CN108121027B

CN108121027B - Method for producing polarizing laminated film with protective film and method for producing polarizing plate

Info

Publication number: CN108121027B
Application number: CN201711191851.9A
Authority: CN
Inventors: 河村真一
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2016-11-28
Filing date: 2017-11-24
Publication date: 2022-03-18
Anticipated expiration: 2037-11-24
Also published as: CN108121027A; JP2018087861A; JP6306675B1; KR20180061012A; KR102404504B1

Abstract

A method for producing a polarizing laminate film with a protective film and a method for producing a polarizing plate. Provided is a method for producing a polarizing laminate film with a protective film, which can provide a polarizing plate in which image distortion is suppressed when the polarizing laminate film is used as an intermediate for producing a polarizing plate. Provided is a method for producing a polarizing laminate film with a protective film, the method comprising: the method for producing the polarizing film comprises a step of forming a polyvinyl alcohol resin layer on at least one surface of a base film to obtain a laminated film, a step of stretching the laminated film to obtain a stretched laminated film, a step of dyeing the polyvinyl alcohol resin layer of the stretched laminated film with a dichroic dye to form a polarizer layer to obtain a polarizing laminated film, and a step of laminating a protective film on the surface of the polarizing laminated film on the polarizer layer side to obtain the polarizing laminated film with the protective film, wherein the arithmetic mean roughness of the surface of the protective film on the polarizer layer side is 0.150 [ mu ] m or less.

Description

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

Technical Field

The present invention relates to a method for producing a polarizing laminated film with a protective film and a method for producing a polarizing plate. The present invention also relates to a polarizing laminated film with a protective film and a polarizing laminated film roll with a protective film.

Background

Polarizing plates are widely used in image display devices represented by liquid crystal display devices and the like. The polarizing plate is generally configured by laminating a thermoplastic resin film such as a protective film on one surface or both surfaces of a polarizer layer made of a polyvinyl alcohol resin. In recent years, with the expansion of image display devices such as mobile devices and thin televisions, there is an increasing demand for thinner polarizing plates or thinner polarizer layers.

As a method for producing a polarizing plate having a thin polarizer layer, the following methods are known: a method for producing a polarizing laminated film having a polarizer layer formed on a base film by applying a coating liquid containing a polyvinyl alcohol resin to the base film to form a polyvinyl alcohol resin layer, stretching the laminated film to form a dyed film, and then applying a dyeing treatment for adsorbing a dichroic pigment to the polyvinyl alcohol resin layer, followed by adhering a thermoplastic resin film such as a protective film to the surface of the polarizer layer opposite to the base film using an adhesive, and then peeling off and removing the base film as necessary (for example, patent document 1).

According to the above method, since the polyvinyl alcohol resin layer is formed by coating, the polyvinyl alcohol resin layer can be easily formed into a film as compared with a single layer (monomer) film containing a polyvinyl alcohol resin, and thus the polarizer layer can be easily formed into a film. In addition, since the polyvinyl alcohol resin layer and the polarizing plate layer of the film are always supported by a certain film in the production process, the film has excellent handling properties in the production process.

As the adhesive for bonding a thermoplastic resin film, an active energy ray-curable adhesive such as an aqueous adhesive or an ultraviolet-curable adhesive is known, and in the case of bonding a thermoplastic resin film having low moisture permeability, etc., an active energy ray-curable adhesive is used in many cases because it is difficult to evaporate and remove water from the adhesive layer after bonding the thermoplastic resin film (for example, patent documents 2 to 5).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2000-338329

Patent document 2: japanese patent laid-open publication No. 2013-205741

Patent document 3: japanese patent laid-open No. 2012-203205

Patent document 4: japanese laid-open patent publication No. 2012-203108

Patent document 5: japanese patent laid-open publication No. 2004-24925

Disclosure of Invention

[ problems to be solved by the invention ]

When a thermoplastic resin film is bonded to a polarizer layer using an active energy ray-curable adhesive and the resulting polarizer is observed from the thermoplastic resin film side under a fluorescent lamp, an image of the fluorescent lamp reflected on the surface of the thermoplastic resin film may be deformed. Hereinafter, in the present specification, such a phenomenon that the reflection image is deformed is referred to as "image deformation". This image distortion is not only undesirable in terms of the appearance of the polarizing plates, but also may have adverse effects such as distortion of the display on the visibility of the display device (the property of the viewing rates of the liquid crystal molecules ) when the polarizing plates are assembled into an image display device.

An object of the present invention is to provide an optical laminate (polarizing laminate film with a protective film) capable of providing a polarizing plate in which the above-described image distortion is suppressed when the optical laminate is used as an intermediate for producing a polarizing plate, and a method for producing the same. Another object of the present invention is to provide a polarizing plate in which the above-described image distortion is suppressed, and a method for manufacturing the same.

[ means for solving the problems ]

The present invention provides a method for producing a polarizing laminated film with a protective film, a method for producing a polarizing plate, a polarizing laminated film with a protective film, and a polarizing laminated film roll with a protective film, as described below.

[1] A method for producing a polarizing laminate film with a protective film, comprising: a step of forming a polyvinyl alcohol resin layer on at least one surface of a base film to obtain a laminated film, a step of stretching the laminated film to obtain a stretched laminated film,

A step of obtaining a polarizing laminated film by dyeing the polyvinyl alcohol resin layer of the stretched laminated film with a dichroic dye to form a polarizer layer, and

a step of laminating a protective film on the surface of the polarizing laminated film on the polarizing plate layer side to obtain a polarizing laminated film with a protective film,

the protective film has a surface on the polarizing plate layer side having an arithmetic mean roughness of 0.150 [ mu ] m or less.

[2] The production process according to [1], wherein,

the protective film is laminated in contact with the surface of the polarizer layer.

[3] The manufacturing method according to [1] or [2], further comprising:

and a step of winding the polarizing laminated film with the protective film to obtain a polarizing laminated film coil with a protective film.

[4] A method of manufacturing a polarizing plate, the method comprising:

a step of obtaining a polarizing laminated film with a protective film by the production method according to [1] or [2 ];

a step of peeling the protective film from the polarizing laminated film with the protective film;

a step of laminating a first thermoplastic resin film on the surface of the polarizing laminate film on the polarizing plate layer side exposed by the step of peeling the protective film, with a layer of an active energy ray-curable adhesive interposed therebetween; and

and curing the active energy ray-curable adhesive layer.

[5] The production method according to [4], wherein,

the method further comprises, between the step of obtaining the polarizing laminated film with a protective film and the step of peeling off the protective film: a step of winding the polarizing laminated film with the protective film to obtain a polarizing laminated film coil with a protective film,

in the step of peeling the protective film, the protective film is peeled from the polarizing laminated film with the protective film unwound from the polarizing laminated film roll with the protective film.

[6] The production method according to [4] or [5], wherein,

the method further includes, after the step of curing the layer of the active energy ray-curable adhesive, the steps of: and a step of peeling the base film.

[7] A polarizing laminate film with a protective film, comprising in this order: a base film, a polarizer layer comprising a polyvinyl alcohol resin, and a protective film,

[8] The polarizing laminate film with a protective film according to [7], wherein the protective film is in contact with a surface of the polarizer layer.

[9] A polarizing laminated film roll with a protective film, which is a wound product of the polarizing laminated film with a protective film according to [7] or [8 ].

[ Effect of the invention ]

An optical laminate (polarizing laminate film with protective film), which can provide a polarizing plate in which image distortion is suppressed when used as an intermediate for the production of a polarizing plate, a roll of the optical laminate, and methods for producing the same can be provided. In addition, a polarizing plate in which image distortion is suppressed and a method for manufacturing the same can be provided.

Drawings

Fig. 1 is a flowchart illustrating a method for manufacturing a polarizing laminated film with a protective film according to an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view showing an example of the layer structure of the laminated film obtained in the resin layer forming step.

Fig. 3 is a schematic cross-sectional view showing an example of the layer structure of the stretched laminated film obtained in the stretching step.

Fig. 4 is a schematic cross-sectional view showing an example of the layer structure of the polarizing laminated film obtained in the dyeing step.

Fig. 5 is a schematic cross-sectional view showing an example of the layer configuration of the polarizing laminated film with a protective film obtained in the protective film laminating step.

Fig. 6 is a flowchart showing a method for manufacturing a polarizing plate according to an embodiment of the present invention.

Fig. 7 is a schematic cross-sectional view showing an example of the layer structure of the film obtained in the protective film peeling step.

Fig. 8 is a schematic cross-sectional view showing an example of the layer structure of the first polarizing plate obtained through the first bonding step and the curing step.

Fig. 9 is a schematic cross-sectional view showing an example of the layer structure of the second polarizing plate obtained in the base film peeling step.

Fig. 10 is a schematic cross-sectional view showing an example of the layer structure of the third polarizing plate.

Detailed Description

The present invention will be described in detail below with reference to embodiments.

< method for producing polarizing laminated film with protective film >

Fig. 1 is a flowchart illustrating a method for manufacturing a polarizing laminated film with a protective film according to an embodiment of the present invention. As shown in fig. 1, a method for producing a polarizing laminate film with a protective film according to an embodiment of the present invention includes the steps of:

a resin layer forming step S10 of forming a polyvinyl alcohol resin layer on at least one surface of a base film to obtain a laminated film;

a stretching step S20 of stretching the laminate film to obtain a stretched laminate film;

a dyeing step S30 of dyeing the polyvinyl alcohol resin layer of the stretched laminated film with a dichroic dye to form a polarizer layer and thereby obtain a polarizing laminated film;

the protective film laminating step S40 is a step of laminating a protective film on the surface of the polarizing laminate film on the polarizing plate layer side to obtain a polarizing laminate film with a protective film.

The method for producing a polarizing laminate film with a protective film may further include, after the protective film lamination step S40: and a winding step of winding the polarizing laminated film with the protective film to obtain a polarizing laminated film coil with the protective film. The polarizing laminate film with a protective film and the polarizing laminate film roll with a protective film can be used as a production intermediate for producing a polarizing plate, as described later.

In the present specification, the "polarizing laminate film" refers to a film including a base film and a polarizer layer laminated on the base film, and not including a thermoplastic resin film such as a protective film laminated (bonded) to the polarizer layer via an adhesive layer. The polarizing laminate film obtained by laminating a protective film on the surface of the polarizing laminate film on the polarizing plate layer side is referred to as a "polarizing laminate film with a protective film" in the present specification. In the present specification, the term "polarizing plate" refers to a film including a polarizer layer and a thermoplastic resin film such as a protective film laminated (bonded) on at least one surface of the polarizer layer with an adhesive layer interposed therebetween. The polarizing plate may also include the above substrate film. In addition, the polarizing plate may include: a polarizer layer; a first thermoplastic resin film such as a protective film laminated (bonded) on at least one surface of the polarizer layer with an adhesive layer interposed therebetween; and a second thermoplastic resin film such as a protective film laminated (bonded) on the other surface with an adhesive layer or pressure-sensitive adhesive layer interposed therebetween.

A thermoplastic resin film such as a protective film laminated (bonded) to a polarizer layer through an adhesive layer is generally an optical film. The optical film is a film which is a member or a part thereof incorporated in an optical device such as a display device. The substrate film is, for example, a film made of a thermoplastic resin, and is usually peeled off and removed before the assembly, without being incorporated into an optical device such as a display device. Therefore, the substrate film is preferably capable of being peeled off from the polarizer layer. However, it is not excluded that the substrate film may serve as an optical film.

The above steps are explained below with reference to the drawings.

[1] Resin layer forming step S10

Referring to fig. 2, this step is a step of forming a polyvinyl alcohol resin layer 6 on at least one surface of a base film 30 to obtain a laminated film 100. The polyvinyl alcohol resin layer 6 is a layer which is stretched and dyed to form a polarizer layer 5 (fig. 4). The polyvinyl alcohol resin layer 6 can be formed by applying a coating liquid containing a polyvinyl alcohol resin to one surface or both surfaces of the base film 30 and drying the coating liquid. Such a method of forming the polyvinyl alcohol resin layer 6 by coating is advantageous, for example, from the viewpoint of easily obtaining the polarizer layer 5 as a film. In the resin layer forming step S10, the resin layer forming step S10 is continuously performed while the base film 30 is continuously unwound from a film roll, which is a wound product of the long base film 30, and conveyed. The film transfer may be performed using a guide roller or the like.

(substrate film)

The base film 30 may be made of a thermoplastic resin, and among them, it is preferably made of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such thermoplastic resins include polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins (norbornene resins, etc.); a polyester resin; (meth) acrylic resins; cellulose ester resins such as triacetyl cellulose and diacetyl cellulose; a polycarbonate-based resin; a polyvinyl alcohol resin; polyvinyl acetate resin; a polyarylate-based resin; a polystyrene-based resin; a polyether sulfone-based resin; a polysulfone-based resin; a polyamide resin; a polyimide-based resin; and mixtures, copolymers, and the like thereof.

In the present specification, "(meth) acrylic" means at least one selected from acrylic and methacrylic. The same applies to the case of "(meth) acryloyl group" or the like.

The substrate film 30 may have a single-layer structure composed of 1 resin layer containing 1 or 2 or more thermoplastic resins, or may have a multilayer structure in which resin layers containing 1 or 2 or more thermoplastic resins are stacked in layers. The base film 30 is preferably made of a resin that can be stretched at a stretching temperature suitable for stretching the polyvinyl alcohol resin layer 6 when the laminate film 100 is stretched in the stretching step S20 described later.

Examples of the chain polyolefin resin include: homopolymers of chain olefins such as polyethylene resins and polypropylene resins, and copolymers containing 2 or more kinds of chain olefins. The base film 30 containing a chain polyolefin resin is preferable in that high-ratio stretching can be easily and stably performed. Among them, the substrate film 30 more preferably contains: polypropylene resins (polypropylene resins as propylene homopolymers and copolymers mainly composed of propylene), polyethylene resins (polyethylene resins as ethylene homopolymers and copolymers mainly composed of ethylene), and the like.

An example of a copolymer mainly composed of propylene, which is preferably used as the thermoplastic resin constituting the base film 30, may be a copolymer of propylene and another monomer copolymerizable therewith.

Examples of the monomer copolymerizable with propylene include ethylene and α -olefin. The alpha-olefin preferably has 4 or more carbon atoms, and more preferably has 4 to 10 carbon atoms. Specific examples of the α -olefin having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene and 4-methyl-1-pentene; vinylcyclohexane, and the like. The copolymer of propylene and another monomer copolymerizable therewith may be a random copolymer or a block copolymer.

The content of the other monomer is, for example, 0.1 to 20% by weight, preferably 0.5 to 10% by weight, in the copolymer. The content of other monomers in the copolymer can be determined by Infrared (IR) spectroscopy according to the method described on page 616 of the handbook of polymer analysis (1995, published by the book store in hei house).

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

The stereoregularity of the polypropylene resin is preferably substantially isotactic or syndiotactic. The base film 30 comprising a polypropylene resin having substantially isotactic or syndiotactic stereoregularity is relatively excellent in handling properties and excellent in mechanical strength under a high-temperature environment.

The cyclic polyolefin resin is a general term for resins polymerized by using a cyclic olefin as a polymerization unit, and examples thereof include those described in Japanese patent application laid-open Nos. 1-240517, 3-14882, and 3-122137. Specific examples of the cyclic polyolefin resin include: ring-opening (co) polymers of cyclic olefins; addition polymers of cyclic olefins; copolymers (typically random copolymers) of cyclic olefins with linear olefins such as ethylene and propylene; and graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof; and hydrides thereof. Among them, it is preferable to use: norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins.

The polyester-based resin is a resin having an ester bond other than the cellulose ester-based resin described below, and generally includes a polycondensate of a polycarboxylic acid or a derivative thereof and a polyhydric alcohol. As the polycarboxylic acid or its derivative, a divalent dicarboxylic acid or its derivative can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyol, a divalent diol can be used, and examples thereof include: ethylene glycol, propylene glycol, butanediol, neopentyl glycol, cyclohexanedimethanol.

Typical examples of the polyester resin include: the polycondensation product of terephthalic acid and ethylene glycol is polyethylene terephthalate. Polyethylene terephthalate is a crystalline resin, and is easily subjected to a treatment such as stretching in a state before crystallization treatment. If necessary, the crystallization treatment may be performed by heat treatment during or after stretching. Further, it is also preferable to use a copolyester obtained by copolymerizing a polyethylene terephthalate skeleton with another monomer to reduce crystallinity (or to make the copolymer amorphous). Examples of such resins include: and (b) a copolymer of cyclohexanedimethanol and isophthalic acid. These resins are also excellent in stretchability and therefore can be suitably used.

Specific examples of the polyester resin other than polyethylene terephthalate and its copolymer include polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polypropylene terephthalate, polypropylene naphthalate, polycyclohexanedimethanol terephthalate, and polycyclohexanedimethanol naphthalate.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include, for example: poly (meth) acrylates such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylate copolymers; methyl methacrylate-acrylate- (meth) acrylic acid copolymer; methyl (meth) acrylate-styrene copolymers (MS resins and the like); copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylic acid norbornyl ester copolymer, etc.). Preferably, a poly (meth) acrylic acid C such as poly (methyl (meth) acrylate) is used_1-6The polymer containing an alkyl ester as a main component is preferably a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include triacetyl cellulose, diacetyl cellulose, cellulose tripropionate, and cellulose dipropionate. Further, copolymers thereof and modified products in which a part of the hydroxyl groups is substituted with another substituent may be mentioned. Among them, cellulose triacetate (triacetyl cellulose) is particularly preferable.

Polycarbonate resins are engineering plastics containing a polymer in which monomer units are bonded via carbonate groups, and are resins having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate-based resin constituting the base film 30 may be: a resin called a modified polycarbonate in which the main chain is modified in order to reduce the photoelastic coefficient, and a copolymerized polycarbonate in which the wavelength dependence is improved.

Among the above, from the viewpoint of stretchability, heat resistance and the like, one of the thermoplastic resins preferably used is a polypropylene-based resin.

The substrate film 30 may contain any appropriate additive other than the thermoplastic resin. Examples of the additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, stainblocker, flame retardants, nucleating agents, antistatic agents, pigments, and colorants. The content of the thermoplastic resin in the base film 30 is preferably 50 to 100 wt%, more preferably 50 to 99 wt%, further preferably 60 to 98 wt%, and particularly preferably 70 to 97 wt%.

The thickness of the base film 30 is usually 1 to 500. mu.m, preferably 1 to 300. mu.m, more preferably 5 to 200. mu.m, and still more preferably 5 to 150. mu.m, from the viewpoint of strength, handling properties, and the like.

(formation of polyvinyl alcohol resin layer)

The coating liquid applied to the base film 30 is preferably a polyvinyl alcohol resin solution obtained by dissolving a powder of a polyvinyl alcohol resin in a good solvent (e.g., water). The coating liquid may contain additives such as a plasticizer and a surfactant as necessary. As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. The polyvinyl acetate resin may be exemplified by: homopolymers of vinyl acetate, i.e., polyvinyl acetate; and copolymers of vinyl acetate with other monomers copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

The saponification degree of the polyvinyl alcohol resin may be in the range of 80.0 to 100.0 mol%, preferably 90.0 to 99.5 mol%, and more preferably 94.0 to 99.0 mol%. If the saponification degree is less than 80.0 mol%, the water resistance and the moist heat resistance of the polarizing laminate film, the polarizing laminate film with a protective film, and the polarizing plate may be lowered. When a polyvinyl alcohol resin having a saponification degree of more than 99.5 mol% is used, the dyeing speed of the dichroic dye may be low, the productivity may be lowered, and a polarizer layer having sufficient polarizing performance may not be obtained.

The degree of saponification is determined by the acetoxy group (acetoxy group: -OCOCH) contained in a polyvinyl acetate resin as a raw material of the polyvinyl alcohol resin₃) The ratio of hydroxyl groups converted by the saponification step is expressed as a unit ratio (mol%), and is defined by the following formula,

degree of saponification (mol%): 100 × (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups). The degree of saponification may be in accordance with JIS K6726: 1994, to obtain.

The polyvinyl alcohol resin may be modified polyvinyl alcohol partially modified. Examples of the polyvinyl alcohol resin include those obtained by using an olefin such as ethylene or propylene; unsaturated carboxylic acids such as (meth) acrylic acid and crotonic acid; modified polyvinyl alcohols obtained by modifying alkyl esters of unsaturated carboxylic acids, and (meth) acrylamides. The proportion of modification is preferably less than 30 mol%, more preferably less than 10%. When the modification is performed at more than 30 mol%, the dichroic dye is less likely to be adsorbed, and it is likely that a polarizer layer having sufficient polarizing performance is not obtained.

The polyvinyl alcohol resin preferably has an average polymerization degree of 100 to 10000, more preferably 1500 to 8000, and further preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol resin may be in accordance with JIS K6726: 1994, to obtain.

The method of applying the coating liquid to the base film 30 may be appropriately selected from: wire bar coating method; roll coating methods such as reverse coating and gravure coating; die coating; comma coating method; die lip coating; spin coating; screen coating; a jet flow (fountain) coating method; dip coating; spraying, etc.

The drying temperature and drying time of the coating layer (polyvinyl alcohol resin layer before drying) are set according to the kind of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ℃ and preferably 60 to 150 ℃. When the solvent contains water, the drying temperature is preferably 80 ℃ or higher.

The polyvinyl alcohol resin layer 6 may be formed on only one surface of the base film 30, or may be formed on both surfaces. When formed on both sides, curling of the film that may occur at the time of manufacturing the polarizing laminated film 300 (see fig. 4) can be suppressed, and 2 polarizing plates can be obtained from 1 polarizing laminated film 300, and thus is also advantageous in terms of the production efficiency of the polarizing plate.

The thickness of the polyvinyl alcohol resin layer 6 in the laminated film 100 is preferably 3 to 30 μm, and more preferably 5 to 20 μm. In the case of the polyvinyl alcohol resin layer 6 having a thickness within this range, the polarizer layer 5 having a dichroic dye with good dyeing properties and excellent polarizing properties and being sufficiently thin (for example, having a thickness of 10 μm or less) can be obtained through the stretching step S20 and the dyeing step S30 described later.

Before the application of the coating liquid, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol resin layer 6, at least the surface of the base film 30 on the side where the polyvinyl alcohol resin layer 6 is to be formed may be subjected to corona treatment, plasma treatment, flame (flame) treatment, or the like. For the same reason, the polyvinyl alcohol resin layer 6 may be formed on the base film 30 via an undercoat layer or the like. The undercoat layer may also function to enable the substrate film 30 to be peeled off from the polarizer layer 5.

The undercoat layer can be formed by applying a coating liquid for forming an undercoat layer to the surface of the base film 30 and then drying the coating liquid. The coating liquid contains a component that exerts a certain degree of strong adhesion to both the base film 30 and the polyvinyl alcohol resin layer 6, and generally contains a resin component and a solvent that impart such adhesion. The resin component is preferably a thermoplastic resin having excellent transparency, thermal stability, stretchability, and the like, and examples thereof include (meth) acrylic resins and polyvinyl alcohol resins. Among them, a polyvinyl alcohol resin which can impart good adhesion is preferably used. More preferably a polyvinyl alcohol resin. The solvent is usually a common organic solvent or aqueous solvent that can dissolve the resin component, and the undercoat layer is preferably formed from a coating liquid using water as a solvent.

In order to increase the strength of the undercoat layer, a crosslinking agent may be added to the coating liquid for forming the undercoat layer. Specific examples of the crosslinking agent include: epoxy-based, isocyanate-based, dialdehyde-based, metal-based (e.g., metal salt, metal oxide, metal hydroxide, organometallic compound), and polymer-based crosslinking agents. When a polyvinyl alcohol resin is used as the resin component for forming the undercoat layer, a polyamide epoxy resin, a methylolated melamine resin, a dialdehyde-based crosslinking agent, a metal chelate compound-based crosslinking agent, or the like is preferably used.

The thickness of the primer layer is preferably about 0.05 to 1 μm, and more preferably 0.1 to 0.4 μm. When the thickness is within this range, a suitable adhesive force between the base film 30 and the polyvinyl alcohol resin layer 6 can be easily obtained.

The method of applying the coating liquid for forming the undercoat layer to the base film 30 may be the same as the method of applying the coating liquid for forming the polyvinyl alcohol resin layer. The drying temperature of the coating layer formed from the coating liquid for forming the undercoat layer is, for example, 50 to 200 ℃, preferably 60 to 150 ℃. When the solvent contains water, the drying temperature is preferably 80 ℃ or higher.

[2] Stretching step S20

Referring to fig. 3, this step is a step of stretching the laminated film 100 to obtain a stretched laminated film 200 including a stretched base film 30 'and a stretched polyvinyl alcohol resin layer 6'. The stretching is usually uniaxial. The stretching step S20 may be performed continuously while the long laminated film 100 is conveyed, for example. The film transfer may be performed using a guide roller or the like.

The stretch ratio of the laminated film 100 may be appropriately selected depending on the desired polarization characteristics, and is preferably greater than 5 times and 17 times or less, and more preferably greater than 5 times and 8 times or less, with respect to the original length of the laminated film 100. When the stretching ratio is 5 times or less, the polyvinyl alcohol resin layer 6' may not be sufficiently oriented, and thus the degree of polarization of the polarizer layer 5 may not be sufficiently high. On the other hand, if the stretch ratio is more than 17 times, film breakage is likely to occur during stretching, and the thickness of the stretched laminated film 200 becomes thinner than necessary, which may reduce processability and workability in subsequent steps.

The stretching treatment is not limited to the one-stage stretching, and may be performed in multiple stages. In this case, all the steps of the multi-step stretching process may be continuously performed before the dyeing step S30, or the stretching process may be performed after the second step at the same time as the dyeing and/or crosslinking process in the dyeing step S30. When the multistage stretching treatment is performed in this manner, the stretching treatment is preferably performed so that the total of all stages of the stretching treatment becomes a stretching ratio of more than 5 times.

The stretching treatment may be longitudinal stretching in which stretching is performed in the film longitudinal direction (film transport direction), or may be transverse stretching in which stretching is performed in the film width direction, oblique stretching, or the like. Examples of the longitudinal stretching method include: inter-roll stretching in which stretching is performed using a roll (a nip roll or the like), compression stretching, stretching using a chuck (a jig), hot-roll stretching using a hot roll, or the like. The transverse stretching method may be a tenter method. The stretching treatment may be performed by either a wet stretching method or a dry stretching method.

The stretching temperature is set to a temperature not lower than the temperature at which the polyvinyl alcohol resin layer 6 and the base film 30 are entirely stretchable, preferably in the range of-30 ℃ to +30 ℃ of the phase transition temperature (melting point or glass transition temperature) of the base film 30, more preferably in the range of-30 ℃ to +5 ℃ of the phase transition temperature, and still more preferably in the range of-25 ℃ to +0 ℃. When the substrate film 30 includes a plurality of resin layers, the phase transition temperature refers to 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-30 ℃, it is difficult to achieve high stretching ratio of more than 5 times, or the fluidity of the base film 30 is too low to make the stretching treatment difficult. If the stretching temperature is higher than the phase transition temperature +30 ℃, the fluidity of the base film 30 becomes too high and stretching tends to be difficult. Since a high stretch ratio of more than 5 times is more easily achieved, the stretching temperature is in the above range, and more preferably 120 ℃.

The method of heating the laminated film 100 in the stretching process includes: a zone heating method (for example, a method of heating in a stretching zone such as a heating furnace adjusted to a predetermined temperature by blowing hot air); a method of heating the roll itself when the roll is used for stretching; a heater heating method (a method in which an infrared heater, a halogen heater, a flat heater, or the like is provided above and below the laminated film 100 and heating is performed by radiant heat) or the like. In the inter-roll stretching method, the zone heating method is preferable from the viewpoint of uniformity of stretching temperature.

A preheating step of preheating the laminated film 100 may be provided before the stretching step S20. The preheating method may be the same as the heating method in the stretching treatment. The preheating temperature is preferably in the range of-50 ℃ to. + -. 0 ℃ for stretching, more preferably in the range of-40 ℃ to-10 ℃ for stretching.

In addition, the heat-setting treatment step may be provided after the stretching treatment in the stretching step S20. The heat-fixing treatment is as follows: while maintaining the tension state in a state where the end of the stretched laminated film 200 is held by a jig, the heat treatment is performed at a temperature equal to or higher than the crystallization temperature of the polyvinyl alcohol resin. By this heat-setting treatment, crystallization of the polyvinyl alcohol resin layer 6' is promoted. The temperature of the heat-setting treatment is preferably in the range of-0 ℃ to-80 ℃ for stretching, and more preferably in the range of-0 ℃ to-50 ℃ for stretching.

[3] Dyeing step S30

Referring to fig. 4, the present process is as follows: the polyvinyl alcohol resin layer 6' of the stretched laminated film 200 is dyed with a dichroic dye and is subjected to adsorption orientation to form the polarizer layer 5. Through this step, a polarizing laminate film 300 in which the polarizer layer 5 is laminated on one surface or both surfaces of the base film 30' can be obtained. The dyeing step S30 may be performed continuously while the long stretched laminate film 200 is being conveyed, for example, in the dyeing step S30. The film transfer may be performed using a guide roller or the like.

Specific examples of the dichroic dye include iodine and a dichroic organic dye. Specific examples of dichroic organic dyes include, for example, red BR, red LR, red R, pink LB, rubine BL, purplish red GS, sky blue LG, lemon yellow, blue BR, blue 2R, tibetan blue RY, green LG, purple LB, purple B, black H, black B, black GSP, yellow 3G, yellow R, orange LR, orange 3R, scarlet GL, scarlet KGL, congo red, bright purple BK, sipelan blue G, sipelan blue GL, sipelan orange GL, direct sky blue, direct fast orange S, fast black. The dichroic pigment may be used alone in 1 kind, or in combination of 2 or more kinds.

The dyeing step S30 can be performed by immersing the stretched laminated film 200 in a liquid (dyeing bath) containing a dichroic dye. The dyeing bath may be a solution prepared by dissolving the dichroic dye in a solvent. The solvent of the dyeing solution is usually water, and an organic solvent compatible with water may be further added. The concentration of the dichroic pigment in the dyeing bath is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight.

When iodine is used as the dichroic dye, it is preferable to further add an iodide to the iodine-containing dye bath because the dyeing efficiency can be 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, titanium iodide, and the like. The concentration of iodide in the dyeing bath is preferably 0.01 to 20 wt%. Among the iodides, potassium iodide is preferably added. In the case of adding potassium iodide, the ratio of iodine to potassium iodide is preferably 1: 5-1: 100, more preferably 1: 6-1: 80. the temperature of the dyeing bath is preferably 10-60 ℃, and more preferably 20-40 ℃.

In the dyeing step S30, an additional stretching process may be further applied to the stretched laminate film 200. The embodiments in this case include the following: 1) after the stretching process is performed at a magnification lower than the target magnification in the stretching process S20, the stretching process is performed in the dyeing process S30 so that the total stretching magnification reaches the target magnification; as described later, in the case where the cross-linking treatment is performed after the dyeing treatment, 2) after the stretching treatment is performed at a magnification lower than the target magnification in the stretching step S20, the stretching treatment is performed in the dyeing treatment in the dyeing step S30 to the extent that the total stretching magnification does not reach the target magnification, and then the stretching treatment is performed in the cross-linking treatment so that the final total stretching magnification reaches the target magnification.

In order to achieve good orientation of the dichroic dye adsorbed on the polyvinyl alcohol resin layer, it is preferable to perform the dyeing step S30 after at least the laminate film 100 is subjected to stretching treatment to some extent.

The dyeing step S30 may include a crosslinking step performed subsequent to the dyeing treatment. The crosslinking treatment step may be performed by immersing the dyed stretched laminate film in a liquid (crosslinking bath) containing a crosslinking agent. Examples of the crosslinking agent include boric acid, boron compounds such as borax, glyoxal, and glutaraldehyde. Only 1 kind of the crosslinking agent may be used, or 2 or more kinds may be used in combination. The crosslinking bath may be a solution prepared by dissolving a crosslinking agent in a solvent. The solvent may be water, or may further contain an organic solvent having compatibility with water. The concentration of the crosslinking agent in the crosslinking bath is preferably 1 to 20% by weight, more preferably 6 to 15% by weight.

The crosslinking bath may further comprise iodide. The in-plane polarization characteristics of the polarizer layer 5 can be made more uniform by the addition of the iodide. Specific examples of the iodide are the same as those described above. The concentration of the iodide in the crosslinking bath is preferably 0.05 to 15 wt%, more preferably 0.5 to 8 wt%. The temperature of the crosslinking bath is preferably 10 to 90 ℃.

The crosslinking treatment may be performed simultaneously with the dyeing treatment by adding a crosslinking agent to the dyeing bath. Further, the treatment of immersing in the crosslinking bath may be performed 2 or more times using 2 or more types of crosslinking baths having different compositions. The stretching treatment may be performed in the crosslinking treatment. The specific embodiment of the stretching treatment in the crosslinking treatment is as described above.

After the dyeing step S30, a washing step and a drying step may be performed. The washing process typically includes a water washing process. The water washing treatment may be performed by immersing the membrane after the dyeing treatment or the crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water cleaning temperature is usually 3 to 50 ℃, preferably 4 to 20 ℃. The washing step may be a combination of a water washing step and a washing step using an iodide solution. The drying step performed after the washing step may be any suitable method such as natural drying, air-blowing drying, or heat drying. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ℃.

The thickness of the polarizer layer 5 of the polarizing laminate film 300 is preferably 10 μm or less, more preferably 8 μm or less, and still more preferably 7 μm or less. By setting the thickness of the polarizer layer 5 to 10 μm or less, a thin polarizing plate can be obtained. The thickness of the polarizer layer 5 is usually 1 μm or more or 2 μm or more.

As described above, when the thermoplastic resin film is bonded to the polarizer layer using the active energy ray-curable adhesive, and the obtained polarizing plate is observed from the thermoplastic resin film side under a fluorescent lamp, an image of the fluorescent lamp reflected on the surface of the thermoplastic resin film may be "deformed". In the case of image deformation, it was found that fine irregularities on the surface of the polarizing plate layer are increased in weight due to curing shrinkage of the adhesive layer caused by rapid curing by irradiation with active energy rays and deformation of the surface of the polarizing plate layer caused by rapid application of heat from the active energy ray light source, and as a result, image deformation occurs. Such a fine unevenness is likely to be increased when the thickness of the polarizer layer 5 is small and the rigidity is low. Therefore, the present invention capable of suppressing image distortion is particularly advantageous when the thickness of the polarizer layer 5 is small, for example, when the thickness of the polarizer layer 5 is 10 μm or less, and further 8 μm or less.

[4] Protective film laminating step S40

Referring to fig. 5, the present step is a step of laminating a protective film 7 on the surface of the polarizing laminate film 300 on the polarizer layer 5 side to obtain a polarizing laminate film 400 with a protective film. The protective film 7 is preferably laminated on the polarizer layer 5 in contact with the surface of the polarizer layer 5 (the surface on the opposite side to the substrate film 30'). In the case where the polarizer layers 5 are laminated on both surfaces of the base film 30', the protective film 7 may be laminated on each polarizer layer 5.

The protective film laminating step S40 includes, for example, the following steps: while the long polarizing laminate film 300 and the protective film 7 are conveyed, these films are laminated, and the laminate is passed between a pair of rollers (laminating rollers) and pressed. The film transfer may be performed using a guide roller or the like. The pressure (nip pressure) applied to the laminate by the bonding roller is, for example, 0.05 to 2MPa, preferably 0.08 to 1 MPa.

The protective film 7 may have an arithmetic average roughness Ra of 0.150 μm or less on the surface on the polarizer layer 5 side. The protective film 7 is advantageous in suppressing image distortion that may occur in a polarizing plate in which a thermoplastic resin film is bonded to the polarizer layer 5 using an active energy ray-curable adhesive.

For example, in the case of a manufacturing method in which the polarizing stack film 300 is supplied directly to the polarizing plate manufacturing process without laminating a protective film on the polarizer layer 5, the polarizer layer 5 is particularly easily scratched or damaged, and therefore the polarizer layer 5 is easily scratched or damaged when the polarizing stack film 300 is conveyed. In addition, when no protective film is laminated on the polarizer layer 5, it is difficult to temporarily wind the polarizing laminated film 300 to form a roll, and even if the roll can be formed, the roll is likely to be scratched or damaged at the time of winding.

The protective film 7 is laminated to prevent or suppress scratches and breakage on the surface of the polarizer layer 5, and the protective-film-attached polarizing laminated film 400 can be wound up to be a roll. When the polarizing plate is in a roll state, the polarizing plate can be temporarily stored in a warehouse (or managed as stock) as a production intermediate for supplying to the polarizing plate production process, for example, so that the degree of freedom and efficiency of the polarizing plate production process can be improved. From these viewpoints, it is advantageous to laminate the protective film 7 on the polarizer layer 5.

However, it was found that when a protective film is laminated on the polarizer layer 5, the polarizing plate obtained by laminating a thermoplastic resin film on the polarizer layer 5 using an active energy ray-curable adhesive is more likely to cause image distortion than when the polarizing laminated film 300 is directly supplied to the polarizing plate production process without laminating a protective film. When the polarizing laminate film 400 with a protective film is wound up to be a roll, or the roll is further stored in a roll state for a certain period of time, image distortion is particularly likely to occur.

By using the protective film 7 having an arithmetic average roughness Ra of 0.150 μm or less on the surface on the polarizer layer 5 side, image distortion can be suppressed. From the viewpoint of effectively suppressing image distortion, the arithmetic average roughness Ra is preferably 0.120 μm or less, more preferably 0.100 μm or less, still more preferably 0.080 μm or less, and still more preferably 0.070 μm or less. The arithmetic average roughness Ra is usually 0.010 μm or more, for example, 0.020 μm or more (or 0.030 μm or more). The arithmetic average roughness Ra in the present specification is a value in accordance with JIS B0601: 2013 can be measured by the method described in the examples below or a method substantially equivalent thereto. For example, an appropriate protective film can be selected and used according to the grade and the lot.

Examples of the protective film 7 include: a thermoplastic resin film having self-adhesiveness; an adhesive film having an adhesive layer on a support film, and the like. Examples of the thermoplastic resin constituting the thermoplastic resin film having self-adhesiveness include linear olefin resins such as polypropylene resins and polyethylene resins. The thermoplastic resin film having self-adhesiveness may be a single-layer structure.

The support film constituting the adhesive film may be made of a thermoplastic resin, for example, a polyolefin resin such as a polyethylene resin, a polypropylene resin, or a cyclic polyolefin resin; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; a polycarbonate-based resin; (meth) acrylic resins, and the like. The adhesive layer may be composed of a (meth) acrylic adhesive, an epoxy adhesive, a urethane adhesive, a silicone adhesive, or the like, and is preferably a (meth) acrylic adhesive. The thickness of the adhesive layer is, for example, 1 to 40 μm, and may be 3 to 25 μm. When an adhesive film is used, the protective film 7 is laminated on the polarizing laminate film 300 through the adhesive layer of the protective film 7.

The thickness of the protective film 7 may be, for example, 5 to 200 μm, preferably 10 to 150 μm, more preferably 20 to 120 μm, and still more preferably 25 to 100 μm (for example, 90 μm or less, and further 75 μm or less).

The protective film 7 is laminated on and adhered to the surface of the polarizing laminate film 300 on the polarizer layer 5 side (preferably, the surface of the polarizer layer 5), and the protective film 7 can be peeled therefrom. The peeling force between the polarizing laminated film 300 and the protective film 7 is, for example, 0.01 to 0.5N/25mm, preferably 0.01 to 0.2N/25 mm. When the peeling force is less than 0.01N/25mm, the adhesion force is too small, and partial peeling of the protective film 7 may occur or the protection of the polarizer layer 5 may be insufficient in the treatment of the polarizing laminate film 400 with a protective film. When the peeling force is greater than 0.5N/25mm, it may be difficult to peel the protective film 7 from the protective-film-attached polarizing laminate film 400.

The peeling force can be determined as follows: the polarizing laminate film 400 with the protective film was cut into a width of 25mm to obtain a measurement sample, and the protective film 7 and the polarizing laminate film 300 of the measurement sample were held and held by a precision universal tester "Autograph AGS-50 NX" manufactured by shimadzu corporation or an equivalent device, and the force at the time of peeling in the 180 ° direction was measured, thereby obtaining the measurement sample. The peel force was measured at a peel speed of 300mm/min under an environment of 23. + -. 2 ℃ and a relative humidity of 50. + -. 5%.

[5] Other procedures

The method for producing a polarizing laminate film with a protective film may include: in the winding step, the obtained polarizing laminated film with protective film 400 is wound by a usual method to obtain a polarizing laminated film roll with protective film. In addition, the method may further include: a storage step of storing the obtained polarizing laminated film roll with the protective film in a certain environment. The certain environment may be a normal storage environment, for example, an environment having a temperature of 23 ℃ and a relative humidity of 55%.

The storage time in the storage step may be within 2 years, preferably within 1.5 years, more preferably within 1 year, and still more preferably within 0.5 years. When the storage time is set to 2 years or less, the image distortion can be effectively suppressed, and the deterioration of the physical properties of the polarizer layer 5 and the like can be prevented. The lower limit of the storage time is not particularly limited, and may be, for example, 4 hours or more.

When the winding step, or the winding step and the storage step are included, the polarizing plate obtained by bonding the thermoplastic resin film to the polarizer layer 5 using the active energy ray-curable adhesive is likely to be deformed. Therefore, the present invention capable of suppressing image deformation is particularly advantageous when the present invention includes a winding step, or a winding step and a storage step.

< polarizing laminated film with protective film and coil thereof >

The polarizing laminated film with a protective film 400 shown in fig. 5 includes a base film 30', a polarizer layer 5 including a polyvinyl alcohol resin, and a protective film 7 in this order. The protective film 7 has an arithmetic mean roughness of 0.150 [ mu ] m or less on the surface on the polarizer layer 5 side. The polarizing laminate film roll with a protective film is a wound product of the polarizing laminate film with a protective film 400.

The protective film-equipped polarizing laminate film 400 and the protective film-equipped polarizing laminate film roll may include a polarizer layer 5 laminated on both surfaces of the base film 7.

In this case, the layers of the protective film-equipped polarizing laminate film 400 and the protective film-equipped polarizing laminate film roll are, for example, protective film 7/polarizer layer 5/base material film 30 '/polarizer layer 5/protective film 7, protective film 7/polarizer layer 5/base material film 30'/polarizer layer 5.

The protective film-equipped polarizing laminate film 400 and the protective film-equipped polarizing laminate film roll can be suitably produced by the above-described production method. In this case, the substrate film is a stretched substrate film 30'. Alternatively, 3 separate members, that is, a base film, a polarizer layer (polarizing film), and a protective film, may be laminated to produce the polarizing plate. In this case, the polarizer layer (polarizing film) may be: a film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin film produced from a monomer (single) film containing a polyvinyl alcohol resin by a known method. The thickness of the polarizer layer (polarizing film) may be, for example, 1 to 25 μm. The substrate film may be a stretched film or an unstretched film.

The protective film 7 is laminated on the polarizer layer 5, and is preferably laminated on the polarizer layer 5 in contact with a surface of the polarizer layer 5 (a surface on the opposite side to the substrate film 30 or 30'). The polarizer layer 5 may be laminated on the base film 30 or 30' with the primer layer or the like interposed therebetween. The substrate film 30 or 30' is preferably capable of being peeled off from the polarizer layer 5. In addition, the substrate film 30 or 30' may be an optical film. In this case, the polarizing laminate film can be used as a polarizing plate.

The use of the protective film 7 having an arithmetic mean roughness Ra of 0.150 μm or less on the surface on the polarizer layer 5 side is advantageous in suppressing image distortion that may occur in a polarizing plate in which a thermoplastic resin film is bonded to the polarizer layer 5 using an active energy ray-curable adhesive. From the viewpoint of effectively suppressing image distortion, the arithmetic average roughness Ra is preferably 0.120 μm or less, more preferably 0.100 μm or less, still more preferably 0.080 μm or less, and still more preferably 0.070 μm or less. The arithmetic average roughness Ra is usually 0.010 μm or more, for example, 0.020 μm or more (or 0.030 μm or more).

From the viewpoint of suppressing image distortion, the protective film-equipped polarizing laminate film 400 and the protective film-equipped polarizing laminate film roll have an arithmetic average roughness Ra of the surface of the polarizer layer 5 on the protective film 7 side, which is preferably 0.100 μm or less, and more preferably 0.090 μm or less. The arithmetic average roughness Ra is usually 0.010 μm or more, for example, 0.020 μm or more (or 0.030 μm or more).

As for the base film 30 or 30 ', the polarizer layer 5, and the protective film 7 provided in the protective film-equipped polarizing laminate film 400 and the protective film-equipped polarizing laminate film roll, the above-mentioned description of the base film 30 or 30', the polarizer layer 5, and the protective film 7 in the section < method for producing a protective film-equipped polarizing laminate film > is cited.

< method for producing polarizing plate >

Fig. 6 is a flowchart showing a method for manufacturing a polarizing plate according to an embodiment of the present invention. As shown in fig. 6, a method for manufacturing a polarizing plate according to an embodiment of the present invention includes the steps of:

a step of obtaining a polarizing laminated film with a protective film by the above-mentioned method for producing a polarizing laminated film with a protective film;

a protective film peeling step S50 of peeling the protective film from the polarizing laminate film with the protective film;

a first laminating step S60 of laminating a first thermoplastic resin film on the surface of the polarizing laminate film on the polarizing plate layer side exposed in the protective film peeling step S50 with a layer of an active energy ray-curable adhesive interposed therebetween; and

the curing step S70 is a step of curing the active energy ray-curable adhesive layer.

The method for producing a polarizing plate may further include a substrate film peeling step of peeling the substrate film after the curing step S70. Although not shown in fig. 6, the method for manufacturing a polarizing plate may further include, between the step of obtaining the polarizing laminate film with a protective film and the protective film peeling step S50: and a step of winding the polarizing laminated film with the protective film to obtain a polarizing laminated film coil with the protective film. The step of obtaining the polarizing laminated film roll with the protective film is as described above. When the step of obtaining the polarizing laminated film roll with the protective film is included, the protective film peeling step S50 may be: and a step of peeling the protective film from the polarizing laminated film with the protective film unwound from the polarizing laminated film roll with the protective film.

The above-described steps are explained below with reference to the drawings.

[1] Process for obtaining polarizing laminated film with protective film

For this step, the above-mentioned section < method for producing a polarizing laminated film with a protective film > is cited.

[2] Protective film peeling step S50

Referring to fig. 7, the process is: and a step of peeling the protective film 7 from the polarizing laminate film 400 with a protective film to obtain a film having the same layer configuration as the polarizing laminate film 300. This step may be continuously performed, for example, while continuously conveying the long polarizing laminated film 400 with the protective film, or while continuously unwinding and conveying the polarizing laminated film 400 with the protective film from a polarizing laminated film roll with the protective film. The film transfer may be performed using a guide roller or the like. A specific method for peeling the protective film 7 may be a general peeling method of the protective film.

From the viewpoint of suppressing image distortion, the arithmetic mean roughness Ra of the surface on the polarizer layer 5 side (or the surface of the polarizer layer 5) exposed by peeling of the protective film 7 is preferably 0.100 μm or less, and more preferably 0.090 μm or less. The arithmetic average roughness Ra is usually 0.010 μm or more, for example, 0.020 μm or more (or 0.030 μm or more).

[3] First bonding step S60

Referring to fig. 8, the process is: and a step of laminating the first thermoplastic resin film 10 on the surface exposed in the protective film peeling step S50 on the polarizer layer 5 side of the film having the same layer configuration as the polarizing laminate film 300 obtained in the protective film peeling step S50, with a layer of an active energy ray-curable adhesive interposed therebetween. This process includes, for example, the following processes: while continuously conveying a long film having the same layer configuration as the polarizing laminate film 300 and a long first thermoplastic resin film 10, an active energy ray-curable adhesive is applied to the surface of the film on the polarizer layer 5 side and/or one surface of the first thermoplastic resin film 10, the films are laminated with the active energy ray-curable adhesive interposed therebetween, and the laminate is passed between a pair of rollers (laminating rollers) and pressed.

The first adhesive layer 15 shown in fig. 8 is a cured layer of a layer of an active energy ray-curable adhesive cured in the curing step S70 described later. The first polarizing plate 500 shown in fig. 8 is a polarizing plate including a first thermoplastic resin film 10 as an optical film on one surface of a polarizer layer 5 and a base film 30' on the other surface.

When the polarizing laminate film 300 has the polarizer layers 5 on both sides of the base film 30', the first thermoplastic resin film 10 is generally bonded to each of the polarizer layers 5 on both sides. In this case, the first thermoplastic resin films 10 may be the same type of thermoplastic resin film or different types of thermoplastic resin films in terms of resin type and configuration.

The layer of the active energy ray-curable adhesive is usually in contact with the surface of the polarizer layer 5 and the surface of the first thermoplastic resin film 10.

The first thermoplastic resin film 10 is an optical film, and may be a polyolefin-based resin including a light-transmitting (preferably optically transparent) thermoplastic resin, for example, a chain polyolefin-based resin (a polypropylene-based resin or the like), a cyclic polyolefin-based resin (a norbornene-based resin or the like); cellulose ester resins such as triacetyl cellulose and diacetyl cellulose; a polyester resin; a polycarbonate-based resin; (meth) acrylic resins; a polystyrene-based resin; or mixtures, copolymers, etc. thereof. Among them, the first thermoplastic resin film 10 is a thermoplastic resin film having low moisture permeability which is not always easily adhered by an aqueous adhesive, and examples thereof include thermoplastic resin films such as polyolefin-based resins, polyester-based resins, (meth) acrylic resins, and polystyrene-based resins. For specific examples of the thermoplastic resin, the description of the base film is cited.

The first thermoplastic resin film 10 may be a protective film for protecting the polarizer layer 5, or may be a protective film having both optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film to which an arbitrary retardation value is given can be produced by stretching a film containing the above thermoplastic resin (uniaxial stretching, biaxial stretching, or the like), or forming a liquid crystal layer or the like on the film.

A surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer may be further formed on the surface of the first thermoplastic resin film 10 on the side opposite to the polarizer layer 5. The surface treatment layer may be formed on the first thermoplastic resin film 10 before the first bonding step S60 is performed, or may be formed after the first bonding step S60 is performed or after the peeling step S80 described later is performed. The first thermoplastic resin film 10 may contain 1 or 2 or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant.

From the viewpoint of thinning of the polarizing plate, the thickness of the first thermoplastic resin film 10 is preferably 90 μm or less, more preferably 50 μm or less, and further preferably 30 μm or less. The thickness of the first thermoplastic resin film 10 is usually 5 μm or more from the viewpoint of strength and workability.

The increase in the fine unevenness on the surface of the polarizer layer 5 is likely to occur when the thickness of the first thermoplastic resin film 10 is small and the rigidity is low. Therefore, the present invention capable of suppressing the image distortion is particularly advantageous when the thickness of the first thermoplastic resin film 10 is small, for example, when the thickness of the first thermoplastic resin film 10 is 30 μm or less.

The first adhesive layer 15 is a layer for adhering and fixing the first thermoplastic resin film 10 to one surface of the polarizer layer 5. The adhesive forming the first adhesive layer 15 is an active energy ray-curable adhesive containing a curable compound that is cured by irradiation with an active energy ray such as ultraviolet ray, visible light, electron beam, or X-ray, and is preferably an ultraviolet-curable adhesive.

The curable compound may be a cationically polymerizable curable compound or a radically polymerizable curable compound. Examples of the cationically polymerizable curable compound include: an epoxy compound (a compound having 1 or 2 or more epoxy groups in a molecule), an oxetane compound (a compound having 1 or 2 or more oxetane rings in a molecule), or a combination thereof. Examples of the radical polymerizable curable compound include: a (meth) acrylic compound (a compound having 1 or 2 or more (meth) acryloyloxy groups in the molecule), another vinyl compound having a radically polymerizable double bond, or a combination thereof. The cationically polymerizable curable compound and the radically polymerizable curable compound may be used in combination. The active energy ray-curable adhesive generally further includes: a cationic polymerization initiator and/or a radical polymerization initiator for initiating the curing reaction of the curable compound.

The active energy ray-curable adhesive may contain additives such as a cationic polymerization accelerator, an ion scavenger, an antioxidant, a chain transfer agent, a thickener, a thermoplastic resin, a filler, a flow control agent, a plasticizer, an antifoaming agent, an antistatic agent, a leveling agent, and a solvent, if necessary.

In order to improve the adhesiveness to the polarizer layer 5 when the first thermoplastic resin film 10 is bonded to the polarizer layer 5, the surface of the first thermoplastic resin film 10 and/or the surface of the polarizer layer 5 to be bonded may be subjected to a surface treatment (easy adhesion treatment) such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, or saponification treatment, and among these, plasma treatment, corona treatment, or saponification treatment is preferably performed.

[4] Curing step S70

Referring to fig. 8, the process is: and a step of curing the active energy ray-curable adhesive layer included in the laminate obtained in the first bonding step S60 to obtain the first polarizing plate 500. The curing of the layer may be performed by irradiating the layer with active energy rays. In this case, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like can be used as the light source.

The thickness (after curing) of the first adhesive layer 15 is usually about 0.001 to 5 μm, and preferably 0.01 to 3 μm.

The first polarizing plate 500 obtained in the above manner is manufactured using the polarizing laminate film 400 with a protective film, and therefore, image deformation can be effectively suppressed when viewed from the first thermoplastic resin 10 side.

From the viewpoint of suppressing image distortion, the arithmetic average roughness Ra of the surface of the polarizer layer 5 on the first thermoplastic resin film 10 side of the first polarizing plate 500 is preferably 0.100 μm or less, and more preferably 0.090 μm or less. The arithmetic average roughness Ra is usually 0.010 μm or more, for example, 0.020 μm or more (or 0.030 μm or more).

[5] Substrate film peeling step S80

Referring to fig. 9, the method of manufacturing a polarizing plate may further include a substrate film peeling process S80 of peeling the substrate film 30' after the curing process S70. Thus, the second polarizing plate 600 including the first thermoplastic resin film 10 on one surface of the polarizer layer 5 can be obtained. This step may be continuously performed, for example, while continuously conveying the long first polarizing plate 500, or while continuously unwinding and conveying the first polarizing plate 500 from a roll of the long first polarizing plate 500. The film transfer may be performed using a guide roller or the like. The specific method for peeling the substrate film 30 'may be a general peeling method of the substrate film 30'.

When the second polarizing plate 600 is incorporated into an image display device such as a liquid crystal display device, the first thermoplastic resin film 10 is preferably disposed on the outer side (the side opposite to the image display element) of the polarizer layer 5. The same applies to the first polarizing plate 500. This enables the first thermoplastic resin film 10 side, in which image distortion is suppressed, to be directed to the viewing side of the image display device. The second polarizing plate 600 and the first polarizing plate 500 may be bonded to the image display element (e.g., a liquid crystal cell) with an adhesive layer interposed therebetween.

The adhesive forming the adhesive layer generally contains an adhesive composition having a (meth) acrylic resin, a styrene resin, a silicone resin, or the like as a base polymer, to which a crosslinking agent such as an isocyanate compound, an epoxy compound, an aziridine compound, or the like is added. In addition, the pressure-sensitive adhesive layer may contain fine particles to exhibit light scattering properties. The thickness of the adhesive layer is usually 1 to 40 μm, preferably 3 to 25 μm.

[6] Other procedures

The method for manufacturing a polarizing plate may include a step of bonding the second thermoplastic resin film 20 to the other surface of the polarizer layer 5 included in the second polarizing plate 600 with an adhesive interposed therebetween. Thus, with reference to fig. 10, one can obtain: and a third polarizing plate 700 in which a first thermoplastic resin film 10 is bonded to one surface of the polarizer layer 5 with a first adhesive layer 15 interposed therebetween, and a second thermoplastic resin film 20 is bonded to the other surface with a second adhesive layer 25 interposed therebetween.

The second thermoplastic resin film 20 is an optical film, and may be a protective film containing the thermoplastic resins exemplified above, or a protective film having optical functions such as a retardation film and a brightness enhancement film, in the same manner as the first thermoplastic resin film 10. As the surface treatment layer and the film thickness and the like that the second thermoplastic resin film 20 may have, the above description of the first thermoplastic resin film 10 is cited. The first thermoplastic resin film 10 and the second thermoplastic resin film 20 may be both films containing the same kind of resin, or may be films containing different kinds of resins.

The second adhesive layer 25 is a layer for adhering and fixing the second thermoplastic resin film 20 to the other surface of the polarizer layer 5, and is generally laminated in contact with the other surface of the polarizer layer 5 so as to be directly adhered to the polarizer layer 5, similarly to the first adhesive layer 15. The second adhesive layer 25 is also usually in contact with the bonding surface (the surface on the polarizer layer 5 side) of the second thermoplastic resin film 20.

The adhesive forming the second adhesive layer 25 may be an aqueous adhesive in which an adhesive component such as a polyvinyl alcohol resin is dissolved or dispersed in water, in addition to the active energy ray-curable adhesive, and is preferably an active energy ray-curable adhesive, similarly to the first adhesive layer 15, from the viewpoint of production efficiency. In particular, when the second thermoplastic resin film 20 has low moisture permeability, an active energy ray-curable adhesive is preferably used. The active energy ray-curable adhesive for forming the second adhesive layer 25 is preferably an ultraviolet-curable adhesive.

In the third polarizing plate 700, the second thermoplastic resin film 20 may be laminated on the other surface of the polarizer layer 5 with an adhesive layer interposed therebetween. For the adhesive layer, the above description is cited.

When the third polarizing plate 700 is incorporated into an image display device such as a liquid crystal display device, the second thermoplastic resin film 20 is preferably disposed on the image display element side with respect to the polarizer layer 5. This enables the first thermoplastic resin film 10 side, in which image distortion is suppressed, to be directed to the viewing side of the image display device. The third polarizing plate 700 may be bonded to the image display device (e.g., liquid crystal cell) with an adhesive layer interposed therebetween.

[ examples ]

The present invention will be described in more detail below by way of examples and comparative examples, but the present invention is not limited to these examples.

In the following examples and comparative examples, the arithmetic mean roughness Ra of the surface of the protective film and the surface of the polarizing plate layer was measured by the following method.

(measurement of arithmetic average roughness Ra)

Using a white interferometer "Vertscan" (manufactured by mitsubishi system, ltd.) as a non-contact surface roughness measuring device, the surface roughness was measured in accordance with JIS B0601: 2013, and the arithmetic average roughness Ra. In this white interferometer, interference fringes caused by an optical path difference due to irregularities on the sample surface are captured by a CCD camera, and the brightness information of the interference fringes is converted into height information of the surface irregularities.

The procedure for measuring the arithmetic mean roughness Ra is as follows. First, a film sheet of 20cm × 20cm was cut out from a film to be measured. The film was placed on a black acrylic plate with the measurement object side facing upward, and the periphery was fixed with an adhesive tape to flatten the measurement object side. The obtained laminate was used as a measurement sample.

The measurement sample was placed on the stage of a white interferometer "Vertscan" and measured by the following apparatus setting, and the arithmetic mean roughness Ra was obtained.

Magnification of the two-beam interference objective: 5 times of

Measurement mode: choose "wave"

Wavelength filter: selection "530 white"

Scan area: -10 μm to 10 μm

Splice (timing) setting: 2X 2, overlap (overlap) rate 20%.

With the above setting, the observation range is as follows.

Longitudinal (x) x lateral (y): 1263.73 μm × 1689.94 μm

Height difference (z): -0.25 μm to 0.25 μm.

< example 1 >

(1) Preparation of coating liquid

Polyvinyl alcohol powder ("Z-200", manufactured by Nippon synthetic chemical Co., Ltd., average degree of polymerization 1100 and degree of saponification of 99.5 mol%) was dissolved in hot water at 95 ℃ to prepare a 3 wt% polyvinyl alcohol aqueous solution. To the obtained aqueous solution, a crosslinking agent ("Sumirez Resin 650" manufactured by takaki chemical corporation) was mixed in a proportion of 1 part by weight to 2 parts by weight of the polyvinyl alcohol powder to obtain a coating liquid for forming an undercoat layer.

In addition, polyvinyl alcohol powder ("PVA 124", manufactured by kuraray corporation, average polymerization degree 2400, and saponification degree 98.0 to 99.0 mol%) was dissolved in hot water at 95 ℃ to prepare a coating liquid for forming a polyvinyl alcohol resin layer as a polyvinyl alcohol aqueous solution having a concentration of 8 wt%.

(2) Formation of undercoat layer and polyvinyl alcohol resin layer (production of laminated film)

Then, a 90 μm thick base film (melting point: 163 ℃) containing polypropylene was continuously conveyed while being subjected to corona treatment on one surface thereof, and then the coating liquid for forming an undercoat layer was continuously applied to the corona-treated surface thereof using a small-diameter gravure coater and dried at 60 ℃ for 3 minutes, thereby forming an undercoat layer having a thickness of 0.2 μm. Then, while continuously conveying the film, the coating liquid for forming a polyvinyl alcohol resin layer was applied to the surface of the primer layer on the base film by a lip coater, and then dried at 80 ℃ for 8 minutes to form a polyvinyl alcohol resin layer having a thickness of 9.3 μm on the primer layer, thereby obtaining a laminated film.

(3) Stretching step (production of stretched laminated film)

While continuously conveying the laminated film obtained in (2) above, a longitudinal uniaxial stretching was performed at a stretching temperature of 140 ℃ by an inter-roll stretching using nip rolls until the stretching ratio became 2.5 times, and then a longitudinal uniaxial stretching was similarly performed at a stretching temperature of 160 ℃ by an inter-roll stretching using nip rolls until the total stretching ratio became 5.8 times, to obtain a stretched laminated film. The thickness of the stretched polyvinyl alcohol resin layer in the stretched laminated film was 5.1 μm.

(4) Dyeing Process (production of polarizing laminate film)

While continuously transporting the stretched film obtained in (3), the polyvinyl alcohol resin layer was dyed by immersing the stretched film in a dyeing aqueous solution containing iodine and potassium iodide at 30 ℃ for a retention time of about 150 seconds, and then the excess dyeing aqueous solution was washed away with pure water at 10 ℃. Subsequently, the crosslinking treatment was carried out by continuously immersing the substrate in a 76 ℃ crosslinking aqueous solution containing boric acid and potassium iodide for a retention time of 600 seconds. After that, the substrate film was washed with pure water at 10 ℃ for 4 seconds and dried at 80 ℃ for 300 seconds to obtain a polarizing laminate film having a polarizer layer on the substrate film. The thickness of the polarizer layer was 5.1 μm.

A film was cut out from the obtained polarizing laminated film, and the arithmetic mean roughness Ra of the surface of the polarizing plate layer (the surface on the side opposite to the base material film) was measured according to the above measurement procedure, and the result was 0.0456 μm.

(5) Protective film lamination step (production of polarizing laminate film with protective film)

While continuously conveying the polarizing laminate film obtained in (4), a protective film a (a self-adhesive polyethylene resin film having an arithmetic mean roughness Ra of 0.0815 μm on the surface of the polarizing plate layer side in the measurement step) having a thickness of 30 μm was laminated on the surface of the polarizing plate layer, the laminate was pressed by a laminating roller to perform a laminating treatment, and the laminate after the laminating treatment was continuously wound to obtain a polarizing laminate film roll with a protective film. The protective film a is in contact with the surface of the polarizer layer. The pressure (nip pressure) applied to the laminate by the bonding roller was 0.1 MPa.

The nip pressure of the bonding roller is obtained as follows: pressure-sensitive paper [ Prescale extra low pressure (LLLW) manufactured by fuji film co., ltd.) was placed in the pressing portion between the bonding rollers, and after pressing, the nip pressure of the pressing portion was measured using a pressure measurement system [ FPD-305E and FPS-307E manufactured by fuji film co., ltd. ], thereby obtaining the nip pressure in advance.

The obtained polarizing laminated film roll with the protective film was stored at 23 ℃ and 55% relative humidity for 2 weeks.

(6) Fabrication of polarizing plates

The protective film a was continuously peeled off while continuously unwinding the protective film-equipped polarizing laminate film from the protective film-equipped polarizing laminate film roll immediately after the storage. A film was cut out from the polarizing laminated film obtained by peeling the protective film a, and the arithmetic average roughness Ra of the surface of the polarizing plate layer (the surface on the opposite side to the base film) exposed by peeling the protective film a was measured according to the above measurement procedure, and found 0.0998 μm.

Then, an ultraviolet-curable adhesive (KR-75T manufactured by ADEKA corporation) was applied to the surface of the polarizing plate layer exposed by peeling the protective film a using a small-diameter gravure coater so that the thickness after curing was about 1.0 μm, a thermoplastic resin film (ZF-14 manufactured by kushoku corporation) having a thickness of 23 μm and containing a cyclic polyolefin resin was laminated on the adhesive layer, the laminate was pressed by a laminating roller to perform a laminating treatment, and then a high-pressure mercury lamp was used from the substrate film side at 200mJ/cm²The adhesive layer is cured by irradiating ultraviolet light with the cumulative light amount of (a), thereby obtaining a polarizing plate in which a thermoplastic resin film is laminated on one surface of the polarizer layer with the cured adhesive layer interposed therebetween and a base film is provided on the other surface.

Next, the base film was peeled while continuously transporting the obtained polarizing plate, and a thermoplastic resin film was laminated on one surface of the polarizer layer with the cured adhesive layer interposed therebetween, to obtain a polarizing plate.

(7) Evaluation of image distortion

The polarizing plate (obtained by peeling the base film) obtained in (6) above was visually observed from the thermoplastic resin film side under a fluorescent lamp, and the degree of deformation of the fluorescent lamp image reflected on the surface of the thermoplastic resin film was evaluated according to the following evaluation criteria. The results are shown in Table 1.

A: in the fluorescent lamp image, the contour of the fluorescent lamp was not completely or substantially confirmed to be deformed, and is relatively better than B described below.

B: in the fluorescent lamp image, the contour of the fluorescent lamp was confirmed to be slightly deformed, relatively better than C described below.

C: in the fluorescent lamp image, a large amount of deformation can be confirmed in the contour of the fluorescent lamp.

< examples 2 to 3, comparative example 1 >

A polarizing laminated film roll with a protective film was produced in the same manner as in example 1, except that the following protective films B to D were used instead of the protective film a, and a polarizing plate (obtained by peeling off a base material film) was produced using the roll. The polarizing plate thus obtained was subjected to the same evaluation test for image deformation as in example 1. The results are shown in Table 1. In examples 2 to 3 and comparative example 1, the arithmetic mean roughness Ra of the surface of the polarizing plate layer before lamination of the protective film was 0.0456 μm as in example 1.

Example 2: a protective film B (a self-adhesive polyethylene resin film having a thickness of 30 μm. the surface on the polarizing plate layer side in the above measurement step had an arithmetic average roughness Ra of 0.0690 μm),

Example 3: protective film C (a protective film having a thickness of 25 μm comprising a base material comprising a polypropylene-based resin and an adhesive layer laminated thereon, the surface of the polarizer layer side (adhesive layer) according to the above-described measurement procedure had an arithmetic average roughness Ra of 0.0621 μm),

Comparative example 1: protective film D (a polyethylene resin film having a thickness of 30 μm and having self-adhesiveness. the arithmetic average roughness Ra of the surface on the polarizer layer side in the above measurement step: 0.1559 μm).

In the polarizing plate production process, a film was cut out from the polarizing laminated film obtained by peeling the protective film, and the arithmetic mean roughness Ra of the surface of the polarizing plate layer (the surface on the opposite side to the base film) exposed by peeling the protective film was measured according to the above measurement procedure, and as a result, it was 0.0618 μm in example 2, 0.0894 μm in example 3, and 0.1072 μm in comparative example 1.

[ Table 1]

[ description of symbols ]

A 5 polarizer layer, a 6 polyvinyl alcohol resin layer, a 6 'stretched polyvinyl alcohol resin layer, a 7 protective film, a 10 first thermoplastic resin film, a 15 first adhesive layer, a 20 second thermoplastic resin film, a 25 second adhesive layer, a 30 base material film, a 30' stretched base material film, a 100 laminated film, a 200 stretched laminated film, a 300 polarizing laminated film, a 400 polarizing laminated film with a protective film, a 500 first polarizing plate, a 600 second polarizing plate, and a 700 third polarizing plate.

Claims

1. A method for producing a polarizing laminate film with a protective film, comprising:

a step of forming a polyvinyl alcohol resin layer on at least one surface of a base film to obtain a laminated film, a step of stretching the laminated film to obtain a stretched laminated film,

a step of laminating a protective film on the surface of the polarizing laminate film on the polarizing plate layer side to obtain a polarizing laminate film with a protective film,

the protective film has an arithmetic mean roughness of 0.030 [ mu ] m or more and 0.150 [ mu ] m or less on the surface on the polarizer layer side.

2. The manufacturing method according to claim 1,

the protective film is laminated in contact with a surface of the polarizer layer.

3. The manufacturing method according to claim 1 or 2, further comprising:

4. A method of manufacturing a polarizing plate, the method comprising:

a step of obtaining a polarizing laminated film with a protective film by the production method according to claim 1 or 2;

a step of laminating a first thermoplastic resin film on a surface of the polarizing laminate film on the polarizing plate layer side exposed by the step of peeling the protective film, with a layer of an active energy ray-curable adhesive interposed therebetween; and

and curing the active energy ray-curable adhesive layer.

5. The manufacturing method according to claim 4,

6. The manufacturing method according to claim 4 or 5,

the method further includes, after the step of curing the active energy ray-curable adhesive layer: and a step of peeling the base film.

7. A polarizing laminate film with a protective film, comprising in this order: a base film, a polarizer layer comprising a polyvinyl alcohol resin, and a protective film,

the protective film has an arithmetic mean roughness of 0.030 [ mu ] m or more and 0.150 [ mu ] m or less on the surface on the polarizer layer side,

the protective film is in contact with a surface of the polarizer layer.

8. A polarizing laminated film roll with a protective film, which is a wound product of the polarizing laminated film with a protective film according to claim 7.