JP2022027466A - Liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal element - Google Patents

Abstract

To provide a liquid crystal aligning agent capable of producing a liquid crystal alignment film which is unlikely to cause afterimages and offers good coatability and high mechanical strength..SOLUTION: A liquid crystal aligning agent provided herein contains a polymer [A] having a structural unit (U1) but not having a structural unit (U2), and a polymer [B] having the structural unit (U2) and a structural unit (U3), the structural unit (U1) being a structural unit derived from diamine having a partial structure represented by a formula (1), the structural unit (U2) being a structural unit derived from diamine having a partial structure represented by a formula (2), and the structural unit (U3) being a structural unit derived from diamine having a partial structure Y (-(CH2)n- etc.). In the formula (1), X1 and X2 represent divalent aromatic ring groups, R1 and R2 represent single bonds, alkanediyl groups having 1 to 4 carbon atoms or the like, Y1 and Y2 represent -NR3-CO-, Z1 represents a divalent organic group or the like, A1 and A2 represent divalent aromatic ring groups, and B1 represents -NR4- or a divalent aromatic heterocyclic group.SELECTED DRAWING: None

Description

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

As the liquid crystal material of the liquid crystal element, a negative type liquid crystal is used in the liquid crystal element such as VA drive method and MVA drive method, and TN type, IPS (In-Plane Switching) drive method, FFS (Fringe Field Switching) drive method and the like are used. A positive liquid crystal is used in the liquid crystal element. Further, in recent years, it has been proposed to use a negative type liquid crystal in an IPS drive type or FFS drive type liquid crystal element in order to further improve the definition of the liquid crystal element (see, for example, Patent Document 1).

In recent years, liquid crystal elements have been applied to a wide range of applications from relatively large display devices such as liquid crystal televisions and information displays to small display devices such as smartphones. With the widespread use of liquid crystal elements, further improvement in quality of liquid crystal elements is required. Therefore, conventionally, a polymer having a nitrogen-containing metaarylene structure is contained in a liquid crystal alignment agent to obtain a liquid crystal alignment film having a low resistance value and high transparency, and there is little seizure (DC afterimage) due to accumulated charges. It has been proposed to obtain a liquid crystal element (see, for example, Patent Document 2).

International Publication No. 2016/152928 International Publication No. 2019/093037

In addition to the DC afterimage, the afterimage generated by the liquid crystal element includes an AC afterimage caused by the orientation direction of the liquid crystal deviating from the initial orientation. In order to suppress the generation of afterimages and further improve the definition of the liquid crystal element, it is required that AC afterimages can be suppressed in addition to DC afterimages. Further, when the metaarylene structure is introduced into the polymer as in the technique of Patent Document 2, the solubility of the polymer is lowered due to the introduction of the rigid structure into the main chain, and the coatability of the liquid crystal alignment agent is lowered. There is concern about doing so. Further, in consideration of obtaining a liquid crystal alignment film by a rubbing method, suppressing a decrease in yield, and the like, a film formed by using a liquid crystal alignment agent is required to have high mechanical strength. However, it is difficult to satisfy these plurality of characteristics at the same time, and there is room for further improvement in the liquid crystal alignment agent.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal alignment agent capable of obtaining a liquid crystal alignment film having less afterimage, good coatability, and high mechanical strength. ..

The present inventors have diligently studied in order to solve the above-mentioned problems, and have found that the above-mentioned problems can be solved by using a plurality of types of polymers having different molecular structures, and have completed the present invention. Specifically, the present invention provides the following means.

（式（１）中、Ｘ^１及びＸ^２は、それぞれ独立に２価の芳香環基である。ただし、Ｘ^１が有する芳香環には、Ｒ^１の結合位置、及び「＊」に結合する基の結合位置とは異なる位置に置換基が結合しておらず、Ｘ^２が有する芳香環には、Ｒ^２の結合位置、及び「＊」に結合する基の結合位置とは異なる位置に置換基が結合していない。Ｒ^１及びＲ^２は、それぞれ独立に単結合、炭素数１～１０のアルカンジイル基又は炭素数１～１０の置換アルカンジイル基である。Ｙ^１及びＹ^２は、それぞれ独立に＊^１－ＮＲ^３－ＣＯ－又は＊^１－ＣＯ－ＮＲ^３－である。Ｒ^３は、水素原子又は１価の有機基である。「＊^１」はＺ^１との結合手を表す。Ｚ^１は、単結合又は２価の有機基である。ｍは０又は１である。ｍが０の場合、Ｒ^１及びＲ^２のうち少なくとも一方は、炭素数１～１０のアルカンジイル基又は置換アルカンジイル基である。「＊」は結合手であることを表す。）

（式（２）中、Ａ^１及びＡ^２は、それぞれ独立に２価の芳香環基である。Ｂ^１は、－ＮＲ^４－又は２価の芳香族複素環基である。Ｂ^１が２価の芳香族複素環基である場合、Ｒ^５及びＲ^６は、それぞれ独立に水素原子又は１価の有機基である。Ｂ^１が－ＮＲ^４－である場合、Ｒ^４、Ｒ^５及びＲ^６は、以下の（ｉ）又は（ｉｉ）である。
（ｉ）Ｒ^４は、水素原子又は１価の有機基である。Ｒ^５及びＲ^６は、それぞれ独立に水素原子若しくは１価の有機基であるか、又はＲ^５とＲ^６とが互いに合わせられてＡ^１、－ＮＲ^４－及びＡ^２と共に構成される環構造を表す。
（ｉｉ）Ｒ^４及びＲ^５は、それぞれ独立に水素原子若しくは１価の有機基であるか、又はＲ^４とＲ^５とが互いに合わせられてＡ^１及び窒素原子と共に構成される環構造を表す。Ｒ^６は、水素原子又は１価の有機基である。
「＊」は結合手であることを表す。） <1> A polymer [A] having the following structural unit (U1) and no following structural unit (U2), and a polymer [B] having the following structural unit (U2) and the following structural unit (U3). , A liquid crystal alignment agent.
Structural unit (U1): Structural unit derived from a diamine having a partial structure represented by the following formula (1) Structural unit (U2): Structural unit derived from a diamine having a partial structure represented by the following formula (2) Structural unit (U3): Structural unit derived from diamine having the following partial structure Y Partial structure Y: Structure represented by-(CH ₂ ) _n- (where n is an integer of 1 to 20),-(CH ₂ ) ) In the structure represented by _{n + 1-} , any methylene group is -O-, -S-, -COO-, -NR ^7- , -NR ⁷ -CO-, -NR ⁷ -COO-, -NR ⁷ -CO. -NR ⁸ -or a structure substituted with a nitrogen-containing non-aromatic heterocyclic group (however, R ⁷ and R ⁸ are independently hydrogen atoms or monovalent organic groups, respectively. When n is 2 or more. , -O-, -S-, -COO-, -NR ^{7-, -NR 7 -CO-, -NR 7 -COO-, -NR 7 -CO - NR 8} -and nitrogen-containing non-aromatic heterocyclic group Are not adjacent to each other.), -O-, -S-, -COO-, -NR ⁷ -CO-, -NR ⁷ -COO-, or -NR ⁷ -CO-NR ^8-

(In the formula (1), X ¹ and X ² are each independently divalent aromatic ring group. However, the aromatic ring of X ¹ is bonded to the bond position of R ¹ and "*". The substituent is not bonded to a position different from the bond position of the group, and the aromatic ring of X ² is replaced with a position different from the bond position of R ² and the bond position of the group bonded to "*". No groups are attached. R ¹ and R ² are independently single-bonded alkandyl groups having 1 to 10 carbon atoms or substituted alkandyl groups having 1 to 10 carbon atoms, respectively. Y ¹ and Y ² are single bonds. Each is independently * ¹ -NR ³ -CO- or * ¹ -CO-NR ^3- . R ³ is a hydrogen atom or a monovalent organic group. "* ¹ " is a bond with Z ¹ . Represented. Z ¹ is a single-bonded or divalent organic group. M is 0 or 1. When m is 0, at least one of R ¹ and R ² is an arcandyl having 1 to 10 carbon atoms. It is a group or a substituted alcoholandiyl group. "*" Indicates that it is a bond.)

(In the formula (2), A ¹ and A ² are independently divalent aromatic ring groups. B ¹ is a -NR ^4- or a divalent aromatic heterocyclic group. B ¹ is 2. When it is a valent aromatic heterocyclic group, R ⁵ and R ⁶ are independently hydrogen atoms or monovalent organic groups. When B ¹ is -NR ^4- , R ⁴ , R ⁵ and R. Reference numeral ⁶ is the following (i) or (ii).
(I) ^R4 is a hydrogen atom or a monovalent organic group. R ⁵ and R ⁶ are independent hydrogen atoms or monovalent organic groups, respectively, or a ring structure in which R ⁵ and R ⁶ are combined with A ¹ , -NR ^4- , and A ² respectively. Represents.
(Ii) R ⁴ and R ⁵ are independent hydrogen atoms or monovalent organic groups, respectively, or represent a ring structure in which R ⁴ and R ⁵ are combined with A ¹ and a nitrogen atom. .. R ⁶ is a hydrogen atom or a monovalent organic group.
"*" Indicates that it is a bond. )

<2> A liquid crystal alignment film formed by the liquid crystal alignment agent of <1> above.
<3> A liquid crystal element provided with the liquid crystal alignment film of <2> above.

According to the liquid crystal alignment agent of the present invention, it is possible to obtain a liquid crystal alignment film which is less likely to generate an afterimage, has excellent coatability, and has high mechanical strength. In particular, according to the liquid crystal alignment agent of the present invention, it is possible to obtain a liquid crystal alignment film capable of achieving both AC afterimage characteristics and DC afterimage characteristics.

The liquid crystal alignment agent of the present disclosure contains a polymer [A] and a polymer [B] which is a polymer different from the polymer [A]. Hereinafter, each component contained in the liquid crystal alignment agent of the present disclosure, and other components optionally blended will be described.

In addition, in this specification, a "hydrocarbon group" means a chain hydrocarbon group, an alicyclic hydrocarbon group and an aromatic hydrocarbon group. The "chain hydrocarbon group" means a linear hydrocarbon group and a branched hydrocarbon group which do not contain a cyclic structure in the main chain and are composed only of a chain structure. However, it may be saturated or unsaturated. The "alicyclic hydrocarbon group" means a hydrocarbon group containing only the alicyclic hydrocarbon structure as the ring structure and not containing the aromatic ring structure. However, it does not have to be composed only of the alicyclic hydrocarbon structure, and some of them have a chain structure. The "aromatic hydrocarbon group" means a hydrocarbon group containing an aromatic ring structure as a ring structure. However, it does not have to be composed only of an aromatic ring structure, and may include a chain structure or an alicyclic hydrocarbon structure as a part thereof. The "structural unit" is a unit that mainly constitutes the main chain structure and includes at least two or more units in the main chain structure. Unless otherwise specified, each component and each compound may be used alone or in combination of two or more.

（式（１）中、Ｘ^１及びＸ^２は、それぞれ独立に２価の芳香環基である。ただし、Ｘ^１が有する芳香環には、Ｒ^１の結合位置、及び「＊」に結合する基の結合位置とは異なる位置に置換基が結合しておらず、Ｘ^２が有する芳香環には、Ｒ^２の結合位置、及び「＊」に結合する基の結合位置とは異なる位置に置換基が結合していない。Ｒ^１及びＲ^２は、それぞれ独立に単結合、炭素数１～１０のアルカンジイル基又は炭素数１～１０の置換アルカンジイル基である。Ｙ^１及びＹ^２は、それぞれ独立に、＊^１－ＮＲ^３－ＣＯ－又は＊^１－ＣＯ－ＮＲ^３－である。Ｒ^３は、水素原子又は１価の有機基である。「＊^１」はＺ^１との結合手を表す。Ｚ^１は、単結合又は２価の有機基である。ｍは０又は１である。Ｒ^１及びＲ^２のうち少なくとも一方は、炭素数１～１０のアルカンジイル基又は置換アルカンジイル基である。「＊」は結合手であることを表す。） <Polymer [A]>
The polymer [A] is a polymer having a structural unit (U1) derived from a diamine having a partial structure represented by the following formula (1) (hereinafter, also referred to as “specific diamine (A)”).

(In the formula (1), X ¹ and X ² are each independently divalent aromatic ring group. However, the aromatic ring of X ¹ is bonded to the bond position of R ¹ and "*". The substituent is not bonded to a position different from the bond position of the group, and the aromatic ring of X ² is replaced with a position different from the bond position of R ² and the bond position of the group bonded to "*". No groups are attached. R ¹ and R ² are independently single-bonded alkandyl groups having 1 to 10 carbon atoms or substituted alkandyl groups having 1 to 10 carbon atoms, respectively. Y ¹ and Y ² are single bonds. Independently, they are * ¹ -NR ³ -CO- or * ¹ -CO-NR ^3- . R ³ is a hydrogen atom or a monovalent organic group. "* ¹ " is a bond with Z ¹ . Z ¹ is a single-bonded or divalent organic group. M is 0 or 1. At least one of R ¹ and R ² is an alcandiyl group or substituted alcandiyl having 1 to 10 carbon atoms. It is a group. "*" Indicates that it is a bond.)

-Structural unit (U1)
The structural unit (U1) is a structural unit derived from a diamine containing two aromatic rings and at least one amide bond (-NR ³ -CO-). In the above formula (1), the divalent aromatic ring group of X ¹ and X ² is preferably an aromatic hydrocarbon group. Specific examples of X ¹ and X ² include a group formed by removing any two hydrogen atoms bonded to carbon atoms constituting a ring of an aromatic hydrocarbon ring such as a benzene ring, a naphthalene ring and an anthracene ring. Be done.

The aromatic rings of X ¹ and X ² do not have a substituent. That is, no substituent is bonded to the aromatic ring of X ¹ at a position different from the bond position of R ¹ and the bond position of the group to be bonded to the bond represented by "*". Similarly, no substituent is bonded to the aromatic ring of X ² at a position different from the bond position with R ² and the bond position of the group to be bonded to the bond represented by “*”. ..

The phenylene group is preferable as the ^divalent aromatic ring group of X1 and X2, and the 1,4 ^- phenylene group is preferable from the viewpoint of increasing the density of the liquid crystal alignment film, reducing the afterimage and increasing the mechanical strength of the film. Especially preferable.

When R ¹ and R ² are alkanediyl groups having 1 to 10 carbon atoms, R ¹ and R ² include a methylene group, an ethylene group, a 1,3-propanediyl group, a 1,4-butandyl group, and 1, Linear alkanediyl groups such as 5-pentanediyl group; branched alkanediyl groups such as 1,2-propanediyl group, 1,2-butanjiyl group, 2-methyl-1,3-propanediyl group and the like can be mentioned. When R ¹ and R ² are substituted alkanediyl groups having 1 to 10 carbon atoms, the substituents include a halogen atom, a hydroxyl group, an amino group, a cyano group, an alkoxy group, a protected hydroxyl group, a protected amino group and the like. Can be mentioned.

At least one of R ¹ and R ² may be an alkanediyl group having 1 to 10 carbon atoms or a substituted alkanediyl group having 1 to 10 carbon atoms in that the voltage holding characteristics and reliability of the liquid crystal element can be improved. It is preferable that both R ¹ and R ² are an alkanediyl group having 1 to 10 carbon atoms or a substituted alkanediyl group having 1 to 10 carbon atoms. The carbon number of R ¹ and R ² is preferably 1 to 8 and more preferably 2 to 8 in terms of exhibiting good voltage holding characteristics and liquid crystal orientation. R ¹ and R ² are preferably linear in that the liquid crystal orientation can be increased and the effect of reducing afterimages is high.

Y ¹ and Y ² are amide bonds (* ¹ -NR ³ -CO- or * ¹ -CO-NR ^3- ). The monovalent organic group of R ³ is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms or a group (protective group) that produces a hydrogen atom by desorption. When R ³ is a monovalent hydrocarbon group, the monovalent hydrocarbon group is preferably an alkyl group having 1 to 3 carbon atoms or a phenyl group, and more preferably an alkyl group having 1 to 3 carbon atoms.

When R ³ is a protecting group, the protecting group is preferably a monovalent group that is desorbed by heat, for example, a carbamate-based protecting group, an amide-based protecting group, an imide-based protecting group, and a sulfonamide-based protecting group. The group etc. can be mentioned. Of these, a carbamate-based protecting group is preferable because it is highly heat-removable, and specific examples thereof include a tert-butoxycarbonyl group, a benzyloxycarbonyl group, and 1,1-dimethyl-2-haloethyloxycarbonyl. Examples thereof include a group, an allyloxycarbonyl group, a 2- (trimethylsilyl) ethoxycarbonyl group, a 9-fluorenylmethyloxycarbonyl group, an allyloxycarbonyl group and the like. Of these, the tert-butoxycarbonyl group (Boc group) is particularly preferable because it is excellent in desorption by heat and the residual amount in the film of the deprotected portion can be reduced.

R ³ is preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a protecting group, and particularly preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a tert-butoxycarbonyl group.

Z ¹ is a single bond or divalent organic group. Z ¹ is preferably a divalent organic group in that the voltage holding characteristics and the liquid crystal orientation of the liquid crystal element can be improved.

When Z ¹ is a divalent organic group, the divalent organic group includes a divalent hydrocarbon group having 1 to 20 carbon atoms, and -O-,-between carbon-carbon bonds of the hydrocarbon group. Examples thereof include a divalent group having S- or -NR ^3- (where R ³ is synonymous with R ³ in Y ¹ and Y ² ). In addition, Z ¹ is bonded with a hydrocarbon group to the amide bond of Y ¹ and Y ² .

Among these, the divalent organic group of Z ¹ is a divalent chain hydrocarbon group having 1 to 20 carbon atoms and 2 having 4 to 20 carbon atoms in that the solubility of the polymer [A] can be increased. It is preferably a valent alicyclic hydrocarbon group or a divalent group having -O-, -S- or -NR ^3-- between carbon-carbon bonds of a chain hydrocarbon group, preferably having 1 to 1 to carbon atoms. A 20-alcandiyl group or a cycloalkylene group having 4 to 12 carbon atoms is particularly preferable.
The carbon number of Z ¹ is preferably 1 to 12, more preferably 1 to 10.
m is 0 or 1, and 1 is preferable in that the effect of reducing the AC afterimage can be further enhanced.

（式（ＤＡ）中、Ｒ^１、Ｒ^２、Ｙ^１、Ｙ^２、Ｚ^１及びｍは上記式（１）と同義である。） The specific diamine (A) is preferably an aromatic diamine, and above all, it is an aromatic diamine having a structure capable of introducing a partial structure represented by the above formula (1) into the main chain of the polymer [A]. Is preferable. Specifically, the specific diamine (A) is particularly preferably a compound represented by the following formula (DA). The "main chain" refers to the part of the "stem" consisting of the longest chain of atoms in the polymer. It is permissible for this "stem" portion to contain a ring structure. For example, "having a specific structure in the main chain" means that the specific structure constitutes a part of the main chain. The "side chain" means a portion branched from the "stem" of the polymer.

(In the formula (DA), R ¹ , R ² , Y ¹ , Y ² , Z ¹ and m are synonymous with the above formula (1).)

In the above formula (DA), the description of the above formula (1) is applied to the examples and preferable examples of R ¹ , R ² , Y ¹ , Y ² , Z ¹ and m.

（式中、「Ｂｏｃ」は、ｔｅｒｔ－ブトキシカルボニル基を表す。） Specific examples of the specific diamine (A) include compounds represented by the following formulas (DA-1) to (DA-23).

(In the formula, "Boc" represents a tert-butoxycarbonyl group.)

The polymer [A] may be a polymer having a structural unit (U1), but is a polyamic acid in that it can form a highly reliable liquid crystal alignment film having high affinity with liquid crystals and mechanical strength. It is preferably at least one selected from the group consisting of polyamic acid esters and polyimides. When the polymer [A] is at least one selected from the group consisting of polyamic acid, polyamic acid ester and polyimide, the partial structure represented by the above formula (1) is introduced into the main chain of the polymer [A]. can do. Further, by introducing the partial structure represented by the above formula (1) into the main chain of the polymer, the effect of reducing the afterimage and improving the film strength can be further enhanced, which is preferable.

(Polyamic acid)
When the polymer [A] is a polyamic acid, the polyamic acid (hereinafter, also referred to as “polyamic acid [A]”) is, for example, a tetracarboxylic dianhydride and a diamine compound containing a specific diamine (A). It can be obtained by reacting.

-Tetracarboxylic acid dianhydride As the tetracarboxylic acid dianhydride used for the synthesis of polyamic acid [A], for example, aliphatic tetracarboxylic acid dianhydride, alicyclic tetracarboxylic acid dianhydride, aromatic tetracarboxylic Acid dianhydride and the like can be mentioned. Specific examples of these include 1,2,3,4-butanetetracarboxylic acid dianhydride, ethylenediamine tetraacetichydride dianhydride and the like as aliphatic tetracarboxylic acid dianhydride; alicyclic tetracarboxylic acid dianhydride. 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 2,3,5-tricarboxycyclopentyl Dianhydride, 5- (2,5-dioxotetratetra-3-yl) -3a, 4,5,9b-tetrahydronaphtho [1,2-c] furan-1,3-dione, 5- (2) , 5-Dioxotetrahydride-3-yl) -8-methyl-3a, 4,5,9b-tetrahydronaphtho [1,2-c] furan-1,3-dione, 2,4,6,8-tetra Carboxybicyclo [3.3.0] octane-2: 4,6: 8-anhydride, cyclopentanetetracarboxylic acid dianhydride, cyclohexanetetracarboxylic acid dianhydride, etc .; aromatic tetracarboxylic acid dianhydride, etc. As, pyromellitic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic anhydride, ethylene glycol bisanhydrotrimate. , 4,4'-(hexafluoroisopropylidene) diphthalic acid anhydride, 4,4'-carbonyldiphthalic acid anhydride, etc .; Acid dianhydride can be used. As the tetracarboxylic dianhydride, one type can be used alone or in combination of two or more types.

The tetracarboxylic acid dianhydride used for the synthesis of the polyamic acid [A] is highly soluble in a solvent, and is capable of obtaining a liquid crystal alignment film exhibiting good electrical properties and low afterimage properties. It is preferable to contain at least one compound selected from the group consisting of acid dianhydride and alicyclic tetracarboxylic acid dianhydride, and more preferably to contain alicyclic tetracarboxylic acid dianhydride. The ratio of the alicyclic tetracarboxylic dianhydride used is preferably 20 mol% or more, preferably 40 mol% or more, based on the total amount of the tetracarboxylic dianhydride used for the synthesis of the polyamic acid [A]. Is more preferable, and 50 mol% or more is further preferable.

-Diamine compound The diamine compound used for the synthesis of the polyamic acid [A] may be only the specific diamine (A), but together with the specific diamine (A), a diamine different from the specific diamine (A) (hereinafter, "other"). Diamine (A) ") may also be used. Examples of the other diamine (A) include aliphatic diamines, alicyclic diamines, aromatic diamines, diaminoorganosiloxanes and the like. Specific examples of other diamines (A) include, for example, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenylpropane, 4-aminophenyl-. 4-Aminobenzoate, 2,5-diaminobenzoic acid, 3,5-diaminobenzoic acid, 1,5-bis (4-aminophenoxy) pentane, 1,2-bis (4-aminophenoxy) ethane, 1,3 -Bis (4-aminophenoxy) propane, 1,6-bis (4-aminophenoxy) hexane, 4,4'-diaminodiphenyl ether, N, N'-di (5-amino-2-pyridyl) -N, N Examples thereof include'-di (tert-butoxycarbonyl) ethylenediamine, 6,6'-(pentamethylenedioxy) bis (3-aminopyridine), 2,2'-dimethyl-4,4'-diaminobiphenyl and the like.

In the synthesis of the polyamic acid [A], the ratio of the specific diamine (A) is used for the synthesis of the polyamic acid [A] from the viewpoint of sufficiently reducing the afterimage and obtaining a liquid crystal alignment film having high mechanical strength. It is preferably 10 mol% or more, more preferably 15 mol% or more, further preferably 20 mol% or more, still more preferably 30 mol% or more, based on the total amount of the diamine compound. It is more preferably 40 mol% or more, and particularly preferably 60 mol% or more. Further, the ratio of the specific diamine (A) can be set in the range of 100 mol% or less with respect to the total amount of the diamine compound used for the synthesis of the polyamic acid [A].

-Synthesis of polyamic acid The polyamic acid [A] can be obtained by reacting a tetracarboxylic dianhydride and a diamine compound with a molecular weight adjusting agent, if necessary. In the polyamic acid synthesis reaction, the ratio of the tetracarboxylic acid dianhydride to the diamine compound is 0.2 to 2 for the acid anhydride group of the tetracarboxylic acid dianhydride with respect to 1 equivalent of the amino group of the diamine compound. The equivalent ratio is preferable. Examples of the molecular weight adjusting agent include acid monoanhydrides such as maleic anhydride, phthalic anhydride and itaconic anhydride, monoamine compounds such as aniline, cyclohexylamine and n-butylamine, and monoisocyanate compounds such as phenylisocyanate and naphthylisocyanate. Can be mentioned. The proportion of the molecular weight adjusting agent used is preferably 20 parts by mass or less with respect to 100 parts by mass in total of the tetracarboxylic dianhydride and the diamine compound used.

The polyamic acid synthesis reaction is preferably carried out in an organic solvent. The reaction temperature at this time is preferably −20 ° C. to 150 ° C., and the reaction time is preferably 0.1 to 24 hours. Examples of the organic solvent used in the reaction include an aprotonic polar solvent, a phenol solvent, an alcohol solvent, a ketone solvent, an ester solvent, an ether solvent, a halogenated hydrocarbon, and a hydrocarbon. Specific examples of these include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, tetramethylurea, hexamethylphosphortriamide, m-cresol, and the like. One or more selected from the group consisting of xylenol and halogenated phenol is used as a reaction solvent, or a mixture of one or more of these with another organic solvent (for example, butyl cellosolve, diethylene glycol diethyl ether, etc.) is used. Is preferable. The amount (a) of the organic solvent used shall be such that the total amount (b) of the tetracarboxylic dianhydride and the diamine is 0.1 to 50% by mass with respect to the total amount (a + b) of the reaction solution. Is preferable.

As described above, a polymer solution obtained by dissolving the polyamic acid [A] is obtained. This polymer solution may be used as it is for the preparation of the liquid crystal alignment agent, or the polyamic acid [A] contained in the polymer solution may be isolated and then used for the preparation of the liquid crystal alignment agent.

(Polyamic acid ester)
When the polymer [A] is a polyamic acid ester, the polyamic acid ester is, for example, a method for reacting [I] polyamic acid [A] with an esterifying agent, [II] tetracarboxylic acid diester, and a specific diamine. It can be obtained by a method of reacting with a diamine compound containing (A), a method of reacting [III] a tetracarboxylic acid diester dihalide with a diamine compound containing a specific diamine (A), or the like. The polyamic acid ester may have only an amic acid ester structure, or may be a partial esterified product in which an amic acid structure and an amic acid ester structure coexist. The reaction solution obtained by dissolving the polyamic acid ester may be used as it is for the preparation of the liquid crystal alignment agent, or the polyamic acid ester contained in the reaction solution may be isolated and then used for the preparation of the liquid crystal alignment agent.

(Polyimide)
When the polymer [A] is a polyimide, the polyimide can be obtained, for example, by dehydrating and ring-closing the polyamic acid [A] synthesized as described above to imidize it. The polyimide may be a completely imidized product in which all of the amic acid structure possessed by its precursor polyamic acid is dehydrated and ring-closed, and only a part of the amic acid structure is dehydrated and ring-closed to form an amic acid structure and an imide. It may be a partially imidized product in which a ring structure coexists. The imidization ratio of the polyimide is preferably 20 to 99%, more preferably 30 to 90%. The imidization ratio is the ratio of the number of imide ring structures to the total number of amic acid structures and the number of imide ring structures of polyimide expressed as a percentage. Here, a part of the imide ring may be an isoimide ring.

The dehydration ring closure of the polyamic acid is preferably carried out by dissolving the polyamic acid in an organic solvent, adding a dehydrating agent and a dehydration ring closure catalyst to this solution, and heating as necessary. In this method, as the dehydrating agent, an acid anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride can be used. The amount of the dehydrating agent used is preferably 0.01 to 20 mol per 1 mol of the amic acid structure of the polyamic acid. As the dehydration ring closure catalyst, for example, tertiary amines such as pyridine, collagen, lutidine, and triethylamine can be used. The amount of the dehydration ring closure catalyst used is preferably 0.01 to 10 mol with respect to 1 mol of the dehydrating agent used. Examples of the organic solvent used for the dehydration ring closure reaction include organic solvents exemplified as those used for the synthesis of polyamic acid. The reaction temperature of the dehydration ring closure reaction is preferably 0 to 180 ° C. The reaction time is preferably 1.0 to 120 hours. The reaction solution containing the polyimide may be used as it is for the preparation of the liquid crystal alignment agent, or the polyimide may be isolated and then used for the preparation of the liquid crystal alignment agent.

<Polymer [B]>
The polymer [B] is a polymer having a structural unit (U2) and a structural unit (U3). Hereinafter, each structural unit of the polymer [B] will be described in detail.

（式（２）中、Ａ^１及びＡ^２は、それぞれ独立に２価の芳香環基である。Ｂ^１は、－ＮＲ^４－又は２価の芳香族複素環基である。Ｂ^１が２価の芳香族複素環基である場合、Ｒ^５及びＲ^６は、それぞれ独立に水素原子又は１価の有機基である。Ｂ^１が－ＮＲ^４－である場合、Ｒ^４、Ｒ^５及びＲ^６は、以下の（ｉ）又は（ｉｉ）である。
（ｉ）Ｒ^４は、水素原子又は１価の有機基である。Ｒ^５及びＲ^６は、それぞれ独立に水素原子若しくは１価の有機基であるか、又はＲ^５とＲ^６とが互いに合わせられてＡ^１、－ＮＲ^４－及びＡ^２と共に構成される環構造を表す。
（ｉｉ）Ｒ^４及びＲ^５は、それぞれ独立に水素原子若しくは１価の有機基であるか、又はＲ^４とＲ^５とが互いに合わせられてＡ^１及び窒素原子と共に構成される環構造を表す。Ｒ^６は、水素原子又は１価の有機基である。
「＊」は結合手であることを表す。） -Structural unit (U2)
The structural unit (U2) is a structural unit derived from a diamine having a partial structure represented by the following formula (2) (hereinafter, also referred to as “specific diamine (B1)”). The structural unit (U2) imparts a function of relaxing the accumulated charge in the liquid crystal alignment film to the polymer [B]. The above-mentioned polymer [A] does not have a structural unit (U2), and the polymer [B] is different from the polymer [A] in this respect.

(In the formula (2), A ¹ and A ² are independently divalent aromatic ring groups. B ¹ is a -NR ^4- or a divalent aromatic heterocyclic group. B ¹ is 2. When it is a valent aromatic heterocyclic group, R ⁵ and R ⁶ are independently hydrogen atoms or monovalent organic groups. When B ¹ is -NR ^4- , R ⁴ , R ⁵ and R. Reference numeral ⁶ is the following (i) or (ii).
(I) ^R4 is a hydrogen atom or a monovalent organic group. R ⁵ and R ⁶ are independent hydrogen atoms or monovalent organic groups, respectively, or a ring structure in which R ⁵ and R ⁶ are combined with A ¹ , -NR ^4- , and A ² respectively. Represents.
(Ii) R ⁴ and R ⁵ are independent hydrogen atoms or monovalent organic groups, respectively, or represent a ring structure in which R ⁴ and R ⁵ are combined with A ¹ and a nitrogen atom. .. R ⁶ is a hydrogen atom or a monovalent organic group.
"*" Indicates that it is a bond. )

In the present specification, another polymer has a structural unit (hereinafter referred to as "specific unit") possessed by at least one of the plurality of polymers contained in the liquid crystal aligning agent. "No" means that it is permissible for another polymer to have that particular unit as long as it does not impair the effectiveness of the invention. When another polymer does not have a specific unit, the content of the specific unit in another polymer is preferably 1 mol% or less, more preferably 0, with respect to the total structural units of the other polymer. It is 5.5 mol% or less, more preferably 0.1 mol or less.

In the above formula (2), examples of the divalent aromatic ring group of A ¹ and A ² include a divalent aromatic hydrocarbon group and a divalent aromatic heterocyclic group. Examples of the divalent aromatic heterocyclic group include a nitrogen-containing aromatic heterocyclic group, an oxygen-containing aromatic heterocyclic group, a sulfur-containing aromatic heterocyclic group and the like, and a nitrogen-containing aromatic heterocyclic group is preferable. In addition, A ¹ and A ² may have a substituent in the aromatic ring portion. Examples of the substituent include an alkyl group having 1 to 5 carbon atoms, a halogen atom and the like.

As a specific example of A ¹ and A ² , any two hydrogen atoms bonded to the carbon atoms constituting the ring of the benzene ring, the naphthalene ring or the anthracene ring are removed as the divalent aromatic hydrocarbon group. A group; as a divalent nitrogen-containing aromatic heterocyclic group, a group obtained by removing any two hydrogen atoms bonded to carbon atoms constituting a pyridine ring, a pyrimidine ring, a pyridazine ring, or a pyrazine ring; As a divalent oxygen-containing aromatic heterocyclic group, a group formed by removing any two hydrogen atoms bonded to carbon atoms constituting the ring of the furan ring; as a divalent sulfur-containing aromatic heterocyclic group. The groups formed by removing any two hydrogen atoms bonded to the carbon atoms constituting the ring of the thiophene ring can be mentioned respectively. From the viewpoint of increasing the density and high permeability of the liquid crystal alignment film, the divalent aromatic ring group of A ¹ and A ² is preferably a divalent aromatic hydrocarbon group, and more preferably a phenylene group.

B ¹ is a -NR ^4- or a divalent aromatic heterocyclic group. When B ¹ is a divalent aromatic heterocyclic group, examples of the aromatic heterocyclic group include divalent aromatic heterocyclic groups exemplified by A ¹ and A ² . Of these, the divalent aromatic heterocyclic group of B ¹ has a high effect of relaxing the accumulated charge, and any two of them are bonded to the carbon atoms constituting the rings of the pyrrole ring, the furan ring and the thiophene ring. It is preferably a group from which a hydrogen atom has been removed.

When B ¹ is a divalent aromatic heterocyclic group, R ⁵ and R ⁶ are independently hydrogen atoms or monovalent organic groups, respectively. For specific examples and preferable examples of R ⁵ , the above description of R ³ can be incorporated. Examples of the monovalent organic group of R ⁶ include an alkyl group having 1 to 3 carbon atoms, a halogen atom, a cyano group and the like.

When B ¹ is −NR ⁴⁻ , R ⁴ , R ⁵ and R ⁶ satisfy the above (i) or (ii). When R ⁴ , R ⁵ and R ⁶ satisfy the above (i), R ⁴ is a hydrogen atom or a monovalent organic group. For specific examples and preferable examples of R ⁴ , the above description of R ³ can be incorporated. Similarly, the above description of R ³ can be incorporated with respect to specific examples and preferable examples in which R ⁵ and R ⁶ are hydrogen atoms or monovalent organic groups. When R ⁵ and R ⁶ form a ring structure together with A ¹ , -NR ^4- and A ² in which R ⁵ and R ⁶ are combined with each other, the ring structure includes a carbazole structure and 9-methyl. Examples thereof include a carbazole structure and a 9-ethylcarbazole structure.

When R ⁴ , R ⁵ and R ⁶ satisfy the above (ii), the above description of R ³ may be incorporated for specific examples and preferable examples when R ⁴ is a hydrogen atom or a monovalent organic group. can. When R ⁵ and R ⁶ are hydrogen atoms or monovalent organic groups, examples of the monovalent organic groups include alkyl groups having 1 to 3 carbon atoms, halogen atoms, cyano groups and the like.
When R ⁴ and R ⁵ form a ring structure together with A ¹ and a nitrogen atom in which R ⁴ and R ⁵ are combined with each other, examples of the ring structure include an indoline structure and an isoindoline structure.

（式（２－１）～式（２－１０）中、Ｒ^４及びＲ^３３は、それぞれ独立に水素原子又は１価の有機基である。「＊」は結合手であることを表す。） As a preferable specific example of the partial structure represented by the above formula (2), when B ¹ is −NR ⁴ −, it is represented by each of the following formulas (2-1) to (2-7). Substructures and the like; As a case where B ¹ is a divalent aromatic heterocyclic group, partial structures and the like represented by the following formulas (2-8) to (2-10) can be mentioned. ..

(In formulas (2-1) to (2-10), R ⁴ and R ³³ are independently hydrogen atoms or monovalent organic groups. “*” Indicates a bond.)

The specific diamine (B1) may have only one partial structure represented by the above formula (2), or may have two or more. From the viewpoint of ensuring the solubility of the polymer [B], the number is preferably one or two. The specific diamine (B1) is preferably an aromatic diamine, and above all, it is an aromatic diamine having a structure capable of introducing a partial structure represented by the above formula (2) into the main chain of the polymer [B]. Is preferable. Specific examples of the specific diamine (B1) include compounds represented by the following formulas (DB-1) to (DB-21). The specific diamine (B1) does not have the partial structure Y of the structural unit (U3).

-Structural unit (U3)
The structural unit (U3) is a structural unit derived from a diamine having the following partial structure Y (hereinafter, also referred to as “specific diamine (B2)”). The specific diamine (B2) is a compound having no partial structure represented by the above formula (2), and is different from the specific diamine (B1). Since the polymer [B2] has a structural unit (U3) together with a structural unit (U2), the solubility of the polymer [B2] can be enhanced and low afterimage characteristics (particularly, reduction of AC afterimage) are exhibited. A liquid crystal alignment film can be obtained.
Partial structure Y:-(CH ₂ ) _n- (where n is an integer of 1 to 20),-(CH ₂ ) _{n + 1-} , any methylene group is -O-, -S-, -COO-, -NR ^{7-, -NR 7 -CO-, -NR 7 -COO-, -NR 7 -CO - NR 8-} , or replaced with nitrogen-containing non-aromatic heterocyclic group (However, R ⁷ and R ⁸ are independently hydrogen atoms or monovalent organic groups. When n is 2 or more, -O-, -S-, -COO-, -NR ^7- , -NR ^{7-CO-, -NR 7-COO-, -NR 7 -CO -} NR ^8- and nitrogen-containing aromatic heterocyclic groups are not adjacent to each other.), -O-, -S-, -COO -, -NR ⁷ -CO-, -NR ⁷ -COO-, or -NR ⁷ -CO-NR ^8-

In the partial structure Y, n is 1 from the viewpoint of improving the solubility of the polymer [B], improving the low afterimage characteristics (reducing AC afterimage and DC afterimage), and the mechanical strength of the liquid crystal alignment film. ~ 14 is preferable, and 1 to 12 is more preferable. When the partial structure Y is a structure in which an arbitrary methylene group is replaced with -O- or the like in the structure represented by-(CH ₂ ) _{n + 1-} (hereinafter, also referred to as "heteroatom-containing structure"), n is It is preferably 2 or more, and more preferably 2 to 14.
In the partial structure Y, the nitrogen-containing non-aromatic heterocyclic group includes a piperidine-1,4-diyl group, a piperazine-1,4-diyl group, and a 2-oxo-4-imidazolidinone-1,3-diyl group. And so on.
For the examples and preferred examples of R ⁷ and R ⁸ , the above description of R ³ can be incorporated.
Of these, the partial structure Y is preferably a structure represented by-(CH ₂ ) _n- , a heteroatom-containing structure, or -O-, and a structure represented by-(CH ₂ ) _n- , or a hetero. Atom-containing structures are more preferred.

（式（ＤＢ２）中、Ｙ^３は、－（ＣＨ_２）_ｎ－で表される構造、－（ＣＨ_２）_ｎ＋１－で表される構造において任意のメチレン基が－Ｏ－、－Ｓ－、－ＣＯＯ－、－ＮＲ^７－、－ＮＲ^７－ＣＯ－、－ＮＲ^７－ＣＯＯ－、－ＮＲ^７－ＣＯ－ＮＲ^８－、若しくは窒素含有非芳香族複素環基に置き換えられてなる構造（ヘテロ原子含有構造）、－Ｏ－、－Ｓ－、－ＣＯＯ－、－ＮＲ^７－ＣＯ－、－ＮＲ^７－ＣＯＯ－、又は－ＮＲ^７－ＣＯ－ＮＲ^８－である。Ａ^３及びＡ^４は、それぞれ独立して、単結合、置換若しくは無置換のシクロへキシレン基、又は置換若しくは無置換のフェニレン基である。ｎ、Ｒ^７及びＲ^８の定義は上記と同義である。ｎが２以上の場合、上記ヘテロ原子含有構造において、－Ｏ－、－Ｓ－、－ＣＯＯ－、－ＮＲ^７－、－ＮＲ^７－ＣＯ－、－ＮＲ^７－ＣＯＯ－、－ＮＲ^７－ＣＯ－ＮＲ^８－及び窒素含有非芳香族複素環基は互いに隣接していない。） The specific diamine (B2) is not particularly limited as long as it is a diamine having a partial structure Y, and examples thereof include aliphatic diamines, alicyclic diamines, aromatic diamines, and diaminoorganosiloxanes. The specific diamine (B2) preferably has a structure in which the partial structure Y can be introduced into the main chain of the polymer [B], and specifically, is a compound represented by the following formula (DB2). Is preferable.

(In the formula (DB2), Y3 has a structure represented by-(CH ² ) n-, and any methylene group in the structure represented _{by-(CH 2 ) n + 1-} , which is -O-, -S-, -COO-, -NR ^{7-, -NR 7 -CO-, -NR 7 -COO-, -NR 7 -CO - NR 8-} , or a structure (hetero) replaced with a nitrogen-containing non-aromatic heterocyclic group. Atomic-containing structure), -O-, -S-, -COO-, -NR ⁷ -CO-, -NR ⁷ -COO-, or -NR ⁷ -CO-NR ^8- . A ³ and A ⁴ are. , Independently, a single ^- bonded, substituted or unsubstituted cyclohexylene group, or a substituted or unsubstituted phenylene group. The definitions of n, ^R7 and R8 are synonymous with the above. In the above heteroatom-containing structure, -O-, -S-, -COO-, -NR ^{7-, -NR 7 -CO-, -NR 7 -COO-, -NR 7 -CO - NR 8-} And nitrogen-containing non-aromatic heterocyclic groups are not adjacent to each other.)

Specific examples of the specific diamine (B2) include metaxylylene diamine, pentamethylenediamine, hexamethylenediamine and the like as aliphatic diamines; 4,4'-methylenebis (cyclohexylamine) and the like as alicyclic diamines; As aromatic diamines, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenylpropane, 4-aminophenyl-4-aminobenzoate, 4,4'-diaminobenzanilide, 1,3-bis (4-aminophenyl) urea, 1,3-bis (4-aminophenethyl) urea, 1,3-bis (4-aminobenzyl) urea, 1,5-bis (4-aminophenoxy) Pentan, 1,2-bis (4-aminophenoxy) ethane, 1,3-bis (4-aminophenoxy) propane, 1,6-bis (4-aminophenoxy) hexane, bis [2- (4-aminophenyl) ) Ethyl] hexane diic acid, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 4,4'-[4. 4'-Propane-1,3-diylbis (piperidin-1,4-diyl)] dianiline, diethylene glycol bis (4-aminophenyl) ether, 1,4-bis (4-aminophenoxy) benzene, the above formula (DA-). 1) -A compound represented by each of the formulas (DA-15) and (DA-17) to (DA-20), and each of the following formulas (DC-1) to (DC-7). Examples of the diaminoorganosiloxane include 1,3-bis (3-aminopropyl) -tetramethyldisiloxane and the like.

Among these, the specific diamine (B2) includes 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenyl ether, 1,2-bis (4-aminophenoxy) ethane, and the like. 4,4'-[4,4'-Propane-1,3-diylbis (piperidine-1,4-diyl)] dianiline, bis [2- (4-aminophenyl) ethyl] hexanediic acid, diethylene glycol bis (4) -It is preferable to use at least one selected from the group consisting of (aminophenyl) ether, hexamethylenediamine, hexamethylenediamine, and the compound represented by the above formula (DC-5).

The polymer [B] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester and polyimide in that it has a high affinity with the polymer [A]. In particular, since the polymer [B] has a partial structure represented by the above formula (2) and a partial structure Y in the main chain, the solubility of the polymer [B] is enhanced and the accumulated charge is rapidly increased. It is preferable in that it can be alleviated and the AC afterimage can be sufficiently reduced.

When the polymer [B] is a polyamic acid, the polyamic acid (hereinafter, also referred to as “polyamic acid [B”) is a diamine containing a tetracarboxylic acid dianhydride and a specific diamine (B1) and a specific diamine (B2). It can be obtained by reacting with a compound. The polymer [B], polyamic acid [B], polyamic acid ester, and polyimide can also be produced in the same manner as in the polymer [A].

As the tetracarboxylic dianhydride used for the synthesis of the polymer [B], examples of the tetracarboxylic dianhydride used for the synthesis of the polymer [A] and explanations of preferable examples can be incorporated. That is, the tetracarboxylic acid dianhydride used for the synthesis of the polyamic acid [B] contains at least one compound selected from the group consisting of the aliphatic tetracarboxylic acid dianhydride and the alicyclic tetracarboxylic acid dianhydride. It is preferable, and it is more preferable to contain an alicyclic tetracarboxylic acid dianhydride. The ratio of the alicyclic tetracarboxylic dianhydride used is preferably 20 mol% or more, preferably 40 mol% or more, based on the total amount of the tetracarboxylic dianhydride used for the synthesis of the polyamic acid [B]. Is more preferable, and 50 mol% or more is further preferable.

Further, in the synthesis of the polyamic acid [B], which is the polymer [B], the polyamic acid ester, and the polyimide, the diamine compound is a compound different from the specific diamine (B1) and the specific diamine (B2) (hereinafter, “other diamines (hereinafter,“ other diamines ”). B) ”) may be further used. Other diamines (B) include p-phenylenediamine, 3,5-diaminobenzoic acid, 2,5-diaminobenzoic acid, 4,4-diamino-2,2'-dimethylbiphenyl, 3,5-diamino-. Examples thereof include N, N-bis (pyridine-3-ylmethyl) benzamide and the like. In the synthesis, the amount of the other diamine (B) used is preferably 20 mol% or less, preferably 10 mol% or less, based on the total amount of the diamine compound used in the synthesis of the polymer [B]. More preferred.

The amount of the specific diamine (B1) used in the synthesis of the polymer [B] is used for the synthesis of the polymer [B] in that the residual charge can be quickly relaxed and the DC afterimage can be sufficiently reduced. It is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 15 mol% or more, based on the total amount of the diamine compound. Further, from the viewpoint of suppressing the AC afterimage and ensuring the solubility of the polymer [B], the amount of the specific diamine (B1) used is relative to the total amount of the diamine compound used for the synthesis of the polymer [B]. It is preferably 95 mol% or less, more preferably 80 mol% or less, and further preferably 70 mol% or less.

The amount of the specific diamine (B2) used is 5 mol% or more based on the total amount of the diamine compound used for the synthesis of the polymer [B] in that the solubility of the polymer [B] can be increased. It is preferably present, more preferably 10 mol% or more, still more preferably 15 mol% or more. Further, from the viewpoint of sufficiently reducing the DC afterimage, the amount of the specific diamine (B2) used is preferably 90 mol% or less with respect to the total amount of the diamine compound used for the synthesis of the polymer [B]. , 80 mol% or less, more preferably 70 mol% or less.

As for various conditions and the like in the method for synthesizing each polymer such as polyamic acid [B], the above-mentioned description of the polymer [A] can be incorporated.

The solution viscosities of the polymer [A] and the polymer [B] used for preparing the liquid crystal aligning agent are preferably those having a solution viscosity of 10 to 800 mPa · s when a solution having a concentration of 10% by mass is used. , It is more preferable that the solution has a viscosity of 15 to 500 mPa · s. The solution viscosity (mPa · s) is the E-type rotational viscosity for a polymer solution having a concentration of 10% by mass prepared using a good solvent for the polymer (for example, γ-butyrolactone, N-methyl-2-pyrrolidone, etc.). It is a value measured at 25 ° C. using a meter.

For each of the polymer [A] and the polymer [B], the polystyrene-equivalent weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) is preferably 1,000 to 500,000, and more. It is preferably 2,000 to 300,000. The molecular weight distribution (Mw / Mn) represented by the ratio of Mw to the polystyrene-equivalent number average molecular weight (Mn) measured by GPC is preferably 7 or less, more preferably 5 or less.

In the liquid crystal alignment agent, the content of the polymer [A] is preferably 1% by mass or more with respect to the total amount of the polymer components contained in the liquid crystal alignment agent from the viewpoint of sufficiently reducing the AC afterimage. It is more preferably 2% by mass or more, further preferably 5% by mass or more, and further preferably 10% by mass or more. Further, the content of the polymer [A] is preferably 90% by mass or less with respect to the total amount of the polymer components contained in the liquid crystal alignment agent from the viewpoint of reducing the DC afterimage by relaxing the residual charge. It is more preferably 80% by mass or less, and further preferably 70% by mass or less.

The content of the polymer [B] is preferably 10% by mass or more, more preferably 20% by mass or more, and more preferably 30% by mass or more, based on the total amount of the polymer components contained in the liquid crystal alignment agent. Is more preferable. The content of the polymer [B] is preferably 99% by mass or less, more preferably 98% by mass or less, and 95% by mass, based on the total amount of the polymer components contained in the liquid crystal alignment agent. It is more preferably% or less, and even more preferably 90% by mass or less.

<Other ingredients>
In addition to the polymer [A] and the polymer [B], the liquid crystal alignment agent contains components different from the polymer [A] and the polymer [B] (hereinafter, also referred to as “other components”), if necessary. It may be contained.

(Other polymers)
The liquid crystal alignment agent of the present disclosure may contain a polymer different from the polymer [A] and the polymer [B] (hereinafter, also referred to as “other polymer”) as a polymer component. The main skeleton of other polymers is not particularly limited. Examples of other polymers include polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, polyester, polyenamine, polyurea, polyamide, polyamideimide, polybenzoxazole precursor, polybenzoxazole, cellulose derivative, polyacetal, and (meth). ) Acrylic polymer, styrene polymer, maleimide polymer, or styrene-maleimide polymer can be mentioned. From the viewpoint of having high affinity with the liquid crystal when used in combination with the polymer [A] and the polymer [B] and increasing the reliability of the liquid crystal element, other polymers are polyamic acid, polyamic acid ester and polyimide. It is preferably at least one selected from the group consisting of.

When the other polymer is contained in the liquid crystal alignment agent, the content of the other polymer in the liquid crystal alignment agent is the total amount of the polymer [A], the polymer [B] and the other polymer. , 30% by mass or less, more preferably 20% by mass or less, further preferably 10% by mass or less, still more preferably 5% by mass or less.

(solvent)
The liquid crystal alignment agent of the present disclosure is a liquid composition in which the polymer [A], the polymer [B] and other components used as necessary are preferably dispersed or dissolved in a suitable solvent. Prepared.

As the solvent, an organic solvent is preferably used. Specific examples thereof include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,2-dimethyl-2-imidazolidinone, 1,3-dimethyl-2-imidazolidinone, phenol, and γ-. Butylolactone, γ-butyrolactam, N, N-dimethylformamide, N, N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone, diacetone alcohol, 1-hexanol, 2-hexanol, propane-1,2- Dire, 3-methoxy-1-butanol, ethylene glycol monomethyl ether, methyl lactate, ethyl lactate, butyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl acetoacetate, ethyl acetoacetate, ethyl propionate, methyl methoxypropione- Ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i-propyl ether, ethylene glycol-n-butyl ether (butyl cellosolve), ethylene glycol dimethyl ether, ethylene. Glycolethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diisobutylketone, isoamylpropionate, isoamylisobutyrate, diisopentyl ether, Ethylene carbonate, propylene carbonate, propylene glycol monomethyl ether (PGME), diethylene glycol diethyl ether acetate, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol diacetate, cyclopentanone, cyclohexanone and the like can be mentioned.

In addition to the above, examples of other components contained in the liquid crystal alignment agent include antioxidants, metal chelate compounds, curing accelerators, surfactants, fillers, dispersants, photosensitizers and the like. The blending ratio of the other components can be appropriately selected according to each compound as long as the effects of the present disclosure are not impaired.

The solid content concentration in the liquid crystal alignment agent (the ratio of the total mass of the components other than the solvent of the liquid crystal alignment agent to the total mass of the liquid crystal alignment agent) is appropriately selected in consideration of viscosity, volatility, etc., but is preferable. It is in the range of 1 to 10% by mass. When the solid content concentration is 1% by mass or more, the film thickness of the coating film can be sufficiently secured, and a liquid crystal alignment film showing good liquid crystal alignment can be easily obtained. On the other hand, when the solid content concentration is 10% by mass or less, the coating film can be made to have an appropriate thickness, it is easy to obtain a liquid crystal alignment film showing good liquid crystal alignment, and the viscosity of the liquid crystal alignment agent is appropriate. There is a tendency that the coatability can be improved.

≪Liquid crystal alignment film and liquid crystal element≫
The liquid crystal alignment film of the present disclosure is produced by the liquid crystal alignment agent prepared as described above. Further, the liquid crystal element of the present disclosure includes a liquid crystal alignment film formed by using the liquid crystal alignment agent described above. The drive method of the liquid crystal in the liquid crystal element is not particularly limited, and for example, TN type, STN type, VA type (including VA-MVA type, VA-PVA type, etc.), IPS type, FFS type, OCB (Optically Compensated Bend). It can be applied to various modes such as type and PSA type (Polymer Sustained Alignment). The liquid crystal element can be manufactured, for example, by a method including the following steps 1 to 3. In step 1, the substrate used differs depending on the desired operation mode. Step 2 and step 3 are common to each operation mode.

<Step 1: Formation of coating film>
First, a liquid crystal alignment agent is applied on the substrate, and preferably the coated surface is heated to form a coating film on the substrate. As the substrate, for example, glass such as float glass and soda glass; a transparent substrate made of plastic such as polyethylene terephthalate, polybutylene terephthalate, polyether sulfone, polycarbonate, and poly (lipid ring type olefin) can be used. As the transparent conductive film provided on one surface of the substrate, a NESA film made of tin oxide (SnO ₂ ) (registered trademark of PPG, USA) and an ITO film made of indium oxide-tin oxide (In ₂ O ₃ -SnO ₂ ) are used. And so on. When manufacturing a TN type, STN type or VA type liquid crystal element, two substrates provided with a patterned transparent conductive film are used. On the other hand, in the case of manufacturing an IPS type or FFS type liquid crystal element, a substrate provided with a comb-shaped patterned electrode and a facing substrate not provided with an electrode are used.

The method of applying the liquid crystal alignment agent to the substrate is not particularly limited, and for example, a spin coating method, a printing method (for example, an offset printing method, a flexographic printing method, etc.), an inkjet method, a slit coating method, a bar coater method, and an extension die. It can be performed by a method, a direct gravure coater method, a chamber doctor coater method, an offset gravure coater method, an impregnation coater method, an MB coater method, or the like.

After the liquid crystal alignment agent is applied, preheating is preferably performed for the purpose of preventing the applied liquid crystal alignment agent from dripping. The prebake temperature is preferably 30 to 200 ° C., and the prebake time is preferably 0.25 to 10 minutes. Then, a firing (post-baking) step is carried out for the purpose of completely removing the solvent and, if necessary, thermally imidizing the amic acid structure present in the polymer. The firing temperature (post-baking temperature) at this time is preferably 80 to 280 ° C, more preferably 80 to 250 ° C. The post-bake time is preferably 5 to 200 minutes. The film thickness of the formed film is preferably 0.001 to 1 μm.

<Step 2: Orientation treatment>
When manufacturing a TN type, STN type, IPS type or FFS type liquid crystal element, a treatment (alignment treatment) for imparting a liquid crystal alignment ability to the coating film formed in the above step 1 is performed. As a result, the alignment ability of the liquid crystal molecules is imparted to the coating film to form a liquid crystal alignment film. As the alignment treatment, it is preferable to use a rubbing treatment in which the surface of the coating film formed on the substrate is rubbed with cotton or the like, or a photoalignment treatment in which the coating film is irradiated with light to impart a liquid crystal alignment ability. When manufacturing a vertically oriented liquid crystal element, the coating film formed in step 1 may be used as it is as a liquid crystal alignment film, and the coating film is subjected to an alignment treatment in order to further enhance the liquid crystal alignment ability. You may.

The light irradiation for photo-alignment includes a method of irradiating the coating film after the post-baking process, a method of irradiating the coating film after the pre-baking process and before the post-baking process, and a pre-baking process and a post-baking process. At least one of them can be used by a method of irradiating the coating film while heating the coating film, or the like. As the radiation to irradiate the coating film, for example, ultraviolet rays including light having a wavelength of 150 to 800 nm and visible light can be used. Preferably, it is ultraviolet light containing light having a wavelength of 200 to 400 nm. When the radiation is polarized, it may be linearly polarized or partially polarized. When the radiation to be used is linearly polarized light or partially polarized radiation, the irradiation may be performed from a direction perpendicular to the substrate surface, may be performed from an oblique direction, or may be performed in combination thereof. In the case of unpolarized radiation, the irradiation direction is diagonal.

Examples of the light source used include a low pressure mercury lamp, a high pressure mercury lamp, a deuterium lamp, a metal halide lamp, an argon resonance lamp, a xenon lamp, an excimer laser and the like. The irradiation amount of radiation is preferably 200 to 30,000 J / m ² , and more preferably 500 to 10,000 J / m ² . After irradiation with light to impart orientation ability, the surface of the substrate is washed with, for example, water, an organic solvent (eg, methanol, isopropyl alcohol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, etc.) or a mixture thereof. Or a process of heating the substrate may be performed.

<Step 3: Construction of LCD cell>
A liquid crystal cell is manufactured by preparing two substrates on which a liquid crystal alignment film is formed as described above and arranging the liquid crystal between the two substrates arranged opposite to each other. In order to manufacture a liquid crystal cell, for example, two substrates are arranged facing each other with a gap so that the liquid crystal alignment films face each other, and the peripheral portions of the two substrates are bonded with a sealing agent, and the substrate surface and the sealing agent are bonded to each other. Examples thereof include a method of injecting and filling a liquid crystal display in a cell gap surrounded by, and a method of sealing an injection hole, a method by an ODF method, and the like. As the sealing agent, for example, an epoxy resin containing a curing agent and aluminum oxide spheres as a spacer can be used. As the liquid crystal, either a positive type or a negative type may be used, but a negative type is preferable. Examples of the negative liquid crystal display include "MLC-6608", "MLC-6609", "MLC-6610", and "MLC-7026-100" manufactured by Merck. In particular, when a negative type liquid crystal is used in the IPS type and FFS type liquid crystal elements, it is preferable in that the transmission loss at the upper part of the electrode can be reduced and the contrast can be improved. Examples of the liquid crystal include a nematic liquid crystal and a smectic liquid crystal, and among them, the nematic liquid crystal is preferable.

When manufacturing a liquid crystal display device, a polarizing plate is subsequently attached to the outer surface of the liquid crystal cell to obtain a liquid crystal display element. Examples of the polarizing plate include a polarizing plate in which a polarizing film called "H film" in which polyvinyl alcohol is stretched and oriented and iodine is absorbed is sandwiched between a cellulose acetate protective film, or a polarizing plate made of the H film itself.

The liquid crystal element of the present invention can be effectively applied to various uses. Specifically, for example, various display devices such as watches, portable game machines, word processors, notebook computers, car navigation systems, camcorders, PDAs, digital cameras, mobile phones, smartphones, various monitors, LCD TVs, information displays, etc. , Can be used as a dimmer, a retardation film and the like.

Hereinafter, embodiments will be described in more detail based on the examples, but the present invention is not limitedly interpreted by the following examples.

In the following example, the imidization ratio of polyimide in the polymer solution was measured by the following method. The required amounts of the raw material compounds and polymers used in the following examples were secured by repeating the synthesis on the synthetic scale shown in the following synthesis examples as necessary.
[Imidization rate of polyimide]
The polyimide solution was poured into pure water, the obtained precipitate was sufficiently dried under reduced pressure at room temperature, then dissolved in deuterated dimethyl sulfoxide, and ¹ H-NMR was measured at room temperature using tetramethylsilane as a reference substance. From the obtained ¹ H-NMR spectrum, the imidization rate [%] was determined by the following mathematical formula (1).
Imidization rate [%] = (1- (β1 / (β2 × α))) × 100… (1)
(In formula (1), β1 is the peak area derived from the proton of the NH group appearing near the chemical shift of 10 ppm, β2 is the peak area derived from other protons, and α is the precursor of the polymer (polyamic acid). The ratio of the number of other protons to one proton of the NH group.)

The abbreviations of the monomers used in the examples are as follows.
(Tetracarboxylic dianhydride)
-Compound (c-1) to compound (c-5): A compound represented by each of the following formulas (c-1) to (c-5).

(Diamine compound)
-Compound (DA-1) to compound (DA-14): Compound / compound (DB-1) to compound (DB-20) represented by each of the above formulas (DA-1) to (DA-14). : Compound / compound (d-1) to compound (d-5) represented by each of the above formulas (DB-1) to (DB-20): The following formulas (d-1) to (d-5). Compounds / compounds (b-1) to compounds (b-11) represented by each of): Compounds represented by the following formulas (b-1) to (b-11).

<Synthesis of polymer>
1. 1. Synthesis of polyamic acid [Synthesis example 1]
100 parts of compound (c-2) as a tetracarboxylic dianhydride and 100 parts of compound (DA-1) as a diamine compound were dissolved in N-methyl-2-pyrrolidone (NMP) and reacted at room temperature for 6 hours. This was carried out to obtain a solution containing 15% by mass of polyamic acid (referred to as "polymer (PAA-1)").
[Synthesis Examples 2 to 17, 23 to 46]
The same operation as in Synthesis Example 1 was carried out except that the types and amounts of the tetracarboxylic dianhydride and the diamine compound used were changed as shown in Tables 1 and 2 below, and the polyamic acid (polymer (PAA-2)) was used. A solution containing (PAA-41)) was obtained. In Tables 1 and 2, the blending amount of the tetracarboxylic dianhydride represents the ratio (mol%) to the total amount of the tetracarboxylic dianhydride used for the synthesis of each polymer. The blending amount of the diamine compound represents a ratio (mol%) to the total amount of the diamine compound used for the synthesis of each polymer.

2. 2. Polyimide synthesis [Synthesis example 18]
90 parts of compound (c-1) and 10 parts of compound (c-5) as tetracarboxylic dianhydride and 100 parts of compound (DA-2) as diamine compound were dissolved in NMP and reacted at room temperature for 6 hours. Was carried out to obtain a solution containing 15% by mass of polyamic acid. Next, NMP was added to the obtained polyamic acid solution to prepare a solution having a polyamic acid concentration of 10% by mass, pyridine and acetic anhydride were added, and a dehydration ring closure reaction was carried out at 60 ° C. for 4 hours. After the dehydration ring closure reaction, the solvent in the system is replaced with a new NMP to contain 15% by mass of a polyimide having an imidization rate of about 80% (referred to as "polymer (PI-1)"). Got
[Synthesis Examples 19 to 22]
The same operation as in Synthesis Example 18 was carried out except that the types and amounts of the tetracarboxylic dianhydrides and diamine compounds used were changed as shown in Table 1 below, and the polyimides (polymers (PI-2) to (PI-). A solution containing 5)) was obtained.

[Example 1]
1. 1. Preparation of liquid crystal alignment agent Using the solution of the polymer (PAA-1) obtained in Synthesis Example 1 and the solution of the polymer (PAA-36) obtained in Synthesis Example 41, diluted with NMP and butyl cellosolve (BC). A solution having a solid content concentration of 4.0% by mass and a solvent composition ratio of NMP: BC = 80: 20 (mass ratio) was obtained. A liquid crystal alignment agent (R-1) was prepared by filtering this solution with a filter having a pore size of 0.2 μm.

2. 2. Manufacture of FFS type liquid crystal cell using rubbing method A glass substrate (referred to as the first substrate) in which a flat plate electrode (bottom electrode), an insulating layer and a comb-shaped electrode (top electrode) are laminated on one side in this order, and an electrode. A glass substrate (referred to as a second substrate) not provided with the above was prepared. Next, the liquid crystal alignment agent (R-1) was applied to each of the electrode forming surface of the first substrate and one surface of the second substrate using a spinner, and heated (prebaked) on a hot plate at 110 ° C. for 3 minutes. Then, the inside of the refrigerator was dried (post-baked) for 30 minutes in a nitrogen-substituted oven at 230 ° C. to form a coating film having an average film thickness of 0.08 μm. Next, the surface of the coating film was subjected to a rubbing treatment using a rubbing machine having a roll wrapped with a rayon cloth at a roll rotation speed of 1000 rpm, a stage moving speed of 3 cm / sec, and a fluff pushing length of 0.3 mm. Then, it was ultrasonically washed in ultrapure water for 1 minute and then dried in a 100 ° C. clean oven for 10 minutes to obtain a pair of substrates having a liquid crystal alignment film.
Next, for a pair of substrates having a liquid crystal alignment film, an epoxy resin adhesive containing aluminum oxide spheres having a diameter of 3.5 μm was screen-printed and applied, leaving a liquid crystal injection port on the edge of the surface on which the liquid crystal alignment film was formed. Then, the substrates were overlapped and crimped, and the adhesive was thermoset at 150 ° C. for 1 hour. Next, a negative liquid crystal display (MLC-6608, manufactured by Merck) was filled in the gap between the pair of substrates from the liquid crystal injection port, and then the liquid crystal injection port was sealed with an epoxy adhesive. Further, in order to remove the flow orientation at the time of liquid crystal injection, the liquid crystal cell was manufactured by heating it at 120 ° C. and then slowly cooling it to room temperature. When stacking a pair of substrates, the rubbing method of each substrate was set to be antiparallel.

3. 3. Evaluation of inkjet coatability (evaluation of solubility)
As a substrate to which the liquid crystal alignment agent is applied, a glass substrate with a transparent electrode made of ITO is heated on a hot plate at 200 ° C. for 1 minute, and then UV / ozone cleaning is performed to reduce the contact angle of water on the transparent electrode surface to 10 ° or less. The one immediately after was used. Above 1. The liquid crystal alignment agent (R-1) prepared in 1 was applied onto the transparent electrode surface of the glass substrate with a transparent electrode using an inkjet coating machine (manufactured by Shibaura Mechatronics Co., Ltd.). The coating conditions at this time were 2,500 times / (nozzle / minute) and 2 reciprocations (4 times in total) with a discharge rate of 250 mg / 10 seconds. After the coating, the coating film was allowed to stand for 1 minute and then heated at 80 ° C. to form a coating film having an average film thickness of 0.1 μm. With respect to the obtained coating film, the number of unevenness and repellent was observed with the naked eye under the irradiation of the interference fringe measurement lamp (sodium lamp). When the total number of unevenness and repellent parts is 0, it is regarded as "excellent (◎)", when the total number of unevenness and repellent parts is 1 or more and less than 3, it is "good (○)", and when the total number of unevenness and repellent parts is 0, the total number of unevenness and repellent parts is "good (○)". A case of 3 or more was evaluated as "defective (x)". When the inkjet coatability is good, it can be said that the polymer used for preparing the liquid crystal alignment agent has good solubility. As a result, the inkjet coating property of the liquid crystal alignment agent of this example was "excellent".

4. Evaluation of AC afterimage characteristics 2. The FFS type liquid crystal cell manufactured in the above equation (2) is expressed by the following formula (2) using a device in which a splitter and an analyzer are arranged between a light source and a light amount detector after being driven at an AC voltage of 10 V for 72 hours. The minimum relative transmittance (%) was measured.
Minimum relative transmittance (%) = (β-B0) / (B100-B0) × 100 ... (2)
(In the formula (2), B0 is the amount of light transmitted under the cross Nicol in the blank. B100 is the amount of light transmitted under the paranicol in the blank. β is the amount of light transmitted under the cross Nicol. It is the minimum amount of light transmission with a liquid crystal cell sandwiched between them.)
The black level in the dark state is represented by the minimum relative transmittance of the liquid crystal cell, and in the FFS type liquid crystal cell, it can be said that the smaller the black level in the dark state, the better the contrast characteristic and the better the AC afterimage characteristic. Those with a minimum relative transmittance of less than 0.3% are "excellent (◎)", those with a minimum relative transmittance of 0.3% or more and less than 2.0% are "good (〇)", and those with a minimum relative transmittance of 2.0% or more are "poor". (×) ”. As a result, it was evaluated as "excellent" in this example.

5. Evaluation of electrical characteristics 2. After allowing the FFS type liquid crystal cell manufactured in 1V to stand in an oven at 60 ° C., the voltage holding ratio (VHR) was measured under the conditions of 1V and 1670 msec using a VHR measuring device "VHR-1" manufactured by Toyo Technica. The evaluation criteria are "excellent (◎)" when the VHR is 80% or more, "good (○)" when the VHR is less than 80% and 70% or more, and "possible (△)" when the VHR is less than 70% and 60% or more. , If it is less than 60%, it is regarded as "impossible (x)". As a result, the evaluation of VHR of this example was "excellent".

6. Evaluation of reliability after light irradiation Above 2. The reliability of the FFS type liquid crystal cell manufactured in 1 was evaluated. The evaluation was performed as follows. First, a voltage of 1 V was applied to the liquid crystal cell for 60 microseconds, and then the voltage holding ratio (VHR1) was measured 1670 milliseconds after the application was released. Next, the liquid crystal cell was irradiated with CCFL (backlight) at 60 ° C. for 1 week, and then allowed to stand at room temperature for natural cooling to room temperature. After cooling, a voltage of 1 V was applied to the liquid crystal cell for 60 microseconds, and then the voltage retention rate (VHR2) was measured 1670 milliseconds after the application was released. As the measuring device, a VHR measuring device "VHR-1" manufactured by Toyo Corporation was used. The rate of change of VHR (ΔVHR) at this time was calculated by the difference between VHR1 and VHR2 (ΔVHR = VHR1-VHR2), and the reliability was evaluated by ΔVHR. When ΔVHR is less than 10%, it is "excellent (◎)", when it is 10% or more and less than 15%, it is "good (○)", and when it is 15% or more and less than 20%, it is "acceptable (Δ)". ) ”, And when it was 20% or more, it was judged as“ impossible (×) ”. As a result, the reliability was "excellent" in this example.

7. Evaluation of DC afterimage characteristics 2. For the liquid crystal cell manufactured in, after driving with AC2.5V and setting the luminance difference between any two pixels to 0, while driving with AC2.5V, DC1V is applied to only one pixel for 20 minutes to charge. Was accumulated. When the application of DC1V was terminated and the drive was returned only to AC2.5V, the accumulated charge caused a difference in luminance between the two pixels. By observing the change over time in this luminance difference, the relaxation time in the process of decaying the residual DC value was calculated. When the relaxation time is less than 10 seconds, it is "excellent (◎)", when the relaxation time is 10 seconds or more and less than 20 seconds, it is "good (〇)", and when the relaxation time is 20 seconds or more. It was determined to be "defective (x)". As a result, it was evaluated as "excellent" in this example.

8. Evaluation of rubbing resistance Above 1. The liquid crystal alignment agent (R-1) prepared in 1 was applied onto a glass substrate using a spinner, and heated (prebaked) on a hot plate at 110 ° C. for 3 minutes. Then, the inside of the refrigerator is dried (post-baked) for 30 minutes in a nitrogen-substituted oven at 230 ° C. to form a coating film having an average film thickness of 0.08 μm, and the haze value of the coating film is measured using a hazemeter. It was measured. Next, the coating film was subjected to a rubbing treatment 5 times by a rubbing machine having a roll wrapped with a cotton cloth at a roll rotation speed of 1000 rpm, a stage moving speed of 3 cm / sec, and a hair-foot pushing length of 0.3 mm. Then, the haze value of the liquid crystal alignment film was measured using a haze meter, and the difference (haze change value) from the haze value before the rubbing treatment was calculated by the following mathematical formula (3).
Haze change value (%) = [Haze value of film after rubbing treatment (%)]-[Haze value of film before rubbing treatment (%)] ... (3)
Regarding the rubbing resistance of the liquid crystal alignment film, when the haze change value is less than 0.8, it is "excellent (◎)", and when the haze change value is 0.8 or more and less than 1.5, it is "good (○)". , When the haze change value was 1.5 or more, it was evaluated as "defective (x)". When the haze change value is less than 1.5 (more preferably less than 0.8), it can be said that the film strength is sufficiently high and the rubbing resistance is excellent. As a result, the rubbing resistance was "excellent" in this example.

[Examples 2 to 21 and Comparative Examples 1 to 8]
A liquid crystal alignment agent was prepared in the same manner as in Example 1 except that the composition of the liquid crystal alignment agent was changed as shown in Table 3 below. Further, using the obtained liquid crystal alignment agent, an FFS type liquid crystal cell was manufactured by a rubbing method in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 4 below. In Table 3, the blending amount represents the blending amount (parts by mass) of each polymer in terms of solid content with respect to the total amount of the polymer components used for preparing the liquid crystal alignment agent.

[Examples 22 and 23]
The liquid crystal alignment agent was prepared in the same manner as in Example 1 except that the composition of the liquid crystal alignment agent was changed as shown in Table 3 below and the photoalignment method was used instead of the rubbing method for the liquid crystal alignment film. An FFS type liquid crystal cell was manufactured and various evaluations were performed. The results are shown in Table 4. The liquid crystal alignment film was formed by the photo-alignment method according to the following procedure.
(Formation of liquid crystal alignment film by photo-alignment method)
A liquid crystal alignment agent on each surface of a glass substrate in which a flat plate electrode (bottom electrode), an insulating layer and a comb-shaped electrode (top electrode) are laminated on one side in this order, and a facing glass substrate on which no electrode is provided. Was applied with a spinner and heated (pre-baked) on a hot plate at 80 ° C. for 1 minute. Then, the inside of the refrigerator was dried (post-baked) for 30 minutes in a nitrogen-substituted oven at 230 ° C. to form a coating film having an average film thickness of 0.1 μm. The obtained coating film was subjected to photoalignment treatment by irradiating the obtained coating film with ultraviolet rays of 1,000 J / m ² including a linearly polarized 254 nm emission line from the normal direction of the substrate using an Hg-Xe lamp. It should be noted that this irradiation amount is a value measured using a photometer measured based on a wavelength of 254 nm. Next, the coating film subjected to the photo-alignment treatment was heated in a clean oven at 230 ° C. for 30 minutes to perform a heat treatment to form a liquid crystal alignment film.
Further, by carrying out the above series of operations by changing the ultraviolet irradiation amount after post-baking in the range of 100 to 10,000 J / m ² , three or more liquid crystal cells having different ultraviolet irradiation amounts can be manufactured. Then, various evaluations were carried out in the same manner as in Example 1 using a liquid crystal cell having an exposure amount (optimum exposure amount) showing the best orientation characteristics.

As shown in Table 4, in Examples 1 to 23, as compared with Comparative Examples 1 to 8, various characteristics such as inkjet coating property, AC afterimage characteristic, VHR, reliability, DC afterimage characteristic and rubbing resistance are well balanced. rice field. In particular, in Examples 1 to 6, 8, 9, 11 and 14 to 22, all the characteristics were evaluated as "◎" and were excellent. On the other hand, in Comparative Examples 1 to 8, at least one of the ink jet coatability, AC afterimage characteristic, reliability, DC afterimage characteristic and rubbing resistance was evaluated as “x”.

From the above results, it is clear that the liquid crystal alignment agent containing the polymer [A] and the polymer [B] can reduce the afterimage of the liquid crystal display element and can produce a liquid crystal alignment film having high mechanical strength. rice field. Further, it was clarified that the polymer [A] and the polymer [B] have good solubility and can obtain a liquid crystal alignment agent having excellent coatability.

Claims (7)

A polymer [A] having the following structural unit (U1) and not the following structural unit (U2),
A polymer [B] having the following structural unit (U2) and the following structural unit (U3),
A liquid crystal alignment agent containing.
Structural unit (U1): Structural unit derived from a diamine having a partial structure represented by the following formula (1) Structural unit (U2): Structural unit derived from a diamine having a partial structure represented by the following formula (2) Structural unit (U3): Structural unit derived from diamine having the following partial structure Y Partial structure Y: Structure represented by-(CH ₂ ) _n- (where n is an integer of 1 to 20),-(CH ₂ ) ) In the structure represented by _{n + 1-} , any methylene group is -O-, -S-, -COO-, -NR ^7- , -NR ⁷ -CO-, -NR ⁷ -COO-, -NR ⁷ -CO. -NR ⁸ -or a structure substituted with a nitrogen-containing non-aromatic heterocyclic group (however, R ⁷ and R ⁸ are independently hydrogen atoms or monovalent organic groups, respectively. When n is 2 or more. , -O-, -S-, -COO-, -NR ^{7-, -NR 7 -CO-, -NR 7 -COO-, -NR 7 -CO - NR 8} -and nitrogen-containing non-aromatic heterocyclic group Are not adjacent to each other.), -O-, -S-, -COO-, -NR ⁷ -CO-, -NR ⁷ -COO-, or -NR ⁷ -CO-NR ^8-

(In the formula (1), X ¹ and X ² are each independently divalent aromatic ring group. However, the aromatic ring of X ¹ is bonded to the bond position of R ¹ and "*". The substituent is not bonded to a position different from the bond position of the group, and the aromatic ring of X ² is replaced with a position different from the bond position of R ² and the bond position of the group bonded to "*". No groups are attached. R ¹ and R ² are independently single-bonded alkandyl groups having 1 to 10 carbon atoms or substituted alkandyl groups having 1 to 10 carbon atoms, respectively. Y ¹ and Y ² are single bonds. Each is independently * ¹ -NR ³ -CO- or * ¹ -CO-NR ^3- . R ³ is a hydrogen atom or a monovalent organic group. "* ¹ " is a bond with Z ¹ . Represented. Z ¹ is a single-bonded or divalent organic group. M is 0 or 1. When m is 0, at least one of R ¹ and R ² is an arcandyl having 1 to 10 carbon atoms. It is a group or a substituted alcoholandiyl group. "*" Indicates that it is a bond.)

(In the formula (2), A ¹ and A ² are independently divalent aromatic ring groups. B ¹ is a -NR ^4- or a divalent aromatic heterocyclic group. B ¹ is 2. When it is a valent aromatic heterocyclic group, R ⁵ and R ⁶ are independently hydrogen atoms or monovalent organic groups. When B ¹ is -NR ^4- , R ⁴ , R ⁵ and R. Reference numeral ⁶ is the following (i) or (ii).
(I) ^R4 is a hydrogen atom or a monovalent organic group. R ⁵ and R ⁶ are independent hydrogen atoms or monovalent organic groups, respectively, or a ring structure in which R ⁵ and R ⁶ are combined with A ¹ , -NR ^4- , and A ² respectively. Represents.
(Ii) R ⁴ and R ⁵ are independent hydrogen atoms or monovalent organic groups, respectively, or represent a ring structure in which R ⁴ and R ⁵ are combined with A ¹ and a nitrogen atom. .. R ⁶ is a hydrogen atom or a monovalent organic group.
"*" Indicates that it is a bond. ) The liquid crystal alignment agent according to claim 1, wherein the polymer [A] and the polymer [B] are at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. The liquid crystal alignment agent according to claim 1 or 2, wherein at least one of R ¹ and R ² is an alkanediyl group or a substituted alkanediyl group having 1 to 10 carbon atoms. The liquid crystal alignment agent according to any one of claims 1 to 3, wherein the diamine having a partial structure represented by the above formula (1) is a compound represented by the following formula (DA).

(In the formula (DA), R ¹ , R ² , Y ¹ , Y ² and Z ¹ are synonymous with the above formula (1).) The invention according to any one of claims 1 to 4, wherein the polymer [B] contains the structural unit (U2) in an amount of 5 to 95% by mass based on the total amount of the diamine units contained in the polymer [B]. Liquid crystal alignment agent. A liquid crystal alignment film formed by using the liquid crystal alignment agent according to any one of claims 1 to 5. A liquid crystal element provided with the liquid crystal alignment film according to claim 6.