WO2014024885A1

WO2014024885A1 - Liquid crystal aligning agent, and liquid crystal alignment film produced using same

Info

Publication number: WO2014024885A1
Application number: PCT/JP2013/071262
Authority: WO
Inventors: 勇歩野口
Original assignee: 日産化学工業株式会社
Priority date: 2012-08-06
Filing date: 2013-08-06
Publication date: 2014-02-13
Also published as: KR20150042227A; KR102116155B1; JPWO2014024885A1; TW201412824A; CN104685412B; TWI626259B; CN104685412A; JP6152849B2

Abstract

Provided is a liquid crystal aligning agent, from which a coating film having excellent thickness uniformity in a coating surface and excellent linearity and dimensional stability in a periphery of a coated part can be produced, and which is suitable particularly for the coating by an ink-jet method. A liquid crystal aligning agent characterized by comprising at least one polymer selected from the group consisting of polyimide and a polyimide precursor and a solvent comprising an alkyl cellosolve acetate compound represented by formula (1) and dipropylene glycol monomethyl ether. (In the formula, R¹ represents an alkyl group having 1 to 8 carbon atoms.)

Description

Liquid crystal alignment agent and liquid crystal alignment film using the same

The present invention relates to a liquid crystal aligning agent suitable for application by an ink jet method and having high dimensional stability when applied, and a liquid crystal alignment film obtained from the liquid crystal aligning agent.

As the liquid crystal alignment film, a so-called polyimide liquid crystal alignment film is widely used, which is obtained by applying and baking a liquid crystal alignment agent mainly composed of a polyimide precursor such as polyamic acid (also called polyamic acid) or a solution of soluble polyimide. in use.
Generally, spin coating, dip coating, flexographic printing, and the like are known as film forming methods for such a liquid crystal alignment film. Actually, there are many applications by flexographic printing.
However, flexographic printing requires various types of resin plates due to differences in the types of liquid crystal panels, complicated plate replacement in the manufacturing process, and deposition on a dummy substrate to stabilize the deposition process. In other words, there are problems such as that the production of the plate contributes to an increase in the manufacturing cost of the liquid crystal display panel.

For this reason, an inkjet method has attracted attention as a new method for applying a liquid crystal alignment film without using a printing plate. The ink jet method is a method in which fine droplets are dropped on a substrate and a film is formed by wetting and spreading of the liquid. Not only the printing plate is not used, but also the printing pattern can be set freely, so that the manufacturing process of the liquid crystal display element can be simplified. In addition, there is an advantage that the waste of the coating liquid is reduced because the film formation on the dummy substrate which is necessary for flexographic printing is not necessary.
Application by the inkjet method is expected to reduce the cost of liquid crystal panels and improve production efficiency.

The liquid crystal alignment film formed by the ink jet method is required to have small film thickness unevenness inside the coating surface and high film forming accuracy in the peripheral part of the coating. In general, a liquid crystal alignment film formed by an ink-jet method has a trade-off relationship between the uniformity of the film thickness in the coating surface and the film forming accuracy in the periphery of the coating. Usually, a material with high in-plane uniformity has poor dimensional stability in the periphery of the coating, and the film protrudes from the set dimensions. On the other hand, the material in which the coating peripheral part is a straight line has poor uniformity in the coated surface.
In order to improve the film forming accuracy of the coating peripheral part, a method of confining the alignment film in a predetermined range with a structure has been proposed (see Patent Document 1, Patent Document 2, and Patent Document 3).
However, these methods have the disadvantage that additional structures are required.

Japanese Unexamined Patent Publication No. 2004-361623 Japanese Unexamined Patent Publication No. 2008-145461 Japanese Unexamined Patent Publication No. 2010-281925

An object of the present invention is to form a polyimide-based liquid crystal aligning agent suitable for the ink jet method, which can form a coating film having excellent uniformity of film thickness within the coating surface, linearity and dimensional stability of the coating peripheral portion, and the same. The object is to provide a liquid crystal alignment film.

The inventor has conducted research to achieve the above object, and has arrived at the present invention having the following summary.
1. It contains at least one polymer selected from the group consisting of polyimide and a polyimide precursor, and a solvent containing an alkyl cellosolve acetate compound represented by the following formula (1) and dipropylene glycol monomethyl ether. Liquid crystal aligning agent.

(R ¹ is an alkyl group having 1 to 8 carbon atoms.)
2. 2. The liquid crystal aligning agent according to 1 above, wherein the polyimide precursor contains at least one selected from the group consisting of a polyamic acid ester and a polyamic acid.
3. 3. The liquid crystal aligning agent according to 1 or 2 above, wherein the solvent contains at least one selected from the group consisting of N-methylpyrrolidone and γ-butyrolactone.
4). 4. The liquid crystal aligning agent according to any one of 1 to 3, wherein the alkyl cellosolve acetate compound is at least one selected from the group consisting of methyl cellosolve acetate, ethyl cellosolve acetate, and butyl cellosolve acetate.
5. 5. The liquid crystal aligning agent according to any one of 1 to 4 above, containing 1 to 5% by mass of the polymer.
6). 6. The liquid crystal aligning agent according to any one of 1 to 5 above, containing 95 to 99% by mass of the solvent.
7). 7. The liquid crystal aligning agent according to any one of 1 to 6 above, wherein the solvent contains 0.5 to 20% by mass of an alkyl cellosolve acetate compound and 1 to 30% by mass of dipropylene glycol monomethyl ether.
8). 8. The liquid crystal aligning agent according to any one of 1 to 7 above, having a viscosity of 5 to 20 mPa · s.
9. 9. A method for forming a liquid crystal alignment film, wherein the liquid crystal aligning agent according to any one of 1 to 8 is applied by an inkjet method.
10. 9. A liquid crystal alignment film obtained by applying the liquid crystal aligning agent according to any one of 1 to 8 above, drying and firing.
11. 11. The liquid crystal alignment film as described in 10 above, having a thickness of 5 to 300 nm.
12 12. A liquid crystal display device having the liquid crystal alignment film as described in 10 or 11 above.

The liquid crystal aligning agent of the present invention, particularly when applied by an ink jet method, is excellent in the uniformity of the film thickness in the coating surface, and is excellent in the linearity and dimensional stability of the peripheral portion of the application. Then, the coating film which has the outstanding characteristic which was difficult to obtain simultaneously is obtained. Such a liquid crystal alignment film of the present invention has excellent characteristics in terms of in-plane uniformity and linearity in the peripheral portion.

<Polyimide precursor>
The polyimide precursor contained in the liquid crystal aligning agent of this invention produces | generates a polyimide by imidating this, and means a polyamic acid ester and / or a polyamic acid.
The polyamic acid ester and the polyamic acid have the following formula (1) and the following formula (2), respectively.

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

The above alkyl group, alkenyl group, or 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 by the substituent. Note that forming a ring structure with a substituent means that the substituents or a substituent and a part of the mother skeleton are bonded to form a ring structure.

Examples of such substituents are halogen groups, hydroxyl groups, thiol groups, nitro groups, aryl groups, organooxy groups, organothio groups, organosilyl groups, acyl groups, ester groups, thioester groups, phosphate ester groups, amide groups, alkyls. Group, alkenyl group, alkynyl group and the like.
Examples of the halogen group as a substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

A phenyl group is mentioned as an aryl group which is a substituent. This aryl group may be further substituted with the other substituent described above.
The organooxy group as a substituent can have a structure represented by —O—R. The R may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These Rs may be further substituted with the substituent described above. Specific examples of the organooxy group include methoxy group, ethoxy group, propyloxy group, butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group and the like.

The organothio group as a substituent can have a structure represented by —S—R.
Examples of R include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. These Rs may be further substituted with the substituent described above. Specific examples of the 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.

The organosilyl group as a substituent can have a structure represented by —Si— (R) ₃ . The R may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These Rs may be further substituted with the substituent described above. Specific examples of the 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.

The acyl group as a substituent can have a structure represented by —C (O) —R.
Examples of R include the above-described alkyl group, alkenyl group, and aryl group. These Rs may be further substituted with the substituent described above. Specific examples of the acyl group include formyl group, acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group, isovaleryl group, benzoyl group and the like.
As the ester group which is a substituent, a structure represented by —C (O) O—R or —OC (O) —R can be shown. Examples of R include the aforementioned alkyl group, alkenyl group, alkynyl group, aryl group, and the like. These Rs may be further substituted with the substituent described above.

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

The amide group as a substituent includes —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. The R may be the same or different, and examples thereof include the alkyl group, alkenyl group, alkynyl group, and aryl group described above. These Rs may be further substituted with the substituent described above.
Examples of the aryl group as a substituent include the same aryl groups as described above. This aryl group may be further substituted with the other substituent described above.
Examples of the alkyl group as a substituent include the same alkyl groups as described above. This alkyl group may be further substituted with the other substituent described above.

Examples of the alkenyl group as a substituent include the same alkenyl groups as described above. This alkenyl group may be further substituted with the other substituent described above.
Examples of the alkynyl group that is a substituent include the same alkynyl groups as described above. This alkynyl group may be further substituted with the other substituent described above.
In general, when a bulky structure is introduced, there is a possibility that the reactivity of the amino group and the liquid crystal orientation may be lowered. Therefore, as A ₁ and A ₂ , a hydrogen atom or a carbon atom that may have a substituent is 1 An alkyl group of 1 to 5 is more preferable, and a hydrogen atom, a methyl group, or an ethyl group is particularly preferable.

In the above formulas (1) and (2), X ₁ and X ₂ are each independently a tetravalent organic group, and Y ₁ and Y ₂ are each independently a divalent organic group.
X ₁ and X ₂ are tetravalent organic groups and are not particularly limited. Two or more kinds of X ₁ and X ₂ may be mixed in the polyimide precursor. Specific examples of X ₁ and X ₂ include X-1 to X-46 shown below.

Among these, X ₁ and X ₂ are 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 and the like are preferable.
The amount of tetracarboxylic dianhydride having these preferable X ₁ and X ₂ is preferably 2 to 100 mol%, more preferably 40 to 100 mol% of the total tetracarboxylic dianhydride.

In the above formulas (1) and (2), Y ₁ and Y ₂ are each independently a divalent organic group and are not particularly limited. Specific examples of Y ₁ and Y ₂ include the following Y-1 to Y-104. Two or more kinds of Y ₁ and Y ₂ may be mixed.

Among them, in order to introduce a highly linear diamine to the polyamic acid or polyamic acid ester to obtain a good liquid crystal alignment property, 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- Diamines having 46, Y-48, Y-61, Y-63, Y-64, Y-71, Y-72, Y-73, Y-74, Y-75, Y-98 and the like are preferred.
The amount of the diamine having a preferable Y ₁ as described above is preferably 1 to 100 mol%, more preferably 50 to 100 mol% of the total diamine.
Among them, when it is desired to increase the pretilt angle, it is preferable to introduce a diamine having a long-chain alkyl group, an aromatic ring, an aliphatic ring, a steroid skeleton, or a combination thereof in the side chain into the polyamic acid ester. . In this case, 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, Y-87, Y-88, Y-89, Y-90, Y-91, Y-92, Y-93, Y-94, Y-95, Y-96, Y-97 and the like are more preferable.
Among these, as Y _1, particularly preferably at least one selected from structures represented by the following formula.

By introducing a diamine having a heteroatom structure, a polycyclic aromatic structure, or a biphenyl skeleton into a polyamic acid, the volume resistivity of the polyamic acid or polyamic acid ester is lowered, thereby reducing afterimages due to DC voltage accumulation. For this purpose, Y- ₂ is represented by Y-19, Y-23, Y-25, Y-26, Y-27, Y-30, Y-31, Y-32, Y-33, Y-34, Y- 35, Y-36, Y-40, Y-41Y-42, Y-44, Y-45, Y-49, Y-50, Y-51, Y-61 and the like are more preferable.
Particularly preferred is a diamine having the following Y-31 or Y-40 structure.
The amount of the diamine having a preferable Y ₂ as described above is preferably 1 to 100 mol%, more preferably 50 to 100 mol% of the total diamine.

<Method for producing polyamic acid ester>
The polyamic acid ester represented by the above formula (1) is obtained by reaction of any of the tetracarboxylic acid derivatives represented by the following formulas (6) to (8) with the diamine compound represented by the formula (9). be able to.

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

The polyamic acid ester represented by the above formula (1) can be synthesized by the following methods (1) to (3) using the above monomer.
(1) 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 a 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.
The esterifying agent is preferably one that can be easily removed by purification, 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, and more preferably 2 to 4 molar equivalents, per 1 mol of the polyamic acid repeating unit.

The solvent used in the reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, γ-butyrolactone or the like from the solubility of the polymer, and these may be used alone or in combination.
The 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 is unlikely to occur and a high molecular weight product is easily obtained.

(2) When synthesized by reaction of tetracarboxylic acid diester dichloride and diamine Polyamic acid ester can be synthesized from tetracarboxylic acid diester dichloride and diamine.

Specifically, tetracarboxylic acid diester dichloride and diamine are reacted in the presence of a base and a solvent at −20 to 150 ° C., preferably 0 to 50 ° C., for 30 minutes to 24 hours, preferably 1 to 4 hours. Can be synthesized.
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, preferably 2 to 3 times mol with respect to tetracarboxylic acid diester dichloride, from the viewpoint of easy removal and high molecular weight. More preferred.

The solvent used in the reaction is preferably N-methyl-2-pyrrolidone, γ-butyrolactone or the like in view of 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 is difficult to occur and a high molecular weight product is easily obtained.
In order to prevent hydrolysis of the tetracarboxylic acid diester dichloride, the solvent used for the synthesis of the polyamic acid ester is preferably dehydrated as much as possible, and the reaction is preferably prevented from mixing outside air in a nitrogen atmosphere.

(3) When synthesize | combining by reaction with tetracarboxylic-acid diester and diamine Polyamic acid ester is compoundable by polycondensing tetracarboxylic-acid diester and diamine.
Specifically, tetracarboxylic acid diester and diamine are reacted in the presence of a condensing agent, a base, and a solvent at 0 to 150 ° C., preferably 0 to 100 ° C., for 30 minutes to 24 hours, preferably 3 to 15 hours. Can be synthesized.

Examples of the condensing agent include triphenyl phosphite, dicyclohexylcarbodiimide, 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride, N, N′-carbonyldiimidazole, dimethoxy-1,3,5-triazide. Nylmethylmorpholinium, 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. The addition amount of the condensing agent is preferably 2 to 3 times the molar amount of 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 moles, more preferably 2 to 3 moles, relative to the diamine component from the viewpoint of easy removal and high molecular weight.

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 times mol, more preferably 0.2 to 0.8 times mol based on the diamine component.
Among the methods for synthesizing the three polyamic acid esters, since a high molecular weight polyamic acid ester is obtained, the method (1) or (2) is particularly preferable.
In the polyamic acid ester solution obtained as described above, the polymer can be precipitated by pouring into a poor solvent while stirring well. A purified polyamic acid ester powder can be obtained by performing precipitation several times, washing with a poor solvent, and drying at room temperature or by heating.
Although a poor solvent is not specifically limited, Water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene etc. are mentioned.
The weight average molecular weight of the polyamic acid ester is preferably 5,000 to 300,000, and more preferably 10,000 to 200,000. The number average molecular weight is preferably 2,500 to 150,000, and more preferably 5,000 to 100,000.

<Method for producing polyamic acid>
The polyamic acid represented by the above formula (2) can be obtained by a reaction between a tetracarboxylic dianhydride represented by the following formula (10) and a diamine compound represented by the formula (11).

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

Specifically, tetracarboxylic dianhydride and diamine are reacted in the presence of a solvent at −20 to 150 ° C., preferably 0 to 50 ° C., for 30 minutes to 24 hours, preferably 1 to 12 hours. Can be synthesized.
The solvent used in the reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, γ-butyrolactone, etc. in view of the solubility of the monomer and polymer. These may be used alone or in combination of two or more. Also good.
The concentration of the polymer 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.
The polyamic acid obtained as described above can be recovered by precipitating a polymer by pouring into a poor solvent while thoroughly stirring the reaction solution. In addition, a purified polyamic acid powder can be obtained by performing precipitation several times, washing with a poor solvent, and drying at room temperature or by heating.
Although a poor solvent is not specifically limited, Water, methanol, ethanol, hexane, butyl cellosolve, acetone, toluene etc. are mentioned.
The weight average molecular weight of the polyamic acid is preferably 10,000 to 305,000, and more preferably 20,000 to 210,000. The number average molecular weight is preferably 5,000 to 152,500, and more preferably 10,000 to 105,000.
<Polyimide>

The polyimide contained in the liquid crystal aligning agent of the present invention can be obtained by imidizing the above polyimide precursor. As the method of imide, thermal imidization by heating and catalyst imidization using a catalyst are generally used. However, the catalyst imidation in which the imidization reaction proceeds at a relatively low temperature is lower in the molecular weight of the resulting polyimide. Is less likely to occur.

Catalytic imidation can be carried out in a solvent by stirring the polyamic acid in the presence of a basic catalyst and an acid anhydride, or stirring the polyamic acid ester in the presence of a basic catalyst. The reaction temperature at this time is −20 to 250 ° C., preferably 0 to 180 ° C. In the catalytic imidation of polyamic acid, the higher the reaction temperature, the faster the imidization proceeds. However, when the reaction temperature is too high, the molecular weight of the polyimide may decrease.
The amount of the basic catalyst is 1 to 60 moles, preferably 2 to 40 moles per mole of the repeating unit of the polyamic acid or polyamic acid ester.
The amount of the acid anhydride for catalytic imidization of the polyamic acid is 2 to 100 moles, preferably 6 to 60 moles per mole of the repeating unit of the polyamic acid.
If the amount of the basic catalyst or acid anhydride is small, the reaction does not proceed sufficiently. If the amount is too large, it becomes difficult to completely remove the reaction after completion of the reaction.
Examples of the basic catalyst used for the catalytic imidation of polyamic acid include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc. Among them, pyridine is preferable because it has an appropriate basicity for proceeding with the reaction. .
Examples of the basic catalyst used for the catalytic imidation of the polyamic acid ester include triethylamine, trimethylamine, tributylamine, trioctylamine and the like, and triethylamine is particularly preferable because of its fast reaction.

Examples of acid anhydrides used for catalytic imidization of polyamic acid include acetic anhydride, trimellitic anhydride, pyromellitic anhydride, etc. Among them, use of acetic anhydride facilitates purification after completion of the reaction. preferable.
The solvent is not limited as long as it dissolves polyamic acid or polyamic acid ester. Specific examples thereof include N, N′-dimethylformamide, N, N′-dimethylacetamide, N-methyl-2. -Pyrrolidone, N-methylcaprolactam, dimethyl sulfoxide, tetramethyl urea, dimethyl sulfone, hexamethyl sulfoxide, γ-butyrolactone and the like can be mentioned. The imidization rate by catalytic imidation can be controlled by adjusting the amount of catalyst, reaction temperature, and reaction time.

The produced polyimide is obtained by putting the reaction solution into a poor solvent and collecting the produced precipitate. In that case, the poor solvent to be used is not particularly limited, and examples thereof include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, and water.
The polyimide that has been poured into a poor solvent and precipitated is filtered, and then can be powdered by drying at normal temperature or under reduced pressure at normal temperature or under reduced pressure. The polyimide can also be purified by repeating the steps of dissolving the polyimide powder in a solvent and reprecipitating it 2 to 10 times. When the impurities cannot be removed by a single precipitation recovery operation, it is preferable to perform this purification step.
The molecular weight of the polyimide is not particularly limited, but is preferably 2,000 to 200,000, more preferably 4,000 to 50,000 in terms of weight average molecular weight from the viewpoint of ease of handling and stability of characteristics when a film is formed. 000.
The above molecular weights are all determined by GPC (gel permeation chromatography).

<End modification of polyimide or polyimide precursor>
The ends of the polyimide, polyamic acid and polyamic acid ester used in the present invention may be modified. By using a terminal-modified polymer, solubility and coating properties can be improved. The terminal modification can be synthesized by adding an acid anhydride, a monoamine compound, an acid chloride compound, a monoisocyanate compound or the like when synthesizing a polyamic acid or polyamic acid ester.

<Liquid crystal aligning agent>
The liquid crystal aligning agent of the present invention is in the form of a solution in which at least one polymer selected from the group consisting of the polyimide precursor and polyimide is dissolved in a solvent. As long as it has such a form, for example, when a polyimide precursor such as polyamic acid ester or polyamic acid and a polyimide are synthesized in a solvent, the reaction solution obtained may be used. It may be diluted. Moreover, when a polyimide precursor and a polyimide are obtained as a powder, this may be dissolved in a solvent to form a solution.

The solvent contained in the liquid crystal aligning agent of the present invention needs to contain an alkyl cellosolve acetate compound. In-plane uniformity is improved by adding alkyl cellosolve acetate.
The alkyl cellosolve acetate compound contained in the solvent is preferably a cellosolve acetate compound having an alkyl group having 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms. Preferable examples include at least one selected from the group consisting of methyl cellosolve acetate, ethyl cellosolve acetate, and butyl cellosolve acetate. Of these, butyl cellosolve acetate is preferred from the viewpoint of an appropriate boiling point and volatilization rate. When the alkyl chain length of the alkyl cellosolve acetate is too long, the boiling point becomes high, causing a problem that it is difficult to dry in the step of drying the liquid crystal alignment film.

In addition, the solvent contained in the liquid crystal aligning agent of the present invention needs to contain dipropylene glycol monomethyl ether. By adding dipropylene glycol monomethyl ether, the expansion width from the set dimension is suppressed, and the dimensional stability is improved.

The solvent is not particularly limited as long as the polymer can be dissolved uniformly. Specific examples include γ-butyrolactone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N -Methylcaprolactam, 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethyl sulfoxide, dimethyl sulfone, 1,3-dimethyl-imidazolidinone, 3-methoxy-N, N-dimethylpropanamide and the like. You may use these 1 type or in mixture of 2 or more types. Of these, γ-butyrolactone or N-methyl-2-pyrrolidone is preferable from the viewpoint of versatility and solubility.

The viscosity of the liquid crystal aligning agent of the present invention is preferably 5 to 20 mPa · s, particularly preferably 5 to 15 mPa · s, from the viewpoint of inkjet coating.
The content of the solvent in the liquid crystal aligning agent of the present invention is selected in consideration of the above viscosity, and is preferably 95 to 99% by mass, and particularly preferably 96 to 98% by mass. In this case, a concentrated solution of the polymer may be prepared in advance and diluted when the liquid crystal aligning agent is used from the concentrated solution. When the content of the solvent is higher than 99% by mass, the film thickness of the liquid crystal alignment film becomes too small to obtain a good liquid crystal alignment film, and when the content of the solvent is lower than 95% by mass, the ink jet printing is performed. , Ejectability from the head is deteriorated.

The content of the alkyl cellosolve acetate compound in the solvent is preferably 0.5 to 20% by mass, more preferably 0.8 to 10% by mass, and still more preferably 0.9 to 5% by mass. When the content is small, the in-plane uniformity and dimensional stability of the ink jet coating film are insufficient, and when the content is too large, the storage stability of the liquid crystal aligning agent during freezing deteriorates.

The content of dipropylene glycol monomethyl ether in the solvent is preferably 1 to 30% by mass, more preferably 1 to 15% by mass, and further preferably 1.5 to 6% by mass. When the content is small, the dimensional stability of the inkjet coating film becomes insufficient, and when the content is too large, the in-plane uniformity is deteriorated.

Furthermore, the content of dipropylene glycol monomethyl ether is preferably the same as or more than the content of the alkyl cellosolve acetate compound, in order to achieve both dimensional stability and in-plane uniformity.

On the other hand, the content of the polymer in the liquid crystal aligning agent of the present invention can be appropriately changed by setting the thickness of the polyimide film to be formed, but from the viewpoint of forming a uniform and defect-free coating film. The content is preferably 1 to 5% by mass, particularly preferably 2 to 4% by mass.

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 agent is applied and the liquid crystal alignment film formed thereon. Existing silane coupling agents are added.
If the addition amount of the silane coupling agent is too large, unreacted ones may adversely affect the liquid crystal alignment, and if it is too small, the effect on adhesion will not appear, so the solid content of the polymer in the liquid crystal alignment agent The content is preferably 0.01 to 5.0% by weight, more preferably 0.1 to 1.0% by weight. 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.

In addition, an imidization accelerator may be added to the liquid crystal aligning agent of the present invention in order to efficiently advance imidization of the polyimide precursor when the coating film is baked. Existing imidation accelerators are used.
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 the present invention is a film obtained by applying the liquid crystal aligning agent to a substrate, drying and baking. The substrate to which the liquid crystal aligning agent of the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, a plastic substrate such as an acrylic substrate or a polycarbonate substrate, or the like can be used. In addition, it is preferable to use a substrate on which an ITO electrode or the like for driving liquid crystal is formed from the viewpoint of simplifying the process.
Further, in the reflection type liquid crystal display element, an opaque object such as a silicon wafer can be used as long as it is only a substrate on one side, and a material that reflects light such as aluminum can be used for the electrode in this case.

As a coating method of the liquid crystal aligning agent of the present invention, an ink jet method, a spin coat method, a printing method, or the like can be used. As described above, the ink jet method is particularly suitable.
The coating film formed by applying the liquid crystal aligning agent of the present invention by the ink jet method is excellent in the uniformity of the film thickness in the coating surface, the linearity and the dimensional stability of the coating peripheral part.

Arbitrary temperature and time can be selected for the drying and baking steps after applying the liquid crystal aligning agent of the present invention. Usually, in order to sufficiently remove the contained solvent, it is dried at 50 to 120 ° C., preferably 60 to 90 ° C. for 1 to 10 minutes, and then 150 to 300 ° C., preferably 180 to 250 ° C. for 5 to 120 ° C. It is fired in minutes.
The thickness of the coating film after baking is not particularly limited, but if it is too thin, the reliability of the liquid crystal display element may be lowered, and therefore it is 5 to 300 nm, preferably 10 to 200 nm.

The liquid crystal alignment treatment agent of the present invention can be applied as a liquid crystal alignment film without applying an alignment treatment in a vertical alignment application or the like after being applied and baked on a substrate and then subjected to an alignment treatment or the like.

[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 manufacturing method of 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 for injecting liquid crystal after reducing the pressure inside the produced liquid crystal cell, and a dropping method for sealing after dropping the liquid crystal.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not construed as being limited to these examples.
Abbreviations in the compounds used in Examples and Comparative Examples are as follows.
1,3DMCBDE-Cl: Dimethyl 1,3-bis (chlorocarbonyl) -1,3-dimethylcyclobutane-2,4-dicarboxylate BDA: 1,2,3,4-butanetetracarboxylic dianhydride PMDA: Pyromellitic anhydride DADDA: 4,4′-diaminodiphenylamine DBA: 3,5-diaminobenzoic acid p-PDA: p-phenylenediamine DA-A: diamine of the following formula DA-A

(solvent)
NMP: N-methyl-2-pyrrolidone GBL: γ-butyrolactone BCA: Butyl cellosolve acetate BCS: Butyl cellosolve DPM: Dipropylene glycol monomethyl ether

[viscosity]
The viscosity of the polyamic acid ester and the polyamic acid body solution was measured using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.), a sample amount of 1.1 mL (milliliter), cone rotor TE-1 (1 ° 34 ′, R24), measured at a temperature of 25 ° C.

[Measurement of molecular weight]
The molecular weights of the polyimide, polyamic acid, and polyamic acid ester are measured by a GPC (room temperature gel permeation chromatography) apparatus, and the number average molecular weight (hereinafter also referred to as Mn) and the weight average molecular weight as polyethylene glycol and polyethylene oxide equivalent values. (Hereinafter also referred to as Mw) was calculated.
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) 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) of about 900,000, 150,000, 100,000, and 30000) manufactured by Tosoh Corporation, and polyethylene glycol (peak top) manufactured by Polymer Laboratory Molecular weight (Mp) about 12000, 4000, and 1000).
In order to avoid the overlapping of peaks, two samples of 90000, 100000, 12000, and 1000 mixed samples and 2 samples of 150,000, 30000, and 4000 mixed samples were measured separately.

[Measurement of imidization rate]
20 mg of polyimide powder was put into an NMR sample tube, and 0.53 mL of deuterated dimethyl sulfoxide (DMSO-d6 and 0.05 mass% TMS (tetramethylsilane) mixture) was added and completely dissolved. This solution was measured for proton NMR at 500 MHz with an NMR measuring instrument (JNM-ECA500) manufactured by JEOL Datum.
The imidation rate is determined based on protons derived from structures that do not change before and after imidation as reference protons, and the peak integrated value of these protons and proton peaks derived from NH groups of polyamic acid appearing in the vicinity of 9.5 to 10.0 ppm. It calculated | required by following Formula using the integrated value.
Imidization rate (%) = (1−α · x / y) × 100
In the above formula, x is the proton peak integrated value derived from the NH group of the polyamic acid, y is the peak integrated value of the reference proton, and α is one NH group proton of the polyamic acid in the case of the polyamic acid (imidation rate is 0%). The number ratio of the reference protons.

<Synthesis Example 1>
A 300 mL four-necked flask was charged with p-PDA (114.59 g, 1.06 mol) and DA-A (44.68 g, 0.12 mol), and NMP (1814 mL), GBL (5175 mL), and pyridine (210 0.1 g, 2.66 mol) was added and dissolved. Next, while stirring this solution, 1,3DMCBDE-Cl (359.85 g, 1.11 mol) was added and reacted for 4 hours under water cooling. The resulting polyamic acid solution was diluted by adding 500 mL of GBL. This solution was added to 47300 g of IPA with stirring, and the precipitated white precipitate was collected by filtration, washed 5 times with 23649 g of IPA, and dried to obtain 428.0 g of white polyamic acid ester resin powder. . The yield was 96%. Moreover, the molecular weight of this polyamic acid ester was Mn = 15182 and Mw = 30115.

<Synthesis Example 2>
As tetracarboxylic dianhydride components, BDA (175.94 g, 0.74 mol) and PMDA (52.34 g, 0.20 mol), and as diamine components, DADPA (191.28 g, 0.80 mol) and DBA ( 36.52 g, 0.20 mol) was reacted in NMP 516.9 g and GBL 2068 g at room temperature for 4 hours to obtain a polyamic acid solution. The molecular weight of this polyamic acid solution was Mn = 15058 and Mw = 35072.

<Example 1>
In a 100 mL Erlenmeyer flask containing a stir bar, 5.76 g of GBL was added to 0.64 g of the polyamic acid ester obtained in Synthesis Example 1, and dissolved by stirring. Next, 8.46 g of polyamic acid obtained in Synthesis Example 2, NMP 0.84 g, GBL 32.6 g, BCA 0.50 g, and DPM 1.25 g were added and stirred to obtain a liquid crystal aligning agent.

<Example 2>
In a 100 mL Erlenmeyer flask containing a stir bar, 5.76 g of GBL was added to 0.64 g of the polyamic acid ester obtained in Synthesis Example 1, and dissolved by stirring. Next, 8.46 g of polyamic acid obtained in Synthesis Example 2, 0.81 g of NMP, 31.8 g of GBL, 1.27 g of BCA and 1.26 g of DPM were added and stirred to obtain a liquid crystal aligning agent.

<Example 3>
In a 100 mL Erlenmeyer flask containing a stir bar, 5.76 g of GBL was added to 0.64 g of the polyamic acid ester obtained in Synthesis Example 1, and dissolved by stirring. Next, 8.47 g of the polyamic acid obtained in Synthesis Example 2, 0.74 g of NMP, 30.6 g of GBL, 1.25 g of BCA, and 2.51 g of DPM were added and stirred to obtain a liquid crystal aligning agent.

<Comparative Example 1>
In a 100 mL Erlenmeyer flask containing a stir bar, 5.76 g of GBL was added to 0.64 g of the polyamic acid ester obtained in Synthesis Example 1, and dissolved by stirring. Next, 8.46 g of polyamic acid obtained in Synthesis Example 2, NMP 0.82 g, GBL 31.9 g, and DPM 2.51 g were added and stirred to obtain a liquid crystal aligning agent.

<Comparative Example 2>
In a 100 mL Erlenmeyer flask containing a stir bar, 5.76 g of GBL was added to 0.64 g of the polyamic acid ester obtained in Synthesis Example 1, and dissolved by stirring. Next, 8.46 g of polyamic acid obtained in Synthesis Example 2, 0.67 g of NMP, 29.5 g of GBL, and 5.02 g of DPM were added and stirred to obtain a liquid crystal aligning agent.

<Comparative Example 3>
To a 100 mL Erlenmeyer flask containing a stir bar, 5.76 g of GBL was added to 0.64 g of the polyamic acid ester obtained in Synthesis Example 1, and dissolved by stirring. Next, 8.47 g of polyamic acid obtained in Synthesis Example 2, 0.81 g of NMP, 31.8 g of GBL, and 2.50 g of BCA were added and stirred to obtain a liquid crystal aligning agent.

<Comparative example 4>
In a 100 mL Erlenmeyer flask containing a stir bar, 5.76 g of GBL was added to 0.64 g of the polyamic acid ester obtained in Synthesis Example 1, and dissolved by stirring. Next, 8.46 g of polyamic acid obtained in Synthesis Example 2, 0.67 g of NMP, 29.5 g of GBL, and 5.01 g of BCA were added and stirred to obtain a liquid crystal aligning agent.

<Comparative Example 5>
In a 100 mL Erlenmeyer flask containing a stir bar, 5.76 g of GBL was added to 0.64 g of the polyamic acid ester obtained in Synthesis Example 1, and dissolved by stirring. Next, 8.47 g of polyamic acid obtained in Synthesis Example 2, 0.80 g of NMP, 31.8 g of GBL, and 2.51 g of BCS were added and stirred to obtain a liquid crystal aligning agent.

<Comparative Example 6>
In a 100 mL Erlenmeyer flask containing a stir bar, 5.76 g of GBL was added to 0.64 g of the polyamic acid ester obtained in Synthesis Example 1, and dissolved by stirring. Next, 8.46 g of polyamic acid obtained in Synthesis Example 2, 0.66 g of NMP, 29.5 g of GBL, and 5.00 g of BCS were added and stirred to obtain a liquid crystal aligning agent.

<Comparative Example 7>
In a 100 mL Erlenmeyer flask containing a stir bar, 5.76 g of GBL was added to 0.64 g of the polyamic acid ester obtained in Synthesis Example 1, and dissolved by stirring. Next, 8.46 g of the polyamic acid obtained in Synthesis Example 2, 0.81 g of NMP, 31.8 g of GBL, 1.27 g of BCA, and 1.25 g of BCS were added and stirred to obtain a liquid crystal aligning agent.

<Comparative Example 8>
In a 100 mL Erlenmeyer flask containing a stir bar, 5.76 g of GBL was added to 0.64 g of the polyamic acid ester obtained in Synthesis Example 1, and dissolved by stirring. Next, 8.46 g of polyamic acid obtained in Synthesis Example 2, 0.67 g of NMP, 29.5 g of GBL, 2.51 g of BCA and 2.51 g of BCS were added and stirred to obtain a liquid crystal aligning agent.

[Formation of liquid crystal alignment film by inkjet printing]
Using the liquid crystal aligning agents obtained in Examples 1 to 3 and Comparative Examples 1 to 8, application to a substrate by ink jet printing and baking of the applied film were performed with the following apparatuses and conditions.
The viscosity of each liquid crystal aligning agent in Examples 1 to 3 and Comparative Examples 1 to 8 was 9 mPa · s.
Device name: Fine pattern coating device by inkjet printing (HIS-200-1H, manufactured by Hitachi Plant Technologies, Ltd.)
Coating substrate: 100 mm × 100 mm ITO substrate Coating area: 72 mm × 80 mm
Coating conditions: 15 μm resolution, stage speed 40 mm / sec, frequency 2000 Hz, pulse width 9.6 μsec, appropriate amount 42 pl, pitch width 60 μm, pitch length 141 μm, applied voltage: 15 V, and nozzle gap 0.5 mm, coating film After the standing time of 30 sec, drying was performed at a drying temperature of 50 ° C. and a drying time of 2 minutes (hot plate), and baking was performed at a main baking temperature of 230 ° C. and a main baking time of 30 minutes (IR oven).

[Evaluation of membrane]
The obtained film was observed visually and with an optical microscope to confirm the coatability.
Enlarged width from set dimensions: With respect to coating set dimensions of 72 mm x 80 mm, the dimensions of the alignment film after firing were measured with calipers, and the average of the expanded width in the vertical and horizontal directions was calculated.
In-plane uniformity: A film having no film thickness unevenness and having a uniform coating surface was marked with ◎ to ◯, and a film with uneven skin or line-shaped unevenness was marked with △ to x.

The liquid crystal aligning agent of the present invention and the liquid crystal alignment film using the same are widely useful for TN elements, STN elements, TFT liquid crystal elements, and vertical alignment type liquid crystal display elements.
The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2012-174317 filed on August 6, 2012 are incorporated herein as the disclosure of the specification of the present invention. Is.

Claims

A solvent containing at least one polymer selected from the group consisting of polyimide and polyimide precursor, an alkyl cellosolve acetate compound represented by the following formula (1) and dipropylene glycol monomethyl ether;
A liquid crystal aligning agent characterized by containing.

(R 1 is an alkyl group having 1 to 8 carbon atoms.)
The liquid crystal aligning agent according to claim 1, wherein the polyimide precursor contains at least one selected from the group consisting of a polyamic acid ester and a polyamic acid.
3. The liquid crystal aligning agent according to claim 1, wherein the solvent contains at least one selected from the group consisting of N-methylpyrrolidone and γ-butyrolactone.
The liquid crystal aligning agent according to any one of claims 1 to 3, wherein the alkyl cellosolve acetate compound is at least one selected from the group consisting of methyl cellosolve acetate, ethyl cellosolve acetate, and butyl cellosolve acetate.
5. The liquid crystal aligning agent according to claim 1, comprising 1 to 5% by mass of the polymer.
6. The liquid crystal aligning agent according to claim 1, comprising 95 to 99% by mass of the solvent.
7. The liquid crystal aligning agent according to claim 1, wherein the solvent contains 0.5 to 20% by mass of an alkyl cellosolve acetate compound and 1 to 30% by mass of dipropylene glycol monomethyl ether.
The liquid crystal aligning agent according to any one of claims 1 to 7, which has a viscosity of 5 to 20 mPa · s.
A method for forming a liquid crystal alignment film, wherein the liquid crystal aligning agent according to any one of claims 1 to 8 is applied by an inkjet method.
A liquid crystal alignment film obtained by applying the liquid crystal aligning agent according to claim 1, drying and firing.
The liquid crystal alignment film according to claim 10, wherein the film thickness is 5 to 300 nm.
A liquid crystal display element having the liquid crystal alignment film according to claim 10.