TW201420314A - Method for manufacturing polarized laminated film and method for manufacturing polarizing plate - Google Patents

Abstract

A method for manufacturing a polarized laminated film provided with a resin-layer-forming step for obtaining a laminated film by coating a substrate film with a coating liquid containing a polyvinyl alcohol resin, a drawing step for obtaining a drawn film by longitudinal uniaxial drawing of the laminated film, and a dyeing step for dyeing the polyvinyl alcohol resin layer of the drawn film with a dichroic dye to form a polarizer layer; and a method for manufacturing a polarizing plate using the polarized laminated film obtained by said method. The drawing step includes two or more drawing process steps, the draw ratio used in the first drawing process step is at least 50% of the draw ratio used in the second drawing process step and the total draw ratio of the polarizer layer is greater than 500%.

Description

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

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

A polarizing plate has been widely used as a polarizing supply element in a liquid crystal display device, and a polarizing detecting element. Conventionally, a polarizing plate has been mainly used as a polarizing film which is formed by bonding a protective film made of triethylenesulfonyl cellulose or the like and a polarizing film made of a polyvinyl alcohol-based resin via an adhesive; however, in recent years, With the development of liquid crystal display devices for mobile devices such as notebook personal computers and mobile phones, even with the development of large-scale televisions, the polarizing plates have been required to be lighter in weight.

However, the polarizing film is obtained by stretching and dyeing a film original film of a polyvinyl alcohol-based resin (generally, a thickness of about 75 μm), and the thickness of the stretched film is usually about 30 μm. When the thickness is less than the above-mentioned value, there is a problem that productivity of the film is likely to be broken during stretching.

Therefore, it has been proposed to apply a coating liquid containing a polyvinyl alcohol-based resin on a base film to form a polyvinyl alcohol-based resin layer to obtain a laminated film, and then to stretch the laminated film. A method of producing a laminated film (polarizing plate) having a polarizing layer and a polarizing layer by imparting a polarizing function to the polyvinyl alcohol-based resin layer by a dyeing treatment (for example, Patent Documents 1 to 3).

Patent Document 1: JP-A-2009-93074

Patent Document 2: JP-A-2011-150313

Patent Document 3: JP-A-2012-159778

According to the method of forming a polarizing layer by applying a coating liquid containing a polyvinyl alcohol-based resin as described in Patent Documents 1 to 3, it is possible to obtain a film which is larger than a film of a polyvinyl alcohol-based resin. In the case where a polarizing film is produced, the polarizing layer is also thin, so this method is advantageous from the viewpoint of weight reduction of the sheet of the polarizing plate.

However, when the laminated film having the polyvinyl alcohol-based resin layer is subjected to a stretching treatment, the stretched film is wrinkled, and stretching unevenness (non-uniform stretching) occurs in the film width direction. There is a problem that the stretched film has a thickness unevenness in the film width direction.

Accordingly, an object of the present invention is to provide a film which can suppress the occurrence of wrinkles and uneven stretching, and can stretch the laminated film, and can produce a thin polarizing property which is excellent in both appearance and optical properties in a good yield. In the method of laminating a film or a polarizing plate, the polarizing laminated film or the polarizing plate is produced by coating a coating liquid containing a polyvinyl alcohol-based resin on a substrate film to form a polyvinyl alcohol-based resin. After the laminated film is obtained as a layer, the laminated film is subjected to stretching and dyeing treatment, and the polyvinyl alcohol-based resin layer is used as a polarizing sub-layer.

The invention includes the following.

[1] A method for producing a polarizing laminated film, comprising: a resin layer forming step of applying a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of a base film, and then applying Drying to form a polyvinyl alcohol-based resin layer to obtain a laminated film; stretching step, longitudinally uniaxially stretching the laminated film to obtain a stretched film; and dyeing step of stretching the film by a dichroic dye The polyvinyl alcohol-based resin layer is dyed to form a polarizing layer to obtain a polarizing laminated film; The stretching step is a stretching treatment step comprising two or more stages; the ratio of the stretching ratio in the first-stage stretching treatment step to the stretching ratio in the second-stage stretching treatment step is 0.5 or more, and the aforementioned polarizer The total draw ratio of the layer was more than five times the basis of the polyvinyl alcohol-based resin layer of the laminated film.

[2] The method for producing a polarizing laminated film according to [1], wherein the polyvinyl alcohol-based resin layer is formed on both surfaces of the base film in the resin layer forming step.

[3] The production method according to [1] or [2], wherein the polyvinyl alcohol-based resin layer of the laminated film has a thickness of from 3 μm to 30 μm.

[4] The production method according to any one of [1] to [3] wherein the stretching ratio in the first stretching treatment step is less than 5 times.

[5] The production method according to any one of [1] to [4] wherein the base film is made of a polypropylene resin.

[6] A method of producing a polarizing plate, comprising: a step of preparing a polarizing laminated film obtained by the production method according to any one of [1] to [5]; and the polarizing laminated film a step of bonding a protective film to the polarizing sublayer to obtain a bonded film; and a step of peeling the base film from the bonded film.

According to the method of the present invention, wrinkles occurring during stretching of the laminated film and uneven stretching in the width direction of the film (and thus uneven thickness in the width direction of the film) can be effectively suppressed, so that good production can be achieved. A polarizing laminated film or a polarizing plate having good appearance and optical characteristics is produced.

1,2,3,4‧‧‧rolls

5‧‧‧Guide

6,7,8,9‧‧‧Hot rolls

10‧‧‧ laminated film

15‧‧‧ stretch film

20,30‧‧‧heating furnace

40‧‧‧Clamp

Fig. 1 is a flow chart showing a preferred embodiment of a method for producing a polarizing laminate film and a method for producing a polarizing plate according to the present invention.

Fig. 2 is a view showing an example of the multi-stage stretching in the stretching step S20.

Fig. 3 is a view showing another example of the multi-stage stretching in the stretching step S20.

Fig. 4 is a schematic view for explaining a longitudinal uniaxial stretching method using a jig.

Hereinafter, the method for producing a polarizing laminated film according to the present invention and a method for producing the polarizing plate will be described in detail by exemplifying the embodiments.

<Method for Producing Polarized Multilayer Film>

Fig. 1 is a flow chart showing a preferred embodiment of a method for producing a polarizing laminate film and a method for producing a polarizing plate according to the present invention. The method for producing a polarizing laminated film of the present embodiment includes the following steps: a resin layer forming step S10, by applying a coating liquid containing a polyvinyl alcohol-based resin to at least one surface of the base film. Thereafter, drying is further performed to form a polyvinyl alcohol-based resin layer to obtain a laminated film; in the stretching step S20, the laminated film is longitudinally uniaxially stretched to obtain a stretched film; and the dyeing step S30 is performed by dichroism. The dye dyes the polyvinyl alcohol-based resin layer of the stretched film to form a polarizing layer to obtain a polarizing laminated film.

As described later, in the polarizing plate, the protective film can be bonded to the polarizing layer of the polarizing laminated film obtained in the dyeing step S30 to obtain a bonded film (the bonding step). S40), and then removing the base film from the bonded film (peeling step S50) Arrived.

Hereinafter, each step of S10 to S30 included in the method for producing a polarizing laminated film of the present embodiment will be described in more detail.

[1] Resin layer forming step S10

This step is a step of forming a polyvinyl alcohol-based resin layer on at least one side of the base film to obtain a laminated film. The polyvinyl alcohol-based resin layer is a layer that becomes a polarizing sub-layer through the stretching step S20 and the dyeing step S30. The polyvinyl alcohol-based resin layer can be formed by applying a coating liquid containing a polyvinyl alcohol-based resin on one surface or both surfaces of a base film, and drying the coating layer. According to such a method, the thickness of the polyvinyl alcohol-based resin layer and the polarizer layer can be reduced, which is advantageous in terms of weight reduction of the polarizing laminated film and the sheet of the polarizing plate.

(substrate film)

The base film may be composed of a thermoplastic resin, and is preferably composed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, and stretchability. Specific examples of such a thermoplastic resin include, for example, a polyolefin resin such as a chain polyolefin resin or a cyclic polyolefin resin (such as a decene-based resin); a polyester resin; An acrylic resin; a cellulose ester resin such as cellulose triacetate or cellulose diacetate; a polycarbonate resin; a polyvinyl alcohol resin; a polyvinyl acetate resin; a polyarylate resin; Polystyrene resin; polyether oxime resin; polyfluorene resin; polyamine resin; polyimine resin; and mixtures, copolymers and the like.

The base film may be a single layer structure formed of one resin layer composed of one or two or more kinds of thermoplastic resins, or may be a multilayer structure in which a plurality of layers of a resin layer composed of one or two or more kinds of thermoplastic resins are laminated. .

The chain polyolefin resin may be, for example, a single polymer of a chain olefin such as a polyethylene resin or a polypropylene resin, or may be a copolymer composed of two or more chain olefins. . The base film composed of a chain polyolefin resin preferably has stability, High magnification and easy to stretch. Among them, the base film is more preferably a polypropylene resin (a polypropylene resin of a single polymer of propylene or a copolymer mainly composed of propylene), a polyethylene resin (a polyethylene resin of a single polymer of ethylene, or A copolymer composed of ethylene or the like.

A copolymer mainly composed of propylene which is an example of a thermoplastic resin constituting a base film, which is a copolymer of propylene and another monomer copolymerizable with other monomers.

Other monomers which can be copolymerized with propylene, for example, may be ethylene or an α-olefin. The α-olefin is preferably an α-olefin having 4 or more carbon atoms, more preferably an α-olefin having 4 to 10 carbon atoms. Specific examples of the α-olefin having 4 to 10 carbon atoms include, for example, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, and the like. Linear monoolefins; branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene; vinyl rings Hexane, etc. The copolymer of propylene and other monomers copolymerizable with other monomers may be a random copolymer or a block copolymer.

The content of the other monomer described above is, for example, 0.1% by weight to 20% by weight in the copolymer, preferably 0.5% by weight to 10% by weight. The content of the other monomer in the copolymer can be determined by performing infrared spectroscopy according to the method described in the "Handbook of Polymer Analysis" (1995, issued by Kiyoshiya Shoten).

The polypropylene-based resin among the above is preferably a single polymer of propylene, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer or a propylene-ethylene-1-butene random copolymer.

The stereoregularity of the polypropylene resin is preferably substantially isotactic or syndiotactic. A base film composed of a polypropylene-based resin having substantially uniform or syndiotactic stereoregularity is relatively excellent in handleability and excellent in mechanical strength in a high-temperature environment.

The base film may be composed of a chain polyolefin resin, or may be composed of a mixture of two or more chain polyolefin resins, or may be composed of two or more chain polyolefins. A resin composed of a resin.

The cyclic polyolefin resin is a resin obtained by polymerizing a cyclic olefin as a polymerization unit. For example, the resin described in JP-A No. 1-240517, JP-A No. 3-148882, and JP-A No. 3-122137 can be used. Specific examples of the cyclic polyolefin-based resin may, for example, be a ring-opened (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a chain olefin, and a chain such as ethylene or propylene. The copolymer of olefin (the representative is a random copolymer), and the graft polymer which has been modified by an unsaturated carboxylic acid or a derivative thereof, and the like, and the like. Among them, the cyclic olefin is preferably a norbornene-based resin obtained by using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer.

The cyclic polyolefin-based resin is commercially available in various products. Examples of commercially available products of the cyclic polyolefin resin include "Topas" (manufactured by TOPAS ADVANCED POLYMERS GmbH, available from Polyplastics Co., Ltd.) and "Atong" (manufactured by JSR Co., Ltd.) , "ZEONOR" (made by Japan Jayne Co., Ltd.), "ZEONEX" (made by Japan Jayne Co., Ltd.), and "Apollo" (made by Mitsui Chemicals Co., Ltd.).

In addition, "Aisna" (made by Sekisui Chemical Co., Ltd.), "SCA40" (made by Sekisui Chemical Industry Co., Ltd.), and "Jenno Film" (Japanese Jayne Co., Ltd.) can be used. A commercially available product of a cyclic polyolefin-based resin film made of a film or the like is used as a base film.

The base film may be composed of one type of cyclic polyolefin resin, or may be composed of a mixture of two or more kinds of cyclic polyolefin resins, or may be composed of two or more kinds of cyclic polyolefins. A resin composed of a resin.

The polyester resin is a resin having an ester bond, and is generally composed of a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a dibasic dicarboxylic acid or a derivative thereof can be used; for example, it may be p-citric acid, isodecanoic acid, dimethyl p-nonanoate or dimethyl naphthalate. Wait. As the polyol, a binary diol can be used; for example, it may be ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, cyclohexane dimethanol or the like.

A representative example of the polyester resin is, for example, a polyethylene terephthalate which is a polycondensate of citric acid and ethylene glycol. Although the polyethylene terephthalate is a crystalline resin, it is easy to carry out a treatment such as stretching in a state before the crystallization treatment. If necessary, the crystallization treatment can be carried out by heat treatment at the time of stretching or after stretching. Further, it is also suitably used in a copolymerized polyester which is further polymerized with a monomer of another type of polyethylene terephthalate to reduce crystallinity (or become amorphous). An example of such a resin may be, for example, a product obtained by copolymerizing cyclohexanedimethanol or isononic acid. These resins are excellent in stretchability and can be used very suitably.

Specific examples of the polyester-based resin other than the polyethylene terephthalate and the copolymer thereof may be, for example, polybutylene terephthalate, polyethylene naphthalate, or polybutylene naphthalate. , poly(p-methylene phthalate), poly-methylene naphthalate, polycyclohexane dimethyl phthalate, dimethyl polycyclohexane naphthalate, and the like.

The base film may be composed of one type of polyester resin, or may be composed of a mixture of two or more kinds of polyester resins, or may be composed of a copolymer of two or more kinds of polyester resins.

The (meth)acrylic resin is a resin mainly composed of a compound having a (meth)acryloyl group. Specific examples of the (meth)acrylic resin include, for example, poly(meth)acrylate such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methacrylic acid Ester-(meth)acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; (meth)acrylic acid methyl-styrene copolymer (MS resin, etc.); methacrylic acid A copolymer of an ester and a compound having an alicyclic hydrocarbon group (for example, a methyl methacrylate-cyclohexyl methacrylate copolymer, a methyl methacrylate-methyl (meth) acrylate thioglycolate copolymer, etc.). Preferably, a polymer containing a poly(meth)acrylic acid C _1-6 alkyl ester such as poly(methyl) methacrylate as a main component is used, and more preferably methyl methacrylate is used. A methyl methacrylate-based resin having a composition (50% by weight to 100% by weight; preferably 70% by weight to 100% by weight).

The base film may be composed of a single (meth)acrylic resin, or may be composed of a mixture of two or more kinds of (meth)acrylic resins, or may be composed of two or more kinds (meth). It is composed of a copolymer of an acrylic resin.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose dipropionate, and the like. Further, for example, the copolymer or a part of the hydroxyl group may be modified with another substituent. Among these, a particularly preferred one is cellulose triacetate (triethyl fluorenyl cellulose). There are many commercially available products of cellulose triacetate, which are also advantageous from the viewpoint of availability and cost. For example, Fujitsu TD80 (made by Fujifilm Co., Ltd.) and "Fujitec TD80UF" (Fuji Film Co., Ltd.), which are commercial names, may be used as a commercial product of the cellulose triacetate. System), "Fujitec TD80UZ" (made by Fujifilm Co., Ltd.), "Fujitec TD40UZ" (made by Fujifilm Co., Ltd.), "KC8UX2M" (made by Konica Minolta Co., Ltd.), "KC4UY ("Konica Minolta Co., Ltd.").

The base film may be composed of one type of cellulose ester resin, or may be composed of a mixture of two or more kinds of cellulose ester resins, or may be a copolymer of two or more kinds of cellulose ester resins. Composition.

The polycarbonate resin is a stepped plastic composed of a polymer obtained by permeating a monomer unit of a carbonate-based bond, and is a resin having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate resin constituting the base film may be a resin called a modified polycarbonate such as a modified polymer skeleton, and a wavelength-dependent modified product in order to reduce the photoelastic coefficient. Polymerized polycarbonate and the like.

There are various commercially available products of polycarbonate resins. As an example of a commercial product of a polycarbonate resin, for example, it may be a "pumper" of each product name (Teijin Chemical Co., Ltd.) Company system), "Brand Dragon" (manufactured by Mitsubishi Plastics Co., Ltd.), "SD Polyka" (manufactured by Sumitomo Daewoo Co., Ltd.), "Kali Ba" (manufactured by Daewoo Chemical Co., Ltd.), etc.

The base film may be composed of a polycarbonate resin, a mixture of two or more polycarbonate resins, or a copolymer of two or more polycarbonate resins. Composition.

In addition to the above-mentioned thermoplastic resin, a suitable additive may be arbitrarily added to the base film. Such additives may, for example, be ultraviolet absorbers, antioxidants, smoothing agents, plasticizers, release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and color formers. The content of the thermoplastic resin in the base film is preferably 50% by weight to 100% by weight, more preferably 50% by weight to 99% by weight, still more preferably 60% by weight to 98% by weight, and particularly preferably 70% by weight. Weight%~97% by weight. When the content of the thermoplastic resin in the base film is less than 50% by weight, there is a fear that the high transparency and the like inherent in the thermoplastic resin may not be sufficiently found.

The thickness of the base film can be appropriately determined. However, from the viewpoint of workability such as strength and handleability, it is preferably 1 μm to 500 μm, more preferably 1 μm to 300 μm. The thickness is 5 μm to 200 μm, and the best is 5 μm to 150 μm.

(coating liquid containing polyvinyl alcohol resin)

The coating liquid is preferably a polyvinyl alcohol-based resin solution obtained by dissolving a powder of a polyvinyl alcohol-based resin in a good solvent (for example, water). The polyvinyl alcohol-based resin may be, for example, a polyvinyl alcohol resin and a derivative thereof. The derivative of the polyvinyl alcohol resin may, for example, be a polyvinyl formal ester, a polyvinyl formal ester or the like. In addition, an olefin-based modified polyethylene such as ethylene or propylene may be used. a product of a base alcohol resin; a substance modified with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid; a substance modified with an alkyl ester of an unsaturated carboxylic acid; A substance modified from guanamine. The proportion of the modification is preferably less than 30 mol%, more preferably less than 10 mol%. In the case of a modification of more than 30 mol%, it may become difficult to suck A dichroic dye is attached, and the polarizing performance is unsuitable. 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 8,000. ~5000 range. The average degree of polymerization can be determined in accordance with the method specified in JIS K 6726-1994 "Test method 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 becomes 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 range of the degree of saponification is preferably 80% by mole or more, more preferably 90% by mole or more, and particularly preferably 94% by mole or more. When the degree of saponification is too low, the water resistance or the moist heat resistance when the polarizing laminated film and the polarizing plate are formed may become insufficient. Further, even if it is a completely saponified product (the degree of saponification is 100 mol%), when the degree of saponification is too high, the dyeing speed is slowed, and in order to obtain sufficient polarizing performance, the production time becomes long, according to Depending on the situation, sometimes a polarizing sub-layer with sufficient polarizing properties may not be obtained. Therefore, the degree of saponification is preferably 99.5 mol% or less, more preferably 99.0 mol% or less.

The degree of saponification refers to the ratio of the acetoxy group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin of the polyvinyl alcohol-based resin material to hydroxy group by saponification treatment, in unit ratio (% by mole), that is, as defined by the following formula; degree of saponification (% by mole) = [(number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups)] × 100

The higher the degree of saponification, the greater the proportion of hydroxyl groups, which means that the proportion of the acetate groups which hinder crystallization is less. The degree of saponification can be determined by a method specified in JIS K 6726-1994 "Testing methods for polyvinyl alcohol".

The polyvinyl acetate-based resin may be, for example, a polyvinyl acetate which is a single polymer of vinyl acetate, and may be, for example, another polymerization sheet which can be copolymerized with vinyl acetate. Copolymers and the like. Other polymerizable monomers which can be copolymerized with vinyl acetate may, for example, be unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated decanoic acids, ammonium amides having an ammonium group, and the like.

Examples of commercially available polyvinyl alcohol-based resins that can be suitably used include "PVA124" (saponification degree: 98.0 mol% to 99.0 mol%) and "PVA117" manufactured by Kuraray Co., Ltd., each of which is a trade name. (Saponification degree: 98.0 mol% to 99.0 mol%), "PVA117H" (saponification degree: 99.5 mol% or more), "PVA624" (saponification degree: 95.0 mol% to 96.0 mol%) and "PVA617" (Saponification degree: 94.5 mol%~95.5 mol%); "AH-26" manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (saponification degree: 97.0 mol%~98.8 mol%), "AH-22" (saponification degree: 97.5 mol%~98.5 mol%), "NH-18" (saponification degree: 98.0 mol% to 99.0 mol%) and "N-300" (saponification degree: 98.0 mol% to 99.0) Moer%); Japan Vam. "JC-33" manufactured by JAPAN VAM & POVAL CO., LTD. (saponification degree: 99.0 mol% or more), "JM-33" (saponification degree: 93.5 mol%~95.5 Mo Ear %), "JM-26" (saponification degree: 95.5 mol% ~ 97.5 mol%), "JP-45" (saponification degree: 86.5 mol% ~ 89.5 mol%), "JF-17" ( Saponification degree: 98.0 mol%~99.0 mol%), "JF-17L" (saponification degree: 98.0 mol%~99.0 mol%) and "JF-20" (saponification degree: 98.0 mol%~99.0 mo ear%).

The coating liquid may contain an additive such as a plasticizer, a surfactant, or the like, as needed. As the plasticizer, a polyhydric alcohol or a condensate thereof or the like can be used, and for example, it may be glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, polyethylene glycol or the like. The blending amount of the additive is preferably 20% by weight or less based on the polyvinyl alcohol-based resin.

(application of coating liquid and drying of coating layer)

The method for applying the coating liquid to the substrate film may be a wire bar coating method; a roll coating method such as reverse coating or gravure coating; a die coating method; a spot coating method; a grid coating method; The spin coating method; the sieve coating method; the smear coating method; the dip coating method; the spraying method, and the like are appropriately selected.

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) are set in accordance with the kind of the solvent contained in the coating liquid. The drying temperature is, for example, 50 ° C to 200 ° C, preferably 60 ° C to 150 ° C. In the case where the solvent contains water, the drying temperature is preferably 80 ° C or higher. Drying time, for example, 2 minutes to 20 minutes.

The polyvinyl alcohol-based resin layer may be formed only on one surface of the base film or may be formed on both surfaces. When it is formed on both surfaces, it is possible to suppress curling of the film which occurs when the polarizing laminated film and the polarizing plate are produced, and to obtain two polarizing plates from one polarizing laminated film, so that the production efficiency of the polarizing plate is obtained. In terms of aspect, it is also advantageous.

The thickness of the polyvinyl alcohol-based resin layer in the laminated film is preferably from 3 μm to 30 μm, more preferably from 5 μm to 20 μm. The polyvinyl alcohol-based resin layer having a thickness within the range can be obtained by the stretching step S20 and the dyeing step S30 which will be described later, and the dyeability of the dichroic dye is excellent, the polarizing performance is excellent, and the thickness is sufficiently small. The polarizing sublayer. When the thickness of the polyvinyl alcohol-based resin layer is more than 30 μm, the thickness of the polarizer layer may exceed 10 μm. In addition, when the thickness of the polyvinyl alcohol-based resin layer is less than 3 μm, it tends to be too thin after stretching and the dyeability tends to be deteriorated.

Before the application of the coating liquid, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, the surface of the base film on the side where the polyvinyl alcohol-based resin layer is formed may be At least corona treatment, plasma treatment, combustion (flame) treatment, and the like are performed.

Further, before the application of the coating liquid, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, the base layer or the adhesive layer may be passed through the base film to form a polyvinyl group. An alcohol resin layer.

(base layer)

The underlayer can be formed by applying a coating liquid for forming a base layer on the surface of the base film and then drying it. The coating liquid for forming a base layer includes a component which can exert a certain strong adhesion to both the base film and the polyvinyl alcohol-based resin layer. The coating liquid for forming a base layer usually contains like this A resin component and a solvent which impart an adhesive force. The resin component is preferably a thermoplastic resin which is excellent in transparency, heat stability, and stretchability, and examples thereof include a (meth)acrylic resin and a polyvinyl alcohol-based resin. Among them, a polyvinyl alcohol-based resin which provides a good adhesion is preferred.

The polyvinyl alcohol-based resin may be, for example, a polyvinyl alcohol resin and a derivative thereof. The derivative of the polyvinyl alcohol resin may, for example, be a polyvinyl formal ester or a polyvinyl formal ester, or may be an olefin-based modified polyethylene base such as ethylene or propylene. An alcohol resin; a modified product of an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid; a substance modified with an alkyl ester of an unsaturated carboxylic acid; Amine modified material, etc. Among the above polyvinyl alcohol-based resins, a polyvinyl alcohol resin is preferably used.

As the solvent, a general organic solvent and an aqueous solvent capable of dissolving the above resin component can be usually used. Examples of the solvent may, for example, be an aromatic hydrocarbon such as benzene, toluene or xylene; a ketone such as acetone, methyl ethyl ketone or methyl isobutyl ketone; for example, ethyl acetate An ester of isobutyl acetate; a chlorinated hydrocarbon such as dichloromethane, trichloroethylene or chloroform; an alcohol such as ethanol, 1-propanol, 2-propanol or 1-butanol class. However, when the underlayer is formed using the coating liquid for forming an underlayer containing an organic solvent, the base film may be dissolved. Therefore, when the solvent is selected, the solubility of the substrate film is preferably also considered. . When the influence on the environment is also considered together, it is preferred to form the underlayer from the coating liquid of the aqueous solvent.

In order to increase the strength of the underlayer, a crosslinking agent may be added to the coating liquid for forming the underlayer. The crosslinking agent is determined according to the type of the thermoplastic resin to be used, and an appropriate one is appropriately selected from known ones such as an organic system and an inorganic system. Examples of the crosslinking agent may be, for example, an epoxy-based, isocyanate-based, dialdehyde-based, or metal-based crosslinking agent.

As the epoxy-based crosslinking agent, for example, one of a one-liquid hardening type and a two-liquid hardening type, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and glycerin can be used. Di- or tri-glycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, Diglycidyl aniline, diglycidylamine, and the like.

The isocyanate crosslinking agent may be, for example, tolyl diisocyanate, hydrogenated tolyl diisocyanate, trimethylolpropane-tolyl diisocyanate adduct, triphenylmethylene triisocyanate, Methylene bis(4-phenylmethylene) triisocyanate, isophorone diisocyanate, and such ketoxime blocks or phenolic blocks.

The dialdehyde crosslinking agent may, for example, be glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, maleic dialdehyde, sebacaldehyde or the like.

The metal-based crosslinking agent may be, for example, a metal salt, a metal oxide, a metal hydroxide, or an organometallic compound. Metal salts, metal oxides, metal hydroxides, for example, may be, for example, magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, hafnium, boron, zinc, copper, vanadium, chromium, tin, and the like. A metal salt, an oxide, and a hydroxide having a divalent or higher valence.

The organometallic compound refers to a compound in which the organic group is a structure in which a metal atom is directly bonded, or an organic group having at least one of a molecule bonded through an oxygen atom and a nitrogen atom. The organic group means a monovalent or polyvalent group containing at least a carbon element, and may, for example, be an alkyl group, an alkoxy group, a decyl group or the like. Further, the bond does not mean only a shared bond, and may be a coordinate bond such as a chelate compound.

Suitable examples of the organometallic compound include an organic titanium compound, an organic zirconium compound, an organoaluminum compound, and an organic cerium compound. The organometallic compounds may be used alone or in combination of two or more.

The organotitanium compound, for example, may be, for example, tetra-n-butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetrakis(2-ethylhexyl) titanate, tetrakis tetrahydrate Titanium orthoesters such as esters; such as titanium acetylacetonate, titanium tetraethylpyruvate, titanium polyacetyl phthalate, titanium glycolate, titanium lactate, titanium triethanolamine, ethyl Titanium chelating such as titanium acetate; titanium hydride such as titanium hydroxystearate.

The organic zirconium compound, for example, may be zirconium n-propoxide, zirconium n-butoxide, or Zirconium acetylacetonate, zirconium monoethyl phthalate, zirconium bisacetonate, zirconium acetyl acetonate, bisethyl acetonitrile acetic acid, and the like.

The organoaluminum compound, for example, may be aluminum acetylacetonate, an aluminum organic acid chelate or the like. The organic ruthenium compound, for example, may be a compound in which a ligand exemplified in the organotitanium compound and the organozirconium compound is bonded to ruthenium.

In addition to the above low molecular crosslinking agent, a polymer crosslinking agent such as a methylolated melamine resin or a polyamide resin may be used. An example of a commercially available product of a polyamide resin is, for example, "amine series resin 650 (30)" and "amine series resin 675" sold by Tiangang Chemical Industry Co., Ltd. (either All are product names) and so on.

When a polyvinyl alcohol-based resin is used as a resin component for forming a base layer, a polyamide solvent, a methylolated melamine resin, a dialdehyde crosslinking agent, or a metal chelate compound is preferably used. A crosslinking agent or the like is used as a crosslinking agent.

The ratio of the resin component to the crosslinking agent in the coating liquid for forming a base layer can be 0.1 weight from the crosslinking agent depending on the kind of the resin component, the type of the crosslinking agent, and the like with respect to 100 parts by weight of the resin component. It is suitably determined in the range of about 100 parts by weight, and is preferably selected from the range of about 0.1 part by weight to about 50 parts by weight. Moreover, it is preferable that the coating liquid for forming a base layer has a solid content concentration of about 1% by weight to about 25% by weight.

The thickness of the underlayer is preferably from about 0.05 μm to about 1 μm, more preferably from 0.1 μm to 0.4 μm. When it is thinner than 0.05 μm, the effect of increasing the adhesion between the base film and the polyvinyl alcohol-based resin layer is small, and when it is thicker than 1 μm, it is disadvantageous for the film of the polarizing laminated film and the polarizing plate. Chemical.

The method of applying the coating liquid for forming a base layer onto the base film may be the same as the coating liquid for forming a polyvinyl alcohol-based resin layer. The base layer is coated on the surface (one surface or both surfaces of the base film) coated with the coating liquid for forming the polyvinyl alcohol-based resin layer. Coating by base layer formation The drying temperature and drying time of the coating layer made of the liquid are set according to the kind of the solvent contained in the coating liquid. The drying temperature is, for example, 50 ° C to 200 ° C, preferably 60 ° C to 150 ° C. In the case where the solvent is aqueous, the drying temperature is 80 ° C or higher. The drying time is, for example, 30 seconds to 20 minutes.

[2] stretching step S20

This step is a step of obtaining a stretched film by longitudinally uniaxially stretching a laminated film composed of a base film and a polyvinyl alcohol-based resin layer. In the present invention, the stretching step S20 can be carried out by dividing into two or more stretching treatment steps. That is, the stretching step S20 is composed of a plurality of stages of stretching, and includes two or more stages of stretching treatment steps. Here, the "stretching step including two or more stages" means at least a first stage (first) stretching treatment step of longitudinally uniaxially stretching the laminated film at a certain stretching ratio, and a laminated film. The section (time interval) that is not stretched (the film conveyance direction is not stretched), and the second section of the longitudinal uniaxial stretching at a certain stretching ratio for the laminated film subjected to the first stretch treatment The meaning of the stretching process step. The stretching step S20 may be a stretching treatment step including three or more stages, and in this case, between the stretching treatment steps of the respective stages, a section (time interval) in which the laminated film is not stretched.

The longitudinal uniaxial stretching in the stretching treatment step of each stage may be, for example, sometimes using inter-roll stretching, calendering, hot roll stretching, jig stretching, or the like. The stretching manner of each segment may be the same or a combination of different stretching methods. However, even in the case of a high draw ratio, when the necking ratio is low, sufficient polarizing performance of the polarizer layer obtained in the dyeing step S30 may not be provided, so that a sufficient necking ratio cannot be ensured, so Preferably, the stretching step for at least one of the sections should be free-end stretching between rolls.

The above-mentioned necking ratio is defined by the following formula: necking ratio (%) = [(W1 - W2) ÷ W1] × 100

W1 is the width of the laminated film before being supplied to the stretching step S20. W2 is the minimum width of the film after all the stretching treatment with respect to the laminated film. For example, only the product is accumulated in the stretching step S20. In the case where the layer film is subjected to a stretching treatment, W2 is the minimum width of the stretched film finally obtained in the stretching step S20. Further, as will be described later, the additional stretching treatment may be performed in the dyeing step S30. However, in this case, W2 is the minimum width of the polarizing laminated film after the additional stretching treatment. The necking ratio is preferably about 50% or more.

An example of the plurality of multi-stage stretching in the stretching step S20 will be described with reference to the drawings. In each of the figures, the arrow indicates the direction in which the film is conveyed.

Fig. 2 is a view showing that the stretching step S20 includes two stretching treatment steps, and the stretching treatment steps are all inter-roll stretching, that is, in the manner of stretching between rolls of different rotation speeds. example. Specifically, the laminated film 10 to be conveyed is first stretched between the rolls 1 and 2 at different rotational speeds while being heated in the heating furnace 20 at a desired temperature (first stage). Stretching step)). The film which has been subjected to the first stretching treatment is further conveyed via the guide roll 5, passes through the heating furnace 30 set at a desired temperature, and is heated at the same time at the rolls 3 and 4 at different rotational speeds. The film is stretched (the second stretching treatment step) to form the stretched film 15. On the contrary, in the section from the roll 2 to the roll 3, since the number of rotations of the roll 2 is the same as the number of revolutions of the roll 3, the film is not stretched.

Fig. 3 is a view showing that the stretching step S20 includes three stages of stretching treatment steps, and any of the stretching treatment steps is a method of stretching by a hot roll, that is, stretching between heated rolls. The case of the case. Specifically, the laminated film 10 to be conveyed is firstly adjusted to a desired temperature, and is stretched in a gap between the heat roller 6 and the heat roller 7 which are different in rotation speed (first stretching treatment step). Next, after the non-stretching section, that is, the section contacting the heat roller 7, the surface is adjusted to a desired temperature, and is stretched by a gap between the heat roller 7 and the heat roller 8 which are mutually different rotational speeds (No. Two-stage stretching treatment step). The film stretched through the second stage passes through the unstretched section, that is, the section contacting the heat roller 8, adjusts the surface to a desired temperature, and passes the heat roller 8 and the heat roller at mutually different rotational speeds. The gap between the nine is stretched (the third stretching treatment step) to form the stretched film 15.

Fig. 4 is a view for explaining a longitudinal uniaxial stretching method using a jig (clip), and a view of the stretched laminated film as viewed from above. The longitudinal uniaxial stretching method using the jig, as shown in the drawing, means that a plurality of jigs 40 (usually a certain interval) are attached to both end portions in the width direction of the laminated film 10, and are heated to a desired temperature while being conveyed. The laminated film 10 is gradually stretched by extending the distance R between the jigs in the film conveyance direction. Although not shown, the multi-stage stretching by the longitudinal uniaxial stretching method using the jig may be performed to expand the inter-clamp distance R to perform the stretching treatment (the first-stage stretching treatment step), and the conveyance is fixed. The section of the laminated film 10 having the distance R between the jigs is again stretched by the inter-clamp distance R (the second-stage stretching process step). The stretching process steps after the third stage are also the same.

The method of controlling the distance R between the jigs at the time of stretching is not particularly limited, and various methods can be used. For example, each of the clamps can be independently driven; the clamps can be independently controlled to control the distance R between the clamps; or the clamps can be coupled to each other, and a plurality of clamps can be controlled by one drive system to control the distance between the clamps. R. In the present invention, any method can be suitably used.

A specific method of independently driving each of the jigs may be, for example, a method of using a magnetic force represented by a linear motor driving method, a method of attaching a rotary driving motor to each jig, or the like. Further, it is also possible to prevent all of the jigs from being independently driven, but only a part of the jigs can be driven independently, and the other jigs are not particularly controlled.

A specific method of controlling a plurality of jigs by a drive system, which is represented by a collector mode or the like. The so-called current collector method refers to a method of switching the current collector to control the distance R between the clamps by controlling the distance between the two rails.

Referring to the above-described multi-stage stretching illustrated in Figs. 2 to 4, any of the stretching treatment steps does not cause the film to be taken up/out. An implementation like this is ideal in terms of productivity. However, it is not limited to the above example, but may be at the end of the stretching process step of each segment. The film is taken up and re-rolled out when the second stretching step is carried out.

In the present invention, the ratio of the stretching ratio in the first stretching treatment step to the stretching ratio in the second stretching treatment step (hereinafter also referred to as "stretching ratio") is 0.5 or more. . The "stretching ratio in the first-stage stretching treatment step" means the length in the long-axis direction (stretched direction) of the polyvinyl alcohol-based resin layer having the laminated film before the stretching step S20. When it is set to 1, the length of the polyvinyl alcohol-type resin layer in the long-axis direction at the end of the first-stage stretching process step. For example, the length in the long axis direction (or the length of a part of the polyvinyl alcohol-based resin layer) of the polyvinyl alcohol-based resin layer having the laminated film before the stretching step S20 is set to 1, by the first When the length of the polyvinyl alcohol-based resin layer (or the length of a certain portion) is 2 in one stretching treatment step, the stretching ratio in the first-stage stretching treatment step is twice.

The "stretching ratio in the second-stage stretching treatment step" means the second-stage stretching when the length of the polyvinyl alcohol-based resin layer in the long-axis direction at the end of the first-stage stretching treatment step is set to 1. The length in the long axis direction of the polyvinyl alcohol-based resin layer at the end of the treatment step.

The stretching step S20 is divided into two or more stretching treatment steps, and the first and second stretching treatment steps satisfying the above stretching ratio are carried out until the desired total stretching ratio is obtained. In the process of stretching the film, since the necking caused by the stretching can be maintained at an appropriate level and the laminated film can be stretched, the effect of wrinkles occurring during stretching can be effectively suppressed, and the film can be effectively suppressed. Uneven stretching in the width direction of the film (non-uniform stretching).

The occurrence of wrinkles not only causes uneven dyeing in the dyeing step S30, but also causes poor appearance, or causes uneven optical properties such as polarizing properties and transmittance, and also causes a poor yield. . The unevenness in stretching occurs in the thickness unevenness in the film width direction, and similarly, the optical characteristics such as polarization performance and transmittance are uneven.

According to the method of the present invention, a stretched film having a thickness difference of less than 5 μm or even less than 4 μm in the width direction of the film can be produced, so that a polarizing property and a uniform transmittance can be produced. Light laminated film and polarizing plate. The "thickness difference in the width direction of the film" is a film thickness measured at a position of 50 mm from one end in the width direction of the film, and the thickness of the film at one point in the center in the width direction of the film is measured. The meaning of the absolute value of the difference in thickness.

The draw ratio is preferably 0.6 or more, more preferably 0.7 or more, and particularly preferably 1.0 or more in order to obtain the effect as described above more effectively. When the draw ratio is less than 0.5, stretching unevenness in the film width direction occurs. Moreover, when the draw ratio is too large, wrinkles are likely to occur, so that the draw ratio is preferably 5 or less, more preferably 4 or less, and particularly preferably 3 or less.

The stretching ratio in the first stretching treatment step is preferably less than 5 times, more preferably 4 times or less. When the draw ratio is 5 times or more, wrinkles are likely to occur. In other words, in order to impart good polarizing performance to the polarizing sub-layer obtained in the dyeing step S30, it is expected that the total stretching ratio of the stretching treatment on the laminated film as described later is 5 times or more. Wrinkles are inevitable when stretching at high magnification. In the present invention, the stretching treatment is carried out by dividing into two or more stages in consideration of such a thing.

The above-mentioned "total stretching ratio" means a stretching treatment step in each stage (may also be subjected to additional stretching treatment in the dyeing step S30 as will be described later. However, in this case, the additional stretching is also included. The stretching ratio in the treatment step is added to the final stretching ratio obtained; in other words, the long-axis direction (stretching direction) of the polyvinyl alcohol-based resin layer having the laminated film before the stretching step S20 is supplied. The length of the polyvinyl alcohol-based resin layer (that is, the polarizing layer) at the end of all the stretching treatments when the length of the film is 1 is the length in the long axis direction.

As described above, the total stretching ratio of the polarizing sub-layer when the polyvinyl alcohol-based resin layer having the laminated film is used as a reference is preferably more than 5 times. When the draw ratio is less than 5 times, since the polyvinyl alcohol-based resin layer is not sufficiently aligned, the degree of polarization of the polarizer layer tends to be insufficient. Further, the total draw ratio is preferably 8 times or less. When the total draw ratio exceeds 8 times, there will be a film during stretching The fracture tends to occur, the thickness of the stretched film becomes thinner than the desired thickness, and the workability and handleability in the subsequent step are lowered.

The stretching temperature in each step of the stretching step S20 is set to a temperature at which the fluidity of the polyvinyl alcohol-based resin layer and the entire base film exhibits a degree of stretchability, that is, a preferred range of the stretching temperature. From 30 ° C below the melting point of the substrate film to 30 ° C above the melting point of the substrate film, the stretching temperature is more preferably from 30 ° C below the melting point of the substrate film to 5 ° C above the melting point of the substrate film, The stretching temperature is more desirably ranged from 25 ° C below the melting point of the base film to the melting point of the base film. When the base film is composed of a plurality of resin layers, the melting point is the highest melting point among the melting points of the plurality of resin layers.

When the stretching temperature is set to be less than 30 ° C below the melting point of the base film, the fluidity of the base film is too low, and the stretching treatment tends to be difficult. When the stretching temperature is set to be higher than 30 ° C above the melting point of the base film, the fluidity of the base film is too large, and the stretching treatment tends to be difficult. In view of the easiness of the stretching treatment, the stretching temperature is preferably within the above range, and more preferably 120 ° C or higher.

The heating method of the laminated film of the stretching process of each stage may be a zone heating method (for example, a method of heating in a stretching zone such as a heating furnace in which hot air is blown to a predetermined temperature. See Fig. 2). In the case of stretching using a roll, the method of heating the roll itself (refer to Fig. 3); heater heating method (infrared heater, halogen heater, panel heater, etc. are placed under the laminated film to heat with radiant heat) Method) and so on. In the inter-roll stretching method, from the viewpoint of the uniformity of the stretching temperature, a zone heating method is preferred. In this case, the two pairs of rolls may be disposed in the temperature-controlled stretching zone or may be disposed outside the stretching zone. However, in order to prevent the bonding film from adhering to the rolls, it is preferably disposed in the stretching. Outside the area (see Figure 2).

In addition, the case where the stretching temperature is in the zone heating method means the ambient temperature in the zone (for example, in the heating furnace); the case where the heating is performed in the furnace in the heater heating method means the ring in the furnace The meaning of the temperature. Further, in the case of the method of heating the roll itself, it means the surface temperature of the roll.

A preheating step of preheating the laminated film may also be provided before the stretching step S20. The preheating method can use the same method as the heating method in the stretching treatment. The stretching treatment method is a case of stretching between rolls, and the preheating may be performed in a time interval before passing through the upstream side rolls, passing through, and passing through. The stretching treatment is a case where the hot roll is stretched, and the preheating is preferably carried out in a time interval before passing through the heat roller. The stretching treatment method is a case of stretching using a jig, and preheating is preferably performed in a time interval before the distance between the jigs is enlarged. The preheating temperature is preferably in the range of from -50 ° C to the stretching temperature of ± 0 ° C, more preferably in the range of from -40 ° C to -10 ° C.

Further, after the stretching treatment of the final stage in the stretching step S20, a heat fixing treatment step may be provided. The heat-fixing treatment is a treatment in which the heat treatment is performed at a crystallization temperature or higher while maintaining the tensioned state while holding the end portion of the stretched film with a clip. The crystallization of the polyvinyl alcohol-based resin layer can be promoted by heat setting treatment. The temperature of the heat setting treatment is preferably in the range of stretching temperature - 0 ° C - stretching temperature - 80 ° C, more preferably in the range of stretching temperature - 0 ° C - stretching temperature - 50 ° C.

[3] Dyeing step S30

This step is a step of dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to adsorb and align to form a polarizing layer. Through this step, a polarizing laminated film having a polarizing sublayer on one or both of the base film layers can be obtained.

The dichroic dye, specifically, for example, may be iodine or a dichroic organic dye. Specific examples of the dichroic organic dye include, for example, Red BR, Red LR, Red R, Pink LB, Ruby BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Bronze RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Bright Violet BK, Spencer Blue G, Spencer Blue GL Sip Diligent Orange GL, Zhengtian Blue, Fresh Orange S, Fresh Black, etc. The dichroic dye may be used alone or in combination of two or more.

The dyeing step can be carried out by immersing the entire stretched film in a solution (dyeing solution) containing a dichroic dye. As the dyeing solution, a solution obtained by dissolving the above dichroic dye in a solvent can be used. Although the solvent of the dyeing solution is generally water, it is also possible to further add an organic solvent having compatibility with water. The concentration of the dichroic dye in the dyeing solution is preferably from 0.01% by weight to 10% by weight, more preferably from 0.02% by weight to 7% by weight, even more preferably from 0.025% by weight to 5% by weight.

In the case where iodine is used as the dichroic dye, since the dyeing efficiency can be further improved, it is preferred to further add the iodide in the dye solution containing iodine. Iodide, for example, may be potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, iodide Titanium, etc. The concentration of the iodide in the dyeing solution is preferably from 0.01% by weight to 20% by weight. Among the iodides, potassium iodide is preferred. In the case of adding potassium iodide, the ratio of iodine to potassium iodide is preferably in the range of 1:5 to 1:100 by weight ratio, more preferably in the range of 1:6 to 1:80. The range is from 1:7 to 1:70.

The immersion time of the stretched film in the dyeing solution is usually in the range of 15 seconds to 15 minutes, preferably 30 seconds to 3 minutes. Further, the temperature of the dyeing solution is preferably in the range of 10 ° C to 60 ° C, and more preferably in the range of 20 ° C to 40 ° C.

Further, in the dyeing step S30, the stretched film may be further subjected to a stretching treatment. In an embodiment of this case, for example, it may be (1) after the stretching treatment is performed at a magnification lower than the target in the stretching step S20, and then in the dyeing treatment in the dyeing step S30. a state in which the stretching treatment is performed in such a manner that the stretching ratio reaches the target magnification; and the crosslinking treatment is performed after the dyeing treatment as described later. (2) After the stretching treatment is performed at a lower than the target magnification in the stretching step S20, Further, the stretching treatment is performed in the dyeing treatment in the dyeing step S30 until the total stretching ratio has not reached the target magnification, and then the final total stretching ratio is set to the target magnification. The aspect of the stretching treatment in the crosslinking treatment, and the like.

The dyeing step S30 may contain a crosslinking treatment step which is continued by the dyeing treatment. The crosslinking treatment can be carried out by immersing the dyed film in a solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, those well known in the art can be used; for example, a boron compound such as boric acid or borax; glyoxal, glutaraldehyde or the like. The crosslinking agent may be used alone or in combination of two or more.

Specifically, the crosslinking solution may be a solution in which a crosslinking agent is dissolved in a solvent. As the solvent, for example, water can be used, but it is also possible to further contain an organic solvent having compatibility with water. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of 1% by weight to 20% by weight, more preferably in the range of 6% by weight to 15% by weight.

The cross-linking solution may contain an iodide. By adding an iodide, the polarization performance in the plane of the polarizing sub-layer can be made more uniform. Iodide, for example, may be potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, iodide Titanium, etc. The concentration of the iodide in the crosslinking solution is preferably from 0.05% by weight to 15% by weight, more preferably from 0.5% by weight to 8% by weight.

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

Further, the crosslinking treatment can be carried out simultaneously with the dyeing treatment by blending the crosslinking agent in the dyeing solution. Further, the stretching treatment may be performed in the crosslinking treatment. The specific aspect in which the stretching treatment is carried out in the crosslinking treatment is as described above.

After the dyeing step S30, it is preferred to carry out the washing step and the drying step before the bonding step S40 to be described later. The washing step typically includes a water washing step. The water washing treatment may be performed by immersing the film after the dyeing treatment or the crosslinking treatment in pure such as ion-exchanged water or distilled water. Come in the water. The water washing temperature is usually from 3 ° C to 50 ° C, preferably from 4 ° C to 20 ° C. The immersion time in water is usually from 2 seconds to 300 seconds, preferably from 3 seconds to 240 seconds.

The washing step may be a combination of a water washing step and a washing step using an iodide solution. Further, in the washing liquid used in the water washing step and/or the washing treatment using the iodide solution, in addition to water, it may be appropriately contained such as methanol, ethanol, isopropyl alcohol, butanol, A liquid alcohol such as propanol.

The drying step performed after the washing step may be any suitable method such as natural drying, air drying, heat drying or the like. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C; the drying time is usually about 1 to 15 minutes. The polarizing laminated film obtained as described above can be used as a polarizing element as it is, and can also be used as an intermediate for forming a polarizing plate composed of a polarizing layer and a protective film.

The thickness of the polarizer layer of the polarizing laminated film is preferably 10 μm or less, and more preferably 7 μm or less. By making the thickness of the polarizer layer 10 μm or less, a thin polarizing laminated film can be formed.

<Method of Manufacturing Polarizing Plate>

In the method for producing a polarizing plate of the present invention, the step of preparing the above-mentioned polarizing laminated film and the bonding of the protective film to the polarizing layer of the polarizing laminated film to obtain a bonded film may be carried out in a step S40. The peeling step S50 of peeling off the substrate film by the film.

[4] bonding step S40

In this step, a protective film is bonded to the polarizing layer of the polarizing laminated film (that is, the surface opposite to the side of the base film side of the polarizing layer) to obtain a bonded film. The protective film can be attached to the polarizing layer by using an adhesive or a binder. In the case where the polarizing laminated film has a polarizing layer on both surfaces of the base film, the protective film is usually bonded to the polarizing layer on both sides. In this case, the protective film may be the same protective film or a different protective film.

(protective film)

The protective film may be, for example, a polyolefin-based resin such as a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a decene-based resin); for example, cellulose triacetate. a cellulose ester resin such as cellulose diacetate; a polyester resin such as polyethylene terephthalate, polyethylene naphthalate or polybutylene terephthalate; a resin; a (meth)acrylic resin; or a film composed of a mixture, a copolymer or the like. Examples of the commercially available products which can be used for the cyclic polyolefin resin, the film thereof, and the cellulose triacetate are as described above.

The protective film may also be a protective film having optical functions such as a retardation film and a luminance increasing film. For example, a resin film made of the above material is stretched (uniaxially stretched or biaxially stretched), and a liquid crystal layer or the like is formed on the film to form a phase difference film to which an arbitrary retardation value is imparted.

An optical layer such as a hard coat layer, an antiglare layer, an antireflection layer or the like may be formed on the surface opposite to the polarizing sublayer of the protective film. The method of forming the optical layers on the surface of the protective film is not particularly limited, and a well-known method can be used. The optical layer may be formed on the protective film in advance before the bonding step S40 is performed, or may be formed after the bonding step S40 is performed or after the peeling step S50 described later.

When the protective film is bonded to the polarizer layer, plasma treatment, corona treatment, ultraviolet irradiation treatment, and combustion (flame) may be performed on the surface of the polarizing layer of the protective film in order to improve the bonding property with the polarizing layer. Surface treatment (easy bonding treatment) such as treatment, saponification treatment or the like; wherein, preferably, it is subjected to plasma treatment, corona treatment or saponification treatment. For example, when the protective film is made of a cyclic polyolefin resin, it is usually subjected to plasma treatment or corona treatment. Moreover, in the case of being composed of a cellulose ester-based resin, it is usually subjected to a saponification treatment. The saponification treatment may, for example, be a method of immersing in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide.

Although the thickness of the protective film is preferably thin, when it is too thin, the strength is lowered. The workability is deteriorated. When one side is too thick, the transparency is lowered, and the ripening time required after the bonding becomes long. Therefore, the thickness of the protective film is preferably 90 μm or less, more preferably 5 μm to 60 μm, and still more preferably 5 μm to 50 μm. Moreover, from the viewpoint of thinning of the polarizing plate, the total thickness of the polarizing layer and the protective film is preferably 100 μm or less, more preferably 90 μm or less, and still more preferably 80 μm or less.

(adhesive)

As the adhesive, an aqueous adhesive or a photocurable adhesive can be used. The water-based adhesive may be, for example, an adhesive composed of a polyvinyl alcohol-based resin aqueous solution or an aqueous two-liquid urethane-based emulsion adhesive. In particular, when a cellulose ester-based resin film subjected to surface treatment (hydrophilization treatment) by saponification treatment or the like is used as the protective film, it is preferred to use a water-based adhesive composed of a polyvinyl alcohol-based resin aqueous solution. .

As the polyvinyl alcohol-based resin, a vinyl alcohol homopolymer obtained by saponifying a polyvinyl acetate of a single polymer of vinyl acetate may be used, and vinyl acetate may be used. A polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of another copolymerized monomer of another copolymerization, or a modified polyvinyl alcohol-based polymer obtained by modifying a hydroxyloxy moiety. The aqueous adhesive may contain an additive such as a polyvalent aldehyde, a water-soluble epoxy compound, a melamine compound, a zircon compound, or a zinc compound. When a water-based adhesive is used, the thickness of the adhesive layer obtained from the other is usually 1 μm or less.

Applying a water-based adhesive to the polarizer layer of the polarizing laminate film and/or the protective film, and bonding the films through the adhesive layer, preferably by pressurizing with a bonding roll or the like. The bonding step is performed by close fitting. The coating method of the water-based adhesive (the same applies to the photocurable adhesive) is not particularly limited, and a casting method, a bar coating method, a gravure coating method, a spot coating method, a doctor blade method, and a die coating method can be used. Methods such as the method, the dip coating method, the spray method, and the like are well known.

In the case of using a water-based adhesive, it is preferred to carry out the above-mentioned bonding and carry out A drying step for removing the water contained in the aqueous adhesive to dry the film. Drying can be carried out, for example, by introducing the film into a drying oven. The drying temperature (temperature of the drying oven) is preferably from 30 ° C to 90 ° C. When it is less than 30 ° C, there is a tendency that the protective film is easily peeled off from the polarizing sub-layer. Further, when the drying temperature exceeds 90 ° C, there is a possibility that the polarizing performance of the polarizing layer is deteriorated due to heat. The drying time may be from about 10 seconds to about 1000 seconds, and from the viewpoint of productivity, it is preferably from 60 seconds to 750 seconds, and more preferably from 150 seconds to 600 seconds.

After the drying step, it may be set at room temperature or slightly higher than other temperatures, for example, at a temperature of about 20 ° C to 45 ° C, and a ripening step of about 12 hours to 600 hours. The ripening temperature is generally set to be lower than the drying temperature.

The photocurable adhesive is an adhesive which is cured by irradiation with an active energy ray such as ultraviolet rays. For example, it may be a material containing a polymerizable compound and a photopolymerization initiator, or a photoreactive resin, and may be contained. A combination of a resin and a photoreactive crosslinking agent. The polymerizable compound may, for example, be a photopolymerizable monomer such as a photocurable epoxy monomer, a photocurable acrylic monomer, or a photocurable urethane monomer; and An oligomer or the like derived from a polymerizable monomer. The photopolymerization initiator may be, for example, a substance containing an active species called a neutral radical, an anionic radical, or a cationic radical by irradiation with an active energy ray such as ultraviolet rays. The photocurable adhesive containing a polymerizable compound and a photopolymerization initiator is preferably one containing a photocurable epoxy monomer and a photocationic polymerization initiator.

When a photocurable adhesive is used, after performing the above-mentioned bonding, a drying step may be performed as needed (a photocurable adhesive is a solvent-containing material, etc.), and then an active energy ray is irradiated to make a photocurable adhesive. Hardening step of hardening. The light source of the active energy ray is not particularly limited, but preferably has an illuminating distribution of active energy rays having 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, and a chemistry are preferably used. Lamps, black lights, microwave-activated mercury lamps, methyl halide lamps.

The light irradiation intensity of the photocurable adhesive is appropriately determined by the composition of the photocurable adhesive, and it is preferable that the irradiation intensity in the wavelength region effective for activation of the polymerization initiator becomes 0.1 mW/ Set by the way of cm ² ~ 6000mW/cm ² . When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time becomes too long, and in the case of 6000 mW/cm ² or less, there is little heat which is radiated from the light source and heat when the photocurable adhesive hardens. As a result, the photocurable adhesive is yellowed and the photonic layer is deteriorated.

In the light-curing adhesive light irradiation time, it is also appropriately determined by the composition of the photocurable adhesive. Preferably, the integrated light amount expressed by the product of the irradiation intensity and the irradiation time is set to 10 mJ/cm. ² ~ 10000mJ / cm ² . When the integrated light amount is 10 mJ/cm ² or more, a sufficient amount of the active species from the polymerization initiator can be generated, so that the hardening reaction can be performed more reliably; in the case of 10000 mJ/cm ² or less, the irradiation time can be made not. It becomes too long to maintain good productivity.

Further, the thickness of the adhesive layer after the active energy ray irradiation is usually about 0.001 μm to 5 μm, preferably 0.01 μm to 2 μm, and more preferably 0.01 μm to 1 μm.

(adhesive)

The adhesive which can be used for the adhesion of the protective film is usually made of an acrylic resin, a styrene resin, a polyoxymethylene resin or the like as a base polymer, and an isocyanate compound, an epoxy compound, an aziridine is added thereto. A binder composition of a crosslinking agent such as a compound. It is also possible to further contain fine particles as a binder layer for exhibiting light scattering properties.

The thickness of the adhesive layer may be 1 μm to 40 μm, and is preferably applied thinly within a range that does not impair the properties of workability and durability. Specifically, it is preferably 3 μm to 25 μm. The thickness of 3 μm to 25 μm is suitable for the viewpoint of having good workability and suppressing dimensional change of the polarizing sub-layer. When the adhesive layer is less than 1 μm, the adhesiveness is lowered; when it exceeds 40 μm, the adhesive bleed out and the like are liable to occur. Bonding the protective film to the polarizing sublayer using a binder In the method, the polarizer layer may be attached after the adhesive layer is disposed on the surface of the protective film; or after the adhesive layer is disposed on the polarizer layer, the protective film may be attached thereto.

The method of forming the adhesive layer is not particularly limited, and a binder composition (binder solution) containing each component mainly composed of the above-mentioned base polymer may be applied to the protective film surface or the photoreceptor layer. After drying to form a binder layer, the protective film and the polarizer layer are bonded together; after the adhesive layer is formed on the separator (release film), the adhesive layer is transferred onto the protective film surface or On the surface of the polarizing film, the separator is peeled off from the adhesive layer, and then the protective film and the polarizing layer are bonded together. When the adhesive layer is formed on the surface of the protective film or the photoreceptor layer, surface treatment may be performed on the protective film surface or the polarizing polarizer layer or on one or both sides of the adhesive layer as needed, for example, corona treatment. Wait.

[5] Stripping step S50

This step is a step of peeling off the base film from the bonded film obtained by bonding the protective film. Through this step, a polarizing plate in which a protective film is laminated on a polarizing sub-layer can be obtained. The polarizing laminated film has a polarizing layer on both surfaces of the base film, and a protective film is bonded to the polarizing layer on both sides, and the peeling step S50 can be obtained from one polarizing laminated film. Two polarizers.

The method of peeling off the base film is not particularly limited, and it can be peeled off by the same method as the peeling step of the separator (release film) which is generally performed with the adhesive polarizer. The base film may be peeled off as it is after the bonding step S40, or may be once rolled into a roll shape after the bonding step S40, and peeled off while being rolled out in the subsequent steps.

The polarizing plate manufactured as described above can also be used as an optical film in which another optical layer is laminated in actual use. Further, the protective film may have a function as an optical layer like this. The other optical layer may be, for example, a reflective polarizing film that allows a certain polarized light to pass through and reflects a polarized light having a property opposite to that of the opposite side; the surface has an uneven shape with anti-glare Functional film; anti-reflective film on the surface; reflective film with reflective function on the surface; semi-transparent reflective film with reflective and transmissive functions; viewing angle compensation film.

It is a commercial product of a reflective polarizing film that allows a certain kind of polarized light to pass through and reflects the polarized light of the opposite nature. For example, "DBEF" (made by 3M company, available from Sumitomo in Japan) 3M Co., Ltd. acquired, "APF" (3M company, available from Sumitomo 3M Co., Ltd. in Japan).

The viewing angle compensation film may be, for example, an optical compensation film obtained by coating a liquid crystal compound on a surface of a substrate and being aligned/fixed; a retardation film made of a polycarbonate resin; A retardation film made of an olefin resin or the like.

A commercially available product of an optical compensation film which is coated with a liquid crystal compound and which is aligned/fixed on the surface of the substrate. For example, "WV film" (made by Fujifilm Co., Ltd.) and "NH film" (JX) "Nippon Mining Co., Ltd.", "NR film" (made by JX Nippon Mining & Energy Co., Ltd.).

A commercially available product of a phase difference film made of a cyclic polyolefin resin, for example, "Atong Film" (manufactured by JSR Co., Ltd.) and "Esna" (manufactured by Sekisui Chemical Co., Ltd.) "Jenno Film" (made by Japan Jayne Co., Ltd.).

[Examples]

Hereinafter, the present invention will be further specifically described by way of examples, but the present invention is not limited by the examples.

<Example 1>

(1) Fabrication of substrate film

Using a multilayer extrusion molding machine, by co-extrusion molding: a random copolymer of propylene/ethylene containing about 5% by weight of ethylene unit (Sumitomo Nippon W151, manufactured by Sumitomo Chemical Co., Ltd.), melting point Tm = 138 ° C) on both sides of the resin layer, configured with a separate polymer of propylene (live A strip-shaped base film of a three-layer structure formed by a resin layer composed of "Sumitomo Nuofu FLX80E4" and a melting point Tm = 163 ° C) manufactured by Toyo Chemical Co., Ltd. The total thickness of the base film was 100 μm, and the thickness ratio of each layer (FLX80E4/W151/FLX80E4) was 3/4/3.

(2) Production of laminated film (resin layer forming step)

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Co., Ltd., average polymerization degree 1100, average saponification degree: 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a concentration of 3% by weight. An aqueous solution of polyvinyl alcohol. In the obtained aqueous solution, a crosslinking agent ("Amine series resin 650" manufactured by Tajika Chemical Industry Co., Ltd.) was added in a ratio of 1 part by weight based on 2 parts by weight of the polyvinyl alcohol powder. A coating liquid for forming a base layer.

Further, polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree: 98.0 mol% to 99.0 mol%) was dissolved in hot water at 95 ° C to prepare a concentration. A 8% by weight aqueous solution of polyvinyl alcohol was used as a coating liquid for forming a polyvinyl alcohol-based resin layer.

The substrate film produced in the above (1) is continuously conveyed, and one side thereof is subjected to corona treatment, and the base layer is continuously applied to the corona-treated surface using a micro gravure coater. The coating liquid for formation was dried at 80 ° C for 3 minutes to form a base layer having a thickness of 0.2 μm . Then, the coating liquid for forming a polyvinyl alcohol-based resin layer was continuously applied onto the underlayer by a spot coater while the film was conveyed, and dried at 90 ° C for 1 minute, dried at 70 ° C for 3 minutes, and then at 60 ° The mixture was dried at ° C for 4 minutes to form a polyvinyl alcohol-based resin layer having a thickness of 10.0 μm on the base layer.

Further, the surface of the base film opposite to the surface on which the polyvinyl alcohol-based resin layer is formed is subjected to the same treatment as described above, and the underlayer and the polyvinyl alcohol-based resin layer are formed in this order, and the base film is formed. A base layer having a thickness of 0.2 μm and a polyvinyl alcohol-based resin layer having a thickness of 10.0 μm are formed on both sides, thereby obtaining a polyvinyl alcohol-based resin layer/base layer/base film/base layer/polyvinyl alcohol system. The layer of the resin layer constitutes a laminated film formed.

(3) Production of stretched film (stretching step)

By using the stretching apparatus shown in Fig. 2, the laminated film produced in the above (2) is continuously conveyed, and the two-stage longitudinal uniaxial stretching treatment is performed by the inter-roll stretching method (toward the film conveying direction). The free end is uniaxially stretched), and a stretched film is produced. The stretching temperature in the two-stage drawing treatment (the ambient temperature in the heating furnaces 20, 30) was set to 160 °C. The stretching ratio in the first and second stretching processes was adjusted to adjust the rotation speeds of the rolls 1, 2, 3, and 4 to 2.00 times and 2.90 times, respectively. The total draw ratio was 5.80 times. The thickness of the polyvinyl alcohol-based resin layer in the stretched film was 4.6 μm on one side and 4.8 μm on the other side.

It was confirmed that the obtained stretched film did not cause wrinkles due to stretching. When the obtained stretched film was measured for the difference in thickness in the film width direction as defined above, it was 3 μm; and in the film width direction, it was stretched to a substantially uniform thickness distribution.

(4) Production of polarizing laminated film (dyeing step)

While continuously carrying the impregnated film produced in the above (3), the immersion was carried out in a warm water bath at 60 ° C for 60 seconds, and then in a dyeing solution containing 30% of iodine and potassium iodide, the residence time was The immersion was performed for about 150 seconds to carry out the dyeing treatment of the polyvinyl alcohol-based resin layer, and then the excess dyeing solution was washed away with pure water at 10 °C. Next, immersion was carried out in a crosslinking solution containing boric acid and potassium iodide at 76 ° C for a residence time of 600 seconds to carry out a crosslinking treatment. Thereafter, the film was washed with pure water at 10 ° C for 4 seconds and dried at 80 ° C for 300 seconds to prepare a polarizing laminated film.

(5) Production of polarizing plate (bonding step and peeling step)

Polyvinyl alcohol powder ("KL-318" manufactured by Kuraray Co., Ltd., average polymerization degree: 1800) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight. The obtained aqueous solution is prepared by mixing a crosslinking agent ("Amine series resin 650" manufactured by Takaoka Chemical Industry Co., Ltd.) in a ratio of 1 part by weight based on 2 parts by weight of the polyvinyl alcohol powder. An aqueous solution of the adhesive.

Next, while continuously transporting the polarizing laminated film produced in the above (4), After applying the above aqueous solution of the adhesive on the polarizing layer on both sides, the saponified protective film (the transparent protective film made of triethylenesulfonyl cellulose (TAC)) is applied to the bonding surface (Konica Minolta Co., Ltd.) "KC4UY" manufactured by the company, thickness 40 μm], which is bonded to the polarizing sub-layer, and is pressed by a pair of bonding rolls to form a TAC polarizing layer/base layer/substrate The film/base layer/polarized sub-layer/TAC layer constitutes a laminated film (bonding step).

Next, the base film was peeled off from the bonded film to obtain two polarizing plates made of a TAC/polarized sublayer/base layer and a transparent protective film made of TAC laminated on the polarizing layer through the adhesive layer. In the step of peeling off the above-mentioned base film, no breakage or the like is caused.

<Example 2>

A polarizing plate was produced in the same manner as in Example 1 except that the stretching ratio in the first and second stretching treatments was changed to 2.50 times and 2.32 times (total stretching ratio of 5.80 times). The thickness of the polyvinyl alcohol-based resin layer in the stretched film was 4.8 μm on one side and 5.0 μm on the other side. It was confirmed that there was no wrinkle in the stretched film, and the difference in thickness in the film width direction was 2 μm, and the stretching was uniform. The bonding step and the peeling step are also polarized plates in which a protective film is laminated without any problem.

<Example 3>

A polarizing plate was produced in the same manner as in Example 1 except that the stretching ratios in the first and second stages of the stretching treatment were 2.80 times and 2.07 times (total stretching ratio of 5.80 times), respectively. The thickness of the polyvinyl alcohol-based resin layer in the stretched film was 5.2 μm on one side and 5.4 μm on the other side. It was confirmed that there was no wrinkle in the stretched film, and the difference in thickness in the film width direction was 2 μm, and the stretching was uniform. The bonding step and the peeling step are also polarized plates in which a protective film is laminated without any problem.

<Example 4>

A polarizing plate was produced in the same manner as in Example 1 except that the draw ratios in the first and second stages of the stretching treatment were 3.40 times and 1.70 times, respectively (total stretching ratio of 5.78 times). The thickness of the polyvinyl alcohol-based resin layer in the stretched film was 5.1 μm on one side and 5.3 μm on the other side. Confirm that there are no wrinkles in the stretched film, The difference in thickness in the film width direction was 2 μm, and the stretching was uniform. The bonding step and the peeling step are also polarized plates in which a protective film is laminated without any problem.

<Comparative Example 1>

A stretched film was produced in the same manner as in Example 1 except that the draw ratio in the first stretch treatment was 5.80 times, and the second stretch treatment was not performed. In the obtained stretched film, strong wrinkles were generated in the stretching direction.

<Comparative Example 2>

A stretched film was produced in the same manner as in Example 1 except that the draw ratios in the first and second stretch treatments were 1.54 times and 3.80 times, respectively (total draw ratio of 5.85 times). The thickness of the polyvinyl alcohol-based resin layer in the stretched film was 4.7 μm on one side and 5.2 μm on the other side. Although no wrinkles were observed in the obtained stretched film, the difference in thickness in the film width direction was as large as 7 μm, and the stretching was not uniform.

The ratio of the stretching ratio and the stretching ratio in the stretching treatment of the first and second stages (the ratio of the stretching ratio in the first stretching step to the stretching ratio in the second stretching step) The measurement results of the total draw ratio and the difference in thickness between the wrinkles of the stretched film and the film width direction are summarized in Table 1.

<Possibility of industrial use>

According to the method of the present invention, since the occurrence of wrinkles at the time of stretching the laminated film and the stretching unevenness in the film width direction (that is, the thickness unevenness in the film width direction) can be effectively suppressed, it is possible to obtain a good yield. A polarizing laminate film or a polarizing plate having good appearance and optical characteristics is produced.

S10‧‧‧ resin layer forming step

S20‧‧‧ stretching step

S30‧‧‧Staining step

S40‧‧‧Finishing steps

S50‧‧‧ peeling step

Claims (6)

A method for producing a polarizing laminated film, comprising: a resin layer forming step of applying a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of a base film, followed by drying a polyvinyl alcohol-based resin layer to form a laminated film; a stretching step of longitudinally uniaxially stretching the laminated film to obtain a stretched film; and a dyeing step of stretching the film by a dichroic dye The polyvinyl alcohol-based resin layer is dyed to form a polarizing sub-layer to obtain a polarizing laminated film; wherein the stretching step is a stretching treatment step including two or more stages; and the stretching ratio in the first-stage stretching treatment step is relatively The ratio of the draw ratio meter in the second stretching treatment step is 0.5 or more, and the total stretch ratio of the polarizer layer is more than 5 times based on the polyvinyl alcohol-based resin layer of the laminated film. The production method according to claim 1, wherein the polyvinyl alcohol-based resin layer is formed on both surfaces of the base film in the resin layer forming step. The production method according to the first or second aspect of the invention, wherein the polyvinyl alcohol-based resin layer of the laminated film has a thickness of from 3 μm to 30 μm. The manufacturing method according to any one of claims 1 to 3, wherein the stretching ratio in the first stretching treatment step is less than 5 times. The production method according to any one of claims 1 to 4, wherein the base film is made of a polypropylene resin. A method for producing a polarizing plate, comprising: a step of preparing a polarizing laminated film obtained by the manufacturing method according to any one of claims 1 to 5; a step of bonding a protective film to the polarizing layer of the polarizing laminate film to obtain a bonded film, and a step of peeling the base film from the bonded film.