JP7800038B2 - Pressure-sensitive adhesive sheet, its manufacturing method, and method for measuring adhesion - Google Patents

Description

This disclosure relates to a pressure-sensitive adhesive sheet, a method for manufacturing the same, and a method for measuring adhesion.

Decorative sheets have traditionally been used to decorate and protect the surfaces of, for example, interior and exterior building components, fixtures or fittings, surface decorative panels, and interior or exterior vehicle components.

After being applied to an adherend, a decorative sheet must adhere to the adherend for an extended period of time without lifting or peeling. Therefore, decorative sheets must have a strong adhesive layer made of adhesive on the entire surface of the decorative sheet that comes into contact with the adherend. On the other hand, if a decorative sheet has strong adhesive strength, it becomes difficult to reuse the decorative sheet by peeling it off and reapplying it to the adherend. For example, if wrinkles occur during application, they cannot be corrected, and the only option is to peel off and discard the decorative sheet once it has been applied to the adherend. Furthermore, when reusing the adherend, it is necessary to remove any adhesive (also known as "adhesive residue") that remains on the surface of the adherend when the decorative sheet is peeled off.

Because decorative sheets that have been given strong adhesive strength by an adhesive layer have such strong adhesive strength, special equipment and skilled techniques are required to produce and apply decorative materials using the decorative sheets, which makes the production and application of decorative materials highly difficult tasks.
Therefore, in order to make decorative sheets easier to use, there has been a demand for sheets that maintain the necessary long-term adhesion while also improving reworkability, so that if application fails, the sheets can be peeled off and reapplied as is.

For example, Patent Document 1 proposes an adhesive sheet that improves adhesion while eliminating adhesive residue, in which a primer containing a foaming agent is heated and foamed on one or both sides of a substrate sheet made of a soft synthetic resin, to form a primer layer whose surface has bubbles or irregularities caused by the destruction of the bubbles, and an adhesive layer is laminated on the primer layer.
Furthermore, Patent Document 2 proposes a pressure-sensitive adhesive sheet having excellent interlayer adhesion and removability with little adhesive residue, the pressure-sensitive adhesive sheet having a primer layer formed from a forming composition containing a specific aqueous polyester resin between a base layer and a pressure-sensitive adhesive layer.

Japanese Patent Application Publication No. 7-145354 JP 2016-94517 A

The pressure-sensitive adhesive sheets proposed in the above Patent Documents 1 and 2 are said to have excellent adhesion to the adherend (referred to as "adhesion" and "interlayer adhesion" in the respective documents), and are also excellent in reworkability with little adhesive residue.
However, the pressure-sensitive adhesive sheets described in Patent Documents 1 and 2 both have room for improvement in the primer layer for achieving adhesion to the adherend. That is, the pressure-sensitive adhesive sheet described in Patent Document 1 requires a step of foaming the primer layer by heating during its production, and the pressure-sensitive adhesive sheet described in Patent Document 2 uses a special resin composition for forming the primer layer. Therefore, there are problems such as poor productivity and a lack of versatility.

Incidentally, excellent reworkability is required even when the decorative sheet is placed in a harsh environment, for example, under high temperatures such as direct sunlight exposure or outdoor exposure, from the time it is adhered to the adherend until it is peeled off. Furthermore, excellent reworkability is required for any adherend, regardless of the type of adherend. Thus, in recent years, increasingly high performance has been required for the reworkability of PSA sheets.
However, the pressure-sensitive adhesive sheets proposed in the above-mentioned Patent Documents 1 and 2 do not have such high reworkability.

The present disclosure therefore aims to provide a pressure-sensitive adhesive sheet with excellent reworkability, a method for manufacturing the same, and a method for measuring adhesion strength.

The present inventors have conducted extensive research to solve the above-mentioned problems, and have found that the above-mentioned problems can be solved by making the adhesive layer a porous layer in a pressure-sensitive adhesive sheet having a base layer, an adhesive layer, and a release sheet layer, and by setting the adhesion strength between the base layer and the adhesive layer, and the adhesion strength between the adhesive layer and a predetermined SUS304 steel plate, within predetermined ranges.
The adhesive tape has a base layer, an adhesive layer, and a peelable sheet layer in this order,
The adhesive layer is porous,
The adhesion strength A between the base layer and the adhesive layer measured by a predetermined measurement method is 17.0 N/25 mm or more,
The adhesion strength B between the adhesive layer and the SUS304 steel plate measured by a predetermined measurement method is 1.0 N/25 mm or more and 10.0 N/25 mm or less,
Adhesive sheet,
to provide.

The present disclosure also provides the following method for producing a pressure-sensitive adhesive sheet:
an adhesive coating layer forming step of applying an adhesive layer-forming resin composition to the releasable surface of the release sheet layer to form an adhesive coating layer of the adhesive layer-forming resin composition;
an adhesive layer forming step of drying the adhesive coating layer to form a porous adhesive layer; and an adhesion step of adhering the adhesive layer to a substrate layer.
Including,
The adhesion strength A between the base layer and the adhesive layer measured by a predetermined measurement method is 17.0 N/25 mm or more,
The adhesion strength B between the adhesive layer and the SUS304 steel plate measured by a predetermined measurement method is 1.0 N/25 mm or more and 10.0 N/25 mm or less,
A method for manufacturing a pressure-sensitive adhesive sheet,
to provide.

Furthermore, the present disclosure provides the following methods for measuring adhesion:
(i) A method for measuring the adhesion strength A of a pressure-sensitive adhesive sheet, in which a pressure-sensitive adhesive sheet having a base layer and a pressure-sensitive adhesive layer is measured in accordance with Method 3 (180° peel adhesion strength of double-sided tape) of JIS Z0237:2009 (Test methods for pressure-sensitive adhesive tapes and pressure-sensitive adhesive sheets), by adhering a SUS304 steel plate and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (width: 25 mm, length: 100 mm) via double-sided pressure-sensitive adhesive tape, and one hour after adhering, a peel strength meter is used to perform 180° peeling (peel speed: 300 mm/min) so that the base layer and the pressure-sensitive adhesive layer are peeled off, and the adhesion strength is measured;
(ii) A measurement method for adhesion B in which, for a pressure-sensitive adhesive sheet having at least an adhesive layer, the pressure-sensitive adhesive sheet (width: 25 mm, length: 100 mm) is attached to a SUS304 steel plate in accordance with Method 1 (180° peel adhesion to test plate) of JIS Z0237:2009 (Test methods for pressure-sensitive adhesive tapes and pressure-sensitive adhesive sheets), and immediately after attachment and 24 hours after attachment, the pressure-sensitive adhesive sheet is peeled at 180° (peel speed: 300 mm/min) using a peel strength meter to measure the adhesion;
to provide.

This disclosure provides a pressure-sensitive adhesive sheet with excellent reworkability, a method for manufacturing the same, and a method for measuring adhesion.

1 is a cross-sectional view showing one embodiment of a pressure-sensitive adhesive sheet according to the present disclosure. 1 is a cross-sectional view showing one embodiment of a substrate layer of a pressure-sensitive adhesive sheet according to the present disclosure. 1 is a cross-sectional view showing one embodiment of a substrate layer of a pressure-sensitive adhesive sheet according to the present disclosure.

The pressure-sensitive adhesive sheet and the method for producing the same according to the present disclosure will be specifically described below. Note that the present disclosure is not limited to the following embodiments and may be modified as desired within the scope of the invention.
Furthermore, in this specification, the numerical values associated with "greater than or equal to,""less than or equal to," and "to" in describing a numerical range are numerical values that can be arbitrarily combined. For example, when a certain numerical range is described as "A to B" and "C to D," the numerical ranges "A to D" and "C to B" are also included.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present disclosure has, in order, a base layer, a pressure-sensitive adhesive layer, and a release sheet layer,
The adhesive layer is porous,
The adhesion strength A between the base layer and the adhesive layer measured by the following measurement method is 17.0 N/25 mm or more,
The adhesive strength B between the adhesive layer and the SUS304 steel plate, measured by the following measurement method, is 1.0 N/25 mm or more and 10.0 N/25 mm or less.

(Method for measuring adhesion strength A)
In accordance with Method 3 (180° peel adhesion of double-sided tape) of JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets), an SUS304 steel plate and the adhesive layer of the adhesive sheet (width: 25 mm, length: 100 mm) are attached via double-sided adhesive tape, and one hour after attachment, a peel strength meter is used to perform 180° peeling (peel speed: 300 mm/min) so that the base layer and the adhesive layer are peeled off, and the adhesion strength measured is defined as adhesion strength A.
(Method for measuring adhesion strength B)
In accordance with Method 1 (180° peel adhesion to test plate) of JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets), the adhesive sheet (width: 25 mm, length: 100 mm) was attached to an SUS304 steel plate, and immediately after attachment and 24 hours after attachment, the adhesive sheet was peeled at 180° (peel speed: 300 mm/min) using a peel strength meter, and the measured adhesion strength was designated adhesion strength B.

The pressure-sensitive adhesive sheet of the present disclosure has an adhesion strength B between the pressure-sensitive adhesive layer and the SUS304 steel plate of 1.0 N/25 mm or more and 10.0 N/25 mm or less. The adhesion strength B includes both the adhesion strength measured immediately after the pressure-sensitive adhesive layer is attached to the SUS304 steel plate (also referred to as "initial adhesion strength _B1 ") and the adhesion strength measured 24 hours after attachment (also referred to as "normal adhesion strength _B2 "). In other words, when the pressure-sensitive adhesive sheet of the present disclosure has an adhesion strength B of 1.0 N/25 mm or more and 10.0 N/25 mm or less, this means that both the initial adhesion strength _B1 and the normal adhesion strength _B2 are 1.0 N/25 mm or more and 10.0 N/25 mm or less.

As shown in the examples described below, the normal adhesion strength _B2 increases slightly compared to the initial adhesion strength _B1 , and then shows almost no decrease over time. This tendency can be said to be one of the major characteristics of the porous adhesive layer. Therefore, the adhesion strength B is considered to represent the adhesion strength between the adhesive sheet of the present disclosure and the adherend over a medium to long term, starting immediately after application. Here, "medium to long term" refers to a period ranging from 24 hours (1 day) to several years (approximately 10 years). Furthermore, a "slight increase" in adhesion strength means that the increase is 10% or less.

Note that the above-mentioned adhesion force A is the adhesion force measured after peeling one hour after application, and therefore can be said to be the adhesion force corresponding to normal adhesion force _B1 of the above-mentioned adhesion force B. Since adhesion force A is the adhesion force between the base layer and the adhesive layer after a certain time has passed since the pressure-sensitive adhesive sheet of the present disclosure was produced, the adhesion force is already stable, but due to the attachment to the double-sided adhesive tape, variations occur and the adhesion force becomes unstable for about 30 minutes after application. Therefore, with regard to adhesion force A, the adhesion force one hour after application is taken as normal adhesion force _A1 and applied to adhesion force A.

Judging from the magnitude of adhesion force B, the adhesive sheet of the present disclosure does not generally have a strong adhesion to the adherend. Therefore, if application fails, it can be easily peeled off and reapplied as is. Furthermore, as mentioned above, the adhesive force does not decrease much even with medium to long-term use, so after application to the adherend, the sheet will not lift or peel off from the adherend, and has sufficient adhesive force to withstand medium to long-term use. Thus, the adhesive sheet of the present disclosure has excellent reworkability, allowing it to be peeled off and reapplied as is if application fails, while maintaining the necessary long-term adhesion.

On the other hand, if attention is focused only on the adhesion strength B, when the adhesive sheet is not properly attached and is peeled off, the adhesive sheet may experience interlayer delamination, for example, between the base layer and the adhesive layer, which may result in adhesive residue. Therefore, in the present disclosure, attention is also focused on the adhesion strength A between the base layer and the adhesive layer.
The adhesive sheet of the present disclosure has an adhesion strength A between the base layer and the adhesive layer of 17.0 N/25 mm or more. That is, the adhesive sheet of the present disclosure requires that the adhesion strength A between the base layer and the adhesive layer be greater than the adhesion strength B between the adhesive layer and the SUS304 steel plate. By having such an adhesion strength A, when the adhesive sheet of the present disclosure fails to be attached and is peeled off, the adhesive layer does not undergo cohesive failure, but rather peels off due to interfacial failure between the adhesive layer and the adherend. This prevents adhesive residue from occurring, and also makes it possible to reuse the peeled adhesive sheet by re-attaching it as is.

As mentioned above, Adhesion Strength B is the adhesion strength between the adhesive layer and the SUS304 steel plate, and it is assumed that the adherend to which the adhesive sheet is attached is a SUS304 steel plate. The adhesion strength between the adhesive sheet and the adherend can vary depending on the material of the adherend. Therefore, even if Adhesion Strength A and Adhesion Strength B are within the above-mentioned specified ranges, it is conceivable that excellent reworkability may not be achieved. However, as will be verified in the examples described below, when the adhesive strength for various adherends was measured, no adherends exceeded 17.0 N/25 mm, which is the minimum value for Adhesion Strength A.

Therefore, even if adhesion strength B is taken as the adhesive strength between the adhesive layer and the SUS304 steel plate, it has no effect whatsoever on the quality of reworkability. Furthermore, when measuring adhesion strength B, by using a specified SUS304 steel plate as the adherend, the measured value of adhesion strength B is stable. This makes it possible to more reliably measure the difference between adhesion strength A and adhesion strength B, ensuring excellent reworkability.

In the pressure-sensitive adhesive sheet of the present disclosure, adjustment of the adhesion strength A and the adhesion strength B can be performed mainly by the adhesive layer. Specifically, the adhesive layer is a layer that exerts adhesive strength, but it is required to be porous. That is, in the pressure-sensitive adhesive sheet of the present disclosure, by employing a porous layer as the adhesive layer, it is possible to adjust the adhesion strength A and the adhesion strength B. Furthermore, in the pressure-sensitive adhesive sheet of the present disclosure, adjustment of the adhesion strength A and the adhesion strength B can be performed by employing at least a porous layer as the adhesive layer, and can also be performed by other factors, such as the type of substrate, the type of resin constituting the adhesive used in the adhesive layer, additives to the adhesive, and the lamination pressure when adhering the substrate layer and the adhesive layer in the manufacturing method of the pressure-sensitive adhesive sheet.
The adhesive layer and other details regarding adjustment of the adhesive strength will be described later.

The adhesive strength A must be 17.0 N/25 mm or more, and in order to obtain better reworkability, it is preferably 17.5 N/25 mm or more, more preferably 18.0 N/25 mm or more. There is no particular upper limit in order to obtain better reworkability, but in consideration of the ease of forming the adhesive layer, it is preferably 30.0 N/25 mm or less, more preferably 28.0 N/25 mm or less, even more preferably 25.0 N/25 mm or less, and even more preferably 24.0 N/25 mm or less.
In the method for measuring adhesion force A, the double-sided pressure-sensitive adhesive tape used for measuring adhesion force A is not particularly limited as long as the adhesion force between the double-sided pressure-sensitive adhesive tape and the SUS304 steel plate is stronger than the adhesion force A between the base layer and the adhesive layer and the adhesion force between the double-sided pressure-sensitive adhesive tape and the adhesive layer, and may be appropriately selected from commercially available products.

The adhesion strength B must be 1.0 N/25 mm or more and 10.0 N/25 mm or less. To achieve better reworkability, it is preferably 1.5 N/mm or more, more preferably 2.0 N/25 mm or more, and even more preferably 2.5 N/25 mm or more. The upper limit is preferably 6.0 N/25 mm or less, more preferably 4.5 N/25 mm or less, even more preferably 3.5 N/25 mm or less, and even more preferably 3.0 N/25 mm or less.

[Adhesive layer]
In the pressure-sensitive adhesive sheet of the present disclosure, the pressure-sensitive adhesive layer is a porous layer. A porous pressure-sensitive adhesive layer is a layer that is composed of pores and a resin portion formed by the pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer.
If the adhesive layer is a porous layer, the contact area between the adhesive layer and the adherend can be maintained at an appropriate level, making it easier to suppress excessive increases and decreases in adhesion strength B and keep it within the above-mentioned specified range. As a result, the adhesive sheet does not lift or peel from the adherend, has sufficient adhesion strength to withstand medium- to long-term use, and is also easy to peel.
On the other hand, in terms of the relationship between the adhesive layer and the base material layer, if the adhesive layer is a porous layer, then by adjusting the lamination pressure, etc., in laminating the base material layer and the adhesive layer in the manufacturing process of the adhesive sheet of the present disclosure, it becomes easier to make the adhesion force A greater than the adhesion force B and within the above-mentioned predetermined range. Therefore, the adhesion force A can be reliably made greater than the force required to peel the adhesive sheet, and cohesive peeling of the adhesive layer does not occur, thereby suppressing the occurrence of adhesive residue.
In this way, by providing the pressure-sensitive adhesive sheet of the present disclosure with a porous pressure-sensitive adhesive layer, the adhesive strengths A and B fall within predetermined ranges, and the pressure-sensitive adhesive sheet has excellent reworkability.

A cross-sectional view 1 in a plan view showing one embodiment of the pressure-sensitive adhesive sheet of the present disclosure has a base layer 2, a pressure-sensitive adhesive layer 3, and a release sheet layer 4, and shows that the pressure-sensitive adhesive layer has pores.
As shown in FIG. 1, the pores in the adhesive layer may have the following forms: (i) spherical pores 31; (ii) concave shapes 32 formed on the surface of the adhesive layer, i.e., at the interface with the substrate layer and the interface with the release sheet layer; and combinations of these (i) spherical pores 31 and (ii) concave shapes 32.

The above-mentioned (i) spherical pores and (ii) concave shapes, or a combination thereof, can be easily obtained, for example, by forming the adhesive layer from an adhesive resin composition containing air bubbles. That is, to make the pores of the adhesive layer into the above-mentioned (i) spherical pores and (ii) concave shapes, or a combination thereof, it is preferable to form the adhesive layer using an adhesive resin composition containing air bubbles. Furthermore, simply by incorporating air bubbles into the adhesive resin composition, pores with the above-mentioned (i) spherical pores and (ii) concave shapes can be formed, forming a porous adhesive layer, making the formation of the adhesive layer extremely easy.

When the adhesive layer is formed from an adhesive resin composition containing bubbles, the above-mentioned (i) spherical voids are formed when the bubbles themselves become voids, and (ii) concave shapes are formed when bubbles burst on the surface of the adhesive layer, i.e., the interface with the base layer and the interface with the release sheet layer, and in the vicinity thereof.
In the pressure-sensitive adhesive sheet of the present disclosure, the pores preferably have the above-mentioned (ii) concave shape. This is because the adhesion between the substrate in contact with the pressure-sensitive adhesive layer, and the adhesive layer in contact with an adherend when the pressure-sensitive adhesive sheet of the present disclosure is used, is more likely to be within the respective predetermined ranges of adhesion A and B. For the same reason, it is also preferable that the (ii) concave shape is evenly present on the surface of the pressure-sensitive adhesive layer, i.e., at the interface with the substrate layer and the interface with the release sheet layer.

Regarding the above (ii) that the recesses are evenly distributed, more specifically, it is preferable that the following conditions are satisfied.
When the average diameter of each concave opening present on the surface of the adhesive layer facing the substrate is defined as D ^ave ₁ and the average diameter of each concave opening present on the surface of the release sheet layer opposite the surface facing the substrate layer (when an adhesive sheet is used, this is also the surface that comes into contact with the adherend) is defined as D ^ave ₂ , it is preferable that the following condition (1) is satisfied.
|D ^ave ₁ - D ^ave ₂ |/D ^ave ₂ ≦0.5 (1)
Regarding the condition (1), it is more preferable that |D ^ave ₁ - D ^ave ₂ |/D ^ave ₂ ≦0.25, and even more preferable that |D ^ave ₁ - D ^ave ₂ |/D ^ave ₂ ≦0.15.

Furthermore, when the pores of the adhesive layer have the above-mentioned (i) spherical pores, the average diameter D ^ave ₃ of the spheres preferably satisfies the following condition (2).
D ^ave ₁ ≦ D ^ave ₃ ≦ D ^ave ₂ or D ^ave ₂ ≦ D ^ave ₃ ≦ D ^ave ₁ (2)

Regarding the above conditions (1) and (2), it is practically impossible to determine the average diameters for all concave openings and spherical holes when measuring the average diameters D ^ave ₁ , D ^ave ₂ , and D ^ave ₃ of each opening, etc. Therefore, within an observation range of 1500 μm × 1100 μm, diameters were measured at three locations, starting with the largest diameter concave opening and spherical hole, and the average was taken as the average diameter of each opening.

When the (ii) concave shape of the pores in the adhesive layer satisfies condition (1), the physical properties of the adhesive layer can be made more uniform, making it easier to make the adhesiveness more uniform across the entire surface of the adhesive layer. As a result, the substrate layer, the release sheet layer, and the adhesive sheet, after use, tend to uniformly exhibit the above-mentioned adhesion strengths A and B to the adherend, thereby improving reworkability.
Furthermore, among the pores in the adhesive layer, (i) spherical pores satisfying condition (2) also improve reworkability by making the physical properties of the adhesive layer more uniform, similar to condition (1).

There are no particular restrictions on the average diameter of the (i) spherical pores and (ii) concave openings as long as they satisfy the above conditions (1) and (2). While this cannot be generalized as it varies depending on the thickness of the adhesive layer, it is typically between 1 μm and 300 μm. Considering improved reworkability, the average diameter is preferably between 3 μm and 300 μm, more preferably between 5 μm and 10 μm, and the upper limit is preferably between 250 μm and 200 μm, more preferably between 100 μm and 250 μm.

In consideration of improving reworkability, the density of the adhesive layer is preferably 0.1 g/ ^cm3 or more, more preferably 0.2 g/ ^cm3 or more, and even more preferably 0.3 g/ ^cm3 or more, and the upper limit is preferably 0.8 g/ ^cm3 or less, more preferably 0.7 g/ ^cm3 or less, and even more preferably 0.6 g/ ^cm3 or less.

The thickness of the adhesive layer is preferably 10 μm or more, more preferably 15 μm or more, even more preferably 18 μm or more, and even more preferably 20 μm or more. When the thickness of the adhesive layer is within the above range, the concave shape (ii) above is particularly easily formed, and the opening can have a sufficient diameter, thereby improving reworkability.
On the other hand, the upper limit of the thickness of the adhesive layer is preferably 100 μm or less, more preferably 85 μm or less, even more preferably 75 μm or less, and even more preferably 70 μm or less. By setting the upper limit of the thickness of the adhesive layer within the above range, the thickness of the adhesive sheet of the present disclosure can be reduced, making it easier to apply, peel, and reapply the adhesive sheet, resulting in improved reworkability. In addition, handling and storage in each workplace are easier, improving usability.

(Resin composition for forming adhesive layer)
The resin composition used to form the adhesive layer (hereinafter also referred to as "resin composition for forming an adhesive layer") can be any resin composition that can form a porous adhesive layer and satisfy the above-mentioned adhesion strengths A and B. As the resin composition for forming an adhesive layer, an adhesive resin composition containing bubbles, as described above, is preferred.

Preferably, the adhesive resin composition containing bubbles is a resin composition containing an adhesive resin, salt, and, if necessary, a solvent and various additives.

Preferred examples of adhesive resins include rubber-based resins such as urethane rubber, styrene butadiene polymer (styrene butadiene rubber), polyisoprene, natural rubber, acrylonitrile butadiene rubber, ethylene propylene rubber (EPR), ethylene propylene diene terpolymer rubber (EPDM), polynorbornene, polybutadiene, nitrile rubber, chloroprene rubber, butyl rubber, halogenated butyl rubber, ethylene-vinyl acetate rubber (EVA), silicone rubber, fluororubber, ethylene acrylic rubber, polyester elastomer, epichlorohydrin rubber, and polysulfide rubber; adhesive resins such as acrylic polymer, polyurethane, chlorinated polyethylene, polyethylene, polystyrene, polyimide, polyvinyl chloride, and polypropylene; and thermoplastic elastomers such as polyolefin, polyurethane, polyester, polyamide, and polystyrene. The use of these resins facilitates the formation of a porous adhesive layer and facilitates the satisfaction of the above-mentioned adhesion strengths A and B, thereby improving reworkability.

The rubber-based resin may be in either a liquid or solid state, or a mixture thereof may be used. The resin may be in either a homopolymer or a copolymer, or a mixture thereof may be used.
Among the above resins, acrylic polymers and styrene-butadiene polymers are preferred as adhesive resins. In the adhesive resin composition, the above resins may be used alone or in combination.

The weight-average molecular weight of the adhesive resin is preferably 250,000 or more, more preferably 260,000 or more, and even more preferably 270,000 or more, with the upper limit being preferably 12,000,000 or less, more preferably 10,000,000 or less, and even more preferably 8,000,000 or less. When the weight-average molecular weight of the resin is within the above range, it is easy to form a porous adhesive layer and it is easy to satisfy the above-mentioned adhesion strengths A and B, so that reworkability is improved.
The weight average molecular weight in this specification is an average molecular weight measured by GPC analysis and converted into standard polystyrene.

As the salt, various salts such as inorganic salts and organic salts can be used.
Preferred examples of inorganic salts include sulfates, sulfites, carbonates, hydrogencarbonates, nitrates, nitrites, chlorates, hypochlorites, chlorites, perchlorates, permanganates, chromates, phosphates, hydrogenphosphates, chlorides, bromides, and iodides of metals such as sodium, magnesium, aluminum, potassium, calcium, iron, nickel, copper, zinc, silver, lead, tin, and barium; and also ammonium sulfate, ammonium carbonate, ammonium hydrogencarbonate, ammonium nitrate, ammonium chloride, and potassium aluminum sulfate (alum).

Examples of organic salts include salts of carboxylic acids having 1 to 18 carbon atoms, such as formates, acetates, propanoates, butanoates, and pentanoates, of metals such as sodium, magnesium, aluminum, potassium, calcium, iron, nickel, copper, zinc, silver, lead, tin, and barium; and ammonium salts of carboxylic acids having 1 to 18 carbon atoms.
In addition to the above, examples of the organic salt include ammonium-based, pyridinium-based, imidazolium-based, pyrrolidinium-based, choline-based, phosphonium-based, sulfonium-based, and pyrazolium-based ionic liquids.
The inorganic salts and organic salts exemplified above can be used alone or in combination of two or more.

In the resin composition for forming an adhesive layer, the salt content per 100 parts by mass of the adhesive resin is preferably 1 part by mass or more, more preferably 1.3 parts by mass or more, even more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 6.0 parts by mass or more, and the upper limit is preferably 80 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less.

The adhesive resin composition for forming an adhesive may contain a solvent in consideration of ease of application, that is, ease of forming an adhesive layer.
The solvent may be either water or an organic solvent.

Examples of water include distilled water, tap water, deionized water, carbonated water, and water purified by other known purification processes.
Preferred examples of the organic solvent include water-miscible solvents such as methanol, ethanol, propanol, butanol, ethylene glycol, tetrahydrofuran, acetone, acetonitrile, dimethylformamide, triethylamine, pyridine, dimethyl sulfoxide, diethyl ether, and ethyl acetate; and water-immiscible solvents such as diisopropyl ether, carbon tetrachloride, chloroform, dichloromethane, dichloroethane, benzene, toluene, xylene, cyclohexane, pentane, hexane, nitromethane, and carbon disulfide.

Of the above, water, ethanol, and hexane are preferred, with water being more preferred. These solvents are easily available, inexpensive, and evaporate easily, allowing for the adhesive layer to be formed more quickly.

The solvent content in the adhesive resin composition for forming an adhesive is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and even more preferably 40% by mass or more, based on the total amount of the adhesive resin and solvent, and the upper limit is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

Other additives can be appropriately selected and used depending on the desired performance, and examples thereof include surfactants, foam stabilizers, foaming agents (foaming agents), foaming aids, foam stabilizers, antifoam agents (foam suppressors, foam breakers), emulsifiers, dispersants, wetting agents, propellants, thickeners, curing agents, crosslinking agents, polymerization initiators, colorants (pigments, dyes), plasticizers, adhesives, fillers, antifouling agents, viscoelasticity modifiers, rust inhibitors, slip agents, driers, stabilizers, ultraviolet absorbers, antibacterial agents, antifungal agents, and flame retardants.
Among these, in consideration of making it easier for the adhesive resin composition to contain bubbles, it is preferable to use a surfactant, a foam stabilizer, a foaming agent (foaming agent), a foaming assistant, or a foam stabilizer.

The content of other additives can be set appropriately depending on the desired performance and is not particularly limited, but is preferably at least 0.1 parts by mass, more preferably at least 0.5 parts by mass, relative to 100 parts by mass of the adhesive resin, and the upper limit is preferably no more than 10 parts by mass, more preferably no more than 8.5 parts by mass, even more preferably no more than 5 parts by mass, and even more preferably no more than 1.9 parts by mass.

As described above, the adhesive resin composition for forming a pressure-sensitive adhesive is preferably an adhesive resin composition containing bubbles. The method for making the composition containing bubbles is not particularly limited, but can be, for example, as follows.
First, the adhesive resin and solvent are used to prepare a form such as a colloid, suspension, sol, or emulsion, and then a salt and, if necessary, additives are added to prepare a stock solution. By stirring the stock solution while supplying nitrogen gas, bubbles can be incorporated into the stock solution, and an adhesive resin composition containing bubbles can be prepared.

When nitrogen gas is supplied, the density of the bubble-containing adhesive resin composition can be adjusted by adjusting the amount of nitrogen gas supplied. Adjusting the density of the bubble-containing adhesive resin composition makes it easier for the adhesive layer formed using it to satisfy the above-mentioned pore shape, density, etc., and therefore makes it easier to adjust the adhesion strengths A and B within the above-mentioned specified ranges, as described above, resulting in improved reworkability.

The density of the adhesive resin composition containing bubbles is preferably 0.1 g/cm ^or more, more preferably 0.2 g/cm ^or more, and even more preferably 0.3 g/cm ^or more, with the upper limit being preferably 0.8 g/cm ^or less, more preferably 0.7 g/cm ^or less, and even more preferably 0.6 g/cm ^or less. When the density of the adhesive resin composition is within the above range, the reworkability is improved as described above.

[Base material layer]
The substrate layer is a layer that forms the surface layer of the adherend when the pressure-sensitive adhesive sheet of the present disclosure is attached to the adherend via the pressure-sensitive adhesive layer. Therefore, the substrate layer is preferably a layer that has various properties desired for the adherend, and for example, it is preferable to use a decorative sheet as the substrate layer.
The decorative sheet preferably used for the base layer can be any commercially available decorative sheet without any restrictions. For example, a typical preferred decorative sheet is one having a support layer 21, a decorative layer 22 (further including a colored layer 22a and a patterned layer 22b), and a surface layer 23, as shown in Figure 2. In this case, the decorative sheet as the base layer is provided so that the support layer and the adhesive layer face each other.
The support layer, decorative layer and surface layer will be described below.

(Support layer)
When the base layer has a support layer, the support layer not only holds the decorative layer and surface layer that the decorative sheet preferably has, but also contacts the adhesive layer, and therefore can have a significant effect on the adhesive strength A between the base layer and the adhesive layer. As the support layer, any material that is normally used as a base material for decorative sheets can be used without limitation, and typical examples include base materials made of fibrous materials such as paper, nonwoven fabric and woven fabric, resins, wood-based materials, metals, non-metallic inorganic materials, etc.
Of the above materials constituting the support layer, resin and paper are preferably used in consideration of ease of manufacturing the decorative sheet, ease of availability, etc., and resin is more preferably used in consideration of ensuring mechanical strength, water resistance, etc. Furthermore, by using a substrate composed of resin and paper as the support layer, it becomes easier to achieve adhesion strength A of 17.0 N/25 mm or more, and therefore reworkability is improved in relation to adhesion strength B.

The support layer may be a single layer, or a composite layer comprising two or more layers made of the above materials. If the support layer is a composite layer comprising two or more layers, it is preferable to have two or more layers made of different materials, with the materials of each layer combining to complement each other's performance characteristics.

Examples of fibrous material support layers include paper substrates such as kraft paper, titanium paper, wallpaper backing paper, tissue paper, fine paper, Japanese paper, and plasterboard base paper. Furthermore, examples of paper substrate layers include interlayer reinforced paper and resin-impregnated paper, which have been improved in interlayer strength by adding various resins such as acrylic resin, styrene-butadiene rubber, and melamine resin.

Examples of nonwoven or woven fabric support layers include inorganic fibers made from inorganic materials such as glass, alumina, and carbon; organic fibers made from various synthetic resins such as polyester resin, acrylic resin, polyethylene, and polypropylene; protein-based or cellulose-based natural fibers such as silk, cotton, and hemp; and nonwoven or woven fabrics made from various fibers such as glass fiber and carbon fiber, as well as composites of these.

Examples of the resin support layer include resin substrates made of various resins such as synthetic resins and natural resins.
Examples of synthetic resins include polyolefin resins such as polypropylene, polyethylene, polymethylpentene, polyolefin-based thermoplastic elastomers, and ionomers; vinyl chloride resins such as polyvinyl chloride, polyvinylidene chloride, and vinyl chloride-vinyl acetate copolymers; polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyester-based thermoplastic elastomers; acrylic resins such as polymethyl (meth)acrylate, polybutyl (meth)acrylate, and methyl (meth)acrylate-butyl (meth)acrylate copolymers; polyamide resins typified by nylon 6 and nylon 66; cellulose-based resins such as cellulose triacetate, cellophane, and celluloid; styrene-based resins such as polystyrene, acrylonitrile-styrene copolymers, and acrylonitrile-butadiene-styrene resins (ABS resins); and thermoplastic resins such as polyvinyl alcohol, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, polycarbonate resins, polyarylate resins, and polyimide resins.
Examples of natural resins include natural rubber, pine resin, and amber.

Examples of the substrate layer of wood-based materials include wood substrates made from various species of wood, such as cedar, cypress, pine, zelkova, oak, walnut, lauan, teak, and rubber tree. The wood substrate can be in the form of a film or sheet known as veneer, or in the form of a board, such as veneer, plywood, laminated wood, particle board, or fiberboard.

Examples of metals include aluminum, aluminum-containing alloys such as duralumin, iron-containing alloys such as iron, carbon steel, and stainless steel, copper-containing alloys such as copper, brass, and bronze, gold, silver, chromium, nickel, cobalt, tin, and titanium. Furthermore, as the metal substrate layer made of a metal, it is also possible to use those metals that have been subjected to a treatment such as plating.
Examples of non-metallic inorganic materials include non-ceramic ceramic materials such as cement, ALC (lightweight aerated concrete), gypsum, calcium silicate, and wood chip cement; ceramic ceramic materials such as porcelain, earthenware, glass, and enamel; and natural stones such as limestone (including marble), granite, andesite.

The support layer may be colored or uncolored (it may be transparent). If it is colored, there are no particular restrictions on the coloring method, and it may be transparently colored or opaquely colored (hiding colored), and these can be selected as desired. Considering the ability to conceal the hue of the adherend, stabilize the color tone of the decorative layer described below, and improve the design, it is preferable for it to be colored.

Examples of colorants include white pigments such as titanium white, inorganic pigments such as iron black, yellow lead, titanium yellow, red iron oxide, cadmium red, ultramarine blue, and cobalt blue; organic pigments or dyes such as quinacridone red, isoindolinone yellow, phthalocyanine blue, nickel-azo complexes, azomethine azo-based black pigments, and perylene-based black pigments; metallic pigments consisting of scaly flakes such as aluminum and brass; and pearlescent pigments consisting of scaly flakes such as titanium dioxide-coated mica and basic lead carbonate. Considering the need to conceal the hue of the substrate and the color stability of the decorative layer, it is recommended to use inorganic pigments such as white pigments.

When coloring a synthetic resin, any of the following methods can be used: adding a colorant to the resin (mixing or kneading), applying a coating film of a paint containing the resin and the colorant, etc. When coloring paper, nonwoven fabric, or woven fabric, the coloring can be carried out by mixing with pulp or a fiber material, forming a coating film, or by a combination of these methods.
In the case of coloring wood, it can be done by dyeing with a dye or by forming a coating film, or by a combination of these. In the case of coloring metals, in addition to forming a coating film, electrolytic coloring methods that form a metal oxide film on the surface using anodization can be used. In addition, in the case of non-metallic inorganic materials, it can be done by forming a coating film or by adding a dye to the substrate, or by a combination of these.

The support layer may contain additives as needed.
Examples of additives, mainly in the case of resins, include weathering agents such as ultraviolet absorbers and light stabilizers, inorganic fillers such as calcium carbonate and clay, flame retardants such as magnesium hydroxide, antioxidants, lubricants, foaming agents, antioxidants, etc. The amount of additives to be added is not particularly limited as long as it is within a range that does not impair surface properties, processing properties, etc., and can be set appropriately depending on the required properties, etc.

From the viewpoint of improving the weather resistance of the laminate of the present disclosure, it is preferable to use weather resistance agents such as ultraviolet absorbers and light stabilizers among the above additives.
As the ultraviolet absorber, any ultraviolet absorber commonly used in decorative sheets can be used without any particular limitation, and examples thereof include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, triazine-based ultraviolet absorbers, and hydroxyphenyltriazine-based ultraviolet absorbers.

As the light stabilizer, any light stabilizer commonly used in decorative sheets can be used without particular limitation, and examples thereof include hindered amine light stabilizers such as piperidinyl sebacate light stabilizers. Furthermore, these ultraviolet absorbers and light stabilizers may have a reactive functional group with an ethylenic double bond in the molecule, such as a (meth)acryloyl group, a vinyl group, or an allyl group.
These weathering agents such as ultraviolet absorbers and light stabilizers may be used alone or in combination of two or more kinds.

The thickness of the support layer is not particularly limited, but generally, taking into consideration suitability for manufacturing and processing, mechanical strength, ease of use and handling, and economic efficiency, the thickness is about 10 μm or more and 10 cm or less, preferably 20 μm or more, and more preferably 40 μm or more, with the upper limit being preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less.
When the base layer is a paper base, the basis weight is usually preferably 20 g/m ² or more and 150 g/m ² or less, and more preferably 30 g/m ² or more and 100 g/m ² or less.

To improve adhesion to other layers that make up the decorative sheet, such as the decorative layer and surface layer, the support layer may be provided with a separate primer layer (described below), or one or both sides may be subjected to a physical surface treatment, such as an oxidation method or a roughening method, or a chemical surface treatment.

Examples of oxidation methods include corona discharge treatment, chromium oxidation treatment, flame treatment, hot air treatment, and ozone-ultraviolet treatment, while examples of textured methods include sandblasting and solvent treatment. These surface treatments are selected appropriately depending on the type of substrate, but considering the effects of the surface treatment and ease of use, corona discharge treatment is generally preferred.

(Decorative layer)
The decorative layer is a layer that imparts decoration to the decorative sheet used in the base layer and improves the design, and is a layer that improves the design of the pressure-sensitive adhesive sheet of the present disclosure.
The decorative layer may be provided between the substrate layer and the surface layer described later, or, if a transparent resin layer described later is included, may be provided between the substrate layer and the transparent resin layer described later (see Figure 2).

The decorative layer may be, for example, a colored layer that covers the entire surface (a so-called solid colored layer, "22a" in Figure 2), or a patterned layer ("22b" in Figure 2) formed by printing various patterns using ink and a printing press. Alternatively, as shown in Figure 2, it may be a combination of a solid colored layer 22a and a patterned layer 22b.

The design (pattern) of the design layer is not particularly limited and may be any desired design, such as wood grain patterns such as tree rings and vessel grooves on the surface of a wooden board, stone grain patterns on the surface of marble, granite, etc., fabric grain patterns on the surface of fabric, leather grain patterns on the surface of leather, geometric patterns, letters, figures, or combinations of these.

The ink used for the decorative layer is a mixture of a binder resin with an appropriate amount of pigment, colorant such as dye, extender pigment, solvent, stabilizer, plasticizer, catalyst, hardener, ultraviolet absorber, light stabilizer, etc.
The binder resin for the decorative layer is not particularly limited, and examples thereof include urethane resin, acrylic polyol resin, acrylic resin, ester resin, amide resin, butyral resin, styrene resin, urethane-acrylic copolymer, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-acrylic copolymer resin, chlorinated propylene resin, nitrocellulose resin, cellulose acetate resin, etc. Furthermore, various types of resins can be used, such as one-component curing resins and two-component curing resins containing a curing agent such as an isocyanate compound.

As the colorant, a pigment having excellent hiding power and weather resistance is preferred. The pigment may be the same as those exemplified as the pigments that can be used for the substrate.
The content of the colorant is preferably 5 to 90 parts by mass, more preferably 15 to 80 parts by mass, and even more preferably 30 to 70 parts by mass, per 100 parts by mass of the resin constituting the decorative layer.

The decorative layer may contain additives such as a weathering agent, an ultraviolet absorber, a light stabilizer, and a colorant.
The thickness of the decorative layer may be appropriately selected depending on the desired pattern, and in consideration of concealing the hue of the adherend and improving the design, the thickness is preferably 0.5 μm or more and 20 μm or less, more preferably 1 μm or more and 10 μm or less, and even more preferably 2 μm or more and 5 μm or less.

(Surface layer)
The surface layer is a layer provided on the surface of the decorative sheet, i.e., the surface of the PSA sheet of the present disclosure, and is provided as a layer having surface properties such as abrasion resistance, weather resistance, stain resistance, etc., as desired. Here, the surface of the PSA sheet refers to the surface of the substrate layer opposite to the surface on which the PSA layer is located.
The surface layer is preferably a layer formed from a cured product of a resin composition, since this makes it easier to develop the above-mentioned surface properties.

Resins contained in the resin composition used to form the surface layer include curable resins such as ionizing radiation curable resins and thermosetting resins.

The ionizing radiation curable resin is a resin having an ionizing radiation curable functional group, and the ionizing radiation curable functional group is a group that crosslinks and cures upon irradiation with ionizing radiation. Preferred examples of such groups include functional groups having an ethylenic double bond, such as a (meth)acryloyl group, a vinyl group, and an allyl group. In this specification, the term "(meth)acryloyl group" refers to an acryloyl group or a methcroyl group. In this specification, the term "(meth)acrylate" refers to an acrylate or a methacrylate.
Furthermore, ionizing radiation refers to electromagnetic waves or charged particle beams that have an energy quantum capable of polymerizing and/or crosslinking molecules. Typically, ultraviolet rays (UV) or electron beams (EB) are used, but other examples include electromagnetic waves such as X-rays and gamma rays, and charged particle beams such as alpha rays and ion beams.

Examples of the ionizing radiation curable resin include electron beam curable resins and ultraviolet curable resins, and either one may be used.
Specifically, the ionizing radiation curable resin can be appropriately selected from polymerizable monomers and polymerizable oligomers that have been conventionally used as ionizing radiation curable resins.

The polymerizable monomer is preferably a (meth)acrylate monomer having a radically polymerizable unsaturated group in the molecule.
The (meth)acrylate monomer is a monomer having at least a (meth)acryloyl group as an ionizing radiation-curable functional group, and examples thereof include monofunctional (meth)acrylate monomers having one ionizing radiation-curable resin and polyfunctional (meth)acrylate monomers having two or more ionizing radiation-curable resins, and either can be used.

When using a polyfunctional monomer, the number of functional groups is preferably 2 or more, with the upper limit being preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.

Examples of polymerizable oligomers include (meth)acrylate oligomers that have two or more ionizing radiation-curable functional groups in the molecule, and that have at least a (meth)acryloyl group as one of the functional groups. Preferred examples include urethane (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, polyester (meth)acrylate oligomers, polyether (meth)acrylate oligomers, polycarbonate (meth)acrylate oligomers, and acrylic (meth)acrylate oligomers.

Other polymerizable oligomers include highly hydrophobic polybutadiene (meth)acrylate oligomers with (meth)acrylate groups in the side chains of polybutadiene oligomers, silicone (meth)acrylate oligomers with polysiloxane bonds in the main chain, aminoplast resin (meth)acrylate oligomers modified with aminoplast resins that have many reactive groups in their small molecules, and oligomers with cationically polymerizable functional groups in the molecules of novolac epoxy resins, bisphenol epoxy resins, aliphatic vinyl ethers, aromatic vinyl ethers, etc.

The number of functional groups of the polymerizable oligomer may be appropriately selected depending on the desired surface properties, and is preferably 2 or more, more preferably 3 or more, with the upper limit being preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less. When the number of functional groups is within the above range, the above-mentioned various surface properties are easily obtained.
For the same reason, the weight-average molecular weight of these polymerizable oligomers is preferably from 1,000 to 7,500, more preferably from 1,500 to 6,500, even more preferably from 1,750 to 5,000, and even more preferably from 1,900 to 4,000. Here, the weight-average molecular weight is an average molecular weight measured by GPC analysis and converted into standard polystyrene.

In the present disclosure, polymerizable monomers can be used alone or in combination of multiple types, and polymerizable oligomers can be used alone or in combination of multiple types. It is also possible, of course, to use a combination of polymerizable monomers and polymerizable oligomers.

Examples of the thermosetting resin include acrylic resin, urethane resin, phenol resin, urea melamine resin, epoxy resin, unsaturated polyester resin, silicone resin, etc. These may be used alone or in combination of two or more kinds.
The thermosetting resin composition may be one in which a curing agent such as an isocyanate-based curing agent or an epoxy-based curing agent is added to these resins. Among these, acrylic resins are preferred, and acrylic resins to which an isocyanate curing agent is added are more preferred.

The resin composition that forms the surface layer may contain various additives in addition to the resin described above, depending on the desired surface characteristics. Preferred examples of such additives include weathering agents, photopolymerization initiators, and photopolymerization accelerators.

As the weatherproofing agent, various weatherproofing agents such as ultraviolet absorbers and light stabilizers are preferably used.
The ultraviolet absorber and light stabilizer can be appropriately selected from those exemplified as the ultraviolet absorber and light stabilizer that can be used in the support layer.

The content of the ultraviolet absorber relative to 100 parts by mass of the resin forming the surface layer is preferably 0.1 parts by mass or more, more preferably 1.0 parts by mass or more, even more preferably 2.0 parts by mass or more, and still more preferably 3.0 parts by mass or more, with the upper limit being preferably 10.0 parts by mass or less, more preferably 8.0 parts by mass or less, even more preferably 7.0 parts by mass or less, and still more preferably 6.0 parts by mass or less. When the content of the ultraviolet absorber is within the above range, the effect of using the ultraviolet absorber efficiently can be obtained.
The content of the light stabilizer is the same as that of the ultraviolet absorber.

The photopolymerization initiator and the photopolymerization accelerator are preferably used when an ultraviolet curable resin is used as the curable resin.
The photopolymerization initiator may be one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler's ketone, benzoin, benzil dimethyl ketal, benzoyl benzoate, α-acyloxime ester, thioxanthones, and the like.
The photopolymerization accelerator can reduce polymerization inhibition caused by air during curing and increase the curing rate, and examples thereof include one or more selected from p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, and the like.

The content of the photopolymerization initiator relative to 100 parts by mass of the resin forming the surface layer is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and the upper limit is preferably 5 parts by mass or less, more preferably 1.5 parts by mass or less. When the content of the photopolymerization initiator is within the above range, the effect of using the photopolymerization initiator efficiently can be obtained.
The content of the photopolymerization accelerator is the same as that of the photopolymerization initiator.

(Other layers that the decorative sheet may have)
The decorative sheet preferably used as the substrate layer of the pressure-sensitive adhesive sheet of the present disclosure preferably has the layer structure shown in Figure 2, i.e., the support layer, decorative layer, and surface layer described above, and the layer structure having these layers in order is the simplest and most preferred layer structure.
Furthermore, the decorative sheet used as the substrate layer may have other layers, such as a primer layer, a transparent resin layer, and an adhesive layer, as needed. A typical layer configuration of the decorative sheet when these layers are included is a layer configuration having, in order, a support layer 21, a decorative layer 22, an adhesive layer 24, a transparent resin layer 25, a primer layer 26, and a surface layer 23, as shown in Figure 3.

(Primer layer)
As already mentioned, the primer layer is a layer provided to improve the interlayer adhesion between the multiple layers that make up the decorative sheet.
For example, when a support layer and a surface layer are provided, a primer layer can be provided between the support layer and the surface layer, or when a transparent resin layer is provided as shown in FIG. 3, a primer layer can be provided between the transparent resin layer and the surface layer to improve interlayer adhesion.

The primer layer is primarily composed of a binder resin, and may contain additives such as ultraviolet absorbers and light stabilizers as needed.

Preferred binder resins include urethane resin, acrylic polyol resin, acrylic resin, ester resin, amide resin, butyral resin, styrene resin, urethane-acrylic copolymer, polycarbonate-based urethane-acrylic copolymer (urethane-acrylic copolymer derived from a polymer (polycarbonate polyol) having a carbonate bond in the polymer main chain and two or more hydroxyl groups at the terminals and side chains), vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-acrylic copolymer resin, chlorinated propylene resin, nitrocellulose resin (nitrocellulose), and cellulose acetate resin, and these can be used alone or in combination.

The binder resin may also be a resin that is crosslinked and cured by adding a curing agent such as an isocyanate-based curing agent or an epoxy-based curing agent to the above resin. For example, a resin that is crosslinked and cured by adding an isocyanate-based curing agent to a polyol-based resin such as an acrylic polyol resin is preferred, and a resin that is crosslinked and cured by adding an isocyanate-based curing agent to an acrylic polyol resin is more preferred.

The thickness of the primer layer is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more, with an upper limit of preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less.

(Transparent resin layer)
The transparent resin layer is preferably provided to increase the strength of the decorative sheet and, if a decorative layer is provided, to protect the decorative layer. In particular, when the pressure-sensitive adhesive sheet of the present disclosure is used for interior components of buildings such as flooring materials, or frequently used fittings such as window frames, doors, door frames, and handrails, it is effective to provide the transparent resin layer.
The transparent resin layer may be provided, for example, between the support layer and the surface layer, or, if a decorative layer is provided, between the decorative layer and the surface layer to protect the decorative layer (see FIG. 3).

Resins that can be used to form the transparent resin layer include polyolefin resins, polyester resins, polycarbonate resins, acrylonitrile-butadiene-styrene resins (hereinafter also referred to as "ABS resins"), acrylic resins, and vinyl chloride resins. Considering processability, polyolefin resins and vinyl chloride resins are preferred. Furthermore, two or more of these resins may be laminated or mixed together for use.

The transparent resin layer need only be transparent enough to allow the substrate side to be visible through the transparent resin layer, and if a decorative layer is present, it need only be transparent enough to allow the decorative layer to be visible. It may be colorless and transparent, colored and transparent, or translucent. In other words, in this specification, "transparent" includes not only colorless and transparent, but also colored and transparent and translucent.

The transparent resin layer may contain additives such as weather resistance agents, such as ultraviolet absorbers and light stabilizers, and colorants. The additives, such as weather resistance agents and colorants, may be appropriately selected from those already described.
Considering protection of the decorative layer, processability, etc., the thickness of the transparent resin layer is preferably 20 μm to 150 μm, more preferably 40 μm to 120 μm, and even more preferably 60 μm to 100 μm.

(Adhesive layer)
When the decorative sheet has a support layer and a transparent resin layer, the adhesive layer is a layer that is preferably provided between the support layer and the transparent resin layer in order to improve the adhesion between these layers.
When a decorative layer is further provided between the support layer and the transparent resin layer, the positional relationship between the adhesive layer and the decorative layer is not particularly limited. Specifically, the decorative layer, adhesive layer, and transparent resin layer may be provided in this order from the side closest to the support layer (see Figure 3), or the adhesive layer, decorative layer, and transparent resin layer may be provided in this order from the side closest to the support layer.

The adhesive layer can be made of, for example, an adhesive such as a urethane adhesive, an acrylic adhesive, an epoxy adhesive, a rubber adhesive, etc. Among these adhesives, a urethane adhesive is preferred in terms of adhesive strength.
Examples of urethane adhesives include adhesives that utilize two-component curing urethane resins containing various polyol compounds such as polyether polyol, polyester polyol, and acrylic polyol, and a curing agent such as an isocyanate compound.

From the viewpoint of efficiently achieving the desired adhesive strength, the thickness of the adhesive layer is preferably 0.1 μm or more and 30 μm or less, more preferably 1 μm or more and 15 μm or less, and even more preferably 2 μm or more and 10 μm or less.

[Method for manufacturing decorative sheet]
A decorative sheet preferably used as the substrate layer in the pressure-sensitive adhesive sheet of the present disclosure can be prepared, for example, by the following method when the decorative sheet comprises a support layer and a surface layer:
a surface coating layer forming step of applying a resin composition for forming a surface layer to one main surface of a substrate to form a coating layer; and a surface layer forming step of curing the surface coating layer by irradiation with ionizing radiation such as ultraviolet rays to form a surface layer.
In addition, when the resin composition for forming the surface layer contains a solvent, a solvent drying step may be carried out after the coating layer forming step.

(Surface coating layer forming step)
In the surface coating layer forming step, the resin composition for forming the surface layer is applied by a known method such as gravure printing, bar coating, roll coating, reverse roll coating, or comma coating to form a coating layer composed of the uncured resin composition.

The resin composition for forming the surface layer used in the surface coating layer forming process is the resin composition described in the description of the surface layer above, and is preferably a resin composition that contains an ionizing radiation curable resin as a resin and may also contain other additives such as a photopolymerization initiator and a weathering agent.
In the surface coating layer forming step, the thickness of the surface coating layer formed by applying the resin composition for forming the surface layer is the same as the thickness described above as the thickness of the surface layer.

(Surface layer formation process)
In the surface layer forming process, the surface coating layer formed from the uncured resin composition formed in the surface coating layer forming process is cured by irradiation with ionizing radiation such as electron beams or ultraviolet rays to form a surface layer.

When an electron beam is used as the ionizing radiation, the acceleration voltage can be appropriately selected depending on the resin used and the thickness of the layer, but it is usually preferable to cure the uncured resin layer at an acceleration voltage of about 70 to 300 kV. The irradiation dose is preferably an amount at which the crosslink density of the ionizing radiation-curable resin is saturated, and is usually selected in the range of 5 to 300 kGy (0.5 to 30 Mrad), preferably 10 to 50 kGy (1 to 5 Mrad).
The electron beam source is not particularly limited, and various electron beam accelerators such as Cockcroft-Walton type, Van de Graaf type, resonant transformer type, insulating core transformer type, linear type, dynamitron type, and high frequency type can be used.
When ultraviolet light is used as the ionizing radiation, ultraviolet light having a wavelength of 190 to 380 nm is emitted. There are no particular limitations on the source of ultraviolet light, and examples that can be used include high-pressure mercury lamps, low-pressure mercury lamps, metal halide lamps, and carbon arc lamps.

(Formation of other layers)
The above has described a manufacturing method for a decorative sheet used in the pressure-sensitive adhesive sheet of the present disclosure having a layer structure including a support layer and a surface layer, but the decorative sheet may have other layers in addition to the support layer and surface layer, such as a primer layer, a transparent resin layer, a decorative layer, an adhesive layer, etc.

For example, the decorative layer, adhesive layer, and primer layer can be formed by applying a coating liquid containing a composition for forming each layer using the known method described above, and drying and curing it as necessary.
When a transparent resin layer is formed, a resin film for forming the transparent resin layer can be formed by dry lamination or the like.

[Releasable sheet layer]
The pressure-sensitive adhesive sheet of the present disclosure has, in that order, a base layer, an adhesive layer, and a release sheet layer, i.e., the pressure-sensitive adhesive sheet of the present disclosure has a release sheet layer on the side of the adhesive layer opposite to the side on which the base layer is provided. The release sheet layer is provided opposite the adhesive layer, thereby protecting the adhesive layer and preventing blocking between adhesive layers of the pressure-sensitive adhesive sheets when the pressure-sensitive adhesive sheet of the present disclosure is stored in a rolled form or stacked.
In addition, the release sheet layer is preferably provided so as to be in contact with the adhesive layer in order to protect the adhesive layer.

The adhesive sheet of the present disclosure is used by peeling the adhesive layer and base layer from the peelable sheet layer, and then attaching the adhesive layer to the adherend so that the adhesive layer faces the adherend. In other words, the peelable sheet layer is peeled and removed from the surface of the adhesive layer when using the adhesive sheet, such as by attaching it to an adherend.

The peelable sheet layer is not particularly limited as long as it is a sheet layer that can be peeled off from the adhesive layer, and various forms such as release film, separation paper, separation film, separator paper, peeling film, and release paper can be used as appropriate. Examples of peelable sheet layers that can be used include fine paper, coated paper, impregnated paper, plastic film, etc., with a peelable layer formed on one or both sides.

The release layer is not particularly limited as long as it is made of a material that has releasability (also known as "mold-releasing properties"). Preferred examples of materials with releasability include silicone resins, organic resin-modified silicone resins, fluororesins, aminoalkyd resins, melamine resins, acrylic resins, and polyester resins. These resins may be emulsion-type, solvent-type, or solventless.

When a release film having a release layer is used, for example, a silicone release type PET (polyethylene terephthalate) film, an untreated PET film, a PP (polypropylene) film, a silicone release type paper, or the like can be used.
When the release sheet layer has a release layer, the release sheet layer is preferably provided so that the adhesive layer and the release layer face each other, and more preferably so that the adhesive layer and the release layer are in contact with each other.

The thickness of the peelable sheet layer is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more, with an upper limit of preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 125 μm or less. When the thickness of the peelable sheet layer is within the above range, the peelable sheet layer can be made stiff, making it easier to peel off and improving workability during application.

[Method for manufacturing pressure-sensitive adhesive sheet]
The method for producing a pressure-sensitive adhesive sheet according to the present disclosure includes:
an adhesive coating layer forming step of applying an adhesive layer-forming resin composition to the releasable surface of the release sheet layer to form an adhesive coating layer of the adhesive layer-forming resin composition;
an adhesive layer forming step of drying the adhesive coating layer to form a porous adhesive layer; and an adhesion step of adhering the adhesive layer to a substrate layer.
Including,
The adhesion strength A between the base layer and the adhesive layer measured by a predetermined measurement method is 17.0 N/25 mm or more,
The adhesion strength B between the adhesive layer and the SUS304 steel plate measured by a predetermined measurement method is 1.0 N/25 mm or more and 10.0 N/25 mm or less,
Method for producing a pressure-sensitive adhesive sheet The pressure-sensitive adhesive sheet of the present disclosure can be easily produced by the method for producing a pressure-sensitive adhesive sheet of the present disclosure.

(Adhesive coating layer forming process)
The resin composition for forming an adhesive layer can be applied by a known method such as gravure printing, bar coating, roll coating, reverse roll coating, or comma coating.
The adhesive layer-forming resin composition used in the adhesive coating layer-forming step is as described above, and is preferably an adhesive resin composition containing bubbles. The method for incorporating bubbles into the adhesive resin composition is also as described above.

The amount of application may be such that the thickness of the adhesive layer is as described above, and is preferably 10 g/ ^m2 or more, more preferably 15 g/ ^m2 or more, even more preferably 18 g/ ^m2 or more, and even more preferably 20 g/ ^m2 or more, with the upper limit being preferably 100 g/ ^m2 or less, more preferably 85 g/ ^m2 or less, even more preferably 75 g/ ^m2 or less, and even more preferably 70 g/ ^m2 or less.

(Adhesive layer formation process)
The adhesive layer forming step is a step of drying the adhesive coating layer formed in the adhesive coating layer forming step to form an adhesive layer.
The method for drying the adhesive coating layer includes, for example, a method of drying by heating, a method of drying while blowing air, etc., and drying can be performed using a dryer capable of performing such drying. The drying temperature cannot be generalized because it can vary depending on the type of solvent used in the adhesive resin composition, but it is usually 60 ° C or higher and 140 ° C or lower. In consideration of more efficient drying, it is preferably 80 ° C or higher, more preferably 90 ° C or higher, and the upper limit is preferably 130 ° C or lower, more preferably 120 ° C or lower.

The drying time cannot be generalized as it can vary depending on the type of solvent used in the adhesive resin composition, drying temperature conditions, etc., but it should usually be between 20 seconds and 10 minutes. To ensure more efficient drying, the drying time is preferably at least 30 seconds, more preferably at least 45 seconds, and even more preferably at least 1 minute, with the upper limit being preferably 5 minutes, more preferably 3 minutes 30 seconds, and even more preferably 2 minutes 30 seconds.

By drying the adhesive resin composition containing bubbles in this manner, the adhesive resin is dried appropriately, causing the bubbles to burst, leaving part of the bubble shape more likely to remain. This makes it easier to form uniformly recessed shapes on the surface of the adhesive resin composition containing bubbles. As a result, the adhesive layer becomes porous, the adhesive strengths A and B fall within the specified ranges, and the adhesive layer has excellent reworkability.

(Adhesion process)
The adhesion step is a step of adhering the base material layer and the adhesive layer formed in the adhesive layer forming step.
When a decorative sheet is used as the substrate layer, the decorative sheet may be a commercially available product, or may be manufactured by the manufacturing method described above.

The adhesive layer can be bonded to the base layer by, for example, laminating a decorative sheet, which is preferably used as the base layer, with a release sheet layer on which an adhesive layer has been formed in the adhesive layer-forming step, so that the decorative sheet and the adhesive layer face each other. Lamination can be performed using a known laminating method.

In this case, the lamination pressure for bonding the base layer and adhesive layer is preferably 0.30 MPa or higher. By bonding them together at a lamination pressure within the above range, it becomes easier to achieve the adhesion force A between the base layer and adhesive layer within the above range, i.e., 17.0 N/25 mm or higher. From the same perspective, the lamination pressure is more preferably 0.32 MPa or higher, and even more preferably 0.35 MPa or higher. There is no particular upper limit for the adhesion force A within the above range, but for manufacturing convenience, it is usually sufficient to set it to 0.65 MPa or lower, and preferably 0.60 MPa or lower.

[Method for measuring adhesion]
The method for measuring the adhesive strength A of the present disclosure, i.e., the method for measuring the adhesive strength A between the base layer and the adhesive layer of the adhesive sheet, is as follows:
In accordance with Method 3 (180° peel adhesion of double-sided tape) of JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets), an SUS304 steel plate and the adhesive layer of the adhesive sheet (width: 25 mm, length: 100 mm) are attached via double-sided adhesive tape, and one hour after attachment, a peel strength meter is used to perform 180° peeling (peel speed: 300 mm/min) so that the base layer and the adhesive layer are peeled off, and the adhesion strength measured is defined as adhesion strength A.
This is the measurement method.

The method of measuring the adhesion strength A between the base layer and adhesive layer of an adhesive sheet according to the present disclosure can be applied to measuring the adhesion strength between a base layer and an adhesive layer in an adhesive sheet having at least a base layer and an adhesive layer. Therefore, the method of measuring the adhesion strength A of an adhesive sheet according to the present disclosure is not limited to the adhesive sheet of the present disclosure, but can be widely applied to other adhesive sheets having at least a base layer and an adhesive layer.

The measurement of adhesion strength A in this disclosure basically conforms to Method 3 (180° peel adhesion strength of double-sided tape) of JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets), but is particularly characterized by the use of double-sided adhesive tape, which allows the adhesion strength between the base layer and adhesive layer to be measured. This allows for reliable peeling from the interface between the base layer and adhesive layer, making it possible to reliably measure the adhesion strength between these layers.

As described above, the double-sided adhesive tape used in the method for measuring adhesion strength A disclosed herein can be any tape with an adhesion strength between the double-sided adhesive tape and the SUS304 steel plate that is stronger than the adhesion strength A between the base layer and the adhesive layer, and the adhesion strength between the double-sided adhesive tape and the adhesive layer. Any commercially available product can be appropriately selected and used.

The method for measuring the adhesion strength B of the present disclosure, i.e., the method for measuring the adhesion strength B between the adhesive layer of the adhesive sheet and the SUS304 steel plate, is as follows:
In accordance with Method 1 (180° peel adhesion to test plate) of JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets), the adhesive sheet (width: 25 mm, length: 100 mm) was attached to an SUS304 steel plate, and immediately after attachment and 24 hours after attachment, the adhesive sheet was peeled at 180° (peel speed: 300 mm/min) using a peel strength measuring device, and the measured adhesion strength was designated adhesion strength B.
This is the measurement method.

The method of measuring the adhesion strength B between the adhesive layer of a pressure-sensitive adhesive sheet and a SUS304 steel sheet according to the present disclosure is a method of measuring both the adhesion strength measured immediately after application (initial adhesion strength _B1 ) and the adhesion strength measured 24 hours after application (normal adhesion strength _B2 ). In other words, the adhesion strength B measured by the measurement method of the present disclosure is an adhesion strength that includes both the initial adhesion strength _B1 and the normal adhesion strength _B2 .
It should be noted that, since it is not possible to measure the adhesive strength 24 hours after application of a pressure-sensitive adhesive sheet that is peeled off immediately after application, it is advisable to prepare multiple samples of the pressure-sensitive adhesive sheet for measuring the adhesive strength.

The method of measuring the adhesion strength B between an adhesive layer of an adhesive sheet and a SUS304 steel plate according to the present disclosure can be applied to measuring the adhesion strength between an adhesive layer and a SUS304 steel plate for adhesive sheets having at least an adhesive layer, or adhesive sheets having a base layer and an adhesive layer. Therefore, the method of measuring the adhesion strength B of an adhesive sheet according to the present disclosure is not limited to the adhesive sheet of the present disclosure, but can be widely applied to other adhesive sheets having at least an adhesive layer.

The method for measuring adhesion strength B disclosed herein assumes that the adherend is a SUS304 steel plate, as described above. However, as shown in the Reference Example below, it is also possible to easily measure the adhesion strength between a pressure-sensitive adhesive sheet and an adherend when the adherend is a material other than a SUS304 steel plate. In other words, the method for measuring adhesion strength B disclosed herein is not limited to SUS304 steel plate, and can be widely applied to any adherend to which a pressure-sensitive adhesive sheet can be adhered.

[Decorative materials]
The pressure-sensitive adhesive sheet of the present disclosure can be laminated with an adherend and used as a decorative member that forms the surface of buildings, various furniture, vehicles, home appliances, and the like.
The decorative member comprises the adhesive sheet of the present disclosure and an adherend, and specifically, is formed by laminating the adhesive layer of the adhesive sheet of the present disclosure facing the surface of the adherend that requires decoration, etc.

(adherent material)
The adherend may be a member made of a material appropriately selected from the materials exemplified above as materials that can be used for the base layer.
The adherend may be selected appropriately from the above depending on the application. When the application is for interior building components such as walls, ceilings, and floors; exterior building components such as exterior walls, roofs, eaves ceilings, fences, and gates; or fixtures or fittings such as window frames, doors, handrails, baseboards, moldings, and other fixtures or fittings, it is preferable to use at least one member selected from wood members made of wood-based materials, metal members made of metal, and resin members made of resin. When the application is for exterior building components such as entrance doors, or fixtures such as window frames and doors, it is preferable to use at least one member selected from metal members and resin members.

The thickness of the adherend can be selected appropriately depending on the application and material, and is preferably 0.1 mm or more, more preferably 0.3 mm or more, and even more preferably 0.5 mm or more, with an upper limit of preferably 100 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less.

(Adhesive layer)
In order to obtain excellent adhesion, the pressure-sensitive adhesive sheet of the present disclosure and the adherend are preferably attached via an adhesive layer.
The adhesive used in the adhesive layer is not particularly limited, and any known adhesive can be used, and may be appropriately selected depending on the application. Preferred examples include moisture-curing adhesives, anaerobic-curing adhesives, dry-curing adhesives, UV-curing adhesives, heat-sensitive adhesives (e.g., hot-melt adhesives), and pressure-sensitive adhesives.

Resins used in these adhesives include, for example, acrylic resins, urethane resins, vinyl chloride resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, styrene-acrylic copolymers, polyester resins, amide resins, cyanoacrylate resins, and epoxy resins, which can be used alone or in combination. Two-component curing urethane adhesives and ester adhesives that use an isocyanate compound or the like as a curing agent can also be used.
The adhesive layer may also contain a pressure-sensitive adhesive, which may be appropriately selected from various pressure-sensitive adhesives such as acrylic, urethane, silicone, and rubber-based pressure-sensitive adhesives.

There are no particular restrictions on the thickness of the adhesive layer, but it is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, with the upper limit being preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. When the thickness of the adhesive layer is within the above range, excellent adhesion can be efficiently achieved.

(Method for manufacturing decorative member)
The decorative member can be produced through a process of laminating the pressure-sensitive adhesive sheet of the present disclosure and an adherend.
This step is a step of laminating the pressure-sensitive adhesive sheet of the present disclosure and an adherend, and involves laminating the adhesive sheet so that the surface of the adherend that requires decoration, etc. faces the adhesive layer of the pressure-sensitive adhesive sheet. Examples of methods for laminating the pressure-sensitive adhesive sheet and the adherend include a lamination method in which the laminate is pressed onto the plate-shaped adherend via the adhesive layer using a pressure roller.

When using a hot melt adhesive (heat-sensitive adhesive) as the adhesive, the heating temperature is preferably 160°C or higher and 200°C or lower, although this depends on the type of resin that makes up the adhesive. For reactive hot melt adhesives, the heating temperature is preferably 100°C or higher and 130°C or lower.

[Application]
The decorative member using the pressure-sensitive adhesive sheet of the present disclosure can be cut as desired, and the surface or end grain can be arbitrarily decorated, such as groove processing or chamfering, using a cutting machine such as a router or cutter.Then, it can be suitably used for various applications, such as interior components of buildings such as walls, ceilings, and floors; exterior components such as exterior walls, eaves ceilings, roofs, fences, and fences; fittings or fixtures such as window frames, doors, door frames, handrails, baseboards, moldings, and other building components; general furniture such as chests of drawers, shelves, and desks; kitchen furniture such as dining tables and sinks; various furniture and components used in wet areas such as kitchens, toilets, bathrooms, and washbasins; surface decorative panels for cabinets and the like for home appliances and office automation equipment; interior or exterior components for vehicles; and the like.When the laminate of the present disclosure is in the form of a sheet, it can be suitably used as a decorative sheet for the above-mentioned various components.

In addition to the various components mentioned above, the pressure-sensitive adhesive sheet of the present disclosure can be used alone or in a laminated or composite form with other materials for packaging materials, anti-glare films for displays, white or black boards, various cards such as credit cards, cash cards, telephone cards, and various certificates, keys on various keyboards, transparent panels (such as window glass) for windows, doors, and partitions, artificial leather, etc.

Next, the present disclosure will be explained in more detail using examples, but the present disclosure is not limited to these examples in any way.

(Measurement of Adhesion A and B)
Using the pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples, the adhesive strengths A and B were measured by the above-mentioned measuring method.
Regarding the adhesive strength B, the initial adhesive strength _B1 immediately after the adhesive sheet was applied to the SUS304 steel plate, as well as the normal adhesive strength _B2 24 hours after application were measured.

(Evaluation of adhesive residue ("reworkability"))
A sample of the pressure-sensitive adhesive sheet (length: 150 mm, width: 2.5 mm) prepared in each of the examples and comparative examples was attached to the vinyl chloride decorative sheet of a stainless steel plate (SUS304, No. 2B, thickness 2 mm) to which a vinyl chloride decorative sheet (product name "Dinoc Film ME1174", manufactured by 3M) had been attached, and left at 40°C for one week. After leaving under the above conditions, the pressure-sensitive adhesive sheet sample was peeled off and reattached to the vinyl chloride decorative sheet of a newly prepared stainless steel plate, and the reworkability was evaluated according to the following evaluation criteria.
A: When peeled off, no adhesive was left on the vinyl chloride decorative sheet, and the tape could be reattached to a newly prepared vinyl chloride decorative sheet on a stainless steel plate.
C: When peeled off, adhesive remained on the vinyl chloride decorative sheet, the adhesive sheet itself was torn, etc., and the sheet could not be peeled off cleanly. Alternatively, the sheet could be peeled off cleanly, but it was not possible to re-attach the sheet to the vinyl chloride decorative sheet of a newly prepared stainless steel plate.

(Preparation of bubble-containing adhesive resin composition)
An acrylic emulsion containing an acrylic polymer (acrylic polymer: "DICNAL MFP-20 (trade name)" (manufactured by DIC Corporation), weight average molecular weight: 270,000, acrylic polymer concentration: 50%, solvent: water) was charged with ammonium sulfate as a salt in a mixer at a ratio of 1/15 relative to the mass of the acrylic polymer (6.7 parts by mass per 100 parts by mass of acrylic polymer). The acrylic emulsion was stirred while mixing with nitrogen gas, thereby incorporating bubbles into the acrylic emulsion, and a bubble-containing adhesive resin composition was prepared. The density of the resulting bubble-containing adhesive resin composition was 0.4 g/ ^cm3 .

[Example 1]
A polyethylene terephthalate film (product name "SP-PET PET-O3-BU", manufactured by Mitsui Chemicals Tocello, Inc., thickness: 40 μm) with a release-treated surface was used as a release sheet layer. The bubble-containing adhesive resin composition prepared as described above was applied to the release-treated surface so that the dry coating amount was 30 g/ ^m² , and the composition was dried in a drying oven at 100°C for 2 minutes to form an adhesive layer. The density of the formed adhesive layer was 0.4 g/ ^cm³ . Next, a decorative sheet (model number "WS-5022E", manufactured by Dai Nippon Printing Co., Ltd., having a support layer, decorative layer, adhesive layer, transparent resin layer, primer layer, and surface layer in that order, with the surface layer being a cured product of an ionizing radiation-curable resin) was laminated at a lamination pressure of 0.35 MPa so that the adhesive layer faced the support layer, thereby obtaining an adhesive sheet.
The adhesive strengths A and B of the obtained pressure-sensitive adhesive sheets were measured by the above-mentioned methods, and the adhesive residue was evaluated. The measurement results and evaluation results are shown in Table 1.

[Examples 2 to 5 and Comparative Examples 1 and 2]
Pressure-sensitive adhesive sheets of Examples 2 to 5 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that the lamination pressure was changed to the pressure shown in Table 1.
The adhesive strengths A and B of the obtained pressure-sensitive adhesive sheets were measured by the above-mentioned methods, and the adhesive residue was evaluated. The measurement results and evaluation results are shown in Table 1.

According to Examples 1 to 5, the adhesive sheet of the present disclosure has an adhesion strength A of 17.0 N/25 mm or more and an adhesion strength B of 1.0 N/25 mm or more and 10.0 N/25 mm or less, respectively, and therefore it was confirmed that the adhesive sheet has excellent adhesive residue evaluation and excellent reworkability.
On the other hand, the adhesive sheets of Comparative Examples 1 and 2 had a low adhesive strength A, i.e., a low adhesive strength between the base layer and the adhesive layer, and therefore were poorly rated for adhesive residue and did not exhibit excellent reworkability.

(Reference example)
Using the pressure-sensitive adhesive sheet obtained in Example 1, the adhesion between the pressure-sensitive adhesive sheet and plates of the various materials shown in Table 2 was measured using the above-mentioned method for measuring adhesion B, except that the SUS304 steel plate was replaced with plates of the various materials shown in Table 2. The measurement results are shown in Table 2. In addition, adhesive residue was also evaluated based on the above-mentioned method for evaluating adhesive residue. The evaluation results are shown in Table 2.

Note)
Plates of various materials 1: Aluminum plate (A5052)
Plate 2 made of various materials: Acrylic plate (product name: Acrylite, manufactured by Mitsubishi Chemical Corporation)
Various material boards 3: ABS boards Various material boards 4: Urethane coated boards (decorative sheet flooring material, manufactured by Daiken Corporation)
Plate 5 made of various materials: Melamine baked paint plate (product number: 58181, manufactured by Japan Green Cross Co., Ltd. )

In the Reference Examples, the SUS304 steel plate used in the above-mentioned method for measuring adhesion B was replaced with plates of the various materials mentioned above to investigate the effect on adhesive residue when simulating changes in adhesion B. This shows that by satisfying the adhesion B possessed by the pressure-sensitive adhesive sheet of the present disclosure, excellent evaluation of adhesive residue is achieved and excellent reworkability can be obtained .
From the above results, it can be seen that the adhesive sheet of the present disclosure has excellent adhesive residue evaluation and excellent reworkability, as it has adhesion strengths A and B of 17.0 N/25 mm or more and 1.0 N/25 mm or more and 10.0 N/25 mm or less, respectively.

The PSA sheet of the present disclosure is suitable for use in a variety of applications, for example, as various components such as interior building components such as walls, ceilings, and floors; exterior components such as exterior walls, eaves ceilings, roofs, fences, and fences; fittings or fixtures such as window frames, doors, door frames, handrails, baseboards, moldings, and other building components; general furniture such as chests of drawers, shelves, and desks; kitchen furniture such as dining tables and sinks; various furniture and components used in wet areas such as kitchens, toilets, bathrooms, and washbasins; surface decorative panels such as cabinets for home appliances, office automation equipment, and the like; and interior or exterior components for vehicles.
Furthermore, in addition to the various components described above, the laminate can be used alone or in a form laminated or combined with other materials as packaging materials, antiglare films for displays, whiteboards or blackboards, various cards such as credit cards, cash cards, telephone cards, and various certificates, keys of various keyboards, transparent plates (window glass, etc.) for windows, doors, partitions, etc., artificial leather, etc.

DESCRIPTION OF SYMBOLS 1 Adhesive sheet 2 Base layer 21 Support layer 22 Decorative layer 22a Colored layer 22b Design layer 23 Surface layer 24 Adhesive layer 25 Transparent resin layer 26 Primer layer 3 Adhesive layer 31 Pores (spherical holes)
32 Pore (concave shape)
4. Peelable sheet layer

Claims (11)

The adhesive tape has a base layer, an adhesive layer, and a peelable sheet layer in this order,
The adhesive layer is porous,
The adhesion strength A between the base layer and the adhesive layer measured by the following measurement method is 17.0 N/25 mm or more,
The adhesion strength B between the adhesive layer and the SUS304 steel plate measured by the following measurement method is 1.0 N/25 mm or more and 10.0 N/25 mm or less,
Adhesive sheet.
(Method for measuring adhesion strength A)
In accordance with Method 3 (180° peel adhesion of double-sided tape) of JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets), an SUS304 steel plate and the adhesive layer of the adhesive sheet (width: 25 mm, length: 100 mm) are attached via double-sided adhesive tape, and one hour after attachment, a peel strength meter is used to perform 180° peeling (peel speed: 300 mm/min) so that the base layer and the adhesive layer are peeled off, and the adhesion strength measured is defined as adhesion strength A.
(Method for measuring adhesion strength B)
In accordance with Method 1 (180° peel adhesion to test plate) of JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets), the adhesive sheet (width: 25 mm, length: 100 mm) was attached to an SUS304 steel plate, and immediately after attachment and 24 hours after attachment, the adhesive sheet was peeled at 180° (peel speed: 300 mm/min) using a peel strength meter, and the measured adhesion strength was designated adhesion strength B. The adhesive sheet according to claim 1, wherein the adhesive layer is a porous layer due to air bubbles contained in the adhesive resin composition that forms the adhesive layer. The adhesive sheet according to claim 1 or 2, wherein the thickness of the adhesive layer is 10 μm or more and 100 μm or less. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the adhesion strength A is 17.0 N/25 mm or more and 35.0 N/25 mm or less. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the base layer is a decorative sheet having a support layer, a decorative layer, and a surface layer, and the decorative sheet is disposed so that the support layer faces the pressure-sensitive adhesive layer. an adhesive coating layer forming step of applying an adhesive layer-forming resin composition to the releasable surface of the release sheet layer to form an adhesive coating layer of the adhesive layer-forming resin composition;
The method includes: an adhesive layer forming step of drying the adhesive coating layer to form a porous adhesive layer; and an adhesion step of adhering the adhesive layer to a substrate layer.
The adhesion strength A between the base layer and the adhesive layer measured by the following measurement method is 17.0 N/25 mm or more,
The adhesion strength B between the adhesive layer and the SUS304 steel plate measured by the following measurement method is 1.0 N/25 mm or more and 10.0 N/25 mm or less,
A method for manufacturing an adhesive sheet.
(Method for measuring adhesion strength A)
In accordance with Method 3 (180° peel adhesion of double-sided tape) of JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets), an SUS304 steel plate and the adhesive layer of the adhesive sheet (width: 25 mm, length: 100 mm) are attached via double-sided adhesive tape, and one hour after attachment, a peel strength meter is used to perform 180° peeling (peel speed: 300 mm/min) so that the base layer and the adhesive layer are peeled off, and the adhesion strength measured is defined as adhesion strength A.
(Method for measuring adhesion strength B)
In accordance with Method 1 (180° peel adhesion to test plate) of JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets), the adhesive sheet (width: 25 mm, length: 100 mm) is attached to an SUS304 steel plate, and the adhesive sheet is peeled at 180° (peel speed: 300 mm/min) using a peel strength measuring device, and the measured adhesion strength is defined as adhesion strength B. The method for manufacturing a pressure-sensitive adhesive sheet according to claim 6, wherein the adhesion is performed at a lamination pressure of 0.30 MPa or more. The method for producing a pressure-sensitive adhesive sheet according to claim 6 or 7, wherein the resin composition for forming the pressure-sensitive adhesive layer is a pressure-sensitive adhesive resin composition containing bubbles. The method for producing a pressure-sensitive adhesive sheet according to any one of claims 6 to 8, wherein the resin composition for forming a pressure-sensitive adhesive layer is applied in an amount of 10 g/ ^m2 or more and 100 g/ ^m2 or less. For a pressure-sensitive adhesive sheet having a base layer and a pressure-sensitive adhesive layer, a measurement method for adhesion strength A of a pressure-sensitive adhesive sheet is performed in accordance with Method 3 (180° peel adhesion strength of double-sided tape) of JIS Z0237:2009 (Test methods for pressure-sensitive adhesive tapes and pressure-sensitive adhesive sheets), in which an SUS304 steel plate and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet (width: 25 mm, length: 100 mm) are attached via double-sided pressure-sensitive adhesive tape, and one hour after attachment, a peel strength meter is used to perform 180° peeling (peel speed: 300 mm/min) so that the base layer and the pressure-sensitive adhesive layer are peeled off, the adhesion strength is measured, and it is confirmed that the adhesion strength is 17.0 N/25 mm or more . For a pressure-sensitive adhesive sheet having at least an adhesive layer, a measurement method for adhesion force B is carried out in accordance with Method 1 (180° peel adhesion to test plate) of JIS Z0237:2009 (Test methods for pressure-sensitive adhesive tapes and pressure-sensitive adhesive sheets), in which the pressure-sensitive adhesive sheet (width: 25 mm, length: 100 mm) is attached to an SUS304 steel plate, and immediately after attachment and 24 hours after attachment, the pressure-sensitive adhesive sheet is peeled at 180° (peel speed: 300 mm/min) using a peel strength meter to measure the adhesion force, and it is confirmed that the adhesion force is 1.0 N/25 mm or more and 10.0 N/25 mm or less .