JP2012133296A - Polarizing laminate film and manufacturing method of polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a thin polarizing laminate film and a polarizing plate, which allows easy handling and prevents an edge of a base film from folding in and from cracking.SOLUTION: The present invention is a manufacturing method of a polarizing laminate film and a polarizing plate, which has; a resin layer-forming step of forming a resin layer by coating a solution containing a polyvinyl alcohol resin on a first face of a base film followed by drying to obtain a laminate film; a stretching step of uniaxially stretching the laminate film to obtain a stretched film; a support film-sticking step of sticking a support film to a second face of the base film; a coloring step of coloring the resin layer of the stretched film with a dichroic dye; and a crosslinking step by applying crosslinking treatment to the resin layer in a crosslinking solution followed by drying to form a polarizer layer, in this order.

Description

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

  A polarizing plate is widely used as a polarization supplying element in a display device such as a liquid crystal display device. Conventionally, a polarizing plate made of a polyvinyl alcohol-based resin and a protective film such as triacetyl cellulose are used as the polarizing plate. The polarizer layer (polarizing film) is required to have high optical performance, and in recent years, with the development of liquid crystal display devices such as notebook personal computers and mobile phones, reduction in thickness and weight is required.

  As an example of a method for producing a thin polarizing plate, after applying a solution containing a polyvinyl alcohol-based resin on the surface of a base film to provide a resin layer, the laminate film composed of the base film and the resin layer is stretched, There has been proposed a method of obtaining a polarizing laminated film having a polarizer layer by dyeing, crosslinking (fixing), drying, and forming a polarizer layer from a resin layer (see, for example, Patent Document 1). The method of using this as a polarizing plate as it is, or using the thing which peeled the base film after bonding a protective film to this film as a polarizing plate is disclosed.

JP 2000-338329 A

  In the manufacturing method of the polarizing plate described above, the crosslinking treatment is performed in a crosslinking solution containing boric acid. However, in the drying step after the crosslinking treatment, the crosslinking of boric acid significantly proceeds and the resin layer extends in the width direction of the polarizing laminated film. May shrink, and a phenomenon may occur in which both ends of the base film warp toward the resin layer. If the base film provided with the resin layer is continuously flowed in this state, the end of the base film may be folded at the drying furnace or at the outlet of the drying furnace. In addition, there is a problem that a load is generated on the laminated film due to stretching, and cracks are easily generated in the stretching direction in the subsequent steps.

  By thickening the base film, it is possible to suppress the folding and cracking of the edges to some extent, but in order to completely suppress the base film, it is necessary to make the base film considerably thicker. When handling a long film with a roll, there exists a problem of becoming bulky. Moreover, there exists a problem that control in an extending process becomes difficult.

  Therefore, an object of the present invention is to provide a method for producing a thin polarizing laminated film and a polarizing plate that is easy to handle, but does not cause folding or cracking of the end of the base film. There is.

The present invention is a method for producing a polarizing laminate film comprising a substrate film and a polarizer layer formed on the first surface of the substrate film,
A resin layer forming step of applying a solution containing a polyvinyl alcohol-based resin to the first surface of the base film and then drying to form a resin layer to obtain a laminated film;
A stretching process for obtaining a stretched film by uniaxially stretching the laminated film;
A support film laminating step of laminating a support film on the second surface of the base film;
A dyeing step of dyeing the resin layer of the stretched film with a dichroic dye;
The present invention provides a method for producing a polarizing laminate film, which comprises a crosslinking step of forming a polarizer layer by subjecting the resin layer to a crosslinking treatment in a crosslinking solution and then drying.

  In the above-described support film bonding step, for example, a support film is bonded to the second surface of the base film via an adhesive layer or an adhesive layer.

  In the resin layer forming step described above, the thickness of the base film is preferably 5 to 200 μm. Moreover, in the above-described support film bonding step, the thickness of the support film is preferably 10 to 150 μm.

  In the present invention, the base film is preferably made of a polyolefin resin, and the support film is preferably made of a polyester resin.

Further, the present invention is a method for producing a polarizing plate comprising a polarizer layer and a protective film formed on one surface of the polarizer layer,
After producing a polarizing laminate film by the production method of the present invention,
A protective film laminating step for laminating a protective film on the surface of the polarizer layer in the polarizing laminated film opposite to the surface on the substrate film side;
The manufacturing method of a polarizing plate which has the base film peeling process which peels the said base film from the said polarizing laminated film in this order is provided.

  According to the present invention, a thin polarizing laminated film and a polarizing plate can be produced without being bent or cracked at the end of the base film, while being easy to handle.

It is a flowchart which shows one Embodiment of the manufacturing method of the light-polarizing laminated film of this invention. It is a flowchart which shows one Embodiment of the manufacturing method of the polarizing plate of this invention.

  Hereinafter, with reference to the drawings, preferred embodiments of a method for producing a polarizing laminate film and a method for producing a polarizing plate according to the present invention will be described in detail.

  In the present specification, a laminate in which a resin layer made of polyvinyl alcohol resin (hereinafter also referred to as “polyvinyl alcohol resin layer”) is formed on the first surface of a base film is referred to as “laminated film”, a polarizer. A resin layer having the above function is referred to as a “polarizer layer”, and a laminate including the polarizer layer on the first surface of the base film is referred to as a “polarizing laminate film”. And the laminated body provided with the protective film on one surface of a polarizer layer is called "polarizing plate."

[Method for producing polarizing laminated film]
FIG. 1 is a flowchart showing an embodiment of a method for producing a polarizing laminated film according to the present invention. The polarizing laminated film produced in the present embodiment includes a base film and a polarizer layer formed on the first surface (one surface) of the base film. In the manufacturing method of the light-polarizing laminated film of the present embodiment, a resin layer forming step of forming a resin layer by applying a solution containing a polyvinyl alcohol-based resin on the first surface of the base film and then drying to form a laminated film (S10), a stretching step (S20) for uniaxially stretching the laminated film to obtain a stretched film, a support film laminating step (S30) for laminating the support film on the second surface of the base film, and a stretched film A dyeing step (S40) for dyeing the resin layer with a dichroic dye, and a crosslinking step (S50) for forming a polarizer layer by performing a crosslinking treatment on the resin layer in a crosslinking solution and then drying are performed in this order. To do. After the cross-linking step (S50), the support film may be peeled off or may be used as a component of the polarizing laminated film that protects the polarizing layer without peeling off.

  By the above production method, a polarizing laminated film having a sufficient polarizing performance, for example, a polarizer layer having a thickness of 10 μm or less can be obtained on the base film. The thickness of the polarizer layer of the polarizing laminate film obtained by the above production method is preferably 10 μm or less, more preferably 1 to 8 μm. As will be described later, this polarizing laminated film can also be used as an intermediate product for transferring a polarizer layer to a protective film, and when the substrate film has the function of a protective film, this polarizing film The laminated film can be used as a polarizing plate as it is.

[Production method of polarizing plate]
FIG. 2 is a flowchart showing an embodiment of a method for producing a polarizing plate according to the present invention. The polarizing plate produced in the present embodiment includes a polarizer layer and a protective film formed on one surface of the polarizer layer. The manufacturing method of the polarizing plate of this embodiment is a resin layer forming step (S10) in which a solution containing a polyvinyl alcohol-based resin is applied to the first surface of the base film and then dried to form a resin layer to obtain a laminated film. ), A stretching step (S20) for uniaxially stretching the laminated film to obtain a stretched film, a support film laminating step (S30) for laminating the support film on the second surface of the base film, and a resin layer of the stretched film The dyeing step (S40) for dyeing the dichroic dye with the dichroic dye and the crosslinking step (S50) for forming the polarizer layer by drying the resin layer after crosslinking the resin layer in the crosslinking solution are performed in order. After obtaining a laminated film, from the polarizing laminated film, a protective film laminating step (S60) for laminating a protective film on the surface of the polarizer layer opposite to the surface on the base film side of the polarizer layer, and Base material Base film peeling step of peeling the Lum and (S70) are sequentially performed.

  By the above production method, a polarizing plate having a sufficient polarization performance on the protective film, for example, a polarizer layer having a thickness of 10 μm or less can be obtained. The thickness of the polarizer layer of the polarizing plate obtained by the above production method is preferably 10 μm or less, more preferably 1 to 8 μm. This polarizing plate can be used by, for example, bonding to another optical film or a liquid crystal cell via an adhesive.

  Hereafter, each process of S10-S70 in FIG.1 and FIG.2 is demonstrated in detail. The steps S10 to S50 in FIGS. 1 and 2 are similar steps.

<Resin layer forming step (S10)>
Here, the laminated film which consists of a base film and a polyvinyl alcohol-type resin layer is obtained by coating and drying the solution containing a polyvinyl alcohol-type resin on the 1st surface of a base film, and forming a resin layer.

  The thickness (before stretching) of the polyvinyl alcohol resin layer to be formed is preferably more than 3 μm and not more than 30 μm, and more preferably 5 to 20 μm. If it is 3 μm or less, it becomes too thin after stretching and the dyeability is remarkably deteriorated. If it exceeds 30 μm, the thickness of the finally obtained polarizer layer may exceed 10 μm.

  The polyvinyl alcohol-based resin layer is preferably dried by applying a polyvinyl alcohol-based resin solution obtained by dissolving a polyvinyl alcohol-based resin powder in a good solvent onto one surface of the base film and evaporating the solvent. It is formed by doing. By forming the polyvinyl alcohol-based resin layer in this manner, it can be formed thin. As a method of coating a polyvinyl alcohol resin solution on a base film, a wire bar coating method, a reverse coating, a roll coating method such as gravure coating, a die coating method, a comma coating method, a lip coating method, a spin coating method, a screen A known method such as a coating method, a fountain coating method, a dipping method, or a spray method can be appropriately selected and employed. A drying temperature is 50-200 degreeC, for example, Preferably it is 60-150 degreeC. The drying time is, for example, 2 to 20 minutes.

  There are various drying methods such as a method of blowing hot air, a method of contacting with a hot roll, and a method of heating with an IR heater, all of which can be suitably used. The drying temperature means the atmospheric temperature in the drying furnace in the case of a drying equipment provided with a drying furnace such as a method of blowing hot air or an IR heater, and in the case of a contact type drying equipment such as a hot roll. Means the surface temperature of the hot roll.

(Base film)
As the resin used for the base film, for example, thermoplastic resins excellent in transparency, mechanical strength, thermal stability, stretchability, etc. are used, and an appropriate resin is selected according to their glass transition temperature Tg or melting point Tm. You can choose. It is preferable to use a base film that can be stretched in a temperature range suitable for stretching a polyvinyl alcohol-based resin layer laminated thereon.

  Specific examples of thermoplastic resins include polyolefin resins, polyester resins, cyclic polyolefin resins (norbornene resins), (meth) acrylic resins, cellulose ester resins, polycarbonate resins, polyvinyl alcohol resins, vinyl acetate. Resin, polyarylate resin, polystyrene resin, polyethersulfone resin, polysulfone resin, polyamide resin, polyimide resin, and mixtures and copolymers thereof.

  The base film may be a film made of only one kind of the above-mentioned resin, or may be a film made by blending two or more kinds of resins. The base film may be a single layer film or a multilayer film.

  Examples of the polyolefin resin include polyethylene and polypropylene, which are preferable because they can be stably stretched at a high magnification. Moreover, an ethylene-polypropylene copolymer obtained by copolymerizing propylene with ethylene can also be used. Copolymerization can be performed with other types of monomers, and examples of other types of monomers copolymerizable with propylene include ethylene and α-olefins. 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 α-olefin having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; Branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene; vinylcyclohexane and the like. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer. The content of the structural unit derived from the other monomer in the copolymer is determined by infrared (IR) spectrum according to the method described on page 616 of “Polymer Analysis Handbook” (1995, published by Kinokuniya). It can be obtained by measuring.

  Among the above, propylene-based resins constituting the propylene-based resin film include propylene homopolymer, propylene-ethylene random copolymer, propylene-1-butene random copolymer, and propylene-ethylene-1-butene. Random copolymers are preferably used.

  The stereoregularity of the propylene resin constituting the propylene resin film is preferably substantially isotactic or syndiotactic. A propylene-based resin film made of a propylene-based resin having substantially isotactic or syndiotactic stereoregularity has relatively good handleability and excellent mechanical strength in a high-temperature environment.

  The polyester resin is a polymer having an ester bond and is mainly a polycondensate of a polyvalent carboxylic acid and a polyhydric alcohol. As the polyvalent carboxylic acid used, divalent dicarboxylic acid is mainly used, and examples thereof include isophthalic acid, terephthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. In addition, divalent diol is mainly used as the polyhydric alcohol used, and examples thereof include propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol. Specific examples of the resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, polycyclohexane dimethyl naphthalate, and the like. . These blend resins and copolymers can also be suitably used.

  As the cyclic polyolefin resin, a norbornene resin is preferably used. Cyclic polyolefin resin is a general term for resins that are polymerized using cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And graft polymers obtained by modifying them with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as cyclic polyolefin resins. As specific examples, Topas (registered trademark) (manufactured by Ticona), Arton (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (manufactured by Nippon Zeon Corporation), ZEONEX (ZEONEX) (Registered trademark) (manufactured by ZEON CORPORATION) and Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.).

  Any appropriate (meth) acrylic resin can be adopted as the (meth) acrylic resin. For example, poly (meth) acrylic acid ester 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) acrylic acid methyl-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer) And methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, C1-6 alkyl poly (meth) acrylates, such as poly (meth) acrylate methyl, are mentioned. More preferably, as the (meth) acrylic resin, a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is used.

  The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, these copolymers and those obtained by modifying a part of the hydroxyl group with other types of substituents are also included. Among these, cellulose triacetate is particularly preferable. 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 include Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UZ (Fuji Film ( Co., Ltd.), Fujitac (registered trademark) TD40UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Opto Co., Ltd.), KC4UY (Konica Minolta Opto Co., Ltd.), and the like.

  The polycarbonate resin is an engineering plastic made of a polymer in which monomer units are bonded via a carbonate group, and is a resin having high impact resistance, heat resistance, and flame retardancy. Moreover, since it has high transparency, it is suitably used in optical applications. In optical applications, resins called modified polycarbonates in which the polymer skeleton is modified in order to lower the photoelastic coefficient, copolymerized polycarbonates with improved wavelength dependency, and the like are commercially available and can be suitably used. Such polycarbonate resins are widely commercially available. For example, Panlite (registered trademark) (Teijin Chemicals Ltd.), Iupilon (registered trademark) (Mitsubishi Engineering Plastics), SD Polyca (registered trademark) (Sumitomo) Dow Co., Ltd.), Caliber (registered trademark) (Dow Chemical Co., Ltd.) and the like.

  Arbitrary appropriate additives other than said thermoplastic resin may be added to the base film. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and coloring agents. . The content of the thermoplastic resin exemplified above in the base film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97%. % By weight. This is because, if the content of the thermoplastic resin in the base film is less than 50% by weight, the high transparency inherent in the thermoplastic resin may not be sufficiently exhibited.

  The thickness of the base film in the resin layer forming step, that is, the thickness of the base film before stretching can be determined as appropriate, but from the viewpoint of workability such as strength and handleability, preferably 5 to 200 μm, more Preferably it is 5-150 micrometers. By using a base film having a thickness in this range, even when a long film is handled with a roll in continuous production, it is not bulky.

  The base film is subjected to corona treatment, plasma treatment, flame treatment, etc. on at least the surface (first surface) on which the polyvinyl alcohol resin layer is formed in order to improve adhesion with the polyvinyl alcohol resin layer. You may go.

  Moreover, in order to improve the adhesiveness of a base film and a polyvinyl alcohol-type resin layer, you may provide a primer layer in the 1st surface of a base film. The primer layer is preferably formed from a composition containing a polyvinyl alcohol-based resin and a crosslinking agent from the viewpoint of adhesion.

(Polyvinyl alcohol resin layer)
As the polyvinyl alcohol resin forming the polyvinyl alcohol resin layer, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The polyvinyl alcohol resin is preferably a completely saponified product. The range of the saponification degree is preferably 80.0 mol% to 100.0 mol%, more preferably 90.0 mol% to 100 mol%, and further preferably 94.0 mol% to 100 mol%. Most preferred are those in the mol% range. If the degree of saponification is less than 80.0 mol%, there is a problem that the water resistance and heat-and-moisture resistance after forming the polarizer layer are remarkably inferior.

  The saponification degree as used herein is a unit ratio (mol%) representing the ratio of the acetate group contained in the polyvinyl acetate resin, which is a raw material for the polyvinyl alcohol resin, to a hydroxyl group by the saponification step. Is a numerical value defined by the following formula. It can be determined by the method defined in JIS K 6726 (1994).

Saponification degree (mol%) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100
The higher the degree of saponification, the higher the proportion of hydroxyl groups, that is, the lower the proportion of acetate groups that inhibit crystallization.

  The polyvinyl alcohol-based resin may be modified polyvinyl alcohol partially modified. For example, polyvinyl alcohol resins modified with olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, alkyl esters of unsaturated carboxylic acids, acrylamide, and the like can be used. The proportion of modification is preferably less than 30 mol%, and more preferably less than 10%. When the modification exceeding 30 mol% is performed, it is difficult to adsorb the dichroic dye, resulting in a problem that the polarization performance is lowered.

  The average degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but is preferably 100 to 10,000, more preferably 1500 to 8000, and most preferably 2000 to 5000. The average degree of polymerization here is also a numerical value determined by a method defined by JIS K 6726 (1994).

  Examples of the polyvinyl alcohol resin having such characteristics include PVA124 (degree of saponification: 98.0 to 99.0 mol%) and PVA117 (degree of saponification: 98.0 to 99.0) manufactured by Kuraray Co., Ltd. Mol%), PVA624 (degree of saponification: 95.0 to 96.0 mol%) and PVA617 (degree of saponification: 94.5 to 95.5 mol%); for example, AH- manufactured by Nippon Synthetic Chemical Industry Co., Ltd. 26 (degree of saponification: 97.0-98.8 mol%), AH-22 (degree of saponification: 97.5-98.5 mol%), NH-18 (degree of saponification: 98.0-99. 0 mol%), and N-300 (degree of saponification: 98.0 to 99.0 mol%); for example, JC-33 (degree of saponification: 99.0 mol% or more) of Nippon Vinegar Pival Co., Ltd. , JM-33 (degree of saponification: 93.5 to 95.5 mol%), JM 26 (degree of saponification: 95.5-97.5 mol%), JP-45 (degree of saponification: 86.5-89.5 mol%), JF-17 (degree of saponification: 98.0-99. 0 mol%), JF-17L (degree of saponification: 98.0 to 99.0 mol%), JF-20 (degree of saponification: 98.0 to 99.0 mol%), and the like. Can be suitably used in the formation of the polyvinyl alcohol-based resin layer of the present invention.

(Primer layer)
A primer layer may be formed on the surface (first surface) of the base film on which the polyvinyl alcohol-based resin layer is formed. The primer layer is not particularly limited as long as it is a material that exhibits a certain degree of strong adhesion to both the base film and the polyvinyl alcohol-based resin layer. For example, a thermoplastic resin excellent in transparency, thermal stability, stretchability, etc. is used. Specific examples include acrylic resins and polyvinyl alcohol resins, but are not limited thereto. Among these, a polyvinyl alcohol resin having good adhesion is preferably used.

  As a polyvinyl alcohol-type resin used as a primer layer, polyvinyl alcohol resin and its derivative (s) are mentioned, for example. Derivatives of polyvinyl alcohol resin include polyvinyl formal, polyvinyl acetal, etc., olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, and alkyl esters of unsaturated carboxylic acids. And those modified with acrylamide or the like. Among the above-mentioned polyvinyl alcohol-based resin materials, it is preferable to use a polyvinyl alcohol resin.

  In order to increase the strength of the primer layer, a crosslinking agent may be added to the thermoplastic resin. As the cross-linking agent to be added to the thermoplastic resin, known ones such as organic and inorganic can be used. What is necessary is just to select a more suitable thing suitably with respect to the thermoplastic resin to be used. For example, in addition to low molecular crosslinkers such as epoxy crosslinkers, isocyanate crosslinkers, dialdehyde crosslinkers, metal chelate crosslinkers, high molecular weight polymers such as methylolated melamine resins and polyamide epoxy resins. A crosslinking agent or the like can also be used. When a polyvinyl alcohol resin is used as the thermoplastic resin, it is particularly preferable to use a polyamide epoxy resin, a methylolated melamine, a dialdehyde, a metal chelate crosslinking agent, or the like as the crosslinking agent.

  The thickness of a primer layer becomes like this. Preferably it is 0.05-1 micrometer, More preferably, it is 0.1-0.4 micrometer. If the thickness is less than 0.05 μm, the adhesive force between the base film and the polyvinyl alcohol film is reduced, and if it is greater than 1 μm, the polarizing plate becomes thick.

<Extension process (S20)>
Here, the laminated film consisting of the base film and the polyvinyl alcohol-based resin layer is uniaxially stretched. Preferably, uniaxial stretching is performed so that the stretching ratio is more than 5 times and not more than 17 times. More preferably, it is uniaxially stretched so that the stretch ratio is more than 5 times and not more than 8 times. When the draw ratio is 5 times or less, the polyvinyl alcohol-based resin layer is not sufficiently oriented, and as a result, the degree of polarization of the polarizer layer may not be sufficiently high. On the other hand, when the draw ratio exceeds 17 times, the laminated film at the time of stretching tends to break, so that the workability and handling properties in the subsequent process may be reduced. The stretching process in the stretching step (S20) is not limited to one-stage stretching, and can be performed in multiple stages. In the case of performing in multiple stages, it is preferable to perform the stretching treatment so that the stretching ratio is more than 5 times by combining all the stages of the stretching treatment.

  In the extending process (S20) in this invention, the longitudinal stretch process performed with respect to the longitudinal direction of a laminated | multilayer film, the horizontal stretch process extended | stretched with respect to the width direction, etc. can be implemented. Examples of the longitudinal stretching method include an inter-roll stretching method and a compression stretching method, and examples of the transverse stretching method include a tenter method.

<Support film bonding step (S30)>
Here, the laminated body which consists of a support film, a base film, and a resin layer is obtained by bonding a support film to the 2nd surface of a base film. The pasting method of the base film and the support film is a method in which the base film and the support film are pasted with an adhesive force that does not peel off in the subsequent dyeing step (S40) and the crosslinking step (S50). There is no limitation as long as there is. For example, a base film and a support film can be bonded via an adhesive layer or an adhesive layer. In the support film laminating step (S30), by laminating the support film on the base film, the base film remains in a thickness that is easy to handle, and the base film is folded in the subsequent process, Generation of cracks can be prevented.

(Support film)
The support film is not limited as long as it has a stiffness that prevents folding of the base film, and is made of, for example, a thermoplastic resin that is excellent in mechanical strength, thermal stability, and the like. As the thermoplastic resin used for the support film, a suitable resin can be selected according to the strength of shrinkage generated in the drying process in the subsequent crosslinking step (S50). Specific examples include polyolefin resins, polyester resins, cyclic polyolefin resins (norbornene resins), (meth) acrylic resins, cellulose ester resins, polycarbonate resins, polyvinyl alcohol resins, vinyl acetate resins, poly Examples include arylate resins, polystyrene resins, polyethersulfone resins, polysulfone resins, polyamide resins, polyimide resins, and mixtures and copolymers thereof. Of these, polyester resins are preferably used because of their strength.

  The polyester resin is a polymer having an ester bond and is mainly a polycondensate of a polyvalent carboxylic acid and a polyhydric alcohol. As the polyvalent carboxylic acid used, divalent dicarboxylic acid is mainly used, and examples thereof include isophthalic acid, terephthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. In addition, divalent diol is mainly used as the polyhydric alcohol used, and examples thereof include propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol. Specific examples of the resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, and polycyclohexane dimethyl naphthalate. Mixtures and copolymers thereof can also be suitably used. Further, a single layer or a multilayer film may be formed.

  The support film may be uniaxially stretched or biaxially stretched. By stretching, desired strength can be imparted. Stretching is usually performed continuously while winding a film roll, and is stretched in a heating furnace in a roll traveling direction, a direction perpendicular to the traveling direction, or both.

  The support film may be a film having no optical function or a film having an optical function such as a retardation film or a brightness enhancement film. When it is set as the component of a light-polarizing laminated film without peeling, the below-mentioned protective film is preferably used as a support film.

  Although the thickness of the support film in a support film bonding process can be determined suitably, it is 10-150 micrometers from the point which ensures the firmness and intensity | strength which prevent the folding of a base film, and favorable workability | operativity. A range is preferred. The support film preferably has a flexural modulus of 1000 MPa or more, more preferably 2000 MPa or more, from the viewpoint of ensuring sufficient stiffness and strength. Moreover, the melting | fusing point of a support film can select a 150 degreeC or more thing, for example.

(Adhesive layer)
The pressure-sensitive adhesive layer includes, for example, a self-adhesive layer made of an ethylene-vinyl acetate copolymer, an acrylic resin, a styrene resin, a silicone resin, or the like as a base polymer, and an isocyanate compound, an epoxy compound, or aziridine. It can be set as the pressure-sensitive adhesive layer which consists of a composition which added crosslinking agents, such as a compound. Furthermore, a pressure-sensitive adhesive layer exhibiting light scattering properties can be formed by mixing fine particles in the pressure-sensitive adhesive.

  The thickness of the pressure-sensitive adhesive layer is preferably 1 to 40 μm, but it is preferably applied thinly, and more preferably 3 to 25 μm as long as the workability and adhesive properties are not impaired. It has favorable workability as it is 3 to 25 μm. When the pressure-sensitive adhesive layer is less than 1 μm, the adhesiveness is lowered, and when it exceeds 40 μm, problems such as the pressure-sensitive adhesive protruding easily occur.

  The method for forming the pressure-sensitive adhesive layer on the base film or the support film is not particularly limited, and a solution containing each component including the above-mentioned base polymer is applied to the base film surface or the support film surface. Then, after forming the pressure-sensitive adhesive layer by drying, it may be bonded to another type of film, or after forming the pressure-sensitive adhesive layer on the separator, it is laminated on the base film surface or the support film surface. May be. In addition, when forming the pressure-sensitive adhesive layer on the base film or the support film surface, if necessary, the base film surface or the support film film surface, or one or both of the pressure-sensitive adhesive layer is adhered, for example, corona treatment, etc. May be applied.

(Adhesive layer)
Bonding of the base film can also be performed via an adhesive layer. Examples of the adhesive constituting the adhesive layer include a water-based adhesive using a polyvinyl alcohol-based resin aqueous solution, a water-based two-component urethane-based emulsion adhesive, and the like. Among these, a polyvinyl alcohol resin aqueous solution is preferably used. Polyvinyl alcohol resins used as adhesives include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as other single quantities copolymerizable with vinyl acetate. And vinyl alcohol copolymers obtained by saponifying the copolymer with the polymer, and modified polyvinyl alcohol polymers obtained by partially modifying the hydroxyl groups. A polyhydric aldehyde, a water-soluble epoxy compound, a melamine compound, a zirconia compound, a zinc compound, or the like may be added as an additive to the water-based adhesive. When such a water-based adhesive is used, the adhesive layer obtained therefrom is usually much thinner than 1 μm, and even when the cross section is observed with a normal optical microscope, the adhesive layer is practically not observed.

  The method of laminating the film using the water-based adhesive is not particularly limited, and the adhesive is uniformly applied or poured onto the surface of the protective film or the polyvinyl alcohol-based resin layer, and the other film is applied to the coated surface. Examples of the method include stacking and pasting with rolls and drying. Usually, an adhesive agent is apply | coated at the temperature of 15-40 degreeC after the preparation, and the bonding temperature is the range of 15-30 degreeC normally.

  When using a water-system adhesive, after bonding a film, in order to remove the water contained in a water-system adhesive, it is made to dry. The temperature of the drying furnace is preferably 30 ° C to 90 ° C. If it is less than 30 ° C., the adhesive surface tends to be peeled off. If it is 90 ° C. or higher, the optical performance of a polarizer or the like may be deteriorated by heat. The drying time can be 10 to 1000 seconds.

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

  Moreover, a photocurable adhesive can also be used as a non-aqueous adhesive. Examples of the photocurable adhesive include a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

  As a method of laminating the base film and the support film with the photocurable adhesive, a conventionally known method can be used, for example, casting method, Mayer bar coating method, gravure coating method, comma coater method, Examples include a method of applying an adhesive to the adhesive surface of one film and superimposing two films by a doctor plate method, a die coating method, a dip coating method, a spraying method, or the like. The casting method is a method in which two films as an object to be coated are moved in a substantially vertical direction, generally in a horizontal direction, or in an oblique direction between the two, and an adhesive is allowed to flow down and spread on the surface. is there.

  After the adhesive is applied to the surface of one film, it is bonded by sandwiching the film with a nip roll or the like. Moreover, the method of pressing this laminated body with a roll etc. and spreading it uniformly can also be used suitably. In this case, a metal, rubber, or the like can be used as the material of the roll. Furthermore, a method in which this laminate is passed between rolls and pressed to spread is preferably employed. In this case, these rolls may be made of the same material or different materials. The thickness of the adhesive layer after being bonded using the nip roll or the like before drying or curing is preferably 5 μm or less and 0.01 μm or more.

  In order to improve adhesiveness, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment, and the like may be appropriately performed on the adhesion surfaces of the base film and the support film. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

  When a photocurable resin is used as an adhesive, the photocurable adhesive is cured by irradiating active energy rays after laminating the films. 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 preferable. Specifically, the low-pressure mercury lamp, the medium-pressure mercury lamp, the high-pressure mercury lamp, the ultrahigh-pressure mercury lamp, the chemical lamp, and the black light lamp A microwave excitation mercury lamp, a metal halide lamp and the like are preferably used.

The light irradiation intensity to the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 6000 mW / it is preferable that the cm ^2. When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when it is 6000 mW / cm ² or less, the epoxy is generated by the heat radiated from the light source and the heat generated when the photo-curable adhesive is cured. There is little risk of yellowing of the resin or deterioration of the polarizing layer. The light irradiation time to the photocurable adhesive is not particularly limited and is applied according to the photocurable adhesive to be cured, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time. Is preferably set to be 10 to 10,000 mJ / cm ² . When the cumulative amount of light to the photocurable adhesive is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to allow the curing reaction to proceed more reliably, and at 10,000 mJ / cm ² or less. In some cases, irradiation time does not become too long and good productivity can be maintained. The thickness of the adhesive layer after irradiation with active energy rays is usually about 0.001 to 5 μm, preferably 0.01 μm or more and 2 μm or less, more preferably 0.01 μm or more and 1 μm or less. .

  When curing a photocurable adhesive on a film by irradiation with active energy rays, various properties of the polarizing laminated film or polarizing plate after all the steps such as transmittance, hue, transparency of these films and polarizer layers, etc. It is preferable to perform the curing under conditions where the function does not decrease.

<Dyeing process (S40)>
Here, the polyvinyl alcohol resin layer of the laminated film is dyed with a dichroic dye. Examples of the dichroic dye include iodine and organic dyes. Examples of organic dyes include 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, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc. can be used. One kind of these dichroic substances may be used, or two or more kinds may be used in combination.

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

  When iodine is used as the dichroic dye, it is preferable to further add an iodide because 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, and iodide. Examples include titanium. The addition ratio of these iodides is preferably 0.01 to 20% by weight in the dyeing solution. Of the iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably in the range of 1: 6 to 1:80 by weight. , Particularly preferably in the range of 1: 7 to 1:70.

  The immersion time of the stretched film with a support film in the dyeing solution is not particularly limited, but is usually preferably in the range of 15 seconds to 15 minutes, and more preferably 1 minute to 3 minutes. Moreover, it is preferable that it is in the range of 10-60 degreeC, and, as for the temperature of a dyeing | staining solution, it is more preferable that it exists in the range of 20-40 degreeC.

<Crosslinking step (S50)>
(Crosslinking treatment)
A cross-linking step is performed after the dyeing step. In the crosslinking step, first, a crosslinking treatment is performed in which the stretched film with a support film is immersed in a solution containing a crosslinking agent (crosslinking solution). Conventionally known substances can be used as the crosslinking agent. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One kind of these may be used, or two or more kinds may be used in combination.

  As the crosslinking solution, a solution in which a crosslinking agent is dissolved in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further included. Although the density | concentration of the crosslinking agent in a crosslinking solution is not limited to this, It is preferable to exist in the range of 1-20 weight%, and it is more preferable that it is 6-15 weight%.

  Iodide may be added to the crosslinking solution. By adding iodide, the in-plane polarization characteristics of the resin layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Is mentioned. The iodide content is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

  The immersion time of the stretched film with a support film in the crosslinking solution is usually preferably from 15 seconds to 20 minutes, and more preferably from 30 seconds to 15 minutes. Moreover, it is preferable that the temperature of a crosslinking solution exists in the range of 10-80 degreeC.

(Cleaning process)
A washing treatment is preferably performed after the crosslinking treatment. As the cleaning process, a water cleaning process can be performed. The water washing treatment can be usually performed by immersing the laminated film in pure water such as ion exchange water or distilled water. The water washing temperature is usually in the range of 3 to 50 ° C, preferably 4 to 20 ° C. The immersion time is usually 2 to 300 seconds, preferably 3 to 240 seconds.

  The washing treatment may be a combination of a washing treatment with an iodide solution and a water washing treatment, and a solution appropriately mixed with a liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, propanol or the like can also be used.

(Drying process)
After the cleaning process, a drying process is performed. Any appropriate method (for example, natural drying, ventilation drying, heat drying) can be adopted as the drying treatment. For example, the drying temperature in the case of heat drying is usually 20 to 95 ° C., and the drying time is usually about 1 to 15 minutes. Through the above steps, the polyvinyl alcohol-based resin layer has a function as a polarizer layer, and a polarizing laminated film including the polarizer layer on one surface of the base film is manufactured. In this embodiment, since the support film is bonded to the second surface of the base film, the base film is prevented from warping during the drying process, and thus the base film is folded in the subsequent process. There is no such thing. Further, there is no problem that the laminated film is cracked in the dyeing process and the crosslinking process.

(Polarizer layer)
Specifically, the polarizer layer is obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol-based resin layer. The draw ratio is preferably more than 5 times, more preferably more than 5 times and not more than 17 times.

  The thickness of the polarizer layer (the thickness of the stretched polyvinyl alcohol resin layer) is preferably 10 μm or less, more 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.

<Protective film bonding step (S60)>
A protective film is bonded to the surface opposite to the surface on the base film side of the polarizer layer in the polarizing laminated film. The method for bonding the polarizer layer and the protective film is not particularly limited. For example, a pressure-sensitive adhesive layer or an adhesive layer is formed on the bonding surface of the polarizer layer and / or the protective film, and both are bonded via the pressure-sensitive adhesive layer or the adhesive layer. The material suitable as the pressure-sensitive adhesive layer or the adhesive layer is the same as the pressure-sensitive adhesive layer described in the above-described support film bonding step (S30).

(Protective film)
The protective film may be a simple protective film having no optical function, or may be a protective film having both optical functions such as a retardation film and a brightness enhancement film.

  The material of the protective film is not particularly limited, but for example, a cyclic polyolefin resin film, a cellulose acetate resin film made of a resin such as triacetyl cellulose or diacetyl cellulose, polyethylene terephthalate, polyethylene naphthalate, poly Examples of the film conventionally used in this field include a polyester resin film made of a resin such as butylene terephthalate, a polycarbonate resin film, an acrylic resin film, and a polypropylene resin film.

  Examples of the cyclic polyolefin-based resin include appropriate commercial products such as Topas (registered trademark) (manufactured by Ticona), Arton (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (Nippon ZEON ( ZEONEX (registered trademark) (manufactured by Nippon Zeon Co., Ltd.), Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.) can be suitably used. When such a cyclic polyolefin resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. In addition, pre-filmed cyclic polyolefins such as Essina (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), Zeonoa (registered trademark) film (manufactured by Optes Co., Ltd.), etc. A commercial product of a film made of a resin may be used.

  The cyclic polyolefin resin film may be uniaxially stretched or biaxially stretched. An arbitrary retardation value can be imparted to the cyclic polyolefin-based resin film by stretching. Stretching is usually performed continuously while unwinding the film roll, and is stretched in the heating furnace in the roll traveling direction, the direction perpendicular to the traveling direction, or both. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the cyclic polyolefin resin to the glass transition temperature + 100 ° C. The draw ratio is usually 1.1 to 6 times, preferably 1.1 to 3.5 times in one direction.

  Since the cyclic polyolefin resin film generally has poor surface activity, the surface to be bonded to the polarizer layer is subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment. Is preferred. Among these, plasma treatment and corona treatment that can be performed relatively easily are preferable.

  Examples of the cellulose acetate-based resin film include commercially available products such as Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), and Fujitac (registered trademark). TD80UZ (Fuji Film Co., Ltd.), Fujitac (registered trademark) TD40UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Opto Co., Ltd.), KC4UY (Konica Minolta Opto Co., Ltd.) are preferably used. be able to.

  A liquid crystal layer or the like may be formed on the surface of the cellulose acetate-based resin film in order to improve viewing angle characteristics. Moreover, in order to provide a phase difference, what stretched the cellulose acetate type-resin film may be used. The cellulose acetate-based resin film is usually subjected to a saponification treatment in order to improve the adhesiveness with the polarizing film. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be employed.

  Optical layers such as a hard coat layer, an antiglare layer, and an antireflection layer can be formed on the surface of the protective film as described above. 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 thickness of the protective film is preferably as thin as possible from the demand for thinning, is preferably 90 μm or less, and more preferably 50 μm or less. On the other hand, if it is too thin, the strength is lowered and the processability is poor, and therefore it is preferably 5 μm or more.

<Base film peeling step (S70)>
In the manufacturing method of the polarizing plate of this embodiment, as shown in FIG. 2, a base film peeling process (S70) is performed after the protective film bonding process (S60) which bonds a protective film to a polarizer layer. In the base film peeling step (S70), the base film is peeled from the polarizing laminated film. In addition, when it is in the state by which the support film was bonded on the 2nd surface of a base film, in a base film peeling process (S70), the laminated body of a base film and a support film is from a polarizing laminated film. It is peeled off. The peeling method of a base film is not specifically limited, The method similar to the peeling process of the peeling film performed with a normal polarizing plate with an adhesive can be employ | adopted. After the protective film laminating step (S60), it may be peeled off as it is, or after winding it up into a roll once, it may be peeled off by providing another peeling step. Through the above steps, a polarizing plate having a protective film on one surface of the polarizer layer is produced.

(Other optical layers)
In practical use, the polarizing plate can be used as a polarizing plate in which other optical layers are laminated. Moreover, the said protective film may have a function of these optical layers.

  Examples of other optical layers include a reflective polarizing film that transmits certain types of polarized light and reflects polarized light that exhibits the opposite properties, a film with an antiglare function having an uneven shape on the surface, and a surface antireflection function. Examples thereof include an attached film, a reflective film having a reflective function on the surface, a transflective film having both a reflective function and a transmissive function, and a viewing angle compensation film.

  Commercially available products corresponding to reflective polarizing films that transmit certain types of polarized light and reflect polarized light that exhibits the opposite properties include DBEF (available from 3M, Sumitomo 3M Co., Ltd.), APF (Available from 3M, available from Sumitomo 3M Limited). Examples of the viewing angle compensation film include an optical compensation film coated with a liquid crystal compound on the surface of the substrate and oriented, a retardation film made of a polycarbonate resin, and a retardation film made of a cyclic polyolefin resin. Commercially available products corresponding to an optical compensation film coated with a liquid crystal compound on the substrate surface and oriented are WV film (Fuji Film Co., Ltd.), NH film (Shin Nippon Oil Co., Ltd.), NR Examples include films (manufactured by Nippon Oil Corporation). Commercial products corresponding to retardation films made of cyclic polyolefin resins include Arton (registered trademark) film (manufactured by JSR Corporation), Essina (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), Zeonor ( Registered trademark) film (manufactured by Optes Co., Ltd.).

[Example 1]
<Resin layer forming step (S10)>
After forming a primer layer on one surface of the base film, a polyvinyl alcohol resin layer was formed to produce a laminated film.

(Base film)
Propylene / ethylene random copolymer (trade name: Sumitomo Nobrene W151, melting point Tm = 138 ° C., manufactured by Sumitomo Chemical Co., Ltd.) Co-extrusion molding using a multi-layer extrusion molding machine with a three-layer base film in which a resin layer made of a certain homopolypropylene (trade name: Sumitomo Noblen FLX80E4, melting point Tm = 163 ° C., manufactured by Sumitomo Chemical Co., Ltd.) is arranged It was produced by. The total thickness of the obtained base film was 90 μm, and the thickness ratio (FLX80E4 / W151 / FLX80E4) of each layer was 3/4/3. Corona treatment was applied to the resin layer forming surface of the base film.

(Primer layer)
Polyvinyl alcohol powder (trade name: Z-200, average polymerization degree 1100, saponification degree 99.5 mol%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) is dissolved in 95 ° C. hot water to obtain an aqueous solution having a concentration of 3% by weight. Prepared. The resulting aqueous solution was mixed with 5 parts by weight of a crosslinking agent (trade name: Sumires (registered trademark) Resin 650, manufactured by Sumitomo Chemical Co., Ltd.) with respect to 6 parts by weight of the polyvinyl alcohol powder. The obtained mixed aqueous solution was applied on a corona-treated base film using a micro gravure coater and dried at 80 ° C. for 5 minutes to form a primer layer having a thickness of 0.2 μm.

(Polyvinyl alcohol resin layer)
Polyvinyl alcohol powder (trade name: PVA124, average polymerization degree 2400, saponification degree 98.0 to 99.0 mol%, manufactured by Kuraray Co., Ltd.) is dissolved in hot water at 95 ° C. to a concentration of 8% by weight polyvinyl alcohol. An aqueous solution was prepared. The obtained aqueous solution was applied onto the primer layer using a lip coater and dried at 80 ° C. for 5 minutes to form a polyvinyl alcohol-based resin layer.

<Extension process (S20)>
The laminated film was subjected to 5.8-fold free end uniaxial stretching at 160 ° C. using a tenter apparatus to obtain a stretched film. The thickness of the resin layer after stretching was 5.1 μm.

<Support film bonding step (S30)>
The support film was bonded via the adhesive layer to the surface on the opposite side to the surface where the polyvinyl alcohol-type resin layer of the base film was formed.

(Support film)
As the support film, a polyethylene terephthalate-based protective film (AS3-304, the thickness of the support film part 38 μm, the thickness of the adhesive layer part 20 μm, manufactured by Fujimori Kogyo Co., Ltd.), which is a support film with an adhesive layer, was used.

<Dyeing process (S40)>
Thereafter, the stretched film with a support film is immersed in a 60 ° C. warm bath for 60 seconds, immersed in a dyeing solution that is a mixed aqueous solution of iodine and potassium iodide at 30 ° C. for about 150 seconds, and then dyed with 10 ° C. pure water. Excess iodine solution was washed away.

The mixing ratio of the dyeing solution is
(Dyeing solution)
Water: 100 parts by weight, iodine: 0.6 parts by weight, potassium iodide: 10 parts by weight.

<Crosslinking step (S50)>
Next, the stretched film with a support film was immersed in a crosslinking solution, which is a mixed aqueous solution of boric acid and potassium iodide at 76 ° C. for 600 seconds. Thereafter, it was washed with pure water at 10 ° C. for 4 seconds, and finally, excess water on the surface was removed with a nip roll. Then, it was dried at 80 ° C. for 5 minutes.

The blending ratio of the crosslinking solution is
(Crosslinking solution)
Water: 100 parts by weight, boric acid: 9.5 parts by weight, potassium iodide: 5 parts by weight.

<Protective film bonding step (S60)>
Polyvinyl alcohol powder (trade name: KL-318, average polymerization degree 1800, manufactured by Kuraray Co., Ltd.) was dissolved in 95 ° C. hot water to prepare an aqueous solution having a concentration of 3% by weight. The resulting aqueous solution was mixed with 1 part by weight of a crosslinking agent (trade name: Sumires (registered trademark) Resin 650, manufactured by Sumitomo Chemical Co., Ltd.) with respect to 2 parts by weight of polyvinyl alcohol powder to obtain an adhesive solution. The protective film (TAC, trade name: KC4UY, Konica Minolta Opt Co., Ltd.) is applied to the surface of the polarizer layer of the polarizing laminate film opposite to the surface of the polarizer film on the side opposite to the base film side. ) Manufactured) was dried at 80 ° C. for 10 minutes to obtain a polarizing plate comprising 6 layers of a protective film, an adhesive layer, a polarizer layer, a primer layer, a substrate film and a support film.

<Base film peeling step (S70)>
The laminated body of the base film and the support film was peeled from the obtained polarizing plate. The laminate of the base film and the support film was easily peeled off to obtain a polarizing plate having good polarizing performance comprising 4 layers of a protective film, an adhesive layer, a polarizer layer, and a primer layer. The thickness of the polarizer layer was 5.1 μm.

  After the stretching step (S20), there is no problem that the stretched film tears, and there is no folding at the edge of the base film in the drying step after the cross-linking treatment, and the film is stable. Can be transported continuously.

[Comparative Example 1]
A polarizing plate was produced in the same manner as in Example 1 except that the support film was not bonded to the base film. The resin layer contracted remarkably during drying in the cross-linking step, causing folding at the end of the base film, and the film could not be stably conveyed continuously. Moreover, the trouble that the part of the stretched film was torn in the stretching direction during continuous conveyance of the stretched film after the stretching process occurred.

Claims (6)

A method for producing a polarizing laminated film comprising a base film and a polarizer layer formed on the first surface of the base film,
A resin layer forming step of applying a solution containing a polyvinyl alcohol-based resin on the first surface of the base film and then drying to form a resin layer to obtain a laminated film;
A stretching step of uniaxially stretching the laminated film to obtain a stretched film;
A support film laminating step of laminating a support film on the second surface of the base film;
A dyeing step of dyeing the resin layer of the stretched film with a dichroic dye;
A method for producing a polarizing laminate film, comprising: a crosslinking step of forming a polarizer layer by subjecting the resin layer to a crosslinking treatment in a crosslinking solution, followed by drying.   The manufacturing method of the polarizing laminated film of Claim 1 which bonds the said support film to the 2nd surface of the said base film through an adhesive layer or an adhesive bond layer in the said support film bonding process.   The manufacturing method of the light-polarizing laminated film of Claim 1 or 2 whose thickness of the said base film in the said resin layer formation process is 5-200 micrometers.   The manufacturing method of the light-polarizing laminated film in any one of Claims 1-3 whose thickness of the said support film in the said support film bonding process is 10-150 micrometers.   The said base film consists of polyolefin resin, The said support film consists of polyester resin, The manufacturing method of the light-polarizing laminated film in any one of Claims 1-4. A method for producing a polarizing plate comprising a polarizer layer and a protective film formed on one surface of the polarizer layer,
After producing a polarizing laminated film by the production method according to claim 1,
A protective film laminating step of laminating a protective film on a surface opposite to the surface on the base film side of the polarizer layer in the polarizing laminated film;
The manufacturing method of a polarizing plate which has the base film peeling process which peels the said base film from the said polarizing laminated film in this order.

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