Heat-releasable adhesive sheet

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical Field of Invention]

The present invention relates to a heat-removable pressure-sensitive adhesive sheet which can reduce the adhesive force by heat treatment, can be easily peeled off from an adherend with good non-staining property, and is suitable for application to electronic parts and the like.

【0002】

[Conventional technology]

Conventionally, a heat-release type pressure-sensitive adhesive sheet in which a foaming agent-containing pressure-sensitive adhesive layer is provided on a base material has been known (Japanese Patent Publication No. 50-13878, No. 51-24534, No. 56-61468). , 56-61469, 60-252681, etc.). This is a product in which the adhesive force can be reduced by foaming or expansion treatment by heating the adhesive layer so that the adhesive layer can be easily peeled off from the adherend, and is used, for example, for temporary fixing in the manufacturing process of a ceramic capacitor. ..

【0003】

However, when the conventional heat-peeling adhesive sheet is used for dicing or polishing the back surface of a semiconductor wafer, a large amount of extremely fine contamination that cannot be visually recognized remains on the wafer from which the sheet has been peeled after the heat treatment. There was a problem that caused a problem and was not suitable for practical use. Such a pollution problem is due to a dramatic increase in contaminants due to heat treatment rather than a comparison of the pollution status before and after heating. By the way, in the measurement of the number of particles on a 4-inch silicon wafer via a laser surface inspection device, the number of particles was less than 1,000 when the sheet was peeled off before heating, but after heating it was more than 10,000 and more than 10 times more contaminated. It is customary for the degree to increase.

【0004】

PROBLEM TO BE SOLVED: To

INDUSTRIAL APPLICABILITY The present invention provides a heat-peeling adhesive sheet in which the degree of contamination does not increase due to heat treatment for reducing adhesive strength, and is applicable to an adherend after heat peeling which can be practically used for manufacturing electronic parts made of semiconductor wafers. The challenge is to develop a product with a low degree of pollution.

【0005】

[Means for Solving Problems]

The present invention provides a heat-release type pressure-sensitive adhesive sheet containing a heat-expandable microsphere and having a non-heat-expandable pressure-sensitive adhesive layer on at least one surface of the heat-expandable layer that expands by heating. ..

【0006】

[Effect of the invention]

According to the present invention, the heat-expandable layer using the heat-expandable microspheres and the adhesive layer arranged on the heat-expandable layer achieve the desired adhesive properties such as excellent adhesive force before heating, and are heated. It is possible to obtain a heat-peelable pressure-sensitive adhesive sheet that can quickly achieve excellent reduction in adhesive strength and that does not increase the degree of contamination of the adherend due to the treatment for reducing the adhesive strength. The effect of preventing the increase in contamination is considered to be due to the covering action of the adhesive layer on the heat-expandable layer, but considering that the reduction of the adhesive force is also achieved, the details of the function of exhibiting such an effect are unknown.

【0007】

However, the practical significance of simultaneously achieving the reduction of the adhesive force and the prevention of the increase in contamination by the structure in which the adhesive layer is arranged on the heat-expandable layer is great. By the way, by using a pollution-preventing type adhesive layer with less contamination after peeling such as adhesive residue, it is also possible to manufacture electronic parts made of semiconductor wafers with less contamination in the adherend after heat peeling. A practical heat-release type sheet can be obtained. As a result, the wafer thickness, which has been constrained by the problem of breakage during peeling due to residual adhesive force, such as a stain-preventing adhesive layer due to UV curing, can be further reduced by achieving a smaller adhesive force with such a sheet. It will be possible.

【0008】

BEST MODE FOR CARRYING OUT THE INVENTION

The heat-release type pressure-sensitive adhesive sheet according to the present invention comprises a heat-expandable pressure-sensitive adhesive layer containing heat-expandable microspheres and having a non-heat-expandable pressure-sensitive adhesive layer on at least one surface of the heat-expandable layer that expands by heating. Examples are shown in Fig. 1 and Fig. 2. 2,21 is a heat-expandable layer, and 3,31 is an adhesive layer. Reference numerals 1, 4 and 5 are a base material, a separator and a rubber-like organic elastic layer, which are provided as needed, respectively.

【0009】

The heat-expandable layer contains heat-expandable microspheres and expands by heating, and the adhesive layer on the surface is also unevenly deformed through the uneven deformation due to the expansion to reduce the adhesive force to the adherend. Therefore, the heat-releaseable pressure-sensitive adhesive sheet adhered to the adherend can be easily peeled off from the adherend by heat-treating the heat-expandable layer at any time.

【0010】

The heat-expandable layer can be formed as, for example, a mixed layer of a heat-expandable microsphere and a binder. As the binder, appropriate ones such as polymers and waxes that allow foaming and / or expansion by heating of heat-expandable microspheres can be used. In particular, those that do not constrain the foaming and / or expansion of the thermally expandable microspheres as much as possible are preferable. A binder that can be particularly preferably used from the viewpoint of the heat expansion property of the heat-expandable microspheres and the controllability of adhesive properties such as the adhesive force to the adherend via the adhesive layer is an adhesive.

【0011】

The pressure-sensitive adhesive is not particularly limited, and for example, polymers such as rubber-based and acrylic-based, vinyl alkyl ether-based and silicone-based, polyester-based and polyamide-based, urethane-based and fluorine-based, and styrene-diene block copolymer-based polymers can be used. Those used, those with improved creep characteristics by blending a heat-meltable resin with a melting point of about 200 ° C or less, UV-curable ones, and if necessary, for example, cross-linking agents, tackifiers, and plasticizers. One or more of appropriate ones such as those containing various additives such as agents, softeners, fillers and pigments, colorants and antioxidants, and surfactants can be used. 56-61468, 61-174857, 63-17981, 56-13040, etc.).

【0012】

Adhesives that are preferable in terms of the balance between the controllability of the appropriate adhesive force before heating to the adherend via the adhesive layer and the reduction of the adhesive force due to heating are dynamic in the temperature range from room temperature to 150 ° C. Elastic modulus is 50,000 to 10 million dyn / cm²The polymer of the above is used as a base polymer, but the present invention is not limited to this.

【0013】

The pressure-sensitive adhesives generally used in the above are, for example, natural rubber, polyisobutylene rubber, styrene / butadiene rubber, styrene / isoprene / styrene block copolymer rubber, styrene / butadiene / styrene block copolymer rubber, recycled rubber, butyl rubber, and poly. Rubber-based pressure-sensitive adhesives using a rubber-based polymer such as isobutylene or NBR as the base polymer, and acrylic-based pressure-sensitive adhesives using an acrylic polymer containing an alkyl ester of acrylic acid or methacrylic acid as a base polymer.

【0014】

Examples of the acrylic polymer include methyl group and ethyl group, propyl group and butyl group, amyl group and hexyl group, heptyl group and 2-ethylhexyl group, isooctyl group and isononyl group, isodecyl group and dodecyl group and lauryl. Acrylic having a linear or branched alkyl group having 1 to 20 carbon atoms, especially 4 to 18 carbon atoms, such as a group or tridecyl group, a tetradecyl group or a pentadecyl group, a hexadecyl group or a heptadecyl group, an octadecyl group or a nonadecil group or an eicosyl group. Examples thereof include those using one or more kinds of esters of acid or methacrylic acid.

【0015】

Further, the acrylic polymer used may be one or two or more copolymers of appropriate monomers for the purpose of modifying cohesive force, heat resistance, crosslinkability and the like. The copolymerization monomer is not particularly limited as long as it can be copolymerized with the acrylic acid-based alkyl ester.

【0016】

Incidentally, examples of the copolymerized monomer include acrylic acid and methacrylic acid, carboxyethyl acrylate and carboxypentyl acrylate, itaconic acid and maleic acid, carboxyl group-containing monomers such as fumaric acid and crotonic acid, and maleic anhydride and itaconic anhydride. Such acid anhydride monomers, (meth) hydroxyethyl acrylate, (meth) hydroxypropyl acrylate, (meth) hydroxybutyl acrylate, (meth) hydroxyhexyl acrylate, (meth) hydroxyoctyl acrylate and (meth) acrylic Examples thereof include hydroxyl group-containing monomers such as hydroxydecyl acid acid, hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) -methylmethacrylate.

【0017】

Also, sulfonic acids such as styrene sulfonic acid and allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate and (meth) acryloyloxynaphthalene sulfonic acid. Group-containing monomers, phosphate group-containing monomers such as 2-hydroxyethylacryloyl phosphate, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N- (N-substituted) amide-based monomers such as methylolpropane (meth) acrylamide, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate. (Meta) Alkyl Acrylate Amino Sulfonate, (Meta) Alkyl Acrylic Acid Sulfonate such as methoxyethyl acrylate and ethoxyethyl (meth) Acrylic Acid, N-Cyclohexyl Maleimide, N-Isopropyl Maleimide, N-Lauryl Maleimide-based monomers such as maleimide and N-phenylmaleimide, N-methylitaconimide and N-ethylitaconimide, N-butylitaconimide and N-octylitaconimide, N-2-ethylhexylitaconimide and N-cyclohexylitaconimide, Itaconimide-based monomers such as N-laurylitaconimide, N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyoctamethylene succinimide. Examples of copolymerized monomers include succinimide-based monomers.

【0018】

Furthermore, vinyl acetate and vinyl propionate, N-vinylpyrrolidone and methylvinylpyrrolidone, vinylpyridine and vinylpiperidone, vinylpyrimidine and vinylpiperazin, vinylpyrazine and vinylpyrrole, vinylimidazole and vinyloxazole, vinylmorpholin and N-vinylcarboxylic acid amides , Vinyl-based monomers such as styrene and α-methylstyrene, N-vinylcaprolactam, cyanoacrylate-based monomers such as acrylonitrile and methacrylonitrile, epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate, (meth) acrylic acid Glycol-based acrylic ester monomers such as polyethylene glycol, (meth) polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, and fluorine (meth) acrylate. , Acrylate-based monomers such as silicone (meth) acrylate and 2-methoxyethyl acrylate, hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate and Neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropanthry (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, urethane Polyfunctional monomers such as acrylate and divinylbenzene, butyl diacrylate and hexyl diacrylate, isoprene and butadiene, isobutylene and vinyl ether are also examples of copolymerizable monomers.

【0019】

On the other hand, as the heat-expandable microspheres to be blended in the heat-expandable layer, an appropriate substance that easily gasifies and exhibits thermal expansion, such as isobutane, propane, and pentane, is appropriately used by a core selvation method, an interfacial polymerization method, or the like. From shell-forming substances such as vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethylmethacrylate, polyvinylidene chloride, polyvinylidene chloride, polysulfone, and other heat-meltable substances and substances that are destroyed by thermal expansion. Examples include microcapsules encapsulated inside the shell.

【0020】

By using the heat-expandable microspheres, it is possible to stably suppress an increase in the degree of contamination of the adherend due to heating. In the case of a foaming agent that is not microencapsulated, the effect of suppressing the increase in the degree of contamination is poor, probably because the adhesive layer forming the surface is coagulated and broken. From the points of operability of reducing the adhesive force by heating, especially the stable achievement of the reduction of the adhesive force, the volume expansion until bursting is 5 times or more, especially 7 times or more, especially 10 times or more thermal expansion. Sexual microspheres are preferably used.

【0021】

The average particle size of the heat-expandable microspheres to be used can be appropriately determined, and is generally 100 μm or less, particularly 80 μm or less, particularly 1 to 50 μm, but is not limited thereto. The heat-expandable microspheres include commercially available products such as Microsphere (trade name, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.).

【0022】

The amount of the heat-expandable microspheres used may be appropriately determined depending on the expansion ratio of the heat-expandable layer, the reduction of the adhesive force, and the like. Generally, in the case of the above-mentioned binders and adhesives, 1 to 150 parts by weight, particularly 10 to 130 parts by weight, particularly 25 to 100 parts by weight of heat-expandable microspheres are used per 100 parts by weight of the base polymer. Be done.

【0023】

To form the heat-expandable layer, for example, a heat-expandable microsphere and a compounding component such as a binder are mixed using a solvent as necessary, and the mixture is developed by an appropriate method such as a coating method to form a sheet-like layer. It can be done by a method of forming. The layer thickness can be appropriately determined depending on the reduceability of the adhesive force and the like.

【0024】

In general, it is possible to prevent the adhesive layer provided on the surface from being uneven due to the unevenness of the surface based on the heat-expandable microspheres due to the excessive thickness and not to develop sufficient adhesive force, or to prevent the adhesive layer provided on the adhesive layer from being developed. 300 μm or less, especially 2 to 200 μm, from the viewpoint of preventing the layers from coagulating and breaking and increasing the degree of contamination of the adherend, and preventing insufficient reduction of adhesive force due to poor thermal deformation due to excessive thickness. Especially, the thickness is 5 to 150 μm.

【0025】

When forming the heat-expandable layer, the heat-expandable layer 2 may be supported by the base material 1 as required, as shown in the figure. In such a support form, the heat-expandable layer and eventually the adhesive layer are supported and reinforced by the base material to improve the handleability of the heat-release type adhesive sheet, and the adhesive to the adherend and the adhesive to be peeled from the adherend after heating. It has the advantage of being able to do such things efficiently.

【0026】

As the base material, for example, a heat-expandable layer such as paper or cloth, a porous material such as a non-woven fabric or a net, a plastic film or a rubber sheet, a foam sheet or a metal leaf, or a laminate thereof can be supported as appropriate. A thin leaf body or the like can be used. Among them, those having excellent heat resistance that does not melt at the heat treatment temperature of the heat-expandable layer are preferable from the viewpoint of handleability after heating.

【0027】

Further, the base material may be one in which the deformability such as the elongation rate is controlled by a stretching treatment or the like. When the adhesive layer is treated with ultraviolet rays or the like, a base material that transmits the treatment line is used. The thickness of the base material can be appropriately determined according to the strength, flexibility, purpose of use, etc., and is generally 500 μm or less, particularly 3 to 300 μm, and particularly 5 to 250 μm, but is not limited thereto.

【0028】

The sheet in the base material support form is, for example, a method in which the above-mentioned unfolding operation is performed on the base material to directly attach a heat-expandable layer on the base material, or a heat-expandable layer is provided on a separator according to the method. It can be formed by an appropriate method such as a method of transferring the heat-expandable layer to the base material.

【0029】

The separator is, for example, a substrate obtained by surface-treating the base material with an appropriate release agent such as silicone-based, long-chain alkyl-based, fluorine-based, molybdenum sulfide, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, or the like. Low adhesive substrate made of fluorine-based polymer such as polyvinylidene fluoride, tetrafluoroethylene / hexafluoropropylene copolymer or chlorotrifluoroethylene / vinylidene fluoride copolymer, low made of non-polar polymer such as polyethylene or polypropylene It can be obtained as an adhesive base material or the like. The separator can also be used as a base material for supporting the thermally expandable layer.

【0030】

In the above, the heat-expandable layer can be provided on one side or both sides of the base material as shown in the figure, and the base material can be embedded inside the heat-expandable layer. The base material having excellent adhesion to the heat-expandable layer is a method using a film made of a highly polar polymer such as polyester, chemical treatment such as chromic acid treatment, ozone exposure, flame exposure, high piezoelectric shock exposure, and ionizing radiation treatment. Alternatively, it can be obtained by a method of applying an appropriate treatment such as a surface oxidation treatment by a physical method to the base material.

【0031】

Further, in order to improve the adhesion between the base material and the heat-expandable layer, a method of providing an undercoat layer on the base material is also effective. When the heat-expandable layer is supported by the base material in this way, one or more intermediate layers may be provided between the base material and the heat-expandable layer. The intermediate layer may have an appropriate purpose such as the coat layer of the release agent for the purpose of imparting the peelability and the undercoat layer for the purpose of improving the adhesion.

【0032】

By the way, as an example of the intermediate layer other than the above-mentioned release coat layer and undercoat layer, a layer for the purpose of imparting good deformability, a layer for the purpose of increasing the adhesive area to the adherend, and an improvement of the adhesive force. Detachability from the target layer, the layer intended to follow the surface shape of the adherend well, the layer intended to improve the processability of reducing the adhesive force by heating, and the adherend after heating. There are layers for the purpose of improvement.

【0033】

From the viewpoint of imparting deformability and improving peelability after heating, a method in which the rubber-like organic elastic layer 5 is provided as an intermediate layer as illustrated in FIG. 2 is effective. In such a rubber-like organic elastic layer, when the heat-release type adhesive sheet is adhered to the adherend, the adhesive layer on the surface works well to follow the surface shape of the adherend to provide a large adhesive area, and during heating. It works to improve the controllability of expansion of the heat-expandable layer, expands the heat-expandable layer more predominantly in the thickness direction than in the plane direction by heating, and forms an expansion layer with excellent thickness uniformity. Is.

【0034】

The rubber-like organic elastic layer preferable from the viewpoint of the above-mentioned working properties is a natural rubber or synthetic rubber of 50 or less, especially 45 or less, particularly 40 or less, based on the D-type hardness of the D-type shore of ASTM D-2240, or It is formed of a synthetic resin having rubber elasticity. The thickness is usually 500 μm or less, especially 3 to 300 μm, and particularly 5 to 150 μm in terms of the above-mentioned functions, but the thickness is not limited to this.

【0035】

Examples of the synthetic rubber or synthetic resin include synthetic rubbers such as nitrile-based, diene-based and acrylic-based, thermoplastic elastomers such as polyolefin-based and polyester-based, ethylene-vinyl acetate copolymers and polyurethanes, polybutadienes and soft polychlorides. Examples thereof include synthetic resins having rubber elasticity such as vinyl. In the present invention, a polymer having rubber elasticity in combination with a compounding agent such as a plasticizer or a softening agent can be used even if it is an essentially hard polymer such as polyvinyl chloride.

【0036】

The rubber-like organic elastic layer may be formed of an adhesive substance containing the above-mentioned forming material as a main component, or may be formed of a foamed film or the like containing such a component as a main component. The rubber-like organic elastic layer can be formed by an appropriate method such as a method of applying a solution of the forming material on the base material or a method of adhering a film or the like made of the forming material to the base material. , It is preferable that the rubber-like organic elastic layer is superimposed on the side opposite to the side where the adhesive layer of the heat-expandable layer is provided from the viewpoint of the above-mentioned actions and the like. When the adhesive layer is treated with ultraviolet rays or the like, it is an intermediate layer capable of transmitting the treatment line.

【0037】

In the present invention, the adhesive layer provided on the heat-expandable layer prevents the increase of contaminants, particularly microscopic contaminants, on the adherend during the treatment of adhering to the adherend and reducing the adhesive force by heating. The purpose. The adhesive layer can be formed by using an appropriate adhesive depending on the desired adhesive properties such as the adhesive force to the adherend, and the type thereof is not particularly limited. Therefore, any of the pressure-sensitive adhesives and known substances exemplified in the above-mentioned heat-expandable layer can be used, and those that do not restrain the deformation of the heat-expandable layer due to heating as much as possible are preferable.

【0038】

Among them, polyfunctional isocyanate-based cross-linking agents such as tolylene diisocyanate, trimethylolpropane tolylene diisocyanate, and diphenylmethane triisocyanate, and epoxy-based cross-linking agents such as polyethylene glycol diglycidyl ether, diglycidyl ether, and trimethylolpropane triglycidyl ether. Melamine-based cross-linking agents such as alkyl etherified melamine compounds, metal salt-based cross-linking agents, metal chelate-based cross-linking agents and amino-based cross-linking agents, peroxide-based cross-linking agents and coupling agent-based cross-linking agents such as silane-based coupling agents, etc. A pressure-sensitive adhesive containing an appropriate cross-linking agent comprising the above is preferably used.

【0039】

Further, when an electronic component made of a semiconductor wafer is obtained, for example, when a semiconductor wafer having a circuit pattern formed on the back surface is polished on the back surface and then diced to obtain a semiconductor chip, when it is particularly desired to prevent contamination of an adherend. An appropriate anticontamination type pressure-sensitive adhesive represented by a UV-curable type or a non-UV-curable type pressure-sensitive adhesive such as an acrylic type or a radiation-curable type such as an electron beam is preferably used.

【0040】

By the way, the above-mentioned ultraviolet curable pressure-sensitive adhesive is, for example, a pressure-sensitive adhesive containing a polymer obtained by copolymerizing a monomer having a cross-linking functional group such as a polyfunctional monomer, or a pressure-sensitive adhesive containing a cross-linking low-volume compound such as a polyfunctional monomer. A photopolymerization initiator is added to the agent to enable cross-linking and curing by irradiation with ultraviolet rays. The cross-linking and curing reduces contaminants on the adherend and, if necessary, provides adhesive strength. The decline is also measurable.

【0041】

The ultraviolet curable pressure-sensitive adhesive used includes, for example, 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α'-dimethylacetophenone, and methoxy as its photopolymerization initiator. Acetphenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, 1-hydroxycyclohexylphenylketone, 2-methyl-1- [4- (methylthio) -phenyl] -2-morpholinopropane-1 Acetphenone-based initiators such as benzoin ethyl ether and benzoin isopropyl ether, benzoin ether-based initiators such as anizoine methyl ether, α-ketol compounds such as 2-methyl-2-hydroxypropiophenone, and benzyl dimethyl ketal. Ketal compounds such as, aromatic sulfonyl chloride compounds such as 2-naphthalene sulfonyl chloride, photoactive oxime compounds such as 1-phenone-1,1-propanedione-2- (ο-ethoxycarbonyl) oxime, benzophenone and benzoyl Benzophenone compounds such as benzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, thioxanthone and 2-chlorothioxanthone, 2-methylthioxanthone and 2,4-dimethylthioxanthone, isopropylthioxanthone and 2 , 4-Dichlorothioxanson, 2,4-diisopropylthioxanson, 2,4-diisopropylthioxanson, and other thioxane compounds, as well as benzophenone, halogenated ketone, acylphosphinoxide, acylphosphonate, etc. It may be an appropriate ultraviolet curable type using.

【0042】

As described above, the pressure-sensitive adhesive used to form the pressure-sensitive adhesive layer may be a mixture of appropriate additives such as a plasticizer, a filler, a surfactant, an anti-aging agent, and a pressure-sensitive adhesive. For applications where transfer of the additive to an adherend is a problem, as in the case where low pollution is desired, a pressure-sensitive adhesive having a composition that does not contain the additive can also be used.

【0043】

The pressure-sensitive adhesive layer is formed by an appropriate method such as a method of applying a liquid pressure-sensitive adhesive on the heat-expandable layer or a method of transferring the pressure-sensitive adhesive layer formed on the separator to the heat-expandable layer. Can be done at. The thickness of the adhesive layer can be appropriately determined depending on the purpose of use of the adhesive sheet, the ability to reduce the adhesive force by heating, and the like.

【0044】

In general, if the thickness of the adhesive layer is too thin, cohesive failure is likely to occur when the adhesive force is insufficient or the uneven deformation of the thermally expandable layer is caused by heating, and if it is too thick, it is difficult to follow the uneven deformation of the thermally expandable layer due to heating. Therefore, the ability to prevent cohesive failure during thermal deformation, the ability to prevent the increase of adherend contaminants, the ability to follow the uneven deformation of the thermally expandable layer, and the ability to reduce or lose the adhesive force to the adherend. From these points, the adhesive layer thickness is 20 μm or less, especially 0.1 to 10 μm, especially 1 to 5 μm.

【0045】

As described above, the heat-release type pressure-sensitive adhesive sheet according to the present invention can be formed into an appropriate form. In that case, for example, the heat-expandable layer may have an adhesive layer on one side or both sides, or the base material may have a heat-expandable layer and an adhesive layer on one side and an ordinary adhesive layer on the other side. It can also be in the form of having. Further, even in the form of being supported by the base material, the base material can be a separate type that can be easily peeled off from the rubber-like organic elastic layer or the heat-expandable layer, or the base material and the rubber-like organic elastic layer or heat. It is also possible to use a fixed type in which the expansive layer is strongly adhered.

【0046】

The separation type heat peeling type adhesive sheet can be formed by using, for example, the above-mentioned separator or low adhesive base material, and the fixing type heat peeling type pressure-sensitive adhesive sheet can be formed by, for example, the above-mentioned strong adhesive base material or surface. It can be formed by using a base material such as an oxidation treatment. As shown in FIG. 1, it is preferable to prevent a decrease in adhesive strength due to contamination of the adhesive layer until the separator 4 or the like is temporarily attached and put into practical use.

【0047】

The heat-release type adhesive sheet according to the present invention can be used for various purposes similar to the conventional adhesive sheet such as adhesion of an adherend by molding it into an appropriate form such as a sheet shape, a tape shape, or a label shape, but it is optional. Since it can be easily separated from the adherend by reducing the adhesive force by heat treatment at the time, it is required to take advantage of its features to adhere to the adherend for a predetermined period of time and then release the adhered state. Or can be preferably used for desired applications. The adherend is not particularly limited, and may be made of any material such as metal, ceramic, plastic, wood, or paper, and the adhesive surface may have an arbitrary shape such as a plate shape, a curved surface shape, or a fibrous shape. May have.

【0048】

Incidentally, examples of the above-mentioned applications include the formation of adhesive composites for the purpose of recycling two or more articles, for example, articles made of polymers and articles made of metals, fibers, paper, etc., various electric devices or electronic devices, and the like. Carrier tapes, temporary fixing materials or fixing materials for transporting or temporarily fixing parts in the assembly process of display devices, etc., surface protective materials and masking materials for the purpose of preventing contamination and damage of metal plates, plastic plates, glass plates, etc. And so on.

【0049】

In particular, in the present invention, adhesive properties such as adhesive strength can be appropriately set through the adhesive layer according to the purpose of use, and there is little increase in contaminants, especially microscopic contaminants, due to the treatment for reducing the adhesive strength by heating. Therefore, it is desired that the wafer can be adhered to the adherend with a strong adhesive force during processing, such as the back surface polishing process and dicing process of a semiconductor wafer, and that the adherend is less contaminated when the adhered state is released. It can be preferably used for various purposes.

【0050】

In the above, the heat treatment for reducing the adhesive force of the heat-release type adhesive sheet can be performed via an appropriate heating means such as a hot plate, a hot air dryer, or a near-infrared lamp. The conditions of the heat treatment should be appropriately determined according to the conditions such as the surface condition of the adherend, the decreaseability of the adhesive area depending on the type of the heat-expandable fine particles, the heat resistance of the base material and the adherend, the heat capacity and the heating means. Can be done.

【0051】

Generally, it is heat-treated for 5 to 90 seconds (hot plate, etc.) or 1 to 15 minutes (hot air dryer, etc.) at a temperature of 100 to 250 ° C, but is not limited to this. In the heat treatment under the above conditions, the heat-expandable fine particles are usually expanded and / or foamed to deform the heat-expandable layer unevenly, and accordingly, the adhesive layer is also unevenly deformed to reduce or lose the adhesive force.

【0052】

[Example]

Example 1 Acrylic adhesive containing 2 parts of an isocyanate-based cross-linking agent in a toluene solution containing 100 parts of an acrylic copolymer consisting of 100 parts of butyl acrylate (weight part, the same applies hereinafter), 5 parts of acrylonitrile and 3 parts of hydroxyethyl acrylate. 35 parts of heat-expandable microspheres (Microsphere F-50D) are mixed with A, and it is applied to one side of a PET film with a thickness of 50 μm and dried to form a heat-expandable layer with a thickness of 40 μm. A pollution-preventing adhesive layer having a thickness of 3 μm was provided on the adhesive layer to obtain a heat-release adhesive sheet.

【0053】

The antifouling adhesive layer is prepared by adding 3 parts of an epoxy-based cross-linking agent to a toluene solution containing 100 parts of an acrylic copolymer consisting of 50 parts of butyl acrylate, 50 parts of ethyl acrylate, 10 parts of acrylonitrile and 5 parts of acrylic acid. An acrylic pressure-sensitive adhesive containing the above-mentioned material was applied and dried on a separator to form an acrylic pressure-sensitive adhesive, which was then transferred.

【0054】

Example 2 Acrylic adhesive containing 3 parts of an isocyanate-based cross-linking agent in a toluene solution containing 100 parts of an acrylic copolymer B consisting of 70 parts of ethyl acrylate, 30 parts of butyl acrylate and 5 parts of hydroxyethyl acrylate. 30 parts of microspheres (Microsphere F-30) are blended, applied to one side of a transparent PET film with a thickness of 25 μm and dried to form a heat-expandable layer with a thickness of 30 μm, on which a thickness of 2 μm is formed. An ultraviolet curable adhesive layer was provided to prevent contamination, and a heat-release adhesive sheet was obtained.

【0055】

The anti-contamination type and ultraviolet curable adhesive layer is obtained by applying an acrylic pressure-sensitive adhesive containing 100 parts of urethane acrylate and 3 parts of a photopolymerization initiator in 100 parts of an acrylic copolymer B and drying it. It was formed and provided by transfer.

【0056】

Comparative example 1 A heat-release type pressure-sensitive adhesive sheet was obtained according to Example 1 except that the pressure-sensitive adhesive layer was not provided on the heat-expandable layer.

【0057】

Comparative example 2 A heat-release type pressure-sensitive adhesive sheet was obtained according to Example 2 except that the pressure-sensitive adhesive layer was not provided on the heat-expandable layer.

【0058】

Comparative example 3 An adhesive sheet was obtained according to Example 1 except that an acrylic pressure-sensitive adhesive A was used, a simple pressure-sensitive adhesive layer was formed without blending the heat-expandable fine particles, and no pressure-sensitive adhesive layer was provided on the acrylic pressure-sensitive adhesive A.

【0059】

Evaluation test Adhesive strength The 20 mm wide (heat peeling type) adhesive sheet obtained in Examples and Comparative Examples was adhered to a polyester film (Toray Industries, Inc., Lumirror S-10) with a thickness of 25 μm, and its 180 degree peel adhesive force (peeling speed 300 mm). / Minute, 23 ° C) was examined. The measurements were taken before heating for Example 1 and Comparative Examples 1, 2 and 3, and when heat-treated in a hot air dryer at 130 ° C for 3 minutes. For Example 2, before irradiation with ultraviolet rays and before heating. After irradiation with an air-cooled high-pressure mercury lamp (46 mJ / min) for 10 seconds (same below) and before heating, before irradiation with ultraviolet rays and after heating for 3 minutes in a hot air dryer at 100 ° C (same below), and It was performed after irradiation with ultraviolet rays and after heating.

【0060】

Number of particles The number of particles on the wafer when the (heat-peeling type) adhesive sheet obtained in Examples and Comparative Examples was adhered to a mirror-treated 4-inch silicon wafer, left for 1 hour, and then peeled according to the above-mentioned adhesive force measurement test. Was examined with a laser surface inspection device.

【0061】

The above results are shown in Table 1 for Example 1 and Comparative Examples 1, 2 and 3, and in Table 2 for Example 2. table 1 Adhesive strength (gf / 20mm) Number of particles Before heating After heating Before heating After heating Example 1 300 2 650 760 Comparative example 1 350 0 800 10000 or more Comparative example 2 280 0 720 10000 or more Comparative Example 3 310 420 800 830 [0062]

Table 2 Example 2 Before irradiation After irradiation Before irradiation After irradiation Before heating Before heating After heating After heating Adhesive strength (gf / 20mm) 150 30 90 0 Number of particles 300 20 4700 47

[Simple explanation of drawings]

[Figure 1]

Sectional view of the embodiment [Figure 2]

Sectional view of another embodiment [Code description]

1: Base material 2,21: Thermally expandable layer 3,31: Adhesive layer 4: Separator 5: Rubbery organic elastic layer