TWI869328B - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

The present invention relates to a liquid crystal alignment agent, which contains: (A) a polymer composed of a diamine component including a diamine represented by the following formula (1), and an acid component including at least one selected from cyclobutanetetracarboxylic dianhydride represented by the following formula (2-1) and cyclobutanetetracarboxylic diester represented by the following formula (2-2) (in formula (2-2), R is independently an alkyl group having 1 to 5 carbon atoms), and (B) an organic solvent. The present invention can provide a substrate having a liquid crystal alignment film for a transverse electric field driven liquid crystal display element that has high efficiency in imparting alignment control capability and excellent burning characteristics, and a transverse electric field driven liquid crystal display element having the substrate.

Description

Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element

The present invention relates to a liquid crystal alignment agent, a liquid crystal alignment film and a liquid crystal display element for manufacturing a liquid crystal display element with excellent burning characteristics.

Liquid crystal display elements are known as lightweight, thin, and low-power display devices, and have been used in large-scale television applications in recent years, and have achieved significant development. Liquid crystal display elements are composed of, for example, a pair of transparent substrates with electrodes to sandwich a liquid crystal layer. In addition, in a liquid crystal display element, an organic film composed of an organic material is used as a liquid crystal alignment film in order to achieve a desired alignment state of the liquid crystal between the substrates.

That is, the liquid crystal alignment film is a component of the liquid crystal display element, and is formed on the surface where the substrates holding the liquid crystal are in contact with the liquid crystal, and plays a role in aligning the liquid crystal in a certain direction between the substrates. In addition, in addition to requiring the liquid crystal to align in a certain direction such as a direction parallel to the substrates, the liquid crystal alignment film is sometimes also required to control the pre-tilt angle of the liquid crystal. The ability to control the alignment of the liquid crystal in such a liquid crystal alignment film (hereinafter referred to as alignment control ability) can be imparted by performing an alignment treatment on the organic film constituting the liquid crystal alignment film.

As an alignment treatment method for imparting alignment control capability to a liquid crystal alignment film, a rubbing method has long been known. The so-called rubbing method refers to a method in which an organic film such as polyvinyl alcohol, polyamide, or polyimide on a substrate is wiped (rubbed) in a certain direction using a cloth such as cotton, nylon, or polyester to align the liquid crystal in the wiping direction (rubbing direction). This rubbing method can easily achieve a relatively stable alignment state of the liquid crystal, so it has been used in the manufacturing process of conventional liquid crystal display elements. In addition, as an organic film used in the liquid crystal alignment film, a polyimide-based organic film with excellent reliability such as heat resistance or electrical properties is mainly selected.

However, the rubbing method of rubbing the surface of the liquid crystal alignment film composed of polyimide or the like has the problem of generating dust or static electricity. In addition, due to the high precision of liquid crystal display elements in recent years, or the unevenness caused by the electrodes on the corresponding substrate or the active switch element for liquid crystal driving, it is sometimes impossible to wipe the surface of the liquid crystal alignment film evenly with a cloth, and it is impossible to achieve uniform liquid crystal alignment. Therefore, as another alignment processing method of the liquid crystal alignment film without rubbing, the optical alignment method is being actively studied.

There are various methods for photo-alignment, but linearly polarized light or collimated light is used to form anisotropy in the organic film constituting the liquid crystal alignment film, and the liquid crystal is aligned according to the anisotropy. As the main photo-alignment method, a decomposition-type photo-alignment method is known. For example, a polyimide film is irradiated with polarized ultraviolet light, and the polarization direction dependence of the ultraviolet absorption of the molecular structure is utilized to cause anisotropic decomposition. Alternatively, the liquid crystal is aligned using the polyimide that remains without being decomposed (for example, refer to Patent Document 1).

In addition, photo-alignment methods of photo-crosslinking type or photo-isomerization type are also known. For example, polyvinyl cinnamate is used and polarized ultraviolet light is irradiated to cause a dimerization reaction (crosslinking reaction) in the double bond part of the two side chains parallel to the polarization. In addition, the liquid crystal is aligned in a direction orthogonal to the polarization direction (for example, refer to non-patent document 1). In addition, when a side-chain polymer having azobenzene in the side chain is used, polarized ultraviolet light is irradiated to cause an isomerization reaction in the azobenzene part of the side chain parallel to the polarization, so that the liquid crystal is aligned in a direction orthogonal to the polarization direction (for example, refer to non-patent document 2).

In addition, as a photo-alignment film for improving the afterimage characteristics caused by AC driving, there is a known method of using polyamide produced by diamine containing a cyclobutane ring and an imide group (for example, refer to Patent Document 3).

As in the above example, the method of treating the alignment of the liquid crystal alignment film by the optical alignment method does not require friction and does not generate dust or static electricity. Furthermore, even the substrate of the liquid crystal display element with uneven surfaces can be treated with the alignment treatment, which will become a method of treating the alignment of the liquid crystal alignment film suitable for industrial production processes. [Prior art literature] [Patent literature]

[Patent Document 1] Japanese Patent No. 3893659 [Patent Document 2] Japanese Patent No. 3612832 [Patent Document 3] Korean Patent Application Publication No. 10-2016-0142614 [Non-Patent Document]

[Non-patent document 1] M. Shadt et al., Jpn. J. Appl. Phys. 31, 2155(1992). [Non-patent document 2] K. Ichimura et al., Chem. Rev. 100, 1847(2000).

[The problem that the invention wants to solve]

As described above, compared with the rubbing method that has been used in the industry as an alignment processing method for liquid crystal display elements, the optical alignment method does not require a rubbing step, so it has a great advantage. In addition, compared with the rubbing method in which the alignment control ability is roughly constant by rubbing, the optical alignment method can change the amount of polarized light irradiation to control the alignment control ability. However, in the optical alignment method, if you want to achieve the same degree of alignment control ability as the case of the rubbing method, sometimes a large amount of polarized light irradiation is required, or stable liquid crystal alignment cannot be achieved.

For example, in the decomposition type photo-alignment method described in the above-mentioned patent document 1, it is necessary to irradiate the polyimide film with ultraviolet light from a high-pressure mercury lamp with an output of 500W for 60 minutes, which requires long-term and large-scale ultraviolet irradiation. Moreover, even in the case of dimerization type or photoisomerization type photo-alignment method, sometimes a large amount of ultraviolet irradiation of several J (joules) to tens of J is required. Furthermore, in the case of photo-crosslinking type or photoisomerization type photo-alignment method, since the thermal stability or optical stability of the alignment of the liquid crystal is poor, when used as a liquid crystal display element, there will be problems such as poor alignment or display burn-in. In particular, in a transverse electric field driven liquid crystal display element, since the liquid crystal molecules are switched in-plane, the liquid crystal orientation shifts easily after the liquid crystal drive, making display burn-in caused by AC drive a major issue.

Therefore, in the photo-alignment method, it is required to realize high efficiency of alignment processing or stable liquid crystal alignment, and it is required to have a liquid crystal alignment film and a manufacturing method thereof that can efficiently impart high alignment control capability to the liquid crystal alignment film.

The object of the present invention is to provide a substrate having a liquid crystal alignment film for a lateral electric field driven liquid crystal display element that has high efficiency in imparting alignment control capability and excellent burning characteristics, and a lateral electric field driven liquid crystal display element having the substrate and a method for manufacturing the same. [Means for Solving the Problem]

The inventors of the present invention have discovered the following invention as a result of in-depth research to achieve the above-mentioned problem.

1. A liquid crystal alignment agent comprising: (A) a polymer composed of a diamine component comprising a diamine represented by the following formula (1) and an acid component comprising at least one selected from cyclobutanetetracarboxylic dianhydride represented by the following formula (2-1) and a cyclobutanetetracarboxylic diester represented by the following formula (2-2); and (B) an organic solvent.

(In formula (2-2), R is independently an alkyl group having 1 to 5 carbon atoms).

2. The liquid crystal alignment agent as described in 1 above, wherein the polymer is at least one selected from the group of polyimides consisting of polyimide precursors and their imide products. 　　3. The liquid crystal alignment agent as described in any one of 1 or 2 above, wherein R in the above formula (2-2) is a methyl group. 　　4. The liquid crystal alignment agent as described in any one of 1 to 3 above, wherein the polymer is represented by the following formula (3),

(In formula (3), _X1 is a tetravalent organic group derived from a tetracarboxylic acid derivative and the tetracarboxylic acid derivative includes at least one structure selected from the above formulas (2-1) and (2-2), _Y1 is a divalent organic group derived from a diamine and the diamine includes the structure of formula (1), and _R11 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms). 5. The liquid crystal alignment agent as described in 4 above, wherein the liquid crystal alignment agent contains 10 mol% or more of a polymer having a structural unit represented by the above formula (3) relative to the total polymer contained in the liquid crystal alignment agent. 6. A liquid crystal alignment film for a transverse electric field driven liquid crystal display element, which is obtained using a liquid crystal alignment agent as described in any one of 1 to 5 above. 7. A substrate having the liquid crystal alignment film for a transverse electric field driven liquid crystal display element as described in 6 above. 8. A transverse electric field driven liquid crystal display device having a substrate as described in 7 above. [Effects of the invention]

The present invention can provide a substrate having a liquid crystal alignment film for a transverse electric field driven liquid crystal display element that has high efficiency in imparting alignment control capability and excellent burning characteristics, and a transverse electric field driven liquid crystal display element having the substrate. 　　The transverse electric field driven liquid crystal display element manufactured by the method of the present invention has high efficiency in imparting alignment control capability, so even long-term continuous driving will not impair the display characteristics.

The polymer composition used in the manufacturing method of the present invention is a photosensitive main-chain polymer (hereinafter, also referred to as the main-chain polymer) that can exhibit self-organization ability, so the coating obtained using the aforementioned polymer composition is a main-chain polymer film that has a photosensitive ability to exhibit self-organization ability. The coating is not subjected to a friction treatment, but is instead subjected to an alignment treatment by polarized light irradiation. In addition, after the polarized light irradiation, the main-chain polymer film is subjected to a heating step to become a coating film endowed with an alignment control ability (hereinafter, also referred to as a liquid crystal alignment film). At this time, a slight anisotropy exhibited by the polarized light irradiation becomes a driving force, so the main-chain polymer itself is efficiently realigned by self-organization. As a result, highly efficient alignment processing is achieved as a liquid crystal alignment film, and a liquid crystal alignment film endowed with high alignment control capability can be obtained.

Furthermore, the liquid crystal alignment film formed by the polymer composition of the present invention has excellent film strength, and therefore, when used as a liquid crystal display element, even if thinning processing is performed by chemical polishing, it is difficult to cause grinding or peeling of the liquid crystal alignment film.

[Best Mode for Carrying Out the Invention]

The following is a detailed description of the implementation form of the present invention. The liquid crystal alignment agent of the present invention is a polymer (hereinafter also referred to as a specific polymer or main chain polymer) obtained by comprising a diamine component including a diamine represented by the above formula (1) and an acid component including at least one selected from the cyclobutanetetracarboxylic dianhydride represented by the above formula (2-1) and the cyclobutanetetracarboxylic acid diester represented by the above formula (2-2). Each condition is described in detail below.

The liquid crystal alignment agent of the present invention is a liquid crystal alignment agent containing a polymer and an organic solvent as described below, wherein the polymer is a polymer composed of a diamine component including a diamine represented by the above formula (1) (also referred to as a specific diamine in the present invention) and an acid component including at least one selected from cyclobutanetetracarboxylic dianhydride represented by the above formula (2-1) (also referred to as a specific tetracarboxylic dianhydride in the present invention) and a cyclobutanetetracarboxylic diester represented by the above formula (2-2) (also referred to as a specific tetracarboxylic diester in the present invention).

<Polymer> The polymer used in the liquid crystal alignment agent of the present invention is a polymer obtained by a diamine component including a diamine represented by the above formula (1) and an acid component including at least one selected from the cyclobutanetetracarboxylic dianhydride represented by the above formula (2-1) and the cyclobutanetetracarboxylic diester represented by the above formula (2-2). As specific examples, polyamic acid, polyamic acid ester, polyimide, polyurea, polyamide, etc. can be cited, but from the perspective of use as a liquid crystal alignment agent, it is preferably selected from at least one of a polyimide precursor containing a structural unit represented by the following formula (3) and a polyimide as its imide compound. In the heating step after polarized light irradiation, polyimide precursors are more preferred because they have more free rotation sites in the polymer and can be re-oriented in a higher order.

In the above formula (3), _X1 is a tetravalent organic group derived from a tetracarboxylic acid derivative and the tetracarboxylic acid derivative comprises at least one structure selected from the above formulas (2-1) and (2-2), _Y1 is a divalent organic group derived from a diamine and the diamine comprises the structure of formula (1), and _R11 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. In terms of ease of imidization by heating, _R11 is preferably a hydrogen atom, a methyl group or an ethyl group, and more preferably a hydrogen atom.

<Tetracarboxylic acid derivative> _X1 is a tetravalent organic group derived from a tetracarboxylic acid derivative, and the tetracarboxylic acid derivative includes at least one structure selected from the above formulae (2-1) and (2-2).

(In formula (2-2), R is independently an alkyl group having 1 to 5 carbon atoms)

In the above structure, R is preferably a methyl group from the viewpoint of ease of imidization by heating.

<Diamine> In the formula (3), _Y1 is a structure obtained by removing two amino groups from the diamine represented by the above formula (1).

<Polymer (other structural units)> The polyimide precursor containing the structural unit represented by formula (3) may contain at least one type of structural unit selected from the structural unit represented by the following formula (4) and the polyimide which is its imide product within the range not impairing the effect of the present invention.

In formula (4), _X2 is a tetravalent organic group derived from a tetracarboxylic acid derivative, _Y2 is a divalent organic group derived from a diamine, _R12 is the same as the definition of _R11 in the above formula (3), and _R22 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. In addition, at least one of the two _R22s is preferably a hydrogen atom. _X2 is a tetravalent organic group derived from a tetracarboxylic acid derivative, and its structure is not particularly limited. In addition, _X2 in the polyimide precursor is appropriately selected according to the degree of required characteristics such as the solubility of the polymer in the solvent or the coating property of the liquid crystal alignment agent, the alignment of the liquid crystal when the liquid crystal alignment film is prepared, the voltage retention rate, the stored charge, etc., and can be one type in the same polymer, or two or more types can be mixed.

If specific examples of X ₂ must be shown, the structures of formulas (X-1) to (X-46) disclosed in Items 13 and 14 of International Publication No. 2015/119168 can be cited.

The following are preferred structures of _X2 , but the present invention is not limited thereto.

In addition, _Y2 in the polyimide precursor is a divalent organic group derived from diamine, and its structure is not particularly limited. In addition, _Y2 is appropriately selected according to the solubility of the polymer in the solvent or the coating property of the liquid crystal alignment agent, the alignment of the liquid crystal when the liquid crystal alignment film is made, the voltage retention rate, the storage charge and other required properties, and can be one type in the same polymer, or two or more types can be mixed.

If specific examples of _Y2 must be shown, the structure of formula (2) disclosed in item 4 of International Publication No. 2015/119168 and the structures of formulas (Y-1) to (Y-97) and (Y-101) to (Y-118) disclosed in items 8 to 12 can be cited; the divalent organic group obtained by removing two amine groups from formula (2) disclosed in item 6 of International Publication No. 2013/008906; The divalent organic group obtained by removing two amine groups from formula (1) disclosed in item 8; the structure of formula (3) disclosed in item 8 of International Publication No. 2015/060360; the divalent organic group obtained by removing two amine groups from formula (1) recorded in item 8 of Japanese Patent Application Publication No. 2012-173514; the divalent organic group obtained by removing two amine groups from formulas (A) to (F) disclosed in item 9 of International Publication No. 2010-050523, etc.

As a preferred structure of Y ₂ , the structure of the following formula (5) can be cited.

In formula (5), R ³² is a single bond or a divalent organic group, preferably a single bond. R ³³ is a structure represented by -(CH ₂ ) _n -. n is an integer of 2 to 10, preferably 3 to 7. In addition, any -CH ₂ - can be substituted into an ether, ester, amide, urea, or carbamate bond under non-adjacent conditions. R ³⁴ is a single bond or a divalent organic group. Any hydrogen atom on the benzene ring can be substituted with a monovalent organic group, preferably a fluorine atom or a methyl group.

As the structure represented by formula (5), the following structures can be specifically mentioned, but the structure is not limited to these.

Among them, as the diamine that provides the structure of _Y2 , the diamine represented by the following formula (10) is preferred.

(In formula (10), L is a divalent organic group having 2 or more carbon atoms and comprising an alkylene group and a bond selected from an ether bond and an ester bond, _R1 and _R2 are each independently a monovalent organic group, p1 and p2 are each independently an integer of 0 to 4, p is 0 or 1, and q1 and q2 are each independently 1 or 2).

Examples of the monovalent organic group include alkyl, alkenyl, alkoxy, fluoroalkyl, fluoroalkenyl, or fluoroalkoxy groups having 1 to 10 carbon atoms (preferably 1 to 3 carbon atoms). Among them, the monovalent organic group is preferably a methyl group.

Examples of the divalent organic group include a group consisting of an alkylene group and an ether bond, a group consisting of an alkylene group and an ester bond, a group consisting of an alkylene group in which a part or all of the hydrogen atoms are replaced by halogens and an ether bond, or a group consisting of an alkylene group in which a part or all of the hydrogen atoms are replaced by halogens and an ester bond. Among them, the divalent organic group is preferably a group consisting of an alkylene group and an ether bond. The carbon number is preferably 2 to 20, and more preferably 2 to 10.

In addition, among the number of atoms of L, if the total number of carbon atoms and oxygen atoms participating in the length of the main chain is an even number, the linearity of the obtained polymer will become higher, and as a result, a liquid crystal alignment film endowed with high alignment control ability can be obtained by realigning in a higher order in the heating step after polarized light irradiation, which is preferred. In addition, the total number of carbon atoms and oxygen atoms participating in the length of the main chain refers to the total number when the number of each methylene group in the main chain is set to 1, the number of each ether bond is set to 1, and the number of each ester bond is set to 2.

As p1 and p2, 0 is preferred because steric hindrance is small, phenyl groups are easily overlapped, and realignment can be performed in a higher order.

As for p, in terms of a point for realignment in a higher order, an alkylene group having a function as a free rotation site is preferably 1.

Among the diamines of the above formula (10), specific examples of the diamines in which p is 1 are as follows, but the present invention is not limited to these.

Here, when the sum of r, t and u is an even number such as 2, 4, 6, 8 and 10, the linearity of the obtained polymer becomes higher, and as a result, a liquid crystal alignment film with high alignment control ability can be obtained by realigning in a higher order in the heating step after polarized light irradiation. For the above reasons, s is preferably an odd number such as 1, 3, 5.

Among the diamines represented by the above formula (10), a specific example of the diamine in which p is 0 is p-phenylenediamine.

When a polyimide precursor containing a structural unit represented by formula (3) also contains a structural unit represented by formula (4), from the viewpoint of the alignment property of the resulting liquid crystal alignment film, the structural unit represented by formula (4) is preferably in the range of 10 mol % to 90 mol %, more preferably 20 mol % to 80 mol %, and particularly preferably 30 mol % to 70 mol %, relative to the total of formula (3) and formula (4).

The molecular weight of the polyimide precursor used in the present invention is preferably 2,000 to 500,000, more preferably 5,000 to 300,000, and even more preferably 10,000 to 100,000 in terms of weight average molecular weight.

As the polyimide used in the present invention, there can be cited a polyimide obtained by ring-closing the aforementioned polyimide precursor. In the polyimide, the ring-closing rate of the amide group (also called the imidization rate) is not necessarily 100%, and can be arbitrarily adjusted according to the application or purpose. For the polymer of the present invention, from the viewpoint of liquid crystal alignment, the imidization rate is preferably 0 to 70%, and more preferably 0 to 50%. In addition, the imidization rate here is the imidization rate calculated by removing the imide structure derived from the diamine represented by formula (1). As a method for imidizing a polyimide precursor, there can be cited thermal imidization in which a solution of the polyimide precursor is directly heated, or catalytic imidization in which a catalyst is added to the solution of the polyimide precursor.

<Liquid crystal alignment agent> The liquid crystal alignment agent of the present invention contains a polymer (specific polymer) obtained by a diamine component including a diamine represented by the above formula (1) and an acid component including at least one selected from the cyclobutanetetracarboxylic dianhydride represented by the above formula (2-1) and the cyclobutanetetracarboxylic diester represented by the above formula (2-2), but as long as it is within the scope that can exert the effect described in the present invention, it can contain two or more specific polymers with different structures. In addition to the specific polymer, it can contain other polymers, that is, polymers that do not have a divalent group derived from the diamine represented by formula (1). As other types of polymers, polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivatives, polyacetal, polystyrene or its derivatives, poly(styrene-phenylmaleimide) derivatives, poly(meth)acrylate, etc. can be cited. If the liquid crystal alignment agent of the present invention contains other polymers, the ratio of the specific polymer relative to the total polymer components is preferably 10% by mass or more, and as an example, 10 to 100% by mass can be cited.

Liquid crystal alignment agents are used to make liquid crystal alignment films, and generally take the form of coating liquids from the viewpoint of forming a uniform thin film. Even the liquid crystal alignment agent of the present invention is preferably a coating liquid containing the aforementioned polymer component and an organic solvent that dissolves the polymer component. At this time, the concentration of the polymer in the liquid crystal alignment agent can be appropriately changed according to the thickness of the coating to be formed. From the point of view of forming a uniform and defect-free coating, 1% by mass or more is preferred, and from the point of view of the storage stability of the solution, 10% by mass or less is preferred. The particularly preferred polymer concentration is 2 to 8% by mass.

The organic solvent contained in the liquid crystal alignment agent is not particularly limited as long as the polymer component can be uniformly dissolved. Specific examples thereof include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethylsulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, etc. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ-butyrolactone is preferably used.

In addition, the organic solvent contained in the liquid crystal alignment agent is generally a mixed solvent in addition to the solvents as described above. The mixed solvent is a solvent that improves the coating property when the liquid crystal alignment agent is coated or the surface smoothness of the coating film. Therefore, even the liquid crystal alignment agent of the present invention can be suitable for using such a mixed solvent. Specific examples of the organic solvent used in combination are listed below, but the invention is not limited to these examples.

For example, ethanol, isopropanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentanol, tert-pentanol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-ethanediol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1, 4-Butanediol, 2,3-Butanediol, 1,5-Pentanediol, 2-Methyl-2,4-pentanediol, 2-Ethyl-1,3-Hexanediol, Dipropyl Ether, Dibutyl Ether, Dihexyl Ether, Dioxane, Ethylene Glycol Dimethyl Ether, Ethylene Glycol Diethyl Ether, Ethylene Glycol Dibutyl Ether, 1,2-Butoxyethane, Diethylene Glycol Dimethyl Ether, Diethylene Glycol Diethyl Ether, 4-Hydroxy-4-methyl-2-pentanone, Diethylene Glycol Methyl Ether, Diethylene Glycol Dibutyl Ether, 2-Pentanone, 3-Pentanone, 2-Hexanone, 2-Heptanone, 4-Heptanone, 3-Ethoxybutyl Acetate, 1-Methylpentyl Acetate, 2-Ethylbutyl Acetate, 2-Ethylhexyl Acetate, Ethylene Glycol Monoacetic Acid Ester, ethylene glycol diacetate, propylene carbonate, ethyl carbonate, 2-(methoxymethoxy)ethanol, ethylene glycol monobutyl ether, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, 2-(hexyloxy)ethanol, furfuryl alcohol, diethylene glycol, propylene glycol, propylene glycol monobutyl ether, 1-(butoxyethoxy)propanol, propylene glycol monomethyl ether acetate, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether ethyl esters, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, propyl 3-methoxypropionate, butyl 3-methoxypropionate, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate, solvents represented by the following formulas [D-1] to [D-3], and the like.

In the formula [D-1], ^D1 represents an alkyl group having 1 to 3 carbon atoms, in the formula [D-2], ^D2 represents an alkyl group having 1 to 3 carbon atoms, and in the formula [D-3], ^D3 represents an alkyl group having 1 to 4 carbon atoms.

The type and content of such solvents can be appropriately selected according to the coating equipment, coating conditions, coating environment, etc. of the liquid crystal alignment agent.

The liquid crystal alignment agent of the present invention may also contain additional components other than polymer components and organic solvents within the scope that does not impair the effects of the present invention. As such additional components, adhesion aids for improving the adhesion between the liquid crystal alignment film and the substrate or the adhesion between the liquid crystal alignment film and the sealant, crosslinking agents for improving the strength of the liquid crystal alignment film, dielectrics or conductive substances for adjusting the dielectric constant or resistance of the liquid crystal alignment film, etc. Specific examples of such additional components include various components disclosed in well-known literature related to liquid crystal alignment agents, but if an example must be given, the components disclosed on pages 53 [0105] to 55 [0116] of the specification of the Publication No. 2015/060357, etc. can be cited.

<Method for manufacturing substrate having liquid crystal alignment film> and <Method for manufacturing liquid crystal display element> 　　The method for manufacturing a substrate having a liquid crystal alignment film of the present invention comprises the following steps: 　　[I] a step of coating a polymer composition on a substrate having a conductive film for transverse electric field driving, and then drying to form a coating, wherein the polymer composition contains: (A) a polymer composed of a diamine component comprising a diamine represented by the above formula (1) and an acid component comprising at least one selected from the group consisting of cyclobutanetetracarboxylic dianhydride represented by the above formula (2-1) and cyclobutanetetracarboxylic diester represented by the above formula (2-2), and (B) an organic solvent; 　　[II] a step of irradiating the coating obtained by [I] with polarized ultraviolet light; and 　　[III] a step of heating the coating obtained by [II]. Through the above steps, a liquid crystal alignment film for a lateral electric field driven liquid crystal display element endowed with alignment control capability can be obtained, and a substrate having the liquid crystal alignment film can be obtained.

Furthermore, in addition to the substrate (first substrate) obtained above, a transverse electric field driven liquid crystal display element can be obtained by preparing a second substrate. The second substrate is obtained by using a substrate without a transverse electric field driven conductive film instead of a substrate with a transverse electric field driven conductive film, and by using the above steps [I] to [III] (because a substrate without a transverse electric field driven conductive film is used, for convenience, this case is referred to as steps [I'] to [III']) to obtain a second substrate having a liquid crystal alignment film endowed with alignment control capability.

The manufacturing method of the transverse electric field driven liquid crystal display element comprises the following steps: [IV] the step of arranging the first and second substrates obtained above opposite to each other with the liquid crystals interposed therebetween and the liquid crystal alignment films of the first and second substrates being opposite to each other, thereby obtaining a liquid crystal display element. Thus, a transverse electric field driven liquid crystal display element can be obtained.

The following describes each of steps [I] to [III] and [IV] of the manufacturing method of the present invention. <Step [I]> In step [I], a polymer composition containing a photosensitive main chain polymer and an organic solvent is coated on a substrate having a conductive film for transverse electric field driving, and then dried to form a coating film.

<Substrate> There is no particular limitation on the substrate, but if the liquid crystal display element to be manufactured is a transmissive type, it is better to use a substrate with higher transparency. In this case, there is no particular limitation, and a glass substrate, or a plastic substrate such as an acrylic substrate or a polycarbonate substrate can be used. In addition, considering the applicability to a reflective liquid crystal display element, an opaque substrate such as a silicon wafer can be used.

<Conductive film for transverse electric field drive> The substrate has a conductive film for transverse electric field drive. As the conductive film, if the liquid crystal display element is a transmission type, ITO (Indium Tin Oxide: indium tin oxide), IZO (Indium Zinc Oxide: indium zinc oxide) and the like can be cited, but it is not limited to them. In addition, if it is a reflective liquid crystal display element, the conductive film can be a material that reflects light such as aluminum, but it is not limited to them. The method of forming the conductive film on the substrate can use a conventionally known method.

There is no particular limitation on the method of coating the above-mentioned polymer composition on a substrate having a conductive film for transverse electric field driving. The coating method is generally performed in industry by screen printing, flat printing, flexographic printing or inkjet printing. Other coating methods include immersion method, roller coating machine method, slit coating machine method, spin coating method (rotary coating method) or spray method, etc., which can be used according to the purpose.

After coating the polymer composition on the substrate having the conductive film driven by the transverse electric field, the solvent can be evaporated at 30 to 150°C, preferably 70 to 110°C by heating means such as a heating plate, a heat cycle oven or an IR (infrared) oven to obtain a coating. If the drying temperature is too low, the drying of the solvent will tend to be insufficient, and if the heating temperature is too high, thermal imidization will proceed. As a result, the photodecomposition reaction will proceed excessively due to polarized light exposure. In this case, it will become difficult to realign in a certain direction by self-organization, so the alignment stability will be damaged. Therefore, from the viewpoint of liquid crystal alignment stability, the drying temperature at this time is preferably a temperature at which thermal imidization of the specific polymer does not substantially proceed. If the thickness of the coating is too thick, it is disadvantageous in terms of power consumption of the liquid crystal display element. If it is too thin, the reliability of the liquid crystal display element may be reduced. Therefore, it is preferably 5nm to 300nm, and more preferably 10nm to 150nm. In addition, after step [I] and before the next step [II], a step of cooling the substrate formed with the coating to room temperature can also be provided.

<Step [II]> In step [II], the coating obtained in step [I] is irradiated with polarized ultraviolet light. When the film surface of the coating is irradiated with polarized ultraviolet light, the polarized ultraviolet light is irradiated through a polarizing plate in a certain direction relative to the substrate. As the ultraviolet light used, ultraviolet light in the wavelength range of 100nm to 400nm can be used. It is preferred to select the most appropriate wavelength through a filter or the like depending on the type of coating used. Alternatively, for example, ultraviolet light in the wavelength range of 240nm to 400nm can be selected for use by selectively inducing photoluminescent decomposition reaction. As the ultraviolet light, for example, light emitted from a high-pressure mercury lamp or a metal halogen lamp can be used.

The irradiation amount of polarized ultraviolet light depends on the coating used. The irradiation amount is preferably set in the range of 1% to 70% of the amount of polarized ultraviolet light that achieves the maximum value of ΔA (hereinafter also referred to as ΔAmax), and more preferably in the range of 1% to 50%, wherein ΔA is the difference between the absorbance of ultraviolet light in the coating in a direction parallel to the polarization direction of the polarized ultraviolet light and the absorbance of ultraviolet light in a direction perpendicular to the polarization direction.

<Step [III]> In step [III], the coating irradiated with polarized ultraviolet light in step [II] is heated. By heating, the coating can be given the ability to control its orientation. Heating can be performed using a heating plate, a heat circulation oven, or an IR (infrared) oven. The heating temperature is determined based on the temperature at which the coating used can exhibit good liquid crystal alignment stability and electrical properties.

The heating temperature is preferably within the temperature range where the main chain polymer exhibits good liquid crystal alignment stability. If the heating temperature is too low, the amplification effect of the anisotropy by heat or the thermal imidization will tend to be insufficient. If the heating temperature is higher than the temperature range, the anisotropy given by polarized light exposure will tend to disappear. Therefore, it will become difficult to realign in a certain direction by self-organization.

The thickness of the coating formed after heating is preferably 5 nm to 300 nm, more preferably 50 nm to 150 nm, for the same reason as described in step [I].

By having the above steps, the manufacturing method of the present invention can achieve high efficiency in introducing anisotropy into the coating film, and can also efficiently manufacture a substrate with a liquid crystal alignment film.

<Step [IV]> Step [IV] is a step of manufacturing a transverse electric field driven liquid crystal display element by arranging a substrate (first substrate) having a liquid crystal alignment film on the transverse electric field driven conductive film obtained in [III] with liquid crystal separated therebetween, and a substrate (second substrate) having a liquid crystal alignment film without a conductive film obtained in the same manner as in [I’] to [III’] above, with the liquid crystal alignment films on both sides facing each other, and manufacturing liquid crystal cells by a known method. In addition, steps [I’] to [III’] are the same as steps [I] to [III] except that a substrate without the transverse electric field driven conductive film is used instead of a substrate with the transverse electric field driven conductive film in step [I]. The only difference between steps [I] to [III] and steps [I'] to [III'] is the presence or absence of the conductive film, so the description of steps [I'] to [III'] is omitted.

If an example of the production of a liquid crystal cell or a liquid crystal display element is given, the following method can be used as an example: prepare the above-mentioned first and second substrates, spread spacers on the liquid crystal alignment film of one substrate, adhere the other substrate in a manner that the liquid crystal alignment film surface becomes the inner side, reduce the pressure to inject liquid crystal and seal, or drip liquid crystal on the surface of the liquid crystal alignment film on which the spacers are spread, and then adhere the substrates and seal them. At this time, it is preferred that the substrate on one side use a substrate having an electrode with a comb-shaped structure such as for transverse electric field drive. At this time, the diameter of the spacer is preferably 1μm to 30μm, and more preferably 2μm to 10μm. The diameter of the spacer determines the distance between a pair of substrates that clamp the liquid crystal layer, that is, the thickness of the liquid crystal layer.

The method for manufacturing a substrate with a coating of the present invention comprises coating a polymer composition on a substrate to form a coating, and then irradiating the substrate with polarized ultraviolet light. Next, heating is performed to achieve efficient introduction of anisotropy into the main chain polymer film, and to manufacture a substrate with a liquid crystal alignment film having the ability to control the alignment of liquid crystals. The coating used in the present invention utilizes the principle of molecular realignment induced by self-organization based on the photoreaction of the main chain, thereby achieving efficient introduction of anisotropy into the coating. In the manufacturing method of the present invention, if the main chain polymer has a structure with a photodegradable group as a photoreactive group, the main chain polymer is used to form a coating on a substrate, and then polarized ultraviolet light is irradiated and then heated to produce a liquid crystal display element.

Therefore, the coating used in the method of the present invention is irradiated with polarized ultraviolet light and heated in sequence, thereby producing a liquid crystal alignment film with highly efficient introduction of anisotropy and excellent alignment control capability.

In addition, the coating used in the method of the present invention optimizes the amount of polarized ultraviolet light irradiated to the coating and the heating temperature during the heating process, thereby achieving more efficient introduction of anisotropy into the coating.

The optimal polarized ultraviolet irradiation amount for efficient anisotropy introduction into the coating used in the present invention is the polarized ultraviolet irradiation amount optimized for the amount of photosensitive groups in the coating that undergo photodecomposition reaction. When the coating used in the present invention is irradiated with polarized ultraviolet ray, if the amount of photosensitive groups that undergo photodecomposition reaction is small, the amount of photoreaction cannot be sufficient. In this case, sufficient self-organization will not proceed even if it is subsequently heated.

Therefore, for the coating used in the present invention, the optimal amount of the photosensitive group to undergo photodecomposition reaction by irradiation with polarized ultraviolet light is preferably 0.1 mol% to 90 mol% of the polymer film, and more preferably 0.1 mol% to 80 mol%. By setting the amount of the photosensitive group that undergoes photoreaction within such a range, self-organization in the subsequent heat treatment can be efficiently performed, and highly efficient anisotropy can be formed in the film.

The coating used in the method of the present invention optimizes the amount of photodecomposition reaction of the photosensitive group in the main chain of the polymer film by optimizing the irradiation amount of polarized ultraviolet light. In addition, combined with the subsequent heat treatment, the anisotropy of the coating used in the present invention is efficiently introduced. In this case, the amount of suitable polarized ultraviolet light can be evaluated based on the ultraviolet absorption of the coating used in the present invention.

That is, for the coating used in the present invention, the absorption of ultraviolet light in a direction parallel to the polarization direction of the polarized ultraviolet light and the absorption of ultraviolet light in a direction perpendicular to the polarization direction after irradiation with polarized ultraviolet light are measured respectively. Based on the measurement results of ultraviolet absorption, the difference between the absorbance of ultraviolet light in a direction parallel to the polarization direction of the polarized ultraviolet light and the absorbance of ultraviolet light in a direction perpendicular to the polarization direction in the coating, i.e., ΔA, is evaluated. In addition, the maximum value (ΔAmax) of ΔA that can be achieved in the coating used in the present invention and the irradiation amount of polarized ultraviolet light that achieves the maximum value are determined. The manufacturing method of the present invention can use the irradiation amount of polarized ultraviolet light that achieves the ΔAmax as a reference to determine the optimal amount of polarized ultraviolet light irradiated in the manufacture of the liquid crystal alignment film.

According to the above, in order to achieve efficient anisotropy introduction to the coating in the manufacturing method of the present invention, the temperature range in which the main chain polymer provides liquid crystal alignment stability can be used as a reference to determine the appropriate heating temperature as described above. Therefore, for example, the temperature range in which the main chain polymer used in the present invention provides liquid crystal alignment stability can be determined by considering the temperature at which the coating used can exhibit good liquid crystal alignment stability and electrical properties, and can be set based on the temperature range of the liquid crystal alignment film composed of the previous polyimide, etc. That is, the heating temperature after polarized ultraviolet irradiation is preferably set to 150°C to 300°C, and is more preferably set to 180°C to 250°C. By setting in this way, the coating film used in the present invention can be given greater anisotropy.

Thus, the liquid crystal display device provided by the present invention exhibits high reliability against external stress such as light or heat.

As described above, the substrate for a transverse electric field driven liquid crystal display element made of the polymer of the present invention or the transverse electric field driven liquid crystal display element having the substrate can be used in large-screen and high-precision liquid crystal televisions, etc., due to its excellent reliability. In addition, the liquid crystal alignment film made by the method of the present invention can also be used in a variable phase shifter using liquid crystal, because it has excellent liquid crystal alignment stability and reliability. The variable phase shifter can be used in, for example, an antenna that can change the resonant oscillation frequency. [Example]

The abbreviations used in the embodiments are as follows. NMP: N-methyl-2-pyrrolidone BCS: Butylthiocyanate DA-1: The following structural formula (DA-1) DA-2: The following structural formula (DA-2) DA-3: The following structural formula (DA-3) DA-4: The following structural formula (DA-4) DA-5: The following structural formula (DA-5) DA-6: The following structural formula (DA-6) DA-7: The following structural formula (DA-7) DA-8: The following structural formula (DA-8) DA-9: The following structural formula (DA-9) DA-10: The following structural formula (DA-10) CA-1: The following structural formula (CA-1) CA-2: The following structural formula (CA-2) DE-1: The following structural formula (DE-1) DBOP: Diphenyl (2,3-dihydro-2-thio-3-benzoxazolyl) phosphonate

(However, Boc is a group represented by the following formula)

<Measurement of viscosity> In the synthesis example, the viscosity of the polymer solution was measured using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) with a sample volume of 1.1 mL, a conical rotor TE-1 (1°34’, R24), and a temperature of 25°C.

(Synthesis Example 1) In a 50mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, weigh 0.485g of DA-1 (1.20mmol) and 0.763g of DA-2 (2.80mmol), add 11.6g of NMP, and stir while introducing nitrogen to disperse it. While stirring the diamine suspension under water cooling, add 0.721g of CA-1 (3.68mmol) and further add 2.9g of NMP, and stir at 23°C for 5 hours in a nitrogen environment to obtain a solution of polyamine-polyimide copolymer. The viscosity of the polyamine-polyimide copolymer solution at a temperature of 25°C is 268mPa.s. 7.8 g of the polyamine-polyimide copolymer solution was separated and placed in a 100 mL Erlenmeyer flask with a stirrer, and 6.8 g of NMP and 6.2 g of BCS were added. The mixture was stirred at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-1).

(Synthesis Example 2) In a 100mL four-necked flask with a stirrer, weigh 1.89g of DE-1 (7.25mmol), add 41.1g of NMP, and stir to dissolve. Next, add 2.37g of triethylamine (23.4mmol), 0.946g of DA-1 (2.34mmol), and 1.49g of DA-2 (5.46mmol), and stir to disperse. While stirring the suspension, add 5.71g of DBOP (14.9mmol), and then add 5.6g of NMP, and stir for 13 hours under water cooling to obtain a solution of polyamic acid ester-polyimide copolymer. The viscosity of the polyamic acid ester-polyimide copolymer solution at a temperature of 25°C is 24.7mPa. s. The obtained polyamic acid ester solution-polyimide copolymer was added into 354 g of methanol while stirring, and the precipitated precipitate was filtered. After washing the precipitate three times with methanol, it was dried under reduced pressure at a temperature of 100°C to obtain a powder of the polyamic acid ester-polyimide copolymer. 2.11 g of the obtained polyamic acid ester-polyimide copolymer powder was measured into a 100 mL Erlenmeyer flask with a stirrer, 15.5 g of NMP was added, and it was stirred at room temperature for 20 hours to dissolve it. Next, 15.2 g of NMP and 14.1 g of BCS were added, and the mixture was stirred at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-2).

(Synthesis Example 3) In a 100mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 1.94g of DA-1 (4.80mmol), 0.436g of DA-2 (1.60mmol), 0.477g of DA-3 (1.60mmol) were weighed, and 22.1g of NMP was added, and nitrogen was introduced while stirring and dispersing. While stirring the diamine suspension under water cooling, 1.44g of CA-1 (7.36mmol) was added, and then 9.5g of NMP was added, and stirred at 23°C for 5 hours in a nitrogen environment to obtain a solution of a polyamine-polyimide copolymer. The viscosity of the polyamine-polyimide copolymer solution at a temperature of 25°C is 347mPa.s. Separate 14.5 g of the polyamine-polyimide copolymer solution into a 100 mL Erlenmeyer flask with a stirrer, add 12.6 g of NMP and 11.6 g of BCS, and stir at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-3).

(Synthesis Example 4) In a 50mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 1.62g of DA-1 (4.00mmol), 1.38g of DA-4 (6.00mmol), and 30.0g of NMP were added, and nitrogen was introduced while stirring to disperse. While stirring the diamine suspension under water cooling, 1.76g of CA-1 (9.00mmol) was added, and then 12.9g of NMP was added, and stirred at 40°C for 16 hours in a nitrogen environment to obtain a solution of polyamine-polyimide copolymer. The viscosity of the polyamine-polyimide copolymer solution at a temperature of 25°C is 104mPa.s. Separate 15.3 g of the polyamine-polyimide copolymer solution into a 100 mL Erlenmeyer flask with a stirrer, add 6.1 g of NMP and 9.2 g of BCS, and stir at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-4).

(Synthesis Example 5) In a 50mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 1.21g of DA-1 (3.00mmol), 1.71g of DA-5 (7.00mmol), and 29.5g of NMP were added, and nitrogen was introduced while stirring to disperse. While stirring the diamine suspension under water cooling, 1.76g of CA-1 (9.00mmol) was added, and further 12.7g of NMP was added, and stirred at 40°C for 16 hours in a nitrogen environment to obtain a solution of polyamine-polyimide copolymer. The viscosity of the polyamine-polyimide copolymer solution at a temperature of 25°C is 142mPa.s. Separate 15.6 g of the polyamine-polyimide copolymer solution into a 100 mL Erlenmeyer flask with a stirrer, add 6.2 g of NMP and 9.4 g of BCS, and stir at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-5).

(Synthesis Example 6) In a 50mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 1.61g of DA-1 (4.00mmol), 1.55g of DA-6 (6.00mmol), and 31.1g of NMP were added, and nitrogen was introduced while stirring to disperse. While stirring the diamine suspension under water cooling, 1.76g of CA-1 (9.00mmol) was added, and further 13.3g of NMP was added, and stirred at 40°C for 16 hours in a nitrogen environment to obtain a solution of polyamine-polyimide copolymer. The viscosity of the polyamine-polyimide copolymer solution at a temperature of 25°C is 117mPa.s. Separate 15.2 g of the polyamine-polyimide copolymer solution into a 100 mL Erlenmeyer flask with a stirrer, add 6.1 g of NMP and 9.1 g of BCS, and stir at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-6).

(Synthesis Example 7) In a 50 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 1.46 g of DA-1 (3.60 mmol), 1.62 g of DA-7 (5.40 mmol), and 29.4 g of NMP were added, and nitrogen was introduced while stirring to disperse. While stirring the diamine suspension under water cooling, 1.59 g of CA-1 (8.10 mmol) was added, and then 12.6 g of NMP was added, and stirred at 40°C for 16 hours in a nitrogen environment to obtain a solution of a polyamine-polyimide copolymer. The viscosity of the polyamine-polyimide copolymer solution at a temperature of 25°C is 139 mPa. s. Separate 15.6 g of the polyamine-polyimide copolymer solution into a 100 mL Erlenmeyer flask with a stirrer, add 6.2 g of NMP and 9.4 g of BCS, and stir at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-7).

(Synthesis Example 8) In a 50mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, weigh 2.59g of DA-1 (6.40mmol), 0.638g of DA-8 (1.60mmol), and add 29.2g of NMP, and stir while introducing nitrogen to disperse it. While stirring the diamine suspension under water cooling, add 1.41g of CA-1 (7.20mmol), and then add 12.5g of NMP, and stir at 40°C for 16 hours in a nitrogen environment to obtain a solution of polyamine-polyimide copolymer. The viscosity of the polyamine-polyimide copolymer solution at a temperature of 25°C is 191mPa.s. 14.7 g of the polyamine-polyimide copolymer solution was separated and placed in a 100 mL Erlenmeyer flask with a stirrer, and 5.9 g of NMP and 8.8 g of BCS were added. The mixture was stirred at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-8).

(Synthesis Example 9) In a 50mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 1.46g of DA-1 (3.60mmol), 1.08g of DA-7 (3.60mmol), 0.615g of DA-9 (1.80mmol) were weighed, and 29.9g of NMP was added, and nitrogen was introduced while stirring to disperse. While stirring the diamine suspension under water cooling, 1.59g of CA-1 (8.10mmol) was added, and then 12.8g of NMP was added, and stirred at 40°C for 16 hours in a nitrogen environment to obtain a solution of polyamine-polyimide copolymer. The viscosity of the polyamine-polyimide copolymer solution at a temperature of 25°C is 108mPa.s. 15.1 g of the polyamine-polyimide copolymer solution was separated and placed in a 100 mL Erlenmeyer flask with a stirrer, and 6.0 g of NMP and 9.1 g of BCS were added. The mixture was stirred at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-9).

(Synthesis Example 10) In a 50mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 1.29g of DA-1 (3.20mmol), 0.961g of DA-7 (3.20mmol), 0.891g of DA-10 (1.60mmol) were weighed, and 28.7g of NMP was added, and nitrogen was introduced while stirring to disperse them. While stirring the diamine suspension under water cooling, 1.41g of CA-1 (7.20mmol) was added, and then 12.3g of NMP was added, and stirred at 40°C for 16 hours in a nitrogen environment to obtain a solution of polyamine-polyimide copolymer. The viscosity of the polyamine-polyimide copolymer solution at a temperature of 25°C is 116mPa. s. 15.0 g of the polyamine-polyimide copolymer solution was separated and placed in a 100 mL Erlenmeyer flask with a stirrer, and 6.0 g of NMP and 9.0 g of BCS were added, and stirred at room temperature for 2 hours to obtain a liquid crystal alignment agent (A-10).

(Comparative Synthesis Example 1) In a 50mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 0.364g of DA-1 (0.90mmol), 0.572g of DA-2 (2.10mmol), and 9.2g of NMP were added, and nitrogen was introduced while stirring to disperse. While stirring the diamine suspension under water cooling, 0.632g of CA-2 (2.82mmol) was added, and then 2.3g of NMP was added, and stirred at 40°C for 15 hours in a nitrogen environment to obtain a solution of a polyamine-polyimide copolymer. The viscosity of the polyamine-polyimide copolymer solution at a temperature of 25°C is 326mPa.s. 7.5 g of the polyamine-polyimide copolymer solution was separated and placed in a 100 mL Erlenmeyer flask with a stirrer, and 6.5 g of NMP and 6.0 g of BCS were added. The mixture was stirred at room temperature for 2 hours to obtain a liquid crystal alignment agent (B-1).

<Preparation of liquid crystal cells for evaluating liquid crystal alignment> The following is a method for preparing liquid crystal cells for evaluating liquid crystal alignment. 　　Prepare a liquid crystal cell having the structure of a liquid crystal display element having an FFS method. First, prepare a substrate with electrodes. The substrate is a glass substrate with a size of 30mm×35mm and a thickness of 0.7mm. An IZO electrode constituting a counter electrode is formed entirely on the substrate as the first layer. On top of the first layer of the counter electrode, a SiN (silicon nitride) film formed by the CVD method is formed as the second layer. The second layer of the SiN film has a thickness of 500nm and functions as an interlayer insulating film. On the second layer of SiN film, a comb-shaped pixel electrode formed by patterning the IZO film is arranged as the third layer, thereby forming two types of pixels, the first pixel and the second pixel. The size of each pixel is 10mm in length and about 5mm in width. At this time, the counter electrode of the first layer and the pixel electrode of the third layer are electrically insulated by the action of the second layer of SiN film.

The pixel electrode of the third layer is the same as the figure described in Japanese Patent Publication No. 2014-77845 (Japanese Public Patent Gazette), and has a comb-like shape formed by arranging a plurality of electrode elements in the shape of a "く" character with a curved center portion. The width of each electrode element in the short side direction is 3μm, and the interval between the electrode elements is 6μm. The pixel electrode forming each pixel is composed of a plurality of electrode elements in the shape of a "く" character with a curved center portion, so the shape of each pixel is not a rectangle, but has a shape similar to a bold "く" character with a curved center portion like the electrode elements. Each pixel is divided into upper and lower parts with the curved portion in the center thereof as a boundary, and has a first region on the upper side of the curved portion and a second region on the lower side.

When comparing the first area and the second area of each pixel, the formation direction of the electrode elements constituting such pixel electrodes is different. That is, when the direction of the polarization plane of the polarized ultraviolet light described later projected onto the line segment of the substrate is used as a reference, in the first area of the pixel, the electrode elements of the pixel electrode are formed at an angle of +10° (clockwise), and in the second area of the pixel, the electrode elements of the pixel electrode are formed at an angle of -10° (clockwise). That is, the first area and the second area of each pixel are constructed as follows: the direction of the rotation action (in-plane switching) of the liquid crystal substrate surface induced by applying a voltage between the pixel electrode and the counter electrode will be opposite to each other.

Next, the liquid crystal alignment agent obtained in the synthesis example and the comparative synthesis example is filtered using a 1.0μm filter, and then applied to the prepared substrate with the above-mentioned electrode by rotation coating. Next, it is dried on a heating plate set at 70°C for 90 seconds. Next, using an exposure device manufactured by Ushio Electric Co., Ltd.: APL-L050121S1S-APW01, the substrate is irradiated with linear polarized ultraviolet light in the vertical direction through a wavelength selection filter and a polarizing plate. At this time, the polarization plane of the polarized ultraviolet light is projected onto the direction of the line segment of the substrate, and the direction of the polarization plane is set in a manner that it is tilted 10° relative to the IZO comb electrode of the third layer. Next, it was baked in an IR (infrared) oven set at 230°C for 30 minutes to obtain a substrate with a polyimide liquid crystal alignment film having a film thickness of 100 nm that was subjected to an alignment treatment. In addition, a glass substrate with a columnar spacer having an ITO electrode formed therein as an opposing substrate was also processed in the same manner as described above to obtain a substrate with a polyimide liquid crystal alignment film that was subjected to an alignment treatment. The two substrates with liquid crystal alignment films were grouped as a set, and a sealant was printed in the form of a liquid crystal injection port on one substrate, and the other substrate was bonded and pressed in a manner such that the liquid crystal alignment film surfaces were facing each other and the polarization plane of the polarized ultraviolet light was projected onto the substrate in a parallel direction. After that, the sealant was cured to produce an empty cell with a cell gap of 4 μm. Liquid crystal MLC-7026-100 (negative liquid crystal manufactured by Merck) was injected into the empty cell by the reduced pressure injection method and the injection port was sealed to obtain a liquid crystal cell of the FFS method. After that, the obtained liquid crystal cell was heated at 120°C for 30 minutes and left at 23°C overnight before being used for the evaluation of liquid crystal alignment.

＜Evaluation of Liquid Crystal Orientation＞ The liquid crystal cell was used in a constant temperature environment of 70°C and an AC voltage of 16VPP was applied at a frequency of 30Hz for 96 hours. Afterwards, the pixel electrode and the counter electrode of the liquid crystal cell were short-circuited and left at 23°C overnight.

After placement, the liquid crystal cell is set between two polarizing plates arranged in a manner that the polarization axes are orthogonal. The backlight is turned on in advance without an external voltage, and the configuration angle of the liquid crystal cell is adjusted to minimize the brightness of the transmitted light. In addition, the rotation angle of the liquid crystal cell from the angle at which the second area of the first pixel becomes the darkest to the angle at which the first area becomes the darkest is calculated as the angle Δ. Similarly, for the second pixel, the second area is compared with the first area, and the same angle Δ is calculated. In addition, the average value of the angle Δ values of the first pixel and the second pixel is calculated as the angle Δ of the liquid crystal cell. If the value of the angle Δ of the liquid crystal cell is less than 0.2°, it is defined and evaluated as "good", and if the value of the angle Δ is greater than 0.2°, it is defined and evaluated as "poor".

<Evaluation of film strength> The liquid crystal alignment agent obtained in the synthesis example and the comparative synthesis example was filtered using a 1.0μm filter and then applied to the prepared substrate with the above-mentioned electrode by spin coating. Next, it was dried on a heating plate set at 70°C for 90 seconds. Next, it was fired in an IR (infrared) type oven set at 230°C for 30 minutes to obtain a substrate with a polyimide liquid crystal alignment film with a film thickness of 100nm that was subjected to an alignment treatment. The polyimide film was rubbed with rayon cloth YA-20-R manufactured by Yoshikawa Chemical Industry Co., Ltd. (roller diameter 120 mm, roller rotation number 1000 rpm, moving speed 20 mm/sec, pressing length 0.3 mm). The presence of scratches or grinding debris on the surface of the polyimide film was observed using a confocal laser microscope. The film without scratches or grinding debris was rated as "good", and the film with scratches or grinding debris was rated as "bad".

(Example 1) Using the liquid crystal alignment agent (A-1) obtained in Synthesis Example 1, a liquid crystal cell as described above was prepared. The polarized ultraviolet ray irradiation was performed using a high-pressure mercury lamp, and through a wavelength selection filter: 240LCF, and a 254nm type polarizing plate. The irradiation amount of the polarized ultraviolet ray was measured using an illuminometer UVD-S254SB manufactured by Ushio Electric Co., Ltd., and three types of liquid crystal cells were prepared with polarized ultraviolet ray irradiation amounts of 200, 300, and 400 mJ/ ^cm2 at a wavelength of 254nm.

The results of evaluating the liquid crystal alignment of these liquid crystal cells showed that the polarized ultraviolet irradiation dose with the best angle Δ was 300 mJ/cm ² and the angle Δ was 0.05°, which was good. The film strength was evaluated as described above using the liquid crystal alignment agent (A-1) obtained in Synthesis Example 1 and was good.

(Examples 2 to 10) Except for using the liquid crystal alignment agents obtained in Synthesis Examples 2 to 10, the liquid crystal alignment and film strength were evaluated in the same manner as in Example 1.

(Comparative Example 1) Except for using the liquid crystal alignment agent obtained in Comparative Synthesis Example 1, the liquid crystal alignment and film strength were evaluated in the same manner as in Example 1.

Table 1 shows the polarized ultraviolet irradiation amount at which the angle Δ is optimal when the liquid crystal alignment agents obtained in the synthesis examples and the comparative synthesis examples are used, the results of the evaluation of the liquid crystal alignment, and the results of the evaluation of the film strength.

As shown in Table 1, the difference in the orientation angle before and after AC driving in Examples 1 to 10 (i.e., angle Δ) is less than 0.2°, which is good, so the display quality of the liquid crystal display element is improved to be excellent. In addition, because the film strength is also good, when the liquid crystal display element is manufactured, even if thinning processing by thinning (chemical polishing) is performed, it is not easy to cause grinding or peeling of the liquid crystal orientation film. On the other hand, in Comparative Example 1, the angle Δ is more than 0.2°, which is bad, and the film strength is also bad.

The liquid crystal display device manufactured by the method of the present invention can be confirmed to exhibit very excellent afterimage characteristics and film strength. [Industrial Applicability]

The substrate for a transverse electric field driven liquid crystal display element manufactured using the composition of the present invention or the transverse electric field driven liquid crystal display element having the substrate is suitable for use in large-screen and high-precision liquid crystal televisions, etc., because the long-term stability of the liquid crystal alignment is excellent. In addition, since the substrate for a transverse electric field driven liquid crystal display element manufactured using the composition of the present invention or the transverse electric field driven liquid crystal display element having the substrate has excellent film strength, it can also be suitable for use in thinned small mobile phones or smart phones, etc. Furthermore, the liquid crystal alignment film manufactured by the method of the present invention can also be used in a variable phase shifter using liquid crystal, and the variable phase shifter can be suitable for use in, for example, an antenna that can change the resonant oscillation frequency.

Claims (8)

A liquid crystal alignment agent comprises: (A) a polymer composed of a diamine component comprising a diamine represented by the following formula (1) and a diamine represented by the following formula (10) (in the formula (10), L is a divalent organic group having 2 or more carbon atoms and bonded to an alkylene group and any one of an ether bond and an ester bond, _R1 and _R2 are each independently a monovalent organic group, p1 and p2 are each independently an integer of 0 to 4, p is 1, and q1 and q2 are each independently 1 or 2), and an acid component comprising at least one cyclobutanetetracarboxylic acid diester represented by the following formula (2-2) (in the formula (2-2), R is each independently an alkylene group having 1 to 5 carbon atoms), and (B) an organic solvent.

As in claim 1, the liquid crystal alignment agent, wherein the polymer is at least one selected from the group consisting of polyimide precursors and polyimide imides thereof. As in claim 1 or 2, the liquid crystal alignment agent, wherein R in the above formula (2-2) is methyl. The liquid crystal alignment agent of claim 1 or 2, wherein the polymer is represented by the following formula (3):

(In formula (3), _X1 is a tetravalent organic group derived from a tetracarboxylic acid derivative and the tetracarboxylic acid derivative comprises the structure of the above-mentioned (2-2), _Y1 is a divalent organic group derived from a diamine and the diamine comprises the structure of formula (1), and _R11 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms). As in claim 4, the liquid crystal alignment agent contains more than 10 mol% of polymers having the structural unit represented by the aforementioned formula (3) relative to the total polymers contained in the liquid crystal alignment agent. A liquid crystal alignment film for a transverse electric field driven liquid crystal display element, which is obtained using a liquid crystal alignment agent as described in any one of claims 1 to 5. A substrate having a liquid crystal alignment film for a lateral electric field driven liquid crystal display element as claimed in claim 6. A transverse electric field driven liquid crystal display device has a substrate as claimed in claim 7.