JP7193782B2 - Liquid crystal alignment agent, liquid crystal alignment film and liquid crystal display element - Google Patents

Description

The present invention relates to a liquid crystal aligning agent, a liquid crystal aligning film and a liquid crystal display element.

Liquid crystal display elements are known as lightweight, thin and low power consumption display devices. In recent years, high-definition liquid crystal display elements for mobile phones and tablet terminals, which have rapidly expanded their market share, have made remarkable progress to the extent that high display quality is required.

A liquid crystal display element is constructed by sandwiching a liquid crystal layer between a pair of transparent substrates provided with electrodes. In the liquid crystal display element, an organic film made of an organic material is used as a liquid crystal alignment film so that the liquid crystal is in a desired alignment state between the substrates. That is, the liquid crystal alignment film is a constituent member of the liquid crystal display element, is formed on the surfaces of the substrates that sandwich the liquid crystal and is in contact with the liquid crystal, and plays the role of orienting the liquid crystal in a certain direction between the substrates.
In recent years, liquid crystal display elements have been used for mobile applications such as smart phones and mobile phones. In these applications, in order to secure as many display surfaces as possible, it is necessary to make the width of the sealant used for bonding the substrates of the liquid crystal display element narrower than before. Furthermore, for the reasons described above, it is also required to position the sealant at a position in contact with the edge of the liquid crystal alignment film where the adhesiveness to the sealant is weak, or at the upper portion of the liquid crystal alignment film. In such a case, especially when used under high-temperature and high-humidity conditions, water tends to enter between the sealant and the liquid crystal alignment film, resulting in display unevenness near the frame of the liquid crystal display element.
In order to solve this problem, a liquid crystal aligning agent using an additive having a specific structure has been proposed (see Patent Document 1).

WO2015/072554

However, in recent years, there has been a demand for further improvement in adhesion between the liquid crystal alignment film and the sealant.

Of these, it is known that it is difficult to achieve both the adhesion property between the sealant and the liquid crystal alignment film and the moisture permeation prevention property of the sealant in the property improvement from the sealant. There is a demand for improvement in characteristics.
Accordingly, an object of the present invention is to provide a liquid crystal aligning agent capable of enhancing adhesion between a sealing agent and a liquid crystal aligning film and suppressing occurrence of display unevenness in the vicinity of the frame of a liquid crystal display element under high-temperature and high-humidity conditions. and

Thus, the present invention is based on the above findings and has the following gist.
1. A liquid crystal aligning agent containing at least one polymer selected from polyimide precursors and polyimides having a structure represented by the following formula (1) at the end of the polymer main chain.

R ₁ represents an organic group having 1 to 20 carbon atoms which may contain a photoreactive functional group such as an acryl group or a methyl methacrylate group at its terminal.

By using the liquid crystal aligning agent of the present invention, the adhesiveness between the sealing agent and the liquid crystal alignment film is increased, and a liquid crystal alignment film that can suppress the occurrence of display unevenness near the frame of the liquid crystal display element under high temperature and high humidity conditions can be obtained. . A liquid crystal display element having this liquid crystal alignment film can solve display unevenness in the vicinity of the frame by increasing the adhesiveness between the sealing agent and the liquid crystal alignment film, so that it can be suitably used for large-screen, high-definition liquid crystal displays.

It is a figure showing the preparation method of the evaluation sample produced when performing adhesion evaluation of the liquid crystal aligning film obtained using the liquid crystal aligning agent of this invention. Details will be described later.

<Terminal structure>
The liquid crystal aligning agent of the present invention contains at least one polymer selected from polyimide precursors and polyimides having a structure represented by the following formula (1) at the terminal of the main chain of the polymer.

R ₁ represents an organic group having 1 to 20 carbon atoms which may contain a photoreactive functional group such as an acryl group or a methyl methacrylate group at its terminal.
Here, R ₁ is preferably a group selected from the following structures of R-1 to R-10.

In order to introduce such a structure into polyimide, it is preferable to use a compound represented by the following formula (2) during and after polymerization of the polyimide precursor.

Specific examples of the compound of formula (2) include compounds Z-1 to Z-10 illustrated below, but from the relationship between seal adhesion and rubbing resistance, Z-1 is more preferable, and Z-2 is more preferable. Especially preferred.

<Tetracarboxylic acid derivative>
The polyimide precursor contained in the liquid crystal aligning agent of the present invention is obtained from the reaction of a tetracarboxylic acid derivative and a diamine, and the polyimide contained in the liquid crystal aligning agent of the present invention imidizes the polyimide precursor. obtained by Specific examples of materials used and manufacturing methods are described in detail below.
As the tetracarboxylic acid derivative used for the production of the polyimide precursor, not only tetracarboxylic dianhydride but also derivatives thereof such as tetracarboxylic acid, tetracarboxylic acid dihalide compound, tetracarboxylic acid dialkyl ester, tetracarboxylic acid dialkyl Examples include ester dihalides.
As the tetracarboxylic dianhydride or derivative thereof, among others, one represented by the following formula (3) is preferable.

_The structure of X1 is not particularly limited. Preferable specific examples include the following formulas (X1-1) to (X1-44). Among them, (X1-1), (X1-5), (X1-8) and (X1-27) are particularly preferred.

In formulas (X1-1) to (X1-4), R ₃ to R ₂₃ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, It is an alkynyl group having 2 to 6 carbon atoms, a monovalent organic group having 1 to 6 carbon atoms containing a fluorine atom, or a phenyl group. From the viewpoint of liquid crystal orientation, R ₃ to R ₂₃ are preferably hydrogen atoms, halogen atoms, methyl groups, or ethyl groups, and particularly preferably hydrogen atoms or methyl groups.
Specific examples of formula (X1-1) include the following formulas (X1-1-1) to (X1-1-6). (X1-1-1) is particularly preferred from the viewpoint of liquid crystal orientation and photoreaction sensitivity.

<Diamine>
The diamine used for producing the polyimide precursor is represented by the following formula (4).

A ₁ and A ₂ are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkynyl group having 2 to 5 carbon atoms.
_The structure of Y1 is not particularly limited. Preferred structures include the following (Y-1) to (Y-182).

上記式中、Ｍｅは、メチル基を表し、Ｒ^１は水素原子または炭素数１～５の炭化水素基を表す。

In the above formula, Me represents a methyl group, and R ¹ represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms.

Among them, the structures of Y ₁ are (Y-7), (Y-8), (Y-16), (Y-17), (Y-18), (Y-20), (Y-21 ), (Y-22), (Y-28), (Y-35), (Y-38), (Y-43), (Y-48), (Y-64), (Y-66), (Y-71), (Y-72), (Y-76), (Y-77), (Y-80), (Y-81), (Y-82), (Y-83), (Y -156), (Y-159), (Y-160), (Y-161), (Y-162) (Y-168), (Y-169), (Y-170) are preferred, particularly (Y-7), (Y-8), (Y-16), (Y-17), (Y-18), (Y-21), (Y-22), (Y-28), (Y -38), (Y-64), (Y-66), (Y-72), (Y-76), (Y-81), (Y-156), (Y-159), (Y-160 ), (Y-161), (Y-162), (Y-168), (Y-169), (Y-170), (Y-171), (Y-173), (Y-175) preferable.

<Polyamic acid>
A polyamic acid, which is a polyimide precursor used in the present invention, can be produced by the following method. Specifically, a tetracarboxylic dianhydride and a diamine are reacted in the presence of an organic solvent at -20°C to 150°C, preferably 0°C to 50°C, for 30 minutes to 24 hours, preferably 1 to 12 hours. It can be synthesized by By reacting the compound shown in (2) above during and/or after the polymerization, a polyimide precursor having a specific structure introduced at the terminal can be obtained.

The organic solvent used in the above reaction is preferably N,N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone in view of the solubility of the monomer and polymer, and these may be used singly or in combination of two or more. may be used. The concentration of the polymer is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, from the viewpoints that precipitation of the polymer hardly occurs and that a high molecular weight product is easily obtained.

The polyamic acid obtained as described above can be collected by precipitating a polymer by injecting the reaction solution into a poor solvent while stirring well. Further, a purified polyamic acid powder can be obtained by performing precipitation several times, washing with a poor solvent, and drying at room temperature or by heating. Poor solvents include, but are not limited to, water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.

<Polyamic acid ester>
A polyamic acid ester, which is one of the polyimide precursors used in the present invention, can be produced by the following method (I), (II) or (III). By reacting the compound shown in (2) above during and/or after the polymerization, a polyimide precursor having a specific structure introduced at the terminal can be obtained.

(I) When manufacturing from polyamic acid
A polyamic acid ester can be synthesized by esterifying a polyamic acid obtained from a tetracarboxylic dianhydride and a diamine. Specifically, a polyamic acid and an esterifying agent are reacted in the presence of an organic solvent at -20°C to 150°C, preferably 0°C to 50°C, for 30 minutes to 24 hours, preferably 1 to 4 hours. Can be synthesized.

As the esterifying agent, those that can be easily removed by purification are preferable, and include N,N-dimethylformamide dimethyl acetal, N,N-dimethylformamide diethyl acetal, N,N-dimethylformamide dipropyl acetal, and N,N-dimethylformamide. Dineopentyl butyl acetal, N,N-dimethylformamide di-t-butyl acetal, 1-methyl-3-p-tolyltriazene, 1-ethyl-3-p-tolyltriazene, 1-propyl-3-p -tolyltriazene, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride and the like. The amount of the esterifying agent to be used is preferably 2 to 6 molar equivalents per 1 mol of repeating units of the polyamic acid.

The solvent used in the above reaction is preferably N,N-dimethylformamide, N-methyl-2-pyrrolidone, or γ-butyrolactone in view of the solubility of the polymer, and these may be used singly or in combination of two or more. good. The concentration of the polymer in the reaction solution is preferably from 1 to 30% by mass, more preferably from 5 to 20% by mass, from the viewpoints that precipitation of the polymer hardly occurs and that a high molecular weight product is easily obtained.

(II) Production by reaction of tetracarboxylic acid diester dichloride and diamine Polyamic acid ester can be produced from tetracarboxylic acid diester dichloride and diamine. Specifically, a tetracarboxylic acid diester dichloride and a diamine are mixed in the presence of a base and an organic solvent at -20°C to 150°C, preferably 0°C to 50°C, for 30 minutes to 24 hours, preferably 1 to 4 hours. It can be synthesized by reacting.

Pyridine, triethylamine, 4-dimethylaminopyridine and the like can be used as the base, but pyridine is preferred because the reaction proceeds moderately. The amount of the base to be used is preferably 2 to 4 times the molar amount of the tetracarboxylic acid diester dichloride from the viewpoints of easy removal and high molecular weight.

The solvent used in the above reaction is preferably N-methyl-2-pyrrolidone or γ-butyrolactone in terms of solubility of the monomer and polymer, and these may be used alone or in combination of two or more. The polymer concentration in the reaction solution is preferably from 1 to 30% by mass, more preferably from 5 to 20% by mass, from the viewpoints that precipitation of the polymer hardly occurs and that a high molecular weight product is easily obtained. In order to prevent hydrolysis of the tetracarboxylic acid diester dichloride, the solvent used in the synthesis of the polyamic acid ester is preferably dehydrated as much as possible, and is preferably kept in a nitrogen atmosphere to prevent contamination with outside air.

(III) Production by reaction of tetracarboxylic acid diester and diamine Polyamic acid ester can be produced by polycondensation of tetracarboxylic acid diester and diamine. Specifically, a tetracarboxylic acid diester and a diamine are mixed in the presence of a condensing agent, a base, and an organic solvent at 0° C. to 150° C., preferably 0° C. to 100° C., for 30 minutes to 24 hours, preferably 3 to 15 hours. It can be produced by time reaction.

The condensing agent includes triphenylphosphite, dicyclohexylcarbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N,N'-carbonyldiimidazole, dimethoxy-1,3,5-triazide Nylmethylmorpholinium, O-(benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium Tetrafluoroborate, O-(benzotriazol-1-yl)-N,N , N′,N′-tetramethyluronium hexafluorophosphate, diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate and the like can be used. The amount of the condensing agent to be added is preferably 2 to 3 times the molar amount of the tetracarboxylic acid diester.

Tertiary amines such as pyridine and triethylamine can be used as the base. The amount of the base to be used is preferably 2 to 4 times the molar amount of the diamine component from the viewpoint of easy removal and high molecular weight.

Moreover, in the above reaction, the reaction proceeds efficiently by adding a Lewis acid as an additive. Preferred Lewis acids are lithium halides such as lithium chloride and lithium bromide. The amount of the Lewis acid to be added is preferably 0 to 1.0 times the molar amount of the diamine component.

Among the above three methods for producing a polyamic acid ester, the production method (I) or (II) above is particularly preferable because a high-molecular-weight polyamic acid ester can be obtained.

The solution of the polyamic acid ester obtained as described above is poured into a poor solvent while stirring well to precipitate the polymer. Precipitation is carried out several times, washed with a poor solvent, and dried at room temperature or by heating to obtain a purified polyamic acid ester powder. Poor solvents include, but are not limited to, water, methanol, ethanol, hexane, butyl cellosolve, acetone, and toluene.

<Polyimide>
The polyimide used in the present invention can be produced by imidating the polyamic acid or polyamic acid ester. The imidization rate of the polyimide used in the present invention is not limited to 100%. 20 to 99% is preferable from the viewpoint of electrical properties. When producing a polyimide from a polyamic acid ester, chemical imidization by adding a basic catalyst to the polyamic acid solution obtained by dissolving the polyamic acid ester solution or the polyamic acid ester resin powder in an organic solvent is convenient. Chemical imidization is preferable because the imidization reaction proceeds at a relatively low temperature and the molecular weight of the polymer is less likely to decrease during the imidization process.

Chemical imidization can be carried out by stirring polyamic acid or polyamic acid ester to be imidized in an organic solvent in the presence of a basic catalyst and an acid anhydride. At that time, by reacting the compound shown in (2) above, a polyimide precursor having a specific structure introduced at the terminal can be obtained. As the organic solvent, the solvent used in the polymerization reaction described above can be used. Basic catalysts include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Among them, pyridine is preferable because it has an appropriate basicity for advancing the reaction. Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. Among them, acetic anhydride is preferred because it facilitates purification after the reaction is completed. Generally, in the case of conventional polyimides, acetylation is generated as main chain ends when acetic anhydride is used, but the present invention can suppress acetylation.

The imidization reaction temperature is, for example, −20° C. to 120° C., preferably 0° C. to 100° C., and the reaction time is 1 to 100 hours. The amount of the basic catalyst is 0.5 to 30 times the molar amount of the amic acid group, preferably 2 to 20 times the molar amount, and the amount of the acid anhydride is 1 to 50 times the molar amount of the amic acid group, preferably 3 to 30 times the molar amount. Double. The imidization rate of the resulting polymer can be controlled by adjusting the catalyst amount, temperature and reaction time.

Since the added catalyst and the like remain in the solution after the imidization reaction of the polyamic acid ester or polyamic acid, the resulting imidized polymer is recovered by the means described below and redissolved in an organic solvent. It is preferable to set it as the liquid crystal aligning agent of this invention.

The polyimide solution obtained as described above is poured into a poor solvent while stirring well to precipitate a polymer. Precipitation is carried out several times, washed with a poor solvent, and dried at room temperature or by heating to obtain a purified polyamic acid ester powder.

The poor solvent is not particularly limited, but examples include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, and benzene.

<Liquid crystal aligning agent>
The liquid crystal aligning agent of the present invention has the form of a solution in which a polymer containing a specific polymer is dissolved in an organic solvent containing a specific solvent. The polyimide precursor and polyimide according to the present invention have a weight average molecular weight of preferably 2,000 to 500,000, more preferably 5,000 to 300,000, and still more preferably 10,000 to 100. , 000. Also, the number average molecular weight is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, still more preferably 5,000 to 50,000.

The concentration of the polymer of the liquid crystal aligning agent used in the present invention can be appropriately changed by setting the thickness of the coating film to be formed. % or more is preferable, and 10% by weight or less is preferable from the viewpoint of storage stability of the solution.

The solvent in the liquid crystal aligning agent of the present invention is a solvent (also referred to as a good solvent) that dissolves the polyimide precursor and polyimide, or a solvent that improves the coating properties and surface smoothness of the liquid crystal alignment film when the liquid crystal aligning agent is applied. (also referred to as a poor solvent) is preferably used. Specific examples of other solvents are listed below, but are not limited to these examples.

Specific examples of good solvents include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone, 1,3-dimethylimidazolidinone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, methyl ethyl ketone, cyclohexanone, cyclopentanone, 3-methoxy-N,N-dimethylpropanamide or 4-hydroxy-4-methyl-2-pentanone, etc. be able to.
Specific examples of poor solvents include 1-butoxy-2-propanol, 2-butoxy-1-propanol, 2-propoxyethanol, 2-(2-propoxyethoxy)ethanol, 1-propoxy-2-propanol ethanol, and isopropyl alcohol. , 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol, tert-pentyl alcohol, 3 -methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3 -heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-ethanediol, 1,2 -propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-methyl- 2,4-pentanediol, 2-ethyl-1,3-hexanediol, dipropyl ether, dibutyl ether, dihexyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-butoxyethane , diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol dibutyl ether, 2-pentanone, 3-pentanone, 2-hexanone, 2-heptanone, 4-heptanone, 3-ethoxybutyl acetate, 1-methylpentyl acetate, 2-ethyl butyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, 2-(methoxymethoxy)ethanol, butyl cellosolve, ethylene glycol monoisoamyl ether, ethylene glycol monohexyl ether, 2-(hexyloxy)ethanol, furfuryl alcohol, diethylene glycol, propylene glycol, 1-(butoxyethoxy)propane Nol, propylene glycol monomethyl ether acetate, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol mono Butyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, propylene glycol diacetate, diisopentyl ether, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy) ethylacetate tart, diethylene glycol acetate, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl ether acetate, methyl pyruvate , ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, 3-methoxypropionate Butyl acid, lactic acid methyl ester, lactic acid ethyl ester, lactic acid n-propyl ester, lactic acid n-butyl ester, lactic acid isoamyl ester, diisobutyl ketone, ethyl carbitol and the like.
Solvents represented by the following formulas are also preferably used as the poor solvent.

R _{24 and} R ₂₅ are each independently a linear or branched alkyl group having 1 to 8 carbon atoms. However, R ₂₄ +R ₂₅ is an integer larger than 3.

As the poor solvent, when the polyimide precursor and polyimide contained in the liquid crystal aligning agent are highly soluble in the solvent, solvents represented by the following [D-1] to [D-3] are preferable.

In formula [D-1], D ¹ represents an alkyl group having 1 to 3 carbon atoms, in formula [D-2], D ² represents an alkyl group having 1 to 3 carbon atoms, and formula [D-3] Among them, D3 represents an alkyl group having 1 to ⁴ carbon atoms.

Further, the liquid crystal aligning agent of the present invention contains at least one substituted compound selected from the group consisting of a crosslinkable compound having an epoxy group, an isocyanate group, an oxetane group or a cyclocarbonate group, a hydroxyl group, a hydroxyalkyl group and a lower alkoxyalkyl group. A crosslinkable compound having a group or a crosslinkable compound having a polymerizable unsaturated bond may be included.

Various known compounds can be used as such a crosslinkable compound depending on the purpose. The following compounds are preferably used.

The content of the crosslinkable compound is preferably 0.1 to 150 parts by mass with respect to 100 parts by mass of all polymer components. Among them, 0.1 to 100 parts by mass is preferable, and 1 to 50 parts by mass is more preferable, in order for the crosslinking reaction to proceed and the intended effects to be exhibited.

The liquid crystal aligning agent of the present invention can contain a compound that improves the uniformity of the film thickness and the surface smoothness of the liquid crystal aligning film when the liquid crystal aligning agent is applied.

Compounds that improve the uniformity of the film thickness and the surface smoothness of the liquid crystal alignment film include fluorine-based surfactants, silicone-based surfactants, and nonionic surfactants.
The amount of surfactant used is preferably 0.01 to 2 parts by mass, more preferably 0.01 to 1 part by mass, based on 100 parts by mass of all polymer components contained in the liquid crystal aligning agent.

<Liquid crystal alignment film, liquid crystal display element>
The liquid crystal aligning film of the present invention is a film obtained by applying the above liquid crystal aligning agent to a substrate, drying, and baking. The substrate to which the liquid crystal aligning agent of the present invention is applied is not particularly limited as long as it is a highly transparent substrate, and a glass substrate, a silicon nitride substrate, a plastic substrate such as an acrylic substrate, a polycarbonate substrate, or the like can also be used. In that case, it is preferable to use a substrate on which an ITO electrode or the like for driving the liquid crystal is formed, from the viewpoint of simplification of the process. In addition, in a reflective liquid crystal display element, if only one substrate is used, an opaque material such as a silicon wafer can be used, and in this case, a light-reflecting material such as aluminum can be used for the electrodes.

Industrially, the method of applying the liquid crystal aligning agent is generally performed by screen printing, offset printing, flexographic printing, inkjet method, or the like, and other coating methods include dip method, roll coater method, slit coater. methods, spinner methods or spray methods are known.

After coating the liquid crystal aligning agent on the substrate, the solvent can be evaporated by heating means such as a hot plate, a thermal circulation oven, or an IR (infrared) oven to form a liquid crystal alignment film. The drying after applying a liquid crystal aligning agent and a baking process can select arbitrary temperature and time. Usually, in order to sufficiently remove the contained solvent, the conditions are calcination at 50 to 120° C. for 1 to 10 minutes, followed by calcination at 150 to 300° C. for 5 to 120 minutes. The thickness of the liquid crystal alignment film after baking is preferably 5 to 300 nm, more preferably 10 to 200 nm, because if the thickness is too thin, the reliability of the liquid crystal display element may deteriorate.

The liquid crystal aligning agent of the present invention can be used as a liquid crystal aligning film after being coated on a substrate and baked, followed by alignment treatment such as rubbing treatment or photo-alignment treatment. Known methods and devices can be used for alignment treatments such as rubbing treatments and photo-alignment treatments.
As an example of a method of manufacturing a liquid crystal cell, a liquid crystal display device having a passive matrix structure will be described as an example. A liquid crystal display element having an active matrix structure in which a switching element such as a TFT (Thin Film Transistor) is provided in each pixel portion forming an image display may be used.

Specifically, transparent glass substrates are prepared, a common electrode is provided on one substrate, and a segment electrode is provided on the other substrate. These electrodes can be ITO electrodes, for example, and are patterned so as to display a desired image. Next, an insulating film is provided on each substrate so as to cover the common electrodes and the segment electrodes. The insulating film can be, for example, a SiO ₂ —TiO ₂ film formed by a sol-gel method.

Next, a liquid crystal alignment film is formed on each substrate, one substrate is overlaid on the other substrate so that the liquid crystal alignment film surfaces face each other, and the periphery is bonded with a sealant. In order to control the gap between the substrates, the sealant is usually mixed with spacers, and it is preferable that the spacers for controlling the gap between the substrates are also dispersed in the in-plane portions where the sealant is not provided. A part of the sealant is provided with an opening through which liquid crystal can be filled from the outside. Next, a liquid crystal material is injected into the space surrounded by the two substrates and the sealing agent through the opening provided in the sealing agent, and then the opening is sealed with an adhesive. For injection, a vacuum injection method may be used, or a method utilizing capillary action in the atmosphere may be used. The liquid crystal material may be either a positive liquid crystal material or a negative liquid crystal material, preferably a negative liquid crystal material. Next, a polarizing plate is installed. Specifically, a pair of polarizing plates are attached to the surfaces of the two substrates opposite to the liquid crystal layer.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these. The abbreviations of the compounds and the methods for measuring each property are as follows.

<Tetracarboxylic dianhydride>
CBDA: 1,2,3,4,-cyclobutanetetracarboxylic dianhydride
1,3-DM-CBDA: (1,3-dimethyl)-1,2,3,4-cyclobutanetetracarboxylic dianhydride BDA: 1,2,3,4-butanetetracarboxylic dianhydride BPDA: 3,3'4,4'-biphenyltetracarboxylic dianhydride

<Diamine>
DA-1: bis (4-aminophenoxy) ethane DA-2: tert-butyl bis (4-aminophenyl) carbamate DA-3: di-tert-butyl ((adipoyl bis (azanediyl)) bis (3-amino-6 ,1-phenylene)) dicarbamate
DA-4: paraphenylenediamine DA-5: 5-((4-(4-heptylcyclohexyl)phenoxy)methyl)benzene-1,3-diamine DA-6: 4,4'-(1H-pyrrole-2, 5-diyl)dianiline DA-7: 4,4'-diaminodiphenylamine DA-8: 4,4'-diaminodiphenylmethane

<Isothiocyanate>
SCN-1: ethyl isothiocyanate SCN-2: allyl isothiocyanate

<Additive>
AD-1: 3-glycidoxypropyltriethoxysilane AD-2: N,N,N',N'-tetrakis(2-hydroxyethyl)adipinamide

<Organic solvent>
NMP: N-methyl-2-pyrrolidone
BCS: butyl cellosolve
GBL: gamma-butyrolactone

In Examples, the molecular weights and imidization ratios of polyamic acids, polyimide precursors, and polyimides were evaluated as follows.

<Molecular weight measurement>
For the molecular weights of polyamic acid and polyimide, room temperature gel permeation chromatography (GPC) apparatus (GPC-101) manufactured by Showa Denko and columns (KD-803, KD-805) manufactured by Shodex were used. The measurement conditions are as follows.
Column temperature: 50°C
Eluent: N,N'-dimethylformamide (additives: lithium bromide-hydrate (LiBr H2O) 30 mmol/L, phosphoric acid/anhydride crystals (o-phosphoric acid) 30 mmol/L, tetrahydrofuran (THF ) is 10 ml/L)
Flow rate: 1.0 ml/min
Standard samples for creating a calibration curve: TSK standard polyethylene oxide manufactured by Tosoh Corporation (molecular weights of about 900,000, 150,000, 100,000, 30,000) and polyethylene glycol manufactured by Polymer Laboratory (molecular weights of about 12,000, 4 ,000, 1,000)

<Measurement of imidization rate>
20 mg of polyimide powder is placed in an NMR sample tube (manufactured by Kusano Kagaku, NMR sampling tube standard φ5), and 0.53 ml of deuterated dimethyl sulfoxide (DMSO-d6, 0.05% TMS (tetramethylsilane) mixture) is added. and completely dissolved by applying ultrasonic waves. Proton NMR at 500 MHz was measured for this solution using an NMR spectrometer (JNW-ECA500) manufactured by JEOL Datum. For the imidization rate, a proton derived from a structure that does not change before and after imidization is determined as a reference proton. It was obtained by the following formula (1) using the integrated value.

Imidation rate (%) = (1-α x/y) x 100 (1)

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

<Synthesis Example 1>
1,3-DM-CBDA (12.68 g, 56.6 mmol), DA-2 (10.4 g, 26.1 mmol), DA-3 (7.26 g, 13.1 mmol), DA-1 (11.69 g , 47.9 mmol) was mixed in NMP (191.48 g) and reacted at 40° C. for 1 hour. C. for 2 hours to obtain a polyamic acid solution (a). This polyamic acid solution (a) had a number average molecular weight of 11,440 and a weight average molecular weight of 23,220.
Polyimide precursor (a- 1) A solution was obtained. NMP was added to this polyimide precursor (a-1) solution (30.0 g) to dilute the content of the polyimide precursor (a-1) to 12% by mass, and then acetic anhydride ( 3.52 g) and pyridine (0.91 g) were added and reacted at 50° C. for 2.5 hours. This reaction solution was poured into methanol (300 ml), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 100° C. to obtain a specific imidized polymer (A-1) having a specific structure introduced at the terminal. The imidization rate of this specific polymer (A-1) was 76%.

<Synthesis Example 2>
Allyl isothiocyanate (0.51 g, 5.2 mmol) was added to the polyamic acid solution (a) (30.0 g) prepared in Synthesis Example 1 and reacted at 20-25° C. for 20 hours to introduce a specific structure at the polyamic acid terminal. A polyimide precursor (a-2) solution was obtained. NMP was added to this polyimide precursor (a-2) solution (30.0 g) to dilute the content of the polyimide precursor (a-2) to 12% by mass, and then acetic anhydride ( 3.52 g) and pyridine (0.91 g) were added and reacted at 50° C. for 2.5 hours. This reaction solution was poured into methanol (300 ml), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 100° C. to obtain a specific imidized polymer (A-2) having a specific structure introduced at the terminal. The imidization rate of this specific imidized polymer (A-2) was 76%.

<Synthesis Example 3>
BDA (8.9 g, 45 mmol), DA-5 (14.21 g, 36.0 mmol), DA-4 (5.84 g, 54.0 mmol) were mixed in NMP (164.11 g) and heated at 40° C. for 2 After reacting for hours, CBDA (8.65 g, 44.1 mmol) and NMP (49.0 g) were added and reacted at 40° C. for 2 hours to obtain a polyamic acid solution (b). This polyamic acid solution (b) had a number average molecular weight of 9,100 and a weight average molecular weight of 34,500. Polyimide precursor (b -1) A solution was obtained. NMP was added to this polyimide precursor (b-1) solution (30.0 g) to dilute the content of the polyimide precursor (b-1) to 7% by mass, and then acetic anhydride ( 5.47 g) and pyridine (1.70 g) were added and reacted at 40° C. for 3.5 hours. This reaction solution was poured into methanol (300 ml), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 100° C. to obtain a specific imidized polymer (B-1) having a specific structure introduced at the terminal. The imidization rate of this specific imidized polymer (B-1) was 65%.

<Synthesis Example 4>
Allyl isothiocyanate (0.54 g, 5.4 mmol) was added to the polyamic acid (b) prepared in Synthesis Example 3 and reacted at 20-25° C. for 20 hours to obtain a polyimide precursor (b -2) A solution was obtained. NMP was added to this polyimide precursor (b-2) solution (30.0 g) to dilute the content of the polyimide precursor (b-2) to 7% by mass, and then acetic anhydride ( 5.47 g) and pyridine (1.70 g) were added and reacted at 40° C. for 3.5 hours. This reaction solution was poured into methanol (300 ml), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 100° C. to obtain a specific imidized polymer (B-2) having a specific structure introduced at its terminal. The imidization rate of this specific imidized polymer (B-2) was 65%.

<Synthesis Example 5>
CBDA (4.20 g, 21.4 mmol), DA-7 (6.68 g, 33.5 mmol), DA-6 (5.01 g, 20.1 mmol), DA-8 (2.66 g, 13.4 mmol) After mixing in NMP (24.65 g) and GBL (111.38 g) and reacting at 40°C for 1 hour, BPDA (11.83 g, 40.2 mmol) and NMP (86.73 g) were added and heated to 50°C. for 15 hours to obtain a polyamic acid solution (c). This polyamic acid solution (c) had a number average molecular weight of 9,370 and a weight average molecular weight of 20,690.

<Synthesis Example 6>
NMP was added to the polyamic acid solution (a) (30.0 g) prepared in Synthesis Example 1 to dilute the polyamic acid (a) content to 12% by mass, and then acetic anhydride (3 .52 g), and pyridine (0.91 g) were added and allowed to react at 50° C. for 2.5 hours. This reaction solution was poured into methanol (300 ml), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 100° C. to obtain an imidized polymer (A). The imidization rate of this imidized polymer (A) was 75%.

<Synthesis Example 7>
NMP was added to the polyamic acid solution (b) (30.0 g) prepared in Synthesis Example 3 to dilute the polyamic acid (b) content to 7% by mass, and then acetic anhydride (5 .47 g) and pyridine (1.70 g) were added and reacted at 40° C. for 3.5 hours. This reaction solution was poured into methanol (300 ml), and the resulting precipitate was filtered off. This precipitate was washed with methanol and dried under reduced pressure at 100° C. to obtain an imidized polymer (B). The imidization rate of this imidized polymer (B) was 65%.

Preparation of liquid crystal aligning agent:
<Example 1>
NMP (36.6 g) was added to the specific imidized polymer (A-1) (5.0 g) obtained in Synthesis Example 1 and dissolved by stirring at 70° C. for 20 hours. Liquid crystal aligning agent [A] was obtained by adding NMP (25.1g) and BCS (16.6g) to this solution, and stirring at 25 degreeC for 2 hours.

<Example 2>
NMP (36.6 g) was added to the specific imidized polymer (A-2) (5.0 g) obtained in Synthesis Example 2 and dissolved by stirring at 70° C. for 20 hours. NMP (25.1 g) and BCS (16.6 g) were added to this solution, and the mixture was stirred at 25° C. for 2 hours to obtain a liquid crystal aligning agent [B].

<Example 3>
NMP (36.6 g) was added to the specific imidized polymer (B-1) (5.0 g) obtained in Synthesis Example 3 and dissolved by stirring at 70° C. for 20 hours. NMP (8.4 g) and BCS (33.3 g) were added to this solution, and the mixture was stirred at 25° C. for 2 hours to obtain a liquid crystal aligning agent [C].

<Example 4>
NMP (36.6 g) was added to the specific imidized polymer (B-2) (5.0 g) obtained in Synthesis Example 4 and dissolved by stirring at 70° C. for 20 hours. NMP (8.4 g) and BCS (33.3 g) were added to this solution, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent [D].

<Example 5>
NMP (36.6 g) was added to the specific imidized polymer (A-2) (5.0 g) obtained in Synthesis Example 2 and dissolved by stirring at 70° C. for 20 hours. This solution (3.63 g) and the polyamic acid solution (c) (8.5 g) obtained in Synthesis Example 5 were weighed, NMP (2.85 g), GBL (5.36 g), BCS (5.1 g), Add 3-glycidoxypropyltriethoxysilane (0.0145 g) and N,N,N',N'-tetrakis(2-hydroxyethyl)adipinamide (0.043 g) and stir at 25° C. for 2 hours. Thus, a liquid crystal aligning agent [E] was obtained.

<Comparative Example 1>
NMP (36.6 g) was added to the imidized polymer (A) (5.0 g) obtained in Synthesis Example 6 and dissolved by stirring at 70° C. for 20 hours. NMP (25.1 g) and BCS (16.6 g) were added to this solution, and the mixture was stirred at 25°C for 2 hours to obtain a liquid crystal aligning agent [F].

<Comparative Example 2>
NMP (36.6 g) was added to the imidized polymer (B) (5.0 g) obtained in Synthesis Example 7 and dissolved by stirring at 70° C. for 20 hours. NMP (8.4 g) and BCS (33.3 g) were added to this solution, and the mixture was stirred at 25° C. for 2 hours to obtain a liquid crystal aligning agent [G].

<Comparative Example 3>
NMP (36.6 g) was added to the imidized polymer (A) (5.0 g) obtained in Synthesis Example 6 and dissolved by stirring at 70° C. for 20 hours. This solution (3.63 g) and the polyamic acid solution (c) (8.5 g) obtained in Synthesis Example 5 were weighed, NMP (2.85 g), GBL (5.36 g), BCS (5.1 g), 3-Glycidoxypropyltriethoxysilane (0.0145 g) and N,N,N',N'-tetrakis(2-hydroxyethyl)adipinamide were added and stirred at 25°C for 2 hours to effect liquid crystal orientation. Agent [H] was obtained.

<Comparative Example 4>
The seal adhesion of Comparative Example 4 is the result of the seal adhesion (N/mm ² ) between the ITO substrate and the sealant.

<Preparation of Adhesion Evaluation Sample>
After filtering the liquid crystal aligning agent with a 1.0 μm filter, it was spin-coated on a glass substrate with ITO of 30 mm × 40 mm, dried on a hot plate at 80 ° C. for 2 minutes, and baked at 230 ° C. for 20 minutes. A polyimide film having a thickness of 100 nm was obtained. A substrate with a polyimide film thus obtained and a glass substrate with ITO of 30 mm × 40 mm were prepared, and on the polyimide film surface of one substrate, bead spacers with a diameter of 4 µm were scattered, followed by a UV-curable seal. The agent was applied in dots. Next, as shown in FIG. 1, the substrates were laminated so that the sealant was positioned at the center of the portion where the substrates overlapped. At that time, the amount of the sealant dropped was adjusted so that the diameter of the sealant after bonding was about 3 mm. After fixing the two substrates bonded to each other with a clip and irradiating UV with a high-pressure mercury lamp at 3 J, they were thermally cured at 120° C. for 1 hour to prepare a sample for adhesion evaluation.

<Measurement of adhesion>
The prepared sample was fixed with a tabletop precision universal testing machine (QC-H42A2-S00) manufactured by Yang Huang Technology Co., Ltd. After fixing the 5 mm wide part at each end of the upper and lower substrates, the lower substrate was direction, and the upper substrate was pulled upward, and the pressure (N) at which the seal was peeled off was measured. A standardized value obtained by dividing the pressure (N) by the area (mm ² ) estimated from the measured diameter of the sealant was used as an index of seal adhesion.

<Evaluation of rubbing resistance>
After filtering the liquid crystal aligning agent with a 1.0 μm filter, it was spin-coated on a glass substrate with ITO of 30 mm × 40 mm, dried on a hot plate at 80 ° C. for 2 minutes, and baked at 230 ° C. for 20 minutes. A polyimide film having a thickness of 100 nm was obtained. This polyimide film was rubbed once with a rayon cloth (roll system 120 mm, number of revolutions 1000 rpm, moving speed 20 mm/sec, pushing depth 0.6 mm). The surface of this film was observed with an optical microscope at a magnification of 200 to observe the presence or absence of shavings and the presence or absence of scratches. A sample with few scrapes and scratches was defined as "good", and a sample with many scrapes and rubbing scratches was defined as "poor" and evaluated.

<Production of liquid crystal cell>
After filtering the liquid crystal aligning agents obtained in Examples 1, 2 and 5 and Comparative Examples 1 and 3 with a 1.0 μm filter, a liquid crystal cell was produced in the following procedure. The liquid crystal aligning agent was spin-coated on a glass substrate with ITO, dried on a hot plate at 80° C. for 2 minutes, and then baked at 230° C. for 20 minutes to obtain a coating film with a thickness of 100 nm. After rubbing this polyimide film with a rayon cloth (roll diameter 120 mm, number of revolutions 1000 rpm, moving speed 20 mm/sec, pushing amount 0.4 mm), ultrasonic irradiation was performed in pure water for 1 minute, followed by 10 minutes at 80°C. Dried. Two substrates with the liquid crystal alignment film thus obtained were prepared, a 4 μm spacer was placed on the liquid crystal alignment film surface of one substrate, and then the two substrates were combined so that the rubbing directions were antiparallel. An empty cell with a cell gap of 4 .mu.m was produced by sealing the periphery while leaving a liquid crystal injection port. A liquid crystal (MLC-2041, manufactured by Merck & Co.) was injected into this cell under vacuum at normal temperature, and the injection port was sealed to form an anti-parallel liquid crystal cell.

<Production of liquid crystal cell (PSA cell)>
After each of the liquid crystal aligning agents obtained in Examples 3 and 4 and Comparative Example 2 was filtered through a 1.0 μm filter, a liquid crystal cell was produced in the following procedure. The liquid crystal aligning agent was spin-coated on a glass substrate with ITO, dried on a hot plate at 80° C. for 2 minutes, and then baked at 230° C. for 20 minutes to obtain a coating film with a thickness of 100 nm. Two substrates with the liquid crystal alignment film thus obtained are prepared, a 4 μm spacer is installed on the surface of the liquid crystal alignment film of one substrate, the two substrates are combined, and the surroundings are surrounded by leaving the liquid crystal injection port. It was sealed to produce an empty cell with a cell gap of 4 μm. A liquid crystal (MLC-3023, manufactured by Merck & Co., Ltd.) was vacuum injected into this cell at room temperature, and after the injection port was sealed, a metal halide lamp with an illuminance of 140 mW was applied to the obtained liquid crystal cell while applying a DC voltage of 15 V. A liquid crystal cell (PSA cell) in which the alignment direction of the liquid crystal is controlled is obtained by cutting the wavelength of 325 nm or less using a UV light and irradiating ultraviolet rays of 5 J/cm ² in terms of 365 nm.

<Liquid crystal orientation>
The alignment state of the prepared liquid crystal cell was observed with a polarizing microscope, and the cell with no alignment defect was evaluated as "good", and the cell with alignment defect was evaluated as "bad".

The liquid crystal aligning agent of the present invention can solve display unevenness near the frame by increasing the adhesiveness between the sealant and the liquid crystal alignment film in a narrow frame liquid crystal display element that can secure a large number of display surfaces. Useful.

Claims (7)

A liquid crystal aligning agent containing at least one polymer selected from polyimide precursors and polyimides having a structure represented by the following formula (1) at the end of the polymer main chain.

R ₁ represents an organic group having 1 to 20 carbon atoms which may contain a photoreactive functional group such as an acryl group or a methyl methacrylate group at its terminal. 2. The liquid crystal aligning agent according to claim 1, wherein said R ₁ is a group selected from the following structures of R-1 to R-10.

The polyimide is an imidized product of a polyimide precursor obtained by the reaction of a tetracarboxylic acid derivative component and a diamine component, and the tetracarboxylic acid derivative component contains a tetracarboxylic dianhydride represented by the following formula: The liquid crystal aligning agent according to claim 1 or 2.

X ₁ represents a tetravalent organic group selected from the following.

R ₃ to R ₆ each independently contain a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, and a fluorine atom. It is a monovalent organic group having 1 to 6 carbon atoms or a phenyl group. The polyimide is an imidized product of a polyimide precursor obtained by a reaction between a tetracarboxylic acid derivative component and a diamine component, and a compound of the following formula (2) is added to a solution during and/or after polymerization of the polyimide precursor. 4. The method for producing a polyimide according to any one of claims 1 to 3, which is added.

R ₁ is the same as R ₁ above.
5. The method for producing a polyimide according to claim 4, wherein the compound of formula (2) is selected from compounds Z-1 to Z-10 exemplified below.

A liquid crystal alignment film obtained from the liquid crystal alignment agent according to any one of claims 1 to 3. A liquid crystal display device comprising the liquid crystal alignment film according to claim 6 .

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