JPH111671A - Method for producing adhesive sheet and cut piece - Google Patents

Abstract

(57) [Summary] [PROBLEMS] While satisfying a strong adhesive holding force that can withstand cutting processing of an adherend and a bonding characteristic of reducing or losing the adhesive holding force when collecting formed cut pieces, Development of an adhesive sheet that has both heat resistance to withstand heat treatment and extensibility when collecting cut pieces. SOLUTION: A holding layer (3) that can be cut through an adhesive layer (2) is provided on an extensible base material (1), and has an adhesive property containing thermally expandable microspheres thereon. An adhesive sheet having at least a heat-expandable layer (4), and a cut-off body (5) adhered to and held by the heat-expandable layer in the adhesive sheet, and the cut-off body has a predetermined size, and a holding layer for the adhesive sheet Cutting (6) at a depth that does not separate the base material,
After the cutting step, at least a step of heating the heat-expandable layer of the adhesive sheet to expand or expand the base material by expanding or expanding the base material and expanding the base material, and recovering a cut piece formed by cutting. Method of manufacturing cut pieces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention has excellent adhesive strength and can easily remove an adherend by heating at any time.
The present invention relates to an adhesive sheet suitable for forming a semiconductor chip or a multilayer capacitor chip, and a method for manufacturing a cut piece using the same.

[0002]

2. Description of the Related Art Conventionally, an object to be cut, such as a semiconductor wafer or a laminated capacitor sheet, is cut and cut to a predetermined size by holding it through a pressure-sensitive adhesive layer of an adhesive sheet, and a cut piece such as a formed chip is cut from the adhesive sheet. As an adhesive sheet used in the method of peeling and recovering, a sheet provided with a pressure-sensitive adhesive layer containing a foaming agent on a supporting substrate has been known (Japanese Patent Publication No. 50-1387).
No. 8, No. 51-24534, JP-A-56-6
No. 1468, No. 56-61469, No. 60-
No. 252681). This is to reduce the adhesive force by foaming or expanding the pressure-sensitive adhesive layer by heating, and to achieve both strong adhesive holding force to withstand the cutting work of the adherend and easy peeling and recovery of the formed cut piece. It is intended for.

However, in the above-mentioned conventional sheet, for example, a semiconductor chip pickup and recovery method by a method of gripping a chip side surface so as not to damage an IC circuit on the surface, or a re-adhesion of a formed chip through a binder for retaining a ceramic powder. However, there is a problem that it is difficult to apply a more advanced cut piece recovery method accompanying the spread of the method, such as a method of recovering a multilayer capacitor chip in which the above-described problem is prevented.

[0004]

SUMMARY OF THE INVENTION Based on the idea that the above-described new method can be applied by extending the adhesive sheet at the time of collecting the cut pieces to expand the gap between the cut pieces, the present inventors have proposed a conventional method. Various attempts have been made to give the support base material of the adhesive sheet extensibility, but when the extensibility is given, the foaming agent-containing pressure-sensitive adhesive layer does not withstand heat treatment during foaming or expansion treatment, When used as a supporting base material that can withstand the heat treatment, the stretchability is poor. Therefore, it is difficult to achieve both heat resistance and stretchability with a conventional adhesive sheet, and it is necessary to develop a new type of adhesive sheet. I determined that.

Accordingly, the present invention provides a method for heating a steel sheet while satisfying a strong adhesive holding force capable of withstanding a cutting process of an adherend and a bonding property of reducing or losing the adhesive holding force when collecting formed cut pieces. An object of the present invention is to develop a new type of adhesive sheet having both heat resistance to withstand processing and extensibility when collecting formed cut pieces.

[0006]

According to the present invention, there is provided a heat-expandable base material having a heat-expandable microsphere-containing adhesive on a stretchable base substrate having a holding layer severable through an adhesive layer. An adhesive sheet characterized by having at least a layer, and a cut base having a predetermined size by bonding and holding the cut body to the heat-expandable layer in the adhesive sheet, including a holding layer of the adhesive sheet and a base substrate. Step of cutting at a depth that does not separate, after the cutting step, heating and expanding or expanding the heat-expandable layer of the adhesive sheet to reduce or lose the adhesive force and extend the base material, formed by cutting. An object of the present invention is to provide a method for producing a cut piece, comprising at least a step of collecting the cut piece.

[0007]

According to the adhesive sheet of the present invention, the adherend can be strongly adhered and held through the heat-expandable layer so as to withstand cutting and the like, and the heat treatment of the heat-expandable layer can be performed via the holding layer. And the heat-expandable layer can be heat-treated to reduce or lose its adhesive holding power, and the base material can be stretched to increase the gap between the cut pieces. Therefore, it has a strong adhesive holding force that can withstand the cutting process of the adherend, and an adhesive property of reducing or losing the adhesive holding force when collecting the formed cut pieces, and has heat resistance and forming that can withstand heat treatment. Also equipped with both extensibility when collecting cut pieces, a pickup recovery method such as a method of gripping the chip side surface of a semiconductor chip, and a recovery method of preventing re-adhesion of a multilayer capacitor chip via a binder can be applied. An adhesive sheet can be obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The adhesive sheet of the present invention has a holding layer which can be cut through an adhesive layer on an extensible base material, and has an adhesive property containing heat-expandable microspheres thereon. It has at least a heat-expandable layer. Examples thereof are shown in FIGS. 1 is a base substrate, 2 is an adhesive layer, 3 is a holding layer, 4
Is a heat-expandable layer. 11 is a pressure-sensitive adhesive layer, 41 is a rubber-like organic elastic layer, and 7 is a separator, which are provided as necessary. Note that FIG. 1 shows a state where the object 5 indicated by a virtual line is adhered and held to the thermally expandable layer 4 and cut into a predetermined size, and a virtual line 6 is the cutting line.

In the present invention, the base substrate can be formed of an appropriate material exhibiting extensibility, that is, extensibility by tensile force, for the purpose of imparting elongation performance to the adhesive sheet. Examples thereof include, but are not limited to, polyolefins such as polyethylene and polypropylene and copolymers thereof, (soft) polyvinyl chloride and copolymers thereof, rubber-based polymers such as synthetic rubbers such as natural rubber and polybutylene, and the like. Synthetic resins having rubber elasticity as exemplified by the rubbery organic elastic layer described above, and the like, and such polymers may be crosslinked.

[0010] Rather than the expansion of the gap between the cut pieces,
Tensile elongation at break is 10% or more, especially 25% or more,
Particularly, a base material of 50% or more is preferable. The thickness of the base substrate can be appropriately determined, but is generally 5 to 500 μm.
m, especially 10 to 300 μm, especially 20 to 200 μm. A base material that can be preferably used from the viewpoint of extensibility and the like is a (soft) polyvinyl chloride film.

[0011] The holding layer serves as a supporting matrix of the heat-expandable layer,
The heat-expandable layer is formed so as to be cuttable for the purpose of imparting heat resistance against heating during foaming and / or expansion processing.
Therefore, for the formation of the holding layer, a film made of a plastic such as polyester, polycarbonate, polyimide or polyamide is generally used, which shows heat resistance and cutability by a cutter or the like that endure the heat treatment,
In the present invention, an appropriate thin leaf such as paper, cloth, nonwoven fabric, metal foil, a plastic laminate thereof, or a laminate of plastics may be used. The thickness of the holding layer can be determined as appropriate, but is generally 500 μm or less, especially 5 to 5 μm.
It is 300 μm, especially 10 to 200 μm.

The base layer and the holding layer are adhered through an adhesive layer, and an appropriate adhesive can be used for forming the adhesive layer, and there is no particular limitation. Generally, a low-temperature activation type heat-activated adhesive, water or organic solvent-activated adhesive, or a pressure-sensitive adhesive is used.

Examples of the low-temperature activation type heat-activatable adhesive and water or organic solvent-activable adhesive include hot melt adhesives, silicone adhesives, fluorine-based adhesives, and the like.
An ultraviolet-curing adhesive, a heat-sensitive pressure-sensitive adhesive containing a low melting point heat-fusible resin and exhibiting a strong adhesive force by heating at room temperature with a low adhesive force (JP-A-56-13040, JP-B-56-13040, -50146).

Examples of the pressure-sensitive adhesive include a rubber-based pressure-sensitive adhesive, an acrylic-based pressure-sensitive adhesive, a styrene / conjugated diene block copolymer-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and an ultraviolet-curable adhesive. Examples of the pressure-sensitive adhesive include a creep-improved type pressure-sensitive adhesive containing a low-melting point, particularly, a hot-melt resin having a melting point of about 200 ° C. or less (JP-A-56-61468).
JP-A-61-174857 and JP-A-63-174857
-17981, JP-B-56-13040). The pressure-sensitive adhesive may contain appropriate additives such as a crosslinking agent, a tackifier, a plasticizer, a filler, and an antioxidant.

Incidentally, specific examples of the rubber-based pressure-sensitive adhesive include those using natural rubber or various synthetic rubbers as base polymers, and specific examples of the acrylic-based pressure-sensitive adhesive include a methyl group, an ethyl group, and a propyl group. Group, butyl group, isobutyl group, amyl group, isoamyl group, hexyl group, heptyl group, cyclohexyl group, 2-ethylhexyl group, isooctyl group, isononyl group, isodecyl group, dodecyl group, lauryl group, tridecyl group, pentadecyl group, hexadecyl One or more alkyl esters of acrylic acid or methacrylic acid having a straight-chain or branched alkyl group having 20 or less carbon atoms, such as a group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an eicosyl group. Examples include those using an acrylic polymer as a base polymer.

An acrylic base polymer comprising, as a base polymer, a polymer obtained by copolymerizing the above-mentioned alkyl (meth) acrylate and one or more other monomers for the purpose of improving adhesive properties and the like. Pressure-sensitive adhesives and the like are also included. 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; acid anhydride monomers such as maleic anhydride and itaconic anhydride; 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate;
Examples include hydroxyl group-containing monomers such as 4-hydroxybutyl acrylate.

Further, sulfonic acid group-containing monomers such as styrenesulfonic acid, allylsulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid and (meth) acrylamidopropanesulfonic acid, and 2-hydroxyethylacryloyl phosphate. Phosphoric acid group-containing monomer, (meth) acrylamide or N-butyl (meth)
(N-substituted) amide monomers such as acrylamide, N-methylol (meth) acrylamide and N-methylolpropane (meth) acrylamide, aminoethyl (meth) acrylate and N, N-dimethylaminoethyl (meth) acrylate Alkylaminoalkyl (meth) acrylate monomers such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate
Alkoxyalkyl acrylate monomers and the like are also examples of the above-mentioned copolymerized monomers.

In addition, maleimide monomers such as N-cyclohexylmaleimide and N-isopropylmaleimide, itaconimide monomers such as N-methylitaconimide and N-ethylitaconimide, N- (meth) acryloyloxymethylenesuccinimide and N- Succinimide monomers such as (meth) acryloyl-6-oxyhexamethylene succinimide; vinyl acetate and vinyl propionate; vinyl monomers such as N-vinylpyrrolidone and methylvinylpyrrolidone; styrene and α-methylstyrene; acrylonitrile and methacrylonitrile Cyanoacrylate monomers such as glycidyl (meth) acrylate; epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate; polyethylene glycol (meth) acrylate and (meth) acrylic acid Such as such as glycol acrylic ester monomers polypropylene glycol may be mentioned as examples of the copolymerizable monomer described above.

Further, acrylate monomers such as tetrahydrofurfuryl (meth) acrylate and fluorine (meth) acrylate, silicone (meth) acrylate and 2-methoxyethyl acrylate, hexanediol di (meth) acrylate and (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, pentaerythritol tri ( Polyfunctional monomers such as (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate; Isoprene and butadiene, isobutylene and vinyl ether may be mentioned as examples of the copolymerizable monomer described above.

The formation of the adhesive layer for bonding the base material and the holding layer may be performed, for example, by applying a liquid adhesive to one or both of the bonding surfaces of the base material and the holding layer, or by forming an adhesive layer formed on the separator. May be formed by an appropriate method such as a method of transferring to a bonding surface of one or both of the base material and the holding layer.
The thickness of the adhesive layer can be appropriately determined according to the adhesive strength and the like, but is generally 1 to 500 μm, preferably 5 to 200 μm, particularly 10 to 100 μm.

The surface of the base material or the holding layer, such as the adhesive layer or the heat-expandable layer, on which the adhesive layer and the heat-expandable layer are attached, may be used for the purpose of improving the adhesion.
For example, a surface treatment can be performed by an appropriate method such as a chromic acid treatment method, an ozone exposure method, a flame exposure method, a high-voltage piezoelectric exposure method, and an ionizing radiation treatment method.

The heat-expandable layer having an adhesive property provided above the holding layer is used for bonding and holding an adherend that can withstand processing such as cutting.
To reduce or lose the adhesive force with the adherend through foaming and / or expansion treatment by heating so that the adherend after processing such as cutting can be easily peeled off from the adhesive sheet at any time. For the purpose, it is formed by blending the heat-expandable microspheres with the adhesive substance.

As the adhesive substance used for forming the heat-expandable layer, a substance which allows the expansion and / or expansion of the heat-expandable microspheres is used. Generally, the low-temperature activation type exemplified in the above-mentioned adhesive layer is used. A heat activated adhesive, a water or organic solvent activated adhesive, a pressure sensitive adhesive, or the like is used. Above all,
It is preferable that the expansion and / or expansion of the heat-expandable microspheres is not restricted as much as possible, and a pressure-sensitive adhesive is preferable in view of this point and the simplicity of the adhesion treatment of the adherend.

As the heat-expandable microspheres, for example, an appropriate substance which easily gasifies and exhibits a heat expansion property, such as isobutane, propane, or pentane, is put into a shell-forming substance by a coacervation method, an interfacial polymerization method, or the like. Included ones. The heat-expandable microspheres having an average particle size of 1 to 50 μm are preferable from the viewpoint of mixing properties and thin-layer forming properties.

As the shell-forming substance forming the heat-expandable microspheres, for example, vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, polysulfone and the like are generally used. However, in the present invention, any material may be used as long as it is made of a heat-meltable substance or a substance which is destroyed by thermal expansion.

The heat-expandable layer is formed, for example, by mixing an adhesive substance and heat-expandable microspheres with a solvent as necessary, and applying the mixture onto a holding layer or a rubber-like organic elastic layer described later. It can be performed by a method or the like.

The amount of the heat-expandable microspheres can be appropriately determined according to the degree of expansion of the heat-expandable layer and the rate of reduction in adhesive strength.
1 to 200 parts by weight, preferably 10 to 150 parts by weight, especially 25
To 120 parts by weight. The thickness of the heat-expandable layer is 300 μm or less, preferably 5 to 250 μm, from the viewpoint of foaming or swelling and preventing adhesive residue on the adherend due to cohesive failure after expansion.
μm, particularly preferably 10 to 150 μm.

In the present invention, a rubbery organic elastic layer can be interposed between the holding layer and the heat-expandable layer. The rubber-like organic elastic layer works to increase the adhesion between the holding layer and the heat-expandable layer, and the surface of the adhesive sheet adheres well to the surface shape of the adherend when the adhesive sheet is adhered to the adherend. When the thermally expandable layer is heated and expanded and / or expanded, the expansion and / or expansion in the surface direction of the adhesive sheet is reduced so that the thermally expandable layer becomes uneven. It helps to transform into a three-dimensional structure.

That is, in the above description, the heat-expandable layer forms an uneven surface by heating and foaming and / or expanding. However, the foaming of the heat-expandable layer is performed by interposing the rubber-like organic elastic layer. And / or the expanding force overcomes the drag due to the elastic modulus of the rubber-like organic elastic layer, so that the unevenness of the thermally expandable layer becomes large, and the three-dimensionally large undulation structure or corrugated structure as illustrated in FIG. The deformation can be formed stably, and the reduction in the bonding area by the heat treatment is efficiently achieved, and the reduction or loss of the bonding strength that facilitates the peeling of the adherend is more reliably realized.

In order to form the rubber-like organic elastic layer from the viewpoint of the irregular three-dimensional structural deformability of the heat-expandable layer, AST is used.
Natural rubber or synthetic rubber having a Shore D hardness of 50 or less, preferably 40 or less based on the D-type Shore of MD-2240, or a synthetic resin having rubber elasticity can be preferably used.

Examples of the synthetic rubber or synthetic resin include synthetic rubbers such as nitrile, diene, and acrylic resins, 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 and the like can be mentioned. 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.

The rubbery organic elastic layer may be formed by a method of applying a solution of natural rubber, synthetic rubber or synthetic resin having rubber elasticity to the holding layer, a method of bonding a film or the like comprising the above components to the holding layer, or the like. It may be performed by an appropriate method. In the present invention, the rubbery organic elastic layer may be formed of a pressure-sensitive adhesive layer containing natural rubber, synthetic rubber, or a synthetic resin having rubber elasticity as a main component, or a foamed film mainly containing such a component. May be formed.

A rubbery organic elastic layer composed of a pressure-sensitive adhesive layer is preferred from the viewpoint of the adhesion between the holding layer and the heat-expandable layer and the deformability for increasing the adhesion area with the adherend. The thickness of the rubber-like organic elastic layer is 0.1 to 300 μm, preferably 5 to 5 μm, in view of the three-dimensional structural deformability of the thermal expansion layer.
250 μm, particularly preferably 10 to 150 μm, is preferred.

As shown in FIG. 2, the adhesive sheet of the present invention has a pressure-sensitive adhesive layer 11 for fixing the adhesive sheet to a support on the side of the base substrate 1 having no holding layer. Can also be provided. For the formation of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive exemplified for the above-mentioned adhesive layer can be used.

When the heat-expandable layer or the pressure-sensitive adhesive layer is exposed on the surface of the adhesive sheet, it is preferable to temporarily attach and protect the separator 7 until practical use as shown in FIG. . The separator is, for example, a substrate provided with a surface coat of a release agent represented by a silicone-based resin, a long-chain acrylic resin, a fluorine-based resin, or the like, or a substrate having a weak adhesive force made of a nonpolar polymer such as polyethylene or polypropylene. Can be obtained as

The adhesive sheet of the present invention can be used for the purpose of permanently bonding an adherend made of an appropriate article or the like, but can firmly adhere the adherend via a heat-expandable layer, and When the adhesion state is desired to be released, the adherence is reduced or lost by a heat treatment, and the adherend can be easily peeled off. It can be preferably used for applications where it is required or desired to unravel.

Incidentally, examples of the above-mentioned applications include a wafer fixing material in a step of polishing and thinning the back surface of a semiconductor wafer on which a circuit pattern is formed, and a method of assembling parts in an assembling step of various electric or electronic devices and display devices. Carrier tapes for transporting and temporary fixing, temporary fixing materials or fixing materials, surface protective materials and masking materials for the purpose of preventing contamination and damage of metal plates, plastic plates, glass plates and the like.

A particularly preferable application is, for example, a step of cutting a semiconductor wafer on which a circuit pattern is formed into a predetermined chip size, if necessary, or a ceramic green sheet on an adhesive sheet, if necessary. This is a method used for fixing a body to be cut when manufacturing a cut piece such as a step of printing and laminating and fixing a predetermined circuit and cutting the multilayer capacitor sheet into a predetermined chip size.

The method of manufacturing the cut piece is carried out, for example, by bonding and holding the object 5 to the thermally expandable layer 4 of the adhesive sheet of the present invention as shown in FIG. A step of cutting 6 at a depth that does not separate the base substrate 1 including the holding layer 3 of the adhesive sheet; The method can be performed as a method having at least a step of recovering the cut pieces formed by cutting by elongating the base substrate while losing (FIG. 3: 4).

The adhesive treatment between the heat-expandable layer and the adherend as the object to be cut can be carried out by, for example, a method such as a rubber roller, a laminating roll, or a pressure-bonding treatment through an appropriate pressing means such as a press device. . At this time, depending on the type of the adhesive substance, if necessary, the adhesive may be heated in a temperature range where the thermally expandable microspheres do not expand, or the adhesive substance may be activated by applying water or an organic solvent.

On the other hand, the heating conditions of the foaming and / or expansion treatment for facilitating the peeling of the adherend (cut pieces) by reducing or losing the adhesive force of the heat-expandable layer depend on the surface condition of the adherend and the heat treatment. It is determined by conditions such as the decrease in the adhesive area due to the type of the expandable microspheres, the heat resistance of the adhesive sheet and the adherend, etc., but general conditions are 350 ° C. or less, especially 300 ° C. or less, and particularly 10 ° C. or less.
0 to 250 ° C, 5 minutes or less, especially 3 minutes or less, especially 1 to
90 seconds. The heat treatment can be performed at an appropriate stage depending on the purpose of use of the adhesive sheet.

The formed cut pieces are collected in a state where the base material is elongated to widen the gap between the cut pieces. Therefore, it is necessary to collect a cut piece by applying an appropriate method such as a pickup method of a semiconductor chip by a method of gripping a chip side surface or a method of collecting a multilayer capacitor chip that prevents re-adhesion of a formed chip via a binder. Can be. Note that a conventional method using a pressing blade, a rotary blade, or the like can be used for cutting the adherend. The step of extending the base material may be before or after foaming or expanding the thermally expandable layer.

[0043]

【Example】

Example 1 A toluene solution of an acrylic pressure-sensitive adhesive A was applied to one side of a soft polyvinyl chloride film having a thickness of 75 μm and dried to form a pressure-sensitive adhesive layer having a thickness of 10 μm. On the other hand, thickness 50
A mixture of heat-expandable microspheres and a toluene solution of the acrylic pressure-sensitive adhesive A was applied to one side of a μm polyester film and dried to form a heat-expandable layer having a thickness of 40 μm. Then, the polyester film was disposed on the pressure-sensitive adhesive layer of the soft polyvinyl chloride film via the exposed surface thereof and pressed to obtain an adhesive sheet.

The acrylic pressure-sensitive adhesive A was a copolymer 1 comprising 50 parts of butyl acrylate (parts by weight, the same applies hereinafter), 50 parts of ethyl acrylate and 5 parts of acrylic acid.
The heat-expandable layer is composed of heat-expandable microspheres (Matsumoto Microsphere F-50D, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.) in which 00 parts are blended with 25 parts of a phenolic resin tackifier and 3 parts of a polyisocyanate crosslinker. ) 25 parts additionally.

Next, a ceramic sheet having a length of 120 mm, a width of 100 mm and a thickness of 0.5 mm is pressure-bonded and held on the surface of the heat-expandable layer of the adhesive sheet, attached and fixed to a dicing ring, and fixed through a pressing blade. 5mm x 5mm chip size,
After the full cut at a depth that does not reach the polyester film and that of the flexible polyvinyl chloride film, the flexible polyvinyl chloride film is expanded by pressing it on a jig of the same length and width as the ceramic sheet while being fixed to the dicing ring. And increase the chip spacing to 13
The heat-expandable layer was expanded by heating on a hot plate at 0 ° C. for 60 seconds, cooled on an iron plate, and then inverted and vibrated through a dicing ring to drop the chip onto a cushion and collect it.

Example 2 A toluene solution of an acrylic pressure-sensitive adhesive B was applied to one side of a soft polyvinyl chloride film having a thickness of 100 μm and dried to form a pressure-sensitive adhesive layer having a thickness of 10 μm. On the other hand, thickness 5
A 50 μm thick rubbery organic elastic layer was provided on one side of a 0 μm rayon nonwoven fabric. On the other hand, a toluene solution of the acrylic pressure-sensitive adhesive B containing heat-expandable microspheres mixed on a separator is applied and dried to form a heat-expandable layer having a thickness of 50 μm. Transferred over layer. Then, the rayon nonwoven fabric was placed on the pressure-sensitive adhesive layer of the soft polyvinyl chloride film via the exposed surface thereof and pressed to obtain an adhesive sheet.

The acrylic pressure-sensitive adhesive B is prepared by blending 100 parts of a copolymer consisting of 100 parts of butyl acrylate, 5 parts of vinyl acetate and 3 parts of acrylic acid with 5 parts of a polyisocyanate crosslinking agent. The heat-expandable layer is obtained by additionally blending 100 parts of heat-expandable microspheres (Matsumoto Microsphere F-301D, manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.). The rubber-like organic elastic layer is formed of the copolymer 100
A toluene solution in which 40 parts of a phenolic resin-based tackifier and 2 parts of a polyisocyanate-based cross-linking agent were applied was coated and dried.

Next, using the above-mentioned adhesive sheet, treatment was carried out in accordance with Example 1 (full cut of rayon nonwoven fabric) to collect chips. However, the chip size was 2 mm × 2 mm, and the thermal expansion layer was expanded at 100 ° C. for 60 seconds.

Comparative Example 1 An adhesive sheet having no flexible polyvinyl chloride film and no pressure-sensitive adhesive layer thereon was obtained according to Example 1, and chips were produced and recovered using the adhesive sheet.

Comparative Example 2 An adhesive sheet in which a polyester film was replaced with a soft polyvinyl chloride film was obtained according to Comparative Example 1, and chips were produced and recovered using the adhesive sheet.

Evaluation Test The adhesive sheet having a width of 20 mm obtained in each of Examples and Comparative Examples was adhered to a SUS304BA plate having a thickness of 0.5 mm, and its 180-degree peel adhesive force (peeling speed: 300 mm / min, 23 ° C.) was measured. The adhesive strength before (initial) heating and the adhesive strength after heat treatment under the above conditions were examined.

The above results are shown in the following table together with the chip recovery rate. Note that the chip recovery rate was evaluated as the yield of standard-accepted products that did not require separation work because there was no bonding between chips by a binder and that omitted defective products such as defective products.

In Example 2 described above, the rubber-like organic elastic layer and the thermally expandable layer in the expanded state are integrally three-dimensionally deformed from the enlarged photograph of the state including the cross section after the heat treatment. Thus, it was confirmed that an undulation structure was formed. In Example 1, although small irregularities were formed based on the size of the expanded state of the thermally expandable layer, it was not recognized as a undulating structure.

In Comparative Example 1, many of the polyester films were adhered due to insufficient elongation of the polyester film, and a separation treatment was required. On the other hand, in the case of a soft polyvinyl chloride film, the film softens during the heat treatment after the expansion, and the expansion energy of the heat-expandable layer does not work to peel off the chip. Remained adhered to the heat-expandable layer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of an adhesive sheet.

FIG. 2 is a cross-sectional view of another example of an adhesive sheet.

FIG. 3 is an explanatory diagram of a state of an adhesive sheet after a heat treatment.

[Description of sign]

 1: base material 2: adhesive layer 3: holding layer 4: thermally expandable layer 41: rubber-like organic elastic layer 5: cut object (adhered object) 6: cut line

Claims (8)

[Claims] 1. An extensible base material having a holding layer that can be cut through an adhesive layer, and at least a heat-expandable layer having heat-expandable microsphere-containing adhesive thereon. An adhesive sheet characterized by the above-mentioned. 2. The adhesive sheet according to claim 1, wherein a rubbery organic elastic layer is provided between the holding layer and the thermally expandable layer. 3. The adhesive sheet according to claim 1, wherein the heat-expandable layer forms an uneven three-dimensional structure by foaming or expanding by heating. 4. The adhesive sheet according to claim 1, wherein the heat-expandable layer comprises a pressure-sensitive adhesive layer. 5. The adhesive sheet according to claim 2, wherein the rubbery organic elastic layer comprises a pressure-sensitive adhesive layer. 6. The adhesive sheet according to claim 1, wherein a pressure-sensitive adhesive layer is provided on a side of the base material having no holding layer. 7. The adhesive sheet according to claim 1, wherein the base material comprises a polyvinyl chloride film. 8. An adhesive sheet according to claim 1, wherein the object to be cut is adhered to and held by the heat-expandable layer, and the object to be cut is separated into a predetermined size. Step of cutting at a depth that does not, after the cutting step, heating the heat-expandable layer of the adhesive sheet to expand or expand the base material while reducing or losing the adhesive force by foaming or expanding treatment,
A method for producing cut pieces, comprising at least a step of collecting cut pieces formed by cutting.