TW201344259A - Method of manufacturing polarising laminated film - Google Patents

Abstract

There are provided: a lateral elongation step and a dyeing step. The lateral elongation step is a step in which: both side edges in the width direction of a laminated film that is being fed are gripped by a plurality of clips arranged in the feed direction and, in an elongation zone, the clip separation in the width direction is widened while the clips travel together with the laminated film; the laminated film is thereby shrunk in the direction of travel by elongation of the laminated film in the width direction and narrowing of the clip separation in the feed direction. The clip separation in the feed direction at the time point of entry into this elongation zone is 50 to 100 mm. The clip separation in the feed direction at the time point of exiting this elongation zone is no more than 50 mm. The width of each of the clips is no more than 40 mm.

Description

Method for producing polarizing laminated film

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

The polarizing plate is widely used as a polarizing supply element or the like in a display device such as a liquid crystal display device. As the polarizing plate, a polarizing element layer containing a polyvinyl alcohol-based resin and a protective film of triacetyl cellulose have been used in the prior art. The polarizing element layer (polarizing film) is required to have high optical performance, and in recent years, with the development of liquid crystal display devices for mobile devices such as notebook computers and mobile phones, thin wall thickness has been demanded.

An example of a method for producing a thin polarizing plate is to apply a solution containing a polyvinyl alcohol-based resin to a surface of a base film to form a resin layer, and then to extend a laminated film including the base film and the resin layer. Subsequently, dyeing, crosslinking (fixing), and drying were carried out, and a polarizing element layer was formed from a resin layer, whereby a polarizing laminated film including a polarizing element layer was obtained. It is known that it is used as a polarizing plate directly as a polarizing plate, or after a protective film is bonded to the film, the base film is peeled off and used as a polarizing plate.

In the step of extending the laminated film, the laminated film is shrunk in a direction perpendicular thereto while extending in one direction, whereby an original sheet having a relatively high degree of alignment with a substantially uniaxial alignment, that is, a high degree of polarization can be obtained. The polarizing film, usually, extends in such a manner that the free end extends longitudinally. However, if the free end longitudinal uniaxial stretching is performed, there is a case where the width of the original sheet is significantly narrowed due to the natural neck-in in the width direction. On the other hand, if by This problem can be avoided by extending laterally in the width direction. A method of manufacturing a polarizing film that extends in the lateral direction extending in the width direction is described in Japanese Laid-Open Patent Publication No. 2003-43257 (Patent Document 1).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-43257

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-300768

Patent Documents 1 and 2 describe a method of stretching a film in the width direction by using a tenter. The tenter is a device in which the both ends of the polarizing film in the width direction are held by a jig, and the jig is moved together with the film, and the film is extended by the jig spacing in the width direction. In the case of using a tenter, the jig spacing for the traveling direction can be initially enlarged and reduced in the lateral direction, whereby the width direction of the film is extended and the film is shrunk in the traveling direction. However, when the laminated film in which the base film and the polyvinyl alcohol-based resin are laminated, for example, when the stretching ratio in the width direction is 4 or more, a large neck is formed between the jigs in the traveling direction. A long ear-shaped overhanging portion is formed at the end portion of the film held by the jig, and if the stretching ratio is further increased, there is a case where the film is broken at the excessive extension portion of the ear.

The present invention has been made in view of the above problems, and an object of the invention is to provide a method for producing a polarizing laminated film which can be stably produced without causing breakage of a film or the like when extending in the width direction, and a method for extending the laminated film.

As a result of intensive research by the inventors of the present invention, it has been found that there is a correlation between the occurrence of the above-mentioned excessive extension portion of the film end portion and the jig interval of the migration direction before the extension, thereby The present invention has been completed.

The present invention relates to a method for producing a polarizing laminated film, comprising: a lateral stretching step of extending a substrate film and a laminated film of a polyvinyl alcohol-based resin having a thickness of 3 μm or more in a width direction; and dyeing In the step, the polyvinyl alcohol-based resin layer of the stretched laminated film is dyed by a dichroic dye to form a polarizing laminated film. The lateral stretching step is a step of holding both ends of the transition film in the width direction by a plurality of jigs arranged in the traveling direction, and moving the jig together with the laminated film in the extended region while The jig interval in the width direction is enlarged to extend the laminated film in the width direction, and the laminated film is shrunk in the traveling direction by reducing the jig interval in the traveling direction. Further, the jig interval of the traveling direction at the time point of entering the extended region is 50 to 100 mm, and the jig interval of the moving direction away from the extending region is 50 mm or less, and the width of each jig is 40 mm or less. Furthermore, the jig spacing in this specification is the distance between the centers of the jig, and the width of the jig is the longest length of the jig in the direction of travel.

In the above invention, the jig interval in the traveling direction from the time point of the extended region is preferably 50% or less of the jig interval in the traveling direction of the time point to the extended region.

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

Moreover, the present invention is a method for extending a laminated film, which comprises a lateral stretching step of extending a substrate film and a laminated film of a polyvinyl alcohol-based resin having a thickness of 3 μm or more in the width direction. The lateral stretching step is a step of holding both ends of the transition film in the width direction by a plurality of jigs arranged in the traveling direction, and moving the jig together with the laminated film in the extended region while The jig interval in the width direction is enlarged to extend the laminated film in the width direction, and the laminated film is shrunk in the traveling direction by reducing the jig interval in the traveling direction. Furthermore, the time point to enter the above extended area The jig interval of the moving direction is 50 to 100 mm, and the jig interval of the moving direction away from the extended region is 50 mm or less, and the width of each jig is 40 mm or less.

According to the present invention, it is possible to provide a method for producing a polarizing laminated film which can stably extend in the width direction and shrink in the traveling direction without breaking the laminated film.

1‧‧‧ laminated film

1a‧‧‧necking

1b‧‧‧ Ear-shaped overextension

2‧‧‧ original film reel

3‧‧‧Polarized laminated film

4‧‧‧Base film

4a‧‧‧neck area

4b‧‧‧Overextension of the ear

10‧‧‧ Horizontal Extension Steps

11‧‧‧Clamp

12‧‧‧Circular chain

13‧‧‧Active sprocket

14‧‧‧Driven sprocket

20‧‧‧Staining tank

111‧‧‧Frame

112‧‧‧Baffle

113‧‧‧Pole

A ₁ ‧‧‧Transition path

A ₂ ‧‧‧Travel path between the driven sprocket 14 and the drive sprocket 13

D ₁ ‧‧‧Clamp spacing in the width direction of the point in time to the extended area

D ₂ ‧‧‧Clamp spacing in the width direction from the point in time of the extension

G ₁ ‧‧‧Clamp interval for the direction of travel to the extended zone

G ₂ ‧‧‧Clamping interval in the direction of travel from the point of extension

The width of the lateral direction of the L1‧‧‧ ear-excessive extension 4b

L2‧‧‧Width of necked area 4a

W‧‧‧Width of clamp 11

Fig. 1 is a view schematically showing an apparatus which can be preferably used in the method for producing a polarizing laminated film of the present invention.

Fig. 2 is a view for explaining the mechanism by which the laminated film is broken in the stretching step.

Fig. 3 is a plan view schematically showing an example of the internal configuration of a tenter used in the manufacturing method of the present invention.

4(a) and 4(b) are diagrams showing the configuration of a clamp of a tenter in a mode.

Fig. 5 is a view for explaining a method of calculating the ratio of the ear-shaped overextended portion of the stretched laminated film.

The method for producing a polarizing laminated film of the present invention comprises: a lateral stretching step of extending a base film and a laminated film of a polyvinyl alcohol-based resin having a thickness of 3 μm or more in a width direction; and a dyeing step, The polyvinyl alcohol-based resin layer of the stretched laminated film is dyed by a dichroic dye to form a polarizing laminated film.

Fig. 1 is a view schematically showing an apparatus which can be preferably 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 drawn from the original roll 2 is sequentially passed through the lateral extending step portion 10 for performing the lateral stretching step, and the dyeing groove 20 for performing the dyeing step. The polarizing laminated film 3 was obtained. Not shown in FIG. 1, after the step portion 10 is laterally extended, the laminated film may be temporarily taken out, and then the laminated film may be passed through the dyeing tank 20. In the extension device 10, an extension step is performed in which both end portions in the width direction of the laminated laminated film 1 are held by a plurality of jigs arranged in the traveling direction, In the extended region, while the jig is moved together with the laminated film, the laminated film 1 is extended in the width direction by enlarging the jig spacing in the width direction, and the laminated film 1 is moved in the traveling direction by reducing the jig spacing in the traveling direction. shrink.

Further, although the swelling tank for performing the swelling treatment, the crosslinking tank for performing the crosslinking treatment, and the drying furnace for performing the drying treatment are not shown in Fig. 1, these portions may be appropriately provided as needed.

[Laminated film]

In the production method of the present invention, a laminate film obtained by laminating a base film and a polyvinyl alcohol-based resin having a thickness of 3 μm or more is used.

(substrate film)

As the resin used for the base film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, and elongation can be used, and a suitable resin can be selected according to the glass transition temperature Tg or the melting point Tm. The base film is preferably extended by using a temperature range which is extendable to the polyvinyl alcohol-based resin layer which is laminated thereon.

Specific examples of the thermoplastic resin include a chain polyolefin resin, a polyester resin, and a cyclic polyolefin resin. Ethylene resin, (meth)acrylic resin, cellulose ester resin, polycarbonate resin, polyvinyl alcohol resin, vinyl acetate resin, polyarylate resin, polystyrene resin, poly An ether oxime resin, a polyfluorene-based resin, a polyamine-based resin, a polyimide-based resin, a mixture or a copolymer thereof, and the like.

The base film may be a film composed of only one of the above resins, or a film obtained by blending two or more kinds of resins. The substrate film may be a single layer film or a multilayer film.

Examples of the polyolefin-based resin include polyethylene, polypropylene, and the like, and these are preferably easily and stably extended at a high rate. Further, an ethylene-polypropylene copolymer obtained by copolymerizing propylene with ethylene or the like can also be used. The copolymerization may be another type of monomer, and examples of other types of monomers copolymerizable with propylene include ethylene and an α-olefin. As the α-olefin, it is preferred to use an α-olefin having 4 or more carbon atoms, more preferably an α-ene having 4 to 10 carbon atoms. hydrocarbon. Specific examples of the α-olefin having 4 to 10 carbon atoms include linear chains such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene. a monoolefin; a branched monoolefin such as 3-methyl-1-butene, 3-methyl-1-pentene or 4-methyl-1-pentene; vinylcyclohexane or 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 can be determined by infrared (IR) spectrometry according to the method described in the "Handbook of Polymer Analysis" (1995, published by Kiyoshiya Shoten).

Among the above, as the propylene resin constituting the propylene resin film, a homopolymer of propylene, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, and propylene-ethylene are preferably used. 1-butene random copolymer.

Further, the stereoregularity of the propylene-based resin constituting the propylene-based resin film is preferably substantially isotactic or syndiotactic. The propylene-based resin film containing a propylene-based resin having substantially uniform or regular stereoregularity is relatively excellent in handleability and excellent in 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. The polycarboxylic acid to be used mainly uses a dicarboxylic acid such as isophthalic acid, terephthalic acid, dimethyl terephthalate or dimethyl naphthalate. Further, as the polyol to be used, a binary diol is mainly used, and examples thereof include propylene glycol, butanediol, neopentyl glycol, and cyclohexane dimethanol. Specific examples of the resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polytrimethylene terephthalate. (polytrimethylene terephthalate), polytrimethylene naphthalate, poly(cyclohexanedimethylene terephthalate), polynaphthalene dicarboxylate dimethyl dimethyl ester, and the like. These blended resins or copolymers may also preferably be used.

As the cyclic polyolefin resin, it is preferred to use a drop An olefinic resin. The cyclic polyolefin-based resin is a general term for a resin obtained by polymerizing a cyclic olefin as a polymerization unit, and examples thereof include a Japanese Patent Laid-Open No. Hei. A resin described in Japanese Laid-Open Patent Publication No. 3-122137. Specific examples thereof include a ring-opening (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a copolymer of a cyclic olefin and an α-olefin such as ethylene or propylene (typically random) a copolymer), and a graft polymer obtained by modifying the unsaturated carboxylic acid or a derivative thereof, and the like, and the like. Specific examples of the cyclic olefin include a descending An olefinic monomer.

Cylindrical polyolefin resins are commercially available in various products. Specific examples include Topas (registered trademark) (manufactured by Ticona Co., Ltd.), Arton (registered trademark) (manufactured by JSR Co., Ltd.), ZEONOR (registered trademark) (manufactured by Zeon Co., Ltd.), and ZEONEX (registered trademark) (manufactured by Zeon Co., Ltd.), Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.).

As the (meth)acrylic resin, any suitable (meth)acrylic resin can be used. For example, poly(meth)acrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth) acrylate copolymer, methyl group Methyl acrylate-acrylate-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-A) Cyclohexyl acrylate copolymer, methyl methacrylate-(meth) acrylate Ester copolymers, etc.). Preferably, a poly(meth)acrylic acid C1-6 alkyl ester such as poly(methyl) acrylate is used. 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 more preferably used.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of such a cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, the copolymer or the like, or a part of the hydroxyl group may be modified by another type of substituent or the like. Among these, Tejia is three Acetyl cellulose ester. Triacetyl cellulose esters are commercially available in large quantities and are also advantageous in terms of availability or cost. As an example of the commercial product of the triacetin cellulose ester, Fujitac (registered trademark) TD80 (manufactured by Fujifilm Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fujifilm Co., Ltd.), Fujitac (registered trademark) TD80UZ (manufactured by Fujifilm Co., Ltd.), Fujitac (registered trademark) TD40UZ (manufactured by Fujifilm Co., Ltd.), KC8UX2M (manufactured by Konica Minolta Opto Co., Ltd.), KC4UY (manufactured by Konica Minolta Opto Co., Ltd.) )Wait.

The polycarbonate resin is an engineering plastic containing a polymer obtained by bonding a monomer unit via a carbonate group, and is a resin having high impact resistance, heat resistance, and flame retardancy. Moreover, it is also preferably used for optical applications because of its high transparency. In optical applications, a resin called modified polycarbonate or a copolymerized polycarbonate having improved wavelength dependence, which is modified to reduce the photoelastic coefficient and which has a polymer skeleton, is preferably commercially available. use. Such a polycarbonate resin is widely sold on the market, and examples thereof include Panlite (registered trademark) (Teijin Chemical Co., Ltd.), Iupilon (registered trademark) (Mitsubishi Engineering-Plastics Co., Ltd.), and SD Polyca (registered trademark). (Sumitomo Dow Co., Ltd.), Calibre (registered trademark) (Dow Chemical Co., Ltd.), and the like.

In addition to the above thermoplastic resin, any suitable additive may be added to the base film. Examples of such an additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the above-exemplified thermoplastic resin in the base film is preferably from 50 to 100% by weight, more preferably from 50 to 99% by weight, still more preferably from 60 to 98% by weight, particularly preferably from 70 to 97% by weight. The reason for this is that when the content of the thermoplastic resin in the base film is less than 50% by weight, the high transparency and the like which the thermoplastic resin originally has cannot be sufficiently expressed.

The thickness of the base film before stretching can be appropriately determined, and it is preferably from 1 to 500 μm, more preferably from 1 to 300 μm, and even more preferably from 5 to 200 μm in terms of workability such as strength or workability. The best is 5~150 μm.

In order to improve the adhesion between the base film and the resin layer containing the polyvinyl alcohol-based resin, corona treatment, plasma treatment, flame treatment, or the like may be performed on at least the surface on the side where the polyvinyl alcohol-based resin layer is formed. Further, in order to improve the adhesion, a thin layer such as an undercoat layer may be formed on the surface of the base film on the side where the polyvinyl alcohol-based resin layer is formed.

(primer coating)

The undercoat layer is not particularly limited as long as it has a strong adhesion to both the base film and the polyvinyl alcohol-based resin layer. For example, a thermoplastic resin excellent in transparency, heat stability, and elongation is used. Specific examples thereof include an acrylic resin and a polyvinyl alcohol resin, but are not limited thereto.

The resin constituting the undercoat layer can be used in a state of being dissolved in a solvent. Depending on the solubility of the resin, the following common organic solvents may be used: aromatic hydrocarbons such as benzene, toluene, and xylene; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; And esters such as isobutyl acetate; chlorinated hydrocarbons such as dichloromethane, trichloroethylene, chloroform; alcohols such as ethanol, 1-propanol, 2-propanol and 1-butanol. However, if the undercoat layer is formed by using a solution containing an organic solvent, the substrate may be dissolved. Therefore, it is preferred to select a solvent in consideration of the solubility of the substrate. In consideration of the influence on the environment, it is preferred to form an undercoat layer from a coating liquid using water as a solvent. Among them, a polyvinyl alcohol-based resin having good adhesion is preferably used.

Examples of the polyvinyl alcohol-based resin used as the undercoat layer include a polyvinyl alcohol resin and a derivative thereof. Examples of the derivative of the polyvinyl alcohol resin include, in addition to polyvinyl formal, polyvinyl acetal, and the like, a polyvinyl alcohol resin, an olefin such as ethylene or propylene, acrylic acid, methacrylic acid or crotonic acid. It is modified by an unsaturated carboxylic acid, an alkyl ester of an unsaturated carboxylic acid, acrylamide or the like. Among the above polyvinyl alcohol-based resin materials, polyethylene is preferably used. Alcohol resin.

In order to increase the strength of the undercoat layer, a crosslinking agent may be added to the above thermoplastic resin. A known agent such as an organic system or an inorganic system can be used as the crosslinking agent to be added to the resin. As long as the thermoplastic resin to be used is appropriately selected, it is more suitable. For example, an epoxy-based, isocyanate-based, dialdehyde-based, or metal-based crosslinking agent can be selected. As the epoxy-based crosslinking agent, either one-liquid curing type epoxy-based crosslinking agent or two-liquid curing type epoxy-based crosslinking agent can be used. Examples thereof include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, Epoxy such as diglycidyl aniline or diglycidylamine.

Examples of the isocyanate-based crosslinking agent include toluene diisocyanate, hydrogenated toluene diisocyanate, trimethylolpropane-toluene diisocyanate adduct, triphenylmethane triisocyanate, and methylene bis(4-phenylmethane three). Isocyanates, isophorone diisocyanates, and isocyanates such as ketone oxime blocks or phenolic blocks.

Examples of the dialdehyde-based crosslinking agent include glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, maleic aldehyde, and o-phthalaldehyde.

Examples of the metal-based crosslinking agent include a metal salt, a metal oxide, a metal hydroxide, and an organometallic compound. The type of the metal is not particularly limited, and may be appropriately selected. Examples of the metal salt, the metal oxide, and the metal hydroxide include sodium, potassium, magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, lanthanum, boron, zinc, copper, vanadium, chromium, tin, and the like. a salt of a metal having a valence above two valences and an oxide or hydroxide thereof.

The organometallic compound refers to a compound having at least one organic group bonded to a metal atom in the molecule or bonded to a metal atom via an oxygen atom or a nitrogen atom. The organic group means a functional group containing at least a carbon element, and may be, for example, an alkyl group, an alkoxy group, a fluorenyl group or the like. Further, the term "bonding" means not only covalent bonding, but also coordination bonding using a coordination such as a chelate compound.

Preferred examples of the above metal organic compound include titanium organic compounds, Zirconium organic compounds, aluminum organic compounds and cerium organic compounds. These metal organic compounds may be used alone or in combination of two or more.

Specific examples of the titanium organic compound include, for example, tetra-n-butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetrakis(2-ethylhexyl) titanate, and titanic acid. Titanium orthoesters such as tetramethyl ester; titanium phthalate pyruvate, titanium tetraacetate pyruvate, titanium polyacetylate pyruvate, titanium octyl glycolate, titanium lactate, titanium triethanolaminate, A titanium chelate compound such as ethyl acetate and titanium; a titanium halide such as polyhydroxystearate or the like.

Specific examples of the zirconium organic compound include zirconium n-propoxide, zirconium n-butoxide, zirconium tetraethate pyruvate, zirconium monoacetate, zirconium acetoacetate, and bis(ethyl acetamidine). Acetic acid) Zirconium acetylacetonate or the like.

Specific examples of the aluminum organic compound include, for example, aluminum acetylacetonate, an aluminum organic acid chelate, and the like. Specific examples of the above-mentioned cerium organic compound include compounds having a ligand exemplified in the above titanium organic compound and zirconium organic compound.

In addition to the above-mentioned low molecular weight crosslinking agent, a polymer-based crosslinking agent such as a methylolated melamine resin or a polyamide resin may be used. As a commercial product of the polyamide resin, "Sumirez (registered trademark) Resin 650 (30)" or "Sumirez (registered trademark) Resin 675" (all trade names) sold by Sumika Chemtex Co., Ltd. Wait.

When a polyvinyl alcohol-based resin is used as the thermoplastic resin, it is particularly preferably a polyamine epoxy resin, a methylolated melamine, a dialdehyde, a metal chelate crosslinking agent or the like.

The ratio of the thermoplastic resin to the crosslinking agent to form the undercoat layer is appropriately determined within a range of from 0.1 to 100 parts by weight based on 100 parts by weight of the resin, depending on the type of the resin or the type of the crosslinking agent. It is preferable to select from about 0.1 to 50 parts by weight. Further, the coating liquid for the undercoat layer preferably has a solid content concentration of about 1 to 25% by weight.

The thickness of the undercoat layer is preferably from 0.05 to 1 μm. Further preferably, it is 0.1 to 0.4 μm. When it is thinner than 0.05 μm, the effect of improving the adhesion between the base film and the polyvinyl alcohol layer is small, and if it is thicker than 1 μm, the polarizing plate becomes thick, which is not preferable.

When the undercoat layer is formed, the coating method to be used is not particularly limited, and a roll coating method such as a wire bar coating method, a reverse coating method, a gravure coating method, or the like can be appropriately selected from known methods. Method, comma coating method, lip coating method, spin coating method, screen coating method, spray coating method, dipping method, spray method, and the like.

(polyvinyl alcohol resin layer)

As the polyvinyl alcohol-based resin used for the polyvinyl alcohol-based resin layer, a polyvinyl acetate-based resin can be used for saponification. Polyvinyl acetate-based resin In addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable may be exemplified. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The polyvinyl alcohol-based resin is preferably a completely saponified product. The degree of saponification is preferably in the range of 80.0 mol% to 100.0 mol%, more preferably in the range of 90.0 mol% to 99.5 mol%, and further preferably in the range of 94.0 mol% to 99.0 mol%. When the degree of saponification is less than 80.0 mol%, there is a problem that the water resistance and the moist heat resistance after the formation of the polarizing element layer are remarkably deteriorated.

In the present specification, the "saponification degree" is a ratio of the acetic acid group contained in the polyvinyl acetate-based resin which is a raw material of the polyvinyl alcohol-based resin to a hydroxyl group by a saponification step in a unit ratio (% by mole). The person to be represented is a numerical value defined by the following formula. It can be obtained by the method prescribed by JIS K 6726 (1994).

Degree of saponification (% by mole) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100

The higher the degree of saponification, the higher the ratio of the hydroxyl groups, that is, the lower the ratio of the acetate groups which hinder crystallization.

Further, the polyvinyl alcohol-based resin may be a part of the modified modified polyvinyl alcohol. example For example, the polyvinyl alcohol-based resin is modified by an olefin such as ethylene or propylene, an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid, an alkyl ester of an unsaturated carboxylic acid, or acrylamide. . The ratio of modification is preferably less than 30 mol%, more preferably less than 10%. When the modification is performed in excess of 30 mol%, it is difficult to adsorb the dichroic dye and the polarizing performance is lowered.

The average degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but is preferably from 100 to 10,000, more preferably from 1,500 to 8,000, and still more preferably from 2,000 to 5,000. The average degree of polymerization as referred to herein is also a value obtained by the method specified in JIS K 6726 (1994).

Examples of the polyvinyl alcohol-based resin having such a property include PVA124 (saponification degree: 98.0 to 99.0 mol%) manufactured by Kuraray Co., Ltd., PVA117 (saponification degree: 98.0 to 99.0 mol%), and PVA624 (saponification). Degree: 95.0~96.0 mol%) and PVA617 (saponification degree: 94.5~95.5 mol%); for example, AH-26 (saponification degree: 97.0~98.8 mol%) manufactured by Nippon Synthetic Chemical Industry Co., Ltd., AH- 22 (saponification degree: 97.5 to 98.5 mol%), NH-18 (saponification degree: 98.0 to 99.0 mol%) and N-300 (saponification degree: 98.0 to 99.0 mol%); for example, Japan Vam & Poval shares limited JC-33 (saponification degree: 99.0 mol% or more), JM-33 (saponification degree: 93.5~95.5 mol%), JM-26 (saponification degree: 95.5~97.5 mol%), JP-45 (JP-45) Saponification degree: 86.5~89.5 mol%), JF-17 (saponification degree: 98.0~99.0 mol%), JF-17L (saponification degree: 98.0-99.0 mol%) and JF-20 (saponification degree: 98.0~) 99.0 mol%) or the like is preferably used in the formation of the polyvinyl alcohol-based resin film of the present invention.

An additive such as a plasticizer or a surfactant may be added to the polyvinyl alcohol-based resin as needed. As the plasticizer, a polyhydric alcohol, a condensate thereof, or the like can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the additive to be added is not particularly limited, but is preferably 20% by weight or less in the polyvinyl alcohol-based resin.

The thickness of the polyvinyl alcohol-based resin layer is 3 μm or more. In the polyvinyl alcohol resin layer When the thickness is 3 μm or more, the stress at the time of extending the resin layer on the substrate becomes large. Therefore, if an excessive extension portion is formed in the grip portion of the jig when extending, the stress of the resin layer is concentrated on the Excessive extension of the ear is prone to breakage.

Fig. 2 is a view for explaining the mechanism by which the laminated film is broken in the stretching step. As shown in FIG. 2, in the extending step, the laminated film 1 is held at both ends by a plurality of jigs 11 and extends in the width direction. At this time, the necking 1a is generated between the jigs due to the interval of the moving direction of the jig, and the ear-shaped overhanging portion 1b is formed in the portion held by the jig. The stress of the polyvinyl alcohol-based resin layer produced by the stretching tends to occur in the ear-shaped overhanging portion 1b. Therefore, it is considered that if the stress of the excessively elongated portion 1b of the ear exceeds a certain limit, it is in the form of an ear. The excessive extension 1b is broken.

In the production method of the present invention, it is preferable that the thickness of the polyvinyl alcohol-based resin layer which is likely to be broken by the conventional method is 3 μm or more. In addition, when 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 from 3 to 30 μm, more preferably from 5 to 20 μm. If it exceeds 30 μm, the thickness of the finally obtained polarizing element layer exceeds 10 μm, which is not preferable.

The resin layer in the present invention is preferably formed by applying a polyvinyl alcohol-based resin solution obtained by dissolving a powder of a polyvinyl alcohol-based resin in a good solvent onto one surface of a base film to evaporate the solvent. By forming the resin layer in this manner, the resin layer can be formed thin. As a method of applying the polyvinyl alcohol-based resin solution to the base film, a roll coating method such as a bar coating method, a reverse coating method, or a gravure coating method, or a squeeze coating method can be appropriately selected from known methods. Method, Kama coating method, lip coating method, spin coating method, screen coating method, spray coating method, dipping method, spray method, and the like. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. The drying time is, for example, 2 to 20 minutes.

Further, the resin layer in the present invention may be formed by laminating an original sheet film containing a polyvinyl alcohol-based resin on one surface of a base material film. Also, the resin layer may be formed only on the substrate film On one of the surfaces, they may be formed on both surfaces, respectively.

(horizontal extension step)

The lateral stretching step in the present invention is carried out by, for example, the laterally extending step portion 10 shown in Fig. 1. A tenter can be used in the lateral extension step portion 10. The tenter used in the present invention holds the both ends of the transition laminated film in the width direction by a plurality of jigs arranged in the traveling direction, and moves the jig and the laminated film together in the extended region. The laminated film is stretched in the width direction by enlarging the jig interval in the width direction, and the laminated film is shrunk in the traveling direction by reducing the jig spacing in the traveling direction.

The contraction in the width direction and the contraction direction are preferably performed simultaneously, but the extension in the width direction and the contraction in the direction of travel are not necessarily performed at the same time, as long as the sections which are simultaneously performed are partially present. For example, the extension in the width direction may be performed in the entire extension region, and the contraction direction may be contracted only in one of the extension regions; the contraction direction may be contracted in the entire extension region, and only a part of the interval is accompanied by the width. The extension of direction. Further, when the stretching in the width direction and the direction of the migration are performed at different timings, in order to preferably shrink the crystalline polymer such as polyvinyl alcohol in the traveling direction, it is preferred that the processing is not vacated. And continue.

In the tenter used in the manufacturing method of the present invention, when the jig interval of the moving direction of the time point to the extending region is G ₁ , the interval G ₁ is 50 to 100 mm, preferably 50 to 85. In the case where the jig interval of the traveling direction at the time point of leaving the extended region is G ₂ , the interval G ₂ is 50 mm or less, preferably 45 mm or less. In the extended region, the laminated film can be shrunk in the traveling direction by narrowing the jig interval of the traveling direction in this manner, and a polarizing laminated film including a polarizing element layer having a very high degree of polarization and excellent polarizing performance can be obtained. Further, the interval G _{2 is} preferably 50% or less of the interval G ₁ . Further, the width of each jig (the length of the traveling direction) is 40 mm or less, preferably 30 mm or less. The state in which the jigs are adjacent to each other in the traveling direction is the lower limit of the jig interval in the traveling direction, and therefore, the lower limit corresponds to the width of the jig (the length of the traveling direction). For example, when the width of the jig is 30 mm, in the manufacturing method of the present invention, the jig spacing G _{2 in} the traveling direction from the time point of the extended region is 30 mm or more and 50 mm or less.

If the jig interval G ₁ of the traveling direction at the time point of entering the extended region exceeds 100 mm, there is a problem that the ratio of the excessive extension of the ear formed when extending in the width direction in the extended region increases. When the width direction is extended in the width direction, the over-extension portion of the ear shape is elongated and the stretching ratio cannot be increased, or the stress is concentrated on the excessive extension portion of the ear shape, and if it is desired to extend at a high magnification, the ear-shaped excessive extension portion is broken. In particular, when the stretching ratio in the width direction is set to 4 or more, such a problem is likely to occur. Moreover, when the jig spacing G ₁ of the traveling direction at the time point of entering the extended region is less than 50 mm, since the jig spacing G ₂ of the traveling direction away from the extended region can be reduced only to the width of the jig, That is, it is easy to minimize the jig spacing of the transition direction in the extended region, and it is also difficult to sufficiently shrink the laminated film in the traveling direction. In particular, it is difficult to achieve a sufficient migration direction of more than 50%. Similarly, when the width of the jig exceeds 30 mm, it is also difficult to sufficiently shrink the laminated film in the traveling direction. When the shrinkage in the direction of migration is insufficient, the degree of polarization of the polarizing element layer may not be sufficiently high.

The jig spacing of the direction of travel outside the extended area can be appropriately adjusted. For example, the interval between the jigs can be set to a distance convenient for transport before the laminated film is held or after the laminated film is released. Further, the interval between the jigs may be intentionally adjusted in the region before or after the extended region to eliminate wrinkles or tension applied to the laminated film.

In the lateral stretching step of the present invention, it is preferred to extend the laminated film in the width direction so as to achieve a stretching ratio of 4 times or more and 17 times or less. Further, it is preferable to extend in the width direction so as to achieve a stretching ratio of 5 times or more and 8 times or less. When the stretching ratio is less than 4 times, the polyvinyl alcohol-based resin layer cannot be sufficiently aligned, and as a result, there is a case where the degree of polarization of the polarizing element layer is not sufficiently increased. On the other hand, when the stretching ratio exceeds 17 times, the laminated film is likely to be broken at the time of stretching, and At the same time, the thickness of the stretched film is reduced to a level higher than necessary, and the workability and workability in the subsequent steps are lowered. The extension processing in the lateral stretching step is not limited to the extension of one stage, and may be performed in multiple stages. The stretching treatment can be performed, for example, simultaneously with the dyeing treatment or the crosslinking treatment. In this case, it is preferred to extend the dyeing step to an auxiliary extension at a lower magnification and to prevent shrinkage in the direction of migration. In the case of performing in multiple stages, the stretching process is performed in such a manner that the total length of all the stages of the stretching process is preferably 4 times or more.

The stretching ratio in the width direction generally means the magnification of the length in the width direction of the laminated film after stretching with respect to the length in the width direction of the laminated film before stretching. Therefore, in the tenter used in the lateral stretching step, the tenter spacing D _{1 in} the width direction of the time point of entering the extending region and the jig spacing D _{2 in} the width direction from the time point of the extending region can be calculated. In the present invention, the stretching ratio in the width direction in the extended region is defined as D ₂ /D ₁ . Further, the length of the laminated film used in the present invention in the width direction before stretching is, for example, 100 to 1000 mm.

The temperature in the extended region must be a temperature at which the substrate film can be stretched, and it is preferably selected from the range of 80 to 180 ° C. However, in order to reduce the stress during elongation of the polyvinyl alcohol resin, it is preferably carried out at 120 ° C or higher. . When the temperature in the extended region is too low, the stress at the time of extension of the polyvinyl alcohol-based resin becomes too strong and the laminated film is easily broken. On the contrary, if the stretching temperature is too high, the polyvinyl alcohol-based resin is liable to be dehydrated and deteriorated and yellowed. Bad condition. Of course, a plurality of different temperatures can also be set in the extended area. The extended region can be managed to a specific temperature, for example, by supplying hot air to the laminated film from above or below, or in both directions.

Further, a preheating zone may be disposed upstream of the extension region, and a heat fixation zone and a thermal relaxation zone may be sequentially disposed downstream of the extension zone. The preheating zone is a zone where the laminated film is preheated, and the laminated film is heated without enlarging the interval between the jigs. The preheated laminate film in the preheating zone is moved to the extended region. The extended region is a region in which the laminated film is extended in the width direction by enlarging the interval between the jigs as described above. In the present invention, also in the extension area The shrinkage of the traveling direction of the laminated film is performed in the domain. The stretched laminated film in the extended region moves to the heat-fixed region. The heat-fixing region is a region where heat treatment is performed at a temperature equal to or higher than the crystallization temperature while maintaining the end portion of the laminated film in a state of being held by the jig. The crystallization of the polyvinyl alcohol-based resin layer is promoted by heat treatment in the heat-fixing region. The heat-treated laminated film in the heat-fixed region is moved to the thermally relaxed region. The thermally relaxed region is a step of heat-treating the laminated film in a state of being relaxed, and the residual stress or strain component inside the laminated film is removed by the thermally relaxed region. The temperature in each region can be appropriately selected depending on the properties of the material of the base film or the polyvinyl alcohol-based resin layer. Hereinafter, a preferred tenter used in the production method of the present invention will be described in detail using the drawings.

Fig. 3 is a plan view schematically showing an example of the internal configuration of a tenter used in the manufacturing method of the present invention. As shown in Fig. 3, the tenter includes a plurality of jigs 11 that hold both end portions in the width direction of the laminated film 1, and the jigs 11 are attached to the endless chain 12 at specific intervals. The endless chain 12 is disposed on both sides of the laminated film 1 and is disposed between the drive sprocket 13 on the inlet side and the driven sprocket 14 on the outlet side. The drive sprocket 13 is connected to a motor (not shown), and the drive sprocket 13 is rotated by driving the motor. Thereby, the endless chain 12 is circumferentially moved between the drive sprocket 13 and the driven sprocket 14, so that the jig 11 mounted on the endless chain 12 wraps around.

The traveling path of the endless chain 12 is configured such that the jig in the width direction is gradually enlarged in the extending region, and is configured as a time interval D ₁ from the width direction of the jig 11 at the time point of entering the extending region, and a time point from the extending region The interval D _{2 in} the width direction of the jig 11 becomes large.

The tenter further includes a position adjusting mechanism which is not shown, and adjusts the interval between the jigs 11 mounted on the endless chain 12, that is, the interval of the jig 11 in the traveling direction, to a desired interval, and is as follows The mode is adjusted: in the transition path A ₁ of the extended area, the interval between the clamps 11 is gradually reduced, and in the travel path A ₂ between the driven sprocket 14 and the drive sprocket 13, the time to enter the extended area The interval G ₁ of the jig 11 of the point is adjusted to a desired value. Thereby, the interval G ₁ between the jigs 11 in the traveling direction of the time point to the extending region and the interval G ₂ of the jig 11 at the time point from the extending region can be controlled to a desired interval. In the manufacturing method of the present invention, the interval G _{1 of} the jig is controlled to be 50 to 100 mm, preferably 50 to 85 mm, and the interval G _{2 of the} jig is controlled to be 50 mm or less, preferably 45 mm or less. Further, the interval G _{2 is} preferably 50% or less of the interval G ₁ .

4 is a view schematically showing the configuration of the jig 11, and (a) is a view showing the jig 11 from above, and (b) is a cross-sectional view showing the jig 11. As shown in FIG. 4, the jig 11 includes a frame 111, a lever 113, and a flapper 112. The frame 111 is formed in a U shape, and the lower stage serves as a film stage. A lever 113 is rotatably mounted on the upper portion of the frame 111, and a shutter 112 is attached to the lower end of the lever 113. The lever 113 is rotated by the weight of the shutter 112 so that the shutter 112 is closest to the lower stage of the frame 111, and the end of the laminated film is held between the two. On the other hand, if the lever 113 is rotated from the state in which the laminated film is held and the shutter 112 is separated from the lower portion of the frame 111, the laminated film that is held is released. In the tenter shown in Fig. 3, the laminated film holding operation of the jig 11 is performed at the position of the driving sprocket 13, and the releasing operation of the jig 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 of the traveling direction) of the jig 11 is 40 mm or less, preferably 30 mm or less.

The method of controlling the position adjusting mechanism for adjusting the interval of the jig in the traveling direction is not particularly limited, and various methods can be employed. For example, it may be a type of independent driving jig, or may be a type in which a plurality of jigs are connected and a plurality of jigs are controlled by one driving system. Specific examples of the type of the independently-actuatable jig include a control method using a magnetic force typified by a linear motor drive method, or a case where a rotary drive motor is attached to each jig. In such cases, control can be independently driven for all of the clamps, or a method in which only a portion of the clamps are controlled and the remaining clamps are not controlled. Further, as a specific example of the type in which a plurality of jigs are controlled by one drive system, a person who is represented by a pantograph method can be exemplified. The institute The scaler method refers to a method of controlling the distance between the clamps by controlling the distance between the two rails to open and close the scaler.

By using either method, by adjusting the position of the jig 11 on the endless chain 12, it is possible to make the interval G ₁ of the jig 11 which enters the traveling direction of the time point of the extended region and the traveling direction of the time point from the extended region. The interval G ₂ between the jigs 11 is a desired interval, and is controlled such that the interval between the jigs 11 in the traveling direction in the extended region is gradually reduced. Furthermore, the tenter shown in FIG. 3 is an example, and the tenter used in the manufacturing method of the present invention may be configured as follows: a chain 12 without wraparound travel, by using the position adjusting mechanism as described above By controlling the position of the jig, the jig can be moved together with the laminated film while gradually increasing the interval between the width directions of the jigs, and gradually reducing the interval between the moving directions of the jigs.

(staining step)

Here, the resin layer of the stretched laminated film is dyed by a dichroic dye. Examples of the dichroic dye include iodine or an organic dye. As the organic dye, for example, red BR, red LR, red R, pink LB, jade red BL, purple red GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy blue RY, green LG, purple LB, purple B can be used. , Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Bright Purple BK, Super Blue G, Super Blue GL, Super Orange GL, Direct Blue, Directly resistant to light orange S, light fast black, etc. These dichroic substances may be used alone or in combination of two or more.

The dyeing step is performed, for example, by immersing the entire laminated film in a solution (dyeing solution) containing the above-described dichroic dye in the dyeing tank 20. As the dyeing solution, a solution in which the above dichroic dye is dissolved in a solvent can be used. As the solvent of the dyeing solution, water is usually 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, particularly preferably 0.025 to 5% by weight.

When iodine is used as the dichroic dye, the dyeing efficiency can be further improved. Therefore, it is preferred to further add the iodide. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. Wait. The addition ratio of the iodides is preferably from 0.01 to 20% by weight in the dyeing solution. Among the iodides, potassium iodide is preferably added. In the case of adding potassium iodide, the ratio of iodine to potassium iodide is preferably in the range of 1:5 to 1:100 by weight ratio, more preferably in the range of 1:6 to 1:80, and particularly preferably in the range of 1:5 to 1:80. : Within the range of 7~1:70.

The immersion time of the stretched film in the dyeing solution is not particularly limited, but is usually preferably in the range of 15 seconds to 15 minutes, more preferably 30 seconds to 3 minutes. Further, the temperature of the dyeing solution is preferably in the range of 10 to 60 ° C, more preferably in the range of 20 to 40 ° C.

In the dyeing step, the crosslinking treatment may be carried out after the dyeing. The crosslinking treatment can be carried out, for example, by immersing the laminated film in a solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, a previously known substance can be used. For example, a boron compound such as boric acid or borax, glyoxal or glutaraldehyde can be mentioned. These may be one type or two or more types may be used in combination.

As the crosslinking solution, a solution obtained by dissolving a crosslinking agent in a solvent can be used. As the solvent, for example, water may be used, and further, an organic solvent compatible with water may be contained. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of 1 to 20% by weight, more preferably 6 to 15% by weight, but is not limited thereto.

Iodide may also be added to the crosslinking solution. By adding an iodide, the polarization characteristics in the surface 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, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The content of the iodide is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

The immersion time of the laminate film in the crosslinking solution is usually preferably from 15 seconds to 20 minutes, more preferably from 30 seconds to 15 minutes. Moreover, the temperature of the crosslinking solution is preferably in the range of 10 to 90 ° C Inside.

Preferably, the washing step and the drying step are finally performed. As a washing step, a water washing treatment can be performed. The water washing treatment can be usually carried out by immersing the stretched film in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually from 3 to 50 ° C, preferably from 4 ° C to 20 ° C. The immersion time is usually 2 to 300 seconds, preferably 3 seconds to 240 seconds.

The washing step may also be a combination of a washing treatment using an iodide solution and a water washing treatment, or a solution in which a liquid alcohol such as methanol, ethanol, isopropanol, butanol or propanol is appropriately formulated.

Preferably, the drying step is carried out after the washing step. As the drying step, any appropriate method (for example, natural drying, air drying, and heat drying) can be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C, and the drying time is usually about 1 to 15 minutes. Through the above dyeing step, the resin layer becomes a function as a polarizing element. In the present specification, a resin layer having a function as a polarizing element is referred to as a polarizing element layer, and a layered body including a polarizing element layer on a base film is referred to as a polarizing laminated film.

(polarized element layer)

Specifically, the polarizing element layer is a method in which a dichroic dye is adsorbed and aligned on a uniaxially stretched polyvinyl alcohol-based resin layer.

The thickness of the polarizing element layer (the thickness of the polyvinyl alcohol-based resin film after stretching) of the polarizing laminated film produced by the production method of the present invention is preferably 10 μm or less, and more preferably 7 μm or less. By making the thickness of the polarizing element layer 10 μm or less, a thin polarizing laminated film can be formed.

The method for producing the polarizing laminated film of the present invention has been described above, and the lateral stretching step of the laminated film described above can also be used as a method for extending the laminated film.

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

[Examples]

(1) Fabrication of substrate film

By using co-extrusion molding of a multilayer extrusion molding machine, a substrate film of a three-layer structure based on random copolymerization of propylene/ethylene containing 5% by weight of ethylene units was produced. On both sides of the resin layer (Sumitomo Noblen W151, manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 138 °C), homopolymer containing homopolymer of propylene (Sumitomo Chemical Co., Ltd.) Noblen FLX80E4", melting point Tm = 163 ° C) resin layer. The total thickness of the obtained base film was 100 μm, and the thickness ratio of each layer (FLX80E4/W151/FLX80E4) was 3/4/3.

(2) Formation of undercoat layer

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a concentration of 3% by weight. Aqueous polyvinyl alcohol solution. To the obtained aqueous solution, 5 parts by weight of a crosslinking agent (Sumirez Resin 650) manufactured by Sumitomo Chemical Co., Ltd.) was mixed with 6 parts by weight of the polyvinyl alcohol powder. The obtained mixed aqueous solution was continuously applied to the corona-treated surface of the substrate film subjected to corona treatment using a gravure coater, and dried at 80 ° C for 10 minutes, thereby forming a primer having a thickness of 0.2 μm. The layer is formed into a film comprising a composition of an undercoat layer/substrate film. Further, the same treatment was carried out on the opposite side of the substrate film to form a 0.2 μm undercoat layer, and a film comprising a primer layer/base film/undercoat layer was obtained.

(3) Formation of a 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 hot water at 95 ° C to prepare polyethylene having a concentration of 3% by weight. An aqueous alcohol solution. The obtained aqueous solution was continuously applied onto the undercoat layer using a Kama coater, and dried at 80 ° C for 5 minutes, thereby producing a substrate film/undercoat layer/polyvinyl alcohol-based resin layer. A three-layer laminated film. Poly The thickness of the enol type resin layer was 10.6 μm. Further, the same treatment was applied to the surface on the opposite side of the substrate film to form a 10.3 μm polyvinyl alcohol-based resin layer, thereby obtaining a resin layer/undercoat layer/base film/undercoat layer/resin layer. A laminated film formed.

(4) Extension step

The both end portions of the laminated film are held by a jig so that the distance G ₁ between the jigs in the traveling direction is the value described in Table 1, and in the extended region, in the width direction at a hot air of 160 ° C The method of extending the magnification described in Table 1 was carried out. Simultaneously with the extension of the width direction, the distance between the jigs in the traveling direction is gradually reduced, so that the interval G ₂ of the jigs in the direction of travel from the time point of the extension region becomes the value described in Table 1.

(5) Dyeing step

For the stretched laminated film, a polarizing stretch film was produced in the following order. First, the stretched film was immersed in a dyeing solution at 30 ° C for about 150 seconds to dye a polyvinyl alcohol-based resin layer which was an aqueous solution containing iodine and potassium iodide, and then the excess iodine solution was washed with pure water at 10 ° C. Next, the mixture was immersed in a crosslinking solution at 76 ° C for 600 seconds, and the crosslinking solution was an aqueous solution containing 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 polarizing element layer, thereby obtaining a polarizing laminated film.

(6) Fitting step

A polarizing plate was produced in the following order using a polarizing laminated film. First, polyvinyl alcohol powder ("KL-318" manufactured by Kuraray Co., Ltd., average polymerization degree 1800) was dissolved in hot water of 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight. To the obtained aqueous solution, 1 part by weight of a crosslinking agent ("Sumirez Resin 650" manufactured by Sumitomo Chemical Co., Ltd.) was added to 2 parts by weight of the polyvinyl alcohol powder to prepare an adhesive solution.

Then, on both surfaces of the obtained polarizing laminated film, triethyl fluorene cellulose ("KC4UY" manufactured by Konica Minolta Opto Co., Ltd.) was saponified by using the above-mentioned adhesive solution. Thereafter, it was dried at 80 ° C for 5 minutes to obtain a product. Layer film. A laminated film comprising a transparent protective film/adhesive layer/polarizing element layer/undercoat layer/substrate film/undercoat layer/polarizing element layer/adhesive layer/transparent protective film was obtained. The base film is peeled off from the laminated film, and a polarizing plate having a structure of "transparent protective film/adhesive layer/polarizing element layer/undercoat layer" existing on both sides of the substrate film is obtained.

[Examples 1 to 3]

The laminated film of Examples 1 to 3 produced by carrying out the above steps (1) to (3) was subjected to the stretching step of (4) under the conditions described in Table 1, and the side surface was tapered along the width direction. The direction extends. As a result, an excessively elongated portion of the ear shape is hardly formed during the stretching, and the elongation can be favorably extended without causing the fracture.

[Example 4]

The same procedure as in Examples 1 to 3 was carried out except that a 180 μm film produced by melt-extruding a cycloolefin polymer resin (glass transition temperature Tg of 135 ° C) was used instead of the above (1) as a base film. The laminate film of Example 4 was produced by carrying out the steps (2) and (3). The laminate film of Example 4 produced in this manner was subjected to the extension step of (4) under the conditions described in Table 1, and was stretched in the width direction while being contracted in the traveling direction. As a result, an excessively elongated portion of the ear shape is hardly formed during the stretching, and the elongation can be favorably extended without causing the fracture.

[Comparative Examples 1 to 5]

The laminate film of Comparative Examples 1 to 5 produced by carrying out the above steps (1) to (3) was subjected to the extension step of (4) under the conditions described in Table 1, and the film was contracted along the traveling direction while being along the width. The direction extends. As a result, the ear-shaped overhanging portion at the end portion in the width direction of the laminated film is elongated from the middle of the stretching, and the stress is concentrated on the excessively extended portion of the ear shape, and the laminated film is broken during the stretching, and the film cannot be stably obtained.

[Comparative Examples 6 to 8]

Using the same base film as in Example 4, the steps (2) and (3) described above were carried out to prepare laminated films of Comparative Examples 6 to 8. The laminated film of Comparative Examples 6 to 8 produced in this manner is shown in Table 1. The extension step of (4) is carried out under the conditions described so as to extend in the width direction while being contracted in the traveling direction. As a result, the ear-shaped overhanging portion at the end portion in the width direction of the laminated film is elongated from the middle of the stretching, and the stress is concentrated on the excessively extended portion of the ear shape, and the laminated film is broken during the stretching, and the film cannot be stably obtained.

From the above results, it is understood that whether or not the resin constituting the base film is a crystalline resin or an amorphous resin, whether or not the elongation can be favorably performed is related to the distance G ₁ between the jigs in the traveling direction before stretching. That is, the first to fourth embodiments in which the interval G ₁ of the jig in the traveling direction before the extension is 100 mm or less can be favorably extended, whereas the interval G ₁ of the jig in the traveling direction before the extension exceeds 100 mm. In Examples 1 to 8, the fracture occurred and the elongation could not be performed satisfactorily.

Further, no film fracture occurred in the case where the base film was separately stretched, whether it was a crystalline resin such as a polyolefin resin or an amorphous resin such as a cycloolefin polymer resin. Therefore, it is considered that the elongation at the time of stretching in the results of Table 1 is caused by the elongation stress of the polyvinyl alcohol-based resin layer laminated on the base film.

When the polyvinyl alcohol-based resin is extended, if it is extended at a temperature exceeding 180 ° C, the resin is likely to be deteriorated and yellowed, which is usually at 180 ° C or lower. The extension is carried out at the temperature. However, this temperature zone is a temperature which is considerably lower than the crystalline melting point (Tm) of the polyvinyl alcohol resin. Therefore, the stress of the polyvinyl alcohol resin layer at the time of stretching is very high. On the other hand, when the base film is extended at 160 ° C as described above, if it is a crystalline resin such as polypropylene, it is a temperature near the melting point, and is amorphous such as a cycloolefin polymer resin. The resin is a temperature near or above the glass transition temperature (Tg), so it is extended in a state where the stress is low, and it is considered that it is difficult to break. Actually, it is understood from the reference examples shown below that the ear-like overhanging portion is formed only when the base film is stretched, but the crack is not caused.

[Reference Example 1~8]

The base film similar to the base film used in Examples 1 to 3 and the base film used in Example 4 was stretched by the method shown in the above (4) under the conditions shown in Table 2. The results are shown in Table 2.

A method of calculating the ratio of the ear-shaped excessive extension portion in the results shown in Table 2 will be described with reference to Fig. 5 . Fig. 5 is a view schematically showing a substrate film after stretching. As shown in Fig. 5, in the base film 4, a necked region 4a is formed between the portions held by the jig, and an ear-shaped overhanging portion 4b is formed in a portion held by the jig. The ratio of the ear-shaped overextended portion is a value calculated by (L1 - L2) / L1 × 100 using the width L1 of the ear-shaped overhanging portion 4b and the width L2 of the necked region 4a.

According to the results shown in Table 2, if only the base film was used, no fracture occurred in any of Reference Examples 1 to 8, but the distance between the jigs before the extension exceeded 100 mm (Reference Examples 4 to 8). In the middle, the ratio of the excessively extended portion of the ear to the width direction of the film exceeded 10%, and the elongation ratio was 10% or more lower than the setting described in Table 2. Further, in the films of Reference Examples 4 to 8, the alignment between the region (the over-extended portion 4b in the ear shape) held by the jig and the jig (the necked region 4a) was caused by the difference in the stretching manner. Poor, under the orthogonal polarization, a stripe pattern can be observed, lacking uniformity. Therefore, it can be seen that when the jig interval of the traveling direction before the extension exceeds 100 mm, a good polarizing plate cannot be obtained even if no breakage occurs.

[Example 5]

The polarizing plate of Example 5 was produced by carrying out the above steps (5) and (6) using the laminated film obtained by the extension obtained in Example 2. The obtained polarizing plate was uniform without uniformity. Further, the obtained polarizing plate was measured for the monomer transmittance and the degree of polarization by using an ultraviolet-visible spectrophotometer V-7100 (manufactured by JASCO Corporation). The results are shown in Table 3.

[Comparative Example 9]

The laminated film produced by performing the above steps (1) to (3) has a gap G ₁ of the jig in the traveling direction before the extension is 50 mm, and extends 5.8 times in the width direction in the extended region without moving. The contraction of the direction. Further, other conditions of the extending step are as described in the above (4). Thereafter, the steps of (5) and (6) above were carried out to produce a polarizing plate of Comparative Example 9. The polarizing plate obtained was uniform. Further, the obtained polarizing plate was measured for the monomer transmittance and the degree of polarization by using an ultraviolet-visible spectrophotometer V-7100 (manufactured by JASCO Corporation). The results are shown in Table 3.

As shown in the results shown in Table 3, the polarizing plate of Example 5 which was shrunk in the traveling direction obtained excellent polarizing characteristics, whereas the polarizing plate of Comparative Example 9 which did not shrink in the traveling direction was inferior in polarization degree, and was not obtained. Fully polarized properties.

[Industrial availability]

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

1‧‧‧ laminated film

11‧‧‧Clamp

12‧‧‧Circular chain

13‧‧‧Active sprocket

14‧‧‧Driven sprocket

A ₁ ‧‧‧Transition path

A ₂ ‧‧‧Travel path between the driven sprocket 14 and the drive sprocket 13

D ₁ ‧‧‧Clamp spacing in the width direction of the point in time to the extended area

D ₂ ‧‧‧Clamp spacing in the width direction from the point in time of the extension

G ₁ ‧‧‧Clamp interval for the direction of travel to the extended zone

G ₂ ‧‧‧Clamping interval in the direction of travel from the point of extension

Claims (5)

A method for producing a polarizing laminated film, comprising: a lateral stretching step of extending a substrate film and a laminated film of a polyvinyl alcohol-based resin having a thickness of 3 μm or more in a width direction; and a dyeing step, The polyvinyl alcohol-based resin layer of the stretched laminated film is dyed by a dichroic dye to form a polarizing laminated film; and the lateral stretching step is a step of: extending both ends of the laminated film in the width direction By holding a plurality of jigs arranged in the traveling direction, the jig is moved along with the laminated film in the extended region, and the laminated film is extended in the width direction by enlarging the jig spacing in the width direction, and The laminated film is shrunk in the traveling direction by narrowing the jig interval of the moving direction; the jig interval of the moving direction entering the extending region is 50 to 100 mm, and the jig interval of the moving direction away from the extending region For a size of 50 mm or less, the width of each of the above jigs is 40 mm or less. The method for producing a polarizing laminated film according to claim 1, wherein the jig interval in the traveling direction from the time point of the extending region is 50% or less of the jig interval in the traveling direction of the time point to the extending region. The method for producing a polarizing laminated film according to claim 1 or 2, wherein the stretching ratio in the lateral stretching step is 4 times or more. The method for producing a polarizing laminated film according to any one of claims 1 to 3, wherein the polyvinyl acetate-based resin layer of the stretched laminated film has a thickness of 10 μm or less. A method for extending a laminated film, comprising: a lateral stretching step of extending a substrate film and a laminated film of a polyvinyl alcohol-based resin having a thickness of 3 μm or more in a width direction; and the lateral stretching step is as follows : the width direction of the laminated film that will be transferred The two end portions are held by a plurality of jigs arranged in the traveling direction, and the jig is moved along with the laminated film in the extended region, and the laminated film is formed in the width direction by enlarging the jig interval in the width direction. Extending, and shrinking the laminated film in the traveling direction by narrowing the jig spacing of the moving direction; the jig interval of the moving direction entering the extending region is 50 to 100 mm, and moving away from the extended region The jig interval of the direction is 50 mm or less, and the width of each of the above jigs is 40 mm or less.