JP2016071349A - Production method of polarizing laminate film and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polarizing laminate film that is thin and excellent in strength.SOLUTION: A production method of a polarizing laminate film having a polarizing film layer on a substrate film is provided, the method including the steps of: forming a polyvinyl alcohol resin layer on a substrate film; stretching the laminate obtained in the step of forming the resin layer; and dyeing the polyvinyl alcohol resin layer with a dichroic dye after the stretching step to form a polarizing film layer. The step of forming the polarizing film layer includes a drying process after dyeing the polyvinyl alcohol resin layer with the dichroic dye, in which a temperature parameter represented by a product of a drying temperature (°C) and a drying time (min) is 220 to 350.SELECTED DRAWING: None

Description

  The present invention relates to a polarizing laminate film and a method for producing a polarizing plate.

  The polarizing plate is widely used as a polarized light supplying element and a polarized light detecting element in a display device such as a liquid crystal display device. As a polarizing plate, the thing of the structure which bonded the protective film on the single side | surface or both surfaces of the polarizing film using the adhesive agent is common. In recent years, with the thinning of liquid crystal display devices, there has been a demand for thinning of polarizing plates.

  In Patent Document 1, a polyvinyl alcohol-based resin layer is formed on a base film, and the laminate is stretched and dyed to obtain a polarizing laminate film, and a protective film is laminated thereon to produce a polarizing plate. How to do is described. According to this method, although a thin polarizing film having a small shrinkage force can be produced, the strength of the polarizing laminated film and the polarizing film is reduced as the thickness is reduced. there were.

  The polarizing film is required to have high absorbance at a wavelength of 700 nm in order to suppress redness during the heat resistance test. However, the inventors have found a tendency that when the absorbance at a wavelength of 700 nm in the polarizing plate is increased, the puncture strength per unit film thickness when the polarizing film is torn in the absorption axis direction is decreased. Specifically, when the hue of the polarizing film is made equal, if the stretching ratio is increased, the puncture strength per unit film thickness when the polarizing film is torn in the absorption axis direction is decreased and the absorbance at a wavelength of 700 nm is increased. I found a trend. In addition, the absorbance at a wavelength of 700 nm can be increased by decreasing the single hue b value to make the transmitted hue blue, but it is preferable that the hue is not changed as much as possible. That is, on the premise that the hue is not changed as much as possible, it is necessary to achieve both an increase in puncture strength and an increase in absorbance at a wavelength of 700 nm, and a polarizing plate is required to have both.

JP 2013-72951 A

  This invention is providing the method of manufacturing the light-polarizing laminated film which is thin and excellent in intensity | strength.

That is, the present invention includes the following.
[1] A method for producing a polarizing laminated film having a polarizing film layer on a substrate film,
The manufacturing method includes:
Forming a polyvinyl alcohol-based resin layer on the base film,
A step of stretching the laminate obtained in the step of forming the resin layer, and a step of dyeing the polyvinyl alcohol-based resin layer with a dichroic dye to form a polarizing film layer after the step of stretching. In the step of forming the polarizing film layer, the temperature parameter represented by the product of the drying temperature (° C.) and the drying time (min) is 220 to 350 after the polyvinyl alcohol resin layer is dyed with a dichroic dye. A method for producing a polarizing laminated film comprising a drying treatment.
[2] The method for producing a polarizing laminated film according to [1], wherein the drying treatment includes a drying treatment performed at a temperature of at least 50 to 90 ° C.
[3] A method for producing a polarizing plate comprising a step of laminating a first protective film on a polarizing film layer of the polarizing laminated film according to [1] or [2],
A step of obtaining a laminated film in which the first protective film is laminated on the polarizing film layer of the polarizing laminated film according to [1] or [2];
The manufacturing method of a polarizing plate including the process of peeling and removing a base film and obtaining the polarizing plate with a single-sided protective film.
[4] The method for producing a polarizing plate according to [3], further including a bonding step of bonding a second protective film to the polarizing film layer surface to obtain a polarizing plate with a double-sided protective film.

  According to the present invention, it is possible to produce a polarizing plate that is thin and has a small shrinkage rate when heat is applied. This polarizing plate is excellent in durability because cracks generated in the polarizing film are suppressed in an environment where high and low temperatures are repeated.

  The present invention is a method for producing a polarizing laminated film having a polarizing film layer on a base film, the step of forming a polyvinyl alcohol-based resin layer on the base film (resin layer forming step), and resin layer formation A step of stretching the laminate obtained in the step (stretching step), and a step of dyeing the polyvinyl alcohol-based resin layer with a dichroic dye after the stretching step (dyeing step). The dyeing process includes a drying process in which the temperature parameter represented by the product of the drying temperature (° C.) and the drying time (minutes) is 220 to 350 after the polyvinyl alcohol resin layer is dyed with the dichroic dye. It is characterized by. The manufactured polarizing laminated film can manufacture a polarizing plate by providing the process of laminating | stacking a protective film on a polarizing film layer.

[Method for producing polarizing laminated film]
(Resin layer forming process)
This step is a step of forming a polyvinyl alcohol resin layer by applying a coating liquid containing a polyvinyl alcohol resin to at least one surface of the base film and then drying it to obtain a laminated film. This polyvinyl alcohol-based resin layer is a layer that becomes a polarizing film through a stretching process and a dyeing process. A polyvinyl alcohol-type resin layer can be formed by applying the coating liquid containing a polyvinyl alcohol-type resin to the single side | surface or both surfaces of a base film, and drying a coating layer. The method of forming the polyvinyl alcohol-based resin layer by such coating is advantageous in that it is easy to obtain a thin polarizing film.

  The base film can be composed of a thermoplastic resin, and among them, it is preferably composed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability and the like. Specific examples of such thermoplastic resins include, for example, polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins; polyester resins; (meth) acrylic resins; and celluloses such as cellulose triacetate and cellulose diacetate. Polyester resin; Polyvinylate resin; Polyarylate resin; Polystyrene resin; Polyethersulfone resin; Polysulfone resin; Polyamide resin; Polyimide resin; and mixtures thereof And copolymers. In the present specification, “(meth) acryl” means at least one selected from acryl and methacryl. The same applies to “(meth) acryloyl”.

  The base film may have a single-layer structure composed of one resin layer composed of one or two or more thermoplastic resins, or a plurality of resin layers composed of one or two or more thermoplastic resins are laminated. It may be a multilayer structure.

  Examples of chain polyolefin-based resins include homopolymers of chain olefins such as polyethylene resins and polypropylene resins, and copolymers composed of two or more chain olefins. A base film made of a chain polyolefin-based resin is preferable in that it is easily stretched stably at a high magnification. Among them, the base film is composed mainly of polypropylene resin (polypropylene resin which is a homopolymer of propylene or a copolymer mainly composed of propylene), polyethylene resin (polyethylene resin which is a homopolymer of ethylene or ethylene). More preferably, it is made of a copolymer.

  A copolymer mainly composed of propylene, which is one of the examples suitably used as the thermoplastic resin constituting the base film, is a copolymer of propylene and another monomer copolymerizable therewith. Examples of other monomers copolymerizable with propylene include ethylene and α-olefin. As the α-olefin, an α-olefin having 4 or more carbon atoms is preferably used, and more preferably an α-olefin having 4 to 10 carbon atoms. The α-olefin having 4 to 10 carbon atoms is, for example, a linear monoolefin such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; 3-methyl-1- Examples include branched monoolefins such as butene, 3-methyl-1-pentene and 4-methyl-1-pentene; vinylcyclohexane. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer.

  The content of other monomers in the copolymer is, for example, 0.1 to 20% by weight, preferably 0.5 to 10% by weight. The content of other monomers in the copolymer can be determined by measuring infrared (IR) spectrum according to the method described on page 616 of "Polymer Analysis Handbook" (1995, published by Kinokuniya Shoten). Can be sought.

  Among these, as the polypropylene resin, a propylene homopolymer, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer or a propylene-ethylene-1-butene random copolymer is preferably used.

  It is preferable that the stereoregularity of the polypropylene resin is substantially isotactic or syndiotactic. A base film made of a polypropylene-based resin having substantially isotactic or syndiotactic stereoregularity has relatively good handleability and excellent mechanical strength in a high temperature environment.

  The polyester resin is a resin having an ester bond, and is generally made of a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a divalent diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

  A typical example of the polyester resin is polyethylene terephthalate which is a polycondensate of terephthalic acid and ethylene glycol. Polyethylene terephthalate is a crystalline resin, but the one in a state before crystallization treatment is more easily subjected to treatment such as stretching. If necessary, it can be crystallized during stretching or by heat treatment after stretching. Further, a copolymerized polyester having a crystallinity lowered (or made amorphous) by further copolymerizing another monomer with a polyethylene terephthalate skeleton is also preferably used. Examples of such resins include those obtained by copolymerizing cyclohexanedimethanol and isophthalic acid. Since these resins are also excellent in stretchability, they can be suitably used.

  Specific examples of polyester resins other than polyethylene terephthalate and copolymers thereof include, for example, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate. , Polycyclohexanedimethyl naphthalate, and mixtures and copolymers thereof.

  The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Examples of the (meth) acrylic resin include poly (meth) acrylic esters such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylic acid ester copolymer Compound: Methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin, etc.); Compound having methyl methacrylate and alicyclic hydrocarbon group (For example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl copolymer of (meth) acrylate) and the like. As the (meth) acrylic resin, a polymer mainly comprising a poly (meth) acrylic acid alkyl ester having 1 to 6 carbon atoms in the alkyl group is preferable, and methyl methacrylate is the main component (50 to 100% by weight). And preferably from 70 to 100% by weight).

  The polycarbonate-based resin is an engineering plastic made of a polymer in which monomer units are bonded via a carbonate group, and is a resin having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate-based resin may be a resin called a modified polycarbonate in which the polymer skeleton is modified in order to lower the photoelastic coefficient, a copolymerized polycarbonate with improved wavelength dependency, or the like. An appropriate commercial product can be used for the polycarbonate resin. Examples of commercially available products are trade names, “Panlite (registered trademark)” manufactured by Teijin Chemicals Ltd., “Iupilon (registered trademark)” manufactured by Mitsubishi Engineering Plastics, Inc., manufactured by Sumika Stylon Polycarbonate Co., Ltd. "SD Polyca (registered trademark)", "Caliber (registered trademark)" manufactured by Dow Chemical Company, etc.

  Among these, polypropylene resins are preferably used from the viewpoints of stretchability and heat resistance.

  For the cyclic polyolefin resin and cellulose ester resin used as the base film, the matters described for the protective film are cited. The chain polyolefin resin, polyester resin, (meth) acrylic resin and polycarbonate resin described above in relation to the base film can also be used as a constituent material of the protective film.

  Arbitrary appropriate additives other than said thermoplastic resin may be added to the base film. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, an anti-coloring agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the thermoplastic resin in the base film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. If the content of the thermoplastic resin in the base film is less than 50% by weight, the high transparency inherent in the thermoplastic resin may not be sufficiently exhibited.

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

  The tensile elastic modulus of the base film is preferably 100 MPa to 1500 MPa, more preferably 140 MPa to 1000 MPa, and even more preferably 150 MPa to 500 MPa at 80 ° C. If the tensile elastic modulus is too small, the base film is not sufficiently hard during stretching, and defects such as wrinkles are likely to occur, and if it is too high, workability in stretching becomes poor.

  The tensile elastic modulus can be obtained by cutting a base film into a test piece having a predetermined size and conducting a tensile test. In order to obtain the tensile elastic modulus at 80 ° C., a tensile tester equipped with a thermostatic bath is used.

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

  The method of coating the coating liquid on the base film is as follows: wire bar coating method; roll coating method such as reverse coating and gravure coating; die coating method; comma coating method; lip coating method; spin coating method; It can be appropriately selected from known methods such as fountain coating method; dipping method; spray method. When coating the coating liquid on both sides of the base film, it can be performed one side at a time using the above method, or the base film can be used using a dipping method, spray coating method, or other special equipment. It is also possible to apply to both sides simultaneously.

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

  A polyvinyl alcohol-type resin layer may be formed only in the single side | surface of a base film, and may be formed in both surfaces. When it is formed on both sides, curling of the film that may occur during the production of the polarizing laminated film can be suppressed, and two polarizing plates can be obtained from one polarizing laminated film. It is advantageous.

  The thickness of the polyvinyl alcohol-based resin layer in the laminated film is preferably 3 to 60 μm, more preferably 3 to 30 μm, and still more preferably 5 to 20 μm. When the thickness is within this range, it is possible to obtain a polarizing film having good dyeability of the dichroic dye, excellent polarization performance, and a sufficiently small thickness. When the thickness of the polyvinyl alcohol resin layer exceeds 60 μm, the thickness of the polarizing film may exceed 20 μm, and when the thickness of the polyvinyl alcohol resin layer is less than 3 μm, it becomes too thin after stretching and is dyed. Sex tends to get worse.

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

  Prior to coating the coating liquid, in order to improve the adhesion between the base film and the polyvinyl alcohol resin layer, a polyvinyl alcohol resin layer is formed on the base film via a primer layer or an adhesive layer. It may be formed.

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

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

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

  A crosslinking agent may be added to the primer layer forming coating solution in order to increase the strength of the primer layer. A suitable crosslinking agent is appropriately selected from known ones such as organic and inorganic based on the type of thermoplastic resin to be used. Examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, and metal-based crosslinking agents.

  As the epoxy-based crosslinking agent, either one-component curable type or two-component curable type can be used. Ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6- Examples include hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine, and the like.

  Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylenebis (4-phenylmethane) triisocyanate, isophorone diisocyanate, and ketoximes thereof. A block thing or a phenol block thing etc. are mentioned.

  Examples of the dialdehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleidialdehyde, phthaldialdehyde and the like.

  Examples of the metal-based crosslinking agent include metal salts, metal oxides, metal hydroxides, and organometallic compounds. Examples of the metal salt, metal oxide, and metal hydroxide include divalent or higher atoms such as magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, silicon, boron, zinc, copper, vanadium, chromium, and tin. Examples thereof include salts, oxides and hydroxides of metals having a valence.

  An organometallic compound is a compound having in the molecule at least one structure in which an organic group is bonded directly to a metal atom or an organic group is bonded through an oxygen atom, a nitrogen atom or the like. The organic group means a monovalent or polyvalent group containing at least a carbon element, and can be, for example, an alkyl group, an alkoxy group, an acyl group, or the like. The bond does not mean only a covalent bond, but may be a coordinate bond by coordination such as a chelate compound.

  Suitable examples of the organometallic compound include an organotitanium compound, an organozirconium compound, an organoaluminum compound, and an organosilicon compound. An organometallic compound may be used individually by 1 type, and may use 2 or more types together.

  Examples of the organic titanium compound include titanium orthoesters such as tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate and tetramethyl titanate; titanium acetylacetonate, titanium tetraacetylacetonate, poly Examples include titanium chelates such as titanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamate, and titanium ethyl acetoacetate; and titanium acylates such as polyhydroxytitanium stearate.

  Examples of the organic zirconium compound include zirconium normal propionate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium bisacetylacetonate, zirconium acetylacetonate bisethylacetoacetate and the like.

  Examples of the organoaluminum compound include aluminum acetylacetonate and aluminum organic acid chelate. Examples of the organic silicon compound include compounds in which the ligands exemplified above for the organic titanium compound and the organic zirconium compound are bonded to silicon.

  In addition to the above cross-linking agents (low molecular cross-linking agents), high-molecular cross-linking agents such as methylolated melamine resins and polyamide epoxy resins can also be used. Examples of commercially available polyamide epoxy resins include “Smileys Resin (registered trademark) 650 (30)” and “Smileys Resin (registered trademark) 675 sold by Taoka Chemical Industry Co., Ltd., respectively. "and so on.

  When the primer layer is formed from a polyvinyl alcohol resin, a polyamide epoxy resin, a methylolated melamine resin, a dialdehyde crosslinking agent, a metal chelate compound crosslinking agent, or the like is suitably used as the crosslinking agent.

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

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

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

  When providing a primer layer, the order of application to the base film is not particularly limited. For example, when forming a polyvinyl alcohol-based resin layer on both sides of the base film, the primer is provided on both sides of the base film. After forming the layer, a polyvinyl alcohol-based resin layer may be formed on both sides, or a primer layer and a polyvinyl alcohol-based resin layer are formed in this order on one side of the base film, and then a primer on the other side of the base film. You may form a layer and a polyvinyl alcohol-type resin layer in order.

(Stretching process)
This step is a step of obtaining a stretched film composed of the stretched base film and the polyvinyl alcohol resin layer by subjecting the laminated film composed of the base film and the polyvinyl alcohol resin layer to a stretching treatment. The stretching ratio of the laminated film can be appropriately selected according to the desired polarization characteristics, but is preferably more than 5 times and 17 times or less, more preferably more than 5 times and 8 times the original length of the laminated film. It is as follows. When the draw ratio is 5 times or less, the polyvinyl alcohol-based resin layer is not sufficiently oriented, so the polarization degree of the polarizing film may not be sufficiently high. On the other hand, when the draw ratio exceeds 17 times, it is difficult to obtain a high puncture strength P. Further, the film is easily broken during stretching, and the thickness of the stretched film becomes unnecessarily thin, and the workability and handleability in subsequent processes may be reduced. The stretching process is usually uniaxial stretching.

  The stretching process is not limited to stretching in one stage, and can be performed in multiple stages. In this case, all of the multistage stretching processes may be performed continuously before the dyeing process, or the second and subsequent stretching processes may be performed simultaneously with the dyeing process and / or the crosslinking process in the dyeing process. . Thus, when performing a extending | stretching process in multistage, it is preferable to perform an extending | stretching process so that it may become a draw ratio exceeding 5 times combining all the stages of an extending | stretching process.

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

  The stretching temperature is set to be equal to or higher than the temperature at which the polyvinyl alcohol-based resin layer and the entire substrate film can be stretched, and preferably −30 ° C. of the phase transition temperature (melting point or glass transition temperature) of the substrate film. To + 30 ° C, more preferably from -30 ° C to + 5 ° C, and even more preferably from -25 ° C to + 0 ° C. When the base film is composed of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures exhibited by the plurality of resin layers.

  When the stretching temperature is lower than the phase transition temperature of −30 ° C., high-strength stretching exceeding 5 times is difficult to achieve, or the fluidity of the base film tends to be too low to make stretching treatment difficult. When the stretching temperature exceeds + 30 ° C. of the phase transition temperature, the fluidity of the base film tends to be too high and stretching tends to be difficult. The stretching temperature is within the above range and is more preferably 120 ° C. or higher because it is easy to perform high-magnification stretching exceeding 5 times. This is because when the stretching temperature is 120 ° C. or higher, there is no difficulty in the stretching process even if the stretching ratio is higher than 5 times.

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

  The stretching temperature means the atmospheric temperature in the zone (for example, in the heating furnace) in the case of the zone heating method, and also means the atmospheric temperature in the furnace in the case of heating in the furnace even in the heater heating method. Moreover, in the case of the method of heating roll itself, the surface temperature of a roll is meant.

  Prior to the stretching step, a preheat treatment step for preheating the laminated film may be provided. As the preheating method, the same method as the heating method in the stretching process can be used. When the stretching method is inter-roll stretching, preheating may be performed at any timing before passing through the upstream nip roll, during passing, or after passing. When the stretching method is hot roll stretching, preheating is preferably performed at a timing before passing through the hot roll. When the stretching method is stretching using a chuck, preheating is preferably performed at a timing before increasing the distance between chucks. The preheating temperature is preferably in the range of −50 ° C. to ± 0 ° C. of the stretching temperature, and more preferably in the range of −40 ° C. to −10 ° C. of the stretching temperature.

  Moreover, you may provide the heat setting process process after the extending | stretching process in an extending | stretching process. The heat setting process is a process of performing a heat treatment at a temperature equal to or higher than the crystallization temperature while maintaining the tensioned state with the end of the stretched film held by a clip. By this heat setting treatment, crystallization of the polyvinyl alcohol-based resin layer is promoted. The temperature of the heat setting treatment is preferably in the range of −0 ° C. to −80 ° C. of the stretching temperature, and more preferably in the range of −0 ° C. to −50 ° C. of the stretching temperature.

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

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

  The immersion time of the stretched film in the dyeing solution is usually in the range of 15 seconds to 15 minutes, preferably 30 seconds to 3 minutes. Moreover, it is preferable that it is in the range of 10-60 degreeC, and, as for the temperature of a dyeing | staining solution, it is more preferable that it exists in the range of 20-40 degreeC.

  In addition, you may perform an additional extending | stretching process with respect to a stretched film during a dyeing process. As an embodiment in this case, 1) In the above stretching step, after performing the stretching process at a lower ratio than the target, the stretching process is performed so that the total stretching ratio becomes the target ratio during the dyeing process in the dyeing process. In a case where the crosslinking treatment is performed after the dyeing treatment, as described later, 2) In the above drawing step, after the drawing treatment is performed at a lower magnification than the target, the total draw ratio is set during the dyeing treatment in the dyeing step. And a mode in which the stretching treatment is performed until the final total stretching ratio becomes the target ratio, and then the stretching process is performed during the crosslinking process.

  The dyeing process may include a cross-linking process performed after the dyeing process. The crosslinking treatment can be performed by immersing the dyed film in a solution containing a crosslinking agent (crosslinking solution). As the crosslinking agent, conventionally known substances can be used, and examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. A crosslinking agent may be used individually by 1 type, and may use 2 or more types together.

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

  The cross-linking solution can contain iodide. By adding iodide, the polarization performance in the plane of the polarizing film can be made more uniform. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Is mentioned. The concentration of iodide in the crosslinking solution is preferably from 0.05 to 15% by weight, more preferably from 0.5 to 8% by weight, and even more preferably from 0.5 to 7% by weight.

  Moreover, the crosslinking solution may contain other components, such as a pH adjuster. As a pH adjuster, for example, sulfuric acid, hydrochloric acid, acetic acid, ascorbic acid and the like may be added.

  The immersion time of the dyed film in the crosslinking solution is usually 15 seconds to 20 minutes, and preferably 30 seconds to 15 minutes. Moreover, it is preferable that the temperature of a crosslinking solution exists in the range of 10-90 degreeC.

  In addition, a crosslinking process can also be performed simultaneously with a dyeing | staining process by mix | blending a crosslinking agent in a dyeing solution. Further, a stretching process may be performed during the crosslinking process. The specific mode for carrying out the stretching treatment during the crosslinking treatment is as described above.

  In the dyeing process, it is preferable to perform a washing process and a drying process after the dyeing process. The washing process usually includes a water washing process. The water washing treatment can be performed by immersing the film after the dyeing treatment or after the crosslinking treatment in pure water such as ion exchange water and distilled water. The water washing temperature is usually in the range of 3 to 50 ° C, preferably 4 to 20 ° C. The immersion time is usually 2 to 300 seconds, preferably 3 to 240 seconds.

  The cleaning process may be a combination of a water cleaning process and a cleaning process using an iodide solution. In addition to water, liquids such as methanol, ethanol, isopropyl alcohol, butanol, and propanol can be appropriately contained in the cleaning liquid used in the water cleaning process and / or the cleaning process using the iodide solution.

  As a drying process performed after the washing process, any appropriate method such as natural drying, blow drying, and heat drying may be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C., and the drying time is usually about 1 to 15 minutes. The drying process is divided into multiple stages, and the drying temperature and drying time of each stage may be different. The drying process is preferably a multistage drying of two stages or three or more stages.

  In the drying step, the drying temperature in at least one drying step is preferably in the range of about 50 to 90 ° C. If the temperature is too low, the drying time becomes long, and thus the production efficiency tends to decrease. On the other hand, if the drying temperature is too high, the single hue b value increases, and the resulting polarizing film tends to be yellowish. The drying time may be appropriately adjusted together with the drying temperature so as to satisfy the temperature parameter, but from the preferable range of the drying temperature, it is preferably about 100 seconds to 10 minutes, more preferably 2 minutes or more, and preferably 9 minutes. Below, more preferably 8 minutes or less.

  The temperature parameter is expressed by the product of the drying temperature (° C.) and the drying time (minutes). In the present invention, the drying process is performed so that the numerical value is 220 to 350. If the temperature parameter is less than 220, the strength of the polarizing film tends to be difficult to increase, and if it exceeds 350, the hue of the polarizing film tends to change to yellow. The temperature parameter is preferably 300 or less. In addition, the drying process may be performed only once or may be performed in a plurality of times. When the drying process is performed a plurality of times, the total of the temperature parameters in each drying process is in a range of 220 to 350. .

  When the drying process is two-stage drying, the temperature parameter of the second stage is preferably larger than the temperature parameter of the first stage. When the drying process is drying of three or more stages, it is preferable that there is at least one stage in which the temperature parameter of a certain stage is larger than the temperature parameter of the preceding stage.

  The strength of the polarizing film can be determined by using the piercing strength per unit film thickness as an index. The puncture strength per unit film thickness varies depending on the protective film, the adhesive layer, the pressure-sensitive adhesive layer, and the like to be used, but can be practically used as long as it is 3.6 gf / μm or more, for example. The puncture strength per unit film thickness is preferably 3.6 to 15.0 gf / μm, more preferably 5.0 to 10.0 gf / μm, still more preferably 5.0 to 7.0 gf / μm. μm.

  The puncture strength per unit film thickness is the strength when a puncture tool is pierced perpendicularly to a polarizing film and the polarizing film is torn along its stretching axis (absorption axis). Can be measured with a compression tester equipped with Examples of the compression tester include a handy compression tester “KES-G5 type” manufactured by Kato Tech Co., Ltd., and a small desktop tester “EZ Test” manufactured by Shimadzu Corporation.

The polarizing film used for the measurement may be the one before the protective film is laminated to form a polarizing plate, or the protective film may be one obtained by removing the protective film from the polarizing plate laminated with an adhesive or the like. A polarizing film in which the protective film is removed from the polarizing plate is preferable in consideration of the influence of the load and the like.
As a method of removing the protective film from the polarizing plate, if the polarizing film is not damaged, a method of dissolving the protective film using a solvent, a method of immersing in a solution having a good affinity with the adhesive, and a method of peeling off the protective film, etc. A conventionally known method can be used.

  Examples of the method for removing the protective film from the polarizing plate include a method of dissolving the protective film with a solvent. The solvent that dissolves the protective film may be any solvent that dissolves the protective film and does not dissolve the polarizing film. When the protective film is a cellulose resin film, an alkyl halide solvent is preferable, and dichloromethane is particularly preferable. When the protective film is an olefin resin film, a cycloalkane solvent is preferable, and cyclohexane is particularly preferable. When the protective film is an acrylic resin film, a benzene solvent or an alkyl halide solvent is preferable. Of the benzene-based solvents, toluene is preferable. Of the alkyl halide solvents, dichloromethane is preferred.

  The measurement is performed by sandwiching a polarizing film between two sample bases having a circular hole with a diameter of 15 mm or less through which a piercing jig can pass. The piercing jig is a cylindrical bar, and preferably includes a piercing needle whose tip contacting the polarizing film is spherical or hemispherical. The spherical or hemispherical portion at the tip has a diameter of 0.5 mmφ or more and preferably 5 mmφ or less, and its radius of curvature is preferably larger than 0R and smaller than 0.7R. The puncture speed of the compression tester is 0.05 cm / second or more and preferably 0.5 cm / second or less.

  The puncture strength can be measured by fixing the test piece to a jig and piercing it from the normal direction, and measuring the strength when tearing at one place horizontally with the stretching direction (absorption axis direction). . The measurement is performed on five or more polarizing film test pieces, and the average value can be obtained as the piercing strength. By dividing the measured piercing strength by the thickness of the polarizing film used for the measurement, the piercing strength per unit film thickness can be calculated. In this method, the breaking strength when the polarizing film is pulled in the transmission axis direction and is torn in the absorption axis direction can be quantitatively measured. Therefore, the transmission axis that could not be measured until now because the polarizing film was easily torn. Directional strength can be measured.

[Production method of polarizing plate]
The light-polarizing laminated film manufactured by the above method includes a step of laminating the first protective film on the polarizing film layer (first bonding step) and a step of peeling and removing the base film (peeling step). Thus, a polarizing plate can be produced. The manufacturing method of this polarizing plate can be equipped with the process (2nd bonding process) of bonding a 2nd protective film to the other surface of a polarizing film after a peeling process.

  When manufacturing the polarizing plate by which the 1st bonding process and the 2nd bonding process were performed, and the protective film was laminated | stacked on both surfaces of the polarizing film, a 2nd protective film was laminated | stacked at a 1st bonding process, and 2nd bonding. You may laminate | stack a 1st protective film at a joint process.

(1st bonding process)
This process is a process of bonding a 1st protective film on the polarizing film of a light-polarizing laminated film, ie, the surface on the opposite side to the base film side of a polarizing film, and obtaining a bonding film. When a polarizing laminated film has a polarizing film on both surfaces of a base film, a protective film is normally bonded on the polarizing film of both surfaces, respectively. In this case, these protective films may be the same type of protective film or different types of protective films.

(Peeling process)
This step is a step of obtaining a polarizing plate with a single-sided protective film by peeling and removing the base film from the bonded film obtained by bonding the first protective film. Through this step, a polarizing plate with a single-side protective film in which the first protective film is laminated on one side of the polarizing film is obtained. When the polarizing laminated film has polarizing films on both sides of the base film, and a protective film is bonded to both of these polarizing films, this peeling step causes two single sides from one polarizing laminated film. A polarizing plate with a protective film is obtained.

  The method of peeling and removing the substrate film can be peeled by the same method as the separator (peeling film) peeling step performed with a normal pressure-sensitive adhesive polarizing plate. After a 1st bonding process, a base film may peel immediately as it is, and after a 1st bonding process, it may wind up in roll shape once and may peel, unwinding in the subsequent process.

(2nd bonding process)
In this step, the other protective film is bonded via an adhesive on the polarizing film of the polarizing plate with a single-sided protective film, that is, the surface opposite to the protective film bonded in the first bonding step. To obtain a polarizing plate. When performing a 2nd bonding process, a 2nd protective film may be bonded at a 1st bonding process, and in this case, a 1st protective film is bonded at this process.

[Polarizer]
The polarizing plate obtained by the manufacturing method described above is thin and has a small shrinkage rate when heat is applied. This polarizing plate is excellent in durability because cracks generated in the polarizing film are suppressed in an environment where high and low temperatures are repeated.

(Optical characteristics of polarizing film)
The polarizing performance of the polarizing film can be mainly expressed by numerical values called single transmittance and degree of polarization, which are respectively defined by the following formulas.
Single transmittance (λ) = 0.5 × (Tp (λ) + Tc (λ))
Polarization degree (λ) = 100 × (Tp (λ) −Tc (λ)) / (Tp (λ) + Tc (λ))

  Here, Tp (λ) is the transmittance (%) of the polarizing plate or polarizing film measured in the relationship between the linearly polarized light having the incident wavelength λnm and the parallel Nicol, and Tc (λ) is the straight line having the incident wavelength λnm. It is the transmittance (%) of the polarizing plate or polarizing film measured by the relationship between polarized light and crossed Nicol, both of which are measured values obtained by measuring the polarized UV-visible absorption spectrum with a spectrophotometer. In addition, the single transmittance (λ) and the degree of polarization (λ) obtained for each wavelength are subjected to sensitivity correction called visibility correction, respectively, and the visibility correction single transmittance (Ty) and the visibility correction polarization, respectively. Called degrees (Py). These Ty and Py values can be easily measured with, for example, a spectrophotometer (model number: V7100) manufactured by JASCO Corporation.

  In order to ensure good image clarity when the polarizing plate is applied to a display device such as a liquid crystal display device, the polarizing film according to the present invention has a visibility corrected single transmittance (Ty) of 40% or more. It is preferable that the visibility correction polarization degree (Py) is 99% or more. More preferably, the visibility corrected single transmittance is 41% or more, and the visibility corrected polarization degree is 99.95% or more. Further, it is more preferable that the visibility corrected single transmittance is 41.5% or more and the visibility corrected polarization degree is 99.99% or more.

The polarizing film preferably has an absorbance (A700) at a wavelength of 700 nm of 2.8 or more, more preferably 3.0 or more. As the absorbance value is larger, the deterioration of the optical characteristics in a high temperature environment is suppressed. The absorbance at a wavelength of 700 nm can be obtained from the orthogonal transmittance (Tc) of the polarizing film, and the MD transmittance and TD transmittance of the polarizing film can be measured and calculated by the following formula.
Tc (700) (%) = [MD (700 nm) / 100] × [TD (700 nm) / 100] × 100
A700 = -log [Tc (700) / 100]

  In the formula, “MD” means MD transmittance, which is the transmittance when the direction of polarized light emitted from the Glan-Thompson prism is parallel to the transmission axis of the polarizing film sample (exfoliated from the base film). In addition, “TD” means TD transmittance, which is the transmittance when the direction of polarized light emitted from the Glan-Thompson prism is orthogonal to the transmission axis of the polarizing plate sample. The optical characteristics of the polarizing film can be measured with, for example, a spectrophotometer with an integrating sphere. This measurement may be performed by setting a measurement sample (polarizing plate sample) in a spectrophotometer with the polarizing film side as a detector side and measuring MD transmittance and TD transmittance.

  The polarizing film preferably has a transmission hue b value in the range of 1 to 6, more preferably in the range of 2 to 4, and most preferably in the range of 2 to 3.5. The single hue b value is appropriately designed in combination with the hue of the color filter of the liquid crystal display device, but can be within the hue design range of a color filter of a general liquid crystal display device within the above range.

The above-mentioned transmission hue means the hue of light transmitted from the other surface when light is applied from one surface of the polarizing plate. The hue here can be expressed by a value and b value in the Lab color system, and is measured using standard light. In the present invention, the transmission hue of the polarizing film is actually measured in a state where a pressure-sensitive adhesive layer is provided on one side of the polarizing film and bonded to a glass plate on the pressure-sensitive adhesive layer side. The Lab color system is represented by Hunter's lightness index L and hues a and b as described in “5.5 Accelerated Weathering Test” of JIS K 5981: 2006 “Synthetic Resin Powder Coating”. Is. As a concept similar to the Lab color system, there is an L ^* a ^* b ^* color system defined in JIS Z 8781-4: 2013 “Colorimetry-Part 4: CIE 1976 L ^* a ^* b ^* Space”. However, the Lab color system is adopted in the present invention. The values of the lightness index L and the hues a and b are calculated from the tristimulus values X, Y and Z defined in JIS Z 8722: 2009 “Color Measurement Method—Reflection and Transmission Object Color” by the following formula. .

L = 10Y ^1/2
a = 17.5 (10.2 XY) / Y ^1/2
b = 7.0 (Y-0.847Z) / Y1 / ² .

  In the Lab color system, the hue a value and the b value can indicate positions corresponding to saturation, and when the hue a value increases, the hue becomes red, and when the hue b value increases, the hue becomes yellow. Change. Also, the closer to 0, the closer to both achromatic colors.

(Polarizing film)
The polarizing film can be obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol resin layer. When the polarizing film is usually 20 μm or less in thickness, the polarizing plate can be made thinner. In the present invention, a polarizing film having a thickness of 10 μm or less is employed, and the thickness of the polarizing film is preferably 8 μm or less.

  As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acid, olefin, vinyl ether, unsaturated sulfonic acid, and acrylamide having an ammonium group.

  The saponification degree of the polyvinyl alcohol-based resin can be in the range of 80 mol% or more, but is preferably in the range of 90 to 99.5 mol%, and more preferably in the range of 94 to 99 mol%. The polyvinyl alcohol resin may be a modified polyvinyl alcohol partially modified. For example, the polyvinyl alcohol resin may be an olefin such as ethylene and propylene; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, and crotonic acid. And those modified with alkyl esters of unsaturated carboxylic acids and acrylamide. The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10,000, more preferably 1500 to 8000, and further preferably 2000 to 5000.

  The dichroic dye contained (adsorption orientation) in the polarizing film can be iodine or a dichroic organic dye, and conventionally known ones can be used. A dichroic dye may be used individually by 1 type, and may use 2 or more types together.

  The polarizing film preferably has a shrinkage force of 2 N or less, more preferably 1.8 N or less when held at 80 ° C. for 240 minutes, with a width of 2 mm in the absorption axis direction. More preferably, it is 6N or less. If the shrinkage force is greater than 2N, the amount of dimensional change under a high temperature environment increases, and the shrinkage force of the polarizing film increases, so that the polarizing film tends to crack. The shrinkage force of the polarizing film tends to be 2N or less when the draw ratio is lowered and the thickness of the polarizing film is reduced.

(First protective film and second protective film)
A first protective film is laminated on at least one surface of the polarizing film. In addition, when laminating | stacking a 1st protective film on the single side | surface of a polarizing film and a 2nd protective film on the other side, as a 2nd protective film, you may use the thing similar to a 1st protective film, other A resin film may be used. Each of the first protective film and the second protective film can be a transparent resin film composed of a thermoplastic resin. Examples of the thermoplastic resin include polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins such as polypropylene resins; cellulose ester resins such as cellulose triacetate and cellulose diacetate; polyethylene terephthalate, polyethylene naphthalate And polyester resins such as polybutylene terephthalate; polycarbonate resins; (meth) acrylic resins; or mixtures and copolymers thereof.

  The cyclic polyolefin-based resin is a general term for resins that are polymerized with a cyclic olefin as a polymerization unit, and is described, for example, in JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. The resin currently used is mentioned. Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, and copolymers of chain olefins and cyclic olefins such as ethylene and propylene (typically Random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among these, norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as cyclic olefins are preferably used.

  Various products are commercially available for the cyclic polyolefin resin. Examples of commercial products of cyclic polyolefin resins are “TOPAS” (registered trademark) and JSR Corporation, both of which are produced by TOPAS ADVANCED POLYMERS GmbH under the trade name and sold in Japan by Polyplastics Co., Ltd. "ARTON" (registered trademark) sold by ZEON CORPORATION, "ZEONOR" (registered trademark) and "ZEONEX" (registered trademark) sold by ZEON CORPORATION, "APEL" sold by Mitsui Chemicals, Inc. (Registered trademark).

  Moreover, you may use the commercial item of the cyclic polyolefin resin film formed into a film as a protective film. Examples of commercial products are “Arton Film” sold by JSR Corporation (“Arton” is a registered trademark of the company) and “Essina” sold by Sekisui Chemical Co., Ltd. ( Registered trademark) and “SCA40”, “ZEONOR FILM” (registered trademark) sold by Zeon Corporation.

  The formed cyclic polyolefin-based resin film is stretched like uniaxial stretching or biaxial stretching, or a liquid crystal layer or the like is formed on this film, so that an arbitrary retardation value is given. It can also be set as a phase difference film.

  The cellulose ester resin is usually an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, those copolymerized with these, and those in which a part of the hydroxyl group is modified with another substituent can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercial products of cellulose triacetate are “Fujitac (registered trademark) TD80”, “Fujitac (registered trademark) TD80UF”, “Fujitac (registered trademark) TD80UZ” sold by Fuji Film Co., Ltd. And “Fujitac (registered trademark) TD40UZ”, TAC films “KC8UX2M” and “KC4UY” manufactured by Konica Minolta Co., Ltd.

  The formed cellulose ester resin film is subjected to stretching such as uniaxial stretching or biaxial stretching, or a liquid crystal layer or the like is formed on this film, whereby an arbitrary retardation value is given. It can also be set as a phase difference film.

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

  As said other polymerizable monomer which can comprise a (meth) acrylic-type resin, polymeric monomers other than acrylic ester, methacrylic ester, and acrylic ester can be mentioned, for example. As the acrylate ester, alkyl acrylate ester can be used. Specific examples thereof include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylic It includes alkyl acrylates having 1 to 8 carbon atoms in the alkyl group such as t-butyl acid, 2-ethylhexyl acrylate, cyclohexyl acrylate, and 2-hydroxyethyl acrylate. The alkyl group preferably has 1 to 4 carbon atoms. In the (meth) acrylic resin, acrylic ester may be used alone or in combination of two or more.

  Examples of polymerizable monomers other than methacrylic acid esters and acrylic acid esters include, for example, monofunctional monomers having one polymerizable carbon-carbon double bond in the molecule, and polymerizable carbon-carbon double bonds in the molecule. Can be mentioned, but a monofunctional monomer is preferably used. Specific examples of the monofunctional monomer include styrene monomers such as styrene, α-methylstyrene, vinyltoluene, halogenated styrene and hydroxystyrene; vinyl cyanide such as acrylonitrile and methacrylonitrile; acrylic acid and methacrylic acid. Unsaturated acids such as maleic anhydride and itaconic anhydride; maleimides such as N-methylmaleimide, N-cyclohexylmaleimide and N-phenylmaleimide; allyl alcohols such as methallyl alcohol and allyl alcohol; vinyl acetate and vinyl chloride , Other monomers such as ethylene, propylene, 4-methyl-1-pentene, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinyl pyrrolidone, N-vinyl carbazole.

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

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

  Further, the (meth) acrylic resin may have a ring structure in the polymer main chain because the durability of the film can be improved. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure, or a lactone ring structure. Specific examples include cyclic acid anhydride structures such as glutaric anhydride structure and succinic anhydride structure, cyclic imide structures such as glutarimide structure and succinimide structure, and lactone ring structures such as butyrolactone and valerolactone. As the content of the ring structure in the main chain is increased, the glass transition temperature of the (meth) acrylic resin can be increased. The cyclic acid anhydride structure or cyclic imide structure is introduced by copolymerizing monomers having a cyclic structure such as maleic anhydride or maleimide, and the cyclic acid anhydride structure is introduced by dehydration / demethanol condensation reaction after polymerization. It can be introduced by a method, a method of reacting an amino compound and introducing a cyclic imide structure. A resin having a lactone ring structure (polymer) is prepared by preparing a polymer having a hydroxyl group and an ester group in a polymer chain, and then heating the hydroxyl group and the ester group in the obtained polymer by heating. Accordingly, it can be obtained by a method in which a lactone ring structure is formed by cyclocondensation in the presence of a catalyst such as an organic phosphorus compound.

  Polymers having a hydroxyl group and an ester group in the polymer chain are, for example, methyl 2- (hydroxymethyl) acrylate, 2- (hydroxymethyl) ethyl acrylate, 2- (hydroxymethyl) isopropyl acrylate, 2- It can be obtained by using (meth) acrylic acid ester having a hydroxyl group and an ester group such as n-butyl (hydroxymethyl) acrylate and t-butyl 2- (hydroxymethyl) acrylate as a part of the monomer. it can. A more specific method for preparing a polymer having a lactone ring structure is described in, for example, JP-A-2007-254726.

  A (meth) acrylic resin can be prepared by radical polymerization of a monomer composition containing the monomer as described above. A monomer composition can contain a solvent and a polymerization initiator as needed.

  The (meth) acrylic resin may contain a resin other than the (meth) acrylic resin described above. The content of the other resin is preferably 0 to 70% by weight, more preferably 0 to 50% by weight, and still more preferably 0 to 30% by weight. Examples of the resin include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and chlorinated vinyl resins; polystyrene Styrene-based polymers such as styrene-methyl methacrylate copolymer and styrene-acrylonitrile copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; polyarylate composed of aromatic diol and aromatic dicarboxylic acid Biodegradable polyesters such as polylactic acid and polybutylene succinate; polycarbonates; polyamides such as nylon 6, nylon 66 and nylon 610; polyacetals; polyphenylene oxides; Nsurufido; polyether ether ketone; polyether nitrile; polysulfone; polyether sulfone; can be a polyamide-imide and the like; polyoxyethylene Penji Ren.

  The (meth) acrylic resin may contain rubber particles from the viewpoint of improving the impact resistance and film forming property of the film. The rubber particle may be a particle composed only of a layer exhibiting rubber elasticity, or may be a particle having a multilayer structure having another layer together with a layer exhibiting rubber elasticity. Examples of the rubber elastic body include an olefin elastic polymer, a diene elastic polymer, a styrene-diene elastic copolymer, an acrylic elastic polymer, and the like. Among these, acrylic elastic polymers are preferably used from the viewpoints of light resistance and transparency.

  The acrylic elastic polymer can be a polymer mainly composed of alkyl acrylate, that is, a polymer containing 50% by weight or more of a structural unit derived from alkyl acrylate based on the total amount of monomers. The acrylic elastic polymer may be a homopolymer of alkyl acrylate, and contains 50 wt% or more of structural units derived from alkyl acrylate and 50 wt% or less of structural units derived from other polymerizable monomers. A copolymer may also be used.

  As the alkyl acrylate constituting the acrylic elastic polymer, those having 4 to 8 carbon atoms in the alkyl group are usually used. Examples of the other polymerizable monomers include, for example, alkyl methacrylates such as methyl methacrylate and ethyl methacrylate; styrene monomers such as styrene and alkyl styrene; non-polymers such as acrylonitrile and methacrylonitrile. Monofunctional monomers such as saturated nitriles, as well as alkenyl esters of unsaturated carboxylic acids such as allyl (meth) acrylate and methallyl (meth) acrylate; dialkenyl esters of dibasic acids such as diallyl maleate; alkylene Polyfunctional monomers such as unsaturated carboxylic acid diesters of glycols such as glycol di (meth) acrylate.

  The rubber particles containing an acrylic elastic polymer are preferably multi-layered particles having an acrylic elastic polymer layer. Specifically, a two-layer structure having a hard polymer layer mainly composed of alkyl methacrylate outside the acrylic elastic polymer layer, or an alkyl methacrylate inside the acrylic elastic polymer layer. And a three-layer structure having a hard polymer layer mainly composed of.

  Examples of the monomer composition in the polymer mainly composed of alkyl methacrylate constituting the hard polymer layer formed outside or inside the acrylic elastic polymer layer are given as examples of (meth) acrylic resins. This is the same as the monomer composition example of a polymer mainly composed of alkyl methacrylate, and a monomer composition mainly composed of methyl methacrylate is preferably used. Such acrylic rubber elastic particles having a multilayer structure can be produced, for example, by the method described in Japanese Patent Publication No. 55-27576.

  From the viewpoint of film-forming properties of (meth) acrylic resin, impact resistance of the film, and slipperiness of the film surface, the rubber particles are included in the rubber elastic layer (acrylic elastic polymer layer) contained therein. The average particle size is preferably in the range of 10 to 350 nm. The average particle diameter is more preferably 30 nm or more, further 50 nm or more, and more preferably 300 nm or less, further 280 nm or less.

  The average particle size of the rubber particles up to the rubber elastic layer (acrylic elastic polymer layer) is measured as follows. That is, when such rubber particles are mixed with a (meth) acrylic resin to form a film and the cross section thereof is dyed with an aqueous solution of ruthenium oxide, only the rubber elastic body layer is colored and observed in a substantially circular shape. This (meth) acrylic resin is not dyed. Therefore, from the cross section of the film dyed in this way, a thin piece is prepared using a microtome or the like, and this is observed with an electron microscope. And after extracting 100 dye | stained rubber particles at random and calculating each particle diameter (diameter to a rubber elastic body layer), the number average value is made into the said average particle diameter. In order to measure by such a method, the obtained average particle diameter is a number average particle diameter.

  When the outermost layer is a hard polymer mainly composed of methyl methacrylate, and rubber particles in which a rubber elastic layer (acrylic elastic polymer layer) is encapsulated, the matrix (meta ) When mixed with an acrylic resin, the outermost layer of rubber particles is mixed with the base (meth) acrylic resin. Therefore, when the cross section is dyed with ruthenium oxide and observed with an electron microscope, the rubber particles are observed as particles in a state excluding the outermost layer. Specifically, when the inner layer is an acrylic elastic polymer and the outer layer is a rubber particle having a two-layer structure, which is a hard polymer mainly composed of methyl methacrylate, the acrylic elastic polymer portion of the inner layer Are dyed and observed as particles having a single layer structure. The innermost layer is a hard polymer mainly composed of methyl methacrylate, the intermediate layer is an acrylic elastic polymer, and the outermost layer is a rigid polymer mainly composed of methyl methacrylate. In the case of rubber particles, the central part of the innermost layer is not dyed, and only the acrylic elastic polymer part of the intermediate layer is dyed and observed as a two-layered particle.

  From the viewpoint of the film-forming property of the (meth) acrylic resin, the impact resistance of the film, and the slipperiness of the film surface, the rubber particles are combined with the (meth) acrylic resin constituting the (meth) acrylic resin film. Is preferably 3 to 60% by weight, more preferably 45% by weight or less, and still more preferably 35% by weight or less. If the amount of the elastic rubber particles exceeds 60% by weight, the dimensional change of the film becomes large, and the heat resistance is lowered. On the other hand, when the amount of rubber elastic particles is less than 3% by weight, the heat resistance of the film is good, but the winding property during film formation is poor, and the productivity may be lowered. In the present invention, when the rubber elastic particle is a multi-layered particle having another layer together with the rubber elastic layer, the weight of the portion composed of the rubber elastic layer and the inner layer is determined. The weight of the elastic rubber particles. For example, when the acrylic rubber elastic particles having the above three-layer structure are used, the total weight of the acrylic rubber elastic polymer portion of the intermediate layer and the hard polymer portion mainly composed of methyl methacrylate of the innermost layer Is the weight of the rubber elastic particles. When the acrylic rubber elastic particles having the above three-layer structure are dissolved in acetone, the acrylic rubber elastic polymer portion of the intermediate layer and the hard polymer portion mainly composed of methyl methacrylate in the innermost layer are insoluble. Therefore, the total weight ratio of the intermediate layer and the innermost layer in the acrylic rubber elastic particles having a three-layer structure can be easily obtained.

  When the (meth) acrylic resin film contains rubber particles, the (meth) acrylic resin composition containing the rubber particles used for producing the film is obtained by melt-kneading the (meth) acrylic resin and the rubber particles. In addition, it can be obtained by a method of first producing rubber particles and polymerizing a monomer composition as a raw material for the (meth) acrylic resin in the presence thereof.

  In addition to the rubber particles, the (meth) acrylic resin contains ordinary additives such as ultraviolet absorbers, organic dyes, pigments, inorganic dyes, antioxidants, antistatic agents, surfactants, and the like. You may let them. Among these, an ultraviolet absorber is preferably used for improving weather resistance. Examples of the ultraviolet absorber include 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (5 -Methyl-2-hydroxyphenyl) -2H-benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3,5-di -Tert-butyl-2-hydroxyphenyl) -2H-benzotriazole, 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chloro-2H-benzotriazole, 2- (3,5 -Di-tert-butyl-2-hydroxyphenyl) -5-chloro-2H-benzotriazole, 2- (3,5-di-tert-amyl-2-hydroxypheny ) Benzotriazole ultraviolet absorbers such as -2H-benzotriazole, 2- (2'-hydroxy-5'-tert-octylphenyl) -2H-benzotriazole; 2-hydroxy-4-methoxybenzophenone, 2- Hydroxy-4-octyloxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxy-4'-chlorobenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4, 2-hydroxybenzophenone ultraviolet absorbers such as 4'-dimethoxybenzophenone; salicylic acid phenyl ester ultraviolet absorbers such as p-tert-butylphenyl salicylic acid ester and p-octylphenyl salicylic acid ester; 2,4-diphenyl-6 (2-hydroxy-4-methoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-ethoxyphenyl) -1,3,5-triazine, 2,4- Diphenyl- (2-hydroxy-4-propoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4- Diphenyl-6- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3,5-triazine 2,4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-dodeci) Oxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-benzyloxyphenyl) -1,3,5-triazine, 2- (2-hydroxy-4- [ 1-octyloxycarbonylethoxy] phenyl) -4,6-bis (4-phenylphenyl) -1,3,5-triazine, 4-bis [2-hydroxy-4-butoxyphenyl] -6- (2,4 -Dibutoxyphenyl) -1,3,5-triazine, 2- [4-[(2-hydroxy-3- (2'-ethyl) hexyloxy] -2-hydroxyphenyl] -4,6-bis (2 , 4-Dimethylphenyl) -1,3,5-triazine, 2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl) -5-hydroxyphenyl, 2- [ , 6-Bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl] -5- (octyloxy) phenol, 2- [2,6-di (2,4-xylyl)- 1,3,5-triazin-2-yl] -5-octyloxyphenol, 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5- [2- (2-ethyl) Hexanoyl) ethoxy] phenol, 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methoxyphenyl) -1,3,5 triazine and other triazine ultraviolet absorbers, and the like. Two or more of them may be used.

    Commercially available products may be used as the UV absorber. For example, as a triazine UV absorber, “Kemisorb 102” (registered trademark) manufactured by Chemipro Kasei Co., Ltd., “Adekastab (registered trademark)” manufactured by ADEKA Co., Ltd. “LA46”, “ADK STAB (registered trademark) LAF70”, “TINUVIN (registered trademark) 460”, “TINUVIN (registered trademark) 405”, “TINUVIN (registered trademark) 400”, and “TINUVIN (registered trademark)” 477 manufactured by BASF "CYASORB (registered trademark) UV-1164" (all are trade names) manufactured by Sun Chemical Co., Ltd. As benzotriazole ultraviolet absorbers, “ADEKA STAB (registered trademark) LA31” and “ADEKA STAB (registered trademark) LA36” manufactured by ADEKA Corporation, “Sumisorb (registered trademark) 200”, “Sumisorb” manufactured by Sumika Chemtex Co., Ltd. (Registered trademark) 250 ”,“ Sumisorb (registered trademark) 300 ”,“ Sumisorb (registered trademark) 340 ”and“ Sumisorb (registered trademark) 350 ”,“ Kemisorb 74 ”(registered trademark) manufactured by Chemipro Kasei Co., Ltd.,“ Kemisorb 79 "(registered trademark) and" Kemisorb 279 "(registered trademark)," TINUVIN (registered trademark) 99-2 "," TINUVIN (registered trademark) 900 "and" TINUVIN (registered trademark) 928 "manufactured by BASF ( As mentioned above, all are brand names). When the (meth) acrylic resin film contains an ultraviolet absorber, the amount is usually 0.1% by weight or more, preferably 0.3% by weight or more with respect to 100% by weight of the (meth) acrylic resin. And preferably 3% by weight or less.

  A conventionally well-known film forming method can be employ | adopted for preparation of a (meth) acrylic-type resin film. The (meth) acrylic resin film may have a multilayer structure, and the (meth) acrylic resin film having a multilayer structure is a variety of generally known methods such as a method using a feed block and a method using a multi-manifold die. Can be used. Among them, for example, a method of laminating via a feed block, multilayer melt extrusion from a T die, and forming a film by contacting at least one side of the obtained laminated film material with a roll or a belt is a film having good surface properties. It is preferable at the point obtained. In particular, from the viewpoint of improving the surface smoothness and surface glossiness of the (meth) acrylic resin film, the film is obtained by bringing both surfaces of the laminated film obtained by the multilayer melt extrusion molding into contact with the roll surface or the belt surface. The method of making is preferable. In the roll or belt used in this case, the surface of the roll or belt in contact with the (meth) acrylic resin has a mirror surface for imparting smoothness to the (meth) acrylic resin film surface. Is preferred.

  The (meth) acrylic resin film may be obtained by subjecting the film produced as described above to stretching treatment. A stretching process may be required to obtain a film having desired optical properties and mechanical properties. Examples of the stretching treatment include uniaxial stretching and biaxial stretching. Examples of the stretching direction include a machine flow direction (MD) of an unstretched film, a direction orthogonal to the machine flow direction (TD), and a direction oblique to the machine flow direction (MD). Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction.

  For the stretching process, for example, two or more pairs of nip rolls with increased peripheral speed on the outlet side are used to stretch in the longitudinal direction (machine flow direction: MD), or the both ends of the unstretched film are gripped with a chuck and machine flow is performed. It is performed by spreading in a direction (TD) orthogonal to the direction.

The draw ratio by the drawing treatment is preferably more than 0% and 300% or less, and more preferably 100 to 250%. If the draw ratio exceeds 300%, the film thickness becomes too thin and breaks easily, or the handleability decreases. A draw ratio is calculated | required from the following Formula.
Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / (Length before stretching)

The stretched (meth) acrylic resin film preferably has an absolute value of the plane orientation coefficient ΔP of 2 × 10 ⁻⁴ or less from the viewpoint of enhancing the adhesion to the surface treatment layer and the polarizing film.

The plane orientation coefficient ΔP is a physical property value that serves as an index relating to the orientation state of the molecular chains of the polymer constituting the film, and the refractive index in the in-plane slow axis direction (the direction in which the refractive index becomes maximum in the plane). when n _x, the refractive index n _y in-plane fast axis direction (perpendicular to the plane slow axis direction), the refractive index in the thickness direction of the film and n _z, is defined by the following equation.
Plane orientation coefficient _{ΔP = (n x + n y} ) / 2-n z

  For example, in the case of a film biaxially stretched in MD and TD, the larger the absolute value of the plane orientation coefficient ΔP, the higher the molecular chain of the polymer is oriented perpendicular to the thickness direction of the film. In general, the plane orientation coefficient ΔP of the stretched (meth) acrylic resin film takes a negative value.

  Moreover, in order to provide desired optical properties and mechanical properties, instead of or along with the stretching treatment, a heat-shrinkable film is bonded to the (meth) acrylic resin film, and the film is shrunk. Also good.

  In order to increase the adhesive strength between the (meth) acrylic resin film and the polarizing film, an easy adhesion layer may be provided on the surface of the (meth) acrylic resin film facing the polarizing film.

  The easy adhesion layer provided in the surface facing the polarizing film of a protective film should just be what can improve the adhesiveness of a protective film and an adhesive agent. Examples of materials for forming such an easy-adhesion layer include polyester resins, urethane resins, acrylic resins having a polar group in the skeleton, a relatively low molecular weight, and a relatively low glass transition temperature. Can do. The polar group present in the skeleton is preferably selected so that the resin is hydrophilic or water-dispersible, and examples thereof include a hydrophilic substituent, an ether bond, and a plurality of ether bonds.

  Specific examples of hydrophilic substituents include sulfonic acid groups, carboxylic acid groups, and phosphoric acid groups, and lithium salts, sodium salts, potassium salts, and ammonium salts thereof. The ether bond or the plurality of ether bonds can be a structural unit derived from diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, or the like. By introducing a monomer having these substituents or structural units into a polyester resin, a urethane resin, or an acrylic resin, a material constituting the easy-adhesion layer can be obtained.

  Moreover, the material which comprises this easily bonding layer can also mix | blend a crosslinking agent, an organic or inorganic filler, surfactant, a lubricant, etc. as needed.

  The formation of the easy-adhesive is, for example, a solution containing the material constituting the easy-adhesive layer described above, or a solution containing a precursor of such a material and a polymerization initiator (hereinafter referred to as “composition for easy-adhesive layer”). May be applied to one side of a protective film made of a methacrylic resin and then dried or dried and cured. The easy adhesion layer may be formed immediately after forming a protective film made of a methacrylic resin, or may be formed immediately before being bonded to the polarizing film.

  The thickness of the easy-adhesion layer is preferably 0.01 to 5 μm, more preferably 0.03 to 0.6 μm after drying or after drying / curing. If the easy adhesion layer is too thin, the adhesive strength between the polarizing film and the protective film may be insufficient. On the other hand, if the easy-adhesion layer is too thick, its hydrophilicity becomes excessive, and the resulting polarizing plate may be inferior in water resistance.

  The method for applying the easy-adhesion layer composition to the surface of the protective film facing the polarizing film is a die coater, comma coater, reverse roll coater, gravure coater, rod coater, wire bar coater, doctor blade coater, air doctor coater, etc. Ordinary coating technology using can be used. Moreover, the method and conditions for drying the applied composition for an easy-adhesion layer are not particularly limited. For example, a method of drying using a hot air dryer or an infrared dryer can be employed. Moreover, when the solution containing the precursor of the material which comprises an easily bonding layer is used as an easily bonding layer composition, you may provide a curing process after drying and hardening. Even when a curing process is employed, curing proceeds to some extent with the heat used to dry the composition for an easy-adhesion layer, and further curing proceeds in the subsequent bonding process between the polarizing film and the protective film using an adhesive. Even with room temperature curing, sufficient physical properties can be obtained.

  In order to adjust the affinity for the adhesive on the surface of the protective film provided with the easy-adhesion layer, the surface of the easy-adhesion layer provided on the protective film is later bonded to the polarizing film via the adhesive, For example, corona discharge treatment, plasma treatment, ozone spraying, ultraviolet irradiation, flame treatment, chemical treatment, and other conventionally known surface treatments can be performed.

  The first protective film and the second protective film can also be protective films having an optical function such as a brightness enhancement film.

  The brightness enhancement film is used for the purpose of improving the brightness in a liquid crystal display device or the like. For example, a plurality of thin film films having different refractive index anisotropies are laminated to produce anisotropy in reflectance. And a reflection-type polarization separation sheet designed in the above, a cholesteric liquid crystal polymer alignment film, and a circular polarization separation sheet in which the alignment liquid crystal layer is supported on a film substrate.

  Surface treatment layers (coating layers) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer and an antifouling layer are provided on the surface of the first protective film and the second protective film opposite to the polarizing film. It can also be formed. A well-known method can be used for forming the surface treatment layer on the surface of the protective film.

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

  The thickness of the first protective film and the second protective film is preferably thin from the viewpoint of thinning the polarizing plate, but if it is too thin, the strength is lowered and the processability is poor. Therefore, the thickness of the first protective film and the second protective film is preferably 5 to 90 μm or less, more preferably 60 μm or less, still more preferably 50 μm or less, and further preferably 30 μm or less.

  As the first protective film and the second protective film, a cyclic polyolefin resin film is preferable. Even if the cyclic polyolefin resin film is thin, it has a feature of low moisture permeability. When the polarizing film becomes thinner, the polarizing film generally tends to deteriorate under a high temperature and high humidity environment, but this can be prevented by using a protective film having low moisture permeability.

(Adhesive layer)
Lamination | stacking with a polarizing film and a 1st protective film and lamination | stacking with a polarizing film and a 2nd protective film are each performed through an adhesive bond layer. As the adhesive forming the adhesive layer, an active energy ray-curable adhesive that can be cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays, an adhesive component dissolved in water, or Examples thereof include a water-based adhesive dispersed in water.

  When an active energy ray-curable adhesive is employed, the adhesive layer becomes the cured product layer. As the adhesive, an active energy ray-curable adhesive having an epoxy compound that is cured by cationic polymerization as a curable component is more preferable, and an ultraviolet curable adhesive having an epoxy compound as a curable component is more preferable. The epoxy compound here means a compound having an average of 1 or more, preferably 2 or more epoxy groups in the molecule. Epoxy compounds may be used alone or in combination of two or more.

  An example of an epoxy compound that can be suitably used is a hydrogenated epoxy compound (aliphatic compound) obtained by reacting an alicyclic polyol obtained by hydrogenating an aromatic ring of an aromatic polyol with epichlorohydrin. A glycidyl ether of a polyol having a cyclic ring); an aliphatic epoxy compound such as an aliphatic polyhydric alcohol or a polyglycidyl ether of an alkylene oxide adduct thereof; one or more epoxy groups bonded to the alicyclic ring in the molecule An alicyclic epoxy compound that is an epoxy compound is included.

  The active energy ray-curable adhesive may further contain a (meth) acrylic compound that is radically polymerizable as a curable component. The (meth) acrylic compound is a (meth) acrylate monomer having at least one (meth) acryloyloxy group in the molecule; obtained by reacting two or more functional group-containing compounds, and at least two in the molecule. And (meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers having (meth) acryloyloxy groups.

  When the active energy ray-curable adhesive contains an epoxy compound that is cured by cationic polymerization as a curable component, it preferably contains a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-arene complexes. Moreover, when the active energy ray-curable adhesive contains a radical polymerizable curable component such as a (meth) acrylic compound, it is preferable to contain a photo radical polymerization initiator. Examples of the photo radical polymerization initiator include acetophenone initiators, benzophenone initiators, benzoin ether initiators, thioxanthone initiators, xanthone, fluorenone, camphorquinone, benzaldehyde, anthraquinone, and the like.

  Active energy ray-curable adhesives are optionally charged with cationic polymerization accelerators such as oxetane and polyol, photosensitizers, ion trapping agents, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, and filling. An additive such as an agent, a flow modifier, a plasticizer, an antifoaming agent, an antistatic agent, a leveling agent, and a solvent can be contained.

  The thickness of the adhesive layer formed from the active energy ray-curable adhesive is, for example, about 0.01 to 10 μm, preferably about 0.01 to 5 μm, and more preferably 2 μm or less (for example, 1 μm or less). ).

  As the water-based adhesive, for example, an adhesive composition using a polyvinyl alcohol resin or a urethane resin as a main component is preferable. The thickness of the adhesive layer formed from the water-based adhesive is usually 1 μm or less.

  When a polyvinyl alcohol-based resin is used as the main component of the adhesive, the polyvinyl alcohol-based resin may be partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, or methylol group. Modified polyvinyl alcohol resins such as modified polyvinyl alcohol and amino group-modified polyvinyl alcohol may also be used. Polyvinyl alcohol resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymerization of vinyl acetate and other monomers copolymerizable therewith. It may be a polyvinyl alcohol copolymer obtained by saponifying the coalescence.

  A water-based adhesive having a polyvinyl alcohol resin as an adhesive component is usually an aqueous solution of a polyvinyl alcohol resin. The density | concentration of the polyvinyl alcohol-type resin in an adhesive agent is 1-10 weight part normally with respect to 100 weight part of water, Preferably it is 5 weight part or less.

  Adhesives composed of an aqueous solution of a polyvinyl alcohol-based resin include curable components such as polyhydric aldehydes, melamine-based compounds, zirconia compounds, zinc compounds, glyoxal, and water-soluble epoxy resins to improve adhesion. It is preferable to add an agent. Examples of water-soluble epoxy resins include polyamide polyamine epoxy resins obtained by reacting polychloroalkylenes such as diethylenetriamine and triethylenetetramine with polycarboxylic acid polyamines such as adipic acid and epichlorohydrin. Can be suitably used. Commercially available products of such polyamide polyamine epoxy resins include “Smiles Resin (registered trademark) 650” and “Smiles Resin (registered trademark) 675” manufactured by Taoka Chemical Co., Ltd., and “WS-525” manufactured by Seiko PMC Co., Ltd. ". The addition amount of these curable components and crosslinking agents (the total amount when added together as the curable component and the crosslinking agent) is usually 1 to 100 parts by weight, preferably 1 with respect to 100 parts by weight of the polyvinyl alcohol resin. ~ 50 parts by weight. When the addition amount of the curable component or the crosslinking agent is less than 1 part by weight with respect to 100 parts by weight of the polyvinyl alcohol-based resin, the effect of improving adhesiveness tends to be reduced. When the addition amount of the crosslinking agent exceeds 100 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin, the adhesive layer tends to become brittle.

  When a urethane resin is used as the main component of the adhesive, examples of a suitable adhesive composition include a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group. The polyester ionomer type urethane resin is a urethane resin having a polyester skeleton, into which a small amount of an ionic component (hydrophilic component) is introduced. Such an ionomer-type urethane resin is suitable as a water-based adhesive because it is emulsified directly in water without using an emulsifier to form an emulsion.

[Display device]
The polarizing plate produced by the present invention can be cut as necessary and used in various display devices. A display device is a device having a display element and includes a light-emitting element or a light-emitting device as a light-emitting source. Examples of the display device include a liquid crystal display device, an organic electroluminescence (EL) display device, an inorganic electroluminescence (EL) display device, an electron emission display device (for example, a field emission display device (FED), a surface field emission display device (SED). )), Electronic paper (display device using electronic ink or electrophoretic element, plasma display device, projection display device (eg, display device having a grating light valve (GLV) display device, digital micromirror device (DMD)), and Examples of the liquid crystal display device include a transmissive liquid crystal display device, a transflective liquid crystal display device, a reflective liquid crystal display device, a direct view liquid crystal display device, and a projection liquid crystal display device. These display devices may be display devices that display a two-dimensional image. And it may be a stereoscopic display apparatus for displaying a three-dimensional image.

  In the display device, the polarizing plate is usually laminated on the liquid crystal cell via an adhesive layer or an adhesive layer. In this invention, it is preferable to laminate | stack through an adhesive layer, and it is preferable that the storage elastic modulus in 23 degreeC of an adhesive layer is 100-1000 KPa. When the storage elastic modulus of the pressure-sensitive adhesive layer is less than 100 KPa, shrinkage of the polarizing plate during a high temperature test cannot be suppressed, and appearance defects such as peeling tend to occur. Moreover, when the storage elastic modulus of the pressure-sensitive adhesive layer is larger than 1000 KPa, the pressure-sensitive adhesive cannot relax the strain generated between the glass and the polarizing plate during the thermal shock test, and PVA cracking tends to occur.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, corona treatment, measurement of the storage elastic modulus of the pressure-sensitive adhesive layer, measurement of the tensile elastic modulus of the protective film, and measurement of the contraction force in the absorption axis direction of the polarizing film were performed by the following methods.

<Corona treatment>
The corona treatment was performed with a corona discharge device manufactured by Kasuga Electric Co., Ltd. Specifically, a corona surface treatment frame “STR-1764”, a high frequency power supply “CT-0212”, and a high voltage transformer “CT-T02W” were used. The film or sheet subjected to corona treatment was subjected to corona discharge treatment at an output intensity of 280 W on the target surface (bonding surface) for corona treatment while being moved at a speed of 10 m / min.

<Measurement of storage modulus of adhesive layer>
As the storage elastic modulus of the pressure-sensitive adhesive layer, the storage elastic modulus (G ′) of the pressure-sensitive adhesive layer at 23 ° C. was measured by the following method. First, a pressure-sensitive adhesive layer is provided on one side of a polarizing plate (trade name “Sumikaran (registered trademark) SRW062” manufactured by Sumitomo Chemical Co., Ltd.) having a protective film (TAC) having a thickness of 40 μm laminated on both sides of the polarizing film. A polarizing plate with an agent was prepared, and then a 4 cm × 4 cm piece was cut therefrom. The release film is peeled off from the adhesive layer, and the exposed adhesive layer conforms to JIS K7244-10: 1999 "Plastics-Test method for dynamic mechanical properties-Part 10: Complex shear viscosity by parallel plate vibration rheometer". The storage elastic modulus was measured with a measuring instrument “Physica MCR301” manufactured by Anton-Paar. For measurement, a parallel plate having a diameter of 25 mm was used, and a storage elastic modulus at 23 ° C. was determined by a torsional shear method with a frequency of 1 Hz.

<Measurement of tensile modulus of protective film>
The tensile elastic modulus of the protective film was measured as follows. First, using a universal testing machine “Autograph AG-I” manufactured by Shimadzu Corporation equipped with a thermostatic bath, the protective film to be measured was cut into a piece of width 10 mm × length 200 mm, and the distance between the marked lines of the measuring machine was set to 100 mm. I set this. Next, in accordance with JIS K 7127: 1999 “Plastic Film and Sheet Tensile Test Method”, the elastic modulus when pulled at a test speed of 50 mm / min was determined. In addition, unless otherwise indicated, it is a measurement result in a 23 degreeC environment below.

<Measurement of shrinkage force in the direction of absorption axis of polarizing film>
To the laminated film (base film / primer layer / polarizing film layer) of the three layers that have gone through the dyeing process, a piece of 2 mm wide × 50 mm long so that the absorption axis direction of the laminated film is the long axis. Cut with a super cutter made by Seisakusho. The base film was peeled from the obtained strip-shaped laminated film to prepare a shrinkage force measurement sample. Set the sample for contraction force measurement to a thermomechanical analyzer ("TMA / 6100" manufactured by Hitachi High-Tech Science Co., Ltd.) with a distance between chucks of 10 mm, and leave the specimen in a room at 20 ° C for a sufficient time. The room temperature was set so that the temperature was raised from 20 ° C. to 80 ° C. over 1 minute, and the temperature in the sample chamber was maintained at 80 ° C. after the temperature rise. After allowing the temperature to rise for 4 hours, the contraction force in the long side direction of the measurement sample was measured in an environment at 80 ° C. In this measurement, the static load was 0 mN, and a SUS probe was used as the jig.

[Example 1]
(1) Resin layer forming step An unstretched polypropylene (PP) film (melting point: 163 ° C.) having a thickness of 90 μm was used as a base film, and the surface thereof was subjected to corona treatment to form a primer layer on the corona-treated surface. . The primer layer was prepared by dissolving polyvinyl alcohol powder (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, saponification degree 99.5 mol%, trade name “Z-200”) in hot water at 95 ° C., concentration 3 An aqueous solution of 5% by weight was prepared, and a mixed aqueous solution in which 5 parts by weight of a crosslinking agent [trade name “Smileze Resin (registered trademark) 650, manufactured by Taoka Chemical Co., Ltd.] was blended with 6 parts by weight of polyvinyl alcohol powder. The primer layer was formed by coating this mixed aqueous solution on the corona-treated surface of the base film with a small-diameter gravure coater, and drying it at 80 ° C. for 10 minutes, with a primer layer thickness of 0.2 μm. Met.

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

(2) Stretching process The laminated film was subjected to 5.3 times free end uniaxial stretching at 160 ° C. using a floating longitudinal uniaxial stretching apparatus to obtain a stretched film.

(3) Dyeing Step After that, the stretched film was dyed by immersing it in a dyeing solution that is a mixed aqueous solution of iodine and potassium iodide at 30 ° C. for about 180 seconds, and then the excess iodine solution was washed away with 10 ° C. pure water. Subsequently, it was immersed in the crosslinking solution 1 which is an aqueous solution of boric acid at 78 ° C. for 120 seconds, and then immersed in the crosslinking solution 2 at 70 ° C. containing boric acid and potassium iodide for 60 seconds. Thereafter, it was washed with pure water at 10 ° C. for 10 seconds, finally dried at 40 ° C. for 150 seconds, and then dried at 55 ° C. for 150 seconds. The polarizing film layer was formed from the resin layer by the above process, and the polarizing laminated film was obtained. The blending ratio of each solution is as follows.

<Dyeing solution>
Water: 100 parts by weight Iodine: 0.6 parts by weight Potassium iodide: 10 parts by weight <Crosslinking solution 1>
Water: 100 parts by weight Boric acid: 9.5 parts by weight <Crosslinking solution 2>
Water: 100 parts by weight Boric acid: 5.0 parts by weight Potassium iodide: 6 parts by weight

(4) Preparation of adhesive The following components were mixed and defoamed to prepare an ultraviolet curable resin adhesive in a liquid state. The photocationic polymerization initiator used was obtained in the form of a 50% propylene carbonate solution. The amount (2.25 parts) shown below is the solid content.

3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate 75 parts 1,4-butanediol diglycidyl ether 20 parts 2-ethylhexyl glycidyl ether 5 parts triarylsulfonium hexafluorophosphate-based photocationic polymerization initiator
2.25 parts

(5) 1st bonding process As a 1st protective film, the 23-micrometer-thick protective film [trade name "Zeonor film (made by Nippon Zeon Co., Ltd.) formed from the cyclic polyolefin-type resin which gave the bonding surface the corona treatment. Registered trademark) ZF14-023 ", tensile elastic modulus in the transport direction: 2100 MPa, tensile elastic modulus in the direction perpendicular to the transport direction: 2100 MPa. The same UV curable adhesive was applied to the corona-treated surface of the first protective film with a micro gravure coater, and the polarizing film layer of the polarizing laminated film prepared in (3) was placed on the surface opposite to the base film side. Pasted. Then, using an ultraviolet irradiation device with a belt conveyor to which an ultraviolet lamp “D bulb” manufactured by Fusion UV Systems is attached, ultraviolet rays are irradiated from the protective film side so that the integrated light amount becomes 250 mJ / cm ² . The adhesive was cured. As described above, a five-layer film composed of base film / primer layer / polarizing film layer / ultraviolet curable adhesive layer / first protective film was obtained. The thickness of the polarizing film layer was 5.6 μm. The thickness of the adhesive layer after curing was 1.0 μm.

(6) Peeling step and second laminating step The base film was peeled and removed from the five-layer film produced in (5) above to obtain a polarizing plate with a single-side protective film. The base film could be easily peeled off. Next, the same protective film as used in (5) is used as the second protective film, and the same UV curable adhesive is applied to the corona-treated surface using a microgravure coater, which is used for the above-mentioned single-side protection. It bonded on the primer layer surface in a polarizing plate with a film. Next, the adhesive layer was cured by irradiating ultraviolet rays from the second protective film side under the same conditions as in (5) to obtain a polarizing plate. The thickness of the adhesive layer after curing was 1.0 μm.

[Example 2]
(3) A polarizing plate was produced in the same manner as in Example 1 except that the drying condition in the dyeing process was changed to 150 ° C. for 150 seconds after drying at 50 ° C. for 150 seconds. The thickness of the polarizing film layer was 5.7 μm.

[Example 3]
(3) A polarizing plate was produced in the same manner as in Example 1 except that the drying conditions in the dyeing process were changed to dry at 50 ° C. for 150 seconds and then at 85 ° C. for 150 seconds. The thickness of the polarizing film layer was 5.4 μm.

[Comparative Example 1]
(3) A polarizing plate was produced in the same manner as in Example 1 except that the drying condition in the dyeing process was changed to dry at 40 ° C. for 150 seconds and then at the same temperature for 150 seconds. The thickness of the polarizing film layer was 5.4 μm.

[Comparative Example 2]
(3) Example except that the amount of potassium iodide in the crosslinking solution 2 in the dyeing process was changed to 8 parts and the drying conditions were changed to dry at 40 ° C. for 150 seconds and then at the same temperature for 150 seconds. A polarizing plate was prepared in the same manner as in 1. The thickness of the polarizing film layer was 5.5 μm.

[Comparative Example 3]
(2) After changing the draw ratio in the drawing step to 5.8 times, and (3) the amount of potassium iodide in the crosslinking solution 2 in the dyeing step is 6 parts, and the drying condition is 40 ° C. for 150 seconds. A polarizing plate was produced in the same manner as in Example 1 except that each was changed to dry at the same temperature for 150 seconds. The thickness of the polarizing film layer was 5.7 μm.

<Measurement of puncture strength per unit film thickness of polarizing film>
The polarizing plates produced in Examples and Comparative Examples were subjected to an ultrasonic cleaner while being immersed in cyclohexane, and the protective film bonded on both sides was dissolved and removed to take out the polarizing film, and a piercing test was performed. The piercing test uses a handy compression tester “KES-G5 needle penetration force measurement specification” manufactured by Kato Tech Co., Ltd. equipped with a needle with a tip diameter of 1 mmφ and 0.5 R, in an environment of a temperature of 23 ± 3 ° C. The piercing speed was 0.33 cm / sec. The puncture strength measured in the puncture test was a puncture test performed on 12 test pieces, and the average value was obtained. The thickness of the polarizing film was measured with a contact-type film thickness meter (trade name “DIGIMICRO (registered trademark) MH-15M” manufactured by Nikon Corporation), and the puncture strength (strength P) per unit film thickness was determined.

<Measurement of optical properties of polarizing film>
The polarizing films obtained by the Examples and Comparative Examples (exfoliated from the base film) were bonded to soda glass using an optically transparent acrylic pressure-sensitive adhesive to obtain an optical property measurement sample. The optical properties of the polarizing film were measured with a spectrophotometer with an integrating sphere (trade name “V7100” manufactured by JASCO Corporation), and the measurement results are shown in Table 1.

In the measurement, the optical property measurement sample was set in a spectrophotometer with the polarizing film side as a detector side. A specific measurement method will be described. MD transmittance (MD) and TD transmittance (TD) are obtained in a wavelength range of 380 to 780 nm, and a single substance at each wavelength is calculated based on the following formulas (3) and (4). Transmittance and degree of polarization are calculated, and further, visibility correction is performed using a two-degree field of view (C light source) of JIS Z 8701: 1999 “Color Display Method-XYZ Color System and X10Y10Z10 Color System”. The transmittance (Ty) and the visibility correction polarization degree (Py) were obtained.
Single transmittance (%) = (MD + TD) / 2 (3)
Degree of polarization (%) = [(MD-TD) / (MD + TD)] × 100 (4)

  Here, “MD transmittance” is the transmittance when the direction of polarized light emitted from the Glan-Thompson prism is parallel to the transmission axis of the polarizing plate sample, and “TD transmittance” is from the Glan-Thompson prism. This is the transmittance when the direction of polarized light exiting and the transmission axis of the polarizing plate sample are orthogonal to each other.

(Measurement of hue)
The single hue of the polarizing film (single a, single b) was also measured with a spectrophotometer with an integrating sphere [trade name “V7100” manufactured by JASCO Corporation]. Here, the single hue means the hue of transmitted light when light is incident on one polarizing plate. The a value and the b value are color values expressed in the Hunter Lab color system, and the tristimulus values X, Y, and JIS Z 8722: 2009 “Color measurement method—reflection and transmission object color” are defined. Calculated from Z. The results are shown in Table 1.

(Measurement of absorbance at a wavelength of 700 nm)
The polarizing performance on the long wavelength side of the polarizing film was judged by the absorbance at a wavelength of 700 nm. Absorbance is a positive number obtained by taking the logarithm of orthogonal transmittance (Tc) obtained from MD transmittance (MD) and TD transmittance (TD) at a wavelength of 700 nm, and is obtained by the following equation. The greater the value of the absorbance, the smaller the optical property deterioration under a high temperature environment, and the better the heat resistance.
Tc (700) (%) = [MD (700 nm) / 100] × [TD (700 nm) / 100] × 100
A700 = −log [Tc (700) / 100]

<Cooling heat shock test of polarizing plate>
The second protective film side of the polarizing plate prepared in Examples and Comparative Examples was subjected to corona treatment, and an adhesive (storage modulus: 390 KPa, thickness: 20 μm) was bonded to prepare an adhesive-attached polarizing plate. . A polarizing plate with an adhesive was cut out with a super cutter at a long side of 100 mm and a short side of 60 mm so that the absorption axis was parallel to the long side, and used as a thermal shock test evaluation sample. This evaluation sample is bonded to an alkali-free glass plate (“Eagle-XG (registered trademark)” manufactured by Corning) on the pressure-sensitive adhesive layer side, and is applied for 20 minutes in an autoclave at a temperature of 50 ° C. and a pressure of 5 MPa. Pressure treatment was performed, and the mixture was left for 1 day in an atmosphere having a temperature of 23 ° C. and a relative humidity of 60%. Then, with a thermal shock tester (TSA-301L-W) manufactured by ESPEC Corporation, holding for 30 minutes at −40 ° C. on the low temperature side and then holding for 30 minutes at 85 ° C. on the high temperature side constitute one cycle. A durability test was conducted for 100 cycles. During the test, it was not exposed to room temperature. Each of the 50 evaluation samples was subjected to a durability test of 100 cycles, and among the 50 evaluation samples, the number of visually confirmed occurrences of cracked appearance defects was shown in the column of “Cool Thermal Shock Test” in Table 1. . For example, “0/50” in Example 1 means that the number of cracked appearance defects that could be visually confirmed in 50 evaluation samples was 0.

  ADVANTAGE OF THE INVENTION According to this invention, the polarizing plate which is thin and has the small shrinkage rate at the time of applying heat is provided. Moreover, according to this invention, the crack which arises in a polarizing film is suppressed in the environment which repeats high temperature and low temperature, and the polarizing plate which is excellent in durability is provided. Since the polarizing plate of the present invention has a small shrinkage rate, even if it is applied to a liquid crystal panel with a narrow frame, the polarizing plate end shrinks in a high temperature environment and the polarizing plate edge enters the viewing area. Can be suppressed.

Claims (4)

A method for producing a polarizing laminated film having a polarizing film layer on a base film,
The manufacturing method includes:
Forming a polyvinyl alcohol-based resin layer on the base film,
A step of stretching the laminate obtained in the step of forming the resin layer, and a step of dyeing the polyvinyl alcohol-based resin layer with a dichroic dye to form a polarizing film layer after the step of stretching. In the step of forming the polarizing film layer, the temperature parameter represented by the product of the drying temperature (° C.) and the drying time (min) is 220 to 350 after the polyvinyl alcohol resin layer is dyed with a dichroic dye. A method for producing a polarizing laminated film comprising a drying treatment.   The said drying process is a manufacturing method of the light-polarizing laminated film of Claim 1 containing the drying process performed at the temperature of at least 50-90 degreeC. It is a manufacturing method of a polarizing plate provided with the process of laminating the 1st protective film on the polarizing film layer of the polarizing lamination film according to claim 1 or 2,
A step of obtaining a laminated film in which the first protective film is laminated on the polarizing film layer of the polarizing laminated film according to claim 1 or 2,
The manufacturing method of a polarizing plate including the process of peeling and removing a base film and obtaining the polarizing plate with a single-sided protective film.   Furthermore, the manufacturing method of the polarizing plate of Claim 3 including the bonding process of bonding a 2nd protective film to the polarizing film layer surface, and obtaining a polarizing plate with a double-sided protective film.