adhesive film

Abstract

To provide a self-adhesive film simultaneously realizing excellent easy-detachability and peeling resistance.SOLUTION: A self-adhesive tape includes an adhesive layer (B) disposed at least on one surface of a base material (A) directly or with another layer interposed. The self-adhesive tape being a hard coat film has a 180° peel adhesion force of 0.5 to 4.0 N / 25 mm with a peel rate of 300 mm / min after standing for one hour in an environment at a temperature of 23°C, a relative humidity of 50%RH, a 180° peel adhesion force of 0.5 to 4.0 N / 25 mm with a peel rate of 300 mm / min after standing for 30 mins. in an environment at a temperature of 120°C and a loss tangent (Tanδ120) of 1.0 or less at 120°C and 1 Hz.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive film that can be suitably used for transporting, protecting the surface of, and using optical films, for example. [Background technology]

[0002] Liquid crystal displays (LCDs) installed in electronic devices such as smartphones and tablet computers incorporate optical films such as polarizing plates and retardation plates as part of their construction.

[0003] The optical film undergoes various processing and assembly processes, and during these processes, an adhesive film is usually attached to the optical film to facilitate transportation and prevent scratches, dirt, etc. from adhering to the surface. The adhesive film is used only in the manufacturing process of the liquid crystal display and the manufacturing and processing process of the optical film, and is peeled off and removed from the optical film when the optical film is assembled into the liquid crystal display. Due to the way in which the adhesive film is used, it is also commonly called a protective film or a processing film. Known examples of such adhesive films include surface protection films in which an adhesive containing an acrylic polymer, an antistatic agent, and a crosslinking agent is formed on one or both sides of a resin film (see, for example, Patent Document 1). In recent years, the processing steps have sometimes included a heating step in which the optical film is heated to a high temperature of approximately 100°C to 150°C, and there is a need for an adhesive film that can reliably transport and protect the optical film even during the heating step.

[0004] However, conventional adhesive films often have insufficient adhesive strength initially and at high temperatures. For example, when transported roll-to-roll, the optical film can peel off from the adhesive film during the heating process due to stresses generated during processing and passing through support rolls, causing problems in subsequent processes. Furthermore, when the optical film is peeled off from the adhesive film after the heating step, the adhesive may remain on the surface of the optical film, contaminating the optical film. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-216738 A Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a pressure-sensitive adhesive film that combines excellent peelability and peel resistance. [Means for solving the problem]

[0007] The present invention provides a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer (B) on at least one surface of a substrate (A) directly or via another layer, wherein the pressure-sensitive adhesive tape is pressure-bonded to an optical film in an environment of 23°C and 50% RH with a 2 kg roller in one reciprocating motion, and after leaving to stand for 1 hour in an environment of 23°C and 50% RH, the 180° peel adhesion strength is 0.5 to 4.0 N / 25 mm at a peel rate of 300 mm / min, and the loss tangent (Tanδ) at 120°C and 1 Hz ... after leaving to stand for 30 seconds in an environment of 23°C and 50% RH, the loss tangent (Tanδ) at 120°C and 1 Hz is 0.5 to 4.0 N / 25 mm at a peel rate of 300 mm / min. 120 ) is set to 1.0 or less, thereby solving the above problem. [Effects of the Invention]

[0008] The adhesive film of the present invention has excellent peelability and peel resistance, and can therefore be used particularly as a process film and protective film for the purpose of transporting and temporarily protecting optical films such as polarizing plates and retardation films during processing. DETAILED DESCRIPTION OF THE INVENTION

[0009] The pressure-sensitive adhesive film of the present invention is preferably thin from the viewpoint of use as a carrier film or a protective film. Specifically, the pressure-sensitive adhesive film preferably has a total thickness of 100 μm or less, and more preferably 60 μm or less. There is no particular lower limit to the total thickness of the pressure-sensitive adhesive film, but it is preferably 40 μm or more, and more preferably 50 μm or more. The pressure-sensitive adhesive film of the present invention can achieve both excellent peelability and peel resistance by adopting the specific laminate structure.

[0010] [Base material (A)] The substrate (A) constituting the pressure-sensitive adhesive film of the present invention is preferably 12 μm to 250 μm thick, more preferably 25 μm to 100 μm thick, and even more preferably 38 μm to 50 μm thick, in order to achieve both excellent peelability and peel resistance.

[0011] As the substrate (A), it is preferable to use a resin film having excellent optical properties. For example, polyethylene terephthalate film, polybutylene terephthalate film, polyethylene naphthalate film, polyethylene film, polypropylene film, cellophane film, diacetyl cellulose film, triacetyl cellulose film, acetyl cellulose butyrate film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, polyether ether ketone film, polyethersulfone film, polyetherimide film, polyimide film, fluorine resin film, nylon film, acrylic resin film, norbornene-based resin film (e.g., Arton manufactured by JSR Corporation), cyclic olefin-based polymer film (e.g., Zeonor Film manufactured by Zeon Corporation), etc. can be used.

[0012] Among these, it is preferable to use polyethylene terephthalate film, polycarbonate film, polypropylene film, acrylic resin film, triacetyl cellulose film, etc. as the substrate (A), and it is more preferable to use polyethylene terephthalate film, and among these, it is preferable to use polyethylene terephthalate film having a heat shrinkage rate at 120°C of 1.0% or less, more preferably 0.5% or less, and even more preferably 0.1% or less, in order to produce a pressure-sensitive adhesive tape with even better peelability and peel resistance. The heat shrinkage rate of the substrate (A) at 120°C refers to a value measured by the method described in the Examples.

[0013] The substrate (A) may have an easy-adhesion layer on its surface for the purpose of improving adhesion to the pressure-sensitive adhesive layer (B).The substrate (A) may be subjected to a surface roughening treatment such as sandblasting or solvent treatment, or an oxidation treatment such as corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, ozone treatment, or ultraviolet irradiation treatment, for the purpose of further improving the adhesion.

[0014] [Adhesive layer (B)] The pressure-sensitive adhesive layer (B) constituting the protective film of the present invention is preferably 50 μm or less, more preferably in the range of 1 μm to 30 μm, and even more preferably in the range of 5 μm to 15 μm. By providing the pressure-sensitive adhesive layer (B) with the above thickness, a protective film that combines excellent peelability and heat resistance can be obtained.

[0015] The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer (B) may be a pressure-sensitive adhesive composition used in ordinary pressure-sensitive adhesive films. Examples of such pressure-sensitive adhesive compositions include (meth)acrylic pressure-sensitive adhesives, urethane pressure-sensitive adhesives, synthetic rubber pressure-sensitive adhesives, natural rubber pressure-sensitive adhesives, and silicone pressure-sensitive adhesives. However, a (meth)acrylic pressure-sensitive adhesive composition having an acrylic copolymer consisting of a (meth)acrylate alone or a copolymer of a (meth)acrylate and another monomer as a base polymer, to which additives such as a tackifying resin and a crosslinking agent can be added as needed, is preferably used.

[0016] As the acrylic copolymer, an acrylic copolymer having a (meth)acrylate monomer having 1 to 12 carbon atoms as the main monomer component can be preferably used, and examples of the (meth)acrylate having 1 to 12 carbon atoms include monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, cyclohexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, and one or more of these can be used. Among these, (meth)acrylates having an alkyl group with 4 to 12 carbon atoms are preferred, and (meth)acrylates having a linear or branched structure with 4 to 9 carbon atoms are more preferred. Among these, acrylates having a linear or branched structure with 4 to 9 carbon atoms are more preferred.

[0017] The content of the (meth)acrylate having 1 to 12 carbon atoms in the acrylic copolymer is preferably 80 to 98.5 mass %, more preferably 90 to 98.5 mass %, of the monomer components constituting the acrylic copolymer.

[0018] The acrylic copolymer used in the present invention may be copolymerized with a highly polar monomer. Examples of the highly polar monomer include a monomer having a hydroxyl group, a monomer having a carboxyl group, and a monomer having an amide group, and one or more of these may be used.

[0019] Examples of the monomer having a hydroxyl group that can be used include hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate.

[0020] Examples of monomers having a carboxyl group that can be used include acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth)acrylic acid dimer, crotonic acid, and ethylene oxide-modified succinic acid acrylate, and among these, it is preferable to use acrylic acid as a copolymerization component.

[0021] Examples of monomers having an amide group include N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, and N,N-dimethylacrylamide.

[0022] Other highly polar vinyl monomers include vinyl acetate, ethylene oxide-modified succinic acid acrylate, sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropanesulfonic acid, and terminal alkoxy-modified (meth)acrylates such as 2-methoxyethyl (meth)acrylate and 2-phenoxyethyl (meth)acrylate.

[0023] The content of the highly polar vinyl monomer in the monomer components constituting the acrylic copolymer is preferably 0.2 to 15 mass %, more preferably 2 to 10 mass %, and even more preferably 4 to 8 mass %. By containing the highly polar vinyl monomer in this range, it is easy to adjust the cohesive strength, holding power, and adhesiveness of the pressure-sensitive adhesive to suitable ranges.

[0024] For the adhesive layer (B), a (meth)acrylic adhesive can be used, which uses an acrylic copolymer consisting of a copolymer of (meth)acrylate and a hydroxyl group-containing monomer as the base polymer, to which additives such as a tackifying resin and a crosslinking agent can be blended as needed. The acrylic copolymer can be obtained by copolymerization using known polymerization methods such as solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization, etc., but solution polymerization and bulk polymerization are preferred in terms of the water resistance of the adhesive. The polymerization initiation method can be arbitrarily selected from thermal initiation methods using peroxide-based thermal polymerization initiators such as benzoyl peroxide and lauroyl peroxide, or azo-based thermal polymerization initiators such as azobisisobutylnitrile, ultraviolet irradiation initiation methods using acetophenone-based, benzoin ether-based, benzil ketal-based, acylphosphine oxide-based, benzoin-based, and benzophenone-based photopolymerization initiators, and electron beam irradiation methods.

[0025] The molecular weight of the acrylic copolymer is preferably 500,000 or more in terms of standard polystyrene as measured by gel permeation chromatography (GPC), and is preferably 500,000 to 1,500,000 in order to achieve even better peelability and peel resistance.

[0026] Here, the molecular weight measured by the GPC method is a value converted into standard polystyrene using a GPC apparatus (HLC-8329GPC) manufactured by Tosoh Corporation, and the measurement conditions are as follows. Sample concentration: 0.5% by mass (THF solution) Sample injection volume: 100 μL Eluent:THF Flow rate: 1.0mL / min Measurement temperature: 40℃ Main column: TSKgel GMHHR-H(20) x 2 Guard column: TSKgel HXL-H Detector: differential refractometer Standard polystyrene molecular weight: 10,000 to 20 million (Tosoh Corporation)

[0027] The adhesive that can be used in the present invention may contain a tackifier resin in order to obtain an adhesive sheet with even better peel adhesive strength. Examples of the tackifying resin that can be used include rosin-based tackifying resins, polymerized rosin-based tackifying resins, polymerized rosin ester-based tackifying resins, rosin phenol-based tackifying resins, stabilized rosin ester-based tackifying resins, disproportionated rosin ester-based tackifying resins, hydrogenated rosin ester-based tackifying resins, terpene-based tackifying resins, terpene phenol-based tackifying resins, petroleum resin-based tackifying resins, and (meth)acrylate resin-based tackifying resins. In addition, the pressure-sensitive adhesive preferably contains a crosslinking agent in order to form a pressure-sensitive adhesive layer with even better cohesive strength.

[0028] The crosslinking agent may be, for example, an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a metal chelate-based crosslinking agent, an aziridine-based crosslinking agent, etc. Among these, it is preferable to use a crosslinking agent that can be easily mixed with the acrylic copolymer or a solution thereof prepared in advance and that can rapidly promote the crosslinking reaction, and specifically, it is more preferable to use an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent. Examples of the isocyanate crosslinking agent that can be used include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and trimethylolpropane-modified tolylene diisocyanate. It is preferable to use tolylene diisocyanate and trimethylolpropane-modified tolylene diisocyanate.

[0029] The crosslinking agent is preferably used in an amount such that the gel fraction of the pressure-sensitive adhesive layer relative to toluene is 40% by mass to 95% by mass, and more preferably in an amount such that the gel fraction is 50% by mass to 90% by mass, in order to obtain a pressure-sensitive adhesive film that has both excellent peelability and peel resistance. The gel fraction refers to a value measured by the method described below.

[0030] The adhesive was applied to the release-treated surface of the release liner so that the thickness after drying would be 10 μm, and the applied adhesive was dried in an environment at 100°C for 3 minutes, and then aged in an environment at 40°C for 2 days to form an adhesive layer. The pressure-sensitive adhesive layer was cut into a square measuring 50 mm in length and 50 mm in width to prepare a test piece. After measuring the mass (G1) of the test piece, the test piece was immersed in toluene in an environment of 23° C. for 24 hours. After the immersion, the mixture of the test piece and toluene was filtered using a 300-mesh wire screen to extract the insoluble components in toluene. The insoluble components were dried at 110°C for 1 hour, and the mass (G2) of the product was measured. The gel fraction was calculated based on the mass (G1) and mass (G2) and the following formula. Gel fraction (mass%) = (G2 / G1) × 100

[0031] The pressure-sensitive adhesive layer (B) has a loss tangent (Tanδ) at 120°C. 120 ) is 1.0 or less, preferably 1.2 or less, more preferably 0.05 or more and 0.8 or less, and even more preferably 0.2 or more and 0.6 or less, in order to obtain a PSA film that combines excellent peelability and peel resistance. 120 ) indicates a value measured by the method described in the Examples.

[0032] The adhesive may contain additives such as plasticizers, softeners, antioxidants, flame retardants, fillers such as glass or plastic fibers, balloons, beads, metals, metal oxides, and metal nitrides, colorants such as pigments and dyes, leveling agents, thickeners, water repellents, and antifoaming agents. The PSA preferably contains a solvent in order to maintain good coating workability, etc. Examples of the solvent that can be used include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, and hexane. When a water-based PSA composition is prepared, water or an aqueous solvent mainly composed of water can be used.

[0033] [Adhesive film] The pressure-sensitive adhesive film of the present invention can be produced, for example, by applying the pressure-sensitive adhesive to at least one surface of the substrate using an applicator, roll coater, gravure coater, reverse coater, spray coater, air knife coater, die coater, etc., and drying the applied pressure-sensitive adhesive. Alternatively, the pressure-sensitive adhesive film can be produced by a transfer method in which the pressure-sensitive adhesive is applied in advance to the surface of a release liner using a knife coater, roll coater, die coater, etc., and dried to form a pressure-sensitive adhesive layer, and then the pressure-sensitive adhesive layer is bonded to at least one surface of the substrate.

[0034] The release liner is not particularly limited, but examples thereof include substrates such as resin films such as polyethylene, polypropylene, and polyester films, paper, nonwoven fabric, cloth, foam sheets, and metal foils, as well as laminates thereof, on at least one side of which a release treatment such as a silicone-based treatment, a long-chain alkyl-based treatment, or a fluorine-based treatment has been applied to enhance releasability from the pressure-sensitive adhesive. Among these, high-quality paper laminated on both sides with polyethylene having a thickness of 10 to 40 μm, and release liners in which one or both sides of a polyester film have been subjected to a silicone release treatment are preferred.

[0035] The pressure-sensitive adhesive layer may be dried for 30 seconds to 10 minutes at 50° C. to 140° C. After drying, the pressure-sensitive adhesive layer may be further aged at a temperature in the range of 30° C. to 50° C. to promote the curing reaction. The pressure-sensitive adhesive film of the present invention is pressed against an optical film using a 2 kg roller in a single back-and-forth motion in an environment of 23°C temperature and 50% RH, and after being left to stand for 1 hour in an environment of 23°C temperature and 50% RH relative humidity, the 180° peel adhesive strength at a peel rate of 300 mm / min is 0.5 to 4.0 N / 25 mm, preferably in the range of 0.7 N / 25 mm to 2.5 N / 25 mm, and more preferably in the range of 0.9 N / 25 mm to 1.7 N / 25 mm. Furthermore, when the adhesive film is pressed against an optical film using a 2 kg roller in one back-and-forth motion at a temperature of 23°C and a relative humidity of 50%RH, and then allowed to stand for 30 seconds in an environment at a temperature of 120°C, the 180° peel adhesive strength at a peel rate of 300 mm / min is 0.5 to 4.0 N / 25 mm, preferably in the range of 0.7 N / 25 mm to 2.5 N / 25 mm, and more preferably in the range of 0.9 N / 25 mm to 1.7 N / 25 mm, in order to obtain excellent peelability and peel resistance. The 180° peel adhesive strength of the pressure-sensitive adhesive film and the 180° peel adhesive strength after exposure to a 120°C environment refer to values ​​measured by the method described in the Examples.

[0036] The pressure-sensitive adhesive film of the present invention has suitable peelability and peel resistance, and therefore can be applied to various applications. In particular, the pressure-sensitive adhesive film of the present invention can be suitably applied to optical films. In particular, the pressure-sensitive adhesive film of the present invention has suitable peelability and peel resistance, and therefore can be suitably applied as a carrier film or protective film in the processing step of optical films, and can transport optical films without peeling or lifting even in high-temperature environments while preventing scratches on the surface of the optical film.

[0037] Examples of optical films include polarizing plates, retardation plates, films with high light transmittance, etc. As the polarizing plate, a general one in which a polarizer protective layer is laminated on both sides or one side of a polarizer can usually be used. The polarizer can be, for example, a polarizer obtained using a polyvinyl alcohol-based resin. The polyvinyl alcohol-based resin can be produced by saponifying a polyvinyl acetate-based resin. The polarizer can also be produced by, for example, adsorbing and orienting a dichroic dye on a formed polyvinyl alcohol-based resin film. A polarizing plate can be produced by laminating polarizer protective layers such as triacetyl cellulose films on both sides of the polarizer obtained above via adhesive layers.

[0038] Iodine or a dichroic organic dye can be used as the dichroic dye. Dyeing a polyvinyl alcohol-based resin film with a dichroic dye can be achieved by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dye. When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film by immersing it in an aqueous solution containing iodine and potassium iodide is usually employed.

[0039] The polarizer protective layer is not particularly limited, but it is preferable to use a layer obtained by using a resin having excellent transparency, assuming that the polarizer protective layer will be used as a display material.

[0040] Examples of the polarizer protective layer include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, diacetyl cellulose film, triacetyl cellulose film, acetyl cellulose butyrate film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, cycloolefin resin film, polymethylpentene film, polysulfone film, polyether ether ketone film, polyether sulfone film, polyetherimide film, polyimide film, fluororesin film, nylon film, and acrylic resin film.

[0041] When forming polarizer protective layers on both sides of the polarizer layer, it is possible to form polarizer protective layers made of different resins on each side. For example, a polarizer protective layer made of a triacetyl cellulose film can be formed on one side of the polarizer layer, and a polarizer protective layer made of a cycloolefin-based resin film can be formed on the other side.

[0042] Furthermore, a hard coat layer may be formed on both surfaces of the polarizer protective layer. The resin used to form the hard coat layer is not particularly limited, and examples thereof include ultraviolet-curable resins such as ultraviolet-curable acrylic urethane resins, ultraviolet-curable polyester acrylate resins, and ultraviolet-curable epoxy acrylate resins. It is preferable to use a polarizing plate having a thickness of 50 μm to 200 μm, as this contributes to making information display devices and portable electronic terminals lighter and thinner. [Example]

[0043] The present invention will be described in more detail below with reference to examples and comparative examples.

[0044] [Adjustment example 1] A reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer was charged with 65 parts by mass of n-butyl acrylate, 28 parts by mass of methyl acrylate, 7 parts by mass of 2-hydroxyethyl (meth)acrylate, and 200 parts by mass of ethyl acetate, and the mixture was held at 72°C for 4 hours with stirring, and then at 75°C for 5 hours. Next, 2 parts by mass of a 2,2'-azobis(2-methylbutyronitrile) solution (solid content 0.1% by mass) previously dissolved in ethyl acetate was added to the mixture, and the mixture was kept at 72°C for 4 hours under stirring, and then at 75°C for 5 hours. Next, ethyl acetate was added to the above mixture, mixed uniformly, and filtered through a 200 mesh wire screen to obtain a solution of acrylic copolymer (A-1) having a weight-average molecular weight of 570,000. An adduct of tolylene diisocyanate and trimethylolpropane ("Burnoc D-40" manufactured by DIC Corporation, hereinafter abbreviated as "D-40") was blended with the acrylic copolymer (A-1) so that the gel fraction was 60%, to obtain a pressure-sensitive adhesive composition (P-1).

[0045] [Adjustment example 2] A reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer was charged with 82 parts by mass of 2-ethylhexyl acrylate, 14 parts by mass of methyl acrylate, 4 parts by mass of 2-hydroxyethyl acrylate, and 200 parts by mass of ethyl acetate, and the mixture was held at 72°C for 4 hours with stirring, and then at 75°C for 5 hours. Next, 2 parts by mass of a 2,2'-azobis(2-methylbutyronitrile) solution (solid content 0.1% by mass) previously dissolved in ethyl acetate was added to the mixture, and the mixture was kept at 72°C for 4 hours under stirring, and then at 75°C for 5 hours. Next, ethyl acetate was added to the above mixture, and the mixture was mixed uniformly. The mixture was filtered through a 200 mesh wire screen to obtain a solution of acrylic copolymer (A-2) having a weight-average molecular weight of 880,000. D-40 was blended with the acrylic copolymer (A-2) so that the gel fraction was 81%, to obtain a pressure-sensitive adhesive composition (P-2).

[0046] [Adjustment example 3] A pressure-sensitive adhesive composition (P-3) was obtained in the same manner as in Preparation Example 1, except that an adduct of tolylene diisocyanate and trimethylolpropane ("Burnoc D-40" manufactured by DIC Corporation, hereinafter abbreviated as "D-40") was blended with the acrylic copolymer (A-1) so that the gel fraction was 43%.

[0047] [Adjustment example 4] A pressure-sensitive adhesive composition (P-4) was obtained in the same manner as in Preparation Example 1, except that an adduct of tolylene diisocyanate and trimethylolpropane ("Burnoc D-40" manufactured by DIC Corporation, hereinafter abbreviated as "D-40") was blended with the acrylic copolymer (A-1) so that the gel fraction was 91%.

[0048] [Comparative adjustment example 1] A reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer was charged with 88 parts by mass of 2-ethylhexyl acrylate, 8 parts by mass of 2-methoxyethyl acrylate, 1 part by mass of acrylic acid, 3 parts by mass of 4-hydroxybutyl acrylate, and 150 parts by mass of ethyl acetate. Next, 2 parts by mass of a 2,2'-azobis(2-methylbutyronitrile) solution (solid content: 0.1% by mass) previously dissolved in ethyl acetate was added to the mixture, and the mixture was kept at 72°C for 4 hours with stirring, and then at 75°C for 5 hours. Next, ethyl acetate was added to the above mixture, and the mixture was mixed uniformly. The mixture was filtered through a 200 mesh wire screen to obtain a solution of acrylic copolymer (B-1) having a weight-average molecular weight of 1.2 million. D-40 was blended with the acrylic copolymer (B-1) so that the gel fraction was 89%, to obtain a pressure-sensitive adhesive composition (Q-1).

[0049] [Comparative adjustment example 2] A reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer was charged with 93.4 parts by mass of 2-ethylhexyl acrylate, 3.5 parts by mass of acrylic acid, 3 parts by mass of vinyl acetate, 0.1 parts by mass of 2-hydroxyethyl acrylate, and 100 parts by mass of ethyl acetate, and the mixture was held at 72°C for 4 hours with stirring, and then at 75°C for 5 hours. Next, 2 parts by mass of a 2,2'-azobis(2-methylbutyronitrile) solution (solid content 0.1% by mass) previously dissolved in ethyl acetate was added to the mixture, and the mixture was kept at 72°C for 4 hours under stirring, and then at 75°C for 5 hours. Next, 9.4 parts by mass of "Super Ester A100" (glycerin ester of disproportionated rosin) manufactured by Arakawa Chemical Co., Ltd. and 9.4 parts by mass of "Haritack PCJ" (pentaerythritol ester of polymerized rosin) manufactured by Harima Chemical Co., Ltd. were added to 100 parts by mass of the above mixture, and ethyl acetate was added and mixed uniformly. The mixture was then filtered through a 200-mesh wire mesh to obtain a solution of acrylic copolymer (B-2) with a weight-average molecular weight of 1 million. D-40 was blended with the acrylic copolymer (B-2) so that the gel fraction was 51%, to obtain a pressure-sensitive adhesive composition (Q-2).

[0050] [Comparative adjustment example 3] A reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer was charged with 95 parts by mass of 2-ethylhexyl acrylate, 4 parts by mass of ethyl acrylate, 1.0 part by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate, and the mixture was held at 72°C for 4 hours with stirring, and then at 75°C for 5 hours. Next, 2 parts by mass of a 2,2'-azobis(2-methylbutyronitrile) solution (solid content 0.1% by mass) previously dissolved in ethyl acetate was added to the mixture, and the mixture was kept at 72°C for 4 hours under stirring, and then at 75°C for 5 hours. Next, ethyl acetate was added to the above mixture, mixed uniformly, and filtered through a 200 mesh wire screen to obtain a solution of acrylic copolymer (B-3) having a weight-average molecular weight of 290,000. D-40 was blended with the acrylic copolymer (B-3) so that the gel fraction was 55%, to obtain a pressure-sensitive adhesive composition (Q-3).

[0051] [Example 1] The adhesive composition (P-1) obtained in Preparation Example 1 was applied to the release-treated surface of a release liner (a 75 μm-thick polyethylene terephthalate film with one side treated for release) so that the adhesive layer would be 5 μm thick after drying, and the applied adhesive was dried at 100°C for 3 minutes to produce an adhesive layer with a thickness of 5 μm. Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (thermal shrinkage rate: 0.03%), and the release liner was laminated from the top surface with a roll at a linear pressure of 5 kg / cm. Thereafter, the film was aged in an environment of 40° C. for 48 hours to obtain a 55 μm thick adhesive film (T-1).

[0052] [Example 2] The adhesive composition (P-1) obtained in Preparation Example 1 was applied to the release-treated surface of a release liner (a 75 μm-thick polyethylene terephthalate film with one side treated for release) so that the adhesive layer would have a thickness of 10 μm after drying, and the applied adhesive was dried at 100°C for 3 minutes to produce an adhesive layer with a thickness of 10 μm. Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (thermal shrinkage rate: 0.03%), and the release liner was laminated from the top surface with a roll at a linear pressure of 5 kg / cm. Thereafter, the film was aged in an environment of 40° C. for 48 hours to obtain a 60 μm thick adhesive film (T-2).

[0053] [Example 3] The adhesive composition (P-2) obtained in Preparation Example 2 was applied to the release-treated surface of a release liner (a 75 μm-thick polyethylene terephthalate film with one side treated for release) so that the adhesive layer would be 10 μm thick after drying, and the applied adhesive was dried at 100°C for 3 minutes to produce an adhesive layer with a thickness of 10 μm. Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (thermal shrinkage rate: 0.03%), and the release liner was laminated from the top surface with a roll at a linear pressure of 5 kg / cm. Thereafter, the film was aged in an environment of 40° C. for 48 hours to obtain a 60 μm thick adhesive film (T-3).

[0054] [Example 4] The adhesive composition (P-1) obtained in Preparation Example 1 was applied to the release-treated surface of a release liner (a 75 μm-thick polyethylene terephthalate film with one side treated for release) so that the adhesive layer would be 5 μm thick after drying, and the applied adhesive was dried at 100°C for 3 minutes to produce an adhesive layer with a thickness of 5 μm. Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (thermal shrinkage rate: 0.20%), and the release liner was laminated from the top surface with a roll at a linear pressure of 5 kg / cm. Thereafter, the film was aged in an environment of 40° C. for 48 hours to obtain a 55 μm thick adhesive film (T-4).

[0055] [Example 5] The adhesive composition (P-3) obtained in Preparation Example 1 was coated onto the release-treated surface of a release liner (a 75 μm-thick polyethylene terephthalate film with one side treated for release) so that the adhesive layer would be 5 μm thick after drying, and the coated film was dried at 100°C for 3 minutes to produce an adhesive layer with a thickness of 5 μm. Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (thermal shrinkage rate: 0.03%), and the release liner was laminated from the top surface with a roll at a linear pressure of 5 kg / cm. Thereafter, the film was aged in an environment of 40° C. for 48 hours to obtain a 55 μm thick adhesive film (T-5).

[0056] [Example 6] The adhesive composition (Q-1) obtained in Comparative Preparation Example 1 was coated onto the release-treated surface of a release liner (a 75 μm-thick polyethylene terephthalate film with one side treated for release) so that the adhesive layer would be 5 μm thick after drying, and the coated film was dried at 100°C for 3 minutes to produce an adhesive layer with a thickness of 5 μm. Next, in a 23°C environment, the 5 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (thermal shrinkage rate: 0.03%), and the release liner was laminated from the top surface with a roll at a linear pressure of 5 kg / cm. Thereafter, the film was aged in an environment of 40° C. for 48 hours to obtain a 55 μm thick adhesive film (T-6).

[0057] [Comparative Example 1] The adhesive composition (Q-1) obtained in Comparative Preparation Example 1 was coated onto the release-treated surface of a release liner (a 75 μm-thick polyethylene terephthalate film with one side treated for release) so that the adhesive layer would have a thickness of 10 μm after drying, and the coated film was dried at 100°C for 3 minutes to produce an adhesive layer with a thickness of 5 μm. Next, in a 23°C environment, the 10 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (thermal shrinkage rate: 0.03%), and the release liner was laminated from the top surface with a roll at a linear pressure of 5 kg / cm. Thereafter, the film was aged in an environment of 40° C. for 48 hours to obtain a 60 μm thick adhesive film (U-1).

[0058] Comparative Example 2 The adhesive composition (Q-2) obtained in Comparative Preparation Example 2 was coated onto the release-treated surface of a release liner (a 75 μm-thick polyethylene terephthalate film with one side treated for release) so that the adhesive layer would be 10 μm thick after drying, and the coated film was dried at 100°C for 3 minutes to produce an adhesive layer 5 μm thick. Next, in a 23°C environment, the 10 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (thermal shrinkage rate: 0.03%), and the release liner was laminated from the top surface with a roll at a linear pressure of 5 kg / cm. Thereafter, the film was aged in an environment of 40° C. for 48 hours to obtain a 60 μm thick adhesive film (U-2).

[0059] Comparative Example 3 The adhesive composition (Q-3) obtained in Comparative Preparation Example 3 was coated onto the release-treated surface of a release liner (a 75 μm-thick polyethylene terephthalate film with one side treated for release) so that the adhesive layer would be 10 μm thick after drying, and the coated film was dried at 100°C for 3 minutes to produce an adhesive layer 5 μm thick. Next, in a 23°C environment, the 10 μm thick adhesive layer was attached to one side of a 50 μm thick polyethylene terephthalate film (thermal shrinkage rate: 0.03%), and the release liner was laminated from the top surface with a roll at a linear pressure of 5 kg / cm. Thereafter, the film was aged in an environment of 40° C. for 48 hours to obtain a 60 μm thick adhesive film (U-3).

[0060] [180° peel adhesive strength] The 180° peel adhesive strength of the pressure-sensitive adhesive films of the Examples and Comparative Examples was measured by the following method. (1) At 23°C and 50% RH, the film was pressed and attached to an optical film (a polarizing plate made of triacetyl cellulose, with a hard coat layer on the surface) using a 2 kg roller, with one reciprocating motion. (2) After leaving the sample at rest for 1 hour at 23°C and 50% RH, the strength was measured when the sample was peeled off in a 180° direction at a pulling speed of 300 mm / powder at 23°C and 50% RH (unit: N / 25 mm).

[0061] [180° peel strength after exposure to 120°C environment] The 180° peel adhesive strength of the pressure-sensitive adhesive films of the Examples and Comparative Examples after being placed in a 120°C environment was measured by the following method. (1) At 23°C and 50% RH, the film was pressed and attached to an optical film (a polarizing plate made of triacetyl cellulose, with a hard coat layer on the surface) using a 2 kg roller, with one reciprocating motion. (2) After leaving the sample at 23°C and 50% RH for 1 hour, the sample was left at 120°C for 30 seconds, and then peeled off in a 180° direction at a tensile speed of 300 mm / min at 23°C and 50% RH, and the strength was measured (unit: N / 25 mm).

[0062] [Easy peelability] The peelability of the pressure-sensitive adhesive films of the Examples and Comparative Examples was measured by the following method. 1) A 25mm x 50mm adhesive film was pressed and attached to a 30mm x 100mm optical film (a polarizing plate made of triacetyl cellulose with a hard coating layer on the surface) at 23°C and 50% RH using a 2kg roller in one stroke. 2) After leaving the film standing at 23°C and 50% RH for 1 hour, it was left standing at 120°C for 30 seconds, and then the adhesive film was peeled off by hand at 23°C and 50% RH, and the condition of the optical film was evaluated. ◎: The adhesive film was peeled off without deformation or damage to the optical film. ◯: There was resistance to peeling, but the adhesive film was peeled off without deformation or damage to the optical film. ×: Peeling was not possible and the optical film was destroyed.

[0063] [Peel resistance at 120°C] The peel resistance at 120°C of the pressure-sensitive adhesive films of the Examples and Comparative Examples was measured by the following method. (1) An optical film having an outer diameter of 25 mm x 25 mm was pressed and attached to the center of an adhesive film having an outer diameter of 50 mm x 50 mm at 23°C and 50% RH with a 2 kg roller going back and forth once. (2) After leaving the film at 23°C and 50% RH for 1 hour, a 500g weight was placed on the center of the adhesive film from the adhesive film side at 120°C and left to stand for 30 seconds. After that, the weight was removed and the degree of peeling of the optical film was checked at 23°C and 50% RH. ⊚: The optical film was not peeled off from the adhesive film at all. ○: Peeling occurred about 1 to 2 mm from the edge of the optical film. △: Peeling occurred about 5 to 10 mm from the edge of the optical film. ×: The optical film peeled off from the adhesive film.

[0064] [Loss tangent at 120℃ (Tanδ 120 ) Measurement method] Each of the adhesive compositions obtained above was coated on the surface of a release liner and heated in an oven at 85°C for 4 minutes to prepare an adhesive layer with a thickness of 50 μm. The obtained adhesive layers were then stacked to prepare an adhesive layer with a thickness of 2 mm. Next, the pressure-sensitive adhesive layer was cut into a circle having a diameter of 8 mm to prepare a test piece. Next, using a viscoelasticity tester (manufactured by Rheometrics, product name: Ares 2KSTD), the test piece was sandwiched between parallel disks, which are the measurement section of the tester, and the storage modulus (G') and loss modulus (G") were measured at a temperature of 120°C and a frequency of 1 Hz. The loss tangent (Tanδ) was calculated from G' and G". 120 ) was calculated.

[0065] [Heat shrinkage rate at 120℃] The substrate (A) cut into a size of 100 mm x 100 mm was left standing at 120°C for 30 seconds, and the outer dimensions were measured at 23°C and 50% RH, and the heat shrinkage at 120°C was calculated using the following formula. Heat shrinkage rate at 120°C = [(100-L) / 100] x 100 (unit: %) (L is the external dimension after leaving it at 120℃ for 30 seconds, unit is mm)

[0066] [Checking for residual adhesive after peeling off the adhesive film] After measuring the 180° peel adhesion strength after placing the optical film in the 120°C environment, the area where the adhesive film had been attached to the optical film (a polarizing plate made of triacetyl cellulose, with a hard coat layer on the surface) was visually inspected to confirm whether any adhesive residue from the adhesive film remained on the optical film. Next, the water contact angle (AN1) of the optical film at the location where the adhesive film had been attached was measured, and compared with the water contact angle (AN2) of the polarizing plate before the adhesive film was attached. ⊚: No adhesive residue was found, and there was no change in the water contact angle. ◯: No adhesive residue was found, but AN1 was higher than AN2. ×: Residue of adhesive remained on the optical film.

[0067] [Table 1]

Claims

1. A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer (B) on at least one surface of a substrate (A) directly or via another layer, The substrate (A) is cut into a piece of 100 mm x 100 mm, left to stand at 120°C for 30 seconds, and then the outer dimension L is measured at 23°C and 50% RH. The shrinkage rate of the substrate (A) calculated by the formula [(100-L) / 100] x 100 (unit: %) is 1.0% or less. the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer (B) is a (meth)acrylic pressure-sensitive adhesive composition, the (meth)acrylic pressure-sensitive adhesive composition contains an acrylic copolymer having a (meth)acrylate monomer having 1 to 12 carbon atoms as a main monomer component, the content of the (meth)acrylate monomer having 1 to 12 carbon atoms is 80 to 98.5 mass% of the monomer components constituting the acrylic copolymer, the pressure-sensitive adhesive layer (B) contains an isocyanate-based crosslinking agent, the pressure-sensitive adhesive layer (B) has a gel fraction of 50% to 90%; the adhesive is pressed against an optical film using a 2 kg roller in one reciprocating motion under an environment of 23°C temperature and 50% RH, and the adhesive is left to stand for 1 hour under an environment of 23°C temperature and 50% RH, after which the adhesive has a 180° peel adhesive strength of 0.7 to 4 N / 25 mm at a peel speed of 300 mm / min, The pressure-sensitive adhesive layer (B) is pressed against an optical film using a 2 kg roller in a single reciprocating motion under an environment of 23°C temperature and 50% RH, and then allowed to stand for 30 seconds under an environment of 120°C temperature, after which the 180° peel adhesive strength at a peel rate of 300 mm / min is 0.6 to 4 N / 25 mm, and the loss tangent (Tanδ) of the pressure-sensitive adhesive layer (B) at 120°C and 1 Hz is １２０ ) is 0.05 or more and 1.0 or less.

2. The pressure-sensitive adhesive film according to claim 1, which is used to protect the surface of a polarizing plate.

3. An adhesive film as described in claim 1, wherein the substrate (A) is at least one selected from the group consisting of polyethylene terephthalate film, polyethylene naphthalate film, polycarbonate film, polyethylene film, polypropylene film, triacetyl cellulose film, polyimide film, acrylic resin film, and cyclic olefin polymer film.

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