TWI661238B - Method for producing polarizable laminated film - Google Patents

Abstract

A method for manufacturing a polarizing laminated film, comprising: a step of forming a polyvinyl alcohol-based resin layer on a base film to obtain a laminated film; a step of extending the laminated film to obtain an extended film; and The step of conveying the stretched film and dyeing the polyvinyl alcohol-based resin layer with a dichroic dye by the conveying path; the dyeing step includes the steps of conveying the first film along the conveying path and immersing it in the dyeing tank; and joining the terminal of the first film A step of forming a bonding portion with the starting portion of the second film and the second film; and a step of transporting the bonding portion along the transport path and immersing the bonding portion in the dyeing tank; at least one of the first and second films is an stretched film.

Description

Manufacturing method of 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.

The polarizing plate is provided with a polarizer layer having a polarizing function, and an optical element for protecting the protective film, and is widely used as a polarizing light supplying element or a polarizing light detecting element in a liquid crystal display device. In the past, polarizing plates have mainly used a polarizing film made of a film blank of a polyvinyl alcohol resin as a polarizer layer, and a protective film composed of triethylfluorinated cellulose or the like was adhered to one side or Duplex. In recent years, with the progress of liquid crystal display devices toward portable devices such as notebook personal computers and mobile phones, and progress toward large-scale televisions, thinner and lighter polarizing plates have been sought.

The thickness of the polarizing film produced by stretching the film blank (typically about 75 μm) of the polyvinyl alcohol-based resin and then dyeing it is generally about 30 μm. Thinning above this level is difficult to achieve due to productivity problems such as easy breakage of the film during stretching.

On the other hand, when the polarizing plate is continuously manufactured as a long In the case of a multi-layered film, for example, in the conventional polarizing plate as described above, it is necessary to continuously manufacture a polarizing film as one of the members of the polarizing plate. The continuous production of polarizing films generally includes the steps of continuously dipping the long film from the film roll while dipping the dyeing solution in the tank to perform the dyeing, and the continuous production of the polarizing film is performed on the roll. When the long film is about to be used up, the switching operation of the film roll including the operation of joining the terminal portion of the long film with the beginning of the long film of another film roll prepared in advance is performed, and then the new long film is operated. The strip film is subjected to a dyeing step.

However, in the continuous production of the above-mentioned polarizing film, when the joint portion (connection portion) of the film is immersed in the dyeing solution, the film may be broken at the joint portion, or the joint portion may be missing. As a method for solving this problem, Japanese Patent Application Laid-Open No. 2006-350224 (Patent Document 1) has proposed a method for continuously manufacturing a polarizing film from a film blank of a polyvinyl alcohol-based resin at a joint portion of the film. When passing through various processing steps such as the dyeing step, the method of raising all the elevating rollers of the manufacturing apparatus to make the film conveying path linear, so as to prevent the joint portion from being immersed in a chemical solution such as a dyeing solution.

However, in the method described in Patent Document 1, since the film cannot be subjected to any treatment until the joint portion of the film has passed through the treatment step, a corresponding amount of film loss occurs. In addition, even after the joint passes the processing step, even if the conveying path for implementing the processing step is constructed again by lowering the elevating roller, it takes time until the state of the film reaches a stable state. Even if a processing step is performed on the film that has not returned to a stable state, it cannot be expected that a good-quality polarizing film can be produced, so that film loss will occur until the stable state is restored.

Japanese Patent Application Laid-Open No. 2007-171897 (Patent Document 2) describes a method for continuously producing a polarizing film by sequentially applying a dyeing treatment, a crosslinking treatment, and an extension treatment to a film base material of a polyvinyl alcohol resin. In the middle, the heat sealing in the temperature range of 55 to 90 ° C is used to join the terminal part of the preceding film blank and the start of the continuous film blank, so that uniaxial extension in the longitudinal direction can be suppressed. The resulting film is broken or the joint is peeled off. However, even when the bonding method described in Patent Document 2 is used, when the chemical solution which is liable to deform the bonding portion of the film is immersed, for example, when the temperature is high, the film may be broken or the bonding portion may be peeled off. .

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a polarizing laminated layer with a polarizer layer that can be used as a polarizing plate by itself and also as a manufacturing intermediate for a polarizing plate with a protective film The method of manufacturing a film is such that even if the dipping process in the dyeing step is performed, the film is not cracked or peeled off at the joint between the terminal portion of the preceding film blank and the beginning of the subsequent film blank. A method for continuously and stably manufacturing a polarizing laminated film including a polarizer layer having a thin film.

The present invention is as follows.

[1] A method for manufacturing a polarizing laminated film, comprising: sequentially forming a resin layer on which a polyvinyl alcohol resin layer is formed on at least one side of a base film to obtain a laminated film; and extending the laminated film to obtain an extension Film stretching step; and transport along a transport path through a dyeing tank containing a dichroic pigment The stretching film, thereby dyeing the polyvinyl alcohol-based resin layer of the stretching film with the dichroic dye to form a polarizer layer; the dyeing step includes: transporting the first film along the transport path, A step of immersing in the dyeing tank by this; a step of joining the terminal portion of the first film and the beginning of the second film to form a joint; and transporting the joint along the transport path to immerse in the aforementioned Step of dyeing tank; at least one of the first film and the second film is the stretched film.

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

[3] The method according to the above [1] or [2], wherein the transport path further passes through a cross-linking tank arranged behind the dyeing tank and containing a cross-linking agent.

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

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

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

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

According to the method of the present invention, the polarizing film provided to the dyeing step is a stretched film that is subjected to a stretching treatment for each base film, and is sufficiently stretched in advance. Therefore, even if the first film is bonded to the second film, The immersion in the dyeing tank or the cross-linking tank can also suppress the deformation of the joint portion, and can effectively suppress the cracking or peeling of the film on the joint portion.

If the film is not substantially stretched in the step of immersing in the dyeing tank, the deformation of the joint portion caused by the above-mentioned dipping treatment can be more effectively suppressed, and the wrinkle caused by extending the joint portion can be prevented. occur.

The continuous production of polarized laminated film will inevitably be accompanied by the switching of the film roll, and with this, the bonding of the preceding film and the succeeding film will inevitably occur. According to the method of the present invention, it is possible to directly pass through a general conveying path for carrying out the dyeing step (through a conveying path such as a dyeing tank) without causing breakage or peeling of the film to the joint portion. Therefore, a polarizing laminated film can be continuously and efficiently manufactured.

In addition, according to the method of the present invention, since a polarizer layer can be formed by application of a coating liquid, a polarizing laminated film and a polarizing plate having a polarizer layer including a thin film can be manufactured.

1‧‧‧Guide roller

10‧‧‧ stretch film

15‧‧‧Joint

15a‧‧‧ Adhesive area of the joint

20‧‧‧Polarized laminated film

40‧‧‧dyeing tank

41‧‧‧ dyeing solution

50‧‧‧ Crosslinking tank

51‧‧‧ Cross-linking solution

100‧‧‧ Terminal of the first film

200‧‧‧ the beginning of the second film

FIG. 1 is a flowchart showing a method for manufacturing a polarizing laminated film of the present invention.

Fig. 2 is a schematic side view showing an example of an embodiment of a dyeing step. Illustration.

FIG. 3 is a schematic upper view showing an example of a bonding form in a bonding portion between a terminal portion of the first film and a starting end portion of the second film.

FIG. 4 is a schematic upper view showing another example of a bonding form in a bonding portion between a terminal portion of the first film and a starting end portion of the second film.

FIG. 5 is a flowchart showing a method of manufacturing a polarizing plate.

<Manufacturing method of polarizing laminated film>

FIG. 1 is a flowchart showing a method for manufacturing a polarizing laminated film of the present invention. As shown in FIG. 1, the method for manufacturing a polarizing laminated film of the present invention includes the following steps [1] to [3] in sequence.

[1] A resin layer forming step S10 in which a polyvinyl alcohol-based resin layer is formed on at least one side of the base film to obtain a laminated film.

[2] Step S20 of extending the laminated film to obtain an extended film.

[3] The polarizing layer is formed by dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye, thereby obtaining a dyeing step S30 of the polarizing laminated film.

As will be described later, a polarizing plate having a polarizer layer and a protective film laminated thereon can be pasted by attaching the protective film to the polarizer layer of the polarizing laminated film obtained up to the dyeing step S30. The film is laminated (laminating step S40), and then the base film is peeled from the laminated film and removed (peeling step S50).

Hereinafter, each of steps S10 to S30 included in the method for manufacturing 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 side of the base film. This polyvinyl alcohol-based resin layer is a layer that becomes a polarizer layer after the stretching step S20 and the dyeing step S30. The polyvinyl alcohol-based resin layer is preferably formed by applying a coating solution containing a polyvinyl alcohol-based resin to one or both sides of the base film, and drying the coating layer. According to this method, the thickness of the polyvinyl alcohol-based resin layer and even the polarizer layer can be reduced, so it is advantageous for reducing the weight of the polarizing laminated film and the polarizing plate. Although a polyvinyl alcohol-based resin layer can be formed by bonding a polyvinyl alcohol-based resin film formed in advance to a base film, from the viewpoint of thinning the polarizer layer, as described above, it is preferred A polyvinyl alcohol-based resin layer is formed by application of a coating liquid.

The resin layer forming step S10 is typically performed by continuously rolling out a base film from a long roll of the base film, and transporting the base film. The film conveyance system can be performed using a guide roller or the like.

(Base film)

The base film may be made of a thermoplastic resin. Among them, it is preferably made of a thermoplastic resin that is excellent in transparency, mechanical strength, thermal stability, and extensibility. Specific examples of such thermoplastic resins include, for example, polyolefin resins including chain polyolefin resins and cyclic polyolefin resins (such as norbornene resins); polyester resins; (meth) acrylic resins ; Cellulose ester resins of cellulose triacetate and cellulose diacetate; polycarbonate resins; polyvinyl alcohol resins; polyvinyl acetate resins; polyarylate resins; polystyrene resins Resins; Polyether fluorene-based resins; Polyfluorene-based resins; Polyfluorene-based resins; Polyfluorene-imide-based resins; and mixtures and copolymers thereof.

The base film may have a single-layer structure formed of one resin layer composed of one or two or more thermoplastic resins, or a laminate of a plurality of resin layers composed of one or two or more thermoplastic resins. Multi-layer construction.

The chain polyolefin resin is a copolymer of a chain olefin such as a polyethylene resin, a polypropylene resin, or the like, and a copolymer composed of two or more kinds of chain olefins. A base film made of a chain polyolefin resin is preferred from the viewpoint of easy and stable stretching at a high rate. Among them, the base film is particularly preferably made of polypropylene resin (polypropylene resin of propylene monopolymer or copolymer mainly composed of propylene), polyethylene resin (polyethylene resin of ethylene monopolymer, Or a copolymer mainly composed of ethylene).

As an example of the thermoplastic resin constituting the base film, a copolymer mainly composed of propylene, and a copolymer of propylene and other monomers copolymerizable therewith can be suitably used.

Examples of other monomers copolymerizable with propylene include ethylene and α-olefins. The α-olefin is preferably an α-olefin having 4 or more carbon atoms, and particularly preferably an α-olefin having 4 to 10 carbon atoms. Specific examples of α-olefins having 4 to 10 carbon atoms include, for example, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene linear monomers Alkenes; 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene branched monoolefins; vinyl cyclohexane, etc. Copolymers of propylene and other monomers copolymerizable therewith may be random copolymers or block copolymers.

The content of the other monomers in the copolymer is, for example, 0.1 to 20% by weight, preferably 0.5 to 10% by weight. The content of other monomers in the copolymer can be determined by infrared (IR) according to the method described on page 616 of the "Handbook of Polymer Analysis (Original: Handbook of Polymer Analysis)" (1995, issued by Kii Kokuya Bookstore). Obtain by spectrum measurement.

Among the above, the polypropylene-based resin is preferably a propylene monopolymer, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, or a propylene-ethylene-1-butene random copolymer.

The three-dimensional regularity of the polypropylene-based resin is preferably substantially the same or opposite. A base film made of a polypropylene-based resin having substantially regular or opposite rows of three-dimensional regularity has good handling properties and excellent mechanical strength in a high-temperature environment.

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

Cyclic polyolefin resin is a generic term for a resin polymerized by using a cyclic olefin as a polymerization unit, and examples thereof include Japanese Patent Laid-Open No. 1-240517, Japanese Patent Laid-Open No. 3-14882, and Japanese Patent Laid-Open No. 3-122137. Resin described in bulletins and the like. Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, and copolymerization of cyclic olefins with ethylene and propylene-like chain olefins. Polymers (typically random copolymers), graft polymers modified with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among them, a norbornene-based resin using norbornene or a polycyclic norbornene-based monomer as the cyclic olefin is preferably used.

Various products of cyclic polyolefin resins are commercially available. Examples of commercially available products of cyclic polyolefin resins, each of which is represented by a trade name, include "Topas" (manufactured by TOPAS ADVANCED POLYMERS GmbH, available from Polyplastics Co., Ltd.), "ARTON" (JSR Shares Limited Company), "ZEONOR" (Zeon Corporation), "ZEONEX" (Zeon Corporation), "APEL" (Mitsui Chemical Co., Ltd.).

Can also be used: Each is represented by a trade name, "S-SINA" (made by Sekisui Chemical Industry Co., Ltd.), "SCA40" (made by Sekisui Chemical Industry Co., Ltd.), "ZEONOR FILM" (Zeon Corporation) A commercially available cyclic polyolefin-based resin film, such as a film), is used as a base film.

The base film may be composed of one type of cyclic polyolefin resin, or a mixture of two or more types of cyclic polyolefin resin, or a copolymer of two or more types of cyclic polyolefin resin. Make up.

The polyester resin is a resin having an ester bond, and is generally composed of a polycondensate of a polycarboxylic acid or a derivative thereof and a polyhydric alcohol. The polyvalent carboxylic acid or a derivative thereof may be a divalent dicarboxylic acid or a derivative thereof. Examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalate. Wait. As the polyhydric alcohol, a divalent diol can be used, and examples thereof include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, and cyclohexanedimethanol.

Typical examples of the polyester-based resin include polyethylene terephthalate, which is a polycondensate of terephthalic acid and ethylene glycol. Parylene Although ethylene formate is a crystalline resin, it is easy to apply a treatment such as stretching to a state before the crystallization treatment. If necessary, a crystallization treatment may be performed by heat treatment or the like during or after stretching. In addition, a copolymerized polyester that reduces the crystallinity (or becomes amorphous) by copolymerizing other types of monomers on the backbone of polyethylene terephthalate can also be preferably used. Examples of such a polyester include a copolymer of cyclohexanedimethanol and isophthalic acid. These resins are also suitable for use because they are excellent in extensibility.

Specific examples of polyester resins other than polyethylene terephthalate and its copolymers are listed, and examples include polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. Esters, polytrimethylene terephthalate, polytrimethylene naphthalate, cyclohexanedimethyl terephthalate, and the like.

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

The (meth) acrylic resin is a resin having a (meth) acrylfluorenyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include, for example, poly (meth) acrylate of polymethyl methacrylate; methyl methacrylate- (meth) acrylic copolymer; and methyl methacrylate- ( (Meth) acrylate copolymer; methyl methacrylate-acrylate- (meth) acrylic copolymer; methyl (meth) acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and having Copolymers of alicyclic hydrocarbon-based compounds (such as methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth) acrylate copolymer, etc.). It is preferable to use a polymer containing poly (meth) acrylic acid C _1-6 alkyl ester as a polymethyl (meth) acrylate as a main component, and it is more preferable to use a polymer containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) of a methyl methacrylate resin.

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

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include, for example, cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. In addition, copolymers such as those mentioned above, or those in which a part of the hydroxyl group is modified by another substituent, and the like can also be mentioned. Among these, cellulose triacetate (triethylammonium cellulose) is particularly preferred. Many products of cellulose triacetate are commercially available, and it is also advantageous from the viewpoint of availability or cost. Examples of commercially available products of cellulose triacetate are each represented by a trade name, and examples include "Fujitac TD80" (manufactured by Fuji Film Co., Ltd.) and "Fujitac TD80UF" (manufactured by Fuji Film Co., Ltd.) , "Fujitac TD80UZ" (manufactured by Fuji Film Co., Ltd.), "Fujitac TD40UZ" (manufactured by Fuji Film Co., Ltd.), "KC8UX2M" (manufactured by Konica Minolta Opto Co., Ltd.), "KC4UY" (Konica Minolta Opto Co., Ltd.制) and so on.

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

Polycarbonate resins are engineering plastics composed of polymers whose monomer units are bonded via carbonate groups, and are resins with high impact resistance, heat resistance, flame resistance, and transparency. The polycarbonate-based resin constituting the substrate film may also be a resin called modified polycarbonate for modifying the polymer skeleton to reduce the photoelastic coefficient, or a copolymerized polycarbonate having improved wavelength dependence. Esters, etc.

Many polycarbonate-based resins are commercially available. Examples of commercially available polycarbonate resins are each represented by a trade name, and examples thereof include "Panlite" (manufactured by Teijin Chemicals Co., Ltd.), "Iupilon" (manufactured by Mitsubishi Engineering Plastics Co., Ltd.), " "SD Polyca" (manufactured by Sumitomo Dow Co., Ltd.), "Calibre" (manufactured by Dow Chemical Co., Ltd.), etc.

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

Among the above, from the viewpoints of extensibility and heat resistance, it is preferable to use a polyolefin resin, a polyester resin, a (meth) acrylic resin, or a polycarbonate resin, and a polypropylene resin is particularly preferred. The resin or polyester resin is particularly preferably a polypropylene resin.

Any appropriate additives may be added to the base film in addition to the above-mentioned thermoplastic resin. Examples of the additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, and coloring resistance. Agents, flame retardants, nucleating agents, anti-charge agents, pigments, and coloring agents. The content of the thermoplastic resin in the base film is preferably 50 to 100% by weight, particularly preferably 50 to 99% by weight, 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, there is a concern that the high transparency originally possessed by the thermoplastic resin cannot be sufficiently exhibited.

The thickness of the substrate film can be appropriately determined. Generally, from the viewpoints of workability such as strength and handleability, it is preferably 1 to 500 μm, particularly preferably 1 to 300 μm, more preferably 5 to 200 μm, and most preferably 5 Up to 150 μm.

(Coating liquid containing polyvinyl alcohol resin)

The coating liquid is preferably a polyvinyl alcohol-based resin solution obtained by dissolving a powder of the polyvinyl alcohol-based resin in a good solvent (for example, water). Examples of the polyvinyl alcohol resin include a polyvinyl alcohol resin and a derivative thereof. In addition to polyvinyl alcohol-based resin derivatives, in addition to polyvinyl formaldehyde, polyvinyl acetal, etc., examples include those modified with polyvinyl alcohol-based olefins such as ethylene and propylene; acrylic acid and methacrylic acid 2. Those who are modified by crotonic acid-like unsaturated carboxylic acids; those who are modified by alkyl esters of unsaturated carboxylic acids; those who are modified by acrylamide. The modification ratio is preferably less than 30 mole%, and even more preferably less than 10 mole%. When the modification exceeds 30 mol%, it is difficult to adsorb the dichroic pigment, and the lack of polarization performance may occur. Among the polyvinyl alcohol-based resins, a polyvinyl alcohol resin is preferably used.

The average degree of polymerization of the polyvinyl alcohol resin is preferably in the range of 100 to 10,000, and more preferably in the range of 1000 to 10,000. The better line is in the range of 1500 to 8000, and the best line is in the range of 2000 to 5000. The average degree of polymerization can be determined in accordance with the method specified in JIS K 6726-1994 "Test Method for Polyvinyl Alcohol". When the average polymerization degree is less than 100, it is difficult to obtain polarizing performance, and when it exceeds 10,000, the solubility in a solvent is deteriorated, and it is difficult to form a polyvinyl alcohol-based resin layer.

The polyvinyl alcohol-based resin is preferably a saponified product of a polyvinyl acetate-based resin. The range of the saponification degree is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 94 mol% or more. When the degree of saponification is too low, the water resistance or moist heat resistance may be insufficient when forming a polarizing laminated film or a polarizing plate. In addition, although it can be completely saponified (saponification degree of 100 mol%), when the saponification degree is too high, the dyeing speed becomes slower, and the manufacturing time required to impart sufficient polarizing performance increases. Depending on the situation, it may not be possible. A polarizer layer having sufficient polarization performance was obtained. Therefore, the saponification degree is preferably 99.5 mol% or less, and more preferably 99.0 mol% or less.

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

Saponification degree (mol%) = [(hydroxyl number) ÷ (hydroxyl number + acetate number)] × 100

The higher the degree of saponification, the higher the ratio of hydroxyl groups, and therefore the smaller the ratio of acetic acid groups that hinder crystallization. The degree of saponification can be determined in accordance with the method specified in JIS K 6726-1994 "Test Method for Polyvinyl Alcohol".

Examples of polyvinyl acetate resins other than polyvinyl acetate, which is a single polymer of vinyl acetate, include copolymers with vinyl acetate. Copolymers of other monomers, etc. Examples of other monomers that can be copolymerized 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-based resins that can be suitably used are each represented by a trade name, and include "PVA124" (degree of saponification: 98.0 to 99.0 mol%) manufactured by Kuraray Co., Ltd., " "PVA117" (degree of saponification: 98.0 to 99.0 mole%), "PVA117H" (degree of saponification: 99.5 mole% or more), "PVA624" (degree of saponification: 95.0 to 96.0 mole%), and "PVA617" (degree of saponification: 94.5 to 95.5 mol%); "AH-26" (Saponification degree: 97.0 to 98.0 mol%), "AH-22" (Saponification degree: 97.5 to 98.5 mol%) made by Japan Synthetic Chemical Industry Co., Ltd. "NH-18" (degree of saponification: 98.0 to 99.0 mole%) and "N-300" (degree of saponification: 98.0 to 99.0 mole%); "JC-33" (made by Japan Vam and Poval Co., Ltd. Saponification degree: 99.0 mol% or more), "JM-33" (Saponification degree: 93.5 to 95.5 mol%), "JM-26" (Saponification degree: 95.5 to 97.5 mol%), "JP-45" ( Saponification degree: 86.5 to 89.5 mol%), "JF-17" (Saponification degree: 98.0 to 99.0 mol%), "JF-17L" (Saponification degree: 98.0 to 99.0 mol%), and "JF-20" (Saponification degree: 98.0 to 99.0 mole%).

The coating liquid may contain additives such as a plasticizer and a surfactant, as needed. As the plasticizer, a polyhydric alcohol or a condensate thereof can be used, and examples thereof include glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol, and polyethylene glycol. The blending amount of the additive is more preferably 20% by weight or less of the polyvinyl alcohol resin.

(Coating of coating liquid and drying of coating layer)

The method for applying the coating liquid to the substrate film may be appropriately selected from a wire rod coating method; a roll coating method such as reverse roller coating or gravure coating; a die coating method; Wheel coating method; die lip coating method; spin coating method; screen coating method; fountain coating method; dipping method; spraying method and other commonly known methods.

When the coating solution is applied to both sides of the base film, the above method can be used to sequentially perform one-sided and one-sided order, or it can be applied to the substrate film simultaneously by dipping method, spray coating method, or other special equipment. Both sides of the base film.

The drying temperature and drying time of the coating layer (the polyvinyl alcohol-based resin layer before drying) can be set in accordance with the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, and 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 formed on both sides, curling of the film that may occur during the manufacture of polarizing laminated film or polarizing plate can be suppressed, and two polarizing plates can be obtained from one polarizing laminated film, also in terms of production efficiency of polarizing plate. As favorable.

The thickness of the polyvinyl alcohol-based resin layer in the laminated film is preferably 3 to 30 μm, and particularly preferably 5 to 20 μm. If the polyvinyl alcohol-based resin layer has a thickness within this range, a polarizer layer having excellent dyeability, excellent polarizing performance, and extremely small thickness of the dichroic pigment can be obtained through the extension step S20 and the dyeing step S30 described later. When the thickness of the polyvinyl alcohol-based resin layer exceeds 30 μm, the thickness of the polarizer layer may exceed 10 μm. this In addition, if the thickness of the polyvinyl alcohol-based resin layer is less than 3 μm, it becomes too thin after stretching, and there is a tendency that the dyeability is deteriorated.

Before the application of the coating liquid, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, a corona treatment may be applied to the surface of the base film at least on the side where the polyvinyl alcohol-based resin layer is formed. , Plasma treatment, flame treatment, etc.

In addition, in order to improve the adhesion between the substrate film and the polyvinyl alcohol-based resin layer, the polyvinyl alcohol-based resin layer may be formed on the substrate film via a primer layer or an adhesive layer.

(Primer layer)

The primer layer can be formed by applying a coating liquid for forming a primer layer on the surface of a substrate film and then drying it. The coating liquid system for forming a primer layer contains a component that exhibits a certain degree of strong adhesion to both the substrate film and the polyvinyl alcohol-based resin layer. The coating liquid for forming a primer layer generally contains a resin component and a solvent capable of imparting such adhesion. The resin component is preferably a thermoplastic resin excellent in transparency, thermal stability, and extensibility, and examples thereof include (meth) acrylic resins and polyvinyl alcohol resins. Among them, it is preferable to use a polyvinyl alcohol-based resin that can impart good adhesion.

Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol-based resin and a derivative thereof. In addition to polyvinyl alcohol-based resin derivatives other than polyvinyl formaldehyde, polyvinyl acetal, etc., examples include those modified with polyvinyl alcohol-based olefins such as ethylene and propylene; acrylic acid, methacrylic acid, Those who have been modified with unsaturated carboxylic acids of crotonic acid; those who have been modified with alkyl esters of unsaturated carboxylic acids; those who have been modified with acrylamide. Polyvinyl alcohol Among the resins, a polyvinyl alcohol resin is preferably used.

The solvent is generally a general organic solvent or an aqueous solvent that can dissolve the resin component. Examples of solvents are listed, such as aromatic hydrocarbons such as benzene, toluene, and xylene; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; such as ethyl acetate and isobutyl acetate; dichloromethane , Trichloroethylene, chloroform-like chlorinated hydrocarbons; ethanol, 1-propanol, 2-propanol, 1-butanol-like alcohols. However, when a primer layer is formed using a coating liquid for forming a primer layer containing an organic solvent, the base film may be dissolved. Therefore, the solvent is preferably selected in consideration of the solubility of the base film. If the environmental impact is also considered, it is preferable to form the primer layer from a coating liquid using water as a solvent.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the coating liquid for forming a primer layer. The cross-linking agent can be appropriately selected from generally known organic and inorganic systems in accordance with the type of thermoplastic resin used. Examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, and metal-based crosslinking agents.

The epoxy-based cross-linking agent can be used in either a single-liquid curing type or a two-liquid curing type, and examples thereof include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, diglycerol, and triglycidyl. Ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diglycidylamine, and the like.

Examples of the isocyanate-based crosslinking agent include toluene diisocyanate, hydrogenated toluene diisocyanate, trimethylolpropane-toluene diisocyanate adduct, triphenylmethane triisocyanate, methylenebis (4-phenylmethane) triisocyanate, Isophorone diisocyanate, and ketoxime end caps or Phenol end caps, etc.

Examples of the dialdehyde-based crosslinking agent include glyoxal, malonaldehyde, succinaldehyde, glutaraldehyde, malealdialdehyde, and o-phthalaldehyde.

Examples of the metal-based crosslinking agent include metal salts, metal oxides, metal hydroxides, and organic metal compounds. Examples of the metal salt, metal oxide, and metal hydroxide include magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, silicon, boron, zinc, copper, vanadium, chromium, and tin. Valence metal salts, oxides and hydroxides.

The organometallic compound is a compound having a structure in which at least one organic group is directly bonded to a metal atom, or an organic group is bonded to a metal atom via an oxygen atom or a nitrogen atom. The organic group means a group containing at least a monovalent or polyvalent carbon element, and examples thereof include an alkyl group, an alkoxy group, and a fluorenyl group. In addition, the bonding does not only mean a covalent bond, but also a coordination bond formed by coordination of a chelate compound or the like.

Examples of suitable organometallic compounds include organic titanium compounds, organic zirconium compounds, organic aluminum compounds, and organic silicon compounds. The organometallic compound may be used alone or in combination of two or more.

Examples of the organic titanium compound include tetra-n-butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, and tetramethyl titanate. Acid esters; titanium acetoacetate, titanium tetraacetate pyruvate, titanium polyacetate pyruvate, titanium octyl glycolate, titanium lactate, titanium triethanolamine, titanium acetate ethyl acetate Substances: Titanium halides such as polyhydroxystearate.

Examples of the organic zirconium compound include zirconium n-propionate, Zirconium n-butyrate, zirconium tetraacetamidine pyruvate, zirconium monoacetamidine pyruvate, zirconium diacetamidine pyruvate, zirconium acetamidine pyruvate, diethyl acetate diacetate, and the like.

Examples of the organoaluminum compound include aluminum acetopyruvate and organic acid chelate aluminum. Examples of the organic silicon compound include compounds in which the ligands previously exemplified for the organic titanium compound and the organic zirconium compound are bonded to silicon.

In addition to the above low-molecular-weight cross-linking agents, polymer-type cross-linking agents such as methylolated melamine resins and polyamine epoxy resins can also be used. Examples of commercially available products of polyamide epoxy resins are "Sumirez Resin 650 (30)" or "Sumirez Resin 675" (Either of which is a trade name) sold by Taoka Chemical Industry Co., Ltd. )Wait.

When a polyvinyl alcohol-based resin is used as a resin component for forming the primer layer, polyamine epoxy resin, methylated melamine resin, dialdehyde-based crosslinking agent, and metal chelate compound-based crosslinking agent can be suitably used. And so on as a crosslinking agent.

The ratio of the resin component to the cross-linking agent in the coating liquid for forming the primer layer ranges from about 0.1 to 100 parts by weight of the cross-linking agent relative to 100 parts by weight of the resin component. The type of the agent and the like may be appropriately determined, and it is particularly preferably selected from a range of about 0.1 to 50 parts by weight. Moreover, it is preferable that the coating liquid for primer layer formation is so that solid content concentration may become about 1 to 25 weight%.

The thickness of the primer layer is preferably 0.05 to 1 μm, and more preferably 0.1 to 0.4 μm. If it is thinner than 0.05 μm, the effect of improving the adhesion between the substrate film and the polyvinyl alcohol resin layer is small. If it is thicker than 1 μm, it is not good for it. Thinning of a polarizing laminated film or a polarizing plate.

The method for applying the coating liquid for forming a primer layer to a base film may be the same as in the case of the coating liquid for forming a polyvinyl alcohol-based resin layer. The primer layer is applied to the surface (one or both sides of the base film) on which the coating liquid for forming a polyvinyl alcohol resin layer is applied. The drying temperature and drying time of the coating layer composed of the coating liquid for forming a primer layer can be set according to the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, and 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 the primer layer is provided, the order of coating the base film is not particularly limited. For example, when a polyvinyl alcohol-based resin layer is formed on both sides of the base film, the primer layer may be formed on the base film. After double-sided, a polyvinyl alcohol-based resin layer is formed on both sides, or a primer layer and a polyvinyl alcohol-based resin layer are sequentially formed on one side of the base film, and then a base is sequentially formed on the other side of the base film. Lacquer layer and polyvinyl alcohol resin layer.

The laminated film obtained by the manufacturing method of the polarizing laminated film of this invention is typically a long film. The long laminated film can be sequentially wound up after forming a polyvinyl alcohol-based resin layer to temporarily become the form of a film roll, or the obtained laminated film can be continuously supplied to a continuous extension without being wound up. Step S20 is followed by an extension process.

[2] Extending step S20

This step is a step of obtaining a stretched film by extending a laminated film composed of a base film and a polyvinyl alcohol resin layer. The stretching step S20 is typically to carry a long laminated film or to continuously roll it from a film roll of the long laminated film The laminated film is taken out continuously while being conveyed. Film conveyance can be performed using a guide roll or the like.

The stretch ratio of the laminated film can be appropriately selected depending on desired polarization characteristics, and is preferably more than 5 times and 17 times or less, and more preferably more than 5 times and 8 times or less with respect to the original length of the laminated film. When the stretching ratio is 5 times or less, the polymer chains of the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin layer are not sufficiently aligned, and the degree of polarization of the polarizer layer may not be sufficiently high in some cases. On the other hand, when the stretching ratio exceeds 17 times, film breakage is likely to occur during stretching, and the thickness of the stretched film is reduced to more than necessary, and there is a concern that the workability and handling properties in the subsequent steps are reduced. Stretching is generally uniaxial.

The stretching treatment may be a longitudinal extension extending in the film length direction (film transport direction), or a lateral extension or oblique extension extending in the film width direction. Longitudinal stretching methods include: roll-to-roll stretching [while conveying between two nip rollers set apart at a distance, while performing the vertical uniaxial by waiting for the peripheral speed difference between the two nip rollers Extension method]; heat roller extension [by heating the surface of the heat roller to a desired temperature that can be extended, and a guide roller with a peripheral speed different from the thermal roller (larger peripheral speed) (or a thermal roller) In the heating state generated by contact with the heat roller, the method of longitudinal uniaxial extension when contacting the heat roller (on the heat roller) or near it]; compression extension; extension using a chuck (clamp) The lateral stretching method includes a tenter method and the like. The stretching treatment can be performed by either a wet stretching method or a dry stretching method. However, a dry stretching method is preferred from the viewpoint that a wide range of stretching temperatures can be selected.

The elongation temperature is set to a temperature at which the entire polyvinyl alcohol-based resin layer and the base film exhibit fluidity to such an extent that it can be stretched, and is preferably [phase transition temperature (melting point or glass transition temperature) of the base film-30] ℃ to [phase transition temperature of substrate film +30] ° C, particularly preferably [phase transition temperature of substrate film -30] ° C to [phase transition temperature of substrate film +5] ° C, more preferably The range is [phase transition temperature of the base film -25] ° C to [phase transition temperature of the base film] ° C. When the substrate film is composed of a plurality of resin layers, the above-mentioned phase transition temperature means the highest phase transition temperature among the phase transition temperatures displayed by the plurality of resin layers.

When the stretching temperature is lower than [phase transition temperature of the base film -30] ° C, it is difficult to achieve a high-rate stretching of more than 5 times, or the fluidity of the base film is too low, and it is difficult to perform the stretching treatment. tendency. When the elongation temperature exceeds [phase transition temperature of the base material film + 30] ° C, the fluidity of the base material film becomes too large, and it tends to be difficult to extend. In order to more easily achieve a high magnification extension of more than 5 times, the extension temperature is within the above range, and more preferably 120 ° C or higher. When the stretching temperature is 120 ° C or higher, even if it is stretched at a high rate of more than 5 times, there is no difficulty in the stretching process.

The heating method of the laminated film in the stretching treatment includes a hot zone heating method (for example, a heating method in a stretching hot zone like a heating furnace adjusted to a predetermined temperature by blowing hot air); and a stretching method using a heat roller. When stretching, the method of heating the roll itself; the heater heating method (a method of setting an infrared heater, a halogen heater, a flat plate heater, etc. above and below the laminated film and heating it with radiant heat) and the like. In the stretching method between rolls, a hot zone heating method is preferred from the viewpoint of uniformity of the stretching temperature. At this time, 2 The nip roller can be set in the extended hot zone after temperature adjustment, or outside the extended hot zone, but in order to prevent the laminated film and the nip roller from adhering, it is preferably set outside the extended hot zone.

The so-called extension temperature refers to the ambient temperature in the hot zone (for example, in a heating furnace) when the hot zone heating method is used. In the heater heating method, it means the ambient temperature in the furnace when heating is also performed in the furnace. In addition, when the hot roll is extended, it means the surface temperature of the roll.

The extension processing is not limited to one-stage extension, and may be performed in multiple stages. In this case, it is preferable to perform the stretching process so that the entire length of the stretching process becomes a total stretching ratio of more than 5 times.

Before the extending step S20, a preheating step for preheating the laminated film may be provided. As the preheating method, the same method as the heating method of the stretching treatment can be used. When the stretching treatment method is stretching between rolls, preheating can be performed before, during, and after passing through the nip roll on the upstream side. When the stretching treatment method is hot roll stretching, the preheating is preferably performed before the heat roller is passed. When the extension processing method is an extension using a chuck, the preheating is preferably performed at a time before the distance between the chucks is extended. The preheating temperature is preferably in a range of -50 ° C to ± 0 ° C of the extension temperature, and particularly preferably in a range of [drawing temperature-40] ° C to [extension temperature-10] ° C.

In addition, after the stretching process in the stretching step S20, a heat fixing process step may also be provided. The heat-fixing treatment is a treatment in which the end of the stretched film is held by a clamp, and the heat treatment is performed at a temperature higher than the crystallization temperature while maintaining the tension. By this heat setting treatment, crystallization of the polyvinyl alcohol-based resin layer can be promoted. The temperature of the heat fixing treatment is preferably [elongation temperature] The range of ℃ to [elongation temperature-80] ℃, particularly preferably the range of [elongation temperature] ℃ to [elongation temperature -50] ℃.

The stretched film obtained by the manufacturing method of the polarizing laminated film of this invention is typically a long film. Generally, it is sequentially taken up after the stretching treatment and obtained in the form of a film roll.

[3] Dyeing step S30

This step is a step of forming a polarizer layer by dyeing a polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye, adsorbing and aligning the polyvinyl alcohol-based resin layer. After this step, a polarizing laminated film having a polarizer layer on one or both sides of the substrate film can be obtained. The dyeing of the dichromatic dye is to continuously roll out the stretched film from the long film roll of the stretched film, and transport the stretched film along the conveying path (production line path) through the dyeing tank containing the dichromatic dye to continuously immerse it. It is performed in a dyeing tank. 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] A step of immersing the first film in the dyeing tank by transporting the first film along the transport path passing through the dyeing tank.

[b] The step of joining the terminal portion of the first film and the starting end portion of the second film to form a joint portion.

[c] A step of immersing the joint in the dyeing tank by transporting the joint along the transport path.

At least one of the first film and the second film is an stretched film obtained in the stretching step S20. According to the dyeing step S30 including the above steps [a] to [c], in step [a], it is transported first along the transport path When the long first film is near the end, it may be performed by joining the terminal portion of the first film with the start portion of another second film prepared in advance (the second film is generally prepared as a film roll). The switching operation of the operated film roll (step [b]), and then the second film to be bonded is subjected to a dyeing treatment, so that a polarizing laminated film can be continuously manufactured. In the present invention, the third film can be bonded to the second film, or the fourth film (or further the fifth film, the sixth film, etc.) can be bonded to the third film according to the desired production amount of the polarizing laminated film. .

At least one of the first film and the second film provided to the dyeing step S30 is sufficiently stretched in advance for the stretched film subjected to the stretching process in the stretching step S20. Therefore, as in the method described in Patent Document 2, when a film blank of a polyvinyl alcohol resin is immersed in a dyeing tank in an unstretched state, it is possible to effectively suppress the bonding of the first film and the second film Deformation of the joint when the part is immersed in the dyeing tank. By resisting this deformation, it is possible to effectively suppress the breakage or peeling of the film on the joint caused by the deformation.

Since the joining portion is excellent in deformation resistance, in the present invention, the joining portion can be directly passed through the above-mentioned conveying path through the dyeing tank (step [c]). That is, it is not necessary to worry about breakage or peeling of the joint portion as in the method described in Patent Document 1, and the conveyance path is changed so that the joint portion is not immersed in the dyeing tank. According to the method of the present invention, not only the tedious work of changing the conveying path can be avoided, but also the part of the film that cannot be dyed can be avoided, and after the film roll is switched in step [b], the film state can be significantly shortened to reach a stable Therefore, almost no film loss occurs, and the polarizing laminated film can be continuously produced with extremely high production efficiency.

As a method for suppressing cracking or peeling of the film in the dyeing step S30, a method of conveying the film by reducing the tension applied to the film is conceivable, but in this case, it is likely to be generated in a dyeing tank or an arbitrary swelling tank. fracture. In addition, when the tension is low, the meandering of the film is liable to occur. At this time, after the tension is restored, it takes some time until the travel of the film reaches stability, the loss of the film increases, and the manufacturing efficiency decreases. When the tension is low, the fluidity of the film is deteriorated when it passes through the nip rolls, so wrinkles and the like are easily generated.

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 the implementation state of the dyeing step S30, which shows that the stretched film 10 as the first film in advance passes through the dyeing tank 40 and the cross-linking tank 50 (only the cross-linking tank 50). This is a slot provided arbitrarily), whereby the polarizing laminated film 20 is continuously produced, and the stretched film 10 as the second film bonded to the terminal portion of the first film passes through the dyeing tank 40. The first film is located further downstream than the bonding portion 15, and the second film is located upstream. The arrows show the transport direction of the film. As shown in the figure, according to the method of the present invention, it is not necessary to intentionally change the conveying path, and the joint portion 15 of the first film and the second film can be directly passed through the conveying path for performing the dyeing step S30 including at least the dyeing tank 40.

The film conveyance in the dyeing step S30 can be performed using the guide roller 1 or the like, as in the other steps. The film is immersed in the dyeing solution 41 containing the dichroic pigment contained in the dyeing tank 40 or the crosslinking solution 51 containing the crosslinking agent contained in the crosslinking tank 50, as shown in the figure, in the dyeing tank 40 or the crosslinking tank 50 A plurality of guide rollers 1 may be provided on the upper and lower sides, as long as the film is conveyed along these. The number of the guide rollers 1, the distance between the guide rollers, and the like can be adjusted according to the desired residence time (soak time) of the film in the solution.

The dyeing solution 41 in the dyeing tank 40 may be a solution in which a dichroic pigment 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 dichroic organic dyes include: Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB , Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Sky Red GL, Sky Red KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue, Direct Fast Orange S, Fast Black, etc. The dichroic pigment may be used alone or in combination of two or more.

The solvent contained in the dyeing solution 41 is generally water, and an organic solvent compatible with water may be further added. The concentration of the dichroic pigment in the dyeing solution 41 is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight, and still more preferably 0.025 to 5% by weight.

When using iodine as a dichroic pigment, in order to further improve the dyeing efficiency, it is preferable to further add iodide to the dyeing solution 41 containing iodine. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. The concentration of the iodide in the dyeing solution 41 is preferably 0.01 to 20% by weight. To the iodide, potassium iodide is preferably added. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100 by weight ratio, particularly preferably in the range of 1: 6 to 1:80, and more preferably in the range of 1: 7 to 1:70 range.

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

As shown in FIG. 2, on the conveyance path of the stretched film 10 passing through the dyeing tank 40, a cross-linking tank 50 is preferably provided after the dyeing tank 40 (downstream side). That is, the dyeing step S30 preferably includes a crosslinking treatment step performed after the dyeing treatment step in the dyeing tank 40. The crosslinking solution 51 in the crosslinking tank 50 may be a solution in which a crosslinking agent is dissolved in a solvent. As the crosslinking agent, generally known ones can be used, and examples thereof include boric acid, borax-like borides, glyoxal, and glutaraldehyde. The crosslinking agent may be used alone or in combination of two or more.

The solvent contained in the crosslinking solution 51 generally uses water, and may further contain an organic solvent compatible with water. The concentration of the crosslinking agent in the crosslinking solution 51 is preferably 1 to 20% by weight, and particularly preferably 6 to 15% by weight.

The crosslinking solution 51 may contain iodide. The addition of iodide can make the polarization performance in the plane of the polarizer layer more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. The concentration of the iodide in the crosslinking solution 51 is preferably 0.05 to 15% by weight, and particularly preferably 0.5 to 8% by weight.

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

The cross-linking treatment may be performed simultaneously with the dyeing treatment by blending the cross-linking agent in the dyeing solution 41.

The dyeing step S30 may include, in addition to the dyeing and cross-linking treatment steps described above, a swelling treatment step of swelling the stretch film 10 before the dyeing treatment step; between the dyeing treatment step and the cross-linking treatment step The first washing step performed; after the cross-linking treatment step, the second washing step performed.

The swelling treatment step can be performed by immersing the stretched film 10 in a water bath (ion-exchanged water, pure water bath such as distilled water) at about 0 to 40 ° C, for example.

The first and second washing steps generally include a water washing step. The water washing step can be performed by immersing the membrane after the dyeing treatment or the crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water washing temperature is generally in the range of 3 to 40 ° C, preferably in the range of 4 to 20 ° C. The immersion time in water is generally 2 to 300 seconds, preferably 3 to 240 seconds.

The first and second washing steps may be a combination of a water washing step and a washing step using an iodide solution. In addition, the washing liquid used in the water washing step and / or the washing treatment with the iodide solution may contain, in addition to water, a liquid alcohol such as methanol, ethanol, isopropanol, and butanol as appropriate. .

In the step of immersing the stretched film 10 in the dyeing tank and the step of immersing the joint portion 15 in the dyeing tank, it is preferable that substantially no one is subjected to the stretching treatment. This makes it possible to more effectively suppress the deformation of the joint portion 15 caused by the dipping treatment in the dyeing tank 40. When immersed in the dyeing tank 40 When the stretching treatment is performed, the amount of deformation of the joint portion 15 increases, and there is a possibility that the film on the joint portion is cracked or peeled.

In addition, in the step of immersing the stretched film 10 in the dyeing tank 40 and the step of immersing the bonding portion 15 in the dyeing tank, substantially no stretching treatment is performed, which can be prevented from being caused by the stretching processing of the bonding portion 15. The occurrence of wrinkles. If wrinkles occur, it takes some time to resolve the wrinkles, so the manufacturing efficiency decreases. In the step of immersing in the cross-linking tank 50, an extension treatment may be applied as required.

The "substantially no stretching treatment" in the step of immersing in the dyeing tank 40 means that the stretching ratio in this step is 1.5 times or less with respect to the original length of the stretching film 10 provided to this step, preferably 1 Times (not extended).

In order to sufficiently increase the tension applied to the film and to perform the dyeing step without substantially performing the stretching treatment, the base film is preferably a polyolefin-based resin, a polyester-based resin, a (meth) acrylic resin, or a cellulose ester-based resin. Resins, polycarbonate resins, polyvinyl acetate resins, polyarylate resins, polystyrene resins, polyether fluorene resins, polyfluorene resins, polyamine resins, and polyimide resins Resin.

Next, a method of forming the joint portion 15 between the terminal portion 100 of the first film and the start portion 200 of the second film in step [b] of the dyeing step S30 will be described with reference to FIGS. 3 and 4. The method for forming the joint portion 15 is not particularly limited as long as the film is not easily peeled by dipping in the dyeing tank 40 or the cross-linking tank 50. For example, a double-sided tape (Adhesive layer film) bonding or using heat-sealed bonding to form the bonding Department 15. From the standpoint of not having to use a special machine, joining with double-sided tape is simpler and better. For the heat sealing system, a conventionally known device (heat sealing machine) can be used.

In the method of the present invention, since the stretching treatment is not required in the dyeing step S30, even if a particularly strong bonding method is not used, it is not easy to cause the film to be broken or peeled, and the occurrence of wrinkles is not easy to occur.

There is no particular limitation on the film bonding form in the bonding portion 15 of the terminal portion 100 of the first film and the starting end portion 200 of the second film. For example, as shown in FIG. 3, it can be formed by double-sided tape or heat sealing. One of the strip-shaped adhesive regions 15a is adhered for bonding, or as shown in FIG. 4, a plurality of adhesive regions 15a are provided.

For the film roll switching in step [b], a conventionally known automatic paper receiving device such as a turret system can be used. In addition, there are also devices on the market that integrate the automatic paper receiving device and the heat sealer, and the device can also be used appropriately.

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 the first film and the second film are both the stretched film 10 is explained, but it is not limited to this. Any one of the first film and the second film is the stretched film 10. One is a guide membrane.

The guide film is a film for holding a transport path (line of production path), and is a film that passes through the transport path (temporarily placed on the transport path) before the dyeing step S30 is started or when the dyeing step S30 is interrupted. When the dyeing step S30 is interrupted, the guide film is passed through the conveying path, and the dyeing step after the interruption can be performed. When S30 is restarted, it is not necessary to perform the operation of re-transmitting the stretched film 10 through the transport path again.

As described above, on the conveying path of the dyeing step S30, a chemical tank (such as a heated chemical tank) may be provided, such as a dyeing tank 40, a crosslinking tank 50, or a high-temperature drying furnace. Therefore, after the interruption of the dyeing step S30, since the operation of re-passing the stretched film 10 is performed again from the beginning, the medicine must be discharged from the liquid tank, the guide roller forming the transport path must be operated, or the drying furnace must be turned on. Tedious homework and so on. If this operation is carried out, in addition to the time for the membrane to pass again, it will take an extremely long time to return the temperature of the chemical tank or the temperature of the drying furnace to a stable state again, which will significantly reduce the manufacturing efficiency.

In order to stop the line transportation while the guide film is passing through the conveying path, the conveying path in the dyeing step S30 can be directly maintained for a long time, so when the dyeing step S30 is restarted, it is not necessary to discharge the medicine or make the guide roller Action, or open the door of the drying tank. Therefore, when the dyeing step S30 is restarted, the time for making the transport path to a stable state can be significantly shortened, and the process can be restarted smoothly.

The guide film is preferably a film which is inexpensive, is not easily broken, does not easily generate wrinkles, and is not easily corroded even when immersed in a chemical solution for a long time. Specifically, it is preferable to use stretched polyethylene terephthalate, stretched polypropylene film, or the like. The guiding film does not necessarily have to be a stretched film, but by applying the stretching treatment, the tear resistance or heat resistance of the film can be improved, and characteristics suitable for the guiding film can be easily obtained. In addition, if the stretching process is performed, the film area will increase, so the film after the stretching process is roughly Cheaper than unextended.

It is not good to use the stretched film 10 obtained in the stretching step S20 as a guide film. If the stretched film 10 is used as the guide film, the loss of the stretched film 10 is increased, which is disadvantageous in terms of manufacturing cost. In addition, if the film conveyance is stopped for a long time while the stretched film 10 is passed through the conveyance path, the polyvinyl alcohol-based resin layer will gradually dissolve in a medicine tank such as a dyeing tank and contaminate the medicine tank.

Therefore, when the first film and the second film used in the dyeing step S30 are both the stretched film 10, not one of the films is used as a guide film, but the stretched film 10 of both sides that are joined is dyed. In step S30, the polarizing laminated film 20 is obtained.

On the other hand, when the first film is the stretch film 10 and the second film is the guide film, for example, in order to interrupt the dyeing step S30, the terminal portion of the stretch film 10 before the interruption is joined to the guide film and directly follows The transport path transports the joint and passes the guide film through the transport path. When the first film is the guide film and the second film is the stretch film 10, for example, the stretch film 10 is bonded to the terminal portion of the guide film from the interrupted state of the guide film through the transport path to restart the dyeing step S30 Situation. At this time, the second portion is further transported along the transport path and the second film is dyed to obtain a polarizing laminated film 20.

After the dyeing step S30, it is preferable to provide a drying step for drying the obtained wet polarized laminated film. The drying step can be performed by any appropriate method such as natural drying, air drying, and heating drying. For example, when heating and drying, the drying temperature is generally 20 to 95 ° C, and the drying time is It usually takes 1 to 15 minutes. The polarizing laminated film 20 obtained as described above can be directly used as a polarizing element (polarizing plate), and also can be used as a manufacturing intermediate for manufacturing the polarizing plate described later including a polarizer layer and a protective film.

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

(Manufacturing method of polarizing plate>

According to the polarizing laminated film obtained by the manufacturing method described above, according to the flowchart shown in FIG. 5, a protective film is attached to the polarizer layer of the polarizing laminated film to obtain a laminating step. S40; and a peeling step S50 of peeling and removing the base film from the bonding film; forming a polarizing plate with a protective film bonded on the polarizer layer. The laminated body containing the base film, the polarizer layer, and the protective film obtained by laminating step S40 without performing the peeling step S50 may be used as a polarizing plate.

[4] Laminating step S40

This step is a step of attaching the protective film to the polarizer layer of the polarizing laminated film, that is, attaching the protective film to the surface of the polarizer layer opposite to the substrate film side to obtain a laminating film. The protective film can be bonded to the polarizer layer using an adhesive or an adhesive. When the polarizing laminated film has polarizer layers on both sides of the base film, a protective film is generally attached to each of the double-sided polarizer layers. In this case, the protective films may be the same type of protective films or may be different types of protective films.

(Protective film)

The protective film may be, 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 triacetate; or a fiber. Cellulose diacetate-like resin; polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate-based polyester resin; polycarbonate resin ; (Meth) acrylic resin; or a film made of such mixtures, copolymers, and the like. Examples of commercially available products such as cyclic polyolefin resin and the film, and cellulose triacetate are as described above.

The protective film may also be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a resin film composed of the above-mentioned materials may be stretched (uniaxially stretched or biaxially stretched), or a liquid crystal layer may be formed on the film, thereby constituting a retardation film that gives an arbitrary retardation value.

An optical layer such as a hard coat layer, an anti-glare layer, or an anti-reflection layer may be formed on the surface of the protective film on the side 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 generally known method can be used. The optical layer may be formed on the protective film in advance before the bonding step S40 is performed, or may be formed after the bonding step S40 is performed or after the peeling step S50 described later is performed.

When the protective film is bonded to the polarizer layer, on the side surface of the polarizer layer of the protective film, in order to improve the adhesion with the polarizer layer, plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) ) Treatment, saponification treatment, and other surface treatments (easy-adhesion treatment), it is preferable to perform plasma treatment, corona treatment, or saponification treatment. For example when the protective film consists of a ring When the resin composition is formed into a polyolefin resin, a plasma treatment or a corona treatment is generally performed. In addition, when composed of a cellulose ester resin, a saponification treatment is generally performed. Examples of the saponification treatment include a method of immersing in an alkali 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 is reduced and the workability is deteriorated. On the other hand, if it is too thick, problems such as a decrease in transparency or an increase in the curing time required after bonding may occur. Therefore, the thickness of the protective film is preferably 90 μm or less, more preferably 5 to 60 μm, and even 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, particularly preferably 90 μm or less, and more 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 composed of an aqueous solution of a polyvinyl alcohol resin, an aqueous two-liquid urethane-based emulsified adhesive, and the like. In particular, when a cellulose ester-based resin film subjected to a surface treatment (hydrophilization treatment) by a saponification treatment or the like is used as a protective film, a water-based adhesive composed of a polyvinyl alcohol-based resin aqueous solution is preferably used.

In addition to the polyvinyl alcohol homopolymer obtained by saponifying the polyvinyl acetate monopolymer of polyvinyl acetate, the polyvinyl alcohol resin can also be used for vinyl acetate and other monomers copolymerizable therewith. A polyvinyl alcohol-based copolymer obtained by saponifying the copolymer, or a modified polyvinyl alcohol-based copolymer in which the hydroxyl groups are partially modified. Water-based adhesives may contain polyaldehydes, water-soluble epoxy compounds, and melamine-based compounds Compounds, zirconium compounds, zinc compounds and other additives. When a water-based adhesive is used, the thickness of the adhesive layer thus obtained is generally 1 μm or less.

The water-based adhesive is coated on the polarizer layer and / or the protective film of the polarizing laminated film, and these films are bonded via the adhesive layer. It is preferable to press and use a bonding roller and the like. It is made tight to perform the bonding step. The coating method of the water-based adhesive (the same applies to the photocurable adhesive) is not particularly limited, and a vertical flow method, a wire rod coating method, a gravure coating method, a notch wheel coating method, and a doctor blade can be used. Conventionally known methods such as a die coating method, a die coating method, a dip coating method, and a spray method.

When a water-based adhesive is used, it is preferable to perform a drying step for removing the water contained in the water-based adhesive and drying the film after the above-mentioned bonding is performed. The drying system can be performed, for example, by introducing the film into a drying furnace. The drying temperature (temperature of the drying furnace) is preferably 30 to 90 ° C. When it does not reach 30 degreeC, there exists a tendency for a protective film to peel easily from a polarizer layer. In addition, when the drying temperature exceeds 90 ° C., there is a concern that the polarization performance of the polarizer layer is deteriorated due to heat. The drying time can be set to 10 to 1000 seconds, and from the viewpoint of productivity, it is preferably 60 to 750 seconds, and particularly preferably 150 to 600 seconds.

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

The photocurable adhesive refers to an adhesive that is cured by irradiating active energy rays such as ultraviolet rays, and examples thereof include those containing a polymerizable compound and a photopolymerization initiator, those containing a photoreactive resin, and those containing a binder. Resin and photoreactive crosslinker. Examples of polymerizable compounds A photopolymerizable monomer such as a photocurable epoxy-based monomer, a photocurable acrylic-based monomer, a photocurable urethane-based monomer, or an oligomer derived from the photopolymerizable monomer. Examples of the photopolymerization initiator include those containing an active energy ray irradiated with an ultraviolet ray or the like to generate an activated substance such as a neutral radical, an anionic radical, or a cationic radical. As the photocurable adhesive containing a polymerizable compound and a photopolymerization initiator, a photocurable epoxy-based monomer and a photocationic polymerization initiator are preferably used.

When a photocurable adhesive is used, after the above-mentioned bonding is performed, a drying step (when the photocurable adhesive contains a solvent, etc.) may be performed as necessary, and then light is irradiated with active energy rays. Hardening step of hardening adhesive. The light source of the active energy ray is not particularly limited, and preferably an active energy ray having a luminous distribution below a wavelength of 400 nm. Specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, and an ultra-high-pressure mercury lamp are preferably used , Chemical lamp, black lamp, microwave excited mercury lamp, metal halide lamp, etc.

The light irradiation intensity of the photocurable adhesive can be appropriately determined depending on the composition of the photocurable adhesive, and it is preferable that the irradiation intensity in the wavelength region effective for activation of the polymerization initiator is 0.1 to 6000mW / cm ² of the embodiment is set. When the irradiation intensity of 0.1mW / cm ² or more, the reaction time is not too long, when 6000mW / cm ² or less, because when the heat radiated from the heat source and a light-curing bonding agent in the curing caused by There is little doubt about yellowing of the photocurable adhesive or deterioration of the polarizer layer.

The light irradiation time to the photocurable adhesive may be appropriately determined depending on the composition of the photocurable adhesive, and it is preferable that the total light amount expressed by the product of the above-mentioned irradiation intensity and irradiation time is 10 to 10000mJ / cm ² of the embodiment is set. When the accumulated light quantity is 10mJ / cm ² or more, can be sufficiently generated from the active material of the photopolymerization initiator, the curing reaction more reliably performed, when 10000mJ / cm ² or less, the irradiation time is not too long, can be maintained Good productivity.

The thickness of the adhesive layer after active energy ray irradiation is generally 0.001 to 5 μm, preferably 0.01 to 2 μm or less, and more preferably 0.01 to 1 μm.

(Adhesive)

Adhesives that can be used for the adhesion of protective films generally consist of an acrylic resin, a styrene resin, a polysiloxane resin, or the like as a matrix, and an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. It is composed of an adhesive composition of a crosslinking agent. It may be configured as an adhesive layer further containing fine particles to express light scattering properties.

The thickness of the adhesive layer may be 1 to 40 μm, and as long as the processability and durability are not impaired, thin coating is preferable, and specifically, 3 to 25 μm is preferable. It has a thickness of 3 to 25 μm, has good processability, and is also suitable for suppressing the dimensional change of the polarizer layer. When the adhesive layer is less than 1 μm, the adhesiveness is reduced, and when it exceeds 40 μm, it is easy to cause the loss of the adhesive such as bleeding. In the method of bonding the protective film to the polarizer layer using an adhesive, the adhesive layer may be mounted on the protective film surface and then bonded to the polarizer layer, or the adhesive layer may be mounted on the polarizer layer. Then, attach the protective film.

The method for forming the adhesive layer is not particularly limited. An adhesive composition (adhesive solution) containing each component including the above matrix polymer is coated on a protective film surface or a polarizer layer, and dried to form an adhesive layer, and then the protective film and the polarizer layer are bonded, Alternatively, after the adhesive layer is formed on the separator (release film), the adhesive layer is transferred to the protective film surface or the polarizing film surface, and then the protective film and the polarizer layer are bonded together. When the adhesive layer is formed on the surface of the protective film or the polarizer, the surface of the protective film or the surface of the polarizer or one or both sides of the adhesive layer may be subjected to surface treatment, such as corona treatment, as required.

[5] Stripping step S50

This step is a step of peeling and removing the base film from the bonding film obtained by bonding the protective film. After this step, a polarizing plate with a protective film and no base film laminated on the polarizer layer can be obtained. When the polarizing laminated film has polarizer layers on both sides of the base film, and a protective film is attached to the polarizer layers of these two, by peeling off step S50, one polarizing laminated film can be obtained. 2 polarizing plates.

The method for peeling and removing the base film is not particularly limited, and it can be peeled in the same manner as the peeling step of a separator (release film) performed by a polarizing plate with an adhesive generally attached. The base film can be peeled off immediately after the bonding step S40, or after the bonding step S40, it can be rolled up into a roll shape and peeled off after being rolled out in the subsequent steps.

The polarizing plate manufactured as described above can also be used as an optical film laminated with other optical layers in actual use. In addition, the protective film may also function as such an optical layer. Examples of other optical layers include: a type of polarized light that can penetrate and exhibits the opposite property Reflective reflective polarizing film; film with anti-glare function on the surface with concave and convex shape; film with anti-reflection function on the surface; reflective film with reflective function on the surface; semi-transparent reflection with both reflection function and transmission function Film; viewing angle compensation film, etc.

It is equivalent to a commercially available reflective polarizing film that can penetrate a certain type of polarized light and reflect the polarized light of the opposite property. For example, "DBEF" (manufactured by 3M Corporation, available from Sumitomo 3M in Japan) Co., Ltd.), "APF" (manufactured by 3M, available in Japan from Sumitomo 3M Co., Ltd.).

Examples of the viewing angle compensation film include an optical compensation film coated with a liquid crystal compound on the surface of the substrate, aligned and fixed, a retardation film made of a polycarbonate resin, and a cyclic polyolefin resin. Retardation film, etc.

Commercial products equivalent to optical compensation films that are coated with a liquid crystal compound on the substrate surface and aligned and fixed include "WV Film" (manufactured by Fuji Film Co., Ltd.) and "NH Film" (JX Nippon Oil and Energy Co., Ltd.), "NR Film" (JX Nippon Oil and Energy Co., Ltd.), etc.

Examples of commercially available products equivalent to a retardation film made of a cyclic polyolefin resin include "ARTON Film" (made by JSR Corporation), "S-SINA" (made by Sekisui Chemical Industry Co., Ltd.), "ZEONOR Film" (manufactured by Zeon Corporation).

Examples

Hereinafter, the present invention will be described more specifically by showing examples. The invention is not limited to these examples.

<Example 1>

(1) Production of substrate film

A three-layer structured long base film is produced by co-extrusion molding using a multilayer extrusion molding machine; and the three-layer structure long base film is made of a propylene monomer "Sumitomo Nobrene" FLX80E4 ", melting point Tm = 163 ° C) resin layer composed of an ethylene / propylene random copolymer (" Sumitomo Nobrene W151 "manufactured by Sumitomo Chemical Co., Ltd., containing about 5 wt% of ethylene units, melting point Tm = 138 ° C) on both sides of the resin layer. The 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 degree of polymerization 1100, average degree of saponification 99.5 mole%) was dissolved in hot water at 95 ° C to prepare a 3% by weight Polyvinyl alcohol aqueous solution. A cross-linking agent ("Sumirez Resin 650" made by Taoka Chemical Industry Co., Ltd.) was mixed with the obtained aqueous solution at a ratio of 5 parts by weight to 6 parts by weight of the polyvinyl alcohol powder to obtain a primer layer-forming coating. Cloth fluid.

Corona treatment was applied to the one side while the base film produced in (1) was continuously conveyed, and the coating solution for forming the primer layer was continuously applied to the corona using a microgravure coater. The treated surface was dried at 80 ° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm. In addition, the other side of the substrate film was also subjected to a corona treatment, and a primer layer having a thickness of 0.2 μm was formed on the corona treated surface in the same manner as described above to obtain a primer on both sides. Layer of substrate film.

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

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

While continuously conveying the base film having the primer layer on both sides produced in the above (2), the coating liquid for forming a polyvinyl alcohol-based resin layer was continuously applied to a substrate using a die lip coater. The surface of the primer layer was dried at 80 ° C for 2 minutes, then at 70 ° C for 2 minutes, and then at 60 ° C for 4 minutes, thereby forming a polyvinyl alcohol-based resin layer on the primer layer. In addition, a polyvinyl alcohol-based resin layer was formed on the surface of the other primer layer in the same manner as described above, thereby obtaining a laminated film. The thickness of the polyvinyl alcohol-based resin layer of the laminated film was 10.5 μm and 10.2 μm, respectively.

(4) Production of stretch film (stretching step)

While continuously transporting the laminated film produced in the above (3), using a roll-to-roll stretching device, a free end sheet was applied in a longitudinal direction at a stretching temperature of 160 ° C (ambient temperature in a heating furnace) at a magnification of 5.8 times. The shaft is stretched, a stretched film is continuously produced, and then sequentially wound up to obtain a film roll of the stretched film. The thickness of the two polyvinyl alcohol-based resin layers of the stretched film was 5.1 μm and 4.9 μm, respectively.

The steps (1) to (4) described above are repeated to produce a total of 2 rolls of stretched film rolls.

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

The conveying path (production line path) for performing the dyeing step includes a first washing tank between the dyeing tank 40 and the cross-linking tank 50, and a second washing tank after the cross-linking tank 50. In other cases, the same device as in FIG. 2 was used to perform the dyeing step to produce a polarizing laminated film. A drying furnace is installed on the downstream side of the second washing tank. Therefore, the stretched film transported along this transport path passes through the dyeing tank 40, the first cleaning tank, the cross-linking tank, the second cleaning 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. of 0.35 parts by weight of iodine per 100 parts by weight of water and 10 parts by weight of potassium iodide. In the cross-linking tank 50, a cross-linking solution 51 at 75 ° C. containing 9.5 parts by weight of boric acid per 5 parts by weight of water and 5 parts by weight of potassium iodide was contained. In the first and second washing tanks, pure water at 10 ° C was stored. In the drying furnace, the temperature in the furnace was adjusted to 80 ° C.

Specifically, the dyeing step is performed in the following manner to produce a polarizing laminated film. First, from one of the stretched film rolls produced in the above (4), the stretched film as the first film is continuously rolled out and continuously conveyed along the conveying path, so that the first film is sequentially sequentially Implementation: Dyeing treatment of the polyvinyl alcohol-based resin layer in the dyeing tank 40 by immersion (retention time: 150 seconds), washing with excess dyeing solution in the first washing tank by immersion (retention time: 4 seconds) The first washing treatment is performed by dipping (retention time: 600 seconds) in the crosslinking tank 50, and the dipping (retention time: 4 seconds) is performed by removing excess crosslinking solution in the second washing tank. The second washing treatment is a drying treatment that passes through a drying furnace (residence time: 300 seconds).

Extending with another stretch film roll made in (4) above The film was used as the second film.

When the unwinding of the first film from the film roll is nearing the end, in a state in which the transport of the first film is temporarily stopped, a double-sided tape is used, as shown in FIG. After the terminal portion of the first film and the start portion of the second film are joined, the transport of the film is restarted, and then the joint portion of the first film and the second film is continuously transported along the transport path, and the second The film is thereby subjected to a dyeing treatment, a first washing treatment, a crosslinking treatment, a second washing treatment, and a drying treatment up to the terminal portion of the second film. The tension applied to the film conveyed along the conveyance path was measured near the dyeing tank 40, and it was 125 N / m.

<Example 2>

A polarizing laminated film was produced in the same manner as in Example 1 except that the tension applied to the film transported along the transport 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 transported along the transport path was changed to 1000 N / m.

<Example 4>

A polarizing laminated film was produced in the same manner as in Example 3 except that a guide film composed of a biaxially stretched polypropylene film rolled out from a film roll was used as the first film.

<Example 5>

Except for using a guide film composed of a biaxially stretched polypropylene film rolled out from a film roll as the second film, it was produced in the same manner as in Example 3. Make a polarizing laminated film.

<Example 6>

A polarizing laminated film was produced in the same manner as in Example 3, except that the terminal portion of the first film and the starting portion of the second film were joined by heat sealing so as to have two band-shaped adhesive regions 15a.

<Example 7>

A polarizing laminated film was produced in the same manner as in Example 6 except that a guide film composed of a biaxially stretched polypropylene film rolled out from a film roll was used as the first film.

<Example 8>

A polarizing laminated film was produced in the same manner as in Example 6 except that a guide film composed of a biaxially stretched polypropylene film rolled out from a film roll was used as the second film.

<Comparative Example 1>

In addition to using a film roll of a single-layer film ("VF-PS 7500" made by Kuraray Co., Ltd.) made of polyvinyl alcohol instead of the roll of the stretched film produced in (1) to (4) of Example 1 The film rolls as the first and second films are longitudinally uniaxially stretched so that the total stretching ratio becomes 5.0 times in the dyeing tank 40 and the cross-linking tank 50, and have a single tape-shaped adhesive region 15a. The method is the same as in Example 1 except that the terminal portion of the first film and the start portion of the second film are joined by heat sealing, and the tension applied to the film to be transported along the transport path is changed to 400 N / m. A polarizing laminated film was produced.

<Comparative Example 2>

Except for joining the first film with two band-shaped adhesive regions 15a A polarizing laminated film was produced in the same manner as in Comparative Example 1 except for the terminal portion of the second film and the starting portion of the second film.

[Evaluation of continuous manufacturability and evaluation of polarizing performance of polarizing laminated film]

(Evaluation of continuous manufacturing)

For each Example and Comparative Example, the continuous manufacturability of the polarizing laminated film was evaluated according to the following evaluation criteria. The results are shown in Table 1.

A: Between the dyeing step, no breaks, peeling, or wrinkles were observed at the joint between the first film and the second film, and the first film and the film can be continuously transported along the transport path of the dyeing step without problems. The second film bonded to this makes it possible to continuously manufacture a polarizing laminated film.

B: In the implementation of the dyeing step, cracks, peeling of the joint portion, and wrinkles of the joint portion were observed on the film. It is difficult to say that the polarizing laminated film can be continuously manufactured without problems.

(Evaluation of polarizing performance of polarizing laminated film)

For the polarized laminated films obtained in each example, the polarization performance (light-emitting factor-corrected monomer transmittance and light-factor-corrected polarization) of the film portion near the junction between the first film and the second film was measured, The polarization performance of the film portion of the joint was compared and evaluated based on the following evaluation criteria. The results are shown in Table 1. The film portions near the joint portion are the portions after the joint portion in Examples 4 and 7 using the guide film as the first film, and the embodiments 5 and 8 using the guide film as the second film are the joint portion. The front film portion, for other embodiments, is the film portion before and after the joint.

A: The polarization performance of the film portion near the junction is equivalent to the polarization performance of the film portion far from the junction.

B: The polarization performance of the film portion in the vicinity of the bonding portion is significantly lower than that of the film portion away from the bonding portion.

The luminous factor correction monomer transmittance and the luminous factor correction polarization of the polarizing laminated film are obtained by using an adhesive tape to peel off and remove one of the polarizer layers on one of the two polarizer layers on the base film. As a measurement sample, a spectrophotometer "V7100" manufactured by Japan Spectroscopy Co., Ltd. was used, and the measurement was performed by making light incident from a polarizer layer.

As shown in Table 1, in Examples 1 to 8, even if the joint portion of the first film and the second film is transported along the transport path for performing the dyeing step, no film breakage, Delamination, wrinkles, etc. are missing, and a polarizing laminated film can be continuously manufactured. In Examples 1 to 8, in addition to the dyeing solution 41, the joint portion was immersed in the cross-linking solution 51 at a high temperature of 76 ° C. However, even if the joint portion was immersed in such a chemical solution that easily deformed, it did not occur Break and peel. In addition, in Examples 2 to 8, as compared with Example 1, the dyeing step was performed under the condition that the tension applied to the film was increased and film breakage was more likely to occur, but film breakage or peeling did not occur. Furthermore, in Examples 1 to 8, the polarization performance in the vicinity of the bonding portion of the polarizing laminated film was equivalent to the polarization performance in the portion far from the bonding portion, and no reduction in polarization performance due to bonding was observed. The film loss is suppressed to less than 1m.

On the other hand, in Comparative Examples 1 and 2 in which an unstretched polyvinyl alcohol monolayer film is provided to the dyeing step and the stretching process is performed in the dyeing step, the stretching process in the dyeing tank 40 is generated at the joint portion. Rupture of the membrane.

In Examples 2 to 8, the tension applied to the film was larger than that of Comparative Examples 1 and 2. However, since polypropylene-based resin was used as the base film, it did not extend 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 3% by weight aqueous polyvinyl alcohol solution. Take relative to polyvinyl alcohol powder 2 The weight part is a ratio of 1 weight part, and the crosslinking agent ("Sumirez Resin 650" made by Taoka Chemical Industry Co., Ltd.) was mixed with the obtained aqueous solution, and the adhesive aqueous solution was formed.

While continuously transporting the polarizing laminated film produced in Example 1, the above-mentioned aqueous adhesive solution was applied to the polarizer layer on both sides, and then a protective film of saponification treatment was applied to the bonding surface [from three A transparent protective film ("KC4UY" made by Konica Minolta Opto Co., Ltd., thickness 40 μm) made of acetyl cellulose (TAC) is laminated on the polarizer layer and borrowed between a pair of laminating rollers. This lamination is performed to produce a bonding film composed of a layer structure of TAC / polarizer layer / primer layer / base film / primer layer / polarizer layer / TAC (bonding step).

Next, the bonding film is peeled off and separated at the interface between the base film and the primer layer to obtain a film composed of TAC / polarizer layer / primer layer / base film, and a primer layer / polarizer layer After the polarizing plate composed of / TAC, the base film was peeled off from the former film and removed to obtain another polarizing plate. In the step of peeling the base film, no defects such as breakage occurred.

[Industrial use possibility]

According to the method of the present invention, the polarizing film provided to the dyeing step is a stretched film that is subjected to a stretching treatment for each base film and is fully stretched in advance. The immersion in the dyeing tank or the cross-linking tank can also suppress the deformation of the joint portion, and can effectively suppress the cracking or peeling of the film on the joint portion.

If it is comprised so that the film may not be substantially stretched in the step of immersing in a dyeing tank, the joining by the said immersion treatment can be suppressed more effectively The deformation of the portion can be prevented, and the occurrence of wrinkles caused by extending the joint portion can be prevented.

The continuous production of polarized laminated film will inevitably be accompanied by the switching of the film roll. With this, the joint between the preceding film and the succeeding film will inevitably be produced. However, according to the method of the present invention, the joint will not If the film is broken or peeled off, it can be directly passed through a general conveyance path (through a conveyance path such as a dyeing tank) for performing the dyeing step. Therefore, it is possible to continuously and efficiently manufacture a polarizing laminated film.

In addition, according to the method of the present invention, since a polarizer layer can be formed by application of a coating liquid, a polarizing laminated film and a polarizing plate including a thin film polarizer layer can be manufactured.

Claims (6)

A method for manufacturing a polarizing laminated film, comprising: sequentially forming a resin layer forming a laminated film by forming a polyvinyl alcohol resin layer on at least one side of a base film; and extending the laminated film to obtain an extension film. Step; and a dyeing step of forming a polarizer layer by conveying the stretched film along a conveying path passing through a dyeing tank containing a dichroic dye, thereby dyeing the polyvinyl alcohol-based resin layer of the stretched film with the dichroic dye. The dyeing step includes: a step of conveying the first film along the conveying path to be immersed in the dyeing tank; and a step of joining a terminal portion of the first film and a start portion of the second film to form a joint portion ; And a step of dipping in the dyeing tank by transporting the joint along the transport path; at least one of the first film and the second film is the stretched film, and the step of dipping in the dyeing tank In the above, the stretching film is not subjected to a stretching treatment, or when the stretching treatment is performed, the stretching ratio of the stretching treatment is 1.5 times or less. The method according to item 1 of the scope of patent application, wherein the transport path further passes through a cross-linking tank which is arranged behind the dyeing tank and contains a cross-linking agent. The method according to item 1 or 2 of the scope of patent application, wherein any one of the first film and the second film are the stretched films. The method according to item 1 or 2 of the scope of patent application, wherein any one of the first film and the second film is the stretched film, and the other is a guide film. The method according to item 1 or 2 of the scope of patent application, wherein in the aforementioned stretching step, the aforementioned laminated film is stretched at a stretching rate exceeding 5 times. The method according to item 1 or 2 of the scope of patent application, wherein the thickness of the polyvinyl alcohol-based resin layer of the laminated film is 3 to 30 μm.