CN106575061B

CN106575061B - Liquid crystal aligning agent, liquid crystal alignment film, and liquid crystal display element

Info

Publication number: CN106575061B
Application number: CN201580045518.XA
Authority: CN
Inventors: 巴幸司; 野田尚宏; 坂本谦治; 川野勇太
Original assignee: Nissan Chemical Corp
Current assignee: Nissan Chemical Corp
Priority date: 2014-06-25
Filing date: 2015-06-24
Publication date: 2020-10-16
Anticipated expiration: 2035-06-24
Also published as: TW201615695A; JP6593603B2; JPWO2015199149A1; KR20170021856A; KR102421827B1; CN106575061A; WO2015199149A1; TWI561556B

Abstract

A liquid crystal aligning agent comprising a soluble polyimide obtained from a diamine component containing at least 1 diamine selected from the group consisting of diamines of the following formulae (i) and (ii) and a tetracarboxylic dianhydride component. The symbols in the formula are defined as described in the specification.

Description

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

Technical Field

The present invention relates to a liquid crystal aligning agent mainly used for a liquid crystal display element of a transverse electric field driving method, a liquid crystal alignment film using the same, and a liquid crystal display element of a transverse electric field driving method.

Background

In the liquid crystal display element, the liquid crystal alignment film functions to align liquid crystal in a certain direction. A major liquid crystal alignment film that is industrially used today is produced by applying a polyimide-based liquid crystal alignment agent containing a solution of Polyamic acid (also referred to as "polyimide acid") that is a polyimide precursor and polyimide to a substrate and forming a film. When the liquid crystal is aligned in parallel or obliquely with respect to the substrate surface, a surface stretching treatment is further performed by a brush rubbing after film formation. Further, as an alternative to the brushing treatment, a method utilizing anisotropic photochemical reaction by polarized ultraviolet irradiation or the like has been proposed, and in recent years, studies have been made for industrialization.

In order to improve the display characteristics of liquid crystal display elements, various techniques have been proposed in which the structures of polyamic acid and polyimide are variously modified and optimized, resins having different characteristics are blended, additives are added, and the like, whereby the liquid crystal alignment properties, the pretilt angle control, the electrical characteristics, and the like can be improved, and further, the display characteristics can be improved. For example, in order to obtain a high voltage holding ratio, it has been proposed to use a polyimide resin having a specific repeating structure (see patent document 1 and the like). In addition, it has been proposed to use a soluble polyimide having a nitrogen atom in addition to an imide group for the afterimage phenomenon, thereby reducing the time until the afterimage disappears (see patent document 2 and the like). Further, a polyamic acid obtained from a specific diamine having an oxazole or imidazole skeleton and a tetracarboxylic dianhydride, and a derivative thereof have been proposed (patent document 3).

In recent years, liquid crystal display elements have been used in large-screen, high-definition liquid crystal televisions, and in-vehicle applications such as car navigation systems and instrument panels. In such applications, a backlight having a large heat radiation amount may be used in order to obtain high luminance. Therefore, from another viewpoint, the liquid crystal alignment film is required to have high reliability, that is, high stability against light and heat from a backlight. In particular, if the voltage holding ratio, which is one of the electrical characteristics, is lowered by light irradiation from the backlight, an afterimage defect (line afterimage) which is one of the display defects of the liquid crystal display element is likely to occur, and a highly reliable liquid crystal display element cannot be obtained. Further, the problem of the transverse electric field mode is that an afterimage (AC afterimage) due to the deviation of the orientation direction is particularly liable to be generated by heat, and thus it is difficult to solve the afterimage. Therefore, the liquid crystal alignment film is required to have good initial characteristics and, for example, to have a voltage holding ratio that is not easily lowered even after exposure to light for a long period of time.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2-287324

Patent document 2: japanese laid-open patent publication No. 10-104633

Patent document 3: japanese patent application laid-open No. 2010-54872

Patent document 4: WO2006-126555 publication

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal alignment agent having good printability (solubility of a polymer in a solvent) to a substrate or the like, and a liquid crystal alignment film for a liquid crystal display element of a lateral electric field driving system having excellent rubbing resistance, good display characteristics, and excellent reliability even when a liquid crystal lacking reliability is used, or even when exposed to high temperature and/or a backlight for a long period of time.

Means for solving the problems

The inventors of the present invention conducted extensive studies and found that: the liquid crystal aligning agent comprising a specific soluble polyimide and polyamic acid is extremely effective for achieving the above object, and thus the present invention has been completed.

That is, the present invention has the following gist.

<1> a liquid crystal aligning agent, characterized by comprising a soluble polyimide obtained from a diamine component and a tetracarboxylic dianhydride component, wherein the diamine component comprises at least 1 diamine selected from the group consisting of diamines of the following formulae (i) and (ii).

Wherein D represents a saturated hydrocarbon group having 1 to 20 carbon atoms and having a valence of 2, an unsaturated hydrocarbon group, an aromatic hydrocarbon group or a heterocycle, and D optionally has various substituents. E is a single bond or a 2-valent saturated hydrocarbon group, unsaturated hydrocarbon group, aromatic hydrocarbon group or heterocyclic ring having 1 to 20 carbon atoms, and F is a single bond or an ether bond (-O-), an ester bond (-OCO-, -COO-). m is 1 or 0.

<2> the liquid crystal aligning agent according to <1>, which further comprises a polyamic acid obtained by using at least 1 or more of the compounds represented by the formulae (iii) to (vi).

In the formula (vi), R represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.

<3> the liquid crystal aligning agent according to <1> or <2>, wherein the soluble polyimide is a soluble polyimide obtained from a diamine component containing 10 to 90 mol% of at least 1 diamine selected from the diamines of the formulae (i) and (ii) and a tetracarboxylic dianhydride.

<4> the liquid crystal aligning agent according to any one of <1> to <3>, wherein the soluble polyimide has an imidization ratio of 20% to 100%.

<5> the liquid crystal aligning agent according to any one of <1> to <4>, wherein the soluble polyimide is a soluble polyimide obtained from a diamine component containing at least 1 or more kinds of diamines selected from the group consisting of formulae (vii) to (x) and a tetracarboxylic dianhydride.

n represents an integer of 1 to 6, R₃Is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R₄Is a linear alkylene group having 1 to 5 carbon atoms.

<6> the liquid crystal aligning agent according to any one of <1> to <5>, wherein the soluble polyimide and the polyamic acid are contained in an amount of 1 to 10% by mass in total, and a ratio of the weight of the polyimide to the weight of the polyamic acid is 95:5 to 5: 95.

<7> a liquid crystal alignment film obtained by using the liquid crystal aligning agent <1> to <6 >.

<8> A liquid crystal display element, characterized by comprising the liquid crystal alignment film <7 >.

ADVANTAGEOUS EFFECTS OF INVENTION

The liquid crystal aligning agent of the present invention is characterized by containing a soluble polyimide obtained from a diamine component containing at least 1 kind of diamine (hereinafter, also referred to as a specific diamine) selected from the diamines of the formulae (i) and (ii) and a tetracarboxylic dianhydride. Since the soluble polyimide has high solubility in a solvent and has very good compatibility with polyamic acid when blended with polyamic acid, a liquid crystal aligning agent using the soluble polyimide and polyamic acid can provide a film excellent in coating and film-forming properties on a substrate and having few irregularities. Further, since the specific diamine is characterized in that a highly active substituent is generated by heating, a part of the diamine undergoes a self-condensation reaction to form a structure having good linearity, and a part of the diamine in contact with the amic acid reacts with a specific site of the amic acid, a liquid crystal alignment film having excellent liquid crystal alignment properties and excellent rubbing resistance can be obtained. Accordingly, high-quality black display can be performed.

Further, the soluble polyimide is very stable to light and heat, and has an action of extremely reducing the influence of ionic impurities and the like, and therefore, a liquid crystal alignment film containing the soluble polyimide can obtain very high reliability even in a negative-type liquid crystal and the like which are very resistant to contamination.

Further, the polyamic acid using the compounds represented by the formulae (iii) to (vi) has a property of quickly releasing residual charges accumulated in the alignment film, and thus an alignment film having excellent residual image characteristics can be obtained. On the other hand, although the alignment film using such polyamic acid tends to lack reliability, it can be combined with the soluble polyimide of the present invention to obtain excellent reliability and excellent afterimage characteristics.

Detailed Description

The present invention will be described in detail below.

< soluble polyimide >

The liquid crystal aligning agent comprises soluble polyimide obtained from diamine component containing specific diamine and tetracarboxylic dianhydride. The specific diamine has an organic group which can be detached by heat. An amino group can be generated by the elimination of the organic group.

The substitution position of the amino group in the formulae (i) and (ii) is not particularly limited, and is preferably a meta-position or a para-position based on an amide bond from the viewpoint of ease of synthesis and reagent availability, and is particularly preferably a para-position from the viewpoint of liquid crystal alignment. In addition, for aminobenzene having no amino group (i.e., -NHBoc) protected with a tert-butoxycarbonyl group (hereinafter also referred to as Boc group), when an amide bond is similarly used as a reference, a meta-position or a para-position is preferable, a meta-position is preferable from the viewpoint of solubility, and a para-position is preferable from the viewpoint of liquid crystal alignment. Further, the hydrogen of the aminobenzene having no-NHBoc is optionally substituted with an organic group, a halogen atom such as fluorine, or the like.

D in formula (i) is not limited, and various structures can be selected depending on the structure of the dicarboxylic acid, tetracarboxylic dianhydride, or the like used as a raw material. D is preferably a 2-valent hydrocarbon group or the like from the viewpoint of solubility, and preferable examples thereof include a linear alkylene group, a cyclic alkylene group, and the like, and the hydrocarbon group may have an unsaturated bond. In addition, from the viewpoint of liquid crystal alignment properties and electrical characteristics, 2-valent aromatic hydrocarbon groups, heterocyclic rings, and the like are preferable. D preferably has no substituent from the viewpoint of liquid crystal alignment properties, but a hydrogen atom is preferably substituted with a carboxylic acid group, a fluorine atom, or the like from the viewpoint of solubility.

The ratio of the specific diamine in the diamine component in the synthesis of the soluble polyimide in the liquid crystal aligning agent of the present invention is not particularly limited, and may be adjusted in order to provide various functions such as improvement of solubility and improvement of electrical characteristics. When used in the transverse electric field system, the diamine represented by the formula (vii) to the formula (x) is combined to obtain a very excellent liquid crystal alignment property.

In the formulas (viii) and (ix), n represents an integer of 1 to 6; in the formula (x), R₃Is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; r₄Is a linear alkylene group having 1 to 5 carbon atoms.

Specifically, the proportion of the specific diamine used in the present invention is 1 to 90 mol%, preferably 1 to 50 mol%, and more preferably 5 to 30 mol%. The diamine represented by (vii) to (x) is preferably contained in an amount of at least 10 mol%.

In order to impart various functions to the diamine used for synthesizing the soluble polyimide, other diamines may be used in combination with the above diamines. The specific structure of the other diamine is shown in the following general formula (3).

H₂N-Y-NH₂(3)

Y represents a divalent organic group. An example thereof will be described below, but the present invention is not limited thereto. In addition, the dotted moiety is a group with-NH₂The nitrogen-bonded moiety of (a).

Examples of diamines which are preferably introduced to improve the liquid crystal alignment include Y-20, Y-29, Y-30, Y-31, Y-32, Y-33, Y-40, Y-47, Y-48, Y-53, Y-54, Y-55, Y-56, Y-58, Y-59, Y-60, Y-61, Y-64, Y-68, Y-69, Y-70, and Y-71. On the other hand, many monomers having good orientation have a linear structure, and when used for a soluble polyimide, the solubility of the polyimide may be insufficient and cannot be adjusted. This problem can be solved by variously selecting the structure of the tetracarboxylic dianhydride described later. Particularly preferred structures from the viewpoint of solubility and liquid crystal alignment include Y-29, Y-30, Y-31, Y-32, Y-60 and the like. Y-29, Y-30, Y-31 and Y-32 are preferably those in which one hydrogen atom of the aliphatic amine is optionally substituted with an alkyl group, alkenyl group or alkynyl group having a small carbon number such as a methyl group or ethyl group, because good characteristics can be obtained.

Further, the image sticking characteristics can be improved by using a heterocyclic compound or a diamine containing a nitrogen atom, a sulfur atom, or the like. An example of a preferred structure thereof is shown below.

In addition, for the purpose of improving the mechanical strength, long-term reliability, solubility, and the like of the liquid crystal alignment film, it is preferable to use a diamine having a side chain-like functional group as shown below in combination.

Tetracarboxylic dianhydride used for synthesizing polyamic acid and soluble polyimide is represented by the following formula (4).

X is a 4-valent organic group, and the structure thereof is not particularly limited.

The type of tetracarboxylic dianhydride used in the present invention is not particularly limited, and 1 type or 2 or more types may be used in combination depending on the characteristics such as liquid crystal alignment properties, pretilt angle, voltage holding characteristics, and accumulated charge when a liquid crystal alignment film is formed.

Specific examples of X are shown below, but the X is not limited to these structures.

Among the above structures, alicyclic tetracarboxylic dianhydrides such as those represented by X-1 to 26 are preferred, and X-2, X-3, X-4, X-6, X-9, X-10, X-11, X-12, X-13, X-14, X-15, X-16, X-17, X-18, X-19, X-20, X-21, X-22, X-23, X-24, X-25 and X-26 are preferred, from the viewpoint of solubility. On the other hand, from the viewpoint of orientation, aromatic tetracarboxylic dianhydrides such as X-27 to 46 are preferred, and X-27, X-28, X-33, X-34, X-35, X-40, X-41, X-42, X-43, X-44, X-45 and X-46 are particularly preferred.

Particularly preferably X-1, X-2, X-18 to 22, X-25 and X-26 having good orientation and solubility.

< Polyamic acid >

The polyamic acid used in the liquid crystal aligning agent of the present invention plays a role of rapidly releasing residual charges (hereinafter, RDC) generated in the liquid crystal alignment film, and is characterized in that at least 1 or more of the compounds represented by the formulae (iii) to (vi) are used as a raw material. The tetracarboxylic dianhydrides represented by the formulae (iii) to (v) may be used alone or in combination. When the diamine represented by the formula (vi) is used, the release of RDC can be further promoted by using tetracarboxylic dianhydrides represented by the formulae (iii) to (v) in combination. On the other hand, since the diamine of the formula (vi) alone has an excellent RDC releasing ability, it can obtain good characteristics even in combination with an aliphatic tetracarboxylic dianhydride.

(iii) The tetracarboxylic acid dianhydride represented by (a) to (v) is preferably 20 to 100 mol%, more preferably 40 to 100 mol%, based on the whole tetracarboxylic acid dianhydride used for synthesizing the polyamic acid used in the present invention. The diamine represented by the formula (vi) is preferably 20 to 100 mol%, more preferably 40 to 90 mol%, based on the whole diamine component used for synthesizing the polyamic acid used in the present invention.

In the polyamic acid used in the present invention, the diamine and the tetracarboxylic dianhydride may be used in combination in addition to at least 1 compound selected from the compounds of formulae (iii) to (vi), and formulae (i) and (ii) may also be used. Further, as required, a side chain diamine represented by the following Y-112 to 143 can be used.

H2N-Y-NH2 (3)

In Y-112 to Y-116, A₁Is an alkyl group having 2 to 24 carbon atoms or a fluoroalkyl group.

In the formulae Y-117 to Y-118, A₂represents-O-, -OCH₂-、-CH₂O-、-COOCH₂-or-CH₂OCO-，A₃Is an alkyl group, alkoxy group, fluoroalkyl group or fluoroalkoxy group having 1 to 22 carbon atoms.

In the formulae Y-119 to Y-121, A₄represents-COO-, -OCO-, -CONH-, -NHCO-, -COOCH₂-、-CH₂OCO-、-CH₂O-、-OCH₂-or-CH₂-，A₅Is an alkyl group, alkoxy group, fluoroalkyl group or fluoroalkoxy group having 1 to 22 carbon atoms.

In the formulae Y-122 to Y-123, A₆represents-COO-, -OCO-, -CONH-, -NHCO-, -COOCH₂-、-CH₂OCO-、-CH₂O-、-OCH₂-、-CH₂-, -O-or-NH-, A₇Is fluoro, cyano, trifluoromethyl, nitro, azo, formyl, acetyl, acetoxy or hydroxy.

Y-124 and in the formula Y-125, A₈The cis-trans isomer of the 1, 4-cyclohexylidene is a trans isomer.

In formulae Y-126 and Y-127, A₉The cis-trans isomer of the 1, 4-cyclohexylidene is a trans isomer.

Formula [ Y-136 ]]-formula [ Y-141]In (A)₁₂represents-COO-, -OCO-, -CONH-, -NHCO-, -CH₂-, -O-, -CO-or-NH-, A₁₃Represents an alkyl group having 1 to 22 carbon atoms or a fluorine-containing alkyl group.

< production of soluble polyimide and Polyamic acid >

In the production of the polyimide used in the present invention, the weight average molecular weight of the polyamic acid as a polyimide precursor is preferably 10000 to 305000, more preferably 20000 to 210000. The number average molecular weight is preferably 5000 to 152500, more preferably 10000 to 105000.

The soluble polyimide and polyamic acid contained in the liquid crystal aligning agent of the present invention are produced as follows. The soluble polyimide is obtained by imidizing a polyamic acid as a precursor thereof, and the difference between the polyamic acid as a precursor of the soluble polyimide and the polyamic acid to be mixed with the soluble polyimide is that the former uses a specific diamine as a diamine component to be a raw material thereof.

Both of the polyamic acid to be mixed with the soluble polyimide and the polyamic acid as a precursor of the soluble polyimide are produced by polycondensing a diamine component and a tetracarboxylic dianhydride component in an organic solvent.

Examples of the method for polycondensing the tetracarboxylic dianhydride component and the diamine component in the organic solvent include: a method in which a solution obtained by dispersing or dissolving a diamine component in an organic solvent is stirred, and a tetracarboxylic dianhydride component is directly added or a tetracarboxylic dianhydride component is dispersed or dissolved in an organic solvent and added; conversely, a method of adding a diamine component to a solution in which a tetracarboxylic dianhydride component is dispersed or dissolved in an organic solvent; a method of alternately adding a tetracarboxylic dianhydride component and a diamine component. When the tetracarboxylic dianhydride component or the diamine component contains a plurality of compounds, the plurality of compounds may be subjected to a polycondensation reaction in a state of being mixed in advance, or may be subjected to a polycondensation reaction in sequence.

The temperature at which the tetracarboxylic dianhydride component and the diamine component are subjected to the polycondensation reaction in the organic solvent is usually 0 to 150 ℃, preferably 5 to 100 ℃, and more preferably 10 to 80 ℃. When the temperature is high, the polycondensation reaction is terminated quickly, but when the temperature is too high, a polymer having a high molecular weight may not be obtained.

The polycondensation reaction may be carried out at any concentration, and if the concentration is too low, it is difficult to obtain a polymer having a high molecular weight, and if the concentration of the total mass of the tetracarboxylic dianhydride component and the diamine component is too high, the viscosity of the reaction solution becomes too high and uniform stirring becomes difficult, and therefore, it is preferably 1 to 50% by mass, and more preferably 5 to 30% by mass. The polycondensation reaction may be carried out at a high concentration in the initial stage, and then an organic solvent may be added.

The organic solvent used in the above reaction is not particularly limited as long as it dissolves the produced polyamic acid. Specific examples thereof include N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1, 3-dimethylimidazolidinone, N-methylcaprolactam, dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfoxide, hexamethylphosphoric triamide, and γ -butyrolactone. These may be used alone or in combination. Further, even if the solvent does not dissolve the polyamic acid, the solvent may be mixed and used within a range where the produced polyamic acid does not precipitate.

Further, the water content in the organic solvent inhibits the polycondensation reaction and causes hydrolysis of the formed polyamic acid, and therefore, the organic solvent is preferably used after being dehydrated and dried as much as possible.

The ratio of the tetracarboxylic dianhydride component to the diamine component used in the polycondensation reaction of the polyamic acid is preferably 1:0.8 to 1:1.2 in terms of a molar ratio, and the molecular weight of the polyamic acid obtained increases as the molar ratio approaches 1:1.

The polyamic acid prepared by the above-described process is mixed with a soluble polyimide and used as one component of the liquid crystal aligning agent of the present invention. On the other hand, polyamic acid as a soluble polyimide precursor is imidized. The imidization of the polyamic acid is carried out by stirring in an organic solvent, preferably in the presence of a basic catalyst and an acid anhydride, preferably for 1 to 100 hours.

Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among them, pyridine is preferable because it has a basicity suitable for the reaction.

Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. Among them, acetic anhydride is preferred because purification of the obtained polyimide can be easily performed after completion of imidization. As the organic solvent, a solvent used in the polycondensation reaction of the polyamic acid can be used.

The imidization rate of the soluble polyimide can be controlled by adjusting the amount of the catalyst, the reaction temperature, and the reaction time. The amount of the basic catalyst in this case is preferably 0.2 to 10 times by mol, more preferably 0.5 to 5 times by mol, based on the amic acid group. The amount of the acid anhydride is preferably 1 to 30 times by mol, more preferably 1 to 10 times by mol, based on the amic acid group. The reaction temperature is preferably-20 to 250 ℃, and more preferably 0 to 180 ℃. The reaction time is preferably 1 to 100 hours, more preferably 1 to 20 hours.

The imidization ratio of the soluble polyimide is not particularly limited, but is preferably 40% or more, and in order to obtain a high voltage holding ratio, 60% or more, and more preferably 80% or more. Since the added catalyst and the like remain in the solution of the soluble polyimide obtained, it is preferable that the soluble polyimide is recovered and washed and then used as the liquid crystal aligning agent of the present invention.

The soluble polyimide can be recovered by pouring the imidized solution into a poor solvent under stirring to precipitate the polyimide and then filtering. Examples of the poor solvent in this case include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, and benzene. The recovered soluble polyimide may be washed with the poor solvent.

The polyimide thus recovered/washed can be made into a powder by drying at normal temperature or under reduced pressure or drying by heating.

< liquid Crystal alignment agent >

The liquid crystal aligning agent of the present invention contains the soluble polyimide and polyamic acid in a form dissolved in an organic solvent. The liquid crystal aligning agent preferably contains 3 to 10 mass%, more preferably 4 to 7 mass% of soluble polyimide. The liquid crystal aligning agent preferably contains 3 to 10 mass%, more preferably 4 to 7 mass% of polyamic acid. The total content of the soluble polyimide and polyamic acid in the liquid crystal aligning agent is preferably 3 to 10% by mass, more preferably 4 to 7% by mass.

In addition, the polyamic acid is preferably contained in an amount of 10 to 1000 parts by mass, more preferably 10 to 800 parts by mass, based on 100 parts by mass of the soluble polyimide.

The organic solvent contained in the liquid crystal aligning agent is preferably 90 to 97% by mass, more preferably 93 to 96% by mass.

In the liquid crystal aligning agent of the present invention, the organic solvent (solvent) used in the liquid crystal aligning agent of the present invention is not particularly limited as long as it is an organic solvent that dissolves a polymer component, as an organic solvent for dissolving soluble polyimide and polyamic acid. Specific examples thereof are listed below.

Examples thereof include N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, dimethyl sulfoxide, tetramethylurea, pyridine, dimethyl sulfone, γ -butyrolactone, 3-methoxy-N, N-dimethylpropionamide, 3-ethoxy-N, N-dimethylpropionamide, 3-butoxy-N, N-dimethylpropionamide, 1, 3-dimethyl-imidazolidinone, ethyl amyl ketone, methyl nonyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, cyclohexanone, ethylene carbonate, propylene carbonate, diethylene glycol dimethyl ether, propylene glycol dimethyl, 4-hydroxy-4-methyl-2-pentanone, and the like. They may be used alone or in combination.

The liquid crystal aligning agent of the present invention may contain components other than the above-mentioned polymer components. Examples thereof include solvents and compounds for improving the film thickness uniformity and surface smoothness when the liquid crystal aligning agent is applied; and compounds for improving the adhesion between the liquid crystal alignment film and the substrate.

Specific examples of the solvent (poor solvent) for improving the film thickness uniformity and the surface smoothness include the following solvents.

Examples thereof include isopropyl alcohol, methoxymethylpentanol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, butyl carbitol, ethyl carbitol acetate, ethylene glycol monoacetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, propylene glycol monoacetate, propylene glycol monomethyl ether, propylene glycol tert-butyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, diethylene glycol monoacetate, diethylene glycol dimethyl ether, dipropylene glycol monoacetate monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monoacetate monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoacetate monopropyl ether, 3-methyl-3-methoxybutyl acetate, tripropylene glycol methyl ether, 3-methyl-3-methoxybutanol, methyl cellosolve acetate, ethyl cellosolve acetate, ethylene glycol monobutyl ether, propylene glycol monoacetate, propylene glycol monobutyl ether, propylene glycol, Diisopropyl ether, ethyl isobutyl ether, diisobutylene, amyl acetate, butyl butyrate, butyl ether, diisobutyl ketone, methylcyclohexanone, propyl ether, dihexyl ether, 1-hexanol, n-hexane, n-pentane, n-octane, diethyl ether, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol, 1-phenoxy-2-propanol, butyl butyrate, butyl ether, diisobutyl ketone, methylcyclohexanone, propyl ether, dihexyl ether, 1-hexanol ether, n-pentane, n-octane, diethyl ether, methyl lactate, ethyl lactate, And solvents having low surface tension such as propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether-2-acetate, dipropylene glycol, 2- (2-ethoxypropoxy) propanol, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, and isoamyl lactate.

These poor solvents may be used in 1 kind, or may be used in combination of two or more kinds. When the solvent as described above is used, it is preferably 5 to 80% by mass, more preferably 20 to 60% by mass of the entire solvent contained in the liquid crystal aligning agent.

Examples of the compound for improving the film thickness uniformity and the surface smoothness include a fluorine-based surfactant, a silicone-based surfactant, and a nonionic surfactant.

More specifically, for example, Eftop EF301, EF303, EF352 (manufactured by Tohkem products corporation)); megafac F171, F173 and R-30 (manufactured by Dainippon ink Co., Ltd.); fluorad FC430, FC431 (manufactured by Sumitomo 3M Limited); asahiguard AG710, Surflon S-382, SC101, SC102, SC103, SC104, SC105, SC106 (manufactured by Asahi glass Co., Ltd.), etc. The amount of the surfactant is preferably 0.01 to 2 parts by mass, more preferably 0.01 to 1 part by mass, per 100 parts by mass of the resin component contained in the liquid crystal aligning agent.

Specific examples of the compound for improving the adhesion between the liquid crystal alignment film and the substrate include a functional silane-containing compound and an epoxy-containing compound described below.

Examples thereof 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-aminopropyltrimethoxysilane, N-ethoxycarbonyl-3-aminopropyltriethoxysilane, N-triethoxysilylpropyltriethylenetriamine, N-trimethoxysilylpropyltriethylenetriamine, 10-trimethoxysilyl-1, 4, 7-triazacyclodecane, 10-triethoxysilyl-1, 4, 7-triazacyclodecane, 9-trimethoxysilyl-3, 6-diazanonylacetate, 9-triethoxysilyl-3, 6-diazanonylacetate, N-benzyl-3-aminopropyltrimethoxysilane, N-benzyl-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, N-bis (oxyethylene) -3-aminopropyltrimethoxysilane, N-bis (oxyethylene) -3-aminopropyltriethoxysilane, ethylene glycol diglycidyl ether, N-bis (oxyethylene) -3-aminopropyltrimethoxysilane, N-bis (oxyethylene) -3-aminopropyltriethoxysilane, N-bis (oxyethylene) -3-aminopropyl-trimethoxysilane, ethylene glycol diglycidyl ether, N-bis (oxyethylene) -3-aminopropyl-trimethoxysilane, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, glycerol diglycidyl ether, 2-dibromoneopentyl glycol diglycidyl ether, 1,3,5, 6-tetraglycidyl-2, 4-hexanediol, N ', -tetraglycidyl-m-xylylenediamine, 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane, N ', -tetraglycidyl-4, 4 ' -diaminodiphenylmethane, and the like.

Further, in order to improve the adhesion between the substrate and the film and further prevent the deterioration of the electrical characteristics due to the backlight, the following phenol plastic-based additives, blocked isocyanate, hydroxyethyl amide-based crosslinking agent, and the like may be introduced. Specific additives are shown below, but the present invention is not limited to this structure.

When a compound for improving adhesion to a substrate is used, the amount thereof is preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass, per 100 parts by mass of the polymer component contained in the liquid crystal aligning agent. If the amount is less than 0.1 part by mass, the effect of improving the adhesion cannot be expected, and if it is more than 30 parts by mass, the liquid crystal alignment may be deteriorated.

In the liquid crystal aligning agent of the present invention, in addition to the above-mentioned substances, a dielectric substance, a conductive substance, and a crosslinkable compound for improving the film hardness and/or the density when the liquid crystal alignment film is formed may be added for the purpose of changing electric characteristics such as a dielectric constant, conductivity, and the like of the liquid crystal alignment film within a range not to impair the effects of the present invention.

< liquid Crystal alignment film, liquid Crystal display element >

The liquid crystal aligning agent of the present invention can be used as a liquid crystal alignment film by applying it to a substrate or the like, baking it, and then performing alignment treatment such as brushing or light irradiation, or without performing alignment treatment in vertical alignment applications or the like. In this case, the substrate used is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a plastic substrate such as an acryl substrate or a polycarbonate substrate, or the like can be used. In addition, from the viewpoint of simplifying the process, a substrate on which an ITO (Indium Tin Oxide) electrode or the like for driving a liquid crystal is formed is preferably used. In the case of a reflective liquid crystal display element, an opaque material such as a silicon wafer may be used as long as it is a single-sided substrate, and a material that reflects light such as aluminum may be used as an electrode in this case.

The method of applying the liquid crystal aligning agent is not particularly limited, and a method of applying the liquid crystal aligning agent by screen printing, gravure printing, flexo printing, inkjet, or the like is generally industrially used. Other coating methods include dipping, roll coater, slit coater, spin coater, and the like, and they can be used according to the purpose. The liquid crystal aligning agent of the present invention is excellent in printability because the polymers contained therein and obtained using the diamines represented by the formulae (1) and (2) have good solubility in solvents. Therefore, deposition and whitening (i.e., generation of aggregates) at the time of coating on a substrate or the like are suppressed, and coating/film-forming properties are improved. Further, even if the standing time is prolonged after the coating on a substrate or the like, a liquid crystal alignment film having excellent uniformity and transparency can be produced.

The firing after the liquid crystal alignment agent is applied to the substrate can be carried out at 50 to 300 ℃, preferably 80 to 250 ℃ by heating means such as a hot plate, and the solvent is evaporated to form a coating film. By this firing, the organic group a derived from the diamine represented by the formulae (1) and (2) and capable of being eliminated by heat is eliminated from the polyamic acid, polyamic acid ester, polyimide, and polyamide, and consumed by the above-mentioned cyclization reaction and intermolecular reaction. Therefore, the resulting liquid crystal alignment film is less likely to undergo film reduction during the rubbing treatment, has excellent rubbing resistance, and is less likely to suffer from a decrease in voltage holding ratio even when exposed to high temperature and high humidity or a backlight for a long period of time. Further, it is presumed that the structure of the polymer after firing is close to that of liquid crystal due to the cyclization reaction, and thus, good liquid crystal alignment properties are exhibited.

When the thickness of the coating film formed after firing is too large, the power consumption of the liquid crystal display element is not good, and when the thickness is too small, the reliability of the liquid crystal display element may be lowered, and therefore, the thickness is preferably 5 to 300nm, more preferably 10 to 100 nm. When the liquid crystal is aligned horizontally or obliquely, the fired coating film is treated by brushing, polarized ultraviolet irradiation, or the like.

The liquid crystal display element of the present invention is produced by obtaining a substrate with a liquid crystal alignment film from the liquid crystal aligning agent of the present invention by the above-described method, and then producing a liquid crystal cell by a known method. For example, the liquid crystal display element includes a liquid crystal cell having: 2 substrates arranged in an opposing manner, a liquid crystal layer provided between the substrates, and the liquid crystal alignment film provided between the substrates and the liquid crystal layer and formed of the liquid crystal alignment agent of the present invention. As a method for manufacturing a liquid crystal cell, the following method can be exemplified: a method of preparing a pair of substrates on which liquid crystal alignment films are formed, spreading spacers on the liquid crystal alignment film of one substrate, attaching the other substrate with the liquid crystal alignment film surface facing inward, injecting liquid crystal under reduced pressure, and sealing; or a method of dropping a liquid crystal on the liquid crystal alignment film surface on which the spacer is dispersed, and then attaching a substrate and sealing the same. The thickness of the spacer is preferably 1 to 30 μm, more preferably 2 to 10 μm.

As the liquid crystal, a positive type liquid crystal having positive dielectric anisotropy or a negative type liquid crystal having negative dielectric anisotropy can be used, and specifically, for example, MLC-2003, MLC-2041, MLC-6608, MLC-6609, and the like manufactured by MERCK CORPORATION are used.

The liquid crystal display element produced by using the liquid crystal aligning agent of the present invention as described above has excellent reliability, and is applicable to a large-screen, high-definition liquid crystal television set and the like.

Examples

The present invention will be described with reference to examples, but it is understood that the present invention is not limited thereto.

The abbreviations of the compounds used in examples and comparative examples are as follows.

< tetracarboxylic dianhydride >

A-1: 1,2,3, 4-cyclobutanetetracarboxylic dianhydride

A-2: 1,2,3, 4-butanetetracarboxylic dianhydride

A-3: 3, 4-dicarboxy-1, 2,3, 4-tetrahydro-1-naphthalene succinic dianhydride

A-4: pyromellitic dianhydride

A-5: 3,3 ', 4, 4' -biphenyltetracarboxylic dianhydride

< diamine >

B-1: 1, 4-phenylenediamine

B-2 and B-3: 4, 4-diaminodiphenylmethane

B-3: 4, 4' -diaminodiphenylamine

B-4: 3, 5-diaminobenzoic acid

B-5: 1, 2-bis (4-aminophenoxy) ethane

B-6: 1, 5-bis (4-aminophenoxy) pentane

B-7: n1, N4-bis (2-tert-butoxycarbonylamino-4-aminophenyl) adipamide

B-8: 4-amino-N- (2-tert-butoxycarbonylamino-4-aminophenyl) benzamide

< organic solvent >

NMP: n-methyl-2-pyrrolidone

GBL: gamma-butyrolactone

BCS: butyl cellosolve

The evaluation method performed in this example is shown below.

< measurement of viscosity >

In the synthesis examples or comparative synthesis examples, the viscosity of the polyamic acid solution was measured at a temperature of 25 ℃ with a sample volume of 1.1mL and a cone rotor TE-1(1 ℃ C., 34', R24) using an E-type viscometer TVE-22H (manufactured by Toyobo industries, Ltd.).

< measurement of imidization Rate >

The imidization ratio of polyimide was measured in the following manner. 20mg of polyimide powder was put into an NMR sample tube, and deuterated dimethyl sulfoxide (DMSO-d) was added thereto₆0.05% TMS mixture) was added to the reaction solution to 0.53ml, and the mixture was completely dissolved. The proton NMR at 500MHz was measured for the solution using an NMR measuring instrument (JNM-ECA500) manufactured by JEOL DATUM.

The imidization ratio was calculated by the following formula. The imidization ratio of the polyimide not using the diamine represented by formula (1) was calculated by setting the value of "the amount of the diamine represented by formula (1) introduced during the polymerization of the polyamic acid" in the following formula to zero.

Imidization ratio (%)

(100-Polyamide acid polymerization of the formula (1) diamine introduction amount (mol%)/2) × α

Wherein α is a proton derived from a structure which does not change before and after imidization, and is defined as a reference proton, and the peak cumulative value of the proton derived from the NH group of amic acid appearing in the vicinity of 9.5 to 10.0ppm are determined by the following equation.

α＝(1-α·x/y)

In the above formula, x is a peak cumulative value of a proton derived from an NH group of amic acid, y is a peak cumulative value of a reference proton, and α is a ratio of the number of reference protons to 1 NH group proton of amic acid in the case of polyamic acid (imidization ratio of 0%).

< preparation of liquid Crystal alignment agent >

Synthesis example-1

Synthesis and varnish preparation of A-3/B-1(70), B-8(30) soluble polyimides

In a 200ml four-necked flask equipped with a nitrogen introduction tube and a mechanical stirrer, 2.27g (20.98mmol) of B-1 and 5.00g (8.99mmol) of B-8 as diamine components were weighed, 64.3g of NMP was added to confirm complete dissolution of the diamine components, 8.81g (29.37mmol) of A-3 was added while cooling in an ice bath, and after stirring for 10 minutes, the temperature was raised to 50 ℃ to react until the viscosity became stable, thereby obtaining a 20 mass% polyamic acid solution [ PAA-1 ]. The viscosity after stabilization was about 1500 mPas. Further, the reaction was performed under a nitrogen atmosphere.

60.0g of the obtained polyamic acid solution was transferred into a 300ml round bottom flask, and 140.0g of NMP was added to prepare a 6.0 wt% solution. To the solution were added 11.41g (111.76mmol) of acetic anhydride and 8.84g (111.76mmol) of pyridine, and the mixture was stirred at room temperature for 30 minutes, and then heated to 45 ℃ to react for 3 hours.

After the reaction, the solution was gradually poured into 770g of methanol cooled to 10 ℃ or lower to precipitate a solid. The solid was recovered by suction filtration, repulped 2 times with 500g of methanol, and then vacuum-dried at 60 ℃ to obtain polyimide [ SPI-1] of the present invention. The imidization rate was 84%.

2.00g of SPI-1 was weighed in a50 ml Erlenmeyer flask equipped with a stirrer, 18.0g of GBL was added thereto, and the mixture was stirred at 50 ℃ for 24 hours to dissolve it, and it was confirmed that the mixture was completely dissolved, 13.33g of GBL was added thereto, and the mixture was stirred at room temperature for 30 minutes, whereby a polyimide solution [ SPI-1S ] having 6.0 mass% of SPI-1 and 94 mass% of GBL was obtained.

Synthesis example 2

Synthesis and varnish preparation of A-3/B-1(70), B-9(30) soluble polyimides

2.95g (27.29mmol) of B-1 and 4.00g (11.70mmol) of B-9 as diamine components were weighed out in a 100ml four-necked flask equipped with a nitrogen introduction tube and a mechanical stirrer, 73.64g of NMP was added to confirm complete dissolution of the diamine components, 11.46g (38.21mmol) of A-3 was added while cooling in an ice bath, and after stirring for 10 minutes, the temperature was raised to 50 ℃ to allow the reaction to stabilize the viscosity, thereby obtaining a 20 mass% polyamic acid solution [ PAA-2 ]. The viscosity after stabilization was about 1300 mPas. Further, the reaction was performed under a nitrogen atmosphere.

70.0g of the obtained polyamic acid solution was transferred into a 300ml round bottom flask, and 163.0g of NMP was added to prepare a 6.0 wt% solution. To the solution were added 15.12g (148.10mmol) of acetic anhydride and 11.72g (148.10mmol) of pyridine, and the mixture was stirred at room temperature for 30 minutes, and then heated to 45 ℃ to react for 3 hours.

After the reaction, the solution was gradually poured into 800g of methanol cooled to 10 ℃ or lower to precipitate a solid. The solid was recovered by suction filtration, repulped 2 times with 500g of methanol, and then vacuum-dried at 60 ℃ to obtain polyimide [ SPI-2] of the present invention. The imidization rate was 81%.

2.00g of SPI-2 was weighed into a50 ml Erlenmeyer flask equipped with a stirrer, 18.0g of GBL was added thereto, and the mixture was stirred at 50 ℃ for 24 hours to dissolve the mixture, and it was confirmed that the mixture was completely dissolved, 13.33g of GBL was added thereto, and the mixture was stirred at room temperature for 30 minutes to obtain a polyimide solution [ SPI-2S ] having 6.0 mass% of SPI-2 and 94 mass% of GBL.

Synthesis example 3

Polymerization of A-1, A-4(50)/B-2 Polyamic acid and varnish preparation

In a 200ml four-necked flask equipped with a nitrogen inlet tube and a mechanical stirrer, 9.91g (50.00mmol) of B-2 was weighed and dissolved by adding 56.04g of NMP and 56.04g of GBL, and cooled to about 10 ℃, 4.41g (22.50mmol) of A-1 was weighed and added in small portions, 5.45g (25.00mmol) of A-4 was added in small portions, and the mixture was returned to room temperature to react until the viscosity became stable, thereby obtaining a 15 mass% polyamic acid solution [ PAA-3 ]. The viscosity after stabilization was about 350 mPas. The reaction was performed under a nitrogen atmosphere.

100.0g of the polyamic acid solution obtained above was weighed into a500 ml Erlenmeyer flask equipped with a stirrer, and γ BL23.33g, NMP 26.67g, and BCS 50.00g were added thereto and stirred at room temperature for 30 minutes to obtain a polyamic acid solution [ PAA-1S ] having PAA-3 of 6.0 mass%, γ BL of 59 mass%, NMP of 20 mass%, and BCS of 15 mass%.

Synthesis example 4

Polymerization of A-1, A-3(20)/B-2, B-3(20) Polyamic acid and varnish preparation

In a 200ml four-necked flask equipped with a nitrogen introduction tube and a mechanical stirrer, 1.98g (10.00mmol) of B-2 and 38.40 g (40.00mmol) of B-38.78 g were weighed, and NMP 152.10g was added and dissolved, and cooled to about 10 ℃ to add A-1: 7.35g (38.00mmol), followed by small multiple additions of A-3: 3.00g (10.00mmol), returned to room temperature and reacted until the viscosity stabilized to obtain a 15 mass% polyamic acid solution [ PAA-4 ]. The viscosity after stabilization was about 180 mPas. The reaction was performed under a nitrogen atmosphere.

100.0g of the polyamic acid solution obtained above was weighed into a500 ml Erlenmeyer flask equipped with a stirrer, and NMP40g and BCS 60.00g were added thereto, followed by stirring at room temperature for 30 minutes, whereby a polyamic acid solution [ PAA-2S ] having 6.0 mass% of PAA-3, 64 mass% of NMP, and 30 mass% of BCS was obtained.

Synthesis example 5

Synthesis and varnish preparation of soluble polyimides A-1, A-2(65)/B-6 and B-8(30)

6.84g (28.00mmol) of B-6 and 6.68g (12.00mmol) of B-8 as diamine components were weighed out in a 100ml four-necked flask equipped with a nitrogen introduction tube and a mechanical stirrer, 57.60g of NMP was added to confirm complete dissolution of the diamine components, 5.15g (26.00mmol) of A-2 was added while cooling in an ice bath, 2.26g (11.50mmol) of A-1 was added, 25.8g of NMP was added and stirred for 10 minutes, and then the temperature was raised to 40 ℃ to allow the reaction to stabilize the viscosity, thereby obtaining a 20 mass% polyamic acid solution [ PAA-5 ]. The viscosity after stabilization was about 1200 mPas. The reaction was performed under a nitrogen atmosphere.

The obtained polyamic acid solution was transferred to a 200ml eggplant type flask by 40.0g, and 83.0g of NMP was added to prepare a 6.5 wt% solution. To the solution were added 3.90g (3.79mmol) of acetic anhydride and 1.81g (2.28mmol) of pyridine, and the mixture was heated to 50 ℃ to react for 2 hours.

After the reaction, 450g of methanol cooled to 10 ℃ or lower was gradually poured into the solution to precipitate a solid. The solid was recovered by suction filtration, repulped 2 times with 200g of methanol, and then vacuum-dried at 60 ℃ to obtain polyimide [ SPI-3] of the present invention. The imidization rate was 65%.

5.3g of SPI-3 was weighed in a 100ml Erlenmeyer flask equipped with a stirrer, 19.4g of NMP and 10.6g of GBL10 were added and dissolved by stirring at 50 ℃ for 20 hours to confirm complete dissolution, and 12.4g of NMP, 14.1g of γ BL and 20.6g of BCS were added and stirred at room temperature for 30 minutes to obtain a polyimide solution [ SPI-3S ] having 6.0 mass% of SPI-3, 39.0 mass% of NMP, 30.0 mass% of GBL and 25.0 mass% of BCS.

Synthesis example 6

Polymerization of A-1, A-5(45)/B-3, B-6(50) Polyamic acid and varnish preparation

In a 100ml four-necked flask equipped with a nitrogen inlet tube and a mechanical stirrer, 3.98g (20.00mmol) of B-3 and 4.88g (20.00mmol) of B-6 were weighed and dissolved, 32.50g of NMP and 32.50g of GBL were added to the mixture, the mixture was cooled to about 10 ℃ and 3.68g (18.80mmol) of A-1 was weighed and added in small portions, 13.50g of NMP and 13.50g of γ BL were added to the mixture and stirred for 2 hours, and thereafter 5.30g (18.00mmol) of A-5 was added in small portions and in large portions, 19.40g of NMP and 19.40g of γ BL were added to the mixture and the mixture was reacted at 40 ℃ until the viscosity became stable, thereby obtaining a 12 mass% polyamic acid solution [ PAA-6 ]. The viscosity after stabilization was about 270 mPas. The reaction was performed under a nitrogen atmosphere.

40.0g of the polyamic acid solution obtained above was weighed into a 100ml Erlenmeyer flask equipped with a stirrer, and γ BL23.33g, NMP 26.67g, and BCS 20.00g were added thereto, and stirred at room temperature for 30 minutes, thereby obtaining a polyamic acid solution [ PAA-3S ] having a PAA-3 content of 6.0 mass%, a γ BL content of 30.0 mass%, an NMP content of 39.0 mass%, and a BCS content of 25.0 mass%.

Synthesis example 7

Polymerization of A-5/B-3, B-5(20) Polyamic acid and preparation of varnish

A12 mass% polyamic acid solution [ PAA-7] was obtained by dissolving 8.21g (41.20mmol) of B-3 and 15.60g (10.30mmol) of B-5 in a 200ml four-necked flask equipped with a nitrogen inlet tube and a mechanical stirrer by adding 69.5g of NMP and 69.5g of GBL, cooling to about 10 ℃ and measuring and adding 13.90g (47.20mmol) of A-5 in small amounts, adding 17.4g of NMP and 17.4g of γ BL, stirring for a while, and reacting at 40 ℃ until the viscosity became stable. The viscosity after stabilization was about 300 mPas. The reaction was performed under a nitrogen atmosphere.

40.0g of the polyamic acid solution obtained above was weighed into a 100ml Erlenmeyer flask equipped with a stirrer, and γ BL23.33g, NMP 26.67g, and BCS 20.00g were added thereto, followed by stirring at room temperature for 30 minutes, thereby obtaining a polyamic acid solution [ PAA-4S ] having a PAA-3 content of 6.0 mass%, a NMP content of 39.0 mass%, a γ BL content of 30.0 mass%, and a BCS content of 25.0 mass%.

Synthesis example 8

Synthesis of A-3/B-6 soluble polyimide and varnish preparation

In a 100ml four-necked flask equipped with a nitrogen introduction tube and a mechanical stirrer, 5.00g (20.47mmol) of B-6 as a diamine component was weighed, 44.6g of NMP was added to confirm complete dissolution of the diamine component, 6.14g (20.47mmol) of A-3 was added while cooling in an ice bath, and after stirring for 10 minutes, the temperature was raised to 50 ℃ to allow reaction until the viscosity became stable, thereby obtaining a 20 mass% polyamic acid solution [ PAA-4 ]. The viscosity after stabilization was about 1100 mPas. The reaction was performed under a nitrogen atmosphere.

30.0g of the obtained polyamic acid solution was transferred into a 200ml eggplant type flask, and 60.0g of NMP was added to prepare a 6.0 wt% solution. To the solution were added 5.60g (55.13mmol) of acetic anhydride and 4.36g (55.13mmol) of pyridine, and the mixture was stirred at room temperature for 30 minutes, and then heated to 40 ℃ to react for 3 hours.

After the reaction, the solution was gradually poured into 350g of methanol cooled to 10 ℃ or lower to precipitate a solid. The solid was recovered by suction filtration, repulped 2 times with 200g of methanol, and then vacuum-dried at 60 ℃ to obtain polyimide [ SPI-4] which was a comparative object. The imidization rate was 63%.

2.00g of SPI-4 was weighed into a50 ml Erlenmeyer flask equipped with a stirrer, 18.0g of GBL was added, and the mixture was stirred at 50 ℃ for 24 hours to dissolve it, and it was confirmed that the mixture was completely dissolved, 13.33g of GBL was added, and the mixture was stirred at room temperature for 30 minutes, whereby a polyimide solution [ SPI-4S ] having 6.0 mass% of SPI-4 and 94 mass% of GBL was obtained.

Synthesis example 9

Polymerization of A-4/B-7 Polyamic acid and varnish preparation

In a 200ml four-necked flask equipped with a nitrogen introduction tube and a mechanical stirrer, 5.00g (17.46mmol) of B-7 was weighed out, 56.67g of NMP was added thereto and dissolved, and then cooled to about 10 ℃ to obtain 3.50g (16.06mmol) of A-4, which was weighed out and added in small amounts, and the mixture was returned to room temperature to react until the viscosity became stable, thereby obtaining a 15 mass% polyamic acid solution [ PAA-5 ]. The viscosity after stabilization was about 420 mPas. The reaction was performed under a nitrogen atmosphere. The PAA-obtained had a number average molecular weight of 12500 and a weight average molecular weight of 33800.

50.0g of the polyamic acid solution obtained above was weighed into a500 ml Erlenmeyer flask equipped with a stirrer, and γ BL11.67g, NMP 13.34g, and BCS 25.00g were added thereto, followed by stirring at room temperature for 30 minutes to obtain a polyamic acid solution [ PAA-5S ] having PAA-4 of 6.0 mass%, NMP of 20 mass%, and BCS of 15 mass%.

Example 1

Preparation of liquid Crystal Aligning agent-1 [ SPI-1S/PAA-1S 30:70 (weight ratio) ] and evaluation of liquid Crystal alignment film

30.0g of SPI-1S obtained by the method of Synthesis example 1 and 70.0g of PAA-1S obtained by the method of Synthesis example 3 were weighed into a 100ml Erlenmeyer flask equipped with a stirrer, and stirred for 20 hours under a nitrogen atmosphere. Thereafter, the mixture was subjected to pressure filtration using a membrane filter having a pore size of 1 μm, thereby obtaining a liquid crystal aligning agent-1 of the present invention.

Example 2

Preparation of liquid Crystal Aligning agent-2 [ SPI-2S/PAA-2S 30:70 (weight ratio) ] and evaluation of liquid Crystal alignment film

30.0g of SPI-2S obtained by the method of Synthesis example 2 and 70.0g of PAA-2S obtained by the method of Synthesis example 4 were weighed in a 100ml Erlenmeyer flask equipped with a stirrer, and stirred for 20 hours under a nitrogen atmosphere. Thereafter, the mixture was subjected to pressure filtration using a membrane filter having a pore size of 1 μm, thereby obtaining a liquid crystal aligning agent-2 of the present invention.

Example 3

Preparation of liquid Crystal Aligning agent-3 [ SPI-3S/PAA-3S 30:70 (weight ratio) ] and evaluation of liquid Crystal alignment film

30.0g of SPI-3S obtained by the method of Synthesis example 5 and 70.0g of PAA-3S obtained by the method of Synthesis example 6 were weighed into a 100ml Erlenmeyer flask equipped with a stirrer, and stirred for 20 hours under a nitrogen atmosphere. Thereafter, the mixture was subjected to pressure filtration using a membrane filter having a pore size of 1 μm, thereby obtaining a liquid crystal aligning agent-3 of the present invention.

Example 4

Preparation of liquid Crystal Aligning agent-4 [ SPI-3S/PAA-4S 30:70 (weight ratio) ] and evaluation of liquid Crystal alignment film

30.0g of SPI-3S obtained by the method of Synthesis example 5 and 70.0g of PAA-4S obtained by the method of Synthesis example 7 were weighed into a 100ml Erlenmeyer flask equipped with a stirrer, and stirred for 20 hours under a nitrogen atmosphere. Thereafter, the mixture was subjected to pressure filtration using a membrane filter having a pore size of 1 μm, thereby obtaining a liquid crystal aligning agent-4 of the present invention.

Comparative example 1

Preparation of liquid Crystal Aligning agent-5 [ SPI-4S/PAA-3S 30:70 (weight ratio) ] and evaluation of liquid Crystal alignment film

30.0g of SPI-4S obtained by the method of Synthesis example 8 and 70.0g of PAA-3S obtained by the method of Synthesis example 6 were weighed into a 100ml Erlenmeyer flask equipped with a stirrer, and stirred for 20 hours under a nitrogen atmosphere. Thereafter, pressure filtration was carried out using a membrane filter having a pore size of 1 μm, whereby a liquid crystal aligning agent-5 to be compared was obtained.

Comparative example 2

Preparation of liquid Crystal Aligning agent-6 [ PAA-5S/PAA-2S 20:80 (weight ratio) ] and evaluation of liquid Crystal alignment film

20.0g of PAA-5S obtained by the method of Synthesis example 9 and 80.0g of PAA-2S obtained by the method of Synthesis example 4 were weighed into a 100ml Erlenmeyer flask equipped with a stirrer, and stirred for 20 hours under a nitrogen atmosphere. Thereafter, the resulting mixture was subjected to pressure filtration using a membrane filter having a pore size of 1 μm, to obtain a liquid crystal aligning agent-6 to be compared.

The liquid crystal alignment films were evaluated by the following methods using the liquid crystal alignment agents obtained in examples 1 to 4 and comparative examples 1 to 2.

< evaluation of film uniformity of alignment agent >

The liquid crystal aligning agent was filtered through a 1.0 μm filter, and then applied by spin coating onto a substrate with an electrode (a glass substrate having a size of 30mm in width by 40mm in length and a thickness of 1.1mm, an ITO electrode having a rectangular shape of 10mm in width by 40mm in length and a thickness of 35 nm). After the spin coating, the resultant film was left at room temperature of 23 ℃ and humidity of 50% for 5 minutes, and fired in an IR oven at 220 ℃ for 20 minutes, and surface analysis was carried out using DFM (DIRECT FORCE atomic microscope: manufactured by Hitachi High-Technologies Corporation) for uniformity of the obtained film, and roughness of 10 μm on average was calculated and compared. The smaller the roughness, the better the uniformity and film forming property of the film.

< evaluation of backlight resistance of Voltage holding ratio >

The backlight resistance of the voltage holding ratio was evaluated as follows.

[ preparation of liquid Crystal cell for measuring Voltage holding ratio ]

The liquid crystal aligning agent was filtered through a 1.0 μm filter, and then applied to a substrate with an electrode (a glass substrate having a size of 30mm in width by 40mm in length and a thickness of 1.1 mm; the electrode was an ITO electrode having a rectangular shape of 10mm in width by 40mm in length and a thickness of 35 nm) by spin coating. After drying on a hot plate at 50 ℃ for 5 minutes, the film was baked in an IR oven at 230 ℃ for 20 minutes to form a coating film having a film thickness of 100nm, thereby obtaining a substrate with a liquid crystal alignment film. The liquid crystal alignment film was brushed with rayon cloth (YA-20R manufactured by Giken chemical Co., Ltd.) to give a substrate with a liquid crystal alignment film (roll diameter: 120mm, roll rotation speed: 1000rpm, moving speed: 20mm/sec, press-in length: 0.4mm), then the substrate was cleaned by ultrasonic irradiation in pure water for 1 minute, and then dried at 80 ℃ for 15 minutes after removing water droplets by air blowing to give a substrate with a liquid crystal alignment film.

2 sheets of the substrates with the liquid crystal alignment films were prepared, spacers of 4 μm were spread on one of the liquid crystal alignment films, and then a sealant was printed thereon, and another 1 sheet of the substrates was pasted with the brushing direction being reversed and the films facing each other, and then the sealant was cured to prepare an empty cell. Negative liquid crystals MLC-7206 (manufactured by merckcorroporation) and MLC-2041 (manufactured by MERCK CORPORATION) were injected into the empty cell by a reduced pressure injection method, and the injection port was sealed to obtain a liquid crystal cell. Then, the resulting liquid crystal cell was heated at 110 ℃ for 1 hour and left at 23 ℃ overnight to obtain a liquid crystal cell for measuring voltage holding ratio.

[ evaluation of backlight resistance ]

The voltage holding ratio was measured by applying a voltage of 1V for 60 μ sec to the liquid crystal cell for measuring voltage holding ratio at a temperature of 60 ℃ and measuring the voltage after 100msec, and the voltage holding ratio was calculated as how much the voltage can be held. This was taken as the initial voltage holding ratio.

Next, as a backlight resistance test, the liquid crystal cell was left at 70 ℃ for 72 hours under an LED light source (1000 cd). The voltage holding ratio of the liquid crystal cell was measured in the same manner as described above. This was used as the voltage holding ratio after the resistance test.

The backlight resistance of the voltage holding ratio was evaluated by the magnitude of the voltage holding ratio measured in the above-described manner. Namely, the method comprises the following steps: the smaller the amount of change in the voltage holding ratio after the resistance test is, the better the backlight resistance is.

[ relaxation Properties of RDC ]

The liquid crystal cell for measuring voltage holding ratio is arranged between 2 polarizing plates arranged so that the polarization axes are perpendicular to each other, and the LED backlight is irradiated from below the 2 polarizing plates in a state where the pixel electrode and the counter electrode are short-circuited and at the same potential, and the angle of the liquid crystal cell is adjusted so that the luminance of the LED backlight transmitted light measured above the 2 polarizing plates becomes minimum.

Then, while applying a rectangular wave having a frequency of 30Hz to the liquid crystal cell, the V-T characteristics (voltage-transmittance characteristics) at a temperature of 23 ℃ were measured, and an AC voltage at which the relative transmittance reached 23% was calculated. Since this ac voltage corresponds to a region in which the luminance change with respect to the voltage is large, it is suitable to evaluate RDC by luminance.

Then, a dc voltage of +3.0V was superimposed and driven for 1 hour while applying an ac voltage having a relative transmittance of 23% and a rectangular wave having a frequency of 30 Hz. Thereafter, the dc voltage was cut off, and only a rectangular wave having a frequency of 30Hz and an ac voltage having a relative transmittance of 23% was applied again for 30 minutes, and the recovery time of flicker (flicker) generated at this time was measured.

The faster the relaxation of the accumulated charge and the shorter the time, the better the relaxation characteristics of the RDC.

Further, the calculation of the flicker intensity may be performed by converting the luminance into a direct-current voltage using a photodiode and an AC-DC converter, and reading it with an oscilloscope. When the flicker occurs, the flicker can be monitored as an ac voltage with respect to a rectangular wave of 30Hz, and therefore, the time when the ac voltage becomes a dc voltage can be regarded as the relaxation time of the RDC.

In terms of driving of liquid crystal, MLC-7206, which is a negative type liquid crystal, cannot be evaluated, and therefore, this measurement was performed using MLC-2041.

< evaluation of liquid Crystal alignment >

The liquid crystal alignment was evaluated in the following manner.

[ preparation of substrate with FFS-mode electrode ]

A substrate with an electrode for FFS system is prepared. The substrate was a glass substrate having dimensions of 30mm × 35mm and a thickness of 0.7 mm. An IZO electrode constituting a counter electrode was formed as a 1 st layer on the entire surface of the substrate. A SiN (silicon nitride) film formed by CVD was formed as the 2 nd layer on the IZO electrode of the 1 st layer. The SiN film of the 2 nd layer has a film thickness of 500nm and functions as an interlayer insulating film. On the SiN film of the 2 nd layer, a comb-shaped pixel electrode formed by patterning an IZO film is disposed as a 3 rd layer, and two kinds of pixels, i.e., a 1 st pixel and a 2 nd pixel, are formed. The size of each pixel is 10mm in length and about 5mm in width. At this time, the counter electrode of the 1 st layer and the pixel electrode of the 3 rd layer are electrically insulated by the SiN film of the 2 nd layer.

The pixel electrode of the 3 rd layer has a comb-tooth shape formed by arranging a plurality of "<" -shaped electrode elements whose central portions are bent. The width of each electrode element in the width direction was 3 μm, and the interval between the electrode elements was 6 μm. Since the pixel electrode forming each pixel is formed by arranging a plurality of "<" -shaped electrode elements each having a bent central portion, each pixel has a shape similar to a bold "<" -shaped electrode element, which is bent at the central portion in the same manner as the electrode elements, instead of a rectangular shape. Each pixel is divided vertically with a curved portion at the center thereof as a boundary, and has a 1 st region on the upper side and a 2 nd region on the lower side of the curved portion.

When comparing the 1 st region and the 2 nd region of each pixel, the forming directions of the electrode elements constituting the pixel electrodes are different. That is, when the alignment treatment direction of the liquid crystal alignment film described later is set as a reference, the electrode elements of the pixel electrode are formed so as to make an angle of +10 ° (clockwise) in the 1 st region of the pixel, and the electrode elements of the pixel electrode are formed so as to make an angle of-10 ° (clockwise) in the 2 nd region of the pixel. That is, the 1 st region and the 2 nd region of each pixel are configured as follows: the directions of the rotation (planar switching) of the liquid crystal in the substrate plane induced by applying a voltage between the pixel electrode and the counter electrode are opposite to each other.

< preparation of liquid Crystal cell for evaluating liquid Crystal orientation >

The liquid crystal aligning agent was filtered through a 1.0 μm filter and then applied to the substrate with the FFS mode electrode by spin coating. After drying on a hot plate at 100 ℃ for 100 seconds, the film was baked in a hot air circulation oven at 230 ℃ for 20 minutes to obtain a polyimide film having a film thickness of 60 nm. This polyimide film was brushed with rayon cloth (YA-20R manufactured by Giken chemical Co., Ltd.) (roll diameter: 120mm, roll rotation speed: 500rpm, moving speed: 30mm/sec, pressing length: 0.3mm, brushing direction: direction inclined at 80 degrees to IZO comb electrode of the 3 rd layer), then washed by ultrasonic irradiation for 1 minute in 3/7 mixed solvent of isopropyl alcohol and pure water, and dried at 80 ℃ for 15 minutes after removing water droplets by air blowing, to obtain a substrate with a liquid crystal alignment film.

Further, as the counter substrate, a polyimide film was formed in the same manner as described above on a glass substrate having a columnar spacer with a height of 4 μm and an ITO formed on the back surface, and a substrate with a liquid crystal alignment film subjected to an alignment treatment was obtained in the same manner as described above.

The 2 substrates with liquid crystal alignment films were set as 1 set, a sealant was printed so that a liquid crystal injection port remained on the substrates, another 1 substrate was attached so that the liquid crystal alignment films were opposed to each other and the brushing direction was antiparallel, and then the sealant was cured to produce an empty cell having a cell gap of 4 μm.

A negative type liquid crystal MLC-7206 (manufactured by MERCK CORPORATION) or a comparative MLC-2041 (manufactured by MERCK CORPORATION) was injected into the empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS type liquid crystal cell. Then, the resulting liquid crystal cell was heated at 110 ℃ for 30 minutes and left at 23 ℃ overnight to obtain a liquid crystal cell for evaluation of liquid crystal alignment properties.

[ evaluation of liquid Crystal alignment Properties ]

An ac voltage having a frequency of 30Hz and a relative transmittance of 100% was applied to the liquid crystal cell for evaluating the liquid crystal alignment property for 168 hours in a constant temperature environment of 60 ℃. Thereafter, a short circuit state was caused to occur between the pixel electrode and the counter electrode of the liquid crystal cell, and the liquid crystal cell was left to stand at room temperature for one day. After the placement, the liquid crystal cell was placed between 2 polarizing plates arranged so that the polarization axes were perpendicular, and the backlight was turned on in a state where no voltage was applied, and the arrangement angle of the liquid crystal cell was adjusted so that the luminance of transmitted light became minimum. Then, the rotation angle when the liquid crystal cell is rotated from the 2 nd area of the 1 st pixel to the 1 st area is the darkest angle is calculated as an angle Δ. Similarly, in the 2 nd pixel, the 2 nd area and the 1 st area are compared, and the same angle Δ is calculated. Then, the average value of the angle Δ values of the 1 st pixel and the 2 nd pixel is calculated as the angle Δ of the liquid crystal cell, and the liquid crystal alignment property is evaluated by the magnitude of the value. That is, the smaller the value of the angle Δ, the better the liquid crystal alignment.

[ Table 1]

※P＝MLC-2041、N＝MLC-7206

[ Table 2]

※1P＝MLC-2041、N＝MLC-7206

The assay was performed in the same 2 as MLC-2041.

The scintillation occurs again after the scintillation recovers in the color field 3.

Industrial applicability

The liquid crystal aligning agent of the present invention can provide a liquid crystal alignment film which has good coating and film-forming properties, is highly resistant to film peeling and/or chipping during brushing, is less likely to cause initial charge accumulation even when a direct-current voltage is applied, has good reliability even when a liquid crystal lacking reliability is used, and is less likely to decrease in voltage holding ratio even when exposed to a backlight for a long period of time. Therefore, the liquid crystal display element produced using the liquid crystal aligning agent of the present invention can be used as a highly reliable liquid crystal display element, and can be applied to display elements of various types such as TN liquid crystal display elements, STN liquid crystal display elements, TFT liquid crystal display elements, VA liquid crystal display elements, IPS liquid crystal display elements, and OCB liquid crystal display elements.

Claims

1. A liquid crystal aligning agent comprising a soluble polyimide obtained from a diamine component comprising at least 1 diamine selected from the group consisting of diamines of the following formulae (i) and (ii) and a tetracarboxylic dianhydride component,

in the formula, D represents a saturated alkyl group, an unsaturated alkyl group, an aromatic alkyl group or a heterocyclic ring with the valence of 2 and the carbon number of 1-20, and D optionally has various substituents, wherein the substituents are carboxylic acid groups or fluorine atoms; e is a single bond or a 2-valent saturated alkyl group, unsaturated alkyl group, aromatic alkyl group or heterocyclic ring with 1-20 carbon atoms; f represents a single bond or an ether bond (-O-), an ester bond (-OCO-, -COO-); m is 1 or 0.

2. The liquid crystal aligning agent according to claim 1, further comprising a polyamic acid obtained by using at least 1 or more of the compounds represented by the formulae (iii) to (vi),

3. The liquid crystal aligning agent according to claim 1 or 2, wherein the soluble polyimide is a soluble polyimide obtained from a diamine component containing 10 to 90 mol% of at least 1 diamine selected from the diamines of the formulae (i) and (ii) and a tetracarboxylic dianhydride.

4. The liquid crystal aligning agent according to claim 1 or 2, wherein the soluble polyimide has an imidization ratio of 20% to 100%.

5. The liquid crystal aligning agent according to claim 1 or 2, wherein the soluble polyimide is a soluble polyimide obtained from a diamine component containing at least 1 or more diamine selected from the group consisting of formulae (vii) to (x) and a tetracarboxylic dianhydride,

n represents an integer of 1 to 6; r₃Is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; r₄Is a linear alkylene group having 1 to 5 carbon atoms.

6. The liquid crystal aligning agent according to claim 2, wherein the soluble polyimide and the polyamic acid are contained in an amount of 1 to 10% by mass in total, and a ratio of the weight of the polyimide to the weight of the polyamic acid is 95:5 to 5: 95.

7. A liquid crystal alignment film obtained by using the liquid crystal aligning agent according to any one of claims 1 to 6.

8. A liquid crystal display element comprising the liquid crystal alignment film according to claim 7.