WO2025023119A1 - 粘着シート - Google Patents

粘着シート Download PDF

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Publication number
WO2025023119A1
WO2025023119A1 PCT/JP2024/025647 JP2024025647W WO2025023119A1 WO 2025023119 A1 WO2025023119 A1 WO 2025023119A1 JP 2024025647 W JP2024025647 W JP 2024025647W WO 2025023119 A1 WO2025023119 A1 WO 2025023119A1
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WO
WIPO (PCT)
Prior art keywords
weight
adhesive layer
less
pressure
heat
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2024/025647
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English (en)
French (fr)
Japanese (ja)
Inventor
健太 熊倉
哲士 本田
敬介 佐藤
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
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Nitto Denko Corp filed Critical Nitto Denko Corp
Priority to JP2025535763A priority Critical patent/JPWO2025023119A1/ja
Priority to CN202480048483.4A priority patent/CN121548620A/zh
Priority to KR1020267005403A priority patent/KR20260041875A/ko
Publication of WO2025023119A1 publication Critical patent/WO2025023119A1/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, and more particularly to a double-sided pressure-sensitive adhesive sheet.
  • adhesives also called pressure-sensitive adhesives; the same applies below
  • adhesives are in a soft solid (viscoelastic) state at temperatures around room temperature, and have the property of easily adhering to an adherend when pressure is applied.
  • adhesives are widely used in a variety of 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 having no support. Some such adhesives are used by adhering to an adherend, and are removed from the adherend after their adhesive purpose has been fulfilled.
  • Adhesives used in applications where the adhesive is peeled off from an adherend are required to have good adhesion while attached to the adherend, and to have the ability to be easily peeled off from the adherend after the adhesive has served its purpose.
  • a technique is known in which the adhesive contains heat-expandable microspheres that expand when heated to a specified temperature (see, for example, Patent Document 1).
  • this type of heat-peeling adhesive sheet exerts its heat-peeling function by expanding the heat-expandable microspheres when heated, thereby reducing the adhesive area between the adhesive surface and the adherend. Therefore, it tends to be difficult to control the peeling force after heating, and may not be suitable for fixing applications involving a heating process. For example, depending on how the sheet is placed on the adherend after heating, or how it is handled, such as when it is subjected to vibration, it may unintentionally separate from the adherend.
  • the present invention aims to provide an adhesive sheet that can be easily peeled off by heating and is also suitable for fixing applications that involve a heating process.
  • a double-sided adhesive sheet (double-sided adhesive sheet) is provided.
  • the adhesive sheet includes a first adhesive layer and a second adhesive layer.
  • the first adhesive layer constitutes a first adhesive surface which is a first surface of the adhesive sheet.
  • the second adhesive layer constitutes a second adhesive surface which is a second surface of the adhesive sheet, where the second surface of the adhesive sheet is the surface opposite to the first surface.
  • the first adhesive layer contains at least one of a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule and a polymer having an ethylenically unsaturated group, and further contains a thermal polymerization initiator.
  • the adhesive sheet has a post-heat peel strength Fa1 [N/20 mm] measured in an environment of 23°C and 50% RH after the first adhesive layer is attached to a glass plate and heat-treated at 180°C for 30 minutes, and a post-heat peel strength Fb1 [N/20 mm] measured in an environment of 23°C and 50% RH after the second adhesive layer is attached to a glass plate and heat-treated at 180°C for 30 minutes.
  • the adhesive sheet having such a configuration can exhibit the desired heat-induced easy peeling function by including a first adhesive layer that contains a thermal polymerization initiator and is thermally cured by thermally polymerizing ethylenically unsaturated groups.
  • a first adhesive layer that contains a thermal polymerization initiator and is thermally cured by thermally polymerizing ethylenically unsaturated groups.
  • the peeling force after heating can be easily controlled, and the sheet can be preferably used for fixing applications involving a heating process.
  • the first adhesive layer and the second adhesive layer are designed to have different peeling forces after heating, the ease of dismantling and the reusability (recyclability, reuse, etc.) of the dismantled parts are good when dismantling an assembly in which a first member and a second member are joined via the adhesive sheet after heating.
  • ) calculated from the post-heat peel force Fa1 [N/20 mm] and the post-heat peel force Fb1 [N/20 mm] is 0.5 N/20 mm or more.
  • a pressure-sensitive adhesive sheet satisfying the above-mentioned characteristics exhibits a sufficient heat-facilitated peeling function on the first adhesive surface, and can appropriately suppress the phenomenon of unintentional separation from an adherend after heating.
  • the first adhesive layer and the second adhesive layer are laminated via a substrate. That is, the adhesive sheet has a configuration in which the first adhesive layer, the substrate, and the second adhesive layer are laminated in this order (double-sided adhesive sheet with substrate).
  • the double-sided adhesive sheet of this configuration is provided with strength (e.g., tensile strength) by the substrate, so that, for example, when dismantling a bonded body in which a first member and a second member are bonded via the adhesive sheet, after the first and second members are separated, the double-sided adhesive sheet remaining on the separated member can be easily peeled off from the member.
  • the adhesive sheet being reinforced by the substrate is advantageous, for example, from the viewpoint of reworkability (ease of repositioning) when attaching the adhesive sheet to an adherend.
  • the second adhesive layer contains at least one of a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule and a polymer having an ethylenically unsaturated group, and further contains a thermal polymerization initiator.
  • the adhesive sheet having the second adhesive layer can exhibit a stable heat-induced easy peeling function even on the second adhesive surface.
  • a pressure-sensitive adhesive sheet satisfying the above-mentioned characteristics exhibits a suitable heat-easy peeling function also on the second pressure-sensitive adhesive surface, and can appropriately suppress the phenomenon of unintentional separation from the adherend after thermal curing.
  • the pre-heat peeling force Fa0 [N/20 mm] measured in an environment of 23° C. and 50% RH with the first adhesive layer attached to a glass plate, and the pre-heat peeling force Fb0 [N/20 mm] measured in an environment of 23° C. and 50% RH with the second adhesive layer attached to a glass plate are both preferably 4.0 N/20 mm or more.
  • An adhesive sheet satisfying the above characteristics has excellent fixing performance of the adherend before heating (before thermal curing).
  • the post-heat peeling force Fa1 [N/20 mm] of the first adhesive layer and the post-heat peeling force Fb1 [N/20 mm] of the second adhesive layer are both preferably less than 3.0 N/20 mm.
  • the adhesive sheet satisfying the above characteristics for example, in a use mode in which an assembly in which a first member and a second member are joined via the adhesive sheet is heated and then dismantled, the dismantling workability of the assembly and the reusability of the dismantled product are good.
  • An adhesive sheet that meets the above characteristics can exhibit good fixing performance during use, and after use can be easily separated from the adherend by utilizing its heat-sensitive peeling function.
  • the adhesive sheet disclosed herein may be preferably used, for example, as a component of an assembly including a first member to which a first adhesive surface of the adhesive sheet is adhered, and a second member to which a second adhesive surface of the adhesive sheet is adhered.
  • the assembly can be easily dismantled, for example, by a dismantling method including a step of subjecting the assembly to a heat treatment, and then separating the first member from the first adhesive surface while leaving the adhesive sheet on the second member. This is therefore preferable from the standpoint of ease of dismantling and reusability (recyclability, reuse, etc.) of the dismantled products.
  • FIG. 1 is a cross-sectional view illustrating a schematic configuration of a pressure-sensitive adhesive sheet according to an embodiment.
  • FIG. 1 is a cross-sectional view illustrating a schematic configuration of a bonded body according to an embodiment.
  • 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 adhesive sheet disclosed herein is a double-sided adhesive sheet (double-sided adhesive sheet), and has a first adhesive layer constituting the first adhesive surface of the adhesive sheet, and a second adhesive layer constituting the second adhesive surface.
  • the adhesive sheet may be a double-sided adhesive sheet with a substrate in which the first adhesive layer and the second adhesive layer are laminated via a substrate, or may be a double-sided adhesive sheet without a substrate.
  • the concept of the adhesive sheet here may include those called adhesive tapes, adhesive labels, adhesive films, etc.
  • the adhesive sheet disclosed herein may be in the form of a roll or a sheet. Alternatively, it may be an adhesive sheet in the form of a processed form into various shapes.
  • the structure of an adhesive sheet according to one embodiment is shown in FIG. 1.
  • the adhesive sheet 1 is configured as a substrate-attached double-sided adhesive sheet having a substrate 20 having a first surface and a second surface, a first adhesive layer 21 arranged on the first surface of the substrate 20, and a second adhesive layer 22 arranged on the second surface of the substrate 20, which is the surface opposite to the first surface.
  • the adhesive sheet 1 has a first surface and a second surface opposite to the first surface.
  • the surface of the first adhesive layer 21 constitutes a first adhesive surface 1A that also serves as the first surface of the adhesive sheet 1
  • the surface of the second adhesive layer 22 constitutes a second adhesive surface 1B that also serves as the second surface of the adhesive sheet 1.
  • the adhesive sheet disclosed herein may also be configured as a substrate-less double-sided adhesive sheet consisting of an adhesive layer having a structure in which the substrate 20 is omitted from the structure shown in FIG. 1, that is, a structure in which the first adhesive layer 21 and the second adhesive layer 22 are directly laminated (without a substrate).
  • the adhesive sheet 1 is used, for example, by attaching the first adhesive surface 1A and the second adhesive surface 1B to different locations on an adherend.
  • the locations to which the adhesive surfaces 1A and 1B are attached may be different locations on different members, or may be different locations on a single member.
  • the adhesive sheet 1 before use i.e., before being attached to an adherend
  • release liners 31 and 32 for example, a sheet-like substrate (liner substrate) having a release layer made of a release treatment agent on one side thereof, so that the one side is the release surface, may be preferably used.
  • the release liner 32 may be omitted, and a release liner 31 with release surfaces on both sides may be used, which is then superimposed on the adhesive sheet 1 and rolled up in a spiral shape, so that the second adhesive surface 1B is in contact with the back surface of the release liner 31 and protected, forming an adhesive sheet with a release liner in a roll shape.
  • the pressure-sensitive adhesive sheet disclosed herein has a first adhesive surface constituted by a first adhesive layer and a second adhesive surface constituted by a second adhesive layer.
  • the pressure-sensitive adhesive sheet has a post-heat peel strength Fa1 [N/20 mm] measured in an environment of 23°C and 50% RH after the first adhesive layer is attached to a glass plate and heat-treated at 180°C for 30 minutes, and a post-heat peel strength Fb1 [N/20 mm] measured in an environment of 23°C and 50% RH after the second adhesive layer is attached to a glass plate and heat-treated at 180°C for 30 minutes.
  • ) calculated as the absolute value of the difference between the post-heat peel strengths Fa1 and Fb1 is greater than 0 N/20 mm.
  • ) may be, for example, 0.03 N/20 mm or more, suitably 0.05 N/20 mm or more, preferably 0.1 N/20 mm or more, and more preferably 0.5 N/20 mm or more.
  • ) is large, the predictability of which of the first and second members the adhesive sheet will remain on when the two members are separated tends to increase.
  • the post-heat peeling force difference may be, for example, 0.7 N/20 mm or more, 0.9 N/20 mm or more, 1.2 N/20 mm or more, 1.5 N/20 mm or more, 1.7 N/20 mm or more, or 2.0 N/20 mm or more.
  • the post-heat peeling force difference (
  • the post-heat peel force difference may be, for example, approximately 30 N/20 mm or less, 25 N/20 mm or less, 15 N/20 mm or less, 10 N/20 mm or less, 5.0 N/20 mm or less, 3.0 N/20 mm or less, or 2.5 N/20 mm or less.
  • both of the post-heat peel forces Fa1 and Fb1 are 0 N/20 mm or more.
  • the adhesive sheet disclosed herein includes a first adhesive layer configured to be easily peeled by thermal polymerization, and therefore can be preferably implemented in an embodiment in which the peel strength after heating Fa1 is smaller than the peel strength after heating Fb1, i.e., Fa1 [N/20 mm] ⁇ Fb1 [N/20 mm]. According to such an embodiment, the adhesive surface of the adhesive sheet after heating can maintain a relatively large peel strength on the second adhesive surface while exhibiting easy peeling on the first adhesive surface.
  • An adhesive sheet designed in this way is preferable from the viewpoint of ease of dismantling the assembled body and reusability (recyclability, reusability, etc.) of the dismantled body, for example, when dismantling an assembled body in which a first member and a second member are joined via the adhesive sheet after heating, since the first member can be easily separated from the first adhesive surface while leaving the adhesive sheet on the second member.
  • the post-heating peel strength Fa1 of the first pressure-sensitive adhesive layer is not particularly limited and may be appropriately set so that the desired ease of peeling is exhibited after heating, and the post-heating peel strength difference (
  • the post-heating peel strength 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 peeling force Fa1 of the first pressure-sensitive adhesive layer after heating may be, for example, less than 1.0 N/20 mm, preferably 0.8 N/20 mm or less, more preferably 0.6 N/20 mm or less, even more preferably 0.5 N/20 mm or less, may be 0.4 N/20 mm or less, may be 0.3 N/20 mm or less, may be 0.2 N/20 mm or less, or may be less than 0.2 N/20 mm.
  • a pressure-sensitive adhesive sheet with a low peeling force Fa1 after heating can easily peel off the adherend from the first pressure-sensitive adhesive layer (first adhesive surface) after heating while suppressing the load applied to the adherend.
  • the first adhesive surface is attached to an adherend made of a brittle material (typically a hard and brittle material) such as a glass material or a semiconductor material.
  • the peeling force Fa1 after heating is typically more than 0 N/20 mm, and is suitably 0.01 N/20 mm or more in terms of the adherend retention after heating, etc.
  • the peeling force Fa1 after heating may be, for example, 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 peeling force Fa1 after heating may be 0.5 N/20 mm or more, 0.8 N/20 mm or more, 1.0 N/20 mm or more, 1.5 N/20 mm or more, or 2.0 N/20 mm or more.
  • the post-heat peel force Fb1 of the second pressure-sensitive adhesive layer is not particularly limited and may be appropriately set so that the post-heat peel force difference (
  • the post-heat peel force Fb1 is typically greater than 0 N/20 mm, and from the viewpoint of adherend retention after heating, etc., it is appropriate that the post-heat peel force Fb1 is 0.01 N/20 mm or greater.
  • the post-heat peel strength ratio (Fb1/Fa1) calculated from the post-heat peel strength Fa1 [N/20 mm] of the first pressure-sensitive adhesive layer and the post-heat peel strength Fb1 [N/20 mm] of the second pressure-sensitive adhesive layer is greater than 1.0. This allows the pressure-sensitive adhesive sheet to maintain a relatively large peel strength on the second pressure-sensitive adhesive surface while exhibiting easy peelability on the first pressure-sensitive adhesive surface after heating.
  • the pre-heating peel force Fa0 may be, for example, 1.2 N/20 mm or more, 1.5 N/20 mm or more, 1.8 N/20 mm or more, 2.0 N/20 mm or more, 3.0 N/20 mm or more, 4.0 N/20 mm or more, 5.0 N/20 mm or more, 7.0 N/20 mm or more, 8.0 N/20 mm or more, 9.0 N/20 mm or more, or 10 N/20 mm or more.
  • the upper limit of the pre-heat peeling force Fa0 is appropriately set according to the adhesiveness required for the first adhesive surface, and is not limited to a specific range, 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, 5.0 N/20 mm or less, or 3.0 N/20 mm or less.
  • the pre-heat peeling force Fa0 of the first adhesive layer refers to the peel strength (peeling force) against a glass plate measured under conditions of a peeling angle of 180 degrees and a speed of 300 mm/min in an environment of 23°C. More specifically, the pre-heat peeling force Fa0 is measured by the method described in the Examples below.
  • the first adhesive surface 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 pre-heating (initial) peeling force Fb0 of the second pressure-sensitive adhesive layer is not particularly limited and can be appropriately set according to the purpose.
  • the pre-heating peeling force Fb0 of the second pressure-sensitive adhesive layer may be, for example, 0.2 N/20 mm or more, suitably 0.5 N/20 mm or more, and preferably 0.8 N/20 mm or more.
  • the second pressure-sensitive adhesive surface can exhibit good adhesion to an adherend, and can, for example, appropriately hold the adherend.
  • the pre-heating peeling force Fb0 may be, for example, 1.0 N/20 mm or more, 1.2 N/20 mm or more, 1.5 N/20 mm or more, 2.0 N/20 mm or more, 3.0 N/20 mm or more, 4.0 N/20 mm or more, 5.0 N/20 mm or more, or 7.0 N/20 mm or more.
  • the upper limit of the pre-heat peeling force Fb0 of the second adhesive layer is not limited to a specific range, 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, 5.0 N/20 mm or less, or 3.0 N/20 mm or less.
  • the pre-heat peeling force Fb0 of the second adhesive layer refers to the peel strength (peeling force) against a glass plate measured under conditions of a peeling angle of 180 degrees and a speed of 300 mm/min in an environment of 23°C. More specifically, the pre-heat peeling force Fb0 is measured by the method described in the examples below.
  • the relationship between the pre-heating peel strength Fb0 and the post-heating peel strength Fb1 of the second pressure-sensitive adhesive layer is not particularly limited.
  • the post-heating peel strength Fb1 may be greater than the pre-heating peel strength Fb0, may be smaller than the pre-heating peel strength Fb0, or may be approximately the same as the pre-heating peel strength Fb0.
  • the post-heat peel force reduction rate B may be, for example, greater than 20%, greater than 30%, greater than 40%, or greater than 50%, or may be 60% or more, 70% or more, 80% or more, 85% or more, or 90% or more.
  • the pre-heat peel strengths Fa0 and Fb0 [N/20 mm] are suitably 1.0 N/20 mm or more, and may be 2.0 N/20 mm or more.
  • the pre-heat peel strengths Fa0 and Fb1 are 3.0 N/20 mm or more, more preferably 4.0 N/20 mm or more, and even more preferably 5.0 N/20 mm or more, and may be 7.0 N/20 mm or more, or may be 8.0 N/20 mm or more.
  • a pressure-sensitive adhesive sheet having both pre-heat peel strengths Fa0 and Fa1 of 4.0 N/20 mm or more or a higher predetermined value or more has good fixing performance to the adherend on the first and second pressure-sensitive adhesive surfaces before heating (initial stage), and is suitable for use in producing a bonded body in which two members are firmly bonded via the pressure-sensitive adhesive sheet.
  • the post-heat peel strengths Fa1 and Fb1 [N/20 mm] are, for example, preferably less than 4.0 N/20 mm, and preferably less than 3.0 N/20 mm.
  • a pressure-sensitive adhesive sheet satisfying the above characteristics provides good dismantling workability of the bonded body and good reusability of the dismantled body, for example, in a use mode in which a bonded body in which two members are bonded via the pressure-sensitive adhesive sheet is heated and then dismantled.
  • a pressure-sensitive adhesive sheet in which the pre-heat peel strengths Fa0, Fb0 are both equal to or greater than a specified lower limit value and the post-heat peel strengths Fa1, Fb1 are both equal to or less than a specified upper limit value is preferred because it can exhibit good fixing performance during use and can be easily separated from the adherend after use by utilizing the heat-induced easy-peel function.
  • the pre-heating peel strength, post-heating peel strength and the relative relationship between them of the first and second adhesive layers can be achieved and adjusted 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 gel fraction increase (Ga1-Ga0) calculated from the pre-heating (initial) gel fraction Ga0 [%] and the post-heating gel fraction Ga1 [%] of the first pressure-sensitive adhesive layer is typically greater than 0%, and is suitably, for example, 5% or more, and preferably 10% or more.
  • a first pressure-sensitive adhesive layer satisfying the above gel fraction increase (Ga1-Ga0) exhibits good thermosetting properties and tends to easily exhibit a peel force reduction effect (heat-induced peelability) due to heating on the first pressure-sensitive adhesive surface.
  • the gel fraction increase (Ga1-Ga0) of the first pressure-sensitive adhesive layer is more preferably 13% or more, and may be, for example, 16% or more, 20% or more, 25% or more, 30% or more, 35% or more, or 40% or more.
  • the gel fraction increase (Ga1-Ga0) of the first pressure-sensitive adhesive layer is, from the viewpoint of favorably achieving both the adhesiveness before heating and the easy releasability after heating, suitably, for example, 70% or less, preferably 60% or less, or may be 50% or less, or may be 40% or less.
  • the pre-heat gel fraction Ga0 of the first adhesive layer is determined as the weight ratio of the ethyl acetate insoluble matter of an adhesive sample taken from the initial (before heating) first adhesive layer.
  • the post-heat gel fraction Ga1 of the first adhesive layer is determined in the same manner as the pre-heat gel fraction Ga0 of an adhesive sample taken from the first adhesive layer after heat treatment at 180°C for 30 minutes. More specifically, the pre-heat gel fraction Ga0 and the post-heat gel fraction Ga1 are measured by the method described in the Examples below.
  • the pre-heat gel fraction Gb0 and the post-heat gel fraction Gb1 of the second adhesive layer described below are determined in the same manner as the pre-heat gel fraction Ga0 and the post-heat gel fraction Ga1 of the first adhesive layer for an adhesive sample taken from the second adhesive layer or the second adhesive layer after heat treatment at 180°C for 30 minutes.
  • the post-heat gel fraction Ga1 is preferably 83% or more, more preferably 85% or more, may be 88% or more, may be 90% or more, may be 93% or more, 95% or more, or may be 97% or more.
  • the post-heat gel fraction Ga1 of the first pressure-sensitive adhesive layer is typically less than 100%, and is suitably 99.8% or less (e.g., 99.5% or less) from the viewpoint of adherend retention after heating, etc., and is preferably 99% or less, may be 98% or less, may be 95% or less, 92% or less, or may be 90% or less.
  • the post-heat gel fraction Ga1 of the first pressure-sensitive adhesive layer may be 85% or less, 80% or less, or 75% or less.
  • the pre-heat (initial) gel fraction Gb0 and the post-heat gel fraction Gb1 of the second pressure-sensitive adhesive layer are not particularly limited.
  • the pre-heating gel fraction Gb0 of the second adhesive layer is suitably about 99.8% or less, preferably 99.5% or less (e.g., 99% or less), from the viewpoint of the adhesiveness of the second adhesive surface, etc.
  • the pre-heating gel fraction Gb0 may be, for example, 98% or less, 95% or less, 90% or less, 85% or less, 80% or less, 70% or less, 65% or less, or 60% or less.
  • the pre-heating gel fraction Gb0 is suitably 20% or more, preferably 30% or more, more preferably 40% or more, even more preferably 50% or more, and may be 60% or more, or may be 70% or more.
  • the gel fraction Gb1 after heating of the second pressure-sensitive adhesive layer is typically less than 100%, and is suitably 99.8% or less from the viewpoint of the adherend retention after heating, etc., and is preferably 99.5% or less, and may be 99% or less, or may be 98.5% or less. In some embodiments, the gel fraction Gb1 after heating may be 95% or less, 92% or less, or 90% or less. In some embodiments, from the viewpoint of easily obtaining appropriate cohesiveness and retention after heating, the gel fraction Gb1 after heating is suitably 50% or more (e.g., more than 50%), and is preferably 60% or more, more preferably 70% or more, and may be 80% or more, 90% or more, or 95% or more.
  • the gel fraction increase (Gb1-Gb0) calculated from the pre-heat gel fraction Gb0 [%] and post-heat gel fraction Gb1 [%] of the second pressure-sensitive adhesive layer is not particularly limited and may be, for example, in the range of 0% to 80%. A more specific range of the gel fraction increase (Gb1-Gb0) may vary depending on the purpose, for example, on the presence or absence of thermosetting of the second pressure-sensitive adhesive layer.
  • the gel fraction increase (Gb1-Gb0) of the second pressure-sensitive adhesive layer may have a lower limit of, for example, 0% or more or more than 0%, and an upper limit of, for example, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less.
  • the lower limit of the gel fraction increase (Gb1-Gb0) of the second pressure-sensitive adhesive layer may be, for example, 5% or more, 10% or more, or 15% or more
  • the upper limit may be, for example, 80% or less, 70% or less, 60% or less, 50% or less, or 40% or less.
  • the adhesive sheet disclosed herein may be, for example, an adhesive sheet in which the gel fraction of the first adhesive layer is roughly equal to or lower than the gel fraction of the second adhesive layer initially (before heating), and the gel fraction of the first adhesive layer is higher than the gel fraction of the second adhesive layer after heat treatment at 180° C. for 30 minutes.
  • the value of pre-heating gel fraction Gb0 [%] - pre-heating gel fraction Ga0 [%] may be, for example, -5% or more, preferably 0% or more, more preferably 5% or more, 10% or more, 20% or more, or 30% or more
  • the value of post-heating gel fraction Ga1 [%] - post-heating gel fraction Gb1 [%] may be, for example, more than 0%, preferably 5% or more, more preferably 10% or more, 15% or more, 20% or more, or 30% or more.
  • an adhesive sheet in which the gel fractions of the first and second adhesive layers satisfy the above relative relationship before and after heating in an embodiment in which the peel strength after heating is Fb1>Fa1, it is easy to obtain an adhesive sheet in which the peel strength difference after heating (
  • 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 Young's modulus Ya1 after heating may be, for example, 15 MPa or more, 20 MPa or more, 30 MPa or more, 40 MPa or more, 50 MPa or more, 60 MPa or more, or 70 MPa or more, or 90 MPa or more, or 110 MPa or more.
  • the Young's modulus Ya1 after heating is suitably, for example, 2000 MPa or less, preferably 1000 MPa or less, more preferably 500 MPa or less, and may be 300 MPa or less, 200 MPa or less, 150 MPa or less, 100 MPa or less, or 75 MPa or less.
  • 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 post-heat Young's modulus Yb1 of the second adhesive layer are measured in the same manner as the pre-heat Young's modulus Ya0 and post-heat Young's modulus Ya1 of the first adhesive layer, respectively. More specifically, the above Young's moduli Ya0, Ya1, Yb0, and Yb1 are measured by the method described in the examples, described below.
  • the first pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet disclosed herein is suitably thermosetting to such an extent that the Young's modulus increase ratio (Ya1/Ya0) calculated from the pre-heating Young's modulus Ya0 [MPa] measured under an environment of 23° C. and 50% RH and the above-mentioned post-heating Young's modulus Ya1 [MPa] is 2.0 or more (e.g., 5.0 or more, 10 or more, 20 or more, or 30 or more).
  • the Young's modulus increase ratio (Ya1/Ya0) of the first pressure-sensitive adhesive layer is preferably 50 or more, more preferably 80 or more, 100 or more, or 150 or more, and even more preferably 200 or more, or 250 or more.
  • the upper limit of the Young's modulus increase ratio (Ya1/Ya0) of the first pressure-sensitive adhesive layer is not particularly limited. In some embodiments, the Young's modulus increase ratio (Ya1/Ya0) may be, for example, approximately 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 Ya0 [MPa] before heating of the first adhesive layer constituting the adhesive sheet disclosed herein is not particularly limited.
  • the Young's modulus Ya0 before heating can be appropriately selected so as to obtain the desired adhesiveness (e.g., peel strength Fa0 before heating) according to the intended use of the adhesive sheet.
  • the Young's modulus Ya0 before heating is, for example, suitable to be less than 5.0 MPa from the viewpoint of the adhesiveness of the first adhesive surface, advantageously 3.0 MPa or less, preferably 1.0 MPa or less or 0.7 MPa or less, more preferably 0.5 MPa or less (e.g., less than 0.5 MPa), and may be 0.4 MPa or less, 0.3 MPa or less, or 0.2 MPa or less.
  • the pre-heating Young's modulus Ya0 may be, for example, 0.001 MPa or more, and from the viewpoint of easily obtaining appropriate cohesiveness and retention, it is advantageous to have it 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, or may be 0.1 MPa or more.
  • 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 of the second pressure-sensitive adhesive layer is, for example, suitable to be less than 5.0 MPa from the viewpoint of the adhesiveness of the second pressure-sensitive adhesive surface, and is preferably 3.0 MPa or less, and may be 2.0 MPa or less, 1.0 MPa or less, or may be 0.8 MPa or less.
  • 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, and may be 0.08 MPa or more, 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.
  • a more specific range of the Young's modulus increase ratio (Yb1/Yb0) may vary depending on the purpose, for example, on the presence or absence of thermosetting of the second pressure-sensitive adhesive layer.
  • the Young's modulus increase ratio (Yb1/Yb0) of the second pressure-sensitive adhesive layer may have a lower limit of 1.0 or more or more than 1.0, and an upper limit of less than 2.0 or less than 1.5.
  • 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 of the above-mentioned Young's modulus ratios after heating (Ya1/Yb1), in an embodiment in which the peeling force after heating is Fb1>Fa1, a pressure-sensitive adhesive sheet in which the peeling force difference 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 pre-heating Young's modulus ratio (Ya0/Yb0) calculated as the ratio of the pre-heating Young's modulus Ya0 of the first pressure-sensitive adhesive layer to the pre-heating Young's modulus Yb0 of the second pressure-sensitive adhesive layer is not particularly limited.
  • the upper limit of the pre-heating Young's modulus ratio (Ya0/Yb0) may be, for example, 0.001 or more, 0.01 or more, or 0.1 or more.
  • the lower limit of the upper pre-heating Young's modulus ratio (Ya0/Yb0) may be, for example, 10,000 or less, 1,000 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 of the adhesive sheet disclosed herein is an adhesive layer having thermosetting properties.
  • the adhesive layer (adhesive) having thermosetting properties means that the adhesive layer (adhesive) has a property that at least one of the gel fraction and the Young's modulus becomes higher than the initial value (before heating) by performing a heat treatment at 180°C for 30 minutes.
  • a suitable example of an adhesive layer having thermosetting properties is an adhesive layer whose gel fraction increases by 5% or more or 10% or more by the heat treatment.
  • Another suitable example of an adhesive layer having thermosetting properties is an adhesive layer whose Young's modulus increases by 2.0 times or more, 5.0 times or more, or 10 times or more by the heat treatment.
  • 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.
  • alkoxy group-containing (meth)acrylates include alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and ethoxypropyl (meth)acrylate; alkoxy(poly)alkylene glycol (meth)acrylates such as methoxydiethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, ethoxydipropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, and ethoxypolyprop
  • alkoxyalkyl (meth)acrylates are preferred, and among these, alkoxyalkyl (meth)acrylates having an alkoxy group with 1 to 4 carbon atoms (e.g., 1, 2 or 3 carbon atoms) are more preferred, with methoxyethyl (meth)acrylate being particularly preferred.
  • the content of the alkoxy group-containing (meth)acrylate in the monomer component constituting the acrylic polymer is not particularly limited. From the viewpoint of effectively obtaining the effect of using the alkoxy group-containing (meth)acrylate, the content of the alkoxy group-containing (meth)acrylate in the monomer component is usually about 1 weight % or more, for example, 10 weight % or more, 30 weight % or more, or 50 weight % or more.
  • 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 upper limit of the content of the alkoxy group-containing (meth)acrylate in the monomer component is 100% by weight, and in some embodiments, from the viewpoint of obtaining the effect of other copolymerizable monomers such as functional group-containing monomers, the content of the alkoxy group-containing (meth)acrylate is advantageously about 99% by weight or less, and may be 95% by weight or less, 93% by weight or less, or 90% by weight or less. In other embodiments, the content of the alkoxy group-containing (meth)acrylate may be about 80% by weight or less, 70% by weight or less, 65% by weight or less, or 60% by weight or less.
  • 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
  • Monomers containing a sulfonic acid group or a phosphoric acid group for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethylacryloylphosphate, and the like.
  • 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 nitrogen atom-containing ring for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidone N-vinyl morpholine, N-(meth)acryloylmorpholine, N-vinyl morpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinyl
  • 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.
  • Itaconimides for example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, and the like.
  • Aminoalkyl (meth)acrylates for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate.
  • Alkoxysilyl group-containing monomers for example, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane.
  • Vinyl esters for example, vinyl acetate, vinyl propionate, etc.
  • Vinyl ethers for example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.
  • Aromatic vinyl compounds for example, styrene, ⁇ -methylstyrene, vinyltoluene, etc.
  • Olefins For example, ethylene, butadiene, isoprene, isobutylene, etc.
  • (Meth)acrylic acid esters having an alicyclic hydrocarbon group for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, and the like.
  • (Meth)acrylic acid esters having an aromatic hydrocarbon group for example, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, and the like.
  • heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, silicon atom-containing (meth)acrylates such as silicone (meth)acrylate, and (meth)acrylic acid esters obtained from alcohols derived from terpene compounds.
  • the amount used is not particularly limited, but it is appropriate that it be 0.01% by weight or more of the total monomer components. From the viewpoint of better exerting the effect of using the other monomers, the amount of the other monomers used may be 0.1% by weight or more of the total monomer components, or may be 0.5% by weight or more. Also, from the viewpoint of making it easier to balance the adhesive properties, it is appropriate that the amount of the other monomers used is 50% by weight or less of the total monomer components, and preferably 40% by weight or less.
  • 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.
  • R 1 is a divalent organic group, specifically -(CH 2 ) n -.
  • n is an integer of 2 to 7 (preferably 2, 3 or 4).
  • N-vinyl-2-pyrrolidone (NVP) can be preferably used.
  • N,N-dialkyl (meth)acrylamides such as (meth)acrylamide and N,N-dimethyl (meth)acrylamide
  • N-monoalkyl (meth)acrylamides such as N-isopropyl (meth)acrylamide
  • N-hydroxyalkyl (meth)acrylamides such as N-(2-hydroxyethyl)acrylamide (HEAA); N-acryloylmorpholine (ACMO); alkoxy diacetone (meth)acrylamide; vinyl formamide; vinyl acetamide; and the like.
  • NVP, HEAA, and ACMO are more preferable.
  • the amount of the monomer having a nitrogen atom (preferably a monomer having a nitrogen atom-containing ring) used is not particularly limited, and may be, for example, 1% by weight or more, or 3% by weight or more of the total monomer components. In some embodiments, the amount of the monomer having a nitrogen atom used in the monomer components is preferably 5% by weight or more, more preferably 7% by weight or more, and even more preferably 9% by weight or more. In other embodiments, the amount of the monomer having a nitrogen atom used in the monomer components may be 10% by weight or more, 12% by weight or more, or 15% by weight or more.
  • the monomer component may contain a hydroxyl group-containing monomer.
  • a hydroxyl group-containing monomer can adjust the cohesive strength and crosslink density of the adhesive, improving the adhesive strength.
  • examples of the hydroxyl group-containing monomer that can be used include those exemplified above, and for example, 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) can be preferably used.
  • the hydroxyl group-containing monomer can be used alone or in combination of two or more types.
  • the amount used is not particularly limited, and may be, for example, 0.01% by weight or more of the total monomer components, 0.1% by weight or more, or 0.5% by weight or more.
  • the amount of the hydroxyl group-containing monomer used is 1% by weight or more of the total monomer components, more preferably 2% by weight or more, even more preferably 3% by weight or more, and may be, for example, 5% by weight or more.
  • the amount of the hydroxyl group-containing monomer used is, for example, 40% by weight or less of the total monomer components, and is preferably 30% by weight or less, more preferably 20% by weight or less, even more preferably 10% by weight or less, and may be 7% by weight or less.
  • the monomer component of the acrylic polymer is a monomer having a polar group (polar group-containing monomer) that is a combination of a monomer having a nitrogen atom (e.g., an amide group-containing monomer such as (meth)acrylamide, a monomer having a nitrogen atom-containing ring such as NVP) and a hydroxyl group-containing monomer (e.g., HEA, 4HBA).
  • a polar group-containing monomer that is a combination of a monomer having a nitrogen atom (e.g., an amide group-containing monomer such as (meth)acrylamide, a monomer having a nitrogen atom-containing ring such as NVP) and a hydroxyl group-containing monomer (e.g., HEA, 4HBA).
  • the weight ratio (A N /A OH ) of the amount of the monomer having a nitrogen atom A N to the amount of the hydroxyl group-containing monomer A OH is not particularly limited, and may be, for example, 0.1 or more, 0.5 or more, 1.0 or more, 1.2 or more, 1.5 or more, or 1.8 or more.
  • the weight ratio (A N /A OH ) may be, for example, 10 or less, 5 or less, 3 or less, or 2.5 or less.
  • the monomer component includes a carboxyl group-containing monomer.
  • suitable examples of the carboxyl group-containing monomer include acrylic acid (AA) and methacrylic acid (MAA).
  • the carboxyl group-containing monomer may be used alone or in combination of two or more. For example, 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, 0.05% by weight or more, 0.1% by weight or more, 0.3% by weight or more, or 0.5% by weight or more of the total monomer components.
  • the proportion of the carboxyl group-containing monomer may be, for example, 15% by weight or less, 10% by weight or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, or 1% by weight or less (for example, less than 1% by weight).
  • 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 other monomer having functional group A for example, a carboxy group-containing monomer, an epoxy group-containing monomer, a hydroxyl group-containing monomer, or an isocyanate group-containing monomer is preferable, and a hydroxyl group-containing monomer is particularly preferable.
  • a hydroxyl group-containing monomer as the other monomer, the acrylic polymer has a hydroxyl group.
  • an isocyanate group-containing monomer as the compound having an ethylenically unsaturated group, the hydroxyl group of the acrylic polymer reacts with the isocyanate group of the compound, and the ethylenically unsaturated group derived from the compound is introduced into the acrylic polymer.
  • the amount of the other monomers is appropriately set to about 1% by weight or more of the total monomer components from the viewpoint of the thermosetting property of the adhesive and adhesive properties such as cohesive strength, and is preferably about 5% by weight or more, more preferably about 10% by weight or more, and may be about 12% by weight or more.
  • the acrylic polymer may contain, as another monomer component, a polyfunctional monomer having at least two polymerizable functional groups (typically radically polymerizable functional groups) having an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group.
  • a polyfunctional monomer typically radically polymerizable functional groups having an unsaturated double bond
  • the polyfunctional monomer can be used as a crosslinking agent.
  • one suitable one from those described below as polyfunctional monomers that can be contained in the first adhesive layer can be used alone or in combination of two or more.
  • 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 method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as methods for synthesizing acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be appropriately adopted.
  • solution polymerization can be preferably adopted.
  • a monomer supply method when performing solution polymerization a lump-sum charging method in which all monomer raw materials are supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, and the like can be appropriately adopted.
  • the polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, and the like, and can be, for example, about 20°C to 170°C (typically about 40°C to 140°C).
  • the solvent (polymerization solvent) used in solution polymerization can be appropriately selected from conventionally known organic solvents.
  • aromatic compounds such as toluene (typically aromatic hydrocarbons); acetate esters such as ethyl 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.
  • the initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators depending on the type of polymerization method. For example, but not limited to, azo-based polymerization initiators, peroxide-based polymerization initiators, redox-based polymerization initiators formed by combining peroxides with reducing agents, substituted ethane-based polymerization initiators, etc. can be used.
  • the polymerization initiator for example, one or more of the examples of the thermal polymerization initiators added to the adhesive layer described below can be selected and used.
  • 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.
  • the upper limit of the Mw of the polymer is not particularly limited, and may be, for example, about 1000 ⁇ 10 4 or less, or about 100 ⁇ 10 4 or less.
  • Mw refers to a value calculated in terms of standard polystyrene obtained by gel permeation chromatography (GPC).
  • GPC gel permeation chromatography
  • a model named "HLC-8320GPC” (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) may be used.
  • 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 for 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.
  • the amount of the ethylenically unsaturated group in the polymer is measured by the following method, for example, when the ethylenically unsaturated group is a (meth)acryloyl group.
  • 0.25 mg of the polymer to be measured is dissolved in 50 mL of THF (tetrahydrofuran), and 15 mL of methanol is added to obtain a solution.
  • 10 mL of 4N aqueous sodium hydroxide is added to the above solution to obtain a mixed solution.
  • the above mixed solution is stirred at a liquid temperature of 40° C. for 2 hours.
  • 10.2 mL of 4N methanesulfonic acid solution is added to the above mixed solution and stirred.
  • 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 compound having an ethylenically unsaturated group may have a functional group B capable of reacting with functional group A, as described above.
  • Suitable examples of such compounds include the isocyanate group-containing monomers (isocyanate group-containing compounds) given as examples of other monomers that may be used in the polymerization of acrylic polymers. Among these, 2-(meth)acryloyloxyethyl isocyanate is more preferred.
  • An acrylic polymer having an ethylenically unsaturated group can be obtained by reacting the isocyanate group of the isocyanate group-containing compound having an ethylenically unsaturated group with the hydroxyl group of the acrylic polymer to form a bond (specifically a urethane bond).
  • 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 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 number of ethylenically unsaturated groups contained in one molecule of the polyfunctional monomer is suitably 3 or more, preferably 4 or more, more preferably 5 or more, and may be 6 or more.
  • the more ethylenically unsaturated groups in the polyfunctional monomer the better the curing property when heated, and the easier it is to obtain heat-peelability.
  • a polyfunctional monomer having a larger number of ethylenically unsaturated groups (functional groups) can obtain heat-peelability with a relatively small amount of use. This is advantageous because it also leads to a reduction in the amount of outgassing derived from the polyfunctional 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 having the above number of ethylenically unsaturated groups tend to provide both good adhesion and easy peelability upon heating, and also have excellent storage stability.
  • 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
  • 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 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.
  • 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), 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 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 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 thermal polymerization initiator relative to 100 parts by weight of the polyfunctional monomer is, for example, approximately 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 within 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-based 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 may be, for example, approximately 0.0001 parts by weight or more, approximately 0.001 parts by weight or more, or approximately 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 may be approximately 1 part by weight or less, approximately 0.1 parts by weight or less, or approximately 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.
  • 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., 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 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, as the polymer (preferably a base polymer), 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.
  • 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 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 may be less than 1% by weight.
  • 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.
  • the adhesive sheet disclosed herein may include a substrate.
  • various sheet-like substrates can be used, such as resin films, paper, cloth, rubber sheets, foam sheets, metal foils, and composites thereof.
  • 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.
  • 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 molding, and calendar roll molding can be appropriately used.
  • 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 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 surface of the substrate may also be subjected to the various surface treatments described above, antistatic treatment, etc. Such surface treatments may be applied to one or both sides of the substrate.
  • 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.
  • 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 total thickness of the first and second adhesive layers 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. In some embodiments, the total thickness of the first and second adhesive layers may be, for example, 15 ⁇ m or more, 20 ⁇ m or more, 25 ⁇ m or more, 30 ⁇ m or more, 35 ⁇ m or more, or 40 ⁇ m or more. The total thickness of the first and second adhesive layers is suitably, for example, about 250 ⁇ m or less, and may be 150 ⁇ m or less, 100 ⁇ m or less, or 80 ⁇ m or less.
  • a small total thickness of the first and second adhesive layers is advantageous in terms of making the adhesive sheet thinner, and tends to have excellent conformability to the adherend.
  • the total thickness of the first and second adhesive layers 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 (including the first and second adhesive layers, and may further include a substrate, but not including a 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 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.
  • the adhesive sheet disclosed herein can be used in a bonded structure disposed between two members (adherends) to bond the two members.
  • the adhesive sheet disclosed herein is used in a bonding portion that bonds the two members.
  • the bonded structure can include, for example, a first member to which a first adhesive surface of the adhesive sheet is bonded, and a second member to which a second adhesive surface of the adhesive sheet is bonded.
  • the bonded body disclosed herein may have, for example, a cross-sectional structure as shown in FIG. 2.
  • the bonded body 100 includes a first member 71, a second member 72, and a bonding portion 80 disposed between the first member 71 and the second member 72.
  • the bonded body 100 has a laminate structure including the first member 71, the bonding portion 80, and the second member 72 in this order.
  • the first member 71 and the second member 72 are sheet-shaped or plate-shaped, and the bonding portion 80 is a layered body.
  • At least one of the first member 71 and the second member 72 may be made of a brittle material (e.g., a hard brittle material such as glass or a semiconductor wafer).
  • the bonding portion 80 includes any one of the adhesive sheets 90 disclosed herein, and bonds the first member 71 and the second member 72.
  • the first member 71 and the second member 72 are bonded via the bonding portion 80 including the adhesive sheet 90.
  • the adhesive sheet 90 has one adhesive surface (first adhesive surface) 80A adhered to the first member 71 as an adherend, and the other adhesive surface (second adhesive surface, the surface opposite to the first adhesive surface) 80B adhered to the second member 72 as an adherend.
  • the adhesive sheet 90 includes a first adhesive layer and a second adhesive layer (not shown in FIG. 2), the first adhesive surface 80A being composed of the first adhesive layer, and the second adhesive surface 80B being composed of the second adhesive layer.
  • the adhesive sheet 90 may further include a substrate disposed between the first adhesive layer and the second adhesive layer.
  • the adhesive sheet 90 may be a substrate-less adhesive sheet composed of only adhesive layers including the first adhesive layer and the second adhesive layer, or a substrate-attached double-sided adhesive sheet.
  • the first member, second member, and joint that constitute the joint are all configured in a layered, sheet-like, or plate-like shape, and the joint has the form of a laminated structure (laminate); however, the shapes of the first member, second member, and joint do not have to be layered, sheet-like, or plate-like, and can have various shapes.
  • the first member and second member only need to have a surface that contacts the joint, and may have various three-dimensional member shapes, such as complex shapes or curved shapes, based on the application or purpose of use.
  • the joint can also have various shapes to match the surface shapes of the first member and second member.
  • first member and second member are used to mean components of a joint, and are not particularly limited other than that meaning.
  • first member and the second member may each be separate, independent articles or parts, or each may be members that constitute separate articles.
  • the bonded body may also include other members and components in addition to the first and second members.
  • the first and second members are part of a product such as an electronic device, the bonded body may be composed of multiple members and elements.
  • a method for dismantling the bonded body includes a step of subjecting the bonded body to a heat treatment, and then separating the first member from the first adhesive surface while leaving the adhesive sheet on the second member.
  • the adhesive sheet disclosed herein includes a first adhesive layer suitable for exhibiting heat peelability (heat-resistant peelability), and is designed so that the post-heat peel strengths Fa1 and Fb1 of the first and second adhesive layers are different (typically, Fa1 ⁇ Fb1), so that the adhesive sheet is suitable for carrying out a step of separating the first member from the first adhesive surface while leaving the adhesive sheet on the second member after the heat treatment.
  • the temperature of the heat treatment 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 use of the adhesive sheet disclosed herein is not particularly limited.
  • the adhesive sheet disclosed herein can be used in various applications in which the first adhesive layer (first adhesive surface) is adhered to an adherend, and is removed from the adherend after the adhesive purpose is completed, since at least the first adhesive layer can exhibit heat peelability.
  • 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 peeling adhesive cannot be applied, such as when the adherend is non-transparent to light.
  • the adhesive sheet disclosed herein may also 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.
  • a suitable application of the adhesive sheet disclosed herein is the manufacturing application of semiconductor elements.
  • the adhesive sheet may 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 may also be preferably used as a protective sheet that protects the wafer in the above-mentioned wafer processing.
  • the wafer may be exposed to heat in the processing step, etc., so an adhesive sheet having heat resistance and easy peelability is preferably used.
  • the adhesive sheet disclosed herein may also be applied to optical applications requiring heat resistance. More specifically, the adhesive sheet disclosed herein may be used as an optical adhesive sheet used in applications such as bonding optical members (for bonding optical members) and manufacturing applications of products using the above-mentioned optical members (optical products).
  • the optical component refers to a component that has optical properties (e.g., polarization, light refraction, light scattering, light reflectivity, light transmission, 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
  • the matters disclosed in this specification include the following.
  • a double-sided adhesive sheet The pressure-sensitive adhesive sheet includes a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer, the first pressure-sensitive adhesive layer constitutes a first adhesive surface which is a first surface of the pressure-sensitive adhesive sheet, and the second pressure-sensitive adhesive layer constitutes a second adhesive surface which is a second surface of the pressure-sensitive adhesive sheet, the second surface being a surface opposite to the first surface;
  • the first pressure-sensitive adhesive layer contains at least one of a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule and a polymer having an ethylenically unsaturated group, and further contains a thermal polymerization initiator;
  • ⁇ 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.
  • the resin film various resin films that can be used as the substrate of the adhesive sheet disclosed herein can be used, and suitable examples include polyimide (PI) film, polyethylene terephthalate (PET) film, etc.
  • the thickness of the resin film is suitably about 10 ⁇ m to 100 ⁇ m, and preferably about 10 ⁇ m to 75 ⁇ m (for example, about 25 ⁇ m to 75 ⁇ m).
  • a Shimadzu product named "EZ-S 500N” or an equivalent product can be used.
  • the adhesive sheet used to prepare the evaluation sample is a double-sided adhesive sheet
  • the non-measurement surface may be backed with a PET film before the measurement.
  • Post-heat peel strength 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 post-heat peel strength difference (
  • 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 so that the cross-sectional area of the adhesive layer in the cross section along the width direction is within the range of about 2 to 2.5 mm2 . 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.
  • 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, and a polymerization reaction (solution polymerization) was carried out for 6 hours 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 carried out in an air stream at 50 ° C. for 48 hours to obtain a solution of an acrylic polymer A having a methacryloyl group at the side chain end.
  • MOI methacryloyloxyethyl isocyanate
  • Second adhesive composition To the solution of the acrylic polymer A, 0.3 parts of crosslinking agent CL1 and 0.8 parts of thermal polymerization initiator TO1 were added per 100 parts of the acrylic polymer A, and 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.
  • 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 30 ⁇ m.
  • the second adhesive layer was laminated on the second surface of a 12.5 ⁇ m thick polyimide (PI) film (product name "Kapton 50H", manufactured by Toray DuPont Co., Ltd.) as a substrate, and then the first adhesive layer was laminated on the first surface of the PI film.
  • PI polyimide
  • the adhesive sheet double-sided adhesive sheet with substrate
  • the first and second adhesive surfaces of the adhesive sheet were protected by the release liners used to form the first and second adhesive layers, respectively.
  • Examples 2 to 14> A first pressure-sensitive 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.
  • a substrate-attached double-sided pressure-sensitive adhesive sheet according to each example was produced in the same manner as in Example 1, using the obtained first pressure-sensitive adhesive composition and the same second pressure-sensitive adhesive composition as in Example 1.
  • the thermal polymerization initiator TO2 is product name "Niper BMT” (manufactured by NOF Corporation, benzoyl peroxide-based thermal polymerization initiator), the thermal polymerization initiator TA1 is AIBN, the polymerization initiator TA2 is 2,2'-azobis(2,4,4-trimethylpentane) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name "VR-110"), HDDA is 1,6-hexanediol diacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.), and the crosslinking agent CL2 is an epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name "Tetrad C").
  • Example 15 to 17> The adhesive sheets (double-sided adhesive sheets with substrate) of each Example were prepared in the same manner as in Example 9, except that a 25 ⁇ m thick polyimide (PI) film (product name "Kapton 100H", manufactured by DuPont-Toray Co., Ltd.), a 50 ⁇ m thick polyimide (PI) film (product name "Kapton 200H", manufactured by DuPont-Toray Co., Ltd.), or a 25 ⁇ m thick PET film (product "Lumirror S10", manufactured by Toray Co., Ltd.) was used as the substrate.
  • PI polyimide
  • PI polyimide
  • a pressure-sensitive adhesive composition according to this example was prepared by adding 0.5 parts of crosslinking agent CL2 per 100 parts of acrylic polymer B to the solution of acrylic polymer B and mixing uniformly.
  • a pressure-sensitive adhesive sheet according to this example double-sided pressure-sensitive adhesive sheet with substrate was prepared in the same manner as in Example 1, except that this pressure-sensitive adhesive composition was used to prepare first and second pressure-sensitive adhesive layers having the thicknesses shown in Table 2.
  • the post-heat peel strength Fa1 of the first adhesive layer was smaller than the post-heat peel strength Fb1 of the second adhesive layer. More specifically, in the adhesive sheets of Examples 1 to 17, Fb1-Fa1 was 0.5 N/20 mm or more. In the adhesive sheets of these Examples, the first adhesive layer exhibited a high peel-ease effect upon heating treatment, while the second adhesive layer exhibited a relatively mild peel-ease effect compared to the first adhesive layer. On the other hand, in the adhesive sheet of Comparative Example 1, the post-heat peel strength of the first and second adhesive layers was equivalent.
  • the adhesive sheet of Example 9 was cut to a size of 165 mm x 65 mm, and the second adhesive surface was attached to an alkaline glass plate B (manufactured by Matsunami Glass Industry Co., Ltd., thickness 1.35 mm, blue plate edge polished product) as the second member, and then the first adhesive surface was attached to an alkaline glass plate A (manufactured by Matsunami Glass Industry Co., Ltd., thickness 1.35 mm, blue plate edge polished product) as the first member. This was then introduced into an autoclave and autoclaved at 50°C, 5 atm, and for 15 minutes, after which it was removed from the autoclave and left to stand for 30 minutes in a room temperature and normal pressure environment (23°C, 1 atm).
  • alkaline glass plate A/adhesive sheet/alkaline glass plate B assembly was heat-treated in an oven at 180°C for 30 minutes, removed from the oven and left to stand for 30 minutes in a 23°C, 50% RH environment, and an attempt was made to disassemble the assembly by hand (adult female, all evaluations were performed by the same person). Specifically, a ruler (or a metal plate) was inserted between the layers at the end of the bonded body, and after inserting it about 10 mm, force was applied in the vertical direction (thickness direction of the evaluation sample) to attempt dismantling.
  • the bonded body was able to be dismantled in such a way that the alkali glass plate A was peeled off from the first adhesive layer, leaving the entire adhesive sheet on the alkali glass plate B.
  • the adhesive sheet remaining on the alkali glass plate B was able to be peeled off from the alkali glass plate B without tearing by first peeling off an area of about 10 mm from one end of the adhesive sheet from the alkali glass plate B, and then grabbing that part with a human hand and pulling it in a direction of about 150 to 180 degrees.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Adhesive Tapes (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Adhesives Or Adhesive Processes (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Laminated Bodies (AREA)
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Citations (6)

* 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
JP2010278427A (ja) * 2009-04-30 2010-12-09 Nitto Denko Corp 積層フィルム及び半導体装置の製造方法
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
WO2022185612A1 (ja) * 2021-03-05 2022-09-09 日東電工株式会社 ライナー付両面粘着シート
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 (6)

* 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
JP2010278427A (ja) * 2009-04-30 2010-12-09 Nitto Denko Corp 積層フィルム及び半導体装置の製造方法
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
WO2022185612A1 (ja) * 2021-03-05 2022-09-09 日東電工株式会社 ライナー付両面粘着シート
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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