JP2008134385A - Polarizing plate for liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate for liquid crystal display, the plate preventing failure in visibility due to leakage of light, color irregularity by interference fringes or the like, coloring or reflection of external light, having high surface hardness, flexibility, excellent scratch resistance and excellent adhesiveness between a polarizer and a protective layer, and capable of maintaining a high polarization degree even under high temperature and high humidity conditions, and to provide a liquid crystal display device. <P>SOLUTION: A resin composition is obtained by dispersing particles of elastic materials having a number average particle diameter of 2.0 μm or less in a thermoplastic acrylic resin, and the resin composition and a thermoplastic acrylic resin are co-extruded to obtain a view side protective layer that has a structure of thermoplastic acrylic resin layer-resin composition layer-thermoplastic acrylic resin layer, that contains the particles of the elastic material locally present in the center along the thickness direction of the film, and has an average thickness of less than 100 μm. The view side protective layer and a liquid crystal cell side protective layer are layered on the respective surfaces of a polarizer, via a photo-cation curing adhesive comprising an aliphatic epoxy, an alicyclic epoxy and/or oxetane, and a photopolymerization initiator, to obtain the polarizing plate for liquid crystal display. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polarizing plate for liquid crystal display. More specifically, the present invention relates to a polarizing plate for liquid crystal display that protects the viewing-side surface of a liquid crystal display device, does not cause color unevenness due to interference fringes or the like, or poor visibility due to reflection of external light, has a high surface hardness, and has flexibility. .

The viewing side surface (display screen) of a display device or the like has many occasions where a human touches the surface, and the surface becomes dirty or the surface is scratched, and the display image may be difficult to see. Therefore, a protective layer is stuck on the display screen surface.
As a film used for protecting a display screen of a display device or the like, for example, Patent Document 1 discloses an acrylic made of 50 to 70 parts by mass of methyl methacrylate, 10 to 20 parts by mass of maleic anhydride, and 20 to 35 parts by mass of styrene. A composition containing a resin based resin (A) and a toughness improving agent (B) made of an impact-resistant acrylic rubber-methyl methacrylate graft copolymer, butyl-modified acetylcellulose, or the like at a mass ratio of 60 to 90 / 40-10 A polarizing film protective film made of a material has been proposed.

Patent Document 2 discloses an acrylic resin film containing 60 to 90% by mass of an acrylic resin (A) containing a glutaric anhydride unit and 7 to 40% by mass of acrylic elastic particles (B). An acrylic resin film in which the average particle diameter of the body particles (B) is 70 to 300 nm, the breaking elongation of the film is 15% or more, and the 1% deformation temperature under high tension is 100 ° C. or more has been proposed. However, these protective layers have a problem in that the surface hardness is small and the surface is scratched or soiled by rubbing the surface.
Japanese Patent Laid-Open No. 5-119217 JP 2005-314534 A

On the other hand, in Patent Document 3, a rubber-like elastic body is dispersed in the form of particles having a particle diameter of 0.15 to 4 μm in a continuous resin phase mainly composed of methyl methacrylate and dispersed in an amount of 5 to 70% by mass. 0.5 μm on one surface or both surfaces of the base material portion, with the impact-resistant acrylic resin used as the base material portion and the general acrylic resin having an alkyl methacrylate unit having an alkyl group having 1 to 4 carbon atoms as the laminated portion. The haze value is 1.0% or less and the glossiness is 130% or more when the thickness is 100 μm to 100 μm and the total thickness of the laminated part is within 30% of the total thickness of the sheet. An impact-resistant acrylic resin laminate sheet having optical properties and excellent weather resistance has been proposed. Patent Document 3 discloses that this film is used for applications that require impact resistance, such as signs, lighting covers, and automobile sun visors.
JP-A-4-59246

Patent Documents 4 and 5 propose an acrylic resin laminated film including a layer containing acrylic rubber particles and an acrylic resin, and an acrylic resin layer not containing an impact-resistant material. It is disclosed that this film is used for exteriors of household electrical appliances, automobile interiors, building materials, etc. that require high impact strength.
JP 2002-292808 A JP 2001-260288 A

Patent Document 6 includes an acrylic resin layer that includes an acrylic resin layer in which rubber particles are dispersed in methacrylic resin as a film for protecting a display screen of a portable information terminal, and has a thickness of 100 μm or more and 1,800 μm or less. A scratch-resistant acrylic resin film in which a scratch-resistant film obtained by curing a curable paint is formed on the surface of a resin film has been proposed. This protective layer is suitable as a narrow viewing-side protective layer such as a portable information terminal, but has insufficient surface hardness as a protective layer for a display device having a wide display screen.
JP 2004-143365 A

  The object of the present invention is to prevent light leakage, color unevenness due to interference fringes, etc., coloring and poor visibility due to reflection of external light, hard surface hardness, flexibility, excellent scratch resistance, protection of polarizers An object of the present invention is to provide a polarizing plate for liquid crystal display and a liquid crystal display device which are excellent in adhesiveness with a layer and can maintain a high degree of polarization even under high temperature and high humidity conditions.

  As a result of investigations to achieve the above object, the inventors of the present invention include a thermoplastic acrylic resin as a main component, and an elastic particle having a number average particle size of 2.0 μm or less is a central portion in the thickness direction of the protective layer. And a protective layer having an average thickness of less than 100 μm, a polarizer, an aliphatic epoxy, an alicyclic epoxy and / or an oxetane, and a photopolymerization initiator. By using a polarizing plate laminated through an adhesive, light leakage, color unevenness due to interference fringes, etc., and poor visibility due to coloring or reflection of external light do not occur, the surface hardness is hard, and has flexibility, It was found that a liquid crystal display device having excellent scratch resistance, excellent adhesion between a polarizer and a protective layer, and capable of maintaining a high degree of polarization even under high temperature and high humidity conditions can be obtained. The present invention has been completed as a result of further studies based on this finding.

That is, the present invention includes the following.
(1) Protection comprising a thermoplastic acrylic resin, wherein elastic particles having a number average particle size of 2.0 μm or less are unevenly distributed in the central portion in the thickness direction of the viewing-side protective layer, and the average thickness is less than 100 μm Layers,
With a polarizer,
Laminated via a photocationic curable adhesive containing an aliphatic epoxy, an alicyclic epoxy and / or oxetane, and a photopolymerization initiator,
A polarizing plate for liquid crystal display.
(2) The average thickness having a layer composed of a thermoplastic acrylic resin and elastic particles having a number average particle diameter of 2.0 μm or less and a layer composed of a thermoplastic acrylic resin laminated on both sides of the layer is less than 100 μm A protective layer,
With a polarizer,
Laminated via a photocationic curable adhesive containing an aliphatic epoxy, an alicyclic epoxy and / or oxetane, and a photopolymerization initiator,
A polarizing plate for liquid crystal display.
(3) The polarizing plate for liquid crystal displays according to (1) or (2), wherein the protective layer contains an ultraviolet absorber.
(4) The polarizing plate for liquid crystal display according to any one of (1) to (3), wherein the protective layer has a moisture permeability of 10 g · m ⁻² day ⁻¹ or more and 200 g · m ⁻² day ⁻¹ or less.
(5) A liquid crystal display device comprising the polarizing plate according to any one of (1) to (4).

  The polarizing plate of the present invention is flexible and excellent in flexibility, and does not cause visual defects such as interference fringes on the display screen, and further has no visual defects due to light leakage, color unevenness, coloring, etc. near the frame of the display screen. Equipment can be provided. Furthermore, since the surface hardness is high, it has excellent scratch resistance. Furthermore, the polarizing plate of the present invention has little reflection of external light, excellent adhesion between the polarizer and the protective layer, and can maintain a high degree of polarization even under high temperature and high humidity conditions.

    In the polarizing plate of the present invention, a protective layer and a polarizer are laminated via a photocationically curable adhesive containing an aliphatic epoxy, an alicyclic epoxy and / or oxetane, and a photopolymerization initiator. It will be. Further, usually, another protective layer is laminated on the polarizer on the side opposite to the side where the protective layer is laminated.

(Photocationic curable adhesive)
The photocationically curable adhesive used in the present invention contains an aliphatic epoxy, an alicyclic epoxy and / or oxetane, and a photopolymerization initiator.
The aliphatic epoxy used in the present invention contains a polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof. As aliphatic epoxy, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6- Examples include hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, trimethylolpropane diglycidyl ether, and polyethylene glycol diglycidyl ether. From the viewpoint of low viscosity, trimethylolpropane triglycidyl ether and trimethylolpropane diglycidyl ether are preferable. Examples of commercially available aliphatic epoxy products include “Epolite 100MF” (manufactured by Kyoeisha Chemical Co., Ltd., trimethylolpropane triglycidyl ether), “EX-321L” (manufactured by Nagase ChemteX Corporation, trimethylolpropane diglycidyl ether), and the like.

  Examples of the alicyclic epoxy used in the present invention include vinylcyclohexene monooxide, 1,2-epoxy-4-vinylcyclohexane, 1,2: 8,9 diepoxy limonene, 3,4-epoxycyclohexenylmethyl-3′4. And '-epoxycyclohexenecarboxylate. Examples of commercially available products include “CEL2000”, “CEL3000”, and “CEL2021P” manufactured by Daicel Chemical Industries.

  The oxetane compound is a compound having a 4-membered ring ether, that is, an oxetane ring in the molecule. As the oxetane compound used in the present invention, 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [{(3-ethyl-3-oxetanyl) methoxy} methyl] benzene, 3-ethyl-3- (phenoxymethyl) ) Oxetane, bis (3-ethyl-3-oxetanylmethyl) ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane), 3-ethyl-[{(3-triethoxysilylpropoxy) methyl) oxetane , Oxetanylsilsesquioxane, phenol novolac oxetane and the like. Among these oxetane compounds, 3-ethyl-3-hydroxymethyloxetane, bis (3-ethyl-3-oxetanylmethyl) ether, and 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane are preferable. Examples of commercially available oxetane compounds include “OXT-101” (3-ethyl-3-hydroxymethyloxetane), “OXT-211” (3-ethyl-3- (phenoxymethyl) oxetane) manufactured by Toagosei Co., Ltd. OXT-221 "(di [1-ethyl (3-oxetanyl)] methyl ether)," OXT-212 "(3-ethyl-3- (2-ethylhexyloxymethyl) oxetane).

Examples of the photopolymerization initiator include sulfonium salts and iodonium salts.
Examples of the sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, 4,4′-bis [diphenylsulfonio] diphenyl sulfide bishexafluorophosphate, 4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluoroantimonate, 4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluorophosphate 7- [Di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate, 7- [Di (p-toluyl) sulfonio]- -Isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenyl sulfide hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4'-diphenylsulfonio-diphenyl sulfide Hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4′-di (p-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate and the like can be mentioned.

Examples of the iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di (4-nonylphenyl) iodonium hexafluorophosphate, and the like.
These photopolymerization initiators may be used alone or in combination of two or more. Examples of commercially available products of these photopolymerization initiators include “PI-2074” manufactured by Rhodia.

Furthermore, you may make a photosensitizer contain in an adhesive agent as needed. By using a photosensitizer, the reactivity is improved, and the mechanical strength and adhesive strength of the cured product can be improved.
The photosensitizer is not particularly limited. Examples include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes. As photosensitizers, benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, α, α-dimethoxy-α-phenylacetophenone; benzophenone, 2,4-dichlorobenzophenone, methyl o-benzoylbenzoate, 4,4 ′ A benzophenone derivative such as bis (diethylamino) benzophenone; a thioxanthone derivative such as 2-chlorothioxanthone and 2-isopropylthioxanthone; an anthraquinone derivative such as 2-chloroanthraquinone and 2-methylanthraquinone; N-methylacridone, N- Acridone derivatives such as butylacridone; other examples include α, α-diethoxyacetophenone, benzyl, fluorenone, xanthone, uranyl compounds, halogen compounds, and photoreductive dyes. . These may be used alone or in combination of two or more. Examples of commercially available photosensitizers include “Kayacure DETX-S” manufactured by Nippon Kayaku Co., Ltd.

  The polarizing plate of the present invention is obtained by laminating a protective layer on one surface of the polarizer via the above-mentioned photocation curable adhesive, then curing the adhesive, and fixing the protective layer to the polarizer.

There is no particular limitation on the method of applying the adhesive to the resin film of the substrate, and 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 photocation curable adhesive is cured by light irradiation. Although the light source to be used is not particularly limited, for example, a metal halide lamp, a mercury xenon lamp, high-pressure mercury, or other light emitting light having a light emission distribution at a wavelength of 450 to 300 nm can be used. The light irradiation intensity varies depending on the target adhesive or resin film, and is not limited, but the irradiation intensity in the wavelength region effective for activation of the initiator is preferably 1 to 2000 mW / cm ² (365 nm). The light irradiation time varies depending on the adhesive or resin film to be cured, and is not limited, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 1500 to 3000 mJ / cm ² (365 nm). Is preferred.

  Prior to bonding of the protective layer to the polarizer, the bonding surface may be subjected to easy adhesion processing such as saponification treatment, corona treatment, primer treatment, and anchor coating treatment.

(Polarizer)
The polarizer used in the present invention is obtained by adsorbing iodine or dichroic dye on a polyvinyl alcohol film and then uniaxially stretching in a boric acid bath, or iodine or dichroic dye on a polyvinyl alcohol film. And the like obtained by adsorbing and stretching, and further modifying a part of the polyvinyl alcohol unit in the molecular chain into a polyvinylene unit. In addition, a polarizer having a function of separating polarized light into reflected light and transmitted light, such as a grid polarizer, a multilayer polarizer, and a cholesteric liquid crystal polarizer, can also be used as the polarizer. Among these, a polarizer comprising polyvinyl alcohol is preferable. The polarization degree of the polarizer is preferably 98% or more, more preferably 99% or more. The thickness (average thickness) of the polarizer is preferably 5 μm to 80 μm.

(Protective layer)
The protective layer used in the present invention comprises a thermoplastic acrylic resin, elastic particles having a number average particle diameter of 2.0 μm or less are unevenly distributed in the central portion in the thickness direction of the protective layer, and the average thickness is 100 μm. Less than. This protective layer is disposed on at least one side of the polarizing plate. This protective layer may function as a viewing side protective layer of the polarizing plate, or may function as a liquid crystal cell side protective layer. When this protective layer is disposed only on one side of the polarizing plate, another protective layer (hereinafter referred to as a protective layer on the other side) is usually disposed on the opposite surface.

As thermoplastic acrylic resins, homopolymers of (meth) acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate; the hydrogen of the alkyl group is an OH group, a COOH group, or an NH ₂ group Homopolymer of (meth) acrylic acid alkyl ester substituted with a functional group such as: or (meth) acrylic acid alkyl ester and styrene, vinyl acetate, α, β-monoethylenically unsaturated carboxylic acid, vinyl toluene, Examples thereof include a copolymer with a vinyl monomer having an unsaturated bond such as α-methylstyrene. As a thermoplastic acrylic resin, only 1 type may be used among these and it may use it in combination of 2 or more type. More preferably, the thermoplastic acrylic resin contains polymethyl methacrylate and polybutyl methacrylate as monomer units.

  The thermoplastic acrylic resin used in the present invention preferably has a glass transition temperature Tg in the range of 80 to 120 ° C. Further, the thermoplastic acrylic resin used in the present invention has a high surface hardness when formed into a film, specifically, pencil hardness (except for the test load of 500 g, in JIS K 5600-5-4). That are harder than 2H.

  Thermoplastic acrylic resins include colorants such as pigments and dyes, optical brighteners, dispersants, heat stabilizers, light stabilizers, infrared absorbers, ultraviolet absorbers, antistatic agents, antioxidants, lubricants, solvents A compound in which a compounding agent other than the elastic particles described later is appropriately blended can be used. In addition, it is preferable that these compounding agents are unevenly distributed in the thickness direction center part of a visual recognition side protective layer like the elastic body particle mentioned later. For example, a layer made of a thermoplastic acrylic resin containing an infrared absorber and / or an ultraviolet absorber and a layer made of a thermoplastic acrylic resin not containing an infrared absorber and / or an ultraviolet absorber sandwiching this layer are laminated. The protective layer formed is mentioned as a suitable aspect.

  The thermoplastic acrylic resin used in the present invention is preferably selected from those having a melt flow rate value in the range of 10 to 100 g / 10 min (280 ° C., load 2.16 kgf). Moreover, when a protective layer is comprised from several thermoplastic acrylic resin, it is preferable that the value of the melt flow rate of the thermoplastic acrylic resin of each layer is comparable. Specifically, the difference in the melt flow rate value of the thermoplastic acrylic resin constituting the adjacent layers is preferably 0 to 30 g / 10 minutes (280 ° C., load 2.16 kgf).

The ultraviolet absorber is added to improve durability by absorbing ultraviolet rays of 400 nm or less.
As the ultraviolet absorber, known ones such as a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, and an acrylonitrile ultraviolet absorber can be used. Among them, 2,2'-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3 '-Tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2,2'-dihydroxy- 4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone and the like are preferably used. Among these, 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) is particularly preferable. The concentration of the ultraviolet absorber can be selected within a range where the transmittance at a wavelength of 370 nm or less is preferably 10% or less, more preferably 5% or less, and still more preferably 2% or less. Examples of the method of containing the ultraviolet absorber include a method of previously blending the ultraviolet absorber into the thermoplastic acrylic resin; a method of supplying it directly at the time of melt extrusion molding, and any method may be employed.

  It is preferable that the ultraviolet absorber is unevenly distributed in the central portion in the thickness direction of the protective layer. When the protective layer is composed of a laminate, the ultraviolet absorber concentration contained in the thermoplastic acrylic resin layer containing elastic particles is the ultraviolet absorption contained in the thermoplastic acrylic resin layer not containing elastic particles. The concentration should be higher than the agent concentration. Specifically, the concentration of the ultraviolet absorber in the thermoplastic acrylic resin layer not containing the elastic particles is preferably 0 to 1.0% by weight, more preferably 0 to 0.5% by weight. The concentration of the ultraviolet absorber in the thermoplastic acrylic resin layer containing the body particles is preferably 0.5 to 10% by weight, more preferably 1.0 to 5.0% by weight. When the content of the ultraviolet absorber is within the above range, it is possible to efficiently block ultraviolet rays without deteriorating the color tone of the polarizing plate, and to prevent a decrease in the degree of polarization during long-term use. If the content of the ultraviolet absorber in the thermoplastic acrylic resin layer containing the elastic particles is too small, the light transmittance at a wavelength of 370 nm or less increases and the degree of polarization tends to decrease. On the other hand, when the content of the ultraviolet absorber is too large, the light transmittance on the short wavelength side becomes small, and the laminate tends to be yellowish.

  Infrared absorbers include nitroso compounds, metal complexes thereof, cyanine compounds, squarylium compounds, thiol nickel complex compounds, phthalocyanine compounds, naphthalocyanine compounds, triallylmethane compounds, imonium compounds, diimonium compounds, Infrared absorption of naphthoquinone compounds, anthraquinone compounds, amino compounds, aminium salt compounds, carbon black, indium tin oxide, antimony tin oxide, oxides of metals belonging to Group 4A, 5A or 6A, carbides, borides, etc. An agent etc. can be mentioned. These infrared absorbers are preferably selected so as to be able to absorb the entire infrared ray (light having a wavelength in the range of about 800 nm to 1100 nm), and two or more types may be used in combination. The amount of the infrared absorber can be appropriately adjusted so that, for example, the light transmittance at a wavelength of 800 nm or more is 10% or less.

<Elastic particles>
The elastic particles used in the present invention are particles made of a rubber-like elastic body. Examples of the rubber-like elastic body include an acrylate-based rubber-like polymer, a rubber-like polymer containing butadiene as a main component, and an ethylene-vinyl acetate copolymer. Examples of the acrylic ester rubbery polymer include those containing butyl acrylate, 2-ethylhexyl acrylate, or the like as a main component. Of these, acrylate polymers based on butyl acrylate and rubbery polymers based on butadiene are preferred. The elastic particles may be formed by laminating two kinds of polymers, and typical examples thereof include an alkyl acrylate such as butyl acrylate, a grafted rubber elastic component of styrene, and polymethyl. Examples thereof include elastic particles in which a hard resin layer made of a copolymer of methacrylate and / or methyl methacrylate and an alkyl acrylate forms a core-shell structure.

  The elastic particles used in the present invention have a number average particle diameter of 2.0 μm or less, preferably 0.1 to 1.0 μm, more preferably 0.1 to 0.5 μm, in a state dispersed in a thermoplastic acrylic resin. It is. Even if the primary particle size of the elastic particles is small, if the number average particle size of the secondary particles formed by aggregation or the like is large, the haze (cloudiness) of the protective layer becomes too high and the light transmittance is low. , Not suitable for the viewing side. Moreover, when the number average particle size becomes too small, the flexibility tends to decrease.

In the present invention, the refractive index n _a (λ) at a wavelength 380nm~780nm of elastic particles are between the refractive index n _b (λ) at a wavelength 380nm~780nm thermoplastic acrylic resin as a matrix, | n _a It is preferable that the relationship (λ) −n _b (λ) | ≦ 0.05 is satisfied. In particular, it is more preferable that | n _a (λ) −n _b (λ) | ≦ 0.045. Incidentally, n _a (lambda) and n _b (lambda) is the average value of the principal refractive index at a wavelength lambda. When the value of | n _a (λ) −n _b (λ) | exceeds the above value, transparency may be impaired due to interface reflection caused by a difference in refractive index at the interface.

  The elastic particles are unevenly distributed in the central portion in the thickness direction of the protective layer mainly composed of thermoplastic acrylic resin. That is, there are few elastic particles near the surface of the protective layer, and many elastic particles are distributed in the central portion in the thickness direction of the protective layer. The distribution of the elastic particles in the thickness direction of the protective layer may gradually increase from the surface toward the center or may increase stepwise.

  As an aspect that increases stepwise, a layer composed of a thermoplastic acrylic resin and elastic particles having a number average particle diameter of 2.0 μm or less and a layer composed of a thermoplastic acrylic resin on both sides of the layer are laminated. And a protective layer having an average thickness of less than 100 μm. There is no particular limitation on the method for obtaining this protective layer. For example, a base film is obtained by molding a composition comprising a thermoplastic acrylic resin and elastic particles having a number average particle size of 2.0 μm or less. The method of apply | coating the thermoplastic acrylic resin which does not contain an elastic body particle | grain on both surfaces of a film is mentioned. As another method, there is a method in which a film formed by molding a thermoplastic acrylic resin not containing elastic particles is bonded to both surfaces of the base film through an adhesive as necessary. As another method, there is a method in which a composition comprising a thermoplastic acrylic resin and elastic particles having a number average particle size of 2.0 μm or less and a thermoplastic acrylic resin not containing elastic particles are co-extruded. Can be mentioned. In addition, a method in which a film in which elastic particles having a number average particle size of 2.0 μm or less are unevenly distributed on one side is bonded so that the surfaces in which the elastic particles are unevenly contacted is also mentioned.

  As described above, the elastic particles are unevenly distributed in the central portion in the thickness direction of the layer, whereby the central portion in the thickness direction of the viewing-side protective layer becomes a flexible layer, and both surfaces of the protective layer become hard layers. By setting it as such a structure, the flexibility of a polarizing plate can be improved, ensuring sufficient hardness of the surface of a protective layer.

  When obtaining a protective layer in which a layer composed of a thermoplastic acrylic resin and elastic particles and a layer composed of a thermoplastic acrylic resin not containing elastic particles are laminated on both sides of the layer, an adhesive (including an adhesive) ), The average thickness of the adhesive layer made of an adhesive is usually 0.01 μm to 30 μm, preferably 0.1 μm to 15 μm. The adhesive layer is a layer having a tensile fracture strength according to JIS K 7113 of 40 MPa or less. As an adhesive constituting this adhesive layer, an acrylic adhesive, a urethane adhesive, a polyester adhesive, a polyvinyl alcohol adhesive, a polyolefin adhesive, a modified polyolefin adhesive, a polyvinyl alkyl ether adhesive, Rubber adhesive, ethylene-vinyl acetate adhesive, vinyl chloride-vinyl acetate adhesive, SEBS (styrene-ethylene-butylene-styrene block copolymer) adhesive, SIS (styrene-isoprene-styrene block copolymer) Adhesive) -based adhesives, ethylene-based adhesives such as ethylene-styrene copolymer, acrylic acid ester-based adhesives such as ethylene- (meth) methyl acrylate copolymer, ethylene- (meth) ethyl acrylate copolymer Etc. Among these, those that maintain a predetermined elasticity after curing are more preferable, and examples of such adhesives include SEBS adhesives, SIS adhesives, and ethylene-vinyl acetate adhesives.

The protective layer has a thickness (average thickness) of less than 100 μm, preferably 80 μm or less, more preferably 40 μm or more and 80 μm or less.
The difference between the thickness of the layer made of the thermoplastic acrylic resin not containing one elastic particle and the thickness of the layer made of the thermoplastic acrylic resin not containing the other elastic particle on both surfaces of the protective layer is 20 μm or less. Preferably, it is 10 μm or less, more preferably closer to 0 μm.

The protective layer preferably has a residual solvent content of 0.01% by mass or less. When the residual solvent amount is in the above range, for example, it is possible to prevent the protective layer from being deformed in a high temperature / high humidity environment and to prevent the optical performance from deteriorating. The protective layer in which the residual solvent amount falls within the above range can be obtained, for example, by coextrusion molding of a plurality of resins, or by laminating a single thermoplastic acrylic resin layer by dry lamination or thermal lamination. What was obtained by coextrusion molding from the point of productivity is preferable. In the case of coextrusion molding, it is not necessary to go through a complicated process (for example, a drying process or a coating process). Therefore, there is little mixing of external foreign matters such as dust, and excellent optical performance can be exhibited.
The residual solvent content was determined by placing 50 mg of the protective layer in a 4 mm inner diameter glass tube sample container from which moisture and organic matter adsorbed on the surface had been completely removed, heating the container at a temperature of 200 ° C. for 30 minutes, and removing it from the container. It is the value which collected the collected gas continuously and analyzed the collected gas with the thermal desorption gas chromatography mass spectrometer (TDS-GC-MS).

The protective layer preferably has a moisture permeability of 10 g · m ⁻² day ⁻¹ or more and 200 g · m ⁻² day ⁻¹ or less. By setting the moisture permeability of the viewing-side protective layer within the above-described preferable range, the adhesion between the layers constituting the viewing-side protective layer can be improved. The moisture permeability can be measured by the cup method described in JIS Z 0208 under the test conditions for 24 hours in an environment of 40 ° C. and 92% RH.

When the protective layer used in the present invention is used as a protective layer on the liquid crystal cell side of the polarizing plate described later, the protective layer is preferably optically isotropic, and specifically, Re is preferably 10 nm or less. More preferably, it is 5 nm or less. The absolute value of Rth is preferably 10 nm or less, more preferably 5 nm or less.
The in-plane direction retardation Re, retardation Rth in the thickness direction, the thickness of the film upon the d (nm), Re = ( n x -n y) × d, Rth = ((n _x + _ny ) / 2- _nz ) × d. _nx and _ny are in-plane main refractive indexes ( _nx ≧ _ny ); _nz is a refractive index in the thickness direction; and d is an average thickness.

  It is preferable that the surface of the protective layer used in the present invention is substantially free from irregularly formed linear recesses and linear protrusions, and the surface is a flat surface. The fact that it is not substantially formed means that even if a linear recess or a linear protrusion is formed, a linear recess having a depth of less than 50 nm or a width of more than 500 nm, and a height of less than 50 nm or a width of 500 nm. It is a larger linear convex part. More preferably, it is a linear concave portion having a depth of less than 30 nm or a width of 700 nm, and a linear convex portion having a height of less than 30 nm or a width of greater than 700 nm. By adopting such a configuration, it is possible to prevent the occurrence of light interference and light leakage based on the light refraction at the linear concave portions or the linear convex portions, and the optical performance can be improved. In addition, irregularly occurring means that it is formed with an unintended size, shape, or the like at an unintended position.

  The thermoplastic acrylic resin layer having no linear convex part and linear concave part having such a size is used, for example, in a T-die type extrusion molding method, to reduce the surface roughness of the lip part of the die. The part is plated with chromium, nickel, titanium, etc., ceramic is sprayed on the tip of the lip, the inner surface of the lip is TiN, TiAlN, TiC, CrN, DLC (diamond-like carbon) by PVD (Physical Vapor Deposition) method, etc. Select a resin that has the same melt flow rate value as the resin that forms the thermoplastic resin layer that uniformly adjusts the temperature distribution around the molten resin immediately after being extruded from the die, the air flow, etc. In the cast molding method, the cast support with a small surface roughness is used. It can be obtained by using a holding film, reducing the surface roughness of the coating machine, and further adjusting the temperature distribution, drying temperature, and drying time during drying of the coating layer.

  Other means for making the size of the irregularly formed linear recesses and linear projections within the above range include those adhered to the die lip in the T-die type extrusion molding method (for example, burns or Such as removing dust), improving die lip releasability, making die lip wettability uniform over the entire surface, reducing resin powder, reducing the amount of dissolved oxygen in resin pellets, installing a polymer filter in the melt extruder, etc. A method is mentioned.

  The depth of the linear concave portion described above, the height of the linear convex portion, and the width thereof can be obtained by the following method. The protective layer is irradiated with light, the transmitted light is projected onto the screen, and the light or dark stripes of light appearing on the screen (this part has a large depth of linear recesses and a large height of linear protrusions) Cut out at 30 mm square. The surface of the cut film piece is observed using a three-dimensional surface structure analysis microscope (field region 5 mm × 7 mm), converted into a three-dimensional image, and a cross-sectional profile in the MD direction is obtained from the three-dimensional image. The cross-sectional profile is obtained at 1 mm intervals in the visual field region. In this cross-sectional profile, an average line is drawn, the length from the average line to the bottom of the linear recess is the linear recess depth, or the length from the average line to the top of the linear protrusion is the linear protrusion height. It becomes. The distance between the intersection of the average line and the profile is the width. The maximum values are obtained from the measured values of the linear concave portion depth and the linear convex portion height, respectively, and the width of the linear concave portion or the linear convex portion showing the maximum value is obtained. The maximum value of the linear recess depth and the height of the linear convex portion obtained from the above, the width of the linear concave portion and the width of the linear convex portion showing the maximum value, the depth of the linear concave portion of the film Let the height of the linear protrusions and their widths.

  The method for obtaining the protective layer is not particularly limited, but preferably includes a coextrusion T die method, a coextrusion inflation method, a coextrusion lamination method and the like; a film lamination molding method such as dry lamination, and elastic particles. A known method such as a coating molding method in which the resin solution constituting the surface layer is coated on the film constituting the layer can be appropriately used. Among these, the coextrusion molding method is preferable from the viewpoint of production efficiency and not leaving volatile components such as a solvent in the film.

  Among the coextrusion molding methods, the coextrusion T-die method is preferable. Further, examples of the coextrusion T-die method include a feed block method and a multi-manifold method, but the multi-manifold method is more preferable in that variation in the thickness of the layer 1 containing elastic particles can be reduced.

  Furthermore, in the polarizing plate of the present invention, functional layers such as a hard coat layer, an antireflection layer, and an antifouling layer may be formed on the outer surface of the protective layer. In particular, these layers exhibit their functions when the protective layer is the viewer side protective layer.

(Hard coat layer)
The hard coat layer is a layer having a function of increasing the surface hardness of the protective layer, and may exhibit a hardness of H or higher in a pencil hardness test (a test plate is a glass plate) shown in JIS K5600-5-4. preferable. The protective layer provided with such a hard coat layer preferably has a pencil hardness of 4H or higher. The material for forming the hard coat layer (hard coat material) is preferably a material that is cured by heat or light. For example, organic hard such as organic silicone, melamine, epoxy, acrylic, urethane acrylate, etc. Coating materials; inorganic hard coat materials such as silicon dioxide; and the like. Among these, urethane acrylate-based and polyfunctional acrylate-based hard coat materials are preferable from the viewpoint of good adhesive strength and excellent productivity.

  The hard coat layer contains various fillers for the purpose of adjusting the refractive index, improving the flexural modulus, stabilizing the volume shrinkage, and improving heat resistance, antistatic properties, and antiglare properties, as desired. it can. Further, the hard coat layer can contain additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a leveling agent, and an antifoaming agent.

(Antireflection layer)
The antireflection layer is a layer for preventing the transfer of external light, and is laminated on the surface of the protective layer (surface exposed to the outside) directly or via another layer such as a hard coat layer. The protective layer provided with the antireflection layer preferably has a reflectance at an incident angle of 5 ° and a wavelength of 430 nm to 700 nm of 2.0% or less, and a reflectance at a wavelength of 550 nm of 1.0% or less. preferable.

  The thickness of the antireflection layer is preferably 0.01 μm to 1 μm, more preferably 0.02 μm to 0.5 μm. The antireflection layer has a refractive index smaller than the refractive index of a layer (such as a protective layer or a hard coat layer) on which the antireflection layer is laminated, specifically a low refractive index of 1.30 to 1.45. Examples thereof include those composed of a refractive index layer; those obtained by alternately laminating a plurality of low refractive index layers of a thin film made of an inorganic compound and high refractive index layers of a thin film made of an inorganic compound.

  The material for forming the low refractive index layer is not particularly limited as long as it has a low refractive index. Examples thereof include a resin material such as an ultraviolet curable acrylic resin, a hybrid material in which inorganic fine particles such as colloidal silica are dispersed in the resin, and a sol-gel material using a metal alkoxide such as tetraethoxysilane. The material for forming these low refractive index layers may be a polymerized polymer, or may be a monomer or oligomer serving as a precursor. Moreover, it is preferable that each material contains the compound containing a fluorine group, in order to provide antifouling property.

As the sol-gel material, a sol-gel material containing a fluorine group is preferably used. Examples of the sol-gel material containing a fluorine group include perfluoroalkylalkoxysilane. Perfluoroalkylalkoxysilane is, for example, CF ₃ (CF ₂ ) _n CH ₂ CH ₂ Si (OR) ₃ (wherein R represents an alkyl group having 1 to 5 carbon atoms, and n is 0 to 12). A compound represented by an integer). Specifically, as perfluoroalkylalkoxysilane, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane , And heptadecafluorodecyltriethoxysilane. Among these, the compound whose said n is 2-6 is preferable.

  The low refractive index layer can be made of a cured product of a thermosetting fluorine-containing compound or an ionizing radiation curable fluorine-containing compound. The cured product preferably has a dynamic friction coefficient of 0.03 to 0.15, and a contact angle with water of 90 to 120 degrees. Examples of the curable fluorine-containing compound include a perfluoroalkyl group-containing silane compound (for example, (heptadecafluoro-1,1,2,2-tetradecyl) triethoxysilane) and the like, and a fluorine-containing polymer having a crosslinkable functional group. Can be mentioned.

  The fluorine-containing polymer having a crosslinkable functional group is obtained by copolymerizing a fluorine-containing monomer and a monomer having a crosslinkable functional group, or by copolymerizing a fluorine-containing monomer and a monomer having a functional group, and then in the polymer. It can be obtained by adding a compound having a crosslinkable functional group to the functional group.

  Examples of the fluorine-containing monomer include fluoroolefins such as fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole; “Biscoat 6FM” ( (Organic Organic Chemicals Co., Ltd.), “M-2020” (Daikin Co., Ltd.) and other (meth) acrylic acid partial or fully fluorinated alkyl ester derivatives, and fully or partially fluorinated vinyl ethers.

  Monomers having a crosslinkable functional group or compounds having a crosslinkable functional group include monomers having a glycidyl group such as glycidyl acrylate and glycidyl methacrylate; monomers having a carboxyl group such as acrylic acid and methacrylic acid; hydroxyalkyl acrylate and hydroxyalkyl Monomers having a hydroxyl group such as methacrylate; methylol acrylate, methylol methacrylate; monomers having a vinyl group such as allyl acrylate and allyl methacrylate; monomers having an amino group; monomers having a sulfonic acid group;

  As a material for forming the low refractive index layer, a material containing a sol in which fine particles such as silica, alumina, titania, zirconia, magnesium fluoride and the like are dispersed in an alcohol solvent is used because it can improve scratch resistance. Can do. From the viewpoint of antireflection properties, the fine particles preferably have a lower refractive index. Such fine particles may have voids, and silica hollow fine particles are particularly preferable. The average particle size of the hollow fine particles is preferably 5 nm to 2,000 nm, and more preferably 20 nm to 100 nm. Here, the average particle diameter is a number average particle diameter obtained by observation with a transmission electron microscope.

(Anti-fouling layer)
The antifouling layer is a layer that can impart water repellency, oil repellency, sweat resistance, antifouling properties, and the like. As a material used for forming the antifouling layer, a fluorine-containing organic compound is suitable. Examples of the fluorine-containing organic compound include fluorocarbon, perfluorosilane, and polymer compounds thereof. As a method for forming the antifouling layer, a physical vapor deposition method such as vapor deposition or sputtering, a chemical vapor deposition method, a wet coating method, or the like can be used depending on the material to be formed. The average thickness of the antifouling layer is preferably 1 nm to 50 nm, more preferably 3 nm to 35 nm.
Furthermore, other layers such as an antiglare layer, a gas barrier layer, a transparent antistatic layer, a primer layer, an electromagnetic wave shielding layer, and an undercoat layer may be provided on the protective layer (particularly the viewing side protective layer).

When the functional layer as described above is formed, it is preferable to perform chemical treatment on the surface to be formed. Examples of the chemical treatment include corona discharge treatment, sputtering treatment, low-pressure UV irradiation treatment, and plasma treatment. In addition to the chemical treatment, the visual side protective layer of the present invention is subjected to mechanical treatment by etching, sandblasting, embossing roll, etc. for the purpose of enhancing adhesion with the functional layer and imparting antiglare property. May be.
There is no particular limitation on the method for forming these functional layers, and a general method may be employed for forming each functional layer.

(Protective layer on the other side)
When a protective layer (protective layer on the other surface) is laminated on the surface opposite to the surface on which the protective layer is formed on the polarizing plate, the protective layer on the other surface may be the same as the protective layer described above. Alternatively, it may be a protective layer conventionally used for polarizing plates. One of the protective layer formed on the protective layer and the protective layer on the other surface functions as a viewing-side protective layer, and the other functions as a liquid crystal cell-side protective layer.
The moisture permeability of the protective layer on the other side used in the present invention is preferably 5 g · m ⁻² day ⁻¹ or more, 400 g · m ⁻² day ⁻¹ or less, more preferably 10 g · m ⁻² day ⁻¹ or more. 200 g · m ⁻² day ⁻¹ or less.
By setting the moisture permeability of the protective layer within the above range, it is possible to obtain a polarizing plate excellent in durability even in a high temperature and high humidity environment.

  As the resin constituting this conventional protective layer, polycarbonate resin, polyether sulfone resin, polyethylene terephthalate resin, polyimide resin, polymethyl methacrylate resin, polysulfone resin, polyarylate resin, polyethylene resin, polystyrene resin, polyvinyl chloride resin, Examples thereof include cellulose esters and alicyclic olefin polymers. Examples of the alicyclic olefin polymer include cyclic olefin random multi-component copolymers described in JP-A No. 05-310845 or US Pat. No. 5,179,171, JP-A No. 05-97978 or US Pat. No. 5,202,388. Examples thereof include the hydrogenated polymers described, the thermoplastic dicyclopentadiene ring-opened polymers described in JP-A-11-124429, and WO99 / 20676, and hydrogenated products thereof.

  There is no particular limitation on the method of laminating the protective layer on the polarizer, and for example, a general method of laminating a protective film serving as the protective layer with the polarizer through an adhesive or the like can be employed as necessary. As an adhesive for bonding the protective layer to the polarizer, the above-mentioned photocationic curable adhesive may be used, or a conventionally known adhesive may be used.

  The protective layer is preferably formed of a material having a light transmittance of 80% or more, more preferably 85% or more, and still more preferably 90% or more in the visible region of 400 to 700 nm at a thickness of 1 mm.

The polarizing plate of this invention can laminate | stack the film which shows birefringence other than the above-mentioned protective layer, polarizer, and the protective layer of the other surface. At this time, the film showing birefringence is generally laminated on the liquid crystal cell side protective layer side.
In this case, the liquid crystal cell side is preferably optically isotropic. Specifically, Re is preferably 10 nm or less, more preferably 5 nm or less. The absolute value of Rth is preferably 10 nm or less, more preferably 5 nm or less.
The in-plane direction retardation Re, retardation Rth in the thickness direction, the thickness of the film upon the d (nm), Re = ( n x -n y) × d, Rth = ((n _x + _ny ) / 2- _nz ) × d. _nx and _ny are in-plane main refractive indexes ( _nx ≧ _ny ); _nz is a refractive index in the thickness direction; and d is an average thickness.

  Birefringent films include those obtained by stretching a film containing a thermoplastic resin, those obtained by forming an optically anisotropic layer on an unstretched thermoplastic resin film, and optical on a film containing a thermoplastic resin. After forming the anisotropic layer, it can be further stretched. The film showing birefringence may be a single layer film or a laminated film.

Moreover, you may use the film which shows the above birefringence as a liquid crystal cell side protective layer.
When a birefringent film is used as the liquid crystal cell side protective layer, or when a birefringent film is laminated on the liquid crystal cell side protective layer, optical compensation functions such as color compensation and viewing angle compensation are provided. The visibility of the liquid crystal display device is improved.

  In addition, the polarizing plate of the present invention preferably exhibits a hardness of 3H or higher in a pencil hardness test (test plate is a glass plate) shown in JIS K 5600-5-4, preferably 4H or higher. More preferred.

<Liquid crystal display device>
The liquid crystal display device of the present invention can be manufactured using the polarizing plate of the present invention. In the liquid crystal display device, a light source, an incident side polarizing plate, a liquid crystal cell, and an output side polarizing plate are usually arranged in this order. The polarizing plate of the present invention can be provided on the emission side (viewing side) and / or the incident side (light source side) of the device, but it is preferable to dispose the polarizing plate of the present invention at least on the emission side. The liquid crystal display device of the present invention may further include a retardation plate, a brightness enhancement film, a light guide plate, a light diffusion plate, a light diffusion sheet, a light collection sheet, a reflection plate, and the like.

An Example and a comparative example are shown and this invention is demonstrated in detail. Parts and% are based on mass unless otherwise specified.
The protective films obtained in Examples and Comparative Examples were evaluated by the following methods.

<Water permeability of protective film>
The measurement was performed by a method according to the cup method described in JIS Z 0208 under the test conditions of leaving for 24 hours in an environment of 40 ° C. and 92% RH. The unit of moisture permeability is g · m ⁻² · day ⁻¹ .

<Melt flow rate>
According to JIS K 7210, measurement was performed with a melt indexer F-B01 manufactured by Toyo Seiki Seisakusho under the conditions of 280 ° C. and 2.16 kgf (Condition S).

<Tensile modulus>
A thermoplastic resin is formed into a single layer to obtain a film having a thickness of 100 μm, a 1 cm × 25 cm test piece is cut out, and a tensile tester (manufactured by Toyo Baldwin, Tensilon UTM-10T-PL) is used based on ASTM D882. Then, the measurement was performed under the condition of a tensile speed of 25 mm / min. The same measurement is performed 5 times, and the arithmetic average value is set as the representative value of the tensile elastic modulus.

<Thickness of each resin layer>
The protective film was embedded in an epoxy resin, sliced using a microtome (RUB-2100, manufactured by Yamato Kogyo Co., Ltd.), and the cross section was observed and measured using a scanning electron microscope.

(Production of polarizer)
A polyvinyl alcohol film having a refractive index of 1.545 at a wavelength of 380 nm and a refractive index of 1.521 at a wavelength of 780 nm and a thickness of 75 μm is uniaxially stretched 2.5 times to obtain 0.2 g of iodine and 60 g of potassium iodide. Was immersed in an aqueous solution containing 30 g / L for 30 seconds and then immersed in an aqueous solution containing 70 g / L of boric acid and 30 g / L of potassium iodide and simultaneously uniaxially stretched 6.0 times and held for 5 minutes. Finally, it was dried at room temperature for 24 hours to obtain a polarizer P having an average thickness of 30 μm and a polarization degree of 99.95%.

(Preparation of protective film)
Polymethylmethacrylate resin not containing elastic particles (melt flow rate 18 g / 10 min (280 ° C., 2.16 kgf), tensile elastic modulus 3.3 GPa, Tg = 110 ° C., water absorption 0.3%; hereinafter, “PMMA Is mounted on a double flight type single screw extruder (ratio of effective screw length L to screw diameter D L / D = 28) with a leaf disk-shaped polymer filter with an opening of 10 μm. The molten resin was fed into one of the multi-manifold dies having a die slip surface roughness Ra of 0.1 μm at an extruder outlet temperature of 260 ° C. and an extruder gear pump speed of 6 rpm.

At the same time, polymethyl methacrylate resin (melt flow rate 20 g / 10 min (280 ° C., 2.16 kgf), elastic modulus 2.8 GPa, Tg = 100 ° C., water absorption rate, containing elastic particles having a number average particle size of 0.4 μm 0.3%; hereinafter referred to as “R ¹ -PMMA”) is introduced into a double flight type single screw extruder provided with a leaf disk-shaped polymer filter having an opening of 10 μm, and the exit temperature of the extruder At 260 ° C., the molten resin was supplied to the other of the multi-manifold dies having a die slip surface roughness Ra of 0.1 μm.

The molten PMMA and R ¹ -PMMA are each discharged from the multi-manifold die at 260 ° C., cast into a cooling roll adjusted to 130 ° C., and then passed through a cooling roll adjusted to 50 ° C. Thus, a protective film having a width of 600 mm and a thickness of 80 μm composed of a three-layer structure of PMMA layer (20 μm) / R ¹ -PMMA layer (40 μm) / PMMA layer (20 μm) was obtained by coextrusion molding. The haze of the protective film was 1% or less, and the moisture permeability was 51 g · m ⁻² · day ⁻¹ .

(Preparation of Photocationic Curable Adhesive Composition 1)
Epolite 100MF (manufactured by Kyoeisha Chemical Co., Ltd., aliphatic epoxy compound) 100 parts by mass, CEL3000 (manufactured by Daicel Chemical Industries, Ltd., alicyclic epoxy compound) 7.5 parts by mass, OXT-221 (manufactured by Toagosei) .5 parts by mass, PI 2074 (manufactured by Rhodia, photopolymerization initiator) 3.8 parts by mass, and DETX-S (manufactured by Nippon Kayaku Co., Ltd., photosensitizer) 2.3 parts by mass in a uniform liquid The mixture was stirred until the photocation curable adhesive composition 1 was prepared.

(Preparation of Photocationic Curable Adhesive Composition 2)
EPOLIGHT 100MF (Kyoeisha Chemical Co., Ltd., aliphatic epoxy compound) 100 parts by mass, CEL3000 (Daicel Chemical Industries, Ltd. m alicyclic epoxy compound) 7.5 parts by mass, OXT-221 (Toagosei Co., Ltd., oxetane compound) 7 0.5 parts by mass, 7.5 parts by mass of OXT-211 (manufactured by Toagosei Co., Ltd., oxetane compound), 5 parts by mass of OXT-101 (manufactured by Toagosei Co., Ltd., oxetane compound), PI 2074 (manufactured by Rhodia, photopolymerization initiator) 3.8 parts by mass and 2.3 parts by mass of DETX-S (manufactured by Nippon Kayaku Co., Ltd., photosensitizer) are stirred in a container until a uniform liquid is prepared to prepare a photocationically curable adhesive composition 2 did.

Example 1
The above photocationic curable adhesive composition 1 is applied to both sides of the polarizer P, then a protective film is overlaid, pressed by a roller, and then irradiated with light of 3000 mJ / cm ² (365 nm metal halide lamp). A polarizing plate 1 was obtained.

Example 2
A polarizing plate 2 was obtained in the same manner as in Example 1 except that the photocation curable adhesive composition 2 was used in place of the photo cation curable adhesive composition 1.

Comparative Example 1
Epicoat YX8000 (Japan Epoxy Resin, Aromatic Epoxy Compound) 100 parts by mass, PI 2074 (Rhodia, photopolymerization initiator) 3.8 parts by mass, and DETX-S (Nippon Kayaku Co., Ltd., photosensitizer) ) 2.3 parts by mass of the mixture was stirred until it became a uniform liquid in the container to prepare an adhesive composition 3.
A polarizing plate 3 was obtained in the same manner as in Example 1 except that the adhesive composition 3 was used in place of the photocationically curable adhesive composition 1.

<Peel test>
A test piece having a width of 15 mm and a length of 40 mm was cut out from the polarizing plate, and the protective film and the polarizer were peeled off by hand to confirm the state of peeling. In the table, “destruction” means that the film was not peeled but was broken with an applied force.

<Change in polarization degree>
Two polarizing plates cut out in a size of 10 inches square are prepared, and the transmittance (H ₀ ) at the intersection of diagonal lines of the overlapping polarizing plates so that the polarization axes are parallel to each other is shown in the JIS Z 8701 2 ° field of view (C The light source was measured using a spectrophotometer. Next, the transmittance (H ₉₀ ) at the diagonal intersection of the stacked polarizing plates was measured in the same manner so that the polarization axes were orthogonal. The polarization degree was calculated from the measured value based on the following formula.
Polarization degree (%) = [(H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )] ^1/2 × 100
(H ₀ and H ₉₀ are Y values with corrected visibility.)
Next, the two polarizing plates were sequentially exposed to the following environment, and the degree of polarization at the diagonal intersection of the polarizing plate was determined in the same manner, and the change in the degree of polarization before and after being left under high temperature and high humidity was determined.
1. 1. High temperature environment: 80 ° C., humidity 50%, 500 hours 2. High temperature and high humidity environment 1: Temperature 60 ° C, humidity 90%, 500 hours High-temperature and high-humidity environment 2: temperature 80 ° C, humidity 90%, 100 hours Low temperature environment: −30 ° C., humidity 10%, 500 hours Water-resistant environment: A wet tissue is placed on a laminated film at a temperature of 80 ° C. and a humidity of 90% and left for 30 minutes.
○: The change width of the polarization degree is 0.5 or less ×: The change width of the polarization degree exceeds 0.5

<Moisture resistance>
From the commercially available liquid crystal monitor (IPS mode 20V type liquid crystal monitor), the polarizing plate and viewing angle compensation film installed on the viewing side among the polarizing plate and viewing angle compensation film sandwiching the liquid crystal cell are peeled off, The polarizing plates 1 to 3 obtained in Examples and Comparative Examples were re-bonded to the liquid crystal cell.
The reassembled liquid crystal display device was allowed to stand in a constant temperature and humidity chamber at 80 ° C. and 95% RH for 24 hours, and then left in a constant temperature and humidity chamber at 20 ° C. and 40% RH for 24 hours. Each layer of the protective layer and the laminated state between the polarizer and the protective layer are visually observed, and if the part that peels off and appears white is 1 mm or longer from the end of the polarizing plate, the length is less than 1 mm. Evaluated as ○ if any.

<Flexibility test>
A polarizing plate was punched into 1 cm × 5 cm to obtain a test film. The obtained test film was wound around a 3 mmφ steel rod, and it was tested whether the wound film was broken at the rod. The test was conducted a total of 10 times, and the flexibility was expressed by the following index according to the number of times the test was not broken.
○: No broken film pieces △: One broken film piece ×: Two or more broken film pieces

Claims (5)

A protective layer comprising a thermoplastic acrylic resin, wherein elastic particles having a number average particle size of 2.0 μm or less are unevenly distributed in the central portion in the thickness direction of the protective layer, and the average thickness is less than 100 μm;
With a polarizer,
Laminated via a photocationic curable adhesive containing an aliphatic epoxy, an alicyclic epoxy and / or oxetane, and a photopolymerization initiator,
A polarizing plate for liquid crystal display. A protective layer having an average thickness of less than 100 μm having a layer made of a thermoplastic acrylic resin and elastic particles having a number average particle diameter of 2.0 μm or less and a layer made of a thermoplastic acrylic resin laminated on both sides of the layer When,
With a polarizer,
Laminated via a photocationic curable adhesive containing an aliphatic epoxy, an alicyclic epoxy and / or oxetane, and a photopolymerization initiator,
A polarizing plate for liquid crystal display.   The polarizing plate for liquid crystal display according to claim 1, wherein the protective layer contains an ultraviolet absorber. The polarizing plate for liquid crystal display according to any one of claims 1 to 3, wherein the viewing-side protective layer has a moisture permeability of 10 g · m ^-2 day ^-1 or more and 200 g · m ^-2 day ^-1 or less.   A liquid crystal display provided with the polarizing plate as described in any one of Claims 1-4.