JP7051342B2 - Polarizer - Google Patents

Description

The present invention relates to a laminate including a polarizing plate and a retardation film.

The liquid crystal display device is provided with a polarizing plate for the liquid crystal cell because of its display principle. The main body of the polarizing plate is a low-strength polarizing element layer, and a protective film that gives physical strength to the polarizing plate layer is generally laminated on one side or both sides. Various improvements have been made to the protective film in order to prevent cracks from entering the polarizing layer (see, for example, Patent Document 1).

Further, in the liquid crystal display device, various optical films other than the polarizing plate are used in order to improve visibility, viewing angle, transmittance and brightness. As for the optical film, the protective film also serves as the protective film, or is bonded to the polarizing plate as a laminated film different from the protective film.

A retardation film is mentioned as a kind of optical film. The phase difference film is a film for compensating for a phase change based on the birefringence of the liquid crystal, and is attached to the liquid crystal cell together with the polarizing plate.

JP-A-2015-11094

Similar to the polarizing layer, the retardation film is prone to cracks in a high temperature and high humidity environment or in an environment where low temperature and high temperature are repeated. In particular, the retardation film composed of a styrene polymer has low strength, which is improved. Is desired.

Therefore, the present invention provides a laminate provided with a polarizing plate and a retardation film, which is resistant to cracks in the retardation film in a high temperature and high humidity environment or an environment in which low temperature and high temperature are repeated. The purpose.

The laminate of the present invention comprises a polarizing plate and a retardation film bonded to the polarizing plate via a cured product of an active energy ray-curable resin composition, and the retardation film comprises styrene as a monomer. The retardation film has a retardation value ( _Rth ) of -30 nm or less in the thickness direction at a wavelength of 589 nm, and the active energy ray-curable resin composition is a photoradical polymerization. Contains an initiator.

According to this, it is possible to provide a laminated body in which cracks are less likely to occur in the retardation film in a high temperature and high humidity environment or an environment in which low temperature and high temperature are repeated.

In this laminated body, the polarizing plate has a polarizing film and a protective film laminated on at least one surface of the polarizing film, and the retardation film may be bonded to the protective film. Further, the thermoplastic resin may have a negative intrinsic birefringence.

The retardation film may be a single-layer film and may have a thickness of 15 μm or less. If the retardation film is a single-layer film or its thickness is 15 μm or less, the retardation film tends to be more easily broken, so that the effect of the present invention is greatly benefited.

Further, the glass transition temperature of the cured product of the active energy ray-curable resin composition may be less than 50 ° C. When the glass transition temperature of the cured product is less than 50 ° C., the retardation film is more difficult to break.

The laminate of the present invention may further include an adhesive layer on the side where the polarizing plate of the retardation film is not laminated. The pressure-sensitive adhesive is used when incorporating a polarizing plate and a retardation film into a liquid crystal display device.

According to the present invention, there is provided a laminate provided with a polarizing plate and a retardation film, wherein the retardation film is less likely to be cracked in a high temperature and high humidity environment and an environment in which low temperature and high temperature are repeated. Can be done.

It is sectional drawing of the laminated body of one Embodiment of this invention. It is sectional drawing when the laminated body is attached to a display element.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same parts or corresponding parts are designated by the same reference numerals, and duplicate description will be omitted.

<Laminated body>
As shown in FIG. 1, the laminate 10 of the present embodiment is formed by laminating a polarizing plate 1 and a retardation film 2 via a cured product 3 of an active energy ray-curable resin composition. Hereinafter, each configuration will be described in detail. In the present specification, the "laminated body" is also referred to as a "polarizing plate with a retardation film".

<Polarizer>
The polarizing plate 1 has a polarizing film 11 as its main body. The protective film 12 may be laminated on at least one surface of the polarizing film 11. The polarizing plate 1 in the present embodiment shows an embodiment in which the protective films 12 and 12 are laminated on both sides of the polarizing film 11.

(Polarizing film)
The polarizing film 11 can be a uniaxially stretched layer of a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented. Generally, when the thickness of the polarizing film 11 is 20 μm or less, the polarizing plate can be thinned. The thickness of the polarizing film 11 is preferably 10 μm or less, more preferably 8 μm or less. The thickness of the polarizing film 11 may be, for example, 3 μm or more.

As the above-mentioned polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamide having an ammonium group.

The degree of saponification of the polyvinyl alcohol-based resin can be in the range of 80 mol% or more, preferably in the range of 90 to 99.5 mol%, and more preferably in the range of 94 to 99 mol%. The polyvinyl alcohol-based resin may be a partially modified modified polyvinyl alcohol. For example, the polyvinyl alcohol-based resin may be an olefin such as ethylene and propylene; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid and crotonic acid. ; Examples include those modified with an alkyl ester of unsaturated carboxylic acid and acrylamide. The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10000, more preferably 1500 to 8000, and further preferably 2000 to 5000.

The dichroic dye contained (adsorption orientation) in the polarizing film 11 can be iodine or a dichroic organic dye, and conventionally known dyes can be used. As the dichroic dye, only one kind may be used alone, or two or more kinds may be used in combination.

(Protective film)
The protective film 12 is a film for supporting the polarizing film 11 having low mechanical strength. A protective film (first protective film) 12 is laminated on one side of the polarizing film 11, and another protective film (second protective film) 12 is laminated on the other side. As the second protective film 12, the same one as the first protective film 12 may be used, or another resin film may be used.

The first protective film 12 and the second protective film 12 can each be a transparent resin film made of a thermoplastic resin. Examples of the thermoplastic resin include polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins such as polypropylene resins; cellulose ester resins such as cellulose triacetate and cellulose diacetate; polyethylene terephthalates and polyethylene naphthalates. And polyester resins such as polybutylene terephthalate; polycarbonate resins; (meth) acrylic resins; or mixtures, copolymers and the like thereof.

Cyclic polyolefin resin is a general term for resins that are usually polymerized using a cyclic olefin as a polymerization unit. Examples thereof include resins that have been polymerized. Specific examples of the cyclic polyolefin resin include a ring-opened (co) polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a chain olefin such as ethylene and propylene and a cyclic olefin (typically). Random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among them, a norbornene-based resin using a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer is preferably used as the cyclic olefin.

Various products of the cyclic polyolefin resin are commercially available. Examples of commercially available cyclic polyolefin resins are "TOPAS" (registered trademark) and JSR (registered trademark), which are produced under TOPAS ADVANCED POLYMERS GmbH and sold by Polyplastics Co., Ltd. in Japan. "Arton" (registered trademark) sold by Japan Zeon Co., Ltd., "Zeonoa" (registered trademark) and "Zeonex" (registered trademark) sold by Nippon Zeon Co., Ltd., and Mitsui Chemicals Co., Ltd. There is "Apel" (registered trademark).

Further, a commercially available product of the formed cyclic polyolefin resin film may be used as the protective film. Examples of commercial products are "Arton Film" sold by JSR Co., Ltd. ("Arton" is a registered trademark of the company) and "Scina" sold by Sekisui Chemical Co., Ltd. "(Registered trademark) and" SCA40 "," Zeonoa film "(registered trademark) sold by Zeon Corporation, and the like.

The above-mentioned cellulose ester-based resin is usually an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, those obtained by copolymerizing these groups or those in which a part of the hydroxyl group is modified with another substituent can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available products of cellulose triacetate are all trade names, "Fujitac (registered trademark) TD80", "Fujitac (registered trademark) TD80UF", and "Fujitac (registered trademark) TD80UZ" sold by FUJIFILM Corporation. , "Fujitac (registered trademark) TD40UZ", TAC film "KC8UX2M", "KC2UA" and "KC4UY" manufactured by Konica Minolta Co., Ltd.

The above (meth) acrylic resin is usually a polymer mainly composed of a methacrylic acid ester. The methacrylic resin may be a homopolymer of one kind of methacrylic acid ester, or may be a copolymer of a methacrylic acid ester and another methacrylic acid ester, an acrylic acid ester, or the like. Examples of the methacrylic acid ester include alkyl methacrylates such as methyl methacrylate, ethyl methacrylate and butyl methacrylate, and the alkyl group thereof usually has about 1 to 4 carbon atoms. Further, cycloalkyl methacrylate such as cyclopentyl methacrylate, cyclohexyl methacrylate and cycloheptyl methacrylate, aryl methacrylate such as phenyl methacrylate, cycloalkylalkyl methacrylate such as cyclohexylmethyl methacrylate, and aralkyl methacrylate such as benzyl methacrylate. Can also be used.

Examples of the above-mentioned other polymerizable monomers that can constitute the (meth) acrylic resin include acrylic acid esters and polymerizable monomers other than methacrylic acid esters and acrylic acid esters. As the acrylic acid ester, an acrylic acid alkyl ester can be used, and specific examples thereof include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, and acrylic. Includes an acrylic acid alkyl ester having 1 to 8 carbon atoms in an alkyl group such as t-butyl acid, 2-ethylhexyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate. The number of carbon atoms of the alkyl group is preferably 1 to 4. In the (meth) acrylic resin, only one type of acrylic acid ester may be used alone, or two or more types may be used in combination.

Examples of the polymerizable monomer other than the methacrylic acid ester and the acrylic acid ester include a monofunctional monomer having one polymerizable carbon-carbon double bond in the molecule and a polymerizable carbon-carbon double bond in the molecule. A polyfunctional monomer having at least two of these can be mentioned, but a monofunctional monomer is preferably used. Specific examples of the monofunctional monomer include styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene, halogenated styrene, and hydroxystyrene; vinyl cyanide such as acrylonitrile and methacrylonitrile; acrylic acid, methacrylic acid, and anhydrous. Unsaturated acids such as maleic acid and itaconic anhydride; maleimides such as N-methylmaleimide, N-cyclohexylmaleimide and N-phenylmaleimide; allyl alcohols such as metallical alcohol and allyl alcohol; vinyl acetate, vinyl chloride, ethylene and propylene. , 4-Methyl-1-pentene, 2-hydroxymethyl-1-butene, methylvinylketone, N-vinylpyrrolidone, N-vinylcarbazole and other monomers.

Specific examples of the polyfunctional monomer include polyunsaturated carboxylic acid esters of polyhydric alcohols such as ethylene glycol dimethacrylate, butanediol dimethacrylate, and trimethylolpropane triacrylate; allyl acrylate, allyl methacrylate, and allyl silicate. Alkenyl esters of unsaturated carboxylic acids such as; polyalkenyl esters of polybasic acids such as diallyl phthalate, diallyl maleate, triallyl cyanurate, triallyl isocyanurate, and aromatic polyalkenyl compounds such as divinylbenzene. As the polymerizable monomer other than the methacrylic acid ester and the acrylic acid ester, only one kind may be used alone, or two or more kinds may be used in combination.

The preferable monomer composition of the (meth) acrylic resin is 50 to 100% by weight of methacrylic acid alkyl ester, 0 to 50% by weight of acrylic acid alkyl ester, and 0 to 0 to other polymerizable monomers based on the total amount of monomers. It is 50% by weight, more preferably 50 to 99.9% by weight of methacrylic acid alkyl ester, 0.1 to 50% by weight of acrylic acid alkyl ester, and 0 to 49.9% by weight of other polymerizable monomers. be.

Further, the (meth) acrylic resin may have a ring structure in the polymer main chain because the durability of the film can be enhanced. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure, or a lactone ring structure. Specific examples thereof include a cyclic acid anhydride structure such as a glutaric anhydride structure and a succinic anhydride structure, a cyclic imide structure such as a glutarimide structure and a succinic anhydride structure, and a lactone ring structure such as butyrolactone and valerolactone. The glass transition temperature of the (meth) acrylic resin can be increased by increasing the content of the ring structure in the main chain. A cyclic acid anhydride structure or a cyclic imide structure is introduced by a method of introducing by copolymerizing a monomer having a cyclic structure such as maleic anhydride or maleimide, and a cyclic acid anhydride structure is introduced by a dehydration / demethanol condensation reaction after polymerization. It can be introduced by a method, a method of reacting an amino compound to introduce a cyclic imide structure, or the like. For a resin (polymer) having a lactone ring structure, after preparing a polymer having a hydroxyl group and an ester group in a polymer chain, the hydroxyl group and the ester group in the obtained polymer are required by heating. Accordingly, it can be obtained by a method of forming a lactone ring structure by cyclization condensation in the presence of a catalyst such as an organic phosphorus compound.

Polymers having a hydroxyl group and an ester group in the polymer chain include, for example, methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2-. It can be obtained by using a (meth) acrylic acid ester having a hydroxyl group and an ester group such as n-butyl (hydroxymethyl) acrylate and t-butyl 2- (hydroxymethyl) acrylate as a part of the monomer. .. A more specific method for preparing a polymer having a lactone ring structure is described in, for example, Japanese Patent Application Laid-Open No. 2007-254726.

A (meth) acrylic resin can be prepared by radically polymerizing a monomer composition containing the above-mentioned monomers. The monomer composition may contain a solvent and a polymerization initiator, if necessary.

The first protective film 12 and the second protective film 12 can also be protective films having an optical function such as a luminance improving film.

The brightness improving film is used for the purpose of improving the brightness in a liquid crystal display device or the like, and as an example, a plurality of thin films having different refractive indices are laminated so that the reflectance becomes anisotropic. Examples thereof include a reflective polarizing separation sheet designed in the above, an alignment film of a cholesteric liquid crystal polymer, and a circular polarization separation sheet in which the oriented liquid crystal layer is supported on a film substrate.

The surfaces of the first protective film 12 and the second protective film 12 on the opposite side of the polarizing film 11 are surface-treated layers (coatings) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer. Layers) can also be formed. As a method for forming the surface treatment layer on the surface of the protective film, a known method can be used.

The first protective film 12 and the second protective film 12 may be the same protective film or different protective films. Examples of cases where the protective films are different are combinations in which the types of thermoplastic resins constituting the protective film are at least different; presence / absence of optical function of the protective film or at least different combinations in the type; presence / absence of a surface treatment layer formed on the surface. Or there are at least different combinations in the type.

The thickness of the first protective film 12 and the second protective film 12 is preferably thin from the viewpoint of thinning the polarizing plate 1, but if it is too thin, the strength is lowered and the processability is inferior. Therefore, the thickness of the first protective film and the second protective film is preferably 5 to 90 μm or less, more preferably 60 μm or less, still more preferably 50 μm or less.

(Photo-curing adhesive)
A photocurable adhesive can be used as an adhesive for adhering the polarizing film 11 and the protective film 12. The photocurable adhesive contains (A) a photocationic curable component and (B) a photocationic polymerization initiator. The photocurable adhesive adheres the polarizing film 11 and the protective film 12 to form a cured product 13 (see FIG. 1).

(A) Photocationic Curable Component The photocationic curable component (A), which is the main component of the photocurable adhesive and imparts adhesive strength by polymerization curing, contains the following three types of compounds.
(A1) An alicyclic diepoxy compound represented by the following formula (I),
(A2) Weight consisting of the diglycidyl compound represented by the following formula (II) and (A3) at least one ethylenically unsaturated monomer selected from the monomers represented by the following formula (III) or (IV). A polymer with an average molecular weight of 5000 to 100,000.

In the formula, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and when the alkyl group has 3 or more carbon atoms, it may have an alicyclic structure. X represents an oxygen atom, an alkanediyl group having 1 to 6 carbon atoms, or a divalent group represented by any of the following formulas (Ia) to (Id).

In the formula, Y ¹ to Y ⁴ independently represent an alkanediyl group having 1 to 20 carbon atoms, and when the number of carbon atoms is 3 or more, they may have an alicyclic structure. a and b each independently represent an integer of 0 to 20.

In the formula, Z represents an alkylene group having 1 to 9 carbon atoms, an alkylidene group having 3 or 4 carbon atoms, or a divalent alicyclic hydrocarbon group, and the methylene group in the alkylene group is an oxygen atom. It may be interrupted on a divalent group represented by -CO-O-, -O-CO-, -SO _2- , -SO- or -CO-.

In the formula, X is an alkyl group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or a part of these functional groups. It is substituted with one or more groups selected from the group consisting of an epoxy group, an oxetane group, a hydroxyl group and a carboxyl group.

In the formula, R ₃ represents a hydrogen atom, a methyl group or a halogen atom, and X is the same as the above formula (III).

(A1) Alicyclic Diepoxy Compound The amount of the alicyclic diepoxy compound (A1) in the photocationic curable component (A) is 10 to 60% by weight based on the total amount of the photocationic curable component (A). .. By containing 10% by weight or more of the alicyclic diepoxy compound (A1) in the photocationic curable component (A), the reactivity of the cationic polymerization becomes high and the curability is excellent. On the other hand, when the amount exceeds 60% by weight, the amount of the polymer (A3) composed of the diglycidyl compound (A2) and the ethylenically unsaturated monomer described below becomes relatively small, which is the embodiment of the present embodiment. It becomes difficult to reduce the viscosity of the photocurable adhesive and improve the adhesion between the polarizing film and the protective film.

In the above formula (I) representing the alicyclic diepoxy compound (A1), R ¹ and R ² are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, but the alkyl group has 3 or more carbon atoms. In some cases, it may have an alicyclic structure. This alkyl group has the position of the cyclohexane ring bonded to X in the formula (I) at the 1-position (therefore, the positions of the epoxy groups on the two cyclohexane rings are both at the 3- and 4-positions) and are at the 1-position. It can be coupled to any of the ~ 6-positions. Of course, this alkyl group may be linear or may be branched when it has 3 or more carbon atoms. Further, as described above, when the number of carbon atoms is 3 or more, it may have an alicyclic structure. Typical examples of alkyl groups having an alicyclic structure include cyclopentyl and cyclohexyl.

Similarly, in the formula (I), X connecting the two 3,4-epoxycyclohexane rings is represented by an oxygen atom, an alkanediyl group having 1 to 6 carbon atoms, or any of the above formulas (Ia) to (Id) 2. It is the basis of the value. Here, the alkanediyl group is a concept including alkylene and alkylidene, and the alkylene may be linear or may be branched when the number of carbon atoms is 3 or more.

When X is a divalent group represented by any of the above formulas (Ia) to (Id), the linking groups Y ¹ , Y ² , Y ³ and Y ⁴ in each formula have 1 to 1 carbon atoms, respectively. It is an alkanediyl group of 20, and when this alkanediyl group has 3 or more carbon atoms, it may have an alicyclic structure. Of course, these alkanediyl groups may be linear, or may be branched when the number of carbon atoms is 3 or more. Further, as described above, when the number of carbon atoms is 3 or more, it may have an alicyclic structure. Typical examples of alkanediyl groups having an alicyclic structure are cyclopentylene and cyclohexylene.

Specifically, the alicyclic diepoxy compound (A1) represented by the formula (I) will be specifically described. X in the formula (I) is a divalent group represented by the above formula (Ia), and a in the formula is The compounds of 0 are 3,4-epoxycyclohexylmethanol (an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring) and 3,4-epoxycyclohexanecarboxylic acid (carbon to the cyclohexane ring). It is an esterified product with (may be bonded to an alkyl group of number 1 to 6). As a specific example thereof, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate [formula (I) (where X is a divalent group represented by the formula (Ia) where a = 0)). In formula (I) having the same X as above, R ¹ = R ² = H compound], 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate. R ¹ = 6-methyl, R ² = 6-methyl compound], 3,4-epoxy-1-methylcyclohexylmethyl-3,4-epoxy-1-methylcyclohexanecarboxylate [formula with the same X as above (same as above) In I), R ¹ = 1-methyl, R ² = 1-methyl compound], 3,4-epoxy-3-methylcyclohexylmethyl-3,4-epoxy-3-methylcyclohexanecarboxylate [same as above X]. In the formula (I) having, R ¹ = 3-methyl, R ² = 3-methyl compound] and the like can be mentioned.

The compound in which X in the formula (I) is a divalent group represented by the above formula (Ib) may have an alkyl group bonded to alkylene glycols and 3,4-epoxycyclohexanecarboxylic acids (the cyclohexane ring thereof). ) Is an esterified product. The compound in which X in the formula (I) is a divalent group represented by the above formula (Ic) may have an alkyl group bonded to an aliphatic dicarboxylic acid and 3,4-epoxycyclohexylmethanol (the cyclohexane ring thereof). ) Is an esterified product. Further, the compound in which X in the formula (I) is a divalent group represented by the above formula (Id) is an ether of 3,4-epoxycyclohexylmethanol (an alkyl group may be bonded to the cyclohexane ring thereof). A compound (b> 0) of the body (when b = 0) or an etherified product of alkylene glycols or polyalkylene glycols and 3,4-epoxycyclohexylmethanol (an alkyl group may be bonded to the cyclohexane ring thereof). In the case of).

(A2) Diglycidyl compound The amount of the diglycidyl compound (A2) in the photocationic curable component (A) is 20 to 75% by weight based on the total amount of the photocationic curable component (A). By blending 20% by weight or more of the diglycidyl compound (A2) in the photocationic curable component (A), the viscosity of the photocurable adhesive at 25 ° C. can be adjusted to 2 to 300 mPa · s. On the other hand, if the amount exceeds 75% by weight, the adhesive force between the polarizing element and the protective film becomes insufficient.

From the viewpoint of viscosity adjustment, it is preferable that the amount of the diglycidyl compound (A2) exceeds 50% by weight with respect to the total amount of the alicyclic diepoxy compound (A1) and the diglycidyl compound (A2).

In the above formula (II) representing the diglycidyl compound (A2), Z is an alkylene group having 1 to 9 carbon atoms, an alkylidene group having 3 or 4 carbon atoms, a divalent alicyclic hydrocarbon group, SO ₂ , SO or It is CO. Typical examples of divalent alicyclic hydrocarbon groups are cyclopentylene and cyclohexylene.

The compound in which Z is an alkylene group in the formula (II) is a diglycidyl ether of an alkylene glycol. Specific examples thereof include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,3-propanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, and 1,6-hexanediol diglycidyl ether. be.

(A3) Polymer made of ethylenically unsaturated monomer The amount of polymer (A3) made of at least one kind of ethylenically unsaturated monomer is 5 to 50 based on the total amount of the photocationically curable component (A). It is% by weight, preferably 7 to 30% by weight. By blending 5% by weight or more of the polymer (A3) in the photocationic curable component (A), the viscosity of the photocurable adhesive can be lowered, and good coatability can be imparted to the photocurable adhesive. , The effect of increasing the adhesive force between the polarizing element and the protective film can be exhibited. On the other hand, if the amount exceeds 50% by weight, the viscosity becomes high, which is not preferable.

The polymer (A3) composed of at least one ethylenically unsaturated monomer polymerizes at least one ethylenically unsaturated monomer selected from the monomers represented by the above formula (III) or (IV). Obtained by The weight average molecular weight is 5000 to 100,000.

X in the above formulas (III) and (IV) is
(I) An alkyl group having 1 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or
(Ii) Alkyl group having 1 to 7 carbon atoms and aryl having 6 to 12 carbon atoms partially substituted with one or more groups selected from the group consisting of an epoxy group, an oxetane group, a hydroxyl group and a carboxyl group. Represents a group or an alicyclic hydrocarbon group having 6 to 10 carbon atoms.

Alkyl groups having 1 to 7 (preferably 1 to 4) carbon atoms include methyl, ethyl, propyl, iso-propyl, butyl, sec-butyl, tert-butyl, iso-butyl, amyl, iso-amyl and tert. -Amil, hexyl, 2-hexyl, 3-hexyl, cyclohexyl, 4-methylcyclohexyl, heptyl, 2-heptyl, 3-heptyl, iso-heptyl, tert-heptyl and the like can be mentioned. Among these, a methyl group or a branched alkyl group having 2 to 4 carbon atoms, or a methyl group partially substituted with one or more groups selected from the group consisting of an epoxy group, an oxetane group, a hydroxyl group and a carboxyl group. Alternatively, a branched alkyl group having 2 to 4 carbon atoms is preferable from the viewpoint of film durability.

Examples of the aryl group having 6 to 12 carbon atoms (preferably 6 to 10) include phenyl, methylphenyl, naphthyl and the like.

Examples of the alicyclic hydrocarbon group having 6 to 10 carbon atoms include cyclohexyl, methylcyclohexyl, norbornyl, bicyclopentyl, bicyclooctyl, trimethylbicycloheptyl, tricyclooctyl, tricyclodecanyl, spirooctyl, and spirobicyclopentyl. , Adamantyl, isobornyl and the like.

In the above formula (III), the ethylenically unsaturated monomer represented by the formula (III) in the case where a part of X is substituted with an epoxy group or an oxetane group is, for example, the following formulas (1) to Examples thereof include the monomer represented by (3).

(In the formula, R ₄ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and m is an integer of 1 to 6).

(In the formula, R ₅ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and n is an integer of 1 to 6).

(In the formula, R ₆ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and s is an integer of 1 to 6).

In the above formula (IV), examples of the halogen atom that can be R ₃ include fluorine, chlorine, bromine, and iodine.

In the above formula (IV), the ethylenically unsaturated monomer represented by the formula (IV) in the case where a part of X is substituted with an epoxy group or an oxetane group is described in the following formulas (4) to (4).
The one represented by (6) can be mentioned.

(In the formula, R ₃ is the same as the above formula (IV), R ₇ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and t is an integer of 1 to 6).

(In the formula, R ₃ is the same as the above formula (IV), R ₈ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and x is an integer of 1 to 6).

(In the formula, R ₃ is the same as the above formula (IV), R ₉ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and y is an integer of 1 to 6).

The ethylenically unsaturated monomer is
The X is a methyl group partially substituted with one or more groups selected from the group consisting of an epoxy group, an oxetane group and a hydroxyl group, a branched alkyl group having 2 to 7 carbon atoms, and 6 to 12 carbon atoms. , Or an alicyclic hydrocarbon group having 6 to 10 carbon atoms, preferably containing an ethylenically unsaturated monomer represented by the above formula (III) or (IV).

Further, the ethylenically unsaturated monomer is used.
(I) When the above X is a methyl group, a branched alkyl group having 2 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alicyclic hydrocarbon group having 6 to 10 carbon atoms. , 20-90% by weight of the ethylenically unsaturated monomer represented by the above formula (III) or (IV).
(Ii) The above X is a methyl group partially substituted with one or more groups selected from the group consisting of an epoxy group, an oxetane group and a hydroxyl group, a branched alkyl group having 2 to 7 carbon atoms, and a number of carbon atoms. 10 to 80 weight by weight of the ethylenically unsaturated monomer represented by the above formula (III) or (IV) in the case of an aryl group of 6 to 12 or an alicyclic hydrocarbon group having 6 to 10 carbon atoms. It is preferable to include%.

The weight average molecular weight of the polymer (A3) is 5,000 to 100,000, preferably 7,000 to 70,000.

It is preferable that the glass transition temperature (Tg) of the polymer (A3) is 40 ° C. or higher from the viewpoint of film durability.

The photocationic curable component (A) constituting the photocurable adhesive is a polymer (A3) composed of the above-mentioned alicyclic diepoxy compound (A1), diglycidyl compound (A2), and ethylenically unsaturated monomer. Are contained in the above-mentioned ratios. In order to further effectively reduce the viscosity of the photocurable adhesive before curing and improve the adhesion between the stator and the protective film, the alicyclic type is based on the total amount of the photocurable adhesive. It is preferable that the total amount of the diepoxy compound (A1) and the polymer (A3) composed of the ethylenically unsaturated monomer is 25% by weight or more.

(Other photocationic curable components)
The photocationic curable component (A) may be another polymer (A3) composed of an alicyclic diepoxy compound (A1), a diglycidyl compound (A2) and an ethylenically unsaturated monomer, as long as the above amount is used. The photocationic curable component may be contained in an amount of 1 to 30 parts by weight with respect to 100 parts by weight of the photocationic curable component. Here, "100 parts by weight of the photocationic curable component" refers to the weight not including "other photocationic curable components".

Examples of other photocationic curable components include epoxy compounds other than (A1) to (A3), oxetane compounds, cyclic lactone compounds, cyclic acetal compounds, cyclic thioether compounds, spiro-ortho ester compounds, vinyl compounds and the like.

Examples of the vinyl compound include aliphatic or alicyclic vinyl ether compounds, for example, n-amyl vinyl ether, i-amyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, 2-ethylhexyl vinyl ether, and n-dodecyl vinyl ether. , Stearyl vinyl ethers, oleyl vinyl ethers and other vinyl ethers having 5 to 20 carbon atoms or alkenyl alcohols, 2-hydroxyethyl vinyl ethers, 3-hydroxypropyl vinyl ethers, 4-hydroxybutyl vinyl ethers and other hydroxyl group-containing vinyl ethers, cyclohexyl vinyl ethers, 2- Monoalcohol vinyl ethers having an aliphatic ring or aromatic ring such as methylcyclohexylvinyl ether, cyclohexylmethylvinyl ether, benzylvinyl ether, glycerol monovinyl ether, 1,4-butanediol monovinyl ether, 1,4-butanediol divinyl ether, 1 , 6-Hexanediol divinyl ether, neopentyl glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol tetravinyl ether, trimethylolpropane divinyl ether, trimethylolpropanetrivinyl ether, 1,4-dihydroxycyclohexanemonovinyl ether, 1,4-dihydroxy Polyhydric alcohols such as cyclohexane divinyl ether, 1,4-dihydroxymethylcyclohexane monovinyl ether, 1,4-dihydroxymethylcyclohexanedivinyl ether, mono-polyvinyl ethers, diethylene glycol divinyl ether, triethylene glycol divinyl ether, diethylene glycol monobutyl monovinyl ether. Examples thereof include polyalkylene glycol mono-divinyl ethers such as, glycidyl vinyl ether, and other vinyl ethers such as ethylene glycol vinyl ether methacrylate.

(B) Photocationic Polymerization Initiator In a photocurable adhesive, the above-mentioned cationically polymerizable compounds are cured by cationic polymerization by irradiation with active energy rays to form an adhesive layer, and thus photocationic curable. The photocationic polymerization initiator (B) is added to the component (A) (hereinafter, also referred to as “cationically polymerizable compound (A)”). The photocationic polymerization initiator (B) generates a cationic species or Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates the polymerization reaction of the cationically polymerizable compound (A). It is something to do. Since the photocationic polymerization initiator acts catalytically with light, it is excellent in storage stability and workability even when mixed with the cationically polymerizable compound (A). Examples of compounds that generate cation species and Lewis acids by irradiation with active energy rays include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; and iron-allene complexes.

Examples of the aromatic diazonium salt include, for example.
Benzenediazonium hexafluoroantimonate,
Benzenediazonium hexafluorophosphate,
Benzenediazonium hexafluoroborate can be mentioned.

Examples of aromatic iodonium salts include, for example.
Diphenyliodonium Tetrakis (Pentafluorophenyl) Borate,
Diphenyliodonium hexafluorophosphate,
Diphenyliodonium hexafluoroantimonate,
Di (4-nonylphenyl) iodonium hexafluorophosphate may be mentioned.

Examples of the aromatic sulfonium salt include, for example.
Triphenylsulfonium hexafluorophosphate,
Triphenylsulfonium hexafluoroantimonate,
Triphenylsulfonium tetrakis (pentafluorophenyl) borate,
4,4'-Bis [Diphenyl Sulfonio] Diphenyl Sulfide Bishexafluorophosphate,
4,4'-Bis [di (β-hydroxyethoxy) phenylsulfonio] diphenylsulfide bishexafluoroantimonate,
4,4'-Bis [di (β-hydroxyethoxy) phenylsulfonio] diphenylsulfide bishexafluorophosphate,
7- [di (p-toluyl) sulfonate] -2-isopropylthioxanthone hexafluoroantimonate,
7- [di (p-toluyl) sulfonate] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate,
4-Phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide hexafluorophosphate,
4- (p-tert-Butylphenylcarbonyl) -4'-diphenylsulfonio-diphenylsulfide hexafluoroantimonate,
Examples thereof include 4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonate-diphenylsulfide tetrakis (pentafluorophenyl) borate.

Examples of the iron-allene complex include, for example.
Xylene-Cyclopentadienyl Iron (II) Hexafluoroantimonate,
Cumene-Cyclopentadienyl Iron (II) Hexafluorophosphate,
Examples thereof include xylene-cyclopentadienyl iron (II) tris (trifluoromethylsulfonyl) metanide.

These photocationic polymerization initiators may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorption characteristics even in the wavelength region near 300 nm, and thus can give a cured product having excellent curability and good mechanical strength and adhesive strength. Be done.

The blending amount of the photocationic polymerization initiator (B) is 1 to 10 parts by weight with respect to 100 parts by weight of the entire cationically polymerizable compound (A). By blending 1 part by weight or more of the photocationic polymerization initiator (B) per 100 parts by weight of the cationically polymerizable compound (A), the cationically polymerizable compound (A) can be sufficiently cured, and the obtained polarizing plate can be obtained. Gives high mechanical strength and adhesive strength. On the other hand, if the amount is large, the amount of ionic substances in the cured product increases, which increases the hygroscopicity of the cured product and may reduce the durability of the polarizing plate. Therefore, the photocationic polymerization initiator (B) ) Is 10 parts by weight or less per 100 parts by weight of the cationically polymerizable compound (A). The blending amount of the photocationic polymerization initiator (B) is preferably 2 parts by weight or more, and preferably 6 parts by weight or less per 100 parts by weight of the cationically polymerizable compound (A).

The photocurable adhesive may contain a photosensitizer in addition to the cationically polymerizable compound (A) containing the epoxy compound and the photocationic polymerization initiator (B) as described above. The photocationic polymerization initiator (B) exhibits maximum absorption at a wavelength near 300 nm or shorter, and generates a cationic species or Lewis acid in response to light at a wavelength near that, and is a cationically polymerizable compound (A). ), But the photosensitizer is preferably a light sensitizer that exhibits maximum absorption in light having a wavelength longer than 380 nm so as to be sensitive to light having a wavelength longer than that. As such a photosensitizer, an anthracene-based compound is preferably used.

Specific examples of anthracene compounds include
9,10-dimethoxyanthracene,
9,10-diethoxyanthracene,
9,10-Dipropoxyanthracene,
9,10-diisopropoxyanthracene,
9,10-Dibutoxyanthracene,
9,10-Dipentyloxyanthracene,
9,10-dihexyloxyanthracene,
9,10-Bis (2-methoxyethoxy) anthracene,
9,10-Bis (2-ethoxyethoxy) anthracene,
9,10-Bis (2-butoxyethoxy) anthracene,
9,10-Bis (3-butoxypropoxy) anthracene,
2-Methyl or 2-Ethyl-9,10-dimethoxyanthracene,
2-Methyl or 2-Ethyl-9,10-diethoxyanthracene,
2-Methyl or 2-Ethyl-9,10-dipropoxyanthracene,
2-Methyl or 2-Ethyl-9,10-diisopropoxyanthracene,
2-Methyl or 2-Ethyl-9,10-dibutoxyanthracene,
2-Methyl or 2-Ethyl-9,10-dipentyloxyanthracene,
Examples include 2-methyl or 2-ethyl-9,10-dihexyloxyanthracene.

By blending the above-mentioned photosensitizer with the photocurable adhesive, the curability of the adhesive is improved as compared with the case where it is not blended. Such an effect is exhibited by setting the blending amount of the photosensitizer with respect to 100 parts by weight of the cationically polymerizable compound (A) constituting the photocurable adhesive to 0.1 parts by weight or more. On the other hand, if the blending amount of the photosensitizer is large, problems such as precipitation during low temperature storage occur. Therefore, the amount thereof should be 2 parts by weight or less with respect to 100 parts by weight of the cationically polymerizable compound (A). From the viewpoint of maintaining the neutral gray of the polarizing plate, it is advantageous to reduce the amount of the photosensitizer to be blended within a range in which the adhesive force between the polarizing element and the protective film is appropriately maintained. For example, it is cationically polymerizable. The amount of the photosensitizer is preferably in the range of 0.1 to 0.5 parts by weight, more preferably 0.1 to 0.3 parts by weight, based on 100 parts by weight of the compound (A).

Further, the photocurable adhesive of the present embodiment may contain an additive component as another component which is an optional component as long as the effect of the present embodiment is not impaired. Additive components include thermal cationic polymerization initiators, polyols, ion trapping agents, antioxidants, photostabilizers, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow modifiers, plasticizers, and defoamers. Foaming agents, leveling agents, dyes, organic solvents and the like can be blended.

When the additive component is contained, the amount of the additive component used is preferably 1000 parts by weight or less with respect to 100 parts by weight of the above-mentioned photocationic curable component (A). When the amount used is 1000 parts by weight or less, the storage stability is obtained by the combination of the photocationic curable component (A) and the photocationic polymerization initiator (B), which are essential components of the photocurable adhesive of the present embodiment. It is possible to satisfactorily exert the effects of improving the quality, preventing discoloration, improving the curing speed, and ensuring good adhesiveness.

<Phase difference film>
The retardation film 2 contains a thermoplastic resin, and the thermoplastic resin may be a homopolymer or a copolymer.

When the thermoplastic resin is a copolymer, it shall be composed of a monomer component containing an aromatic vinyl monomer, a (meth) acrylic acid ester monomer, and an unsaturated dicarboxylic acid anhydride monomer. Is preferable. That is, the copolymer is preferably a copolymer of a monomer component containing an aromatic vinyl monomer, a (meth) acrylic acid ester monomer, and an unsaturated dicarboxylic acid anhydride monomer. In other words, the copolymer preferably contains an aromatic vinyl monomer unit, a (meth) acrylic acid ester monomer unit, and an unsaturated dicarboxylic acid anhydride monomer unit. .. The retardation film 2 may be composed of only the above-mentioned copolymer.

Hereinafter, each monomer component constituting the above-mentioned copolymer will be described.

Examples of the aromatic vinyl monomer (hereinafter, may be referred to as component (a)) include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, and p-. Examples thereof include monomers such as tert-butyl styrene, α-methyl styrene, and α-methyl-p-methyl styrene. These can be used alone or in combination of two or more. From the viewpoint of easy availability and handleability, it is preferable to use styrene.

Examples of the (meth) acrylic acid ester monomer (hereinafter, may be referred to as component (b)) include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, dicyclopentanyl methacrylate, and isobornyl methacrylate. Examples thereof include methacrylic acid ester monomers such as, and acrylic acid ester monomers such as methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, and decyl acrylate. These can be used alone or in combination of two or more. From the viewpoint of easy availability and handleability, it is preferable to use methyl methacrylate.

As the unsaturated dicarboxylic acid anhydride monomer (hereinafter, may be referred to as the component (c)), an anhydride monomer such as maleic acid anhydride, itaconic acid anhydride, citraconic acid anhydride, and aconitic acid anhydride. Can be mentioned. These can be used alone or in combination of two or more. From the viewpoint of easy availability and handleability, it is preferable to use maleic anhydride.

The copolymer in the present embodiment may be composed of a monomer component consisting of only the above-mentioned component (a), (b) and (c), and may be copolymerized with the above-mentioned monomer component. It may contain a monomer component (hereinafter, may be referred to as a component (d)). Further, the copolymer may be composed of a monomer component consisting only of the above component (a).

Examples of the component (d) include vinyl cyanide monomers such as acrylonitrile and methacrylonitrile, vinyl carboxylic acid monomers such as acrylic acid and methacrylic acid, N-methylmaleimide, N-ethylmaleimide, and N-butyl. Examples thereof include N-alkylmaleimide monomer such as maleimide and N-cyclohexylmaleimide, and N-arylmaleimide monomer such as N-phenylmaleimide, N-methylphenylmaleimide and N-chlorphenylmaleimide. These can be used alone or in combination of two or more.

The content of the aromatic vinyl monomer (component (a)) is preferably 55% by mass or more, and preferably 65% by mass or more, based on the total amount of the monomer components constituting the copolymer. More preferred. (A) When the content of the component is not more than the above lower limit value, the optical characteristics of the retardation film, particularly the negative birefringence, are likely to be improved. Further, when the content of the component (a) is at least the above lower limit value, the thermal stability of the copolymer is likely to be improved, and the appearance defect of the film is likely to be suppressed during the extrusion molding step. The content of the component (a) is preferably 85% by mass or less, more preferably 83% by mass or less, based on the total amount of the monomer components constituting the copolymer. (A) When the content of the component is not more than the above upper limit value, the heat resistance and mechanical strength of the retardation film are likely to be improved. Here, "heat resistance" means that the phase difference (particularly, the phase difference in the thickness direction) in the retardation film is unlikely to change in a high temperature environment.

The content of the (meth) acrylic acid ester monomer (component (b)) is preferably 5% by mass or more, preferably 7% by mass or more, based on the total amount of the monomer components constituting the copolymer. It is more preferable to have. (B) When the content of the component is at least the above lower limit value, the transparency and mechanical strength of the retardation film are likely to be improved. The content of the component (b) is preferably 45% by mass or less, more preferably 35% by mass or less, and further preferably 25% by mass or less. (B) When the content of the component is not more than the above upper limit value, the optical characteristics of the retardation film, particularly the negative birefringence, are likely to be improved. Further, when the content of the component (b) is not more than the above upper limit value, the thermal stability of the copolymer is likely to be improved, and the appearance defect of the film is likely to be suppressed during the extrusion molding step described later.

The content of the unsaturated dicarboxylic acid anhydride monomer (component (c)) is preferably 5% by mass or more, preferably 10% by mass or more, based on the total amount of the monomer components constituting the copolymer. It is more preferable to have. (C) When the content of the component is not more than the above lower limit value, the heat resistance of the retardation film is likely to be improved. The content of the component (c) is preferably 20% by mass or less, more preferably 15% by mass or less, based on the total amount of the monomer components constituting the copolymer. (C) When the content of the component is not more than the above upper limit value, the mechanical low strength of the retardation film is likely to be improved. Further, when the content of the component (c) is not more than the above upper limit value, the thermal stability of the copolymer is likely to be improved, and the appearance defect of the film is likely to be suppressed during the extrusion molding step.

The content of the component (d) may be 0% by mass or more and may be 5% by mass or more with respect to the total amount of the monomer components constituting the copolymer. The content of the component (d) is preferably 45% by mass or less, more preferably 40% by mass or less, based on the total amount of the monomer components constituting the copolymer.

The content of each of the above monomeric components is summarized as follows. That is, the content of the aromatic vinyl monomer unit in the above-mentioned copolymer may be 55 to 86% by mass, and the content of the (meth) acrylic acid ester-based monomer unit in the above-mentioned copolymer is 5. It may be up to 45% by mass or 5 to 35% by mass, and the content of the unsaturated dicarboxylic acid anhydride monomer unit in the above-mentioned copolymer may be 5 to 20% by mass. Alternatively, the content of the aromatic vinyl monomer unit in the above-mentioned copolymer may be 65 to 83% by mass, and the content of the (meth) acrylic acid ester monomer unit in the above-mentioned copolymer is 7 to 25. The content may be% by mass, and the content of the unsaturated dicarboxylic acid anhydride monomer unit in the above-mentioned copolymer may be 10 to 15% by mass.

The content of each monomer component in the copolymer may be determined by, for example, ¹³ C-NMR method.

The above-mentioned copolymer is obtained by polymerizing the above-mentioned monomer component. The polymerization method is not particularly limited, and may be a known polymerization method such as solution polymerization, suspension polymerization, and bulk polymerization. Solution polymerization is preferred because of its ease of operation. The solvent used in solution polymerization is preferably non-polymerizable from the viewpoint that by-products are less likely to be generated and the influence on the polymerization reaction is reduced.

Examples of the solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and acetophenone, ethers such as tetrahydrofuran and 1,4-dioxane, and aromatic hydrocarbons such as toluene, ethylbenzene, xylene and chlorobenzene. Methyl ethyl ketone or methyl isobutyl ketone is preferable from the viewpoint of solubility of the monomer or copolymer and ease of solvent recovery. The amount of the solvent added is preferably 10 to 100 parts by mass, more preferably 30 to 80 parts by mass with respect to 100 parts by mass of the obtained copolymer. When the amount of the solvent added is 10 parts by mass or more, the reaction rate and the viscosity of the polymer solution can be easily controlled. Further, when the amount of the solvent added is 100 parts by mass or less, it is easy to control the number average molecular weight Mn and the weight average molecular weight Mw of the copolymer.

Examples of the polymerization initiator include water-soluble polymerization initiators such as lithium persulfate, potassium persulfate, sodium persulfate, and ammonium persulfate, cumene hydroperoxide, benzoyl peroxide, t-butyl hydroperoxide, and acetyl peroxide. Oil-soluble peroxides such as diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutylhydroperoxide, methylisobutylketone, 2,2'-azobisisobutyronitrile, 2,2'-azobis Examples thereof include oil-soluble azo compounds such as (methyl isobutyrate). These can be used alone or in combination of two or more. Of these, it is preferable to use an oil-soluble azo compound, and more preferably 2,2'-azobisisobutyronitrile, because the polymerization reaction can be carried out under relatively mild conditions. The blending amount of the polymerization initiator can be appropriately adjusted in consideration of the type and content of the monomer component.

The thermoplastic resin constituting the retardation film 2 preferably has a negative intrinsic birefringence. Specifically, it is preferably ^{−10 × 100 to -1 × 10 -4 ,} and more preferably −5.0 × 100 to ^−5.0 × 10 ^-3 .

The glass transition temperature Tg of the thermoplastic resin is preferably 125 ° C. or higher, more preferably 128 ° C. or higher. The glass transition temperature Tg of the thermoplastic resin in the present embodiment is preferably 160 ° C. or lower, more preferably 150 ° C. or lower. When the glass transition temperature Tg of the thermoplastic resin is within the above range, a retardation film having better heat resistance can be obtained. The glass transition temperature of the thermoplastic resin can be adjusted by the type and content of the monomer component.

The glass transition temperature Tg is measured using, for example, a differential scanning calorimeter (DSC) (trade name “DSC-7 type” manufactured by PerkinElmer Co., Ltd.). The mass of the sample (thermoplastic resin) used for measuring Tg may be 10 mg. The rate of temperature rise of the sample in the measurement of Tg may be 10 ° C./min. Tg may be measured in an air atmosphere.

The number average molecular weight Mn of the thermoplastic resin is preferably 63000 or more, and more preferably 67000 or more. The number average molecular weight Mn of the thermoplastic resin is preferably 80,000 or less, and more preferably 75,000 or less. When the number average molecular weight of the thermoplastic resin is within the above range, the thermoplastic resin is more excellent in processability.

The weight average molecular weight Mw of the thermoplastic resin is preferably 170000 or more, and more preferably 175,000 or more. The weight average molecular weight Mw of the thermoplastic resin is preferably 240000 or less, more preferably 230000 or less. When the weight average molecular weight of the thermoplastic resin is within the above range, the thermoplastic resin is more excellent in processability.

The number average molecular weight Mn and the weight average molecular weight Mw may be measured by gel permeation chromatography (GPC). The number average molecular weight Mn and the weight average molecular weight Mw may be values converted by a calibration curve prepared using standard polystyrene.

The photoelastic modulus of the thermoplastic resin is preferably 6.0 × ^10-12 Pa ^-1 or less, and more preferably 4.0 × ^10-12 Pa ^-1 or less. When the photoelastic coefficient of the thermoplastic resin is within the above range, even if thermal expansion or thermal contraction of the retardation film occurs in a high temperature environment, the phase difference value R _th in the thickness direction and the in-plane retardation value R ₀ It is easy to suppress the change of. The photoelastic modulus of the thermoplastic resin can be adjusted by the type and content of the monomer component. The smaller the photoelasticity coefficient, the smaller the change in birefringence due to external force.

The retardation film 2 may further contain not only the above-mentioned thermoplastic resin but also other resins as long as the effects of the present invention are not impaired. Examples of other resins include polymethylmethacrylate and the like.

The thickness of the retardation film 2 may be 15 μm or less. Generally, when the thickness of the retardation film is 15 μm or less, cracks tend to occur, so that the effect of this embodiment is greatly benefited.

The retardation value _Rth in the thickness direction of the retardation film 2 is −30 nm or less. On the other hand, the absolute value of the in-plane retardation value R ₀ is preferably 0 nm or more and 130 nm or less. It is preferable that the absolute value of the retardation value Rth in the thickness direction of the retardation film _{2 is larger than the absolute value of the in-plane retardation value R0 .} When the phase difference value R _th in the thickness direction and the in-plane phase difference value R ₀ have the above relationship, they can be suitably used for a retardation film for an IPS (In-Plane Switching) type liquid crystal display device. Further, when the retardation value _Rth in the thickness direction is negative, that is, when the retardation value _Rth in the thickness direction is −300 nm or more and -50 nm or less, the retardation film is for an IPS type liquid crystal display device. Suitable for retardation film.

_Rth is a retardation value in the thickness direction of the retardation film measured with light having a wavelength of 589 nm at 23 ° C. Rth is determined by the following formula (A) when the thickness of the film is _dnm .
Equation (A): R _th = [{(Nx + Ny) / 2} -Nz] × d
= {(Nx-Nz) x d + (Ny-Nz) x d} / 2
= (ΔNxz × d + ΔNyz × d) / 2
R ₀ is a retardation value measured by light having a wavelength of 589 nm at 23 ° C. and in a direction perpendicular to the thickness direction of the retardation film. R ₀ is obtained by the following formula (B).
Equation (B): R ₀ = (Nx-Ny) × d = ΔNxy × d
In the above formula (A) and the above formula (B), Nx is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow phase axis direction), and Ny is orthogonal to the slow phase axis in the plane. It is the refractive index in the direction (that is, the phase-advancing axis direction), and Nz is the refractive index in the thickness direction.

In a high temperature environment, the amount of change ΔR _th of the phase difference value R _th in the thickness direction of the retardation film 2 and the amount of change ΔR ₀ of the in-plane retardation value R ₀ are sufficiently small. That is, in this embodiment, changes in _Rth and _R0 in a high temperature environment are suppressed. Therefore, the retardation film 2 can maintain a desired optical compensation function even in a high temperature environment.

For example, the amount of change ΔR _th of the retardation value R _th in the thickness direction of the retardation film after being allowed to stand in a dry atmosphere of 105 ° C. for 1000 hours can be 4 nm or less, or 3 nm or less. ..

For example, the amount of change ΔR ₀ of the in-plane retardation value R ₀ of the retardation film after being allowed to stand in a dry atmosphere at 105 ° C. for 1000 hours can be 4 nm or less, or 3 nm or less.

The retardation film 2 can have a haze of 0.8% or less, or 0.3 or less. Therefore, the contrast of the image display device including the retardation film is increased. The haze can be obtained by JIS K 7105 or the like.

The retardation film 2 can have a total light transmittance of 89% or more, or 91% or more. Therefore, the brightness of the image display device including the retardation film 2 is increased. The total light transmittance is the transmittance of all light rays (light in the wavelength range of 380 to 780 nm) in a retardation film having a film thickness of 4 to 80 μm, and is usually 100% or less. The transmittance may be measured using a spectrophotometer (for example, trade name HZ-1 manufactured by Suga Test Instruments Co., Ltd.).

In a high temperature environment, the rate of change ΔT _t of the total light transmittance of the retardation film 2 is relatively small. Therefore, the image display device provided with the retardation film 2 can maintain the desired high luminance even in a high temperature environment.

For example, the rate of change ΔT _t of the total light transmittance of the retardation film after being allowed to stand in a dry atmosphere of 105 ° C. for 1000 hours can be 5% or less, or 3% or less.

The haze value of the retardation film 2 is preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% or less, and 0.5% or less. It is particularly preferable to have. The haze value of the retardation film 2 may be 0.01% or more. When the haze value is in the above range, the brightness of the image display device including the retardation film 2 is increased.

The haze value may be measured using a turbidity meter (for example, trade name "NDH-1001DP" manufactured by Nippon Denshoku Industries Co., Ltd.).

The retardation film 2 is manufactured by, for example, the following manufacturing method. That is, the method for producing the retardation film 2 includes an extrusion molding step of extruding the molten thermoplastic resin from a die to obtain a film, and stretching the film while heating it at a temperature equal to or higher than the glass transition temperature Tg of the thermoplastic resin. A stretching step of obtaining a retardation film is provided. The conditions of each step for controlling the phase difference value R _th in the thickness direction and the in-plane phase difference value R ₀ to desired values are as follows.

The temperature of the film in the stretching step is preferably Tg or more (Tg + 20) ° C. or lower, and more preferably Tg or more (Tg + 15) ° C. or lower, which is the glass transition temperature of the thermoplastic resin. By setting the temperature at the time of stretching in the above range, the phase difference value Rth in the thickness direction and the in-plane phase difference _{value R0 can} be easily adjusted.

When the stretch ratio of the film in the _MD direction in the stretching step is expressed as EMD and the stretching ratio of the film in the _TD direction in the stretching step is expressed as ETD, the ratio of the stretching ratio _ETD / _EMD is preferable. May be adjusted to 0.35 to 1.9, more preferably 0.5 to 1.7. The MD direction means the flow direction (conveyance direction) of the film or the length direction of the film in the stretching step. The TD direction means a direction perpendicular to the MD direction or a width direction of the film. The ratio _ETD / _EMD of the draw ratio may be adjusted according to the target values of the thickness of the retardation film, the retardation value Rth in the thickness direction, and the in-plane retardation _{value R0 .}

The draw ratio EMD in the _MD direction is preferably 1.7 times or more, and more preferably 1.9 times or more. The draw ratio E _MD in the MD direction may be 3.2 times or less.

The draw ratio ETD in the _TD direction is preferably 3.2 times or less, and more preferably 3.0 times or less. The stretch ratio ETD in the _TD direction may be 1.2 times or more.

The stretching method may be either simultaneous biaxial stretching or sequential biaxial stretching. Sequential biaxial stretching is a stretching method in which uniaxial stretching in the MD direction and uniaxial stretching in the TD direction are performed separately. In the stretching step, it is preferable to stretch the film by sequential biaxial stretching because it is easy to develop the uniformity of the entire film having the retardation value _Rth and the in-plane retardation value _R0 in the thickness direction. The film may be stretched to the target value of the stretch ratio by one-step stretching. The film may be stretched to the target value of the stretch ratio by the multi-step stretching.

The line speed of the film in the stretching step is preferably 0.3 to 30 m / min, more preferably 0.5 to 25 m / min. When the line speed is in the above range, it is easy to control the phase difference value R _th in the thickness direction and the in-plane phase difference value R ₀ . The line speed may be adjusted according to the target values of the thickness of the retardation film, the retardation value Rth in the thickness direction, and the in-plane retardation _{value R0 .}

The retardation film 2 may be used alone (single layer), or may be used in combination with another retardation film, an optical compensation film, a protective film, a polarizing element film, or other members. For example, another film may be laminated on one side or both sides of the retardation film 2. Generally, when the retardation film is a single layer, cracks tend to occur easily, but as an effect of the present embodiment, cracks are unlikely to occur in the retardation film 2, so this is particularly the case when the retardation film 2 is a single layer. The benefits of the effects of the embodiments are great.

<Active energy ray-curable resin composition>
An active energy ray-curable resin composition is used to bond the polarizing plate 1 and the retardation film 2. The active energy ray-curable resin composition contains a compound that is cured by being irradiated with active energy rays, that is, a curable component, and a photoradical polymerization initiator. In the present embodiment, a composition containing N-substituted (meth) acrylamide as a curable component and a compound having a (meth) acryloyloxy group in the molecule as a curable component is adopted. The active energy ray-curable resin composition adheres the polarizing plate 1 and the retardation film 2 to form a cured product 3 (see FIG. 1).

N-substituted (meth) acrylamide N-substituted (meth) acrylamide is a (meth) acrylamide having a substituent at the N-position. A typical example of the substituent is an alkyl group which may be further substituted, but may form a ring with a nitrogen atom of (meth) acrylamide, which ring is a carbon atom and a (meth) atom. In addition to the nitrogen atom of acrylamide, an oxygen atom may be included as a ring member. Further, a substituent such as alkyl or oxo (= O) may be bonded to the carbon atom constituting the ring. N-substituted (meth) acrylamide can generally be produced by the reaction of (meth) acrylic acid or its chloride with a primary or secondary amine.

The N-substituted (meth) acrylamide is particularly preferably one represented by the following formula (11). In the following formula (11) representing a suitable N-substituted (meth) acrylamide, when Q ₂ is an alkyl group and when Q ₃ is an alkyl group which may have a hydroxyl group, each alkyl group is. As long as it has 3 or more carbon atoms, it may be linear or branched. When _Q3 is an alkyl group having a hydroxyl group, the hydroxyalkyl group corresponds to this. When Q ₂ and Q ₃ together form a 5-membered or 6-membered ring that may have an oxygen atom as a ring member, together with the nitrogen atom to which they are bonded, the 5-membered or 6-membered ring is formed. To give an example of the ring in the form of a group leading to a carbonyl (C = O) at the N-position, 1-pyrrolidinyl (C ₄ H ₈ N-), 2-oxazolidinone-3-yl (C ₂ H ₄ OC (C 2 H 4 OC) = O) N-), piperidino (C ₅ H ₁₀ N-), morpholino (C ₂ H ₄ OC ₂ H ₄ N-) and the like.

(In the formula, Q ₁ represents a hydrogen atom or a methyl group, Q ₂ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and Q ₃ represents an alkyl group having 1 to 6 carbon atoms which may have a hydroxyl group. Or Q ₂ and Q ₃ together to form a 5- or 6-membered ring that may have an oxygen atom as a ring member, together with the nitrogen atom to which they are bonded).

Specific examples of N-substituted (meth) acrylamides corresponding to formula (11), where _Q2 is a hydrogen atom and _Q3 is an alkyl group, are N-methyl (meth) acrylamide and N-ethyl (meth). ) Acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, N-tert-butyl (meth) acrylamide, N-hexyl (meth) acrylamide and the like. Specific examples of N-substituted (meth) acrylamide in which both Q ₂ and Q ₃ are alkyl groups include N, N-dimethyl (meth) acrylamide and N, N-diethyl (meth) acrylamide. Similarly, N-hydroxymethyl (meth) acrylamide and N- (2-hydroxyethyl) are specific examples of N-substituted (meth) acrylamide in which Q ₂ is a hydrogen atom and Q ₃ is an alkyl group having a hydroxyl group. There are (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide and the like. Further, as a specific example of N-substituted (meth) acrylamide in the formula (11), Q ₂ and Q ₃ together form a 5-membered ring or a 6-membered ring together with the nitrogen atom to which they are bonded. There are N-acrylloylpyrrolidine, 3-acryloyl-2-oxazolidinone, 4-acryloylmorpholine, N-acryloylpiperidin, N-methacryloylpiperidin and the like. Of these, N-hydroxyalkyl (meth) acrylamide, such as N-hydroxymethylacrylamide and N- (2-hydroxyethyl) acrylamide, is particularly preferred.

In addition, N-alkyl (meth) acrylamide having long-chain alkyl such as N-dodecyl (meth) acrylamide, N- (methoxymethyl) acrylamide, N- (ethoxymethyl) acrylamide, N- (propoxymethyl) acrylamide. And N- (alkoxyalkyl) (meth) acrylamide, such as N- (butoxymethyl) acrylamide, can also be used as the N-substituted (meth) acrylamide that constitutes the curable component of the active energy ray-curable resin composition. can.

-A compound having a (meth) acryloyloxy group A compound having a (meth) acryloyloxy group in the molecule, which is another curable component of the active energy ray-curable resin composition, has a (meth) acryloyloxy group in the molecule. It can be of various kinds having at least one of, and may be simply referred to as "(meth) acrylate" below. Specifically, it is obtained by reacting two or more kinds of a (meth) acrylate monomer having at least one (meth) acryloyloxy group in the molecule and a compound having a functional group, and the (meth) acryloyloxy in the molecule. A (meth) acrylate oligomer having at least two groups corresponds to this.

The (meth) acrylate monomer includes a monofunctional (meth) acrylate monomer having one (meth) acryloyloxy group in the molecule, and a bifunctional (meth) acrylate monomer having two (meth) acryloyloxy groups in the molecule. And there are trifunctional or higher functional (meth) acrylate monomers having three or more (meth) acryloyloxy groups in the molecule.

Among these, a monofunctional (meth) acrylate monomer is preferable, and an alkyl (meth) acrylate represented by the following formula (12) is more preferable. In the following formula (12) representing an alkyl (meth) acrylate, when R ₂ is an alkyl group, the alkyl group may be linear or branched as long as it has 3 or more carbon atoms. Specific examples of the alkyl (meth) acrylate represented by the following formula (12) include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and isobutyl (meth) acrylate. There are tert-butyl (meth) acrylate and the like. Of these, methyl acrylate is particularly preferred.

(In the formula, R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkyl group having 1 to 6 carbon atoms).

Also, alkyl (meth) acrylates with more carbon atoms in alkyl groups such as 2-ethylhexyl (meth) acrylates, aralkyl (meth) acrylates such as benzyl (meth) acrylates, and terpene alcohols such as isobornyl (meth) acrylates. (Meta) acrylates, aminoalkyl (meth) acrylates such as N, N-dimethylaminoethyl (meth) acrylates, as well as 2-phenoxyethyl (meth) acrylates, ethylcarbitol (meth) acrylates, and phenoxypolyethylene glycols. A (meth) acrylate having an ether bond at the alcohol moiety, such as a (meth) acrylate, can also be used as the monofunctional (meth) acrylate.

Further, a monofunctional (meth) acrylate having a hydroxyl group at the alcohol moiety and a monofunctional (meth) acrylate having a carboxyl group at the alcohol moiety can also be used. Specific examples of monofunctional (meth) acrylates having a hydroxyl group at the alcohol moiety include 2-hydroxyethyl (meth) acrylate, 2- or 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2 -Hydroxy-3-phenoxypropyl (meth) acrylate, trimethylolpropane mono (meth) acrylate, pentaerythritol mono (meth) acrylate and the like. Specific examples of monofunctional (meth) acrylates having a carboxyl group at the alcohol moiety include 2-carboxyethyl (meth) acrylate, 1- [2- (meth) acryloyloxyethyl] phthalic acid, and 1- [2-(. Meta) Acryloyloxyethyl] hexahydrophthalic acid, 1- [2- (meth) acryloyloxyethyl] succinic acid, 4- [2- (meth) acryloyloxyethyl] trimellitic acid and the like.

The above is an example of a compound having one (meth) acryloyloxy group in the molecule, but a polyfunctional compound having a plurality of (meth) acryloyloxy groups in the molecule is also used as a curable component ( It can be a meta) acrylate. As described above, the polyfunctional (meth) acrylate has a bifunctional (meth) acrylate monomer having two (meth) acryloyloxy groups in the molecule and three (meth) acryloyloxy groups in the molecule. A polyfunctional (meth) acrylate monomer having the above trifunctionality or more, a (meth) acrylate oligomer having at least two (meth) acryloyloxy groups in the molecule obtained by reacting two or more kinds of compounds having a functional group, etc. be. Hereinafter, these monomers and oligomers will be specifically described.

Typical examples of bifunctional (meth) acrylate monomers include alkylene glycol di (meth) acrylates, polyoxyalkylene glycol di (meth) acrylates, halogen-substituted alkylene glycol di (meth) acrylates, and aliphatic polyols. Di (meth) acrylates, hydrogenated dicyclopentadiene or tricyclodecane dialkanol di (meth) acrylates, dioxane glycol or dioxane dialkanol di (meth) acrylates, bisphenol A or bisphenol F alkylene oxide adducts Di (meth) acrylates, bisphenol A or bisphenol F epoxy di (meth) acrylates and the like can be mentioned.

To give a more specific example of the bifunctional (meth) acrylate monomer, ethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1 , 6-Hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethyl propandi (meth) acrylate, pentaerythritol di (meth) acrylate, ditri Methylol propanedi (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, Polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, 2,2-bis [4- {2- (2- (meth) acryloyl) Oxyethoxy) ethoxy} phenyl] propane, 2,2-bis [4- {2- (2- (meth) acryloyloxyethoxy) ethoxy} cyclohexyl] propane, hydrogenated dicyclopentadienyldi (meth) acrylate, tri Cyclodecane dimethanol di (meth) acrylate, 1,3-dioxane-2,5-diyldi (meth) acrylate [also known as dioxane glycol di (meth) acrylate], acetylated product of hydroxypivalaldehyde and trimethylolpropane [ Chemical name: 2- (2-hydroxy-1,1-dimethylethyl) -5-ethyl-5-hydroxymethyl-1,3-dioxane] di (meth) acrylate, 1,3,5-tris (2-) Hydroxyethyl) isocyanurate di (meth) acrylate and the like.

A typical trifunctional or higher polyfunctional (meth) acrylate monomer is a poly (meth) acrylate of a trivalent or higher aliphatic polyol. Specific examples thereof include glycerintri (meth) acrylate, trimethylolpropane tri (meth) acrylate, dimethylolpropane tri (meth) acrylate, dimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, and penta. There are erythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate and the like.

In addition, poly (meth) acrylates of trivalent or higher halogen-substituted polyols, tri (meth) acrylates of alkylene oxide adducts of glycerin, tri (meth) acrylates of alkylene oxide adducts of trimethylolpropane, 1,1,1 -Tris [2- {2- (meth) acryloyloxyethoxy} ethoxy] propane, 1,3,5-tris [2- (meth) acryloyloxyethyl] isocyanurate, etc. can also be polyfunctional (meth) acrylate monomers. ..

On the other hand, the (meth) acrylate oligomer includes urethane (meth) acrylate oligomer, polyester (meth) acrylate oligomer, epoxy (meth) acrylate oligomer and the like.

The urethane (meth) acrylate oligomer refers to a compound having at least two (meth) acryloyloxy groups in the molecule and having a urethane bond (-NHCOO-). Specifically, the urethanization reaction product of a hydroxyl group-containing (meth) acrylate monomer having one hydroxyl group and at least one (meth) acryloyloxy group in the molecule and polyisocyanate, and polyols are polyisocyanate. A urethanization reaction product of a terminal isocyanato group-containing urethane compound obtained by reacting with and a hydroxyl group-containing (meth) acrylate monomer having one hydroxyl group and at least one (meth) acryloyloxy group in the molecule, etc. Can be.

Specific examples of the hydroxyl group-containing (meth) acrylate monomer used in the urethanization reaction include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 2-hydroxy. -3-Phenoxypropyl (meth) acrylate, glycerindi (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate and the like can be mentioned.

Specific examples of the polyisocyanate to be subjected to the urethanization reaction with the hydroxyl group-containing (meth) acrylate monomer include hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, and aromatics. Compounds obtained by hydrogenating diisocyanates, for example, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, triphenylmethane triisocyanate, dibenzylbenzene triisocyanate, and diisocyanates among these can be obtained in large quantities. Examples include polyisocyanate.

Further, as the polyols for producing the terminal isocyanato group-containing urethane compound by the reaction with the polyisocyanate, a polyester polyol, a polyether polyol, or the like can be used in addition to an aliphatic or alicyclic polyol. Specific examples of the aliphatic or alicyclic polyol include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, and tri. Examples thereof include methylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, dimethylolheptan, dimethylolpropionic acid, dimethylolbutyric acid, glycerin, and hydrogenated bisphenol A.

The polyester polyol is a compound obtained by subjecting the above-mentioned polyols to a dehydration condensation reaction of a polybasic carboxylic acid or an anhydride thereof. Specific examples of polybasic carboxylic acids and their anhydrides, which may be anhydrous, are labeled as "(anhydrous)", and include (anhydrous) succinic acid, adipic acid, and (anhydrous) maleic acid. There are (anhydrous) itaconic acid, (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, (anhydrous) phthalic acid, isophthalic acid, terephthalic acid, hexahydro (anhydrous) phthalic acid and the like.

The polyether polyol may be a polyoxyalkylene-modified polyol obtained by reacting the above-mentioned polyols or bisphenols with an alkylene oxide, in addition to the polyalkylene glycol.

The polyester (meth) acrylate oligomer refers to a compound having at least two (meth) acryloyloxy groups in the molecule and having an ester bond. Specifically, it can be obtained by a dehydration condensation reaction of (meth) acrylic acid, a polybasic carboxylic acid or an anhydride thereof, and a polyol. Specific examples of the polybasic carboxylic acid or its anhydride used in the dehydration condensation reaction, which may be an anhydrate, are labeled as "(anhydrous)", and include (anhydrous) succinic acid and adipic acid. There are (anhydrous) maleic acid, (anhydrous) itaconic acid, (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, hexahydro (anhydrous) phthalic acid, (anhydrous) phthalic acid, isophthalic acid, terephthalic acid and the like. Specific examples of the polyol used in the dehydration condensation reaction include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, and tri. There are methylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, dimethylolheptan, dimethylolpropionic acid, dimethylolbutyric acid, glycerin, hydrogenated bisphenol A and the like.

The epoxy (meth) acrylate oligomer refers to one obtained by an addition reaction between polyglycidyl ether and (meth) acrylic acid, and also has at least two (meth) acryloyloxy groups in the molecule. Specific examples of the polyglycidyl ether used in this addition reaction include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and bisphenol A diglycidyl ether. and so on.

Quantitative Ratio of N-Substituted (Meta) Acrylamide and (Meta) Acrylate In the present embodiment, the N-substituted (meth) acrylamide and (meth) acrylate described above are used in the active energy ray-curable resin composition. Although they are used together as a curable component, their quantitative relationship is based on the total amount of the curable component, including both, and if a compound that is cured by irradiation with active energy rays is also included. In addition, N-substituted (meth) acrylamide is preferably 60 to 80% by weight, more preferably 70 to 80% by weight, and (meth) acrylate is preferably 20 to 40% by weight, more preferably 20 to 30% by weight. Similarly, when the N-substituted (meth) acrylamide represented by the formula (11) and the alkyl (meth) acrylate represented by the formula (12) are used, the formula (11) is also based on the total amount of the curable component. The proportion of N-substituted (meth) acrylamide represented by is 60 to 80 parts by weight, further 70 to 80% by weight, and the proportion of alkyl (meth) acrylate represented by the formula (12) is 20 to 40% by weight, further. Is preferably 20 to 30% by weight. The proportion of N-substituted (meth) acrylamide represented by the compound represented by the formula (11) is less than 60% by weight in the total curable component, in other words, the compound represented by the formula (12). When the ratio of the (meth) acrylate as a typical example exceeds 40% by weight in the entire curable component, the adhesive force to the cycloolefin resin film tends to decrease. On the other hand, the proportion of N-substituted (meth) acrylamide represented by the compound represented by the formula (11) exceeds 80% by weight in the entire curable component, in other words, it is represented by the formula (12). When the proportion of the (meth) acrylate represented by the compound is less than 20% by weight in the entire curable component, the adhesive force to the retardation film containing the (meth) acrylic resin layer tends to decrease.

-Photoradical polymerization initiator The active energy ray-curable resin composition contains the N-substituted (meth) acrylamide and (meth) acrylate described above as curable components. Since these are all radically polymerizable compounds, a photoradical polymerization initiator is added to this composition. As the photoradical polymerization initiator, any conventionally known one can be used as long as it can initiate the polymerization of the radically polymerizable compound by irradiation with active energy rays. Specific examples of photoradical initiators include acetophenone, 3-methylacetophenone, benzyldimethylketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane-1-one, 2-methyl-1. -[Acetphenone-based initiators such as 4- (methylthio) phenyl-2-morpholinopropane-1-one and 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzophenone, 4-chlorobenzophenone and 4 , Benzophenone-based initiators such as 4'-diaminobenzophenone; Benzophenone-based initiators such as benzoinpropyl ether and benzoin ethyl ether; Thioxanthone-based initiators such as 4-isopropylthioxanthone; , Benzaldehyde, anthraquinone, etc.

The blending amount of the photoradical polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 to 1 part by weight, based on 100 parts by weight of the radically polymerizable compound containing N-substituted (meth) acrylamide and (meth) acrylate. 6 parts by weight. If the amount of the photoradical polymerization initiator is small, the curing tends to be insufficient, and the mechanical strength and the adhesiveness tend to decrease. On the other hand, if the amount of the photoradical polymerization initiator is too large, the amount of the active energy ray-curable compound in the curable resin composition may be relatively small, and the durability performance of the obtained laminate may be deteriorated. ..

-Other optional components that can be blended in the active energy ray-curable resin composition The active energy ray-curable resin composition may further contain a photosensitizer, if necessary. By blending a photosensitizer, the reactivity of radical polymerization can be improved, and the mechanical strength and adhesiveness of the adhesive layer can be improved. The photosensitizer may be a compound having maximum absorption at a wavelength longer than 380 nm, for example, a carbonyl compound, an organic sulfur compound, a persulfide, a redox-based compound, an azo and a diazo compound, a halogen compound, an anthracene-based compound, and the like. Examples include photoreducing dyes. Examples of carbonyl compounds that can be photosensitizers are benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether and 2,2-dimethoxy-2-phenylacetophenone; benzophenone, 2,4-dichlorobenzophenone, o-benzoyl. Benzophenone compounds such as methyl benzoate, 4,4'-bis (dimethylamino) benzophenone and 4,4'-bis (diethylamino) benzophenone; thioxanthone derivatives such as 2-chlorothioxanthone and 2-isopropylthioxanthone; 2- Anthraquinone derivatives such as chloroanthraquinone and 2-methylanthraquinone; acridone derivatives such as N-methylacridone and N-butylacridone. The anthracene-based compound preferably has an alkoxy group at the 9-position and the 10-position of the anthracene, and examples of the anthracene-based compound that can be a photosensitizer include 9,10-dipropoxyanthracene, 2-methyl-9, 10-Dipropoxyanthracene, 2-ethyl-9,10-dipropoxyanthracene, 9,10-dibutoxyanthracene, 2-methyl-9,10-dibutoxyanthracene, 2-ethyl-9,10-dibutoxyanthracene, etc. There is. These photosensitizers may be used alone or in combination of two or more. When the photosensitizer is blended, the amount thereof is usually about 0.1 to 20 parts by weight, with 100 parts by weight of the entire active energy ray-curable compound.

Further, the active energy ray-curable resin composition may contain an antistatic agent for imparting antistatic performance. Various known antistatic agents can be used. For example, cationic surfactants, anionic surfactants, nonionic surfactants, ionic compounds having organic cations other than the cationic surfactants, ionic compounds having organic anions other than the anionic surfactants, conductive. Inorganic particles, conductive polymers and the like can be used. The blending ratio of these antistatic agents is appropriately determined according to the desired characteristics, but is usually about 0.1 to 10 parts by weight with the entire active energy ray-curable compound as 100 parts by weight.

The active energy ray-curable resin composition can also contain known polymer additives usually used for polymers. Examples thereof include primary antioxidants such as phenols and amines, sulfur-based secondary antioxidants, hindered amine-based photostabilizers (HALS), benzophenone-based, benzotriazole-based, and benzoate-based ultraviolet absorbers. ..

A leveling agent can also be added to the active energy ray-curable resin composition. When this curable resin composition is applied to the polarizing plate 1 or the retardation film 2, if the coatability is poor, the wettability can be improved by adding a leveling agent. As the leveling agent, various compounds having a leveling effect such as silicone-based, fluorine-based, polyether-based, acrylic copolymer-based, and titanate-based can be used. The blending ratio of the leveling agent is about 0.01 to 1 part by weight with respect to 100 parts by weight of the active energy ray-curable compound contained in the curable resin composition.

Further, the active energy ray-curable resin composition may contain a solvent, if necessary. The solvent is appropriately selected in consideration of the solubility of the components constituting the curable resin composition. Commonly used solvents include aliphatic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; alcohols such as methanol, ethanol, propanol, isopropanol and butanol; acetone, Ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; esters such as methyl acetate, ethyl acetate and butyl acetate; cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve; halogenated hydrocarbons such as methylene chloride and chloroform. Examples include hydrogens. The mixing ratio of the solvent is appropriately determined from the viewpoint of adjusting the viscosity according to the processing purpose such as film forming property and the optimum viscosity range in the coating method to be adopted.

The active energy ray-curable resin composition may contain a photocationic polymerization initiator, but it is preferable that the photocationic polymerization initiator is substantially not contained. By substantially not containing it, it means that the blending amount of the photocationic polymerization initiator is 0.1 part by weight or less with respect to 100 parts by weight of the solid content of the active energy ray-curable resin composition. When the active energy ray-curable resin composition contains a photocationic polymerization initiator, the blending amount thereof may be 2 parts by weight or less with respect to 100 parts by weight of the solid content of the active energy ray-curable resin composition. It is preferably 1 part by weight or less, and more preferably 1 part by weight or less.

When the polarizing plate and the retardation film are bonded to each other with an active energy ray-curable resin composition containing a photocationic polymerization initiator, acid is generated by irradiation with the active energy rays. Since this acid may cause cracks in the retardation film, it is desirable that the blending amount of the photocationic polymerization initiator is in the above range.

The active energy ray-curable resin composition forming the cured product 3 of the active energy ray-curable resin composition is coated on either the adhesive surface of the polarizing plate 1 and the retardation film 2, and the other is laminated thereto. .. For coating the active energy ray-curable resin composition, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used.

The light source used for irradiating the active energy beam is not particularly limited, and has a emission distribution having a wavelength of 400 nm or less, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, and a microwave-excited mercury lamp. , Metal halide lamps and the like can be used. The light irradiation intensity of the active energy ray-curable resin composition varies depending on the composition, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is preferably 10 to 2,500 mW / cm ² . .. If the intensity of light irradiation of the active energy ray-curable resin composition is too small, it takes a long time for the reaction to proceed sufficiently, and conversely, if it is too large, the heat and active energy rays radiated from the lamp are emitted. The heat generated during the polymerization of the curable resin composition may cause yellowing of the active energy ray-curable resin composition and deterioration of the film to be attached. The light irradiation time of the active energy ray-curable resin composition is also controlled for each composition and is not particularly limited, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 2, It is preferable to set it to 500 mJ / cm ² . If the integrated light amount to the active energy ray-curable resin composition is too small, the generation of the active species derived from the polymerization initiator may not be sufficient, and the curing of the obtained adhesive layer may be insufficient. Further, if the integrated light amount is too large, the irradiation time becomes very long, which is disadvantageous for improving productivity.

The active energy ray-curable composition becomes a cured product by irradiation with active energy rays. The cured product preferably has a glass transition temperature of less than 50 ° C. When the glass transition temperature is less than 50 ° C., cracks in the retardation film 2 are further suppressed.

The thickness of the cured product 3 of the active energy ray-curable composition is preferably 0.05 to 10 μm, more preferably 0.1 to 3 μm.

<Adhesive layer>
The laminated body 10 may further include the pressure-sensitive adhesive layer 4 on the side of the retardation film 2 on which the polarizing plate 1 is not laminated. When the pressure-sensitive adhesive layer 4 is provided, the polarizing plate 1 and the retardation film 2 can be used when being incorporated into a liquid crystal display device.

The pressure-sensitive adhesive layer 4 is preferably composed of a pressure-sensitive pressure-sensitive adhesive. Further, the pressure-sensitive adhesive layer 4 preferably has high adhesive strength to glass, and can be made of an acrylic resin, a silicone-based resin, polyester, polyurethane, a polyether, or the like.

The thickness of the pressure-sensitive adhesive layer 4 is preferably 2 to 500 μm, more preferably 2 to 200 μm, and even more preferably 2 to 50 μm.

As a method of laminating the pressure-sensitive adhesive layer 4 on the retardation film 2, for example, a method of applying a solution containing the above resin or an arbitrary additive component to the retardation film 2 may be used, and the pressure-sensitive adhesive layer 4 is adhered on a separately prepared separator. A method of forming the agent layer 4 and then transferring it onto the retardation film 2 may also be used.

<Manufacturing method of laminated body>
The laminate 10 can be manufactured, for example, through the following resin layer forming step, stretching step, dyeing step, first bonding step, peeling step, and second bonding step. In these steps, a polyvinyl alcohol-based resin layer is formed by applying a coating liquid containing a polyvinyl alcohol-based resin to one side of the base film, and then a predetermined treatment is applied to the obtained laminated film to obtain polyvinyl alcohol. The alcohol-based resin layer is used as a polarizing film. After the first protective film and the retardation film are bonded to the obtained polarizing laminated film, the base film is peeled off, and the second protective film is bonded to the peeled place.

(Resin layer forming process)
This step is a step of forming a polyvinyl alcohol-based resin layer by applying a coating liquid containing a polyvinyl alcohol-based resin to one side of the base film and then drying the film to obtain a laminated film. This polyvinyl alcohol-based resin layer is a layer that becomes a polarizing film through a stretching step and a dyeing step. The polyvinyl alcohol-based resin layer can be formed by applying a coating liquid containing a polyvinyl alcohol-based resin to one side of the base film and drying the coating layer. The method of forming the polyvinyl alcohol-based resin layer by such coating is advantageous in that a thin-film polarizing film can be easily obtained.

The base film can be made of a thermoplastic resin, and it is particularly preferable that the base film is made of a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such thermoplastic resins include, for example, polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins; polyester resins; (meth) acrylic resins; cellulose such as cellulose triacetate and cellulose diacetate. Ester-based resin; Polycarbonate-based resin; Polyvinyl alcohol-based resin; Polyvinyl acetate resin; Polyallylate-based resin; Polystyrene-based resin; Polyether sulfone-based resin; Polysulfone-based resin; Polyamide-based resin; Polyimide-based resin; , Copolymers and the like.

The base film may have a single-layer structure composed of one resin layer made of one or more kinds of thermoplastic resins, or a plurality of resin layers made of one kind or two or more kinds of thermoplastic resins are laminated. It may have a multi-layered structure.

The thickness of the base film can be appropriately determined, but in general, it is preferably 1 to 500 μm, more preferably 300 μm or less, further preferably 200 μm or less, and 5 to 150 μm from the viewpoint of workability such as strength and handleability. Most preferred.

The coating liquid containing the polyvinyl alcohol-based resin to be coated on the base film is preferably a polyvinyl alcohol-based resin solution obtained by dissolving the powder of the polyvinyl alcohol-based resin in a good solvent (for example, water). The coating liquid may contain additives such as a plasticizer and a surfactant, if necessary. As the plasticizer, a polyol or a condensate thereof can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, polyethylene glycol and the like. The blending amount of the additive is preferably 20% by weight or less of the polyvinyl alcohol-based resin.

The method of applying the coating liquid on the base film is a wire bar coating method; a roll coating method such as reverse coating and gravure coating; a die coating method; a comma coating method; a lip coating method; a spin coating method; a screen coating method; It can be appropriately selected from known methods such as fountain coating method; dipping method; spray method.

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) are set according to the type of solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C. or higher. The drying time is, for example, 2 to 20 minutes.

The thickness of the polyvinyl alcohol-based resin layer in the laminated film is preferably 3 to 60 μm, more preferably 3 to 30 μm, and even more preferably 5 to 20 μm. Within this range, a polarizing film having good dyeability of the dichroic dye, excellent polarization performance, and a sufficiently small thickness can be obtained. If the thickness of the polyvinyl alcohol-based resin layer exceeds 60 μm, the thickness of the polarizing film may exceed 20 μm, and if the thickness of the polyvinyl alcohol-based resin layer is less than 3 μm, the thickness becomes too thin after stretching and dyeing. Sex tends to worsen.

Prior to coating the coating liquid, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, at least the surface of the base film on the side where the polyvinyl alcohol-based resin layer is formed is treated with corona. Plasma treatment, frame (flame) treatment, or the like may be applied.

Further, prior to the coating of the coating liquid, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, a polyvinyl alcohol-based resin layer is placed on the base film via a primer layer and an adhesive layer. It may be formed.

The primer layer can be formed by applying a coating liquid for forming a primer layer to the surface of a base film and then drying it. The coating liquid for forming the primer layer preferably contains a component that exhibits a certain degree of strong adhesion to both the base film and the polyvinyl alcohol-based resin layer. The coating liquid for forming a primer layer usually contains such a resin component and a solvent. As the resin component, a thermoplastic resin having excellent transparency, thermal stability, stretchability and the like is preferably used, and examples thereof include (meth) acrylic resin and polyvinyl alcohol resin. Of these, polyvinyl alcohol-based resins that provide good adhesion are preferably used.

Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol resins and derivatives thereof. Derivatives of polyvinyl alcohol resin include polyvinyl formal, polyvinyl acetal and the like, as well as polyvinyl alcohol resin modified with olefins such as ethylene and propylene; modified with unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid. Those modified with an alkyl ester of unsaturated carboxylic acid; those modified with acrylamide, and the like. Among the above-mentioned polyvinyl alcohol-based resins, it is preferable to use a polyvinyl alcohol resin.

As the solvent, a general organic solvent or an aqueous solvent capable of dissolving the resin component is usually used. Examples of solvents include aromatic hydrocarbons such as benzene, toluene and xylene; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; esters such as ethyl acetate and isobutyl acetate; chlorine such as methylene chloride, trichloroethylene and chloroform. Hydrocarbons; alcohols such as ethanol, 1-propanol, 2-propanol and 1-butanol. However, if the primer layer is formed using a primer layer forming coating solution containing an organic solvent, the base film may be dissolved. Therefore, the solvent should be selected in consideration of the solubility of the base film. Is preferable. Considering the influence on the environment, it is preferable to form the primer layer from the coating liquid using water as a solvent.

A cross-linking agent may be added to the coating liquid for forming the primer layer in order to increase the strength of the primer layer. As the cross-linking agent, an appropriate one is appropriately selected from known organic and inorganic cross-linking agents according to the type of the thermoplastic resin to be used. Examples of the cross-linking agent include epoxy-based, isocyanate-based, dialdehyde-based, and metal-based cross-linking agents.

The ratio of the resin component and the cross-linking agent in the coating liquid for forming the primer layer is in the range of about 0.1 to 100 parts by weight of the cross-linking agent with respect to 100 parts by weight of the resin component, and the type of the resin component and the type of the cross-linking agent. It may be appropriately determined depending on the above, and it is particularly preferable to select from the range of about 0.1 to 50 parts by weight. Further, it is preferable that the coating liquid for forming the primer layer has a solid content concentration of about 1 to 25% by weight.

The thickness of the primer layer is preferably about 0.05 to 1 μm, more preferably 0.1 to 0.4 μm. When it is thinner than 0.05 μm, the effect of improving the adhesion between the base film and the polyvinyl alcohol-based resin layer is small, and when it is thicker than 1 μm, it is disadvantageous for thinning the polarizing plate.

The method of applying the coating liquid for forming the primer layer to the base film can be the same as the coating liquid for forming the polyvinyl alcohol-based resin layer. The primer layer is applied to the surface (one side or both sides of the base film) to which the coating liquid for forming the polyvinyl alcohol-based resin layer is applied. The drying temperature and drying time of the coating layer composed of the coating liquid for forming the primer layer are set according to the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C. or higher. The drying time is, for example, 30 seconds to 20 minutes.

(Stretching process)
This step is a step of subjecting a laminated film composed of a base film and a polyvinyl alcohol-based resin layer to a stretching treatment to obtain a stretched film composed of the stretched base film and a polyvinyl alcohol-based resin layer. The draw ratio of the laminated film can be appropriately selected depending on the desired polarization characteristics, but is preferably more than 4 times and 17 times or less, more preferably more than 4.5 times the original length of the laminated film. It is 8 times or less. When the draw ratio is 4 times or less, the polyvinyl alcohol-based resin layer is not sufficiently oriented, so that the degree of polarization of the polarizing film may not be sufficiently high. On the other hand, when the draw ratio exceeds 17 times, it becomes difficult to obtain high piercing strength. Further, the film is likely to break during stretching, and the thickness of the stretched film becomes thinner than necessary, which may reduce processability and handleability in a subsequent process. The stretching treatment is usually uniaxial stretching.

The stretching treatment is not limited to one-stage stretching, and may be performed in multiple stages. In this case, all of the multi-step stretching treatment may be continuously performed before the dyeing step, or the second and subsequent stretching treatments may be performed simultaneously with the dyeing treatment and / or the crosslinking treatment in the dyeing step. .. In this case, the stretching ratio in the stretching step can be set to more than 1 times and 3.5 times or less in anticipation of stretching in the dyeing step described later. When the stretching treatment is performed in multiple stages as described above, it is preferable to perform the stretching treatment so that the total stretching ratio of all the stages of the stretching treatment is more than 4.5 times.

The stretching treatment may be longitudinal stretching that stretches in the film longitudinal direction (film transport direction), or may be lateral stretching or diagonal stretching that stretches in the film width direction. Examples of the longitudinal stretching method include inter-roll stretching using rolls, compression stretching, stretching using a chuck (clip), and the like, and examples of the transverse stretching method include a tenter method. As the stretching treatment, either a wet stretching method or a dry stretching method can be adopted, but it is preferable to use the dry stretching method in that the stretching temperature can be selected from a wide range.

The stretching treatment may be performed while heating the laminated film. As a heating method, a zone heating method (for example, a method of blowing hot air to heat in a stretching zone such as a heating furnace adjusted to a predetermined temperature); a method of heating the roll itself when stretching with a roll; a heater heating method (for example). Infrared heaters, halogen heaters, panel heaters, etc. are installed above and below the laminated film and heated by radiant heat). In the inter-roll stretching method, the zone heating method is preferable from the viewpoint of uniformity of stretching temperature. In this case, the two nip roll pairs may be installed in the temperature-controlled stretching zone or outside the stretching zone, but are installed outside the stretching zone in order to prevent adhesion between the laminated film and the nip roll. Is preferable.

(Dyeing process)
This step is a step of dyeing a polyvinyl alcohol-based resin layer of a stretched film with a dichroic dye and adsorbing and orienting the layer to form a polarizing film to obtain a polarizing laminated film. Through this step, a polarizing laminated film in which a polarizing film is laminated on one side or both sides of a base film can be obtained. The dyeing step can be performed by immersing the entire stretched film in a solution containing a dichroic dye (dyeing solution). As the dyeing solution, a solution in which the above dichroic dye is dissolved in a solvent can be used. Water is generally used as the solvent for the dyeing solution, but an organic solvent compatible with water may be further added. The concentration of the dichroic dye in the dyeing solution is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight, and further preferably 0.025 to 5% by weight. preferable.

When iodine is used as the dichroic dye, it is preferable to further add iodide to the dyeing solution containing iodine because the dyeing efficiency can be further improved. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide and the like. Can be mentioned. The concentration of iodide in the dyeing solution is preferably 0.01 to 20% by weight. Among the iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably in the range of 1: 6 to 1:80 in terms of weight ratio. It is preferably in the range of 1: 7 to 1:70, more preferably.

The immersion time of the stretched film in the dyeing solution is usually in the range of 15 seconds to 15 minutes, preferably 30 seconds to 3 minutes. The temperature of the dyeing solution is preferably in the range of 10 to 60 ° C, more preferably in the range of 20 to 40 ° C.

The dyeing step can include a cross-linking treatment step carried out following the dyeing treatment. The cross-linking treatment can be performed by immersing the dyed film in a solution containing a cross-linking agent (cross-linking solution). As the cross-linking agent, conventionally known substances can be used, and examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. Only one type of cross-linking agent may be used alone, or two or more types may be used in combination.

Specifically, the cross-linking solution can be a solution in which a cross-linking agent is dissolved in a solvent. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further contained. The concentration of the cross-linking agent in the cross-linking solution is preferably in the range of 1 to 20% by weight, more preferably in the range of 6 to 15% by weight.

The cross-linking solution can contain iodide. By adding iodide, the in-plane polarization performance of the polarizing film can be made more uniform. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide and the like. Can be mentioned. The concentration of iodide in the cross-linked solution is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

In addition, the cross-linking solution may contain other components such as a pH adjuster. As the pH adjuster, for example, sulfuric acid, hydrochloric acid, acetic acid, ascorbic acid and the like may be added.

The immersion time of the dyed film in the cross-linking solution is usually 15 seconds to 20 minutes, preferably 30 seconds to 15 minutes. The temperature of the cross-linking solution is preferably in the range of 10 to 90 ° C.

It is preferable to perform a washing step and a drying step after the dyeing step and before the first bonding step described later. The cleaning step usually includes a water cleaning step. The water washing treatment can be performed by immersing the film after the dyeing treatment or the crosslinking treatment in pure water such as ion-exchanged water and distilled water. The water washing temperature is usually in the range of 3 to 50 ° C, preferably 4 to 20 ° C. The soaking time is usually 2 to 300 seconds, preferably 3 to 240 seconds.

The cleaning step may be a combination of a water cleaning step and a cleaning step with an iodide solution. Further, the cleaning liquid used in the water cleaning step and / or the cleaning treatment with an iodide solution may appropriately contain liquid alcohols such as methanol, ethanol, isopropyl alcohol, butanol and propanol in addition to water. Examples of the iodide include potassium iodide, and the concentration of potassium iodide in the iodide solution is usually 0.5 to 10% by weight.

As the drying step performed after the washing step, any appropriate method such as natural drying, blast drying, and heat drying can be adopted. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C., and the drying time is usually about 1 to 15 minutes.

(1st bonding process)
This step is a step of laminating the first protective film and the retardation film on the polarizing film of the polarizing laminated film, that is, on the surface of the polarizing film opposite to the base film side. A photocurable adhesive is applied to the corona-treated first protective film and bonded to the polarizing film. Then, the photocurable adhesive is cured by irradiating it with active energy rays.

Next, the retardation film is laminated so as to be overlapped with the retardation film. That is, the active energy ray-curable resin composition is applied to the corona-treated retardation film and bonded to the first protective film. Then, the active energy ray is irradiated to cure the active energy ray curable resin composition. The active energy ray-curable resin composition may be applied to the first protective film side instead of the retardation film side.

(Peeling process)
This step is a step of peeling off the base film from the laminated film to obtain a laminated body with a single-sided protective film. The method of peeling and removing the base film can be peeled off by the same method as the peeling step of the separator (peeling film) performed by a normal polarizing plate with an adhesive. The base film may be peeled off immediately after the first bonding step, or may be wound into a roll once after the first bonding step and then peeled off while being unwound in the subsequent steps.

(Second bonding process)
This step is a step of attaching the other protective film to the surface of the polarizing film exposed by the peeling step via an adhesive to obtain a polarizing plate. The procedure is the same as that of the first bonding step.

Through the above steps, the laminated body 10 can be manufactured.

In some cases, as shown in FIG. 2, the pressure-sensitive adhesive layer 4 may be formed on the retardation film 2. As a method of forming the pressure-sensitive adhesive layer 4, a method of applying a solution containing a pressure-sensitive adhesive component on the retardation film 2 may be used, and after forming the pressure-sensitive adhesive layer 4 with the solution on a separately prepared separator, the pressure-sensitive adhesive layer 4 is formed. A method of transferring onto the retardation film 2 may also be used. When the laminate 10 includes the pressure-sensitive adhesive layer 4, the laminate 10 can be attached to the display element 5 (for example, a liquid crystal cell).

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the above-mentioned manufacturing process of the laminated body, a method of applying a coating liquid containing a polyvinyl alcohol-based resin on a base film was shown, but a method of applying the coating liquid on a protective film was used. May be good.

Hereinafter, the contents of the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

<Manufacturing of retardation film>
The following two types of copolymers, which are thermoplastic resins, were prepared.

・ Copolymer 1
A copolymer of 85.3 parts by mass of styrene units and 14.7 parts by mass of maleic anhydride.
Glass transition temperature Tg: 129 ° C
Weight average molecular weight Mw: 160000
Intrinsic birefringence: -0.06
Photoelastic modulus: 4.6 × ^10-12 Pa ^-1

-Copolymer 2
A copolymer of 78.8 parts by mass of styrene unit, 7.4 parts by mass of methylmethacrylate unit, and 13.8 parts by mass of maleic anhydride unit.
Glass transition temperature Tg: 132 ° C
Weight average molecular weight Mw: 187000
Intrinsic birefringence: -0.07
Photoelastic modulus: 3.7 × ^10-12 Pa ^-1

(1) Extrusion Molding Step An unstretched film was obtained by molding the molten copolymer 1 or the copolymer 2 using an extrusion molding apparatus. The temperature (melting temperature) of the copolymer 1 or the copolymer 2 in the extrusion molding step was 270 ° C. The thickness of the unstretched film was 80 μm.

(2) Stretching Step The unstretched film was cut to obtain a square unstretched film having a piece of 120 mm. A single-layer retardation film was obtained by simultaneously biaxially stretching the unstretched film while heating the square-shaped unstretched film. The strain rate of the film in the simultaneous biaxial stretching was 0.5 m / min. The stretching temperature, the stretching ratio, and the thickness of the retardation film after stretching are as shown in Table 1. The retardation films obtained from the copolymers 1 and 2 are referred to as retardation films A and B, respectively.

(3) Measurement of each phase difference The birefringence measuring device manufactured by Oji Measuring Instruments Co., Ltd. determines the phase difference value _{Rth in the thickness direction, the phase difference value R0 in} the in-plane direction, and the haze value of the obtained retardation films A and B. Measured by (trade name KOBRA-WPR). The measurement results are shown in Table 1. Both the thickness direction retardation value R _th and the in-plane retardation value R ₀ shown in Table 1 are averages of the measured values of the three samples (phase difference films). The phase difference values shown in Table 1 are values at a wavelength of 589 nm.

(4) Corona Treatment Corona treatment was performed on the retardation films A and B using a corona discharge device manufactured by Kasuga Electric Works Ltd. Specifically, a corona surface treatment frame "STR-1764", a high frequency power supply "CT-0212", and a high voltage transformer "CT-T02W" were used. The film or sheet to be corona-treated was subjected to corona discharge treatment with an output strength of 280 W on the target surface (bonded surface) of the corona treatment while moving at a speed of 10 m / min.

[Example 1]
<Manufacturing of polarizing plate with retardation film>
(1) Resin layer forming step An unstretched polypropylene (PP) film (melting point 163 ° C.) having a thickness of 90 μm was used as a base film, and the surface thereof was subjected to corona treatment to form a primer layer on the corona treated surface. .. For the primer layer, polyvinyl alcohol powder [manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average degree of polymerization 1100, degree of crosslink 99.5 mol%, trade name "Z-200"] is dissolved in hot water at 95 ° C. and has a concentration of 3. A mixed aqueous solution prepared by preparing a weight% aqueous solution and blending 5 parts by weight with a cross-linking agent [manufactured by Taoka Chemical Industry Co., Ltd., trade name "Smiley's Resin (registered trademark) 650]" with 6 parts by weight of polyvinyl alcohol powder. The primer layer was formed by applying this mixed aqueous solution to the corona-treated surface of the substrate film with a small-diameter gravure coater and drying it at 80 ° C. for 10 minutes. The thickness of the primer layer was 0.2 μm. Met.

Next, polyvinyl alcohol powder [trade name "PVA124" manufactured by Kuraray Co., Ltd., average degree of polymerization 2400, saponification degree 98.0-99.0 mol%] was dissolved in hot water at 95 ° C. to a concentration of 8% by weight. An aqueous solution of polyvinyl alcohol was prepared. The obtained aqueous solution was applied onto the primer layer using a lip coater and dried at 80 ° C. for 20 minutes to prepare a three-layer laminated film composed of a base film, a primer layer and a resin layer.

(2) Stretching Step The laminated film was stretched 5.3 times at 160 ° C. using a floating longitudinal uniaxial stretching device to obtain a stretched film.

(3) Dyeing step After that, the stretched film is immersed in a dyeing solution (see below) which is a mixed aqueous solution of iodine and potassium iodide at 30 ° C. for about 180 seconds for dyeing, and then an excess iodine solution is used with pure water at 10 ° C. Was washed away. It was then immersed in a cross-linking solution 1 (see below), which is a 78 ° C. boric acid aqueous solution, for 120 seconds, and then in a 70 ° C. cross-linking solution 2 (see below) containing boric acid and potassium iodide for 60 seconds. Then, it was washed with pure water at 10 ° C. for 10 seconds, finally dried at 40 ° C. for 150 seconds, and then dried at 55 ° C. for 150 seconds. A polarizing film layer was formed from the resin layer by the above steps, and a polarizing laminated film was obtained. The compounding ratio of each solution is as follows.

-Staining solution Water: 100 parts by weight Iodine: 0.6 parts by weight Potassium iodide: 10 parts by weight-Crosslink solution 1
Water: 100 parts by weight Boric acid: 9.5 parts by weight, cross-linking solution 2
Water: 100 parts by weight Boric acid: 5.0 parts by weight Potassium iodide: 6 parts by weight

(4) Preparation of Curable Resin Composition The following components were mixed and defoamed to prepare an ultraviolet curable resin composition in a liquid state. The glass transition temperature of the cured product of the curable resin composition A was −20 ° C., and the glass transition temperature of the cured product of the curable resin composition B was 105 ° C.
-Curable resin composition A (composition containing a photoradical polymerization initiator):
N- (2-Hydroxyethyl) Acrylamide 80 parts Methyl acrylate 20 parts 2-Methyl-1- [4- (methylthio) phenyl] -2-Moliphorinopropan-1-one (photoradical polymerization initiator, manufactured by BASF) , "Irgacure (registered trademark) 907") 3 parts Silicone leveling agent (manufactured by Toray Dow Corning Co., Ltd., "SH710") 0.2 parts

-Curable resin composition B (composition containing a photocationic polymerization initiator):
As the curable resin composition B, the one obtained in the form of a 50% propylene carbonate solution was used. The blending amount (2.25 parts) shown below is the amount of solid content.
3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate ... 75 parts 1,4-butanediol diglycidyl ether ... 20 parts 2-ethylhexyl glycidyl ether ... 5 parts Triarylsulfonium hexafluorophosphate-based photocationic polymerization Initiator ... 2.25 copies

(5) First bonding step As the first protective film, a protective film having a thickness of 23 μm formed from a cyclic polyolefin resin having a corona treatment on the bonded surface [trade name “ZT12” manufactured by Nippon Zeon Corporation]. I prepared. The curable resin composition B prepared in (4) was coated on the corona-treated surface of the first protective film with a microgravure coater, and the film side of the polarizing film of the polarizing laminated film prepared in (3) was formed. Was affixed to the opposite side. After that, using an ultraviolet irradiation device with a belt conveyor equipped with an ultraviolet lamp "D valve" manufactured by Fusion UV Systems, ultraviolet rays are irradiated from the first protective film side so that the integrated light amount becomes 250 mJ / cm ² and cured. The sex resin composition B was cured. As a result, a five-layer film composed of a base film, a primer layer, a polarizing film, a cured layer of the curable resin composition B, and a first protective film was obtained.

After that, the first protective film side of this laminated film and the retardation film A are subjected to corona treatment, and the curable resin composition A prepared in (4) is coated on the surface side of the first protective film with a microgravure coater. Then, the first protective film and the retardation film A were bonded together. After that, using an ultraviolet irradiation device with a belt conveyor equipped with an ultraviolet lamp "D valve" manufactured by Fusion UV Systems, ultraviolet rays were irradiated from the first protective film side so that the integrated light amount was 250 mJ / cm ² . The curable resin composition A was cured. From the above, a seven-layer film composed of a base film / primer layer / polarizing film / cured layer of the curable resin composition B / first protective film / cured layer of the curable resin composition A / retardation film A was obtained. .. The thickness of the polarizing film layer was 5.6 μm. The thickness of each resin composition layer after curing was 1.0 μm.

(6) Peeling Step and Second Laminating Step The base film was peeled off and removed from the 7-layer structure film produced in (5) above to obtain a laminate with a single-sided protective film. The base film could be easily peeled off. Next, as the second protective film, a protective film formed of a cyclic polyolefin resin having an antistatic function and a hard coat layer was used. The second protective film was corona-treated, and the curable resin composition B was applied to the corona-treated surface using a microgravure coater, and this was bonded to the primer layer surface of the polarizing plate with a single-sided protective film. Next, the curable resin composition was cured by irradiating ultraviolet rays from the second protective film side under the same conditions as in (5) to obtain a polarizing plate (laminated body) with a retardation film. The thickness of the curable resin composition after curing was 1.0 μm.

[Example 2]
A polarizing plate with a retardation film was obtained in the same manner as in Example 1 except that the retardation film A was changed to the retardation film B.

[Comparative Example 1]
A polarizing plate with a retardation film was obtained in the same manner as in Example 1 except that all of the curable resin compositions used in the process of producing the polarizing plate were the curable resin composition B.

[Comparative Example 2]
A polarizing plate with a retardation film was obtained in the same manner as in Example 2 except that all of the curable resin compositions used in the process of producing the polarizing plate were the curable resin composition B.

<Cold thermal impact test of polarizing plate with retardation film>
Corona treatment was carried out on the retardation film side of the polarizing plates produced in Examples and Comparative Examples, and a pressure-sensitive adhesive (storage elastic modulus: 390 KPa, thickness: 20 μm) was bonded to prepare a polarizing plate with a pressure-sensitive adhesive. A polarizing plate with an adhesive was cut out with a super cutter on a long side of 100 mm and a short side of 60 mm so that the absorption axis was parallel to the long side, and used as a thermal shock test evaluation sample. This evaluation sample was attached to a non-alkali glass plate [“Eagle-XG (registered trademark)” manufactured by Corning Inc.] on the pressure-sensitive adhesive layer side, and applied in an autoclave at a temperature of 50 ° C. and a pressure of 5 MPa for 20 minutes. The pressure treatment was performed, and the mixture was left at a temperature of 23 ° C. and an atmosphere of 60% relative humidity for one day. After that, in a cold shock tester (TSA-301L-W) manufactured by ESPEC CO., LTD., Holding at -40 ° C on the low temperature side for 30 minutes and then holding at 85 ° C on the high temperature side for 30 minutes was set as one cycle. A durability test was performed for 100 cycles.

<Moist heat durability test of polarizing plate with retardation film>
Corona treatment was carried out on the retardation film side of the polarizing plates produced in Examples and Comparative Examples, and a pressure-sensitive adhesive (storage elastic modulus: 390 KPa, thickness: 20 μm) was bonded to prepare a polarizing plate with a pressure-sensitive adhesive. A polarizing plate with an adhesive was cut out with a super cutter on a long side of 100 mm and a short side of 60 mm so that the absorption axis was parallel to the long side, and used as a wet heat durability test evaluation sample. This evaluation sample was attached to a non-alkali glass plate [“Eagle-XG (registered trademark)” manufactured by Corning Inc.] on the pressure-sensitive adhesive layer side, and applied in an autoclave at a temperature of 50 ° C. and a pressure of 5 MPa for 20 minutes. The pressure treatment was performed, and the mixture was left at a temperature of 23 ° C. and an atmosphere of 60% relative humidity for one day. Then, it was put into an oven under the moist heat condition of 65 ° C. and 90%, and the durability test of 50 evaluation samples was performed for 750 hours each.

<Evaluation method of polarizing plate with retardation film>
Of the 50 evaluation samples each of which were subjected to the thermal impact test and the wet heat durability test, the occurrence of crack-like appearance defects in the retardation film was visually confirmed. The results are shown in Table 2.

According to these results, when a curable resin composition for bonding the retardation film and the polarizing plate using a photoradical polymerization initiator is used, the retardation is obtained in both the thermal shock test and the wet heat durability test. It was found that the film did not crack.

The present invention can be used, for example, in the manufacture of a liquid crystal display device.

1 ... Polarizing plate, 2 ... Phase difference film, 3 ... Cured product of active energy ray-curable resin composition, 4 ... Adhesive layer, 5 ... Display element, 10 ... Laminated body, 11 ... Polarizing film, 12 ... Protective film , 13 ... A cured product of a photocurable adhesive.

Claims (6)

With a polarizing plate
A retardation film bonded to the polarizing plate via a cured product of an active energy ray-curable resin composition is provided.
The retardation film contains a thermoplastic resin containing a structural unit containing styrene as a monomer.
The retardation film has a thickness direction retardation value ( _Rth ) of −30 nm or less at a wavelength of 589 nm.
There is no other retardation film between the polarizing plate and the retardation film,
The active energy ray-curable resin composition contains a photoradical polymerization initiator.
A laminate in which the glass transition temperature of the cured product of the active energy ray-curable resin composition is less than 50 ° C. The polarizing plate has a polarizing film and a protective film laminated on at least one surface of the polarizing film.
The laminate according to claim 1, wherein the retardation film is bonded to the protective film. The laminate according to claim 1 or 2, wherein the thermoplastic resin has a negative intrinsic birefringence. The laminate according to any one of claims 1 to 3, wherein the retardation film is a single-layer film. The laminate according to any one of claims 1 to 4, wherein the retardation film has a thickness of 15 μm or less. The laminate according to any one of claims 1 to 5 , further comprising an adhesive layer on the side of the retardation film on which the polarizing plate is not laminated.

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