TWI848062B - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element using the same - Google Patents

Abstract

The present invention provides a liquid crystal alignment agent, which can obtain a liquid crystal alignment film with good alignment and good adhesion to a sealant. The liquid crystal alignment agent of the present invention is characterized in that it contains a polymer (A), wherein the polymer (A) has repeating units represented by the following formulas (1), (2), (3) and (4), ( _R1 to _R4 independently represent a hydrogen atom, a halogen atom, an alkyl group or the like, _Y1 represents a divalent organic group having a partial structure represented by formula (H), ^Q3 is a structure represented by -( _CH2 ) _n- , _X2 is a tetravalent organic group having an alicyclic structure having 5 or more members, _Y2 represents a divalent organic group having a partial structure represented by formula (H), _R31 to _R34 are synonymous with the above-mentioned _R1 to _R4 , _X4 is synonymous with _X2 , and _Y3 and _Y4 represent divalent organic groups represented by formula (I)).

Description

Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element using the same

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

Liquid crystal devices have been widely used as display units for personal computers, mobile phones, smart phones, and video receivers. Liquid crystal devices include, for example, the following components: a liquid crystal layer sandwiched between an element substrate and a filter substrate, a pixel electrode and a common electrode for applying an electric field to the liquid crystal layer, an alignment film for controlling the alignment of liquid crystal molecules in the liquid crystal layer, and a thin film transistor (TFT) for switching the electric signal supplied to the pixel electrode. As a method for driving liquid crystal molecules, longitudinal electric field methods such as the TN method and the VA method, and transverse electric field methods such as the IPS method and the FFS (Fringe field switching) method are known.

At present, the most popular liquid crystal alignment film in industry can be produced as follows: using cloth such as cotton, nylon, polyester, etc., to rub the surface of the film formed by polyamide and/or its imidized polyimide formed on the electrode substrate in a single direction, and perform the so-called friction treatment to produce it. The friction treatment is a simple method applicable in industry with excellent productivity. However, with the high performance, high precision and large size of liquid crystal display elements, it has been clearly known that the scratches, dust, mechanical force or static electricity on the surface of the alignment film generated during the friction treatment will cause various problems such as unevenness in the alignment treatment surface. As a liquid crystal alignment treatment method replacing the rubbing treatment, a photo-alignment method is known that imparts alignment energy to the liquid crystal by irradiating polarized radiation. The liquid crystal alignment treatment by the photo-alignment method has been proposed: liquid crystal alignment treatment using photoisomerization reaction, liquid crystal alignment treatment using photocrosslinking reaction, liquid crystal alignment treatment using photodecomposition reaction, etc. (refer to non-patent document 1, patent document 1).

The liquid crystal alignment film, which is a component of the liquid crystal display element, is a film used to evenly arrange the liquid crystal. However, it is not only the uniformity of the liquid crystal alignment, but also various characteristics are required. For example, the voltage driving the liquid crystal causes the charge to accumulate in the liquid crystal alignment film, which affects the display in the form of afterimage or burning (hereinafter referred to as afterimage from residual DC), and there are problems such as a significant reduction in the display quality of the liquid crystal display element. Therefore, a liquid crystal alignment agent that overcomes these problems is proposed (see patent document 2).

Furthermore, in the IPS method or FFS driving method, the stability of the liquid crystal alignment is also important. If the stability of the liquid crystal alignment is low, the liquid crystal will not be able to return to the initial state when the liquid crystal is driven for a long time, which will cause a decrease in contrast or burn-in (hereinafter referred to as AC afterimage). As a method for solving the above problem, a specific liquid crystal alignment agent is disclosed in Patent Document 3.

Furthermore, with the popularity of tablets and smartphones, the development of liquid crystal display elements with narrow frames is continuing, which can ensure that the display area is as wide as possible. Due to the narrow frame, the sealant must be applied to the liquid crystal alignment film, so patent document 4 discloses a liquid crystal alignment agent that can maintain the liquid crystal alignment and has good adhesion with the sealant. [Prior technical document] [Patent document]

[Patent Document 1] Japanese Patent Publication No. 9-297313 [Patent Document 2] International Publication No. 2005/083504 [Patent Document 3] International Publication No. 2015/050135 [Patent Document 4] International Publication No. 2015/060360 [Non-Patent Document]

[Non-patent document 1] "Liquid crystal photo-alignment film" Kidowaki, Ichimura, Functional Materials, November 1997, Vol. 17, No. 11, pages 13-22

[The problem that the invention wants to solve]

In addition, the demand for high-precision liquid crystal display elements is increasing, and it is more important than ever to show good display quality. The present invention is completed in view of the above situation. The main purpose of the present invention is to provide a liquid crystal alignment agent, which can obtain: a liquid crystal alignment film with good liquid crystal alignment and good adhesion to a sealant, and a liquid crystal display element that can be miniaturized and show good display quality due to the good adhesion between the liquid crystal alignment film and the sealant. [Means for solving the problem]

As a result of in-depth research, the inventors found that the above-mentioned problem can be solved by using a liquid crystal alignment agent containing a polymer component having a specific repeating unit, thereby completing the present invention. The present invention is an invention with the following gist. A liquid crystal alignment agent is characterized in that it contains a polymer (A), and the aforementioned polymer (A) has a repeating unit represented by the following formula (1), the following formula (2), the following formula (3) and the following formula (4). ( _R1 to _R4 are independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group, and _R1 to _R4 may be the same or different, but at least one of _R1 to _R4 represents a group other than a hydrogen atom in the above definition, and _Y1 represents a divalent organic group having a partial structure represented by the following formula (H)) (Q ³ is a structure represented by -(CH ₂ ) _n - (n is an integer of 2 to 20), any -CH ₂ - may be substituted by a group selected from -O- and -C(＝O)-, but the oxygen atoms are not directly bonded to each other, and any hydrogen atoms on the two benzene rings may be substituted by a monovalent organic group, and * indicates a bond) ( _X2 is a tetravalent organic group having an alicyclic structure having 5 or more ring members, and _Y2 is a divalent organic group having a partial structure represented by the above formula (H)) (R ₃₁ to R ₃₄ in formula (3) are synonymous with R ₁ to R ₄ in formula (1), respectively; X ₄ in formula (4) is synonymous with X ₂ in formula (2); Y ₃ and Y ₄ represent a divalent organic group represented by the following formula (I)) (＊indicates a key). [Effect of invention]

According to the liquid crystal alignment agent of the present invention, a liquid crystal alignment film having good liquid crystal alignment and good adhesion to the sealant can be obtained, and a liquid crystal display element having a good display quality and capable of further miniaturization of the frame due to the good adhesion between the liquid crystal alignment film and the sealant can be obtained.

[Best Mode for Carrying Out the Invention]

The following describes the components contained in the liquid crystal alignment agent of the present invention and other components that can be arbitrarily formulated as needed. ＜Polymer (A)＞ The liquid crystal alignment agent of the present invention contains a polymer (A), and the polymer (A) has the repeating units represented by the above formula (1), the above formula (2), the above formula (3), and the above formula (4). By setting such a structure, a liquid crystal alignment film with less AC afterimage can be obtained, and a liquid crystal display element with excellent contrast can be obtained.

In the above formulae (1) and (2), X ₂ , Y ₁ , Y ₂ , R ₁ , R ₂ , R ₃ , and R ₄ are as defined above.

As specific examples of the alkyl group having 1 to 6 carbon atoms in the above R ₁ to R ₄ , there can be mentioned a methyl group, an ethyl group, a propyl group, an i-propyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group, an n-pentyl group, etc. As specific examples of the alkenyl group having 2 to 6 carbon atoms in R ₁ to R ₄ , there can be mentioned a vinyl group, a propenyl group, a butenyl group, etc., which can be in a straight chain or a branched form. As specific examples of the alkynyl group having 2 to 6 carbon atoms in the above R ₁ to R ₄ , there can be mentioned an ethynyl group, a 1-propynyl group, a 2-propynyl group, etc. As the halogen atom in the above R ₁ to R ₄ , there can be mentioned a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. As the monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, there can be mentioned a fluoromethyl group, a trifluoromethyl group, etc. From the viewpoint of high photoreactivity, R ₁ to R ₄ are hydrogen atoms or methyl groups, preferably at least one of R ₁ to R ₄ is a methyl group, and more preferably at least two of R ₁ to R ₄ are methyl groups. More preferably, R ₁ and R ₄ are methyl groups, and R ₂ and R ₃ are hydrogen atoms.

Specific examples of the monovalent organic group that replaces any hydrogen atom on the benzene ring in the above formula (H) include a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, and a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, and the structures exemplified by the above R ₁ to R _4. From the viewpoint of less generation of AC afterimages as a partial structure represented by the above formula (H), a partial structure represented by any of the following formulas (H-1) to (H-7) can be cited.

As a preferred specific example of _Y1 in the above formula (1), from the viewpoint of less generation of AC afterimage, there can be mentioned a divalent organic group represented by any one of the following formulas (h-1) to (h-8).

From the viewpoint of improving heat resistance, the polymer (A) has a repeating unit represented by the above formula (2). As the tetravalent organic group of _X2 in formula (2), a tetravalent organic group having an alicyclic structure with 5 to 8 ring members is preferred, and a tetravalent organic group having an alicyclic structure with 5 to 7 ring members is more preferred. In addition, the so-called alicyclic structure with 5 or more ring members means that when the alicyclic structure to which the imide group is bonded is a polycyclic structure, the number of atoms constituting each ring contained in the polycyclic structure is 5 or more. Furthermore, the alicyclic structure mentioned above only needs to be bonded to at least one of the two imide groups, and may have a chain hydrocarbon structure or an aromatic ring structure at the same time as the alicyclic structure.

As a preferred specific example of _X2 , a tetravalent organic group represented by any one of the following formulas (X2-1) to (X2-12) can be cited.

_X2 in formula (2) is preferably any one of (X2-1) to (X2-4) from the viewpoint of reducing the generation of AC afterimages and improving the contrast of the liquid crystal display device. Preferred specific examples of _Y2 in formula (2) are the same as the preferred specific examples of _Y1 in formula (1).

From the viewpoint of reducing AC afterimage, the polymer (A) preferably contains 1 to 95 mol% of the repeating units represented by the above formula (1) and the repeating units represented by the above formula (2) relative to all repeating units, and more preferably 5 to 90 mol%. In addition, the ratio ((1):(2)) of the repeating units represented by the above formula (1) and the repeating units represented by the above formula (2) in the polymer (A) is preferably 70:30 to 99:1, more preferably 75:25 to 98:2, and even more preferably 80:20 to 97:3.

From the viewpoint of improving the contrast and sealing tightness of the liquid crystal display element, the polymer (A) has the repeating unit represented by the above formula (3) and the repeating unit represented by the above formula (4). From the viewpoint of reducing AC afterimage, the polymer (A) preferably contains 5 to 99 mol% of the repeating unit represented by the above formula (3) and the repeating unit represented by the above formula (4) in total, and more preferably contains 10 to 95 mol% relative to all the repeating units. The ratio ((3):(4)) of the repeating unit represented by the above formula (3) and the repeating unit represented by the above formula (4) in the polymer (A) is preferably 70:30 to 99:1, more preferably 75:25 to 98:2, and even more preferably 80:20 to 97:3.

The ratio ((1):(3)) of the repeating units represented by the above formula (1) and the repeating units represented by the above formula (3) in the polymer (A) is preferably 1:99 to 99:1, more preferably 5:95 to 80:20, and even more preferably 10:90 to 70:30. The ratio ((2):(4)) of the repeating units represented by the above formula (2) and the repeating units represented by the above formula (4) in the polymer (A) is preferably 1:99 to 99:1, more preferably 5:95 to 80:20, and even more preferably 10:90 to 70:30.

The polymer (A) preferably contains 6 to 100 mol % of the repeating units represented by the above formula (1), formula (2), formula (3) and formula (4) in total, and more preferably contains 15 to 100 mol % of the repeating units in total, based on all the repeating units in the polymer (A).

From the viewpoint of further improving the adhesion with the sealant, the polymer (A) may have at least one type of repeating unit selected from the group consisting of a repeating unit represented by the following formula (5) and a repeating unit represented by the following formula (6). ( _R51 to _R54 are synonymous with _R1 to _R4 (including preferred specific examples) in the above formula (1), _Y5 and _Y6 are independently a divalent organic group having a partial structure represented by the following formula (J-1) or a divalent organic group represented by the following formula (J-2), and _X6 in formula (6) is synonymous with _X2 in the above formula (2))

In the above formula (J-1) and formula (J-2), _Q5 is a single bond, -( _CH2 ) _n- (n is an integer of 1 to 20) or a group in which any _-CH2- of -( _CH2 ) _n- is substituted with -O-, -COO-, -OCO-, _-NQ9- , _-NQ9CO- , _-CONQ9- , _-NQ9CONQ10- , _-NQ9COO- or -OCOO- under non-adjacent conditions. _Q9 and _Q10 each independently represent a hydrogen atom or a monovalent organic group. Furthermore, _Q6 and _Q7 each independently represent -H, -NHD, -N(D) ₂ , a group having -NHD or _a group having -N(D) ₂ . _Q8 represents -NHD, -N(D) ₂ , a group having -NHD or a group having -N(D) ₂ . D represents a carbamate protecting group, and examples of the carbamate protecting group include tert-butyloxycarbonyl and 9-fluorenylmethoxycarbonyl. However, at least one of _Q5 , _Q6 and _Q7 has a carbamate protecting group in the group. *1 represents a bonding bond.

Preferred specific examples of Y ₅ and Y ₆ include divalent organic groups represented by any of the following formulae (J-1-a) to (J-1-d) and (J-2-1) from the viewpoint of less AC afterimage. Boc represents a tert-butoxycarbonyl group.

In addition to the repeating units represented by the above formulae (1) to (4) and the repeating units represented by the above formulae (5) and (6), the polymer (A) may further have at least one repeating unit selected from the group consisting of the repeating units represented by the following formulae (PI-A-1) and the repeating units represented by (PA-1).

In formula (PI-A-1), X _I1 represents a tetravalent organic group, and Y _I1 represents a divalent organic group. However, when X _I1 is synonymous with the tetravalent organic group represented by the following formula (g) or X ₂ in the above formula (2), Y _I1 represents a structure other than a divalent organic group having a partial structure represented by the above formula (H), a divalent organic group represented by the above formula (I), a divalent organic group having a partial structure represented by the above formula (J-1), or a divalent organic group represented by the above formula (J-2). Examples of X _I1 include, in addition to the tetravalent organic group represented by the following formula (g) and the tetravalent organic group exemplified by _X2 in the above formula (2), a tetravalent organic group represented by any of the following formulas (X _I1-1 ) to (X _I1-13 ), a tetravalent organic group derived from an aromatic tetracarboxylic dianhydride, and the like. (R ₁ , R ₂ , R ₃ , and R ₄ are synonymous with R ₁ , R ₂ , R ₃ , and R ₄ in the above formula (1))

The aromatic tetracarboxylic dianhydride to which the tetravalent organic group of _X11 is given is an acid dianhydride obtained by intramolecular dehydration of a carboxyl group bonded to an aromatic ring such as a benzene ring or a naphthalene ring. Specific examples include a tetravalent organic group represented by any one of the following formulas (X3-1) to (X3-2) and a tetravalent organic group represented by any one of the following formulas (Xr-1) to (Xr-7). (x and y are independently a single bond, ether (-O-), carbonyl (-CO-), ester (-COO-), an alkanediyl group having 1 to 5 carbon atoms, 1,4-phenylene, sulfonyl or amide, j and k are 0 or 1, and * represents a bond)

In formula (PI-A-1), as a specific example of the divalent organic group of Y _I1 , in addition to the divalent organic group having a partial structure represented by the above formula (H), the divalent organic group represented by the above formula (I), the divalent organic group having a partial structure represented by the above formula (J-1), and the divalent organic group represented by the above formula (J-2), a divalent organic group represented by any one of the following formulas (o-1) to (o-23), a base represented by any one of the formulas (Y-1) to (Y-167) described in International Publication (hereinafter also referred to as WO) 2018/117239, etc.

In formula (PA-1), X _A1 represents a tetravalent organic group, and Y _A1 represents a divalent organic group. Specific examples of X _A1 include the structures exemplified by X _I1 in the above formula (PI-A-1). Specific examples of Y _A1 include the structures exemplified by Y _I1 in the above formula (PI-A-1).

In formula (PA-1), _RA1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. _ZA11 and _ZA12 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, an alkenyl group having 2 to 10 carbon atoms which may have a substituent, an alkynyl group having 2 to 10 carbon atoms which may have a substituent, a tert-butoxycarbonyl group, or a 9-fluorenylmethoxycarbonyl group.

Specific examples of the alkyl group having 1 to 5 carbon atoms in the above-mentioned R _A1 include methyl, ethyl, propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, etc. From the viewpoint of the ease of imidization by heating, R ₁ is preferably a hydrogen atom or a methyl group.

Specific examples of the alkyl group having 1 to 10 carbon atoms in Z _A11 and Z _A12 include, in addition to the specific examples of the alkyl group having 1 to 5 carbon atoms exemplified in R ₁ , hexyl, heptyl, octyl, nonyl, decyl, and the like. Specific examples of the alkenyl group having 2 to 10 carbon atoms in Z _A11 and Z _A12 include vinyl, propenyl, butenyl, and the like, which may be in a linear or branched form. Specific examples of the alkynyl group having 2 to 10 carbon atoms in Z _A11 and Z _A12 include ethynyl, 1-propynyl, 2-propynyl, and the like. Z _A11 and Z _A12 may have a substituent, and examples of the substituent include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), hydroxyl, cyano, alkoxy, and the like.

When the polymer A contains the repeating units represented by the formula (5) and the repeating units represented by the formula (6), the ratio ((5):(6)) is preferably 70:30 to 99:1, more preferably 75:25 to 98:2, and even more preferably 80:20 to 97:3.

The polymer (A) preferably contains 1 to 40 mol% of the repeating units represented by the above formula (5) and the repeating units represented by the above formula (6) relative to all repeating units of the polymer (A), more preferably 1 to 30 mol%, and more preferably 5 to 30 mol%. In this case, the polymer (A) preferably contains 6 to 99 mol% of the repeating units represented by the above formula (1), formula (2), formula (3) and formula (4) relative to all repeating units of the polymer (A), more preferably 15 to 99 mol%, and even more preferably 15 to 95 mol%.

<Second polymer> The liquid crystal alignment agent of the present invention is a composition containing the above-mentioned polymer (A) and an organic solvent, and may also contain two or more polymers (A) with different structures. In addition, the liquid crystal alignment agent of the present invention may also contain polymers other than polymer (A) (hereinafter also referred to as the second polymer) or various additives. If the liquid crystal alignment agent of the present invention contains the second polymer, the content ratio of polymer (A) relative to all polymer components is preferably 5% by mass or more, preferably 5 to 95% by mass, and more preferably 10 to 90% by mass.

Examples of the second polymer include polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivatives, polyacetal, polystyrene or its derivatives, poly(styrene-maleimide) derivatives, and poly(meth)acrylate.

As the second polymer, a polyamide obtained from a tetracarboxylic dianhydride component and a diamine component (hereinafter also referred to as a second polyamide) is particularly preferred.

Examples of the tetracarboxylic dianhydride component for obtaining the second polyamic acid include compounds represented by the following formula (11): The tetracarboxylic dianhydride component may be composed of two or more types of compounds. (A is a tetravalent organic group, preferably a tetravalent organic group having 4 to 30 carbon atoms)

The following are examples of preferred A, but the invention is not limited thereto.

Among the above, (A-1) and (A-2) are preferred from the perspective of further improving the photo-orientation property, (A-4) is preferred from the perspective of further improving the relaxation rate of accumulated charges, and (A-15) to (A-17) are preferred from the perspective of further improving the liquid crystal orientation property and the relaxation rate of accumulated charges.

The diamine component for obtaining the second polyamine acid can be appropriately determined according to the purpose, and for example, a diamine represented by the following formula (12) can be used. (Y ₉ represents a divalent organic group, and two A _9s are independently a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms. From the viewpoint of liquid crystal alignment, A ₉ is preferably a hydrogen atom or a methyl group)

For the purpose of improving electrical properties or relaxing properties, _Y9 is preferably a divalent organic group having a secondary or tertiary nitrogen atom, or a divalent organic group having -NH-CO-NH- in the molecule. When _Y9 is a divalent organic group having a secondary or tertiary nitrogen atom, specific examples of the diamine represented by formula (12) include any of the following diamines (a) to (d).

(a) The diamine having a pyrrole structure described in WO2017/126627 is preferably a diamine having a structure represented by the following formula (pr). ( ^R1 represents a hydrogen atom, a fluorine atom, a cyano group, a hydroxyl group or a methyl group, two ^R2s each independently represent a single bond or the group "*1- ^R3 -Ph-*2", ^R3 represents a divalent organic group selected from a single bond, -O-, -COO-, -OCO-, -( _CH2 ) _1- , -O( _CH2 ) _mO- , -CONH- and -NHCO-, l and m represent integers of 1 to 5, *1 represents a site bonded to the benzene ring in formula (pr), *2 represents a site bonded to the amino group in formula (pr), Ph represents a phenylene group, and n is 1 to 3)

(b) The diamine having a pyrrole structure described in WO2018/062197 is preferably a diamine having a structure represented by the following formula (pn).

( ^R1 and ^R2 each independently represent a hydrogen atom or a methyl group, ^R3 represents a single bond or a group "*1- ^R4 -Ph-*2", ^R4 represents a divalent organic group selected from a single bond, -O-, -COO-, -OCO-, -( _CH2 ) _1- , -O( _CH2 ) _mO- , -CONH- and -NHCO- (l and m represent integers of 1 to 5), *1 represents a site bonded to the benzene ring in formula (pn), *2 represents a site bonded to the amino group in formula (pn), Ph represents a phenylene group, and n represents 1 to 3)

(c) The diamine having a carbazole structure described in WO2018/110354 is preferably a diamine having a structure represented by the following formula (cz). ( ^R1 represents a hydrogen atom or a methyl group, ^R2 represents a methyl group)

(d) a diamine having a nitrogen-containing heterocyclic ring as described in [0173] to [0188] in WO2015/046374 or a diamine having a nitrogen-containing structure as described in [0050] in JP-A-2016-218149, or a diamine represented by the following formula (BP), (X is a biphenyl ring or a fluorene ring, Y is a group selected from a benzene ring, a biphenyl ring or -Ph-Z-Ph-, Ph represents a phenylene group, and Z is -O-, -NH-, -CH ₂ -, -SO ₂ -, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -represented by a divalent group, A and B are hydrogen atoms or methyl groups), 2,3-diamino arsenic, 2,6-diamino arsenic, 3,4-diamino arsenic, 2,4-diamino pyrimidine, 5,6-diamino-2,3-dicyano pyrazine, 5,6-diamino-2,4-dihydroxy pyrimidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, 1,4-bis(3-aminopropyl)piperazine, 4,4'-[4,4'-propane-1,3-diylbis(piperidin-1,4-diyl)]bisaniline, 2,4-diamino-6-isopropoxy-1,3,5-triazine, 2,4-diamino-6-methoxy-1,3,5-triazine, 2,4-diamino-6-phenyl- 1,3,5-triazine, 2,4-diamino-6-methyl-1,3,5-triazine, 2,4-diamino-1,3,5-triazine, 4,6-diamino-2-vinyl-1,3,5-triazine, 3,5-diamino-1,2,4-triazole, 6,9-diamino-2-ethoxyacridine lactate, 3,8-diamino-6-phenylphenanthene, 1,4-diaminopiperazine, 3,6-diaminoacridine, bis(4-aminophenyl)-N-phenylamine, 4,4'-diphenyl-N-methylamine, 4,4'-diaminodiphenylamine, 3,6-diaminocarbazole, 9-methyl-3,6-diaminocarbazole, 9-ethyl-3,6-diaminocarbazole, or a diamine represented by the following formula (w1) or (w2).

(Sp represents phenylene, pyrrolidine, piperidine, piperazine, a divalent chain hydrocarbon group having 2 to 20 carbon atoms, or a group in which _-CH2- of the divalent chain hydrocarbon group is substituted with a group selected from -O-, -CO-, -CO-O-, -NRCO- (R represents a hydrogen atom or a methyl group), -NRCOO- (R represents a hydrogen atom or a methyl group), -CONR- (R represents a hydrogen atom or a methyl group), -COS-, -NR- (R represents a methyl group), pyrrolidine, piperidine and piperazine).

When _Y9 is a divalent organic group having -NH-CO-NH- in the molecule, specific examples of the diamine represented by the above formula (12) include a diamine in which _A1 is -NH-CO-NH-, or a diamine in which _A1 is an alkylene group having 2 to 20 carbon atoms in which at least one _-CH2- is substituted with -NH-CO-NH-, or a diamine in which _A1 is an alkylene group having 2 to 20 carbon atoms in which at least one _-CH2- is substituted with -NH-CO-NH-, and the other _-CH2- is substituted with -NH-CO-NH-. - is substituted with a group selected from -O-, -CO-, -CO-O-, -NRCO- (R represents a hydrogen atom or a methyl group), -NRCOO- (R represents a hydrogen atom or a methyl group), -CONR- (R represents a hydrogen atom or a methyl group), -COS- and -NR- (R represents a methyl group). A specific example of a more preferred diamine is a diamine represented by any one of the following formulas (U-1) to (U-9).

( _A1 represents a single bond, -NH-CO-NH-, or an alkylene group having 2 to 20 carbon atoms (however, _{any -CH2-} in the alkylene group may be substituted by -O-, -CO-, -CO-O-, -NRCO- (R represents a hydrogen atom or a methyl group), -NRCOO- (R represents a hydrogen atom or a methyl group), -CONR- (R represents a hydrogen atom or a methyl group), -COS-, -NR- (R represents a methyl group) or -NH-CO-NH-), _A2 represents a halogen atom, a hydroxyl group, or an alkyl or alkoxy group having 1 to 5 carbon atoms (any hydrogen atom in the above alkyl or alkoxy group may be substituted by a halogen atom), a is an integer of 0 to 4, and when a is 2 or more, _A2 may be the same or different, and b and c are integers of 1 or 2)

Preferred specific examples of the diamine represented by the above formula (w1) or (w2) include diamines represented by any one of the following formulas (n3-1) to (n3-7), diamines represented by any one of the following formulas (n4-1) to (n4-6), and the like.

For the purpose of improving printability, diamines having a carboxyl group (COOH group) or a hydroxyl group (OH group) may be used. Specifically, 2,4-diaminophenol, 3,5-diaminophenol, 3,5-diaminobenzyl alcohol, 2,4-diaminobenzyl alcohol, 4,6-diaminoresorcinol, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid or 3,5-diaminobenzoic acid may be mentioned. Among them, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid or 3,5-diaminobenzoic acid is preferred. In addition, diamines represented by the following formulas [3b-1] to [3b-4], or diamines in which the amine groups are secondary amine groups, may be used.

In the formula [3b-1], ^Q1 represents a single bond, _-CH2- , _{-C2H4- ,} -C( _CH3 ) _2- , _-CF2- , -C( _CF3 ) _2- , -O-, -CO-, -NH-, -N( _CH3 )-, -CONH-, -NHCO-, -CH2O-, -OCH2-, -COO-, -OCO-, -CON( _CH3 )- or N( _CH3 )CO-, ^m1 and ^m2 each independently represent an integer of 0 to 4, and m1 + m2 each independently represents an integer of 1 to 4. In the formula [ ^3b _{- 2} ], ^m3 and ^m4 each independently represent an integer of 1 to 5. In the formula [3b-3], ^Q2 represents a linear or branched alkylene group having 1 to 5 carbon atoms, ^{and m5} represents an integer of 1 to 5. In formula [3b-4], ^Q3 and ^Q4 independently represent a single bond, _-CH2- , _-C2H4- , -C( _CH3 ) _2- , _-CF2- , -C( _CF3 ) _2- , -O-, -CO-, -NH-, -N( _CH3 )-, -CONH-, -NHCO-, _-CH2O- , _{-OCH2- ,} -COO-, -OCO, -CON( _CH3 )- or -N( _CH3 )CO-, and ^m6 represents an integer of 1 to 4)

As the diamine component for obtaining the second polyamine, in addition to the above, the diamine used for obtaining the polymer (A) or a known diamine can be used. The diamine component for obtaining the second polyamine may be a combination of two or more diamines.

<Methods for producing polyamic acid, polyamic acid ester and polyimide> The polyamic acid ester, polyamic acid and polyimide used as the polyimide precursor in the present invention can be produced according to a known method such as that described in WO2013/157586.

<Liquid crystal alignment agent> The liquid crystal alignment agent of the present invention may contain other polymers in addition to the polymer (A) and the desired second polymer. Examples of other polymers include polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivative, polyacetal, polystyrene or its derivative, poly(styrene-maleimide) derivative, poly(meth)acrylate, etc.

The liquid crystal alignment agent is used to make a liquid crystal alignment film, so from the perspective of forming a uniform film, it takes the form of a coating liquid. Among the liquid crystal alignment agents of the present invention, a coating liquid containing the above-mentioned polymer components and an organic solvent is also preferred. At this time, the concentration (content) of the polymer in the liquid crystal alignment agent can be appropriately changed according to the setting of the thickness of the coating to be formed. From the perspective of forming a uniform and defect-free coating, 1% by mass or more is preferred, and from the perspective of the storage stability of the solution, 10% by mass or less is preferred. The particularly preferred polymer concentration is 2~8% by mass.

The organic solvent contained in the liquid crystal alignment agent is not particularly limited as long as it is a solvent (also called a good solvent) that can uniformly dissolve the polymer component. Specific examples include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethylsulfoxide, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, and the like. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide or γ-butyrolactone is preferred. The good solvent is preferably 20-99 mass % of the total solvent contained in the liquid crystal alignment agent, more preferably 20-90 mass %, and particularly preferably 30-80 mass %.

Furthermore, the organic solvent contained in the liquid crystal alignment agent is preferably a mixed solvent containing, in addition to a good solvent, a solvent (also called a poor solvent) that improves the coating property when the liquid crystal alignment agent is applied or the surface smoothness of the coating film. Specific examples of poor solvents are given below, but are not limited to these examples. For example, diisopropyl ether, diisobutyl ether, diisobutyl carbinol (2,6-dimethyl-4-heptanol), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, 4-hydroxy-4-methyl-2-pentanone, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethyl carbonate, ethylene glycol monobutyl ether, ethylene glycol monoisopentyl ether, ethylene glycol monohexyl ether, propylene glycol monobutyl ether, 1-(2-butoxyethoxy)-2-propanol, 2-(2-butoxyethoxy)-2-propanol, oxy)-1-propanol, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, propylene glycol diacetate, n-butyl acetate, propylene glycol monoethyl ether, 3-methoxypropionic acid methyl ester, 3-ethoxypropionic acid ethyl ester, 3-methoxypropionic acid ethyl ester, 3-methoxypropionic acid propyl ester, 3-methoxypropionic acid butyl ester, n-butyl lactate, isoamyl lactate, diethylene glycol monoethyl ether, diisobutyl ketone (2,6-dimethyl-4-heptanone), and the like.

As for the poor solvent, diisobutyl carbinol, propylene glycol monobutyl ether, propylene glycol diacetate, diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, and diisobutyl ketone are preferred.

As a preferred solvent combination of a good solvent and a poor solvent, there can be cited: N-methyl-2-pyrrolidone and ethylene glycol monobutyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone and ethylene glycol monobutyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone and propylene glycol monobutyl ether; N-ethyl-2-pyrrolidone and propylene glycol monobutyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone, 4-hydroxy-4-methyl-2-pentanone and diethylene glycol diethyl ether; N-methyl- 2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and 2,6-dimethyl-4-heptanone; N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and diisopropyl ether; N-methyl-2-pyrrolidone, γ-butyrolactone, propylene glycol monobutyl ether and 2,6-dimethyl-4-heptanol; N-methyl-2-pyrrolidone, γ-butyrolactone and dipropylene glycol dimethyl ether; N-methyl-2-pyrrolidone, propylene glycol monobutyl ether and dipropylene glycol dimethyl ether. The poor solvent is preferably 1-80% by mass of the total solvent contained in the liquid crystal alignment agent, more preferably 10-80% by mass, and particularly preferably 20-70% by mass. The type and content of such solvents can be appropriately selected according to the coating equipment, coating conditions, coating environment, etc. of the liquid crystal alignment agent.

The liquid crystal alignment agent of the present invention may also contain additional components other than the polymer component and the organic solvent. Such additional components include: an adhesion promoter for improving the adhesion between the liquid crystal alignment film and the substrate or between the liquid crystal alignment film and the sealant, a compound for improving the strength of the liquid crystal alignment film (hereinafter also referred to as a cross-linking compound), a dielectric or conductive substance for adjusting the dielectric constant or resistance of the liquid crystal alignment film, etc.

As the above-mentioned crosslinking compound, from the viewpoint of less generation of AC afterimage and high improvement effect of film strength, it is preferred to be: a compound having at least one group selected from the group consisting of an oxiranyl group, an oxetanyl group, a protected isocyanate group, a protected isothiocyanate group, a group containing an oxazoline ring structure, a group containing a Meldrum's acid structure, a cyclic carbonate group, and a group represented by the following formula (d), or a compound represented by the following formula (e) (hereinafter collectively referred to as compound (C)). (R ₇₁ is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or "*-CH ₂ -OH", R ₇₂ and R ₇₃ are independently a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or "*-CH ₂ -OH", * represents a bond, A represents an (m+n)-valent organic group having an aromatic ring, m represents an integer of 1 to 6, and n represents an integer of 0 to 4)

As specific examples of compounds having an oxirane group, compounds having two or more oxirane groups, such as compounds described in [0037] of Japanese Patent Laid-Open No. 10-338880 or compounds having a triazine ring in the skeleton described in WO2017/170483, can be cited. Among them, nitrogen-containing compounds such as N,N,N',N'-tetraglycidyl-m-xylene diamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-p-phenylenediamine, and compounds represented by any one of the following formulas (r-1) to (r-3) are particularly preferred.

Specific examples of the compound having an oxacyclobutane group include compounds having two or more oxacyclobutane groups described in [0170] to [0175] in WO2011/132751.

As specific examples of compounds having protected isocyanate groups, compounds having two or more protected isocyanate groups described in [0046] to [0047] of Japanese Patent Application Laid-Open No. 2014-224978, compounds having three or more protected isocyanate groups described in [0119] to [0120] of WO2015/141598, etc. can be cited. Among them, compounds represented by any one of the following formulas (bi-1) to (bi-3) are preferred.

As a specific example of a compound having a protected isothiocyanate group, a compound having two or more protected isothiocyanate groups described in Japanese Patent Publication No. 2016-200798 can be cited. As a specific example of a compound containing an oxazoline ring structure, a compound containing two or more oxazoline structures described in [0115] in Japanese Patent Publication No. 2007-286597 can be cited.

As specific examples of compounds having a group containing a Michaelis acid structure, compounds having two or more Michaelis acid structures described in WO2012/091088 can be cited. As specific examples of compounds having a cyclic carbonate group, compounds described in WO2011/155577 can be cited. As alkyl groups having 1 to 3 carbon atoms in R ₁ , R ₂ , and R ₃ in the group represented by the above formula (d), methyl, ethyl, and propyl can be cited.

As specific examples of compounds having a group represented by the above formula (d), compounds having two or more groups represented by the above formula (d) described in WO2015/072554 or Japanese Patent Application Laid-Open No. 2016-118753 [0058], compounds described in Japanese Patent Application Laid-Open No. 2016-200798, etc. are cited. Among them, compounds represented by any one of the following formulas (hd-1) to (hd-8) are preferred.

As the (m+n)-valent organic group having an aromatic ring of A in the above formula (e), there can be mentioned: an (m+n)-valent aromatic hydrocarbon group having 5 to 30 carbon atoms, an (m+n)-valent organic group obtained by directly or via a linking group bonding an aromatic hydrocarbon group having 5 to 30 carbon atoms, and an (m+n)-valent group having an aromatic heterocyclic ring. Examples of the above aromatic hydrocarbon group include benzene and naphthalene. Examples of the aromatic heterocyclic ring include a pyrrole ring, an imidazole ring, a pyrazole ring, a pyridine ring, a pyrimidine ring, a quinoline ring, an isoquinoline ring, a carbazole ring, a tantalum ring, and the like. Ring, pyrazine ring, benzimidazole ring, benzimidazole ring, indole ring, quinone ring As the above-mentioned linking group, there can be cited: an alkylene group having 1 to 10 carbon atoms or a group obtained by removing a hydrogen atom from the above-mentioned alkylene group; a divalent or trivalent cyclohexane ring, etc. Moreover, any hydrogen atom of the above-mentioned alkylene group can be substituted by an organic group such as a fluorine atom or a trifluoromethyl group. If a specific example is given, the compounds described in WO2010/074269 can be cited. As a preferred specific example, any one of the following formulas (e-1) to (e-9) can be cited.

The above-mentioned compound is an example of a crosslinking compound, but is not limited thereto. For example, the components other than those disclosed in [0105] to [0116] of WO2015/060357 can be cited. In addition, the crosslinking compound contained in the liquid crystal alignment agent of the present invention can be used in combination of two or more types. The content of the crosslinking compound in the liquid crystal alignment agent of the present invention is preferably 0.5 to 20 parts by mass relative to 100 parts by mass of the polymer component contained in the liquid crystal alignment agent. From the perspective of allowing the crosslinking reaction to proceed and exhibit the intended effect and generating less AC afterimages, it is preferably 1 to 15 parts by mass.

Examples of the adhesion aid include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, 2-aminopropyltrimethoxysilane, 2-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-ethoxycarbonyl-3-aminopropyltrimethoxysilane, N-ethoxy Carbonyl-3-aminopropyl triethoxysilane, N-triethoxysilylpropyl triethylenetriamine, N-trimethoxysilylpropyl triethylenetriamine, 10-trimethoxysilyl-1,4,7-triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate, N-benzyl-3-aminopropyl trimethoxysilane, N-benzyl-3-aminopropyl triethoxysilane, N-phenyl-3-aminopropyl trimethoxysilane, N-phenyl- 3-aminopropyl triethoxysilane, N-bis(ethylene oxide)-3-aminopropyl trimethoxysilane, N-bis(ethylene oxide)-3-aminopropyl triethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 3-glycidyloxypropyl methyl dimethoxysilane, 3-glycidyloxypropyl trimethoxysilane, 3-glycidyloxypropyl methyl diethoxysilane, 3-glycidyloxypropyl triethoxysilane, p Silane coupling agents include 3-(trimethoxysilyl)propylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-butylpropylmethyldimethoxysilane, 3-butylpropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane. The amount of the silane coupling agent used is preferably 0.1-30 parts by weight, more preferably 0.1-20 parts by weight, relative to 100 parts by weight of the polymer component contained in the liquid crystal alignment agent, from the viewpoint of minimizing the generation of AC afterimages.

<Method for manufacturing liquid crystal alignment film> The liquid crystal alignment film using the liquid crystal alignment agent of the present invention can be manufactured as follows: using the liquid crystal alignment agent of the present invention and using a known method for obtaining a liquid crystal alignment film from the liquid crystal alignment agent. The liquid crystal alignment film using the liquid crystal alignment agent of the present invention can be manufactured more efficiently by sequentially performing the following steps (1), (2), and (3), and then preferably performing step (4).

<Step (1)> A step of applying the liquid crystal alignment agent of the present invention on a substrate. The substrate on which the liquid crystal alignment agent is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, an acrylic substrate, a plastic substrate such as a polycarbonate substrate, etc. may also be used. At this time, from the perspective of simplifying the process, it is preferred to use a substrate formed with an ITO electrode or the like for driving the liquid crystal. In addition, in a reflective liquid crystal display element, if only a single-sided substrate is used, an opaque material such as a silicon wafer may be used, and in this case, the electrode may be a light-reflecting material such as aluminum. In industry, the method of applying the liquid crystal alignment agent generally includes screen printing, flat plate printing, flexographic printing, or inkjet printing. As other coating methods, there are also dipping method, roll coating method, slit coating method, rotary method or spray method, etc., which can be used according to the purpose.

<Step (2)> Step (2) is a step of heating the coating film of the liquid crystal alignment agent obtained in step (1). After the liquid crystal alignment agent is coated on the substrate, the solvent can be evaporated or the amide or amide ester in the polymer can be thermally imidized by heating means such as a heating plate, a heat circulation oven or an IR (infrared) oven. The drying and calcining steps after coating the liquid crystal alignment agent can be selected at any temperature and time, and can also be performed multiple times. The temperature of the organic solvent used to remove the liquid crystal alignment agent can be, for example, 40 to 150°C. From the perspective of shortening the process, it can be performed at 40 to 120°C. The calcination time is not particularly limited, and may be 1 to 10 minutes or 1 to 5 minutes. When the acylaminate or acylaminate ester in the polymer is thermally imidized, the calcination may be performed at, for example, 190 to 250° C. or 200 to 240° C. after the above-mentioned step of removing the organic solvent. The calcination time is not particularly limited, and may be 5 to 40 minutes or 5 to 30 minutes.

<Step (3)> Step (3) is a step of irradiating the film obtained in step (2) with polarized ultraviolet light. The wavelength of the ultraviolet light is preferably 200~400nm, and more preferably 200~300nm. In order to improve the liquid crystal alignment, the substrate coated with the liquid crystal alignment film is heated at 50~250℃ and irradiated with ultraviolet light. The irradiation amount of the above radiation is preferably 1~10,000mJ/ ^cm2 , and more preferably 100~5,000mJ/ ^cm2 . The liquid crystal alignment film produced in this way can stably align the liquid crystal molecules in a certain direction. When the extinction ratio of the polarized ultraviolet light is higher, a higher anisotropy can be imparted, which is better. Specifically, the extinction ratio of the linearly polarized ultraviolet light is preferably 10:1 or more, and more preferably 20:1 or more.

<Step (4)> Step (4) is a step of calcining the film obtained in step (3) at a temperature of 100°C or higher and higher than that in step (2). The calcination temperature is not particularly limited as long as it is 100°C or higher and higher than that in step (2), but is preferably 150-300°C, more preferably 150-250°C, and more preferably 200-250°C. The calcination time is preferably 5-120 minutes, more preferably 5-60 minutes, and more preferably 5-30 minutes. If the thickness of the liquid crystal alignment film after firing is too thin, the reliability of the liquid crystal display element will be reduced. Therefore, 5~300nm is preferred, and 10~200nm is more preferred.

Furthermore, after performing any of the above steps (3) or (4), the obtained liquid crystal alignment film can be contact treated using water and/or a solvent. As the solvent used for the above contact treatment, any solvent that can dissolve the decomposition product generated by the liquid crystal alignment film due to ultraviolet irradiation is not particularly limited. As specific examples, water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, 1-methoxy-2-propanol acetate, butyl solvent, ethyl lactate, methyl lactate, diacetone alcohol, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, propyl acetate, butyl acetate or cyclohexyl acetate can be cited. Among them, water, 2-propanol, 1-methoxy-2-propanol or ethyl lactate are preferred in terms of versatility or safety of the solvent. Water, 1-methoxy-2-propanol or ethyl lactate are more preferred. Two or more solvents may be used in combination.

As the above-mentioned contact treatment (i.e., a method of using water or a solvent to treat the liquid crystal alignment film that has been irradiated with polarized ultraviolet rays), immersion treatment or spray treatment (also called spray treatment) can be cited. From the perspective of effectively dissolving the decomposition products generated by the liquid crystal alignment film due to ultraviolet rays, the treatment time in such treatments is preferably 10 seconds to 1 hour. Among them, immersion treatment for 1 to 30 minutes is preferred. In addition, the solvent during the above-mentioned contact treatment may be at room temperature or heated, but preferably 10 to 80°C. Among them, 20 to 50°C is preferred. In addition, from the perspective of the solubility of the decomposition products, ultrasonic treatment or the like may be performed as needed.

After the above-mentioned contact treatment, it is preferred to perform rinsing (also called rinsing) with a low-boiling point solvent such as water, methanol, ethanol, 2-propanol, acetone or methyl ethyl ketone or to bake the liquid crystal alignment film. At this time, either rinsing or baking can be performed, or both can be performed. The baking temperature is preferably 150~300℃, preferably 180~250℃, and more preferably 200~230℃. In addition, the baking time is preferably 10 seconds to 30 minutes, and preferably 1~10 minutes.

The liquid crystal alignment film of the present invention is suitable as a liquid crystal alignment film for a liquid crystal display element of a lateral electric field mode such as an IPS mode or an FFS mode, and is particularly useful as a liquid crystal alignment film for a liquid crystal display element of an FFS mode. After obtaining a substrate with a liquid crystal alignment film (which is made of a liquid crystal alignment agent), a liquid crystal cell is prepared according to a known method, and a liquid crystal display element can be obtained by using the liquid crystal cell. As an example of a method for preparing a liquid crystal cell, a liquid crystal display element of a passive matrix structure will be described as an example. In addition, it can also be a liquid crystal display element of an active matrix structure in which each pixel portion constituting a screen display is provided with a switching element such as a TFT (Thin Film Transistor).

Specifically, transparent glass substrates are prepared, and a common electrode is set on one substrate, and a segment electrode is set on the other substrate. Such electrodes can be set as ITO electrodes, for example, and are patterned in a manner that can form a desired screen display. Next, an insulating film is set on each substrate in a manner to cover the common electrode and the segment electrode. The insulating film can be set as a _SiO2 - _TiO2 film formed by, for example, a sol-gel method. Next, a liquid crystal alignment film is formed on each substrate, and the substrate on one side and the substrate on the other side are overlapped in a manner that the liquid crystal alignment film surfaces of each other are opposite to each other, and the periphery is connected using a sealant. In order to control the gap between the substrates, spacers are usually mixed into the sealant. In addition, it is also preferred to scatter spacers for controlling the gap between the substrates in the surface where the sealant is not provided. An opening is provided in a part of the sealant so that the liquid crystal can be filled from the outside. Next, the liquid crystal material is injected into the space surrounded by the two substrates and the sealant through the opening provided in the sealant, and then the opening is sealed with an adhesive. The injection can be performed by a vacuum injection method or by a method utilizing the capillary phenomenon in the atmosphere. The liquid crystal material can be either a positive liquid crystal material or a negative liquid crystal material. Next, a polarizing plate is provided. Specifically, a pair of polarizing plates are attached to the surface opposite to the liquid crystal layer of the two substrates.

According to the above-mentioned method, by using the manufacturing method of the present invention, afterimages caused by long-term AC driving in a liquid crystal display element of an IPS drive method or an FFS drive method can be suppressed. In addition, after removing the organic solvent at 40-150°C in step (2), step (3) is performed, thereby obtaining a liquid crystal alignment film with fewer steps than before. The liquid crystal alignment agent of the present invention is particularly suitable for use in a manufacturing method of a liquid crystal alignment film comprising the following steps: after removing the organic solvent at 40-150°C in step (2), step (3) is performed.

According to the above-mentioned method, by using the liquid crystal alignment agent of the present invention, a liquid crystal alignment film with less residual DC or AC residual image and high sealing tightness can be obtained. In particular, a liquid crystal display element with excellent contrast that can suppress uneven brightness within the surface when displaying black can be obtained, and a liquid crystal display element with good display quality can be obtained. [Example]

The following are examples to more specifically illustrate the present invention, but the present invention is not limited to them. The codes of the following compounds and the measurement methods of each property are as follows. (Solvent) NMP: N-methyl-2-pyrrolidone, GBL: γ-butyrolactone, BCS: Butyl solvent, (Diamine) DA-1~DA-4: Compounds represented by the following formula (DA-1)~(DA-4), (Tetracarboxylic dianhydride) CA-1, CA-2: Compounds represented by the following formula (CA-1) and (CA-2), (Additive) C-1: Compound represented by the following formula (C-1) C-2: 2,2'-Bis(4-hydroxy-3,5-dihydroxymethylphenyl)propane S-1: Compound represented by the following formula (S-1),

<Viscosity measurement> Measurement was performed using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.) with a sample volume of 1.1 mL, a conical rotor TE-1 (1°34', R24) and a temperature of 25°C.

<Measurement of imidization ratio> 20 mg of polyimide powder was placed in an NMR sample tube (NMR sampling tube standard, φ5 (manufactured by Kusano Scientific Co., Ltd.)), dimethyl sulfoxide (DMSO-d6, 0.05% TMS (tetramethylsilane) mixture) (0.53 mL) was added, and ultrasonicated to completely dissolve. The solution was measured by 500 MHz proton NMR using an NMR measuring instrument (JNW-ECA500) (manufactured by JEOL DATUM). The imidization rate can be calculated by the following formula using the peak accumulation value of the proton derived from the structure that does not change before and after imidization as the reference proton and the peak accumulation value of the proton derived from the NH group of acylamidin appearing around 9.5ppm~10.0ppm. In the above formula, x is the peak accumulation value of the protons from the NH group of the acylamidin; y is the peak accumulation value of the reference proton; and α is the ratio of the reference proton to the number of protons of one NH group of the acylamidin when the polyacylamidin (acylimidization rate is 0%).

[Synthesis Examples of Polymers] The following are synthesis examples of polyamide and polyimide. PI stands for polyimide.

<Synthesis Example 1> In a 200 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 7.33 g (0.03 mol) of DA-1 was weighed and 99.1 g of NMP was added, and the mixture was dissolved by stirring while nitrogen was supplied. While stirring the diamine solution, 6.19 g (0.028 mol) of CA-1 was added, and the mixture was stirred at 40°C for 24 hours to obtain a polyamide solution (A-1) (viscosity: 107 mPa·s).

<Synthesis Example 2> In a 200 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 4.10 g (0.0168 mol) of DA-1 and 8.32 g (0.0392 mol) of DA-3 were weighed, and 176 g of NMP was added, and the mixture was dissolved by stirring while nitrogen was supplied. While stirring the diamine solution, 11.6 g (0.0518 mol) of CA-1 was added, and the mixture was stirred at 40°C for 24 hours to obtain a polyamide solution (A-2) (viscosity: 219 mPa·s).

<Synthesis Example 3> In a 100 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 6.37 g (0.03 mol) of DA-3 was weighed and 92.3 g of NMP was added, and the mixture was dissolved by stirring while nitrogen was supplied. While stirring the diamine solution, 6.22 g (0.0278 mol) of CA-1 was added, and the mixture was stirred at 40°C for 24 hours to obtain a polyamide solution (A-3) (viscosity: 347 mPa·s).

<Synthesis Example 4> In a 100 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 2.05 g (0.0084 mol) of DA-1 and 4.16 g (0.0196 mol) of DA-3 were weighed, and 88.6 g of NMP was added, and the mixture was dissolved by stirring while nitrogen was supplied. While stirring the diamine solution, 5.52 g (0.0246 mol) of CA-1 and 0.35 g (0.0014 mol) of CA-2 were added, and the mixture was stirred at 40°C for 24 hours to obtain a polyamide solution (A-4) (viscosity: 213 mPa·s).

<Synthesis Example 5> In a 200 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 3.23 g (0.0084 mol) of DA-2 and 4.16 g (0.0196 mol) of DA-3 were weighed, and 97.3 g of NMP was added, and the mixture was dissolved by stirring while nitrogen was supplied. While stirring the diamine solution, 5.52 g (0.0246 mol) of CA-1 and 0.35 g (0.0014 mol) of CA-2 were added, and the mixture was stirred at 40°C for 24 hours to obtain a polyamide solution (A-5) (viscosity: 198 mPa·s).

<Synthesis Example 6> In a 200 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 1.37 g (0.0056 mol) of DA-1, 4.16 g (0.0196 mol) of DA-3, and 1.56 g (0.0028 mol) of DA-4 were weighed, and 95.1 g of NMP was added, and the mixture was dissolved by stirring while nitrogen was supplied. While stirring the diamine solution, 5.52 g (0.0246 mol) of CA-1 and 0.35 g (0.0014 mol) of CA-2 were added, and the mixture was stirred at 40°C for 24 hours to obtain a polyamide solution (A-6) (viscosity: 224 mPa·s).

<Synthesis Example 7> In a 200 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 1.37 g (0.0056 mol) of DA-1, 4.16 g (0.0196 mol) of DA-3, and 1.56 g (0.0028 mol) of DA-4 were weighed, and 95.3 g of NMP was added, and stirred while nitrogen was supplied to dissolve. While stirring the diamine solution, 5.21 g (0.0232 mol) of CA-1 and 0.700 g (0.0028 mol) of CA-2 were added, and stirred at 40°C for 24 hours to obtain a polyamide solution (A-7) (viscosity: 177 mPa·s).

<Synthesis Example 8> In a 200 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 1.37 g (0.0056 mol) of DA-1, 4.16 g (0.0196 mol) of DA-3, and 1.56 g (0.0028 mol) of DA-4 were weighed, and 95.6 g of NMP was added, and stirred while nitrogen was supplied to dissolve. While stirring the diamine solution, 4.90 g (0.0218 mol) of CA-1 and 1.05 g (0.0042 mol) of CA-2 were added, and stirred at 40°C for 24 hours to obtain a polyamide solution (A-8) (viscosity: 176 mPa·s).

<Synthesis Example 9> In a 100 mL four-necked flask equipped with a stirring device and a nitrogen inlet tube, 35 g (0.0093 mol) of the obtained polyamine solution (A-1) was weighed, and 11.7 g of NMP was added and stirred for 30 minutes. 2.84 g of acetic anhydride (3 equivalents based on the molar ratio of polyamine) and 0.73 g of pyridine (equivalent based on the molar ratio of polyamine) were added to the obtained polyamine solution, and heated at 50°C for 3 hours to perform chemical imidization. The obtained reaction solution was added to 150 ml of methanol while stirring, and the precipitated precipitate was filtered out. The same operation was performed twice, and the resin powder was washed and dried at 60°C for 12 hours to obtain a polyimide resin powder. The imidization rate of the polyimide resin powder was 71%. 3.60 g of the obtained polyimide resin powder was measured into a 100 ml conical flask, 26.4 g of NMP was added so that the solid concentration became 12%, and it was dissolved by stirring at 70°C for 24 hours to obtain a polyimide solution (A-1-PI).

<Synthesis Examples 10 to 16> The same method as in Synthesis Example 9 was used except that the raw materials listed in Table 1 below were used. The specifications of the polyimides obtained in Synthesis Examples 10 to 16 are shown in Table 1 together with those in Synthesis Example 9.

The values in parentheses in Table 1 are: for tetracarboxylic acid components, it indicates the blending ratio (mol parts) of each compound relative to 100 mol parts of the total amount of tetracarboxylic acid derivatives used in the synthesis; for diamine components, it indicates the blending ratio (mol parts) of each compound relative to 100 mol parts of the total amount of diamines used in the synthesis. For organic solvents, it indicates the blending ratio (mass parts) of each organic solvent relative to 100 mass parts of the total amount of organic solvents contained in the polyamide solution or polyimide solution.

[Preparation of liquid crystal alignment agent] <Comparative Example 1> In a 20 ml sample tube containing a stirrer, 7.5 g of polyimide solution (A-1-PI) was weighed, 2.23 g of NMP, 5.10 g of GBL, 4.0 g of BCS, 0.90 g of GBL solution containing 1 wt % of S-1, and 0.27 g of NMP solution containing 10 wt % of C-1 were added, and stirred for 30 minutes using a magnetic stirrer to obtain a liquid crystal alignment agent (R1).

<Example 1> In a 20 ml sample tube containing a stirrer, 7.5 g of a polyimide solution (A-4-PI) was weighed, 2.23 g of NMP, 5.10 g of GBL, 4.0 g of BCS, 0.90 g of a GBL solution containing 1 wt % of S-1, and 0.27 g of a NMP solution containing 10 wt % of C-1 were added, and stirred for 30 minutes using a magnetic stirrer to obtain a liquid crystal alignment agent (1).

<Examples 2 to 5, Comparative Examples 2 and 3> Examples 2 to 5 and Comparative Examples 2 and 3 are implemented in the same manner as Comparative Example 1 and Example 1, except that the polyimide solutions, additives and organic solvents listed in Table 2 below are used, to obtain the respective liquid crystal alignment agents. The specifications of the obtained liquid crystal alignment agents are shown in Table 1 together with the liquid crystal alignment agents of Example 1 and Comparative Example 1.

The numerical values in parentheses represent the mixing ratio (mass %) of each component relative to 100 parts by mass of the total amount of the liquid crystal alignment agent.

<Production of liquid crystal display element> Prepare a substrate with electrodes. The substrate is a glass substrate with a size of 30mm×35mm and a thickness of 0.7mm. An IZO electrode with a solid pattern constituting a counter electrode is formed on the substrate as the first layer. A SiN (silicon nitride) film formed by CVD is formed as the second layer on the counter electrode of the first layer. The second layer of SiN film has a film thickness of 500nm and functions as an interlayer insulating film. On the second layer of SiN film, a comb-shaped pixel electrode formed by patterning the IZO film is arranged as the third layer to form two pixels, the first pixel and the second pixel. The size of each pixel is 10mm long and about 5mm wide. At this time, the counter electrode of the first layer and the pixel electrode of the third layer are electrically insulated by the action of the SiN film of the second layer.

The pixel electrode of the third layer is a comb-shaped electrode element having a plurality of arranged "く"-shaped electrode elements with a curved central portion. The width of each electrode element in the short side direction is 3μm, and the interval between the electrode elements is 6μm. Since the pixel electrode forming each pixel is composed of a plurality of arranged "く"-shaped electrode elements with a curved central portion, the shape of each pixel is not a rectangle, but has a roughly bold "く" shape with a curved central portion, which is the same as the electrode elements. In addition, each pixel is divided into an upper and lower part with the central curved portion as a boundary, and has a first area located on the upper side of the curved portion and a second area located on the lower side.

The liquid crystal alignment agent filtered by a filter with an average pore size of 1.0 μm was applied by spin coating to the surfaces of the substrate with the above-mentioned electrode and the glass substrate with a columnar spacer with a height of 4 μm formed on the back with an ITO film, and dried on a heating plate at 80°C for 2 minutes. After that, the coated surface was irradiated with 254nm ultraviolet light with an extinction ratio of 26:1 and a wavelength of linear polarization at 150-350mJ/ ^cm2 through a polarizing plate, and then fired in a hot air circulation oven at 230°C for 30 minutes to obtain each substrate with a liquid crystal alignment film with a film thickness of 100nm. Next, a sealant was printed on one of the glass substrates with a liquid crystal alignment film in the above set, and the other substrates were bonded so that the liquid crystal alignment film surfaces faced each other, and the sealant was cured to produce an empty cell. Liquid crystal MLC-3019 (Merck) was injected into the empty cell by a reduced pressure injection method and the injection port was sealed to obtain an FFS-driven liquid crystal cell. After that, the obtained liquid crystal cell was heated at 120°C for 1 hour and left overnight before being used for evaluation.

[Evaluation] <Evaluation of liquid crystal alignment> Using the liquid crystal cells before ISO treatment, those with initial flow alignment were evaluated as "poor", and those without initial flow alignment were evaluated as "good".

<Evaluation of sealing adhesion> [Sample preparation] The prepared liquid crystal alignment agent was applied to a 30 mm × 40 mm ITO substrate by spin coating. After drying on a heating plate at 80°C for 2 minutes, the coated surface was irradiated with 254 nm ultraviolet light through a polarizing plate, and then baked in a hot air circulation oven at 230°C for 20 minutes to form a coating with a thickness of 100 nm. Two substrates obtained in this manner were prepared, and a 4 μm bead spacer was applied to the liquid crystal alignment film surface of one substrate, and then a sealant (XN-1500T manufactured by Kyoritsu Chemical Industry Co., Ltd.) was dripped. Next, the liquid crystal alignment film surface of the other substrate is placed inside, and the substrates are laminated so that the overlap width becomes 1 cm. At this time, the amount of sealant dripping is adjusted so that the diameter of the sealant after lamination becomes 3 mm. After fixing the two laminated substrates with clamps, they are heated at 150°C for 1 hour to prepare samples for adhesion evaluation.

[Measurement of Sealing Adhesion] The sample substrates prepared above were fixed with a table-top precision universal testing machine (AGS-X 500N, manufactured by Shimadzu Corporation). After fixing the ends of the upper and lower substrates, the substrates were pressed from the upper center to measure the strength (N) during peeling. The peeling strength (N) was divided by the bonding area (mm ² ) to obtain a standardized value (peeling strength (N)/bonding area (mm ² )) as the sealing adhesion (N/mm ² ) of each sample. If the sealing adhesion is greater than 4N/mm ² , it is evaluated as "good". If the sealing adhesion is less than 4N/mm ² , it is evaluated as "poor".

[Industrial Utilization]

The liquid crystal alignment agent of the present invention is useful for forming a liquid crystal alignment film in a wide range of liquid crystal display elements such as IPS drive mode or FFS drive mode. The entire contents of the specification, patent application scope, drawings and abstract of Japanese Patent Application No. 2019-034305 filed on February 27, 2019 are cited here and cited as the disclosure contents of the specification of the present invention.

Claims (15)

A liquid crystal alignment agent, characterized in that it contains a polymer (A), wherein the polymer (A) has a repeating unit represented by the following formula (1), a repeating unit represented by the following formula (2), a repeating unit represented by the following formula (3), and a repeating unit represented by the following formula (4),

( _R1 to _R4 are independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group, and _R1 to _R4 may be the same or different, but at least one of _R1 to _R4 represents a group other than a hydrogen atom in the above definition, and _Y1 represents a divalent organic group having a partial structure represented by the following formula (H))

(Q ³ is a structure represented by -(CH ₂ ) _n - (n is an integer of 2 to 20), any -CH ₂ - may be substituted by a group selected from -O- and -C(=O)-, but the oxygen atoms are not directly bonded to each other, and any hydrogen atom on the two benzene rings may be substituted by a monovalent organic group, and * indicates a bond)

( _X2 is a tetravalent organic group having an alicyclic structure having 5 or more ring members, and _Y2 is a divalent organic group having a partial structure represented by the above formula (H))

(R ₃₁ to R ₃₄ in formula (3) are synonymous with R ₁ to R ₄ in formula (1), respectively; X ₄ in formula (4) is synonymous with X ₂ in formula (2); Y ₃ and Y ₄ represent a divalent organic group represented by the following formula (I))

(＊indicates key binding). The liquid crystal alignment agent of claim 1, wherein _X2 in the aforementioned formula (2) or _X4 in the aforementioned formula (4) is a tetravalent organic group represented by any one of the following formulas (X2-1) to (X2-12),

The liquid crystal aligner of claim 1 or 2, wherein Y ₁ and Y ₂ in the above formula (1) or (2) are divalent organic groups having a partial structure represented by any one of the following formulas (H-1) to (H-7),

The liquid crystal aligner of claim 1 or 2, wherein Y ₁ and Y ₂ in the above formula (1) or (2) are divalent organic groups represented by any one of the following formulas (h-1) to (h-8),

The liquid crystal alignment agent of claim 1 or 2, wherein the polymer (A) contains 6 to 100 mol% of the repeating units represented by formula (1), the repeating units represented by formula (2), the repeating units represented by formula (3) and the repeating units represented by formula (4) in total relative to all the repeating units of the polymer (A). The liquid crystal alignment agent of claim 1 or 2, wherein the polymer (A) contains 1 to 95 mol% of the repeating units represented by formula (1) and the repeating units represented by formula (2) in total, and contains 5 to 99 mol% of the repeating units represented by formula (3) and the repeating units represented by formula (4) in total, relative to all repeating units. The liquid crystal alignment agent of claim 1 or 2, wherein the polymer (A) further comprises at least one type of repeating unit selected from the group consisting of a repeating unit represented by the following formula (5) and a repeating unit represented by the following formula (6),

( _R51 to _R54 are synonymous with _R1 to _R4 in the aforementioned formula (1), _Y5 and _Y6 are independently a divalent organic group having a partial structure represented by the following formula (J-1) or a divalent organic group represented by the following formula (J-2), and _X6 is synonymous with _X2 in the aforementioned formula (2))

( _Q5 is a single bond, -( _CH2 ) _n- (n is an integer of 1 to ₂₀ ) or a group in which any _-CH2- of -(CH2) _n- is substituted with -O-, -COO-, -OCO-, _-NQ9- , _-NQ9CO- , _-CONQ9- , _-NQ9CONQ10- , _-NQ9COO- or -OCOO- under non-adjacent conditions, _Q9 and _Q10 each independently represent a hydrogen atom or a monovalent organic group, _Q6 and _Q7 each independently represent -H, -NHD, _-N (D) ₂ , a group having -NHD or a group having -N(D) ₂ , _Q8 represents -NHD, -N(D) ₂ , a group having -NHD or a group having -N(D) ₂ , D represents a carbamate protecting group, but at least one of Q ₅ , Q ₆ and Q ₇ has a carbamate protecting group in the group, and *1 represents a bond). The liquid crystal alignment agent of claim 7, wherein the partial structure represented by the aforementioned formula (J-1) is a partial structure represented by any one of the following formulas (J-1-a) to (J-1-d),

(Boc represents tert-butyloxycarbonyl). As in claim 7, the liquid crystal alignment agent, wherein the polymer (A) contains 1 to 40 mol% of at least one type of repeating unit selected from the group consisting of the repeating unit represented by formula (5) and the repeating unit represented by formula (6), relative to all the repeating units possessed by the polymer (A). A liquid crystal alignment film obtained from a liquid crystal alignment agent as described in any one of claims 1 to 9. A liquid crystal display element having a liquid crystal alignment film as claimed in claim 10. A method for manufacturing a liquid crystal alignment film, characterized by comprising the following steps (1) to (3), step (1): coating a liquid crystal alignment agent of any one of claims 1 to 9 on a substrate; step (2): heating the coating film of the liquid crystal alignment agent obtained in step (1); step (3): irradiating the film obtained in step (2) with polarized ultraviolet light. The method for manufacturing a liquid crystal alignment film as claimed in claim 12 further comprises the following step (4): step (4): calcining the film obtained in step (3) at a temperature above 100°C and higher than that in step (2). A method for manufacturing a liquid crystal alignment film as claimed in claim 12 or 13, wherein in the aforementioned step (2), the coating film of the liquid crystal alignment agent is heated at a temperature of 40-180°C. A liquid crystal display element having a liquid crystal alignment film obtained by the method for manufacturing a liquid crystal alignment film as described in any one of claims 12 to 14.