CN110398800B - Laminated body - Google Patents

Abstract

The invention provides a laminate which is subjected to grooving processing, and when a peeling film is peeled from an end edge with a notch part, peeling failure of the peeling film is not generated. The laminate is a laminate in which a surface protection film is laminated on one surface of a polarizing plate, a release film is laminated on the other surface of the polarizing plate, and the polarizing plate includes a polarizer, and has a notch portion in a plan view, and when the release film is peeled from an edge having the notch portion, the maximum value of the peeling force is 1.0N or less.

Description

Laminated body

Technical Field

The present invention relates to a laminate.

Background

Polarizing plates are widely used in image display devices such as liquid crystal display devices and organic Electroluminescence (EL) display devices, and in particular, in various mobile devices such as smart phones in recent years. As the polarizing plate, a polarizing plate in which a protective film is laminated on one surface or both surfaces of a polarizing plate obtained by adsorbing and orienting a dichroic dye on a polyvinyl alcohol resin film has been conventionally used.

Polarizing plates are generally distributed in the market as a laminate in which a releasable surface protection film (also referred to as a protective film) and a release film (also referred to as a separator) are bonded to the surfaces thereof for preventing contamination and scratches on the surfaces.

When a polarizing plate is bonded to a display element such as a liquid crystal cell or an organic EL element, the release film bonded to the surface thereof is peeled off, and the polarizing plate is bonded to the display element with the exposed adhesive layer interposed therebetween. When the release film is peeled off, the surface protective film side of the laminate (a film in which a surface protective film is laminated on one surface of a polarizing plate and a release film is laminated on the other surface thereof) is fixed to a holding stage by suction, adsorption, or the like, and a release tape is bonded to the release film. Thereafter, the release tape is pulled to remove the release film from the surface of the polarizing plate.

The laminate is often processed into a shape other than a rectangle in accordance with the design of the image display device. Specifically, the laminate is subjected to in-plane hole forming, R-forming at a corner portion in a plan view, or grooving in a plan view (cutting 12426missing 12365. In particular, when the laminated body is subjected to grooving in a plan view, if the peeling film is peeled from the edge having the notch portion, the peeling film cannot be peeled when the peeling tip approaches the notch portion. The originally fixed polarizing plate and surface protective film follow the movement of the release film, and are lifted from the holding base, and the fixation of the polarizing plate and surface protective film is released, so that the release film cannot be easily peeled.

This problem can be solved by increasing the force such as the suction force or the suction force when fixing the laminate or by decreasing the adhesive force of the release film, but a new problem arises. That is, when the force applied to the laminate such as the suction force or the suction force is increased, the polarizing plate remains with a mark, and the appearance is deteriorated. Further, if the adhesive force of the release film is reduced, a gap is formed between the release film and the polarizing plate when an impact is applied to the laminate during transportation or the like.

Documents of the prior art

Patent document

Patent document 1: WO2018/016285A1

Disclosure of Invention

Problems to be solved by the invention

The invention aims to provide a laminate which does not cause peeling failure of a peeling film.

Means for solving the problems

[1] A laminate comprising a polarizing plate and a surface protective film laminated on one surface of the polarizing plate, and a release film laminated on the other surface of the polarizing plate, wherein the polarizing plate comprises a polarizing plate,

the laminate has a notch portion in a plan view,

when the release film is peeled from the edge having the notch, the maximum value of the peeling force is 1.0N or less.

[2] The laminate according to [1], wherein the shape of the notch portion satisfies the following formula (1).

r＞3d－14 (1)

In expression (1), d (mm) represents the depth of the notch, and r (mm) represents the radius of curvature of the corner inside the notch. Angle (c)

[3] The laminate according to [1] or [2], wherein the polarizing plate has an adhesive layer on a surface on the side of the release film,

the adhesion force between the release film and the pressure-sensitive adhesive layer is 0.02N/25mm or more and 0.10N/25mm or less.

[4] A method for manufacturing a polarizing plate with a surface protective film, comprising:

a sticking step of sticking an adhesive tape to a corner portion of one end of the edge having the notch portion of the laminate according to any one of [1] to [3 ]; and

a peeling step of pulling up the tape to peel the release film from the laminate,

in the peeling step, an angle formed by the peeling direction of the adhesive tape and the edge side orthogonal to the edge side having the notch portion is 25 ° or more and 65 ° or less.

Effects of the invention

According to the present invention, a laminate in which peeling failure of a peeling film does not occur can be provided.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of a layer structure included in the laminate of the present invention.

Fig. 2 is a schematic cross-sectional view showing an example of the layer structure of the laminate of the present invention.

Fig. 3 is a schematic plan view showing an example of the notch portion of the laminate of the present invention.

Fig. 4 is a schematic plan view showing an example of the cutout portion of the laminate of the present invention.

Fig. 5 is a schematic plan view showing an example of a method for peeling the release film from the laminate.

Description of the symbols

10 polarizing plate, 11 polarizer, 12 protective film, 13 protective film, 14 retardation film, 15 adhesive layer, 16 adhesive layer, 17 brightness enhancement film, 20 release film, 30 surface protective film, 31 base material film, 32 adhesive layer, 40 gap part, 100 laminated body, 101 laminated body, 102 laminated body, 103 laminated body, 104 laminated body, 200 release tape, 300 area, 400 release direction.

Detailed Description

< laminate >

The laminate has a surface protective film laminated on one surface of a polarizing plate and a release film laminated on the other surface of the polarizing plate. The polarizing plate has at least a polarizer. An example of the layer structure of the laminate of the present invention will be described below with reference to the drawings. The polarizing plate may further include a protective film, a retardation film, a brightness enhancement film, an adhesive layer, and the like in addition to the polarizer.

Fig. 1 is a schematic cross-sectional view showing an example of the laminate of the present invention. The laminate 100 shown in fig. 1 (a) is composed of a polarizing plate 10, a surface protective film 30 laminated on one surface of the polarizing plate 10, and a release film 20 laminated on the other surface of the polarizing plate 10. The polarizing plate 10 is configured by laminating a protective film 12 on one surface of a polarizing plate 11 with an adhesive layer not shown interposed therebetween, a retardation film 14 on the other surface with an adhesive layer 16 interposed therebetween, and an adhesive layer 15 on the retardation film 14.

The laminate 101 shown in fig. 1 (b) is composed of a polarizing plate 10, a surface protective film 30 laminated on one surface of the polarizing plate 10, and a release film 20 laminated on the other surface of the polarizing plate 10. The polarizing plate 10 is configured by laminating a protective film 12 on one surface of a polarizer 11 with an adhesive layer not shown interposed therebetween, a protective film 13 on the other surface with an adhesive layer not shown interposed therebetween, a retardation film 14 on the protective film 13 with an adhesive layer 16 interposed therebetween, and an adhesive layer 15 on the retardation film 14.

The laminate 102 shown in fig. 2 (a) is composed of a polarizing plate 10, a surface protective film 30 laminated on one surface of the polarizing plate 10, and a release film 20 laminated on the other surface of the polarizing plate 10. The polarizing plate 10 is formed by laminating a protective film 13 on one surface of a polarizer 11 with an adhesive layer not shown interposed therebetween, a brightness enhancement film 17 on the other surface with an adhesive layer 16 interposed therebetween, and an adhesive layer 15 on the protective film 13.

The laminate 103 shown in fig. 2 (b) is composed of a polarizing plate 10, a surface protective film 30 laminated on one surface of the polarizing plate 10, and a release film 20 laminated on the other surface of the polarizing plate 10. The polarizing plate 10 is formed by laminating a protective film 12 on one surface of a polarizer 11 with an adhesive layer not shown interposed therebetween, a protective film 13 on the other surface with an adhesive layer not shown interposed therebetween, a brightness enhancement film 17 on the protective film 12 with an adhesive layer 16 interposed therebetween, and an adhesive layer 15 on the protective film 13.

In the laminated bodies 100 to 103, the surface protective film 30 and the release film 20 are preferably members constituting the outermost surfaces of the laminated bodies, respectively. The laminated bodies 100 to 103, the polarizing plate 10, the release film 20, and the surface protective film 30 may have layers other than those shown in the drawings.

The laminate preferably has a substantially rectangular main surface. The main surface is a surface having the largest area corresponding to the display surface. The substantially rectangular shape means that the laminate may have a shape in which at least 1 corner of 4 corners (corners) of the main surface is cut off to form an obtuse angle or a shape in which an arc is provided, or may have a recessed portion (notch portion) in which a portion of an end surface perpendicular to the main surface is recessed in an in-plane direction, or may have an opening portion in which a portion of the main surface is hollowed out to have a shape such as a circle, an ellipse, a polygon, or a combination thereof.

The laminate has a notch portion on at least one end surface in a plan view. The notch portion is a portion in which a part of an end face perpendicular to the main face is recessed in the in-plane direction in a plan view, as described above. The laminate may have 1 or more notch portions. The laminate may have a plurality of cut portions at 1 end edge, and preferably has 1 cut portion at 1 end edge. The notch portion may be formed at an end edge perpendicular or parallel to the absorption axis of the polarizing plate. Since the laminate has a notch portion on the end face in a plan view, the end portion is recessed into the plane when the laminate is viewed from the top surface.

The laminate of the present invention has a maximum value of peeling force of 1.0N or less when peeling the release film from the edge having the notch. The maximum value of the peeling force is preferably 0.8N or less. The maximum value of the peeling force may be 0.1N or more. The maximum value of the peeling force is controlled by the shape of the notch portion and the like as described later. The maximum value of the peeling force can be measured by the method described in the examples described later. By setting such a peeling force, peeling failure is less likely to occur.

The shape of the notch portion provided in the laminate of the present invention preferably satisfies the following formula (1).

When the laminate has a plurality of cut portions, at least 1 cut portion may satisfy formula (1), and all cut portions may satisfy formula (1). By making the shape of the notch portion satisfy the above formula (1), the force required for peeling the release film can be reduced.

r＞3d－14(1)

In expression (1), d (mm) represents the depth of the notch, and r (mm) represents the radius of curvature of the inner corner of the notch. Angle (c)

Fig. 3 is a schematic view of an example 104 of the laminate of the present invention as viewed from above. The laminate 104 has a cutout 40 in a plan view from the top. The notch 40 is recessed from the end toward the inside. The depth of the notch corresponds to the length of the double-headed arrow d in fig. 3, and is the distance from the end edge to the deepest part of the recess. The radius of curvature of the inside corner of the notch corresponds to the radius of curvature of the corner indicated by a single arrow R in fig. 3. When the 2 inner corners have different radii of curvature, r represents the smaller radius of curvature. The radii of curvature of the 2 inside corners are preferably the same as each other.

r and d are both values greater than 0. Although not particularly limited, the upper limit value of r may be 17mm. Although not particularly limited, the upper limit value of d may be 20mm. d may be 10mm or less, or 7mm or less.

When d is 2mm or more and 5mm or less, r is preferably 2mm or more. When d is larger than 5mm and 6mm or less, r is preferably 8mm or more. When d is more than 6mm and less than 8mm, r is preferably 13mm or more. When d is 8mm or more, r is preferably 17mm or more.

The width of the notch portion may be set to 5mm to 50mm, preferably 5mm to 20mm. The width of the notch portion is the longest distance of the notch portion, which is the length parallel to the end edge.

The shape of the notch may be specifically the shape shown in fig. 4. Fig. 4 is a schematic view showing an example of the notch 40 of the laminate of the present invention in a plan view, and the notch 40 may be formed in a shape in which an arc is provided at 2 corners inside the rectangular recessed portion as shown in fig. 4 (a) or in a shape in which an arc is provided at 4 corners of the rectangular recessed portion as shown in fig. 4 (b) in a plan view seen from the top surface. As shown in fig. 4 (c), the notch may have a circular arc shape at the corner of the trapezoidal recess. As shown in fig. 4 (a) to (c), the notch portion may have a straight portion at the bottom, or as shown in fig. 4 (d), the notch portion may not have a straight portion at the bottom.

The laminate may be obtained by producing a long laminate in a roll-to-roll manner while conveying the members constituting the laminate, and cutting the laminate, or may be obtained by preparing each member in a predetermined shape and sequentially laminating the members.

When the laminate is rectangular (or substantially rectangular) having long sides and short sides, the length of the long sides is preferably 35 to 5cm, more preferably 25 to 10cm, and the length of the short sides is preferably 25 to 5cm, more preferably 20 to 6cm. By setting the size in such a range, the peelability can be further improved.

Hereinafter, each member of the laminate will be described.

< polarizing plate >

The polarizing plate 10 is a polarizing element including at least a polarizer, and usually further includes a thermoplastic resin film attached to one or both surfaces thereof. The thermoplastic resin film may be a protective film for protecting the polarizing plate, another film having an optical function, or the like. The thermoplastic resin film may include a resin layer (for example, at least one optical layer selected from a hard coat layer, an antistatic layer, an antiglare layer, a light diffusion layer, an antireflection layer, a low refractive index layer, an antifouling layer, and the like) laminated on the surface thereof. The thermoplastic resin film may be bonded to the polarizing plate with an adhesive layer interposed therebetween. The surface protective film 30 may be laminated on the surface of the resin layer.

When the laminate further includes a brightness enhancement film and a retardation film, the effect of the present invention is remarkable. Polarizing plates including a brightness enhancement film and the like have low rigidity and are likely to suffer from peeling failure.

According to the present invention, even when the laminate includes a brightness enhancement film or the like, the occurrence of peeling failure can be reduced.

The thickness (μm) of the polarizing plate is usually 150 μm or less, and the effect of the present invention is remarkable when the rigidity is low, i.e., 75 μm or less and 70 μm or less. The thickness of the polarizing plate 10 is preferably 30 μm or more, and more preferably 50 μm or more.

(1) Polarizing plate

The polarizing plate constituting the polarizing plate 10 is an absorption type polarizing plate having a property of absorbing a linearly polarized light having a vibration plane parallel to the absorption axis thereof and transmitting a linearly polarized light having a vibration plane orthogonal to the absorption axis (parallel to the transmission axis), and a polarizing plate obtained by adsorbing a dichroic dye onto a uniaxially stretched polyvinyl alcohol resin film and orienting the resin film can be suitably used. The polarizing plate can be manufactured, for example, by a method including: a step of uniaxially stretching a polyvinyl alcohol resin film; a step of dyeing a polyvinyl alcohol resin film with a dichroic dye to allow the polyvinyl alcohol resin film to adsorb the dichroic dye; treating the polyvinyl alcohol resin film having the dichroic dye adsorbed thereon with a crosslinking liquid such as an aqueous boric acid solution; and a step of washing with water after the treatment with the crosslinking liquid.

As the polyvinyl alcohol resin, a resin obtained by saponifying a polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other copolymerizable monomers. 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, and the like.

The term "(meth) acrylic" as used herein means at least one member selected from the group consisting of acrylic and methacrylic. The same applies to "(meth) acryloyl group", "(meth) acrylate", and the like.

The saponification degree of the polyvinyl alcohol resin is usually 85 to 100mol%, preferably 98mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes may be used. The polyvinyl alcohol resin has an average polymerization degree of usually 1000 to 10000, preferably 1500 to 5000. The average polymerization degree of the polyvinyl alcohol resin can be determined in accordance with JIS K6726.

A film obtained by forming such a polyvinyl alcohol resin film is used as a material film of a polarizing plate (polarizing plate). The method for forming the film from the polyvinyl alcohol resin is not particularly limited, and a known method can be used. The thickness of the polyvinyl alcohol-based material film is not particularly limited, but a material film of 5 to 35 μm is preferably used in order to set the thickness of the polarizing plate to 15 μm or less. More preferably 20 μm or less.

The uniaxial stretching of the polyvinyl alcohol resin film may be performed before, simultaneously with, or after the dyeing of the dichroic dye. In the case where the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before or during the crosslinking treatment. In addition, uniaxial stretching may be performed in a plurality of stages of these.

In the case of uniaxial stretching, the stretching may be performed uniaxially between rolls having different peripheral speeds, or may be performed uniaxially using a heat roll. The uniaxial stretching may be dry stretching in which stretching is performed in the air, or wet stretching in which stretching is performed in a state where the polyvinyl alcohol resin film is swollen with a solvent or water. The stretch ratio is usually 3 to 8 times.

As a method for dyeing a polyvinyl alcohol resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing a dichroic dye is employed. Iodine or a dichroic organic dye is used as the dichroic dye. The polyvinyl alcohol resin film is preferably subjected to an immersion treatment in water before the dyeing treatment.

As the crosslinking treatment after dyeing with the dichroic dye, a method of immersing a dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid is generally employed. In the case of using iodine as the dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide.

The thickness of the polarizing plate is usually 30 μm or less, preferably 20 μm or less, more preferably 15 μm or less, and still more preferably 10 μm or less. In particular, when the thickness of the polarizing plate is 15 μm or less, it is advantageous to make the laminate thin. The thickness of the polarizer is usually 2 μm or more, and is preferably 3 μm or more from the viewpoint of providing the polarizing plate with stiffness.

As the polarizing plate, for example, as described in japanese patent application laid-open No. 2016-170368, a polarizing plate in which a dichroic dye is aligned in a cured film obtained by polymerizing a liquid crystal compound can be used. As the dichroic dye, a dichroic dye having absorption in a wavelength range of 380 to 800nm can be used, and an organic dye is preferably used. Examples of the dichroic dye include azo compounds.

The liquid crystal compound is a polymerizable liquid crystal compound capable of maintaining an alignment state, and may have a polymerizable group in a molecule.

(2) Protective film

The protective film which may be laminated on one surface or both surfaces of the polarizing plate may be a polyolefin-based resin having light transmittance (preferably optically transparent) and containing a thermoplastic resin, for example, a chain polyolefin-based resin (polypropylene-based resin, etc.) or a cyclic polyolefin-based resin (norbornene-based resin, etc.); cellulose resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; a polycarbonate-based resin; (meth) acrylic resins such as methyl methacrylate resins; a polystyrene-based resin; a polyvinyl chloride resin; acrylonitrile/butadiene/styrene resins; acrylonitrile/styrene resins; polyvinyl acetate resin; a polyvinylidene chloride resin; a polyamide resin; a polyacetal resin; modified polyphenylene ether resin; a polysulfone-based resin; a polyether sulfone-based resin; a polyarylate-based resin; a polyamide imide resin; polyimide resin, and the like.

Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resins (polyethylene resins that are homopolymers of ethylene, and copolymers mainly composed of ethylene), polypropylene resins (polypropylene resins that are homopolymers of propylene, and copolymers mainly composed of propylene), and copolymers containing 2 or more kinds of chain olefins.

The cyclic polyolefin-based resin is a general term for resins obtained by polymerizing a cyclic olefin as a polymerization unit, and examples thereof include those described in Japanese patent application laid-open Nos. H1-240517, H3-14882, and H3-122137. Specific examples of the cyclic polyolefin resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with linear olefins such as ethylene and propylene (a random copolymer is a typical example), graft polymers obtained by modifying these with unsaturated carboxylic acids and derivatives thereof, and hydrogenated products of these. Among these, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins are preferably used.

The polyester resin is a resin having an ester bond other than the following cellulose ester resins, and generally includes a polycondensate of a polycarboxylic acid or a derivative thereof and a polyol. As the polycarboxylic acid or a derivative thereof, a 2-valent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a 2-valent diol can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexanedimethanol. A typical example of the polyester resin is polyethylene terephthalate which is a condensation product of terephthalic acid and ethylene glycol.

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 with compounds having alicyclic hydrocarbon groups (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate copolymerMethyl acrylate- (norbornyl meth) acrylate copolymers, and the like). Preference is given to using poly (meth) acrylic acid C such as polymethyl (meth) acrylate _1-6 The polymer containing an alkyl ester as a main component is more 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-based resin include cellulose triacetate, cellulose diacetate, cellulose propionate, and cellulose dipropionate. Further, copolymers thereof and resins in which a part of the hydroxyl groups is modified 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 a carbonate group.

It is also useful to control the retardation value of the protective film to a value suitable for an image display device such as a liquid crystal display device. For example, in an in-plane switching (IPS) mode liquid crystal display device, a film having substantially zero retardation value is preferably used as the protective film.

The phrase "substantially zero phase difference" means an in-plane phase difference R at a wavelength of 590nm ₀ A thickness direction phase difference R of 10nm or less at a wavelength of 590nm _th Has an absolute value of 10nm or less and a phase difference R in the thickness direction at a wavelength of 480 to 750nm _th The absolute value of (A) is 15nm or less.

For example, the protective film may be subjected to stretching and/or shrinking processing to provide an appropriate phase difference value according to the mode of the liquid crystal display device. For example, a retardation layer (or film) of a single layer or multilayer structure may be used as a protective film for the purpose of viewing angle compensation. In this case, the polarizing plate 10 may be an elliptical polarizing plate or a circular polarizing plate having a laminated structure including a polarizer and a phase difference layer, or a polarizing plate having a function of compensating viewing angle including a phase difference layer.

The thickness of the protective film is usually 1 to 100 μm, but from the viewpoint of strength, handling property, and the like, it is preferably 5 to 60 μm, more preferably 10 to 55 μm, and still more preferably 15 to 40 μm.

When protective films are attached to both surfaces of the polarizing plate, the protective films may be made of the same type of thermoplastic resin or different types of thermoplastic resins.

The thicknesses may be the same or different. Further, the retardation film may have the same retardation characteristics or may have different retardation characteristics.

As described above, at least one of the protective films may have a surface treatment layer (coat layer) such as a hard coat layer, an antiglare layer, a light diffusion layer, an antireflection layer, a low refractive index layer, an antistatic layer, and an antifouling layer on its outer surface (surface opposite to the polarizing plate). The thickness of the protective film includes the thickness of the surface treatment layer.

From the viewpoint of suppressing the incorporation of air bubbles between the surface protective film and the polarizing plate, the surface of the polarizing plate 10 on the surface protective film 30 side (the surface to which the surface protective film 30 is bonded, or the surface treatment layer) is preferably set to a value in accordance with JIS B0601: 2013 has a small arithmetic average roughness Ra. Specifically, ra of the surface is preferably 0.3 μm or less, more preferably 0.2 μm or less, and still more preferably 0.15 μm or less. The Ra of the surface is usually 0.001 μm or more, for example, 0.005 μm or more.

The protective film may be bonded to the polarizing plate with an adhesive layer interposed therebetween. As the adhesive for forming the adhesive layer, an aqueous adhesive, an active energy ray-curable adhesive, or a thermosetting adhesive can be used, and an aqueous adhesive or an active energy ray-curable adhesive is preferable.

Examples of the aqueous adhesive include an adhesive containing a polyvinyl alcohol resin aqueous solution, an aqueous two-pack type urethane emulsion adhesive, and the like. Among them, an aqueous adhesive containing an aqueous solution of a polyvinyl alcohol resin can be suitably used. As the polyvinyl alcohol resin, not only a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate as a homopolymer of vinyl acetate, but also a polyvinyl alcohol copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith, a modified polyvinyl alcohol polymer obtained by partially modifying hydroxyl groups thereof, and the like can be used. The aqueous adhesive may contain a crosslinking agent such as an aldehyde compound (e.g., glyoxal), an epoxy compound, a melamine compound, a methylol compound, an isocyanate compound, an amine compound, or a polyvalent metal salt.

When an aqueous adhesive is used, it is preferable to perform a drying step for removing water contained in the aqueous adhesive after the polarizing plate and the protective film are bonded. After the drying step, an aging step of aging at a temperature of, for example, 20 to 45 ℃ may be performed.

The active energy ray-curable adhesive is an 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 ray-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), and a combination thereof. Examples of the radically 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, and a combination thereof. The cationically polymerizable curable compound may be used in combination with the radically polymerizable curable compound. The active energy ray-curable adhesive usually further contains a cationic polymerization initiator and/or a radical polymerization initiator for initiating a curing reaction of the curable compound.

When the polarizing plate and the protective film are bonded, at least one of the bonding surfaces may be subjected to a surface activation treatment in order to improve the adhesiveness. Examples of the surface activation treatment include dry treatments such as corona treatment, plasma treatment, discharge treatment (glow discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, and ionizing active ray treatment (ultraviolet treatment, electron beam treatment, etc.); a wet process such as an ultrasonic treatment, a saponification treatment, and an anchor coat treatment using a solvent such as water or acetone is used. These surface activation treatments may be performed alone or in combination of two or more.

When protective films are bonded to both surfaces of the polarizing plate, the adhesives used for bonding these protective films may be the same type of adhesive or different types of adhesives.

(3) Other membranes

The polarizing plate 10 may include other films than a polarizer and a protective film, and typical examples thereof include a brightness enhancement film and a retardation film. In the case where the polarizing plate 10 includes another film, the surface protective film 30 may be laminated on a surface of the film or a surface of a surface treatment layer laminated on the film.

The brightness enhancement film is a film also called a reflective polarizing plate, and uses a polarization conversion element having a function of separating light emitted from a light source (backlight) into transmission polarized light and reflection polarized light or scattering polarized light. By disposing the brightness enhancement film on the polarizing plate, the emission efficiency of the linearly polarized light emitted from the polarizing plate can be improved by using the return light which is the reflected polarized light or the scattered polarized light. The brightness enhancement film may be laminated on the polarizer with an adhesive layer therebetween.

Another film such as a protective film may be interposed between the polarizing plate and the brightness enhancement film.

The brightness enhancing film may be, for example, an anisotropic reflective polarizer. An example of the anisotropic reflective polarizing plate is an anisotropic multiple film which transmits a linearly polarized light in one vibration direction and reflects a linearly polarized light in the other vibration direction, and a specific example thereof is "APF" manufactured by 3M company. Another example of the anisotropic reflective polarizer is a composite of a cholesteric liquid crystal layer and a λ/4 plate, and an example thereof is "PCF" manufactured by ritonao electric co. Another example of the anisotropic reflective polarizing plate is a reflective grid polarizing plate, and specific examples thereof include a metal lattice reflective polarizing plate which can emit a reflective polarized light even in a visible light region after metal is finely processed, and a film obtained by adding metal fine particles to a polymer matrix and stretching the polymer matrix.

As described above, a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, a light diffusion layer, a retardation layer (a retardation layer having a retardation value of 1/4 wavelength, or the like), an antireflection layer, a low refractive index layer, an antistatic layer, and an antifouling layer may be provided on the outer surface of the brightness enhancement film. By forming this layer, adhesion to the backlight tape and uniformity of a displayed image can be improved. The thickness of the brightness enhancement film 50 is generally 10 to 100 μm, preferably 10 to 50 μm, and more preferably 10 to 30 μm.

Examples of the retardation film include a positive a plate such as a 1/4 wavelength (λ/4) plate and a 1/2 wavelength (λ/2) plate, and a positive C plate. The lambda/4 plate is a layer whose in-plane phase difference value Re (550) at a wavelength of 550nm satisfies the relationship of 100nm < Re (550) < 200 nm. The λ/4 plate can also exhibit reverse wavelength dispersibility satisfying Re (450) < Re (550) < Re (650). The lambda/2 plate is a layer in which Re (550) satisfies 210 nm. Ltoreq. Re (550). Ltoreq.300 nm. The positive C plate satisfies Nz > Nx ≧ Ny, and the phase difference value in the thickness direction at the wavelength λ nm, rth (λ), preferably satisfies-300 nm ≦ Rth (550) ≦ -20 nm.

The retardation film can be formed of, for example, the resins exemplified as the materials of the protective film, and among them, a cyclic olefin resin and a styrene resin are preferable. The retardation layer may be formed of a single layer or a plurality of layers. Examples of the retardation layer having a plurality of layers include a resin film (base film) exemplified as a material of the protective film, a retardation layer including a layer obtained by curing a liquid crystal compound after polymerization of a liquid crystal compound, and a retardation layer including a plurality of layers (for example, 2 layers) obtained by curing a liquid crystal compound. The layer having a retardation may be a resin film and/or a layer obtained by curing a liquid crystal compound. The resin film can also function as the protective film.

The retardation film may include 1 retardation layer or a plurality of retardation layers. When the retardation film includes a plurality of retardation layers, a combination of a 1/4 wavelength plate and a 1/2 wavelength plate, and a combination of a 1/4 wavelength plate and a positive C plate are preferable.

The retardation film preferably includes a layer obtained by curing a liquid crystal compound, and when the retardation film includes a plurality of retardation layers, any one of the retardation layers may include a layer obtained by curing a liquid crystal compound. The type of the liquid crystal compound is not particularly limited, but the liquid crystal compound can be classified into a rod-like type (rod-like liquid crystal compound) and a discotic type (discotic liquid crystal compound ) depending on the shape thereof. Further, there are a low-molecular type and a high-molecular type, respectively. The term "polymer" generally refers to a compound having a polymerization degree of 100 or more (polymer physical/phase transition kinetics, tujing university, page 2, kyobo Shu, 1992). In this embodiment, any liquid crystal compound can be used. In addition, 2 or more kinds of rod-like liquid crystal compounds, 2 or more kinds of discotic liquid crystal compounds, or a mixture of rod-like liquid crystal compounds and discotic liquid crystal compounds may be used.

The rod-like liquid crystal compound may be suitably used, for example, as the compound described in claim 1 of Japanese patent application laid-open No. 11-513019 or paragraphs [0026] to [0098] of Japanese patent application laid-open No. 2005-289980. As the discotic liquid crystal compound, for example, compounds described in paragraphs [0020] to [0067] of jp 2007-108732 a, or paragraphs [0013] to [0108] of jp 2010-244038 a can be suitably used.

The retardation layer is more preferably formed using a liquid crystal compound having a polymerizable group (rod-like liquid crystal compound or discotic liquid crystal compound). This can reduce temperature change and humidity change in the optical characteristics.

The liquid crystal compound may be a mixture of 2 or more. In this case, at least 1 species preferably has 2 or more polymerizable groups. That is, the retardation layer is preferably a layer in which a rod-like liquid crystal compound having a polymerizable group or a discotic liquid crystal compound having a polymerizable group is fixed by polymerization. In this case, it is not necessary to exhibit liquid crystallinity even after the layer is formed.

The type of the polymerizable group contained in the rod-like liquid crystal compound or the discotic liquid crystal compound is not particularly limited, and for example, a functional group capable of undergoing an addition polymerization reaction, such as a polymerizable ethylenically unsaturated group or a cyclopolymerizable group, is preferable. More specifically, examples thereof include a (meth) acryloyl group, a vinyl group, a styryl group, and an allyl group. Among them, (meth) acryloyl groups are preferable. The term "(meth) acryloyl" refers to a concept including both methacryloyl and acryloyl.

The method for forming the retardation layer is not particularly limited, and known methods can be used. For example, a retardation layer can be produced by applying a composition for forming an optically anisotropic layer (hereinafter, simply referred to as "composition") containing a liquid crystal compound having a polymerizable group to a predetermined substrate (including a temporary substrate) to form a coating film, and subjecting the obtained coating film to a curing treatment (irradiation of ultraviolet rays (light irradiation treatment) or heating treatment). The produced retardation layer may be transferred onto, for example, a polarizer or a protective film.

The composition can be applied by a known method, for example, a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method.

The composition may contain components other than the above-mentioned liquid crystal compound. For example, in the composition, a polymerization initiator may be contained. The polymerization initiator used may be selected, for example, from thermal polymerization initiators and photopolymerization initiators depending on the form of the polymerization reaction. Examples of the photopolymerization initiator include α -carbonyl compounds, acyloin ethers (125251245212556\\12540861252323), α -hydrocarbon-substituted aromatic acyloin compounds, polyquinone compounds, combinations of triarylimidazole dimers and p-aminophenyl ketones. The amount of the polymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the total solid content of the composition.

The composition may contain a polymerizable monomer in view of the uniformity of the coating film and the strength of the film. Examples of the polymerizable monomer include a radically polymerizable or cationically polymerizable compound. Among them, polyfunctional radical polymerizable monomers are preferable.

The polymerizable monomer is preferably a polymerizable monomer copolymerizable with the polymerizable group-containing liquid crystal compound. Specific examples of the polymerizable monomer include polymerizable monomers described in paragraphs [0018] to [0020] in Japanese patent laid-open No. 2002-296423. The amount of the polymerizable monomer used is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, based on the total mass of the liquid crystal compound.

The composition may contain a surfactant in view of the uniformity of the coating film and the strength of the film. Examples of the surfactant include conventionally known compounds. Among them, fluorine compounds are particularly preferable.

In addition, a solvent may be contained in the composition, and an organic solvent is preferably used. Examples of the organic solvent include amides (e.g., N-dimethylformamide), sulfoxides (e.g., dimethyl sulfoxide), heterocyclic compounds (e.g., pyridine), hydrocarbons (e.g., benzene, hexane), alkyl halides (e.g., chloroform, dichloromethane), esters (e.g., methyl acetate, ethyl acetate, butyl acetate), ketones (e.g., acetone, methyl ethyl ketone), and ethers (e.g., tetrahydrofuran, 1, 2-dimethoxyethane).

Among them, alkyl halides and ketones are preferable. In addition, 2 or more organic solvents may be used in combination.

The composition may contain various alignment agents such as a vertical alignment promoter such as a polarizing plate interface side vertical alignment agent and an air interface side vertical alignment agent, and a horizontal alignment promoter such as a polarizing plate interface side horizontal alignment agent and an air interface side horizontal alignment agent. The composition may further contain an adhesion improving agent, a plasticizer, a polymer, and the like in addition to the above components.

The retardation film may include an alignment film having a function of defining an alignment direction of the liquid crystal compound. The alignment film generally contains a polymer as a main component. The polymer material for an alignment film is described in many documents, and many commercially available products are available. Among these, polyvinyl alcohol, polyimide, and derivatives thereof are preferably used as the polymer material, and particularly, modified or unmodified polyvinyl alcohol is preferably used.

The alignment film is subjected to a generally known alignment treatment. For example, rubbing treatment, photo-alignment treatment by irradiation with polarized light, and the like can be mentioned, but photo-alignment treatment is preferable from the viewpoint of surface roughness of the alignment film.

The thickness of the layer obtained by curing the liquid crystal compound is not particularly limited, but is preferably 0.5 to 10 μm, and more preferably 1.0 to 5 μm. The thickness of the alignment film is not particularly limited, but is at most 20 μm or less, and among them, it is preferably 0.01 to 10 μm, more preferably 0.01 to 5 μm, and still more preferably 0.01 to 1 μm.

(4) Adhesive layer

The polarizing plate 10 preferably has an adhesive layer 15 on the outermost surface thereof. The pressure-sensitive adhesive layer may be used for bonding the polarizing plate 10 to a display element (for example, a liquid crystal cell or an organic EL element) or another optical member, and is exposed after the release film 20 is peeled off. The pressure-sensitive adhesive layer may be used for laminating a polarizing plate, a protective film, a brightness enhancement film, and a retardation film. In fig. 1 and 2, the adhesive layer 16 corresponds to the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer may be composed of a pressure-sensitive adhesive composition containing a resin such as a (meth) acrylic, rubber, urethane, ester, silicone, or polyvinyl ether resin as a main component. Among them, the pressure-sensitive adhesive composition is suitable for use as a base polymer of a (meth) acrylic resin which is excellent in transparency, weather resistance, heat resistance and the like. The adhesive composition may be an active energy ray-curable type or a heat-curable type.

As the (meth) acrylic resin (base polymer) used in the adhesive composition, for example, a polymer or copolymer using 1 or 2 or more kinds of (meth) acrylic acid esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate as monomers can be suitably used. The polar monomer is preferably copolymerized with the base polymer. Examples of the polar monomer include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.

The adhesive composition may comprise only the above-mentioned base polymer, but typically also contains a crosslinking agent. Examples of the crosslinking agent include a metal ion having a valence of 2 or more and a metal carboxylate salt formed between the metal ion and a carboxyl group; a compound which is a polyamine compound and forms an amide bond with a carboxyl group; a compound which is a polyepoxy compound or a polyol and forms an ester bond with a carboxyl group; a compound which is a polyisocyanate compound and forms an amide bond with a carboxyl group. Among them, polyisocyanate compounds are preferable.

The active energy ray-curable pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition having a property of being cured by irradiation with an active energy ray such as ultraviolet ray or electron beam, and having a property of having adhesiveness before irradiation with an active energy ray and being capable of being closely adhered to an adherend such as a film, and being cured by irradiation with an active energy ray to adjust the adhesion force. The active energy ray-curable adhesive composition is preferably an ultraviolet ray-curable adhesive composition. The active energy ray-curable adhesive composition contains an active energy ray-polymerizable compound in addition to the base polymer and the crosslinking agent. Further, a photopolymerization initiator, a photosensitizer and the like may be contained as necessary.

The adhesive composition may contain additives such as fine particles, beads (resin beads, glass beads, and the like), glass fibers, resins other than the base polymer for imparting light scattering properties, antistatic agents, tackifiers, fillers (metal powder, other inorganic powder, and the like), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, antifoaming agents, preservatives, and photopolymerization initiators.

The pressure-sensitive adhesive layer can be formed by applying a diluted solution of the pressure-sensitive adhesive composition in an organic solvent to a substrate and drying the applied solution. The substrate may be other optical films such as a polarizing plate, a protective film, and a brightness enhancement film, a release film (e.g., release film 20), and the like. When an active energy ray-curable pressure-sensitive adhesive composition is used, a cured product having a desired degree of curing can be produced by irradiating the pressure-sensitive adhesive layer formed with an active energy ray.

The thickness of the pressure-sensitive adhesive layer 15 is usually 1 to 40 μm, but is preferably 3 to 25 μm (for example, 3 to 20 μm, more preferably 3 to 15 μm) from the viewpoint of making the laminate thin and from the viewpoint of suppressing dimensional change of the polarizing plate 10 while maintaining good processability. The thickness of the adhesive layer 16 is usually 1 to 20 μm, preferably 3 to 10 μm.

The adhesive force between the pressure-sensitive adhesive layer 15 and the release film in the laminated release film 20 is 0.10N/25mm or less, preferably 0.04N/25mm or less. By providing such an adhesive force, the peeling property is further improved without causing lifting of the polarizing plate when the peeling film is peeled. The adhesive force is 0.02N/25mm or more. By providing such an adhesion force, even if an impact is applied to the laminate during conveyance or the like, it is easy to prevent a gap from being generated between the release film and the adhesive layer. In the present specification, the adhesion force between the pressure-sensitive adhesive layer and the release film is a value measured by the method described in the examples described below.

< surface protective film >

The surface protective film 30 may be a surface protective film comprising a base film 31, and an adhesive layer 32 laminated thereon. The surface protection film 30 is a film for protecting the surface of the polarizing plate 10, and is usually peeled off and removed together with an adhesive layer included therein after the laminate is attached to, for example, a display element or another optical member.

The surface protective film generally has stiffness as compared with a brightness enhancement film, and is important for improving the releasability of a release film. In the present specification, the thickness of the surface protective film is the sum of the thickness of the base film and the thickness of the pressure-sensitive adhesive layer laminated thereon, and is preferably 30 μm or more, and more preferably 50 μm or more. On the other hand, if the thickness of the surface protective film is too large, peeling between the surface protective film and the polarizing plate is likely to occur when the peeling film is peeled, and therefore the thickness of the surface protective film is preferably 100 μm or less, more preferably 70 μm or less.

The substrate film is preferably a thermoplastic resin film. Examples of the thermoplastic resin constituting the thermoplastic resin film include polyolefin resins such as polyethylene resins and polypropylene resins; a cyclic polyolefin resin; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; a polycarbonate-based resin; (meth) acrylic resins, and the like. The substrate film may have a single-layer structure or a multilayer structure.

The thickness of the substrate film may be 20 to 150 μm (for example, 30 to 80 μm, preferably 30 to 60 μm). The structure of the adhesive layer is basically described in the adhesive layer included in the polarizing plate.

In particular, the storage modulus of the pressure-sensitive adhesive layer is preferably 0.15MPa or less, more preferably 0.14MPa or less, and still more preferably 0.10MPa or less at 80 ℃. The pressure-sensitive adhesive layer generally has a storage modulus at 80 ℃ of 0.01MPa or more. In the present specification, the storage modulus of the pressure-sensitive adhesive layer can be measured using a commercially available viscoelasticity measuring apparatus, for example, a viscoelasticity measuring apparatus "DYNAMIC ANALYZER RDA II" manufactured by REMOMETRIC.

The surface protective film 30 may contain an antistatic agent. For example, the adhesive layer may contain an antistatic agent. The antistatic layer containing the antistatic agent may be provided on the surface of the base film opposite to the surface on which the pressure-sensitive adhesive layer is laminated, without containing the antistatic agent in the pressure-sensitive adhesive layer, or the antistatic layer containing the antistatic agent may be provided on the surface of the base film opposite to the surface on which the pressure-sensitive adhesive layer is laminated, while containing the antistatic agent in the pressure-sensitive adhesive layer.

Examples of the antistatic agent include ionic compounds. The ionic compound is a compound having an inorganic cation or an organic cation and an inorganic anion or an organic anion.

2 or more kinds of ionic compounds may also be used.

< peeling film >

The release film 20 is a film temporarily bonded to protect the surface of a display element (for example, a liquid crystal cell or an organic EL element) or other optical member before the adhesive layer is bonded thereto. The release film 20 can be subjected to a release treatment using a release agent such as a silicone-based or fluorine-based release agent on one surface thereof to adjust the adhesion force with the pressure-sensitive adhesive layer 15. The release film 20 is made of a thermoplastic resin film subjected to a release treatment, and an adhesive layer may be bonded to the release-treated surface thereof.

The thermoplastic resin constituting the release film 20 may be, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, or the like. The thickness of the release film 20 is, for example, 10 to 50 μm.

The laminated bodies 100 to 103 can be bonded to a display element (for example, a liquid crystal cell or an organic EL element) by peeling the release film 20. The surface protective film 30 can be peeled off and incorporated into a display device (for example, a liquid crystal display device or an organic EL display device). In the case of constructing a display device, the laminate of the present invention may be used for a polarizing plate disposed on the viewing side with respect to the display element, a polarizing plate disposed on the side opposite to the viewing side, or both the viewing side and the side opposite to the viewing side.

< method for producing laminate >

The laminate may be obtained by producing a long laminate in a roll-to-roll manner while conveying the members constituting the laminate, and cutting the laminate, or may be obtained by preparing each member in a predetermined shape and sequentially laminating the members.

The grooving, the boring, and the R-machining of the corner can be performed using a planing process (\124591253112490). The processing mechanism for grooving and boring is preferably an end mill. An end mill is a kind of cutting tool. Unlike a drill in which machining is performed only in the axial direction (only for drilling), end mill machining may be performed in a direction perpendicular to the rotation axis. The shaving processing is processing for shaving a processing surface in parallel by a cutter having a rotating shaft parallel to the processing surface and provided to protrude. Specifically, the processing apparatus and processing method described in japanese patent application laid-open No. 2018-22140 can be used.

Method for manufacturing polarizing plate with surface protective film

A method of peeling the release film from the laminate 104 will be described as a specific example with reference to fig. 5.

The surface of the laminate on the surface protective film side was fixed to a holding table, and the tape 200 was bonded to a release film. The method of fixing the laminate 104 is not particularly limited, and the laminate may be fixed by a force of suction from the surface protective film side or may be fixed by an adhesive force. The adhesion force between the fixed surface protective film and the holding base is preferably 0.1 to 0.3N/60mm, and more preferably 0.15 to 0.2N/60mm, from the viewpoint of preventing the occurrence of a mark in the polarizing plate. According to the laminate of the present invention, good peelability is exhibited even if the laminate is fixed with such a small pressure. The position of the adhesive tape 200 may be, for example, a corner portion having one end of the edge of the notch portion, as shown in fig. 5.

Then, the tape 200 is pulled up to peel off the release film. In fig. 5, an angle θ formed by the edge side orthogonal to the edge side having the notch portion and the peeling direction 400 of the tape may be 0 ° or more and 90 ° or less. When the release film is peeled off after the tape is adhered to the corner portion of one end of the edge having the notch portion, a peeling failure is likely to occur when the peeling tip approaches the notch portion, particularly when the peeling tip approaches the region 300 shown in fig. 5. That is, when the peeling front end is close to the corner portion on the inner side of the position far from the adhesive tape, which is the corner portion on the inner side of the notch portion, peeling failure is likely to occur. According to the present invention, even when the peeling front end approaches the notch portion, peeling failure is less likely to occur. In order to reduce the force of peeling the release film in the region 300, the angle θ is preferably 25 ° or more and 65 ° or less. The peeling angle may be set to 90 to 180 degrees, and the peeling speed may be set to 0.1 to 10m/min.

[ example ] A

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

(1) Method for measuring film thickness

The measurement was carried out using MH-15M as a digital micrometer manufactured by Nikon corporation.

(2) Method for measuring adhesive force

The adhesion force between the release film and the pressure-sensitive adhesive layer of the polarizing plate was measured by using an Autograph (registered trademark) AGS-X as a bench-top precision universal tester manufactured by shimadzu corporation.

(3) Peeling force of release film

The laminate produced in each example was fixed to a glass plate (holding stage) so that the surface protective film was positioned on the lower side. The pressure-sensitive adhesive sheet is used for fixation, and the force (adhesive force) for fixation is 0.1 to 0.3N/60mm. As shown in fig. 5, the adhesive tape is bonded to the corner portion of one end of the edge having the notch portion such that the longitudinal direction of the adhesive tape is parallel to the longitudinal direction of the laminate. The tape was a polyester adhesive tape No.315 manufactured by Nindon electric corporation, and the width was 12mm and the length of the bonded portion was 10mm. One end of the tape was held with a chuck to peel off the release film. The angle (angle θ in fig. 5) formed by the peeling direction of the tape and the edge side orthogonal to the edge side having the notch portion was set to 45 °. The peeling speed was set to 3 m/min, and the peeling angle was set to 180 °. The peel force during peeling of the release film was measured to determine the maximum value of the peel force.

(4) Method for evaluating peelability of release film

The laminate produced in each example was fixed to a glass plate (holding stage) so that the surface protective film was positioned on the lower side. The pressure-sensitive adhesive sheet is used for fixation, and the force (adhesive force) for fixation is 0.1 to 0.3N/60mm. As shown in fig. 5, the adhesive tape is bonded to the corner portion of one end of the edge having the notch portion so that the longitudinal direction of the adhesive tape is parallel to the longitudinal direction of the laminate. The tape was a polyester adhesive tape No.315 manufactured by Nindon electric corporation, and the width was 12mm and the length of the bonded portion was 10mm. One end of the tape was held with a chuck to peel off the release film. The angle (angle θ in fig. 5) formed by the peeling direction of the tape and the edge side orthogonal to the edge side having the notch portion was set to 45 °. The peeling speed was 3 m/min, and the peeling angle was 180 °. At this time, the case where the layer including the polarizing plate and the surface protective film was lifted from the glass to which the laminate was fixed was judged as peeling failure (NG), and the case where the peeling film could be peeled without lifting was judged as peeling failure (OK).

[ production of laminate ]

A polarizing plate (8 μm thick) was produced in which iodine was adsorbed and oriented in a polyvinyl alcohol resin.

A hard coat layer-formed cyclic olefin resin (COP) film (thickness 25 μm) was bonded to one surface of the polarizer with an ultraviolet-curable adhesive interposed therebetween, and a triacetyl cellulose (TAC) film (thickness 20 μm) was bonded to the other surface of the polarizer with the same adhesive interposed therebetween.

Then, a retardation film including a layer obtained by curing the polymerizable liquid crystal compound is prepared. The retardation film had a layer structure in which a lambda/4 plate (thickness 2 μm) and a positive C plate (thickness 3 μm) were laminated with an ultraviolet-curable adhesive (thickness 2 μm) interposed therebetween. The phase difference film and the TAC film were bonded to each other with an adhesive layer (thickness 5 μm) interposed therebetween so that the λ/4 plate and the TAC film were bonded to each other.

On the positive C plate, an acrylic pressure-sensitive adhesive layer (thickness 25 μm) formed on a release film was laminated. On the COP film, a surface protection film formed of a base film containing a polyester resin and an acrylic pressure-sensitive adhesive layer is laminated.

The obtained film was cut into a rectangle having a long side of 150mm and a short side of 70 mm. The long side direction is parallel to the absorption axis of the polarizer. The laminate has a layer structure of a release film/an adhesive layer/a phase difference layer (including 2 layers of a liquid crystal compound cured layer)/a TAC film/a polarizing plate/a COP film with a hard coat layer/a surface protective film. The thickness of the polarizing plate was 80 μm, the thickness of the release film was 38 μm, and the thickness of the surface protective film was 53 μm.

The adhesive force between the adhesive layer and the release film was 0.02N/25mm, and no peeling was observed between the adhesive layer and the release film due to conveyance or the like.

[ example 1]

And (3) carrying out slotting machining on one short edge of the laminated body by using an end milling cutter. The notch portion has a shape in which the depth d is 2mm and the radius of curvature r of 2 inner corners is 2mm. The shape of the notch is as shown in fig. 4 (d) when viewed from above.

Examples 2 to 15 and comparative examples 1 to 11

Grooving was performed on the laminate in the same manner as in example 1, except that the shape of the notch portion was set to the shape shown in table 1.

Comparative example 12

A notch portion is formed by cutting one short side of the laminate with a knife. The 2 inner corners were not subjected to R processing, but the 2 inner corners were each set at right angles.

The maximum value of the peeling force was measured for the laminates produced in examples 1 to 15 and comparative examples 1 to 11, and the peelability was evaluated. The results are shown in table 1. As shown in table 1, the laminates of examples 1 to 15 were able to satisfactorily peel the release film. In any of the examples, no peeling failure occurred between the polarizing plate and the surface protective film. The laminates of comparative examples 1 to 12 could not easily peel the release film. The maximum value of the peel force of comparative example 12 was more than 1.0N. In any laminate, the maximum value of the peeling force was recorded when the peeling front end approached the region 300 shown in fig. 5. That is, the maximum value of the peeling force is recorded when the peeling front end approaches the corner portion on the inner side of the position far from the position where the tape is attached, which is the corner portion on the inner side of the notch portion.

[ TABLE 1]

Industrial applicability

The present invention is useful for providing a laminate in which peeling failure of a peeling film does not occur.

Claims (3)

1. A laminate comprising a polarizing plate and a surface protective film laminated on one surface of the polarizing plate and a release film laminated on the other surface of the polarizing plate, wherein the polarizing plate comprises a polarizing plate,

the polarizing plate is provided with an adhesive layer on the surface on the side of the release film,

the adhesion force between the release film and the pressure-sensitive adhesive layer is 0.02N/25mm or more and 0.10N/25mm or less,

the laminate has a notch portion in a plan view,

when d is the depth of the notch and r is the curvature radius of the corner inside the notch,

d is 2mm to 20mm inclusive,

when d is 2mm or more and 5mm or less, r is 2mm or more,

when d is more than 5mm and not more than 6mm, r is not less than 8mm,

when d is more than 6mm and less than 8mm, r is 13mm or more,

when d is 8mm or more, r is 17mm or more,

wherein the units of d and r are mm,

a maximum value of the peeling force is 1.0N or less when the peeling film is peeled from the edge having the notch portion,

the maximum value of the peel force was determined as follows: the laminate was fixed to a glass plate as a holding table with the surface protective film on the lower side, a polyester adhesive tape having a width of 12mm was attached to a corner portion of one end of the edge having the notch portion so that the longitudinal direction of the polyester adhesive tape was parallel to the edge of the laminate orthogonal to the edge having the notch portion and the length of the attached portion became 10mm, one end of the polyester adhesive tape was held with a chuck, and the release film was peeled, wherein the angle formed by the peeling direction of the polyester adhesive tape and the orthogonal edge was 45 °, the peeling speed was 3 m/min, the peeling angle was 180 °, and the peeling force during the peeling of the release film was measured to determine the maximum value of the peeling force.

2. The laminate according to claim 1, wherein,

the shape of the notch portion satisfies the following formula (1):

r＞3d-14 (1)

in the formula (1), d represents the depth of the notch, r represents the curvature radius of the corner inside the notch,

wherein d and r are in mm.

3. A method for manufacturing a polarizing plate with a surface protective film, comprising:

a joining step of joining an adhesive tape to a corner portion of one end of the edge having the notch portion of the laminate according to claim 1 or 2; and

a peeling step of pulling up the tape to peel the release film from the laminate,

in the peeling step, an angle formed by the peeling direction of the adhesive tape and an edge side orthogonal to the edge side having the notch portion is 25 ° or more and 65 ° or less.

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