JP6479362B2 - Polarizer protective film and polarizing plate - Google Patents

Description

  The present invention relates to a polarizer protective film.

  In a liquid crystal display device, two polarizing plates are usually disposed on both sides of a liquid crystal cell. The polarizing plate generally has a polarizer protective film bonded to both sides of a polarizer, and a film made of a cellulose-based material is usually used as the polarizer protective film. In recent years, for the purpose of improving the durability, a polarizer protective film made of a (meth) acrylic material has been proposed.

  Because of the low strength of (meth) acrylic films, studies such as biaxial stretching and the like, crosslinking elastic bodies, etc. have been conducted to improve strength.

  However, in general, (meth) acrylic films have poor affinity to polarizers as compared to cellulose films, and thus the (meth) acrylic films are subjected to a hydrophilization treatment (corona discharge treatment or the like) in order to improve adhesion. It has been proposed to perform plasma treatment) or to provide an easily bonding layer (for example, Patent Documents 1 and 2).

  In particular, since a (meth) acrylic resin film containing a crosslinked elastic body tends to be further inferior in adhesion to a polarizer, a method for improving adhesion improvement suitable for a (meth) acrylic resin film containing a crosslinked elastic body Need to consider.

JP, 2007-127893, A JP 2008-216910 A

  An object of the invention is to provide a polarizer protective film which is excellent in adhesion to a polarizer and excellent in strength. An object of the present invention is to provide a polarizing plate excellent in durability.

  As a result of intensive studies conducted by the present inventors, an easy adhesion comprising an adhesive composition containing a polyurethane having a carboxyl group and a crosslinking agent having an epoxy group in a (meth) acrylic protective film comprising a crosslinked elastic body By forming a layer, it discovers that the above-mentioned subject can be solved and completed the present invention.

  That is, the present invention relates to a polarizer having an easily adhesive layer comprising an adhesive composition comprising a polyurethane having a carboxyl group and a crosslinking agent having an epoxy group, and a (meth) acrylic resin film containing a crosslinked elastic body. It relates to a protective film.

  In a preferred embodiment, the crosslinked elastic body is a core-shell type elastic body having a core layer made of a rubbery polymer and a shell layer made of a glassy polymer.

In a preferred embodiment, the orientation birefringence of the (meth) acrylic resin film containing the crosslinked elastic body is -1.7 × 10 ^-4 to 1.7 × 10 ^-4 .

  In a preferred embodiment, the (meth) acrylic resin film containing the crosslinked elastic body has an in-plane retardation Δnd of 5.0 nm or less and a thickness direction retardation Rth of 20.0 nm or less.

In a preferred embodiment, the photoelastic coefficient of the (meth) acrylic resin film containing the crosslinked elastic body is −10 × 10 ⁻¹² to 10 × 10 ⁻¹² Pa ⁻¹ .

  The polarizing plate of the present invention has a polarizer, an adhesive layer, and the polarizer protective film of the present invention.

  In a preferred embodiment, the adhesive layer comprises an adhesive composition comprising a polyvinyl alcohol resin.

  The polarizer protective film of the present invention is excellent in strength and excellent in adhesion to a polarizer. By using the polarizer protective film of the present invention, a polarizing plate excellent in durability can be obtained.

It is a schematic sectional drawing of the polarizing plate by one preferable embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments.
A. (Meth) Acrylic Resin Film Containing Crosslinked Elastic Body (Meth) Acrylic Resin Film Containing Crosslinked Elastic Body (hereinafter sometimes referred to as "acrylic resin film of the present invention") is (meth) acrylic resin It forms from the acrylic resin composition containing resin. In the present application, "(meth) acrylic" means "acrylic or methacrylic".

  The acrylic resin film of the present invention is obtained, for example, by melt-extruding a resin component containing a (meth) acrylic resin as a main component.

  As said (meth) acrylic-type resin, 90 degreeC or more is preferable, Tg (glass transition temperature) is 105 degreeC or more more preferable, and 120 degreeC or more is more preferable. By containing a (meth) acrylic resin having a Tg of 90 ° C. or more as a main component, the resin is excellent in heat resistance and durability.

  Any appropriate (meth) acrylic resin can be adopted as the (meth) acrylic resin. For example, poly (meth) acrylic acid esters such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester -(Meth) acrylic acid copolymer, (meth) acrylic acid methyl styrene copolymer (MS resin etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer And methyl methacrylate- (meth) acrylic acid norbornyl copolymer and the like. Preferably, poly (meth) acrylic acid C1-6 alkyl (a C1-C6 alkyl group (meth) acrylic-ester type resin), such as poly (meth) acrylic acid methyl, is mentioned. More preferably, methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is mentioned.

  Further, as a (meth) acrylic resin having higher heat resistance, a (meth) acrylic resin having a glutaric acid anhydride structure, a (meth) acrylic resin having a lactone ring structure, and a glutarimide structure (meth) Acrylic resin and (meth) acrylic resin having an N-substituted maleimide structure can be mentioned.

  Among these, (meth) acrylic resins having a glutarimide structure are particularly preferable.

  As the (meth) acrylic resin having a glutarimide structure, JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328329, JP-A-2006-328334, and JP-A-2006- (Meth) acrylic resins having a glutarimide structure described in JP-A-2006-337492, JP-A-2006-337493, JP-A-2006-337569, JP-A-2007-009182, etc. Resin is mentioned.

  50-100 weight% is preferable, and, as for content of the said (meth) acrylic resin in a (meth) acrylic-type resin film, 50-99 weight% is more preferable. When the content of the (meth) acrylic resin in the (meth) acrylic resin film is less than 50% by weight, heat resistance and transparency may not be sufficient.

  The acrylic resin film of the present invention contains a crosslinked elastic body in order to improve the mechanical strength of the (meth) acrylic resin. The crosslinked elastic body can be produced by known polymerization methods such as suspension polymerization, dispersion polymerization, emulsion polymerization, solution polymerization and bulk polymerization. In particular, in order to produce a crosslinked elastic body having a core-shell type structure as described below, it is preferable to use a polymerization method such as suspension polymerization, dispersion polymerization, emulsion polymerization and the like.

  As the crosslinked elastic body, a core-shell type elastic body having a core layer made of a rubbery polymer and a shell layer made of a glassy polymer (hard polymer) is preferable. Furthermore, the core layer made of a rubbery polymer may have one or more layers made of a glassy polymer as an innermost layer or an intermediate layer.

  20 degreeC or less is preferable, as for Tg of the rubber-like polymer which comprises a core layer, -60-20 degreeC is more preferable, and -60-10 degreeC is further more preferable. When the Tg of the rubbery polymer constituting the core layer exceeds 20 ° C., the mechanical strength of the (meth) acrylic resin may not be sufficiently improved. 50 degreeC or more is preferable, as for Tg of the glass-like polymer (hard polymer) which comprises a shell layer, 50-140 degreeC is more preferable, and 60-130 degreeC is further more preferable. If the Tg of the glassy polymer constituting the shell layer is lower than 50 ° C., the heat resistance of the (meth) acrylic resin may be reduced.

  In the present application, the glass transition temperatures of the “rubbery polymer” and “glassy polymer” polymers are the values described in the polymer handbook [Polymer Hand Book (J. Brandrup, Interscience 1989)]. The values calculated using the Fox equation are to be used (e.g. polymethyl methacrylate is 105 <0> C, polybutyl acrylate is -54 <0> C).

  The content of the core layer in the core-shell type elastic body is preferably 30 to 95% by weight, more preferably 50 to 90% by weight. The proportion of the glassy polymer layer in the core layer is 0 to 60%, preferably 0 to 45%, more preferably 10 to 40% based on 100% by weight of the total amount of the core layer. The content of the shell layer in the core-shell type elastic body is preferably 5 to 70% by weight, more preferably 10 to 50% by weight.

  The core-shell type elastic body may contain any appropriate other component as long as the effects of the present invention are not impaired.

  Any appropriate polymerizable monomer may be used as the polymerizable monomer for forming the rubber-like polymer constituting the core layer.

  It is preferable that the polymerizable monomer which forms the said rubber-like polymer contains an alkyl (meth) acrylate. The alkyl (meth) acrylate is preferably contained in an amount of 50% by weight or more, more preferably 50 to 99.9% by weight, with respect to 100% by weight of the polymerizable monomer forming the rubbery polymer, and more preferably 60 to 99. More preferably, 9% by weight is included.

  Examples of the alkyl (meth) acrylate include ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, lauroyl Examples of the alkyl (meth) acrylate and the stearyl (meth) acrylate include alkyl (meth) acrylates having 2 to 20 carbon atoms in the alkyl group. These alkyl groups may have alicyclic or aromatic cyclic substituents, branched structures, or functional groups. Among these, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isononyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate and the like are preferable, and butyl acrylate, More preferred is 2-ethylhexyl acrylate or isononyl acrylate. These may be used alone or in combination of two or more.

  It is preferable that the polymerizable monomer which forms the said rubber-like polymer contains the polyfunctional monomer which has a 2 or more vinyl group in a molecule | numerator. The polymerizable monomer forming the rubbery polymer preferably contains 0.01 to 20% by weight, preferably 0.1 to 20% by weight, of a polyfunctional monomer having two or more vinyl groups in the molecule. It is more preferably contained, 0.1 to 10% by weight is further preferable, and 0.2 to 5% by weight is particularly preferable.

  Examples of polyfunctional monomers having two or more vinyl groups in the molecule include aromatic divinyl monomers such as divinylbenzene, ethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, hexanediol di ( Alkanepolyol such as (meth) acrylate, oligo ethylene glycol di (meth) acrylate, trimethylol propane di (meth) acrylate, trimethylol propane tri (meth) acrylate, poly (meth) acrylate, etc., urethane di (meth) acrylate, epoxy di ( There may be mentioned meta) acrylate, triallyl isocyanurate and the like. Moreover, as a polyfunctional monomer which has a different reactive vinyl group, an allyl (meth) acrylate, a diallyl maleate, a diallyl fumarate, a diallyl itaconate etc. can be mentioned, for example. Among these, ethylene glycol dimethacrylate, butylene glycol diacrylate and allyl methacrylate are preferable. These may be used alone or in combination of two or more.

  The polymerizable monomer forming the rubbery polymer may contain another polymerizable monomer copolymerizable with the alkyl (meth) acrylate and a polyfunctional monomer having two or more vinyl groups in the molecule. . It is preferable that 0-49.9 weight% of another polymerizable monomer is contained in the polymerizable monomer which forms the said rubber-like polymer, and it is more preferable that 0-39.9 weight% is contained.

  Examples of the other polymerizable monomer include aromatic vinyl such as styrene, vinyl toluene and α-methylstyrene, vinyl cyanide such as aromatic vinylidene, acrylonitrile and methacrylonitrile, vinylidene cyanide, methyl methacrylate and urethane acrylate. And urethane methacrylates. The other polymerizable monomer may be a monomer having a functional group such as an epoxy group, a carboxyl group, a hydroxyl group or an amino group. Specifically, examples of monomers having an epoxy group include glycidyl methacrylate, and examples of monomers having a carboxyl group include methacrylic acid, acrylic acid, maleic acid, itaconic acid, etc. As a monomer which has a hydroxyl group, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate etc. can be mentioned, for example, A diethylaminoethyl methacrylate, a diethylaminoethyl acrylate etc. can be mentioned as a monomer which has an amino group. These may be used alone or in combination of two or more.

  In addition, as the polymerizable monomer forming the rubbery polymer, a small amount of a chain transfer agent may be used in combination. As such a chain transfer agent, although a widely known one can be used, alkyl mercaptan such as octyl mercaptan, dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid derivative, etc. can be exemplified.

  Any appropriate polymerizable monomer may be used as the polymerizable monomer for forming the glassy polymer constituting the glassy polymer layer in the shell layer and the core layer.

  The polymerizable monomer for forming the glassy polymer preferably contains at least one monomer selected from alkyl (meth) acrylates and aromatic vinyl monomers. It is preferable that 50 to 100% by weight of at least one selected from alkyl (meth) acrylate and aromatic vinyl monomer be contained in 100% by weight of the polymerizable monomer forming the glassy polymer, and 60 to 100% by weight It is more preferable that

  As said alkyl (meth) acrylate, the thing whose carbon number of an alkyl group is 1-8 is preferable. In addition, these alkyl groups may have an alicyclic or aromatic cyclic substituent, a branched structure, or a functional group. As such an alkyl (meth) acrylate, for example, methyl (meth) acrylate, ethyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and the like Can be mentioned. Among these, methyl methacrylate is particularly preferred. These may be used alone or in combination of two or more.

  As said aromatic vinyl monomer, styrene, vinyl toluene, alpha-methylstyrene etc. can be mentioned, for example, Among these, styrene is preferable. These may be used alone or in combination of two or more.

  The polymerizable monomer forming the glassy polymer may contain a polyfunctional monomer having two or more vinyl groups in the molecule. In 100% by weight of the polymerizable monomer forming the glassy polymer, the polyfunctional monomer having two or more vinyl groups is preferably contained in an amount of 0 to 10% by weight, and contained in an amount of 0 to 8% by weight. More preferably, 0 to 5% by weight is further preferable.

  Specific examples of the polyfunctional monomer having two or more vinyl groups in the molecule may include the same ones as described above.

  The polymerizable monomer forming the glassy polymer may contain other polymerizable monomers copolymerizable with the alkyl (meth) acrylate and the polyfunctional monomer having two or more vinyl groups in the molecule. good. The content of the other polymerizable monomer is preferably 0 to 50% by weight, and more preferably 0 to 40% by weight in 100% by weight of the polymerizable monomer forming the glassy polymer.

  Examples of the other polymerizable monomer include vinyl cyanide such as acrylonitrile and methacrylonitrile, vinylidene cyanide, alkyl (meth) acrylates other than those described above, urethane acrylate, urethane methacrylate and the like. In addition, it may have a functional group such as an epoxy group, a carboxyl group, a hydroxyl group or an amino group. Examples of monomers having an epoxy group include glycidyl methacrylate, and examples of monomers having a carboxyl group include methacrylic acid, acrylic acid, maleic acid, itaconic acid, etc., and have a hydroxyl group. As a monomer, a 2-hydroxy methacrylate, 2-hydroxy acrylate etc. can be mentioned, for example, As a monomer which has an amino group, a diethyl aminoethyl methacrylate, a diethyl amino ethyl acrylate etc. can be mentioned, for example. These may be used alone or in combination of two or more.

  Furthermore, it is also preferable to use a small amount of a known chain transfer agent similar to that used for the rubbery polymer layer as the polymerizable monomer for forming the above glassy polymer.

  As a method of producing the core-shell type elastic body in the present invention, any suitable method capable of producing core-shell type particles can be adopted.

  For example, a suspension or emulsion dispersion containing rubber-like polymer particles is produced by suspending or emulsion-polymerizing a polymerizable monomer that forms a rubber-like polymer constituting the core layer, and subsequently, the suspension Alternatively, a core-shell type having a multi-layered structure in which a glassy polymer coats the surface of a rubbery polymer particle by adding a polymerizable monomer forming a glassy polymer constituting the shell layer to the emulsion dispersion and radically polymerizing it. The method of obtaining an elastic body is mentioned. Here, the polymerizable monomer forming the rubbery polymer and the polymerizable monomer forming the glassy polymer may be polymerized in one step, or may be polymerized in two or more steps by changing the composition ratio. It is also good.

  In order to ensure the balance of physical properties of the acrylic resin film of the present invention, it is desirable to appropriately control the structure of the core-shell type elastic body.

  As a preferable structure of the said core-shell type elastic body, for example, it has a soft rubber-like core layer and a hard glassy shell layer, and the said core layer is a (meth) acrylic-type crosslinked elastic polymer layer And (b) the rubbery core layer has a multilayer structure having one or more glassy layers in the inside, and further has a glassy shell layer outside the core layer, and the like. . By appropriately selecting the monomer type of each layer, various physical properties (mechanical properties, optical properties, in particular, orientation birefringence and photoelastic coefficient) of the (meth) acrylic resin can be arbitrarily controlled. The soft, rubbery layer preferably has a glass transition temperature of the polymer less than 20 ° C., preferably less than 0 ° C. The hard glassy layer preferably has a glass transition temperature of the polymer of 0 ° C. or more, preferably Is preferably 20 ° C. or higher.

  As a specific example of a further preferable structure of the core-shell type elastic body, for example, (i) The shell layer of the above-mentioned core-shell type elastic body preferably contains 3% by weight or more, more preferably 10% by weight or more, still more preferably 15% by weight of alkyl acrylate. A non-crosslinked methacrylic resin containing at least% by weight, (ii) The shell layer of the above core-shell type elastic body is composed of two or more multi-layered layers with different contents of alkyl acrylate, and in total 10% by weight of alkyl acrylate is preferable. A non-crosslinked methacrylic resin containing 15% by weight or more, and (iii) the core layer of the core-shell type elastic material polymerizing a mixture of alkyl methacrylate, polyfunctional monomer, alkyl mercaptan, and other monomers as appropriate Acrylic acrylate in the presence of a crystallized glassy polymer layer Having a multi-layered structure in which a rubbery polymer layer is formed by polymerizing a mixture of a conductive monomer, alkyl mercaptan and other monomer as appropriate, (iv) the core layer of the above core-shell type elastic body is obtained by redox polymerization of organic peroxide Peroxy acid (persulfuric acid, perphosphate, etc.) was used as a thermal decomposition initiator to form a rubbery polymer layer polymerized in the presence of a glassy polymer layer polymerized using as an initiator Those having a multilayer structure are exemplified. The total amount of alkyl acrylate used in the shell layer is preferably 60% by weight or less, more preferably 50% by weight or less, and still more preferably 40% by weight or less. When it exceeds 60% by weight, the dispersibility of the core-shell type elastic body in the matrix is apt to deteriorate, the mechanical strength and the transparency are deteriorated, and further, foreign matters such as fish eyes are likely to be caused. In addition, in terms of productivity of the core-shell type elastic body, it is easy to cause troubles, such as the product tends to be coarse particles. The structural design element of such a preferable core-shell type elastic body may have only one, or two or more design elements may be used in combination. By having such a structure, the core-shell type elastic body is easily dispersed in the (meth) acrylic resin of the present invention, and when forming a film, there are few defects due to undispersion and aggregation, and strength It is excellent in toughness, heat resistance, transparency and appearance, and further, whitening due to temperature change and stress is suppressed, and a film of excellent quality can be obtained.

  When the core-shell type elastic body in the present invention is produced by emulsion polymerization, suspension polymerization or the like, a known polymerization initiator can be used. Particularly preferable polymerization initiators include persulfates such as potassium persulfate, ammonium persulfate, ammonium persulfate, perphosphates such as sodium perphosphate, organic azo compounds such as azobisisobutyronitrile, cumene hydroperoxide Tertiary butyl hydroperoxide, hydroperoxide compounds such as 1,1 dimethyl-2 hydroxyethyl hydroperoxide, tertiary butyl isopropyloxy carbonate, peresters such as tertiary butyl peroxybutyrate, benzoyl peroxide, And organic peroxide compounds such as dibutyl peroxide and lauryl peroxide. These may be used as thermal decomposition type polymerization initiators, and may be used as redox type polymerization initiators in the presence of catalysts such as ferrous sulfate and water-soluble reducing agents such as ascorbic acid and sodium formaldehyde sulfoxylate. It may be selected appropriately according to the monomer composition to be polymerized, the layer structure, the polymerization temperature conditions and the like.

  When the core-shell type elastic body in the present invention is produced by emulsion polymerization, it can be produced by ordinary emulsion polymerization using a known emulsifier. Examples of known emulsifiers include anionic salts such as sodium alkyl sulfonate, sodium alkyl benzene sulfonate, sodium dioctyl sulfosuccinate, sodium lauryl sulfate, sodium fatty acid, phosphate salts such as sodium polyoxyethylene lauryl ether phosphate, etc. Surfactants, nonionic surfactants such as alkylphenols, reaction products of aliphatic alcohols with propylene oxide, ethylene oxide, etc. are shown. These surfactants may be used alone or in combination of two or more. Further, if necessary, cationic surfactants such as alkylamine salts may be used. Among these, from the viewpoint of improving the thermal stability of the obtained core-shell type elastic body, in particular, polymerization is performed using a phosphate ester salt (alkali metal or alkaline earth metal) such as polyoxyethylene lauryl ether sodium phosphate. It is preferable to do. The core-shell type elastic material latex obtained by the emulsion polymerization coagulates a polymer component by spray drying or, as is generally known, by adding an electrolyte or an organic solvent as a coagulant to the latex, and appropriately heating, washing and cleaning. An operation such as separation of the aqueous phase is carried out to dry the polymer, whereby a bulk or powdery core-shell type elastic body is obtained. As the coagulant, known materials such as water-soluble electrolytes and organic solvents can be used, but from the viewpoint of improving the thermal stability at the time of molding of the obtained copolymer and from the aspect of productivity, magnesium chloride or sulfuric acid It is preferable to use a magnesium salt such as magnesium or a calcium salt such as calcium acetate or calcium chloride.

  The acrylic resin film of the present invention preferably contains 1 to 40 parts by weight, more preferably 2 to 35 parts by weight, and still more preferably 3 to 3 parts by weight of a core-shell type elastic body with respect to 100 parts by weight of (meth) acrylic resin. It is 25 parts by weight. When the content of the core-shell type elastic body is less than 1 part by weight, the mechanical strength of the (meth) acrylic resin is not sufficiently improved. When it exceeds 40 parts by weight, the heat resistance of the (meth) acrylic resin is It may decrease.

  As a preferable particle size of the core-shell type elastic body, the particle size of the soft core layer is preferably 1 to 500 nm, more preferably 10 to 400 nm, and still more preferably 50 to 300 nm. It is particularly preferred that it is -300 nm. When the particle diameter of the core layer of the core-shell type elastic body is less than 1 nm, the mechanical strength of the (meth) acrylic resin is not sufficiently improved, and when it is larger than 500 nm, the heat resistance of the (meth) acrylic resin And transparency may be impaired. Here, the particle diameter is determined by, for example, a dynamic light scattering method using MICROTRAC UPA 150 (manufactured by Nikkiso Co., Ltd.), or a turbidity method in which the transmittance of a polymerization solution per unit weight is measured using a turbidity meter. It can be asked. Further, a film obtained by forming a compound obtained by blending a core-shell crosslinked elastic body and a polymethyl methacrylate (for example, Sumipex EX manufactured by Sumitomo Chemical Co., Ltd.) at a weight ratio of 20:80 is a transmission electron microscope (JEM-made by JEOL) It is also possible to photograph 100 rubber particle images at random from the obtained photograph taken at an accelerating voltage of 80 kV and RuO 4 -stained ultrathin section method at 1200 EX), and it is also possible to calculate the average value of their particle diameters.

The smaller the orientation birefringence, the better the acrylic resin film of the present invention, and the range of -1.7 x 10 ^-4 to 1.7 x 10 ^-4 is preferable. By using such a resin, the retardation value of the (meth) acrylic protective film containing a crosslinked elastic body can be reduced.

The smaller the photoelastic coefficient of the acrylic resin film of the present invention, the better, and -10 × 10 ^-12 to 10 × 10 ^-12 Pa ^-1 is preferable, and -4 × 10 ^-12 to 4 × 10 ^-12 Pa ^-1 is preferable. Is more preferred.

  The breaking elongation of the acrylic resin film of the present invention is not particularly limited, but the breaking elongation measured by the method according to JIS K 7127 is preferably 10% or more, more preferably 25% or more, still more preferably 50% or more It is more preferably 80% or more, and even more preferably 100%. If the breaking elongation is less than 10%, the strength may be low and film handling may be difficult.

  The acrylic resin film of the present invention may contain another thermoplastic resin in addition to the (meth) acrylic resin. Other thermoplastic resins include olefin polymers, vinyl halide polymers, styrene polymers, ester polymers, amide polymers and the like.

  0 to 50 weight% is preferable in 100 weight% of acrylic resin compositions, and, as for the content rate of the other thermoplastic resin in the acrylic resin film of this invention, 0 to 30 weight% is more preferable.

  The acrylic resin film of the present invention may optionally contain any additive. Examples of the additive include antioxidants, light stabilizers, weather stabilizers, stabilizers such as heat stabilizers, ultraviolet light absorbers, flame retardants, antistatic agents, fillers, plasticizers, lubricants, and the like.

  Although there is no restriction | limiting in particular as a manufacturing method of the acrylic resin film of this invention, For example, (meth) acrylic resin, a crosslinked elastic body, another polymer, an additive, etc. are mixed by arbitrary appropriate methods Can be formed into a film.

  Although there is no restriction | limiting in particular as said mixing method, After pre-mixing said film raw material, the method of melt-kneading with an extruder is mentioned.

  Examples of the film forming method include any suitable film forming method such as a solution casting method, a melt extrusion method, a calendar method, and a compression molding method. Among these molding methods, the melt extrusion method is preferred from the balance of cost and performance.

  Examples of the above-mentioned melt extrusion method include a T-type die method and an inflation method. 150-350 degreeC is preferable and 200-300 degreeC of a shaping | molding temperature is more preferable.

  In the case of film forming by the T-die method, a T-die is attached to the tip of a single-screw extruder or twin-screw extruder, and a film extruded into a film is wound to produce a roll film. be able to.

  The acrylic resin film of the present invention may be an extruded film (unstretched film) or a stretched film. The stretched film may be either a uniaxially stretched film or a biaxially stretched film. When it is a biaxially stretched film, it may be either a simultaneous biaxial stretched film or a sequential biaxially stretched film.

  The stretching temperature is preferably in the vicinity of the glass transition temperature of the thermoplastic resin composition which is a film material, specifically (Tg-20 ° C) to (Tg + 100 ° C), and (Tg) to (Tg + 50 ° C) Is more preferred. If the stretching temperature is less than (Tg-20 ° C.), the film is likely to break and stretching may not be sufficiently performed, and if it exceeds (Tg + 100 ° C.), the film may be melted and the like.

  Although there is no restriction | limiting in particular in the magnification of extending | stretching, 1.1-10 times are preferable and 1.4-5 times are more preferable. When the draw ratio is less than 1.1 times, the strength improvement effect by drawing is not sufficient.

  The acrylic resin film of the present invention is suitably used as any of an unstretched film, a uniaxially stretched film, and a biaxially stretched film because the mechanical strength of the film is excellent.

  The smaller the retardation value of the acrylic resin film of the present invention, the better. The in-plane retardation Δnd is 5.0 nm or less, the thickness direction retardation Rth is preferably 20.0 nm or less, Δnd is 2.0 nm or less, Rth 5 The thickness is more preferably not more than 0 nm, Δnd is not more than 1.0 nm, and Rth is not more than 3.0 nm. If the value of the phase difference exceeds these values, the optical characteristics may be degraded.

  5-200 micrometers is preferable and, as for the thickness of the acrylic resin film of this invention, 10-100 micrometers is more preferable. When the thickness is less than 5 μm, sufficient strength can not be obtained, and when the thickness exceeds 200 μm, the transparency decreases and the solvent (such as water) of the adhesive dries slowly, and the thickness of the polarizing plate May become thick.

  40 mN / m or more is preferable and, as for the wetting tension of the surface of the acrylic resin film of this invention, 50 mN / m or more is more preferable. If the surface wet tension is at least 40 mN / m or less, the adhesive strength between the acrylic protective film of the present invention and the polarizer may be reduced.

In order to increase the surface wet tension, corona discharge treatment, plasma treatment, ozone treatment, ultraviolet irradiation, flame treatment, chemical treatment or the like may be performed. Among these, corona discharge treatment and plasma treatment are preferable.
B. Adhesive layer The adhesive layer is an adhesive composition comprising a polyurethane having a carboxyl group and a crosslinking agent having an epoxy group on the surface of the acrylic resin film of the present invention (hereinafter referred to as “the adhesive of the present invention It may form by drying after apply | coating an adhesive composition ".

  By applying and drying the easy adhesive composition of the present invention on the adhesive surface of the acrylic protective film of the present invention with the polarizer, the adhesion to the polarizer is significantly improved.

  The easy adhesive composition of the present invention includes a water-based one and an organic one. From the viewpoint of environment and workability, a water-based easy adhesion composition is preferable, but from the viewpoint of dispersibility and solubility , May contain a small amount of organic solvent. As the organic solvent, alcohol solvents, ketone solvents, ester solvents and ether solvents are preferable in terms of compatibility with water and ease of handling.

  Specific examples of alcohol solvents include methanol, ethanol, propanol, isopropanol, butanol, ethylene glycol, propylene glycol and the like.

  Specific examples of the ketone solvent include acetone, methyl ethyl ketone, isobutyl ketone and the like.

  Examples of ester solvents include ethyl acetate and butyl acetate.

  Examples of the ether solvents include dimethoxyethane and tetrahydrofuran.

  The polyurethane having a carboxyl group is obtained, for example, by reacting a polyol, a polyisocyanate, and a chain length agent having a free carboxyl group.

  The polyol is not particularly limited as long as it has two or more hydroxyl groups in the molecule, and any suitable polyol can be used. For example, polyacrylic polyol, polyester polyol, polyether polyol and the like can be mentioned. These can be used alone or in combination of two or more.

  The polyisocyanate is not particularly limited as long as it has two or more isocyanate groups in the molecule, and any suitable polyisocyanate can be used. For example, aliphatic isocyanate, aromatic isocyanate and the like can be mentioned. These can be used alone or in combination of two or more.

  Examples of chain extenders having a free carboxyl group include dihydroxycarboxylic acid and dihydroxysuccinic acid. Examples of dihydroxycarboxylic acids include dialkylolalkanoic acids such as dimethylolalkanoic acid (eg, dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, dimethylolbutyric acid, dimethylolbutanoic acid). These can be used alone or in combination of two or more.

  Any appropriate urethane reaction catalyst may be used in the production of the polyurethane having a carboxyl group.

  The number average molecular weight of the polyurethane having a carboxyl group is preferably 5,000 to 600,000, and more preferably 10,000 to 400,000. The acid value of the polyurethane is preferably 10 or more, more preferably 10 to 50, and particularly preferably 20 to 45. When the acid value is in such a range, the adhesion between the polarizer and the protective film may be more excellent.

  In the easy adhesive composition of the present invention, a crosslinking agent having an epoxy group is used.

  The epoxy crosslinking agent used in the present invention is not particularly limited as long as it has at least one epoxy group in the molecule. For example, bisphenol type epoxy compounds, novolac type epoxy compounds, alicyclic epoxy compounds, aliphatic epoxy compounds, aromatic epoxy compounds, glycidyl amine type epoxy compounds, halogenated epoxy compounds and the like can be mentioned.

Specifically, bisphenol type epoxy compounds such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether;
Novolac epoxy compounds such as phenol novolac epoxy compounds and cresol novolac epoxy compounds;
3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-meta-dioxane, bis (3 , 4-Epoxycyclohexylmethyl) adipate, vinylcyclohexene oxide, 4-vinylepoxycyclohexane, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxy-6-methylcyclohexyl-3'4, '-Epoxy-6'-methylcyclohexanecarboxylate, methylene bis (3,4-epoxycyclohexane), dicyclopentadiene diepoxide, di (3,4-epoxycyclohexylmethyl) ether of ethylene glycol, ethylene bis (3,4 Epoxycyclohexanecarboxylate), epoxidized tetrabenzyl alcohol, lactone modified 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexane carboxylate, lactone modified epoxidized tetrahydrobenzyl alcohol, cyclohexene oxide, hydrogenated bisphenol A diglycidyl Alicyclic epoxy compounds such as ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol AD diglycidyl ether;
Aliphatic epoxy compounds such as 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether;
Halogenated epoxy compounds such as brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, brominated bisphenol S diglycidyl ether;
Examples thereof include glycidyl amine type epoxy compounds such as tetraglycidyl aminophenylmethane.

The solid content concentration of the adhesive composition of the present invention is preferably 1 to 50% by weight, and more preferably 5 to 40% by weight from the viewpoint of workability when forming the adhesive layer. Crosslinking in the adhesive composition is more preferable. The content of the agent is preferably 0.01 to 30 parts by weight, more preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the polyurethane having a carboxyl group.

  The thickness of the easy adhesion layer can be set to any appropriate value. It is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm, and particularly preferably 0.2 to 1.5 μm. By setting it in such a range, excellent adhesion with a polarizer can be exhibited.

  Before application of the easy adhesive composition of the present invention, it is preferable to subject the surface of the acrylic resin film of the present invention to corona discharge treatment and plasma treatment in advance.

  Any appropriate method can be adopted as a method of applying the easy adhesive composition of the present invention. For example, a bar coating method, a roll coating method, a gravure coating method, a rod coating method, a slot orifice coating method, a curtain coating method, a fountain coating method and the like can be mentioned.

  As drying temperature of the easily adhesive composition of this invention, 50 degreeC or more is preferable, and 80 degreeC or more is more preferable.

The easy adhesive composition of the present invention may further contain any suitable additive. Additives include, for example, antiblocking agents, dispersion stabilizers, thixotropic agents, antioxidants, ultraviolet light absorbers, antifoaming agents, thickeners, dispersing agents, surfactants, catalysts, fillers, lubricants, antistatics Agents and the like.
C. Overall Configuration of Polarizing Plate FIG. 1 is a schematic cross-sectional view of a polarizing plate according to a preferred embodiment of the present invention.

The polarizing plate 5 is formed by laminating the polarizer 1, the adhesive layer 2, the easily adhesive layer 3, and the acrylic resin film 4 in this order.
C-1. Polarizer As the above-mentioned polarizer 1, for example, one obtained by adsorbing a dichroic substance such as iodine or a dichroic dye to a hydrophilic film such as a polyvinyl alcohol-based film and uniaxially stretching it is preferably used. The thickness of these polarizers is not particularly limited, but is about 1 to 80 μm.

  The polarizer which made iodine adsorb | suck to a polyvinyl alcohol-type film, and uniaxially stretched is produced by, for example, extending | stretching, after immersing polyvinyl alcohol in iodine aqueous solution.

  The polyvinyl alcohol-based film may be rinsed before dyeing, if necessary. By washing the polyvinyl alcohol-based film with water, generation of uneven dyeing can be prevented.

Stretching may be performed after dyeing with iodine, may be stretched while dyeing, or may be stretched and then dyed with iodine.
C-2. Adhesive Layer Any appropriate adhesive can be used as an adhesive for forming the above-mentioned adhesive layer 2. An adhesive composition containing a polyvinyl alcohol-based resin is preferable from the viewpoint of affinity to a polarizer, and an acetoacetyl group-containing polyvinyl alcohol resin is particularly preferable. By using the adhesive composition containing the acetoacetyl group-containing polyvinyl alcohol resin, the adhesion between the polarizer and the acrylic resin film of the present invention is further improved.

  Although there is no restriction | limiting in particular in the average polymerization degree of the said polyvinyl alcohol-type resin, Preferably it is about 100-5000, More preferably, it is 1000-4000.

  The above adhesive composition may optionally contain a crosslinking agent. As a crosslinking agent, what has a functional group which has reactivity with said polyvinyl alcohol-type resin is preferable.

  Examples of functional groups having reactivity with polyvinyl alcohol resins include amine groups, isocyanate groups, epoxy groups, aldehyde groups, methylol groups and the like. Among them, compounds having a methylol group are preferable, and methylolmelamine is particularly preferable.

  Although the compounding quantity of the said crosslinking agent does not have a restriction | limiting in particular, It is about 10-60 weight part with respect to 100 weight part of polyvinyl alcohol-type resin, Preferably it is 20-50 weight part.

  Various coupling agents and tackifiers may be added to the adhesive composition to further improve adhesion. As a coupling agent, a silane coupling agent is preferable. In addition, an ultraviolet absorber, an antioxidant, a heat-resistant stabilizer, a hydrolysis resistant stabilizer, etc. may be added.

  The adhesive composition is usually used as an aqueous solution. The concentration of the resin is preferably 0.1 to 15% by weight, and more preferably 0.5 to 10% by weight, in view of the balance between coatability and stability.

The thickness of the adhesive layer formed from the above-mentioned adhesive composition is set up according to the composition etc. of an adhesive composition. The thickness is preferably 10 to 300 nm, and particularly preferably 20 to 150 nm from the viewpoint of adhesion.
C-3. Adhesive Layer The adhesive layer 3 is formed by applying and drying the adhesive composition of the present invention as described above.
C-4. (Meth) acrylic Resin Film Containing Crosslinked Elastic Body The (meth) acrylic resin film 4 containing the above crosslinked elastic body can be obtained by melt-extruding an acrylic resin composition containing a crosslinked elastic body as described above .
C-5. Other
Any appropriate protective film can be used as the second protective film. Representative examples of the material forming the second protective film include cellulose-based polymers such as triacetyl cellulose and cycloolefin-based polymers. The second protective film may be formed of the same material as the acrylic resin film of the present invention. The second protective film and the polarizer are laminated with any suitable adhesive.
D. Manufacturing Method Any appropriate method may be adopted as a method of manufacturing the polarizing plate of the present invention. One embodiment will be described below. The said polarizer and an acrylic resin film are laminated | stacked via an easily bonding layer. For example, the easy adhesion layer is previously formed on one side of the acrylic resin film. The easy adhesion layer is formed by applying the easy adhesive composition to one side of the acrylic resin film and drying it. As a method of applying the easy adhesive composition, any suitable method described above can be adopted.

As described above, at least one side of the acrylic resin film (the side on which the polarizer is disposed) may be subjected to surface treatment. In this case, the surface treatment described above is applied before forming the easy adhesion layer. The surface treatment is preferably corona discharge treatment or plasma treatment. The corona discharge treatment can further improve the adhesion and adhesion between the polarizer and the acrylic resin film. Corona discharge treatment is performed under any suitable conditions. For example, the amount of corona discharge electron irradiation is preferably 50 to 150 W / m ² / min, and more preferably 70 to 100 W / m ² / min.

  A polarizer and an acrylic resin film are laminated via an adhesive layer. Specifically, after the above-mentioned adhesive composition is applied to one side of either the polarizer or the acrylic resin film, a method of laminating the polarizer and the acrylic resin film and drying them may be mentioned. Examples of the method of applying the adhesive composition include a roll method, a spray method, and an immersion method. The drying temperature is typically 5 to 150 ° C, preferably 30 to 120 ° C. The drying time is typically 120 seconds or more, preferably 300 seconds or more.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. In addition, the evaluation method of an acrylic resin film is as follows. In the following, "parts" and "%" mean "parts by weight" and "% by weight" unless otherwise specified.

<Optical characteristics>
The in-plane retardation Δnd and the thickness direction retardation Rth were measured using KOBRA-WR manufactured by Oji Scientific Instruments. The visible light transmittance (total light transmittance) was measured using a haze meter (HAZE METER) manufactured by Nippon Denshoku Industries Co., Ltd.

<Average particle size of rubber-containing graft copolymer up to rubber layer (average particle size of crosslinked elastic body to soft core layer)>
The average particle size (average particle size of acrylic rubber particles) up to the rubber layer of the rubber-containing graft copolymer was measured in the state of acrylic rubber particle latex. As a measurement apparatus, it measured using light scattering of a wavelength of 546 nm, using Hitachi High-Technologies Corporation U-5100 ratio beam spectrophotometer.

(Production Example 1)
<Manufacture of crosslinked elastic body>
A mixture of the following composition is charged in a glass reactor, heated to 80 ° C. with stirring in a nitrogen stream, and then a monomer mixture consisting of 25 parts of methyl methacrylate and 1 part of allyl methacrylate and t-butyl hydro: Twenty-five percent of the mixed solution with 0.1 part of peroxide was charged at one time, and polymerization was carried out for 45 minutes.
220 parts of deionized water
0.3 parts of boric acid
Sodium carbonate 0.03 parts N-lauroyl sarcosinate sodium 0.09 parts sodium formaldehyde sulfoxylate 0.09 parts ethylenediaminetetraacetic acid-2-sodium 0.006 parts ferrous sulfate 0.002 parts subsequently The remaining 75% of the mixture was added continuously over 1 hour. After completion of the addition, the temperature was maintained at the same temperature for 2 hours to complete the polymerization. In addition, 0.2 parts of sodium N-lauroyl sarcosinate was added during this time. The polymerization conversion (polymerization amount / monomer charging amount) of the obtained innermost layer crosslinked methacrylic polymer latex was 98%.

  The innermost polymer latex thus obtained is maintained at 80 ° C. in a nitrogen stream, 0.1 part of potassium persulfate is added, and then 41 parts of n-butyl acrylate, 9 parts of styrene, 1 part of allyl methacrylate is used. The mixture of monomers was added continuously over 5 hours. During this, 0.1 part of potassium oleate was added in three portions. After completion of the addition of the monomer mixture, 0.05 parts of potassium persulfate was further added to complete the polymerization, and the mixture was held for 2 hours to obtain rubber particles. The polymerization conversion of the obtained rubber particles was 99%, and the particle size was 225 nm.

  The obtained rubber particle latex was kept at 80 ° C., 0.02 part of potassium persulfate was added, and then a monomer mixture of 14 parts of methyl methacrylate and 1 part of n-butyl acrylate was continuously added over 1 hour. The graft copolymer latex was obtained by holding for 1 hour after the addition of the monomer mixture was completed. The polymerization conversion was 99%.

  The obtained graft copolymer latex was kept at 80 ° C., and a monomer mixture of 5 parts of methyl methacrylate and 5 parts of n-butyl acrylate was continuously added over 0.5 hours. It hold | maintained for 1 hour after completion of addition of a monomer mixture, and obtained rubber-containing graft copolymer latex. The polymerization conversion was 99%. The obtained rubber-containing graft copolymer latex was subjected to salting-out coagulation with calcium chloride, heat treatment and drying to obtain a white powdery crosslinked elastic body.

(Production of (meth) acrylic resin film containing crosslinked elastic body)
90 parts by weight of parapet HR-S {copolymer monomer weight ratio = methyl methacrylate / methyl acrylate = 99/1} and 10 parts by weight of the cross-linked elastic body obtained in Production Example 1 are kneaded with a twin-screw extruder Pelletized. The resulting pellets were fed to a twin-screw extruder and melt extruded into a sheet at about 280 ° C. to obtain a 100 μm thick film. This unstretched film is stretched 1.6 times in the longitudinal direction and 1.6 times in the lateral direction at a temperature of 130 ° C., and a (meth) acrylic resin film (thickness 40 μm, in-plane retardation Δnd 0) containing a crosslinked elastic body .8 nm, thickness direction retardation Rth 1.5 nm) was obtained.

(Corona discharge treatment)
Corona discharge treatment (corona discharge electron irradiation amount: 77 W / m 2 / min) was applied to one side of the (meth) acrylic resin film containing the crosslinked elastic body obtained above.

(Formation of easy adhesion layer)
Epoxy-based crosslinking agent (Nagase Chemtex Co., Ltd., trade name: Denacol EX, based on 100 parts by weight of a water-based polyurethane (made by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name: Superflex 210, solid content: 33%) having a carboxyl group -810, solid content: 100%, epoxy equivalent weight: 113 g / eq), 1.3 parts by weight, 250 parts by weight of pure water, corona discharge treated corona-treated (meth) acrylic protective film containing crosslinked elastic body It coated by the bar coater (# 3) on the electric-discharge-treated surface, and formed the coating film. Thereafter, the film was put into a hot air drier (80 ° C.), and the coated film was dried for about 5 minutes to form an easy adhesion layer (0.2 to 0.4 μm) to obtain a polarizer protective film.

(Preparation of adhesive composition)
20 parts by weight of methylol melamine at 70 ° C. per 100 parts by weight of acetoacetyl group-containing polyvinyl alcohol resin (average polymerization degree: 1200, saponification degree: 98.5 mol%, acetoacetyl group modification degree: 5 mol%) It was dissolved in pure water under temperature conditions to obtain an aqueous solution with a solid concentration of 1.0%. The resulting aqueous solution was used as an adhesive composition at a temperature of 25 ° C.

(Pasting of PVA and polarizer protective film)
The adhesive composition was applied to the side of the easily adhesive layer of the polarizer protective film such that the thickness after drying was 50 nm. After that, a polyvinyl alcohol film BOBLONRO EX (film thickness 12 μm) made by Nippon Gohsei Chemical Co., Ltd. and a polarizer protective film are laminated via a coating film of an adhesive composition, put into a hot air drier (100 ° C.) and dried for 5 minutes. Then, a laminate was obtained.

  A polyvinyl alcohol film and a (meth) acrylic protective film containing a crosslinked elastic body were bonded in the same manner as in Example 1 except that the amount of the epoxy crosslinking agent used was 5.2 parts by weight.

(Comparative example 1)
A polyvinyl alcohol film and a (meth) acrylic protective film containing a crosslinked elastic body were laminated in the same manner as in Example 1 except that the easily adhesive layer was not formed.

(Comparative example 2)
A polyvinyl alcohol film was prepared in the same manner as in Example 1, except that an oxazoline-based crosslinking agent (manufactured by Nippon Shokuhin Co., Ltd., trade name: Epocross WS 700, solid content: 25%, oxazoline equivalent 220 g / eq) was used as 10 parts by weight. And a (meth) acrylic protective film containing a crosslinked elastic body.

(Comparative example 3)
A polyvinyl alcohol film and a (meth) acrylic protective film containing a crosslinked elastic body were bonded in the same manner as in Comparative Example 2 except that the amount of the oxazoline crosslinking agent was 40 parts by weight.
A T-peel test was performed on the laminates produced in Examples 1 and 2 and Comparative Examples 1 to 3 in accordance with JIS K 6854. The results are shown in Table 1.

  As apparent from Table 1, the laminate produced in the example was excellent in adhesion, but the laminate produced in Comparative Example 1 was inferior in adhesion. From this, it is possible to obtain a polarizer protective film having excellent adhesion to a polarizer by forming the easily adhesive layer with an easily adhesive composition containing a polyurethane having a carboxyl group and a crosslinking agent having an epoxy group. It is clear.

  By using an epoxy-based crosslinking agent, it is understood that the adhesion is superior to the case where an oxazoline-based crosslinking agent is used. Moreover, although the oxazoline crosslinking agent may have poor adhesion depending on the amount used, the epoxy crosslinking agent exhibits stable adhesion.

  The polarizing plate of the present invention can be suitably used for an image display device such as a liquid crystal display device or a self-luminous display device.

1 Polarizer 2 Adhesive Layer 3 Easy Adhesion Layer 4 (Meth) acrylic Film 5 Containing Cross-Linked Elastic Material Polarizer

Claims (7)

  A polarizer protective film comprising: an easily adhesive layer comprising a polyurethane having a carboxyl group and an adhesive composition containing a crosslinking agent having an epoxy group, and a (meth) acrylic resin film containing a crosslinked elastic body.   The polarizer protective film according to claim 1, wherein the crosslinked elastic body is a core-shell type elastic body having a core layer made of a rubbery polymer and a shell layer made of a glassy polymer. The polarizer protective film according to claim 1 or 2, wherein the orientation birefringence of the (meth) acrylic resin film containing the crosslinked elastic body is -1.7 x 10 ^-4 to 1.7 x 10 ^-4. .   The retardation value of the (meth) acrylic protective film containing the crosslinked elastic body has an in-plane retardation Δnd of 5.0 nm or less and a thickness direction retardation Rth of 20.0 nm or less. The polarizer protective film as described in any one. The photoelastic coefficient of the (meth) acrylic resin film containing the crosslinked elastic body is -10 × 10 ^-12 to 10 × 10 ^-12 Pa ^-1 , according to any one of claims 1 to 4, Polarizer protective film.   The polarizing plate which has a polarizer, an adhesive bond layer, and the polarizer protective film as described in any one of Claims 1-5.   The polarizing plate according to claim 6, wherein the adhesive layer comprises an adhesive composition containing a polyvinyl alcohol resin.

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