JP4702058B2 - Liquid crystal aligning agent and liquid crystal display element - Google Patents

Description

  The present invention relates to a liquid crystal alignment treatment agent used for forming a liquid crystal alignment film of a liquid crystal display element, and a liquid crystal display element produced using the same.

  A liquid crystal display element that is currently popular has a structure in which a liquid crystal material is filled between two opposing substrates, and the liquid crystal material is in a desired initial alignment state by the action of a liquid crystal alignment film provided on the substrate surface. Is maintained. As the liquid crystal alignment film, a method of rubbing and using a polyimide resin film (rubbing film) is generally widely used. Further, as a method for replacing the rubbing film, a method (photo-alignment film) in which the organic film is irradiated with polarized ultraviolet rays or the like has been energetically studied.

  It is known that the applied voltage-transmittance characteristics of such a liquid crystal display element generally vary depending on the environmental temperature, which is an obstacle for stable and high-quality display. The first factor that causes the fluctuation of the characteristics is that the liquid crystal characteristics have temperature dependency, but there is also a factor derived from the liquid crystal alignment film. For example, when the pretilt angle of the liquid crystal varies depending on the environmental temperature, a shift occurs in the threshold voltage when the liquid crystal is driven, and as a result, the applied voltage-transmittance characteristics of the liquid crystal display element also vary. The variation of the pretilt angle due to the environmental temperature is noticeable when the liquid crystal alignment regulating force of the liquid crystal alignment film is weak, such as a liquid crystal alignment film having a high pretilt angle or a photo alignment film. In extreme cases, the pretilt angle is greatly reduced at high temperatures, causing problems such as failure of normal liquid crystal driving. Therefore, it becomes a particularly important problem in a liquid crystal display element that requires a high pretilt angle and a photo-alignment film that is attracting attention as a method for replacing a rubbing film.

  Usually, the pretilt angle of the liquid crystal obtained from a polyimide-type liquid crystal alignment film having a simple structure is not so high. However, as a method of increasing the pretilt angle to an arbitrary value, a long-chain alkyl group or fluorocarbon is added to the polyimide side chain. A method for introducing an alkyl group is known (for example, see JP-A-2-282726).

  As a method for improving the stability with respect to the temperature at which the liquid crystal alignment film is formed with respect to the pretilt angle increased as described above and the stability with respect to the heat treatment after forming the liquid crystal display element, a cyclic substituent is added to the side chain structure of polyimide. There is also known a method for introducing (see, for example, JP-A-9-278724).

  However, the pre-tilt angle stabilization technology that has been proposed in the past is mostly related to the stability of the manufacturing process and durability, and there are examples of reports on the pre-tilt angle stabilization technology against changes in environmental temperature. Absent.

  The present invention has been made to solve the problem of the stability of the pretilt angle of the liquid crystal with respect to changes in environmental temperature, particularly the problem of the stability of the pretilt angle at high temperatures. That is, an object of the present invention is to provide a liquid crystal alignment treatment agent that can form a liquid crystal alignment film that has a small change in pretilt angle with respect to a change in environmental temperature and that stably gives a high pretilt angle even at high temperatures. The object of the present invention is to provide a liquid crystal display element capable of stable and high-quality display against changes in environmental temperature.

  It has been found that the above-described problems of the present invention can be solved by the following liquid crystal aligning agent and liquid crystal display element.

Thus, the present invention has the following gist.
1. A liquid crystal comprising an addition polymer containing a structural unit represented by the following formula (1) and at least one polymer selected from the group consisting of polyamic acid, polyimide, polyamide, polyester and polyurea Alignment treatment agent.

（式中、Ａは付加重合によって得られる重合体の主鎖構造であり、Ｂは単結合又はエステル、エーテル、アミド、及びウレタンからなる群より選ばれる結合基である。Ｘ１とＸ２は独立して芳香族環、脂肪族環、又はヘテロ環を表し、Ｒ１は炭素数３〜１８のアルキル基、炭素数３〜１８のアルコキシ基、炭素数１〜５のフルオロアルキル基、炭素数１〜５のフルオロアルコキシ基、シアノ基、又はハロゲン原子を表す。）
２．付加重合体が、前記ポリアミド酸、ポリイミド、ポリアミド、ポリエステル及びポリウレアからなる群から選ばれる少なくとも一種類の重合体と化学的に結合した状態で含有されている、請求項１に記載の液晶配向処理剤
３．液晶配向処理剤に含有される重合体成分全体の中で、式（１）で示される構造単位が占める重量割合が０．０１〜５０重量％である、上記１又は２に記載の液晶配向処理剤
４．付加重合体が、式（１）で示される構造単位を、構造単位の数換算で５０％以上含有し、かつ全重合体成分における前記付加重合体の比率が０．１〜２０重量％である上記１〜３のいずれかに記載の液晶配向処理剤。
５．付加重合体が、式（１）の構造単位を構造単位数換算で５％以上含有する上記１〜４のいずれかに記載の液晶配向処理剤。
６．付加重合体が、その構造単位の式（１）において、Ａ−Ｂで示される部分が、下記式（２）で示される構造を有する上記１〜５のいずれかに記載の液晶配向処理剤。

(In the formula, A is a main chain structure of a polymer obtained by addition polymerization, and B is a single bond or a linking group selected from the group consisting of ester, ether, amide, and urethane. X1 and X2 are independent. R1 represents an alkyl group having 3 to 18 carbon atoms, an alkoxy group having 3 to 18 carbon atoms, a fluoroalkyl group having 1 to 5 carbon atoms, or 1 to 5 carbon atoms. fluoroalkoxy group, a cyano group table to or halogen atom.)
2. Addition polymer is, the polyamic acid, polyimide, polyamide, are contained in a state of being chemically bonded to at least one polymer selected from the group consisting of polyesters and polyureas, liquid crystal orientation treatment according to claim 1 Agent 3. 3. The liquid crystal alignment treatment according to 1 or 2 above, wherein the weight ratio of the structural unit represented by the formula (1) is 0.01 to 50% by weight in the entire polymer component contained in the liquid crystal alignment treatment agent. Agent
4). The addition polymer contains 50% or more of the structural unit represented by the formula (1) in terms of the number of structural units, and the ratio of the addition polymer in all polymer components is 0.1 to 20% by weight. The liquid-crystal aligning agent in any one of said 1-3.
5. 5. The liquid crystal aligning agent according to any one of 1 to 4 above, wherein the addition polymer contains 5% or more of the structural unit of the formula (1) in terms of the number of structural units.
6). The liquid crystal aligning agent according to any one of 1 to 5 above, wherein the addition polymer has a structure represented by the following formula (2), wherein the portion represented by AB in the structural unit formula (1).

（式中、Ｒ２は水素原子、メチル基、又はハロゲン原子を表す。）
７．上記１〜６のいずれかに記載された液晶配向処理剤を用いた液晶表示素子。

(In the formula, R 2 represents a hydrogen atom, a methyl group, or a halogen atom.)
7 . The liquid crystal display element using the liquid-crystal aligning agent described in any one of said 1-6 .

  The liquid crystal alignment film formed from the liquid crystal aligning agent of the present invention has a small change in the pretilt angle of the liquid crystal with respect to a change in the environmental temperature, and can give a thermally stable high pretilt angle. Moreover, the liquid crystal display element using the liquid-crystal aligning agent of this invention can display a high quality display stably, with little fluctuation of an applied voltage-transmittance characteristic with respect to the change of environmental temperature.

The graph showing the VT curve of Example 1 The graph showing the VT curve of the comparative example 4

Explanation of symbols

V: Applied voltage (V) T: Transmittance (%)
23 ° C .: VT curve at 23 ° C. 60 ° C .: VT curve at 60 ° C.

The present invention is described in detail below.
The liquid crystal aligning agent of the present invention is a coating liquid for forming a liquid crystal alignment film on a substrate, and an addition polymer containing a structural unit represented by formula (1) is used as a pretilt angle imparting stabilizer for liquid crystals. It contains.

式（１）において、Ａは付加重合反応によって得られる重合体の主鎖構造であり、Ｂは単結合又は、エステル、エーテル、アミド、及びウレタンからなる群より選ばれる結合基である。付加重合反応によって得られる上記重合体としては、ポリビニル、ポリ（メタ）アクリル酸、ポリマレイミド、などが挙げられる。以下にＡで示される部分の具体的構造例を記載するが、この限りではない。

In the formula (1), A is a main chain structure of a polymer obtained by an addition polymerization reaction, and B is a single bond or a linking group selected from the group consisting of esters, ethers, amides, and urethanes. Examples of the polymer obtained by the addition polymerization reaction include polyvinyl, poly (meth) acrylic acid, and polymaleimide. Although the specific structural example of the part shown by A below is described, it is not this limitation.

（上記式中、Ｒ２は水素原子、メチル基、又はフッ素原子、塩素原子などのハロゲン原子を表す。）
重合性や側鎖導入の容易性の観点から、付加重合反応によって得られる重合体としてはポリ（メタ）アクリル酸が好ましい。具体的な構造としては、式（１）のＡ−Ｂで示される部分が、式（２）で示される構造が好ましい。

(In the above formula, R2 represents a hydrogen atom, a methyl group, or a halogen atom such as a fluorine atom or a chlorine atom.)
From the viewpoint of polymerizability and ease of side chain introduction, the polymer obtained by the addition polymerization reaction is preferably poly (meth) acrylic acid. As a specific structure, a structure represented by Formula (2) in the portion represented by AB in Formula (1) is preferable.

（式中、Ｒ２は水素原子、メチル基、又はフッ素原子、塩素原子などのハロゲン原子を表す。）

(In the formula, R2 represents a hydrogen atom, a methyl group, or a halogen atom such as a fluorine atom or a chlorine atom.)

  In Formula (1), X1 and X2 independently represent an aromatic ring, an aliphatic ring, or a heterocycle, and R1 represents an alkyl group having 3 to 18 carbon atoms, an alkoxy group having 3 to 18 carbon atoms, or 1 carbon atom. Represents a fluoroalkyl group of -5, a fluoroalkoxy group of 1 to 5 carbon atoms, a cyano group, or a halogen atom. The portion composed of X1-X2-R1 preferably has a liquid crystal-like structure.

  Specific examples of X1 or X2 include the following. As an aromatic ring, a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, an indane ring, etc., as an aliphatic ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a bicyclooctane ring, etc., as a hetero ring, Examples include a furan ring, a thiophene ring, a thiazole ring, a pyridine ring, a pyrimidine ring, a quinoline ring, an acylidine ring, a phenanthridine ring, a benzothiazole ring, and a dioxane ring. The bonding position of these ring structures in Formula (1) is preferably higher in linearity. For example, in the case of a benzene ring, a para bond is preferable. Although the preferable example of X1 or X2 is shown below, it is not this limitation. X1 and X2 may have different structures.

上記構造において、環構造上の任意の水素原子は、メチル基、エチル基、又はフッ素原子、塩素原子などのハロゲン原子等で置換されていてもよい。

In the above structure, any hydrogen atom on the ring structure may be substituted with a methyl group, an ethyl group, or a halogen atom such as a fluorine atom or a chlorine atom.

  The combination of X1 and X2 is more preferably a combination selected from the group consisting of a benzene ring, a cyclohexane ring, a pyridine ring, and a pyrimidine ring in view of compatibility with the current liquid crystal, and in particular, It is preferably selected from the group consisting of cyclohexane rings. Specifically, the combination of X1 and X2 is particularly preferably selected from the group consisting of biphenyl, bicyclohexyl, phenylcyclohexyl, and cyclohexylphenyl.

  R1 is an alkyl group having 3 to 18 carbon atoms, an alkoxy group having 3 to 18 carbon atoms, a fluoroalkyl group having 1 to 5 carbon atoms, in accordance with the compatibility with the liquid crystal to be used and the target pretilt angle. It can select suitably from a C1-C5 fluoro alkoxy group, a cyano group, or a halogen atom. Among these, an alkyl group having 5 to 8 carbon atoms and an alkoxy group having 5 to 8 carbon atoms are particularly preferable because of wide application range.

  A part of specific examples of the portion consisting of X1-X2-R1 are shown below, but this is not restrictive. In the following structure, n is preferably an integer of 3 to 12, particularly preferably 5 to 10.

  The addition polymer containing the structural unit represented by the formula (1) is a homopolymer of the structural unit represented by the formula (1), a random copolymer with other structural units obtained by addition polymerization, or an alternating copolymer. Any of a polymer, a block copolymer, or a graft copolymer may be used. These polymers can be synthesized by known radical polymerization, cationic polymerization, anionic polymerization and the like. The polymerization means may be either thermal polymerization or photopolymerization.

  The addition polymer containing the structural unit represented by the formula (1) is a monomer corresponding to the formula (1), that is, a substituent composed of -X1-X2-R1 through a linking group represented by B. It can be obtained by a general addition polymerization reaction using a vinyl compound, maleimide compound or the like having

  The structure of the monomer corresponding to the structure represented by the formula (1) is shown below, but this is not restrictive. In addition, R1, R2, X1, and X2 in the following formula are as described above.

  The above monomers may be used alone or in combination. In addition, the polymer having the structure represented by the formula (1) is used to control the pretilt angle, the solubility of the polymer in an organic solvent, and other polymers contained in the liquid crystal aligning agent. One or more other monomers capable of addition polymerization reaction are used in combination for the purpose of compatibility control, improvement of the coating property of the liquid crystal aligning agent, and heat resistance of the liquid crystal alignment film. It can be a polymer, a block copolymer, or the like.

  Specific examples of other monomers capable of addition polymerization reaction include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth) Hexyl acrylate, hydroxyethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate , Phenyl (meth) acrylate, benzyl (meth) acrylate, glycidyl (meth) acrylate, styrene, hydroxystyrene, carboxystyrene, methacrylamide, N-arylmethacrylamide, N-hydroxyethyl-N-methylmethacrylamide, N-methyl-N-phenylmethacrylamide, acrylamide N- aryl acrylamide, N, N- aryl acrylamide, N- methyl -N- phenyl acrylamide, N- vinyl-2-pyrrolidone, N- phenylmaleimide, vinyl carbazole, vinyl pyridine, vinyl imidazole, and the like. Among these, glycidyl methacrylate is particularly preferable because it is effective in improving the solubility and compatibility of the polymer.

  As described above, the structural unit represented by the formula (1) using the monomer corresponding to the structure represented by the formula (1) and, if necessary, other monomer components capable of addition polymerization reaction An example of a technique for obtaining an addition polymer containing benzene by radical polymerization is described below. The corresponding monomer is dissolved in an organic solvent and a reaction initiator is added. The solvent for the above reaction is not particularly limited as long as it can dissolve the resulting polymer. For example, γ-butyrolactone, cyclohexanone, dimethyl sulfoxide, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, ethyl lactate (EL), methoxypropanol (PGME), propylene glycol monomethyl ether acetate (PGMEA), or a mixture thereof. Examples of the reaction initiator include azo compounds such as AIBN (azobisisobutyronitrile), peroxides such as benzoyl peroxide, and the like. Further, the reaction system may be heated for the purpose of promoting the reaction or completing the reaction. The polymer thus obtained may be used as it is, or may be used after being introduced into a poor solvent and recovering the desired polymer.

  In the addition polymer containing the structural unit represented by the formula (1), the content ratio of the structural unit represented by the formula (1) can be freely set, but in order to stably develop the pretilt angle, the number of structural units is converted. Is preferably 5% or more, more preferably 30% or more. As will be described later, when the liquid crystal aligning agent of the present invention contains an addition polymer containing the structural unit represented by the formula (1) and a polymer other than this polymer, the formula (1) The content ratio of the structural unit shown is preferably 50% or more, more preferably 60% or more, and particularly preferably 70% or more.

  The molecular weight of the polymer having the structure represented by the formula (1) is not particularly limited, but is, for example, 1,000 to 1,000,000, 2000 to 400,000, 5000 to 100,000 in terms of weight average molecular weight measured by GPC (Gel Permeation Chromatography) method. Etc. are suitable.

  In addition to the addition polymer containing the structural unit represented by the formula (1), the polymer component contained in the liquid crystal alignment treatment agent of the present invention is a polymer for giving liquid crystal alignment control in the horizontal direction to the substrate. It is preferable to contain. As such a polymer, a polymer used in a general liquid crystal alignment film can be used, and polyamic acid, polyimide, polyamide, polyester, polyurea and the like are preferable. In particular, polyamic acid or polyimide is excellent in liquid crystal alignment and heat resistance, and is widely used as a material for liquid crystal alignment films, and is preferable as a polymer component to be contained in the liquid crystal alignment treatment agent of the present invention.

  The structure of the above polyamic acid or polyimide is not particularly limited, but when the liquid crystal alignment treatment agent of the present invention is used in a method of forming a liquid crystal alignment film by irradiating polarized ultraviolet rays or the like, so-called photo alignment film, It is desirable that the main chain contains a cyclobutane ring, an amide bond, an olefin structure, and a benzophenone structure that chemically react with each other.

  Usually, polyamic acid can be obtained by reacting a tetracarboxylic dianhydride and a diamine compound in an organic solvent. Polyimide can be obtained by imidizing (dehydrating and cyclizing) polyamic acid.

  Examples of the polyamic acid that can be contained in the liquid crystal aligning agent of the present invention include one or more tetracarboxylic dianhydrides selected from the following tetracarboxylic dianhydrides and diamine compounds, and one type. The polyamic acid obtained by reaction with the above diamine compound is mentioned, but not limited thereto.

  Examples of tetracarboxylic dianhydrides used for the polyamic acid synthesis reaction include pyromellitic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 1,4 , 5,8-Naphthalenetetracarboxylic acid, 2,3,6,7-anthracenetetracarboxylic acid, 1,2,5,6-anthracenetetracarboxylic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid 2,3,3 ′, 4-biphenyltetracarboxylic acid, bis (3,4-dicarboxyphenyl) ether, 3,3′4,4′-benzophenonetetracarboxylic acid, 3,3′4,4′- Chalconetetracarboxylic acid, bis (3,4-dicarboxyphenyl) sulfone, bis (3,4-dicarboxyphenyl) methane, 2,2-bis (3,4-dicarboxy) Enyl) propane, 1,1,1,3,3,3-hexafluoro-2,2-bis (3,4-dicarboxyphenyl) propane, bis (3,4-dicarboxyphenyl) dimethylsilane, bis ( Dianhydrides of aromatic tetracarboxylic acids such as 3,4-dicarboxyphenyl) diphenylsilane, 2,3,4,5-pyridinetetracarboxylic acid, 2,6-bis (3,4-dicarboxyphenyl) pyridine 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 2,3,5-tricarboxycyclopentyl Dianhydrides of alicyclic tetracarboxylic acids such as acetic acid, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic acid, 1,2,3 Dianhydride of an aliphatic tetracarboxylic acid such as 4-butane tetracarboxylic acid, and the like.

  Examples of the diamine compound used in the polyamic acid synthesis reaction include p-phenylenediamine, m-phenylenediamine, N, N-diallyl-1,2,4-benzenetriamine, 2,5-diaminobenzonitrile, and 2,5- Diaminotoluene, 2,6-diaminotoluene, 4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, diaminodiphenylmethane , Diaminodiphenyl ether, diaminodiphenylamine, 2,2′-diaminodiphenylpropane, bis (3,5-diethyl-4-aminophenyl) methane, diaminodiphenylsulfone, diaminobenzophenone, 3,3′-diaminochalcone, 4,4 ′ -Diaminochalcone, 3,3'-diamy Stilbene, 4,4′-diaminostilbene, diaminonaphthalene, 1,4-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenyl) benzene, 9,10-bis (4-aminophenyl) Anthracene, 1,3-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) diphenylsulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2, Aromatic diamines such as 2-bis (4-aminophenyl) hexafluoropropane and 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,6-diaminopyridine, 2,4-diamino Pyridine, 2,7-diaminobenzofuran, 2,7-diaminocarbazole, 3,7-diaminophenothiazine Heterocyclic diamines such as 2,5-diamino-1,3,4-thiadiazole, 2,4-diamino-s-triazine, bis (4-aminocyclohexyl) methane, bis (4-amino-3-methylcyclohexyl) Alicyclic diamines such as methane and aliphatic diamines such as 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,6-diaminohexane, 1,3-diamino-4-octadecyl Oxybenzene, 1,3-diamino-4-hexadecyloxybenzene, 1,3-diamino-4-dodecyloxybenzene, 4- [4- (4-trans-n-heptylcyclohexyl) phenoxy] -1,3- Alkyl groups such as diaminobenzene and (4-trans-n-pentylbicyclohexyl) -3,5-diaminobenzoate And a diamine having a liquid crystal-like structure in the side chain, and a silicon diamine such as 1,3-bis (3-aminopropyl) -1,1,3,3-tetramethyldisiloxane.

  The polyamic acid contained in the liquid crystal aligning agent of the present invention is preferably 2,000 to 500,000 in terms of weight average molecular weight {Mw} measured by GPC (Gel Permeation Chromatography) method. When the molecular weight is too small, the strength of the coating film obtained therefrom is insufficient, and when the molecular weight is too large, the workability at the time of forming the coating film may be deteriorated. The molecular weight of the polyamic acid can be controlled by adjusting the molar ratio of the tetracarboxylic dianhydride and the diamine compound used in the polyamic acid synthesis reaction. As in the normal polycondensation reaction, the degree of polymerization of the polymer produced increases as this molar ratio approaches 1.0.

  The synthesis reaction of polyamic acid is usually carried out in an organic solvent at a reaction temperature of 0 to 150 ° C., preferably 0 to 100 ° C. The organic solvent at this time is not particularly limited as long as the obtained polyamic acid can be dissolved. Specific examples include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, dimethyl sulfoxide, tetramethyl urea, pyridine, dimethyl sulfone, hexamethyl sulfoxide. , Γ-butyrolactone, and the like. These may be used alone or in combination. Furthermore, even if it is a solvent which does not melt | dissolve a polyamic acid, you may mix and use it for the said solvent in the range which does not precipitate the polyamic acid produced | generated by the polymerization reaction.

  As an example of the polyimide which can be contained in the liquid-crystal aligning agent of this invention, what carried out the imidation (dehydration ring closure) of the above-mentioned polyamic acid is mentioned. The term “polyimide” as used herein means that even if all of the repeating units of the polyamic acid are not imidized, they are included in the category and are also suitably used for the liquid crystal aligning agent of the present invention.

  Usually, imidization (dehydration ring closure) of polyamic acid can be performed in a solution. In the method of imidizing polyamic acid in a solution, the reaction temperature is usually 50 to 200 ° C., preferably 60 to 170 ° C. When the reaction temperature is less than 50 ° C., the dehydration ring-closing reaction does not proceed sufficiently, and when the reaction temperature exceeds 200 ° C., the molecular weight of the imidized polymer obtained may decrease. In the imidization reaction, it is preferable to add a dehydrating agent and a dehydration ring-closing catalyst because the molecular weight of the polyimide that can proceed at a relatively low temperature is unlikely to decrease. As the dehydrating agent, for example, tertiary amines such as pyridine and triethylamine can be used. The amount of the dehydrating agent used is preferably 0.01 to 20 mol per 1 mol of the polyamic acid repeating unit. Moreover, as a dehydration ring closure catalyst, tertiary amines, such as a pyridine and a triethylamine, can be used, for example. The amount of the dehydration ring closure catalyst used is preferably 0.01 to 10 moles per mole of the dehydrating agent used. In addition, as an organic solvent used for dehydration ring closure reaction, the organic solvent illustrated as what is used for the synthesis | combination of a polyamic acid can be mentioned. And the reaction temperature at the time of adding a dehydrating agent and a dehydration ring-closing catalyst is 0-180 degreeC normally, Preferably you may be 10-150 degreeC.

  The polyamic acid or polyimide obtained as described above can be used as it is, or may be used after being recovered by precipitation isolation in a poor solvent such as methanol or ethanol.

In the liquid crystal aligning agent of the present invention, the addition polymer containing the structural unit represented by the formula (1) may be contained in a form chemically bonded to the polymer contained as the other polymer component. As the method, for example, a substituent capable of addition polymerization is introduced into the side chain of the polymer contained as the other polymer component, and in the solution in which this polymer is present, What is necessary is just to carry out addition polymerization reaction using the monomer corresponding to the structure shown, and the other monomer component in which addition polymerization reaction is possible as needed. In order to obtain a form in which the polymer having the structure represented by the formula (1) is chemically bonded to the polyamic acid or polyimide, for example, the polyamic acid is synthesized using a diamine having a vinyl group or a methacryloyl group in the side chain. The above reaction may be performed in a solution containing the polyamic acid.
Examples of the diamine having a methacryloyl group in the side chain include the following diamines.

  In addition, a hydroxy group, a carboxyl group, an amino group, an isocyanate group, an acid anhydride group, and the like are introduced into each of the polymer having the structure represented by the formula (1) and the polymer contained as the other polymer component. Alternatively, they may be bonded by a reaction between a hydroxy group or a carboxyl group and an isocyanate group or a reaction between an amino group and an acid anhydride group.

  The weight ratio of the structural unit represented by the formula (1) in the entire polymer component contained in the liquid crystal aligning agent of the present invention is arbitrarily set according to the target pretilt angle. However, the weight ratio is preferably 0.01 to 50% by weight, more preferably 0.1 to 20% by weight.

  Moreover, the liquid crystal aligning agent of this invention is made to contain the addition polymer containing the structural unit shown by Formula (1), and the polymer for giving the liquid crystal alignment regulation of a horizontal direction with respect to a board | substrate other than that. In the case, the content ratio of the addition polymer containing the structural unit represented by the formula (1) is preferably 0.1 to 20% by weight of the total polymer component contained in the liquid crystal aligning agent, more preferably. Is 0.3 to 5% by weight. By adding a relatively small amount of the addition polymer having a high content of the structural unit represented by the formula (1) to the polymer for regulating the liquid crystal alignment in the horizontal direction with respect to the substrate, the pretilt angle is increased. It is possible to obtain a liquid crystal alignment film that is stable and also excellent in liquid crystal alignment regulation in the horizontal direction with respect to the substrate.

  From the above, if a preferable example is given as a composition of the polymer component contained in the liquid crystal aligning agent of the present invention, (A) the content ratio of the structural unit represented by the formula (1) is converted into the number of structural units. 50% or more, more preferably 60% or more, particularly preferably 70% or more, and (B) at least one polymer selected from polyamic acid, polyimide, polyamide, polyester or polyurea The ratio of (A) in all polymer components is 0.1 to 20% by weight, more preferably 0.3 to 5% by weight.

  The liquid crystal aligning agent of this invention is a coating liquid containing the polymer component described above. The solvent contained in the coating solution is not particularly limited as long as it can dissolve the polymer component. These may be used alone or in combination of two or more solvents. Furthermore, even if it is a solvent that does not dissolve the polymer alone, it can be added within a range in which the polymer component does not precipitate. Although the specific example of a solvent component is shown below, it is not this limitation.

  N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, γ-butyrolactone, dimethyl sulfoxide, tetramethylurea, hexamethylphosphotriamide, m-cresol, methyl alcohol, ethyl alcohol, diethyl Ether, ethylene glycol monomethyl ether, ethylene glycol ethyl ether, ethylene glycol-n-butyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, cyclohexanone, hexane, heptane, toluene, xylene.

  The liquid-crystal aligning agent of this invention may contain the functional silane containing compound for providing adhesiveness with a board | substrate. For example, N-trimethylsilylacetamide, diacetoxydimethylsilane, tetramethoxysilane, 3-aminopropyldiethoxymethylsilane, 3-aminopropyltriethoxysilane, 1,4-bis (dimethylsilyl) benzene, bis (dimethylamino) dimethyl Examples thereof include, but are not limited to, silane, bis (ethylamino) dimethylsilane, 1-trimethylsilylimidazole, methyltriacetoxysilane, dietoxymethylphenylsilane, phenyltriethoxysilane, and diphenylsilanediol.

  In order to obtain the liquid-crystal aligning agent of this invention, what is necessary is just to make it each solution mentioned above and making it the solution of the density | concentration which can be apply | coated to a board | substrate. Although the polymer component density | concentration in the liquid-crystal aligning agent of this invention can be suitably changed with the setting of the thickness of the liquid crystal aligning film to form, it is preferable to set it as 1 to 15 weight%. If it is less than 1% by weight, it is difficult to form a uniform and defect-free coating film, and if it exceeds 15% by weight, the storage stability of the solution may be deteriorated.

  The liquid crystal aligning agent of the present invention obtained as described above can be filtered as necessary, applied to a substrate, dried and fired to form a coating film. It can be used as a liquid crystal alignment film by performing an alignment treatment such as irradiating polarized ultraviolet rays in a certain direction with respect to the substrate surface.

  Examples of the method for applying the liquid crystal aligning agent include a spin coating method, a printing method, an ink jet method, and the like, but the transfer printing method is widely used industrially from the viewpoint of productivity, and the liquid crystal aligning treatment of the present invention. It is also preferably used in agents.

  The drying process after applying the liquid crystal alignment treatment 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, the drying process is performed. Inclusion 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 the conveyance of the substrate or the like. If a specific example is given, the method of drying on a hotplate of 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 a liquid-crystal aligning agent can be performed at 100-350 degreeC arbitrary temperatures, Preferably it is 150 to 300 degreeC, More preferably, it is 200 to 250 degreeC. When polyamic acid is contained in the liquid crystal aligning agent, the conversion rate from polyamic acid to polyimide varies 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 coating film after baking is too thick, it will be 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, so it is 5 to 300 nm, preferably 10 to 100 nm. It is.

  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 method described above, and then preparing a liquid crystal cell by a known method. As an example of liquid crystal cell production, a pair of substrates on which a liquid crystal alignment film is formed are sandwiched between 1 to 30 μm, preferably 2 to 10 μm spacers, 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 substrate used for the liquid crystal display element 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 prepared 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.
The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

<Synthesis Example 1>
5.16 g (49.36 mmol) of methacryloyl chloride, 11.06 g (44.87 mmol) of 4- (4-trans-n-pentylcyclohexyl) phenol, and 4.99 g (49.36 mmol) of triethylamine in 200 mL of tetrahydrofuran at room temperature. For 30 minutes and then at 50 ° C. for 1 hour. The reaction solution was gradually cooled to room temperature, extracted with ethyl acetate, and the organic layer was dried over anhydrous sodium sulfate. The organic layer was concentrated and purified by silica gel column chromatography (ethyl acetate: hexane = 3: 1), and 14.15 g of 4- (4-trans-n-pentylcyclohexyl) phenoxy methacrylate having an HPLC relative purity of 99% or more. Obtained.

<Synthesis Example 2>
4- (4-trans-n-pentylcyclohexyl) phenoxy methacrylate (20.10 g, 0.07 mol) and glycidyl methacrylate (4.27 g, 0.03 mol) obtained in the same manner as in Synthesis Example 1 were added to N-methyl-2- After dissolving in 87.48 g of pyrrolidone (hereinafter abbreviated as NMP), the inside of the flask was replaced with nitrogen, and the temperature was raised to 70 ° C. After the temperature increase, 0.2 g of azoisobutyronitrile (hereinafter abbreviated as AIBN) dissolved in 10 g of NMP was added under a nitrogen atmosphere and reacted for 24 hours to obtain an addition polymer containing the structural unit of the formula (1). It was. The weight average molecular weight {Mw} of this addition polymer was 28000.

<Synthesis Example 3>
10.81 g (0.1 mol) of p-phenylenediamine is dissolved in 172.4 g of NMP, 19.61 g (0.1 mol) of cyclobutanetetracarboxylic dianhydride is added thereto, and reacted at room temperature for 24 hours. Got. The resulting polyamic acid had a weight average molecular weight {Mw} of 156000.

<Example 1>
NMP was added to the reaction solution of the addition polymer obtained in Synthesis Example 2 to obtain a solution having an addition polymer concentration of 3 wt%. Further, NMP was added to the polyamic acid reaction solution obtained in Synthesis Example 3 to obtain a polyamic acid concentration 3 wt% solution. 1 g of the 3 wt% solution of the addition polymer was added to 99 g of the 3 wt% solution of the polyamic acid, and the mixture was sufficiently stirred to obtain a uniform solution to obtain the liquid crystal alignment treatment agent of the present invention.

  This liquid crystal aligning agent was pressure filtered through a membrane filter having a pore size of 0.5 μm, and then spin-coated on a glass substrate with a transparent electrode. The substrate was placed on a hot plate at 80 ° C. and dried for 5 minutes, and then baked in a hot air circulation oven at 210 ° C. for 60 minutes to obtain a coating film having a thickness of 50 nm on the substrate. This coating surface was rubbed using a rubbing apparatus equipped with a rayon cloth under the conditions of a roll rotation speed of 300 rpm, a moving speed of 20 mm / s, and an indentation of 0.5 mm, to obtain a substrate with a liquid crystal alignment film.

  Prepare two substrates with the above-mentioned liquid crystal alignment film, spray a 6 μm spacer on the liquid crystal alignment film surface of one of the substrates, and paste them together so that the rubbing direction is perpendicular, and apply nematic liquid crystal (ZLI-4792 manufactured by Merck). A liquid crystal cell was prepared by injection. This liquid crystal cell was treated at 120 ° C. for 30 minutes, and the subsequent alignment state of the liquid crystal was observed with a polarizing microscope, and it was confirmed that the liquid crystal cell had a uniform alignment without defects.

  When the pretilt angle of this liquid crystal cell at 23 ° C. was measured by a pretilt angle measuring device (PAS-301) manufactured by ELSICON, it was 22.1 °. Next, the voltage-transmittance characteristics (VT curve) of this liquid crystal cell are measured at temperatures of 23 ° C. and 60 ° C., and the value of the applied voltage (V90) when the transmittance is 90% is compared. The thermal stability was evaluated. As a result, V90 at 23 ° C. was 0.72 V, and V90 at 60 ° C. was 0.66 V. Although a shift toward the low voltage side due to the temperature characteristics of the liquid crystal was observed, it was due to a decrease in the pretilt angle. No shift to the high voltage side was observed, and it was confirmed that the pretilt angle was very stable regardless of the environmental temperature.

In addition, the measurement of VT curve and calculation of V90 were performed as follows.
(1) A polarizing microscope with a light receiving element installed in the eyepiece was used, and the angle between the polarizing microscope and the analyzer was set to 90 degrees.
(2) The liquid crystal cell was installed so that the orientation processing directions of the upper and lower substrates coincided with the polarization direction of the polarizer or analyzer, respectively, so that the amount of light transmission was maximized when no voltage was applied.
(3) A 30 Hz AC rectangular wave was applied to the liquid crystal cell in the range of 0 to ± 5 V in increments of 0.01 V, and the light transmission amount at that time was detected and recorded by the light receiving element.
(4) The relationship between the applied voltage and the transmittance is graphed, assuming that the transmitted light amount when no voltage is applied is 100% transmittance and the transmitted light amount when ± 5V is applied is 0%. From this graph, the transmittance is 90%. The value of the applied voltage at the time of reading is read and used as the value of V90.
(5) Measurement at 23 ° C. was performed at room temperature of 23 ° C., and measurement at 60 ° C. was performed by heating the liquid crystal cell to 60 ° C. on the stage of a polarizing microscope.

<Example 2>
Instead of rubbing the coating film obtained in the same manner as in Example 1, an ELSICON light irradiation device, OptoAlign ^™ (E3-UV-600-A) was used, and the lamp angle was 0 deg and the irradiation amount was 20 J. The substrate with a liquid crystal alignment film was obtained by photo-alignment treatment.

  Prepare two substrates with the above-mentioned liquid crystal alignment film, spray a 6 μm spacer on the liquid crystal alignment film surface of one of the substrates, and paste them together so that the deflection direction of light irradiation is perpendicular. 4792) was injected to make a liquid crystal cell. This liquid crystal cell was treated at 120 ° C. for 30 minutes, and the subsequent alignment state of the liquid crystal was observed with a polarizing microscope, and it was confirmed that the liquid crystal cell had a uniform alignment without defects.

  For this liquid crystal cell, the pretilt angle and the VT curve were measured in the same manner as in Example 1. As a result, the pretilt angle was 22.5 °. In addition, V90 at 23 ° C. is 0.78 V and V90 at 60 ° C. is 0.66 V. Although a shift toward the low voltage side due to the temperature characteristics of the liquid crystal was observed, a high value due to a decrease in the pretilt angle was observed. No shift to the voltage side was observed, and it was confirmed that the pretilt angle was very stable regardless of the environmental temperature.

<Comparative Example 1>
9.73 g (0.9 mol) of p-phenylenediamine and 3.77 g (0.1 mol) of 1,3-diamino-4-octadecyloxybenzene were dissolved in 187.8 g of N-methylpyrrolidone (NMP), and cyclobutane was dissolved therein. 19.61 g (0.1 mol) of tetracarboxylic dianhydride was added and reacted at room temperature for 24 hours to obtain polyamic acid. The weight average molecular weight {Mw} of the obtained polyamic acid was 126000. NMP was added to this polyamic acid reaction solution to obtain a solution having a concentration of 3 wt%, which was used as a liquid crystal alignment treatment agent for comparison.

  A liquid crystal cell was produced in the same manner as in Example 1 using the liquid crystal alignment treatment agent. When the alignment state of the liquid crystal cell was observed with a polarizing microscope, it was confirmed that the liquid crystal cell had a uniform alignment without defects.

  For this liquid crystal cell, the pretilt angle and the VT curve were measured in the same manner as in Example 1. As a result, the pretilt angle was 16.5 °. Further, V90 at 23 ° C. is 0.87 V, V90 at 60 ° C. is 1.01 V, a shift to the high voltage side due to the decrease in the pretilt angle is observed at 60 ° C., and the pretilt angle is unstable. there were.

<Comparative example 2>
9.73 g (0.09 mol) of p-phenylenediamine and 3.81 g (0.01 mol) of 4- [4- (4-trans-n-heptylcyclohexyl) phenoxy] -1,3-diaminobenzene were mixed with N-methylpyrrolidone. (NMP) It melt | dissolved in 187.8g, and cyclobutane tetracarboxylic dianhydride 19.61g (0.1 mol) was added to this, and it was made to react at room temperature for 24 hours, and the polyamic acid was obtained. The obtained polyamic acid had a weight average molecular weight {Mw} of 143,000. NMP was added to this polyamic acid reaction solution to obtain a solution having a concentration of 3 wt%, which was used as a liquid crystal alignment treatment agent for comparison.

  A liquid crystal cell was produced in the same manner as in Example 1 using the liquid crystal alignment treatment agent. When the alignment state of the liquid crystal cell was observed with a polarizing microscope, it was confirmed that the liquid crystal cell had a uniform alignment without defects.

  For this liquid crystal cell, the pretilt angle and the VT curve were measured in the same manner as in Example 1. As a result, the pretilt angle was 20.9 °. Further, V90 at 23 ° C. is 0.63 V, V90 at 60 ° C. is 0.76 V, and a shift to the high voltage side due to the decrease in the pretilt angle is observed at 60 ° C., and the pretilt angle is unstable. there were.

<Comparative Example 3>
After dissolving 12.72 g (0.05 mol) of n-dodecyl methacrylate and 7.11 g (0.05 mol) of glycidyl methacrylate in 69.3 g of NMP, the inside of the flask was replaced with nitrogen, and the temperature was raised to 70 ° C. After raising the temperature, 0.2 g of azoisobutyronitrile (AIBN) dissolved in 10 g of NMP was added under a nitrogen atmosphere and reacted for 24 hours to obtain an addition polymer for comparison. The weight average molecular weight {Mw} of this addition polymer was 32000.

  8.65 g (0.8 mol) of p-phenylenediamine and 7.61 g (0.2 mol) of 4- [4- (4-trans-n-heptylcyclohexyl) phenoxy] -1,3-diaminobenzene were added to N-methylpyrrolidone. (NMP) It melt | dissolved in 203.3g, and cyclobutane tetracarboxylic dianhydride 19.61g (0.1 mol) was added to this, and it was made to react at room temperature for 24 hours, and the polyamic acid was obtained. The obtained polyamic acid had a weight average molecular weight {Mw} of 143,000.

  NMP was added to the reaction solution of the addition polymer obtained above to obtain a solution having an addition polymer concentration of 3 wt%. Further, NMP was added to the polyamic acid reaction solution obtained above to obtain a polyamic acid concentration of 3 wt%. 1 g of the 3 wt% solution of the addition polymer was added to 99 g of the 3 wt% solution of the polyamic acid, and the mixture was sufficiently stirred to obtain a uniform solution to obtain a liquid crystal alignment treatment agent for comparison.

  A liquid crystal cell was produced in the same manner as in Example 2 using the liquid crystal alignment treatment agent. When the alignment state of the liquid crystal cell was observed with a polarizing microscope, it was confirmed that the liquid crystal cell had a uniform alignment without defects.

  For this liquid crystal cell, the pretilt angle and the VT curve were measured in the same manner as in Example 1. As a result, the pretilt angle was 22.1 °. Moreover, V90 at 23 ° C. is 0.70 V, V90 at 60 ° C. is 1.28 V, and a large shift to the high voltage side due to the decrease of the pretilt angle is observed at 60 ° C., and the pretilt angle is very high. It was unstable.

<Comparative example 4>
A 3 wt% solution of polyamic acid prepared in Comparative Example 3 was used as a liquid crystal alignment treatment agent for comparison.
Using this liquid crystal aligning agent, a liquid crystal cell was produced in the same manner as in Example 2. When the alignment state of the liquid crystal cell was observed with a polarizing microscope, it was confirmed that the liquid crystal cell had a uniform alignment without defects.

  For this liquid crystal cell, the pretilt angle and the VT curve were measured in the same manner as in Example 1. As a result, the pretilt angle was 15.9 °. Moreover, V90 at 23 ° C. is 0.78 V, V90 at 60 ° C. is 1.42 V, and a large shift to the high voltage side due to a decrease in the pretilt angle is observed at 60 ° C., and the pretilt angle is very high. It was unstable.

<Comparative Example 5>
A 3 wt% solution of polyamic acid prepared in Example 1 was used as a liquid crystal aligning agent for comparison.
Using this liquid crystal aligning agent, a liquid crystal cell was produced in the same manner as in Example 2. When the alignment state of the liquid crystal cell was observed with a polarizing microscope, it was confirmed that the liquid crystal cell had a uniform alignment without defects.

  For this liquid crystal cell, the pretilt angle and the VT curve were measured in the same manner as in Example 1. As a result, the pretilt angle was as low as 0.3 °. Further, V90 at 23 ° C. was 1.41 V, and V90 at 60 ° C. was 1.33 V, and a shift toward the low voltage side derived from the temperature characteristics of the liquid crystal was observed. This indicates that since the pretilt angle hardly appears at 23 ° C., no decrease in the pretilt angle was observed even when the temperature was raised to 60 ° C.

Claims (7)

Addition polymer comprising structural units represented by the following formula (1), and, characterized in that it contains at least one kind of polymer polyamic acid is selected polyimides, polyamides, from the group consisting of polyesters and polyureas Liquid crystal aligning agent.

(In the formula, A is a main chain structure of a polymer obtained by addition polymerization, and B is a single bond or a linking group selected from the group consisting of ester, ether, amide, and urethane. X1 and X2 are independent. R1 represents an alkyl group having 3 to 18 carbon atoms, an alkoxy group having 3 to 18 carbon atoms, a fluoroalkyl group having 1 to 5 carbon atoms, or 1 to 5 carbon atoms. Represents a fluoroalkoxy group, a cyano group, or a halogen atom.) Addition polymer is, the polyamic acid, polyimide, polyamide, are contained in a state of being chemically bonded to at least one polymer selected from the group consisting of polyesters and polyureas, liquid crystal orientation treatment according to claim 1 Agent The liquid crystal alignment of Claim 1 or 2 whose weight ratio for which the structural unit shown by Formula (1) accounts in the polymer component contained in a liquid-crystal aligning agent is 0.01 to 50 weight%. Processing agent The addition polymer contains 50% or more of the structural unit represented by the formula (1) in terms of the number of structural units, and the ratio of the addition polymer in all polymer components is 0.1 to 20% by weight. The liquid-crystal aligning agent in any one of Claims 1-3. The liquid-crystal aligning agent in any one of Claims 1-4 in which an addition polymer contains 5% or more of structural units of Formula (1) in conversion of the number of structural units. The liquid crystal aligning agent according to any one of claims 1 to 5 , wherein the addition polymer has a structure represented by the following formula (2) in the part represented by AB in the structural unit formula (1). .

(In the formula, R 2 represents a hydrogen atom, a methyl group, or a halogen atom.) The liquid crystal display element using the liquid-crystal aligning agent described in any one of Claims 1-6 .

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