaction and further causes hydrolysis of the generated polyamic acid, it is preferable to use a dehydrated organic solvent as much as possible.

  When reacting a tetracarboxylic dianhydride and a diamine component in an organic solvent, a solution obtained by dispersing or dissolving the diamine component in the organic solvent is stirred, and the tetracarboxylic dianhydride as it is or in the organic solvent. Dispersion or dissolution method of addition, and conversely, tetracarboxylic dianhydride method of adding or diamine component to a solution obtained by dispersing or dissolving in organic solvent, tetracarboxylic dianhydride and diamine component are added alternately And the like, and any of these methods may be used. Further, when the tetracarboxylic dianhydride or the diamine component is composed of a plurality of compounds, they may be reacted in a premixed state, may be reacted individually sequentially, or may be individually reacted low molecular weight compounds. May be mixed to form a high molecular weight product.

The polymerization temperature at that time can be selected from any temperature in the range of -20 to 150 ° C, but is preferably in the range of -5 to 100 ° C.
The reaction can be carried out at any concentration.However, if the concentration is too low, it is difficult to obtain a polymer having a high molecular weight.If the concentration is too high, the viscosity of the reaction solution becomes too high, and uniform stirring is not achieved. Since it becomes difficult, the total concentration of the tetracarboxylic dianhydride and the diamine component in the reaction solution is preferably 1 to 50% by weight, more preferably 5 to 30% by weight. The initial stage of the reaction is carried out at a high concentration, after which an organic solvent can be added.

  In the polymerization reaction of the polyamic acid, the ratio of the total number of moles of the tetracarboxylic dianhydride to the total number of moles of the diamine component is preferably 0.8 to 1.2. As in the ordinary polycondensation reaction, the molecular weight of the generated polyamic acid increases as the molar ratio approaches 1.0.

<Production method of polyimide precursor-production of polyamic acid ester>
The polyamic acid ester, which is a polyimide precursor having a structural unit represented by the above formula (3), is prepared by using a tetracarboxylic acid derivative and a diamine compound as shown in the following method (A), (B) or (C). Can be manufactured.

(A) When Producing from Polyamic Acid The polyamic acid ester can be produced by esterifying a polyamic acid obtained from tetracarboxylic dianhydride and diamine.
Specifically, it is produced 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 for 1 to 4 hours. be able to.

  As the esterifying agent, those which can be easily removed by purification are preferable, 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. The addition amount of the esterifying agent is preferably 2 to 6 molar equivalents per 1 mol of the repeating unit of the polyamic acid.

  The solvent used in the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone from the viewpoint of solubility of the polymer. These solvents may be used alone or in combination of two or more. Is also good. The concentration at the time of production is preferably from 1 to 30% by weight, more preferably from 5 to 20% by weight, from the viewpoint that precipitation of a polymer hardly occurs and a high molecular weight substance is easily obtained.

(B) When Producing by Reaction of Tetracarboxylic Diester Dichloride and Diamine Polyamic acid ester can be produced from tetracarboxylic diester dichloride and diamine.

Specifically, tetracarboxylic diester dichloride and diamine, in the presence of a base and an organic solvent, at -20 to 150 ° C, preferably at 0 to 50 ° C, for 30 minutes to 24 hours, preferably for 1 to 4 hours. It can be produced 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 amount of the base to be added is preferably 2 to 4 times the molar amount of the tetracarboxylic diester dichloride, from the viewpoint of easy removal and easy production of a high molecular weight compound.

  The solvent used in the above reaction is preferably N-methyl-2-pyrrolidone or γ-butyrolactone from the viewpoint of solubility of the monomer and the polymer, and these may be used alone or as a mixture of two or more. The polymer concentration at the time of production is preferably from 1 to 30% by weight, more preferably from 5 to 20% by weight, from the viewpoint that precipitation of the polymer hardly occurs and a high molecular weight substance is easily obtained. Further, in order to prevent hydrolysis of the tetracarboxylic diester dichloride, the solvent used for producing the polyamic acid ester is preferably dehydrated as much as possible, and the reaction is preferably performed in a nitrogen atmosphere to prevent outside air from being mixed.

(C) When producing from a tetracarboxylic acid diester and a diamine A polyamic acid ester can be produced by polycondensing a tetracarboxylic acid diester and a diamine.

  Specifically, tetracarboxylic diester and diamine are condensed with 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 be produced by reacting.

  Examples of the condensing agent include triphenyl phosphite, dicyclohexylcarbodiimide, 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride, N, N′-carbonyldiimidazole, dimethoxy-1,3,5-triadiazole. Nylmethylmorpholinium, O- (benzotriazol-1-yl) -N, N, N ', N'-tetramethyluronium tetrafluoroborate, O- (benzotriazol-1-yl) -N, N , N ', N'-tetramethyluronium hexafluorophosphate, diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl) phosphonate and the like can be used. The amount of the condensing agent to be added is preferably 2 to 3 times by mole, more preferably 2 to 2.5 times by mole, based on the tetracarboxylic acid diester.

  Tertiary amines such as pyridine and triethylamine can be used as the base. The amount of the base to be added is preferably 2 to 4 mol times, more preferably 2.5 to 3.5 mol times with respect to the diamine component, from the viewpoint of easy removal and easy production of a high molecular weight compound.

  In addition, in the above reaction, the reaction proceeds efficiently by adding a 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 mole times the diamine component.

  Among the three methods for producing a polyamic acid ester described above, the production method (C) is particularly preferable because a high molecular weight polyamic acid ester is obtained with good reproducibility.

  The solution of the polyamic acid ester obtained as described above can be poured into a poor solvent with good stirring to precipitate a polymer. After performing precipitation several times, washing with a poor solvent, and drying at room temperature or under heating, purified polyamic acid ester powder can be obtained. The poor solvent is not particularly limited, and examples thereof include water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene, and isopropyl alcohol.

<Polyimide>
The polyimide used in the present invention can be produced by imidizing the above-mentioned polyamic acid ester or polyamic acid, which is a polyimide precursor. The imidation reaction for dehydrating and ring-closing the polyimide precursor is generally performed by thermal imidization or chemical imidization, but the chemical imidization in which the imidization reaction proceeds at a relatively low temperature reduces the molecular weight of the resulting polyimide. It is difficult to occur and is preferable.

Chemical imidization can be carried out by stirring the polyimide precursor in an organic solvent in the presence of a basic catalyst and an acid anhydride. The reaction temperature at this time is −20 to 250 ° C., preferably 0 to 180 ° C., and the reaction time can be 1 to 100 hours.
The amount of the basic catalyst is 0.5 to 30 mol times, preferably 2 to 20 mol times of the polyimide precursor, and the amount of the acid anhydride is 1 to 50 mol times, preferably 3 to 30 mol times of the polyimide precursor. It is twice. If the amount of the basic catalyst or the acid anhydride is small, the reaction does not proceed sufficiently. If the amount is too large, it is difficult to completely remove the reaction after the reaction is completed.
Examples of the basic catalyst used for imidization include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among them, pyridine is preferable because it has an appropriate basicity for causing the reaction to proceed.

Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. Among them, acetic anhydride is preferred because purification after the reaction is facilitated.
As the organic solvent, the solvent used in the above-described polyamic acid polymerization reaction can be used. The imidation rate by chemical imidization can be controlled by adjusting the amount of the catalyst, the reaction temperature, and the reaction time.

  In the polyimide solution thus obtained, since the added catalyst remains in the solution, in order to use the polyimide solution in the liquid crystal aligning agent of the present invention, the polyimide solution is poured into a stirring poor solvent. It is preferable that the polyimide be recovered by precipitation. The poor solvent used for the precipitation and recovery of the polyimide is not particularly limited, and examples thereof include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, and benzene. The polyimide precipitated by being introduced into the poor solvent can be recovered by filtration and washing, and then dried at normal temperature or under reduced pressure at normal temperature or under heat to form a powder. By repeating the operation of dissolving this powder in a good solvent and reprecipitating 2 to 10 times, the polyimide can be purified. When impurities cannot be completely removed by a single precipitation recovery operation, it is preferable to repeat this purification step. It is preferable to mix or sequentially use three or more kinds of poor solvents such as alcohols, ketones, and hydrocarbons as the poor solvent in the repetitive purification step, because the purification efficiency is further increased, and thus it is preferable.

  The imidation ratio of the polyimide contained in the liquid crystal alignment agent of the present invention is not particularly limited. Any value may be set in consideration of the solubility of the polyimide. The molecular weight of the polyimide contained in the liquid crystal alignment agent of the present invention is not particularly limited, but if the molecular weight of the polyimide is too small, the strength of the obtained coating film may be insufficient, and conversely the molecular weight of the polyimide is too large. If the viscosity of the liquid crystal aligning agent to be produced becomes too high, the workability in forming a coating film and the uniformity of the coating film may be deteriorated. Therefore, the weight average molecular weight of the polyimide used for the liquid crystal aligning agent of the present invention is preferably from 2,000 to 500,000, more preferably from 5,000 to 300,000.

<Blocked isocyanate compound>
The liquid crystal aligning agent of the present invention contains a compound having a blocked isocyanate group (hereinafter, also simply referred to as a blocked isocyanate compound).
A blocked isocyanate compound has a blocked isocyanate group in a molecule in which an isocyanate group (-NCO) is blocked by a protecting group, and when exposed to a high temperature during heating and baking during the formation of a liquid crystal alignment film, a protecting group (block portion). Is released by thermal dissociation, and a crosslinking reaction proceeds with a polymer such as polyimide constituting the liquid crystal alignment film via the generated isocyanate group. For example, a compound having a group represented by the formula (4) in a molecule is exemplified.

（式（４）中、Ｒ^２はブロック部の有機基を表す。）

(In the formula (4), R ² represents an organic group in a block portion.)

In the present invention, a compound having a blocked isocyanate group represented by the above formula (1) is used. In the above formula (1), Z is each independently an alkyl group having 1 to 3 carbon atoms, preferably a methyl group, a hydroxyl group, or an organic group represented by the following formula (2), and at least one of Z Is an organic group represented by the following formula (2).

The blocked isocyanate compound can be obtained, for example, by reacting a compound having an isocyanate group in the molecule with an appropriate blocking agent.
Examples of the blocking agent include alcohols such as methanol, ethanol, isopropanol, n-butanol, 2-ethoxyhexanol, 2-N, N-dimethylaminoethanol, 2-ethoxyethanol and cyclohexanol; phenol, o-nitrophenol Phenols such as, p-chlorophenol, o-, m- or p-cresol; lactams such as ε-caprolactam; oximes such as acetone oxime, methyl ethyl ketone oxime, methyl isobutyl ketone oxime, cyclohexanone oxime, acetophenone oxime and benzophenone oxime. Pyrazoles such as pyrazole, 3,5-dimethylpyrazole and 3-methylpyrazole; thiols such as dodecanethiol and benzenethiol;

  In a block isocyanate compound, at a high temperature such as the temperature of heating and baking at the time of forming a liquid crystal alignment film, thermal dissociation of a block portion occurs and a crosslinking reaction proceeds through an isocyanate group. It is preferable that the crosslinking by the isocyanate group does not progress in a low temperature state such as time. In order to achieve such thermal reactivity, the blocked isocyanate compound is preferably one in which the temperature of thermal dissociation of the block portion is considerably higher than that during storage of the liquid crystal aligning agent, for example, 50 to 230 ° C. What is -180 degreeC is more preferable.

  As described above, the blocked isocyanate compound can improve rubbing resistance in a liquid crystal alignment film formed using a liquid crystal alignment agent containing the compound. In this case, a blocked isocyanate compound having three or more blocked isocyanate groups in one molecule is particularly effective for improving the rubbing resistance of the liquid crystal alignment film.

  The compound having three or more blocked isocyanate groups in one molecule can be obtained, for example, by reacting the above-mentioned blocking agent with a compound having three or more isocyanate groups in one molecule.

  Specific examples of such a compound having three or more blocked isocyanate groups in one molecule include a compound represented by the following formula (X1).

When the liquid crystal aligning agent of the present invention contains a blocked isocyanate compound, the blocked isocyanate compound may be used alone or in combination of two or more.
Further, the blocked isocyanate compound is contained at a ratio of 0.1 to 10% by weight, preferably 0.2 to 8% by weight, based on 100% by weight of the polymer component in the liquid crystal aligning agent.
If the content of the blocked isocyanate compound is less than the lower limit of the above range, thermal curing becomes insufficient, and a satisfactory effect of improving rubbing resistance in a liquid crystal alignment film cannot be obtained. On the other hand, when the content of the blocked isocyanate compound exceeds the upper limit of the above range, there is a concern that the stretchability of the polymer is reduced and the liquid crystal alignment of the formed liquid crystal alignment film is reduced. On the other hand, the organic solvent stability of the liquid crystal alignment film is considered to be better as the content of the blocked isocyanate compound is larger.

<Liquid crystal aligning agent>
The liquid crystal alignment agent of the present invention is a coating liquid for forming a liquid crystal alignment film, and is a solution in which a resin component for forming a resin film is dissolved in an organic solvent. Here, the resin component is a resin component containing at least one polymer selected from the group consisting of the above-mentioned polyimide precursor and polyimide. The content of the resin component in the liquid crystal alignment agent is preferably 1 to 20% by weight, more preferably 3 to 15% by weight, and further preferably 3 to 10% by weight.

  In the present invention, all of the above resin components may be the above-mentioned polymers, or other polymers may be mixed. At that time, the content of the polymer other than the above-mentioned polymer in the resin component is 0.5 to 15% by weight, preferably 1 to 10% by weight.

  The organic solvent used for the liquid crystal aligning agent of the present invention is not particularly limited as long as it is an organic solvent that dissolves the above-mentioned resin component such as a polymer and the above-mentioned blocked isocyanate compound. Specific examples are given below.

  N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, dimethylsulfoxide, tetramethylurea, pyridine, Dimethyl sulfone, hexamethyl sulfoxide, γ-butyrolactone, 3-methoxy-N, N-dimethylpropanamide, 3-ethoxy-N, N-dimethylpropanamide, 3-butoxy-N, N-dimethylpropanamide, 1,3 -Dimethyl-imidazolidinone, ethyl amyl ketone, methyl nonyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, cyclohexanone, ethylene carbonate, propylene carbonate, diglyme, 4-hydroxy-4 Methyl-2-pentanone and the like. These may be used alone or as a mixture.

  The liquid crystal aligning agent of the present invention may contain components other than those described above. Examples thereof include solvents and compounds that improve the uniformity of the film thickness and surface smoothness when the liquid crystal alignment agent is applied, and compounds that improve the adhesion between the liquid crystal alignment film and the substrate.

Specific examples of the solvent (poor solvent) for improving the uniformity of the film thickness and the surface smoothness include the following.
For example, isopropyl alcohol, methoxymethyl pentanol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, butyl carbitol, ethyl carbitol, ethyl carbitol acetate, ethylene glycol, ethylene glycol monoacetate, ethylene glycol monoacetate Isopropyl ether, ethylene glycol monobutyl ether, propylene glycol, propylene glycol monoacetate, propylene glycol monomethyl ether, propylene glycol-tert-butyl ether, dipropylene glycol monomethyl ether, diethylene glycol, diethylene glycol monoacetate, diethylene glycol dimethyl ether, dipro Lenglycol monoacetate monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monoacetate monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoacetate monopropyl ether, 3-methyl-3 -Methoxybutyl acetate, tripropylene glycol methyl ether, 3-methyl-3-methoxybutanol, diisopropyl ether, ethyl isobutyl ether, diisobutylene, amyl acetate, butyl butyrate, butyl ether, diisobutyl ketone, methylcyclohexene, propyl ether, dihexyl Ether, 1-hexanol, n-hexane, n-pentane, n-octane Diethyl ether, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, Ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, 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, dipropylene glycol, 2- (2-ethoxypropoxy) propanol, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, n-butyl lactate, isoamyl lactate, etc. Solvents having a surface tension are exemplified.

  These poor solvents may be used alone or in combination of two or more. When the above-mentioned solvent is used, its content is preferably 5 to 80% by weight, more preferably 20 to 60% by weight, based on the entire solvent contained in the liquid crystal aligning agent.

Examples of the compound that improves the uniformity of the film thickness and the surface smoothness include a fluorine-based surfactant, a silicone-based surfactant, and a nonionic surfactant.
More specifically, for example, F-top EF301, EF303, EF352 (the above are trademarks of Tochem Products), Megafac (F171, F173, R-30 (the above is a trademark of Dainippon Ink), Florard FC430, FC431 (the above is a trademark of Sumitomo 3M), Asahi Guard AG710, Surflon S-382, SC101, SC102, SC103, SC104, SC105, SC106 (the above is a trademark of Asahi Glass Co., Ltd.) and the like.

  The use ratio of these surfactants is preferably 0.01 to 2 parts by weight, more preferably 0.01 to 1 part by weight, based on 100 parts by weight of the resin component contained in the liquid crystal aligning agent.

Specific examples of the compound that improves the adhesion between the liquid crystal alignment film and the substrate include the following functional silane-containing compounds and epoxy group-containing compounds.
For example, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxy Carbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl-1,4,7-triazadecane, 10-to Ethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate, N-benzyl-3-aminopropyl triacetate Methoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-bis (oxyethylene) -3-amino Propyltrimethoxysilane, N-bis (oxyethylene) -3-aminopropyltriethoxysilane, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether , Polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, 1,3,5,6-tetra Glycidyl-2,4-hexanediol, N, N, N ′, N ′,-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ', N',-tetraglycidyl-4,4'-diaminodiphenylmethane and the like.

  When a compound that improves the adhesion to the substrate is used, the amount used is preferably 0.1 to 30 parts by weight, more preferably 100 parts by weight, of the resin component contained in the liquid crystal aligning agent. Is 1 to 20 parts by weight. If the amount is less than 0.1 part by weight, the effect of improving the adhesion cannot be expected, and if the amount exceeds 30 parts by weight, the liquid crystal alignment of the formed liquid crystal alignment film may be reduced.

  In addition to the above, the liquid crystal aligning agent of the present invention may be a dielectric or conductive substance for the purpose of changing the electrical properties of the liquid crystal alignment film, such as the dielectric constant or conductivity, as long as the effects of the present invention are not impaired. Further, a cross-linkable compound for the purpose of increasing the hardness and denseness of the liquid crystal alignment film may be added.

<Liquid crystal alignment film>
Preferably, the liquid crystal aligning agent of the present invention can be formed into a coating film by filtering before coating on a substrate, coating the substrate, drying by pre-baking, and then heating and baking. Then, a liquid crystal alignment film can be formed by rubbing the coating film surface.
The liquid crystal alignment agent of the present invention contains the above-described blocked isocyanate compound, and the formed liquid crystal alignment film has high rubbing resistance.

  When the liquid crystal aligning agent of the present invention is applied to a substrate, a highly transparent substrate can be used as the substrate to be used. As the substrate, for example, a plastic substrate such as an acrylic substrate or a polycarbonate substrate other than a glass substrate can be used. In the case of using the liquid crystal alignment agent of the present invention in manufacturing a liquid crystal display element, it is preferable to form a liquid crystal alignment film using a substrate on which an ITO (Indium Tin Oxide) electrode for driving liquid crystal is formed. When a reflective liquid crystal display element is manufactured, an opaque substrate such as a silicon wafer can be used as long as only one substrate is used. In this case, the electrode uses a material that reflects light such as aluminum. You can also.

  As a method of applying the liquid crystal aligning agent of the present invention on a substrate, for example, screen printing, offset printing, flexographic printing, or an inkjet method may be used. Other coating methods include a dip method, a roll coater method, a slit coater method, a spinner method, a spray method and the like, and these may be used according to the purpose.

  The step of drying by pre-baking after applying the liquid crystal aligning agent is not necessarily required, but when the time from application to heating and firing is not constant for each substrate, or when heating and firing are not performed immediately after application, It is preferable to include a drying step. The drying by prebaking may be performed at a temperature at which the solvent is evaporated to such an extent that the shape of the coating film is not deformed due to the transfer of the substrate or the like, and the above-mentioned blocked isocyanate compound contained in the liquid crystal aligning agent does not react. Is preferred.

  The drying means is not particularly limited. As a specific example, a method of drying on a hot plate at 50 to 120 ° C., preferably 80 to 120 ° C. for 0.5 to 30 minutes, preferably 1 to 5 minutes is preferable.

  The baking of the substrate coated with the liquid crystal aligning agent can be performed at a temperature of 120 to 350 ° C. by a heating means of a hot plate, a heat circulation type oven or an IR (infrared) type oven. The firing temperature is preferably 140 to 300C, more preferably 180 to 250C, in consideration of the reactivity of the blocked isocyanate compound contained in the liquid crystal alignment agent. However, it is preferable that the baking is performed at a temperature higher by 10 ° C. or more than a heat treatment temperature such as a curing of a sealant required in a manufacturing process of the liquid crystal display element.

  If the thickness of the coating film after firing is too thick, it is disadvantageous in terms of power consumption of the liquid crystal display element, and if too thin, the reliability of the liquid crystal display element may be reduced. It is 50-100 nm.

  The rubbing treatment of the surface of the coating film formed on the substrate as described above can use an existing rubbing device. The material of the rubbing cloth at this time includes cotton, rayon, nylon and the like. As the conditions of the rubbing treatment, generally, the conditions of a rotation speed of 300 to 2000 rpm, a feed speed of 5 to 100 mm / s, and a pushing amount of 0.1 to 1.0 mm are used. Thereafter, the residue generated by the rubbing is removed by ultrasonic cleaning using pure water or alcohol.

  After the liquid crystal aligning agent of the present invention forms a liquid crystal alignment film on a substrate by the above-described method, a liquid crystal display element can be manufactured by a known method using the substrate with the liquid crystal alignment film.

<Liquid crystal display device>
The liquid crystal display element of the present invention is obtained by obtaining a substrate with a liquid crystal alignment film from the liquid crystal alignment agent of the present invention by the above-mentioned method, and then manufacturing a liquid crystal cell by a known method to obtain a liquid crystal display element.
An example of a method for manufacturing a liquid crystal display element is as follows. First, a pair of substrates on which a liquid crystal alignment film is formed is prepared, and the rubbing direction is set to an arbitrary angle of 0 ° to 270 ° with a spacer of preferably 1 to 30 μm, more preferably 2 to 10 μm interposed therebetween. And fix the periphery with a sealant. Next, liquid crystal is injected between the substrates and sealed. The method of sealing liquid crystal is not particularly limited, and examples thereof include a vacuum method in which liquid crystal is injected after reducing the pressure in the manufactured liquid crystal cell and a dropping method in which liquid crystal is dropped and then sealed.

Hereinafter, the present invention will be described in more detail with reference to Examples. Note that the present invention is not construed as being limited to these.
The structures and abbreviations of main compounds used in Examples and Comparative Examples are as follows.
<Tetracarboxylic diester, tetracarboxylic dianhydride>
Y-1: 1,2,3,4-butanetetracarboxylic dianhydride Y-2: Pyromellitic dianhydride Y-3: 2,5-bis (ethoxycarbonyl) benzene-1,4-dicarboxylic acid Y-4: 2,4-bis (methoxycarbonyl) cyclobutane-1,3-dicarboxylic acid

<Diamine>
Z-1: bis (4-aminophenoxy) methane Z-2: 1,3-bis (4-aminophenoxy) propane Z-3: 4,4′-diaminodiphenylamine Z-4: 1,3-bis (4 -Aminophenoxy) benzene Z-5: 1,3-bis (4-aminophenethyl) urea <condensing agent>
DBOP: diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl) phosphonate

<Structural formula>

<Blocked isocyanate compound>

  Hereinafter, evaluation methods performed in the present example and the comparative example will be described.

[viscosity]
The viscosity of the polyamic acid solution, polyimide solution or polyamic acid ester solution was measured using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) using a sample volume of 1.1 mL and a cone rotor TE-1 (1 ° 34 ′, R24). ) At a temperature of 25 ° C.
[Solid content concentration]
Calculation of the solid concentration of the polyamic acid solution, the polyimide solution or the polyamic acid ester solution was performed as follows.
About 1.1 g of a polyamic acid solution, a polyimide solution or a polyamic acid ester solution is placed in an aluminum cup No. 2 with a handle (manufactured by AS ONE Corporation) and placed in an oven DNF400 (manufactured by Yamato Kagaku) at a temperature of 200 ° C. for 2 hours. Heated. Then, the mixture was left at room temperature for 5 minutes, and the weight of the solid content remaining in the aluminum cup was measured. The solid content concentration was calculated from the solid content weight and the original solution weight value.

[Molecular weight]
The molecular weight of the polyamic acid solution, the polyimide solution or the polyamic acid ester solution is measured by a GPC (room temperature gel permeation chromatography) apparatus, and the number average molecular weight (hereinafter, also referred to as Mn) and weight average molecular weight are calculated as polyethylene glycol or polyethylene oxide. (Hereinafter, also referred to as Mw).
GPC device: manufactured by Shodex (GPC-101)
Column: Shodex (KD803, KD805 in series)
Column temperature: 50 ° C
Eluent: N, N-dimethylformamide (as an additive, lithium bromide hydrate (LiBr.H ₂ O) 30 mmol / L, phosphoric acid / anhydrous crystal (o-phosphoric acid) 30 mmol / L, tetrahydrofuran (THF) is 10 ml / L)
Flow rate: 1.0 ml / min Standard sample for preparing a calibration curve: TSK standard polyethylene oxide (weight average molecular weight (Mw): about 900,000, 150,000, 100,000 and 30,000) manufactured by Tosoh Corporation, and polymer laboratory Polyethylene glycol (Peak top molecular weight (Mp): about 12,000, 4,000 and 1,000). For the measurement, in order to avoid overlapping peaks, four kinds of samples of 900,000, 100,000, 12,000 and 1,000 were mixed, and three kinds of 150,000, 30,000 and 4,000 were used. Two samples of the mixed sample are measured separately.

[Measurement of imidation ratio of polyimide]
20 mg of the polyimide powder is placed in an NMR (nuclear magnetic resonance) sample tube (NMR sampling tube standard, φ5 (manufactured by Kusano Science)), and deuterated dimethyl sulfoxide (DMSO-d6, 0.05% by weight TMS (tetramethylsilane)) (Mixture) (0.53 ml) was added and the mixture was completely dissolved by sonication. The solution was subjected to proton NMR measurement at 500 MHz using an NMR measuring device (JNW-ECA500) (manufactured by JEOL Datum). The imidation rate is determined by using a proton derived from a structure that does not change before and after imidation as a reference proton, and a peak integrated value of this proton and a proton peak derived from an NH group of amic acid appearing in the vicinity of 9.5 to 10.0 ppm. It was determined by the following equation using the integrated value.
Imidation ratio (%) = (1−α · x / y) × 100
In the above formula, x is the integrated value of the proton peak derived from the NH group of the amic acid, y is the integrated value of the peak of the reference proton, α is one proton of the NH group of the amic acid in the case of polyamic acid (imidation ratio is 0%). Is the ratio of the number of reference protons to

[Rubbing resistance]
The rubbing resistance was evaluated by observing the amount of deposits on the polyimide film formed on the substrate after the rubbing treatment. Specifically, after a liquid crystal aligning agent obtained in Examples and Comparative Examples to be described later is filtered through a 1.0 μm filter, it is spin-coated on an ITO-deposited glass substrate, and is placed on a hot plate at a temperature of 80 ° C. for 5 minutes. Was dried and baked at a temperature of 230 ° C. for 20 minutes to obtain a polyimide film having a thickness of 100 nm. This polyimide film was rubbed with a rayon cloth (roll diameter: 120 mm, rotation speed: 1000 rpm, moving speed: 20 mm / sec, indentation length: 0.5 mm) to form a liquid crystal alignment film.
Next, the film surface state of the liquid crystal alignment film was observed using a confocal laser microscope, and attached matter was observed at a magnification of 10 times (observation area: about 680 μm × 680 μm, microscope magnification: 100 times). When there was almost no attached matter, "O" was given, and when attached matter was observed, "x" was given.

[Liquid Crystal Alignment-1] Organic Solvent Stability of Optical Anisotropy The liquid crystal alignment agent obtained in each of Examples and Comparative Examples was filtered through a 1.0 μm filter, and then spin-coated on an ITO vapor-deposited glass substrate. After drying on a hot plate at 80 ° C. for 5 minutes and baking at 230 ° C. for 20 minutes, a polyimide film having a thickness of 100 nm was obtained. This polyimide film was rubbed with a rayon cloth (roll diameter: 120 mm, rotation speed: 1000 rpm, moving speed: 20 mm / sec, indentation length: 0.4 mm) to form a liquid crystal alignment film.
The optical anisotropy was measured using a liquid crystal alignment film evaluation system “Ray Scan Lab H” (LYS-LH30S-1A) manufactured by Moritex Corporation.
Next, ultrasonic cleaning was performed for 1 minute in a mixed solution of isopropyl alcohol / pure water = 50/50 (weight ratio), and drying was performed at 80 ° C. for 10 minutes.
Thereafter, the optical anisotropy was measured again using a liquid crystal alignment film evaluation system “Ray Scan Lab H” (LYS-LH30S-1A) manufactured by Moritex Corporation.
When the change amount of the LAW-ANISOTROPY before and after the washing of the mixed solution of isopropyl alcohol / pure water = 50/50 was evaluated as “」 ”when the change amount was less than 5%,“ X ”when the change amount was 5% or more.

[Production of liquid crystal cell]
A liquid crystal cell having a configuration of an FFS type liquid crystal display element is manufactured.
First, a substrate with electrodes was prepared. The substrate is a glass substrate having a size of 30 mm × 35 mm and a thickness of 0.7 mm. As a first layer, an IZO electrode having a solid pattern and constituting a counter electrode is formed on the substrate. On the counter electrode of the first layer, an SiN (silicon nitride) film formed by a CVD method is formed as a second layer. The thickness of the second-layer SiN film is 500 nm, and functions as an interlayer insulating film. A comb-shaped pixel electrode formed by patterning an IZO film as a third layer is disposed on the second layer of the SiN film, and two pixels of a first pixel and a second pixel are formed. ing. Each pixel is about 10 mm long and about 5 mm wide. At this time, the first layer counter electrode and the third layer pixel electrode are electrically insulated by the action of the second layer SiN film.

  The third-layer pixel electrode has a comb-like shape formed by arranging a plurality of U-shaped electrode elements having a bent central portion. The width in the lateral direction of each electrode element is 3 μm, and the interval between the electrode elements is 6 μm. Since the pixel electrode forming each pixel is formed by arranging a plurality of electrode elements in the shape of a V-shape bent at the center, the shape of each pixel is not rectangular, but is similar to the electrode element. With a shape resembling a bold U-shape. Each pixel is vertically divided by a center bent portion, and has a first region above the bent portion and a second region below the bent portion.

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

  Next, the obtained liquid crystal aligning agent was filtered through a 1.0 μm filter, and then applied to the prepared substrate with electrodes by spin coating. After drying on a hot plate at 100 ° C. for 100 seconds, baking was performed in a hot air circulation oven at 230 ° C. for 20 minutes to obtain a polyimide film having a thickness of 60 nm. This polyimide film is rubbed with rayon cloth (roller diameter: 120 mm, roller rotation speed: 500 rpm, moving speed: 30 mm / sec, indentation length: 0.3 mm, rubbing direction: inclined by 10 ° with respect to the third-layer IZO comb-teeth electrode. After washing in a mixed solvent of isopropyl alcohol and pure water at a volume ratio of 3/7 (volume ratio), ultrasonic irradiation was performed for 1 minute to remove water droplets by air blow. After drying for 15 minutes, a substrate with a liquid crystal alignment film was obtained. In addition, a polyimide film is formed in the same manner as described above on a glass substrate having a columnar spacer having a height of 4 μm and having an ITO electrode formed on the back surface, and orientation treatment is performed in the same procedure as described above. The obtained substrate with a liquid crystal alignment film was obtained. A pair of these two substrates with a liquid crystal alignment film was formed, and a sealant was printed on the substrate while leaving a liquid crystal injection port, and the other substrate was aligned with the liquid crystal alignment film surfaces facing in the anti-parallel rubbing direction. After bonding, the sealant was cured to form an empty cell having a cell gap of 4 μm. Liquid crystal MLC-2041 (manufactured by Merck) was injected into the empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS type liquid crystal cell. Thereafter, the obtained liquid crystal cell was heated at 110 ° C. for 30 minutes, left at 23 ° C. overnight, and then used for each evaluation.

[Liquid Crystal Alignment-2] Alignment Control Force in Long-Term Driving FFS Cell An AC voltage at which relative transmittance becomes 100% at a frequency of 30 Hz under a constant temperature environment of 60 ° C. is applied to a liquid crystal cell manufactured by the above-described method. Time applied.
Thereafter, the pixel electrode of the liquid crystal cell and the counter electrode were short-circuited and left at room temperature for one day.
After standing, the liquid crystal cell is placed between two polarizing plates arranged so that the polarization axes are orthogonal to each other, and the backlight is turned on in a state where no voltage is applied so that the luminance of transmitted light is minimized. The arrangement angle of the liquid crystal cell was adjusted. Then, the rotation angle when the liquid crystal cell was rotated from the angle at which the second area of the first pixel was darkest to the angle at which the first area was darkest was calculated as the angle Δ. Similarly, the second pixel was compared with the second region and the first region, and the same angle Δ was calculated. Then, the average value of the angle Δ values of the first pixel and the second pixel was calculated as the angle Δ of the liquid crystal cell. The case where the value of the angle Δ of the liquid crystal cell was 0.2 degrees or less was defined as ○, and the case where the value of the angle Δ was 0.2 degrees or more was defined as x.

(Synthesis example 1)
97.92 g (425.3 mmol) of Z-1 was placed in a 2000 mL separable flask containing a stirrer, and 924.8 g of N-methyl-2-pyrrolidone was added thereto. While stirring this diamine solution, 83.41 g (420.7 mmol) of Y-1 was added, and 102.8 g of N-methyl-2-pyrrolidone was further added. The mixture was stirred at 23 ° C. for 15 hours under a nitrogen atmosphere to obtain a polyamic acid. An acid solution was obtained. The viscosity at a temperature of 25 ° C. of this polyamic acid solution was 172 mPa · s.
NMP was added to 562.0 g of the obtained polyamic acid solution to dilute the solution to 6% by weight, and then 197.5 g of acetic anhydride and 76.55 g of pyridine were added as imidation catalysts, followed by a reaction at 50 ° C. for 5 hours. This reaction solution was poured into 5772 ml of methanol, and the obtained precipitate was separated by filtration. The precipitate was washed with methanol and dried at 100 ° C. under reduced pressure to obtain a polyimide powder. The imidation ratio of this polyimide powder was 85%, Mn was 9,800, and Mw was 19,300.

(Synthesis example 2)
In a 1000 mL four-necked flask containing a stirrer, 51.7 g (200.0 mmol) of Z-2 was added, 672.2 g of N-methyl-2-pyrrolidone was added, and the mixture was stirred and dissolved while sending nitrogen. . While stirring this diamine solution, 41.7 g (191.2 mmol) of Y-2 was added, and 168.1 g of N-methyl-2-pyrrolidone was further added. After stirring at 23 ° C. for 2 hours under a nitrogen atmosphere, The mixture was stirred at 50 ° C. for 24 hours to obtain a polyamic acid solution (PA-1). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 135 mPa · s. Further, Mn of this polyamic acid was 12,600 and Mw was 0,900.

(Synthesis example 3)
After putting 51.2 g (165.0 mmol) of Y-3 and 91.6 g (352.0 mmol) of Y-4 into a 5000 mL separable flask containing a stirrer, 2739 g of N-methyl-2-pyrrolidone was added. The mixture was stirred and dissolved. Next, 109.6 g (1083 mmol) of triethylamine, 32.9 g (165.0 mmol) of Z-3, 48.2 g (165.0 mmol) of Z-4, and 65.6 g (220.0 mmol) of Z-5. Was added and stirred to dissolve.
While stirring the solution, 415.4 g (1084 mmol) of DBOP was added, 376.3 g of N-methyl-2-pyrrolidone was further added, and the mixture was stirred at room temperature for 16 hours to obtain a solution of a polyamic acid ester. The viscosity at a temperature of 25 ° C. of this polymic acid ester solution was 26.2 mPa · s.
This polymic acid ester solution was put into 23579 g of isopropyl alcohol, and the obtained precipitate was separated by filtration. The precipitate was washed with isopropyl alcohol and then dried under reduced pressure at a temperature of 100 ° C. to obtain a polyamic acid ester powder. Mn of this polyamic acid ester was 10,300 and Mw was 20,600.

(Comparative Example 1)
41.8 g of the polyimide powder obtained in Synthesis Example 1 was placed in a 1000 mL Erlenmeyer flask containing a stirrer, 306.3 g of N-methyl-2-pyrrolidone was added, and the mixture was stirred at room temperature for 18 hours to dissolve. Subsequently, 194.9 g of N-methyl-2-pyrrolidone and 30.88 g of butyl cellosolve were added, and the mixture was stirred for 2 hours to obtain a polyimide solution having a solid content concentration of 7.11% by weight. C-1).
A polyimide film is prepared using the liquid crystal aligning agent (C-1), and the rubbing resistance of the polyimide film, the organic solvent stability of optical anisotropy, and the alignment regulating force in a long-term driving FFS cell are determined by the methods described above. It was evaluated based on: Table 1 shows the obtained results.

(Example 1)
The polyimide powder obtained in Synthesis Example 1 was prepared in the same manner as in Comparative Example 1 except that the block isocyanate compound (X1) as an additional component was added in an amount of 3.00% by weight based on the solid content of the polyimide. Using this, the liquid crystal aligning agent (E-1) of Example 1 was prepared.
A polyimide film is prepared using the liquid crystal aligning agent (E-1), and the rubbing resistance of the polyimide film, the organic solvent stability of optical anisotropy, and the alignment regulating force in a long-term driving FFS cell are determined by the above-described method. It was evaluated based on: Table 1 shows the obtained results.

(Comparative Example 2)
12.5 g of the polyamic acid solution obtained in Synthesis Example 2 was placed in a 100 mL Erlenmeyer flask containing a stirrer, 1.21 g of N-methyl-2-pyrrolidone and 5.87 g of butyl cellosolve were added, and the mixture was stirred for 2 hours and solidified. A polyamic acid solution having a concentration of 6.06% by weight was obtained, and used as a liquid crystal aligning agent (C-2) of Comparative Example 2.
A polyimide film is prepared using the liquid crystal aligning agent (C-2), and the rubbing resistance of the polyimide film, the organic solvent stability of optical anisotropy, and the alignment regulating force in the long-term driving FFS cell are determined by the above-described method. It was evaluated based on: Table 1 shows the obtained results.

(Example 2)
The polyamic acid obtained in Synthesis Example 2 in the same manner as in Comparative Example 2 except that the block isocyanate compound (X1) as an additional component was added in an amount of 3.00% by weight based on the solid content of the polyamic acid. Using the solution, a liquid crystal aligning agent (E-2) of Example 2 was prepared.
A polyimide film is prepared using the liquid crystal aligning agent (E-2), and the rubbing resistance of the polyimide film, the organic solvent stability of optical anisotropy, and the alignment regulating force in the long-term driving FFS cell are determined by the method described above. It was evaluated based on: Table 1 shows the obtained results.

(Comparative Example 3)
5.81 g of the polyamic acid ester powder obtained in Synthesis Example 3 was placed in a 100 mL Erlenmeyer flask containing a stirrer, 42.6 g of N-methyl-2-pyrrolidone was added, and the mixture was stirred at room temperature for 18 hours to dissolve. Subsequently, 18.8 g of N-methyl-2-pyrrolidone and 22.4 g of butyl cellosolve were added, and the mixture was stirred for 2 hours to obtain a polyamic acid ester solution having a solid content of 6.00% by weight. Agent (C-3) was obtained.
A polyimide film is prepared using the liquid crystal aligning agent (C-3), and the rubbing resistance of the polyimide film, the organic solvent stability of optical anisotropy, and the alignment regulating force in the long-term driving FFS cell are determined by the method described above. It was evaluated based on: Table 1 shows the obtained results.

(Example 3)
Polyamic acid obtained in Synthesis Example 3 in the same manner as in Comparative Example 3 except that a blocked isocyanate compound (X1) as an additive component was added in an amount of 3.00% by weight based on the solid content of the polyamic acid ester. The liquid crystal aligning agent (E-3) of Example 3 was prepared using the acid ester powder.
A polyimide film is prepared using the liquid crystal aligning agent (E-3), and the rubbing resistance of the polyimide film, the organic solvent stability of optical anisotropy, and the alignment regulating force in a long-term driving FFS cell are determined by the method described above. It was evaluated based on: Table 1 shows the obtained results.

(Comparative Example 4)
Polyamic acid obtained in Synthesis Example 2 in the same manner as in Comparative Example 2 except that a blocked isocyanate compound (X2) as an additional component was added in an amount of 3.00% by weight based on the solid content of the polyamic acid. Using the solution, a liquid crystal aligning agent (C-4) of Comparative Example 4 was prepared.
A polyimide film is prepared using the liquid crystal aligning agent (C-4), and the rubbing resistance of the polyimide film, the organic solvent stability of optical anisotropy, and the alignment regulating force in a long-term driving FFS cell are determined by the above-described method. It was evaluated based on: Table 1 shows the obtained results.

  As shown in Table 1, it was found that the liquid crystal alignment films formed using the liquid crystal alignment agents of Examples 1 to 3 have good rubbing resistance and also have excellent liquid crystal alignment properties.

  On the other hand, it was found that the liquid crystal alignment films formed using the liquid crystal alignment agents of Comparative Examples 1 to 3 had low rubbing resistance and poor organic solvent stability of optical anisotropy. And it turned out that the liquid crystal alignment property of the liquid crystal alignment film formed using the liquid crystal aligning agent containing a blocked isocyanate compound (X2) as an additional component is inferior to the liquid crystal alignment film of this invention.

  From the above, it was found that the liquid crystal alignment agents of Examples 1 to 3 can form a liquid crystal alignment film having both good rubbing resistance and good liquid crystal alignment.

  The liquid crystal alignment film formed using the liquid crystal alignment agent of the present invention has high rubbing resistance and good liquid crystal alignment. Therefore, in order to realize excellent display quality, a strong rubbing treatment is required, and an alignment film for a large liquid crystal TV or a liquid crystal display element for a portable information terminal such as a smartphone which displays a high-definition image. Can be suitably used. That is, the liquid crystal display device of the present invention having the liquid crystal alignment film of the present invention can be suitably used as a display device for a large-sized TV or a portable information terminal such as a smartphone that displays a high-definition image.

  The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2014-053902 filed on Mar. 17, 2014 are incorporated herein by reference as the disclosure of the specification of the present invention. Things.

Claims (8)

It is characterized by containing at least one polymer selected from the group consisting of a polyimide precursor and a polyimide obtained by imidizing the polyimide precursor, and a compound having a blocked isocyanate group represented by the following formula (X1). Liquid crystal aligning agent.

The liquid crystal aligning agent according to claim 1, wherein a thermal dissociation temperature of a block portion of the compound having a blocked isocyanate group represented by the formula (X1) is 50 to 230C. The liquid crystal aligning agent according to claim 1, wherein the polyimide precursor has a structural unit represented by the following formula (3).

(However, R ₁ is a hydrogen atom or 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 5 carbon atoms which may have a substituent. An alkyl group, an alkenyl group having 2 to 10 carbon atoms, or an alkynyl group having 2 to 10 carbon atoms. X ₁ is a tetravalent organic group, and Y ₁ is a divalent organic group.   The liquid crystal aligning agent according to any one of claims 1 to 3, wherein the compound having a blocked isocyanate group is contained in an amount of 0.1% by weight to 10% by weight based on 100% by weight of the polymer.   The polymer is at least one selected from the group consisting of a primary amine, a secondary amine, a polyimide precursor having a carboxylic acid or a urea group, and a polyimide obtained by imidizing the polyimide precursor. The liquid crystal aligning agent according to any one of the above.   A liquid crystal alignment film obtained from the liquid crystal alignment agent according to claim 1.   A method for producing a liquid crystal alignment film, wherein the liquid crystal alignment agent according to claim 1 is applied to a substrate and baked.   A liquid crystal display device comprising the liquid crystal alignment film according to claim 6.