WO2017038914A1

WO2017038914A1 - Adhesive sheet

Info

Publication number: WO2017038914A1
Application number: PCT/JP2016/075601
Authority: WO
Inventors: 高野　健; 和浩菊池; 貴志杉野
Original assignee: リンテック株式会社
Priority date: 2015-09-01
Filing date: 2016-09-01
Publication date: 2017-03-09
Also published as: KR102549654B1; TW201726852A; CN107922810A; TWI712667B; JPWO2017038914A1; CN107922810B; JP6220481B2; KR20180048676A

Abstract

This adhesive sheet (10) is used at the time of sealing a semiconductor element on the adhesive sheet, and comprises a substrate (11) and an adhesive agent layer (12). The adhesive agent layer (12) includes an acrylic copolymer including 2-ethylhexyl acrylate as a main monomer.

Description

Adhesive sheet

The present invention relates to an adhesive sheet.

Various properties are required for adhesive sheets used in the manufacturing process of semiconductor devices. In recent years, pressure-sensitive adhesive sheets are required not to contaminate devices, members, and adherends used in the manufacturing process even after a process in which high temperature conditions are imposed. Furthermore, after peeling off the pressure-sensitive adhesive sheet at room temperature after the process under high temperature conditions, it is also required that there are few problems (so-called adhesive residue) that the pressure-sensitive adhesive remains on the adherend and the like and that the peeling force is small.

For example, Patent Document 1 discloses a mask sheet for suppressing adhesive residue of an adhesive and stably producing a QFN (Quad Flat Non-lead) semiconductor package. In Patent Document 1, a mask sheet is prepared using a specific heat-resistant film and a silicone-based pressure-sensitive adhesive to withstand an environment of 150 to 180 ° C. for 1 to 6 hours in a die attach process and a resin sealing process. It is stated that you get.

JP 2002-275435 A

However, since the heat-resistant film such as polyimide film and the silicone-based adhesive used for the production of the mask sheet described in Patent Document 1 are expensive, the mask sheet is used for some applications such as a QFN package. Limited. Moreover, when using a silicone type adhesive, after peeling a mask sheet, low molecular weight siloxane may remain on a to-be-adhered body surface, and there exists a possibility of producing an electrical contact failure. Furthermore, the residue of a silicone type adhesive is water-repellent and oil-repellent. For this reason, the plating suitability of the electrical connection portion may be reduced, or the adhesive strength of the protective material on the circuit surface may be reduced, resulting in a decrease in package reliability such as an increase in electrical resistance and a failure due to the occurrence of cracks.
In addition, various studies have been made on adhesives with little adhesive residue, but the adhesive strength becomes excessively high after a process in which high temperature conditions are imposed, which may make it difficult to peel off the adhesive sheet.

An object of the present invention is to provide a pressure-sensitive adhesive sheet that is easy to peel off from an adherend and has little adhesive residue even after a process subject to high temperature conditions.

According to one aspect of the present invention, there is provided a pressure-sensitive adhesive sheet used for sealing a semiconductor element on a pressure-sensitive adhesive sheet, comprising a base material and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is an acrylic sheet. There is provided a pressure-sensitive adhesive sheet containing an acrylic copolymer containing 2-ethylhexyl acid as a main monomer.

In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, after heating at 100 ° C. and 30 minutes, followed by heating at 180 ° C. and 30 minutes, the pressure-sensitive adhesive force at room temperature with respect to the copper foil of the pressure-sensitive adhesive layer is 0.7N / 25mm or more and 2.0N / 25mm or less is preferable.

In the pressure-sensitive adhesive sheet according to one aspect of the present invention, the pressure-sensitive adhesive layer is obtained by crosslinking a composition containing at least the acrylic copolymer and a crosslinking agent containing a compound having an isocyanate group as a main component. The adhesive preferably contains at least an adhesive, and the cross-linking agent mainly composed of the compound having an isocyanate group preferably has an isocyanurate ring.

In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the proportion of the copolymer component derived from 2-ethylhexyl acrylate in the acrylic copolymer is preferably 50% by mass or more and 95% by mass or less.

In the pressure-sensitive adhesive sheet according to an aspect of the present invention, the acrylic copolymer further includes a copolymer component derived from acrylic acid, and the copolymer component derived from the acrylic acid in the acrylic copolymer. The ratio is preferably 1% by mass or less.

In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the thickness of the pressure-sensitive adhesive layer is preferably 5 μm or more and 60 μm or less.

According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that easily peels from an adherend and has little adhesive residue even after undergoing a process in which high temperature conditions are imposed.

It is a section schematic diagram of the adhesive sheet concerning a first embodiment. It is a figure explaining a part of manufacturing process of the semiconductor device using the adhesive sheet which concerns on 1st embodiment. It is a figure explaining a part of manufacturing process of the semiconductor device using the adhesive sheet which concerns on 1st embodiment. It is a figure explaining a part of manufacturing process of the semiconductor device using the adhesive sheet which concerns on 1st embodiment. It is a figure explaining a part of manufacturing process of the semiconductor device using the adhesive sheet which concerns on 1st embodiment. It is a figure explaining a part of manufacturing process of the semiconductor device using the adhesive sheet which concerns on 1st embodiment.

[First embodiment]
(Adhesive sheet)
FIG. 1 shows a schematic cross-sectional view of the pressure-sensitive adhesive sheet 10 of the present embodiment.
The pressure-sensitive adhesive sheet 10 has a base material 11 and a pressure-sensitive adhesive layer 12. On the pressure-sensitive adhesive layer 12, a release sheet RL is laminated as shown in FIG. The shape of the pressure-sensitive adhesive sheet 10 can take any shape such as a sheet shape, a tape shape, and a label shape.

(Adhesive layer)
The pressure-sensitive adhesive layer 12 according to this embodiment includes a pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition contains an acrylic copolymer having 2-ethylhexyl acrylate as a main monomer. In this specification, 2-ethylhexyl acrylate is the main monomer, and the ratio of the mass of the copolymer component derived from 2-ethylhexyl acrylate to the total mass of the acrylic copolymer is 50% by mass or more. Means. In the present embodiment, the proportion of the copolymer component derived from 2-ethylhexyl acrylate in the acrylic copolymer is preferably 50% by mass or more and 95% by mass or less, and 60% by mass or more and 95% by mass or less. It is more preferable that it is 80 mass% or more and 95 mass% or less, and it is still more preferable that it is 85 mass% or more and 93 mass% or less. If the proportion of the copolymer component derived from 2-ethylhexyl acrylate is 50% by mass or more, the adhesive strength does not become too high after heating, and the adhesive sheet is more easily peeled off from the adherend, and 80% by mass or more. If it is, it will become still easier to peel. If the proportion of the copolymer component derived from 2-ethylhexyl acrylate is 95% by mass or less, the initial adhesive force is insufficient and the substrate is deformed during heating, or the adhesive sheet is peeled off from the adherend due to the deformation. Can be prevented.

The type and number of copolymer components other than 2-ethylhexyl acrylate in the acrylic copolymer are not particularly limited. For example, as the second copolymer component, a functional group-containing monomer having a reactive functional group is preferable. As a reactive functional group of a 2nd copolymer component, when using the crosslinking agent mentioned later, it is preferable that it is a functional group which can react with the said crosslinking agent. This reactive functional group is preferably at least one substituent selected from the group consisting of, for example, a carboxyl group, a hydroxyl group, an amino group, a substituted amino group, and an epoxy group. These substituents are more preferable, and a carboxyl group is still more preferable.

Examples of the monomer having a carboxyl group (carboxyl group-containing monomer) include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among the carboxyl group-containing monomers, acrylic acid is preferable from the viewpoint of reactivity and copolymerization. A carboxyl group-containing monomer may be used independently and may be used in combination of 2 or more type.

Examples of the monomer having a hydroxyl group (hydroxyl group-containing monomer) include, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth) acrylic acid 2 And (meth) acrylic acid hydroxyalkyl esters such as hydroxybutyl, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among the hydroxyl group-containing monomers, 2-hydroxyethyl (meth) acrylate is preferred from the viewpoint of hydroxyl reactivity and copolymerization. A hydroxyl-containing monomer may be used independently and may be used in combination of 2 or more type. In the present specification, “(meth) acrylic acid” is a notation used to represent both “acrylic acid” and “methacrylic acid”, and the same applies to other similar terms.

Examples of the acrylate ester having an epoxy group include glycidyl acrylate and glycidyl methacrylate.

Examples of other copolymer components in the acrylic copolymer include (meth) acrylic acid alkyl esters having an alkyl group with 2 to 20 carbon atoms. Examples of the (meth) acrylic acid alkyl ester include, for example, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth) acrylate, and (meth) acrylic acid n. -Hexyl, 2-ethylhexyl methacrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, and ( Examples thereof include stearyl methacrylate. Among these (meth) acrylic acid alkyl esters, (meth) acrylic acid esters having an alkyl group with 2 to 4 carbon atoms are preferred, and n-butyl (meth) acrylate is more preferred from the viewpoint of further improving the adhesiveness. preferable. The (meth) acrylic acid alkyl ester may be used alone or in combination of two or more.

Examples of other copolymer components in the acrylic copolymer include, for example, alkoxyalkyl group-containing (meth) acrylic acid ester, (meth) acrylic acid ester having an aliphatic ring, and (meth) acrylic acid having an aromatic ring. A copolymer component derived from at least one monomer selected from the group consisting of an ester, a non-crosslinkable acrylamide, a (meth) acrylic acid ester having a non-crosslinkable tertiary amino group, vinyl acetate, and styrene; Can be mentioned.
Examples of the alkoxyalkyl group-containing (meth) acrylic acid ester include methoxymethyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate, and ethoxyethyl (meth) acrylate. .
Examples of the (meth) acrylic acid ester having an aliphatic ring include cyclohexyl (meth) acrylate.
Examples of the (meth) acrylic acid ester having an aromatic ring include phenyl (meth) acrylate.
Examples of non-crosslinkable acrylamides include acrylamide and methacrylamide.
Examples of the (meth) acrylic acid ester having a non-crosslinkable tertiary amino group include (meth) acrylic acid (N, N-dimethylamino) ethyl and (meth) acrylic acid (N, N-dimethylamino). Propyl.
These monomers may be used independently and may be used in combination of 2 or more type.

In the present embodiment, a carboxyl group-containing monomer or a hydroxyl group-containing monomer is preferable as the second copolymer component, and acrylic acid is more preferable. When the acrylic copolymer includes a copolymer component derived from 2-ethylhexyl acrylate and a copolymer component derived from acrylic acid, the copolymer component derived from acrylic acid occupies the total mass of the acrylic copolymer. The mass ratio is preferably 1% by mass or less, and more preferably 0.1% by mass or more and 0.5% by mass or less. If the ratio of acrylic acid is 1 mass% or less, when an adhesive composition contains a crosslinking agent, crosslinking of the acrylic copolymer can be prevented from proceeding too quickly.

The acrylic copolymer may contain a copolymer component derived from two or more kinds of functional group-containing monomers. For example, the acrylic copolymer may be a ternary copolymer, preferably an acrylic copolymer obtained by copolymerizing 2-ethylhexyl acrylate, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer, The carboxyl group-containing monomer is preferably acrylic acid, and the hydroxyl group-containing monomer is preferably 2-hydroxyethyl acrylate. The ratio of the copolymer component derived from 2-ethylhexyl acrylate in the acrylic copolymer is 80% by mass or more and 95% by mass or less, and the ratio of the mass of the copolymer component derived from acrylic acid is 1% by mass or less. And the balance is preferably a copolymer component derived from 2-hydroxyethyl acrylate.

The weight average molecular weight (Mw) of the acrylic copolymer is preferably from 300,000 to 2,000,000, more preferably from 600,000 to 1,500,000, and even more preferably from 800,000 to 1,200,000. preferable. If the weight average molecular weight Mw of the acrylic copolymer is 300,000 or more, the acrylic copolymer can be peeled without a residue of the adhesive on the adherend. When the weight average molecular weight Mw of the acrylic copolymer is 2 million or less, it can be reliably attached to the adherend.
The weight average molecular weight Mw of the acrylic copolymer is a standard polystyrene equivalent value measured by a gel permeation chromatography (GPC) method.

The acrylic copolymer can be produced according to a conventionally known method using the above-mentioned various raw material monomers.

The form of copolymerization of the acrylic copolymer is not particularly limited, and any of a block copolymer, a random copolymer, and a graft copolymer may be used.
In the present embodiment, the content of the acrylic copolymer in the pressure-sensitive adhesive composition is preferably 40% by mass or more and 90% by mass or less, and more preferably 50% by mass or more and 90% by mass or less.

The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer 12 preferably contains at least a pressure-sensitive adhesive obtained by crosslinking a composition containing a crosslinking agent in addition to the above-mentioned acrylic copolymer. The pressure-sensitive adhesive composition is also preferably substantially composed of a pressure-sensitive adhesive obtained by cross-linking the above-mentioned acrylic copolymer and the cross-linking agent as described above. Here, “substantially” means that it is composed only of the pressure-sensitive adhesive except for a small amount of impurities that are inevitably mixed in the pressure-sensitive adhesive.

In the present embodiment, examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, a metal chelate crosslinking agent, an amine crosslinking agent, and an amino resin crosslinking agent. These cross-linking agents may be used alone or in combination of two or more.
In the present embodiment, from the viewpoint of improving the heat resistance and adhesive strength of the pressure-sensitive adhesive layer 12, among these crosslinking agents, a crosslinking agent (isocyanate-based crosslinking agent) containing a compound having an isocyanate group as a main component is preferable. Examples of the isocyanate crosslinking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4′-diisocyanate, Polyvalent isocyanates such as diphenylmethane-2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and lysine isocyanate Compounds.
Further, the polyvalent isocyanate compound may be a trimethylolpropane adduct type modified product of the above compound, a burette type modified product reacted with water, or an isocyanurate type modified product having an isocyanurate ring.
In this specification, the crosslinking agent containing a compound having an isocyanate group as a main component means that the ratio of the mass of the compound having an isocyanate group to the total mass of the components constituting the crosslinking agent is 50% by mass or more. means.

In the present embodiment, the content of the crosslinking agent in the pressure-sensitive adhesive composition is preferably 0.1 parts by mass or more and 20 parts by mass or less, more preferably 1 part by mass or more with respect to 100 parts by mass of the acrylic copolymer. 15 parts by mass or less, more preferably 5 parts by mass or more and 10 parts by mass or less. If content of the crosslinking agent in an adhesive composition is in such a range, the adhesiveness of the adhesive layer 12 and the base material 11 can be improved, and the adhesive characteristic is stabilized after manufacture of an adhesive sheet. The curing period for making it possible can be shortened.

In the present embodiment, from the viewpoint of heat resistance of the pressure-sensitive adhesive layer 12, the isocyanate-based crosslinking agent is more preferably a compound having an isocyanurate ring (isocyanurate-type modified product). The compound having an isocyanurate ring is preferably blended in an amount of 0.7 to 1.5 equivalents with respect to the hydroxyl equivalent of the acrylic copolymer. If the compounding quantity of the compound which has an isocyanurate ring is 0.7 equivalent or more, the adhesive strength will not become too high after heating, the adhesive sheet will be easily peeled off, and the adhesive residue can be reduced. If the compounding quantity of the compound which has an isocyanurate ring is 1.5 equivalent or less, it can prevent that an initial stage adhesive force becomes low too much, or can prevent a sticking fall.

When the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer 12 in the present embodiment includes a cross-linking agent, the pressure-sensitive adhesive composition preferably further includes a cross-linking accelerator. The crosslinking accelerator is preferably selected and used as appropriate according to the type of the crosslinking agent. For example, when the pressure-sensitive adhesive composition contains a polyisocyanate compound as a crosslinking agent, it is preferable to further contain an organic metal compound-based crosslinking accelerator such as an organic tin compound.

The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer 12 preferably contains a reactive pressure-sensitive adhesive aid. Examples of the reactive adhesion assistant include a polybutadiene resin having a reactive functional group and a hydrogenated product of a polybutadiene resin having a reactive functional group. The reactive functional group possessed by the reactive adhesive aid is one or more functional groups selected from the group consisting of hydroxyl groups, isocyanate groups, amino groups, oxirane groups, acid anhydride groups, alkoxy groups, acryloyl groups, and methacryloyl groups. It is preferably a group. When the pressure-sensitive adhesive composition contains a reactive pressure-sensitive adhesive aid, the adhesive residue when the pressure-sensitive adhesive sheet 10 is peeled off from the adherend can be reduced.

In the present embodiment, the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer 12 may contain other components as long as the effects of the present invention are not impaired. Other components that can be included in the pressure-sensitive adhesive composition include, for example, organic solvents, flame retardants, tackifiers, ultraviolet absorbers, antioxidants, antiseptics, antifungal agents, plasticizers, antifoaming agents, and wetting And a sex modifier.

More specific examples of the pressure-sensitive adhesive composition according to this embodiment include the following pressure-sensitive adhesive compositions, but the present invention is not limited to such examples.
An example of the pressure-sensitive adhesive composition according to this embodiment includes an acrylic copolymer and a crosslinking agent, and the acrylic copolymer is at least 2-ethylhexyl acrylate, a hydroxyl group-containing monomer, and a carboxyl group-containing monomer. A pressure-sensitive adhesive composition in which the crosslinking agent is an isocyanate-based crosslinking agent.
As an example of the pressure-sensitive adhesive composition according to this embodiment, an acrylic copolymer and a crosslinking agent are included, and the acrylic copolymer is at least 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and acrylic. A pressure-sensitive adhesive composition, which is an acrylic copolymer obtained by copolymerizing an acid, and the crosslinking agent is an isocyanate crosslinking agent.
In these examples of the pressure-sensitive adhesive composition according to this embodiment, the proportion of the copolymer component derived from 2-ethylhexyl acrylate in the acrylic copolymer is 80% by mass or more and 95% by mass or less. The proportion of the mass of the copolymer component derived from the group-containing monomer is preferably 1% by mass or less, and the remainder is preferably another copolymer component. The other copolymer component is a copolymer derived from a hydroxyl group-containing monomer. It preferably contains a polymer component.
In these examples of the pressure-sensitive adhesive composition according to this embodiment, the isocyanate-based crosslinking agent is preferably a compound having an isocyanurate ring, and more preferably an isocyanurate-type modified product of hexamethylene diisocyanate. .

The thickness of the pressure-sensitive adhesive layer 12 is appropriately determined according to the use of the pressure-sensitive adhesive sheet 10. In the present embodiment, the thickness of the pressure-sensitive adhesive layer 12 is preferably 5 μm to 60 μm, and more preferably 5 μm to 50 μm. If the thickness of the pressure-sensitive adhesive layer 12 is too thin, the pressure-sensitive adhesive layer 12 may not follow the irregularities on the circuit surface of the semiconductor chip, and a gap may be generated. For example, an interlayer insulating material and a sealing resin may enter the gap, and the wiring connection electrode pad on the chip circuit surface may be blocked. When the thickness of the pressure-sensitive adhesive layer 12 is 5 μm or more, the pressure-sensitive adhesive layer 12 easily follows the unevenness of the chip circuit surface, and the generation of a gap can be prevented. If the thickness of the pressure-sensitive adhesive layer 12 is too thick, the semiconductor chip sinks into the pressure-sensitive adhesive layer, and there is a risk that a step between the semiconductor chip portion and the resin portion that seals the semiconductor chip occurs. If such a step occurs, the wiring may be disconnected during rewiring. If the thickness of the pressure-sensitive adhesive layer 12 is 60 μm or less, a step is hardly generated.

(Base material)
The substrate 11 is a member that supports the pressure-sensitive adhesive layer 12.
The base material 11 has a first surface 11a and a second surface 11b opposite to the first surface 11a. In the adhesive sheet 10 of this embodiment, the adhesive layer 12 is laminated | stacked on the 1st surface 11a. In order to improve the adhesion between the substrate 11 and the pressure-sensitive adhesive layer 12, the first surface 11a may be subjected to at least one surface treatment such as primer treatment, corona treatment, and plasma treatment. An adhesive may be applied to the first surface 11a of the substrate 11 to perform an adhesion treatment. Examples of the pressure-sensitive adhesive used for the pressure-sensitive adhesive treatment of the substrate include acrylic, rubber-based, silicone-based, and urethane-based pressure-sensitive adhesives.

The thickness of the substrate 11 is preferably 10 μm or more and 500 μm or less, more preferably 15 μm or more and 300 μm or less, and further preferably 20 μm or more and 250 μm or less.

As the substrate 11, for example, a sheet material such as a synthetic resin film can be used. Examples of synthetic resin films include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film. , Polyurethane film, ethylene vinyl acetate copolymer film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film, and polyimide film Etc. In addition, examples of the substrate 11 include these cross-linked films and laminated films.

The base material 11 preferably includes a polyester-based resin, and more preferably includes a material having a polyester-based resin as a main component. In this specification, the material having a polyester-based resin as a main component means that the ratio of the mass of the polyester-based resin to the total mass of the material constituting the substrate is 50% by mass or more.
The polyester resin is, for example, any resin selected from the group consisting of polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polybutylene naphthalate resin, and copolymer resins of these resins. Is preferred, and polyethylene terephthalate resin is more preferred.
As the base material 11, a polyethylene terephthalate film and a polyethylene naphthalate film are preferable, and a polyethylene terephthalate film is more preferable. The oligomers contained in the polyester film are derived from polyester-forming monomers, dimers, trimers, and the like.

(Peeling sheet)
The release sheet RL is not particularly limited. For example, from the viewpoint of ease of handling, the release sheet RL preferably includes a release substrate and a release agent layer formed by applying a release agent on the release substrate. Moreover, the release sheet RL may include a release agent layer only on one side of the release substrate, or may include a release agent layer on both sides of the release substrate. Examples of the release substrate include a paper substrate, a laminated paper obtained by laminating a thermoplastic resin such as polyethylene on the paper substrate, and a plastic film. Examples of the paper substrate include glassine paper, coated paper, and cast coated paper. Examples of the plastic film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene. Examples of the release agent include olefin resins, rubber elastomers (eg, butadiene resins, isoprene resins, etc.), long chain alkyl resins, alkyd resins, fluorine resins, and silicone resins.

The thickness of the release sheet RL is not particularly limited. The thickness of the release sheet RL is usually 20 μm or more and 200 μm or less, and preferably 25 μm or more and 150 μm or less.
The thickness of the release agent layer is not particularly limited. When a release agent layer is formed by applying a solution containing a release agent, the thickness of the release agent layer is preferably 0.01 μm or more and 2.0 μm or less, and preferably 0.03 μm or more and 1.0 μm or less. More preferred.
When a plastic film is used as the peeling substrate, the thickness of the plastic film is preferably 3 μm or more and 50 μm or less, and more preferably 5 μm or more and 40 μm or less.

The pressure-sensitive adhesive sheet 10 according to this embodiment preferably exhibits the following adhesive strength after heating. First, the pressure-sensitive adhesive sheet 10 is attached to an adherend (copper foil), heated under conditions of 100 ° C. and 30 minutes, and subsequently heated under conditions of 180 ° C. and 30 minutes, and then the copper foil of the pressure-sensitive adhesive layer 12 It is preferable that the adhesive force at room temperature is 0.7 N / 25 mm or more and 2.0 N / 25 mm or less. If the adhesive strength after such heating is 0.7 N / 25 mm or more, the adhesive sheet 10 can be prevented from peeling off from the adherend when the substrate and the adherend are deformed by heating. Moreover, if the adhesive force after a heating is 2.0 N / 25mm or less, peeling force will not become high too much and it will be easy to peel the adhesive sheet 10 from a to-be-adhered body. In this specification, room temperature is a temperature of 22 ° C. or higher and 24 ° C. or lower. In this specification, the adhesive strength is a value measured by a 180 ° peeling method at a pulling speed of 300 mm / min and a width of 25 mm of the adhesive sheet.

(Method for producing adhesive sheet)
The manufacturing method of the adhesive sheet 10 is not particularly limited.
For example, the adhesive sheet 10 is manufactured through the following processes. First, an adhesive composition is applied on the first surface 11a of the substrate 11 to form a coating film. Next, this coating film is dried to form the pressure-sensitive adhesive layer 12. Then, release sheet RL is stuck so that adhesive layer 12 may be covered.
Moreover, as another manufacturing method of the adhesive sheet 10, it manufactures through the following processes. First, an adhesive composition is applied on the release sheet RL to form a coating film. Next, the coating film is dried to form the pressure-sensitive adhesive layer 12, and the first surface 11 a of the substrate 11 is bonded to the pressure-sensitive adhesive layer 12.

When the pressure-sensitive adhesive composition is applied to form the pressure-sensitive adhesive layer 12, it is preferable to prepare and use a coating liquid by diluting the pressure-sensitive adhesive composition with an organic solvent. Examples of the organic solvent include toluene, ethyl acetate, and methyl ethyl ketone. The method for applying the coating liquid is not particularly limited. Examples of the coating method include spin coating, spray coating, bar coating, knife coating, roll knife coating, roll coating, blade coating, die coating, and gravure coating.
In order to prevent the organic solvent and the low-boiling component from remaining in the pressure-sensitive adhesive layer 12, it is preferable to apply the coating liquid to the substrate 11 or the release sheet RL, and then heat and dry the coating film. Moreover, when a crosslinking agent is mix | blended with the adhesive composition, it is preferable to heat a coating film also in order to advance a crosslinking reaction and to improve cohesion force.

(Use of adhesive sheet)
The pressure-sensitive adhesive sheet 10 is used when sealing a semiconductor element. The pressure-sensitive adhesive sheet 10 is not mounted on a metal lead frame, and is preferably used when sealing a semiconductor element that is stuck on the pressure-sensitive adhesive sheet 10. Specifically, the pressure-sensitive adhesive sheet 10 is not used when sealing a semiconductor element mounted on a metal lead frame, but seals a semiconductor element that is stuck to the pressure-sensitive adhesive layer 12. Preferably used. As a form of packaging a semiconductor element without using a metal lead frame, a panel scale package (Panel Scale Package; PSP) and a wafer level package (Wafer Level Package; WLP) can be cited.
The pressure-sensitive adhesive sheet 10 includes a step of attaching a frame member in which a plurality of openings are formed to the pressure-sensitive adhesive sheet 10; a step of attaching a semiconductor chip to the pressure-sensitive adhesive layer 12 exposed at the openings of the frame member; It is preferably used in a process having a step of covering the semiconductor chip with a sealing resin and a step of thermosetting the sealing resin.

(Method for manufacturing semiconductor device)
A method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet 10 according to this embodiment will be described.
2A to 2E are schematic views illustrating the method for manufacturing the semiconductor device according to the present embodiment.
The manufacturing method of the semiconductor device according to the present embodiment includes a step of attaching the frame member 20 in which a plurality of openings 21 are formed on the adhesive sheet 10 (adhesive sheet attaching step), and an opening 21 of the frame member 20. A step of bonding the semiconductor chip CP to the exposed adhesive layer 12 (bonding step), a step of covering the semiconductor chip CP with the sealing resin 30 (sealing step), and a step of thermosetting the sealing resin 30 ( A thermosetting step) and a step of peeling the pressure-sensitive adhesive sheet 10 (peeling step) are carried out after thermosetting. As needed, you may implement the process (reinforcing member sticking process) of sticking the reinforcement member 40 to the sealing body 50 sealed with the sealing resin 30 after the thermosetting process. Each step will be described below.

-Adhesive sheet sticking process The schematic explaining the process of sticking the frame member 20 to the adhesive layer 12 of the adhesive sheet 10 is shown by FIG. 2A. In addition, when peeling sheet RL is affixed on the adhesive sheet 10, peeling sheet RL is peeled previously.
The frame member 20 according to the present embodiment is formed in a lattice shape and has a plurality of openings 21. The frame member 20 is preferably formed of a material having heat resistance. Examples of the material of the frame member 20 include metals such as copper and stainless steel, and heat resistant resins such as polyimide resin and glass epoxy resin.
The opening 21 is a hole that penetrates the front and back surfaces of the frame member 20. The shape of the opening 21 is not particularly limited as long as the semiconductor chip CP can be accommodated in the frame. The depth of the hole of the opening 21 is not particularly limited as long as the semiconductor chip CP can be accommodated.

Bonding Step FIG. 2B shows a schematic diagram for explaining a step of attaching the semiconductor chip CP to the adhesive layer 12.
When the pressure-sensitive adhesive sheet 10 is adhered to the frame member 20, the pressure-sensitive adhesive layer 12 is exposed in each opening 21 according to the shape of the opening 21. The semiconductor chip CP is adhered to the adhesive layer 12 of each opening 21. The semiconductor chip CP is stuck so that its circuit surface is covered with the adhesive layer 12.

The semiconductor chip CP is manufactured, for example, by performing a back grinding process for grinding the back surface of the semiconductor wafer on which the circuit is formed and a dicing process for dividing the semiconductor wafer into individual pieces. In the dicing step, a semiconductor chip CP (semiconductor element) is obtained by sticking the semiconductor wafer to the adhesive layer of the dicing sheet and separating the semiconductor wafer using a cutting means such as a dicing saw.
The dicing apparatus is not particularly limited, and a known dicing apparatus can be used. Also, the dicing conditions are not particularly limited. Note that a laser dicing method or a stealth dicing method may be used instead of the dicing method using a dicing blade.

After the dicing process, an expanding process may be performed in which the dicing sheet is extended to widen the interval between the plurality of semiconductor chips CP. By carrying out the expanding step, the semiconductor chip CP can be picked up using a conveying means such as a collet. Further, by performing the expanding process, the adhesive force of the adhesive layer of the dicing sheet is reduced, and the semiconductor chip CP can be easily picked up.
When the energy ray polymerizable compound is blended in the adhesive composition of the dicing sheet or the adhesive layer, the energy ray polymerizable compound is applied to the adhesive layer by irradiating the adhesive layer from the substrate side of the dicing sheet. Harden. When the energy ray polymerizable compound is cured, the cohesive force of the adhesive layer is increased, and the adhesive force of the adhesive layer can be reduced. Examples of the energy rays include ultraviolet rays (UV) and electron beams (EB), and ultraviolet rays are preferable. The energy beam irradiation may be performed at any stage after the semiconductor wafer is pasted and before the semiconductor chip is peeled off (pickup). For example, the energy beam may be irradiated before or after dicing, or the energy beam may be irradiated after the expanding step.

-Sealing process and thermosetting process The schematic diagram explaining the process of sealing the semiconductor chip CP and the frame member 20 which were affixed on the adhesive sheet 10 is shown by FIG. 2C.
The material of the sealing resin 30 is a thermosetting resin, and examples thereof include an epoxy resin. The epoxy resin used as the sealing resin 30 may include, for example, a phenol resin, an elastomer, an inorganic filler, a curing accelerator, and the like.
The method for covering the semiconductor chip CP and the frame member 20 with the sealing resin 30 is not particularly limited.
In the present embodiment, an embodiment using a sheet-like sealing resin 30 will be described as an example. The sheet-shaped sealing resin 30 is placed so as to cover the semiconductor chip CP and the frame member 20, and the sealing resin 30 is heated and cured to form the sealing resin layer 30A. In this way, the semiconductor chip CP and the frame member 20 are embedded in the sealing resin layer 30A. When the sheet-shaped sealing resin 30 is used, it is preferable to seal the semiconductor chip CP and the frame member 20 by a vacuum laminating method. By this vacuum laminating method, it is possible to prevent a gap from being generated between the semiconductor chip CP and the frame member 20. The temperature condition range for heating by the vacuum laminating method is, for example, 80 ° C. or more and 120 ° C. or less.

In the sealing step, a laminated sheet in which the sheet-shaped sealing resin 30 is supported by a resin sheet such as polyethylene terephthalate may be used. In this case, after the laminated sheet is placed so as to cover the semiconductor chip CP and the frame member 20, the resin sheet may be peeled off from the sealing resin 30 and the sealing resin 30 may be heated and cured. Examples of such a laminated sheet include an ABF film (manufactured by Ajinomoto Fine Techno Co., Ltd.).

As a method for sealing the semiconductor chip CP and the frame member 20, a transfer molding method may be employed. In this case, for example, the semiconductor chip CP and the frame member 20 adhered to the pressure-sensitive adhesive sheet 10 are accommodated inside the mold of the sealing device. A fluid resin material is injected into the mold to cure the resin material. In the case of the transfer mold method, the heating and pressure conditions are not particularly limited. As an example of normal conditions in the transfer molding method, a temperature of 150 ° C. or higher and a pressure of 4 MPa to 15 MPa are maintained for 30 seconds to 300 seconds. Thereafter, the pressure is released, the cured product is taken out from the sealing device, and left in an oven, and a temperature of 150 ° C. or higher is maintained for 2 hours to 15 hours. In this way, the semiconductor chip CP and the frame member 20 are sealed.

When the sheet-shaped sealing resin 30 is used in the above-described sealing process, the first heat pressing process may be performed before the process of thermosetting the sealing resin 30 (thermosetting process). In the first heating press step, the semiconductor chip CP and the pressure-sensitive adhesive sheet 10 with the frame member 20 covered with the sealing resin 30 are sandwiched by plate members from both sides, and pressed under conditions of a predetermined temperature, time, and pressure. . By performing the first heat pressing step, the sealing resin 30 is easily filled into the gap between the semiconductor chip CP and the frame member 20. Moreover, the unevenness | corrugation of 30 A of sealing resin layers comprised with the sealing resin 30 can also be planarized by implementing a heat press process. As the plate member, for example, a metal plate such as stainless steel can be used.

When the pressure-sensitive adhesive sheet 10 is peeled after the thermosetting step, the semiconductor chip CP and the frame member 20 sealed with the sealing resin 30 are obtained. Hereinafter, this may be referred to as a sealing body 50.

-Reinforcing member sticking process The schematic diagram explaining the process of sticking the reinforcing member 40 to the sealing body 50 is shown by FIG. 2D.
After the adhesive sheet 10 is peeled off, a rewiring process and a bumping process for forming a rewiring layer on the exposed circuit surface of the semiconductor chip CP are performed. In order to improve the handleability of the sealing body 50 in such a rewiring process and a bumping process, a process (reinforcing member attaching process) of attaching the reinforcing member 40 to the sealing body 50 is performed as necessary. May be. When implementing a reinforcement member sticking process, it is preferable to carry out before peeling the adhesive sheet 10. FIG. As illustrated in FIG. 2D, the sealing body 50 is supported in a state of being sandwiched between the adhesive sheet 10 and the reinforcing member 40.

In the present embodiment, the reinforcing member 40 includes a heat-resistant reinforcing plate 41 and a heat-resistant adhesive layer 42. Examples of the reinforcing plate 41 include a plate-like member containing a heat resistant resin such as a glass epoxy resin. The adhesive layer 42 adheres the reinforcing plate 41 and the sealing body 50. The adhesive layer 42 is appropriately selected according to the material of the reinforcing plate 41 and the sealing resin layer 30A.

In the reinforcing member sticking step, the adhesive layer 42 is sandwiched between the sealing resin layer 30A of the sealing body 50 and the reinforcing plate 41, and is further sandwiched between the reinforcing plate 41 side and the adhesive sheet 10 side by plate members, respectively. It is preferable to carry out the second hot pressing step of pressing under the conditions of temperature, time and pressure. The sealing body 50 and the reinforcing member 40 are temporarily fixed by the second heating press process. In order to cure the adhesive layer 42 after the second heat pressing step, it is preferable to heat the temporarily fixed sealing body 50 and the reinforcing member 40 under conditions of a predetermined temperature and time. The conditions for heat curing are appropriately set according to the material of the adhesive layer 42, and are, for example, 185 ° C., 80 minutes, and 2.4 MPa. Also in the second heat pressing step, as the plate-like member, for example, a metal plate such as stainless steel can be used.

-Peeling process The schematic explaining the process of peeling the adhesive sheet 10 is shown by FIG. 2E.
In this embodiment, when the base material 11 of the adhesive sheet 10 is bendable, the adhesive sheet 10 can be easily peeled from the frame member 20, the semiconductor chip CP, and the sealing resin layer 30A while being bent. Although peeling angle (theta) is not specifically limited, It is preferable to peel the adhesive sheet 10 with peeling angle (theta) of 90 degree | times or more. When the peeling angle θ is 90 degrees or more, the pressure-sensitive adhesive sheet 10 can be easily peeled from the frame member 20, the semiconductor chip CP, and the sealing resin layer 30A. The peeling angle θ is preferably 90 degrees or more and 180 degrees or less, and more preferably 135 degrees or more and 180 degrees or less. By peeling the adhesive sheet 10 while bending the adhesive sheet 10 in this way, the peeling can be performed while reducing the load applied to the frame member 20, the semiconductor chip CP, and the sealing resin layer 30A. Damage to the chip CP and the sealing resin layer 30A can be suppressed. After the pressure-sensitive adhesive sheet 10 is peeled off, the above-described rewiring process and bumping process are performed. After the pressure-sensitive adhesive sheet 10 is peeled off, before the rewiring step and the bumping step, etc., the aforementioned reinforcing member sticking step may be performed as necessary.

When the reinforcing member 40 is attached, the reinforcing member 40 is peeled off from the sealing body 50 at the stage where the support by the reinforcing member 40 becomes unnecessary after the rewiring process and the bumping process are performed.
Thereafter, the sealing body 50 is separated into individual semiconductor chips CP (individualization step). A method for dividing the sealing body 50 into individual pieces is not particularly limited. For example, the semiconductor wafer can be separated into pieces by the same method as that used when dicing the semiconductor wafer. The step of dividing the sealing body 50 into pieces may be performed in a state where the sealing body 50 is adhered to a dicing sheet or the like. By separating the sealing body 50 into individual pieces, a semiconductor package in units of the semiconductor chip CP is manufactured, and this semiconductor package is mounted on a printed wiring board or the like in a mounting process.

According to the present embodiment, it is possible to provide the pressure-sensitive adhesive sheet 10 that is easily peeled off from the adherend and has little adhesive residue even after undergoing a process in which high temperature conditions are imposed. In the present embodiment, the adherend to which the pressure-sensitive adhesive layer 12 contacts is the semiconductor chip CP and the frame member 20. The pressure-sensitive adhesive layer 12 is exposed to high temperature conditions in contact with the semiconductor chip CP and the frame member 20. Compared to the pressure-sensitive adhesive sheet used in the conventional high-temperature process, the pressure-sensitive adhesive sheet 10 is easy to peel off even after being exposed to high-temperature conditions, and has less adhesive residue on the semiconductor chip CP and the frame member 20. .

[Modification of Embodiment]
The present invention is not limited to the above-described embodiment, but includes modifications and improvements as long as the object of the present invention can be achieved. In the following description, if it is the same as the member described in the above embodiment, the same reference numeral is given and the description is omitted or simplified.

In the said embodiment, although the aspect in which the adhesive layer 12 of the adhesive sheet 10 was covered with the peeling sheet RL was mentioned as an example, this invention is not limited to such an aspect.
Moreover, the adhesive sheet 10 may be a single wafer or may be provided in a state where a plurality of adhesive sheets 10 are laminated. In this case, for example, the pressure-sensitive adhesive layer 12 may be covered with the base material 11 of another pressure-sensitive adhesive sheet to be laminated.
Moreover, the adhesive sheet 10 may be a long sheet or may be provided in a state of being wound in a roll. The pressure-sensitive adhesive sheet 10 wound up in a roll shape can be used by being unwound from a roll and cut into a desired size.

In the above embodiment, the case where the sealing resin 30 is a thermosetting resin has been described as an example, but the present invention is not limited to such a mode. For example, the sealing resin 30 may be an energy ray curable resin that is cured by energy rays such as ultraviolet rays.

In the above embodiment, in the description of the method for manufacturing a semiconductor device, an example in which the frame member 20 is attached to the adhesive sheet 10 has been described as an example, but the present invention is not limited to such an embodiment. The adhesive sheet 10 may be used in a method for manufacturing a semiconductor device that seals a semiconductor element without using a frame member.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples.

〔Evaluation methods〕
Evaluation of the pressure-sensitive adhesive sheet was performed according to the following method.

[Adhesive strength evaluation]
The adhesive sheet cut to a width of 25 mm was laminated on a copper foil as an adherend at room temperature to obtain a sheet with a copper foil. As the copper foil, a C1220R-H standard 0.08 mm thick drawn copper foil was used.
This sheet with copper foil was heated under conditions of 100 ° C. and 30 minutes, and subsequently heated under conditions of 180 ° C. and 30 minutes. After heating, the peel angle was 180 degrees, the pulling speed (peeling speed) was 300 mm / min, and the adhesive strength when the tape was peeled from the copper foil at room temperature was measured. When the adhesive strength measured in this way is 0.7 N / 25 mm or more and 2.0 N / 25 mm or less, it is determined as “A”, and the adhesive strength is less than 0.7 N / 25 mm or 2.0 N / 25 mm. When it exceeded, it determined with "B". “Tensilon” (product name) manufactured by Orientec Co., Ltd. was used as an adhesive force measuring device.

[Adhesive residue evaluation]
The sheet with copper foil in the above-described evaluation of adhesive strength was heated under the conditions of 180 ° C. and 1 hour. After heating, the peeling angle was 180 degrees, the pulling rate (peeling rate) was 3 mm / min, and the adhesive sheet was peeled from the copper foil at room temperature. The surface of the copper foil after peeling was visually observed to confirm the presence or absence of residues on the adherend surface. After the tape was peeled off, it was determined as “A” when the adhesive could be peeled without residue, and “B” was determined when there was little adhesive remaining and the tape sticking could be confirmed.

[Preparation of adhesive sheet]
Example 1

(1) Preparation of pressure-sensitive adhesive composition The following materials (polymer, cross-linking agent, and dilution solvent) were blended and sufficiently stirred to prepare a pressure-sensitive adhesive liquid for application according to Example 1.

-Polymer: Acrylic ester copolymer, 40 parts by mass (solid content)
The acrylic ester copolymer was prepared by copolymerizing 92.8% by mass of 2-ethylhexyl acrylate, 7.0% by mass of 2-hydroxyethyl acrylate, and 0.2% by mass of acrylic acid.

Crosslinking agent: Aliphatic isocyanate having hexamethylene diisocyanate (isocyanurate type modified product of hexamethylene diisocyanate) [manufactured by Nippon Polyurethane Industry Co., Ltd .; Coronate HX], 3.5 parts by mass (solid content)

Diluting solvent: Methyl ethyl ketone was used, and the solid content concentration of the coating adhesive solution was adjusted to 30% by mass.

(2) Preparation of pressure-sensitive adhesive layer 38 μm transparent polyethylene terephthalate provided with a silicone-based release layer so that the thickness of the prepared pressure-sensitive adhesive solution for coating after drying using a comma coater (registered trademark) is 50 μm. It is applied to the release layer side of a release film made of a film [manufactured by Lintec Corporation; SP-PET382150], heated at 90 ° C. for 90 seconds, and then heated at 115 ° C. for 90 seconds to form a coating film. It was made to dry and the adhesive layer was produced.

(3) Preparation of pressure-sensitive adhesive sheet After the coating film of the pressure-sensitive adhesive liquid for application was dried, the pressure-sensitive adhesive layer and the substrate were bonded together to obtain a pressure-sensitive adhesive sheet according to Example 1. A transparent polyethylene terephthalate film [manufactured by Toyobo Co., Ltd .; PET50A-4300] was used as the base material, and the pressure-sensitive adhesive layer was bonded to the easy adhesion surface of the base material.

(Example 2)
The pressure-sensitive adhesive sheet according to Example 2 was produced in the same manner as in Example 1 except that the polymer contained in the pressure-sensitive adhesive layer was different from that in Example 1.
The polymer used in Example 2 is an acrylate copolymer prepared by copolymerizing 93.0% by mass of 2-ethylhexyl acrylate and 7.0% by mass of 2-hydroxyethyl acrylate.

(Comparative Example 1)
The pressure-sensitive adhesive sheet according to Comparative Example 1 was prepared in the same manner as in Example 1 except that the polymer contained in the pressure-sensitive adhesive layer was different from that in Example 1.
The polymer used in Comparative Example 1 was an acrylic ester prepared by copolymerizing 92.8% by mass of lauryl acrylate, 7.0% by mass of 2-hydroxyethyl acrylate, and 0.2% by mass of acrylic acid. It is a copolymer.

(Comparative Example 2)
The pressure-sensitive adhesive sheet according to Comparative Example 2 was produced in the same manner as in Example 1 except that the polymer contained in the pressure-sensitive adhesive layer was different from that in Example 1.
The polymer used in Comparative Example 2 was an acrylate prepared by copolymerizing 92.8% by weight of butyl acrylate, 7.0% by weight of 2-hydroxyethyl acrylate, and 0.2% by weight of acrylic acid. It is a copolymer.

Table 1 shows the composition of the adhesive liquid for coating used in Examples 1 and 2 and Comparative Examples 1 and 2.

HEA: 2-hydroxyethyl acrylate 2EHA: 2-ethylhexyl acrylate AAc: acrylic acid LMA: lauryl acrylate BA: butyl acrylate

Table 2 shows the evaluation results of the pressure-sensitive adhesive sheets according to Examples 1 and 2 and Comparative Examples 1 and 2.

The pressure-sensitive adhesive sheets according to Examples 1 and 2 contained an acrylic copolymer containing 2-ethylhexyl acrylate as a main monomer, and as a result, adhesive residue on the adherend could be reduced. Furthermore, according to the adhesive sheet which concerns on Example 1 and 2, compared with the adhesive sheet which concerns on Comparative example 1 and 2, the adhesive force after heat processing was able to be reduced. Thus, it turns out that the adhesive sheet which concerns on this invention can be utilized suitably in the semiconductor device manufacturing process including the process in which high temperature conditions are imposed.

DESCRIPTION OF SYMBOLS 10 ... Adhesive sheet, 11 ... Base material, 12 ... Adhesive layer, 20 ... Frame member, 21 ... Opening part.

Claims

A pressure-sensitive adhesive sheet used when sealing a semiconductor element on a pressure-sensitive adhesive sheet,
A substrate and an adhesive layer;
The pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet containing an acrylic copolymer containing 2-ethylhexyl acrylate as a main monomer.
After heating at 100 ° C. and 30 minutes, and subsequently heating at 180 ° C. and 30 minutes, the adhesive strength of the adhesive layer to the copper foil at room temperature is 0.7 N / 25 mm to 2.0 N / The pressure sensitive adhesive sheet according to claim 1 which is 25 mm or less.
The said adhesive layer contains at least the adhesive obtained by bridge | crosslinking the composition which mix | blended at least the said acrylic copolymer and the crosslinking agent which has a compound which has an isocyanate group as a main component. Item 3. The pressure-sensitive adhesive sheet according to item 2.
The pressure-sensitive adhesive sheet according to claim 3, wherein the cross-linking agent mainly comprising a compound having an isocyanate group has an isocyanurate ring.
The pressure-sensitive adhesive according to any one of claims 1 to 4, wherein a ratio of a copolymer component derived from 2-ethylhexyl acrylate in the acrylic copolymer is 50% by mass or more and 95% by mass or less. Sheet.
The acrylic copolymer further includes a copolymer component derived from acrylic acid,
The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein a ratio of the copolymer component derived from the acrylic acid in the acrylic copolymer is 1% by mass or less.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the pressure-sensitive adhesive layer has a thickness of 5 µm or more and 60 µm or less.