Pressure-sensitive adhesive sheet and method for using pressure-sensitive adhesive sheet

Abstract

The present invention addresses the problem of providing a pressure-sensitive adhesive sheet which can be made to exhibit pressure-sensitive adhesiveness with a desired timing by a non-contact operation without any operation involving physical contact, such as pressing, and which can retain this pressure-sensitive adhesiveness over a long period. The pressure-sensitive adhesive sheet comprises a substrate or a release material, a pressure-sensitive adhesive layer (α) formed thereon and including a pressure-sensitive adhesive resin, and a sacrificial layer (β) directly formed on the pressure-sensitive adhesive layer (α) and including a resin not having pressure-sensitive adhesiveness. The sacrificial layer (β) has a thermal decomposition temperature (Tβ) which is lower than the thermal decomposition temperature (Tα) of the pressure-sensitive adhesive layer (α).

Description

Adhesive sheets and how to use them

[0001] The present invention relates to a pressure-sensitive adhesive sheet and a method for using the pressure-sensitive adhesive sheet.

[0002] Typically, adhesive sheets are stored, distributed, sold, etc. with their adhesive surface covered with a release material such as release paper or release film, but once the release material is peeled off at the time of use to expose the adhesive surface, the release material becomes unnecessary. Therefore, recently, from the perspectives of resource conservation and cost reduction, various adhesive sheets that can exhibit adhesiveness at the time of use without using a release material have been proposed.

[0003] As such an adhesive sheet, Patent Document 1 describes an adhesive sheet coated with a heat-sensitive delayed-tack adhesive that exhibits adhesiveness upon heating. The heat-sensitive delayed-tack adhesive contains a thermoplastic resin, a crystalline plasticizer that is solid at room temperature, and a tackifier. The thermoplastic resin is the source of adhesive strength and bonding strength, and the crystalline plasticizer is solid at room temperature and does not impart plasticity to the resin, but melts upon heating, swelling or softening the resin and thereby exhibiting adhesiveness. Therefore, an adhesive sheet coated with a heat-sensitive delayed-tack adhesive is non-adhesive at room temperature, but can exhibit adhesiveness by heating during use.

[0004] Also known is an adhesive sheet coated with a pressure-sensitive adhesive layer that exhibits adhesiveness upon application of pressure. For example, the adhesive sheet described in Patent Document 2 exhibits adhesiveness by applying pressure to a layer containing pressure-sensitive adhesive microcapsules encapsulating a radiation-curable adhesive agent, causing the microcapsules to break. Therefore, although the sheet is non-adhesive before pressure is applied, adhesiveness can be exhibited by applying pressure during use.

[0005] Japanese Patent No. 2914029 Japanese Patent Application Laid-Open No. 2015-151479

[0006] However, when heating of an adhesive sheet coated with a heat-sensitive delayed-tack adhesive is stopped, the adhesiveness decreases and eventually disappears as the crystalline plasticizer melted by heating gradually crystallizes.

[0007] On the other hand, adhesive sheets coated with a pressure-sensitive adhesive layer exhibit adhesiveness when pressure is applied, causing the microcapsules to break and the adhesive encapsulated in the microcapsules to leak out. Therefore, unlike heat-sensitive delayed-tack adhesives, the adhesiveness does not decrease with crystallization, and it is thought that the adhesiveness is maintained for a longer period of time than adhesive sheets coated with heat-sensitive delayed-tack adhesives. However, if the adherend is a precision instrument, applying pressure to the adhesive sheet can cause damage to the precision instrument, etc. Furthermore, depending on the adherend, it may be difficult to perform operations involving physical contact, such as applying pressure.

[0008] Therefore, the present invention aims to provide an adhesive sheet that can exhibit adhesiveness through a non-contact operation at a desired timing without requiring an operation involving physical contact such as the application of pressure, and that has a surface that can maintain the exhibited adhesiveness for a long period of time, and a method for using this adhesive sheet.

[0009] The inventors have discovered that the above problem can be solved by configuring an adhesive sheet such that a sacrificial layer containing a non-adhesive resin is directly laminated on an adhesive layer containing an adhesive resin, and by setting the thermal decomposition temperature of the sacrificial layer lower than the thermal decomposition temperature of the adhesive layer.

[0010] That is, the present invention relates to the following [1] to

[12] . [1] A pressure-sensitive adhesive layer (α) containing a pressure-sensitive adhesive resin is provided on a substrate or a release material, and a sacrificial layer (β) containing a non-adhesive resin is further provided on the pressure-sensitive adhesive layer (α), and the thermal decomposition temperature (T β ) is the thermal decomposition temperature (T α [2] The pressure-sensitive adhesive sheet according to the above [1], wherein the glass transition temperature of the non-adhesive resin contained in the sacrificial layer (β) is 15°C or higher. [3] The thermal decomposition temperature (T α ) and the thermal decomposition temperature (T β ) and the difference [T α -T β [4] The pressure-sensitive adhesive sheet according to the above-mentioned [1] or [2], wherein the thermal decomposition temperature (Tα [5] The pressure-sensitive adhesive sheet according to any one of the above-mentioned [1] to [3], wherein the thermal decomposition temperature (T β ) is 290°C or less. [6] The pressure-sensitive adhesive sheet according to any one of the above [1] to [5], wherein the thickness of the sacrificial layer (β) is 0.01 to 10 μm. [7] The pressure-sensitive adhesive sheet according to any one of the above [1] to [6], wherein the thickness of the pressure-sensitive adhesive layer (α) is 1 to 50 μm. [8] The pressure-sensitive adhesive sheet according to any one of the above [1] to [7], wherein the content of the non-adhesive resin in the sacrificial layer (β) is 70 mass% or more. [9] The pressure-sensitive adhesive sheet according to any one of the above [1] to [8], wherein the adhesive strength of the surface of the sacrificial layer (β) opposite to the side laminated with the pressure-sensitive adhesive layer (α) is less than 0.1 N / 25 mm.

[10] The pressure-sensitive adhesive sheet according to any one of the above [1] to [9], wherein the pressure-sensitive adhesive sheet is heat-treated at 200°C for 1 hour to decompose the sacrificial layer (β), and the adhesive strength of the exposed pressure-sensitive adhesive layer (α) on the adhesive surface is 0.1 N / 25 mm or more.

[11] The thermal decomposition temperature (T β

[12] The pressure-sensitive adhesive sheet according to any one of the above [1] to

[11] , which can exhibit adhesiveness by heating at a temperature equal to or higher than the thermal decomposition temperature (T β ) or higher to decompose the sacrificial layer (β) and expose the adhesive surface of the adhesive layer (α), and then use the adhesive sheet.

[0011] The pressure-sensitive adhesive sheet of the present invention can exhibit adhesiveness at a desired timing by performing heating, which is a contactless operation, without requiring a physical contact operation such as pressure application, and can maintain the exhibited adhesiveness for a long period of time.

[0012] 1 is a cross-sectional view of a pressure-sensitive adhesive sheet, showing an example of the configuration of the pressure-sensitive adhesive sheet of the present invention.

[0013] In the present invention, the determination of whether a target resin is an "adhesive resin" or a "non-adhesive resin" is made based on the following procedures (1) to (4). Procedure (1): A 20 μm-thick resin layer made solely from the target resin is provided on a 50 μm-thick polyethylene terephthalate (PET) film, and the film is cut into a test piece measuring 300 mm long x 25 mm wide. Procedure (2): The surface of the exposed resin layer of the test piece is attached to a stainless steel plate (SUS304, polished #360) at 23°C and 50% RH (relative humidity) and allowed to stand for 24 hours. Procedure (3): After standing, the adhesive strength is measured at 23°C and 50% RH (relative humidity) using the 180° peel method according to JIS Z0237:2000 at a pulling rate of 300 mm / min. Step (4): If the measured adhesive strength is 0.1 N / 25 mm or more, the resin is judged to be a "sticky resin." On the other hand, if the measured adhesive strength is less than 0.1 N / 25 mm, the resin is judged to be a "non-sticky resin."

[0014] In the present invention, the term "active ingredient" refers to the components contained in the target composition excluding the diluent solvent.

[0015] In the present invention, the "mass average molecular weight (Mw)" and the "number average molecular weight (Mn)" are values ​​calculated as standard polystyrene measured by gel permeation chromatography (GPC), and specifically, are values ​​measured based on the method described in the examples.

[0016] In the present invention, for example, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid", and the same applies to other similar terms.

[0017] In this specification, the "thickness" of an object means the thickness of the entire object, and for example, if the object is made up of multiple layers, it means the total thickness of all layers that make up the object.

[0018] In the present invention, for preferred numerical ranges (e.g., ranges of content, etc.), the lower limit and upper limit values ​​described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60."

[0019] <Configuration of Pressure-Sensitive Adhesive Sheet of the Present Invention> The configuration of the pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as it has a pressure-sensitive adhesive layer (α) containing a pressure-sensitive adhesive resin on a substrate or a release material, and further has a sacrificial layer (β) containing a non-adhesive resin laminated directly on the pressure-sensitive adhesive layer (α). Figure 1 is a cross-sectional schematic diagram of a pressure-sensitive adhesive sheet of the present invention, showing one example of the configuration of the pressure-sensitive adhesive sheet.

[0020] An example of a pressure-sensitive adhesive sheet according to one embodiment of the present invention is a pressure-sensitive adhesive sheet 1, as shown in FIG. 1( a), having a pressure-sensitive adhesive layer (α) 13 on a substrate 11, and further having a sacrificial layer (β) 14 laminated directly on the pressure-sensitive adhesive layer (α) 13. When the pressure-sensitive adhesive sheet 1 shown in FIG. 1( a) is heated, which is a non-contact operation, the sacrificial layer (β) 14 is thermally decomposed, exposing the surface 13a of the pressure-sensitive adhesive layer (α) 13 and thereby exhibiting adhesive properties. Prior to heating, the surface 13a of the pressure-sensitive adhesive layer (α) 13 is protected by being covered with the sacrificial layer (β) 14. Therefore, the pressure-sensitive adhesive sheet shown in FIG. 1( a) does not require a release material to be provided on the sacrificial layer (β) 14. However, the surface 13a of the pressure-sensitive adhesive layer (α) 13 is protected by the sacrificial layer (β) 14 during storage, distribution, sales, and other pre-use stages. At the same time, the sacrificial layer (β) 14 can be thermally decomposed at a desired time to expose the surface 13a of the pressure-sensitive adhesive layer (α) 13 and thereby exhibit adhesive properties. In the present invention, "exposed" means a state in which at least a part of the surface 13a of the pressure-sensitive adhesive layer (α) 13 is exposed. In other words, the entire surface 13a of the pressure-sensitive adhesive layer (α) 13 does not have to be exposed, as long as a part of the surface 13a of the pressure-sensitive adhesive layer (α) 13 is exposed. Preferably, 50% or more of the surface 13a of the pressure-sensitive adhesive layer (α) 13 is exposed, more preferably 70% or more, even more preferably 90% or more, and most preferably the entire surface is exposed.

[0021] 1(b), a pressure-sensitive adhesive sheet according to one embodiment of the present invention may be a pressure-sensitive adhesive sheet 2 in which the substrate 11 in the pressure-sensitive adhesive sheet 1 shown in FIG. 1(a) is replaced with a release material 15. The pressure-sensitive adhesive sheet 2 is a double-sided pressure-sensitive adhesive sheet in which the surface 13b opposite to the surface 13a of the pressure-sensitive adhesive layer (α) 13 is also adhesive. Therefore, after the surface 13b of the pressure-sensitive adhesive layer (α) 13 is attached to an adherend, the pressure-sensitive adhesive sheet 2 can be heated, which is a non-contact operation, to expose the surface 13a of the pressure-sensitive adhesive layer (α) 13 and thereby develop adhesiveness, without the need to peel off the release material.

[0022] 1(c), for example, a pressure-sensitive adhesive sheet 3 may be provided in which the pressure-sensitive adhesive sheet shown in FIG. 1(a) has a pressure-sensitive adhesive layer (γ) 23 containing a pressure-sensitive adhesive resin on the surface of the substrate 11 opposite to the surface on which the pressure-sensitive adhesive layer (α) 13 is directly laminated, and a release material 15 is provided on the pressure-sensitive adhesive layer (γ) 23. After the release material 15 is peeled off to attach the surface 23b of the pressure-sensitive adhesive layer (γ) 23 to an adherend, the release sheet 3 can be heated, which is a non-contact operation, to expose the surface 13a of the pressure-sensitive adhesive layer (α) 13, thereby exhibiting adhesiveness, without the need to peel off the release material.

[0023] Here, "the sacrificial layer (β) 14 is directly laminated on the pressure-sensitive adhesive layer (α) 13" refers to a configuration in which the pressure-sensitive adhesive layer (α) 13 and the sacrificial layer (β) 14 are in direct contact with each other without any other layer interposed therebetween. Therefore, for example, in the pressure-sensitive adhesive sheets 1 and 3 shown in Figures 1(a) and 1(c), a layer other than the substrate 11 and the pressure-sensitive adhesive layer (α) 13 may be provided between the substrate 11 and the pressure-sensitive adhesive layer (α) 13. Furthermore, in the pressure-sensitive adhesive sheet 3 shown in Figure 1(c), a layer other than the substrate 11 and the pressure-sensitive adhesive layer (γ) 23 may also be provided between the substrate 11 and the pressure-sensitive adhesive layer (γ) 23.

[0024] 1(a) to 1(c) , the sacrificial layer (β) may have a multilayer structure consisting of two or more layers. In this case, the sacrificial layer on the surface side functions as a protective layer to protect the sacrificial layer on the lower side before use, such as during storage, distribution, or sales. Then, by performing heating, a non-contact operation, at a desired timing, the sacrificial layer on the surface side is thermally decomposed to release its protective function, and the sacrificial layer on the lower side is thermally decomposed to expose the surface 13a of the pressure-sensitive adhesive layer (α) 13, thereby exhibiting adhesiveness.

[0025] The shape of the pressure-sensitive adhesive sheet of one embodiment of the present invention may be, for example, a square, a rectangle, a polygon, a circle, an annular shape, etc., but is not limited to these shapes and may be appropriately selected depending on the application of the pressure-sensitive adhesive sheet. Furthermore, the pressure-sensitive adhesive sheet of one embodiment of the present invention may be, for example, a rolled body obtained by winding a long pressure-sensitive adhesive sheet into a roll or a wound body obtained by winding the long pressure-sensitive adhesive sheet around a core material.

[0026] <Thermal decomposition temperature of the adhesive layer and the sacrificial layer> The adhesive sheet of the present invention has a thermal decomposition temperature (T α ) is the thermal decomposition temperature (T β By adjusting in this way, the thermal decomposition temperature (T β ) or higher, the pressure-sensitive adhesive layer (α) can be stably maintained without being thermally decomposed while the sacrificial layer (β) is thermally decomposed, and the adhesiveness of the pressure-sensitive adhesive layer (α) itself can be maintained. Therefore, by performing this heating, the pressure-sensitive adhesive layer (α) can be stably maintained without being thermally decomposed, while the sacrificial layer (β) is thermally decomposed to expose the surface 13a of the pressure-sensitive adhesive layer (α), thereby allowing the pressure-sensitive adhesive layer (α) to exhibit adhesiveness.

[0027] Here, the thermal decomposition temperature (T α ) and the thermal decomposition temperature (T β ) and the difference [T α -T β From the viewpoint of thermally decomposing the sacrificial layer (β) while stably maintaining the pressure-sensitive adhesive layer (α) without thermal decomposition, [T α -T β The upper limit of the temperature is not particularly limited, but is, for example, 450°C, preferably 360°C, and more preferably 270°C.

[0028] The thermal decomposition temperature (T α ) is adjusted to be preferably 320°C or higher, more preferably 350°C or higher, and even more preferably 380°C or higher, from the viewpoint of stably maintaining the pressure-sensitive adhesive layer (α) without thermal decomposition when the sacrificial layer (β) is thermally decomposed. α ) is not particularly limited to an upper limit, but is usually 550°C or lower, preferably 500°C or lower, and more preferably 450°C or lower.

[0029] The thermal decomposition temperature (T β) is adjusted to be preferably 290°C or less, more preferably 250°C or less, and even more preferably 210°C or less, from the viewpoint of thermally decomposing the sacrificial layer (β) while stably maintaining the pressure-sensitive adhesive layer (α) without thermal decomposition. β ) has no particular lower limit, but is usually 100°C or higher, preferably 140°C or higher, and more preferably 180°C or higher.

[0030] In the present invention, the "thermal decomposition temperature" is a value measured by simultaneous thermogravimetry and differential thermal analysis, specifically, a value measured based on the method described in the examples.

[0031] <Thickness of the Pressure-Sensitive Adhesive Layer (α) and the Sacrificial Layer (β)> The thickness of the sacrificial layer (β) is preferably 0.01 to 10 μm, more preferably 0.10 to 8 μm, even more preferably 0.50 to 6 μm, and even more preferably 0.80 to 4 μm. If the sacrificial layer (β) is too thick, the pressure-sensitive adhesive layer (α) is less likely to be exposed when the sacrificial layer (β) is thermally decomposed. If the sacrificial layer (β) is too thin, the pressure-sensitive adhesive layer (α) may be partially exposed and exhibit adhesiveness before the sacrificial layer (β) is thermally decomposed. The thickness of the pressure-sensitive adhesive layer (α) is appropriately selected depending on the application of the pressure-sensitive adhesive sheet, but is preferably 1 to 50 μm, more preferably 3 to 40 μm, even more preferably 5 to 30 μm, and even more preferably 10 to 20 μm. Furthermore, when the thickness of the pressure-sensitive adhesive layer (α) is taken as 100, the thickness of the sacrificial layer (β) is preferably 0.1 to 40, more preferably 1 to 35, even more preferably 3 to 30, and still more preferably 6 to 25.

[0032] <Adhesive Layer (α)> The adhesive layer (α) of the adhesive sheet of the present invention contains an adhesive resin, but may also contain adhesive additives such as a crosslinking agent or a tackifier. Here, the adhesive layer (α) can be formed from an adhesive composition containing an adhesive resin and, if necessary, adhesive additives. Hereinafter, each component contained in the adhesive composition that forms the adhesive layer (α) will be described. In the following description, the "content of each component relative to the total amount of active ingredients in the adhesive composition" can also be considered as the "content of each component in the adhesive layer (α) formed from the adhesive composition." The adhesive layer (α) may consist of one layer (single layer) or two or more layers. When the adhesive layer (α) consists of multiple layers, these multiple layers may be the same or different.

[0033] [Adhesive Resin] The adhesive resin used in one embodiment of the present invention may be any resin whose thermal decomposition temperature is higher than that of the sacrificial layer (β), and examples thereof include acrylic resins, urethane resins, polyisobutylene resins, polyester resins, and olefin resins. These adhesive resins may be used alone or in combination of two or more. Furthermore, when these adhesive resins are copolymers having two or more structural units, the form of the copolymer is not particularly limited and may be any of a block copolymer, a random copolymer, and a graft copolymer. In the present invention, the mass average molecular weight (Mw) of the adhesive resin is preferably 10,000 or more, more preferably 20,000 to 2,000,000, even more preferably 30,000 to 1,500,000, and even more preferably 40,000 to 1,000,000, from the viewpoint of improving adhesive strength.

[0034] The content of the adhesive resin is preferably 30 to 99.99 mass%, more preferably 40 to 99.95 mass%, more preferably 50 to 99.90 mass%, even more preferably 55 to 99.80 mass%, and still more preferably 60 to 99.70 mass%, relative to the total amount (100 mass%) of the active ingredients of the adhesive composition.

[0035] In one embodiment of the present invention, from the viewpoint of making the thermal decomposition temperature of the pressure-sensitive adhesive layer (α) higher than the thermal decomposition temperature of the sacrificial layer (β) and from the viewpoint of further improving the interfacial adhesion with the substrate, it is preferable that the adhesive resin contains an acrylic resin. From the above viewpoints, the content of the acrylic resin in the adhesive resin is preferably 30 to 100 mass%, more preferably 50 to 100 mass%, even more preferably 70 to 100 mass%, and even more preferably 85 to 100 mass%, relative to the total amount (100 mass%) of the pressure-sensitive adhesive resin. Acrylic resins preferred for use as the adhesive resin are described below.

[0036] [Acrylic Resin] Examples of acrylic resins that can be used as adhesive resins include polymers containing structural units derived from alkyl (meth)acrylates having a linear or branched alkyl group, and polymers containing structural units derived from (meth)acrylates having a cyclic structure.

[0037] The mass average molecular weight (Mw) of the acrylic resin is preferably 100,000 to 1,500,000, more preferably 150,000 to 1,300,000, even more preferably 200,000 to 1,100,000, and still more preferably 300,000 to 1,000,000.

[0038] The acrylic resin used in one embodiment of the present invention can be produced by combining various monomers. However, an acrylic polymer (A0) having a structural unit (a1) derived from an alkyl (meth)acrylate (a1') (hereinafter also referred to as "monomer (a1')") is preferred, and an acrylic copolymer (A1) having a structural unit (a2) derived from a functional group-containing monomer (a2') (hereinafter also referred to as "monomer (a2')") in addition to the structural unit (a1) is more preferred. From the viewpoint of improving adhesive properties, the number of carbon atoms in the alkyl group of the monomer (a1') is preferably 1 to 24, more preferably 1 to 12, even more preferably 1 to 8, and even more preferably 4 to 8. The alkyl group of the monomer (a1') may be a linear alkyl group or a branched alkyl group.

[0039] Examples of the monomer (a1') include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, and stearyl (meth)acrylate. These monomers (a1') may be used alone or in combination of two or more. However, as the monomer (a1'), butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate, which are monomers having an alkyl group having 4 to 8 carbon atoms, are preferred, and butyl (meth)acrylate is more preferred.

[0040] The content of the structural unit (a1) is preferably 50 to 100% by mass, more preferably 60 to 99.9% by mass, even more preferably 70 to 99.5% by mass, still more preferably 80 to 99.0% by mass, and even more preferably 85 to 98.0% by mass, based on all structural units (100% by mass) of the acrylic polymer (A0) or acrylic copolymer (A1). Furthermore, the content of the structural unit (a1) derived from a monomer (a1') having an alkyl group having 4 to 8 carbon atoms is preferably 40 to 100% by mass, more preferably 50 to 99.9% by mass, even more preferably 60 to 99.5% by mass, still more preferably 70 to 99.0% by mass, even more preferably 80 to 98.0% by mass, and even more preferably 85 to 98.0% by mass, based on all structural units (100% by mass) of the acrylic polymer (A0) or acrylic copolymer (A1).

[0041] The functional group possessed by the monomer (a2') refers to a functional group that can react with a crosslinking agent described below and serve as a crosslinking initiation point or a functional group that has a crosslinking-accelerating effect, and examples thereof include a hydroxyl group, a carboxyl group, an amino group, and an epoxy group. That is, examples of the monomer (a2') include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an amino group-containing monomer, and an epoxy group-containing monomer. These monomers (a2') may be used alone or in combination of two or more. As the monomer (a2'), a hydroxyl group-containing monomer and a carboxyl group-containing monomer are preferred.

[0042] Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; etc. It is preferable to use 2-hydroxyethyl (meth)acrylate as the hydroxyl group-containing monomer.

[0043] Examples of the carboxy group-containing monomer include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid, ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid and citraconic acid and their anhydrides, 2-(acryloyloxy)ethyl succinate, 2-carboxyethyl (meth)acrylate, etc. It is preferable to use (meth)acrylic acid as the carboxy group-containing monomer.

[0044] The content of the structural unit (a2) relative to all structural units (100% by mass) of the acrylic copolymer (A1) is preferably 0.1 to 40% by mass, more preferably 0.3 to 30% by mass, even more preferably 0.5 to 20% by mass, still more preferably 1 to 15% by mass, and even more preferably 3 to 13% by mass. By ensuring that the content is within such a range, the cohesive strength and heat resistance of the pressure-sensitive adhesive layer (α) can be made appropriate.

[0045] The acrylic copolymer (A1) may further contain a structural unit (a3) ​​derived from a monomer (a3') other than the monomers (a1') and (a2'). The content of the structural units (a1) and (a2) in the acrylic copolymer (A1) is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, even more preferably 90 to 100% by mass, and still more preferably 95 to 100% by mass, based on all structural units (100% by mass) of the acrylic copolymer (A1).

[0046] Examples of the monomer (a3') include olefins such as ethylene, propylene, and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; diene monomers such as butadiene, isoprene, and chloroprene; (meth)acrylates having a cyclic structure such as cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and imide (meth)acrylate; styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, (meth)acrylamide, (meth)acrylonitrile, (meth)acryloylmorpholine, and N-vinylpyrrolidone.

[0047] [Crosslinking Agent] In one embodiment of the present invention, when the pressure-sensitive adhesive composition contains a pressure-sensitive adhesive resin having a functional group such as the above-mentioned acrylic copolymer (A1) as the pressure-sensitive adhesive resin, it is preferable that the pressure-sensitive adhesive composition further contains a crosslinking agent that reacts with the functional group of the pressure-sensitive adhesive resin to crosslink the resins.

[0048] Examples of crosslinking agents include isocyanate-based crosslinking agents such as tolylene diisocyanate (TDI), hexamethylene diisocyanate, and adducts thereof; epoxy-based crosslinking agents such as ethylene glycol glycidyl ether; aziridine-based crosslinking agents such as hexa[1-(2-methyl)-aziridinyl]triphosphatriazine; and chelate-based crosslinking agents such as aluminum chelate. These crosslinking agents may be used alone or in combination of two or more. Among these crosslinking agents, isocyanate-based crosslinking agents are preferred from the viewpoints of increasing cohesive strength and improving adhesive strength, and ease of availability, and among isocyanate-based crosslinking agents, tolylene diisocyanate (TDI) is preferred.

[0049] The content of the crosslinking agent is adjusted appropriately depending on the number of functional groups possessed by the adhesive resin, and is, for example, preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, even more preferably 0.05 to 4 parts by mass, and still more preferably 0.1 to 2 parts by mass relative to 100 parts by mass of the adhesive resin having the above-mentioned functional groups, such as the acrylic copolymer.

[0050] [Tackifier] In one embodiment of the present invention, the pressure-sensitive adhesive composition may further contain a tackifier in order to obtain a pressure-sensitive adhesive sheet with improved adhesive strength. Here, the term "tackifier" refers to a component that supplementarily improves the adhesive strength of the pressure-sensitive adhesive resin, and refers to an oligomer having a mass-average molecular weight (Mw) of less than 10,000, and is distinguished from the above-mentioned pressure-sensitive adhesive resin. The mass-average molecular weight (Mw) of the tackifier is preferably 400 or more and less than 10,000, more preferably 5,000 to 8,000, and even more preferably 800 to 5,000.

[0051] Examples of tackifiers include rosin resins such as rosin resins, rosin ester resins, and rosin-modified phenolic resins; hydrogenated rosin resins obtained by hydrogenating these rosin resins; terpene resins, aromatic-modified terpene resins, and terpene phenolic resins; hydrogenated terpene resins obtained by hydrogenating these terpene resins; styrene resins obtained by copolymerizing a styrene monomer such as α-methylstyrene or β-methylstyrene with an aliphatic monomer; hydrogenated styrene resins obtained by hydrogenating these styrene resins; C5 petroleum resins obtained by copolymerizing C5 fractions such as pentene, isoprene, piperine, and 1.3-pentadiene produced by thermal decomposition of petroleum naphtha, and hydrogenated petroleum resins of these C5 petroleum resins; C9 petroleum resins obtained by copolymerizing C9 fractions such as indene and vinyltoluene produced by thermal decomposition of petroleum naphtha, and hydrogenated petroleum resins of these C9 petroleum resins; and the like. These tackifiers may be used alone or in combination of two or more types having different softening points or structures.

[0052] The softening point of the tackifier is preferably 60 to 170°C, more preferably 65 to 160°C, and even more preferably 70 to 150°C. When two or more tackifiers are used in combination, it is preferable that the weighted average of the softening points of the multiple tackifiers falls within the above range. In the present invention, the "softening point" of the tackifier means a value measured in accordance with JIS K 2531.

[0053] Here, from the viewpoint of easily preventing softening, flow, etc. of the pressure-sensitive adhesive layer (α) when the sacrificial layer (β) is thermally decomposed, the content of the tackifier in the pressure-sensitive adhesive composition is preferably small. Specifically, the content of the tackifier is preferably 0 to 10 parts by mass, more preferably 0 to 5 parts by mass, even more preferably 0 to 1 part by mass, still more preferably 0 to 0.1 parts by mass, relative to 100 parts by mass of the pressure-sensitive adhesive resin contained in the pressure-sensitive adhesive composition, and most preferably no tackifier is contained.

[0054] [Other Pressure-Sensitive Adhesive Additives] In one embodiment of the present invention, the pressure-sensitive adhesive composition may contain, in addition to the crosslinker and tackifier, pressure-sensitive adhesive additives used in general pressure-sensitive adhesives, provided that the effects of the present invention are not impaired. Such pressure-sensitive adhesive additives are appropriately selected depending on the type of pressure-sensitive adhesive resin used, and examples include antioxidants, rust inhibitors, pigments, dyes, retarders, reaction accelerators (catalysts), and UV absorbers. These pressure-sensitive adhesive additives may be used alone or in combination of two or more. When the pressure-sensitive adhesive composition contains these pressure-sensitive adhesive additives, the content of each pressure-sensitive adhesive additive is preferably 0.0001 to 20 parts by mass, more preferably 0.001 to 10 parts by mass, per 100 parts by mass of the pressure-sensitive adhesive resin.

[0055] [Dilution Solvent] In one embodiment of the present invention, from the viewpoint of improving the coatability to substrates, release materials, release sheets for transfer, etc., the PSA composition may be in the form of a solution by adding a dilution solvent together with the various active ingredients described above. Examples of the dilution solvent include water and organic solvents. Examples of organic solvents include toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropyl alcohol, t-butanol, s-butanol, acetylacetone, cyclohexanone, n-hexane, and cyclohexane. Two or more of these dilution solvents may be used in combination. The organic solvent used in the synthesis of the PSA resin may be used as the dilution solvent as is, or the organic solvent used in the synthesis of the PSA resin and / or one or more other organic solvents may be added to enable uniform coating of the PSA composition.

[0056] It is preferable to blend a dilution solvent so that the concentration of the active ingredient (solid content) in the solution of the pressure-sensitive adhesive composition is preferably 5 to 60 mass %, more preferably 10 to 45 mass %, and even more preferably 15 to 30 mass %.

[0057] <Sacrificial Layer (β)> The sacrificial layer (β) of the pressure-sensitive adhesive sheet of the present invention contains a non-tacky resin, and may further contain additives such as an acid generator or a base generator. Here, the sacrificial layer (β) can be formed from a resin composition containing a non-tacky resin and, if necessary, the above-mentioned additives. Hereinafter, each component contained in the resin composition that is the material for forming the sacrificial layer (β) will be described. In the following description, the "content of each component relative to the total amount of active components of the resin composition" can also be considered as the "content of each component in the sacrificial layer (β) formed from the resin composition." As described above, the sacrificial layer (β) may consist of one layer (single layer) or two or more layers. When the sacrificial layer (β) consists of multiple layers, these multiple layers may be the same or different from each other.

[0058] [Non-sticky resin] The non-sticky resin used in one embodiment of the present invention may be a non-sticky resin whose thermal decomposition temperature is lower than the thermal decomposition temperature of the pressure-sensitive adhesive layer (α), but a resin with a glass transition temperature of 15 ° C or higher is preferred. A resin with a glass transition temperature of 15 ° C or higher is considered to be a non-sticky resin because it maintains a solid state in a temperature range below 15 ° C or near 15 ° C. Therefore, by using a resin with a glass transition temperature of 15 ° C or higher as the non-sticky resin, it is possible to easily solidify the sacrificial layer (β) containing the non-sticky resin before use, such as storage, distribution, or sales, thereby improving the handleability of the pressure-sensitive adhesive sheet. In addition, from the viewpoint of more reliably maintaining the solid state of the sacrificial layer (β) containing the non-sticky resin before use, such as storage, distribution, or sales, and more reliably ensuring the handleability of the pressure-sensitive adhesive sheet, the glass transition temperature of the non-sticky resin is more preferably 20 ° C or higher, and even more preferably 25 ° C or higher. The upper limit of the glass transition temperature of the non-sticky resin is not particularly limited, but from the viewpoint of flexibility, it is preferably 150° C. or less, more preferably 130° C. or less, even more preferably 110° C. or less, and particularly preferably 50° C. or less. In the present invention, the "glass transition temperature" is a value measured by differential scanning calorimetry, and specifically, a value measured based on the method described in the examples.

[0059] The content of the non-sticky resin in the sacrificial layer (β) is preferably 70 to 100 mass%, more preferably 80 to 99.99 mass%, even more preferably 85 to 99.95 mass%, still more preferably 90 to 99.90 mass%, and even more preferably 94 to 99.80 mass%, relative to the total amount (100 mass%) of the sacrificial layer (β).

[0060] In one aspect of the present invention, from the viewpoint of setting the thermal decomposition temperature of the sacrificial layer (β) lower than the thermal decomposition temperature of the pressure-sensitive adhesive layer (α), the non-sticky resin preferably contains an aliphatic polycarbonate. Aliphatic polycarbonates decompose from the end of the main chain when heated. The heating temperature can be set lower than the thermal decomposition temperature of the pressure-sensitive adhesive layer (α). Therefore, by including an aliphatic polycarbonate in the non-sticky resin, the heating temperature can be set lower than the thermal decomposition temperature of the pressure-sensitive adhesive layer (α), and the aliphatic polycarbonate in the sacrificial layer (β) can be thermally decomposed, exposing the pressure-sensitive adhesive layer (α) and exhibiting adhesiveness, while maintaining the pressure-sensitive adhesive layer (α) stably.

[0061] From the above viewpoints, the content of the aliphatic polycarbonate in the non-sticky resin is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, even more preferably 70 to 100% by mass, and still more preferably 85 to 100% by mass, relative to the total amount (100% by mass) of the non-sticky resin. Aliphatic polycarbonates preferred for use as the non-sticky resin are described below.

[0062] [Aliphatic Polycarbonate] The aliphatic polycarbonate that can be used as the non-sticky resin is preferably a resin having a structural unit (b1) represented by the following general formula (b-1).

[0063]

[0064] In formula (b-1), Z is an alkylene group, which may have a substituent. The number of carbon atoms in the alkylene group that can be selected as Z is preferably 2 to 10, more preferably 2 to 8, and even more preferably 2 to 4, from the viewpoint of obtaining a non-stick resin with a relatively low thermal decomposition temperature.

[0065] The alkylene group that can be selected as Z may be a linear alkylene group or a branched alkylene group. Examples of linear alkylene groups include a methylene group, an ethylene group, an n-propylene group, and an n-butylene group. Examples of branched alkylene groups include an isopropylene group, a methylethylene group, an ethylethylene group, a 2-methylpropylene group, an isobutylene group, and a 2-methylbutylene group.

[0066] The alkylene group may have a substituent. Examples of the substituent include an alkoxy group, an alkenyl group, an alkenyloxy group, a hydroxyl group, a carboxy group, and a halogen atom. Examples of the alkoxy group include linear or branched alkoxy groups having 1 to 8 carbon atoms, such as a methoxy group and an ethoxy group. Examples of the alkenyl group include linear or branched alkenyl groups having 2 to 8 carbon atoms, such as a vinyl group and an allyl group. Examples of the alkenyloxy group include linear or branched alkenyloxy groups having 2 to 8 carbon atoms, such as a vinyloxy group and an allyloxy group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0067] With regard to the structural unit (b1) possessed by the aliphatic polycarbonate used in one embodiment of the present invention, consideration of the following (1) to (5) facilitates preparation of a non-sticky resin with a low thermal decomposition temperature. Note that the following items are merely examples, and preparation can also be carried out taking into account other items. (1) Z in the general formula (b-1) is a branched-chain alkylene group. (2) When Z in the general formula (b-1) is a linear alkylene group, it is a linear alkylene group having a substituent. (3) When Z in the general formula (b-1) is a linear alkylene group having a substituent, the number of substituents possessed by the linear alkylene group is preferably adjusted to two or less, more preferably one. Furthermore, the total number of carbon atoms in the linear alkylene group, including the substituent, is preferably adjusted to 2 to 8, more preferably 2 to 6, and even more preferably 2 to 4. (4) When Z in the general formula (b-1) is an unsubstituted branched-chain alkylene group, the number of carbon atoms in the branched-chain alkylene group is adjusted to 3 to 8, preferably 3 to 6, and more preferably 3 to 4. The number of branches is also adjusted to 2 or less, preferably 1. (5) When Z in the general formula (b-1) is a branched-chain alkylene group having a substituent, the number of carbon atoms in the branched-chain alkylene group is adjusted to 3 to 8, preferably 3 to 6, and more preferably 3 to 4. The sum of the number of substituents and the number of branches in the branched-chain alkylene group is adjusted to 2 or less, preferably 1. The total number of carbon atoms, including the number of substituents, is adjusted to 3 to 8, preferably 3 to 6, and more preferably 3 to 4.

[0068] The aliphatic polycarbonate used in one embodiment of the present invention may be a homopolymer having only one type of structural unit (b1), a copolymer having two or more types of structural units (b1), or a copolymer having structural units other than the structural unit (b1). The aliphatic polycarbonate used in one embodiment of the present invention preferably has a mass average molecular weight (Mw) of 10,000 to 1,000,000. Furthermore, the molecular weight distribution (Mw / Mn) of the aliphatic polycarbonate used in one embodiment of the present invention is preferably 10.0 or less. The molecular weight distribution (Mw / Mn) of the aliphatic polycarbonate is typically 1.01 or more.

[0069] Here, the aliphatic polycarbonate used in one embodiment of the present invention can be easily adjusted to a non-sticky resin with a low thermal decomposition temperature by taking into account the following factors (1) to (3). Note that the following factors are merely examples, and adjustments can also be made taking into account factors other than these. (1) The content of the structural unit (b1) in all structural units of the aliphatic polycarbonate is increased. The content of the structural unit (b1) is adjusted to preferably 60 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, and even more preferably 90 to 100 mass%, relative to all structural units of the aliphatic polycarbonate (100 mass%). (2) The weight average molecular weight (Mw) of the aliphatic polycarbonate is adjusted to preferably 10,000 to 700,000, more preferably 20,000 to 400,000, even more preferably 30,000 to 300,000, and particularly preferably 40,000 to 100,000. (3) The molecular weight distribution (Mw / Mn) of the aliphatic polycarbonate is adjusted to preferably 8.5 or less, more preferably 7.0 or less.

[0070] Here, it is preferable that the aliphatic polycarbonate represented by the above formula (b-1) does not have a carboxylic acid ester structure (RC(=O)-OR) in its main chain.

[0071] Furthermore, it is preferable that the aliphatic polycarbonate represented by the above formula (b-1) does not have a urethane bond (-NH-C(=O)-O-) in its main chain.

[0072] Here, the thermal decomposition temperature (T β From the viewpoint of lowering the viscosity, the aliphatic polycarbonate preferably has a structural unit (b2) represented by the following general formula (b-2):

[0073]

[0074] In formula (b-2), R １ ~R ４ are each independently a hydrogen atom, an alkyl group, a hydroxyl group, a carboxy group, or an alkoxy group.

[0075] R １ ~R ４The alkyl group that can be selected as may be a linear alkyl group or a branched alkyl group, but is preferably a linear alkyl group. The number of carbon atoms in the alkyl group is preferably 1 to 8, more preferably 1 to 4, even more preferably 1 or 2, and still more preferably 1.

[0076] R １ ~R ４ The alkoxy group as may be a linear alkoxy group or a branched alkoxy group, but is preferably a linear alkoxy group. The number of carbon atoms in the alkoxy group is preferably 1 to 8, more preferably 1 to 4, even more preferably 1 or 2, and still more preferably 1.

[0077] From the viewpoint of making the resin non-sticky with a low thermal decomposition temperature, R １ ~R ４ It is preferable that any one of R is a hydrogen atom, １ ~R ４ It is more preferable that any two of R are hydrogen atoms. １ ~R ４ It is more preferable that any three of R are hydrogen atoms. １ ~R ４ It is most preferable that all of R are hydrogen atoms. １ ~R ４ When the structural unit has a group other than a hydrogen atom, the group is preferably an alkyl group, a hydroxyl group, or a carboxy group, and from the viewpoint of easy availability of the compound, an alkyl group is more preferable. As mentioned above, the number of carbon atoms in the alkyl group is preferably 1 to 8, more preferably 1 to 4, even more preferably 1 to 2, and still more preferably 1. Aliphatic polycarbonates having such structural units can have improved decomposition properties by heating and can be more susceptible to thermal decomposition.

[0078] In the aliphatic polycarbonate used in one embodiment of the present invention, the content of the structural unit (b2) is preferably 60 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, and still more preferably 90 to 100 mass%, based on all structural units (100 mass%) of the aliphatic polycarbonate.

[0079] [Method for Producing Aliphatic Polycarbonate] Aliphatic polycarbonates can be produced by a method comprising a step of polymerizing a monomer containing a substituted linear alkylene group with carbon dioxide in the presence of a metal catalyst such as a zinc catalyst, while optionally controlling the water content to a predetermined level or less. For example, an aliphatic polycarbonate having the structural unit (b2) can be produced by a method comprising a step of polymerizing ethylene oxide and an ethylene oxide derivative with carbon dioxide in the presence of a metal catalyst such as a zinc catalyst, while optionally controlling the water content to a predetermined level or less. The ethylene oxide derivative refers to a compound in which one or more hydrogen atoms of ethylene oxide are substituted with a group (substituent) other than a hydrogen atom, and the substituent here includes R in the aliphatic polycarbonate represented by the above formula (b-2) １ ~R ４ Examples of the alkyl group and the alkoxy group include alkyl groups and alkoxy groups that can be selected as the alkyl group and the alkoxy group.

[0080] [Acid Generator, Base Generator] In one embodiment of the present invention, from the viewpoint of accelerating the thermal decomposition of the aliphatic polycarbonate and making the sacrificial layer (β) more easily thermally decomposed, the resin composition preferably further contains an acid generator or a base generator. When the sacrificial layer (β) contains an acid generator or a base generator, the acid or base generated by adding energy comes into contact with the aliphatic polycarbonate, making the aliphatic polycarbonate more easily decomposable. As a result, it becomes possible to thermally decompose the sacrificial layer (β) at a lower temperature or in a shorter time.

[0081] The acid generator or base generator may be a photoacid generator or photobase generator, or a thermal acid generator or thermal base generator, depending on the type of energy applied.

[0082] Photoacid generators or photobase generators generate an acid or a base when energy is applied by irradiation with active energy rays such as visible light, ultraviolet light, or electron beams. Among these, photobase generators include, for example, α-aminoacetophenone compounds; oxime ester compounds; and compounds having a substituent such as an acyloxyimino group, an N-formylated aromatic amino group, an N-acylated aromatic amino group, a nitrobenzyl carbamate group, or an alkoxybenzyl carbamate group. As the α-aminoacetophenone compound, those having two or more nitrogen atoms are particularly preferred. Furthermore, commercially available photobase generators such as 9-anthramethyl N,N'-diethylcarbamate, (E)-1-[3-(2-hydroxyphenyl)-2-propenoyl]piperidine, guanidinium 2-(3-benzoylphenyl)propionate, 1-(anthraquinone-2-yl)ethylimidazolecarboxylate, 1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidinium 2-(3-benzoylphenyl)propionate, and 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidinium n-butyltriphenylborate may be used. One of the above photobase generators may be used alone, or two or more may be used in combination.

[0083] Examples of the photoacid generator include onium salts such as sulfonium salts, iodonium salts, diazonium salts, selenium salts, pyridinium salts, ferrocenium salts, phosphonium salts, and thiopyrium salts, and aromatic sulfonium salts and aromatic iodonium salts are more preferred. Aromatic sulfonium salts and aromatic iodonium salts are commercially available, and commercially available products may be used. In addition, examples of the anion component include BF ４ － , P.F. ６ － , AsF ６ － , SbF ６ － , and B(C ６ F ５ ) ４ － Among them, PF is particularly preferred. ６－ , and B(C ６ F ５ ) ４ － The above photoacid generators may be used alone or in combination of two or more.

[0084] A thermal acid generator or thermal base generator generates an acid or base when thermal energy is applied. Examples of the thermal acid generator include pyridinium salt derivatives such as N-(4-methylbenzyl)4'-pyridinium hexafluoroantimonate; hydrazinium salts; phosphonium salts; sulfonium salts such as dimethylphenylsulfonium hexafluorophosphate; phosphonate esters; sulfonate esters such as cyclohexyl(4-methylphenyl)sulfonate and isopropyl(4-methylphenyl)sulfonate; and vinyl ether adduct derivatives of carboxylic acids such as propyl vinyl ether of 1,2,4-trimellitic acid. The above thermal acid generators may be used alone or in combination of two or more.

[0085] Examples of thermal base generators include carbamate derivatives such as 1-methyl-1-(4-biphenylyl)ethyl carbamate, 1,1-dimethyl-2-cyanoethyl carbamate, N-(isopropoxycarbonyl)-2,6-dimethylpiperazine, N-(benzyloxycarbonyl)-2,6-dimethylpiperazine, and N-(2-nitrobenzyloxycarbonyl)cyclohexylamine; urea derivatives such as urea and N,N-dimethyl-N'-methylurea; guanidine trichloroacetate, methylguanidine trichloroacetate, guanidine phenylsulfonylacetate, p-methanesulfonylguanidine acetate, and phenyl Examples of the thermal base generators include guanidine derivatives such as guanidine propiolate, p-phenylene-bis-phenylpropiolate, 1,2-ethane-bis(N,N'-diethylguanidinium)4-phenyl(sulfonylphenylsulfonyl)acetic acid, and (1,4-butane-bisguanidinium)4-phenyl(sulfonylphenylsulfonyl)acetic acid; dihydropyridine derivatives such as 1,4-dihydronicotinamide; quaternary ammonium salts of organosilanes and organoboranes, quaternary ammonium salts such as tetraammonium phenylsulfonylacetate and tetraammonium phenylpropiolate; dicyandiamide; and the like. One of the above thermal base generators may be used alone, or two or more may be used in combination.

[0086] Among these, it is preferable to use a photobase generator having a cation made of a biguanide derivative, which can promote the decomposition of aliphatic polycarbonates with the addition of a small amount. Examples of photobase generators having a cation made of a biguanide derivative include the above-mentioned 1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidinium 2-(3-benzoylphenyl)propionate and 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidinium n-butyltriphenylborate.

[0087] The content of the acid generator or base generator is preferably 0.01 to 50 parts by mass, more preferably 0.1 to 40 parts by mass, even more preferably 0.1 to 30 parts by mass, even more preferably 0.1 to 20 parts by mass, and even more preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of the aliphatic polycarbonate. When the content of the acid generator or base generator is equal to or greater than the above-mentioned lower limit, the thermal decomposition of the aliphatic polycarbonate can be more efficiently promoted. Furthermore, when the content of the acid generator or base generator is equal to or less than the above-mentioned upper limit, the amount of the acid generator or base generator as a solid is reduced when a solution of the resin composition is applied to form a coating film, resulting in good coatability.

[0088] [Other Additives for Resin Composition] In one embodiment of the present invention, the resin composition may contain additives other than the acid generator, base generator, and sensitizer, as long as the effects of the present invention are not impaired. Examples of such additives include antioxidants, antidegradants, antiblocking agents, and oxidizing agents such as peroxides. These additives may be used alone or in combination of two or more. When the resin composition contains these additives, the content of each additive is preferably 0.0001 to 30 parts by mass, more preferably 0.001 to 20 parts by mass, and even more preferably 0.01 to 10 parts by mass per 100 parts by mass of the non-sticky resin.

[0089] [Dilution Solvent] In one aspect of the present invention, from the viewpoint of improving the coatability to the pressure-sensitive adhesive layer (α) or a release sheet for transfer, the resin composition may be in the form of a solution by adding a dilution solvent together with the various active ingredients described above. Examples of the dilution solvent include water and organic solvents. Examples of organic solvents include toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropyl alcohol, t-butanol, s-butanol, acetylacetone, cyclohexanone, n-hexane, and cyclohexane. Two or more of these dilution solvents may be used in combination. The organic solvent used in the synthesis of the non-sticky resin may be used as the dilution solvent, or the organic solvent used in the synthesis of the non-sticky resin and / or one or more other organic solvents may be added to enable uniform coating of the resin composition.

[0090] <Substrate> The substrate used in the pressure-sensitive adhesive sheet of one embodiment of the present invention is appropriately selected according to the application of the pressure-sensitive adhesive sheet.Specific examples include various papers such as high-quality paper, art paper, coated paper, glassine paper, etc., and laminated paper obtained by laminating a thermoplastic resin such as polyethylene on these paper substrates; porous materials such as nonwoven fabrics; plastic films or sheets containing one or more resins selected from polyolefin resins such as polyethylene resins and polypropylene resins, polyester resins such as polybutylene terephthalate resins and polyethylene terephthalate resins, acetate resins, ABS resins, polystyrene resins, vinyl chloride resins, polyimide resins, etc.; glass substrates; metal substrates made of iron, aluminum, gold, silver, copper, etc.The substrate used in one embodiment of the present invention may be a single-layer film or sheet, or a multilayer film or sheet that is a laminate of two or more layers.In addition, the plastic film or sheet may be unstretched, or may be stretched uniaxially or biaxially, e.g., longitudinally or transversely. Furthermore, the plastic film or sheet may contain an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a slip agent, an antiblocking agent, a colorant, and the like.

[0091] Furthermore, when the substrate used in one embodiment of the present invention is a plastic film or sheet, from the viewpoint of improving the adhesion between the substrate and the pressure-sensitive adhesive layer (α) and / or the pressure-sensitive adhesive layer (γ), it is preferable to subject the surface of the substrate to a surface treatment such as an oxidation method or a roughening method, as necessary. Examples of oxidation methods include corona discharge treatment, plasma treatment, chromic acid oxidation (wet), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment, etc. Furthermore, examples of roughening methods include sandblasting and solvent treatment. These surface treatments are appropriately selected depending on the type of substrate, but corona discharge treatment is preferred from the viewpoint of the effect of improving the adhesion to the pressure-sensitive adhesive layer and operability. Furthermore, the surface of the substrate may be subjected to a primer treatment.

[0092] The thickness of the substrate is appropriately selected depending on the application of the PSA sheet, but from the viewpoint of handleability, it is preferably 10 to 250 μm, more preferably 15 to 200 μm, and even more preferably 20 to 150 μm. The substrate may consist of one layer (single layer), or may consist of two or more layers. When the substrate consists of multiple layers, these multiple layers may be the same or different from each other.

[0093] <Release Material> The release material used in the pressure-sensitive adhesive sheet of one embodiment of the present invention is not particularly limited, and examples thereof include release sheets that have been subjected to a single-sided release treatment or a double-sided release treatment, and examples thereof include a release material substrate coated with a release agent.

[0094] Examples of substrates for release materials include papers such as fine paper, glassine paper, and kraft paper; plastic films such as polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin; and olefin resin films such as polypropylene resin and polyethylene resin.

[0095] 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-based resins.

[0096] The thickness of the release material is not particularly limited, but is preferably 10 to 200 μm, more preferably 25 to 170 μm, and even more preferably 35 to 80 μm.

[0097] <Adhesive layer (γ)> In the configuration of the adhesive sheet 3 shown in Fig. 1(c), the adhesive layer (γ) 23 provided on the surface of the substrate 11 opposite to the adhesive layer (α) 13 is not particularly limited, and an adhesive layer made of an adhesive composition known as a raw material for general adhesive layers can be appropriately selected and used. However, if the thermal conductivity of the substrate is high or if the thermal conductivity of the adherend is high, the heat generated during the thermal decomposition of the sacrificial layer (β) may be conducted to the adhesive layer (γ). In anticipation of such a case, the thermal decomposition temperature (T γ ) is the thermal decomposition temperature (T β ) may be adjusted to be higher than the temperature at which the adhesive layer (γ) is heated. Specifically, the adhesive layer (γ) may have the same configuration as the above-mentioned adhesive layer (α). The adhesive layer (γ) may consist of one layer (single layer), or may consist of two or more layers. When the adhesive layer (γ) consists of multiple layers, these multiple layers may be the same or different from each other.

[0098] Furthermore, from the viewpoint of improving the coatability to substrates, release materials, release sheets for transfer, etc., the pressure-sensitive adhesive composition may contain the dilution solvent for the pressure-sensitive adhesive layer (α) described above together with the various active ingredients for the pressure-sensitive adhesive layer (α), and may be in the form of a solution of the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer (γ).

[0099] The thickness of the pressure-sensitive adhesive layer (γ) is appropriately selected depending on the application of the pressure-sensitive adhesive sheet, but is preferably 1 to 50 μm, more preferably 3 to 40 μm, even more preferably 6 to 30 μm, and still more preferably 10 to 20 μm.

[0100] <Method for manufacturing pressure-sensitive adhesive sheet> The method for manufacturing the pressure-sensitive adhesive sheet of the present invention is not particularly limited. For example, the pressure-sensitive adhesive sheet 1 shown in Fig. 1(a) can be produced by applying a solution of a pressure-sensitive adhesive composition onto a substrate 11 and drying it to form a pressure-sensitive adhesive layer (α) 13, and then applying a solution of a resin composition onto the pressure-sensitive adhesive layer (α) 13 and drying it to form a sacrificial layer (β) 14.

[0101] Furthermore, the adhesive sheet 2 shown in FIG. 1(b) can be produced, for example, by applying a solution of an adhesive composition onto a release material 15, drying the applied solution to form an adhesive layer (α) 13, and then applying a solution of a resin composition onto the adhesive layer (α) 13, and drying the applied solution to form a sacrificial layer (β) 14.

[0102] 1(c), for example, a solution of the adhesive composition is applied to a release material 15, followed by drying to form a laminate of the release material 15 and the adhesive layer (γ).Then, the adhesive sheet 3 can be produced by bonding the surface of the adhesive layer (γ) of this laminate to the surface of the substrate 11 of the adhesive sheet 1 in FIG. 1(a) opposite to the surface on which the adhesive layer (α) 13 is laminated.

[0103] Here, the pressure-sensitive adhesive layer (α) may be formed on the substrate 11 or the release material 15 by a transfer coating method in which a solution of the pressure-sensitive adhesive composition is applied to a release sheet, dried to form the pressure-sensitive adhesive layer (α), and then the pressure-sensitive adhesive layer (α) is laminated to the surface of the substrate 11 or the release material 15. The same applies to the pressure-sensitive adhesive layer (γ) and the sacrificial layer (β).

[0104] Examples of methods for applying a solution of the adhesive composition onto the substrate 11 or the release material 15, and methods for applying a solution of the resin composition onto the adhesive (α), include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0105] In order to prevent solvents and low-boiling-point components from remaining and, if a crosslinking agent is included, to promote crosslinking (reaction) and exhibit adhesiveness, it is preferable to apply the pressure-sensitive adhesive composition to the substrate 11 or the release material 15 to form a coating film, followed by heat treatment. The same applies to the resin composition. The temperature conditions for the heat treatment are, for example, 70 to 150°C, preferably 80 to 120°C. The treatment time for the heat treatment is preferably 30 seconds to 5 minutes, more preferably 40 to 180 seconds.

[0106] <Physical Properties of Pressure-Sensitive Adhesive Sheet> In the pressure-sensitive adhesive sheet of one embodiment of the present invention, the adhesive strength of the surface of the sacrificial layer (β) opposite to the side laminated with the pressure-sensitive adhesive layer (α) is preferably less than 0.1 N / 25 mm.

[0107] The pressure-sensitive adhesive sheet of one embodiment of the present invention is preferably heat-treated at 200°C for 1 hour to decompose the sacrificial layer (β), and the adhesive strength of the adhesive surface (surface 13a) of the exposed pressure-sensitive adhesive layer (α) is preferably 0.1 N / 25 mm or more, more preferably 0.2 N / 25 mm or more, even more preferably 0.3 N / 25 mm or more, still more preferably 0.5 N / 25 mm or more, and particularly preferably 0.7 N / 25 mm or more. Note that the adhesive strength specified here is the adhesive strength immediately after the pressure-sensitive adhesive sheet is heat-treated at 200°C for 1 hour, but this adhesive strength is maintained even 24 hours after the heat treatment.

[0108] <Uses of the Pressure-Sensitive Adhesive Sheet> Uses of the pressure-sensitive adhesive sheet of the present invention will be described below. In recent years, various devices have become smaller and more functional, and dust that enters or is generated within the devices can cause major problems in the functionality of the devices. For example, in the case of a camera's imaging element, dust adhering to an imaging section such as a lens can cause major problems in imaging. The pressure-sensitive adhesive sheet of the present invention is used by being attached to the periphery of a portion where it is desirable to reliably prevent dust from adhering or entering, such as an imaging section such as a lens in a camera's imaging element. After peeling off the release material 15 and bonding the surface 13b of the pressure-sensitive adhesive layer (α) or the surface 23b of the pressure-sensitive adhesive layer (γ) to the surface of an adherend, the pressure-sensitive adhesive sheet of the present invention (e.g., the pressure-sensitive adhesive sheet 2 shown in FIG. 1(b) and the pressure-sensitive adhesive sheet 3 shown in FIG. 1(c)) can be heated, a non-contact operation, at a desired timing without peeling off the release material, to thermally decompose the sacrificial layer (β) 14, exposing the surface 13a of the pressure-sensitive adhesive layer (α), and thereby exhibiting adhesive properties. Therefore, there is no need to peel off the release liner inside the adherend device. Peeling off the release liner inside the adherend device can generate dust from the release liner, which can adversely affect the device. In contrast, the pressure-sensitive adhesive sheet of the present invention can exhibit adhesiveness by heating, a non-contact operation, without the need to peel off the release liner inside the adherend device, thereby eliminating the generation of dust due to the peeling operation of the release liner. Furthermore, because adhesiveness can be exhibited by heating, a non-contact operation, at the desired timing, there is no risk of damaging the device through contact operations such as pressure application. Therefore, the pressure-sensitive adhesive sheet of the present invention is extremely suitable for use in devices that are susceptible to the intrusion of dust and the application of pressure, a contact operation. Furthermore, the pressure-sensitive adhesive sheet of the present invention maintains its adhesive strength exhibited by heating for a long period of time, and can therefore continue to adsorb and capture dust that subsequently invades the device or is generated inside the device. Therefore, device malfunctions (e.g., poor imaging in the case of an image sensor) that may be caused by dust can be suppressed for a long period of time.

[0109] Here, when the sacrificial layer (β) contains an aliphatic polycarbonate as a non-tacky resin and also contains a photoacid generator or a photobase generator, the thermal decomposition of the sacrificial layer (β) can be promoted by irradiating the sacrificial layer (β) with active energy rays before or simultaneously with heating to thermally decompose the sacrificial layer (β). Therefore, the thermal decomposition temperature of the sacrificial layer (β) can be lowered and the time required for thermal decomposition of the sacrificial layer (β) can be shortened. Examples of active energy rays include ionizing radiation, i.e., X-rays, ultraviolet rays, and electron beams. Among these, ultraviolet rays are preferred because they are relatively easy to install in irradiation equipment.

[0110] When ultraviolet light is used as the ionizing radiation, near ultraviolet light containing ultraviolet light with a wavelength of about 200 to 380 nm may be used for ease of handling. The light intensity may be appropriately selected depending on the type and amount of the photoacid generator or photobase generator, as well as the thickness of the sacrificial layer (β). Typically, it is 50 to 2000 mJ / cm. ２ about 100 to 1700 mJ / cm ２ is preferred, and 200 to 1400 mJ / cm ２ is more preferred.

[0111] The UV irradiance is usually 50 to 500 mW / cm ２ about 100 to 450 mW / cm ２ is preferred, and 200 to 400 mW / cm ２ The ultraviolet light source is not particularly limited, and for example, a high-pressure mercury lamp, a metal halide lamp, a UV-LED, etc. may be used.

[0112] When an electron beam is used as the ionizing radiation, the acceleration voltage may be appropriately selected depending on the type and amount of the photoacid generator or photobase generator, as well as the thickness of the sacrificial layer (β). An acceleration voltage of approximately 10 to 1000 kV is usually preferred. The irradiation dose may be set within a range in which an acid or base is appropriately generated from the photoacid generator or photobase generator, and is usually selected within a range of 10 to 1000 krad. The electron beam source is not particularly limited, and various electron beam accelerators such as Cockcroft-Walton type, Pandegraaf type, resonant transformer type, insulating core transformer type, linear type, dynamitron type, and high-frequency type may be used.

[0113] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The physical properties in the following examples were measured by the following methods.

[0114] <Weight average molecular weight (Mw)> Measurement was performed using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8220GPC") under the following conditions, and the value measured in terms of standard polystyrene was used. (Measurement conditions) Column: "TSK guard column SuperH-H", "TSK gel SuperHM-H", "TSK gel SuperHM-H", and "TSK gel SuperH2000" (all manufactured by Tosoh Corporation) connected in sequence Column temperature: 40°C Developing solvent: chloroform Flow rate: 1.0 mL / min

[0115] <Thermal decomposition temperature> Using a simultaneous thermogravimetry and differential thermal analysis (TG-DTA) device (Shimadzu Corporation, product name "DTG-60"), the adhesive layer (α) or the sacrificial layer (β) was used as a sample, and the mass of the sample was continuously measured while changing the sample temperature. The temperature at which the mass change rate of the sample reached -50% was determined as the thermal decomposition temperature. The measurement conditions are as follows: (Measurement conditions) - Sample amount: 20 mg - Heating rate: 10°C / min - Measurement temperature range: 40°C to 500°C - Nitrogen (N ２) Flow rate: 100 mL / min The mass change rate of the sample was calculated using the following formula: In the formula, "Wb" is the mass of the sample before the start of measurement, and "Wa" is the mass of the sample at a temperature of a°C. (Sample mass change rate) = {(Wa - Wb) / Wb} x 100

[0116] <Glass Transition Temperature (Tg)> The glass transition temperatures of the aliphatic polycarbonate resins used in Examples 1 and 2 were measured using a differential scanning calorimeter (manufactured by TA Instruments, product name "DSC Q2000") under the following conditions: (Measurement Conditions) Heating rate: 20°C / min Measurement temperature range: -20°C to 150°C

[0117] <Measurement of Laminate Thickness> Measurement was performed using a constant pressure thickness gauge (model number "PG-02J", conforming to the standard specifications "JIS K6783, Z1702, Z1709") manufactured by Teclock Corporation. Specifically, the total thickness of the pressure-sensitive adhesive sheet to be measured was measured, and the value obtained by subtracting the thickness of the substrate, which was measured in advance, was defined as the "total thickness of the pressure-sensitive adhesive layer (α) and the sacrificial layer (β)."

[0118] <Measurement of thickness of each layer> Using a scanning electron microscope (manufactured by ZEISS, product name "CrossBeam 550"), the cross section of the pressure-sensitive adhesive sheet to be measured in the thickness direction was observed, and the thickness ratio of the pressure-sensitive adhesive layer (α) to the sacrificial layer (β) was measured. Then, based on the thickness ratio of the pressure-sensitive adhesive layer (α) to the sacrificial layer (β), the thickness of each layer was calculated from the actual measured value of "the total thickness of the pressure-sensitive adhesive layer (α) and the sacrificial layer (β)" measured by the above-mentioned method.

[0119] Example 1 A pressure-sensitive adhesive sheet was prepared by directly laminating a pressure-sensitive adhesive layer (α) and a sacrificial layer (β) in this order onto a substrate. (1) Substrate: A 25 μm thick polyimide film (manufactured by DuPont-Toray Co., Ltd., product name "Kapton (registered trademark) 100H") was used as the substrate. (2) Pressure-sensitive adhesive layer (α): 100 parts by mass (solids ratio) of an acrylic copolymer (an adhesive resin having structural units derived from raw material monomers consisting of n-butyl acrylate (BA) / acrylic acid (AAc) = 90.0 / 10.0 (mass ratio), mass average molecular weight (Mw): 410,000) (dilution solvent: ethyl acetate, active ingredient (solids) concentration: 40% by mass) was blended with 0.5 parts by mass (solids ratio) of a TDI (tolylene diisocyanate) crosslinking agent, an isocyanate-based crosslinking agent, and mixed. The mixture was further diluted with ethyl acetate and stirred uniformly to prepare a pressure-sensitive adhesive composition solution. Next, the solution of this adhesive composition was applied to a release sheet and dried to form a 15 μm thick adhesive layer (α), and this adhesive layer (α) was bonded to a substrate. The thermal decomposition temperature of the adhesive layer (α) was 397°C. (3) Sacrificial Layer (β) A non-adhesive resin, polypropylene carbonate (manufactured by EMPOWER MATERIALS, mass average molecular weight: 60,000, product name "QPAC40"), was diluted with ethyl acetate and stirred uniformly to prepare a solution of a resin composition with an active ingredient concentration (solid content concentration) of 40% by mass. The structural unit of the polypropylene carbonate used in this example is shown in the following formula (b-3).

[0120]

[0121] The polypropylene carbonate represented by formula (b-3) can be obtained by the reaction of R １ is CH ３ and R ２ ~R ４ has a constitutional unit in which

[0122] Next, the solution of this resin composition is applied onto a release sheet and dried to form a 3 μm thick sacrificial layer (β), and this sacrificial layer (β) and a pressure-sensitive adhesive layer (α) are bonded together to prepare a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer (α) and the sacrificial layer (β) are directly laminated in this order on the substrate.The glass transition temperature of the polypropylene carbonate used in this example is 29 ° C.The thermal decomposition temperature of the sacrificial layer (β) is 269 ° C.

[0123] Example 2 A pressure-sensitive adhesive sheet was produced under the same conditions as in Example 1, except that the thickness of the sacrificial layer (β) was changed to 1 μm.

[0124] The adhesive strength of the pressure-sensitive adhesive sheets prepared in Examples 1 and 2 was measured before heating, immediately after heating, and after standing for 24 hours. The results are shown in Table 1. The adhesive strength was measured by attaching a stainless steel plate (SUS304, polished #360) to a pressure-sensitive adhesive sheet cut into 25 mm x 200 mm at 23°C and 50% RH (relative humidity) and standing for 24 hours in the same environment. Then, the adhesive strength was measured in the same environment using a 180° peel method at a pulling rate of 300 mm / min according to JIS Z0237:2000. The "adhesive strength before heating" was measured before the pressure-sensitive adhesive sheets prepared in Examples 1 and 2 were heated in an oven at 200°C with the sacrificial layer (β) exposed. The "adhesive strength immediately after heating" was measured after the pressure-sensitive adhesive sheets prepared in Examples 1 and 2 were placed in an oven at 200°C for 1 hour, with the sacrificial layer (β) exposed, and then removed from the oven and allowed to cool to room temperature (23°C). The "adhesive strength when left standing for 24 hours after heating" was measured by placing the pressure-sensitive adhesive sheets produced in Examples 1 and 2 in an oven at 200°C with the sacrificial layer (β) exposed, heating them for 1 hour, and then leaving them standing for 24 hours in an environment of 23°C and 50% RH. The measurement results are shown in Table 1. In Table 1, "<0.1" means less than 0.1.

[0125]

[0126] It is clear from Table 1 that the pressure-sensitive adhesive sheets of Examples 1 and 2 were non-adhesive before heating and developed adhesiveness after heating. Furthermore, the adhesive strength was maintained even after being kept in a room temperature (23°C) environment for 24 hours after heating, which also revealed that the adhesive strength developed by heating was maintained over a long period of time.

[0127] The pressure-sensitive adhesive sheet of the present invention can exhibit adhesiveness at a desired timing by performing heating, a non-contact operation, without requiring a physical contact operation such as pressure application. Moreover, the exhibited adhesiveness can be maintained for a long period of time. Therefore, it is suitable for use as a dust adsorption / capture device used in precision equipment that is sensitive to dust adhesion, such as a camera imaging element.

[0128] DESCRIPTION OF SYMBOLS 1, 2, 3 Pressure-sensitive adhesive sheet 11 Substrate 13 Pressure-sensitive adhesive layer (α) 13a Surface of pressure-sensitive adhesive layer (α) 13b Surface opposite to the surface of pressure-sensitive adhesive layer (α) 14 Sacrificial layer (β) 15 Release material 23 Pressure-sensitive adhesive layer (γ) 23b Surface of pressure-sensitive adhesive layer (γ)

Claims

1. A substrate or a release material has an adhesive layer (α) containing an adhesive resin, and further has a sacrificial layer (β) containing a non-adhesive resin laminated directly on the adhesive layer (α), and the thermal decomposition temperature (T β ) is the thermal decomposition temperature (T α ) lower than adhesive sheet.

2. The pressure-sensitive adhesive sheet according to claim 1, wherein the glass transition temperature of the non-adhesive resin contained in the sacrificial layer (β) is 15°C or higher.

3. The thermal decomposition temperature (T α ) and the thermal decomposition temperature (T β ) and the difference [T α -T β 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the temperature is 50° C. or higher.

4. The thermal decomposition temperature (T α 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the temperature (T) of the adhesive sheet is 320° C. or higher.

5. The thermal decomposition temperature (T β 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the temperature of the adhesive layer is 290°C or lower.

6. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the thickness of the sacrificial layer (β) is 0.01 to 10 μm.

7. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer (α) has a thickness of 1 to 50 μm.

8. The adhesive sheet according to claim 1 or 2, wherein the content of the non-adhesive resin in the sacrificial layer (β) is 70 mass % or more.

9. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the adhesive strength of the surface of the sacrificial layer (β) opposite to the side on which the pressure-sensitive adhesive layer (α) is laminated is less than 0.1 N / 25 mm.

10. An adhesive sheet according to claim 1 or 2, which is heat-treated at 200°C for 1 hour to decompose the sacrificial layer (β), and the adhesive strength of the adhesive surface of the exposed adhesive layer (α) is 0.1 N / 25 mm or more.

11. The thermal decomposition temperature (T β 3. The pressure-sensitive adhesive sheet according to claim 1, which can exhibit adhesiveness by heating at a temperature of 1000 K or higher.

12. The adhesive sheet according to claim 1 or 2 is heated to a temperature above the thermal decomposition temperature (T β ) or higher to decompose the sacrificial layer (β) and expose the adhesive surface of the adhesive layer (α), and then use the adhesive sheet.

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