TW201350933A - Method for manufacturing polarizing laminated film - Google Patents

Abstract

This invention provides a method for manufacturing a polarizing laminated film, in which stretching and shrinking are performed while the following relation (1) is satisfied during a first period and the following relation (2) is satisfied during a second period: MD magnification ≤ (-0.2) *TD magnification +1.2 Formula (1) MD magnification ≤ (-0.1/3) *TD magnification +0.7 Formula (2) wherein: the TD magnification means a multiplying power of the length of stretching of the width of a polyvinyl alcohol resin layer at the stretching process with respect to the length of width at the starting of the stretching process; and the MD magnification means a multiplying power of the longitudinal length at the shrinking process with respect to the longitudinal length at the starting of the stretching process; while the first period means a period in which 1.0 < TD magnification ≤ 3.0, and the second period means a period in which TD magnification > 3.0.

Description

Method for producing polarizing laminated film

The present invention relates to a method of producing a polarizing laminated film.

A polarizing plate is widely used as a polarizing supply element of a display device such as a liquid crystal display device. Such a polarizing plate has been conventionally formed by using a polarizing layer made of a polyvinyl alcohol-based resin and a protective film such as triacetyl cellulose. In addition to the development of mobile devices such as notebook personal computers and mobile phones that are facing liquid crystal display devices, the polarizing layer (polarizing film) is required to have high optical performance.

As an example of a method for producing a thin polarizing plate, it is proposed to apply a solution containing a polyvinyl alcohol-based resin to a surface of a base film and to provide a laminated layer of a base film and a resin layer, and then by using a resin layer. A method of forming a polarizing layer having a polarizing layer by dyeing, crosslinking (fixing), drying, and forming a polarizing layer from a resin layer. A method of directly using this as a polarizing plate or a method of using a polarizing plate by peeling off a base film after bonding a protective film to the film is known.

In the step of extending the laminated film, one side is extended in one direction The stretched side is contracted in a direction perpendicular thereto, whereby a uniaxially oriented polarizing film can be obtained, but a free end longitudinal uniaxial stretching is generally employed as the aforementioned extension. However, when the free end longitudinal uniaxial stretching is performed, the width of the raw material is remarkably narrowed due to the natural necking in the width direction. On the other hand, as a method of avoiding such a problem, a method of manufacturing a polarizing film by extending in the width direction (laterally extending) is described in Japanese Laid-Open Patent Publication No. 2003-43257 (Patent Document 1).

(previous technical literature)

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

When the lateral uniaxial stretching is described in Patent Document 1, the polarizing performance of the polarizing film is improved by shrinking by 2% or more in the direction perpendicular to the extending direction, but it is required to further improve the polarizing performance.

An object of the present invention is to provide a method of stretching in the width direction while shrinking in the longitudinal direction and manufacturing a polarizing laminated film, and a method of producing a polarizing laminated film having good polarizing properties.

As a result of intensive studies, the present inventors have found that even if the stretching ratio in the final width direction and the shrinking magnification in the longitudinal direction are the same, a difference in polarization performance occurs due to the stretching speed in the width direction and the shrinking speed in the longitudinal direction during the stretching process, thereby completing the present invention. invention. The invention includes the following.

[1] A method for producing a polarizing laminated film, which is a kit The step of extending the elongated laminated film and the long laminated film of the polyvinyl alcohol-based resin layer in the width direction while shrinking in the longitudinal direction to obtain an extended film; and the polyvinyl alcohol which will stretch the film a dyeing step in which the resin layer is dyed with a dichroic dye; wherein, in the stretching step, the length of the polyvinyl alcohol-based resin layer in the width direction is greater than the length at the start of the stretching step, and the longitudinal direction is TD magnification, and the longitudinal direction When the ratio of the length at the time of the contraction to the length at the start of the extension step is the MD magnification, the relationship of the following formula (1) is satisfied in the first period of 1.0 < TD magnification ≦ 3.0, and the second period in the TD magnification > 3.0 is satisfied. In the relationship of the following formula (2), the above extension and the above contraction are performed.

MD magnification -(-0.2)×TD magnification+1.2 Equation (1)

MD magnification -0 (-0.1/3) × TD magnification + 0.7 Equation (2)

[2] The method for producing a polarizing laminated film according to [1], wherein the final TD ratio is 4.0 or more in the stretching step.

[3] The method for producing a polarizing laminated film according to [1], wherein the final MD magnification in the stretching step is 0.5 or less.

[4] The method for producing a polarizing laminated film according to any one of [1] to [3] wherein the final MD magnification in the stretching step is 0.2 or more.

The method for producing a polarizing laminated film according to any one of the above aspects, wherein the polyvinyl alcohol-based resin layer after the extending step has a thickness of 10 μm or less.

According to the production method of the present invention, a method of stretching in the width direction while shrinking in the longitudinal direction can produce a polarizing laminated film having better polarizing characteristics.

1‧‧‧ laminated film

2‧‧‧ Raw material rolls

3‧‧‧Polarized laminated film

4‧‧‧Substrate film

10‧‧‧Extension device

11‧‧‧ clip

12‧‧‧Circular chain

13‧‧‧Power gear

14‧‧‧ driven gear

20‧‧‧Staining tank

111‧‧‧Frame

112‧‧‧Baffle

113‧‧‧Leverage

D ₁ , D ₂ ‧‧‧ spacing in the width direction

G ₁ , G ₂ ‧‧‧ spacing in the direction of travel

Fig. 1 is a view schematically showing an apparatus suitable for use in a method for producing a polarizing laminated film of the present invention.

Fig. 2 is a plan view schematically showing an example of the internal configuration of a tenter used in the production method of the present invention.

Fig. 3 is a view schematically showing the configuration of a clip of a tenter.

Fig. 4 is a view showing a route of TD magnification and MD magnification in the extending step of the method for producing a polarizing laminated film of Examples 1 to 8 and Comparative Examples 1 to 5.

Fig. 5 is a graph showing the polarizing performance of the polarizing laminated films of Examples 1 to 8 and Comparative Examples 1 to 5.

In the method for producing a polarizing laminate film of the present invention, the long laminated film of the long base film and the polyvinyl alcohol-based resin layer is stretched in the longitudinal direction while being stretched in the longitudinal direction to obtain a stretched film. An extending step; and a dyeing step of dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye.

An embodiment of the present invention will be described below with reference to the drawings. In the drawings, the same reference numerals are used to refer to the same or equivalent parts. Moreover, the dimensions of length, width, thickness, depth, etc. The system is appropriately changed for the sake of clarity and simplification of the drawing, and does not indicate the actual dimensional relationship.

Figure 1 is a schematic representation of polarized light suitable for use in the present invention. A diagram of an apparatus for producing a laminated film. In the example shown in Fig. 1, the laminated film 1 pulled out from the material roll 2 is sequentially passed through the stretching device 10 for performing the stretching step, and the dyeing tank 20 for the dyeing step is carried out to obtain a polarizing laminated film. 3 ways to form. Although not shown in Fig. 1, the laminated film can be taken out once by the extension device 10, and then the laminated film is passed through the dyeing tank 20. In the extension device 10, both end portions in the width direction of the traveling laminated film 1 are sandwiched by a plurality of clips arranged in the traveling direction, and the clips are advanced together with the laminated film in the extending region while expanding the width direction. The slit interval extends the laminated film 1 in the width direction, and at the same time, the laminate film 1 is contracted in the traveling direction by narrowing the slit interval in the traveling direction (longitudinal direction), and the stretching step is performed.

Furthermore, although it is not shown in Figure 1, the swelling is performed. A swelling tank to be used, a crosslinking tank for crosslinking treatment, and a drying furnace for drying treatment, but may be appropriately provided as needed.

[Laminated film]

In the production method of the present invention, a long laminated film in which a long-length base film and a polyvinyl alcohol-based resin layer are laminated 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 depending on the glass transition temperature Tg or the melting point Tm. Substrate film It is preferable to use an extendable temperature range in which the polyvinyl alcohol-based resin layer laminated thereon is suitable for stretching.

Specific examples of the thermoplastic resin, such as a chain polyolefin Resin, polyester resin, cyclic polyolefin resin (northene based resin), (meth)acrylic resin, cellulose ester resin, polycarbonate resin, polyvinyl alcohol resin, vinyl acetate An ester resin, a polyacrylate resin, a polystyrene resin, a polyether oxime resin, a polyfluorene resin, a polyamide resin, a polyimine resin, a mixture or a copolymer thereof.

The base film may be composed of only one type of the above resin. The film may be a film composed of a mixture of two or more kinds of resins. The substrate film may be a single layer film or a multilayer film.

Examples of the polyolefin resin include polyethylene and polypropylene. It is easy to stabilize and extend at high magnification, so it is ideal. Further, an ethylene-polypropylene copolymer or the like obtained by copolymerizing ethylene and propylene can be used. The copolymerization may be another type of monomer, and examples of other types of monomers which may be copolymerized with propylene include ethylene and an α-olefin. The α-olefin is preferably an α-olefin having 4 or more carbon atoms, 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. 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, and the content ratio of the constituent units derived from other monomers in the copolymer may be based on "polymer analysis". The method described in page 616 of the Handbook (published in Kiyoshiya, 1995) was obtained by infrared (IR) spectrometry.

Among the above, a propylene tree constituting a propylene resin film The lipid is preferably a homopolymer using propylene, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, and a propylene-ethylene-1-butene random copolymer.

Further, the propylene resin constituting the propylene resin film The stereoregularity is preferably substantially isotactic or syndiotactic. The propylene-based resin film having a unidirectional regular propylene-based resin which is substantially in the same row or in the opposite row has better usability and good mechanical strength in a high-temperature environment.

Polyester-based resin is an ester-bonded polymer, mainly A polycondensate of a polycarboxylic acid and a polyhydric alcohol. The polycarboxylic acid to be used mainly uses a divalent dicarboxylic acid such as isophthalic acid, terephthalic acid, dimethyl terephthalate or dimethyl naphthalene dicarboxylate. Further, as the polyol to be used, a divalent diol such as propylene glycol, butylene glycol, neopentyl glycol, cyclohexane dimethanol or the like is mainly used. Specific examples of the resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, and poly Propylene dicarboxylate, dimethyl dimethyl terephthalate, cyclohexane dimethyl phthalate, and the like. These mixed resins and copolymers can be suitably used.

The cyclic polyolefin resin is preferably a norbornene resin. The cyclic polyolefin resin is a general term for a resin obtained by polymerizing a cyclic olefin as a polymerization unit, for example, Japanese Patent Laid-Open No. 1-240517 The resin described in Japanese Laid-Open Patent Publication No. Hei No. Hei No. Hei. Specific examples thereof include a ring-opened (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 (represented as a random copolymer), And such graft copolymers modified with an unsaturated carboxylic acid or a derivative thereof, and such hydrides and the like. Specific examples of the cyclic olefin include a norbornene-based monomer.

The cyclic polyolefin resin has various commercially available products. Specific example For example, 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) (Japanese Zeon) Co., Ltd.), APL (registered trademark) (manufactured by Mitsui Chemicals, Inc.), etc.

(Meth)acrylic resin can be any suitable (Meth)acrylic resin. For example, poly(meth)acrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth) acrylate copolymer, methacrylic acid Ester-acrylate-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-methacrylic acid) Cyclohexyl ester copolymer, methyl methacrylate-methyl (meth) acrylate copolymer, etc.). Preferably, a poly(meth)acrylic acid C1-6 alkyl ester such as polymethyl methacrylate is used. The (meth)acrylic resin is more preferably a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

The cellulose ester resin is an ester of cellulose and a fatty acid. Such as Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, examples of such a copolymer and a part of a hydroxyl group which are modified by other substituents may be mentioned. Particularly preferred among these are cellulose triacetate. Cellulose triacetate has many commercially available products, and it is also advantageous in terms of availability and cost. Examples of commercially available cellulose triacetate include, for example, Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), and Fujitac (registered trademark) ) TD80UZ (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD40UZ (made by Fuji Film Co., Ltd.), KC8UX2M (manufactured by Konica Minolta Co., Ltd.), KC4UY (manufactured by Konica Minolta Co., Ltd.) )Wait.

Polycarbonate-based resin is a carbonate-bonding monomer The engineering plastic composed of the polymer of the unit is a resin having high impact resistance, heat resistance and flame retardancy. Moreover, since it has high transparency, it is also suitable for optical use. A resin called a modified polycarbonate in which a polymer skeleton is modified for optical use in an optical application, a copolymerized polycarbonate having improved wavelength dependency, and the like are commercially available, and can be suitably used. Such polycarbonate resins are widely marketed, for example, PANLITE (registered trademark) (Teijin Chemical Co., Ltd.), IUPILON (registered trademark) (Mitsubishi Engineering Plastics Co., Ltd.), SD POLYCA (registered trademark) (Sumitomo Dow) Co., Ltd.), CALIBER (registered trademark) (Dow Chemical Co., Ltd.), etc.

In addition to the above thermoplastic resin, the base film can be added Add any suitable additives. Examples of such additives include ultraviolet absorbers, antioxidants, slip agents, plasticizers, release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and color formers. 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. 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 may not be sufficiently found.

The thickness of the substrate film before stretching can be appropriately determined, generally from The viewpoint of workability such as strength, usability, and the like is preferably from 1 to 500 μm, more preferably from 1 to 300 μm, still more preferably from 5 to 200 μm. The thickness of the substrate film is preferably from 5 to 150 μm.

The base film is used to improve the resin with polyvinyl alcohol The adhesion of the resin layer to be formed may be subjected to corona treatment, plasma treatment, flame treatment or the like at least on 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 of the polyvinyl alcohol-based resin layer.

(primer coating)

The undercoat layer is not particularly limited as long as it can exhibit a certain strength of adhesion between the base film and the polyvinyl alcohol-based resin layer. For example, a thermoplastic resin such as transparency, thermal 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 dissolved in a solvent use. 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; and esters such as ethyl acetate and isobutyl acetate; For example, chlorinated hydrocarbons such as dichloromethane, trichloroethylene, and chloroform; and general organic solvents such as alcohols such as ethanol, 1-propanol, 2-propanol, and 1-butanol. However, when the undercoat layer is formed using a solution containing an organic solvent, since the substrate is dissolved, it is preferred to select a solvent in consideration of the solubility of the substrate. When considering 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 a good adhesion is preferably used.

The polyvinyl alcohol resin used as the undercoat layer can be mentioned Polyvinyl alcohol resin and its derivatives. Examples of the polyvinyl alcohol resin derivative include, in addition to polyethylene formaldehyde and polyvinyl acetal, an olefin such as ethylene or propylene; and an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid; Modified by alkyl esters of saturated carboxylic acids, acrylamide and the like. Among the above polyvinyl alcohol-based resin materials, a polyvinyl alcohol resin is preferably used.

In order to increase the strength of the undercoat layer, the above thermoplastic resin A crosslinking agent can be added. A conventional agent such as an organic system or an inorganic system can be used as the crosslinking agent to be added to the resin. For the thermoplastic resin to be used, it is sufficient to appropriately select the thermoplastic resin. 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 or two-liquid curing type can be used. Ethylene glycol diepoxypropyl ether, polyethylene glycol diepoxypropyl ether, glycerol di or triepoxypropyl ether, 1,6-hexanediol diepoxypropyl ether, Epoxy such as trimethylolpropane triepoxypropyl ether, diepoxypropyl aniline or diepoxypropylamine.

The isocyanate-based crosslinking agent is exemplified by toluene diisocyanate. Ester, hydrogenated toluene diisocyanate, trimethylolpropane-toluene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis(4-phenylmethane) triisocyanate, isophorone diisocyanate and the like An isocyanate such as a ketoxime block or a phenol block.

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

The metal-based crosslinking agent may, for example, be a metal salt, a metal oxide, a metal hydroxide or an organometallic compound, and the type of the metal is not particularly limited, and may be appropriately selected. The metal salt, the metal oxide, and the metal hydroxide may have, for example, sodium, potassium, magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, lanthanum, boron, zinc, copper, vanadium, chromium, tin, etc. The above-mentioned valence metal salt and its oxides and hydroxides.

The organometallic compound refers to a structure in which at least one metal atom in the molecule directly bonds an organic group or a structure in which an organic group is bonded 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 a covalent bond but also a coordinating bond such as a chelate compound.

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

Specific examples of the above titanium organic compound include titanium, for example. Titanium orthoesters such as tetra-n-butyl acid ester, tetraisopropyl titanate, butyl titanate dimer, tetrakis(2-ethylhexyl) titanate, and tetramethyl titanate; Titanium tongs such as titanium acetonate, titanium tetraacetate, titanium acetylacetonate, titanium octyl acrylate, titanium lactic acid, titanium triethanolamine, ethyl acetate and titanium acetate; titanium such as titanium hydroxystearate Telluride class.

Specific examples of the above zirconium organic compound include, for example, positive Zirconium propoxide, zirconium n-butoxide, zirconium tetraethoxide, zirconium monoacetate, zirconium acetoacetate, ethyl acetoacetate, acetonitrile, ethyl acetate, zirconium, and the like.

Specific examples of the above aluminum organic compound include, for example, B. Acetone aluminum, aluminum organic acid clamp. Specific examples of the above-mentioned cerium organic compound include a compound having a ligand exemplified by the above titanium organic compound and zirconium organic compound.

In addition to the above low molecular crosslinking agents, methylolated three can be used. A polymer-based crosslinking agent such as a melamine resin or a polyamide resin. "SUMIREZ (registered trademark) RESIN 650 (30)" and "SUMIREZ (registered trademark) RESIN 675" (both are trade names) sold by the company Chemtex Co., Ltd. )Wait.

When a polyvinyl alcohol resin is used as the thermoplastic resin, Preferably, it is a polyamine epoxy resin, a methylolated melamine, a dialdehyde, a metal clamp crosslinker, and the like.

The thermoplastic resin used to form the undercoat layer The ratio of the crosslinking agent may be appropriately determined depending on the type of the resin, the type of the crosslinking agent, and the like, and the range of the crosslinking agent is from 0.1 to 100 parts by weight based on 100 parts by weight of the resin, particularly from 0.1 to 50. Scope of weight The selection is ideal. 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. Better 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.

The coating method used to form the undercoat layer is not limited. The roll coating method such as a bar coating method, a reverse coating method, or a gravure coating method; a slit coating method, a comma coating method, and a lip coating method (lip) A conventional method such as a coating method, a spin coating method, a screen coating method, a fountain coating method, a dip coating method, or a spray coating method is appropriately selected and used.

(polyvinyl alcohol resin layer)

The polyvinyl alcohol-based resin used for the polyvinyl alcohol-based resin layer can be saponified with a polyvinyl acetate-based resin. Polyvinyl acetate-based resin A copolymer of vinyl acetate and another monomer copolymerizable therewith can be exemplified in addition to the polyvinyl acetate of the homopolymer of vinyl acetate. 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. soap The degree of chemical conversion 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%, still more preferably in the range of 94.0 mol% to 99.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance and the moist heat resistance after the formation of the polarizing layer are remarkably deteriorated.

The term "saponification degree" in this specification means a polyvinyl alcohol tree. The ratio of the acetic acid group contained in the polyvinyl acetate-based resin of the raw material of the fat to the hydroxyl group by the saponification step is expressed by the unit ratio (% by mole) and is a value defined by the following formula: Degree of saponification (% by mole) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100

It can be obtained according to the method specified in JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of the hydroxyl group, that is, the lower the proportion of the acetate group which hinders crystallization.

Moreover, the polyvinyl alcohol resin can be modified by a part of the modification. Polyvinyl alcohol. Examples of the polyvinyl alcohol-based resin include 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; and a modified acrylamide. The proportion of the modification is preferably less than 30 mol%, more preferably less than 10%. When the modification exceeds 30 mol%, the dichroic dye becomes difficult to adsorb and causes a problem that the polarizing performance is lowered.

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

A polyvinyl alcohol-based resin having such characteristics can be exemplified For example, Kuraray PVA124 (saponification degree: 98.0 to 99.0 mol%), PVA117 (saponification degree: 98.0 to 99.0 mol%), PVA624 (saponification degree: 95.0 to 96.0 mol%), and PVA617 (saponification degree) : 94.5 to 95.5 mol%), etc.; for example, AH-26 (saponification degree: 97.0 to 98.8 mol%), AH-22 (saponification degree: 97.5 to 98.5 mol%), NH-, manufactured by Nippon Synthetic Chemical Co., Ltd. 18 (saponification degree: 98.0 to 99.0 mol%) and N-300 (saponification degree: 98.0 to 99.0 mol%), etc.; for example, Japan VAM & POVAL Co., Ltd. JC-33 (saponification degree: 99.0 mol% or more), JM -33 (saponification degree: 93.5 to 95.5 mol%), JM-26 (saponification degree: 95.5 to 97.5 mol%), JP-45 (saponification degree: 86.5 to 89.5 mol%), JF-17 (saponification degree) : 98.0 to 99.0 mol%), JF-17L (saponification degree: 98.0 to 99.0 mol%), and JF-20 (saponification degree: 98.0 to 99.0 mol%), etc., which are suitable for use in the present invention. Formation of a vinyl alcohol resin film.

Adding plastic to the above polyvinyl alcohol resin as needed Additives such as chemicals and surfactants. As the plasticizer, polyalcohol, a polycondensate thereof, or the like 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-based resin. The thickness of the polyvinyl alcohol-based resin layer is preferably from 3 to 30 μm. 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. When the thickness exceeds 30 μm, the thickness of the polarizing layer finally obtained exceeds 10 μm, which is not preferable.

The resin layer of the present invention is preferably made of polyvinyl alcohol The polyvinyl alcohol resin solution obtained by dissolving the powder of the resin in a good solvent is applied to the surface of the base film side and evaporates the solvent. A thin resin layer can be formed by forming a resin layer in this manner. A method of applying a polyvinyl alcohol-based resin solution to a base film can be carried out by wire bar coating or reverse coating Roll coating method such as cloth method or gravure coating method; slit coating method, corner wheel coating method, lip coating method, spin coating method, screen coating method, spray coating method, Conventional methods such as dip coating and spray coating are appropriately selected and used. 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 of the present invention can be formed by laminating a raw material film composed of a polyvinyl alcohol-based resin on the surface of the base film side. Further, the resin layer may be formed only on the surface of one side of the base film, or may be formed on the surfaces on both sides.

(extension step)

In the extending step of the present invention, the laminated film is stretched in the width direction while being contracted in the longitudinal direction. In the stretching step, the ratio of the length of the polyvinyl alcohol-based resin layer in the width direction to the length at the start of the stretching step is TD magnification, and the length in the longitudinal direction is the ratio of the length at the start of the stretching step to the length at the start of the stretching step. In the case of the MD magnification, the above-described extension and the aforementioned contraction are performed while satisfying the relationship of the following formula (1) in the first period of 1.0 < TD magnification ≦ 3.0 and satisfying the relationship of the following formula (2) in the second period of TD magnification > 3.0. .

MD magnification -(-0.2)×TD magnification+1.2 Equation (1)

MD magnification -0 (-0.1/3) × TD magnification + 0.7 Equation (2)

In addition, since the laminated film is extended in the width direction in the extending step, the TD magnification becomes a value larger than 1.0, and the laminated film shrinks in the longitudinal direction, so that the MD magnification becomes a value of less than 1.0.

According to the above formulas (1), (2), one step of the extension step The upper limit of the MD magnification at the intermediate point is defined by the TD magnification. The upper limit value of the MD magnification indicates the degree of shrinkage in the longitudinal direction which should satisfy the minimum at a certain point in the extending step, and therefore, for example, the MD magnification is the upper limit value of the formula (1) or the formula (2). When the stretching step is performed in the state where the degree of shrinkage is the least, the amount of change in the MD magnification is larger than the amount of change in the TD magnification in the first period of 1.0 < TD magnification ≦ 3.0 in the second period of TD magnification > 3.0. And more rapid contraction.

Especially in the initial stage of extension, in the vertical extension The direction of the direction naturally produces a large contraction. Therefore, with respect to the extension in the width direction, the degree of shrinkage in the longitudinal direction does not catch up with the natural shrinkage amount of the film in the initial stage, and becomes low in the orientation in the extending direction. In the present invention, the MD magnification of the extending step satisfies the relationship of the formula (1) or the formula (2), and particularly the initial stage (first period) of 1.0 < TD magnification ≦ 3.0 satisfies the formula (1). In the first period, the shrinkage in the longitudinal direction is sufficiently performed, and a high alignment property can be obtained in the polyvinyl alcohol-based resin layer, and a polarizing laminated film having high polarization performance can be obtained.

The extent of the extension is not limited as long as the above relationship is satisfied, and there may be a period in which the MD magnification does not change even if the TD magnification changes. Further, there may be a period in which the MD magnification changes even if the TD magnification does not change.

In the extension step of the present invention, the final TD magnification is preferably 4.0 or more and 17.0 or less. More preferably, it is 5.0 or more and 8.0 or less. When the final TD magnification is less than 4.0, the polyvinyl alcohol-based resin layer cannot be sufficiently aligned, and as a result, the degree of polarization of the polarizing layer is not sufficiently increased. On the other hand, when the final TD rate exceeds 17.0, it is easy to produce when extended. When the laminated film is broken and the thickness of the stretched film becomes too thin, the workability and workability of the subsequent step may be lowered.

In the extension step of the present invention, the final MD ratio is higher. Preferably, it is 0.5 or less, more preferably 0.45 or less. When the final MD magnification exceeds 0.5, the alignment in the width direction is hindered by the contraction stress in the longitudinal direction, and as a result, the degree of polarization of the polarizing layer is not sufficiently increased. On the other hand, when the final MD magnification becomes small, the stretched film becomes short, and the productivity is lowered because the winding roll or the like must be frequently exchanged in the subsequent step. Therefore, the final MD magnification is preferably 0.2 or more, more preferably 0.3 or more. Further, the final MD magnification becomes too small, and the laminated film may be slack and wrinkled in the stretching step, and may cause a defect at the time of winding. In order not to cause such a bad situation, the final TD magnification becomes larger, and the final MD magnification becomes smaller. It is preferable that the final MD magnification is matched with the final TD magnification, and is appropriately selected in the range in which the laminated film does not cause slack in the stretching step.

The extension processing of the extension step is not limited to one extension Stretch, can be extended in multiple stages. Even when the multi-stage is performed, the extension is performed in such a manner as to satisfy the relationship of (1) or (2). The stretching treatment can be performed, for example, simultaneously with the dyeing treatment and the crosslinking treatment. In this case, it is preferable that the extension of the dyeing step is a small amount of extension, and the shrinkage in the traveling direction may not be performed. In the case of performing in multiple stages, all stages of the integration extension process are performed, and it is preferable to carry out the extension process in such a manner that the TD magnification is 4.0 times or more.

In the extension step of the present invention, for example, as shown in FIG. The extension device 10 is performed. The stretching device 10 is a device that allows the laminated film to extend in the width direction while being contracted in the longitudinal direction. The extension device 10 can be used, for example, to pull Amplitude machine. One form of the tenter which can be used in the present invention will be described below. The tenter clips the both ends of the traveling laminated film in the width direction with a plurality of clips arranged in the traveling direction, and enlarges the clip interval in the width direction while advancing the clip together with the laminated film in the extended region. On the other hand, the laminated film is stretched in the width direction, and the laminated film is narrowed in the traveling direction to shrink the laminated film in the traveling direction (longitudinal direction).

Figure 2 is a schematic representation of the manufacturing method of the present invention. A plan view of an example of the internal configuration of the tenter used. As shown in Fig. 2, the tenter has a large number of clips 11 that sandwich both end portions of the laminated film 1 in the width direction, and the clips 11 are attached to the endless chain 12 at predetermined intervals. The endless chain 12 is disposed on both sides of the laminated film 1 and is placed between the power gear 13 on the inlet side and the driven gear 14 on the outlet side. The power gear 13 is coupled to a motor not shown, and the power gear 13 is rotated by the motor drive. Thereby, the endless chain 12 travels around the power gear 13 and the driven gear 14, and the clip 11 attached to the endless chain 12 travels around.

The traveling path of the endless chain 12 is configured such that the clip spacing in the width direction is gradually widened in the extending portion, and the interval D ₂ in the width direction of the clip 11 at the time point of leaving from the extending portion is longer than the time point entering the extending portion constituting the distance D the width direction of the clip 11 of the embodiment ₁ wide.

The tenter further has a position adjusting mechanism not shown on the figure, which adjusts the interval of the clips 11 mounted on the endless chain 12, that is, the interval of the clips 11 in the traveling direction, in the traveling path A1 of the extending portion, so that the clip 11 The interval in which the interval satisfies the relationship of the formula (1) or the formula (2) is narrowed, and the interval G ₂ in the traveling direction of the clip 11 at the time point of departure from the extension region is larger than the clip 11 at the time point of entering the extension region. The interval G _{1 in the} traveling direction is narrow. Further, in the traveling path A2 from the driven gear 14 to the power gear 13, the interval G ₁ of the clip 11 at the time point of entering the extended region is adjusted to a desired value.

Fig. 3 is a schematic view showing the configuration of the clip 11, (a) showing the clip 11 as viewed from above, and (b) showing a cross-sectional view of the clip 11. As shown in Fig. 3, the clip 11 is composed of a frame 111, a lever 113, and a shutter 112. The frame 111 is formed in a U shape, and the lower portion serves as a mounting table for the film. A lever 113 is attached to the upper portion of the frame 111 so as to be freely rotatable, and a shutter 112 is attached to the lower end of the lever 113. The lever 113 is rotated by the weight of the baffle 112, and the baffle 112 is closest to the lower portion of the frame 111, sandwiching the end portion of the laminated film therebetween. On the other hand, when the lever 113 is rotated from the state in which the laminated film is sandwiched, and the shutter 112 is separated from the lower portion of the frame 111, the sandwiched laminated film is released. In the tenter shown in Fig. 2, the sandwiching operation of the laminated film by the clip 11 is performed at the position of the power gear 13, and the releasing operation of the clip 11 is performed at the position of the driven gear 14.

The method of controlling the position adjustment mechanism for adjusting the interval of the clips in the traveling direction is not particularly limited, and various methods can be employed. For example, it can be a clip-independent drive type, or a plurality of clips can be connected and a plurality of clip types can be controlled by one drive system. Specific examples of the clip-independent drive type include, for example, a control method using a magnetic force represented by a linear motor drive method, or a case where a rotary drive motor is attached to each clip. In these cases, it is possible to control to drive all the clips independently, but it is also possible to use only a part of the clips. The rest of the free way. Alternatively, a specific example of controlling the plural clip type by one drive system may be, for example, a pantograph system. The pantograph method refers to a method of switching the pantograph and controlling the distance between the clips by controlling the distance between the two tracks.

Taking the tenter shown in FIG. 2 as an example, in the present invention The tenter used in the manufacturing method may be configured to have no chain 12 that travels around, and control the position of the clip by the position adjusting mechanism as described above, thereby causing the clip to travel together with the laminated film and making the width of the clip The interval of the directions is gradually enlarged, and the interval of the traveling direction of the clip is narrowed in such a manner as to satisfy the formula (1) or the formula (2).

The temperature of the extension must be the temperature at which the substrate film can be extended. The degree can be appropriately selected from the range of 80 to 180 ° C, and is preferably carried out at 120 ° C or higher in order to reduce the stress at the time of stretching the polyvinyl alcohol-based resin. When the temperature of the extension region is too low, the stress at the time of stretching of the polyvinyl alcohol-based resin becomes too strong to cause the laminate film to be easily broken. On the contrary, when the elongation temperature is too high, the polyvinyl alcohol-based resin dehydrates and deteriorates and is liable to yellow. Bad situation. Of course, a plurality of different temperatures can be set in the extension zone. The extension zone can, for example, impart hot air to the top or bottom of the laminate film, or both, and manage to a predetermined temperature.

Furthermore, a preheating zone can be provided upstream of the more extended zone, A heat fixing zone and a heat relaxation zone are sequentially disposed downstream of the extension zone. The preheating zone is a zone where the laminated film is preheated, the interval of the clips is not widened, and the laminated film is heated. The laminated film preheated in the preheating zone is moved to the extension zone. The extension is as described above in the width direction by enlarging the interval of the clips Extended area. In the present invention, shrinkage in the traveling direction of the laminated film is also performed in the extension region. The laminated film that has extended over the extension extends to the heat-fixing zone. In the heat-fixing zone, a region where the heat treatment is performed at a crystallization temperature or higher while maintaining the tension state while sandwiching the end portion of the laminated film. The crystallization of the polyvinyl alcohol-based resin layer is promoted by heat treatment in the heat-fixing zone. The laminated film which has been heat-treated in the heat-fixing zone is moved to the heat relaxation zone. The heat relaxation zone is a step of heat-treating in a state where the laminated film is relaxed, and the residual stress and the deformation component in the laminated film are removed by the heat relaxation zone. The temperature of each zone can be appropriately selected depending on the material properties of the base film or the polyvinyl alcohol-based resin layer.

(staining step)

Here, the resin layer of the extended laminated film is dyed with a dichroic dye. Examples of the dichroic dye include iodine, an organic dye, and the like. For the organic dye, for example, red BR, red LR, red R, pink LB, ruby red BL, red wine (bordeaux) GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy blue RY, green LG can be used. , purple LB, purple B, black H, black B, black GSP, yellow 3G, yellow R, orange LR, orange 3R, scarlet GL, scarlet KGL, Congo red, brilliant violet BK, Super Blue G, Super Blue GL, Super Orange GL, Direct Sky Blue, Direct Fast Orange S, Lightfast Black, etc. These dichroic substances may be used alone or in combination of two or more.

The dyeing step is for example due to the layering in the dyeing tank 20 The entire film is immersed in a solution (dyeing solution) containing the above dichroic dye. The dyeing solution can be dissolved in a solvent using the above dichroic dye liquid. The solvent of the dyeing solution is generally water, but an organic solvent compatible with water may be further added. The concentration of the dichroic dye is preferably from 0.01 to 10% by weight, more preferably from 0.02 to 7% by weight, particularly preferably from 0.025 to 5% by weight.

When using iodine as a dichroic dye, it can be further It is preferred to add an iodide to increase the dyeing efficiency. 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 proportion of the iodide added is preferably from 0.01 to 20% by weight in the dyeing solution. Preferably, potassium iodide is added to the iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1:5 to 1:100 by weight, more preferably in the range of 1:6 to 1:80, and particularly preferably 1:7 to 1:70. The scope.

There is no special limit for the immersion time of the stretching film on the dyeing solution. The system is usually preferably in the range of 15 seconds to 15 minutes, more preferably in the range of 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 dyeing can be followed by cross-linking Reason. The crosslinking treatment can be carried out by, for example, immersing a layer in a solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, a conventionally known one can be used. For example, a boron compound such as boric acid or borax; glyoxal or glutaraldehyde can be given. These may be used alone or in combination of two or more.

The crosslinking solution can be dissolved in a solvent using a crosslinking agent. liquid. The solvent may, for example, be water, but may further comprise an organic solvent compatible with water. The crosslinking agent concentration of the crosslinking solution is not particularly limited, but is preferably 1 It is in the range of 20% by weight, more preferably in the range of 6 to 15% by weight.

Iodide can be added to the crosslinking solution. By adding iodinated The material can make the in-plane polarization characteristics of the resin layer 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 from 0.05 to 15% by weight, preferably from 0.5 to 8% by weight.

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

It is preferred to carry out the washing step and the drying step at the end. wash The net step can be carried out by a water washing process. The water washing treatment is 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 from 2 to 300 seconds, preferably from 3 seconds to 240 seconds.

The washing step can be combined with the washing of the iodide solution For the treatment with water washing, a solution of a liquid alcohol such as methanol, ethanol, isopropanol, butanol or propanol may be suitably blended.

Preferably, the drying step is carried out after the washing step. Drying step Any suitable method (for example, natural drying, air drying, and heat drying) may be employed. For example, the drying temperature at the time of heat drying is usually from 20 to 95 ° C, and the drying time is usually from about 1 to 15 minutes. By the above dyeing step, the resin layer can have a function as a polarizer. In the present specification, a resin layer having a function of a polarizer is referred to as a polarizing layer, and a laminated system having a polarizing layer on a base film is referred to as a polarizing laminated film.

(polarizing layer)

Specifically, the polarizing layer adsorbs and aligns a dichroic dye in a uniaxially stretched polyvinyl alcohol-based resin layer.

The thickness of the polarizing layer (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. A thin polarizing laminated film can be formed by the thickness of the polarizing layer being 10 μm or less.

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 layer, and then the base film can be peeled off and used as a polarizing plate composed of a polarizing layer and a protective film. use.

(Example)

The polarizing laminated films of Examples 1 to 8 and Comparative Examples 1 to 5 were produced in the following manner.

[Examples 1 to 8]

(1) Fabrication of substrate film

The homopolymerization of propylene on both sides of a resin layer composed of a random copolymer of propylene/ethylene containing 5% by weight of ethylene unit (Sumitomo Chemical Co., Ltd. "Sumitomo Noprene W151", melting point Tm = 138 ° C) A base film having a three-layer structure of a resin layer composed of a homopolypropylene (Sumitomo Chemical Co., Ltd. "Sumitomo Noprene FLX80E4" and a melting point of Tm = 163 ° C) is coextruded by a multilayer extrusion molding machine. Made by molding. 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 polyvinyl alcohol having a concentration of 3 wt%. Aqueous solution. In 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 onto the corona-treated surface of the substrate film subjected to corona treatment using a gravure coater, and dried at 80 ° C for 10 minutes to form an undercoat layer having a thickness of 0.2 μm. A film composed of an undercoat layer/substrate film. Further, the same treatment was carried out on the opposite side of the substrate film to form an undercoat layer having a thickness of 0.2 μm, and a film composed of an undercoat layer/substrate film/undercoat layer was formed.

(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 to 99.0 mol%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 8 wt%. The obtained aqueous solution was coated on the undercoat layer continuously and dried at 80 ° C for 5 minutes, thereby preparing a base film/base coat layer/polyvinyl alcohol-based resin layer. Constructed laminated film. The thickness of the polyvinyl alcohol-based resin layer was 10.6 μm. Further, the same treatment was applied to the surface on the opposite side of the base film to form a 10.3 μm polyvinyl alcohol-based resin layer, thereby obtaining a laminate of a resin layer/primer coat layer/base film/base coat layer/resin layer. membrane.

(4) Extension step

The laminated film was shrunk in the MD direction under hot air at 160 ° C It extends in the TD direction. In the middle of the stretching step, while controlling the MD magnification and the TD magnification, an extended film having a final MD magnification of 0.4 and a final TD magnification of 5.8 was obtained. In the middle of the extension step, the MD magnification when the TD magnification is 1.6 is 0.71, the MD magnification when the TD magnification is 2.0 is 0.63, the MD magnification when the TD magnification is 3.0 is 0.52, and the MD when the TD magnification is 4.0. The magnification was 0.45, and the MD magnification when the TD magnification was 5.0 was 0.41, and the stretched film having a final TD magnification of 5.8 and an MD magnification of 0.4 was produced. Fig. 4 shows a route from the start point of the extension step (MD magnification 1.0, TD magnification 1.0) to the end point (MD magnification 0.40, TD magnification 5.8) through which the TD magnification and the MD magnification pass. In addition, in FIG. 4, the upper limit defined by the formula (1) and the upper limit defined by the formula (2) are shown. As is apparent from Fig. 4, in the first to eighth embodiments, the route of the MD magnification is lower than the upper limit value defined by the formula (1) and the upper limit value defined by the formula (2).

(5) Dyeing step

For the extended laminated film, a polarizing stretch film was produced in the following order. First, the stretched film was immersed in a dyeing solution containing an aqueous solution of iodine and potassium iodide at 30 ° C for a time shown in the following Table 1, and the polyvinyl alcohol-based resin layer was dyed, and then the excess iodine solution was washed with pure water at 10 °C. Then, it was immersed in a 72 ° C crosslinking solution containing an aqueous solution of boric acid and potassium iodide for 600 seconds. Thereafter, the film was washed with pure water at 10 ° C for 4 seconds, and finally dried at 80 ° C for 300 seconds to obtain a polarizing laminated film.

(6) Production of polarizing plate

Using a polarizing laminated film, a polarizing plate was produced in the following procedure. First, polyvinyl alcohol powder (KL-318, manufactured by Kuraray Co., Ltd.) The degree of polymerization (1800) was dissolved in hot water at 95 ° C to prepare a 3 wt% aqueous solution of polyvinyl alcohol. In the obtained aqueous solution, 1 part by weight of a crosslinking agent ("SUMIREZ RESIN 650" manufactured by Sumitomo Chemical Co., Ltd.) was mixed with 2 parts by weight of the polyvinyl alcohol powder as a binder solution.

Then, on both sides of the obtained polarizing laminated film, use In the aqueous solution of the bonding agent, a transparent protective film obtained by saponifying triacetyl cellulose ("KC4UY" manufactured by Konica Minolta Optical Co., Ltd.) was attached. Then, it was dried at 80 ° C for 5 minutes to obtain a laminated film of a transparent protective film / bonding layer / polarizing layer / undercoat layer / substrate film / undercoat layer / polarizing layer / bonding layer / transparent protective film. .

The base film is peeled off from the laminated film to obtain a substrate. A polarizing plate having a structure of "protective film / adhesive layer / polarizer / undercoat layer" is present on both sides of the film.

[Comparative Examples 1 to 5]

Except for the TD multiplication rate and the MD multiplication route which are different from the starting point (MD magnification 1.0, TD magnification 1.0) to the end point (MD magnification 0.40, TD magnification 5.8) of the extension step, the immersion time for the dyeing solution is the following table. Comparative Examples 1 to 5 were produced in the same manner as in Examples 1 to 8, except for the time indicated by 2. Specifically, the route of the extension step is 0.9 times when the TD magnification is 1.6, the MD magnification when the TD magnification is 2.0 is 0.88, the MD magnification when the TD magnification is 3.0 is 0.75, and the MD magnification when the TD magnification is 4.0. The film was stretched so as to have a MD magnification of 0.50 at a TD magnification of 5.0, and an extended film having a final TD magnification of 5.8 and a final MD magnification of 0.4 was produced. Figure 4 shows the starting point from the extension step (MD) The route of the TD magnification and the MD magnification after the magnification of 1.0, TD magnification of 1.0) to the end point (MD magnification of 0.40, TD magnification of 5.8). It is understood from Fig. 4 that in Comparative Examples 1 to 5, the TD magnification change amount is extended for a route in which the MD magnification change amount is fixed, and the MD magnification is higher than the upper limit value defined by the formula (1) and the equation (2) The case where the predetermined upper limit value is high.

(7) Evaluation

For the polarizing plates of Examples 1 to 8 and Comparative Examples 1 to 5, the monomer transmittance and the degree of polarization were measured using an ultraviolet-visible spectrophotometer V-7100 (manufactured by JASCO Corporation). The results are shown in Tables 1 and 2. Fig. 5 is a graph showing the polarization degree and the monomer transmittance of the polarizing plates of Examples 1 to 8 and Comparative Examples 1 to 5.

From Table 1, Table 2, and Figure 5, it is known from Comparative Example 1 to The polarizing plates of Examples 1 to 8 have better polarizing properties than the polarizing plates of 5. Further, in Fig. 5, the polarizing performance shown by the curve B1 was exhibited when the stretching step was carried out under the same conditions as those of the polarizing plates of Examples 1 to 8. When the stretching step was carried out under the same conditions as those of the polarizing plates of Comparative Examples 1 to 5, the polarizing performance shown by the curve B2 was exhibited.

(industrial availability)

The polarizing laminated film produced by the production method of the present invention can be produced by using a polarizing plate which can be effectively applied to various displays typified by liquid crystal display devices.

1‧‧‧ laminated film

2‧‧‧ Raw material rolls

3‧‧‧Polarized laminated film

10‧‧‧Extension device

20‧‧‧Staining tank

Claims (5)

A method for producing a polarizing laminated film, comprising: extending a long laminated film and a long laminated film of a polyvinyl alcohol-based resin layer in a width direction while shrinking in a longitudinal direction to obtain an extending step of the stretched film And a dyeing step of dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye; wherein, in the extending step, the length-to-extension step of the polyvinyl alcohol-based resin layer in the width direction is extended When the magnification at the start of the length is the TD magnification and the length at the time of the contraction in the longitudinal direction is the MD magnification of the length at the start of the extension step, the following formula (1) is satisfied in the first period of 1.0 < TD magnification ≦ 3.0. The relationship between the following equation (2) is satisfied in the second period of the TD magnification > 3.0, and the above-described extension and the contraction are performed; MD magnification ≦ (-0.2) × TD magnification + 1.2 Equation (1) MD magnification ≦ (- 0.1/3) × TD magnification + 0.7 Equation (2). The method for producing a polarizing laminated film according to the first aspect of the invention, wherein the final TD magnification is 4.0 or more in the extending step. The method for producing a polarizing laminate film according to the first or second aspect of the invention, wherein the final MD magnification in the stretching step is 0.5 or less. The method for producing a polarizing laminated film according to claim 1 or 2, wherein the final MD ratio in the extending step is 0.2 or more. The method for producing a polarizing laminate film according to the first aspect of the invention, wherein the polyvinyl alcohol-based resin layer after the extending step has a thickness of 10 μm or less.