JPH11166164A - Thermally releasable pressure-sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermally releasable pressure-sensitive adhesive sheet which is excellent in the ability to lower in adhesiveness upon heat treatment even when the adhesiveness to an adherend before foaming has a high set value and is satisfactory both in adhesiveness to the adherend and easy releasability from the adherend. SOLUTION: There is provided a thermally releasable pressure-sensitive adhesive sheet, wherein it has a thermally expandable microsphere-containing pressure-sensitive adhesive layer 3 on at least either surface of a base 1 through, optionally, a rubbery organic elastomeric layer 2, the thermally expandable microspheres have a mean particle diameter of 18 μm or above, and 90% or above of them have a particle diameter of 10 μm or above. It is desirable that the adhesive sheet has the rubbery organic elastomeric layer between the base and the pressure-sensitive adhesive layer and that the rubbery organic elastomeric layer comprises a pressure-sensitive adhesive substance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-peelable pressure-sensitive adhesive sheet which has excellent adhesive strength and can be easily peeled off from an adherend by heating at any time.

[0002]

2. Description of the Related Art Conventionally, as a heat-peelable pressure-sensitive adhesive sheet whose adhesive strength is reduced or lost by a heat treatment, a heat-release type pressure-sensitive adhesive sheet in which a foaming agent-containing pressure-sensitive adhesive layer is simply provided on a base material has been known (see, for example, Japanese Patent Application Laid-Open No. H11-157556). Japanese Patent Publication No. 50-13878, 51-2453
4, JP-A-56-61468, and JP-A-56-6.
Nos. 1469 and 60-252681). These are made by foaming a foaming agent contained in an adhesive layer so as to reduce the adhesive force so that the adhesive can be easily peeled off from an adherend. It is used in the field.

[0003] However, the conventional heat-peelable pressure-sensitive adhesive sheet has a problem in that it is difficult to balance the adhesive strength before the foaming treatment and the decrease in the adhesive strength due to the foaming treatment. By the way, if the adhesive strength before foaming treatment is set to be as high as 500 gf / 20 mm or more, it is difficult to peel off from the adherend due to insufficient decrease in adhesive strength due to foaming treatment. When the removability from the body is prioritized, there is a problem that the adhesive strength before the foaming treatment is poor and the above-mentioned temporarily fixed electronic components are displaced or fall off.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to provide an excellent adhesive strength to an adherend due to excellent heat-treating adhesive strength even when the adhesive strength before foaming to the adherend is set high, and to facilitate the peeling of the adhesive strength to the adherend. It is an object of the present invention to obtain a heat-peelable pressure-sensitive adhesive sheet which is compatible with the properties.

[0005]

According to the present invention, there is provided one or both surfaces of a substrate,
A heat-expandable microsphere-containing pressure-sensitive adhesive layer is provided via a rubber-like organic elastic layer as required, and the heat-expandable microspheres have an average particle size of 18 μm or more, and 90% or more of them have a particle size of 10 μm or more. A heat-peelable pressure-sensitive adhesive sheet is provided.

[0006]

According to the present invention, even if the adhesive strength before foaming to the adherend is set high by using the heat-expandable microspheres satisfying the above conditions, the adhesive area can be increased by foaming and / or expanding the adhesive layer by heating. Can be stably reduced, the adhesive strength can be stably reduced, the strong adhesive strength before foaming to the adherend, and the easy peelability due to the decrease or loss of the adhesive strength after heat treatment. Thus, it is possible to obtain a heat-peelable pressure-sensitive adhesive sheet in which the desired setting of the adhesive strength and easy peelability are compatible.

In the above, when a rubber-like organic elastic layer is disposed between the substrate and the adhesive layer, it is possible to more easily achieve strong adhesive strength before foaming and easy peelability after foaming. it can. That is, at the processing temperature for foaming and / or expanding the pressure-sensitive adhesive layer, the force at which the pressure-sensitive adhesive layer expands and / or expands exceeds the drag due to the elastic modulus of the rubber-like organic elastic layer, and the pressure-sensitive adhesive layer has a three-dimensional wave-like or corrugated structure. Deformed to form a continuous peak structure of mountain-shaped protrusions. As a result, the reduction of the bonding area by the heat treatment is efficiently achieved, and even when the bonding force before foaming is set to 500 gf / 20 mm or more. By the treatment such as foaming, the adhesive strength can be stably reduced to 10 gf / 20 mm or less, and the easy releasability is reliably realized.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-peelable pressure-sensitive adhesive sheet of the present invention comprises:
Adhesive layer containing heat-expandable microspheres having an average particle size of 18 μm or more and a particle size of 10 μm or more occupying 90% or more on one or both surfaces of a base material through a rubbery organic elastic layer if necessary. It has what has. An example is shown in FIG.
1 is a substrate, 2 is a rubbery organic elastic layer, and 3 is an adhesive layer.
4 is a separator.

The adhesive layer containing the heat-expandable microspheres can be provided on one or both sides of the substrate, and a rubbery organic elastic layer can be interposed on one or both sides of the substrate if necessary. . In the present invention, the substrate may be of a type that can be easily peeled off from the adhesive layer or the rubbery organic elastic layer, or may be a fixed type in which the substrate and the adhesive layer or the rubbery organic elastic layer are strongly bonded. You can also. A heat-peelable pressure-sensitive adhesive sheet having a heat-expandable microsphere-containing pressure-sensitive adhesive layer on one side of the substrate and a normal adhesive layer on the other side can also be used.

The substrate serves as a supporting base for the adhesive layer and the like. Generally, a plastic film or sheet is used. For example, paper, cloth, non-woven fabric, metal foil, or a plastic laminate of these or plastics An appropriate thin leaf such as a laminate can be used. The thickness of the substrate is 5
00 μm or less, especially 1 to 300 μm, especially 5 to 250 μm
Is common but not limited to this. The substrate may have a conductor layer or a magnetic layer or / and may contain a conductive powder or a magnetic powder and be capable of induction heating through high frequency.

The above-mentioned heat-peelable pressure-sensitive adhesive sheet of the substrate-peelable type can be formed, for example, using a low-adhesive substrate. Known low-adhesion base materials include, for example, a method of coating a release agent typified by a silicone-based resin or a fluorine-based resin, and a method of using a base material having a low adhesive strength made of a nonpolar polymer such as polyethylene or polypropylene. Can be obtained by the following method.

The heat-peelable pressure-sensitive adhesive sheet of the substrate-fixing type can be formed, for example, using a strongly adhesive substrate. Strongly adherent base materials include, for example, chromic acid treatment, ozone exposure, flame exposure, high piezoelectric shock exposure, chemical or physical treatment that oxidizes the surface by ionizing radiation treatment, etc., and highly polar polymers such as polyester. It can be obtained by a known method such as a method using a substrate having a strong adhesive force.

The pressure-sensitive adhesive layer contains heat-expandable microspheres (microcapsules) so that the pressure-sensitive adhesive sheet adhered to the adherend can be easily peeled off from the adherend by heat treatment. By heating the adhesive layer at any time and subjecting the heat-expandable microspheres to foaming and / or expansion treatment, the adhesive area between the adhesive layer and the adherend can be reduced and the adhesive sheet can be peeled off. . With a foaming agent that is not microencapsulated, good releasability cannot be stably achieved.

As the above-mentioned heat-expandable microspheres, for example, an appropriate substance which is easily gasified and exhibits a heat expansion property such as isobutane, propane or pentane is contained in a shell-forming substance by a coacervation method or an interfacial polymerization method. The shell can be used, and the shell is made of a heat-meltable substance such as vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, polysulfone, or a thermal expansion material. What is necessary is just to consist of an appropriate substance destroyed by. In addition, there is a commercially available product such as microspheres (trade name, manufactured by Matsumoto Yushi Co., Ltd.) as such thermally expandable microspheres.

In the present invention, the thermally expandable microspheres include:
From the standpoint of achieving a stable decrease in adhesive strength due to the heat treatment, a material having an average particle size of 18 μm or more and 90% or more of a particle size of 10 μm or more is used. The preferred average particle size of the heat-expandable microspheres depends on the thickness of the target adhesive layer, but generally the thickness is 300 μm or less, preferably 5 to 200 μm.
m, especially 20 to 150 μm when forming an adhesive layer,
１００100 μm, especially 20-50 μm. The achievement of the particle size condition can be achieved using an appropriate classifier such as a centrifugal air classifier.

When the average particle diameter is less than 18 μm and the content of particles having a particle diameter of 10 μm or more is less than 90%, the degree of deformation of the pressure-sensitive adhesive layer due to the heat treatment is small, and the adhesive strength is poor. The pressure-sensitive adhesive layer may be formed as a layer thicker than the average particle size of the heat-expandable microspheres, particularly, a layer thicker than the maximum particle size of the heat-expandable microspheres, by smoothing the surface of the pressure-sensitive adhesive layer. It is more preferable that a stable adhesive strength before the heat treatment is achieved.

If the thickness of the pressure-sensitive adhesive layer is excessive in the above, cohesive failure occurs at the time of peeling after heat treatment, and adhesive residue that contaminates the adherend is likely to be generated. From this point, the thickness of the pressure-sensitive adhesive layer is 500 μm. Hereinafter, it is particularly preferable that the thickness be 300 μm or less. On the other hand, if the thickness of the pressure-sensitive adhesive layer is too small, the degree of deformation of the pressure-sensitive adhesive layer due to the heat treatment is small, and the adhesive strength is poorly reduced. From this point, the thickness of the pressure-sensitive adhesive layer is 5 μm or more, especially 1
It is preferably at least 0 μm, particularly preferably at least 20 μm.

The heat-expandable microspheres which can be preferably used from the viewpoint of lowering the adhesive strength of the pressure-sensitive adhesive layer due to the heat treatment are formed by foaming until the volume expansion rate becomes 5 times or more, especially 7 times or more, especially 10 times or more. It does not burst. The amount of the heat-expandable microspheres can be appropriately determined depending on the expansion ratio of the pressure-sensitive adhesive layer and the property of lowering the adhesive strength, but is generally 1 to 150 parts by weight per 100 parts by weight of the base polymer forming the pressure-sensitive adhesive layer. Department,
In particular, it is 10 to 130 parts by weight, especially 25 to 100 parts by weight.

The pressure-sensitive adhesive layer can be formed of a pressure-sensitive adhesive that allows the expansion and / or expansion of the heat-expandable microspheres when heated, and does not restrict the expansion and / or expansion of the heat-expandable microspheres as much as possible when heated. Are preferably used. Therefore, for example, rubber-based, acrylic-based, vinyl alkyl ether-based or silicone-based, polyester-based or polyamide-based, urethane-based or styrene-diene block copolymer-based, heat-melting with a melting point of about 200 ° C. or less Known pressure-sensitive adhesives such as those having improved creep characteristics by blending a resin (for example, JP-A-56-61468, JP-A-61-1748)
No. 57, Japanese Unexamined Patent Publication No. 63-17981, Japanese Patent Publication No. 5
Or the like can be used. The pressure-sensitive adhesive may be a mixture of appropriate additives such as a cross-linking agent, a tackifier, a plasticizer, a filler, and an antioxidant.

In general, a rubber-based pressure-sensitive adhesive having a base polymer of natural rubber or various synthetic rubbers, methyl group, ethyl group, propyl group, butyl group, amyl group, hexyl group, heptyl group, cyclohexyl group, 2-ethylhexyl Group, isooctyl group, isodecyl group, dodecyl group, lauryl group, tridecyl group, pentadecyl group, hexadecyl group,
Acrylic using one or more acrylic acid alkyl esters comprising an ester of acrylic acid or methacrylic acid having an alkyl group having 20 or less carbon atoms such as a heptadecyl group, an octadecyl group, a nonadecyl group or an eicosyl group. An acrylic adhesive having a polymer as a base polymer is used.

The above-mentioned acrylic polymer may be used, for example, in order to improve cohesive strength, heat resistance, crosslinkability, etc., if necessary, for example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, or the like. Carboxyl group-containing monomers such as maleic acid, fumaric acid and crotonic acid, or acid anhydride monomers such as maleic anhydride and itaconic anhydride, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, (meth) acrylic Hydroxybutyl or (meth)
Hydroxyl group-containing monomers such as hydroxyhexyl acrylate, hydroxyoctyl (meth) acrylate, hydroxydecyl (meth) acrylate, hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate, styrene sulfonic acid, Allylsulfonic acid, 2- (meth) acrylamide-
Sulfonic acid group-containing monomers such as 2-methylpropanesulfonic acid and (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate and (meth) acryloyloxynaphthalenesulfonic acid, and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate (N-substituted) amide monomers such as, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide Alkylaminoalkyl (meth) acrylate monomers such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, (meth) acrylic Alkoxyalkyl (meth) acrylate monomers such as methoxyethyl and ethoxyethyl (meth) acrylate; maleimide monomers such as N-cyclohexylmaleimide and N-isopropylmaleimide; N-laurylmaleimide and N-phenylmaleimide; N-methyl Itaconimide-based monomers such as itaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide; ) Acryloyloxymethylene succinimide and N-
Succinimide-based monomers such as (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyoctamethylene succinimide, vinyl acetate and vinyl propionate, N-vinyl pyrrolidone, methyl vinyl pyrrolidone, vinyl pyridine, Vinylpiperidone, vinylpyrimidine and vinylpiperazine, vinylpyrazine and vinylpyrrole, vinylimidazole and vinyloxazole, vinylmorpholine and N-
Vinylcarboxylic acid amides, vinyl monomers such as styrene and α-methylstyrene, N-vinylcaprolactam, cyanoacrylate monomers such as acrylonitrile and methacrylonitrile, and epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate; Glycol-based acrylic ester monomers such as polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate and methoxy polypropylene glycol (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, Acrylic ester monomers such as fluorine (meth) acrylate, silicone (meth) acrylate and 2-methoxyethyl acrylate; hexanediol di (meth) acrylate Relate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, One or two suitable monomer components such as polyfunctional monomers such as pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate, isoprene, butadiene, isobutylene, and vinyl ether. Those obtained by copolymerizing the above may be used.

The pressure-sensitive adhesive which can be used more preferably, for example, in order to achieve a large adhesive force before heating and a large decrease in adhesive force due to heating, has a dynamic elastic modulus at room temperature to 150 ° C. of 5
A polymer of 10,000 to 10 million dyn / cm ² is used as a base polymer.

The pressure-sensitive adhesive layer is formed, for example, by mixing heat-expandable microspheres with a pressure-sensitive adhesive using a solvent as necessary, and applying the mixture to a substrate via a rubber-like organic elastic layer as necessary. Alternatively, it can be carried out by an appropriate method such as a method of transferring an adhesive layer formed on a separator onto a substrate according to the method.

The rubbery organic elastic layer disposed between the base material and the pressure-sensitive adhesive layer, if necessary, has a surface that conforms to the surface shape of the pressure-sensitive adhesive sheet when the pressure-sensitive adhesive sheet is adhered to the pressure-sensitive adhesive sheet. Following the function of providing a large adhesive area, and foaming and / or foaming in the surface direction of the heat-peelable pressure-sensitive adhesive sheet when heating and foaming and / or expanding the pressure-sensitive adhesive layer for peeling from the adherend.
Alternatively, the adhesive layer serves to reduce the restraint of expansion and promote the three-dimensional deformation of the adhesive layer into a continuous peak structure, a swelling structure, or a corrugated structure of the mountain-shaped protrusions.

The rubber-like organic elastic layer is made of a natural rubber or synthetic rubber having a Shore D hardness of 50 or less, especially 40 or less, or a rubber elasticity based on the D-shore of ASTM D-2240. It is preferred to be formed of a synthetic resin having The thickness is generally 500 μm or less, especially 5 to 300 μm, particularly 20 to 150 μm.

Examples of the synthetic rubber or synthetic resin include nitrile, diene, and acrylic synthetic rubbers, thermoplastic elastomers such as polyolefin and polyester, ethylene-vinyl acetate copolymer, polyurethane, polybutadiene, and the like. Synthetic resins having rubber elasticity, such as soft polyvinyl chloride. In the present invention, an essentially hard polymer, such as polyvinyl chloride, having rubber elasticity in combination with a compounding agent such as a plasticizer or a softening agent may be used. Adhesive substances such as the adhesive exemplified in the above-mentioned adhesive layer can also be preferably used for forming the rubbery organic elastic layer.

The formation of the rubbery organic elastic layer is carried out by an appropriate method such as a method of applying a solution of the above-mentioned forming material on a base material or a method of bonding a film or the like made of the above forming material to the base material. May be. In the present invention, the rubber-like organic elastic layer may be formed of an adhesive substance containing a natural rubber, a synthetic rubber, or a synthetic resin having rubber elasticity as a main component,
Further, it may be formed of a foamed film or the like mainly composed of such components.

As described above, the heat-peelable pressure-sensitive adhesive sheet of the present invention is formed by separately forming a composite comprising, for example, a pressure-sensitive adhesive layer and an optional rubbery organic elastic layer, and bonding the composite to a substrate. The heat-peelable pressure-sensitive adhesive sheet obtained can be adhered to an adherend with a predetermined adhesive force at the time of adhesion, and firmly adheres to the adherend when it is desired to release the adhesive state. In this case, it can be easily separated or separated by heat treatment.

Accordingly, the heat-peelable pressure-sensitive adhesive sheet of the present invention
It is also possible to use it for the purpose of permanently bonding two or more adherends made of appropriate articles or the like, but the preferred use is to adhere the adherends for a predetermined period and achieve the bonding purpose. This is an application where solving the condition is required or desired.

There are various uses as described above. Incidentally, examples thereof include formation of an adhesive composite for the purpose of recycling two or more articles, for example, an article made of a polymer and an article made of metal, fiber or paper, various electric or electronic devices, and display devices. Carrier tapes and temporary fixing or fixing materials for transporting and temporarily fixing parts in the assembly process such as surface protection materials and masking materials for preventing contamination and damage of metal plates, plastic plates, glass plates, etc. Use is raised.

The heat treatment conditions for allowing the heat-peelable pressure-sensitive adhesive sheet to be easily peeled off from the adherend include the following: the surface area of the adherend, the type of the heat-expandable microspheres, etc .; The general condition is 100 to 250 ° C. for 1 to 90 seconds (hot plate or the like) or 5 to 15 minutes (hot air dryer or the like). Under such heating conditions, the heat-expandable microspheres of the adhesive layer usually expand or / and foam, and the adhesive layer expands and deforms.
Adhesive strength is reduced or lost. Note that the heat treatment can be performed at an appropriate stage depending on the purpose of use.

[0032]

EXAMPLES Example 1 Microsphere F-50D having an average particle size of 13.4 μm
(Integrated 10% particle size 7.1 μm) is classified by a centrifugal force type air classifier to obtain thermally expandable microspheres having an average particle size of 19.9 μm and 90% or more of which have a particle size of 10 μm or more (integrated). 10
% Particle size 11.4 μm), 50 parts of which are mixed with 100 parts (solid content) of an acrylic pressure-sensitive adhesive, applied to one side of a 100 μm-thick polyester film, dried, and dried to a thickness of 40 μm.
To form a heat-peelable pressure-sensitive adhesive sheet.

The acrylic pressure-sensitive adhesive was prepared by adding 15 parts of a terpene-based tackifier to a toluene solution of 100 parts of an acrylic copolymer A composed of 50 parts of butyl acrylate, 50 parts of ethyl acrylate, and 5 parts of acrylic acid. It was prepared by blending 5 parts of a polyurethane crosslinking agent.

Example 2 Into a toluene solution of 100 parts of the acrylic copolymer A was added:
25 parts of terpene-based tackifier and polyurethane-based crosslinking agent 3
Example 1 except that an acrylic pressure-sensitive adhesive material having a blended part was applied to one side of a polyester film and dried to form a rubbery organic elastic layer having a thickness of 35 μm, and an acrylic pressure-sensitive adhesive layer was provided thereon. A heat-peelable pressure-sensitive adhesive sheet was obtained in accordance with The acrylic pressure-sensitive adhesive layer was formed by a method in which it was separately formed on a separator and then transferred onto the rubbery organic elastic layer.

Example 3 A toluene solution of 100 parts of an acrylic copolymer B consisting of 100 parts of butyl acrylate, 5 parts of vinyl acrylate and 3 parts of acrylic acid was mixed with 40 parts of a phenolic tackifier and 2 parts of a polyurethane crosslinking agent. Acrylic adhesive material is applied to rayon non-woven fabric and dried to a thickness of 50μ.
m rubber-like organic elastic layer, and 100 parts of an acrylic pressure-sensitive adhesive obtained by blending 5 parts of a polyurethane-based cross-linking agent with a toluene solution of 100 parts of an acrylic copolymer B formed on a separator. ) Was transferred with an acrylic pressure-sensitive adhesive layer having a thickness of 50 μm mixed with 100 parts of the thermally expandable microspheres subjected to the same classification treatment as in Example 1 to obtain a heat-peelable pressure-sensitive adhesive sheet.

Example 4 A heat-peelable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 2 except that high-quality paper having a thickness of 50 μm was used instead of the polyester film.

Comparative Example 1 Microsphere F-50D (average particle size: 13.4 μm, integrated 10% particle size: 7.1 μm) before classification was used as the heat-expandable microspheres in the same manner as in Example 1. A heat-peelable pressure-sensitive adhesive sheet was obtained.

Comparative Example 2 Ten parts of a terpene-based tackifier and a polyurethane-based crosslink were added to a toluene solution of 100 parts of an acrylic copolymer C composed of 70 parts of ethyl acrylate, 30 parts of 2-ethylhexyl acrylate, and 5 parts of methyl methacrylate. Acrylic adhesive composed of 0.8 part of the agent and 30 parts of Microsphere F-50D before classification treatment is applied on a 38 μm thick polyester film to form an acrylic adhesive layer having a thickness of 40 μm and heated. A peelable pressure-sensitive adhesive sheet was obtained.

Comparative Example 3 A heat-peelable pressure-sensitive adhesive sheet was obtained in the same manner as in Comparative Example 2, except that the compounding amount of the terpene-based tackifier was 4 parts and the compounding amount of the polyurethane-based crosslinking agent was 4 parts.

Evaluation Test The heat-peelable pressure-sensitive adhesive sheet having a width of 20 mm obtained in each of Examples and Comparative Examples was applied to a 0.5 mm-thick stainless steel plate (SUS304, BA).
Finish) and adhere to 1 according to JIS Z 0237.
80 degree peel adhesion (peeling speed 300mm / min, 23 ° C)
The adhesive strength before (initial) heating and the adhesive strength after heat treatment at 130 ° C. for 10 minutes in a hot air drier were examined. The results are shown in the following table.

[0041]

In the examples, when the stainless steel plate was examined for peeling after the heat treatment, no adhesive residue was found in any case. In addition, when the state including the cross section after the heat treatment of the heat-peelable pressure-sensitive adhesive sheets of Example 2 and Comparative Example 1 was photographed by an enlarged photograph and observed, in Example 2, the rubber-like organic elastic layer 2 and the foam were formed as shown in FIG. It was confirmed that the composite composed of the adhesive layer 31 and / or the expanded adhesive layer 31 was integrally deformed three-dimensionally to form an undulating or mountain-shaped convex part.

On the other hand, in the case of Comparative Example 1, as shown in FIG. 3, small irregularities based on the size of the expanded and / or expanded state of the heat-expandable microspheres were formed in the adhesive layer 5, but the undulation structure was formed. Was not found.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment.

FIG. 2 is a partial cross-sectional view after heating in Example 2.

FIG. 3 is a partial cross-sectional view after heating in Comparative Example 1.

[Description of sign]

 1: base material 2: rubbery organic elastic layer 3: adhesive layer 4: separator 31, 5: adhesive layer after heating

Claims (4)

[Claims] An adhesive layer containing heat-expandable microspheres is provided on one or both surfaces of a substrate, wherein the heat-expandable microspheres have an average particle size of 18 μm or more, and 90% or more of the particles have a particle size of 90% or more. 10 μm
A heat-peelable pressure-sensitive adhesive sheet characterized by the above. 2. The heat-peelable pressure-sensitive adhesive sheet according to claim 1, wherein a rubber-like organic elastic layer is provided between the substrate and the pressure-sensitive adhesive layer. 3. The heat-peelable pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer forms a continuous peak structure of mountain-shaped protrusions by foaming or expanding treatment by heating. 4. The heat-peelable pressure-sensitive adhesive sheet according to claim 2, wherein the rubbery organic elastic layer is made of a pressure-sensitive adhesive substance.