WO2014157732A1 - Method of manufacturing polarizing laminate film - Google Patents

Abstract

This method of manufacturing polarizing laminate film involves a step for obtaining a laminate film by forming a polyvinyl alcohol resin layer on a substrate film, a step for obtaining a stretched film by stretching the laminate film, and a step for conveying the stretched film along a conveyance path passing through a dye tank to dye the polyvinyl alcohol resin layer with a dichroic dye, wherein the dyeing step involves a step for conveying a first film along the conveyance path and immersing the same in the dye tank, a step for forming a bond by bonding the terminal end of the first film and the initial end of the second film, and a step for conveying the bonded area along the conveyance path and immersing the same in the dye tank, wherein the first and/or second film is a stretched film.

Description

Method for producing polarizing laminated film

The present invention relates to a method for producing a polarizing laminated film having a polarizer layer on one or both sides of a base film.

A polarizing plate is an optical element including a polarizer layer having a polarizing function and a protective film for protecting the polarizing layer, and is widely used as a polarized light supplying element and a polarized light detecting element in a liquid crystal display device. . Conventionally, as a polarizing plate, a polarizing film manufactured from a polyvinyl alcohol-based resin film raw material is used as a polarizer layer, and a protective film made of triacetyl cellulose or the like is bonded to one or both surfaces thereof. . In recent years, with the development of liquid crystal display devices in mobile devices such as notebook personal computers and mobile phones, and further development in large-sized televisions, there has been a demand for thinner and lighter polarizing plates.

The thickness of a polarizing film produced by drawing and dyeing a polyvinyl alcohol-based resin film original (usually about 75 μm thick) is usually about 30 μm. Thinning beyond this is difficult because of problems in productivity such as the film during stretching being easily broken.

On the other hand, when a polarizing plate is continuously manufactured as a long multilayer film, for example, in the conventional polarizing plate as described above, a long polarizing film that is one of the members of the polarizing plate is continuously manufactured. There is a need. Continuous production of a polarizing film usually includes a step of dyeing by immersing in a dyeing solution in a tank while continuously unwinding a long film from a film roll, so that the continuous production of a polarizing film is possible. In addition, when the unwinding long film is approaching the end, a roll switching operation including an operation of joining the end of the long film and the starting end of the long film of another film roll prepared in advance. Then, the dyeing process is continued for a new long film.

However, in the continuous production of the polarizing film as described above, when the joining portion (joining portion) of the film is immersed in the dyeing solution, there is a problem that the film breaks at the joining portion or the joining portion is peeled off. was there. As a method for solving this problem, Japanese Patent Application Laid-Open No. 2006-350224 (Patent Document 1) discloses a method for continuously producing a polarizing film from a raw film of a polyvinyl alcohol-based resin. When passing through these various processing steps, a method has been proposed in which all the lifting rolls of the manufacturing apparatus are raised to straighten the film transport path so that the joint is not immersed in a chemical solution such as a dyeing solution. Yes.

However, in the case of the method described in Patent Document 1, since no processing can be performed on the film until the joint portion of the film finishes passing through the processing step, the film is lost accordingly. Moreover, even if the transport path for carrying out the processing step is re-established by lowering the lifting roll after the joining portion has passed the processing step, it takes time for the film to stabilize for a while after that. Cost. Even if the processing step is performed on a film that has not recovered the stable state, it is not possible to produce a polarizing film having a good quality. Therefore, the film is lost until the stable state is recovered.

JP-A-2007-171897 (Patent Document 2) discloses a method for continuously producing a polarizing film by subjecting a polyvinyl alcohol-based resin film raw material to a dyeing process, a crosslinking process, and a stretching process in this order. Breaking of the film by uniaxial stretching in the longitudinal direction is performed by heat sealing in the temperature range of 55 to 90 ° C., by joining the end of the preceding film original and the start of the next film original. And that it is possible to suppress peeling of the joint. However, even when the bonding method described in Patent Document 2 is adopted, when the film is immersed in a chemical solution that easily causes deformation in the bonded portion of the film, for example, a high-temperature chemical solution, the film is broken or the bonded portion is peeled off. May occur.

The present invention has been made in view of the above-described problems of the prior art, and the purpose thereof is a polarizing plate that can be used as a polarizing plate and is also useful as a production intermediate for a polarizing plate provided with a protective film. This is a method for producing a polarizing laminated film having a child layer, and the film is broken or peeled off at the junction between the terminal end of the preceding film and the starting end of the next film even by the dipping process in the dyeing process. The object is to provide a method capable of stably and continuously producing a polarizing laminated film having a thin polarizer layer.

The present invention is as follows.
[1] A resin layer forming step of obtaining a laminated film by forming a polyvinyl alcohol-based resin layer on at least one surface of the base film;
A stretching step of stretching the laminated film to obtain a stretched film;
By transporting the stretched film along a transport path passing through a dyeing tank containing a dichroic dye, the polyvinyl alcohol resin layer of the stretched film is dyed with the dichroic dye to form a polarizer layer. A dyeing process in this order,
The dyeing step includes
A step of immersing in the dyeing tank by conveying the first film along the conveying path;
Joining the terminal end of the first film and the starting end of the second film to form a joint;
Immersing in the dyeing tank by transporting the joint along the transport path, and
The method for producing a polarizing laminated film, wherein at least one of the first film and the second film is the stretched film.

[2] The method according to [1] above, wherein in the step of immersing in the dyeing tank, substantially no stretching treatment is performed.

[3] The method according to [1] or [2], wherein the transport path is disposed after the dyeing tank and further passes through a crosslinking tank containing a crosslinking agent.

[4] The method according to any one of [1] to [3], wherein each of the first film and the second film is the stretched film.

[5] The method according to any one of [1] to [3], wherein either one of the first film and the second film is the stretched film, and the other is a lead film.

[6] The method according to any one of [1] to [5] above, wherein in the stretching step, the laminated film is stretched at a stretch ratio of more than 5 times.

[7] The method according to any one of [1] to [6] above, wherein the thickness of the polyvinyl alcohol resin layer of the laminated film is 3 to 30 μm.

According to the method of the present invention, the film to be subjected to the dyeing process is a stretched film that has been stretched together with the base film, and is sufficiently stretched in advance, so that the first film and the second film are joined together. Even when the part is immersed in a dyeing tank or a crosslinking tank, the deformation of the joint can be suppressed, and the breakage or peeling of the film at the joint can be effectively suppressed.

If it is assumed that the film is not substantially stretched in the step of immersing in the dyeing tank, it is possible to more effectively suppress deformation of the joint due to the above-described immersion treatment, and by stretching the joint. Generation of wrinkles that can occur can be prevented.

Continuous production of a polarizing laminated film entails switching of film rolls, and as a result, a joining portion between the preceding film and the next film is inevitably produced. According to the method of the present invention, the joining is performed. Also about a part, it can pass as it is to the normal conveyance path | route (conveyance path | route which passes along a dyeing tank etc.) for performing a dyeing process, without producing a fracture | rupture and peeling of a film. Therefore, the polarizing laminated film can be continuously produced stably and efficiently.

Further, according to the method of the present invention, a polarizer layer can be formed by coating a coating solution, and therefore a polarizing laminated film and a polarizing plate having a thin polarizer layer can be produced.

FIG. 1 is a flowchart showing a method for producing a polarizing laminated film according to the present invention.
FIG. 2 is a schematic side view showing an example of an embodiment of the dyeing process.
FIG. 3 is a schematic top view showing an example of a joining form at the joining portion between the terminal end portion of the first film and the starting end portion of the second film.
FIG. 4 is a schematic top view showing another example of the joining form at the joining portion between the terminal end portion of the first film and the starting end portion of the second film.
FIG. 5 is a flowchart showing a method for manufacturing a polarizing plate.

<Method for producing polarizing laminated film>
FIG. 1 is a flowchart showing a method for producing a polarizing laminated film according to the present invention. As shown in FIG. 1, the manufacturing method of the light-polarizing laminated film according to the present invention includes the following steps [1] to [3] in this order.
[1] Resin layer forming step S10 in which a polyvinyl alcohol resin layer is formed on at least one surface of the base film to obtain a laminated film.
[2] Stretching step S20 that stretches the laminated film to obtain a stretched film.
[3] A dyeing step S30 for obtaining a polarizing laminated film by dyeing a polyvinyl alcohol-based resin layer of a stretched film with a dichroic dye to form a polarizer layer.

As will be described later, a polarizing plate comprising a polarizer layer and a protective film laminated thereon is laminated with a protective film on the polarizer layer of a polarizing laminated film obtained by carrying out the dyeing step S30. To obtain a bonding film (bonding step S40), and then peel and remove the base film from the bonding film (peeling step S50).

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

[1] Resin layer forming step S10
This step is a step of obtaining a laminated film by forming a polyvinyl alcohol-based resin layer on at least one surface of the base film. This polyvinyl alcohol-based resin layer is a layer that becomes a polarizer layer through the stretching step S20 and the dyeing step S30. The polyvinyl alcohol-based resin layer is preferably formed by applying a coating liquid containing a polyvinyl alcohol-based resin to one or both sides of the base film and drying the coating layer. According to such a method, the thickness of the polyvinyl alcohol-based resin layer and thus the polarizer layer can be reduced, which is advantageous for reducing the weight of the polarizing laminated film and the polarizing plate. A polyvinyl alcohol-based resin layer can be formed by pasting a pre-formed polyvinyl alcohol-based resin film on a base film, but from the viewpoint of thinning the polarizer layer, as described above, coating It is preferable to form a polyvinyl alcohol-based resin layer by coating the liquid.

The resin layer forming step S10 is typically performed continuously by continuously unwinding the base film from a long base film roll and transporting it. Film conveyance can be performed using a guide roll or the like.

(Base film)
The base film can be composed of a thermoplastic resin, and among them, it is preferably composed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability and the like. Specific examples of such thermoplastic resins include, for example, polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins (norbornene resins, etc.); polyester resins; (meth) acrylic resins; cellulose triacetate, Cellulose ester resins such as cellulose diacetate; Polycarbonate resins; Polyvinyl alcohol resins; Polyvinyl acetate resins; Polyarylate resins; Polystyrene resins; Polyethersulfone resins; Polysulfone resins; Polyamide resins; Resin, and mixtures and copolymers thereof.

The base film may have a single-layer structure composed of one resin layer composed of one or two or more thermoplastic resins, or a plurality of resin layers composed of one or two or more thermoplastic resins are laminated. It may be a multilayer structure.

Examples of the chain polyolefin-based resin include homopolymers of chain olefins such as polyethylene resins and polypropylene resins, and copolymers composed of two or more chain olefins. A base film made of a chain polyolefin-based resin is preferable in that it is easily stretched stably at a high magnification. Among them, the base film is composed mainly of polypropylene resin (polypropylene resin which is a homopolymer of propylene or a copolymer mainly composed of propylene), polyethylene resin (polyethylene resin which is a homopolymer of ethylene or ethylene). It is more preferable to consist of a copolymer).

The copolymer mainly composed of propylene, which is one example suitably used as a thermoplastic resin constituting the base film, is a copolymer of propylene and another monomer copolymerizable therewith.

Examples of other monomers copolymerizable with propylene include 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 α-olefin having 4 to 10 carbon atoms include, for example, linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; 3 -Branched monoolefins such as methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene; and vinylcyclohexane. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer.

The content of the other monomer in the copolymer is, for example, 0.1 to 20% by weight, and preferably 0.5 to 10% by weight. The content of other monomers in the copolymer can be determined by measuring infrared (IR) spectrum according to the method described on page 616 of "Polymer Analysis Handbook" (1995, published by Kinokuniya Shoten). Can be sought.

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

The stereoregularity of the polypropylene resin is preferably 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 in 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 resins, or may be composed of two or more types of chain polyolefin-based resins. You may be comprised from the copolymer of resin.

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

Various products are commercially available for cyclic polyolefin resins. Examples of commercially available products of cyclic polyolefin resins are trade names, “Topas” (TOPAS ADVANCED POLYMERS GmbH, available from Polyplastics), “Arton” (manufactured by JSR Corporation), Includes “ZEONOR” (manufactured by Nippon Zeon Co., Ltd.), “ZEONEX” (manufactured by Nippon Zeon Co., Ltd.), and “Apel” (manufactured by Mitsui Chemicals, Inc.).

In addition, film names such as “ESCINA” (manufactured by Sekisui Chemical Co., Ltd.), “SCA40” (manufactured by Sekisui Chemical Co., Ltd.), “ZEONOR FILM” (manufactured by Nippon Zeon Co., Ltd.), etc. You may use the commercial item of the made cyclic polyolefin resin film as a base film.

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

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

A typical example of the polyester resin is polyethylene terephthalate, which is a polycondensate of terephthalic acid and ethylene glycol. Polyethylene terephthalate is a crystalline resin, but the one in a state before crystallization treatment is more easily subjected to treatment such as stretching. If necessary, it can be crystallized during stretching or by heat treatment after stretching. Further, a copolymerized polyester having a crystallinity lowered (or made amorphous) by further copolymerizing another monomer with a polyethylene terephthalate skeleton is also preferably used. Examples of such resins include those obtained by copolymerizing cyclohexanedimethanol and isophthalic acid. Since these resins are also excellent in stretchability, they can be suitably used.

Specific examples of polyester resins other than polyethylene terephthalate and copolymers thereof include, for example, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, Examples include polycyclohexanedimethyl naphthalate.

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

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of (meth) acrylic resins include, for example, 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 ester- (meth) acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin etc.); methyl methacrylate and alicyclic hydrocarbon group And a copolymer (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, a polymer based on a poly (meth) acrylic acid C _1-6 alkyl ester such as poly (meth) acrylic acid methyl is used, and more preferably methyl methacrylate is the main component (50 to 100). (Methyl methacrylate resin) having a weight%, preferably 70 to 100 wt%) is used.

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

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 in which a part of the hydroxyl group is modified with another substituent are also included. Among these, cellulose triacetate (triacetyl cellulose) is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available cellulose triacetate are “Fujitac TD80” (Fuji Film Co., Ltd.), “Fujitac TD80UF” (Fuji Film Co., Ltd.), and “Fujitac TD80UZ” (Fuji Film (Fujifilm)). Co., Ltd.), “Fujitac TD40UZ” (manufactured by FUJIFILM Corporation), “KC8UX2M” (manufactured by Konica Minolta Opto Corporation), “KC4UY” (manufactured by Konica Minolta Opto Corporation), and the like.

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

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, flame retardancy, and transparency. The polycarbonate-based resin constituting the base film may be a resin called a modified polycarbonate in which the polymer skeleton is modified in order to lower the photoelastic coefficient, a copolymer polycarbonate having improved wavelength dependency, or the like.

Polycarbonate resin is available in various products. Examples of commercially available polycarbonate-based resins are all “Panlite” (manufactured by Teijin Chemicals Ltd.), “Iupilon” (manufactured by Mitsubishi Engineering Plastics), “SD Polyca” (Sumitomo Dow). (Manufactured by Dow Chemical Co., Ltd.).

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

Among these, from the viewpoints of stretchability and heat resistance, polyolefin resins, polyester resins, (meth) acrylic resins, or polycarbonate resins are preferable, polypropylene resins or polyester resins are more preferable, and polypropylene resins. Is particularly preferred and used.

Any appropriate additive may be added to the base film in addition to the above thermoplastic resin. 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 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. When 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 can be determined as appropriate, but generally it is preferably 1 to 500 μm, more preferably 1 to 300 μm, further preferably 5 to 200 μm, and more preferably 5 to 150 μm from the viewpoint of workability such as strength and handleability. Is most preferred.

(Coating liquid containing polyvinyl alcohol resin)
The coating liquid is preferably a polyvinyl alcohol resin solution obtained by dissolving polyvinyl alcohol resin powder in a good solvent (for example, water). Examples of the polyvinyl alcohol resin include polyvinyl alcohol resins and derivatives thereof. Polyvinyl alcohol resin derivatives include polyvinyl formal, polyvinyl acetal, etc., as well as polyvinyl alcohol resins modified with olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid. Denatured; modified with alkyl ester of unsaturated carboxylic acid; modified with acrylamide. The proportion of modification is preferably less than 30 mol%, and more preferably less than 10 mol%. When the modification exceeding 30 mol% is performed, it is difficult to adsorb the dichroic dye, which may cause a problem that the polarization performance is lowered. Among the above-mentioned polyvinyl alcohol resins, 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, still more preferably in the range of 1500 to 8000, and in the range of 2000 to 5000. Most preferably. The average degree of polymerization can be determined by a method defined in JIS K 6726-1994 “Testing method for polyvinyl alcohol”. If the average degree of polymerization is less than 100, it is difficult to obtain a preferable polarization performance, and if it exceeds 10,000, the solubility in a solvent is deteriorated, and it becomes difficult to form a polyvinyl alcohol-based resin layer.

The polyvinyl alcohol resin is preferably a saponified product of a polyvinyl acetate resin. The range of the saponification degree is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 94 mol% or more. If the degree of saponification is too low, the water resistance and heat-and-moisture resistance may not be sufficient when a polarizing laminate film or a polarizing plate is formed. Further, it may be a completely saponified product (having a saponification degree of 100 mol%), but if the saponification degree is too high, the dyeing speed becomes slow, and the production time is required to give sufficient polarization performance. In some cases, a polarizer layer having sufficient polarization performance may not be obtained. Therefore, the saponification degree is preferably 99.5 mol% or less, more preferably 99.0 mol% or less.

The degree of saponification is the unit ratio (mol%) of the ratio of acetate groups (acetoxy groups: —OCOCH ₃ ) contained in polyvinyl acetate resin, which is a raw material for polyvinyl alcohol resins, to hydroxyl groups by saponification treatment. It is expressed and defined by the following formula.
Saponification degree (mol%)
= [(Number of hydroxyl groups) ÷ (Number of hydroxyl groups + Number of acetate groups)] × 100

The higher the degree of saponification, the greater the proportion of hydroxyl groups, and hence the smaller the proportion of acetate groups that inhibit crystallization. The saponification degree can be determined by a method defined in JIS K 6726-1994 “Testing method for polyvinyl alcohol”.

Examples of the polyvinyl acetate-based 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.

Examples of commercially available polyvinyl alcohol resins that can be suitably used are trade names, “PVA124” (degree of saponification: 98.0 to 99.0 mol%), “PVA117” (manufactured by Kuraray Co., Ltd.) Saponification degree: 98.0 to 99.0 mol%), "PVA117H" (saponification degree: 99.5 mol% or more), "PVA624" (saponification degree: 95.0 to 96.0 mol%) and “PVA617” (degree of saponification: 94.5 to 95.5 mol%); “AH-26” (degree of saponification: 97.0 to 98.8 mol%) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. AH-22 "(degree of saponification: 97.5 to 98.5 mol%)," NH-18 "(degree of saponification: 98.0 to 99.0 mol%) and" N-300 "(degree of saponification) : 98.0 to 99.0 mol%); “JC-33” (degree of saponification: 99) manufactured by Nippon Vinegar Poval Co., Ltd. 0 mol% or more), “JM-33” (degree of saponification: 93.5 to 95.5 mol%), “JM-26” (degree of saponification: 95.5 to 97.5 mol%), “JP -45 "(degree of saponification: 86.5 to 89.5 mol%)," JF-17 "(degree of saponification: 98.0 to 99.0 mol%)," JF-17L "(degree of saponification: 98.0 to 99.0 mol%) and "JF-20" (degree of saponification: 98.0 to 99.0 mol%).

The coating liquid may contain additives such as a plasticizer and a surfactant as necessary. As the plasticizer, a polyol or a condensate thereof can be used, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The blending amount of the additive is preferably 20% by weight or less of the polyvinyl alcohol resin.

(Coating of coating liquid and drying of coating layer)
The above coating solution is applied to the base film by wire bar coating method; roll coating method such as reverse coating and gravure coating; die coating method; comma coating method; lip coating method; spin coating method; A fountain coating method; a dipping method; and a known method such as a spray method.

When coating the coating liquid on both sides of the substrate film, it can be performed one side at a time using the above method, or the substrate can be used using a dipping method, spray coating method, or other special equipment. It can also be applied to both sides of the film simultaneously.

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 to 200 ° C., preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C. or higher. The drying time is, for example, 2 to 20 minutes.

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

The thickness of the polyvinyl alcohol-based resin layer in the laminated film is preferably 3 to 30 μm, and more preferably 5 to 20 μm. If the polyvinyl alcohol-based resin layer has a thickness within this range, the dichroic dye has good dyeability and excellent polarization performance through a stretching step S20 and a dyeing step S30, which will be described later. A child layer can be obtained. When the thickness of the polyvinyl alcohol-based resin layer exceeds 30 μm, the thickness of the polarizer layer may exceed 10 μm. Moreover, when the thickness of the polyvinyl alcohol-based resin layer is less than 3 μm, the film becomes too thin after stretching and the dyeability tends to deteriorate.

Prior to coating the coating liquid, in order to improve the adhesion between the base film and the polyvinyl alcohol resin layer, at least the surface of the base film on which the polyvinyl alcohol resin layer is formed is subjected to corona treatment and plasma. You may perform a process, a flame | frame (flame) process, etc.

Further, in order to improve the adhesion between the base film and the polyvinyl alcohol resin layer, a polyvinyl alcohol resin layer may be formed on the base film via a primer layer or an adhesive layer.

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

Examples of the polyvinyl alcohol resin include polyvinyl alcohol resins and derivatives thereof. Polyvinyl alcohol resin derivatives include polyvinyl formal, polyvinyl acetal, etc., as well as polyvinyl alcohol resins modified with olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid. Denatured; modified with alkyl ester of unsaturated carboxylic acid; modified with acrylamide. Among the above-mentioned polyvinyl alcohol resins, 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 solvents include, for example, 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 trichlorethylene and chloroform; alcohols such as ethanol, 1-propanol, 2-propanol and 1-butanol. However, if the primer layer is formed using a primer layer forming coating solution containing an organic solvent, the base film may be dissolved, so the solvent should be selected in consideration of the solubility of the base film. Is preferred. In consideration of the influence on the environment, the primer layer is preferably formed from a coating solution containing water as a solvent.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the primer layer forming coating solution. A suitable 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 include epoxy-based, isocyanate-based, dialdehyde-based, and metal-based crosslinking agents.

As the epoxy-based crosslinking agent, either one-component curable type or two-component curable type can be used. Ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di- or tri-glycidyl ether, 1,6-hexane Examples include diol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine and the like.

Examples of isocyanate crosslinking agents include tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (4-phenylmethane) triisocyanate, isophorone diisocyanate, and ketoximes thereof. A block thing or a phenol block thing etc. are mentioned.

Examples of the dialdehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleidialdehyde, phthaldialdehyde and the like.

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 divalent or higher valent metals such as magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, silicon, boron, zinc, copper, vanadium, chromium, and tin. Examples thereof include salts, oxides and hydroxides of metals having a valence.

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

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

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

Examples of the organic zirconium compound include zirconium normal propionate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium bisacetylacetonate, zirconium acetylacetonate bisethylacetoacetate and the like.

Examples of the organoaluminum compound include aluminum acetylacetonate and aluminum organic acid chelate. Examples of the organosilicon compound include compounds in which the ligands exemplified above for the organotitanium compound and the organozirconium compound are bonded to silicon.

In addition to the above-described low molecular weight crosslinking agents, high molecular weight crosslinking agents such as methylolated melamine resins and polyamide epoxy resins can also be used. Examples of commercially available polyamide epoxy resins include “Smiles Resin 650 (30)” and “Smiles Resin 675” (both trade names) sold by Taoka Chemical Co., Ltd.

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

The ratio of the resin component and the crosslinking agent in the primer layer forming coating solution is within the range of about 0.1 to 100 parts by weight of the crosslinking agent with respect to 100 parts by weight of the resin component. It may be appropriately determined depending on the above, and it is particularly preferable to select from the range of about 0.1 to 50 parts by weight. The primer layer forming coating solution preferably has a solid content concentration of about 1 to 25% by weight.

The thickness of the primer layer is preferably about 0.05 to 1 μm, and more preferably 0.1 to 0.4 μm. When the thickness is less 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 the thickness is more than 1 μm, it is disadvantageous for thinning the polarizing laminated film and the polarizing plate.

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

When providing a primer layer, the order of application to the base film is not particularly limited. For example, when forming a polyvinyl alcohol-based resin layer on both sides of the base film, the primer is provided on both sides of the base film. After forming the layer, a polyvinyl alcohol-based resin layer may be formed on both sides, or after forming a primer layer and a polyvinyl alcohol-based resin layer in order on one side of the base film, the other side of the base film A primer layer and a polyvinyl alcohol-based resin layer may be sequentially formed.

The laminated film obtained in the method for producing a polarizing laminated film of the present invention is typically a long film. This long laminated film may be in the form of a film roll once by sequentially winding it after forming the polyvinyl alcohol-based resin layer, or the obtained laminated film may be continuously rolled up without being wound up. It may be supplied to the stretching step S20 to continue the stretching process.

[2] Stretching step S20
This step is a step of obtaining a stretched film by stretching a laminated film composed of a base film and a polyvinyl alcohol-based resin layer. The stretching step S20 is typically performed continuously while conveying a long laminated film or continuously unwinding a laminated film from a film roll of a long laminated film and conveying this. . Film conveyance can be performed using a guide roll or the like.

The stretching ratio of the laminated film can be appropriately selected according to the desired polarization characteristics, but is preferably more than 5 times and 17 times or less, more preferably more than 5 times and 8 times the original length of the laminated film. It is as follows. When the draw ratio is 5 times or less, the polymer chain of the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin layer is not sufficiently oriented, and the polarization degree of the polarizer layer may not be sufficiently high. On the other hand, if the draw ratio exceeds 17 times, the film is likely to be broken during stretching, and the thickness of the stretched film becomes unnecessarily thin, and the workability and handleability in subsequent processes may be reduced. The stretching process is usually uniaxial stretching.

The stretching treatment may be longitudinal stretching that extends in the film longitudinal direction (film transport direction), and may be lateral stretching or oblique stretching that extends in the film width direction. As the longitudinal stretching method, stretching between rolls by stretching using a roll (a method of performing longitudinal uniaxial stretching by a difference in peripheral speed between these two nip rolls while transporting between two nip rolls installed at a distance) , Hot roll stretching [between a hot roll whose surface is heated to a desired stretchable temperature and a guide roll having a different peripheral speed (high peripheral speed) (or a hot roll) , A method in which longitudinal uniaxial stretching is performed at the time of contact with the heat roll (on the heat roll) or in the vicinity thereof under the heating state caused by contact with the heat roll], compression stretching, and a chuck (clip) were used. Stretching and the like can be mentioned, and examples of the transverse stretching method include a tenter method. As the stretching treatment, either a wet stretching method or a dry stretching method can be adopted. However, it is preferable to use the dry stretching method because the stretching temperature can be selected from a wide range.

The stretching temperature is set to be equal to or higher than the temperature at which the polyvinyl alcohol-based resin layer and the entire base film can be stretched, and preferably [the phase transition temperature of the base film (melting point or glass transition temperature) -30]. ℃ ~ [base film phase transition temperature +30] ℃, more preferably [base film phase transition temperature -30] ℃ ~ [base film phase transition temperature +5] ℃ range, More preferably, it is in the range of [phase transition temperature of base film −25] ° C. to [phase transition temperature of base film] ° C. When the base film is composed of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures exhibited by the plurality of resin layers.

If the stretching temperature is lower than [phase transition temperature of base film −30] ° C., it is difficult to achieve a high-magnification stretching of more than 5 times, or the fluidity of the base film is too low to make the stretching process difficult. There is a tendency. When the stretching temperature exceeds [phase transition temperature of base film + 30] ° C., the fluidity of the base film tends to be too high and stretching tends to be difficult. Since it is easier to achieve a high draw ratio of more than 5 times, the drawing temperature is within the above range, and more preferably 120 ° C. or higher. This is because when the stretching temperature is 120 ° C. or higher, there is no difficulty in the stretching treatment even at a high stretching ratio of more than 5 times.

As a heating method of the laminated film in the stretching process, a zone heating method (for example, a method of heating in a stretching zone such as a heating furnace adjusted to a predetermined temperature by blowing hot air); There is a method of heating the roll itself; a heater heating method (a method in which infrared heaters, halogen heaters, panel heaters, etc. are installed above and below the laminated film and heated by radiant heat). In the inter-roll stretching method, the zone heating method is preferable from the viewpoint of the uniformity of the stretching temperature. In this case, the two nip rolls may be installed in the temperature-controlled stretching zone or outside the stretching zone, but in order to prevent adhesion between the laminated film and the nip roll, Is preferred.

The stretching temperature means the atmospheric temperature in the zone (for example, in the heating furnace) in the case of the zone heating method, and means the atmospheric temperature in the furnace in the case of heating in the furnace also in the heater heating method. In the case of hot roll stretching, it means the surface temperature of the roll.

The stretching process is not limited to one-stage stretching, and can be performed in multiple stages. In this case, it is preferable to perform the stretching treatment so as to obtain a stretching ratio of more than 5 times by combining all stages of the stretching treatment.

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

Further, a heat setting treatment step may be provided after the stretching treatment in the stretching step S20. The heat setting process is a process of performing a heat treatment at a temperature equal to or higher than the crystallization temperature while maintaining the tensioned state with the end of the stretched film held by a clip. By this heat setting treatment, crystallization of the polyvinyl alcohol-based resin layer is promoted. The temperature of the heat setting treatment is preferably in the range of [stretching temperature] ° C. to [stretching temperature−80] ° C., and more preferably in the range of [stretching temperature] ° C. to [stretching temperature−50] ° C.

The stretched film obtained in the method for producing a polarizing laminate film of the present invention is typically a long film, and is usually obtained in the form of a film roll by sequentially winding it after the stretching treatment.

[3] Dyeing step S30
In this step, 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 step, a polarizing laminated film in which a polarizer layer is laminated on one side or both sides of a base film is obtained. Dyeing with dichroic dyes unwinds a stretched film continuously from a film roll of a long stretched film and transports the stretched film along a transport path (pass line) that passes through a dyeing tank containing the dichroic dye. And it can carry out by immersing in a dyeing tank continuously. Film conveyance can be performed using a guide roll or the like.

In the present invention, the dyeing step S30 includes the following steps [a] to [c].
[A] The process of immersing a 1st film in a dyeing tank by conveying along the conveyance path | route which passes along the above-mentioned dyeing tank.
[B] A step of joining the terminal end of the first film and the starting end of the second film to form a joint.
[C] A step of immersing the joining portion in the dyeing tank by transporting the joining portion along the transport path.

At least one of the first film and the second film is a stretched film obtained in the stretching step S20. According to the dyeing step S30 including the steps [a] to [c] described above, when the long first film transported in advance along the transport path approaches the end by the step [a]. The roll switching operation including the operation of joining the end portion of the first film and the start end portion of another second film prepared in advance (the second film is usually prepared as a film roll) is performed. (Step [b]), the dyeing process can be subsequently performed on the bonded second film, so that the polarizing laminated film can be continuously produced. In the present invention, a third film is bonded to the second film, or a fourth film (and further a fifth film, a sixth film,.・ ・) Can be joined.

At least one of the first film and the second film subjected to the dyeing step S30 is a stretched film that has been stretched in the stretching step S20, and has been sufficiently stretched in advance. Therefore, unlike the case where the original film of polyvinyl alcohol resin is immersed in a dyeing tank in an unstretched state as in the method described in Patent Document 2, the joint between the first film and the second film is dyed in the dyeing tank. It is possible to effectively suppress the deformation of the joint when immersed in the substrate. Due to such resistance to deformation, breakage and peeling of the film at the joint caused by the deformation can be effectively suppressed.

Since the joined portion is excellent in deformation resistance, in the present invention, the joined portion can be directly passed through the conveying path passing through the dyeing tank (step [c]). That is, unlike the method described in Patent Document 1, there is no need to change the conveyance path so that the joint portion is not immersed in the dyeing tank because of fear of breakage or peeling of the joint portion. According to the method of the present invention, it is possible not only to avoid a complicated operation of changing the conveyance path, but also to avoid the generation of a film portion that cannot be dyed, and furthermore, after the roll is switched in step [b]. Since the time until the state of the film is stabilized can be drastically shortened, the loss of the film hardly occurs, and the polarizing laminated film can be continuously produced with extremely high production efficiency.

In addition, as a possible method for suppressing the breakage and peeling of the film in the dyeing step S30, it is possible to lower the tension applied to the film and transport the film. In the swelling tank provided, it is rather easy to break. Further, when the tension is low, the film is likely to meander. In this case, since it takes some time for the film to stabilize after the tension is restored, the loss of the film increases and the production efficiency decreases. When the tension is low, the flow of the film becomes worse when passing through the nip roll, so that problems such as wrinkles are likely to occur.

The dyeing step S30 will be described more specifically with reference to the drawings. FIG. 2 is a schematic side view showing an example of an embodiment of the dyeing step S30, in which the stretched film 10 which is the preceding first film is a dyeing tank 40, a crosslinking tank 50 (however, the crosslinking tank 50 is an optional tank provided). The polarizing laminated film 20 is continuously produced by sequentially passing through the film, and the stretched film 10 that is the second film bonded to the terminal portion of the first film passes through the dyeing tank 40. It shows how it goes. The downstream side from the joint 15 is the first film, and the upstream side is the second film. Arrows indicate the film transport direction. As shown in the figure, according to the method of the present invention, the dyeing step S30 including at least the dyeing tank 40 is performed on the joint 15 between the first film and the second film without particularly changing the transport path. It can be passed directly through the transport path.

The conveyance of the film in the dyeing step S30 can be performed using the guide roll 1 and the like as in the other steps. The immersion of the film in the dyeing solution 41 containing the dichroic dye accommodated in the dyeing tank 40 or the crosslinking solution 51 containing the cross-linking agent accommodated in the crosslinking tank 50 is performed, for example, as shown in FIG. In the crosslinking tank 50, a plurality of guide rolls 1 may be provided on the upper and lower sides, and the film may be conveyed along these. The number of guide rolls 1 installed, the distance between the guide rolls, and the like are adjusted according to the desired residence time (immersion time) of the film in the solution.

The staining solution 41 in the staining tank 40 can be a solution in which a dichroic dye is dissolved in a solvent. Examples of the dichroic dye contained in the dyeing solution 41 include iodine or a 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, Splat Blue G, Splat Blue GL, Splat Orange GL , Direct Sky Blue, Direct First Orange S, First Black, etc. A dichroic dye may be used individually by 1 type, and may use 2 or more types together.

As a solvent contained in the dyeing solution 41, 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 41 is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight, and 0.025 to 5% by weight. Further preferred.

When iodine is used as the dichroic dye, it is preferable to further add an iodide to the dyeing solution 41 containing iodine because the dyeing efficiency can be further improved. Examples of 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 concentration of iodide in the dyeing solution 41 is preferably 0.01 to 20% by weight. 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. Preferably, it is in the range of 1: 7 to 1:70.

The immersion time of the stretched film 10 in the dyeing solution 41 is usually in the range of 15 seconds to 15 minutes, preferably 30 seconds to 3 minutes. Further, the temperature of the dyeing solution 41 is preferably in the range of 10 to 60 ° C., more preferably in the range of 20 to 40 ° C.

As shown in FIG. 2, it is preferable to provide a crosslinking tank 50 after the dyeing tank 40 (downstream side) in the transport path of the stretched film 10 passing through the dyeing tank 40. That is, it is preferable that dyeing process S30 includes the bridge | crosslinking process process implemented after the dyeing process process in the dyeing tank 40. FIG. The crosslinking solution 51 in the crosslinking tank 50 can be a solution in which a crosslinking agent is dissolved in a solvent. 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. A crosslinking agent may be used individually by 1 type, and may use 2 or more types together.

As the solvent contained in the crosslinking solution 51, for example, water can be used, but an organic solvent compatible with water may be further included. The concentration of the crosslinking agent in the crosslinking solution 51 is preferably in the range of 1 to 20% by weight, and more preferably in the range of 6 to 15% by weight.

The crosslinking solution 51 can contain iodide. By adding iodide, the polarization performance in the plane of the polarizer layer can be made more uniform. Examples of 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 concentration of iodide in the cross-linking solution 51 is preferably 0.05 to 15% by weight, and more preferably 0.5 to 8% by weight.

The immersion time of the film in the crosslinking solution 51 after immersion in the dyeing tank 40 is usually 15 seconds to 20 minutes, and preferably 30 seconds to 15 minutes. The temperature of the crosslinking solution 51 is preferably in the range of 10 to 90 ° C.

The crosslinking treatment can be performed simultaneously with the dyeing treatment by blending a crosslinking agent into the dyeing solution 41.

In addition to the dyeing process and the crosslinking process described above, the dyeing process S30 is a swelling process that swells the stretched film 10 prior to the dyeing process; a process that is performed between the dyeing process and the crosslinking process. 1 washing | cleaning process; The 2nd washing | cleaning process implemented after a bridge | crosslinking treatment process can be included.
The swelling treatment step can be performed, for example, by immersing the stretched film 10 in a water bath of about 0 to 40 ° C. (pure water bath such as ion exchange water or distilled water).

The first and second cleaning steps usually include a water cleaning step. The water washing treatment can be performed by immersing the film after the dyeing treatment or after the crosslinking treatment in pure water such as ion exchange water or distilled water. The water washing temperature is usually 3 to 50 ° C, preferably 4 to 20 ° C. The immersion time in water is usually 2 to 300 seconds, preferably 3 to 240 seconds.

The first and second cleaning steps may be a combination of a water cleaning step and a cleaning step with an iodide solution. In addition to water, liquids such as methanol, ethanol, isopropyl alcohol, butanol, and propanol can be appropriately contained in the cleaning liquid used in the water cleaning step and / or the cleaning process using the iodide solution.

In both the step of immersing the stretched film 10 in the dyeing tank and the step of immersing the bonding portion 15 in the dyeing tank, it is preferable that substantially no stretching treatment is performed. Thereby, the deformation | transformation of the junction part 15 by the immersion process to the dyeing tank 40 can be suppressed more effectively. When the stretching process is performed during the immersion in the dyeing tank 40, the deformation amount of the joint portion 15 increases, and the film may be broken or peeled off at the joint portion.

Further, in the step of immersing the stretched film 10 in the dyeing tank 40 and the step of immersing the bonding part 15 in the dyeing tank, the wrinkles that may occur due to the stretching process on the bonding part 15 are not performed. Occurrence can be prevented. When wrinkles are generated, it takes a certain amount of time to eliminate the wrinkles, so that the manufacturing efficiency is lowered. In the step of immersing in the crosslinking tank 50, a stretching treatment can be performed as necessary.

In the step of immersing in the dyeing tank 40, “substantially no stretching treatment” means that the stretch ratio in the step is 1.5 times the original length of the stretched film 10 used in the step. In the following, it means that it is preferably 1 time (not stretched).
In order to carry out the dyeing process without substantially stretching the film while the tension applied to the film is sufficiently high, as a base film, a polyolefin resin, a polyester resin, a (meth) acrylic resin, a cellulose ester type Resins, polycarbonate resins, polyvinyl acetate resins, polyarylate resins, polystyrene resins, polyethersulfone resins, polysulfone resins, polyamide resins, and polyimide resins are preferred.

Next, with reference to FIG. 3 and FIG. 4, a method of forming the joint portion 15 between the first film end portion 100 and the second film start end portion 200 in the step [b] of the dyeing step S30 will be described. The method for forming the joining portion 15 is not particularly limited as long as the film is not easily peeled off even when immersed in the dyeing tank 40 or the crosslinking tank 50. For example, a double-sided tape (a film having an adhesive layer on both surfaces of the base material) is used. The joining portion 15 can be formed by joining, or joining using heat sealing. From the viewpoint that no special equipment is required, joining with a double-sided tape is simple and preferable. A conventionally known apparatus (heat sealer) can be used for heat sealing.

In the method of the present invention, since it is not necessary to carry out a stretching process in the dyeing step S30, problems such as film breakage, peeling, and generation of wrinkles are unlikely to occur without using a particularly strong bonding method.

There is also no particular limitation on the film bonding form at the bonding portion 15 between the terminal end portion 100 of the first film and the starting end portion 200 of the second film. For example, as shown in FIG. Bonding may be performed by bonding in the bonding region 15a, or a plurality of bonding regions 15a may be provided as shown in FIG.

For the roll switching in the step [b], a conventionally known automatic paper splicing device such as a turret method can be used. Also, an apparatus in which an automatic paper splicing device and a heat sealer are integrated is commercially available, and such a device can also be used suitably.

Here, as described above, at least one of the first film and the second film used in the dyeing step S30 is the stretched film 10 obtained in the stretching step S20. In the above description using FIG. 2, the case where both the first film and the second film are stretched films 10 has been described. However, the present invention is not limited to this, and either the first film or the second film is a stretched film. 10 and the other may be a lead film.

The lead film is a film for holding the conveyance path (pass line), and is passed through the conveyance path before the dyeing step S30 is started or when the dyeing step S30 is interrupted (temporarily placed on the conveyance path). It is a film. By passing the lead film through the conveyance path when the dyeing process S30 is interrupted, an operation of passing the stretched film 10 again through the conveyance path when the dyeing process S30 after the interruption is resumed becomes unnecessary.

As described above, a chemical tank (sometimes a heated chemical tank) such as the dyeing tank 40 and the cross-linking tank 50, a high-temperature drying furnace, and the like are arranged in the conveyance path of the dyeing step S30. Therefore, in order to carry out the operation of passing the stretched film 10 from the beginning again after the dyeing step S20 is interrupted, the chemical solution is extracted from the chemical solution tank, the guide roll forming the transport path is moved, or the door of the drying furnace is opened. Complicated work such as opening is required. If such an operation is performed, in addition to the time for passing the film through again, it takes a very long time to return the temperature of the chemical bath and the temperature of the drying furnace to a steady state again, and the production efficiency is significantly reduced. .

By stopping the line conveyance in a state where the lead film is passed through the conveyance path, the conveyance path at the time of the dyeing step S30 can be maintained as it is for a long time. There is no need to move the guide roll or open the drying oven door. Therefore, when the dyeing step S30 is resumed, it is possible to dramatically reduce the time for which the conveyance path is in a steady state, and the resumption can be performed smoothly.

As the lead film, it is preferable to use a film having characteristics such as being inexpensive, difficult to break, not easily wrinkled, and not easily corroded even when immersed in a chemical solution for a long time. Specifically, a stretched polyethylene terephthalate film, a stretched polypropylene film and the like can be preferably used. The lead film does not necessarily have to be a stretched film, but the stretch treatment can improve the tear resistance and heat resistance of the film, and it is easy to obtain characteristics suitable for the lead film. Moreover, since the film area increases when the stretching treatment is performed, the stretched film is generally less expensive than the unstretched one.

In addition, it is not preferable to use the stretched film 10 obtained in the stretching step S20 as the lead film. The use of the stretched film 10 as a lead film is disadvantageous in terms of manufacturing cost because the stretched film 10 has a huge loss. Moreover, when line conveyance is stopped for a long time in a state where the stretched film 10 is passed through the conveyance path, the polyvinyl alcohol-based resin layer is gradually dissolved in a chemical solution tank such as a dyeing tank, and the chemical solution tank is contaminated.

Therefore, the case where both the first film and the second film used in the dyeing step S30 are the stretched film 10 means that either one of the films is not used as a lead film, but both the stretched films 10 joined together. Means that the polarizing laminated film 20 is obtained through the dyeing step S30.

On the other hand, when the first film is the stretched film 10 and the second film is the lead film, for example, in order to interrupt the dyeing step S30, the lead film is joined to the end of the stretched film 10 immediately before the interruption. In this case, the joining portion is transported as it is along the transport path, and the lead film is passed through the transport path. When the first film is the lead film and the second film is the stretched film 10, for example, the stretched film 10 is joined to the end of the lead film from the interrupted state where the lead film is passed through the transport path and dyed. This is a case where step S30 is resumed. In this case, the polarizing film 20 is obtained by carrying out the dyeing process of the second film by carrying the joining portion and further the second film along the carrying path.

After the dyeing step S30, it is preferable to provide a drying step for drying the wet polarizing laminated film obtained. Arbitrary appropriate methods, such as natural drying, ventilation drying, and heat drying, can be employ | adopted as a drying process. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C., and the drying time is usually about 1 to 15 minutes. The polarizing laminated film 20 obtained as described above can be used as a polarizing element (polarizing plate) as it is, and as a production intermediate for producing a polarizing plate described later including a polarizer layer and a protective film. Is also useful.

The thickness of the polarizer layer of the polarizing laminate film 20 is 10 μm or less, preferably 7 μm or less. By setting the thickness of the polarizer layer to 10 μm or less, the thin polarizing laminated film 20 can be configured.

<Production method of polarizing plate>
The polarizing laminated film obtained by the manufacturing method as described above is a bonding step S40 in which a protective film is bonded onto the polarizer layer of the polarizing laminated film to obtain a bonding film according to the flowchart shown in FIG. And it can be set as the polarizing plate by which the protective film was bonded on the polarizer layer through peeling process S50 which peels and removes a base film from a bonding film. Without implementing peeling process S50, the laminated body containing the base film obtained by bonding process S40, a polarizer layer, and a protective film can also be used as a polarizing plate.

[4] Pasting step 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 substrate film side of the polarizer layer. The protective film can be bonded to the polarizer layer using an adhesive or a pressure-sensitive adhesive. When a polarizing laminated film has a polarizer layer on both surfaces of a base film, a protective film is normally bonded on the polarizer layers on both surfaces. In this case, these protective films may be the same type of protective film or different types of protective films.

(Protective film)
The protective film is, for example, a polyolefin resin such as a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a norbornene resin); a cellulose ester resin such as cellulose triacetate or cellulose diacetate; The film may be a polyester resin such as terephthalate, polyethylene naphthalate or polybutylene terephthalate; a polycarbonate resin; a (meth) acrylic resin; or a mixture or copolymer thereof. Examples of commercially available products such as cyclic polyolefin resins and films thereof, and cellulose triacetate are as described above.

The protective film may be a protective film having both optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film provided with an arbitrary retardation value by stretching a resin film made of the above material (uniaxial stretching or biaxial stretching) or forming a liquid crystal layer or the like on the film; can do.

An optical layer such as a hard coat layer, an antiglare layer, or an antireflection layer can be formed on the surface of the protective film opposite to the polarizer layer. 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 formed in advance 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.

When bonding a protective film on the polarizer layer, plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) is applied to the surface of the protective film on the polarizer layer side in order to improve adhesion to the polarizer layer. ) Treatment, saponification treatment, and other surface treatments (easy adhesion treatment) can be performed, and among these, plasma treatment, corona treatment, or saponification treatment is preferably performed. 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, a saponification process is normally performed. Examples of the saponification treatment include a method of immersing in an alkaline aqueous 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 decreases and the processability is poor. On the other hand, when too thick, problems, such as transparency falling and the curing time required after bonding, will arise. Therefore, the thickness of the protective film is preferably 90 μm or less, more preferably 5 to 60 μm, and still more preferably 5 to 50 μm. From the viewpoint of thinning 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 further preferably 80 μm or less.

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

Polyvinyl alcohol resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. A polyvinyl alcohol copolymer obtained by saponifying a polymer or a modified polyvinyl alcohol polymer obtained by partially modifying the hydroxyl group thereof can be used. The water-based adhesive can include additives such as polyvalent aldehydes, water-soluble epoxy compounds, melamine 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.

A water-based adhesive is applied onto the polarizer layer and / or protective film of the polarizing laminated film, and these films are bonded through the adhesive layer, preferably pressed and bonded using a bonding roll or the like. A pasting process is carried out by making it. The coating method of the water-based adhesive (same for the photo-curable adhesive) is not particularly limited, and casting method, Meyer bar coating method, gravure coating method, comma coater method, doctor plate method, die coating method, dip coating method A conventionally known method such as a spraying method can be used.

When using a water-based adhesive, it is preferable to carry out a drying step for drying the film in order to remove water contained in the water-based adhesive after performing the above-mentioned bonding. Drying can be performed, for example, by introducing the film into a drying furnace. The drying temperature (drying furnace temperature) is preferably 30 to 90 ° C. When it is lower than 30 ° C., the protective film tends to be peeled off from the polarizer layer. If the drying temperature exceeds 90 ° C., the polarizing performance of the polarizer layer may be deteriorated by heat. The drying time can be about 10 to 1000 seconds. From the viewpoint of productivity, the drying time is preferably 60 to 750 seconds, and more preferably 150 to 600 seconds.

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

The photocurable adhesive refers to an adhesive that cures when irradiated with active energy rays such as ultraviolet rays. For example, an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, and a binder. Examples include those containing a resin and a photoreactive cross-linking agent. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and oligomers derived from the photopolymerizable monomer. As a photoinitiator, what contains the substance which generate | occur | produces active species, such as a neutral radical, an anion radical, and a cation radical by irradiation of active energy rays, such as an ultraviolet-ray, can be mentioned. As a photocurable adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.

When using a photocurable adhesive, after performing the above-mentioned pasting, a drying process is performed as necessary (such as when the photocurable adhesive contains a solvent), and then light is irradiated by activating active energy rays. A curing step for curing the curable adhesive is performed. 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 the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 6000 mW / cm ^2. It is preferable to set to. When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and when the irradiation intensity is 6000 mW / cm ² or less, the light emitted from the light source and the light generated by the heat generated when the photocurable adhesive is cured. There is little risk of yellowing of the curable adhesive and deterioration of the polarizer layer.

The light irradiation time for the photocurable adhesive is also determined appropriately depending on the composition of the photocurable adhesive, and the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 10,000 mJ / cm ^2. It is preferable to set to. When the integrated light quantity is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to advance the curing reaction more reliably, and when it is 10000 mJ / cm ² or less, the irradiation time is long. It does not become too much, 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 to 2 μm, more preferably 0.01 to 1 μm.

(Adhesive)
The pressure-sensitive adhesive that can be used for bonding the protective film is usually based on an acrylic resin, styrene resin, silicone resin, or the like, and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound. It consists of the added adhesive composition. Furthermore, it can also be set as the adhesive layer which contains microparticles | fine-particles and shows light-scattering property.

The thickness of the pressure-sensitive adhesive layer can be 1 to 40 μm, but it is preferably applied thinly, as long as it does not impair the workability and durability characteristics, and specifically 3 to 25 μm. A thickness of 3 to 25 μm has good processability and is suitable for suppressing dimensional change of the polarizer layer. When the pressure-sensitive adhesive layer is less than 1 μm, the tackiness is lowered, and when it exceeds 40 μm, problems such as the pressure-sensitive adhesive protruding easily occur. In the method of bonding the protective film to the polarizer layer using the pressure-sensitive adhesive, after the pressure-sensitive adhesive layer is provided on the protective film surface, it may be bonded to the polarizer layer, or the pressure-sensitive adhesive layer on the surface of the polarizer layer. After providing, you may paste a protective film here.

The method for forming the pressure-sensitive adhesive layer is not particularly limited, and a pressure-sensitive adhesive composition (pressure-sensitive adhesive solution) containing each component including the above-mentioned base polymer is applied to the protective film surface or the polarizer layer surface. After drying and forming the pressure-sensitive adhesive layer, the protective film and the polarizer layer may be bonded together, or after forming the pressure-sensitive adhesive layer on the separator (release film), the pressure-sensitive adhesive layer is applied to the surface of the protective film. Or you may make it transfer on a polarizing film surface, and then affix a protective film and a polarizer layer. When forming the pressure-sensitive adhesive layer on the protective film surface or the polarizer layer surface, surface treatment such as corona treatment may be applied to the protective film surface or the polarizer layer surface, or one or both surfaces of the pressure-sensitive adhesive layer as necessary. Good.

[5] Peeling step S50
This process is a process which peels and removes a base film from the bonding film obtained by bonding a protective film. Through this step, it is possible to obtain a polarizing plate that does not have a base film in which a protective film is laminated on the polarizer layer. When the polarizing laminated film has a polarizer layer on both sides of the base film, and a protective film is bonded to both of these polarizer layers, this peeling step S50 allows the two polarizing laminate films to be removed. A sheet of polarizing plate is obtained.

The method of peeling and removing the base film is not particularly limited, and can be peeled by the same method as the separator (peeling film) peeling step performed by a normal pressure-sensitive adhesive polarizing plate. After the bonding step S40, the base film may be peeled off as it is, or after the bonding step S40, it may be wound up into a roll and peeled off in the subsequent step.

The polarizing plate produced as described above can be used as an optical film in which other optical layers are laminated in practical use. Moreover, the protective film may have the function of such an optical layer. As another optical layer, a reflective polarizing film that transmits a certain kind of polarized light and reflects polarized light having the opposite properties; a film with an antiglare function having an uneven shape on the surface; a film with a surface antireflection function 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.

For example, “DBEF” (manufactured by 3M, Sumitomo 3M Co., Ltd. in Japan) can be used as a commercial product corresponding to a reflective polarizing film that transmits certain types of polarized light and reflects polarized light that exhibits the opposite properties. Available), “APF” (manufactured by 3M, available from Sumitomo 3M Limited in Japan).

Examples of the viewing angle compensation film include an optical compensation film in which a liquid crystal compound is applied to the substrate surface, and is oriented / fixed, a retardation film made of a polycarbonate resin, a retardation film made of a cyclic polyolefin resin, and the like. .

Commercially available products corresponding to the optical compensation film in which a liquid crystal compound is applied to the substrate surface and aligned and fixed are “WV film” (manufactured by Fujifilm Corporation), “NH film” (JX Nippon Mining & Metals). Energy Co., Ltd.), “NR Film” (manufactured by JX Nippon Oil & Energy Corporation), and the like.

Commercial products corresponding to retardation films made of cyclic polyolefin resins include “Arton Film” (manufactured by JSR Corporation), “Essina” (manufactured by Sekisui Chemical Co., Ltd.), “Zeonor Film” (Nippon Zeon ( Etc.).

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

<Example 1>
(1) Production of base film Both surfaces of a resin layer comprising a random copolymer of propylene / ethylene containing about 5% by weight of ethylene units (“Sumitomo Noblen W151” manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 138 ° C.) A long base film having a three-layer structure in which a resin layer composed of a propylene homopolymer (“Sumitomo Noblen FLX80E4” manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 163 ° C.) is disposed on a multilayer extruder It was produced by the coextrusion molding used. 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.

(2) Primer layer forming step Polyvinyl alcohol powder (“Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%) is dissolved in 95 ° C. hot water. A polyvinyl alcohol aqueous solution having a concentration of 3% by weight was prepared. The resulting aqueous solution was mixed with a crosslinking agent (“Smiles Resin 650” manufactured by Taoka Chemical Co., Ltd.) at a ratio of 5 parts by weight to 6 parts by weight of the polyvinyl alcohol powder to form a primer layer forming coating solution. Got.

While continuously transporting the substrate film prepared in (1) above, one side thereof is subjected to corona treatment, and the corona treatment surface is continuously coated with the primer layer forming coating solution using a micro gravure coater. And a primer layer having a thickness of 0.2 μm was formed by drying at 80 ° C. for 10 minutes. Further, the other surface of the base film is subjected to corona treatment, and a primer layer having a thickness of 0.2 μm is formed on the corona treatment surface in the same manner as described above, thereby obtaining a base film having a primer layer on both sides. It was.

(3) Production of laminated film (resin layer forming step)
Polyvinyl alcohol powder (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C. to a concentration of 8% by weight polyvinyl alcohol. An aqueous solution was prepared and used as a coating solution for forming a polyvinyl alcohol-based resin layer.

While continuously transporting the substrate film having the primer layer on both sides prepared in (2) above, the above-mentioned polyvinyl alcohol-based resin layer forming coating solution is continuously applied to the surface of one primer layer using a lip coater. It was coated and dried at 80 ° C. for 2 minutes, 70 ° C. for 2 minutes, and then 60 ° C. for 4 minutes to form a polyvinyl alcohol-based resin layer on the primer layer. Furthermore, a laminated film was obtained by forming a polyvinyl alcohol resin layer on the other primer layer surface in the same manner as described above. The thickness of the polyvinyl alcohol-type resin layer in a laminated film was 10.5 micrometers and 10.2 micrometers, respectively.

(4) Production of stretched film (stretching process)
While continuously transporting the laminated film prepared in (3) above, it is 5.8 times in the longitudinal direction (film transport direction) at a stretching temperature of 160 ° C. (atmosphere temperature in the heating furnace) using an inter-roll stretching device. A free end uniaxial stretching was performed at a magnification of, and a stretched film was continuously produced, and wound in order to obtain a film roll of a stretched film. The thicknesses of the two polyvinyl alcohol resin layers in the stretched film were 5.1 μm and 4.9 μm, respectively.
The above steps (1) to (4) were repeated to produce a total of two stretched film rolls.

(5) Preparation of polarizing laminated film (dyeing process)
The conveyance path (pass line) for carrying out the dyeing process includes the first washing tank between the dyeing tank 40 and the crosslinking tank 50 and includes the second washing tank after the crosslinking tank 50. Using the same apparatus as in No. 2, the dyeing process was carried out to produce a polarizing laminated film. A drying furnace is provided on the downstream side of the second cleaning tank. Therefore, the stretched film conveyed along this conveyance path passes through the dyeing tank 40, the first washing tank, the crosslinking tank, the second washing tank, and the drying furnace in this order to become a polarizing laminated film.

The dyeing tank 40 contains a dyeing solution 41 at 30 ° C. containing 0.35 parts by weight of iodine and 10 parts by weight of potassium iodide per 100 parts by weight of water. The crosslinking tank 50 contains a 76 ° C. crosslinking solution 51 containing 9.5 parts by weight of boric acid and 5 parts by weight of potassium iodide per 100 parts by weight of water. Each of the first cleaning tank and the second cleaning tank contains 10 ° C. pure water. The oven temperature is adjusted to 80 ° C. in the drying oven.

Specifically, the dyeing process was carried out as follows to produce a polarizing laminated film. First, the stretched film, which is the first film, is continuously unwound from one of the stretched film rolls prepared in (4) above, and is continuously transported along the transport path described above. Dyeing treatment of polyvinyl alcohol resin layer by dipping (residence time: 150 seconds), first washing treatment for washing away excess dyeing solution by dipping (residence time: 4 seconds) in first washing tank, to crosslinking tank 50 Cross-linking treatment by dipping (residence time: 600 seconds), second washing treatment for washing away excess cross-linking solution by dipping in the second washing tank (residence time: 4 seconds), passage in a drying furnace (residence time: 300 seconds) was carried out continuously in this order on the first film.

Let the stretched film of another stretched film roll produced by said (4) be a 2nd film.
When the unwinding of the first film from the film roll is approaching the end, in a state where the conveyance of the first film is temporarily stopped, the end portion of the first film and the starting end portion of the second film are double-sided. After using a tape and joining so as to have one strip-like adhesive region 15a as shown in FIG. 3, the transport of the film is restarted to join the first film and the second film, and the second By continuously transporting the film along the transport path, the dyeing process, the first cleaning process, the crosslinking process, the second cleaning process, and the drying process were performed up to the end of the second film. It was 125 N / m when the tension | tensile_strength concerning the film conveyed along said conveyance path | route was measured in the dyeing tank 40 vicinity.

<Example 2>
A polarizing laminated film was produced in the same manner as in Example 1 except that the tension applied to the film conveyed along the conveyance path was changed to 500 N / m.

<Example 3>
A polarizing laminated film was produced in the same manner as in Example 1 except that the tension applied to the film conveyed along the conveyance path was changed to 1000 N / m.

<Example 4>
A polarizing laminate film was produced in the same manner as in Example 3 except that a lead film made of a biaxially stretched polypropylene film unwound from a film roll was used as the first film.

<Example 5>
A polarizing laminated film was produced in the same manner as in Example 3 except that a lead film made of a biaxially stretched polypropylene film unwound from a film roll was used as the second film.

<Example 6>
A polarizing laminated film was produced in the same manner as in Example 3 except that the end portion of the first film and the start end portion of the second film were joined so as to have two strip-shaped adhesive regions 15a by heat sealing.

<Example 7>
A polarizing laminated film was produced in the same manner as in Example 6 except that a lead film made of a biaxially stretched polypropylene film unwound from a film roll was used as the first film.

<Example 8>
A polarizing laminate film was produced in the same manner as in Example 6 except that a lead film made of a biaxially stretched polypropylene film unwound from a film roll was used as the second film.

<Comparative Example 1>
Instead of the film roll of the stretched film produced through (1) to (4) of Example 1, a film roll of a single layer film made of polyvinyl alcohol (“VF-PS 7500” manufactured by Kuraray Co., Ltd.) is used. Used as film rolls for the first and second films, longitudinally uniaxially stretched in the dyeing tank 40 and the crosslinking tank 50 so that the total draw ratio is 5.0 times, and a belt-like adhesive region 15a by heat sealing. Except that the end portion of the first film and the start end portion of the second film are joined so as to have one place, and that the tension applied to the film conveyed along the conveying path is changed to 400 N / m, A polarizing laminated film was produced in the same manner as in Example 1.

<Comparative example 2>
A polarizing laminated film was produced in the same manner as in Comparative Example 1 except that the terminal end of the first film and the starting end of the second film were joined so as to have two strip-shaped adhesive regions 15a.

[Evaluation of continuous manufacturability and polarizing performance of polarizing laminated film]
(Evaluation of continuous manufacturability)
About each Example and the comparative example, continuous productivity of the light-polarizing laminated film was evaluated based on the following evaluation criteria. The results are shown in Table 1.

A: During the dyeing process, no defects such as breakage, peeling, wrinkles, etc. are observed at the joint between the first film and the second film, and the first film and the second film joined thereto are used as a transport path for the dyeing process. Can be transported continuously without problems, and a polarizing laminated film can be continuously produced.
B: During the dyeing process, problems such as breakage, peeling of the joints, and wrinkles of the joints occur in the film, and it cannot be said that the polarizing laminated film can be continuously produced without problems.

(Evaluation of polarization performance of polarizing laminated film)
About the polarizing laminated film obtained in each example, the polarization performance (the visibility corrected single transmittance and the visibility corrected polarization degree) of the film portion in the vicinity of the joined portion between the first film and the second film was measured and joined. In comparison with the polarization performance of the film part away from the part, the evaluation was made based on the following evaluation criteria. The results are shown in Table 1. The film portion in the vicinity of the bonding portion is the film portion immediately after the bonding portion for Examples 4 and 7 using the lead film for the first film, and the bonding portion for Examples 5 and 8 using the lead film for the second film. The film part immediately before and the film part immediately before and immediately after the joint part in the other examples.

A: The polarization performance of the film part in the vicinity of the joint is equivalent to the polarization performance of the film part away from the joint,
B: The polarization performance of the film part in the vicinity of the joint is significantly lower than the polarization performance of the film part away from the joint.

For the polarizing laminated film, the visibility correction polarization degree and the visibility correction single transmittance are measured samples obtained by removing one of the polarizer layers on both sides of the base film using an adhesive tape. Using a spectrophotometer “V7100” manufactured by JASCO Corporation, the light was incident from the polarizer layer side.

As shown in Table 1, in Examples 1 to 8, even if the joint between the first film and the second film is transported along the transport path for carrying out the dyeing step, the film at the joint is The polarizing laminated film could be continuously produced without causing problems such as breakage, peeling, and wrinkles. In Examples 1 to 8, in addition to the dyeing solution 41, the joint portion is immersed in the crosslinking solution 51 having a high temperature of 76 ° C. However, even if the joint portion is immersed in a chemical solution that easily causes deformation as described above, it breaks. Neither peeling nor peeling occurred. In Examples 2 to 8, the tension applied to the film was increased as compared with Example 1, and the dyeing process was performed under conditions where the film was more likely to break. However, the film was not broken or peeled off. Furthermore, in Examples 1 to 8, the polarizing performance in the vicinity of the joint in the polarizing laminated film is equivalent to the polarizing performance in the portion away from the joint, and no decrease in the polarizing performance due to the joint was observed. The loss could be less than 1 m.

On the other hand, in Comparative Examples 1 and 2 in which an unstretched polyvinyl alcohol monolayer film was subjected to a dyeing process and subjected to a stretching process in the dyeing process, the film was bonded at the joint during the stretching process in the dyeing tank 40. Breakage occurred.
In Examples 2 to 8, the tension applied to the film is larger than those in Comparative Examples 1 and 2, but since a polypropylene resin is used as the base film, the film is not stretched in the dyeing tank 40 under the above conditions.

<Reference Example: Production of Polarizing Plate>
Polyvinyl alcohol powder (“KL-318” manufactured by Kuraray Co., Ltd., average polymerization degree 1800) was dissolved in hot water at 95 ° C. to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% by weight. The resulting aqueous solution was mixed with a crosslinking agent (“Smile Resin 650” manufactured by Taoka Chemical Co., Ltd.) at a ratio of 1 part by weight to 2 parts by weight of the polyvinyl alcohol powder to obtain an aqueous adhesive solution.

Next, while continuously transporting the polarizing laminate film prepared in Example 1, the adhesive aqueous solution was coated on the polarizer layers on both sides, and then the protective film was subjected to saponification treatment on the bonding surface. [Transparent protective film made of triacetyl cellulose (TAC) (“KC4UY” manufactured by Konica Minolta Opto Co., Ltd.), thickness 40 μm] is bonded onto the polarizer layer, and crimped by passing between a pair of bonding rolls. And the bonding film which consists of a layer structure of TAC / polarizer layer / primer layer / base film / primer layer / polarizer layer / TAC was produced (bonding process).

Next, the laminated film is peeled and divided at the interface between the base film and the primer layer, and a film composed of TAC / polarizer layer / primer layer / base film and polarized light composed of primer layer / polarizer layer / TAC. After obtaining the plate, the base film was further peeled off from the former film to obtain another polarizing plate. In the process of peeling the base film, no troubles such as breakage occurred.

According to the method of the present invention, the film to be subjected to the dyeing process is a stretched film that has been stretched together with the base film, and is sufficiently stretched in advance, so that the first film and the second film are joined together. Even when the part is immersed in a dyeing tank or a crosslinking tank, the deformation of the joint can be suppressed, and the breakage or peeling of the film at the joint can be effectively suppressed.
If it is assumed that the film is not substantially stretched in the step of immersing in the dyeing tank, it is possible to more effectively suppress deformation of the joint due to the above-described immersion treatment, and by stretching the joint. Generation of wrinkles that can occur can be prevented.
Continuous production of a polarizing laminated film entails switching of film rolls, and as a result, a joining portion between the preceding film and the next film is inevitably produced. According to the method of the present invention, the joining is performed. Also about a part, it can pass as it is to the normal conveyance path | route (conveyance path | route which passes along a dyeing tank etc.) for performing a dyeing process, without producing a fracture | rupture and peeling of a film. Therefore, the polarizing laminated film can be continuously produced stably and efficiently.
Further, according to the method of the present invention, a polarizer layer can be formed by application of a coating liquid, so that a polarizing laminated film and a polarizing plate having a thin polarizer layer can be produced.

DESCRIPTION OF SYMBOLS 1 Guide roll, 10 Stretched film, 15 Bonding part, 15a Bonding area of bonding part, 20 Polarized laminated film, 40 Dyeing tank, 41 Dyeing solution, 50 Crosslinking tank, 51 Crosslinking solution, 100 Termination part of first film, 200 The starting end of the second film.

Claims (7)

1. A resin layer forming step of forming a polyvinyl alcohol resin layer on at least one surface of the base film to obtain a laminated film;
   A stretching step of stretching the laminated film to obtain a stretched film;
   By transporting the stretched film along a transport path passing through a dyeing tank containing a dichroic dye, the polyvinyl alcohol resin layer of the stretched film is dyed with the dichroic dye to form a polarizer layer. A dyeing process in this order,
   The dyeing step includes
   A step of immersing in the dyeing tank by conveying the first film along the conveying path;
   Joining the terminal end of the first film and the starting end of the second film to form a joint;
   Immersing in the dyeing tank by transporting the joint along the transport path, and
   At least one of the first film and the second film is the stretched film,
   Manufacturing method of polarizing laminated film.
2. The method according to claim 1, wherein in the step of immersing in the dyeing tank, any stretching treatment is not substantially performed.
3. The method according to claim 1 or 2, wherein the transport path is disposed after the dyeing tank and further passes through a crosslinking tank containing a crosslinking agent.
4. The method according to any one of claims 1 to 3, wherein both the first film and the second film are the stretched film.
5. 4. The method according to claim 1, wherein one of the first film and the second film is the stretched film, and the other is a lead film.
6. The method according to any one of claims 1 to 5, wherein in the stretching step, the laminated film is stretched at a stretch ratio of more than 5 times.
7. The method according to any one of claims 1 to 6, wherein the thickness of the polyvinyl alcohol-based resin layer of the laminated film is 3 to 30 µm.

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