KR102091301B1 - Method for manufacturing polarized laminated film and method for manufacturing polarizing plate - Google Patents

Abstract

A resin layer forming process of coating a coating solution containing a polyvinyl alcohol-based resin on a base film to obtain a laminated film; Stretching process to obtain a stretched film by longitudinally uniaxially stretching the laminated film; The dyeing process includes dyeing a polyvinyl alcohol-based resin layer of a stretched film with a dichroic dye to form a polarizer layer, and the stretching step includes two or more steps of stretching treatment, and a draw ratio in the second step of stretching treatment. A polarizing plate using a method for producing a polarizing laminated film obtained by the method and a method for producing a polarizing laminated film in which the ratio of the stretching ratio in the first-stage stretching treatment step is 0.5 or more, and the total stretching ratio of the polarizer layer is more than 5 times. It is a manufacturing method.

Description

A manufacturing method of a polarizing laminated film and a manufacturing method of a polarizing plate {METHOD FOR MANUFACTURING POLARIZED LAMINATED FILM AND METHOD FOR MANUFACTURING POLARIZING PLATE}

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

The polarizing plate is widely used as a supply element for polarization in a liquid crystal display device and as a detection element for polarization. Conventionally, as a polarizing plate, a thing in which a protective film made of triacetyl cellulose or the like is bonded to a polarizing film made of a polyvinyl alcohol-based resin through an adhesive is recently used, but has recently been applied to mobile devices such as notebook personal computers and mobile phones. 2. Description of the Related Art With the development of liquid crystal display devices and the development of large-sized televisions, thinning and lightening of polarizing plates is required.

However, the polarizing film is produced by stretching and dyeing a film base (typically, about 75 μm thick) of a polyvinyl alcohol-based resin, and the thickness of the film after stretching is usually about 30 μm. The thinning of the above-mentioned thin film was difficult because there was a problem of productivity such that the film during stretching tends to break.

Thus, a polyvinyl alcohol-based resin layer was formed on the base film by coating a coating solution containing a polyvinyl alcohol-based resin to obtain a laminated film, and then subjected to stretching and dyeing treatment on the laminated film to obtain polyvinyl alcohol-based resin. A method for producing a laminated film (polarizing plate) having a polarizer layer by providing a polarizing function to the base layer to form a polarizer layer has been proposed (for example, Patent Documents 1 to 3).

Patent Document 1: Japanese Patent Publication No. 2009-93074 Patent Document 2: Japanese Patent Publication No. 2011-150313 Patent Document 3: Japanese Patent Publication No. 2012-159778

According to the method of forming a polarizer layer by coating of a coating solution containing a polyvinyl alcohol-based resin as described in Patent Documents 1 to 3, than when a polarizing film is produced from a film disk of a polyvinyl alcohol-based resin Since a thin polarizer layer can be obtained, it is advantageous from the viewpoint of thinning and reducing the thickness of the polarizing plate.

However, when the laminated film having a polyvinyl alcohol-based resin layer is subjected to stretching treatment, wrinkles are generated in the film after stretching, or uneven stretching (uniform stretching) occurs in the film width direction, and in the film width direction in the film after stretching. There was a problem that thickness unevenness occurred.

Therefore, the object of the present invention is to form a polyvinyl alcohol-based resin layer by coating a coating liquid containing a polyvinyl alcohol-based resin on a base film, to obtain a laminated film, and then to polyvinyl by stretching and dyeing the laminated film. In the method of manufacturing a polarizing laminated film or a polarizing plate by using an alcohol-based resin layer as a polarizer layer, the laminated film can be stretched while suppressing the occurrence of wrinkles or stretching unevenness, so that the appearance and optical properties are thin. It is to provide a method for producing a light-emitting laminated film or a polarizing plate with good yield.

The present invention includes the following ones.

[1] a resin layer forming step of forming a polyvinyl alcohol-based resin layer by coating a coating solution containing a polyvinyl alcohol-based resin on at least one side of the base film, followed by drying to obtain a laminated film;

Stretching step of obtaining a stretched film by longitudinally uniaxially stretching the laminated film,

It includes a dyeing process to obtain a polarizing laminated film by dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form a polarizer layer,

The stretching process includes two or more steps of stretching treatment,

The ratio of the stretching ratio in the stretching treatment step in the first stage to the stretching ratio in the stretching treatment step in the second stage is 0.5 or more,

The total stretch magnification of the polarizer layer is a method of manufacturing a polarizing laminated film that is more than 5 times based on the polyvinyl alcohol-based resin layer of the laminated film.

[2] The method for producing the polarizing laminated film according to [1], in which 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 thickness of the polyvinyl alcohol-based resin layer of the laminated film is 3 µm to 30 µm.

[4] The production method according to any one of [1] to [3], wherein the stretching ratio in the first-stage 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-based resin.

[6] a step of preparing a polarizing laminated film obtained according to the production method according to any one of [1] to [5],

The process of bonding a protective film on the polarizer layer of the polarizing laminated film to obtain a bonding film,

Step of peeling the base film from the bonding film

Method of manufacturing a polarizing plate comprising a.

According to the method of the present invention, it is possible to effectively suppress the occurrence of wrinkles during stretching of the laminated film and uneven stretching in the film width direction (thus, uneven thickness in the film width direction), so that appearance and optical characteristics can be suppressed. This good polarizing laminated film or polarizing plate can be produced with good yield.

1 is a flowchart showing a preferred embodiment of a method of manufacturing a polarizing laminated film and a method of manufacturing a polarizing plate according to the present invention.
2 is a schematic view showing an example of multi-stage stretching in the stretching step (S20).
3 is a schematic view showing another example of multi-stage stretching in the stretching step (S20).
4 is a schematic view for explaining a longitudinal uniaxial stretching method using a chuck.

Hereinafter, an embodiment and a method of manufacturing the polarizing laminated film according to the present invention and a method of manufacturing the polarizing plate will be described in detail.

<Method for producing a polarizing laminated film>

1 is a flowchart showing a preferred embodiment of a method of manufacturing a polarizing laminated film and a method of manufacturing a polarizing plate according to the present invention. The manufacturing method of the polarizing laminated film of this embodiment is the following process:

A resin layer forming step (S10) of coating a coating solution containing a polyvinyl alcohol-based resin on at least one surface of the base film, followed by drying to form a polyvinyl alcohol-based resin layer to obtain a laminated film.

Stretching step (S20) to obtain a stretched film by longitudinally uniaxially stretching the laminated film,

Dyeing process to obtain a polarizing laminated film by dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form a polarizer layer (S30),

Include in this order.

As will be described later, in the present embodiment, the polarizing plate is bonded to a protective film on the polarizer layer of the polarizing laminated film obtained by performing the dyeing process (S30) to obtain a bonding film (bonding process (S40)), and then It can be obtained by peeling and removing the base film from the bonding film (peeling step (S50)).

Hereinafter, each process of S10-S30 included in the manufacturing method of the polarizing laminated film of this embodiment is demonstrated in detail.

[1] Resin layer forming process (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. This polyvinyl alcohol-based resin layer is a layer that becomes a polarizer layer through a stretching step (S20) and a dyeing step (S30). The polyvinyl alcohol-based resin layer can be formed by coating a coating liquid containing a polyvinyl alcohol-based resin on one side or both sides of a base film and drying the coating layer. According to such a method, since the thickness of the polyvinyl alcohol-based resin layer and, moreover, the polarizer layer can be made small, it is advantageous for thinning and reducing the thickness of the polarizing laminated film and the polarizing plate.

(Substrate film)

The base film may be composed of a thermoplastic resin, and among them, it is preferable to be composed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of the thermoplastic resin include, for example, polyolefin-based resins such as chain polyolefin-based resins and cyclic polyolefin-based resins (norbornene-based resins); Polyester resins; (Meth) acrylic resin; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polycarbonate resins; Polyvinyl alcohol-based resins; Polyvinyl acetate resin; Polyarylate resins; Polystyrene-based resins; Polyethersulfone-based resins; Polysulfone-based resins; Polyamide resins; Polyimide resins; And mixtures and copolymers thereof.

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

Examples of the chain-type polyolefin-based resin include copolymers composed of two or more types of chain-type olefins in addition to homopolymers of chain-type olefins such as polyethylene resins and polypropylene resins. A base film made of a chain-type polyolefin-based resin is preferable because it is easy to stably stretch at a high magnification. Among them, the base film includes polypropylene-based resins (polypropylene resins which are homopolymers of propylene and copolymers mainly composed of propylene) and polyethylene-based resins (polyethylene resins that are homopolymers of ethylene and copolymers mainly composed of ethylene). ) And the like.

A copolymer mainly composed of propylene, which is one of examples that are suitably used as a thermoplastic resin constituting the base film, is a copolymer of propylene and other monomers copolymerizable therewith.

Other monomers copolymerizable with propylene include, for example, ethylene and α-olefin. As the α-olefin, an α-olefin having 4 or more carbon atoms is preferably used, and more preferably an α-olefin having 4 to 10 carbon atoms. Specific examples of the C4-C10 α-olefin include, for example, straight-chain monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; Branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene, and 4-methyl-1-pentene; Vinyl cyclohexane and the like. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer.

Content of the said other monomer is 0.1 weight%-20 weight% in a copolymer, for example, Preferably it is 0.5 weight%-10 weight%. The content of other monomers in the copolymer can be determined by performing infrared (IR) spectral measurement according to the method described on page 616 of the "Polymer Analysis Handbook" (Kinokuniya Shoten, 1995).

Among the above, as the polypropylene-based resin, a homopolymer of propylene, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, or a propylene-ethylene-1-butene random copolymer is preferably used.

It is preferable that the stereoregularity of the polypropylene-based resin is substantially isotactic or syndiotactic. A base film made of a polypropylene-based resin having substantially isotactic or syndiotactic stereoregularity has relatively good handleability and excellent mechanical strength under a high temperature environment.

The base film may be composed of one type of chain polyolefin-based resin, may be composed of a mixture of two or more types of chain polyolefin-based resin, or may be composed of a copolymer of two or more types of chain polyolefin-based resin.

The cyclic polyolefin-based resin is a generic term for a resin that is polymerized by using a cyclic olefin as a polymerization unit, for example, Japanese Patent Application Publication No. Hei1-240517, Japanese Patent Publication No. 3-14882, Japanese Patent Publication No. 3-122137. And resins described in publications and the like. Specific examples of the cyclic polyolefin-based resin include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with chain olefins such as ethylene and propylene (typically random copolymers), and Graft polymers modified with unsaturated carboxylic acids and derivatives thereof, and hydrides thereof. Among them, a norbornene-based resin using norbornene-based monomers such as norbornene or polycyclic norbornene-based monomer is preferably used as the cyclic olefin.

Various products are commercially available for the cyclic polyolefin-based resin. Examples of commercial products of cyclic polyolefin-based resins are all brand names, `` Topas '' (manufactured by TOPAS ADVANCED POLYMERS GmbH, available from Polyplastics Co., Ltd.), `` Atone '' (manufactured by JSR Corporation), `` Zeo Noah (ZEONOR) (manufactured by Nippon Zeon Co., Ltd.), "ZEONEX" (manufactured by Nippon Zeon Co., Ltd.), and "Apel" (manufactured by Mitsui Chemicals Co., Ltd.).

In addition, all are brand names, such as `` Essina '' (manufactured by Sekisui Kagaku Kogyo Co., Ltd.), `` SCA40 '' (manufactured by Sekisui Kagaku Kogyo Co., Ltd.), `` Zeonoa film '' (manufactured by Nippon Zeon Co., Ltd.), etc. You may use the commercial item of the film-made cyclic polyolefin resin film as a base film.

The base film may be composed of one cyclic polyolefin-based resin, a mixture of two or more cyclic polyolefin-based resins, or a copolymer of two or more cyclic polyolefin-based resins.

The polyester resin is a resin having an ester bond, and is generally composed of a polycondensate of a polyhydric carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylic acid. As the polyhydric alcohol, divalent diols can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

Polyethylene terephthalate, which is a polycondensation of terephthalic acid and ethylene glycol, is exemplified as a representative example of the polyester resin. Polyethylene terephthalate is a crystalline resin, but the one in the state before the crystallization treatment is easy to perform treatment such as stretching. If necessary, the crystallization treatment may be performed at the time of stretching or by heat treatment after stretching. In addition, a copolymerized polyester having a low crystallinity (or made amorphous) by further copolymerizing another type of monomer on the skeleton of polyethylene terephthalate is also suitably used. Examples of such resins include those obtained by copolymerization of cyclohexanedimethanol or isophthalic acid. Since these resins are excellent in stretchability, they can be suitably used.

Specific examples of polyethylene terephthalate and polyester-based resins other than copolymers thereof include, for example, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclo And hexane dimethyl terephthalate and polycyclohexane dimethyl naphthalate.

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

(Meth) acrylic-type resin is a resin which has a (meth) acryloyl group as a main structural monomer. Specific examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate; Methyl methacrylate- (meth) acrylic acid copolymer; Methyl methacrylate- (meth) acrylic acid ester copolymer; Methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer; (Meth) methyl acrylate-styrene copolymer (MS resin, etc.); Copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group (eg, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) norbornyl acrylate copolymer, and the like). Preferably, a polymer based on a poly (meth) acrylic acid C _1-6 alkyl ester such as methyl poly (meth) acrylate is used, more preferably, methyl methacrylate as the main component (50% to 100% by weight) %, Preferably 70% to 100% by weight), a methyl methacrylate-based resin is used.

The base film may be composed of one (meth) acrylic resin, a mixture of two or more (meth) acrylic resins, or a copolymer of two or more (meth) acrylic resins. .

The cellulose ester-based resin is an ester of cellulose and fatty acids. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose dipropionate, and the like. Moreover, these copolymers and the part in which a part of hydroxyl group was modified with another substituent are mentioned. Among these, cellulose triacetate (triacetylcellulose) is particularly preferred. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available products of cellulose triacetate are `` Fujitaek TD80 '' (manufactured by Fujifilm Co., Ltd.), `` Fujitaek TD80UF '' (manufactured by Fujifilm Co., Ltd.), and `` Fujitaek TD80UZ '' (Fujifilm Co., Ltd.) ) Manufacturing), `` Fujitaek TD40UZ '' (manufactured by Fujifilm Co., Ltd.), `` KC8UX2M '' (manufactured by Konica Minolta Opto Co., Ltd.), `` KC4UY '' (manufactured by Konica Minolta Opto Co., Ltd.), and the like.

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

The polycarbonate-based resin is an engineering plastic made of a polymer in which monomer units are bonded through a carbonate group, and is a resin having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate-based resin constituting the base film may be a resin called a modified polycarbonate such as modified polymer skeleton to lower the photoelastic coefficient, or a copolymerized polycarbonate with improved wavelength dependence.

Various products are commercially available for the polycarbonate resin. Examples of commercially available products of polycarbonate-based resins are all brand names, such as `` Panlight '' (Teijin Kasei Co., Ltd.), `` Yupron '' (Mitsubishi Engineering Plastics Co., Ltd.), `` SD Polycar '' (Sumitomodow ( Co., Ltd.), a "caliber" (manufactured by Dow Chemical Co., Ltd.), and the like.

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

In addition to the thermoplastic resin, any suitable additive may be added to the base film. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and coloring agents. 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, further preferably 60% by weight to 98% by weight, particularly preferably 70% by weight % To 97% by weight. When the content of the thermoplastic resin in the base film is less than 50% by weight, there is a concern that the high transparency and the like inherent in the thermoplastic resin may not be sufficiently exhibited.

Although the thickness of the base film can be appropriately determined, generally 1 µm to 500 µm is preferable, 1 µm to 300 µm is more preferable, and 5 µm to 200 µm is more preferable from the viewpoint of workability such as strength and handling. Preference is given, and 5 µm to 150 µm are most preferred.

(Coating solution containing polyvinyl alcohol-based resin)

The coating solution 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). As a polyvinyl alcohol-type resin, polyvinyl alcohol resin and its derivative (s) are mentioned, for example. Examples of the derivative of the polyvinyl alcohol resin include polyvinyl formal, polyvinyl acetal, etc., and polyvinyl alcohol resin modified with olefins such as ethylene and propylene; Modified with unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; Modified with an alkyl ester of an unsaturated carboxylic acid; And those modified with acrylamide. The ratio of denaturation is preferably less than 30 mol%, more preferably less than 10 mol%. When denaturation of more than 30 mol% is performed, it becomes difficult to adsorb the dichroic dye, and a problem that polarization performance is lowered can be generated. Among the polyvinyl alcohol-based resins described above, it is preferable to use a polyvinyl alcohol resin.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably in the range of 100 to 10000, more preferably in the range of 1000 to 10000, more preferably in the range of 1500 to 8000, and in the range of 2000 to 5000 It is most desirable to be in. The average degree of polymerization can be determined according to the method specified in JIS K 6726-1994 "Method for Testing Polyvinyl Alcohol". When the average polymerization degree is less than 100, it is difficult to obtain a desirable polarization performance, and when it exceeds 10000, solubility in a solvent deteriorates, and formation of a polyvinyl alcohol-based resin layer becomes difficult.

The polyvinyl alcohol-based resin is preferably a saponified product of a polyvinyl acetate-based resin. It is preferable that the range of saponification degree is 80 mol% or more, further 90 mol% or more, especially 94 mol% or more. When the degree of saponification is too low, there is a possibility that the water resistance and the moisture heat resistance when the polarizing laminated film or polarizing plate is used are insufficient. In addition, although a completely saponified product (the degree of saponification is 100 mol%) may be used, if the degree of saponification is too high, the dyeing speed becomes slow, and in order to provide sufficient polarization performance, manufacturing time is long, or in some cases sufficient polarization performance. There may be cases in which a polarizer layer having a or is not obtained. Therefore, the saponification degree is preferably 99.5 mol% or less, and more preferably 99.0 mol% or less.

The saponification degree is a ratio of the ratio of acetic acid groups (acetoxy group: -OCOCH ₃ ) contained in polyvinyl acetate-based resin, which is a raw material of polyvinyl alcohol-based resin, changed to hydroxyl groups by saponification treatment in unit ratio (mol%). , The following formula:

Saponification degree (mol%) = [(Number of hydroxyl groups) ÷ (Number of hydroxyl groups + Number of acetic acid groups) x 100

Is defined as

The higher the degree of saponification, the greater the proportion of hydroxyl groups, and thus the smaller the proportion of acetic acid groups that inhibit crystallization. Saponification degree can be calculated | required according to the method prescribed | regulated to JIS K 6726-1994 "Polyvinyl alcohol test method".

Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of other monomers copolymerizable with vinyl acetate. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having ammonium groups.

Examples of commercially available products of polyvinyl alcohol-based resins that can be suitably used are all trade names of "PVA124" manufactured by Kurare Co., Ltd. (soapiness degree: 98.0 mol% to 99.9 mol%), and "PVA117" (nonsaponification degree: 98.0 mol% to 99.9 mol%), "PVA117H" (dehydration degree: 99.5 mol% or more), "PVA624" (degradation degree: 95.0 mol% to 96.0 mol%), and "PVA617" (degradation degree: 94.5 mol% to 95.5 mole%); "AH-26" (soap degree: 97.0 mol% to 98.8 mol%), "AH-22" (soap degree: 97.5 mol% to 98.5 mol%), "NH-18" manufactured by Nippon Kosei Chemical Co., Ltd. (Degree of saponification: 98.0 mol% to 99.9 mol%) and "N-300" (degree of saponification: 98.0 mol% to 99.9 mol%); `` JC-33 '' manufactured by Nihon Sakubi-Foam Co., Ltd. (soap level: 99.0 mol% or more), `` JM-33 '' (soap level: 93.5 mol% to 95.5 mol%), `` JM-26 '' (soap Fig .: 95.5 mol% to 97.5 mol%), JP-45 (soap level: 86.5 mol% to 89.5 mol%), `` JF-17 '' (soap level: 98.0 mol% to 99.9 mol%), `` JF- 17L ”(degree of saponification: 98.0 mol% to 99.9 mol%) and“ JF-20 ”(degree of saponification: 98.0 mol% to 99.9 mol%).

If necessary, the coating solution may contain additives such as plasticizers and surfactants. As the plasticizer, polyol or a condensate thereof can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. It is suitable that the additive amount of the additive is 20% by weight or less of the polyvinyl alcohol-based resin.

(Coating of coating solution and drying of coating layer)

A method of coating the coating solution on the base film includes a wire bar coating method; Roll coating methods such as reverse coating and gravure coating; Die coat method; Comma coat method; Lip coat method; Spin coating method; Screen coating method; Fountain coating method; Dipping method; It can be appropriately selected from known methods such as the spray method.

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

The polyvinyl alcohol-based resin layer may be formed on only one side of the base film or may be formed on both sides. When formed on both sides, curling of a film that may occur during the production of a polarizing laminated film or a polarizing plate can be suppressed, and since two polarizing plates can be obtained from one polarizing laminated film, it is also advantageous in terms of production efficiency of the polarizing plate. Do.

The thickness of the polyvinyl alcohol-based resin layer in the laminated film is preferably 3 μm to 30 μm, more preferably 5 μm to 20 μm. If it is a polyvinyl alcohol-based resin layer having a thickness within this range, after the stretching step (S20) and dyeing step (S30) described later, the dyeability of the dichroic dye is good, the polarization performance is excellent, and the polarizer is sufficiently small in thickness. You can get a layer. When the thickness of the polyvinyl alcohol-based resin layer exceeds 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 become too thin after stretching and deteriorate dyeability.

Prior to coating of the coating solution, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, at least the surface of the base film on which the polyvinyl alcohol-based resin layer is formed is corona treated, plasma treated, frame (flame) treated Etc. may be performed.

In addition, prior to coating of the coating liquid, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, a polyvinyl alcohol-based resin layer may be formed on the base film through a primer layer or an adhesive layer.

(Primer layer)

The primer layer can be formed by coating a coating solution for forming a primer layer on the surface of the base film and then drying it. The coating liquid for forming a primer layer contains a component that exhibits a certain degree of strong adhesion to both the base film and the polyvinyl alcohol-based resin layer. The coating solution for forming a primer layer usually contains a resin component and a solvent that impart such adhesion. As the resin component, a thermoplastic resin excellent in transparency, thermal stability, stretchability, etc. is preferably used, and examples thereof include (meth) acrylic resin, polyvinyl alcohol resin, and the like. Among them, polyvinyl alcohol-based resins that provide good adhesion are preferably used.

As a polyvinyl alcohol-type resin, polyvinyl alcohol resin and its derivative (s) are mentioned, for example. Examples of the derivative of the polyvinyl alcohol resin include polyvinyl formal, polyvinyl acetal, etc., and polyvinyl alcohol resin modified with olefins such as ethylene and propylene; Modified with unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; Modified with an alkyl ester of an unsaturated carboxylic acid; And those modified with acrylamide. Among the polyvinyl alcohol-based resins described above, it is preferable to use a polyvinyl alcohol resin.

As the solvent, a general organic solvent or an aqueous solvent capable of dissolving the resin component is usually used. Examples of the solvent include aromatic hydrocarbons such as benzene, toluene, and xylene; Ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; Esters such as ethyl acetate and isobutyl acetate; Chlorinated hydrocarbons such as methylene chloride, trichloroethylene and chloroform; Alcohols such as ethanol, 1-propanol, 2-propanol, and 1-butanol. However, when a primer layer is formed using a coating solution for forming a primer layer containing an organic solvent, the base film may be dissolved, and it is preferable to select a solvent in consideration of the solubility of the base film. Considering the influence on the environment, it is preferable to form a primer layer with a coating solution using water as a solvent.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the coating solution for forming the primer layer. The crosslinking agent is appropriately selected from known ones such as organic and inorganic based on the type of thermoplastic resin used. Examples of the crosslinking agent are, for example, epoxy-based, isocyanate-based, dialdehyde-based, and metal-based crosslinking agents.

As the epoxy-based crosslinking agent, either a one-liquid curing type or a two-liquid curing type can be used, and ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di- or tri-glycidyl ether, 1,6- And hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, and diglycidyl amine.

Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (4-phenylmethane) triisocyanate, isophorone diisocyanate, and keto And an oxime block product or a phenol block product.

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

Examples of the metal-based crosslinking agent include metal salts, metal oxides, metal hydroxides and organometallic compounds. Examples of the metal salt, metal oxide, and metal hydroxide include salts of metals having a valence of two or more such as magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, silicon, boron, zinc, copper, vanadium, chromium, and tin, Oxides and hydroxides.

An organometallic compound is a compound having at least one structure in a molecule in which an organic group is directly bonded to a metal atom or an organic group is bonded through an oxygen atom or a nitrogen atom. The organic group means a monovalent or polyvalent group containing at least a carbon element, and may be, for example, an alkyl group, an alkoxy group, an acyl group, or the like. In addition, a bond does not mean only a covalent bond, but may be a coordination bond by coordination, such as a chelating compound.

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

Examples of the organic titanium compound include titanium orthoesters such as tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, and tetramethyl titanate; Titanium chelates such as titanium acetylacetonate, titanium tetraacetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamine, titanium ethyl acetoacetate; And titanium acylates such as polyhydroxy titanium stearate.

Examples of the organic zirconium compound include zirconium normal propionate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium bisacetylacetonate, zirconiumacetylacetonate bisethyl acetoacetate, and the like.

Examples of the organoaluminum compound include aluminum acetylacetonate and aluminum organic acid chelate. Examples of the organosilicon compound include a compound in which the ligands exemplified in the organotitanium compound and the organ zirconium compound are first bound to silicon.

In addition to the low-molecular-based crosslinking agents described above, polymer-based crosslinking agents such as methylolated melamine resins and polyamide epoxy resins can also be used. Examples of commercially available products of polyamide epoxy resins include "Sumirez Resin 650 (30)" and "Sumirez Resin 675" (all brand names) sold by Takaoka Chemical Co., Ltd.

When a polyvinyl alcohol-based resin is used as a resin component for forming the primer layer, polyamide epoxy resin, methylolated melamine resin, dialdehyde-based crosslinking agent, metal chelate compound-based crosslinking agent, and the like are suitably used as a crosslinking agent.

The ratio of the resin component and the crosslinking agent in the coating solution for forming the primer layer may be appropriately determined depending on the type of the resin component, the type of the crosslinking agent, etc., in a range of about 0.1 parts by weight to 100 parts by weight of the crosslinking agent relative to 100 parts by weight of the resin component. In particular, it is preferable to select from a range of about 0.1 parts by weight to about 50 parts by weight. Moreover, it is preferable that the coating liquid for forming a primer layer has a solid content concentration of about 1% to 25% by weight.

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

The method of coating the coating solution for forming the primer layer on the base film may be the same as the coating solution for forming the polyvinyl alcohol-based resin layer. The primer layer is coated on the surface (one side or both sides of the base film) on which the coating solution for forming the polyvinyl alcohol-based resin layer is coated. The drying temperature and drying time of the coating layer made of the coating solution for forming the primer layer are set according to the type of solvent contained in the coating solution. The drying temperature is, for example, 50 ° C to 200 ° C, and preferably 60 ° C to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C or higher. Drying time is 30 seconds-20 minutes, for example.

(2) Stretching process (S20)

This step is a step of vertically uniaxially stretching a laminated film composed of a base film and a polyvinyl alcohol-based resin layer to obtain a stretched film. In the present invention, the stretching step (S20) is divided into two or more stretching treatment steps. That is, the stretching step (S20) is made of multi-stage stretching, and includes two or more stretching treatment steps. Here, the term "includes two or more stretching treatment steps" means a first-stage (first) stretching treatment step in which the laminated film is uniaxially stretched at a certain stretching ratio, and the laminated film is not stretched (stretched in the film conveying direction). It does not mean that it has at least the 2nd stage | stretching process of extending | stretching longitudinally uniaxially to the laminated | multilayer film which performed the 1st stage | stretching process over a section (time zone), and is stretched at a certain draw ratio again. The stretching step (S20) may include three or more steps of stretching treatment, and even in this case, a section (time zone) in which the laminated film is not stretched is interposed between the stretching treatment steps of each stage.

The longitudinal uniaxial stretching in the stretching treatment step of each stage may be, for example, inter-roll stretching, rolling, hot roll stretching, stretching using a chuck, or the like. The stretching methods of each stage may be all the same, or different stretching methods may be combined. However, even when the elongation magnification is high, when the neck-in rate is low, sufficient polarization performance may not be imparted to the polarizer layer obtained through the dyeing step (S30). It is preferable that the one-stage stretching treatment process is performed by inter-roll stretching which is free-end stretching.

The neck-in rate is the following formula:

Neck rate (%) = (((W1-W2) ÷ W1) x 100

Is defined as W1 is the width of the laminated film before being provided in the stretching step (S20). W2 is the minimum width of the film after all stretching treatments have been applied to the laminated film. For example, when the stretching treatment is performed on the laminated film only in the stretching step (S20), W2 is the minimum width of the stretched film finally obtained in the stretching step (S20). Further, as described later, in the dyeing step (S30), additional stretching treatment can be performed, but in this case, W2 is the minimum width of the polarizing laminated film after the additional stretching treatment. The neck-in rate is preferably about 50% or more.

Some examples of multi-stage stretching in the stretching step (S20) will be described with reference to the drawings. In each figure, the arrow indicates the conveying direction of the film.

2 shows an example in the case where the stretching step S20 includes a two-stage stretching treatment step, and these stretching treatment steps are a roll-to-roll stretching method, that is, a method of stretching between nip rolls having different circumferential speeds. Specifically, the conveyed laminated film 10 is first heated by passing through a heating furnace 20 set at a desired temperature, while being stretched between nip rolls 1-nip rolls 2 having different peripheral speeds (1). Step stretching process). The first-stretched film is conveyed again by the guide roll 5 and heated by passing through the heating furnace 30 set to a desired temperature, while the nip rolls 3 and nip rolls 4 having different circumferential speeds are formed. Stretched in between (the second-stage stretching treatment step), the stretched film 15 is formed. In general, in the section from the nip roll 2 to the nip roll 3, since the peripheral speed of the nip roll 2 and the peripheral speed of the nip roll 3 are the same, the film is not stretched.

3 shows an example in the case where the stretching step (S20) includes a three-stage stretching treatment step, and all of these stretching treatment steps are a hot roll stretching method, that is, a method of stretching between heated rolls. Specifically, the conveyed laminated film 10 is first stretched while the surface is adjusted to a desired temperature, and passing between the heat rolls 6-heat rolls 7 having different circumferential speeds (first-stage stretching treatment process) ). Subsequently, after a section in which stretching does not occur, that is, a section in contact with the hot roll 7, the surface is adjusted to a desired temperature, and is stretched while passing between the hot rolls 7-hot rolls 8 having different circumferential speeds. (The second-stage stretching treatment step). The film subjected to the second-stage stretching treatment passes through a section in which stretching does not occur, that is, a section in contact with the heat roll 8, the surfaces are adjusted to a desired temperature, and the heat rolls 8-heat rolls 9 having different circumferential speeds from each other ) During the passage, the film is stretched (the third-stage stretching treatment step) to form a stretched film 15.

4 is a schematic view for explaining a longitudinal uniaxial stretching method using a chuck (clip), and is a view when a laminated film to be stretched is viewed from above. As shown in the longitudinal uniaxial stretching method using a chuck, as shown, a plurality of chucks 40 are attached to both ends in the width direction of the laminated film 10 (normally a constant interval), and the laminated film 10 heated to a desired temperature It refers to a method of stretching by gradually increasing the distance R between chucks in the film conveying direction while conveying). Although not shown, in order to perform multi-stage stretching by a longitudinal uniaxial stretching method using a chuck, after extending the distance between the chucks and performing stretching treatment (the first-stage stretching treatment process), the distance between the chucks is fixed. After passing through the section for transporting the laminated film 10, it is sufficient to extend the distance R between the chucks and perform stretching treatment (the second-stage stretching treatment step). The drawing process after the third stage is also the same.

The method for controlling the distance between the chucks R during stretching is not particularly limited, and various methods can be used. For example, since each chuck can be driven independently, each chuck can be independently controlled to control the distance (R) between chucks, and chucks are connected to each other, so that multiple chucks can be controlled by one drive system to control chucks. The distance R may be controlled. In the present invention, any method can be suitably used.

As a specific method of independently driving each chuck, a method using a magnetic force as represented by a linear motor driving method, a method of laying a rotary drive motor, etc. on each chuck may be mentioned. In addition, not all chucks can be driven independently, but only some chucks can be driven independently, and special control may not be performed on the other chucks.

As a specific method of controlling a plurality of chucks with a single drive system, a pantograph method or the like is typical. The pantograph method is a method such as controlling the distance R between chucks by opening and closing the pantograph by controlling the distance between two rails.

All of the aforementioned multi-stage stretching illustrated with reference to Figs. 2 to 4 does not involve winding and unwinding of the film for each stretching treatment step. This embodiment is preferred in terms of productivity. However, the present invention is not limited to the above-described example, and the film may be wound each time the one-stage stretching treatment step is finished, and may be unwound again when the next stretching treatment step is performed.

In the present invention, the ratio of the stretching ratio in the first-stage stretching treatment step to the stretching ratio in the second-stage stretching treatment step (hereinafter, also referred to as "the stretching ratio") is 0.5 or more. The "stretching ratio in the first-stage stretching treatment step" means when the length in the longitudinal direction (stretching direction) of the polyvinyl alcohol-based resin layer of the laminated film before being provided in the stretching step (S20) is 1 , It is the length in the longitudinal direction of the polyvinyl alcohol-type resin layer at the end of the first-stage stretching treatment process. For example, the length in the longitudinal direction of the polyvinyl alcohol-based resin layer (or the length of any part of the polyvinyl alcohol-based resin layer) of the laminated film before being provided in the stretching step (S20) is 1, and the first-stage stretching treatment is performed. When the length (or the length of any portion) of the polyvinyl alcohol-based resin layer is 2 by the process, the draw ratio in the first-stage stretching treatment step is doubled.

The "stretching ratio in the second-stage stretching treatment step" means when the length in the longitudinal direction of the polyvinyl alcohol-based resin layer at the end of the first-stage stretching treatment step is 1, when the second-stage stretching treatment step ends It is the length in the longitudinal direction of the polyvinyl alcohol-based resin layer.

In the process of stretching the laminated film to a desired total stretching ratio by dividing the stretching step (S20) into two or more stretching treatment steps, and performing the first and second stretching treatment steps so as to satisfy the stretching ratio. , Since the laminated film can be stretched while maintaining a proper neck-in by stretching, it is possible to effectively suppress the occurrence of wrinkles during stretching, and uneven stretching (uniform stretching) in the film width direction. It can be effectively suppressed.

The occurrence of wrinkles may not only cause uneven dyeing in the dyeing step (S30), but also poor appearance, non-uniformity in optical properties such as polarization performance and transmittance, and may cause a decrease in yield. The stretching non-uniformity appears as a thickness non-uniformity in the film width direction, and may likewise cause non-uniformity of optical properties such as polarization performance and transmittance.

According to the method of the present invention, a stretched film having a thickness difference in the film width direction of less than 5 μm and more than less than 4 μm can be produced, so that a polarizing laminated film and a polarizing plate having uniform polarization performance or transmittance can be produced. The "thickness difference in the film width direction" means that a film thickness at a position of 50 mm from one end in the film width direction is measured by one point, and a film thickness at a central position in the film width direction is measured by one point. It means the absolute value of the difference of these film thickness at the time.

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 more effectively obtain the effects described above. When the draw ratio is less than 0.5, uneven stretching occurs in the film width direction. In addition, if the draw ratio is too large, wrinkles tend to occur, so the draw ratio is preferably 5 or less, more preferably 4 or less, and particularly preferably 3 or less.

The draw ratio in the first-stage stretching treatment step is preferably less than 5 times, and more preferably 4 times or less. When the stretching ratio is 5 times or more, wrinkles are likely to occur. That is, in order to give good polarization performance to the polarizer layer obtained through the dyeing step (S30), it is preferable to increase the total draw ratio of the stretching treatment performed on the laminated film to 5 times or more as described later, but such high magnification stretching When the treatment is performed in one step, wrinkles are generated. In the present invention, the stretching treatment is performed by dividing into two or more stages in consideration of these.

The "total draw ratio" means the stretching treatment step of each stage (as described later, additional stretching treatment may be performed in the dyeing step (S30), but in this case, the additional stretching treatment step is also included). It means the final draw magnification multiplied by the draw magnification in, in other words, the length in the longitudinal direction (stretching direction) of the polyvinyl alcohol-based resin layer of the laminated film before being provided in the stretching step (S20) is 1 It is the length in the longitudinal direction of the polyvinyl alcohol-type resin layer at the end of all extending | stretching processing, ie, a polarizer layer.

As described above, it is preferable that the total draw ratio of the polarizer layer when it is based on the polyvinyl alcohol-based resin layer of the laminated film is more than 5 times. When the draw ratio is 5 times or less, since the polyvinyl alcohol-based resin layer is not sufficiently oriented, the polarization degree of the polarizer layer tends not to be sufficiently high. In addition, the total draw ratio is preferably 8 times or less. When the total draw magnification exceeds 8 times, the film tends to break during stretching, and the stretched film becomes thinner than necessary, and there is a fear that workability and handling properties in the subsequent steps may deteriorate.

The stretching temperature at each stage of the stretching step (S20) is set to a temperature higher than or equal to the temperature at which the polyvinyl alcohol-based resin layer and the entire base film exhibit a fluidity to the extent that it can be stretched, preferably the melting point of the base film-30 ° C to It is in the range of melting point + 30 ° C, more preferably in the range of its melting point-30 ° C to its melting point + 5 ° C, and more preferably in the range of its melting point-25 ° C to its melting point + 0 ° C. When the base film is composed of a plurality of resin layers, the melting point means the highest melting point among the melting points indicated by the plurality of resin layers.

When the stretching temperature is lower than the melting point of the base film-30 ° C, the fluidity of the base film is too low, and the stretching treatment tends to be difficult. When the stretching temperature exceeds the melting point + 30 ° C, the fluidity of the base film is too large, and likewise, the stretching treatment tends to be difficult. In view of the ease of stretching treatment, the stretching temperature is within the above range, more preferably 120 ° C or higher.

As a heating method of the laminated film in the stretching treatment of each stage, 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 and adjusted to a predetermined temperature. See Fig. 2); In the case of extending | stretching using a roll, the method of heating the roll itself (refer FIG. 3); Heater heating methods (infrared heaters, halogen heaters, panel heaters, etc., installed above and below the laminated film to heat with radiant heat) and the like. In the roll-to-roll stretching method, the zone heating method is preferred from the viewpoint of uniformity in stretching temperature. In this case, the two nip roll pairs may be installed in the temperature-controlled stretching zone or outside the stretching zone, but it is preferable to install them outside the stretching zone to prevent adhesion of the laminated film and the nip roll (see FIG. 2). .

In addition, the extending | stretching temperature means the atmosphere temperature in a zone (for example, in a heating furnace) in the case of a zone heating method, and also means the atmosphere temperature in a furnace when heating in a furnace also in a heater heating method. In addition, in the case of the method of heating the roll itself, it means the surface temperature of the roll.

Prior to the stretching step (S20), a preheating treatment step of preheating the laminated film may be provided. As a preheating method, the same method as the heating method in the stretching treatment can be used. When the stretching treatment method is roll-to-roll stretching, preheating may be performed at any timing before, during, or after passing through the upstream nip roll. When the stretching treatment method is hot roll stretching, it is preferable to perform preheating at a timing before passing through the hot roll. When the stretching processing method is stretching using a chuck, it is preferable to perform preheating at a timing before the distance between the chucks is increased. The preheating temperature is preferably in the range of the stretching temperature-50 ° C to the stretching temperature ± 0 ° C, and more preferably in the range of the stretching temperature-40 ° C to the stretching temperature-10 ° C.

In addition, a heat fixation treatment step may be provided after the stretching treatment at the final stage in the stretching step (S20). The heat fixation treatment is a treatment in which a heat treatment is performed at a crystallization temperature or higher, while the end portion of the stretched film is held in a tensioned state while held by a clip. Crystallization of the polyvinyl alcohol-based resin layer is promoted by this heat fixation treatment. The temperature of the heat fixation treatment is preferably in the range of the stretching temperature-0 ° C to the stretching temperature-80 ° C, and more preferably in the range of the stretching temperature-0 ° C to the stretching temperature-50 ° C.

(3) Dyeing process (S30)

This step is a step in which the polyvinyl alcohol-based resin layer of the stretched film is dyed with a dichroic dye and adsorbed and oriented to form a polarizer layer. Through this process, a polarizing laminated film in which a polarizer layer is laminated on one or both surfaces of a base film is obtained.

Examples of the dichroic dye include iodine or dichroic organic dye. Specific examples of the dichroic organic dye include, for example, red BR, red LR, red R, pink LB, rubin BL, Bordeaux GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy RY, green LG, violet LB , Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo-Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL , Direct Sky Blue, Direct First Orange S, First Black, etc. As for the dichroic dye, only one type may be used alone, or two or more types may be used in combination.

The dyeing process can be performed by immersing the entire stretched film in a solution (dyeing solution) containing a dichroic dye. As the dyeing solution, a solution in which the dichroic dye is dissolved in a solvent can be used. As a solvent of the dyeing solution, water is generally used, but an organic solvent compatible with water may be further added. The concentration of the dichroic dye in the dyeing solution is preferably 0.01% by weight to 10% by weight, more preferably 0.02% by weight to 7% by weight, and even more preferably 0.025% by weight to 5% by weight.

When iodine is used as a dichroic dye, it is preferable to further add iodide to a dyeing solution containing iodine, since the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. It is preferable that the concentration of iodide in a dyeing solution is 0.01 to 20 weight%. It is preferable to add potassium iodide among iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100 by weight ratio, more preferably in the range of 1: 6 to 1:80, and 1: It is more preferably in the range of 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, and preferably 30 seconds to 3 minutes. Further, the temperature of the dyeing solution is preferably in the range of 10 ° C to 60 ° C, more preferably in the range of 20 ° C to 40 ° C.

Further, during the dyeing step (S30), the stretched film may be further subjected to a stretch treatment. As an embodiment in this case, 1) In the said extending | stretching process (S20), after extending | stretching treatment at a magnification lower than a target, during the dyeing process in the dyeing process (S30), the total draw ratio is a target magnification. When the crosslinking treatment is performed after the dyeing treatment, as described later, or as described later, 2) in the stretching step (S20), after the stretching treatment is performed at a lower magnification than the target, the dyeing step (S30) In the dyeing treatment in), the stretching treatment is performed to the extent that the total draw ratio does not reach the target magnification, and then, an embodiment in which stretching treatment is performed during the crosslinking treatment so that the final total draw magnification becomes the target magnification is exemplified. You can.

The dyeing step (S30) may include a crosslinking treatment step performed following the dyeing treatment. The crosslinking treatment can be performed by immersing the dyed film in a solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, conventionally known substances can be used, and examples thereof include boron compounds such as boric acid and borax, glyoxal and glutaraldehyde. 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 may be used, but an organic solvent compatible with water may further be included. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of 1% by weight to 20% by weight, and more preferably in the range of 6% by weight to 15% by weight.

The crosslinking solution may include iodide. By adding iodide, polarization performance in the plane of a polarizer layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. The concentration of iodide in the crosslinking solution is preferably 0.05% by weight to 15% by weight, and more preferably 0.5% by weight to 8% by weight.

The immersion time of the dyed film in the crosslinking solution is usually 15 seconds to 20 minutes, and preferably 30 seconds to 15 minutes. Moreover, it is preferable that the temperature of a bridge | crosslinking solution exists in the range of 10 degreeC-90 degreeC.

Moreover, crosslinking treatment can also be performed simultaneously with a dyeing treatment by mixing a crosslinking agent in a dyeing solution. Moreover, you may perform extending | stretching process during a bridge | crosslinking process. The specific embodiment of performing the stretching treatment during the crosslinking treatment is as described above.

After the dyeing step (S30), it is preferable to perform a washing step and a drying step before the bonding step (S40) described later. The washing process usually includes a water washing process. The water washing treatment can be performed by immersing the film after dyeing treatment or crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually in the range of 3 ° C to 50 ° C, preferably 4 ° C to 20 ° C. The immersion time in water is usually 2 seconds to 300 seconds, preferably 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. In addition, in addition to water, liquid alcohols such as methanol, ethanol, isopropyl alcohol, butanol, and propanol can be appropriately contained in the washing liquid used in the water washing step and / or washing treatment with an iodide solution.

As a drying step performed after the washing step, any suitable method such as natural drying, blow drying, and heating drying can be adopted. For example, in the case of heat drying, the drying temperature is usually 20 ° C to 95 ° C, and the drying time is usually about 1 minute to 15 minutes. The polarizing laminated film obtained as described above can be used as a polarizing element as it is, and is also useful as an intermediate for producing a polarizing plate comprising a polarizer layer and a protective film.

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

<Method of manufacturing a polarizing plate>

The manufacturing method of the polarizing plate of this invention is the process of preparing the polarizing laminated film mentioned above, the bonding process (S40) which bonds a protective film on the polarizer layer of a polarizing laminated film, and a bonding film (S40), and a base film from a bonding film The peeling process (S50) for peeling and removing is included in this order.

[4] Joining process (S40)

This step is a step of obtaining a bonding film by bonding a protective film on the polarizer layer of the polarizing laminated film, that is, on the surface opposite to the base film side of the polarizer layer. The protective film can be bonded to the polarizer layer using an adhesive or an adhesive. When a polarizing laminated film has a polarizer layer on both sides of a base film, a protective film is normally bonded on each of the polarizer layers on both sides. In this case, these protective films may be the same type of protective film, or different types of protective film.

(Protective film)

The protective film includes, for example, polyolefin-based resins such as chained polyolefin-based resins (polypropylene-based resins) and cyclic polyolefin-based resins (norbornene-based resins); Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; Polycarbonate resins; (Meth) acrylic resin; Or it may be a film composed of a mixture of these, a copolymer or the like. Examples of commercially available products such as cyclic polyolefin-based resins and films thereof, and cellulose triacetate are as described above.

The protective film may be a protective film having optical functions such as a retardation film and a brightness enhancing film. For example, a resin film made of the above material can be stretched (uniaxially stretched or biaxially stretched), or a liquid crystal layer or the like formed on the film can be used as a retardation film to which an arbitrary retardation value is applied.

On the surface opposite to the polarizer layer of the protective film, an optical layer such as a hard coat layer, an antiglare layer, or an antireflection layer can also be formed. The method for forming these optical layers on the surface of the protective film is not particularly limited, and a known method can be used. The optical layer may be previously formed on the protective film prior to the bonding step (S40), or may be formed after the bonding step (S40) or after the peeling step (S50) described later.

In bonding the protective film onto the polarizer layer, on the surface of the polarizer layer side of the protective film, plasma treatment, corona treatment, ultraviolet irradiation treatment, frame (flame) treatment, saponification treatment, etc., in order to improve adhesion to the polarizer layer It is possible to perform a surface treatment (two-sided adhesive treatment) of, and, among them, it is preferable to perform plasma treatment, corona treatment, or saponification treatment. For example, when the protective film is made of a cyclic polyolefin-based resin, plasma treatment or corona treatment is usually performed. Moreover, when it consists of a cellulose-ester type resin, saponification process is normally performed. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

The thickness of the protective film is preferably thin, but if it is too thin, the strength is lowered and the workability is poor. On the other hand, when it is too thick, there arises a problem such as a decrease in transparency or a long curing time required after bonding. Therefore, the thickness of the protective film is preferably 90 μm or less, more preferably 5 μm to 60 μm, and even more preferably 5 μm to 50 μm. In addition, from the viewpoint of thinning of the polarizing plate, the total thickness of the polarizer layer and the protective film is preferably 100 μm or less, more preferably 90 μm or less, and even more preferably 80 μm or less.

(glue)

As the adhesive, an aqueous adhesive or a photo-curable adhesive can be used. Examples of the water-based adhesive include an adhesive composed of an aqueous polyvinyl alcohol-based resin, an aqueous two-component urethane emulsion adhesive, and the like. In particular, when a cellulose ester-based resin film subjected to surface treatment (hydrophilization treatment) by saponification or the like is used as the protective film, it is preferable to use an aqueous adhesive composed of an aqueous polyvinyl alcohol-based resin solution.

As the polyvinyl alcohol-based resin, in addition to the vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, a polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of vinyl acetate and other monomers copolymerizable therewith Alternatively, a modified polyvinyl alcohol-based polymer or the like having partially modified these hydroxyl groups can be used. The water-based adhesive may include additives such as polyhydric aldehydes, water-soluble epoxy compounds, melamine-based compounds, zirconia compounds, and zinc compounds. When an aqueous adhesive is used, the thickness of the adhesive layer obtained therefrom is usually 1 µm or less.

The bonding process is carried out by coating the water-based adhesive on the polarizer layer and / or the protective film of the polarizing laminated film, bonding these films through the adhesive layer, and preferably pressing and bonding using a bonding roll or the like. The coating method of the water-based adhesive (which is the same for the photo-curable adhesive) is not particularly limited, and includes a flexible method, a Meyer bar coat method, a gravure coat method, a comma coater method, a doctor plate method, a die coat method, a dip coat method, and a spray method. A conventionally known method can be used.

When using a water-based adhesive, it is preferable to perform a drying step of drying the film to remove water contained in the water-based adhesive after performing the above-described bonding. Drying can be performed, for example, by introducing a film into a drying furnace. The drying temperature (temperature of the drying furnace) is preferably 30 ° C to 90 ° C. If it is less than 30 ° C, the protective film tends to be easily peeled from the polarizer layer. In addition, when the drying temperature exceeds 90 ° C, there is a fear that the polarization performance of the polarizer layer is deteriorated by heat. The drying time can be about 10 seconds to 1000 seconds, and from the viewpoint of productivity, it is preferably 60 seconds to 750 seconds, more preferably 150 seconds to 600 seconds.

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

The photocurable adhesive refers to an adhesive that is cured by irradiating active energy rays such as ultraviolet rays, for example, those containing a polymerizable compound and a photopolymerization initiator, those containing a photoreactive resin, and binder resins and photoreactive crosslinking agents. And the like. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, and oligomers derived from photopolymerizable monomers. As a photoinitiator, what contains the substance which generate | occur | produces active species, such as a neutral radical, an anion radical, and a cationic radical by irradiation of active energy rays, such as ultraviolet rays, is mentioned, for example. As a photocurable adhesive containing a polymerizable compound and a photopolymerization initiator, those containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.

In the case of using a photo-curable adhesive, after performing the above-mentioned bonding, a drying process is performed as necessary (when the photo-curable adhesive contains a solvent, etc.), and then a curing process for curing the photo-curable adhesive by irradiating active energy rays Do it. The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferred, specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, and a micro Wave-excited mercury lamps, metal halide lamps, and the like are preferably used.

The light irradiation intensity to the photo-curable adhesive is appropriately determined according to the composition of the photo-curable adhesive, and it is preferable that the irradiation intensity in the wavelength region effective for activation of the polymerization initiator is set to be 0.1 Pa / cm2 to 6000 Pa / cm2. . When the irradiation intensity is 0.1 ㎽ / cm 2 or more, the reaction time is not too long, and when it is 6000 ㎽ / cm 2 or less, yellowing of the photo-curable adhesive or polarizer layer due to heat radiating from the light source and curing of the photo-curable adhesive There is little risk of deterioration.

The light irradiation time to the photo-curable adhesive is also appropriately determined according to the composition of the photo-curable adhesive, and is set to be 10 mJ / cm 2 to 10000 mJ / cm 2 as the accumulated light amount expressed as a product of the irradiation intensity and the irradiation time. desirable. When the cumulative light amount is 10 mJ / cm 2 or more, a sufficient amount of active species derived from the polymerization initiator is generated, and the curing reaction can proceed more reliably, and when it is 10000 mJ / cm 2 or less, the irradiation time does not become too long and maintains good productivity You can.

The thickness of the adhesive layer after irradiation with active energy rays is usually about 0.001 µm to 5 µm, preferably 0.01 µm to 2 µm, more preferably 0.01 µm to 1 µm.

(adhesive)

The pressure-sensitive adhesive that can be used for bonding the protective film is usually an acrylic resin, styrene-based resin, silicone-based resin or the like as a base polymer, to which an isocyanate compound, an epoxy compound, a crosslinking agent such as an aziridine compound is added as a pressure-sensitive adhesive composition. Is done. Moreover, it can also be set as the adhesive layer containing fine particles and showing light scattering property.

The thickness of the pressure-sensitive adhesive layer may be 1 µm to 40 µm, but it is preferable to apply a thin coat, and specifically 3 µm to 25 µm, in a range that does not impair the properties of processability and durability. The thickness of 3 µm to 25 µm has good workability and is also suitable for suppressing dimensional changes of the polarizer layer. If the pressure-sensitive adhesive layer is less than 1 µm, the tackiness decreases, and when it exceeds 40 µm, problems such as sticking out of the adhesive tend to occur. In the method of bonding a protective film to a polarizer layer using an adhesive, after providing an adhesive layer on a protective film surface, you may bond to a polarizer layer, or after providing an adhesive layer on a polarizer layer surface, bonding a protective film here It is also good.

The method of forming the pressure-sensitive adhesive layer is not particularly limited, and after coating the pressure-sensitive adhesive composition (adhesive solution) containing each component including the above-described base polymer on the protective film surface or the polarizer layer surface, and drying to form the pressure-sensitive adhesive layer, , You may bond the protective film and the polarizer layer, and after forming the pressure-sensitive adhesive layer on the separator (peel film), transfer the pressure-sensitive adhesive layer to a protective film surface or a polarizing film surface, peel the separator from the pressure-sensitive adhesive layer, and then protect The film and the polarizer layer may be bonded. When the pressure-sensitive adhesive layer is formed on the protective film surface or the polarizer layer surface, a surface treatment such as corona treatment or the like may be applied to the protective film surface or the polarizer layer surface, or to one or both surfaces of the pressure-sensitive adhesive layer, if necessary.

[5] Peeling process (S50)

This process is a process of peeling and removing a base film from the bonding film obtained by bonding a protective film. Through this process, a polarizing plate in which a protective film is laminated on a polarizer layer can be obtained. When the polarizing laminated film has polarizer layers on both sides of the base film and a protective film is bonded to both polarizer layers, two polarizing plates are obtained from one polarizing laminated film by this peeling step (S50). Lose.

The method of peeling and removing the base film is not particularly limited, and can be peeled in the same manner as the peeling step of the separator (peel film) performed on a polarizing plate having a conventional adhesive. The base film may be peeled off immediately after the bonding step (S40), or may be rolled up once in a roll form after the bonding step (S40) and peeled off while being unwound in the subsequent step.

The polarizing plate manufactured as mentioned above can also be used as an optical film which laminated another optical layer in practical use. Moreover, the protective film may have the function of such an optical layer. As another optical layer, a reflective polarizing film which transmits some kind of polarized light and reflects polarized light showing the opposite properties; A film having an anti-glare function having an uneven shape on the surface; A film having a surface antireflection function; A reflective film having a reflective function on the surface; A transflective film having a reflection function and a transmission function together; And a viewing angle compensation film.

As a commercially available product that corresponds to a reflective polarizing film that transmits some kind of polarized light and reflects polarized light exhibiting properties opposite thereto, for example, "DBEF" (manufactured by 3M, manufactured by Sumitomo 3M Co., Ltd. in Japan) And "APF" (manufactured by 3M, available from Sumitomosurim Co., Ltd. in Japan).

As a viewing angle compensation film, a liquid crystal compound is apply | coated to the surface of a base material, the optical compensation film which is aligned and fixed, the retardation film which consists of polycarbonate-type resin, the retardation film which consists of cyclic polyolefin type resin, etc. are mentioned.

As a commercial item corresponding to the optical compensation film in which a liquid crystal compound is applied to the substrate surface and is aligned and fixed, "WV film" (manufactured by Fuji Film Co., Ltd.) and "NH film" (JX Nikko Nisekene Energy Co., Ltd.) Production), "NR film" (manufactured by JX Nikko Niseki Energy Co., Ltd.) and the like.

As commercial products corresponding to the retardation film made of a cyclic polyolefin-based resin, "Aton Film" (manufactured by JSR Corporation), "Essina" (manufactured by Sekisui Chemical Co., Ltd.), "Zeo Noah Film" (Nippon Zeon ( Note) Manufacturing).

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by these examples.

<Example 1>

(1) Preparation of base film

The propylene / ethylene random copolymer containing about 5% by weight of an ethylene unit (Sumitomo Nogaku W151 manufactured by Sumitomo Chemical Co., Ltd., melting point (Tm) = 138 ° C) made of propylene alone on both sides of the resin layer A three-layered long base film in which a resin layer made of a polymer (Sumitomo Nogaku Co., Ltd. `` Sumitomo Noblen FLX80E4 '', melting point (Tm) = 163 ° C) is disposed is used to form a ball using a multi-layer extrusion molding machine. ) It was produced by extrusion molding. The total thickness of the base film was 100 µm, and the thickness ratio (FLX80E4 / W151 / FLX80E4) of each layer was 3/4/3.

(2) Preparation of laminated film (resin layer formation process)

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Kosei Chemical Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%) was dissolved in hot water at 95 ° C to obtain a polyvinyl alcohol aqueous solution having a concentration of 3% by weight. Was prepared. A crosslinking agent ("Sumirez Resin 650" manufactured by Takaoka Chemical Co., Ltd.) was mixed with the obtained aqueous solution at a ratio of 1 part by weight to 2 parts by weight of polyvinyl alcohol powder to obtain a coating solution for forming a primer layer.

Further, polyvinyl alcohol powder ("PVA124" manufactured by Kurare Co., Ltd., average polymerization degree 2400, average saponification degree 98.0 mol% to 99.9 mol%) was dissolved in hot water at 95 DEG C, and polyvinyl alcohol at a concentration of 8 wt% An aqueous solution was prepared, and this was used as a coating solution for forming a polyvinyl alcohol-based resin layer.

While continuously transporting the base film produced in (1), corona treatment was performed on one surface thereof, and the coating solution for forming the primer layer was continuously coated on the corona-treated surface using a micro gravure coater at 80 ° C. Was dried for 3 minutes to form a primer layer having a thickness of 0.2 µm. Subsequently, while conveying the film, the coating solution for forming the polyvinyl alcohol-based resin layer was continuously coated on the primer layer using a comma coater, and then at 90 ° C for 1 minute, at 70 ° C for 3 minutes, and then at 60 ° C for 4 minutes. By drying, a polyvinyl alcohol-based resin layer having a thickness of 10.0 µm was formed on the primer layer.

Further, the same treatment as above was performed on the surface of the base film on the opposite side to the surface on which the polyvinyl alcohol-based resin layer was formed to sequentially form the primer layer and the polyvinyl alcohol-based resin layer, and the thickness on both sides of the base film was 0.2. A primer layer of µm and a polyvinyl alcohol-based resin layer of 10.0 µm in thickness were formed to obtain a laminated film comprising a layer structure of a polyvinyl alcohol-based resin layer / primer layer / base film / primer layer / polyvinyl alcohol-based resin layer. .

(3) Production of stretched film (stretching process)

Using the stretching device shown in Fig. 2, while continuously conveying the laminated film produced in (2) above, two stages of uniaxial stretching treatment (free end uniaxial stretching in the film conveying direction) by a nip-roll stretching method. ) To produce a stretched film. The stretching temperature (ambient temperature in the heating furnaces 20 and 30) in the two-stage stretching treatment was set to 160 ° C together. The draw ratios in the first-stage and second-stage stretching treatments were adjusted to the peripheral speeds of the nip rolls (1, 2, 3, 4) to be 2.00 and 2.90, respectively. The total draw magnification is 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.

Wrinkles by stretching were not observed in the obtained stretched film. About the obtained stretched film, when the thickness difference in the film width direction defined above was measured, it was 3 micrometers and it was confirmed that it extended | stretched with a substantially uniform thickness distribution in the film width direction.

(4) Preparation of polarizing laminated film (dyeing process)

After continuously conveying the stretched film produced in (3), the immersion was performed in a 60 ° C. hot water bath for a residence time of 60 seconds, followed by a residence time in a dyeing solution of 30 ° C. containing iodine and potassium iodide for 150 seconds. Immersed so as to dye the polyvinyl alcohol-based resin layer, and then wash the excess dyeing solution with pure water at 10 ° C. Subsequently, the crosslinking treatment was performed by immersing in a crosslinking solution of 76 ° C containing boric acid and potassium iodide so that the residence time was 600 seconds. Then, it washed with pure water of 10 degreeC for 4 second, and dried at 80 degreeC for 300 second, and produced the polarizing laminated film.

(5) Preparation of polarizing plate (bonding process and peeling process)

A polyvinyl alcohol powder (“KL-318” manufactured by Kurare 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. A crosslinking agent ("Sumirez Resin 650" manufactured by Takaoka Chemical Co., Ltd.) was mixed with the obtained aqueous solution at a ratio of 1 part by weight with respect to 2 parts by weight of polyvinyl alcohol powder to obtain an aqueous adhesive solution.

Next, while continuously conveying the polarizing laminated film prepared in (4), a protective film [triacetylcellulose (TAC)] which was coated with the adhesive aqueous solution on both sides of the polarizer layer and subjected to saponification treatment on the bonding surface. A transparent protective film ("KC4UY" manufactured by Konica Minolta Opto Co., Ltd.) having a thickness of 40 µm) was bonded onto a polarizer layer, and pressed by passing through a pair of bonding rolls, followed by compression, and thus a TAC / polarizer layer / primer layer / A bonding film comprising a layer structure of a base film / primer layer / polarizer layer / TAC was produced (bonding process).

Subsequently, the base film was peeled off from the bonding film to obtain two polarizing plates comprising a TAC / polarizer layer / primer layer, and a transparent protective film made of TAC laminated on the polarizer layer through an adhesive layer. In the process of peeling the base film, problems such as rupture did not occur.

<Example 2>

A polarizing plate was produced in the same manner as in Example 1, except that the stretching magnifications in the first-stage and second-stage stretching treatments were respectively 2.50 times and 2.32 times (total stretching ratio 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. Wrinkles were not observed in the stretched film, and the difference in thickness in the film width direction was 2 µm, and stretching was uniformly performed. The bonding process and the peeling process also proceeded without problems, and a polarizing plate with a protective film laminated thereon was obtained.

<Example 3>

A polarizing plate was produced in the same manner as in Example 1, except that the stretching magnifications in the first-stage and second-stage stretching treatments were respectively 2.80 and 2.07 times (total stretching ratio of 5.80). 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. Wrinkles were not observed in the stretched film, and the difference in thickness in the film width direction was 2 µm, and stretching was uniformly performed. The bonding process and the peeling process also proceeded without problems, and a polarizing plate with a protective film laminated thereon was obtained.

<Example 4>

A polarizing plate was produced in the same manner as in Example 1, except that the stretching magnifications in the first-stage and second-stage stretching treatments were respectively 3.40 times and 1.70 times (total draw ratio 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. Wrinkles were not observed in the stretched film, and the difference in thickness in the film width direction was 2 µm, and stretching was uniformly performed. The bonding process and the peeling process also proceeded without problems, and a polarizing plate with a protective film laminated thereon was obtained.

<Comparative Example 1>

A stretched film was produced in the same manner as in Example 1 except that the draw ratio in the first-stage stretching treatment was 5.80 times, and the second-stage stretching 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-stage and second-stage stretching treatments were 1.54 and 3.80, respectively (total draw ratio of 5.85). 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. Wrinkles were not observed in the obtained stretched film, but the difference in thickness in the film width direction was as large as 7 µm, and the stretch was uneven.

Stretching ratio and stretching ratio in the stretching treatment in the first and second stages (ratio of the stretching ratio in the stretching treatment step in the first stage to the stretching ratio in the stretching treatment step in the second stage), the total stretching ratio, And, the measurement results of the difference in thickness in the width direction of the wrinkles and the film with respect to the stretched film are summarized in Table 1.

According to the method of the present invention, it is possible to effectively suppress the occurrence of wrinkles during stretching of the laminated film and uneven stretching in the film width direction (thus, uneven thickness in the film width direction), so that appearance and optical characteristics can be suppressed. This good polarizing laminated film or polarizing plate can be produced with good yield.

1, 2, 3, 4 nip rolls, 5 guide rolls, 6, 7, 8, 9 heat rolls, 10 laminated films, 15 stretched films, 20, 30 heating furnaces, 40 chucks.

Claims (6)

A resin layer forming step of coating a coating solution containing a polyvinyl alcohol-based resin on at least one side of the base film, followed by drying to form a polyvinyl alcohol-based resin layer to obtain a laminated film;
Stretching step of obtaining a stretched film by longitudinally uniaxially stretching the laminated film,
It includes a dyeing process to obtain a polarizing laminated film by dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to form a polarizer layer,
The stretching process includes two or more steps of stretching treatment,
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,
The total stretch magnification of the polarizer layer is a method of manufacturing a polarizing laminated film that is more than 5 times based on the polyvinyl alcohol-based resin layer of the laminated film. The method according to claim 1, wherein in the resin layer forming step, the polyvinyl alcohol-based resin layer is formed on both surfaces of the base film. The method according to claim 1 or 2, wherein a thickness of the polyvinyl alcohol-based resin layer of the laminated film is 3 µm to 30 µm. The manufacturing method according to claim 1 or 2, wherein the stretching ratio in the first-stage stretching treatment step is less than 5 times. The manufacturing method according to claim 1 or 2, wherein the base film is made of a polypropylene-based resin. The process of preparing the polarizing laminated film obtained by the manufacturing method of Claim 1 or 2, and
A step of bonding a protective film on the polarizer layer of the polarizing laminated film to obtain a bonding film,
Step of peeling the base film from the bonding film
Method of manufacturing a polarizing plate comprising a.

Images