JP4779974B2 - Liquid crystal aligning agent and liquid crystal display element using the same - Google Patents

Description

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

  Liquid crystal display elements are currently widely used as display devices that are thin and light. Usually, in this liquid crystal display element, a liquid crystal alignment film is used to determine the alignment state of the liquid crystal. Further, except for some vertical alignment type liquid crystal display elements and the like, most of the liquid crystal alignment film is produced by subjecting the surface of the polymer film formed on the electrode substrate to some alignment treatment.

  As the polymer used for the liquid crystal alignment film, polyimide, polyamide, polyamideimide and the like are known, and a liquid crystal aligning agent obtained by dissolving these polymers and their precursors in a solvent is generally used. A polyamic acid is generally used as a polyimide precursor.

  The most widely used method for orienting a polymer film formed on an electrode substrate is a method of rubbing the surface of the film by applying pressure with a cloth made of rayon or the like. is there. However, in the rubbing process, a part of the film may be peeled off, or the surface of the liquid crystal alignment film may be damaged due to the rubbing process, so-called “film scraping” may occur. This abnormality is considered to be one of the causes of deteriorating the characteristics of the liquid crystal display element and further reducing the yield.

In order to deal with the problem of film abrasion associated with such rubbing treatment, a method of using a liquid crystal aligning agent containing a specific thermally crosslinkable compound together with at least one polymer of polyamic acid or polyimide (for example, Patent Document 1). And a method of improving rubbing resistance by using a curing agent, such as a method of using a liquid crystal aligning agent containing an epoxy group-containing compound (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 9-185065 JP-A-9-146100

  As described above, in the liquid crystal aligning agent used for rubbing, the rubbing resistance of the coating film is one of the important characteristics, and a liquid crystal aligning agent with little film scraping due to the rubbing treatment is desired. In addition, with the advancement of technology for increasing the size and definition of liquid crystal display elements, the demand for countermeasures against display defects resulting from film scraping of the liquid crystal alignment film has become stricter than before, and a film with excellent rubbing resistance has been obtained. The importance of the obtained liquid crystal aligning agent is increasing.

  The present invention has been made in view of the above circumstances. An object of the present invention is to provide a new liquid crystal aligning agent that can obtain a good liquid crystal alignment film with little film shaving due to rubbing treatment, and display defects due to film shaving are reduced. Another object is to provide a liquid crystal display device.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. The present invention is as follows.
1. It is a polyimide obtained by dehydrating and ring-closing and imidizing a polyamic acid obtained by reaction polymerization of a diamine containing a diamine component represented by the following general formula [1] and a tetracarboxylic dianhydride component , and an imidization ratio A liquid crystal aligning agent for rubbing treatment , comprising a polymer having a content of 60% or more .

(式［１］中、ｎ及びｍは０〜４の整数であり、Ｒは水酸基、炭素数１〜３のアルキル基、炭素数１〜３のアルコキシ基、炭素数２または３のアルケニル基、カルボン酸基、シアノ基及びハロゲン原子からなる群から選ばれる少なくとも一種類の有機基であり、ｎ＋ｍが２以上の場合、Ｒはそれぞれ同じであっても異なってもよい。)

(In formula [1], n and m are integers of 0 to 4, R is a hydroxyl group, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, an alkenyl group having 2 or 3 carbon atoms, (At least one organic group selected from the group consisting of a carboxylic acid group, a cyano group and a halogen atom, and when n + m is 2 or more, each R may be the same or different.)

2. 2. The liquid crystal aligning agent according to 1 above, which is a diamine having two amino groups at positions 4, 4 ′ in the general formula [1].
3. The diamine represented by the general formula [1] is 1,2-bis (4-aminophenyl) ethyne, 1- (4-aminophenyl) -2- (4-amino-3-methylphenyl) ethyne, 1- 1 or 2 above, which is (4-aminophenyl) -2- (4-amino-3-methoxyphenyl) ethyne or 1- (4-aminophenyl) -2- (4-amino-3-fluorophenyl) ethyne Liquid crystal aligning agent as described in.
4). The liquid crystal aligning agent in any one of said 1-3 which a diamine component contains 10-100 mol% of diamine represented by General formula [1].
5. The liquid crystal aligning agent in any one of said 1-4 whose at least 10 mol% of tetracarboxylic dianhydride component is aromatic tetracarboxylic dianhydride.
6). The liquid crystal aligning agent in any one of said 1-5 whose at least 10 mol% of tetracarboxylic dianhydride component is the tetracarboxylic dianhydride which has an alicyclic structure or an aliphatic structure.
7). The liquid crystal aligning agent in any one of said 1-6 whose imidation ratio of the polyimide obtained by dehydrating and ring-closing polyamic acid is 80 % or more.
8). The liquid crystal display element which has a liquid crystal aligning film obtained from the liquid crystal aligning agent in any one of said 1-7.

  Since the liquid crystal aligning agent of this invention shown by said 1 can obtain the film which is excellent in rubbing tolerance, it can obtain the liquid crystal aligning film with few film | membrane abrasions. Therefore, the liquid crystal display element which has the liquid crystal aligning film obtained from the liquid crystal aligning agent of this invention can reduce the display defect caused by film | membrane shaving. Further, by selecting tetracarboxylic dianhydride or diamine combined with the diamine of the general formula [1], it is possible to obtain a liquid crystal alignment film showing a high voltage holding ratio and a low accumulated charge in addition to the rubbing resistance of the coating. Therefore, it is possible to obtain a liquid crystal display element in which display defects are reduced and contrast deterioration and image sticking hardly occur.

The present invention is described in detail below.
The liquid crystal aligning agent of the present invention is a polyamic acid obtained by using a specific diamine as a part of this diamine component when a diamine component and a tetracarboxylic dianhydride component are polymerized to form a polyamic acid. It is a polyimide obtained by dehydrating and ring-closing (hereinafter also referred to as a specific polyamic acid ), and is a liquid crystal aligning agent containing a polymer having an imidization ratio of 60% or more . That liquid crystal aligning agent of the present invention, a specific polyamic acid cyclodehydration state, and are not imidization contains polyimide is 60% or more, obtained by cyclodehydration specific polyamic acid and the polyamic acid It may contain both polyimides.

  The specific diamine has a structure in which one amino group is bonded to each of two benzene rings of a tolan structure (diphenylethine), and at the same time, each of the benzene rings has a substitution other than the amino group. A diamine having no groups or having a total of 1 to 4 relatively small substituents. By using this specific diamine, film abrasion of the coating can be reduced during the rubbing treatment.

The reason why the film obtained from the liquid crystal aligning agent of the present invention is less likely to be scraped is not necessarily clear, but due to the partial polymer rigidity derived from the Tran structure and the packing property between molecular chains. I think. Also, structurally, a crosslinking reaction of the acetylene portion may be considered, but it is known that the crosslinking temperature of acetylene is 350 ° C. or higher. On the other hand, the liquid crystal aligning agent of the present invention is good even at a heat treatment of about 220 ° C. Since the result is obtained, it is thought that the effect on film abrasion is not due to the crosslinking reaction of acetylene.
The specific diamine is represented by the following general formula [1].

  In the general formula [1], R is a relatively small substituent. Specific examples thereof include a hydroxyl group; an alkyl group having 1 to 3 carbon atoms such as methyl, ethyl, and propyl; and 1 to 1 carbon atoms such as methoxy, ethoxy, and propoxy. 3 alkoxy groups; alkenyl groups having 2 or 3 carbon atoms such as ethenyl and propenyl; halogen atoms; and cyano groups. Especially, a C1-C3 alkyl group, a C1-C3 alkoxy group, and a halogen atom are preferable.

In general formula [1], n and m represent the number of substitution of the substituent R, and the value is an integer of 0-4 each independently. Preferred values for n and m are each independently 0 or 1. When n + m is 2 or more, the substituents R may be the same or different.
In the general formula [1], the substitution positions of the two amino groups are not particularly limited. However, from the viewpoint of the reactivity with tetracarboxylic dianhydride and the liquid crystal orientation when the alignment film is formed, The 'position is preferred.
Specific examples of the diamine represented by the general formula [1] are shown below.

  1,2-bis (4-aminophenyl) ethyne, 1- (2-aminophenyl) -2- (4-aminophenyl) ethyne, 1,2-bis (3-aminophenyl) ethyne, 1- (4- Aminophenyl) -2- (4-amino-3-methylphenyl) ethyne, 1- (4-aminophenyl) -2- (4-amino-2-methylphenyl) ethyne, 1- (4-aminophenyl)- 2- (4-amino-3-methoxyphenyl) ethyne, 1- (4-aminophenyl) -2- (4-amino-2-methoxyphenyl) ethyne, 1- (4-aminophenyl) -2- (4 -Amino-3-hydroxyphenyl) ethyne, 1- (4-aminophenyl) -2- (4-amino-2-hydroxyphenyl) ethyne, 1- (4-aminophenyl) -2- (4-amino-3) -Carboxyphe E) Ethyne, 1- (4-aminophenyl) -2- (4-amino-2-carboxyphenyl) ethyne, 1- (3-aminophenyl) -2- (3-amino-5-methylphenyl) ethyne, 1- (3-aminophenyl) -2- (3-amino-2-methylphenyl) ethyne, 1- (3-aminophenyl) -2- (3-amino-2-methoxyphenyl) ethyne, 1- (3 -Aminophenyl) -2- (3-amino-5-hydroxyphenyl) ethyne, 1- (3-aminophenyl) -2- (3-amino-2-hydroxyphenyl) ethyne, 1- (3-aminophenyl) 2- (3-amino-5-carboxyphenyl) ethyne, 1- (3-aminophenyl) -2- (3-amino-2-carboxyphenyl) ethyne, 1,2-bis (4-amino-3-) Methylph Nyl) ethyne, 1,2-bis (4-amino-2-methylphenyl) ethyne, 1- (4-amino-2-methylphenyl) -2- (4-amino-3-methylphenyl) ethyne, 1, 2-bis (4-amino-3-methoxyphenyl) ethyne, 1,2-bis (4-amino-2-methylphenyl) ethyne, 1- (4-amino-2-methoxyphenyl) -2- (4- Amino-3-methoxyphenyl) ethyne, 1,2-bis (4-amino-3-hydroxyphenyl) ethyne, 1,2-bis (4-amino-2-hydroxyphenyl) ethyne, 1- (4-amino-) 2-hydroxyphenyl) -2- (4-amino-3-hydroxyphenyl) ethyne, 1,2-bis (4-amino-3-carboxyphenyl) ethyne, 1,2-bis (4-amino-2-methoxy) Feni L) ethyne, 1- (4-amino-2-carboxyphenyl) -2- (4-amino-3-carboxyphenyl) ethyne, 1,2-bis (3-amino-5-methylphenyl) ethyne, 1, 2-bis (3-amino-2-methylphenyl) ethyne, 1- (3-amino-2-methylphenyl) -2- (3-amino-5-methylphenyl) ethyne, 1,2-bis (3- Amino-5-methoxyphenyl) ethyne, 1,2-bis (3-amino-2-methoxyphenyl) ethyne, 1- (3-amino-2-methoxyphenyl) -2- (3-amino-5-methoxyphenyl) ) Ethyne, 1,2-bis (3-amino-5-hydroxyphenyl) ethyne, 1- (3-amino-2-hydroxyphenyl) -2- (3-amino-5-hydroxyphenyl) ethyne, 1,2 -Screw 3-amino-5-carboxyphenyl) ethyne, 1,2-bis (3-amino-2-hydroxyphenyl) ethyne, 1- (3-amino-2-carboxyphenyl) -2- (3-amino-5- Carboxyphenyl) ethyne, 1,2-bis (3-amino-5-carboxyphenyl) ethyne, 1- (4-aminophenyl) -2- (4-amino-3-fluorophenyl) ethyne and the like.

  Among the above specific examples, 1,2-bis (4-aminophenyl) ethyne, 1- (4-aminophenyl) -2- (4-amino-3-methylphenyl) ethyne, 1- (4-aminophenyl) 2- (4-amino-3-methoxyphenyl) ethyne and 1- (4-aminophenyl) -2- (4-amino-3-fluorophenyl) ethyne are preferred.

<Diamine component>
In the diamine component for obtaining the specific polyamic acid, other diamines can be used in addition to the diamine represented by the general formula [1]. The preferable ratio of the diamine represented by the general formula [1] in this diamine component is 10 to 100 mol%, more preferably 30 to 100 mol%, still more preferably 50 to 100 mol%. Moreover, you may use diamine represented by General formula [1] in combination of multiple types.

In the diamine component for obtaining the specific polyamic acid, other diamines that can be used in combination with the diamine represented by the general formula [1] are not particularly limited, and the diamine may be one type or two or more types.
Specific examples of other diamines are as follows.
Examples of the alicyclic diamine include 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 4,4′-diaminodicyclohexylmethane, 4,4′-diamino-3,3′-dimethyldicyclohexylamine, and isophoronediamine. Is mentioned.

  As aromatic diamines, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2,6-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminotoluene, 2,3-diaminotoluene, 1 , 4-Diamino-2-methoxybenzene, 2,5-diamino-p-xylene, 1,3-diamino-4-chlorobenzene, 3,5-diaminobenzoic acid, 1,4-diamino-2,5-dichlorobenzene 4,4′-diamino-1,2-diphenylethane, 4,4′-diamino-2,2′-dimethylbibenzyl, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 3,4 '-Diaminodiphenylmethane, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 2,2'-diaminostilbene 4,4′-diaminostilbene, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl Sulfone, 4,4′-diaminobenzophenone, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 3 , 5-bis (4-aminophenoxy) benzoic acid, 4,4′-bis (4-aminophenoxy) bibenzyl, 2,2-bis [(4-aminophenoxy) methyl] propane, 2,2-bis [4 -(4-Aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] Lopan, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, 1,1-bis (4-aminophenyl) cyclohexane, α, α′-bis ( 4-aminophenyl) -1,4-diisopropylbenzene, 9,9-bis (4-aminophenyl) fluorene, 2,2-bis (3-aminophenyl) hexafluoropropane, 2,2-bis (4-amino) Phenyl) hexafluoropropane, 4,4′-diaminodiphenylamine, 2,4-diaminodiphenylamine, 1,8-diaminonaphthalene, 1,5-diaminonaphthalene, 1,5-diaminoanthraquinone, 1,3-diaminopyrene, 1 , 6-Diaminopyrene, 1,8-diaminopyrene, 2,7-diaminofluorene, 1,3-bis (4-a Minophenyl) tetramethyldisiloxane, benzidine, 2,2′-dimethylbenzidine, 1,2-bis (4-aminophenyl) ethane, 1,3-bis (4-aminophenyl) propane, 1,4-bis (4 -Aminophenyl) butane, 1,5-bis (4-aminophenyl) pentane, 1,6-bis (4-aminophenyl) hexane, 1,7-bis (4-aminophenyl) heptane, 1,8-bis (4-aminophenyl) octane, 1,9-bis (4-aminophenyl) nonane, 1,10-bis (4-aminophenyl) decane, 1,3-bis (4-aminophenoxy) propane, 1,4 -Bis (4-aminophenoxy) butane, 1,5-bis (4-aminophenoxy) pentane, 1,6-bis (4-aminophenoxy) hexane, 1,7-bis 4-aminophenoxy) heptane, 1,8-bis (4-aminophenoxy) octane, 1,9-bis (4-aminophenoxy) nonane, 1,10-bis (4-aminophenoxy) decane, di (4- Aminophenyl) propane-1,3-dioate, di (4-aminophenyl) butane-1,4-dioate, di (4-aminophenyl) pentane-1,5-dioate, di (4-aminophenyl) hexane- 1,6-dioate, di (4-aminophenyl) heptane-1,7-dioate, di (4-aminophenyl) octane-1,8-dioate, di (4-aminophenyl) nonane-1,9-dioate Di (4-aminophenyl) decane-1,10-dioate, 1,3-bis [4- (4-aminophenoxy) phenoxy] propane, 1, -Bis [4- (4-aminophenoxy) phenoxy] butane, 1,5-bis [4- (4-aminophenoxy) phenoxy] pentane, 1,6-bis [4- (4-aminophenoxy) phenoxy] hexane 1,7-bis [4- (4-aminophenoxy) phenoxy] heptane, 1,8-bis [4- (4-aminophenoxy) phenoxy] octane, 1,9-bis [4- (4-aminophenoxy) ) Phenoxy] nonane, 1,10-bis [4- (4-aminophenoxy) phenoxy] decane, and the like.

  Heterocyclic diamines include 2,6-diaminopyridine, 2,4-diaminopyridine, 2,4-diamino-1,3,5-triazine, 2,7-diaminodibenzofuran, 3,6-diaminocarbazole, 2, Examples include 4-diamino-6-isopropyl-1,3,5-triazine, 2,5-bis (4-aminophenyl) -1,3,4-oxadiazole. And as aliphatic diamine, 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1, 8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,3-diamino-2,2-dimethylpropane, 1,6-diamino-2,5-dimethylhexane, 1,7-diamino- 2,5-dimethylheptane, 1,7-diamino-4,4-dimethylheptane, 1,7-diamino-3-methylheptane, 1,9-diamino-5-methylheptane, 1,12-diaminododecane, , 18-diaminooctadecane, 1,2-bis (3-aminopropoxy) ethane and the like.

  Among the other diamines as described above, when a diamine having an alicyclic structure or an aliphatic structure is used in combination with at least 10 mol% of the diamine component, a good rubbing resistance is obtained and a liquid crystal alignment film having a high voltage holding ratio is obtained. Can be obtained.

  Further, at least 10 mol% of the diamine component contains o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2,6-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminotoluene, 2,3- Diaminotoluene, 1,4-diamino-2-methoxybenzene, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diamino-3,3′- When dimethyldiphenylmethane, 4,4′-diamino-2,2′-dimethyldiphenylmethane, 2,6-diaminopyridine, 2,4-diaminopyridine, 4,4′-diaminodiphenylamine, 3,6-diaminocarbazole, etc. are used in combination Good rubbing resistance and high voltage holding ratio It can charge obtain a low liquid crystal alignment film.

  In addition to the above-mentioned diamine, when used as a raw material for polyamic acid or polyimide for forming a liquid crystal alignment film, good rubbing resistance can be obtained by using a diamine known to increase the pretilt angle of the liquid crystal. In addition, it is possible to obtain a liquid crystal alignment film that gives the liquid crystal an arbitrarily high pretilt angle. Examples of diamines that are known to increase the pretilt angle of liquid crystals include long-chain alkyl groups, perfluoro groups, organic groups having aromatic cyclic substituents, organic groups having aliphatic cyclic substituents, and steroid skeleton groups. The diamine which has. Although the specific example of such diamine is shown below, it is not limited to these. In the following formulas [8] to [28], j is an integer of 5 to 20, and k is an integer of 1 to 20.

<Tetracarboxylic dianhydride component>
The tetracarboxylic dianhydride contained in the tetracarboxylic dianhydride component for obtaining the specific polyamic acid and its composition are not particularly limited, and a plurality of types of tetracarboxylic dianhydrides may be used in combination.

Specific examples of tetracarboxylic dianhydride are shown below, but are not limited thereto.
As having an alicyclic structure or an aliphatic structure, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3 , 4-Dicarboxy-1-cyclohexylsuccinic dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride, 1,2,3,4-butanthate Carboxylic dianhydride, bicyclo [3,3,0] octane-2,4,6,8-tetracarboxylic dianhydride, 3,3 ′, 4,4′-dicyclohexyltetracarboxylic dianhydride, 2 , 3,5-tricarboxycyclopentylacetic acid dianhydride, cis-3,7-dibutylcycloocta-1,5-diene-1,2,5,6-tetracarboxylic dianhydride, tricyclo [4.2. 1.0 ^2,5 ] nonane-3,4,7,8-tetracarboxylic acid-3,4: 7,8-dianhydride, hexacyclo [6.6.0.12, 7.03, 6.19 , 14.010, 13] hexadecane-4,5,11,12-tetracarboxylic acid-4,5: 11,12-dianhydride, and the like.

  As aromatic acid dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 2,3,3 ′, 4′-benzophenonetetracarboxylic Acid dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride 2,3,6,7-naphthalenetetracarboxylic dianhydride and the like.

Among the above tetracarboxylic dianhydrides, when a tetracarboxylic dianhydride having an alicyclic structure or an aliphatic structure is used in at least 10 mol% of the tetracarboxylic dianhydride component, good rubbing resistance In addition, a liquid crystal alignment film having a high voltage holding ratio can be obtained.
Moreover, when aromatic tetracarboxylic dianhydride is used for at least 10 mol% of the tetracarboxylic dianhydride component, a good rubbing resistance can be obtained and a liquid crystal alignment film with better liquid crystal alignment can be obtained. Can do.

<Polyamic acid>
The specific polyamic acid in the present invention is a polyamic acid obtained by reaction polymerization of the diamine component and the tetracarboxylic dianhydride component shown above. Although the reaction method of a diamine component and a tetracarboxylic dianhydride component is not specifically limited, The method of mixing both in an organic solvent is common.

  As a method of mixing the diamine component and the tetracarboxylic dianhydride component in an organic solvent, the solution in which the diamine component is dispersed or dissolved in the organic solvent is stirred, and the tetracarboxylic dianhydride component is left as it is or organically. A method of adding by dispersing or dissolving in a solvent, a method of adding a diamine component to a solution in which a tetracarboxylic dianhydride component is dispersed or dissolved in an organic solvent, and a tetracarboxylic dianhydride component and a diamine component. The method of adding alternately etc. are mentioned, In this invention, any of these methods may be sufficient. Moreover, when a tetracarboxylic dianhydride component or a diamine component consists of multiple types of compounds, these multiple types of compounds may be reacted in a premixed state, or may be sequentially reacted individually.

  The temperature at the time of making a diamine component and a tetracarboxylic dianhydride component react in an organic solvent is 0-150 degreeC normally, Preferably it is 5-100 degreeC, More preferably, it is 10-80 degreeC. When the temperature is higher, the polymerization reaction is completed earlier, but when it is too high, a high molecular weight polymer may not be obtained. The reaction can be carried out at any concentration, but if the concentration is too low, it is difficult to obtain a high molecular weight polymer, and if the concentration is too high, the viscosity of the reaction solution becomes too high and uniform stirring is difficult. Therefore, it is preferably 1 to 50% by weight, more preferably 5 to 30% by weight. The initial reaction may be carried out at a high concentration, and then an organic solvent may be added.

  The organic solvent used in the above reaction is not particularly limited as long as the generated polyamic acid dissolves. Specific examples include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, dimethyl sulfoxide, tetramethyl urea, pyridine, dimethyl sulfone, hexamethyl sulfoxide. And γ-butyrolactone. These may be used alone or in combination of two or more. 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 produced polyamic acid does not precipitate. In addition, 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 and dried organic solvent as much as possible.

  The ratio of the diamine component and the tetracarboxylic dianhydride component used for the polymerization reaction of the polyamic acid is such that the tetracarboxylic dianhydride component is 0.8 to 1.2 with respect to the diamine component 1 in terms of molar ratio. preferable. Similar to the normal polycondensation reaction, the closer the molar ratio is to 1: 1, the higher the molecular weight of the polyamic acid obtained. If the molecular weight of the polyamic acid is too small, the strength of the coating film obtained therefrom may be insufficient. Conversely, if the molecular weight of the polyamic acid is too large, the viscosity of the liquid crystal aligning agent produced therefrom will increase. Thus, workability during coating film formation and uniformity of the coating film may be deteriorated. Therefore, the weight average molecular weight of the polyamic acid used for the liquid crystal aligning agent of the present invention is preferably 2,000 to 500,000, more preferably 5,000 to 300,000.

<Polyimide>
The polyamic acid obtained as described above is used as a polyimide subjected to dehydration and ring closure so that the imidization rate is 60% or more . However, depending on the structure of the polyamic acid, it may become insoluble in an organic solvent as conversion to polyimide proceeds, making it difficult to use it as a liquid crystal aligning agent. In this case, all of the amic acid groups in the polyamic acid may not be dehydrated and cyclized, and may be made into polyimide within a range in which appropriate solubility can be maintained within the range of the imidization rate .

In general, when the polyamic acid is contained in the liquid crystal aligning agent and when the polyamic acid is dehydrated and ring-closed and the polyimide is contained in the liquid crystal aligning agent, the latter is the liquid crystal alignment property or voltage of the liquid crystal alignment film. While the retention rate is high, the rubbing resistance of the coating tends to be low. However, the specific polyamic acid in the present invention is excellent in the rubbing resistance of the coating even when it is contained in the liquid crystal aligning agent in the state of a polyimide that has been dehydrated and cyclized, so that the imidation ratio of the specific polyamic acid is 60% or more . Inclusion in the liquid crystal aligning agent after conversion to polyimide is preferable because liquid crystal alignment and voltage holding ratio are improved without impairing rubbing resistance. In this case, the imidization ratio of the polyimide obtained by cyclodehydration specific polyamic acid is at 6 0% or more, preferably 80% or more.

  The imidation reaction for dehydrating and cyclizing polyamic acid is generally thermal imidization by heating the polyamic acid solution as it is, or chemical imidization by adding a catalyst to the polyamic acid solution, but at a relatively low temperature, the imidation reaction is performed. The chemical imidation in which the chemical progression proceeds is preferable because the molecular weight of the resulting polyimide is less likely to decrease.

  Chemical imidation can be performed by stirring polyamic acid in an organic solvent in the presence of a basic catalyst and an acid anhydride. The reaction temperature at this time is -20-250 degreeC, Preferably it is 0-180 degreeC, and reaction time can be performed in 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 amic acid group, and the amount of the acid anhydride is 1 to 50 mol times, preferably 3 to 30 mol of the amic acid group. Is double. 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 at this time include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Among them, pyridine is preferable because it has an appropriate basicity for proceeding with the reaction. Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, pyromellitic anhydride, and the like. Among them, use of acetic anhydride is preferable because purification after completion of the reaction is facilitated. As an organic solvent, the solvent used at the time of the polyamic acid synthesis mentioned above can be used. The imidation rate by chemical imidation can be controlled by adjusting the amount of catalyst, reaction temperature, and reaction time.

  In the polyimide solution thus obtained, the added catalyst remains in the solution. Therefore, in order to use it for the liquid crystal aligning agent of the present invention, the polyimide solution is put into a poor solvent which is stirred and precipitated. It is preferable to collect. Although it does not specifically limit as a poor solvent used for precipitation collection | recovery of a polyimide, Methanol, acetone, hexane, a butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene etc. can be illustrated. The polyimide precipitated by adding it to a poor solvent can be recovered by filtration, washing and drying at room temperature or under reduced pressure at normal temperature or by heating. If the operation of dissolving this powder in a good solvent and reprecipitating is repeated 2 to 10 times, the polyimide can be purified. When the impurities cannot be removed by a single precipitation recovery operation, it is preferable to perform this purification step. In this case, it is preferable to use three or more kinds of poor solvents such as alcohols, ketones, and hydrocarbons as the poor solvent because the purification efficiency is further increased.

  Polyamic acid can also be collected and purified by the same operation. When it is not desired to include the solvent used for the polymerization of the polyamic acid in the liquid crystal aligning agent of the present invention, or when unreacted monomer components and impurities are present in the reaction solution, this precipitation recovery and purification can be performed. Good.

<Liquid crystal aligning agent>
The liquid crystal aligning agent of the present invention is a polyimide specific polyamic click acid was cyclodehydration obtained as described above, be obtained by dissolving the polymer imidization of 60% or more in an organic solvent it can.
The organic solvent is not particularly limited as long as it can dissolve the contained polymer component. Specific examples are N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, dimethyl. Examples thereof include sulfoxide, tetramethylurea, pyridine, dimethylsulfone, hexamethylsulfoxide, γ-butyrolactone, and the like. These may be used alone or in combination.

  Further, even if the solvent alone does not dissolve the polymer component, it can be mixed with the liquid crystal aligning agent of the present invention as long as the polymer component does not precipitate. In particular, it is known that the coating film uniformity is improved at the time of application to a substrate by appropriately mixing a solvent having a low surface tension, and it is also suitably used in the liquid crystal aligning agent of the present invention. Specific examples of such solvents include ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, ethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy. 2-propanol, 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether-2-acetate, dipropylene Glycol, 2- (2-ethoxypropoxy) propanol, lactate methyl ester, lactate ethyl ester, lactate n-propyl ester, lactate n-butyl ester, lactyl isoamyl ester, etc. It can be mentioned.

  Although the solid content concentration of the liquid crystal aligning agent of this invention can be suitably changed with the thickness of the film to form, it is preferable to set it as 1 to 10 weight%. If it is less than 1% by weight, it is difficult to form a uniform and defect-free film, and if it exceeds 10% by weight, the storage stability of the solution may be deteriorated.

The liquid crystal aligning agent of the present invention must contain at least one of a specific polyamic acid, that is, a polyamic acid using a diamine represented by the general formula [1], or a polyimide obtained by dehydrating and ring-closing the polyamic acid. However, as long as the effects of the present invention are not impaired, other separately polymerized polyamic acid or polyimide may be contained. Similarly, a resin other than polyamic acid or polyimide may be contained.
In addition, a known additive such as a silane coupling agent can be added to the liquid crystal aligning agent of the present invention in order to further improve the adhesion of the coating film to the substrate.

  The liquid crystal aligning agent of the present invention obtained as described above can be filtered, applied to a substrate, dried and baked to form a film, and the coating surface is subjected to an alignment treatment by rubbing, whereby liquid crystal Used as alignment film.

  At this time, the substrate to be used is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a plastic substrate such as an acrylic substrate or a polycarbonate substrate can be used, and an ITO electrode for driving a liquid crystal is formed. It is preferable to use a new substrate from the viewpoint of simplification of the process. Further, in the reflection type liquid crystal display element, an opaque material such as a silicon wafer can be used as long as the substrate is only on one side, and in this case, a material that reflects light such as aluminum can be used.

  Examples of the method for applying the liquid crystal aligning agent include a spin coating method, a printing method, and an ink jet method. From the viewpoint of productivity, the transfer printing method is widely used industrially, and the liquid crystal aligning agent of the present invention is used. Is also preferably used.

  The drying process after applying the liquid crystal aligning agent is not necessarily required, but if the time from application to baking is not constant for each substrate, or if baking is not performed immediately after application, a drying process is included. Is preferred. The drying is not particularly limited as long as the solvent is evaporated to such an extent that the shape of the coating film is not deformed by transporting the substrate or the like. If a specific example is given, the method of drying on the hotplate of temperature 50-150 degreeC, Preferably 80-120 degreeC for 0.5 to 30 minutes, Preferably it is 1 to 5 minutes is taken.

  Although baking of the coating film formed using the liquid crystal aligning agent can be performed at arbitrary temperature of 100-350 degreeC, Preferably it is 150 to 300 degreeC, More preferably, it is 200 to 250 degreeC. . When the liquid crystal aligning agent contains a polyamic acid, the conversion rate from the polyamic acid to the polyimide changes depending on the baking temperature, but the liquid crystal aligning agent of the present invention does not necessarily need to be imidized 100%. However, baking is preferably performed at a temperature higher by 10 ° C. or more than the heat treatment temperature required for the liquid crystal cell manufacturing process, such as sealing agent curing.

  If the thickness of the film after baking is too thick, it is disadvantageous in terms of power consumption of the liquid crystal display element, and if it is too thin, the reliability of the liquid crystal display element may be lowered, and therefore preferably 5 to 300 nm, preferably 10 to 10 nm. 100 nm.

  The film obtained as described above can be made into a liquid crystal alignment film by rubbing with a rubbing cloth made of various materials such as rayon, cotton and nylon.

<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 using the liquid crystal aligning agent of the present invention by the method as described above, and then creating a liquid crystal cell by a known method. It is. The type of the liquid crystal display element is not particularly limited. Examples of the liquid crystal display element include TN type, STN type, TFT type, lateral electric field type (IPS), vertical alignment type (VA), ferroelectric liquid crystal type, and antiferroelectric liquid crystal type. In particular, in the IPS type liquid crystal display element, since the rubbing conditions at the time of element preparation are severe and film scraping is likely to occur compared to other liquid crystal display elements, the liquid crystal aligning agent of the present invention which is excellent in the rubbing resistance of the film is preferably used. be able to.

  If an example of liquid crystal cell production is given, a pair of substrates on which a liquid crystal alignment film is formed are sandwiched by spacers of 1 to 30 μm, preferably 2 to 10 μm, and the rubbing direction is an arbitrary angle of 0 to 270 °. A general method is to fix the periphery with a sealant and inject liquid crystal to seal. The method for enclosing the liquid crystal is not particularly limited, and examples thereof include a vacuum method of injecting liquid crystal after reducing the pressure inside the produced liquid crystal cell, and a dropping method of sealing after dropping the liquid crystal.

  The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

Explanation of abbreviations used in this example (tetracarboxylic dianhydride)
CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride TDA: 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride PMDA: pyromellitic acid 2 Anhydride (diamine)
DAT: 1,2-bis (4-aminophenyl) ethyne 3MDAT: 1- (4-aminophenyl) -2- (4-amino-3-methoxyphenyl) ethyne 3FDAT: 1- (4-aminophenyl) -2 -(4-Amino-3-fluorophenyl) ethyne p-PDA: p-phenylenediamine DDM: 4,4'-diaminodiphenylmethane DDE: 4,4'-diaminodiphenyl ether DADB: 1,3-diamino-4-dodecyloxy Benzene (organic solvent)
NMP: N-methyl-2-pyrrolidone BCS: Butyl cellosolve GBL: γ-butyrolactone (others)
{SPI}: Polyimide obtained by dehydrating and ring-closing polyamic acid.

(Measurement of molecular weight and imidation rate)
In the following synthesis examples, the molecular weight of polyamic acid or polyimide is measured by using Senshu Kagaku Co., Ltd., room temperature gel permeation chromatography (GPC) apparatus (SSC-7200), Shodex column (KD803, 805). The number average molecular weight and the weight average molecular weight used were polyethylene glycol and polyethylene oxide equivalent values. Moreover, the imidation ratio of the polyimide was determined by dissolving the polyimide in deuterated DMF (dimethyl sulfoxide-d ₆ ), measuring ¹ H-NMR, and determining the ratio of the amic acid group remaining without imidization. It calculated | required and calculated | required from the ratio of the integrated value of a proton peak.

(Synthesis Example 1) CBDA / DAT
CBDA 9.10 g (0.046 mol) as a tetracarboxylic dianhydride component and 1.00 g (0.048 mol) DAT as a diamine component were mixed in 176 g of NMP and reacted at room temperature for 5 hours to obtain a polyamic acid solution. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 14826 and a weight average molecular weight of 31766. NMP and BCS were added to 50 g of this polyamic acid solution to prepare 5% by weight of polyamic acid, 75% by weight of NMP, and 20% by weight of BCS to obtain the liquid crystal aligning agent of the present invention.

(Synthesis Example 2) CBDA / 3MDAT
As a tetracarboxylic dianhydride component, 13.60 g (0.069 mol) of CBDA and 15.60 g (0.070 mol) of 3MDAT as a diamine component were mixed in 255 g of NMP and reacted at room temperature for 5 hours to obtain a polyamic acid solution. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 16582 and a weight average molecular weight of 32256. NMP and BCS were added to 50 g of this polyamic acid solution to prepare 6 wt% polyamic acid, 74 wt% NMP, and 20 wt% BCS to obtain the liquid crystal aligning agent of the present invention.

(Synthesis Example 3) CBDA / p-PDA / DAT (30)
CBDA 13.75 g (0.070 mol) as tetracarboxylic dianhydride component, p-PDA 4.98 g (0.046 mol) and DAT 4.11 g (0.020 mol) as diamine component were mixed in 205 g of NMP, and at room temperature for 5 hours. A polyamic acid solution was obtained by reaction. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 10121 and a weight average molecular weight of 17563. NMP and BCS were added to 50 g of this polyamic acid solution to prepare 6 wt% polyamic acid, 74 wt% NMP, and 20 wt% BCS to obtain the liquid crystal aligning agent of the present invention.

(Synthesis Example 4) CBDA / p-PDA / DAT (50)
14.90 g (0.076 mol) of CBDA as a tetracarboxylic dianhydride component, 4.30 g (0.040 mol) of p-PDA and 8.30 g (0.040 mol) of DAT as a diamine component were mixed in 308 g of NMP, and at room temperature for 5 hours. A polyamic acid solution was obtained by reaction. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 11054 and a weight average molecular weight of 21235. NMP and BCS were added to 50 g of this polyamic acid solution, and the liquid crystal aligning agent of the present invention was obtained by adjusting to 4 wt% polyamic acid, 76 wt% NMP, and 20 wt% BCS.

(Synthesis Example 5) PMDA / DAT
PMDA 15.70 g (0.072 mol) as a tetracarboxylic dianhydride component and DAT 16.70 g (0.080 mol) as a diamine component were mixed in 300 g of NMP and reacted at room temperature for 5 hours to obtain a polyamic acid solution. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 12042 and a weight average molecular weight of 22482. NMP and BCS were added to 50 g of this polyamic acid solution to prepare 5% by weight of polyamic acid, 75% by weight of NMP, and 20% by weight of BCS to obtain the liquid crystal aligning agent of the present invention.

(Synthesis Example 6) CBDA / PMDA / DAT
CBDA 7.80 g (0.040 mol) and PMDA 7.00 g (0.032 mol) as tetracarboxylic dianhydride components and DAT 16.70 g (0.080 mol) as diamine components are mixed in 290 g of NMP and reacted at room temperature for 10 hours. Thus, a polyamic acid solution was obtained. The polymerization reaction proceeded easily and uniformly. The obtained polyamic acid had a number average molecular weight of 10454 and a weight average molecular weight of 18772. NMP and BCS were added to 50 g of this polyamic acid solution to prepare 5% by weight of polyamic acid, 75% by weight of NMP, and 20% by weight of BCS to obtain the liquid crystal aligning agent of the present invention.

(Synthesis Example 7) TDA / DAT
29.90 g (0.100 mol) of TDA as a tetracarboxylic dianhydride component and 20.80 g (0.100 mol) of DAT as a diamine component were mixed in 280 g of NMP and reacted at room temperature for 5 hours to obtain a polyamic acid solution. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 17726 and a weight average molecular weight of 30398. NMP and BCS were added to 50 g of this polyamic acid solution to prepare 5% by weight of polyamic acid, 75% by weight of NMP, and 20% by weight of BCS to obtain the liquid crystal aligning agent of the present invention.

(Synthesis Example 8) TDA / DAT {SPI}
NMP is added to 50 g of the polyamic acid solution obtained in Synthesis Example 7 to dilute the polyamic acid to 5% by weight. Further, 16.07 g of acetic anhydride and 7.47 g of pyridine are added as an imidization catalyst and reacted at 35 ° C. for 3 hours. I let you. This reaction solution was poured into 625 ml of methanol, and the resulting precipitate was filtered off, thoroughly washed with methanol, and then dried under reduced pressure at 100 ° C. to obtain a light yellow polyimide powder having an imidization rate of 92%. . This polyimide had a number average molecular weight of 16276 and a weight average molecular weight of 28839. 3.0 g of this polyimide powder was dissolved in a mixed solvent of 39.5 g of GBL and 7.5 g of BCS to obtain the liquid crystal aligning agent of the present invention.

Synthesis Example 9 CBDA / DAT: CBDA / p-PDA = 4: 6
CBDA 9.10 g (0.046 mol) as a tetracarboxylic dianhydride component and 1.00 g (0.048 mol) DAT as a diamine component were mixed in 176 g of NMP and reacted at room temperature for 5 hours to obtain a polyamic acid solution. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 14826 and a weight average molecular weight of 31766.

  Separately, 19.61 g (0.100 mol) of CBDA as a tetracarboxylic dianhydride component and 10.38 g (0.096 mol) of p-PDA as a diamine component are mixed in 345 g of NMP and reacted at room temperature for 5 hours to obtain a polyamic acid solution. Got. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 22382 and a weight average molecular weight of 40395.

  The above two types of polyamic acid solutions were mixed such that the former and the latter were 4: 6 by weight ratio of the polyamic acid. Further, NMP and BCS were added to 50 g of this mixed solution, and the liquid crystal aligning agent of the present invention was obtained by preparing 6 wt% polyamic acid, 76 wt% NMP, and 20 wt% BCS.

(Synthesis Example 10) CBDA / DAT / DADB (10)
CBDA 19.61 g (0.100 mol) as a tetracarboxylic dianhydride component, DAT 18.11 g (0.087 mol) and DADB 2.92 g (0.010 mol) as diamine components are mixed in 365 g of NMP and reacted at room temperature for 3 hours. Thus, a polyamic acid solution was obtained. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 18742 and a weight average molecular weight of 40386. NMP and BCS were added to 50 g of this polyamic acid solution to prepare 6 wt% polyamic acid, 74 wt% NMP, and 20 wt% BCS to obtain the liquid crystal aligning agent of the present invention.

(Synthesis Example 11) CBDA / 3FDAT
13.60 g (0.069 mol) of CBDA as a tetracarboxylic dianhydride component and 16.80 g (0.074 mol) of 3FDAT as a diamine component were mixed in 270 g of NMP and reacted at room temperature for 21 hours to obtain a polyamic acid solution. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 23647 and a weight average molecular weight of 49752. NMP and BCS were added to 50 g of this polyamic acid solution to prepare 6 wt% polyamic acid, 74 wt% NMP, and 20 wt% BCS to obtain the liquid crystal aligning agent of the present invention.

(Synthesis Example 12) TDA / DAT / p-PDA (50) {SPI}
As a tetracarboxylic dianhydride component, 5.88 g (0.020 mol) of TDA, 2.08 g (0.010 mol) of DAT as a diamine component, and 1.08 (0.010 mol) of p-PDA were mixed in 51.3 g of NMP, and at room temperature. Reaction was performed for 24 hours to obtain a polyamic acid solution. NMP was added to 30 g of this polyamic acid solution to dilute the polyamic acid to 5% by weight, and then 10.70 g of acetic anhydride and 4.97 g of pyridine were added as an imidization catalyst, followed by reaction at 35 ° C. for 3 hours. This reaction solution was poured into 400 ml of methanol, and the resulting precipitate was filtered off, thoroughly washed with methanol, and then dried under reduced pressure at 100 ° C. to obtain a light yellow polyimide powder having an imidization rate of 91%. . This polyimide had a number average molecular weight of 8830 and a weight average molecular weight of 15247. 3.0 g of this polyimide powder was dissolved in a mixed solvent of 39.5 g of GBL and 7.5 g of BCS to obtain the liquid crystal aligning agent of the present invention.

(Synthesis Example 13) TDA / DAT / p-PDA (40) / DADB (10) {SPI}
30.03 g (0.100 mol) of TDA as a tetracarboxylic dianhydride component, 10.41 g (0.050 mol) of DAT as a diamine component, 4.33 g (0.040 mol) of p-PDA, 2.92 g (0.010 mol) of DADB, and 270 g of NMP Then, the mixture was reacted at 50 ° C. for 36 hours to obtain a polyamic acid solution. NMP was added to 50 g to dilute the polyamic acid to 5% by weight. Further, 16.05 g of acetic anhydride and 7.64 g of pyridine were added as an imidization catalyst and reacted at 35 ° C. for 3 hours. This reaction solution was poured into 625 ml of methanol, and the resulting precipitate was filtered off, thoroughly washed with methanol, and then dried under reduced pressure at 100 ° C. to obtain a light yellow polyimide powder having an imidization rate of 92%. . This polyimide had a number average molecular weight of 10599 and a weight average molecular weight of 23952. 3.0 g of this polyimide powder was dissolved in a mixed solvent of 39.5 g of GBL and 7.5 g of BCS to obtain the liquid crystal aligning agent of the present invention.

(Comparative Synthesis Example 1) CBDA / p-PDA
19.61 g (0.100 mol) of CBDA as a tetracarboxylic dianhydride component and 10.38 g (0.096 mol) of p-PDA as a diamine component were mixed in 345 g of NMP and reacted at room temperature for 5 hours to obtain a polyamic acid solution. . The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 22382 and a weight average molecular weight of 40395. NMP and BCS were added to 50 g of this polyamic acid solution to prepare polyamic acid 4% by weight, NMP 76% by weight, and BCS 20% by weight as a liquid crystal aligning agent for comparison.

(Comparative Synthesis Example 2) PMDA / DDE
PMDA 20.30 g (0.093 mol) as a tetracarboxylic dianhydride component and DDE 20.00 g (0.100 mol) as a diamine component were mixed in 296 g of NMP and reacted at room temperature for 24 hours to obtain a polyamic acid solution. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 43382 and a weight average molecular weight of 89467. NMP and BCS were added to 50 g of this polyamic acid solution to prepare a liquid crystal aligning agent for comparison so as to be 5% by weight of polyamic acid, 75% by weight of NMP, and 20% by weight of BCS.

(Comparative Synthesis Example 3) TDA / DDM
29.73 g (0.099 mol) of TDA as a tetracarboxylic dianhydride component and 19.83 g (0.100 mol) of DDM as a diamine component were mixed in 281 g of NMP and reacted at room temperature for 24 hours to obtain a polyamic acid solution. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 10127 and a weight average molecular weight of 19746. NMP and BCS were added to 50 g of this polyamic acid solution to prepare a liquid crystal aligning agent for comparison so as to be 5% by weight of polyamic acid, 75% by weight of NMP, and 20% by weight of BCS.

(Comparative Synthesis Example 4) TDA / p-PDA {SPI}
23.50 g (0.078 mol) of TDA as a tetracarboxylic dianhydride component and 8.65 g (0.080 mol) of p-PDA as a diamine component were mixed in 180 g of NMP and reacted at room temperature for 24 hours to obtain a polyamic acid solution. . 50 g of this polyamic acid solution was diluted to 5% by weight with NMP, and then 14.50 g of acetic anhydride and 6.75 g of pyridine were added as an imidization catalyst and reacted at 35 ° C. for 3 hours. This reaction solution was poured into 625 ml of methanol, and the resulting precipitate was filtered off, thoroughly washed with methanol, and then dried under reduced pressure at 100 ° C. to obtain a white polyimide powder having an imidation ratio of 93%. This polyimide had a number average molecular weight of 16276 and a weight average molecular weight of 28839. 3.0 g of this polyimide powder was dissolved in a mixed solvent of 39.5 g of GBL and 7.5 g of BCS, and used as a liquid crystal aligning agent for comparison.

(Comparative Synthesis Example 5) CBDA / DDM: CBDA / p-PDA = 4: 6
As a tetracarboxylic dianhydride component, 19.22 g (0.098 mol) of CBDA and 19.83 g (0.100 mol) of DDM as a diamine component were mixed in 221 g of NMP and reacted at room temperature for 24 hours to obtain a polyamic acid solution. The polymerization reaction proceeded easily and uniformly. The obtained polyamic acid had a number average molecular weight of 20832 and a weight average molecular weight of 36395.

  Separately, 19.61 g (0.100 mol) of CBDA as a tetracarboxylic dianhydride component and 10.38 g (0.096 mol) of p-PDA as a diamine component are mixed in 345 g of NMP and reacted at room temperature for 5 hours to obtain a polyamic acid solution. Got. The polymerization reaction proceeded easily and uniformly. The resulting polyamic acid had a number average molecular weight of 22382 and a weight average molecular weight of 40395.

  The above two types of polyamic acid solutions were mixed such that the former and the latter were 4: 6 by weight ratio of the polyamic acid. Further, NMP and BCS were added to 50 g of this mixed solution to prepare polyamic acid 6% by weight, NMP 76% by weight, and BCS 20% by weight, and used as a liquid crystal aligning agent for comparison.

(Examples 1 to 3 )
The liquid crystal aligning agent obtained in the above various synthesis examples is spin-coated on a glass substrate with a transparent electrode, dried on an 80 ° C. hot plate for 5 minutes, and then baked in a hot air circulation oven at 220 ° C. for 30 minutes. A film having a thickness of 100 nm was formed. This coating film surface was rubbed with a rubbing apparatus having a roll diameter of 120 mm using a rayon cloth under the conditions of a roll rotation speed of 700 rpm, a roll traveling speed of 10 mm / sec, and an indentation amount of 0.45 mm to obtain a substrate with a liquid crystal alignment film.

The surface of the liquid crystal alignment film in the vicinity of the center of the substrate was randomly observed with a laser microscope set at a magnification of 100 times, and the rubbing scratches and rubbing residue (about the observation visual field of about 6.5 mm square) The rubbing resistance was evaluated from the average value of the amount of deposits). The results are shown in Table 1 described later. The evaluation criteria were determined as follows.
Evaluation criteria A: 10 or less rubbing scratches and rubbing residues.
B: 11 to 19 rubbing scratches and rubbing residues.
C: 20 to 29 rubbing scratches and rubbing residues.
D: There are 30 or more rubbing scratches and rubbing residues.

(Examples 4 to 6)
Was spin-coated on the resulting liquid crystal aligning agent A transparent electrode-attached glass substrate in the synthesis example above various, dried for 5 minutes at 80 ° C. on a hot plate, a baked for 30 minutes at 220 ° C. in a circulating hot air oven And a coating film having a thickness of 100 nm was formed. The surface of the coating film was rubbed with a rubbing apparatus having a roll diameter of 120 mm using a rayon cloth under the conditions of a roll rotation speed of 300 rpm, a roll traveling speed of 20 mm / sec, and an indentation amount of 0.5 mm to obtain a substrate with a liquid crystal alignment film.

  In order to evaluate the alignment state of the liquid crystal cell, two substrates with the above-mentioned liquid crystal alignment film were prepared, and after spraying a 6 μm spacer on the surface of the one liquid crystal alignment film, a sealant was printed from above, The other substrate was bonded so that the liquid crystal alignment film faces each other and the rubbing direction was antiparallel, and then the sealing agent was cured to produce an empty cell. An antiparallel liquid crystal cell was obtained by injecting liquid crystal MLC-2003 (manufactured by Merck Japan) into this empty cell by a reduced pressure injection method and sealing the injection port.

Evaluation of liquid crystal alignment state It evaluated by arrange | positioning the said liquid crystal cell between the polarizing plates installed in cross Nicol, and observing the liquid crystal alignment state immediately after liquid crystal injection visually. Thereafter, the liquid crystal cell was heated at 105 ° C. for 10 minutes to perform isotropic phase treatment, and the liquid crystal alignment state after the isotropic phase treatment was visually observed. The results are shown in Table 2 described later.

(Examples 7 to 9 )
Was spin-coated on the resulting liquid crystal aligning agent A transparent electrode-attached glass substrate in the synthesis example above various, dried for 5 minutes at 80 ° C. on a hot plate, a baked 60 minutes at 250 ° C. in a hot-air circulation oven And a coating film having a thickness of 100 nm was formed. The surface of the coating film was rubbed with a rubbing apparatus having a roll diameter of 120 mm using a rayon cloth under the conditions of a roll rotation speed of 700 rpm, a roll traveling speed of 10 mm / sec, and an indentation amount of 0.4 mm to obtain a substrate with a liquid crystal alignment film.

  In order to evaluate the electrical characteristics of the liquid crystal cell, two substrates with the above-mentioned liquid crystal alignment film were prepared, and after spraying a 6 μm spacer on the surface of the one liquid crystal alignment film, a sealant was printed from above, The other substrate was bonded so that the liquid crystal alignment film faces each other and the rubbing direction was orthogonal, and then the sealing agent was cured to produce an empty cell. Liquid crystal MLC-2003 (Merck Japan Co., Ltd.) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain a twisted nematic liquid crystal cell.

Evaluation of Voltage Holding Characteristics A voltage of 4 V was applied to the liquid crystal cell at a temperature of 23 ° C. for 60 μs, the voltage after 16.67 ms was measured, and how much the voltage was held was calculated as a voltage holding ratio. The results are shown in Table 3 described later.

Since the liquid crystal aligning agent of this invention can obtain the film excellent in rubbing tolerance, it can be used conveniently for the liquid crystal display element of various systems which require a rubbing process in the manufacture process of an element. The liquid crystal display element of the present invention can be used in various devices for displaying characters, moving images, still images, etc., such as liquid crystal displays and liquid crystal televisions.

The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2004-370328 filed on Dec. 22, 2004 are incorporated herein as the disclosure of the specification of the present invention. Is.

Claims (8)

It is a polyimide obtained by dehydrating and ring-closing and imidizing a polyamic acid obtained by reaction polymerization of a diamine containing a diamine component represented by the following general formula [1] and a tetracarboxylic dianhydride component , and an imidization ratio A liquid crystal aligning agent for rubbing treatment , comprising a polymer having a content of 60% or more .

(In formula [1], n and m are integers of 0 to 4, R is a hydroxyl group, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, an alkenyl group having 2 or 3 carbon atoms, (At least one organic group selected from the group consisting of a carboxylic acid group, a cyano group and a halogen atom, and when n + m is 2 or more, each R may be the same or different.)   The liquid crystal aligning agent of Claim 1 which is a diamine which has two amino groups in the position of 4 and 4 'in General formula [1].   The diamine represented by the general formula [1] is 1,2-bis (4-aminophenyl) ethyne, 1- (4-aminophenyl) -2- (4-amino-3-methylphenyl) ethyne, 1- It is (4-aminophenyl) -2- (4-amino-3-methoxyphenyl) ethyne or 1- (4-aminophenyl) -2- (4-amino-3-fluorophenyl) ethyne 2. A liquid crystal aligning agent according to 2.   The liquid crystal aligning agent of any one of Claims 1-3 in which a diamine component contains 10-100 mol% of diamine represented by General formula [1].   The liquid crystal aligning agent of any one of Claims 1-4 whose at least 10 mol% of a tetracarboxylic dianhydride component is an aromatic tetracarboxylic dianhydride.   The liquid crystal aligning agent according to any one of claims 1 to 5, wherein at least 10 mol% of the tetracarboxylic dianhydride component is a tetracarboxylic dianhydride having an alicyclic structure or an aliphatic structure. The liquid crystal aligning agent of any one of Claims 1-6 whose imidation ratio of the polyimide obtained by dehydrating and ring-closing polyamic acid is 80 % or more.   The liquid crystal display element which has a liquid crystal aligning film obtained from the liquid crystal aligning agent of any one of Claims 1-7.