JP6653990B2 - Polarizing plate and image display device having the same - Google Patents

Description

  The present invention relates to a polarizing plate and an image display device including the same. In particular, the present invention relates to a polarizing plate provided with a protective layer containing an aromatic epoxy resin as a main component and an image display device including the same.

  2. Description of the Related Art A liquid crystal display device includes a polarizing plate together with a liquid crystal for blocking transmission of light in a predetermined direction. As a polarizing plate, a structure in which a thermoplastic protective film such as a TAC (triacetyl cellulose) film, a PET (polyethylene terephthalate) film, an acrylic resin film or the like is attached to both sides of a polarizer using an adhesive, or Attaching the protective film to one side of the polarizer via an adhesive layer, and bonding a retardation film made using a COP (cycloolefin resin) film, TAC film, PC (polycarbonate) film, etc. to the other side 2. Description of the Related Art A structure in which an adhesive layer is attached via an agent layer is conventionally known.

  Further, in order to reduce the thickness, weight, and durability of the polarizing plate, a structure in which an adhesive layer is omitted and a protective film is directly formed on the polarizer is also being studied. For example, Patent Document 1 proposes a protective layer made of a cured product of a curable resin composition containing an active energy ray-curable compound including an epoxy compound laminated on one surface of a polarizing film, Patent Literature 2 proposes a protective film containing a cured product obtained by polymerizing a photopolymerizable compound including an acrylic compound, which is directly applied to the surface of a polarizer. Patent Document 3 discloses a protective film mainly composed of a cured product of an active energy ray-curable resin composition containing an alicyclic epoxy compound and an acrylic compound provided on at least one side of a polarizing film. Proposed.

  However, a protective film containing a cured product of an epoxy resin proposed in Patent Document 1 and a protective film containing a cured product containing an epoxy resin and an acrylic resin proposed in Patent Document 3 are elastic. However, there is a problem that the polarizing film is easily cracked due to heat shrinkage due to heat shrinkage. Further, since the protective film containing a cured product of an acrylic resin proposed in Patent Document 2 has a large shrinkage at the time of curing the resin, the adhesiveness to the polarizing film is weak and cracks of the polarizing film easily occur. There was a problem.

Patent No. 5267920 Patent No. 4326268 JP 2009-2111057 A

  Therefore, the present invention is to solve the above-mentioned problem, and to provide a polarizing plate provided with a protective layer having good adhesion to a polarizer and having high durability, and an image display device including the same. With the goal.

  According to one embodiment of the present invention, the polarizer includes a polarizer and a protective layer disposed on at least one surface of the polarizer and formed of a cured product of a resin composition containing an aromatic epoxy compound. A polarizing plate is provided.

  The polarizing plate according to one embodiment of the present invention includes a protective layer containing a rigid aromatic epoxy resin obtained by curing a resin composition containing an aromatic epoxy compound on at least one surface of a polarizer. An elastic modulus and high durability can be realized, and heat shrinkage of the polarizer can be suppressed. Further, since the adhesion of the protective layer to the polarizer is good, the protective layer can be formed directly on the surface of the polarizer, and there is no need to use an adhesive or the like. Therefore, the thickness and weight of the polarizing plate can be reduced.

The aromatic epoxy compound may be a compound represented by the following general formula (1).

  When the aromatic epoxy compound contains the compound represented by the general formula (1), a high elastic modulus of the protective layer can be realized.

  The resin composition contains an aromatic epoxy compound as a main component, and the aromatic epoxy compound may be contained in an amount of 40% by mass or more and 90% by mass or less based on the entire resin composition.

  Since the resin composition contains an aromatic epoxy compound as a main component, the protective layer obtained by curing the resin composition contains an aromatic epoxy resin as a main component, thereby achieving a higher elastic modulus. Therefore, heat shrinkage of the polarizer can be further suppressed, and the durability of the polarizing plate can be further improved.

  The resin composition may further include an epoxy compound having no aromatic ring.

  When the resin composition further contains an epoxy compound having no aromatic ring, the viscosity of the resin composition is diluted, and the protective layer can be easily formed on the polarizer.

  The resin composition may further include a cationic photopolymerization initiator.

  A polarizing plate having a high elastic modulus and high durability and capable of suppressing heat shrinkage of a polarizer can be realized.

  The thickness of the protective layer may be 25 μm or less.

  When the thickness of the protective layer is 25 μm or less, the reliability and flexibility of the protective layer can be improved.

  According to one embodiment of the present invention, there is provided an image display device including any one of the polarizing plates.

  The image display device according to one embodiment of the present invention includes one of the polarizing plates described above, so that durability can be improved and a long life can be realized.

  The polarizing plate according to the present invention includes a protective layer containing an aromatic epoxy resin on at least one surface of the polarizer, so that heat shrinkage of the polarizer is suppressed. As a result, cracking of the polarizer due to thermal shock can be suppressed, and a polarizing plate with excellent durability can be realized. Further, since the protective layer has good adhesiveness to the polarizer, it is possible to form the protective layer directly on the surface of the polarizer without using an adhesive or the like. Therefore, the polarizing plate according to the present invention can achieve a reduction in thickness and weight.

FIG. 1 is a cross-sectional view illustrating a polarizing plate according to an embodiment of the present invention. It is a figure for explaining the manufacturing method of the polarizing plate concerning one embodiment of the present invention.

  As a result of intensive studies to solve the above-described problems, the present inventor has realized thinning, lightening, and high durability by using an aromatic epoxy resin having a rigid skeleton as a main component of the resin composition. And completed the present invention.

  Hereinafter, a polarizing plate provided with a protective layer according to the present invention and an image display device including the polarizing plate will be described in detail with reference to the drawings. However, the polarizing plate provided with the protective layer of the present invention and an image display device including the polarizing plate can be implemented in different modes, and are interpreted as being limited to the description of the embodiments below. Not something. Note that in the drawings referred to in this embodiment, the same portions or portions having similar functions are denoted by the same reference numerals, and description thereof will not be repeated.

  FIG. 1 is a cross-sectional view illustrating an example of a polarizing plate 100 according to an embodiment of the present invention. As shown in FIG. 1, a polarizing plate 100 includes a polarizer 101 and a protective layer for a polarizing plate that is attached to a surface of the polarizer 101 and functions as a polarizer protecting member (hereinafter, simply referred to as a “protective layer”). 103 and 105 are provided.

The polarizer 101 is not particularly limited, and a conventionally known polarizer can be used. For example, a dichroic material such as iodine or a dichroic dye is adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film. And a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride. In particular, a polarizer produced by dyeing a polyvinyl alcohol film having an average degree of polymerization of 2,000 to 2,800 and a degree of saponification of 90 to 100 mol% with iodine and uniaxially stretching the film 5 to 6 times is preferable. More specifically, such a polarizer is obtained by, for example, immersing a polyvinyl alcohol film in an aqueous iodine solution, dyeing the film, and stretching the film. As the iodine aqueous solution, for example, an aqueous solution of iodine / potassium iodide of 0.1% by mass or more and 1.0% by mass or less is preferable. If necessary, the film may be immersed in an aqueous solution of boric acid or potassium iodide at 50 to 70 ° C, or may be immersed in water at 25 to 35 ° C for washing or preventing uneven dyeing. Stretching may be performed after dyeing with iodine, stretching while dyeing, or dyeing with iodine after stretching. After dyeing and stretching, it may be washed with water and dried at 35 to 55 ° C. for about 1 to 10 minutes.

Resin composition The protective layers 103 and 105 according to the present invention include an aromatic epoxy resin. That is, the protective layer according to the present invention is a cured product of a resin composition containing an aromatic epoxy compound. In the resin composition according to the present invention, in order to realize high durability, it is preferable that the aromatic epoxy compound is contained as a main component of the resin composition. The content of the aromatic epoxy compound is preferably 40% by mass or more and 90% by mass or less, more preferably 50% by mass or more and 85% by mass or less, and more preferably 60% by mass or less from the viewpoint of the cured film elastic modulus. % To 80% by mass. As the aromatic epoxy compound, an epoxy compound having two or more aromatic rings in a molecule and being bifunctional or more is preferable. In particular, the aromatic epoxy compound is preferably a diglycidyl ether having a naphthalene skeleton.

That is, the aromatic epoxy compound may be, for example, a compound represented by the following chemical formula (1).

  The protective layer according to the present invention is formed by polymerizing a resin composition containing a resin monomer which is an aromatic epoxy compound such as diglycidyl ether having a naphthalene skeleton represented by the chemical formula (1).

  The resin composition further contains an epoxy compound having no aromatic ring from the viewpoint of improving photoreactivity and diluting the viscosity of the resin composition. The content of the epoxy compound having no aromatic ring is preferably from 10% by mass to 60% by mass, more preferably from 20% by mass to 50% by mass, and more preferably from 20% by mass to 40% by mass, based on the whole resin composition. % Is particularly preferred. It may be. The epoxy compound having no aromatic ring is not particularly limited, and examples thereof include an aliphatic epoxy resin monomer and an alicyclic epoxy resin monomer.

  Examples of the aliphatic epoxy resin monomer include aliphatic polyhydric alcohols and polyglycidyl ether compounds of alkylene oxide adducts thereof, for example, 1,4-butanediol diglycidyl ether and 1,6-hexanediol diglycidyl ether. , Diethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane diglycidyl ether, polyethylene glycol diglycidyl Ether and the like.

  Examples of the alicyclic epoxy resin monomer include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 1,2: 8,9 diepoxylimonene, and 1,2-epoxy-4-vinylcyclohexane. Is mentioned.

  Further, the resin composition of the protective layer according to the present invention includes, in addition to the aromatic epoxy compound and the epoxy compound having no aromatic ring, other resin monomers, a photoacid generator (photocationic polymerization initiator), It may contain a sensitizer and the like.

Photoacid Generator As the photoacid generator, a conventionally known photoacid generator can be used without particular limitation. Specific examples include onium salts such as aromatic diazonium salts, aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes. These may be used alone or in combination of two or more.

  Examples of the aromatic diazonium salt include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, and benzenediazonium hexafluoroborate.

  Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di (4-nonylphenyl) iodonium hexafluorophosphate, and the like.

  As aromatic sulfonium salts, for example, triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl] sulfonium hexafluoroantimonate, 4,4′-bis [diphenylsulfonio] diphenylsulfidebishexafluorophosphate, 4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenylsulfidebishexafluoroantimonate, 4,4′-bis [Di (β-hydroxyethoxy) phenylsulfonio] diphenylsulfidebishexafluorophosphate, 7- [di (p-toluyl) sulfonio] -2-isopropylthioxa 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthonetetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4′-diphenylsulfonio-diphenylsulfidehexafluorophosphate, 4- (P-tert-butylphenylcarbonyl) -4'-diphenylsulfonio-diphenylsulfide hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenylsulfidetetrakis (Pentafluorophenyl) borate, diphenyl [4- (phenylthio) phenyl] sulfonium phosphate, and the like.

  Examples of the iron-allene complex include xylene-cyclopentadienyliron (II) hexafluoroantimonate, cumene-cyclopentadienyliron (II) hexafluorophosphate, xylene-cyclopentadienyliron (II) -tris (Trifluoromethylsulfonyl) methanide and the like.

  As the photoacid generator, commercially available products may be used. For example, CPI-100P, 101A, 200K, 210S (manufactured by San Apro Co., Ltd.), Kayarad (registered trademark) PCI-220, PCI-620 (manufactured by Nippon Kayaku Co., Ltd.) ), UVI-6990 (manufactured by Union Carbide), Adeka Optomer SP-150, SP-170 (manufactured by ADEKA), CI-5102, CIT-1370, 1682, CIP-1866S, 2048S, 2064S, (Nippon Soda Co., Ltd.), DPI-101, 102, 103, 105, MPI-103, 105, BBI-101, 102, 103, 105, TPS-101, 102, 103, 105, MDS-103, 105, DTS-102 , 103 (Midori Chemical Co., Ltd.), PI-2074 (Rhodia Japan K.K.) and the like.

  In addition, from the viewpoint of preventing a decrease in the curability of the resin composition after irradiation with active energy rays, and a decrease in durability, the content of the photoacid generator is determined based on the entire resin composition forming the protective layer. It is preferably from 0.1% by mass to 15% by mass, more preferably from 0.5% by mass to 10% by mass, and particularly preferably from 1% by mass to 8% by mass.

Photosensitizer The resin composition forming the protective layer of the present invention contains a photosensitizer, whereby the reactivity of cationic polymerization is improved, and the mechanical strength and adhesiveness of the resin composition of the present embodiment are improved. Can be improved.

  Examples of the photosensitizer include a carbonyl compound, an organic sulfur compound, a persulfide, a redox compound, an azo and diazo compound, a halogen compound and a photoreducing dye, and more specifically, benzoin methyl ether. Benzoin derivatives such as benzoin isopropyl ether, α, α-dimethoxy-α-phenylacetophenone; benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4′-bis (dimethylamino) benzophenone, Benzophenone derivatives such as 4'-bis (diethylamino) benzophenone; thioxanthone derivatives such as 2-chlorothioxanthone and 2-isopropylthioxanthone; anthraquinone derivatives such as 2-chloroanthraquinone and 2-methylanthraquinone; Don, acridone derivatives, such as N- butyl acridone; and, alpha, alpha-diethoxyacetophenone, benzyl, fluorenone, xanthone, uranyl compounds, halogen compounds and the like.

  From the viewpoint of improving curability and weather resistance, the content of the photosensitizer is preferably 0% by mass or more and 5% by mass or less, and more preferably 0% by mass or less, based on the entire resin composition forming the protective layer. % Or more and 35% by mass or less is particularly preferable.

Resin having photopolymerizable functional group other than epoxy group The protective layer according to the present invention may contain a resin having a photopolymerizable functional group other than epoxy group. That is, the resin composition forming the protective layer according to the present invention may further contain a resin monomer having a photopolymerizable functional group other than the epoxy group. By containing such a resin monomer, the photoreactivity can be further improved, and the viscosity of the resin composition can be easily diluted.

  Examples of the resin having a photopolymerizable functional group other than the epoxy group include oxetane resins and vinyl ether resins that are cationically polymerizable compounds, and acrylic resins that are radically polymerizable compounds.

The oxetane resin is not particularly limited as long as it has at least one oxetanyl group in the molecule. For example, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3- Phenoxymethyloxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-[(3-ethyloxetane-3-yl) methoxymethyl] oxetane, 1,4-bis [(3-ethyloxetane-3- Yl) methoxymethyl] benzene, 1,4-bis [(3-ethyloxetane-3-yl) methoxy] benzene, 1,3-bis [(3-ethyloxetane-3-yl) methoxy] benzene, 1,2 -Bis [(3-ethyloxetane-3-yl) methoxy] benzene, 4,4'-bis [(3-ethyloxetane-3-yl) methoxy] biphenyl, 2,2'-bis [(3-ethyloxeta -3-yl) methoxy] biphenyl, 3,3 ', 5,5'-tetramethyl-4,4'-bis [(3-ethyloxetane-3-yl) methoxy] biphenyl, 2,7-bis [( 3-ethyloxetane-3-yl) methoxy] naphthalene, bis [4-{(3-ethyloxetane-3-yl) methoxy} phenyl] methane, bis [2-{(3-ethyloxetane-3-yl) methoxy {Phenyl] methane, 2,2-bis [4-{(3-ethyloxetane-3-yl) methoxy} phenyl] propane, novolak-type phenol-formaldehyde resin by etherification with 3-chloromethyl-3-ethyloxetane Compound, 3 (4), 8 (9) -bis [(3-ethyloxetane-3-yl) methoxymethyl] -tricyclo [5.2.1.0 ^2,6 ] decane, 2,3-bis [(3-ethyloxetane -3-yl) methoxymethyl] norbo Lanane, 1,1,1-tris [(3-ethyloxetane-3-yl) methoxymethyl] propane, 1-butoxy-2,2-bis [(3-ethyloxetane-3-yl) methoxymethyl] butane, 1,2-bis [{2- (3-ethyloxetane-3-yl) methoxy} ethylthio] ethane, bis [{4- (3-ethyloxetane-3-yl) methylthio} phenyl] sulfide, 1,6- Bis [(3-ethyloxetane-3-yl) methoxy] -2,2,3,3,4,4,5,5-octafluorohexane, 3-[(3-ethyloxetane-3-yl) methoxy] Resins having a hydrolyzed condensate of propyltriethoxysilane, a condensate of tetrakis [(3-ethyloxetane-3-yl) methyl] silicate, and the like in the skeleton are exemplified.

  As the acrylic resin, conventionally known ones can be used without particular limitation as long as they exhibit radical polymerizability. Typically, a resin having a (meth) acryloyl group, a (meth) acrylamide group or the like in the skeleton can be mentioned, and (meth) acrylic acid and its derivative, (meth) acrylonitrile, (meth) acrylamide and its derivative And the like having in the skeleton. These resins may be used alone or in combination of two or more.

  More specifically, examples of the acrylic resin include (meth) acrylic acid and salts thereof. That is, methyl (meth) acrylate, ethyl (meth) acrylate, methylphenoxyethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) Acrylate, pentyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylate, 2-methoxyethyl (meth) acrylate, (meth) acrylate, 2-hydroxy Ethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate, 3 -Chloro-2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, ethylene glycol di (meth) acrylate, phenoxyethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, phenoxy Diethylene glycol (meth) acrylate, triethylene glycol di (meth) acrylate, phenoxytriethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, nonaethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, Dipropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,3-butanediol di (meth) acryle 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate Acrylate, trimethylolmethane tri (meth) acrylate, isobornyl (meth) acrylate, N-vinylpyrrolidone, acryloylmorpholine, urethane (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, mono-ε-caprolactone addition of tetrahydrofurfuryl alcohol (Meth) acrylate, tetrahydrofurfuryl alcohol di-ε-caprolactone adduct (meth) acrylate, tetrahydrofurfuryl alcohol mono β-methyl-δ-valerolacto (Meth) acrylate-based compounds such as (meth) acrylates of adducts of adduct, (meth) acrylates of di-β-methyl-δ-valerolactone adducts of tetrahydrofurfuryl alcohol, and ω-carboxy-polycaprolactone monoacrylate; Vinyl compounds containing nitrile groups such as acrylonitrile and methacrylonitrile; and (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide , N-butyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N- (hydroxyethyl) acrylamide, N Resins having an amide group-containing vinyl compound such as -isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, diacetone (meth) acrylamide, and N, N-methylenebis (meth) acrylamide in the skeleton are exemplified.

  Among these, at least one of a hydroxy group-containing acrylic monomer and a phenoxy group-containing acrylic monomer is excellent in initial curing property as a resin composition for forming a protective layer and from the viewpoint of improving adhesiveness with a polarizer. More preferred, especially 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, methylphenoxyethyl (meth) acrylate and phenoxydiethylene glycol (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate are even more preferred. .

  Examples of the vinyl ether resin include resins having diethylene glycol divinyl ether, triethylene glycol divinyl ether, cyclohexyl vinyl ether, polyethylene glycol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, and the like in the skeleton. Of these, triethylene glycol divinyl ether and cyclohexyl vinyl ether are particularly preferred from the viewpoints of availability and handleability.

  From the viewpoint of improving curability and weather resistance, the content of the resin monomer having a photopolymerizable functional group other than the epoxy group is 0% by mass or more based on the entire resin composition forming the protective layer. It is preferably 50% by mass or less, particularly preferably 0% by mass or more and 35% by mass or less.

Method for Producing Resin Composition for Protective Layer The method for producing the resin composition for the protective layer according to the present invention is not particularly limited, and is usually the above-described aromatic epoxy compound, an epoxy compound having no aromatic skeleton, A resin composition can be obtained by mixing a resin monomer having a photopolymerizable functional group other than an epoxy group, a photoacid generator, and a photosensitizer. Note that an organic solvent may be appropriately used for viscosity adjustment. The mixing method is not particularly limited, and may be sufficiently stirred and mixed at room temperature (25 ° C.) until the mixture becomes uniform.

Method for Manufacturing Polarizing Plate With reference to FIG. 2, a method for manufacturing a polarizing plate having a protective layer according to the present invention will be described. As shown in FIG. 2, first, a polarizer 201 is sandwiched between a PET film 203 and a PET film 205, and the obtained resin composition 207 for a protective layer is placed between the PET film 203 and the polarizer 201. An appropriate amount is dropped by a dropper between the PET film 205 and the polarizer 201, and the films are bonded by the roll presses 209 and 201. As the PET films 203 and 205, commercially available products (for example, manufactured by Toray Industries, Inc., thickness: 50 μm) can be used.

Next, the polarizing plate thus laminated before irradiation with ultraviolet light is applied to the polarizing plate at 300 to 3000 mJ / cm ² , preferably 500 to 2000 mJ / cm ² , more preferably 800 to 1500 mJ / cm ² (based on 356 nm, metal halide). After irradiating from both sides with ultraviolet rays having an irradiation amount (using a lamp), the PET films 203 and 205 are peeled off, and the polarizing plate 100 with the protective layers 103 and 105 shown in FIG. 1 is manufactured.

  In FIG. 1, the protective layers 103 and 105 are provided on both sides of the polarizer 100, and the polarizer 101 is sandwiched between the protective layers 103 and 105. However, the protective layer 103 or 105 is provided only on one side of the polarizer 101. May be provided.

  In addition, from the viewpoint of improving reliability and flexibility, the resin composition is preferably applied so that the thickness of the protective layer 103 after curing is 25 μm or less, and is applied so that the thickness is 15 μm or less. Is more preferred.

  The protective layer according to the present invention includes an aromatic epoxy resin obtained by curing an aromatic epoxy compound with a resin composition. The aromatic epoxy compound has a rigid skeleton, and the aromatic epoxy resin obtained by curing the aromatic epoxy compound is also a rigid polymer. Therefore, the protective layer containing the aromatic epoxy resin can realize a high elastic modulus and can suppress heat shrinkage of the polarizer. Further, the protective layer according to the present invention has good adhesiveness to a polarizer, and can form a protective layer directly on a substrate. Therefore, the protective layer according to the present invention can be applied as a protective film for protecting a polarizer of a polarizing plate used in an image display device. When an aromatic epoxy compound is contained as a main component, a protective layer containing an aromatic epoxy resin as a main component obtained by curing a resin composition is preferable because durability is improved.

  The polarizing plate according to the present invention can suppress the heat shrinkage of the polarizer by including the protective layer according to the present invention on at least one surface of the polarizer. As a result, cracking of the polarizer due to thermal shock can be suppressed, and a polarizing plate with excellent durability can be realized. Further, since the protective layer according to the present invention has good adhesion to the polarizer, the protective layer can be formed directly on the surface of the polarizer. Therefore, it is not necessary to use an adhesive. Therefore, the polarizing plate of the present invention can achieve a reduction in thickness and weight.

  The polarizing plate according to the present invention can be used for an image display device such as a liquid crystal display device. For example, a polarizing plate having the protective layer according to the present invention on both surfaces of a polarizer may be applied to an IPS mode liquid crystal display device. Further, a polarizing plate having the protective layer according to the present invention on at least one surface of a polarizer may be applied to a VA-mode liquid crystal display device. Since the image display device according to the present invention includes the polarizing plate with improved durability, the life can be extended.

  Hereinafter, the polarizing plate according to the present invention will be described based on Examples 1 to 6 and Comparative Examples 1 to 3.

<Example 1>
Preparation of resin composition 80 parts by mass of EPICLON HP-4032D (manufactured by DIC) as an aromatic epoxy compound, 20 parts by mass of Cel3000 (manufactured by Daicel) as an epoxy compound containing no aromatic ring, and a photoacid generator A resin composition obtained by mixing 4 parts by mass of CPI100-P (manufactured by San Apro Corporation) as a (photocationic polymerization initiator) and 0.5 parts by mass of DETX-S (manufactured by Nippon Kayaku Co., Ltd.) as a photosensitizer Was prepared.

Production of Polarizer A polarizer was produced by the following method. Polyvinyl alcohol film having an average degree of polymerization of 2400, a degree of saponification of 99.9% and a thickness of 75 μm is immersed in warm water at 28 ° C. for 90 seconds to swell, and then a concentration of iodine / potassium iodide (2/3 by weight) 0.6% by weight , And the polyvinyl alcohol film was dyed while being stretched 2.1 times. Thereafter, the film was stretched in a boric acid ester aqueous solution at 60 ° C. so that the total stretching ratio became 5.8 times, washed with water, and dried at 45 ° C. for 3 minutes to produce a polarizer (25 μm in thickness).

Preparation of Polarizing Plate Next, in a constant temperature room at room temperature (25 ° C.) and a humidity of 50% RH, using the polarizer prepared as described above and the prepared resin composition, the above-described method for producing a polarizing plate was used. And a polarizing plate. The ultraviolet irradiation conditions were 1000 mJ / cm ² from each side (365 nm standard, using a metal halide lamp). After the ultraviolet irradiation, the polarizing plate was stored in the constant temperature chamber for 24 hours, and the resin composition was aged and cured. A polarizing plate was completed. The thickness of one surface of the protective layer was 10 to 15 μm. Incidentally, the protective layers were formed on both surfaces of the polarizer.

<Example 2>
70 parts by mass of EPICLON HP-4032D (manufactured by DIC) as an aromatic epoxy compound, 30 parts by mass of EX214L (manufactured by Nagase ChemteX Corporation) as an epoxy compound not containing an aromatic ring, and CPI100- as a photoacid generator A resin composition was prepared by mixing 4 parts by mass of P (manufactured by San Apro Corporation) and 0.5 parts by mass of DETX-S (manufactured by Nippon Kayaku Co., Ltd.) as a photosensitizer. Thereafter, a polarizing plate was produced in the same manner as in Example 1 using the produced resin composition.

<Example 3>
70 parts by mass of EPICLON HP-4032D (manufactured by DIC) as an aromatic epoxy compound, 15 parts by mass of Cel3000 (manufactured by Daicel Corporation) as an epoxy compound not containing an aromatic ring, and OXT-221 (as a resin monomer) 15 parts by mass of Toagosei Co., Ltd., 4 parts by mass of CPI100-P (manufactured by San Apro) as a photoacid generator, and 0.5 parts by mass of DETX-S (manufactured by Nippon Kayaku Co., Ltd.) as a photosensitizer The mixture was mixed to prepare a resin composition. Thereafter, a polarizing plate was produced in the same manner as in Example 1 using the produced resin composition.

<Example 4>
70 parts by mass of EPICLON HP-4032D (manufactured by DIC) as an aromatic epoxy compound, 10 parts by mass of Cel3000 (manufactured by Daicel) as an epoxy compound containing no aromatic ring, and OXT-121 ( 20 parts by mass of Toagosei Co., Ltd., 4 parts by mass of CPI100-P (San Apro Co.) as a photoacid generator, and 0.5 parts by mass of DETX-S (Nippon Kayaku Co., Ltd.) as a photosensitizer The mixture was mixed to prepare a resin composition. Thereafter, a polarizing plate was produced in the same manner as in Example 1 using the produced resin composition.

<Example 5>
60 parts by mass of EPICLON HP-4032D (manufactured by DIC) as an aromatic epoxy compound, 20 parts by mass of Cel3000 (manufactured by Daicel) as an epoxy compound containing no aromatic ring, and OXT-121 ( 20 parts by mass of Toagosei Co., Ltd., 4 parts by mass of CPI100-P (San Apro Co.) as a photoacid generator, and 0.5 parts by mass of DETX-S (Nippon Kayaku Co., Ltd.) as a photosensitizer The mixture was mixed to prepare a resin composition. Thereafter, a polarizing plate was produced in the same manner as in Example 1 using the produced resin composition.

<Example 6>
50 parts by mass of EPICLON HP-4032D (manufactured by DIC) as an aromatic epoxy compound, 25 parts by mass of EX214L (manufactured by Nagase ChemteX Corporation) as an epoxy compound containing no aromatic ring, and OXT- as another resin monomer 25 parts by mass of 121 (manufactured by Toagosei Co., Ltd.), 4 parts by mass of CPI100-P (manufactured by San Apro Co.) as a photoacid generator, and DETX-S (manufactured by Nippon Kayaku Co., Ltd.) as a photosensitizer By mixing 0.5 parts by mass, a resin composition was prepared. Thereafter, a polarizing plate was produced in the same manner as in Example 1 using the produced resin composition.

<Comparative Example 1>
20 parts by mass of EPICLON HP-4032D (manufactured by DIC) as an aromatic epoxy compound, 30 parts by mass of Cel3000 (manufactured by Daicel) and 25 parts of Cel2021P (manufactured by Daicel) as an epoxy compound containing no aromatic ring Parts by mass, 20 parts by mass of OXT-221 (manufactured by Toagosei Co., Ltd.) as other resin monomer, 4 parts by mass of CPI100-P (manufactured by San Apro Co.) as photoacid generator, and DETX- as photosensitizer 0.5 parts by mass of S (manufactured by Nippon Kayaku Co., Ltd.) was mixed to prepare a resin composition. Thereafter, a polarizing plate was produced in the same manner as in Example 1 using the produced resin composition.

<Comparative Example 2>
35 parts by mass of Cel2021P (manufactured by Daicel Co., Ltd.) as an epoxy compound containing no aromatic ring, 15 parts by mass of OXT-221 (manufactured by Toagosei Co., Ltd.) and OXT-121 (manufactured by Toagosei Co., Ltd.) as other resin monomers ) Was mixed with 2.5 parts by mass of CPI100-P (manufactured by San-Apro) and 2.5 parts by mass of Irg184 (manufactured by BASF) as a photopolymerization initiator to prepare a resin composition. Thereafter, a polarizing plate was produced in the same manner as in Example 1 using the produced resin composition.

<Comparative Example 3>
75 parts by mass of Cel2021P (manufactured by Daicel Corporation) as an epoxy compound containing no aromatic ring, 25 parts by mass of OXT-221 (manufactured by Toagosei Co., Ltd.) as another resin monomer, and CPI100-P ( 4 parts by mass of San Apro Co., Ltd.) and 1 part by mass of Irg184 (manufactured by BASF) were mixed to prepare a resin composition. Thereafter, a polarizing plate was produced in the same manner as in Example 1 using the produced resin composition.

Table 1 below summarizes the compounding ratio (weight ratio) of each material of the resin compositions prepared in Examples 1 to 6 and Comparative Examples 1 to 3.

(Adhesion test)
Glass is bonded to one protective layer side of the polarizing plate prepared in Examples 1 to 6 and Comparative Examples 1 to 3 via a pressure-sensitive adhesive, and a cutter knife is attached to the surface of the protective layer of the polarizing plate opposite to the glass surface. A 1 mm square cross section was cut into 100 pieces, a cellophane tape was stuck there, and a peeling test was performed, and the adhesion was evaluated by the number of cross sections of the cross section where the protective layer remained without being peeled off from the polarizer. . The case where the number of remaining crosses was 100/100 was evaluated as ○, the case where it was 80 to 99/100 as Δ, and the case where it was less than 80/100 as X.

(Hot water immersion test)
The polarizing plates prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were cut into a size of 50 mm × 50 mm with a Thomson blade, immersed in a water bath at 60 ° C., and held for 2 hours. Thereafter, each sample was taken out of the water tank, and the degree of shrinkage of the polarizer was measured. As an evaluation standard, a size of shrinkage of less than 1.0 mm was accepted. The evaluation results are shown in Table 2 below. Preferred results are 0.5 mm or less, more preferably 0.3 mm or less, particularly preferably 0 mm.

(Heat resistance test)
The polarizing plates prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were cut into a size of 50 mm × 50 mm with a Thomson blade, and bonded to glass via a pressure-sensitive adhesive. After leaving the produced polarizing plate with glass for 500 hours in an environment of 85 ° C., cracking of the polarizer was confirmed. When there was no crack in the polarizer, it was evaluated as ○, and when there was crack, it was evaluated as x.

(Cool heat shock test)
The polarizing plates prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were cut into a size of 50 mm × 50 mm with a Thomson blade, and bonded to glass via a pressure-sensitive adhesive. After leaving the produced polarizing plate with glass in an environment of −40 ° C. to 85 ° C. and 200 cycles, cracking of the polarizer was confirmed. When there was no crack in the polarizer, it was evaluated as ○, and when there was crack, it was evaluated as x.

Table 2 below shows the evaluations and results of the adhesion test, the hot water immersion test, the heat resistance test, and the thermal shock test.

  Referring to the evaluation of the adhesion test, in any of the polarizing plates of Examples 1 to 6, the adhesion between the protective layer according to the present invention and the polarizer was good. In particular, the adhesion between the protective layer and the polarizer of Examples 1 to 5 in which the content of the aromatic epoxy compound in the resin composition was 60 parts by mass or more was good.

  Referring to the results of the hot water immersion test, in the polarizing plates of Comparative Examples 1 to 3, the shrinkage of the polarizer exceeded 0.5 mm, whereas in the polarizing plates of Examples 1 to 6, the shrinkage of the polarizer was none. 0.5 mm or less. Therefore, it can be seen that the polarizing plate according to the present invention suppressed the shrinkage of the polarizer as compared with the comparative example and improved the durability.

  Referring to the results of the heat resistance test, cracking of the polarizer was confirmed in the polarizing plates of Comparative Examples 1 to 3, whereas cracking of the polarizer was not confirmed in the polarizing plates of Examples 1 to 6. Therefore, in the polarizing plate according to the present invention, it can be seen that the shrinkage of the polarizer due to heat can be suppressed, and the durability has been improved.

  Referring to the results of the thermal shock test, cracking of the polarizer was confirmed in the polarizing plates of Comparative Examples 1 to 3, whereas cracking of the polarizer was not confirmed in the polarizing plates of Examples 1 to 6. . Therefore, it can be seen that the polarizing plate according to the present invention was able to suppress the shrinkage of the polarizer at low and high temperatures, and improved the durability.

  As can be seen from the evaluations and results of the tests of the polarizing plates of Examples 1 to 6 and Comparative Examples 1 to 3, the polarizing plate including the protective layer according to the present invention has excellent adhesiveness and excellent durability. ing. Therefore, the polarizing plate according to the present invention can be suitably used for an image display device such as a liquid crystal display device.

100: polarizing plate 101: polarizer 103: protective layer 105: protective layer 201: polarizer 203: PET film 205: PET film 207: resin composition 209: roll press 2011: roll press

Claims (6)

A polarizer,
Disposed on at least one surface of the polarizer, a protective layer formed of a cured product of a resin composition containing a bifunctional or more aromatic epoxy compound having a naphthalene skeleton,
The including a polarizing plate,
The resin composition further includes an epoxy compound having no aromatic ring including an aliphatic epoxy resin monomer or an alicyclic epoxy resin monomer,
The aromatic epoxy compound accounts for 40% by mass or more and 90% by mass with respect to the entire resin composition,
The epoxy compound having no aromatic ring accounts for 10% by mass or more and 60% by mass with respect to the entire resin composition;
The polarizing plate was cut into a size of 50 mm × 50 mm, and the cut polarizing plate piece was immersed in a water bath at 60 ° C. for 2 hours. The following is a polarizing plate. The polarizing plate according to claim 1, wherein the aromatic epoxy compound is a compound represented by the following general formula (1).

The epoxy compound having no aromatic ring includes 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, ethylene glycol diglycidyl ether, and propylene. Glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane diglycidyl ether, polyethylene glycol diglycidyl ether, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, , 2: 8,9 diepoxylimonene, and 1,2-epoxy-4-vinylcyclohexane. Polarizing plate according to Motomeko 1 or 2. The polarizing plate according to any one of claims 1 to 3 , wherein the resin composition further includes a cationic photopolymerization initiator. The polarizing plate according to any one of claims 1 to 4, wherein the thickness of the protective layer is 25μm or less. An image display device comprising a polarizing plate according to any one of claims 1 to 5.