JP2011138104A - Liquid crystal aligner and liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal aligner giving a liquid crystal alignment layer which has excellent afterimage characteristics, and with which light transmittance in a dark state in the absence of electric field application is reduced, in a lateral electric field mode liquid crystal display element. <P>SOLUTION: The liquid crystal aligner contains one kind of polymer, selected from a group of a polyamic acid and a polyimide, and having at least two diamine compounds with respectively predetermined structures as a diamine component. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid crystal aligning agent and a liquid crystal display element. More specifically, the present invention relates to a liquid crystal aligning agent that provides a liquid crystal display element that is excellent in dark state display when no electric field is applied, particularly when applied to a horizontal electric field display type liquid crystal display element, and the liquid crystal display element.

A liquid crystal of a lateral electric field display type in which an electrode is formed only on one side of a pair of substrates arranged to face each other and an electric field is generated in a direction parallel to the substrate, for example, IPS (In-Plane Switching) mode, FFS (Fringe Field Switching) mode Compared with the conventional vertical electric field type liquid crystal display device, which has electrodes on both substrates and generates an electric field in the direction perpendicular to the substrate, the display device has wider viewing angle characteristics and enables high-quality display. It is known that there is. Such horizontal electric field display mode liquid crystal display elements are described in, for example, Patent Documents 1 and 2 and Non-Patent Document 1. Since the horizontal electric field type liquid crystal display element responds to the electric field only in the direction in which the liquid crystal molecules are parallel to the substrate, the change in the refractive index in the major axis direction of the liquid crystal molecules is not a problem. There is little change in the contrast and the contrast of the displayed color, so that high-quality display is possible regardless of the viewing angle.
In this lateral electrolysis type liquid crystal display device, the device is applied in the dark state-bright state when switching the application of no electric field to the device for the purpose of further improving the display performance and reducing the power consumption by increasing the utilization efficiency of the backlight. There is a demand for a liquid crystal display element having a high transmittance ratio (contrast).
Here, in a lateral electrolysis type liquid crystal display element having a liquid crystal layer in an anti-parallel alignment state between two polarizing plates arranged in crossed Nicols, the alignment axis of the liquid crystal is the first polarization in the dark state when no electric field is applied. The linearly polarized light that passes through the liquid crystal layer when it coincides with the polarization axis of the plate passes through the liquid crystal layer without disturbing the phase of the plate, and the passing light passes through the second polarizing plate arranged perpendicular to the first polarizing plate. By being blocked by the polarizing plate, black display can be secured. At this time, when the alignment of the liquid crystal is disturbed without being aligned with the polarization axis of the polarizing plate, the linearly polarized light transmitted through the liquid crystal layer becomes circularly polarized light (or elliptically polarized light), and a part thereof is the second sheet. The light passes through the polarizing plate and light leakage occurs.

Accordingly, there is an urgent need to develop a liquid crystal alignment film that achieves a high degree of uniaxial alignment of liquid crystals. In past research, attempts have been made to improve the uniaxial orientation of liquid crystal molecules by using a polyimide synthesized from an aromatic tetracarboxylic dianhydride and an aromatic diamine (Non-patent Document 2). However, this technique does not provide satisfactory results for improving the dark state when no electric field is applied.
Furthermore, in a horizontal electric field type liquid crystal display element, afterimages and image sticking may become problems, and improvements are desired. In this regard, Patent Document 6 proposes a method for improving afterimage characteristics and image sticking characteristics by using a liquid crystal alignment film made of a polymer containing an aromatic structure in a large proportion. However, when a liquid crystal alignment film containing an aromatic structure in a large proportion is used, the pretilt angle is inevitably increased, and the advantageous effects as described above in the lateral electric field type display element are diminished.
In a horizontal electric field type liquid crystal display element, a liquid crystal display element that can sufficiently exhibit the above advantageous effects and provides a liquid crystal alignment film exhibiting improved afterimage characteristics and image sticking characteristics is not yet known, Providing such a liquid crystal aligning agent is strongly desired.

U.S. Pat. No. 5,928,733 JP 56-91277 A JP-A-6-222366 JP-A-6-281937 JP-A-5-107544 JP 2008-15497 A JP 2010-97188 A

“Liq. Cryst.”, Vol. 22, p379 (1996) “Functional Materials”, vol. 27, p69 (2007)

The present invention has been made in view of the above circumstances, and its purpose is to effectively exhibit the advantageous effects of the horizontal electrolysis type liquid crystal display element, and to reduce the light transmittance in a dark state when no electric field is applied, Furthermore, it is providing the liquid crystal aligning agent which provides the liquid crystal aligning film which has the outstanding afterimage characteristic, and a liquid crystal display element with a large contrast.
Still other objects and advantages of the present invention will become apparent from the following description.

According to the present invention, the object of the present invention is firstly as follows:
At least one polymer selected from the group consisting of polyamic acid and polyimide, provided that the polymer has both structures represented by the following formulas (1) and (2) in at least a part of the molecule. It is achieved by a liquid crystal aligning agent characterized by containing.

(In Formula (1), each R ¹ is independently an alkyl group having 1 to 6 carbon atoms, and each R ² is independently an alkyl group having 1 to 6 carbon atoms, a halogen atom, a cyano group, or a hydroxyl group. Or a carboxyl group, n is an integer of 1 to 10, a is independently an integer of 0 to 4, and "*" indicates a bond;
In Formula (2), R ³ is an alkyl group having 1 to 6 carbon atoms, R ⁴ is each independently an alkyl group having 1 to 6 carbon atoms, a halogen atom, a cyano group, a hydroxyl group, or a carboxyl group, b is an integer of 0 to 5, c is an integer of 0 to 4, d is an integer of 0 to 3, and “*” indicates a bond. )
The above object of the present invention is secondly,
This is achieved by a liquid crystal display element comprising a liquid crystal alignment film formed from the above liquid crystal aligning agent.

The liquid crystal aligning agent of the present invention effectively exhibits the advantageous effects of a lateral electrolysis type liquid crystal display element, has a reduced light transmittance in a dark state when no electric field is applied, and has excellent afterimage characteristics. Can be formed. The liquid crystal display element of the present invention having the liquid crystal alignment film formed from the liquid crystal aligning agent of the present invention has a large contrast and excellent afterimage characteristics.
Accordingly, the liquid crystal aligning agent of the present invention is preferably used for forming a liquid crystal alignment film of a lateral electrolysis type liquid crystal display element, but is also suitable for various other liquid crystal display elements such as a TN type, STN type, and VA type. It is.
Such a liquid crystal display element of the present invention can be effectively applied to various devices such as watches, portable games, word processors, notebook computers, car navigation systems, camcorders, PDAs, digital cameras, cellular phones, and various monitors. It can be used for a display device such as a liquid crystal television.

Schematic which shows the structure of the transparent conductive film pattern of 2 systems which the liquid crystal display element manufactured for the evaluation of the afterimage characteristic in an Example and a comparative example has.

Hereinafter, the present invention will be described in detail.
The liquid crystal aligning agent of the present invention is at least one polymer selected from the group consisting of polyamic acid and polyimide, provided that each of the above formulas (1) and (2) is present in at least a part of the molecule. Having a structure represented by Hereinafter, such a polymer is referred to as a “specific polymer” in the present specification. In the specific polymer, the structure represented by the formula (1) may be present in the main chain of the polymer, may be present in the side chain of the polymer, or may be present in the polymer. May be present in both main and side chains;
The structure represented by the above formula (2) may be present in the main chain of the polymer, may be present in the side chain of the polymer, or may be present in the main chain and side chain of the polymer. It may exist in both.
R ¹ in the above formula (1) is preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. The alkyl group having 1 to 6 carbon atoms of R ² is preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. Each a is preferably 0. n is preferably from 1 to 4, and more preferably from 2 to 4.
R ³ in the above formula (2) is preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. The alkyl group having 1 to 6 carbon atoms of R ² is preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. b is preferably an integer of 1 to 5, more preferably 3, particularly b is 3, and the substitution position of the three groups R ³ is at the 1,3,3-position of the indane ring. Is preferred. c and d are each preferably 0. The phenylene group (optionally having group R ⁴ ) is preferably bonded to the 1-position of the indane ring.

The specific polymer in the present invention preferably contains the structure represented by the above formula (1) in the range of 0.001 to 0.002 mol / g;
The structure represented by the above formula (2) is preferably contained in the range of 0.0002 to 0.001 mol / g.
The polyamic acid having both the structures represented by the above formulas (1) and (2) as described above in at least a part of the molecule includes, for example, the structure represented by the above formula (1) and two carboxylic acid anhydrides. A tetracarboxylic dianhydride containing both a compound having a physical group and a structure represented by the above formula (2) and a compound having two carboxylic anhydride groups, and a diamine, or a tetracarboxylic acid Reaction of dianhydride with a diamine containing both the structure represented by the above formula (1) and a compound having two amino groups and the structure represented by the above formula (2) and a compound having two amino groups Can be obtained by
A polyimide having both structures represented by the above formulas (1) and (2) in at least a part of the molecule can be obtained, for example, by dehydrating and ring-closing the polyamic acid obtained as described above. .
The specific polymer contained in the liquid crystal aligning agent of the present invention includes a tetracarboxylic dianhydride, a structure represented by the above formula (1), a compound having two amino groups, and the above formula (2). At least one polymer selected from the group consisting of a polyamic acid obtained by reacting a diamine containing both of the structure and a compound having two amino groups, and a polyimide obtained by dehydrating and ring-closing the polyamic acid It is preferable that

<Polyamic acid>
As described above, preferred polyamic acids in the present invention are tetracarboxylic dianhydride, a structure represented by the above formula (1) and a compound having two amino groups, and a structure represented by the above formula (2) and It is obtained by reacting a diamine containing both compounds having two amino groups.
[Tetracarboxylic dianhydride]
Examples of the tetracarboxylic dianhydride used for synthesizing the polyamic acid in the present invention include an aromatic tetracarboxylic dianhydride, a tetracarboxylic dianhydride having an aliphatic dicarboxylic anhydride structure, and an alicyclic ring. And tetracarboxylic dianhydrides having an aliphatic dicarboxylic anhydride structure, tetracarboxylic dianhydrides having both an aliphatic dicarboxylic anhydride structure and an aromatic dicarboxylic anhydride structure. Here, the tetracarboxylic dianhydride having an aliphatic dicarboxylic anhydride structure includes an aliphatic tetracarboxylic dianhydride;
Examples of the tetracarboxylic dianhydride having an alicyclic dicarboxylic anhydride structure include alicyclic tetracarboxylic dianhydrides.
Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, the following formula (T-1)

(In formula (T-1), R ⁵ is each independently an alkyl group having 1 to 6 carbon atoms, a halogen atom, a cyano group, or a hydroxyl group, and e is each independently an integer of 0 to 3. .)
The compound etc. which are represented by these can be mentioned. The alkyl group having 1 to 6 carbon atoms of R ^{5 in} the above formula (T-1) is preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. Each e is preferably 0. Specific examples of the compound represented by the formula (T-1) include, for example, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic An acid dianhydride etc. can be mentioned.

  Examples of the aliphatic tetracarboxylic dianhydride include butanetetracarboxylic dianhydride. Examples of the tetracarboxylic dianhydride having both the aliphatic dicarboxylic acid anhydride structure and the aromatic dicarboxylic acid anhydride structure include the following formula (T-2):

(In Formula (T-2), R ⁶ and R ⁷ are each independently an alkyl group having 1 to 6 carbon atoms, a halogen atom, a cyano group, or a hydroxyl group, f is an integer of 0 to 8, and g Is 0 or 1.)
The compound etc. which are represented by these can be mentioned. The alkyl group having 1 to 6 carbon atoms of R ⁶ and R ⁷ in the above formula (T-2) is preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. f and g are each preferably 0. Specific examples of the compound represented by the formula (T-2) include 1,3,3a, 4,5,9b-hexahydro-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho. [1,2-c] furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-8-methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione and the like can be mentioned.

Examples of the alicyclic tetracarboxylic dianhydride include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 3-oxabicyclo [3 2.1] Octane-2,4-dione-6-spiro-3 ′-(tetrahydrofuran-2 ′, 5′-dione), 5- (2,5-dioxotetrahydro-3-furanyl) -3- Methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 3,5,6-tricarboxy-2-carboxymethylnorbornane-2: 3,5: 6-dianhydride, 2,4,6,8- Tetracarboxybicyclo [3.3.0] octane-2: 4,6: 8-dianhydride, 4,9-dioxatricyclo [5.3.1.0 ^2,6 ] undecane-3,5 8,10-tetraone, etc. It can be mentioned, respectively. In addition to the above, the tetracarboxylic dianhydride described in Patent Document 7 (Japanese Patent Laid-Open No. 2010-97188) can be used as the tetracarboxylic dianhydride for synthesizing the polyamic acid in the present invention. One or more selected from among them can be used.
Here, preferred among the tetracarboxylic dianhydrides having an alicyclic dicarboxylic anhydride structure are 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 2,3,5-tri Mention may be made of carboxycyclopentylacetic acid dianhydride.

As tetracarboxylic dianhydride used for synthesizing the polyamic acid in the present invention,
At least one selected from aromatic tetracarboxylic dianhydrides and a tetracarboxylic dianhydride having an aliphatic dicarboxylic anhydride structure, a tetracarboxylic dianhydride having an alicyclic dicarboxylic anhydride structure, and It is preferable to include at least one selected from tetracarboxylic dianhydrides having both an aliphatic dicarboxylic anhydride structure and an aromatic dicarboxylic anhydride structure. At this time, the preferable use rate with respect to all the tetracarboxylic dianhydrides of each said tetracarboxylic dianhydride, a more preferable use rate, and a still more preferable use rate are respectively as the following table | surface.

  By using a mixture of tetracarboxylic dianhydrides in the proportions as shown in the above table, it is ensured to form a liquid crystal alignment film with better liquid crystal alignment performance, which is preferable.

The tetracarboxylic dianhydride used for synthesizing the polyamic acid in the present invention is at least one selected from aromatic tetracarboxylic dianhydrides within the above range, and
Tetracarboxylic dianhydride having an aliphatic dicarboxylic anhydride structure, tetracarboxylic dianhydride having an alicyclic dicarboxylic anhydride structure, and aliphatic and aromatic dicarboxylic anhydride structures. It is most preferable to use at least one selected from tetracarboxylic dianhydrides having both and not containing other tetracarboxylic dianhydrides.

[Diamine]
The diamine used for synthesizing a preferred polyamic acid in the present invention includes a compound represented by the above formula (1) and a compound having two amino groups, and a structure represented by the above formula (2) and two amino groups. It includes both compounds having a group.
Preferable examples of the compound having the structure represented by the above formula (1) and two amino groups include, for example, a compound represented by the following formula (D-1);
Preferable examples of the compound having the structure represented by the above formula (2) and two amino groups include, for example, a compound represented by the following formula (D-2).

(R ¹ , R ² , n and a in the formula (D-1) have the same meanings as in the above formula (1);
R ³ , R ⁴ , b, c and d in the formula (D-2) are respectively synonymous with those in the above formula (2). )
Examples of the compound represented by the formula (D-1) include 2,2-bis- (4-aminophenyl) -propane, 2,2-bis- (3-aminophenyl) -propane, and 4,4 ′. -[1,3-phenylenebis (1-methylethylidene)] bisaniline, 4,4 ′-[1,4-phenylenebis (1-methylethylidene)] bisaniline, and the like, among these, 4 , 4 ′-[1,3-phenylenebis (1-methylethylidene)] bisaniline is preferred.
Examples of the compound represented by the formula (D-2) include 1- (4-aminophenyl) -1,3,3-trimethyl-1H-indan-5-amine, 1- (4-aminophenyl)- Examples include 1,3,3-trimethyl-1H-indan-6-amine.
As a diamine for synthesizing a preferred polyamic acid in the present invention, only the compound represented by the above formula (D-1) and the compound represented by the above formula (D-2) may be used. Other diamines may be used in combination with the compound represented by (D-1) and the compound represented by the above formula (D-2).

Examples of other diamines that can be used here include aliphatic diamines, alicyclic diamines, aromatic diamines, and diaminoorganosiloxanes. Specific examples thereof include aliphatic diamines such as 1,1-metaxylylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine and the like;
Examples of alicyclic diamines include 1,4-diaminocyclohexane, 4,4′-methylenebis (cyclohexylamine), 1,3-bis (aminomethyl) cyclohexane and the like;
Examples of aromatic diamines include p-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfide, 1,5-diaminonaphthalene, 2,2′-dimethyl-4,4′-diaminobiphenyl, 4,4′-diamino-2,2′-bis (trifluoromethyl) biphenyl, 2,7-diaminofluorene, 4,4′-diaminodiphenyl ether, 2,2-bis [4- (4-aminophenoxy) phenyl ] Propane, 9,9-bis (4-aminophenyl) fluorene, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane 4,4 ′-(p-phenylenediisopropylidene) bisaniline, 4,4 ′-(m-phenylenediisopropylene Riden) bisaniline, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diamino Pyrimidine, 3,6-diaminoacridine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, N , N′-bis (4-aminophenyl) -benzidine, N, N′-bis (4-aminophenyl) -N, N′-dimethylbenzidine, 1,4-bis- (4-aminophenyl) -piperazine, 3,5-diaminobenzoic acid, cholestanyloxy-3,5-diaminobenzene, cholestenyloxy-3,5-diaminobenzene, Lestanyloxy-2,4-diaminobenzene, cholestenyloxy-2,4-diaminobenzene, cholestanyl 3,5-diaminobenzoate, cholestenyl 3,5-diaminobenzoate, lanostannyl 3,5-diaminobenzoate, 3 , 6-bis (4-aminobenzoyloxy) cholestane, 3,6-bis (4-aminophenoxy) cholestane, 4- (4′-trifluoromethoxybenzoyloxy) cyclohexyl-3,5-diaminobenzoate, 4- (4′-trifluoromethylbenzoyloxy) cyclohexyl-3,5-diaminobenzoate, 1,1-bis (4-((aminophenyl) methyl) phenyl) -4-butylcyclohexane, 1,1-bis (4 -((Aminophenyl) methyl) phenyl) -4-heptylcyclohexane, 1,1 -Bis (4-((aminophenoxy) methyl) phenyl) -4-heptylcyclohexane, 1,1-bis (4-((aminophenyl) methyl) phenyl) -4- (4-heptylcyclohexyl) cyclohexane and the following formula (D-3)

(In the formula (D-3), ^{X I} is an alkylene group having 1 to 3 carbon ^atoms, * ^-O-, * -COO- or ^* -OCO- (where bond marked with "*" is diaminophenyl group And m1 is 0 or 1, m2 is an integer of 0 to 2, and h is an integer of 1 to 20.)
A compound represented by:
Examples of the diaminoorganosiloxane include 3,3 ′-(tetramethyldisiloxane-1,3-diyl) bis (propylamine), respectively.
Diamines described in Patent Document 7 (Japanese Patent Laid-Open No. 2010-97188) can be used.

^{X I} in the above formula (D-3) is an alkyl group having 1 to 3 carbon ^atoms, * -O- or ^* -COO- (provided that a bond marked with "*" is bonded to the diamino phenyl group.) It is preferable that Specific examples of the group C _h H _{2h + 1-} include, for example, methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n -Nonyl group, n-decyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n -An eicosyl group etc. can be mentioned. The two amino groups in the diaminophenyl group are preferably in the 2,4-position or 3,5-position with respect to the other groups.

  Specific examples of the compound represented by the formula (D-3) include, for example, dodecanoxy-2,4-diaminobenzene, tetradecanoxy-2,4-diaminobenzene, pentadecanoxy-2,4-diaminobenzene, hexadecanoxy-2, 4-diaminobenzene, octadecanoxy-2,4-diaminobenzene, dodecanoxy-2,5-diaminobenzene, tetradecanoxy-2,5-diaminobenzene, pentadecanoxy-2,5-diaminobenzene, hexadecanoxy-2,5-diaminobenzene, Octadecanoxy-2,5-diaminobenzene, the following formulas (D-3-1) to (D-3-3)

And the like, and the like. The liquid crystal aligning agent containing at least one polymer selected from the group consisting of polyamic acid and polyimide obtained using a diamine containing a compound represented by the above formula (D-3) is a vertical alignment type It can be suitably used as a liquid crystal aligning agent.
In the above formula (D-3), it is preferable that m1 and m2 are not 0 at the same time.
Other diamines include p-phenylenediamine, 3,5-diaminobenzoic acid, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, and 3,3 ′-(tetramethyldisiloxane It is preferable to use at least one selected from the group consisting of 1,3-diyl) bis (propylamine).

The diamine used for synthesizing the polyamic acid in the present invention is:
It is preferable that the compound represented by the above formula (D-1) contains 50 to 90 mol% with respect to the total diamines;
It is preferable that the compound represented by the formula (D-2) is contained in an amount of 10 to 50 mol% based on the total diamines;
The said other diamine can be contained in 40 mol% or less with respect to all the diamines.

[Synthesis of polyamic acid]
The polyamic acid in the present invention includes a tetracarboxylic dianhydride as described above, a diamine containing both the compound represented by the formula (D-1) and the compound represented by the formula (D-2), Can be obtained by reacting.
The ratio of the tetracarboxylic dianhydride and the diamine used in the polyamic acid synthesis reaction is 0.2 to 2 for the tetracarboxylic dianhydride acid anhydride group to 1 equivalent of the amino group of the diamine. It is preferable to set it as the ratio used as an equivalent, More preferably, it is a ratio used as 0.7-1.2 equivalent.
The polyamic acid is preferably synthesized in an organic solvent, preferably at −20 ° C. to 150 ° C., more preferably at 0 to 100 ° C., preferably 1 to 72 hours, more preferably 3 to 48 hours. Done. Here, the organic solvent is not particularly limited as long as it can dissolve the produced polyamic acid. For example, 1-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, 3-butoxy Amide compounds such as -N, N-dimethylpropanamide, 3-methoxy-N, N-dimethylpropanamide, 3-hexyloxy-N, N-dimethylpropanamide, dimethyl sulfoxide, γ-butyrolactone, tetramethylurea, hexa Aprotic compounds such as methylphosphotriamide;
Examples thereof include phenolic compounds such as m-cresol, xylenol, phenol and halogenated phenol. The amount of organic solvent used (α: when used in combination with a poor solvent described later, means the total amount of organic solvent and poor solvent used) is the total amount of tetracarboxylic dianhydride and diamine ( It is preferable that β) is 0.1 to 30% by weight based on the total amount of the reaction solution (α + β).

For the organic solvent, alcohols, ketones, esters, ethers, halogenated hydrocarbons, hydrocarbons, etc., which are generally believed to be poor solvents for polyamic acids, may be used in combination as long as the resulting polyamic acid does not precipitate. Good. Specific examples of the poor solvent include, for example, methanol, ethanol, isopropanol, cyclohexanol, 4-hydroxy-4-methyl-2-pentanone, ethylene glycol, propylene glycol, 1,4-butanediol, triethylene glycol, ethylene glycol. Monomethyl ether, ethyl lactate, butyl lactate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, diethyl oxalate, diethyl malonate, Diethyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i-propyl ether Ethylene glycol-n-butyl ether, ethylene glycol dimethyl ether, 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, tetrahydrofuran, dichloromethane, 1, 2-dichloroethane, 1,4-dichlorobutane, trichloroethane, chlorobenzene, o-dichlorobenzene, hexane, heptane, octane, benzene, toluene, xylene, diisobutyl ketone, isoamyl propionate, isoamyl isobutyrate, diisopentyl ether , And the like ether.
When the organic solvent and the poor solvent as described above are used in combination, the amount of the poor solvent used can be appropriately set within the range in which the produced polyamic acid does not precipitate, but is 30 wt% or less with respect to the total amount of the solvent. It is preferable that it is 20% by weight or less.

  This reaction solution may be used as it is for the preparation of the liquid crystal aligning agent, may be used for the preparation of the liquid crystal aligning agent after isolating the polyamic acid contained in the reaction solution, or the isolated polyamic acid was purified. You may use for preparation of a liquid crystal aligning agent. When polyamic acid is dehydrated and cyclized into a polyimide, the above reaction solution may be directly subjected to dehydration and cyclization reaction, or may be subjected to dehydration and cyclization reaction after isolating the polyamic acid contained in the reaction solution. Alternatively, the isolated polyamic acid may be purified and then subjected to a dehydration ring closure reaction. The polyamic acid is isolated by pouring the reaction solution into a large amount of poor solvent to obtain a precipitate, and drying the precipitate under reduced pressure, or by distilling off the organic solvent in the reaction solution under reduced pressure using an evaporator. Can be performed. Also, a method of dissolving this polyamic acid again in an organic solvent and then precipitating with a poor solvent, or after washing a solution obtained by dissolving polyamic acid in an organic solvent again, the organic solvent contained in the washed solution The polyamic acid can be purified by a method in which the step of evaporating the solvent under reduced pressure with an evaporator is performed once or several times.

<Polyimide>
The polyimide as a specific polymer that can be contained in the liquid crystal aligning agent of the present invention can be obtained by dehydrating and ring-closing the polyamic acid as described above.
Examples of the tetracarboxylic dianhydride used for the synthesis of the polyimide include the same compounds as the tetracarboxylic dianhydride used for the synthesis of the polyamic acid described above, and preferred ones are also used for the synthesis of the polyamic acid. The same as in the case of the tetracarboxylic dianhydride obtained.
Examples of the diamine used for synthesizing the polyimide contained in the liquid crystal aligning agent of the present invention include the same diamine as the diamine used for the synthesis of the polyamic acid.

The polyimide in the present invention may be a completely imidized product obtained by dehydrating and cyclizing all of the amic acid structure possessed by the polyamic acid as a raw material, dehydrating and cyclizing only a part of the amic acid structure, It may be a partially imidized product in which an imide ring structure coexists. The polyimide in the present invention preferably has an imidization ratio of 40 mol% or more, and more preferably 80 mol% or more. By using a polyimide having an imidization ratio of 40 mol% or more, a liquid crystal aligning agent capable of forming a liquid crystal alignment film that gives a liquid crystal display element exhibiting higher contrast can be obtained.
The said imidation rate represents the ratio which the number of the imide ring structure accounts with respect to the sum total of the number of the amic acid structures of polyimide, and the number of imide ring structures in percentage. At this time, a part of the imide ring may be an isoimide ring. The imidation rate is as follows from the result of measuring ¹ H-NMR at room temperature (for example, 25 ° C.) using tetramethylsilane as a reference substance by dissolving polyimide in a suitable deuterated solvent (for example, deuterated dimethyl sulfoxide). It can obtain | require by Numerical formula (1).
Imidation rate (%) = (1-A ¹ / A ² × α) × 100 (1)
(In Formula (1), A ¹ is a peak area derived from protons of NH groups appearing near a chemical shift of 10 ppm, A ² is a peak area derived from other protons, and α is a polyimide precursor (polyamic acid). The number ratio of other protons to one proton of NH group in

The dehydration ring closure of the polyamic acid is preferably performed by (i) a method of heating the polyamic acid, or (ii) dissolving the polyamic acid in an organic solvent, and adding a dehydrating agent and a dehydration ring closure catalyst to this solution as necessary. This is done by heating.
The reaction temperature in the method (i) of heating the polyamic acid is preferably 50 to 200 ° C, more preferably 60 to 170 ° C. The reaction time is preferably 1 to 8 hours, more preferably 3 to 5 hours. When the reaction temperature is less than 50 ° C., the dehydration ring-closing reaction does not proceed sufficiently, and when the reaction temperature exceeds 200 ° C., the molecular weight of the resulting polyimide may decrease.

On the other hand, in the method (ii) of adding a dehydrating agent and a dehydrating ring-closing catalyst to the polyamic acid solution, an acid anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride is used as the dehydrating agent. Can do. Although the usage-amount of a dehydrating agent is based on the imidation ratio desired, it is preferable to set it as 0.01-20 mol with respect to 1 mol of the amic acid structure of a polyamic acid. Moreover, as a dehydration ring closure catalyst, tertiary amines, such as a pyridine, a collidine, a lutidine, a triethylamine, can be used, for example. However, it is not limited to these. It is preferable that the usage-amount of a dehydration ring-closing catalyst shall be 0.01-10 mol with respect to 1 mol of dehydrating agents to be used. The imidation rate can be increased as the amount of the above dehydrating agent and dehydrating ring-closing agent increases. Examples of the organic solvent used in the dehydration ring-closing reaction include the organic solvents exemplified as those used for the synthesis of polyamic acid. The reaction temperature of the dehydration ring closure reaction is preferably 0 to 180 ° C, more preferably 10 to 150 ° C. The reaction time is preferably 1 to 8 hours, more preferably 3 to 5 hours.
In the method (ii), a reaction solution containing polyimide is obtained as described above. This reaction solution may be used as it is for the preparation of the liquid crystal aligning agent, or may be used for the preparation of the liquid crystal aligning agent after removing the dehydrating agent and the dehydrating ring-closing catalyst from the reaction solution. It may be used for the preparation of a liquid crystal aligning agent or may be used for the preparation of a liquid crystal aligning agent after purifying the isolated polyimide. In order to remove the dehydrating agent and the dehydrating ring-closing catalyst from the reaction solution, for example, a method such as solvent replacement can be applied. The isolation and purification of the polyimide can be performed by performing the same operation as described above as the isolation and purification method of the polyamic acid.

[End-modified polymer]
The polyamic acid and the polyimide in the present invention may each be a terminal-modified polymer having a controlled molecular weight. By using the terminal-modified polymer, the coating properties of the liquid crystal aligning agent can be further improved without impairing the effects of the present invention. Such a terminal-modified polymer can be obtained by adding a molecular weight modifier to a polymerization reaction system when synthesizing a polyamic acid. Examples of molecular weight regulators include acid monoanhydrides, monoamine compounds, monoisocyanate compounds, and the like.
Examples of the acid monoanhydride include maleic anhydride, phthalic anhydride, itaconic anhydride, n-decylsuccinic anhydride, n-dodecylsuccinic anhydride, n-tetradecylsuccinic anhydride, n -Hexadecyl succinic anhydride etc. can be mentioned. Examples of the monoamine compound include aniline, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, n-undecylamine, Examples include n-dodecylamine, n-tridecylamine, n-tetradecylamine, n-pentadecylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, and n-eicosylamine. it can. Examples of the monoisocyanate compound include phenyl isocyanate and naphthyl isocyanate.
The use ratio of the molecular weight modifier is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, with respect to 100 parts by weight of the total of tetracarboxylic dianhydride and diamine used when synthesizing the polyamic acid. is there.

[Solution viscosity]
The polyamic acid and polyimide obtained as described above each preferably have a solution viscosity of 20 to 800 mPa · s, and a solution of 30 to 500 mPa · s, when a solution having a concentration of 10% by weight is obtained. More preferably, it has a viscosity.
The solution viscosity (mPa · s) of the polymer is a value measured at 25 ° C. using an E-type rotational viscometer for a polymer solution having a concentration of 10% by weight prepared using a good solvent for the polymer. .

<Other additives>
The liquid crystal alignment film of the present invention contains, as an essential component, a specific polymer that is at least one selected from the group consisting of the polyamic acid as described above and a polyimide obtained by dehydrating and ring-closing the same, as required. The component may be contained. Examples of such other components include other polymers and adhesion improvers.
These other polymers can be used to improve solution and electrical properties. Such other polymers are polymers other than the specific polymer, for example, tetracarboxylic dianhydride, a compound represented by the above formula (D-1), and a compound represented by the above formula (D-2). A polyamic acid obtained by reacting with a diamine not containing at least one of them (hereinafter referred to as “other polyamic acid”), a polyimide obtained by dehydrating and ring-closing the polyamic acid (hereinafter referred to as “other polyimide”). ), Polyamic acid ester, polyester, polyamide, polysiloxane, cellulose derivative, polyacetal, polystyrene derivative, poly (styrene-phenylmaleimide) derivative, poly (meth) acrylate, and the like. Of these, other polyamic acids or other polyimides are preferred, and it is more preferred to use other polyamic acids.

The proportion of the other polymer used can be preferably 90% by weight or less, more preferably based on the total amount of the polymer (referring to the total of the specific polymer and other polymers; the same shall apply hereinafter). May be 85 wt% or less. When the liquid crystal aligning agent of the present invention contains other polymer, the use ratio thereof is 30% by weight or more based on the total amount of the polymer from the viewpoint of the electrical characteristics of the liquid crystal aligning film to be formed. Is preferable, and it is more preferable to set it as 50 weight% or more.
The said adhesive improvement agent can be used in order to improve the adhesiveness with respect to the substrate surface of the liquid crystal aligning film obtained. Examples of the adhesion improver include a compound having at least one epoxy group in the molecule (hereinafter referred to as “epoxy compound”), a functional silane compound, and the like.

Examples of the epoxy compound 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, and 1,6-hexane. Diol diglycidyl ether, glycerin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, 1,3,5,6-tetraglycidyl-2,4-hexanediol, N, N, N ′, N′— Tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-4,4′-diame Diphenylmethane, 3- (N-allyl--N- glycidyl) aminopropyltrimethoxysilane, 3- (N, N- diglycidyl) and the like aminopropyltrimethoxysilane.
The use ratio of the epoxy compound as described above is preferably 40 parts by weight or less, more preferably 0.1 to 30 parts by weight with respect to 100 parts by weight of the total amount of the polymer.

Examples of the functional silane compound include 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-aminopropyl Trimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl-1,4 7-triazadecane, 10-triethoxysilyl-1,4,7-triazadecane, 9-trimethoxysilyl-3,6-diazanonyl acetate, 9-triethoxysilyl-3,6-diazanonyl acetate, N- Benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-bis ( Examples thereof include oxyethylene) -3-aminopropyltrimethoxysilane and N-bis (oxyethylene) -3-aminopropyltriethoxysilane.
The use ratio of the functional silane compound as described above is preferably 2 parts by weight or less, more preferably 0.01 to 0.2 parts by weight with respect to 100 parts by weight of the total amount of the polymer.

The liquid crystal aligning agent of the present invention preferably contains at least one selected from the group consisting of polyamic acid and polyimide as described above and other additives optionally blended as necessary, preferably dissolved in an organic solvent. Configured.
Examples of the organic solvent that can be used in the liquid crystal aligning agent of the present invention include N-methyl-2-pyrrolidone, γ-butyrolactone, γ-butyrolactam, N, N-dimethylformamide, N, N-dimethylacetamide, 4-hydroxy-4. -Methyl-2-pentanone, ethylene glycol monomethyl ether, butyl lactate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, Ethylene glycol-i-propyl ether, ethylene glycol-n-butyl ether (butyl cellosolve), ethylene glycol dimethyl ether, 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, 3-butoxy-N, N-dimethylpropanamide, 3-methoxy-N, N-dimethylpropanamide, 3-hexyloxy-N, N-dimethylpropanamide and the like can be mentioned.

The solid content concentration in the liquid crystal aligning agent of the present invention (the ratio of the total weight of components other than the solvent of the liquid crystal aligning agent to the total weight of the liquid crystal aligning agent) is appropriately selected in consideration of viscosity, volatility, and the like. The range is preferably 1 to 10% by weight. That is, the liquid crystal aligning agent of the present invention is applied to the substrate surface as described later, and preferably, when heated, a coating film that becomes a liquid crystal aligning film is formed, but the solid content concentration is less than 1% by weight. In this case, the film thickness of the coating film becomes too small to obtain a good liquid crystal alignment film. On the other hand, when the solid content concentration exceeds 10% by weight, the film thickness of the coating film becomes excessive. Thus, a good liquid crystal alignment film cannot be obtained, and the viscosity of the liquid crystal aligning agent increases, resulting in poor coating properties.
The particularly preferable range of the solid content concentration varies depending on the method used when the liquid crystal aligning agent is applied to the substrate. For example, when the spinner method is used, the solid content concentration is particularly preferably in the range of 1.5 to 4.5% by weight. In the case of the printing method, it is particularly preferable that the solid content concentration is in the range of 3 to 9% by weight, and the solution viscosity is in the range of 12 to 50 mPa · s. In the case of the inkjet method, it is particularly preferable that the solid content concentration is in the range of 1 to 5% by weight, and thereby the solution viscosity is in the range of 3 to 15 mPa · s.
The temperature at the time of preparing the liquid crystal aligning agent of this invention becomes like this. Preferably it is 0 to 200 degreeC, More preferably, it is 20 to 60 degreeC.

<Liquid crystal display element>
The liquid crystal display element of the present invention comprises a liquid crystal alignment film formed from the liquid crystal aligning agent of the present invention as described above.
A preferable operation mode in the liquid crystal display element of the present invention is a horizontal electrolysis type, but it can also be suitably applied to a TN type, an STN type, or a VA type.
The liquid crystal display element of the present invention can be produced, for example, by the following steps (1) to (3). In step (1), the substrate to be used varies depending on the desired operation mode. Steps (2) and (3) are common to each operation mode.
(1) First, the liquid crystal aligning agent of this invention is apply | coated on a board | substrate, Then, a coating film is formed on a board | substrate by heating an application surface.

(1-1) When manufacturing a TN type, STN type, or VA type liquid crystal display element, a pair of two substrates provided with a patterned transparent conductive film is used as a pair on each transparent conductive film formation surface. The liquid crystal aligning agent of the present invention is preferably applied by an offset printing method, a spin coating method, a roll coater method or an ink jet printing method, and then each coated surface is heated (preferably pre-heated (pre-baked) and fired (post-baked). ) To form a coating film. Here, as the substrate, for example, a glass such as float glass or soda glass; a transparent substrate made of a plastic such as polyethylene terephthalate, polybutylene terephthalate, polyethersulfone, polycarbonate, or poly (alicyclic olefin) can be used. As a transparent conductive film provided on one surface of the substrate, an 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 ), etc. In order to obtain a patterned transparent conductive film which can be used, for example, a method of forming a pattern by photo-etching after forming a transparent conductive film without a pattern, a mask having a desired pattern when forming the transparent conductive film The method using can be used. When applying the liquid crystal aligning agent, in order to further improve the adhesion between the substrate surface and the transparent conductive film and the coating film, a functional silane compound or functional titanium is formed on the surface of the substrate surface on which the coating film is to be formed. You may give the pretreatment which apply | coats a compound etc. previously.
The coated surface after application of the liquid crystal aligning agent is then pre-heated (pre-baked) and further baked (post-baked) to form a coating film. The pre-bake conditions are, for example, 0.1 to 5 minutes at 40 to 120 ° C., and the post-bake conditions are preferably 120 to 300 ° C., more preferably 150 to 250 ° C., preferably 5 to 200 minutes, more preferably 10 to 100 minutes. The film thickness of the formed coating film is preferably 0.001-1 μm, more preferably 0.005-0.5 μm.

(1-2) On the other hand, when manufacturing a lateral electrolysis type liquid crystal display element, the conductive film formation surface of the board | substrate with which the transparent conductive film patterned by the comb-tooth shape is provided, and the opposing board | substrate with which the conductive film is not provided The liquid crystal aligning agent of this invention is apply | coated to one surface, respectively, Then, a coating film is formed by heating each application surface.
Regarding the material used for the substrate and the transparent conductive film, the coating method, the heating conditions after coating, the patterning method for the transparent conductive film, the pre-treatment of the substrate, and the preferred film thickness of the coating film to be formed (1-1) ).
In both cases (1-1) and (1-2), the liquid crystal aligning agent of the present invention forms a coating film that becomes an alignment film by removing the organic solvent after coating. When the polymer contained in the agent is a polyamic acid or a polyimide having both an imide ring structure and an amic acid structure, the dehydration cyclization reaction proceeds by further heating after the coating film is formed, resulting in more imidization. It is good also as a coating film.

(2) When manufacturing a VA liquid crystal display element, the coating film formed as described above can be used as a liquid crystal alignment film as it is, but a rubbing treatment described below may be performed.
On the other hand, when manufacturing a TN type, STN type or lateral electrolysis type liquid crystal display element,
The coating film formed as described above is rubbed in a certain direction with a roll wound with a cloth made of fibers such as nylon, rayon, and cotton. Thereby, the orientation ability of liquid crystal molecules is imparted to the coating film to form a liquid crystal orientation film.
Furthermore, the liquid crystal alignment film formed by irradiating a part of the liquid crystal alignment film with ultraviolet rays is applied to the liquid crystal alignment film formed by the liquid crystal alignment agent of the present invention as shown in, for example, Patent Document 3 and Patent Document 4. A process for changing the pretilt angle of a part of the region, or a rubbing process in a direction different from the previous rubbing process after forming a resist film on a part of the liquid crystal alignment film surface as described in Patent Document 5. It is possible to improve the visual field characteristics of the liquid crystal display element obtained by performing the process of removing the resist film after the process so that the liquid crystal alignment film has different liquid crystal alignment ability for each region.

(3) The pair of substrates on which the liquid crystal alignment films are formed as described above are arranged to face each other through a gap (cell gap) so that the rubbing directions of the liquid crystal alignment films of the two substrates are orthogonal or antiparallel. Then, the peripheral portions of the two substrates are bonded using a sealing agent, liquid crystal is injected and filled into the cell gap defined by the substrate surface and the sealing agent, and the injection hole is sealed to form a liquid crystal cell. And a liquid crystal display element can be obtained by bonding a polarizing plate on the outer surface of a liquid crystal cell so that the polarization direction thereof coincides with or is orthogonal to the rubbing direction of a liquid crystal alignment film formed on each substrate.
Here, as the sealing agent, for example, an epoxy resin containing a curing agent and aluminum oxide spheres as a spacer can be used.

Examples of the liquid crystal include nematic liquid crystals and smectic liquid crystals. Among them, nematic liquid crystals are preferable. For example, Schiff base liquid crystals, azoxy liquid crystals, biphenyl liquid crystals, phenylcyclohexane liquid crystals, ester liquid crystals, terphenyl liquid crystals. Liquid crystals, biphenylcyclohexane liquid crystals, pyrimidine liquid crystals, dioxane liquid crystals, bicyclooctane liquid crystals, cubane liquid crystals, and the like can be used. In addition, cholesteric liquid crystals such as cholestyl chloride, cholesteryl nonate, and cholesteryl carbonate; chiral products such as those sold under the trade names “C-15” and “CB-15” (manufactured by Merck) Agent: Ferroelectric liquid crystal such as p-decyloxybenzylidene-p-amino-2-methylbutylcinnamate may be added and used.
As a polarizing plate to be bonded to the outer surface of the liquid crystal cell, a polarizing film or an H film itself in which a polarizing film called “H film” in which iodine is absorbed while stretching and aligning polyvinyl alcohol is sandwiched between cellulose acetate protective films The polarizing plate which consists of can be mentioned.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
In the following synthesis examples, 4,4 ′-[1,3-phenylenebis (1-methylethylidene)] bisaniline used as it was was a commercial product “Bisaniline M” manufactured by Mitsui Chemicals.
Moreover, the solution viscosity of the polymer in each synthesis example is a value measured at 25 ° C. using an E-type viscometer.

<Polymer synthesis example>
Synthesis Examples 1-7 and Comparative Synthesis Examples 1-3
To the N-methyl-2-pyrrolidone, the amounts of diamine and tetracarboxylic dianhydride shown in Table 1 were added in this order to obtain a solution having a monomer concentration of 15% by weight, and the reaction was performed at room temperature for 6 hours. The solutions containing polyamic acids (PA-1) to (PA-7) and (PAR-1) to (PAR-3) were obtained, respectively. A small amount of each solution was sampled, and the solution viscosity measured as a solution having a polyamic acid concentration of 10% by weight by adding N-methyl-2-pyrrolidone is shown in Table 1.
Half of each of these polyamic acid solutions was secured and used in the following Examples 1 to 6 and 12 and Comparative Examples 1 to 3, respectively.
Among the above polyamic acids, (PA-1) to (PA-5), (PA-7), and (PAR-1) were subjected to dehydration ring-closing reaction as follows to obtain polyimides.

N-methyl-2-pyrrolidone is added to the remaining half of each polyamic acid solution to give a polyamic acid concentration of 6% by weight, and pyridine and acetic anhydride are added to 1 mol of the amic acid unit of the polyamic acid, respectively. Then, the mixture was added so as to have the molar ratio shown in Table 1, and then heated to 110 ° C. to conduct dehydration ring closure reaction for 4 hours. After the dehydration ring-closing reaction, the solvent in the system was replaced with new N-methyl-2-pyrrolidone (in this operation, pyridine and acetic anhydride used for the dehydration ring-closing reaction were removed from the system), and polyimide was obtained. A solution containing 15% by weight of (PI-1) to (PI-5) and (PI-7) and (PIR-1) was obtained. Table 1 shows the imidization ratio of each polyimide contained in these polyimide solutions and the solution viscosities measured as N-methyl-2-pyrrolidone solutions having a polyimide concentration of 10% by weight.
These polyimide solutions were used in Examples 7 to 12 and Comparative Example 4 below.

In Table 1, the abbreviations for diamine and tetracarboxylic anhydride have the following meanings, respectively.
<Diamine>
d-1: 4,4 ′-[1,3-phenylenebis (1-methylethylidene)] bisaniline d-2: 1- (4-aminophenyl) -1,3,3-trimethyl-1H-indane-5 -Amine d-3: p-phenylenediamine d-4: 4,4'-diaminodiphenylmethane d-5: 4,4'-diaminodiphenyl ether d-6: 3,3'-bis (tetramethyldisiloxane-1, 3-Diyl) -bis (propylamine)
d-7: 3,5-diaminobenzoic acid <tetracarboxylic dianhydride>
t-1: 2,3,5-tricarboxycyclopentylacetic acid dianhydride t-2: 1,2,3,4-cyclobutanetetracarboxylic dianhydride t-3: pyromellitic dianhydride t-4: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride

Example 1
<Preparation of liquid crystal aligning agent>
Γ-butyrolactone (BL), N-methyl-2-pyrrolidone (NMP) and butyl cellosolve (BC) are added to the solution containing the polyamic acid (PA-1) obtained in Synthesis Example 1, and an adhesion improver. As an epoxy compound, N, N, N ′, N′-tetraglycidyl-4,4′-diaminodiphenylmethane is added in an amount of 10 parts by weight to 100 parts by weight of polyamic acid (PA-1), and the solvent ratio is BL. : NMP: BC = 40: 40: 20 (weight ratio), solid content concentration 4.0 wt% solution. After sufficiently stirring this solution, a liquid crystal aligning agent was prepared by filtering using a filter having a pore size of 1 μm.
Evaluation was performed as follows using this liquid crystal aligning agent.

<Manufacture and evaluation of liquid crystal cells>
[Manufacture of liquid crystal cells]
A liquid crystal cell for evaluation of liquid crystal alignment and dark state was produced as follows.
After applying the liquid crystal aligning agent prepared above on a glass substrate having a thickness of 1 mm having a comb electrode on one side with a spinner and prebaking on a hot plate at 80 ° C. for 1 minute. The film was post-baked on a hot plate at 230 ° C. for 10 minutes to form a coating film having a thickness of about 800 mm. Using a rubbing machine having a roll around which a nylon cloth is wound on the formed coating surface, the roll rotation speed is 1,000 rpm, the stage moving speed is 25 mm / second, and the length of pushing the hair foot is 0.4 mm. A rubbing treatment was performed to give liquid crystal alignment ability. Further, this substrate was ultrasonically cleaned in ultrapure water for 1 minute and dried in a 100 ° C. clean oven for 10 minutes to produce a substrate having a liquid crystal alignment film on the surface having comb-like chrome electrodes.
Separately, a liquid crystal aligning agent coating film is formed on one surface of a 1 mm thick glass substrate having no electrode in the same manner as described above, followed by rubbing treatment, and then washed and dried. A substrate having a liquid crystal alignment film was manufactured.
A pair of these substrates is coated with an epoxy resin adhesive containing aluminum oxide spheres having a diameter of 5.5 μm on the outer edge of the surface of the substrate having the liquid crystal alignment film subjected to the rubbing treatment, and then the rubbing direction in each liquid crystal alignment film is antiparallel. The two substrates were arranged so as to face each other with a gap therebetween, and the outer edges were brought into contact with each other and pressed to cure the adhesive. Next, a nematic liquid crystal (MLC-2042, manufactured by Merck & Co., Inc.) is filled between the pair of substrates from the liquid crystal injection port, and then the liquid crystal injection port is sealed with an acrylic photo-curing adhesive. A cell was manufactured.

[Liquid crystal cell evaluation]
(1) Evaluation of liquid crystal orientation About the liquid crystal cell manufactured above, it observed using the polarizing microscope. At this time, the liquid crystal orientation was “excellent” when no light leakage was observed, the liquid crystal orientation was “good” when very little light leakage was observed, and the liquid crystal orientation was clearly recognized with light leakage. When the orientation was evaluated as “bad”, the liquid crystal orientation of this liquid crystal cell was “excellent”.
(2) Evaluation of dark state The liquid crystal cell produced above was sandwiched between a pair of polarizing plates, and the degree of the dark state when no voltage was applied was examined.
The light transmittance when the pair of polarizing plates is arranged in a crossed Nicol arrangement with the rubbing direction of the liquid crystal alignment film is 0%,
When a pair of polarizing plates has a rubbing direction of the liquid crystal alignment film and a paranicol arrangement, and the light transmittance when a voltage is applied is 100%,
A pair of polarizing plates were attached as the rubbing direction of the liquid crystal alignment film and the paranicol arrangement, and the light transmittance in a state where no voltage was applied was examined. When the light transmittance was less than 0.1%, the dark state was “excellent”, and when it was 0.1% or more and less than 0.2%, the dark state was “good”, 0.2% or more. The case was defined as a “bad” dark state.
This (2) evaluation of the dark state is “higher” or “good” in the evaluation of (1) liquid crystal alignment, and higher accuracy can be obtained for a liquid crystal cell that exhibits a suitable liquid crystal alignment. This is an evaluation that serves as an indicator of display quality at a high image quality level in recent years.

(3) Evaluation of afterimage In the above [Manufacture of liquid crystal cell], a pair of a glass substrate having two lines of comb-like transparent conductive film patterns made of chromium and a glass substrate having no transparent conductive film are used as a pair of comb-like transparent A liquid crystal cell was produced in the same manner as in [Manufacture of liquid crystal cell] except that the liquid crystal aligning agent was applied to the transparent conductive film of the substrate having the conductive film and one surface of the other substrate. Furthermore, a liquid crystal display element was manufactured by laminating polarizing plates on both sides of the substrate of the liquid crystal cell in a paranicol arrangement with the rubbing direction of the liquid crystal alignment film.
A schematic diagram showing the configuration of the transparent electrode pattern on the glass substrate is shown in FIG.
The liquid crystal display device manufactured as described above was placed in an environment of 25 ° C. and 1 atm. A voltage of AC voltage 3.5 V and DC voltage 5 V was applied to electrode A for 2 hours without applying voltage to electrode B. Immediately thereafter, an AC voltage of 4 V was applied to both electrode A and electrode B. The time from the start of applying an AC voltage of 4 V to both electrodes until the difference in light transmission between the electrodes A and B disappeared was measured. In addition, when this time is 300 seconds or less, the afterimage characteristic is “excellent”, and when it exceeds 300 seconds and is 500 seconds or less, the afterimage characteristic is “good”. Shorter is preferable.

Examples 2-12 and Comparative Examples 1-4
In Example 1 above, a liquid crystal aligning agent was prepared in the same manner as in Example 1 except that a solution containing the polymer shown in Table 2 was used as the polymer solution, and a liquid crystal cell was produced and evaluated. . In Example 12, two types of polymers were mixed and used. Here, the adhesion improver was used in an amount of 10 parts by weight with respect to a total of 100 parts by weight of the polymer.
The evaluation results are shown in Table 2.

Claims (5)

At least one polymer selected from the group consisting of polyamic acid and polyimide, provided that the polymer has both structures represented by the following formulas (1) and (2) in at least a part of the molecule. A liquid crystal aligning agent characterized by comprising:

(In Formula (1), each R ¹ is independently an alkyl group having 1 to 6 carbon atoms, and each R ² is independently an alkyl group having 1 to 6 carbon atoms, a halogen atom, a cyano group, or a hydroxyl group. Or a carboxyl group, n is an integer of 1 to 10, a is independently an integer of 0 to 4, and "*" indicates a bond;
In Formula (2), R ³ is an alkyl group having 1 to 6 carbon atoms, R ⁴ is each independently an alkyl group having 1 to 6 carbon atoms, a halogen atom, a cyano group, a hydroxyl group, or a carboxyl group, b is an integer of 0 to 5, c is an integer of 0 to 4, d is an integer of 0 to 3, and “*” indicates a bond. ) A polyamic obtained by reacting the polymer with a diamine containing both a tetracarboxylic dianhydride, a compound represented by the following formula (D-1) and a compound represented by the following formula (D-2) A liquid crystal aligning agent, which is at least one selected from the group consisting of an acid and a polyimide formed by dehydrating and ring-closing the polyamic acid.

(R ¹ , R ² , n and a in the formula (D-1) have the same meanings as in the above formula (1);
R ³ , R ⁴ , b, c and d in the formula (D-2) are respectively synonymous with those in the above formula (2). ) The tetracarboxylic dianhydride is
At least one selected from aromatic tetracarboxylic dianhydrides and at least one selected from tetracarboxylic dianhydrides having an aliphatic dicarboxylic anhydride structure or an alicyclic dicarboxylic anhydride structure. The liquid crystal aligning agent of Claim 2 which is a thing. The diamine is
p-phenylenediamine, 3,5-diaminobenzoic acid, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether and 3,3 '-(tetramethyldisiloxane-1,3-diyl) bis (propylamine) The liquid crystal aligning agent according to claim 2 or 3, further comprising at least one selected from the group consisting of:   A liquid crystal display element comprising a liquid crystal alignment film formed from the liquid crystal aligning agent according to claim 1.

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