TW201446484A - Method for producing polarizable laminated film and polarizing plate - Google Patents

Abstract

This invention provides a method for producing a polarizable laminated film comprising a step of coating a coating liquid containing a polyvinyl alcohol-based resin on a substrate film to obtain a laminated film; a step of stretching the laminated film to obtain an stretched film; and a step of dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichronic dye. The step of stretching comprises a first stretching step which is conducted to stretch the stretched film such that the first width residual ratio is 60% or more and less than 100%; and a second streching step which is conducted with an uni-axial stretching with a free end such that the second width residual ratio is smaller than the first width residual ratio. The present invention also provides a method for producing a polarizing plate comprising the polarizable laminated film obtained by using the above-mentioned method.

Description

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

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

The polarizing plate is widely used as a polarizing supply element in a liquid crystal display device and as a polarizing detecting element. Conventionally, a polarizing film has been mainly used as a polarizing film in which a protective film containing cellulose triacetate or the like is bonded to a polarizing film containing a polyvinyl alcohol resin via an adhesive, but in recent years, with a liquid crystal display device The research and development of mobile devices such as notebook PCs and mobile phones, and the development of large-scale televisions, require thinner and lighter polarizing plates.

Conventionally, a polarizing film is produced by stretching and dyeing an original film of a polyvinyl alcohol-based resin (generally having a thickness of about 75 μm), and the thickness of the film after stretching is generally about 30 μm. Further thinning is difficult because of the productivity problem such as the film tends to be broken when stretched.

In JP-A-2000-338329 (Patent Document 1), it has been proposed to apply a coating liquid containing a polyvinyl alcohol-based resin onto a thermoplastic resin film to form a polyvinyl alcohol-based resin layer. Extend A method in which the polyvinyl alcohol-based resin layer is a polarizing element layer of a film by uniaxial stretching and dyeing treatment at a magnification of 2 times or more and 5 times or less.

In the same manner as the method described in Patent Document 1, the coating liquid containing a polyvinyl alcohol-based resin is applied onto a thermoplastic resin substrate, as described in Japanese Patent No. 4751481 (Patent Document 2). After the polyvinyl alcohol-based resin layer is formed, it is stretched in the air, followed by dyeing treatment, followed by stretching in boric acid water to form the polyvinyl alcohol-based resin layer as a polarizing film.

According to the methods described in Patent Documents 1 and 2, a polyvinyl alcohol-based resin layer is formed on a substrate by coating as a dyed polarizer layer, and the obtained laminated film is The substrate is extended together, and thus is not only advantageous for thin film formation of the polarizer layer, but also extremely advantageous for thin film formation of the polarizing plate. However, there is still room for improvement in the polarizing performance of the resulting polarizer layer.

In other words, as for the method of improving the polarizing performance, it is conceivable to increase the stretching ratio in the stretching step. However, if only the stretching ratio is increased, even if it is advantageous for film formation, it is difficult to exhibit extremely excellent polarizing performance. Furthermore, extremely high stretching ratios cause production problems such as cracking of the film or extremely thin film width.

In view of the above, an object of the present invention is to provide a polarizing laminate film (a laminate of a base film and a polarizer layer) or a method for producing a polarizing plate, which comprises coating a coating liquid containing a polyvinyl alcohol resin. After the base film is formed into a polyvinyl alcohol-based resin layer to obtain a laminated film, This laminated film is subjected to stretching and dyeing treatment to form a polyvinyl alcohol-based resin layer as a polarizer layer. This method is a method for producing a polarizing laminated film or a polarizing plate excellent in polarizing performance.

The present invention provides the following means.

[1] A method for producing a polarizing laminated film, comprising the steps of: forming a resin layer forming step by applying a coating liquid containing a polyvinyl alcohol-based resin to at least one side of a base film; Drying to form a polyvinyl alcohol-based resin layer to obtain a laminated film; extending step of extending the laminated film to obtain a stretched film; and dyeing step of forming a polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye Dyeing to form a polarizer layer, thereby obtaining a polarizing laminated film; wherein the extending step sequentially includes the following steps: the first extending step is performed to extend the first width remaining as shown in the following formula (1) The rate R1 is 60% or more and less than 100%: the first width residual ratio R1 = film width after the first stretching step / film width before the first stretching step × 100 (%) (1); and the second stretching step And the second width residual ratio R2 shown by the following formula (2) is smaller than the first width residual ratio R1: the second width residual ratio R2 = the film after the second extension step Width / film width after the first extension step × 100 (%) (2).

[2] The method according to [1] above, wherein In the second extending step, the free end is uniaxially stretched so that the second width residual ratio R2 is 70% or less.

[3] The method according to the above [1] or [2] wherein the total stretching ratio of the extension of the laminated film is more than 5 times.

[4] The method according to any one of [1] to [3] wherein, in the first extending step, the heated roll is brought into contact with the laminated film to extend; In the second extension step, the extension is performed by extending in the air in a heated environment.

[5] The method according to any one of the above [1] to [4] wherein the polyvinyl alcohol-based resin layer of the laminated film has a thickness of 3 to 30 μm.

[6] The method according to any one of the above [1] to [5] wherein the base film comprises a polypropylene resin.

[7] A method of producing a polarizing plate, comprising the step of producing a polarizing laminated film by the method according to any one of the above [1] to [6], and bonding the protective film to the polarizing property. The step of obtaining a bonded film on the polarizer layer of the laminated film and the step of peeling the base film from the bonded film.

According to the method of the present invention, a polarizing laminate film or a polarizing plate excellent in polarizing performance can be produced.

1‧‧‧Hot roll

2‧‧‧guide roller

3‧‧‧1st nip roll

4‧‧‧2nd nip roll

10‧‧‧ laminated film

15‧‧‧film after the first extension step

20‧‧‧heating furnace

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

Fig. 2 is a side view showing an example of a method of extending a heat roller in a schematic manner.

Fig. 3 is a side view showing an example of a manner of extending between rolls in a heating furnace in a schematic manner.

Hereinafter, an embodiment will be described to explain in detail the method for producing the polarizing laminated film of the present invention and the method for producing the polarizing plate.

<Method for Producing Polarized Laminated Film>

Fig. 1 is a flow chart showing a preferred embodiment of a method for producing a polarizing laminate film of the present invention and a method for producing a polarizing plate. The method for producing a polarizing laminated film of the present embodiment includes the following steps [1] to [3] in order.

[1] Resin layer forming step S10, after applying a coating liquid containing a polyvinyl alcohol-based resin to at least one surface of a base film, and drying to form a polyvinyl alcohol-based resin layer, a laminated film is obtained.

[2] In the extending step S20, the laminated film is stretched to obtain a stretched film.

[3] Dyeing step S30, the polyvinyl alcohol-based resin layer of the stretched film is dyed with a dichroic dye to form a polarizer layer, thereby obtaining a polarizing laminated film.

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

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

[1] Resin layer forming step S10

This step is a step of forming a polyvinyl alcohol-based resin layer on at least one side of the base film to obtain a laminated film. This polyvinyl alcohol-based resin layer becomes a layer of a polarizer layer via the extending step S20 and the dyeing step S30. The polyvinyl alcohol-based resin layer can be formed by applying a coating liquid containing a polyvinyl alcohol-based resin to one surface or both surfaces of a base film and drying the coating layer. According to this method, since the thickness of the polyvinyl alcohol-based resin layer or even the polarizer layer can be made small, it is advantageous in that the polarizing laminated film and the polarizing plate are made thinner and lighter. In general, in the resin layer forming step S10, the substrate film is continuously wound up from the film roll of the long base film, and the film is continuously carried while being transported. Film transport can be carried out using a guide roller or the like.

(substrate film)

The base film may be composed of a thermoplastic resin, and is preferably composed of a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, and elongation. Specific examples of the thermoplastic resin include, for example, a polyolefin resin such as a chain polyolefin resin or a cyclic polyolefin resin (norbornene resin); a polyester resin; Acrylic resin; cellulose ester resin such as cellulose triacetate or cellulose diacetate; polycarbonate resin; polyvinyl alcohol resin; polyvinyl acetate resin; polyarylate Resin; polystyrene Resin; polyether oxime resin; polyfluorene resin; polyamine resin; polyimine resin; and mixtures, copolymers thereof, and the like.

The base film may have a single-layer structure including a single resin layer containing one or two or more kinds of thermoplastic resins, or a multilayer structure in which a resin layer containing one or two or more kinds of thermoplastic resins is laminated.

The chain-like polyolefin resin may, for example, be a copolymer of a chain olefin such as a polyethylene resin or a polypropylene resin, and may be a copolymer containing two or more kinds of chain olefins. The base film comprising a chain polyolefin resin is preferred because it is easily and stably extended at a high magnification. Among them, the base film is more preferably a polypropylene resin (a polypropylene resin belonging to a single polymer of propylene or a copolymer mainly composed of propylene) or a polyethylene resin (a polyethylene belonging to a single polymer of ethylene). Resin, or a copolymer mainly composed of ethylene).

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

Other monomers which can be copolymerized with propylene include, for example, ethylene and an α-olefin. As the α-olefin, it is preferred to use an α-olefin having 4 or more carbon atoms, more preferably an α-olefin having 4 to 10 carbon atoms. Specific examples of the α-olefin having 4 to 10 carbon atoms include, for example, a linear single such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, and the like. An olefin; a branched monoolefin such as 3-methyl-1-butene, 3-methyl-1-pentene or 4-methyl-1-pentene; vinylcyclohexane or the like. a copolymer of propylene and other monomers copolymerizable with the propylene, which may be a random copolymer or may be embedded Block copolymer.

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

Among the above, as the polypropylene-based resin, it is preferred to use a single polymer of propylene, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, or a random copolymer of propylene-ethylene-1-butene. Things.

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

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

The cyclic polyolefin-based resin is a general term for a resin in which a cyclic olefin is used as a polymerization unit. For example, JP-A No. 1-240517, JP-A No. 3-148882, and JP-A No. 3-122137 The resin described. Specific examples of the cyclic polyolefin-based resin include a ring-opened (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymerization of a cyclic olefin with a chain olefin such as ethylene or propylene. A material (typically a random copolymer), a graft polymer obtained by modifying an unsaturated carboxylic acid or a derivative thereof, and the like, and the like. among them, It is suitable to use a norbornene-based resin having a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer as a cyclic olefin.

Cyclic polyolefin resins are available in a variety of commercially available products. Examples of commercial products of the cyclic polyolefin resin include "Topas" (manufactured by TOPAS ADVANCED POLYMERS GmbH, available from Polyplastics Co., Ltd.), "ARTON" (manufactured by JSR Co., Ltd.), and "ZEONOR" ( "Manufactured by Japan ZEON Co., Ltd.", "ZEONEX" (manufactured by Japan ZEON Co., Ltd.), and "APEL" (manufactured by Mitsui Chemicals Co., Ltd.), all of which are trade names.

In addition, it is also possible to use "ESUSHINA" (made by Sekisui Chemical Co., Ltd.), "SCA40" (made by Sekisui Chemical Industry Co., Ltd.), "ZEONOR membrane" (made by Japan ZEON Co., Ltd.), etc. A commercially available product of a film-formed cyclic polyolefin resin film is used as a base film, and any of them is a trade name.

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

The polyester resin is a resin having an ester bond, and is generally a polycondensate containing a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a dibasic dicarboxylic acid or a derivative thereof can be used, and examples thereof include p-nonanoic acid, isodecanoic acid, dimethyl p-nonanoate, dimethyl naphthalene dicarboxylate, and the like. . As the polyol, a binary diol can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

A representative example of the polyester resin Polyethylene terephthalate with a polycondensate of ethylene glycol. The polyethylene terephthalate-based crystalline resin is preferably subjected to treatment such as stretching in a state before the crystallization treatment. If necessary, the crystallization treatment may be carried out by heat treatment at the time of stretching or extension. Further, a copolyester which copolymerizes another kind of monomer in the skeleton of polyethylene terephthalate to lower the crystallinity (or become amorphous) is also suitable. Examples of such a resin include, for example, a copolymer of cyclohexanedimethanol or isononanoic acid. Such a resin is applicable because it has excellent elongation.

Specific examples of the polyester-based resin other than the polyethylene terephthalate and the copolymer thereof include, for example, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polypyrene. Acid propylene diester, polybutylene naphthalate, poly(p-hexane dimethyl phthalate), polydimethylene naphthalate cyclohexane, and the like.

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

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

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

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose dipropionate, and the like. Further, those copolymers or a part of hydroxyl groups may be exemplified by other substituents. Among them, cellulose triacetate (cellulose triacetate) is particularly preferred. Cellulose triacetate is available in a variety of commercially available products and is also advantageous from the standpoint of availability or cost. Examples of commercial products of cellulose triacetate include "FUJITAC TD80" (manufactured by Fuji FILM Co., Ltd.), "FUJITAC TD80UF" (manufactured by Fuji FILM Co., Ltd.), and "FUJITAC TD80UZ" (Fuji FILM Co., Ltd.) Manufactured by the company, "FUJITAC TD40UZ" (manufactured by Fuji FILM Co., Ltd.), "KC8UX2M" (manufactured by Konica Minolta Opto Co., Ltd.), "KC4UY" (manufactured by Konica Minolta Opto Co., Ltd.), etc. All are trade names.

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

The polycarbonate resin is an engineering plastic containing a polymer obtained by bonding a monomer unit via a carbonic acid group, and is a resin having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate resin constituting the base film may be a resin called modified polycarbonate which has a polymer skeleton modified to reduce the photoelastic coefficient, or a copolymerization which has improved wavelength dependence. Carbonate and the like.

There are various commercially available products of polycarbonate resin. Examples of the commercially available polycarbonate resin are "Panlite" (manufactured by Teijin Chemical Co., Ltd.), "Iupilon" (manufactured by Mitsubishi Engineering Plastics Co., Ltd.), and "SD POLICA" (Sumitomo Dow Co., Ltd.) Any of the products manufactured by the company, "CALIBRE" (manufactured by Dow Chemical Co., Ltd.), etc., are all trade names.

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

Among them, from the viewpoints of elongation, heat resistance, etc., it is preferred to use a polyolefin resin, a polyester resin, a (meth)acrylic resin, or a polycarbonate resin, and more preferably a polypropylene resin. A resin or a polyester resin is particularly preferably a polypropylene resin.

In addition to the above thermoplastic resin, any appropriate additive may be added to the substrate film. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-colorants, flame retardants, nucleating agents, antistatic agents, pigments, and color formers. . The content of the thermoplastic resin in the substrate film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the base film is less than 50% by weight, the thermoplastic resin may not sufficiently exhibit the original high transparency and the like.

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

(coating liquid containing polyvinyl alcohol resin)

The coating liquid is preferably a polyvinyl alcohol-based resin solution obtained by dissolving a powder of a polyvinyl alcohol-based resin in a good solvent (for example, water). Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol resins and derivatives thereof. Examples of the derivative of the polyvinyl alcohol resin include, for example, polyvinyl formal, polyvinyl acetal, and the like, and examples thereof include a polyvinyl alcohol resin such as an olefin such as ethylene or propylene. Those who have been upgraded by upgrading with unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; those modified with alkyl esters of unsaturated carboxylic acids; and modified with acrylamide And so on. The ratio of the modification is preferably less than 30% by mole, more preferably less than 10% by mole. When the modification is performed in excess of 30 mol%, a problem that it becomes difficult to adsorb the dichroic dye and the polarizing performance is lowered may occur. Among the above polyvinyl alcohol-based resins, a polyvinyl alcohol resin is preferably used.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably in the range of from 100 to 10,000, more preferably in the range of from 1,000 to 10,000, still more preferably in the range of from 1,500 to 8,000, most preferably in the range of from 2,000 to 5,000. Average poly The degree of combination can be determined in accordance with the method specified in JIS K 6726-1994 "Testing methods for polyvinyl alcohol". When the average degree of polymerization is less than 100, it is difficult to obtain a preferable polarizing performance, and if it exceeds 10,000, the solubility in a solvent is deteriorated, and it becomes difficult to form a polyvinyl alcohol-based resin layer.

The polyvinyl alcohol-based resin is preferably a saponified product of a polyvinyl acetate-based resin. The degree of saponification 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 the moist heat resistance when the polarizing laminated film or the polarizing plate is formed may be insufficient. In addition, although it may be a completely saponified product (the degree of saponification is 100% by mole), if the degree of saponification is too high, the dyeing speed is slow, and the production time is prolonged in order to impart sufficient polarizing performance, and depending on the case, it may not be possible. A polarizer layer having sufficient polarizing properties is obtained. Therefore, the degree of saponification is preferably 99.5 mol% or less, and more preferably 99.0 mol% or less.

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

Degree of saponification (% by mole) = [(hydroxyl number) ÷ (hydroxyl number + number of acetate groups)] × 100

The higher the degree of saponification, the higher the ratio of the hydroxyl group, and therefore, the ratio of the acetate group which hinders crystallization is small. The degree of saponification can be determined in accordance with the method specified in JIS K 6726-1994 "Testing methods for polyvinyl alcohol".

The polyvinyl acetate-based resin may, for example, be a polyvinyl acetate which is a single polymer belonging to vinyl acetate, and may be, for example, a copolymer of vinyl acetate and another copolymerizable monomer. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

Examples of commercially available polyvinyl alcohol-based resins include "PVA124" manufactured by Kuraray Co., Ltd. (saponification degree: 98.0 to 99.0 mol%), and "PVA 117" (saponification degree: 98.0 to 99.0) Mohr%), "PVA 117H" (saponification degree: 99.5 mol% or more), "PVA 624" (saponification degree: 95.0 to 96.0 mol%) and "PVA 617" (saponification degree: 94.5 to 95.5 mol%) "AH-26" (saponification degree: 97.0 to 98.8 mol%), "AH-22" (saponification degree: 97.5 to 98.5 mol%), "NH-18" manufactured by Nippon Synthetic Chemical Industry Co., Ltd. (Saponification degree: 98.0 to 99.0% by mole) and "N-300" (saponification degree: 98.0 to 99.0% by mole); "JC-33" manufactured by Japan VAM & POVAL Co., Ltd. (saponification degree: 99.0) More than Mole), "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 mol%), either of which is a trade name.

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

(Coating of coating liquid and drying of coating layer)

The method of applying the coating liquid to the substrate film can be appropriately selected from the group consisting of a wire bar coating method, a reverse coating method, a gravure coating method, and the like; a die coating method; Die coating; comma coating; lip coating; spin coating; screen coating; fountain coating; A well-known method such as dipping or spray.

When the coating liquid is applied to both surfaces of the substrate film, each of the single faces may be sequentially applied by the above method, or both sides of the substrate film may be simultaneously coated by a dipping method or a spray coating method or other special device. .

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

The polyvinyl alcohol-based resin layer may be formed only on one surface of the base film or on both sides. When it is formed on both sides, film curl generated when a polarizing laminated film or a polarizing plate is produced can be suppressed, and two polarizing plates can be obtained from one polarizing laminated film, and therefore, the production efficiency of the polarizing plate is also For the benefit.

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

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

Further, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, a polyvinyl alcohol-based resin layer may be formed on the base film 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 the base film and then drying it. The coating liquid for forming a primer layer contains a component that exerts a certain degree of strong adhesion to both the base film and the polyvinyl alcohol-based resin layer. The coating liquid for forming a primer layer usually contains a resin component and a solvent which impart such an adhesive force. The resin component is preferably a thermoplastic resin which is excellent in transparency, heat stability, and elongation, and examples thereof include a (meth)acrylic resin and a polyvinyl alcohol resin. Among them, it is preferred to use a polyvinyl alcohol-based resin which imparts a good adhesion.

Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol resins and derivatives thereof. Examples of the derivative of the polyvinyl alcohol resin include, for example, polyethylene formaldehyde, polyvinyl acetal, and the like, and the polyvinyl alcohol resin is modified with an olefin such as ethylene or propylene; , methacrylic acid, crotonic acid and other unsaturated carboxylic acids are upgraded; Modified with a carboxylate alkyl ester; modified with acrylamide, etc. Among the above polyvinyl alcohol-based resins, a polyvinyl alcohol resin is preferably used.

As the solvent, a general organic solvent or an aqueous solvent which can dissolve the above resin component can be used. Examples of the solvent include aromatic hydrocarbons such as benzene, toluene, and xylene; ketones such as acetone, methyl ethyl ketone, and methyl isopropyl ketone; and esters such as ethyl acetate and isobutyl acetate; Chlorinated hydrocarbons such as methyl chloride, trichloroethylene, and chloroform; alcohols such as ethanol, 1-propanol, 2-propanol, and 1-butanol. However, when the primer layer is formed by using the coating liquid for forming a primer layer containing an organic solvent, the base film may be dissolved. Therefore, it is preferred to select a solvent in consideration of the solubility of the base film. It is preferred to form a primer layer from a coating liquid using water as a solvent in consideration of the influence on the environment.

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 is appropriately selected from those known to the organic system and the inorganic system depending on the type of the thermoplastic resin to be used. Examples of the crosslinking agent include an epoxy group-based, isocyanate-based, dialdehyde-based, and metal-based crosslinking agent.

As the epoxy group-based crosslinking agent, either one-liquid curing type or two-liquid curing type can be used, and examples thereof include ethylene glycol diepoxypropyl ether, polyethylene glycol diepoxypropyl ether, and glycerin di- Or tri-epoxypropyl ether, 1,6-hexanediol diepoxypropyl ether, trimethylolpropane triepoxypropyl ether, diepoxypropyl aniline, dipoxypropylamine, and the like.

Examples of the isocyanate crosslinking agent include toluene diisocyanate, hydrogenated diisocyanate, trimethylolpropane-toluene diisocyanate adduct, triphenylmethane triisocyanate, and triisocyanate. Acid methylene bis (4-phenyl group) Alkyl esters, isophorone diisocyanates, and ketone oxime blocks or phenolic blocks, and the like.

Examples of the dialdehyde crosslinking agent include glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, maleic aldehyde, and phthalaldehyde.

The metal-based crosslinking agent may, for example, be a metal salt, a metal oxide, a metal hydroxide or an organometallic compound. The metal salt, the metal oxide, and the metal hydroxide may, for example, have a valence of two or more valences such as magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, lanthanum, boron, zinc, copper, vanadium, chromium, or tin. Metal salts, oxides and hydroxides.

The organometallic compound refers to a compound having at least one structure in which a molecule 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 one or more valences of a carbon element, and may be, for example, an alkyl group, an alkoxy group, a fluorenyl group or the like. Further, the bonding does not mean only a covalent bond, but also a coordination bond by coordination of a chelate compound or the like.

Preferred examples of the organometallic compound include an organotitanium compound, an organozirconium compound, an organoaluminum compound, and an organic ruthenium compound. The organometallic compound may be used alone or in combination of two or more.

Examples of the organic titanium compound include titanium orthoester such as tetra-n-butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetrakis(2-ethylhexyl) titanate, and tetramethyl titanate. Titanium orthoester; titanium acetonide, titanium tetraacetate, titanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamine, titanium acetonitrile, etc. Chelates; titanium oxides such as titanium polyhydroxystearate.

Examples of the organic zirconium compound include zirconium n-propionate, zirconium n-butoxide, zirconium tetraethoxide, zirconium monoacetate, zirconium acetonate, ethyl zirconium acetonate, and ethyl acetate.

Examples of the organoaluminum compound include aluminum acetonate, an aluminum organic acid chelate, and the like. The organic ruthenium compound may, for example, be a compound in which the ligand exemplified in the above-mentioned organotitanium compound and organozirconium compound is bonded to ruthenium.

In addition to the above low molecular crosslinking agent, a polymer crosslinking agent such as a methylolated melamine resin or a polyamide resin may be used. For example, "SUMIREZ RESIN 650 (30)" or "SUMIREZ RESIN 675" (any of which is a trade name) sold by Takaoka Chemical Industry Co., Ltd., etc., may be mentioned as an example of the commercial product of the polyamide resin.

When a polyvinyl alcohol-based resin is used as the resin component for forming the primer layer, it is preferred to use a polyamide resin, a methylolated melamine resin, a dialdehyde crosslinking agent, and a metal chelate compound crosslinking agent. Etc. as a crosslinking agent.

The ratio of the resin component to the crosslinking agent in the coating liquid for forming a primer layer is from about 0.1 to 100 parts by weight based on 100 parts by weight of the resin component, depending on the kind or cross-linking of the resin component. The type of the agent may be appropriately determined, and it is particularly preferably selected from the range of about 0.1 to 50 parts by weight. Further, the coating liquid for forming a primer layer preferably has a solid content concentration of about 1 to 25% by weight.

The thickness of the primer layer is preferably from about 0.05 to 1 μm, more preferably from 0.1 to 0.4 μm. If it is thinner than 0.05μm, the substrate film and polyethylene The effect of improving the adhesion of the alcohol-based resin layer is small, and if it is thicker than 1 μm, it is disadvantageous for the film formation of the polarizing laminate film or the polarizing plate.

The method of applying the coating liquid for forming a primer layer to the substrate film may be the same as when the coating liquid for forming a polyvinyl alcohol-based resin layer is used. The primer layer is applied to a surface (on one surface or both surfaces of the substrate film) to which the coating liquid for forming a polyvinyl alcohol-based resin layer is applied. The drying temperature and drying time of the coating layer containing the coating liquid for forming a primer layer are set depending on the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C or higher. The drying time is, for example, 30 seconds to 20 minutes.

When the primer layer is provided, the order of application of the base film is not particularly limited. For example, when a polyvinyl alcohol-based resin layer is formed on both surfaces of the base film, a primer layer may be formed on both surfaces of the base film, and then on both sides. When the polyvinyl alcohol-based resin layer is formed, a primer layer or a polyvinyl alcohol-based resin layer may be sequentially formed on one surface of the base film, and then a primer layer or a polyvinyl alcohol-based resin may be sequentially formed on the other surface of the base film. Floor.

[2] Extension step S20

This step is a step of stretching a laminated film including a base film and a polyvinyl alcohol-based resin layer to obtain a stretched film. The extension step S20 in the present invention comprises a plurality of extensions. That is, the steps include the following steps: the first extending step is performed such that the first width residual ratio R1 is 60% or more and less than 100%; and the second extending step is performing the free end uniaxial stretching. The second width residual ratio R2 is made smaller than the first width residual ratio R1.

In this paper, the "first width residual ratio R1" is as follows (1) As shown in the figure, the "second width residual ratio R2" is expressed by the following formula (2).

The first width residual ratio R1 = the film width after the first stretching step 膜 the film width before the first stretching step × 100 (%) (1)

The second width residual ratio R2 = film width after the second stretching step 膜 film width after the first stretching step × 100 (%) (2)

In addition, the term "extension step is a plurality of extensions" means at least the following steps: a first-stage extension processing step of extending the laminated film; and a section (time zone) through the non-extended laminate film (not extending in the film transport direction) And extending the second step of the laminated film stretched by the first step to the second step. The extending step S20 may include three or more extension processing steps. In this case, a section (time zone) in which the laminated film does not extend is also interposed between the extension processing steps.

In the extending step S20, it is typically carried out while transporting the long laminated film or continuously rolling up the laminated film from the film roll of the long laminated film and transporting the laminated film. Film transport can be carried out using a guide roller or the like.

Conventionally, in order to improve the polarizing performance of the polarizer layer, it is preferable to carry out the film formation in order to highly orient the polymer chain of the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin layer. The free end of the wide direction is uniaxially extended. However, according to the present invention, it is known that the film width shrinkage is restricted to some extent by the uniaxial stretching at the free end (the second stretching step) (first extension step) It exhibits higher polarization performance than when only the free end uniaxial extension is performed.

(1st extension step)

The first stretching step is a step of stretching to minimize shrinkage of the laminated film width, and specifically, stretching is performed so that the first width residual ratio R1 defined above is 60% or more and less than 100%. The first width residual ratio R1 is preferably 62% or more, more preferably 65% or more. Further, the first width residual ratio R1 is preferably 95% or less, more preferably 90% or less, still more preferably 80% or less. By suppressing the shrinkage of the laminated film width and extending it, and making the first width residual ratio R1 60% or more, the effect of improving the polarizing performance can be obtained. When the first width residual ratio R1 is too high, the significance of providing the first stretching step tends to be small.

The extension in the first stretching step may be an extension method in which the film width shrinkage can be restricted by heat roller stretching, simultaneous biaxial stretching or calendering, and among them, a heat roller stretching method is preferred. In the heat roller stretching method, a heat roller 1 which is heated to a desired temperature which can be stretched by passing the laminated film 10 is described with reference to FIG. 2 which is an example of a schematic display, and heat is applied thereto. The roller 2 has a different rotation speed (greater than the rotation speed of the heat roller 1) between the guide roller 2 (or may be a heat roller), and in a heated state due to contact with the heat roller 1, in contact with the heat roller 1 Longitudinal uniaxial extension (on the hot roll 1) or adjacent to it. Further, the arrow on the laminated film 10 in Fig. 2 indicates the direction in which the film is conveyed.

Further, the method of extending the heat roller is not limited to the embodiment shown in Fig. 2 . For example, the heat roller 1 in FIG. 2 can be exchanged with the guide roller 2, and the number of revolutions of the heat roller 1 on the downstream side can be changed to be large, and the laminated film 10 can be transported, and the heat roller 1 on the downstream side can be brought into contact with the heat roller 1 on the downstream side. Extended processing.

A plurality of heat rollers 1 may also be provided to make the first extension step Extend for multiple segments. When a plurality of heat rolls 1 are provided, a preheating step to be described later can be carried out using a hot roll upstream of the heat roll for performing the first stretching step. Further, the heat setting treatment step after the first stretching step may be performed using a heat roller downstream of the heat roller for performing the first stretching step. The meaning or processing conditions regarding the heat setting treatment step are as described later.

Referring to Fig. 2, a heat roller 1 is provided instead of the guide roller 2, and an extension is performed between the two heat rollers 1 having different rotation speeds. At this time, in order to prevent the first width residual ratio R1 from being reduced as much as possible, it is preferable to shorten the distance between the two heat rollers 1.

In the heat roller stretching method, since the laminated film 10 is extended in the film transport direction on or near the heat roller 1 in a heated state, it is possible to restrict the contraction of the film width while extending. The first width residual ratio R1 in the heat roller extending mode can be adjusted according to the stretching ratio, and the stretching ratio can be adjusted according to the conveying speed of the laminated film 10, the surface temperature of the heat roller 1, the difference in the rotational speed of the heat roller 1 and the guide roller 2, and the like. . In the heat roller stretching method, generally, the higher the stretching ratio, the larger the first width residual ratio R1. This is because if the stretching ratio is higher, the contribution of the thickness reduction of the film to the stretching ratio becomes greater than the contribution of the reduction in the width of the film.

The stretching ratio B1 of the first stretching step is not particularly limited as long as the first width residual ratio R1 is 60% or more. However, in the case of the heat roller stretching method, it is usually 1.1 times or more, preferably 1.5 times or more. In addition, when the stretching ratio of the first stretching step is too high, the biaxiality is strong, and the orientation of the polymer chain of the polyvinyl alcohol-based resin is not sufficiently high. Therefore, the stretching ratio B1 of the first stretching step is usually 3.9 times or less, preferably 3.5 times or less. The extension ratio B1 of the first extension step is when the length of the laminated film 10 before the step S20 is extended (the film transport direction (longitudinal direction)) is 1 and the first extension step is completed. The length of the direction in which the film extends.

The elongation temperature of the first stretching step (the surface temperature of the heat roller in the case of the heat roller stretching method) is set to a temperature at which the polyvinyl alcohol-based resin layer and the base film as a whole have a degree of fluidity which is extensible, Preferably [the phase transition temperature of the substrate film (melting point or glass transition temperature) -30] ° C to the [phase transition temperature of the substrate film + 30] ° C range, more preferably [the phase transition temperature of the substrate film -30 The range from °C to [phase transition temperature of the substrate film + 5] ° C is more preferably in the range of [phase transition temperature of the substrate film - 25 ] ° C [phase transition temperature of the substrate film] ° C. When the base film contains a plurality of resin layers, the above phase transition temperature means the highest phase transition temperature among the phase transition temperatures exhibited by the plurality of resin layers.

When the stretching temperature is lower than [the phase transition temperature of the substrate film is -30] ° C, the fluidity of the base film is too low, and the stretching treatment tends to be difficult. When the stretching temperature exceeds [the phase transition temperature of the substrate film + 30] ° C, the fluidity of the base film is too large, and the stretching treatment tends to be difficult. In view of the easiness of the elongation treatment, the extension temperature is within the above range, and more preferably 120 ° C or more.

(2nd extension step)

In the second extending step, the step of performing the free end uniaxial stretching and the second width residual ratio R2 defined above is smaller than the first width residual ratio R1 is performed after the first extending step. For the free end uniaxial extension When the first stretching step for restricting the film width shrinkage is not performed before the second stretching step, as described above, the high polarization performance required by the present invention cannot be obtained, and the first stretching step is not performed and the second stretching step is not performed. When the second width residual ratio R2 becomes equal to or higher than the first width residual ratio R1, the high polarization performance required by the present invention cannot be obtained. In the first stretching step, the film is contracted in the width direction of the film to restrict shrinkage and stretching, so that the film has a stretching effect in the film width direction, and the polymer chain of the polyvinyl alcohol resin in the film transport direction is obtained. The orientation is not high enough. Therefore, in order to obtain excellent polarizing performance, the first extending step of the present invention and the second extending step step of reducing the film width shrinkage restriction are all necessary steps.

In the second stretching step, in order to improve the orientation of the polymer chain of the polyvinyl alcohol-based resin, in addition to satisfying R1 > R2, it is preferred to carry out uniaxial stretching at a small residual ratio. Specifically, the second width residual ratio R2 is preferably 70% or less, more preferably 68% or less, still more preferably 65% or less, and particularly preferably less than 60%. Further, when the second width residual ratio R2 is too low, the film width as a product is reduced, and the production efficiency is lowered. Therefore, the second width residual ratio R2 is preferably 40% or more, and more preferably 50% or more. When the second width residual ratio R2 exceeds 70%, the orientation of the polymer chain of the polyvinyl alcohol-based resin is not sufficiently high, and excellent polarizing performance cannot be obtained.

A preferred extension of the free end uniaxial extension in which the second width residual ratio R2 is smaller than the first width residual ratio R1 and preferably the second width residual ratio R2 is 70% or less is exemplified. Extends in the air in a heated environment. A typical example of this aerial extension is in a furnace. The inside of the roller extends. By extending between the rolls, the free end can be longitudinally uniaxially extended.

The inter-roller stretching method is carried out by transporting between two nip rolls provided at a distance, and by extending the difference between the two nip rolls. Referring to Fig. 3 which is an example of an example, and more specifically, the film 15 after the first stretching step is conveyed and sequentially passed through the first nip roll 3, the heating furnace 20, and the second nip roll. 4. The rotation speed of the second nip roll 4 is larger than that of the first nip roll 3. The film 15 after the first stretching step in which the heating furnace 20 is heated to a predetermined temperature is interposed between the first nip roll 3 and the second nip roll 4, and is longitudinally and uniaxially stretched by the difference in rotation speed. Further, the arrow on the film 15 after the first extending step in Fig. 3 indicates the direction in which the film is conveyed.

The heating furnace 20 includes, for example, a heating furnace heated by hot air, and an infrared heater, a halogen heater, and a plate heater which are provided on the upper and lower sides of the film to be transported and which are heated by radiant heat. (panel heater) heaters such as heaters. Further, the first and/or second nip rolls 3, 4 may be provided in the heating furnace 20, but are preferably disposed outside the heating furnace 20 in order to prevent adhesion of the film to the nip rolls.

In the inter-roller stretching mode, the second width residual ratio R2 can be adjusted according to the stretching ratio, and the stretching ratio can be based on the conveying speed of the film 15 after the first stretching step, the ambient temperature in the heating furnace 20, and the first nip rolls 3 and 2 The rotation speed difference between the nip rolls 4 is adjusted. In the inter-roller stretching method, generally, the second width residual ratio R2 is smaller as the stretching ratio is higher.

The extension ratio B2 of the second extension step is as long as 2 The width residual ratio R2 is not particularly limited as long as it is smaller than the first width residual ratio R1. However, it is usually 1.1 times or more, preferably 1.5 times or more, depending on the manner of stretching between rolls in the heating furnace. Further, if the stretching ratio B2 of the second stretching step is too high, the film width as a product is reduced, and the production efficiency is lowered. Therefore, the stretching ratio B2 of the second stretching step is usually 4 times or less, preferably 3 times or less. The stretching ratio B2 of the second stretching step is a film when the length of the film 15 in the direction in which the film 15 is extended after the first stretching step (the film transport direction (longitudinal direction)) is 1 and the film is finished at the end of the second stretching step. The length of the direction in which it extends.

The total stretching ratio of the stretching with respect to the laminated film 10 is preferably more than 5 times. When the stretching ratio is 5 times or less, since the polymer chain of the polyvinyl alcohol-based resin is not sufficiently oriented, the polarizing performance tends to be insufficient. Further, the total stretching ratio is preferably 8 times or less. If the total stretching ratio exceeds 8 times, the film is likely to be broken in any of the stretching steps, and the thickness of the stretching film may become thinner than the desired thickness, and the workability and handleability of the subsequent step may be lowered.

The "total stretching ratio" means the step of extending the extensions (as described later, the additional stretching processing may be performed in the dyeing step S30, and in this case, the additional stretching processing step is also included). The final stretching ratio, in other words, the length in the direction in which the film in which the stretching process is completed is the length when the length in the direction in which the laminated film 10 before the stretching step S20 is extended is taken as 1. For example, when the extending step S20 is constituted only by the first and second extending steps, and the additional extending process is not performed in the dyeing step S30, the total stretch ratio is B1 × B2.

The extension temperature of the second extension step (the ambient temperature when the air is extended in the heating environment, and the ambient temperature in the heating furnace when the air is extended between the rollers in the heating furnace) is the first The extension temperature of the extension step is the same, and the above-mentioned contents described in relation to the extension temperature of the first extension step are cited.

The extending step S20 may include an extending step other than the first and second extending steps. That is, an additional extension step may be included in the period selected from the first extension step, the first extension step, the second extension step, and the second extension step. However, even if the extending step S20 is composed only of the first and second extending steps, sufficiently excellent polarizing performance can be obtained.

In the extending step S20, the film may be taken up at the end of each step of the stretching step, and may be rolled out again when the stretching step of the next stage is performed, or the film may be taken up and unwound without continuous filming. Segment extension step.

A preheating step of preheating the laminated film may be provided before the extending step S20. As the preheating method, the same heating method as that between the rolls can be used. The preheating temperature is preferably in the range of [extension temperature - 50] ° C [extension temperature ± 0] ° C, more preferably in the range of [extension temperature - 40] ° C to [extension temperature - 10] ° C.

Furthermore, after the extension processing of the final stage of the step S20 is extended, a heat fixing processing step may be provided. The heat-fixing treatment is performed by heat treatment at a crystallization temperature or higher while maintaining the tension state while sandwiching the end portion of the stretched film with a clip. By this heat fixing treatment, The crystallization of the polyvinyl alcohol-based resin layer is promoted. The temperature of the heat setting treatment is preferably in the range of [extension temperature] °C to [extension temperature - 80] °C, more preferably in the range of [extension temperature] °C to [extension temperature - 50] °C.

[3] Dyeing step S30

In this step, the polyvinyl alcohol-based resin layer of the stretched film is dyed with a dichroic dye, and adsorbed and oriented to form a polarizer layer. Through this step, a polarizing laminated film having a polarizer layer on one side or two layers of the base film can be obtained. The dyeing step S30 is continuously performed while continuously transporting the stretched film of the long strip or continuously stretching the stretched film from the film roll of the elongated stretched film and transporting the film. Film transport can be carried out using a guide roll or the like.

Specific examples of the dichroic dye include iodine and a dichroic organic dye. Specific examples of the dichroic organic dye include, for example, red BR, red LR, red R, pink LB, rube BL, bordeaux GS, sky blue LG, lemon yellow, blue BR, blue 2R, Navy RY, Green LG, Purple LB, Purple B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Blush KGL, Congo Red, Bright Purple (brilliant violet) BK, supra blue G, turquoise GL, supra orange GL, direct sky blue, direct fast orange S, fast black, etc. The dichroic dye may be used alone or in combination of two or more.

The dyeing step can be carried out by immersing the entire stretched film in a solution (dyeing solution) containing a dichroic dye. As the dyeing solution, a solution in which the above dichroic dye is dissolved in a solvent can be used. About dyeing The solvent of the liquid is generally water, but an organic solvent compatible with the water can be further added. The concentration of the dichroic dye in the dyeing solution is preferably from 0.01 to 10% by weight, more preferably from 0.02 to 7% by weight, still more preferably from 0.025 to 5% by weight.

When iodine is used as the dichroic dye, since the dyeing efficiency can be further improved, it is preferred to further add the iodide to the iodine-containing dyeing solution. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The concentration of the iodide in the dyeing solution is preferably from 0.01 to 20% by weight. Among the iodides, potassium iodide is preferably added. When potassium iodide is added, the ratio of iodine to potassium iodide is in a weight ratio, preferably in the range of 1:5 to 1:100, more preferably in the range of 1:6 to 1:80, still more preferably 1:7 to 1 : 70 range.

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

Further, an additional stretching treatment may be applied to the stretched film in the dyeing step S30. In the above-described extension step S20, after the stretching process lower than the target magnification is applied, the dyeing process in the dyeing step S30 is performed to extend the total stretching ratio to the target magnification. In the state of the treatment, as described later, when the crosslinking treatment is performed after the dyeing treatment, 2) in the above-described stretching step S20, after performing at a lower than the target magnification, the stretching treatment is performed in the dyeing treatment in the dyeing step S30. Until the total stretch ratio is less than the target magnification, the state in which the final total stretch ratio is the extension process of the target magnification is performed in the cross-linking process.

The dyeing step S30 may include a crosslinking treatment step carried out subsequent to the dyeing treatment. The crosslinking treatment can be carried out by immersing the dyed film in a solution containing a crosslinking agent (crosslinking solution). As the crosslinking agent, a conventionally known one can be used, and examples thereof include a boron compound such as boric acid or borax, glyoxal, and glutaraldehyde. The crosslinking agent may be used alone or in combination of two or more.

Specifically, the crosslinking solution may be a solution in which a crosslinking agent is dissolved in a solvent. The solvent system may be, for example, water, or may contain an organic solvent compatible with the water. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of from 1 to 20% by weight, more preferably from 6 to 15% by weight.

The crosslinking solution can comprise an iodide. By the addition of iodide, the polarizing performance inside the surface of the polarizer layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The concentration of the iodide in the crosslinking solution is preferably from 0.05 to 15% by weight, more preferably from 0.5 to 8% by weight.

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

Further, the crosslinking treatment can be carried out simultaneously with the dyeing treatment by blending the crosslinking agent in the dyeing solution. Furthermore, it can also be cross-linked In the extension process. The specific state in which the elongation treatment is carried out in the crosslinking treatment is as described above.

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

The washing step may also be a combination of a water washing step and a washing step by an iodide solution. Further, the washing step used in the water washing step and/or the washing treatment by the iodide solution may contain methanol, ethanol, isopropanol, butanol or pentanol in addition to water. Such as liquid alcohols.

The drying step performed after the washing step may be any suitable method such as natural drying, air drying, and heat drying. For example, when heat drying is employed, the drying temperature is usually from 20 to 95 ° C, and the drying time is usually from about 1 to 15 minutes. The polarizing laminate film obtained as described above can be directly used as a polarizing member, and is also suitable as an intermediate for producing a polarizing plate including a polarizer layer and a protective film.

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

<Method of Manufacturing Polarizing Plate>

The method for manufacturing a polarizing plate of the present invention basically comprises the following steps in sequence Step: a step of producing the polarizing laminated film, a bonding film in which a protective film is bonded to a polarizer layer of a polarizing laminated film to obtain a bonding film, and a peeling step S50 of removing a substrate film from the bonding film . Further, the layered body including the base film, the polarizer layer, and the protective film obtained by the bonding step S40 may be used as the polarizing plate without performing the peeling step S50.

[4] Fitting step S40

In this step, the protective film is bonded to the polarizer layer of the polarizing laminate film, that is, the film is bonded to the surface of the polarizer layer opposite to the substrate film side to obtain a film. The protective film may be attached to the polarizer layer using an adhesive or an adhesive. When the polarizing laminated film has a polarizer layer on both surfaces of the base film, the protective film is usually bonded to the polarizer layers on both sides. In this case, the protective films may be the same kind of protective film, or may be different kinds of protective films.

(protective film)

The protective film may be a polyolefin resin such as a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a decylene resin); cellulose triacetate or cellulose diacetate; a cellulose ester resin; a polyester resin such as polyethylene terephthalate, polyethylene naphthalate or polybutylene terephthalate; a polycarbonate resin; or a (meth)acrylic resin; Films of such mixtures, copolymers, and the like. Examples of the commercially available products which can be used for the cyclic polyolefin resin and the film thereof, and cellulose triacetate are as described above.

The protective film may be a protective film having an optical function such as a retardation film or a brightness enhancement film. For example, by extending a resin film including the above material (uniaxial stretching or biaxial stretching, etc.), or forming a liquid crystal layer on the film Alternatively, it can be a retardation film that imparts an arbitrary phase difference value.

An optical layer such as a hard coat layer, an antiglare layer, or an antireflection layer may be formed on the surface of the protective film opposite to the polarizer layer. The method of forming the optical layers on the surface of the protective film is not particularly limited, and a known method can be used. The optical layer may be formed on the protective film before the bonding step S40 is performed, or may be formed after the bonding step S40 is performed or after the stripping step S50 is performed.

After bonding the protective film to the polarizer layer, in order to improve the adhesion to the polarizer layer, the surface of the polarizer layer of the protective film may be subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, etc. The treatment (easy to proceed) is preferably a plasma treatment, a corona treatment or a saponification treatment. For example, when the protective film contains a cyclic polyolefin-based resin, it is usually subjected to plasma treatment or corona treatment. Further, when a cellulose ester-based resin is contained, it is usually subjected to a saponification treatment. The saponification treatment may, for example, be a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

The thickness of the protective film is preferably thin, but if it is too thin, the strength is lowered and the workability is poor. On the other hand, when the thickness is too large, the transparency is lowered, and the curing time required after the bonding becomes long. Therefore, the thickness of the protective film is preferably 90 μm or less, more preferably 5 to 60 μm, still more preferably 5 to 50 μm. Further, from the viewpoint of film formation of the polarizing plate, the total thickness of the polarizer layer and the protective film is preferably 100 μm or less, more preferably 90 μm or less, still more preferably 80 μm or less.

(adhesive)

As the subsequent agent, a water-based adhesive or a photocurable adhesive can be used. Water connection Examples of the coating agent include an adhesive containing a polyvinyl alcohol resin aqueous solution, and an aqueous two-liquid urethane emulsion adhesive. In particular, when a cellulose ester-based resin film subjected to surface treatment (hydrophilization treatment) such as saponification treatment is used as the protective film, a water-based adhesive containing a polyvinyl alcohol-based resin aqueous solution is preferably used.

In the case of a polyvinyl alcohol-based resin, in addition to a vinyl alcohol homopolymer obtained by saponifying a polyvinyl acetate which is a separate polymer of vinyl acetate, vinyl acetate can be used and can be used together. The copolymer of the other monomer of the polymerization is subjected to a saponification treatment of the polyvinyl alcohol-based copolymer or a modified polyvinyl alcohol-based polymer obtained by modifying the hydroxyl group. The aqueous binder may include an additive such as a polyvalent aldehyde, a water-soluble epoxy compound, a melamine-based compound, a zirconia compound, or a zinc compound. When a water-based adhesive is used, the thickness of the obtained adhesive layer is usually 1 μm or less.

The water-based adhesive is applied onto the polarizer layer of the polarizing laminate film and/or the protective film, and the film is bonded through the adhesive layer, and is preferably pressure-bonded using a bonding roll or the like. This performs the bonding step. The coating method of the water-based adhesive (the same applies to the photocurable adhesive) is not particularly limited, and a casting method, a Meyer bar coating method, a gravure coating method, a comma coating method, and a doctor blade method can be used. A conventionally known method such as a doctor blade method, a die coating method, a dipping method, and a spray method.

When a water-based adhesive is used, it is preferred to carry out a drying step of drying the film in order to remove moisture contained in the aqueous adhesive after the above-mentioned bonding. The drying can be carried out, for example, by introducing the film into a drying oven. The drying temperature (temperature of the drying oven) is preferably from 30 to 90 °C. If it is less than 30 ° C, there is a tendency that the protective film is easily peeled off from the polarizer layer. Further, when the drying temperature exceeds 90 ° C, there is a fear that the polarizing performance of the polarizer layer is deteriorated by heat. The drying time may be from about 10 to 1,000 seconds, and from the viewpoint of productivity, it is preferably from 60 to 750 seconds, more preferably from 150 to 600 seconds.

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

The photocurable adhesive agent is an adhesive which is cured by irradiation with an active energy ray such as ultraviolet rays, and includes, for example, a polymerizable compound and a photopolymerization initiator, a photoreactive resin, and a binder resin. And photoreactive cross-linkers, etc. Examples of the polymerizable compound include a photopolymerizable monomer such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, or an oligomer derived from a photopolymerizable monomer. Things and so on. The photopolymerization initiator may be one which contains an active species such as a neutral radical, an anionic radical, or a cationic radical by irradiation with an active energy ray such as ultraviolet rays. A photocurable adhesive containing a polymerizable compound and a photopolymerization initiator can be suitably used in the case of a photocurable epoxy-based monomer and a photocationic polymerization initiator.

When a photocurable adhesive is used, after performing the above-described bonding, a drying step is performed as needed (in the case where a photocurable adhesive contains a solvent), and then photocuring is performed by irradiating an active energy ray. Hardening step of hardening of the agent. The light source of the active energy ray is not particularly limited, and is preferably an active energy ray having a luminescent distribution at a wavelength of 400 nm or less. Preferably, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light, a microwave excited mercury lamp, a metal halide lamp, or the like is used.

The light intensity of the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive, and it is preferable to set the irradiation intensity in a wavelength region effective for activation of the polymerization initiator to 0.1 to 6000 mW/cm. ² . When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time does not become too long, and when it is 6000 mW/cm ² or less, heat generated by the light source and heat generated by curing of the photocurable adhesive are less likely to occur. Yellowing of the photocurable adhesive or deterioration of the polarizer layer.

The light irradiation time of the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive, and it is preferable to set the integrated light amount indicated by the product of the irradiation intensity and the irradiation time to 10 to 10000 mJ/cm. ² . When the integrated light amount is 10 mJ/cm ² or more, the active species derived from the polymerization initiator can be sufficiently produced to carry out the curing reaction more reliably, and when the amount is 10000 mJ/cm ² or less, the irradiation time does not become too long and can be maintained. Good productivity.

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

(adhesive)

The adhesive which can be used for the adhesion of the protective film usually contains an acrylic resin, a styrene resin, a silicone resin or the like as a base polymer, and an isocyanate compound, an epoxy compound, and a nitrogen are added thereto. An adhesive composition made of a crosslinking agent such as an aziridine compound. Further, fine particles may be contained as an adhesive layer for exhibiting light scattering properties.

The thickness of the adhesive layer may be from 1 to 40 μm, but in the range of characteristics of non-destructive workability and durability, it is preferably a thin coating, and specifically, it is preferably from 3 to 25 μm. A thickness of 3 to 25 μm has good processability and is also suitable in terms of suppressing dimensional change of the polarizer layer. When the adhesive layer is less than 1 μm, the adhesiveness is lowered, and if it exceeds 40 μm, defects such as an overflow of the adhesive tend to occur. In the method of bonding a protective film to a polarizer layer using an adhesive, an adhesive layer may be disposed on the surface of the protective film, and then attached to the polarizer layer, or an adhesive layer may be disposed on the polarizer layer, and then the protective layer may be further protected. The film is bonded to this point.

The method of forming the adhesive layer is not particularly limited, and an adhesive composition (adhesive solution) containing each component including the above-mentioned base polymer may be applied to a protective film surface or a polarizer layer, and dried. After forming the adhesive layer, the protective film is bonded to the polarizer layer, and 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. Then, the protective film is bonded to the polarizer layer. When the adhesive layer is formed on the protective film surface or the polarizer layer, surface treatment such as corona treatment may be performed on the protective film surface or the polarizing polarizer layer or on one side or both sides of the adhesive layer as needed.

[5] Stripping step S50

This step is a step of peeling off the substrate film from the bonded film obtained by bonding the protective film. Through this step, a polarizing plate in which a protective film is laminated on the polarizer layer but does not have a substrate film can be obtained. When the polarizing laminated film is attached to the substrate film When the polarizer layer is provided on both sides, and the protective film is bonded to both of the polarizer layers, the two polarizing plates can be obtained from one polarizing laminated film by the peeling step S50.

The method of peeling off the base film is not particularly limited, and it can be peeled off in the same manner as the peeling step of the separator (release film) which is performed on the polarizing plate of the general adhesive. The base film film may be peeled off immediately after the bonding step S40, or may be wound into a roll once after the bonding step S40, and then unrolled and peeled off in the subsequent step.

The polarizing plate produced by the above process can also be used as an optical film for laminating other optical layers in actual use. Furthermore, the protective film may also have the function of such an optical layer. The other optical layer may be, for example, a reflective polarizing film that transmits a polarized light and reflects polarized light having a property opposite thereto; a film having an anti-glare function having a concave-convex shape on the surface; and an anti-surface reflection function a film; a reflective film having a reflective function on the surface; a semi-transmissive reflective film having a reflective function and a penetrating function; a viewing angle compensation film.

A commercially available product of a reflective polarizing film that transmits a polarized light and reflects polarized light of a reverse polarity is exemplified by "DBEF" (manufactured by 3M Co., Ltd., which is available from Sumitomo 3M Co., Ltd. in Japan). The company obtained), "APF" (manufactured by 3M Co., Ltd., available from Sumitomo 3M Co., Ltd. in Japan).

The viewing angle compensation film may be, for example, an optical compensation film coated with a liquid crystal compound on the surface of the substrate, fixed by orientation, a retardation film containing a polycarbonate resin, or a retardation film containing a cyclic polyolefin resin. Wait.

"WV film" (manufactured by FUJIFIL Co., Ltd.) and "NH film" (JX Nippon Mining & Stone Co., Ltd.) are commercially available as an optical compensation film which is coated with a liquid crystal compound on the surface of the substrate. "Manufactured by Energy Co., Ltd.", "NR film" (manufactured by JX Nippon Mining & Energy Co., Ltd.).

Commercial products corresponding to a retardation film containing a cyclic polyolefin resin include "ARTON film" (manufactured by JSR Co., Ltd.), "ESUSHINA" (manufactured by Sekisui Chemical Co., Ltd.), and "ZEONOR film". (manufactured by Japan ZEON Co., Ltd.), etc.

Example

The invention is illustrated by the following examples, but the invention is not limited by the examples.

<Example 1>

(1) Fabrication of substrate film

A three-layer structure of a base film comprising a propylene/ethylene random copolymer containing about 5% by weight of ethylene units (Sumitomo) was produced by co-extrusion molding using a multilayer extrusion molding machine. "Sumitomo NOBLEN FLX80E4" manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., manufactured by Sumitomo Chemical Co., Ltd., "Sumitomo NOBLEN W 151", melting point Tm = 138 °C) 163 ° C) resin layer. The total thickness of the substrate film was 90 μm, and the thickness ratio of each layer (FLX80E4/W151/FLX80E4) was 3/4/3.

(2) Step of forming the primer layer

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a concentration of 3% by weight. Aqueous polyvinyl alcohol solution. A crosslinking agent is mixed with the obtained aqueous solution in a ratio of 6 parts by weight of the polyvinyl alcohol powder to 5 parts by weight of a crosslinking agent ("SUMIREZ RESIN 650" manufactured by Tajika Chemical Industry Co., Ltd.) to obtain a primer layer. Coating solution.

While continuously transporting the base film produced in the above (1), a corona treatment is applied to one surface thereof, and the coating liquid for forming a primer layer is continuously applied to the corona using a small-diameter gravure coater. The treated surface was dried at 80 ° C for 10 minutes, thereby forming a primer layer having a thickness of 0.2 μm. Further, a corona treatment was applied to the other surface of the substrate film, 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, thereby obtaining a substrate having a primer layer on both sides. membrane.

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

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

The base coat film having the primer layer formed on the both sides of the above (2) is continuously applied, and the coating liquid for forming the polyvinyl alcohol-based resin layer is continuously applied to one side of the coating liquid using a lip coater. The surface of the layer was dried at 80 ° C for 2 minutes, dried at 70 ° C for 2 minutes, and then dried at 60 ° C for 4 minutes, whereby a polyvinyl alcohol-based resin layer was formed on the primer layer. Again, in The surface of the primer layer on the other side was also subjected to the same operation as described above to form a polyvinyl alcohol-based resin layer, whereby a laminated film was obtained. The thickness of the polyvinyl alcohol-based resin layer in the laminated film was 10.5 μm and 10.2 μm, respectively.

(4) Production of stretch film (extension step)

The laminated film produced in the above (3) was continuously conveyed by the hot roll stretching device shown in Fig. 2, and the longitudinal uniaxial stretching of the laminated film was carried out by a heat roll stretching method (first stretching step). The extension temperature of the first stretching step (surface temperature of the heat roller 1) was set to 150 °C. Further, the first width residual ratio R1 in the first stretching step was 65.7%, and the stretching ratio B1 was 2.00 times.

Then, while continuing to transport the film which has completed the first stretching step, the extending end of the film is longitudinally uniaxially extended by stretching between the rolls (air extension) while using the stretching device shown in FIG. 2 extension steps). The extension temperature of the second extension step (the ambient temperature of the heating furnace 20) was set to 160 °C. Further, the second width residual ratio R2 in the second stretching step was 55.2%, and the stretching ratio B2 was 2.90 times.

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

While continuing to transport the stretched film produced in the above (4), the film was continuously immersed in a dyeing aqueous solution containing 30% by weight of iodine and potassium iodide (containing 0.35 parts by weight of iodine per 100 parts by weight of water, and 10 parts by weight of potassium iodide). The dyeing treatment of the polyvinyl alcohol-based resin layer was carried out. At this time, the residence time of the film in the dyeing aqueous solution was adjusted so that the degree of visibility correction polarization described later became about 99.997%.

Then, the excess dye solution was washed away with pure water at 10 °C. Then, the film is continuously immersed in 76 ° C containing boric acid and potassium iodide. The crosslinked aqueous solution (containing 9.5 parts by weight of boric acid, 5 parts by weight of potassium iodide per 100 parts by weight of water) and having a residence time of 600 seconds was subjected to a crosslinking treatment. Thereafter, the film was washed with pure water of 10 ° C for 4 seconds and dried at 80 ° C for 300 seconds to obtain a polarizing laminated film having a polarizer layer on both surfaces of the substrate film.

<Example 2>

The second width residual ratio R2 of the second extending step was changed to 64.7% and the stretching ratio B2 was changed, except that the first width residual ratio R1 of the first extending step was changed to 68.0% and the stretching ratio B1 was changed to 3.00 times. A polarizing laminated film was obtained in the same manner as in Example 1 except for 1.93 times. In the same manner as in the first embodiment, in the dyeing treatment, the residence time of the film in the dyeing aqueous solution was adjusted so that the degree of visibility correction polarization described later became about 99.997%.

<Comparative Example 1>

A polarizing laminated film was obtained in the same manner as in Example 1 except that the first stretching step was not carried out, and the second width residual ratio R2 of the second stretching step was changed to 39.9% and the stretching ratio B2 was changed to 5.80 times. . In the same manner as in the first embodiment, in the dyeing treatment, the residence time of the film in the dyeing aqueous solution was adjusted so that the degree of visibility correction polarization described later became about 99.997%.

<Comparative Example 2>

A polarizing laminated film was obtained in the same manner as in Example 1 except that the first stretching step was not carried out, and the second width residual ratio R2 of the second extending step was changed to 41.9% and the stretching ratio B2 was changed to 5.20 times. . In the same manner as in Example 1, in the dyeing treatment, the film was adjusted in the dyeing aqueous solution. The retention time is such that the degree of visibility correction to be described later becomes about 99.997%.

<Comparative Example 3>

In addition to changing the first width residual ratio R1 of the first extending step to 74.3% and changing the stretching ratio B1 to 4.00 times, the second width residual ratio R2 of the second extending step was changed to 76.7% and the stretching ratio B2 was changed to A polarizing laminated film was obtained in the same manner as in Example 1 except 1.45 times.

[Evaluation of Polarization Properties of Polarized Laminated Films]

The polarizing performance of the polarizer is usually evaluated by the two parameters of the visual sensitivity correction monomer transmittance and the visual sensitivity correction polarization. The visual sensitivity correction polarizedness is a parameter indicating the degree of separation of polarized light. The higher the parameter, the better the separation. Regarding the visual sensitivity to correct the monomer transmittance, the higher the parameter, the greater the amount of light that is transmitted, and thus the loss of light is reduced. That is, the polarizer having higher visual sensitivity correction polarizing degree and higher visual transmittance correcting monomer transmittance is superior in polarizing performance.

As described above, in Examples 1 to 2 and Comparative Examples 1 to 2, the viewing sensitivity correction polarization of the polarizing laminated film was unified to about 99.997% due to the residence time of the adjustment film in the dyeing aqueous solution, so the visual sensitivity correction sheet was The higher the bulk transmittance, the better the polarizing performance can be evaluated.

Based on the evaluation method as described above, the visual sensitivity of the polarizing laminated film was measured to correct the monomer transmittance, and the polarizing performance was evaluated. The results are shown in Table 1. The illuminance correction film of the polarizing laminated film and the sensitization degree correcting the monomer transmittance are obtained by peeling and removing one of the polarizer layers on the polarizer layers on both sides of the substrate film using an adhesive tape, and The spectrophotometer "V7100" manufactured by JASCO Corporation was measured by incident light from the side of the polarizer layer.

As shown in Table 1, the polarizing laminated films of Examples 1 and 2 exhibited a visual sensitivity correction monomer transmittance of 0.5% or more higher than that of the polarizing laminated films of Comparative Examples 1 and 2. In the polarizing laminated film of Comparative Example 3, when the visual sensitivity correction monomer transmittance is 40% or more, the visual sensitivity correction polarization degree is 99.994% or less, and the visual sensitivity correction polarization degree of 99.997% cannot be achieved.

<Example 3: 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 wt% aqueous solution of polyvinyl alcohol. A crosslinking agent was mixed with the obtained aqueous solution in a ratio of 2 parts by weight of the polyvinyl alcohol powder to 1 part by weight of the crosslinking agent ("SUMIREZ RESIN 650" manufactured by Tajika Chemical Industry Co., Ltd.) to prepare an aqueous solution of the adhesive.

Then, while the polarizing laminated film produced in Example 1 was continuously applied, the above-mentioned aqueous solution of the adhesive was applied to the polarizer layers on both surfaces, and then the protective surface was subjected to a saponification treatment (including cellulose triacetate). (TAC) a transparent protective film ("KC4UY" manufactured by Konica Minolta Opto Co., Ltd.) having a thickness of 40 μm] is attached to the polarizer layer, and is pressed by a pair of bonding rolls to be pressed. A bonding film comprising a layer of a TAC/polarizer layer/primer layer/base film/primer layer/polarizer layer/TAC (bonding step).

Then, the bonding film is peeled off from the interface between the substrate film and the primer layer to obtain a film including a TAC/polarizer layer/primer layer/substrate film, and a polarizing layer including a primer layer/polarizer layer/TAC. After the plate, the base film was peeled off from the film of the former to obtain another polarizing plate. In the step of peeling off the substrate film, defects such as cracking did not occur.

[Industrial availability]

According to the method of the present invention, a polarizing laminate film or a polarizing plate excellent in polarizing performance can be produced.

Claims (7)

A method for producing a polarizing laminated film, comprising the steps of: forming a resin layer forming step by applying a coating liquid containing a polyvinyl alcohol-based resin to at least one side of a base film, and drying by drying a polyvinyl alcohol-based resin layer to obtain a laminated film; an extending step of extending the laminated film to obtain a stretched film; and a dyeing step of dyeing the polyvinyl alcohol-based resin layer of the stretched film by a dichroic dye And forming a polarizer layer to obtain a polarizing laminated film; wherein the extending step includes the following steps: the first extending step is performed to extend the first width residual ratio R1 represented by the following formula (1) 60% or more and less than 100%: first width residual ratio R1 = film width after the first stretching step 膜 film width before the first stretching step × 100 (%) (1); and the second stretching step is performed The free end is uniaxially extended so that the second width residual ratio R2 represented by the following formula (2) becomes smaller than the first width residual ratio R1: the second width residual ratio R2 = the film width after the second extension step ÷ first Film width after extension step × 100 (%) (2). The manufacturing method according to the first aspect of the invention, wherein in the second extending step, the free end uniaxially extends and the second width residual ratio R2 is 70% or less. The manufacturing method according to claim 1 or 2, wherein The total extension ratio of the extension of the laminated film described above is more than 5 times. The manufacturing method according to any one of claims 1 to 3, wherein in the first extending step, the heated roll is brought into contact with the laminated film to extend the second extension In the step, the extension is carried out by extending in the air in a heated environment. The production method according to any one of claims 1 to 4, wherein the polyvinyl alcohol-based resin layer of the laminated film has a thickness of 3 to 30 μm. The production method according to any one of claims 1 to 5, wherein the base film comprises a polypropylene resin. A method of producing a polarizing plate, comprising the steps of: producing a polarizing laminated film by the manufacturing method according to any one of claims 1 to 6, and attaching a protective film to the polarizing laminated film; The step of obtaining a bonded film on the polarizer layer and the step of peeling the base film from the bonded film.