WO2018055859A1 - Adhesive sheet for semiconductor processing - Google Patents

Abstract

The present invention relates to an adhesive sheet for semiconductor processing, the adhesive sheet being provided with: a base material; and an adhesive layer which is disposed on the base material and is formed of an adhesive composition. The adhesive composition includes: a polymer (A) that contains a reactive functional group (A1); a polymer (B) that contains a reactive functional group (B1) which is different from the functional group (A1), and that contains an actinic ray-polymerizable group (B2); a crosslinking agent (C) that reacts with the reactive functional group (A1); and a crosslinking agent (D) that reacts with the reactive functional group (B1).

Description

Adhesive sheet for semiconductor processing

The present invention relates to an adhesive sheet for semiconductor processing, and more particularly to an adhesive sheet for protecting a semiconductor wafer surface used for protecting the surface of a semiconductor wafer with bumps.

As information terminal devices are rapidly becoming thinner, smaller, and multifunctional, semiconductor devices mounted on them are also required to be thinner and denser, and semiconductor wafers are also required to be thinner. ing. Conventionally, in order to meet the demand, the back surface of a semiconductor wafer is ground and thinned. In recent years, bumps made of solder or the like having a height of about several tens to several hundreds of micrometers are sometimes formed on the surface of a semiconductor wafer. When such a semiconductor wafer with bumps is subjected to back grinding, a surface protective sheet is attached to the wafer surface on which the bumps are formed in order to protect the bump portions.

As a surface protective sheet, as disclosed in Patent Document 1, it is conventionally known that an adhesive sheet in which an intermediate layer and an adhesive layer are provided in this order on a base material is used. In Patent Document 1, a conventional pressure sensitive adhesive such as an acrylic pressure sensitive adhesive, a silicone pressure sensitive adhesive, or a rubber pressure sensitive adhesive is used for the pressure sensitive adhesive layer. It has also been shown that a crosslinking structure may be introduced by blending a crosslinking agent with the pressure-sensitive adhesive.
Further, in Patent Document 1, an energy beam curable oligomer is blended in the pressure-sensitive adhesive, or a carbon-carbon double bond is introduced into the polymer constituting the pressure-sensitive adhesive to make the pressure-sensitive adhesive curable. Is also disclosed. The surface protective sheet is easily peeled off from the semiconductor wafer after use because the adhesive strength of the pressure-sensitive adhesive layer is reduced by irradiation with energy rays because the energy ray-curable pressure-sensitive adhesive is used.

Also, conventionally, an ultra-high strength gel having a double network structure is known. For example, as shown in Non-Patent Document 1, an ultra-high-strength gel is obtained by polymerizing poly (2-acrylamido-2-methylpropanesulfonic acid) to obtain a gel (PAMPS gel), and the PAMPS gel is converted into an acrylamide monomer solution. It is obtained by polymerizing acrylamide inside the PAMPS gel after being immersed in the gel.

Japanese Patent No. 4367769 Drug discovery of ultra-high-strength Double そ の Network gel and its strengthening mechanism, Polymer papers, Vol. 65, No. 12, (2008) 707 pp.707-715

In recent years, the bump height tends to increase as the density and size of semiconductor devices increase. However, for a semiconductor wafer having a large bump height, an adhesive residue (glue residue) is likely to be generated on the bump when the surface protective sheet is peeled off. The adhesive residue tends to be reduced by making the adhesive an energy ray curable, but in recent years, it has been demanded that the contamination of the semiconductor wafer be further reduced. May not be reduced to the desired level.
Further, in Non-Patent Document 1, no attempt is made to apply an ultrahigh strength gel having a double network structure to an adhesive or to modify it to energy ray curability.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pressure-sensitive adhesive sheet for semiconductor processing that is less likely to cause adhesive residue on the surface of a workpiece such as a semiconductor wafer when peeled. .

As a result of intensive studies, the present inventors blended two types of polymers into the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer, cross-linked each polymer with different cross-linking systems, and cured one type of polymer with energy rays. As a result, the inventors have found that the above-mentioned problems can be solved, and have completed the present invention described below. That is, the present invention provides the following semiconductor processing pressure-sensitive adhesive sheets (1) to (10).
(1) A semiconductor processing pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer provided on one surface of the base material and formed of a pressure-sensitive adhesive composition,
The pressure-sensitive adhesive composition has a polymer (A) having a reactive functional group (A1), a reactive functional group (B1) different from the reactive functional group (A1), and an energy beam polymerizable group (B2). A pressure-sensitive adhesive sheet for semiconductor processing, comprising a polymer (B), a crosslinking agent (C) that reacts with the reactive functional group (A1), and a crosslinking agent (D) that reacts with the reactive functional group (B1).
(2) The pressure-sensitive adhesive sheet for semiconductor processing according to (1), wherein the weight average molecular weight of the polymer (A) is higher than the weight average molecular weight of the polymer (B).
(3) The pressure-sensitive adhesive sheet for semiconductor processing according to (1) or (2), wherein the polymer (A) and the polymer (B) are both acrylic polymers.
(4) The weight average molecular weight of the acrylic polymer constituting the polymer (A) is higher than the weight average molecular weight of the acrylic polymer constituting the polymer (B), and the difference is 200,000 or more. Adhesive sheet for semiconductor processing.
(5) The weight average molecular weight of the acrylic polymer constituting the polymer (A) is 300,000 to 1,000,000, and the weight average molecular weight of the acrylic polymer constituting the polymer (B) is 5,000 to 100. The adhesive sheet for semiconductor processing according to the above (4), which is 1,000.
(6) The acrylic polymer constituting the polymer (A) contains a structural unit derived from the functional monomer (a1) having a reactive functional group (A1) and a structural unit derived from the alkyl (meth) acrylate (a2). 6. The semiconductor processing pressure-sensitive adhesive sheet according to any one of the above (3) to (5), which is an acrylic copolymer (A ′).
(7) The acrylic polymer constituting the polymer (B) contains a structural unit derived from the functional group monomer (b1) having a reactive functional group (B1) and a structural unit derived from the alkyl (meth) acrylate (b2). It is a reaction product obtained by reacting an energy beam polymerizable group-containing compound (S) having an energy beam polymerizable group (B2) with a part of the reactive functional group (B1) of the acrylic copolymer (B ′). The semiconductor processing pressure-sensitive adhesive sheet according to any one of (3) to (6) above.
(8) The adhesive sheet for semiconductor processing according to any one of (1) to (7) above, wherein the reactive functional group (A1) is a carboxy group and the reactive functional group (B1) is a hydroxyl group.
(9) The adhesive sheet for semiconductor processing according to (8), wherein the crosslinking agent (C) is an epoxy crosslinking agent and the crosslinking agent (D) is an isocyanate crosslinking agent.
(10) The content of the crosslinking agent (D) is larger than the content of the crosslinking agent (C) on a mass basis in the pressure-sensitive adhesive composition, and the content of the crosslinking agent (D) in the pressure-sensitive adhesive composition is a polymer ( B) The pressure-sensitive adhesive sheet for semiconductor processing according to any one of the above (1) to (9), which is 2 to 20 parts by mass with respect to 100 parts by mass.

In the present invention, it is possible to provide a pressure-sensitive adhesive sheet for semiconductor processing that makes it difficult for adhesive residue to occur on the workpiece surface when it is peeled.

3 is a stress-strain curve created by performing a cyclic tensile test on the pressure-sensitive adhesive layer after energy beam curing in Example 1. FIG. 2 is a stress-strain curve created by performing a cyclic tensile test on the pressure-sensitive adhesive layer before energy beam curing in Example 1. FIG. 2 is a stress-strain curve created by performing a cyclic tensile test on the pressure-sensitive adhesive layer after energy beam curing in Comparative Example 1. FIG.

In the following description, “weight average molecular weight (Mw)” is a value in terms of polystyrene measured by gel permeation chromatography (GPC), and specifically measured based on the method described in the examples. Value.
In the description of the present specification, for example, “(meth) acrylate” is used as a word indicating both “acrylate” and “methacrylate”, and the same applies to other similar terms.

Hereinafter, the present invention will be described in more detail using embodiments.
The pressure-sensitive adhesive sheet for semiconductor processing of the present invention (hereinafter also simply referred to as “pressure-sensitive adhesive sheet”) includes a base material and a pressure-sensitive adhesive layer provided on one surface of the base material. Moreover, the adhesive sheet may have an intermediate | middle layer between a base material and an adhesive layer. As described above, the pressure-sensitive adhesive sheet may be composed of two or three layers, or may be provided with other layers. For example, a release material may be further provided on the pressure-sensitive adhesive layer.
Hereinafter, each member which comprises an adhesive sheet is demonstrated in detail.

<Base material>
Although the base material used for an adhesive sheet is not specifically limited, It is preferable that it is a resin film. Resin films are preferable because they are less likely to generate dust than paper, non-woven fabrics, etc., and are suitable for processed parts of electronic parts, and are easily available. The substrate may be a single layer film made of one resin film or a multilayer film in which a plurality of resin films are laminated.
Examples of the resin film used as the base material include polyolefin film, vinyl halide polymer film, acrylic resin film, rubber film, cellulose film, polyester film, polycarbonate film, polystyrene film, and polyphenylene sulfide. Examples thereof include a system film and a cycloolefin polymer film.
Among these, from the viewpoint that the wafer can be stably held when grinding the wafer to an extremely thin thickness, and from the viewpoint of being a film having a high thickness accuracy, a polyester film is preferable, and among the polyester films, From the viewpoint of easy availability and high thickness accuracy, a polyethylene terephthalate film is more preferable.
The thickness of the substrate is not particularly limited, but is preferably 10 to 200 μm, more preferably 25 to 150 μm, and still more preferably 25 to 100 μm.

In addition, you may use the base material which provided the easily bonding layer further on the surface of the resin film from a viewpoint of improving the adhesiveness with respect to the adhesive layer or intermediate | middle layer of a base material. Furthermore, the base material used in the present invention may contain a filler, a colorant, an antistatic agent, an antioxidant, an organic lubricant, a catalyst, and the like as long as the effects of the present invention are not impaired. The substrate may be transparent or may be colored as desired, but is preferably one that transmits energy rays to a degree sufficient to cure the pressure-sensitive adhesive layer.

<Adhesive layer>
An adhesive layer is provided on a base material, and when an intermediate layer is provided, it is provided on the intermediate layer. The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition contains the polymer (A) and the polymer (B), and the crosslinking agent (C) and the crosslinking agent (D). Hereinafter, each of these components will be described in detail.

[Polymer (A), (B)]
The polymer (A) has a reactive functional group (A1). Moreover, the polymer (B) has a reactive functional group (B1) which is a functional group different from the reactive functional group (A1), and an energy ray polymerizable group (B2). The reactive functional group (A1) of the polymer (A) does not undergo a crosslinking reaction with the crosslinking agent (D) but preferentially undergoes a crosslinking reaction with the crosslinking agent (C). In addition, the reactive functional group (B1) of the polymer (B) does not undergo a crosslinking reaction with the crosslinking agent (C) but preferentially undergoes a crosslinking reaction with the crosslinking agent (D).

The reactive functional group (A1) and the reactive functional group (B1) are not particularly limited, and may be selected from a hydroxyl group, a carboxy group, an amino group, an epoxy group, and the like. Is preferred.
And it is more preferable that either one of the reactive functional group (A1) or the reactive functional group (B1) is a carboxy group and the other is a hydroxyl group. Thereby, the polymer (A) reacts with the cross-linking agent (C) and the polymer (B) easily reacts with the cross-linking agent (D) to form separate network structures.
Here, the reactive functional group (A1) may be a hydroxyl group and the reactive functional group (B1) may be a carboxy group. However, the reactive functional group (A1) is a carboxy group and the reactive functional group (B1). ) Is more preferably a hydroxyl group. When the reactive functional group (B1) of the polymer (B) is a hydroxyl group, it easily reacts with the energy ray polymerizable group-containing compound (S) described later.

The polymer (A) is a compound that does not have an energy ray polymerizable group, and is therefore a non-energy ray curable compound that does not cure even when irradiated with energy rays. On the other hand, since the polymer (B) has an energy ray polymerizable group (B2), it is an energy ray curable compound that is cured by irradiation with energy rays. When the pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition is irradiated with energy rays, the polymer (B) is cured and the adhesive strength is lowered.
In addition, an energy ray means what has an energy quantum in electromagnetic waves or a charged particle beam, and an ultraviolet ray, an electron beam, etc. are mentioned as the example. Among these, it is preferable to cure the pressure-sensitive adhesive layer using ultraviolet rays.
Examples of the energy beam polymerizable group (B2) include those having a carbon-carbon double bond such as a (meth) acryloyl group, a vinyl group, and an allyl group, and among these, a (meth) acryloyl group is preferable. .

The polymer (A) has a reactive functional group (A1), the polymer (B) has a reactive functional group (B1) different from the reactive functional group (A1), and the polymer (A) is a crosslinking agent. (C) and the polymer (B) are each crosslinked by a crosslinking agent (D) different from the crosslinking agent (C). Therefore, in the pressure-sensitive adhesive layer, the three-dimensional network structure (hereinafter also referred to as “first network”) composed of the polymer (A) and the crosslinking agent (C), the polymer (B) and the crosslinking agent (D). A configured three-dimensional network structure (hereinafter also referred to as “second network”) is formed. Moreover, since the energy network polymerizable group (B2) is contained in the polymer (B), the second network is presumed to have a denser network and a hard and brittle structure when irradiated with the energy beam. On the other hand, it is presumed that the first network is composed of the polymer (A) and the crosslinking agent (C), so that the first network has a structure that is flexible and easily stretched as compared to the second network.
In the pressure-sensitive adhesive layer, after irradiation with energy rays, a so-called double network in which a rigid second mesh is intricately formed on the flexible first mesh as described above is formed. Therefore, the breaking properties such as breaking strength, breaking elongation, breaking energy, etc. of the pressure-sensitive adhesive layer after irradiation with energy rays are likely to be good, and when the pressure-sensitive adhesive sheet is peeled off from a workpiece such as a semiconductor wafer, adhesive residue is hardly generated on the workpiece. .

Each of the polymer (A) and the polymer (B) is an adhesive component (adhesive resin) capable of expressing adhesiveness in the adhesive layer, and is selected from, for example, an acrylic polymer, a urethane polymer, a rubber-based polymer, and a polyolefin. . Among these, the polymer (A) and the polymer (B) are preferably selected from an acrylic polymer and a urethane polymer, and more preferably an acrylic polymer.
As the polymer (A) and the polymer (B), it is preferable to use the same kind of polymers from the viewpoint of compatibility and the like. That is, when the polymer (A) is an acrylic polymer, the polymer (B) is also preferably an acrylic polymer. In addition, when the polymer (A) is a urethane polymer, the polymer (B) is also preferably a urethane polymer.

In the pressure-sensitive adhesive layer, when the weight average molecular weight of the polymer (A) is high, the first network tends to have a more flexible and stretchable structure, whereas when the weight average molecular weight of the polymer (B) is low, the second network is more Hard and brittle structure is likely. Furthermore, the second mesh easily enters between the first meshes, and a double network is easily formed. From these viewpoints, the weight average molecular weight of the polymer (A) is preferably higher than the weight average molecular weight of the polymer (B).

In the pressure-sensitive adhesive composition, the content of the polymer (B) is preferably 10 to 100 parts by mass, more preferably 20 to 80 parts by mass with respect to 100 parts by mass of the polymer (A). More preferably, it is 30 to 70 parts by mass.
By making content of a polymer (B) more than the said lower limit, it becomes easy to provide energy-beam sclerosis | hardenability appropriately to an adhesive layer. Moreover, by making content into the said range, the coating property of an adhesive composition, the film formability of an adhesive layer, etc. become easy to become favorable. Furthermore, the first mesh and the second mesh are formed in a well-balanced manner, and it becomes easy to improve the breaking property of the pressure-sensitive adhesive layer.
In the pressure-sensitive adhesive composition, the polymer (A) and the polymer (B) are preferably main components. The main component means that the total content of the polymer (A) and the polymer (B) is 50% by mass or more based on the total amount of the pressure-sensitive adhesive composition (solid content basis), more preferably 70. It is -98 mass%, More preferably, it is 80-95 mass%. In addition, in this invention, solid content means all components other than an organic solvent, and a liquid state is also included at room temperature (25 degreeC).

(Acrylic polymer)
Hereinafter, the case where each of the above-described polymer (A) and polymer (B) is an acrylic polymer will be described in more detail.
The acrylic polymer constituting the polymer (A) is a polymer containing a structural unit derived from (meth) acrylate, preferably a functional group monomer (a1) having a reactive functional group (A1) (hereinafter simply referred to as “ An acrylic copolymer (A ′) containing a structural unit derived from the functional group monomer (a1) ”, the structural unit derived from the functional group monomer (a1), and an alkyl (meth) acrylate (a2) An acrylic copolymer (A ′) containing a derived structural unit is more preferred. A polymer (A) becomes easy to make the adhesiveness of an adhesive layer favorable by containing the structural unit derived from an alkyl (meth) acrylate (a2).

The functional group monomer (a1) is a monomer having the reactive functional group (A1) described above, and preferably a carboxy group-containing monomer. Examples of the carboxy group-containing monomer include carboxylic acids having an ethylenically unsaturated bond such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used individually by 1 type and may be used in combination of 2 or more type. In these, acrylic acid and methacrylic acid are preferable and acrylic acid is more preferable.

The content of the structural unit derived from the functional group monomer (a1) (for example, carboxy group-containing monomer) is preferably 0.5 to 15% by mass based on the acrylic copolymer (A ′). More preferably, it is more preferably 1.5 to 5% by mass. When the content of the functional group monomer (a1) such as a carboxy group-containing monomer is within the above range, an appropriate adhesive force can be easily imparted to the pressure-sensitive adhesive layer. Moreover, it becomes possible to form a 1st network suitably by bridge | crosslinking by a crosslinking agent (C).

Examples of the alkyl (meth) acrylate (a2) include alkyl (meth) acrylates having an alkyl group having 1 to 20 carbon atoms.
Examples of the alkyl (meth) acrylate having an alkyl group having 1 to 20 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl ( (Meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl ( Examples include meth) acrylate and stearyl (meth) acrylate. These may be used individually by 1 type and may be used in combination of 2 or more type.
Among the above, alkyl (meth) acrylates having an alkyl group having 1 to 8 carbon atoms are preferable from the viewpoint of appropriately exhibiting adhesiveness, and alkyl (meth) acrylates having an alkyl group having 4 to 8 carbon atoms (hereinafter, referred to as “alkyl (meth) acrylate”). “Monomer (α)” is sometimes preferred. Specifically, the monomer (α) is preferably 2-ethylhexyl (meth) acrylate or n-butyl (meth) acrylate, and more preferably n-butyl (meth) acrylate.

The content of the structural unit derived from the alkyl (meth) acrylate (a2) is preferably 50 to 99.5% by mass and preferably 60 to 99% by mass based on the acrylic copolymer (A ′). More preferred is 70 to 98.5% by mass.
As the alkyl (meth) acrylate (a2), it is more preferable to use an alkyl (meth) acrylate having an alkyl group having 4 to 8 carbon atoms, that is, a monomer (α) as described above. All of the alkyl (meth) acrylate (a2) contained in the polymer (A ′) may be the monomer (α) or a part thereof may be the monomer (α).
Specifically, the monomer (α) is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, and still more preferably 90 to 100% by mass based on the total amount of the alkyl (meth) acrylate (a2).

The acrylic copolymer (A ′) used in the polymer (A) may be a copolymer of the functional group monomer (a1) and the alkyl (meth) acrylate (a2), but (a1) It may be a copolymer of the component, the component (a2), and another monomer (a3) other than the components (a1) and (a2).
The other monomer (a3) means a copolymerizable monomer other than the above components (a1) to (a2), and specifically, a cycloalkyl (meta) having 3 to 20 carbon atoms in the cycloalkyl group. ) (Meth) acrylates having a cyclic skeleton such as acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate; vinyl ester compounds such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene and isobutylene; vinyl chloride and vinylidene And halogenated olefins such as chloride; styrene monomers such as styrene and α-methylstyrene; diene monomers such as butadiene, isoprene and chloroprene; and nitrile monomers such as acrylonitrile and methacrylonitrile.
The other monomer (a3) may be used alone in the acrylic copolymer (A ′), or two or more kinds may be used in combination.

The acrylic polymer constituting the polymer (B) is a polymer containing a structural unit derived from (meth) acrylate, preferably a functional group monomer (b1) having a reactive functional group (B1) (hereinafter simply referred to as “ The energy ray polymerizable group-containing compound (S) having the energy ray polymerizable group (B2) is added to the acrylic copolymer (B ′) containing the structural unit derived from the functional group monomer (b1) ”. It is a reaction product obtained by reacting. The energy beam polymerizable group-containing compound (S) reacts with a part of the reactive functional group (B1) of the acrylic copolymer (B ′). Moreover, it is more preferable that the acrylic copolymer (B ′) further contains a structural unit derived from an alkyl (meth) acrylate (b2).
That is, the acrylic polymer constituting the polymer (B) contains a structural unit derived from the functional monomer (b1) having a reactive functional group (B1) and a structural unit derived from the alkyl (meth) acrylate (b2). It is a reaction product obtained by reacting an energy beam polymerizable group-containing compound (S) having an energy beam polymerizable group (B2) with a part of the reactive functional group (B1) of the acrylic copolymer (B ′). Is preferred.

The functional group monomer (b1) is a monomer having the reactive functional group (B1) described above, and preferably a hydroxyl group-containing monomer.
Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxybutyl (meth) ) Acrylate, and hydroxyalkyl (meth) acrylates such as 4-hydroxybutyl (meth) acrylate. Among them, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meta) from the viewpoint of reactivity with the crosslinking agent (D) and the energy beam polymerizable group-containing compound (S) and copolymerization with other monomers. ) Acrylate is preferred, and 2-hydroxyethyl (meth) acrylate is more preferred.

In the acrylic copolymer (B ′) for forming the polymer (B), the content of the structural unit derived from the functional group monomer (b1) (for example, a hydroxyl group-containing monomer) is based on the acrylic copolymer (B ′). Is preferably 10 to 45% by mass, more preferably 15 to 40% by mass, and still more preferably 20 to 35% by mass. When the content of the functional group monomer (b1) such as a hydroxyl group-containing monomer is within the above range, an appropriate adhesive force can be easily imparted to the pressure-sensitive adhesive layer. Moreover, it becomes possible to form suitably the three-dimensional network structure which consists of a 2nd network by bridge | crosslinking by a crosslinking agent (D). Furthermore, by reacting the energy beam polymerizable group-containing compound (S) with the reactive functional group (B1), an appropriate amount of the energy beam polymerizable group (B2) can be introduced into the polymer (B). become.

Specific examples of the alkyl (meth) acrylate (b2) include the same ones that can be selected as the component (a2) described above, and these may be used alone or in combination of two or more. May be used. Further, like the component (a2), an alkyl (meth) acrylate having 1 to 8 carbon atoms is preferable, and a monomer (α) is more preferably used. The same applies to suitable compounds as the monomer (α), and n-butyl (meth) acrylate is preferred.
The content of the alkyl (meth) acrylate (b2) is preferably 50 to 90% by mass, more preferably 60 to 85% by mass, based on the acrylic copolymer (B ′), and 65 to 80%. More preferred is mass%.
In addition, the alkyl (meth) acrylate (b2) is preferably the monomer (α) as in the case of the component (a2), but the alkyl (meth) acrylate (B ′) contains an alkyl (meth) acrylate ( All of b2) may be a monomer (α) or a part thereof may be a monomer (α). In addition, the detail of the content is the same as that of what was demonstrated by the said polymer (A).

The acrylic copolymer (B ′) may be a copolymer of the functional group monomer (b1) and the alkyl (meth) acrylate (b2), but the component (b1), the component (b2), Copolymers with other monomers (b3) other than these components (b1) and (b2) may also be used. The other monomer (b3) means a copolymerizable monomer other than the above components (b1) to (b2), and specific monomers can be appropriately selected from those listed as the monomer (a3). It is.

(Energy beam polymerizable group-containing compound (S))
The energy beam polymerizable group-containing compound (S) includes an energy beam polymerizable group (B2) and a functional group (B3) capable of reacting with the reactive functional group (B1) (hereinafter simply referred to as “functional group (B3 ) ”(Sometimes). The functional group (B3) may be any functional group that can react with the reactive functional group (B1), and examples thereof include an isocyanate group, an epoxy group, and a carboxy group.
Moreover, as above-mentioned, if a reactive functional group (B1) is a hydroxyl group, it is preferable that the functional group (B3) contained in an energy-beam polymeric group containing compound (S) is an isocyanate group. In addition, when the reactive functional group (B1) is a carboxy group, the functional group (B3) is preferably an epoxy group. Furthermore, if the reactive functional group (B1) is an epoxy group, the functional group (B3) is preferably a carboxy group.
Among these, from the viewpoint of reactivity and the like, it is more preferable that the reactive functional group (B1) is a hydroxyl group and the functional group (B3) is an isocyanate group.

The preferred embodiment of the energy beam polymerizable group (B2) is as described above. Therefore, the energy beam polymerizable group-containing compound (S) is preferably a compound having an isocyanate group and a (meth) acryloyl group.
Specific examples of the energy beam polymerizable group-containing compound (S) include isocyanate groups such as 2-isocyanatoethyl (meth) acrylate, isocyanatopropyl (meth) acrylate, and 1,1- (bisacryloyloxymethyl) ethyl isocyanate. And a compound having a (meth) acryloyl group; a compound having an epoxy group such as glycidyl (meth) acrylate and a (meth) acryloyl group, among which 2-isocyanatoethyl (meth) acrylate is preferable. .

Here, the reactive functional group (B1) of the acrylic copolymer (B ′) is partially reacted with the energy ray polymerizable group-containing compound (S). Therefore, in the polymer (B), the reactive functional group (B1) that does not react with the energy ray polymerizable group-containing compound (S) remains, whereby the polymer (B) has the reactive functional group (B1) and the energy. It has both of the linear polymerizable groups (B2).
The addition rate of the energy linear polymerizable group-containing compound (S) is preferably 75 to 97 equivalents relative to the total amount (100 equivalents) of the reactive functional groups (B1) of the acrylic copolymer (B ′). More preferably, it is 80 to 95 equivalents, and still more preferably 85 to 93 equivalents.
While keeping the content of the structural unit derived from the functional group monomer (b1) within the above preferred range (10 to 45% by mass, more preferably 15 to 40% by mass, and further preferably 20 to 35% by mass) When it is within the range, a certain amount of the reactive functional group (B1) remains in the polymer (B). Therefore, the polymer (B) is appropriately cross-linked by the cross-linking agent (D), and it becomes easy to adjust the adhesive force of the pressure-sensitive adhesive layer to an appropriate value. Furthermore, an appropriate amount of energy beam polymerizable group (B2) can be introduced into the polymer (B).

The acrylic copolymer (A ′) and the acrylic copolymer (B ′) may be a random copolymer or a block copolymer.
The acrylic copolymer (A ′) and the acrylic copolymer (B ′) can be produced by polymerizing a mixture of monomers constituting each copolymer by an ordinary radical polymerization method. The polymerization can be carried out by a solution polymerization method or the like using a polymerization initiator as desired. Examples of the polymerization initiator include known azo compounds and organic peroxides.

When the polymer (A) and the polymer (B) are both acrylic polymers, the weight average molecular weight of the acrylic polymer constituting the polymer (A) is higher than the weight average molecular weight of the acrylic polymer constituting the polymer (B). And the difference is preferably 200,000 or more. As described above, when the molecular weight difference between the two polymers is increased, the characteristic difference between the first network and the second network is easily developed, and a double network is easily formed. For this reason, the breaking property is improved and the adhesive residue is easily reduced. From these viewpoints, the difference in the weight average molecular weight is more preferably 300,000 or more, and further preferably 400,000 or more.
On the other hand, the upper limit value of the difference in weight average molecular weight is not particularly limited, but the difference is preferably 850,000 or less, more preferably 750,000 or less, and further preferably 700,000 or less. preferable.

In the pressure-sensitive adhesive composition, the weight average molecular weight of the acrylic polymer constituting the polymer (A) is 300,000 to 1,000,000, and the weight average molecular weight of the acrylic polymer constituting the polymer (B) is 5,000. It is preferable that it is ~ 100,000.
Among them, the weight average molecular weight of the acrylic polymer constituting the polymer (A) is more preferably 350,000 to 850,000, and further preferably 400,000 to 750,000.
On the other hand, the acrylic polymer constituting the polymer (B) preferably has a weight average molecular weight of 15,000 to 90,000, and more preferably 30,000 to 80,000.

By setting the weight average molecular weight of the polymer (A) to the lower limit value or more, the structure of the first network is more flexible and easily stretched. Moreover, the film-forming property of the pressure-sensitive adhesive layer is likely to be favorable, and further, the cohesive force of the pressure-sensitive adhesive layer is likely to be high, and the adhesive residue is hardly generated. On the other hand, by making the weight average molecular weight of the polymer (A) not more than the above upper limit value, it becomes easy to improve the coating property of the pressure-sensitive adhesive composition.
Moreover, by making the weight average molecular weight of the polymer (B) not more than the above upper limit value, it becomes easy to form the above-mentioned second network with a harder and more brittle structure, and it becomes easier to form a suitable double network. Moreover, by setting it as the said lower limit or more, the cohesive force of an adhesive layer becomes suitable and it becomes difficult to produce adhesive residue.

(Urethane polymer)
Next, the case where the polymer (A) and the polymer (B) are urethane polymers will be described. The urethane polymer used for the polymer (A) and the polymer (B) is a polymer containing at least one of a urethane bond and a urea bond.
The urethane polymer constituting the polymer (A) has the above-described reactive functional group (A1), and examples thereof include carboxy group-containing polyurethane.
Examples of the urethane polymer constituting the polymer (B) include those obtained by reacting the above-mentioned energy beam polymerizable group-containing compound (S) with a part of the hydroxyl groups of the hydroxyl group-containing polyurethane. The hydroxyl group-containing polyurethane preferably has a hydroxyl group at the terminal. Examples of the polyurethane having a hydroxyl group at the terminal include a polyurethane polyol obtained by reacting a polyol and a polyisocyanate compound. As the polyol and polyisocyanate compound, various compounds conventionally used in urethane pressure-sensitive adhesives can be used.

When both the polymer (A) and the polymer (B) are urethane polymers, the weight average molecular weight of the polymer (A) is higher than the weight average molecular weight of the polymer (B), and the difference is 25,000 or more. It is preferable that it is 50,000 or more. The upper limit of the difference in weight average molecular weight is not particularly limited, but the difference is preferably 230,000 or less, and more preferably 120,000 or less.
The weight average molecular weight of the urethane polymer constituting the polymer (A) is preferably 30,000 to 250,000, and more preferably 40,000 to 150,000.
The weight average molecular weight of the urethane polymer constituting the polymer (B) is preferably 2,000 to 25,000, more preferably 3,000 to 20,000.

[Crosslinking agent (C), (D)]
The crosslinking agent (C) is a crosslinking agent that reacts with the reactive functional group (A1), and is used for crosslinking the polymer (A). The crosslinking agent (D) is a crosslinking agent that reacts with the reactive functional group (B1), and is used for crosslinking the polymer (B).
Crosslinking by the crosslinking agent (C) and the crosslinking agent (D) is usually performed by heating the pressure-sensitive adhesive composition. That is, as will be described later, the pressure-sensitive adhesive composition is heated in a state where it is applied and made into a thin film, thereby being crosslinked with the crosslinking agent (C) and the crosslinking agent (D) to form a pressure-sensitive adhesive layer.
Each of the crosslinking agent (C) and the crosslinking agent (D) is, for example, an isocyanate crosslinking agent, an epoxy crosslinking agent, an amine crosslinking agent, a melamine crosslinking agent, an aziridine crosslinking agent, a hydrazine crosslinking agent, or an aldehyde crosslinking agent. , An oxazoline-based crosslinking agent, a metal alkoxide-based crosslinking agent, a metal chelate-based crosslinking agent, a metal salt-based crosslinking agent, and an ammonium salt-based crosslinking agent. Each of the crosslinking agent (C) and the crosslinking agent (D) may be used alone or in combination of two or more thereof.

The crosslinking agent (C) is appropriately selected according to the type of the reactive function (A1) possessed by the polymer (A), and the crosslinking agent (D) is selected according to the type of the reactive functional group (B1) possessed by the polymer (B). It is selected as appropriate. That is, as the crosslinking agent (C), one that does not undergo a crosslinking reaction with the reactive functional group (B1) but reacts with the reactive functional group (A1) may be selected. Further, as the cross-linking agent (D), one that does not undergo a cross-linking reaction with the reactive functional group (A1) and reacts with the reactive functional group (B1) may be selected. Therefore, different types of crosslinking agent (C) and crosslinking agent (D) are used.
For example, as described above, when the reactive functional group (A1) is a carboxy group, the crosslinking agent (C) is preferably selected from an epoxy crosslinking agent and a metal chelate crosslinking agent, Epoxy crosslinking agents are more preferred. Moreover, when a reactive functional group (A2) is a hydroxyl group, an isocyanate type crosslinking agent is preferable as a crosslinking agent (D).

Examples of the epoxy-based crosslinking agent include 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl. Examples include ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine and the like. These may be used individually by 1 type and may be used in combination of 2 or more type. Of these, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane is preferred as the epoxy crosslinking agent.

Examples of the metal chelate-based crosslinking agent include acetylacetone, ethyl acetoacetate, tris (2, 4), polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. -Pentandionate) and the like are exemplified. These may be used individually by 1 type and may be used in combination of 2 or more type.

Moreover, a polyisocyanate compound is mentioned as an isocyanate type crosslinking agent. Specific examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. Etc. Further, biuret bodies, isocyanurate bodies, and adduct bodies that are a reaction product with a low molecular active hydrogen-containing compound such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, and the like are also included.
These may be used individually by 1 type and may be used in combination of 2 or more type. Of the above, polyhydric alcohols of aromatic polyisocyanates such as tolylene diisocyanate (for example, trimethylolpropane) adducts are preferred.

By suppressing the content of the crosslinking agent (C), it becomes easy to form a structure in which the first network is flexible and stretched, and it is easy to reduce adhesive residue. Therefore, it is preferable that the content of the crosslinking agent (C) is relatively small. Specifically, the content of the crosslinking agent (C) in the pressure-sensitive adhesive composition is 0.05 to 5 with respect to 100 parts by mass of the polymer (A), although it depends on the type, molecular weight and the like of the polymer (A). Mass parts are preferred, 0.1 to 3 parts by mass are more preferred, and 0.1 to 0.3 parts by mass are even more preferred.

On the other hand, when the crosslinking agent (D) is contained in the pressure-sensitive adhesive composition in a large amount, the second network is easily hard and brittle. Therefore, it is preferable that the content of the crosslinking agent (D) is relatively large, and the content of the crosslinking agent (D) in the pressure-sensitive adhesive composition is larger than the content of the crosslinking agent (C) on a mass basis. Is preferred.
The content of the crosslinking agent (D) in the pressure-sensitive adhesive composition depends on the type, molecular weight and the like of the polymer (B), but specifically, 2 to 20 parts by mass with respect to 100 parts by mass of the polymer (B). It is preferably 4 to 16 parts by mass, more preferably 5 to 12 parts by mass.

[Photoinitiator (E)]
The pressure-sensitive adhesive composition preferably contains a photopolymerization initiator (E). By containing the photopolymerization initiator (E), the pressure-sensitive adhesive layer can easily promote energy ray curing by ultraviolet rays or the like of the pressure-sensitive adhesive layer.
Examples of the photopolymerization initiator (E) include acetophenone, 2,2-diethoxybenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, Michler's ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl Ether, benzoin isobutyl ether, benzyl diphensulfide, tetramethyl thiuram monosulfide, benzyl dimethyl ketal, dibenzyl, diacetyl, 1-chloroanthraquinone, 2-chloroanthraquinone, 2-ethylanthraquinone, 2,2-dimethoxy-1,2- Diphenylethane-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1, -Benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2-hydroxy-2-methyl-1-phenyl-propan-1-one, diethylthioxanthone, isopropylthioxanthone, 2,4,6 Low molecular weight polymerization initiators such as trimethylbenzoyldiphenyl-phosphine oxide; oligomerized polymerization initiators such as oligo {2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone} Etc. These may be used alone or in combination of two or more.

The content of the photopolymerization initiator (E) is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass with respect to 100 parts by mass of the total amount of the polymer (A) and the polymer (B). Preferably, 2 to 12 parts by mass is more preferable.

In addition, the pressure-sensitive adhesive layer is a component other than the above as long as the effects of the present invention are not impaired, tackifier, dye, pigment, anti-degradation agent, antistatic agent, flame retardant, silane coupling agent, chain transfer agent , Plasticizers, fillers, resin components other than the above-described polymer (A) and polymer (B) may be contained.
The thickness of the pressure-sensitive adhesive layer can be appropriately adjusted according to the surface state of the adherend surface to which the pressure-sensitive adhesive sheet is adhered, such as the bump height on the wafer surface, but is preferably 2 to 150 μm, more preferably 5 to The thickness is 100 μm, more preferably 8 to 50 μm.

[Rupture characteristics of adhesive layer]
The pressure-sensitive adhesive layer is cured by irradiation with energy rays as described above, and it is preferable that the fracture characteristics after curing with energy rays are as follows.
That is, the pressure-sensitive adhesive layer after energy beam curing preferably has a breaking stress of 1.5 MPa or more, a breaking elongation of 80% or more, and a breaking energy of 1.0 MJ / m ³ or more. When the rupture stress, rupture elongation, and rupture energy have such relatively high values, the rupture strength of the pressure-sensitive adhesive layer becomes good, and adhesive residue is hardly generated. Further, from the viewpoint of further preventing adhesive residue, it is more preferable that the breaking stress is 1.8 MPa or more, the breaking elongation is 100% or more, and the breaking energy is 1.4 MJ / m ³ or more. More preferably, it is 0 MPa or more, the breaking elongation is 180% or more, and the breaking energy is 1.8 J / m ³ or more.
In addition, although the upper limit is not particularly limited, it is practically preferable that the breaking stress is 10 MPa or less, the breaking elongation is 400% or less, the breaking energy is 5.0 MJ / m ³ or less, and the breaking stress is 6 MPa. Hereinafter, it is more preferable that the breaking elongation is 300% or less and the breaking energy is 3.5 MJ / m ³ or less.
The breaking stress, breaking elongation, and breaking energy mean values measured by performing a tensile test in accordance with JIS K7127: 1999, specifically measured by the method described in the examples described later. It is the obtained value.

(Hysteresis)
When the pressure-sensitive adhesive layer after energy ray curing has the above-described double network, the second network is destroyed when a certain strain is applied, while the first network remains without being destroyed. Therefore, the pressure-sensitive adhesive layer after curing with energy rays is subjected to a certain strain and then strained again so that the stress-strain characteristics are different from the initial one due to the destruction of the second network. Become. Although such a property is called hysteresis property, the presence or absence and size of the hysteresis property can be confirmed by a cyclic tensile test shown below.
That is, every time the number of stretching increases, the elongation (%) is increased, and a cyclic tensile test in which the sample is stretched (strained) and released until the sample breaks is performed. As shown in FIG. Create a stress-strain curve. Then, for example, by detecting the maximum value (DSmax) of the stress difference between the curves at the same elongation in a plurality of stress-strain curves, the presence or absence and the magnitude of the hysteresis can be confirmed.

FIG. 1 shows a stress-strain curve when a cyclic tensile test is performed on a sample after curing of the pressure-sensitive adhesive layer used in Example 1 described later. Fig. 1 shows that when the maximum elongation at each extension was increased from 50% (first time) to 50% each time, and the extension and release were repeated, the sample broke at 233% at the fifth extension. It is an example. Here, FIG. 1 shows a stress-strain curve at each elongation, and the maximum value (DSmax) of the stress difference is obtained from the plurality of stress-strain curves as shown in FIG. In the example of FIG. 1, the maximum value (DSmax) of the stress difference is calculated from a curve produced from two consecutive times, the fourth time and the fifth time, but it is not continuous as in the third time and the fifth time. You may calculate from the curve produced from two times. The elongation is the percentage of the increase when the sample is pulled divided by the original length and expressed in%.

The more the double network is properly formed and the higher the hysteresis is, the more the stress-strain curves are separated from each other, and the maximum value (DSmax) of the stress difference is increased. From the viewpoint of appropriately forming a double network, the maximum value of the stress difference (DSmax) is preferably 20% or more, and preferably 25% or more with respect to the stress (BS) at the time of breaking in the cycle tensile test. Is more preferable, and it is still more preferable that it is 35% or more. The maximum value of the stress difference (DSmax) is preferably 90% or less, and more preferably 60% or less from the viewpoint of manufacturability and the like.

[Peeling strength of adhesive sheet]
Since the pressure-sensitive adhesive layer is energy ray curable, it can be made relatively soft before irradiation with energy rays, thereby making it easier for the pressure-sensitive adhesive layer to follow the irregularities formed on the workpiece surface. Moreover, an adhesive sheet is easy to peel from a workpiece | work, when an energy beam is irradiated and hardened | cured and adhesive force falls.
The adhesive strength of the adhesive sheet after irradiation with energy rays is preferably 1,700 mN / 25 mm or less. When the pressure-sensitive adhesive sheet is affixed to a workpiece having bumps or other protrusions on the surface, the protrusions are usually embedded in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, or the pressure-sensitive adhesive layer and the intermediate layer. For this reason, when the pressure-sensitive adhesive sheet is peeled from the adhesive sheet, adhesive residue is likely to be generated. However, by setting the adhesive force to 1,700 mN / 25 mm or less, it becomes easy to prevent the generation of such adhesive residue. It is also possible to easily peel the adhesive sheet from the workpiece. The adhesive strength of the adhesive sheet after irradiation with energy rays is preferably 50 to 1,500 mN / 25 mm, more preferably 100 to 1,300 mN / 25 mm.

The adhesive strength of the adhesive sheet before irradiation with energy rays is, for example, greater than 1,700 mN / 25 mm, preferably 1,800 to 20,000 mN / 25 mm, more preferably 1,800 to 9,000 mN. / M. When the adhesive strength before energy ray irradiation is within such a range, the adhesion to the workpiece surface is good, and the protection performance of the adhesive sheet to the workpiece is easily improved.
The adhesive strength of the pressure-sensitive adhesive sheet is measured when the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet is attached to a silicon mirror wafer and peeled at a peeling angle of 180 ° and a peeling speed of 300 mm / min in an environment of 23 ° C. Specifically, it is measured by the method described in the examples described later.

The adhesive strength is adjusted by appropriately changing the types of the polymer (A) and the polymer (B), the blending amount of these polymers, the types of the crosslinking agent (C) and the crosslinking agent (D), the blending amount of these crosslinking agents, and the like. Is possible. For example, by making the polymer (A) and the polymer (B) an acrylic polymer as described above, an adhesive sheet having the above-described adhesive force can be easily obtained. Moreover, it becomes easy to make adhesive force low by increasing the compounding quantity of a crosslinking agent (C) and a crosslinking agent (D).
Moreover, the adhesive force after energy beam irradiation can be adjusted by the amount of energy beam polymerizable group (B2) and the blending amount of polymer (B). For example, the adhesive strength after irradiation with energy rays tends to decrease when the amount of the energy beam polymerizable group (B2) contained in the pressure-sensitive adhesive composition is increased and increase when the amount is decreased.

<Intermediate layer>
In the pressure-sensitive adhesive sheet of the present invention, an intermediate layer may be provided on one surface of the substrate. The pressure-sensitive adhesive sheet has an intermediate layer, so that bumps are provided on the workpiece, and even if the unevenness of the surface of the workpiece is large, the convex portion is embedded in the pressure-sensitive adhesive layer and the intermediate layer. Become. Therefore, it becomes easy to keep the surface of the adhesive sheet opposite to the surface attached to the workpiece flat.
The thickness of the intermediate layer can be appropriately adjusted according to the state of the adherend surface to which the pressure-sensitive adhesive sheet is attached, but is preferably 10 from the viewpoint of being able to absorb a relatively high bump. It is ˜600 μm, more preferably 25 to 550 μm, still more preferably 35 to 500 μm.
An intermediate | middle layer is formed from the resin composition for intermediate | middle layers. Moreover, it is preferable that the resin composition for intermediate | middle layers contains urethane (meth) acrylate (X).

(Urethane (meth) acrylate (X))
Urethane (meth) acrylate (X) is a compound having at least a (meth) acryloyl group and a urethane bond, and has a property of being polymerized by irradiation with energy rays. The number of (meth) acryloyl groups in the urethane (meth) acrylate (X) may be monofunctional, bifunctional, or trifunctional or higher, but the intermediate layer resin composition preferably contains a monofunctional urethane (meth) acrylate. . Since the monofunctional urethane (meth) acrylate does not participate in the formation of the three-dimensional network structure in the polymerization structure, it is difficult to form the three-dimensional network structure in the intermediate layer, and it becomes easy to follow the unevenness of the workpiece surface.
As urethane (meth) acrylate (X), for example, a compound (x3) having a (meth) acryloyl group on a terminal isocyanate urethane prepolymer obtained by reacting a polyol compound (x1) with a polyisocyanate compound (x2). ) Can be obtained by reaction.
Urethane (meth) acrylate (X) may be used alone or in combination of two or more.

The polyol compound (x1) for forming the urethane (meth) acrylate (X) is not particularly limited as long as it is a compound having two or more hydroxy groups. Specific examples of the polyol compound (x1) include alkylene diol, polyether type polyol, polyester type polyol, and polycarbonate type polyol. Among these, polyether type polyols are preferable.
The polyol compound (x1) may be any of a bifunctional diol, a trifunctional triol, and a tetrafunctional or higher polyol, but from the viewpoint of availability, versatility, reactivity, etc. Functional diols are preferred, and polyether diols are more preferred. Specific examples of polyether-type diols include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

The polyester type polyol is obtained by polycondensation of a polyol component and a polybasic acid component. Examples of the polyol component include various alkanediols such as ethylene glycol, diethylene glycol, and butanediol (preferably alkanediol having about 2 to 10 carbon atoms), and various glycols.
As the polybasic acid component used for the production of the polyester type polyol, a compound generally known as a polybasic acid component of polyester can be used. Specifically, it corresponds to aliphatic dibasic acids having about 4 to 20 carbon atoms such as adipic acid and sebacic acid, aromatic dibasic acids such as terephthalic acid, aromatic polybasic acids such as trimellitic acid, and the like. Examples thereof include anhydrides, derivatives thereof, dimer acid, hydrogenated dimer acid, and the like.
The polycarbonate type polyol is not particularly limited, and examples thereof include a reaction product of glycols and alkylene carbonate.

Examples of the polyisocyanate compound (x2) include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and more specifically, for example, a crosslinking agent (C) and a crosslinking agent (D Various polyisocyanate compounds exemplified as) can be used.
Moreover, as a compound (x3) which has a (meth) acryloyl group, the (meth) acrylate which has a hydroxyl group is mentioned. Although it does not specifically limit as (meth) acrylate which has a hydroxy group, For example, a hydroxyalkyl (meth) acrylate is preferable. As hydroxyalkyl (meth) acrylate, the thing similar to what was illustrated by the above-mentioned hydroxyl-containing monomer can be used.

The weight average molecular weight of the urethane (meth) acrylate (X) for the intermediate layer resin composition is preferably 1,000 to 100,000, more preferably 3,000 to 80,000, still more preferably 5,000 to 65,000. If the weight average molecular weight is 1,000 or more, moderate hardness is imparted to the intermediate layer in the polymer of urethane (meth) acrylate (X) and a polymerizable monomer (Z) described later. become.

The blending amount of urethane (meth) acrylate (X) in the intermediate layer resin composition is preferably 10 to 70% by mass, more preferably 20 to 70%, based on the total amount of the intermediate layer resin composition (solid content basis). The mass is more preferably 25 to 60% by mass, still more preferably 30 to 50% by mass. If the blending amount of urethane (meth) acrylate (X) is within such a range, the intermediate layer can easily follow the irregularities on the workpiece surface.

In addition to the urethane (meth) acrylate (X), the intermediate layer resin composition contains, for example, one or more selected from the group consisting of a thiol group-containing compound (Y) and a polymerizable monomer (Z). Furthermore, it is preferable to contain, and it is more preferable to contain both of these.

(Thiol group-containing compound (Y))
The thiol group-containing compound (Y) is not particularly limited as long as it is a compound having at least one thiol group in the molecule, but a polyfunctional thiol group-containing compound is preferable, and a tetrafunctional thiol group-containing compound is more preferable. .
Specific examples of the thiol group-containing compound (Y) include nonyl mercaptan, 1-dodecanethiol, 1,2-ethanedithiol, 1,3-propanedithiol, triazinethiol, triazinedithiol, triazinetrithiol, 1,2 , 3-propanetrithiol, tetraethylene glycol-bis (3-mercaptopropionate), trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptopropionate), pentaerythritol tetrakisthio Glucolate, dipentaerythritol hexakis (3-mercaptopropionate), tris [(3-mercaptopropionyloxy) -ethyl] -isocyanurate, 1,4-bis (3-mercaptobutyryloxy) Butane, pentaerythritol tetrakis (3-mercaptobutyrate), 1,3,5-tris (3-mercaptobutyloxyethyl) -1,3,5-triazine-2,4,6- (1H, 3H, 5H) -Triions and the like.
In addition, you may use these thiol group containing compounds (Y) 1 type or in combination of 2 or more types.
The amount of the thiol group-containing compound (Y) is preferably 1.0 to 4.9 masses per 100 mass parts in total of the urethane (meth) acrylate (X) and the polymerizable monomer (Z) described later. Parts, more preferably 1.5 to 4.8 parts by mass.

(Polymerizable monomer (Z))
It is preferable that the resin composition for intermediate | middle layers contains a polymerizable monomer (Z) further from a viewpoint of improving film forming property. The polymerizable monomer (Z) is a polymerizable compound other than the urethane (meth) acrylate (X), and is a compound that can be polymerized by irradiation with energy rays. However, the polymerizable monomer (Z) means one excluding the resin component. The polymerizable monomer (Z) is preferably a compound having at least one (meth) acryloyl group.
In the present specification, the “resin component” refers to an oligomer or high molecular weight body having a repeating structure in the structure, and refers to a compound having a weight average molecular weight of 1,000 or more.
Examples of the polymerizable monomer (Z) include an alkyl (meth) acrylate having an alkyl group having 1 to 30 carbon atoms, a (meth) acrylate having a functional group such as a hydroxyl group, an amide group, an amino group, and an epoxy group, Examples include (meth) acrylates having an alicyclic structure, (meth) acrylates having an aromatic structure, (meth) acrylates having a heterocyclic structure, and other vinyl compounds.

Examples of the (meth) acrylate having a functional group include hydroxyalkyl (meth) acrylate. As hydroxyalkyl (meth) acrylate, the thing similar to what was illustrated by the above-mentioned hydroxyl-containing monomer can be used.
Examples of the (meth) acrylate having an alicyclic structure include isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxy (meth) acrylate, cyclohexyl (meth) ) Acrylate, adamantane (meth) acrylate and the like.
Examples of the (meth) acrylate having an aromatic structure include phenylhydroxypropyl (meth) acrylate, benzyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, and the like.
Examples of the (meth) acrylate having a heterocyclic structure include tetrahydrofurfuryl (meth) acrylate and morpholine (meth) acrylate.
These may be used alone or in combination of two or more.
As the polymerizable monomer (Z), it is preferable to use at least a (meth) acrylate having an alicyclic structure, both a (meth) acrylate having a functional group and a (meth) acrylate having an alicyclic structure. Is more preferable, and it is more preferable to use both hydroxyalkyl (meth) acrylate and isobornyl (meth) acrylate.

The blending amount of the polymerizable monomer (Z) in the intermediate layer resin composition is preferably 20 to 80% by mass, more preferably 30 to 80%, based on the total amount of the intermediate layer resin composition (solid content basis). The mass is more preferably 40 to 75 mass%, still more preferably 50 to 70 mass%. If the blending amount of the polymerizable monomer (Z) is within such a range, the intermediate layer is flexible because the portion formed by polymerization of the polymerizable monomer (Z) in the intermediate layer has high mobility. The intermediate layer easily follows the unevenness on the workpiece surface.
The blending amount of the (meth) acrylate having an alicyclic structure with respect to the total amount of the polymerizable monomer (Z) contained in the intermediate layer resin composition is preferably 52 to 87% by mass, more preferably It is 55 to 85% by mass, more preferably 60 to 80% by mass. When the blending amount of (meth) acrylate having an alicyclic structure is in such a range, the intermediate layer easily follows the unevenness on the workpiece surface.
From the same viewpoint, the mass ratio of urethane (meth) acrylate (X) and polymerizable monomer (Z) in the resin composition for intermediate layer [urethane (meth) acrylate (X) / polymerizable monomer The body (Z)] is preferably 20/80 to 60/40, more preferably 30/70 to 50/50, still more preferably 35/65 to 45/55.

(Photopolymerization initiator)
The intermediate layer resin composition preferably further contains a photopolymerization initiator. By containing the photopolymerization initiator, the intermediate layer resin composition can be easily cured by energy rays such as ultraviolet rays.
As a photoinitiator, it can use suitably selecting from what was illustrated by the above-mentioned photoinitiator (E), for example. You may use a photoinitiator 1 type or in combination of 2 or more types.
The blending amount of the photopolymerization initiator is preferably 0.05 to 15 parts by mass, more preferably 0.005 parts per 100 parts by mass in total of the urethane (meth) acrylate (X) and the polymerizable monomer (Z). 1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass.

(Other additives)
The resin composition for intermediate layers may contain other additives as long as the effects of the present invention are not impaired. Examples of other additives include cross-linking agents, antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, and dyes. When these additives are blended, the blending amount of the other additives is preferably 0.01 to 100 parts by mass with respect to a total of 100 parts by mass of the urethane (meth) acrylate (X) and the polymerizable monomer (Z). The amount is 6 parts by mass, more preferably 0.1 to 3 parts by mass.
In addition, the resin composition for intermediate | middle layers may contain resin components other than urethane (meth) acrylate (X) in addition to urethane (meth) acrylate (X) in the range which does not impair the effect of this invention. .
Moreover, an intermediate | middle layer may be formed with the resin composition for intermediate | middle layers containing other resin components, such as an olefin resin, instead of urethane (meth) acrylate (X).

<Release material>
As the release material provided on the pressure-sensitive adhesive layer and the release material used in the steps of the production method described later, a release sheet subjected to a single-sided release process, a release sheet subjected to a double-sided release process, and the like are used. The thing etc. which apply | coated the release agent on the base material of this are mentioned.
Examples of the base material for the release material include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin and polyethylene naphthalate resin; and plastic films such as polyolefin resin films such as polypropylene resin and polyethylene resin.
Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long chain alkyl resins, alkyd resins, and fluorine resins.
The thickness of the release material is not particularly limited, but is preferably 5 to 200 μm, more preferably 10 to 120 μm.

[Method for producing adhesive sheet]
The production method of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, and can be produced by a known method.
The intermediate layer can be formed, for example, by directly applying the intermediate layer resin composition on one surface of the substrate to form a coating film, and then drying and curing treatment as necessary. In addition, the intermediate layer is semi-cured on the release material by applying the resin composition for the intermediate layer to the release treatment surface of the release material to form a coating film, and then drying and semi-curing treatment as necessary. A layer may be formed, this semi-cured layer may be bonded to a substrate, and the semi-cured layer may be completely cured. At this time, the release material may be appropriately removed before or after the semi-cured layer is completely cured. The intermediate layer is preferably cured by polymerizing by irradiating the coating film with energy rays. The energy ray is preferably ultraviolet light. Moreover, when forming an intermediate | middle layer using an olefin resin, you may form an intermediate | middle layer by extrusion molding etc.

The pressure-sensitive adhesive layer is preferably formed by applying the pressure-sensitive adhesive composition, heating and cross-linking the pressure-sensitive adhesive composition, and drying as necessary. At this time, the pressure-sensitive adhesive composition may be applied directly to the intermediate layer or the base material, or may be applied to the release treatment surface of the release material to form a pressure-sensitive adhesive layer, and then the intermediate layer or the base material. You may form by sticking an adhesive layer together. The release material disposed on the pressure-sensitive adhesive layer may be peeled off as necessary.
The heating temperature and heating time of the pressure-sensitive adhesive composition may be any temperature and time at which the polymer (A) is crosslinked by the crosslinking agent (C) and the polymer (B) is crosslinked by the crosslinking agent (D). The heating temperature is usually 80 to 110 ° C., preferably 90 to 100 ° C. The heating time is usually 1 to 5 minutes, preferably 2 to 3 minutes.

When forming the intermediate layer or the pressure-sensitive adhesive layer, an organic solvent is further added to the resin composition for the intermediate layer or the pressure-sensitive adhesive composition, so that it can be used as a diluent for the resin composition for the intermediate layer or the pressure-sensitive adhesive composition. Good. Examples of the organic solvent to be used include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, isopropanol and the like.
In addition, as these organic solvents, the organic solvent used at the time of the synthesis | combination of each component contained in the resin composition for intermediate | middle layers or an adhesive composition may be used as it is, and 1 or more types of other organic solvents other than that may be used. May be added.
The intermediate layer resin composition or the pressure-sensitive adhesive composition can be applied by a known application method. Examples of the coating method include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[Usage of adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention is used when affixing to various workpieces and processing a workpiece such as a semiconductor wafer, and is preferably affixed to a workpiece surface having irregularities and protrusions.
Moreover, it is more preferable to affix on the semiconductor wafer surface, especially the wafer surface in which the bump was formed, and to use as a semiconductor wafer surface protection adhesive sheet. The adhesive sheet is more preferably used as a bag grind tape that is attached to the surface of a semiconductor wafer and protects a circuit formed on the wafer surface during subsequent grinding of the wafer back surface. In the case where the pressure-sensitive adhesive sheet of the present invention has an intermediate layer, the embedding property is good even if there is a height difference due to bumps or the like on the wafer surface, so that the protection performance of the wafer surface is good.

In the present invention, the pressure-sensitive adhesive layer is energy-ray curable, and the pressure-sensitive adhesive sheet attached to the work surface of a semiconductor wafer or the like is peeled off from the work surface after being irradiated with energy rays and cured with energy rays. is there. Therefore, the pressure-sensitive adhesive sheet is peeled off after the pressure-sensitive adhesive force is lowered, and therefore the peelability is good. Further, as described above, the adhesive sheet after curing is less likely to have adhesive residue when peeled off.
In addition, when using for an adhesive sheet, an adhesive sheet is not limited to a back grind sheet, It can also be used for another use. For example, the pressure-sensitive adhesive sheet may be used as a dicing sheet that holds the wafer when the wafer is diced on the back side of the wafer. In this case, the wafer may have a through-electrode or the like, or may have bumps or other protrusions or irregularities formed on the back surface of the wafer.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

The measurement method and evaluation method in the present invention are as follows.
[Weight average molecular weight (Mw), number average molecular weight (Mn)]
Using a gel permeation chromatograph (product name “HLC-8220”, manufactured by Tosoh Corporation), measurement was performed under the following conditions, and values measured in terms of standard polystyrene were used.
(Measurement condition)
Column: “TSK guard column HXL-H” “TSK gel GMHXL (× 2)” “TSK gel G2000HXL” (both manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Developing solvent: Tetrahydrofuran Flow rate: 1.0 mL / min

[Tensile test]
The tensile test was performed by the method shown below based on JIS K7127: 1999.
In addition, the measurement sample used by the tensile test was produced as follows, and the value obtained by measuring using the measurement sample was set as the breaking stress, breaking elongation, and breaking energy of the adhesive layer.
(Measurement sample preparation)
In the same manner as in Example 1, a pressure-sensitive adhesive layer (thickness 40 μm) was prepared by attaching a polyethylene terephthalate (PET) -based release film (product name “SP-PET 381031”, thickness 38 μm) on both sides to both sides. did. Further, five pressure-sensitive adhesive layers sandwiched between the same release films were prepared in the same procedure. Next, two pressure-sensitive adhesive layers were prepared by peeling off one of the release films, and the surfaces of the pressure-sensitive adhesive layers were laminated to face each other. By repeating this procedure, five pressure-sensitive adhesive layers were laminated to obtain a pressure-sensitive adhesive layer having a thickness of 200 μm sandwiched between two release films.
Using the UV irradiation device (trade name “RAD-2000m / 12” manufactured by Lintec Corporation) for the obtained laminate, the irradiation speed is 15 mm / second, the illuminance is 220 mW / cm, and the light intensity is 500 mJ / cm ² . The pressure-sensitive adhesive layer was cured by irradiating ultraviolet rays under conditions. The cured product of the obtained pressure-sensitive adhesive layer was cut out to 15 mm × 140 mm to obtain a measurement sample.

(Measurement of the breaking stress, breaking elongation, breaking energy of the adhesive layer)
Labels for film tension were attached to 20 mm portions at both ends of the measurement sample, and a sample having a measurement target portion of 15 mm × 100 mm was produced. About this sample, using a tensile tester (manufactured by Shimadzu Corporation, trade name “Autograph AG-IS 1 kN”), the breaking stress and breaking when measured under conditions of 100 mm between chucks and 200 mm / min tensile speed The elongation was measured. In addition, a stress-strain curve was created when measuring the breaking stress and breaking elongation, and the area under the curve was calculated to obtain the breaking energy.

[Cycle tensile test]
A measurement sample was prepared in the same manner as in the tensile test. The tensile test in the cycle tensile test is performed using a tensile tester (manufactured by Shimadzu Corporation, trade name “Autograph AG-IS 1kN”) using the measurement sample, and a tensile speed of 200 mm / min and a release speed of 600 mm. Per minute.
In the cyclic tensile test, the elongation (%) was increased each time the number of elongations increased, and the elongation (strain) and release of the sample were repeated until the sample broke. At that time, the elongation of each cycle was set so as to increase at a constant increase% every time from 0% elongation. Specifically, the percent increase in elongation is 3%, 5%, 8%, 10%, 20%, 30%, 50%, 100%, (100 + 100n)% (n is an integer of 1 or more) From either, the samples were chosen to break in 4-6 cycles. That is, for example, when the percent increase in elongation is 50%, the elongation was increased to 50%, 100%, 150%, 200%, 250%.
In the cyclic tensile test, a stress-strain curve is created for each extension, and the created stress-strain curve is written on the same chart. From the obtained stress-strain curves, between the curves at the same elongation The maximum stress difference (DSmax) was detected.

[Adhesive strength after energy beam irradiation]
The pressure-sensitive adhesive sheets of Examples and Comparative Examples were evenly cut to a width of 25 mm, and temporarily placed on the silicon mirror wafer as the adherend so that the pressure-sensitive adhesive layer was on the adherend side. The pressure-sensitive adhesive sheet was affixed to the adherend by reciprocating a roll of 1 kg in weight on the temporarily placed pressure-sensitive adhesive sheet and applying a load due to its own weight. After pasting, it is stored for 20 minutes in an environment of 23 ° C. and 50% relative humidity, and using a UV irradiation apparatus (trade name “RAD-2000m / 12” manufactured by Lintec Corporation), the illuminance is 220 mW / cm ² and the light intensity is 560 mJ. UV light was irradiated from the pressure-sensitive adhesive sheet side under the conditions of / cm ² and an irradiation speed of 15 mm / second. Next, after leaving it to stand in an environment of 23 ° C. and a relative humidity of 50% for 5 minutes, using a tensile tester (product name “Tensilon” manufactured by Orientec Co., Ltd.), the peeling angle in an environment of 23 ° C. and a relative humidity of 50%. The adhesive strength when the adhesive sheet was peeled was measured under the conditions of 180 ° and a peeling speed of 300 mm / min.
[Adhesive strength before energy beam irradiation]
The measurement was performed in the same manner as above except that the ultraviolet irradiation and the subsequent 5-minute standing were omitted.

[Adhesive residue evaluation]
As an adherend, a wafer with spherical bumps having a bump height of 250 μm, a pitch of 500 μm, and a diameter of 300 μm in plan view (manufactured by Waltz, 8-inch wafer, bump specification Sn / Ag / Cu = 96.5 / 3 / 0.5 A mass%, wafer surface material SiO ₂ ) was prepared.
Using the laminator (product name “RAD-3510F / 12”, manufactured by Lintec Corporation) with the pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples in a state where the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet faces the bump forming surface of the wafer. An adhesive sheet was attached to the wafer. When applying, the laminator laminate table and laminate roll were set at 60 ° C.
After lamination, using a UV irradiation device (trade name “RAD-2000m / 12” manufactured by Lintec Corporation), pressure-sensitive adhesive sheet under the conditions of an illuminance of 220 mW / cm ² , an amount of light of 560 mJ / cm ² , and an irradiation speed of 15 mm / sec. Ultraviolet rays were irradiated from the side.
Next, using a tensile tester (manufactured by Shimadzu Corporation, product name “Autograph AG-IS 1KN”) in an environment of 50 ° C. and 50% relative humidity, the wafer is subjected to a tensile speed of 120 mm / min. The pressure-sensitive adhesive sheet was peeled off.
After peeling, the bump formation surface of the exposed wafer was observed with a digital microscope (manufactured by Keyence Corporation, product name “VHX-1000”) to confirm the presence or absence of adhesive residue. Also, using a scanning electron microscope (manufactured by Keyence Co., Ltd., product name “VE-9800”), the bumps of the wafer were observed to confirm the presence of adhesive residue. The scanning electron microscope was compared with a digital microscope. It is possible to observe a finer adhesive residue.
The adhesive residue was evaluated according to the following evaluation criteria.
A: No adhesive residue was observed with any of the microscopes.
B: No adhesive residue was observed with the digital microscope, but a slight adhesive residue was observed with the scanning electron microscope.
C: Adhesive residue was observed with any microscope.

Next, a substrate with an intermediate layer and an adhesive sheet were prepared by the following procedure. In addition, in the following description, each mass part shows what was diluted with diluents, such as an organic solvent, in solid content conversion.
[Production of substrate with intermediate layer]
Monofunctional urethane acrylate 40 parts by mass, isobornyl acrylate (IBXA) 45 parts by mass, 2-hydroxypropyl acrylate (HPA) 15 parts by mass, pentaerythritol tetrakis (3-mercaptobutyrate) (Showa Denko Co., Ltd., product name “ Karenz MT PE1 ", secondary tetrafunctional thiol-containing compound, solid concentration 100% by mass) 3.5 parts by mass, crosslinking agent 1.8 parts by mass, and 2-hydroxy-2-methyl as a photopolymerization initiator A resin composition for an intermediate layer was prepared by blending 1.0 part by mass of 1-phenyl-propan-1-one (manufactured by BASF, product name “Darocur 1173”, solid content concentration: 100% by mass). This intermediate layer resin composition was applied on a PET-based release film (manufactured by Lintec Corporation, product name “SP-PET381031”, thickness 38 μm) by a fountain die method to form a coating film.
And the ultraviolet-ray was irradiated from the coating-film side, and the semi-hardened layer was formed. In addition, ultraviolet irradiation uses a belt conveyor type ultraviolet irradiation device (product name “ECS-401GGX”, manufactured by Eye Graphics Co., Ltd.) as an ultraviolet irradiation device, and a high pressure mercury lamp (product name, manufactured by Eye Graphics Co., Ltd.) as an ultraviolet ray source. “H04-L41”), and the irradiation conditions were as follows: illuminance of 112 mW / cm ^{2 with} a light wavelength of 365 nm and light amount of 177 mJ / cm ² (measured by the product name “UVPF-A1” manufactured by I-Graphics Co., Ltd.) I went.
On the formed semi-cured layer, a base material made of a PET film (product name “Cosmo Shine A4100”, thickness 50 μm, manufactured by Toyobo Co., Ltd.) is laminated, and further irradiated with UV rays from the PET film side (the above UV irradiation). Using an apparatus and an ultraviolet light source, the irradiation conditions are irradiance of 271 mW / cm ² and light intensity of 1,200 mJ / cm ² ), and the film is completely cured to form an intermediate layer having a thickness of 300 μm on the PET film of the base material. Thus, a base material with an intermediate layer was obtained.

[Example 1]
An acrylic polymer (weight average molecular weight: 600,000) obtained by copolymerizing 97 parts by mass of n-butyl acrylate (BA) and 3 parts by mass of acrylic acid (AA) was prepared as the polymer (A).
An acrylic copolymer (B ′) obtained by copolymerizing 70 parts by mass of n-butyl acrylate (BA) and 30 parts by mass of 2-hydroxyethyl acrylate (2HEA) was added to 2-isocyanate ethyl methacrylate (B ′). An acrylic polymer (weight average molecular weight: 50,000) obtained by adding Showa Denko Co., Ltd. product name “Karenz MOI”) to 2HEA-derived hydroxyl group (100 equivalents) so that the addition rate is 90 equivalents. ) Was prepared as a polymer (B).
To a mixture of 100 parts by mass of the polymer (A) and 50 parts by mass of the polymer (B), 2,2-dimethoxy-1,2-diphenylethane-1-one (manufactured by BASF, as a photopolymerization initiator (E), 14.9 parts by mass of the product name “Irgacure 651”), 4.2 parts by mass of trimethylolpropane adduct tolylene diisocyanate (product name “Coronate L” manufactured by Tosoh Corporation) as a crosslinking agent (D), 0.19 parts by mass of 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (product name “TETRAD-C” manufactured by Mitsubishi Gas Chemical Co., Ltd.) as C) is added, and an organic solvent (methyl ethyl ketone) is added. Was diluted to a solid content concentration of 20% by mass and stirred for 30 minutes to prepare a diluted solution of the pressure-sensitive adhesive composition.
Next, the diluted solution of the prepared pressure-sensitive adhesive composition was applied to a PET-based release film (product name “SP-PET381031”, thickness 38 μm, manufactured by Lintec Corporation), dried by heating at 100 ° C. for 2 minutes, and then released. An adhesive layer having a thickness of 10 μm was formed on the film.
After removing the release film on the base material with the intermediate layer previously prepared and pasting the exposed intermediate layer to the adhesive layer on the release film, the unnecessary portion at the end in the width direction is cut and removed. A pressure-sensitive adhesive sheet consisting of a substrate / intermediate layer / pressure-sensitive adhesive layer / release sheet was obtained. The obtained adhesive sheet and the adhesive layer used for the adhesive sheet were evaluated for breaking stress, breaking elongation, breaking energy, adhesive force, and adhesive residue according to the above evaluation methods. The results are shown in Table 1.

A cycle tensile test was performed on the pressure-sensitive adhesive layer after curing with energy rays used in Example 1. A plurality of stress-strain curves obtained in the cyclic tensile test are shown in FIG. The% increase in the elongation of the test is 50%, and the elongation (%) is 50% for the first time, 100% for the second time, 150% for the third time, 200% for the fourth time, and 200% for the fifth time. 250%.
As shown in FIG. 1, in the cycle tensile test, the sample broke at an elongation of 233% during the fifth elongation, and the stress at that time was 3.26 MPa.
Moreover, the maximum value (DSmax) of the stress difference between the curves at the same elongation that can be read from FIG. 1 was 1.55 MPa, and DSmax was 48% with respect to the stress at break in the cycle tensile test.

Similarly, a cyclic tensile test was performed on the pressure-sensitive adhesive layer before energy beam curing used in Example 1, and a plurality of stress-strain curves obtained in the test are shown in FIG. The percent increase in elongation of the test is 100%, and the set elongation (%) is 100% for the first time, 200% for the second time, 300% for the third time, and 400% for the fourth time.
As shown in FIG. 2, before the energy beam curing, the sample was broken at an elongation of 321%, and the stress at that time was 1.41 MPa.
Moreover, the maximum value (DSmax) of the stress difference between the curves at the same elongation that can be read from FIG. 2 was 0.20 MPa, and DSmax was 14% with respect to the stress at break in the cycle tensile test.

[Example 2]
The amount of 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (product name of Mitsubishi Gas Chemical Co., Ltd., product name “TETRAD-C”) used as the crosslinking agent (C) was changed to 0.38 parts by mass. A pressure-sensitive adhesive sheet was produced in the same procedure as in Example 1 except that.

[Example 3]
The amount of 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (product name “TETRAD-C” manufactured by Mitsubishi Gas Chemical Co., Ltd.) as the crosslinking agent (C) was changed to 0.57 parts by mass. A pressure-sensitive adhesive sheet was produced in the same procedure as in Example 1 except that.

[Comparative Example 1]
For an acrylic copolymer obtained by copolymerizing 90 parts by mass of 2-ethylhexyl acrylate (2EHA) and 10 parts by mass of 4-hydroxybutyl acrylate (4HBA), 2-isocyanatoethyl methacrylate (manufactured by Showa Denko KK) , Product name “Karenz MOI”) was added to a hydroxyl group derived from 4HBA (100 equivalents) so that the addition rate was 65 equivalents to obtain an acrylic polymer (weight average molecular weight: 1,000,000). 3 parts by mass of 1-hydroxycyclohexyl phenyl ketone (product name “Irgacure 184”, manufactured by BASF) is added as a photopolymerization initiator to 100 parts by mass of this acrylic polymer, and trimethylolpropane adduct tolylene diisocyanate (as a crosslinking agent). 1.1 parts by weight of Tosoh Corporation product name “Coronate L”) was added, diluted with an organic solvent (methyl ethyl ketone) to a concentration of 20% by mass, and stirred for 30 minutes to prepare a diluted solution of an adhesive composition. did. Next, the diluted solution of the prepared pressure-sensitive adhesive composition was applied to a PET-based release film (product name “SP-PET381031”, thickness 38 μm, manufactured by Lintec Corporation), dried by heating at 100 ° C. for 2 minutes, and then released. An adhesive layer having a thickness of 10 μm was formed on the film.
After removing the release film on the intermediate layer-prepared substrate previously prepared and pasting the exposed intermediate layer and the pressure-sensitive adhesive layer together, the unnecessary portion at the end in the width direction is cut and removed to form the substrate An adhesive sheet comprising / intermediate layer / adhesive layer / release sheet was obtained. The obtained adhesive sheet and the adhesive layer used for the adhesive sheet were evaluated according to the evaluation method. The results are shown in Table 1.

Moreover, the cycle tension test was implemented with respect to the adhesive layer after energy beam hardening used in the comparative example 1. FIG. FIG. 3 shows a plurality of stress-strain curves obtained in the cycle tensile test. The percent increase in elongation of the test is 5%, and the set elongation (%) is 5% for the first time, 10% for the second time, 15% for the third time, and 20% for the fourth time.
As shown in FIG. 3, in the cyclic tensile test, the sample broke at an elongation of 20% during the fourth elongation, and the stress at that time was 0.94 MPa.
Further, as shown in FIG. 3, the stress-strain curves at the first to fourth elongations all overlapped. Therefore, the maximum value (DSmax) of the stress difference between the curves at the same elongation that can be read from the stress-strain curve was 0 MPa, and 0% with respect to the stress at break in the cyclic tensile test.

The pressure-sensitive adhesive compositions of Examples 1 to 3 contain a polymer (A) and a polymer (B), and a crosslinking agent (C) and a crosslinking agent (D) that cross-link these, respectively, and the polymer (B) Since it had an energy ray polymerizable group (B2), an appropriate double network was formed after the energy ray irradiation. Therefore, as is clear from FIG. 1, the pressure-sensitive adhesive layer exhibits a peculiar hysteresis property and also has a good breaking property, so that the pressure-sensitive adhesive sheet is peeled off from the workpiece (that is, the bump-forming surface of the wafer) onto the workpiece surface. The adhesive residue could be effectively prevented. Moreover, the value of adhesive force became appropriate both before and after irradiation with energy rays. As is clear from FIG. 2, the pressure-sensitive adhesive compositions of Examples exhibited hysteresis properties before irradiation with energy rays, but were insufficient, and a double network was not properly formed.
On the other hand, in Comparative Example 1, since only one polymer and a crosslinking agent for crosslinking the polymer were blended one by one, the breaking characteristics were not good, and the adhesive residue could not be prevented appropriately. .

Claims (10)

A pressure-sensitive adhesive sheet for semiconductor processing comprising a base material, and a pressure-sensitive adhesive layer provided on one surface of the base material and formed of a pressure-sensitive adhesive composition,
The pressure-sensitive adhesive composition has a polymer (A) having a reactive functional group (A1), a reactive functional group (B1) different from the reactive functional group (A1), and an energy beam polymerizable group (B2). A pressure-sensitive adhesive sheet for semiconductor processing, comprising a polymer (B), a crosslinking agent (C) that reacts with the reactive functional group (A1), and a crosslinking agent (D) that reacts with the reactive functional group (B1). The pressure-sensitive adhesive sheet for semiconductor processing according to claim 1, wherein the weight average molecular weight of the polymer (A) is higher than the weight average molecular weight of the polymer (B). The pressure-sensitive adhesive sheet for semiconductor processing according to claim 1 or 2, wherein the polymer (A) and the polymer (B) are both acrylic polymers. The weight average molecular weight of the acrylic polymer constituting the polymer (A) is higher than the weight average molecular weight of the acrylic polymer constituting the polymer (B), and the difference is 200,000 or more. Adhesive sheet. The acrylic polymer constituting the polymer (A) has a weight average molecular weight of 300,000 to 1,000,000, and the acrylic polymer constituting the polymer (B) has a weight average molecular weight of 5,000 to 100,000. The pressure-sensitive adhesive sheet for semiconductor processing according to claim 4. The acrylic polymer that constitutes the polymer (A) contains a structural unit derived from the functional monomer (a1) having a reactive functional group (A1) and a structural unit derived from the alkyl (meth) acrylate (a2). The pressure-sensitive adhesive sheet for semiconductor processing according to any one of claims 3 to 5, which is a polymer (A '). Acrylic copolymer in which the acrylic polymer constituting the polymer (B) contains a structural unit derived from the functional monomer (b1) having a reactive functional group (B1) and a structural unit derived from the alkyl (meth) acrylate (b2). The reaction product obtained by reacting an energy beam polymerizable group-containing compound (S) having an energy beam polymerizable group (B2) with a part of the reactive functional group (B1) of the polymer (B '). The pressure-sensitive adhesive sheet for semiconductor processing according to any one of 3 to 6. The pressure-sensitive adhesive sheet for semiconductor processing according to any one of claims 1 to 7, wherein the reactive functional group (A1) is a carboxy group and the reactive functional group (B1) is a hydroxyl group. The pressure-sensitive adhesive sheet for semiconductor processing according to claim 8, wherein the crosslinking agent (C) is an epoxy-based crosslinking agent and the crosslinking agent (D) is an isocyanate-based crosslinking agent. The content of the crosslinking agent (D) is larger than the content of the crosslinking agent (C) on a mass basis in the pressure-sensitive adhesive composition, and the content of the crosslinking agent (D) in the pressure-sensitive adhesive composition is 100% of the polymer (B). The pressure-sensitive adhesive sheet for semiconductor processing according to any one of claims 1 to 9, wherein the pressure-sensitive adhesive sheet is 2 to 20 parts by mass with respect to part by mass.

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