Surface protective film and optical laminate

Abstract

To provide a surface protection film that prevents deformation of the edges of the adherend, and an optical laminate equipped with such a surface protection film. [Solution] The protective film according to an embodiment of the present invention comprises a base film and an adhesive layer, and has a peel force of 0.025 N / 25 mm or more for an adherend with a water contact angle of 70° or more and less than 90°, and an in-plane tensile shear force of 5.0 N or more for the adherend: where the in-plane tensile shear force for the adherend is the breaking force measured in accordance with JIS K 6850:1999.

Description

Technical Field

[0001] The present invention relates to a surface protection film and an optical laminate.

Background Art

[0002] As a surface treatment layer of a polarizing plate, a fluorine-based material is used (for example, see Patent Document 1). In recent years, from the perspective of environmental impact and the like, there has been an increasing demand to switch from fluorine-based materials to non-fluorine-based materials. Under such demands, switching from fluorine-based materials to non-fluorine-based materials has been studied. However, when the roll of the polarizing plate is punched into a chip shape in a state where the surface protection film protecting the surface treatment layer is laminated, deformation may occur at the end of the polarizing plate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made to solve the above problems, and its main object is to provide a surface protection film in which deformation does not occur at the end of the adherend, and an optical laminate provided with such a surface protection film.

Means for Solving the Problems

[0005] [1] The protective film according to an embodiment of the present invention comprises a base film and an adhesive layer, and has a peel force of 0.025 N / 25 mm or more on an adherend with a water contact angle of 70° or more and less than 90°, and an in-plane tensile shear force of 5.0 N or more on the adherend: where the in-plane tensile shear force on the adherend is the breaking force measured in accordance with JIS K 6850:1999. [2] An optical laminate according to an embodiment of the present invention comprises a polarizing plate and a surface protective film described in item [1] above which is peelably attached to the polarizing plate, wherein the polarizing plate comprises a polarizer, a protective layer disposed on one side of the polarizer, and a surface treatment layer formed on one side of the protective layer, the water contact angle of the surface treatment layer is 70° or more and less than 90°, and the adhesive layer of the surface protective film is bonded to the surface treatment layer. [3] One embodiment is the optical laminate described in item [2] above, wherein the surface treatment layer substantially does not contain a fluorine-based material. [4] One embodiment is the optical laminate according to item [2] or [3] above, further comprising a phase difference layer on the other side of the polarizer. [Effects of the Invention]

[0006] According to embodiments of the present invention, a surface protective film can be realized that prevents deformation of the edges of the polarizing plate. Furthermore, according to embodiments of the present invention, an optical laminate can be realized that prevents deformation of the edges of the polarizing plate. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a schematic cross-sectional view of a surface protective film according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. [Modes for carrying out the invention]

[0008] The embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. In addition, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the embodiments in order to make the explanation clearer, but these are merely examples and do not limit the interpretation of the present invention.

[0009] A. Overview of surface protection film The surface protection film according to an embodiment of the present invention comprises a base film and an adhesive layer, and has a peel force of 0.025 N / 25 mm or more for an adherend with a water contact angle of 70° or more and less than 90°, and an in-plane tensile shear force of 5.0 N or more for the adherend. With such a configuration, the adhesion between the surface protection film and the adherend (e.g., a polarizing plate) can be improved, and deformation of the adhesive layer can be suppressed. As a result, a surface protection film that can suppress deformation of the edges of the adherend can be realized. The inventors of the present invention have found that when a fluorine-based material contained in the adherend is changed to a non-fluorine-based material, the wettability of the adherend decreases, that is, the water contact angle increases, which weakens the adhesion between the adherend and the surface protective film, resulting in deformation of the edges of the adherend. The inventors further investigated this problem and, focusing on the adhesive layer of the surface protective film, found that by setting the peel force and tensile shear force of the surface protective film to above a certain value, the adhesion between the adherend and the surface protective film can be improved, and deformation of the adhesive layer can be suppressed, thus completing the present invention.

[0010] In one embodiment, the adhesive layer comprises an acrylic adhesive, the acrylic adhesive comprises a (meth)acrylic polymer, and the (meth)acrylic polymer comprises 0.1% to 5.0% by weight of a polyoxyalkylene compound having radical polymerizable groups relative to the total weight of the monomer components. With such a configuration, the peel strength and tensile shear strength of the protective film can be improved.

[0011] B. Details of the surface protection film The surface protection film according to an embodiment of the present invention is a film for protecting the surface of an object by being applied to the surface of that object. Figure 1 is a schematic cross-sectional view of a surface protective film according to one embodiment of the present invention. The illustrated example surface protection film 2 comprises a base film 10 and an adhesive layer 20 on one side of the base film.

[0012] The base film 10 is composed of any suitable resin film that can be used as a surface protective film. Examples of constituent materials for the base film include ester resins such as polyethylene terephthalate (PET) resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Preferably, the constituent material of the base film is an ester resin (for example, polyethylene terephthalate resin). The base film may contain antioxidants, ultraviolet absorbers, light stabilizers, nucleating agents, fillers, pigments, surfactants, antistatic agents, etc. A treatment layer (such as an easy-adhesion layer, an easy-slip layer, an anti-blocking layer, an antistatic layer, an anti-reflective layer, an oligomer-preventing layer, etc.) (not shown) may be provided on the other side of the base film 10 (the side opposite to the side on which the adhesive layer 20 is provided). The thickness of the base film 10 is, for example, 10 μm to 150 μm, preferably 20 μm to 100 μm, and more preferably 25 μm to 50 μm. If a treatment layer is provided, the thickness of the base film includes the thickness of the treatment layer.

[0013] The adhesive layer 20 is provided on one side of the base film 10 in order to bond the surface protective film 2 to the object to be protected. The adhesive layer 20 typically contains an acrylic adhesive (acrylic adhesive composition). Acrylic adhesives typically contain (meth)acrylic polymers. (Meth)acrylic polymers are obtained by (co)polymerizing predetermined monomer components. (Meta)acrylic polymers typically contain, as monomer components, an alkyl (meth)acrylate and a polyoxyalkylene compound having a radically polymerizable group. Here, (meth)acrylate refers to acrylate and / or methacrylate.

[0014] Examples of the alkyl (meth)acrylate include alkyl (meth)acrylates having a linear or branched alkyl group with 1 to 24 carbon atoms. The alkyl (meth)acrylate may be used alone or in combination of two or more. Examples of the alkyl group of the alkyl (meth)acrylate include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, pentyl group, hexyl group, cyclohexyl group, heptyl group, 2-ethylhexyl group, isooctyl group, nonyl group, decyl group, isodecyl group, dodecyl group, isomyristyl group, lauryl group, tridecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group. The alkyl group of the alkyl (meth)acrylate is preferably a 2-ethylhexyl group. These can be used alone or in combination. The average carbon number of the alkyl group is preferably 3 to 10, more preferably 6 to 9. The content ratio of the alkyl (meth)acrylate in the (meth)acrylic polymer is, for example, 70.0% to 98.9% by weight, preferably 90.0% to 97.8% by weight, more preferably 95.0% to 96.6% by weight based on the total weight of the monomer components.

[0015] The polyoxyalkylene compound having a radically polymerizable group is, for example, a compound having a radically polymerizable group portion and a polyoxyalkylene group portion, and is preferably a polyoxyalkylene alkenyl ether. If the polyoxyalkylene compound having a radically polymerizable group is a polyoxyalkylene alkenyl ether, the adhesion to a substrate substantially free of fluorine-based materials can be improved. The content ratio of the polyoxyalkylene compound having a radical polymerizable group in the (meth)acrylic polymer is, for example, 0.1% by weight to 5.0% by weight, preferably 0.2% by weight to 3.0% by weight, and more preferably 0.4% by weight to 1.0% with respect to the total weight of the monomer components.

[0016] (Meth)acrylic polymers may preferably further contain, as monomer components, monomers having polar functional groups. Examples of the monomers having polar functional groups include hydroxy group-containing monomers and carboxy group-containing monomers. These can be used alone or in combination. Preferably, the monomer having a polar functional group is a hydroxy group-containing monomer.

[0017] Hydroxy group-containing monomers are compounds having a hydroxy group and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of hydroxy group-containing monomers include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. Preferably, the hydroxy group-containing monomers are 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, and more preferably 2-hydroxyethyl (meth)acrylate. Only one kind of hydroxy group-containing monomer may be used, or two or more kinds may be used in combination.

[0018] Carboxyloid monomers are compounds that have a carboxyl group and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of carboxyloid monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Carboxyloid monomers may be used individually or in combination of two or more.

[0019] If the monomer having polar functional groups is such a monomer, the durability of the adhesive layer can be improved.

[0020] The content of monomers having polar functional groups in the (meth)acrylic polymer is, for example, 1% to 10% by weight, preferably 2% to 8% by weight, and more preferably 3% to 6% by weight, based on the total weight of the monomer components. If the content of monomers having polar functional groups in the (meth)acrylic polymer is below this upper limit, the peel strength of the adhesive layer can be improved, and if the content of monomers having polar functional groups in the (meth)acrylic polymer is above this lower limit, the tensile shear strength of the adhesive layer can be improved.

[0021] The (meth)acrylic polymer may further contain, if necessary, monomers copolymerizable with other monomer components (hereinafter sometimes referred to as copolymer monomers) as monomer components. Examples of copolymer monomers include vinyl esters such as vinyl acetate and vinyl propionate. These can be used alone or in combination.

[0022] (Meth)acrylic polymers may contain polymerization initiators. Any suitable polymerization initiator may be used. Examples of polymerization initiators include azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidine)disulfate, and 2,2'-azobis(N,N'-dimethyleneisobutylamidine); potassium persulfate, and ammonium persulfate. Examples of polymerization initiators include persulfates such as benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide; and redox polymerization initiators formed by combinations of peroxides and reducing agents, such as combinations of peroxide and ascorbic acid (e.g., hydrogen peroxide solution and ascorbic acid), combinations of peroxide and iron(II) salts (e.g., hydrogen peroxide solution and iron(II) salts), and combinations of persulfate and sodium bisulfite. Preferably, the polymerization initiator is an azo polymerization initiator, and more preferably 2,2'-azobisisobutyronitrile (AIBN). The polymerization initiator may be used alone or in combination of two or more. The polymerization initiator can be used in any appropriate amount depending on the type of polymerization initiator used and the composition of the monomer components used. The content ratio of the polymerization initiator is, for example, 0.01 parts by weight to 1.0 part by weight, preferably 0.02 parts by weight to 0.5 parts by weight, per 100 parts by weight of the monomer components.

[0023] The weight-average molecular weight Mw of the (meth)acrylic polymer is, for example, 50,000 to 2,000,000, and preferably 200,000 to 1,000,000.

[0024] The above acrylic adhesive contains, for example, 70% or more by weight, preferably 90% or more by weight, of a (meth)acrylic polymer.

[0025] Acrylic adhesives may contain crosslinking agents. The crosslinking agent is typically included in the resulting adhesive layer in the form after the crosslinking reaction. Any suitable crosslinking agent can be used. Examples of crosslinking agents include isocyanate crosslinking agents (e.g., isocyanurate crosslinking agents), epoxy crosslinking agents, silicone crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, silane crosslinking agents, alkyl etherified melamine crosslinking agents, metal chelate crosslinking agents, peroxides, and polyfunctional monomers. Preferably, the crosslinking agent is an isocyanate crosslinking agent. These can be used alone or in combination. By including such crosslinking agents, the tensile shear strength of the surface protective film comprising the adhesive layer can be improved. The crosslinking agent content is, for example, 0.1 to 10 parts by weight, preferably 1 to 8 parts by weight, per 100 parts by weight of (meth)acrylic polymer.

[0026] (Meth)acrylic adhesives may contain a silane coupling agent in an appropriate proportion. Acrylic adhesives may contain any suitable additives. Examples of additives include leveling agents, crosslinking catalysts, crosslinking aids, tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, conductive materials, antistatic agents, UV absorbers, light stabilizers, release modifiers, softeners, surfactants, flame retardants, and antioxidants. Preferably, the additive is an antistatic agent. If an antistatic agent is included in the acrylic adhesive, the antistatic properties of the acrylic adhesive when peeling the release liner from the acrylic adhesive can be improved. The additive content is, for example, 0.01 to 1.00 parts by weight, preferably 0.02 to 0.50 parts by weight, per 100 parts by weight of (meth)acrylic polymer.

[0027] Any suitable method can be used to produce the acrylic adhesive. For example, one method for producing the acrylic adhesive is to dissolve or disperse the above-mentioned monomer component and, if necessary, the above-mentioned polymerization initiator in a solvent and polymerize them to obtain an acrylic adhesive containing a (meth)acrylic polymer.

[0028] Any suitable solvent can be used. Examples of solvents include alcohols such as methanol, ethanol, isopropyl alcohol, butanol, TBA (tert-butyl alcohol), and 2-methoxyethanol; ketones such as acetone, methyl ethyl ketone, MIBK (methyl isobutyl ketone), and cyclopentanone; esters such as methyl acetate, ethyl acetate, butyl acetate, and PMA (propylene glycol monomethyl ether acetate); ethers such as diisopropyl ether and propylene glycol monomethyl ether; glycols such as ethylene glycol and propylene glycol; cellosolves such as ethyl cellosolve and butyl cellosolve; aliphatic hydrocarbons such as hexane, heptane, and octane; and aromatic hydrocarbons such as benzene, toluene, and xylene. These solvents may be used individually or in combination of two or more. Preferably, the solvent is an ester, and more preferably ethyl acetate. Any suitable polymerization method can be employed. For example, radical solution polymerization is one such polymerization method. The polymerization temperature is, for example, 50°C to 80°C, preferably 60°C to 70°C. The polymerization time is, for example, 1 hour to 18 hours, preferably 3 hours to 9 hours.

[0029] The thickness of the adhesive layer 20 is, for example, 1 μm to 50 μm, preferably 5 μm to 30 μm, and more preferably 5 μm to 25 μm.

[0030] Such an adhesive layer may be formed directly on the surface of the base film or by transfer. When formed directly, an acrylic adhesive is applied directly to the surface of the base film to form the adhesive layer. When formed by transfer, an acrylic adhesive is applied to the surface of a release liner to form the adhesive layer, and then the base film is attached to the adhesive layer.

[0031] Any suitable method can be used to form the adhesive layer. For example, one method for forming the adhesive layer is to include the crosslinking agent in the acrylic adhesive, apply the acrylic adhesive to a base film, and then dry and crosslink it to form the adhesive layer. Any suitable drying and crosslinking method can be employed. The drying (crosslinking) temperature is, for example, 100°C to 150°C, preferably 110°C to 140°C. The drying (crosslinking) time is, for example, 1 minute to 30 minutes, preferably 2 minutes to 10 minutes.

[0032] The peel force of the surface protective film against the substrate is typically 0.0250 N / 25 mm or more, preferably 0.0260 N / 25 mm or more, and more preferably 0.0270 N / 25 mm or more. If the peel force of the surface protective film against the substrate is above this lower limit, lifting and peeling of the surface protective film from the substrate can be suppressed. The peel force of the surface protective film against the substrate is, for example, 0.09 N / 25 mm or less, and 0.08 N / 25 mm or less. If the peel force of the surface protective film against the substrate is below this upper limit, the peelability when peeling the surface protective film after lamination of the optical laminate to the panel can be improved. The peel force of the surface protective film against the substrate is measured by attaching the surface protective film to the substrate, cutting a sample to a size of 50 mm wide and 100 mm long, and peeling it in the length direction at a peeling speed of 300 mm / min and a peeling angle of 180° in an environment of 23°C and 50% RH.

[0033] The in-plane tensile shear force of the surface protective film against the adherend is typically 5.0 N or more, preferably 5.7 N or more, more preferably 6.0 N or more, and even more preferably 7.0 N or more. If the in-plane tensile shear force of the surface protective film against the adherend is above this lower limit, deformation of the adherend can be suppressed. The in-plane tensile shear force of the surface protective film against the adherend is, for example, 20 N or less, preferably 15 N or less. If the in-plane tensile shear force of the surface protective film against the adherend is within this range, deformation of the adhesive layer against external forces can be suppressed while maintaining a constant adhesive force. The method for measuring the in-plane tensile shear force of the surface protective film against the adherend is the method for measuring breaking force in accordance with JIS K 6850:1999.

[0034] C. Substrate (polarizing plate) and optical laminate A typical example of a substrate to which the coating is applied is a polarizing plate. The following describes polarizing plates, which are typical examples of substrates, and optical laminates equipped with polarizing plates. Figure 2 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 1 comprises the surface protective film 2 described in sections A and B above, and a polarizing plate 3. The polarizing plate 3 comprises a polarizer 30, a protective layer 40 disposed on one side of the polarizer, and a surface treatment layer 50 formed on one side of the protective layer. A protective layer (not shown) may be further provided on the other side of the polarizer. Polarizing plates are typically long and can be wound into a roll. Here, "long" refers to an elongated shape in which the length is sufficiently longer than the width, for example, an elongated shape in which the length is 10 times or more, preferably 20 times or more, than the width. In one embodiment of the present invention, an optical laminate 1 is peelably bonded (temporarily attached) to the surface treatment layer 50 of the polarizing plate 3 by a surface protective film 2 (the adhesive layer 20 of the surface protective film 2). The surface protective film may be removed before the polarizing plate is put into use (for example, before it is laminated onto the image display panel body), or during the manufacturing process of the final product (image display device), or it may be mounted on the final product as is.

[0035] The polarizer 30 and the protective layer 40 can be laminated, for example, via any suitable adhesive layer. Specific examples of adhesive layers include adhesive layers and tack layers. For example, the polarizer 30 and the protective layer 40 are bonded together via an adhesive layer. Specifically, the polarizer 30 and the protective layer 40 are bonded together using an active energy ray curable adhesive. The thickness of the active energy ray curable adhesive after curing (thickness of the adhesive layer) is, for example, 0.2 μm to 3.0 μm, preferably 0.4 μm to 2.0 μm, and more preferably 0.6 μm to 1.5 μm.

[0036] Any suitable polarizer can be used as the polarizer 30. For example, the resin film forming the polarizer may be a single-layer resin film or may be obtained using a laminate of two or more layers. In one embodiment, the polarizer 30 is preferably obtained using a laminate of two or more layers. Specific examples of polarizers obtained using laminates of two or more layers, and details of methods for manufacturing polarizers, are described, for example, in Japanese Patent Application Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of these publications are incorporated herein by reference.

[0037] The protective layer 40 may be formed from any suitable film that can be used as a protective layer for the polarizer. Specific examples of materials that make up the main component of the film include cellulose-based resins such as cellulose triacetate (TAC), polyester-based resins, polyvinyl alcohol-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyethersulfone-based resins, polysulfone-based resins, polystyrene-based resins, cycloolefin-based resins such as polynorbornene, polyolefin-based resins, (meth)acrylic-based resins, acetate-based resins, and other resins.

[0038] The thickness of the protective layer 40 is, for example, 5 μm to 80 μm, preferably 10 μm to 60 μm, and more preferably 15 μm to 50 μm.

[0039] The surface treatment layer 50 is, for example, a surface treatment layer such as a hard coat (HC) treatment, anti-reflective treatment, anti-sticking treatment, anti-glare treatment, or anti-fouling treatment. Preferably, the surface treatment layer is a hard coat treatment. The surface treatment layer may contain antioxidants, UV absorbers, light stabilizers, nucleating agents, fillers, pigments, surfactants, antistatic agents, etc. Preferably, the surface treatment layer is substantially free of fluorine-based materials. "Substantially free of fluorine-based materials" means that fluorine-based materials are not intentionally or actively introduced into the surface treatment layer. Specifically, the surface treatment layer contains, for example, 0.1% by weight or less of fluorine-based materials, preferably 0.01% by weight or less, and more preferably 0% by weight. By substantially free of fluorine-based materials in the surface treatment layer, the environmental impact of products equipped with this surface treatment layer can be reduced. When a fluorine-based material is included in a surface treatment layer, it is typically included in the surface treatment layer as, for example, a fluorine-based leveling agent. However, in embodiments of the present invention, a fluorine-based material, such as a fluorine-based leveling agent, is not intentionally or actively introduced into the surface treatment layer. The surface treatment layer more preferably contains a non-fluorine-based material, and even more preferably contains a silicon-based material (e.g., a silicone-based material). Examples of silicone-based materials include silicone-based leveling agents. Examples of silicone-based leveling agents include GRANDIC PC4100 (manufactured by DIC Corporation).

[0040] The thickness of the surface treatment layer 50 is, for example, 1 μm to 20 μm, preferably 2 μm to 15 μm, and more preferably 3 μm to 10 μm.

[0041] The water contact angle of the surface of the surface treatment layer 50 (adherend) is typically 70° or more and less than 90°, preferably 71° or more and 80° or less, and more preferably 72° or more and 75° or less. The water contact angle of the surface of the surface treatment layer (adherend) is measured using a contact angle meter by the liquid contact method in an environment of 23°C and 50%RH.

[0042] D. Retardation layer The illustrated optical laminate 1 may optionally further include a phase difference layer 60 on the other side of the polarizer 30. The optical properties of the phase difference layer 60 (e.g., refractive index properties, in-plane phase difference (Re), phase difference in the thickness direction (Rth), Nz coefficient) can be appropriately set according to the purpose and application. [Examples]

[0043] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement and evaluation methods for each characteristic are as follows. Unless otherwise specified, "parts" and "%" in the examples and comparative examples are based on weight.

[0044] (1) Peeling force After applying the surface protection film to the surface treatment layer, samples cut to a size of 50 mm wide and 100 mm long were tested using a universal tensile testing machine (Shimadzu Corporation, product name "AUTOGRAPH AG-X plus") at a peeling speed of 300 mm / min and a peeling angle of 180°. The peeling force (unit: N / 25 mm) was measured in the longitudinal direction. Specifically, the peeling force of the surface protection film to the surface treatment layer of the optical laminate was measured. The measurements were performed under conditions of 23°C and 50% RH.

[0045] (2) Tensile shear force The breaking force measured in accordance with JIS K 6850:1999 was defined as the tensile shear force.

[0046] (3) Water contact angle Under conditions of 23°C and 50% RH, the water contact angle of the surface of the surface-treated layer (surface-treated layer of the adherend) obtained in the manufacturing example was measured using the liquid contact method with a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DMo-501", control box "DMC-2", control and analysis software "FAMAS (version 5.0.30)"). The amount of distilled water dropped was 2 μL, and the contact angle was calculated from the image 5 seconds after dropping using the θ / 2 method.

[0047] (4) Measurement of thickness Thicknesses of 10 μm or less were measured using an interferometer (Otsuka Electronics Co., Ltd., product name "MCPD-3000"). Thicknesses exceeding 10 μm were measured using a digital micrometer (Anritsu Corporation, product name "KC-351C").

[0048] (5) Method for evaluating end deformation The release liners were peeled off the surface protection films with release liners obtained in the examples and comparative examples, and samples were prepared by bonding the adhesive layer of the surface protection film to the surface treatment layer obtained in the manufacturing example. Reflectance tests were performed visually on these samples by shining LED light (product name "Z-208", manufactured by Yamada Lighting Co., Ltd.) at a distance that resulted in an illuminance of 1000 lux in a darkroom at 23°C and 55% RH, and evaluated according to the following evaluation criteria. If edge deformation occurs, a boundary line will appear within 10 mm from the outer edge of the sample, separating the undeformed area from the deformed area. The presence or absence of this boundary line can be used to determine the presence or absence of edge deformation, and thus evaluate the edge deformation. "○": No boundary line was detected in the reflection test. "×": The boundary line was confirmed by reflection testing.

[0049] <Manufacturing Example 1> [Preparation of Acrylic Polymer A] In a reaction vessel equipped with a thermometer, stirrer, condenser, and nitrogen gas inlet tube, 99.5 parts by weight (95.67% by weight) of 2-ethylhexyl acrylate (2-EHA), 4 parts by weight (3.85% by weight) of hydroxyethyl acrylate (HEA), 0.5 parts by weight (0.48% by weight) of polyoxyalkylene alkenyl ether (trade name "Ramtel PD-420", manufactured by Kao Corporation), and 0.2 parts by weight (0.19 parts by weight per 100 parts by weight of monomer component) of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator were charged together with 150 parts by weight of ethyl acetate. The mixture was then gently stirred at 23°C and nitrogen gas was introduced to purge the mixture with nitrogen. Subsequently, the polymerization reaction was carried out for 6 hours while maintaining the liquid temperature at around 65°C to obtain a solution of acrylic polymer A (solid content concentration 40% by weight).

[0050] <Manufacturing Example 2> [Preparation of Acrylic Polymer B] In a reaction vessel equipped with a thermometer, stirrer, condenser, and nitrogen gas inlet tube, 100 parts by weight (96.15% by weight) of 2-ethylhexyl acrylate (2-EHA), 4 parts by weight (3.85% by weight) of hydroxyethyl acrylate (HEA), and 0.2 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator (0.19 parts by weight per 100 parts by weight of monomer component) were charged together with 150 parts by weight of ethyl acetate. Nitrogen gas was introduced and the mixture was purged with nitrogen while gently stirring at 23°C. Subsequently, the polymerization reaction was carried out for 6 hours while maintaining the liquid temperature at around 65°C to obtain a solution of acrylic polymer B (solid content concentration 40% by weight).

[0051] <Manufacturing Example 3> [Preparation of surface treatment layer A] A resin solution (DIC Corporation, product name "UNIDIC 17-806", solids content 80%) in which UV-curable resin monomers and oligomers mainly composed of urethane acrylate were dissolved in butyl acetate was prepared. Five parts of a photopolymerization initiator (BASF Corporation, product name "IRGACURE 906") and 0.006 parts of a silicone-based material (DIC Corporation, product name "GRANDIC PC4100") were added per 100 parts of solids in the solution. Cyclopentanone and propylene glycol monomethyl ether were added to the above mixture in a ratio of 45:55 to achieve a solids content of 36%. A hard coat layer forming material was thus prepared. This hard coat layer forming material was applied to a transparent plastic film substrate (cellulose triacetate film, manufactured by Konica Minolta Advanced Layers, product name "KC4UY", thickness: 40 μm) to form a coating film such that the hard coat thickness after curing was 7.8 μm. Next, it was dried at 90°C for 1 minute, and then exposed to a high-pressure mercury lamp at an integrated light intensity of 300 mJ / cm². 2 The above coating film was cured by irradiating it with ultraviolet light to form a surface treatment layer A (hard coat layer A) on a transparent substrate. The water contact angle measurement results are shown in Table 1.

[0052] <Manufacturing Example 4> [Fabrication of surface treatment layer B] Surface treatment layer B (hard coat layer B) was formed on a transparent substrate in the same manner as in Manufacturing Example 3, except that 0.001 parts of a fluorine-based material (DIC Corporation, product name "Megafac F-556") was added instead of a silicone-based material as a leveling agent. The results of the water contact angle measurement are shown in Table 1.

[0053] <Example 1> [Preparation of acrylic adhesive composition A] The solution of acrylic polymer A obtained in Production Example 1 was diluted to a solid content concentration of 20% by weight by adding ethyl acetate. To 500 parts by weight (100 parts by weight of solids) of this diluted solution, 0.35 parts by weight of an ionic liquid (trade name "CIL-312", manufactured by Nippon Carlit Co., Ltd.) was added as an antistatic agent, 5 parts by weight of isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation) was added as a crosslinking agent, and 6 parts by weight (0.03 parts by weight of solids) of a 0.5% ethyl acetate solution of dioctyl suzuraurate (trade name "Envirizer OL-1", manufactured by Tokyo Fine Chemical Co., Ltd.) was added as a crosslinking catalyst, and the mixture was stirred to prepare acrylic adhesive composition A. [Preparation of surface protective film A] An acrylic adhesive composition A obtained above was applied to a base film made of polyester resin (product name "T100-C38", thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation), and heated at 130°C for 2 minutes to form an adhesive layer A with a thickness of 15 μm. The release-treated side of a release liner (a 25 μm thick polyester film with one side treated with silicone release treatment) was laminated to the surface of adhesive layer A to produce a surface protective film A with a release liner.

[0054] <Comparative Example 1> [Preparation of acrylic adhesive composition B] The solution of acrylic polymer B obtained in Production Example 2 was diluted to a solid content concentration of 20% by weight by adding ethyl acetate. To 500 parts by weight of this diluted solution (100 parts by weight of solids), 2.5 parts by weight (0.25 parts by weight of solids) of an ethyl acetate solution of a polyether compound (trade name "Aqualon KH-10", manufactured by Daiichi Kogyo Seiyaku Co., Ltd., diluted 10 times) was added, 5 parts by weight of isocyanurate of hexamethylene diisocyanate (trade name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent, and 6 parts by weight (0.03 parts by weight of solids) of a 0.5% ethyl acetate solution of dioctyl suzuraurate (trade name "Envirizer OL-1", manufactured by Tokyo Fine Chemical Co., Ltd.) was added as a crosslinking catalyst, and the mixture was stirred to prepare acrylic adhesive composition B. [Preparation of surface protective film B] An acrylic adhesive composition B obtained above was applied to a base film made of polyester resin (product name "T100-C38", thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation), and heated at 130°C for 2 minutes to form an adhesive layer B with a thickness of 15 μm. The release-treated side of a release liner (a 25 μm thick polyester film with one side treated with silicone release treatment) was laminated to the surface of adhesive layer B to produce a surface protective film B with a release liner.

[0055] <Performance evaluation of the fabricated surface protection film> The release liners were peeled off the surface protection films with release liners obtained in the examples and comparative examples, and samples were prepared by bonding the adhesive layer of each surface protection film to the surface treatment layer A obtained in Manufacturing Example 3. The peel force and tensile shear force of these samples were measured. Subsequently, the samples were punched into chip shapes using a cutting tool, and the edge deformation of the punched samples was evaluated by visual reflection testing. As a reference example, the surface protection film B obtained in Comparative Example 1 and the surface treatment layer B containing a fluorine-based material obtained in Manufacturing Example 4 were bonded together, and the peel force and tensile shear force were measured, and the edge deformation was evaluated in the same manner as above. The measurement and evaluation results are shown in Table 1.

[0056] [Table 1]

[0057] [evaluation] As is clear from Table 1, edge deformation occurred when the surface protection film of Comparative Example 1 was used, whereas no edge deformation occurred when the surface protection film of Example 1 was used. Therefore, it can be seen that if a surface protection film has a peel force of 0.025 N / 25 mm or more on the surface treatment layer and a tensile shear force of 5.0 N or more in the in-plane direction, edge deformation of the surface treatment layer can be suppressed. Furthermore, in the case of the surface treatment layer containing the fluorine-based material of the Reference Example, edge deformation of the surface treatment layer did not occur even when the surface protection film of Comparative Example 1 was used, indicating that the problem of the present application does not arise when the surface treatment layer contains a fluorine-based material. [Industrial applicability]

[0058] The surface protection film according to the embodiment of the present invention is suitably used to protect the surface of a polarizing plate, and the optical laminate comprising the surface protection film according to the embodiment of the present invention can be suitably used in image display devices such as liquid crystal displays and EL displays. [Explanation of symbols]

[0059] 1 Optical laminate 2. Surface protective film 3. Polarizing plate 10. Base film 20 Adhesive layer 30 polarizers 40 protective layer 50 Surface treatment layer 60 Retardation layer

Claims

1. It comprises a base film and an adhesive layer, The peeling force for an adherend with a water contact angle of 70° or more and less than 90° is 0.025 N / 25 mm or more. The in-plane tensile shear force on the adherend is 5.0 N or more. Surface protective film: Here, the in-plane tensile shear force on the adherend is the fracture force measured in accordance with JIS K 6850:1999.

2. The device comprises a polarizing plate and a surface protective film according to claim 1 that is peelably attached to the polarizing plate, The polarizing plate comprises a polarizer, a protective layer disposed on one side of the polarizer, and a surface treatment layer formed on one side of the protective layer. The water contact angle of the surface treatment layer is 70° or more and less than 90°. The adhesive layer of the surface protective film is bonded to the surface treatment layer. Optical laminate.

3. The optical laminate according to claim 2, wherein the surface treatment layer substantially does not contain a fluorine-based material.

4. The optical laminate according to claim 2 or 3, further comprising a phase difference layer on the other side of the polarizer.

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