JP7633608B2 - Diamine, its production method and polymer - Google Patents

Description

The present invention relates to a novel liquid crystal alignment agent and liquid crystal alignment film, a liquid crystal display element, and a novel diamine and its manufacturing method and polymer.

Currently, liquid crystal display elements are widely used as display units for personal computers, mobile phones, television receivers, etc. Liquid crystal display elements include, for example, a liquid crystal layer sandwiched between an element substrate and a color filter substrate, pixel electrodes and a common electrode that apply an electric field to the liquid crystal layer, a liquid crystal alignment film that controls the alignment of the liquid crystal molecules in the liquid crystal layer, and thin film transistors (TFTs) that switch the electrical signals supplied to the pixel electrodes. Of these, the liquid crystal alignment film is produced by applying a polyimide-based liquid crystal alignment agent made of a solution of polyimide, which is a polyimide precursor (also called "polyamic acid"), or its imidized product, to a substrate to form a film.

In recent years, liquid crystal display elements have become more powerful, larger in area, and more energy-efficient. In addition, they are now used in a variety of environments, and the properties required of liquid crystal alignment films are becoming more stringent. Therefore, various methods such as changing the structure of polyamic acid or polyimide, blending polyamic acid or polyimide with different properties, or adding additives are being used to improve liquid crystal alignment and electrical properties, as well as to control the pretilt angle.

As an example of a method for improving the properties of a liquid crystal alignment film, the application of a diamine with a novel structure, which is a raw material for polyamic acid, has been proposed. For example, Patent Document 1 discloses a liquid crystal alignment agent that contains a diamine with a novel structure and an aliphatic tetracarboxylic acid derivative, and by using this liquid crystal alignment agent, it is possible to provide a liquid crystal display element that has an excellent voltage retention rate and is capable of reducing charge accumulation.

However, as liquid crystal display elements become more sophisticated, the characteristics required of liquid crystal alignment films are becoming more stringent, and it is difficult to satisfy all of the required characteristics using conventional technology alone.

On the other hand, a common method for aligning liquid crystals is the rubbing method, in which a polymer film such as polyimide is applied to a substrate such as glass, and the surface is rubbed in a predetermined direction with fibers such as nylon or polyester. However, this rubbing method generates fine dust and static electricity discharges due to friction between the fibers and the polymer film, which can cause serious problems when manufacturing liquid crystal panels.

To solve the problems of the rubbing method, a photo-alignment method is known in which there is no friction in the polymer film and anisotropy is induced by light irradiation to align the liquid crystal. In the photo-alignment method, the polymer contained in the liquid crystal alignment film is irradiated with polarized ultraviolet light to cause a photoreaction such as a photodecomposition reaction or a photodimerization reaction, thereby fixing the alignment direction of the liquid crystal. As the demand for high-definition and high-quality liquid crystal display elements increases, such photo-alignment methods are being applied to liquid crystal display elements of the IPS (In-Plane Switching) and FFS (Fringe Field Switching) types, which are horizontal electric field driving methods (see, for example, Patent Document 2). In addition, a method of combining the IPS type with the PSA type has been developed in recent years to further improve the alignment ability.

However, polyimides used in photo-alignment methods generally have poor solubility in solvents, making it difficult to directly apply polyimide in the process of forming an alignment film by applying the polyimide in solution state. For this reason, precursors such as polyamic acid or polyamic acid esters, which have good solubility, are applied, and polyimide is formed through a heat treatment process, after which it is oriented by light irradiation. However, a large amount of energy is required to obtain sufficient liquid crystal alignment by irradiating a polyimide film with light. Therefore, it is difficult to actually ensure productivity, and there is also the constraint that an additional heat treatment process is required to obtain alignment stability after light irradiation.

International Publication No. 2010/053128 JP 2013-080193 A

In view of the above circumstances, the present invention aims to provide a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element using a novel diamine to improve the characteristics of a liquid crystal display element, as well as a diamine and a method for producing the same, and a polymer.

An embodiment of the present invention that solves the above problem is a liquid crystal alignment agent that contains at least one polymer selected from a polyimide precursor containing a structural unit represented by the following formula [3-1] and a polyimide that is an imide compound thereof.

式中、Ｖ^０は、テトラカルボン酸誘導体由来の四価の有機基であり、Ｗ^１は、下記式［２－１］で表される二価の有機基であり、Ｒ^３及びＲ^４は、それぞれ独立して水素原子又は炭素原子数１～５のアルキル基を表す。

In the formula, ^V0 is a tetravalent organic group derived from a tetracarboxylic acid derivative, ^W1 is a divalent organic group represented by the following formula [2-1], and ^R3 and ^R4 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

式中、Ｙ^１は、脂環式構造を有する四価の有機基であり、Ｘ^１、Ｘ^２は、二価の有機基であり、Ｚ^１、Ｚ^２はそれぞれ独立して、単結合、－ＮＨ－、または－Ｏ－であり、Ｒ^１及びＲ^２はそれぞれ独立して、炭素原子数１～５のアルキル基を表し、＊は、結合する部位を表す。

In the formula, ^Y1 is a tetravalent organic group having an alicyclic structure, ^X1 and ^X2 are divalent organic groups, ^Z1 and ^Z2 are each independently a single bond, -NH-, or -O-, ^R1 and ^R2 are each independently an alkyl group having 1 to 5 carbon atoms, and * represents a bonding site.

The present invention provides a novel liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element for improving the characteristics of a liquid crystal display element, as well as a novel diamine and its manufacturing method and polymer.

The present invention will be described in more detail below.

The liquid crystal alignment agent of the present invention contains at least one polymer (hereinafter also referred to as specific polymer A) selected from a polyimide precursor containing a structural unit represented by the following formula [3-1] and a polyimide which is an imide compound thereof. More specifically, the liquid crystal alignment agent contains the specific polymer A and an organic solvent.

式中、Ｖ^０は、テトラカルボン酸誘導体由来の四価の有機基であり、Ｗ^１は、下記式［２－１］で表される二価の有機基であり、Ｒ^３及びＲ^４は、それぞれ独立して水素原子又は炭素原子数１～５のアルキル基を表す。

In the formula, ^V0 is a tetravalent organic group derived from a tetracarboxylic acid derivative, ^W1 is a divalent organic group represented by the following formula [2-1], and ^R3 and ^R4 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

式中、Ｙ^１は、脂環式構造を有する四価の有機基であり、Ｘ^１、Ｘ^２は、二価の有機基であり、Ｚ^１、Ｚ^２はそれぞれ独立して、単結合、－ＮＨ－、または－Ｏ－であり、Ｒ^１及びＲ^２はそれぞれ独立して、炭素原子数１～５のアルキル基を表し、＊は、結合する部位を表す。

In the formula, ^Y1 is a tetravalent organic group having an alicyclic structure, ^X1 and ^X2 are divalent organic groups, ^Z1 and ^Z2 are each independently a single bond, -NH-, or -O-, ^R1 and ^R2 are each independently an alkyl group having 1 to 5 carbon atoms, and * represents a bonding site.

Since the structure of formula [2-1] is a divalent group derived from a diamine represented by the following formula [1] (hereinafter also referred to as the diamine of the present invention), the diamine of the present invention will be described first. Specific examples and preferred structures of Y ¹ , X ¹ , X ² , Z ¹ , Z ² , R ¹ and R ² in formula [2-1] are the same as the specific examples and preferred structures shown in the explanation of formula [1]. In addition, in formula [3-1], W ¹ may be one type in the same polymer as long as it is a divalent organic group represented by formula [2-1], or two or more types may be mixed.

<Diamine>
The diamine of the present invention is represented by the following formula [1].

式中、Ｙ^１は、脂環式構造を有する四価の有機基であり、Ｘ^１、Ｘ^２は、二価の有機基であり、Ｚ^１、Ｚ^２はそれぞれ独立して、単結合、－ＮＨ－、または－Ｏ－であり、Ｒ^１及びＲ^２はそれぞれ独立して、炭素原子数１～５のアルキル基を表す。

In the formula, Y ¹ is a tetravalent organic group having an alicyclic structure, X ¹ and X ² are divalent organic groups, Z ¹ and Z ² are each independently a single bond, -NH-, or -O-, and R ¹ and R ² are each independently an alkyl group having 1 to 5 carbon atoms.

Examples of the alkyl group having 1 to 5 carbon atoms represented by R ¹ and R ² include, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, an isopentyl group, an s-pentyl group, and a t-pentyl group. Examples of the alkenyl group having 2 to 5 carbon atoms include, for example, a vinyl group, an allyl group, a 1-propenyl group, a 1-butenyl group, a 2-butenyl group, a 3-butenyl group, a 1-pentenyl group, a 2-pentenyl group, a 3-pentenyl group, and a 4-pentenyl group. Examples of the alkynyl group having 2 to 5 carbon atoms include, for example, an ethynyl group, a 1-propynyl group, a 2-propynyl (propargyl) group, a 3-butynyl group, and a pentynyl group. Among these, from the viewpoint of liquid crystal alignment, R ¹ and R ² are preferably a methyl group or an ethyl group, and more preferably a methyl group.

X ¹ and X ² are divalent organic groups, and the structure thereof is not particularly limited, but is preferably an organic group having 30 or less carbon atoms.
From the viewpoint of liquid crystal alignment, it is preferable that the compound has a phenylene group.
A particularly preferred structure is a divalent group represented by the following formula [2-2].

In the formula, ^X3 and ^X5 independently represent a phenylene group which may have a substituent; ^X4 represents a divalent group having 10 or less carbon atoms; ^L1 and ^L2 independently represent a single bond, -O-, or -S-; n1 and n2 independently represent 0 or 1; *1 and *2 represent bonding sites. One of *1 and *2 is bonded to ^Z1 or ^Z2 , and the other is bonded to a nitrogen atom.

Specific examples of the substituent that the phenylene group of X ³ and X ⁵ may have include alkyl groups and alkoxy groups having 1 to 5 carbon atoms, fluoroalkyl groups and fluoroalkoxy groups having 1 to 5 carbon atoms, and a fluorine atom.

Preferred specific examples of ^X4 include divalent groups selected from the following (a) to (d).
(a): A group in which two hydrogen atoms have been removed from a hydrocarbon having 1 to 10 carbon atoms.
(b): a group having a structure in which a linking group selected from --O--, --S--, and _--SO.sub.2-- is sandwiched between one or more carbon-carbon bonds of the (a).
(c): A group having a structure in which one or more carbon atoms in the above (a) or (b) are replaced with a silicon atom or a nitrogen atom.
(d): A group having a structure in which one or more methylene groups (--CH ₂ --) in the above (a) to (c) are replaced with a carbonyl group (--CO--).
The "hydrocarbon" in (a) may be a saturated hydrocarbon or an unsaturated hydrocarbon, and may have a linear or branched chain structure, or a cyclic structure or a structure containing a cyclic structure.
In the case of (c) above, when a structure is created in which a carbon atom is replaced with a nitrogen atom, the original carbon atom is limited to one having a hydrogen atom bonded thereto, and in the structure after replacement with a nitrogen atom, the hydrogen atom is deleted.

More preferred structures for X ¹ and X ² include structures represented by (X-1) to (X-11).

（ｎは１～６の整数を表す。）

(n represents an integer of 1 to 6.)

In the above formula [1], the tetravalent organic group having an alicyclic structure is not particularly limited in structure, but specific examples include the following formulae [Y ¹ -1] to [Y ¹ -20].

式［Ｙ^１－１］～式［Ｙ^１－４］において、Ｒ^５～Ｒ^２５は、それぞれ独立して、水素原子、ハロゲン原子、炭素原子数１～６のアルキル基、炭素原子数２～６のアルケニル基、炭素原子数２～６のアルキニル基、フッ素原子を含有する炭素原子数１～６の１価の有機基又はフェニル基であり、同一でも異なってもよい。液晶配向性の観点から、Ｒ^５～Ｒ^２５は、水素原子、ハロゲン原子、メチル基又はエチル基が好ましく、水素原子又はメチル基がより好ましい。

In formulae [Y ¹ -1] to [Y ¹ -4], R ⁵ to R ²⁵ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group, and may be the same or different. From the viewpoint of liquid crystal alignment, R ⁵ to R ²⁵ are preferably a hydrogen atom, a halogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom or a methyl group.

Among the above, formula [Y ¹ -1] is preferred, and specific examples of the formula [Y ¹ -1] include structures represented by the following formulas [Y ¹ -1-1] to [Y ¹ -1-6]. From the viewpoint of the liquid crystal alignment property of the liquid crystal aligning agent and the sensitivity of the photoreaction, the structure represented by the following formula [Y ¹ -1-1] is particularly preferred.

The synthesis method for diamine is explained below.

The method for synthesizing the diamine of formula [1] has a first step of obtaining an amine derivative of formula (13) from an isocyanate compound of formula (12) or an isocyanate compound, starting from a tetracarboxylic acid dialkyl ester having an alicyclic structure represented by the following formula (11).

Examples of a method for obtaining an isocyanate compound of formula (12) from a tetracarboxylic acid dialkyl ester having an alicyclic structure of formula (11) include a method in which a carboxylic acid azide (-COON ₃ ) is generated from a carboxylic acid (-COOH) of formula (11), and the generated carboxylic acid azide is converted to an isocyanate compound (-NCO) via a rearrangement reaction such as Curtius rearrangement or Schmidt rearrangement, or a method utilizing Rossen rearrangement in which an isocyanate compound is generated from a carboxylic acid (-COOH) via a hydroxyamide derivative (-CONHOH, -CONHOTs; Ts is a tosyl group (p-toluenesulfonic acid group)). The isocyanate compound thus generated can be converted to an amine derivative of formula (13) by reacting it with water, tert-butyl alcohol, or the like, and such a compound can be generated directly from the compound of formula (11). In addition, when R ³¹ and R ³² in the compound of formula (13) are hydrogen atoms, that is, when the diisocyanate compound of formula (12) is reacted with water, purification may be facilitated by reacting with an amino group protecting reagent such as di-tert-butyl dicarbonate, 4-nitrobenzyl chloride, benzyl chloroformate, or fluorenylmethyl chloroformate to obtain an amino-protected product, which may result in easier synthesis.

In formulas (11) to (13), ^Y1 is a divalent organic group having an alicyclic structure, and ^R1 and ^R2 each independently represent an alkyl group having 1 to 5 carbon atoms. In addition, in formula (13), ^R31 and ^R32 represent a hydrogen atom or a protecting group for an amino group.
Here, examples of the protecting group for the amino group represented by R ³¹ and R ³² include, but are not limited to, a benzyl group, a nitrobenzyl group, a CBz group (benzyloxycarbonyl group), a Boc group (tert-butoxycarbonyl group), and an Fmoc group (9-fluorenylmethyloxycarbonyl group).

The method for synthesizing the diamine compound of the present invention includes a method of reacting an isocyanate compound of formula (12) with an amine compound or alcohol compound represented by H-Z ² -X ² -N ⁰ (Z ² represents -O- or -NH-, X ² represents a divalent organic group, and N ⁰ represents a group that can be converted into an amino group. Specific examples and preferred structures of X ² are the same as those shown in the explanation of formula [1]), or a method of converting an amine compound of formula (13) into an active amine compound, if necessary through a step such as deprotection, to obtain an acid chloride compound represented by Cl-C(═O)-X ² -N ⁰ (X ² represents a divalent organic group, and N ⁰ represents a group that can be converted into an amino group), an isocyanate compound represented by OCN-X ² -N ⁰ (X ² represents a divalent organic group, and N ⁰ represents a group that can be converted into an amino group), or an isocyanate compound represented by Cl-C(═O)-O-X ² The method includes a second step of reacting a chloroformic acid derivative represented by -N ⁰ (X ² represents a divalent organic group, and N ⁰ represents a group that can be converted into an amino group) to obtain a diamine compound precursor represented by the following formula (14). N ⁰ is a group that can be converted into an amino group, and examples of such a group include a nitro group or a protected amino group. The protected amino group is not particularly limited as long as it is a group that can be easily deprotected and converted into an amino group, and examples of such a protected amino group include a group in which one hydrogen atom of an amino group is substituted with a benzyl group, a nitrobenzyl group, a CBz group (benzyloxycarbonyl group), a Boc group (tert-butoxycarbonyl group), or an Fmoc group (9-fluorenylmethyloxycarbonyl group).

Ｎ^０はニトロ基又は保護アミノ基を表す。

N ⁰ represents a nitro group or a protected amino group.

Specific examples of the compound of formula (14) include the following formulas (15) to (17). Here, the compound of formula (15) is produced by reacting the isocyanate compound of formula (12) with a compound having an amino group and a nitro group or a protected amino group (for example, a compound represented by H ₂ N-X ² -N ⁰ ). The compound of formula (16) is produced by reacting the isocyanate compound of formula (12) with a compound having a hydroxyl group and a nitro group or a protected amino group (for example, a compound represented by HO-X ² -N ⁰ ). The compound of formula (17) is produced by reacting the diamide compound of formula (13) with an acid chloride compound having a nitro group or a protected amino group, or a carboxylic acid having a nitro group or a protected amino group in the presence of a suitable condensing agent.

The method for synthesizing a diamine compound of the present invention includes a third step of converting the nitro group or the protected amino group of the compound of formula (14) to an amino group, thereby producing a diamine compound of formula (1). In the present invention, the first and second steps can be carried out separately, but the first and second steps can also be carried out consecutively or as one step.

<Specific Polymer A>
The specific polymer A of the present invention is at least one polymer selected from a polyimide precursor containing a structural unit represented by the following formula [3-1] and a polyimide which is an imide compound thereof, and is obtained by reacting a diamine represented by the above formula [1] with a tetracarboxylic acid derivative.

式において、Ｒ^３及びＲ^４は、それぞれ独立して水素原子又は炭素原子数１～５のアルキル基を表す。炭素原子数１～５のアルキル基としては、例えば、メチル基、エチル基、ｎ－プロピル基、イソプロピル基、ｎ－ブチル基、イソブチル基、ｔ－ブチル基、ｎ－ペンチル基、イソペンチル基、ｓ－ペンチル基、ｔ－ペンチル基等が挙げられ、炭素原子数２～５のアルケニル基としては、例えば、ビニル基、アリル基、１－プロペニル基、１－ブテニル基、２－ブテニル基、３－ブテニル基、１－ペンテニル基、２－ペンテニル基、３－ペンテニル基、４－ペンテニル基等が挙げられ、炭素原子数２～５のアルキニル基としては、例えば、エチニル基、１－プロピニル基、２－プロピニル（プロパルギル）基、３－ブチニル基、ペンチニル基等が挙げられる。これらの中で、加熱時のイミド化反応の進行のし易さの観点から、Ｒ^３及びＲ^４は水素原子、メチル基又はエチル基が好ましく、水素原子又はメチル基がより好ましい。

In the formula, R ³ and R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group having 1 to 5 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, an n-pentyl group, an isopentyl group, an s-pentyl group, and a t-pentyl group. Examples of the alkenyl group having 2 to 5 carbon atoms include a vinyl group, an allyl group, a 1-propenyl group, a 1-butenyl group, a 2-butenyl group, a 3-butenyl group, a 1-pentenyl group, a 2-pentenyl group, a 3-pentenyl group, and a 4-pentenyl group. Examples of the alkynyl group having 2 to 5 carbon atoms include an ethynyl group, a 1-propynyl group, a 2-propynyl (propargyl) group, a 3-butynyl group, and a pentynyl group. Among these, from the viewpoint of ease of progression of the imidization reaction during heating, ^R3 and ^R4 are preferably a hydrogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom or a methyl group.

^V0 is a tetravalent organic group derived from a tetracarboxylic acid derivative, and its structure is not particularly limited. ^V0 is appropriately selected depending on the degree of required properties such as the solubility of the polymer in a solvent, the coatability of the liquid crystal alignment agent, the alignment of the liquid crystal when formed into a liquid crystal alignment film, the voltage holding rate, the accumulated charge, etc., and may be one type or two or more types mixed in the same polymer.

Examples of the tetracarboxylic acid derivative include tetracarboxylic acid dianhydrides, tetracarboxylic acid dihalide compounds, tetracarboxylic acid dialkyl ester compounds, and tetracarboxylic acid dialkyl ester dihalide compounds. For example, an example of the tetracarboxylic acid dianhydride from which V ⁰ in the formula [3-1] is derived is a compound represented by the following formula [5].

式［３－１］及び式［５］におけるＶ^０の具体例としては、前記式［１］においてＹ^１の具体例として示した脂環式構造を有する四価の有機基、及び下記式［Ｖ－１］～［Ｖ－１６］に示される四価の有機基などを挙げることができるが、本発明はこれらに限定されるものではない。

Specific examples of ^V0 in the formula [3-1] and the formula [5] include the tetravalent organic groups having an alicyclic structure shown as specific examples of ^Y1 in the formula [1] above, and the tetravalent organic groups shown in the following formulas [V-1] to [V-16], but the present invention is not limited thereto.

The specific polymer A of the present invention may contain a structural unit other than the structural unit represented by the formula [3-1]. For example, an example of a structural unit other than the formula [3-1] is a structural unit represented by the following formula [3-2].

式中、Ｖ^０は、テトラカルボン酸誘導体由来の四価の有機基であり、Ｗ^２は、前記式［２－１］で表される構造以外の二価の有機基であり、Ｒ³、Ｒ^４、Ａ^１及びＡ^２は、それぞれ独立して水素原子又は炭素原子数１～５のアルキル基を表す。
Ｖ^０、Ｒ³、Ｒ^４の具体例及び好ましい構造は、それぞれ式［３－１］と同じものを挙げることができる。ただし、本発明の実施形態において、式［３－１］で表される構造単位と式［３－２］で表される構造単位とでＶ^０、Ｒ³、Ｒ^４の具体的構造が必ずしも同じである必要は無い。
Ａ^１及びＡ^２における炭素原子数１～５のアルキル基の具体例は、Ｒ^３及びＲ^４で示した具体例を挙げることができる。液晶配向性の観点から、Ａ^１及びＡ^２は水素原子又はメチル基が好ましい。

In the formula, ^V0 is a tetravalent organic group derived from a tetracarboxylic acid derivative, ^W2 is a divalent organic group other than the structure represented by formula [2-1], and ^R3 , ^R4 , ^A1 , and ^A2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.
Specific examples and preferred structures of V ⁰ , R ³ , and R ⁴ are the same as those in formula [3-1]. However, in the embodiment of the present invention, the specific structures of V ⁰ , R ³ , and R ⁴ in the structural unit represented by formula [3-1] and the structural unit represented by formula [3-2] are not necessarily the same.
Specific examples of the alkyl group having 1 to 5 carbon atoms in A ¹ and A ² include the specific examples shown for R ³ and R ^4. From the viewpoint of liquid crystal alignment, A ¹ and A ² are preferably a hydrogen atom or a methyl group.

^W2 is a divalent organic group derived from a diamine other than the diamine represented by the formula [1] (hereinafter, also referred to as other diamine), and its structure is not particularly limited as long as it is a divalent organic group other than the structure represented by the formula [2-1]. Examples of other diamines include compounds represented by the following formula [2-2].

Ｗ^２、Ａ^１及びＡ^２は、それぞれ式［３－２］と同じことを表す。

W ² , A ¹ and A ² each have the same meaning as in formula [3-2].

Specific examples of the structure of ^W2 are given below, but the present invention is not limited to these.

The Boc group in the formula represents the tert-butoxycarbonyl group shown below.

When the specific polymer A contains structural units of the formula [3-2] in addition to the structural units of the formula [3-1], the structural units of the formula [3-1] are preferably 10 mol % or more, more preferably 20 mol % or more, and particularly preferably 30 mol % or more, of the total of the structural units of the formula [3-1] and the structural units of the formula [3-2].

When a liquid crystal alignment film is obtained from a liquid crystal alignment agent containing the polymer, the molecular weight of the specific polymer A is preferably a weight average molecular weight of 2,000 to 500,000, more preferably 5,000 to 300,000, and even more preferably 10,000 to 100,000, measured by GPC (Gel Permeation Chromatography) method, taking into consideration the strength of the coating film (liquid crystal alignment film), the workability during coating film formation, and the uniformity of the coating film.

<Method of Producing Polymer>
Next, a main method for producing the polymer contained in the liquid crystal alignment agent of the present invention will be described. Note that the method described below is a production example, and is not limited thereto.

For example, when the specific polymer A is a polyamic acid, the polymer is obtained by reacting a tetracarboxylic acid derivative, tetracarboxylic dianhydride, with a diamine component. A known synthesis method can be used to obtain a polyamic acid by this reaction. The synthesis method is a method in which a tetracarboxylic dianhydride is reacted with a diamine component in an organic solvent. This method is advantageous in that it proceeds relatively easily in an organic solvent and does not produce by-products.

The organic solvent used in the above reaction is not particularly limited as long as it dissolves the produced polyamic acid (polymer), and examples thereof include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methylcaprolactam, dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfone, hexamethylsulfoxide, γ-butyrolactone, isopropyl alcohol, methoxymethylpentanol, dipentene, ethyl amyl ketone, methyl nonyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, methyl cellosolve, ethyl cellosolve, and methyl cellosolve acetate. , ethyl cellosolve acetate, butyl carbitol, ethyl carbitol, ethylene glycol, ethylene glycol monoacetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, propylene glycol, propylene glycol monoacetate, propylene glycol monomethyl ether, propylene glycol-tert-butyl ether, dipropylene glycol monomethyl ether, diethylene glycol, diethylene glycol monoacetate, diethylene glycol dimethyl ether, dipropylene glycol monoacetate monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol Cholesterol monoethyl ether, dipropylene glycol monoacetate monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoacetate monopropyl ether, 3-methyl-3-methoxybutyl acetate, tripropylene glycol methyl ether, 3-methyl-3-methoxybutanol, diisopropyl ether, ethyl isobutyl ether, diisobutylene, amyl acetate, butyl butyrate, butyl ether, diisobutyl ketone, methylcyclohexene, propyl ether, dihexyl ether, dioxane, n-hexane, n-pentane, n-octane, diethyl ether, cyclohexanone, ethylene carbonate ester, propylene carbonate, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, diglyme, 4-hydroxy-4-methyl-2-pentanone, 3-methoxy-N,N-dimethylpropanamide, 3-ethoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, etc. These may be used alone or in combination. In addition, even if the solvent does not dissolve the polyamic acid (polymer), it may be mixed with the organic solvent and used as long as the generated polyamic acid does not precipitate. In particular, moisture in the organic solvent inhibits the polymerization reaction and can even cause the generated polyamic acid to hydrolyze, so it is preferable to use an organic solvent that has been dehydrated and dried as much as possible.

When reacting the tetracarboxylic dianhydride with the diamine component in an organic solvent, a method of stirring a solution in which the diamine component is dispersed or dissolved in an organic solvent and adding the tetracarboxylic dianhydride as is or after being dispersed or dissolved in an organic solvent, a method of adding the diamine component to a solution in which the tetracarboxylic dianhydride is dispersed or dissolved in an organic solvent, a method of adding the tetracarboxylic dianhydride and the diamine component alternately, etc., may be used, and any of these methods may be used. In addition, when the tetracarboxylic dianhydride or the diamine component is composed of multiple types of compounds, they may be reacted in a pre-mixed state, or may be reacted individually in sequence, and further low molecular weight compounds that have been reacted individually may be mixed and reacted to form a high molecular weight compound.

The polycondensation temperature can be selected from the range of -20°C to 150°C, but is preferably in the range of -5°C to 100°C. The polycondensation reaction can be carried out at any concentration, but if the concentration is too low it becomes difficult to obtain a polymer with a high molecular weight, and if the concentration is too high the viscosity of the reaction solution becomes too high, making uniform stirring difficult. Therefore, the total concentration of the tetracarboxylic dianhydride and diamine components in the reaction solution is preferably 1 to 50% by mass, more preferably 5 to 30% by mass. The reaction may be carried out at a high concentration in the early stages, and then an organic solvent may be added.

In the polymerization reaction of polyamic acid, the ratio of the total number of moles of tetracarboxylic dianhydride to the total number of moles of diamine components (total number of moles of tetracarboxylic dianhydride/total number of moles of diamine components) is preferably 0.8 to 1.2. As with normal polycondensation reactions, the closer this molar ratio is to 1.0, the larger the molecular weight of the polyamic acid produced.

When the specific polymer A is a polyamic acid ester, it can be obtained by reacting a tetracarboxylic acid diester dichloride with a diamine component, or by reacting a tetracarboxylic acid diester with a diamine component in the presence of a suitable condensing agent or base. Alternatively, it can be obtained by synthesizing a polyamic acid in advance by the above method and esterifying the carboxylic acid in the amic acid using a polymer reaction.

Specifically, for example, a polyamic acid ester can be synthesized by reacting a tetracarboxylic acid diester dichloride with a diamine in the presence of a base and an organic solvent at -20°C to 150°C, preferably 0°C to 50°C, for 30 minutes to 24 hours, preferably 1 hour to 4 hours.

As the base, pyridine, triethylamine, 4-dimethylaminopyridine, etc. can be used, but pyridine is preferred because the reaction proceeds mildly. The amount of base added is preferably 2 to 4 times the molar amount of tetracarboxylic acid diester dichloride, from the viewpoints that it is an amount that can be easily removed and that it is easy to obtain a high molecular weight product.

When the tetracarboxylic acid diester and the diamine component are polycondensed in the presence of a condensing agent, the base that can be used may be triphenyl phosphite, dicyclohexylcarbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N,N'-carbonyldiimidazole, dimethoxy-1,3,5-triazinylmethylmorpholinium, O-(benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium tetrafluoroborate, O-(benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate, (2,3-dihydro-2-thioxo-3-benzoxazolyl)diphenylphosphonate, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)4-methoxymorpholinium chloride n-hydrate, or the like.

In the method using the above condensing agent, the reaction proceeds efficiently by adding a Lewis acid as an additive. As the Lewis acid, lithium halides such as lithium chloride and lithium bromide are preferred. The amount of Lewis acid added is preferably 0.1 to 1.0 times the molar amount of the diamine or tetracarboxylic acid diester to be reacted.

The solvent used in the above reaction can be the same as that used in synthesizing the polyamic acid shown above, but N-methyl-2-pyrrolidone and γ-butyrolactone are preferred in terms of the solubility of the monomer and polymer, and these may be used alone or in combination of two or more. From the viewpoint of preventing precipitation of the polymer and facilitating the production of a high molecular weight product, the total concentration of the tetracarboxylic acid derivative such as tetracarboxylic acid diester dichloride or tetracarboxylic acid diester and the diamine component in the reaction solution is preferably 1% by mass to 30% by mass, more preferably 5% by mass to 20% by mass. In addition, in order to prevent hydrolysis of the tetracarboxylic acid diester dichloride, it is preferable that the solvent used in the synthesis of the polyamic acid ester is as dehydrated as possible, and it is preferable to use a nitrogen atmosphere to prevent the inclusion of outside air.

When the specific polymer A is a polyimide, it is obtained by ring-closing imidization of a polyimide precursor, such as a polyamic acid or a polyamic acid ester. In this polyimide, the ring-closing rate (imidization rate) does not necessarily have to be 100%, and can be adjusted as desired depending on the application or purpose.

Methods for imidizing polyamic acid include thermal imidization, in which a solution of polyamic acid is heated as is, and catalytic imidization, in which a catalyst is added to a solution of polyamic acid.

When thermally imidizing polyamic acid in a solution, the temperature is 100°C to 400°C, preferably 120°C to 250°C, and it is preferable to carry out the imidization while removing the water produced by the imidization reaction from the system.

The catalytic imidization of polyamic acid can be carried out by adding a basic catalyst and an acid anhydride to a solution of polyamic acid and stirring at -20°C to 250°C, preferably 0°C to 180°C. The amount of the basic catalyst is 0.5 to 30 molar times, preferably 2 to 20 molar times, the amount of the amide acid group, and the amount of the acid anhydride is 1 to 50 molar times, preferably 3 to 30 molar times, the amount of the amide acid group. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc., and among them, pyridine is preferred because it has a suitable basicity for promoting the reaction. Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, pyromellitic anhydride, etc., and among them, acetic anhydride is preferred because it makes purification after the reaction easy. The imidization rate by catalytic imidization can be controlled by adjusting the amount of the catalyst, the reaction temperature, and the reaction time.

As mentioned above, polyimide can also be obtained by heating polyamic acid ester at high temperatures to promote de-alcoholization and ring closure.

When recovering the polyamic acid, polyamic acid ester, or polyimide produced from a polyimide precursor such as polyamic acid or polyamic acid ester, or a reaction solution of polyimide, the reaction solution may be poured into a poor solvent to cause precipitation. Examples of poor solvents used for precipitation include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, and water. The polyimide precursor or polyimide precipitated by pouring into a poor solvent can be recovered by filtration, and then dried at room temperature or by heating under normal or reduced pressure. The polyimide precursor or polyimide precipitated and recovered can be redissolved in an organic solvent and the reprecipitation and recovery operation repeated 2 to 10 times to reduce impurities in the polymer. Examples of poor solvents in this case include alcohols, ketones, and hydrocarbons. It is preferable to use three or more poor solvents selected from these because the efficiency of purification is further improved.

The polymer of the present invention thus obtained can be dissolved in a specific organic solvent and used as a liquid crystal alignment agent. This liquid crystal alignment agent is used in a liquid crystal alignment film that controls the alignment of liquid crystal molecules in a liquid crystal layer in a liquid crystal display element. The liquid crystal alignment agent containing the polymer of the present invention will be described below.

<Liquid crystal alignment agent>
The liquid crystal aligning agent of the present invention contains at least one polymer selected from the specific polymer A.

However, the polymers contained in the liquid crystal aligning agent of the present invention may all be the specific polymer A of the present invention, or may contain two or more different structures of the specific polymer A of the present invention. Alternatively, in addition to the specific polymer A of the present invention, other polymers may be contained. Examples of the other polymers include polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivatives, polyacetal, polystyrene or derivatives thereof, poly(styrene-phenylmaleimide) derivatives, poly(meth)acrylates, etc.
Among them, polyamic acid is preferable. An example of the polyamic acid as the other polymer is a polyamic acid consisting of a structural unit in which R ³ and R ⁴ are both hydrogen atoms in the formula [3-2]. In particular, it is preferable to mix a polyamic acid having a nitrogen atom bonded to a nitrogen-containing aromatic heterocycle or aromatic group in W ² of the formula [3-2] with the liquid crystal aligning agent of the present invention from the viewpoint of improving the relaxation speed of the accumulated charge of a liquid crystal display element produced using the liquid crystal aligning agent of the present invention.

When the liquid crystal aligning agent of the present invention contains other polymers, the ratio of the polymer of the present invention to the total polymer components is preferably 5% by mass or more, and an example of this is 5 to 95% by mass. The ratio of the polymer of the present invention can be appropriately selected depending on the properties of the liquid crystal aligning agent and the liquid crystal alignment film.

The liquid crystal aligning agent of the present invention is used to prepare a liquid crystal alignment film, and generally takes the form of a coating liquid from the viewpoint of forming a uniform thin film. The liquid crystal aligning agent of the present invention is also preferably a coating liquid containing the above-mentioned polymer component and an organic solvent that dissolves this polymer component. In this case, the concentration of the polymer in the liquid crystal aligning agent can be appropriately changed depending on the thickness of the coating film to be formed. From the viewpoint of forming a uniform and defect-free coating film, it is preferable that the concentration is 1% by mass or more, and from the viewpoint of storage stability of the solution, it is preferable that the concentration is 10% by mass or less. A particularly preferable polymer concentration is 2 to 8% by mass.

The organic solvent contained in the liquid crystal alignment agent of the present invention is not particularly limited as long as it is an organic solvent that dissolves the polymer. Specific examples thereof include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethylsulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, and 4-hydroxy-4-methyl-2-pentanone. Among them, it is preferable to use N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and γ-butyrolactone. The organic solvents exemplified here may be used alone or in combination. Furthermore, even if the solvent does not dissolve the polymer, it may be mixed with an organic solvent to the extent that the resulting polymer does not precipitate.

In addition, the organic solvent contained in the liquid crystal alignment agent is generally a mixed solvent containing the above-mentioned solvent and a solvent that improves the coatability and surface smoothness of the coating film when applying the liquid crystal alignment agent, and such a mixed solvent is preferably used in the liquid crystal alignment agent of the present invention. Specific examples of the organic solvent to be used in combination are listed below, but are not limited to these.

For example, ethanol, isopropyl alcohol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, tert-pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-ethyl 1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2, 3-butanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, dipropyl ether, dibutyl ether, dihexyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-butoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 2-pentanone, 3-pentanone, 2-hexanone, 2-heptanone, 4-heptanone, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate ester, ethylene carbonate, 2-(methoxymethoxy)ethanol, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, 2-(hexyloxy)ethanol, furfuryl alcohol, diethylene glycol, propylene glycol, propylene glycol monobutyl ether, 1-(butoxyethoxy)propanol, propylene glycol monomethyl ether acetate, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, ethylene glycol di Examples of solvents include acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, methyl lactate ester, ethyl lactate ester, n-propyl lactate ester, n-butyl lactate ester, and isoamyl lactate ester.

In addition to the above-mentioned solvents, the solvents represented by the following formulas [S-1] to [S-3] can be used.

式［Ｓ－１］及び式［Ｓ－２］において、Ｒ^２８及びＲ^２９は、炭素原子数１～３のアルキル基を示す。炭素原子数１～３のアルキル基としては、例えば、メチル基、エチル基、ｎ－プロピル基、イソプロピル基等が挙げられる。また、式［Ｓ－３］において、Ｒ^３０は、炭素原子数１～４のアルキル基を示す。炭素原子数１～４のアルキル基としては、例えば、メチル基、エチル基、ｎ－プロピル基、イソプロピル基、ｎ－ブチル基、イソブチル基、ｓｅｃ－ブチル基、ｔｅｒｔ－ブチル基等が挙げられる。

In formula [S-1] and formula [S-2], R ²⁸ and R ²⁹ represent an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. In addition, in formula [S-3], R ³⁰ represents an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group.

Among the organic solvents used in combination, it is preferable to use 1-hexanol, cyclohexanol, 1,2-ethanediol, 1,2-propanediol, propylene glycol monobutyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monobutyl ether or dipropylene glycol dimethyl ether. The type and content of such solvents are appropriately selected depending on the coating device, coating conditions, coating environment, etc. of the liquid crystal alignment agent.

These solvents preferably account for 20% to 99% by mass of the total solvent contained in the liquid crystal alignment agent. Of these, 20% to 90% by mass is more preferable. More preferably, it is 20% to 70% by mass.

The liquid crystal aligning agent of the present invention may additionally contain components other than the polymer component and the organic solvent. Examples of such additional components include adhesion aids for improving the adhesion between the liquid crystal alignment film and the substrate or between the liquid crystal alignment film and the sealant, crosslinking agents for increasing the strength of the liquid crystal alignment film, and dielectrics and conductive substances for adjusting the dielectric constant and electrical resistance of the liquid crystal alignment film. Specific examples of these additional components are as disclosed in various known documents related to liquid crystal aligning agents, but examples include the components disclosed in paragraphs [0105] to [0116] of WO 2015/060357.

<Liquid crystal alignment film>
The liquid crystal alignment film of the present invention is obtained from the liquid crystal alignment agent described above. One example of a method for obtaining a liquid crystal alignment film from a liquid crystal alignment agent is to apply a liquid crystal alignment agent in the form of a coating liquid to a substrate, dry, and bake the resulting film, and then perform an alignment treatment by a rubbing treatment method or a photo-alignment treatment method.

The substrate on which the liquid crystal alignment agent of the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and in addition to glass substrates and silicon nitride substrates, plastic substrates such as acrylic substrates and polycarbonate substrates can also be used. In this case, it is preferable to use a substrate on which an ITO electrode for driving the liquid crystal is formed in terms of simplifying the process. In addition, in a reflective liquid crystal display element, an opaque material such as a silicon wafer can be used for only one substrate, and in this case, a light-reflecting material such as aluminum can also be used for the electrode.

The method for applying the liquid crystal alignment agent is not particularly limited, but in industry, screen printing, offset printing, flexographic printing, inkjet printing, etc. are commonly used. Other application methods include the dip method, roll coater method, slit coater method, spinner method, spray method, etc., and these may be used depending on the purpose.

After the liquid crystal alignment agent is applied to the substrate, it is baked at 50 to 300°C, preferably 80 to 250°C, using a heating means such as a hot plate, hot air circulation oven, or infrared oven to evaporate the solvent and form a coating film (liquid crystal alignment film). The thickness of the coating film formed after baking is preferably 5 nm to 300 nm, more preferably 10 nm to 100 nm, since if it is too thick, it is disadvantageous in terms of power consumption of the liquid crystal display element, and if it is too thin, the reliability of the liquid crystal display element may decrease. When aligning the liquid crystal horizontally or tilted, the coating film after baking is treated by rubbing or exposure to polarized ultraviolet light, etc.

After the liquid crystal alignment agent is applied to the substrate, the solvent is evaporated and the substrate is baked using a heating means such as a hot plate, a heat circulation oven, or an IR (infrared) oven. The temperature and time for the drying and baking process after the liquid crystal alignment agent is applied can be selected as desired. Typically, the substrate is baked at 50°C to 120°C for 1 to 10 minutes to sufficiently remove the contained solvent, and then baked at 150°C to 300°C for 5 to 120 minutes.

The liquid crystal alignment film of the present invention is suitable as a liquid crystal alignment film for in-plane switching type liquid crystal display elements such as IPS type and FFS type, and is particularly useful as a liquid crystal alignment film for FFS type liquid crystal display elements.

<Liquid crystal display element>
The liquid crystal display element of the present invention is provided with the above-mentioned liquid crystal alignment film, and is obtained by preparing a substrate with a liquid crystal alignment film obtained from the above-mentioned liquid crystal alignment agent, and then preparing a liquid crystal cell by a known method, and using the liquid crystal cell to form an element. For example, the liquid crystal display element is provided with a liquid crystal cell having two substrates arranged to face each other, a liquid crystal layer provided between the substrates, and a liquid crystal alignment film formed by the liquid crystal alignment agent of the present invention provided between the substrates and the liquid crystal layer.

The substrate used in the liquid crystal display element of the present invention is not particularly limited as long as it is a highly transparent substrate, but is usually a substrate on which a transparent electrode for driving the liquid crystal is formed. Specific examples include the same substrates as those described above for the liquid crystal alignment film.

The liquid crystal alignment film is formed by applying the liquid crystal alignment agent of the present invention onto the substrate and then baking it, as described above in detail.

The liquid crystal material constituting the liquid crystal layer of the liquid crystal display element of the present invention is not particularly limited, and examples thereof include nematic liquid crystal and smectic liquid crystal, among which nematic liquid crystal is preferred, and either positive type liquid crystal material or negative type liquid crystal material may be used. Specifically, for example, MLC-2003, MLC-6608, MLC-6609, MLC-3019, MLC-2041, MLC-7026-100, etc. manufactured by Merck can be used.

Specifically, transparent glass substrates are prepared, and a common electrode is provided on one substrate, and a segment electrode is provided on the other substrate. These electrodes may be, for example, ITO electrodes, and are patterned so as to display a desired image. Next, an insulating film is provided on each substrate so as to cover the common electrode and the segment electrode. The insulating film may be, for example, a film made of SiO ₂ -TiO ₂ formed by the sol-gel method. Next, a liquid crystal alignment film is formed on each substrate under the above-mentioned conditions.

Next, a UV-curable sealant, for example, is placed at a predetermined location on one of the two substrates on which the liquid crystal alignment film is formed, and liquid crystal is placed at several predetermined locations on the liquid crystal alignment film surface. The other substrate is then attached and pressed so that the liquid crystal alignment film faces the other substrate, spreading the liquid crystal over the front surface of the liquid crystal alignment film. The entire surface of the substrate is then irradiated with UV light to cure the sealant, thereby obtaining a liquid crystal cell.

Alternatively, as a process after forming a liquid crystal alignment film on the substrates, when placing a sealant at a specified location on one of the substrates, an opening is provided that can be filled with liquid crystal from the outside, and after bonding the substrates together without placing liquid crystal, liquid crystal material is injected into the liquid crystal cell through the opening provided in the sealant, and this opening is then sealed with an adhesive to obtain a liquid crystal cell. The liquid crystal material can be injected by a vacuum injection method or a method utilizing capillary action in the atmosphere.

In any of the above methods, in order to secure a space in the liquid crystal cell for filling with the liquid crystal material, it is preferable to take measures such as providing columnar protrusions on one of the substrates, dispersing spacers on one of the substrates, mixing spacers into the sealing agent, or a combination of these.

Next, polarizing plates are installed. Specifically, it is preferable to attach a pair of polarizing plates to the surfaces of the two substrates opposite the liquid crystal layer.

The liquid crystal alignment film and liquid crystal display element of the present invention are not limited to the above description as long as they use the liquid crystal alignment agent of the present invention, and may be produced by other known methods. The process of obtaining a liquid crystal display element from a liquid crystal alignment agent is disclosed in, for example, paragraphs [0074] to [0081] of JP 2015-135393 A, as well as in many other documents.

As described above, the liquid crystal display element produced using the liquid crystal alignment agent of the present invention has excellent reliability and can be suitably used in large-screen, high-definition liquid crystal televisions, etc.

The present invention will be explained in more detail below with reference to the following examples. However, the present invention should not be construed as being limited to these examples.

The general-purpose solvents used to dissolve the materials used in the examples and the chemical structural formulas of the monomers that are the raw materials for the materials used in the examples are as follows:
NMP: N-methyl-2-pyrrolidone GBL: gamma butyrolactone BCS: butyl cellosolve DC-1: 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride DC-2: bicyclo[3,3,0]octane-2,4,6,8-tetracarboxylic dianhydride DC-3: 1,2,3,4-cyclobutane tetracarboxylic dianhydride DC-4: pyromellitic anhydride DC-5: tetrahydro-1H-5,9-methanopyrano[3,4-d]oxepin-1,3,6,8(4H)-tetranon DA-1: dimethyl 2,4-bis((4-aminobenzamido)cyclobutane-1,3-dicarboxylate DA-2: dimethyl 2,4-bis((4-aminophenyl)carbamoyl)cyclobutane-1,3-dicarboxylate DA-3: 1,2-bis(4-aminophenoxy)ethane DA-4: 1,2-bis(4-aminophenoxy)hexane DA-5: 1-tertbutoxycarbonyl-1,3-bis(4-aminophenethyl)urea DA-6: Dimethyl 2,4-bis((4-aminophenyl)ureido)cyclobutane-1,3-dicarboxylate

The synthesis methods for each material used in the examples and the methods for measuring each property are as follows:

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

[Molecular weight]
The molecular weight was measured by a GPC (gel permeation chromatography) device, and the number average molecular weight (Mn) and weight average molecular weight (Mw) were calculated as values converted into polyethylene glycol and polyethylene oxide.

GPC apparatus: Shodex (GPC-101), column: Shodex (KD803, KD805 in series), column temperature: 50°C, eluent: N,N-dimethylformamide (additives: lithium bromide hydrate (LiBr.H ₂ O) 30 mmol/L, phosphoric acid anhydrous crystal (o-phosphoric acid) 30 mmol/L, tetrahydrofuran (THF) 10 ml/L), flow rate: 1.0 ml/min. Standard samples for creating calibration curves: TSK standard polyethylene oxide (weight average molecular weight (Mw) about 900,000, 150,000, 100,000, 30,000) manufactured by Tosoh Corporation, and polyethylene glycol (peak top molecular weight (Mp) about 12,000, 4,000, 1,000) manufactured by Polymer Laboratory. In order to avoid overlapping peaks, two samples, a mixture of four types of 900,000, 100,000, 12,000, and 1,000, and a mixture of three types of 150,000, 30,000, and 4,000, were measured separately.

[Measurement of imidization rate]
20 mg of polyimide powder was placed in an NMR sample tube (NMR sampling tube standard, φ5 (Kusano Scientific Co., Ltd.)), deuterated dimethyl sulfoxide (DMSO-d6, 0.05% TMS (tetramethylsilane) mixture) (0.53 ml) was added, and the mixture was completely dissolved by applying ultrasonic waves. This solution was measured for proton NMR at 500 MHz using an NMR measurement device (JNW-ECA500) (JEOL Datum Co., Ltd.). The imidization rate was calculated by the following formula using a proton derived from a structure that does not change before and after imidization as a reference proton and the integrated value of the peak of this proton and the integrated value of the proton peak derived from the NH group of the amic acid that appears around 9.5 ppm to 11.0 ppm. However, the imidization rate calculated by the following formula is a value when the proton peak derived from the NH group contained in the monomer that is not involved in the polymerization reaction is excluded.

Imidation rate (%) = (1-α x/y) x 100

In the above formula, x is the integrated value of the proton peak derived from the NH group of the amide acid, y is the integrated value of the peak of the reference proton, and α is the ratio of the number of reference protons to one NH group proton of the amide acid in the case of polyamide acid (imidization rate 0%).

[Preparation of FFS mode liquid crystal cell]
A liquid crystal cell having a fringe field switching (FFS) mode liquid crystal display element configuration is fabricated.

First, a substrate with electrodes was prepared. The substrate was a glass substrate with a size of 30 mm x 35 mm and a thickness of 0.7 mm. An ITO electrode with a solid pattern was formed on the substrate as the first layer, which constituted the counter electrode. A SiN (silicon nitride) film formed by CVD was formed as the second layer on the first layer of the counter electrode. The thickness of the second layer of the SiN film was 500 nm, and it functions as an interlayer insulating film. A comb-shaped pixel electrode formed by patterning the ITO film as the third layer was arranged on the second layer of the SiN film, forming two pixels, a first pixel and a second pixel. The size of each pixel was about 10 mm in length and about 5 mm in width. At this time, the first layer of the counter electrode and the third layer of the pixel electrode were electrically insulated by the action of the second layer of the SiN film.

The pixel electrode in the third layer has a comb-like shape consisting of multiple electrode elements arranged in a L-shape with a bent central portion. The width of each electrode element in the short direction is 3 μm, and the distance between the electrode elements is 6 μm. Because the pixel electrodes forming each pixel are arranged in multiple L-shaped electrode elements arranged in a L-shape with a bent central portion, the shape of each pixel is not rectangular, but has a bold L-shape that is bent in the center like the electrode elements. Each pixel is divided into upper and lower parts by the central bend, and has a first region above the bent part and a second region below the bent part.

Comparing the first and second regions of each pixel, the electrode elements of the pixel electrodes that compose them are formed in different directions. That is, based on the polarization direction of linearly polarized ultraviolet (LPUV) light of the liquid crystal alignment film described below, the electrode elements of the pixel electrodes in the first region of the pixel are formed to form an angle of +80° (clockwise), and the electrode elements of the pixel electrodes in the second region of the pixel are formed to form an angle of -80° (counterclockwise). That is, the first and second regions of each pixel are configured so that the directions of rotational movement (in-plane switching) of the liquid crystal within the substrate surface induced by application of a voltage between the pixel electrode and the opposing electrode are opposite to each other.

Next, the liquid crystal alignment agent was filtered through a 1.0 μm filter, and then spin-coated onto the above-prepared electrode-attached substrate and a glass substrate having a columnar spacer with a height of 4 μm and an ITO film formed on the back side. The substrate was dried on a hot plate at 80°C for 2 minutes, and the coating surface was irradiated with linearly polarized ultraviolet light with a wavelength of 254 nm and an extinction ratio of 26:1 or more through a polarizing plate, and then baked in a hot air circulating oven at 230°C for 30 minutes to form a coating film with a thickness of 100 nm. The above two substrates were combined into a set, a sealant was printed on the substrate, and the other substrate was attached so that the liquid crystal alignment film surfaces faced each other and the alignment direction was 0°, and then the sealant was cured to prepare an empty cell. Liquid crystal MLC-3019 (manufactured by Merck) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS-driven liquid crystal cell.

[Afterimage evaluation]
The polarizers were arranged so that the angle between the two polarizers was 90°, and this state was called crossed Nicol. The liquid crystal cell for evaluating the afterimage described above was arranged between these two polarizers, and the orientation state of the injected liquid crystal was observed. The specific evaluation method was determined by observing whether the injected liquid crystal was uniformly oriented in the liquid crystal cell. If the liquid crystal in the liquid crystal cell was not uniformly oriented, bright lines were observed, and a clear bright/dark field could not be observed depending on the angle between the two polarizers and the orientation direction of the liquid crystal. On the other hand, if the liquid crystal in the liquid crystal cell was uniformly oriented, bright lines were not observed, and a clear bright/dark field could be observed depending on the angle between the two polarizers and the orientation direction of the liquid crystal. As the evaluation criteria, if the above-mentioned bright lines were not observed at all and a clear bright/dark field was observed, it was rated as "good", if a clear bright/dark field was observed but only a slight bright line was observed, it was rated as "fair", and if a clear bright/dark field was not observed and a clear bright line was observed, it was rated as "poor".

[Display failure evaluation]
The liquid crystal cell prepared above was evaluated for display defects. The evaluation was performed by heating the liquid crystal cell prepared above in a heating oven at 60° C. for 2 weeks or more, and then observing it with a polarizing microscope (ECLIPSE E600WPOL) (manufactured by Nikon Corporation). Specifically, the liquid crystal cell was placed in a crossed Nicol position with respect to the polarizer, and observed with a polarizing microscope with a lens magnification of 5 times, and the number of confirmed bright spots was counted, and the number of bright spots less than 5 was evaluated as "good", and the number of bright spots more than 5 was evaluated as "bad".

[Liquid crystal alignment evaluation]
The alignment of the liquid crystal cell prepared above was evaluated. As an evaluation method, the liquid crystal cell was placed under a polarizing plate crossed Nicol in a state where the luminance was the smallest, and the alignment state was compared immediately after preparation and after realignment treatment (heating at 110°C for 1 hour and returning to room temperature). If no flow alignment or domains were observed immediately after preparation of the liquid crystal cell, it was marked as ◯, if flow alignment or domains disappeared by the realignment treatment, it was marked as △, and if the alignment defects were observed even after realignment, it was marked as ×.

"Monomer synthesis example"
Synthesis Example 1 Synthesis of Dimethyl 2,4-bis(3-(4-aminophenyl)ureido)cyclobutane-1,3-dicarboxylate

<First step>
Synthesis of Dimethyl 2,4-bis(3-(4-nitrophenyl)ureido)cyclobutane-1,3-dicarboxylate Bis(methoxycarbonyl)cyclobutane-1,3-dicarboxylate (100.0 g: 384.23 mmol) was weighed into a 1 L four-neck flask equipped with a nitrogen inlet tube, toluene (500.0 g) was added, triethylamine (97.2 g: 960.58 mmol) and diphenylphosphoryl azide [DPPA] (232.6 g: 845.31 mmol) were added, and the mixture was stirred at room temperature for 30 minutes under a nitrogen atmosphere, and then heated to 60° C. and reacted for another 3 hours. As the reaction proceeded, gas was generated, and it was confirmed that the generation of gas had ceased. The reaction solution was returned to room temperature, 1,4-diaza-bicyclo[2.2.2]octane[DABCO] (2.15 g: 19.21 mmol), 4-nitroaniline (116.76 g: 845.31 mmol), and tetrahydrofuran (200.0 g) were added, and the temperature was raised to 60°C again, and the reaction was carried out for 24 hours under a nitrogen atmosphere. After confirming the disappearance of the raw materials by TLC, the reaction solution was transferred to a separatory funnel. At this time, the organic layer was separated into two layers, so the lower layer was separated and poured into methanol and stirred, and a solid precipitated. This solid was collected by filtration. One of the upper layers was washed three times with 100 ml of pure water, and the organic layer was subjected to solvent distillation using a rotary evaporator, and a solid precipitated. This crude product was collected, mixed with the solid obtained above, heated and washed twice with methanol (300.0 g) (reflux: 1 hour), and vacuum dried to obtain a pale yellow solid (136.56 g: yield 67%). The structure was confirmed by nuclear magnetic resonance spectroscopy [ ¹ H-NMR (400 MHz)], and it was confirmed that it was the target product. The measurement data are shown below.

¹ H-NMR (400MHz: D6-DMSO) δ: 9.34 (s: 2H), 8.11 (q: 4H), 7.60 (q: 4H), 7.04 (d: 2H), 4.78 (q: 2H), 4.07 (m: 2H), 3.60 (s: 6H)

<Second step>
Synthesis of Dimethyl 2,4-bis(3-(4-amonophenyl)ureido)cyclobutane-1,3-dicarboxylate Dimethyl 2,4-bis(3-(4-nitro-phenyl)ureido)-cyclobutane-1,3-dicarboxylate (100.0 g: 188.52 mmol) obtained by the above operation, 10% palladium carbon (10.0 g), and sufficiently degassed N,N-dimethylformamide (500.0 g) were added to a 1 L four-neck flask, hydrogen gas was replaced, and the mixture was reacted at 60° C. for 24 hours with vigorous stirring. After confirming the disappearance of the raw materials, palladium carbon was removed by filtration in a hot state, activated carbon (30 g) was added, and the mixture was stirred at 60° C. for 3 hours, followed by hot filtration. The filtrate was poured into 1 L of methanol and stirred for a while at 10° C., whereupon a solid precipitated. The resulting solid was collected by filtration, washed twice with 300.0 g of methanol under heating, and dried in vacuum to obtain 74.5 g of the target milky white solid. The structure was confirmed by nuclear magnetic resonance spectroscopy [ ¹ H-NMR (400 MHz)], and it was confirmed that the product was the target. The measurement data are shown below.

¹ H-NMR (400MHz: D6-DMSO) δ: 8.01 (s: 4H), 6.95 (q: 4H), 6.49 (d: 2H) , 6.45 (q: 4H), 4.75 (q: 2H), 4.73 (br: 4H), 3.64 (s: 6H), 3.35 (m: 2H)

Synthesis Example 2
Synthesis of Dimethyl 2,4-bis(4-aminobenzoamide)cyclobutane-1,3-dicarboxylate

<First step>
Synthesis of Dimethyl 2,4-bis((tert-butoxycarbonyl)amino)cyclobutane-1,3-dicarboxylate Bis(methoxycarbonyl)cyclobutane-1,3-dicarboxylate (100 g, 418 mmol) was weighed into a 2 L four-neck flask equipped with a nitrogen inlet tube, and toluene (1000 g) was added. Triethylamine (92.0 g, 916 mmol) and diphenylphosphoryl azide [DPPA] (252 g, 916 mmol) were added, and the mixture was stirred at room temperature for 30 minutes under a nitrogen atmosphere, and then heated to 60° C. and reacted for an additional 3 hours. As the reaction proceeded, gas was generated, and it was confirmed that the gas generation had ceased. The reaction solution was cooled to room temperature, and 1,4-diaza-bicyclo[2.2.2]octane[DABCO] (2.35:20.9 mmol) and tert-butyl alcohol (155 g:2.09×10 ³ mmol) were added, and the temperature was raised to 80° C., and the mixture was heated and stirred for 24 hours under a nitrogen atmosphere. After the reaction was completed, the reaction solution was cooled to −20° C., and the product was recrystallized. The solid was recrystallized using ethyl acetate as a good solvent and hexane as a poor solvent, and the solid was vacuum dried to obtain the desired white solid (60.0 g:145 mmol, yield: 35%). The structure of the product was confirmed by nuclear magnetic resonance spectroscopy [ ¹ H-NMR (400 MHz)], and it was confirmed that it was the desired product. The measurement data are shown below.

¹ H-NMR (400MHz: D6-DMSO) δ: 7.40-7.38 (ss: 2H), 4.51-4.49 (q: 2H), 3.56 (s: 6H), 3.42-3.38 (q: 2H), 1.36 (s: 18H)

<Second step>
Synthesis of Dimethyl 2,4-bis(4-nitrobenzomido)cyclobutane-1,3-dicarboxylate Dimethyl 2,4-bis((tert-butoxycarbonyl)amino)cyclobutane-1,3-dicarboxylate (60.0 g: 145 mmol) obtained in the above procedure was weighed into a 2 L four-neck flask equipped with a nitrogen inlet tube, chloroform (600.0 g) was added, trifluoroacetic acid [TFA] (164 g: 1.45×10 ³ mmol) was added in an ice bath, and the mixture was heated and stirred at 40° C. for 12 hours. The reaction solution was cooled to about 0° C., triethylamine (32.1 g: 318 mmol) was added, and the mixture was stirred at room temperature for 0.5 hours. Then, 4-nitrobenzoic acid chloride (67.0 g: 602 mmol) dissolved in 670 g of chloroform was gently added dropwise, and the mixture was stirred at room temperature for 6 hours. After the reaction was completed, the reaction solution was concentrated, washed three times with 200 ml of pure water, and washed once with 200 ml of saturated saline. Then, the mixture was recrystallized using chloroform as a good solvent and hexane as a poor solvent, and the obtained solid was vacuum-dried to obtain 56.0 g (112 mmol) of the target light yellow solid. The structure of the product was confirmed by nuclear magnetic resonance spectroscopy [ ¹ H-NMR (400 MHz)], and it was confirmed that it was the target product. The measurement data are shown below.

¹ H-NMR (400MHz: D6-DMSO) δ: 9.29-9.27 (d: 2H), 8.37 (dd: 4H), 8.06 (dd: 4H), 5.23-5.17 (m: 2H), 3.86-3.82 (m: 2H), 3.55 (s: 6H)

<Third step>
Synthesis of Dimethyl 2,4-bis(4-aminobenzomido)cyclobutane-1,3-dicarboxylate Dimethyl 2,4-bis(4-nitrobenzomido)cyclobutane-1,3-dicarboxylate (20.0 g: 112 mmol) obtained by the above operation, activated carbon (11.2 g) supporting 10% palladium, and fully degassed N,N-dimethylformamide (500 g) were added to a 1 L four-neck flask, hydrogen gas was filled into the system, and the mixture was stirred vigorously at room temperature for 48 hours. After the reaction was completed, the palladium carbon was removed, and N,N-dimethylformamide was concentrated under reduced pressure. The precipitated solid was dissolved in a minimum amount of DMF and recrystallized using hexane as a poor solvent. The obtained solid was dispersed in methanol and heated and stirred at 80° C. for 6 hours. The solid was then collected by filtration and dried under reduced pressure to obtain the target white solid (35.0 g: 79.5 mmol, yield: 71%). The structure was confirmed by nuclear magnetic resonance spectroscopy [ ¹ H-NMR (400 MHz)], and it was confirmed that it was the target product. The measurement data are shown below.

¹ H-NMR (400MHz: D6-DMSO) δ: 8.36-8.34 (dd: 2H), 7.56-7.53 (q: 4H), 6.55-6 .52 (q: 4H), 5.65 (br: 4H), 5.14-5.08 (q: 2H), 3.76-3.72 (q: 2H), 3.49 (s: 6H)

[Synthesis Example 1]
5.06 g (11.5 mmol) of DA-1 was taken in a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and 20.3 g of NMP was added. The mixture was heated and stirred at 70° C. for 30 minutes while feeding nitrogen, and dissolved. After cooling this diamine solution to room temperature by water cooling, 2.37 g (11.3 mmol) of DC-1 was added while stirring, and 9.50 g of NMP was further added, and the mixture was heated and stirred at 40° C. for 24 hours to obtain a polyamic acid solution (PAA-1). The viscosity of this polyamic acid solution at a temperature of 25° C. was 300 mPa·s. The molecular weight and molecular weight distribution of this polyamic acid were Mn=1.27×10 ⁴ , Mw=3.07×10 ⁴ , and Mw/Mn=2.41.

[Synthesis Examples 2, 3, 4, 5, and 6]
The diamine components, tetracarboxylic acid components, and NMP shown in Table 1 below were used, and the reaction temperature, solid content, and procedure were carried out in the same manner as in Synthesis Example 1, to obtain polyamic acid solutions PAA-2, PAA-3, PAA-4, PAA-5, and PAA-6 shown in Table 1 below. The viscosities and molecular weights of the obtained polyamic acids are shown in Table 2 below.

[Synthesis Example 7]
55.0 g of the obtained polyamic acid solution (PAA-1) was taken in a 100 ml four-neck flask equipped with a stirrer and a nitrogen inlet tube, 18.3 g of NMP was added, and the mixture was stirred at room temperature for 30 minutes. 5.12 g (50.7 mmol) of acetic anhydride and 1.59 g (20.1 mmol) of pyridine were added to the obtained polyamic acid solution, and the mixture was heated and stirred at 55 ° C. for 6 hours to perform chemical imidization. The obtained reaction solution was poured into 218 ml of methanol while stirring, and the precipitate was collected, and then washed three times with 218 ml of methanol. The obtained resin powder was dried at 60 ° C. for 12 hours to obtain a polyimide resin powder (PIP-1). The imidization rate of this polyimide resin powder was 95% or more.

[Synthesis Example 8]
Chemical imidization was carried out using a polyamic acid solution (PAA-2) in the same manner as in Synthesis Example 7 with respect to the amounts of acetic anhydride and pyridine introduced and the reaction temperature. However, a gel-like solid matter precipitated during heating and stirring, and accurate chemical imidization was not possible.

[Synthesis Example 9]
24.0 g of the obtained polyamic acid solution (PAA-3) was taken in a 50 ml four-neck flask equipped with a stirrer and a nitrogen inlet tube, 8.00 g of NMP was added, and the mixture was stirred at room temperature for 30 minutes. 2.56 g (25.0 mmol) of acetic anhydride and 1.19 g (15.1 mmol) of pyridine were added to the obtained polyamic acid solution, and the mixture was heated and stirred at 55 ° C. for 4 hours to perform chemical imidization. The obtained reaction solution was poured into 107 ml of methanol while stirring, and the precipitate was collected, and then washed three times with 107 ml of methanol. The obtained resin powder was dried at 60 ° C. for 12 hours to obtain a polyimide resin powder (PIP-3). The imidization rate of this polyimide resin powder was 95% or more.

[Synthesis Example 10]
18.0 g of the obtained polyamic acid solution (PAA-3) was taken in a 50 ml four-neck flask equipped with a stirrer and a nitrogen inlet tube, 6.00 g of NMP was added, and the mixture was stirred at room temperature for 30 minutes. 0.77 g (7.53 mmol) of acetic anhydride and 0.30 g (3.80 mmol) of pyridine were added to the obtained polyamic acid solution, and the mixture was heated and stirred at 55 ° C. for 2 hours to perform chemical imidization. The obtained reaction solution was poured into 75.2 ml of methanol while stirring, and the precipitate was collected, and then washed three times with 75.2 ml of methanol. The obtained resin powder was dried at 60 ° C. for 12 hours to obtain a polyimide resin powder (PIP-4). The imidization rate of this polyimide resin powder was 73%.

[Synthesis Example 11]
44.0 g of the obtained polyamic acid solution (PAA-4) was taken in a 50 ml four-neck flask equipped with a stirrer and a nitrogen inlet tube, 14.7 g of NMP was added, and the mixture was stirred at room temperature for 30 minutes. 4.50 g (44.1 mmol) of acetic anhydride and 2.09 g (26.5 mmol) of pyridine were added to the obtained polyamic acid solution, and the mixture was heated and stirred at 55 ° C. for 2 hours to perform chemical imidization. The obtained reaction solution was poured into 196 ml of methanol while stirring, and the precipitate was collected, and then washed three times with 196 ml of methanol. The obtained resin powder was dried at 60 ° C. for 12 hours to obtain a polyimide resin powder (PIP-5). The imidization rate of this polyimide resin powder was 95% or more.

[Synthesis Example 12]
96.5 g of the obtained polyamic acid solution (PAA-5) was taken in a 100 ml four-neck flask equipped with a stirrer and a nitrogen inlet tube, 32.2 g of NMP was added, and the mixture was stirred at room temperature for 30 minutes. 7.03 g (68.9 mmol) of acetic anhydride and 3.64 g (46.0 mmol) of pyridine were added to the obtained polyamic acid solution, and the mixture was heated and stirred at 55 ° C. for 2 hours to perform chemical imidization. The obtained reaction solution was poured into 433 ml of methanol while stirring, and the precipitate was collected, and then washed three times with 433 ml of methanol. The obtained resin powder was dried at 60 ° C. for 12 hours to obtain a polyimide resin powder (PIP-6). The imidization rate of this polyimide resin powder was 62%.

[Synthesis Example 13]
Polyimide resin powder (PIP-7) was obtained by chemical imidization using the polyamic acid solution (PAA-6) in the same manner as in Synthesis Example 12, with respect to the amounts of acetic anhydride and pyridine introduced and the reaction temperature. The imidization rate of this polyimide resin powder was 68%.

The imidization rates of the polyimide resin powders obtained in Synthesis Examples 7, 8, 9, 10, 11, 12, and 13 are shown in Table 3 below.

[Synthesis Example 14]
5.56 g of polyimide resin powder (PIP-1) was placed in a 50 ml eggplant flask, 40.7 g of NMP was added so that the solid content concentration was 12%, and the mixture was stirred at 70°C for 24 hours to dissolve the powder, obtaining a polyimide solution (PIS-1). No abnormalities such as turbidity or precipitation were observed in this liquid crystal alignment agent, and it was confirmed that the solution was homogeneous. The molecular weight and molecular weight distribution of this polyimide solution were Mn = 1.30 x 10 ⁴ , Mw = 3.35 x 10 ⁴ , and Mw/Mn = 2.56.

[Synthesis Example 15]
A polyimide solution (PIS-2) was obtained using the polyimide resin solid (PIP-2) in the same manner as in Synthesis Example 14. However, unnecessary substances were generated, and a uniform polyimide solution could not be obtained.

[Synthesis Examples 16, 17, 18, 19, and 20]
Polyimide resin powders (PIP-3, PIP-4, PIP-5, PIP-6, PIP-7) were used to obtain polyimide solutions (PIS-3, PIS-4, PIS-5, PIS-6, PIS-7) in the same manner as in Synthesis Example 14. The molecular weights of the obtained polyimide solutions are shown in Table 4 below.

When the polyamic acid solution obtained by sequential polymerization of DA-1 or DA-2 and DC-1 was chemically imidized, the polyamic acid made from DA-1 successfully underwent chemical ring closure, whereas the polyamic acid made from DA-2 precipitated a gel-like solid during chemical ring closure and could not be evaluated.

By using the DA-1 analogues included in this claim, the solubility in solvents is specifically improved when the polyamic acid and the polyimide formed by chemically closing the ring from the polyamic acid are used, compared to the DA-2 analogues. In addition, the materials PIS-1, PIS-3, PIS-4, and PIS-5 included in this claim exhibit properties that are practical for use as liquid crystal alignment films, and can also reduce the risk of display defects, as described below.

[Synthesis Example 21]
In a 20 ml sample tube containing a stirrer, 6.50 g of the polyimide solution (PIS-1) obtained in Synthesis Example 1 was taken, 1.00 g of NMP, 3.53 g of GBL solution, and 3.00 g of BCS were added, and the mixture was stirred with a magnetic stirrer for 2 hours to obtain a liquid crystal alignment agent (A-1). Using this liquid crystal alignment agent (A-1), a liquid crystal cell for liquid crystal alignment evaluation and bright spot evaluation was prepared according to the procedure shown below.

[Synthesis Example 22]
Using the polyimide solutions (PIS-3, PIS-4, PIS-5, PIS-6, PIS-7), liquid crystal alignment agents (A-2, A-3, A-4, A-5, A-6, A-7) were obtained in the same manner as in Synthesis Example 21.

Using these liquid crystal alignment agents (A-2, A-3, A-4, A-5, A-6, A-7), liquid crystal cells for evaluating liquid crystal alignment and bright spots were prepared according to the procedure described below.

[Example 1]
After filtering the liquid crystal alignment agent (A-1) obtained in Synthesis Example 21 with a 1.0 μm filter, the liquid crystal alignment agent was spin-coated on a 30 mm × 40 mm ITO substrate, dried on a hot plate at 80 ° C. for 2 minutes, and the coating surface was irradiated with linearly polarized ultraviolet light having a wavelength of 254 nm and an extinction ratio of 26: 1 through a polarizing plate at various exposure amounts between 0.15 J / cm ² and 0.40 J / cm ² , and then baked for 17 minutes in a hot air circulation oven at 230 ° C. to obtain a substrate with a liquid crystal alignment film. The above two substrates obtained were combined into a set, a sealant was printed on the substrate, and the other substrate was laminated so that the liquid crystal alignment film surfaces faced each other and the alignment direction was 0 °, and then the sealant was cured to prepare an empty cell. Liquid crystal MLC-3019 (manufactured by Merck) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain a liquid crystal alignment liquid crystal cell. The afterimage evaluation results for each are shown in Table 5 below. The liquid crystal alignment was evaluated based on the above-mentioned evaluation criteria.

[Examples 2, 3, and 4]
Instead of the liquid crystal alignment agent (A-1), each liquid crystal alignment agent (A-2, A-3, A-4) was used, and the UV irradiation amount and baking temperature were the same as in Example 1 to prepare liquid crystal cells for afterimage evaluation. The afterimage evaluation results for each are shown in Table 5 below.

[Comparative Examples 1 and 2]
Instead of the liquid crystal alignment agent (A-1), each liquid crystal alignment agent (A-5, A-6) was used, and the amount of ultraviolet light irradiation and the baking temperature were the same as in Example 1 to prepare liquid crystal cells for afterimage evaluation. The afterimage evaluation results for each are shown in Table 5 below.

The liquid crystal alignment agent (A-1, A-2, A-3, A-4) consisting of DA-1 and DC-1 described in this claim exhibits very good afterimage characteristics at an exposure dose between 0.10 J/cm ² and 0.40 J/cm ^2. Also, copolymerized polyimides using DA-1, other diamine components, and DC-1 exhibit good afterimage characteristics, and the quality of the afterimage characteristics and the exposure dose vary depending on the diamine components to be combined. As an example, in the liquid crystal alignment agent (A-2) obtained by copolymerizing DA-1 and DA-3, the exposure dose is between 0.10 J/cm ² and 0.40 J/cm ² , and the afterimage characteristics are better in a wider range of exposure doses. Furthermore, the liquid crystal alignment agent (A-3) prepared using a polyimide solution (PIS-3) in which the imidization rate was controlled in the process of chemically imidizing the polyamide consisting of DA-1 and DA-3 exhibits good afterimage characteristics at around 0.10 J/cm ² , and is therefore a material that can obtain good afterimage characteristics at a very low exposure dose. Furthermore, the liquid crystal alignment agent (A-4) consisting of DA-1 and DA-4 can also obtain very good afterimage characteristics at a very low exposure dose, similar to the above-mentioned liquid crystal alignment agent (A-3).

On the other hand, the liquid crystal alignment agent (A-5) consisting of DA-3 and DA-5 and DC-1 and DC-2 shown in Comparative Example 1 exhibits good afterimage characteristics, but requires an exposure dose of 0.20 J/ ^cm2 or more. In terms of the required exposure dose, the above liquid crystal alignment agents (A-2, A-3, A-4) require only about 0.10 J/ ^cm2 of exposure dose when exhibiting good afterimage characteristics, suggesting the superiority of DA-1 included in this claim. Furthermore, since the required exposure dose can be adjusted by the combination of polymer units, it is also possible to realize the takt time desired by the user when considering the actual manufacturing site.

In addition, the liquid crystal alignment agent (A-6) obtained from DA-3, DA-5, and DC-1 has a similar backbone to the above liquid crystal alignment agents (A-1, A-2, A-3, A-4), but does not provide good image retention properties, suggesting the superiority of using DA-1, which is included in this claim.

[Example 5]
The liquid crystal cell for evaluating afterimages, which was prepared using the liquid crystal alignment agent (A-1) in Example 1, was heated in a heating oven at 60°C for 2 weeks or more, and then observed with a polarizing microscope (ECLIPSE E600WPOL) (manufactured by Nikon Corporation). As described above, the criteria for evaluation were based on the number of bright spots confirmed by polarizing microscope observation, with less than 5 bright spots being rated as "good" and more than 5 being rated as "bad." The bright spot evaluation results of this liquid crystal cell after long-term AC driving in each case are shown in Table 6.

[Examples 6, 7, and 8]
Instead of the liquid crystal alignment agent (A-1), each liquid crystal alignment agent (A-2, A-3, A-4) was used, and the ultraviolet ray irradiation amount and baking temperature were the same as in Example 5 to prepare liquid crystal cells for evaluating display defects. The display defect evaluation results for each are shown in Table 6 below.

[Comparative Examples 3 and 4]
Instead of the liquid crystal alignment agent (A-1), each liquid crystal alignment agent (A-5, A-6) was used, and the ultraviolet ray irradiation amount and baking temperature were the same as in Example 5 to prepare liquid crystal cells for evaluating display defects. The display defect evaluation results for each are shown in Table 6 below.

The liquid crystal alignment agents (A-1, A-2, A-3, A-4) made of DA-1 and DC-1 described in this claim show very good results in the evaluation of defectiveness. On the other hand, the liquid crystal alignment agents made of soluble polyimides obtained by copolymerizing DA-3 and DA-5, and DC-1 and DC-2 shown in Comparative Example 1, and the liquid crystal alignment agents made of soluble polyimides obtained by copolymerizing DA-3, DA-5, and DC-1, showed defects. The liquid crystal alignment agent made of soluble polyimide using DA-1 included in this claim is also effective in suppressing display defects.

[Synthesis Example 23]
Polymerization of DC-3/DA-6 polyamic acid 4.00 g (8.50 mmol) of DA-6 was taken in a 50 mL four-neck flask equipped with a stirrer and a nitrogen inlet tube, and 40.58 g of NMP was added. The mixture was stirred at room temperature for 10 minutes while feeding nitrogen, and dissolved. 1.54 g (7.64 mmol) of DC-3 was added to this diamine solution while stirring, and the mixture was stirred at room temperature for 24 hours to obtain a polyamic acid solution (PAA-8) having a concentration of 12% by mass. The viscosity of this polyamic acid solution at a temperature of 25° C. was 420 mPa·s. The molecular weight and molecular weight distribution of this polyamic acid were Mn=9.82×10 ³ , Mw=2.16×10 ⁴ , and Mw/Mn=2.20.

[Synthesis Examples 24, 25, 26, 27, 28, and 29]
The diamine components, tetracarboxylic acid components, and NMP shown in Table 7 below were used, and the reaction temperature, solid content, and procedure were carried out in the same manner as in Synthesis Example 1, to obtain polyamic acid solutions PAA-9, PAA-10, PAA-11, PAA-12, PAA-13, and PAA-14 shown in Table 7 below. The viscosities and molecular weights of the obtained polyamic acids are shown in Table 8 below.

[Synthesis Example 30]
30.0 g of each of the obtained polyamic acid solutions (PAA-8, PAA-9, PAA-10, PAA-11, PAA-12, PAA-13, PAA-14) was taken in a 100 ml four-neck flask equipped with a stirrer and a nitrogen inlet tube, 30.0 g of NMP was added, and the mixture was stirred at room temperature for 30 minutes. To the obtained polyamic acid solution, 5 mol of acetic anhydride and 5 mol of pyridine were added relative to the carboxylic acid of the polyamic acid, and the mixture was heated and stirred at 70 ° C. for 3 hours to perform chemical imidization. The obtained reaction solution was poured into 500 ml of methanol while stirring, and the precipitate was collected, followed by washing three times with 300 ml of methanol. The obtained resin powder was dried at 80 ° C. for 12 hours to obtain polyimide resin powders (PIP-8, PIP-9, PIP-10, PIP-11, PIP-12, PIP-13). As for PIP-14, it gelled during chemical imidization, and therefore it was not possible to obtain it as a polyimide. The molecular weight and imidization rate of this polyimide resin powder are shown in Table 9 below.

[Examples 7 to 12]
In a 50 ml eggplant flask, 10.0 g of the polyamic acid solution (PAA-8 to PAA-14) obtained above was weighed out, 4.00 g of NMP and 6.0 g of BCS were added, and the mixture was stirred at room temperature for 24 hours to obtain liquid crystal alignment agents (A-8 to A-14). A-14 was used as a comparison.

[Examples 13 to 18]
2.0 g of the polyimide resin powder (PIP-8 to PIP-13) obtained above was weighed out in a 50 ml eggplant flask, 18.0 g of NMP was added, and the mixture was stirred at room temperature for 24 hours. Further, 6.67 g of NMP and 6.67 g of BCS were added, and the mixture was stirred for 1 hour to obtain liquid crystal alignment agents (A-15 to A-20).

[Test Example 1]
The alignment agents A-8 to A-20 obtained in Examples 7 to 18 were evaluated for the liquid crystal alignment film based on the following method. A-14 (Comparative Example 3) and SE-6414 (Comparative Example 4) manufactured by Nissan Chemical Industries, Ltd. were used as comparison objects.

<Evaluation of Liquid Crystal Alignment, Voltage Holding Ratio, and Pretilt Angle>
The liquid crystal alignment, voltage holding ratio and pretilt angle were evaluated as follows.

[Preparation of liquid crystal cells for observing liquid crystal alignment and measuring voltage holding ratio and pretilt angle]
After filtering the liquid crystal alignment agent with a 1.0 μm filter, the liquid crystal alignment agent was applied by spin coating to a substrate with electrodes (a glass substrate with a size of 30 mm wide x 40 mm long and a thickness of 0.7 mm. The electrode was a rectangular shape with a width of 10 mm and a length of 40 mm, and an ITO electrode with a thickness of 35 nm). After drying for 1 minute on a hot plate at 80 ° C., a substrate was baked for 20 minutes at 120 ° C. using an IR oven, and a substrate was baked at 230 ° C. The film thickness was set to 100 nm after baking. This liquid crystal alignment film was rubbed with a rayon cloth (YA-20R manufactured by Yoshikawa Kako) (roller diameter: 120 mm, roller rotation speed: 1000 rpm, moving speed: 20 mm / sec, indentation length: 0.4 mm), and then ultrasonically irradiated in pure water for 1 minute to perform cleaning, and water droplets were removed by air blowing, and then dried at 80 ° C. for 15 minutes to obtain a substrate with a liquid crystal alignment film.

Two substrates with the above liquid crystal alignment film were prepared, 4 μm spacers were sprayed onto the liquid crystal alignment film surface of one of them, and then a sealant was printed on top of them. The other substrate was attached with the rubbing direction in the opposite direction and the film surfaces facing each other, and the sealant was cured to create an empty cell. MLC-3019 (Merck Ltd.) was injected into this empty cell by the reduced pressure injection method, and the injection port was sealed to obtain a liquid crystal cell. After that, the alignment of the liquid crystal was observed, and the liquid crystal cell was heated at 110°C for 1 hour and left at 23°C overnight to obtain a liquid crystal cell for measuring the voltage holding ratio.

Using the liquid crystal cell for measuring voltage retention obtained by the above procedure, a voltage of 1 V was applied for 60 μs at a temperature of 60°C, the voltage after 166.7 ms was measured, and the extent to which the voltage was retained was calculated as the voltage retention rate. Note that a VHR-1 voltage retention rate measuring device manufactured by Toyo Corporation was used to measure the voltage retention rate.

[Evaluation of pretilt angle]
The pretilt angle was measured using an Axo Scan Mueller matrix polarimeter manufactured by Optometrics.

[Evaluation of rubbing resistance]
After filtering the liquid crystal alignment agent with a 1.0 μm filter, the liquid crystal alignment agent was applied by spin coating to a substrate with electrodes (a glass substrate with a size of 30 mm wide x 40 mm long and a thickness of 1.1 mm. The electrode was a rectangle with a width of 10 mm and a length of 40 mm, and an ITO electrode with a thickness of 35 nm). After drying for 1 minute on a hot plate at 80 ° C., a substrate was baked for 20 minutes at 120 ° C. using an IR oven, and a substrate was baked at 230 ° C. to prepare a substrate. The film thickness was adjusted to 100 nm after baking. This liquid crystal alignment film was rubbed (roller diameter: 120 mm, roller rotation speed: 1000 rpm, moving speed: 20 mm / sec, indentation length: 0.5 mm) with a rayon cloth (YA-20R manufactured by Yoshikawa Kako Co., Ltd.), and then the rubbing resistance was evaluated using a confocal laser microscope. If peeling occurred, peeling was judged to be peeled, if many scrapes or scratches were observed, it was judged to be poor, and if good, it was judged to be good.

[Evaluation of liquid crystal alignment]
The liquid crystal alignment property was evaluated based on the same evaluation criteria as in Example 1. In the evaluation criteria, "◯" was defined as "good" and "×" was defined as "bad."
The results of the above-mentioned various evaluations are shown in Tables 10 to 13.

<Evaluation results of alignment agent printability, rubbing resistance, and cell display characteristics>

When a film is formed by baking at 120°C, polyamic acid in particular cannot be imidized under these conditions, so the physical strength becomes very weak, and the film tends to be scraped off by rubbing treatment, causing the alignment of the liquid crystal to deteriorate. However, polyamic acid and polyimide using the diamine of the present invention have excellent rubbing resistance even when baked at a low temperature, and also have good liquid crystal alignment. In addition, they are characterized by a very small pretilt angle and high VHR.

Furthermore, the diamine of the present invention can achieve extremely high solubility; while unincorporated PAA-14 could not be chemically imidized, PIP-13, which contains 50 mol% of the diamine component, can be adjusted to an imidization rate of 95% or more without any problems, and good alignment film properties are obtained. Generally, when a component with very poor solubility such as DC-1 or DC-4 is incorporated, chemical imidization is often difficult, but by using the diamine of the present invention, it is possible to adjust a soluble polyimide with a high imidization rate. Making it a soluble polyimide can also further improve reliability.

When baked at 230°C, the material in the comparative example also undergoes imidization, improving rubbing resistance, liquid crystal alignment, and reliability. However, the alignment agent of the present invention exhibits good characteristics, and although there is a tendency for the pretilt angle to improve slightly, this advantage is very small compared to the comparative example. Furthermore, reliability is also very high.

Therefore, by using the diamine of the present invention, it is possible to create a liquid crystal alignment agent that can be baked at low to high temperatures, and furthermore, to obtain an alignment film with a very low pretilt.

[Test Example 2]
The liquid crystal alignment agents (A-16, A-17, A-20) obtained in Examples 14, 15, and 18, and the liquid crystal alignment agent A-5 of the comparative example were filtered through a 1.0 μm filter, and then the liquid crystal alignment agent was spin-coated on a 30 mm x 40 mm ITO substrate, dried on a hot plate at 80 ° C. for 2 minutes, and the coating surface was irradiated with linearly polarized ultraviolet light having a wavelength of 254 nm and an extinction ratio of 26: 1 in the range of 0.1 to 1.0 J / cm ² through a polarizing plate, and then baked for 20 minutes in a hot air circulation oven at 150 ° C. to obtain a substrate with a liquid crystal alignment film. The above two substrates obtained were combined into a set, a sealant was printed on the substrate, and the other substrate was attached so that the liquid crystal alignment film surfaces faced each other and the alignment direction was 0 °, and then the sealant was cured to produce an empty cell. The liquid crystal MLC-3019 (Merck) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain a liquid crystal cell with liquid crystal alignment. The results of the liquid crystal alignment in each case are shown in Table 14 below. The evaluation was performed based on the same evaluation criteria as in Example 1.

It was found that the soluble polyimide made using the diamine of the present invention and DC-1 exhibited orientation when pre-dried, irradiated with UV light, and baked at 150°C. The material of Comparative Example 1 exhibited orientation at high temperatures, but did not exhibit orientation at low temperatures, regardless of the UV irradiation intensity. It was therefore found that photo-alignment at low temperatures is possible by using the diamine of the present invention.

The polyamic acid and polyimide obtained from the diamine of the present invention have excellent solubility in solvents, making it possible to manufacture liquid crystal alignment agents and films that were previously not possible from the standpoint of solubility. In addition, a wide range of applications are possible, from alignment films for rubbing to photo-alignment films. In particular, it is expected to be possible to accommodate low-temperature baking, low pretilt angle materials, and simplified photo-alignment processes, which will become trends in the in-plane switching method in the future.

A liquid crystal display element having a liquid crystal alignment film manufactured from the material of the present invention has excellent afterimage characteristics and long-term display stability, and can be suitably used in large-screen, high-definition liquid crystal televisions, small and medium-sized car navigation systems, smartphones, etc. Furthermore, since it can be manufactured more simply in the manufacturing process, it is expected to improve yield and production efficiency.

Claims (3)

A diamine represented by the following formula [1]:

In formula [1], Y ¹ is a tetravalent organic group represented by formula [Y ¹ -1], X ¹ and X ² are divalent organic groups having a phenylene group, Z ¹ and Z ² each independently represent a single bond, -NH-, or -O-, and R ¹ and R ² each independently represent an alkyl group having 1 to 5 carbon atoms.

(In formula [Y ¹ -1], R ⁵ to R ⁸ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group, and may be the same or different.) A polymer obtained from a diamine component comprising the diamine according to claim 1 . A method for producing a diamine compound, comprising starting from a compound of the following formula (11) and producing the diamine according to claim 1 via a compound of the following formula (12) or a compound of the following formula (13).

In formulas (11) to (13), Y ¹ is a tetravalent organic group represented by the formula [Y ¹ -1], R ¹ and R ² each independently represent an alkyl group having 1 to 5 carbon atoms, and in formula (13), R ³¹ and R ³² represent a hydrogen atom or a protecting group for an amino group.

(In formula [Y ¹ -1], R ⁵ to R ⁸ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group, and may be the same or different.)