JP7472799B2 - Liquid crystal alignment agent, liquid crystal alignment film, and liquid crystal display element using the same - Google Patents

Description

The present invention relates to a liquid crystal alignment agent, a liquid crystal alignment film, and a liquid crystal display element using the same.

In liquid crystal display elements, the role of the liquid crystal alignment film is to align the liquid crystal in a certain direction. Until now, the main liquid crystal alignment films used have been polyimide-based liquid crystal alignment films, which are made by applying a liquid crystal alignment agent whose main component is a polyimide precursor such as polyamic acid or a solution of a soluble polyimide to a glass substrate or the like and then baking it.

As liquid crystal display elements become more functional, liquid crystal alignment films are required to have properties such as excellent liquid crystal alignment and stable pretilt angle, as well as a high voltage retention rate, small residual charge when a DC voltage is applied, and/or rapid relaxation of residual charge accumulated due to DC voltage.

In order to meet the above demands, various proposals have been made. For example, Patent Document 1 proposes a liquid crystal aligning agent made of an imidized polymer that satisfies the following formula (1).

Japanese Patent Publication No. 2005-179429

As liquid crystal display elements have become more powerful in recent years, they are now being used in large-screen, high-definition liquid crystal televisions and in-vehicle applications, such as car navigation systems and meter panels. In these applications, in addition to having good initial characteristics, they are required to have a voltage retention rate that is not easily reduced even after long periods of exposure to high temperatures and humidity.

In general, when a liquid crystal alignment agent with a high imidization rate is used, a high voltage retention rate is easily obtained, but there are problems with reduced solubility in solvents and the tendency for polyimide to precipitate due to moisture absorption when printed on a substrate, resulting in whitening of the varnish. For this reason, there is also a demand for the voltage retention rate of the liquid crystal alignment film to be less likely to decrease, even when a liquid crystal alignment agent with a low imidization rate is used.

However, Patent Document 1 does not disclose the voltage retention rate after exposure to high temperature and high humidity. In addition, the examples in Patent Document 1 only disclose the use of a liquid crystal alignment agent with a high imidization rate.

The present invention has been made in consideration of the above circumstances, and aims to provide a liquid crystal alignment agent that can provide a liquid crystal alignment film that maintains its voltage holding ratio even after exposure to high temperature and high humidity. Another aim of the present invention is to provide a liquid crystal alignment agent that can provide a liquid crystal alignment film that maintains its voltage holding ratio even when the imidization rate is low.

As a result of extensive investigations aimed at solving the above problems, the present inventors have found that a liquid crystal aligning agent containing a specific polymer satisfies the above problems.
The present invention is based on these findings and has the following gist.
A liquid crystal aligning agent comprising at least one polymer selected from the group consisting of a polyimide precursor obtained by polymerizing any one of the following diamine components (1) and (2) with a tetracarboxylic acid component, and a polyimide obtained by imidizing the polyimide precursor:
Diamine component (1): A diamine component containing a diamine having a protecting group that is substituted with a hydrogen atom by heat, and a diamine having a siloxane skeleton.
Diamine component (2): A diamine component containing a diamine having a siloxane skeleton and a protecting group that is substituted with a hydrogen atom by heat.

According to the liquid crystal alignment agent of the present invention, it is possible to obtain a liquid crystal alignment film that maintains its voltage holding ratio even after exposure to high temperature and high humidity. Furthermore, according to the liquid crystal alignment agent of the present invention, it is possible to obtain a liquid crystal alignment film that maintains its voltage holding ratio even when the imidization rate is low. In addition, the liquid crystal alignment agent of the present invention is also excellent in terms of solubility and seal adhesion.

<Specific Polymer>
The liquid crystal aligning agent of the present invention contains at least one polymer (hereinafter also referred to as a specific polymer) selected from the group consisting of a polyimide precursor obtained by polymerizing any one of the following diamine components (1) and (2) with a tetracarboxylic acid component, and a polyimide obtained by imidizing the polyimide precursor.
Diamine component (1): A diamine component containing a diamine having a protecting group that is substituted with a hydrogen atom by heat, and a diamine having a siloxane skeleton.
Diamine component (2): A diamine component containing a diamine having a siloxane skeleton and a protecting group that is substituted with a hydrogen atom by heat.

<Diamine Component (1)>
In the diamine component (1), the diamine having a protecting group that is replaced by a hydrogen atom by heat is, for example, a diamine represented by the following formula [1]. In the diamine component (1), the diamine having a siloxane skeleton is, for example, a diamine represented by the following formula [2]. In the diamine component (1), the diamine having a protecting group that is replaced by a hydrogen atom by heat is a diamine represented by the following formula [1], and the diamine having a siloxane skeleton may be a diamine represented by the following formula [2].

（式［１］中、Ｘ^Ｄは下記式［１ａ］、式［１ｂ］及び式［１ｃ］からなる群から選ばれる少なくとも１種の構造を有する炭素数１～５０の有機基を示し、Ａ^１及びＡ^２はそれぞれ独立して、水素原子又は炭素数１～５のアルキル基を示す。）

（式［１ａ］～式［１ｃ］中、Ｘ^ａは水素原子又は炭素数１～２０の有機基を示す。Ｘ^ｄは単結合又は炭素数１～２０の有機基を示す。Ｘ^ｅは水素原子又は炭素数１～２０の有機基を示す。Ｄは熱により水素原子に置き換わる保護基を示す。＊は結合手を示す。） (Diamine represented by formula [1])
The diamine represented by the formula [1] is as follows:

(In formula [1], ^XD represents an organic group having 1 to 50 carbon atoms and having at least one structure selected from the group consisting of the following formulas [1a], [1b], and [1c], and ^A1 and ^A2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

(In formulas [1a] to [1c], ^Xa represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. ^Xd represents a single bond or an organic group having 1 to 20 carbon atoms. ^Xe represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. D represents a protecting group which is substituted with a hydrogen atom by heat. * represents a bond.)

Here, in the present invention, the term "protective group that is replaced by a hydrogen atom by heat" refers to a protective group that is eliminated by heat and replaced by a hydrogen atom. The temperature at which such a protective group is eliminated by heat and replaced by a hydrogen atom is the baking temperature when preparing a liquid crystal alignment film, and is preferably 150 to 300°C, more preferably 200 to 270°C. As such a protective group (D), a protective group represented by the following formula [P] is preferred.

（式中、Ｘ^Ａは下記の式［ａ－１］～式［ａ－６］からなる群から選ばれる構造を示し、Ｒ^１は炭素数１～５のアルキレン基を示す。）

(In the formula, ^XA represents a structure selected from the group consisting of the following formulas [a-1] to [a-6], and ^R1 represents an alkylene group having 1 to 5 carbon atoms.)

式［１ａ－１］中、Ｘ^１は単結合、炭素数１～１０のアルキレン基、－Ｏ－、－Ｎ（Ｒ^１）－、－ＣＯＮ（Ｒ^２）－、－Ｎ（Ｒ^３）ＣＯ－、－ＣＨ_２Ｏ－、－ＣＯＯ－及びＯＣＯ－から選ばれる少なくとも１種を示す。但し、Ｒ^１、Ｒ^２及びＲ^３はそれぞれ独立して、水素原子又は炭素数１～３のアルキル基を示す。特に、単結合、－Ｏ－、－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＯＯ－又はＯＣＯ－が好ましい。 Specifically, it is preferable to use, as the diamine represented by the formula [1], diamines represented by the following formulas [1a-1] to [1c-1].

In formula [1a-1], X ¹ represents at least one selected from a single bond, an alkylene group having 1 to 10 carbon atoms, -O-, -N(R ¹ )-, -CON(R ² )-, -N(R ³ )CO-, -CH ₂ O-, -COO-, and OCO-. However, R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In particular, a single bond, -O-, -CONH-, -NHCO-, -COO-, or OCO- is preferred.

In formula [1a-1], ^X2 represents a single bond or an alkylene group having 1 to 10 carbon atoms. Of these, a single bond or an alkylene group having 1 to 5 carbon atoms is preferred. ^Xa represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, more preferably a hydrogen atom or an organic group having 1 to 10 carbon atoms. The organic group having 1 to 10 carbon atoms is preferably -( _CH2 ) _n -COO-tBu (n represents an integer of 1 to 5, and tBu represents a tert-butyl group).
In formula [1a-1], ^Xb represents a structure selected from the group consisting of formulas [a-1] to [a-6] above.
In formula [1a-1], m represents an integer of 1 or 2, and in this case, when m is 2, there is no substituent for ^Xa . p represents an integer of 1 to 4. Among them, from the viewpoints of availability of raw materials and ease of synthesis, 1 to 3 is preferable, and 1 to 2 is more preferable. q represents an integer of 1 to 4. Among them, from the viewpoints of availability of raw materials and ease of synthesis, 1 to 3 is preferable, and 1 to 2 is more preferable.

In formula [1b-1], ^X3 and ^X7 each independently represent at least one organic group selected from the group consisting of a single bond, an alkylene group having 1 to 10 carbon atoms, -O-, -N( ^R1 )-, -CON( ^R2 )-, -N( ^R3 )CO-, _-CH2O- , -COO-, and OCO-. However, ^R1 , ^R2 , and ^R3 each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Among these, a single bond, -O-, -CONH-, -NHCO-, -COO-, or OCO- is preferred.
In formula [1b-1], ^X4 and ^X6 each independently represent a single bond or an alkylene group having 1 to 10 carbon atoms. In particular, a single bond or an alkyl group having 1 to 5 carbon atoms is preferable.
^X5 represents a single bond or an alkylene group having 1 to 10 carbon atoms. Of these, a single bond or an alkylene group having 1 to 5 carbon atoms is preferable. ^Xc represents a structure selected from the group consisting of the above formulas [a-1] to [a-6].
In formula [1b-1], r represents an integer of 1 to 4. Among them, from the viewpoints of availability of raw materials and ease of synthesis, 1 to 3 is preferable, and 1 or 2 is more preferable.

In formula [1c-1], ^X8 represents at least one organic group selected from the group consisting of a single bond, an alkylene group having 1 to 10 carbon atoms, -O-, -N( ^R1 )-, -CON( ^R2 )-, -N( ^R3 )CO-, _-CH2O- , -COO-, and OCO-. However, ^R1 , ^R2 , and ^R3 each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In particular, a single bond, -O-, -CONH-, -NHCO-, -COO-, or OCO- is preferred.
In formula [1c-1], ^X9 represents a single bond or an alkylene group having 1 to 10 carbon atoms, and preferably represents a single bond or an alkylene group having 1 to 5 carbon atoms. ^Xd represents a single bond or an organic group having 1 to 20 carbon atoms. Of these, a single bond or an organic group having 1 to 10 carbon atoms is preferred. More preferably, a single bond or a carbon atom (>CH-). ^Xe represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. In this case, when ^Xd is a single bond, ^Xe does not exist. Of these, a hydrogen atom or NH-COO-tBu (tBu represents a tert-butyl group) is preferred.
In formula [1c-1], ^Xf represents a structure selected from the group consisting of formulas [a-1] to [a-6]. n represents an integer of 1 to 4. Among them, from the viewpoints of availability of raw materials and ease of synthesis, 1 to 3 is preferable, and 1 to 2 is more preferable. s represents an integer of 1 to 4, from the viewpoints of availability of raw materials and ease of synthesis, 1 to 3 is preferable, and 1 to 2 is more preferable. t represents an integer of 1 to 4, from the viewpoints of availability of raw materials and ease of synthesis, 1 to 3 is preferable, and 1 to 2 is more preferable.

In formulas [1a-1] to [1c-1], A ¹ to A ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

（式［１ｄ－１］～式［１ｄ－５］中、Ｒ^１～Ｒ^７はそれぞれ独立して、下記の式［ａ－１］～式［ａ－６］からなる群から選ばれる少なくとも１種の構造を示し、式［１ｄ－１］～式［１ｄ－５］中、Ａ^１～Ａ^１０はそれぞれ独立して、水素原子又は炭素数１～５のアルキル基を示す。）

（式［ａ－２］中、Ｒ１は炭素数１～５のアルキレン基を示す。） More specifically, examples of the diamine represented by the formula [1] include diamines represented by the following formulas [1d-1] to [1d-11].

(In formulas [1d-1] to [1d-5], R ¹ to R ⁷ each independently represent at least one structure selected from the group consisting of the following formulas [a-1] to [a-6], and in formulas [1d-1] to [1d-5], A ¹ to A ¹⁰ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

(In formula [a-2], R1 represents an alkylene group having 1 to 5 carbon atoms.)

（式［１ｄ－６］～式［１ｄ－９］中、Ｒ^８～Ｒ^１４はそれぞれ独立して、前記式［ａ－１］～式［ａ－６］で示される構造からなる群から選ばれる少なくとも１種の構造を示し、式［１ｄ－６］～式［１ｄ－９］中、Ａ^１１～Ａ^１８はそれぞれ独立して、水素原子又は炭素数１～５のアルキル基を示す）。

(In formulas [1d-6] to [1d-9], R ⁸ to R ¹⁴ each independently represent at least one structure selected from the group consisting of structures represented by formulas [a-1] to [a-6], and in formulas [1d-6] to [1d-9], A ¹¹ to A ¹⁸ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms).

Among them, it is preferable to use the diamines represented by formula [1] as those represented by formulas [1d-1] to [1d-5].

（式［１ｄ－１０］及び式［１ｄ－１１］中、Ｒ^１５～Ｒ^１８はそれぞれ独立して、前記式［ａ－１］～式［ａ－６］で示される構造からなる群から選ばれる少なくとも１種の構造を示し、式［１ｄ－１１］中、Ａ^１９及びＡ^２０はそれぞれ独立して、水素原子又は炭素数１～５のアルキル基を示す。） Furthermore, as the diamine represented by the formula [1], diamines represented by the following formulas [1d-10] and [1d-11] can also be used.

(In formula [1d-10] and formula [1d-11], R ¹⁵ to R ¹⁸ each independently represent at least one structure selected from the group consisting of structures represented by formula [a-1] to formula [a-6], and in formula [1d-11], A ¹⁹ and A ²⁰ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

The content of the diamine represented by the formula [1] is preferably 5 to 70 mol % in 100 mol % of the total diamine components, more preferably 5 to 30 mol %, and even more preferably 5 to 20 mol %.
The diamine represented by the formula [1] can be used alone or in combination of two or more depending on the solubility of the specific polymer in a solvent, the coatability of the liquid crystal alignment agent, and the properties such as liquid crystal alignment, voltage holding rate, and accumulated charge when formed into a liquid crystal alignment film.

（式［２］中、Ｒ_１，Ｒ_２，Ｒ_３，Ｒ_４は、それぞれ独立して、メチル基又はエチル基を示す。Ｘ_１及びＸ_２は、それぞれ独立して、単結合、－ＮＨＣＯ－、－ＣＯＮＨ－、－ＣＯＯ－又は－ＯＣＯ－を示す。Ｐ_１及びＰ_２は、それぞれ独立して、－ＮＨ_２、又は以下の式［Ｐａ］～式［Ｐｂ］で示される構造を示す。ｎ１及びｎ２は、それぞれ独立して０～６の整数を示す。ｍは１～５の整数を示す。但し、式［Ｐａ］～式［Ｐｂ］のフェニルはハロゲンで置換されていてもよい。）

（式［Ｐａ］～式［Ｐｂ］中、Ｘ^Ｄ２は下記式［２ａ］、式［２ｂ］及び式［２ｃ］からなる群から選ばれる少なくとも１種の構造を有する炭素数１～５０の有機基を示す。ｐは、０～１の整数を示す。＊は、結合手を示す。）

（式［２ａ］～式［２ｃ］中、Ｘ^ａは水素原子又は炭素数１～２０の有機基を示す。Ｘ^ｄは単結合又は炭素数１～２０の有機基を示す。Ｘ^ｅは水素原子又は炭素数１～２０の有機基を示す。Ｄは熱により水素原子に置き換わる保護基を示す。＊は結合手を示す。） (Diamine represented by formula [2])
The diamine represented by the formula [2] is as follows:

(In formula [2], R ₁ , R ₂ , R ₃ and R ₄ each independently represent a methyl group or an ethyl group. X ₁ and X ₂ each independently represent a single bond, -NHCO-, -CONH-, -COO- or -OCO-. P ₁ and P ₂ each independently represent -NH ₂ or a structure represented by the following formulae [Pa] to [Pb]. n1 and n2 each independently represent an integer of 0 to 6. m represents an integer of 1 to 5. However, the phenyl in formulae [Pa] to [Pb] may be substituted with a halogen.)

(In formulas [Pa] to [Pb], ^XD2 represents an organic group having 1 to 50 carbon atoms and having at least one structure selected from the group consisting of the following formulas [2a], [2b], and [2c]. p represents an integer of 0 to 1. * represents a bond.)

(In formulas [2a] to [2c], ^Xa represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. ^Xd represents a single bond or an organic group having 1 to 20 carbon atoms. ^Xe represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. D represents a protecting group which is substituted with a hydrogen atom by heat. * represents a bond.)

In particular, in the above formula [2], R ₁ , R ₂ , R ₃ and R ₄ are preferably methyl groups. X ₁ and X ₂ are preferably a single bond, -CONH- or -COO-. P ₁ and P ₂ are preferably -NH ₂ or formula [2a]. n1 and n2 are preferably 3 or 4. m is preferably 1 or 2, more preferably 1.

（式［２ａ－１］中、Ｘ^１は単結合、炭素数１～１０のアルキレン基、－Ｏ－、－Ｎ（Ｒ^１）－、－ＣＯＮ（Ｒ^２）－、－Ｎ（Ｒ^３）ＣＯ－、－ＣＨ_２Ｏ－、－ＣＯＯ－及びＯＣＯ－からなる群から選ばれる少なくとも１種の有機基を示す。但し、Ｒ^１、Ｒ^２、Ｒ^３はそれぞれ独立して、水素原子又は炭素数１～３のアルキル基を示す。Ｘ^２は単結合、炭素数１～１０のアルキレン基を示し、Ｘ^ａは水素原子又は炭素数１～２０の有機基を示し、Ｘ^ｂは上記の式［１ａ－１］で定義されたものである。ｍは１又は２の整数を示し、その際、ｍが２の場合はＸ^ａは水素原子を示す。ｐは１～４の整数を示し、ｑは１～４の整数を示す。
式［２ｂ－１］中、Ｘ^８は単結合、炭素数１～１０のアルキレン基、－Ｏ－、－Ｎ（Ｒ^１）－、－ＣＯＮ（Ｒ^２）－、－Ｎ（Ｒ^３）ＣＯ－、－ＣＨ_２Ｏ－、－ＣＯＯ－及びＯＣＯ－からなる群から選ばれる少なくとも１種を示す。但し、Ｒ^１、Ｒ^２、Ｒ^３はそれぞれ独立して、水素原子又は炭素数１～３のアルキル基を示す。Ｘ^９は単結合、炭素数１～１０のアルキレン基を示し、Ｘ^ｄは単結合又は炭素数１～２０の有機基を示し、Ｘ^ｅは水素原子又は炭素数１～２０の有機基を示し、Ｘ^ｆは上記の式［１ａ－３］で定義されたものである。ｎは１～４の整数を示し、ｓは１～４の整数を示し、ｔは１～４の整数を示す。） In the diamine represented by the above formula [2], ^XD2 preferably represents a structure selected from the following formulas [2a-1] and [2b-1].

(In formula [2a-1], X ¹ represents a single bond, an alkylene group having 1 to 10 carbon atoms, and at least one organic group selected from the group consisting of -O-, -N(R ¹ )-, -CON(R ² )-, -N(R ³ )CO-, -CH ₂ O-, -COO-, and OCO-. However, R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. X ² represents a single bond or an alkylene group having 1 to 10 carbon atoms, X ^a represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and X ^b is defined in the above formula [1a-1]. m represents an integer of 1 or 2, and in this case, when m is 2, X ^a represents a hydrogen atom. p represents an integer of 1 to 4, and q represents an integer of 1 to 4.)
In formula [2b-1], ^X8 represents at least one selected from the group consisting of a single bond, an alkylene group having 1 to 10 carbon atoms, -O-, -N( ^R1 )-, -CON( ^R2 )-, -N( ^R3 )CO-, _-CH2O- , -COO- and OCO-. However, ^R1 , ^R2 and ^R3 each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. ^X9 represents a single bond or an alkylene group having 1 to 10 carbon atoms, ^Xd represents a single bond or an organic group having 1 to 20 carbon atoms, ^Xe represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and ^Xf is defined in formula [1a-3] above. n represents an integer of 1 to 4, s represents an integer of 1 to 4, and t represents an integer of 1 to 4.)

（Ａは、単結合又は炭素数１～４の炭化水素基からなる２価の基を示す。） In formula [2], X ^D2 more preferably represents a group represented by formula (tB) below, and further preferably represents an --N-Boc group.

(A represents a single bond or a divalent group consisting of a hydrocarbon group having 1 to 4 carbon atoms.)

Preferred examples of the diamine represented by the formula [2] include the following.

The content of the diamine represented by the formula [2] is preferably 1 to 50 mol % in 100 mol % of the total diamine components, more preferably 5 to 30 mol %, and even more preferably 5 to 20 mol %.
The diamine represented by the formula [2] can be used alone or in combination of two or more depending on the solubility of the specific polymer in a solvent, the coatability of the liquid crystal alignment agent, and the properties such as liquid crystal alignment, voltage holding rate, and accumulated charge when formed into a liquid crystal alignment film.

（式［３］中、Ｒ_１，Ｒ_２，Ｒ_３，Ｒ_４は、それぞれ独立して、メチル基又はエチル基を示す。Ｘは、－ＮＨＣＯ－、－ＣＯＮＨ－、－ＣＯＯ－又は－ＯＣＯ－を示す。Ｘ^Ｄ２は、上記の式［Ｐａ］及び［Ｐｂ］で定義されたものである。ｎは０～６の整数を示し、ｍは１～５の整数を示す。ｐは、０～１の整数を示し、ｑは０～１の整数を示す。但し、ｐおよびｑの少なくとも１つは１を示す。） <Diamine Component (2)>
In the diamine component (2), the diamine having a siloxane skeleton and a protecting group that is substituted with a hydrogen atom by heat is, for example, a diamine represented by the following formula [3].
(Diamine represented by formula [3])
The diamine represented by the formula [3] is as follows:

(In formula [3], R ₁ , R ₂ , R ₃ and R ₄ each independently represent a methyl group or an ethyl group. X represents -NHCO-, -CONH-, -COO- or -OCO-. ^XD2 are defined in formulas [Pa] and [Pb] above. n represents an integer of 0 to 6, m represents an integer of 1 to 5, p represents an integer of 0 to 1 and q represents an integer of 0 to 1, with the proviso that at least one of p and q represents 1.)

In the above formula [3], X is preferably —CONH— or —COO—. m is preferably 1 or 2, and more preferably 1. R ₁ to R ₄ are preferably methyl groups. n is preferably 1 to 4.

The content of the diamine represented by the formula [3] is preferably 1 to 50 mol % in 100 mol % of the total diamine components, more preferably 5 to 30 mol %, and even more preferably 5 to 20 mol %.
The diamine represented by the formula [3] can be used alone or in combination of two or more depending on the solubility of the specific polymer in a solvent, the coatability of the liquid crystal alignment agent, and the properties such as liquid crystal alignment, voltage holding rate, and accumulated charge when formed into a liquid crystal alignment film.

(Other diamines)
The diamine component (1) and the diamine component (2) for obtaining the specific polymer may contain a diamine (hereinafter, also referred to as "other diamine") other than the diamines represented by the above formulas [1] to [3]. As the other diamine, first, a diamine having the following side chain structure can be mentioned.

(Diamine having a specific side chain structure exhibiting vertical alignment property)
The diamine having a specific side chain structure that exhibits vertical alignment has at least one side chain structure selected from the group represented by the following formulas [S1] to [S3]. The diamines represented by the formulas [S1] to [S3], which are examples of diamines having such specific side chain structures, will be described in order below.

上記式［Ｓ１］中、Ｘ^１及びＸ^２は、それぞれ独立して、単結合、－（ＣＨ_２）_ａ－（ａは１～１５の整数を示す。）、－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＯＮ（ＣＨ_３）－、－ＮＨ－、－Ｏ－、－ＣＯＯ－、－ＯＣＯ－又は－（（ＣＨ_２）_ａ１－Ａ_１）_ｍ１－を表す。このうち、複数のａ１はそれぞれ独立して１～１５の整数を示す。複数のＡ_１はそれぞれ独立して酸素原子又は－ＣＯＯ－を示す。ｍ１は１～２を示す。 [A]: Diamine having a specific side chain structure represented by the following formula [S1]

In the above formula [S1], ^X1 and ^X2 each independently represent a single bond, -( _CH2 ) _a- (a represents an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, -NH-, -O-, -COO-, -OCO- or -(( _CH2 ) _a1 - _A1 ) _m1- . Among these, a1's each independently represent an integer of 1 to 15. _A1 's each independently represent an oxygen atom or -COO-. m1 represents 1 or 2.

Among these, from the viewpoints of availability of raw materials and ease of synthesis, ^X1 and ^X2 are each preferably independently a single bond, -( _CH2 ) _a- (a is an integer of 1 to 15), -O-, _-CH2O- or -COO-, and more preferably a single bond, -( _CH2 ) _a- (a is an integer of 1 to 10), -O-, _-CH2O- or -COO-.

In the above formula [S1], ^G1 and ^G2 each independently represent a divalent cyclic group selected from the group consisting of a divalent aromatic group having 6 to 12 carbon atoms and a divalent alicyclic group having 3 to 8 carbon atoms. Any hydrogen atom on the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom. m and n each independently represent an integer of 0 to 3, and the sum of m and n is 1 to 4.

In the above formula [S1], R ¹ represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an alkoxyalkyl group having 2 to 20 carbon atoms. Any hydrogen atom forming R ¹ may be substituted with fluorine. Among these, examples of the divalent aromatic group having 6 to 12 carbon atoms include phenylene, biphenylene, and naphthalene. Examples of the divalent alicyclic group having 3 to 8 carbon atoms include cyclopropylene and cyclohexylene.

Therefore, preferred specific examples of the above formula [S1] include the following formulas [S1-x1] to [S1-x7].

In the above formulas [S1-x1] to [S1-x7], R ¹ is the same as in the above formula [S1]. X ^p represents -(CH ₂ ) _a - (a represents an integer of 1 to 15), -CONH-, -NHCO-, -CON(CH ₃ )-, -NH-, -O-, -CH ₂ O-, -COO- or -OCO-. _{A 1} represents an oxygen atom or -COO-* (the bond marked with "*" bonds to (CH ₂ ) _a2 ). A ₂ represents an oxygen atom or *-COO- (the bond marked with "*" bonds to (CH ₂ ) _a2 ). _{a 1} represents an integer of 0 or 1, and a ₂ represents an integer of 2 to 10. Cy represents a 1,4-cyclohexylene group or a 1,4-phenylene group.

上記式［Ｓ２］中、Ｘ^３は単結合、－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＯＮ（ＣＨ_３）－、－ＮＨ－、－Ｏ－、－ＣＨ_２Ｏ－、－ＣＯＯ－又は－ＯＣＯ－を表す。なかでも、液晶配向剤の液晶配向性の点から、Ｘ^３は－ＣＯＮＨ－、－ＮＨＣＯ－、－Ｏ－、－ＣＨ_２Ｏ－、－ＣＯＯ－又は－ＯＣＯ－が好ましい。 [B]: Diamine having a specific side chain structure represented by the following formula [S2]

In the above formula [S2], ^X3 represents a single bond, -CONH-, -NHCO-, -CON( _CH3 )-, -NH-, -O-, _-CH2O- , -COO- or -OCO-. Among these, from the viewpoint of the liquid crystal alignment property of the liquid crystal aligning agent, ^X3 is preferably -CONH-, -NHCO-, -O-, _-CH2O- , -COO- or -OCO-.

In the above formula [S2], ^R2 represents an alkyl group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms. Any hydrogen atom forming ^R2 may be substituted with a fluorine atom. Among them, from the viewpoint of the liquid crystal alignment property of the liquid crystal alignment agent, ^R2 is preferably an alkyl group having 3 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms.

上記式［Ｓ３］中、Ｘ^４は－ＣＯＮＨ－、－ＮＨＣＯ－、－Ｏ－、－ＣＯＯ－又は－ＯＣＯ－を表す。Ｒ^３はステロイド骨格を有する構造を表す。ここでのステロイド骨格は、３つの六員環及び１つの五員環が結合した下記式（ｓｔ）で表される骨格を有する。

[C]: Diamine having a specific side chain structure represented by the following formula [S3]

In the above formula [S3], ^X4 represents -CONH-, -NHCO-, -O-, -COO- or -OCO-. ^R3 represents a structure having a steroid skeleton. The steroid skeleton here has a skeleton represented by the following formula (st) in which three six-membered rings and one five-membered ring are bonded.

An example of the above formula [S3] is the following formula [S3-x].

In the above formula [S3-x], X represents the above formula [X1] or [X2]. Col represents at least one selected from the group consisting of the above formulas [Col1] to [Col3], and G represents at least one selected from the group consisting of the above formulas [G1] to [G4]. * represents a site that bonds to another group.

In the above formula [S3-x], preferred examples of combinations of X, Col, and G include the following combinations: [X1], [Col1], and [G1], [X1], [Col1], and [G2], [X1], [Col2], and [G1], [X1], [Col2], and [G2], [X1], [Col3], and [G2], [X1], [Col3], and [G1], [X2], [Col1], and [G2], [X2], [Col2], and [G2], [X2], [Col2], and [G1], [X2], [Col3], and [G2], [X2], [Col1], and [G1].

Specific examples of the above formula [S3] include the structure obtained by removing a hydroxyl group (hydroxy group) from the steroid compound described in paragraph [0024] of JP 4-281427 A, the structure obtained by removing an acid chloride group from the steroid compound described in paragraph [0030] of the same publication, the structure obtained by removing an amino group from the steroid compound described in paragraph [0038] of the same publication, the structure obtained by removing a halogen group from the steroid compound described in paragraph [0042] of the same publication, and the structure described in paragraphs [0018] to [0022] of JP 8-146421 A.

A typical example of a steroid skeleton is cholesterol (a combination of [Col1] and [G2] in the above formula [S3-x]), but a steroid skeleton that does not contain cholesterol can also be used. That is, an example of a diamine having a steroid skeleton is cholestanyl 3,5-diaminobenzoate, but it is also possible to use a diamine component that does not contain a diamine having a cholesterol skeleton. In addition, as a diamine having a specific side chain structure, one that does not contain an amide at the linking position between the diamine and the side chain can also be used. Even if such a diamine is used, in this embodiment, even if a diamine component that does not contain a diamine having a cholesterol skeleton is used, a liquid crystal alignment agent that can obtain a liquid crystal alignment film or liquid crystal display element that can maintain a high voltage retention rate for a long period of time can be provided.

上記式［１－Ｓ１］中、Ｘ^１、Ｘ^２、Ｇ^１、Ｇ^２、Ｒ^１、ｍ及びｎは、上記式［Ｓ１］における場合と同様である。上記式［１－Ｓ２］中、Ｘ^３及びＲ^２は、上記式［Ｓ２］における場合と同様である。上記式［１－Ｓ３］中、Ｘ^４及びＲ^３は、上記式［Ｓ３］における場合と同様である。 The diamines having the side chain structures represented by the above formulas [S1] to [S3] are represented by the structures of the following formulas [1-S1] to [1-S3], respectively.

In the above formula [1-S1], ^X1 , ^X2 , ^G1 , ^G2 , ^R1 , m and n are the same as those in the above formula [S1]. In the above formula [1-S2], ^X3 and ^R2 are the same as those in the above formula [S2]. In the above formula [1-S3], ^X4 and ^R3 are the same as those in the above formula [S3].

(Diamine having a characteristic two-side chain structure that exhibits vertical alignment properties)
The diamine having a characteristic two-side-chain structure that exhibits vertical alignment properties is represented, for example, by the following formula [N1].

In the above formula [N1], X represents a single bond, -O-, -C(CH ₃ ) ₂ -, -NH-, -CO-, -NHCO-, -COO-, -(CH ₂ ) _m -, -SO ₂ -, or a divalent organic group consisting of any combination thereof. Among these, X preferably represents a single bond, -O-, -NH-, or -O-(CH ₂ ) _m -O-. Examples of "any combination thereof" include -O-( _CH2 ) _m -O-, -O-C( _CH3 ) _2- , -CO-( _CH2 ) _m- , -NH-(CH2) _{m- , -SO2-} ( _CH2 ) _m- , -CONH-( _CH2 ) _m- , -CONH-( _CH2 ) _m -NHCO-, -COO-( _CH2 ) _m -OCO- and the like, where m is an integer of 1 to 8.
In addition, in the above formula [N1], two Y's each independently represent a structure of the following formula [1-1].

In the above formula [1-1], Y ¹ and Y ³ each independently represent a single bond, -(CH ₂ ) _a - (a represents an integer of 1 to 15), -O-, -CH ₂ O-, -COO- or -OCO-. Y ² represents a single bond or -(CH ₂ ) _b - (b represents an integer of 1 to 15). However, when Y ¹ or Y ³ represents a single bond or -(CH ₂ ) _a -, Y ² represents a single bond. In addition, when Y ¹ represents -O-, -CH ₂ O-, -COO- or -OCO- and/or Y ³ represents -O-, -CH ₂ O-, -COO- or -OCO-, Y ² represents a single bond or -(CH ₂ ) _b -.
In addition, in formula [1-1], ^Y4 represents at least one divalent cyclic group selected from the group consisting of a benzene ring, a cyclohexane ring, and a heterocycle, or a divalent organic group having a steroid skeleton and having 17 to 51 carbon atoms. Any hydrogen atom forming the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom.

In the above formula [1-1], ^Y5 represents at least one cyclic group selected from the group consisting of a benzene ring, a cyclohexane ring, and a heterocycle, and any hydrogen atom forming the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom.
In the above formula [1-1], ^Y6 represents at least one selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, a fluorine-containing alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, and a fluorine-containing alkoxy group having 1 to 18 carbon atoms. n represents an integer of 0 to 4.

In addition, in the above formula [N1], Y may be in the meta position or the ortho position relative to the position of X, but is preferably in the ortho position. That is, the above formula [N1] is preferably the following formula [1'].

In addition, in the above formula [N1], the positions of the two amino groups (-NH ₂ ) may be any positions on the benzene ring, but the positions represented by the following formulas [1]-a1 to [1]-a3 are preferred, and the following formula [1]-a1 is more preferred. In the following formulas, X is the same as in the above formula [N1]. Note that the following formulas [1]-a1 to [1]-a3 explain the positions of the two amino groups, and the notation of Y represented in the above formula [N1] is omitted.

Therefore, based on the above formulas [1'] and [1]-a1 to [1]-a3, the above formula [N1] is preferably any structure selected from the group consisting of the following formulas [1]-a1-1 to [1]-a3-2, and more preferably a structure represented by the following formula [1]-a1-1. In the following formulas, X and Y are each the same as in formula [N1].

Examples of the formula [1-1] include the following formulas [1-1]-1 to [1-1]-22. Of these, preferred examples of the formula [1-1] include the following formulas [1-1]-1 to [1-1]-4, [1-1]-8, and [1-1]-10. In the formulas below, * represents the bonding position with the phenyl group in the formulas [1], [1'], and [1]-a1 to [1]-a3.

When the diamine component contains a two-side chain diamine having a predetermined structure, the liquid crystal alignment film is one in which the ability to vertically align liquid crystals is less likely to decrease even when exposed to excessive heat. Furthermore, when the diamine component contains the two-side chain diamine, the liquid crystal alignment film is one in which the ability to vertically align liquid crystals is less likely to decrease even when the film comes into contact with some foreign matter and is damaged. In other words, when the diamine component contains the two-side chain diamine, it becomes possible to provide a liquid crystal alignment agent that can obtain a liquid crystal alignment film that is excellent in the various above-mentioned properties.

Secondly, other diamines include diamines represented by the following general formula (Y).

In the above formula (Y), _A1 and _A2 each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms. From the viewpoint of liquid crystal alignment, _A1 and _A2 are preferably a hydrogen atom or a methyl group. Examples of the structure of _Y1 are as shown in the following formulae (Y-1) to (Y-68).

（式中のＢｏｃは、ｔｅｒｔ－ブトキシカルボニル基を表す。＊は結合手を表す。）

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

（Ｙ_１は硫黄原子又は酸素原子を表し、Ｒ_２はそれぞれ独立して単結合又は基「＊１－Ｒ^５－Ｐｈ－＊２」を表し、Ｒ^５は単結合、－Ｏ－、－ＣＯＯ－、－ＯＣＯ－、－（ＣＨ_２）_ｌ－、－Ｏ（ＣＨ_２）_ｍＯ－、－ＣＯＮＨ－、及び－ＮＨＣＯ－からなる群から選ばれる２価の有機基を表し（ｌ、ｍは１～５の整数を表す）、＊１は式（ｐｎ）中のベンゼン環と結合する部位を表し、＊２は式（ｐｎ）中のアミノ基と結合する部位を表す。Ｐｈはフェニレン基を表す。ｎは１～３を表す。）、２,３－ジアミノピリジン、２,６－ジアミノピリジン、３,４－ジアミノピリジン、２,４－ジアミノピリミジン、１，３－ビス（３－アミノプロピル）－テトラメチルジシロキサン等のジアミノオルガノシロキサン、メタキシレンジアミン等の脂肪族ジアミン、４，４－メチレンビス（シクロヘキシルアミン）等の脂環式ジアミン等を挙げることができる。
その他のジアミンは１種又は２種以上を併用することもできる。 Thirdly, as other diamines, there may be mentioned diamines having a thiophene or furan structure as described in International Publication WO2018/092759, preferably diamines having a structure represented by the following formula (sf):

(Y ₁ represents a sulfur atom or an oxygen atom, R ₂ each independently represents a single bond or a group "*1-R ⁵ -Ph-*2", R ⁵ represents a single bond, -O-, -COO-, -OCO-, -(CH ₂ ) _l -, -O(CH ₂ ) _m represents a divalent organic group selected from the group consisting of -O-, -CONH-, and -NHCO- (l and m represent integers of 1 to 5), *1 represents a site bonded to the benzene ring in formula (pn), *2 represents a site bonded to the amino group in formula (pn). Ph represents a phenylene group. n represents 1 to 3. ), 2,3-diaminopyridine, 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, diaminoorganosiloxane such as 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, aliphatic diamines such as metaxylenediamine, and alicyclic diamines such as 4,4-methylenebis(cyclohexylamine).
The other diamines can be used alone or in combination of two or more kinds.

(Tetracarboxylic acid component)
As the tetracarboxylic acid component for obtaining the specific polymer, a tetracarboxylic acid dianhydride represented by the following formula [4] or a derivative thereof (tetracarboxylic acid, tetracarboxylic acid dihalide, tetracarboxylic acid dialkyl ester, or tetracarboxylic acid dialkyl ester dihalide) (collectively referred to as specific tetracarboxylic acid) can be used.

（式［４］中、Ｚは下記の式［４ａ］～式［４ｑ］からなる群から選ばれる少なくとも１種の構造を示す。）

(In formula [4], Z represents at least one structure selected from the group consisting of the following formulas [4a] to [4q].)

In formula [4a], Z ¹ to Z ⁴ each independently represent a hydrogen atom, a methyl group, an ethyl group, a propyl group, a chlorine atom or a benzene ring, and Z ⁵ and Z ⁶ each independently represent a hydrogen atom or a methyl group.
Among ^Z1 in formula [4], in terms of ease of synthesis and ease of polymerization reactivity in producing a polymer, tetracarboxylic dianhydrides having a structure represented by formula [4a], formula [4c] to formula [4g], formula [4k] to formula [4m], or formula [4p] and tetracarboxylic acid derivatives thereof are preferred. More preferred are those having a structure represented by formula [4a], formula [4e] to formula [4g], formula [41], formula [4m], or formula [4p]. Particularly preferred are tetracarboxylic dianhydrides having a structure represented by formula [4a], formula [4e], formula [4f], formula [41], formula [4m], or formula [4p] and tetracarboxylic acid derivatives thereof.

特定テトラカルボン酸は、すべてのテトラカルボン酸成分１００モル％中、５０～１００モル％であることが好ましい。なかでも、７０～１００モル％が好ましい。より好ましいのは、８０～１００モル％である。 More specifically, it is preferable to use the following formula [4a-1] or [4a-2].

The specific tetracarboxylic acid is preferably 50 to 100 mol % relative to 100 mol % of all tetracarboxylic acid components, more preferably 70 to 100 mol %, and even more preferably 80 to 100 mol %.

Specific tetracarboxylic acids can be used alone or in a mixture of two or more types depending on the properties such as the solubility of the specific polymer in the solvent, the coatability of the liquid crystal alignment agent, the alignment of the liquid crystal when made into a liquid crystal alignment film, the voltage retention rate, and the stored charge.

The tetracarboxylic acid component for obtaining the specific polymer may contain a tetracarboxylic acid other than the above-mentioned specific tetracarboxylic acid (hereinafter, also referred to as other tetracarboxylic acid).
Examples of other tetracarboxylic acids include the following tetracarboxylic acid compounds, tetracarboxylic dianhydrides, tetracarboxylic acid dihalide compounds, tetracarboxylic acid dialkyl ester compounds, and tetracarboxylic acid dialkyl ester dihalide compounds.

That is, other tetracarboxylic acids include 1,2,5,6-naphthalenetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 1,2,5,6-anthracenetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4-biphenyltetracarboxylic acid, bis(3,4-dicarboxyphenyl)ether, 3,3',4,4'-benzophenonetetracarboxylic acid, bis(3,4-dicarboxyphenyl)sulfone, bis(3,4-dicarboxyphenyl)methane, 2,2-bis(3,4-dicarboxyphenyl)sulfone, bis(3,4-dicarboxyphenyl)methane ... 1,1,1,3,3,3-hexafluoro-2,2-bis(3,4-dicarboxyphenyl)propane, bis(3,4-dicarboxyphenyl)dimethylsilane, bis(3,4-dicarboxyphenyl)diphenylsilane, 2,3,4,5-pyridinetetracarboxylic acid, 2,6-bis(3,4-dicarboxyphenyl)pyridine, 3,3',4,4'-diphenylsulfonetetracarboxylic acid, 3,4,9,10-perylenetetracarboxylic acid, or 1,3-diphenyl-1,2,3,4-cyclobutanetetracarboxylic acid.
Other tetracarboxylic acids can be used alone or in combination of two or more depending on the solubility of the specific polymer in a solvent, the coatability of the liquid crystal alignment agent, and properties such as liquid crystal alignment, voltage holding rate, and stored charge when formed into a liquid crystal alignment film.

<Method of Producing Specific Polymer>
The specific polymer is at least one selected from the group consisting of a polyimide precursor obtained by a polymerization reaction between a diamine component and a tetracarboxylic acid component, and a polyimide obtained by imidizing the polyimide precursor.

The reaction between the diamine component and the tetracarboxylic acid component is usually carried out in a solvent. The solvent used in this reaction is not particularly limited as long as it dissolves the generated polyimide precursor. Specific examples of the solvent used in the reaction are listed below, but are not limited to these examples.
Examples of the solvent include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, N,N-dimethylformamide, N,N-dimethylacetamide, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, dimethylsulfoxide, and 1,3-dimethyl-imidazolidinone. In addition, when the polyimide precursor has high solvent solubility, methyl ethyl ketone, cyclohexanone, cyclopentanone, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, and the like can be used.

These solvents may be used alone or in combination. Furthermore, even if the solvent does not dissolve the polyimide precursor, it may be mixed with the above solvent to the extent that the resulting polyimide precursor does not precipitate. Furthermore, since moisture in the solvent inhibits the polymerization reaction and further causes hydrolysis of the resulting polyimide precursor, it is preferable to use a solvent that has been dehydrated and dried.

When reacting the diamine component and the tetracarboxylic acid component in a solvent, any of the following methods may be used: a solution in which the diamine component is dispersed or dissolved in a solvent is stirred, and the tetracarboxylic acid component is added as is or dispersed or dissolved in the solvent; conversely, the diamine component is added to a solution in which the tetracarboxylic acid component is dispersed or dissolved in a solvent; or the diamine component and the tetracarboxylic acid component are added alternately to the reaction system. When reacting multiple diamine components or multiple tetracarboxylic acid components, they may be reacted in a premixed state, or may be reacted individually in sequence, or low molecular weight components that have been reacted individually may be mixed and reacted to form a polymer.

The temperature at which the diamine component and the tetracarboxylic acid component are polycondensed can be selected from any temperature between -20 and 150°C, but is preferably in the range of -5 to 100°C. The 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 liquid becomes too high, making uniform stirring difficult. Therefore, the polymer concentration is preferably 1 to 50% by mass, more preferably 5 to 30% by mass. The reaction can be carried out at a high concentration in the early stages, and then a solvent can be added.
In the polymerization reaction to obtain the polyimide precursor, the ratio of the total number of moles of the tetracarboxylic acid components to the total number of moles of the diamine components is preferably 0.8 to 1.2. As in the case of a normal polycondensation reaction, the closer this molar ratio is to 1.0, the higher the molecular weight of the polyimide precursor produced will be.

An imidized polymer is a polyimide obtained by ring-closing a polyimide precursor. In this polyimide, the ring-closure rate (also called the imidization rate) of amic acid groups (amide acid groups) does not necessarily need to be 100% and can be adjusted as desired depending on the application or purpose.
Methods for imidizing the polyimide precursor include thermal imidization, in which a solution of the polyimide precursor is heated as is, and catalytic imidization, in which a catalyst is added to a solution of the polyimide precursor.

When the polyimide precursor is thermally imidized in a solution, the temperature is preferably 100 to 400°C, more preferably 120 to 250°C, and it is preferable to carry out the imidization while removing the water generated by the imidization reaction from the system. Catalytic imidization of the polyimide precursor can be carried out by adding a basic catalyst and an acid anhydride to a solution of the polyimide precursor and stirring at -20 to 250°C, preferably 0 to 180°C.

The amount of the basic catalyst is preferably 0.5 to 30 times by mole, more preferably 2 to 20 times by mole, the amount of the amic acid group, and the amount of the acid anhydride is preferably 1 to 50 times by mole, more preferably 3 to 30 times by mole, the amount of the amic acid group.
Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, etc. Among these, pyridine is preferred because it has an appropriate basicity for promoting the reaction.
Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. In particular, the use of acetic anhydride is preferred because it facilitates purification after the reaction. The imidization rate by catalytic imidization can be controlled by adjusting the amount of catalyst, reaction temperature, and reaction time.

The imidization rate of the polyimide precursor or its imidized polymer of the present invention is preferably 1 to 95%, more preferably 20% or more and 80% or less, and even more preferably 40% or more and 70% or less.

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

In the present invention, when the polyimide precursor is a polyamic acid alkyl ester, a specific method for producing it may be, for example, the method described in paragraphs [0054] to [0062] of International Publication WO2011-115077.

<Liquid crystal alignment agent>
The content of the specific polymer in the liquid crystal aligning agent of the present invention is preferably from 2 to 10% by mass, more preferably from 3 to 8% by mass, in the liquid crystal aligning agent.

The liquid crystal alignment agent of the present invention may contain other polymers in addition to the specific polymer. Examples of other polymers include cellulose-based polymers, acrylic polymers, methacrylic polymers, polystyrene, polyamides, polysiloxanes, etc. The content of other polymers is preferably 0.5 to 15 parts by mass, more preferably 1 to 10 parts by mass, per 100 parts by mass of the specific polymer.

The liquid crystal alignment agent usually contains an organic solvent, and the content of the organic solvent is preferably 70 to 99.9% by mass relative to the liquid crystal alignment agent. This content can be appropriately changed depending on the coating method of the liquid crystal alignment agent and the intended film thickness of the liquid crystal alignment film.
The organic solvent used in the liquid crystal alignment agent is preferably a solvent (also called a good solvent) that dissolves a specific polymer. For example, 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, 4-hydroxy-4-methyl-2-pentanone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, etc. Among them, it is preferable to use N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, or γ-butyrolactone.

The good solvent in the liquid crystal alignment agent of the present invention preferably accounts for 20 to 99% by mass of the total solvent contained in the liquid crystal alignment agent, more preferably 20 to 90% by mass, and particularly preferably 30 to 80% by mass.

The liquid crystal aligning agent of the present invention can use a solvent (also called a poor solvent) that improves the coating property and surface smoothness of the liquid crystal alignment film when the liquid crystal aligning agent is applied. Specific examples thereof are given below.
For example, diisopropyl ether, diisobutyl ether, diisobutyl carbinol (2,6-dimethyl-4-heptanol), 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, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, propylene glycol monobutyl ether, 1-(2-butoxyethoxy)-2-propanol, 2-(2-butoxyethoxy)-2-propanol, Examples of the dimethyl ether include 1-propanol, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, propylene glycol diacetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, n-butyl lactic acid ester, isoamyl lactic acid ester, diethylene glycol monoethyl ether, and diisobutyl ketone (2,6-dimethyl-4-heptanone).

Among them, preferred combinations of solvents include N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, and ethylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, and propylene glycol monobutyl ether, N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether, N-methyl-2-pyrrolidone, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone, and diethylene glycol diethyl ether. Examples of poor solvents include 1 to 80% by mass of the entire solvent contained in the liquid crystal alignment agent, more preferably 10 to 80% by mass, and particularly preferably 20 to 70% by mass. The type and content of such solvents are appropriately selected depending on the coating device, coating conditions, and coating environment of the liquid crystal alignment agent.

The liquid crystal alignment agent of the present invention may contain a dielectric material for changing the electrical properties of the liquid crystal alignment film, such as the dielectric constant and conductivity, a silane coupling agent for improving the adhesion between the liquid crystal alignment film and the substrate, a crosslinking compound for increasing the hardness and density of the film when made into a liquid crystal alignment film, and an imidization accelerator for efficiently promoting imidization by heating the polyimide precursor when baking the coating film.

Compounds that improve the adhesion between the liquid crystal alignment film and the substrate include functional silane-containing compounds and epoxy group-containing compounds, such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldi Methoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl-1,4,7-triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6- Diazanonyl acetate, N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-bis(oxyethylene)-3-aminopropyltrimethoxysilane, N-bis(oxyethylene)-3-aminopropyltriethoxysilane, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, 1,3,5,6-tetraglycidyl-2,4-hexanediol, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, or N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane.

The liquid crystal aligning agent of the present invention may contain the following additives (CL-1) to (CL-15) in order to increase the mechanical strength of the liquid crystal alignment film.

The amount of the additive is preferably 0.1 to 30 parts by mass per 100 parts by mass of the polymer component contained in the liquid crystal alignment agent. More preferably, it is 0.5 to 20 parts by mass.

<Method of manufacturing liquid crystal alignment film>
The liquid crystal alignment film is obtained by forming a coating of the liquid crystal alignment agent on a substrate by coating, etc., preferably drying, and then baking. As the substrate, a substrate with high transparency is preferable, and as the material, glass, ceramics such as silicon nitride, plastics such as acrylic and polycarbonate, etc. can be used. From the viewpoint of simplifying the process, it is preferable to use a substrate on which an ITO (Indium Tin Oxide) electrode for driving the liquid crystal is formed as the substrate. In addition, in a reflective liquid crystal display element, an opaque substrate such as a silicon wafer can be used for one substrate, and a light-reflecting material such as aluminum can be used for the electrode.

As a method for forming a coating on a substrate from a liquid crystal alignment agent, screen printing, offset printing, flexographic printing, an inkjet method, etc. can be used industrially. In addition, a dip method, a roll coater method, a slit coater method, a spinner method, a spray method, etc. can also be used depending on the purpose.
After forming a coating of the liquid crystal alignment agent on the substrate, the coating is preferably dried by a heating means such as a hot plate, a heat circulation type oven, or an IR (infrared) type oven at preferably 30 to 120° C., more preferably 50 to 120° C., for preferably 1 to 10 minutes, more preferably 1 to 5 minutes, to evaporate the solvent.

When thermal imidization of the imide precursor in the polymer is performed, the coating obtained from the liquid crystal alignment agent is then baked by the same heating means as in the drying treatment described above, preferably at 120 to 250°C, more preferably at 150 to 230°C. The baking time varies depending on the baking temperature, but is preferably 5 minutes to 1 hour, more preferably 5 minutes to 40 minutes.

The thickness of the coating after the above-mentioned baking treatment is not particularly limited, but if it is too thin, the reliability of the liquid crystal display element may decrease, and if it is too thick, the electrical resistance of the resulting liquid crystal alignment film will be high, so a thickness of 5 to 300 nm is preferable, and 10 to 200 nm is more preferable.

After the above-mentioned baking process, the obtained coating is subjected to an alignment process. Methods for the alignment process include a rubbing process and a photoalignment process.

A specific example of the photo-alignment treatment is to irradiate the surface of the coating with radiation deflected in a certain direction. As the radiation, ultraviolet light or visible light having a wavelength of 100 to 800 nm can be used. Among them, ultraviolet light having a wavelength of 100 to 400 nm is preferred, and more preferably ultraviolet light having a wavelength of 200 to 400 nm. In order to improve the liquid crystal alignment, the substrate coated with the liquid crystal alignment film may be irradiated with ultraviolet light while being heated at 50 to 250°C. The radiation dose is preferably 1 to 10,000 mJ/ ^cm2 . Among them, 100 to 5,000 mJ/ ^cm2 is preferred. The liquid crystal alignment film thus produced can stably align liquid crystal molecules in a certain direction.
The higher the extinction ratio of the polarized UV light, the higher the anisotropy that can be imparted, which is preferable. Specifically, the extinction ratio of the linearly polarized UV light is preferably 10:1 or more, and more preferably 20:1 or more.

The coating that has been subjected to the above-mentioned alignment treatment may further be subjected to at least one treatment selected from the group consisting of a heat treatment and a contact treatment with a solvent.
The heat treatment after the alignment treatment can be carried out by the same heating means as in the drying treatment and baking treatment, and is preferably carried out at 180 to 250° C., more preferably 180 to 230° C. When the heat treatment is carried out at a temperature within the above range, the contrast of the liquid crystal display element obtained by the obtained liquid crystal alignment film can be improved.
The heat treatment time varies depending on the heating temperature, but is preferably 5 minutes to 1 hour, more preferably 5 to 40 minutes.

The solvent used in the contact treatment with the solvent is not particularly limited as long as it dissolves impurities adhering to the liquid crystal alignment film.
Specific examples include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl cellosolve, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate, cyclohexyl acetate, and the like. Among these, from the viewpoint of versatility and safety of the solvent, water, 2-propanol, 1-methoxy-2-propanol, or ethyl lactate is preferred. More preferred are water, 1-methoxy-2-propanol, or ethyl lactate. These solvents may be used alone or in combination of two or more kinds.

Examples of the contact treatment include immersion treatment and spray treatment (also called spray treatment). The treatment time in these treatments is preferably 10 seconds to 1 hour, and particularly immersion treatment for 1 to 30 minutes is an example. The temperature during the contact treatment may be room temperature or heated, but is preferably 10 to 80°C, and 20 to 50°C is an example. During the contact treatment, ultrasonic treatment or the like may be further carried out as necessary.

After the contact treatment, rinsing (also called "rinsing") with a low boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone, or methyl ethyl ketone, or drying may be performed. In this case, either rinsing or drying may be performed, or both may be performed. The drying temperature is preferably 50 to 150°C, and can be 80 to 120°C. The drying time is preferably 10 seconds to 30 minutes, and preferably 1 to 10 minutes.

After the contact treatment with the above-mentioned solvent, a heat treatment after the alignment treatment may be performed. By adopting such an embodiment, a liquid crystal alignment film with excellent liquid crystal alignment properties can be obtained.

<Liquid crystal display element>
The liquid crystal alignment film of the present invention can be applied to various driving modes such as TN mode, STN mode, IPS mode, FFS mode, VA mode, MVA mode, PSA mode, etc., but is suitable as a liquid crystal alignment film for a liquid crystal display element of a horizontal electric field mode such as IPS mode or FFS mode, and is particularly useful for a liquid crystal display element of an FFS mode. The liquid crystal display element of the present invention is obtained by obtaining a substrate with a liquid crystal alignment film obtained from the above liquid crystal alignment agent, producing a liquid crystal cell by a known method, and using the liquid crystal cell to form an element.
As an example of a method for producing a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described below. However, a liquid crystal display element having an active matrix structure in which a switching element such as a TFT is provided in each pixel portion constituting an image display may also be used.

Specifically, a transparent glass substrate is prepared, and a common electrode is provided on one substrate, and a segment electrode is provided on the other substrate. These electrodes can 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 can be, for example, a film made of SiO ₂ -TiO ₂ formed by the sol-gel method. Next, under the above-mentioned conditions, a liquid crystal alignment film is formed on each substrate, and one substrate is superimposed on the other substrate so that the liquid crystal alignment film surfaces face each other, and the periphery is bonded with a sealant. In order to control the substrate gap, it is usually preferable to mix a spacer into the sealant. It is also preferable to scatter spacers for controlling the substrate gap even in the in-plane portion where the sealant is not provided. It is preferable to provide an opening in a part of the sealant that can be filled with liquid crystal from the outside.

Thereafter, a liquid crystal material is injected into the space surrounded by the two substrates and the sealant through an opening provided in the sealant. The opening is then sealed with an adhesive. The injection may be performed by a vacuum injection method or a method utilizing a capillary phenomenon in the atmosphere, or an ODF (One Drop Fill) method may be used. The liquid crystal material may have either positive or negative dielectric anisotropy. In the present invention, liquid crystals having negative dielectric anisotropy are preferred from the viewpoint of liquid crystal alignment, but they may be used according to the application.
After the liquid crystal material is injected into the liquid crystal cell, polarizing plates are provided. Specifically, it is preferable to attach a pair of polarizing plates to the surfaces of the two substrates opposite to the liquid crystal layer.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The abbreviations of the compounds used are as follows:

（テトラカルボン酸成分）

（溶媒）
ＮＭＰ：Ｎ－メチル－２－ピロリドン
ＢＣＳ：エチレングリコールモノブチルエーテル (Diamine component)

(Tetracarboxylic acid component)

(solvent)
NMP: N-methyl-2-pyrrolidone BCS: Ethylene glycol monobutyl ether

<Measurement of molecular weight of polyimide>
The molecular weight of the polyimide was measured using a room temperature gel permeation chromatography (GPC) apparatus (SSC-7200) manufactured by Senshu Scientific Co., Ltd. and columns (KD-803, KD-805) manufactured by Shodex Co., Ltd. as follows.
Column temperature: 50 ° C.
Eluent: N,N'-dimethylformamide (additives: lithium bromide hydrate (LiBr.HO) 30mmol/L, phosphoric acid anhydrous crystal (o-phosphoric acid) 30mmol/L, tetrahydrofuran (THF) 10ml/L)
Flow rate: 1.0 ml/min. Standard samples for preparing calibration curves: TSK standard polyethylene oxide (molecular weights: approximately 9,000,000, 150,000, 100,000, and 30,000) manufactured by Tosoh Corporation, and polyethylene glycol (molecular weights: approximately 12,000, 4,000, and 1,000) manufactured by Polymer Laboratory.

<Measurement of imidization rate>
20 mg of the polyimide powder was placed in an NMR sample tube (Kusano Scientific NMR Sampling Tube Standard φ5), 0.53 ml of deuterated dimethyl sulfoxide (DMSO-d ₆ , 0.05% TMS mixture) was added, and the mixture was sonicated to completely dissolve it.
This solution was subjected to 500 MHz proton NMR measurement using an NMR measuring device (JNW-ECA500) manufactured by 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 peak integrated value of this proton and the proton peak integrated value derived from the NH group of the amic acid appearing in the vicinity of 9.5 to 10.0 ppm.
Imidization rate (%)=(1−α·x/y)×100

<Synthesis of polyimide polymer>
<Synthesis Example 1>
D1 (9.14 g), DA-1 (4.68 g, molar ratio to all diamine components: 0.3), DA-2 (3.25 g, molar ratio to all diamine components: 0.4), DA-3 (1.95 g, molar ratio to all diamine components: 0.2), and DA-4 (1.02 g, molar ratio to all diamine components: 0.1) were mixed in NMP solvent (80.17 g) and reacted at 60° C. for 12 hours to obtain a polyamic acid solution.
NMP (103.85 g) was added to this polyamic acid solution (50.0 g) and diluted to 6.5 mass %, and then acetic anhydride (20.84 g) and pyridine (3.23 g) were added as imidization catalysts and reacted at 80 ° C for 5 hours. This reaction solution was poured into methanol (622.70 g), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 60 ° C to obtain polyimide powder (A). The imidization rate of this polyimide was 72%, Mn was 11,800, and Mw was 41,800.

<Synthesis Examples 2 to 4, Comparative Synthesis Examples 1 and 2>
Polyimide powders of Synthesis Examples 2 to 4 (B to D) and polyimide powders of Comparative Synthesis Examples 1 and 2 (E and F) were obtained in the same manner as in Synthesis Example 1, except that the materials and ratios in Synthesis Example 1 were changed as shown in Tables 1 and 2.
<Synthesis Example 5>
D2 (5.12 g), DA-7 (3.26 g, molar ratio to all diamine components: 0.4), DA-8 (3.97 g, molar ratio to all diamine components: 0.4), DA-9 (3.24 g, molar ratio to all diamine components: 0.2) were mixed in NMP solvent (62.43 g) and reacted at 60° C. for 3 hours, then cooled to room temperature, D3 (3.86 g) and NMP solvent (15.44 g) were added, and reacted at 40° C. for 12 hours to obtain polyamic acid solution (G). The Mn of this polyamic acid solution (G) was 10,600 and the Mw was 35,700.

表１において、ジアミン成分の名称の後の括弧内右側は、反応に用いた全ジアミン成分に対する各ジアミンのモル比を表す。

In Table 1, the numbers in parentheses on the right side after the names of the diamine components indicate the molar ratio of each diamine to the total diamine components used in the reaction.

Example 1
NMP (44.0 g) was added to the polyimide powder (A) (6.0 g) obtained in Synthesis Example 1, and the mixture was stirred at 70° C. for 40 hours to dissolve the powder. BCS (50.0 g) was added to the solution, and the mixture was stirred for 5 hours to obtain a liquid crystal alignment agent [1] of Example 1. No abnormalities such as turbidity or precipitation were observed in the liquid crystal alignment agent, and it was confirmed that the resin component was uniformly dissolved.
<Examples 2 to 4, Comparative Examples 1 and 2>
In Example 1, except that the polyimide material was changed as shown in Table 3, liquid crystal alignment agents [2] to [4] of Examples 2 to 4 and liquid crystal alignment agents [5] and [6] of Comparative Examples 1 and 2 were obtained in the same manner as in Example 1. No abnormalities such as turbidity or precipitation were observed in these liquid crystal alignment agents, and it was confirmed that the resin components were uniformly dissolved.
Example 5
NMP (29.0 g) was added to the polyamic acid solution (G) (21.0 g) obtained in Synthesis Example 5, and stirred for 30 minutes, BCS (35.0 g) was added and stirred for another 30 minutes, and then liquid crystal alignment agent [1] (30.0 g) was added and stirred for 5 hours to obtain liquid crystal alignment agent [7] of Example 5. No abnormalities such as turbidity or precipitation were observed in this liquid crystal alignment agent, and it was confirmed that the resin components were uniformly dissolved.

<Preparation of Liquid Crystal Cell>
The liquid crystal alignment agents of Examples 1 to 5 and Comparative Examples 1 and 2 were spin-coated on the ITO surface of a glass substrate (length 30 mm, width 40 mm, thickness 0.7 mm) with ITO that had been washed with pure water and IPA (isopropyl alcohol), baked on a hot plate at 70° C. for 90 seconds, and then baked in an infrared heating furnace at 230° C. for 20 minutes to prepare a polyimide-coated substrate with a film thickness of 100 nm.
Two polyimide-coated substrates were prepared by the above method, and 4 μm bead spacers were sprayed on the liquid crystal alignment film surface of one of the substrates, and then a thermosetting sealant (XN-1500T manufactured by Kyoritsu Chemical Co., Ltd.) was printed on top of the bead spacers. Next, the other substrate was attached to the previous substrate with the side on which the liquid crystal alignment film was formed facing inward, and the sealant was cured to prepare an empty cell. PSA polymerizable compound-containing liquid crystal MLC-3023 (product name manufactured by Merck & Co., Ltd.) was injected into this empty cell by a reduced pressure injection method to prepare a liquid crystal cell. The voltage holding ratio of this liquid crystal cell was measured.

Next, with a DC voltage of 15 V applied to the liquid crystal cell, the liquid crystal cell was irradiated with 10 J/ ^cm2 UV light through a 325 nm cut filter from the outside (also referred to as a primary PSA treatment). The UV illuminance was measured using a UV-MO3A manufactured by ORC Corporation.
Thereafter, in order to inactivate the unreacted polymerizable compound remaining in the liquid crystal cell, the cell was irradiated with UV (UV lamp: FLR40SUV32/A-1) for 30 minutes in a state where no voltage was applied, using a UV-FL irradiation device manufactured by Toshiba Lighting & Technology Corp. (referred to as secondary PSA treatment). Thereafter, the voltage holding ratio was measured.

<Evaluation of Voltage Holding Ratio>
Using the liquid crystal cell prepared above, a voltage of 1 V was applied for 60 μs in a hot air circulating oven at 60° C., and the voltage was measured 1667 msec later, and the voltage retention rate was calculated as the extent to which the voltage was retained. To measure the voltage retention rate, VHR-1 manufactured by Toyo Corporation was used.
<Evaluation of high temperature and high humidity resistance>
The liquid crystal cell prepared above was left to stand for 7 days in a thermohygrostat (PR-2KP manufactured by Espec Corp.) at a temperature of 85°C and a humidity of 85%, and then the voltage holding ratio was measured. The difference between the voltage holding ratio measured here and the voltage holding ratio after the secondary PSA treatment was taken as the VHR change.

As shown in Table 3, in Comparative Examples 1 and 2, the VHR after the secondary PSA treatment is lower than 86%, but in Examples 1 to 5 it is 86% or higher. Furthermore, in Comparative Examples 1 and 2, placing the liquid crystal cell under high temperature and high humidity caused a significant change in VHR of 65% or more, but it was confirmed that in Examples 1 to 5 the VHR change could be reduced to a small amount of 50% or less.

<Preparation of Liquid Crystal Cell for Tilt Angle Evaluation>
The liquid crystal alignment agents of Examples 1 to 5 and Comparative Examples 1 and 2 were spin-coated on the ITO surface of a 3.5 x 3 mm ITO electrode substrate (length 35 mm, width 30 mm, thickness 0.5 mm) with an ITO electrode pattern having a pixel size of 200 μm x 600 μm and a line/space of 3 μm each, which had been washed with pure water and IPA (isopropyl alcohol), and a glass substrate (length 35 mm, width 30 mm, thickness 0.7 mm) with an ITO electrode patterned with a photospacer having a height of 3.2 μm. Next, the substrate was baked on a hot plate at 70 ° C. for 90 seconds, and then baked in an infrared heating furnace at 230 ° C. for 20 minutes or 60 minutes to prepare a polyimide-coated substrate with a film thickness of 100 nm.
The ITO electrode substrate on which this ITO electrode pattern is formed is divided into four areas in a cross-checkered pattern, so that each of the four areas can be driven separately.

Two polyimide-coated substrates were prepared using the above method, and a thermosetting sealant (XN-1500T manufactured by Kyoritsu Chemical Co., Ltd.) was printed on them. Next, the other substrate was attached to the previous substrate with the side on which the liquid crystal alignment film was formed facing inward, and the sealant was cured to prepare an empty cell. PSA polymerizable compound-containing liquid crystal MLC-3023 (product name manufactured by Merck & Co., Ltd.) was injected into this empty cell by a reduced pressure injection method to prepare a liquid crystal cell. The voltage retention rate of this liquid crystal cell was measured.
Next, with a DC voltage of 15 V applied to the liquid crystal cell, the liquid crystal cell was irradiated with 10 J/ ^cm2 UV light through a 325 nm cut filter from the outside (also referred to as a primary PSA treatment). The UV illuminance was measured using a UV-MO3A manufactured by ORC Corporation.
Thereafter, in order to inactivate the unreacted polymerizable compound remaining in the liquid crystal cell, UV (UV lamp: FLR40SUV32/A-1) was irradiated for 30 minutes (referred to as secondary PSA treatment) using a UV-FL irradiation device manufactured by Toshiba Lighting & Technology Corp. in a state where no voltage was applied, and then the pretilt angle was measured.

<Evaluation of pretilt angle>
The pretilt angle of the liquid crystal cell for evaluating the pretilt angle prepared above was measured using an LCD analyzer (LCA-LUV42A manufactured by Meiryo Technica Corporation). The pretilt angle difference was determined by subtracting the pretilt angle measured using the polyimide-coated substrate baked for 60 minutes from the pretilt angle measured using the polyimide-coated substrate baked for 20 minutes in an infrared heating furnace at 230°C. The evaluation results are shown in Table 4.

As shown in Table 4, in Comparative Example 1, in which a siloxane skeleton is not introduced, the pretilt angle difference is 2.0°, but in Examples 1 to 5, it was confirmed that the pretilt angle difference can be reduced to 0.4° or less.

<Evaluation of Solubility>
BCS was dropped into 10 g of the liquid crystal alignment agents of Examples 1 to 5 and Comparative Examples 1 and 2 while stirring, and the solubility was calculated from the weight of the solution that became cloudy using the following formula. The evaluation results are shown in Table 5.
Solubility (%) = (amount of BCS in liquid crystal alignment agent + amount of BCS dropped) /
(amount of liquid crystal alignment agent + amount of BCS dropped) x 100

<Preparation of substrate for measuring seal adhesion>
The liquid crystal alignment agents of Examples 1 to 5 and Comparative Examples 1 and 2 were spin-coated on the ITO surface of a glass substrate (length 30 mm, width 40 mm, thickness 0.7 mm) with ITO that had been washed with pure water and IPA (isopropyl alcohol), baked on a hot plate at 70°C for 90 seconds, and then baked in an infrared heating furnace at 230°C for 20 minutes to prepare a polyimide-coated substrate with a film thickness of 100 nm.
Two polyimide-coated substrates were prepared using the above method, and 4 μm bead spacers were applied to the liquid crystal alignment film surface of one of the substrates, after which a sealant (XN-1500T, manufactured by Kyoritsu Chemical Co., Ltd.) was dropped onto it. Next, the liquid crystal alignment film surface of the other substrate was placed inside, and the substrates were laminated together so that the overlap width of the substrates was 1 cm and the diameter of the sealant was a circle close to 3 mm. After fixing the two laminated polyimide-coated substrates, they were baked for 1 hour in a hot air circulating oven at 150°C to prepare a sample for adhesion evaluation.

<Evaluation of Seal Adhesion>
The adhesion evaluation sample was fixed to the lower part (64 cm interval) of a three-point bending jig of a tabletop precision universal testing machine (Shimadzu Corporation, AGS-X 500N), and the adhesion evaluation substrate was then pressed from the upper center of the substrate at a speed of 5 mm/min to measure the force (N) required for peeling. The force (N) required for peeling measured by the above method was divided by the diameter of the sealant to evaluate the seal adhesion. The seal evaluation results are shown in Table 5.

As shown in Table 5, the solubility was lower than 60% in Comparative Examples 1 and 2, but was confirmed to be 60% or higher in Examples 1 to 5. The seal adhesion was also lower than 2 N/mm in Comparative Examples 1 and 2, but was confirmed to be 2.5 N/mm or higher in Examples 1 to 5.

The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2019-021819, filed on February 8, 2019, are hereby incorporated by reference as the disclosure of the specification of the present invention.

Claims (17)

A liquid crystal aligning agent comprising at least one polymer selected from the group consisting of a polyimide precursor obtained by polymerizing any one of the following diamine components (1) and (2) with a tetracarboxylic acid component, and a polyimide obtained by imidizing the polyimide precursor , wherein the imidization rate of the polyimide obtained by imidizing the polyimide precursor is 20% or more and 74% or less :
Diamine component (1): A diamine component containing a diamine having a tert-butoxycarbonyl group and a diamine having a siloxane skeleton.
Diamine component (2): A diamine component containing a diamine having a tert-butoxycarbonyl group and a siloxane skeleton. The liquid crystal aligning agent according to claim 1, wherein the diamine component (2) further contains at least one diamine having a specific side chain structure selected from the group represented by the following formulas [S1] to [S3].

(In the above formula [S1], ^X1 and ^X2 each independently represent a single bond, -( _CH2 ) _a- (a represents an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, -NH-, -O-, -COO-, -OCO- or -(( _CH2 ) _a1 - _A1 ) _m1- . Among these, a1 each independently represents an integer of 1 to 15. _A1 each independently represents an oxygen atom or -COO-. m1 represents 1 or 2. ^G1 and G Each of ^{R 2} independently represents a divalent cyclic group selected from the group consisting of a divalent aromatic group having 6 to 12 carbon atoms and a divalent alicyclic group having 3 to 8 carbon atoms. Any hydrogen atom on the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom. R ¹ represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an alkoxyalkyl group having 2 to 20 carbon atoms. Any hydrogen forming R ¹ may be substituted with a fluorine atom. Each of m and n independently represents an integer of 0 to 3, and the sum of m and n is 1 to 4.)

(In the above formula [S2], ^X3 represents a single bond, -CONH-, -NHCO-, -CON( _CH3 )-, -NH-, -O-, _-CH2O- , -COO- or -OCO-. ^R2 represents an alkyl group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms. Any hydrogen atom forming ^R2 may be substituted with a fluorine atom.);

(In the above formula [S3], ^X4 represents -CONH-, -NHCO-, -O-, -COO- or -OCO-. ^R3 represents a structure having a steroid skeleton.) 3. The liquid crystal aligning agent according to claim 1, wherein the diamine having a tert-butoxycarbonyl group in the diamine component (1) is a diamine represented by the following formula [1]:

(In formula [1], ^XD represents an organic group having 1 to 50 carbon atoms and having at least one structure selected from the group consisting of the following formulas [1a], [1b], and [1c], and ^A1 and ^A2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

(In formulas [1a] to [1c], ^Xa represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. ^Xd represents a single bond or an organic group having 1 to 20 carbon atoms. ^Xe represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. D represents a tert-butoxycarbonyl group. * represents a bond.) The liquid crystal aligning agent according to any one of claims 1 to 3, wherein the diamine having a siloxane skeleton in the diamine component (1) is a diamine represented by the following formula [2]:

(In formula [2], R ₁ , R ₂ , R ₃ and R ₄ each independently represent a methyl group or an ethyl group. X ₁ and X ₂ each independently represent a single bond, -NHCO-, -CONH-, -COO- or -OCO-. P ₁ and P ₂ each independently represent -NH ₂ or a structure represented by the following formulae [Pa] to [Pb]. n1 and n2 each independently represent an integer of 0 to 6. m represents an integer of 1 to 5. However, the phenyl in formulae [Pa] to [Pb] may be substituted with a halogen.)

(In formulas [Pa] to [Pb], ^XD2 represents an organic group having 1 to 50 carbon atoms and having at least one structure selected from the group consisting of the following formulas [2a], [2b], and [2c]. p represents an integer of 0 to 1. * represents a bond.)

(In formulas [2a] to [2c], ^Xa represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. ^Xd represents a single bond or an organic group having 1 to 20 carbon atoms. ^Xe represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. D represents a protecting group which is substituted with a hydrogen atom by heat. * represents a bond.) The liquid crystal aligning agent according to claim 3, wherein the diamine represented by the formula [1] is at least one diamine selected from the group consisting of the following formulas [1a-1] to [1c-1].

(In formula [1a-1], X ¹ represents a single bond, an alkylene group having 1 to 10 carbon atoms, and at least one organic group selected from the group consisting of -O-, -N(R ¹ )-, -CON(R ² )-, -N(R ³ )CO-, -CH ₂ O-, -COO-, and OCO-. However, R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. X ² represents a single bond or an alkylene group having 1 to 10 carbon atoms, and X ^a represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. X ^b represents a structure of formula [a-1] below. m represents an integer of 1 or 2, and in this case, when m is 2, X ^a represents a hydrogen atom. p represents an integer of 1 to 4, and q represents an integer of 1 to 4.)
In formula [1b-1], ^X3 and ^X7 each independently represent at least one selected from the group consisting of a single bond, an alkylene group having 1 to 10 carbon atoms, -O-, -N( ^R1 )-, -CON( ^R2 )-, -N( ^R3 )CO-, _-CH2O- , -COO- and OCO-. However, ^R1 , ^R2 and ^R3 each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. ^X4 and ^X6 each independently represent a single bond or an alkylene group having 1 to 10 carbon atoms, ^X5 represents a single bond or an alkylene group having 1 to 10 carbon atoms, and ^Xc represents a structure of formula [a-1] below. r represents an integer of 1 to 4.
In formula [1c-1], ^X8 represents at least one selected from the group consisting of a single bond, an alkylene group having 1 to 10 carbon atoms, -O-, -N( ^R1 )-, -CON( ^R2 )-, -N( ^R3 )CO-, _-CH2O- , -COO- and OCO-. However, ^R1 , ^R2 and ^R3 each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. ^X9 represents a single bond or an alkylene group having 1 to 10 carbon atoms, ^Xd represents a single bond or an organic group having 1 to 20 carbon atoms, ^Xe represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and ^Xf represents a structure of the following formula [a-1]. n represents an integer of 1 to 4, s represents an integer of 1 to 4, and t represents an integer of 1 to 4.
In formulas [1a-1] to [1c-1], A ¹ to A ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

The diamine represented by the formula [1a-1] to formula [1c-1] is at least one diamine selected from the group consisting of the following formulas [1d-1] to [1d-5]. The liquid crystal aligning agent according to claim 5.

(In formulas [1d-1] to [1d-5], R ¹ to R ⁷ each independently represent a structure of formula [a-1] below, and in formulas [1d-1] to [1d-5], A ¹ to A ¹⁰ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

The liquid crystal aligning agent according to claim 4, wherein m is 1 in the diamine represented by the formula [2]. The liquid crystal aligning agent according to claim 4 or 7, wherein in the diamine represented by the formula [2], X ^D2 represents a structure selected from the following formulas [2a-1] and [2b-1].

(In formula [2a-1], X ¹ represents a single bond, an alkylene group having 1 to 10 carbon atoms, and at least one organic group selected from the group consisting of -O-, -N(R ¹ )-, -CON(R ² )-, -N(R ³ )CO-, -CH ₂ O-, -COO-, and OCO-. However, R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. X ² represents a single bond or an alkylene group having 1 to 10 carbon atoms, X ^a represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and X ^b represents a structure of the following formula [a-1] . m represents an integer of 1 or 2, and in this case, when m is 2, X ^a represents a hydrogen atom. p represents an integer of 1 to 4, and q represents an integer of 1 to 4.)

In formula [2b-1], ^X8 represents at least one selected from the group consisting of a single bond, an alkylene group having 1 to 10 carbon atoms, -O-, -N( ^R1 )-, -CON( ^R2 )-, -N( ^R3 )CO-, _-CH2O- , -COO- and OCO-. However, ^R1 , ^R2 and ^R3 each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. ^X9 represents a single bond or an alkylene group having 1 to 10 carbon atoms, ^Xd represents a single bond or an organic group having 1 to 20 carbon atoms, ^Xe represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and ^Xf represents a structure selected from the group consisting of the following formulae [a-1] to [a-6]. n represents an integer of 1 to 4, s represents an integer of 1 to 4, and t represents an integer of 1 to 4.)

( ^R1 represents an alkylene group having 1 to 5 carbon atoms.) The liquid crystal aligning agent according to claim 4 or 7, wherein the diamine represented by the formula [2] is represented by the following formula:

The liquid crystal aligning agent according to claim 1, wherein the diamine having a tert-butoxycarbonyl group and a siloxane skeleton in the diamine component (2) is a diamine represented by the following formula [3]:

(In formula [3], R ₁ , R ₂ , R ₃ and R ₄ each independently represent a methyl group or an ethyl group. X represents -NHCO-, -CONH-, -COO- or -OCO-. ^XD2 represents an organic group having 1 to 50 carbon atoms and at least one structure selected from the group consisting of the following formulas [2a], [2b] and [2c]. p represents an integer of 0 to 1. * represents a bond. n represents an integer of 0 to 6, m represents an integer of 1 to 5, p represents an integer of 0 to 1 and q represents an integer of 0 to 1, with the proviso that at least one of p and q represents 1.)

(In formulas [2a] to [2c], ^Xa represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. ^Xd represents a single bond or an organic group having 1 to 20 carbon atoms. ^Xe represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. D represents a tert-butoxycarbonyl group. * represents a bond.) The liquid crystal aligning agent according to any one of claims 1 to 10, wherein the tetracarboxylic acid component is a tetracarboxylic acid compound represented by the following formula [4]:

(Z represents at least one structure selected from the group consisting of the following formulas [4a] to [4q].)

(In formula [4a], Z ¹ to Z ⁴ each independently represent a hydrogen atom, a methyl group, an ethyl group, a propyl group, a chlorine atom, or a benzene ring, and in formula [4g], Z ⁵ and Z ⁶ each independently represent a hydrogen atom or a methyl group.) The diamine component (1) further contains at least one diamine having a specific side chain structure selected from the group represented by the following formulas [S1] to [S3]. The liquid crystal aligning agent according to any one of claims 1 to 11.

(In the above formula [S1], ^X1 and ^X2 each independently represent a single bond, -( _CH2 ) _a- (a represents an integer of 1 to 15), -CONH-, -NHCO-, -CON( _CH3 )-, -NH-, -O-, -COO-, -OCO- or -(( _CH2 ) _a1 - _A1 ) _m1- . Among these, a1 each independently represents an integer of 1 to 15. _A1 each independently represents an oxygen atom or -COO-. m1 represents 1 or 2. ^G1 and G Each of ^{R 2} independently represents a divalent cyclic group selected from the group consisting of a divalent aromatic group having 6 to 12 carbon atoms and a divalent alicyclic group having 3 to 8 carbon atoms. Any hydrogen atom on the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom. R ¹ represents an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, or an alkoxyalkyl group having 2 to 20 carbon atoms. Any hydrogen forming R ¹ may be substituted with a fluorine atom. Each of m and n independently represents an integer of 0 to 3, and the sum of m and n is 1 to 4.)

(In the above formula [S2], X ³ represents a single bond, -CONH-, -NHCO-, -CON(CH ₃ )-, -NH-, -O-, -CH ₂ O-, -COO- or -OCO-. R ² represents an alkyl group having 1 to 20 carbon atoms or an alkoxyalkyl group having 2 to 20 carbon atoms. Any hydrogen atom forming R ² may be substituted with a fluorine atom.);

(In the above formula [S3], ^X4 represents -CONH-, -NHCO-, -O-, -COO- or -OCO-. ^R3 represents a structure having a steroid skeleton.) The liquid crystal aligning agent according to any one of claims 1 to 12, wherein the diamine component (1) and the diamine component (2) further contain a two-side chain diamine represented by the following formula [N1].

(In the above formula [N1], X represents a single bond, -O-, -C(CH ₃ ) ₂ -, -NH-, -CO-, -NHCO-, -COO-, -(CH ₂ ) _m -, -SO ₂ -, or a divalent organic group consisting of any combination thereof. m represents an integer of 1 to 8. Each Y independently represents a structure of the following formula [1-1].)

(In the above formula [1-1], Y ¹ and Y ³ each independently represent a single bond, -(CH ₂ ) _a - (a represents an integer of 1 to 15), -O-, -CH ₂ O-, -COO- or -OCO-. Y ² represents a single bond or -(CH ₂ ) _b - (b represents an integer of 1 to 15). However, when Y ¹ or Y ³ represents a single bond or -(CH ₂ ) _a -, Y ² represents a single bond. Furthermore, when Y ¹ represents -O-, -CH ₂ O-, -COO- or -OCO- and/or Y ³ represents -O-, -CH ₂ O-, -COO- or -OCO-, Y ² represents a single bond or -(CH ₂ ) _b -.
^Y4 represents at least one divalent cyclic group selected from the group consisting of a benzene ring, a cyclohexane ring, and a heterocycle, or a divalent organic group having a steroid skeleton and having 17 to 51 carbon atoms, any hydrogen atom forming the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom.
^Y5 represents at least one cyclic group selected from the group consisting of a benzene ring, a cyclohexane ring, and a heterocycle, and any hydrogen atom forming the cyclic group may be substituted with an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or a fluorine atom.
^Y6 represents at least one selected from the group consisting of an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, a fluorine-containing alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, and a fluorine-containing alkoxy group having 1 to 18 carbon atoms. n represents an integer of 0 to 4. The liquid crystal aligning agent according to claim 3, 5 or 6, wherein the content of the diamine represented by the formula [1] is 5 to 70 mol % in 100 mol % of the total diamine components. The liquid crystal alignment agent according to claim 4 or 7, wherein the content of the diamine represented by the formula [2] is 1 to 50 mol % in 100 mol % of the total diamine components. A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of claims 1 to 15. A liquid crystal display element having the liquid crystal alignment film according to claim 16.