TWI841588B - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element - Google Patents

Abstract

The present invention provides a liquid crystal alignment film having a small change in pre-tilt angle even after long-term driving, excellent display reliability, high voltage holding characteristics, and reduced charge accumulation, a liquid crystal display element having the same, and a liquid crystal alignment agent provided therewith. The present invention provides a liquid crystal alignment agent, which contains a polymer having a photoalignment group and a thermal crosslinking group A represented by the following formula (pa-1) as component (A), a polymer selected from polyimide and its precursor and a solvent as component (B), and satisfies at least one of the following requirements Z1 and Z2 at the same time; The following formula (pa-1) (wherein, A represents phenyl, etc., _R1 is a single bond, an oxygen atom, etc., _R2 is a divalent aromatic group, etc., _R3 is a single bond, an oxygen atom, etc., _R4 represents a linear or branched alkyl group with 1 to 40 carbon atoms or a monovalent organic group with 3 to 40 carbon atoms containing an alicyclic group, D represents an oxygen atom, a sulfur atom or _-NRd- , a is an integer of 0 to 3, and * represents a bonding position. The thermal crosslinking group A and the thermal crosslinking group B are selected so that the thermal crosslinking group A and the thermal crosslinking group B can undergo a crosslinking reaction by heat) Z1: The polymer of the component (A) further has a thermal crosslinking group B. Z2: It further contains a compound having two or more thermal crosslinking groups B in the molecule as the component (C).

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 obtained thereby, and a liquid crystal display element having the obtained liquid crystal alignment film. More specifically, the invention relates to a liquid crystal alignment agent that can impart good liquid crystal alignment, excellent pre-tilt angle performance, and obtain a liquid crystal alignment film with high reliability, and a liquid crystal display element with excellent display quality.

For liquid crystal display elements, the liquid crystal alignment film plays the role of aligning the liquid crystal in a certain direction. At present, the main liquid crystal alignment films used in industry are made by coating the polyimide precursor polyamide (Polyamic acid), polyamide ester, or polyimide-containing solution on the substrate to form a film. In addition, when the liquid crystal is aligned parallel or tilted on the substrate surface, the surface is further extended by friction after film formation.

On the other hand, when the substrates are vertically aligned and the liquid crystal is aligned (called vertical alignment (VA) mode), a liquid crystal alignment film is used in which a hydrophobic group such as a long-chain alkyl group or a cyclic group or a combination of a cyclic group and an alkyl group (for example, see Patent Document 1) or a steroid skeleton (for example, see Patent Document 2) is introduced into the side chain of polyimide. At this time, when a voltage is input between the substrates and the liquid crystal molecules tilt in a parallel direction on the substrates, the liquid crystal molecules must be tilted from the normal direction of the substrate to one direction within the substrate plane. As means at this time, for example, a method of providing protrusions on the substrate, a method of providing slits on the display electrode, a method of tilting the liquid crystal molecules slightly from the normal direction of the substrate to one direction within the substrate surface by friction (making them pre-tilted), and a method of pre-adding photopolymerizable compounds to the liquid crystal composition, using a vertical alignment film such as polyimide, inputting a voltage to the liquid crystal unit while irradiating it with ultraviolet rays to pre-tilt the liquid crystal (for example, refer to Patent Document 3), etc.

In recent years, there have also been proposals for the formation of protrusions or slits in the VA liquid crystal alignment control, and for a method that uses anisotropic photochemical reactions such as polarized ultraviolet irradiation (photoalignment method) as an alternative to the PSA technology. That is, it is known that for a photoreactive vertically aligned polyimide film, by irradiating polarized ultraviolet light, the tilt direction of the liquid crystal molecules when a voltage is input can be uniformly controlled by imparting directional adjustment capability and pre-tilt angle performance (see patent document 4).

VA-type liquid crystal display elements have the characteristics of high contrast and wide viewing angle, and can be used in TV or car displays. LCD display elements for TV use a backlight that generates a lot of heat to obtain high brightness, or LCD display elements used in car applications, such as car navigation systems or instrument panels, are used or placed in a high-temperature environment for a long time. Under such harsh conditions, when the pre-tilt angle gradually changes, the initial display characteristics cannot be obtained, or the display may become uneven. In addition, the voltage retention characteristics or charge accumulation characteristics when driving the liquid crystal are also affected by the liquid crystal alignment film. When the voltage retention rate is low, the contrast of the display screen will be reduced, and when the charge accumulation of the DC voltage is large, the display screen will be burned. [Prior art literature] [Patent literature]

[Patent Document 1] Japanese Patent Publication No. 3-179323 [Patent Document 2] Japanese Patent Publication No. 4-281427 [Patent Document 3] Japanese Patent No. 4504626 [Patent Document 4] Japanese Patent No. 4995267

[Problem solved by the invention]

The present invention was made in view of the above circumstances, and the subject is to provide a liquid crystal alignment film that has excellent display reliability with little change in pre-tilt angle even after long-term driving, has high voltage retention characteristics, and can reduce charge accumulation, a liquid crystal display element having the same, and a liquid crystal alignment agent provided therewith. [Means for solving the problem]

The inventors of the present invention have found the following <X> as the main idea. <X> A liquid crystal alignment agent, which contains as component (A) a polymer having a photoalignment group represented by the following formula (pa-1) and a thermal crosslinking group A, as component (B) a polymer selected from polyimide and its precursor, which is a polymer having at least one group selected from a vertical alignment group and a tert-butyloxycarbonyl group, or a polymer and a solvent which have been chemically imidized, and simultaneously satisfies at least one of the following requirements Z1 and Z2; Z1: The polymer of component (A) further has a thermal crosslinking group B. Z2: Further contains as component (C) a compound having two or more thermal crosslinking groups B in the molecule.

In the formula, A is a group selected from fluorine, chlorine, and cyano, or a pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,5-thiophene, 2,5-furan, 1,4- or 2,6-naphthylene, or benzene substituted by an alkoxy group having 1 to 5 carbon atoms, a linear or branched alkyl residue (which is substituted by one cyano group or one or more halogen atoms as required), _R1 is a single bond, an oxygen atom, -COO- or -OCO-, _R2 is a divalent aromatic group, a divalent alicyclic group, a divalent heterocyclic group, or a divalent condensed cyclic group, _R3 is a single bond, an oxygen atom, -COO- or -OCO-, R _R represents a linear or branched alkyl group having 1 to 40 carbon atoms or a monovalent organic group having 3 to 40 carbon atoms and containing an alicyclic group, D represents an oxygen atom, a sulfur atom or -NR _d - (wherein R _d represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), a represents an integer of 0 to 3, and * represents a bonding position. The thermally crosslinkable group A and the thermally crosslinkable group B are each independently an organic group selected from the group consisting of a carboxyl group, an amino group, an alkoxymethylamide group, a hydroxymethylamide group, a hydroxyl group, a group containing an epoxy moiety, an oxadiazole group, a thiol group, an isocyanate group, and a blocked isocyanate group. The thermally crosslinkable group A and the thermally crosslinkable group B are selected so as to be crosslinkable by heat, but the thermally crosslinkable group A and the thermally crosslinkable group B may be the same. [Effect of the invention]

According to the present invention, a liquid crystal alignment film and a liquid crystal alignment agent can be provided, which have good liquid crystal alignment, excellent pre-tilt angle performance, and little change in pre-tilt angle even after long-term driving, excellent display reliability, high voltage retention characteristics, and can reduce charge accumulation. In addition, the liquid crystal display element manufactured by the method of the present invention has excellent display characteristics.

[Type of implementation of the invention]

The liquid crystal alignment agent of the present invention contains the following (A) component and (B) component and a solvent, and satisfies at least one of the following requirements Z1 and Z2, wherein the (A) component is a polymer having a photoalignment group and a thermal crosslinking group A shown in the following formula (pa-1), and the (B) component is a polymer selected from polyimide and its precursor, which is a polymer selected from polyimide and its precursor, having at least one group selected from a vertical alignment group and a tert-butyloxycarbonyl group, or a polymer and a solvent that have been chemically imidized. Z1: The polymer of the (A) component further has a thermal crosslinking group B. Z2: It further contains a compound having two or more thermal crosslinking groups B in the molecule as the (C) component.

In the formula, A represents a group selected from fluorine, chlorine, and cyano, or a pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,5-thiophene, 2,5-furan, 1,4- or 2,6-naphthylene, or benzene substituted by an alkoxy group having 1 to 5 carbon atoms, a linear or branched alkyl residue (which is substituted by one cyano group or one or more halogen atoms as required), _R1 represents a single bond, an oxygen atom, -COO- or -OCO-, _R2 represents a divalent aromatic group, a divalent alicyclic group, a divalent heterocyclic group, or a divalent condensed cyclic group, _R3 represents a single bond, an oxygen atom, -COO- or -OCO-, R _R represents a linear or branched alkyl group having 1 to 40 carbon atoms or a monovalent organic group having 3 to 40 carbon atoms and containing an alicyclic group, D represents an oxygen atom, a sulfur atom or -NR _d - (wherein R _d represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), a represents an integer from 0 to 3, and * represents a bonding position. The thermal crosslinking group A and the thermal crosslinking group B are each independently an organic group selected from the group consisting of a carboxyl group, an amino group, an alkoxymethylamide group, a hydroxymethylamide group, a hydroxyl group, a group containing an epoxy moiety, an oxadiazole group, a thiol group, an isocyanate group, and a blocked isocyanate group. The thermal crosslinking group A and the thermal crosslinking group B are selected so as to be crosslinkable by heat, but the thermal crosslinking group A and the thermal crosslinking group B may be the same.

Here, "having two or more groups in the molecule" means that, in addition to containing two or more groups of the same type, such as two or more epoxy groups, the molecule also contains two or more heterogeneous groups in total, such as an epoxy group and a thiocyclopropane group. "Having two or more groups in the molecule" preferably means containing two or more groups of the same type in the molecule.

The polymer of component (A) contained in the liquid crystal alignment agent of the present invention has high sensitivity to light, and therefore can show alignment control ability even under polarized ultraviolet irradiation with low exposure. In addition, the polymer of component (A) contains a thermal crosslinking group A, and by simultaneously including a thermal crosslinking group B in the component, the crosslinking reaction of the polymer containing component (A) can be performed even if the firing time of the liquid crystal alignment agent is short. Thereby, when anisotropy is expressed by photoreaction in the photoalignment part, since the liquid crystal alignment film easily retains anisotropy (memory), the liquid crystal alignment can be improved, and the pre-tilt angle of the liquid crystal can be expressed.

Furthermore, the liquid crystal alignment agent of the present invention can achieve improvement in electrical properties such as improvement in voltage holding ratio or suppression of residual charge accumulation by containing the polymer of component (B).

Furthermore, the photo-alignment group, the thermal crosslinking group A and the thermal crosslinking group B shown in the above formula (pa-1) can all become side chains in the polymer, so they can also be referred to as "side chains" as necessary. The following is a detailed description of each component of the present invention.

<Component (A): Specific polymer> [Photo-alignment group represented by formula (pa-1)] For the present invention, the site having the photo-alignment represented by the above formula (pa-1) in the molecule is represented by, for example, the following formula (a-1). In addition, although the site can be derived from the structure of the monomer represented by the following formula (a-1-m), it is not limited to this. In the formula, I _a is a monovalent organic group represented by the following formula (pa-1).

In formula (pa-1), A represents a group selected from fluorine, chlorine, and cyano, or a pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,5-thiophene, 2,5-furan, 1,4- or 2,6-naphthylene, or benzene substituted by an alkoxy group having 1 to 5 carbon atoms, a linear or branched alkyl residue (which is substituted by one cyano group or one or more halogen atoms as required), _R1 represents a single bond, an oxygen atom, -COO- or -OCO-, _R2 represents a divalent aromatic group, a divalent alicyclic group, a divalent heterocyclic group, or a divalent condensed cyclic group, _R3 represents a single bond, an oxygen atom, -COO- or -OCO-, R ₄ represents a linear or branched alkyl group having 1 to 40 carbon atoms or a monovalent organic group having 3 to 40 carbon atoms containing an alicyclic group, D represents an oxygen atom, a sulfur atom or -NR _d - (wherein R _d represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), a represents an integer of 0 to 3, and * represents a bonding position with _Sa.

In the above formula (a-1) or (a-1-m), _Sa represents a spacer unit, and the left-hand bonding group of _Sa represents bonding to the main chain of the specific polymer via an arbitrary spacer. _Sa can represent, for example, the structure of the following formula (Sp).

In formula (Sp), the left bond of _W1 represents a bond to _Mb , the right bond of _W3 represents a bond to _Ia , _W1 , _W2 and _W3 each independently represent, a single bond, a divalent heterocyclic ring, -( _CH2 ) _n- (wherein n represents ₁ to 20), _-OCH2- , -CH2O-, -COO-, -OCO-, -CH=CH-, _-CF =CF-, -CF2O-, _-OCF2- , _-CF2CF2- or -C≡C-, but for these substituents _, one or more non-adjacent _CH2 groups may be independently -O-, -CO-, -CO-O-, -O-CO-, -Si( _CH3 ) ₂ -O-Si( _CH3 ) ₂ -, -NR-, -NR-CO-, -CO-NR-, -NR-CO-O-, -OCO-NR-, -NR-CO-NR-, -CH=CH-, -C≡C- or -O-CO-O- (wherein R independently represents hydrogen or a linear or branched alkyl group having 1 to 5 carbon atoms), _A1 and _A2 are each independently a group selected from a single bond, a divalent alkyl group, a divalent aromatic group, a divalent alicyclic group, or a divalent heterocyclic group, and each group may be unsubstituted or one or more hydrogen atoms may be substituted by a fluorine atom, a chlorine atom, a cyano group, a methyl group or a methoxy group.

In formula (a-1-m), _Ma represents a polymerizable group. Examples of the polymerizable group include (meth)acrylate, fumarate, maleate, α-methylene-γ-butyrolactone, styrene, vinyl, maleimide, norbornene, (meth)acrylamide and free radical polymerizable groups of derivatives thereof, and siloxane. Preferred are (meth)acrylate, α-methylene-γ-butyrolactone, styrene, vinyl, maleimide, and acrylamide. r is an integer satisfying 1≦r≦3. _{Mb is} a group selected from a single bond, a (r+1)-valent heterocyclic group, a linear or branched alkyl group having 1 to 10 carbon atoms, a (r+1)-valent aromatic group, and a (r+1)-valent alicyclic group. Each group may be unsubstituted, or one or more hydrogen atoms may be substituted by a fluorine atom, a chlorine atom, a cyano group, a methyl group, or a methoxy group.

Examples of the aromatic group in A ₁ , A _{2 ,} and M _b include aromatic hydrocarbons having 6 to 18 carbon atoms, such as benzene, biphenyl, and naphthalene. Examples of the alicyclic group in A ₁ , A _{2 ,} and M _b include alicyclic hydrocarbons having 6 to 12 carbon atoms, such as cyclohexane and bicyclohexane. Examples of the heterocyclic group in A ₁ , A _{2 ,} and M _b include nitrogen-containing heterocyclic groups such as pyridine, piperidine, and piperazine. Examples of the alkyl group in A ₁ and A ₂ include linear or branched alkyl groups having 1 to 10 carbon atoms.

From the viewpoint of showing good vertical alignment control and stable pre-tilt angle, it is preferred that the group represented by (pa-1) is the group represented by (pa-1-a) below. In addition, the structure of the site can be derived from the monomer represented by the following formula (pa-1-ma), but it is not limited thereto.

In the formula (pa-1-a) or (pa-1-ma), _Ma , _Mb and _Sa have the same definitions as above. In addition, Z is an oxygen atom or a sulfur atom. _Xa and _Xb are each independently a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group or an alkyl group having 1 to 3 carbon atoms. _R1 is a single bond, an oxygen atom, -COO- or -OCO-. _R2 is a divalent aromatic group, a divalent alicyclic group or a divalent heterocyclic group. _R3 is a single bond, an oxygen atom, -COO- or -OCO-. _R4 is a linear or branched alkyl group having 1 to 40 carbon atoms or a monovalent organic group having 3 to 40 carbon atoms containing an alicyclic group. _R5 is an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine atom or a cyano group, preferably a methyl group, a methoxy group or a fluorine atom. a is an integer from 0 to 3, and b is an integer from 0 to 4.

In the formula (pa-1-a) or (pa-1-ma), the linear or branched alkylene group having 1 to 10 carbon atoms as _Sa is preferably a linear or branched alkylene group having 1 to 8 carbon atoms, such as methylene, ethyl, n-propyl, n-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, and n-octyl. Examples of the divalent aromatic group as _Sa include 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, and 2,3,5,6-tetrafluoro-1,4-phenylene.

In formula (pa-1-a) or (pa-1-ma), examples of the divalent alicyclic group of _Sa include trans-1,4-cyclohexane and trans-trans-1,4-bicyclic hexane. Examples of the divalent heterocyclic group of _Sa include 1,4-pyridyl, 2,5-pyridyl, 1,4-furanyl, 1,4-piperazinyl, and 1,4-piperidinyl. _{Sa is} preferably an alkylene group having 1 to 8 carbon atoms, more preferably an alkylene group having 1 to 6 carbon atoms, and more preferably an alkylene group having 1 to 4 carbon atoms.

Examples of the divalent aromatic group for _R2 include 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,3,5,6-tetrafluoro-1,4-phenylene, and naphthylene. Examples of the divalent alicyclic group for _R2 include trans-1,4-cyclohexene and trans-trans-1,4-bicyclic hexene. Examples of the divalent heterocyclic group for _R2 include 1,4-pyridylene, 2,5-pyridylene, 1,4-furanylene, 1,4-piperazinyl, and 1,4-piperidinyl. _R2 is preferably 1,4-phenylene, trans-1,4-cyclohexene, and trans-trans-1,4-bicyclic hexene.

Examples of the linear or branched alkyl group having 1 to 40 carbon atoms for R ₄ include linear or branched alkyl groups having 1 to 20 carbon atoms, and a part or all of the hydrogen atoms of the alkyl group may be substituted by fluorine atoms. Examples of the alkyl group include methyl, ethyl, n-propyl, n-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-lauryl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-eicosyl, 4,4,4-trifluorobutyl, 4,4,5,5,5-pentafluoropentyl, 4,4,5,5,6,6,6-heptafluorohexyl, 3,3,4,4,5,5,5-heptafluoropentyl, 2,2,2-trifluoroethyl, 2,2,3,3,3-pentafluoropropyl, 2-(perfluorobutyl)ethyl, 2-(perfluorooctyl)ethyl, and 2-(perfluorodecyl)ethyl.

Examples of the monovalent organic group having 3 to 40 carbon atoms and containing an alicyclic group as _R4 include cholesteryl, cholesterol, adamantyl, and groups represented by the following formula (Alc-1) or (Alc-2) (wherein _R7 is a hydrogen atom, a fluorine atom or an alkyl group having 1 to 20 carbon atoms, the alkyl group having 1 to 20 carbon atoms may be substituted by a fluorine atom, and * indicates a bonding position).

Examples of the monomer represented by the above formula (pa-1-ma) include structures represented by formulas (paa-1-ma1) to (paa-1-ma18), but the present invention is not limited thereto. In the formula, "E" represents the E-form, and "t" represents the trans form of the cyclohexyl group.

[Thermal crosslinking group A and thermal crosslinking group B] The thermal crosslinking group A and the thermal crosslinking group B are each independently an organic group selected from the group consisting of a carboxyl group, an amino group, an alkoxymethylamide group, a hydroxymethylamide group, a hydroxyl group, a group containing an epoxy moiety, an oxadiazole group, a thiopropane group, an isocyanate group, and a blocked isocyanate group. The thermal crosslinking group A and the thermal crosslinking group B are selected so as to be crosslinkable by heat. However, the thermal crosslinking group A and the thermal crosslinking group B may be the same.

As the combination of the thermally crosslinkable group A and the thermally crosslinkable group B, one is a carboxyl group and the other is an epoxy group, cyclobutylene oxide or thiopropane group; one is a hydroxyl group and the other is a blocked isocyanate group; one is a phenolic hydroxyl group and the other is an epoxy group, cyclobutylene oxide or thiopropane group; one is a carboxyl group and the other is a blocked isocyanate group; one is an amine group and the other is a blocked isocyanate group; both are N-alkoxymethylamides, etc. Preferred combinations are a carboxyl group and an epoxy group, a hydroxyl group and a blocked isocyanate group, etc.

In order to introduce the thermally crosslinkable group A into the polymer of the component (A), a monomer having the thermally crosslinkable group A may be copolymerized.

When the liquid crystal alignment agent of the present invention satisfies requirement Z1, when producing the polymer of component (A), both the monomer having a thermally crosslinkable group A and the monomer having a thermally crosslinkable group B may be copolymerized.

Examples of the monomer having a thermally crosslinkable group include monomers having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, mono-(2-(acryloxy)ethyl)phthalate, mono-(2-(methacryloxy)ethyl)phthalate, N-(carboxyphenyl)maleimide, N-(carboxyphenyl)methacrylamide, and N-(carboxyphenyl)acrylamide;

Monomers having a hydroxyl group such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 2,3-dihydroxypropyl acrylate, 2,3-dihydroxypropyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, 2-(acryloyloxy)ethyl caprolactone, 2-(methacryloyloxy)ethyl caprolactone, poly(ethylene glycol) ethyl ether acrylate, poly(ethylene glycol) ethyl ether methacrylate, 5-acryloyloxy-6-hydroxynorbornene-2-carboxy-6-lactone, and 5-methacryloyloxy-6-hydroxynorbornene-2-carboxy-6-lactone;

Monomers having a phenolic hydroxyl group such as hydroxystyrene, N-(hydroxyphenyl)methacrylamide, N-(hydroxyphenyl)acrylamide, N-(hydroxyphenyl)maleimide, and N-(hydroxyphenyl)maleimide;

Monomers having an amino group such as aminoethyl acrylate, aminoethyl methacrylate, aminopropyl acrylate, and aminopropyl methacrylate;

(meth)acrylamide compounds substituted with a hydroxymethyl group or an alkoxymethyl group, such as N-hydroxymethyl (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide;

Allyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, 2-methyl glycidyl methacrylate, α-ethyl glycidyl acrylate, α-n-propyl glycidyl acrylate, α-n-butyl glycidyl acrylate, 3,4-epoxybutyl acrylate, 3,4-epoxybutyl methacrylate, 6,7-epoxyheptyl acrylate, 6,7-epoxyheptyl methacrylate, Monomers having a group containing an epoxy moiety, such as 6,7-epoxyheptyl α-ethylacrylate, o-vinylbenzyl glycidyl ether, m-vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, 3,4-epoxycyclohexylmethyl methacrylate, 3-vinyl-7-oxacyclo[4.1.0]heptane, 1,2-epoxy-5-hexene, and 1,7-octadiene monoepoxide;

3-(Acryloyloxymethyl)oxycyclobutane, 3-(Acryloyloxymethyl)-2-methyloxycyclobutane, 3-(Acryloyloxymethyl)-3-ethyloxycyclobutane, 3-(Acryloyloxymethyl)-2-trifluoromethyloxycyclobutane, 3-(Acryloyloxymethyl)-2-pentafluoroethyloxycyclobutane, 3-(Acryloyloxymethyl)-2-pentafluoroethyloxycyclobutane 3-(Acryloyloxymethyl)-2,2-difluorooxycyclobutane, 3-(Acryloyloxymethyl)-2,2,4-trifluorooxycyclobutane, 3-(Acryloyloxymethyl)-2,2,4,4-tetrafluorooxycyclobutane, 3-(2-Acryloyloxyethyl)cyclobutane alkane, 3-(2-acryloxyethyl)-2-ethyloxycyclobutane, 3-(2-acryloxyethyl)-3-ethyloxycyclobutane, 3-(2-acryloxyethyl)-2-trifluoromethyloxycyclobutane, 3-(2-acryloxyethyl)-2-pentafluoroethyloxycyclobutane, 3-(2-acryloxyethyl)-2-phenyloxycyclobutane, 3-(2-acryloxyethyl)-2,2-difluorooxycyclobutane, 3-(2-acryloxyethyl)-2,2,4-trifluorooxycyclobutane, 3-(2-acryloxyethyl)-2,2,4,4-tetrafluorooxycyclobutane and the like acrylic acid esters; 3-(methacryloxymethyl) Oxycyclobutane, 3-(methacryloxymethyl)-2-methyloxycyclobutane, 3-(methacryloxymethyl)-3-ethyloxycyclobutane, 3-(methacryloxymethyl)-2-trifluoromethyloxycyclobutane, 3-(methacryloxymethyl)-2-pentafluoroethyloxycyclobutane, 3-(methacryloxymethyl)- )-2-phenyloxycyclobutane, 3-(methacryloyloxymethyl)-2,2-difluorooxycyclobutane, 3-(methacryloyloxymethyl)-2,2,4-trifluorooxycyclobutane, 3-(methacryloyloxymethyl)-2,2,4,4-tetrafluorooxycyclobutane, 3-(2-methacryloyloxyethyl)oxycyclobutane, 3 -monomers having an oxycyclobutane group such as (2-methacryloxyethyl)-2-ethyloxycyclobutane, 3-(2-methacryloxyethyl)-3-ethyloxycyclobutane, 3-(2-methacryloxyethyl)-2-trifluoromethyloxycyclobutane, 3-(2-methacryloxyethyl)-2-pentafluoroethyloxycyclobutane, 3-(2-methacryloxyethyl)-2-phenyloxycyclobutane, 3-(2-methacryloxyethyl)-2,2-difluorooxycyclobutane, 3-(2-methacryloxyethyl)-2,2,4-trifluorooxycyclobutane, and 3-(2-methacryloxyethyl)-2,2,4,4-tetrafluorooxycyclobutane;

2,3-epithiopropyl acrylate or methacrylate, and monomers having a thiol propane group such as 2-, 3-, or 4-(β-epithiopropylthiomethyl)styrene, 2-, 3-, or 4-(β-epithiopropoxymethyl)styrene, 2-, 3-, or 4-(β-epithiopropylthio)styrene, and 2-, 3-, or 4-(β-epithiopropoxy)styrene;

Monomers having a blocked isocyanate group such as 2-(0-(1'-methylpropyleneamino)carboxylamino)ethyl acrylate, 2-(3,5-dimethylpyrazolyl)carbonylamino)ethyl acrylate, 2-(0-(1'-methylpropyleneamino)carboxylamino)ethyl methacrylate, and 2-(3,5-dimethylpyrazolyl)carbonylamino)ethyl methacrylate. The so-called (meth)acrylamide refers to both acrylamide and methacrylamide.

Furthermore, in the present invention, when a specific copolymer is to be obtained, in addition to the monomer having the photoalignment group represented by the above formula (a-1-m), and the monomer having the thermal crosslinking group A and the thermal crosslinking group B as necessary, other monomers that can be copolymerized with these monomers can be used.

Specific examples of such other monomers include acrylate compounds, methacrylate compounds, maleimide compounds, acrylonitrile, maleic anhydride, styrene compounds, vinyl compounds, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, acrylamide and other acrylamide compounds, and monomers having a nitrogen-containing aromatic heterocyclic group and a polymerizable group.

Examples of the acrylate compound include methacrylate, ethyl acrylate, isopropyl acrylate, benzyl acrylate, naphthalene acrylate, anthracene acrylate, anthracene methacrylate, phenyl acrylate, 2,2,2-trifluoroethyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isobornyl acrylate, 2-methoxyethyl acrylate, methoxytriethylene glycol acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, 3-methoxybutyl acrylate, 2-methyl-2-adamantyl acrylate, 2-propyl-2-adamantyl acrylate, 8-methyl-8-tricyclodecyl acrylate, and 8-ethyl-8-tricyclodecyl acrylate.

Examples of the methacrylate compound include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, hexadecyl methacrylate, octadecyl methacrylate, benzyl methacrylate, naphthyl methacrylate, anthracenyl methacrylate, anthracenyl methyl methacrylate, phenyl methacrylate, 2,2,2-trifluoroethyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, 2-methoxyethyl methacrylate, methoxytriethylene glycol methacrylate, 2-ethoxyethyl methacrylate, tetrahydrofurfuryl methacrylate, 3-methoxybutyl methacrylate, 2-methyl-2-adamantyl methacrylate, 2-propyl-2-adamantyl methacrylate, 8-methyl-8-tricyclodecyl methacrylate, and 8-ethyl-8-tricyclodecyl methacrylate.

Examples of the (meth)acrylamide compound include acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, and N,N-diethylacrylamide.

Examples of the vinyl compound include methyl vinyl ether, benzyl vinyl ether, vinyl naphthalene, vinyl carbazole, allyl glycidyl ether, and 3-vinyl-7-oxacyclo[4.1.0]heptane.

Examples of the styrene compound include styrene, methylstyrene, chlorostyrene, and bromostyrene.

Examples of the maleimide compound include maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide.

The nitrogen-containing aromatic heterocyclic ring contains at least one structure selected from the group consisting of the following formulas [Na] to [Nb] (wherein _Z2 is a linear or branched alkyl group having 1 to 5 carbon atoms), and preferably contains 1 to 4 aromatic cyclic hydrocarbons.

Specifically, oxazole ring, thiazole ring, pyridine ring, pyrimidine ring, quinoline ring, 1-pyrazoline ring, isoquinoline ring, thiadiazole ring, oxazine ring, triazine ring, pyrazine ring, phenanthroline ring, quinoxaline ring, benzothiazole ring, oxadiazole ring, acridine ring, etc. can be mentioned. Furthermore, the carbon atom of these aromatic heterocyclic rings containing nitrogen may have a substituent containing a heteroatom. Among them, for example, pyridine ring can be mentioned.

Examples of the monomer having a nitrogen-containing aromatic heterocyclic group and a polymerizable group include 2-(2-pyridylcarbonyloxy)ethyl (meth)acrylate, 2-(3-pyridylcarbonyloxy)ethyl (meth)acrylate, and 2-(4-pyridylcarbonyloxy)ethyl (meth)acrylate.

The other monomers used in the present invention may be used alone or in combination of two or more monomers.

The photoreactive site represented by the above formula (pa-1) in the polymer of the component (A) of the liquid crystal alignment agent of the present invention may be used alone or in combination of two or more sites.

The photoreactive part represented by the formula (pa-1) is preferably contained in an amount of 5 to 95 mol%, 10 to 60 mol%, or 15 to 50 mol% of all repeating units of the polymer of the component (A).

The site with a thermal crosslinking group contained in the polymer of the present invention may use the thermal crosslinking group A alone, or may use a combination of two or more sites containing the thermal crosslinking group A and the thermal crosslinking group B. The amount of the site with a thermal crosslinking group introduced is preferably 5 to 95 mol%, 40 to 90 mol% or 50 to 85 mol% of the total repeating units of the polymer of component (A).

The content of the structure derived from the above-mentioned other monomers is preferably 0 to 40 mol%, 0 to 30 mol% or 0 to 20 mol% of the total repeating units of the polymer containing the component (A).

<Method for producing specific polymer> The specific polymer of component (A) contained in the liquid crystal alignment agent of the present invention can be obtained by copolymerizing a monomer having a photoalignment group represented by the above formula (pa-1), a monomer having the above thermal crosslinking group A, and a monomer having the above thermal crosslinking group B as required. In addition, it can also be copolymerized with the above other monomers.

There is no particular limitation on the method for producing the specific polymer of component (A) in the present invention, but a general method used in industry can be used. Specifically, it can be produced by cationic polymerization, free radical polymerization, or negative ion polymerization of the vinyl group of the monomer. Among these, free radical polymerization is particularly preferred from the perspective of ease of reaction control. As a polymerization initiator for free radical polymerization, a known compound such as a free radical polymerization initiator or a reversible addition-fragmentation chain transfer (RAFT) polymerization reagent can be used.

The free radical thermal polymerization initiator is a compound that generates free radicals when heated above the decomposition temperature. Examples of such free radical thermal polymerization initiators include ketone peroxides (methyl ethyl ketone peroxide, cyclohexanone peroxide, etc.), diacyl peroxides (acetyl peroxide, benzoyl peroxide, etc.), hydroperoxides (hydrogen peroxide, tert-butyl hydroperoxide, isopropyl hydroperoxide, etc.), dialkyl peroxides (di-tert-butyl peroxide, dicumyl peroxide, dilauryl hydroperoxide, etc.), and dialkyl peroxides (di-tert-butyl peroxide, dicumyl peroxide, dilauryl hydroperoxide, etc.). peroxides, etc.), peroxyketals (dibutyl peroxycyclohexane, etc.), alkyl peresters (tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, tert-pentyl peroxy-2-ethylcyclohexane, etc.), persulfates (potassium persulfate, sodium persulfate, ammonium persulfate, etc.), azo compounds (azobisisobutyronitrile and 2,2'-bis(2-hydroxyethyl)azobisisobutyronitrile, etc.).

Such a radical thermal polymerization initiator may be used alone or in combination of two or more.

The radical photopolymerization initiator is not particularly limited as long as it is a compound that can initiate radical polymerization by light irradiation. As such a radical photopolymerization initiator, known compounds such as benzophenone, Michler's ketone, 4,4'-bis(diethylamino)benzophenone, xanthone, thioxanthone, isopropylxanthone can be cited. These compounds can be used alone or in combination of two or more. The radical polymerization method is not particularly limited, and emulsion polymerization, suspension polymerization, dispersion polymerization, precipitation polymerization, bulk polymerization, solution polymerization, etc. can be used.

The solvent used in the polymerization reaction of the specific polymer of component (A) is not particularly limited as long as it can dissolve the generated polymer. As specific examples, the solvents listed in the <Solvent> described later can be cited, such as N-alkyl-2-pyrrolidone, dialkyl imidazolidinone, lactone, carbonate, ketone, compound represented by formula (Sv-1) and compound represented by formula (Sv-2), tetrahydrofuran, 1,4-dioxane, dimethyl sulfone, dimethyl sulfoxide, etc. These solvents can be used alone or in combination. Even if the solvent cannot dissolve the generated polymer, it can be mixed with the above solvent and used as long as the polymer does not precipitate. In addition, for free radical polymerization, since oxygen in the solvent may hinder the polymerization reaction, it is better to use an organic solvent that has been degassed as much as possible.

The polymerization temperature during free radical polymerization can be selected from any temperature of 30 to 150°C, but preferably in the range of 50 to 100°C. In addition, the reaction can be carried out at any concentration, but the monomer concentration is preferably 1 to 50% by mass, and more preferably 5 to 30% by mass. The reaction is carried out at a high concentration at the initial stage, and an organic solvent can be added thereafter. For the above-mentioned free radical polymerization reaction, if the ratio of the free radical polymerization initiator to the monomer is high, the molecular weight of the obtained polymer will become small, because if it is too low, the molecular weight of the obtained polymer will become large, so the ratio of the free radical initiator to the polymerized monomer is preferably 0.1 to 10 mol%. In addition, various monomer components, solvents, initiators, etc. can be added during polymerization.

[Recovery of polymer] When recovering the polymer produced from the reaction solution obtained by the above reaction, the reaction solution is put into a weak solvent, and any polymer can be precipitated. Examples of the weak solvent used for precipitation include methanol, acetone, hexane, heptane, butyl solvent, heptane, ethanol, toluene, benzene, diethyl ether, methyl ethyl ether, water, etc. The polymer put into the weak solvent and precipitated is recovered by filtration and then dried at normal pressure or reduced pressure, at room temperature or by heating. In addition, the polymer recovered by precipitation is dissolved in an organic solvent again and recovered by precipitation again by repeating the operation 2 to 10 times, so that the impurities in the polymer can be reduced. Examples of the weak solvent in this case include alcohols, ketones, hydrocarbons, and the like. It is preferred to use three or more weak solvents selected from these because the purification efficiency can be further improved.

The molecular weight of the specific polymer of component (A) is preferably 2,000 to 1,000,000, more preferably 5,000 to 100,000, as measured by GPC (Gel Permeation Chromatography) method, taking into account the strength of the resulting coating, workability during coating formation, and uniformity of the coating.

<Component (B)> The component (B) contained in the liquid crystal alignment agent of the present invention is a polymer selected from polyimide and its precursor, which is a polymer having at least one group selected from a vertical alignment group and a tert-butyloxycarbonyl group, or at least one of which is chemically imidized.

The polymer of the component (B) is polyimide and its precursor (hereinafter also referred to as the polyimide component), and preferably has a surface energy close to that of the polymer of the component (A). For example, the acrylic component of the component (A) basically has low polarity and low surface energy. On the other hand, the polyimide component has high polarity and high surface energy. However, if the difference in surface energy of the two components is too large, they cannot be fully miscible and agglomerate to form a film with bumps, or there is concern that the process range becomes narrow due to dripping and unevenness. Therefore, by reducing the polarity of the polyimide component, although the surface energy is higher than that of the acrylic component, the difference can be controlled to a small value. As a method for reducing the polarity of the polyimide component, there are a method of mixing it with the (A) component after chemical imidization or a method of introducing a side chain.

Examples of such polymers include polymers obtained by polymerizing a tetracarboxylic acid derivative such as a known tetracarboxylic dianhydride with a known diamine and chemically imidizing the polymer, a polyimide precursor obtained by imidizing a diamine having a side chain, a polyimide obtained by imidizing a diamine having a tert-butoxycarbonyloxy group, and a polyimide obtained by imidizing the polymer. Since the surface energy can be made close to that of the acrylic polymer of the component (A) by such side chain or chemical imidization, when a liquid crystal alignment agent is applied and a cured film is formed by firing, aggregation does not occur, and a flat cured film can be provided. Examples of diamines having a side chain include diamines represented by formulas (2), (3), (4), and (5) described in paragraphs [0023] to [0039] of International Patent Application Publication WO2016/125870 and diamines represented by formulas [A-1] to [A-32] as specific examples thereof. Examples of diamines having a tert-butoxycarbonyloxy group include diamines having structures of formulas [A-1], [A-2], and [A-3] described in paragraphs [0011] to [0034] of International Patent Application Publication WO2017/119461 and diamines exemplified as specific examples thereof.

The content ratio of the polymer of component (A) to the polymer of component (B) in the liquid crystal alignment agent of the present invention is preferably a mass ratio of component (A) to component (B) of 5:95 to 95:5, more preferably 10:90 to 90:10, and even more preferably 20:80 to 60:40.

<Component (C)> When the liquid crystal alignment agent used in the present invention satisfies requirement Z2, it contains a crosslinking agent as component (C). As component (C), a crosslinking agent having two or more thermally crosslinkable groups B can be cited.

Examples of the crosslinking agent as the component (C) include low molecular weight compounds such as epoxy compounds, compounds having two or more amino groups, hydroxymethyl compounds, isocyanate compounds, phenolic resin compounds, and blocked isocyanate compounds, polymers such as polymers of N-alkoxymethyl acrylamide, polymers of compounds having epoxy groups, and polymers of compounds having isocyanate groups.

Specific examples of the epoxy compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerol diglycidyl ether, 2,2-dibromo Neopentyl glycol diglycidyl ether, 1,3,5,6-tetraglycidyl-2,4-hexanediol, N,N,N',N',-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, etc.

Examples of the compound having two or more amino groups include diamines such as alicyclic diamines, aromatic diamines, aromatic-aliphatic diamines, and aliphatic diamines.

Examples of the alicyclic diamines include 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 4,4'-diaminodicyclohexylmethane, 4,4'-diamino-3,3'-dimethyldicyclohexylamine, and isophoronediamine.

Examples of aromatic diamines include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 3,5-diaminotoluene, 1,4-diamino-2-methoxybenzene, 2,5-diamino-p-xylene, and 1,3-diamino-4-chlorobenzene.

Examples of aromatic-aliphatic diamines include 3-aminobenzylamine, 4-aminobenzylamine, 3-amino-N-methylbenzylamine, 4-amino-N-methylbenzylamine, 3-aminophenethylamine, 4-aminophenethylamine, 3-amino-N-methylphenethylamine, 4-amino-N-methylphenethylamine, 3-(3-aminopropyl)aniline, 4-(3-aminopropyl)aniline, 3-(3-methylaminopropyl)aniline, 4-(3-methylaminopropyl)aniline. , 3-(4-aminobutyl)aniline, 4-(4-aminobutyl)aniline, 3-(4-methylaminobutyl)aniline, 4-(4-methylaminobutyl)aniline, 3-(5-aminopentyl)aniline, 4-(5-aminopentyl)aniline, 3-(5-methylaminopentyl)aniline, 4-(5-methylaminopentyl)aniline, 2-(6-aminonaphthyl)methylamine, 3-(6-aminonaphthyl)methylamine, 2-(6-aminonaphthyl)ethylamine, 3-(6-aminonaphthyl)ethylamine, etc.

Examples of aliphatic diamines include 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,3-diamino-2,2-dimethylpropane, 1,6-diamino-2,5-dimethylhexane, 1,7-diamino-2,5-dimethylheptane, 1,7-diamino-4,4-dimethylheptane, 1,7-diamino-3-methylheptane, and 1,9-diamino-5-methylheptane.

Specific examples of the hydroxymethyl compound include alkoxymethylated ethylene glycol urea, alkoxymethylated benzoguanamine, and alkoxymethylated melamine.

Specific examples of alkoxymethylated glycol urea include 1,3,4,6-tetrakis(methoxymethyl)glycol urea, 1,3,4,6-tetrakis(butoxymethyl)glycol urea, 1,3,4,6-tetrakis(hydroxymethyl)glycol urea, 1,3-bis(hydroxymethyl)urea, 1,1,3,3-tetrakis(butoxymethyl)urea, 1,1,3,3-tetrakis(methoxymethyl)urea, 1,3-bis(hydroxymethyl)-4,5-dihydroxy-2-imidazolidinone, and 1,3-bis(methoxymethyl)-4,5-dimethoxy-2-imidazolidinone. Examples of the products for sale include ethylene glycol urea compounds (trade names: Cymel (registered trademark) 1170, Powder link (registered trademark) 1174) manufactured by Mitsui Cytec Co., Ltd., methylated urea resins (trade names: UFR (registered trademark) 65), butylated urea resins (trade names: UFR (registered trademark) 300, U-VAN10S60, U-VAN10R, U-VAN11HV), and urea/formaldehyde-based resins (highly condensed type, trade names: Becamine (registered trademark) J-300S, P-955, N) manufactured by DIC Co., Ltd.

Specific examples of alkoxymethylated benzoguanamine include tetramethoxymethylbenzoguanamine, etc. Commercial products include products manufactured by Mitsui Cytec Co., Ltd. (trade name: Cymel (registered trademark) 1123), and products manufactured by Sanwa Chemical Co., Ltd. (trade name: Nicaraq (registered trademark) BX-4000, BX-37, BL-60, and BX-55H).

Specific examples of alkoxymethylated melamine include hexamethoxymethylmelamine. Examples of the products for sale include methoxymethyl melamine compounds (trade names: Cymel (registered trademark) 300, 301, 303, 350) manufactured by Mitsui Cytec Co., Ltd., butoxymethyl melamine compounds (trade names: My coat (registered trademark) 506, 508) manufactured by Sanwa Chemical Co., Ltd., methoxymethyl melamine compounds (trade names: Nicaraq (registered trademark) MW-30, MW-22, MW-11, MS-001, MX-002, MX-730, MX-750, MX-035) manufactured by Sanwa Chemical Co., Ltd., and butoxymethyl melamine compounds (trade names: Nicaraq (registered trademark) MX-45, MX-410, MX-302) manufactured by Sanwa Chemical Co., Ltd.

Furthermore, compounds obtained by condensing melamine compounds, urea compounds, glycol urea compounds and benzoguanamine compounds in which the hydrogen atoms of these amino groups are replaced with hydroxymethyl groups or alkoxymethyl groups may be used. For example, high molecular weight compounds produced from melamine compounds and benzoguanamine compounds described in U.S. Patent No. 6,323,310 may be cited. Examples of the commercial products of the aforementioned melamine compounds include the trade name: Cymel (registered trademark) 303 (manufactured by Mitsui Cytec (Co., Ltd.)), and examples of the commercial products of the aforementioned benzoguanamine compounds include the trade name: Cymel (registered trademark) 1123 (manufactured by Mitsui Cytec (Co., Ltd.)).

Specific examples of the isocyanate compound include VESTANAT B1358/100, VESTAGON BF 1540 (above, isocyanurate type modified polyisocyanate, manufactured by Degussa Japan Co., Ltd.), Takenate (registered trademark) B-882N, and B-7075 (above, isocyanurate type modified polyisocyanate, manufactured by Mitsui Chemicals Co., Ltd.), etc.

As specific examples of the phenolic resin compound, the following compounds can be cited, but the phenolic resin compound is not limited to the following compound examples.

Specific examples of the compound having two or more hydroxyalkylamide groups at the molecular ends include the following compounds, Primid XL-552, and Primid SF-4510.

Examples of the blocked isocyanate compound include Coronate AP Stable M, Coronate 2503, 2515, 2507, 2513, 2555, and Millionate MS-50 (all manufactured by Nippon Polyurethane Industries, Ltd.), and Takenate B-830, B-815N, B-820NSU, B-842N, B-846N, B-870N, B-874N, and B-882N (all manufactured by Mitsui Chemicals, Ltd.).

Further, examples of the above-mentioned N-alkoxymethylacrylamide polymer include polymers produced using acrylamide compounds or methacrylamide compounds substituted with a hydroxymethyl group or an alkoxymethyl group such as N-hydroxymethyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide.

Specific examples of such polymers include poly(N-butoxymethylacrylamide), copolymers of N-butoxymethylacrylamide and styrene, copolymers of N-hydroxymethylmethacrylamide and methyl methacrylate, copolymers of N-ethoxymethylmethacrylamide and benzylmethacrylate, and copolymers of N-butoxymethylacrylamide, benzylmethacrylate and 2-hydroxypropylmethacrylate, etc. The weight average molecular weight of such polymers is 1,000 to 200,000, preferably 3,000 to 150,000, and more preferably 3,000 to 50,000.

Examples of polymers of compounds having an epoxy group include polymers produced using compounds having an epoxy group such as glycidyl methacrylate, 3,4-epoxyepoxyhexylmethyl methacrylate, and 3,4-epoxyepoxyhexylmethyl methacrylate.

Specific examples of such polymers include poly(3,4-epoxyhexylmethyl methacrylate), poly(glycidyl methacrylate), copolymers of glycidyl methacrylate and methyl methacrylate, copolymers of 3,4-epoxyhexylmethyl methacrylate and methyl methacrylate, copolymers of glycidyl methacrylate and styrene, etc. The weight average molecular weight of such polymers is 1,000 to 200,000, preferably 3,000 to 150,000, and more preferably 3,000 to 50,000.

Examples of polymers of compounds having an isocyanate group include compounds having an isocyanate group such as 2-isocyanate ethyl methacrylate (KarenzMOI [registered trademark], manufactured by Showa Denko K.K.), 2-isocyanate ethyl acrylate (KarenzAOI [registered trademark], manufactured by Showa Denko K.K.), and polymers produced using compounds having a blocked isocyanate group such as 2-(0-[1'-methylpropyleneamino]carboxylamino)ethyl methacrylate (KarenzMOI-BM [registered trademark], manufactured by Showa Denko K.K.), and 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate (KarenzMOI-BP [registered trademark], manufactured by Showa Denko K.K.).

Specific examples of such polymers include poly(2-isocyanatoethyl acrylate), poly(2-(0-[1'-methylpropyleneamino]carboxylamino)ethyl methacrylate), copolymers of 2-isocyanatoethyl methacrylate and styrene, copolymers of 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate and methyl methacrylate, etc. The weight average molecular weight of such polymers is 1,000 to 200,000, preferably 3,000 to 150,000, and more preferably 3,000 to 50,000.

These crosslinking agents may be used alone or in combination of two or more.

When the crosslinking agent (C) is contained in the liquid crystal alignment agent of the present invention, the content thereof is preferably 1 to 100 parts by weight, more preferably 1 to 80 parts by weight, based on 100 parts by weight of the resin (A).

[Preparation of liquid crystal alignment agent] The liquid crystal alignment agent used in the present invention is preferably prepared as a coating liquid suitable for forming a liquid crystal alignment film. That is, the liquid crystal alignment agent of the present invention is preferably prepared by dissolving a resin component to form a resin film in a solution of an organic solvent. The so-called resin component is the specific polymer of the component (A) and the polymer of the component (B) as described above. At this time, the total content of the specific polymer of the component (A) and the polymer of the component (B) is preferably 0.5 to 20% by mass, more preferably 1 to 20% by mass, more preferably 1 to 15% by mass, and particularly preferably 1 to 10% by mass, based on the entire liquid crystal alignment agent.

<Solvent> The solvent used in the liquid crystal alignment agent of the present invention is not particularly limited as long as it can dissolve the (A) component, the (B) component, and the (C) component as required. The solvent contained in the liquid crystal alignment agent may be one type, or a mixture of two or more types may be used. Furthermore, even if it is not a solvent that dissolves the (A) component or the (B) component, a solvent that dissolves the (A) component or the (B) component may be used in combination. In this case, if the surface energy of the solvent that does not dissolve the (A) component or the (B) component is lower than that of the solvent that dissolves the (A) component or the (B) component, it is preferred because the liquid crystal alignment agent can be applied to the substrate better.

Specific examples include water, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and other N-alkyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylcaprolactam, tetramethylurea, 3-methoxy-N,N-dimethylpropaneamide, 3-ethoxy-N,N-dimethylpropaneamide, 3-butoxy-N,N-dimethylpropaneamide, 1,3-dimethyl-2-imidazolidinone and other dialkyl imidazolidinone, γ-butyrolactone, γ-valerolactone, δ-valerolactone and other lactones, ethyl carbonate, propyl carbonate and other carbonyl carbonate. Acid esters, methanol, ethanol, propanol, isopropanol, 3-methyl-3-methoxybutanol, ethyl amyl ketone, methyl nonyl ketone, methyl ethyl ketone, isoamyl methyl ketone, methyl isopropyl ketone, diisobutyl ketone, cyclohexanone, cyclopentanone, methyl isobutyl ketone, 4-hydroxy-4-methyl-2-pentanone and the like, compounds represented by the following formula (Sv-1) and the following formula (Sv-2), 4-methyl-2-pentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, 2-methylcyclohexyl acetate, butyl butyrate, isoamyl butyrate, diisobutyl carbinol, diisoamyl ether and the like.

In formula (Sv-1) to (Sv-2), _Y1 and _Y2 are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms, _X1 is an oxygen atom or -COO-, _X2 is a single bond or a carbonyl group, and _R1 is an alkanediyl group having 2 to 4 carbon atoms. _n1 is an integer from 1 to 3. When _n1 is 2 or 3, the plurality of _R1s may be the same or different. _Z1 is a divalent hydrocarbon group having 1 to 6 carbon atoms, and _Y3 and _Y4 are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms).

In formula (Sv-1), examples of the monovalent alkyl group having 1 to 6 carbon atoms for _Y1 and _Y2 include a monovalent chain alkyl group having 1 to 6 carbon atoms, a monovalent alicyclic alkyl group having 1 to 6 carbon atoms, and a monovalent aromatic alkyl group having 1 to 6 carbon atoms. Examples of the monovalent chain alkyl group having 1 to 6 carbon atoms include an alkyl group having 1 to 6 carbon atoms. The alkanediyl group for _R1 may be a linear or branched chain group.

In formula (Sv-2), as a divalent alkyl group having 1 to 6 carbon atoms for _Z1 , for example, an alkanediyl group having 1 to 6 carbon atoms can be mentioned. As a monovalent alkyl group having 1 to 6 carbon atoms for _Y3 and _Y4 , for example, a monovalent chain alkyl group having 1 to 6 carbon atoms, a monovalent alicyclic alkyl group having 1 to 6 carbon atoms, and a monovalent aromatic alkyl group having 1 to 6 carbon atoms can be mentioned. As a monovalent chain alkyl group having 1 to 6 carbon atoms, for example, an alkyl group having 1 to 6 carbon atoms can be mentioned.

Specific examples of the solvent represented by formula (Sv-1) include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i-propyl ether, ethylene glycol monobutyl ether (butyl solvent), ethylene glycol monohexyl ether, ethylene glycol dimethyl ether, ethylene glycol monoacetate, ethylene glycol diacetate, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monomethyl ether, propylene glycol diacetate, ethylene glycol, 1,4-butanediol, 3-methoxybutyl acetate, 3-ethoxybutyl acetate, etc.; Specific examples of the solvent represented by (Sv-2) include methyl glycolate, ethyl glycolate, butyl glycolate, ethyl lactate, butyl lactate, isoamyl lactate, ethyl-3-ethoxypropionate, methyl-3-methoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, etc.

The solvent preferably has a boiling point of 80 to 200°C. More preferably, it is 80 to 180°C. Examples of the preferred solvent include N,N-dimethylformamide, tetramethylurea, 3-methoxy-N,N-dimethylpropaneamide, propanol, isopropanol, 3-methyl-3-methoxybutanol, ethyl amyl ketone, methyl ethyl ketone, isoamyl methyl ketone, methyl isopropyl ketone, diisobutyl ketone, cyclohexanone, cyclopentanone, methyl isobutyl ketone, 4-hydroxy-4-methyl-2-pentanone, 4-methyl-2-pentyl acetate, 2-hydroxy-4-methyl-2-pentyl acetate, and 2-hydroxy-4-methyl-2-pentyl acetate. Ethyl butyl ester, cyclohexyl acetate, 2-methylcyclohexyl acetate, butyl butyrate, isoamyl butyrate, diisobutyl carbinol, diisoamyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i-propyl ether, ethylene glycol monobutyl ether (butyl solvent), ethylene glycol dimethyl ether, ethylene glycol monoacetate, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, Propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monomethyl ether, 3-methoxybutyl acetate, methyl glycolate, ethyl glycolate, butyl glycolate, ethyl lactate, butyl lactate, isoamyl lactate, ethyl-3-ethoxypropionate, methyl-3-methoxypropionate, ethyl-3-methoxypropionate, etc. When the boiling point is within this range, it is particularly preferred to apply the liquid crystal alignment agent containing the above solvent on the plastic substrate described below.

<Other components> The liquid crystal alignment agent used in the present invention may also contain other components other than the above-mentioned (A) component, (B) component and (C) component as required. Such other components include crosslinking catalysts, compounds that can improve film thickness uniformity or surface smoothness when applied to the liquid crystal alignment agent, compounds that are intended to improve the adhesion between the liquid crystal alignment film and the substrate, etc., but are not limited to these.

<Crosslinking catalyst> In the liquid crystal alignment agent used in the present invention, a crosslinking catalyst may be added for the purpose of promoting the reaction between the thermally crosslinkable group A and the thermally crosslinkable group B. Examples of such a crosslinking catalyst include p-toluenesulfonic acid, camphoric acid, trifluoromethanesulfonic acid, p-phenolsulfonic acid, 2-naphthalenesulfonic acid, trimethylbenzenesulfonic acid, p-xylene-2-sulfonic acid, m-xylene-2-sulfonic acid, 4-ethylbenzenesulfonic acid, 1H,1H,2H,2H-perfluorooctanesulfonic acid, perfluoro(2-ethoxyethane)sulfonic acid, pentafluoroethanesulfonic acid, nonafluorobutane-1-sulfonic acid, dodecylbenzenesulfonic acid and other sulfonic acids or their hydrates or salts. Examples of the compound that generates an acid by heat include bis(toluenesulfonyloxy)ethane, bis(toluenesulfonyloxy)propane, bis(toluenesulfonyloxy)butane, p-nitrobenzyl toluenesulfonate, o-nitrobenzyl toluenesulfonate, 1,2,3-toluenesulfonate, p-pyridinium toluenesulfonate, p-toluenesulfonate morpholinium salt, p-toluenesulfonate ethyl ester, p-toluenesulfonate propyl ester, p-toluenesulfonate butyl ester, p-toluenesulfonate isobutyl ester, p-toluenesulfonate methyl ester, p-toluenesulfonate phenethyl ester, cyanomethyl p-toluenesulfonate, 2,2,2-trifluoroethyl p-toluenesulfonate, 2-hydroxybutyl p-toluenesulfonate, and N-ethyl-p-toluenesulfonamide.

[Compounds for improving uniformity of film thickness or surface smoothness] Compounds for improving uniformity of film thickness or surface smoothness include fluorine-based surfactants, silicone-based surfactants, and non-ionic surfactants. Specifically, for example, EFTOP (registered trademark) 301, EF303, EF352 (manufactured by Tochem Products), Megafac (registered trademark) F171, F173, R-30 (manufactured by DIC), FLUORAD FC430, FC431 (manufactured by Sumitomo 3M), Asahi Guard (registered trademark) AG710 (manufactured by Asahi Glass Co., Ltd.), Surflon (registered trademark) S-382, SC101, SC102, SC103, SC104, SC105, SC106 (manufactured by AGC Seimi Chemical Co., Ltd.), etc. The usage ratio of these surfactants is preferably 0.01 to 2 parts by mass, and more preferably 0.01 to 1 part by mass, based on 100 parts by mass of the resin component contained in the polymer composition.

[Compounds for improving the adhesion between the liquid crystal alignment film and the substrate] As specific examples of compounds for improving the adhesion between the liquid crystal alignment film and the substrate, the following compounds containing functional silanes can be cited. For example, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropylamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl -1,4,7-triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-dinonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate, N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-bis(oxyethyl)-3-aminopropyltrimethoxysilane, N-bis(oxyethyl)-3-aminopropyltriethoxysilane and other amino-based silane compounds. When a compound is used to improve adhesion to a substrate, the amount used is preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass, based on 100 parts by mass of the resin component contained in the polymer composition.

In certain embodiments, a photosensitizer may be used as an additive to enhance the photoreactivity of the photoalignment group. Specific examples thereof include aromatic 2-hydroxy ketones (benzophenones), coumarins, ketocoumarins, carbonyl dicoumarins, acetophenones, anthraquinones, xanthones, thioxanthones, and acetophenone ketal.

<Liquid crystal alignment film and liquid crystal display element> The liquid crystal alignment agent of the present invention is applied on a substrate, fired, and then oriented by rubbing or light irradiation, or can be used as a liquid crystal alignment film without orientation treatment in some vertical orientation applications. As the substrate, for example, glass such as float glass and soda glass can be cited; transparent substrates made of plastics such as polyethylene terephthalate, polybutylene terephthalate, polypropylene, polystyrene, polyether sulfone, polycarbonate, poly(aliphatic cycloolefin), polyvinyl chloride, polyvinylidene chloride, polyether ether ketone (PEEK) resin film, polysulfone (PSF), polyether sulfone (PES), polyamide, polyimide, acrylic acid, and triacetyl cellulose can be cited. As the transparent conductive film provided on one side of the substrate, a NESA film (registered trademark of PPG, USA) made of tin oxide (SnO ₂ ), an ITO film made of indium oxide-tin oxide (In ₂ O ₃ -SnO ₂ ), or the like can be used.

<Coating film forming step> The coating method of the liquid crystal alignment agent of the present invention is not particularly limited, but includes screen printing, flexographic printing, offset printing, inkjet, dip coating, roll coating, slit coating, rotary coating, etc., which can be used in accordance with the purpose. After coating on the substrate by these methods, the solvent is evaporated by heating means such as a heating plate to form a coating film.

The calcination after the liquid crystal alignment agent is applied can be carried out at any temperature of 40 to 300°C, but preferably 40 to 250°C, more preferably 40 to 230°C. The thickness of the coating formed on the substrate is preferably 5 to 1,000 nm, more preferably 10 to 500 nm or 10 to 300 nm. The calcination can be carried out by a heating plate, a hot air circulation furnace, an infrared furnace, etc. For the friction treatment, rayon cloth, nylon cloth, cotton cloth, etc. can be used.

<Light irradiation step> For one embodiment, the alignment treatment can be performed by light irradiation, for example, it can include the step of applying the above-mentioned liquid crystal alignment agent on the substrate to form a coating film, and the step of irradiating the above-mentioned coating film with light in a state where the above-mentioned coating film is not in contact with the liquid crystal layer or in a state where the above-mentioned coating film is in contact with the liquid crystal layer.

As the light for irradiation for the alignment treatment by light irradiation, for example, ultraviolet light having a wavelength of 150 to 800 nm, visible light, etc. can be cited. Among them, ultraviolet light having a wavelength of 300 to 400 nm is preferred. The irradiation light may be polarized light or non-polarized light. As polarized light, light having linear polarization is preferably used.

When the light used is polarized light, the irradiation may be performed in a direction perpendicular to the substrate surface or in an oblique direction, or a combination of these. When the light is non-polarized light, it is preferably performed in an oblique direction relative to the substrate surface. The irradiation amount of light is preferably 0.1mJ/ ^cm2 or more and less than 1,000mJ/ ^cm2 , preferably 1 to 500mJ/ ^cm2 , and more preferably 2 to 200mJ/ ^cm2 .

The liquid crystal display element of the present invention can be manufactured by a common method, and the manufacturing method is not particularly limited. The above pair of substrates are face-to-face with an appropriate gap, and it is preferred to arrange a spacer between the substrates for the purpose of making the thickness of the liquid crystal held between the substrates uniform. As the spacer, in addition to the known spacer materials such as the conventional dispersed spacer and the spacer formed by the photosensitive spacer forming composition, the concavo-convex formed on the layer formed by the liquid crystal cured material can also be used as the spacer.

<Liquid crystal clamping step> When constructing a liquid crystal unit that clamps liquid crystal between substrates, for example, the following two methods can be cited. As the first method, a pair of substrates are arranged opposite to each other with a gap (cell gap) between them so that each liquid crystal alignment film faces each other, the peripheral portions of the pair of substrates are bonded together using a sealant, and liquid crystal is injected into the substrate surface and the cell gap divided by an appropriate sealant, and then the injection hole is sealed to manufacture a liquid crystal unit.

As a second method, a UV-curable sealing material is applied at a predetermined location on one of the two substrates forming a liquid crystal alignment film, and liquid crystal is further dripped at a predetermined number of locations on the surface of the liquid crystal alignment film. The other substrate is then bonded so that the liquid crystal alignment films are face to face, and the liquid crystal is simultaneously spread over the entire surface of the substrate. Next, the entire surface of the substrate is irradiated with UV light to cure the sealant, thereby manufacturing a liquid crystal unit (ODF (One Drop Fill) method).

As liquid crystal, fluorine-based liquid crystal or cyano-based liquid crystal with positive or negative dielectric anisotropy can be used according to the application, and liquid crystal compounds or liquid crystal compositions (hereinafter also referred to as polymerizable liquid crystal or curable liquid crystal compositions) that are polymerized by at least one of heating and light irradiation are preferred. For one embodiment, the step of forming the coating of the aforementioned liquid crystal alignment agent can be performed by a roll-to-roll method. When the roll-to-roll method is used, the manufacturing steps of the liquid crystal display element can be simplified and the manufacturing cost can be reduced. Then, by attaching polarizing plates to the outer two surfaces of the aforementioned liquid crystal unit, a liquid crystal display element can be obtained.

As the polarizing plate used on the outer side of the liquid crystal unit, there can be cited a polarizing film called "H film" in which polyvinyl alcohol is stretched and aligned on one side and iodine is absorbed on the other side, a polarizing plate sandwiched by a cellulose acetate protective film, or a polarizing plate formed by the H film itself. As mentioned above, the liquid crystal alignment film obtained by the liquid crystal alignment agent of the present invention has good liquid crystal alignment, excellent pre-tilt angle performance, and can obtain high reliability. In addition, the liquid crystal display element manufactured by the method of the present invention has excellent display characteristics. [Example]

The abbreviations used in the embodiments are as follows. <Methacrylic acid monomer> (Photo-aligned monomer) "MA1" means a monomer synthesized by the synthesis method described in the patent document (WO2017/115791). "MA2" means a monomer synthesized by the synthesis method described in the patent document (WO2017/115791).

(Polar monomer) MAA: Methacrylic acid

(Cross-linking monomer) GMA: Glycidyl methacrylate

(Isocyanate monomer) MOI-BP: 2-[(3,5-dimethyl-1-pyrazolyl)carbonylamino]ethyl methacrylate

<Tetracarboxylic dianhydride monomer> A1: Tetracarboxylic dianhydride represented by the following formula [A1] A2: Tetracarboxylic dianhydride represented by the following formula [A2] A3: Tetracarboxylic dianhydride represented by the following formula [A3] A4: Tetracarboxylic dianhydride represented by the following formula [A4] A5: Tetracarboxylic dianhydride represented by the following formula [A5] A6: Tetracarboxylic dianhydride represented by the following formula [A6] A7: Tetracarboxylic dianhydride represented by the following formula [A7] A8: Tetracarboxylic dianhydride represented by the following formula [A8]

<Side-chain diamine monomer> B1: Side-chain diamine monomer represented by the following formula [B1] B2: Side-chain diamine monomer represented by the following formula [B2] B3: Side-chain diamine monomer represented by the following formula [B3] B4: Side-chain diamine monomer represented by the following formula [B4] B5: Side-chain diamine monomer represented by the following formula [B5] B6: Side-chain diamine monomer represented by the following formula [B6] B7: Side-chain diamine monomer represented by the following formula [B7] B8: a side-chain diamine monomer represented by the following formula [B8] B9: a side-chain diamine monomer represented by the following formula [B9] B10: a side-chain diamine monomer represented by the following formula [B10] B11: a side-chain diamine monomer represented by the following formula [B11] B12: a side-chain diamine monomer represented by the following formula [B12] B13: a side-chain diamine monomer represented by the following formula [B13] B14: a side-chain diamine monomer represented by the following formula [B14]

<Other diamine monomers> C1: Other diamine monomers represented by the following formula [C1] C2: Other diamine monomers represented by the following formula [C2] C3: Other diamine monomers represented by the following formula [C3] C4: Other diamine monomers represented by the following formula [C4] C5: Other diamine monomers represented by the following formula [C5] C6: Other diamine monomers represented by the following formula [C6] C7: Other diamine monomers represented by the following formula [C7] C8: Other diamine monomers represented by the following formula [C8] C9: Other diamine monomers represented by the following formula [C9] C10: Other diamine monomers represented by the following formula [C10] C11: Other diamine monomers represented by the following formula [C11] C12: Other diamine monomers represented by the following formula [C12] C13: Other diamine monomers represented by the following formula [C13] C14: Other diamine monomers represented by the following formula [C14] C15: Other diamine monomers represented by the following formula [C15] C16: Other diamine monomers represented by the following formula [C16] C17: Other diamine monomers represented by the following formula [C17] C18: Other diamine monomers represented by the following formula [C18] C19: Other diamine monomers represented by the following formula [C19] C20: Other diamine monomers represented by the following formula [C20]

(Crosslinking agent component) D-1: Crosslinking agent component represented by the following formula [D1] D-2: Crosslinking agent component represented by the following formula [D2] D-3: Crosslinking agent component represented by the following formula [D3]

The abbreviations of other reagents used in this embodiment are as follows. (Polymerization initiator) AIBN: azobisisobutyronitrile (Solvent) NMP: N-methyl-2-pyrrolidone BCS: Butyl solvent THF: Tetrahydrofuran DMF: N,N-dimethylformamide

(Molecular weight determination) The molecular weight of the polymer in the synthesis example was determined as follows using a room temperature gel permeation chromatography (GPC) apparatus (SSC-7200 manufactured by Senshu Science Co., Ltd., columns (KD-803, KD-805) manufactured by Shodex Co., Ltd. Column temperature: 50°C, solvent: DMF (as an additive, lithium bromide monohydrate (LiBr･H ₂ O) 30mmol/L, phosphoric acid･anhydrous crystals (o-phosphoric acid) 30mmol/L, THF 10ml/L), flow rate: 1.0ml/min. Standard samples for preparing the standard curve: TSK standard polyethylene oxide (molecular weight of about 9000,000, 150,000, 100,000, 30,000) and Polymer manufactured by Tosoh Co., Ltd. Polyethylene glycol (molecular weight approximately 12,000, 4,000, 1,000) manufactured by laboratory company.

(Determination of imidization rate) The imidization rate in the synthesis example was determined as follows. 20 mg of polyimide powder was placed in an NMR sample tube (NMR sample tube standard φ5 manufactured by Kusano Scientific Co., Ltd.), 1.0 ml of dimethyl sulfoxide deuterated (DMSO-d6, 0.05% TMS mixture) was added, and the solution was completely dissolved using ultrasound. The solution was measured by 500 MHz proton NMR using an NMR analyzer (JNW-ECA500) manufactured by JEC Data Corporation. The imidization rate was determined by using a proton from a structure that did not change before and after imidization as a reference proton, and the absorption peak integral value of the proton and the absorption peak integral value of the proton from the NH group of the amide appearing near 9.5 to 10.0 ppm were used to obtain the following formula. In the following formula, x represents the proton absorption peak integral value from the NH group of acylamidin, y represents the absorption peak integral value of the reference proton, and α represents the ratio of the number of reference protons to the protons of the NH group of acylamidin in the case of polyacylamidin (acylamidinization rate is 0%). Acylamidinization rate (%) = (1-α･x/y) × 100

<Methacrylate polymer synthesis example 1> MA1 (1.65 g, 4.00 mmol) and MAA (1.38 g, 16.00 mmol) were dissolved in NMP (18.1 g), degassed with a diaphragm pump, and AIBN (0.16 g, 0.5 mmol) was added as a polymerization initiator, and degassed again. Thereafter, the reaction was carried out at 60°C for 13 hours to obtain a polymer solution. Next, NMP (5.0 g) and BCS (6.0 g) were added to the polymer solution (4.0 g), and the mixture was stirred at room temperature to obtain a methacrylate polymer solution (MP1). The number average molecular weight of the polymer was 34,200, and the weight average molecular weight was 116,000.

<Methacrylate polymer synthesis example 2> MA1 (3.30 g, 8.00 mmol), GMA (0.56 g, 4.00 mmol) and MAA (0.69 g, 8.00 mmol) were dissolved in NMP (26.8 g), degassed with a diaphragm pump, and AIBN (0.16 g, 0.5 mmol) was added as a polymerization initiator, and degassed again. Thereafter, the reaction was carried out at 60°C for 13 hours to obtain a polymer solution. Next, NMP (5.0 g) and BCS (6.0 g) were added to the polymer solution (4.0 g), and the mixture was stirred at room temperature to obtain a methacrylate polymer solution (MP2). The number average molecular weight of the polymer was 45,000, and the weight average molecular weight was 150,000.

<Methacrylate polymer synthesis example 3> MA1 (2.48 g, 6.00 mmol) and MOI-BP (3.52 g, 14.00 mmol) were dissolved in NMP (34.9 g), and degassed with a diaphragm pump. AIBN (0.16 g, 0.5 mmol) was added as a polymerization initiator, and degassed again. Thereafter, the reaction was carried out at 60°C for 13 hours to obtain a polymer solution. Next, NMP (5.0 g) and BCS (6.0 g) were added to the polymer solution (4.0 g), and the mixture was stirred at room temperature to obtain a methacrylate polymer solution (MP3). The number average molecular weight of the polymer was 48,000, and the weight average molecular weight was 148,000.

<Polyamine polymer synthesis example 4> B1 (2.28 g, 3.00 mmol), C2 (1.22 g, 4.00 mmol), C7 (1.45 g, 3.00 mmol) and A1 (2.23 g, 6.00 mmol) were dissolved in NMP (27.2 g), and reacted at 60°C for 5 hours. Then, A2 (1.00 g, 2.00 mmol) and A4 (0.87 g, 2.00 mmol) and NMP (9.1 g) were added, and reacted at 40°C for 10 hours to obtain a polyamine polymer solution (MP4).

<Polyamine polymer synthesis examples 5 to 20> In the composition shown in Table 1, polyamine polymer solutions MP5 to MP20 were synthesized using the same method as polymer synthesis example 1.

<Example 21 of Synthesis of Polyamine Polymer> C8 (5.17 g, 5.00 mmol) and A4 (2.18 g, 10.00 mmol) were dissolved in NMP (26.6 g) and reacted at 60°C for 5 hours. Then, C17 (5.17 g, 5.00 mmol) and NMP (9.5 g) were added and reacted at 40°C for 10 hours to obtain a polyamine polymer solution (MP21).

<Example 22 of Synthesis of Polyamine Polymer> C2 (0.61 g, 2.00 mmol), C11 (3.19 g, 8.00 mmol) and A2 (2.50 g, 5.00 mmol) were dissolved in NMP (24.78 g) and reacted at 60°C for 5 hours. Then, A1 (1.96 g, 5.00 mmol) and NMP (8.26 g) were added and reacted at 40°C for 10 hours to obtain a polyamine polymer solution (MP22).

<Polyimide polymer synthesis example 23> NMP was added to the polyimide polymer solution (MP4) (50g) and diluted to 6.5% by mass. Acetic anhydride (8.8g) and pyridine (2.7g) were added as imidization catalysts and reacted at 75°C for 2.5 hours. The reaction solution was poured into methanol (700ml) and the obtained precipitate was separated by filtration. The precipitate was washed with methanol and dried under reduced pressure at 100°C to obtain a polyimide polymer powder (E). The imidization rate of the polyimide polymer was 71%, the number average molecular weight was 13000, and the weight average molecular weight was 42000.

NMP (44.0 g) was added to the obtained polyimide powder (E) (6.0 g), and the mixture was stirred at 70°C for 20 hours to dissolve. NMP (10.0 g) and BCS (40.0 g) were added to the solution, and the mixture was stirred at room temperature for 5 hours to obtain a polyimide polymer solution (MP23).

<Polyimide polymer synthesis examples 24 and 25> The polymer solutions obtained in polymer synthesis examples 21 and 22 were synthesized into polyimide polymer solutions (MP24) and (MP25) using the same method as polymer synthesis example 23.

<Methacrylate polymer synthesis example 26> MA2 (3.04 g, 6.00 mmol), GMA (0.71 g, 5.00 mmol) and MAA (0.77 g, 9.00 mmol) were dissolved in NMP (18.8 g), degassed with a diaphragm pump, and AIBN (0.16 g, 0.5 mmol) was added as a polymerization initiator, and degassed again. Thereafter, the reaction was carried out at 60°C for 13 hours to obtain a polymer solution. Next, NMP (5.0 g) and BCS (6.0 g) were added to the polymer solution (4.0 g), and the mixture was stirred at room temperature to obtain a methacrylate polymer solution (MP26). The number average molecular weight of the polymer was 44,000, and the weight average molecular weight was 143,000.

(Example 1) The polymer solution (MP4) (7.0 g) obtained in the polyimide polymer synthesis example 4 was added to the polymer solution (MP2) (3.0 g) obtained in the methacrylate polymer synthesis example 2, and then D2 (0.06 g) was added, and the mixture was stirred at room temperature to obtain a liquid crystal alignment treatment agent (PM1).

(Examples 2 to 24) For the composition shown in Table 2, the same method as in Example 1 was used to obtain liquid crystal alignment treatment agents (PM2) to (PM24).

(Comparative Example 1) D1 (0.06 g) was added to the polymer solution (MP1) (4.0 g) obtained in the methacrylate polymer synthesis example 1, and the mixture was stirred at room temperature to obtain a liquid crystal alignment treatment agent (RPM1).

(Comparative Example 2) D2 (0.06 g) was added to the polymer solution (MP1) (4.0 g) obtained in the methacrylate polymer synthesis example 1, and the mixture was stirred at room temperature to obtain a liquid crystal alignment treatment agent (RPM2).

(Comparative Example 3) D2 (0.06 g) was added to the polymer solution (MP2) (4.0 g) obtained in the methacrylate polymer synthesis example 2, and the mixture was stirred at room temperature to obtain a liquid crystal alignment treatment agent (RPM3).

(Comparative Example 4) The polymer solution (MP2) (3.0 g) obtained in the methacrylate polymer synthesis example 2 was added with the polymer solution (MP21) (7.0 g) obtained in the amide polymer synthesis example 21, and D2 (0.06 g) was further added. The mixture was stirred at room temperature to obtain a liquid crystal alignment treatment agent (RPM4).

(Comparative Example 5) The polymer solution (MP2) (3.0 g) obtained in the methacrylate polymer synthesis example 2 was added with the polymer solution (MP22) (7.0 g) obtained in the amide polymer synthesis example 22, and D2 (0.06 g) was further added. The mixture was stirred at room temperature to obtain a liquid crystal alignment treatment agent (RPM5).

(Comparative Example 6) D3 (0.06 g) was added to the polymer solution (MP26) (4.0 g) obtained in the methacrylate polymer synthesis example 26, and the mixture was stirred at room temperature to obtain a liquid crystal alignment treatment agent (RPM6).

<Production of Liquid Crystal Display Element> The liquid crystal alignment treatment agents (PM1) to (PM22) obtained in the embodiment and the liquid crystal alignment treatment agents (RPM1) to (RPM5) obtained in the comparative example were pressure filtered with a thin film filter with a pore size of 1 μm. The obtained solution was rotationally coated on the ITO surface of a glass substrate with a transparent electrode formed by an ITO film, dried on a heating plate at 70°C for 90 seconds, and then fired on a heating plate at 200°C for 30 minutes to form a liquid crystal alignment film with a film thickness of 100 nm. Next, the coated surface is irradiated with 313nm linear polarized ultraviolet light of 4.3mW/ ^cm2 at an angle of 40° from the substrate normal direction to obtain ^a substrate with a liquid crystal alignment film. The linear polarized ultraviolet light is modulated by passing the ultraviolet light of a high-pressure mercury lamp through a 313nm bandpass filter and then through a 313nm polarizing plate. Two of the above substrates are prepared, and after 4μm bead spacers are spread on the liquid crystal alignment film of one substrate, a sealant (XN-1500T manufactured by Kyoritsu Chemical Co., Ltd.) is applied. Next, the other substrate is bonded so that the alignment direction facing the liquid crystal alignment film surface becomes 180°, and the sealant is thermally cured at 120°C for 90 minutes to produce a hollow cell. Liquid crystal (MLC-3022 manufactured by Merck) was injected into the empty cell by a reduced pressure injection method to obtain a liquid crystal display element.

<Evaluation of coating properties> The liquid crystal display element obtained above was rotated and coated on the ITO electrode surface of a glass substrate with an ITO electrode formed by an ITO film, dried on a 70°C heating plate for 90 seconds, and the coated surface was observed. The coating surface was evaluated as "poor" when unevenness or bounce occurred, and "good" when there was no dripping or unevenness. The coating properties of the liquid crystal display element were evaluated. The evaluation results are shown in Table 3.

<Evaluation> (Liquid crystal alignment) The liquid crystal display element obtained above was subjected to isotropic treatment at 120°C for 1 hour, and then the unit was observed using a polarizing microscope. The condition where there was no light leakage or poor alignment in some areas, or when a voltage was input to the liquid crystal unit, a uniform liquid crystal drive was obtained was considered good. The evaluation results are shown in Table 4.

(Pre-tilt angle) For the liquid crystal display element manufactured above, the pre-tilt angle of the liquid crystal cell was measured by the Mueller matrix method using AxoScan manufactured by Axo Metrix. The evaluation results are shown in Table 4.

(Voltage holding ratio (VHR) evaluation) The evaluation of VHR is to input a voltage of 1V for 60μs at a temperature of 60°C to the liquid crystal unit produced above, measure the voltage after 1667ms, and calculate the voltage holding ratio to what extent the voltage can be maintained. In addition, the voltage holding ratio measurement device VHR-1 manufactured by Toyo TEKNIKA Corporation was used for the measurement of the voltage holding ratio. The evaluation results are shown in Table 4.

(Evaluation of residual DC) For the liquid crystal unit produced above, an AC voltage of 6.8Vpp and a DC voltage of 1V were input for 48 hours, and the voltage (residual DC) generated in the liquid crystal unit was obtained by the flicker elimination method immediately after the DC voltage was removed. This value was used as an indicator of the residual image characteristic, and a value below ±30mV was evaluated as good. The evaluation results are shown in Table 4.

(Evaluation of tilt angle change) After measuring the pre-tilt angle, a DC voltage of 15V was input into the liquid crystal unit. After 36 hours, the tilt angle was measured again and the tilt angle change was calculated. The evaluation results are shown in Table 4.

From the results in Table 3, it can be seen that, by comparing Examples 1 to 24 with Comparative Examples 4 and 5, the blend of the polymethacrylate solution and the polyamide solution containing no side chain diamine is poor in coating properties. In contrast, the blend of the polyimide solution containing no side chain, the polyamide solution containing side chain, and the polyimide solution can obtain a liquid crystal alignment film with excellent coating properties. In addition, as can be seen from the results in Table 4, by comparing Examples 1 to 24 with Comparative Examples 1 to 6, the polymethacrylate solution is blended with the polyamide solution and the polyimide solution, so that a liquid crystal alignment film with excellent tilt angle change, VHR and residual DC can be obtained. [Industrial Applicability]

The liquid crystal alignment agent of the present invention and the liquid crystal display element using the liquid crystal alignment film obtained therefrom can be suitably used in liquid crystal display elements requiring durability such as those for vehicle use.

Claims (7)

A liquid crystal alignment agent, characterized by comprising (A) a polymer having a photoalignment group represented by the following formula (pa-1) and a thermal crosslinking group A,

(wherein, A represents a pyrimidine-2,5-diyl group, a pyridine-2,5-diyl group, a 2,5-thiophene group, a 2,5-furan group, a 1,4- or 2,6-naphthylene group or a benzene group which may be substituted with fluorine, chlorine, a cyano group, an alkoxy group having 1 to 5 carbon atoms or a linear or branched alkyl residue (which may be substituted with one cyano group or one or more halogen atoms as required), X and Y are each independently a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group or an alkyl group having 1 to 3 carbon atoms, _R1 represents a single bond, an oxygen atom, -COO- or -OCO-, _R2 represents a divalent aromatic group, a divalent alicyclic group, a divalent heterocyclic group or a divalent condensed cyclic group, _R3 represents a single bond, an oxygen atom, -COO- or -OCO-, R ₄ represents a linear or branched alkyl group having 1 to 40 carbon atoms or a monovalent organic group having 3 to 40 carbon atoms and containing an alicyclic group, D represents an oxygen atom or -NR _d - (wherein R _d represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms), a represents an integer of 0 to 3, and * represents a bonding position), (B) a polymer selected from polyimide and its precursor, which is a polymer having at least one group selected from a vertical alignment group and a tert-butyloxycarbonyl group, or a polymer subjected to chemical imidization, and a solvent; the liquid crystal alignment agent is, Z1: the aforementioned (A) polymer further has a thermal crosslinking group B, and/or Z2: further contains (C) a compound having two or more thermal crosslinking groups B in the molecule; the thermal crosslinking group A and the thermal crosslinking group B, each independently, may be the same or different from each other, and are selected from the group consisting of carboxyl group, amino group, alkoxymethylamide group, hydroxymethylamide group, hydroxyl group, group containing epoxy part, cyclobutylene group, thiopropyl group, isocyanate group and blocked isocyanate group, and the thermal crosslinking group A and the thermal crosslinking group B are selected so that they can undergo crosslinking reaction by heat. As in claim 1, the liquid crystal alignment agent, wherein component (B) is a polymer having a vertical alignment group. As in claim 1, the liquid crystal alignment agent, wherein component (B) is a polymer having a tert-butoxycarbonyl group. As in claim 1, the liquid crystal alignment agent, wherein component (B) is a chemically imidized polymer. A liquid crystal alignment film, characterized in that it is formed using a liquid crystal alignment agent as described in any one of claims 1 to 4. A method for manufacturing a liquid crystal alignment film, characterized by comprising the steps of coating a liquid crystal alignment agent as described in any one of claims 1 to 4 on a substrate to form a coating film, and irradiating the coating film with light in a state where the coating film is not in contact with a liquid crystal layer or in a state where the coating film is in contact with a liquid crystal layer. A liquid crystal display element characterized by having a liquid crystal alignment film as in claim 5, or a liquid crystal alignment film obtained by a manufacturing method as in claim 6.