Polyimide precursor, liquid crystal aligning agent, liquid crystal alignment film, method for producing liquid crystal alignment film, and liquid crystal display element

Abstract

The present invention relates to a polyimide precursor characterized by being represented by formula (4) (in formula (4), X4 is a tetravalent organic group derived from a tetracarboxylic acid derivative, Y4 is a divalent organic group derived from a diamine, and R4 is a hydrogen atom or a C1-5 alkyl group. The diamine has one or a combination of two of a biphenyl rigid aromatic ring structure, t-butyloxycarbonyl and fluorenylmethoxycarbonyl. The present invention provides a liquid crystal alignment film having good afterimage and wear resistance, and excellent adhesion to a substrate, and a liquid crystal display element having the liquid crystal alignment film. # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the field of liquid crystal display, and specifically relates to a polyimide precursor, a liquid crystal alignment agent, a liquid crystal alignment film obtained therefrom, a manufacturing method thereof, and a liquid crystal display element having the obtained liquid crystal alignment film. Background Art

[0002] Liquid crystal display elements are known as lightweight, thin, and low-power-consuming display devices, and have been used in large-format televisions and the like in recent years, achieving remarkable development.

[0003] Liquid crystal display elements are constructed, for example, by sandwiching a liquid crystal layer between a pair of transparent substrates equipped with electrodes. In liquid crystal display elements, an organic film (a liquid crystal alignment film formed by coating a polymer such as polyamic acid, polyimide, or polysiloxane onto substrates and then baking it) made of an organic material is used as the liquid crystal alignment film to achieve a desired alignment between the substrates. Rubbing and photo-alignment methods are commonly used to impart alignment control to the liquid crystal alignment film.

[0004] However, the brushing method, which rubs the surface of a liquid crystal alignment film made of polyimide or the like, has problems with dust generation and static electricity. Furthermore, due to the recent advancements in the definition of liquid crystal display elements and the unevenness caused by electrodes on the corresponding substrates or the switching active elements used to drive the liquid crystal, it is sometimes impossible to evenly rub the surface of the liquid crystal alignment film with a cloth, making it difficult to achieve uniform liquid crystal alignment.

[0005] Therefore, photo-alignment methods have been actively studied as alternative alignment treatment methods for liquid crystal alignment films that do not require brushing. Decomposition-type photo-alignment methods are a common method. For example, a polyimide film is irradiated with polarized ultraviolet light, causing anisotropic decomposition by exploiting the polarization-dependent ultraviolet absorption of its molecular structure. The remaining undecomposed polyimide then aligns the liquid crystal.

[0006] Compared to liquid crystal alignment films produced by rubbing alignment methods, liquid crystal alignment films produced by photo-alignment methods do not have problems such as dust generation and static electricity, and can be expected to improve the contrast and viewing angle characteristics of liquid crystal display elements.

[0007] On the one hand, the requirements for the long-term residual image of liquid crystal display elements, i.e., "afterimage", have become increasingly stringent with the development of display panel technology. 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 produce afterimages. On the other hand, although the photo-alignment method does not require a brushing process, in order to improve the reliability of liquid crystal display elements, the wear resistance of the liquid crystal alignment film must be improved to prevent the spacers inside the liquid crystal display element from scratching the liquid crystal alignment film, destroying the orientation characteristics of the liquid crystal alignment film, and causing the liquid crystal display element to leak light in the dark state and produce bright spots. In addition, with the narrow frame of liquid crystal display panels, it is impossible to form a covalent bond with the sealant component on the traditional non-polar group polyimide, and the adhesion between the substrates is low, resulting in poor reliability.

[0008] There is an urgent need to discover a new type of liquid crystal alignment film to solve the problems existing in the existing technology. Summary of the Invention

[0009] In view of the problems existing in the prior art, the present invention provides a polyimide precursor in a first aspect, characterized in that the polyimide precursor is represented by the following formula (4):

[0010] (4)

[0011] In formula (4), X4 is a tetravalent organic group derived from a tetracarboxylic acid derivative, Y4 is a divalent organic group derived from a diamine, and R4 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

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

[0013] (1)

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

[0015] (2-1) (2-2);

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

[0017] ;

[0018] Furthermore, the tetracarboxylic dianhydride comprises one or a combination of 1,3-dimethylcyclobutanetetracarboxylic dianhydride as shown in formula (3-2) and 3,3',4,4'-biphenyltetracarboxylic dianhydride as shown in formula (3-17),

[0019] (3-2) (3-17);

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

[0021] The second aspect of the present invention provides a liquid crystal alignment agent, comprising at least one selected from the group consisting of the polyimide precursor and its imide product, i.e., polyimide, described in the first aspect of the present invention, and an organic solvent;

[0022] Furthermore, the liquid crystal alignment agent contains 20 mol% to 30 mol% of the polyimide precursor relative to all polymers contained in the liquid crystal alignment agent;

[0023] Further, the organic solvent includes one or more combinations 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, the organic solvent is one or more combinations of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and γ-butyrolactone. More preferably, the organic solvent is N-methyl-2-pyrrolidone.

[0024] The third aspect of the present invention provides a liquid crystal alignment film for a transverse electric field driven liquid crystal display element, which is obtained using the liquid crystal alignment agent described in the second aspect of the present invention;

[0025] A fourth aspect of the present invention provides a method for manufacturing a liquid crystal alignment film for a transverse electric field driven liquid crystal display element, comprising the following steps:

[0026] Step [I], coating the liquid crystal alignment agent of the second aspect of the present invention on a substrate having a conductive film for lateral electric field driving to form a coating film;

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

[0028] In step [III], the coating film obtained in step [II] is heated.

[0029] The fifth aspect of the present invention provides a transverse electric field driven liquid crystal display element having the liquid crystal alignment film according to the third aspect of the present invention or the liquid crystal alignment film manufactured by the preparation method according to the fourth aspect of the present invention.

[0030] Beneficial effects:

[0031] The liquid crystal alignment agent of the present invention contains a biphenyl rigid aromatic ring structure as the main diamine structure. After forming the liquid crystal alignment film, it can exhibit better mechanical strength. The liquid crystal alignment film has a stable orientation effect and is not easily scratched by the spacers of the liquid crystal display element, resulting in excellent residual image and friction resistance of the liquid crystal display element. At the same time, the tert-butyloxycarbonyl group and fluorenylmethyloxycarbonyl group contained in the specific diamine act as thermally leaving protective groups. After the main curing process, they produce exposed polar amino groups on the surface of the liquid crystal alignment film. These groups form covalent bonds with functional groups such as epoxy and carboxyl groups in the sealant, thereby improving the adhesion between the liquid crystal alignment film and the sealant, thereby improving the reliability of the liquid crystal display element. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] <Diamine>

[0034] The present invention provides a diamine, wherein the diamine is represented by the following formula (1):

[0035] (1)

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

[0037] (2-1) (2-2).

[0038] The diamine in the present invention has a biphenyl main structure, tert-butyloxycarbonyl (-Boc) and fluorenylmethyloxycarbonyl (-Fmoc). The biphenyl structure enhances molecular rigidity, while tert-butyloxycarbonyl (-Boc) and fluorenylmethyloxycarbonyl (-Fmoc) are two commonly used protecting groups that can act as thermally removable protecting groups to produce exposed amino groups on the surface of the liquid crystal alignment film after the primary curing process.

[0039] From the perspective of the source of diamine monomer raw materials and the ease of synthesis, the diamine component of the diamine represented by the above formula (1) preferably includes a diamine represented by the following structure:

[0040]

[0041]

[0042] Further preferably, the diamine comprises one or a combination of the following two structures:

[0043]

[0044] More preferably, the diamine has the following structure:

[0045]

[0046] The method for synthesizing the specific diamine is not particularly limited, but an example thereof includes a method in which a dinitro compound represented by the following formula (5) is used and its nitro group is converted into an amino group by a reduction reaction.

[0047] (5)

[0048] In formula (5), n and R have the same definitions as those in formula (1).

[0049] The catalyst used in the above-mentioned reduction reaction is preferably an activated carbon-supported metal catalyst that can be obtained as a commercial product, for example, palladium-activated carbon, platinum-activated carbon, rhodium-activated carbon, etc. can be listed. In addition, palladium hydroxide, platinum oxide, Raney nickel, etc. can also be used, and activated carbon-supported metal catalysts are not necessarily required. Generally, palladium-activated carbon, which is widely used, easily obtains good results and is therefore preferred.

[0050] In order to carry out the reduction reaction more effectively, the reaction is sometimes carried out in the presence of activated carbon. In this case, the amount of activated carbon used is not particularly limited, and is preferably in the range of 1 to 30% by mass, more preferably 10 to 20% by mass, relative to the dinitro compound of formula (5). For the same reason, the reaction is sometimes carried out under pressure. In this case, in order to avoid reduction of the benzene ring, the reaction is carried out in a pressure range of atmospheric pressure to 20 atmospheres. The reaction is preferably carried out in the range of atmospheric pressure to 10 atmospheres.

[0051] The solvent used in the synthesis of the specific diamine can be used without limitation as long as it does not react with the raw materials. For example, aprotic polar organic solvents (such as dimethylformamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone); ethers (such as diethyl ether, diisopropyl ether, tert-butyl methyl ether, cyclopentyl methyl ether, tetrahydrofuran, and dioxane); aliphatic hydrocarbons (such as pentane, hexane, heptane, and petroleum ether); aromatic hydrocarbons (such as benzene, toluene, xylene, mesitylene, chlorobenzene, dichlorobenzene, nitrobenzene, and tetralin); halogenated hydrocarbons (such as chloroform, dichloromethane, carbon tetrachloride, and ethylene dichloride); lower fatty acid esters (such as methyl acetate, ethyl acetate, butyl acetate, and methyl propionate); and nitriles (such as acetonitrile, propionitrile, and butyronitrile). These solvents can be used alone or in combination. Furthermore, the solvent can be dried using an appropriate dehydrating agent or drying agent and used as a non-aqueous solvent.

[0052] The amount of the solvent used (reaction concentration) is not particularly limited, but is 0.1 to 100 times by mass, preferably 0.5 to 30 times by mass, and more preferably 1 to 10 times by mass, relative to the dinitro compound of formula (5).

[0053] The reaction temperature is not particularly limited but is within the range of -100° C. to the boiling point of the solvent used, preferably -50 to 150° C. The reaction time is usually 0.05 to 350 hours, preferably 0.5 to 100 hours.

[0054] The method for synthesizing the dinitro compound of the above formula (5) is not particularly limited. For example, as shown in the following reaction process, dinitrobiphenyldicarboxylic acid is reacted with an aliphatic amine whose one end is protected by Boc / Fmoc in the presence of a condensing agent and a catalyst to obtain the dinitro compound represented by formula (5).

[0055]

[0056] In the above reaction process, the definitions of n and R are the same as those in the above formula (1).

[0057] Examples of the condensing agent used in the above reaction are not particularly limited as long as they can be synthesized, and include triphenyl phosphite, dicyclohexylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N,N'-carbonyldiimidazole, dimethoxy-1,3,5-triazinylmethylmorpholine, O-(benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium tetrafluoroborate, O-(benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate, and diphenyl (2,3-dihydro-2-thia-3-benzoxazolyl)phosphonate. The amount of the condensing agent used is preferably 1 to 1.5 times the molar amount of the carboxyl groups, and particularly preferably 1 to 1.25 times the molar amount. As the catalyst, triethylamine, pyridine, 4-dimethylaminopyridine, 1-hydroxybenzotriazole, 1-hydroxy-7-azidobenzotriazole, triethylenediamine or the like can be used.

[0058] <Polymers (Specific Polymers, Side Chain Polymers)>

[0059] The specific polymer of the present invention, as a component of a liquid crystal alignment film, is applied to a liquid crystal alignment film for a transverse electric field driven liquid crystal display element. Due to the organic group of the diamine shown in formula (1), the diamine of the rigid biphenyl structure can improve the orientation stability of the liquid crystal alignment film, maintain the orientation characteristics undamaged when facing the isolation column inside the liquid crystal display element, and has good residual image and wear resistance. At the same time, the tert-butyloxycarbonyl and fluorenylmethyloxycarbonyl groups possessed by the specific diamine act as thermally 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 functional groups such as epoxy and carboxyl groups in the sealant, thereby improving the adhesion between the liquid crystal alignment film and the sealant, thereby improving the reliability of the liquid crystal display element.

[0060] Specific examples include polyamic acid, polyamic acid ester, polyimide, polyurea, and polyamide. From the viewpoint of use as a liquid crystal aligning agent, at least one of a polyimide precursor obtained by reacting the above-mentioned diamine with tetracarboxylic dianhydride and its imide product, that is, a polyimide, is preferably used.

[0061] Tetracarboxylic dianhydride comprises one or more combinations of the following structures:

[0062] .

[0063] Preferably, the tetracarboxylic dianhydride comprises one or a combination of 1,3-dimethylcyclobutanetetracarboxylic dianhydride as shown in formula (3-2) and 3,3',4,4'-biphenyltetracarboxylic dianhydride as shown in formula (3-17),

[0064] (3-2) (3-17)

[0065] From the perspective of solubility of the liquid crystal alignment agent in the solvent, the polyimide precursor represented by formula (4) is more preferred:

[0066] (4)

[0067] In formula (4), X4 is a tetravalent organic group derived from a tetracarboxylic acid derivative containing at least one structure selected from formulas (3-2) and (3-17), Y4 is a structure derived from the diamine represented by formula (1) by removing two amino groups, and R4 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. From the perspective of ease of imidization by heating, R4 is preferably a hydrogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom.

[0068] The molecular weight of the polyimide precursor used in the present invention is preferably 2,000 to 500,000 g / mol, more preferably 5,000 to 300,000 g / mol, and further preferably 70,000 to 100,000 g / mol in terms of weight average molecular weight.

[0069] <Polymer (other structural units)>

[0070] In addition to the polyimide precursor containing the structural unit represented by formula (4), at least one selected from polyimide precursors containing the structural unit represented by formula (6) below and imide products thereof, i.e., polyimides, may be contained within a range not impairing the effects of the present invention.

[0071] (6)

[0072] In formula (6), X6 is a tetravalent organic group derived from a tetracarboxylic acid derivative, Y6 is a divalent organic group derived from a diamine, and R6 has the same definition as R4 in formula (4) above and is preferably a hydrogen atom.

[0073] X6 is a tetravalent organic group derived from a tetracarboxylic acid derivative, and its structure is not particularly limited. In addition, X6 in the polyimide precursor can be appropriately selected based on the solubility of the polymer in the solvent, the coating properties of the liquid crystal alignment agent, the orientation of the liquid crystal when the liquid crystal alignment film is prepared, the voltage holding ratio, the degree of accumulated charge and other required characteristics. It can be one type in the same polymer or two or more types can be mixed.

[0074] Preferred structures of X6 are shown below, but the present invention is not limited to these structures.

[0075]

[0076] In addition, Y6 in the polyimide precursor of the structural unit represented by formula (6) is a divalent organic group derived from a diamine that does not contain the structure of formula (1), and its structure is not particularly limited. In addition, Y6 can be appropriately selected based on the degree of desired characteristics such as the solubility of the polymer in the solvent, the coating properties of the liquid crystal alignment agent, the orientation of the liquid crystal when formed into a liquid crystal alignment film, the voltage holding ratio, and the accumulated charge. In the same polymer, one type can be used, or two or more types can be mixed.

[0077] Preferred structures of Y6 are shown below, but the present invention is not limited to these structures.

[0078]

[0079] In the case where a polyimide precursor containing a structural unit represented by formula (4) also contains a polyimide precursor containing a structural unit represented by formula (6), from the viewpoint of the orientation properties of the resulting liquid crystal alignment film, the relative proportion of the structural unit represented by formula (6) to the sum of formula (4) and formula (6) is 30 mol% to 70 mol%.

[0080] As the polyimide used in the present invention, the polyimide obtained by ring-closing the aforementioned polyimide precursor can be listed. In the polyimide, the ring-closure rate (also referred to as imidization rate) of the amic acid group is not necessarily 100%, and can be arbitrarily adjusted according to the application and purpose. About the polymer of the present invention, from the viewpoint of liquid crystal orientation, preferably 10 to 100%, more preferably 50 to 100%, further preferably 50 to 80%.

[0081] As a method of imidating a polyimide precursor, thermal imidation which heats the solution of a polyimide precursor as it is, or catalytic imidation which adds a catalyst to the solution of a polyimide precursor is mentioned.

[0082] <Liquid Crystal Alignment Agent>

[0083] The liquid crystal aligning agent of the present invention contains a polymer (specific polymer) obtained by a diamine component comprising a diamine shown in the above formula (1) and an acid component comprising at least one of 1,3-dimethylcyclobutane tetracarboxylic dianhydride and 3,3',4,4'-biphenyl tetracarboxylic dianhydride shown in the above formula (3-2). In addition to the specific polymer, other polymers may also be contained, that is, a polymer that does not have a divalent group derived from the diamine shown in formula (1). As the types of other polymers, polyamic acid, polyimide, polyamic acid ester, polyester, polyamide, polyurea, polyorganosiloxane, cellulose derivatives, polyacetals, polystyrene or its derivatives, poly (styrene-phenylmaleimide) derivatives, poly (methyl) acrylates, etc. can be listed. When the liquid crystal aligning agent of the present invention contains other polymers, the ratio of the specific polymer to the total polymer components is preferably 20 mol% to 30 mol%.

[0084] Liquid crystal alignment agents are used to make liquid crystal alignment films. From the perspective of forming a uniform thin film, they are generally in the form of a coating liquid. The liquid crystal alignment agent of the present invention is also preferably a coating liquid containing the aforementioned polymer component and an organic solvent that can dissolve the polymer component. At this time, the concentration of the polymer in the liquid crystal alignment agent can be appropriately changed according to the thickness of the coating film to be formed. From the perspective of forming a uniform and defect-free coating film, it is preferably 1% by mass or more, and from the perspective of the storage stability of the solution, it is preferably set to 10% by mass or less. The particularly preferred polymer concentration is 2 to 8% by mass.

[0085] The organic solvent contained in the liquid crystal alignment agent is not particularly limited as long as it is an organic solvent in which the polymer components can be uniformly dissolved. Specific examples thereof include 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. Among them, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, or γ-butyrolactone is preferably used, and N-methyl-2-pyrrolidone is a more preferred organic solvent.

[0086] In addition, the organic solvent contained in the liquid crystal alignment agent is generally a mixed solvent formed by combining the above-mentioned solvents with a solvent that can improve the coating properties and surface smoothness of the coating film when the liquid crystal alignment agent is applied. Such a mixed solvent is also preferably used in the liquid crystal alignment agent of the present invention. Specific examples of the organic solvents used in combination are listed below, but are not limited to these examples.

[0087] For example, ethanol, isopropanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentanol, tert-pentanol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, cyclohexanol, 1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 1,2-ethanediol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, dipropyl ether, dibutyl ether, dihexyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, 1,2-butoxyethane, diethylene glycol dimethyl ether, diethylene glycol 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-ethyl 1-(Butoxyethoxy)propanol, propylene glycol monomethyl ether acetate, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monoacetate, ethylene glycol diacetate Ester, 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 acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate, butyl 3-methoxypropionate, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate, and the like.

[0088] The type and content of the solvent can be appropriately selected depending on a coating device, coating conditions, coating environment, and the like of the liquid crystal aligning agent.

[0089] The liquid crystal alignment agent of the present invention may also contain additional components other than the polymer component and the organic solvent, within the scope that does not impair the effects of the present invention. Examples of such additional components include: adhesion aids for improving the adhesion between the liquid crystal alignment film and the substrate, and the adhesion between the liquid crystal alignment film and the sealing material; cross-linking agents for improving the strength of the liquid crystal alignment film; dielectrics or conductive substances for adjusting the dielectric constant and resistance of the liquid crystal alignment film, etc.

[0090] <Liquid Crystal Alignment Film>

[0091] The present invention provides a liquid crystal alignment film for a transverse electric field driven liquid crystal display element, wherein the liquid crystal alignment film is obtained by using the above-mentioned liquid crystal alignment agent.

[0092] A method for manufacturing a liquid crystal alignment film for a transverse electric field driven liquid crystal display element comprises the following steps:

[0093] Step [I], coating a polymer composition on a substrate having a conductive film for transverse electric field driving, and drying the coating film to form the coating film, wherein the polymer composition comprises a polymer obtained from a diamine component including a diamine represented by the above formula (1), an acid component including at least one selected from 1,3-dimethylcyclobutanetetracarboxylic dianhydride represented by the above formula (3-2) and 3,3',4,4'-biphenyltetracarboxylic dianhydride represented by the above formula (3-17), and an organic solvent;

[0094] Step [II], irradiating the coating film obtained in step [I] with polarized ultraviolet rays; and

[0095] In step [III], the coating film obtained in step [II] is heated.

[0096] In the manufacturing method of the substrate with coating of the present invention, after the composition of polyamic acid and organic solvent is coated on the substrate to form a coating, polarized ultraviolet light is irradiated. Then, the small molecules produced by photodecomposition are removed by heating and anisotropy is introduced to manufacture a substrate with a liquid crystal alignment film having liquid crystal orientation control ability. Through the above-mentioned process, a liquid crystal alignment film for a lateral electric field driven liquid crystal display element with orientation control ability and a substrate with the liquid crystal alignment film can be obtained. There is no particular limitation on the substrate. When the manufactured liquid crystal display element is a transmission type, a substrate with high transparency is preferably used. In this case, there is no particular limitation, and plastic substrates such as glass substrates, acrylic substrates, polycarbonate substrates, etc. can be used. In addition, considering the application in reflective liquid crystal display elements, opaque substrates such as silicon wafers can also be used.

[0097] Furthermore, by preparing a second substrate in addition to the substrate (first substrate) obtained above, a transverse electric field driven liquid crystal display element can be obtained.

[0098] By using the above-described steps [I] to [III] (due to the use of a substrate without a lateral electric field driving conductive film, for convenience, sometimes referred to as steps [I'] to [III'] in this application), except that a substrate without a lateral electric field driving conductive film is used instead of a substrate with a lateral electric field driving conductive film, a second substrate having a liquid crystal alignment film imparted with alignment control capability can be obtained. It should be noted that steps [I'] to [III'] can be performed in the same manner as steps [I] to [III], except that a substrate without a lateral electric field driving conductive film is used instead of a substrate with a lateral electric field driving conductive film in step [I]. The only difference between steps [I] to [III] and steps [I'] to [III'] is the presence or absence of the above-described conductive film, so the description of steps [I'] to [III'] is omitted.

[0099] Process [I]

[0100] In step [I], the substrate has a conductive film for transverse electric field driving. Examples of this conductive film include, but are not limited to, ITO (Indium Tin Oxide) and IZO (Indium Zinc Oxide) when the liquid crystal display element is transmissive. Furthermore, examples of the conductive film include, but are not limited to, materials that reflect light, such as aluminum, when the liquid crystal display element is reflective.

[0101] A conventionally known method can be used to form a conductive film on a substrate. There is no particular limitation on the method for coating the polymer composition on the substrate having the conductive film for transverse electric field driving.

[0102] Industrially, coating methods generally utilize screen printing, offset printing, flexographic printing, or inkjet printing. Other coating methods include dipping, roll coating, slit coating, spin coating, and spray coating, and these methods can be used depending on the intended purpose.

[0103] After coating the polymer composition on a substrate having a 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 circulation oven, or an IR (infrared) oven to obtain a coating film. When the drying temperature is too low, the solvent tends to be insufficiently dried, while when the heating temperature is too high, thermal imidization proceeds, resulting in excessive photolysis reaction due to polarized light exposure, thereby impairing the alignment stability. Therefore, from the perspective of liquid crystal alignment stability, the drying temperature at this time is preferably a temperature at which the specific polymer is substantially not thermally imidized.

[0104] If the coating film is too thick, it is disadvantageous in terms of power consumption of the liquid crystal display element, and if it is too thin, the reliability of the liquid crystal display element may decrease. Therefore, it is preferably 5 nm to 300 nm, more preferably 10 nm to 150 nm.

[0105] Note that, after step [I] and before the next step [II], a step of cooling the substrate on which the coating film is formed to room temperature may be provided.

[0106] Process [II]

[0107] In step [II], the coating film obtained in step [I] is irradiated with polarized ultraviolet light. When irradiating the film surface with polarized ultraviolet light, the polarized ultraviolet light is irradiated onto the substrate from a specific direction through a polarizing plate. As ultraviolet light used, ultraviolet light with a wavelength in the range of 100 nm to 400 nm can be used. Preferably, the optimal wavelength is selected using a filter or the like depending on the type of coating film used. In addition, for example, in order to selectively induce a photolysis reaction, ultraviolet light with a wavelength in the range of 240 nm to 400 nm can be selected. As ultraviolet light, light emitted by a high-pressure mercury lamp or a metal halide lamp, for example, can be used.

[0108] For the coating film used in the method of the present invention, the amount of photolysis reaction of the photosensitive groups in the polymer backbone is optimized by optimizing the amount of polarized ultraviolet irradiation. The appropriate amount of polarized ultraviolet irradiation can be determined based on the evaluation of the ultraviolet absorption of the coating film used in the present invention.

[0109] That is, for the coating used in the present invention, the ultraviolet absorption in the direction parallel to the polarization direction of the polarized ultraviolet and the ultraviolet absorption in the direction perpendicular to the polarization direction of the polarized ultraviolet are measured respectively after irradiation with polarized ultraviolet rays. Based on the measurement results of ultraviolet absorption, ΔA is evaluated, and the ΔA is the difference between the ultraviolet absorbance in the direction parallel to the polarization direction of the polarized ultraviolet and the ultraviolet absorbance in the direction perpendicular to the polarization direction of the polarized ultraviolet in the coating. Then, the maximum value ΔAmax of ΔA that can be achieved in the coating used in the present invention and the amount of polarized ultraviolet radiation that achieves this value are determined. In the manufacturing method of the present invention, the amount of polarized ultraviolet radiation that achieves this ΔAmax is used as a benchmark to determine the preferred amount of polarized ultraviolet radiation to be irradiated in the manufacture of the liquid crystal alignment film.

[0110] The amount of polarized UV radiation varies depending on the coating used. It is preferably set to 1% to 70% of the amount of polarized UV radiation required to achieve the maximum value of ΔA (the difference between the UV absorbance parallel to the polarization direction of the polarized UV radiation and the UV absorbance perpendicular to the polarization direction of the polarized UV radiation of the coating) (hereinafter also referred to as ΔAmax), and more preferably 1% to 50%.

[0111] The optimal polarized ultraviolet irradiation dose for efficiently introducing anisotropy into the coating film used in the present invention corresponds to the dose that optimizes the photolytic reaction of the photosensitive groups in the coating film. If the number of photosensitive groups undergoing photolytic reaction is low when irradiating the coating film used in the present invention with polarized ultraviolet light, a sufficient photoreaction may not be achieved. Therefore, in the coating film used in the present invention, the optimal amount of photosensitive groups undergoing photolytic reaction upon irradiation with polarized ultraviolet light is preferably 0.1 to 90 mol%, and more preferably 0.1 to 80 mol%, based on the polymer film.

[0112] Process [III]

[0113] In step [III], the coating film irradiated with polarized ultraviolet rays in step [II] is heated. Heating can impart orientation control capability to the coating film.

[0114] Heating can be performed using a heating unit such as a hot plate, a heat circulation oven, or an IR (infrared) oven. The heating temperature can be determined in consideration of a temperature at which the coating film to be used exhibits good liquid crystal alignment stability and electrical properties.

[0115] The heating temperature is preferably within the temperature range in which the polyimide liquid crystal alignment film exhibits good liquid crystal orientation stability. Specifically, the heating temperature after polarized ultraviolet irradiation is preferably set to 150°C to 300°C, and more preferably 180°C to 250°C. This imparts greater anisotropy to the coating film used in the present invention. If the heating temperature is too low, the anisotropy amplified by heat may result, leading to insufficient thermal imidization. If the heating temperature is excessively above the temperature range, the anisotropy imparted by polarized light exposure may be lost.

[0116] For the same reasons as described in step [I], the thickness of the coating film formed after heating is preferably 5 nm to 300 nm, more preferably 50 nm to 150 nm. By including the above steps, the production method of the present invention can efficiently introduce anisotropy into the coating film. Furthermore, substrates with liquid crystal alignment films can be efficiently produced.

[0117] <Liquid Crystal Display Element>

[0118] The present invention provides a transverse electric field driven liquid crystal display element having the above-mentioned liquid crystal alignment film.

[0119] The method for manufacturing a transverse electric field driven liquid crystal display element includes:

[0120] Step [IV]: The first substrate and the second substrate obtained above are arranged facing each other so that the liquid crystal alignment films of the first substrate and the second substrate face each other with the liquid crystal interposed therebetween, thereby obtaining a liquid crystal display element. Thus, a transverse electric field driven liquid crystal display element can be obtained.

[0121] Process [IV]

[0122] Step [IV] is the following step: the substrate having a liquid crystal orientation film on a conductive film for transverse electric field driving obtained in [III] (first substrate) and the substrate with a liquid crystal orientation film without a conductive film obtained in the same manner from the above-mentioned [I'] to [III'] (second substrate) are arranged opposite to each other in such a manner that their liquid crystal orientation films are opposite to each other with liquid crystals interposed therebetween, and a liquid crystal unit is produced by a known method to produce a transverse electric field driven liquid crystal display element.

[0123] If we take an example of making a liquid crystal cell or liquid crystal display element, we can illustrate the following method: prepare the above-mentioned first and second substrates, spread spacers on the liquid crystal alignment film of one substrate, adhere the other substrate with the liquid crystal alignment film surface facing inward, inject liquid crystal under reduced pressure and seal; or, after dripping liquid crystal onto the liquid crystal alignment film surface with spacers spread, adhere the substrates and seal. In this case, it is preferable to use a substrate with an electrode structured like comb teeth for transverse electric field drive on one side. The diameter of the spacer in this case is preferably 1μm to 30μm, more preferably 2μm to 10μm. The diameter of the spacer will determine the distance between the pair of substrates that sandwich the liquid crystal layer, that is, the thickness of the liquid crystal layer.

[0124] As described above, a substrate for a transverse electric field-driven liquid crystal display element, or a transverse electric field-driven liquid crystal display element comprising such a substrate, manufactured using the polymer of the present invention, exhibits excellent reliability against external stresses such as light and heat, and is therefore suitable for use in large-screen, high-definition liquid crystal televisions. Furthermore, the liquid crystal alignment film manufactured using the method of the present invention exhibits excellent liquid crystal alignment stability and reliability, and can therefore also be used in variable phase shifters utilizing liquid crystals. Such variable phase shifters can be suitably used, for example, in antennas with variable resonant frequencies.

[0125] The above and other advantages of the present invention may be better understood through the following examples, but the following examples are not intended to limit the scope of the present invention.

[0126] Example

[0127] The present invention is described below with reference to examples, but the present invention is not limited to the following examples.

[0128] The abbreviations of the compounds used in the Examples and Comparative Examples are as follows:

[0129] NMP: N-methyl-2-pyrrolidone

[0130] BCS: Butyl Cellosolve

[0131] DA-1: The following structural formula (DA-1)

[0132] DA-2: The following structural formula (DA-2)

[0133] DA-3: The following structural formula (DA-3)

[0134] DA-4: The following structural formula (DA-4)

[0135] DA-5: The following structural formula (DA-5)

[0136] DA-6: The following structural formula (DA-6)

[0137]

[0138] <Polymer Molecular Weight Measurement>

[0139] The measurement was performed as follows using a room temperature gel permeation chromatography (GPC) apparatus (Agilent 1260) (manufactured by Agilent Technologies, Inc.) and a column (PLgei 5µm MIXED-C 300*7.5mm) (manufactured by Agilent Technologies, Inc.).

[0140] Column temperature: 50°C

[0141] Eluent: N,N′-dimethylformamide (as an additive, phosphoric acid / anhydrous crystals (orthophosphoric acid) is 25 mmol / L)

[0142] Flow rate: 1.0 mL / min

[0143] Standard samples for preparing the calibration curve: standard polystyrene (molecular weight; approximately 10,000, 20,000, 40,000, 100,000, 200,000, and 400,000) (manufactured by Agilent Technologies).

[0144] <Synthesis of Diamine Monomer>

[0145] Synthesis example 1

[0146] [Synthesis of DA-1]

[0147] Step 1: Synthesis of N3,N3'-bis(2-((tert-butyloxycarbonyl)amino)ethyl)-4,4'-dinitro-1,1'-biphenyl-3,3'-dicarboxamide (DA-1-1)

[0148]

[0149] 4,4'-dinitro-1,1'-biphenyl-3,3'-dicarboxylic acid (33.22 g, 100 mmol) was weighed and 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. N-Boc-ethylenediamine (35.25 g, 220 mmol) was then added and stirred at room temperature under nitrogen atmosphere for 12 h. The reaction solution was washed thoroughly with deionized water and dried over anhydrous sodium sulfate. o The solvent was removed by drying under reduced pressure at 4°C. The crude product was washed with ethanol, and the solid was dissolved in 200 mL of toluene at 75°C. The product was filtered while hot, cooled, and recrystallized. The solid was then filtered, washed again with ethanol, and dried under vacuum to obtain the product DA-1-1 (39.46 g, 64% yield, 97.8% purity) as a light yellow powder.

[0150] Step 2: Synthesis of N3,N3'-bis(2-((tert-butyloxycarbonyl)amino)ethyl)-4,4'-diamino-1,1'-biphenyl-3,3'-dicarboxamide (DA-1)

[0151]

[0152] DA-1-1 (10.01 g, 16.2 mmol) was dissolved in 150 g of propylene glycol methyl ether, and 5% by weight palladium-carbon (7.5 g) was added. The mixture was stirred at room temperature under a hydrogen atmosphere for 2 h. 1000 g of propylene glycol methyl ether was added to the reaction solution, which was then filtered to remove the palladium-carbon. The solution was concentrated and then filtered through water. The solid was washed and dissolved in a mixture of 75 g of acetonitrile and 75 g of ethanol at 45°C. The product was filtered while hot, cooled, recrystallized, filtered, and dried to obtain DA-1 (8.30 g, 92% yield, 98.8% purity) as a white solid.

[0153] Synthesis example 2

[0154] [Synthesis of DA-2]

[0155] Step 1: Synthesis of N3,N3'-bis(4-((fluorenylmethyloxycarbonyl)amino)butyl)-4,4'-dinitro-1,1'-biphenyl-3,3'-dicarboxamide (DA-2-1)

[0156]

[0157] 4,4'-dinitro-1,1'-biphenyl-3,3'-dicarboxylic acid (33.22 g, 100 mmol) was weighed and 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. N-Fmoc-butylene diamine (68.29 g, 220 mmol) was then added and stirred at room temperature under nitrogen atmosphere for 12 h. The reaction solution was washed thoroughly with deionized water and dried over anhydrous sodium sulfate. o The solvent was removed by drying under reduced pressure at 4°C. The crude product was washed with ethanol, and the solid was dissolved in 200 mL of toluene at 75°C. The product was filtered while hot, cooled, and recrystallized. The solid was then filtered, washed again with ethanol, and dried under vacuum to obtain the product DA-1-1 (63.27 g, 69% yield, 98.3% purity) as a light yellow powder.

[0158] Step 2: Synthesis of N3,N3'-bis(4-((fluorenylmethyloxycarbonyl)amino)butyl)-4,4'-diamino-1,1'-biphenyl-3,3'-dicarboxamide (DA-2)

[0159]

[0160] DA-2-1 (20.00 g, 21.8 mmol) was dissolved in 300 g of propylene glycol methyl ether, and 5% palladium-on-carbon (15 g) was added. The mixture was stirred at room temperature under a hydrogen atmosphere for 2 h. 1000 g of propylene glycol methyl ether was added to the reaction solution, which was then filtered to remove the palladium-on-carbon. The mixture was concentrated and then filtered through water. The solid was washed and dissolved in a mixture of 100 g of acetonitrile and 100 g of ethanol at 45°C. The mixture was filtered while hot, cooled, recrystallized, filtered, and dried to obtain DA-2 as a white solid (16.44 g, 88% yield, 99.0% purity).

[0161] <Preparation Example of Polymer and Orienting Agent>

[0162] A diamine was weighed into a 50 mL four-necked flask equipped with a stirrer and a nitrogen inlet tube. NMP was added and dissolved while stirring while nitrogen was supplied until clear. Tetracarboxylic dianhydride was added to the diamine solution while stirring, followed by a certain amount of NMP. The solution 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. The types and amounts of substances used in the synthesis examples and comparative synthesis examples, as well as the polymer ratio of the structural unit represented by formula (4), i.e., the specific polymer ratio, are shown in Table 1.

[0163] Table 1

[0164]

[0165] 7.0 g of the polyamic acid-polyimide copolymer solution in the synthesis example and the comparative synthesis example were respectively added to a 50 mL conical flask with a stirrer, 7.0 g of NMP and 6.0 g of BCS were added, and the mixture was stirred at room temperature for 2 hours to obtain liquid crystal alignment agents A-1 to A-15 and B-1 to B-2, respectively. The solid content of the liquid crystal alignment agents was 3.5 wt%.

[0166] Example 1

[0167] <Method for Fabricating a Liquid Crystal Cell for Evaluating Afterimages>

[0168] A liquid crystal unit with a liquid crystal display element structure in FFS mode was produced. First, a substrate with electrodes was prepared. The substrate was a glass substrate with a size of 30 mm × 35 mm and a thickness of 0.7 mm. On the substrate, an ITO electrode constituting a counter electrode was formed on the entire surface as the first layer. On the counter electrode of the first layer, a silicon nitride (SiN) film formed by CVD was formed as the second layer. The thickness of the second layer SiN film was 500 nm, and it functions as an interlayer insulating film. On the second layer SiN film, a comb-shaped pixel electrode formed by patterning the ITO film was arranged as the third layer, thereby forming two pixels, the first pixel and the second pixel. The size of each pixel is 10 mm in length and about 5 mm in width. At this time, the counter electrode of the first layer and the pixel electrode of the third layer are electrically insulated due to the action of the second layer SiN film.

[0169] The pixel electrodes of the third layer have a comb-like shape composed of a plurality of "<"-shaped electrode elements with a bent central portion. The width of each electrode element is 10 μm in the width direction, and the interval between the electrode elements is 10 μm. The pixel electrode forming each pixel is composed of a plurality of "<"-shaped electrode elements with a bent central portion. Therefore, the shape of each pixel is not a rectangle, but a shape similar to a bold "<" character that is bent in the central portion like the electrode elements. In addition, each pixel is divided into upper and lower parts by the central bent portion, with a first area on the upper side of the bent portion and a second area on the lower side.

[0170] Comparing the first and second regions of each pixel, the electrode elements that constitute their pixel electrodes are formed in different directions. Specifically, using the direction of the line segment of the polarization plane of the polarized ultraviolet light projected onto the substrate as a reference, the electrode elements of the pixel electrode in the first region of the pixel are formed at an angle of +10° (clockwise), while the electrode elements of the pixel electrode in the second region of the pixel are formed at an angle of -10° (clockwise). In other words, the first and second regions of each pixel are configured so that the directions of the liquid crystal rotation (in-plane switching) within the substrate plane, induced by applying a voltage between the pixel electrode and the counter electrode, are opposite to each other.

[0171] Next, the liquid crystal alignment agent A-1 was coated onto the prepared electrode substrate using a coater method. The coated film was baked at approximately 100°C for 180 seconds to evaporate the solvent, and then baked at 200°C for 45 minutes to imidize the polyamic acid. Next, an exposure device (APL-L01212S1-AXH01 manufactured by Ushio) was used, using 254 nm polarized light perpendicular to the substrate, with an integrated light intensity of 300-600 mJ / cm 2 The PI film is exposed and then baked at 200°C for 45 minutes to volatilize the small molecules that were cracked after exposure, forming an alignment layer.

[0172] <Preparation of a Liquid Crystal Cell for Liquid Crystal Orientation Evaluation and Transmittance Evaluation>

[0173] Based on the FFS electrode substrate with a liquid crystal alignment film, a glass substrate with a 4 μm high columnar spacer was used as the opposite substrate. The liquid crystal alignment agent was applied and oriented, resulting in a substrate with a polyimide liquid crystal alignment film. A uniform layer of sealant was applied to the substrate using gas extrusion to bond the substrate and seal the liquid crystal. RXA10300 liquid crystal (negative liquid crystal manufactured by Chengzhi Yonghua Company) was dripped using a high-precision titration device, and the two substrates were bonded together under a pressure of 1 Pa. The sealant in the bonded substrates was irradiated with 365 nm UV light, with an accumulated light intensity of 5,000 to 20,000 mJ / cm. 2 , so that its photoinitiator reacts; the UV-cured substrate is baked at a temperature of 100° C. for 2 hours to fully cure the frame glue to obtain an FFS mode liquid crystal unit.

[0174] <Evaluation of LCD unit afterimage>

[0175] The prepared FFS mode liquid crystal cell was used, and the pixel electrode and the counter electrode of the liquid crystal cell were short-circuited, and the cell was left at 25° C. for 8 hours.

[0176] After placement, the liquid crystal cell was placed between two polarizing plates with their polarization axes orthogonal to each other. With no voltage applied, the backlight was illuminated, and the liquid crystal cell's configuration angle was adjusted to minimize the brightness of the transmitted light. A voltage was then applied to the liquid crystal display cell to maximize brightness, and the 127-grayscale brightness was measured. After 24 hours of illumination, the 127-grayscale brightness was measured again. If the change in 127-grayscale brightness between before and after illumination of the liquid crystal display cell was less than 2%, the residual image was evaluated as "good," and if the change in 127-grayscale brightness was greater than 2%, the residual image was evaluated as "poor."

[0177] <Evaluation of abrasion resistance of liquid crystal alignment films>

[0178] Liquid crystal alignment agent A-1 was spin-coated onto an ITO glass substrate, baked at approximately 100°C for 180 seconds to evaporate the solvent, and then baked at 200°C for 45 minutes to imidize the polyamic acid. Next, an exposure device (APL-L01212S1-AXH01 manufactured by Ushio) was used, using 254 nm polarized light perpendicular to the substrate, with an integrated light intensity of 200-400 mJ / cm. 2 The PI film was exposed. The exposed film was baked at 200°C for 45 minutes to volatilize the small molecules that had been cracked after exposure, forming a 100nm thick liquid crystal alignment film. The liquid crystal alignment film on the ITO glass substrate after the alignment process was rubbed on a rubbing device. The roller speed was set to 1000 rpm, the substrate speed of the liquid crystal alignment film was set to 20 mm / s, the rubbing cloth was pressed into the film at 0.5 mm, and rubbed 16 times continuously. The rubbed liquid crystal alignment film was then cleaned with an air gun and tested for haze using a haze meter. A haze value of less than 0.5% was defined and evaluated as "good" mechanical strength, while a haze value of 0.5% or greater was defined and evaluated as "poor" mechanical strength.

[0179] <Evaluation of Adhesion Between Liquid Crystal Alignment Film and Frame Adhesion>

[0180] Liquid crystal alignment agent A-1 was spin-coated onto a blank glass substrate and baked at approximately 100°C for 180 seconds to evaporate the solvent. The substrate was then baked at 200°C for 45 minutes to imidize the polyamic acid. Next, an exposure device (APL-L01212S1-AXH01 manufactured by Ushio) was used, using 254 nm polarized light perpendicular to the substrate, with an integrated light intensity of 200-400 mJ / cm. 2The PI film was exposed. The exposed film was baked at 200°C for 45 minutes to volatilize the small molecules that had been cleaved after exposure, forming a 100 nm thick liquid crystal alignment film. Using the liquid crystal alignment film on a blank glass substrate after the alignment process, a 2 mm diameter circle was scored with a glue marker and a 4.5 mm diameter sealant was applied. After vacuum bonding, UV curing was performed and heat-curing was performed at 120°C for 1 hour. The sample was then removed and cut into a 25 mm x 45 mm cross. One side of the prepared cross sample was taped and secured to the dedicated lower fixture of a Shimadzu AGX-S tensile testing machine. The untaped side was secured to the dedicated upper fixture with a drawstring. After gently stretching, testing was performed. The force required to separate the cross sample was used to determine the adhesion between the liquid crystal alignment film and the sealant. A test result of 20 N or greater was defined as "good" adhesion, while a result of less than 20 N was defined as "poor" adhesion.

[0181] Examples 2 to 15

[0182] Except having used liquid crystal aligning agents A-1 to A-15, it carried out the method similar to Example 1 and evaluated residual image, abrasion resistance, and adhesive force.

[0183] Comparative Examples 1 and 2

[0184] Except having used liquid crystal aligning agents B-1 and B-2, it carried out similarly to Example 1 and evaluated residual image, abrasion resistance, and adhesive force.

[0185] Table 2 shows the afterimage evaluation results of the liquid crystal display cells produced using the liquid crystal aligning agents obtained in Synthesis Examples and Comparative Synthesis Examples.

[0186] Table 2

[0187] Liquid crystal alignment agent <![CDATA[Initial 127 gray-scale brightness of the liquid crystal display unit (cd / m 2 )]]> <![CDATA[127 gray scale brightness (cd / m 2 ) after the liquid crystal display unit is lit for 24 hours 127 Grayscale brightness change rate (%) Example 1 A-1 478.22 481.10 0.60 Example 2 A-2 495.89 501.46 1.12 Example 3 A-3 473.18 476.98 0.80 Example 4 A-4 510.50 517.30 1.33 Example 5 A-5 505.06 510.70 1.12 Example 6 A-6 470.16 479.14 1.91 Example 7 A-7 519.26 529.33 1.94 Example 8 A-8 489.37 496.28 1.41 Example 9 A-9 491.55 498.04 1.32 Example 10 A-10 501.55 508.30 1.35 Example 11 A-11 473.55 479.98 1.36 Example 12 A-12 470.31 476.65 1.35 Example 13 A-13 490.63 496.50 1.20 Example 14 A-14 489.57 499.12 1.95 Example 15 A-15 507.65 517.48 1.94 Comparative Example 1 B-1 497.76 510.26 2.51 Comparative Example 2 B-2 519.3 533.03 2.63

[0188] As shown in Table 2, the 127-grayscale brightness change rate of Examples 1-15 before and after the LCD unit is turned on is less than 2%, which is good. However, the 127-grayscale brightness change rate of Comparative Examples 1-2 before and after the LCD unit is turned on is greater than 2%, which is poor.

[0189] Table 3 shows the evaluation results of abrasion resistance after forming a liquid crystal alignment film using the liquid crystal aligning agents obtained in Synthesis Examples and Comparative Synthesis Examples.

[0190] Table 3

[0191] Liquid crystal alignment agent Haze (%) Example 1 A-1 0.18 Example 2 A-2 0.22 Example 3 A-3 0.34 Example 4 A-4 0.34 Example 5 A-5 0.29 Example 6 A-6 0.46 Example 7 A-7 0.47 Example 8 A-8 0.35 Example 9 A-9 0.36 Example 10 A-10 0.36 Example 11 A-11 0.32 Example 12 A-12 0.31 Example 13 A-13 0.30 Example 14 A-14 0.45 Example 15 A-15 0.46 Comparative Example 1 B-1 0.62 Comparative Example 2 B-2 0.77

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

[0193] Table 4 shows the evaluation results of the adhesiveness of the liquid crystal display elements made of the liquid crystal aligning agents obtained in the synthesis examples and the comparative synthesis examples.

[0194] Table 4

[0195] Liquid crystal alignment agent Adhesion force (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 between the liquid crystal alignment film and the sealant in Examples 1 to 15 is greater than 20 N, indicating good reliability of the liquid crystal alignment film. However, in Comparative Examples 1 and 2, the adhesion is less than 20 N, indicating poor reliability.

[0197] This confirms that, through the method of the present invention, a liquid crystal display element with good afterimage performance can be prepared using a specific monomer, and has excellent wear resistance and adhesion, thereby improving the reliability of the liquid crystal display element.

[0198] It should be noted that, based on the explanations and elaborations of the above description, those skilled in the art may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and equivalent modifications and variations of the present invention should also be within the scope of protection of the claims of the present invention. In addition, although certain specific terms are used in this description, these terms are for convenience only and do not constitute any limitation to the invention.

Claims

1. A polyimide precursor, characterized in that The polyimide precursor is represented by the following formula (4): (4) In formula (4), X4 is a tetravalent organic group derived from a tetracarboxylic acid derivative, Y4 is a divalent organic group derived from a diamine, and R4 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms; The diamine is represented by the following formula (1): (1) In formula (1), 2≤n≤6 and n is an integer, R is one or a combination of the structures represented by formula (2-1) and formula (2-2), (2-1) (2-2)。 2. The polyimide precursor according to claim 1, characterized in that The polyimide precursor is obtained by reacting the diamine represented by formula (1) with tetracarboxylic dianhydride, wherein the tetracarboxylic dianhydride comprises one or more combinations of the following structures: 。 3. The polyimide precursor according to claim 2, characterized in that The tetracarboxylic dianhydride comprises one or a combination of 1,3-dimethylcyclobutanetetracarboxylic dianhydride represented by formula (3-2) and 3,3',4,4'-biphenyltetracarboxylic dianhydride represented by formula (3-17), (3-2) (3-17)。 4. The polyimide precursor according to claim 1, wherein The weight average molecular weight of the polyimide precursor is 70,000-100,000 g / mol.

5. A liquid crystal alignment agent, characterized in that: The liquid crystal aligning agent comprises at least one kind selected from the group consisting of the polyimide precursor according to any one of claims 1 to 4 and its imide product, namely, polyimide, and an organic solvent.

6. The liquid crystal alignment agent according to claim 5, characterized in that: The liquid crystal aligning agent contains 20 mol % to 30 mol % of the polyimide precursor relative to all polymers contained in the liquid crystal aligning agent.

7. The liquid crystal alignment agent according to claim 5, characterized in that: The organic solvent includes one or more combinations 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, the organic solvent is one or more combinations of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and γ-butyrolactone. More preferably, the organic solvent is N-methyl-2-pyrrolidone.

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

9. A method for producing a liquid crystal alignment film for a transverse electric field driven liquid crystal display element, characterized in that: The process includes the following steps: Step [I], coating the liquid crystal alignment agent according to any one of claims 5 to 7 on a substrate having a conductive film for lateral electric field driving to form a coating film; Step [II], irradiating the coating film obtained in step [I] with polarized ultraviolet rays; and In step [III], the coating film obtained in step [II] is heated.

10. A transverse electric field driven liquid crystal display element, characterized in that: The liquid crystal alignment film comprises the liquid crystal alignment film according to claim 8 or the liquid crystal alignment film manufactured by the preparation method according to claim 9.

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