TW201634283A - Laminated film, method for producing laminated film, method for producing polarizing laminated film, method for producing polarizing plate - Google Patents

Abstract

The present invention provides a laminated film, a method for producing laminated film, a method for producing polarizing laminated film, and a method for producing polarizing plate, wherein the laminated film has a resin layer containing polyvinyl alcohol resin formed on a substrate film, and does not generate optical strip while be assembled as a polarizing plate. The laminated film of this invention has a resin layer containing polyvinyl alcohol resin formed on an elongated substrate film, wherein the maximum amplitude of the thickness in the width direction of the resin layer is 2.0 [mu]m or less.

Description

Method for producing laminated film, laminated film, method for producing polarizing laminated film, and method for producing polarizing plate

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

A conventional polarizer is produced by stretching and dyeing a germplasm of a polyvinyl alcohol-based resin (generally, a thickness of about 30 to 75 μm), and the thickness of the film after stretching is usually about 12 to 30 μm. When a film of a polyvinyl alcohol-based resin is used in an amount of 30 μm or less for film formation, there is a problem in that the film is easily broken at the time of stretching.

Therefore, in order to cope with the recent flaking of a polarizing plate, it has been proposed to apply an aqueous solution containing a polyvinyl alcohol-based resin to a base film. In this embodiment, an aqueous solution containing a polyvinyl alcohol-based resin is applied onto a base film to form a resin layer composed of a polyvinyl alcohol-based resin to obtain a laminated film, and then the laminated film is subjected to elongation and dyeing treatment. The resin layer composed of a polyvinyl alcohol-based resin imparts a polarizing function to the polarizing film. Layer (Patent Documents 1 and 2).

In the polarizing plate obtained by applying an aqueous solution containing a polyvinyl alcohol-based resin to the base film, there is a problem that optical stripes are generated in the polarizing plate. The same problem was observed in the polarizing plate obtained from the embryonic film of the polyvinyl alcohol-based resin, and it was found that the thickness of the embryonic film of the polyvinyl alcohol-based resin was uneven (Patent Document 3).

However, in the embodiment in which the aqueous solution containing the polyvinyl alcohol-based resin is applied to the base film, the thickness of the resin layer composed of the polyvinyl alcohol-based resin is measured by the following two methods, but the precise measurement is performed by The thickness of the resin layer composed of the polyvinyl alcohol-based resin and the measurement of the thickness unevenness are not easy. Therefore, the cause of the optical streaks and the method of controlling the cause were not found.

(Method 1) A method of peeling a resin layer composed of a polyvinyl alcohol-based resin from a base film to measure the thickness of the peeled polyvinyl alcohol-based resin layer. In this method, it is possible to extend the resin layer composed of the polyvinyl alcohol-based resin at the time of peeling.

(Method 2) The thickness of the laminated film before peeling off the resin layer consisting of a polyvinyl-alcohol resin, and the thickness of the base film after peeling are calculated from the difference of the polyvinyl alcohol-type resin. The method of the thickness of the resin layer. In this method, it is possible to deviate the measurement position.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2011-150313

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2012-159778

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2002-28941

An object of the present invention is to provide a laminated film, a method for producing the laminated film, a method for producing a polarizing laminated film from the laminated film, and a method for producing a polarizing plate by using the laminated film, which is formed on a substrate film. There is a resin layer composed of a polyvinyl alcohol-based resin, and is a laminated film which does not cause optical streaks when assembled into a polarizing plate.

The present invention encompasses the invention described below.

[1] A laminated film in which a resin layer composed of a polyvinyl alcohol-based resin is formed on a long base film, wherein a maximum amplitude of a thickness of the resin layer in a twist direction is 2.0 μm or less.

[2] The laminated film according to [1], wherein the periodic strength of the film thickness distribution in the twist direction of the resin layer is 0.09 or less.

[3] The laminated film according to [1], wherein the average thickness of the resin layer in the twist direction is 10 μm or less.

[4] The method for producing a laminated film according to any one of [1] to [3], comprising the following steps (1-1) and (2-1): the step (1-1) contains a poly An aqueous solution of a vinyl alcohol resin is applied onto a substrate film to form a coating layer to obtain a coating step of a substrate film having a coating layer; and step (2-1) is to transport the substrate film having a coating layer to a dry film; District, at In the drying zone, a coating layer is dried by at least one of the guide rolls, and the coating layer is dried to form a resin layer composed of a polyvinyl alcohol-based resin, thereby obtaining a step of drying the laminated film.

[5] The method for producing a laminated film according to any one of [1] to [3], comprising the following steps (1-2) and (2-2): the step (1-2) contains a poly An aqueous solution of a vinyl alcohol-based resin is coated on a substrate film to form a coating layer to obtain a coating step of a substrate film having a coating layer; and the step (2-2) is performed by floating a substrate having a coating layer The material film is transported to a drying zone, and the coating layer is dried to form a resin layer made of a polyvinyl alcohol-based resin having a thickness of 10 μm or less, thereby obtaining a drying step of the laminated film, and the dew point of the environment in the drying zone is 50° C. or less.

[6] A method for producing a polarizing laminated film, comprising the following steps (3) and (4): the step (3), wherein the laminated film according to any one of [1] to [3] is uniaxially stretched, The step of extending the extended laminated film is obtained; and in step (4), the extended laminated film is dyed to obtain a dyeing step of the polarizing laminated film having the polarizing plate layer and the substrate film.

[7] A method of producing a polarizing plate, comprising the following steps (3) to (6): (3) uniaxially stretching the laminated film according to any one of [1] to [3] to obtain an extension a step of extending the laminated film; a step of (4) dyeing the extended laminated film to obtain a polarizing laminated film having a polarizing plate layer and a substrate film; and a step (5) bonding the polarizing layer in the polarizing laminated film Transparent The film is protected to obtain a bonding step of the multilayer film; and the step (6) is to peel off the substrate film from the multilayer film to obtain a peeling step of the polarizing plate having the polarizing plate and the transparent protective film.

[8] A method for producing a monolithic body of a polarizing plate, comprising the following step (7): Step (7): cutting a monolithic body of the polarizing plate by cutting the polarizing plate according to [7] into a rectangular shape step.

According to the laminated film of the present invention, a polarizing plate free from optical stripes can be obtained.

1, 11 to 18 ‧ ‧ guide rollers

2‧‧‧Substrate film with coating layer

3‧‧‧ arrow

4‧‧‧ nozzle

5‧‧‧ arrow

Fig. 1 is a schematic view showing an example of a method of supporting a substrate film having a coating layer by a guide roller.

Fig. 2 (a) to (c) are schematic views showing an example of a method of supporting a base film having a coating layer by a guide roll.

Fig. 3 is a schematic view showing an example of a method of supporting a substrate film having a coating layer by a guide roller.

Fig. 4 is a schematic view showing an example of a method of supporting a base film having a coating layer in a state of floating in the air.

The inventors of the present invention measured the thickness of the resin layer composed of a polyvinyl alcohol-based resin by an interference type film thickness meter, and found that the optical streaks were caused by a long strip of polyvinyl alcohol-based resin. The maximum amplitude of the thickness in the twist direction in the resin layer is more than 2.0 μm. Interference membrane When the thickness is measured by a thickness gauge, it is not necessary to peel the resin layer which consists of a polyvinyl-alcohol-type resin from a base film, and the measurement position does not deviate. Therefore, the thickness of the resin layer composed of the polyvinyl alcohol-based resin can be accurately measured.

Therefore, the resin layer made of the polyvinyl alcohol-based resin of the laminated film of the present invention has a maximum amplitude in the twist direction of 2.0 μm or less. Further, in terms of optical stripes, the maximum amplitude is preferably 1.7 μm or less, more preferably 1.5 μm or less, and still more preferably 1.3 μm or less. Usually, the maximum amplitude is 0.2 μm or more.

The twist direction in the present specification means a direction perpendicular to the longitudinal direction of the elongated laminated film and parallel to the laminated film surface. When the laminated film is produced by a roll-to-roll method, the twist direction is perpendicular to the transport direction (MD direction) of the laminated film and parallel to the laminated film surface, that is, coincides with the TD direction. Of course, the length direction is consistent with the MD direction. At the same time, when the polarizing laminated film is obtained by applying the stretching treatment and the dyeing treatment to the laminated film of the present invention, the extending direction is generally the same as the longitudinal direction of the laminated film, and the absorption axis direction of the polarizing laminated film is the laminated film. The length direction is the same. This relationship is the same even in the case where the transparent protective film is bonded to the polarizing laminated film, and the polarizing plate which peels the base film is the same, and the polarizing plate is cut into a single piece of a predetermined size.

The maximum amplitude in the present specification means a value which can be measured by the following method. First, the thickness of the laminated film in the twist direction is measured by an interference type film thickness meter so that the measurement interval is 0.05 mm or more and 2 mm or less. As long as the above measurement interval is used, the difference in thickness amplitude which causes the streaks can be accurately detected. The thickness is determined by the polyvinyl alcohol in the laminated film. The measurement of the full width of the resin layer composed of the resin in the twist direction. When only a part of the thickness of the resin layer composed of the polyvinyl alcohol-based resin in the twist direction is measured, there is a possibility that the difference in thickness amplitude due to the cause of optical streaking cannot be detected. The magnitude of the difference between the maximum peak and the maximum valley in the thickness distribution in the twist direction obtained in this way is referred to as the maximum amplitude.

At the same time, it is possible to further prevent the optical stripes from being formed, and the resin layer composed of the polyvinyl alcohol-based resin preferably has no periodic structure in the thickness distribution in the twist direction. Therefore, in the laminated film of the present invention, the periodic strength in the thickness distribution in the twist direction of the resin layer composed of the polyvinyl alcohol-based resin is preferably 0.09 or less, more preferably 0.065 or less, and still more preferably 0.050 or less. Usually, the period strength of the film thickness distribution in the width direction is 0.00 or more. In the present invention, the periodic strength of the film thickness distribution means a value which can be obtained by the following method. First, the thickness distribution in the width direction as described above is fast Fourier-transformed. Among the wavenumber spectra obtained in this manner, the periodic intensity of the film thickness distribution refers to the value of the maximum amplitude in the region of the period of 30 to 70 mm.

Hereinafter, a method for producing a laminated film of the present invention, a method for producing a polarizing laminated film, and a method for producing a polarizing plate will be described.

The laminated film of the present invention can be produced by the steps comprising the following steps (1-1) and (2-1), or steps (1-2) and (2-2). The steps are explained below. Further, the step (1-1) and the step (1-2) in the present specification are collectively referred to as the step (1). Step (2-1) and step (2-2) in this specification are also collectively referred to as step (2).

Step (1-1) dissolves water containing polyvinyl alcohol resin Coating step of forming a coating layer on a substrate film to obtain a substrate film having a coating layer

Step (2-1) A drying step of transporting a substrate film having a coating layer to a drying zone to dry the coating layer to form a resin layer composed of a polyvinyl alcohol-based resin, thereby obtaining a laminated film. In the drying step, in the drying zone, the substrate film having the coating layer is carried by at least one guide roller.

Step (1-2) A coating step of applying a coating solution containing a polyvinyl alcohol-based resin onto a substrate film to form a coating layer to obtain a substrate film having a coating layer

Step (2-2) A drying step of transporting a substrate film having a coating layer to a drying zone in a floating manner, and drying the coating layer to form a resin layer composed of a polyvinyl alcohol-based resin having a thickness of 10 μm or less. The drying step of obtaining the laminated film is such that the dew point in the drying zone is 50 ° C or lower.

[step 1)]

In the step (1), an aqueous solution containing a polyvinyl alcohol-based resin is applied onto a substrate film. In particular, in the step (1-2), the aqueous solution containing the polyvinyl alcohol-based resin is applied onto the substrate film so as to have a thickness of 10 μm or less when the step (2-2) is passed.

[Substrate film]

The resin constituting the base film can be applied to a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, and elongation, and an appropriate resin can be selected in accordance with the glass transition temperature (Tg) or melting point (Tm). Specific examples of the thermoplastic resin include a polyolefin resin, a polyester resin, a cyclic polyolefin resin (northene-based resin), a (meth)acrylic resin, and cellulose. Ester resin, polycarbonate resin, polyvinyl alcohol resin, vinyl acetate resin, polyarylate resin, polystyrene resin, polyether oxime resin, polyfluorene resin, polyamine resin Polyimine-based resins, mixtures and copolymers thereof, and the like.

The base film may be a single layer film using only one type of the above resin, or may be a mixture of two or more types of resins. Of course, it is also possible to form a multilayer film instead of a single layer film.

The polyolefin resin is a polymer mainly composed of a chain olefin such as ethylene or propylene. Meanwhile, a propylene-ethylene copolymer obtained by copolymerizing ethylene on propylene or the like can also be used. The copolymerization may be a monomer other than ethylene, and examples of the monomer which can be copolymerized with propylene include, for example, an α-olefin. The α-olefin copolymerizable with propylene has a carbon number of 4 or more, and preferably an α-olefin having 4 to 10 carbon atoms. Specific examples of the α-olefin having 4 to 10 carbon atoms include linear chains of 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene. Monoolefins; branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene; vinylcyclohexane, and the like. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer. The content of the constituent unit derived from the other monomer in the copolymer can be determined by infrared (IR) spectroscopy according to the method described in the "Handbook of Polymer Analysis" (published by Kiyoshiya Shoten, 1995) on page 616. . The polyolefin-based resin is suitable as a base film in the present invention because it is easily and stably extended at a high rate.

Among the polyolefin-based resins, a propylene-based resin is also preferable, and examples thereof include a homopolymer of propylene, a propylene-ethylene random copolymer, and C. An ene-1-butene random copolymer, a propylene-ethylene-1-butene random copolymer, and the like.

The stereo regularity of the propylene resin is preferably isotactic or syndiotactic. A film composed of a propylene-based resin having substantially uniform or regular stereoregularity is excellent in workability and excellent in mechanical strength in a high-temperature environment.

The polyester resin is a polymer having an ester bond, and is specifically composed of a polycondensate of a polyvalent carboxylic acid and a polyhydric alcohol. The polycarboxylic acid used herein is mainly a dicarboxylic acid, that is, a divalent carboxylic acid or a lower alkyl ester thereof, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and naphthalene. Dimethyl dicarboxylate, etc. Meanwhile, the polyol to be used is mainly a diol, that is, a divalent alcohol, and examples thereof include propylene glycol, butylene glycol, neopentyl glycol, and cyclohexane dimethanol.

Representative examples of the polyester resin include polyethylene terephthalate which is a polycondensate of terephthalic acid and ethylene glycol. Although polyethylene terephthalate is a crystalline resin, it is easy to apply a process, such as extension, in the state before a crystallization process. The crystallization treatment may be carried out by heat treatment or the like at the time of stretching or extension as needed. Meanwhile, a copolyester which is reduced in crystallinity (or amorphous) due to copolymerization with a monomer of the polyethylene terephthalate in the skeleton of polyethylene terephthalate can also be applied. Examples of such a resin include, for example, a copolymer of cyclohexanedimethanol or isophthalic acid. These resins can also be used because of their excellent extensibility.

Specific examples of the polyester-based resin other than polyethylene terephthalate and copolymers thereof include polybutylene terephthalate and polynaphthalene. Ethylene diformate, polybutylene naphthalate, trimethyl methylene terephthalate, trimethyl methylene naphthalate, dimethyl dimethyl terephthalate, cyclohexane naphthalate Dimethyl ester and the like. These mixed resins or copolymers can also be used.

The cyclic polyolefin-based resin is a general term for a cyclic olefin, and a general exemplified by a cyclic olefin is exemplified by, for example, JP-A-1-240517, JP-A-3-14882, and JP-A-3-122137. Such as the resin described. 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 by a random copolymer) ), such graft polymers modified with unsaturated carboxylic acids or derivatives thereof, such hydrides and the like. Specific examples of the cyclic olefin include, for example, a norbornene-based monomer. The cyclic polyolefin-based resin is particularly preferably a norbornene-based resin.

A cyclic polyolefin resin has various products available on the market. Specific examples include TOPAS (manufactured by Topas Advanced Polymers GmbH), ARTON (registered trademark) (JSR (share)), and ZEONOR (registered trademark) (made by Japan Zeon) ZEONEX (registered trademark) (made by Japan Zeon Co., Ltd.), APEL (registered trademark) (Mitsui Chemical Co., Ltd.), etc.

The (meth)acrylic resin is a polymer having a (meth)acryloyl group-based compound as a main constituent monomer. For example, polymethacrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth) acrylate copolymer, methacrylic acid a copolymer of a methyl ester-acrylate-(meth)acrylic acid copolymer, a methyl methacrylate-styrene copolymer (referred to as MS resin, etc.), a methyl methacrylate and a compound having an alicyclic hydrocarbon group ( For example, methyl methacrylate-cyclohexyl (meth) acrylate copolymer, methyl methacrylate-methyl (meth) acrylate (meth) acrylate copolymer, etc.). Preferred examples thereof include a polymer having a C ₁ -C ₆ alkyl methacrylate as a main component such as methyl methacrylate. More preferable examples of the (meth)acrylic resin include methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by weight and preferably 70 to 100% by weight). .

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. Meanwhile, examples thereof include those in which the copolymer or the hydroxyl group is modified by another substituent. Among them, cellulose triacetate is particularly preferred. Products having sold a variety of cellulose triacetates have been commercially available and are readily available or cost effective. Examples of the commercially available product of the cellulose triacetate film include FUJITAC (registered trademark) TD80 (Fuji Film Co., Ltd.), FUJITAC (registered trademark) TD80UF (Fuji Film Co., Ltd.), and FUJITAC ( Registered trademark) TD80UZ (Fuji Film Co., Ltd.), FUJITAC (registered trademark) TD40UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Co., Ltd.), KC4UY (Konica Minolta Co., Ltd.), etc.

The polycarbonate resin is a polymer having a carbonate bond (-O-CO-O-) in its main chain. It is a kind of engineering plastic, which is a resin with high impact resistance, heat resistance and flame retardancy. At the same time, due to its high transparency, it is also suitable for optical applications. In optical applications, there are already vendors on the market. A commercially available resin called modified polycarbonate, which is a copolymerized polycarbonate such as a modified polymer skeleton to lower the photoelastic coefficient or to improve wavelength dependence, is commercially available. Such polycarbonate-based resins are widely sold in the market, such as Pan Light (registered trademark) (manufactured by Teijin Chemical Co., Ltd.), Lupilon (registered trademark) (Mitsubishi Engineering Plastics Co., Ltd.), SD Polyca ( Registered trademark) (Sumika Styron Polycarbonate (stock) system), Calibre (registered trademark) (Limited Stallone polycarbonate (stock) system).

In addition to the above thermoplastic resin, an appropriate additive may be arbitrarily added to the base film. Examples of such an additive include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, anti-colorants, flame retardants, nucleating agents, antistatic agents, pigments, colorants, and the like. The proportion of the thermoplastic resin exemplified above in the substrate 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, and still more preferably from 70 to 99% by weight. 97% by weight is particularly good. When the proportion 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 exhibited.

The thickness of the substrate film can be appropriately determined, but it is preferably from 1 to 500 μm, more preferably from 1 to 300 μm, even more preferably from 5 to 200 μm, in terms of strength, usability, and the like. Further, the substrate film having a thickness in the range of 5 to 150 μm is preferred.

The base film has a twist of 50 cm or more, and is usually 5 m or less. When the twist of the base film exceeds 5 m, it is easy to cause slack during transportation, and when an aqueous solution containing a polyvinyl alcohol-based resin is applied, the aqueous solution containing the polyvinyl alcohol-based resin may be unevenly distributed on the base film. because Thus, it is easy to increase the maximum amplitude of the thickness in the twist direction in the resin layer made of the polyvinyl alcohol-based resin. When the substrate film has a twist of less than 50 cm, the yield is not good.

When the adhesion between the base film and the polyvinyl alcohol-based resin layer is to be improved, corona treatment, plasma treatment, flame treatment, or the like can be applied to the surface on the side where the polyvinyl alcohol-based resin layer is formed.

The tensile modulus of the base film in the 80 ° C is preferably 180 MPa or more, and more preferably 200 MPa or more. The tensile modulus of the base film at a high temperature affects the film thickness distribution of the coating layer when the aqueous solution (coating liquid) containing the polyvinyl alcohol resin is applied onto the base film. When a base film having a tensile modulus of 180 MPa or more in 80 ° C is used, when the coating layer is dried after application (step (2)), slack in the twist direction of the film is less likely to occur. Therefore, the film thickness of the resin layer made of the polyvinyl alcohol-based resin can be reduced in the twist direction, and the optical streaks can be prevented.

[Undercoat]

An undercoat layer may be formed on the substrate film before the aqueous solution containing the polyvinyl alcohol-based resin is applied onto the substrate film. The undercoat layer may be formed of a material which can exert a strong binding force between the base film and the resin layer made of a polyvinyl alcohol resin. For example, a thermoplastic resin excellent in transparency, heat stability, and elongation can be used. Specific examples thereof include an acrylic resin and a polyvinyl alcohol resin.

The resin forming the undercoat layer may be coated on the substrate film in a state of being dissolved in a solvent. When considering the influence on the environment, it is preferred to form the undercoat layer with a coating liquid for forming an undercoat layer using water as a solvent. Primer The coating liquid for layer formation may contain a crosslinking agent. Examples of the crosslinking agent include an epoxy crosslinking agent, an isocyanate crosslinking agent, a dialdehyde crosslinking agent, and a metal crosslinking agent.

The ratio of the thermoplastic resin to the crosslinking agent for forming the undercoat layer is in the range of about 0.1 to 100 parts by weight based on 100 parts by weight of the crosslinking agent of the thermoplastic resin, so that the type of the thermoplastic resin or the crosslinking agent is blended. The type and the like may be appropriately determined, and it is particularly preferably selected from the range of about 0.1 to 50 parts by weight. Meanwhile, the coating liquid for forming an undercoat layer is preferably such that the solid content concentration thereof is from about 1 to 25% by weight. Further, in the present specification, the solid fraction refers to the sum of the components from which the solvent is removed.

The thickness of the undercoat layer is preferably in the range of about 0.05 to 1 μm, more preferably 0.1 to 0.4 μm. When the thickness of the undercoat layer is 0.05 to 1 μm, the adhesion between the substrate film and the polyvinyl alcohol-based resin layer can be simultaneously achieved, and the polarizing plate can be thinned.

When the undercoat layer is formed, the coating method to be used is not particularly limited, and may be applied by a wire bar coating method such as a roll coating method such as reverse coating or gravure coating, a die coating method, or a corner wheel coating method. Suitable methods such as a lip coating method, a spin coating method, a screen coating method, a spray coating method, a dip coating method, and a spray coating method are appropriately selected.

[Aqueous solution containing polyvinyl alcohol resin]

Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol resins and derivatives thereof. The derivative of the polyvinyl alcohol resin, in addition to polyvinyl alcohol formaldehyde, polyvinyl acetal, etc., may be, for example, a polyvinyl alcohol resin modified by an olefin such as ethylene or propylene; such as acrylic acid or methacrylic acid. Crotonic acid Unsaturated carboxylic acid modifier; modified by alkyl ester of unsaturated carboxylic acid; modified by acrylamide. The proportion of the modified is preferably less than 30 mol%, and more preferably less than 10 mol%. When the modification is performed at 30 mol% or more, the dichroic dye is less likely to be adsorbed, and the polarizing performance is lowered to cause a problem. Among the above polyvinyl alcohol-based resins, a polyvinyl alcohol resin is preferably used.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably in the range of 100 to 10,000, more preferably in the range of 1,000 to 10,000, more preferably in the range of 1,500 to 8,000, and most preferably in the range of 2,000 to 5,000. . The average degree of polymerization can be determined by the method specified in JIS K 6726-1994 "Testing methods for polyvinyl alcohol". When the average degree of polymerization is less than 100, it is difficult to obtain a preferable polarizing performance, and when it exceeds 10,000, the solubility in a solvent is deteriorated, and it is difficult to form a polyvinyl alcohol-based resin layer.

The polyvinyl alcohol-based resin is preferably a saponified product of a polyvinyl acetate-based resin. The degree of saponification is preferably in the range of 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 94 mol% or more. When the degree of saponification is too low, the water resistance or the moist heat resistance when the polarizing laminated film or the polarizing plate is formed may be insufficient. At the same time, although it may be a completely saponified product (the degree of saponification is 100% by mole), when the degree of saponification is too high, the dyeing speed is slowed, and the manufacturing time for imparting sufficient polarizing performance is elongated, or the case However, it is impossible to obtain a polarizer having sufficient polarizing properties. Therefore, the degree of saponification is preferably 99.5 mol% or less, and more preferably 99.0 mol% or less.

The degree of saponification refers to a ratio of the acetic acid group (acetoxy group: -OCOCH ₃ ) 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 treatment, in terms of a unit ratio ( Mohr %) is expressed by the following formula.

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

The higher the degree of saponification, the more the proportion of the hydroxyl group is represented, and the smaller the proportion of the acetate group which hinders crystallization. The degree of saponification can be determined by the method specified in JIS K 6726-1994 "Testing methods for polyvinyl alcohol".

The polyvinyl acetate-based resin may, for example, be a copolymer of a monomer copolymerizable with vinyl acetate, or the like, in addition to a polyvinyl acetate of a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

For the commercially available product of the polyvinyl alcohol-based resin, for example, "PVA124" (saponification degree: 98.0 to 99.0 mol%) and "PVA117" ("saponification degree" of Kuraray Co., Ltd., which are all trade names: 98.0 to 99.0 mol%), "PVA117H" (saponification degree: 99.5 mol% or more), "PVA624" (saponification degree: 95.0 to 96.0 mol%), "PVA617" (saponification degree: 94.5 to 95.5 mol%) "AH-26" (saponification degree: 97.0 to 98.8 mol%), "AH-22" (saponification degree: 97.5 to 98.5 mol%), "NH-18" manufactured by Japan Synthetic Chemical Industry Co., Ltd. (saponification degree: 98.0 to 99.0 mol%), "N-300" (saponification degree: 98.0 to 99.0 mol%); "JC-33" made by Japan VAM‧Poval Co., Ltd. (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) Moer %), "JF-17" (saponification degree: 98.0 to 99.0 mol%), "JF-17L" (saponification degree: 98.0 to 99.0) Moer%), "JF-20" (saponification degree: 98.0 to 99.0% by mole), and the like.

The aqueous solution containing a polyvinyl alcohol-based resin may contain an additive such as a plasticizer or a surfactant as needed. Examples of the plasticizer include a polyhydric alcohol or a condensate thereof, and specific examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the additive to be added is preferably 20% by weight or less based on the polyvinyl alcohol-based resin.

A method of applying an aqueous solution containing a polyvinyl alcohol-based resin to a substrate film is, for example, the same method as the method of applying a coating liquid for forming an undercoat layer. The aqueous solution containing the polyvinyl alcohol-based resin may be entirely coated in the full twist direction of the base film, or may be applied only to a part of the twist direction. A method of coating only a part of the twist direction may be, for example, a method of leaving an uncoated portion at both end portions of the base film. The aqueous solution containing a polyvinyl alcohol-based resin is preferably 70% or more with respect to the total thickness of the base film, and more preferably 90% or more, more preferably 95% or more.

The thickness of the coating layer depends on the target thickness after drying and the solid content of the aqueous solution containing the polyvinyl alcohol-based resin. The thickness of the coating layer is preferably 145 μm or less, and more preferably 140 μm or less. Since the coating layer is 145 μm or less, the fluidity of the coating liquid on the substrate film can be prevented until the step (2) is carried out, so that the distribution of the film thickness is more uniform, and it is particularly easy to make the maximum after the step (2). The amplitude is 2 μm or less. The thickness of the coating layer can be determined by removing the thickness after drying from the solid content of the aqueous solution containing the polyvinyl alcohol-based resin.

[Step (2-1)]

In the step (2-1), the substrate having the coating layer obtained in the step (1) The film is transported to a drying zone to dry the coating layer. The resin layer composed of a polyvinyl alcohol-based resin is formed by drying the coating layer. In the step (2-1), the substrate film having the coating layer is carried into the aforementioned drying zone by at least one of the guide rolls. However, when there are two or more drying zones as will be described later, the base film having the coating layer may be supported by the guide rolls in at least one drying zone.

At the same time, it is preferred to form the resin layer composed of a polyvinyl alcohol-based resin by curing the coating layer when passing through the final drying zone in the step (2-1). In the step (2-1), after the curing of the coating layer is completed, when the laminated film is transported to the subsequent step, or when the laminated film is wound into a roll, contamination between the laminated film and contamination of surrounding devices can be prevented. Further, uneven distribution of the aqueous solution containing the polyvinyl alcohol-based resin on the substrate film can be prevented. As long as the finger is in contact with the coating layer and does not feel moisture, it can be considered that the curing is completed.

In the present description, a region having a function of drying a coating layer such as heating or blowing is referred to as a drying zone. Examples of the drying zone include a thermo roll, a drying furnace, and a blowing air. When the drying zone is a hot roller, the heating roller itself is a drying zone, and when the drying zone is a drying furnace, the drying furnace is a drying zone, and when the drying zone is air blowing, the wind blowing zone is a drying zone.

In the drying zone in the step (2-1), any of the above-described heat roller, drying oven, and air supply may be employed. The drying zone in the step (2-1) is preferably a drying furnace, more preferably a roll supporting type drying furnace. It is also possible to provide more than two drying zones on the transport path. Further, two or more types of drying zones may be provided. The form at this time may be, for example, a combination of a hot roll and a drying furnace, a combination of a drying furnace and a blowing air, a hot roll and a blowing air. The combination form and the like.

Drying with a hot roll causes the heat roll to contact the substrate film, and the coating layer is heated, and the heat roll serves as a guide roll. The drying temperature at the time of drying with a hot roll is preferably 80 to 140 ° C, and more preferably 90 to 120 ° C. When the drying temperature is set to 80 ° C or higher, the drying time can be shortened and the yield can be improved. Moreover, the drying temperature at the time of drying by a hot roll means the surface temperature of a heat roll. The drying time by drying with a hot roll is preferably from 30 to 1,000 seconds, and more preferably from 30 to 300 seconds. Moreover, the drying time by the hot roll drying means the time when the film to be conveyed contacts the heat roller.

By drying the air, the coating layer that blows the wind onto the substrate film is achieved. In the base film having the coating layer at this time, the portion which can be blown to the wind is supported by the guide rolls. The drying temperature by air blowing drying is preferably 50 to 150 ° C and more preferably 60 to 140 ° C. Since the drying temperature is set to 50 ° C or higher, the drying time can be shortened and the yield can be improved. Moreover, the drying temperature at the time of blowing air drying means the temperature which blows the air to the coating layer. The wind speed is preferably 0.5 to 20 m/s (meters/second), and more preferably 1.0 to 15 m/s. When the wind speed is 0.5 to 20 m/s, since the base film having the coating layer can be prevented from fluttering and the drying time can be shortened, the film thickness distribution in the twist direction can be made more uniform, and the yield can be improved. The drying time by air blowing drying is preferably from 30 to 1,500 seconds, more preferably from 180 to 1,000 seconds, still more preferably from 360 to 600 seconds. The drying time when the air is dried is the sum of the time when the film to be transported is subjected to the wind.

This can be achieved by drying the drying furnace by transporting the substrate film having the coating layer into a drying furnace. Substrate having a coating layer at this time The membrane is supported in a drying oven by at least one guide roller. When the coating layer is dried by a drying furnace, the ambient temperature in the drying furnace is preferably 40 to 130 ° C, and more preferably 50 to 120 ° C. Since the drying temperature is set to 40 ° C or higher, the drying time can be shortened to improve the yield. At the same time, the dew point in the drying furnace is preferably 50 ° C or less, and more preferably 47 ° C or less. Usually the dew point in the drying oven is above 0 °C. Since the dew point is set to 50 ° C or less, the drying efficiency can be further improved, and the flow of the coating liquid can be effectively prevented. The drying time by drying in a drying oven is preferably from 30 to 1,500 seconds, more preferably from 180 to 1,000 seconds, and still more preferably from 360 to 600 seconds. The drying time when drying in a drying oven refers to the sum of time in which the film to be transported is retained in the drying furnace.

In the step (2-1), the substrate film having the coating layer in the above drying zone is supported by at least one guide roller. The substrate film having the coating layer is preferably such that the substrate film is supported on the guide rolls. The guide roller for supporting the base film having the coating layer in the drying zone is preferably two or more, and more preferably seven or more. Since the substrate film having the coating layer is supported by at least one guide roller in the drying zone, it is difficult to cause the substrate film having the coating layer to be slack, and the aqueous solution containing the polyvinyl alcohol-based resin can be on the substrate film. Uniform distribution. Therefore, the maximum amplitude of the thickness in the width direction of the polyvinyl alcohol-based resin layer tends to be small.

Hereinafter, a method of supporting a base film having a coating layer with a guide roller will be described with reference to the drawings. However, the invention is not limited to the illustrated examples.

In Fig. 1, the base film 2 having the coating layer in the above drying zone is supported by at least one guide roller 1. The drying zone at this time may be a drying furnace, which may be a blowing air or a hot roller. When the drying zone is a hot roll, the guide The roller 1 can double as a heat roller. As shown in Fig. 1, when the base film 2 having the coating layer in the drying zone is supported by one roller 1, the base film 2 having the coating layer is preferably supported by the guide roller 1. In other words, the portion of the base film 2 having the coating layer in contact with the guide rolls 1 is preferably 5% or more of the surface area of the peripheral portion of the guide roll 1, and more preferably 25% or more, and usually 50% or less. When the base film 2 having the coating layer is supported by the guide roller 1 in this manner, the base film 2 having the coating layer can be transported in a stable state without being loosened, so that the polyvinyl alcohol-based resin layer is easily formed. The maximum amplitude of the thickness in the twist direction in the medium becomes small. Arrow 3 indicates the direction of rotation of the guide roller.

Further, as shown in Fig. 1, when the base film 2 having the coating layer is supported by one of the guide rolls 1, it is preferable to increase the diameter of the guide roll 1. The diameter of the guide roller 1 is preferably 5 to 100 cm, and more preferably 5 to 50 cm. Although the transport speed of the base film 2 having the coating layer may vary, when the diameter of the guide roll 1 is 5 cm or more, the time of contacting the base film 2 having the coating layer on the guide roll 1 may be changed. long. Therefore, the base film 2 having the coating layer can be transported in a stable state without causing slack on the base film 2 having the coating layer, so that it is easy to cause flaws in the resin layer composed of the polyvinyl alcohol-based resin. The maximum amplitude of the thickness in the direction of the direction becomes small.

In Fig. 2(a), the base film 2 having the coating layer in the drying zone is supported by three guide rolls 11, 12, and 13, and the three guide rolls are disposed on a straight line. In this embodiment, since the base film 2 having the coating layer is supported by a plurality of guide rolls, it is easy to reduce the maximum amplitude of the thickness in the twist direction in the resin layer made of the polyvinyl alcohol-based resin. It is also possible to set the three guide rolls to the same height so that the substrate film 2 having the coating layer is horizontally transported to the ground. give away. At the same time, it is also possible to provide a height-height configuration in the order of the guide rolls 11, 12, 13, or a configuration in which the height of the guide rolls 11, 12, 13 is set to be low, so that the base having the coating layer is provided. The material film 2 is transported obliquely with respect to the ground.

In the second drawing (b), the base film 2 having the coating layer is supported by the three guide rolls 11, 12, 13 in the drying zone, and the guide rolls 12 at the center are provided in comparison with the other guide rolls 11 and 13 higher position. That is, the guide rolls are arranged in an arch shape in which the center guide rolls 12 are apex. Therefore, a moderate tension can be applied to the base film 2 having the coating layer in the drying zone, and the substrate film 2 having the coating layer can be transported without causing slack on the base film 2 having the coating layer. Therefore, it is easy to reduce the maximum amplitude of the thickness in the twist direction in the resin layer composed of the polyvinyl alcohol-based resin. Of course, as shown in Fig. 2(c), the base film having the coating layer is supported by the three guide rolls 11, 12, 13 in the drying zone, and the guide roller 12 at the center portion is disposed in comparison with the other guide. The lower positions of the rolls 11, 13 can apply tension to the base film 2 having the coating layer, but the surface which is in contact with the guide rolls 11, 12, 13 can be formed and coated in the base film. Since the surface of the laminate is opposite to the surface, the method shown in Fig. 2(b) is preferred.

In Fig. 3, the base film 2 having the coating layer is supported by the five guide rolls 14, 15, 16, 17, 18 in the drying zone, and the guide rolls 15, 16, 17 at the center are disposed in comparison with the other. The guide rollers 14 and 18 are in a higher position, and the central guide roller 16 is disposed at a higher position than the other guide rollers 15 and 17. By using the method as shown in Fig. 3, since the guide roller having more branches than the state shown in Fig. 2(b) is used, the distance between the guide rollers can be made small, so that the substrate film 2 having the coating layer is used. It is not easy to produce slack and can be transported in a stable state. The substrate film 2 having a coating layer is supplied. Therefore, the maximum amplitude of the thickness in the twist direction in the resin layer composed of the polyvinyl alcohol-based resin is easily reduced. In this regard, the distance between the guide rolls is preferably from 20 to 150 cm, more preferably from 30 to 100 cm. When the distance between the guide rolls exceeds 150 cm, it is easy to cause slack on the base film 2 having the coating layer, or to apply a large tension to prevent slack, and it is possible to extend the base film 2 having the coating layer.

In addition to the method shown in FIGS. 2 and 3, a method of applying a moderate tension to a base film having a coating layer, for example, a method of arranging a nip roller at the end of the base film before and after the guide roller to restrict the end, A method of combining the pinch rolls. At the same time, a vacuum suction roll can also be used to limit the substrate film having the coating layer by suction force.

The thickness of the resin layer composed of the polyvinyl alcohol-based resin in the laminated film obtained in the above step (2-1) is preferably 2 to 10 μm, more preferably 4 to 10 μm. The thickness of the resin layer composed of the polyvinyl alcohol-based resin may be 2 to 10 μm, and the polarizing performance and durability of the polarizer layer obtained in the subsequent step can be improved.

[Step (2-2)]

In the step (2-2), the substrate film having the coating layer is transported to the drying zone in a floating manner. When the coating layer is dried, a resin layer composed of a polyvinyl alcohol-based resin can be formed. At this time, the dew point of the environment in the drying zone is 50 ° C or less, preferably 47 ° C or less, and more preferably 20 ° C or less. At the same time, the dew point is usually above 0 °C. Since the dew point is set to 50 ° C or less, the drying time can be shortened, and the uneven distribution of the aqueous solution containing the polyvinyl alcohol-based resin on the substrate film can be prevented.

Further, when the final drying zone in the step (2-2) is passed, the coating layer is cured to form a resin layer composed of a polyvinyl alcohol-based resin. In the step (2-2), after the completion of the curing of the coating layer, when the laminated film is transported to the subsequent step, or when the laminated film is wound into a roll, the aqueous solution containing the polyvinyl alcohol-based resin can be prevented from being on the base film. The distribution is uneven. As long as the coating layer is touched with a finger without feeling moisture, it is considered to be completed.

In the floating mode, the nozzle 4 provided on the upper and lower surfaces of the base film 2 having the coating layer is blown as shown in Fig. 4, and the substrate film having the coating layer is floated in the air, and the coating is carried. The manner of the substrate film of the cloth layer. Further, the arrow 5 indicates the direction in which the air is blown. In the step (2-2), the drying zone may be, for example, a hot roll, a drying oven, and a blower. More than two drying zones can be set during transportation. Two or more drying zones can also be provided. The form at this time may be, for example, a combination of a drying furnace and a blowing air.

The drying by the air blowing is achieved by setting the wind blown by the nozzles provided on the upper and lower sides of the base film having the coating layer to a warm air. The drying temperature by air blowing drying is preferably 50 to 150 ° C and more preferably 60 to 140 ° C. Since the drying temperature is set to 50 ° C or higher, the drying time can be shortened and the yield can be improved. Moreover, the drying temperature at the time of drying by air blowing means the temperature of the air blown to the coating layer. The wind speed is preferably 0.5 to 20 m/sec, and more preferably 1.0 to 15 m/sec. When the wind speed is 0.5 to 20 m/sec, since the base film having the coating layer can be prevented from fluttering and the drying time can be shortened, the film thickness distribution in the twist direction can be made more uniform, and the yield can be improved. The drying time by air blowing drying is preferably from 30 to 1,500 seconds, more preferably from 180 to 1,000 seconds, and still more preferably from 360 to 600 seconds. By air supply The drying time during drying refers to the time when the film to be transported is blown to the wind.

This is achieved by drying the drying furnace by transporting the substrate film having the coating layer to the drying furnace in a floating manner. When drying in a drying oven, the ambient temperature in the drying oven is preferably 40 to 130 ° C, and more preferably 50 to 120 ° C. Since the drying temperature is set to 40 ° C or higher, the drying time can be shortened and the yield can be improved. The drying time by drying in a drying oven is preferably from 30 to 1,500 seconds, more preferably from 180 to 1,000 seconds, and still more preferably from 360 to 600 seconds. The drying time when drying in a drying oven refers to the sum of time in which the film to be transported is retained in the drying furnace.

The thickness of the resin layer composed of the polyvinyl alcohol-based resin in the laminated film obtained in the above step (2-2) is 10 μm or less as described above. Meanwhile, the thickness of the resin layer composed of the polyvinyl alcohol-based resin is preferably 2 μm or more, and more preferably 4 μm or more. When the thickness of the resin layer composed of the polyvinyl alcohol-based resin is 2 μm or more, a polarizing sheet having excellent polarizing performance and durability can be obtained.

The laminated film of the present invention can be produced by the steps including the above steps (1-1) and (2-1), or steps (1-2) and (2-2). When the polarizing laminate film or the polarizing plate is produced from the laminated film of the present invention, the following steps (3) and (4) or steps (3) to (6) may be applied to the laminated film of the present invention. When the laminated film of the present invention is produced by roll-to-roll, it may be wound into a roll as a laminated film roll by the stage of the step (2-1) or the step (2-2), or may be directly conveyed to the subsequent one without winding. step. When the laminated film of the present invention is wound into a roll of laminated film, the film thickness distribution in the twist direction is uniform, and the winding of the end portion of the laminated film is less likely to occur, and the steps of the subsequent steps can be improved. Production efficiency in steps (3) to (6). At the same time, when it is directly conveyed to the subsequent step without winding, since the winding step can be omitted, the productivity can be improved.

In the laminated film of the present invention, a resin layer composed of a polyvinyl alcohol-based resin may be formed on one surface of the base film, and of course, a resin composed of a polyvinyl alcohol-based resin may be formed on both surfaces of the base film. Floor. A method of forming a resin layer composed of a polyvinyl alcohol-based resin on both surfaces of a base film. First, after forming a resin layer on one surface of the base film, the surface of the base film on which the resin layer is not formed is applied. The steps of the above steps (1-1) and (2-1), or the steps (1-2) and (2-2) may be included. In the present specification, a laminated film in which a resin layer composed of a polyvinyl alcohol-based resin is formed on one surface of a base film is referred to as a single-area layer, and a polyvinyl alcohol-based layer is formed on both surfaces of the base film. The laminated film of the resin layer composed of the resin is referred to as a two-layer layer. The two-layer laminate is advantageous in terms of productivity because two resin layers composed of a polyvinyl alcohol-based resin are formed on one base film.

Step (3) extending the laminated film uniaxially to obtain an extension step of the extended laminated film

Step (4) dyeing the extended laminated film to obtain a dyeing project of a polarizing laminated film having a polarizing sheet layer and a substrate film

Step (5) bonding a transparent protective film on the polarizer layer in the polarizing laminated film and bonding the multi-layer film

Step (6) a peeling step of peeling off the base film from the multilayer film to obtain a polarizing plate having a polarizing plate and a transparent protective film

[Step (3)]

In the step (3), the laminated film having the base film and the resin layer composed of the polyvinyl alcohol-based resin is uniaxially stretched to obtain an extended laminated film. It is preferable to carry out uniaxial stretching at a stretching ratio of more than 5 times and 17 times or less. A better stretching ratio is more than 5 times and less than 8 times. When the stretching ratio is 5 times or less, the resin layer composed of the polyvinyl alcohol-based resin cannot be sufficiently aligned, resulting in a problem that the polarizing degree of the polarizer layer is not sufficiently increased. On the other hand, when the stretching ratio exceeds 17 times, the cracking of the laminated film is liable to occur at the time of stretching, and at the same time, the elongated laminated film is made thinner than necessary, and the workability or usability in the subsequent step may be lowered. The extension processing in the step (3) is not limited to the extension of one stage, and may be performed in multiple stages. At this time, the stretching step after the second stage may be carried out in the step (3), or may be carried out simultaneously with the dyeing treatment or the crosslinking treatment in the step (4). When such a multi-stage process is performed, the extension process of the merged whole section is performed in such a manner that the stretch ratio is more than 5 times. When the stretching is carried out in a step other than the step (3), the stretching ratio in the step (3) can be made more than 1 time and 3.5 times or less.

In the step (3), a longitudinal extension extending in the longitudinal direction of the laminated film or a lateral extension extending in the direction of the twist may be employed. When the longitudinal stretching is employed, the method may be, for example, a method of extending between rolls, a method of compressing and stretching, or the like. When the film is stretched in the lateral direction, the method may be, for example, a tenter method.

Meanwhile, the stretching treatment may be any one of a wet stretching method and a dry stretching method, but a dry stretching method is preferred because it can select a wide range of temperatures at which the laminated film is stretched.

[Step (4)]

In the step (4), the resin layer of the extended laminated film is dyed with a dichroic dye. As the dichroic dye, specifically, iodine or a dichroic organic dye can be used. Dichromatic organic dyes, for example, red BR, red LR, red R, pink LB, magenta BL, grape red GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy blue RY, green LG, Purple LB, Purple B, 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 sky blue, direct orange S, strong black and so on. These dichroic organic dyes are available on the market. The dichroic property may be used alone or in combination of two or more.

The step (4) is carried out, for example, by immersing the stretched film in a solution (staining solution) containing the above dichroic dye. As the dyeing solution, a solution in which the above dichroic dye has been dissolved in a solvent can be used. As the solvent of the dyeing solution, water can usually be used, and an organic solvent compatible with water can also be added. The concentration of the dichroic dye in the dyeing solution is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight, and particularly preferably 0.025 to 5% by weight.

When iodine is used as the dichroic dye, it is preferable to further add iodide in order to further improve the dyeing efficiency. Therefore, the iodide used is, for example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. . When iodide is added, its proportion in the dyeing solution is preferably from 0.01 to 20% by weight. Among the above-mentioned iodides, potassium iodide is preferably used. When adding potassium iodide, the ratio of iodine to potassium iodide is 1:5 by weight. A range of 1:100 is preferred, and a range of 1:6 to 1:80 is preferred, and a range of 1:7 to 1:70 is preferred.

The time during which the extended laminated film is immersed in the dyeing solution is not particularly limited, and is usually preferably in the range of 15 seconds to 15 minutes, more preferably 30 seconds to 3 minutes. Meanwhile, the temperature of the dyeing solution is preferably in the range of 10 to 60 ° C, and more preferably in the range of 20 to 40 ° C.

Further, the dyeing treatment may be carried out before or at the same time as the stretching step, but in order to give a good alignment of the dichroic dye adsorbed in the polyvinyl alcohol-based resin, the step is carried out in the unstretched laminated film ( 3) It is better to perform dyeing treatment afterwards. At this time, it is possible to simply dye the extension of the target magnification in advance, or to extend the pre-low magnification extension in the dyeing again to achieve the desired magnification. At the same time, when extending in the subsequent cross-linking process, the full stretch ratio of the stage in which the dyeing process is completed is set to be lower than the final magnification of the target. At this time, it is only necessary to appropriately adjust the target magnification after the deal processing.

In the step (4), the crosslinking treatment may be carried out after the dyeing. The crosslinking treatment can be carried out, for example, by immersing a stretched film in a solution containing a crosslinking agent (crosslinking solution). As the crosslinking agent, a conventionally known one can be used. For example, a boron compound such as boric acid or borax, or glyoxal or glutaraldehyde can be mentioned. One type of the crosslinking agent may be used alone or two or more types may be used in combination.

As the crosslinking solution, a solution in which a crosslinking agent has been dissolved in a solvent can be used. As the solvent, for example, water can be used, and an organic solvent compatible with water can also be contained. The concentration of the crosslinking agent in the crosslinking solution, although not limited, is preferably in the range of 1 to 20% by weight, and is in the range of 6 to 15% by weight. Better around.

Iodide may also be added to the cross-linking solution. By the addition of 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 in the crosslinking solution is preferably from 0.05 to 15% by weight, more preferably from 0.5 to 8% by weight.

The soaking time of the extended laminated film in the crosslinking solution is usually from 15 seconds to 20 minutes, more preferably from 30 seconds to 15 minutes. Meanwhile, the temperature of the crosslinking solution is preferably in the range of 10 to 90 °C.

Further, the crosslinking treatment may be carried out simultaneously with the dyeing treatment by blending the crosslinking agent in the dyeing solution. At this time, the film which has been previously extended to the target magnification may be immersed in the dyeing solution which has been prepared with the crosslinking agent, in which only the dyeing and crosslinking are carried out substantially, or in the dyeing solution which has been prepared with the crosslinking agent. At the same time extend. In the step (3), the target multiplying ratio can also be achieved in total by extending the extended laminated film which has been previously extended at a low magnification in the dyeing solution to which the crosslinking agent has been formulated. Of course, it may be carried out in the order of the stretching treatment, the dyeing treatment, and the crosslinking treatment. In this case, the stretching treatment may be additionally performed in the stage of the dyeing treatment and/or the crosslinking treatment. In short, it is only necessary to set the total stretching ratio to the target value in the stage in which the crosslinking treatment is completed.

It is advisable to carry out the washing step and the drying step at the end. In the washing step, water washing treatment can be employed. The water washing treatment is usually carried out by immersing the stretched film in pure water such as ion-exchanged water or distilled water. Water cleaning The temperature is usually from 3 to 50 ° C and preferably in the range of from 4 ° C to 20 ° C. The soaking time in the water is usually 2 to 300 seconds, preferably 3 to 240 seconds.

The washing step may be a combination of a washing treatment of an iodide solution and a water washing treatment, and in the washing step, a liquid alcohol such as methanol, ethanol, propanol, isopropanol or butanol may be suitably used. Aqueous solution. The iodide contained in the iodide solution may, for example, be potassium iodide, and its concentration is usually from 0.5 to 10% by weight.

After the washing step, it is preferred to apply the drying step. In the drying step, any appropriate method (for example, natural drying, air drying, heat drying, etc.) may be employed. For example, the drying temperature at the time of heat drying is usually 20 to 95 ° C, and the drying time is usually about 1 to 15 minutes. From the above step (4), the resin layer can have a function as a polarizer. In the present specification, a resin layer having a function as a polarizer is referred to as a polarizer layer, and a laminate having a polarizer layer on a base film is referred to as a polarizing laminate film.

[Step (5)]

In the step (5), a transparent protective film is bonded to the surface opposite to the surface of the substrate film side of the polarizer layer to form a multi-layer film. In the adhesion of the protective film, an adhesive or an adhesive can be used.

[protective film]

The protective film may be a simple protective film having no optical function, or may be a protective film having an optical function such as a retardation film or a brightness enhancement film. The material constituting the protective film is not particularly limited, and for example, a cyclic polyolefin resin, a cellulose acetate resin such as cellulose triacetate or cellulose diacetate, such as polyethylene terephthalate or poly Polyester of naphthalenedicarboxylate A material widely used in the field such as a resin, a polycarbonate resin, an acrylic resin, or a polypropylene resin.

For the cyclic polyolefin resin, suitable commercial products such as TOPAS (manufactured by Topas Advanced Polymers GmbH), ARTON (registered trademark) (JSR (share)), and ZEONOR (registered) can be used. Trademarks) (made by Japan Zeon Co., Ltd.), ZONEX (registered trademark) (made by Japan Zeon Co., Ltd.), APEL (registered trademark) (Mitsui Chemical Co., Ltd.), etc. When such a cyclic polyolefin resin is produced into a film, a conventional method such as a solvent die casting method or a melt extrusion method can be applied. At the same time, it is also possible to use a pre-formed film such as Esushina (registered trademark) (made by Sekisui Chemicals Co., Ltd.) or ZEONOR FILM (registered trademark) (made by Japan Zeon Co., Ltd.), and a cyclic polyolefin system which gives a phase difference depending on the case. A commercially available product of a resin film.

The cyclic polyolefin resin film may be uniaxially stretched or biaxially stretched. After stretching, any phase difference value can be imparted on the cyclic polyolefin resin film. The stretching is usually carried out continuously while winding up the film roll, and is extended in the direction in which the roll is proceeding, in a direction perpendicular to the direction in which the roll is performed, or both. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the cyclic polyolefin resin to the glass transition temperature + 100 °C. The magnification of the extension is usually 1.1 to 6 times in each direction, and preferably 1.1 to 3.5 times.

Since the cyclic polyolefin-based resin film generally has poor surface activity, it is preferred to carry out a surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, or saponification treatment on the surface adjacent to the polarizer layer. Among them, plasma treatment or corona treatment which is relatively easy to implement is suitable.

For the cellulose acetate-based resin film, suitable commercially available products can be used, for example, FUJITAC (registered trademark) TD80 (Fuji Film Co., Ltd.), FUJITAC (registered trademark) TD80UF (Fuji Film Co., Ltd.), FUJITAC (registered trademark) ) TD80UZ (Fuji Film Co., Ltd.), FUJITAC (registered trademark) TD40UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Co., Ltd.), KC4UY (Konica Minolta Co., Ltd.), and the like.

On the surface of the cellulose acetate-based resin film, a liquid crystal layer or the like can also be formed to improve viewing angle characteristics. At the same time, in order to impart a phase difference, an extended cellulose acetate resin film can also be used. The cellulose acetate-based resin film can usually be subjected to a saponification treatment to improve adhesion to the polarizer layer. The saponification treatment is carried out by immersing the membrane in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

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

In terms of thinning, the thickness of the protective film is preferably as small as possible, preferably 90 μm or less, and more preferably 50 μm or less. On the other hand, if it is too thin, the strength may be lowered to impede the workability, and therefore it is preferably 5 μm or more.

[Adhesive layer]

The adhesive may be generally composed of an acrylic resin, a styrene resin, a polyoxymethylene resin or the like as a matrix polymer, and a composition of a crosslinking agent such as an isocyanate compound, an epoxy compound or an aziridine compound is added thereto. to make. Further, it is also possible to form an adhesive layer containing fine particles and exhibiting light scattering properties.

The adhesive layer is preferably a thickness of from 1 to 40 μm, but it is preferably a thin coater, for example, having a thickness of from 3 to 25 μm, insofar as the properties such as workability or durability are not impaired. . As long as it is set to a thickness of 3 to 25 μm, it is possible to have good workability and even prevent dimensional change of the polarizing plate. When the thickness of the adhesive layer is less than 1 μm, the adhesiveness is lowered. On the other hand, if the thickness exceeds 40 μm, problems such as overflow of the adhesive tend to occur.

The method of forming the adhesive layer on the protective film or the polarizer layer is not particularly limited, and a solution containing each component containing the above-mentioned matrix polymer may be applied to the protective film surface or the polarizer layer to form a solution. After the adhesive layer, the separator or the film thereof is adhered to the adhesive layer, or after the adhesive layer is formed on the separator, it is adhered to the protective film surface or the polarizer layer to be laminated. Meanwhile, when the adhesive layer is formed on the protective film or the polarizer layer, it is also possible to apply, for example, corona treatment, on the protective film or the polarizer layer, or on one or both sides of the adhesive layer to be bonded, as needed. Closely handled.

[adhesive layer]

As the subsequent agent, for example, an aqueous adhesive prepared from a polyvinyl alcohol-based resin aqueous solution or an aqueous two-liquid polyurethane emulsion adhesive can be used. Among them, an aqueous solution of a polyvinyl alcohol-based resin is suitably used. In addition to a vinyl alcohol homopolymer obtained by subjecting a polyvinyl acetate which is a homopolymer of vinyl acetate to a saponification treatment, a vinyl alcohol-based resin which is used as an adhesive may be copolymerized with vinyl acetate. Other monomer copolymers for soap The vinyl alcohol-based copolymer obtained by the treatment also includes a modified polyvinyl alcohol-based polymer obtained by modifying these hydroxyl groups. A polyvalent aldehyde, a water-soluble epoxy compound, a melamine-based compound, a zirconia compound, a zinc compound or the like may be added as an additive to the aqueous adhesive. When such an aqueous adhesive is used, the adhesive layer usually obtained therefrom is much thinner than 1 μm, that is, the cross section is observed using a general optical microscope, and in fact, the adhesive layer is not observed.

The bonding method of the film using the aqueous adhesive is not particularly limited, and for example, the adhesive is uniformly applied or cast on the surface of the film, and the other film is also adhered to the coated surface by a roll or the like. And dry it. Usually, the adhesive is applied at a temperature of 15 to 40 ° C after its preparation, and the bonding temperature is usually in the range of 15 to 30 ° C.

When an aqueous adhesive is used, after the film is bonded, it is dried to remove water contained in the aqueous adhesive. The temperature of the drying oven is preferably in the range of 30 to 90 °C. When the drying temperature is less than 30 ° C, it tends to cause peeling from the adhesive surface. On the other hand, when the drying temperature is 90° C. or more, the optical properties of the polarizer or the like may be deteriorated by heat. The drying time can be set to about 10 to 1,000 seconds.

After drying, it may be further cured at room temperature or slightly above its temperature, for example, at a temperature of about 20 to 45 ° C for 2 to 600 hours. The temperature at which it is cured is usually set at a temperature lower than that used for drying.

Meanwhile, a non-aqueous adhesive may also be a photocurable adhesive. The photocurable adhesive agent may, for example, be a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

When a film is bonded using a photocurable adhesive, it can be used Conventionally known methods include, for example, a casting method, a Meyer bar coating method, a gravure coating method, a notch wheel coating method, a doctor blade method, a die coating method, a dip coating method, a spray method, and the like. A method in which the agent is applied to the back surface of the film to overlap the two films. The casting method refers to a method in which two sheets of the object to be coated are moved in an oblique direction in a direction perpendicular to the vertical direction, in a horizontal direction, or both, and an adhesive is applied to the surface thereof to be diffused and applied.

After the adhesive is applied to the surface of the film, the film may be adhered by nip rolls or the like. At the same time, a method in which the laminate is pressurized by a roll or the like and uniformly pushed is applied. At this time, the material of the roller may be metal or rubber. Further, it is also preferred to adopt a method in which the laminate is passed between a roll and a roll and pressurized. In this case, the rolls can be of the same material or different materials. The adhesive layer after bonding by the nip rolls is preferably a thickness of 0.01 μm or more and 5 μm or less before drying or curing.

Surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, and saponification treatment may be appropriately applied to the subsequent surface of the film to improve adhesion. The saponification treatment is carried out by immersing the membrane in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

When a photocurable resin is used as the adhesive, the film is laminated, and then the photocurable adhesive is cured by irradiation with an active energy ray. The light source of the active energy ray is not particularly limited, but is preferably an active energy ray having a light-emitting distribution at a wavelength of 400 nm or less. Specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, Black light, microwave excited mercury lamps, metal halide lamps, etc. are preferred.

The light irradiation intensity of the photocurable adhesive can be appropriately determined depending on the composition of the photocurable adhesive, and is not particularly limited, but the irradiation intensity in the wavelength region effective for activation of the polymerization initiator is 0.1. The method to 6,000 mW/cm ² is preferred. Since the irradiation intensity is appropriately selected in this range, the reaction time can be made not too long, and at the same time, yellowing of the adhesive or polarizing plate can be prevented from occurring due to heat radiated from the light source and exothermic heat when the photocurable adhesive hardens. Deterioration. The light irradiation time of the photocurable adhesive can be determined in accordance with the photocurable adhesive to be cured, and is not particularly limited, but is set so as to be a product of the above-described irradiation intensity and irradiation time. The cumulative amount of light becomes preferably 10 to 10,000 mJ/cm ² . Since the amount of accumulated light of the photocurable adhesive is appropriately selected in this range, the active species from the polymerization initiator can be sufficiently generated, and the hardening reaction can be performed more surely without causing the irradiation time to be too long. Maintain good yields. The thickness of the adhesive layer after hardening is usually about 0.001 to 5 μm, preferably 0.01 μm or more, and more preferably 2 μm or less.

When the photocurable adhesive between the polarizer layer and the protective film is cured by irradiation with the active energy ray, polarizing, transmittance, and hue of the polarizing layer, and transparency of the protective film can be used. It is good to harden the conditions of the various functions of the board.

[Step (6)]

In the step (6), the base film can be peeled off from the multilayer film having the protective film, the polarizer layer, and the base film in this order. The peeling method of the base film is not particularly limited, and it can be peeled off by the same method as the step of peeling off the release film from the self-adhesive layer used in the polarizing plate which usually has an adhesive. Adhesion step in protective film (5) Thereafter, the base film may be directly peeled off immediately, or after being once wound into a roll shape, a peeling step may be additionally provided, and then the base film may be peeled off. In this way, a polarizing plate having a protective film and a polarizing plate layer can be produced.

Further, after the protective film is bonded to the polarizer layer, a polarizing plate having a protective film, a polarizer layer, and a protective film in this order is obtained. The protective film of the new adhesion may be, for example, the same protective film as the above protective film. For the adhesion of the protective film, the same adhesive or adhesive as described above can be used. It is also possible to bond other optical films to the protective film. Other optical films include, for example, a brightness enhancement film, a film having an anti-glare function having a concave-convex surface, a film having an anti-reflection function on the surface, a reflection film having a reflection function on the surface, and a half of a reflection function and a transmission function. Transmissive reflective film, viewing angle compensation film. Other optical films and protective films may be bonded by the above-mentioned adhesive and the above-mentioned adhesive.

The polarizing plate of the present invention preferably has an adhesive layer which can bond the polarizing plate to the liquid crystal cell on the outer side of the transparent resin film (i.e., the surface opposite to the side on which the polarizing film is laminated). The above adhesive can be used as the adhesive which forms the adhesive layer to bond the polarizing plate to the liquid crystal cell. Among them, in terms of transparency, adhesion, letterability, reworkability, etc., it is preferred to use an acrylic adhesive. It is preferable to protect the adhesive layer by the separator until the polarizing plate is bonded between the liquid crystal cells.

[Step (7)]

In the step (7), the strip-shaped polarizing plate is cut into a chip cutting step of a set size. The polarizing plate manufactured by the above steps is suitable as a member constituting a display such as a liquid crystal display. Fabricating a polarizing plate by roll-to-roll In the meantime, the long polarizing plate can be cut into a single piece of a predetermined size and assembled into the display.

A method of cutting a long polarizing plate into a single piece may be, for example, a method of cutting with a cutting tool having a sharp blade, a method of cutting with laser light, and a method of combining the two methods.

The cutting tool having a sharp blade may be any tool generally used in the field of optical films, and examples thereof include a push-cut type cutter and a slicing type cutter, and a fixed circular blade or a rotating circular blade. The laser light may be, for example, a carbon dioxide (CO ₂ ) laser, a YAG laser, a semiconductor laser or the like, and a carbon dioxide laser or a semiconductor laser is preferred. At the same time, the laser light can be continuous light or pulsed light. In the above-described laser irradiation, the output power and the speed are not limited, and it is possible to cut with one irradiation or several times. The output power of the aforementioned laser irradiation is usually 10W to 800W, preferably 100W to 350W when cutting with one irradiation, and preferably 50W to 200W when cutting with 2 irradiations.

A combination method of cutting by a cutting tool having a sharp blade and cutting by laser light, for example, cutting with laser light on the way to the thickness direction of the polarizing plate, and cutting with a sharp blade Tool cutting method. In such an embodiment, the layer is cut by laser light before or after the layer having an absorptance of 5% or less from the surface layer to the laser light, and the remaining one is preferably cut by a cutting tool having a sharp blade.

The speed at which the polarizing plate is cut is related to the thickness of the polarizing plate to be cut, but it is preferably 1 m/min or more and 5 to 60 m/min as long as the thickness of the polarizing plate is in the range of 70 to 500 μm.

After the long polarizing plate is cut into a single piece in this manner, the polarizing plate monolith is preferably processed by cutting the side surface. A method for cutting a side surface of a polarizing plate by a rotary blade as described in Japanese Laid-Open Patent Publication No. 2001-54845, or a method described in Japanese Laid-Open Patent Publication No. 2003-220512 A method of continuously cutting the peripheral end portion of the polarizing plate by a fly cut method is preferable. By cutting the side wrapping surface by such a method, it is presumed that the adhesive component is uniformly covered on the side wrapping surface, and it is advantageous to prevent the polarizing plate layer from being exposed to the outside.

The shape of the polarizing plate obtained by the above step (7) is not particularly limited, but a rectangular shape is preferred. When the shape of the polarizing plate is a rectangle, the length of the long side is, for example, 5 cm or more, and the length of the short side is, for example, 3 cm or more. Although the upper limit is not particularly limited, the length of the long side and the short side is usually 5 cm or less.

[Examples]

Hereinafter, the present invention will be described by way of Examples, but the present invention is not limited to the scope of the examples.

[evaluation method] <Maximum amplitude of resin layer thickness in the width direction>

The interference film thickness gauge (F20 Filmetrics, Inc.) was used to comprehensively scan the twist direction of the laminated film, and the film thickness profile in the twist direction was measured. The layer structure of the sample was measured, and it was a resin layer composed of a base film/undercoat layer/polyvinyl alcohol resin. The measurement was performed while moving the sample in an automatic stage so that the measurement interval was 2 mm or less. In the contour of the film thickness in the twist direction obtained in this way, the difference between the maximum peak and the largest trough is set to Maximum amplitude.

<Period intensity of film thickness distribution>

The contour of the film thickness in the twist direction obtained as described above was subjected to high speed Fourier transform by Fourier analysis built in Microsoft Excel 2010. Among the wave number spectra obtained in this manner, the value of the maximum amplitude in the region of the period of 30 to 70 mm is taken as the periodic intensity of the film thickness distribution. Specifically, the number of data (A) used in the calculation at this time is smaller than the number of data (B) of the thickness profile in the width direction obtained, and is set to be the multiplier of 2 which is closest to B. When the absolute value of the Fourier transform result is C, the amplitude value is represented by 2C/A, and when the twist position of the Nth data is Ln, the period is represented by Ln/N. For the A data used in the calculation, the respective amplitudes and periods are obtained, and the maximum amplitude in the region of the period of 30 to 70 mm is obtained.

[Example 1] <Production of laminated film> (1) Substrate film

An unstretched polypropylene (PP) film (melting point: 163 ° C) having a thickness of 90 μm was prepared as a substrate film. The tensile modulus of this base film at 80 ° C was 205 MPa.

(2) Preparation of coating liquid for forming an undercoat layer

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1,100, average saponification degree: 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a polyethylene having a concentration of 3% by weight. An aqueous alcohol solution. Mixing cross-linking agent ("SUMIREZ resin" manufactured by Tadaoka Chemical Industry Co., Ltd.) in the obtained aqueous solution (registered trademark) 650"), the amount is 1 part by weight based on 2 parts by weight of the polyvinyl alcohol powder, and a coating liquid for forming an undercoat layer is obtained.

(3) Adjustment of aqueous solution containing polyvinyl alcohol resin

Polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd., average polymerization degree 2,400, 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%. An aqueous solution containing a polyvinyl alcohol-based resin.

(4) Step (1), step (2) ‧ single-area layer

While the base film was continuously conveyed, the corona treatment was applied to one surface thereof, and then the coating liquid for the undercoat layer was continuously applied onto the corona-treated surface by a dicavure coater. Then, it was dried at 60 ° C for 3 minutes to form an undercoat layer having a thickness of 0.2 μm. While continuing to transport the film, the aqueous solution containing the polyvinyl alcohol-based resin was continuously applied to the undercoat layer by a lip coater.

A resin layer composed of a polyvinyl alcohol-based resin having a thickness of 9.5 μm was formed on the undercoat layer by drying at 80 ° C for 10 minutes in a drying oven having 8 guide rolls to obtain a laminated film. At this time, the dew point in the drying furnace was 27 ° C. Before the use of the eighth roll, the feeling of no moisture was confirmed by the contact of the coating layer with a finger, so that the resin layer was judged to be a hardener.

The film thickness profile in the twist direction was obtained at a measurement interval of 0.85 mm. The maximum amplitude of the film thickness in the twist direction was 0.6 μm. At the same time, the periodic strength of the film thickness distribution at this time was 0.06.

‧ two-layer layer

Further, the same treatment was applied to the surface of the base film opposite to the surface on which the resin layer was formed, and an undercoat layer having a thickness of 0.2 μm and a polyvinyl alcohol-based resin having a thickness of 9.5 μm were formed on both surfaces of the substrate. The resin layer formed is a laminated film of a two-area layer. The dew point in the drying oven was 28 °C.

The film thickness profile in the twist direction was obtained at a measurement interval of 0.90 mm. The maximum amplitude of the film thickness in the twist direction was 0.2 μm. At the same time, the periodic intensity of the film thickness distribution at this time was 0.03.

(5) Step (3)

While continuously carrying the laminated film obtained in the above (4), the film was stretched 2.5 times in the longitudinal direction (film transport direction) at an extension temperature of 140 ° C by a stretching method between nip rolls, and then extended by 2.3 times at 160 ° C (total stretching ratio: After 5.8 times), an extended laminated film was obtained. The thickness of the resin layer composed of the polyvinyl alcohol-based resin in the extended laminated film was 5.2 μm and 5.3 μm, respectively.

<Production of polarizing laminated film> (6) Step (4)

The stretched laminated film was immersed in a dyeing solution containing iodine and potassium iodide at 30 ° C for about 150 seconds, and the resin layer made of a polyvinyl alcohol-based resin was subjected to dyeing treatment, followed by 10 ° C. Rinse the excess dye solution with pure water. Next, in a crosslinking solution containing boric acid and potassium iodide at 76 ° C, the residence time was 600 seconds, and the crosslinking treatment was carried out. Then, it was washed with pure water of 10 ° C for 4 seconds, and dried at 80 ° C for 300 seconds to obtain a polarizing laminated film.

<Production of polarizing plate> (7) Step (5), step (6)

Polyvinyl alcohol powder (KL-318, manufactured by Kuraray Co., Ltd., average polymerization degree: 1,800) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3 wt%. In the obtained aqueous solution, a cross-linking agent ("SUMIREZ RESIN (registered trademark) 650") manufactured by Tajika Chemical Industry Co., Ltd. was added in an amount of 1 part by weight based on 2 parts by weight of the polyvinyl alcohol powder.

Next, after applying the above-mentioned adhesive solution to the polarizing plate layers on both surfaces of the polarizing laminated film, the saponified protective film [transparent cellulose triacetate (TAC)) is formed on the adhesive surface. A protective film ("KC4UY" manufactured by Konica Minolta OPT Co., Ltd.) having a thickness of 40 μm was bonded to the polarizer layer, and was crimped by a pair of bonding rolls to obtain a TAC/polarizer/undercoat layer/base. Multilayer film consisting of film/undercoat/polarizer/TAC. The multilayer film was peeled off between the substrate film and the undercoat layer to form a TAC/polarizer/primer/base film, undercoat layer/polarizer/TAC. Next, the base film was peeled off, and a polarizing plate having a laminated protective film was obtained by passing through the adhesive layer on the polarizer layer composed of the TAC/polarizer/undercoat layer. The problem of rupture referred to in the aforementioned stripping step did not occur.

<confirmation of stripes>

The respective polarizing plates were cut in a direction perpendicular to the absorption axis in the direction of the absorption axis of 150 mm, and placed in an oven at 105 ° C for 30 minutes, and then observed on the backlight with respect to the crossed Nicols of the other polarizing plates, and confirmed. There are no particularly noticeable streaks on the polarizing plates on both sides.

[Embodiment 2]

The single-area layer of Example 1 except that it will contain a polyvinyl alcohol tree The number of the guide rolls in the drying zone of the aqueous solution of the fat was set to 3, and it was dried by a drying oven at 90 ° C for 5 minutes, and the same as in Example 1, a polyethylene having a thickness of 9.6 μm was formed on the undercoat layer. A resin layer composed of an alcohol resin. The dew point in the drying furnace was 26 ° C. Since the coating layer was touched with a finger before the third roll, there was no moisture feeling, so it was judged that the resin layer was a cured person.

The film thickness profile in the twist direction was obtained at a measurement interval of 0.83 mm. The maximum amplitude of the film thickness in the twist direction was 0.6 μm. At the same time, the periodic intensity of the film thickness distribution at this time was 0.03.

A polarizing plate was produced in the same manner as in Example 1 except that the single-layer layer state was used. Although no particular problem occurred, significant streaks were confirmed.

[Example 3]

In the single-area layer of Example 2, the number of the guide rolls in the drying zone of the aqueous solution containing the polyvinyl alcohol-based resin was set to one, and the mixture was dried at 90 ° C for 5 minutes in a drying oven. In the same manner as in Example 2, a resin layer composed of a polyvinyl alcohol-based resin having a thickness of 9.4 μm was formed on the undercoat layer. The dew point in the drying furnace was 27 ° C. Since it was confirmed by contact with the coating layer before the exit of the drying furnace that there was no moisture feeling, it was judged that the resin layer was a cured person.

The film thickness profile in the twist direction was obtained at a measurement interval of 0.86 mm. The maximum amplitude of the film thickness in the twist direction was 0.7 μm. At the same time, the periodic strength of the film thickness distribution at this time was 0.06.

Except for the single-area layer state, the rest and the embodiment 1 The polarizing plate was produced in the same manner, and although no particular problem occurred, it was confirmed that the streaks were noticeable.

[Example 4]

In the third embodiment, the drying zone of the aqueous solution containing the polyvinyl alcohol-based resin layer was placed in a floating manner, and dried in a drying oven and air supply at 80 ° C for 20 minutes, and the same as in Example 3, and the primer was applied. A resin layer made of a polyvinyl alcohol-based resin having a thickness of 9.9 μm was formed on the layer. The dew point in the drying oven was 45 °C.

The film thickness profile in the twist direction was obtained at a measurement interval of 0.78 mm. The maximum amplitude of the film thickness in the twist direction was 1.2 μm. At the same time, the periodic strength of the film thickness distribution at this time was 0.07.

The polarizing plate was produced in the same manner as in Example 2, and although no particular problem occurred, significant streaks were confirmed.

[Example 5]

In the same manner as in Example 4 except that the dew point in the drying furnace was changed to 20 ° C, a resin layer composed of a polyvinyl alcohol-based resin having a thickness of 9.1 μm was formed on the undercoat layer.

The film thickness profile in the twist direction was obtained at a measurement interval of 0.78 mm. The maximum amplitude of the film thickness in the twist direction was 0.9 μm. At the same time, the periodic strength of the film thickness distribution at this time was 0.07.

The polarizing plate was produced in the same manner as in Example 4, and although no particular problem occurred, significant streaks were confirmed.

[Comparative Example 1]

In addition to the thickness of the resin layer composed of a polyvinyl alcohol-based resin A resin layer composed of a polyvinyl alcohol-based resin was formed on the undercoat layer in the same manner as in Example 3 except for 11.9 μm.

The film thickness profile in the twist direction was obtained at a measurement interval of 0.83 mm. The maximum amplitude of the film thickness in the twist direction was 2.45 μm. At the same time, the periodic intensity of the film thickness distribution at this time was 0.10.

When the polarizing plate was produced in the same manner as in Example 3, although no particular problem occurred, it was confirmed that the streaks were noticeable.

[Comparative Example 2]

When a film having a modulus of elasticity of 100 MPa at 80 ° C was used as the substrate film, shrinkage at the time of formation of the undercoat layer was very large and wrinkles were generated.

[Industrial availability]

If the laminate film of the present invention is used, it can be used to provide no Optically striped polarizing plate.

1‧‧‧guide roller

2‧‧‧Substrate film with coating layer

3‧‧‧ arrow

Claims (8)

In the laminated film, a resin layer made of a polyvinyl alcohol-based resin is formed on a long base film, and the maximum amplitude of the thickness of the resin layer in the twist direction is 2.0 μm or less. The laminated film according to the first aspect of the invention, wherein the periodic strength of the film thickness distribution in the twist direction of the resin layer is 0.09 or less. The laminated film according to the first or second aspect of the invention, wherein the average thickness of the resin layer in the twist direction is 10 μm or less. The method for producing a laminated film according to any one of claims 1 to 3, which comprises the following steps (1-1) and (2-1): the step (1-1) contains a polyvinyl alcohol An aqueous solution of the resin is coated on the substrate film to form a coating layer to obtain a coating step of the substrate film having the coating layer; and in the step (2-1), the substrate film having the coating layer is transported to the drying zone, In the drying zone, a coating layer is dried by at least one of the guide rolls, and the coating layer is dried to form a resin layer composed of a polyvinyl alcohol-based resin, thereby obtaining a step of drying the laminated film. The method for producing a laminated film according to any one of claims 1 to 3, comprising the following steps (1-2) and (2-2): the step (1-2) contains a polyvinyl alcohol An aqueous solution of the resin is coated on the substrate film to form a coating layer to obtain a coating step of the substrate film having the coating layer; and the step (2-2) is to float the substrate having the coating layer The film is transported to a drying zone, and the coating layer is dried to form a resin layer made of a polyvinyl alcohol-based resin having a thickness of 10 μm or less, thereby obtaining a drying step of the laminated film, and the dew point of the environment in the drying zone is 50° C. or less. A method for producing a polarizing laminated film, comprising the following steps (3) and (4): the step (3) uniaxially stretching the laminated film according to any one of claims 1 to 3 to obtain an extended laminate a step of extending the film; and (4) dyeing the extended laminated film to obtain a dyeing step of the polarizing laminated film having the polarizing plate layer and the substrate film. A method for producing a polarizing plate, comprising the following steps (3) to (6): the step (3) uniaxially stretching the laminated film according to any one of claims 1 to 3 to obtain an extended laminated film. An extending step; a step (4) of dyeing the extended laminated film to obtain a polarizing laminated film having a polarizing sheet layer and a substrate film; and a step (5) bonding a transparent protective film on the polarizing layer of the polarizing laminated film And obtaining a bonding step of the multilayer film; and (6) peeling off the substrate film from the multilayer film to obtain a peeling step of the polarizing plate having the polarizing plate and the transparent protective film. A method for manufacturing a monolithic body of a polarizing plate, comprising the following step (7): Step (7): cutting a polarizing plate into a rectangular shape by a polarizing plate according to claim 7 .