JP7741995B1 - Adhesive sheets and how to use them - Google Patents

Abstract

The objective of the present invention is to provide an adhesive sheet that can exhibit adhesiveness at a desired timing through a non-contact operation without requiring an operation involving physical contact such as the application of pressure, and that can maintain the exhibited adhesiveness for a long period of time. The adhesive sheet has an adhesive layer (α) containing an adhesive resin on a substrate or release material, 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 ) of the sacrificial layer (β) is lower than the thermal decomposition temperature (T _α ) of the adhesive layer (α).

Description

The present invention relates to an adhesive sheet and a method for using the adhesive sheet.

Typically, adhesive sheets are stored, distributed, sold, etc. with the adhesive surface covered with a release material such as release paper or release film. However, once the release material is peeled off at the time of use to expose the adhesive surface, the release material becomes unnecessary. Therefore, in recent years, with a view to resource conservation and cost reduction, various adhesive sheets have been proposed that can exhibit adhesiveness during use without the use of a release material.

As such an adhesive sheet, Patent Document 1 describes an adhesive sheet coated with a heat-sensitive delayed-tack adhesive that exhibits adhesiveness when heated.
A 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 power, and the crystalline plasticizer is solid at room temperature and does not impart plasticity to the resin. However, when heated, it melts and swells or softens the resin, thereby developing adhesive properties. Therefore, an adhesive sheet coated with a heat-sensitive delayed tack adhesive is non-adhesive at room temperature, but can develop adhesive properties by heating during use.

Also known is an adhesive sheet coated with a pressure-sensitive adhesive layer that exhibits adhesiveness when pressure is applied.
For example, in the adhesive sheet described in Patent Document 2, when pressure is applied to a layer containing pressure-sensitive adhesive microcapsules encapsulating a radiation-curable adhesive, the microcapsules are destroyed and adhesiveness is exhibited. Thus, although the sheet is non-adhesive before pressure is applied, adhesiveness can be exhibited by applying pressure during use.

Patent No. 2914029 JP 2015-151479 A

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 the heat gradually crystallizes.

On the other hand, adhesive sheets coated with a pressure-sensitive adhesive layer exhibit adhesiveness when pressure is applied to the microcapsules, causing the adhesive contained 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 a heat-sensitive delayed-tack adhesive.
However, when the adherend is a precision instrument, etc., applying pressure to the PSA sheet can cause damage to the precision instrument, etc. Furthermore, depending on the adherend, it may be difficult to perform an operation that involves physical contact, such as applying pressure.

The present invention therefore aims to provide an adhesive sheet that can exhibit adhesiveness through a non-contact operation at the desired timing, without the need for 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, as well as a method for using this adhesive sheet.

The inventors have discovered that the above problem can be solved by configuring an adhesive sheet in such a way 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.

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 provided directly on the pressure-sensitive adhesive layer (α),
The pressure-sensitive adhesive sheet, wherein the thermal decomposition temperature (T _β ) of the sacrificial layer (β) is lower than the thermal decomposition temperature (T _α ) of the pressure-sensitive adhesive layer (α).
[2] The pressure-sensitive adhesive sheet described in [1] above, wherein the glass transition temperature of the non-adhesive resin contained in the sacrificial layer (β) is 15°C or higher.
[3] The pressure-sensitive adhesive sheet according to the above [1] or [2], wherein the difference [T _α -T _β ] between the thermal decomposition temperature (T _α ) of the pressure-sensitive adhesive layer ( _α ) and the thermal decomposition temperature (T β ) of the sacrificial layer (β) is 50°C or more.
[4] The pressure-sensitive adhesive sheet according to any one of the above [1] to [3], wherein the thermal decomposition temperature (T _α ) of the pressure-sensitive adhesive layer (α) is 320° C. or higher.
[5] The pressure-sensitive adhesive sheet according to any one of the above [1] to [4], wherein the thermal decomposition temperature (T _β ) of the sacrificial layer (β) is 290° C. or lower.
[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 pressure-sensitive adhesive layer (α) has a thickness of 1 to 50 μm.
[8] The pressure-sensitive adhesive sheet according to any one of [1] to [7] above, wherein the content of the non-adhesive resin in the sacrificial layer (β) is 70 mass% or more.
[9] 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. [0041] The pressure-sensitive adhesive sheet according to any one of [1] to [8] above.
[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 surface of the exposed pressure-sensitive adhesive layer (α) has an adhesive strength of 0.1 N/25 mm or more.
[11] The pressure-sensitive adhesive sheet according to any one of the above [1] to [10], which can exhibit adhesiveness by heating at a temperature equal to or higher than the thermal decomposition temperature (T _β ) of the sacrificial layer (β).
[12] A method for using the pressure-sensitive adhesive sheet according to any one of [1] to [11] above, by heating the pressure-sensitive adhesive sheet at a temperature equal to or higher than the thermal decomposition temperature (T _β ) of the sacrificial layer (β), decomposing the sacrificial layer (β), and exposing the adhesive surface of the pressure-sensitive adhesive layer (α).

The adhesive sheet of the present invention can develop adhesiveness at the desired timing by applying heat, a non-contact operation, without requiring physical contact such as pressure application. Moreover, the developed adhesiveness can be maintained for a long period of time.

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.

In the present invention, the determination of whether a target resin belongs to the "adhesive resin" or the "non-adhesive resin" is made based on the following steps (1) to (4).
Procedure (1): A 20 μm thick resin layer formed only from the target resin is placed on a 50 μm thick polyethylene terephthalate (PET) film, and a test piece measuring 300 mm long x 25 mm wide is prepared.
Procedure (2): In an environment of 23°C and 50% RH (relative humidity), the surface of the resin layer of the test piece is attached to a stainless steel plate (SUS304, 360 grit polished), and left to stand in the same environment 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 at a pulling rate of 300 mm/min in accordance with JIS Z0237:2000.
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."

In this invention, "active ingredient" refers to the components contained in the target composition excluding the diluent solvent.

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

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.

In this specification, the "thickness" of an object means the thickness of the entire object; for example, if the object consists of multiple layers, it means the total thickness of all layers that make up the object.

In the present invention, for preferred numerical ranges (e.g., ranges of content, etc.), the lower and upper limits 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."

<Configuration of the 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).
FIG. 1 is a cross-sectional schematic view of an example of the structure of the pressure-sensitive adhesive sheet of the present invention.

An example of a pressure-sensitive adhesive sheet according to one embodiment of the present invention is a pressure-sensitive adhesive sheet 1 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, as shown in FIG. 1( a).
In the pressure-sensitive adhesive sheet 1 shown in Fig. 1(a), heating, which is a non-contact operation, causes the sacrificial layer (β) 14 to thermally decompose, exposing the surface 13a of the pressure-sensitive adhesive layer (α) 13 and thereby exhibiting adhesiveness. On the other hand, before heating, the surface 13a of the pressure-sensitive adhesive layer (α) 13 is covered and protected by the sacrificial layer (β) 14. Therefore, in the pressure-sensitive adhesive sheet shown in Fig. 1(a), without providing a release material on the sacrificial layer (β) 14, the surface 13a of the pressure-sensitive adhesive layer (α) 13 is protected by the sacrificial layer (β) 14 before use, such as storage, distribution, or sales, and 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 exhibit adhesiveness.
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.

Furthermore, the pressure-sensitive adhesive sheet of 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, as shown in FIG. 1( b).
The pressure-sensitive adhesive sheet 2 is a double-sided pressure-sensitive adhesive sheet that also has adhesiveness on the surface 13b opposite to the surface 13a of the pressure-sensitive adhesive layer (α) 13. 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 made to exhibit adhesiveness by heating, which is a non-contact operation, to expose the surface 13a of the pressure-sensitive adhesive layer (α) 13, without the need to peel off the release material.

Also, as shown in Figure 1(c), for example, the adhesive sheet 3 shown in Figure 1(a) may have an adhesive layer (γ) 23 containing an adhesive resin on the side of the substrate 11 opposite to the side on which the adhesive layer (α) 13 is directly laminated, and a release material 15 on the adhesive layer (γ) 23. After the release material 15 is peeled off to attach the surface 23b of the adhesive layer (γ) 23 exposed to the adherend, the release sheet 3 can be heated, a non-contact operation, to expose the surface 13a of the adhesive layer (α) 13 and develop adhesiveness, without the need to peel off the release material.

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

In addition, in the pressure-sensitive adhesive sheets 1, 2, and 3 shown in Figures 1(a) to (c), the sacrificial layer (β) may have a multilayer structure consisting of two or more layers. In this case, before use, such as during storage, distribution, or sales, the sacrificial layer on the surface side functions as a protective layer to protect the sacrificial layer on the lower side. Then, by performing heating, a non-contact operation, at the 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 enabling it to exhibit adhesive properties.

The shape of the adhesive sheet of one embodiment of the present invention may be, for example, a square, a rectangle, a polygon, a circle, or an annular shape, but is not limited to these shapes and may be appropriately selected depending on the intended use of the adhesive sheet. Furthermore, the adhesive sheet of one embodiment of the present invention may be, for example, a rolled body in which a long adhesive sheet is wound into a roll, or a wound body in which the long adhesive sheet is wound around a core material.

<Thermal decomposition temperature of the pressure-sensitive adhesive layer and the sacrificial layer>
In the pressure-sensitive adhesive sheet of the present invention, the thermal decomposition temperature (T _α ) of the pressure-sensitive adhesive layer (α) is adjusted to be higher than the thermal decomposition temperature (T _β ) of the sacrificial layer (β). By adjusting the temperature in this manner, the pressure-sensitive adhesive layer (α) can be stably maintained without being thermally decomposed by heating at or above the thermal decomposition temperature (T _β ) of the sacrificial layer (β), 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 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 adhesive layer (α), thereby allowing the adhesiveness to be expressed.

Here, the difference [T _α - _{T β} ] between the thermal decomposition temperature (T _α ) of the pressure-sensitive adhesive layer (α) and the thermal decomposition temperature (T _β ) of the sacrificial layer (β) is adjusted to preferably 50° C. or higher, more preferably 70° C. or higher, and even more preferably 100° C. or higher, from the viewpoint of thermally decomposing the sacrificial layer (β) while stably maintaining the pressure-sensitive adhesive layer (α) without thermal decomposition. The upper limit of [T _α - _{T β} ] is not particularly limited, but is, for example, 450° C., preferably 360° C., more preferably 270° C.

The thermal decomposition temperature (T _α ) of the pressure-sensitive adhesive layer (α) is adjusted to 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. There is no particular upper limit for the thermal decomposition temperature (T _α ) of the pressure-sensitive adhesive layer (α), but it is usually 550° C. or lower, preferably 500° C. or lower, and more preferably 450° C. or lower.

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

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.

<Thickness of Pressure-Sensitive Adhesive Layer (α) and 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 unlikely 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 develop 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.

<Adhesive Layer (α)>
The pressure-sensitive adhesive layer (α) of the pressure-sensitive adhesive sheet of the present invention contains a pressure-sensitive adhesive resin, and may also contain other pressure-sensitive adhesive additives such as a crosslinking agent and a tackifier.
Here, the pressure-sensitive adhesive layer (α) can be formed from a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive resin and, if necessary, further containing a pressure-sensitive adhesive additive.
Hereinafter, each component contained in the pressure-sensitive adhesive composition, which is a material for forming the pressure-sensitive 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 pressure-sensitive adhesive composition" can also be considered as "the content of each component in the pressure-sensitive adhesive layer (α) formed from the pressure-sensitive adhesive composition."
The pressure-sensitive adhesive layer (α) may consist of one layer (single layer) or two or more layers. When the pressure-sensitive adhesive layer (α) consists of multiple layers, these multiple layers may be the same or different from each other.

[Adhesive resin]
The adhesive resin used in one embodiment of the present invention may be any resin whose thermal decomposition temperature is higher than the thermal decomposition temperature 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 types of 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 still more preferably 40,000 to 1,000,000, from the viewpoint of improving adhesive strength.

The content of the adhesive resin is preferably 30 to 99.99% by mass, more preferably 40 to 99.95% by mass, more preferably 50 to 99.90% by mass, even more preferably 55 to 99.80% by mass, and even more preferably 60 to 99.70% by mass, based on the total amount (100% by mass) of the active ingredients in the adhesive composition.

In one aspect 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 pressure-sensitive 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 still more preferably 85 to 100 mass%, relative to the total amount (100 mass%) of the adhesive resin.
Acrylic resins that are preferred for use as adhesive resins are described below.

[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.

The mass average molecular weight (Mw) of the acrylic resin is preferably 100,000 to 1.5 million, more preferably 150,000 to 1.3 million, even more preferably 200,000 to 1.1 million, and even more preferably 300,000 to 1 million.

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, together with the structural unit (a1), a structural unit (a2) derived from a functional group-containing monomer (a2′) (hereinafter also referred to as “monomer (a2′)”) is more preferred.
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 still more preferably 4 to 8, from the viewpoint of improving adhesive properties.
The alkyl group contained in the monomer (a1') may be a linear alkyl group or a branched alkyl group.

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, with butyl (meth)acrylate being more preferred.

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

The functional group possessed by the monomer (a2') refers to a functional group that can react with a crosslinking agent described below to become a crosslinking initiation point or a functional group that has a crosslinking promoting 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 hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, and epoxy group-containing monomers.
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 carboxy group-containing monomer are preferred.

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; and unsaturated alcohols such as vinyl alcohol and allyl alcohol.
As the hydroxyl group-containing monomer, 2-hydroxyethyl (meth)acrylate is preferably used.

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 anhydrides thereof; 2-(acryloyloxy)ethyl succinate; and 2-carboxyethyl (meth)acrylate.
As the carboxy group-containing monomer, it is preferable to use (meth)acrylic acid.

The content of the structural unit (a2) 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, relative to all structural units (100% by mass) of the acrylic copolymer (A1). By ensuring that the content is within this range, the cohesive strength and heat resistance of the pressure-sensitive adhesive layer (α) tend to be appropriate.

The acrylic copolymer (A1) may further include a structural unit (a3) derived from a monomer (a3') other than the monomers (a1') and (a2').
In the acrylic copolymer (A1), the content of the structural units (a1) and (a2) 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).

Examples of 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.

[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), it is preferable that the pressure-sensitive adhesive composition further contains a crosslinking agent.
The crosslinking agent reacts with the functional groups of the adhesive resin to crosslink the resins together.

Examples of the crosslinking agent 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 viewpoint of increasing cohesive strength and improving adhesive strength, and from the viewpoint of ease of availability, and among isocyanate-based crosslinking agents, tolylene diisocyanate (TDI) is preferred.

The content of the crosslinking agent is adjusted appropriately depending on the number of functional groups possessed by the adhesive resin, but 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 even more preferably 0.1 to 2 parts by mass per 100 parts by mass of the adhesive resin having the above-mentioned functional groups, such as the above-mentioned acrylic copolymer.

[Tackifier]
In one embodiment of the present invention, from the viewpoint of obtaining a pressure-sensitive adhesive sheet with improved adhesive strength, the pressure-sensitive adhesive composition may further contain a tackifier.
Here, the term "tackifier" refers to a component that auxiliary improves the adhesive strength of an adhesive resin, and refers to an oligomer having a mass average molecular weight (Mw) of less than 10,000, and is distinguished from the adhesive resin described above.
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.

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.

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.

Here, from the viewpoint of easily preventing the softening and flow of the pressure-sensitive adhesive layer (α) when the sacrificial layer (β) is thermally decomposed, it is preferable that the content of the tackifier in the pressure-sensitive adhesive composition is 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, per 100 parts by mass of the pressure-sensitive adhesive resin contained in the pressure-sensitive adhesive composition, and most preferably no tackifier is contained.

[Other adhesive additives]
In one embodiment of the present invention, the pressure-sensitive adhesive composition may contain, in addition to the crosslinking agent and the tackifier, a pressure-sensitive adhesive additive used in a general pressure-sensitive adhesive, provided that the effects of the present invention are not impaired.
Such adhesive additives are appropriately selected depending on the type of adhesive resin used, and examples thereof include antioxidants, rust inhibitors, pigments, dyes, retarders, reaction accelerators (catalysts), ultraviolet absorbers, etc.
These 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.

[Dilution solvent]
In one embodiment of the present invention, from the viewpoint of improving the coatability to a substrate, a release material, a release sheet 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.
The dilution solvent may be water or an organic solvent.
Examples of the organic solvent 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.
These dilution solvents may be used in combination of two or more kinds.
The organic solvent used as the dilution solvent may be the same organic solvent used during the synthesis of the adhesive resin, or the organic solvent used during the synthesis of the adhesive resin and/or one or more other organic solvents may be added to enable the adhesive composition to be applied uniformly.

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

<Sacrificial layer (β)>
The sacrificial layer (β) of the pressure-sensitive adhesive sheet of the present invention contains a non-adhesive resin, and may further contain an additive such as an acid generator or a base generator.
Here, the sacrificial layer (β) can be formed from a resin composition containing a non-sticky 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 mentioned 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.

[Non-adhesive resin]
The non-tacky resin used in one embodiment of the present invention may be any non-tacky resin whose thermal decomposition temperature is lower than the thermal decomposition temperature of the pressure-sensitive adhesive layer (α), but a resin whose glass transition temperature is 15°C or higher is preferred.
A resin having a glass transition temperature of 15°C or higher is considered to be a non-sticky resin that remains in a solid state in a temperature range below or near 15°C.
Therefore, by using a resin having a glass transition temperature of 15°C or higher as the non-sticky resin, it is possible to make the sacrificial layer (β) containing the non-sticky resin more likely to become solid before use, such as during storage, distribution, or sales, thereby improving the handleability of the adhesive sheet.
In order to more reliably maintain the solid state of the sacrificial layer (β) containing the non-sticky resin and more reliably ensure the handleability of the pressure-sensitive adhesive sheet during storage, distribution, sales, and other pre-use stages, the glass transition temperature of the non-sticky resin is more preferably 20° C. or higher, and even more preferably 25° C. or higher. In addition, 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 lower, more preferably 130° C. or lower, even more preferably 110° C. or lower, and particularly preferably 50° C. or lower.
In the present invention, the "glass transition temperature" is a value measured by differential scanning calorimetry, specifically, a value measured based on the method described in the examples.

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

In one embodiment of the present invention, from the viewpoint of making the thermal decomposition temperature of the sacrificial layer (β) lower than the thermal decomposition temperature of the pressure-sensitive adhesive layer (α), the non-adhesive resin preferably contains an aliphatic polycarbonate.
When heated, the aliphatic polycarbonate decomposes from the end of the main chain. The heating temperature can be lower than the thermal decomposition temperature of the pressure-sensitive adhesive layer (α). Therefore, when the non-adhesive resin contains an aliphatic polycarbonate, the heating temperature can be 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 while maintaining the pressure-sensitive adhesive layer (α) stable, thereby exposing the pressure-sensitive adhesive layer (α) and exhibiting adhesiveness.

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

[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).

In formula (b-1), Z is an alkylene group, and the alkylene group 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-sticky resin with a relatively low thermal decomposition temperature.

The alkylene group that can be selected as Z may be a straight-chain alkylene group or a branched-chain alkylene group.
Examples of the straight-chain alkylene group 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.

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

With regard to the structural unit (b1) contained in the aliphatic polycarbonate used in one embodiment of the present invention, by taking into consideration the following items (1) to (5), it is easy to prepare a non-sticky resin with a low thermal decomposition temperature.
The following items are merely examples, and adjustments can be made taking into account other items.
(1) In the general formula (b-1), Z is a branched 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 in the linear alkylene group is adjusted to preferably 2 or less, more preferably 1. In addition, the total number of carbon atoms in the linear alkylene group including the substituents is adjusted to preferably 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 alkylene group, the number of carbon atoms in the branched alkylene group is adjusted to 3 to 8, preferably 3 to 6, and more preferably 3 to 4. In addition, the number of branches is 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. In addition, 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 substituents is adjusted to 3 to 8, preferably 3 to 6, and more preferably 3 to 4.

The aliphatic polycarbonate used in one embodiment of the present invention may be a homopolymer having only one type of structural unit (b1), or may be a copolymer having two or more types of structural units (b1), or may be a copolymer having a structural unit 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, and the molecular weight distribution (Mw/Mn) of the aliphatic polycarbonate is usually 1.01 or more.

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 consideration the following points (1) to (3).
The following items are merely examples, and adjustments can be made taking into account other items.
(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 still more preferably 90 to 100 mass%, relative to all structural units (100 mass%) of the aliphatic polycarbonate.
(2) The mass 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.

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.

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.

Here, from the viewpoint of lowering the thermal decomposition temperature (T _β ) as a non-tacky resin, the aliphatic polycarbonate preferably has a structural unit (b2) represented by the following general formula (b-2).

In formula (b-2), R ¹ to R ⁴ each independently represent a hydrogen atom, an alkyl group, a hydroxyl group, a carboxy group, or an alkoxy group.

The alkyl group that can be selected as R ¹ to R ⁴ may be a straight-chain alkyl group or a branched-chain alkyl group, but is preferably a straight-chain alkyl group.
The alkyl group preferably has 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, even more preferably 1 or 2 carbon atoms, and even more preferably 1 carbon atom.

The alkoxy group represented by R ¹ to R ⁴ may be a linear alkoxy group or a branched alkoxy group, but is preferably a linear alkoxy group.
The alkoxy group preferably has 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, even more preferably 1 or 2 carbon atoms, and still more preferably 1 carbon atom.

From the viewpoint of obtaining a non-sticky resin with a low thermal decomposition temperature, it is preferable that any one of R ¹ to R ⁴ is a hydrogen atom, it is more preferable that any two of R ¹ to R ⁴ are hydrogen atoms, it is even more preferable that any three of R ¹ to R ⁴ are hydrogen atoms, and it is most preferable that all of R ¹ to R ⁴ are hydrogen atoms.
Furthermore, when R ¹ to R ⁴ have 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. Furthermore, as described above, 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.
Aliphatic polycarbonates having such structural units have improved decomposition properties when heated, and can be more susceptible to thermal decomposition.

In the aliphatic polycarbonate used in one embodiment of the present invention, the content of structural unit (b2) is preferably 60 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass, relative to the total structural units (100% by mass) of the aliphatic polycarbonate.

[Method for producing aliphatic polycarbonate]
Aliphatic polycarbonates can be produced by a method including 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 controlling the water content to a predetermined amount or less as necessary.
For example, aliphatic polycarbonates having the structural unit (b2) can be produced by a method comprising a step of polymerizing ethylene oxide and ethylene oxide derivatives with carbon dioxide in the presence of a metal catalyst such as a zinc catalyst, while controlling the water content to a predetermined level or less as necessary.
The derivative of ethylene oxide means a compound in which one or more hydrogen atoms of ethylene oxide are substituted with a group (substituent) other than a hydrogen atom, and examples of the substituent include alkyl groups or alkoxy groups that can be selected as R ¹ to R ⁴ in the aliphatic polycarbonate represented by the above formula (b-2).

[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 susceptible to thermal decomposition, it is preferable that the resin composition 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 applying energy comes into contact with the aliphatic polycarbonate, making it easier to decompose the aliphatic polycarbonate. As a result, the sacrificial layer (β) can be thermally decomposed at a lower temperature or in a shorter time.

Depending on the type of energy applied, acid generators or base generators include photoacid generators or photobase generators, thermal acid generators or thermal base generators, etc.

The photoacid generator or photobase generator generates 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, examples of the photobase generator include α-aminoacetophenone compounds, oxime ester compounds, 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, and an alkoxybenzyl carbamate group, etc. 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.
The above photobase generators may be used alone or in combination of two or more.

Examples of photoacid generators include onium salts such as sulfonium salts, iodonium salts, diazonium salts, selenium salts, pyridinium salts, ferrocenium salts, phosphonium salts, and thiopyrium salts, with aromatic sulfonium salts and aromatic iodonium salts being more preferred. Aromatic sulfonium salts and aromatic iodonium salts are commercially available, and commercially available products may be used. _Examples of anion components include BF ₄ ⁻ , PF ₆ ⁻ , AsF 6 − , SbF ₆ ⁻ , and B(C ₆ F ₅ ) ₄ ⁻ , with ^PF ₆ ⁻ and B(C ₆ F ₅ ) ₄ ⁻ being particularly preferred.
The above photoacid generators may be used alone or in combination of two or more.

A thermal acid or 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; phosphonates; 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.

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 include guanidine derivatives such as guanidine propiolate, p-phenylene-bis-phenylguanidine propiolate, 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; and dicyandiamide.
The above thermal base generators may be used alone or in combination of two or more.

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 aforementioned 1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidinium 2-(3-benzoylphenyl)propionate and 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidinium n-butyltriphenylborate.

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, per 100 parts by mass of the aliphatic polycarbonate. Having the content of the acid generator or base generator at or above the lower limit mentioned above allows for more efficient promotion of the thermal decomposition of the aliphatic polycarbonate. Furthermore, having the content of the acid generator or base generator at or below the upper limit mentioned above reduces the amount of solid acid generator or base generator when a solution of the resin composition is applied to form a coating, improving coatability.

[Other additives for resin compositions]
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, anti-deterioration agents, anti-blocking 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.

[Dilution solvent]
In one embodiment of the present invention, the resin composition may be in the form of a solution by adding a diluent solvent together with the above-mentioned various active ingredients, from the viewpoint of improving the coatability to the pressure-sensitive adhesive layer (α) or a release sheet for transfer, etc. Examples of the diluent solvent include water and an organic solvent.
Examples of the organic solvent 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.
These dilution solvents may be used in combination of two or more kinds.
The organic solvent used as the dilution solvent may be the same organic solvent used in the synthesis of the non-sticky resin, 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 the dilution solvent so that the resin composition can be applied uniformly.

<Base material>
The substrate used in the pressure-sensitive adhesive sheet of one embodiment of the present invention is suitably selected according to the use of the pressure-sensitive adhesive sheet.Specifically, it can be exemplified by various papers such as wood-free 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 fabric; 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 such as 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 multi-layer film or sheet that is a laminate of two or more layers.
The plastic film or sheet may be unstretched or may be stretched uniaxially, e.g., longitudinally or transversely, or biaxially.
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.

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 the oxidation method include corona discharge treatment, plasma treatment, chromic acid oxidation (wet), flame treatment, hot air treatment, and ozone/ultraviolet irradiation treatment.
Examples of the roughening method include sandblasting and solvent treatment.
The surface treatment is selected appropriately depending on the type of substrate, but corona discharge treatment is preferred from the viewpoints of improving adhesion to the pressure-sensitive adhesive layer and ease of use. The surface of the substrate may also be subjected to a primer treatment.

The thickness of the substrate is appropriately selected depending on the application of the pressure-sensitive adhesive sheet, but from the viewpoint of ease of handling, 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 two or more layers. When the substrate consists of multiple layers, these multiple layers may be the same or different from each other.

<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 with one-sided release treatment and release sheets with double-sided release treatment, and examples thereof include those in which a release agent is applied to a substrate for the release material.

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

Examples of release agents include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, and butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, and fluorine-based resins.

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.

<Adhesive layer (γ)>
In the configuration of the pressure-sensitive adhesive sheet 3 shown in FIG. 1( c), the pressure-sensitive adhesive layer (γ) 23 provided on the surface of the substrate 11 opposite the pressure-sensitive adhesive layer (α) 13 is not particularly limited, and a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive composition known as a raw material for general pressure-sensitive adhesive layers can be appropriately selected and used. However, if the thermal conductivity of the substrate is high or 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 pressure-sensitive adhesive layer (γ). In anticipation of such a case, the thermal decomposition temperature ( _Tγ ) of the pressure-sensitive adhesive layer (γ) may be adjusted to be higher than the thermal decomposition temperature (Tβ) of the sacrificial layer ( _β ). Specifically, the pressure-sensitive adhesive layer (γ) may have the same configuration as the pressure-sensitive adhesive layer (α) described above.
The pressure-sensitive adhesive layer (γ) may consist of one layer (single layer) or two or more layers. When the pressure-sensitive adhesive layer (γ) consists of multiple layers, these multiple layers may be the same or different from each other.

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 in addition to the various active ingredients in 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).

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

<Method of manufacturing pressure-sensitive adhesive sheet>
The method for producing the pressure-sensitive adhesive sheet of the present invention is not particularly limited.
For example, the adhesive sheet 1 shown in FIG. 1( a) can be produced by applying a solution of an adhesive composition onto a substrate 11, 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.

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

Also, in the case of the adhesive sheet 3 shown in Figure 1(c), for example, a solution of the adhesive composition is applied to the release material 15 and dried to form a laminate of the release material 15 and the adhesive layer (γ). The adhesive sheet 3 can then 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 Figure 1(a) opposite to the surface on which the adhesive layer (α) 13 is laminated.

Here, the 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 adhesive composition is applied to a release sheet, dried to form the adhesive layer (α), and then laminated to the surface of the substrate 11 or the release material 15. The same applies to the adhesive layer (γ) and the sacrificial layer (β).

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

In order to prevent solvents and low-boiling-point components from remaining and, if a crosslinking agent is blended, to promote crosslinking (reaction) and thereby develop adhesiveness, it is preferable to apply the pressure-sensitive adhesive composition onto the substrate 11 or the release material 15 to form a coating film, and then to perform a heat treatment. The same applies to the resin composition.
The temperature condition for the heat treatment is, 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.

<Physical properties of 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.

The 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 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, even 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 adhesive sheet is heat-treated at 200°C for 1 hour, but this adhesive strength is maintained even 24 hours after the heat treatment.

<Applications of adhesive sheets>
The 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 serious problems in terms of the functionality of the devices. For example, in the case of a camera's image sensor, dust adhering to the image capturing section, such as the lens, can cause serious problems in terms of capturing images.
The pressure-sensitive adhesive sheet of the present invention is used by being attached to the periphery of a site where it is desired to reliably prevent the adhesion or intrusion of dust, such as an imaging part such as a lens in a camera imaging element.
In the pressure-sensitive adhesive sheet of the present invention (for example, the pressure-sensitive adhesive sheet 2 shown in FIG. 1(b) and the pressure-sensitive adhesive sheet 3 shown in FIG. 1(c)), 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 the adherend, heating, a non-contact operation, can be performed at a desired timing without peeling off the release material, thereby thermally decomposing the sacrificial layer (β) 14 and exposing the surface 13a of the pressure-sensitive adhesive layer (α), thereby exhibiting adhesiveness. Therefore, there is no need to peel off the release material inside the device that is the adherend. If the release material is peeled off inside the device that is the adherend, this operation may generate dust from the release material, which may 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 peeling off the release material inside the device that is the adherend, and therefore no dust is generated due to the operation of peeling off the release material. Moreover, because adhesiveness can be developed at the desired timing by heating, which is a non-contact operation, there is no risk of damaging equipment, etc., by contact operations such as applying pressure, etc. Therefore, the adhesive sheet of the present invention is extremely suitable for use in equipment, etc., that must be protected from the intrusion of dust, etc., or that must not be subjected to contact operations such as applying pressure, etc.
Furthermore, the adhesive strength developed by heating is maintained for a long period of time, and the adhesive sheet of the present invention can continue to adsorb and capture dust that subsequently enters the device or is generated within the device, thereby preventing device malfunctions (e.g., imaging failures in the case of an imaging element) that may be caused by dust for a long period of time.

Here, when the sacrificial layer (β) contains an aliphatic polycarbonate as a non-adhesive 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 for thermal decomposition of the sacrificial layer (β), thereby lowering the thermal decomposition temperature of the sacrificial layer (β) and shortening the time required for thermal decomposition of the sacrificial layer (β).
Examples of active energy rays include ionizing radiation, i.e., X-rays, ultraviolet rays, electron beams, etc. Among these, ultraviolet rays are preferred because it is relatively easy to introduce irradiation equipment.

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). The light intensity is typically about 50 to 2000 mJ/ ^cm² , preferably 100 to 1700 mJ/ ^cm² , and more preferably 200 to 1400 mJ/ ^cm² .

The ultraviolet irradiance is usually about 50 to 500 mW/cm ² , preferably 100 to 450 mW/cm ² , and more preferably 200 to 400 mW/cm ^2. There are no particular limitations on the ultraviolet source, and for example, a high-pressure mercury lamp, a metal halide lamp, a UV-LED, etc. can be used.

When an electron beam is used as the ionizing radiation, the acceleration voltage can be selected appropriately 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 generally preferred. The exposure dose should be set within a range that allows the photoacid generator or photobase generator to appropriately generate an acid or base, and is generally selected within the range of 10 to 1000 krad. There are no particular limitations on the electron beam source, and various electron beam accelerators can be used, such as Cockcroft-Walton, Pandegraaf, resonant transformer, insulated core transformer, linear, dynamitron, and high-frequency types.

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. Note that the physical properties in the following examples were measured using the following methods.

<Mass average molecular weight (Mw)>
Measurement was carried out using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8220GPC") under the following conditions, and the values measured were converted into standard polystyrene values.
(Measurement conditions)
Column: "TSK guard column Super H-H", "TSK gel Super HM-H", "TSK gel Super HM-H", and "TSK gel Super H2000" (all manufactured by Tosoh Corporation) connected in series. Column temperature: 40°C
Developing solvent: chloroform Flow rate: 1.0 mL/min

<Thermal decomposition temperature>
Using a simultaneous thermogravimetry and differential thermal analysis (TG-DTA) device (Shimadzu Corporation, product name "DTG-60"), the pressure-sensitive 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 defined as the thermal decomposition temperature.
The measurement conditions are as follows:
(Measurement conditions)
Sample amount: 20 mg
Temperature increase rate: 10°C/min
- Measurement temperature range: 40℃ to 500℃
Nitrogen (N ₂ ) flow rate under heated atmosphere: 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}×100

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

<Measurement of Laminate Thickness>
The measurement was carried out using a constant pressure thickness measuring instrument manufactured by Teclock Corporation (model number "PG-02J", conforming to the standard specifications "JIS K6783, Z1702, Z1709").
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 measured in advance was determined as the "total thickness of the pressure-sensitive adhesive layer (α) and the sacrificial layer (β)."

<Measurement of thickness of each layer>
A scanning electron microscope (manufactured by ZEISS, product name "CrossBeam 550") was used to observe a cross section in the thickness direction of the pressure-sensitive adhesive sheet to be measured, 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 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 adhesive layer (α) and the sacrificial layer (β)" measured by the above-mentioned method.

Example 1
A pressure-sensitive adhesive layer (α) and a sacrificial layer (β) were directly laminated in this order on the substrate to prepare a pressure-sensitive adhesive sheet.
(1) Substrate A polyimide film having a thickness of 25 μm (manufactured by DuPont-Toray Co., Ltd., product name "Kapton (registered trademark) 100H") was used as the substrate.
(2) Pressure-sensitive adhesive layer (α)
A solution of a pressure-sensitive adhesive composition was prepared by blending and mixing 100 parts by mass (solids ratio) of an acrylic copolymer (an adhesive resin; an acrylic copolymer 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 mass%) with 0.5 parts by mass (solids ratio) of a TDI (tolylene diisocyanate) crosslinking agent, an isocyanate crosslinking agent, and further diluting with ethyl acetate and stirring uniformly.
Next, the solution of this pressure-sensitive adhesive composition was applied onto a release sheet and dried to form a pressure-sensitive adhesive layer (α) having a thickness of 15 μm, and this pressure-sensitive adhesive layer (α) was then bonded to a substrate.
The thermal decomposition temperature of the pressure-sensitive adhesive layer (α) was 397°C.
(3) Sacrificial layer (β)
A non-sticky 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 mass%. The structural unit of the polypropylene carbonate used in this example is shown in the following formula (b-3).

The polypropylene carbonate represented by formula (b-3) has a structural unit in which R ¹ is CH ₃ and R ² to R ⁴ are H in the general formula (b-2).

Next, a solution of this resin composition was applied onto a release sheet and dried to form a 3 μm thick sacrificial layer (β), and this sacrificial layer (β) was bonded to the adhesive layer (α) to produce an adhesive sheet in which the adhesive layer (α) and the sacrificial layer (β) were directly laminated in this order on the substrate.
The glass transition temperature of the polypropylene carbonate used in this example was 29°C.
The thermal decomposition temperature of the sacrificial layer (β) was 269°C.

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.

The adhesive strength of the pressure-sensitive adhesive sheets prepared in Examples 1 and 2 was measured before heating, immediately after heating, and after being left to stand for 24 hours after heating. The results are shown in Table 1.
The adhesive strength was measured by attaching a stainless steel plate (SUS304, polished to #360) to a pressure-sensitive adhesive sheet cut to a size of 25 mm x 200 mm in an environment of 23°C and 50% RH (relative humidity), leaving the sheet to stand for 24 hours in the same environment, and then measuring the adhesive strength in the same environment using the 180° peel method at a pulling speed of 300 mm/min in accordance with JIS Z0237:2000.
The "adhesive strength before heating" was measured before the pressure-sensitive adhesive sheets produced in Examples 1 and 2 were heated.
The "adhesive strength immediately after heating" was measured by placing the adhesive sheets prepared in Examples 1 and 2 with the sacrificial layer (β) exposed in an oven at 200°C and heating for 1 hour, then removing them from the oven and allowing them to cool to room temperature (23°C).
The "adhesive strength when left undisturbed for 24 hours after heating" was measured by placing the adhesive sheets prepared in Examples 1 and 2 with the sacrificial layer (β) exposed in an oven at 200°C and heating for 1 hour, and then leaving them undisturbed 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.

Table 1 reveals that the 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 left in a room temperature (23°C) environment for 24 hours after heating, demonstrating that the adhesive strength developed by heating is maintained over a long period of time.

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

1, 2, 3 Adhesive sheet 11 Substrate 13 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 (11)

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) directly laminated thereon,
the thermal decomposition temperature (T _β ) of the sacrificial layer (β) is lower than the thermal decomposition temperature (T _α ) of the pressure-sensitive adhesive layer (α);
A pressure-sensitive adhesive sheet in which 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 . The pressure-sensitive adhesive sheet of claim 1, wherein the glass transition temperature of the non-adhesive resin contained in the sacrificial layer (β) is 15°C or higher. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the difference [T _α -T _β ] between the thermal decomposition temperature (T _α ) of the pressure-sensitive adhesive layer (α) and the thermal decomposition temperature (T _β ) of the sacrificial layer (β) is 50°C or more. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer (α) has a thermal decomposition temperature (T _α ) of 320° C. or higher. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the thermal decomposition temperature (T _β ) of the sacrificial layer (β) is 290° C. or lower. 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. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the thickness of the pressure-sensitive adhesive layer (α) is 1 to 50 μm. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the content of the non-adhesive resin in the sacrificial layer (β) is 70% by mass or more. The pressure-sensitive 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 surface of the exposed pressure-sensitive adhesive layer (α) has an adhesive strength of 0.1 N/25 mm or more. The pressure-sensitive adhesive sheet according to claim 1 or 2, which can exhibit adhesiveness by heating at a temperature equal to or higher than the thermal decomposition temperature (T _β ) of the sacrificial layer (β). A method for using the adhesive sheet according to claim 1 or 2, comprising heating the adhesive sheet at a temperature equal to or higher than the thermal decomposition temperature ( _Tβ ) of the sacrificial layer (β) to decompose the sacrificial layer (β) and expose the adhesive surface of the adhesive layer (α).