WO2025023118A1 - 粘着シート - Google Patents

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Publication number
WO2025023118A1
WO2025023118A1 PCT/JP2024/025646 JP2024025646W WO2025023118A1 WO 2025023118 A1 WO2025023118 A1 WO 2025023118A1 JP 2024025646 W JP2024025646 W JP 2024025646W WO 2025023118 A1 WO2025023118 A1 WO 2025023118A1
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WIPO (PCT)
Prior art keywords
adhesive layer
weight
pressure
less
sensitive adhesive
Prior art date
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Pending
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PCT/JP2024/025646
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English (en)
French (fr)
Japanese (ja)
Inventor
健太 熊倉
哲士 本田
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nitto Denko Corp
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Nitto Denko Corp
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Application filed by Nitto Denko Corp filed Critical Nitto Denko Corp
Priority to CN202480048373.8A priority Critical patent/CN121548619A/zh
Priority to JP2025535762A priority patent/JPWO2025023118A1/ja
Priority to KR1020267005402A priority patent/KR20260041874A/ko
Publication of WO2025023118A1 publication Critical patent/WO2025023118A1/ja
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

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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
    • C09J201/00—Adhesives based on unspecified macromolecular compounds
    • C09J201/02—Adhesives based on unspecified macromolecular compounds characterised by the presence of specified groups, e.g. terminal or pendant functional groups
    • 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
    • C09J4/00—Adhesives based on organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond ; adhesives, based on monomers of macromolecular compounds of groups C09J183/00 - C09J183/16
    • 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]

Definitions

  • the present invention relates to a pressure-sensitive adhesive sheet.
  • This application claims priority based on Japanese Patent Application No. 2023-122022, filed on July 26, 2023, the entire contents of which are incorporated herein by reference.
  • adhesives also called pressure-sensitive adhesives; the same applies below
  • Adhesives are in a soft solid (viscoelastic) state at temperatures near room temperature, and have the property of easily adhering to an adherend when pressure is applied.
  • Adhesives are widely used in various fields in the form of a supported adhesive sheet having an adhesive layer on a support, or in the form of a support-less adhesive sheet without a support, because of the ease of application to an adherend. Some such adhesives are used by adhering to an adherend, and are removed from the adherend after their adhesive purpose has been completed. For example, in the backgrinding process in which the backside of a semiconductor wafer is ground to a desired thickness, an adhesive sheet is used to fix the semiconductor wafer to a processing table and to protect the side opposite the grinding surface (for example, Patent Document 1).
  • adhesive sheets used for fixing an adherend (object to be processed) during processing are required to have good adhesion while adhering to the adherend, and to have the ability to be easily peeled off from the adherend after the adhesive purpose is completed.
  • an adhesive having such performance an adhesive that has a certain adhesive strength during adhesion and fixation and can reduce the peel strength at an appropriate time can be used.
  • an adhesive that can reduce the peel strength an ultraviolet irradiation peelable adhesive that reduces the peel strength by irradiating ultraviolet rays is known.
  • an adhesive sheet for fixing an adherend during processing can be used in a manner that adheres and fixes the object to be processed to a part of the surface (adhesive surface) of the adhesive layer, and adheres and fixes a tool or the like that is not to be processed to another part, and after processing the object to be processed, the object to be processed is peeled off and removed from the adhesive surface, while the tool or the like maintains its state of being adhered and fixed on the adhesive surface.
  • ultraviolet light can be irradiated only to the above-mentioned partial area where the workpiece is adhered and fixed, thereby selectively making the above-mentioned partial area lightly peelable while minimizing the effect on the adhesive strength of the other areas.
  • ultraviolet irradiation peelable adhesives have limitations such as being unable to be applied to adherends that are not transparent to light, and the need for ultraviolet irradiation equipment to reduce the peel strength.
  • an adhesive configured so that its peel strength is reduced by heating is used as the adhesive capable of reducing the peel strength, the above limitations do not apply, but unlike ultraviolet irradiation, it is difficult to selectively heat only a partial area of the adhesive layer.
  • the present invention was created in consideration of the above circumstances, and aims to provide an adhesive sheet in which some areas exhibit a lower peel strength than other areas after heating.
  • the pressure-sensitive adhesive sheet has a post-heat peel strength ratio (Fb1/Fa1) of more than 1.0, calculated from the post-heat peel strength Fa1 [N/20 mm] measured in an environment of 23°C and 50% RH after the first pressure-sensitive adhesive layer is attached to a glass plate and heated at 180°C for 30 minutes, and the post-heat peel strength Fb1 [N/20 mm] measured in an environment of 23°C and 50% RH after the second pressure-sensitive adhesive layer is attached to a glass plate and heated at 180°C for 30 minutes.
  • Fb1/Fa1 post-heat peel strength ratio
  • the first region of the adhesive surface is exposed to the first adhesive layer (thermosetting adhesive layer) which has a large increase in gel fraction due to heating (Ga1-Ga0) and a high gel fraction Ga1 after heating, and therefore can exhibit a peel force reduction effect due to heating (easy peelability due to heating).
  • the peel force ratio after heating (Fb1/Fa1) is greater than 1.0, the second region where the second adhesive layer is exposed can maintain the necessary peel force even after heating.
  • the first adhesive layer preferably has a Young's modulus increase ratio (Ya1/Ya0) of 50 or more, calculated from the pre-heat Young's modulus Ya0 [MPa] measured in an environment of 23°C and 50% RH and the post-heat Young's modulus Ya1 [MPa] measured in an environment of 23°C and 50% RH after heating at 180°C for 30 minutes.
  • Young's modulus increase ratio the higher the Young's modulus increase ratio, the higher the degree of hardening of the adhesive layer due to heating, and the easier it tends to be to obtain excellent heat-peelability in the first region of the adhesive surface.
  • the pre-heating Young's modulus Ya0 [MPa] is preferably 0.01 MPa to 1 MPa. With an adhesive sheet having a pre-heating Young's modulus Ya0 in the above range, it is easy to obtain a peel force that can adequately bond and fix an adherend in the first region of the adhesive surface.
  • the pressure-sensitive adhesive sheet disclosed herein can be preferably implemented in such an embodiment that the post-heat peel strength reduction rate A of the first pressure-sensitive adhesive layer is higher than 50% (e.g., higher than 50% and less than 99.9%).
  • the first adhesive layer preferably contains a thermal polymerization initiator.
  • a thermal polymerization initiator By including a thermal polymerization initiator in the first adhesive layer, it is possible to promote thermal curing by heating.
  • the second region is preferably formed surrounding the outside of the first region.
  • the first adhesive layer is partially laminated on the second adhesive layer.
  • Such an adhesive layer with a partially laminated structure makes it easy to form an adhesive surface including a first region where the first adhesive layer is exposed and a second region where the second adhesive layer is exposed.
  • FIG. 1 is a plan view showing a schematic example of an adhesive sheet.
  • the "base polymer” of an adhesive refers to the main component of the rubber-like polymer contained in the adhesive.
  • the rubber-like polymer refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature.
  • the "main component” refers to a component that is contained in an amount of more than 50% by weight, unless otherwise specified.
  • acrylic polymer refers to a polymer that contains, as a monomer unit constituting the polymer, a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule.
  • an acrylic polymer is defined as a polymer that contains a monomer unit derived from an acrylic monomer.
  • acrylic monomer refers to a monomer having at least one (meth)acryloyl group in one molecule.
  • (meth)acryloyl group refers collectively to acryloyl groups and methacryloyl groups. Therefore, the concept of acrylic monomer here can include both monomers having an acryloyl group (acrylic monomers) and monomers having a methacryloyl group (methacrylic monomers).
  • (meth)acrylic acid refers collectively to acrylic acid and methacrylic acid
  • (meth)acrylate refers collectively to acrylate and methacrylate. The same applies to other similar terms.
  • weight may be read as “mass.”
  • % by weight may be read as “% by mass”
  • parts by weight may be read as “parts by mass.”
  • the first and second pressure-sensitive adhesive layers 11 and 12 may be arranged side by side in the surface direction (for example, both directly on the substrate).
  • the periphery of the substrate 20 and the periphery of the second pressure-sensitive adhesive layer 12 are almost the same, but the present invention is not limited thereto, and for example, a part or the entire periphery of the second pressure-sensitive adhesive layer 12 may be located inside the periphery of the substrate 20.
  • a part or the entire periphery of the second pressure-sensitive adhesive layer 12 may be located inside the periphery of the substrate 20.
  • the adhesive sheet 1 before use may be in the form of an adhesive sheet with a release liner, in which the adhesive surface A is protected by a release liner with at least the adhesive layer 10 side serving as a release surface.
  • the adhesive sheet may be in the form in which the other surface (back surface) of the substrate 1 serves as a release surface, and the adhesive sheet 1 is wound into a roll so that the adhesive layer 10 abuts against the back surface, thereby protecting the surface (adhesive surface A).
  • the post-heat peeling force Fa1 of the first pressure-sensitive adhesive layer is not particularly limited, and can be appropriately set so as to exhibit the desired easy peeling property after heating and to satisfy the above-mentioned value of the post-heat peeling force ratio (Fb1/Fa1).
  • the post-heat peeling force Fa1 of the first pressure-sensitive adhesive layer is suitably, for example, less than 3.0 N/20 mm, advantageously 2.0 N/20 mm or less, and preferably 1.0 N/20 mm or less.
  • the post-heat peel force Fa1 may be, for example, 0.01 N/20 mm or more, 0.05 N/20 mm or more, 0.1 N/20 mm or more, 0.2 N/20 mm or more, 0.3 N/20 mm or more, or 0.4 N/20 mm or more.
  • the post-heat peel strength Fb1 of the second pressure-sensitive adhesive layer may be, for example, 0.2 N/20 mm or more, and from the viewpoint of easily exhibiting the desired adherend retention performance after heating, it is appropriate to be 0.5 N/20 mm or more, preferably 0.8 N/20 mm or more, more preferably 1.0 N/20 mm or more, may be 1.5 N/20 mm or more, may be 2.0 N/20 mm or more, may be 2.5 N/20 mm or more, 3.0 N/20 mm or more, 3.3 N/20 mm or more, or may be 3.5 N/20 mm or more.
  • the upper limit of the post-heat peel strength Fb1 of the second pressure-sensitive adhesive layer is not particularly limited, and may be, for example, approximately 30 N/20 mm or less, 20 N/20 mm or less, 15 N/20 mm or less, 10 N/20 mm or less, or 7.0 N/20 mm or less.
  • the post-heat peel strength Fb1 of the second pressure-sensitive adhesive layer is not too high, in which the removability of the adherend attached to the second region after heating is taken into consideration.
  • the post-heat peel strength Fb1 may be, for example, 5.0 N/20 mm or less, 4.0 N/20 mm or less, 3.0 N/20 mm or less, or 2.5 N/20 mm or less.
  • the post-heating peel strength difference (Fb1-Fa1) calculated from the post-heating peel strength Fa1 [N/20 mm] of the first pressure-sensitive adhesive layer and the post-heating peel strength Fb1 [N/20 mm] of the second pressure-sensitive adhesive layer is not particularly limited as long as it is greater than 0 N/20 mm.
  • the upper limit of the post-heat peel force difference (Fb1-Fa1) is not particularly limited, and may be, for example, approximately 30 N/20 mm or less, 20 N/20 mm or less, 15 N/20 mm or less, 10 N/20 mm or less, or 7.0 N/20 mm or less.
  • the post-heat peel force difference (Fb1-Fa1) may be, for example, 5.0 N/20 mm or less, 4.0 N/20 mm or less, 3.0 N/20 mm or less, or 2.5 N/20 mm or less.
  • the first region of the pressure-sensitive adhesive sheet satisfying the above characteristics can exhibit good adhesion to the adherend while exhibiting good easy peelability (easy peelability upon heating) during peeling after heat treatment.
  • the post-heat peel strength reduction rate A may be 60% or more, 70% or more, 80% or more, 85% or more, 90% or more, 95% or more, or 97% or more. The higher the post-heat peel strength reduction rate A, the better the easy peelability upon heating. In some embodiments, the post-heat peel strength reduction rate A is preferably less than 99.9%. According to a pressure-sensitive adhesive sheet having a post-heat peel strength reduction rate A of less than 99.9%, after heating, the first region of the pressure-sensitive adhesive surface has the desired easy peelability from the adherend while maintaining the adhesion state with the adherend.
  • the post-heat peel force reduction rate A may be 99.0% or less, for example, less than 95.0%.
  • the pre-heat gel fraction, post-heat gel fraction and their relative relationship of the first and second adhesive layers can be realized and adjusted mainly based on the contents of this specification by appropriately selecting the type of polymer (monomer composition, etc.) contained in each adhesive layer, the presence or absence, type and amount of other components that may be contained in each adhesive layer (e.g., thermal polymerization initiators, described below, polyfunctional monomers), and combinations thereof, as well as the presence or absence, type and amount of use of a crosslinking agent in each adhesive layer, etc.
  • the post-heat Young's modulus Ya1 of the first adhesive layer is determined from a stress-strain curve (S-S curve) of the first adhesive layer that has been heat-treated at 180°C for 30 minutes, under conditions of 23°C, 50% RH, and a tensile speed of 50 mm/min.
  • the pre-heat (initial) Young's modulus Ya0 of the first adhesive layer is determined in the same manner as the post-heat Young's modulus Ya1, except that the first adhesive layer is not subjected to the heat treatment.
  • the pre-heat (initial) Young's modulus Yb0 and the post-heat Young's modulus Yb1 of the second pressure-sensitive adhesive layer are each not particularly limited and can be, for example, within the range of approximately 0.001 MPa to approximately 1000 MPa.
  • the pre-heating Young's modulus Yb0 may be, for example, 0.001 MPa or more, and from the viewpoint of easily obtaining moderate cohesiveness and holding power, it is advantageous to be 0.005 MPa or more, preferably 0.01 MPa or more, more preferably 0.05 MPa or more, may be 0.08 MPa or more, may be 0.1 MPa or more, or may be 0.3 MPa or more.
  • the Young's modulus Yb1 after heating of the second pressure-sensitive adhesive layer is suitably 100 MPa or less from the viewpoint of the adherend retention after heating, and is preferably 50 MPa or less, and may be, for example, 30 MPa or less, 20 MPa or less, 10 MPa or less, 5.0 MPa or less, 1.0 MPa or less, or 0.8 MPa or less.
  • the Young's modulus Yb1 after heating may be, for example, 0.001 MPa or more, and from the viewpoint of easily obtaining appropriate cohesiveness and retention, it is advantageous to be 0.005 MPa or more, and is preferably 0.01 MPa or more, and may be 0.05 MPa or more, 0.08 MPa or more, 0.1 MPa or more, or 0.3 MPa or more.
  • the Young's modulus increase ratio (Yb1/Yb0) calculated from the pre-heating Young's modulus Yb0 [MPa] and the post-heating Young's modulus Yb1 [MPa] of the second pressure-sensitive adhesive layer is not particularly limited, and may be, for example, in the range of 0 to 10,000.
  • the Young's modulus increase ratio may have a lower limit of, for example, 2.0 or more, 5.0 or more, 10 or more, 30 or more, 50 or more, or 100 or more, and an upper limit of, for example, 10,000 or less, 5,000 or less, 3,000 or less, 2,500 or less, 2,000 or less, 1,500 or less, or 1,000 or less.
  • the Young's modulus ratio after heating (Ya1/Yb1) calculated as the ratio of the Young's modulus after heating Ya1 of the first pressure-sensitive adhesive layer to the Young's modulus after heating Yb1 of the second pressure-sensitive adhesive layer is suitably, for example, more than 1.0, preferably 1.5 or more, may be 2.0 or more, may be 5.0 or more, may be 10 or more, 30 or more, 50 or more, 100 or more, 150 or more, or 200 or more.
  • a pressure-sensitive adhesive sheet satisfying any one of the above-mentioned Young's modulus ratios after heating (Ya1/Yb1) it is easy to preferably achieve both the easy peelability of the first region and the adhesiveness of the second region after heating.
  • the upper limit of the Young's modulus ratio after heating (Ya1/Yb1) is not particularly limited, and may be, for example, 10,000 or less, 5,000 or less, 1,000 or less, 500 or less, or 100 or less.
  • the Young's modulus ratio before heating (Ya0/Yb0) calculated as the ratio of the Young's modulus before heating Ya0 of the first pressure-sensitive adhesive layer to the Young's modulus before heating Yb0 of the second pressure-sensitive adhesive layer is not particularly limited.
  • the upper limit of the Young's modulus ratio before heating (Ya0/Yb0) may be, for example, 0.001 or more, 0.01 or more, or 0.1 or more.
  • the lower limit of the Young's modulus ratio before heating (Ya0/Yb0) may be, for example, 10,000 or less, 1000 or less, 100 or less, or 10 or less.
  • the pre-heating Young's modulus, post-heating Young's modulus and the relative relationship between them of the first and second adhesive layers can be realized and adjusted mainly based on the contents of this specification by appropriately selecting the type of polymer (monomer composition, etc.) contained in each adhesive layer, the presence or absence, type and amount of other components that may be contained in each adhesive layer (e.g., thermal polymerization initiators, described below, polyfunctional monomers), and combinations thereof, as well as the presence or absence, type and amount of use of a crosslinking agent in each adhesive layer, etc.
  • the first adhesive layer typically contains at least a polymer, and may further contain a monomer. From the viewpoint of easily exhibiting the desired thermosetting properties and heat peelability, it is preferable that the first adhesive layer contains at least one of a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule (hereinafter sometimes simply abbreviated as "polyfunctional monomer”) and a polymer having an ethylenically unsaturated group.
  • polyfunctional monomer a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule
  • the first adhesive layer may contain one or more of various rubber-like polymers such as acrylic polymers, rubber polymers (e.g., natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine polymers that can be used in the field of adhesives.
  • the above polymers may be used as base polymers in adhesives and function as structural polymers that form the adhesive. From the viewpoint of adhesive performance, cost, etc., an adhesive containing an acrylic polymer or a rubber polymer as a base polymer may be preferably adopted. Among them, an adhesive (acrylic adhesive) having an acrylic polymer as a base polymer is preferable.
  • the acrylic polymer is an acrylic polymer in which more than 50% by weight of the monomer components constituting the polymer is an acrylic monomer.
  • the proportion of the acrylic monomer in the monomer components is suitably 60% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 85% by weight or more, and may be, for example, 90% by weight or more.
  • the upper limit of the proportion of the acrylic monomer in the monomer components constituting the acrylic polymer is 100% by weight, and the proportion of the acrylic monomer may be, for example, 98% by weight or less, 95% by weight or less, or 92% by weight or less, from the viewpoint of obtaining the effect of using a non-acrylic monomer.
  • the acrylic monomer may be used alone or in combination of two or more kinds.
  • the monomer component includes an alkoxy group-containing (meth)acrylate.
  • An acrylic polymer containing an alkoxy group-containing (meth)acrylate as a monomer component can easily provide a pressure-sensitive adhesive layer that has both good initial adhesion and easy peelability after heating.
  • the first pressure-sensitive adhesive layer contains a polyfunctional monomer
  • compatibility with the polyfunctional monomer can easily be obtained.
  • the acrylic polymer containing an alkoxy group-containing (meth)acrylate as a monomer component can be a polymer that does not have an ethylenically unsaturated group, or can be a polymer that has an ethylenically unsaturated group.
  • the content of the alkoxy group-containing (meth)acrylate in the monomer component is, for example, more than 50 weight %, preferably 60 weight % or more, more preferably 70 weight % or more, and even more preferably 80 weight % or more, from the viewpoint of adhesive properties such as adhesive strength and compatibility with polyfunctional monomers.
  • the monomer component constituting the acrylic polymer may contain a chain alkyl (meth)acrylate having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester end.
  • a chain alkyl (meth)acrylate having an alkyl group having X to Y carbon atoms at the ester end may be referred to as a "C X-Y alkyl (meth)acrylate”.
  • chain is used to mean both linear and branched.
  • the chain alkyl (meth)acrylates may be used alone or in combination of two or more.
  • C 1-20 alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl.
  • a C 4-20 alkyl (meth)acrylate it is preferable to use at least a C 4-20 alkyl (meth)acrylate, and more preferable to use at least a C 4-18 alkyl (meth)acrylate.
  • a C 4-8 alkyl (meth)acrylate as the C 1-20 alkyl (meth)acrylate.
  • the C 4-8 alkyl (meth)acrylate may be used alone or in combination of two or more. The use of a C 4-8 alkyl (meth)acrylate tends to make it easier to obtain good adhesive properties (adhesive strength, etc.).
  • an acrylic polymer containing one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) as the monomer component is preferable, and an acrylic polymer containing at least 2EHA is particularly preferable.
  • a C 1-20 alkyl (meth)acrylate is used, a C 7-12 alkyl (meth)acrylate may be preferably used.
  • the C 7-12 alkyl (meth)acrylate may be used alone or in combination of two or more.
  • a C 7-10 alkyl acrylate is preferred, a C 7-9 alkyl acrylate is more preferred, and a C 8 alkyl acrylate is even more preferred.
  • the content of C 1-20 alkyl (meth)acrylate in the monomer component constituting the acrylic polymer is not particularly limited. From the viewpoint of effectively obtaining the effect of using C 1-20 alkyl (meth)acrylate, the content of C 1-20 alkyl (meth)acrylate in the monomer component is usually about 1% by weight or more, for example, 10% by weight or more, 30% by weight or more, or 50% by weight or more. In some embodiments, the content of C 1-20 alkyl (meth)acrylate in the monomer component is, for example, more than 50% by weight, preferably 60% by weight or more, more preferably 70% by weight or more, and even more preferably 80% by weight or more, from the viewpoint of adhesive properties such as adhesive strength.
  • the upper limit of the content of the C 1-20 alkyl (meth)acrylate in the monomer component is 100% by weight, and in some embodiments, from the viewpoint of obtaining the effects of other copolymerizable monomers such as functional group-containing monomers, the content of the C 1-20 alkyl (meth)acrylate is advantageously about 99% by weight or less, may be 95% by weight or less, may be 93% by weight or less, or may be 90% by weight or less.
  • the range of the content of the C1-20 alkyl(meth)acrylate may be the range of the content of each of the above-mentioned C4-20 alkyl(meth)acrylate, C4-18 alkyl(meth)acrylate, C4-8 alkyl(meth)acrylate, C4-8 alkyl acrylate, C7-12 alkyl(meth)acrylate, C7-10 alkyl acrylate, C7-9 alkyl acrylate, C8 alkyl acrylate, BA , and 2EHA, which are included in the C1-20 alkyl(meth)acrylate.
  • the monomer components constituting the acrylic polymer preferably contain other monomers other than the above alkoxyalkyl (meth)acrylates and linear alkyl (meth)acrylates.
  • Such other monomers may be monomers (copolymerizable monomers) that are copolymerizable with the alkoxyalkyl (meth)acrylates and linear alkyl (meth)acrylates.
  • monomers having polar groups e.g., carboxy groups, hydroxyl groups, nitrogen atom-containing rings, etc.
  • Monomers having polar groups can be useful for introducing crosslinking points into the acrylic polymer or for increasing the cohesive strength of the adhesive.
  • the other monomers can be used alone or in combination of two or more.
  • Non-limiting examples of other monomers include the following: Carboxy group-containing monomers: for example, acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like.
  • Acid anhydride group-containing monomers for example, maleic anhydride, itaconic anhydride.
  • Hydroxyl group-containing monomers for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate.
  • hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyocty
  • Epoxy group-containing monomers for example, epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethyl glycidyl ether (meth)acrylate, allyl glycidyl ether, and glycidyl ether (meth)acrylate.
  • Cyano group-containing monomers for example, acrylonitrile, methacrylonitrile, etc.
  • Isocyanate group-containing monomers for example, 2-isocyanatoethyl (meth)acrylate.
  • Amide group-containing monomers for example, (meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide; N-monoalkyl(meth)acrylamides such as N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and N-n-butyl(meth)acrylamide; N-vinyl carboxylic acid amides such as N-vinylacetamide; monomers having a hydroxyl group and an amide group, for example, N-(2-hydroxyeth
  • Amino group-containing monomers for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate.
  • Monomers having a succinimide skeleton for example, N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyhexamethylene succinimide, and the like.
  • Maleimides for example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, and the like.
  • the monomer component constituting the acrylic polymer may contain a monomer having a nitrogen atom.
  • the use of a monomer having a nitrogen atom can increase the cohesive strength of the pressure-sensitive adhesive and preferably improve the adhesive strength.
  • the monomer having a nitrogen atom may be used alone or in combination of two or more.
  • a suitable example of the monomer having a nitrogen atom is a monomer having a nitrogen atom-containing ring.
  • the monomer having a nitrogen atom and the monomer having a nitrogen atom-containing ring may be one of those exemplified above, and may be, for example, a monomer represented by the general formula (1): N-vinyl cyclic amides represented by the following formula can be used.
  • an acrylic polymer having an ethylenically unsaturated group which will be described later
  • a monomer having a functional group (functional group A) that can react with a functional group (functional group B) of a compound having an ethylenically unsaturated group which will be described later.
  • the type of the other monomer is determined by the above-mentioned compound type.
  • the amount of polyfunctional monomer used is not particularly limited, and can be appropriately set so that the purpose of using the polyfunctional monomer is achieved.
  • the amount of polyfunctional monomer used can be about 3% by weight or less of the monomer component, preferably about 2% by weight or less, and more preferably about 1% by weight or less (e.g., about 0.5% by weight or less).
  • the lower limit of the amount used is not particularly limited as long as it is greater than 0% by weight.
  • the effect of using the polyfunctional monomer can be appropriately achieved by setting the amount of polyfunctional monomer used to about 0.001% by weight or more of the monomer component (e.g., about 0.01% by weight or more).
  • the amount of the polymerization initiator used is not particularly limited and may be a normal amount depending on the polymerization method and polymerization mode. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, e.g., about 0.01 to 1 part by weight) of the polymerization initiator can be used per 100 parts by weight of the total monomer components to be polymerized.
  • the molecular weight of the polymer (e.g., acrylic polymer) is not particularly limited and can be set in an appropriate range according to the required performance.
  • the weight average molecular weight (Mw) of the polymer is suitably about 1 ⁇ 10 4 or more, for example, about 10 ⁇ 10 4 or more.
  • Mw weight average molecular weight
  • the Mw may be 20 ⁇ 10 4 or more, 30 ⁇ 10 4 or more, about 40 ⁇ 10 4 or more, about 50 ⁇ 10 4 or more, for example, about 55 ⁇ 10 4 or more, from the viewpoint of obtaining heat resistance and good adhesiveness.
  • a polymer having an ethylenically unsaturated group such as an acryloyl group, a methacryloyl group, a vinyl group, or an allyl group is preferably used as the polymer.
  • the adhesive containing a polymer having an ethylenically unsaturated group the ethylenically unsaturated group of the polymer is reacted during heating, so that the adhesive is thermally cured and the desired heat peelability can be obtained.
  • the peel force reduction rate after heating can be increased with the use of a smaller amount of the polyfunctional monomer, and the desired heat peelability can be realized.
  • a polymer having an ethylenically unsaturated group for example, a polymer having an ethylenically unsaturated group in a side chain can be used.
  • the monomer component of the polymer having an ethylenically unsaturated group one or more of the monomer components exemplified as the monomer components of the above polymer can be used within the above content range.
  • the amount of ethylenically unsaturated groups in a polymer having ethylenically unsaturated groups is not particularly limited, and from the viewpoint of thermosetting properties, etc., it is appropriate to make it 0.01 mmol per 1 g of polymer (hereinafter also referred to as mmol/g) or more, and it may be 0.1 mmol/g or more, or 0.5 mmol/g or more.
  • the amount of ethylenically unsaturated groups in the above polymer is appropriate to be 10.0 mmol/g or less, and may be 5.0 mmol/g or less, 3.0 mmol/g or less, 2.5 mmol/g or less, or 2.0 mmol/g or less.
  • An example of a method for measuring the content of ethylenically unsaturated groups other than (meth)acryloyl groups is a method for measuring the bromine number in accordance with JIS K2605: 1996.
  • the content of ethylenically unsaturated groups other than (meth)acryloyl groups is determined by converting the number of grams of bromine ( Br2 ) added to 100 g of the polymer to be measured into the number of moles of bromine ( Br2 ) added to 1 g of the polymer.
  • the method of introducing an ethylenically unsaturated group into a polymer is not particularly limited.
  • a method of reacting (typically condensation or addition reaction) a compound having an ethylenically unsaturated group and a functional group (functional group B) capable of reacting with the functional group (functional group A) introduced into the acrylic polymer by copolymerization, so that the ethylenically unsaturated group does not disappear can be preferably adopted.
  • combinations of functional group A and functional group B include a combination of a carboxy group and an epoxy group, a combination of a carboxy group and an aziridyl group, and a combination of a hydroxyl group and an isocyanate group.
  • a combination of a hydroxyl group and an isocyanate group is preferred.
  • a combination in which the acrylic polymer has a hydroxyl group and the above compound has an isocyanate group is particularly preferred.
  • the amount of the compound having an ethylenically unsaturated group (e.g., an isocyanate group-containing monomer) added is not particularly limited, but from the viewpoint of reactivity with the functional group A (e.g., a hydroxyl group) in the polymer, the molar ratio (M A /M B ) of the moles of the functional group A (M A ) to the moles of the functional group B ( isocyanate group) (M B ) may be set in the range of about 0.5 to 2 (e.g., 1 to 1.5).
  • the content of the polymer having an ethylenically unsaturated group in the adhesive layer is not particularly limited.
  • the amount of the polymer having an ethylenically unsaturated group used is suitably about 10% by weight or more of the total polymer (specifically, base polymer) contained in the adhesive layer, and may be about 50% by weight or more (e.g., more than 50% by weight), 70% by weight or more, 90% by weight or more, 95% by weight or more, or 99 to 100% by weight.
  • the base polymer contained in the adhesive layer may consist essentially of a polymer having an ethylenically unsaturated group.
  • the polymer used is a polymer that is substantially free of ethylenically unsaturated groups such as acryloyl groups, methacryloyl groups, vinyl groups, and allyl groups (the amount of ethylenically unsaturated groups is less than 0.01 mmol/g).
  • the amount of such polymer used is suitably about 10% by weight or more of the entire polymer (specifically, base polymer) contained in the adhesive layer, and may be about 50% by weight or more (e.g., more than 50% by weight), 70% by weight or more, 90% by weight or more, 95% by weight or more, or 99 to 100% by weight.
  • the base polymer contained in the adhesive layer may be substantially composed of a polymer that is substantially free of ethylenically unsaturated groups.
  • the first adhesive layer preferably contains a polyfunctional monomer in addition to the polymer.
  • a polyfunctional monomer in addition to the polymer.
  • the polyfunctional monomer reacts when heated at high temperature, reducing the adhesive strength or suppressing the increase in peel strength, thereby realizing easy peeling by heating. More specifically, when the adhesive is heated at high temperature while attached to the adherend, it usually adsorbs to the surface of the adherend. Therefore, the adhesive strength of the adhesive to the adherend is strengthened, resulting in heavy peeling.
  • the reaction of the polyfunctional monomer proceeds quickly when heated, and the adhesive can be cured prior to the adhesive's adsorption to the adherend. This allows the adhesive strength to the adherend to be reduced. Furthermore, even if heating is continued thereafter, the adhesive strength of the adhesive to the adherend does not increase and is maintained within a predetermined range, so that the adhesive can exhibit excellent easy peeling by heating. Note that the technology disclosed herein is not limited to the above interpretation.
  • the polyfunctional monomers can be used alone or in combination of two or more.
  • a polyfunctional monomer refers to a polymerizable compound having two or more ethylenically unsaturated groups in one molecule, and includes those called oligomers.
  • the above ethylenically unsaturated groups function as polymerizable functional groups (typically radically polymerizable functional groups).
  • Examples of ethylenically unsaturated groups that polyfunctional monomers have include, but are not limited to, acryloyl groups, methacryloyl groups, vinyl groups, and allyl groups. Suitable examples of ethylenically unsaturated groups include acryloyl groups and methacryloyl groups. Of these, acryloyl groups are preferred.
  • a compound having two or more acryloyl groups and/or methacryloyl groups may be referred to as a polyfunctional acrylic monomer.
  • a compound having two or more vinyl groups may be referred to as a polyfunctional vinyl monomer.
  • the upper limit of the number of ethylenically unsaturated groups in one molecule of the polyfunctional monomer is not limited to a specific range, and may be, for example, 50 or less, 40 or less, 30 or less, 20 or less, or 15 or less. In some embodiments, the number of ethylenically unsaturated groups in one molecule of the polyfunctional monomer may be, for example, 10 or less, 8 or less, 6 or less, or less than 5. Multifunctional monomers with the above number of ethylenically unsaturated groups tend to provide both good adhesion and easy peelability upon heating, and also have excellent storage stability.
  • polyfunctional acrylate monomers having two or more ethylenically unsaturated groups or polyfunctional vinyl monomers can be used.
  • polyfunctional acrylate monomers can be preferably used.
  • polyfunctional acrylate monomers tend to be compatible and easily exhibit desired properties when used in combination with acrylic polymers.
  • the polyfunctional acrylate monomers and polyfunctional vinyl monomers can each be used alone or in combination of two or more.
  • Multifunctional monomers include 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, allyl (meth)acrylate, alkylene oxide modified bisphenol A di(meth)acrylate, alkylene oxide modified neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, dimethylol dicyclopenta
  • difunctional monomers such as trimethylolpropane tri(meth)acrylate, trimethylolpropane ethoxy tri(meth)acrylate, glycerin propoxy triacrylate, tetramethylolmethane tri(meth)acrylate, and pentaerythritol tri(meth)acrylate; tetrafunctional monomers such as pentaerythritol alkoxy tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and pentaerythritol tetra(meth)acrylate.
  • pentafunctional monomers such as sorbitol penta(meth)acrylate and dipentaerythritol penta(meth)acrylate; hexafunctional monomers such as dipentaerythritol hexa(meth)acrylate, sorbitol hexa(meth)acrylate, alkylene oxide modified hexa(meth)acrylate, and caprolactone modified dipentaerythritol hexa(meth)acrylate; and di- or higher functional epoxy acrylates, polyester acrylates, and urethane acrylates.
  • preferred examples include 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. Of these, dipentaerythritol hexa(meth)acrylate is particularly preferred.
  • the molecular weight of the polyfunctional monomer may be, for example, 150 or more, 250 or more, 300 or more, 350 or more, 400 or more, 450 or more, or 500 or more.
  • the molecular weight of the polyfunctional monomer is usually about 100,000 or less, for example, about 10,000 or less (e.g., less than 10,000) is appropriate, 5,000 or less (e.g., less than 5,000) is preferable, 1,500 or less, 1,000 or less (e.g., less than 1,000), 800 or less, or 600 or less.
  • the use of a polyfunctional monomer having a molecular weight in the above range can be advantageous, for example, in terms of the preparation and coating properties of the adhesive composition.
  • the above molecular weight is a molecular weight calculated from the manufacturer's nominal value or molecular structure.
  • Mw weight average molecular weight
  • a polyfunctional monomer having a weight loss rate of 1% or less (specifically 1.0% or less) at 180°C in TGA (thermogravimetric analysis) under a temperature rise condition of 10°C/min is used as the polyfunctional monomer.
  • a polyfunctional monomer having heat resistance such that the weight loss rate at 180°C is 1% or less hereinafter also referred to as a "heat-resistant polyfunctional monomer"
  • the adhesive layer has heat-resistant peelability based on the use of the polyfunctional monomer, while suppressing outgas generation during heating.
  • the heat-resistant polyfunctional monomer it is possible to achieve both heat-resistant peelability and reduced outgassing.
  • the 180°C heat-resistant weight loss rate of the heat-resistant polyfunctional monomer is 0.9% or less, more preferably 0.8% or less, even more preferably 0.7% or less, particularly preferably 0.6% or less, and may be 0.5% or less.
  • the lower limit of the weight loss rate of the heat-resistant multifunctional monomer at 180°C is theoretically 0%, and may be 0.1% or more in practice, 0.2% or more, or 0.3% or more.
  • the weight loss rate of a polyfunctional monomer when heated to 180°C can be measured using a differential thermal analyzer (manufactured by TA Instruments, product name "Discovery TGA”) under measurement conditions of a temperature rise of 10°C/min, in an air atmosphere, and at a flow rate of 25 mL/min.
  • a differential thermal analyzer manufactured by TA Instruments, product name "Discovery TGA”
  • the content of the polyfunctional monomer in the first adhesive layer is not particularly limited. In some embodiments, the content of the polyfunctional monomer relative to 100 parts by weight of the polymer (specifically, the base polymer, preferably an acrylic polymer) contained in the first adhesive layer may be approximately 1 part by weight or more, or may be 3 parts by weight or more.
  • the appropriate amount of the polyfunctional monomer may vary depending on its molecular weight, the number of functional groups, etc., but in some preferred embodiments, from the viewpoint of easy peelability upon heating, the amount of the polyfunctional monomer relative to 100 parts by weight of the above polymer is appropriately 5 parts by weight or more, preferably 10 parts by weight or more, may be 20 parts by weight or more, may be 30 parts by weight or more, may be 40 parts by weight or more, may be 50 parts by weight or more, may be 60 parts by weight or more, may be 70 parts by weight or more, may be 80 parts by weight or more, may be 90 parts by weight or more, or may be 100 parts by weight or more.
  • the polyfunctional monomer contained in the adhesive layer reacts quickly when heated, and the adhesive layer is thermally cured, thereby realizing easy peeling by heating.
  • the upper limit of the content of the polyfunctional monomer in the adhesive layer is not particularly limited, and can be set to achieve the desired adhesive properties.
  • the amount of the polyfunctional monomer relative to 100 parts by weight of the polymer is appropriately about 200 parts by weight or less, preferably 160 parts by weight or less, more preferably 150 parts by weight or less, and even more preferably 140 parts by weight or less, and may be 120 parts by weight or less, 90 parts by weight or less, or 70 parts by weight or less.
  • the content of the polyfunctional monomer in the first adhesive layer may be less than 50% by weight of the first adhesive layer, although this is not particularly limited. According to the technology disclosed herein, a first adhesive layer having sufficient heat peelability can be realized even in such an embodiment in which the amount of polyfunctional monomer in the adhesive is limited. In some preferred embodiments, the content of the polyfunctional monomer is less than 45% by weight of the first adhesive layer, and may be less than 40% by weight, less than 35% by weight, less than 30% by weight, less than 25% by weight, less than 20% by weight, less than 15% by weight, or less than 10% by weight.
  • the content of the polyfunctional monomer may be 1% by weight or more, 5% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, or 25% by weight or more of the weight of the first adhesive layer, from the viewpoint of effectively exerting the heat peelability based on the inclusion of the polyfunctional monomer.
  • the above range of polyfunctional monomer content can be preferably adopted in an embodiment in which a polymer having an ethylenically unsaturated group is used.
  • the first adhesive layer preferably contains a thermal polymerization initiator.
  • the thermal polymerization initiator refers to a polymerization initiator that generates radicals by heating. By including the thermal polymerization initiator in the adhesive before reaction (unreacted), the thermal polymerization initiator reacts when heated at high temperature, reducing the adhesive strength or suppressing the increase in the adhesive strength, and thus the heat-sensitive peelability can be preferably realized.
  • the thermal polymerization initiator is not particularly limited, and for example, a peroxide-based polymerization initiator, an azo-based polymerization initiator, a redox-based polymerization initiator formed by combining a peroxide with a reducing agent, a substituted ethane-based polymerization initiator, etc. can be used.
  • persulfates such as potassium persulfate and ammonium persulfate
  • peroxide compounds such as benzoyl peroxide (BPO) and t-butyl hydroperoxide
  • azo compounds such as 2,2'-azobisisobutyronitrile (AIBN) and 2,2'-azobis(N-butyl-2-methylpropionamide
  • substituted ethane initiators such as phenyl-substituted ethane
  • redox initiators consisting of a combination of a peroxide and a reducing agent, such as a combination of a persulfate and sodium hydrogen sulfite, or a combination of a peroxide and sodium ascorbate; and the like.
  • thermal polymerization initiators can be used alone or in combination of two or more.
  • thermal polymerization initiators that can be preferably used in the technology disclosed herein include peroxide polymerization initiators and azo polymerization initiators.
  • peroxide polymerization initiators and azo polymerization initiators.
  • a combination of a peroxide polymerization initiator and an azo polymerization initiator may also be used.
  • peroxide-based polymerization initiator for example, organic peroxides such as diacyl peroxides, peroxy esters, peroxy dicarbonates, monoperoxy carbonates, peroxy ketals, dialkyl peroxides, hydroperoxides, and ketone peroxides are preferably used.
  • Suitable examples of peroxide-based polymerization initiators include benzoyl peroxide compounds (typically dibenzoyl peroxide (BPO)) having a benzoyl group that may have a substituent.
  • BPO dibenzoyl peroxide
  • the peroxide-based polymerization initiators can be used alone or in combination of two or more.
  • peroxide polymerization initiators include BPO, 1,1-di(t-hexylperoxy)cyclohexane, cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, n-butyl-4,4-bis(t-butylperoxy)valerate, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 1,3-bis(t- butylperoxy)-m-isopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, diisopropylbenzene hydroperoxide, t-butylcumyl peroxide,
  • Azo polymerization initiators are not particularly limited, and any of azonitrile compounds, azoamide compounds, azoester compounds, alkylazo compounds, azoamidine compounds, azoimidazoline compounds, and polymeric azo compounds can be used.
  • Non-limiting examples of azo polymerization initiators include 2,2'-azobisisobutyronitrile (AIBN), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 4,4-azobis(4-cyanovaleric acid), 2,2'-azobis(2-methylbutyronitrile ...
  • AIBN 2,2'-azobisisobutyronitrile
  • 1,1'-azobis(cyclohexane-1-carbonitrile 2,2'-azobis(4-methoxy-2,
  • Suitable examples of azo-based polymerization initiators include AIBN, 1,1'-azobis(cyclohexane-1-carbonitrile), 4,4-azobis(4-cyanovaleric acid), 2,2'-azobis(N-butyl-2-methylpropionamide, 2,2'-azobis(2,4,4-trimethylpentane), etc.
  • a peroxide-based polymerization initiator it is preferable to use at least a peroxide-based polymerization initiator as the thermal polymerization initiator.
  • a peroxide-based initiator it is likely that heat peelability and heat-resistant peelability can be obtained.
  • One of the reasons for this is the high initiation efficiency of peroxide-based polymerization initiators (particularly organic peroxide-based polymerization initiators).
  • peroxide-based polymerization initiators generate radicals (-O.) by cleaving -O-O- contained in the compound, but since this cleavage reaction is reversible, it is thought that if the radical does not collide with the ethylenically unsaturated group of the polyfunctional monomer or polymer, recombination of -O-O- occurs. This recombined initiator can undergo a cleavage reaction again during a specified heating time, collide with and react with the polyfunctional monomer, etc. Therefore, it is thought that when a peroxide-based polymerization initiator is used, the thermal curing of the adhesive layer proceeds efficiently, and heat peelability and heat-resistant peelability can be obtained. Note that the technology disclosed herein is not limited to the above considerations.
  • the content of the peroxide-based polymerization initiator in the adhesive layer is not particularly limited, and in some embodiments, it is appropriate to set the content to 0.1 parts by weight or more relative to 100 parts by weight of the polymer (specifically, the base polymer, for example, an acrylic polymer) contained in the adhesive layer, preferably 0.2 parts by weight or more, more preferably 0.3 parts by weight or more, and even more preferably 0.4 parts by weight or more, and may be 0.5 parts by weight or more (for example, more than 0.5 parts by weight), 0.6 parts by weight or more, or 0.7 parts by weight or more.
  • the polymer specifically, the base polymer, for example, an acrylic polymer
  • the amount of the peroxide-based polymerization initiator relative to 100 parts by weight of the polymer may be, for example, about 10 parts by weight or less, or about 5 parts by weight or less.
  • the amount of the peroxide-based polymerization initiator relative to 100 parts by weight of the polymer is suitably 3 parts by weight or less (less than 3 parts by weight), preferably 2.5 parts by weight or less, more preferably 2.0 parts by weight or less, even more preferably 1.5 parts by weight or less, particularly preferably less than 1.2 parts by weight (e.g., 1.1 parts by weight or less), and may be 1.0 parts by weight or less (e.g., less than 1.0 parts by weight), 0.9 parts by weight or less, 0.8 parts by weight or less, 0.7 parts by weight or less, or 0.6 parts by weight or less.
  • the total amount of the peroxide-based polymerization initiator within a predetermined range, it is possible to preferably realize a pressure-sensitive adhesive having efficient thermosetting and easy peeling by heating while obtaining adhesive properties such as adhesive strength and storage stability.
  • the content of the peroxide-based polymerization initiator in the first adhesive layer can also be specified by the relative relationship with the content of the polyfunctional monomer.
  • the amount of the peroxide-based polymerization initiator relative to 100 parts by weight of the polyfunctional monomer is appropriately set to 0.1 parts by weight or more from the viewpoint of the frequency of collision with the ethylenically unsaturated group of the polyfunctional monomer, and is preferably 0.2 parts by weight or more, more preferably 0.3 parts by weight or more, and even more preferably 0.4 parts by weight or more, and may be 0.5 parts by weight or more.
  • the amount of the peroxide-based polymerization initiator relative to 100 parts by weight of the polyfunctional monomer is, for example, appropriately set to 1.0 parts by weight or more, and is preferably set to 1.5 parts by weight or more, and may be set to 2.0 parts by weight or more, 2.5 parts by weight or more, 3.0 parts by weight or more, 4.0 parts by weight or more, or 5.0 parts by weight or more.
  • the amount of peroxide-based polymerization initiator relative to 100 parts by weight of the polyfunctional monomer is, for example, suitably about 25 parts by weight or less, preferably 20 parts by weight or less, more preferably 15 parts by weight or less, may be 10 parts by weight or less, may be 8.0 parts by weight or less (for example, less than 8.0 parts by weight), may be 6.0 parts by weight or less, or may be 4.0 parts by weight or less.
  • the amount of peroxide-based polymerization initiator used (the content of peroxide-based polymerization initiator in the first adhesive layer and the amount of peroxide-based polymerization initiator per 100 parts by weight of polyfunctional monomer) can also be applied to the amount of azo-based polymerization initiator used in an embodiment in which an azo-based polymerization initiator is used as the thermal polymerization initiator contained in the first adhesive layer.
  • the first adhesive layer may contain only a peroxide-based polymerization initiator as a thermal polymerization initiator, or may contain a peroxide-based polymerization initiator and a thermal polymerization initiator (non-peroxide-based polymerization initiator) different from the peroxide-based polymerization initiator.
  • a peroxide-based polymerization initiator and a non-peroxide-based polymerization initiator are used in combination, the action and characteristics based on the non-peroxide-based polymerization initiator can be utilized.
  • the proportion of the peroxide-based polymerization initiator in the total thermal polymerization initiator contained in the first adhesive layer is appropriately about 10% by weight or more, and from the viewpoint of effectively exerting the effect of the peroxide-based polymerization initiator, it is preferably 30% by weight or more, more preferably 40% by weight or more, and even more preferably 50% by weight or more (e.g., more than 50% by weight), and may be 55% by weight or more, or may be 60% by weight or more.
  • the ratio of the peroxide-based polymerization initiator to the entire thermal polymerization initiator is, for example, approximately 65% by weight or more, and may be 75% by weight or more, 85% by weight or more, 95% by weight or more, or 99% by weight or more.
  • the upper limit of the ratio of the peroxide-based polymerization initiator to the entire thermal polymerization initiator is 100% by weight, and in some embodiments, it may be, for example, 90% by weight or less, 80% by weight or less, 70% by weight or less, or 60% by weight or less.
  • non-peroxide polymerization initiators used together with peroxide polymerization initiators can be used, for example, azo polymerization initiators, redox polymerization initiators formed by a combination of peroxide and a reducing agent, substituted ethane polymerization initiators, etc.
  • persulfates such as potassium persulfate and ammonium persulfate
  • azo compounds such as 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(2,4,4-trimethylpentane); substituted ethane initiators such as phenyl-substituted ethane; redox initiators formed by a combination of peroxide and a reducing agent, such as a combination of persulfate and sodium hydrogen sulfite, or a combination of peroxide and sodium ascorbate; etc.
  • These non-peroxide polymerization initiators can be used alone or in combination of two or more.
  • the amount of the thermal polymerization initiator contained in the first adhesive layer is not particularly limited, and in some embodiments, it is appropriate to set it to 0.1 parts by weight or more per 100 parts by weight of the polymer (specifically, the base polymer, for example, an acrylic polymer) contained in the first adhesive layer, preferably 0.2 parts by weight or more, more preferably 0.3 parts by weight or more, and even more preferably 0.4 parts by weight or more, and may be 0.5 parts by weight or more (for example, more than 0.5 parts by weight), or may be 0.6 parts by weight or more or 0.7 parts by weight or more.
  • the polymer specifically, the base polymer, for example, an acrylic polymer
  • the content of the thermal polymerization initiator may be, for example, about 10 parts by weight or less, or may be about 5 parts by weight or less.
  • the amount of the peroxide-based polymerization initiator relative to 100 parts by weight of the polymer is suitably 3 parts by weight or less (less than 3 parts by weight), preferably 2.5 parts by weight or less, more preferably 2.0 parts by weight or less, even more preferably 1.5 parts by weight or less, particularly preferably less than 1.2 parts by weight (e.g., 1.1 parts by weight or less), and may be 1.0 parts by weight or less (e.g., less than 1.0 parts by weight), 0.9 parts by weight or less, 0.8 parts by weight or less, 0.7 parts by weight or less, or 0.6 parts by weight or less.
  • the content of the thermal polymerization initiator within a predetermined range, it is possible to preferably realize a pressure-sensitive adhesive having efficient thermosetting and easy peeling by heating while obtaining adhesive properties such as adhesive strength and storage stability.
  • the content of the thermal polymerization initiator in the first adhesive layer can also be specified by the relative relationship with the content of the polyfunctional monomer.
  • the amount of the thermal polymerization initiator relative to 100 parts by weight of the polyfunctional monomer is appropriately 0.1 parts by weight or more from the viewpoint of the frequency of collision with the ethylenically unsaturated group of the polyfunctional monomer, and is preferably 0.2 parts by weight or more, more preferably 0.3 parts by weight or more, and even more preferably 0.4 parts by weight or more, and may be 0.5 parts by weight or more.
  • the amount of the peroxide-based polymerization initiator relative to 100 parts by weight of the polyfunctional monomer is, for example, appropriately 1.0 parts by weight or more, preferably 1.5 parts by weight or more, and may be 2.0 parts by weight or more, 2.5 parts by weight or more, 3.0 parts by weight or more, 4.0 parts by weight or more, or 5.0 parts by weight or more.
  • the amount of the thermal polymerization initiator relative to 100 parts by weight of the polyfunctional monomer may be, for example, about 10 parts by weight or less, or may be about 5 parts by weight or less.
  • the amount of the thermal polymerization initiator relative to 100 parts by weight of the polyfunctional monomer is, for example, suitably about 25 parts by weight or less, preferably 20 parts by weight or less, more preferably 15 parts by weight or less, may be 10 parts by weight or less, may be 8.0 parts by weight or less (e.g., less than 8.0 parts by weight), may be 6.0 parts by weight or less, or may be 4.0 parts by weight or less.
  • the total proportion of the above-mentioned polymer (specifically, a base polymer, for example, an acrylic polymer), polyfunctional monomer (for example, a polyfunctional acrylic monomer) and thermal polymerization initiator (preferably a peroxide-based polymerization initiator) in the entire adhesive layer is suitably 50% by weight or more (for example, more than 50% by weight and less than 100% by weight) from the viewpoint of effectively exerting the peel strength reduction by heating and realizing the desired rate of reduction in peel strength after heating, and is preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more, and may be 95% by weight or more, 98% by weight or more, or 99% by weight or more (for example, 99 to 100% by weight).
  • a base polymer for example, an acrylic polymer
  • polyfunctional monomer for example, a polyfunctional acrylic monomer
  • thermal polymerization initiator preferably a peroxide-based polymerization initiator
  • the adhesive composition used to form the first adhesive layer may contain a crosslinking agent as necessary, mainly for the purpose of crosslinking within the first adhesive layer or crosslinking between the first adhesive layer and its adjacent surface.
  • the crosslinking agent is typically contained in the first adhesive layer in a form after crosslinking reaction. The use of the crosslinking agent allows the cohesive strength of the first adhesive layer to be appropriately adjusted.
  • crosslinking agent is not particularly limited, and can be selected from conventionally known crosslinking agents so that the crosslinking agent exerts an appropriate crosslinking function in the first adhesive layer, for example, depending on the composition of the adhesive.
  • crosslinking agents that can be used include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents.
  • isocyanate-based crosslinking agents epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and carbodiimide-based crosslinking agents are preferred, and isocyanate-based crosslinking agents are particularly preferred.
  • a polyfunctional isocyanate compound having two or more functionalities can be used.
  • aromatic isocyanates such as tolylene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris(p-isocyanatophenyl)thiophosphate, and diphenylmethane diisocyanate
  • alicyclic isocyanates such as isophorone diisocyanate
  • aliphatic isocyanates such as hexamethylene diisocyanate.
  • isocyanate adducts such as trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, product name “Coronate L”), trimethylolpropane/hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, product name “Coronate HL”), isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate HX”), and trimethylolpropane/xylylene diisocyanate adduct (manufactured by Mitsui Chemicals, Inc., product name "Takenate D-110N”), etc.
  • isocyanate adducts such as trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, product name “Coronate L”), trimethylol
  • epoxy crosslinking agent those having two or more epoxy groups in one molecule can be used without any particular restrictions.
  • Epoxy crosslinking agents having 3 to 5 epoxy groups in one molecule are preferred.
  • Specific examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, etc.
  • epoxy crosslinking agents include Mitsubishi Gas Chemical Company's product names “TETRAD-X” and “TETRAD-C”, DIC Corporation's product name “Epicron CR-5L”, Nagase ChemteX Corporation's product name "Denacol EX-512", Nissan Chemical Industries' product name “TEPIC-G”, etc.
  • any agent having one or more oxazoline groups in one molecule can be used without any particular limitation.
  • the aziridine crosslinking agent include trimethylolpropane tris[3-(1-aziridinyl)propionate], trimethylolpropane tris[3-(1-(2-methyl)aziridinylpropionate)], and the like.
  • the carbodiimide crosslinking agent a low molecular weight compound or a high molecular weight compound having two or more carbodiimide groups can be used.
  • an isocyanate-based crosslinking agent is used as the crosslinking agent.
  • the isocyanate-based crosslinking agent is easy to form an adhesive having good heat peelability while exhibiting a good balance of adhesive properties such as adhesive strength and cohesive strength.
  • the isocyanate-based crosslinking agent can be used alone or in combination of two or more.
  • the amount of isocyanate-based crosslinking agent used is preferably less than 1 part by weight per 100 parts by weight of the polymer (specifically, the base polymer, for example, an acrylic polymer) contained in the adhesive layer.
  • the crosslinking density is appropriately suppressed, and at such a crosslinking density, the polyfunctional monomer and the thermal polymerization initiator frequently collide with each other during heat treatment, heat curing progresses, and heat peelability and heat resistance are expressed, and it is believed that the desired post-heat peel strength reduction rate is realized. It is to be noted that the technology disclosed herein is not limited to the above considerations.
  • the amount of the isocyanate-based crosslinking agent used relative to 100 parts by weight of the polymer is 0.9 parts by weight or less, may be 0.8 parts by weight or less, may be 0.7 parts by weight or less, may be 0.6 parts by weight or less, may be 0.5 parts by weight or less, may be 0.4 parts by weight or less, may be 0.3 parts by weight or less, may be 0.2 parts by weight or less, or may be 0.1 parts by weight or less.
  • the amount of the isocyanate-based crosslinking agent used there is a tendency that high adhesive strength is easily obtained.
  • the amount of the isocyanate-based crosslinking agent used can be, for example, 0.01 parts by weight or more relative to 100 parts by weight of the polymer, and in some preferred embodiments, it may be 0.05 parts by weight or more, may be 0.1 parts by weight or more, may be 0.3 parts by weight or more, or may be 0.5 parts by weight or more.
  • the amount used (the total amount when two or more crosslinking agents are used) may be more than 0 parts by weight relative to 100 parts by weight of the polymer (specifically, the base polymer, e.g., an acrylic polymer) contained in the adhesive layer, from the viewpoint of realizing an adhesive that exhibits adhesive properties such as adhesive strength and cohesive strength in a well-balanced manner, and may be, for example, 0.001 parts by weight or more, or may be 0.01 parts by weight or more.
  • the amount of crosslinking agent used relative to 100 parts by weight of the polymer may be 0.05 parts by weight or more, 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more.
  • the upper limit of the amount of crosslinking agent used may vary depending on the type of crosslinking agent used, so is not limited to a specific range, but it is preferable that the amount is limited to a predetermined amount or less from the viewpoint of realizing good heat peelability and heat resistance, and thus realizing the desired post-heat peel strength reduction rate.
  • the amount of crosslinking agent used the crosslinking density is appropriately suppressed, and at such a crosslinking density, the polyfunctional monomer and the thermal polymerization initiator frequently collide with each other during heat treatment, and heat curing proceeds, and heat peelability and heat resistance peelability are expressed, and the desired post-heat peel strength reduction rate is realized. Note that the technology disclosed herein is not limited to the above considerations.
  • the amount of crosslinking agent used is suitably less than 10 parts by weight relative to 100 parts by weight of the polymer, and in some embodiments, it is preferably less than 5 parts by weight, and may be less than 3 parts by weight. In some embodiments, the amount of crosslinking agent used is suitably less than 1 part by weight relative to 100 parts by weight of the polymer, and is preferably 0.9 parts by weight or less, and may be 0.8 parts by weight or less, 0.7 parts by weight or less, 0.6 parts by weight or less, 0.5 parts by weight or less, 0.4 parts by weight or less, 0.3 parts by weight or less, 0.2 parts by weight or less, or 0.1 parts by weight or less.
  • the amount of crosslinking agent used it tends to be easier to achieve high adhesive strength.
  • the amount of the crosslinking catalyst used can be, for example, about 0.0001 parts by weight or more, about 0.001 parts by weight or more, or about 0.005 parts by weight or more, relative to 100 parts by weight of the polymer (specifically, the base polymer, for example, an acrylic polymer) contained in the adhesive layer, and can be about 1 part by weight or less, about 0.1 parts by weight or less, or about 0.05 parts by weight or less.
  • the adhesive composition used to form the first adhesive layer may contain a compound that generates keto-enol tautomerism as a crosslinking retarder, if desired.
  • a compound that generates keto-enol tautomerism may be preferably used in an adhesive composition that contains an isocyanate-based crosslinking agent or an adhesive composition that can be used by blending an isocyanate-based crosslinking agent. This can provide an effect of extending the pot life of the adhesive composition.
  • various ⁇ -dicarbonyl compounds can be used as the compound that causes keto-enol tautomerization.
  • ⁇ -diketones such as acetylacetone and 2,4-hexanedione
  • acetoacetates such as methyl acetoacetate and ethyl acetoacetate
  • propionylacetates such as ethyl propionylacetate
  • isobutyrylacetates such as ethyl isobutyrylacetate
  • malonic acid esters such as methyl malonate and ethyl malonate; and the like.
  • preferred compounds include acetylacetone and acetoacetates.
  • the compounds that cause keto-enol tautomerization can be used alone or in combination of two or more.
  • the amount of the compound that causes keto-enol tautomerization used may be, for example, 0.1 parts by weight or more and 20 parts by weight or less, and appropriately 0.5 parts by weight or more and 15 parts by weight or less, for example, 1 part by weight or more and 10 parts by weight or less, or may be 1 part by weight or more and 5 parts by weight or less, relative to 100 parts by weight of the polymer (specifically, the base polymer, e.g., an acrylic polymer) contained in the pressure-sensitive adhesive layer.
  • the polymer specifically, the base polymer, e.g., an acrylic polymer
  • the first adhesive layer may contain one or more monofunctional monomers containing one ethylenically unsaturated group in one molecule, if desired.
  • the monofunctional monomer is used within a range that does not impair the effects of the technology disclosed herein.
  • the monofunctional monomer a known monofunctional acrylate monomer or vinyl monomer may be used.
  • the content of the monofunctional monomer in the adhesive layer is suitably about 100 parts by weight or less (0 parts by weight or more and 100 parts by weight or less, for example, less than 100 parts by weight) relative to 100 parts by weight of the polyfunctional monomer, and may be less than 50 parts by weight, less than 30 parts by weight, less than 10 parts by weight, or less than 1 part by weight.
  • the technology disclosed herein can be implemented in an embodiment in which the adhesive layer does not substantially contain a monofunctional monomer.
  • the first adhesive layer may contain various additives that are common in the field of adhesives, such as tackifiers, silane coupling agents, peel strength regulators (surfactants, etc.), viscosity regulators (e.g. thickeners), leveling agents, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, antiaging agents, etc.
  • tackifiers silane coupling agents
  • peel strength regulators surfactants, etc.
  • viscosity regulators e.g. thickeners
  • leveling agents plasticizers
  • fillers fillers
  • colorants such as pigments and dyes
  • stabilizers stabilizers
  • preservatives antiaging agents
  • the content of the tackifier in the first adhesive layer may be, for example, less than 10 parts by weight, or even less than 5 parts by weight, relative to 100 parts by weight of the polymer (specifically, the base polymer, for example, an acrylic polymer) contained in the first adhesive layer.
  • the content of the tackifier may be less than 1 part by weight (for example, less than 0.5 parts by weight), or may be less than 0.1 parts by weight (0 parts by weight or more and less than 0.1 parts by weight).
  • the first adhesive layer may not contain a tackifier.
  • the first pressure-sensitive adhesive layer in the technology disclosed herein may exhibit the desired heat-peelability without using heat-expandable microspheres, a foaming agent, or the like.
  • the content of the heat-expandable microspheres in the first pressure-sensitive adhesive layer may be, for example, less than 1 part by weight, or even less than 0.1 part by weight, per 100 parts by weight of the polymer (specifically, the base polymer, e.g., an acrylic polymer) contained in the first pressure-sensitive adhesive layer.
  • the content of the foaming agent in the first pressure-sensitive adhesive layer may be, for example, less than 1 part by weight, or even less than 0.1 part by weight, per 100 parts by weight of the polymer (specifically, the base polymer, e.g., an acrylic polymer) contained in the first pressure-sensitive adhesive layer.
  • the first pressure-sensitive adhesive layer may contain neither heat-expandable microspheres nor a foaming agent.
  • the second adhesive layer of the adhesive sheet disclosed herein typically contains at least a polymer and may further contain a monomer.
  • the second adhesive layer may be a thermosetting adhesive layer, or may be an adhesive layer that does not necessarily require thermosetting.
  • the type of adhesive constituting the second adhesive layer is not particularly limited.
  • the second adhesive layer may contain one or more of various rubber-like polymers such as acrylic polymers, rubber polymers (e.g., natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine polymers that can be used in the field of adhesives.
  • the above polymers may be used as base polymers in adhesives and function as structural polymers that form the adhesive. From the viewpoint of adhesive performance, cost, etc., adhesives containing acrylic polymers or rubber polymers as base polymers can be preferably adopted. Among them, adhesives (acrylic adhesives) using acrylic polymers as base polymers are preferable.
  • the pressure-sensitive adhesive (second pressure-sensitive adhesive) constituting the second pressure-sensitive adhesive layer preferably contains a polymer that does not have an ethylenically unsaturated group.
  • the second pressure-sensitive adhesive layer may, for example, contain a polymer of a monomer raw material that contains a C 1-20 alkyl (meth)acrylate as a main monomer and may further contain a sub-monomer copolymerizable with the main monomer as the polymer (preferably a base polymer).
  • C 1-20 alkyl (meth)acrylate may be the same as those described for the case in which the monomer component constituting the acrylic polymer in the first pressure-sensitive adhesive layer contains a C 1-20 alkyl (meth)acrylate.
  • an acrylic polymer containing one or both of BA and 2EHA as the monomer component is preferred, and an acrylic polymer containing at least BA is particularly preferred.
  • the above-mentioned secondary monomers include, for example, various monomers mentioned as "other monomers" in the description of the first adhesive layer, alkoxyalkyl (meth)acrylates, etc.
  • a monomer having a polar group e.g., a carboxy group, a hydroxyl group, a nitrogen atom-containing ring, etc.
  • a monomer having a polar group can be useful for introducing a crosslinking point into an acrylic polymer or for increasing the cohesive force of the adhesive.
  • the secondary monomers can be used alone or in combination of two or more.
  • the amount used is not particularly limited, but it is appropriate to set it to 0.01% by weight or more of the entire monomer components. From the viewpoint of better exerting the effect of using the secondary monomer, the amount used of the secondary monomer may be 0.1% by weight or more of the entire monomer components, or may be 0.5% by weight or more. In addition, from the viewpoint of easily balancing the adhesive properties, it is appropriate to set the amount used of the secondary monomer to 50% by weight or less of the entire monomer components, and preferably 40% by weight or less.
  • the monomer component includes a carboxyl group-containing monomer as the secondary monomer.
  • suitable examples of the carboxyl group-containing monomer include AA and MAA.
  • the carboxyl group-containing monomer may be used alone or in combination of two or more.
  • AA and MAA may be used in combination.
  • the amount of the carboxyl group-containing monomer used may be, for example, 0.01% by weight or more of the entire monomer component, 0.05% by weight or more, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more, 1.0% by weight or more, 2.0% by weight or more, or 2.5% by weight or more.
  • the amount of the carboxyl group-containing monomer used may be, for example, 15% by weight or less, 10% by weight or less, 5% by weight or less, or 3% by weight or less of the entire monomer component. In some embodiments, the amount of the carboxyl group-containing monomer used may be 2% by weight or less, 1% by weight or less (for example, less than 1% by weight) of the entire monomer component.
  • the monomer component includes an alkoxy group-containing (meth)acrylate as the secondary monomer.
  • alkoxy group-containing (meth)acrylate are the same as those described for the first adhesive layer, so duplicate descriptions will be omitted.
  • the content of the alkoxy group-containing (meth)acrylate in the monomer component is not particularly limited, and may be, for example, 1% by weight or more, 5% by weight or more, 10% by weight or more, 20% by weight or more, or 30% by weight or more.
  • the upper limit of the content of the alkoxy group-containing (meth)acrylate is set so that the total amount with other monomers does not exceed 100% by weight, and may be, for example, 45% by weight or less, 35% by weight or less, 25% by weight or less, 15% by weight or less, 5% by weight or less, 3% by weight or less, or 1% by weight or less, or less than 1% by weight.
  • the second adhesive layer preferably contains at least one of a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule (polyfunctional monomer) and a polymer having an ethylenically unsaturated group, from the viewpoint of easily exhibiting the desired thermosetting properties and easy peeling properties when heated, and preferably further contains a thermal polymerization initiator as necessary.
  • the thermosetting second adhesive layer can be prepared so as to exhibit the desired initial (pre-heating) performance and/or post-heating performance by referring to the above description regarding the first adhesive layer, so redundant description will be omitted.
  • the second adhesive layer preferably does not contain heat-expandable microspheres, a blowing agent, etc., or the content of heat-expandable microspheres, a blowing agent, etc. per 100 parts by weight of polymer is preferably limited to less than 1 part by weight or less than 0.1 part by weight.
  • ⁇ Substrate> As the substrate of the adhesive sheet disclosed herein, various sheet-like substrates can be used, for example, resin films, paper, cloth, rubber sheets, foam sheets, metal foils, composites thereof, etc. can be used.
  • resin films include polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers; polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); vinyl chloride resin films; vinyl acetate resin films; polyamide resin films; fluororesin films; cellophane; and the like.
  • resin films include resin films formed from one or more engineering plastics (which may be super engineering plastics), such as polyphenylene sulfide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polyarylate resins, polyamideimide resins, and polyimide resins.
  • engineering plastics is preferred from the viewpoint of heat resistance.
  • paper include Japanese paper, craft paper, glassine paper, fine paper, synthetic paper, and topcoat paper.
  • the fabric include woven fabrics and nonwoven fabrics made of various fibrous materials, either alone or in a blend.
  • fibrous materials include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, etc.
  • rubber sheet include natural rubber sheet and butyl rubber sheet.
  • foam sheet include foamed polyurethane sheet and foamed polychloroprene rubber sheet.
  • metal foil include aluminum foil and copper foil.
  • a resin film having a predetermined rigidity (strength) and excellent processability and handling properties is used as the substrate.
  • Suitable examples of such resin films include polyester films (e.g., PET films), polyimide (PI) films, and the like.
  • the term "resin film” typically refers to a non-porous film, and typically refers to a resin film that does not substantially contain air bubbles (void-free). Therefore, the resin film is a concept that is distinguished from foam films and nonwoven fabrics.
  • the density of the resin film that can be used as the substrate can be about 0.85 to 1.50 g/cm 3 (e.g., 0.90 g/cm 3 to 1.20 g/cm 3 , typically 0.92 g/cm 3 to 1.05 g/cm 3 ).
  • the resin film may have a single-layer structure or a multi-layer structure of two or more layers (e.g., a three-layer structure).
  • the substrate e.g., a resin film
  • the substrate may contain known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, and antiblocking agents, as necessary.
  • additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, and antiblocking agents, as necessary.
  • the amount of additives to be added is not particularly limited, and can be set appropriately depending on the application, etc.
  • the method for producing the resin film is not particularly limited.
  • conventional resin film molding methods such as extrusion molding, inflation molding, T-die casting, and calendar roll molding can be appropriately used.
  • the substrate may be substantially composed of a resin film.
  • the substrate may include an auxiliary layer in addition to the resin film.
  • the auxiliary layer include an optical property adjusting layer (e.g., a colored layer, an anti-reflection layer), a printed layer or a laminate layer for imparting a desired appearance, an antistatic layer, an undercoat layer, a release layer, and other surface treatment layers.
  • the thickness of the substrate is not particularly limited and can be appropriately selected depending on the purpose, but generally can be 1 to 500 ⁇ m. From the viewpoint of processability, handling, workability, etc., the thickness of the substrate is suitably 2 ⁇ m or more (for example, 3 ⁇ m or more, typically 5 ⁇ m or more), and may be approximately 7 ⁇ m or more, or may be 10 ⁇ m or more. In addition, the thickness of the substrate is suitably approximately 200 ⁇ m or less, and from the viewpoint of weight reduction and thinning, it is preferably approximately 100 ⁇ m or less, more preferably approximately 50 ⁇ m or less, and may be 30 ⁇ m or less, 20 ⁇ m or less, or 15 ⁇ m or less. When the thickness of the substrate is reduced, the flexibility of the adhesive sheet and its ability to follow the surface shape of the adherend tend to improve. The above substrate thickness can also be preferably applied to the thickness of the resin film used as the substrate or a component thereof.
  • the surface of the substrate facing the adhesive layer may be subjected to conventional surface treatments such as corona treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer, etc., as necessary. Such surface treatments may be treatments for improving the adhesion between the substrate and the adhesive layer, in other words, the anchoring ability of the adhesive layer to the substrate.
  • the composition of the primer is not particularly limited, and may be appropriately selected from known ones.
  • the thickness of the undercoat layer is not particularly limited, but is, for example, appropriately about 0.01 ⁇ m to 1 ⁇ m, and preferably about 0.1 ⁇ m to 1 ⁇ m.
  • the back surface of the substrate may be subjected to the various surface treatments mentioned above, antistatic treatment, etc.
  • the adhesive layer of the adhesive sheet disclosed herein can be formed by a conventionally known method.
  • the first adhesive layer and the second adhesive layer can be formed in the form of a layer (adhesive layer) by applying (e.g., coating) the corresponding adhesive composition to an appropriate surface and then appropriately performing a curing treatment.
  • the curing means e.g., drying, crosslinking, polymerization, cooling, etc.
  • the composition is typically dried (preferably further crosslinked) to form an adhesive.
  • the surface to which the adhesive composition is applied may be a surface having releasability (a release surface) or may be a non-release surface.
  • the non-release surface may be a non-release substrate surface, a surface of the second adhesive layer or the first adhesive layer formed in advance, or the like.
  • a method for forming the first or second pressure-sensitive adhesive layer on the first surface (non-release surface) of the substrate a method (direct method) can be adopted in which a corresponding pressure-sensitive adhesive composition is directly applied (typically coated) to the substrate and cured to form a pressure-sensitive adhesive layer.
  • a method (transfer method) can be adopted in which a corresponding pressure-sensitive adhesive composition is applied to a surface (release surface) having releasability, cured to form a pressure-sensitive adhesive layer on the surface, and the pressure-sensitive adhesive layer is transferred to the substrate.
  • Methods for producing an adhesive sheet in which a second adhesive layer is formed on a first surface of a substrate and a first adhesive layer is partially laminated on the second adhesive layer include, for example, a method of laminating a second adhesive layer on a substrate by a direct method or a transfer method, and then partially laminating the first adhesive layer on the second adhesive layer, or a method of partially applying an adhesive composition for forming a first adhesive layer onto the second adhesive layer, and appropriately carrying out a curing treatment to form a first adhesive layer.
  • a method may be adopted in which a pressure-sensitive adhesive composition for forming a first pressure-sensitive adhesive layer is applied to a partial region of a suitable release surface, and a curing treatment is appropriately performed to form a first pressure-sensitive adhesive layer, and then a pressure-sensitive adhesive composition for forming a second pressure-sensitive adhesive layer is applied so that it protrudes outward from the outer edge of the region where the first pressure-sensitive adhesive layer is formed, and a curing treatment is appropriately performed to form a second pressure-sensitive adhesive layer; or a second pressure-sensitive adhesive layer formed on another release surface is laminated to produce a pressure-sensitive adhesive layer including the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer on the release surface, and then the pressure-sensitive adhesive layer is attached to a substrate and transferred.
  • An adhesive sheet in which a first adhesive layer is formed directly on a portion of a first surface of a substrate and a second adhesive layer is formed directly on another portion of the first surface may be produced, for example, by simultaneously or sequentially applying an adhesive composition for forming the first adhesive layer and an adhesive composition for forming the second adhesive layer to the substrate in the above portion and the above other portion of the first surface and then subjecting the substrate to an appropriate curing treatment to form the first and second adhesive layers; or by forming first and second adhesive layers in shapes that match the above portion and the above other portion of the first surface on an appropriate release surface and then transferring them to the substrate.
  • the technology disclosed herein can be preferably implemented using a solvent-based adhesive composition.
  • the above-mentioned solvent-based adhesive composition is an adhesive composition in a form containing adhesive-forming components in an organic solvent.
  • the solvent-based adhesive composition typically contains a solution polymer of a monomer component, a polyfunctional monomer, a thermal polymerization initiator, and optionally other additives.
  • the effects of the technology disclosed herein can be effectively achieved in a form having a solvent-based adhesive (layer).
  • the solvent contained in the solvent-based adhesive composition can be appropriately selected from conventionally known organic solvents.
  • any one solvent selected from aromatic compounds such as toluene (typically aromatic hydrocarbons); esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc., or a mixture of two or more solvents can be used.
  • aromatic compounds such as toluene (typically aromatic hydrocarbons); esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane
  • the pressure-sensitive adhesive composition can be applied using a known or commonly used coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a die coater, a bar coater, a knife coater, a spray coater, etc.
  • the pressure-sensitive adhesive composition may be applied by impregnation, a curtain coating method, or the like.
  • the adhesive composition is preferably dried under heating.
  • the drying temperature is not particularly limited, but can be, for example, about 40 to 100 ° C., and is usually preferably about 60 to 80 ° C.
  • drying at the above temperature for example, drying for about 1 to 10 minutes, more specifically, drying for about 3 to 7 minutes
  • the solvent volatilization is in progress
  • the adhesive composition subjected to the drying contains a polyfunctional monomer or a thermal polymerization initiator
  • the reaction of the polyfunctional monomer and the deactivation of the thermal polymerization initiator are negligible.
  • aging may be performed for the purpose of adjusting the component migration in the adhesive layer, progressing the crosslinking reaction, and relaxing distortion that may exist in the substrate or the adhesive layer.
  • the thickness of each of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is not particularly limited.
  • the thickness of each pressure-sensitive adhesive layer may be, for example, 1 ⁇ m or more, 2 ⁇ m or more, or 3 ⁇ m or more.
  • the greater the thickness of the pressure-sensitive adhesive layer the greater the tendency for the adhesive strength to be improved.
  • the thickness of each pressure-sensitive adhesive layer is 5 ⁇ m or more, 7 ⁇ m or more, 9 ⁇ m or more, 10 ⁇ m or more, more than 10 ⁇ m, 15 ⁇ m or more, 20 ⁇ m or more, 25 ⁇ m or more, or 30 ⁇ m or more.
  • each pressure-sensitive adhesive layer is suitably, for example, about 200 ⁇ m or less, and may be 100 ⁇ m or less (for example, less than 100 ⁇ m), or 50 ⁇ m or less.
  • the thickness of each adhesive layer may be, for example, 40 ⁇ m or less, 30 ⁇ m or less (e.g., less than 30 ⁇ m), 20 ⁇ m or less, or 15 ⁇ m or less.
  • the thickness of the first adhesive layer and the thickness of the second adhesive layer may be approximately the same or different. For example, the thickness of the first adhesive layer may be greater than the thickness of the second adhesive layer, or vice versa.
  • the thickness of the entire adhesive layer including the first adhesive layer and the second adhesive layer may be, for example, 3 ⁇ m or more, suitably 5 ⁇ m or more, preferably 8 ⁇ m or more, and more preferably 10 ⁇ m or more.
  • the thickness of the entire adhesive layer may be, for example, 15 ⁇ m or more, may be 20 ⁇ m or more, may be 25 ⁇ m or more, 30 ⁇ m or more, 35 ⁇ m or more, or 40 ⁇ m or more.
  • the thickness of the entire adhesive layer is suitably, for example, about 250 ⁇ m or less, may be 150 ⁇ m or less, may be 100 ⁇ m or less, or may be 80 ⁇ m or less.
  • a small thickness of the entire adhesive layer is advantageous in terms of making the adhesive sheet thinner, and tends to have excellent conformability to the adherend.
  • the thickness of the entire adhesive layer may be, for example, 60 ⁇ m or less, 50 ⁇ m or less, 45 ⁇ m or less, or 40 ⁇ m or less.
  • the total thickness of the adhesive sheet disclosed herein (which may include the adhesive layer and the substrate, but does not include the release liner) is not particularly limited, and is suitably in the range of about 5 to 1000 ⁇ m.
  • the total thickness of the adhesive sheet may be 10 ⁇ m or more, 15 ⁇ m or more, or 20 ⁇ m or more, from the viewpoints of adhesive properties, handling, and the like.
  • the total thickness of the adhesive sheet may be 30 ⁇ m or more, 40 ⁇ m or more, or 50 ⁇ m or more.
  • the total thickness of the adhesive sheet is 500 ⁇ m or less, or may be 300 ⁇ m or less.
  • the total thickness of the adhesive sheet is 100 ⁇ m or less (e.g., less than 100 ⁇ m), more preferably 80 ⁇ m or less, or may be 70 ⁇ m or less. Reducing the thickness of the adhesive sheet is advantageous in terms of thinning, miniaturization, weight reduction, resource saving, and the like.
  • the total thickness of the adhesive sheet refers to the thickness of the thickest part.
  • the release liner used in the PSA sheet disclosed herein is not particularly limited, and may be, for example, a release liner in which the surface of a liner substrate such as a resin film or paper has been subjected to a release treatment, or a release liner made of a low-adhesion material such as a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin-based resin (polyethylene, polypropylene, etc.).
  • a release-treated resin film may be preferably used as the release liner.
  • a method for peeling an adherend (first member) attached to a first pressure-sensitive adhesive layer (first region) of any of the pressure-sensitive adhesive sheets disclosed herein from the first pressure-sensitive adhesive layer.
  • the peeling method includes a step of subjecting the pressure-sensitive adhesive sheet having the adherend attached to the first pressure-sensitive adhesive layer to a heat treatment (e.g., a heat treatment at a temperature higher than 100°C), and then peeling the adherend from the first pressure-sensitive adhesive layer.
  • a heat treatment e.g., a heat treatment at a temperature higher than 100°C
  • the first pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein has properties suitable for exhibiting heat-sensitive peelability (heat-resistant peelability), and therefore can be easily peeled from the adherend after the heat treatment.
  • the temperature of the heat treatment for the adhesive sheet to which the adherend is attached is not particularly limited, and may be, for example, a temperature higher than 100°C.
  • the heat treatment temperature may be, for example, about 110°C or higher, about 120°C or higher, about 130°C or higher, about 140°C or higher, about 150°C or higher, about 160°C or higher, or 170°C or higher.
  • the upper limit of the heat treatment temperature may vary depending on the purpose of the heat treatment, the heat resistance of the adherend, etc., but is generally about 260°C or lower, about 250°C or lower, 230°C or lower, 200°C or lower, or 180°C or lower.
  • the heat treatment temperature may be less than 180°C, 170°C or lower, 160°C or lower, 150°C or lower, 140°C or lower, 130°C or lower, or 120°C or lower.
  • the time of the heat treatment is not particularly limited, and may be within 10 hours, within 5 hours, or within 3 hours, but in some preferred embodiments, from the viewpoint of the efficiency of the heating process, it may be within 1 hour, within 30 minutes, within 15 minutes, within 10 minutes, or within 5 minutes.
  • the adhesive sheet disclosed herein may be one in which the first adhesive layer is thermally cured by the above-mentioned short-time heat treatment, and exhibits heat-peelability.
  • the time of the heat treatment may be 1 minute or more, 3 minutes or more, 5 minutes or more, 7 minutes or more, or 9 minutes or more. In some embodiments, the time of the heat treatment may be 10 minutes or more, 30 minutes or more, 60 minutes or more, more than 1 hour, more than 3 hours, more than 4 hours, or more than 5 hours.
  • the adhesive sheet disclosed herein can be one in which the first adhesive is thermally cured by heat treatment at the above heating temperature, the peel strength is reduced, and an increase in the peel strength (heavy peeling) does not occur or is suppressed even if the heated state continues for a long time. Therefore, it is possible to maintain heat peelability (heat-resistant peelability) even after a long heat treatment. There is no particular upper limit to the heat treatment time, but from the viewpoint of the efficiency of the heating process, it may be within 10 hours, within 5 hours, or within 3 hours.
  • the above peeling method can be carried out, for example, by taking advantage of the feature that the post-heat peeling force ratio (Fb1/Fa1) of the adhesive sheet disclosed herein is greater than 1.0, in a manner in which the first member is peeled (separated) from the first adhesive layer after the heat treatment, while leaving the adherend (second member) attached to the second adhesive layer (second region) on the second adhesive layer.
  • the heat treatment is carried out in a state in which the first member is attached to the first adhesive layer, and the second member is attached to the second adhesive layer.
  • the adhesive sheet to which the first member is attached may be heat-treated, and then the second member may be attached to the second adhesive layer.
  • the shape of the adhesive sheet can be stabilized (for example, lifting or deformation can be suppressed) by utilizing the adhesiveness of the second adhesive layer to the second member.
  • the second member is a frame-shaped (e.g., annular) member made of a material with a certain degree of rigidity (metal, glass plate, hard plastic material, etc.), and the first member is attached to the opening inside the frame in a positional relationship that makes it possible to optimally achieve the shape stabilization effect.
  • the use of the adhesive sheet disclosed herein is not particularly limited.
  • the adhesive sheet disclosed herein has an adhesive surface including a first region where the first adhesive layer is exposed, and the first adhesive layer can exhibit heat-peelability, so that it can be used in various applications in which an adherend is adhered to the first adhesive layer (first region) and then the adherend is removed from the first adhesive layer after the adhesion purpose is completed.
  • it can be used as an adhesive sheet for fixing (temporarily fixing), masking, protection, etc. during processing of the adherend.
  • the adhesive sheet disclosed herein can be preferably used in situations where an ultraviolet irradiation peelable adhesive cannot be applied, such as when the adherend is non-transparent to light.
  • the adhesive sheet disclosed herein can be preferably used as a process material that is fixed to and peeled off from an adherend in the manufacturing process of electronic devices and electronic components, for example.
  • a suitable use of the adhesive sheet disclosed herein can be used for manufacturing semiconductor elements.
  • it can be preferably used as a wafer fixing sheet that fixes the wafer to a fixing plate (processing table) in semiconductor wafer processing (typically silicon wafer processing).
  • the adhesive sheet disclosed herein can also be preferably used as a protective sheet for protecting the wafer in the wafer processing.
  • the semiconductor elements may be exposed to heat during processing steps, etc., so that adhesive sheets having heat resistance and easy peeling properties are preferably used.
  • the adhesive sheet disclosed herein can also be applied to optical applications requiring heat resistance. More specifically, the adhesive sheet disclosed herein can be used as an optical adhesive sheet used for, for example, bonding optical members (for bonding optical members) or for manufacturing products (optical products) using the optical members.
  • the optical member refers to a member having optical properties (for example, polarizing, light refraction, light scattering, light reflectivity, light transmittance, light absorption, light diffraction, optical rotation, visibility, etc.).
  • the type of material to be attached (adherend material) disclosed herein is not particularly limited.
  • the adhesive sheet disclosed herein can be used for fixing and protecting various members and materials.
  • the adherend material include glass such as alkali glass and non-alkali glass; metal materials such as stainless steel (SUS) and aluminum; ceramic materials such as alumina and silica; resin materials such as polyester resins such as PET, acrylic resins, ABS resins, polycarbonate resins, polystyrene resins, and transparent polyimide resins; and the like.
  • Suitable examples of the adherend material include glass materials such as alkali glass and semiconductor wafers.
  • the above glass material can be, for example, a glass plate having a surface partially provided with a transparent conductive film (e.g., an ITO (indium tin oxide) film) or an FPC (flexible printed circuit board), as used in tablet computers, mobile phones, organic LEDs (light-emitting diodes), and the like.
  • a transparent conductive film e.g., an ITO (indium tin oxide) film
  • FPC flexible printed circuit board
  • a pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer disposed on a first surface of the substrate, the pressure-sensitive adhesive layer includes a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer, and forms an adhesive surface including a first region where the first pressure-sensitive adhesive layer is exposed and a second region where the second pressure-sensitive adhesive layer is exposed;
  • the first pressure-sensitive adhesive layer is made of a thermosetting pressure-sensitive adhesive in which a gel fraction increase (Ga1-Ga0) calculated from a post-heat gel fraction Ga1 [%] measured after a heat treatment at 180°C for 30 minutes and a pre-heat gel fraction Ga0 [%] measured without the heat treatment is 10% or more, and the post-heat gel fraction Ga1 is 80% or more;
  • a pressure-sensitive adhesive sheet in which the post-heating peel strength ratio (Fb1/Fa1) calculated from the post-heating peel strength Fa1 [N/20 mm] measured in an environment of 23°C and
  • a pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer disposed on a first surface of the substrate, the pressure-sensitive adhesive layer includes a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer, and forms an adhesive surface including a first region where the first pressure-sensitive adhesive layer is exposed and a second region where the second pressure-sensitive adhesive layer is exposed;
  • the first pressure-sensitive adhesive layer has a post-heating Young's modulus Ya1 [MPa] measured in an environment of 23°C and 50% RH after heating at 180°C for 30 minutes, of 10 MPa or more and 1000 MPa or less;
  • ⁇ Evaluation method> (Pre-heat peel force F0)
  • the adhesive sheet having the adhesive layer to be evaluated on the resin film is cut to a size of 20 mm wide and 100 mm long, and the adhesive surface of the adhesive layer is pressed and bonded to an alkaline glass plate (manufactured by Matsunami Glass Industry Co., Ltd., thickness 1.35 mm, blue plate edge polished product) as an adherend under an environment of 23 ° C. and 50% RH by rolling a 2 kg roller back and forth once.
  • the adherend to which the adhesive sheet is attached is left for 6 hours under the same environment and used as an evaluation sample.
  • the evaluation sample is set in a tensile tester under an environment of 23 ° C.
  • pre-heat peel force F0 [N / 20 mm width] is measured when the adhesive sheet is peeled off from the adherend under the conditions of a peel angle of 180 degrees and a speed of 300 mm / min.
  • This pre-heat peel force F0 is called pre-heat peel force Fa0 when the adhesive layer to be evaluated is the first adhesive layer, and called pre-heat peel force Fb0 when the adhesive layer is the second adhesive layer.
  • a pressure-sensitive adhesive sheet in which the first and second pressure-sensitive adhesive layers are formed separately on a resin film may be used, or a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on a resin film, the pressure-sensitive adhesive layer having a first region where the first pressure-sensitive adhesive layer is exposed and a second region where the second pressure-sensitive adhesive layer is exposed may be used.
  • the resin film various resin films that can be used as the substrate of the pressure-sensitive adhesive sheet disclosed herein can be used, and suitable examples include polyimide (PI) film and polyethylene terephthalate (PET) film.
  • the thickness of the resin film is suitably about 10 ⁇ m to 100 ⁇ m, and preferably about 25 ⁇ m to 75 ⁇ m.
  • a Shimadzu product named "EZ-S 500N” or an equivalent product can be used.
  • the measurement may be performed by backing the non-measurement surface with a PET film.
  • Post-heat peel force F1 Using a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer to be evaluated on a resin film, an evaluation sample is prepared by the method described in the above-mentioned pre-heat peel force F0 measurement. The obtained evaluation sample is heated in an oven at 180°C for 30 minutes, and then removed from the oven and left to stand in an environment of 23°C and 50% RH for 30 minutes. The evaluation sample is then set in a tensile tester in the same environment, and the peel strength (post-heat peel force) F1 [N/20 mm width] is measured when the pressure-sensitive adhesive sheet is peeled off from the adherend under the conditions of a peel angle of 180° and a speed of 300 mm/min.
  • This post-heat peel force F1 is called post-heat peel force Fa1 when the pressure-sensitive adhesive layer to be evaluated is the first pressure-sensitive adhesive layer, and called post-heat peel force Fb1 when the pressure-sensitive adhesive layer to be evaluated is the second pressure-sensitive adhesive layer.
  • the adherend, tensile tester, and other items are the same as those in the measurement of the pre-heat peel force F0.
  • the gel fraction (weight ratio of the matter insoluble in ethyl acetate) of the pressure-sensitive adhesive layer is measured by the following method.
  • About 0.1 g of the adhesive sample (weight Wg1) is wrapped in a porous polytetrafluoroethylene film (weight Wg2) with an average pore size of 0.2 ⁇ m in a purse shape, and the opening is tied with string (weight Wg3).
  • a porous polytetrafluoroethylene (PTFE) film the product name "Nitoflon (registered trademark) NTF1122" (average pore size 0.2 ⁇ m, porosity 75%, thickness 85 ⁇ m) available from Nitto Denko Corporation or an equivalent product is used.
  • the package is immersed in 50 mL of ethyl acetate and kept at room temperature (typically 23° C.) for 7 days to elute only the sol component in the adhesive layer outside the film, and then the package is taken out and the ethyl acetate adhering to the outer surface is wiped off, and the package is dried at 130° C. for 2 hours, and the weight (Wg4) of the package is measured.
  • the gel fraction of the adhesive layer can be calculated by substituting each value into the following formula.
  • Gel fraction [%] [(Wg4 - Wg2 - Wg3) / Wg1] x 100
  • the gel fraction of the pressure-sensitive adhesive layer is measured initially (gel fraction before heating) and after the pressure-sensitive adhesive layer is heat-treated in an oven at 180° C. for 30 minutes, removed from the oven and allowed to stand in an environment of 23° C. and 50% RH for 30 minutes (gel fraction after heating).
  • the pressure-sensitive adhesive layer to be evaluated is prepared in a state where both sides are covered with release liners, and cut together with the release liners to a size of 80 mm in width (when the thickness of the pressure-sensitive adhesive layer is 30 ⁇ m) and 30 mm in length, and one release liner is removed from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is wound up on the other release liner in the length direction so as not to trap air bubbles, to prepare a rod-shaped sample of 30 mm in length.
  • the rod-shaped sample is set in a tensile tester (manufactured by ORIENTEC, product name "RTC-1150A") and pulled under conditions of a measurement temperature of 23°C, a chuck distance of 10 mm, and a pulling speed of 50 mm/min, and the initial elastic modulus is determined from the rise of the obtained stress-strain curve (S-S curve), and this is defined as the Young's modulus [MPa] of the pressure-sensitive adhesive layer.
  • the Young's modulus of the pressure-sensitive adhesive layer is measured initially (Young's modulus before heating) and after the pressure-sensitive adhesive layer is heat-treated in an oven at 180° C. for 30 minutes, removed from the oven and allowed to stand in an environment of 23° C.
  • the cut width of the adhesive layer is set to 80 mm is to set the cross-sectional area of the adhesive layer in the cross section along the width direction to within the range of about 2.0 to 2.5 mm2 , and it is desirable to adjust the cut width so that the cross-sectional area is approximately the same depending on the thickness of the adhesive layer.
  • the cut width of the adhesive layer is set to 240 mm, and the Young's modulus before and after heating is measured.
  • Example 1 (Preparation of First Pressure-Sensitive Adhesive Composition) A reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer was charged with 100 parts of a monomer mixture containing methoxyethyl acrylate (MEA), acryloylmorpholine (ACMO) and hydroxyethyl acrylate (HEA) in a molar ratio of 80:20:20, and 65 parts of toluene as a polymerization solvent, and 0.2 parts of benzoyl peroxide was added as a thermal polymerization initiator to perform a polymerization reaction (solution polymerization) at 61 ° C.
  • MEA methoxyethyl acrylate
  • ACMO acryloylmorpholine
  • HOA hydroxyethyl acrylate
  • methacryloyloxyethyl isocyanate (MOI) in an amount equivalent to 16 moles relative to 20 moles of HEA used as a raw material for the acrylic polymer a was added, and an addition reaction treatment was performed at 50 ° C. for 48 hours in an air stream to obtain a solution of an acrylic polymer A having a methacryloyl group at the side chain end.
  • MOI methacryloyloxyethyl isocyanate
  • crosslinking agent CL2 an epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name “Tetrad C”; hereinafter referred to as "crosslinking agent CL2") was added per 100 parts of the acrylic polymer B, and the mixture was mixed uniformly to prepare a pressure-sensitive adhesive composition for forming a second pressure-sensitive adhesive layer (second pressure-sensitive adhesive composition) according to this example.
  • the first adhesive composition obtained above was applied to the release surface of a commercially available PET release liner, and dried at 80° C. for 5 minutes to form a first adhesive layer having a thickness of 30 ⁇ m, a width of 30 mm, and a length of 100 mm.
  • the second adhesive composition obtained above was applied to the release surface of a commercially available PET release liner, and dried at 80° C. for 5 minutes to form a second adhesive layer having a thickness of 10 ⁇ m, a width of 80 mm, and a length of 150 mm.
  • the second adhesive layer was laminated on one side of a 50 ⁇ m-thick polyimide (PI) film (product name "Kapton 200H", manufactured by Toray DuPont Co., Ltd.) as a substrate, and then the first adhesive layer was laminated on the center of the film. Then, aging was performed at 50° C. for 3 days. In this manner, the adhesive sheet (single-sided adhesive sheet with substrate) according to this example was produced.
  • PI polyimide
  • the adhesive surface of the pressure-sensitive adhesive sheet has a first region where the first pressure-sensitive adhesive layer is exposed, and a second region where the second pressure-sensitive adhesive layer that is not covered by the first pressure-sensitive adhesive layer is exposed in a ring shape around the first region, and the adhesive surface is protected by the release liner used in forming the first pressure-sensitive adhesive layer.
  • Examples 2 to 14> A first adhesive composition according to each example was prepared in the same manner as in Example 1, except that the type and amount of the crosslinking agent, the type and amount of the thermal polymerization initiator, and the type and amount of the polyfunctional monomer were changed as shown in Tables 1 and 2. Using the obtained first adhesive composition and the same second adhesive composition as in Example 1, a substrate-attached single-sided adhesive sheet according to each example was produced in the same manner as in Example 1.
  • the thermal polymerization initiator TO2 represents the product name "Niper BMT” (manufactured by NOF Corporation, a benzoyl peroxide-based thermal polymerization initiator), the thermal polymerization initiator TA1 represents AIBN, the polymerization initiator TA2 represents 2,2'-azobis(2,4,4-trimethylpentane) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., product name "VR-110”), and HDDA represents 1,6-hexanediol diacrylate (manufactured by Osaka Organic Chemical Industry Ltd.).
  • a pressure-sensitive adhesive layer formed from the same second pressure-sensitive adhesive composition as used in Examples 1 to 14 was used as the first pressure-sensitive adhesive layer. More specifically, the second pressure-sensitive adhesive composition was applied and dried at 80° C. for 5 minutes to form a first pressure-sensitive adhesive layer having a thickness of 10 ⁇ m, a width of 30 mm, and a length of 100 mm.
  • the same second pressure-sensitive adhesive layer as in Examples 1 to 14 was laminated on one side of a 50 ⁇ m-thick PI film (product name "Kapton 200H", manufactured by DuPont Toray Co., Ltd.) as a substrate, and then the first pressure-sensitive adhesive layer was laminated on the center of the film. Then, aging was performed at 50° C. for 3 days. In this manner, a pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet with substrate) according to this example was produced.
  • the adhesive sheets of Examples 1 to 14 which had a configuration in which a first adhesive layer made of a thermosetting adhesive was partially laminated on a second adhesive layer, had a post-heat peel strength ratio (Fb1/Fa1) of the first and second adhesive layers that was greater than 1.0, and the first region exhibited an easy-to-peel effect by heating, while the second region maintained a higher peel strength after heating than the first region.
  • the adhesive sheet of Comparative Example 1 had the same peel strength after heating for the first and second adhesive layers, and was unable to achieve both the effect of making the first region easier to peel and the effect of maintaining a relatively high peel strength in the second region when heated.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Adhesive Tapes (AREA)
  • Adhesives Or Adhesive Processes (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Laminated Bodies (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009161620A (ja) * 2007-12-28 2009-07-23 Sumiron:Kk 加熱剥離型粘着シート
JP2012122027A (ja) * 2010-12-10 2012-06-28 Nitto Denko Corp 粘着テープ又はシート
JP2016222051A (ja) * 2015-05-28 2016-12-28 株式会社ブリヂストン タイヤ
JP2021031676A (ja) * 2019-08-19 2021-03-01 積水化学工業株式会社 粘着テープ
WO2023054085A1 (ja) * 2021-09-29 2023-04-06 日東電工株式会社 粘着剤組成物及び該粘着剤組成物を用いた粘着シート

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009161620A (ja) * 2007-12-28 2009-07-23 Sumiron:Kk 加熱剥離型粘着シート
JP2012122027A (ja) * 2010-12-10 2012-06-28 Nitto Denko Corp 粘着テープ又はシート
JP2016222051A (ja) * 2015-05-28 2016-12-28 株式会社ブリヂストン タイヤ
JP2021031676A (ja) * 2019-08-19 2021-03-01 積水化学工業株式会社 粘着テープ
WO2023054085A1 (ja) * 2021-09-29 2023-04-06 日東電工株式会社 粘着剤組成物及び該粘着剤組成物を用いた粘着シート

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