JP2013068804A - Stretched film and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stretched film capable of forming a polarizer layer by dyeing a resin layer for a suitable time to dye in a dyeing step in manufacturing a polarizing laminated film or a polarizing plate.SOLUTION: The present invention relates to a stretched film comprising a base film and a resin layer which is formed on one surface of the base film and has a thickness of 10 μm or less, wherein the resin layer is stretched and formed from a polyvinyl alcohol resin having a degree of saponification (mol%) and an average degree of polymerization satisfying the following expression (1) or (2): (1) 96 mol% < degree of saponification ≤ 98 mol%, and (2) 93 mol% ≤ degree of saponification ≤ 96 mol% and average degree of polymerization ≥ 2500.

Description

  The present invention relates to a stretched film, a stretched film manufacturing method, a polarizing laminated film manufacturing method, and a polarizing plate manufacturing method.

  A polarizing plate is widely used as a polarization supplying element in a display device such as a liquid crystal display device. Conventionally, a polarizing plate made of a polyvinyl alcohol-based resin and a protective film such as triacetyl cellulose are used as the polarizing plate. The polarizer layer (polarizing film) is required to have high optical performance, and in recent years, with the development of liquid crystal display devices such as notebook personal computers and mobile phones, reduction in thickness and weight is required.

  As an example of a method for producing a thin polarizing plate, after applying a solution containing a polyvinyl alcohol-based resin on the surface of a base film to provide a resin layer, the laminate film composed of the base film and the resin layer is stretched, There has been proposed a method of obtaining a polarizing laminated film having a polarizer layer by dyeing, crosslinking (fixing), drying, and forming a polarizer layer from a resin layer (see, for example, Patent Document 1). There are known methods in which this is used as it is as a polarizing plate, or after a protective film is bonded to the film, a substrate film is peeled off and used as a polarizing plate.

JP 2011-2816 A

  The present invention is a stretched film used in a method for producing a polarizing laminate film or a polarizing plate provided with a polarizer layer as described above, and a dyeing time in a dyeing step when producing the polarizing laminated film or the polarizing plate. An object of the present invention is to provide a stretched film and a method for producing the same. Moreover, this invention aims at providing the manufacturing method of the light-polarizing laminated film or polarizing plate which can be manufactured with high manufacturing efficiency with the short dyeing | staining time in a dyeing process.

  The present invention comprises a base film and a resin layer having a thickness of 10 μm or less formed on one surface of the base film, and the resin layer has a saponification degree (mol%) and an average polymerization degree. A stretched film made of a polyvinyl alcohol-based resin satisfying the relationship of the following formula (1) or formula (2).

96 mol% <degree of saponification ≦ 98 mol% (1)
93 mol% ≦ degree of saponification ≦ 96 mol% and average degree of polymerization ≧ 2500 (2)
The resin layer is preferably uniaxially stretched at a stretch ratio of more than 5 times.

  Moreover, this invention is a manufacturing method of the said stretched film, Comprising: The saponification degree (mol%) and average polymerization degree are the relationship of the above-mentioned formula (1) or formula (2) on one surface of a base film. A resin layer forming step of obtaining a laminated film by forming a resin layer made of a polyvinyl alcohol-based resin satisfying the requirements, and a stretching step of obtaining a stretched film by uniaxially stretching the laminated film.

  Moreover, this invention is a manufacturing method of a light-polarizing laminated film provided with a base film and a 10-micrometer-thick polarizer layer currently formed in one surface of the said base film, Comprising: The said resin layer formation After manufacturing a stretched film through a process and the said extending process, it has the dyeing process of dyeing the resin layer of the said stretched film with a dichroic dye, and forming a polarizer layer.

  Further, the present invention is a method for producing a polarizing plate comprising a protective film and a polarizer layer having a thickness of 10 μm or less formed on one surface of the protective film, wherein the resin layer forming step, the stretching After producing a polarizing laminate film through the steps and the dyeing step, a protective film is bonded to the surface of the polarizer layer on the side opposite to the substrate film side of the polarizer layer to obtain a multilayer film. A bonding step and a peeling step of peeling the base film from the multilayer film.

  According to the stretched film of the present invention and the stretched film produced by the production method of the present invention, good dyeing time in the dyeing process when producing a polarizing laminated film or a polarizing plate without deteriorating polarization performance and water resistance. The dye layer can be dyed to form a polarizer layer. Moreover, according to the manufacturing method of this invention, a light-polarizing laminated film or a polarizing plate can be manufactured efficiently.

It is a flowchart which shows the outline | summary of the manufacturing method of the stretched film of this invention. It is a flowchart which shows the outline | summary of the manufacturing method of the light-polarizing laminated film of this invention. It is a flowchart which shows the outline | summary of the manufacturing method of the polarizing plate of this invention. It is a figure which shows the result plotted according to the center value of the saponification degree of PVA used for formation of a resin layer, and an average polymerization degree about Example 1, 2 and Comparative Examples 1,2.

Hereinafter, the present invention will be described in detail with reference to the drawings.
[Configuration of stretched film]
The stretched film of the present invention includes a base film and a resin layer having a thickness of 10 μm or less formed on one surface of the base film. The resin layer is made of a polyvinyl alcohol-based resin whose degree of saponification (mol%) and average degree of polymerization satisfy the relationship of the following formula (1) or formula (2).

96 mol% <degree of saponification ≦ 98 mol% (1)
93 mol% ≦ degree of saponification ≦ 96 mol% and average degree of polymerization ≧ 2500 (2)
The stretched film can be used for the production of a polarizing laminated film or a polarizing plate. Although a stretched film may be manufactured by the manufacturing method of the stretched film which concerns on this invention mentioned later, it is not limited to this. Hereinafter, each component of the stretched film will be described in detail.

<Resin layer>
As the polyvinyl alcohol resin used for the resin layer, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  A polyvinyl alcohol resin having a saponification degree of 93 mol% to 98 mol% is used (formula (1) and formula (2)). When a polyvinyl alcohol resin having a saponification degree of 93 mol% to 96 mol% is used, one having an average polymerization degree of 2500 or more is selected (formula (2)). When the degree of saponification of the polyvinyl alcohol-based resin is 98 mol% or less, the resin layer is dyed with a good dyeing time in the dyeing process when a polarizing laminated film or a polarizing plate is produced using a stretched film. A child layer can be formed. Further, when the saponification degree of the polyvinyl alcohol-based resin is larger than 96 mol%, or even when the saponification degree is smaller than 96 mol%, it is 93 mol% or more and the average polymerization degree is 2500 or more. When manufacturing a polarizing laminated film or a polarizing plate using a film, even if it is immersed in an aqueous solution in a dyeing process, for example, it has sufficient water resistance.

  The saponification degree as used herein is a unit ratio (mol%) representing the ratio of the acetate group contained in the polyvinyl acetate resin, which is a raw material for the polyvinyl alcohol resin, to a hydroxyl group by the saponification step. Is a numerical value defined by the following formula.

Saponification degree (mol%) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100
The degree of saponification can be determined by a method defined in JIS K 6726 (1994). When the saponification degree of the polyvinyl alcohol resin used in the resin layer is not limited to one value but has a width, the “saponification degree” in the formulas (1) and (2) is the saponification degree of the polyvinyl alcohol resin. Means the central value of the degree of conversion.

  The higher the degree of saponification, the higher the proportion of hydroxyl groups, that is, the lower the proportion of acetate groups that inhibit crystallization.

  The polyvinyl alcohol-based resin may be modified polyvinyl alcohol partially modified. Examples thereof include those obtained by modifying polyvinyl alcohol resins with olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, alkyl esters of unsaturated carboxylic acids, acrylamide and the like. The proportion of modification is preferably less than 30 mol%, and more preferably less than 10%. When modification exceeding 30 mol% is performed, it becomes difficult to adsorb the dichroic dye in a later step, resulting in a problem that the polarization performance is lowered.

  The average degree of polymerization of the polyvinyl alcohol-based resin is a numerical value obtained by a method defined by JIS K 6726 (1994). When the saponification degree of the polyvinyl alcohol-based resin is 96 mol% or less, the average polymerization degree is 2500 or more, preferably 8000 or less, more preferably 5000 or less. Moreover, when a saponification degree exceeds 96 mol%, although average polymerization degree is not specifically limited, Preferably it is 1000-10000, More preferably, it is 1500-5000.

  Examples of the polyvinyl alcohol resin having such characteristics include AH-26 (degree of saponification: 97.0 to 98.8 mol%, average degree of polymerization: 2600) manufactured by Nippon Synthetic Chemical Industry Co., Ltd., AH- 22 (degree of saponification: 97.5 to 98.5 mol%, average degree of polymerization: 2200); for example, JM-33 (degree of saponification: 93.5 to 95.5 mol%) of Nippon Vinegar Pival Co., Ltd. , Average degree of polymerization: 3300), JM-26 (degree of saponification: 95.5-97.5 mol%, average degree of polymerization: 2600) and the like, which are preferably used in the formation of the resin layer of the present invention. be able to.

  In the above-mentioned polyvinyl alcohol resin, additives such as a plasticizer and a surfactant may be added as necessary. As the plasticizer, polyols and condensates 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 not particularly limited, but is preferably 20% by weight or less in the polyvinyl alcohol resin.

  A film formed of such a polyvinyl alcohol-based resin constitutes the resin layer of the stretched film of the present invention. The method for forming the polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. However, from the viewpoint of easily obtaining a resin layer having a desired thickness, It is preferable to form a film by applying the solution on a base film. The resin layer is stretched and is preferably uniaxially stretched at a stretch ratio of more than 5 times, more preferably more than 5 times and not more than 17 times. The thickness of the resin layer after stretching is 10 μm or less, preferably 7 μm or less.

<Base film>
As the resin used for the base film, for example, thermoplastic resins excellent in transparency, mechanical strength, thermal stability, stretchability, etc. are used, and an appropriate resin is selected according to their glass transition temperature Tg or melting point Tm. You can choose.

  Specific examples of such thermoplastic resins include polyolefin resins, polyester resins, cyclic polyolefin resins (norbornene resins), (meth) acrylic resins, cellulose ester resins, polycarbonate resins, polyvinyl alcohol resins. , Vinyl acetate resin, polyarylate resin, polystyrene resin, polyethersulfone resin, polysulfone resin, polyamide resin, polyimide resin, and mixtures and copolymers thereof.

  The base film may be a film made of only one kind of the above-mentioned resin, or may be a film made by blending two or more kinds of resins. The base film may be a single layer film or a multilayer film.

  Examples of the polyolefin resin include polyethylene and polypropylene, which are preferable because they can be stably stretched at a high magnification. Moreover, an ethylene-polypropylene copolymer obtained by copolymerizing propylene with ethylene can also be used. Copolymerization can be performed with other types of monomers, and examples of other types of monomers copolymerizable with propylene include ethylene and α-olefins. 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. Specific examples of the α-olefin having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; Branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene; vinylcyclohexane and the like. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer. The content of the structural unit derived from the other monomer in the copolymer is determined by infrared (IR) spectrum according to the method described on page 616 of “Polymer Analysis Handbook” (1995, published by Kinokuniya). It can be obtained by measuring.

  Among the above, propylene-based resins constituting the propylene-based resin film include propylene homopolymer, propylene-ethylene random copolymer, propylene-1-butene random copolymer, and propylene-ethylene-1-butene. Random copolymers are preferably used.

  The stereoregularity of the propylene resin constituting the propylene resin film is preferably substantially isotactic or syndiotactic. A propylene-based resin film made of a propylene-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 polymer having an ester bond and is mainly a polycondensate of a polyvalent carboxylic acid and a polyhydric alcohol. As the polyvalent carboxylic acid used, divalent dicarboxylic acid is mainly used, and examples thereof include isophthalic acid, terephthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. In addition, divalent diol is mainly used as the polyhydric alcohol used, and examples thereof include propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol. Specific examples of the resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, polycyclohexane dimethyl naphthalate, and the like. . These blend resins and copolymers can also be suitably used.

  As the cyclic polyolefin resin, a norbornene resin is preferably used. Cyclic polyolefin resin is a general term for resins that are polymerized using cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And graft polymers obtained by modifying them with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as cyclic polyolefin resins. As specific examples, Topas (registered trademark) (manufactured by Ticona), Arton (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (manufactured by Nippon Zeon Corporation), ZEONEX (ZEONEX) (Registered trademark) (manufactured by ZEON CORPORATION) and Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.).

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

  The cellulose ester resin is 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, these copolymers and those obtained by modifying a part of the hydroxyl group with other types of substituents are also included. Among these, cellulose triacetate is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available products of cellulose triacetate include Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UZ (Fuji Film ( Co., Ltd.), Fujitac (registered trademark) TD40UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Opto Co., Ltd.), KC4UY (Konica Minolta Opto Co., Ltd.), and the like.

  The polycarbonate 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, and flame retardancy. Moreover, since it has high transparency, it is suitably used in optical applications. In optical applications, resins called modified polycarbonates in which the polymer skeleton is modified in order to lower the photoelastic coefficient, copolymerized polycarbonates with improved wavelength dependency, and the like are commercially available and can be suitably used. Such polycarbonate resins are widely commercially available. For example, Panlite (registered trademark) (Teijin Chemicals Ltd.), Iupilon (registered trademark) (Mitsubishi Engineering Plastics), SD Polyca (registered trademark) (Sumitomo) Dow Co., Ltd.), Caliber (registered trademark) (Dow Chemical Co., Ltd.) and the like.

  Arbitrary appropriate additives other than said thermoplastic resin may be added to the base film. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and coloring agents. . The content of the thermoplastic resin exemplified above 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. This is because, 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.

  The base film is obtained by performing corona treatment, plasma treatment, flame treatment, etc. on at least the surface on which the resin layer is formed in order to improve adhesion with the resin layer made of polyvinyl alcohol resin. May be. Moreover, in order to improve adhesiveness, you may provide thin layers, such as a primer layer, in the surface at the side in which the resin layer which consists of a polyvinyl alcohol-type resin of a base film is formed.

(Primer layer)
The primer layer is not particularly limited as long as it is a material that exhibits a certain degree of strong adhesion to both the base film and the polyvinyl alcohol-based resin layer. For example, a thermoplastic resin excellent in transparency, thermal stability, stretchability, etc. is used. Specific examples include acrylic resins and polyvinyl alcohol resins, but are not limited thereto.

  The resin constituting the primer layer may be used in a state dissolved in a solvent. Depending on the solubility of the resin, 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 A general organic solvent such as fluorinated hydrocarbons, alcohols such as ethanol, 1-propanol, 2-propanol, and 1-butanol can also be used. However, if the primer layer is formed using a solution containing an organic solvent, the base material may be dissolved. Therefore, it is preferable to select the solvent in consideration of the solubility of the base material. In consideration of the influence on the environment, the primer layer is preferably formed from a coating solution containing water as a solvent. Among these, a polyvinyl alcohol resin having good adhesion is preferably used.

  As a polyvinyl alcohol-type resin used as a primer layer, polyvinyl alcohol resin and its derivative (s) are mentioned, for example. Derivatives of polyvinyl alcohol resin include polyvinyl formal, polyvinyl acetal, etc., olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, and alkyl esters of unsaturated carboxylic acids. And those modified with acrylamide or the like. Among the above-mentioned polyvinyl alcohol-based resin materials, it is preferable to use a polyvinyl alcohol resin.

  In order to increase the strength of the primer layer, a crosslinking agent may be added to the thermoplastic resin. As the crosslinking agent to be added to the resin, known ones such as organic and inorganic can be used. What is necessary is just to select a more suitable thing suitably with respect to the thermoplastic resin to be used. For example, an epoxy-based, isocyanate-based, dialdehyde-based, or metal-based crosslinking agent can be selected. As the epoxy-based crosslinking agent, either a one-component curable type or a two-component curable type can be used. Examples include epoxies such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, and diglycidyl amine. .

  Examples of isocyanate-based crosslinking agents include tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (4-phenylmethane triisocyanate, isophorone diisocyanate, and ketoximes thereof. Isocyanates such as block products or phenol block products.

  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, and the type of metal is not particularly limited and may be appropriately selected. Examples of metal salts, metal oxides, and metal hydroxides include sodium, potassium, magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, silicon, boron, zinc, copper, vanadium, chromium, and tin. Examples thereof include metal salts having a valence higher than the valence, oxides thereof, and hydroxides.

  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 functional 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 of a chelate compound or the like.

  Preferable examples of the metal organic compound include a titanium organic compound, a zirconium organic compound, an aluminum organic compound, and a silicon organic compound. Only one kind of these metal organic compounds may be used, or two or more kinds may be appropriately mixed and used.

  Specific examples of the titanium organic compound include titanium orthoesters such as tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, tetramethyl titanate; titanium acetylacetonate, titanium tetra Titanium chelates such as acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamate, titanium ethylacetoacetate; titanium acylates such as polyhydroxytitanium stearate .

  Specific examples of the zirconium organic compound include, for example, zirconium normal propyrate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium bisacetylacetonate, zirconium acetylacetonate bisethylacetoacetate and the like. Can be mentioned.

  Specific examples of the aluminum organic compound include aluminum acetylacetonate and aluminum organic acid chelate. Specific examples of the silicon organic compound include compounds having the ligands exemplified for the titanium organic compound and the zirconium organic compound described above.

  In addition to the above-mentioned low molecular crosslinking agents, polymer crosslinking agents such as methylolated melamine resins and polyamide epoxy resins can also be used. Examples of such commercially available polyamide epoxy resins include “Smiles (registered trademark) Resin 650 (30)” and “Smiles (registered trademark) Resin 675” (all trade names) sold by Sumika Chemtex Co., Ltd. There is.

  When a polyvinyl alcohol-based resin is used as the thermoplastic resin, polyamide epoxy resin, methylolated melamine, dialdehyde, metal chelate crosslinking agent and the like are particularly preferable.

  The ratio of the thermoplastic resin and the cross-linking agent used to form the primer layer ranges from about 0.1 to 100 parts by weight of the cross-linking agent to 100 parts by weight of the resin. Accordingly, it is preferable to select from the range of about 0.1 to 50 parts by weight. The primer layer coating liquid preferably has a solid content concentration of about 1 to 25% by weight.

  The thickness of the primer layer is preferably 0.05 to 1 μm. More preferably, it is 0.1-0.4 micrometer. When the thickness is less than 0.05 μm, the effect of improving the adhesion between the base film and the polyvinyl alcohol layer is small. When the thickness is greater than 1 μm, the stretched film, and further, the polarizing laminated film and the polarizing plate produced using the same are thick. It is not preferable.

[Method for producing stretched film]
FIG. 1 is a flowchart showing an outline of a method for producing a stretched film of the present invention. The method for producing a stretched film of the present invention includes a resin layer forming step (S10) in which a resin layer made of a polyvinyl alcohol resin is formed on one surface of a base film to obtain a laminate film, and the laminate film is uniaxially stretched. Stretching step (S20) to obtain a stretched film. Hereafter, each process of S10-S20 in FIG. 1 is demonstrated in detail.

<Resin layer forming step (S10)>
Here, a resin layer made of a polyvinyl alcohol-based resin is formed on at least one surface of the base film. Suitable materials for the base film are as described in the description of the configuration of the stretched film. In addition, it is preferable to use a base film that can be stretched in a temperature range suitable for stretching the polyvinyl alcohol resin. Although the thickness of the base film before stretching can be determined as appropriate, in general, from the viewpoint of workability such as strength and handleability, it is preferably 1 to 500 μm, more preferably 1 to 300 μm, and still more preferably 5 to 5 μm. 200 μm.

  The thickness of the resin layer formed in the resin layer forming step (S10), that is, the thickness of the resin layer before stretching is preferably more than 3 μm and 60 μm or less. If it exceeds 60 μm, the thickness of the finally obtained stretched resin layer may exceed 10 μm, which is not preferable.

  The resin layer in the present invention is preferably formed by coating a polyvinyl alcohol resin solution obtained by dissolving polyvinyl alcohol resin powder in a good solvent on one surface of the substrate film and evaporating the solvent. It is formed. By forming the resin layer in this way, it can be formed thin. Materials suitable for the resin layer are as described in the description of the configuration of the stretched film. As a method of applying a polyvinyl alcohol resin solution to a base film, a wire bar coating method, a reverse coating, a roll coating method such as gravure coating, a die coating method, a comma coating method, a lip coating method, a spin coating method, a screen coating method A method, a fountain coating method, a dipping method, a spray method and the like can be appropriately selected from known methods and employed. A drying temperature is 50-200 degreeC, for example, Preferably it is 60-150 degreeC. The drying time is, for example, 2 to 20 minutes.

  In addition, the resin layer in this invention can also be formed by sticking the raw film which consists of polyvinyl alcohol-type resins on one surface of a base film.

  Moreover, in order to improve the adhesiveness of a base film and a resin layer, you may provide a primer layer between the base film and the resin layer which consists of polyvinyl alcohol-type resin. The primer layer is preferably formed from a composition containing a polyvinyl alcohol-based resin and a crosslinking agent from the viewpoint of adhesion. The material suitable for the primer layer is as described in the explanation of the configuration of the stretched film. In forming the primer layer, the coating method to be used is not particularly limited, and roll coating method such as wire bar coating method, reverse coating, gravure coating, die coating method, comma coating method, lip coating method, spin coating method. A screen coating method, a fountain coating method, a dipping method, a spray method, and the like can be appropriately selected from known methods and employed.

<Extension process (S20)>
Here, a laminated film composed of a base film and a resin layer is stretched to obtain a stretched film. Preferably, uniaxial stretching is performed so that the stretching ratio is more than 5 times and not more than 17 times. More preferably, it is uniaxially stretched so that the stretch ratio is more than 5 times and not more than 8 times. When the draw ratio is 5 times or less, the resin layer made of the polyvinyl alcohol-based resin is not sufficiently oriented. Therefore, when the polarizing laminated film or the polarizing plate is obtained, the degree of polarization of the polarizer layer obtained by dyeing the resin layer May not be high enough. On the other hand, if the draw ratio exceeds 17 times, the laminated film is likely to break during stretching, and at the same time, the thickness of the stretched film becomes unnecessarily thin, and the workability and handling properties in the subsequent process may be reduced. The stretching process in the stretching step (S20) is not limited to stretching in one stage, and can be performed in multiple stages. When performing in multiple stages, the stretching process is preferably performed so that the stretching ratio of all stages of the stretching process is preferably more than 5 times.

  In the stretching step (S20), a longitudinal stretching process performed in the longitudinal direction of the laminated film, a lateral stretching process stretching in the width direction, and the like can be performed. Examples of the longitudinal stretching method include an inter-roll stretching method and a compression stretching method, and examples of the transverse stretching method include a tenter method.

  In addition, as the stretching treatment, either a wet stretching method or a dry stretching method can be adopted, but the use of the dry stretching method is preferable because the temperature at which the laminated film is stretched can be selected from a wide range.

[Method for producing polarizing laminated film]
FIG. 2 is a flowchart showing an outline of the method for producing a polarizing laminated film of the present invention. The method for producing a polarizing laminated film of the present invention includes a resin layer forming step (S10) in which a resin layer made of a polyvinyl alcohol-based resin is formed on one surface of a base film to obtain a laminated film, and the laminated film is uniaxial. It has the extending process (S20) which stretches and obtains a stretched film, and the dyeing process (S30) which dyes the resin layer of a stretched film with a dichroic dye, and forms a polarizer layer.

  A polarizing laminated film provided with a base film and a polarizer layer having a thickness of 10 μm or less formed on one surface of the base film is obtained through the above steps. This polarizing laminated film can be used, for example, by bonding to another optical film or a liquid crystal cell via a pressure-sensitive adhesive, or used for the production of a polarizing plate described later.

  Hereinafter, each step will be described in detail. Since the resin layer forming step (S10) and the stretching step (S20) are the same steps as the method for producing the stretched film, the description thereof is omitted.

<Dyeing process (S20)>
Here, the resin layer of the stretched film is dyed with a dichroic dye. Examples of the dichroic dye include iodine and organic dyes. Examples of organic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc. can be used. One kind of these dichroic substances may be used, or two or more kinds may be used in combination.

  A dyeing process is performed by immersing the whole stretched film in the solution (dyeing solution) containing the said dichroic dye, for example. 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 is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight, and particularly preferably 0.025 to 5% by weight.

  When iodine is used as the dichroic dye, it is preferable to further add an iodide because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. The addition ratio of these iodides is preferably 0.01 to 20% by weight in the dyeing solution. 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. , Particularly preferably in the range of 1: 7 to 1:70.

  The immersion time of the stretched film in the dyeing solution is preferably in the range of 10 seconds to 5 minutes, and more preferably 30 seconds to 3 minutes. In the present invention, as described above, by using a stretched film having a resin layer made of a polyvinyl alcohol resin that satisfies the relationship of the formula (1) or the formula (2), the resin can be sufficiently used even in the above-described immersion time. The layer can be dyed. 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 the dyeing process, a crosslinking treatment can be performed after dyeing. The crosslinking treatment can be performed, for example, by immersing the stretched film in a solution containing a crosslinking agent (crosslinking solution). Conventionally known substances can be used as the crosslinking agent. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One kind of these may be used, or two or more kinds may be used in combination.

  As the crosslinking solution, a solution in which a crosslinking agent is dissolved in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further included. Although the density | concentration of the crosslinking agent in a crosslinking solution is not limited to this, It is preferable to exist in the range of 1-20 weight%, and it is more preferable that it is 6-15 weight%.

  Iodide may be added to the crosslinking solution. By adding iodide, the in-plane polarization characteristics of the resin layer can be made more uniform. Examples of the 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 iodide content is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

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

  Finally, it is preferable to perform a washing step and a drying step. As the washing step, a water washing treatment can be performed. The water washing treatment can usually be performed by immersing the stretched film in pure water such as ion exchange water or 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.

  In the washing step, washing treatment with an iodide solution and water washing treatment may be combined, and a solution in which liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, propanol or the like is appropriately blended may be used.

  It is preferable to perform a drying process after the washing process. Any appropriate method (for example, natural drying, ventilation drying, heat drying) can be adopted as the drying step. For example, the drying temperature in the case of heat drying is usually 20 to 95 ° C., and the drying time is usually about 1 to 15 minutes. Through the above dyeing step (S30), the resin layer has a function as a polarizer. In this specification, the resin layer which has a function as a polarizer is called a polarizer layer, and the laminated body provided with the polarizer layer on the base film is called a polarizing laminated film.

(Polarizer layer)
Specifically, the polarizer layer is obtained by adsorbing and orienting a dichroic dye on a resin layer made of a uniaxially stretched polyvinyl alcohol resin. As described above, the thickness of the polarizer layer (the thickness of the resin layer after stretching) is 10 μm or less, preferably 7 μm or less. By setting the thickness of the polarizer layer to 10 μm or less, a thin polarizing laminated film can be formed.

[Production method of polarizing plate]
FIG. 3 is a flowchart showing an outline of a method for producing a polarizing plate of the present invention. In the method for producing a polarizing plate of the present invention, a resin layer forming step (S10) in which a resin layer made of a polyvinyl alcohol resin is formed on one surface of a base film to obtain a laminated film, and the laminated film is uniaxially stretched. Thus, a stretching process (S20) for obtaining a stretched film and a dyeing process (S30) for dyeing the resin layer of the stretched film with a dichroic dye to form a polarizer layer are produced in this order to produce a polarizing laminated film. Then, a bonding step (S40) to obtain a multilayer film by bonding a protective film to the surface of the polarizer layer of the polarizing laminated film opposite to the surface on the base film side, and the base film from the multilayer film The peeling process (S50) which peels is provided in this order.

  Through the above steps, a polarizing plate comprising a protective film and a polarizer layer having a thickness of 10 μm or less formed on one surface of the protective film is obtained. This polarizing plate can be used, for example, by bonding to another optical film or a liquid crystal cell via a pressure-sensitive adhesive.

<Pasting step (S40)>
Here, a protective film is bonded to the surface opposite to the base film of the polarizer layer of the polarizing laminated film to obtain a multilayer film. As a method of bonding a protective film, the method of bonding a polarizer layer and a protective film with an adhesive layer, and the method of bonding a polarizer layer surface and a protective film with an adhesive layer are mentioned.

(Protective film)
The protective film may be a simple protective film having no optical function, or may be a protective film having an optical function such as a retardation film or a brightness enhancement film.

  The material of the protective film is not particularly limited, but for example, a cyclic polyolefin resin film, a cellulose acetate resin film made of a resin such as triacetyl cellulose or diacetyl cellulose, polyethylene terephthalate, polyethylene naphthalate, poly Examples of the film that have been widely used in the art include polyester-based resin films made of a resin such as butylene terephthalate, polycarbonate-based resin films, acrylic-based resin films, and polypropylene-based resin films.

  Examples of the cyclic polyolefin-based resin include appropriate commercial products such as Topas (registered trademark) (manufactured by Ticona), Arton (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (Nippon ZEON ( ZEONEX (registered trademark) (manufactured by Nippon Zeon Co., Ltd.), Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.) can be suitably used. When such a cyclic polyolefin resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. In addition, pre-filmed cyclic polyolefins such as Essina (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), Zeonoa (registered trademark) film (manufactured by Optes Co., Ltd.), etc. A commercial product of a film made of a resin may be used.

  The cyclic polyolefin resin film may be uniaxially stretched or biaxially stretched. An arbitrary retardation value can be imparted to the cyclic polyolefin-based resin film by stretching. Stretching is usually performed continuously while unwinding the film roll, and is stretched in the heating furnace in the roll traveling direction, the direction perpendicular to the traveling direction, or both. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the cyclic polyolefin resin to the glass transition temperature + 100 ° C. The draw ratio is usually 1.1 to 6 times, preferably 1.1 to 3.5 times in one direction.

  Examples of the cellulose acetate-based resin film include commercially available products such as Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), and Fujitac (registered trademark). TD80UZ (Fuji Film Co., Ltd.), Fujitac (registered trademark) TD40UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Opto Co., Ltd.), KC4UY (Konica Minolta Opto Co., Ltd.) are preferably used. be able to.

  A liquid crystal layer or the like may be formed on the surface of the cellulose acetate-based resin film in order to improve viewing angle characteristics. Moreover, in order to provide a phase difference, what stretched the cellulose acetate type-resin film may be used. The cellulose acetate-based resin film is usually subjected to a saponification treatment in order to improve the adhesion with the polarizer layer. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be employed.

  Optical layers such as a hard coat layer, an antiglare layer, and an antireflection layer can be formed on the surface of the protective film as described above. The method for forming these optical layers on the surface of the protective film is not particularly limited, and a known method can be used.

  The thickness of the protective film is preferably as thin as possible from the demand for thinning, is preferably 90 μm or less, and more preferably 50 μm or less. On the other hand, if it is too thin, the strength is lowered and the processability is inferior.

(Adhesive layer)
The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is usually a composition in which an acrylic resin, a styrene resin, a silicone resin or the like is used as a base polymer and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto Become. Furthermore, a pressure-sensitive adhesive layer exhibiting light scattering properties can be formed by mixing fine particles in the pressure-sensitive adhesive.

  The thickness of the pressure-sensitive adhesive layer is preferably 1 to 40 μm, but it is preferably applied thinly, and more preferably 3 to 25 μm, as long as the workability and durability characteristics are not impaired. When it is 3 to 25 μm, it has good processability and is also suitable for suppressing the dimensional change of the polarizing film. When the pressure-sensitive adhesive layer is less than 1 μm, the tackiness is lowered, and when it exceeds 40 μm, problems such as the pressure-sensitive adhesive protruding easily occur.

  The method of forming the pressure-sensitive adhesive layer on the polarizer layer or the protective film is not particularly limited, and a solution containing each component including the above-mentioned base polymer is applied on the polarizer layer or the protective film. After drying to form a pressure-sensitive adhesive layer, it may be bonded to a separator or other types of film, or after forming a pressure-sensitive adhesive layer on the separator, it is laminated on the surface of the polarizer layer or the protective film. May be. In addition, when forming the pressure-sensitive adhesive layer on the polarizer layer or the protective film, if necessary, the surface of the polarizer layer or the protective film, or one or both of the pressure-sensitive adhesive layers is subjected to an adhesion treatment, for example, a corona treatment. Also good.

(Adhesive layer)
Examples of the adhesive constituting the adhesive layer include a water-based adhesive using a polyvinyl alcohol-based resin aqueous solution, a water-based two-component urethane-based emulsion adhesive, and the like. Among these, a polyvinyl alcohol resin aqueous solution is preferably used. Polyvinyl alcohol resins used as adhesives include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as other single quantities copolymerizable with vinyl acetate. And vinyl alcohol copolymers obtained by saponifying the copolymer with the polymer, and modified polyvinyl alcohol polymers obtained by partially modifying the hydroxyl groups. A polyhydric aldehyde, a water-soluble epoxy compound, a melamine compound, a zirconia compound, a zinc compound, or the like may be added as an additive to the water-based adhesive. When such a water-based adhesive is used, the adhesive layer obtained therefrom is usually much thinner than 1 μm, and even when the cross section is observed with a normal optical microscope, the adhesive layer is practically not observed.

  The method of laminating the film using the water-based adhesive is not particularly limited, and the adhesive is uniformly applied or poured onto the surface of the polarizer layer or the protective film, and the other film is stacked on the coated surface. The method of bonding by a roll etc. and drying is mentioned. Usually, an adhesive agent is apply | coated at the temperature of 15-40 degreeC after the preparation, and the bonding temperature is the range of 15-30 degreeC normally.

  When using a water-system adhesive, after bonding a film, in order to remove the water contained in a water-system adhesive, it is made to dry. The temperature of the drying furnace is preferably 30 ° C to 90 ° C. If it is less than 30 ° C., the adhesive surface tends to be peeled off. If it is 90 ° C. or higher, the optical performance of the polarizer or the like may be deteriorated by heat. The drying time can be 10 to 1000 seconds.

  After drying, it may be further cured at room temperature or slightly higher temperature, for example, at a temperature of about 20 to 45 ° C. for about 12 to 600 hours. The temperature at the time of curing is generally set lower than the temperature adopted at the time of drying.

  Moreover, a photocurable adhesive can also be used as a non-aqueous adhesive. Examples of the photocurable adhesive include a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

  As a method of laminating a film with a photocurable adhesive, a conventionally known method can be used. For example, casting method, Mayer bar coating method, gravure coating method, comma coater method, doctor plate method, die coating method Examples of the method include applying an adhesive to the adhesive surface of the film by a dip coating method, a spraying method, and the like, and superimposing two films. The casting method is a method in which two films as an object to be coated are moved in a substantially vertical direction, generally in a horizontal direction, or in an oblique direction between the two, and an adhesive is allowed to flow down and spread on the surface. is there.

  After the adhesive is applied to the surface of the polarizer layer or the protective film, the polarizing laminate film and the protective film are sandwiched by a nip roll or the like and bonded together by bonding the films. Moreover, the method of pressing this laminated body with a roll etc. and spreading it uniformly can also be used suitably. In this case, a metal, rubber, or the like can be used as the material of the roll. Furthermore, a method in which this laminate is passed between rolls and pressed to spread is preferably employed. In this case, these rolls may be made of the same material or different materials. The thickness of the adhesive layer after being bonded using the nip roll or the like before drying or curing is preferably 5 μm or less and 0.01 μm or more.

  In order to improve the adhesiveness, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment or the like may be appropriately performed on the adhesion surface of the polarizer layer and the protective film. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

  When a photocurable resin is used as an adhesive, the photocurable adhesive is cured by irradiating active energy rays after laminating the films. The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, the low-pressure mercury lamp, the medium-pressure mercury lamp, the high-pressure mercury lamp, the ultrahigh-pressure mercury lamp, the chemical lamp, and the black light lamp A microwave excitation mercury lamp, a metal halide lamp and the like are preferably used.

The light irradiation intensity to the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 6000 mW / it is preferable that the cm ^2. When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when it is 6000 mW / cm ² or less, the epoxy is generated by the heat radiated from the light source and the heat generated when the photo-curable adhesive is cured. There is little risk of yellowing of the resin or deterioration of the polarizing film. The light irradiation time to the photocurable adhesive is not particularly limited and is applied according to the photocurable adhesive to be cured, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time. Is preferably set to be 10 to 10,000 mJ / cm ² . When the cumulative amount of light to the photocurable adhesive is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to allow the curing reaction to proceed more reliably, and at 10,000 mJ / cm ² or less. In some cases, irradiation time does not become too long and good productivity can be maintained. The thickness of the adhesive layer after irradiation with active energy rays is usually about 0.001 to 5 μm, preferably 0.01 μm or more and 2 μm or less, more preferably 0.01 μm or more and 1 μm or less. .

  When curing a photocurable adhesive on a polarizer layer or a protective film by irradiation with active energy rays, the various functions of the polarizing plate after passing through all steps, such as transmittance, hue, and transparency of these films, do not deteriorate. It is preferable to perform curing under conditions.

<Peeling step (S50)>
In the manufacturing method of the polarizing plate of this invention, as shown in FIG. 3, the peeling process (S50) of a base film is performed after the bonding process (S40) which bonds a protective film to a polarizer layer. In the base film peeling step (S50), the base film is peeled from the multilayer film. The peeling method of a base film is not specifically limited, It can peel by the method similar to the peeling process of the peeling film performed with a normal polarizing plate with an adhesive. After the protective film laminating step (S40), the protective film may be peeled off as it is, or once wound up in a roll shape, a separate peeling step may be provided and peeled off.

(Other optical layers)
In practical use, the polarizing plate can be used as a polarizing plate in which other optical layers are laminated. Moreover, the said protective film may have a function of these optical layers.

  Examples of other optical layers include a reflective polarizing film that transmits certain types of polarized light and reflects polarized light that exhibits the opposite properties, a film with an antiglare function having an uneven shape on the surface, and a surface antireflection function. Examples thereof include an attached film, a reflective film having a reflection function on the surface, a transflective film having both a reflection function and a transmission function, and a viewing angle compensation film.

  Commercially available products corresponding to reflective polarizing films that transmit certain types of polarized light and reflect polarized light that exhibits the opposite properties include DBEF (available from 3M, Sumitomo 3M Co., Ltd.), APF (Available from 3M, available from Sumitomo 3M Limited). Examples of the viewing angle compensation film include an optical compensation film coated with a liquid crystal compound on the surface of the substrate and oriented, a retardation film made of a polycarbonate resin, and a retardation film made of a cyclic polyolefin resin. Commercially available products corresponding to an optical compensation film coated with a liquid crystal compound on the substrate surface and oriented are WV film (Fuji Film Co., Ltd.), NH film (Shin Nippon Oil Co., Ltd.), NR Examples include films (manufactured by Nippon Oil Corporation). Commercial products corresponding to retardation films made of cyclic polyolefin resins include Arton (registered trademark) film (manufactured by JSR Corporation), Essina (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), Zeonor ( Registered trademark) film (manufactured by Optes Co., Ltd.).

(Double-sided resin layer laminated film)
The production method of the stretched film, the polarizing laminate film and the polarizing plate according to the present invention is not limited to the case where the formation of the resin layer in the resin layer forming step (S10) is formed on one surface of the base film. The case where it is formed on both surfaces of the base film is also included.

  When the resin layers are formed on both surfaces, in the method for producing a polarizing plate, two polarizing plates are formed through the steps S10 to S50. In this case, a multilayer film composed of the first protective film / first polarizer layer / base film / second polarizer layer / second protective film is obtained through the bonding step (S40).

  When the resin layers are formed on both surfaces of the base film, the peeling step (S50) of peeling the base film from the multilayer film to obtain a polarizing plate is the same as the first polarizer layer and the base film. A laminate composed of a base film / second polarizer layer / second protective film which is separated from the first peeling step for separation from the material film by peeling, and a base film and a second polarizer layer And a second peeling step of separating by peeling. A first polarizing plate is formed by the first peeling step, and a second polarizing plate is formed by the second peeling step.

[Production of Polarizing Plate of Example 1]
<Preparation of base film>
A propylene / ethylene random copolymer containing 5% by weight of ethylene units (“Sumitomo Noblene W151”; Tm = 138 ° C.) on both sides is a homopropylene homopolymer of propylene (“Sumitomo Nobrene FLX80E4”; Tm = 163 ° C. ) Was prepared with a multilayer extruder to obtain a base film. The thickness ratio of each layer was 3/4/3. The total thickness of the base film was 90 μm.

<Formation of primer layer>
Polyvinyl alcohol powder (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, saponification degree 99.5 mol%, trade name: Z-200) is dissolved in 95 ° C. hot water to give an aqueous solution having a concentration of 3% by weight. It was adjusted. The resulting aqueous solution was mixed with 5 parts by weight of a crosslinking agent (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumirez (registered trademark) resin 650) with respect to 6 parts by weight of polyvinyl alcohol powder. The obtained mixed aqueous solution was applied on a corona-treated substrate film using a microgravure coater and dried at 80 ° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm.

<Resin layer forming step (S10)>
Using polyvinyl alcohol powder, JM-33 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 3300, saponification degree 93.5-95.5 mol%) was dissolved in 95 ° C. hot water. A polyvinyl alcohol aqueous solution having a concentration of 8% by weight was prepared. The obtained aqueous solution was coated on the primer layer using a lip coater, and continuously dried at 80 ° C. for 2 minutes, 70 ° C. for 2 minutes, and 60 ° C. for 4 minutes. A three-layer laminated film composed of a resin layer was prepared.

<Extension process (S20)>
The laminated film was uniaxially stretched 5.8 times at a stretching temperature of 160 ° C. to obtain a stretched film. The thickness of the resin layer of the obtained stretched film was 4.1 μm.

<Dyeing process (S30)>
Then, after dipping in a dyeing solution which is a mixed aqueous solution of iodine and potassium iodide at 30 ° C. (iodine concentration 0.6% by weight, potassium iodide concentration 10% by weight), extra water is added with 10 ° C. pure water. The iodine solution was washed away. Subsequently, it was immersed in the bridge | crosslinking solution which is a 76 degreeC mixed aqueous solution of boric acid and potassium iodide. Thereafter, it was washed with pure water at 10 ° C. for 4 seconds, and finally dried at 80 ° C. for 300 seconds. The polarizer layer was formed from the resin layer by the above process, and the light-polarizing laminated film was obtained.

<Pasting step (S40)>
Polyvinyl alcohol powder (manufactured by Kuraray Co., Ltd., average polymerization degree 1800, trade name: KL-318) was dissolved in 95 ° C. hot water to prepare an aqueous solution having a concentration of 3% by weight. The resulting aqueous solution was mixed with 1 part by weight of a crosslinking agent (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumirez (registered trademark) Resin 650) with respect to 2 parts by weight of polyvinyl alcohol powder to obtain an adhesive solution. After applying this polyvinyl alcohol-based adhesive to the polarizer layer of the polarizing laminate film, a protective film (TAC: KC4UY manufactured by Konica Minolta Opto Co., Ltd.) is bonded, and the protective film / adhesive layer / polarizer layer / A multilayer film consisting of a primer layer / base film was obtained.

<Peeling step (S50)>
The base film was peeled from the multilayer film to obtain a polarizing plate comprising a protective film / adhesive layer / polarizer layer / primer layer. The substrate film was easily peeled from the multilayer film.

<Measurement of polarization performance>
The polarizing plate obtained as described above was attached to a glass plate via a pressure-sensitive adhesive, and after autoclaving at 50 ° C. and 5 kg / cm ² (490.3 kPa) for 20 minutes, the optical characteristics were integrated into an integrating sphere. It was measured with an attached spectrophotometer (manufactured by JASCO Corporation, V7100). MD transmittance and TD transmittance are obtained in the wavelength range of 380 nm to 780 nm, and the single transmittance and polarization degree at each wavelength are calculated based on the following formulas (3) and (4). Further, according to JIS Z 8701 Visibility correction was performed with the field of view twice (C light source), and the visibility correction single transmittance (Ty) and the visibility correction polarization degree (Py) were obtained. In addition, the measurement of the polarizing plate was set in the apparatus so that the protective film side was the detector side and light was incident from the primer layer side.

Single transmittance (%) = (MD + TD) / 2 Formula (3)
Degree of polarization (%) = √ {(MD-TD) / (MD + TD)} × 100 (4)
The “MD transmittance” is a 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 is expressed as “MD” in the equations (3) and (4). . The “TD transmittance” is the transmittance when the direction of polarized light emitted from the Glan-Thompson prism and the polarizing plate sample are orthogonal to the transmission axis. In the formulas (3) and (4), “TD”. It expresses.

  In the dyeing step (S30), various immersion times in the dyeing solution were tested. In order to obtain a polarizing plate having a visibility corrected single transmittance (Ty) of 40.5% and a visibility corrected polarization degree (Py) of 99.99% or more, the time required for immersion in the dyeing solution was 26 seconds. It was.

[Production of Polarizing Plate of Example 2]
Example 1 except that the polyvinyl alcohol powder used in forming the resin layer is JM-26 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 2600, saponification degree 95.5-97.5 mol%). A polarizing plate was prepared by the same method. The thickness of the resin layer of the obtained stretched film was 4.7 μm.

  In order to obtain a polarizing plate having a visibility corrected single transmittance (Ty) of 40.5% and a visibility corrected polarization degree (Py) of 99.99% or more, the time required for immersion in the dyeing solution was 62 seconds. .

[Production of Polarizing Plate of Comparative Example 1]
A polarizing plate was prepared in the same manner as in Example 1 except that the polyvinyl alcohol powder used for forming the resin layer was PVA624 (manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree 95 to 96 mol%). . The thickness of the resin layer of the obtained stretched film was 4.4 μm. In the dyeing process, the resin layer was dissolved before being dyed, and a polarizing plate could not be produced.

[Production of Polarizing Plate of Comparative Example 2]
A polarizing plate was prepared in the same manner as in Example 1 except that the polyvinyl alcohol powder used for forming the resin layer was PVA124 (manufactured by Kuraray Co., Ltd., average polymerization degree 2400, saponification degree 98 to 99 mol%). . The thickness of the resin layer of the obtained stretched film was 5.4 μm. In order to obtain a polarizing plate having a visibility corrected single transmittance (Ty) of 40.5% and a visibility corrected polarization degree (Py) of 99.99% or more, the time required for immersion in the dyeing solution was 330 seconds. .

  The results are shown in Table 1. In Table 1, the kind of polyvinyl alcohol used at the time of forming the resin layer of each Example and Comparative Example, the visibility corrected single transmittance (Ty) of 40.5%, and the visibility corrected polarization degree (Py) of 99.99% In order to obtain the above polarizing plate, the time required for immersion in the dyeing solution and the evaluation results of water resistance are shown. The water resistance was evaluated as “Yes” when dissolution of the resin layer was not observed during the immersion in the dyeing step, and “None” when dissolution of the resin layer was observed within this time.

  FIG. 4 is a plot of the results shown in Table 1. In FIG. 4, the central value of the saponification degree of PVA used for forming the resin layer is shown on the horizontal axis, and the average polymerization degree is shown on the vertical axis. In FIG. 4, the range A that satisfies the formula (1) or the formula (2) is shown in white, and the ranges B1 and B2 that do not satisfy the formula (1) and the formula (2) are indicated by hatching.

  As shown in FIG. 4, when included in the range A satisfying the formula (1) or the formula (2) (Examples 1 and 2), in the dyeing process, the dye solution required for obtaining the desired polarization performance is obtained. The immersion time is short and the water resistance is excellent. When it is included in the range B1 that does not satisfy the formula (1) and does not satisfy the formula (2) in terms of the average degree of polymerization (Comparative Example 1), the water resistance is not sufficient, and the resin layer becomes a dyeing solution in the dyeing step. Easy to dissolve. In the case of being included in the range B2 that does not satisfy both the formula (1) and the formula (2) in terms of the degree of saponification (Comparative Example 2), the dyeing solution required for obtaining the desired polarization performance in the dyeing step The soaking time becomes longer.

  Regarding the polarizing performance of the polarizing laminated film and the polarizing plate, the visibility corrected single transmittance (Ty) is preferably 40% or more, and the visibility corrected polarization degree (Py) is preferably 99.9% or more. .

Claims (5)

A base film and a resin layer having a thickness of 10 μm or less formed on one surface of the base film;
The resin layer is a stretched film made of a polyvinyl alcohol-based resin having a saponification degree (mol%) and an average polymerization degree that satisfy the relationship of the following formula (1) or formula (2).
96 mol% <degree of saponification ≦ 98 mol% (1)
93 mol% ≦ degree of saponification ≦ 96 mol% and average degree of polymerization ≧ 2500 (2)   The stretched film according to claim 1, wherein the resin layer is uniaxially stretched at a stretch ratio of more than 5 times. It is a manufacturing method of the stretched film of Claim 1 or 2, Comprising:
On one surface of the base film, a resin layer made of a polyvinyl alcohol-based resin having a saponification degree (mol%) and an average polymerization degree satisfying the relationship of the following formula (1) or formula (2) is formed and laminated: A resin layer forming step of obtaining a film;
And a stretching process for obtaining a stretched film by uniaxially stretching the laminated film.
96 mol% <degree of saponification ≦ 98 mol% (1)
93 mol% ≦ degree of saponification ≦ 96 mol% and average degree of polymerization ≧ 2500 (2) A method for producing a polarizing laminate film comprising a base film and a polarizer layer having a thickness of 10 μm or less formed on one surface of the base film,
After producing a stretched film by the production method according to claim 3,
The manufacturing method of a light-polarizing laminated film which has a dyeing process of dyeing the resin layer of the stretched film with a dichroic dye to form a polarizer layer. A method for producing a polarizing plate comprising a protective film and a polarizer layer having a thickness of 10 μm or less formed on one surface of the protective film,
After manufacturing a polarizing laminated film by the manufacturing method according to claim 4,
A laminating step of laminating a protective film on a surface opposite to the surface on the base film side of the polarizer layer in the polarizing laminated film to obtain a multilayer film;
A peeling step of peeling the base film from the multilayer film.

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