WO2014084364A1

WO2014084364A1 - Method for producing liquid crystal alignment film, liquid crystal alignment film, and liquid crystal display element

Info

Publication number: WO2014084364A1
Application number: PCT/JP2013/082216
Authority: WO
Inventors: 直樹作本; 洋介飯沼; 勇歩野口; 隆夫堀; 大輝山極
Original assignee: 日産化学工業株式会社
Priority date: 2012-11-30
Filing date: 2013-11-29
Publication date: 2014-06-05
Also published as: CN104823104A; JPWO2014084364A1; TW201435455A; JP6202006B2; TWI598668B; KR20150090119A; CN104823104B; KR102104154B1

Abstract

Provided are: a method for producing a liquid crystal alignment film for photoalignment treatment which is capable of minimizing afterimages resulting from AC driving that occurs in fringe field switching (FFS)-driven and in-plane switching (IPS)-driven liquid crystal elements; a liquid crystal alignment film; and a liquid crystal display element. Polarized radiation is applied to an imidized film obtained by applying and sintering a liquid crystal alignment agent, which contains at least one type of polymer selected from a group comprising polyimide precursors having structural units represented by formula (1) and imidized polymers of said polyimide precursors, on a substrate. Next, the film is brought into contact with a lower alkyl ester of lactic acid with one to five carbons. (X₁ represents the formula (X1-1) or (X1-2); R₁ represents a hydrogen atom, or an alkyl group with one to four carbons.)

Description

Method for producing liquid crystal alignment film, liquid crystal alignment film, and liquid crystal display element

The present invention relates to a method for producing a liquid crystal alignment film for a photo-alignment method, a liquid crystal alignment film obtained by this production method, and a liquid crystal display device comprising the obtained liquid crystal alignment film.

In a liquid crystal display element used for a liquid crystal television, a liquid crystal display, and the like, a liquid crystal alignment film for controlling the alignment state of liquid crystals is usually provided in the element.
Currently, the most widely used liquid crystal alignment film in the industry is made of a polyamic acid formed on an electrode substrate and / or a film made of polyimide obtained by imidizing the same with a cloth such as cotton, nylon or polyester. It is produced by performing a so-called rubbing process that rubs in the direction.
The rubbing treatment of the film surface in the alignment process of the liquid crystal alignment film is an industrially useful method that is simple and excellent in productivity. However, the demand for higher performance, higher definition, and larger size of liquid crystal display elements is increasing, and the surface of the alignment film caused by rubbing treatment, dust generation, the influence of mechanical force and static electricity, Various problems such as non-uniformity in the orientation processing surface have become apparent.

As a method for replacing the rubbing treatment, a photo-alignment method for imparting liquid crystal alignment ability by irradiating polarized radiation is known. As liquid crystal alignment treatment by the photo-alignment method, those utilizing a photoisomerization reaction, those utilizing a photocrosslinking reaction, those utilizing a photodecomposition reaction, and the like have been proposed (see Non-Patent Document 1).
On the other hand, a liquid crystal alignment film for photo-alignment using polyimide is expected to be useful because it has higher heat resistance than others.
Patent Document 1 proposes that a polyimide film having an alicyclic structure such as a cyclobutane ring in the main chain is used for the photo-alignment method.
The photo-alignment method as described above has an advantage that it can be produced by a simple manufacturing process industrially as a rubbing-less alignment treatment method. In the display element, by using the liquid crystal alignment film obtained by the above-mentioned photo-alignment method, the liquid crystal display element can be expected to improve the contrast and viewing angle characteristics compared to the liquid crystal alignment film obtained by the rubbing treatment method. Since it is possible to improve the performance of the display element, it attracts attention as a promising liquid crystal alignment treatment method.
As the liquid crystal alignment film used for the liquid crystal display element of the IPS driving method and the FFS driving method, in addition to the basic characteristics such as excellent liquid crystal alignment property and electrical characteristics, the IPS (In-Place-Switching) driving method and the FFS driving method are used. Therefore, it is necessary to suppress afterimages caused by long-term alternating current driving that occurs in liquid crystal display elements.
However, the liquid crystal alignment film obtained by the photo-alignment method has a problem that anisotropy with respect to the alignment direction of the polymer film is smaller than that by rubbing. If the anisotropy is small, sufficient liquid crystal orientation cannot be obtained, and problems such as occurrence of an afterimage occur when a liquid crystal display element is formed.
On the other hand, as a method for increasing the anisotropy of the liquid crystal alignment film obtained by the photo-alignment method, the main chain of the polyimide is irradiated by light irradiation after light irradiation, by washing treatment with a water-soluble organic solvent or heat treatment. Although it has been proposed to remove low molecular weight components produced by cleavage of, the suppression of afterimages has not been solved (see Patent Document 2).

Japanese Unexamined Patent Publication No. 9-297313 Japanese Unexamined Patent Publication No. 2011-107266

The present invention relates to a liquid crystal alignment film for a photo-alignment processing method capable of suppressing an afterimage caused by alternating current drive generated in a liquid crystal display element of an IPS drive method or an FFS drive method, a method for manufacturing the liquid crystal alignment film, and the liquid crystal alignment An object is to provide a liquid crystal display element having a film.

In order to achieve the above-mentioned object, the present inventors have conducted extensive studies, and as a result, a polyimide film having a specific structure or a polyimide precursor is applied and baked to irradiate polarized radiation. Next, a contact treatment such as immersion is performed using a lower alkyl ester having 1 to 5 carbon atoms of lactic acid, and preferably a liquid crystal alignment film which is then contact-treated with water or a water-soluble organic solvent having a boiling point of 50 to 105 ° C. It has been found that the above object can be achieved.

Thus, the present invention has the following gist.
1. A liquid crystal aligning agent containing at least one polymer selected from the group consisting of a polyimide precursor having a structural unit represented by the following formula (1) and an imidized polymer of the polyimide precursor is applied on a substrate. A method for producing a liquid crystal alignment film, wherein the imidized film obtained by baking is irradiated with polarized radiation and then contact-treated with a lower alkyl ester of lactic acid having 1 to 5 carbon atoms.

(X ₁ is at least one selected from the group consisting of the structures represented by the following formulas (X1-1) and (X1-2), and R ₁ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. .)

2. 2. The method for producing a liquid crystal alignment film according to 1 above, wherein the content of the polymer in the liquid crystal alignment agent is 2 to 8% by mass.
3. 3. The method for producing a liquid crystal alignment film according to 1 or 2, wherein the polymer has a weight average molecular weight of 5,000 to 300,000 and a number average molecular weight of 2,500 to 150,000.
4). 4. The liquid crystal alignment film according to any one of 1 to 3, which is contact-treated with the lower alkyl ester having 1 to 5 carbon atoms of lactic acid and further contacted with water or a water-soluble organic solvent having a boiling point of 50 to 105 ° C. Production method.
5. 5. The method for producing a liquid crystal alignment film according to any one of 4 above, wherein the water-soluble organic solvent having a boiling point of 50 to 105 ° C. is at least one selected from the group consisting of methanol, ethanol, 2-propanol, and acetone.
6). 6. The method for producing a liquid crystal alignment film according to any one of 1 to 5, wherein the lower alkyl ester is ethyl lactate. At least one selected from the group consisting of a polyimide precursor containing 60 mol% or more of the structural unit represented by the formula (1) with respect to 1 mol of the whole polymer and an imidized polymer of the polyimide precursor. 4. The method for producing a liquid crystal alignment film as described in any one of 1 to 3 above.
8). 8. A liquid crystal alignment film obtained by the method for producing a liquid crystal alignment film according to any one of 1 to 7.
9. 9. A liquid crystal display device comprising the liquid crystal alignment film as described in 8 above.

When the liquid crystal alignment film obtained by the method for manufacturing a liquid crystal alignment film of the present invention is a liquid crystal alignment film of a liquid crystal display element of an IPS driving method or an FFS driving method, an afterimage caused by long-term alternating current driving is extremely effectively reduced. Can do.

<Specific structure polyimide precursor and imidized polymer thereof>
The polyimide precursor and its imidized polymer in the present invention are a polyimide precursor having a structural unit represented by the following formula (1) and its imidized polymer.

In the formula (1), X ₁ is at least one selected from the group consisting of structures represented by the following formulas (X1-1) and (X1-2), and R ₁ is a hydrogen atom or a carbon number of 1 4 to 4 alkyl groups.

In the formula (1), R ₁ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. From the viewpoint of ease of imidization by heating, a hydrogen atom or a methyl group is particularly preferable.

The polyimide precursor and the imidized polymer thereof may contain a structural unit represented by the following formula (2) in addition to the structural unit represented by the formula (1).

In formula (2), _{R 1} has the same definition as _{R 1} in the formula (1).
X ₂ is a tetravalent organic group, and its structure is not particularly limited. Specific examples include structures of the above formulas (XA-1), (XA-2), and the following formulas (X-1) to (X-42).
From the viewpoint of availability of compounds, the structure of X is XA-1, XA-2, X-1 to X-9, X-17, X-25, X26, X-27, X-28, X -32, X-39 and the like.
Further, from the viewpoint of obtaining a liquid crystal alignment film in which the residual charge accumulated by direct current voltage can be quickly relaxed, it is preferable to use a tetracarboxylic dianhydride having an aromatic ring structure. X-27, X-28, X-32, X-35, X-37 and the like are more preferable.

In the above formula (2), Y ₂ is a divalent organic group, and its structure is not particularly limited. Specific examples of Y ₂ include structures of the following formulas (Y-1) to (Y-85).

Since an improvement in liquid crystal alignment can be expected, the structure of Y ₂ is preferably a highly linear structure. As specific examples, Y-74, Y-75, Y-76, Y-77, and Y-78 are more preferable.
In addition, since the solubility of the polyimide precursor and polyimide in an organic solvent can be expected, the structure of Y ₂ is Y-8, Y-20, Y-21, Y-22, Y-28, Y-29. Y-30, Y-71, Y-72, Y-73, and Y-85 are more preferable.
In the polyimide precursor and imidized polymer thereof according to the present invention, when the ratio of the structural unit represented by the above formula (1) is low, the liquid crystal alignment property of the liquid crystal alignment film is lowered. The ratio of the structural units represented by is preferably 100 to 60 mol%, more preferably 100 to 80 mol%, relative to 1 mol of all structural units.

<Method for producing polyamic acid ester>
The polyamic acid ester which is a polyimide precursor used in the present invention can be synthesized by the following methods (1) to (3).
(1) When synthesizing from polyamic acid The polyamic acid ester can be synthesized by esterifying a polyamic acid obtained from tetracarboxylic dianhydride and diamine.
Specifically, the polyamic acid and the esterifying agent are synthesized by reacting in the presence of an organic solvent at −20 to 150 ° C., preferably 0 to 50 ° C., for 30 minutes to 24 hours, preferably 1 to 4 hours. be able to.

The esterifying agent is preferably one that can be easily removed by purification, and N, N-dimethylformamide dimethyl acetal, N, N-dimethylformamide diethyl acetal, N, N-dimethylformamide dipropyl acetal, 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 addition amount of the esterifying agent is preferably 2 to 6 molar equivalents, and more preferably 2 to 4 molar equivalents, per 1 mol of the polyamic acid repeating unit.
The organic solvent used in the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, γ-butyrolactone, etc. from the solubility of the polymer, and these are used alone or in combination of two or more. May be.
The concentration of the polymer in the organic solvent at the time of synthesis is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass from the viewpoint that the polymer hardly precipitates and a high molecular weight product is easily obtained.

(2) When synthesized by reaction of tetracarboxylic acid diester dichloride and diamine Polyamic acid ester can be synthesized from tetracarboxylic acid diester dichloride and diamine.
Specifically, tetracarboxylic acid diester dichloride and diamine are reacted in the presence of a base and an organic solvent at −20 to 150 ° C., preferably 0 to 50 ° C. for 30 minutes to 24 hours, preferably 1 to 4 hours. Can be synthesized.

As the base, pyridine, triethylamine, 4-dimethylaminopyridine and the like can be used, but pyridine is preferable because the reaction proceeds gently. The addition amount of the base is preferably 2 to 4 times mol, preferably 2 to 3 times mol with respect to tetracarboxylic acid diester dichloride, from the viewpoint of easy removal and high molecular weight. More preferred.
The organic solvent used in the above reaction is preferably N-methyl-2-pyrrolidone, γ-butyrolactone or the like in view of the solubility of the monomer and polymer, and these may be used alone or in combination.
The polymer concentration in the organic solvent at the time of synthesis is preferably 1 to 30% by mass and more preferably 5 to 20% by mass from the viewpoint that the polymer is hardly precipitated and a high molecular weight product is easily obtained. In order to prevent hydrolysis of the tetracarboxylic acid diester dichloride, the organic solvent used for the synthesis of the polyamic acid ester is preferably dehydrated as much as possible, and the reaction is preferably performed in a nitrogen atmosphere to prevent mixing of outside air. .

(3) When a polyamic acid is synthesized from a tetracarboxylic acid diester and a diamine The polyamic acid ester can be synthesized by polycondensation of a tetracarboxylic acid diester and a diamine.
Specifically, tetracarboxylic diester and diamine are reacted in the presence of a condensing agent, a base, and an organic solvent at 0 to 150 ° C., preferably 0 to 100 ° C., for 30 minutes to 24 hours, preferably 3 to 15 hours. Can be synthesized.

Examples of the condensing agent include triphenyl phosphite, 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, (2,3-dihydro-2-thioxo-3-benzoxazolyl) phosphonate diphenyl, and the like. The addition amount of the condensing agent is preferably 2 to 3 moles, more preferably 2 to 2.5 moles, relative to the tetracarboxylic acid diester.

As the base, tertiary amines such as pyridine and triethylamine can be used. The addition amount of the base is preferably 2 to 4 moles, more preferably 2 to 3 moles, relative to the diamine component from the viewpoint of easy removal and high molecular weight.
Examples of the organic solvent include N-methyl-2-pyrrolidone, γ-butyrolactone, N, N-dimethylformamide and the like.
In the above reaction, the reaction proceeds efficiently by adding Lewis acid as an additive. As the Lewis acid, lithium halides such as lithium chloride and lithium bromide are preferable. The addition amount of the Lewis acid is preferably 0 to 1.0-fold mol, more preferably 2.0 to 3.0-fold mol based on the diamine component.

Among the methods for synthesizing the three polyamic acid esters, since a high molecular weight polyamic acid ester is obtained, the synthesis method (1) or (2) is particularly preferable.
The polyamic acid ester solution obtained as described above can be polymerized by being poured into a poor solvent while being well stirred. Precipitation is performed several times, and after washing with a poor solvent, a purified polyamic acid ester powder can be obtained at room temperature or by heating and drying.
The poor solvent is not particularly limited, and examples thereof include water, methanol, ethanol, 2-propanol, hexane, butyl cellosolve, acetone, toluene and the like, and water, methanol, ethanol, 2-propanol and the like are preferable.

<Method for producing polyamic acid>
The polyamic acid which is a polyimide precursor used in the present invention can be synthesized by the following method.
Specifically, tetracarboxylic dianhydride and diamine are reacted in the presence of an organic solvent at −20 to 150 ° C., preferably 0 to 50 ° C., for 30 minutes to 24 hours, preferably 1 to 12 hours. Can be synthesized.
The organic solvent used in the above reaction is preferably N, N-dimethylformamide, N-methyl-2-pyrrolidone, γ-butyrolactone, etc. in view of the solubility of the monomer and polymer. These may be used alone or in combination of two or more. May be used.

The concentration of the polymer is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass from the viewpoint that polymer precipitation is difficult to occur and a high molecular weight product is easily obtained.
The polyamic acid obtained as described above can be recovered by precipitating a polymer by pouring it into a poor solvent while thoroughly stirring the reaction solution. Moreover, the powder of polyamic acid refine | purified by performing precipitation several times, washing | cleaning with a poor solvent, and normal temperature or heat-drying can be obtained. The poor solvent is not particularly limited, and examples thereof include water, methanol, ethanol, 2-propanol, hexane, butyl cellosolve, acetone, toluene and the like, and water, methanol, ethanol, 2-propanol and the like are preferable.

<Production method of polyimide>
The polyimide used in the present invention can be produced by imidizing the polyamic acid ester or polyamic acid.
When a polyimide is produced from a polyamic acid ester, chemical imidization in which a basic catalyst is added to a polyamic acid solution obtained by dissolving the polyamic acid ester solution or the polyamic acid ester resin powder in an organic solvent is simple. Chemical imidization is preferable because the imidization reaction proceeds at a relatively low temperature and the molecular weight of the polymer is unlikely to decrease during the imidization process.

Chemical imidation can be performed by stirring the polyamic acid ester to be imidized in an organic solvent in the presence of a basic catalyst. As an organic solvent, the solvent used at the time of the polymerization reaction mentioned above can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Of these, triethylamine is preferred because it has sufficient basicity to allow the reaction to proceed.

The temperature for carrying out the imidization reaction is −20 to 140 ° C., preferably 0 to 100 ° C., and the reaction time can be 1 to 100 hours.
The amount of the basic catalyst is 0.5 to 30 times mol, preferably 2 to 20 times mol of the amic acid ester group.
The imidation ratio of the resulting polymer can be controlled by adjusting the amount of catalyst, temperature, and reaction time.
When manufacturing a polyimide from a polyamic acid, chemical imidation which adds a catalyst to the solution of the said polyamic acid obtained by reaction with a diamine component and tetracarboxylic dianhydride is simple. Chemical imidization is preferable because the imidization reaction proceeds at a relatively low temperature and the molecular weight of the polymer does not easily decrease during the imidization process.

Chemical imidation can be performed by stirring a polymer to be imidized in an organic solvent in the presence of a basic catalyst and an acid anhydride. As an organic solvent, the solvent used at the time of the polymerization reaction mentioned above can be used. Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine and the like. Of these, pyridine is preferred because it has an appropriate basicity for proceeding with the reaction. Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, pyromellitic anhydride and the like. Among them, use of acetic anhydride is preferable because purification after completion of the reaction is facilitated.

The temperature for carrying out the imidization reaction is −20 to 140 ° C., preferably 0 to 100 ° C., and the reaction time can be 1 to 100 hours.
The amount of the basic catalyst is 0.5 to 30 times mol, preferably 2 to 20 times mol of the polyamic acid group, and the amount of acid anhydride is 1 to 50 times mol, preferably 3 to 30 times mol of the polyamic acid group. Is a mole.
The imidation ratio of the resulting polymer can be controlled by adjusting the amount of catalyst, temperature, and reaction time.

In the solution after the imidation reaction of polyamic acid ester or polyamic acid, the added catalyst and the like remain, so the obtained imidized polymer is recovered by the means described below, and redissolved in an organic solvent. Thus, the liquid crystal aligning agent of the present invention is preferable.
The polyimide solution obtained as described above can be polymerized by pouring into a poor solvent while stirring well. Precipitation is performed several times, and after washing with a poor solvent, a polymer powder purified by drying at normal temperature or by heating can be obtained.
Examples of the poor solvent include, but are not limited to, methanol, 2-propanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, and the like. Methanol, ethanol, 2-propanol, Acetone is preferred.

<Liquid crystal aligning agent>
The liquid crystal aligning agent used in the present invention has a form of a solution in which a polymer component is dissolved in an organic solvent. The molecular weight of the polymer is preferably 2,000 to 500,000 in terms of weight average molecular weight, more preferably 5,000 to 300,000, and still more preferably 10,000 to 100,000. The number average molecular weight is preferably 1,000 to 250,000, more preferably 2,500 to 150,000, and 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, but it is 1 mass from the point of forming a uniform and defect-free coating film. % From the viewpoint of storage stability of the solution, and preferably 10% by mass or less. A particularly preferred polymer concentration is 2 to 8% by mass.
The organic solvent contained in the liquid crystal aligning agent used for this invention will not be specifically limited if a polymer component melt | dissolves uniformly. Specific examples thereof include N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-methylcaprolactam, Examples include 2-pyrrolidone, N-vinyl-2-pyrrolidone, dimethyl sulfoxide, dimethyl sulfone, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, 3-methoxy-N, N-dimethylpropanamide and the like. You may use these 1 type or in mixture of 2 or more types. Moreover, even if it is a solvent which cannot melt | dissolve a polymer component uniformly by itself, if it is a range which a polymer does not precipitate, you may mix with said organic solvent.

The liquid crystal aligning agent used for this invention may contain the solvent for improving the coating-film uniformity at the time of apply | coating a liquid crystal aligning agent to a board | substrate other than the organic solvent for dissolving a polymer component. . As such a solvent, a solvent having a surface tension lower than that of the organic solvent is generally used. Specific examples thereof include ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, ethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, and 1-butoxy-2-propanol. 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether-2-acetate, butyl cellosolve acetate, dipropylene glycol , 2- (2-ethoxypropoxy) propanol, lactate methyl ester, lactate ethyl ester, lactate n-propyl ester, lactate n-butyl ester, lactate isoa Glycol ester and the like. Two or more of these solvents may be used in combination.

In the liquid crystal aligning agent of the present invention, in addition to the above, the purpose is to change the electrical properties such as the dielectric constant and conductivity of the polymer other than the polymer and the liquid crystal aligning film as long as the effects of the present invention are not impaired. A dielectric or conductive material, a silane coupling agent for the purpose of improving the adhesion between the liquid crystal alignment film and the substrate, a crosslinkable compound for the purpose of increasing the hardness and density of the liquid crystal alignment film, and a coating. When firing the film, an imidization accelerator for the purpose of efficiently imidizing the polyamic acid may be added.

<Method for producing liquid crystal alignment film>
The method for producing a liquid crystal alignment film of the present invention comprises a step of applying a liquid crystal aligning agent to a substrate and baking, a step of irradiating the obtained film with polarized radiation, and a step of irradiating the irradiated film with 1 to 1 carbon atoms of lactic acid. 5 and a step of contact treatment with water or a water-soluble organic solvent having a boiling point of 50 to 105 ° C., preferably.

(1) The process of apply | coating and baking a liquid crystal aligning agent to a board | substrate Applying the liquid crystal aligning agent obtained as mentioned above to a board | substrate, drying and baking, the polyimide film or the polyimide precursor was imidated. A membrane is obtained.
The substrate to which the liquid crystal aligning agent used in 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 or a polycarbonate substrate, or the like can be used. From the viewpoint of simplification of the process, it is preferable to use a substrate on which an ITO (Indium Tin Oxide) electrode or the like for driving the liquid crystal is formed. In the reflection type liquid crystal display element, an opaque material such as a silicon wafer can be used as long as only one substrate is used. In this case, a material that reflects light such as aluminum can be used as the electrode.
Examples of the method for applying the liquid crystal aligning agent used in the present invention include a spin coating method, a printing method, and an ink jet method.

The drying and baking steps after applying the liquid crystal aligning agent can be selected at any temperature and time. Usually, in order to sufficiently remove the organic solvent contained, it is dried at 50 to 120 ° C., preferably 60 to 100 ° C. for 1 to 10 minutes, and then 150 to 300 ° C., preferably 200 to 250 at 5 to 120. It is fired in minutes. The thickness of the coating film after baking is not particularly limited, but if it is too thin, the reliability of the liquid crystal display element may be lowered, and therefore it is 5 to 300 nm, preferably 10 to 200 nm.

(2) A step of irradiating the obtained film with polarized radiation The film obtained by the method of (1) above is irradiated with polarized radiation (hereinafter also referred to as photo-alignment treatment), thereby polarizing the film. Anisotropy is imparted in the direction perpendicular to the direction.
As a specific example of the photo-alignment treatment, there is a method in which the surface of the coating film is irradiated with radiation polarized in a certain direction to impart liquid crystal alignment ability. As the wavelength of the radiation, ultraviolet rays or visible rays having a wavelength of 100 to 800 nm can be used. Among these, ultraviolet rays having a wavelength of 100 to 400 nm are preferable, and ultraviolet rays having a wavelength of 200 to 400 nm are particularly preferable. Dose of the radiation is preferably in the range of 1 ~ 10,000mJ / cm ^2, and particularly preferably in the range of 100 ~ 5,000mJ / cm ^2. The temperature at which the film is irradiated with polarized radiation is preferably 10 to 100 ° C., more preferably 20 to 50 ° C.

(3) Step of contact treatment with lactic acid ester The film irradiated with the polarized radiation in the step (2) is then contact-treated with a lower alkyl ester of lactic acid having 1 to 5 carbon atoms, preferably, The contact treatment is performed with water or a water-soluble organic solvent having a boiling point of 50 to 105 ° C.

Examples of the lower alkyl ester having 1 to 5 carbon atoms of lactic acid used for the contact treatment include ethyl lactate, methyl lactate, butyl lactate and the like, and in particular, alkyl esters having 1 to 3 carbon atoms, especially ethyl lactate. preferable. The lactic acid alkyl ester may be used alone or may contain other solvents or solvents other than the lactic acid alkyl ester as long as the effects of the present invention are not impaired. Examples of these other solvents include, but are not limited to, water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, 1-methoxy-2-propanol, propylene glycol monomethyl ether acetate and the like. In particular, water is more preferable from the viewpoints of versatility and safety.
When the other solvent is contained, the content of the lactic acid alkyl ester is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, more preferably 90 to 90% by mass with respect to the total amount of the solution used for the contact treatment. 100% by mass is particularly preferred.

In the present invention, the contact treatment between the film irradiated with polarized radiation and the lactic acid alkyl ester is preferably a treatment such that the film and the liquid are sufficiently in contact such as immersion treatment or spraying treatment. Among them, a method of immersing the membrane in the lactic acid alkyl ester is preferably 10 seconds to 1 hour, more preferably 1 to 30 minutes. The contact treatment may be performed at normal temperature or preferably at 10 to 80 ° C., more preferably 20 to 50 ° C. Moreover, a means for enhancing contact such as ultrasonic waves can be applied as necessary.
In the present invention, after the contact treatment with the lactic acid alkyl ester, contact treatment with water or a water-soluble organic solvent having a boiling point of 50 to 105 ° C., preferably 50 to 80 ° C. is preferred. As the water-soluble organic solvent having a boiling point of 50 to 105 ° C., methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone and the like are preferable.
The contact treatment with the above lactic acid alkyl ester and the subsequent contact treatment with water or a water-soluble organic solvent having a boiling point of 50 to 105 ° C. may be carried out continuously or after a certain time. In the latter case, it is not preferable that an excessive amount of time is left, and therefore it is preferable to carry out continuously.
After the contact treatment with the above alkyl lactate ester, preferably the subsequent contact treatment with water or a water-soluble organic solvent having a boiling point of 50 to 105 ° C., a drying treatment is preferably carried out. The drying treatment temperature is preferably 80 to 250 ° C., more preferably 80 to 150 ° C., and the drying time is preferably 10 seconds to 30 minutes, more preferably 30 seconds to 10 minutes.

<Liquid crystal display element>
The liquid crystal display element of the present invention is a liquid crystal cell obtained by a known method after obtaining a substrate with a liquid crystal alignment film obtained from the liquid crystal aligning agent obtained by the production method of the present invention, and using the liquid crystal cell. It is a liquid crystal display element.
As an example of a method for manufacturing a liquid crystal cell, a liquid crystal display element having a passive matrix structure will be described as an example. Note that an active matrix liquid crystal display element in which a switching element such as a TFT (Thin Film Transistor) is provided in each pixel portion constituting the image display may be used.

First, a transparent glass substrate is prepared, and 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 electrode and the segment electrode. The insulating film can be, for example, a film made of SiO ₂ —TiO ₂ formed by a sol-gel method.
Next, the liquid crystal alignment film of the present invention is formed on each substrate.
Next, the other substrate is superposed on one substrate so that the alignment film surfaces face each other, and the periphery is bonded with a sealant. In order to control the substrate gap, a spacer is usually mixed in the sealing material. In addition, it is preferable to spray spacers for controlling the substrate gap on the in-plane portion where no sealing material is provided. A part of the sealing material is provided with an opening that can be filled with liquid crystal from the outside.

Next, a liquid crystal material is injected into a space surrounded by two substrates and the sealing material through an opening provided in the sealing material. Thereafter, the opening is sealed with an adhesive. For the injection, a vacuum injection method may be used, or a method utilizing capillary action in the atmosphere may be used. Next, a polarizing plate is installed. Specifically, a pair of polarizing plates is attached to the surfaces of the two substrates opposite to the liquid crystal layer. By passing through the above process, the liquid crystal display element of this invention is obtained.
Since this liquid crystal display element uses the liquid crystal alignment film obtained by the liquid crystal alignment film manufacturing method of the present invention as the liquid crystal alignment film, the liquid crystal display element has excellent afterimage characteristics, and has a large screen and a high-definition liquid crystal television. It can use suitably for.

The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.
The abbreviations of the compounds used in the examples and comparative examples, and the measuring methods of the respective properties are as follows.
NMP: N-methyl-2-pyrrolidone GBL: γ-butyrolactone BCS: Butyl cellosolve IPA: 2-propanol DE-1: Formula (DE-1) below
DA-1: Formula (DA-1) below
DA-2: Formula (DA-2) below
(The Boc group represents a t-butoxycarbonyl group.)
Additive A: N-α- (9-fluorenylmethoxycarbonyl) -N-τ-t-butoxycarbonyl-L-histidine

Hereinafter, methods for evaluating afterimages by viscosity, molecular weight, imidization rate, liquid crystal cell production, and long-term alternating current driving are shown.
[viscosity]
In the synthesis examples, the viscosity of the polyamic acid ester and the polyamic acid solution was measured using an E-type viscometer TVE-22H (manufactured by Toki Sangyo Co., Ltd.), a sample amount of 1.1 mL, and cone rotor TE-1 (1 ° 34 ′, R24 ), Measured at a temperature of 25 ° C.
[Molecular weight]
The molecular weight of the polyamic acid ester was measured by a GPC (room temperature gel permeation chromatography) apparatus, and the number average molecular weight (Mn) and the weight average molecular weight (Mw) were calculated as polyethylene glycol and polyethylene oxide equivalent values.
GPC device: manufactured by Shodex (GPC-101)
Column: manufactured by Shodex (series of KD803 and KD805)
Column temperature: 50 ° C
Eluent: N, N-dimethylformamide (as additives, lithium bromide-hydrate (LiBr · H ₂ O) 30 mmol / L (liter), phosphoric acid / anhydrous crystal (o-phosphoric acid) 30 mmol / L, tetrahydrofuran (THF) is 10 ml / L)
Flow rate: 1.0 ml / min Standard sample for preparation of calibration curve: TSK standard polyethylene oxide (weight average molecular weight (Mw) of about 900,000, 150,000, 100,000, 30,000) manufactured by Tosoh Corporation, and polymer laboratory Polyethylene glycol manufactured by the company (peak top molecular weight (Mp) of about 12,000, 4,000, 1,000). In order to avoid the overlapping of peaks, the measurement was performed by mixing four types of 900,000, 100,000, 12,000 and 1,000, and three types of 150,000, 30,000 and 4,000. Separately performed on two of the mixed samples.

[Measurement of imidization rate]
The imidation ratio of polyimide in the synthesis example was measured as follows. 20 mg of polyimide powder was put into an NMR sample tube (NMR sampling tube standard, φ5 (manufactured by Kusano Kagaku)) and deuterated dimethyl sulfoxide (DMSO-d6, 0.05% TMS (tetramethylsilane) mixed product) (0.0. 53 ml) was added and completely dissolved by sonication. This solution was measured for proton NMR at 500 MHz with an NMR measuring instrument (JNW-ECA500) (manufactured by JEOL Datum). The imidation rate is determined based on protons derived from structures that do not change before and after imidation as reference protons, and the peak integrated value of these protons and proton peaks derived from NH groups of amic acid that appear in the vicinity of 9.5 ppm to 10.0 ppm. It calculated | required by the following formula | equation using the integrated value.
Imidization rate (%) = (1−α · x / y) × 100
In the above formula, x is a proton peak integrated value derived from NH group of amic acid, y is a peak integrated value of reference proton, α is one NH group proton of amic acid in the case of polyamic acid (imidation rate is 0%) Is the number ratio of the reference proton to.

[Production of liquid crystal cell]
A liquid crystal cell having a configuration of a fringe field switching (hereinafter referred to as FFS) mode liquid crystal display element is manufactured.
First, a substrate with electrodes was prepared. The substrate is a glass substrate having a size of 30 mm × 50 mm and a thickness of 0.7 mm. On the substrate, an ITO electrode having a solid pattern constituting a counter electrode as a first layer is formed. A SiN (silicon nitride) film formed by a CVD (Chemical Vapor Deposition) method is formed as a second layer on the counter electrode of the first layer. The second layer SiN film has a thickness of 500 nm and functions as an interlayer insulating film. On the second SiN film, a comb-like pixel electrode formed by patterning an ITO film as the third layer is arranged to form two pixels, a first pixel and a second pixel. ing. The size of each pixel is 10 mm long and about 5 mm wide. At this time, the first-layer counter electrode and the third-layer pixel electrode are electrically insulated by the action of the second-layer SiN film.

The pixel electrode of the third layer has a comb-like shape configured by arranging a plurality of electrode elements having a dogleg shape whose central portion is bent. The width in the short direction of each electrode element is 3 μm, and the distance between the electrode elements is 6 μm. Since the pixel electrode forming each pixel is formed by arranging a plurality of bent-shaped electrode elements in the central portion, the shape of each pixel is not rectangular, but in the central portion like the electrode elements. It has a shape that bends and resembles a bold-faced koji. Each pixel is divided into upper and lower portions with a central bent portion as a boundary, and has a first region on the upper side of the bent portion and a second region on the lower side.

When the first region and the second region of each pixel are compared, the formation directions of the electrode elements of the pixel electrodes constituting them are different. That is, when the rubbing direction of the liquid crystal alignment film described later is used as a reference, the electrode element of the pixel electrode is formed to form an angle of + 10 ° (clockwise) in the first region of the pixel, and the pixel in the second region of the pixel. The electrode elements of the electrode are formed so as to form an angle of −10 ° (clockwise). That is, in the first region and the second region of each pixel, the directions of the rotation operation (in-plane switching) of the liquid crystal induced by the voltage application between the pixel electrode and the counter electrode are mutually in the substrate plane. It is comprised so that it may become a reverse direction.

Next, after filtering the obtained liquid crystal aligning agent through a 1.0 μm filter, the prepared substrate with electrodes and a glass substrate having a columnar spacer with a height of 4 μm on which an ITO film is formed on the back surface, It applied by spin coat application. After drying on an 80 ° C. hot plate for 5 minutes, baking was performed in a hot air circulation oven at 230 ° C. for 20 minutes to form a coating film having a thickness of 100 nm. This coating film surface was irradiated with linearly polarized ultraviolet light having a wavelength of 254 nm with an extinction ratio of 10: 1 or more via a polarizing plate. This substrate was immersed in a solution containing ethyl lactate for 3 minutes, then immersed in pure water for 1 minute, and dried on a hot plate at 80 ° C. for 5 minutes to obtain a substrate with a liquid crystal alignment film. The two substrates are combined as a set, a sealant is printed on the substrate, and the other substrate is bonded so that the liquid crystal alignment film faces and the alignment direction is 0 °, and then the sealant is added. An empty cell was produced by curing. Liquid crystal MLC-2041 (manufactured by Merck & Co., Inc.) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS drive liquid crystal cell. Thereafter, the obtained liquid crystal cell was heated at 110 ° C. for 1 hour and allowed to stand overnight before being used for each evaluation.

[Afterimage evaluation by long-term AC drive]
A liquid crystal cell having the same structure as the liquid crystal cell used for the above-described afterimage evaluation was prepared.
Using this liquid crystal cell, an AC voltage of ± 5 V was applied for 120 hours at a frequency of 60 Hz in a constant temperature environment of 60 ° C. Thereafter, the pixel electrode and the counter electrode of the liquid crystal cell were short-circuited and left as it was at room temperature for one day.
After leaving, the liquid crystal cell is placed between two polarizing plates arranged so that the polarization axes are orthogonal, and the backlight is turned on with no voltage applied so that the brightness of the transmitted light is minimized. The arrangement angle of the liquid crystal cell was adjusted. Then, the rotation angle when the liquid crystal cell was rotated from the angle at which the second region of the first pixel became darkest to the angle at which the first region became darkest was calculated as an angle Δ. Similarly, for the second pixel, the second area was compared with the first area, and a similar angle Δ was calculated. Then, the average value of the angle Δ values of the first pixel and the second pixel was calculated as the angle Δ of the liquid crystal cell.

(Synthesis Example 1)
A 3000 mL four-necked flask equipped with a stirrer was placed in a nitrogen atmosphere, 114.33 g (468 mmol) of 1,2-bis (4-aminophenoxy) ethane was added, 12.33 g (52.0 mmol) of DA-2 was added, 1810 g of NMP was added and dissolved by stirring while feeding nitrogen. While stirring the diamine solution, 96.87 g (494 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and NMP was further added so that the solid concentration was 10% by mass. The solution was stirred for 24 hours to obtain a solution of polyamic acid (PAA-1). The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 159 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 139090 and Mw = 34272.

(Synthesis Example 2)
In a 50 mL sample tube containing a stirrer, 18.0 g of the polyamic acid solution (PAA-1) obtained in Synthesis Example 1 was taken, 6.05 g of NMP, 6.00 g of BCS, and 0.005 g of additive A. 26 g was added and stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (A-1).
(Synthesis Example 3)
In a 3000 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, 124.60 g (510 mmol) of 1,2-bis (4-aminophenoxy) ethane and 0.95 g (90.0 mmol) of DA-2 were taken, 2236g of NMP was added and dissolved by stirring while feeding nitrogen. While stirring the diamine solution, 130.06 g (580.2 mmol) of 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride was added, and the solid content concentration was further increased to 10% by mass. NMP was added and stirred at room temperature for 24 hours to obtain a polyamic acid (PAA-2) solution. The viscosity of this polyamic acid solution at a temperature of 25 ° C. was 511 mPa · s. Moreover, the molecular weight of this polyamic acid was Mn = 19100 and Mw = 46880.

(Synthesis Example 4)
In a 50 mL sample tube containing a stir bar, 18.0 g of the polyamic acid solution (PAA-2) obtained in Synthesis Example 3 was taken, 18.01 g of NMP, 9.03 g of BCS, and 0.03 g of additive A. 25 g was added and stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (A-2).
(Synthesis Example 5)
200 g of the polyamic acid solution (PAA-2) obtained in a 500 ml four-necked flask equipped with a stirrer and a nitrogen introduction tube was taken, 85.68 g of NMP was added, and the mixture was stirred for 30 minutes. To the obtained polyamic acid solution, 22.22 g of acetic anhydride and 6.86 g of pyridine were added and heated at 50 ° C. for 3 hours to perform chemical imidization. The obtained reaction solution was added to 1100 g of methanol while stirring, and the deposited precipitate was collected by filtration, subsequently washed 3 times with 1100 g of methanol, and twice with 200 g of methanol. The obtained resin powder was dried at 60 ° C. for 12 hours to obtain a polyimide resin powder.
The imidation ratio of this polyimide resin powder was 68%, the molecular weight was Mn = 9155, and Mw = 2430.
Furthermore, the polyimide resin powder 12.53 obtained in a 200 ml sample tube containing a stir bar was taken, 91.89 g of NMP was added, and the mixture was stirred and dissolved at room temperature for 24 hours to obtain a polyimide solution (PI-1). .

(Synthesis Example 6)
In a 200 mL sample tube containing a stir bar, 59.59 g of the polyimide solution (PI-1) obtained in Synthesis Example 5 was taken, and an NMP solution of 0.3 mass% 3-glycidoxypropylmethyldiethoxysilane was added. .17 g, 11.26 g of NMP, 26.0 g of BCS, and 2.08 g of additive A were added, and the mixture was stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (A-3).

(Synthesis Example 7)
A 500 mL four-necked flask equipped with a stirrer was placed in a nitrogen atmosphere, 7.01 g (28.7 mmol) of 1,2-bis (4-aminophenoxy) ethane was added, and 1.21 g (3.19 mmol) of DA-2. Then, 76.0 g of NMP, 227.9 g of GBL, and 5.69 g (71.9 mmol) of pyridine as a base were added and dissolved by stirring. Next, while stirring this diamine solution, 29.98 g (30.0 mmol) of DE-1 was added and reacted at 15 ° C. for 24 hours. After stirring for 24 hours, 0.83 g (9.18 mmol) of acryloyl chloride was added and reacted at 15 ° C. for 4 hours. The obtained polyamic acid ester solution was poured into 983 g of 2-propanol with stirring, the precipitated white precipitate was collected by filtration, subsequently washed with 328 g of 2-propanol five times, and dried to give a white Of polyamic acid ester resin powder was obtained. Moreover, the molecular weight of this polyamic acid ester was Mn = 15224 and Mw = 32484.
Further, 3.13 g of the obtained polyamic acid ester resin powder was taken into a 30 mL sample tube containing a stirring bar, 28.12 g of GBL was added, and the mixture was stirred and dissolved at room temperature for 24 hours to obtain a polyamic acid ester solution (PAE -1) was obtained.
(Synthesis Example 8)
In a 30 mL sample tube containing a stir bar, 7.52 g of the polyamic acid ester solution (PAE-1) obtained in Synthesis Example 7 was taken, 5.01 g of GBL, 3.00 g of BCS, and 0 of additive A. .14 g was added and stirred with a magnetic stirrer for 30 minutes to obtain a liquid crystal aligning agent (A-4).

<Example 1>
After the liquid crystal aligning agent (A-1) obtained in Synthesis Example 2 is filtered through a 1.0 μm filter, the prepared substrate with electrodes and a columnar shape with a height of 4 μm on which an ITO film is formed on the back surface. It apply | coated by spin coat application | coating to the glass substrate which has a spacer. After drying on an 80 ° C. hot plate for 5 minutes, baking was carried out in a hot air circulating oven at 230 ° C. for 20 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with 1.0 J / cm ² of linearly polarized UV light having an extinction ratio of 26: 1 and a wavelength of 254 nm through a polarizing plate. This substrate was immersed in ethyl lactate at room temperature (25 ° C.) for 3 minutes, then immersed in pure water for 1 minute, and dried on an 80 ° C. hot plate for 5 minutes to obtain a substrate with a liquid crystal alignment film. The two substrates are combined as a set, a sealant is printed on the substrate, and the other substrate is bonded so that the liquid crystal alignment film faces and the alignment direction is 0 °, and then the sealant is added. An empty cell was produced by curing. Liquid crystal MLC-2041 (manufactured by Merck & Co., Inc.) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS drive liquid crystal cell. Thereafter, the obtained liquid crystal cell was heated at 110 ° C. for 1 hour and left to stand for evaluation of afterimages by long-term AC driving. The value of the angle Δ of this liquid crystal cell after long-term AC driving was 0.44 degrees.
<Example 2>
Using the liquid crystal aligning agent (A-2) obtained in Synthesis Example 4, the polyimide film coated, dried and baked on the substrate was linearly polarized with an extinction ratio of 26: 1 through a polarizing plate, and ultraviolet light having a wavelength of 254 nm. An FFS drive liquid crystal cell was fabricated in the same manner as in Example 1 except that 0.2 J / cm ^{2 was} irradiated. This FFS drive liquid crystal cell was subjected to afterimage evaluation by long-term AC drive. The value of the angle Δ of this liquid crystal cell after long-term AC driving was 0.12 degrees.

<Example 3>
Using the liquid crystal aligning agent (A-3) obtained in Synthesis Example 6, the UV light having a wavelength of 254 nm that is linearly polarized with an extinction ratio of 26: 1 is applied to a polyimide film coated, dried, and fired on a substrate through a polarizing plate. An FFS drive liquid crystal cell was fabricated in the same manner as in Example 1 except that 0.2 J / cm ^{2 was} irradiated. This FFS drive liquid crystal cell was subjected to afterimage evaluation by long-term AC drive. The value of the angle Δ of this liquid crystal cell after long-term AC driving was 0.10 degrees.
<Example 4>
Using a liquid crystal aligning agent (A-3) obtained in Synthesis Example 8, a polyimide film coated, dried and baked on a substrate is linearly polarized with an extinction ratio of 26: 1 through a polarizing plate, and an ultraviolet ray having a wavelength of 254 nm. An FFS drive liquid crystal cell was fabricated in the same manner as in Example 1 except that 0.2 J / cm ^{2 was} irradiated. This FFS drive liquid crystal cell was subjected to afterimage evaluation by long-term AC drive. The value of the angle Δ of this liquid crystal cell after long-term AC driving was 0.08 degrees.

<Comparative Example 1>
After the liquid crystal aligning agent (A-1) obtained in Synthesis Example 2 is filtered through a 1.0 μm filter, the prepared substrate with electrodes and a columnar shape with a height of 4 μm on which an ITO film is formed on the back surface. It apply | coated by spin coat application | coating to the glass substrate which has a spacer. After drying on an 80 ° C. hot plate for 5 minutes, baking was carried out in a hot air circulating oven at 230 ° C. for 20 minutes to form a coating film having a thickness of 100 nm. The surface of the coating film was irradiated with 1.0 J / cm ² of linearly polarized UV light having an extinction ratio of 26: 1 and a wavelength of 254 nm through a polarizing plate.
This substrate was immersed in a mixed solution of IPA and pure water (mass ratio: IPA / pure water = 5/5) at room temperature for 3 minutes, then immersed in pure water for 1 minute, and 5% on an 80 ° C. hot plate. The substrate was dried for 5 minutes to obtain a substrate with a liquid crystal alignment film. The two substrates are combined as a set, a sealant is printed on the substrate, and the other substrate is bonded so that the liquid crystal alignment film faces and the alignment direction is 0 °, and then the sealant is added. An empty cell was produced by curing. Liquid crystal MLC-2041 (manufactured by Merck & Co., Inc.) was injected into this empty cell by a reduced pressure injection method, and the injection port was sealed to obtain an FFS drive liquid crystal cell. Thereafter, the obtained liquid crystal cell was heated at 110 ° C. for 1 hour and left to stand for evaluation of afterimages by long-term AC driving. The value of the angle Δ of this liquid crystal cell after long-term AC driving was 0.52 degrees.

<Comparative Example 2>
Using the liquid crystal aligning agent (A-2) obtained in Synthesis Example 4, the polyimide film coated, dried and baked on the substrate was linearly polarized with an extinction ratio of 26: 1 through a polarizing plate, and ultraviolet light having a wavelength of 254 nm. An FFS drive liquid crystal cell was produced in the same manner as in Comparative Example 1 except that 0.2 J / cm ^{2 was} irradiated. This FFS drive liquid crystal cell was subjected to afterimage evaluation by long-term AC drive. The value of the angle Δ of this liquid crystal cell after long-term AC driving was 0.25 degrees.
<Comparative Example 3>
Using the liquid crystal aligning agent (A-3) obtained in Synthesis Example 6, the UV light having a wavelength of 254 nm that is linearly polarized with an extinction ratio of 26: 1 is applied to a polyimide film coated, dried, and fired on a substrate through a polarizing plate. An FFS drive liquid crystal cell was produced in the same manner as in Comparative Example 1 except that 0.2 J / cm ^{2 was} irradiated. This FFS drive liquid crystal cell was subjected to afterimage evaluation by long-term AC drive. The value of the angle Δ of this liquid crystal cell after long-term AC driving was 0.20 degrees.

The liquid crystal alignment film obtained from the liquid crystal aligning agent of the present invention can reduce afterimages caused by alternating current driving in liquid crystal display elements of the IPS driving method or the FFS driving method, and has an excellent IPS driving method or FFS driving. A liquid crystal display element of the type is obtained. Therefore, it is particularly useful as a liquid crystal alignment film of an IPS driving type or FFS driving type liquid crystal display element or a liquid crystal television.
The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2012-263390 filed on November 30, 2012 are incorporated herein as the disclosure of the specification of the present invention. Is.

Claims

A liquid crystal aligning agent containing at least one polymer selected from the group consisting of a polyimide precursor having a structural unit represented by the following formula (1) and an imidized polymer of the polyimide precursor is applied on a substrate, A method for producing a liquid crystal alignment film, wherein the imidized film obtained by baking is irradiated with polarized radiation, and then contact-treated with a lower alkyl ester of lactic acid having 1 to 5 carbon atoms.

(In the formula (1), X 1 is at least one selected from the group consisting of structures represented by the following formulas (X1-1) and (X1-2), and R 1 is a hydrogen atom or a carbon number of 1 4 to 4 alkyl groups.)
The method for producing a liquid crystal alignment film according to claim 1, wherein the content of the polymer in the liquid crystal alignment agent is 2 to 8% by mass.
3. The method for producing a liquid crystal alignment film according to claim 1, wherein the polymer has a weight average molecular weight of 5,000 to 300,000 and a number average molecular weight of 2,500 to 150,000.
4. The liquid crystal alignment film according to claim 1, wherein the liquid crystal alignment film is contact-treated with the lower alkyl ester of 1 to 5 carbon atoms of lactic acid and further contacted with water or a water-soluble organic solvent having a boiling point of 50 to 105 ° C. Manufacturing method.
The method for producing a liquid crystal alignment film according to claim 4, wherein the water-soluble organic solvent having a boiling point of 50 to 105 ° C is at least one selected from the group consisting of methanol, ethanol, 2-propanol, and acetone.
The method for producing a liquid crystal alignment film according to any one of claims 1 to 5, wherein the lower alkyl ester is ethyl lactate.
At least one selected from the group consisting of a polyimide precursor containing 60 mol% or more of the structural unit represented by the formula (1) with respect to 1 mol of the whole polymer and an imidized polymer of the polyimide precursor. The method for producing a liquid crystal alignment film according to any one of claims 1 to 3.
A liquid crystal alignment film obtained by the method for producing a liquid crystal alignment film according to any one of claims 1 to 7.
A liquid crystal display device comprising the liquid crystal alignment film according to claim 8.