WO2003064552A1 - Heat releasable thermosetting pressure-sensitive adhesive film - Google Patents

Heat releasable thermosetting pressure-sensitive adhesive film Download PDF

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Publication number
WO2003064552A1
WO2003064552A1 PCT/US2002/036467 US0236467W WO03064552A1 WO 2003064552 A1 WO2003064552 A1 WO 2003064552A1 US 0236467 W US0236467 W US 0236467W WO 03064552 A1 WO03064552 A1 WO 03064552A1
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WO
WIPO (PCT)
Prior art keywords
sensitive adhesive
pressure
thermosetting
acrylic
adhesive film
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PCT/US2002/036467
Other languages
French (fr)
Inventor
Masaaki Takeda
Shigeyoshi Ishii
Yorinobu Takamatsu
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3M Innovative Properties Company
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Publication of WO2003064552A1 publication Critical patent/WO2003064552A1/en

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
    • C09J133/04—Homopolymers or copolymers of esters
    • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/10—Esters
    • C08F220/12—Esters of monohydric alcohols or phenols
    • C08F220/16—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms
    • C08F220/18—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms with acrylic or methacrylic acids
    • C08F220/1804—C4-(meth)acrylate, e.g. butyl (meth)acrylate, isobutyl (meth)acrylate or tert-butyl (meth)acrylate
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/20—Adhesives in the form of films or foils characterised by their carriers
    • C09J7/22—Plastics; Metallised plastics
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/38—Pressure-sensitive adhesives [PSA]
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2301/00—Additional features of adhesives in the form of films or foils
    • C09J2301/30—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier
    • C09J2301/302—Additional features of adhesives in the form of films or foils characterized by the chemical, physicochemical or physical properties of the adhesive or the carrier the adhesive being pressure-sensitive, i.e. tacky at temperatures inferior to 30°C

Definitions

  • the present invention relates to a heat releasable thermosetting pressure- sensitive adhesive film. More particularly, it relates to a heat releasable thermosetting pressure-sensitive adhesive film which is useful for masking.
  • Pressure-sensitive adhesives have a tack at ambient temperature and can immediately generate adhesion, without need for activation with water, solvent, heat or the like.
  • Many of pressure-sensitive adhesives include processed film-shaped (tape, strap) and sheet-shaped pressure-sensitive adhesives.
  • these processed pressure-sensitive adhesives are referred to as a "pressure-sensitive adhesive film” or a "pressure-sensitive adhesive sheet”.
  • Typical pressure-sensitive adhesive films contain acrylic pressure-sensitive adhesives as a main component, because the acrylic pressure-sensitive adhesive is generally superior in weatherability.
  • crosslinked-type acrylic adhesive when the acrylic pressure-sensitive adhesive is crosslinked (hereinafter referred to as a "crosslinked-type acrylic adhesive"), effective heat resistance can be provided.
  • An example of the crosslinked-type acrylic adhesive is disclosed in U.S. Patent No. 3,284,423.
  • This crosslinked-type acrylic adhesive contains (a) 35 to 75% by weight of an acrylate ester having 6 to 15 carbon atoms, (b) 10 to 60% by weight of an alkyl acrylate such as methyl acrylate or ethyl acrylate, (c) 0.1 to 10% by weight of an acid component such as (meth)acrylic acid, itaconic acid or crotonic acid, and (d) 0.1 to 10% by weight of glycidyl (meth)acrylate, and is self-crosslinked at room temperature or upon heating.
  • the crosslinked-type acrylic pressure- sensitive adhesive can have both cohesive force and a holding force and a sufficiently high adhesive force at high temperature.
  • glycidyl (meth)acrylate is preferably present in an amount of 1 to 3% by weight, thereby to impart a desired cohesive force to the above crosslinked-type pressure- sensitive acrylic adhesive.
  • a heat releasable thermosetting pressure-sensitive adhesive film typically further contains a heat blowing agent or a heat expanding agent, as disclosed in Japanese Examined Patent Publication
  • the heat blowing agent or the heat expanding agent can reduce an adhesion area between a heat releasable pressure-sensitive adhesive film and an adherend by means of a heat treatment after use and thus releasing and removing the heat releasable pressure-sensitive adhesive film easily from the adherend.
  • the heat blowing agent or the heat expanding agent divides the heat releasable pressure-sensitive adhesive film into separate areas by means of a heat treatment. As a result, areas of the heat releasable pressure-sensitive adhesive film are likely to remain on the adherend.
  • Japanese unexamined Patent Publication (Kokai) No. 10-25456 discloses a pressure-sensitive adhesive sheet which can easily be released and removed upon heating as described above and generally comprises a pressure-sensitive adhesive layer containing 100 parts by weight of a tacky base polymer, 10 to 900 parts by weight of a thermosetting compound and 0.1 to 10 parts by weight of a thermal polymerization initiator.
  • the base polymer of the pressure-sensitive adhesive sheet enables strong adhesion at the time of use. However, when the pressure-sensitive adhesive sheet is heat-treated once after use, the adhesive force is lowered and it becomes possible to easily release the pressure-sensitive adhesive sheet.
  • thermosetting compound is three-dimensionally crosslinked by heating to a temperature of 30° to 150°C in the presence of the thermal polymerization initiator such as organic peroxide which lowers the adhesion of the pressure-sensitive adhesive sheet.
  • the thermal polymerization initiator such as organic peroxide which lowers the adhesion of the pressure-sensitive adhesive sheet.
  • a low-molecular compound or oligomer having at least two carbon-carbon double bonds is commonly used as the thermosetting compound, such a low-molecular compound or oligomer is likely to remain in the pressure-sensitive adhesive layer without being crosslinked, resulting in a residue of adhesive remaining after release.
  • Japanese National Publication (Kohyo) No. 56-500889 of the PCT Application discloses a pressure-sensitive adhesive sheet which can easily be released upon light irradiation in place of heating.
  • this pressure- sensitive adhesive sheet has an epoxy equivalent of 400 to 900, including an epoxy (oxirane ring)-containing acrylic pressure-sensitive adhesive polymer such as glycidyl (meth)acrylate copolymer, and also containing an effective amount of an ionic photoinitiator such as an onium salt compound.
  • this pressure- sensitive adhesive sheet also enables strong adhesion at the time of use. When the pressure-sensitive adhesive sheet is irradiated once with light after use, the adhesive force is lowered and it becomes possible to easily release the adhesive sheet.
  • the photoinitiator accelerates the ionic ring-opening polymerization reaction of the oxirane ring and thus tliree-dimensionally crosslinks the oxirane ring-containing monomer of the adhesive sheet.
  • release and removal of the photocrosslinkable adhesive sheet from an adherend requires light irradiation through the substrate and/or adherend. Therefore, the use of this pressure-sensitive adhesive sheet puts a restriction that the substrate and/or the adherend that it must have light transmission properties.
  • An object of the present invention is to provide a heat releasable thermosetting pressure-sensitive adhesive film, which can avoid the light transmission requirement for use and thus effectively prohibit breakage of an adherend and deposition of residual adhesive on the adherend.
  • the present invention provides a heat releasable thermosetting pressure- sensitive adhesive film, comprising a thermally resistant substrate, and an acrylic thermosetting pressure-sensitive adhesive layer on at least one surface of said substrate, wherein the acrylic thermosetting pressure-sensitive adhesive layer contains a thermosetting acrylic pressure-sensitive adhesive polymer having an epoxy group and a carboxylic group in the molecule.
  • This adhesive film generates releasability upon heating and thus effectively prohibiting breakage of an adherend and deposition of residual adhesive to the adherend upon release. Also, since generation of the releasability does not require light such as ultraviolet light, an opaque substrate can be used as the substrate of the adhesive film.
  • thermosetting pressure-sensitive adhesive film of the present invention (hereinafter referred to as an "adhesive film”) will be further explained by way of preferred embodiments. It is to be understood by a person with an ordinary skill in the art that the present invention is not limited to the described embodiments.
  • the pressure-sensitive adhesive film of the present invention comprises a thermally resistant substrate, and an acrylic thermosetting pressure-sensitive adhesive layer on at least one surface of the substrate.
  • the thermally resistant substrate supports the acrylic thermosetting pressure-sensitive adhesive layer.
  • the thermally resistant substrate may support the acrylic thermosetting pressure-sensitive adhesive layer only on one surface thereof, or may supports the acrylic thermosetting pressure-sensitive adhesive layer on both surfaces thereof.
  • the thermally resistant substrate do not necessarily have light transmission properties and it is preferred to appropriately select the material according to the heating temperature of the pressure-sensitive adhesive film, namely, the curing temperature of the acrylic thermosetting pressure-sensitive adhesive layer.
  • PET polyethylene terephthalate
  • preferred thermally resistant substrate include polyether imide, polyether sulfone, polyethylene naphthalate or polyphenylene sulfide. Further, when the heating temperature or the curing temperature is 200°C or higher, the preferred thermally resistant substrate include polyether ether ketone, polyamideimide or polyimide. Taking account of the availability and chemical stability, PET, polyethylene naphthalate, polyphenylene sulfide and polyimide are particularly preferred because of high versatility.
  • the thermally resistant substrate preferably has a thickness of 1 to 200 ⁇ m, and more preferably 1 to 25 ⁇ m, due to handling and availability considerations.
  • the acrylic thermosetting pressure-sensitive adhesive layer contains a thermosetting acrylic pressure-sensitive adhesive polymer having an epoxy group and a carboxylic group in the molecule.
  • a thermosetting acrylic pressure-sensitive adhesive polymer has a glass transition temperature of -80° to 25°C in order to be provided with tackiness.
  • thermosetting acrylic pressure- sensitive adhesive polymer is cured by rapidly forming a three-dimensional crosslink between the epoxy group and the carboxylic group upon heating, as shown in the following scheme.
  • thermosetting acrylic pressure-sensitive adhesive polymers have an epoxy group in an amount of from 2 mol % to 50 mol% and the molar ratio of the epoxy group to the carboxylic group is 0.15 to 4.0.
  • the epoxy group is present in an amount of more than 50 mol%, the pressure-sensitive adhesive film has lower adhesion to the adherend and the pressure-sensitive adhesive film is more likely to be released during use.
  • the epoxy group is present in an amount of less than 2 mol% or the molar ratio is not within a range from 0.15 to 4.0, the thermosetting reaction of the thermosetting acrylic pressure- sensitive adhesive polymer is likely to become insufficient. As a result, the adhesive force of the pressure-sensitive adhesive film is heightened and it becomes difficult to re-release.
  • the thermosetting acrylic pressure-sensitive adhesive polymer preferably has a weight-average molecular weight of 10,000 to 1,000,000 as measured by gel permeation chromatography based on polystyrene standard. Because, when the weight-average molecular weight is about 10,000 or less, the cohesive force of the thermosetting acrylic pressure-sensitive adhesive polymer is low and this causes an adhesive residual to remain on the adherend. On the other hand, when the weight- average molecular weight is about 1,000,000 or more, stable coating is difficult to perform because the viscosity of the thermosetting acrylic pressure-sensitive adhesive polymer is too high.
  • thermosetting acrylic pressure-sensitive adhesive polymers are copolymers derived from a mixed monomer containing (meth)acrylate having an epoxy group such as glycidyl group and (meth)acrylate having a carboxylic group.
  • the mixed monomer may contain monomers other than (meth)acrylate having an epoxy group and (meth)acrylate having a carboxylic group.
  • Such a monomer is not specifically limited, but glass transition temperature of the resulting copolymer should be within a range from -80° to 25°C.
  • a non-substituted or substituted alkyl (meth)acrylate is preferably used as the monomer.
  • a monomer commonly has 2 to 15 carbon atoms and includes, for example, C 2-8 alkyl acrylate monomer, C 8-15 alkyl methacrylate monomer, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate and alkoxyalkyl acrylate.
  • C 2-8 alkyl acrylate such as ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, 2- methylbutyl acrylate, isoamyl acrylate or n-octyl acrylate; C 8-15 alkyl methacrylate such as isooctyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate and/or n-octyl methacrylate; and phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, methoxyethyl acrylate and ethoxyethyl acrylate.
  • C 8-15 alkyl methacrylate such as isooctyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacryl
  • the (meth)acrylate monomer having an epoxy group is not specifically limited so long as it can crosslink with a carboxylic group of a (meth)acrylate monomer having a carboxylic group and can includes, for example, glycidyl (meth)acrylate and/or (meth)acrylate having an alicyclic epoxy group.
  • a (meth)acrylate monomer having an epoxy group is commercially available, for example, from DAICEL CHEMICAL INDUSTRIES, LTD. under the trade name ofM100 and A200.
  • the (meth)acrylate monomer having a carboxylic group can include, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, 2-acryloyloxy ethylsuccinic acid (HOA-MS, manufactured by Kyoei Chemical Co., Ltd.), 2-acryloyloxyethylphthalic acid (HOA-MPL, manufactured by Kyoei Chemical Co., Ltd.), ⁇ -carboxy-polycaprolactone (repeating unit (n) ⁇ 2) monoacrylate (M-5300, manufactured by TOAGOSEI CO., LTD.), phthalic acid monohydroxyethyl acrylate (M-5400, manufactured by TOAGOSEI CO., LTD.) and/or acrylic acid dimer (M-5600, manufactured by TOAGOSEI CO., LTD.).
  • HOA-MS 2-acryloyloxy ethylsuccinic acid
  • Preferred mixed monomer contains a (meth)acrylate having an epoxy group in an amount of from 4 to 35% by weight based on the total weight and the molar ratio of the (meth)acrylate having an epoxy group to the (meth)acrylate having a carboxylic group is 0.15 to 4.0 for the following reason. That is, as described above, the thermosetting acrylic pressure-sensitive adhesive polymer contains the epoxy group in an amount of 2 to 50 mol% and the molar ratio of the epoxy group to the carboxylic group is 0.15 to 4.0.
  • the above mixed monomer can be radically polymerized in the presence of a polymerization initiator based on an azo compound or a peroxide.
  • a polymerization initiator based on an azo compound or a peroxide.
  • the polymerization method conventionally known methods such as solution polymerization method, emulsion polymerization method, suspension polymerization method and bulk polymerization method can be used.
  • solution polymerization method is particularly preferred because an acrylic thermosetting pressure-sensitive adhesive layer having a thickness described hereinafter can be effectively formed on the thermally resistant substrate.
  • the solution polymerization is usually conducted in a nitrogen atmosphere.
  • the polymerization temperature and the polymerization time are preferably 30° to 80°C and 1 to 24 hours, respectively, so gelation of the thermosetting acrylic pressure-sensitive adhesive polymer is effectively prohibited.
  • the acrylic thermosetting pressure-sensitive adhesive layer preferably has a thickness of 0.1 to 10 ⁇ m.
  • the acrylic thermosetting pressure-sensitive adhesive layer has a thickness of less than 0.1 ⁇ m, the resulting film hardly conforms to the adherend when contacted and is likely to be released during use.
  • the acrylic thermosetting pressure-sensitive adhesive layer has a thickness of more than about 10 ⁇ m, it becomes hard to sufficiently reduce the adhesive force after thermal curing. Also the solvent or chemical penetrates into the space between the pressure-sensitive adhesive film and the adherend during use and delamination of the pressure-sensitive adhesive film and contamination of the adherend are likely to occur.
  • the amount of the thermosetting acrylic pressure-sensitive adhesive polymer is not limited and such a pressure-sensitive adhesive polymer is preferably present in an amount of 70% by weight or more in the acrylic thermosetting pressure-sensitive adhesive layer.
  • the thermosetting acrylic pressure-sensitive adhesive polymer is present in an amount of less than 70% by weight, the adhesive force of the pressure-sensitive adhesive film tends to be only minimally reduced.
  • the acrylic thermosetting pressure-sensitive adhesive layer can contain a small amount of an acrylic polymer, in addition to the thermosetting acrylic pressure-sensitive adhesive polymer.
  • thermosetting acrylic pressure-sensitive adhesive polymer prepared as described above is dissolved in an organic solvent to prepare a coating solution.
  • organic solvent ethyl acetate, methyl ether ketone (MEK), toluene or a mixture thereof can be commonly used.
  • the coating solution is uniformly coated on the thermally resistant substrate by a die coating method, a knife coating method, a bar coating method or other conventionally known coating methods. Since most of the coating solution is made from the above thermosetting acrylic pressure-sensitive adhesive polymer, it can be easily uniformly coated.
  • the solvent is removed by drying the coating solution, together with the thermally resistant substrate, to obtain a pressure-sensitive adhesive film.
  • the pressure-sensitive adhesive film of the present invention can be used as a masking of the adherend such as electric circuit substrate.
  • the pressure-sensitive adhesive film of the present invention is applied at a predetermined position of an electric circuit substrate (hereinafter referred merely to as a "substrate").
  • the pressure-sensitive adhesive film is applied to the electric circuit substrate while heating to 80° to 120°C, so the pressure-sensitive adhesive film sufficiently adheres to the electric circuit substrate.
  • the electric circuit substrate is subjected to an etching process at 100°C or lower to provide an electric circuit on the substrate.
  • the portion coated with the pressure-sensitive adhesive film of the electric circuit substrate is protected by the pressure-sensitive adhesive film at a high adhesive force, and thus prohibits permeation of an etching chemical solution into the adhesive surface.
  • the electric circuit substrate is washed with hot water or an organic solvent.
  • the pressure-sensitive adhesive film also effectively prohibits the permeation of an etching chemical solution into the adhesive surface due to the thermal resistance and the solvent resistance of the adhesive film.
  • the electric circuit on the substrate is sealed with an epoxy resin and then the epoxy resin is cured by heating to 150° to 250°C. Since the pressure-sensitive adhesive film is also heated, the pressure- sensitive adhesive film loses most of its adhesion as a result of curing of the thermosetting acrylic pressure-sensitive adhesive polymer.
  • the pressure-sensitive adhesive film loses adhesion due to heating regardless of the presence or absence of light transmission properties of the supporting substrate of the pressure-sensitive adhesive film and the adherend. Therefore, the supporting substrate of the pressure-sensitive adhesive film and the adherend can be widely varied.
  • the thermosetting acrylic pressure-sensitive adhesive polymer occupies almost the entire acrylic thermosetting pressure-sensitive adhesive layer and the adhesive layer is fairly thin, unreacted monomer is less likely to remain, and little or no outgas is evolved. As a result, the pressure-sensitive adhesive film can be easily released without causing residual adhesive on the electric circuit substrate.
  • thermosetting acrylic pressure-sensitive adhesive polymer may be formed by copolymerizing a copolymerizable monomer other than a non- substituted or substituted alkyl (meth)acrylate having a glass transition temperature of -80° to 0°C and an acrylate monomer having an epoxy group such as glycidyl group and/or a carboxylic group.
  • a copolymerizable monomer is a (meth)acrylate monomer wherein a glass transition temperature of a homopolymer is 0°C or higher.
  • alkyl (meth)acrylate such as methyl (meth)acrylate, ethyl methacrylate, n-butyl (meth)acrylate, isobornyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate or lauryl (meth)acrylate; hydroxyalkyl (meth)acrylate such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate or hydroxybutyl (meth)acrylate; and polar monomer such as acrylamide, dimethylaminoethyl (meth)acrylate, N- vinyl pyrrolidone, 2-hydroxy-3-phenoxypropyl acrylate, dimethylaminopropylamide, N,N-
  • the acrylic thermosetting pressure-sensitive adhesive layer does not need to be limited to a single thermosetting acrylic pressure-sensitive adhesive polymer and may contain a thermosetting acrylic mixed pressure-sensitive adhesive polymer (mixed pressure-sensitive adhesive polymer) containing the following plural pressure-sensitive adhesive polymers:
  • a first acrylic pressure-sensitive adhesive polymer derived from a monomer containing a (meth)acrylate monomer having a glycidyl group
  • the respective pressure-sensitive adhesive polymers of such a mixed pressure-sensitive adhesive polymer are separately polymerized and the mixed pressure-sensitive adhesive polymer can be stored until just before coating. Therefore, the mixed pressure-sensitive adhesive polymer will barely gel upon polymerization and the coating solution has a long life as compared with the single thermosetting acrylic pressure-sensitive adhesive polymer.
  • Each of the first acrylic pressure-sensitive adhesive polymer and the second acrylic pressure-sensitive adhesive polymers, which constitutes the mixed pressure-sensitive adhesive polymer, has a glass transition temperature of -80° to 25°C in order to secure the tackiness of the pressure-sensitive adhesive layer similar to the case of the above single thermosetting acrylic pressure-sensitive adhesive polymer; likewise, the first and second acrylic pressure-sensitive adhesives each have a weight-average molecular weight of from 10,000 to 1,000,000. Further, the monomers constituting the mixed pressure-sensitive adhesive polymer and the proportion thereof are the same as in case of the single thermosetting acrylic pressure-sensitive adhesive polymer and, the acrylic thermosetting pressure-sensitive adhesive layer contains the mixed pressure- sensitive adhesive polymer in the same amount as in case of the single thermosetting acrylic pressure-sensitive adhesive polymer.
  • a crosslinking agent capable of crosslinking carboxyl groups with each other is added in an amount of less than 3% by weight in the acrylic thermosetting pressure-sensitive adhesive layer.
  • a crosslinking agent is preferably capable of crosslinking carboxylic groups with each other at 100°C or lower as that enables the acrylic thermosetting pressure-sensitive adhesive layer to be provided with a high cohesive force and thermal resistance before thermal curing.
  • a preferred crosslinking agent is an isocyanate crosslinking agent, which is commercially available from NIPPON POLYURETHANE INDUSTRY CO., LTD. under the trade name of Colonate L, an aziridine crosslinking agent, which is commercially available from NIPPON SHOKUBAI CO., LTD.
  • the crosslinking can be efficiently conducted in the drying step together with the thermally resistant substrate.
  • the crosslinking agent is added in an amount of less than 3% by weight in the acrylic thermosetting pressure-sensitive adhesive layer. If the crosslinking agent is added in an amount of more than 3% by weight, the acrylic thermosetting pressure-sensitive adhesive layer tends to lose the adhesion.
  • one surface of the thermally resistant substrate may be subjected to a surface treatment for easy bonding using conventionally known technique in order to improve the anchoring property with the acrylic thermosetting pressure-sensitive adhesive layer.
  • Preferred examples of the surface treatment include physical treatments such as corona discharge treatment, flame treatment, plasma treatment or ultraviolet irradiation treatment; or a wet chemical treatment.
  • a corona discharge treatment is particularly preferred because a thermally resistant substrate subjected to the corona discharge treatment is commercially available and readily available.
  • the primer treatment refers to a treatment of providing a coating layer (primer layer) having excellent adhesion with both the thermally resistant substrate and the acrylic thermosetting pressure-sensitive adhesive layer, on the thermally resistant substrate, and the acrylic thermosetting pressure-sensitive adhesive layer can be provided on the primer layer.
  • the thickness of the primer layer is preferably 0.1 to 2 ⁇ m and the total thickness of the acrylic thermosetting pressure-sensitive adhesive layer and the primer layer is preferably 0.2 to 10 ⁇ m by the following reason. If the thickness of the primer layer were 0.1 ⁇ m or less, it will not be effective. On the other hand, when the thickness is 2 ⁇ m or more, the solvent penetrates and both delamination of the pressure-sensitive adhesive film and contamination of the adherend are likely to occur.
  • the opposing surface of the thermally resistant substrate may be subjected to a release treatment.
  • the heat releasable thermosetting pressure-sensitive adhesive film of the present invention can be stored in the form of a rolled tape.
  • Silicone release agents, fluorine release agents, or a (meth)acrylic release agent having a long-chain alkyl group and a vinyl ether release agent having a long-chain alkyl group can be used as a release agent herein.
  • the acrylic thermosetting pressure-sensitive adhesive layer may contain further additives such as antioxidants, ultraviolet absorbers, fillers (for example, inorganic fillers, conductive particles or pigments), lubricants such as waxes, tackifiers, plasticizers, curing accelerators and fluorescent dyes.
  • antioxidants ultraviolet absorbers
  • fillers for example, inorganic fillers, conductive particles or pigments
  • lubricants such as waxes, tackifiers, plasticizers, curing accelerators and fluorescent dyes.
  • butyl acrylate manufactured by Mitsubishi Chemical
  • acrylic acid manufactured by Wako Pure Chemical Industries, Ltd., JIS (Japanese Industrial Standard) guaranteed special grade reagent
  • glycidyl methacrylate manufactured by manufactured by NOF CORPORATION under the trade name of Nissan Blenmer G
  • phenoxyethyl acrylate manufactured by OSAKA ORGANIC CHEMICAL INDUSTRY LTD. under the trade name of Biscoat #192
  • 2-hydroxy-3- phenoxypropyl acrylate manufactured by TOAGOSEI CO., LTD.
  • a mixed solvent prepared by mixing ethyl acetate of a JIS guaranteed special grade, which is commercially available from Wako Pure Chemical Industries, Ltd., with methyl ethyl ketone in a weight ratio of 4:1 was used for the monomer mixtures of Examples 1 to 3, while the solvent of ethyl acetate was used for the monomer mixtures of Comparative Examples 1 and 2.
  • BA butyl acrylate
  • GMA glycidyl methacrylate
  • AA acrylic acid
  • MEK methyl ethyl ketone
  • PEA phenoxyethyl acrylate
  • M-5700 2-hydroxy-3 -phenoxypropyl acrylate
  • thermosetting pressure-sensitive adhesive film was produced in the following manner. First, each of the acrylic pressure-sensitive adhesive polymers was diluted with a mixed solvent of methyl ethyl ketone (MEK) and toluene in a weight mixing ratio of 55:45 to prepare coating solutions each having a solid content of 5% by weight and 10% by weight. The coating solution was knife-coated on the corona-treated surface of a polyphenylene sulfide substrate film (manufactured by Toray under the trade name of Torelina) having a thickness of 12 ⁇ m, and having one surface which has been corona treated). The mixed solvent was then removed by drying in an oven at 100°C for 10 minutes to form an acrylic thermosetting pressure-sensitive adhesive layer.
  • MEK methyl ethyl ketone
  • the thickness of the acrylic thermosetting pressure-sensitive adhesive layer was measured. When using the coating solution having a solids content of 10%, the thickness of the acrylic thermosetting pressure-sensitive adhesive layer was about 5 ⁇ m. When using the coating solution having a solids content of 5%, the thickness of the acrylic thermosetting pressure-sensitive adhesive layer was about 1 ⁇ m.
  • a release film of polyethylene terephthalate subjected to a release treatment using silicone (manufactured by Teijin DuPont Films Japan Limited, under the trade name of Purex A31, thickness: 38 ⁇ m) was laminated onto the acrylic thermosetting pressure-sensitive adhesive layer, and the resulting laminate was used to produce samples for evaluation described hereinafter.
  • thermosetting pressure-sensitive adhesive film Using the above heat releasable thermosetting pressure-sensitive adhesive film, samples for evaluation were produced in the following manner and the adhesive force was measured.
  • an acrylic thermosetting pressure-sensitive adhesive layer was thermally laminated on a hard rolled copper foil having a thickness of 35 ⁇ m manufactured by Nippon Foil Mfg. Co., Ltd. under the following conditions: heating temperature of 80°C, a line speed of 2 meters per minute and a nip pressure of about 1.5 to 2 kg/cm, to obtain samples for evaluation. Each of the samples was allowed to stand at room temperature (at about 25 °C) for 24 or more hours and an adhesive force (initial adhesive force) of 180° peel was determined by releasing the acrylic thermosetting pressure-sensitive adhesive layer together with the film substrate, at 25°C at a speed of 300 mm/minute.
  • the adhesive force (adhesive force after thermal curing) of 180° peel of each sample for evaluation was also determined.
  • the thermal curing was conducted in the following manner.
  • the acrylic thermosetting pressure-sensitive adhesive layer with a substrate film and a hard rolled copper foil was interposed between two plate made of stainless steel 304 (JIS BA material) each having a thickness of 2 mm and then heated at 190°C for 90 minutes while applying a face pressure of 60 kg/cm 2 .
  • the adhesive force of 180° peel of the sample for evaluation was measured after allowing to stand at room temperature (about 25 °C) for one or more hours after thermal curing. Upon measurement, the presence or absence of a residual of adhesive to the copper foil was visually observed.
  • Example 4 This sample was formed in the same manner as in Example 1, except that an aziridine crosslinking agent (isophthaloylbis-2-methylaziridine) was added into the coating solution used in Example 1 in an amount of 0.2% by weight in terms of the solid content as shown in Table 2.
  • An acrylic thermosetting pressure-sensitive adhesive layer was obtained and samples for evaluation were produced and evaluated.
  • Examples 5 to 7 These samples were formed in the same manner as in Example 1, except that the composition shown in Table 2 was used, acrylic thermosetting pressure- sensitive adhesive layers were obtained and samples for evaluation were produced and evaluated.
  • the polymerization temperature was controlled to 55°C and acrylic pressure-sensitive adhesive polymers having a solid content of 35% were obtained.
  • the resulting polymer was bar-coated on a PPS film having a thickness of 16 ⁇ m in place of the polyphenylene sulfide (PPS) film having a thickness of 12 ⁇ m with a coating thickness of about 1 ⁇ m.
  • PPS polyphenylene sulfide
  • MMA denotes methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., JIS (Japanese Industrial Standard) guaranteed special grade reagent) and M- 5300 denotes ⁇ -carboxy-polycaprolactone (repeating unit (n) ⁇ 2) monoacrylate (M-5300, manufactured by TOAGOSEI CO., LTD.), and other monomers are the same as those used in other examples described above.
  • Comparative Example 3 In the same manner as in Example 1, except that an aziridine crosslinking agent (isophthaloylbis-2-methylaziridine) was added in the coating solution used in Comparative Example 2 in an amount of 0.2% by weight in terms of the solid content as shown in Table 2. An acrylic thermosetting pressure-sensitive adhesive layer was obtained and samples for evaluation were produced and evaluated.
  • an aziridine crosslinking agent isophthaloylbis-2-methylaziridine
  • Example 3 the initial adhesive force, the adhesive force after thermal curing, and the presence or absence of an adhesive residual of the pressure- sensitive adhesive films in Examples 1 to 7 and Comparative Examples 1 to 3 are shown. From Table 3, a residual of adhesive was observed after thermal curing in the pressure-sensitive adhesive films of Comparative Examples 1 and 2. In Comparative Example 3, a crosslinking agent was added to improve the cohesive force and the thermal resistance. As a result, residual adhesive was not observed before thermal curing even if the thickness of the pressure-sensitive adhesive is 1 ⁇ m as compared with Comparative Example 2. However, residual adhesive was observed after thermal curing, like Comparative Examples 1 and 2, and a high adhesive force was generated.
  • the pressure-sensitive adhesive films of Examples 1 to 7 have sufficiently high initial adhesive force and, after thermal curing, no residual adhesive, and the film could be released at a very low adhesive force. Therefore, it became apparent that the heat releasable thermosetting pressure-sensitive adhesive film (heat reactive masking tape) of the present invention generates a high adhesive force after applying onto the adherend and that low adhesion attained passing through a thermal curing process enables the film to release easily without causing residual adhesive.
  • Example 8 A thermosetting pressure-sensitive adhesive film having an acrylic thermosetting pressure-sensitive adhesive layer with the composition of Example 3 and a thickness of about 1 ⁇ m was thermally cured at 120°C and 150°C. Thermal curing was conducted in the following manner.
  • the acrylic thermosetting pressure-sensitive adhesive layer with a substrate film and a hard rolled copper foil was interposed between two plates made of stainless steel 304 (JIS BA material) each having a thickness of 2 mm and heated at 120°C for 60 and 120 minutes, or heated at 150°C for 30, 60 and 120 minutes while applying a face pressure of 60 kg/cm .
  • the adhesive force of 180° peel of the sample for evaluation was measured after allowing to stand at room temperature (about 25°C) for one or more hours after thermal curing.
  • thermosetting pressure-sensitive adhesive film still maintains a high adhesive force after thermal curing at 120°C and that the film could be released at very low adhesive force by thermally curing at 150°C or higher. Therefore, the heat releasable thermosetting pressure-sensitive adhesive film (heat reactive masking tape) of the present invention generated low adhesion after being applied applying onto the adherend and passed through a thermal curing process at 150°C or higher and thus enabled the film to release easily.
  • the adhesive film of the present invention generates a releasability upon heating and thus effectively prohibits breakage of an adherend and adhesive residual of adhesive on the adherend. Also, since generation of releasability does not require light such as ultraviolet light, a substrate, which is opaque to light, can be used as the substrate of the adhesive film.

Abstract

The present invention provides a heat releasable thermosetting pressure-sensitive adhesive film which generates a releasability upon heating and thus effectively prohibits breakage of an adherend and adhesive residual to the adherend. The heat releasable thermosetting pressure-sensitive adhesive film comprises a thermally resistant substrate, and on at least one side of the substrate is an acrylic thermosetting pressure-sensitive adhesive layer containing a thermosetting acrylic pressure-sensitive adhesive polymer having an epoxy group and a carboxylic group therein.

Description

HEAT RELEASABLE THERMOSETTING PRESSURE-SENSITIVE
ADHESIVE FILM
Technical Field The present invention relates to a heat releasable thermosetting pressure- sensitive adhesive film. More particularly, it relates to a heat releasable thermosetting pressure-sensitive adhesive film which is useful for masking.
Background of the Invention One of the well-known categories of adhesives is pressure-sensitive adhesives. Pressure-sensitive adhesives have a tack at ambient temperature and can immediately generate adhesion, without need for activation with water, solvent, heat or the like. Many of pressure-sensitive adhesives include processed film-shaped (tape, strap) and sheet-shaped pressure-sensitive adhesives. Hereinafter, these processed pressure-sensitive adhesives are referred to as a "pressure-sensitive adhesive film" or a "pressure-sensitive adhesive sheet". Typical pressure-sensitive adhesive films contain acrylic pressure-sensitive adhesives as a main component, because the acrylic pressure-sensitive adhesive is generally superior in weatherability. Particularly, when the acrylic pressure- sensitive adhesive is crosslinked (hereinafter referred to as a "crosslinked-type acrylic adhesive"), effective heat resistance can be provided. An example of the crosslinked-type acrylic adhesive is disclosed in U.S. Patent No. 3,284,423. This crosslinked-type acrylic adhesive contains (a) 35 to 75% by weight of an acrylate ester having 6 to 15 carbon atoms, (b) 10 to 60% by weight of an alkyl acrylate such as methyl acrylate or ethyl acrylate, (c) 0.1 to 10% by weight of an acid component such as (meth)acrylic acid, itaconic acid or crotonic acid, and (d) 0.1 to 10% by weight of glycidyl (meth)acrylate, and is self-crosslinked at room temperature or upon heating. As a result, the crosslinked-type acrylic pressure- sensitive adhesive can have both cohesive force and a holding force and a sufficiently high adhesive force at high temperature. In the disclosed adhesive, glycidyl (meth)acrylate is preferably present in an amount of 1 to 3% by weight, thereby to impart a desired cohesive force to the above crosslinked-type pressure- sensitive acrylic adhesive. On the other hand, in applications such as masking tape, re-releasability is sometimes required for the pressure-sensitive adhesive film to easily release and remove from the adherend after use. Such a heat releasable thermosetting pressure-sensitive adhesive film typically further contains a heat blowing agent or a heat expanding agent, as disclosed in Japanese Examined Patent Publication
(Kokoku) No. 51-24534, Japanese Unexamined Patent Publication (Kokai) No. 56- 61467; Japanese Unexamined Patent Publication (Kokai) No. 56-61468, Japanese Unexamined Patent Publication (Kokai) No. 56-61469, Japanese Unexamined Patent Publication (Kokai) No. 60-252681, Japanese Unexamined Patent Publication (Kokai) No. 63-186791 and Japanese Unexamined Patent Publication (Kokai) No. 2-305878. The heat blowing agent or the heat expanding agent can reduce an adhesion area between a heat releasable pressure-sensitive adhesive film and an adherend by means of a heat treatment after use and thus releasing and removing the heat releasable pressure-sensitive adhesive film easily from the adherend. The heat blowing agent or the heat expanding agent divides the heat releasable pressure-sensitive adhesive film into separate areas by means of a heat treatment. As a result, areas of the heat releasable pressure-sensitive adhesive film are likely to remain on the adherend.
Japanese unexamined Patent Publication (Kokai) No. 10-25456 discloses a pressure-sensitive adhesive sheet which can easily be released and removed upon heating as described above and generally comprises a pressure-sensitive adhesive layer containing 100 parts by weight of a tacky base polymer, 10 to 900 parts by weight of a thermosetting compound and 0.1 to 10 parts by weight of a thermal polymerization initiator. The base polymer of the pressure-sensitive adhesive sheet enables strong adhesion at the time of use. However, when the pressure-sensitive adhesive sheet is heat-treated once after use, the adhesive force is lowered and it becomes possible to easily release the pressure-sensitive adhesive sheet. The thermosetting compound is three-dimensionally crosslinked by heating to a temperature of 30° to 150°C in the presence of the thermal polymerization initiator such as organic peroxide which lowers the adhesion of the pressure-sensitive adhesive sheet. Although a low-molecular compound or oligomer having at least two carbon-carbon double bonds is commonly used as the thermosetting compound, such a low-molecular compound or oligomer is likely to remain in the pressure-sensitive adhesive layer without being crosslinked, resulting in a residue of adhesive remaining after release.
Japanese National Publication (Kohyo) No. 56-500889 of the PCT Application discloses a pressure-sensitive adhesive sheet which can easily be released upon light irradiation in place of heating. Specifically, this pressure- sensitive adhesive sheet has an epoxy equivalent of 400 to 900, including an epoxy (oxirane ring)-containing acrylic pressure-sensitive adhesive polymer such as glycidyl (meth)acrylate copolymer, and also containing an effective amount of an ionic photoinitiator such as an onium salt compound. Similarly, this pressure- sensitive adhesive sheet also enables strong adhesion at the time of use. When the pressure-sensitive adhesive sheet is irradiated once with light after use, the adhesive force is lowered and it becomes possible to easily release the adhesive sheet. The photoinitiator accelerates the ionic ring-opening polymerization reaction of the oxirane ring and thus tliree-dimensionally crosslinks the oxirane ring-containing monomer of the adhesive sheet. As described above, release and removal of the photocrosslinkable adhesive sheet from an adherend requires light irradiation through the substrate and/or adherend. Therefore, the use of this pressure-sensitive adhesive sheet puts a restriction that the substrate and/or the adherend that it must have light transmission properties.
An object of the present invention is to provide a heat releasable thermosetting pressure-sensitive adhesive film, which can avoid the light transmission requirement for use and thus effectively prohibit breakage of an adherend and deposition of residual adhesive on the adherend.
Summary of the Invention
The present invention provides a heat releasable thermosetting pressure- sensitive adhesive film, comprising a thermally resistant substrate, and an acrylic thermosetting pressure-sensitive adhesive layer on at least one surface of said substrate, wherein the acrylic thermosetting pressure-sensitive adhesive layer contains a thermosetting acrylic pressure-sensitive adhesive polymer having an epoxy group and a carboxylic group in the molecule. This adhesive film generates releasability upon heating and thus effectively prohibiting breakage of an adherend and deposition of residual adhesive to the adherend upon release. Also, since generation of the releasability does not require light such as ultraviolet light, an opaque substrate can be used as the substrate of the adhesive film.
Detailed Description of the Invention The heat releasable thermosetting pressure-sensitive adhesive film of the present invention (hereinafter referred to as an "adhesive film") will be further explained by way of preferred embodiments. It is to be understood by a person with an ordinary skill in the art that the present invention is not limited to the described embodiments.
The pressure-sensitive adhesive film of the present invention comprises a thermally resistant substrate, and an acrylic thermosetting pressure-sensitive adhesive layer on at least one surface of the substrate. The thermally resistant substrate supports the acrylic thermosetting pressure-sensitive adhesive layer. The thermally resistant substrate may support the acrylic thermosetting pressure- sensitive adhesive layer only on one surface thereof, or may supports the acrylic thermosetting pressure-sensitive adhesive layer on both surfaces thereof. Commonly, the thermally resistant substrate do not necessarily have light transmission properties and it is preferred to appropriately select the material according to the heating temperature of the pressure-sensitive adhesive film, namely, the curing temperature of the acrylic thermosetting pressure-sensitive adhesive layer. For example, when the heating temperature or the curing temperature is lower than 150°C, polyethylene terephthalate (PET) can be selected as a thermally resistant substrate. When the heating temperature or the curing temperature is 150° to 200°C, preferred thermally resistant substrate include polyether imide, polyether sulfone, polyethylene naphthalate or polyphenylene sulfide. Further, when the heating temperature or the curing temperature is 200°C or higher, the preferred thermally resistant substrate include polyether ether ketone, polyamideimide or polyimide. Taking account of the availability and chemical stability, PET, polyethylene naphthalate, polyphenylene sulfide and polyimide are particularly preferred because of high versatility. The thermally resistant substrate preferably has a thickness of 1 to 200 μm, and more preferably 1 to 25 μm, due to handling and availability considerations.
The acrylic thermosetting pressure-sensitive adhesive layer contains a thermosetting acrylic pressure-sensitive adhesive polymer having an epoxy group and a carboxylic group in the molecule. Such a thermosetting acrylic pressure- sensitive adhesive polymer has a glass transition temperature of -80° to 25°C in order to be provided with tackiness.
According to the present invention, the thermosetting acrylic pressure- sensitive adhesive polymer is cured by rapidly forming a three-dimensional crosslink between the epoxy group and the carboxylic group upon heating, as shown in the following scheme.
Chemical Formula 1
Figure imgf000006_0001
Δ
Figure imgf000006_0002
As a result of the crosslinking, the tack is lowered and it becomes possible to easily release the pressure-sensitive adhesive film from an adherend.
Preferred thermosetting acrylic pressure-sensitive adhesive polymers have an epoxy group in an amount of from 2 mol % to 50 mol% and the molar ratio of the epoxy group to the carboxylic group is 0.15 to 4.0. When the epoxy group is present in an amount of more than 50 mol%, the pressure-sensitive adhesive film has lower adhesion to the adherend and the pressure-sensitive adhesive film is more likely to be released during use. On the other hand, when the epoxy group is present in an amount of less than 2 mol% or the molar ratio is not within a range from 0.15 to 4.0, the thermosetting reaction of the thermosetting acrylic pressure- sensitive adhesive polymer is likely to become insufficient. As a result, the adhesive force of the pressure-sensitive adhesive film is heightened and it becomes difficult to re-release.
The thermosetting acrylic pressure-sensitive adhesive polymer preferably has a weight-average molecular weight of 10,000 to 1,000,000 as measured by gel permeation chromatography based on polystyrene standard. Because, when the weight-average molecular weight is about 10,000 or less, the cohesive force of the thermosetting acrylic pressure-sensitive adhesive polymer is low and this causes an adhesive residual to remain on the adherend. On the other hand, when the weight- average molecular weight is about 1,000,000 or more, stable coating is difficult to perform because the viscosity of the thermosetting acrylic pressure-sensitive adhesive polymer is too high.
Typical thermosetting acrylic pressure-sensitive adhesive polymers are copolymers derived from a mixed monomer containing (meth)acrylate having an epoxy group such as glycidyl group and (meth)acrylate having a carboxylic group. The mixed monomer may contain monomers other than (meth)acrylate having an epoxy group and (meth)acrylate having a carboxylic group. Such a monomer is not specifically limited, but glass transition temperature of the resulting copolymer should be within a range from -80° to 25°C. When the glass transition temperature of a homopolymer is within a range from -80° to 0°C, it is easy to meet the above conditions and a non-substituted or substituted alkyl (meth)acrylate is preferably used as the monomer. Such a monomer commonly has 2 to 15 carbon atoms and includes, for example, C2-8 alkyl acrylate monomer, C8-15 alkyl methacrylate monomer, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate and alkoxyalkyl acrylate. Specific examples thereof include C2-8 alkyl acrylate such as ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, 2- methylbutyl acrylate, isoamyl acrylate or n-octyl acrylate; C8-15 alkyl methacrylate such as isooctyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate and/or n-octyl methacrylate; and phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, methoxyethyl acrylate and ethoxyethyl acrylate.
The (meth)acrylate monomer having an epoxy group is not specifically limited so long as it can crosslink with a carboxylic group of a (meth)acrylate monomer having a carboxylic group and can includes, for example, glycidyl (meth)acrylate and/or (meth)acrylate having an alicyclic epoxy group. Such a (meth)acrylate monomer having an epoxy group is commercially available, for example, from DAICEL CHEMICAL INDUSTRIES, LTD. under the trade name ofM100 and A200.
Similarly, the (meth)acrylate monomer having a carboxylic group can include, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, 2-acryloyloxy ethylsuccinic acid (HOA-MS, manufactured by Kyoei Chemical Co., Ltd.), 2-acryloyloxyethylphthalic acid (HOA-MPL, manufactured by Kyoei Chemical Co., Ltd.), ω-carboxy-polycaprolactone (repeating unit (n) ^ 2) monoacrylate (M-5300, manufactured by TOAGOSEI CO., LTD.), phthalic acid monohydroxyethyl acrylate (M-5400, manufactured by TOAGOSEI CO., LTD.) and/or acrylic acid dimer (M-5600, manufactured by TOAGOSEI CO., LTD.). Preferred mixed monomer contains a (meth)acrylate having an epoxy group in an amount of from 4 to 35% by weight based on the total weight and the molar ratio of the (meth)acrylate having an epoxy group to the (meth)acrylate having a carboxylic group is 0.15 to 4.0 for the following reason. That is, as described above, the thermosetting acrylic pressure-sensitive adhesive polymer contains the epoxy group in an amount of 2 to 50 mol% and the molar ratio of the epoxy group to the carboxylic group is 0.15 to 4.0.
The above mixed monomer can be radically polymerized in the presence of a polymerization initiator based on an azo compound or a peroxide. As the polymerization method, conventionally known methods such as solution polymerization method, emulsion polymerization method, suspension polymerization method and bulk polymerization method can be used. Among these methods, solution polymerization method is particularly preferred because an acrylic thermosetting pressure-sensitive adhesive layer having a thickness described hereinafter can be effectively formed on the thermally resistant substrate. According to the present invention, the solution polymerization is usually conducted in a nitrogen atmosphere. The polymerization temperature and the polymerization time are preferably 30° to 80°C and 1 to 24 hours, respectively, so gelation of the thermosetting acrylic pressure-sensitive adhesive polymer is effectively prohibited.
The acrylic thermosetting pressure-sensitive adhesive layer preferably has a thickness of 0.1 to 10 μm. When the acrylic thermosetting pressure-sensitive adhesive layer has a thickness of less than 0.1 μm, the resulting film hardly conforms to the adherend when contacted and is likely to be released during use. On the other hand, when the acrylic thermosetting pressure-sensitive adhesive layer has a thickness of more than about 10 μm, it becomes hard to sufficiently reduce the adhesive force after thermal curing. Also the solvent or chemical penetrates into the space between the pressure-sensitive adhesive film and the adherend during use and delamination of the pressure-sensitive adhesive film and contamination of the adherend are likely to occur.
Similarly, as far as the object and effect of the present invention are not adversely affected, the amount of the thermosetting acrylic pressure-sensitive adhesive polymer is not limited and such a pressure-sensitive adhesive polymer is preferably present in an amount of 70% by weight or more in the acrylic thermosetting pressure-sensitive adhesive layer. When the thermosetting acrylic pressure-sensitive adhesive polymer is present in an amount of less than 70% by weight, the adhesive force of the pressure-sensitive adhesive film tends to be only minimally reduced. The acrylic thermosetting pressure-sensitive adhesive layer can contain a small amount of an acrylic polymer, in addition to the thermosetting acrylic pressure-sensitive adhesive polymer.
A method for production of the pressure-sensitive adhesive film is as follows. First, the thermosetting acrylic pressure-sensitive adhesive polymer prepared as described above is dissolved in an organic solvent to prepare a coating solution. As the organic solvent, ethyl acetate, methyl ether ketone (MEK), toluene or a mixture thereof can be commonly used. Subsequently, the coating solution is uniformly coated on the thermally resistant substrate by a die coating method, a knife coating method, a bar coating method or other conventionally known coating methods. Since most of the coating solution is made from the above thermosetting acrylic pressure-sensitive adhesive polymer, it can be easily uniformly coated. Then, the solvent is removed by drying the coating solution, together with the thermally resistant substrate, to obtain a pressure-sensitive adhesive film.
The pressure-sensitive adhesive film of the present invention can be used as a masking of the adherend such as electric circuit substrate. First, the pressure- sensitive adhesive film of the present invention is applied at a predetermined position of an electric circuit substrate (hereinafter referred merely to as a "substrate"). Preferably, the pressure-sensitive adhesive film is applied to the electric circuit substrate while heating to 80° to 120°C, so the pressure-sensitive adhesive film sufficiently adheres to the electric circuit substrate. Then, the electric circuit substrate is subjected to an etching process at 100°C or lower to provide an electric circuit on the substrate. At this time, the portion coated with the pressure-sensitive adhesive film of the electric circuit substrate is protected by the pressure-sensitive adhesive film at a high adhesive force, and thus prohibits permeation of an etching chemical solution into the adhesive surface. Then, the electric circuit substrate is washed with hot water or an organic solvent. During the washing process, the pressure-sensitive adhesive film also effectively prohibits the permeation of an etching chemical solution into the adhesive surface due to the thermal resistance and the solvent resistance of the adhesive film. The electric circuit on the substrate is sealed with an epoxy resin and then the epoxy resin is cured by heating to 150° to 250°C. Since the pressure-sensitive adhesive film is also heated, the pressure- sensitive adhesive film loses most of its adhesion as a result of curing of the thermosetting acrylic pressure-sensitive adhesive polymer. According to the present invention, the pressure-sensitive adhesive film loses adhesion due to heating regardless of the presence or absence of light transmission properties of the supporting substrate of the pressure-sensitive adhesive film and the adherend. Therefore, the supporting substrate of the pressure-sensitive adhesive film and the adherend can be widely varied. As described above, since the thermosetting acrylic pressure-sensitive adhesive polymer occupies almost the entire acrylic thermosetting pressure-sensitive adhesive layer and the adhesive layer is fairly thin, unreacted monomer is less likely to remain, and little or no outgas is evolved. As a result, the pressure-sensitive adhesive film can be easily released without causing residual adhesive on the electric circuit substrate.
The pressure-sensitive adhesive film of the present invention is effectively used to protect a surface of a substrate such as metallic foil or plate from etching, wherein the opposite surface of the substrate has an electric circuit on its surface. As far as the object and effect of the present invention are not adversely affected, the thermosetting acrylic pressure-sensitive adhesive polymer may be formed by copolymerizing a copolymerizable monomer other than a non- substituted or substituted alkyl (meth)acrylate having a glass transition temperature of -80° to 0°C and an acrylate monomer having an epoxy group such as glycidyl group and/or a carboxylic group. An example of such a copolymerizable monomer is a (meth)acrylate monomer wherein a glass transition temperature of a homopolymer is 0°C or higher. Specific examples thereof include alkyl (meth)acrylate such as methyl (meth)acrylate, ethyl methacrylate, n-butyl (meth)acrylate, isobornyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate or lauryl (meth)acrylate; hydroxyalkyl (meth)acrylate such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate or hydroxybutyl (meth)acrylate; and polar monomer such as acrylamide, dimethylaminoethyl (meth)acrylate, N- vinyl pyrrolidone, 2-hydroxy-3-phenoxypropyl acrylate, dimethylaminopropylamide, N,N-dimethylacrylamide, isopropylacrylamide or N-methylolacrylamide.
The acrylic thermosetting pressure-sensitive adhesive layer does not need to be limited to a single thermosetting acrylic pressure-sensitive adhesive polymer and may contain a thermosetting acrylic mixed pressure-sensitive adhesive polymer (mixed pressure-sensitive adhesive polymer) containing the following plural pressure-sensitive adhesive polymers:
(1) a first acrylic pressure-sensitive adhesive polymer derived from a monomer containing a (meth)acrylate monomer having a glycidyl group, and
(2) a second acrylic pressure-sensitive adhesive polymer derived from a monomer containing a (meth)acrylate monomer having a carboxylic group.
Unlike the single thermosetting acrylic pressure-sensitive adhesive polymer, the respective pressure-sensitive adhesive polymers of such a mixed pressure-sensitive adhesive polymer are separately polymerized and the mixed pressure-sensitive adhesive polymer can be stored until just before coating. Therefore, the mixed pressure-sensitive adhesive polymer will barely gel upon polymerization and the coating solution has a long life as compared with the single thermosetting acrylic pressure-sensitive adhesive polymer.
Each of the first acrylic pressure-sensitive adhesive polymer and the second acrylic pressure-sensitive adhesive polymers, which constitutes the mixed pressure-sensitive adhesive polymer, has a glass transition temperature of -80° to 25°C in order to secure the tackiness of the pressure-sensitive adhesive layer similar to the case of the above single thermosetting acrylic pressure-sensitive adhesive polymer; likewise, the first and second acrylic pressure-sensitive adhesives each have a weight-average molecular weight of from 10,000 to 1,000,000. Further, the monomers constituting the mixed pressure-sensitive adhesive polymer and the proportion thereof are the same as in case of the single thermosetting acrylic pressure-sensitive adhesive polymer and, the acrylic thermosetting pressure-sensitive adhesive layer contains the mixed pressure- sensitive adhesive polymer in the same amount as in case of the single thermosetting acrylic pressure-sensitive adhesive polymer.
Preferably, a crosslinking agent capable of crosslinking carboxyl groups with each other is added in an amount of less than 3% by weight in the acrylic thermosetting pressure-sensitive adhesive layer. According to the present invention, such a crosslinking agent is preferably capable of crosslinking carboxylic groups with each other at 100°C or lower as that enables the acrylic thermosetting pressure-sensitive adhesive layer to be provided with a high cohesive force and thermal resistance before thermal curing. A preferred crosslinking agent is an isocyanate crosslinking agent, which is commercially available from NIPPON POLYURETHANE INDUSTRY CO., LTD. under the trade name of Colonate L, an aziridine crosslinking agent, which is commercially available from NIPPON SHOKUBAI CO., LTD. under the trade name of Chemitite PZ-33 or made of bisamide (isophthaloylbis-2-methylaziridine), a polyfunctional epoxy resin crosslinking agent, which is commercially available from The Soken Chemical & Engineering Co., Ltd. under the trade name of E-AX, or a metal chelete crosslinking agent, which is commercially available from The Soken Chemical & Engineering Co., Ltd. under the trade name of M-5A. The crosslinking can be efficiently conducted in the drying step together with the thermally resistant substrate. Preferably, the crosslinking agent is added in an amount of less than 3% by weight in the acrylic thermosetting pressure-sensitive adhesive layer. If the crosslinking agent is added in an amount of more than 3% by weight, the acrylic thermosetting pressure-sensitive adhesive layer tends to lose the adhesion.
If the adhesion (anchoring property) between the thermally resistant substrate and the acrylic thermosetting pressure-sensitive adhesive layer is poor, delamination sometime occurs between the thermally resistant substrate and the acrylic thermosetting pressure-sensitive adhesive layer upon releasing the adhesive film from the adherend. To prevent such delamination, one surface of the thermally resistant substrate may be subjected to a surface treatment for easy bonding using conventionally known technique in order to improve the anchoring property with the acrylic thermosetting pressure-sensitive adhesive layer. Preferred examples of the surface treatment include physical treatments such as corona discharge treatment, flame treatment, plasma treatment or ultraviolet irradiation treatment; or a wet chemical treatment. A corona discharge treatment is particularly preferred because a thermally resistant substrate subjected to the corona discharge treatment is commercially available and readily available.
If the surface treatment is not conducted or the anchoring property is poor even after the surface treatment, a primer treatment may be conducted to further improve the anchoring property. The primer treatment refers to a treatment of providing a coating layer (primer layer) having excellent adhesion with both the thermally resistant substrate and the acrylic thermosetting pressure-sensitive adhesive layer, on the thermally resistant substrate, and the acrylic thermosetting pressure-sensitive adhesive layer can be provided on the primer layer. In that case, the thickness of the primer layer is preferably 0.1 to 2 μm and the total thickness of the acrylic thermosetting pressure-sensitive adhesive layer and the primer layer is preferably 0.2 to 10 μm by the following reason. If the thickness of the primer layer were 0.1 μm or less, it will not be effective. On the other hand, when the thickness is 2 μm or more, the solvent penetrates and both delamination of the pressure-sensitive adhesive film and contamination of the adherend are likely to occur.
The opposing surface of the thermally resistant substrate may be subjected to a release treatment. When the opposing surface is subjected to the release treatment, the heat releasable thermosetting pressure-sensitive adhesive film of the present invention can be stored in the form of a rolled tape. Silicone release agents, fluorine release agents, or a (meth)acrylic release agent having a long-chain alkyl group and a vinyl ether release agent having a long-chain alkyl group can be used as a release agent herein.
As long as the object and effect of the present invention are not adversely affected, the acrylic thermosetting pressure-sensitive adhesive layer may contain further additives such as antioxidants, ultraviolet absorbers, fillers (for example, inorganic fillers, conductive particles or pigments), lubricants such as waxes, tackifiers, plasticizers, curing accelerators and fluorescent dyes.
Examples The present invention will be explained by way of examples. It is to be understood by a person with an ordinary skill in the art that the present invention is not limited to the examples.
Examples 1 to 3 and Comparative Examples 1 to 2
1. Preparation of acrylic pressure-sensitive adhesive polymer
As shown in the left column of Table 1, the following chemicals were mixed in a predetermined composition ratio to prepare a monomer mixture: butyl acrylate (manufactured by Mitsubishi Chemical), acrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., JIS (Japanese Industrial Standard) guaranteed special grade reagent), glycidyl methacrylate (manufactured by manufactured by NOF CORPORATION under the trade name of Nissan Blenmer G), phenoxyethyl acrylate (manufactured by OSAKA ORGANIC CHEMICAL INDUSTRY LTD. under the trade name of Biscoat #192) and 2-hydroxy-3- phenoxypropyl acrylate (manufactured by TOAGOSEI CO., LTD. under the trade name ofM-5700). After adding the monomer mixture in a solvent, a polymerization initiator (manufactured by Wako Pure Chemical Industries, Ltd., JIS guaranteed special grade reagent) of 2,2'-azobis(2,4-dimethylvaleronitrile)(trade name: V-65) was further added in an amount of 0.2% by weight based on the monomer and the mixture was polymerized in a nitrogen atmosphere at 50°C for 24 hours to prepare an acrylic pressure sensitive copolymer which has a solid content of 30% by weight. As shown in the right column of Table 1, the solvent used varied depending on the monomer mixture. For example, a mixed solvent prepared by mixing ethyl acetate of a JIS guaranteed special grade, which is commercially available from Wako Pure Chemical Industries, Ltd., with methyl ethyl ketone in a weight ratio of 4:1 was used for the monomer mixtures of Examples 1 to 3, while the solvent of ethyl acetate was used for the monomer mixtures of Comparative Examples 1 and 2.
Table
Figure imgf000015_0001
(Notes)
BA: butyl acrylate; GMA: glycidyl methacrylate; AA: acrylic acid; MEK: methyl ethyl ketone; PEA: phenoxyethyl acrylate; M-5700: 2-hydroxy-3 -phenoxypropyl acrylate
2. Production of heat releasable thermosetting pressure-sensitive adhesive film Using each of the above acrylic pressure-sensitive adhesive polymers, a thermosetting pressure-sensitive adhesive film was produced in the following manner. First, each of the acrylic pressure-sensitive adhesive polymers was diluted with a mixed solvent of methyl ethyl ketone (MEK) and toluene in a weight mixing ratio of 55:45 to prepare coating solutions each having a solid content of 5% by weight and 10% by weight. The coating solution was knife-coated on the corona-treated surface of a polyphenylene sulfide substrate film (manufactured by Toray under the trade name of Torelina) having a thickness of 12 μm, and having one surface which has been corona treated). The mixed solvent was then removed by drying in an oven at 100°C for 10 minutes to form an acrylic thermosetting pressure-sensitive adhesive layer.
The thickness of the acrylic thermosetting pressure-sensitive adhesive layer was measured. When using the coating solution having a solids content of 10%, the thickness of the acrylic thermosetting pressure-sensitive adhesive layer was about 5 μm. When using the coating solution having a solids content of 5%, the thickness of the acrylic thermosetting pressure-sensitive adhesive layer was about 1 μm.
A release film of polyethylene terephthalate subjected to a release treatment using silicone (manufactured by Teijin DuPont Films Japan Limited, under the trade name of Purex A31, thickness: 38 μm) was laminated onto the acrylic thermosetting pressure-sensitive adhesive layer, and the resulting laminate was used to produce samples for evaluation described hereinafter.
3. Production of samples for evaluation and measurement of adhesive force
Using the above heat releasable thermosetting pressure-sensitive adhesive film, samples for evaluation were produced in the following manner and the adhesive force was measured.
After removing the release film, an acrylic thermosetting pressure-sensitive adhesive layer was thermally laminated on a hard rolled copper foil having a thickness of 35 μm manufactured by Nippon Foil Mfg. Co., Ltd. under the following conditions: heating temperature of 80°C, a line speed of 2 meters per minute and a nip pressure of about 1.5 to 2 kg/cm, to obtain samples for evaluation. Each of the samples was allowed to stand at room temperature (at about 25 °C) for 24 or more hours and an adhesive force (initial adhesive force) of 180° peel was determined by releasing the acrylic thermosetting pressure-sensitive adhesive layer together with the film substrate, at 25°C at a speed of 300 mm/minute. After thermal curing of the acrylic thermosetting pressure-sensitive adhesive layer, the adhesive force (adhesive force after thermal curing) of 180° peel of each sample for evaluation was also determined. The thermal curing was conducted in the following manner. The acrylic thermosetting pressure-sensitive adhesive layer with a substrate film and a hard rolled copper foil, was interposed between two plate made of stainless steel 304 (JIS BA material) each having a thickness of 2 mm and then heated at 190°C for 90 minutes while applying a face pressure of 60 kg/cm2. The adhesive force of 180° peel of the sample for evaluation was measured after allowing to stand at room temperature (about 25 °C) for one or more hours after thermal curing. Upon measurement, the presence or absence of a residual of adhesive to the copper foil was visually observed.
Example 4 This sample was formed in the same manner as in Example 1, except that an aziridine crosslinking agent (isophthaloylbis-2-methylaziridine) was added into the coating solution used in Example 1 in an amount of 0.2% by weight in terms of the solid content as shown in Table 2. An acrylic thermosetting pressure-sensitive adhesive layer was obtained and samples for evaluation were produced and evaluated.
Examples 5 to 7 These samples were formed in the same manner as in Example 1, except that the composition shown in Table 2 was used, acrylic thermosetting pressure- sensitive adhesive layers were obtained and samples for evaluation were produced and evaluated. In Examples 6 and 7, the polymerization temperature was controlled to 55°C and acrylic pressure-sensitive adhesive polymers having a solid content of 35% were obtained. The resulting polymer was bar-coated on a PPS film having a thickness of 16 μm in place of the polyphenylene sulfide (PPS) film having a thickness of 12 μm with a coating thickness of about 1 μm. In the table, MMA denotes methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., JIS (Japanese Industrial Standard) guaranteed special grade reagent) and M- 5300 denotes ω -carboxy-polycaprolactone (repeating unit (n) ^ 2) monoacrylate (M-5300, manufactured by TOAGOSEI CO., LTD.), and other monomers are the same as those used in other examples described above. Comparative Example 3 In the same manner as in Example 1, except that an aziridine crosslinking agent (isophthaloylbis-2-methylaziridine) was added in the coating solution used in Comparative Example 2 in an amount of 0.2% by weight in terms of the solid content as shown in Table 2. An acrylic thermosetting pressure-sensitive adhesive layer was obtained and samples for evaluation were produced and evaluated.
Table 2
Figure imgf000018_0001
In Table 3, the initial adhesive force, the adhesive force after thermal curing, and the presence or absence of an adhesive residual of the pressure- sensitive adhesive films in Examples 1 to 7 and Comparative Examples 1 to 3 are shown. From Table 3, a residual of adhesive was observed after thermal curing in the pressure-sensitive adhesive films of Comparative Examples 1 and 2. In Comparative Example 3, a crosslinking agent was added to improve the cohesive force and the thermal resistance. As a result, residual adhesive was not observed before thermal curing even if the thickness of the pressure-sensitive adhesive is 1 μm as compared with Comparative Example 2. However, residual adhesive was observed after thermal curing, like Comparative Examples 1 and 2, and a high adhesive force was generated. On the other hand, the pressure-sensitive adhesive films of Examples 1 to 7 have sufficiently high initial adhesive force and, after thermal curing, no residual adhesive, and the film could be released at a very low adhesive force. Therefore, it became apparent that the heat releasable thermosetting pressure-sensitive adhesive film (heat reactive masking tape) of the present invention generates a high adhesive force after applying onto the adherend and that low adhesion attained passing through a thermal curing process enables the film to release easily without causing residual adhesive. Table 3
Figure imgf000019_0001
(Notes)
All units of the adhesive force in the table represent N/50 mm. "Contamination" means a residual of adhesive to the adherend.
Example 8 A thermosetting pressure-sensitive adhesive film having an acrylic thermosetting pressure-sensitive adhesive layer with the composition of Example 3 and a thickness of about 1 μm was thermally cured at 120°C and 150°C. Thermal curing was conducted in the following manner. The acrylic thermosetting pressure-sensitive adhesive layer with a substrate film and a hard rolled copper foil, was interposed between two plates made of stainless steel 304 (JIS BA material) each having a thickness of 2 mm and heated at 120°C for 60 and 120 minutes, or heated at 150°C for 30, 60 and 120 minutes while applying a face pressure of 60 kg/cm . The adhesive force of 180° peel of the sample for evaluation was measured after allowing to stand at room temperature (about 25°C) for one or more hours after thermal curing.
Table 4: Adhesive force (N/50 mm) after thermal curing
Figure imgf000020_0001
As is apparent from Table 4, the thermosetting pressure-sensitive adhesive film still maintains a high adhesive force after thermal curing at 120°C and that the film could be released at very low adhesive force by thermally curing at 150°C or higher. Therefore, the heat releasable thermosetting pressure-sensitive adhesive film (heat reactive masking tape) of the present invention generated low adhesion after being applied applying onto the adherend and passed through a thermal curing process at 150°C or higher and thus enabled the film to release easily.
The previous examples show that the adhesive film of the present invention generates a releasability upon heating and thus effectively prohibits breakage of an adherend and adhesive residual of adhesive on the adherend. Also, since generation of releasability does not require light such as ultraviolet light, a substrate, which is opaque to light, can be used as the substrate of the adhesive film.

Claims

What is Claimed is:
1. A heat releasable thermosetting pressure-sensitive adhesive film, comprising: a thermally resistant substrate, and an acrylic thermosetting pressure-sensitive adhesive layer on at least one surface of said substrate, wherein said acrylic thermosetting pressure-sensitive adhesive layer contains a thermosetting acrylic pressure-sensitive adhesive polymer having an epoxy group and a carboxylic group in the molecule.
2. A heat releasable thermosetting pressure-sensitive adhesive film according to claim 1, wherein said thermosetting acrylic pressure-sensitive adhesive polymer has a glass transition temperature of -80° to 25°C.
3. A heat releasable thermosetting pressure-sensitive adhesive film according to claim 1, wherein a monomer including said epoxy group is present in an amount of 4 to 35% by weight in said thermosetting acrylic pressure-sensitive adhesive polymer, and wherein the molar ratio of said epoxy group to said carboxylic group is from 0.15 to 4.0.
4. A heat releasable thermosetting pressure-sensitive adhesive film according to any one of claims 1 to 3, wherein said thermosetting acrylic pressure- sensitive adhesive polymer is a copolymer derived from a mixed monomer comprising (meth)acrylate having an epoxy group and (meth)acrylate having a carboxylic group.
5. A heat releasable thermosetting pressure-sensitive adhesive film according to claim 3, wherein said mixed monomer further comprises (meth)acrylate having an alkyl group having 2 to 15 carbon atoms.
6. A heat releasable thermosetting pressure-sensitive adhesive film according to any one of claims 1 to 5, wherein said acrylic thermosetting pressure- sensitive adhesive layer has a thickness of 0.1 to 10 μm.
7. A heat releasable thermosetting pressure-sensitive adhesive film according to any one of claims 1 to 6, wherein said thermally resistant substrate comprises at least one of thermally resistant material selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide and polyimide.
8. A heat releasable thermosetting pressure-sensitive adhesive film according to any one of claims 1 to 7, wherein said thermally resistant substrate has a thickness of 1 to 200 μm.
PCT/US2002/036467 2002-01-31 2002-11-14 Heat releasable thermosetting pressure-sensitive adhesive film WO2003064552A1 (en)

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TWI718827B (en) 2019-12-25 2021-02-11 達邁科技股份有限公司 Composite film for LED wafer level packaging

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