JP7619178B2 - Liquid crystal alignment agent, liquid crystal alignment film, liquid crystal element, polymer and compound - Google Patents

Description

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

Liquid crystal elements are used in 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. The performance of a liquid crystal element is determined by various characteristics such as the alignment of the liquid crystal, the magnitude of the pretilt angle, and the voltage holding ratio. In order to improve the performance of liquid crystal elements, improvements have been made to the liquid crystal materials as well as the liquid crystal alignment films for aligning the liquid crystal in a certain direction (see, for example, Patent Document 1 and Patent Document 2).

Patent Document 1 discloses that in a liquid crystal alignment agent containing polyamic acid, which is a reaction product of tetracarboxylic dianhydride and diamine, and its derivatives, a polyamic acid obtained by using bis(5-aminobenzimidazole)benzene as the diamine is contained in the liquid crystal alignment agent. In addition, Patent Document 2 discloses that a polyimide obtained by using N1,N4-bis[(2-tert-butoxycarbonylamino)-4-aminophenyl]adipamide as the diamine is contained in the liquid crystal alignment agent.

JP 2010-54872 A International Publication No. 2014/104015

Monomers having a benzimidazole skeleton and polymers obtained using said monomers have low solubility and storage stability, and there is concern that the storage stability of the liquid crystal alignment agent will not be good. In addition, the liquid crystal alignment film obtained using the liquid crystal alignment agent described in Patent Document 2 has low transmittance, and there is concern that the display quality will be insufficient. Furthermore, liquid crystal elements are required to be able to maintain a high voltage retention rate even when used for a long period of time, and to be highly reliable.

In addition, liquid crystal elements for smartphones and in-vehicle applications are required to be resistant to degradation of display quality due to exposure to external forces and to have good touch panel characteristics. In other words, they are required to achieve both touch panel resistance (also known as keystroke durability) and liquid crystal alignment.

The present invention has been made in consideration of the above problems, and the main object of the present invention is to provide a liquid crystal alignment agent that can form a liquid crystal alignment film with high transmittance, that has little decrease in voltage retention rate even when used for a long period of time, that can produce a liquid crystal element with excellent touch panel resistance, and that has good storage stability.

The present inventors have conducted extensive research to solve the above problems and have found that the above problems can be solved by introducing a specific partial structure into a polymer. Specifically, the present invention provides the following means.

（式（１－１）及び式（１－２）中、Ｒ^１及びＲ^４は１価の熱脱離性基である。Ｒ^２、Ｒ^３、Ｒ^５及びＲ^６は、それぞれ独立して、水素原子又は１価の有機基である。Ｒ^７及びＲ^８は、それぞれ独立して、ハロゲン原子又は炭素数１～５のアルキル基である。ｎ１及びｎ２は、それぞれ独立して、０～３の整数である。ｎ１が２又は３の場合、式中の複数のＲ^７は同一又は異なる。ｎ２が２又は３の場合、式中の複数のＲ^８は同一又は異なる。Ｘ^１は、単結合、－Ｏ－、－Ｓ－、－ＣＯ－、＊^１－ＣＯ－Ｏ－、＊^１－Ｏ－ＣＯ－、－ＮＲ^９－、＊^１－ＮＲ^９－ＣＯ－、＊^１－ＣＯ－ＮＲ^９－、＊^１－ＮＲ^９－ＣＯ－Ｏ－又は－ＮＲ^９－ＣＯ－ＮＲ^１０－である。Ｒ^９及びＲ^１０は、それぞれ独立して、水素原子又は１価の有機基である。「＊^１」は、式中のベンゼン環との結合手であることを表す。Ａ^１は、炭素数１～１０のアルカンジイル基である。「＊」は、結合手であることを表す。） <1> A liquid crystal aligning agent comprising a polymer [P] having at least one partial structure (A) selected from the group consisting of a partial structure represented by the following formula (1-1) and a partial structure represented by the following formula (1-2):

(In formula (1-1) and formula (1-2), R ¹ and R ⁴ are monovalent thermally detachable groups. R ² , R ³ , R ⁵ and R ⁶ are each independently a hydrogen atom or a monovalent organic group. R ⁷ and R ⁸ are each independently a halogen atom or an alkyl group having 1 to 5 carbon atoms. n1 and n2 are each independently an integer of 0 to 3. When n1 is 2 or 3, multiple R ^7s in the formula are the same or different. When n2 is 2 or 3, multiple R ^8s in the formula are the same or different. ^{X 1} is a single bond, -O-, -S-, -CO-, * ¹ -CO-O-, * ¹ -O-CO-, -NR ⁹ -, * ¹ -NR ⁹ -CO-, * ¹ -CO-NR ⁹ -, * ¹ -NR ⁹ -CO-O- or -NR ⁹ -CO-NR ¹⁰ -. R ⁹ and R ¹⁰ are each independently a hydrogen atom or a monovalent organic group. "* ¹ " represents a bond to the benzene ring in the formula. ^{A 1} is an alkanediyl group having 1 to 10 carbon atoms. "*" represents a bond.)

<2> A liquid crystal alignment film formed using the liquid crystal aligning agent according to <1> above.
<3> A method for producing a liquid crystal alignment film, comprising: forming a coating film using the liquid crystal aligning agent according to <1>; and subjecting the coating film to a light irradiation treatment to impart liquid crystal aligning ability.
<4> A liquid crystal element comprising the liquid crystal alignment film according to <2> above.

（式（２－１）及び式（２－２）中、Ｒ^１及びＲ^４は、それぞれ独立して、１価の熱脱離性基である。Ｒ^２、Ｒ^３、Ｒ^５及びＲ^６は、それぞれ独立して、水素原子又は１価の有機基である。Ｒ^７及びＲ^８は、それぞれ独立して、ハロゲン原子又は炭素数１～５のアルキル基である。ｎ１及びｎ２は、それぞれ独立して、０～３の整数である。ｎ１が２又は３の場合、式中の複数のＲ^７は同一又は異なる。ｎ２が２又は３の場合、式中の複数のＲ^８は同一又は異なる。Ｘ^１は、単結合、－Ｏ－、－Ｓ－、－ＣＯ－、＊^１－ＣＯ－Ｏ－、＊^１－Ｏ－ＣＯ－、－ＮＲ^９－、＊^１－ＮＲ^９－ＣＯ－、＊^１－ＣＯ－ＮＲ^９－、＊^１－ＮＲ^９－ＣＯ－Ｏ－又は－ＮＲ^９－ＣＯ－ＮＲ^１０－である。Ｒ^９及びＲ^１０は、それぞれ独立して、水素原子又は１価の有機基である。「＊^１」は、式中のベンゼン環との結合手であることを表す。Ａ^１は、炭素数１～１０のアルカンジイル基である。Ｙ^１、Ｙ^２、Ｙ^３及びＹ^４は、それぞれ独立して、２価の有機基である。Ｂ^１及びＢ^２は、それぞれ独立して、単結合又は炭素数１～１０のアルカンジイル基である。） <5> A polyamic acid, a polyamic acid ester, or a polyimide having a structural unit derived from at least one selected from the group consisting of a compound represented by the following formula (2-1) and a compound represented by the following formula (2-2):

(In formula (2-1) and formula (2-2), R ¹ and R ⁴ are each independently a monovalent thermally detachable group. R ² , R ³ , R ⁵ and R ⁶ are each independently a hydrogen atom or a monovalent organic group. R ⁷ and R ⁸ are each independently a halogen atom or an alkyl group having 1 to 5 carbon atoms. n1 and n2 are each independently an integer of 0 to 3. When n1 is 2 or 3, multiple R ^7s in the formula are the same or different. When n2 is 2 or 3, multiple R ^8s in the formula are the same or different. X ¹ is a single bond, -O-, -S-, -CO-, * ¹ -CO-O-, * ¹ -O-CO-, -NR ⁹ -, * ¹ -NR ⁹ -CO-, * ¹ -CO-NR ⁹ -, * ¹ -NR ⁹ -CO-O- or -NR ⁹ -CO-NR ¹⁰ -. R ⁹ and R ¹⁰ are each independently a hydrogen atom or a monovalent organic group. "* ¹ " represents a bond to the benzene ring in the formula. ^{A 1} is an alkanediyl group having 1 to 10 carbon atoms. Y ¹ , Y ² , Y ³ and Y ⁴ are each independently a divalent organic group. ^{B 1} and B ² are each independently a single bond or an alkanediyl group having 1 to 10 carbon atoms.)

<6> A compound represented by the above formula (2-1).
<7> A compound represented by the above formula (2-2).

The liquid crystal alignment agent of the present invention can form a liquid crystal alignment film with high transmittance. In addition, the liquid crystal alignment agent of the present invention can produce a liquid crystal element that has high reliability with little decrease in voltage retention rate even when used for a long period of time and has excellent touch panel resistance. Furthermore, the liquid crystal alignment agent of the present invention has excellent storage stability.

Liquid crystal alignment agent
Hereinafter, each component contained in the liquid crystal aligning agent of the present disclosure and other components that are optionally blended as necessary will be described.

In this specification, the term "hydrocarbon group" includes chain-shaped hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. The term "chain-shaped hydrocarbon group" means a straight-chain hydrocarbon group and a branched hydrocarbon group that do not include a ring structure in the main chain and are composed only of a chain structure. However, they may be saturated or unsaturated. The term "alicyclic hydrocarbon group" means a hydrocarbon group that includes only an alicyclic hydrocarbon structure as a ring structure and does not include an aromatic ring structure. However, it does not have to be composed only of an alicyclic hydrocarbon structure, and it also includes those that have a chain structure as a part of it. The term "aromatic hydrocarbon group" means a hydrocarbon group that includes an aromatic ring structure as a ring structure. However, it does not have to be composed only of an aromatic ring structure, and it may include a chain structure or an alicyclic hydrocarbon structure as a part of it. The term "aromatic ring" includes aromatic hydrocarbon rings and aromatic heterocycles. The term "organic group" means an atomic group obtained by removing any hydrogen atom from a compound that includes carbon (i.e., an organic compound).

（式（１－１）及び式（１－２）中、Ｒ^１及びＲ^４は１価の熱脱離性基である。Ｒ^２、Ｒ^３、Ｒ^５及びＲ^６は、それぞれ独立して、水素原子又は１価の有機基である。Ｒ^７及びＲ^８は、それぞれ独立して、ハロゲン原子又は炭素数１～５のアルキル基である。ｎ１及びｎ２は、それぞれ独立して、０～３の整数である。ｎ１が２又は３の場合、式中の複数のＲ^７は同一又は異なる。ｎ２が２又は３の場合、式中の複数のＲ^８は同一又は異なる。Ｘ^１は、単結合、－Ｏ－、－Ｓ－、－ＣＯ－、＊^１－ＣＯ－Ｏ－、＊^１－Ｏ－ＣＯ－、－ＮＲ^９－、＊^１－ＮＲ^９－ＣＯ－、＊^１－ＣＯ－ＮＲ^９－、＊^１－ＮＲ^９－ＣＯ－Ｏ－又は－ＮＲ^９－ＣＯ－ＮＲ^１０－である。Ｒ^９及びＲ^１０は、それぞれ独立して、水素原子又は１価の有機基である。「＊^１」は、式中のベンゼン環との結合手であることを表す。Ａ^１は、炭素数１～１０のアルカンジイル基である。「＊」は、結合手であることを表す。） The liquid crystal aligning agent of the present disclosure contains a polymer [P] having at least one partial structure (A) selected from the group consisting of a partial structure represented by the following formula (1-1) and a partial structure represented by the following formula (1-2):

(In formula (1-1) and formula (1-2), R ¹ and R ⁴ are monovalent thermally detachable groups. R ² , R ³ , R ⁵ and R ⁶ are each independently a hydrogen atom or a monovalent organic group. R ⁷ and R ⁸ are each independently a halogen atom or an alkyl group having 1 to 5 carbon atoms. n1 and n2 are each independently an integer of 0 to 3. When n1 is 2 or 3, multiple R ^7s in the formula are the same or different. When n2 is 2 or 3, multiple R ^8s in the formula are the same or different. ^{X 1} is a single bond, -O-, -S-, -CO-, * ¹ -CO-O-, * ¹ -O-CO-, -NR ⁹ -, * ¹ -NR ⁹ -CO-, * ¹ -CO-NR ⁹ -, * ¹ -NR ⁹ -CO-O- or -NR ⁹ -CO-NR ¹⁰ -. R ⁹ and R ¹⁰ are each independently a hydrogen atom or a monovalent organic group. "* ¹ " represents a bond to the benzene ring in the formula. ^{A 1} is an alkanediyl group having 1 to 10 carbon atoms. "*" represents a bond.)

<Polymer [P]>
(Partial Structure (A))
In the above formulas (1-1) and (1-2), the monovalent thermally detachable groups represented by ^R1 and ^R4 are groups which are detached by heating and replaced with hydrogen atoms. Specific examples of the thermally detachable group include a tert-butoxycarbonyl group (Boc group), a benzyloxycarbonyl group, a 1,1-dimethyl-2-haloethyloxycarbonyl group, an allyloxycarbonyl group, and a 2-(trimethylsilyl)ethoxycarbonyl group. Among these, the Boc group is particularly preferred in that it has excellent thermal detachment properties and can reduce the amount of the detached structure remaining in the film.

The monovalent organic groups represented by R ² , R ³ , R ⁵ and R ⁶ are preferably monovalent hydrocarbon groups or monovalent thermally dissociable groups having 1 to 10 carbon atoms. When the groups represented by R ² , R ³ , R ⁵ and R ⁶ are monovalent hydrocarbon groups, the monovalent hydrocarbon groups are preferably alkyl groups or phenyl groups having 1 to 3 carbon atoms, more preferably alkyl groups having 1 to 3 carbon atoms. Specific examples of the groups represented by ^{R 2} , R ³ , R ⁵ and R ⁶ that are monovalent thermally dissociable groups include the same groups as those exemplified as the monovalent thermally dissociable groups represented by R ¹ and R ⁴ .

When the groups represented by R ² , R ³ , R ⁵ and R ⁶ are monovalent organic groups, the monovalent organic group is preferably an alkyl group having 1 to 3 carbon atoms or a thermally eliminable group among the above, and more preferably an alkyl group having 1 to 3 carbon atoms or a tert-butoxycarbonyl group.

From the viewpoint of facilitating an intramolecular cyclization reaction by heating during film formation, R ² , R ³ , R ⁵ and R ⁶ are preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a monovalent thermally detachable group, more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a tert-butoxycarbonyl group, and particularly preferably a hydrogen atom.

In ^R7 and ^R8 , examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The alkyl group having 1 to 5 carbon atoms may be linear or branched. The group represented by ^R7 and ^R8 is preferably a halogen atom or an alkyl group having 1 to 3 carbon atoms.
Each of n1 and n2 is preferably 0 or 1, and more preferably 0.

When the group represented by ^X1 is -NR ⁹ -, * ¹ -NR ⁹ -CO-, * ¹ -CO-NR ⁹ -, * ¹ -NR ⁹ -CO-O- or -NR ⁹ -CO-NR ¹⁰ -, the monovalent organic group in R ⁹ and R ¹⁰ is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms or a monovalent thermally eliminable group. Specific examples of the monovalent hydrocarbon group having 1 to 10 carbon atoms include an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, and an aryl group having 6 to 10 carbon atoms. Of these, an alkyl group and a phenyl group having 1 to 3 carbon atoms are preferred, and an alkyl group having 1 to 3 carbon atoms is more preferred.

Specific examples of the monovalent organic groups represented by ^R9 and ^R10 that are monovalent thermally detachable groups include the same groups as the specific examples of ^R1 and ^R4 . Among these, the Boc group is particularly preferred because it has excellent thermal detachability and can minimize the amount of the detached structure remaining in the film. ^R9 and ^R10 are preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a monovalent thermally detachable group, and more preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a tert-butoxycarbonyl group.

From the viewpoint of obtaining a liquid crystal element exhibiting good liquid crystal alignment properties and from the viewpoint of ease of synthesis of the skeleton constituting partial structure (A), ^X1 is preferably -O-, * ¹ -CO-O-, * ¹ -O-CO-, -NR ⁹ -, * ¹ -NR ⁹ -CO- or * ^1- CO-NR ⁹ - among the above.

The alkanediyl group having 1 to 10 carbon atoms represented by A ¹ may be linear or branched. A 1 is preferably a linear alkanediyl group in terms of being able to form a liquid crystal alignment film having a high film density, a high effect of improving voltage holding characteristics and touch panel resistance, and a liquid crystal alignment film in which coloring is suppressed. The number of carbon atoms in ^{A 1 is} preferably 6 or less, more preferably 3 or less, in terms of obtaining a liquid crystal element exhibiting a high voltage holding ratio and a liquid crystal element exhibiting good liquid crystal alignment properties.

（式（３－１）及び式（３－２）中、Ｄ^１及びＤ^２は、それぞれ独立して、炭素数１～１０のアルカンジイル基である。Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７、Ｒ^８、ｎ１、ｎ２、Ｘ^１及びＡ^１は、上記式（１－１）及び式（１－２）と同義である。） From the viewpoint of increasing the density of the film, it is preferable that the carbonyl group in the above formula (1-1) and formula (1-2) is bonded to a saturated chain hydrocarbon structure. Specifically, it is preferable that the polymer [P] has at least one selected from the group consisting of a partial structure represented by the following formula (3-1) and a partial structure represented by the following formula (3-2).

(In formula (3-1) and formula (3-2), ^D1 and ^D2 are each independently an alkanediyl group having 1 to 10 carbon atoms. ^R1 , ^R2 , R3, ^R4 , ^R5 , ^R6 , ^R7 , ^R8 , ⁿ¹ , n2, ^X1 and ^A1 are the same as those in formula (1-1) and formula (1-2) above.)

In the above formulas (1-1) and (1-2), the alkanediyl group having 1 to 10 carbon atoms represented by D ¹ and D ² may be linear or branched. From the viewpoint of forming a liquid crystal alignment film having a high effect of improving the voltage retention characteristics and touch panel resistance by increasing the density of the film, and of forming a liquid crystal alignment film in which coloring is suppressed, it is preferable that D ¹ and D ² are linear alkanediyl groups.

The polymer [P] preferably has a partial structure (A) in the main chain, since it can suppress the deterioration of display quality even when an external force is applied by tapping or the like, and has a high effect of improving touch panel resistance. From the viewpoint of ease of synthesis of a polymer having a partial structure (A) in the main chain, the polymer [P] can be preferably produced by a method of polymerization using a monomer having a partial structure (A). As the monomer having the partial structure (A), a diamine compound having a partial structure (A) (hereinafter also referred to as a "specific diamine") is preferable, since it can form a liquid crystal alignment film having high affinity with liquid crystals and high mechanical strength, and there is a high degree of freedom in selecting the monomer.

In this specification, the "main chain" of a polymer refers to the "trunk" portion of the polymer, which is the longest chain of atoms. It is permissible for this "trunk" portion to contain a ring structure. In other words, when a polymer "has partial structure (A) in its main chain," this means that partial structure (A) constitutes a part of the main chain of the polymer. The "side chain" of a polymer refers to a portion branched off from the "trunk" of the polymer.

（式（２－１）及び式（２－２）中、Ｙ^１、Ｙ^２、Ｙ^３及びＹ^４は、それぞれ独立して、２価の有機基である。Ｂ^１及びＢ^２は、それぞれ独立して、単結合又は炭素数１～１０のアルカンジイル基である。Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４、Ｒ^５、Ｒ^６、Ｒ^７、Ｒ^８、ｎ１、ｎ２、Ｘ^１及びＡ^１は、上記式（１－１）及び式（１－２）と同義である。） (Specific diamine)
The specific diamine may be a monomer having the partial structure (A) and two primary amino groups, and the structure of the other parts is not particularly limited. A preferred specific example of the specific diamine is at least one selected from the group consisting of a compound represented by the following formula (2-1) and a compound represented by the following formula (2-2).

(In formula (2-1) and formula (2-2), Y ¹ , Y ² , Y ³ and Y ⁴ are each independently a divalent organic group. ^{B 1} and B ² are each independently a single bond or an alkanediyl group having 1 to 10 carbon atoms. R ¹ , R ² , R 3 , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , n1, n2, X ¹ and A ¹ are the same as defined in formula (1-1) and ^formula (1-2) above.)

In the above formulas (2-1) and (2-2), the divalent organic groups represented by ^Y1 , ^Y2 , ^Y3 , and ^Y4 include divalent chain groups and cyclic groups, and divalent cyclic groups are preferred. Examples of the divalent cyclic groups include divalent alicyclic groups and aromatic ring groups.

Examples of divalent alicyclic groups include groups in which two hydrogen atoms have been removed from an alicyclic hydrocarbon ring such as a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, or a cycloheptane ring. In a divalent alicyclic group, a substituent may be introduced into the ring portion of the alicyclic hydrocarbon ring. Examples of the substituent include an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a halogen atom.

Examples of the divalent aromatic ring group include divalent aromatic hydrocarbon ring groups and aromatic heterocyclic groups, and preferably divalent aromatic hydrocarbon ring groups and nitrogen-containing aromatic heterocyclic groups. Specific examples of these include, as the divalent aromatic hydrocarbon ring group, a group obtained by removing any hydrogen atom bonded to a carbon atom constituting a ring of a benzene ring, a biphenyl ring, a naphthalene ring, or an anthracene ring; as the divalent nitrogen-containing aromatic heterocyclic group, a group obtained by removing any two hydrogen atoms bonded to a carbon atom constituting a ring of a pyridine ring, a pyrimidine ring, a pyridazine ring, or a pyrazine ring. In the divalent aromatic ring group, a substituent may be introduced into the ring portion of the aromatic ring. Examples of the substituent include an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and a halogen atom.

From the viewpoint of increasing the density of the liquid crystal alignment film, the divalent organic groups represented by ^Y1 , ^Y2 , ^Y3 and ^Y4 are preferably divalent aromatic hydrocarbon ring groups or nitrogen-containing aromatic heterocyclic groups, more preferably substituted or unsubstituted phenylene groups, biphenylene groups or pyridinediyl groups, and further preferably substituted or unsubstituted phenylene groups.

At least one of B ¹ and B ² is preferably an alkanediyl group having 1 to 10 carbon atoms, and more preferably both B ¹ and B ² are alkanediyl groups having 1 to 10 carbon atoms. The alkanediyl group having 1 to 10 carbon atoms represented by ^{B 1} and B ² may be linear or branched. B 1 and B 2 are preferably linear alkanediyl groups in terms of being able to form a liquid crystal alignment film having a high effect of improving the voltage holding characteristics and touch panel resistance by increasing the density of the film, and being able to form a liquid crystal alignment film in which coloring is suppressed. The number of carbon atoms in ^{B 1 and} B ² is ^preferably 6 or less, more preferably 3 or less, from the viewpoint of obtaining a liquid crystal element exhibiting a high voltage holding ratio and a liquid crystal element exhibiting good liquid crystal alignment properties.

Specific examples of the specific diamine include compounds represented by the following formulas (4-1) to (4-12), in which "Boc" represents a tert-butoxycarbonyl group (hereinafter the same).

In the polymer [P], the content of the structural unit (hereinafter also referred to as "structural unit (UA)") derived from a monomer having a partial structure (A) is preferably 2 mol% or more relative to the total amount of monomer units contained in the polymer [P] (100 mol%) from the viewpoint of obtaining a liquid crystal element that exhibits a high voltage holding ratio (VHR), has little decrease in voltage holding ratio even when used for a long period of time, and has excellent touch panel resistance. The content of the structural unit (UA) is more preferably 5 mol% or more, and even more preferably 7 mol% or more, relative to the total amount of monomer units contained in the polymer [P]. In addition, the content of the structural unit (UA) can be appropriately set according to the main chain of the polymer [P], but when the polymer [P] is obtained by condensation polymerization, it is, for example, 50 mol% or less relative to the total amount of monomer units contained in the polymer [P]. The structural unit (UA) contained in the polymer [P] may be of only one type, or may be of two or more types.

The specific diamine can be synthesized by appropriately combining standard methods in organic chemistry. One example of a synthesis method is to synthesize a dinitro intermediate having a nitro group instead of the primary amino group in the above formula (2-1) and the above formula (2-2), and then animate the nitro group of the obtained dinitro intermediate using an appropriate reduction system.

（スキーム中、Ｚ^１はアルカンジイル基である。）

（スキーム中、Ｚ^１はアルカンジイル基である。） The method for synthesizing the dinitro intermediate is not particularly limited, and can be appropriately selected from condensation reaction between carboxylic acid and amine, condensation reaction between carboxylic acid and alcohol, condensation reaction between carboxylic acid and phenol, etc., depending on the target compound. A specific example of synthesis in which the dinitro intermediate is obtained by utilizing the condensation reaction between carboxylic acid and amine is shown below.

(In the scheme, ^Z1 is an alkanediyl group.)

(In the scheme, ^Z1 is an alkanediyl group.)

The reduction reaction of the dinitro intermediate can be preferably carried out in an organic solvent using a catalyst such as palladium on carbon, platinum oxide, zinc, iron, tin, nickel, platinum on carbon, or osmium on carbon. Examples of the organic solvent used here include ethyl acetate, toluene, tetrahydrofuran, and alcohols. Two or more of these organic solvents may be mixed and used. However, the synthesis procedure of the compound represented by the above formula (2-1) and the compound represented by the above formula (2-2) is not limited to the above method.

(Production of Polymer [P])
The main chain of the polymer [P] is not particularly limited. In terms of being able to form a liquid crystal alignment film having high affinity with liquid crystals and mechanical strength and high reliability, the polymer [P] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.

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

(Tetracarboxylic acid dianhydride)
Examples of the tetracarboxylic dianhydride used in the synthesis of the polyamic acid [P] include aliphatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, and aromatic tetracarboxylic dianhydrides. Specific examples of these include aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butane tetracarboxylic dianhydride and ethylenediaminetetraacetic dianhydride; alicyclic tetracarboxylic dianhydrides such as 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 5-(2,5-dioxotetrahydrofuran-3-yl)-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 5-(2,5-dioxotetrahydrofuran-3-yl)-8-methyl-3a,4,5,9b-tetrahydronaphtho[1,2-c]furan-1,3-dione, 2,4,6,8-tetracarboxybiphenyl ether, and the like. Cyclo[3.3.0]octane-2:4,6:8-dianhydride, cyclopentane tetracarboxylic dianhydride, cyclohexane tetracarboxylic dianhydride, 3,5,6-tricarboxy-2-carboxymethylnorbornane-2:3,5:6-dianhydride; aromatic tetracarboxylic dianhydride, pyromellitic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, ethylene glycol bisanhydrotrimate, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 4,4'-carbonyldiphthalic anhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, etc.; and tetracarboxylic dianhydrides described in JP-A-2010-97188 can be used. As the tetracarboxylic dianhydride, one type can be used alone or two or more types can be used in combination.

The tetracarboxylic dianhydride used in the synthesis of the polyamic acid [P] preferably contains at least one selected from the group consisting of aliphatic tetracarboxylic dianhydrides and alicyclic tetracarboxylic dianhydrides, and more preferably contains alicyclic tetracarboxylic dianhydrides, in that it is possible to obtain a liquid crystal alignment film that has high solubility and exhibits good liquid crystal alignment properties and electrical properties. The proportion of the alicyclic tetracarboxylic dianhydride used is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more, based on the total amount of the tetracarboxylic dianhydride used in the synthesis of the polyamic acid [P].

(Diamine Compound)
The diamine compound used in the synthesis of the polyamic acid [P] may be the specific diamine alone, or may be a diamine not having the partial structure (A) (hereinafter also referred to as "other diamines") in addition to the specific diamine. Examples of other diamines include aliphatic diamines, alicyclic diamines, aromatic diamines, and diaminoorganosiloxanes.

（式（Ｄ－１）中、Ｒ^１１及びＲ^１２は、それぞれ独立して、アルカンジイル基である。Ｒ^１３は、水素原子、炭素数１～３のアルキル基又は１価の熱脱離性基である。ｎ３は１～３の整数である。ｎ３が２又は３の場合、複数のＲ^１２は同一又は異なり、複数のＲ^１３は同一又は異なる。）
で表される化合物等の主鎖型ジアミン；
ヘキサデカノキシ－２，４－ジアミノベンゼン、オクタデカノキシ－２，４－ジアミノベンゼン、オクタデカノキシ－２，５－ジアミノベンゼン、コレスタニルオキシ－３，５－ジアミノベンゼン、コレステリルオキシ－３，５－ジアミノベンゼン、コレスタニルオキシ－２，４－ジアミノベンゼン、コレステリルオキシ－２，４－ジアミノベンゼン、３，５－ジアミノ安息香酸コレスタニル、３，５－ジアミノ安息香酸コレステリル、３，５－ジアミノ安息香酸ラノスタニル、３，６－ビス（４－アミノベンゾイルオキシ）コレスタン、３，６－ビス（４－アミノフェノキシ）コレスタン、４－（４’－トリフルオロメトキシベンゾイロキシ）シクロヘキシル－３，５－ジアミノベンゾエート、１，１－ビス（４－（（アミノフェニル）メチル）フェニル）－４－ブチルシクロヘキサン、３，５－ジアミノ安息香酸＝５ξ－コレスタン－３－イル、下記式（Ｅ－１）

（式（Ｅ－１）中、Ｘ^I及びＸ^IIは、それぞれ独立して、単結合、－Ｏ－、＊－ＣＯＯ－又は＊－ＯＣＯ－（ただし、「＊」はＸ^Ｉとの結合手を示す。）である。Ｒ^Ｉは、炭素数１～３のアルカンジイル基である。Ｒ^ＩＩは、単結合又は炭素数１～３のアルカンジイル基である。Ｒ^ＩＩＩは、炭素数１～２０のアルキル基、アルコキシ基、フルオロアルキル基、又はフルオロアルコキシ基である。ａは０又は１である。ｂは０～３の整数である。ｃは０～２の整数である。ｄは０又は１である。ただし、１≦ａ＋ｂ＋ｃ≦３である。）
で表される化合物等の側鎖型ジアミン等を、
ジアミノオルガノシロキサンとして、１，３－ビス（３－アミノプロピル）－テトラメチルジシロキサン等を、それぞれ挙げることができる。 Specific examples of other diamines include aliphatic diamines such as metaxylylenediamine and hexamethylenediamine; alicyclic diamines such as 1,4-diaminocyclohexane and 4,4'-methylenebis(cyclohexylamine); and aromatic diamines such as p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4-aminophenyl-4-aminobenzoate, 4,4'-diaminoazobenzene, 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, 6,6'-(pentamethylenedioxy)bis(3-aminopyridine), N,N'-di(5-amino-2-pyridyl)-N,N'-di(t tert-butoxycarbonyl)ethylenediamine, bis[2-(4-aminophenyl)ethyl]hexanedioic acid, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenethyl urea, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 4,4'-(phenylenediisopropylidene)bisaniline, 2,6-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, 3,6-diaminoacridine, diphenylamine structure-containing monomer, the following formula (D-1):

(In formula (D-1), R ¹¹ and R ¹² are each independently an alkanediyl group. R ¹³ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a monovalent thermally eliminable group. n3 is an integer from 1 to 3. When n3 is 2 or 3, multiple R ¹² 's are the same or different, and multiple R ^13's are the same or different.)
Main chain diamines such as compounds represented by the following formula:
Hexadecanoxy-2,4-diaminobenzene, octadecanoxy-2,4-diaminobenzene, octadecanoxy-2,5-diaminobenzene, cholestanyloxy-3,5-diaminobenzene, cholesteryloxy-3,5-diaminobenzene, cholestanyloxy-2,4-diaminobenzene, cholesteryloxy-2,4-diaminobenzene, cholestanyl 3,5-diaminobenzoate, cholesteryl 3,5-diaminobenzoate , lanostannyl 3,5-diaminobenzoate, 3,6-bis(4-aminobenzoyloxy)cholestane, 3,6-bis(4-aminophenoxy)cholestane, 4-(4'-trifluoromethoxybenzoyloxy)cyclohexyl-3,5-diaminobenzoate, 1,1-bis(4-((aminophenyl)methyl)phenyl)-4-butylcyclohexane, 3,5-diaminobenzoic acid=5ξ-cholestan-3-yl, the following formula (E-1):

(In formula (E-1), X ^I and X ^II are each independently a single bond, -O-, *-COO-, or *-OCO- (wherein "*" represents a bond to X ^I ). R ^I is an alkanediyl group having 1 to 3 carbon atoms. R ^II is a single bond or an alkanediyl group having 1 to 3 carbon atoms. R ^III is an alkyl group, alkoxy group, fluoroalkyl group, or fluoroalkoxy group having 1 to 20 carbon atoms. a is 0 or 1. b is an integer of 0 to 3. c is an integer of 0 to 2. d is 0 or 1, with the proviso that 1≦a+b+c≦3.)
A side chain type diamine such as a compound represented by the formula:
Examples of diaminoorganosiloxanes include 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, and the like.

Examples of the diphenylamine structure-containing monomer include compounds represented by the following formulas (C-1-1) to (C-1-8). Examples of the compound represented by the above formula (D-1) include compounds represented by the following formulas (D-1-1) to (D-1-3). Examples of the compound represented by the above formula (E-1) include compounds represented by the following formulas (E-1-1) to (E-1-4). As the other diamines, one type can be used alone, or two or more types can be used in combination.

In the synthesis of polyamic acid [P], the proportion of the specific diamine used is preferably 5 mol % or more, more preferably 10 mol % or more, and even more preferably 15 mol % or more, based on the total amount of diamine compounds used in the synthesis of polyamic acid [P], from the viewpoint of obtaining a liquid crystal element that exhibits a high VHR, has little decrease in VHR even when used over a long period of time, and has excellent touch panel resistance. As the specific diamine, one type may be used alone, or two or more types may be used in combination.

(Synthesis of polyamic acid)
The polyamic acid [P] can be obtained by reacting a tetracarboxylic dianhydride with a diamine compound, optionally together with a molecular weight modifier. In the synthesis reaction of the polyamic acid [P], the ratio of the tetracarboxylic dianhydride to the diamine compound is preferably such that the acid anhydride group of the tetracarboxylic dianhydride is 0.2 to 2 equivalents per equivalent of the amino group of the diamine compound. Examples of the molecular weight modifier 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 phenyl isocyanate and naphthyl isocyanate. The ratio of the molecular weight modifier to be used is preferably 20 parts by mass or less per 100 parts by mass of the total of the tetracarboxylic dianhydride and diamine compound used.

The synthesis reaction of the polyamic acid [P] is preferably carried out in an organic solvent. The reaction temperature is preferably -20°C to 150°C, and the reaction time is preferably 0.1 to 24 hours. Examples of organic solvents used in the reaction include aprotic polar solvents, phenolic solvents, alcoholic solvents, ketone solvents, ester solvents, ether solvents, halogenated hydrocarbons, and hydrocarbons. Specific examples of these include one or more selected from the group consisting of N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, γ-butyrolactone, tetramethylurea, hexamethylphosphortriamide, m-cresol, xylenol, and halogenated phenols, or a mixture of one or more of these with another organic solvent (e.g., butyl cellosolve, diethylene glycol diethyl ether, etc.). The amount of organic solvent used is preferably such that the total amount of tetracarboxylic dianhydride and diamine is 0.1 to 50% by mass based on the total amount of the reaction solution.

In this manner, a polymer solution in which the polyamic acid [P] is dissolved is obtained. This polymer solution may be used as is to prepare a liquid crystal alignment agent, or the polyamic acid [P] contained in the polymer solution may be isolated and then used to prepare a liquid crystal alignment agent.

Polyamic acid ester When the polymer [P] is a polyamic acid ester, the polyamic acid ester (hereinafter also referred to as "polyamic acid ester [P]") can be obtained, for example, by a method of reacting a polyamic acid [P] with an esterifying agent, a method of reacting a tetracarboxylic acid diester with a diamine compound containing a specific diamine, or a method of reacting a tetracarboxylic acid diester dihalide with a diamine compound containing a specific diamine. The polyamic acid ester [P] may have only an amic acid ester structure, or may be a partially esterified product in which an amic acid structure and an amic acid ester structure coexist. The reaction solution in which the polyamic acid ester [P] is dissolved may be used as it is for the preparation of a liquid crystal alignment agent, or the polyamic acid ester [P] contained in the reaction solution may be isolated and then used for the preparation of a liquid crystal alignment agent.

Polyimide When the polymer [P] is a polyimide, the polyimide (hereinafter also referred to as "polyimide [P]") can be obtained, for example, by dehydrating and cyclizing the polyamic acid [P] synthesized as described above to convert it into an imidized product. The polyimide [P] may be a fully imidized product in which all of the amic acid structures contained in the precursor polyamic acid [P] have been dehydrated and cyclized, or a partially imidized product in which only a portion of the amic acid structures have been dehydrated and cyclized, so that both the amic acid structure and the imide ring structure coexist. The polyimide [P] preferably has an imidization rate of 20 to 99%, more preferably 30 to 90%. The imidization rate is the percentage of the number of imide ring structures relative to the total number of amic acid structures and the number of imide ring structures in the polyimide. Here, some of the imide rings may be isoimide rings.

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

The solution viscosity of the polymer [P] used to prepare the liquid crystal alignment agent is preferably 10 to 800 mPa·s when made into a 10% by mass solution, and more preferably 15 to 500 mPa·s. The solution viscosity (mPa·s) is the value measured at 25°C using an E-type rotational viscometer for a 10% by mass polymer solution prepared using a good solvent for the polymer [P] (e.g., γ-butyrolactone, N-methyl-2-pyrrolidone, etc.).

The weight average molecular weight (Mw) of the polymer [P] in terms of polystyrene measured by gel permeation chromatography (GPC) is preferably 1,000 to 500,000, more preferably 2,000 to 300,000. The molecular weight distribution (Mw/Mn), which is expressed as the ratio of Mw to the number average molecular weight (Mn) in terms of polystyrene measured by GPC, is preferably 7 or less, more preferably 5 or less. When preparing the liquid crystal alignment agent, one type of polymer [P] may be used alone, or two or more types may be used in combination.

<Other ingredients>
The liquid crystal aligning agent may contain, in addition to the polymer [P], a component different from the polymer [P] (hereinafter, also referred to as "other component"), if necessary.

Polymer [Q]
The liquid crystal alignment agent of the present disclosure may further contain a polymer not having a partial structure (A) (hereinafter, also referred to as "polymer [Q]") as a polymer component. The main skeleton of polymer [Q] 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, (meth)acrylic polymer, styrene polymer, maleimide polymer, styrene-maleimide copolymer, etc.

From the viewpoint of obtaining a highly reliable liquid crystal element, the polymer [Q] is preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, polyimide, polyorganosiloxane, and polymers containing structural units derived from a monomer having a polymerizable unsaturated carbon-carbon bond. Examples of polymers containing structural units derived from a monomer having a polymerizable unsaturated carbon-carbon bond include (meth)acrylic polymers, styrene polymers, maleimide polymers, and styrene-maleimide copolymers. Of these, the polymer [Q] is particularly preferably at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide.

When the polymer [Q] is contained in the liquid crystal alignment agent, the content of the polymer [Q] is preferably 1% by mass or more, and more preferably 2% by mass or more, based on the total amount of the polymer [P] and the polymer [Q]. The content of the polymer [Q] is preferably 95% by mass or less, and more preferably 90% by mass or less, based on the total amount of the polymer [P] and the polymer [Q]. As the polymer [Q], one type can be used alone, or two or more types can be used in combination.

Solvent The liquid crystal aligning agent of the present disclosure is preferably prepared as a liquid composition in which the polymer [P] and other components used as necessary are dispersed or dissolved in a suitable solvent.

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, γ-butyrolactone, γ-butyrolactam, N,N-dimethylformamide, N,N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone, diacetone alcohol, 1-hexanol, 2-hexanol, propane-1,2-diol, 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 methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, and ethylene glycol-i-propyl ether. Examples of the solvent include ethylene glycol n-butyl ether (butyl cellosolve), ethylene glycol dimethyl ether, ethylene glycol ethyl 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, diisobutyl ketone, isoamyl propionate, isoamyl isobutyrate, 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, etc. As the solvent, one type can be used alone or two or more types can be mixed and used.

Other components contained in the liquid crystal alignment agent include, in addition to the above, for example, crosslinking agents, antioxidants, metal chelate compounds, curing accelerators, surfactants, fillers, dispersants, photosensitizers, etc. The blending ratio of the other components can be appropriately selected according to each compound within a range that does not impair the effects of the present disclosure.

The solids concentration in the liquid crystal alignment agent (the ratio of the total mass of the components other than the solvent in the liquid crystal alignment agent to the total mass of the liquid crystal alignment agent) is appropriately selected taking into consideration the viscosity, volatility, etc., but is preferably in the range of 1 to 10 mass%. A solids concentration of 1 mass% or more is preferable in that a sufficient thickness of the coating film can be ensured and a liquid crystal alignment film that exhibits better liquid crystal alignment properties can be obtained. On the other hand, a solids concentration of 10 mass% or less allows the coating film to have an appropriate thickness, making it easier to obtain a liquid crystal alignment film that exhibits good liquid crystal alignment properties, and also tends to provide an appropriate viscosity for the liquid crystal alignment agent, resulting in good coatability.

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

<Step 1: Formation of coating film>
First, a liquid crystal alignment agent is applied onto a substrate, and preferably the applied surface is heated to form a coating film on the substrate. As the substrate, for example, a transparent substrate made of glass such as float glass or soda glass; or plastic such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, or poly(alicyclic olefin) can be used. As the transparent conductive film provided on one surface of the substrate, a NESA film (registered trademark of PPG Corporation, USA) made of tin oxide (SnO ₂ ), an ITO film made of indium oxide-tin oxide (In ₂ O ₃ -SnO ₂ ), or the like can be used. When manufacturing a TN-type, STN-type, or VA-type liquid crystal element, two substrates on which a patterned transparent conductive film is provided are used. On the other hand, when manufacturing an IPS-type or FFS-type liquid crystal element, a substrate on which an electrode patterned into a comb tooth shape is provided and an opposing substrate on which no electrode is provided are used.

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

After the liquid crystal alignment agent is applied, pre-heating (pre-baking) is preferably performed to prevent dripping of the applied liquid crystal alignment agent. The pre-baking temperature is preferably 30 to 200°C, and the pre-baking time is preferably 0.25 to 10 minutes. Thereafter, the solvent is completely removed, and if necessary, a baking (post-baking) step is performed to thermally imidize the amic acid structure present in the polymer. The baking temperature (post-baking temperature) at this time is preferably 80 to 280°C, more preferably 80 to 250°C. The post-baking time is preferably 5 to 200 minutes. The thickness of the film formed is preferably 0.001 to 1 μm.

<Step 2: Alignment Treatment>
When a TN-type, STN-type, IPS-type or FFS-type liquid crystal element is manufactured, the coating film formed in the above step 1 is subjected to a treatment (alignment treatment) for imparting liquid crystal alignment ability. This imparts the alignment ability of liquid crystal molecules to the coating film, forming 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, nylon or the like, or a photoalignment treatment in which the coating film is irradiated with light to impart liquid crystal alignment ability. When a vertical alignment type liquid crystal element is manufactured, the coating film formed in the above step 1 may be used as it is as a liquid crystal alignment film, or the coating film may be subjected to an alignment treatment in order to further enhance the liquid crystal alignment ability.

The light irradiation for photo-alignment can be performed by irradiating the coating film after the post-bake process, irradiating the coating film after the pre-bake process but before the post-bake process, or irradiating the coating film while it is being heated in at least one of the pre-bake and post-bake processes. For example, ultraviolet light and visible light containing light with a wavelength of 150 to 800 nm can be used as the radiation to be irradiated to the coating film. Preferably, ultraviolet light containing light with a wavelength of 200 to 400 nm is used. When the radiation is polarized, it may be linearly polarized or partially polarized. When the radiation used is linearly polarized or partially polarized, the radiation may be performed from a direction perpendicular to the substrate surface, from an oblique direction, or a combination of these. When the radiation is non-polarized, the radiation is irradiated from an oblique direction.

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, and an excimer laser. The radiation dose is preferably 200 to 30,000 J/ ^m2 , and more preferably 500 to 10,000 J/ ^m2 . After the light irradiation for imparting alignment ability, the substrate surface may be washed with, for example, water, an organic solvent (e.g., methanol, isopropyl alcohol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, etc.) or a mixture thereof, or the substrate may be heated.

<Step 3: Construction of liquid crystal cell>
Two substrates on which the liquid crystal alignment film is formed as described above are prepared, and liquid crystal is placed between the two substrates arranged opposite to each other to manufacture a liquid crystal cell. For example, the liquid crystal cell can be manufactured by placing two substrates opposite to each other with a gap between them so that the liquid crystal alignment film faces each other, bonding the peripheries of the two substrates with a sealant, injecting liquid crystal into the cell gap surrounded by the substrate surfaces and the sealant, and sealing the injection hole, or by using the ODF method. For example, epoxy resin containing a hardener and aluminum oxide spheres as spacers can be used as the sealant. For example, nematic liquid crystal and smectic liquid crystal can be used as the liquid crystal, and among them, nematic liquid crystal is preferred.

When manufacturing a liquid crystal display device, a polarizing plate is then attached to the outer surface of the liquid crystal cell. Examples of polarizing plates include a polarizing film called an "H film" made by stretching and aligning polyvinyl alcohol and absorbing iodine, sandwiched between cellulose acetate protective films, or a polarizing plate made of the H film itself.

Here, when a liquid crystal alignment agent containing the polymer [P] having the partial structure (A) is applied onto a substrate and heated to form a liquid crystal alignment film, the thermally detachable groups (R ¹ , R ⁴ ) bonded to the nitrogen in the above formula (1-1) or the above formula (1-2) are eliminated, and a cyclization reaction between the carbonyl group and the nitrogen-containing functional group in the above formula (1-1) or the above formula (1-2) occurs, forming a benzimidazole ring structure. Such a polymer [P] does not contain a benzimidazole ring structure when contained in the liquid crystal alignment agent, and has good solubility and good storage stability of the liquid crystal alignment agent. On the other hand, the polymer [P] undergoes a cyclization reaction within the molecule due to heating during film formation, which is believed to form a benzimidazole ring structure in the polymer [P]. In addition, a part of the functional group generated by elimination of the thermally detachable groups (R ¹ , R ⁴ ) bonded to the nitrogen in the above formula (1-1) and the above formula (1-2) is believed to contribute to the crosslinking reaction between molecules. As a result, it is believed that a liquid crystal alignment film formed using a liquid crystal alignment agent containing the polymer [P] exhibits a high VHR, and even when used over a long period of time, there is little decrease in VHR, and it is possible to obtain a liquid crystal element having excellent touch panel resistance.

The liquid crystal element of the present disclosure can be effectively applied to various applications. Specifically, it can be used, for example, in various display devices such as clocks, portable game machines, word processors, notebook computers, car navigation systems, camcorders, PDAs, digital cameras, mobile phones, smartphones, various monitors, liquid crystal televisions, and information displays, as well as in light control devices and retardation films.

The following embodiments are described in more detail with reference to examples, but the present invention should not be construed as being limited to the following examples.

In the following examples, the purity of the monomer, the weight average molecular weight (Mw) of the polymer, the number average molecular weight (Mn) of the polymer, the imidization rate of the polyimide in the polymer solution, and the solution viscosity of the polymer solution were measured by the following methods. The required amounts of the raw material compounds and polymers used in the following examples were ensured by repeating the synthesis on a synthesis scale shown in the following synthesis examples as necessary.
[Monomer Purity]
The purity of the monomer (LC purity) was measured by high performance liquid chromatography under the following conditions.
Column: AGILENT ZORBAX Eclipse XDB C18
Solvent: Mixture of 70% tetrahydrofuran and 30% water containing ammonium acetate Temperature: 40°C
[Weight average molecular weight (Mw) and number average molecular weight (Mn) of polymer]
Mw and Mn are values calculated as polystyrene equivalents measured by GPC under the following conditions.
Column: TSKgel GRCXLII, manufactured by Tosoh Corporation
Solvent: N,N-dimethylformamide solution containing lithium bromide and phosphoric acid Temperature: 40°C
Pressure: 68 kgf/ ^cm2
[Imidization rate of polyimide]
The polyimide solution was poured into pure water, and the resulting precipitate was thoroughly dried under reduced pressure at room temperature, then dissolved in deuterated dimethyl sulfoxide and subjected to ^1H -NMR measurement at room temperature using tetramethylsilane as a standard substance. From the obtained ^1H -NMR spectrum, the imidization rate [%] was calculated using the following formula (1).
Imidization rate [%] = (1 - (A ¹ / (A ² × α))) × 100 ... (1)
(In formula (1), ^A1 is the peak area derived from the proton of the NH group appearing at a chemical shift of about 10 ppm, ^A2 is the peak area derived from other protons, and α is the ratio of the number of other protons to one proton of the NH group in the polymer precursor (polyamic acid).)

The abbreviations of the compounds are as follows: In the following, the compound represented by formula (X) may be simply referred to as "compound (X)".
(Tetracarboxylic acid dianhydride)

(Diamine Compound)

<Synthesis of Monomer>
[Synthesis Example 1A]
Diamine (DA-1) was synthesized according to the following scheme.

2,5-diamino-tert-butoxycarbonylaminobenzene (0.61 g), 4-nitrohydrocinnamic acid (1.18 g), and 4-dimethylaminopyridine (18.1 mg) were placed in a three-neck flask equipped with a nitrogen inlet tube, and the mixture was replaced with nitrogen. 4 mL of dichloromethane was added and stirred under a nitrogen atmosphere. 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (1.32 g) dispersed in 6.5 mL of dichloromethane was added dropwise thereto and stirred at room temperature for 12 hours. After the reaction was completed, 10 mL of water was added to the reaction solution and stirred, and the organic layer was concentrated to precipitate the product. The resulting aqueous dispersion was filtered, and the crude product was washed with water and 2-propanol and dried in vacuum to obtain a white powder of a nitro intermediate product (1.50 g, yield 94%).
Next, 0.75 g of palladium carbon was placed in a three-neck flask equipped with a reflux tube and a nitrogen inlet tube, and the atmosphere was replaced with nitrogen. 10 mL of tetrahydrofuran degassed by nitrogen bubbling and 2.5 mL of ethanol were placed therein, and the nitro intermediate product (1.50 g) was added, followed by stirring to obtain a suspension solution. 0.76 mL of hydrazine monohydrate was slowly dropped into the reaction solution at room temperature. After dropping, the temperature was gradually raised to 60° C., and the mixture was stirred for 4 hours. The reaction solution was diluted with 10 mL of tetrahydrofuran, filtered through Celite, and concentrated to precipitate the product. The resulting precipitate was washed with water and 2-propanol and dried in vacuum to obtain a white solid diamine (DA-1) (1.00 g, yield 75%). Its structure was confirmed by ¹ H-NMR spectrum, which is the nuclear magnetic resonance spectrum of intramolecular hydrogen atoms. The measurement data are shown below.
^1H -NMR (400MHz, [ _D6 ]-DMSO) δ: 9.88 (s, 1H), 9.37 (s, 1H), 8.30 (s, 1H), 7.81 (d, 1H), 7.37 (dd, 1H), 7.21 (d, 1H), 6.88 (dd, 4H), 6.48 (dd, 4H), 4.83 (d, 4H), 2.72 (m, 4H), 2.51 (m, 4H), 1.45 (s, 9H).

<Monomer Evaluation>
[Evaluation Example 1-1: Evaluation of storage stability and coloration]
1 g of diamine (DA-1) was placed in a screw tube and stored at 60° C. for one month, after which the LC purity and the presence or absence of coloration were observed. When the decrease in LC purity was less than 1%, it was rated as "good (○)", when it was 1% or more but less than 5%, it was rated as "passable (△)", and when it was 5% or more, it was rated as "poor (×)". In addition, when there was no coloration, it was rated as "good (○)", and when there was coloration, it was rated as "poor (×)". As a result, both the LC purity and coloration of this evaluation example were "good (○)".

[Evaluation Example 1-2, Comparative Evaluation Examples 1-1 to 1-4, and Reference Evaluation Example 1-1]
The storage stability and coloration of the diamine were evaluated in the same manner as in Evaluation Example 1-1, except that the diamine to be evaluated was changed as shown in Table 1. The results are shown in Table 1.

As shown in Table 1, the specific diamines having partial structure (A) (evaluation examples 1-1 and 1-2) were better in terms of at least one of the reduction in LC purity and coloration than the diamines in comparative evaluation examples 1-1 to 1-4.

<Synthesis of Polymer>
1. Synthesis of polyamic acid [Synthesis Example 1B]
100 parts by mole of compound (TA-1) as a tetracarboxylic dianhydride and 100 parts by mole of compound (DB-1) as a diamine compound were dissolved in N-methyl-2-pyrrolidone (NMP), and the mixture was reacted at room temperature for 6 hours to obtain a solution containing 15% by mass of polyamic acid (referred to as polymer (PA-1)).

[Synthesis Examples 2B to 16B]
The same procedure as in Synthesis Example 1B was repeated except that the types and amounts of the tetracarboxylic dianhydride and diamine compound used were changed as shown in Tables 2 and 3, to obtain polyamic acids (polymers (PA-2) to In Tables 2 and 3, the values of the acid anhydrides indicate the proportion of each compound used relative to 100 parts by mole of the total of the tetracarboxylic dianhydrides used in the synthesis of the polymer. The numerical value of diamine indicates the ratio (parts by mole) of each compound used relative to 100 parts by mole of the total of diamine compounds used in the synthesis of the polymer (the same applies to Table 4).

2. Synthesis of polyimide [Synthesis Example 17B]
100 mol parts of compound (TA-2) as a tetracarboxylic dianhydride, 30 mol parts of compound (DA-4) as a diamine compound, and 70 mol parts of compound (DB-13) were dissolved in NMP, and the reaction was carried out at room temperature for 6 hours to obtain a solution containing 15% by mass of polyamic acid. Next, NMP was added to the obtained polyamic acid solution to obtain a solution with a polyamic acid concentration of 10% by mass, and pyridine and acetic anhydride were added to carry out a dehydration ring-closing reaction at 60° C. for 4 hours. After the dehydration ring-closing reaction, the solvent in the system was replaced with fresh NMP to obtain a solution containing 15% by mass of polyimide (referred to as polymer (PI-1)) with an imidization rate of about 80%.

[Synthesis Examples 18B and 19B]
The same procedure as in Synthesis Example 17B was carried out except that the types and amounts of the tetracarboxylic dianhydride and diamine compound used were changed as shown in Table 4, and polyimides (polymers (PI-2) and (PI-3)) were obtained. ) was obtained.

<Preparation and Evaluation of Liquid Crystal Alignment Agent>
[Evaluation Example 2-1: Evaluation of storage stability and transmittance]
1. Preparation of liquid crystal alignment agent The solution of the polymer (PA-7) obtained in Synthesis Example 7B was diluted with NMP and butyl cellosolve (BC) to obtain a solution with a solvent composition of NMP/BC=80/20 (mass ratio) and a solid content concentration of 3.5 mass%. The solution was filtered through a filter with a pore size of 0.2 μm to prepare a liquid crystal alignment agent (AL-1).

2. Evaluation of storage stability The liquid crystal alignment agent (AL-1) prepared in 1. above was filtered through a 1.0 μm filter and stored at room temperature for one month, after which the presence or absence of precipitates in the liquid crystal alignment agent was observed. When no precipitates were observed in the liquid crystal alignment agent, the result was "good (○)", and when precipitates were observed, the result was "poor (×)". As a result, the storage stability of this example was evaluated as "good (○)".

3. Evaluation of transmittance The liquid crystal alignment agent (AL-1) prepared in 1. above was applied to a glass substrate using a spinner and heated (pre-baked) on a hot plate at 110 ° C. for 3 minutes. Thereafter, the substrate was dried (post-baked) for 30 minutes in an oven at 230 ° C. with the interior replaced with nitrogen, forming a coating film with an average thickness of 0.08 μm. The light transmittance (%) at a wavelength of 400 nm was evaluated for the obtained coating film using a spectrophotometer (Hitachi, Ltd. 150-20 type double beam). The evaluation was as follows: if the light transmittance was 97% or more, it was "good (○)", if it was 95% or more but less than 97%, it was "fair (△)", and if it was less than 95%, it was "poor (×)". As a result, the light transmittance of this coating film was 99.0%, and the transmittance was "good".

[Evaluation Examples 2-2 to 2-6, Comparative Evaluation Examples 2-1 to 2-6, and Reference Evaluation Example 2-1]
A liquid crystal alignment agent was prepared in the same manner as in Evaluation Example 2-1, except that the composition of the liquid crystal alignment agent was changed as shown in Table 5. In addition, the storage stability and transmittance of the obtained liquid crystal alignment agent were evaluated. The results are shown in Table 5.

As shown in Table 5, the liquid crystal alignment agents containing polymer [P] (evaluation examples 2-1 to 2-6) showed better results in at least one of storage stability and transmittance than the liquid crystal alignment agents of comparative evaluation examples 2-1 to 2-6.

Here, the polymer (PA-2) contained in the liquid crystal alignment agent of Comparative Evaluation Example 2-2 is a polymer obtained by using a diamine (DA-3) having a benzimidazole skeleton. As shown in Table 5, the evaluation of the storage stability and transmittance of the liquid crystal alignment agent containing the polymer (PA-2) was "x". In addition, the polymers (PA-3) and (PI-1) contained in the liquid crystal alignment agents of Comparative Evaluation Examples 2-3 and 2-6 are polymers obtained by using a diamine (DA-4) having a structure in which an amide group and a protected amino group are bonded to an aminophenyl group, and the polymer (PA-4) contained in the liquid crystal alignment agent of Comparative Evaluation Example 2-4 is a polymer obtained by using a diamine (DA-5) having a structure in which a benzene ring having a protected amino group is bonded to an aminophenyl group via an amide bond. As shown in Table 5, the evaluation of the film transmittance of the liquid crystal alignment agents containing the polymers (PA-3), (PI-1), and (PA-4) was "x".

[Example 1: Rubbed FFS-type liquid crystal display element]
1. Manufacture of FFS-type liquid crystal display element using rubbing method A glass substrate (first substrate) having a flat electrode (bottom electrode), an insulating layer, and a comb-shaped electrode (top electrode) laminated in this order on one side, and a glass substrate (second substrate) without an electrode were prepared. Next, a liquid crystal alignment agent (AL-1) was applied to the electrode-forming surface of the first substrate and one side of the second substrate by a spinner, and heated (pre-baked) on a hot plate at 110°C for 3 minutes. Then, the substrate was dried (post-baked) for 30 minutes in an oven at 230°C with the interior replaced with nitrogen, to form a coating film with an average thickness of 0.08 μm. Next, the coating film surface was subjected to rubbing treatment by a rubbing machine having a roll wrapped with rayon cloth at a roll rotation speed of 1000 rpm, a stage moving speed of 3 cm/sec, and a pile indentation length of 0.3 mm. Thereafter, ultrasonic cleaning was performed in ultrapure water for 1 minute, and then drying was performed in a clean oven at 100° C. for 10 minutes to obtain a pair of substrates having liquid crystal alignment films.
Next, a pair of substrates having a liquid crystal alignment film was screen-printed with an epoxy resin adhesive containing aluminum oxide spheres having a diameter of 3.5 μm, leaving a liquid crystal injection port at the edge of the surface on which the liquid crystal alignment film was formed. The substrates were then superimposed and pressed together, and the adhesive was thermally cured at 150° C. for 1 hour. Next, a negative liquid crystal (MLC-6608, manufactured by Merck) was filled into the gap between the pair of substrates through the liquid crystal injection port, and the liquid crystal injection port was sealed with an epoxy adhesive. Furthermore, in order to remove the flow orientation during liquid crystal injection, the substrate was heated at 120° C. and then slowly cooled to room temperature to produce a liquid crystal cell. Note that when the pair of substrates were superimposed, the rubbing methods of the respective substrates were set to be antiparallel. Next, polarizing plates were attached to both outer surfaces of the substrates in the liquid crystal cell, and an FFS-type liquid crystal display element was obtained.

2. Evaluation of Initial VHR The liquid crystal display element manufactured in 1 above was placed in an oven at 60°C, and then 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 Corporation. The evaluation criteria were "good (○)" when the VHR was higher than 73%, "fair (△)" when it was 73% or less and 60% or more, and "poor (×)" when it was less than 60%. As a result, the evaluation of the initial VHR of this example was "good (○)".

3. Evaluation of VHR reliability The reliability of the voltage holding ratio was evaluated for the liquid crystal display element manufactured in 1 above. The evaluation was performed as follows. First, a voltage of 1V was applied to the liquid crystal display element for 60 microseconds, and then the voltage holding ratio (VHR1) was measured 1670 milliseconds after the application was removed. Next, the liquid crystal display element was irradiated with a CCFL (backlight) at 60°C for one week, and then left to stand at room temperature to naturally cool to room temperature. After cooling, a voltage of 1V was applied to the liquid crystal display element for 60 microseconds, and then the voltage holding ratio (VHR2) was measured 1670 milliseconds after the application was removed. The measurement device used was a VHR measurement device "VHR-1" manufactured by Toyo Corporation. The rate of change of VHR (ΔVHR) at this time was calculated from the difference between VHR1 and VHR2 (ΔVHR=VHR1-VHR2), and the VHR reliability was evaluated based on ΔVHR. When ΔVHR was less than 15%, it was judged as "good (○)", when it was between 15% and 20%, it was judged as "fair (△)", and when it was more than 20%, it was judged as "poor (×)". As a result, in this example, the VHR reliability was "good (○)".

4. Evaluation of liquid crystal alignment after keystroke test 1 (evaluation by number of bright spots)
The liquid crystal display element manufactured in 1. above was evaluated for its liquid crystal orientation after a keystroke test. The evaluation was performed as follows. A silicone rubber pen 3R (manufactured by Touch Panel Laboratory Co., Ltd.) with a pen tip shape of 3 mm radius was set on the keystroke part (solenoid type) of a keystroke tester (Touch Panel Laboratory Co., Ltd.), and the pen tip was set so that it was at the center position of the liquid crystal display element. After 10,000 keystrokes with the silicone rubber pen at a load of 500 g and 10 Hz, the liquid crystal display element was observed under a microscope (100 times) to evaluate the liquid crystal orientation after the keystroke test. When the number of bright spots was less than 30, it was judged as "excellent (◎)", when it was 30 or more and less than 50, it was judged as "good (○)", when it was 50 or more and less than 100, it was judged as "fair (△)", and when it was 100 or more, it was judged as "poor (×)". As a result, in this example, it was rated as "good (○)".

5. Evaluation of liquid crystal alignment after keystroke test 2 (evaluation based on retardation change rate)
The liquid crystal display element used in 4. above was left standing on a high-luminance backlight of 27,000 cd/ ^m2 for 500 hours, and the liquid crystal alignment was evaluated by the retardation change rate before and after irradiation with the backlight. First, the retardation of the liquid crystal display element used in 4. above was measured using Axoscan manufactured by Optoscience, and the retardation change rate α before and after irradiation with the backlight was calculated using the following formula (z-1). The smaller the change rate α, the better the liquid crystal alignment. When the change rate α was 1% or less, it was rated as "good (○)", when it was greater than 1% and less than 2%, it was rated as "fair (△)", and when it was greater than 2%, it was rated as "poor (×)".
α=Δθ/θ1...(z-1)
(In formula (z-1), Δθ represents the retardation difference before and after irradiation, and θ1 represents the retardation value before irradiation.)
As a result, this example was rated as "good (◯)".

[Examples 2 to 10 and Comparative Examples 1 to 7]
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 6. In addition, using the obtained liquid crystal alignment agent, an FFS-type liquid crystal display element was manufactured by a rubbing method in the same manner as in Example 1, and the initial VHR, VHR reliability, keystroke test, and alignment after the keystroke test were evaluated. The results are shown in Table 6. In Examples 2, 4, 5, 7, and 9, and Comparative Examples 3 and 4, two types of polymers were used as the polymer component, and in Examples 6 and 10, three types of polymers were used as the polymer component. In Table 6, the numerical value in the polymer column represents the blending ratio (parts by mass) of the solid content of each polymer relative to 100 parts by mass of the total amount of the polymer components used in the preparation of the liquid crystal alignment agent.

As shown in Table 6, Examples 1 to 10, which used a liquid crystal alignment agent containing polymer [P], showed better results in terms of initial VHR, VHR reliability, and liquid crystal alignment after the typing test than Comparative Examples 1 to 7, which used a liquid crystal alignment agent that did not contain polymer [P].

The liquid crystal anchoring strength of the liquid crystal alignment film is thought to be largely influenced by the uniaxiality of the film. In this regard, the liquid crystal alignment film formed using the polymer [P] having the partial structure (A) has high uniaxiality and is thought to have good liquid crystal alignment after the keystroke test. In contrast, the polymers (PA-3), (PA-4), and (PI-1), which are thought to form a benzimidazole ring structure by intramolecular cyclization reaction like the polymer [P], are thought to form a mesogenic skeleton containing an imide ring structure and a benzimidazole ring structure when the benzimidazole ring structure is formed by post-baking. When the mesogenic skeleton contains a benzimidazole ring structure, the uniaxiality of the film is lower than that of the polymer [P] used in Examples 1 to 10, and the liquid crystal alignment after the keystroke test is thought to be insufficient.

[Example 11: Optical FFS type liquid crystal display element]
1. Preparation of liquid crystal alignment agent A solution containing 60 parts by mass of the polymer (PA-7) obtained in Synthesis Example 7B and a solution containing 40 parts by mass of the polymer (PA-11) obtained in Synthesis Example 11B were mixed and diluted with NMP and BC to obtain a solution with a solvent composition of NMP/BC=80/20 (mass ratio) and a solid content concentration of 3.5% by mass. The liquid crystal alignment agent (AL-11) was prepared by filtering this solution through a filter with a pore size of 0.2 μm.

2. Manufacturing of FFS-type liquid crystal display element using photo-alignment method The first substrate and the second substrate were prepared similarly to those in Example 1. Next, a liquid crystal alignment agent (AL-11) was applied to the electrode-forming surface of the first substrate and one of the substrate surfaces of the second substrate by a spinner, and heated (pre-baked) on a hot plate at 80°C for 1 minute. Then, the liquid crystal alignment agent (AL-11) was dried (post-baked) for 30 minutes in a 230°C oven with the interior replaced with nitrogen, to form a coating film with an average thickness of 0.1 μm. The obtained coating film was subjected to photo-alignment treatment by irradiating 1,000 J/ ^m2 of linearly polarized ultraviolet light containing a 254 nm emission line from the substrate normal direction using a Hg-Xe lamp. The amount of irradiation was measured using an actinometer that measures based on a wavelength of 254 nm. Next, the coating film subjected to photo-alignment treatment was heated in a clean oven at 230°C for 30 minutes to perform heat treatment, and a liquid crystal alignment film was formed.
Next, for one of the pair of substrates on which the liquid crystal alignment film was formed, an epoxy resin adhesive containing aluminum oxide spheres with a diameter of 3.5 μm was applied by screen printing to the outer edge of the surface having the liquid crystal alignment film. Thereafter, the substrates were overlapped and pressed together so that the projection direction of the polarization axis on the substrate surface during light irradiation was antiparallel, and the adhesive was thermally cured at 150° C. for 1 hour. Next, negative liquid crystal (MLC-6608, manufactured by Merck) was filled between the pair of substrates through the liquid crystal injection port, and the liquid crystal injection port was sealed with an epoxy adhesive to obtain a liquid crystal cell. Furthermore, in order to remove the flow alignment during liquid crystal injection, the liquid crystal cell was heated at 120° C. and then slowly cooled to room temperature. Then, polarizing plates were attached to both outer surfaces of the substrate in the liquid crystal cell to obtain a liquid crystal display element. In addition, by carrying out the above series of operations while varying the amount of ultraviolet light irradiation after post-baking in the range of 100 to 10,000 J/ ^m2 , three or more liquid crystal display elements with different amounts of ultraviolet light irradiation were manufactured, and the liquid crystal display element with the exposure amount (optimum exposure amount) that showed the best alignment characteristics was used for the following evaluation of initial VHR and VHR reliability.

3. Evaluation For the liquid crystal display device manufactured in 2 above, the initial VHR, VHR reliability, and liquid crystal alignment property after a typing test were evaluated in the same manner as in Example 1.

[Examples 12 to 14 and Comparative Example 8]
A liquid crystal alignment agent was prepared in the same manner as in Example 11, except that the composition of the liquid crystal alignment agent was changed as shown in Table 7. In addition, using the obtained liquid crystal alignment agent, an FFS-type liquid crystal display element was manufactured by a photoalignment method in the same manner as in Example 11, and various evaluations were performed. The results are shown in Table 7. In Table 7, the numerical values in the polymer column indicate the blending ratio (parts by mass) of the solid content of each polymer relative to 100 parts by mass of the total amount of the polymer components used in the preparation of the liquid crystal alignment agent.

As shown in Table 7, Examples 11 to 14, which used a liquid crystal alignment agent containing polymer [P], showed better results in initial VHR, VHR reliability, and liquid crystal alignment after the typing test than Comparative Example 8, which used a liquid crystal alignment agent that did not contain polymer [P].

The above results show that a liquid crystal alignment agent containing polymer [P] having partial structure (A) can form a liquid crystal alignment film with high transmittance, and can produce a liquid crystal element that exhibits little decrease in voltage retention rate even when used over a long period of time (i.e., high reliability) and has excellent touch panel resistance. In addition, the liquid crystal alignment agent containing polymer [P] also had good storage stability.

Claims (10)

A liquid crystal aligning agent comprising a polymer [P] having, in its main chain, at least one partial structure (A) selected from the group consisting of a partial structure represented by the following formula (1-1) and a partial structure represented by the following formula (1-2):

(In formula (1-1) and formula (1-2), R ¹ and R ⁴ are each independently a monovalent thermally-releasable group. R ² , R ³ , R ⁵ and R ⁶ are each independently a hydrogen atom or a monovalent organic group. R ⁷ and R ⁸ are each independently a halogen atom or an alkyl group having 1 to 5 carbon atoms. n1 and n2 are each independently an integer from 0 to 3. When n1 is 2 or 3, multiple R ^7s in the formula are the same or different. When n2 is 2 or 3, multiple R ^8s in the formula are the same or different. ^{X 1} is -O-, * ¹ -CO-O-, * ¹ -O-CO-, -NR ⁹ -, * ¹ -NR ⁹ -CO-, or * ¹ -CO-NR ⁹ -. ^{R 9} is a hydrogen atom or a monovalent organic group. "* ¹ " represents a bond to the benzene ring in the formula. ^{A 1} is an alkanediyl group having 1 to 10 carbon atoms. "*" represents a bond.) The liquid crystal alignment agent according to claim 1, wherein the polymer [P] contains a structural unit derived from a diamine having the partial structure (A). The liquid crystal aligning agent according to claim 2, wherein the diamine is at least one selected from the group consisting of a compound represented by the following formula (2-1) and a compound represented by the following formula (2-2):

(In formula (2-1) and formula (2-2), Y ¹ , Y ² , Y ³ and Y ⁴ are each independently a divalent organic group. ^{B 1} and B ² are each independently a single bond or an alkanediyl group having 1 to 10 carbon atoms. R ¹ , R ² , R 3 , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , n1, n2, X ¹ and A ¹ are the same as defined in formula (1-1) and ^formula (1-2) above.) The liquid crystal alignment agent according to any one of claims 1 to 3, wherein the polymer [P] is at least one selected from the group consisting of polyamic acid, polyamic acid ester, and polyimide. The liquid crystal aligning agent according to any one of claims 1 to 4, wherein the polymer [P] has a structural unit derived from an alicyclic tetracarboxylic dianhydride. The liquid crystal alignment agent according to any one of claims 1 to 5, further comprising a polymer [Q] that does not have the partial structure (A). A liquid crystal alignment film formed using the liquid crystal alignment agent according to any one of claims 1 to 6. A step of forming a coating film using the liquid crystal aligning agent according to any one of claims 1 to 6;
a step of subjecting the coating film to a light irradiation treatment to impart liquid crystal alignment ability;
A method for producing a liquid crystal alignment film comprising the steps of: A liquid crystal element comprising the liquid crystal alignment film according to claim 7. A polyamic acid, a polyamic acid ester, and a polyimide each having a structural unit derived from at least one selected from the group consisting of a compound represented by the following formula (2-1) and a compound represented by the following formula (2-2):

(In formula (2-1) and formula (2-2), R ¹ and R ⁴ are each independently a monovalent thermally dissociable group. R ² , R ³ , R ⁵ and R ⁶ are each independently a hydrogen atom or a monovalent organic group. R ⁷ and R ⁸ are each independently a halogen atom or an alkyl group having 1 to 5 carbon atoms. n1 and n2 are each independently an integer of 0 to 3. When n1 is 2 or 3, multiple R ^7s in the formula are the same or different. When n2 is 2 or 3, multiple R ^8s in the formula are the same or different. ^{X 1} is -O-, * ¹ -CO-O-, * ¹ -O-CO-, -NR ⁹ -, * ¹ -NR ⁹ -CO-, or * ¹ -CO-NR ⁹ -. ^{R 9} is a hydrogen atom or a monovalent organic group. "* ¹ " represents a bond to the benzene ring in the formula. ^{A 1} is an alkanediyl group having 1 to 10 carbon atoms. Y ¹ , Y ² , Y ³ and Y ⁴ are each independently a divalent organic group. ^{B 1} and B ² are each independently a single bond or an alkanediyl group having 1 to 10 carbon atoms.)