JP2015232591A - Retardation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a retardation film that prevents the brightness of a display device from decreasing.SOLUTION: A retardation film 20 includes a resin layer (a)21 with a refractive index of 1.50 or less and a total light transmittance of 80% or more, and a resin layer (b)25 with a refractive index of 1.55 or more, an intrinsic birefringence of 0.07 or more, and a total light transmittance of 80% or more, the resin layer (a)21 and the resin layer (b)25 are stacked on one another. At least one resin layer (a) is positioned outside the resin layer (b).

Description

  The present invention relates to a retardation film.

  Patent Document 1 describes a retardation film made of polycarbonate. When such a retardation film is used in a display device, the luminance of the display device may be lowered.

Japanese Patent Laid-Open No. 3-174512

  Polycarbonate has an intrinsic birefringence of 0.07 or more, so it easily develops a phase difference. However, since the refractive index is as high as 1.55 or more, it reduces the brightness of the display device when used as a retardation film. There was a problem.

The present invention includes the following inventions.
[1] A resin layer (a) having a refractive index of 1.50 or less, a total light transmittance of 80% or more, a refractive index of 1.55 or more, and an intrinsic birefringence of 0.07 or more, A phase difference film in which a resin layer (b) having a total light transmittance of 80% or more is laminated,
A retardation film in which at least one resin layer (a) is located outside the resin layer (b).
[2] The retardation film according to [1], wherein the resin layer (b) is a polycarbonate layer.
[3] The retardation film according to [1] or [2], wherein the resin layer (a) is a poly (meth) acrylate layer.
[4] The retardation film according to any one of [1] to [3], which has an optical characteristic represented by the following formula (1).
70 <Re (590) <320 (1)
(Re (590) represents an in-plane retardation value for light having a wavelength of 590 nm.)
[5] The retardation film according to any one of [1] to [4], wherein the volume fraction of the resin layer (b) is 30 to 95%.
[6] The retardation film according to any one of [1] to [5], wherein the resin layer (a) includes poly (meth) acrylate and rubber elastic particles.
[7] The retardation film according to [6], wherein the rubber elastic body particles have a number average particle diameter of 10 to 350 nm.
[8] The retardation film according to [6] or [7], wherein the content of the elastic rubber particles in the resin layer (a) is 3% by mass or more and 60% by mass or less.
[9] The retardation film according to any one of [1] to [8], in which the resin layer (a), the resin layer (b), and the resin layer (a) are laminated in this order.
[10] The retardation film according to any one of [1] to [9], which is a film obtained by stretching the resin layer (a) and the resin layer (b).
[11] An elliptically polarizing plate in which the retardation film according to any one of [1] to [7], an adhesive layer, and a polarizer are laminated in this order.
[12] The elliptically polarizing plate according to [11], wherein the adhesive layer is a cured product of an active energy ray-curable adhesive.

  ADVANTAGE OF THE INVENTION According to this invention, the retardation film which is hard to reduce the brightness | luminance of a display apparatus can be obtained.

It is a schematic diagram of an elliptically polarizing plate provided with the retardation film of this invention. It is a schematic diagram of an elliptically polarizing plate provided with the retardation film of this invention.

Examples of the resin contained in the resin layer (a) having a refractive index of 1.50 or less and a total light transmittance of 80% or more include fluororesin, polyethylene resin, polypropylene resin and poly (meth) acrylate. The resin layer (a) is preferably a poly (meth) acrylate layer containing poly (meth) acrylate.
The resin contained in the resin layer (b) has a refractive index of 1.55 or more, an intrinsic birefringence of 0.07 or more, and a total light transmittance of 80% or more. Polycarbonate, polyester, polyurethane, polyethersulfone , Polyphenylene ether, polyamide, polyimide and the like, and the resin layer (b) is preferably a polycarbonate layer containing polycarbonate.

[Resin layer (a)]
The resin layer (a) preferably further includes rubber elastic particles. The rubber elastic particles are particles including a layer exhibiting rubber elasticity (hereinafter sometimes referred to as a rubber elastic layer). The rubber elastic particles may be particles composed only of a layer exhibiting rubber elasticity, or may be particles having a multilayer structure having other layers together with a layer exhibiting rubber elasticity. The layer exhibiting rubber elasticity includes a rubber elastic polymer. Examples of the rubber elastic polymer include olefin-based elastic polymers, diene-based elastic polymers, styrene-diene-based elastic copolymers, acrylic-based elastic polymers, and the like. Among these, from the viewpoint of light resistance and transparency of the retardation film of the present invention (hereinafter sometimes referred to as the present film), an acrylic elastic polymer is preferably used.

  The acrylic elastic polymer can be composed of a polymer mainly composed of alkyl acrylate. This may be a homopolymer of alkyl acrylate, or a copolymer of 50% by mass or more of alkyl acrylate and 50% by mass or less of other monomers. As the alkyl acrylate, those having 4 to 8 carbon atoms in the alkyl group are usually used. Examples of copolymerization of monomers other than alkyl acrylate include alkyl methacrylates such as methyl methacrylate and ethyl methacrylate, styrene monomers such as styrene and alkylstyrene, acrylonitrile and methacrylo Monofunctional monomers such as unsaturated nitriles such as nitriles, alkenyl esters of unsaturated carboxylic acids such as allyl (meth) acrylate and methallyl (meth) acrylate, and dibasic acids such as diallyl maleate And polyfunctional monomers such as unsaturated carboxylic acid diesters of glycols such as alkylene glycol di (meth) acrylate.

  The rubber elastic particles containing the acrylic elastic polymer are preferably multi-layered particles having an acrylic rubber elastic polymer layer. Specifically, a two-layer structure having a hard polymer layer mainly composed of alkyl methacrylate on the outer side of the acrylic rubber elastic polymer layer, and a methacrylic resin on the outer side of the acrylic rubber elastic polymer layer. Examples thereof include a three-layer structure having a hard polymer layer mainly composed of an alkyl acid and further having a hard polymer layer mainly composed of an alkyl methacrylate inside. The hard polymer layer mainly composed of alkyl methacrylate may be a homopolymer of alkyl methacrylate, or 50% by mass or more of alkyl methacrylate and 50% by mass or less of other monomers. A copolymer may also be used. As the alkyl methacrylate, those having 1 to 4 carbon atoms of the alkyl group are usually used, and methyl methacrylate is preferable. Examples of copolymerizing monomers other than alkyl methacrylates include alkyl acrylates such as methyl acrylate and ethyl acrylate, styrene monomers such as styrene and alkyl styrene, acrylonitrile and methacrylate. Examples include unsaturated nitriles such as rhonitrile. Such a rubber elastic body particle having a multilayer structure can be produced, for example, by the method described in JP-B-55-27576.

  The number average particle diameter of the rubber elastic particles is preferably in the range of 10 to 350 nm. Thereby, since slight unevenness | corrugation is formed in the film surface, slipperiness can be improved. The average particle diameter of the rubber elastic particles is more preferably 30 nm or more, further preferably 50 nm or more, more preferably 300 nm or less, still more preferably 280 nm or less.

  The number average particle diameter of the rubber elastic particles is measured as follows. That is, when such a rubber elastic particle is mixed with a resin to form the resin layer (a) and the cross section is dyed with an aqueous solution of ruthenium oxide, the rubber elastic particle is colored and observed in a substantially circular shape. . Therefore, a slice is prepared from the dyed section using a microtome or the like, and this is observed with an electron microscope. And after extracting 100 dye | stained rubber elastic body particles at random and measuring each diameter, let the number average value be a number average particle diameter.

  However, the number average particle diameter of the rubber elastic particles having a hard polymer layer mainly composed of alkyl methacrylate is defined as the number average particle diameter of the rubber elastic particles. For example, when rubber elastic particles in which an outermost layer is a hard polymer layer mainly composed of methyl methacrylate and an acrylic rubber elastic polymer is encapsulated therein are used, it is made of poly (meth) acrylate. When mixed, the hard polymer layer mainly composed of methyl methacrylate is mixed with poly (meth) acrylate. Therefore, when the cross section is dyed with ruthenium oxide and observed with an electron microscope, the rubber elastic particles are observed as particles excluding the outermost layer. Specifically, when the rubber elastic particles having a two-layer structure in which the inner layer is an acrylic rubber elastic polymer and the outer layer is a hard polymer mainly composed of methyl methacrylate, the inner layer is acrylic. The rubber elastic polymer portion is dyed and observed as particles of a single layer structure, the innermost layer is a hard polymer mainly composed of methyl methacrylate, the intermediate layer is an acrylic rubber elastic polymer, When rubber elastic particles having a three-layer structure, which is a hard polymer mainly composed of methyl methacrylate as an outer layer, are used, the inner-layer particle central portion is not dyed, and an acrylic rubber elastic polymer in the intermediate layer Only the part will be observed as a dyed two-layered particle.

  The content of the rubber elastic body particles is preferably 3% by mass or more and 60% by mass or less, and more preferably 5% by mass or more and 50% by mass or less with respect to the total amount of the resin layer (a). When the amount of the rubber elastic particles is more than 60% by mass, the dimensional change of the resin layer (a) becomes large and the heat resistance is deteriorated. On the other hand, when the amount of rubber elastic particles is less than 3% by mass, the heat resistance of the resin layer (a) is good, but the roll-up property in producing the film is poor, and the productivity may be lowered.

  In the present invention, when the rubber elastic particles are multi-layered particles having other layers together with a layer exhibiting rubber elasticity, the mass of the portion consisting of the layer exhibiting rubber elasticity and the inner layer is determined. The mass of the elastic rubber particles. For example, the elasticity of a three-layer structure having a hard polymer layer mainly composed of alkyl methacrylate outside the acrylic rubber elastic polymer layer and having a hard polymer layer mainly composed of alkyl methacrylate inside. In the case of body particles, the total mass of the acrylic rubber elastic polymer layer and the inner hard polymer layer mainly composed of alkyl methacrylate is defined as the mass of the rubber elastic particles. When such rubber elastic particles are dissolved in acetone, the acrylic rubber elastic polymer layer in the intermediate layer and the hard polymer layer mainly composed of the inner alkyl methacrylate remain as insolubles, so that the rubber elasticity The mass of the portion composed of the layer indicating the inner layer and the inner layer can be easily determined.

  The poly (meth) acrylate contained in the resin layer (a) is a polymer mainly composed of methacrylic acid ester, and may be a homopolymer of methacrylic acid ester or 50% by mass or more of methacrylic acid ester. It may be a copolymer with a monomer other than 50% by mass.

  A preferable monomer composition of the methacrylic resin is 50 to 100% by mass of methacrylic acid ester, 0 to 50% by mass of alkyl acrylate, and 0 to 49% by mass of other monomers based on all monomers. More preferably, the methacrylic acid ester is 50 to 99.9% by mass, the alkyl acrylate is 0.1 to 50% by mass, and the other monomers are 0 to 49% by mass.

  The methacrylic acid ester is preferably an alkyl methacrylate. Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl methacrylate. The alkyl group of the alkyl methacrylate usually has 1 to 8 carbon atoms, Preferably it is 1-4. Of these, methyl methacrylate is particularly preferred.

  Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. The alkyl group of the alkyl acrylate usually has 1 to 8 carbon atoms, preferably 1 to 1 carbon atom. 4.

  Monomers other than methacrylate esters and alkyl acrylates may be monofunctional monomers having one polymerizable carbon-carbon double bond in the molecule, or polymerizable carbon- in the molecule. It may be a polyfunctional monomer having two or more carbon double bonds, and is preferably a monofunctional monomer. Monofunctional monomers include styrene monomers such as styrene, α-methylstyrene and vinyltoluene, alkenyl cyanides such as acrylonitrile and methacrylonitrile, acrylic acid, methacrylic acid, maleic anhydride, itaconic anhydride, etc. And N-substituted maleimides such as N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, and the like. Polyfunctional monomers include polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate and trimethylolpropane triacrylate, allyl acrylate, allyl methacrylate and allyl cinnamate. Alkenyl esters of unsaturated carboxylic acids such as polyalkenyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate and triallyl isocyanurate, and aromatic polyalkenyl compounds such as divinylbenzene Can be mentioned.

  The methacrylic acid ester, alkyl acrylate, and other monomers exemplified here may be used alone or in combination of two or more.

  The resin layer (a) may contain a lubricant. When the resin layer (a) contains a lubricant, it is possible to prevent tightening when the film is wound in a roll shape, thereby improving the package appearance in the wound state. Any lubricant may be used as long as it has a function of improving the slipperiness of the film surface. Examples of the compound having such a function include fatty acid compounds, acrylic compounds, ester compounds, and the like. Preferred are fatty acid compounds having 16 to 20 carbon atoms, and stearic acid compounds are particularly preferred.

  Examples of stearic acid compounds include stearic acid; stearic acid esters such as methyl stearate, ethyl stearate, and monoglyceride stearate; stearic acid amide; sodium stearate, calcium stearate, zinc stearate, lithium stearate, magnesium stearate, etc. 12-hydroxy stearic acid, sodium 12-hydroxystearate, zinc 12-hydroxystearate, calcium 12-hydroxystearate, lithium 12-hydroxystearate, magnesium 12-hydroxystearate, etc. Examples include stearic acid and metal salts thereof. Stearic acid is preferred.

  The content of the lubricant in the resin layer (a) is usually 0.15 parts by mass or less, preferably 0.1 parts by mass or less, with respect to 100 parts by mass in total of the poly (meth) acrylate and the rubber elastic particles. More preferably, it is 0.07 parts by mass or less. When there is too much content of a lubricant, a lubricant may bleed out from a resin layer (a), and the transparency of this film may be reduced.

  The resin layer (a) may also contain additives such as a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant. Good.

  The ultraviolet absorber is a compound that absorbs ultraviolet rays having a wavelength of 400 nm or less. Examples of the UV absorber include benzophenone UV absorbers, benzotriazole UV absorbers, and acrylonitrile UV absorbers. Specific examples include 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (2'- Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2,2 Examples include '-dihydroxy-4,4'-dimethoxybenzophenone and 2,2', 4,4'-tetrahydroxybenzophenone. Among these, 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol] is preferable. The content of the ultraviolet absorber is selected in such a range that the transmittance of the film at a wavelength of 370 nm or less is preferably 10% or less, more preferably 5% or less, and further preferably 3% or less.

  The resin layer (a) is usually formed from a resin composition containing a resin. As a method for producing a resin composition containing a resin and rubber elastic particles, the resin and the rubber elastic particles are mixed by polymerizing a monomer that is a raw material of the resin in the presence of the rubber elastic particles. And a method of obtaining a composition in which a resin and a rubber elastic particle are mixed by melting and kneading the rubber elastic particle and a resin. The lubricant and other additives may be mixed at an arbitrary time.

[Resin layer (b)]
The polycarbonate contained in the preferred resin layer (b) is a method of reacting a dihydric phenol and a carbonylating agent by an interfacial polycondensation method or a melt transesterification method, a method of polymerizing a carbonate prepolymer by a solid phase transesterification method, Alternatively, it can be obtained by a method of polymerizing a cyclic carbonate compound by a ring-opening polymerization method.

  Dihydric phenols include hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, bis {(4-hydroxy-3,5-dimethyl) phenyl} methane, 1,1-bis ( 4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4-hydroxyphenyl) propane (hereinafter sometimes referred to as bisphenol A), 2,2 -Bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dimethyl) phenyl} propane, 2,2-bis {(4-hydroxy-3, 5-dibromo) phenyl} propane, 2,2-bis {(3-isopropyl-4-hydroxy) phenyl} propane, 2,2- Su {(4-hydroxy-3-phenyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2,2-bis ( 4-hydroxyphenyl) -3,3-dimethylbutane, 2,4-bis (4-hydroxyphenyl) -2-methylbutane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2-bis (4- Hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis {(4- Droxy-3-methyl) phenyl} fluorene, α, α′-bis (4-hydroxyphenyl) -o-diisopropylbenzene, α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene, α, α ′ -Bis (4-hydroxyphenyl) -p-diisopropylbenzene, 1,3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane, 4,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfoxide 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl ester, and the like. These may be used alone or in combination of two or more.

Preferred dihydric phenols are bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxy). Phenyl) -3-methylbutane, 2,2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4 -Hydroxyphenyl) -3,3,5-trimethylcyclohexane and α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene.
More preferably, bisphenol A is used alone, or 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane and bisphenol A, 2,2-bis {(4-hydroxy-3- Methyl) phenyl} propane and α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene in combination with at least one selected from the group consisting of.

  Examples of the carbonylating agent include carbonyl halides such as phosgene, carbonate esters such as diphenyl carbonate, and haloformates such as dihaloformates of dihydric phenols. These may be used alone or in combination of two or more.

  The resin layer (b) contains additives such as a lubricant, a fluorescent brightening agent, a dispersant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant. May be. The preferable kind and content of these additives are the same as the preferable aspect in the resin layer (a).

  The resin layer (b) is usually formed from a resin composition containing a resin. The resin composition can be obtained by mixing a resin and optionally a lubricant and other additives by an arbitrary method.

[Retardation film of the present invention]
The film preferably has an optical characteristic represented by the formula (1). More preferably, the present film has a retardation film having an optical property represented by the formula (2) (hereinafter sometimes referred to as a quarter-wave plate) or an optical property represented by the formula (3). A retardation film (hereinafter sometimes referred to as a half-wave plate), particularly preferably a quarter-wave plate.
70 <Re (590) <320 (1)
70 <Re (590) <160 (2)
200 <Re (590) <320 (3)
Re (590) represents an in-plane retardation value for light having a wavelength of 590 nm, and is defined by the formula (I).
_{Re (590) = (n x} -n y) × d (I)

n _x represents the in-plane slow axis direction of the refractive index of the film. n _y represents a refractive index in-plane fast axis direction (direction orthogonal with the slow axis and a plane). d represents the thickness.

  The retardation of this film can be controlled by adjusting the stretch ratio of the resin layer (b) and the resin layer (a).

  The film may have two or more resin layers (b) and may have two or more resin layers (a), but at least one resin layer (a) is formed of the resin layer (b). Located outside. When the present film is provided on the display surface of the display device, the surface on the light emitting side is the resin layer (a), so that the refractive index when light is emitted from the present film is lowered, and the light transmittance is reduced. Since it becomes high, the brightness | luminance of a display apparatus does not fall easily. The present film is preferably a two-layer retardation film (hereinafter sometimes referred to as retardation film A) in which one resin layer (b) and one resin layer (a) are laminated, or a resin layer. (A), a resin layer (b), and a resin layer (a) is a three-layer retardation film (hereinafter, also referred to as retardation film B) laminated in this order, more preferably, Retardation film B. There exists a tendency which is excellent in adhesiveness with other members, such as a polarizer, as the surface by which the other member is bonded is the resin layer (a).

  This film can have a surface treatment layer (coating layer) on the surface of the resin layer (a) present on the most visible side in order to impart desired optical properties or other characteristics. The purpose of the surface treatment layer is to prevent reflection of external light on the surface, anti-glare layer to prevent glare on the surface, and prevention of surface scratches in the assembly process of liquid crystal modules. A hard coat layer, an antifouling layer for improving the water repellency of the surface and preventing dirt, and the like. Further, a functional surface treatment such as an antistatic treatment can also be performed. The method for forming the surface treatment layer is not particularly limited, and a known method can be used.

  In the present film having a plurality of resin layers (a) such as the retardation film B, the content of each layer of the rubber elastic body particles and the additive may be different in each layer. For example, reducing the content of the rubber elastic particles is advantageous in that the heat resistance is improved and the dimensional change can be reduced. Further, when the content of the rubber elastic particles is increased, it is advantageous in that the impact resistance, the winding property, and the adhesion with other members such as a polarizer are improved.

  The thickness of this film is 3-100 micrometers normally, Preferably it is 5-80 micrometers, More preferably, it is 10-60 micrometers.

  The thickness of the resin layer (a) is usually 1 to 70 μm, preferably 2 to 40 μm. The thickness of the resin layer (b) is usually 1 to 97 μm, preferably 2 to 30 μm.

  The ratio of the thickness of the resin layer (b) based on the total film thickness of the film is preferably 30 to 97%. The ratio of the film thickness of the resin layer (b) to the total film thickness of the film is preferably 40% or more, more preferably 55% or more. Moreover, it is preferably 95% or less, more preferably 90% or less. When the ratio of the film thickness of the resin layer (b) to the total film thickness of the present film is too small, the elastic modulus of the present film is lowered and, for example, there is a tendency that durability when an elliptical polarizing plate is formed is deteriorated. On the other hand, if the ratio of the thickness of the resin layer (b) to the total thickness of the film is too large, the surface hardness of the film tends to be insufficient. When this film has a plurality of resin layers (b), the sum of them may be in the above range, and the thickness of each layer may be the same or different.

  The volume ratio of the resin layer (b) based on the total volume of the film is preferably 30 to 97%. The ratio of the volume of the resin layer (b) to the total volume of the film is preferably 40% or more, more preferably 55% or more. Further, it is preferably 95% or less. When the ratio of the volume of the resin layer (b) in the total volume of the film is too small, the elastic modulus of the film is lowered and, for example, durability when an elliptically polarizing plate is formed tends to be deteriorated. On the other hand, if the proportion of the volume of the resin layer (b) in the total volume of the film is too large, the surface hardness of the film tends to be insufficient. When this film has a plurality of resin layers (b), the total of them may be in the above range, and the volume of each layer may be the same or different.

  The ratio of the thickness of the resin layer (a) based on the total film thickness of the film is preferably 3 to 70%. The ratio of the film thickness of the resin layer (a) to the total film thickness of the film is preferably 5% or more, more preferably 10% or more. Further, it is preferably 60% or less, more preferably 45% or less. When this film has a plurality of resin layers (a), the sum of them may be in the above range, and the thickness of each layer may be the same or different. When this film is the retardation film B, it is preferable that the thickness of the two resin layers (a) is the same from the viewpoint of suppressing curling of the retardation film B.

  The volume ratio of the resin layer (a) based on the total volume of the film is preferably 3 to 70%. The ratio of the volume of the resin layer (a) to the total volume of the film is preferably 5% or more. Further, it is preferably 60% or less, more preferably 45% or less. When this film has a plurality of resin layers (a), the sum of them may be in the above range, and the volume of each layer may be the same or different. When this film is the retardation film B, it is preferable that the volume of the two resin layers (a) is the same from the viewpoint of suppressing curling of the retardation film B.

  This film is preferably molded so that the shrinkage ratio in the roll length direction of the film when heated at 100 ° C. for 10 minutes is 2.0% or less. When the shrinkage rate exceeds 2.0%, when the film and the polarizing plate are bonded to each other and exposed to a high temperature, the polarizing plate has a large shrinkage, and the polarizer contained in the polarizing plate may be broken. This is not preferable. This shrinkage rate is preferably 1.5% or less, and more preferably 1.0% or less.

  The film preferably has an internal haze of 5% or less measured according to JIS K7105-1981 “Testing methods for optical properties of plastics”. If the internal haze exceeds 5%, the white luminance when this film is incorporated in a display device is lowered and the screen becomes dark. The internal haze is more preferably 3% or less.

  This film is a coextrusion in which the resin composition for forming the resin layer (b) and the resin composition for forming the resin layer (a) are melted with an extruder and then laminated using a feed block method or a multi-manifold method. After forming the resin layer (b) into a film by an extrusion method or the like after forming, the resin composition for forming the resin layer (a) on the surface of the film is dissolved in a solvent as necessary and coated. It is obtained by stretching the produced film. A preferable production method of the present film is a method of stretching a film obtained by a coextrusion molding method.

  In the coextrusion molding method, a molten resin composition is brought into close contact with a roll or a belt to form a film. The number, arrangement, and material of the rolls and belts at this time are not particularly limited, but the molten resin is sandwiched between two metal rolls or brought into contact with the metal rolls and the metal belts to pass therethrough. The method of transferring the surface shape is preferable for improving the surface accuracy of the film surface and improving the surface treatment property. Alternatively, by sandwiching the molten resin composition between a metal roll and an elastic metal roll, the method of bringing the molten resin composition into contact with each other on the surface and passing it through reduces strain during molding, and reduces strength and heat shrinkage. It is suitable for obtaining a film having reduced property anisotropy. The metal elastic roll includes, for example, a shaft roll and a cylindrical metal thin film that is disposed so as to cover the outer peripheral surface of the shaft roll and that contacts the molten resin, and between the shaft roll and the metal thin film. Examples include those in which a fluid whose temperature is controlled, such as water or oil, is encapsulated, or a metal belt is wound around the surface of a rubber roll.

Examples of the stretching method include uniaxial stretching and biaxial stretching. Examples of the stretching direction include a machine flow direction (MD) of an unstretched film, a direction perpendicular to the machine flow direction (TD), and a direction oblique to the machine flow direction (MD). Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction.
In uniaxial stretching, for example, two or more pairs of nip rolls with increased peripheral speed on the outlet side are used to stretch in the longitudinal direction (machine flow direction: MD), or both sides of the unstretched film are gripped with a chuck to flow in the machine direction. It can be performed by spreading in a direction (TD) orthogonal to the direction. A method in which both sides of the unstretched film are gripped by a chuck and stretched in a direction oblique to the machine flow direction is preferable.
The draw ratio by the drawing treatment can be selected so that a desired phase difference is obtained. Among these, 30 to 500% is preferable, and 50 to 300% is more preferable. When the draw ratio is less than 30%, it is difficult to obtain a desired phase difference. When the draw ratio is more than 300%, the film thickness becomes too thin and the film is easily broken or handling properties are lowered. The draw ratio is the following formula:
Stretch ratio (%) = 100 × {(length after stretching) − (length before stretching)} / (length before stretching)
When performing biaxial stretching, it is preferable that M1 / M2 calculated | required from the larger draw ratio M1 and the smaller draw ratio M2 among the draw ratios of MD direction and TD direction is 3 or more, more preferably 5 or more. is there. If it is smaller than 3, it becomes difficult to obtain a desired phase difference.
The stretching temperature is set to a temperature higher than the temperature at which the entire film can be stretched, and is preferably in the range of −40 ° C. to + 40 ° C. of the glass transition temperature of the resin layer (b), more preferably − It is in the range of 25 ° C to + 25 ° C, more preferably in the range of -15 ° C to + 15 ° C.

[Elliptically polarizing plate]
An elliptically polarizing plate is obtained by bonding this film to one surface of the polarizing plate. Under the present circumstances, it laminates | stacks so that the surface on the opposite side to the surface bonded with the polarizing plate of this film may become a resin layer (a). When an elliptically polarizing plate having this film (hereinafter sometimes referred to as this elliptically polarizing plate) is provided on the display surface of the display device, the surface opposite to the surface on which the polarizing plate is bonded is the resin layer (a). Accordingly, the refractive index when light is emitted from the elliptically polarizing plate is lowered and the light transmittance is increased, so that the luminance of the display device is hardly lowered. Further, if the surface opposite to the surface on which the polarizing plate is bonded is the resin layer (a), the surface hardness of the display device having the resin layer (a) on the display surface is sufficiently high, and the display surface Tend to be hard to scratch.

  The polarizing plate and the present film are usually bonded so that the transmission axis of the polarizing plate and the slow axis (optical axis) of the present film are about 45 °. Usually in the range of 45 ± 20 °. Moreover, the optical film which functions as an optical compensation film can also be obtained by making the optical axis of a polarizing plate and the optical axis of this film correspond or orthogonal.

  As a polarizing plate bonded with this film, the polarizing plate which has a protective film, a polarizer, and a protective film in this order, the polarizing plate which has a polarizer and a protective film, a polarizing plate which consists only of polarizers, etc. are mentioned. Preferably, it is a polarizing plate which has a polarizer and a protective film, Preferably, this film is bonded on the polarizer surface of this polarizing plate.

  Bonding of this film and a polarizing plate is normally performed using an adhesive agent. The adhesive is preferably a curable adhesive or a pressure sensitive adhesive, more preferably a curable adhesive, and still more preferably an active energy ray curable adhesive.

  An example of a layer configuration of an elliptically polarizing plate in which a retardation film A and a polarizing plate are laminated is shown in a schematic cross-sectional view in FIG. Moreover, the example of a layer structure of the elliptically polarizing plate which laminated | stacked retardation film B and the polarizing plate is shown by the cross-sectional schematic diagram in FIG.

  The elliptically polarizing plate 10 shown in FIG. 1 includes a main film 20 in which a resin layer (a) 21 is laminated on one surface of a resin layer (b) 25, and a polarizing plate 31 having a polarizer 30 and a protective film 40. It is what was pasted. The resin layer (a) 21 laminated on one surface of the resin layer (b) 25 may be referred to as a first resin layer (a). An elliptically polarizing plate 10 shown in FIG. 2 includes a main film 20 in which a first resin layer (a) 21 and a second resin layer (a) 22 are laminated on both surfaces of a resin layer (b) 25, and a polarizer. The polarizing plate 31 which has 30 and the protective film 40 is bonded in this order.

  In these drawings, the polarizer 30 and the main film 20 are bonded via an adhesive layer 51, and the polarizer 30 and the protective film 40 are bonded via an adhesive layer 52. Yes. The adhesive layer is formed from an adhesive, and a preferable adhesive layer is a cured product of a curable adhesive, and more preferably a cured product of an active energy ray-curable adhesive.

[Polarizer]
The polarizer 30 constituting the elliptically polarizing plate 10 adsorbs the dichroic dye by uniaxially stretching the polyvinyl alcohol resin film according to a known method, and dyeing the polyvinyl alcohol resin film with the dichroic dye. And a step of treating the polyvinyl alcohol-based resin film on which the dichroic dye is adsorbed with a boric acid aqueous solution, and a step of washing with water after the treatment with the boric acid aqueous solution. The polarizer thus obtained has an absorption axis in the uniaxially stretched direction.

  As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The degree of saponification of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 mol% or more. This polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizer. The method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method such as melt extrusion film formation or solution cast film formation is employed. The film thickness of the polyvinyl alcohol-based raw film is not particularly limited, but is, for example, about 10 to 150 μm.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Moreover, uniaxial stretching can also be performed in these several steps. Moreover, these several processes can also be performed with a support film.

  Uniaxial stretching may be performed by passing between spaced apart rolls having different peripheral speeds, or may be performed by sandwiching with hot rolls. Further, this uniaxial stretching may be dry stretching in which stretching is performed in the air, or wet stretching in which a polyvinyl alcohol-based resin film is stretched using a solvent such as water or an organic solvent. May be. The draw ratio is usually about 3 to 8 times.

  The polyvinyl alcohol resin film can be dyed with the dichroic dye by, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. As the dichroic dye, iodine or a dichroic organic dye is used. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed.
The content of iodine in this aqueous solution is usually about 0.01 to 1 part by mass per 100 parts by mass of water. The content of potassium iodide is usually about 0.5 to 20 parts by mass per 100 parts by mass of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually employed. The content of the dichroic organic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by mass, preferably about 1 × 10 ⁻³ to 1 part by mass per 100 parts by mass of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dichroic dye solution used for dyeing is usually about 20 to 80 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.

  The boric acid treatment after dyeing with a dichroic dye can be performed by a method of immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. The amount of boric acid in the boric acid-containing aqueous solution is usually about 2 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C. The immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain a polarizer. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature of a drying process is about 30-100 degreeC normally, Preferably it is 50-80 degreeC. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

  By the drying treatment, the moisture content of the polarizer is reduced to a practical level. The moisture content is usually 5 to 20% by mass, preferably 8 to 15% by mass. When the moisture content is less than 5% by mass, the flexibility of the polarizing film is lost, and the polarizer may be damaged or broken after drying. On the other hand, when the moisture content exceeds 20% by mass, the thermal stability of the polarizer tends to be insufficient.

  The thickness of the polarizer to which the dichroic dye thus obtained is adsorbed and oriented is usually 2 to 40 μm.

[Protective film]
As the protective film 40, any film can be used depending on the driving method of the liquid crystal cell included in the display device. For example, for a lateral electric field (IPS) mode liquid crystal cell, a liquid crystal cell having an in-plane retardation value of 30 nm or less, preferably 20 nm or less, more preferably 10 nm or less and functioning as a low retardation film is used. preferable. On the other hand, for a vertical alignment (VA) mode liquid crystal cell, one that functions as a retardation film can be used.

  The protective film 40 can be composed of a film made of a cellulose resin, an olefin resin, a polyethylene terephthalate resin, a polycarbonate resin, an acrylic resin, or the like.

  What formed these resin into a film shape and gave the extending | stretching process is good also as a protective film. At this time, the stretching is uniaxial stretching that extends in the MD (flow direction) or TD (direction orthogonal to the flow direction in the plane), biaxial stretching that extends in both directions of MD and TD, and the direction that is neither MD nor TD. It may be performed by any method such as oblique stretching. By performing such a stretching operation, a protective film having high mechanical strength can be obtained.

  Cellulosic resins are those in which some or all of the hydrogen atoms in the hydroxyl groups of cellulose obtained from raw material cellulose such as cotton linter and wood pulp (hardwood pulp, conifer pulp) are acetyl, propionyl and / or butyryl groups. Cellulose organic acid ester or cellulose mixed organic acid ester substituted with an acyl group. Examples include cellulose acetate, propionate, butyrate, and mixed esters thereof. Of these, a triacetyl cellulose film, a diacetyl cellulose film, a cellulose acetate propionate film, a cellulose acetate butyrate film, and the like are preferable.

  The olefin resin is, for example, a resin obtained by polymerizing a chain olefin monomer such as ethylene or propylene or a cyclic olefin monomer such as norbornene or another cyclopentadiene derivative using a polymerization catalyst.

  Examples of the olefin resin obtained from the chain olefin monomer include polyethylene resins and polypropylene resins. Of these, a polypropylene resin which is a homopolymer of propylene is preferable. Also preferred is a polypropylene copolymer resin in which a comonomer mainly composed of propylene and copolymerized therewith is usually copolymerized at a rate of 1 to 20% by mass, preferably at a rate of 3 to 10% by mass.

  The comonomer copolymerizable with propylene is preferably ethylene, 1-butene or 1-hexene. Among these, ethylene is preferably used because it is relatively excellent in transparency and stretch processability, and a polypropylene copolymer resin obtained by copolymerizing ethylene in a proportion of 1 to 20% by mass, particularly 3 to 10% by mass, One of the preferred ones. By making the copolymerization ratio of ethylene 1% by mass or more, an effect of improving transparency and stretch processability appears. On the other hand, when the ratio exceeds 20% by mass, the melting point of the resin is lowered, and the heat resistance required for the protective film or the retardation film may be impaired.

  Polypropylene resins can be easily obtained as commercial products. For example, “Prime Polypro (registered trademark)” sold by Prime Polymer Co., Ltd. and Nippon Polypro Co., Ltd. "Novatech (registered trademark)" and "Wintech (registered trademark)", "Sumitomo Noblen (registered trademark)" sold by Sumitomo Chemical Co., Ltd., "Sun Allomer (registered trademark)" sold by Sun Allomer Co., Ltd. ) ”.

  An olefin resin obtained by polymerizing a cyclic olefin monomer is generally also referred to as a cyclic olefin resin, an alicyclic olefin resin, or a norbornene resin. Here, it is called a cyclic olefin resin.

  Examples of cyclic olefin resins include resins obtained by performing ring-opening metathesis polymerization using cyclopentadiene and olefins by Diels-Alder reaction or a derivative thereof as a monomer, followed by hydrogenation; dicyclopentadiene and A resin obtained by performing ring-opening metathesis polymerization from olefins or (meth) acrylic acid esters by a Diels-Alder reaction or a derivative thereof obtained by Diels-Alder reaction, followed by hydrogenation; norbornene, tetracyclo Resins obtained by conducting ring-opening metathesis copolymerization using dodecene, derivatives thereof, or other cyclic olefin monomers in the same manner and subsequent hydrogenation; norbornene, tetracyclododecene and the like And at least one cyclic olefin selected from derivatives, such as aliphatic or aromatic compound and the addition copolymer are allowed to obtain a resin having a vinyl group.

  Cyclic olefin-based resins can also be easily obtained as commercial products. For example, they are produced by TOPAS ADVANCED POLYMERS GmbH in Germany under the trade name, and are sold by Polyplastics Co., Ltd. in Japan. TOPAS "(Topas) (registered trademark)," Arton "(registered trademark) manufactured and sold by JSR Corporation," ZEONOR "(registered trademark) and" ZEONEX ( Registered trademark) ”and“ Apel ”(registered trademark) manufactured and sold by Mitsui Chemicals, Inc.

  The protective film 40 can be obtained by forming the chain olefin resin or the cyclic olefin resin into a film. The method for forming a film is not particularly limited, but a melt extrusion film forming method is preferably employed.

  Olefin-based resin films can also be easily obtained as commercial products. For example, polypropylene resin films are sold under the trade name “FILMAX CPP film”, Sun Tox Co., Ltd. "Santox" (registered trademark) sold by Tosebo Co., Ltd., "Tosero" (registered trademark) sold by Tosero Co., Ltd., "Toyobo Pyrene (registered trademark) film" sold by Toyobo Co., Ltd., Toray Industries, Inc. Examples include “Trefan (registered trademark)” sold by Film Processing Co., Ltd. For cyclic olefin-based resin films, “ZEONOR FILM” (registered trademark) sold by Nippon Zeon Co., Ltd., “ARTON (registered trademark) film” sold by JSR Corporation, etc. Can be mentioned.

  The polyethylene terephthalate-based resin means a resin in which 80 mol% or more of repeating units are composed of ethylene terephthalate, and may include structural units derived from other copolymerization components. Other copolymer components include isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid And dicarboxylic acid components such as 1,4-dicarboxycyclohexane; propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol A diol component such as These dicarboxylic acid components and diol components can be used in combination of two or more if necessary. It is also possible to use a hydroxycarboxylic acid such as p-hydroxybenzoic acid or p-β-hydroxyethoxybenzoic acid together with the dicarboxylic acid component or diol component. As another copolymer component, a dicarboxylic acid component and / or a diol component having a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be used.

  The polycarbonate resin and the acrylic resin can be the same as the polycarbonate and poly (meth) acrylate described as the resin used for the film 20. A laminated film of polycarbonate resin and acrylic resin can also be used as the protective film 40. In this case, the acrylic resin contains rubber elastic particles as in the resin layer (a) constituting the film 20. It is preferable.

  The protective film 40 can be laminated with an optical functional film on its surface or coated with an optical functional layer. Examples of such an optical functional film and an optical functional layer include an easy adhesion layer and a conductive layer.

  If it is a form shown in FIG. 1, the resin layer (b) 25 side of this film 20 will be bonded to the polarizer 30, and the surface of the polarizer 30 opposite to the surface to which this film 20 is bonded will be The protective film 40 is bonded to obtain the polarizing plate 10. If it is a form shown in FIG. 2, the 2nd resin layer (a) 22 side of this film is bonded to the polarizer 30, and the surface on the opposite side to the surface by which this film 20 of the polarizer 30 is bonded is bonded. The protective film 40 is bonded to the polarizing plate 10. 1 and 2, the present film 20 is bonded to the polarizer 30 via the adhesive layer 51, and the protective film 40 is bonded to the polarizer 30 via the adhesive layer 52. In the bonding of the film 20 and the polarizer 30, an adhesive is applied to either the resin layer (b) 25 side or the second resin layer (a) 22 side of the film 20 and the adhesive surface of the polarizer 30. After the process, both may be bonded. In the bonding between the protective film 40 and the polarizer 30, the adhesive film is applied to one of the adhesive surfaces of the protective film 40 and the polarizer 30, and then both are bonded. What is necessary is just to paste.

[Adhesion]
Bonding of the resin layer (b) 25 or the second resin layer (a) 22 of the film 20 to the polarizer 30 or the protective film 40 of the polarizing plate, and the polarizer 30 and the protective film of the polarizing plate For bonding with 40, an adhesive is used as described above. Prior to bonding, at least one of the bonding surfaces of each film is preferably subjected to corona discharge treatment, plasma irradiation treatment, electron beam irradiation treatment, and other surface activation treatment.

  The adhesive for forming the adhesive layers 51 and 52 shown in FIG. 1 and FIG. 2 can be arbitrarily selected and used from those that exhibit an adhesive force with respect to each member. Typically, an aqueous adhesive that is one of curable adhesives, that is, an adhesive component dissolved in water or an adhesive component dispersed in water, and a component that is cured by irradiation with active energy rays An active energy ray-curable adhesive containing From the viewpoint of productivity, an active energy ray-curable adhesive is preferably used.

  Preferable aqueous adhesives include compositions containing a polyvinyl alcohol resin or a urethane resin as a main component.

  When a polyvinyl alcohol-based resin is used as the main component of the water-based adhesive, the polyvinyl alcohol-based resin includes partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and methylol. It may be a modified polyvinyl alcohol resin such as group-modified polyvinyl alcohol or amino group-modified polyvinyl alcohol. When using a polyvinyl alcohol-based resin as the adhesive component, the adhesive is often prepared as an aqueous solution of a polyvinyl alcohol-based resin. The density | concentration of the polyvinyl alcohol-type resin in adhesive agent aqueous solution is about 1-10 mass parts normally with respect to 100 mass parts of water, Preferably it is 1-5 mass parts.

  In order to improve the adhesiveness, it is preferable to add a curable component such as glyoxal or a water-soluble epoxy resin or a crosslinking agent to the water-based adhesive mainly composed of polyvinyl alcohol-based resin. Examples of water-soluble epoxy resins include polyamide polyamines obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a polycarboxylic acid such as adipic acid and epichlorohydrin. An epoxy resin can be mentioned. Examples of commercially available polyamide polyamine epoxy resins include “Smilees (registered trademark) Resin 650” and “Smiles (registered trademark) Resin 675” sold by Taoka Chemical Industry Co., Ltd., and Seiko PMC Corporation. "WS-525" and the like can be suitably used. The addition amount of these curable components or crosslinking agents is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight, with respect to 100 parts by weight of the polyvinyl alcohol resin. If the amount added is small, the effect of improving the adhesiveness is reduced, while if the amount added is large, the adhesive layer tends to be brittle.

  When a urethane resin is used as the main component of the water-based adhesive, a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group can be given as an example of a suitable adhesive composition. The polyester ionomer type urethane resin here is a urethane resin having a polyester skeleton, into which a small amount of ionic component (hydrophilic component) is introduced. Since the ionomer type urethane resin is emulsified directly in water without using an emulsifier to form an emulsion, it is suitable as an aqueous adhesive. The use of a polyester ionomer type urethane resin for adhesion between a polarizing film and a protective film is known, for example, from JP-A-2005-70139, JP-A-2005-70140, and JP-A-2005-181817. .

  On the other hand, when an activated energy ray-curable adhesive is used, a component that is cured by irradiation of an active energy ray constituting the adhesive (hereinafter sometimes simply referred to as a “curable component”) is an epoxy compound, an oktacene compound, It may be an acrylic compound. When a cationically polymerizable compound such as an epoxy compound or an okitacene compound is used, a cationic polymerization initiator is blended. Further, when a radical polymerizable compound such as an acrylic compound is used, a radical polymerization initiator is blended. Among them, an adhesive having an epoxy compound as one of the curable components is preferable, and an adhesive having an alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated hydrocarbon ring as one of the curable components is particularly preferable. . It is also effective to use an oxetane compound in combination.

  Epoxy compounds can be easily obtained from commercial products. For example, “JER (registered trademark) epoxy resin” series sold by Mitsubishi Chemical Corporation and DIC Corporation are sold under the trade names. "Epicron (registered trademark)" series, "Epototo (registered trademark)" series sold by Nippon Steel & Sumitomo Metal Corporation, "ADEKA (registered trademark) resin" series sold by ADEKA Corporation, Nagase "Denacol (registered trademark)" series sold by Chemtex Co., Ltd., "DER (registered trademark) epoxy resin" series sold by Dow Chemical Company, sold by Nissan Chemical Industries, Ltd. Such as “Tepic (registered trademark)”.

  An alicyclic epoxy compound in which an epoxy group is directly bonded to a saturated hydrocarbon ring can also be easily obtained as a commercial product, for example, sold under the trade name by Daicel Chemical Industries, Ltd. Examples include the “Celoxide (registered trademark)” series and the “Cyclomer (registered trademark)” series, and the “Syracure (registered trademark)” series sold by Dow Chemical.

  Oxetane compounds can also be easily obtained as commercial products. For example, “Aron Oxetane (registered trademark)” series sold by Toagosei Co., Ltd. and Ube Industries, Ltd. "ETERNACOLL (registered trademark)" series.

  Cationic polymerization initiators can also be easily obtained as commercial products. For example, the “Kayacure (registered trademark)” series sold by Nippon Kayaku Co., Ltd., sold by Dow Chemical Co., Ltd. "Syracure (registered trademark)" series, photo acid generators "CPI" series sold by San Apro Co., Ltd., photo acid generators "TAZ", "BBI" sold by Midori Chemical Co., Ltd. and There are “DTS”, “ADEKA (registered trademark) Optmer” series sold by ADEKA Corporation, and “RHODORSIL (registered trademark)” series sold by Rhodia.

  The active energy ray-curable adhesive can contain a photosensitizer as necessary. By using a photosensitizer, the reactivity is improved, and the mechanical strength and adhesive strength of the cured product layer can be further improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, anthracene compounds, halogen compounds, and photoreducible dyes.

  Moreover, various additives can be mix | blended with an active energy ray hardening adhesive in the range which does not impair the adhesiveness. Examples of the additive include an ion trap agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, and an antifoaming agent. Furthermore, a curable component that cures by a reaction mechanism different from cationic polymerization can be blended within a range that does not impair the adhesion.

  The active energy ray-curable adhesive described above is applied to the bonding surface of the present film 20 or the bonding surface of the polarizer 30, and after both films are bonded through the coating layer, the active energy beam is applied thereto. Is cured to form an adhesive layer 51 that joins the polarizer 30 and the film 20. Moreover, after apply | coating to the bonding surface of the polarizer 30 or the bonding surface of the protective film 40 and bonding both films through the application layer, it is hardened by irradiating an active energy ray there, and the polarizer 30 And an adhesive layer 52 to which the protective film 40 is bonded. The adhesive for forming the adhesive layer 51 and the adhesive for forming the adhesive layer 52 may have the same composition or different compositions, but the active energy for curing both It is preferable to perform the irradiation of the rays at the same time.

  The active energy ray used for curing the active energy ray-curable adhesive may be, for example, X-ray having a wavelength of 1 to 10 nm, ultraviolet light having a wavelength of 10 to 400 nm, visible light having a wavelength of 400 to 800 nm, and the like. Among these, ultraviolet rays are preferably used in terms of ease of use and ease of preparation of active energy ray-curable adhesive, stability, and curing performance. Examples of ultraviolet light sources include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, metal halide lamps, and electrodeless lamps having a light emission distribution at wavelengths of 400 nm or less. Can be used.

  The thickness of the adhesive layer obtained using the active energy ray-curable adhesive is usually about 0.1 to 50 μm, and particularly preferably in the range of 0.2 to 10 μm.

[Use of elliptical polarizing plate]
The elliptically polarizing plate 10 having the configuration shown in FIGS. 1 and 2 as a representative example can be attached to the display surface side (viewing side) of a liquid crystal cell to form a liquid crystal panel used in a liquid crystal display device. The light emitted from the light source of the liquid crystal display device is emitted to the viewer side through the elliptically polarizing plate, so that even if the viewer observes the display device through the polarized sunglasses, the display image can be observed well. can do. For example, by providing a pressure-sensitive adhesive layer on the outer side of the protective film 40 of the elliptically polarizing plate 10, that is, on the side opposite to the bonding surface with the polarizing film 30, it can be easily bonded to the liquid crystal cell. . This pressure-sensitive adhesive layer is formed of an acrylic pressure-sensitive adhesive having an acrylic ester as a main component and an acrylic resin copolymerized with a functional group-containing acrylic monomer as a pressure-sensitive adhesive component. It is common. The liquid crystal cell constituting the liquid crystal panel can be various types used in this field.

  Hereinafter, the present invention will be described in more detail with reference to examples. In the examples, “%” and “part” representing the content or the amount used are based on mass unless otherwise specified.

Examples 1-4
[Rubber elastic particles]
In rubber elastic particles, the innermost layer is composed of a hard polymer obtained by polymerizing methyl methacrylate and a small amount of allyl methacrylate, and the intermediate layer is composed of butyl acrylate as a main component, styrene, and a small amount of methacrylic acid. Three-layer rubber elastic particles A composed of a soft rubber elastic body obtained by polymerizing allyl acid and the outermost layer comprising a hard polymer obtained by polymerizing methyl methacrylate and a small amount of ethyl acrylate were used. The number average particle diameter of the rubber elastic body particles A to the rubber elastic body which is the intermediate layer was 240 nm, and the total mass of the innermost layer and the intermediate layer was 70% of the whole particles.

[Resin Composition (a) for Forming Resin Layer (a)]
A methyl methacrylate resin (“SUMIPEX (registered trademark) MH”) manufactured by Sumitomo Chemical Co., Ltd. and rubber elastic body particles A were mixed to obtain a resin composition (a). At this time, mixing was performed so that the content of the elastic rubber particles A with respect to the total amount of the resin composition (a) was 30% by mass. The mass of the rubber elastic particle A is the total mass of the innermost layer and the intermediate layer in the rubber elastic particle A.

[Resin composition (b) for forming resin layer (b)]
“Caliber (registered trademark) 301-15” manufactured by Sumika Stylon Polycarbonate Co., Ltd. was used for the resin composition (b).

  The resin composition (a) is charged into a 65 mmφ single screw extruder and the resin composition (b) is charged into a 45 mmφ single screw extruder and melted, and supplied to a multi-manifold die with a distribution pin for two types and three layers. The melt lamination was integrated and extruded through a T-shaped die having a set temperature of 260 ° C. The obtained film-like material is sandwiched and formed between a pair of metal rolls having a smooth surface, whereby the first resin layer (a), the resin layer (b), and the second resin layer (a And A to D (unstretched) were laminated in this order. At this time, by adjusting the extrusion amount of the extruder, the total thickness, the thickness of the first resin layer (a), the thickness of the resin layer (b), and the thickness of the second resin layer (a) Adjusted. Table 1 shows the thickness of each of the films A to D obtained in Examples 1 to 4. Moreover, the film E (comparative example 1) which consists only of a resin composition (b), and the film F (comparative example 2) which consists only of a resin composition (a) were manufactured by the same method.

[Example 5]
Using a tenter stretching machine, the film A was laterally stretched to obtain a retardation film A. Specifically, after heat-treating film A, heat setting is performed by performing transverse stretching of 2.8 times the unstretched film by inter-chuck stretching, and then heat-treating the film after transverse stretching. Processed. Table 2 shows the temperature conditions for each step.

[Examples 6 to 8, Comparative Examples 3 and 4]
Retardation films B to F were obtained in the same manner as in Example 5 except that the film A was changed to films B to F and the temperature conditions in each step were changed to the temperatures shown in Table 2.

The following physical properties were measured for the retardation films A to F. The results are shown in Table 3 [Total light transmittance]
Using “HAZEMETER HM-150”, the transmittance was measured in accordance with the light source D65 and the optical conditions JIS K7361.
[In-plane retardation value Re (590)]
An in-plane retardation value Re (590) at a wavelength of 590 nm was measured using a phase difference measuring device “KOBRA-WR” manufactured by Oji Scientific Instruments.
[Tensile modulus measurement]
The elastic modulus was measured by the following method with respect to the stretching direction (TD) and the direction (MD) perpendicular to the direction. A strip-shaped resin sample having a width of 2.5 cm and a length of 15 cm was prepared, and the elongation and stress in the longitudinal direction of the strip-shaped resin sample at 85 ° C. were measured using an autograph (manufactured by Shimadzu Corporation, AG-I). The elastic modulus was calculated. The test conditions were a distance between chucks of 5 cm and a pulling speed of 10 mm / min.
[Refractive index]
Using an Abbe refractometer (“DR-M2” manufactured by Atago Co., Ltd.), the refractive index at a wavelength of 590 nm was measured under the condition of a temperature of 23 ° C.
[Intrinsic birefringence]
Using the refractive index obtained by refractive index measurement, it was calculated using a phase difference measuring device “KOBRA-WR” manufactured by Oji Scientific Instruments.

  The refractive index and total light transmittance of the resin layer (a) included in the retardation films A to D are equivalent to the refractive index and total light transmittance of the retardation film F prepared as a single resin layer (a). Further, the refractive index, intrinsic birefringence and total light transmittance of the resin layer (b) of the retardation films A to D are the refractive index, intrinsic birefringence and the retardation of the retardation film E prepared as a resin layer (b) alone. It is equivalent to the total light transmittance.

  It can be seen that the retardation films A to D have high all-line transmittance, and it is difficult to reduce the luminance of the display device. Moreover, since 85 degreeC elasticity modulus of retardation film AD is high enough, when an elliptically polarizing plate is created using these films, for example, durability of an elliptically polarizing plate becomes high.

  According to the present invention, it is possible to obtain a retardation film that hardly reduces the luminance of a display device.

10 Elliptical Polarizer 20 This Film 21 First Resin Layer (a)
22 Second resin layer (a)
25 Resin layer (b)
30 Polarizer 31 Polarizing plate 40 Protective film 51, 52 Adhesive layer

Claims (12)

Resin layer (a) having a refractive index of 1.50 or less and a total light transmittance of 80% or more, a refractive index of 1.55 or more, an intrinsic birefringence of 0.07 or more, and a total light transmission A retardation film obtained by laminating a resin layer (b) having a rate of 80% or more,
A retardation film in which at least one resin layer (a) is located outside the resin layer (b).   The retardation film according to claim 1, wherein the resin layer (b) is a polycarbonate layer.   The retardation film according to claim 1, wherein the resin layer (a) is a poly (meth) acrylate layer. The retardation film in any one of Claims 1-3 which has an optical characteristic represented by following formula (1).
70 <Re (590) <320 (1)
(Re (590) represents an in-plane retardation value for light having a wavelength of 590 nm.)   The phase difference film according to any one of claims 1 to 4, wherein the volume ratio of the resin layer (b) is 30 to 95%.   The phase difference film according to claim 1, wherein the resin layer (a) contains poly (meth) acrylate and rubber elastic particles.   The retardation film according to claim 6, wherein the rubber elastic body particles have a number average particle diameter of 10 to 350 nm.   The retardation film according to claim 6 or 7, wherein the content of the rubber elastic particles in the resin layer (a) is 3% by mass or more and 60% by mass or less.   The phase difference film according to claim 1, wherein the resin layer (a), the resin layer (b), and the resin layer (a) are laminated in this order.   The retardation film according to claim 1, wherein the resin layer (a) and the resin layer (b) are stretched films.   The elliptically polarizing plate which laminated | stacked the retardation film in any one of Claims 1-7, the adhesive bond layer, and the polarizer in this order.   The elliptically polarizing plate according to claim 11, wherein the adhesive layer is a cured product of an active energy ray-curable adhesive.

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