JP2013200511A - Optical orientation film providing high orientation and high pretilt angle, and liquid crystal display element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal orientation film which has high liquid crystal orientation and stably provides a large pretilt angle near 45°, a method of manufacturing the orientation film, and a liquid crystal element comprising the orientation film.SOLUTION: A coated film obtained by applying amine processing to a polyamic acid having optical orientation capability is exposed to light, and then cured at or above the imidization temperature of the polyamic acid thereby to obtain a polyimide optical orientation film, which provides a pretilt angle of 3-70° to liquid crystal and an orientation index (Δ) represented by a formula in Figure of 0.27 or greater.

Description

  The present invention relates to a photo-alignment film capable of imparting a high pretilt angle to a liquid crystal display element, a method for producing the alignment film, and a liquid crystal display element using the same.

  Various display devices such as personal computer monitors, LCD TVs, video camera viewfinders, and projection displays, as well as optoelectronic devices such as optical printer heads, optical Fourier transform elements, and light valves, have been commercialized today. Generally used liquid crystal display elements are display elements using nematic liquid crystals. As a display system of the nematic liquid crystal display element, a TN (Twisted Nematic) mode and an STN (Super Twisted Nematic) mode are well known. In recent years, in order to improve the narrow viewing angle, which is one of the problems of these modes, a TN liquid crystal display device using an optical compensation film, MVA (Multi -domain Vertical Alignment) mode or IPS (In-Plane Switching) mode of a horizontal electric field method has been proposed and put into practical use.

  The development of the technology of the liquid crystal display element is achieved not only by simply improving these driving methods and element structures but also by improving the components used in the elements. Among the components used in liquid crystal display elements, the liquid crystal alignment film is one of important materials related to display quality, and the performance of the liquid crystal alignment film should be improved as the quality of the liquid crystal display element increases. Is becoming important.

  The liquid crystal alignment film is prepared from a liquid crystal aligning agent. The liquid crystal aligning agent mainly used at present is a solution (varnish) obtained by dissolving polyamic acid or soluble polyimide in an organic solvent. After this solution is applied to the substrate, it is formed by means such as heating to form a polyimide-based liquid crystal alignment film.

The liquid crystal alignment film is required to bring the following characteristics to the liquid crystal display element.
(1) Giving an appropriate pretilt angle to liquid crystal molecules. In addition, the pretilt angle is not easily affected by temperature conditions during heating.
(2) High liquid crystal orientation. In addition, alignment defects of liquid crystal molecules due to scratches or scraping of the alignment film should not occur.
(3) Give an appropriate voltage holding ratio (VHR) to the liquid crystal display element.
(4) A phenomenon called “burn-in” in which an image is displayed as an afterimage when an arbitrary image is displayed on the liquid crystal display element for a long time and then changed to another image, is less likely to occur.

  A rubbing method of rubbing the liquid crystal alignment film with a cloth is generally used as a method for imparting a liquid crystal alignment property and a pretilt angle to the liquid crystal alignment film. Recently, a photo alignment method for performing this using light has been proposed and put into practical use. I'm starting. We have been studying a photo-alignment film having a photoreactive group that causes photoisomerization or photodimerization in a polyamic acid structure (see, for example, Patent Documents 1 to 3). However, it has been difficult for these conventional methods to form a liquid crystal alignment film that stably provides a high pretilt angle of around 45 degrees with high liquid crystal alignment.

  On the other hand, in recent various displays, especially for mobile devices such as electronic paper, e-books, smartphones, and smart books, it is required to reduce the power consumption of the displays in order to prevent battery consumption. For this reason, various types of displays have been developed in addition to liquid crystals. However, in terms of power consumption, image quality, and manufacturing cost, there are still many problems to be improved in the practical display.

  As a display that can satisfy such a problem at a high level, a bistable bend-spray mode display type liquid crystal display device that performs display using a bistable birefringence phenomenon has been proposed (for example, non-patented). See reference 1.) This mode utilizes the fact that splay and vent orientation exist bistable at a high pretilt angle of around 45 degrees, and these phases can be converted by voltage application, and since it has memory characteristics, low power consumption can be expected. Further, since it is a liquid crystal display, a high-definition image can be displayed. However, as described above, how to form a liquid crystal alignment film that stably gives a high pretilt angle around 45 degrees is a big problem.

JP 2005-275364 A JP 2007-248637 A JP 2009-0669493 A

Appl. Phys. Lett. 85, 3711 (2005).

  The present invention relates to a liquid crystal alignment film having a high liquid crystal alignment property and stably providing a high pretilt angle of around 45 degrees, a method for producing the alignment film, and a liquid crystal element having the alignment film, particularly a bistable bend-spray mode It aims at providing the liquid crystal aligning film which can be utilized for a display type liquid crystal display element.

  The present inventors have found that a liquid crystal alignment film satisfying the above-described characteristics can be obtained by forming a photo-alignment film on a substrate by amine treatment, and completed the present invention.

The present invention has the following configuration.
[1] Polyimide photo-alignment obtained by exposing a polyamic acid having a photo-alignment ability derived from a photosensitive group contained in a structural unit to an amine-treated coating film, and then firing the polyamic acid at or above the imidization temperature of the polyamic acid. A membrane,
A polyimide photo-alignment characterized in that a pretilt angle of 3 to 70 degrees is given to the liquid crystal, and the orientation index (Δ) of the film represented by the following formula (1) exhibits a value of 0.27 or more. film.
(In formula (1), A‖ represents the main chain of polyimide in a direction perpendicular to the surface of the liquid crystal alignment film and parallel to the surface of the liquid crystal alignment film in the liquid crystal alignment film. Represents the absorbance of the alignment film at a wavelength in the vicinity of the maximum of absorption when being incident on the liquid crystal alignment film so that the polarization direction of the ultraviolet / visible light is parallel to the average alignment direction of The ultraviolet / visible light is perpendicular to the surface of the liquid crystal alignment film and the ultraviolet / visible light is aligned with respect to the average alignment direction of the polyimide main chain in the direction parallel to the surface of the liquid crystal alignment film. This represents the absorbance of the alignment film at a wavelength near the maximum of absorption when the light is incident on the liquid crystal alignment film so that the polarization direction is vertical, d represents the film thickness of the liquid crystal alignment film, and d ′ represents the light of the liquid crystal alignment film. (It represents the effective film thickness of the aligned region.)

  [2] The polyimide photoalignment film according to [1], wherein the polyamic acid is a polyamic acid having an azobenzene skeleton as a photosensitive group.

[3] The polyimide photoalignment film according to [1] or [2], wherein the polyamic acid is made of at least one diamine selected from the following formulas (I-1) to (I-7) as a raw material.

[4] The tetracarboxylic dianhydride as a raw material of the polyamic acid is at least one selected from the group consisting of the following formulas (AN-I) to (AN-VII): [1] to [3] The polyimide photo-alignment film according to any one of the above.
In formulas (AN-I), (AN-IV) and (AN-V), X is independently a single bond or —CH ₂ —;
In the formula (AN-II), G represents a single bond, alkylene having 1 to 20 carbon atoms, —CO—, —O—, —S—, —SO ₂ —, —C (CH ₃ ) ₂ —, or —C. (CF ₃ ) ₂ —;
In formulas (AN-II) to (AN-IV), Y is independently one selected from the group of trivalent groups below,
Any hydrogen in these groups may be replaced by methyl, ethyl or phenyl;
In the formulas (AN-III) to (AN-V), the ring A is a monocyclic hydrocarbon group having 3 to 10 carbon atoms or a condensed polycyclic hydrocarbon group having 6 to 30 carbon atoms. Any hydrogen in may be replaced by methyl, ethyl or phenyl, and the bond on the ring is connected to any carbon constituting the ring, and the two bonds are connected to the same carbon May be;
In the formula (AN-VI), X ¹⁰ is alkylene having 2 to 6 carbons;
Me is methyl;
Ph is phenyl;
In formula (AN-VII), G ¹⁰ is independently —O—, —COO— or —OCO—; and
r is independently 0 or 1.

[5] The diamine that is a raw material of the polyamic acid includes at least one selected from the group consisting of the following formulas (DI-1) to (DI-17): [1] to [4] The polyimide photo-alignment film described.
In formulas (DI-1) to (DI-7), m is an integer of 1 to 12;
G ²¹ is independently a single bond, —O—, —S—, —S—S—, —SO ₂ —, —CO—, —CONH—, —NHCO—, —C (CH ₃ ) ₂ —, — C (CF ₃ ) ₂ —, — (CH ₂ ) _{m ′} —, —O— (CH ₂ ) _{m ′} —O—, or —S— (CH ₂ ) _{m ′} —S—, and m ′ is independent. An integer from 1 to 12;
G ²² is independently a single bond, —O—, —S—, —CO—, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, or alkylene having 1 to 10 carbons;
Arbitrary —H of the cyclohexane ring and the benzene ring in each formula may be replaced by —F, —CH ₃ , —OH, —CF ₃ or benzyl. In addition, in the formula (DI-4), The following formulas (DI-4-a) to (DI-4-c) may be substituted,
In formulas (DI-4-a) to (DI-4-c), R ²⁰ is independently —H or —CH ₃ ;
In formulas (DI-2) to (DI-7), a group whose bonding position is not fixed to any carbon atom constituting the ring indicates that the bonding position in the ring is arbitrary; and
The bonding position of —NH ₂ to the cyclohexane ring or the benzene ring is an arbitrary position excluding the bonding position of G ²¹ or G ²² .
In formula (DI-8), R ²¹ and R ²² are independently alkyl having 1 to 3 carbons or phenyl;
G ²³ is independently alkylene having 1 to 6 carbons, phenylene or alkyl-substituted phenylene;
n is an integer from 1 to 10;
In formula (DI-9), R ²³ is independently alkyl having 1 to 3 carbons;
p is independently an integer from 0 to 3;
q is an integer from 0 to 4;
In the formula (DI-10), R ²⁴ is —H, alkyl having 1 to 4 carbons, phenyl, or benzyl;
In the formula (DI-11), G ²⁴ is —CH ₂ — or —NH—;
In the formula (DI-12), G ²⁵ is a single bond, alkylene having 2 to 6 carbons or 1,4-phenylene;
r is 0 or 1;
In formula (DI-12), a group whose bonding position is not fixed to any carbon atom constituting the ring indicates that the bonding position in the ring is arbitrary; and
In formulas (DI-9), (DI-11) and (DI-12), the bonding position of —NH ₂ bonded to the benzene ring is an arbitrary position;
In the formula (DI-13), G ²⁶ represents a single bond, —O—, —COO—, —OCO—, —CO—, —CONH—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—. , -OCF ₂ -, or - (CH _{2) m '-} it is and, m' is an integer from 1 to 12;
R ²⁵ is alkyl having 3 to 20 carbons, phenyl, a group having a steroid skeleton, or a group represented by the following formula (DI-13-a). In this alkyl, any —H is —F Any —CH ₂ — may be replaced by —O—, —CH═CH— or —C≡C—, and —H of this phenyl is —F, —CH ₃ , _{-OCH 3, -OCH 2 F, -OCHF} 2, -OCF 3, alkyl having 3 to 20 carbon atoms, or may be replaced by alkoxy having 3 to 20 carbon atoms, -H of cyclohexyl 3 carbon atoms Which may be replaced by ˜20 alkyl or C 3-20 alkoxy, and indicates that the bonding position of —NH ₂ bonded to the benzene ring is an arbitrary position in the ring;
In the formula (DI-13-a), G ²⁷ , G ²⁸ and G ²⁹ each represent a bonding group, and these are each independently a single bond or alkylene having 1 to 12 carbons, and one or more —CH ₂ — may be replaced by —O—, —COO—, —OCO—, —CONH—, —CH═CH—;
Ring B ²¹ , Ring B ²² , Ring B ²³ , and Ring B ²⁴ are independently 1,4-phenylene, 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, pyrimidine-2, 5-diyl, pyridine-2,5-diyl, naphthalene-1,4-diyl, naphthalene-1,5-diyl, naphthalene-2,6-diyl, naphthalene-2,7-diyl, or anthracene-9,10 -Diyl;
In ring B ²¹ , ring B ²² , ring B ²³ , and ring B ²⁴ , any —H may be replaced by —F or —CH ₃ ;
s, t and u are independently integers from 0 to 2 and their sum is 1 to 5;
when s, t or u is 2, the two linking groups in each bracket may be the same or different and the two rings may be the same or different;
R ²⁶ represents —F, —OH, alkyl having 1 to 30 carbon atoms, fluorine-substituted alkyl having 1 to 30 carbon atoms, alkoxy having 1 to 30 carbon atoms, —CN, —OCH ₂ F, —OCHF ₂ , or —OCF. _And any —CH ₂ — in the alkyl having 1 to 30 carbon atoms may be replaced by a divalent group represented by the following formula (DI-13-b);
In the formula (DI-13-b), R ²⁷ and R ²⁸ are independently alkyl having 1 to 3 carbons;
v is an integer from 1 to 6;
In formula (DI-14) and formula (DI-15), G ³⁰ is independently a single bond, —CO— or —CH ₂ —;
R ²⁹ is independently —H or —CH ₃ ;
R ³⁰ is —H, alkyl having 1 to 20 carbons, or alkenyl having 2 to 20 carbons;
One -H of the benzene ring in formula (DI-15) may be replaced by alkyl having 1 to 20 carbons or phenyl;
In formula (DI-14) and formula (DI-15), a group whose bonding position is not fixed to any carbon atom constituting the ring indicates that the bonding position in the ring is arbitrary;
Bonded to the benzene ring -NH ₂ indicates that the binding position in the ring is optional;
In formula (DI-16) and formula (DI-17), G ³¹ is independently —O— or alkylene having 1 to 6 carbons;
G ³² is a single bond or alkylene having 1 to 3 carbon atoms;
R ³¹ is —H or alkyl having 1 to 20 carbons, and any —CH ₂ — in the alkyl may be replaced by —O—, —CH═CH— or —C≡C—;
R ³² is alkyl having 6 to 22 carbons;
R ³³ is —H or C 1-22 alkyl;
Ring B ²⁵ is 1,4-phenylene or 1,4-cyclohexylene;
r is 0 or 1; and
-NH ₂ bonded to the benzene ring indicates that the binding position in the ring is optional.

  [6] Applying a liquid crystal aligning agent containing a polyamic acid having photo-alignment ability to a substrate, subjecting the coating film to an amine treatment with a vapor of an amino compound, exposure, and baking at a temperature equal to or higher than the imidization temperature of the polyamic acid. The polyimide photo-alignment film according to any one of [1] to [5], which is a polyimide photo-alignment film obtained by

  [7] Obtained by applying a liquid crystal aligning agent containing a polyamic acid having photoalignment ability derived from a photosensitive group contained in the structural unit to a substrate, exposing the amino compound to the coating film, and then exposing and baking. Manufacturing method of polyimide photo-alignment film.

  [8] The method for producing a polyimide photo-alignment film according to [7], wherein the photosensitive group is an azobenzene derivative.

  [9] A liquid crystal display device having the photo-alignment film according to any one of [1] to [6].

  According to the present invention, it is possible to obtain a liquid crystal alignment film that has a high liquid crystal alignment property and can stably provide a high pretilt angle of around 45 degrees, which could not be obtained by a conventionally known method.

A method for producing a photo-alignment film. Sample and amine arrangement in amine vapor treatment. The conceptual diagram of amine steam processing. The polarized ultraviolet-visible light absorption spectrum of the film | membrane after performing the amine process of Example 1, and a photo-alignment process. The polarized ultraviolet-visible light absorption spectrum of the polyimide alignment film obtained by carrying out the amine process and the photo-alignment process of Example 1 and then thermal imidization. Relationship between the alignment index Δ of the polyamic acid film irradiated with light in Example 1 and Comparative Example 1, and the alignment index Δ of the polyimide alignment film obtained by thermal imidization of the film, and the dose of linearly polarized light . The relationship between the orientation index | exponent (DELTA) of the polyimide alignment film obtained by performing the amine process of Example 2, and a photo-alignment process, and thermal imidization, and the unpolarized irradiation amount. The relationship between the light irradiation amount of non-polarized light irradiation at an incident angle of 45 degrees in the photo-alignment treatment, and the pretilt angle that appears. The polarization micrograph of the anti-parallel cell produced using the polyimide alignment film obtained by performing the photo-alignment process after performing the amine process of Example 2, and performing a thermal imidation. The polarization micrograph of the anti-parallel cell produced using the polyimide alignment film obtained by performing the photo-alignment process of the comparative example 4, and then performing an amine process and thermal imidizing.

The polyimide photo-alignment film of the present invention is obtained by exposing a coating film obtained by subjecting a polyamic acid having a photo-alignment ability derived from a photosensitive group contained in a structural unit to an amine treatment, and then baking at or above the imidization temperature of the polyamic acid. A polyimide photo-alignment film obtained by the following, which gives a pretilt angle of 3 to 70 degrees to the liquid crystal, and the film has an orientation index (Δ) of 0.27 or more represented by the following formula: It is a polyimide photo-alignment film characterized by these. That is, the polyimide photo-alignment film is characterized in that it stably provides a high pretilt angle and is highly oriented.
(In formula (1), A‖ represents the main chain of polyimide in a direction perpendicular to the surface of the liquid crystal alignment film and parallel to the surface of the liquid crystal alignment film in the liquid crystal alignment film. Represents the absorbance of the alignment film at a wavelength in the vicinity of the maximum of absorption when being incident on the liquid crystal alignment film so that the polarization direction of the ultraviolet / visible light is parallel to the average alignment direction of The ultraviolet / visible light is perpendicular to the surface of the liquid crystal alignment film and the ultraviolet / visible light is aligned with respect to the average alignment direction of the polyimide main chain in the direction parallel to the surface of the liquid crystal alignment film. This represents the absorbance of the alignment film at a wavelength near the maximum of absorption when the light is incident on the liquid crystal alignment film so that the polarization direction is vertical, d represents the film thickness of the liquid crystal alignment film, and d ′ represents the light of the liquid crystal alignment film. (It represents the effective film thickness of the aligned region.)

  The coating film obtained by subjecting the polyamic acid having photo-alignment ability to an amine treatment is a coating film obtained by allowing an amine compound to act on a carboxylic acid in the polyamic acid, and its method of operation is particularly limited. However, for example, after applying a liquid crystal aligning agent containing the polyamic acid to a substrate and forming a coating film, a method of performing an amine vapor treatment, or adding an amino compound to the liquid crystal aligning agent containing the polyamic acid, The method of apply | coating to a board | substrate and coating a film etc. are mentioned.

This will be described in more detail below.
The polyamic acid having the photo-alignment ability will be described.
The polyamic acid having photoalignment ability is a polyamic acid having a photosensitive group in a part of the structure. The photosensitive group can be selected from all known photosensitive groups without any particular limitation. Among these, a polyamic acid having an azobenzene skeleton as a photosensitive group can be preferably used. Furthermore, it is particularly preferable that the azobenzene photosensitive group is incorporated in the main chain in order to develop high photo-alignment properties.

  The polyamic acid is a reaction product of tetracarboxylic dianhydride and diamine, and a known azobenzene derivative can be used without particular limitation as a raw material of the polyamic acid having the azobenzene skeleton as a photosensitive group. Among them, diamines represented by the following formulas (I-1) to (I-7) can be suitably used because they have high orientation and little coloration.

  The copolymerization ratio of these azobenzene derivatives is not particularly limited, but is preferably 30 mol% or more, more preferably 50 mol% or more, based on the total diamine amount from the viewpoint of sensitivity to light.

  The polyamic acid may be a derivative thereof. However, in order to express the high pretilt angle and high orientation which are the characteristics of the present invention, it is better to contain amic acid units at a certain ratio. The proportion of this polyamic acid unit is preferably 30% or more, more preferably 50% or more, of all the structural units.

  Examples of polyamic acid derivatives include soluble polyimides, polyamic acid esters, and polyamic acid amides. More specifically, 1) partially polyimide that has undergone dehydration and ring closure reaction, and 2) the carboxyl of polyamic acid is converted to an ester. 3) a polyamic acid-polyamide copolymer obtained by reacting a part of the acid dianhydride contained in the tetracarboxylic dianhydride compound with an organic dicarboxylic acid, and 4) Polyamideimide obtained by subjecting a part of the polyamic acid-polyamide copolymer to a dehydration ring-closing reaction is exemplified. The polyamic acid and the derivative thereof may be one kind of compound or two or more kinds. The polyamic acid and its derivative may be a compound having a structure of a reaction product of tetracarboxylic dianhydride and diamine, and other raw materials may be used except for the reaction of tetracarboxylic dianhydride and diamine. It may contain reaction products from other reactions.

  The tetracarboxylic dianhydride used for producing the polyamic acid will be described. The tetracarboxylic dianhydride used in the present invention can be selected without limitation from known tetracarboxylic dianhydrides. Such tetracarboxylic dianhydrides include aromatic systems (including heteroaromatic ring systems) in which dicarboxylic acid anhydrides are directly bonded to aromatic rings, and aliphatic groups in which dicarboxylic acid anhydrides are not directly bonded to aromatic rings. It may belong to any group of systems (including heterocyclic ring systems).

  Preferred examples of such tetracarboxylic dianhydrides include those represented by the formulas (AN-I) to (AN-VII) from the viewpoint of easy availability of raw materials, ease of polymer polymerization, and electrical characteristics of the film. The tetracarboxylic dianhydride represented is mentioned.

In the formulas (AN-I), (AN-IV), and (AN-V), X is independently a single bond or —CH ₂ —, and in the formula (AN-II), G is a single bond, carbon number 1 to 20 alkylene, —CO—, —O—, —S—, —SO ₂ —, —C (CH ₃ ) ₂ —, or —C (CF ₃ ) ₂ —, which has the formula (AN-II) In (AN-IV), Y is independently one selected from the group of the following trivalent groups, the bond is connected to any carbon, and any hydrogen in this group is methyl, May be replaced by ethyl or phenyl,
In the formulas (AN-III) to (AN-V), the ring A is a monocyclic hydrocarbon group having 3 to 10 carbon atoms or a condensed polycyclic hydrocarbon group having 6 to 30 carbon atoms. Any hydrogen in may be replaced by methyl, ethyl or phenyl, and the bond on the ring is connected to any carbon constituting the ring, and the two bonds are connected to the same carbon In formula (AN-VI), X ¹⁰ is alkylene having 2 to 6 carbon atoms, Me is methyl, and Ph is phenyl, and in formula (AN-VII), G ¹⁰ Is independently —O—, —COO— or —OCO—, and r is independently 0 or 1.

  More specifically, tetracarboxylic dianhydrides represented by the following formulas (AN-1) to (AN-16-14) may be mentioned.

In the formula (AN-1), G ¹¹ is a single bond, alkylene having 1 to 12 carbons, 1,4-phenylene, or 1,4-cyclohexylene. X ¹¹ is independently a single bond or —CH ₂ —. G ¹² is independently CH or N. When G ¹² is CH, the hydrogen of CH may be replaced with —CH ₃ . When G ¹² is N, G ¹¹ is not a single bond or —CH ₂ —, and X ¹¹ is not a single bond. R ¹¹ is —H or —CH ₃ . Examples of the tetracarboxylic dianhydride represented by the formula (AN-1) include compounds represented by the following formula.

In the formulas (AN-1-2) and (AN-1-14), m is an integer of 1 to 12.

In the formula (AN-2), R ¹² is independently —H, —CH ₃ , —CH ₂ CH ₃ , or phenyl. Examples of the tetracarboxylic dianhydride represented by the formula (AN-2) include compounds represented by the following formula.

In the formula (AN-3), the ring A ¹¹ is a cyclohexane ring or a benzene ring. Examples of the tetracarboxylic dianhydride represented by the formula (AN-3) include compounds represented by the following formula.

In the formula (AN-4), G ¹³ represents a single _{bond, -CH 2 -, - CH 2} CH 2 -, - O -, - S -, - C (CH 3) 2 -, - SO 2 -, - CO - or -C (CF _{3) 2} - a. Each ring A ¹¹ is independently a cyclohexane ring or a benzene ring. G ¹³ may be bonded to any position of ring A ¹¹ . Examples of the tetracarboxylic dianhydride represented by the formula (AN-4) include compounds represented by the following formula.

In formula (AN-4-17), m is an integer of 1-12.

In the formula (AN-5), R ¹¹ is —H or —CH ₃ . R ¹¹ whose bond position is not fixed to the carbon atom constituting the benzene ring indicates that the bond position in the benzene ring is arbitrary. Examples of the tetracarboxylic dianhydride represented by the formula (AN-5) include compounds represented by the following formula.

In the formula (AN-6), X ¹¹ is independently a single bond or —CH ₂ —. X ¹² is _{-CH 2 -, - CH 2 CH} 2 - or -CH = CH-. n is 1 or 2. Examples of the tetracarboxylic dianhydride represented by the formula (AN-6) include compounds represented by the following formula.

In the formula (AN-7), X ¹¹ is a single bond or —CH ₂ —. Examples of the tetracarboxylic dianhydride represented by the formula (AN-7) include compounds represented by the following formula.

In formula (AN-8), X ¹¹ each independently represents a single bond or —CH ₂ —. R ¹² is —H, —CH ₃ , —CH ₂ CH ₃ , or phenyl, and ring A ¹² is a cyclohexane ring or a cyclohexene ring. Examples of the tetracarboxylic dianhydride represented by the formula (AN-8) include compounds represented by the following formula.

In the formula (AN-9), each r is independently 0 or 1. Examples of the tetracarboxylic dianhydride represented by the formula (AN-9) include compounds represented by the following formula.

Formula (AN-10) is the following tetracarboxylic dianhydride.

In formula (AN-11), ring A ¹¹ is independently a cyclohexane ring or a benzene ring. Examples of the tetracarboxylic dianhydride represented by the formula (AN-11) include compounds represented by the following formula.

In formula (AN-12), each ring A ¹¹ is independently a cyclohexane ring or a benzene ring. As an example of the tetracarboxylic dianhydride represented by a formula (AN-12), the compound represented by a following formula can be mentioned.

In the formula (AN-13), X ¹³ is alkylene having 2 to 6 carbons. Examples of the tetracarboxylic dianhydride represented by the formula (AN-13) include compounds represented by the following formula.

In the formula (AN-14), G ¹⁴ is independently —O—, —COO— or —OCO—, and r is independently 0 or 1. Examples of the tetracarboxylic dianhydride represented by the formula (AN-14) include compounds represented by the following formula.

In formula (AN-15), w is an integer of 1-10. Examples of the tetracarboxylic dianhydride represented by the formula (AN-15) include compounds represented by the following formula.

Examples of tetracarboxylic dianhydrides other than the above include the following compounds.

  When importance is attached to further improving the orientation of the liquid crystal, among the above acid anhydrides, the formulas (AN-1-1), (AN-3-2), (AN-4-17), and A compound represented by (AN-16-14) is more preferred, and a compound represented by (AN-3-2) is particularly preferred. In the formula (AN-4-17), a compound where m = 8 is particularly preferable.

  In the case where importance is attached to improving the VHR of the liquid crystal display element, among the above acid anhydrides, the formulas (AN-2-1), (AN-3-1), (AN-5-1), and The alicyclic compound represented by (AN-16-1) is more preferred, and the compounds represented by (AN-2-1) and (AN-16-1) are particularly preferred.

  In the case where importance is placed on lowering the volume resistance value of the liquid crystal alignment film, among the above acid anhydrides, the compound represented by (AN-3-2) is more preferable.

The diamine used for producing the polyamic acid will be described.
The diamine compound used for producing the polyamic acid can be selected without limitation from known diamine compounds.

  Here, the structure of the diamine compound will be described. Diamine compounds can be divided into two types according to their structures. That is, when a skeleton connecting two amino groups is viewed as a main chain, a group branched from the main chain, that is, a diamine having a side chain group and a diamine having no side chain group. This side chain group is a group having an effect of increasing the pretilt angle. The side chain group having such an effect needs to be a group having 3 or more carbon atoms. Specific examples include alkyl having 3 or more carbon atoms, alkoxy having 3 or more carbon atoms, alkoxyalkyl having 3 or more carbon atoms, and A group having a steroid skeleton can be exemplified. A group having one or more rings, wherein the terminal ring has any one of alkyl having 1 or more carbon atoms, alkoxy having 1 or more carbon atoms and alkoxyalkyl having 2 or more carbon atoms as a substituent; It has an effect as a side chain group. In the following description, a diamine having such a side chain group may be referred to as a side chain diamine. Such a diamine having no side chain group may be referred to as a non-side chain diamine.

  By properly using the non-side chain diamine and the side chain diamine, it is possible to cope with the pretilt angle required for each. For this purpose, the side chain diamine is preferably used in combination so as not to impair the properties of the present invention. Moreover, it is preferable to select and use each of the side chain type diamine and the non-side chain type diamine for the purpose of improving the voltage holding ratio, the image sticking property, and the photo-alignment property with respect to the liquid crystal.

The non-side chain diamine will be described.
Examples of diamines having no known side chain include diamines of the following formulas (DI-1) to (DI-12).

In said formula (DI-1)-(DI-7), m is an integer of 1-12. G ²¹ is independently a single bond, —O—, —S—, —S—S—, —SO ₂ —, —CO—, —CONH—, —NHCO—, —C (CH ₃ ) ₂ —, — C (CF ₃ ) ₂ —, — (CH ₂ ) _{m ′} —, —O— (CH ₂ ) _{m ′} —O—, or —S— (CH ₂ ) _{m ′} —S—, and m ′ is independent. And an integer of 1 to 12. G ²² is independently a single bond, —O—, —S—, —CO—, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, or alkylene having 1 to 10 carbon atoms. Arbitrary —H of the cyclohexane ring and the benzene ring in each formula may be replaced with —F, —CH ₃ , —OH, —CF ₃ or benzyl. In addition, in formula (DI-4), The formulas (DI-4-a) to (DI-4-c) may be substituted. A group in which the bonding position is not fixed to the carbon atom constituting the ring indicates that the bonding position in the ring is arbitrary. The bonding position of —NH ₂ to the cyclohexane ring or benzene ring is an arbitrary position excluding the bonding position of G ²¹ or G ²² .

In formulas (DI-4-a) to (DI-4-c), R ²⁰ is independently —H or —CH ₃ .

In formula (DI-8), R ²¹ and R ²² are independently alkyl or phenyl having 1 to 3 carbon atoms, and G ²³ is independently alkylene, phenylene or alkyl-substituted phenylene having 1 to 6 carbon atoms. And w is an integer of 1-10.
In the formula (DI-9), R ²³ is independently alkyl having 1 to 3 carbon atoms, p is independently an integer of 0 to 3, and q is an integer of 0 to 4.
In the formula (DI-10), R ²⁴ is —H, alkyl having 1 to 4 carbons, phenyl, or benzyl.
In the formula (DI-11), G ²⁴ is —CH ₂ — or —NH—.
In the formula (DI-12), G ²⁵ is a single bond, alkylene having 2 to 6 carbon atoms or 1,4-phenylene, and r is 0 or 1. A group whose bond position is not fixed to the carbon atoms constituting the ring indicates that the bond position in the ring is arbitrary.
Formula (DI-9), in formula (DI-11) and formula (DI-12), the bonding position of -NH ₂ bonded to the benzene ring is any position.

Specific examples of the following formulas (DI-1-1) to (DI-12-1) can be given as diamines having no side chain of the above formulas (DI-1) to (DI-12).

Examples of diamines represented by formulas (DI-1) to (DI-3) are shown below.

Examples of the diamine represented by the formula (DI-4) are shown below.

Examples of the diamine represented by the formula (DI-5) are shown below.
In formula (DI-5-1), m is an integer of 1-12.

In formula (DI-5-12), m is an integer of 1-12.

In the formula (DI-5-15), v is an integer of 1 to 6.

In the formula (DI-5-29), k is an integer of 1 to 5.

Examples of the diamine represented by the formula (DI-6) are shown below.

Examples of the diamine represented by the formula (DI-7) are shown below.
In formulas (DI-7-3) and (DI-7-4), m is an integer of 1 to 12, and n is independently 1 or 2.

Examples of the diamine represented by the formula (DI-8) are shown below.

Examples of the diamine represented by the formula (DI-9) are shown below.

Examples of the diamine represented by the formula (DI-10) are shown below.

Examples of the diamine represented by the formula (DI-11) are shown below.

Examples of the diamine represented by the formula (DI-12) are shown below.

  Such a non-side chain diamine has an effect of improving electrical characteristics, such as reducing the ion density of the liquid crystal display element. When a non-side chain diamine is used as the diamine used for producing the polyamic acid, the proportion of the total amount of diamine in the total amount of diamine is preferably 0-50 mol%, more preferably 0-30 mol%. .

The side chain type diamine will be described.
Examples of the side chain group of the side chain type diamine include the following groups.

  As a side group, first, alkyl, alkyloxy, alkyloxyalkyl, alkylcarbonyl, alkylcarbonyloxy, alkyloxycarbonyl, alkylaminocarbonyl, alkenyl, alkenyloxy, alkenylcarbonyl, alkenylcarbonyloxy, alkenyloxycarbonyl, alkenylaminocarbonyl, Alkynyl, alkynyloxy, alkynylcarbonyl, alkynylcarbonyloxy, alkynyloxycarbonyl, alkynylaminocarbonyl and the like can be mentioned. Alkyl, alkenyl and alkynyl in these groups are all groups having 3 or more carbon atoms. However, in alkyloxyalkyl, it is sufficient if the entire group has 3 or more carbon atoms. These groups may be linear or branched.

  Next, phenyl, phenylalkyl, phenylalkyloxy, phenyloxy, provided that the terminal ring has alkyl having 1 or more carbon atoms, alkoxy having 1 or more carbon atoms or alkoxyalkyl having 2 or more carbon atoms as a substituent. Phenylcarbonyl, phenylcarbonyloxy, phenyloxycarbonyl, phenylaminocarbonyl, phenylcyclohexyloxy, cycloalkyl having 3 or more carbon atoms, cyclohexylalkyl, cyclohexyloxy, cyclohexyloxycarbonyl, cyclohexylphenyl, cyclohexylphenylalkyl, cyclohexylphenyloxy, bis ( Cyclohexyl) oxy, bis (cyclohexyl) alkyl, bis (cyclohexyl) phenyl, bis (cyclohexyl) phenylalkyl, bis ( Kurohekishiru) oxycarbonyl, and bis (cyclohexyl) phenyloxycarbonyl and cyclohexyl bis (phenyl) group of a ring structure, such as oxycarbonyl,.

  Further, a group having two or more benzene rings, a group having two or more cyclohexane rings, or two or more groups composed of a benzene ring and a cyclohexane ring, wherein the bonding groups are independently a single bond, -O-, -COO-, -OCO-, -CONH-, or alkylene having 1 to 3 carbon atoms, the terminal ring is alkyl having 1 or more carbon atoms as a substituent, fluorine-substituted alkyl having 1 or more carbon atoms, carbon A ring assembly group having an alkoxy of several or more or an alkoxyalkyl having two or more carbons can be given. A group having a steroid skeleton is also effective as a side chain group.

Examples of the diamine having a side chain include compounds represented by the following formulas (DI-13) to (DI-17).
In the formula (DI-13), G ²⁶ represents a single bond, —O—, —COO—, —OCO—, —CO—, —CONH—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—. , -OCF ₂ -, or - (CH _{2) m '-} it is and, m' is an integer from 1 to 12. Preferred examples of G ²⁶ are a single bond, —O—, —COO—, —OCO—, —CH ₂ O—, and alkylene having 1 to 3 carbon atoms, and particularly preferred examples are a single bond, —O—, — COO -, - OCO -, - CH 2 O -, - CH 2 - and -CH ₂ CH ₂ -. R ²⁵ is an alkyl group having 3 to 30 carbon atoms, phenyl, a group having a steroid skeleton, or a group represented by the following formula (DI-13-a). In this alkyl, any —H may be replaced with —F, and any —CH ₂ — may be replaced with —O—, —CH═CH— or —C≡C—. -H in which _{phenyl, -F, -CH 3, -OCH 3} , -OCH 2 F, -OCHF 2, -OCF 3, has been replaced by an alkoxy alkyl or 3 to 30 carbon atoms having 3 to 30 carbon atoms In this cyclohexyl group, —H may be substituted with alkyl having 3 to 30 carbon atoms or alkoxy having 3 to 30 carbon atoms. Although the bonding position of —NH ₂ bonded to the benzene ring indicates an arbitrary position in the ring, the bonding position is preferably meta or para. That is, when the bonding position of the group “R ²⁵ -G ²⁶ —” is the first position, the two bonding positions are preferably the third position and the fifth position, or the second position and the fifth position.

In the formula (DI-13-a), G ²⁷ , G ²⁸ and G ²⁹ are bonding groups, and these are each independently a single bond or alkylene having 1 to 12 carbons, and one or more of these alkylenes in the alkylene —CH ₂ — may be replaced by —O—, —COO—, —OCO—, —CONH—, or —CH═CH—. Ring B ²¹ , Ring B ²² , Ring B ²³ and Ring B ²⁴ are each independently 1,4-phenylene, 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, pyrimidine-2,5 - diyl, pyridine-2,5-diyl, naphthalene-1,5-diyl, naphthalene-2,7-diyl or anthracene-9,10-diyl, ring B ^21, ring B ^22, ring B ²³ and ring In B ²⁴ , any —H may be replaced by —F or —CH ₃ , s, t and u are each independently an integer of 0 to 2, and their sum is 1 to 5, When s, t or u is 2, the two linking groups in each parenthesis may be the same or different, and the two rings may be the same or different. R ²⁶ represents —F, —OH, alkyl having 1 to 30 carbon atoms, fluorine-substituted alkyl having 1 to 30 carbon atoms, alkoxy having 1 to 30 carbon atoms, —CN, —OCH ₂ F, —OCHF ₂ , or —OCF. _And any —CH ₂ — in the alkyl having 1 to 30 carbon atoms may be replaced by a divalent group represented by the following formula (DI-13-b).

In the formula (DI-13-b), R ²⁷ and R ²⁸ are independently alkyl having 1 to 3 carbon atoms, and v is an integer of 1 to 6. Preferred examples of R ²⁶ are alkyl having 1 to 30 carbons and alkoxy having 1 to 30 carbons.

In the formula (DI-14) and the formula (DI-15), G ³⁰ is independently a single bond, —CO— or —CH ₂ —, R ²⁹ is independently —H or —CH ₃ , R ³⁰ is —H, alkyl having 1 to 20 carbons, or alkenyl having 2 to 20 carbons. One -H of the benzene ring in formula (DI-15) may be replaced with alkyl having 1 to 20 carbons or phenyl. A group whose bonding position is not fixed to any carbon atom constituting the ring indicates that the bonding position in the ring is arbitrary. One of the two groups “-phenylene-G ³⁰ —O—” in formula (DI-14) is preferably bonded to the 3-position of the steroid nucleus and the other is bonded to the 6-position of the steroid nucleus. The bonding position of the two groups “-phenylene-G ³⁰ —O—” in the formula (DI-15) to the benzene ring is preferably a meta position or a para position, respectively, with respect to the bonding position of the steroid nucleus. In formula (DI-14) and formula (DI-15), —NH ₂ bonded to the benzene ring indicates that the bonding position in the ring is arbitrary.

In the formula (DI-16) and the formula (DI-17), G ³¹ is independently —O— or alkylene having 1 to 6 carbons, and G ³² is a single bond or alkylene having 1 to 3 carbons. . R ³¹ is —H or alkyl having 1 to 20 carbons, and arbitrary —CH ₂ — of this alkyl may be replaced by —O—, —CH═CH— or —C≡C—. R ³² is alkyl having 6 to 22 carbon atoms, and R ³³ is —H or alkyl having 1 to 22 carbon atoms. Ring B ²⁵ is 1,4-phenylene or 1,4-cyclohexylene, and r is 0 or 1. In addition, —NH ₂ bonded to the benzene ring indicates that the bonding position in the ring is arbitrary, but it is preferably independently a meta position or a para position with respect to the bonding position of G ³¹ .

Specific examples of the side chain diamine are illustrated below.
Examples of the diamine compound having a side chain of the above formulas (DI-13) to (DI-17) include compounds represented by the following formulas (DI-13-1) to (DI-17-3). .

Examples of the compound represented by the formula (DI-13) are shown below.
In formulas (DI-13-1) to (DI-13-11), R ³⁴ is a hydrogen atom, alkyl having 1 to 30 carbons or alkoxy having 1 to 30 carbons, preferably having 5 to 25 carbons. Alkyl or alkoxy having 5 to 25 carbon atoms. R ³⁵ is alkyl having 1 to 30 carbons or alkoxy having 1 to 30 carbons, preferably alkyl having 3 to 25 carbons or alkoxy having 3 to 25 carbons.

In formula (DI-13-12) ~ (DI -13-17), R 36 is alkyl having 1 to 30 carbon atoms, preferably an alkyl having 6 to 25 carbon atoms. R ³⁷ is alkyl having 6 to 30 carbons, preferably alkyl having 8 to 25 carbons.

In the formulas (DI-13-18) to (DI-13-33), R ³⁸ is a hydrogen atom or alkyl having 1 to 30 carbons, preferably alkyl having 6 to 12 carbons. R ³⁹ is a hydrogen atom or alkyl having 6 to 30 carbon atoms, preferably alkyl having 6 to 12 carbon atoms. G ³⁰ is independently a single bond, —CO— or —CH ₂ —.

Examples of the compound represented by the formula (DI-14) are shown below.

Examples of the compound represented by the formula (DI-15) are shown below.

Examples of the compound represented by the formula (DI-16) are shown below.

In the formulas (DI-16-1) to (DI-16-12), R ⁴⁰ is —H or alkyl having 1 to 20 carbons, preferably —H or alkyl having 1 to 10 carbons, and R ⁴¹ Is —H or alkyl having 1 to 12 carbons.

Examples of the compound represented by the formula (DI-17) are shown below.
In formula (DI-17-1) ~ (DI -17-3), R 37 is alkyl of 6 to 30 carbon atoms, R ⁴¹ is -H or alkyl having 1 to 12 carbon atoms.

  When the liquid crystal display device of the present invention requires a large pretilt angle, in order to efficiently express a pretilt angle of 3 degrees or more in a short processing time, a diamine of a side chain diamine is used in the production of the polyamic acid. The proportion of the total amount is preferably 0-20 mol%, more preferably 0-10 mol%.

  Among the specific examples of the diamine, when emphasizing further improving the orientation of the liquid crystal, the formulas (DI-4-1), (DI-5-1), (DI-5-12), It is preferable to use a diamine represented by (DI-6-7), (DI-7-3), (DI-16-2), (DI-16-5), and (DI-16-7). Further preferred are diamines represented by formulas (DI-5-1) and (DI-7-3). In the formula (DI-5-1), a compound where m = 2, 3, 4, or 6 is particularly preferable. In the formula (DI-7-3), a compound in which m = 3 or 6 and n = 1 is particularly preferable.

  Among the specific examples of the diamine, when emphasizing the application of high VHR to the liquid crystal alignment film, the formulas (DI-5-1), (DI-5-29), (DI-9-1) And a diamine represented by (DI-11-1), and a diamine represented by formulas (DI-5-1), (DI-5-29), and (DI-9-1) Is more preferable. In the formula (DI-5-1), a compound where m = 1 is particularly preferable. In the formula (DI-5-29), a compound where k = 2 is particularly preferable.

  The polyamic acid can be obtained by reacting the acid anhydride and diamine in a solvent. In this synthesis reaction, no special conditions other than the selection of the raw materials are required, and the conditions for normal polyamic acid synthesis can be applied as they are. The solvent to be used will be described later.

The amine treatment will be described.
As described above, the amine treatment is a treatment for causing an amino compound to act on the carboxylic acid in the polyamic acid, and the treatment method is not particularly limited as long as it is a known treatment method. For example, after applying a liquid crystal aligning agent containing the polyamic acid to a substrate and forming a coating film, adsorbing an amino compound, adding an amino compound to the liquid crystal aligning agent containing the polyamic acid, applying to the substrate, Examples include a method of coating. As for the former method of adsorbing amine, any method can be used as long as amine can be adsorbed, but since the operation can be easily performed, the coated substrate and the amino compound are allowed to stand in the same container for a certain period of time, An exposure method, for example, a method of adsorbing by vapor treatment or the like is preferable. At this time, the inside of the container may be under normal pressure or reduced pressure, and may be at room temperature, low temperature, or heating. Since a high pretilt angle can be given particularly stably to the coating film, amine vapor treatment can be used more suitably. Specifically, the methods described in the examples described later can be mentioned.

  In the present invention, the method of adding an amino compound to the liquid crystal aligning agent containing a polyamic acid as the amine treatment is basically a treatment different from the termination by an amine in the polymerization reaction when producing the polyamic acid. Termination with amine is for suppressing the growth reaction during the polymerization reaction when polyamic acid is produced. The amine treatment of the present invention gives a high pretilt angle to the coating film particularly stably by bringing the amino compound into contact with a liquid crystal aligning agent containing a polyamic acid that has already stopped the polymerization reaction and allowing it to interact with a carboxyl residue. The present inventors have found for the first time.

  The amino compound that can be used for the amine treatment reacts with a polyamic acid residue or forms a salt, so that it is considered that the desired characteristics are expressed, and therefore, primary, secondary, or 3 Preferably, it is a grade amino compound. The kind of the primary, secondary, or tertiary amino compound is not particularly limited and may be arbitrarily selected from known aliphatic or aromatic amino compounds. In order to obtain a desired high pretilt angle, An aliphatic or aromatic amino compound having 3 or more carbon atoms or fluorinated is preferable.

  Compounds suitable as such amino compounds are shown below. n-propylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, n-undecylamine, n-dodecylamine, n- Tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-eicosylamine, diisopropylamine, 2-ethylhexylamine, cyclohexylamine, Dicyclohexylamine, piperidine, 2,2-trifluoroethylamine, 1H, 1H-heptafluorobutylamine, 1H, 1H-nonafluoropentylamine, 4,4,5,5,6,6,7,7,8,8, 9,9,10,10,11,11,11-heptadecafluoroundecylamine, benzylamine, aniline, o-toluidine, m-toluidine P-toluidine 3-fluoroaniline, 3-aminobenzotrifluoride, p-aminophenyltrimethoxysilane, p-aminophenyltriethoxysilane, m-aminophenyltrimethoxysilane, m-aminophenyltriethoxysilane, 3 -Aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, etc. are mentioned.

The liquid crystal aligning agent which forms the said coating film is demonstrated.
The liquid crystal aligning agent may further contain components other than the polyamic acid. The other component may be one type or two or more types.

  The other component is selected from, for example, an alkenyl-substituted nadiimide compound, a compound having a radical polymerization unsaturated double bond, an oxazine compound, an oxazoline compound, and an epoxy compound for the purpose of stabilizing the electrical characteristics of the liquid crystal display element for a long period of time. It may further contain at least one. The said compound may be used by 1 type and may use 2 or more types together. For the above purpose, the content of the compound is preferably 1 to 50% by weight, more preferably 1 to 30% by weight, and 1 to 20% by weight based on the weight of the polyamic acid. More preferably. As described above, the liquid crystal aligning agent may contain an amino compound in addition to the polyamic acid as one of the amine treatment methods.

  Furthermore, the liquid crystal aligning agent of this invention may further contain polymers other than a polyamic acid from the objective of controlling the electrical property and orientation of a liquid crystal display element. Examples of the polymer include polymers that are soluble in organic solvents. The polymer may be used alone or in combination of two or more. For the above purpose, the content of the polymer is preferably 0.01 to 100% by weight, more preferably 0.1 to 70% by weight, based on the weight of the polyamic acid, More preferably, it is ˜50% by weight. Examples of the polymer include polyimide, polyamideimide, polyamide, polyurethane, polyurea, polyester, polyepoxide, polyester polyol, silicone-modified polyurethane, silicone-modified polyester, polyacrylic acid alkyl ester, polymethacrylic acid alkyl ester, acrylic acid alkyl ester, Examples include methacrylic acid alkyl ester copolymers, polyoxyethylene glycol diacrylate, polyoxyethylene glycol dimethacrylate, polyoxypropylene glycol diacrylate, and polyoxypropylene glycol dimethacrylate.

  Moreover, the liquid crystal aligning agent of this invention may further contain the low molecular compound. Examples of the low molecular weight compound include 1) a surfactant in accordance with this purpose when improvement in coating properties is desired, 2) an antistatic agent when improvement in antistatic properties is required, and 3) improvement in adhesion to the substrate. Silane coupling agents and titanium-based coupling agents, and 4) imidation catalysts when imidization proceeds at low temperatures. From the above viewpoint, the content of the low molecular compound is preferably 0.1 to 50% by weight, more preferably 0.1 to 40% by weight based on the weight of the polyamic acid, and More preferably, it is 1 to 20% by weight.

  The silane coupling agent includes silane compounds containing an epoxy group exemplified as the epoxy compound. In addition to adhesion to the substrate, a silane coupling agent containing an epoxy group may be added to the liquid crystal aligning agent of the present invention for the purpose of stabilizing electrical characteristics for a long period of time.

  Examples of the silane coupling agent include 3-glycidoxypropyltrimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane.

  In addition to one or more kinds of polyamic acids having the photo-alignment ability, other polyamic acids or derivatives thereof may be mixed and used. The mixing ratio when combining other polyamic acids or derivatives thereof is preferably 5 to 50% by weight based on the weight of the polyamic acid having photo-alignment ability.

  The polyimide photo-alignment film of the present invention is formed by applying a predetermined treatment to a substrate by applying a solution (hereinafter, varnish solution) obtained by dissolving polyamic acid or a mixture of polyamic acid and other components in a solvent. At this time, the solvent of the varnish solution can be appropriately selected from known solvents used in the production and use of polyamic acid according to the purpose of use. The solvent may be used alone or in combination of two or more. Examples of these solvents are as follows.

  Examples of the solvent include aprotic polar organic solvents. Examples of aprotic polar organic solvents include N-methyl-2-pyrrolidone (NMP), dimethylimidazolidinone, N-methylcaprolactam, N-methylpropionamide, N, N-dimethylacetamide, dimethyl sulfoxide, N, Examples include lactones such as N-dimethylformamide (DMF), N, N-diethylformamide, N, N-diethylacetamide (DMAc), and γ-butyrolactone (GBL).

  Preferred examples of solvents other than those described above for the purpose of improving coatability include alkyl lactate, 3-methyl-3-methoxybutanol, tetralin, isophorone, ethylene glycol monoalkyl ether (eg, ethylene glycol monoalkyl). Butyl ether (BCS)), diethylene glycol monoalkyl ether (eg: diethylene glycol monoethyl ether), ethylene glycol monophenyl ether, triethylene glycol monoalkyl ether, propylene glycol monoalkyl ether (eg: propylene glycol monobutyl ether), dialkyl malonate ( Example: diethyl malonate), dipropylene glycol monoalkyl ether (eg, dipropylene glycol monomethyl ether), and these glycol monoethers Ester compound of ethers may be mentioned. Of these, NMP, dimethylimidazolidinone, GBL, BCS, diethylene glycol monoethyl ether, propylene glycol monobutyl ether and dipropylene glycol monomethyl ether are particularly preferred.

  The concentration of the polymer in the varnish solution is preferably 0.1 to 40% by weight, and more preferably 1 to 10% by weight. When it is necessary to adjust the film thickness when applying this aligning agent to the substrate, the concentration of the contained polymer can be adjusted by diluting with a solvent in advance.

  The preferable range of the viscosity of the varnish solution varies depending on the method of application, the concentration of polyamic acid, the type of polyamic acid used, and the type and ratio of the solvent. For example, in the case of application by a printing press, it is 5 to 100 mPa · s (more preferably 10 to 80 mPa · s). If it is less than 5 mPa · s, it is difficult to obtain a sufficient film thickness, and if it exceeds 100 mPa · s, printing unevenness may increase. In the case of application by spin coating, 5 to 200 mPa · s (more preferably 10 to 100 mPa · s) is suitable. In the case of coating using an inkjet coating apparatus, 5 to 50 mPa · s (more preferably 5 to 20 mPa · s) is suitable. The viscosity of the liquid crystal aligning agent is measured by a rotational viscosity measuring method, and is measured using a rotational viscometer (TVE-20L type manufactured by Toki Sangyo Co., Ltd.) (measurement temperature: 25 ° C.).

A process for forming the photo-alignment film of the present invention will be described.
As described above, the photo-alignment film of the present invention includes a step of forming a coating film obtained by subjecting a polyamic acid having photo-alignment ability to amine treatment, exposing the coating film, and then baking at a temperature equal to or higher than the imidization temperature of the polyamic acid. After that, it is preferably formed by a predetermined method shown in FIG. 1 below. The steps 1 to 5 shown in FIG. 1 will be described in detail.

<About step 1>
First, the aforementioned varnish solution is applied to a substrate by a spinner method, a printing method, a dipping method, a dropping method, an ink jet method, or the like. Examples of the substrate include a glass substrate on which an electrode such as an ITO (Indium Tin Oxide) electrode or a color filter may be provided.

<About step 2>
Pre-baking is a process of removing the solvent by heating at a relatively low temperature, and is performed at a temperature of 150 ° C. or lower for the purpose of preventing imidization of the polyamic acid. Other conditions are not particularly limited, and there is no limitation on time and atmosphere as long as a uniform film can be formed.

<About step 3>
Step 3 is an amine treatment step. Details are as described above.

<About step 4>
The coating film subjected to the amine treatment is exposed. The type of light at this time may be any combination of linearly polarized light and non-polarized light, non-polarized light, or elliptically polarized light. The light source is not particularly limited as long as it can align the polyamic acid, but it is preferable to use light having a wavelength that matches the absorption spectrum of the film from the viewpoint of improving sensitivity. Examples of the light source include a high-pressure mercury lamp, a deep UV lamp, a xenon lamp, a low-pressure mercury lamp, a metal halide lamp, and various lasers, and any of them may be used.

  In order to align the liquid crystal in the photo-alignment film of the present invention, linearly polarized light, non-polarized light, or elliptically polarized light is used. At this time, it is preferable to use linearly polarized light in order to develop higher liquid crystal orientation in a short time. The irradiation angle of the linearly polarized light on the film surface is not particularly limited, but is preferably as perpendicular to the film surface as possible from the viewpoint of shortening the alignment treatment time.

  In the photo-alignment film of the present invention, non-polarized light or elliptically polarized light is used as light irradiated to the film in order to develop a pretilt angle. Although the irradiation angle with respect to the film | membrane surface of the light irradiated at this time is not specifically limited, It is preferable from a viewpoint of shortening of alignment processing time that it is 30-60 degrees.

<About step 5>
Finally, firing is performed. The main calcination is performed under conditions necessary for the polyamic acid to exhibit dehydration and ring closure reactions. In practice, a method of heating in an oven or an infrared furnace, a method of heat treatment on a hot plate, and the like are known. When the polyimide film is heated to 300 ° C. or higher, the polymer itself often decomposes. In general, it is preferably performed at a temperature of about 150 to 300 ° C for 1 minute to 3 hours, particularly preferably 180 to 280 ° C, and more preferably 200 to 250 ° C.

The liquid crystal display element of the present invention will be described.
The liquid crystal display element according to the present invention includes a pair of substrates disposed opposite to each other, electrodes formed on one or both of the opposed surfaces of the pair of substrates, and the pair of substrates opposed to each other. A liquid crystal display element having the liquid crystal alignment film of the present invention formed on at least one of the surfaces on which the liquid crystal is formed and a liquid crystal layer formed between the pair of substrates.

  The electrode is not particularly limited as long as it is an electrode formed on one surface of the substrate. Examples of such electrodes include ITO and metal vapor deposition films. Further, the electrode may be formed on the entire surface of one surface of the substrate, or may be formed in a desired shape that is patterned, for example. Examples of the desired shape of the electrode include a comb shape or a zigzag structure. The electrode may be formed on one of the pair of substrates, or may be formed on both substrates. The form of electrode formation varies depending on the type of liquid crystal display element. For example, in the case of a bistable bend spray mode display type liquid crystal display element, a comb electrode is disposed on one of the pair of substrates, and a common electrode is disposed on the other. In the OCB mode (optical compensation vent mode), electrodes are disposed on both of the pair of substrates. The liquid crystal alignment film is formed on the substrate or electrode.

  The liquid crystal layer is formed in such a manner that the liquid crystal composition is sandwiched between the pair of substrates facing each other on which the liquid crystal alignment film is formed. In the formation of the liquid crystal layer, a spacer such as fine particles or a resin sheet that is interposed between the pair of substrates to form an appropriate interval can be used as necessary. The liquid crystal composition is not particularly limited, and a known liquid crystal composition can be used.

  The alignment film of the present invention can improve the characteristics of all known liquid crystal compositions when a liquid crystal display element is formed as the liquid crystal alignment film. The alignment film of the present invention produced by the above method is particularly effective for a large screen display that requires an afterimage characteristic. Such a large screen display is driven and controlled by TFTs. Liquid crystal compositions used for such TFT type liquid crystal display elements are described in Japanese Patent No. 3086228, Japanese Patent No. 2635435, Japanese Patent Laid-Open No. 5-501735, and Japanese Patent Laid-Open No. 9-255556. Yes. Therefore, the alignment film of the present invention is preferably used in combination with the liquid crystal composition described therein.

  The liquid crystal display element of the present invention is also excellent in electrical characteristics relating to the reliability of the liquid crystal display element. Such electrical characteristics include voltage holding ratio (VHR) and ion density. The voltage holding ratio is a ratio at which the voltage applied to the liquid crystal display element during the frame period is held in the liquid crystal display element, and indicates the display characteristics of the liquid crystal display element. The liquid crystal display element of the present invention uses a rectangular wave of 5 V and a frequency of 30 Hz, uses a rectangular wave having a voltage holding ratio of 97.0% or more measured at a temperature of 60 ° C., and a rectangular wave of 5 V and a frequency of 0.3 Hz. From the viewpoint of preventing display defects, it is preferable that the voltage holding ratio measured at a temperature of 60 ° C. is 85.0% or more.

  The ion density is a transient current other than that caused by driving of the liquid crystal generated when a voltage is applied to the liquid crystal display element, and indicates the magnitude of the concentration of ionic impurities contained in the liquid crystal in the liquid crystal display element. The liquid crystal display element of the present invention preferably has an ion density of 300 pC or less from the viewpoint of preventing image sticking of the liquid crystal display element.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention, this invention is not limited to these Examples.

The evaluation method of the liquid crystal display element in an Example is as follows.
<Pretilt angle measurement>
Measure the incidence angle dependence of the transmittance of the anti-parallel cell using a He-Ne laser (oscillation wavelength 632.8 nm) in the measurement arrangement of the crystal rotation method, and fit it with the theoretical calculation value (Reference 1 below). Determined by. The temperature at the time of measuring the pretilt angle was 25 ° C. The NI point (nematic / isotropic phase transition temperature) of 5CB is 35 ° C., the measurement temperature is 25 ° C., and the refractive index at a wavelength of 632.8 nm is ne = 1.705 (abnormal light), no = 1.530. (Joko).
Reference 1: KY Han, T. Miyashita, and T. Uchida, Jpn. J. Appl. Phys. 32, L277 (1993).

<Measurement of orientation index of alignment film>
Polarized UV-Visible light absorption spectrum of polyamic acid and polyimide alignment film using a spectroscopic system consisting of a 30W deuterium lamp light source (Hamamatsu L9893), a Glan laser polarizing prism, and a linear CCD array spectrograph (BWTEK BTC112) Measured. Light that was linearly polarized through a Glan laser polarizing prism was irradiated from the direction perpendicular to the alignment film surface. UV-Visible light absorption spectrum (A‖) when measured in parallel with the sample orientation direction (average orientation direction of the polyimide main chain) and the polarization direction, and UV-visible light absorption spectrum (A) Ii) was measured. Measured at the peak value of the absorption band attributed to the π-π ^* transition of azobenzene, that is, the wavelength of the absorption maximum (in the case of polyamic acid film, around 374 nm to 386 nm, in the case of polyimide film, the peak is around 307 nm to 355 nm). The difference in the absorbance of the alignment film (A （−A⊥) and the sum of the absorbance of the alignment film (A‖ + A⊥) are calculated,
The orientation index Δ defined by Here, d represents the film thickness of the liquid crystal alignment film, and d ′ represents the effective film thickness of the region of the liquid crystal alignment film that has been subjected to the photo-alignment treatment. d / d ′ is a conversion factor from the average degree of orientation over the entire thickness of the orientation film to the degree of orientation of the surface layer of the orientation film.

<Weight average molecular weight (Mw)>
The weight average molecular weight (Mw) of the polyamic acid in the liquid crystal aligning agent was determined by using gel permeation chromatography (GPC, manufactured by Shodex, GF7MHQ), and using 0.6% by weight phosphoric acid-containing DMF as an eluent. The column temperature was 50 ° C., and TSK standard polystyrene manufactured by Tosoh Corporation was used as a standard solution.

<Viscosity>
It measured at 25 degreeC using the viscometer (the Toki Sangyo company make, TV-22).

  The names of tetracarboxylic dianhydrides, diamines, solvents and amines used in the examples are abbreviated. This abbreviation may be used in the following description. Compounds PMDA and DAZ were purified from commercially available compounds and used in experiments. Commercially available compounds were used as they were for C18-amine, C12-amine and CF8-C3-amine.

Tetracarboxylic acid dianhydride pyromellitic dianhydride: PMDA
・ Diamine 4,4′-diaminoazobenzene: DAZ
・ Solvent N-methyl-2-pyrrolidone: NMP
・ Amine Octadecylamine: C18-amine Dodecylamine: C12-amine
4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoro-undecylamine: CF8-C3-amine

<Preparation of orientation agent>
2.4660 g of DAZ and 30.00 g of dehydrated NMP were introduced into a 200 ml four-necked flask equipped with a thermometer, a stirrer, a raw material charging inlet and a nitrogen gas inlet, and dissolved under stirring in a dry nitrogen stream. While maintaining the temperature of the reaction system at 5 ° C., 2.5340 g of PMDA was added (PMDA / DAZ raw material molar ratio = 50/50), and after reacting for 30 hours, 65.00 g of dehydrated NMP was added, and 5 wt% A polyamic acid aligning agent was prepared. When the temperature rose due to heat of reaction during the reaction, the reaction was carried out at a reaction temperature of about 70 ° C. or lower. The polyamic acid obtained here had a weight average molecular weight of Mw = 24600 and a polydispersity of 2.9.

<Example 1>
The alignment agent was diluted with NMP to 1.6% by weight, and then applied onto a synthetic quartz glass substrate having a thickness of 1 mm with a spinner. The coating conditions were 3000 rpm and 60 seconds. After the application, it was dried on a hot plate set at 80 ° C. for 2 minutes.

  After coating, a partition is made of aluminum foil in a square case made of polystyrene (outside dimension: 87 mm (width) x 57 mm (depth) 19 mm (height)), and the above four synthetic quartz glass substrates and C18-amine are prepared. After 0.1 g was arranged as shown in FIG. 2 and the case was covered, the whole was wrapped in aluminum foil and placed on a hot plate (ND-1 manufactured by ASONE). Further, as shown in FIG. 3, after covering with a 1 liter Pyrex beaker wrapped with aluminum foil, the hot plate was heated to 55 ° C. and held for 22 hours, whereby C18-amine vapor Was exposed to a polyamic acid film formed on a synthetic quartz glass substrate (amine treatment).

After the amine treatment, a 500 W Deep UV lamp (UXM-501MD) manufactured by Ushio Electric Co., Ltd. is used as a light source, the wavelength region of light is set to 340 to 500 nm through a bandpass filter manufactured by Asahi Spectroscopic Co., Ltd., and linearly polarized light is transmitted through a Grand Taylor polarizing prism. The irradiated light was irradiated for 1 to 30 minutes from the direction perpendicular to the substrate surface to perform photo-alignment treatment. The irradiation light intensity on the sample surface was 81 mW / cm ² .

  After the amine treatment and the photo-alignment treatment, using an inert gas oven (FH-332 manufactured by Advantech), heat treatment was performed at 250 ° C. for 120 minutes in a nitrogen atmosphere to thermally imidize the alignment film.

  Except for not performing amine treatment and photo-alignment treatment, the thickness of the polyamic acid film (before the amine treatment) formed on the quartz glass substrate under the same conditions and after the amine treatment at 250 ° C. in a nitrogen atmosphere The thickness of the polyimide film baked by heat treatment for 120 minutes was determined using an incident angle spectroscopic ellipsometer (M-2000) manufactured by JA Woollam Co., Ltd. with an incident angle of 50 degrees, 60 degrees, and 70 degrees. Measured with

  The polyamic acid film (before amine treatment) had a thickness of 19 nm, and the film obtained by thermal imidization after the amine treatment had a thickness of 13 nm.

<Determination of Conversion Factor d / d ′ from Average Degree of Orientation over Whole Film Thickness of Orientation Film to Degree of Orientation of Surface Layer of Orientation Film>
Since a 500 W Deep UV lamp (UXM-501MD) light source manufactured by USHIO INC. Has a strong emission band at a wavelength of 364 nm, the absorption coefficient α of the polyamic acid film (without amine treatment) at a wavelength of 364 nm is used to The effective film thickness d ′ of the photo-aligned region is determined. Using a multi-incidence angle spectroscopic ellipsometer (M-2000) manufactured by JA Woollam Co., Ltd., the complex refractive index (n + iκ) of the polyamic acid film (without amine treatment) is 50 °, 60 °, 70 °. Measured in degrees. The complex refractive index at a wavelength of 364 nm was 1.87 + i0.816. The absorption coefficient α of the polyamic acid is determined as α = 2k ₀ κ = 2 × (2π / 364) × 0.816 = 0.0282 nm ⁻¹ . Here, k ₀ is the wave number of light propagating in vacuum (air).

When the photo-alignment process is performed by irradiating light from the normal direction of the substrate, the effective film thickness d ′ of the region subjected to the photo-alignment process of the liquid crystal alignment film is obtained from the following equation.
d ′ = (1 / α) × γ
In the above formula, α is the absorption coefficient of the polyamic acid film not subjected to photo-alignment treatment at the wavelength of light used for the photo-alignment treatment. by the correction factor of the thickness of the liquid crystal alignment film according γ imidization, the thickness of imidization before polyamic acid film d _PAA, the thickness of the polyimide film after imidization When d _PI d _PI / d _PAA Given. When the thickness d of the liquid crystal alignment film is smaller than d ′, d ′ = d. In this example and the comparative example, γ = 0.68, d ′ is 24 nm, and d = 13 nm <d ′ = 24 nm, so that d ′ = d.

When the photo-alignment process is performed by irradiating light at an incident angle of 45 ° (the incident angle is defined as an angle from the substrate normal), the effective film thickness d ′ of the photo-aligned region of the liquid crystal alignment film is In consideration of refraction, it is obtained from the following equation.
d ′ = (1 / α) cos θ _r × γ
Here, θ _r is a refraction angle, and when light enters the polyamic acid film from the air at an incident angle of 45 °, θ _r = 22 ° and d ′ is 22 nm. In the case of this example and the comparative example, d = 13 nm <d ′ = 22 nm, and therefore d ′ = d can be obtained even when the incident angle is 45 °.

  FIG. 4 shows a polarized UV-visible light absorption spectrum of a sample subjected to C18-amine treatment on a 19 nm-thick polyamic acid film and then irradiated with linearly polarized light for 30 minutes from the direction perpendicular to the substrate surface and subjected to photo-alignment treatment. Show. The orientation index Δ of this film was 0.28. FIG. 5 shows a polarized ultraviolet-visible light absorption spectrum of a polyimide alignment film obtained by thermal imidization of the sample at 250 ° C. The orientation index Δ of this film was 0.73.

When a C18-amine-treated polyamic acid film is subjected to photo-alignment treatment by changing the irradiation amount of linearly polarized light from 0 to 146 J / cm ² , the alignment index Δ (black circle) of the polyamic acid film irradiated with light and its film FIG. 6 shows the orientation index Δ (black square) of the polyimide photo-alignment film obtained by thermal imidization. It can be seen that the orientation index Δ of the polyamic acid film monotonously increases as the amount of light irradiation increases. It can also be seen that the orientation index Δ is significantly increased during the thermal imidization process. The orientation index Δ of the polyimide photo-alignment film was 0.27 to 0.73 when the dose of linearly polarized light was 5 to 146 J / cm ² .

<Comparative Example 1>
A polyimide alignment film was produced under exactly the same conditions as in Example 1 except that the C18-amine treatment was not performed. FIG. 6 shows the orientation index Δ (centered circle) of the polyamic acid film after the photo-alignment treatment and the orientation index Δ (centered square) of the polyimide alignment film obtained by thermal imidization of the film. The orientation index Δ of the polyamic acid film monotonously increases with the increase in the amount of light irradiation, and the orientation index Δ significantly increases during the thermal imidization process, but the obtained orientation index Δ is obtained when amine treatment is performed. Smaller than that.

<Comparative example 2>
A polyimide alignment film was produced under exactly the same conditions as in Example 1 except that the polyamic acid film was subjected to a photo-alignment treatment for 30 minutes and then subjected to a C18-amine treatment. The orientation index Δ of the polyimide alignment film was 0.38.

  By comparing the dependence of the orientation index Δ of Example 1 and Comparative Example 1 on the amount of light irradiation (FIG. 6), the polyamic acid film was subjected to C18-amine treatment and then irradiated with light. It can be seen that chain rotation is likely to occur, and an orientation index Δ that is approximately twice as large can be obtained. Further, when the C18-amine treatment is performed on the polyimide alignment film after thermal imidization, a very large alignment index Δ is obtained. Further, by combining the results of Comparative Example 2, it can be seen that the photo-alignment efficiency can be increased by performing light irradiation and thermal imidization after the C18-amine treatment is applied to the polyamic acid film.

<Example 2>
A polyamic acid film is formed on a quartz glass substrate under exactly the same conditions as in Example 1, and after C18-amine treatment, a 500 W Deep UV lamp (UXM-501MD) manufactured by USHIO INC. Is used as a light source. The wavelength range of light was set to 340 to 500 nm through a bandpass filter manufactured by Bunko Co., Ltd., and light having been linearly polarized through a Grand Taylor polarizing prism was irradiated for 30 minutes from the direction perpendicular to the substrate surface (light irradiation amount 146 J / cm ² ). In order to develop a pretilt angle, the above-mentioned Grand Taylor polarizing prism is removed, non-polarized light having a wavelength region of 340 to 500 nm is defined as an incident surface that is perpendicular to the polarization direction of the linearly polarized light, and the incident angle (substrate method) Irradiated at 45 degrees for 1-60 minutes. The irradiation light intensity on the sample surface was 129 mW / cm ² . The film was thermally imidized under the same conditions as in Example 1 to obtain a polyimide photo-alignment film. The orientation index Δ of the obtained polyimide photo-alignment film is shown by black squares in FIG. In the working range, an orientation index Δ of 0.55 to 0.64 was obtained.

  A pair of quartz glass substrates manufactured under the same conditions were used as a spacer with a polyester film having a thickness of 25 μm, and the two substrates were opposed to each other with the surface on which the alignment film was formed facing, to produce an anti-parallel cell. The anti-parallel cell here means a cell assembled so that the propagation direction of non-polarized light is antiparallel when a photo-alignment treatment is performed on a substrate coated with an aligning agent. Cyanobiphenyl liquid crystal (5CB) was injected into the cell at 80 ° C. and gradually cooled to room temperature to obtain a pretilt angle measurement cell.

FIG. 8 shows the relationship between the light irradiation amount of non-polarized light irradiation at an incident angle of 45 degrees and the pretilt angle developed in the photo-alignment process. The amount of light irradiated by linearly polarized light along the substrate normal line before unpolarized light irradiation was fixed at 146 J / cm ² . The pretilt angle suddenly increased with an increase in the amount of non-polarized light. When the light irradiation amount was 8 J / cm ² , the pretilt angle reached 8 degrees, and when the light irradiation amount was 464 J / cm ² , the pretilt angle reached 45 degrees. Since the light irradiation amount 464 J / cm ² still tends to increase, a larger pretilt angle was expressed by further increasing the non-polarized light irradiation amount.

Further, as a result of observation with a polarizing microscope, no alignment defect of the liquid crystal was observed in the anti-parallel cell (non-polarized irradiation time: 0 to 60 minutes). Polarization microscope observation was performed under a crossed Nicols condition with a magnification of 100 times. As an example, FIG. 9 shows a polarizing microscope photograph of an anti-parallel cell with a non-polarized light irradiation amount of 464 J / cm ² .

<Comparative Example 3>
Two polyimide photo-alignment films were produced under exactly the same conditions as in Example 2 except that the C18-amine treatment was not performed and the oblique incident non-polarized irradiation time was 30 minutes (light irradiation amount 228 J / cm ² ). did. The orientation index Δ of the polyimide photo-alignment film was 0.30. Using the two polyimide photo-alignment films, an antiparallel liquid crystal cell was assembled and the pretilt angle was measured. The pretilt angle was 2.0 degrees (FIG. 8: black circle). As a result of observation with a polarizing microscope, no alignment failure of the liquid crystal was observed.

<Comparative example 4>
A photo-alignment film was prepared in the same manner as in Comparative Example 3 except that the C18-amine treatment was performed under the same conditions as in Example 1 after the photo-alignment treatment, an antiparallel liquid crystal cell was assembled, and the pretilt angle was measured. The pretilt angle was 8.5 degrees (FIG. 8: black triangle). The orientation index Δ of the polyimide photo-alignment film was 0.26. As a result of observation with a polarizing microscope, alignment defects of the liquid crystal were observed (FIG. 10).

In order to express a larger pretilt angle by comparing the result of the oblique incident non-polarized irradiation time 30 minutes (light irradiation amount 228 J / cm ² ) in Example ^{2 with} the results of Comparative Example 3 and Comparative Example 4, Furthermore, in order to prevent occurrence of alignment defects in the liquid crystal, it is effective to perform C18-amine treatment on the polyamic acid film before the photo-alignment treatment. That is, the order in which photo-alignment treatment is performed after amine treatment and thermal imidization is important.

<Example 3>
Example except that C12-amine is used instead of C18-amine, and amine treatment is performed at room temperature for 16 hours, and irradiation with unpolarized ultraviolet light is performed for 30 minutes at an incident angle (defined from the substrate normal) of 45 degrees. Under the same conditions as 2, two polyimide alignment films were prepared, an antiparallel cell was assembled, and the pretilt angle of the liquid crystal was measured. The orientation index Δ of the polyimide photo-alignment film was 0.77, and the pretilt angle was 26 degrees. As a result of observation with a polarizing microscope, no alignment failure of the liquid crystal was observed.

<Example 4>
Except for using CF8-C3-amine instead of C12-amine, two polyimide alignment films were prepared under exactly the same conditions as in Example 3, an antiparallel cell was assembled, and the pretilt angle of the liquid crystal was measured. The orientation index Δ of the polyimide photo-alignment film was 0.33, and the pretilt angle was 8.6 degrees. As a result of observation with a polarizing microscope, no alignment failure of the liquid crystal was observed.

  From the results of Examples 2, 3, and 4, the amine used for the amine treatment is not limited to a specific amine, and any of the amino compounds described above can be used.

<Example 5>
Two polyimide alignment films were prepared under exactly the same conditions as in Example 2 except that linearly polarized light irradiation was not performed in the photo-alignment treatment and that the oblique non-polarized light irradiation amount was 15 minutes (115 J / cm ² ). Then, an anti-parallel cell was assembled, and the pretilt angle of the liquid crystal was measured. The orientation index Δ of the polyimide photo-alignment film was 0.42. The pretilt angle was 25 degrees. As a result of observation with a polarizing microscope, no alignment failure of the liquid crystal was observed.

By comparing the result of the oblique incident non-polarized irradiation time of 15 minutes (irradiation amount 115 J / cm ² ) in Example ^{2 with} the result of Example 5, it is possible to obtain a high pretilt angle even with only oblique non-polarized light irradiation in the photo-alignment process. It can be seen that a liquid crystal alignment state without alignment defects can be obtained.

  From a comparison between Example 4 and Comparative Example 4, in order to prevent the occurrence of alignment defects in a liquid crystal cell having a pretilt angle of about 8.5 degrees, an alignment index Δ of 0.26 is insufficient, and if 0.33, It turns out that it is enough. Therefore, it can be seen that when the pretilt angle is about 8.5 degrees, an orientation index Δ of at least 0.27 is necessary to prevent the occurrence of alignment defects in the liquid crystal.

Document A describes that when the pretilt angle is about 2 degrees, the occurrence of liquid crystal defects can be prevented if the orientation index Δ is 0.07 or more. However, in Comparative Example 4, although the orientation index Δ was 0.26, orientation defects occurred. In Document B, when a pretilt angle in the range of 30 to 70 degrees is generated using a polyimide photo-alignment film having an orientation index Δ of 0.26 to 0.20, alignment defects of the liquid crystal are generated. Is described. From these results, the minimum alignment index Δ necessary for preventing the occurrence of alignment defects in the liquid crystal depends on the pretilt angle, and at a pretilt angle of 3 to 70 degrees, at least 0. It is expected that an orientation index Δ of 27 or greater is required. Therefore, after applying a polyamic acid having an azobenzene skeleton as a photosensitive group to a substrate, adsorbing an alkylamine to a film made of the polyamic acid, performing an exposure treatment, and then baking the same prevents the occurrence of alignment defects. It is very effective from the viewpoint.
Reference A: K. Sakamoto, K. usami, T. Sasaki, Y. Uehara, and S. Ushioda, Jpn. J.
Appl. Phys. 45, 2705 (2006).
Reference B: K. Usami, K. Sakamoto, J. Yokota, Y. Uehara, and S. Ushioda, J. Appl.
Phys. 104, 113528 (2008).

  By using the liquid crystal photo-alignment film of the present invention, it is possible to obtain a liquid crystal cell having high liquid crystal alignment and exhibiting a large pretilt angle with respect to the liquid crystal. The present invention is suitable for application to, for example, a bistable bend-spray type liquid crystal display element.

Claims (9)

It is a polyimide photo-alignment film obtained by exposing a polyamic acid having photo-alignment ability derived from a photosensitive group contained in a structural unit to an amine-treated coating film, and then baking it at or above the imidization temperature of the polyamic acid. And
A polyimide photo-alignment characterized in that a pretilt angle of 3 to 70 degrees is given to the liquid crystal, and the orientation index (Δ) of the film represented by the following formula (1) exhibits a value of 0.27 or more. film.
(In formula (1), A‖ represents the main chain of polyimide in a direction perpendicular to the surface of the liquid crystal alignment film and parallel to the surface of the liquid crystal alignment film in the liquid crystal alignment film. Represents the absorbance of the alignment film at a wavelength in the vicinity of the maximum of absorption when being incident on the liquid crystal alignment film so that the polarization direction of the ultraviolet / visible light is parallel to the average alignment direction of The ultraviolet / visible light is perpendicular to the surface of the liquid crystal alignment film and the ultraviolet / visible light is aligned with respect to the average alignment direction of the polyimide main chain in the direction parallel to the surface of the liquid crystal alignment film. This represents the absorbance of the alignment film at a wavelength near the maximum of absorption when the light is incident on the liquid crystal alignment film so that the polarization direction is vertical, d represents the film thickness of the liquid crystal alignment film, and d ′ represents the light of the liquid crystal alignment film. (It represents the effective film thickness of the aligned region.)   The polyimide photo-alignment film according to claim 1, wherein the polyamic acid is a polyamic acid having an azobenzene skeleton as a photosensitive group. The polyimide photo-alignment film according to claim 1 or 2, wherein the polyamic acid is made of at least one diamine selected from the following formulas (I-1) to (I-7) as a raw material.
The tetracarboxylic dianhydride which is a raw material of the polyamic acid is at least one selected from the group consisting of the following formulas (AN-I) to (AN-VII). The polyimide photo-alignment film described in 1.
In formulas (AN-I), (AN-IV) and (AN-V), X is independently a single bond or —CH ₂ —;
In the formula (AN-II), G represents a single bond, alkylene having 1 to 20 carbon atoms, —CO—, —O—, —S—, —SO ₂ —, —C (CH ₃ ) ₂ —, or —C. (CF ₃ ) ₂ —;
In formulas (AN-II) to (AN-IV), Y is independently one selected from the group of trivalent groups below,
Any hydrogen in these groups may be replaced by methyl, ethyl or phenyl;
In the formulas (AN-III) to (AN-V), the ring A is a monocyclic hydrocarbon group having 3 to 10 carbon atoms or a condensed polycyclic hydrocarbon group having 6 to 30 carbon atoms. Any hydrogen in may be replaced by methyl, ethyl or phenyl, and the bond on the ring is connected to any carbon constituting the ring, and the two bonds are connected to the same carbon May be;
In the formula (AN-VI), X ¹⁰ is alkylene having 2 to 6 carbons;
Me is methyl;
Ph is phenyl;
In formula (AN-VII), G ¹⁰ is independently —O—, —COO— or —OCO—; and
r is independently 0 or 1. The polyimide of any one of Claims 1-4 in which the diamine which is the raw material of the said polyamic acid contains at least 1 chosen from the group which consists of the following formula | equation (DI-1)-(DI-17). Photo-alignment film.
In formulas (DI-1) to (DI-7), m is an integer of 1 to 12;
G ²¹ is independently a single bond, —O—, —S—, —S—S—, —SO ₂ —, —CO—, —CONH—, —NHCO—, —C (CH ₃ ) ₂ —, — C (CF ₃ ) ₂ —, — (CH ₂ ) _{m ′} —, —O— (CH ₂ ) _{m ′} —O—, or —S— (CH ₂ ) _{m ′} —S—, and m ′ is independent. An integer from 1 to 12;
G ²² is independently a single bond, —O—, —S—, —CO—, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, or alkylene having 1 to 10 carbons;
Arbitrary —H of the cyclohexane ring and the benzene ring in each formula may be replaced by —F, —CH ₃ , —OH, —CF ₃ or benzyl. In addition, in the formula (DI-4), The following formulas (DI-4-a) to (DI-4-c) may be substituted,
In formulas (DI-4-a) to (DI-4-c), R ²⁰ is independently —H or —CH ₃ ;
In formulas (DI-2) to (DI-7), a group whose bonding position is not fixed to any carbon atom constituting the ring indicates that the bonding position in the ring is arbitrary; and
The bonding position of —NH ₂ to the cyclohexane ring or the benzene ring is an arbitrary position excluding the bonding position of G ²¹ or G ²² .
In formula (DI-8), R ²¹ and R ²² are independently alkyl having 1 to 3 carbons or phenyl;
G ²³ is independently alkylene having 1 to 6 carbons, phenylene or alkyl-substituted phenylene;
n is an integer from 1 to 10;
In formula (DI-9), R ²³ is independently alkyl having 1 to 3 carbons;
p is independently an integer from 0 to 3;
q is an integer from 0 to 4;
In the formula (DI-10), R ²⁴ is —H, alkyl having 1 to 4 carbons, phenyl, or benzyl;
In the formula (DI-11), G ²⁴ is —CH ₂ — or —NH—;
In the formula (DI-12), G ²⁵ is a single bond, alkylene having 2 to 6 carbons or 1,4-phenylene;
r is 0 or 1;
In formula (DI-12), a group whose bonding position is not fixed to any carbon atom constituting the ring indicates that the bonding position in the ring is arbitrary; and
In formulas (DI-9), (DI-11) and (DI-12), the bonding position of —NH ₂ bonded to the benzene ring is an arbitrary position;
In the formula (DI-13), G ²⁶ represents a single bond, —O—, —COO—, —OCO—, —CO—, —CONH—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—. , -OCF ₂ -, or - (CH _{2) m '-} it is and, m' is an integer from 1 to 12;
R ²⁵ is alkyl having 3 to 20 carbons, phenyl, a group having a steroid skeleton, or a group represented by the following formula (DI-13-a). In this alkyl, any —H is —F Any —CH ₂ — may be replaced by —O—, —CH═CH— or —C≡C—, and —H of this phenyl is —F, —CH ₃ , _{-OCH 3, -OCH 2 F, -OCHF} 2, -OCF 3, alkyl having 3 to 20 carbon atoms, or may be replaced by alkoxy having 3 to 20 carbon atoms, -H of cyclohexyl 3 carbon atoms Which may be replaced by ˜20 alkyl or C 3-20 alkoxy, and indicates that the bonding position of —NH ₂ bonded to the benzene ring is an arbitrary position in the ring;
In the formula (DI-13-a), G ²⁷ , G ²⁸ and G ²⁹ each represent a bonding group, and these are each independently a single bond or alkylene having 1 to 12 carbons, and one or more —CH ₂ — may be replaced by —O—, —COO—, —OCO—, —CONH—, —CH═CH—;
Ring B ²¹ , Ring B ²² , Ring B ²³ , and Ring B ²⁴ are independently 1,4-phenylene, 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl, pyrimidine-2, 5-diyl, pyridine-2,5-diyl, naphthalene-1,4-diyl, naphthalene-1,5-diyl, naphthalene-2,6-diyl, naphthalene-2,7-diyl, or anthracene-9,10 -Diyl;
In ring B ²¹ , ring B ²² , ring B ²³ , and ring B ²⁴ , any —H may be replaced by —F or —CH ₃ ;
s, t and u are independently integers from 0 to 2 and their sum is 1 to 5;
when s, t or u is 2, the two linking groups in each bracket may be the same or different and the two rings may be the same or different;
R ²⁶ represents —F, —OH, alkyl having 1 to 30 carbon atoms, fluorine-substituted alkyl having 1 to 30 carbon atoms, alkoxy having 1 to 30 carbon atoms, —CN, —OCH ₂ F, —OCHF ₂ , or —OCF. _And any —CH ₂ — in the alkyl having 1 to 30 carbon atoms may be replaced by a divalent group represented by the following formula (DI-13-b);
In the formula (DI-13-b), R ²⁷ and R ²⁸ are independently alkyl having 1 to 3 carbons;
v is an integer from 1 to 6;
In formula (DI-14) and formula (DI-15), G ³⁰ is independently a single bond, —CO— or —CH ₂ —;
R ²⁹ is independently —H or —CH ₃ ;
R ³⁰ is —H, alkyl having 1 to 20 carbons, or alkenyl having 2 to 20 carbons;
One -H of the benzene ring in formula (DI-15) may be replaced by alkyl having 1 to 20 carbons or phenyl;
In formula (DI-14) and formula (DI-15), a group whose bonding position is not fixed to any carbon atom constituting the ring indicates that the bonding position in the ring is arbitrary;
Bonded to the benzene ring -NH ₂ indicates that the binding position in the ring is optional;
In formula (DI-16) and formula (DI-17), G ³¹ is independently —O— or alkylene having 1 to 6 carbons;
G ³² is a single bond or alkylene having 1 to 3 carbon atoms;
R ³¹ is —H or alkyl having 1 to 20 carbons, and any —CH ₂ — in the alkyl may be replaced by —O—, —CH═CH— or —C≡C—;
R ³² is alkyl having 6 to 22 carbons;
R ³³ is —H or C 1-22 alkyl;
Ring B ²⁵ is 1,4-phenylene or 1,4-cyclohexylene;
r is 0 or 1; and
-NH ₂ bonded to the benzene ring indicates that the binding position in the ring is optional.   It is obtained by applying a liquid crystal aligning agent containing a polyamic acid having photo-alignment ability to a substrate, subjecting the coating film to an amine treatment with an amino compound vapor, and then baking it at a temperature higher than the imidization temperature of the polyamic acid. The polyimide photo-alignment film according to claim 1, which is a polyimide photo-alignment film.   Polyimide photo-alignment obtained by applying a liquid crystal aligning agent containing a polyamic acid having photo-alignment ability derived from the photosensitive group contained in the structural unit to the substrate, exposing the amino compound to the coating film, and then exposing and baking. A method for producing a membrane.   The method for producing a polyimide photo-alignment film according to claim 7, wherein the photosensitive group is an azobenzene derivative.   The liquid crystal display element which has a photo-alignment film of any one of Claims 1-6.