Polyimide precursor, liquid crystal alignment agent, liquid crystal alignment film and manufacturing method, liquid crystal display element

Abstract

The present application relates to a polyimide precursor characterized by being represented by formula (4) in which X4 is a 4-valent organic group derived from a tetracarboxylic acid derivative, Y4 is a 2-valent organic group derived from a diamine, and R4 is a hydrogen atom or an alkyl group having a carbon number of 1 to 5. The diamine has one or both of a biphenyl rigid aromatic ring structure, a tert-butyloxycarbonyl group, and a fluorenylmethoxycarbonyl group. The present application can provide a liquid crystal alignment film that is excellent in image sticking and abrasion resistance and has excellent adhesion to a substrate, and a liquid crystal display element having the same.

Description

TECHNICAL FIELD

[0001] The present application relates to a polyimide precursor, a liquid crystal alignment agent, a liquid crystal alignment film, a method for producing the same, and a liquid crystal display element having the liquid crystal alignment film. BACKGROUND

[0002] Liquid crystal display elements are known as display devices that are light in weight, thin in profile, and low in power consumption, and have been used for large television applications and the like in recent years, achieving remarkable development.

[0003] A liquid crystal display element is configured, for example, by sandwiching a liquid crystal layer with a pair of transparent substrates provided with electrodes. Also, in a liquid crystal display element, an organic film (a liquid crystal alignment film formed of a polymer such as polyamic acid, polyimide, or polysiloxane, which is coated on a substrate and baked) formed of an organic material is used as a liquid crystal alignment film to cause a liquid crystal to exhibit a desired alignment state between the substrates, and as a method for orientation processing of a liquid crystal alignment film for imparting alignment control ability, rubbing alignment and photoalignment are commonly used.

[0004] However, the rubbing method, which rubs the surface of a liquid crystal alignment film formed of polyimide or the like, has problems of dust generation and static electricity generation. Also, due to the high definition of liquid crystal display elements in recent years, and the concavities and convexities caused by electrodes or switching active elements for liquid crystal driving on the corresponding substrates, it is sometimes not possible to uniformly rub the surface of a liquid crystal alignment film with a cloth, and uniform liquid crystal alignment cannot be achieved.

[0005] Thus, as another orientation processing method for a liquid crystal alignment film that does not perform rubbing, photoalignment has been actively studied. As a main photoalignment method, a decomposition-type photoalignment method is known. For example, a polarized ultraviolet ray is irradiated to a polyimide film, and anisotropic decomposition is caused by the polarization direction dependency of ultraviolet absorption of the molecular structure. Also, a liquid crystal is aligned by the polyimide that remains without decomposition.

[0006] A liquid crystal alignment film prepared by a photoalignment method does not have problems such as dust generation, static electricity generation, and the like, compared to a liquid crystal alignment film prepared by a rubbing alignment method, and it is possible to expect an improvement in the contrast ratio, viewing angle characteristics, and the like of a liquid crystal display element.

[0007] On one hand, the requirement for the long-time driving residual image, i.e. "image sticking", of liquid crystal display elements is getting higher and higher with the development of display panel technology, and therefore it is necessary to further improve the quality of liquid crystal display elements and manufacture liquid crystal display elements that are less likely to generate image sticking. On the other hand, although the photo-alignment method does not require a rubbing process, in order to improve the reliability of the liquid crystal display element, it is necessary to improve the wear resistance of the liquid crystal alignment film to avoid the spacer inside the liquid crystal display element scratching the liquid crystal alignment film and destroying the alignment properties of the liquid crystal alignment film, so that the liquid crystal display element generates bright spots under dark state. In addition, with the narrow bezel of the liquid crystal display panel, the traditional non-polar group-containing polyimide cannot form a covalent bond with the frame adhesive component, and the adhesion between the substrates is low, so the reliability is poor.

[0008] There is an urgent need to develop a new type of liquid crystal alignment film to solve the problems in the prior art. SUMMARY

[0009] The present application is directed to the problems in the prior art, and the first aspect provides a polyimide precursor, characterized in that the polyimide precursor is represented by the following formula (4):

[0010]

[0011] In formula (4), X4 is a 4-valent organic group derived from a tetracarboxylic acid derivative, Y4 is a 2-valent organic group derived from a diamine, and R4 is a hydrogen atom or an alkyl group with a carbon number of 1-5.

[0012] The diamine is represented by the following formula (1):

[0013]

[0014] In formula (1), 2≤n≤6 and n is an integer, and R is one of the structures represented by formula (2-1) and formula (2-2) or a combination of both,

[0015]

[0016] Further, the polyimide precursor is obtained by reacting the diamine represented by formula (1) with a tetracarboxylic dianhydride, and the tetracarboxylic dianhydride comprises one or a combination of the following structures:

[0017]

[0018] Further, the tetracarboxylic dianhydride comprises one or a combination of 1,3-dimethylcyclobutane tetracarboxylic dianhydride represented by formula (3-2) and 3,3',4,4'-biphenyl tetracarboxylic dianhydride represented by formula (3-17),

[0019]

[0020] Further, the weight average molecular weight of the polyimide precursor is 70,000 to 100,000 g / mol.

[0021] The second aspect of the present application provides a liquid crystal alignment agent comprising at least one of the group consisting of the polyimide precursor of the first aspect of the present application and an imide thereof, i.e., a polyimide, and an organic solvent.

[0022] Further, the liquid crystal alignment agent contains 20 to 30 mole% of the repeating unit in the polyimide precursor, relative to the total amount of polymers contained in the liquid crystal alignment agent.

[0023] Further, the organic solvent includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethylimidazolidinone, methyl ethyl ketone, cyclohexanone, and cyclopentanone, preferably one or more of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and γ-butyrolactone, and further preferably N-methyl-2-pyrrolidone.

[0024] The third aspect of the present application provides a liquid crystal alignment film for a liquid crystal display element of the in-plane switching type, which is obtained using the liquid crystal alignment agent of the second aspect of the present application.

[0025] The fourth aspect of the present application provides a manufacturing method of a liquid crystal alignment film for a liquid crystal display element of the in-plane switching type, comprising the following steps:

[0026] Step [I], applying the liquid crystal alignment agent of the second aspect of the present application to a substrate having a conductive film for in-plane switching to form a coating film;

[0027] Step [II], irradiating the coating film obtained in [I] with polarized ultraviolet rays; and

[0028] Step [III], heating the coating film obtained in [II].

[0029] The fifth aspect of the present application provides a liquid crystal display element of the in-plane switching type having the liquid crystal alignment film of the third aspect of the present application or the liquid crystal alignment film manufactured by the manufacturing method of the fourth aspect of the present application.

[0030] Advantages:

[0031] The liquid crystal alignment agent of the present application contains a biphenyl rigid aromatic ring structure as the main body of the diamine structure, and can exhibit better mechanical strength after forming a liquid crystal alignment film. The alignment effect of the liquid crystal alignment film is stable and is not easily lost due to rubbing by the spacers of the liquid crystal display element, and thus the residual image and the rubbing resistance of the liquid crystal display element are good. Meanwhile, the tert-butyloxycarbonyl and the fluorenylmethoxycarbonyl of the specific diamine serve as thermal leaving protecting groups to produce exposed polar amino groups on the surface of the liquid crystal alignment film after the main curing process, and covalent bonds are formed with the functional groups such as epoxy and carboxyl in the frame adhesive, thereby improving the adhesion of the liquid crystal alignment film to the frame adhesive and improving the reliability of the liquid crystal display element. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0033] <Diamine>

[0034] The present application provides a diamine, which is shown in the following formula (1):

[0035]

[0036] In formula (1), 2≤n≤6 and n is an integer, and R is one or a combination of both of the structures represented by formula (2-1) and formula (2-2),

[0037]

[0038] The diamine in the present application has a biphenyl main structure, a tert-butyloxycarbonyl (-Boc) and a fluorenylmethoxycarbonyl (-Fmoc). Among them, the biphenyl structure can enhance the molecular rigidity, and the tert-butyloxycarbonyl (-Boc) and the fluorenylmethoxycarbonyl (-Fmoc) are two commonly used protecting groups, which can serve as thermal leaving protecting groups to produce exposed amino groups on the surface of the liquid crystal alignment film after the main curing process.

[0039] From the perspective of the source and the ease of synthesis of the diamine monomer raw material, the diamine component of the diamine shown in the above formula (1) structure is preferably a diamine including the following structure:

[0040]

[0041] Further preferably, the diamine includes one or a combination of both of the following two structures:

[0042]

[0043] More preferably, the diamine is the following structure:

[0044]

[0045] The synthesis method of the specific diamine is not particularly limited. For example, the following method can be mentioned: using a dinitro compound represented by the following formula (5), converting the nitro group to an amino group by a reduction reaction.

[0046]

[0047] In formula (5), n and R are the same as the definitions of n and R in the above formula (1).

[0048] The catalyst used in the above reduction reaction is preferably an active carbon-supported metal that can be obtained as a commercial product, and for example, palladium-activated carbon, platinum-activated carbon, rhodium-activated carbon, and the like can be mentioned. In addition, palladium hydroxide, platinum oxide, Raney nickel, and the like can also be used, and it is not necessary that the metal catalyst be an active carbon-supported type. The widely used palladium-activated carbon generally gives good results, and is therefore preferred.

[0049] In order to more effectively perform the reduction reaction, the reaction is sometimes performed in the presence of active carbon. In this case, the amount of active carbon used is not particularly limited, and is preferably in the range of 1 to 30 mass% relative to the dinitro compound of the above formula (5), and more preferably in the range of 10 to 20 mass%. For the same reason, the reaction is sometimes performed under pressure. In this case, in order to avoid reduction of the benzene ring, the reaction is performed in the pressure range of atmospheric pressure to 20 atmospheres. It is preferable to perform the reaction in the range of atmospheric pressure to 10 atmospheres.

[0050] As the solvent used in the synthesis of the specific diamine, any solvent can be used without limitation as long as it does not react with the respective raw materials. For example, the following can be used: aprotic polar organic solvents (dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, and the like); ethers (diethyl ether, diisopropyl ether, tert-butyl methyl ether, cyclopentyl methyl ether, tetrahydrofuran, dioxane, and the like); aliphatic hydrocarbons (pentane, hexane, heptane, petroleum ether, and the like); aromatic hydrocarbons (benzene, toluene, xylene, mesitylene, chlorobenzene, dichlorobenzene, nitrobenzene, tetralin, and the like); halogenated hydrocarbons (chloroform, dichloromethane, carbon tetrachloride, dichloroethane, and the like); lower fatty acid esters (methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and the like); nitriles (acetonitrile, propionitrile, butyronitrile, and the like); and the like. One of these solvents, or two or more of these solvents can be used. In addition, the solvent can be dried using an appropriate dehydrating agent, drying agent, and the like, and used as a non-aqueous solvent.

[0051] The amount of solvent (reaction concentration) is not particularly limited, and is preferably 0.1 to 100 times by mass, more preferably 0.5 to 30 times by mass, and further more preferably 1 to 10 times by mass, relative to the above-described dinitro compound of formula (5).

[0052] The reaction temperature is not particularly limited, and is preferably in the range of -100°C to the boiling point of the solvent used, and more preferably -50 to 150°C. The reaction time is usually 0.05 to 350 hours, and preferably 0.5 to 100 hours.

[0053] The method for synthesizing the above-described dinitro compound of formula (5) is not particularly limited, and for example, the above-described reaction process can be mentioned, in which a dinitro-biphenyl dicarboxylic acid is reacted with an aliphatic amine having one end protected with Boc / Fmoc in the presence of a condensing agent and a catalyst, thereby obtaining a dinitro compound of formula (5).

[0054]

[0055] In the above-described reaction process, n and R are the same as n and R in the above-described formula (1).

[0056] Examples of the condensing agent used in the above-described reaction process are not particularly limited as long as synthesis is possible, and triphenylphosphite, dicyclohexyl carbodiimide, l-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N,N'-carbonyldiimidazole, dimethoxy-l,3,5-triazinylmethylmorpholine, O-(benzotriazol-l-yl)-N,N,N',N'-tetramethyluronium tetrafluoroborate, O-(benzotriazol-l-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate, (2,3-dihydro-2-thia-3-benzoxazolyl)phosphonic acid diphenyl ester, and the like can be used. The amount of the condensing agent is preferably 1 to 1.5 times by mole, and particularly preferably 1 to 1.25 times by mole, relative to the amount of the carboxyl group. The catalyst can be triethylamine, pyridine, 4-dimethylaminopyridine, l-hydroxybenzotriazole, l-hydroxy-7-azabenzotriazole, triethylenediamine, and the like.

[0057] <Polymers (Specific Polymers, Side Chain Type High Molecular Weight)>

[0058] The specific polymer in the present application, as a component of liquid crystal alignment film, is applied to a liquid crystal alignment film for a liquid crystal display element of a lateral electric field driving type. The diamine having a rigid biphenyl structure main body and an organic group derived from a diamine having formula (1) can improve the alignment stability of the liquid crystal alignment film, maintain the alignment characteristics when rubbing against a spacer in the liquid crystal display element, and has good residual image and abrasion resistance. Meanwhile, the tert-butoxycarbonyl and fluorenylmethoxycarbonyl groups of the specific diamine serve as thermal leaving protective groups to generate exposed amino groups on the surface of the liquid crystal alignment film after the main curing process, and form covalent bonds with the epoxy and carboxyl groups in the frame adhesive, thereby improving the adhesion of the liquid crystal alignment film to the frame adhesive and improving the reliability of the liquid crystal display element.

[0059] As specific examples, polyamic acid, polyamic acid ester, polyimide, polyurea, polyamide, etc. can be listed, and from the viewpoint of use as a liquid crystal alignment agent, at least one of a polyimide precursor obtained by reacting the above diamine with a tetracarboxylic dianhydride and an imidized product thereof, i.e., a polyimide, is preferred.

[0060] The tetracarboxylic dianhydride includes one or a combination of the following structures:

[0061]

[0062] Preferably, the tetracarboxylic dianhydride includes one or a combination of 1,3-dimethylcyclobutane tetracarboxylic dianhydride represented by formula (3-2) and 3,3',4,4'-biphenyl tetracarboxylic dianhydride represented by formula (3-17),

[0063]

[0064] From the viewpoint of solubility of the liquid crystal alignment agent in a solvent, more preferably, the polyimide precursor represented by formula (4) is used:

[0065]

[0066] In formula (4), X4 is a 4-valent organic group derived from a tetracarboxylic acid derivative containing at least one structure selected from the group consisting of formula (3-2) and (3-17), Y4 is a structure derived from removing two amino groups from the diamine represented by the above formula (1), and R4 is a hydrogen atom or an alkyl group having a carbon number of 1 to 5. From the viewpoint of the ease of imidization by heating, R4 is preferably a hydrogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom.

[0067] The molecular weight of the polyimide precursor used in the present application is preferably 2000 to 500000 g / mol, more preferably 5000 to 300000 g / mol, and further preferably 70000 to 100000 g / mol, in terms of weight average molecular weight.

[0068] <Polymer (other structural unit)>

[0069] In addition to the polyimide precursor containing the structural unit represented by formula (4), at least one of a polyimide precursor selected from a structural unit represented by formula (6) below and an imide thereof, i.e., a polyimide, can be contained within a range that does not impair the effects of the present application.

[0070]

[0071] In formula (6), X6is a 4-valent organic group derived from a tetracarboxylic acid derivative, Y6is a 2-valent organic group derived from a diamine, and R6is the same as the definition of R4in the aforementioned formula (4), and is preferably a hydrogen atom.

[0072] X6is a 4-valent organic group derived from a tetracarboxylic acid derivative, and the structure thereof is not particularly limited. In addition, X6in the polyimide precursor can be appropriately selected depending on the degree of required properties of the polymer in terms of solubility in a solvent, coatability of the liquid crystal alignment agent, alignment properties of liquid crystals when a liquid crystal alignment film is produced, voltage holding ratio, accumulated charge, and the like, and can be one kind in the same polymer, or two or more kinds can be mixed.

[0073] The structure of the preferred X6is shown below, but the present application is not limited to these structures.

[0074]

[0075] In addition, Y6in the polyimide precursor of the structural unit represented by formula (6) is a 2-valent organic group derived from a diamine not containing the structure of formula (1), and the structure thereof is not particularly limited. In addition, Y6can be appropriately selected depending on the degree of required properties of the polymer in terms of solubility in a solvent, coatability of the liquid crystal alignment agent, alignment properties of liquid crystals when a liquid crystal alignment film is produced, voltage holding ratio, accumulated charge, and the like, and can be one kind in the same polymer, or two or more kinds can be mixed.

[0076] The structure of the preferred Y6is shown below, but the present application is not limited to these structures.

[0077]

[0078] In the case where the polyimide precursor containing the structural unit represented by formula (4) contains the structural unit represented by formula (6), the relative ratio of the structural unit represented by formula (6) to the sum of formula (4) and formula (6) is 30 mol% to 70 mol% from the viewpoint of the alignment properties of the resulting liquid crystal alignment film.

[0079] As the polyimide used in the present application, a polyimide obtained by ring-closing the aforementioned polyimide precursor can be exemplified. In the polyimide, the ring-closing rate of the amic acid group (also referred to as the imidization rate) is not necessarily required to be 100%, and can be arbitrarily adjusted depending on the use, purpose. With respect to the polymer of the present application, from the viewpoint of liquid crystal alignment property, 10 to 100%, more preferably 50 to 100%, further preferably 50 to 80% is preferred.

[0080] As the method of imidizing the polyimide precursor, thermal imidization in which the solution of the polyimide precursor is directly heated, or catalytic imidization in which a catalyst is added to the solution of the polyimide precursor can be exemplified.

[0081] <liquid crystal alignment agent>

[0082] The liquid crystal alignment agent of the present application contains a polymer (specific polymer) obtained from a diamine component containing the diamine represented by the aforementioned formula (1) and an acid component containing at least one selected from the group consisting of 1,3-dimethylcyclobutane tetracarboxylic dianhydride represented by the aforementioned formula (3-2) and 3,3',4,4'-diphenyltetracarboxylic dianhydride represented by formula (3-17). In addition to the specific polymer, other polymers, that is, polymers not having a divalent group derived from the diamine represented by formula (1) can also be contained. As the kind of the other polymers, polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivative, polyacetal, polystyrene or its derivative, poly(styrene-phenylmaleimide) derivative, poly(meth)acrylate, etc. can be exemplified. In the case where the liquid crystal alignment agent of the present application contains the other polymers, the liquid crystal alignment agent contains 20 to 30 mole% of the repeating unit in the aforementioned polyimide precursor, with respect to the total polymers contained in the liquid crystal alignment agent.

[0083] The liquid crystal alignment agent is used for producing a liquid crystal alignment film, and from the viewpoint of forming a uniform thin film, generally in the form of a coating liquid is adopted. The liquid crystal alignment agent of the present application is also preferably a coating liquid containing the aforementioned polymer component and an organic solvent capable of dissolving the polymer component. At this time, the concentration of the polymer in the liquid crystal alignment agent can be appropriately varied depending on the setting of the thickness of the coating film to be formed. From the viewpoint of forming a uniform and defect-free coating film, 1 mass% or more is preferred, and from the viewpoint of the storage stability of the solution, 10 mass% or less is preferably set. The particularly preferred concentration of the polymer is 2 to 8 mass%.

[0084] The organic solvent contained in the liquid crystal aligning agent is not particularly limited if it is an organic solvent that can uniformly dissolve the polymer component. If specific examples are listed, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethylimidazolidinone, methyl ethyl ketone, cyclohexanone, cyclopentanone, and the like can be listed. Among these, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ-butyrolactone is preferably used, and the organic solvent is further preferably N-methyl-2-pyrrolidone.

[0085] In addition, as the organic solvent contained in the liquid crystal aligning agent, a mixed solvent obtained by using, in addition to the above solvent, a solvent that improves the coatability of the coated liquid crystal aligning agent and the surface smoothness of the coating film is generally used, and such a mixed solvent is also preferably used in the liquid crystal aligning agent of the present application. Specific examples of the organic solvent used in combination are listed below, but are not limited to these examples.

[0086] For example, ethanol, isopropanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-l-butanol, isopentanol, tert-pentanol, 3-methyl-2-butanol, neopentanol, 1-hexanol, 2-methyl-l-pentanol, 2-methyl-2-pentanol, 2-ethyl-l-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 2-ethyl-l-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-l,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 diethyl ether, 4-hydroxy-4-methyl-2-pentanone, 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-ethylbutyl acetate, 2-ethylhexyl acetate, ethylene glycol monoacetate, ethylene glycol diacetate, propylene carbonate, ethylene carbonate, 2-(methoxymethoxy)ethanol, ethylene glycol monobutyl ether, ethylene glycol monoisopentyl ether, ethylene glycol monohexyl ether, 2-(hexyloxy)ethanol, furfuryl alcohol, diethylene glycol, propylene glycol, propylene glycol monobutyl ether, 1-(butoxyethoxy)propanol, propylene glycol monomethyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 2-(2-ethoxyethoxy)ethyl acetate, diethylene glycol acetate, 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, 3-methoxypropyl methyl acetate, 3-ethoxypropyl methyl ethyl acetate, 3-methoxypropyl ethyl acetate, 3-ethoxypropionic acid, 3-methoxypropionic acid, 3-methoxypropyl propyl acetate, 3-methoxypropyl butyl acetate, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate, and the like can be mentioned.

[0087] The kind and content of the solvent can be appropriately selected depending on the coating apparatus, coating conditions, coating environment, and the like of the liquid crystal alignment agent.

[0088] The liquid crystal alignment agent of the present application can also contain, within a range not impairing the effects of the present application, a component other than the polymer component and the organic solvent. As such additional components, adhesion aids for improving the adhesion of the liquid crystal alignment film to the substrate, the adhesion of the liquid crystal alignment film to the sealing material, crosslinking agents for improving the strength of the liquid crystal alignment film, dielectric or conductive substances for adjusting the dielectric constant, the resistance of the liquid crystal alignment film, and the like can be exemplified.

[0089] <liquid crystal alignment film>

[0090] The present application provides a liquid crystal alignment film for a lateral electric field driving type liquid crystal display element, which is obtained using the above-described liquid crystal alignment agent.

[0091] A manufacturing method of a liquid crystal alignment film for a lateral electric field driving type liquid crystal display element, comprising the following steps:

[0092] Step [I], after applying a polymer composition on a substrate having a conductive film for lateral electric field driving, drying to form a coating film, the polymer composition containing a polymer obtained from a diamine component containing a diamine represented by the above-described formula (1) and an acid component containing at least one selected from 1,3-dimethylcyclobutane tetracarboxylic dianhydride represented by the above-described formula (3-2) and 3,3',4,4'-biphenyl tetracarboxylic dianhydride represented by formula (3-17), and an organic solvent;

[0093] Step [II], irradiating the coating film obtained in [I] with polarized ultraviolet rays; and

[0094] Step [III], heating the coating film obtained in [II].

[0095] In the manufacturing method of a substrate with a coating film of the present application, after applying a composition of polyamide acid and an organic solvent on a substrate to form a coating film, polarized ultraviolet rays are irradiated. Subsequently, by performing heating, small molecules generated by photodecomposition are removed, anisotropy is introduced, and thus a substrate with a liquid crystal alignment film having liquid crystal alignment control ability is manufactured. By the above-described steps, a liquid crystal alignment film for a lateral electric field driving type liquid crystal display element, which is imparted with alignment control ability, and a substrate having the liquid crystal alignment film can be obtained. The substrate is not particularly limited, and when the manufactured liquid crystal display element is of a transmissive type, a substrate having high transparency is preferably used. In this case, the substrate is not particularly limited, and a glass substrate, or a plastic substrate such as an acrylic substrate, a polycarbonate substrate, or the like can be used. In addition, considering application in a reflective type liquid crystal display element, an opaque substrate such as a silicon wafer can also be used.

[0096] In addition, in addition to the above-described substrate (first substrate), a second substrate is prepared, and thus a lateral electric field driving type liquid crystal display element can be obtained.

[0097] The second substrate is obtained by using the above procedures [I] to [III] (for the sake of convenience, the procedures [I'] to [III'] are sometimes referred to as the procedures [I] to [III] in the present application, since a substrate not having the electrically conductive film for lateral electric field driving is used) except that the substrate having the electrically conductive film for lateral electric field driving is replaced with the substrate not having the electrically conductive film for lateral electric field driving. Note that, for the procedures [I'] to [III'], the procedures [I] to [III] can be performed as they are except that the substrate having the electrically conductive film for lateral electric field driving is replaced with the substrate not having the electrically conductive film for lateral electric field driving in the procedure [I]. The difference between the procedures [I] to [III] and the procedures [I'] to [III'] is only the presence or absence of the electrically conductive film described above, and thus the description of the procedures [I'] to [III'] is omitted.

[0098] Step [I]

[0099] In the procedure [I], the substrate has the electrically conductive film for lateral electric field driving. As the electrically conductive film, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), and the like can be exemplified when the liquid crystal display element is of a transmissive type, but the present application is not limited to these. In the case of a reflective liquid crystal display element, as the electrically conductive film, a material that reflects light such as aluminum, and the like can be exemplified, but the present application is not limited to these.

[0100] The method for forming the electrically conductive film on the substrate can use a publicly known method. The method for applying the above polymer composition to the substrate having the electrically conductive film for lateral electric field driving is not particularly limited.

[0101] As the application method, a method using screen printing, offset printing, flexographic printing, or inkjet method, and the like is generally used in industry. As other application methods, there are immersion method, roll coating method, slit coating method, spin coating method (spin coating method), or spray coating method, and the like, and these methods can be used according to the purpose.

[0102] After the polymer composition is applied to the substrate having the electrically conductive film for lateral electric field driving, the solvent can be evaporated at 30 to 150°C, preferably 70 to 110°C, using a heating unit such as a hot plate, a heat cycle oven, or an IR (infrared) oven, to thereby obtain a coating film. When the drying temperature is too low, there is a tendency that the solvent is not sufficiently dried, and when the heating temperature is too high, thermal imidization proceeds, and as a result, the photodecomposition reaction proceeds excessively due to polarized light exposure, and thus the alignment stability is impaired. Therefore, from the viewpoint of the liquid crystal alignment stability, the drying temperature at this time is preferably a temperature at which the specific polymer does not substantially undergo thermal imidization.

[0103] When the thickness of the coating film is too thick, it is not favorable in terms of power consumption of the liquid crystal display element, and when it is too thin, the reliability of the liquid crystal display element is sometimes reduced, and thus it is preferably 5 nm to 300 nm, and more preferably 10 nm to 150 nm.

[0104] Note that, after the process [I] and before the next process [II], a process of cooling the substrate on which the coating film is formed to room temperature can be provided.

[0105] Step [II]

[0106] In the process [II], the coating film obtained in the process [I] is irradiated with polarized ultraviolet rays. When the coating film is irradiated with the polarized ultraviolet rays, the polarized ultraviolet rays are irradiated on the substrate through a polarizing plate from a specific direction. As the ultraviolet rays to be used, ultraviolet rays having a wavelength in the range of 100 nm to 400 nm can be used. It is preferable that the optimal wavelength be selected by means of a filter or the like depending on the kind of the coating film to be used. Also, for example, in order to be able to selectively induce photolysis reaction, ultraviolet rays having a wavelength in the range of 240 nm to 400 nm can be used. As the ultraviolet rays, for example, light emitted from a high-pressure mercury lamp or a metal halide lamp can be used.

[0107] For the coating film to be used in the method of the present application, the amount of photolysis reaction of the photosensitive group in the polymer main chain is optimized by optimizing the amount of irradiation of the polarized ultraviolet rays. For the appropriate amount of polarized ultraviolet rays, evaluation based on the ultraviolet absorption of the coating film to be used in the present application can be performed.

[0108] That is, for the coating film to be used in the present application, the ultraviolet absorption in the direction parallel to the polarization direction of the polarized ultraviolet rays and the ultraviolet absorption in the direction perpendicular to the polarization direction of the polarized ultraviolet rays after the irradiation of the polarized ultraviolet rays are measured, respectively. Based on the measurement results of the ultraviolet absorption, ΔA, which is the difference between the ultraviolet absorbance in the direction parallel to the polarization direction of the polarized ultraviolet rays and the ultraviolet absorbance in the direction perpendicular to the polarization direction of the polarized ultraviolet rays in the coating film, is evaluated. Then, the maximum value ΔAmax of ΔA that can be achieved in the coating film to be used in the present application and the amount of irradiation of the polarized ultraviolet rays at which this value is achieved are found. In the production method of the present application, the amount of irradiation of the polarized ultraviolet rays at which this ΔAmax is achieved is used as a reference, and the optimal amount of the polarized ultraviolet rays to be irradiated in the production of the liquid crystal alignment film can be determined.

[0109] The amount of irradiation of the polarized ultraviolet rays depends on the coating film to be used. The amount of irradiation is preferably set to be in the range of 1% to 70% of the amount of polarized ultraviolet rays at which the maximum value (hereinafter also referred to as ΔAmax) of ΔA (the difference between the ultraviolet absorbance of the coating film in the direction parallel to the polarization direction of the polarized ultraviolet rays and the ultraviolet absorbance in the direction perpendicular to the polarization direction of the polarized ultraviolet rays) is achieved, and more preferably set to be in the range of 1% to 50%.

[0110] The irradiation amount of the polarized ultraviolet rays that is optimal for efficiently introducing anisotropy into the coating film used in the present application corresponds to the irradiation amount of the polarized ultraviolet rays that optimizes the amount of photolysis reaction of the photosensitive group in the coating film. As a result of irradiating the coating film used in the present application with the polarized ultraviolet rays, if the photosensitive group that undergoes the photolysis reaction is small, the amount of the photoreaction does not become sufficient. Therefore, in the coating film used in the present application, the optimal amount of the photosensitive group that undergoes the photolysis reaction by the irradiation of the polarized ultraviolet rays is preferably set to 0.1 mole% to 90 mole% of the polymer film, and more preferably to 0.1 mole% to 80 mole%.

[0111] Step [III]

[0112] In the process [III], the coating film that has been irradiated with the polarized ultraviolet rays in the process [II] is heated. By heating, the coating film can be given an orientation control ability.

[0113] The heating can use a hot plate, a heat cycle type oven, or an IR (infrared) type oven, or the like as a heating unit. The heating temperature can be determined in consideration of the temperature at which the coating film used exhibits good liquid crystal alignment stability and electrical characteristics.

[0114] The heating temperature is preferably within the temperature range at which the polyimide liquid crystal alignment film exhibits good liquid crystal alignment stability. That is, the heating temperature after the irradiation of the polarized ultraviolet rays is preferably set to 150°C to 300°C, and it is more desirable to be set to 180°C to 250°C. By doing so, the coating film used in the present application can be given a greater anisotropy. When the heating temperature is too low, there is a tendency that the increase effect of the anisotropy by heat and the insufficient thermal imidization are not sufficient, and when the heating temperature is excessively high from the temperature range, there is a tendency that the anisotropy given by the polarized light exposure disappears.

[0115] For the same reason as described in the process [I], the thickness of the coating film formed after the heating is preferably 5 nm to 300 nm, and more preferably 50 nm to 150 nm. By having the above processes, the manufacturing method of the present application can efficiently introduce anisotropy into the coating film. Also, a substrate with a liquid crystal alignment film can be efficiently manufactured.

[0116]

[0117] The present application provides a transverse electric field driving type liquid crystal display element having the above-described liquid crystal alignment film.

[0118] The manufacturing method of the transverse electric field driving type liquid crystal display element includes:

[0119] ​Process [IV] is a process of aligning the substrate (the first substrate) having the liquid crystal alignment film on the electrically conductive film for lateral electric field driving obtained in [III] and the substrate (the second substrate) having the liquid crystal alignment film obtained in the same manner as described above in [I'] to [III'] without the electrically conductive film in such a manner that the liquid crystal alignment films of both face each other with liquid crystal therebetween, and producing a liquid crystal cell by a known method, thereby producing a lateral electric field driving type liquid crystal display element.

[0120] Step [IV]

[0121] Process [IV] is a process of aligning the substrate (the first substrate) having the liquid crystal alignment film on the electrically conductive film for lateral electric field driving obtained in [III] and the substrate (the second substrate) having the liquid crystal alignment film obtained in the same manner as described above in [I'] to [III'] without the electrically conductive film in such a manner that the liquid crystal alignment films of both face each other with liquid crystal therebetween, and producing a liquid crystal cell by a known method, thereby producing a lateral electric field driving type liquid crystal display element.

[0122] If one example of production of a liquid crystal cell or a liquid crystal display element is cited, the following methods can be exemplified: a method of preparing the above-mentioned first substrate and second substrate, scattering spacers on the liquid crystal alignment film of one substrate, adhering the other substrate in such a manner that the liquid crystal alignment film surface is inside, and injecting liquid crystal under reduced pressure and sealing; or a method of dropping liquid crystal on the liquid crystal alignment film surface on which spacers are scattered, adhering the substrates and sealing, and the like. At this time, the substrate on one side is preferably a substrate having an electrode having a comb-tooth-like structure for lateral electric field driving. The diameter of the spacers at this time is preferably 1 μm to 30 μm, and more preferably 2 μm to 10 μm. The diameter of the spacers will determine the distance between a pair of substrates for sandwiching a liquid crystal layer, that is, the thickness of the liquid crystal layer.

[0123] The substrate for lateral electric field driving type liquid crystal display elements or the lateral electric field driving type liquid crystal display element having the same produced using the polymer of the present application, which is operated as described above, is excellent in reliability against external stress such as light and heat, and can be suitably used for a large-screen and high-definition liquid crystal television and the like. In addition, the liquid crystal alignment film produced by the method of the present application has excellent liquid crystal alignment stability and reliability, and thus can also be used for a variable phase shifter using liquid crystal, which can be suitably used for, for example, an antenna whose resonance frequency is variable and the like.

[0124] The above and other advantages of the present application will be more fully understood from the following examples, which are not intended to limit the scope of the present application.

[0125] Example

[0126] The following examples are given to illustrate the present application, but the present application is not limited by the following examples.

[0127] The abbreviations of the compounds used in the examples and comparative examples are shown below.

[0128] NMP: N-methyl-2-pyrrolidone

[0129] BCS: butyl cellosolve

[0130] DA-1: the following structural formula (DA-1)

[0131] DA-2: the following structural formula (DA-2)

[0132] DA-3: the following structural formula (DA-3)

[0133] DA-4: the following structural formula (DA-4)

[0134] DA-5: the following structural formula (DA-5)

[0135] DA-6: the following structural formula (DA-6)

[0136]

[0137] Measurement of molecular weight of polymer

[0138] Measurement was performed using a gel permeation chromatography (GPC) apparatus (Agilent 1260) (manufactured by Agilent Technologies) and a column (PLgel 5 μm MIXED-C 300*7.5 mm) (manufactured by Agilent Technologies) in the following manner.

[0139] Column temperature: 50°C

[0140] Eluent: N,N'-dimethylformamide (as an additive, phosphoric acid / anhydrous crystalline (orthophosphoric acid) 25 mmol / L)

[0141] Flow rate: 1.0 mL / minute

[0142] Standard sample for calibration curve preparation: standard polystyrene (molecular weight; about 10,000, 20,000, 40,000, 100,000, 200,000 and 400,000) (manufactured by Agilent Technologies).

[0143] Synthesis of diamine monomer

[0144] Synthesis Example 1

[0145] Synthesis of DA-1

[0146] First step: synthesis of N3,N3'-bis(2-((tert-butoxycarbonyl)amino)ethyl)-4,4'-dinitro-1,1'-biphenyl-3,3'-dicarboxamide (DA-1-1)

[0147]

[0148] DA-1-1 (10.01 g, 16.2 mmol) was dissolved in 150 g of propylene glycol methyl ether, and 5% by mass of palladium-carbon (7.5 g) was added, and stirred for 2 hours under a hydrogen atmosphere at room temperature. After adding 1000 g of propylene glycol methyl ether to the reaction solution, the palladium-carbon was removed by filtration, and concentrated and precipitated in water. The solid was washed and dissolved in 75 g of acetonitrile and 75 g of ethanol mixed solvent at 45°C, and recrystallized by cooling after filtering while hot, and dried by filtering, and finally obtained as a white solid product DA-1 (8.30 g, yield 92%, purity 98.8%).

[0149] Second step: Synthesis of N3,N3'-bis(2-((tert-butoxycarbonyl)amino)ethyl)-4,4'-diamino-1,1'-biphenyl-3,3'-dicarboxamide (DA-1)

[0150]

[0151] DA-1-1 (10.01 g, 16.2 mmol) was dissolved in 150 g of propylene glycol methyl ether, and 5% by mass of palladium-carbon (7.5 g) was added, and stirred for 2 hours under a hydrogen atmosphere at room temperature. After adding 1000 g of propylene glycol methyl ether to the reaction solution, the palladium-carbon was removed by filtration, and concentrated and precipitated in water. The solid was washed and dissolved in 75 g of acetonitrile and 75 g of ethanol mixed solvent at 45°C, and recrystallized by cooling after filtering while hot, and dried by filtering, and finally obtained as a white solid product DA-1 (8.30 g, yield 92%, purity 98.8%).

[0152] Synthesis Example 2

[0153] [Synthesis of DA-2]

[0154] First step: Synthesis of N3,N3'-bis(4-((fluorenylmethoxycarbonyl)amino)butyl)-4,4'-dinitro-1,1'-biphenyl-3,3'-dicarboxamide (DA-2-1)

[0155]

[0156] To 4,4'-dinitro-1,1'-biphenyl-3,3'-dicarboxylic acid (33.22 g, 100 mmol) dissolved in 700 g of dichloromethane, EDCI (21.09 g, 110 mmol) and DMAP (1.22 g, 10 mmol) were added and activated for 30 min, and then N-Fmoc-butane diamine (68.29 g, 220 mmol) was added and stirred at room temperature under a nitrogen atmosphere for 12 h. The reaction solution was washed with deionized water and dried with anhydrous sodium sulfate, and then the solvent was removed by drying under reduced pressure at 40°C. The crude product was washed with ethanol, and the solid was dissolved in 200 mL of toluene at 75°C, filtered while hot, and then recrystallized by cooling, followed by filtration, washing with ethanol, and drying under vacuum, to thereby obtain a yellowish solid product DA-1-1 (63.27 g, yield 69%, purity 98.3%).

[0157] Second step: Synthesis of N3,N3'-bis(4-((fluorenylmethoxycarbonyl)amino)butyl)-4,4'-diamino-1,1'-biphenyl-3,3'-dicarboxamide (DA-2)

[0158]

[0159] DA-2-1 (20.00 g, 21.8 mmol) was dissolved in 300 g of propylene glycol methyl ether, and 5% by mass of palladium-carbon (15 g) was added, and stirred at room temperature under a hydrogen atmosphere for 2 h. To the reaction solution, 1000 g of propylene glycol methyl ether was added, and then the palladium-carbon was removed by filtration. After concentration, the product was precipitated and filtered in water. The solid was washed and dissolved in a mixed solvent of 100 g of acetonitrile and 100 g of ethanol at 45°C, filtered while hot, and then recrystallized by cooling, followed by filtration and drying, to thereby obtain a white solid product DA-2 (16.44 g, yield 88%, purity 99.0%).

[0160] <Preparation example of polymer, alignment agent>

[0161] Into a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube, a diamine was weighed, and NMP was added, and the diamine was dissolved to be clear while stirring and nitrogen was supplied. To the diamine solution, a tetracarboxylic dianhydride was added while stirring, and a certain amount of NMP was added, and the mixture was heated and stirred at 40°C for 24 hours to obtain a polyamic acid-polyimide copolymer solution. Polymers a-1 to a-15 and b-1 to b-2 were prepared using the above preparation method, and the types and amounts of the substances used in the synthesis examples and comparative synthesis examples and the polymer ratio of the structural unit represented by formula (4), i.e., the specific polymer ratio, are shown in Table 1.

[0162] Table 1

[0163]

[0164] To a 50 mL conical flask with a stirrer, 7.0 g of the polyamic acid-polyimide copolymer solution in the synthesis example and the comparative synthesis example, respectively, was added, 7.0 g of NMP and 6.0 g of BCS were added, and stirring was performed at room temperature for 2 hours, to thereby obtain liquid crystal alignment agents A-1 to A-15 and B-1 to B-2, respectively, each having a solid content of 3.5% by weight.

[0165] Example 1

[0166] Method for producing liquid crystal cell for evaluating residual image

[0167] A liquid crystal cell having a structure of a liquid crystal display element of FFS mode was produced. First, an electrode-equipped substrate was prepared. The substrate was a glass substrate having a size of 30 mm x 35 mm and a thickness of 0.7 mm. On the substrate, as a first layer, an ITO electrode constituting a counter electrode was formed on the entire surface. On the counter electrode of the first layer, as a second layer, a silicon nitride (SiN) film formed by a CVD method was formed. The film thickness of the SiN film of the second layer was 500 nm, and it functioned as an interlayer insulating film. On the SiN film of the second layer, as a third layer, a comb-shaped pixel electrode formed by patterning an ITO film was disposed, thereby forming two pixels of a first pixel and a second pixel. The size of each pixel was 10 mm in the vertical direction and about 5 mm in the horizontal direction. At this time, the counter electrode of the first layer and the pixel electrode of the third layer were electrically insulated by the SiN film of the second layer.

[0168] The pixel electrode of the third layer had a comb-shaped shape constituted by arranging a plurality of "<" shaped electrode elements in which the central portion was bent. The width of each electrode element in the width direction was 10 μm, and the interval between the electrode elements was 10 μm. The pixel electrode forming each pixel was constituted by arranging a plurality of "<" shaped electrode elements in which the central portion was bent, and therefore the shape of each pixel was not a rectangular shape but a shape similar to a bold "<" in which the central portion was bent like the electrode elements. Furthermore, each pixel was divided into an upper side and a lower side with the bent portion of the center as a boundary, and had a first region on the upper side of the bent portion and a second region on the lower side.

[0169] When the first region and the second region of each pixel were compared, the formation direction of the electrode elements of the pixel electrode constituting them was different. That is, when the direction of a line segment on the substrate projected by the polarization plane of the polarized ultraviolet rays described later was taken as a reference, the electrode elements of the pixel electrode were formed at an angle of +10° (clockwise) in the first region of the pixel, and at an angle of -10° (clockwise) in the second region of the pixel. That is, the first region and the second region of each pixel were constituted such that the directions of the rotation movement (planar switching) of the liquid crystal in the substrate surface induced by the application of a voltage between the pixel electrode and the counter electrode were in opposite directions.

[0170] Next, the prepared substrate with electrodes was coated with the liquid crystal alignment agent A-1 using a coater, the coated film was baked at 100°C for 180 seconds to volatilize the solvent, and then imidized at 200°C for 45 minutes to form a polyimide alignment film. Subsequently, the substrate was exposed to 254 nm polarized light from a direction perpendicular to the substrate using an exposure device (APL-L01212S1-AXH01) manufactured by Ushio, with the light intensity being 300 to 600 mJ / cm 2 The PI film was exposed to light. The exposed film was baked at 200°C for 45 minutes to volatilize small molecules that were cleaved after exposure, thereby forming an alignment layer.

[0171] <Preparation of a liquid crystal cell for evaluation of liquid crystal alignment and transmittance>

[0172] On the basis of the FFS electrode substrate with a liquid crystal alignment film, a glass substrate with columnar spacers having a height of 4 μm was used as the counter substrate, and coating and alignment treatment of the liquid crystal alignment agent were performed to obtain a substrate with a polyimide liquid crystal alignment film. A frame adhesive with uniform thickness was coated on the substrate by gas extrusion, and was used to bond the substrates and seal the liquid crystal. The liquid crystal RXA10300 (a negative liquid crystal manufactured by Chisso Corp.) was dropped using a high-precision dropping device, and the two substrates were bonded under a gas pressure of 1 Pa. The frame adhesive in the bonded substrate was irradiated with 365 nm UV light, with the light intensity being 5000 to 20000 mJ / cm 2 The light initiator was allowed to react, and the substrate after UV curing was baked at 100°C for 2 hours to fully cure the frame adhesive, thereby obtaining an FFS mode liquid crystal cell.

[0173] <Evaluation of residual image of a liquid crystal display cell>

[0174] The prepared FFS mode liquid crystal cell was used, and the pixel electrode and the counter electrode of the liquid crystal cell were brought into a short-circuit state. The liquid crystal cell was left to stand in this state at 25°C for 8 hours.

[0175] After the standing, the liquid crystal cell was placed between two polarizing plates arranged in a manner that the polarization axes were orthogonal, and the backlight was turned on in a state without voltage application. The arrangement angle of the liquid crystal cell was adjusted so that the brightness of the transmitted light was minimized. Then, the voltage was applied to the liquid crystal display cell so that the brightness was maximized, and the brightness at 127 gray scale was measured. After the backlight was turned on for 24 hours, the brightness at 127 gray scale was measured again. The case where the ratio of the brightness at 127 gray scale before and after the turning on of the backlight was less than 2% was defined and evaluated as "good" in terms of residual image, and the case where the ratio of the brightness at 127 gray scale was 2% or more was defined and evaluated as "poor" in terms of residual image.

[0176] <Evaluation of abrasion resistance of a liquid crystal alignment film>

[0177] The liquid crystal alignment agent A-1 was coated on an ITO glass substrate using a spin coating method, baked at 100°C for 180 seconds to volatilize the solvent, and then baked at 200°C for 45 minutes to imidize the polyamic acid. Subsequently, an exposure device (APL-L01212S1-AXH01) manufactured by Ushio was used to perform exposure from a direction perpendicular to the substrate using 254 nm polarized light at an accumulated light amount of 200 to 400 mJ / cm 2 The PI film was exposed. The exposed film was baked at 200°C for 45 minutes to volatilize small molecules that were cleaved after exposure, thereby forming a liquid crystal alignment film having a thickness of 100 nm. The liquid crystal alignment film on the ITO glass substrate after the alignment process was rubbed on a rubbing device, and the Roller was set to a rotation speed of 1000 rpm, the substrate glass on which the liquid crystal alignment film was present was set to a travel speed of 20 mm / s, the rubbing cloth was set to a pressure of 0.5 mm, and the rubbing was performed 16 times continuously. The liquid crystal alignment film after rubbing was washed with an air gun and then tested for haze on a haze tester. A case where the haze value was less than 0.5% was defined and evaluated as "good" in terms of mechanical strength, and a case where the haze value was 0.5% or more was defined and evaluated as "poor" in terms of mechanical strength.

[0178] Evaluation of the adhesion of the liquid crystal alignment film to the frame adhesive

[0179] The liquid crystal alignment agent A-1 was coated on a blank glass substrate using a spin coating method, baked at 100°C for 180 seconds to volatilize the solvent, and then baked at 200°C for 45 minutes to imidize the polyamic acid. Subsequently, an exposure device (APL-L01212S1-AXH01) manufactured by Ushio was used to perform exposure from a direction perpendicular to the substrate using 254 nm polarized light at an accumulated light amount of 200 to 400 mJ / cm 2 The PI film was exposed. The exposed film was baked at 200°C for 45 minutes to volatilize small molecules that were cleaved after exposure, thereby forming a liquid crystal alignment film having a thickness of 100 nm. The liquid crystal alignment film on the blank glass substrate after the alignment process was used to draw a circle having a diameter of 2 mm with a frame adhesive machine, and a frame adhesive having a diameter of about 4.5 mm was applied. After vacuum bonding, UV curing was performed, and then the sample was taken out and cut into a cross having a size of 25 mm x 45 mm after heat curing at 120°C for 1 hour. The cross sample was fixed to a special lower jig of a Shimadzu tensile tester AGX-S on one side with a tape, and the other side was fixed to a special upper jig using a pull rope. After being stretched straight, the test was started, and the force required to pull apart the cross sample was the adhesion of the liquid crystal alignment film to the frame adhesive. A case where the test result was 20 N or more was defined and evaluated as "good" in terms of adhesion, and a case where the test result was less than 20 N was defined and evaluated as "poor" in terms of adhesion.

[0180] Examples 2 to 15

[0181] Using liquid crystal alignment agents A-1 to A-15, the residual image, abrasion resistance and adhesion were evaluated in the same manner as in Example 1, except that.

[0182] Comparative Examples 1 to 2

[0183] Using liquid crystal alignment agents B-1 to B-2, the residual image, abrasion resistance and adhesion were evaluated in the same manner as in Example 1, except that.

[0184] Table 2 shows the results of evaluation of the residual image of the liquid crystal display cell prepared using the liquid crystal alignment agents obtained in the synthesis examples and comparative synthesis examples.

[0185] Table 2

[0186]

[0187] As shown in Table 2, the change in the luminance of 127 gray scales before and after lighting of the liquid crystal display cell in Examples 1 to 15 was less than 2%, and was good. In Comparative Examples 1 to 2, the change in the luminance of 127 gray scales before and after lighting of the liquid crystal display cell was more than 2%, and was poor.

[0188] Table 3 shows the results of evaluation of the abrasion resistance of the liquid crystal alignment film prepared using the liquid crystal alignment agents obtained in the synthesis examples and comparative synthesis examples.

[0189] Table 3

[0190]

[0191]

[0192] As shown in Table 3, the haze of the liquid crystal alignment film in Examples 1 to 15 was less than 0.5%, and the abrasion resistance of the liquid crystal alignment film was good. In Comparative Examples 1 to 2, the haze was more than 0.5%, and was poor.

[0193] Table 4 shows the results of evaluation of the adhesion of the liquid crystal display element prepared using the liquid crystal alignment agents obtained in the synthesis examples and comparative synthesis examples.

[0194] Table 4

[0195] Liquid crystal alignment agent Adhesion (N) Example 1 A-1 34.10 Example 2 A-2 32.44 Example 3 A-3 24.22 Example 4 A-4 26.54 Example 5 A-5 28.89 Example 6 A-6 21.10 Example 7 A-7 20.11 Example 8 A-8 25.23 Example 9 A-9 27.30 Example 10 A-10 26.54 Example 11 A-11 25.90 Example 12 A-12 28.73 Example 13 A-13 29.77 Example 14 A-14 21.04 Example 15 A-15 20.47 Comparative Example 1 B-1 15.73 Comparative Example 2 B-2 17.98

[0196] As shown in Table 4, the adhesion of the liquid crystal alignment film to the frame sealant in Examples 1 to 15 was more than 20 N, and the reliability of the liquid crystal alignment film was good. In Comparative Examples 1 to 2, the adhesion was less than 20 N, and was poor.

[0197] Thus, it is confirmed that a liquid crystal display element having a good residual image performance can be produced by using a specific monomer by the method of the present application, and has excellent abrasion resistance and adhesion, thereby improving the reliability of the liquid crystal display element.

[0198] It should be noted that the above-described embodiments can be changed and modified by those skilled in the art in the light of the explanations and elaborations of the above specification. Therefore, the present application is not limited to the specific embodiments disclosed and described above, and some equivalent modifications and changes of the present application should be within the scope of protection of the claims of the present application. Furthermore, although some specific terms are used in the specification, these terms are only for the convenience of explanation and do not constitute any limitation on the application.

Claims

1. A polyimide precursor, characterized in that, The polyimide precursor is represented by the following formula (4): In formula (4), X4 is a 4-valent organic group derived from a tetracarboxylic acid derivative, Y4 is a 2-valent organic group derived from a diamine, and R4 is a hydrogen atom or an alkyl group having a carbon number of 1 to 5; The diamine is represented by the following formula (1): In formula (1), 2 ≤ n ≤ 6 and n is an integer, and R is one or a combination of both of structures represented by formula (2-1) and formula (2-2), 2. The polyimide precursor according to claim 1, wherein The polyimide precursor is obtained by reacting the diamine represented by formula (1) with a tetracarboxylic dianhydride, the tetracarboxylic dianhydride including one or a combination of two or more of the following structures:

3. The polyimide precursor according to claim 2, wherein The tetracarboxylic dianhydride includes one or a combination of two or more of 1,3-dimethylcyclobutane tetracarboxylic dianhydride represented by formula (3-2) and 3,3',4,4'-biphenyl tetracarboxylic dianhydride represented by formula (3-17), 4. The polyimide precursor according to claim 1, wherein The polyimide precursor has a weight average molecular weight of 70,000 to 100,000 g / mol.

5. A liquid crystal aligning agent characterized by comprising the compound according to claim 1. The liquid crystal alignment agent contains at least one of a group consisting of the polyimide precursor according to any one of claims 1 to 4 and an imidized product thereof, that is, a polyimide, and an organic solvent.

6. The liquid crystal aligning agent according to claim 5, characterized by The liquid crystal alignment agent contains 20 to 30 mol% of the repeating unit in the polyimide precursor, relative to the total amount of polymers contained in the liquid crystal alignment agent.

7. The liquid crystal aligning agent according to claim 5, wherein The organic solvent includes one or a combination of two or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethylimidazolidinone, methyl ethyl ketone, cyclohexanone, and cyclopentanone.

8. A liquid crystal alignment film for a lateral electric field driven liquid crystal display element, characterized in that, It is obtained using the liquid crystal alignment agent according to any one of claims 5 to 7.

9. A method for producing a liquid crystal alignment film for a liquid crystal display element of the in-plane switching type, characterized by The process includes the following steps: Step [I], applying the liquid crystal alignment agent according to any one of claims 5 to 7 to a substrate having a conductive film for horizontal electric field driving to form a coating film; Step [II], irradiating the coating film obtained in [I] with polarized ultraviolet rays; and Step [III], heating the coating film obtained in [II].

10. A transverse electric field driven liquid crystal display element, characterized in that, It has the liquid crystal alignment film according to claim 8 or the liquid crystal alignment film manufactured by the production method according to claim 9.

Images