TWI519832B - Method for producing a retardation film and composition for producing retardation film - Google Patents

Description

Method for producing retardation film and composition for retardation film

The present invention relates to a method of producing a retardation film.

In recent years, the retardation film has been utilized in various forms in the field of displays (including flexible displays other than liquid crystal displays, etc.). The retardation film is usually formed by forming a layer (liquid crystal alignment layer) having a liquid crystal alignment ability on a substrate, and then coating a liquid crystal compound on the liquid crystal alignment layer to align it. In such a case, a method of applying a liquid crystal alignment layer to a substrate is known, for example, in which a polymer resin film such as polyimide is coated on the surface of the substrate, and rubbing treatment such as wiping the cloth in one direction is performed. In this method, contamination of the liquid crystal manufacturing line due to generation of fine dust or destruction of the TFT (thin film transistor) element due to static electricity causes a decrease in the yield of the liquid crystal panel, or is difficult to do. Problems such as quantitative alignment control. In addition, there are various proposals for a method of forming a photo-alignment film having a liquid crystal alignment energy by using a photoreactive compound, and using a photoreactive compound to cover the substrate with a light-reactive compound (Patent Documents 1 to 3). However, in any of these methods, it is necessary to separately prepare a film for aligning the liquid crystal, which is cumbersome.

Therefore, a method of directly obtaining a retardation film without separately forming a liquid crystal alignment layer has been studied. For example, Patent Document 4 discloses that a photosensitive layer formed on a substrate and containing a photosensitive compound capable of exhibiting liquid crystallinity is heated to an isotropic phase transition temperature or higher, and then quenched from the state to the glass phase. The method of producing a retardation film is obtained by heat treatment by irradiating polarized light at a temperature lower than the liquid crystal phase transition temperature. However, in this method, if rapid cooling cannot be achieved, there is a problem that the quality of the retardation film is lowered, and it is required to provide a simpler and more reliable method.

[Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 08-015681

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2007-304215

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2008-276149

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2009-109757

In view of the above background, the present invention is directed to a method for producing a retardation film which is simpler and simpler. Further, the present invention provides a composition for a novel retardation film for producing the retardation film.

As a result of intensive research, the inventors of the present invention found that a composition containing a liquid crystalline polymer having a photoreactive group and a solvent is applied to a substrate, and when the solvent is distilled off from the coating film, it is dried under reduced pressure or dried naturally. After heating and drying, the linearly polarized light is irradiated thereafter, and the retardation film can be directly produced by heat treatment, and the present invention is further studied in reverse.

That is, the present invention is

[1] A method for producing a retardation film, comprising: coating a liquid crystal polymer having a photoreactive group on a substrate; a step of forming a solvent; a step of forming a photoreactive layer by extruding the composition under reduced pressure or drying it naturally, followed by heating and drying to form a photoreactive layer; a step of illuminating the linearly polarized light to form a heat-aligning layer; and heating the heat-aligning layer.

[2] The production method according to the above [1], wherein the step of forming a photoreactive layer is carried out by decomposing the solvent in the composition by drying the composition under reduced pressure.

[3] A composition for a retardation film comprising: a copolymerizable (meth)acrylic polymer having a repeating unit represented by the formula (I):

Wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkyl group, or a phenyl group substituted with a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, and the p and q systems are each independently It is indicated that any integer from 1 to 12, m and n monomers account for 0.65 of the copolymer. m 0.95,0.05 n The relationship of 0.35, m+n=1, ring A and ring B are respectively represented independently:

The group shown, wherein each of X ¹ to X ³⁸ independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group.

[4] A composition for a retardation film comprising: a copolymerizable (meth)acrylic polymer having a repeating unit represented by the formula (Ia):

In the formula, R ¹ is a hydrogen atom or a methyl group, and R ² represents an alkyl group or a phenyl group substituted with a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, and each of X ^1A to X ^4A Each independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group, and p and q groups are independently represented by an integer of 1 to 12, and m and n each monomer constitute a copolymer of moir. The rate meets 0.65 m 0.95,0.05 n 0.35, m+n=1 relationship, ring B system:

^Here , each of X ^1B to X ^4B and X ^31B to X ^38B is independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group.

[5] A composition for a retardation film comprising: a copolymerizable (meth)acrylic polymer having a repeating unit represented by the formula (Ib): In the formula, R ¹ is a hydrogen atom or a methyl group, and R ² represents an alkyl group or a phenyl group substituted with a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, X ^1A to X ^4A and X ^31B Each of ~X ^38B is independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group, and p and q are each independently represented, and any integer of 1 to 12, m and n monomers are independently represented. The molar fraction of the copolymer satisfies 0.65 m 0.95,0.05 n The relationship of 0.35, m+n=1.

[6] A composition for a retardation film comprising: a copolymerizable (meth)acrylic polymer having a repeating unit represented by the formula (Ic): In the formula, R ¹ is a hydrogen atom or a methyl group, and R ² represents an alkyl group or a phenyl group substituted with a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, X ^1A to X ^4A and X ^1B Each of ~X ^4B is independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group, and p and q are each independently represented, and any integer of 1 to 12, m and n monomers are independently represented. The molar fraction of the copolymer satisfies 0.65 m 0.95,0.05 n The relationship of 0.35, m+n=1.

According to the production method of the present invention described above, the liquid crystal alignment layer can be formed without a separate route, and the retardation film can be directly obtained from the layer of the liquid crystalline polymer having the photoreactive group formed on the substrate. Further, this can be achieved by drying the composition coated on the substrate under reduced pressure or by naturally drying, followed by heating and drying, and distilling off the solvent from the composition. Therefore, the production method of the present invention can provide an excellent production method of a retardation film in a simple and simple manner and at a low cost.

The substrate to be used in the present invention may, for example, be a glass material such as alkali glass or alkali-free glass, polyimine, polyamine, acrylic resin, polyvinyl alcohol, cellulose triacetate or polyethylene terephthalate. a substrate composed of a resin material such as an alcohol ester, a cycloolefin polymer, polyethylene, polycarbonate, polystyrene or polychlorotrifluoroethylene; or a metal material such as iron, aluminum or copper; A substrate composed of a glass material is preferred.

The thickness of the substrate is not particularly limited, and is usually 0.1 mm to 3 mm for a substrate composed of a glass material, and 10 μm to 300 μm for a substrate composed of a resin material, and a substrate made of a metal material. It is 1~100μm.

The substrate may be peeled off after the retardation film is formed, and if the substrate itself is transparent and optically isotropic, it may be used as it is without being peeled off.

In the case of the liquid crystal polymer having a photoreactive group (hereinafter, referred to simply as "liquid crystal polymer"), it is possible to use, for example, a combination of a liquid crystal element which is used as a liquid crystal polymer. a substituent (liquid crystal cell group) of a phenyl group, a terphenyl group, a naphthyl group, a phenylbenzoic acid group, an azobenzene group, or the like, and a lauryl group, a chalcone, a lauryl group, a β- a side chain having a photoreactive group structure such as a (2-phenyl)propenyl group, a lauric acid group or the like, and an acrylate, a methacrylate, a maleimide, and a N in the main chain. a polymer having a structure such as phenylmaleimide or decane. The polymer may be a homopolymer composed of a single reversing unit or a copolymer composed of two or more reversing units having different side chain structures. The copolymer may comprise an interactive type, a random type, a graft type or the like. Further, in the copolymer, at least with respect to a side chain of a repeating unit, as described above The side chain having a structure of a liquid crystal cell group and a photoreactive group together may be a side chain having no other liquid crystal element or a photoreactive group.

Preferred specific examples of the liquid crystalline polymer of the present invention are shown below. These are novel compounds.

a copolymerizable acrylic polymer having repeating units represented by the formula (I):

In the formula, the symbols have the same meaning as the above.

a copolymerizable acrylic polymer having repeating units represented by the formula (Ia):

In the formula, the symbols have the same meaning as the above.

a copolymerizable acrylic polymer having a repeating unit represented by the formula (Ib):

In the formula, the symbols have the same meaning as the above.

a copolymerizable acrylic polymer having a repeating unit represented by the formula (Ic):

In the formula, the symbols have the same meaning as the above.

It is a general formula (I) of the present invention (including the general formula (Ia), the general formula (Ib), and the general formula (Ic). The same applies hereinafter.) R ¹ is preferably a methyl group. R ^{2 is} preferably an alkyl group or a phenyl group selected from the group consisting of an alkyl group, an alkoxy group, a cyano group and a halogen atom, and a phenyl group substituted with an alkyl group, an alkoxy group or a cyano group is preferred, further The phenyl group substituted with an alkyl group or an alkoxy group is most preferred. X ¹ to X ³⁸ are preferably a hydrogen atom or a halogen atom, and all of them are preferably hydrogen atoms. Both p and q are preferably any integer from 3 to 9, wherein any integer from 5 to 7 is preferred, and 6 is optimal. About m, about 0.75 m A range of about 0.85 is preferred, with an optimum of about 0.8. The preferred range for the corresponding n is a range naturally determined by m+n=1. That is, at about 0.15 n A range of about 0.25 is preferred, with an optimum of about 0.2.

In the general formula (Ia), (Ib) or (Ic) of the present invention, X ^1A to X ^{4A is} preferably a hydrogen atom or a halogen atom, and particularly one of X ^1A to X ^4A is a halogen atom and the other is In the case of a hydrogen atom, or all of them are hydrogen atoms, it is preferred. Further, in the general formula (Ib) of the present invention, X ^31B to X ^38B are preferably a hydrogen atom or a halogen atom, and all of them are preferably hydrogen atoms. Further, in the general formula (Ic) of the present invention, X ^1B to X ^4B are preferably a hydrogen atom or a halogen atom, and all of them are preferably hydrogen atoms.

The alkyl group of the substituent of the R ² alkyl group or the R ² phenyl group may be an alkyl group having 1 to 12 carbon atoms. Among them, those having a carbon number of 1 to 6 are preferred, and those having a carbon number of 1 to 4 are more preferred. , with methyl best. The alkoxy group of the substituent of the phenyl group of R ² may, for example, be an alkoxy group having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and most preferably a methoxy group. good. The halogen atom of the substituent of the phenyl group of R ² may, for example, be a fluorine atom, a chlorine atom, a bromine atom or an iodine atom, and among them, a fluorine atom is preferred. In the case of X ¹ to X ³⁸ , the alkyl group may be a carbon number of 1 to 4, wherein the methyl group is the most preferable, and the alkoxy group may be a carbon number of 1 to 4, wherein the methoxy group is the most preferable, and the halogen atom is a fluorine atom. An atom, a chlorine atom, a bromine atom, and an iodine atom, of which a fluorine atom is preferred.

Further, in the present specification, X ^1A to X ^38A represent X ¹ to X ³⁸ with respect to the substituent on the ring A or the ring B, and these are in the case of the substituent on the ring A, and X ^1B to X ^38B are This indicates the case where the substituents are on the ring B. Therefore, the description of X ¹ to X ³⁸ can be directly applied to X ^1A to X ^38A and X ^1B to X ^38B .

The polymer (I) of the present invention can be obtained by quantitatively determining a methacrylic acid monomer (M1) represented by the general formula (II) and a (meth)acrylic monomer (M2) represented by the general formula (III). ), produced by mixing without solvent or in a solvent, and polymerizing it: Where the symbols have the same meaning as the above, In the formula, the symbols have the same meaning as the above. The polymerization can be carried out using light or heat. In the polymerization step, a method of placing a material, a solvent, or the like is not particularly limited, and the entire material may be previously introduced into the reaction vessel before polymerization to start polymerization, or M1 and M2 may be mixed, and then a part of the mixture and the solvent may be started. After the polymerization, the remaining method of dropping or segmenting is added in a stepwise manner.

Further, in the polymerization of M1 and M2, although it is not essential, other monomers may be contained, and such a monomer may be a polymerizable ethylenic property. The compound which is unsaturatedly bonded is not particularly limited, and may not be liquid crystal.

Examples of such a monomer include methyl (meth)acrylate, tert-butyl (meth)acrylate, stearyl (meth)acrylate, (meth)acrylate cyclohexyl, (meth)acrylic acid. (meth)acrylic acid monomer such as ethoxyethyl ester, hydroxyethyl (meth)acrylate, phenyl (meth)acrylate, N,N-dimethylpropenamide, styrene, α-A Styrene, p-styrene sulfate, ethyl vinyl ether, N-vinylimidazole, vinyl acetate, vinyl pyridine, 2-vinyl naphthalene, vinyl chloride, vinyl fluoride, N-vinyl carbazole, vinyl a vinyl monomer such as an amine, a vinyl phenol or an N-ethylene 2-pyrrolidone, 4-allyl-1,2-dimethoxybenzene, 4-allylphenol, 4-methoxyallyl An allyl monomer such as a phenyl group, a maleimide such as a phenylmaleimide or a cyclohexylmaleimine.

When polymerizing in a solution, a general-purpose organic solvent can be used without particular limitation. Specific examples of the solvent include an alcohol solvent such as ethanol, propanol or butanol, a ketone solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone or cyclopentanone, ethyl acetate or acetic acid. An ester solvent such as butyl ester or propylene glycol monomethyl ether acetate; an ether solvent such as diethyl ether or diglyme; or a hydrocarbon system such as hexane, cyclohexane, methylcyclohexane, toluene or xylene. A solvent such as a nitrile solvent such as acetonitrile or a guanamine solvent such as N-methylpyrrolidone or dimethylacetamide. These solvents may be used singly or in combination of two or more.

At the time of the above polymerization, a polymerization initiator can be used. The polymerization initiator can be used by a general user, and specific examples thereof include azobisisobutyronitrile (AIBN) and Ethyl-2,2'-azobisisobutyrate (V-601), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethylazobismethylpropane An azo-based polymerization initiator such as an acid ester, a peroxide-based polymerization initiator such as benzoyl peroxide, hydrogen peroxide or lauric acid peroxide, or a persulfate-based polymerization such as potassium persulfate or ammonium persulfate Starter and so on. These polymerization initiators may be used singly or in combination of two or more.

The temperature at the time of the polymerization varies depending on the type of M1 and M2 of the monomer, the type of the polymerization solvent, the type of the starting agent, and the like, and is preferably 40 to 150 ° C, more preferably 50 to 120 ° C.

Further, the above formula (I) schematically indicates that M1 and M2 of the raw material monomers are contained in a molar ratio of m:n, and are not necessarily a copolymer of M1 and M2. Therefore, the general formula (1) is a copolymer in which M1 and M2 are polymerized in a molar ratio of m: n, and includes, for example, any of an interactive type, a random type, a graft type and the like. Further, in the general formula (I), the dotted line connecting the monomers is usually a single bond, but when the other monomers are contained in the polymerization of M1 and M2, the monomer may be present in the dotted line. .

The liquid crystalline polymer of the present invention can be dissolved in a solvent to form a composition for a retardation film. Further, in the composition, a component which is usually contained in a polymerizable composition which is polymerized by light and heat may be added in addition to the actinic polymerization initiator, the surfactant, and the like. The content of the solvent is not particularly limited as long as it can dissolve the liquid crystalline polymer, and is usually from about 70 to about 99% by weight based on the total weight of the liquid crystalline polymer. Further, the content of the other optional components is not particularly limited. Usually, the total weight of the liquid crystalline polymer, for example, the photopolymerization initiator is from about 1 to about 10% by weight, and the surfactant is about 0.1 to about 5% by weight is preferred.

The solvent may, for example, be toluene, ethylbenzene, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, propylene glycol methyl ether, dibutyl ether, acetone, methyl ethyl ketone, ethanol, propanol, cyclohexane, cyclopentanone, methyl Cyclohexane, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, methoxybutyl acetate, N-methylpyrrolidone, dimethyl Ethylamine and the like. Among these, from the viewpoint of toxicity or environmental load and/or viewpoints on the solubility resistance of a resin substrate (for example, polyethylene terephthalate (PET), cycloolefin polymer (COP), etc.) It is preferred to use methyl ethyl ketone or cyclohexanone. These may be used alone or in combination of two or more. In particular, the polymer (I) of the present invention has an excellent property of being soluble in methyl ethyl ketone or cyclohexanone.

As the actinic polymerization initiator, a general-purpose actinic polymerization agent which is generally known to form a uniform film by a small amount of light irradiation can be used. Specific examples include azo-based actinic polymerization initiators such as 2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile). ; α-amino ketone-based actinic polymerization initiators such as IRGACURE 907 (manufactured by Ciba Speciality Chemicals Co., Ltd.) and IRGACURE 369 (manufactured by Ciba Speciality Chemicals Co., Ltd.); 4-phenoxydichloroacetophenone, 4-third Butyl dichloroacetophenone, diethoxyacetophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl benzophenone 2 Acetophenone-based actinic polymerization initiators such as -benzyl-2-dimethylamino-1-(4-morpholinylphenyl)-butan-1-one; benzoin, benzoin methyl ether, benzoin ethyl ether Benzoin photopolymerization initiators such as benzoin isopropyl ether and benzoin dimethyl ether; benzophenone, benzamidine benzoate, benzamidine benzoic acid methyl ester, 4-phenyl benzophenone Hydroxybenzophenone, C Benzophenone-based actinic polymerization initiators such as benzoated benzophenone and 4-benzimidazole-4'-methyldiphenyl sulfide; 2-chlorothioxanthone, 2-methylthioxanthone a thioxanthone-based actinic polymerization initiator such as isopropyl thioxanthone or 2,4-diisopropylthioxanthone; 2,4,6-trichloro-s-triazine, 2-phenyl -4,6-screw-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-tolyl)-4 ,6-bis(trichloromethyl)-s-triazine, 2-piperidin-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)- 6-styrene s-triazine, 2-(naphthalen-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxynaphthalen-1-yl) -4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl(piperidinyl)-6-triazine, 2,4-trichloromethyl (4'-methoxy a triazine-based actinic polymerization initiator such as a styryl)-6-triazine; an oxazole-based actinic polymerization initiator; an imidazole-based actinic polymerization initiator; and further, α-oxime Base ester, sulfhydryl phosphine oxide, methyl benzoic acid methyl ester, biphenyl hydrazine, 9,10-phenanthrenequinone, camphorquinone, ethyl hydrazine, 4,4'-diethyldiphenylisophthalic lactone , 3,3',4,4'-tetra (t-butyl peroxy A photopolymerization initiator of carbonyl)benzophenone, 4,4'-diethylaminobenzophenone, thioxanthone or the like. The photopolymerization initiator may be used singly or in combination of two or more.

As the surfactant, a surfactant which is generally a uniform film can be used. Specific examples include sodium lauryl sulfate, ammonium lauryl sulfate, triethanolamine lauryl sulfate, polyoxyethylene alkyl ether sulfate, alkyl ether phosphate, sodium oleate succinate, potassium myristate, and potassium fatty acid potassium carbonate. An anionic surfactant such as sodium lauryl sarcosinate; polyethylene glycol monolaurate, sorbitan stearate, glyceryl myristate, glyceryl dioleate, sorbitan stearate Nonionic interfacial activity of sorbitan oleate a cationic surfactant such as stearic acid trimethylammonium chloride, behenyltrimethylammonium chloride, stearyl dimethylammonium chloride or hexadecyltrimethylammonium chloride; Alkyl betaine, alkylimidazole, sodium laurate, sodium citrate, cocoamphoacetate, etc., such as alkali, alkylsulfonic acid betaine, alkylguanamine betaine, alkyldimethylaminoacetate betaine An amphoteric surfactant such as sodium; further, BYK-361, BYK-306, BYK-307 (BYK Japan), Fluorad FC430 (manufactured by Sumitomo 3M), MEGAFACE F171, R08 (Daily Ink Chemical Industry Co., Ltd.) Surfactant. These surfactants may be used alone or in combination of two or more.

Among the composition for a retardation film of the present invention, a composition for a retardation film which is a copolymerizable acrylic polymer (I) containing a novel compound as a liquid crystalline polymer is a novel composition.

The composition for a phase difference film of the present invention thus obtained is applied onto a substrate. The coating method of the composition for a retardation film may be any method generally known in the art, and may be, for example, a spin coating method, a bar coating method, a die coating method, a screen printing method, a spray coating method, or the like. The composition for a retardation film may be applied only to one surface of the substrate or may be applied to both surfaces of the substrate. The coating amount can be appropriately determined according to the film thickness of the target retardation film.

The composition for phase difference film coated on the substrate in this manner is dried under reduced pressure, or dried naturally, and dried by heating to distill off the solvent contained in the composition. Here, the "distillation solvent" means that the solvent is removed to such an extent that the residual solvent cannot be detected, and is, for example, below the detection limit measured by a gas chromatograph. Here, "drying under reduced pressure" means a drying method of evaporating a solvent under reduced pressure. In addition, the so-called "natural drying" is by placing it in large A drying method for evaporating a solvent under pressure. From the viewpoint of time efficiency, it is preferred to distill off the solvent by drying under reduced pressure. When drying under reduced pressure, it is also possible to have a natural drying step before it. For example, after the composition for a retardation film is applied onto a substrate, it is usually dried in a natural state before being dried under reduced pressure. In addition, in the present specification, the term "natural drying" generally means direct drying, but the drying time is shortened, and the air can be supplied at the time of standing. Natural drying can be performed more efficiently by accompanying air supply.

The conditions for the drying under reduced pressure may vary depending on the type and amount of the liquid crystalline polymer and the solvent contained in the composition, and may be dried, for example, at a pressure of 0.1 to 1 Torr for 1 minute.

In addition, it is naturally dried and can be placed at room temperature. In the case of the case, the type and amount of the liquid crystalline polymer and the solvent contained in the composition vary depending on the thickness of the applied composition, but usually, it is not more than 1 minute in the case of air blowing. Preferably, it is more preferably 3 minutes or more, further preferably 5 minutes or more, and further preferably 10 minutes or more.

The present invention is characterized in that the composition for a retardation film applied to a substrate is reduced in a solvent by drying under reduced pressure or by distilling off the solvent by heating and drying. point. It is not intended to limit the mechanism, and is a composition for a retardation film of the present invention comprising a liquid crystalline polymer and a solvent, and the liquid crystalline polymer adopts an irregular molecular arrangement in a solvent. When the composition for a retardation film is directly heated, the polymer molecules agglomerate each other. Therefore, in the method of the present invention, it is considered that the irregular molecular arrangement of the liquid crystalline polymer can be fixed as it is by distilling off the solvent under reduced pressure. Thereby, as long as the linear polarized light is irradiated afterwards, Then, the polarizing axis of the linearly polarized light is selective, and only a part of the photoreactive group in the side chain of the liquid crystalline polymer reacts (dimerization, isomerization, etc.) to obtain a heat-aligning layer which imparts alignment energy to the liquid crystal. .

Alternatively, the solvent is reduced by natural drying in advance, and the degree of freedom of the liquid crystalline polymer molecules in the composition is reduced, and even if the solvent is distilled off by heating and drying, the liquid-polymer polymer molecules can be prevented from agglomerating, and thus, similarly, Irregular molecular alignment of the liquid crystalline polymer can be fixed. In the case where the solvent is reduced, the amount of the liquid crystal polymer and the solvent varies depending on the type of the liquid crystal polymer and the solvent, but the degree of the change is reduced as shown in the examples. The amount of the solvent (residual solvent) is used to produce each retardation film, and by measuring the birefringence thereof, it is possible to remarkably suppress the decrease in birefringence as an index and to easily obtain it. For example, the preferred residual solvent amount of the composition for a retardation film of Example 1 is about 12% by weight, preferably about 10% by weight, more preferably about 5% by weight, more preferably about 5% by weight of the composition. More preferably about 2% by weight. Further, the composition for a phase difference film of Example 8 is preferably about 20% by weight, more preferably about 5% by weight, still more preferably about 2% by weight.

The conditions for performing heat drying after natural drying are generally sufficient as long as the conditions for the residual solvent can be distilled off. However, in order to prevent a decrease in birefringence as much as possible, the drying temperature is preferably a temperature at which the liquid crystal polymer exhibits a liquid crystal state (liquid crystal phase temperature) or less, and more preferably a glass transition temperature of the liquid crystalline polymer or less. The temperature range is, for example, 15 ° C to 30 ° C depending on the type of the solvent and the liquid crystalline polymer. Further, drying at this time may be carried out, for example, for 8 minutes to 20 minutes.

The layer containing the liquid crystalline polymer of the present invention thus formed on the substrate is referred to as a photoreactive layer.

The photoreactive layer is irradiated with linearly polarized light, and the photoreactive group in the side chain of the liquid crystalline polymer is reacted (dimerization, isomerization, etc.) by the polarization axis selectivity of the linearly polarized light, and the layer is paid. It can be aligned with liquid crystal. Linearly polarized light may be irradiated by either the vertical direction or the oblique direction of the layer, but it is usually preferred to illuminate in a vertical direction.

In the present invention, the term "linear polarization" refers to light in which a plane including a direction of vibration of an electric field (or a magnetic field) is specified. Linear polarized light is obtained by using a polarizing filter or a polarizing prism for light from a light source. The irradiated light may be dimerized by irradiation with a photoreactive group as long as it is infrared rays, visible rays, ultraviolet rays (near ultraviolet rays, far ultraviolet rays, etc.), X-rays, or charged particle lines (for example, electron beams). The irradiation line for isomerization is not particularly limited. Usually, the irradiation line has a wavelength of from 200 nm to 500 nm, and a near ultraviolet light of from 350 nm to 450 nm is preferred. The light source may, for example, be a xenon lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp or the like. The ultraviolet light or the visible light obtained by such a light source can be used to limit the wavelength range of the irradiation using an interference filter or a color filter or the like. Irradiation energy, although depending on the kind and amount of the applied liquid crystal polymer and the like, but is usually about ^{5mJ / cm 2 ~ 50mJ / cm} 2.

Further, when a polarizer is used, when a photomask is used, a liquid crystal alignment energy of a pattern shape can be generated in two or more different directions. Specifically, after the composition for a retardation film of the present invention is applied and dried, the mask is covered with a linear polarized light, and the liquid crystal alignment energy is applied only to the exposed portion, and is changed as necessary. The direction is repeated a plurality of times, and the liquid crystal alignment energy of the shape of the figure can be generated in the plural direction.

The layer thus formed is referred to as a thermally oriented layer.

By heat-treating the heat-aligning layer, the side chain portion of the liquid crystalline polymer which does not undergo photoreaction is aligned in a predetermined direction to form a retardation film. The conditions of the heat treatment are not particularly limited as long as the alignment is sufficiently carried out, and heating to the liquid crystal phase temperature of the liquid crystalline polymer may be carried out. However, the heating temperature is preferably equal to or lower than the isotropic transition temperature of the liquid crystalline polymer. The specific heating temperature is generally about 80 to 250 ° C, preferably about 100 to 200 ° C, and further preferably about 120 to 170 ° C. The heating time is preferably about 5 to 60 minutes, preferably about 10 to 40 minutes, and further preferably about 10 to 20 minutes.

The thickness of the retardation film of the present invention thus obtained varies depending on the use, etc., but is preferably in the range of 0.8 to 3.0 μm, more preferably in the range of 0.9 to 2.0 μm.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the following examples.

[Example 1] 1. Synthesis of copolymerized acrylic polymer

Poly[1-[6-[4-[4-[(E)-2-methoxycarbonylvinyl]phenoxycarbonyl]phenoxy]hexyloxycarbonyl]-1-methylethene-CO-1 -[6-[4-carboxyphenoxy]hexyloxycarbonyl]-1-methylethene] (M1: M2=80:20)

4-[6-(2-Methylpropenyloxy)hexyloxy]benzoic acid 4-[(E)-2-methoxycarbonylvinyl]phenyl ester 8g (17 mmol), 4- [6-(2-Methylacryloxy)hexyloxy]benzoic acid 21g (69 mmol) Ears and 0.28 g (1.7 mmol) of 2,2'-azobisisobutyronitrile were dissolved in 116 g of cyclohexanone. The solution was passed through nitrogen for 1 hour. It was then heated to 80 °C. After 10 hours, the reaction liquid was cooled, and while stirring vigorously, 346 g of n-hexane was added dropwise at room temperature. The separated polymer was filtered, dried under reduced pressure at 50 ° C to give 24 g of polymer 1.

<Measurement of Weight Average Molecular Weight (MW)>

The weight average molecular weight (MW) of the polymer 1 obtained above was measured using a gel permeation chromatography (GPC). The weight average molecular weight (MW) obtained was 31,700.

<Measurement of acid value>

The acid value of the polymer 1 obtained above was measured as follows. Specifically, about 60 mL of THF was taken in a 100 mL Erlenmeyer flask, and phenolphthalein was used as an indicator to neutralize with a 0.1 mol/L sodium hydroxide aqueous solution. 1.5 g of the polymer 1 was uniformly dissolved in the above solution, stirred, and titrated with a 0.1 mol/L sodium hydroxide aqueous solution, and the reddish color did not disappear for about 30 seconds as the end point of the titration.

The acid value was calculated according to the following formula.

Acid value = (0.1 × f × A × 56.1 / B) / (C / 100)

A: titration (mL)

f: titration rate of aqueous sodium hydroxide solution

B: amount of polymer composition (g) (including the amount of solution after completion of titration of the polymer)

C: polymer concentration (%) (amount of polymer / polymer composition × 100)

The acid value of the polymer 1 obtained above was 130 mgKOH/g.

<Measurement of phase transition temperature>

The phase transition temperature of the polymer 1 obtained above was measured by a differential scanning calorimeter (DSC), and as a result, the glass transition temperature was 70 ° C, and the liquid crystal phase temperature was 70 to 152 °C.

2. Fabrication of composition for retardation film

5 g of the polymer 1 was dissolved in 15 g of cyclohexanone as the composition 1 for the retardation film.

3. Fabrication of retardation film

The composition 1 for retardation film was applied onto a glass substrate to a thickness of about 0.93 μm using a spin coater, and dried under reduced pressure of 0.3 Torr for 1 minute (drying under reduced pressure).

The obtained photoreactive layer was converted into linearly polarized ultraviolet rays (10 mW/cm ² ) using a Glan Taylor prism, and the layer was irradiated for 3 seconds in the vertical direction (irradiation energy: 30 mJ/cm ² ).

The heat-aligned layer thus obtained was heated at 140 ° C for 20 minutes and then cooled to room temperature.

The film formed on the substrate was observed by a polarizing microscope, and light and darkness were observed, and it was confirmed that a retardation film was produced.

The birefringence of the retardation film was measured using a polarizing analyzer OPTIPRO (manufactured by SHINTEC Co., Ltd.) (the same applies hereinafter). As a result, the birefringence showed a value of Δn = 0.125 and Re = 116.3 nm.

[Embodiment 2]

The production of the retardation film of the first embodiment was carried out in the same manner as in the production of the retardation film, except that it was dried under reduced pressure for 1 minute, and then dried by heating at 90 ° C for 5 minutes using a hot plate.

The birefringence of the produced retardation film showed a value of Δn=0.096 and Re=89.3 nm.

[Example 3]

In the above Example 2, a phase difference film was produced in the same manner except that the natural drying time was 3 minutes.

The birefringence of the produced retardation film showed a value of Δn = 0.105 and Re = 97.7 nm.

[Example 4]

In the above Example 2, a phase difference film was produced in the same manner except that the natural drying time was 5 minutes.

The birefringence of the produced retardation film showed a value of Δn = 0.111 and Re = 103.2 nm.

[Example 5]

In the above Example 2, a phase difference film was produced in the same manner except that the natural drying time was 7 minutes.

The birefringence of the produced retardation film showed a value of Δn = 0.112 and Re = 104.2 nm.

[Embodiment 6]

In the above Example 2, a phase difference film was produced in the same manner except that the natural drying time was 10 minutes.

The birefringence of the produced retardation film showed a value of Δn = 0.111 and Re = 103.2 nm.

[Embodiment 7]

The production of the retardation film of the above Example 1 is carried out under reduced pressure. Thereafter, the film was further dried by heating at 90 ° C for 5 minutes using a hot plate, and a retardation film was produced in the same manner. Further, this heat drying is not required because the solvent has been distilled off by vacuum drying, but it is carried out in comparison with other examples (especially Example 1).

The birefringence of the produced retardation film showed Δn = 0.125 and Re = 116.3 nm, and the same values as in Example 1 were shown.

[Embodiment 8] 1. Synthesis of copolymerized acrylic polymer

Poly[1-[6-[4-[(E)-2-(4-methoxyphenoxy)carbonylvinyl]phenoxy]hexyloxycarbonyl]-1-methylethene-CO-1- [6-[4-carboxyphenoxy]hexyloxycarbonyl]-1-methylethene] (M1: M2=80:20)

4-[6-(2-Methylacryloxy)hexyloxy] lauric acid 4-methoxyphenyl ester 5g (11 mmol), 4-[6-(2-methylpropene oxime) 14 g of hexyloxy]benzoic acid (46 mmol) and 0.28 g (1.7 mmol) of 2,2'-azobisisobutyronitrile were dissolved in cyclohexanone 76 g. The solution was passed through nitrogen for 1 hour. It was then heated to 80 °C. After 10 hours, the reaction liquid was cooled, and while stirring vigorously, 346 g of n-hexane was added dropwise at room temperature. The separated polymer was filtered, dried under reduced pressure at 50 ° C to give 15 g of polymer 2.

The weight average molecular weight (MW) (27000), the acid value (134 mgKOH/g), and the phase transition temperature (glass transition temperature of 75 ° C, liquid crystal phase temperature of 75 to 145 ° C) were measured in the same manner as in Example 1.

2. Manufacturing a composition for a retardation film

5 g of the polymer 2 was dissolved in 15 g of cyclohexanone to prepare the composition 2 for the retardation film.

3. Manufacturing retardation film

The composition for retardation film 2 was applied onto a glass substrate to a thickness of about 1.1 μm using a spin coater, and dried under reduced pressure of 0.3 Torr for 1 minute (drying under reduced pressure).

The obtained photoreactive layer was converted into linearly polarized ultraviolet rays (10 mW/cm ² ) using a Glan Taylor prism, and the layer was irradiated for 1.5 seconds in the vertical direction (irradiation energy: 15 mJ/cm ² ).

The heat-aligned layer thus obtained was heated at 140 ° C for 20 minutes and then cooled to room temperature.

The film formed on the substrate was observed by a polarizing microscope, and light and darkness were observed, and it was confirmed that a retardation film was produced.

The birefringence of the produced retardation film was measured. As a result, the birefringence showed a value of Δn = 0.151 and Re = 166.1 nm.

[Embodiment 9]

The production of the retardation film of the above-mentioned Example 8 was carried out in the same manner as in the production of the retardation film, except that it was dried under reduced pressure and naturally dried for 1 minute, and then dried by heating at 90 ° C for 5 minutes using a hot plate.

The birefringence of the produced retardation film showed a value of Δn = 0.144 and Re = 158.4 nm.

[Embodiment 10]

In the above-mentioned Example 9, a phase difference film was produced in the same manner except that the natural drying time was 5 minutes.

The birefringence of the produced retardation film showed a value of Δn = 0.149 and Re = 163.9 nm.

(Comparative Example 1)

In the production of the retardation film of the above-described Example 1, a retardation film was produced in the same manner as in the above except that the film was heated and dried at 90 ° C for 5 minutes using a hot plate under reduced pressure.

The birefringence of the produced retardation film showed a value of Δn = 0.066 and Re = 61.4 nm.

(Comparative Example 2)

In the production of the retardation film of the above-described Example 8, a retardation film was produced in the same manner as in the above except that the film was heated and dried at 90 ° C for 5 minutes using a hot plate.

The birefringence of the produced retardation film showed a value of Δn = 0.080 and Re = 88.0 nm.

<evaluation>

As a result of the first embodiment, it is understood that a phase difference film having a good birefringence can be produced by using the polymer 1 as a raw material according to the production method of the present invention which is obtained by distilling off the solvent under reduced pressure. On the other hand, from the results of Comparative Example 1, it was found that sufficient birefringence could not be obtained by distilling off the solvent by heating at 90 ° C for 5 minutes. Therefore, it is presumed that when the composition for a retardation film applied to the substrate is dried, it is heated in a state in which a solvent exists, which adversely affects birefringence.

In order to clarify this point, further, Example 2-7 was carried out using Polymer 1. Among these, in Examples 2 to 6, a natural drying step was carried out before heating and drying at 90 ° C for 5 minutes, and the amount of solvent in the composition for retardation film applied to the substrate was adjusted according to the time of natural drying. Staged reduction less. Further, in Example 7, the solvent was distilled off in advance by subjecting to drying under reduced pressure at 90 ° C for 5 minutes.

With respect to Comparative Example 1 and Examples 2 to 7, the amount of residual solvent in the coating film before and after the heating step at 90 ° C for 5 minutes was measured. The measurement was carried out by gas chromatography (SHIMADZU, GC-2014). These results are shown in Table 1 together with the birefringence (?n).

From these results, it was found that when the heating step at 90 ° C for 5 minutes was carried out, the amount of residual solvent before the heating step increased, and the birefringence of the obtained film tends to decrease. That is, in Example 7 in which the solvent was previously distilled off before the heating step, even after the heating step, the same birefringence as in Example 1 was obtained, and on the other hand, Comparative Example 1 in which residual solvent was present before the heating step was In Examples 2 to 6, the amount of residual solvent is more birefringent according to the amount thereof. There is a downward trend.

Therefore, it is understood that heating in a state in which the solvent is present to some extent or more may adversely affect birefringence. On the other hand, in the present invention, the solvent is distilled off under reduced pressure or dried, and then dried by heating and drying to remove the solvent. Good birefringence can be obtained, and a retardation film can be produced.

In the case where the polymer 2 is used as a raw material, it is the same as the above, that is, when the composition for a retardation film which is applied to the substrate is dried and dried, the heating in a state of a certain degree or more in the solvent adversely affects the birefringence. Further, Examples 8 to 10 and Comparative Example 2 were carried out. The results are shown in Table 2. Further, in Example 8, the amount of residual solvent after drying under reduced pressure was 0% by weight. Further, in the same embodiment, the heating step at 90 ° C for 5 minutes was not carried out.

From these results, it is also known that heating in a state in which the solvent is present to some extent or more adversely affects birefringence (Δn=0.080 when naturally dried for 0 minutes), and on the other hand, according to the present invention, by decompression The solvent is dried by distilling off, or dried by natural drying (1 minute or 5 minutes), followed by heating and drying to distill off the solvent to obtain good birefringence, thereby producing a retardation film.

[Industry profitability]

According to the present invention, the retardation film can be manufactured simply and simply, even at low cost. The retardation film thus obtained can be used as various optical members, and can be used as an optical element of a liquid crystal display device such as an OA device such as a computer or a facsimile machine, a mobile phone, an electronic manual, a liquid crystal television, or a video camera.

Claims (6)

A method for producing a retardation film, comprising: a step of applying a composition comprising a liquid crystalline polymer having a photoreactive group and a solvent to a substrate; and drying the composition under reduced pressure, or After drying naturally, it is heated and dried at a temperature lower than the liquid crystal phase temperature of the liquid crystalline polymer, and the solvent in the composition is distilled off to form a photoreactive layer; the photoreactive layer is irradiated with linear polarized light to form thermal alignment. a step of layering; and a step of heat-treating the heat-alignable layer at a temperature above the liquid crystal phase temperature of the liquid crystalline polymer and less than the isotropic transfer temperature. The production method according to claim 1, wherein the step of forming the photoreactive layer is performed by distilling the composition under reduced pressure to distill the solvent in the composition. A composition for a retardation film comprising: a copolymerizable (meth)acrylic polymer having a repeating unit represented by the formula (I): Wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkyl group, or a phenyl group substituted with a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, and the p and q systems are each independently It means any integer from 1 to 12, and the m and n monomers each account for 0.65 of the copolymer. m 0.95,0.05 n The relationship of 0.35, m+n=1, ring A and ring B are respectively represented independently: The group shown, wherein each of X ¹ to X ³⁸ independently represents a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group. A composition for a retardation film comprising: a copolymerizable (meth)acrylic polymer having a repeating unit represented by the formula (Ia): In the formula, R ¹ is a hydrogen atom or a methyl group, and R ² represents an alkyl group or a phenyl group substituted with a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, and each of X ^1A to X ^4A Each of them is independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group, and p and q each independently represent an integer of from 1 to 12, and m and n each monomer constitute a molar fraction of the copolymer. Rate meets 0.65 m 0.95,0.05 n 0.35, m+n=1 relationship, ring B system: ^Here , each of X ^1B to X ^4B and X ^31B to X ^38B is independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group. A composition for a retardation film comprising: a copolymerizable (meth)acrylic polymer having a repeating unit represented by the formula (Ib): In the formula, R ¹ is a hydrogen atom or a methyl group, and R ² represents an alkyl group or a phenyl group substituted with a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, X ^1A to X ^4A and X ^{31B ~} X ^38B of each system is independently a hydrogen atom, an alkyl group, an alkoxy group, a cyano group or a halogen atom, p and q each independently represents any one of lines 1 to 12 of an integer, m and n are each based monomer comprises The molar fraction of the copolymer satisfies 0.65 m 0.95, 0.05 n The relationship of 0.35, m+n=1. A composition for a retardation film comprising: a copolymerizable (meth)acrylic polymer having a repeating unit represented by the formula (Ic): In the formula, R ¹ is a hydrogen atom or a methyl group, and R ² represents an alkyl group or a phenyl group substituted with a group selected from an alkyl group, an alkoxy group, a cyano group and a halogen atom, X ^1A to X ^4A and X ^1B Each of ~X ^4B is independently a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom or a cyano group, and the p and q groups independently represent any integer from 1 to 12, and the m and n groups each occupy a monomer. The molar fraction of the copolymer satisfies 0.65 m 0.95,0.05 n The relationship of 0.35, m+n=1.