JP2013186399A - Method for producing polarizing laminate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method capable of producing a stable and excellent polarizing laminate film without causing fracture or the like of a film at the time of stretching in a width direction.SOLUTION: There is provided a method for producing a polarizing laminate film which comprises a lateral stretching process and a dyeing process. The lateral stretching process is a step where both end parts in the width direction of a running laminate film is held by a plurality of clips arranged in the running direction, and in the stretching zone, the laminate film in the width direction is stretched by spreading the clip interval in the width direction while driving the clips together with the laminate film and the laminate film in the running direction is shrunk by narrowing the clip interval in the running direction, wherein the clip interval in the running direction at the time of entering the stretching zone is 50 to 100 mm, the clip interval in the running direction at the time of leaving the stretching zone is 50 mm or less and the width of each clip is 40 mm or less.

Description

  The present invention relates to a method for producing a polarizing laminated film and a method for stretching the laminated film.

  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 for obtaining a polarizing laminated film having a polarizer layer by dyeing, crosslinking (fixing), drying, and forming a polarizer layer from a resin layer. 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.

  In the process of stretching the laminated film, by stretching the film in one direction and contracting the direction perpendicular thereto, an original film having a high degree of orientation that is generally uniaxially oriented, that is, a polarizing film having a high degree of polarization is obtained. Such stretching is by free end longitudinal stretching. However, when the free end longitudinal uniaxial stretching is carried out, the width direction may be naturally necked in, so that the width of the original fabric may be significantly narrowed. On the other hand, such a problem can be avoided by the transverse stretching that extends in the width direction. Patent Documents 1 and 2 describe a method of manufacturing a polarizing film that performs transverse stretching that extends in the width direction.

JP 2003-43257 A JP 2009-300768 A

  Patent Documents 1 and 2 describe a method of stretching a film in the width direction using a tenter. The tenter is an apparatus that stretches the film by holding both ends of the polarizing film in the width direction with clips and widening the clip interval in the width direction while running the clips together with the film. When a tenter is used, the clip interval in the running direction is initially widened and narrowed during transverse stretching, whereby the film can be stretched in the width direction and the film can be contracted in the running direction. However, for a laminated film in which a base film and a polyvinyl alcohol-based resin layer are laminated, for example, when the stretching ratio in the width direction is set to 4 times or more, a large neck-in occurs between the clips in the running direction, and the clips are gripped by the clips. A long ear-shaped overstretched portion was formed at the end of the film, and when the draw ratio was further increased, the film could break at the ear-shaped overstretched portion.

  The present invention has been made in view of the above-described problems, and a production method and a laminated film that can stably produce a good polarizing laminated film without causing breakage of the film during stretching in the width direction. It aims at providing the extending | stretching method of this.

  As a result of intensive studies, the present inventors have found that there is a relationship between the occurrence of the overstretched portion at the end of the film at the time of stretching and the clip interval in the running direction before stretching, leading to the present invention.

  The present invention includes a lateral stretching step of stretching a laminated film in which a base film and a polyvinyl alcohol resin layer having a thickness of 3 μm or more are laminated in the width direction, and a polyvinyl alcohol resin layer of the drawn laminated film. And a dyeing step of forming a polarizing laminated film by dyeing with a chromatic dye. In the transverse stretching step, the both ends of the traveling laminated film in the width direction are gripped by a plurality of clips arranged in the traveling direction, and in the stretching zone, the clip interval in the width direction is increased while the clips are traveling together with the laminated film. Is a step of stretching the laminated film in the width direction and shrinking the laminated film in the running direction by narrowing the clip interval in the running direction. The clip interval in the running direction when entering the stretching zone is 50 to 100 mm, the clip interval in the running direction when leaving the stretching zone is 50 mm or less, and the width of each clip is 40 mm or less. Note that the clip interval in this specification is the distance between the centers of the clips, and the width of the clip is the length of the longest piece in the running direction of the clip.

  In the present invention described above, the clip interval in the running direction when leaving the stretching zone is preferably 50% or less of the clip interval in the running direction when entering the stretching zone.

  In the above-described present invention, the stretching ratio in the transverse stretching step is preferably 4 times or more, and the thickness of the polyvinyl alcohol resin layer of the stretched laminated film is preferably 10 μm or less.

  Moreover, this invention is the extending | stretching method of the laminated | multilayer film including the horizontal stretch process of extending | stretching the laminated | multilayer film by which the base film and the polyvinyl alcohol-type resin layer whose thickness is 3 micrometers or more were laminated | stacked in the width direction. In the transverse stretching step, the both ends of the traveling laminated film in the width direction are gripped by a plurality of clips arranged in the traveling direction, and in the stretching zone, the clip interval in the width direction is increased while the clips are traveling together with the laminated film. Is a step of stretching the laminated film in the width direction and shrinking the laminated film in the running direction by narrowing the clip interval in the running direction. The clip interval in the running direction when entering the stretching zone is 50 to 100 mm, the clip interval in the running direction when leaving the stretching zone is 50 mm or less, and the width of each clip is 40 mm or less.

  According to this invention, the manufacturing method of the light-polarizing laminated film which can be extended | stretched to the width direction and shrink | contracted to a running direction stably without breaking a laminated film is provided.

It is a figure which shows typically the apparatus used suitably for the manufacturing method of the light-polarizing laminated film of this invention. It is a figure explaining the mechanism in which a fracture | rupture arises in a laminated film in an extending process. It is a top view which shows typically an example of the internal structure of the tenter used for the manufacturing method of this invention. It is a figure which shows typically the structure of the clip of a tenter. It is a figure explaining the calculation method of the ratio of the ear-like overstretched part of the laminated | multilayer film extended | stretched.

  The manufacturing method of the light-polarizing laminated film of the present invention includes a transverse stretching step of stretching a laminated film in which a base film and a polyvinyl alcohol-based resin layer having a thickness of 3 μm or more are laminated in a width direction, and a drawn laminated film. And a dyeing step of dyeing the polyvinyl alcohol-based resin layer with a dichroic dye to form a polarizing laminated film.

  FIG. 1 is a diagram schematically showing an apparatus suitably used in the method for producing a polarizing laminated film of the present invention. In the example shown in FIG. 1, the laminated film 1 fed out from the raw fabric roll 2 sequentially passes through a transverse stretching process unit 10 for performing a transverse stretching process and a dyeing tank 20 for performing a staining process, so that a polarizing laminate is obtained. It is comprised so that the film 3 may be obtained. Although not shown in FIG. 1, the laminated film may be once taken out after the transverse stretching process unit 10, and then the laminated film may be passed through the dyeing tank 20. In the stretching device 10, both end portions in the width direction of the traveling laminated film 1 are gripped by a plurality of clips arranged in the traveling direction, and the clip interval in the width direction is widened while the clips are traveling together with the laminated film in the stretching zone. Thus, a stretching process for stretching the laminated film 1 in the width direction and shrinking the laminated film 1 in the running direction by narrowing the clip interval in the running direction is performed.

  In addition, in FIG. 1, although the swelling tank for performing a swelling process, the crosslinking tank for performing a crosslinking process, and the drying furnace for performing a drying process are not shown, these can be provided suitably as needed. .

[Laminated film]
In the production method of the present invention, a laminated film in which a base film and a polyvinyl alcohol resin layer having a thickness of 3 μm or more are laminated is used.

(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 appropriate resins according to their glass transition temperature Tg or melting point Tm. Can be selected. It is preferable to use a base film that can be stretched in a temperature range suitable for stretching a polyvinyl alcohol-based resin layer laminated thereon.

  Specific examples of thermoplastic resins include chain polyolefin resins, polyester resins, cyclic polyolefin resins (norbornene resins), (meth) acrylic resins, cellulose ester resins, polycarbonate resins, polyvinyl alcohol resins, Examples thereof include vinyl acetate resins, polyarylate resins, polystyrene resins, polyethersulfone resins, polysulfone resins, polyamide resins, polyimide resins, 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) according to the method described on page 616 of “Polymer Analysis Handbook” (1995, published by Kinokuniya Shoten). It can be obtained by performing a spectrum measurement.

  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.

  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, most preferably 5 to 150 μm.

  The base film is subjected to corona treatment, plasma treatment, flame treatment, etc. on at least the surface on which the polyvinyl alcohol resin layer is formed in order to improve adhesion with the resin layer made of polyvinyl alcohol resin. Also good. Moreover, in order to improve adhesiveness, you may form thin layers, such as a primer layer, in the surface at the side by which the polyvinyl alcohol-type resin layer 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, and when the thickness is more than 1 μm, the polarizing plate becomes thick.

  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.

(Polyvinyl alcohol resin layer)
As the polyvinyl alcohol resin used in the polyvinyl alcohol 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.

  The polyvinyl alcohol resin is preferably a completely saponified product. The range of the saponification degree is preferably 80.0 mol% to 100.0 mol%, more preferably 90.0 mol% to 99.5 mol%, and further 94.0 mol%. Most preferred is a range of ˜99.0 mol%. If the degree of saponification is less than 80.0 mol%, there is a problem that the water resistance and heat-and-moisture resistance after forming the polarizer layer are remarkably inferior.

  The “degree of saponification” in the present specification is the unit ratio (mol%) of the ratio of the acetate group contained in the polyvinyl acetate resin, which is the raw material of the polyvinyl alcohol resin, to the hydroxyl group by the saponification step. Yes, it is a numerical value defined by the following formula. It can be determined by the method defined in JIS K 6726 (1994).

Degree of saponification (mol%) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100
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, resulting in a problem that the polarization performance is lowered.

  The average degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but is preferably 100 to 10,000, more preferably 1500 to 8000, and most preferably 2000 to 5000. The average degree of polymerization here is also a numerical value determined by a method defined by JIS K 6726 (1994).

  Examples of the polyvinyl alcohol resin having such characteristics include PVA124 (degree of saponification: 98.0 to 99.0 mol%) and PVA117 (degree of saponification: 98.0 to 99.0 mol%) manufactured by Kuraray Co., Ltd. ), PVA624 (degree of saponification: 95.0 to 96.0 mol%) and PVA617 (degree of saponification: 94.5 to 95.5 mol%); for example, AH-26 (degree of saponification) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. : 97.0-98.8 mol%), AH-22 (degree of saponification: 97.5-98.5 mol%), NH-18 (degree of saponification: 98.0-99.0 mol%), and N -300 (degree of saponification: 98.0 to 99.0 mol%); for example, JC-33 (degree of saponification: 99.0 mol% or more), JM-33 (degree of saponification: 93) of Nippon Vinegar Poval Co., Ltd. .5-95.5 mol%), JM 26 (degree of saponification: 95.5-97.5 mol%), JP-45 (degree of saponification: 86.5-89.5 mol%), JF-17 (degree of saponification: 98.0-99.0 mol%) ), JF-17L (degree of saponification: 98.0 to 99.0 mol%), JF-20 (degree of saponification: 98.0 to 99.0 mol%), and the like. It can use suitably in formation of an alcohol-type resin film.

  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.

  The thickness of the polyvinyl alcohol-based resin layer is 3 μm or more. When the thickness of the polyvinyl alcohol-based resin layer is 3 μm or more, the stress during stretching of the resin layer on the base material becomes large. Therefore, when an ear-shaped overstretched portion is formed at the grip portion of the clip during stretching, The stress of the resin layer concentrates on the ear-like overstretched portion and breaks easily.

  FIG. 2 is a diagram for explaining a mechanism in which a laminated film breaks in a stretching process. As shown in FIG. 2, the laminated film 1 is gripped by a plurality of clips 11 at both ends in a stretching process and stretched in the width direction. At this time, necking 1a is generated between the clips depending on the interval in the traveling direction of the clip, and the ear-like overstretched portion 1b is formed in the portion gripped by the clip. The stress of the polyvinyl alcohol-based resin layer caused by stretching is likely to occur in the ear-shaped overstretched portion 1b. Therefore, if the stress applied to the ear-shaped overstretched portion 1b exceeds a certain limit, the ear-shaped overstretched portion 1b breaks. It is thought to occur.

  Since the production method of the present invention has an effect of making it difficult to break during stretching, it is suitable when the thickness of the polyvinyl alcohol-based resin layer that is easily broken by the conventional method is 3 μm or more. Moreover, if the thickness of the polyvinyl alcohol-based resin layer is less than 3 μm, it becomes too thin after stretching and the dyeability is remarkably deteriorated. The thickness of the polyvinyl alcohol-based resin layer is preferably 3 to 30 μm, more preferably 5 to 20 μm. If it exceeds 30 μm, the thickness of the finally obtained polarizer 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. 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, the resin layer may be formed only on one surface of the base film, or may be formed on both surfaces.

(Horizontal stretching process)
The transverse stretching process in the present invention is performed, for example, in the transverse stretching process section 10 shown in FIG. In the transverse stretching process section 10, a tenter can be used. The tenter used in the present invention grips both ends of the traveling laminated film in the width direction with a plurality of clips arranged in the running direction, and sets the clip interval in the width direction while running the clip with the laminated film in the stretching zone. The laminated film is stretched in the width direction by spreading, and the laminated film is contracted in the running direction by narrowing the clip interval in the running direction.

  The stretching in the width direction and the contraction in the traveling direction are preferably performed simultaneously, but the stretching in the width direction and the contraction in the traveling direction are not necessarily performed at the same time. For example, the entire stretching zone may be stretched in the width direction, and only a part of the stretching zone may be contracted in the traveling direction, or the entire stretching zone may be contracted in the traveling direction. You may make it extend | stretch in the width direction only in the one part area inside. When the stretching in the width direction and the shrinkage in the running direction are performed at different timings, these treatments do not take time in order to suitably shrink the crystalline polymer such as polyvinyl alcohol in the running direction. It is preferable to continue.

In tenter used in the production method of the present invention, when the clip spacing in the running direction at the time of entering the stretching zone and _{G 1,} gap _{G 1} is 50 to 100 mm, preferably 50～85Mm, at the time of leaving the stretching zone When the clip spacing in the running direction and _{G 2,} gap _{G 2} is less than 50mm, preferably 45mm or less. A polarizing laminated film having a polarizer layer that can shrink the laminated film in the running direction by narrowing the clip interval in the running direction in the stretching zone, has a polarization degree that is sufficiently high and has excellent polarization performance. Can be created. Further, it is preferable that the interval _{G 2} is less than 50% of the distance _{G 1.} Further, the width (length in the running direction) of each clip is 40 mm or less, preferably 30 mm or less. The state in which the clips adjacent to each other in the traveling direction are in contact with each other is the lower limit value of the clip interval in the traveling direction, and therefore the lower limit value corresponds to the width of the clip (length in the traveling direction). For example, if the width of the clip is 30mm, in the manufacturing method of the present invention, the clip spacing _{G 2} in the running direction at the time of leaving the stretching zone is 30mm or more 50mm or less.

When the clip gap G ₁ in the running direction at the time of entering the stretching zone is more than 100 mm, the percentage of ears of the over-extending portion which is formed when subjected to stretching in the width direction in the stretching zone is increased, in the width direction During stretching, the ear-shaped overstretched portion does not stretch and the draw ratio does not increase, or stress concentrates on the ear-shaped overstretched portion and breaks at the ear-shaped overstretched portion when trying to stretch at a high magnification. The problem occurs. In particular, such a problem tends to occur when the stretching ratio in the width direction is set to 4 times or more. Also, if the clip gap G ₁ in the running direction at the time of entering the stretching zone is less than 50 mm, since the clip spacing G ₂ in the running direction at the time of exiting from the stretching zone can not be narrowed only to the width of the clip, in the stretching zone Even if the clip interval in the traveling direction is narrowed to the maximum, it is difficult to sufficiently shrink the laminated film in the traveling direction. In particular, it becomes difficult to perform sufficient shrinkage in the traveling direction exceeding 50%. Similarly, when the width of the clip exceeds 30 mm, it is difficult to sufficiently shrink the laminated film in the traveling direction. If the shrinkage in the running direction is not sufficient, the polarization degree of the polarizer layer may not be sufficiently high.

  The interval between the clips in the running direction outside the stretching zone may be adjusted as appropriate. For example, the clip interval may be set to a convenient distance for conveyance before or after the laminated film is gripped. Moreover, you may adjust the space | interval of a clip intentionally for the wrinkle removal and tension | tensile_strength of a laminated | multilayer film in the zone before and after an extending | stretching zone.

  In the transverse stretching step of the present invention, the laminated film is preferably stretched in the width direction so as to have a stretching ratio of 4 to 17 times. More preferably, the film is stretched in the width direction so that the stretching ratio is more than 5 times and not more than 8 times. When the draw ratio is less than 4, the polyvinyl alcohol-based resin layer is not sufficiently oriented, and as a result, the degree of polarization of the polarizer layer may not be sufficiently high. 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 steps may be reduced. The stretching process in the transverse stretching process is not limited to stretching in one stage, and can be performed in multiple stages. The stretching process may be performed simultaneously with, for example, a dyeing process or a crosslinking process. In this case, the stretching in the dyeing process is preferably an auxiliary performed at a low magnification, and the contraction in the running direction may not be performed. When performing in multiple stages, the stretching process is preferably performed so that the stretching ratio is preferably 4 times or more for all stages of the stretching process.

The stretching ratio in the width direction usually means the ratio of the length in the width direction of the laminated film after stretching to the length in the width direction of the laminated film before stretching. Accordingly, in a tenter used in the transverse stretching step also can be calculated from the clip spacing D ₂ Metropolitan the width direction at the time of leaving the clip distance D ₁ of the widthwise direction at the time of entering the stretching zone from the stretching zone, in the present invention Is defined as D ₂ / D ₁ in the stretching zone in the width direction. In addition, the length of the width direction before extending | stretching of the laminated | multilayer film used by this invention is 100-1000 mm, for example.

  The temperature in the stretching zone needs to be a temperature at which the base film can be stretched, and may be appropriately selected from the range of 80 to 180 ° C. In order to reduce the stress during stretching of the polyvinyl alcohol-based resin, Carry out at 120 ° C or higher. If the temperature in the stretching zone is too low, the stress during stretching of the polyvinyl alcohol resin becomes too strong and the laminated film tends to break. Conversely, if the stretching temperature is too high, the polyvinyl alcohol resin is dehydrated and yellowed. It is easy to cause trouble to do. Of course, a plurality of different temperatures may be set in the stretching zone. In the stretching zone, for example, hot air is supplied to the laminated film from above or below, or both, and can be managed at a predetermined temperature.

  Furthermore, a preheating zone may be provided upstream from the stretching zone, and a heat fixing zone and a thermal relaxation zone may be sequentially provided downstream from the stretching zone. A preheating zone is a zone which preheats a laminated film, and heats a laminated film, without extending the space | interval of a clip. The laminated film preheated in the preheating zone moves to the stretching zone. The stretching zone is a zone in which the laminated film is stretched in the width direction by widening the interval between the clips as described above. In the present invention, shrinkage in the running direction of the laminated film is also performed in the stretching zone. The laminated film stretched in the stretching zone moves to the heat setting zone. The heat setting zone is a zone in which heat treatment is performed at a temperature equal to or higher than the crystallization temperature while maintaining the tensioned state with the end of the laminated film held by the clip. By heat treatment in this heat setting zone, crystallization of the polyvinyl alcohol-based resin layer is promoted. The laminated film heat-treated in the heat setting zone moves to the heat relaxation zone. The thermal relaxation zone is a step of heat-treating the laminated film in a relaxed state, and residual stress and distortion components inside the laminated film are removed by the thermal relaxation zone. The temperature in each zone can be appropriately selected according to the characteristics of the base film and the material of the polyvinyl alcohol resin layer. Hereinafter, preferred tenters used in the production method of the present invention will be described in detail with reference to the drawings.

  FIG. 3 is a plan view schematically showing an example of the internal configuration of the tenter used in the manufacturing method of the present invention. As shown in FIG. 3, the tenter includes a large number of clips 11 that hold both ends of the laminated film 1 in the width direction, and the clips 11 are attached to the endless chain 12 at a predetermined interval. The endless chain 12 is disposed on both sides of the laminated film 1, and each is spanned between a driving sprocket 13 on the inlet side and a driven sprocket 14 on the outlet side. The driving sprocket 13 is connected to a motor (not shown), and the driving sprocket 13 is rotated by driving the motor. Thereby, since the endless chain 12 travels between the driving sprocket 13 and the driven sprocket 14, the clip 11 attached to the endless chain 12 travels around.

The travel path of the endless chain 12 is configured such that the clip interval in the width direction gradually increases in the extending zone, and the clip 11 at the time of exiting the extending zone from the width D ₁ of the clip 11 at the time of entering the extending zone. spacing D ₂ width direction of the is configured to be wider.

The tenter further includes a position adjusting mechanism (not shown) that adjusts the distance between the clips 11 attached on the endless chain 12, that is, the distance between the clips 11 in the traveling direction to a desired distance. gradually reduce the width of the clip 11 in, and in the running path A2 between the driven sprocket 14 and the drive sprocket 13 is adjusted so that the distance G ₁ clip 11 at the time of entering the stretching zone has a desired value . Thereby controlling so that the distance G ₂ time points of the clip 11 leaving the the stretching zone spacing G ₁ in the running direction of the clip 11 at the time of entering the stretching zone becomes a desired distance. In the production method of the present invention, the spacing _{G 1} of the clip is controlled to be 50～85Mm, spacing _{G 2} of the clip is controlled to be 45mm or less. Further, it is preferable that the interval _{G 2} is less than 50% of the distance _{G 1.}

  4A and 4B are diagrams schematically showing the configuration of the clip 11, where FIG. 4A shows a view of the clip 11 viewed from above, and FIG. 4B shows a cross-sectional view of the clip 11. As shown in FIG. 4, the clip 11 includes a frame 111, a lever 113, and a flapper 112. The frame 111 is formed in a U shape, and the lower base is a film mounting base. A lever 113 is rotatably attached to the upper base of the frame 111, and a flapper 112 is attached to the lower end of the lever 113. The lever 113 is rotated by the weight of the flapper 112 so that the flapper 112 and the lower base of the frame 111 are closest to each other, and the end portion of the laminated film is gripped between the two. On the other hand, when the lever 113 rotates and the flapper 112 moves away from the lower base of the frame 111 from the state in which the laminated film is gripped, the gripped laminated film is released. In the tenter shown in FIG. 3, the gripping operation of the laminated film by the clip 11 is performed at the position of the driving sprocket 13 and the opening operation of the clip 11 is performed at the position of the driven sprocket 14. In the tenter used in the manufacturing method of the present invention, the width W (length in the traveling direction) of the clip 11 is 30 mm or less.

  The control method of the position adjustment mechanism for adjusting the distance between the clips in the running direction is not particularly limited, and various methods can be employed. For example, the clip may be of a type that is independently driven, or may be of a type in which a plurality of clips are connected and a plurality of clips are controlled by a single drive system. Specific examples of types that can drive clips independently include a control method using magnetic force as represented by a linear motor drive system, or a method in which each clip has a rotary drive motor. It is done. In these cases, all the clips may be driven and controlled independently, but it is also possible to adopt a method in which only some clips are controlled and the rest are free. As a specific example of a type in which a plurality of clips are controlled by one drive system, one represented by a pantograph method can be cited. The pantograph method is a method in which the distance between the clips is controlled by opening and closing the pantograph by controlling the distance between the two rails.

By any of the methods, by adjusting the position of the clip 11 on the endless chain 12, in the running direction of the clip 11 at the time of exiting from the gap G ₁ between the stretching zone in the running direction of the clip 11 at the time of entering the stretching zone as spacing G ₂ becomes a desired interval, also it can be controlled so that the distance in the running direction of the clip 11 in the stretching zone is narrowed gradually. The tenter shown in FIG. 3 is an example, and the tenter used in the manufacturing method of the present invention does not have the chain 12 that circulates and controls the position of the clip by the position adjusting mechanism as described above. By doing so, the clip may be traveled together with the laminated film, and the interval in the width direction of the clip may be gradually widened, and the interval in the travel direction of the clip may be gradually narrowed.

(Dyeing process)
Here, the resin layer of the stretched laminated 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.

  The dyeing process is performed by, for example, immersing the entire laminated film in a solution (dyeing solution) containing the dichroic dye in the dyeing tank 20. 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 not particularly limited, but it is usually preferably in the range of 15 seconds to 15 minutes, and more 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 the dyeing process, a crosslinking treatment can be performed after dyeing. The crosslinking treatment can be performed, for example, by immersing the laminated 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 laminated 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 process, 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 uniaxially stretched polyvinyl alcohol-based resin layer.

  The thickness of the polarizer layer of the polarizing laminate film produced by the production method of the present invention (the thickness of the stretched polyvinyl alcohol resin film) is preferably 10 μm or less, more 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.

  As mentioned above, although the manufacturing method of the light-polarizing laminated film of this invention was demonstrated, the horizontal stretch process of the laminated film demonstrated above can also be employ | adopted as a stretching method of a laminated film.

  The polarizing laminate film produced by the production method of the present invention can be used as a polarizing plate as it is, or a protective film is bonded to the surface of the polarizer layer, and the base film is further peeled off. It can also be used as a polarizing plate comprising a polarizer layer and a protective film.

(1) Production of base film Propylene / ethylene random copolymer containing 5% by weight of ethylene unit (Sumitomo Chemical Co., Ltd. “Sumitomo Noblen W151”, melting point Tm = 138 ° C.) on both sides of a resin layer A base film having a three-layer structure in which a resin layer made of homopolypropylene (“Sumitomo Noblen FLX80E4” manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 163 ° C.) is used as a homopolymer of It was produced by coextrusion molding. The total thickness of the obtained base film was 100 μm, and the thickness ratio (FLX80E4 / W151 / FLX80E4) of each layer was 3/4/3.

(2) Formation of primer layer Polyvinyl alcohol powder (“Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%) was dissolved in 95 ° C. hot water, A polyvinyl alcohol aqueous solution having a concentration of 3% by weight was prepared. The resulting aqueous solution was mixed with 5 parts by weight of a crosslinking agent (“SUMIREZ RESIN 650” manufactured by Sumitomo Chemical Co., Ltd.) with respect to 6 parts by weight of polyvinyl alcohol powder. The obtained mixed aqueous solution was continuously applied on the corona-treated surface of the base film subjected to the corona treatment using a gravure coater, and dried at 80 ° C. for 10 minutes, whereby a primer layer having a thickness of 0.2 μm. And a film having a primer layer / base film configuration was prepared. Further, the same treatment was applied to the opposite side of the base film to form a 0.2 μm primer layer to obtain a film composed of primer layer / base film / primer layer.

(3) Formation of polyvinyl alcohol-based resin layer Polyvinyl alcohol powder (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree 98.0-99.0 mol%) was dissolved in 95 ° C. hot water. A polyvinyl alcohol aqueous solution having a concentration of 3% by weight was prepared. The obtained aqueous solution was continuously coated on the primer layer using a comma coater and dried at 80 ° C. for 5 minutes, thereby having a three-layer structure consisting of a base film / primer layer / polyvinyl alcohol resin layer. A laminated film was produced. The thickness of the polyvinyl alcohol-based resin layer was 10.6 μm. Further, the same treatment is applied to the opposite surface of the base film to form a 10.3 μm polyvinyl alcohol-based resin layer, and the resin layer / primer layer / base film / primer layer / resin layer structure is used. A laminated film was obtained.

(4) both ends of the stretching process the above laminate film, the interval G ₁ in the running direction of the clip held by the clip to a value described in Table 1, in the width direction under hot air at 160 ° C. in the stretching zone Drawing was performed so that the draw ratios listed in Table 1 were obtained. The width direction of the stretching gradually narrowing the inter-clip distance in the running direction at the same time, spacing G ₂ clips in the running direction at the time of exiting the stretching zone is set to be the value shown in Table 1.

(5) Dyeing process About the laminated | multilayer film which extended | stretched, the polarizing stretched film was produced in the following procedure. First, the stretched film is immersed in a dyeing solution at 30 ° C., which is an aqueous solution containing iodine and potassium iodide, for about 150 seconds to dye the polyvinyl alcohol resin layer, and then an excess iodine solution is added with pure water at 10 ° C. Washed away. Next, it was immersed for 600 seconds in the 76 degreeC bridge | crosslinking solution which is the aqueous solution containing a boric acid and potassium iodide. Thereafter, the film was washed with pure water at 10 ° C. for 4 seconds, and finally dried at 80 ° C. for 300 seconds to form a polarizer layer, thereby obtaining a polarizing laminated film.

(6) Bonding step A polarizing plate was produced by the following procedure using the polarizing laminated film. First, polyvinyl alcohol powder (“KL-318” manufactured by Kuraray Co., Ltd., average polymerization degree 1800) was dissolved in hot water at 95 ° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight. The resulting aqueous solution was mixed with 1 part by weight of a crosslinking agent (“SUMIREZ RESIN 650” manufactured by Sumitomo Chemical Co., Ltd.) with respect to 2 parts by weight of polyvinyl alcohol powder to obtain an adhesive solution.

  Next, saponification treatment of triacetyl cellulose (“KC4UY” manufactured by Konica Minolta Opto Co., Ltd.) was applied to both surfaces of the obtained polarizing laminated film using the above-mentioned adhesive solution. A laminated film was obtained by drying for 5 minutes at 80 ° C. Nine layers of transparent protective film / adhesive layer / polarizer layer / primer layer / substrate film / primer layer / polarizer layer / adhesive layer / transparent protective film From this laminated film, a base film was peeled and removed, and a polarizing plate having a structure of “protective film / adhesive layer / polarizer / primer layer” existing on both sides of the base film. Got.

[Examples 1 to 3]
While carrying out the stretching process of (4) on the laminated films of Examples 1 to 3 produced by carrying out the processes of (1) to (3) described above under the conditions described in Table 1, the film is contracted in the running direction. Stretched in the width direction. As a result, ear-like overstretched portions were hardly formed at the time of stretching, and it was possible to stretch well without breaking.

[Example 4]
The same as in Examples 1 to 3 except that instead of the above (1), a 180 μm film prepared by melt extrusion of a cycloolefin polymer resin (glass transition temperature Tg of 135 ° C.) was used as the base film. Then, the steps (2) and (3) were carried out to produce a laminated film of Example 4. The laminated film of Example 4 produced in this manner was subjected to the stretching step (4) under the conditions described in Table 1, and stretched in the width direction while contracting in the running direction. As a result, ear-like overstretched portions were hardly formed at the time of stretching, and it was possible to stretch satisfactorily without causing breakage.

[Comparative Examples 1-5]
While carrying out the stretching process of (4) under the conditions described in Table 1 and contracting the laminated films of Comparative Examples 1 to 5 produced by performing the above-described processes (1) to (3) in the running direction. Stretched in the width direction. As a result, an ear-shaped overstretched portion at the end in the width direction of the laminated film extends from the middle of the stretching, and stress concentrates there, causing the laminated film to break during the stretching and stably obtaining a film. could not.

[Comparative Examples 6-8]
Using the same base film as in Example 4, the above-described steps (2) and (3) were carried out to produce laminated films of Comparative Examples 6-8. The laminated films of Comparative Examples 6 to 8 thus produced were subjected to the stretching step (4) under the conditions described in Table 1, and stretched in the width direction while contracting in the running direction. As a result, an ear-shaped overstretched portion at the end in the width direction of the laminated film extends from the middle of the stretching, and stress concentrates there, causing the laminated film to break during the stretching and stably obtaining a film. could not.

From the above results, whether or not the stretching can be performed satisfactorily regardless of whether the resin constituting the base film is a crystalline resin or an amorphous resin is determined by the clip in the traveling direction before stretching. it was found that the gap G ₁ is related. That is, while the clip gap G ₁ of the running direction before stretching is the Examples 1 to 4 is 85mm or less can be performed satisfactorily stretching, spacing G ₁ in the running direction of the clip before stretching In Comparative Examples 1 to 8 exceeding 85 mm, breakage occurred and stretching could not be performed satisfactorily.

  In addition, even if it was crystalline resin like polyolefin resin, or amorphous resin like cycloolefin polymer resin, when the base film was extended | stretched independently, the fracture | rupture of the film did not occur. From this, it can be considered that the fracture at the time of stretching in the results of Table 1 is caused by the stretching stress of the polyvinyl alcohol-based resin layer laminated on the base film.

  When a polyvinyl alcohol-based resin is stretched, stretching at a temperature exceeding 180 ° C. tends to cause a problem that the resin deteriorates and yellows, so stretching is usually performed at a temperature of 180 ° C. or lower. However, this temperature range is considerably lower than the crystalline melting point (Tm) of the polyvinyl alcohol resin. For this reason, the stress of the polyvinyl alcohol resin layer at the time of stretching becomes very high. On the other hand, when the base film is stretched at 160 ° C. as described above, if it is a crystalline resin such as polypropylene, the vicinity of the melting point, and if it is an amorphous resin such as a cycloolefin polymer resin, the glass transition temperature ( Since the temperature is in the vicinity of Tg) or higher, it is considered that the film is stretched in a low stress state and is not easily broken. As can be seen from the reference examples shown below, when only the base film was stretched, an ear-shaped overstretched portion was formed but no breakage occurred.

[Reference Examples 1-8]
The base film used in Examples 1 to 3 and the same base film as the base film used in Example 4 were stretched by the method shown in (4) above under the conditions shown in Table 2. Table 2 shows the results.

  The calculation method of the ratio of the ear-shaped overstretched part in the results shown in Table 2 will be described with reference to FIG. FIG. 5 is a diagram schematically showing the base film after stretching. As shown in FIG. 5, in the base film 4, a necking region 4 a is generated between portions gripped by the clip, and an ear-shaped overstretched portion 4 b is formed in the portion gripped by the clip. The ratio of the ear-shaped overstretched portion is a value calculated by (L1−L2) / L1 × 100 using the lateral width L1 of the ear-shaped overstretched portion 4b and the width L2 of the necking region 4a. .

  From the results shown in Table 2, although only the base film did not break in any of Reference Examples 1 to 8, the distance between clips before stretching exceeded 85 mm (Reference Examples 4 to 8). The ratio of the ear-shaped overstretched portion in the direction exceeded 10%, and the problem that the stretching ratio was 10% or more lower than the setting described in Table 2 occurred. Moreover, about the film regarding the reference examples 4-8, the orientation resulting from the method of extending | stretching differing in the area | region (ear-shaped overstretching part 4b) grasped with the clip, and the area | region (necking area | region 4a) between clips. Differences occurred, and when observed under crossed Nicols, striped patterns were observed, which were not uniform. Therefore, it was found that when the clip interval in the running direction before stretching exceeds 85 mm, a good polarizing plate cannot be obtained even if breakage does not occur.

[Example 5]
Using the stretched laminated film obtained in Example 2, the steps (5) and (6) described above were carried out to produce the polarizing plate of Example 5. The obtained polarizing plate was uniform without unevenness. Moreover, about the obtained polarizing plate, the single-piece | unit transmittance | permeability and the polarization degree were measured using the ultraviolet visible spectrophotometer V-7100 (made by JASCO Corporation). Table 3 shows the results.

[Comparative Example 9]
Step a laminated film prepared by carrying out the above-mentioned (1) to (3), the gap G ₁ of a clip in the running direction before the stretching and 50 mm, in the stretching zone, the width without shrinkage direction of travel Stretched in the direction up to 5.8 times. The other conditions for the stretching step are as described in (4) above. Then, the above-mentioned steps (5) and (6) were carried out to produce a polarizing plate of Comparative Example 9. The obtained polarizing plate was uniform. Moreover, about the obtained polarizing plate, the single-piece | unit transmittance | permeability and the polarization degree were measured using the ultraviolet visible spectrophotometer V-7100 (made by JASCO Corporation). Table 3 shows the results.

  As shown in the results shown in Table 3, in the polarizing plate of Comparative Example 9 that did not shrink in the traveling direction, excellent polarizing properties were obtained in the polarizing plate of Example 5 that contracted in the traveling direction. The polarization degree was inferior, and sufficient polarization characteristics could not be obtained.

  The polarizing laminated film produced by the production method of the present invention can be used for producing a polarizing plate that can be effectively applied to various display devices including liquid crystal display devices.

  DESCRIPTION OF SYMBOLS 1 Laminated film, 2 Original fabric roll, 3 Polarizing laminated film, 4 Base film, 10 Horizontal stretch process part, 11 Clip, 12 Endless chain, 13 Driving sprocket, 14 Driven sprocket, 20 Dyeing tank, 111 Frame, 112 Flapper 113 levers.

Claims (5)

A lateral stretching step of stretching a laminated film in which a base film and a polyvinyl alcohol-based resin layer having a thickness of 3 μm or more are laminated in a width direction;
Dyeing the polyvinyl alcohol-based resin layer of the stretched laminated film with a dichroic dye to form a polarizing laminated film, and
In the transverse stretching step, both ends of the traveling laminated film in the width direction are gripped by a plurality of clips arranged in the running direction, and in the stretching zone, the clip interval in the width direction is set while running the clip together with the laminated film. Stretching the laminated film in the width direction by spreading, and shrinking the laminated film in the running direction by narrowing the clip interval in the running direction,
The clip interval in the running direction when entering the stretching zone is 50 to 100 mm, the clip interval in the running direction when leaving the stretching zone is 50 mm or less, and the width of each clip is 40 mm or less. A method for producing a laminated film.   2. The method for producing a polarizing laminated film according to claim 1, wherein the clip interval in the running direction at the time of exiting the stretching zone is 50% or less of the clip interval in the running direction at the time of entering the stretching zone.   The manufacturing method of the polarizing laminated film of Claim 1 or 2 whose draw ratio in the said horizontal extending process is 4 times or more.   The manufacturing method of the polarizing laminated film in any one of Claims 1-3 whose thickness of the said polyvinyl alcohol-type resin layer of the said laminated film is 10 micrometers or less. Including a lateral stretching step of stretching a laminated film in which a base film and a polyvinyl alcohol-based resin layer having a thickness of 3 μm or more are laminated in a width direction;
In the transverse stretching step, both ends of the traveling laminated film in the width direction are gripped by a plurality of clips arranged in the running direction, and in the stretching zone, the clip interval in the width direction is set while running the clip together with the laminated film. Stretching the laminated film in the width direction by spreading, and shrinking the laminated film in the running direction by narrowing the clip interval in the running direction,
The clip interval in the running direction when entering the stretching zone is 50 to 100 mm, the clip interval in the running direction when leaving the stretching zone is 50 mm or less, and the width of each clip is 40 mm or less. Stretching method.

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