Adhesive film for cycloolefin film

Abstract

To provide an adhesive film for a cycloolefin film that maintains its adhesive strength even when using a release film with high adhesive strength on both sides and low residual adhesion rate.SOLUTION: There is provided an adhesive film 10 for a cycloolefin film, in which release films 12 and 13 are bonded to both surfaces of an adhesive layer 11 formed by cross-linking an adhesive composition containing (meth)acrylic polymer and a cross-linking agent. The residual adhesion rate of the release treatment surface 12a of one release film 12 is 70 to 90%, and the residual adhesion rate of the release treatment surface 13a of the other release film 13 is 90 to 110%. The adhesive force of the surface 11a of the adhesive layer 11, to which the one release film 12 was bonded, to the cycloolefin film is 10 N / 25 mm or greater, and is 90% or more of the adhesive force of the surface 11b of the adhesive layer 11, to which the other release film 13 was bonded, to the cycloolefin film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an adhesive film for a cycloolefin film. [Background technology]

[0002] In recent years, displays have been using low-polarity resin films such as norbornene resin films (COP) and polycarbonate films (PC) for polarizing plates and retardation plates. These optically functional films are laminated using adhesives and incorporated into displays. When conventional general adhesives are used, sufficient adhesive strength is not achieved, resulting in problems such as peeling and lifting. Acrylic adhesive films that use rosin-based tackifiers have been proposed as adhesive films that can achieve high adhesive strength for such low-polarity resin films. However, many rosin-based tackifiers are yellow-colored, posing challenges for their use in optical systems (see, for example, Patent Documents 1 to 3).

[0003] Another method for imparting high adhesive strength to low-polarity resin films is known to be effective in the form of acrylic adhesive films in which alicyclic monomers or aromatic-containing monomers are used as copolymerization components to reduce the polarity of the resin (see, for example, Patent Documents 4-5). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7131723 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-213808 [Patent Document 3] Japanese Patent Application Laid-Open No. 2018-158990 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-53976 [Patent Document 5] Japanese Patent Application Laid-Open No. 2010-180283 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when an acrylic adhesive film whose polarity has been reduced using only an alicyclic monomer or an aromatic-containing monomer is used with a silicone release-treated release film with a low residual adhesion rate, the adhesive strength of the adhesive film to a low-polarity resin film is significantly reduced compared to when a silicone release-treated release film with a high residual adhesion rate is used.

[0006] In particular, in a release film / adhesive layer / release film configuration, it is necessary to create a sufficient difference in the release strength of both release films as a method to prevent the adhesive layer from separating when the release film is peeled off. By using a silicone release-treated release film with low residual adhesive strength (light release side release film) as one of the release films, it is easy to set the difference in heavy and light release strength, and the release strength of the other silicone release-treated release film (heavy release side release film) can also be reduced, which is advantageous for preventing problems such as peeling workability, zipping, and stop lines when peeling the heavy release side release film. However, due to the above issues, there are limitations on the selection of release films.

[0007] For this reason, there is a demand for an adhesive film that is suitable for low-polarity substrates, has high adhesive strength on both sides, and does not lose adhesive strength on the other side when used with a silicone release-treated release film that has a low residual adhesion rate.

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide an adhesive film for cycloolefin films, which has high adhesive strength on both sides and does not lose adhesive strength on one side compared to the other side when used with a low-polarity substrate such as a cycloolefin film, even when a silicone release-treated release film with a low residual adhesion rate is used. [Means for solving the problem]

[0009] The present invention provides a pressure-sensitive adhesive film for cycloolefin films, which comprises a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing a (meth)acrylic polymer and a crosslinking agent, and in which the silicone release-treated surfaces of a release film, one side of which has been subjected to a silicone release treatment, are bonded to both sides of the pressure-sensitive adhesive layer, wherein the (meth)acrylic polymer is a pressure-sensitive adhesive composition having a glass transition temperature of −18° C. or lower, which is obtained by copolymerizing 100 parts by weight of component A with 0.1 to 10 parts by weight of component B of a (meth)acrylate containing a functional group that reacts with the crosslinking agent, and the component A contains at least 50 to 90 parts by weight of a (meth)acrylate having a linear or branched alkyl group of C10 or more as component a1, and 0.1 to 10 parts by weight of a (meth)acrylate having an alicyclic hydrocarbon group as component a2. and the total of the a1 component and the a2 component is 75 parts by weight or more, the residual adhesion rate of the release-treated surface of one of the release films of the release film is 70 to 90%, and the residual adhesion rate of the release-treated surface of the other of the release films of the release film is 90 to 110%, the adhesive strength of the surface of the pressure-sensitive adhesive layer to which one of the release films was bonded to a cycloolefin film is 90% or more of the adhesive strength of the surface of the pressure-sensitive adhesive layer to which the other release film was bonded to the cycloolefin film, and the adhesive strength of the surface of the pressure-sensitive adhesive layer to which one of the release films was bonded to the cycloolefin film is 10 N / 25 mm or more. [Effects of the Invention]

[0010] According to the present invention, both sides of the adhesive film have high adhesive strength, and even when a silicone release-treated release film with a low residual adhesion rate is used, the adhesive strength does not decrease compared to the other side when used on a low-polarity substrate such as a cycloolefin film. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing an example of an adhesive film for a cycloolefin film. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described below based on preferred embodiments.

[0013] An example of an adhesive film for cycloolefin films according to this embodiment is shown in Figure 1. In adhesive film 10 for cycloolefin films, silicone release-treated surfaces 12a, 13a of release films 12, 13, each of which has been silicone-release-treated on one side, are bonded to both sides of adhesive layer 11. In other words, adhesive film 10 for cycloolefin films has a configuration of one release film 12 / adhesive layer 11 / other release film 13. In the following description, silicone release-treated surfaces 12a, 13a may be simply referred to as release surfaces 12a, 13a.

[0014] The pressure-sensitive adhesive layer 11 is an adhesive layer formed by crosslinking an adhesive composition containing a (meth)acrylic polymer and a crosslinking agent. The (meth)acrylic polymer is an adhesive composition having a glass transition temperature of −18° C. or lower, which is obtained by copolymerizing 100 parts by weight of component A with 0.1 to 10 parts by weight of a (meth)acrylate containing a functional group that reacts with the crosslinking agent as component B. Here, component A is a monomer other than component B.

[0015] The component A contains at least 50 to 90 parts by weight of a (meth)acrylate having a linear or branched alkyl group of C10 or more as component a1, and 10 to 50 parts by weight of a (meth)acrylate having an alicyclic hydrocarbon group as component a2, and the total amount of the components a1 and a2 is 75 parts by weight or more. Here, (meth)acrylate means acrylate and / or methacrylate.

[0016] Of the release films 12 and 13, the release treated surface 12a of one release film 12 has a residual adhesion rate of 70 to 90%, and the release treated surface 13a of the other release film 13 has a residual adhesion rate of 90 to 110%. In addition, the adhesive strength of the surface 11a of the adhesive layer 11 to which one release film 12 is bonded to the cycloolefin film is 90% or more of the adhesive strength of the surface 11b of the adhesive layer 11 to which the other release film 13 is bonded to the cycloolefin film. Furthermore, the adhesive strength of the surface 11a of the adhesive layer 11 to which one release film 12 has been attached to the cycloolefin film is 10 N / 25 mm or more.

[0017] Of 100 parts by weight of component A, component a1 is a (meth)acrylate having a C10 or higher linear or branched alkyl group used in an amount ranging from 50 to 90 parts by weight. Examples of (meth)acrylates having a C10 or higher linear or branched alkyl group include acyclic alkyl (meth)acrylates in which the alkyl group is a C10 or higher linear or branched alkyl group. Component a1 may be one type or two or more types.

[0018] Examples of the C10 or higher linear or branched alkyl group include a decyl group, an isodecyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, a stearyl group, an isostearyl group, a nonadecyl group, an eicosyl group, a heneicosyl group, a docosyl group, a tricosyl group, a tetracosyl group, a pentacosyl group, a hexacosyl group, a heptacosyl group, an octacosyl group, a nonacosyl group, a triacontyl group, a hentriacontyl group, a dotriacontyl group, a tritriacontyl group, a tetratriacontyl group, a pentatriacontyl group, and a hexatriacontyl group.

[0019] Of 100 parts by weight of component A, component a2 is a (meth)acrylate having an alicyclic hydrocarbon group used in the range of 10 to 50 parts by weight. Examples of the (meth)acrylate having an alicyclic hydrocarbon group include cyclic alkyl (meth)acrylates in which the cyclic alkyl group is an alicyclic hydrocarbon group. Component a2 may be one type or two or more types.

[0020] Examples of the alicyclic hydrocarbon group include a cyclopentyl group, a cyclohexyl group, a bornyl group, an isobornyl group, a bicycloheptyl group, a bicyclooctyl group, a dimethylbicycloheptyl group, a dicyclopentanyl group, and a dicyclopentenyl group.

[0021] 100 parts by weight of component A contains at least component a1 and component a2, and the total of component a1 and component a2 is 75 parts by weight or more. Component A may consist of only component a1 and component a2, or may contain components other than component a1 and component a2. In the following description, components other than component a1 and component a2 may be referred to as component a3. The total of component a3 is 25 parts by weight or less.

[0022] Component a3 may be any component other than component a1, component a2, or component B, but is preferably a component that does not contain a functional group that reacts with a crosslinking agent. For example, component a3 may be a (meth)acrylate having a linear or branched alkyl group of C9 or less. Component a3 may be one type or two or more types.

[0023] Examples of straight-chain or branched-chain alkyl groups of C9 or less include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, pentyl, isopentyl, hexyl, heptyl, octyl, 2-ethylhexyl, isooctyl, nonyl, and isononyl groups.

[0024] As component B, a (meth)acrylate containing a functional group that reacts with a crosslinking agent is used in the range of 0.1 to 10 parts by weight. Examples of the functional group that reacts with a crosslinking agent include a hydroxy group and a carboxy group. Component B may be one type or two or more types.

[0025] Examples of (meth)acrylates containing a hydroxy group include 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2,3-dihydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and other polyalkylene glycol mono(meth)acrylates.

[0026] Examples of the (meth)acrylate containing a carboxy group include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyl tetrahydrophthalate.

[0027] The adhesive composition uses a (meth)acrylic polymer having a glass transition temperature (Tg) of −18° C. or lower. The range of Tg may have two points selected from, for example, −18° C., −20° C., −25° C., −30° C., −35° C., −40° C., −45° C., −50° C., and −55° C. as the lower and upper limits.

[0028] The (meth)acrylic polymer can be synthesized by polymerization through a radical reaction in the presence of a polymerization initiator, such as a peroxide or an azo compound.

[0029] The weight average molecular weight (Mw) of the (meth)acrylic polymer is not particularly limited, but is preferably from 200,000 to 5,000,000, more preferably from 300,000 to 4,000,000, and particularly preferably from 500,000 to 2,000,000. The weight average molecular weight can be determined by GPC (gel permeation chromatography) measurement.

[0030] The crosslinking agent used for crosslinking the pressure-sensitive adhesive composition is preferably an isocyanate compound, more preferably a trifunctional or higher isocyanate compound. Examples of bifunctional isocyanate compounds include diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, and pentamethylene diisocyanate. Examples of trifunctional or higher isocyanate compounds include adducts and isocyanurates of diisocyanates.

[0031] The method for producing a pressure-sensitive adhesive layer by crosslinking a pressure-sensitive adhesive composition containing an acrylic polymer and a crosslinking agent is not particularly limited, but the pressure-sensitive adhesive layer can be formed by applying the pressure-sensitive adhesive composition to a coating substrate such as a release film and then crosslinking the pressure-sensitive adhesive composition. The coating substrate may be a release film used in pressure-sensitive adhesive films for cycloolefin films, or another film. When the pressure-sensitive adhesive layer is formed on another film, it can be transferred from the other film onto the release film. The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 5 to 30 μm, more preferably 10 to 25 μm.

[0032] Examples of cycloolefin films used as an adherend for the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition include films of cycloolefin polymers (COP). Examples of cycloolefin polymers (COP) include polymers of cyclic olefins and copolymers of two or more cyclic olefins. The copolymers of cyclic olefins may be ring-opened polymers obtained by metathesis or the like, or hydrogenated products thereof.

[0033] Examples of the cyclic olefin include at least one of vinylcycloalkanes having a cycloalkane with 3 to 20 carbon atoms and derivatives thereof, monocycloalkenes having 3 to 20 carbon atoms and derivatives thereof, and cyclic olefins having a norbornene skeleton (norbornene-based monomers).

[0034] Of the release films in the adhesive film for cycloolefin film of this embodiment, one release film is a light release side release film, and the residual adhesion rate of the release treated surface is 70 to 90%. The other release film is a heavy release side release film, and the residual adhesion rate of the release treated surface is 90 to 110%. A known adhesive tape can be used as a standard to measure the residual adhesion rate. When a difference in release force is set between the heavy release side and the light release side, the difference between the residual adhesion rate of the release treated surface of the other release film and the residual adhesion rate of the release treated surface of one release film can be, for example, 5 to 25%.

[0035] The adhesive film for cycloolefin film of this embodiment uses a release film with one side treated with silicone release. Examples of the base material for the release film include transparent resin films such as polyester resins. Examples of polyester resins include polyethylene terephthalate (PET) resins. The difference in release strength between the heavy release side and the light release side can be set by, for example, adjusting the type of silicone release agent.

[0036] The adhesive strength (Y) of the surface of the adhesive layer to which one release film has been attached to the cycloolefin film is 90% or more of the adhesive strength (X) of the surface of the adhesive layer to which the other release film has been attached to the cycloolefin film. This makes it possible to provide an adhesive film for cycloolefin films in which the adhesive strength of the surface attached to a release film with a low residual adhesion rate does not decrease compared to the adhesive strength of the surface attached to a release film with a high residual adhesion rate to a low-polarity adherend such as a cycloolefin film.

[0037] The adhesive strength (Y) of the surface of the adhesive layer to which one release film has been attached to the cycloolefin film is 10 N / 25 mm or more, thereby providing an adhesive film for cycloolefin film having high adhesive strength on both sides. Although (Y) / (X) is usually 100% or less, it is preferable that the adhesive strength (X) of the surface of the adhesive layer to which the other release film was attached to the cycloolefin film is also 10 N / 25 mm or more. The range of adhesive strength of (X) and (Y) may be, for example, two points selected from 10N / 25mm, 12N / 25mm, 14N / 25mm, 16N / 25mm, 18N / 25mm, 20N / 25mm, 25N / 25mm, and 30N / 25mm as the lower and upper limits.

[0038] The adhesive film for cycloolefin films of this embodiment can be used for the purpose of laminating the adhesive layer obtained by peeling off the release film to an optical film such as a polarizing plate. Examples of optical films include polarizing films, retardation films, anti-reflection films, anti-glare films, ultraviolet absorbing films, infrared absorbing films, optical compensation films, and brightness enhancing films. Examples of image display devices include liquid crystal display devices (liquid crystal panels), organic EL display devices (liquid crystal panels), touch panels, and electronic paper. [Example]

[0039] The present invention will be specifically described below with reference to examples.

[0040] (Production of adhesive composition) Nitrogen gas was introduced into a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, and the air inside the reactor was replaced with nitrogen gas. Then, the monomers of components A and B shown in Table 1 were added to the reactor together with a solvent (ethyl acetate). The values ​​in parentheses ( ) in Table 1 represent the parts by weight of each monomer. 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise to the resulting monomer solution over 2 hours, and the mixture was allowed to react at 65°C for 6 hours to obtain a (meth)acrylic polymer solution.

[0041] The monomers of components A and B shown in Table 1 are as follows: LMA: Lauryl methacrylate IDMA: Isodecyl methacrylate IBOA: Isobornyl acrylate BA: n-butyl acrylate EA: Ethyl acrylate TBA: t-butyl acrylate 2EHA: 2-ethylhexyl acrylate OCA: Octyl acrylate 4HBA: 4-hydroxybutyl acrylate

[0042] The glass transition temperature of the (meth)acrylic polymer was calculated by the following FOX formula. (FOX formula) 1 / Tg=W1 / Tg1+W2 / Tg2+ W N / Tg N Tg: Glass transition temperature of (meth)acrylic polymer Tg1 to Tg N : Glass transition temperature of homopolymer of each monomer W1 to W N : weight fraction of each monomer 1 to N: Numbers that distinguish each monomer copolymerized in the (meth)acrylic polymer

[0043] (Manufacturing adhesive film) To 100 parts by weight of the (meth)acrylic polymer of each production example, 0.3 parts by weight of a crosslinker (Mitsui Chemicals, Inc., product name: Takenate (registered trademark) D-101E) and a solvent (ethyl acetate) were added to prepare a coating solution with a non-volatile content of 35% by weight. This coating solution was applied to the release-treated surface of a heavy release side release film (the other release film), dried to remove the solvent, and then attached to the release-treated surface of a light release side release film (one release film) to obtain a pressure-sensitive adhesive film.

[0044] The release film on the heavy release side (the other release film) was a 38 μm thick release film (Fujimori Kogyo Co., Ltd., product name: 38E-0010 DG-2) with a residual adhesion rate of 95% on the release-treated surface.

[0045] The light release side release film (one of the release films) used was a 38 μm thick release film with a residual adhesion rate of 74% on the release-treated surface (Fujimori Kogyo Co., Ltd., product name: 38E-0010 KF), and a 38 μm thick release film with a residual adhesion rate of 85% on the release-treated surface (Fujimori Kogyo Co., Ltd., product name: 38E-0010 BD).

[0046] In Tables 2 to 4, the following abbreviations are used: RF-1: Product name 38E-0010 DG-2 RF-2: Product name 38E-0010 KF RF-3: Product name 38E-0010 BD

[0047] (Measurement of residual adhesion rate) A polyester adhesive tape (Nitto Denko Corporation, product name: Polyester Tape No. 31B) was attached to the surface of the release agent layer of the release film, and after aging at 23°C for 20 hours, it was peeled off at a peel speed of 300 mm / min and a peel angle of 180° using a desktop precision universal testing machine (Shimadzu Corporation, product name: Autograph (registered trademark)). The adhesive tape peeled from the release film was pressed against an adherend (stainless steel plate) with a roller and left to stand for 1 hour in an environment of 23°C and 50% RH. After that, the peel force when peeled from the adherend at a peel speed of 300 mm / min and a peel angle of 180° was measured using a desktop precision universal testing machine (Shimadzu Corporation, product name: Autograph (registered trademark)) and recorded as the residual adhesive strength. Separately, an unused adhesive tape was pressed against an adherend (stainless steel plate) made of the same material and the peel strength was measured in the same manner to obtain a reference adhesive strength. The residual adhesion rate was calculated by the formula: residual adhesion rate = (residual adhesive strength) / (standard adhesive strength) x 100 (%).

[0048] (Measurement of adhesive strength (X) to COP) In Tables 2 to 4, the adhesive strength to COP (X) is the adhesive strength to the cycloolefin film (COP) of the surface of the pressure-sensitive adhesive layer to which the heavy release side release film (the other release film) was attached (the heavy release side attachment surface). The adhesive strength to COP (X) was measured as follows. The release film on the light release side of the adhesive film of the manufacturing example was peeled off, and the film was laminated to one side of a 50 μm thick polyester film using a pressure roller. The release film on the heavy release side of the polyester film to which the obtained adhesive film was laminated was peeled off. The heavy release side of the adhesive film laminated to the polyester film was laminated to the surface of a COP film (Zeon Corporation, product name: Zeonor (registered trademark) ZF-16, thickness: 50 μm) fixed to the surface of a 1.8 mm thick soda glass with another adhesive film using a pressure roller. The thus-prepared sample having a configuration of polyester film / (light release side lamination surface) adhesive layer of the manufacturing example (heavy release side lamination surface) / COP film / another adhesive film / soda glass was autoclaved at 50°C, 0.5 MPa, and 20 minutes. After autoclaving, the film was returned to an atmosphere of 23°C and 50% RH for 1 hour, and the peel strength of the adhesive film was measured using a tensile tester in accordance with JIS Z0237 "Test methods for adhesive tapes and adhesive sheets," by peeling the test piece (polyester film / adhesive layer of manufacturing example) against the test plate (COP film / another adhesive film / soda glass). The peel strength measured in this measurement when peeled in a 180° direction at a speed of 300 mm / min was taken as the adhesive strength to COP (X).

[0049] (Measurement of adhesive strength to COP (Y)) In Tables 2 to 4, the adhesive strength to COP (Y) is the adhesive strength to the cycloolefin film (COP) of the surface of the pressure-sensitive adhesive layer to which the easy-release-side release film (one of the release films) was attached (the easy-release-side attachment surface). The adhesive strength to COP (Y) was measured as follows. The release film on the light release side of the adhesive film of the manufacturing example was peeled off. The light release side of the adhesive film was bonded to the surface of a COP film (Zeon Corporation, product name: Zeonor (registered trademark) ZF-16, thickness: 50 μm) fixed to the surface of a 1.8 mm thick soda glass with another adhesive film using a pressure roller. The release film on the heavy release side of the adhesive film bonded to the COP film was peeled off, and one side of a 50 μm thick polyester film was bonded to it using a pressure roller. The sample thus prepared, having a configuration of polyester film / (heavy release side bonding surface) adhesive layer of the manufacturing example (light release side bonding surface) / COP film / another adhesive film / soda glass, was autoclaved at 50°C, 0.5 MPa, and 20 minutes. After autoclaving, the film was returned to an atmosphere of 23°C and 50% RH for 1 hour, and the peel strength of the adhesive film was measured using a tensile tester in accordance with JIS Z0237 "Test methods for adhesive tapes and adhesive sheets," by peeling the test piece (polyester film / adhesive layer of manufacturing example) against the test plate (COP film / another adhesive film / soda glass). From this measurement, the peel strength when peeled in a 180° direction at a speed of 300 mm / min was taken as the adhesive strength to COP (Y).

[0050] [Table 1]

[0051] [Table 2]

[0052] [Table 3]

[0053] [Table 4]

[0054] As shown in Table 1, the PSA films of Examples 1 to 9 had high adhesive strength on both sides, and even when using a silicone release-treated release film with a low residual adhesion rate, the adhesive strength did not decrease compared to the other side when used on a low-polarity adherend such as a cycloolefin film. This confirmed that these PSA films have excellent performance as PSA films for cycloolefin films.

[0055] The adhesive films of Comparative Examples 1 to 9 had a ratio of adhesive strength to COP (Y) / (X) of less than 90%, and the adhesive strength was lower than the adhesive strength to COP (Y) compared with the adhesive strength to COP (X). In particular, in Comparative Examples 2 to 3 and 9 to 13, the adhesive strength to COP (Y) was less than 10 N / 25 mm, and the adhesive strength was low. [Explanation of symbols]

[0056] 10...adhesive film for cycloolefin film, 11...adhesive layer, 12, 13...release film, 12a, 13a...release-treated surface.

Claims

[Claim 1] A pressure-sensitive adhesive film for a cycloolefin film, comprising a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing a (meth)acrylic polymer and a crosslinking agent, and a release film having one surface treated with a silicone release treatment bonded to both surfaces of the pressure-sensitive adhesive layer, the release film comprising: The (meth)acrylic polymer is a pressure-sensitive adhesive composition obtained by copolymerizing 100 parts by weight of component A and 0.1 to 10 parts by weight of a (meth)acrylate containing a functional group reactive with a crosslinking agent as component B, and has a glass transition temperature of −18° C. or lower; The component A is at least 50 to 90 parts by weight of a (meth)acrylate having a linear or branched alkyl group of C10 or more as component a1, 10 to 50 parts by weight of a (meth)acrylate having an alicyclic hydrocarbon group as component a2, and the total amount of the a1 component and the a2 component is 75 parts by weight or more, the residual adhesion rate of the release-treated surface of one of the release films is 70 to 90%; the residual adhesion rate of the release-treated surface of the other release film is 90 to 110%, the adhesive strength of the surface of the pressure-sensitive adhesive layer to which one release film has been bonded to the cycloolefin film is 90% or more of the adhesive strength of the surface of the pressure-sensitive adhesive layer to which the other release film has been bonded to the cycloolefin film; An adhesive film for a cycloolefin film, characterized in that the adhesive strength of the surface of the adhesive layer to which the one release film is attached to the cycloolefin film is 10 N / 25 mm or more.

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