WO2016052331A1

WO2016052331A1 - Method for producing polarizing laminated film and method for producing polarizing plate

Info

Publication number: WO2016052331A1
Application number: PCT/JP2015/077101
Authority: WO
Inventors: 河村　真一
Original assignee: 住友化学株式会社
Priority date: 2014-10-01
Filing date: 2015-09-25
Publication date: 2016-04-07
Also published as: CN107076912A; TW201618921A; JPWO2016052331A1; KR20170065531A; CN107076912B

Abstract

This method for producing a polarizing laminated film comprises, in the following order: a coating step (S10) wherein a coated film is obtained by applying an aqueous solution of a polyvinyl alcohol resin to a base film; a drying step (S20) wherein a laminated film, in which a polyvinyl alcohol resin layer is formed on the base film, is obtained by drying the coated film; a stretching step (S30) wherein a stretched laminated film is obtained by uniaxially stretching the laminated film; and a dyeing step (S40) wherein a polarizing laminated film is obtained by dyeing the polyvinyl alcohol resin layer so as to form a polarizer layer. In the stretching step (S30), the uniaxially stretching is started in a state where the laminated film has a moisture percentage of 0.3% by mass or more.

Description

Method for producing polarizing laminated film or polarizing plate

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

The polarizing plate is widely used as a polarization supplying element in a display device such as a liquid crystal display device. As such a polarizing plate, a polarizing film (polarizer layer) made of a polyvinyl alcohol resin and a protective film made of triacetyl cellulose are conventionally used. However, in recent years, notebook personal computers and portables for liquid crystal display devices have been used. With the development of mobile devices such as telephones, there is a need to reduce the thickness and weight.

Conventionally, after a film made of a polyvinyl alcohol resin is stretched alone or while being stretched, a polarizing film is produced by performing a dyeing treatment or a crosslinking treatment, and laminating this on a protective film or the like to form a polarizing plate. Although it was manufactured, it was possible to reduce the thickness only to the limit thickness of the polarizing film alone. On the other hand, after providing a polyvinyl alcohol-based resin layer to be a polarizer layer on the surface of the base film, the polyvinyl alcohol-based resin layer is stretched together with the base film, and after passing through a dyeing / crosslinking step and a subsequent drying step, the polyvinyl alcohol By making the system resin layer a polarizer layer, the total thickness of the substrate film and the polarizer layer can be reduced to the limit, and the thickness as the polarizer layer (polarizing film) is thinner than before. There is a known method (see, for example, Patent Document 1).

JP 2009-93074 A

In the present invention, after a polyvinyl alcohol resin layer is provided on the surface of the base film, the polyvinyl alcohol resin layer is stretched together with the base film, and the polyvinyl alcohol resin layer is passed through a dyeing / crosslinking step and a subsequent drying step. A method for producing a polarizing laminate film having a polarizer layer having excellent optical performance in a production method capable of producing a polarizing laminate film having a thin polarizer layer by forming a polarizer layer. The purpose is to provide.

The present invention includes the following.
[1] A coating process in which an aqueous solution of a polyvinyl alcohol resin is applied to a base film to obtain a coating film, and the coating film is dried to form a polyvinyl alcohol resin layer on the base film. A drying step for obtaining a laminated film, a stretching step for obtaining a stretched laminated film by uniaxially stretching the laminated film, and a dyeing step for obtaining a polarizing laminated film by dyeing the polyvinyl alcohol-based resin layer to form a polarizer layer. Including this order, the stretching step is a method for producing a polarizing laminated film, wherein the uniaxial stretching is started in a state where the moisture content of the laminated film is 0.3% by mass or more.

[2] The method for producing a polarizing laminated film according to [1], wherein the drying step is performed such that a change in average moisture content of the coated film is 5 to 65% by mass / min.

[3] After the drying step, including a humidity control step of adjusting humidity so that a moisture content of the multilayer film is 0.3% by mass or more, the multilayer film conditioned in the humidity control step is The method for producing a polarizing laminated film according to [1] or [2], which is subjected to the stretching step while maintaining a moisture content.

[4] A first coating step in which an aqueous solution of a polyvinyl alcohol-based resin is coated on one surface of the base film to obtain a coated film, and the coated film is dried to A first drying step for obtaining a laminated film having a polyvinyl alcohol-based resin layer formed on the surface; and a second-side coated film obtained by applying an aqueous solution of a polyvinyl alcohol-based resin to the other surface of the base film. A second drying step of obtaining a double-sided laminated film in which a polyvinyl alcohol-based resin layer is formed on both sides of the base film by drying the double-sided coated film, and uniaxially stretching the double-sided laminated film And a stretching step for obtaining a stretched laminated film, and a dyeing step for dyeing the polyvinyl alcohol-based resin layer to obtain a polarizer layer, and obtaining a polarizing laminated film in this order, Shin step, the moisture content of the double-sided laminated film initiating the uniaxially stretched in a state of more than 0.5 mass%, the production method of the polarizing laminate film.

[5] The method for producing a polarizing laminated film according to [4], wherein the first drying step is performed such that a moisture content of the laminated film after drying is 0.3% by mass or more.

[6] In the first drying step and the second drying step, the change in average moisture content of the coated film and the change in average moisture content of the double-sided coated film are 5 to 65% by mass / min, respectively. The method for producing a polarizing laminate film according to [4] or [5].

[7] The both surfaces that have been conditioned in the humidity adjustment step, including a humidity adjustment step that adjusts the moisture content of the double-sided laminated film to 0.5% by mass or more after the second drying step. The method for producing a polarizing laminated film according to any one of [4] to [6], wherein the laminated film is subjected to the stretching step while maintaining its moisture content.

[8] A step of producing a polarizing laminated film by the production method according to any one of [1] to [7], and a surface of the polarizing laminated film opposite to the base film of the polarizer layer. A bonding step of bonding a protective film to obtain a multilayer film, and a peeling step of peeling the base film from the multilayer film to obtain a polarizing plate comprising the polarizer layer and the protective film. Manufacturing method of polarizing plate.

In the present invention, a polarizing laminate film having a polarizer layer having excellent optical performance can be obtained by controlling the moisture content of the laminate film subjected to the stretching step.

It is a flowchart which shows the manufacturing method of the light-polarizing laminated film and polarizing plate of 1st Embodiment. It is a flowchart which shows the manufacturing method of the light-polarizing laminated film and polarizing plate of 2nd Embodiment.

In this specification, a laminate comprising a polyvinyl alcohol resin layer (a layer comprising a polyvinyl alcohol resin) on a base film is referred to as a “laminated film”, and a polyvinyl alcohol resin layer is formed on both sides of the base film. The laminated film provided with is called “double-sided laminated film”.

In addition, a polyvinyl alcohol-based resin layer having a function as a polarizer is referred to as a “polarizer layer”, and a laminate including a polarizer layer on a base film is referred to as a “polarizing laminate film”. A laminate having a protective film on one side is referred to as a “polarizing plate”. Hereinafter, the constituent elements of the polarizing laminate film and the polarizing plate will be described first, and then the manufacturing method thereof will be described.

<Polarizing laminated film and polarizing plate>
[Base film]
As the resin used for the base film, for example, thermoplastic resins excellent in transparency, mechanical strength, thermal stability, stretchability, etc. are used, and depending on their glass transition temperature (Tg) or melting point (Tm). An appropriate resin can be selected. Specific examples of thermoplastic resins include polyolefin resins, polyester resins, cyclic polyolefin resins (norbornene resins), (meth) acrylic resins, cellulose ester resins, polycarbonate resins, polyvinyl alcohol resins, vinyl acetate. Resin, polyarylate resin, polystyrene resin, polyethersulfone resin, polysulfone resin, polyamide resin, polyimide resin, and mixtures and copolymers thereof.

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

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

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

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

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

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

Various products are commercially available as cyclic polyolefin resins. Specific examples include TOPAS (registered trademark) (Topas Advanced Polymers GmbH), Arton (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (manufactured by Nippon Zeon Corporation), Zeonex ( ZEONEX (registered trademark) (manufactured by ZEON Corporation), Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.).

Any appropriate (meth) acrylic resin can be adopted as the (meth) acrylic resin. For example, polymethacrylate such as polymethylmethacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (meta ) Acrylic acid copolymer, methyl methacrylate-styrene copolymer (MS resin, etc.), polymer having alicyclic hydrocarbon group (for example, methyl methacrylate- (meth) acrylic acid cyclohexyl copolymer, methacrylic acid) Methyl- (meth) acrylate norbornyl copolymer, etc.). Preferably, a polymer mainly composed of a C ₁ -C ₆ alkyl ester of methacrylic acid such as polymethyl methacrylate is used. As the (meth) acrylic resin, a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is more preferably used.

Cellulose ester resin is an ester of cellulose and fatty acid. Specific examples of such a cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, these copolymers and those in which a part of the hydroxyl group is modified with other types of substituents are also included. Among these, cellulose triacetate is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available cellulose triacetate include Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), and Fujitac (registered trademark) TD80UZ (Fuji Film (manufactured by Fujifilm Corporation). Co., Ltd.), Fujitac (registered trademark) TD40UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Co., Ltd.), KC4UY (Konica Minolta Co., Ltd.), and the like.

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

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

Although the thickness of the base film before stretching can be determined as appropriate, from the viewpoint of workability such as strength and handleability, and in the present invention, a laminated film in which a polyvinyl alcohol resin layer is formed on the base film From the viewpoint of adjusting the moisture content, the thickness of the base film is preferably 50 to 200 μm, and more preferably 70 to 130 μm. Moreover, it is preferable that a base film is a value whose melting | fusing point or glass transition temperature is higher than the temperature range of the drying process and extending | stretching process which are mentioned later. By using such a base film, it is possible to prevent the base material from becoming too soft in the drying step and the stretching step, and to avoid deterioration of the in-plane film thickness distribution of the polyvinyl alcohol-based resin layer.

The base film may be subjected to corona treatment, plasma treatment, flame treatment or the like on at least the surface on which the polyvinyl alcohol resin layer is formed in order to improve the adhesion with the polyvinyl alcohol resin layer. Moreover, in order to improve adhesiveness, you may form thin layers, such as a primer layer and an adhesive bond layer, in the surface of the side by which the polyvinyl alcohol-type resin layer of a base film is formed.

(Primer layer)
When the primer layer is formed on the surface of the base film on which the polarizer layer is formed, the primer layer is a material that exhibits a certain degree of strong adhesion to both the base film and the polyvinyl alcohol resin layer. If there is no particular limitation. For example, a thermoplastic resin excellent in transparency, thermal stability, stretchability, etc. is used. Specific examples include acrylic resins and polyvinyl alcohol resins, but are not limited thereto. Among these, a polyvinyl alcohol resin having good adhesion is preferably used.

Examples of the polyvinyl alcohol resin used as the primer layer include polyvinyl alcohol resin and derivatives thereof. Derivatives of polyvinyl alcohol resin include polyvinyl formal, polyvinyl acetal, etc., olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, and alkyl esters of unsaturated carboxylic acids. And those modified with acrylamide or the like. Among the above-mentioned polyvinyl alcohol-based resin materials, it is preferable to use a polyvinyl alcohol resin.

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

The thickness of the primer layer is preferably 0.05 to 1 μm, more preferably 0.1 to 0.4 μm. If the thickness is less than 0.05 μm, the adhesion between the base film and the polyvinyl alcohol-based resin layer is reduced, and if the thickness is more than 1 μm, the polarizing plate becomes thick.

[Polarizer layer]
Specifically, the polarizer layer is obtained by adsorbing and orienting a dichroic dye on a stretched polyvinyl alcohol-based resin layer.

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

The polyvinyl alcohol resin constituting the polarizer layer (polyvinyl alcohol resin layer) is preferably a completely saponified product. The range of the saponification degree is preferably 80.0 mol% to 100.0 mol%, more preferably 90.0 mol% to 99.5 mol%, and even more preferably 94.0 mol%. Most preferred is a range of from% to 99.0 mol%. When the degree of saponification is less than 80.0 mol%, there is a problem that the water resistance and heat-and-moisture resistance after making a polarizing plate are remarkably inferior. In addition, when a polyvinyl alcohol-based resin having a saponification degree exceeding 99.5 mol% is used, the dyeing speed is remarkably slow, and a polarizing laminated film having sufficient polarization performance may not be obtained. In some cases, the production takes several times as long as the usual dyeing time.

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

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

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

The average degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but is preferably 100 to 10,000, more preferably 1500 to 8000, and most preferably 2000 to 5,000. The average degree of polymerization here is also a numerical value obtained by a method defined by JIS K 6726 (1994).

Examples of the polyvinyl alcohol resin having such characteristics include PVA124 (degree of saponification: 98.0 to 99.0 mol%) and PVA117 (degree of saponification: 98.0 to 99.0) manufactured by Kuraray Co., Ltd. Mol%), PVA624 (degree of saponification: 95.0 to 96.0 mol%) and PVA617 (degree of saponification: 94.5 to 95.5 mol%); for example, AH- manufactured by Nippon Synthetic Chemical Industry Co., Ltd. 26 (degree of saponification: 97.0 to 98.8 mol%), AH-22 (degree of saponification: 97.5 to 98.5 mol%), NH-18 (degree of saponification: 98.0 to 99.99%) 0 mol%), and N-300 (degree of saponification: 98.0 to 99.0 mol%); for example, JC-33 (degree of saponification: 99.0 mol% or more) of Nippon Vinegar Poval Co., Ltd. , JM-33 (degree of saponification: 93.5-95.5 mol%), JM-2 (Saponification degree: 95.5-97.5 mol%), JP-45 (saponification degree: 86.5-89.5 mol%), JF-17 (saponification degree: 98.0-99.0) Mol%), JF-17L (degree of saponification: 98.0 to 99.0 mol%), and JF-20 (degree of saponification: 98.0 to 99.0 mol%). Can be suitably used.

Such a polyvinyl alcohol resin is used as an aqueous solution, which is coated on a base film and dried to form a polyvinyl alcohol resin layer.

Such a polyvinyl alcohol-based resin layer is stretched and oriented together with the base film, and further, a dichroic dye is adsorbed and oriented to form a polarizer layer. The draw ratio is preferably more than 5 times, more preferably more than 5 times and not more than 17 times.

The thickness of the polarizer layer (thickness of the stretched polyvinyl alcohol resin layer) is 10 μm or less, preferably 7 μm or less. By setting the thickness of the polarizer layer to 10 μm or less, a thin polarizing plate can be configured.

Examples of the dichroic dye used in the polarizer layer include iodine and organic dyes. Examples of organic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc. can be used. One kind of these dichroic substances may be used, or two or more kinds may be used in combination.

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

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

As the cyclic polyolefin-based resin, appropriate commercial products such as TOPAS (registered trademark) (Topas Advanced Polymers GmbH), Arton (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (Japan) Zeon Co., Ltd.), Zeonex (registered trademark) (ZEONEX) (manufactured by Nippon Zeon Co., Ltd.), and Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.) can be suitably used. When such a cyclic polyolefin resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. In addition, pre-formed annular films such as Essina (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Industry Co., Ltd.), ZEONOR (registered trademark) film (manufactured by Nippon Zeon Co., Ltd.), etc. Commercial products of polyolefin resin films may be used.

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

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

Examples of the cellulose acetate-based resin film include commercially available products such as FUJITAC (registered trademark) TD80 (manufactured by FUJIFILM Corporation), FUJITAC (registered trademark) TD80UF (manufactured by FUJIFILM Corporation), and FUJITAC (registered trademark). TD80UZ (manufactured by FUJIFILM Corporation), FUJITAC (registered trademark) TD40UZ (manufactured by FUJIFILM Corporation), KC8UX2M (manufactured by Konica Minolta Co., Ltd.), KC4UY (manufactured by Konica Minolta Co., Ltd.) can be suitably used. it can.

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

An optical layer such as a hard coat layer, an antiglare layer, or an antireflection layer can be formed on the surface of the protective film as described above. The method for forming these optical layers on the surface of the protective film is not particularly limited, and a known method can be used.

The thickness of the protective film is preferably as thin as possible from the demand for thinning, preferably 90 μm or less, more preferably 50 μm or less. On the other hand, if it is too thin, the strength is lowered and the processability is inferior.

<Production method of polarizing laminated film and polarizing plate>
[First Embodiment]
FIG. 1 is a flowchart showing a method for producing a polarizing laminated film and a polarizing plate according to the first embodiment. The manufacturing method of the light-polarizing laminated film of the first embodiment is as follows.
On one surface of the substrate film, a coating step (S10) for applying a polyvinyl alcohol resin aqueous solution to obtain a coating film;
A drying step (S20) of drying the coated film to obtain a laminated film in which a polyvinyl alcohol-based resin layer is formed on the base film;
Stretching step (S30) to obtain a stretched laminated film by uniaxially stretching the laminated film,
A dyeing step (S40) for obtaining a polarizing laminated film by dyeing the polyvinyl alcohol-based resin layer into a polarizer layer is included in this order.

In order to manufacture a polarizing plate,
A laminating step (S50) for obtaining a multilayer film by laminating a transparent protective film on the surface of the polarizer layer in the polarizing laminate film opposite to the base film;
The peeling process (S60) which peels the said base film from the said multilayer film and obtains the polarizing plate provided with the said polarizer layer and the said transparent protective film is included in this order.

<Each manufacturing process>
Hereinafter, each step of S10 to S60 in FIG. 1 will be described in detail.

[Coating process (S10)]
Here, an aqueous solution of a polyvinyl alcohol-based resin is applied to one surface of the base film to obtain a coated film.

The material suitable for the base film is as described in the description of the constituent elements of the polarizing laminated film. In addition, it is preferable to use a base film that can be stretched in a temperature range suitable for stretching the polyvinyl alcohol resin.

In the coating step (S10), preferably, a polyvinyl alcohol resin solution obtained by dissolving polyvinyl alcohol resin powder in a good solvent is applied onto the surface of the substrate film to obtain a coated film. By forming the polyvinyl alcohol-based resin layer through the coating process, the polyvinyl alcohol-based resin can be thinned. As a method of coating a polyvinyl alcohol resin solution on a base film, a wire bar coating method, a reverse coating, a roll coating method such as gravure coating, a die coating method, a comma coating method, a lip coating method, a spin coating method, a screen A known method such as a coating method, a fountain coating method, a dipping method, or a spray method can be appropriately selected and employed. A comma coat method (knife coater), a die coat method and a lip coat method are preferred.

The thickness of the polyvinyl alcohol-based resin layer of the stretched laminated film after stretching in the stretching step (S30) is preferably 10 μm or less. Therefore, the thickness of the resin layer formed through the coating step (S10) and the drying step (S20) is preferably 3 to 50 μm, and more preferably 5 to 40 μm. If it is 3 μm or less, the film becomes too thin after stretching and the dyeability is remarkably deteriorated. On the other hand, if it exceeds 50 μm, the thickness of the finally obtained polarizer layer may exceed 10 μm, which is not preferable.

In order to improve the adhesion between the base film and the polyvinyl alcohol resin layer, a primer layer may be provided between the base film and the polyvinyl alcohol resin layer. The primer layer is preferably formed from a composition containing a polyvinyl alcohol-based resin and a crosslinking agent from the viewpoint of adhesion. Materials suitable for the primer layer are as described in the description of the components of the polarizing laminated film.

[Drying step (S20)]
By drying the coating film obtained in the coating step (S10) and evaporating the solvent of the aqueous solution of the polyvinyl alcohol resin, a laminated film in which the polyvinyl alcohol resin layer is formed on the base film is obtained. .

The drying step is preferably performed so that the average moisture content change of the coated film is 5 to 65% by mass / min, more preferably 7.5 to 50% by mass / min. More preferably, it is carried out at 5 to 30% by mass / min. The average moisture content change in the drying process referred to in this specification is obtained by dividing the difference between the moisture content (%) of the coated film at the start of drying and the moisture content (%) of the laminated film at the end of drying by time. This is the value obtained. In addition, the calculation method of the moisture content of a coating film or a laminated | multilayer film is mentioned later. When the average moisture content change is larger than 65% by mass / min, it is necessary to increase the drying temperature, which may cause problems such as dissolution of the base film and discoloration of the polyvinyl alcohol resin, which is not preferable. When the average moisture content change is less than 5% by mass / min, the productivity deteriorates, which is not preferable.

The drying temperature in the drying step is, for example, 50 ° C. to 200 ° C., preferably 60 ° C. to 150 ° C. There are various drying methods such as a method of blowing hot air, a method of contacting with a hot roll, and a method of heating with an IR heater, and any of them can be suitably used. The drying temperature in the drying process means the atmospheric temperature in the drying furnace in the case of a drying facility provided with a drying furnace such as a method of blowing hot air or an IR heater, and is a contact type such as a hot roll. In the case of drying equipment, it means the surface temperature of the hot roll. Through the above steps, a laminated film on which a polyvinyl alcohol-based resin layer is formed is produced. The drying time is, for example, 2 minutes to 20 minutes.

[Stretching step (S30)]
Here, the laminated film obtained in the drying step (S20) is stretched. In the stretching step (S30), uniaxial stretching is started in a state where the moisture content of the laminated film in which the polyvinyl alcohol-based resin layer is formed on one surface of the base film is 0.3% by mass or more. When the moisture content at the start of uniaxial stretching is 0.3% by mass or more, a polarizing laminated film or a polarizing plate provided with a polarizer layer having excellent optical performance can be produced. The moisture content can be adjusted, for example, by adjusting the degree of drying in the drying step (S20) or by adjusting in the humidity adjusting step described later.

The degree of drying in the drying step (S20) is the thickness (or weight per unit area) of the polyvinyl alcohol-based resin coating layer formed on the base film, in addition to the drying temperature and drying time described above, and the drying step. Therefore, a simple preliminary experiment is conducted to determine a predetermined moisture content (0.3% by mass to 3% by mass, preferably 0.35% by mass to 1%). .8 mass% or less) and the conditions may be adjusted. In some cases, air adjusted to a predetermined water vapor pressure can be introduced into the drying furnace. In this way, the laminated film dried to a predetermined moisture content is preferably subjected to the stretching step (S30) while maintaining the moisture content, but is adjusted to the predetermined moisture content in the humidity conditioning step described later. Then, it can also be attached to the stretching step (S30).

(Calculation of moisture content of laminated film)
In this specification, the moisture content of a laminated film (or coating film) is a value calculated as follows. First, it samples from a laminated film (or coating film), calculates | requires the mass (A) of the measurement sample, and puts the measurement sample into 105 degreeC oven for 1 hour after that. And the mass (B) of the measurement sample after taking out from oven is calculated | required. The moisture content of the laminated film (or coating film) is expressed by the following formula (1):
Moisture content of laminated film (or coated film) = (A−B) / A × 100 (%)
Is calculated by

(Calculation of moisture content of polyvinyl alcohol resin layer)
In the present specification, the moisture content of the polyvinyl alcohol-based resin layer is a value calculated as follows. First, the laminated film is sampled, the mass (A) of the measurement sample is obtained, and then the measurement sample is put into an oven at 105 ° C. for 1 hour. And the mass (B) of the measurement sample after taking out from oven is calculated | required. Furthermore, a polyvinyl alcohol-type resin layer is removed from the measurement sample, and the mass (C) of a base film simple substance is calculated | required. The moisture content of the polyvinyl alcohol resin layer is expressed by the following formula (2):
Moisture content of polyvinyl alcohol resin layer = (AB) / (AC) × 100 (%)
Is calculated by The moisture content of the polyvinyl alcohol-based resin layer is preferably 2.5% by mass or more. If the value of the moisture content of a polyvinyl alcohol-type resin layer is the said range, since the crack which arises in the polyvinyl alcohol-type resin layer after extending | stretching can be suppressed, it is preferable.

In the stretching step (S30), uniaxial stretching is preferably performed so that the stretching ratio is preferably more than 5 times and not more than 17 times. More preferably, it is uniaxially stretched so that the stretch ratio is more than 5 times and not more than 8 times. When the draw ratio is 5 times or less, the polyvinyl alcohol-based resin layer is not sufficiently oriented, and as a result, the degree of polarization of the polarizer layer may not be sufficiently high. On the other hand, when the draw ratio exceeds 17 times, the laminated film is easily broken during stretching, and at the same time, the thickness of the stretched laminated film after stretching becomes unnecessarily thin, and the workability and handling properties in the subsequent process are reduced. There is a risk. The stretching process in the stretching step (S30) is not limited to one-stage stretching, and can be performed in multiple stages. In the case of performing in multiple stages, the stretching process is performed so that the stretching ratio is more than 5 times by combining all stages of the stretching process.

In the stretching step (S30) in the present embodiment, a longitudinal stretching process performed in the longitudinal direction of the laminated film, a lateral stretching process stretching in the width direction, and the like can be performed. Examples of the longitudinal stretching method include an inter-roll stretching method and a compression stretching method, and examples of the transverse stretching method include a tenter method.

Further, the stretching treatment in the present invention is preferably performed using a dry stretching method. By stretching the polyvinyl alcohol resin layer together with the base film before the dyeing step, a thinner polyvinyl alcohol resin film (polyvinyl alcohol resin layer) than before can be stretched at a high magnification without breaking. This is because the obtained polarizer layer and further the polarizing plate can be made thinner.

(Humidity control process)
After the drying step (S20), a humidity control step for adjusting the humidity so that the moisture content of the laminated film is 0.3% by mass or more and 3% by mass or less, preferably 0.35% by mass or more and 1.8% by mass or less. Furthermore, you may have. In this case, the laminated film conditioned in the humidity adjustment step is subjected to the stretching step (S30) while maintaining a moisture content of 0.3% by mass to 3% by mass. Humidity adjustment in the humidity control step may be performed by, for example, a method of placing a laminated film in a room adjusted to an appropriate humidity and temperature, or a method of passing the laminated film through a humidity adjusting furnace adjusted to an appropriate humidity and temperature. . In the humidity control process, the moisture content can be increased (humidified) or the moisture content can be decreased (dried) according to the state of the previous laminated film, and the moisture content itself is not changed. The polyvinyl alcohol resin layer may be homogenized.

[Dyeing step (S40)]
Here, the polyvinyl alcohol resin layer of the laminated film is dyed with a dichroic dye. As described above, iodine or an organic dye is used as the dichroic dye.

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

When iodine is used as the dichroic dye, it is preferable to further add an iodide because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. The addition ratio of these iodides is preferably 0.01 to 20% by weight in the dyeing solution. Of the iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably in the range of 1: 6 to 1:80 by weight. , Particularly preferably in the range of 1: 7 to 1:70.

The immersion time of the stretched laminated film in the dyeing solution is not particularly limited, but is usually preferably in the range of 15 seconds to 15 minutes, and more preferably 1 minute to 3 minutes. 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.

In the dyeing process, a crosslinking treatment can be performed after dyeing. The crosslinking treatment is performed, for example, by immersing the laminated film in a solution containing a crosslinking agent (crosslinking solution). Conventionally known substances can be used as the crosslinking agent. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One kind of these may be used, or two or more kinds may be used in combination.

As the crosslinking solution, a solution in which a crosslinking agent is dissolved in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further included. The concentration of the crosslinking agent in the crosslinking solution is not limited to this, but is preferably in the range of 1 to 20% by weight, and more preferably 6 to 15% by weight.

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

The immersion time of the stretched laminated film in the crosslinking solution is usually preferably from 15 seconds to 20 minutes, and more preferably from 30 seconds to 15 minutes. The temperature of the crosslinking solution is preferably in the range of 10 to 80 ° C.

By the above dyeing | staining process (S40), a polyvinyl alcohol-type resin layer will have a function as a polarizer layer, and a light-polarizing laminated film is obtained.

[Washing process]
Next, it is preferable to perform a cleaning process for cleaning the polarizing laminated film. As the washing step, a water washing treatment can be performed. The water washing treatment can usually be performed by immersing the stretched film in pure water such as ion exchange water or distilled water. The water washing temperature is usually in the range of 3 to 50 ° C., preferably 4 to 20 ° C. The immersion time is usually 2 to 300 seconds, preferably 3 to 240 seconds.

In the washing step, washing treatment with an iodide solution and water washing treatment may be combined, and a solution in which liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, propanol or the like is appropriately blended may be used. Moreover, you may provide the process of draining using a nip roll, an air knife, etc. after the washing | cleaning process.

It is preferable to dry the polarizing laminated film after the washing step. Such drying preferably includes a drying step at a temperature of 60 ° C. or higher, and more preferably includes a drying step at a temperature of 70 ° C. or higher. Of course, a multi-step drying process with different temperatures may be included. In that case, any drying process should just be 60 degreeC or more among multistage drying processes.

In addition to temperature, in order to enhance the drying power, the hot air circulation method such as the air volume and direction may be optimized, or an IR heater that can apply heat locally may be added. These aids further improve the efficiency of drying and contribute to productivity improvement.

The upper limit of the drying temperature is preferably lower than the boiling point of water, and preferably less than 100 ° C. Furthermore, it is preferably 95 ° C. or lower, and most preferably 90 ° C. or lower.

[Bonding process (S50)]
Here, a protective film is bonded to the surface opposite to the base film of the polarizer layer in the polarizing laminated film that has undergone the above-described process to obtain a multilayer film. As a method of bonding a polarizer layer and a protective film, the method of bonding a polarizer layer and a protective film through an adhesive layer or an adhesive layer is mentioned. Materials suitable as the protective film are as described in the description of the constituent elements of the polarizing plate.

(Adhesive layer)
The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is usually a composition in which an acrylic resin, a styrene resin, a silicone resin, or the like is used as a base polymer and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. Become. Furthermore, a pressure-sensitive adhesive layer exhibiting light scattering properties can be formed by mixing fine particles in the pressure-sensitive adhesive.

The thickness of the pressure-sensitive adhesive layer is preferably 1 to 40 μm, but it is preferably applied thinly, and more preferably 3 to 25 μm, as long as the processability and durability characteristics are not impaired. When the thickness is 3 to 25 μm, it has good processability and is also suitable for suppressing the dimensional change of the polarizing film. When the pressure-sensitive adhesive layer is less than 1 μm, the tackiness is lowered, and when it exceeds 40 μm, problems such as the pressure-sensitive adhesive protruding easily occur.

The method of forming the pressure-sensitive adhesive layer on the protective film or the polarizer is not particularly limited, and a solution containing each component including the above-mentioned base polymer is applied to the protective film surface or the polarizer layer surface, After forming the pressure-sensitive adhesive layer by drying, it may be bonded to a separator or other types of film, or after forming the pressure-sensitive adhesive layer on the separator, it is laminated on the protective film surface or the polarizer layer surface. Also good. Further, when forming the pressure-sensitive adhesive layer on the surface of the protective film or the polarizer layer, if necessary, the protective film or the polarizer layer surface, or one or both of the pressure-sensitive adhesive layers may be subjected to an adhesion treatment such as corona treatment. Good.

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

The method of laminating the film using the water-based adhesive is not particularly limited, and the adhesive is evenly applied or poured on the surface of the film, and the other film is laminated on the coated surface and laminated with a roll or the like. And a drying method. Usually, after the preparation, the adhesive is applied at a temperature of 15 to 40 ° C., and the laminating temperature is usually in the range of 15 to 30 ° C.

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

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

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

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

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

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

When a photocurable resin is used as the adhesive, the photocurable adhesive is cured by irradiating active energy rays after the films are laminated. The light source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, the low-pressure mercury lamp, the medium-pressure mercury lamp, the high-pressure mercury lamp, the ultrahigh-pressure mercury lamp, the chemical lamp, and the black light lamp A microwave excitation mercury lamp, a metal halide lamp and the like are preferably used.

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

When curing a photocurable adhesive of a film containing a polarizer layer or a protective film by irradiation with active energy rays, various polarizing plate properties such as the degree of polarization, transmittance and hue of the polarizer layer, and the transparency of the protective film, etc. It is preferable to perform the curing under conditions where the function does not decrease.

In the bonding step (S50) for bonding the polarizer layer and the protective film, when a solution containing a solvent is used to form the adhesive layer or the pressure-sensitive adhesive layer, the multilayer film is dried. The purpose of such drying is mainly to dry the adhesive layer or the pressure-sensitive adhesive layer, and the drying conditions and the like may be substantially the same as the drying after the washing step described above. In particular, when an aqueous polyvinyl alcohol resin solution or the like is used to form an adhesive layer, it is preferable to perform drying at a temperature of 60 ° C. or higher.

[Peeling step (S60)]
A peeling process (S60) which peels a base film from a multilayer film and obtains a polarizing plate provided with a polarizer layer and a protective film is performed after a pasting process (S50). The method of peeling a base film from a multilayer film is not specifically limited, The method similar to the peeling film peeling process performed with a normal polarizing plate with an adhesive can be employ | adopted. After the bonding step (S50), it may be peeled off as it is, or after being wound up once in a roll shape, it may be peeled off by providing another peeling step.

[Other optical layers]
The polarizing plate obtained by the present invention can be used as a polarizing plate in which other optical layers are laminated in practical use. Moreover, the said protective film may have a function of these optical layers.

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

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

[Second Embodiment]
FIG. 2 is a flowchart showing a method for producing the polarizing laminated film and the polarizing plate of the second embodiment. The manufacturing method of the light-polarizing laminated film of the second embodiment is as follows.
A first coating step (S11) of applying an aqueous solution of a polyvinyl alcohol-based resin on one surface of the base film to obtain a coated film;
A first drying step (S21) for drying the coated film to obtain a laminated film in which a polyvinyl alcohol-based resin layer is formed on one surface of the base film;
A second coating step (S12) for obtaining a double-sided coated film by coating an aqueous solution of a polyvinyl alcohol-based resin on the other surface of the substrate film;
A second drying step (S22) for drying the double-sided coating film to obtain a double-sided laminated film having a polyvinyl alcohol resin layer formed on both sides of the base film;
Stretching step (S31) to obtain a stretched laminated film by uniaxially stretching the double-sided laminated film,
A dyeing step (S40) for obtaining a polarizing laminated film by dyeing the polyvinyl alcohol-based resin layer into a polarizer layer is included in this order.

In this embodiment, two polarizer layers can be formed simultaneously by forming a polyvinyl alcohol-based resin layer on both sides of the base film.

<Each manufacturing process>
Hereafter, each process of 2nd Embodiment in FIG. 2 is demonstrated compared with the process of 1st Embodiment in FIG. Note that points not particularly described are performed in the same manner as the corresponding steps in the first embodiment. The same steps are denoted by the same reference numerals and description thereof is omitted.

[First coating step (S11)]
The first coating step (S11) is the same step as the coating step (S10) in FIG.

[First drying step (S21)]
The first drying step (S21) is performed such that the moisture content of the laminated film after drying is 0.3% by mass or more and 3% by mass or less, preferably 0.35% by mass or more and 1.8% by mass or less. It is preferable. By setting it as such a moisture content, it becomes easy to adjust the moisture content at the time of a uniaxial stretching start to a desired value in the extending process (S31) mentioned below. A preferable numerical range of the average moisture content change of the coated film in the first drying step (S21), preferable drying conditions, and the like are as described in the drying step (S20) in the first embodiment.

[Second coating step (S12)]
In the second coating step (S12), the surface of the substrate film is coated with a polyvinyl alcohol resin on the surface opposite to the surface coated with the polyvinyl alcohol aqueous solution in the first coating step (S11). This is a step of applying an aqueous solution to obtain a double-sided coated film. The coating conditions of the aqueous solution of the polyvinyl alcohol resin in the second coating step (S12) are as described in the coating step (S10) of the first embodiment.

[Second drying step (S22)]
The second drying step (S22) is the same step as the drying step (S20) in the first embodiment. A preferable numerical range of the average moisture content change of the coated film in the second drying step (S22), preferable drying conditions, and the like are also as described in the drying step (S20) in the first embodiment.

[Stretching step (S31)]
Here, the double-sided laminated film obtained in the second drying step (S22) is stretched. In the stretching step (S31), uniaxial stretching is started in a state where the moisture content of the double-sided laminated film is 0.5% by mass or more. When the water content at the start of uniaxial stretching is 0.5% by mass or more, a polarizing laminated film or a polarizing plate provided with a polarizer layer having excellent optical performance can be produced. The moisture content is adjusted by adjusting the degree of drying in the first drying step (S21) and the second drying step (S22), or by adjusting in the humidity adjustment step described later. Can do.

The degree of drying in the first drying step (S21) and the second drying step (S22) is the temperature and time in each step described above, as well as the polyvinyl alcohol-based resin coating layer formed on the base film. Since it also changes depending on the thickness (or weight per unit area), the moisture concentration of the atmosphere in the drying process, the water vapor pressure, the humidity, etc., a simple preliminary experiment is performed and a predetermined value is obtained after the second drying process (S22). The conditions may be adjusted so that the moisture content is (0.5 mass% to 4 mass%, preferably 0.6 mass% to 2.5 mass%). In some cases, air adjusted to a predetermined water vapor pressure can be introduced into the drying furnace. In this way, the laminated film dried to the predetermined moisture content in the second drying step (S22) is preferably subjected to the stretching step (S31) while maintaining the moisture content. It can also attach | subject to an extending process (S31), after adjusting to a predetermined moisture content at a process.

(Humidity control process)
After the second drying step (S22), the moisture content of the double-sided laminated film is adjusted to 0.5% by mass or more and 4% by mass or less, preferably 0.6% by mass or more and 2.5% by mass or less. You may further have a humidity control process. In this case, the double-sided laminated film conditioned in this humidity conditioning step is stretched while maintaining a moisture content of 0.5% by mass or more and 4% by mass or less, preferably 0.6% by mass or more and 2.5% by mass or less. (S31). About the humidity control in this humidity control process, the description similar to what was described previously in the humidity control process of 1st Embodiment is applied.

[Example 1]
As shown in the flowchart of FIG. 2, a double-sided polarizing laminate film was produced by carrying out up to the dyeing step (S40), and a polarizing plate was produced by carrying out until the peeling step (S60).

(Base film)
Propylene / ethylene random copolymer containing about 5% by weight of ethylene unit (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumitomo Nobrene W151, melting point Tm = 138 ° C.) Co-extrusion molding using a multilayer extruder with a three-layer substrate film with a resin layer made of a certain homopolypropylene (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumitomo Nobrene FLX80E4, melting point Tm = 163 ° C.) It was produced by. The total thickness of the obtained base film was 100 μm, and the thickness ratio (FLX80E4 / W151 / FLX80E4) of each layer was 3/4/3.

(Primer solution)
Polyvinyl alcohol powder (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: Z-200, average polymerization degree 1100, average saponification degree 99.5 mol%) is dissolved in hot water at 95 ° C. to a concentration of 3 wt% aqueous solution. Was prepared. The resulting aqueous solution was mixed with 1 part by weight of a crosslinking agent (trade name: Sumire's Resin 650, manufactured by Taoka Chemical Industry Co., Ltd.) with respect to 2 parts by weight of the polyvinyl alcohol powder to obtain a primer solution.

(Aqueous solution of polyvinyl alcohol resin)
Polyvinyl alcohol powder (manufactured by Kuraray Co., Ltd., trade name: PVA124, average polymerization degree 2400, average saponification degree 98.0 to 99.0 mol%) is dissolved in 95 ° C. hot water to give a polyvinyl alcohol concentration of 8% by weight. An aqueous alcohol solution was prepared.

(First coating process, first drying process)
While the substrate film is continuously conveyed, one surface thereof is subjected to corona treatment, and then the primer solution is continuously applied to the corona-treated surface using a small-diameter gravure coater, at 60 ° C. for 3 minutes. By drying, a primer layer having a thickness of 0.2 μm was formed. Subsequently, while transporting the film, the aqueous polyvinyl alcohol solution was continuously applied onto the primer layer using a comma coater (first coating step), and dried at 90 ° C. for 4 minutes (the first coating step). Drying step), a 11.5 μm-thick polyvinyl alcohol-based resin layer (hereinafter referred to as “first PVA layer”) was formed on the primer layer, and a single-area layer film was obtained.

(Measurement of moisture content)
It was 0.39 mass% when the moisture content of the single area layer film produced as mentioned above was measured. From the moisture content and the moisture content of the coated film before entering the first drying step, the drying speed in the first drying step was calculated to be 16.4% by mass / min in terms of the average moisture content change. Moreover, it was 2.76 mass% when the moisture content of the 1st PVA layer single-piece | unit of a single area layer film was measured.

(Second coating process, second drying process)
About the single area layer film produced as described above, a 0.2 μm primer layer is formed on the surface of the base film opposite to the surface on which the first PVA layer is formed in the same manner as described above. A polyvinyl alcohol aqueous solution having a thickness of 10.6 μm is coated on the primer layer by applying a polyvinyl alcohol aqueous solution on the primer layer (second coating step) and drying at 90 ° C. for 4 minutes (second drying step). A layer (hereinafter, “second PVA layer”) was formed to obtain a double-sided laminated film.

(Measurement of moisture content)
It was 0.6 mass% when the moisture content of the double-sided laminated film produced as mentioned above was measured. From this moisture content and the moisture content of the double-sided coated film before entering the second drying step, the drying speed in the second drying step was calculated to be 15.9 mass% / min in terms of the average moisture content change. . Moreover, when the moisture content of the 1st PVA layer single-piece | unit and the moisture content of the 2nd PVA layer single-piece | unit in a double-sided laminated film were measured, they were 4.66 mass% and 3.79 mass%, respectively.

(Stretching process)
While continuously transporting the double-sided laminated film obtained as described above, the stretched laminated film was stretched 5.8 times in the longitudinal direction (film transport direction) at a stretching temperature of 160 ° C. by a stretching method between nip rolls. Obtained. In the stretched laminated film, the thickness of the first PVA layer was 5.7 μm, and the thickness of the second PVA layer was 5.4 μm.

(Dyeing process)
The first PVA layer is immersed in a dyeing solution at 30 ° C. containing iodine and potassium iodide so that the residence time is 180 seconds while continuously transporting the stretched laminated film obtained as described above. After dyeing the second PVA layer, excess dyeing solution was washed away with pure water at 10 ° C. Next, a crosslinking treatment was performed by dipping in a crosslinking solution at 76 ° C. containing boric acid and potassium iodide so that the residence time was about 600 seconds. Thereafter, the film was washed with pure water at 10 ° C. for 4 seconds and dried at 80 ° C. for 300 seconds to obtain a polarizing laminated film.

The mixing ratio of the dyeing solution and the crosslinking solution is
<Dyeing solution>
Water: 100 parts by weight Iodine: 0.6 parts by weight Potassium iodide: 10 parts by weight <Crosslinking solution>
Water: 100 parts by weight Boric acid: 9.5 parts by weight Potassium iodide: 5 parts by weight

(Measurement of optical performance)
For the first PVA layer (first polarizer layer) and the second PVA layer (second polarizer layer) of the obtained polarizing laminated film, the polarizer layer that is not the object of measurement is peeled off and removed. Prepare a laminate consisting of the polarizer layer to be measured and the base film, laminate an acrylic adhesive layer on the polarizer layer of the laminate, and paste it onto the glass via the acrylic adhesive layer This was used as an evaluation sample.

The optical characteristics of the evaluation sample were measured with a spectrophotometer with an integrating sphere (manufactured by JASCO Corporation, V7100). Incident light is from the glass side, MD transmittance and TD transmittance are obtained in the wavelength range of 380 nm to 780 nm, and single transmittance and polarization degree at each wavelength are calculated based on Equation (3) and Equation (4). Furthermore, the visibility correction was performed using a JIS Z 8701 two-degree field of view (C light source), and the visibility correction single transmittance (Ty) and the visibility correction polarization degree (Py) were obtained.

In the above, “MD transmittance” is the transmittance when the direction of polarized light emitted from the Glan-Thompson prism is parallel to the transmission axis of the evaluation sample, and “MD” in Equation (3) and Equation (4). It expresses. The “TD transmittance” is a transmittance when the direction of polarized light emitted from the Glan-Thompson prism and the transmission axis of the evaluation sample are orthogonal to each other. In Expressions (3) and (4), “TD” is To express.

Single transmittance (%) = (MD + TD) / 2 Formula (3)
Polarization degree (%) = {(MD−TD) / (MD + TD)} ^1/2 × 100 Formula (4).

(Adhesive solution)
Polyvinyl alcohol powder (manufactured by Kuraray Co., Ltd., trade name: KL-318, average polymerization degree 1800) was dissolved in 95 ° C. hot water to prepare a 3% by weight polyvinyl alcohol aqueous solution. The resulting aqueous solution was mixed with 1 part by weight of a crosslinking agent (trade name: Sumire's Resin 650, manufactured by Taoka Chemical Industry Co., Ltd.) with respect to 2 parts by weight of polyvinyl alcohol powder to obtain an adhesive solution.

(Bonding process)
While continuously transporting the polarizing laminated film obtained above, the adhesive solution is coated on the polarizer layers on both sides, and then the coating surface is subjected to saponification treatment to a thickness of 40 μm. A film (Konica Minolta Co., Ltd., trade name: KC4UY, transparent protective film made of triacetylcellulose (TAC)) is bonded, and is crimped by passing between a pair of bonding rolls. KC4UY / first polarization A multilayer film composed of a child layer / primer layer / base film / primer layer / second polarizer layer / KC4UY was obtained (bonding step). The multilayer film is peeled off between the base film and the primer layer to form two laminates of KC4UY / first polarizer layer / primer layer / base film and primer layer / second polarizer layer / KC4UY, The base film was peeled and removed (peeling step). A 23 μm-thick cyclic polyolefin resin film (manufactured by Nippon Zeon Co., Ltd., trade name: ZF-14) is bonded on the primer layer of each laminate through an adhesive layer, and KC4UY / polarizer layer Two polarizing plates comprising / primer layer / adhesive layer / ZF-14 were obtained. There was no failure such as breakage in the peeling process.

[Example 2]
The drying conditions in the first drying step and the second drying step are changed to 90 ° C. for 3 minutes, and the thickness of the first PVA layer after the first drying step is 9.2 μm, the second drying step A polarizing laminated film and a polarizing plate were produced in the same manner as in Example 1 except that the thickness of the subsequent second PVA layer was 9.4 μm. There was no failure such as breakage in the peeling process.

[Example 3]
The drying conditions in the first drying step and the second drying step are both changed to 90 ° C. for 2 minutes and then at 80 ° C. for 1.5 minutes for a total of 3.5 minutes. Further, the first drying step Polarizing properties in the same manner as in Example 1 except that the thickness of the later first PVA layer was 9.3 μm and the thickness of the second PVA layer after the second drying step was 9.2 μm. A laminated film and a polarizing plate were produced. There was no failure such as breakage in the peeling process.

[Example 4]
The drying conditions in the first drying step and the second drying step are both changed at 75 ° C. for 2 minutes and then at 80 ° C. for 2 minutes, for a total of 4 minutes, and further after the first drying step The polarizing laminated film and the polarizing film were the same as in Example 1 except that the thickness of the PVA layer was 9.0 μm and the thickness of the second PVA layer after the second drying step was 9.1 μm. A plate was made. There was no failure such as breakage in the peeling process.

[Example 5]
As shown in the flowchart of FIG. 1, a single-sided polarizing laminate film was produced by carrying out up to the dyeing step (S40), and a polarizing plate was produced by carrying out until the peeling step (S60). The same base film, primer solution and polyvinyl alcohol aqueous solution as in Examples 1 to 4 were used.

(First coating process, first drying process)
While the substrate film is continuously conveyed, one surface thereof is subjected to corona treatment, and then the primer solution is continuously applied to the corona-treated surface using a small-diameter gravure coater, at 60 ° C. for 3 minutes. By drying, a primer layer having a thickness of 0.2 μm was formed. Subsequently, the polyvinyl alcohol aqueous solution was continuously applied onto the primer layer using a comma coater while transporting the film (first coating step), followed by 1 minute at 80 ° C. for 2 minutes at 90 ° C. By drying for a total of 3.5 minutes for 5 minutes (first drying step), a first PVA layer having a thickness of 9.2 μm was formed on the primer layer to obtain a one-area layer film.

(Stretching process)
While continuously transporting the single-area layer film obtained as described above, a single-sided stretched laminated film is stretched 5.8 times in the longitudinal direction (film transport direction) at a stretching temperature of 160 ° C. by a stretching method between nip rolls. Got. In the stretched laminated film, the thickness of the first PVA layer was 4.7 μm.

(Dyeing process)
The single-sided stretched laminated film obtained as described above was dyed in the same manner as in Example 1 to obtain a single-sided polarizing laminated film.

(Bonding process)
While continuously transporting the obtained single-sided polarizing laminate film, the same adhesive solution as in Example 1 was applied on the polarizer (first polarizer layer), and then the saponification treatment was performed on the coated surface. A 40 μm thick protective film (Konica Minolta Co., Ltd., trade name: KC4UY, transparent protective film made of triacetyl cellulose (TAC)) is pasted and crimped by passing between a pair of pasting rolls. And the multilayer film which consists of KC4UY / 1st polarizer layer / primer layer / base film was obtained (bonding process).

The base film was peeled and removed from the base film and the primer layer from the multilayer film to obtain a laminate composed of KC4UY / first polarizer layer / primer layer (peeling step). A cyclic polyolefin resin film (made by Nippon Zeon Co., Ltd., trade name: ZF-14) having a thickness of 23 μm was bonded onto the primer layer of the obtained laminate through an adhesive layer, and KC4UY / 1st A polarizing plate comprising a polarizer layer / primer layer / adhesive layer / ZF-14 was obtained. There was no failure such as breakage in the peeling process.

[Example 6]
The drying condition in the first drying step was the same as in Example 4, and the single-sided polarizing laminate film and polarizing plate were the same as in Example 5 except that the thickness of the PVA layer after the first drying step was 9.0 μm. A plate was made. In the peeling process, there was no problem such as breakage.

[Comparative Example 1]
Example 1 except that the thickness of the first PVA layer after the first drying step is 9.0 μm and the thickness of the second PVA layer after the second drying step is 8.9 μm. In the same manner, a polarizing laminated film and a polarizing plate were produced.

[Comparative Example 2]
Example 1 except that the thickness of the first PVA layer after the first drying step is 9.2 μm and the thickness of the second PVA layer after the second drying step is 9.3 μm. In the same manner, a polarizing laminated film and a polarizing plate were produced.

Table 1 is a table in which drying conditions and measurement results in Examples 1 to 6 and Comparative Examples 1 and 2 are described.

As shown in Table 1, in Comparative Examples 1 and 2, the moisture content of the laminated film in the state subjected to the stretching process is less than 0.5% by mass, and the moisture content after the first drying process is 0. It was less than 3% by mass. The polarizing laminated films of Comparative Examples 1 and 2 had a low visibility correction polarization degree Py as compared with the polarizing laminated films of Examples 1 to 6.

An acrylic pressure-sensitive adhesive layer is provided on the KC4UY surface of the polarizing plate made of KC4UY / polarizer layer / primer layer / adhesive layer / ZF-14 produced in Examples 1 to 6, and the adhesive layer is attached to the glass through the pressure-sensitive adhesive layer. The combined sample was used as an evaluation sample, and the following heat and heat resistance test and heat resistance test were performed. As a result, all the evaluation samples had a ΔPy in the wet heat resistance test of around 0.001% and a ΔPy in the heat resistance test of around 0.005%, which was a satisfactory level. The polarizing plates produced in Comparative Examples 1 and 2 were evaluated in the same manner. As a result, ΔPy was larger than the evaluation samples of Examples 1 to 6.

(1) Evaluation of moisture and heat resistance Visibility-corrected polarization degree Py after a moisture and heat resistance test that is allowed to stand in an environment of a temperature of 65 ° C. and a relative humidity of 90% for 500 hours, and Py before the test are measured with an absorptiometer (JASCO ( V7100), and the difference ΔPy between the two (Py before the test−Py after the test) is obtained. In the measurement of Py, an evaluation sample is set so that incident light is irradiated on the glass surface, and the visibility correction polarization degree Py after the test is 23 ° C. and 55% relative humidity after the above-mentioned wet heat resistance test. It is measured after leaving it to stand in the environment of about 12 hours. The smaller the absolute value of ΔPy, the higher the heat and moisture resistance.

(2) Evaluation of heat resistance A heat resistance test is performed by leaving it to stand in a dry environment at a temperature of 85 ° C. for 500 hours. In other cases, the visibility-corrected polarization degree Py before and after the test is obtained in the same manner as described in the above-mentioned wet heat resistance test. The difference ΔPy between the two (Py before the test−Py after the test) is obtained. The smaller the absolute value of ΔPy, the higher the heat resistance.

Claims

A coating process for obtaining a coating film by coating an aqueous solution of a polyvinyl alcohol-based resin on a base film;
A drying step of drying the coated film to obtain a laminated film in which a polyvinyl alcohol-based resin layer is formed on the base film;
Stretching process for obtaining a stretched laminated film by uniaxially stretching the laminated film,
Dyeing the polyvinyl alcohol-based resin layer as a polarizer layer, including a dyeing step in this order to obtain a polarizing laminated film,
The said extending process is a manufacturing method of the polarizing laminated film which starts the said uniaxial stretching in the state whose moisture content of the said laminated film is 0.3 mass% or more.
The method for producing a polarizing laminated film according to claim 1, wherein the drying step is performed so that the change in average moisture content of the coated film is 5 to 65% by mass / min.
After the drying step, including a humidity control step of adjusting the moisture content of the laminated film to be 0.3% by mass or more, the moisture content of the laminated film conditioned in the humidity conditioning step The manufacturing method of the light-polarizing laminated film of Claim 1 or 2 which uses for the said extending process with keeping.
A first coating step of applying an aqueous solution of a polyvinyl alcohol-based resin on one surface of the base film to obtain a coated film;
A first drying step of obtaining a laminated film in which a polyvinyl alcohol-based resin layer is formed on one surface of a base film by drying the coating film;
A second coating step in which an aqueous solution of a polyvinyl alcohol-based resin is applied to the other surface of the base film to obtain a double-sided coating film;
A second drying step of drying the double-sided coating film to obtain a double-sided laminated film in which a polyvinyl alcohol-based resin layer is formed on both sides of the base film;
Stretching process for obtaining a stretched laminated film by uniaxially stretching the double-sided laminated film,
Dyeing the polyvinyl alcohol-based resin layer as a polarizer layer, including a dyeing step in this order to obtain a polarizing laminated film,
The said extending process is a manufacturing method of a polarizing laminated film which starts the said uniaxial stretching in the state whose moisture content of the said double-sided laminated film is 0.5 mass% or more.
The method for producing a polarizing laminated film according to claim 4, wherein the first drying step is performed such that the moisture content of the laminated film after drying is 0.3% by mass or more.
The first drying step and the second drying step are performed so that the average moisture content change of the coated film and the average moisture content change of the double-sided coated film are 5 to 65% by mass / min, respectively. The manufacturing method of the light-polarizing laminated film of Claim 4 or 5.
After the second drying step, the double-sided laminated film that has been conditioned in the humidity-conditioning step, including a humidity-conditioning step for adjusting the moisture content of the double-sided laminated film to be 0.5% by mass or more. The method for producing a polarizing laminated film according to any one of claims 4 to 6, wherein the film is subjected to the stretching step while maintaining its moisture content.
A step of producing a polarizing laminated film by the production method according to any one of claims 1 to 7,
A laminating step of obtaining a multilayer film by laminating a protective film on the surface of the polarizer layer in the polarizing laminated film opposite to the base film;
The manufacturing method of a polarizing plate including the peeling process of peeling the said base film from the said multilayer film, and obtaining the polarizing plate provided with the said polarizer layer and the said protective film.