JP7570175B2 - Adhesive sheet for wafer processing - Google Patents

Description

The present invention relates to an adhesive sheet for wafer processing.

In the manufacturing process of semiconductor devices, a process of grinding, cutting, and the like is generally performed on a wafer (typically a semiconductor wafer) having a circuit-forming surface, with an adhesive sheet attached to the circuit-forming surface. The adhesive sheet typically has an adhesive layer provided on at least one side of a substrate. For example, when grinding the back surface of a semiconductor wafer (backgrinding), backgrinding tape is used to protect the circuit-forming surface (front surface) of the semiconductor wafer and to hold the semiconductor wafer (for example, Patent Document 1).

JP 2017-212441 A JP 2014-003199 A

In recent years, there has been an increasing demand for thinner wafers as semiconductor devices become smaller, thinner, and more highly integrated. However, when processing thin wafers, damage to the wafer is more likely to occur. For example, if a wafer is back-ground until it becomes thinner, the load applied when peeling off the back-grinding tape can easily damage the wafer, resulting in a decrease in yield and a decrease in productivity due to the need to be careful when peeling off the wafer. In particular, in a wafer that is back-ground so that the inside of the annular convex portion is a concave portion as described in Patent Document 2 (a so-called TAIKO (registered trademark) wafer), when the wafer is fixed by adsorption of the annular convex portion, the back surface is not supported by the concave portion, and therefore damage is particularly likely to occur when the back-grinding tape is peeled off.

One of the factors that can damage a wafer when an adhesive sheet is peeled off from a wafer as an adherend is the stick-slip phenomenon of the adhesive sheet. The stick-slip phenomenon is a phenomenon in which when an adhesive sheet is peeled off from an adherend, multiple peeling modes, such as interfacial peeling from the adherend surface (peeling surface) and cohesive failure inside the adhesive, occur periodically in combination, causing the peeling to progress intermittently. When the stick-slip phenomenon occurs, the peeling force oscillates greatly as the peeling progresses, causing a greater burden on the adherend during peeling, which can cause damage to the adherend.

The present invention was created in consideration of the above circumstances, and aims to provide an adhesive sheet for wafer processing that can reduce the load on the adherend by suppressing the stick-slip phenomenon during peeling.

According to this specification, there is provided an adhesive sheet for wafer processing, comprising an adhesive layer constituting an adhesive surface, wherein the adhesive sheet has a stick-slip degree [10 −3 N/10 mm] of 30 or less, measured at a peel rate of 300 mm/ ^min by at least one of the following methods A, B, and C, using an evaluation sample prepared by attaching the adhesive surface of the adhesive sheet to a silicon wafer as an adherend.
(Method A) An aqueous stripping liquid is supplied to the interface between the pressure-sensitive adhesive sheet and the adherend in the evaluation sample, and then the stick-slip degree is measured when the pressure-sensitive adhesive sheet is peeled from the adherend.
(Method B) The evaluation sample is irradiated with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and then the stick-slip degree is measured when the pressure-sensitive adhesive sheet is peeled off from the adherend.
(Method C) The evaluation sample is irradiated with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and an aqueous stripping liquid is supplied to the interface between the pressure-sensitive adhesive sheet and the adherend, and then the stick-slip degree is measured when the pressure-sensitive adhesive sheet is peeled off from the adherend.
Such an adhesive sheet for wafer processing suppresses the stick-slip phenomenon during peeling, so that the load on the adherend during peeling can be reduced, and damage to the adherend can be suppressed.

In some preferred embodiments of the technology disclosed herein, the pressure-sensitive adhesive sheet has a peel strength of 0.10 N/10 mm or less, as measured using the evaluation sample by at least one of the following methods E, F, and G.
(Method E) An aqueous stripping liquid is supplied to the interface between the pressure-sensitive adhesive sheet and the adherend in the evaluation sample, and then the peel force when peeling the pressure-sensitive adhesive sheet from the adherend is measured.
(Method F) The evaluation sample is irradiated with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and then the peel force when peeling the pressure-sensitive adhesive sheet from the adherend is measured.
(Method G) The evaluation sample is irradiated with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and an aqueous stripping liquid is supplied to the interface between the pressure-sensitive adhesive sheet and the adherend, and then the peel force when peeling the pressure-sensitive adhesive sheet from the adherend is measured.
Such an adhesive sheet for wafer processing can be peeled off with a light peeling force in the peeling step from the adherend, thereby reducing the burden on the adherend during peeling.

In a preferred embodiment of the technology disclosed herein, the adhesive sheet has a peel strength of 0.20 N/10 mm or more when the adhesive sheet is peeled from the adherend using the evaluation sample without irradiating the evaluation sample with active energy rays. The wafer processing adhesive sheet is likely to exhibit high adhesive strength in a state where it is not irradiated with active energy rays. For this reason, peeling of the adhesive sheet from the adherend is likely to be suppressed in a process (e.g., a back grinding process) in which the adherend is processed with the adhesive sheet attached to the adherend.

In a preferred embodiment of the technology disclosed herein, the adhesive layer is an active energy ray-curable adhesive layer. With such an adhesive sheet, the peel strength is likely to decrease after irradiation with active energy rays, and the peel strength changes significantly before and after irradiation with active energy rays. For this reason, the adhesive sheet is likely to achieve both adhesive strength in the processing step (e.g., the back grinding step) and easy peeling in the peeling step. In addition, with the adhesive sheet, the stick-slip degree is likely to decrease after irradiation with active energy rays, and therefore the burden on the adherend during peeling is likely to be reduced, and damage to the adherend during peeling is likely to be reduced.

In a preferred embodiment of the technology disclosed herein, the pressure-sensitive adhesive sheet has a stick-slip degree [10 ⁻³ N/10 mm] of 10 or less, measured at a peel speed of 300 mm/min by at least one of the above methods B and C. Such a pressure-sensitive adhesive sheet for wafer processing further suppresses the stick-slip phenomenon during peeling, so that the load on the adherend can be further reduced and damage to the adherend can be further suppressed.

In a preferred embodiment of the technology disclosed herein, the pressure-sensitive adhesive sheet has a stick-slip degree [10 ⁻³ N/10 mm] measured using the evaluation sample at a peel rate of 300 mm/min by method C of less than 3. Since such a pressure-sensitive adhesive sheet for wafer processing particularly suppresses the stick-slip phenomenon during peeling, the load on the adherend can be further reduced and damage to the adherend can be further suppressed.

In a preferred embodiment of the technology disclosed herein, the adhesive sheet has a peel strength of less than 0.050 N/10 mm measured by at least one of the methods F and G using the evaluation sample. The adhesive sheet for wafer processing can achieve particularly light peeling during the peeling process from the adherend.

Note that any combination of the above elements may be included within the scope of the invention for which patent protection is sought through this patent application.

FIG. 1 is a cross-sectional view showing a schematic configuration example of an adhesive sheet for wafer processing. FIG. 2 is a cross-sectional view showing a schematic configuration example of an adhesive sheet for wafer processing. FIG. 2 is a cross-sectional view showing a schematic configuration example of an adhesive sheet for wafer processing. FIG. 2 is a cross-sectional view showing a schematic configuration example of an adhesive sheet for wafer processing. FIG. 2 is a cross-sectional view showing a schematic configuration example of an adhesive sheet for wafer processing. FIG. 2 is a cross-sectional view showing a schematic configuration example of an adhesive sheet for wafer processing. 1 is a graph (x-axis: peel distance, y-axis: peel force) showing a schematic diagram of the peel force of a pressure-sensitive adhesive sheet for wafer processing from an adherend.

The following describes preferred embodiments of the present invention. Note that matters necessary for the implementation of the present invention other than those specifically mentioned in this specification can be understood by a person skilled in the art based on the teachings on the implementation of the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be implemented based on the contents disclosed in this specification and the common general technical knowledge in the field. In addition, in the following drawings, components and parts that perform the same function may be described with the same reference numerals, and duplicated descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are schematic in order to clearly explain the present invention, and do not necessarily accurately represent the size or scale of the product actually provided.

In this specification, the main chain of a polymer refers to the chain structure that forms the skeleton of the polymer. The side chain of a polymer refers to a group (pendant, side group) that is bonded to the main chain, or a molecular chain that can be considered as a pendant.

In this specification, "acrylic polymer" refers to a polymer derived from a monomer raw material containing more than 50% by weight (preferably more than 70% by weight, for example more than 90% by weight) of an acrylic monomer. The acrylic monomer refers to a monomer having at least one (meth)acryloyl group in one molecule. In this specification, "(meth)acryloyl" refers to acryloyl and methacryloyl in a comprehensive sense. Similarly, "(meth)acrylate" refers to acrylate and methacrylate, and "(meth)acrylic" refers to acrylic and methacrylic in a comprehensive sense.

In addition, in this specification, the term "active energy rays" is a concept that includes light such as ultraviolet rays, visible light, and infrared rays, as well as radiation such as alpha rays, beta rays, gamma rays, electron beams, neutron beams, and X-rays.

<Characteristics of adhesive sheet>
The adhesive sheet for wafer processing disclosed herein is one in which the stick-slip phenomenon occurring when peeled off from an adherend is suitably suppressed. Herein, the degree of the stick-slip phenomenon occurring when peeling off an adhesive sheet from an adherend is referred to as the "stick-slip degree" in the present specification. In a preferred embodiment, the adhesive sheet disclosed herein has a stick-slip degree suppressed to a predetermined value or less. Since such an adhesive sheet suitably suppresses the stick-slip phenomenon occurring when peeling off from an adherend, large vibrations of the peeling force accompanying the progress of peeling can be suppressed, and the burden on the adherend can be reduced. Therefore, an adhesive sheet with a low stick-slip degree is likely to suppress damage to the adherend during peeling.

The measurement method of the "stick-slip degree" in this specification will be described with reference to FIG. 7. FIG. 7 is a graph of a typical peel force curve of an adhesive sheet (x-axis is peel distance, y-axis is peel force). The stick-slip degree SS of an adhesive sheet is calculated by the following general formula (1) when the peel force curve is expressed as y=f(x) and only a reference length L is extracted from the peel force curve in the direction of the average line. Here, since the peel behavior of the adhesive sheet is often not stable in the initial stage of peeling from when the adhesive sheet starts to peel from the adherend until it reaches a predetermined peel behavior, it is preferable to start measuring the stick-slip degree when the adhesive sheet has been peeled from the adherend to a predetermined distance. In addition, the reference length L may be appropriately set according to the peel behavior of the adhesive sheet. The stick-slip degree [10 ^-3 N/10 mm] of the adhesive sheet described here is specifically measured by the method described in the Examples below.

The pressure-sensitive adhesive sheet disclosed herein has a stick-slip degree [10 −3 N/10 mm] that is suppressed to a predetermined value or less, as measured at a peel rate of 300 mm/min by at least one of the following methods A, B, and C, using an evaluation sample prepared by attaching the pressure ^- sensitive adhesive sheet to a silicon wafer as an adherend. With such a pressure-sensitive adhesive sheet, the stick-slip phenomenon is suppressed, and therefore damage to the adherend during peeling is likely to be suppressed.

In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the stick-slip degree [10 ^-3 N/10 mm] measured at a peel speed of 300 mm/min by at least one of the following methods B and C is suppressed to a predetermined value or less. With such a pressure-sensitive adhesive sheet, the stick-slip phenomenon during peeling is further suppressed, and therefore damage to the adherend during peeling tends to be further suppressed. From the same viewpoint, a pressure-sensitive adhesive sheet is preferred in which the stick-slip degree [10 ^-3 N/10 mm] measured at a peel speed of 300 mm/min by the following method C is suppressed to a predetermined value or less.

Method A: An aqueous stripping solution is supplied to the interface between the adhesive sheet and the adherend in the evaluation sample, and then the stick-slip degree SSw0 is measured when the adhesive sheet is peeled off from the adherend.

Method B: The evaluation sample is irradiated with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and then the stick-slip degree SSd1 is measured when the pressure-sensitive adhesive sheet is peeled off from the adherend.

Method C: The evaluation sample is irradiated with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and an aqueous stripping solution is supplied to the interface between the pressure-sensitive adhesive sheet and the adherend, and then the stick-slip degree SSw1 is measured when the pressure-sensitive adhesive sheet is peeled off from the adherend.

In a preferred embodiment of the adhesive sheet disclosed herein, the stick-slip degree SSw0 measured by the above method A (hereinafter also referred to as "unirradiated water peeling stick-slip degree SSw0") may be approximately 150 or less. From the viewpoint of suppressing damage to the adherend during peeling, in some embodiments, the unirradiated water peeling stick-slip degree SSw0 may be, for example, 100 or less, 50 or less, preferably 30 or less, more preferably 25 or less, and may be 22 or less. The lower limit of the unirradiated water peeling stick-slip degree SSw0 is not particularly limited, but from the viewpoint of balancing with the adhesive properties, it may be, for example, 0.5 or more, 1 or more, 5 or more, 10 or more, or 15 or more. In addition, when the adhesive layer of the adhesive sheet is an active energy ray curable adhesive layer, the unirradiated water peeling stick-slip degree SSw0 is a value measured when the adhesive sheet is peeled off from the adherend with water in an evaluation sample in which the adhesive sheet is not irradiated with active energy rays.

In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the stick-slip degree SSd1 measured by the above method B (hereinafter also referred to as "post-irradiation normal peel stick-slip degree SSd1") may be approximately 100 or less. From the viewpoint of suppressing damage to the adherend during peeling, in some embodiments, the post-irradiation normal peel stick-slip degree SSd1 may be, for example, 50 or less, preferably 30 or less, more preferably 20 or less, and even more preferably 15 or less (e.g., 10 or less). There is no particular restriction on the lower limit of the post-irradiation normal peel stick-slip degree SSd1, but from the viewpoint of balancing with the adhesive properties, it may be, for example, 0.10 or more, 0.50 or more, 1.0 or more, 1.50 or more, or 2.0 or more.

In a preferred embodiment of the adhesive sheet disclosed herein, the stick-slip degree SSw1 measured by the above method C (hereinafter also referred to as "post-irradiation water peeling stick-slip degree SSw1") may be approximately 100 or less. From the viewpoint of suppressing damage to the adherend during peeling, in some embodiments, the post-irradiation water peeling stick-slip degree SSw1 may be, for example, 50 or less, preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less (e.g., less than 3), and may be less than 1. The lower limit of the post-irradiation water peeling stick-slip degree SSw1 is not particularly limited, but from the viewpoint of balancing with the adhesive properties, it may be, for example, 0.01 or more, 0.10 or more, 0.20 or more, or 0.25 or more.

The stick-slip degree SSd0 (hereinafter also referred to as "unirradiated normal peeling stick-slip degree SSd0") when the pressure-sensitive adhesive sheet is normally peeled from the adherend without irradiating the pressure-sensitive adhesive sheet with active energy rays (i.e., peeled without using a stripping solution such as an aqueous stripping solution) using the evaluation sample is not particularly limited. From the viewpoint of balancing with the adhesive properties, the unirradiated normal peeling stick-slip degree SSd0 is usually appropriate to be 1.0 or more and 200 or less, and may be 5.0 or more and 150 or less, 10 or more and 100 or less, 15 or more and 50 or less, 15 or more and 30 or less, or 15 or more and 25 or less.

In a preferred embodiment of the technology disclosed herein, the peel strength of the pressure-sensitive adhesive sheet, measured using the evaluation sample by at least one of the following methods E, F, and G, is kept low at or below a predetermined value. Such a pressure-sensitive adhesive sheet allows for light peeling in the peeling process, making it easier to suppress damage to the adherend during peeling. Specifically, the peel strength of the pressure-sensitive adhesive sheet is measured by the method described in the Examples below.

In a preferred embodiment of the adhesive sheet disclosed herein, the peel strength measured by at least one of the following methods F and G is kept low at or below a predetermined value. With such an adhesive sheet, a lighter peel can be achieved in the peeling process, making it easier to suppress damage to the adherend during peeling. From the same perspective, an adhesive sheet in which the peel strength measured by the following method G is kept low at or below a predetermined value is more preferred.

In a preferred embodiment of the technology disclosed herein, the adhesive sheet has a peel strength of at least a predetermined value, as measured by the following method H using the evaluation sample. Such an adhesive sheet is likely to exhibit the adhesive strength desired for the adhesive sheet in processing steps such as back grinding.

Method E: An aqueous stripping solution is supplied to the interface between the adhesive sheet and the adherend in the evaluation sample, and then the peel force Fw0 is measured when the adhesive sheet is peeled off from the adherend.

Method F: Irradiate the evaluation sample with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and then measure the peel force Fd1 when peeling the pressure-sensitive adhesive sheet from the adherend.

Method G: Irradiate the evaluation sample with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and then supply an aqueous stripping solution to the interface between the pressure-sensitive adhesive sheet and the adherend, and measure the peel force Fw1 when peeling the pressure-sensitive adhesive sheet from the adherend.

Method H: Measure the peel force Fd0 when peeling the pressure-sensitive adhesive sheet from the adherend without irradiating the evaluation sample with active energy rays.

In a preferred embodiment of the technology disclosed herein, the peeling force Fw0 measured by the above method E (hereinafter also referred to as "unirradiated water peeling force Fw0") is usually 5.0 N/10 mm or less, preferably 2.0 N/10 mm or less, more preferably 1.0 N/10 mm or less, and even more preferably 0.50 N/10 mm or less (e.g., 0.10 N/10 mm or less). The lower limit of the unirradiated water peeling force Fw0 is not particularly limited, but in some embodiments, from the viewpoint of improving adhesion to the adherend, it is preferably 0.01 N/10 mm or more, for example, 0.02 N/10 mm or more, 0.03 N/10 mm or more, 0.05 N/10 mm or more, 0.075 N/10 mm or more, or 0.08 N/10 mm or more. In addition, when the adhesive layer of the adhesive sheet is an active energy ray-curable adhesive layer, the unirradiated water peeling force Fw0 is the value measured when the adhesive sheet is peeled from the adherend with water in an evaluation sample before the adhesive sheet is irradiated with active energy rays.

In a preferred embodiment of the technology disclosed herein, the peel force Fd1 measured by the above method F (hereinafter also referred to as "normal peel force after irradiation Fd1") is usually 1.0 N/10 mm or less, preferably 0.10 N/10 mm or less, more preferably 0.08 N/10 mm or less, and even more preferably 0.05 N/10 mm or less (e.g., 0.03 N/10 mm or less). There is no particular lower limit for the normal peel force after irradiation Fd1, but in some embodiments, from the viewpoint of balancing with adhesive performance, it may be 0.001 N/10 mm or more, 0.002 N/10 mm or more, or 0.004 N/10 mm or more.

In a preferred embodiment of the technology disclosed herein, the peeling force Fw1 measured by the above method G (hereinafter also referred to as "post-irradiation water peeling force Fw1") is usually 1.0 N/10 mm or less, preferably 0.10 N/10 mm or less, more preferably 0.05 N/10 mm or less, and even more preferably 0.01 N/10 mm or less (e.g., 0.008 N/10 mm or less). There is no particular lower limit for the post-irradiation water peeling force Fw1, but in some embodiments, from the viewpoint of balancing with adhesive performance, it may be 0.0005 N/10 mm or more, 0.001 N/10 mm or more, or 0.002 N/10 mm or more.

In a preferred embodiment of the technology disclosed herein, the peel force Fd0 measured by the above method H (hereinafter also referred to as "normal unirradiated peel force Fd0") is usually appropriate to be 0.05 N/10 mm or more, preferably 0.10 N/10 mm or more, more preferably 0.20 N/10 mm or more, and even more preferably 0.30 N/10 mm or more. From the viewpoint of improving the adhesive strength with the adherend during wafer (typically semiconductor wafer) processing, in some embodiments, the normal unirradiated peel force Fd0 is preferably 0.50 N/10 mm or more, more preferably 1.0 N/10 mm or more, and even more preferably 1.50 N/10 mm or more (e.g., 2.0 N/10 mm or more). The upper limit of the unirradiated normal peeling force Fd0 is not particularly limited, but from the viewpoint of achieving light peeling during peeling, it is usually appropriate that it is approximately 15 N/10 mm or less, preferably 10 N/10 mm or less, more preferably 5.0 N/10 mm or less, may be 3.0 N/10 mm or less, or may be 1.0 N/10 mm or less.

The tensile tester used to measure the above-mentioned normal peel stick-slip degrees SSd0, SSd1 and water peel stick-slip degrees SSw0, SSw1 may be a precision universal testing machine "Model: VPA-3" manufactured by Kyowa Interface Science Co., Ltd. or an equivalent. When making the measurements, if necessary, the pressure-sensitive adhesive sheet to be measured may be reinforced by attaching an appropriate backing material (e.g., a PET film with a thickness of about 25 μm).

The tensile tester used to measure the normal peel strengths Fd0, Fd1 and the water peel strengths Fw0, Fw1 can be a precision universal testing machine "Model: DT9503-1000N" manufactured by Tansui Co., Ltd. or an equivalent product. When making the measurements, if necessary, the pressure-sensitive adhesive sheet to be measured can be reinforced by attaching an appropriate backing material (for example, a PET film with a thickness of about 25 μm).

The silicon wafer used as the adherend to prepare the above evaluation sample may be the same as or an equivalent product to the examples described below. Note that the adhesive sheet disclosed herein is not necessarily used for the same wafer as the silicon wafer used to prepare the above evaluation sample. In other words, the use of the adhesive sheet disclosed herein is not limited to processing silicon wafers as the adherend to be used in measuring the stick-slip degree and/or peel force, but may also be used for processing other wafers.

<Examples of adhesive sheet configurations>
The adhesive sheet for wafer processing disclosed herein includes an adhesive layer. This adhesive layer typically constitutes at least one surface of the adhesive sheet. The adhesive sheet may be an adhesive sheet with a substrate having an adhesive layer on one or both surfaces of a substrate (support), or may be an adhesive sheet without a substrate (substrate-less adhesive sheet).
The concept of the adhesive sheet here may include those called adhesive tapes, adhesive labels, adhesive films, etc. In addition, the above-mentioned adhesive layer is typically formed continuously, but is not limited to such a form, and may be an adhesive layer formed in a regular or random pattern such as a dotted or striped pattern. In addition, the adhesive sheet provided by the present specification may be in the form of a roll or a sheet. Alternatively, it may be an adhesive sheet in the form of a processed form into various shapes.

The adhesive sheet disclosed herein may have, for example, a cross-sectional structure as shown in FIG. 1 to FIG. 6. Of these, FIG. 1 and FIG. 2 are structural examples of a substrate-attached adhesive sheet (substrate-attached single-sided adhesive sheet). The adhesive sheet 1 shown in FIG. 1 has an adhesive layer 21 provided on one side 10A (non-removable) of the substrate 10, and the surface (adhesive surface) 21A of the adhesive layer 21 is protected by a release liner 31, at least the adhesive layer side of which is a release surface. The adhesive sheet 2 shown in FIG. 2 has an adhesive layer 21 provided on one side 10A (non-removable) of the substrate 10. In this adhesive sheet 2, the other side 10B of the substrate 10 is a release surface, and when the adhesive sheet 2 is rolled up, the adhesive layer 21 comes into contact with the other side 10B, and the surface (adhesive surface) 21A of the adhesive layer is protected by the other side 10B of the substrate 10.

3 and 4 are configuration examples of a double-sided adhesive type substrate-attached pressure-sensitive adhesive sheet (substrate-attached double-sided pressure-sensitive adhesive sheet). The pressure-sensitive adhesive sheet 3 shown in FIG. 3 has a configuration in which a pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer) 21 and a pressure-sensitive adhesive layer (second pressure-sensitive adhesive layer) 22 are provided on the first surface 10A and the second surface 10B (both of which are non-removable) of the substrate 10, respectively, and the surface (first adhesive surface) of the first pressure-sensitive adhesive layer 21 and the surface (second adhesive surface) of the second pressure-sensitive adhesive layer 22 are protected by release liners 31 and 32, at least the pressure-sensitive adhesive layer side of which is a release surface. The pressure-sensitive adhesive sheet 4 shown in FIG. 4 has a configuration in which a first pressure-sensitive adhesive layer 21 and a second pressure-sensitive adhesive layer 22 are provided on the first surface 10A and the second surface 10B (both of which are non-removable), respectively, and the surface (first adhesive surface) of the first pressure-sensitive adhesive layer 21 is protected by a release liner 31, both of which are release surfaces. The adhesive sheet 4 can be configured so that the second adhesive surface is also protected by the release liner 31 by rolling the adhesive sheet 4 and abutting the surface (second adhesive surface) of the second adhesive layer 22 against the back surface of the release liner 31.

5 and 6 are structural examples of a substrate-less double-sided adhesive pressure-sensitive adhesive sheet (substrate-less double-sided pressure-sensitive adhesive sheet). The pressure-sensitive adhesive sheet 5 shown in FIG. 5 has a structure in which one surface (first adhesive surface) 21A and the other surface (second adhesive surface) 21B of a substrate-less pressure-sensitive adhesive layer 21 are protected by release liners 31 and 32, at least the pressure-sensitive adhesive layer side being a release surface. The pressure-sensitive adhesive sheet 6 shown in FIG. 6 has a structure in which one surface (first adhesive surface) 21A of the pressure-sensitive adhesive layer 21 is protected by a release liner 31, both of which are release surfaces, and when this is rolled up, the other surface (second adhesive surface) 21B of the pressure-sensitive adhesive layer 21 abuts against the back surface of the release liner 31, so that the other surface 21B is also protected by the release liner 31.
A substrate-less or substrate-attached double-sided PSA sheet can be used as a substrate-attached single-sided PSA sheet by laminating a non-releasable substrate to one of the adhesive surfaces.

The adhesive sheet before use (before application to an adherend) may be in the form of an adhesive sheet with a release liner, in which the adhesive surface is protected by a release liner, as shown in, for example, Figures 1 to 6. The release liner is not particularly limited, and examples that can be used include release liners in which the surface of a liner substrate such as a resin film or paper has been treated for release, and release liners made of low-adhesion materials such as fluorine-based polymers (polytetrafluoroethylene, etc.) and polyolefin-based resins (polyethylene, polypropylene, etc.). For the release treatment, for example, a silicone-based or long-chain alkyl-based release treating agent can be used. In some embodiments, a release-treated resin film can be preferably used as the release liner.

When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet with a substrate or a double-sided adhesive sheet without a substrate, the adhesive constituting the first adhesive surface (first adhesive) and the adhesive constituting the second adhesive surface (second adhesive) may have the same composition or different compositions. A substrate-less double-sided adhesive sheet having different compositions on the first adhesive surface and the second adhesive surface can be realized, for example, by an adhesive layer with a multilayer structure in which two or more adhesive layers with different compositions are directly laminated (without a substrate interposed therebetween).

In some embodiments of the adhesive sheet disclosed herein, the adhesive sheet has an adhesive surface constituted by an adhesive layer having active energy ray curability (active energy ray curable adhesive layer). Adhesive sheets according to other embodiments have an adhesive surface constituted by an adhesive layer not having active energy ray curability (non-active energy ray curable adhesive layer). In the case of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, the first adhesive surface and the second adhesive surface may both be adhesive surfaces constituted by an active energy ray curable adhesive layer, or both may be adhesive surfaces constituted by a non-active energy ray curable adhesive layer, or one may be an adhesive surface constituted by an active energy ray curable adhesive layer and the other may be an adhesive surface constituted by a non-active energy ray curable adhesive layer. The adhesive sheet disclosed herein may be preferably implemented in the form of a single-sided adhesive sheet with a substrate, a double-sided adhesive sheet with a substrate, or a double-sided adhesive sheet without a substrate, each of which has at least one adhesive surface constituted by an active energy ray curable adhesive layer or a non-active energy ray curable adhesive layer. Among these, a single-sided adhesive sheet with a substrate having an adhesive surface composed of an active energy ray-curable adhesive layer or a non-active energy ray-curable adhesive layer is preferred.

<Adhesive Layer>
The adhesive layer (e.g., active energy ray curable adhesive layer) constituting the adhesive surface of the adhesive sheet disclosed herein may be an adhesive layer containing one or more types of adhesive selected from various known adhesives such as acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, mixed systems thereof, etc.), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, and fluorine adhesives. Here, the acrylic adhesive refers to an adhesive having an acrylic polymer as the base polymer. The same applies to rubber adhesives and other adhesives.
In this specification, the "base polymer" of a PSA refers to the main component of the polymer contained in the PSA. In addition, in this specification, the "main component" refers to a component contained in the PSA in an amount of more than 50% by weight, unless otherwise specified.

(Acrylic adhesive layer)
In some embodiments of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive layer may be an acrylic pressure-sensitive adhesive layer containing an acrylic pressure-sensitive adhesive as a main component. In a pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer, it is possible to preferably achieve both adhesive properties suitable for wafer processing and easy releasability by water peeling. The acrylic pressure-sensitive adhesive layer is also preferable from the viewpoint of easily imparting active energy ray curability, which will be described later.

As the acrylic adhesive, for example, one containing an acrylic polymer, which is a polymer of a monomer raw material containing an alkyl (meth)acrylate or a modified product thereof by chemical modification or the like, as a base polymer is preferable. As a constituent component of the monomer raw material, an alkyl (meth)acrylate having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester end can be preferably used. Hereinafter, an alkyl (meth)acrylate having an alkyl group having X to Y carbon atoms at the ester end may be expressed as "C _X-Y alkyl (meth)acrylate". As the C _1-20 alkyl (meth)acrylate, C _1-14 (e.g., C _1-12 ) alkyl (meth)acrylate is preferable because it is easy to obtain adhesive properties suitable for wafer processing applications. As the C _1-20 alkyl acrylate, C _1-20 (e.g., C _1-14 , typically C _1-12 ) alkyl acrylate is preferable.

Non-limiting specific examples of C _1-20 alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, and isooctyl. Examples of the alkyl (meth)acrylate include ethyl acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. These alkyl (meth)acrylates can be used alone or in combination of two or more. Examples of preferred alkyl (meth)acrylates include ethyl acrylate (EA), n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and lauryl acrylate (LA). In some embodiments, the monomer feedstock preferably includes at least one of EA, BA, 2EHA, and LA, more preferably includes at least one of EA, BA, and 2EHA, and even more preferably includes at least one of BA and 2EHA.

Since it is easy to balance the properties, in some embodiments, the proportion of the C _1-20 alkyl (meth)acrylate in the monomer raw material is usually suitably 40% by weight or more, and preferably more than 50% by weight, for example, 55% by weight or more, 60% by weight or more, 65% by weight or more, or 70% by weight or more. For the same reason, the proportion of the C _1-20 alkyl (meth)acrylate in the monomer raw material is usually suitably 99.9% by weight or less, and may be 99% by weight or less, or 98% by weight or less. From the viewpoint of facilitating the formation of a PSA sheet suitable for easy release by supplying an aqueous stripping solution to the front of the peeling from the adherend, in some embodiments, the proportion of the C _1-20 alkyl (meth)acrylate in the monomer raw material may be, for example, 95% by weight or less, 85% by weight or less, less than 80% by weight, or 70% by weight or less.

In some preferred embodiments, the alkyl (meth)acrylate includes an alkyl (meth)acrylate A1 having an alkyl group having 9 or less carbon atoms at the ester end (i.e., C _1-9 alkyl (meth)acrylate). The alkyl (meth)acrylate A1 may be used alone or in combination of two or more. In this manner, a structure in which the length of the side chain alkyl group is limited tends to provide high cohesive strength capable of preventing adhesive residue to a high degree. For example, in a structure in which the side chain (typically the side chain end) of the polymer has a carbon-carbon double bond, the reaction of the carbon-carbon double bond can proceed smoothly during the curing treatment due to the limited length of the side chain alkyl group. In addition, due to the limited length of the side chain alkyl group, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a polymer obtained from the monomer can be efficiently peeled off from the adherend by a peeling method in which an aqueous peeling liquid such as water is supplied to the peeling front from the adherend.

The proportion of the alkyl (meth)acrylate A1 in the entire monomer raw material is suitably about 30% by weight or more, and from the viewpoint of better expressing the action of the alkyl (meth)acrylate A1, it is preferably about 40% by weight or more, more preferably about 55% by weight or more. In some embodiments, the proportion of the alkyl (meth)acrylate A1 may be, for example, about 65% by weight or more, about 75% by weight or more, or about 80% by weight or more. In some other embodiments, the proportion of the alkyl (meth)acrylate A1 may be, for example, about 85% by weight or more, about 90% by weight or more, or about 95% by weight or more. The upper limit of the proportion of the alkyl (meth)acrylate A1 in the monomer raw material is not particularly limited, and is usually suitably 99.5% by weight or less, and can be, for example, 99% by weight or less. In some embodiments, for example, from the viewpoint of favorably exerting the action of the carbon-carbon double bond in a pressure-sensitive adhesive layer containing a polymer having a carbon-carbon double bond, the proportion of the alkyl (meth)acrylate A1 in the entire monomer raw material is preferably about 95% by weight or less, more preferably about 90% by weight or less, may be about 85% by weight or less, may be about 75% by weight or less, or may be about 70% by weight or less.

The proportion of alkyl (meth)acrylate A1 in the entire alkyl (meth)acrylate is suitably about 50% by weight or more, and from the viewpoint of favorably expressing the action of alkyl (meth)acrylate A1, it is preferably about 70% by weight or more, more preferably about 80% by weight or more, may be about 90% by weight or more, may be about 95% by weight or more, or may be about 99% by weight or more. The upper limit of the proportion of alkyl (meth)acrylate A1 in the entire alkyl (meth)acrylate is 100% by weight.

In some embodiments, the alkyl (meth)acrylate A1 may contain one or more alkyl (meth)acrylates A3 having an alkyl group with less than 7 carbon atoms at the ester end. A pressure-sensitive adhesive containing a polymer obtained from a monomer raw material containing alkyl (meth)acrylate A3 is easy to provide a pressure-sensitive adhesive sheet that can be efficiently peeled off by a peeling method in which a peeling liquid such as water is supplied to the peeling front from the adherend. In addition, in an active energy ray-curable pressure-sensitive adhesive containing a polymer obtained from a monomer raw material containing alkyl (meth)acrylate A3, a curing reaction due to irradiation with active energy rays can proceed favorably. From such a viewpoint, the number of carbon atoms of the alkyl group in the alkyl (meth)acrylate A3 is preferably 6 or less, more preferably 4 or less, and may be 3 or less or 2 or less. In addition, the number of carbon atoms of the alkyl group in the alkyl (meth)acrylate A3 may be 1 or more, and is preferably 2 or more from the viewpoint of adhesion to the adherend.

In the embodiment in which the monomer raw material contains alkyl (meth)acrylate A3, the proportion of alkyl (meth)acrylate A3 in the entire monomer raw material may be, for example, about 1% by weight or more, and is usually about 5% by weight or more. From the viewpoint of favorably expressing the action of alkyl (meth)acrylate A3, it is preferably about 20% by weight or more, more preferably about 30% by weight or more, even more preferably about 40% by weight or more, and particularly preferably about 50% by weight or more, and may be, for example, 60% by weight or more, about 70% by weight or more, about 80% by weight or more, or about 90% by weight or more. There is no particular upper limit to the proportion of alkyl (meth)acrylate A3 in the entire monomer raw material, and it is usually about 99% by weight or less, and can be, for example, 90% by weight or less. In some embodiments, for example, from the viewpoint of favorably exerting the action of the carbon-carbon double bond in a pressure-sensitive adhesive layer containing a polymer having the carbon-carbon double bond, the proportion of the alkyl (meth)acrylate A3 in the entire monomer raw material is preferably about 80% by weight or less, more preferably about 70% by weight or less, and even more preferably about 60% by weight or less. The above embodiment may be, for example, an embodiment in which a reactive group for curing treatment or a functional group that serves as a crosslinking point is introduced into the polymer.

The proportion of alkyl (meth)acrylate A3 in the entire alkyl (meth)acrylate is suitably about 5% by weight or more, and from the viewpoint of favorably expressing the action of alkyl (meth)acrylate A3, it is preferably about 20% by weight or more, more preferably about 35% by weight or more, even more preferably about 45% by weight or more, and particularly preferably about 55% by weight or more, for example, about 65% by weight or more, about 75% by weight or more, about 85% by weight or more, or about 90% by weight or more. The upper limit of the proportion of alkyl (meth)acrylate A3 in the entire alkyl (meth)acrylate is 100% by weight, and may be, for example, about 98% by weight or less. In some embodiments, for example, in the case where the alkyl (meth)acrylate A2 described later is used in combination with the alkyl (meth)acrylate A3, from the viewpoint of favorably exerting its effect, the proportion of the alkyl (meth)acrylate A3 in the total alkyl (meth)acrylate may be, for example, about 90% by weight or less, about 85% by weight or less, about 75% by weight or less, about 60% by weight or less, about 45% by weight or less, about 30% by weight or less, or about 15% by weight or less. The alkyl (meth)acrylate A3 may not be used.

In some embodiments, the alkyl (meth)acrylate may contain an alkyl (meth)acrylate A2 having an alkyl group with 7 or more carbon atoms at the ester end, either as the alkyl (meth)acrylate A1 or as a monomer different from the alkyl (meth)acrylate A1. The use of the alkyl (meth)acrylate A2 may be advantageous, for example, from the viewpoint of adhesion to an adherend. The number of carbon atoms in the alkyl group in the alkyl (meth)acrylate A2 is preferably 8 or more, and may be 9 or more. In addition, from the viewpoint of adhesive properties such as adhesive strength, the number of carbon atoms in the alkyl group in the alkyl (meth)acrylate A2 is preferably 14 or less, more preferably 12 or less, and even more preferably 10 or less, for example, 9 or less, and may be less than 9.

In the embodiment in which the monomer raw material contains alkyl (meth)acrylate A2, the proportion of alkyl (meth)acrylate A2 in the entire monomer raw material may be, for example, about 1% by weight or more, and is usually about 5% by weight or more. From the viewpoint of better expressing the action of alkyl (meth)acrylate A2, it is preferably about 20% by weight or more, more preferably about 30% by weight or more, even more preferably about 40% by weight or more, and particularly preferably about 50% by weight or more, and may be, for example, 60% by weight or more, about 70% by weight or more, about 80% by weight or more, or about 90% by weight or more. The upper limit of the proportion of alkyl (meth)acrylate A2 in the entire monomer raw material is not particularly limited, and is usually about 99.5% by weight or less, and can be, for example, about 99% by weight or less. In some embodiments, for example, from the viewpoint of favorably exerting the action of the carbon-carbon double bond in a pressure-sensitive adhesive layer containing a polymer having a carbon-carbon double bond, the proportion of the alkyl (meth)acrylate A2 in the entire monomer raw material is preferably about 95% by weight or less, may be about 90% by weight or less, may be about 85% by weight or less, may be about 75% by weight or less, or may be about 70% by weight or less.

The proportion of alkyl (meth)acrylate A2 in the total alkyl (meth)acrylate contained in the monomer raw material is suitably about 5% by weight or more, and from the viewpoint of favorably expressing the action of alkyl (meth)acrylate A2, it is preferably about 20% by weight or more, more preferably about 35% by weight or more, and even more preferably about 45% by weight or more, for example, about 55% by weight or more, about 65% by weight or more, about 75% by weight or more, about 85% by weight or more, about 90% by weight or more, or about 95% by weight or more. The upper limit of the proportion of alkyl (meth)acrylate A2 in the total alkyl (meth)acrylate is 100% by weight. In some embodiments, for example, in the case where the alkyl (meth)acrylate A3 is used in combination with the alkyl (meth)acrylate A2, from the viewpoint of favorably exerting its effect, the ratio of the alkyl (meth)acrylate A2 to the total alkyl (meth)acrylate may be, for example, about 95% by weight or less, about 90% by weight or less, about 80% by weight or less, about 70% by weight or less, about 60% by weight or less, about 45% by weight or less, about 30% by weight or less, about 20% by weight or less, about 10% by weight or less, or about 5% by weight or less. The alkyl (meth)acrylate A2 may not be used.

The monomer raw material used in the synthesis of the acrylic polymer may further contain a secondary monomer having copolymerizability with the alkyl (meth)acrylate as described above. The secondary monomer may be useful for introducing crosslinking points into the acrylic polymer or for increasing the cohesive strength of the acrylic polymer. In addition, for example, in the monomer raw material used in the synthesis of a polymer having a carbon-carbon double bond, it is preferable to use, as the secondary monomer, a monomer having a functional group (hereinafter also referred to as "functional group A") that can react with the functional group (hereinafter also referred to as "functional group B") of the carbon-carbon double bond-containing monomer described below.

As the secondary monomer, for example, the following functional group-containing monomers can be used alone or in combination of two or more.
Hydroxyl group-containing monomers: for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl (meth)acrylate, etc.; unsaturated alcohols such as vinyl alcohol, allyl alcohol, etc.; ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, etc.
Carboxy group-containing monomers: for example, ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), crotonic acid, isocrotonic acid, etc.; ethylenically unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, etc.
Acid anhydride group-containing monomers: for example, maleic anhydride, itaconic anhydride.
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, methyl-N-vinylpyrrolidone, vinylpyridine, vinylpyrazine, vinylpyrimidine, N-vinylpiperidone, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, N-(meth)acryloylmorpholine, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, and the like.
Amide group-containing monomers: for example, (meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide; N-alkyl(meth)acrylamides such as N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and N-n-butyl(meth)acrylamide; N-vinyl carboxylic acid amides such as N-vinylacetamide; monomers having a hydroxyl group and an amide group, for example, N-(2-hydroxyethyl)(meth)acrylamide, N N-hydroxyalkyl(meth)acrylamides such as N-(2-hydroxypropyl)(meth)acrylamide, N-(1-hydroxypropyl)(meth)acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, and N-(4-hydroxybutyl)(meth)acrylamide; monomers having an alkoxy group and an amide group, for example, N-alkoxyalkyl(meth)acrylamide such as N-methoxymethyl(meth)acrylamide, N-methoxyethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide; and N,N-dialkylaminoalkyl(meth)acrylamide such as N,N-dimethylaminopropyl(meth)acrylamide.
Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate.
Monomers having a succinimide skeleton: for example, N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyhexamethylene succinimide, and the like.
Maleimides: for example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, and the like.
Itaconimides: for example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, and the like.
Epoxy group-containing monomers: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether.
Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile.
Keto group-containing monomers: for example, diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.
Alkoxysilyl group-containing monomers: for example, alkoxysilyl group-containing (meth)acrylates such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; and alkoxysilyl group-containing vinyl compounds such as vinyltrimethoxysilane and vinyltriethoxysilane.
Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate.
Monomers having an epoxy group: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether.
Monomers containing a sulfonic acid group or a phosphoric acid group: for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethylacryloylphosphate, and the like.
Isocyanate group-containing monomers: for example, 2-isocyanatoethyl (meth)acrylate, (meth)acryloyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate.

The amount of the functional group-containing monomer is not particularly limited and may be appropriately selected so as to achieve the desired cohesive strength. In order to achieve a good balance between cohesive strength and other properties (e.g., adhesiveness), the amount of the functional group-containing monomer (the total amount of two or more functional group-containing monomers when two or more types of functional group-containing monomers are used) is usually 0.1% by weight or more of the total monomer raw material, and is preferably 0.3% by weight or more, for example 1% by weight or more. The amount of the functional group-containing monomer may be, for example, 50% by weight or less of the total monomer raw material, and is preferably 40% by weight or less, for example 35% by weight or less, and may be 30% by weight or less, 25% by weight or less, or 20% by weight or less.

In some embodiments, the monomer raw material may contain a hydroxyl group-containing monomer as the functional group-containing monomer. The amount of the hydroxyl group-containing monomer used is not particularly limited, and may be, for example, 0.01% by weight or more, 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 5% by weight or more, or 10% by weight or more of the entire monomer raw material. In some embodiments, the amount of the hydroxyl group-containing monomer used may be, for example, 50% by weight or less of the entire monomer raw material, and from the viewpoint of suppressing water absorption of the adhesive, it is usually appropriate to set it to 40% by weight or less, and it may be 30% by weight or less, 25% by weight or less, or 20% by weight or less. In some embodiments, the amount of the hydroxyl group-containing monomer used may be 15% by weight or less, 10% by weight or less, or 5% by weight or less of the entire monomer raw material. Alternatively, the hydroxyl group-containing monomer may not be used.

In some embodiments, the monomer raw material may contain a carboxyl group-containing monomer as the functional group-containing monomer. The proportion of the carboxyl group-containing monomer in the entire monomer raw material used for the synthesis of the acrylic polymer may be, for example, 15% by weight or less, or 10% by weight or less, and is preferably 7% by weight or less from the viewpoint of suppressing water absorption of the adhesive layer during wafer processing, and may be 5% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.5% by weight or less, or less than 0.1% by weight. The monomer raw material may be substantially free of a carboxyl group-containing monomer. Here, substantially free of a carboxyl group-containing monomer means that a carboxyl group-containing monomer is not used at least intentionally. For example, in a monomer raw material used for preparing a polymer having a carbon-carbon double bond in a side chain, a configuration in which the proportion of the carboxyl group monomer is limited as described above may be preferably adopted.

In some embodiments, the monomer raw material may contain a monomer having a nitrogen atom as the functional group-containing monomer. The use of a monomer having a nitrogen atom may impart appropriate polarity to the adhesive. This may be advantageous in realizing an adhesive sheet suitable for easy peeling by supplying an aqueous stripping solution such as water. A suitable example of a monomer having a nitrogen atom is a monomer having a nitrogen atom-containing ring. From the viewpoint of compatibility, etc., it is preferable to use, as the monomer having a nitrogen atom-containing ring, an N-vinyl type compound (such as an N-vinyl cyclic amide) such as N-vinyl-2-pyrrolidone or an N-(meth)acryloyl type compound such as N-(meth)acryloylmorpholine.

When a monomer having a nitrogen atom is used, the amount of the monomer having a nitrogen atom is not particularly limited, and may be, for example, 1% by weight or more, 2% by weight or more, 3% by weight or more, 5% by weight or more, or 7% by weight or more of the total monomer raw material. From the viewpoint of obtaining a higher effect, in some embodiments, the amount of the monomer having a nitrogen atom used may be 10% by weight or more, 15% by weight or more, or 20% by weight or more of the total monomer raw material. Also, from the viewpoint of easily balancing the properties, the amount of the monomer having a nitrogen atom used is usually appropriate to be, for example, 40% by weight or less of the total monomer raw material, and may be 35% by weight or less, 30% by weight or less, or 25% by weight or less. In some embodiments, the amount of the monomer having a nitrogen atom used may be, for example, 20% by weight or less, 15% by weight or less, 10% by weight or less, or 5% by weight or less of the total monomer raw material. Alternatively, the monomer having a nitrogen atom may not be used.

When the above-mentioned monomer raw material is used to prepare a polymer having a carbon-carbon double bond, it is preferable to use a functional group-containing monomer having a functional group (functional group A) that can react with a functional group (functional group B) of a compound having a carbon-carbon double bond described later as a secondary monomer. In such a case, the type of functional group-containing monomer is determined by the above-mentioned compound type. As a secondary monomer having functional group A, for example, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an epoxy group-containing monomer, or an isocyanate group-containing monomer is preferable, and a hydroxyl group-containing monomer is particularly preferable. By using a hydroxyl group-containing monomer as a secondary monomer, the acrylic polymer has a hydroxyl group. On the other hand, by using an isocyanate group-containing monomer as a compound having a carbon-carbon double bond, the hydroxyl group (functional group A) of the acrylic polymer reacts with the isocyanate group (functional group B) of the compound, and a carbon-carbon double bond derived from the compound is introduced into the acrylic polymer.

When a secondary monomer is used for the purpose of reacting with a compound having a carbon-carbon double bond, the amount of the secondary monomer (preferably a hydroxyl group-containing monomer) is preferably about 1% by weight or more of the total monomer raw material, from the viewpoint of easily obtaining an adhesive layer suitable for water peeling, and is preferably about 5% by weight or more, more preferably about 10% by weight or more, and even more preferably about 12% by weight or more, for example about 14% by weight or more. In addition, from the viewpoint of maintaining good adhesive properties such as adhesion, the amount of the secondary monomer is preferably about 40% by weight or less of the total monomer raw material, and is preferably about 30% by weight or less, more preferably about 20% by weight or less, and may be, for example, about 15% by weight or less.

The monomer raw material used in the preparation of the acrylic polymer may contain a sub-monomer (hereinafter also referred to as a copolymerizable monomer) other than the functional group-containing monomer described above, for the purpose of increasing the cohesive strength of the acrylic polymer, etc.
Non-limiting specific examples of the copolymerizable monomer include the following.
Alkoxy group-containing monomers: for example, alkoxyalkyl (meth)acrylates (alkoxyalkyl (meth)acrylates) such as 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, etc.; alkoxy(poly)alkylene glycol (meth)acrylates such as methoxyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, etc.
Vinyl esters: for example, vinyl acetate, vinyl propionate, etc.
Vinyl ethers: for example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.
Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene, etc.
Olefins: For example, ethylene, butadiene, isoprene, isobutylene, etc.
(Meth)acrylic acid esters having an alicyclic hydrocarbon group: for example, (meth)acrylates containing an alicyclic hydrocarbon group such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate.
Aromatic ring-containing (meth)acrylates: for example, aryl (meth)acrylates such as phenyl (meth)acrylate, aryloxyalkyl (meth)acrylates such as phenoxyethyl (meth)acrylate, and arylalkyl (meth)acrylates such as benzyl (meth)acrylate.
Other examples include heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing monomers such as vinyl chloride and fluorine atom-containing (meth)acrylates, organosiloxane chain-containing monomers such as silicone (meth)acrylates, and (meth)acrylic acid esters obtained from alcohols derived from terpene compounds.
Such copolymerizable monomers can be used alone or in combination of two or more. The amount of such other copolymerizable monomers is not particularly limited and may be appropriately selected depending on the purpose and application, but is preferably 20% by weight or less (e.g., 2 to 20% by weight, typically 3 to 10% by weight) of the total monomer raw material of the acrylic polymer, for example.

In a preferred embodiment, the total proportion of alkoxyalkyl (meth)acrylate and alkoxypolyalkylene glycol (meth)acrylate in the monomer raw material is preferably limited to less than 20% by weight from the viewpoint of suppressing gelation. The total proportion of the alkoxyalkyl (meth)acrylate and alkoxypolyalkylene glycol (meth)acrylate is more preferably less than 10% by weight, even more preferably less than 3% by weight, and particularly preferably less than 1% by weight. In one embodiment, the monomer raw material is substantially free of alkoxyalkyl (meth)acrylate and alkoxypolyalkylene glycol (meth)acrylate (content 0 to 0.3% by weight).
Similarly, in one embodiment, the monomer raw material may contain less than 20% by weight of an alkoxy group-containing monomer, or may contain no alkoxy group-containing monomer. The amount of the alkoxy group-containing monomer in the monomer raw material is preferably less than 10% by weight, more preferably less than 3% by weight, and even more preferably less than 1% by weight. In a particularly preferred embodiment, the monomer raw material is substantially free of an alkoxy group-containing monomer (content 0 to 0.3% by weight).

The method of polymerizing the monomer raw material is not particularly limited, and various polymerization methods known as synthesis methods for acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization, can be appropriately adopted. For example, solution polymerization can be preferably adopted. As a monomer supply method when performing solution polymerization, a lump-sum charging method in which all monomer raw materials are supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, etc. can be appropriately adopted. The solvent (polymerization solvent) used in solution polymerization can be appropriately selected from conventionally known organic solvents. For example, any one solvent selected from aromatic compounds such as toluene (typically aromatic hydrocarbons); esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc., or a mixed solvent of two or more solvents can be used. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and can be, for example, about 20°C to 120°C (typically 40°C to 80°C). According to solution polymerization, a polymerization reaction liquid is obtained in which the polymerized product of the monomer raw material is dissolved in the polymerization solvent. The adhesive composition used to form the adhesive layer can be preferably produced using the above-mentioned polymerization reaction liquid. Producing an adhesive composition using the above-mentioned polymerization reaction liquid can include, for example, chemical modification such as introduction of a carbon-carbon double bond to the polymer contained in the above-mentioned polymerization reaction liquid.

In the polymerization, a known or conventional thermal polymerization initiator or photopolymerization initiator may be used depending on the polymerization method, polymerization mode, etc. Examples of thermal polymerization initiators that can be used include azo-based polymerization initiators, peroxide-based initiators, redox-based initiators formed by combining peroxides with reducing agents, and substituted ethane-based initiators. Examples of photopolymerization initiators include α-ketol-based photoinitiators, acetophenone-based photoinitiators, benzoin ether-based photoinitiators, ketal-based photoinitiators, aromatic sulfonyl chloride-based photoinitiators, photoactive oxime-based photoinitiators, benzophenone-based photoinitiators, thioxanthone-based photoinitiators, and acylphosphinoxide-based photoinitiators. The polymerization initiators can be used alone or in appropriate combination of two or more.

The amount of polymerization initiator used may be any amount that is normally used, and may be selected, for example, from the range of about 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) per 100 parts by weight of the total monomer raw materials. In addition, when the polymerization initiator is also used as a photoinitiator, the amount of polymerization initiator used can be set taking this into consideration.

In the above polymerization, various conventionally known chain transfer agents (which may also be understood as molecular weight regulators or polymerization degree regulators) may be used as necessary. As the chain transfer agent, mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid, and α-thioglycerol may be used. Alternatively, a chain transfer agent that does not contain a sulfur atom (non-sulfur chain transfer agent) may be used. Specific examples of non-sulfur chain transfer agents include anilines such as N,N-dimethylaniline and N,N-diethylaniline; terpenoids such as α-pinene and terpinolene; styrenes such as α-methylstyrene and α-methylstyrene dimer; compounds having a benzylidenyl group such as dibenzylideneacetone, cinnamyl alcohol, and cinnamylaldehyde; hydroquinones such as hydroquinone and naphthohydroquinone; quinones such as benzoquinone and naphthoquinone; olefins such as 2,3-dimethyl-2-butene and 1,5-cyclooctadiene; alcohols such as phenol, benzyl alcohol, and allyl alcohol; and benzyl hydrogens such as diphenylbenzene and triphenylbenzene.
The chain transfer agent may be used alone or in combination of two or more. When a chain transfer agent is used, the amount of the chain transfer agent used may be, for example, about 0.01 to 1 part by weight based on 100 parts by weight of the monomer raw material. The technology disclosed herein may also be preferably implemented in an embodiment in which no chain transfer agent is used.

The molecular weight of the acrylic polymer is not particularly limited and can be set in an appropriate range according to the required performance. The weight average molecular weight (Mw) of the acrylic polymer is usually about 10×10 ⁴ or more (for example, 20×10 ⁴ or more), and from the viewpoint of achieving a good balance between cohesive strength and adhesive strength, it is appropriate to set it to more than 30×10 ⁴ , preferably about 40×10 ⁴ or more, may be about 50×10 ⁴ or more, or may be about 55×10 ⁴ or more. The upper limit of the Mw of the acrylic polymer is not particularly limited. From the viewpoint of the coatability of the adhesive composition, the Mw of the acrylic polymer is usually appropriate to be about 500×10 ⁴ or less, for example, may be about 150×10 ⁴ or less, or may be about 75×10 ⁴ or less. The above Mw can be the Mw of the acrylic polymer in either the adhesive composition or the adhesive layer.
Here, Mw refers to a value calculated in terms of standard polystyrene obtained by gel permeation chromatography (GPC). As the GPC device, for example, a model named "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used. The same applies to the examples described later.

The acrylic adhesive layer may further contain a polymer other than the acrylic polymer as a secondary polymer, if necessary. Suitable examples of the secondary polymer include those other than the acrylic polymer among the various polymers exemplified as polymers that may be contained in the adhesive layer. When the adhesive layer disclosed herein is an acrylic adhesive layer that contains a secondary polymer in addition to the acrylic polymer, the content of the secondary polymer is suitably less than 100 parts by weight relative to 100 parts by weight of the acrylic polymer, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and even more preferably 10 parts by weight or less. The content of the secondary polymer may be 5 parts by weight or less, or may be 1 part by weight or less, relative to 100 parts by weight of the acrylic polymer. The technology disclosed herein may be preferably implemented, for example, in an embodiment in which 99.5 to 100% by weight of the polymer contained in the adhesive layer is an acrylic polymer.

(Non-acrylic adhesive layer)
The adhesive layer constituting the adhesive surface in the adhesive sheet disclosed herein may be an adhesive layer having a polymer other than an acrylic polymer as a base polymer, i.e., a non-acrylic adhesive layer. The non-acrylic adhesive layer may further contain a sub-polymer other than the base polymer as necessary, in addition to the base polymer. In this case, the content of the sub-polymer in the non-acrylic adhesive layer may be selected from the above contents exemplified as the content of the sub-polymer in the acrylic adhesive layer. The non-acrylic adhesive layer may be an adhesive layer containing an acrylic polymer as a sub-polymer.

(Glass Transition Temperature)
The glass transition temperature (Tg) of the base polymer (e.g., acrylic polymer) of the adhesive layer constituting the adhesive surface is preferably 15°C or lower. In some embodiments, the Tg is suitably 10°C or lower from the viewpoint of adhesion to the adherend (e.g., conformity to the surface shape of the adherend) and the like, and is preferably 0°C or lower, and may be -10°C or lower, or may be -20°C or lower. In addition, from the viewpoint of the cohesiveness of the adhesive and the ease of easy peeling by water peeling, the Tg of the base polymer may be, for example, -75°C or higher, -60°C or higher, or -50°C or higher. In some embodiments, the Tg of the base polymer may be -45°C or higher, or -40°C or higher.

Here, the glass transition temperature (Tg) of a polymer in this specification refers to the glass transition temperature calculated by the Fox formula based on the composition of the monomer raw materials constituting the polymer. The Fox formula is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.
1/Tg=Σ(Wi/Tgi)
In the above Fox formula, Tg represents the glass transition temperature (unit: K) of the copolymer, Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi represents the glass transition temperature (unit: K) of a homopolymer of monomer i.

The glass transition temperature of the homopolymer used in calculating Tg is a value described in a publicly known document. For example, for the monomers listed below, the following values are used as the glass transition temperatures of the homopolymers of the monomers.
2-Ethylhexyl acrylate -70℃
n-Butyl acrylate -55℃
Isostearyl acrylate -18℃
Methyl methacrylate 105℃
Methyl acrylate 8℃
N-vinyl-2-pyrrolidone 54℃
N-Acryloylmorpholine 145℃
2-Hydroxyethyl acrylate -15℃
4-Hydroxybutyl acrylate -40℃
Acrylic acid 106℃
Methacrylic acid 228℃

For the glass transition temperatures of homopolymers of monomers other than those listed above, the values given in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) should be used. If multiple values are given in this document, the highest value should be used.

For monomers for which the glass transition temperature of the homopolymer is not described in the Polymer Handbook, the value obtained by the following measurement method shall be used (see JP 2007-51271 A). Specifically, 100 parts by weight of monomer, 0.2 parts by weight of azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as a polymerization solvent are charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and stirred for 1 hour while circulating nitrogen gas. After removing oxygen from the polymerization system in this way, the temperature is raised to 63°C and reacted for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution with a solid concentration of 33% by weight. Then, the homopolymer solution is cast and applied onto a release liner, and dried to prepare a test sample (sheet-shaped homopolymer) with a thickness of about 2 mm. The test sample was punched out into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to a shear strain of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics Corporation). Viscoelasticity was measured in shear mode at a temperature range of -70 to 150°C and a heating rate of 5°C/min. The peak top temperature of tan δ was taken as the Tg of the homopolymer.

(Surfactant)
In some preferred embodiments, the pressure-sensitive adhesive layer may contain a surfactant. The pressure-sensitive adhesive layer containing a surfactant can preferably exhibit the effect of reducing the peeling force by supplying an aqueous stripping solution to the peeling interface with the adherend. The reason for this is not particularly limited, but it is believed that the surfactant has a hydrophilic region, which causes it to be unevenly distributed on the surface of the pressure-sensitive adhesive layer and effectively reduces the peeling force when it comes into contact with the aqueous stripping solution. As the surfactant, one or more of known surfactants can be used without any particular restrictions. The surfactant is typically preferably contained in the pressure-sensitive adhesive layer in a free form. As the surfactant, a surfactant that is liquid at room temperature (about 25° C.) is preferably used from the viewpoint of the preparation of the pressure-sensitive adhesive composition.

The HLB of the surfactant is not particularly limited. The HLB of the surfactant may be, for example, 1 or more or 3 or more. The HLB of the surfactant is preferably 5 or more, may be 6 or more, may be 8 or more, or may be 9 or more. This tends to favorably express water peelability. The HLB of the surfactant is more preferably 10 or more, even more preferably 11 or more, even more preferably 12 or more, particularly preferably 13 or more, may be 14 or more, may be 15 or more, or may be 16 or more. A surfactant having an HLB in the above range can more effectively express light peelability by water peeling. The upper limit of the HLB is 20 or less, and may be, for example, 18 or less. In some embodiments, for example, from the viewpoint of compatibility, the HLB of the surfactant may be 16 or less, for example, 15 or less.

The HLB in this specification is the hydrophile-lipophile balance according to Griffin, which is a value indicating the degree of affinity of a surfactant for water or oil, and is a ratio of hydrophilicity to lipophilicity expressed as a number between 0 and 20. The definition of HLB is as described in W. C. Griffin: J. Soc. Cosmetic Chemists, 1,311 (1949), Takahashi Etsutami, Namba Yoshiro, Koike Motoo, and Kobayashi Masao, "Surfactant Handbook," 3rd Edition, Kogaku Toshosha Publishing, November 25, 1972, pp. 179-182, etc. Surfactants having the above HLB can be selected based on the technical common sense of a person skilled in the art, taking into consideration the above references as necessary.

As the surfactant, known nonionic surfactants, anionic surfactants, cationic surfactants, etc. can be used. Among them, nonionic surfactants are preferable. The surfactants can be used alone or in combination of two or more kinds.

Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; polyoxyethylene alkyl phenyl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether; polyoxyethylene fatty acid esters such as polyoxyethylene monolaurate, polyoxyethylene monostearate, and polyoxyethylene monooleate; sorbitan monolaurate, sorbitan monopalmitate, and sorbitan monostearate. Examples of the nonionic surfactant include sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan triisostearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate; polyoxyethylene glyceryl ether fatty acid esters; polyoxyethylene-polyoxypropylene block copolymers; and the like. The nonionic surfactant may be a reactive surfactant having a radical polymerizable functional group such as a propenyl group, a (meth)allyl group, a vinyl group, or a (meth)acryloyl group (for example, a nonionic reactive surfactant such as polyoxyethylene nonylpropenyl phenyl ether). These nonionic surfactants may be used alone or in combination of two or more. From the viewpoint of the performance stability of the pressure-sensitive adhesive sheet, it is preferable to use a nonionic surfactant that does not have a radically polymerizable functional group (nonreactive) as described above.

Examples of anionic surfactants include alkyl sulfates such as lauryl sulfate and octadecyl sulfate; fatty acid salts; alkyl benzene sulfonates such as nonyl benzene sulfonate and dodecyl benzene sulfonate; naphthalene sulfonates such as dodecyl naphthalene sulfonate; alkyl diphenyl ether disulfonates such as dodecyl diphenyl ether disulfonate; polyoxyethylene alkyl ether sulfates such as polyoxyethylene octadecyl ether sulfate and polyoxyethylene lauryl ether sulfate; polyoxyethylene alkyl phenyl ether sulfates such as polyoxyethylene lauryl phenyl ether sulfate; polyoxyethylene styrenated phenyl ether sulfate; sulfosuccinates such as lauryl sulfosuccinate and polyoxyethylene lauryl sulfosuccinate; polyoxyethylene alkyl ether phosphates; polyoxyethylene alkyl ether acetates; and the like. When the anionic surfactant forms a salt, the salt may be, for example, a metal salt (preferably a monovalent metal salt) such as a sodium salt, potassium salt, calcium salt, or magnesium salt, an ammonium salt, or an amine salt. These anionic surfactants can be used alone or in combination of two or more.

The amount of surfactant used is not particularly limited, and can be set so that the peel strength reduction caused by the supply of the aqueous stripping solution is effectively achieved. In some embodiments, the amount of surfactant used may be, for example, about 5 parts by weight or less relative to 100 parts by weight of the base polymer. From the viewpoint of bonding reliability to the adherend, it is appropriate to set it to about 3 parts by weight or less, preferably less than 2 parts by weight, more preferably less than 1 part by weight, less than 0.8 parts by weight, less than 0.6 parts by weight, less than 0.4 parts by weight, less than 0.2 parts by weight, or less than 0.1 parts by weight. Surfactants with a high HLB (for example, 5 or more) tend to exhibit good water peelability even when added in small amounts. In addition, from the viewpoint of exerting the effect of adding the surfactant, in some embodiments, the amount of surfactant relative to 100 parts by weight of the base polymer can be, for example, 0.001 parts by weight or more, and from the viewpoint of more uniformly exhibiting the peel strength reduction effect caused by the supply of the aqueous stripping solution, it is usually appropriate to set it to 0.01 parts by weight or more, preferably 0.03 parts by weight or more (for example, 0.1 parts by weight or more). In compositions where water strippability is important, the amount of surfactant per 100 parts by weight of base polymer may be 0.3 parts by weight or more (e.g., 0.5 parts by weight or more).

(Crosslinking Agent)
In the adhesive layer (which may be an active energy ray curable adhesive layer), a crosslinking agent may be used as necessary for the purpose of adjusting the cohesive force. The crosslinking agent may be included in the adhesive layer in a form after the crosslinking reaction, or in a form before the crosslinking reaction. The type of crosslinking agent is not particularly limited, and may be selected from conventionally known crosslinking agents so that the crosslinking agent exerts an appropriate crosslinking function in the adhesive layer, for example, according to the composition of the adhesive composition. Examples of crosslinking agents that can be used include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents. These may be used alone or in combination of two or more. In some preferred embodiments, at least an isocyanate-based crosslinking agent is used as the crosslinking agent. An isocyanate-based crosslinking agent may be used in combination with another crosslinking agent (e.g., an epoxy-based crosslinking agent).

As the isocyanate-based crosslinking agent, a polyfunctional isocyanate compound having two or more functionalities can be used. Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris(p-isocyanatophenyl)thiophosphate, and diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate. Commercially available products include isocyanate adducts such as trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, product name "Coronate L"), trimethylolpropane/hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, product name "Coronate HL"), and isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate HX").

As the epoxy crosslinking agent, those having two or more epoxy groups in one molecule can be used without any particular restrictions. Epoxy crosslinking agents having 3 to 5 epoxy groups in one molecule are preferred. Specific examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and the like. Commercially available epoxy crosslinking agents include Mitsubishi Gas Chemical Company's product names "TETRAD-X" and "TETRAD-C," DIC Corporation's product name "Epicron CR-5L," Nagase ChemteX Corporation's product name "Denacol EX-512," Nissan Chemical Industries' product name "TEPIC-G," and the like.

As the oxazoline-based crosslinking agent, any agent having one or more oxazoline groups in one molecule can be used without any particular limitation.
Examples of the aziridine crosslinking agent include trimethylolpropane tris[3-(1-aziridinyl)propionate], trimethylolpropane tris[3-(1-(2-methyl)aziridinylpropionate)], and the like.
As the carbodiimide-based crosslinking agent, a low molecular weight compound or a high molecular weight compound having two or more carbodiimide groups can be used.

The metal chelate crosslinking agent may typically have a structure in which a polyvalent metal is covalently or coordinately bonded to an organic compound. Examples of the polyvalent metal atom include Al, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Ba, Mo, La, Sn, and Ti. Among these, Al, Zr, and Ti are preferred. Examples of the organic compound include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds. The metal chelate crosslinking agent may typically be a compound in which an oxygen atom in the organic compound is bonded (covalently or coordinately bonded) to the polyvalent metal.

In some embodiments, peroxides may be used as crosslinking agents. Examples of peroxides include di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxyisobutyrate, and dibenzoyl peroxide. Among these, examples of peroxides that are particularly excellent in crosslinking reaction efficiency include di(4-t-butylcyclohexyl)peroxydicarbonate, dilauroyl peroxide, and dibenzoyl peroxide. When peroxides are used as the polymerization initiator, it is also possible to use the remaining peroxide that is not used in the polymerization reaction in the crosslinking reaction. In this case, the remaining amount of peroxide should be quantified, and if the ratio of peroxide is less than the specified amount, peroxide should be added as necessary to reach the specified amount. The amount of peroxide can be quantified by the method described in Japanese Patent No. 4971517.

The amount of crosslinking agent used (the total amount when two or more crosslinking agents are used) is not particularly limited, and can be appropriately set so as to obtain the desired effect of use. From the viewpoint of adhesion and bonding reliability with the adherend during wafer (typically semiconductor wafer) processing, the amount of crosslinking agent used per 100 parts by weight of base polymer (e.g. acrylic polymer) is usually about 15 parts by weight or less, preferably about 12 parts by weight or less, more preferably about 10 parts by weight or less, and may be less than 7.0 parts by weight, less than 5.0 parts by weight, less than 4.0 parts by weight, less than 3.0 parts by weight, less than 2.0 parts by weight, less than 1.0 parts by weight, or less than 0.5 parts by weight.
In addition, for example, in a pressure-sensitive adhesive sheet having an adhesive surface constituted by an active energy ray-curable pressure-sensitive adhesive layer, from the viewpoint of exhibiting a suitable cohesiveness before the curing treatment by active energy rays, the amount of the crosslinking agent used relative to 100 parts by weight of the base polymer (e.g., acrylic polymer) is usually about 0.005 parts by weight or more, preferably about 0.01 parts by weight or more, may be about 0.05 parts by weight or more, may be about 0.1 parts by weight or more, or may be about 0.2 parts by weight or more. In some embodiments, the amount of the crosslinking agent used relative to 100 parts by weight of the base polymer is preferably more than 0.3 parts by weight, more preferably more than 0.5 parts by weight, may be more than 1.0 parts by weight, may be more than 1.5 parts by weight, may be more than 2.0 parts by weight, may be more than 3.0 parts by weight, or may be more than 4.0 parts by weight. In a pressure-sensitive adhesive sheet that can be used in a form that is peeled off with water after curing treatment with active energy rays, if a larger amount of crosslinking agent is used, the distortion due to cure shrinkage is more likely to be maintained until the time when the aqueous stripping solution is supplied, and the effect of light peeling achieved by applying the water stripping method can be better achieved.

In an embodiment using an isocyanate-based crosslinking agent as a crosslinking agent, the amount of the isocyanate-based crosslinking agent used relative to 100 parts by weight of the base polymer is usually about 0.005 parts by weight or more from the viewpoint of exhibiting appropriate cohesiveness before curing treatment, and is preferably about 0.01 parts by weight or more, may be about 0.05 parts by weight or more, may be about 0.1 parts by weight or more, may be about 0.2 parts by weight or more, may be more than 0.3 parts by weight, may be more than 0.5 parts by weight, may be more than 1.0 parts by weight, may be more than 1.5 parts by weight, may be more than 2.0 parts by weight, may be more than 3.0 parts by weight, or may be more than 4.0 parts by weight. In a pressure-sensitive adhesive sheet that can be used in an embodiment that is peeled off with water after curing treatment with active energy rays, the effect of light peeling due to the application of the water peeling method can be better exhibited by increasing the amount of the isocyanate-based crosslinking agent used.
Furthermore, the amount of isocyanate-based crosslinking agent used per 100 parts by weight of base polymer is usually approximately 15 parts by weight or less, and from the viewpoint of adhesion to an adherend and bonding reliability during wafer (typically semiconductor wafer) processing, it is preferably approximately 12 parts by weight or less, and more preferably approximately 10 parts by weight or less, and may be less than 7.0 parts by weight, less than 5.0 parts by weight, less than 4.0 parts by weight, less than 3.0 parts by weight, less than 2.0 parts by weight, less than 1.0 part by weight, or less than 0.5 parts by weight.

A crosslinking catalyst may be used to promote the crosslinking reaction more effectively. Examples of crosslinking catalysts include metal-based crosslinking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, nursem ferric, butyltin oxide, and dioctyltin dilaurate. Among these, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferred. The amount of the crosslinking catalyst used is not particularly limited. The amount of the crosslinking catalyst used relative to 100 parts by weight of the base polymer may be, for example, approximately 0.0001 parts by weight or more and 1 part by weight or less, 0.001 parts by weight or more and 0.1 parts by weight or less, or 0.005 parts by weight or more and 0.5 parts by weight or less.

(Polyfunctional Monomer)
A polyfunctional monomer may be used in the adhesive layer as necessary. The polyfunctional monomer may be used in place of the crosslinking agent as described above or in combination with the crosslinking agent, and may be useful for purposes such as adjusting the cohesive strength. As the polyfunctional monomer, a compound having two or more carbon-carbon double bonds (for example, an ethylenically unsaturated group such as a (meth)acryloyl group) may be used. The polyfunctional monomer may be contained in the adhesive layer in an unreacted form, or may be contained in the adhesive layer in a reacted (crosslinked) form. The adhesive layer containing the unreacted polyfunctional monomer may be an active energy ray curable adhesive layer that can form a crosslinked structure by reacting the polyfunctional monomer by irradiating the adhesive layer with active energy rays such as ultraviolet rays.

Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl diol (meth)acrylate, hexyl diol di(meth)acrylate, and the like. Among these, trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate can be preferably used. The polyfunctional monomers can be used alone or in combination of two or more.

The appropriate amount of polyfunctional monomer used varies depending on the molecular weight, the number of functional groups, etc., but is usually in the range of about 0.01 to 3.0 parts by weight per 100 parts by weight of base polymer (e.g., acrylic polymer). In some embodiments, the amount of polyfunctional monomer used per 100 parts by weight of base polymer may be, for example, 0.02 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, 1.0 parts by weight or more, or 2.0 parts by weight or more. By increasing the amount of polyfunctional monomer used, there is a tendency to obtain higher cohesive force. On the other hand, from the viewpoint of avoiding a decrease in adhesion during wafer processing and a decrease in the storage stability of the adhesive sheet due to an excessive increase in cohesive force, the amount of polyfunctional monomer used per 100 parts by weight of base polymer may be, for example, 10 parts by weight or less, 5.0 parts by weight or less, or 3.0 parts by weight or less. Alternatively, the polyfunctional monomer may not be used. For example, a pressure-sensitive adhesive layer containing a polymer having a structure (such as a carbon-carbon double bond or a benzophenone structure) that induces a crosslinking reaction upon irradiation with active energy rays may be a pressure-sensitive adhesive layer that is substantially free of unreacted polyfunctional monomers, or may be a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition that is substantially free of polyfunctional monomers. Here, the pressure-sensitive adhesive composition being substantially free of polyfunctional monomers means that the amount of polyfunctional monomer per 100 parts by weight of the base polymer is less than 0.05 parts by weight (e.g., less than 0.01 parts by weight).

(Other optional ingredients)
The adhesive layer (which may be an active energy ray-curable adhesive layer) may contain, as necessary, various additives common in the field of adhesives, such as tackifier resins (e.g., rosin-based, petroleum-based, terpene-based, phenol-based, ketone-based, etc. tackifier resins), viscosity adjusters (e.g., thickeners), leveling agents, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, antioxidants, antiaging agents, etc., as other optional components. As for such various additives, conventionally known ones can be used in the usual manner, and they do not particularly characterize the present invention, so detailed explanations will be omitted.
From the viewpoint of achieving a good balance between adhesion to an adherend during wafer processing and releasability (e.g., releasability by water peeling) when removed from the adherend, in some embodiments, the content of the tackifier resin in the adhesive layer can be, for example, less than 5 parts by weight, or even less than 3 parts by weight, less than 1 part by weight, less than 0.5 parts by weight, or less than 0.1 parts by weight, relative to 100 parts by weight of the base polymer. The adhesive layer may be substantially free of tackifier resin (for example, the content of the adhesive layer relative to 100 parts by weight of the base polymer is 0 to 0.05 parts by weight). Limiting the content of the tackifier resin in this way can be advantageous, for example, from the viewpoint of improving the curability of the active energy ray-curable adhesive layer.

In some preferred embodiments, the adhesive layer may have a composition in which the content of the polymer (typically the base polymer) is approximately 80% by weight or more of the total weight of the adhesive layer. This can preferably achieve the effect of reducing the peeling force by applying water peeling (light peeling effect). From this perspective, the content of the polymer is preferably approximately 85% by weight or more of the total weight of the adhesive layer, more preferably approximately 90% by weight or more, and may be approximately 92% by weight or more, or may be approximately 95% by weight or more.

(Active energy ray-curable adhesive layer)
In some embodiments, the adhesive layer constituting the adhesive surface is preferably an adhesive layer (active energy ray curable adhesive layer) composed of an active energy ray curable adhesive. The adhesive sheet having such an adhesive layer can be particularly effectively reduced in peeling force from the adherend by irradiating active energy rays after pasting to the adherend to cure the active energy ray curable adhesive layer, and then supplying an aqueous release liquid such as water to the peeling front from the adherend to peel (water peeling). The reason for this is not particularly limited, but it is thought that when the active energy ray curable adhesive layer in the state of being pasted to the adherend is irradiated with active energy rays, the adhesive layer undergoes rapid curing shrinkage, causing microscopic lifting from the adherend, or distortion accumulates in the adhesive layer, and when an aqueous release liquid is supplied in this state, the infiltration of the aqueous release liquid into the interface between the adhesive layer and the adherend proceeds quickly, effectively reducing the peeling force. By peeling a pressure-sensitive adhesive sheet configured so that the adhesive layer hardens and the peel strength decreases when irradiated with active energy rays using a water peeling method after irradiation with active energy rays, a particularly remarkable effect of easy peeling can be achieved due to the synergistic effect of the decrease in peel strength due to the hardening of the adhesive layer and the decrease in water peel strength due to the sudden cure shrinkage described above.

In some embodiments, the active energy ray-curable adhesive layer is preferably configured such that, after application to an adherend, it is irradiated with active energy rays to cure, so that the peel strength from the adherend is reduced compared to before irradiation. An adhesive sheet having such an active energy ray-curable adhesive layer has good bonding reliability to an adherend before irradiation with active energy rays, and can significantly reduce the peel strength by peeling using an aqueous stripping solution after irradiation with active energy rays.

A suitable example of an active energy ray-curable adhesive layer is one that exhibits curability by containing a carbon-carbon double bond within the adhesive layer. Carbon-carbon double bonds are chemically stable and do not react with moisture or acidity in the air in normal industrially applicable storage environments. On the other hand, when active energy rays are irradiated to generate radicals, they react (for example, polymerization reaction or crosslinking reaction) and harden. From the viewpoint of ease of handling, light (for example, ultraviolet light) is a preferred active energy ray.

In a pressure-sensitive adhesive layer that exhibits curability by containing a carbon-carbon double bond, the form in which the carbon-carbon double bond is present in the pressure-sensitive adhesive layer is not particularly limited. The carbon-carbon double bond may be contained in the pressure-sensitive adhesive layer in the form of, for example, a polymer having a carbon-carbon double bond (e.g., a base polymer) or a monomer having a carbon-carbon double bond (e.g., an unreacted polyfunctional monomer as described above). These may be used alone or in combination of two or more.

The form of the carbon-carbon double bond contained in the polymer or the form of the carbon-carbon double bond contained in the monomer is not particularly limited. For example, the carbon-carbon double bond may be present in the polymer or monomer in the form of an ethylenically unsaturated group. Examples of the ethylenically unsaturated group include a (meth)acryloyl group, a vinyl group, an allyl group, and a methallyl group. From the viewpoint of reactivity, a (meth)acryloyl group is preferred.

(Polymers having carbon-carbon double bonds)
In some embodiments, the active energy ray-curable pressure-sensitive adhesive layer preferably contains a polymer having a carbon-carbon double bond. Hereinafter, the polymer having a carbon-carbon double bond is also referred to as "polymer (PD)". For example, a polymer (PD) having a carbon-carbon double bond in the form of an ethylenically unsaturated group is preferred. In some preferred embodiments, the polymer (PD) may be included in the active energy ray-curable pressure-sensitive adhesive layer as a base polymer of the pressure-sensitive adhesive layer. In some other embodiments, the polymer (PD) may be included in the active energy ray-curable pressure-sensitive adhesive layer as a subcomponent used in addition to a base polymer not containing a carbon-carbon double bond. The active energy ray-curable pressure-sensitive adhesive layer may contain the polymer (PD) as a base polymer and further contain a monomer having a carbon-carbon double bond (e.g., an unreacted multifunctional monomer) as a subcomponent.

The form of the carbon-carbon double bond in the polymer (PD) is not particularly limited. The polymer (PD) may be a polymer having a carbon-carbon double bond in a side chain, or may be a polymer having a carbon-carbon double bond in the main chain. Here, having a carbon-carbon double bond in the main chain includes the presence of a carbon-carbon double bond in the main chain skeleton of the polymer (PD) and the presence of a carbon-carbon double bond at the end of the main chain. From the viewpoint of the reactivity of the carbon-carbon double bond, a polymer (PD) having a carbon-carbon double bond in a side chain can be preferably used. The method for incorporating a carbon-carbon double bond in the polymer (PD) is not particularly limited, and an appropriate method can be selected from among methods known to those skilled in the art.

The polymer (PD) is not particularly limited, and an appropriate polymer can be selected and used taking into consideration the properties of the adhesive layer, etc. As the polymer (PD), a polymer (primary polymer) that does not contain carbon-carbon double bonds or has a lower carbon-carbon double bond content than the target substance, and in which carbon-carbon double bonds have been introduced by a method such as chemical modification (secondary polymer) can be preferably used.

A specific example of a method for introducing a carbon-carbon double bond into a primary polymer is to prepare a primary polymer in which a monomer having a functional group (functional group A) is copolymerized, and then react the primary polymer with a compound having a functional group (functional group B) capable of reacting with the functional group A and a carbon-carbon double bond in one molecule (hereinafter also referred to as an "unsaturated compound containing functional group B") in such a way that the carbon-carbon double bond does not disappear. The reaction between functional group A and functional group B is preferably a reaction that does not involve the generation of radicals, such as a condensation reaction or an addition reaction.

Examples of combinations of functional groups A and B include a combination of a carboxy group and an epoxy group, a combination of a carboxy group and an aziridyl group, and a combination of a hydroxyl group and an isocyanate group. Among these, a combination of a hydroxyl group and an isocyanate group is preferred from the viewpoint of reaction tracing. In addition, as for the combination of the functional groups A and B, as long as a polymer having a carbon-carbon double bond is obtained, one of the functional groups in the combination may be functional group A and the other may be functional group B, or one of the functional groups may be functional group B and the other may be functional group A. For example, in the case of a combination of a hydroxyl group and an isocyanate group, the functional group A may be a hydroxyl group (in which case, the functional group B is an isocyanate group), or may be an isocyanate group (in which case, the functional group B is a hydroxyl group). Among these, a combination in which the primary polymer has a hydroxyl group and the compound has an isocyanate group is preferred. This combination is particularly preferred when the primary polymer is an acrylic polymer.

In addition, a method of using a vinyl alcohol-based polymer (typically polyvinyl alcohol) as the primary polymer and reacting the vinyl alcohol-based polymer (typically a vinyl alcohol-based polymer not containing a carbon-carbon double bond) with a vinyl halide such as vinyl bromide or an allyl halide such as allyl bromide is also cited as a suitable example of a method for obtaining a polymer having a carbon-carbon double bond. In this method, the reaction is carried out under suitable basic conditions, and a vinyl alcohol-based polymer containing a vinyl group in the side chain is obtained by the reaction. In addition, a method of preparing a polymer having a carbon-carbon double bond using a microorganism that produces a polymer as disclosed in Japanese Patent No. 4502363 may be adopted. The various conditions in this method, such as the microbial species and microbial culture conditions, may be set by adopting the conditions described in the above patent publication, or by appropriately modifying them within the scope of the technical common sense of a person skilled in the art.

The molar ratio ( _MA / _MB ) of the moles of the functional group A ( _MA ) to the moles of the functional group B (MB) is usually 0.2 or more in view of the reactivity of both, and may be 0.5 or more, 0.7 or more, or 1.0 or more. In some embodiments, the molar ratio ( _MA / _MB ) may be more than 1.0, more than 1.5, or more than 2.0. For example, when the functional group A is used in another reaction ( _such as a crosslinking reaction with a crosslinking agent), it is preferable that the molar ratio ( _MA / _MB ) is more than 1.0. In addition, the molar ratio ( _MA / _MB ) may be, for example, 20 or less. In some embodiments, from the viewpoint of achieving a good balance between adhesion to an adherend before light irradiation and releasability from the adherend after light irradiation (e.g., releasability by water stripping), the molar ratio (M _A /M _B ) is preferably 10 or less, or may be 5.0 or less, 2.5 or less, 1.8 or less, or 1.5 or less.

_The amount of the compound having a functional group B and a carbon-carbon double bond (hereinafter also referred to as "functional group _B -containing unsaturated compound") used can be, for example, 1.0 part by weight or more, 3.0 parts by weight or more, 5.0 parts by weight or more, or 7.0 parts by weight or more, relative to 100 parts by weight of the primary polymer having a functional group A, within the range satisfying the above-mentioned molar ratio (M A /M B ). From the viewpoint of achieving a higher level of both adhesion before light irradiation and releasability after light irradiation (for example, releasability by water stripping), in some embodiments, the amount of the functional group B-containing unsaturated compound used relative to 100 parts by weight of the primary polymer is preferably 9.0 parts by weight or more, more preferably 10 parts by weight or more, may be 12 parts by weight or more, may be 14 parts by weight or more, or may be 16 parts by weight or more. The amount of the functional group B-containing unsaturated compound used relative to 100 parts by weight of the primary polymer can be, for example, less than 40 parts by weight, and is usually suitably less than 35 parts by weight, preferably less than 30 parts by weight, may be less than 25 parts by weight, or may be less than 20 parts by weight. In some embodiments, the amount of the functional group B-containing unsaturated compound used relative to 100 parts by weight of the primary polymer can be less than 18 parts by weight, less than 16 parts by weight, less than 13 parts by weight, less than 10 parts by weight, or less than 7 parts by weight.

One suitable example of a polymer having a carbon-carbon double bond is an acrylic polymer with a (meth)acryloyl group introduced into the side chain. Such an acrylic polymer can be obtained, for example, by reacting an acrylic primary polymer with a hydroxyl group (functional group A) introduced by copolymerization with a compound having a carbon-carbon double bond and an isocyanate group (functional group B) in such a way that the carbon-carbon double bond is not lost.

The polymer having a carbon-carbon double bond may be, for example, a diene-based polymer (typically a conjugated diene-based polymer). A diene-based polymer (typically a conjugated diene-based polymer) is typically a polymer obtained by polymerizing or copolymerizing a diene (typically a conjugated diene). Examples of diene-based polymers (typically conjugated diene-based polymers) include butadiene-based polymers such as polybutadiene and styrene-butadiene copolymers; isoprene-based polymers such as polyisoprene and styrene-isoprene copolymers; chloroprene-based polymers such as polychloroprene; and the like.

Another example of an active energy ray-curable adhesive layer is an adhesive layer containing a polymer having a structure that induces a crosslinking reaction upon irradiation with active energy rays and has a structure other than a carbon-carbon double bond. For example, an adhesive containing a polymer having a benzophenone structure in the side chain can exhibit active energy ray curability by photocrosslinking using the benzophenone structure. As a polymer having a benzophenone structure in the side chain, an acrylic polymer having a benzophenone structure in the side chain can be preferably used.

(Photoinitiator)
When ultraviolet rays are used as the active energy rays for curing the active energy ray-curable pressure-sensitive adhesive layer, it is preferable for the pressure-sensitive adhesive layer to contain a photoinitiator from the viewpoint of promoting the reaction or improving the efficiency of using light energy.
Examples of the photoinitiator include benzoin ether-based photoinitiators, acetophenone-based photoinitiators, α-hydroxyketone-based photoinitiators, aromatic sulfonyl chloride-based photoinitiators, photoactive oxime-based photoinitiators, benzoin-based photoinitiators, benzyl-based photoinitiators, benzophenone-based photoinitiators, ketal-based photoinitiators, thioxanthone-based photoinitiators, α-aminoketone-based photoinitiators, acylphosphine oxide-based photoinitiators, etc. The photoinitiators can be used alone or in combination of two or more.

Examples of benzoin ether photoinitiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, and anisole methyl ether. Examples of acetophenone photoinitiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxy-cyclohexyl-phenyl ketone, 4-phenoxydichloroacetophenone, and 4-t-butyl-dichloroacetophenone. Examples of α-hydroxyketone photoinitiators include 2-hydroxy-2-methyl-1-phenyl-propan-1-one and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one. Examples of aromatic sulfonyl chloride photoinitiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime photoinitiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of benzoin photoinitiators include benzoin. Examples of benzyl photoinitiators include benzyl. Examples of benzophenone photoinitiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinyl benzophenone, α-hydroxycyclohexyl phenyl ketone. Examples of ketal photoinitiators include benzyl dimethyl ketal. Examples of thioxanthone photoinitiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, etc. Examples of α-aminoketone photoinitiators include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, etc. Examples of acylphosphine oxide photoinitiators include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc.

As the photoinitiator, a commercially available product may be used. For example, products sold by IGM Regins under the trade names "Omnirad 651", "Omnirad 184", "Omnirad 2959", "Omnirad 907", "Omnirad 369", "Omnirad 1173", "Omnirad TPO", etc. may be mentioned.

In some embodiments, a photoinitiator that is difficult to decompose or generate radicals by heating may be used as the photoinitiator. For example, a heat-resistant photoinitiator having a 10% weight reduction temperature of 200°C or higher may be used as the photoinitiator. By using such a heat-resistant photoinitiator, even if it is exposed to high temperatures before the curing process, the effect of reducing the peeling force due to the curing process using active energy rays can be less likely to be lost. The 10% weight reduction temperature means the environmental temperature at which the weight of the photoinitiator is reduced by 10% by weight compared to the weight before the temperature increase (i.e., the weight of the photoinitiator is 90% by weight compared to the weight before the temperature increase) when the photoinitiator is placed under a nitrogen atmosphere and the environmental temperature is increased from 23°C to 300°C at a heating rate of 2°C/min. The 10% weight reduction temperature of the photoinitiator is more preferably 210°C or higher, and even more preferably 220°C or higher. Examples of photoinitiators with a 10% weight loss temperature in this range include IGM Regins' product names "Omnirad 369", "Omnirad 127", "Omnirad 379", and "Omnirad 819"; BASF Japan's product name "Irgacure OXE02"; Lamberti's product names "Esacure One" and "Esacure 1001m"; and Asahi Denka Kogyo's product names "Adeka Optomer N-1414", "Adeka Optomer N-1606", and "Adeka Optomer N-1717".

The adhesive layer containing a photoinitiator can be formed using an adhesive composition containing the photoinitiator. The method of adding the photoinitiator to the adhesive composition is not particularly limited. For example, it is preferable to add and mix the photoinitiator into the adhesive composition, typically a liquid containing a polymer (polymer in which polymerization has been completed). In this method, the photoinitiator can be added to the composition together with other additive components (e.g., a crosslinking agent, etc.). Another method is to add a polymerization initiator that can function as a photoinitiator during polymer polymerization. In this method, the polymerization initiator is added so that a predetermined amount remains after polymerization. The remaining amount of polymerization initiator (amount of photoinitiator present) can be adjusted not only by the amount of polymerization initiator added, but also by the polymer polymerization conditions, drying conditions and curing conditions when forming the adhesive layer, etc.

When the adhesive layer contains a photoinitiator, the content of the photoinitiator in the adhesive layer is not particularly limited and can be set so that the desired effect is appropriately exhibited. In some embodiments, the content of the photoinitiator may be, for example, about 0.05 parts by weight or more, preferably about 0.1 parts by weight or more, and more preferably about 0.5 parts by weight or more, relative to 100 parts by weight of the base polymer of the adhesive layer. The increase in the content of the photoinitiator improves the active energy ray curability of the adhesive layer. In some embodiments, the content of the photoinitiator relative to 100 parts by weight of the base polymer may be, for example, about 1.0 parts by weight or more, may be about 2.0 parts by weight or more, or may be about 2.5 parts by weight or more. In addition, the content of the photoinitiator relative to 100 parts by weight of the base polymer can be, for example, about 20 parts by weight or less, and is usually appropriate to be about 10 parts by weight or less, and is preferably about 8 parts by weight or less, may be about 6 parts by weight or less, or may be about 4 parts by weight or less. It is preferable that the photoinitiator content is not too high from the viewpoint of the storage stability of the adhesive layer adhesive sheet (e.g., the ability to suppress performance changes due to storage of the adhesive sheet before use).

<Formation of Pressure-Sensitive Adhesive Layer>
The adhesive layer (e.g., active energy ray curable adhesive layer) of the adhesive sheet disclosed herein may be an adhesive layer formed from an adhesive composition containing a base polymer (e.g., an acrylic polymer) and, if necessary, other optional components. The adhesive composition may be in various forms, such as a solvent-based adhesive composition containing an adhesive (adhesive component) in an organic solvent, an active energy ray curable adhesive composition prepared to be cured by active energy rays such as ultraviolet rays or radiation to form an adhesive, a water-dispersed adhesive composition in which an adhesive is dispersed in water, or a hot melt adhesive composition that is applied in a heated and molten state and forms an adhesive when cooled to around room temperature. The active energy curable adhesive composition is typically a liquid composition that exhibits a degree of fluidity that allows application at room temperature (approximately 0°C to 40°C, for example, about 25°C) and is cured by irradiation with active energy to form an adhesive (viscoelastic body).
The pressure-sensitive adhesive sheet according to some embodiments may have a pressure-sensitive adhesive layer formed using a solvent-based pressure-sensitive adhesive composition or an active energy ray-curable pressure-sensitive adhesive composition. As the pressure-sensitive adhesive composition for forming the active energy ray-curable pressure-sensitive adhesive layer, a solvent-based pressure-sensitive adhesive composition may be preferably used from the viewpoint of ease of controlling the active energy ray curability.

The adhesive layer of the adhesive sheet disclosed herein can be formed by applying (e.g., coating) an adhesive composition to a suitable surface, followed by an appropriate curing treatment (drying, crosslinking, polymerization, etc.). When two or more types of curing treatments are performed, these can be performed simultaneously or in multiple stages. An adhesive layer having a multi-layer structure of two or more layers can be produced by laminating adhesive layers that have been previously formed. Alternatively, an adhesive composition can be applied onto a first adhesive layer that has been previously formed, and the adhesive composition can be cured to form a second adhesive layer.

The adhesive composition can be applied using a conventional coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, or spray coater. In an adhesive sheet having a support, the adhesive layer can be provided on the support by a direct method in which the adhesive composition is directly applied to the support to form an adhesive layer, or by a transfer method in which the adhesive layer formed on the release surface is transferred to the support.

In the adhesive sheet disclosed herein, the thickness of the adhesive layer is not particularly limited and can be appropriately selected depending on the purpose. Usually, the thickness of the adhesive layer is about 5 to 200 μm, and from the viewpoint of adhesion, etc., it is preferably about 10 μm or more (e.g., 15 μm or more), may be 25 μm or more, and is preferably 150 μm or less, more preferably 100 μm or less, and even more preferably about 80 μm or less (e.g., 60 μm or less, typically 40 μm or less), and may be 35 μm or less or less than 30 μm. When the adhesive sheet disclosed herein is a double-sided adhesive sheet having adhesive layers on both sides of a substrate, the thicknesses of the adhesive layers may be the same or different.

<Additional Adhesive Layer>
In some embodiments of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet may have a configuration in which an additional pressure-sensitive adhesive layer is laminated on the back side (opposite side to the pressure-sensitive adhesive layer) of the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface. The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface and the additional pressure-sensitive adhesive layer are preferably laminated in direct contact with each other. That is, it is preferable that a separator layer (e.g., a resin film such as a polyester film) that completely separates both pressure-sensitive adhesive layers is not interposed between the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface and the additional pressure-sensitive adhesive layer. The additional pressure-sensitive adhesive layer may be a pressure-sensitive adhesive layer that includes one or more types of pressure-sensitive adhesive selected from various known pressure-sensitive adhesives such as, for example, acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives (natural rubber-based, synthetic rubber-based, mixed systems thereof, etc.), silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, urethane pressure-sensitive adhesives, polyether pressure-sensitive adhesives, polyamide pressure-sensitive adhesives, and fluorine pressure-sensitive adhesives. In some embodiments, an acrylic pressure-sensitive adhesive may be preferably used as a constituent material of the additional pressure-sensitive adhesive layer from the viewpoint of transparency, weather resistance, etc. As for other details of the additional adhesive layer, the same configuration as that of the adhesive layer described above can be adopted, or an appropriate configuration can be adopted depending on the application and purpose based on publicly known or commonly used technologies and technical common sense, so detailed explanations are omitted here.

<Substrate>
In a single-sided or double-sided adhesive substrate-attached adhesive sheet, the substrate supporting (backing) the adhesive layer can be, for example, a resin film, paper, cloth, rubber sheet, foam sheet, metal foil, or a composite of these. The substrate can be a single layer or a laminate of the same or different substrates. In this specification, a single layer refers to a layer of the same composition, and includes a form in which multiple layers of the same composition are laminated.

In a preferred embodiment, a substrate (resin film substrate) having a resin sheet as a main component may be used. Examples of resins constituting the substrate include polyolefin resins such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, very low-density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolypropylene, polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester (random, alternating) copolymer, ethylene-butene copolymer, and ethylene-hexene copolymer; polyurethane; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonate; polyimide; polyether ether ketone; polyetherimide; polyamides such as aramid and fully aromatic polyamide; polyphenyl sulfide; fluororesin; polyvinyl chloride; polyvinylidene chloride; cellulose resin; silicone resin; and the like. The above resins can be used alone or in combination to form the whole or part of the substrate (for example, any layer in a substrate having a laminated structure of two or more layers). When the adhesive layer constituting the adhesive surface is an active energy ray curable adhesive layer, the substrate preferably has active energy ray transparency. In some embodiments, a substrate having an ultraviolet ray transmittance of 40% to 100% (more preferably 60% to 100%) at a wavelength of 365 nm can be preferably used. When a substrate with high transparency is used, the adhesive layer can be easily cured.

The base material may contain various additives such as fillers (inorganic fillers, organic fillers, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, colorants (pigments, dyes, etc.), etc., as necessary.

The substrate can be manufactured by any suitable method. For example, it can be manufactured by known methods such as a calendar method, a casting method, an inflation extrusion method, or a T-die extrusion method. If necessary, it may be manufactured by carrying out a stretching process.

The surface of the substrate facing the adhesive layer may be subjected to known or conventional surface treatments, such as physical treatments such as corona discharge treatment, plasma treatment, sand mat processing treatment, ozone exposure treatment, flame exposure treatment, high-voltage shock exposure treatment, and ionizing radiation treatment; chemical treatments such as acid treatment, alkali treatment, and chromate treatment; and adhesion-improving treatments using a coating agent (primer). In addition, a conductive vapor deposition layer containing a metal, alloy, or oxide thereof may be provided on the substrate surface for the purpose of imparting antistatic properties.

In some preferred embodiments, an undercoat layer is provided on the adhesive layer side surface of the substrate. In other words, an undercoat layer may be disposed between the substrate and the adhesive layer. The undercoat layer forming material is not particularly limited, and one or more of urethane (polyisocyanate) resins, polyester resins, acrylic resins, polyamide resins, melamine resins, olefin resins, polystyrene resins, epoxy resins, phenol resins, isocyanurate resins, polyvinyl acetate resins, etc. may be used. When an acrylic adhesive layer is provided on a resin film substrate via an undercoat layer, a polyester, urethane, or acrylic undercoat layer is preferred. When an acrylic adhesive layer is provided on a polyester substrate such as a PET film via an undercoat layer, a polyester undercoat layer is particularly preferred. The thickness of the undercoat layer is not particularly limited, and may usually be in the range of about 0.1 μm to 10 μm (for example, 0.1 μm to 3 μm, typically 0.1 μm to 1 μm). The undercoat layer can be formed using a known or conventional coater such as a gravure roll coater or a reverse roll coater.

When the adhesive sheet disclosed herein is a one-sided adhesive sheet in which an adhesive layer is provided on one side of a substrate, the surface of the substrate on which the adhesive layer is not formed (back surface) may be subjected to a release treatment using a release treatment agent (back surface treatment agent). There are no particular limitations on the back surface treatment agent that can be used to form the back surface treatment layer, and silicone-based back surface treatment agents, fluorine-based back surface treatment agents, long-chain alkyl-based back surface treatment agents, and other known or commonly used treatment agents can be used depending on the purpose and application.

The thickness of the substrate is not particularly limited and can be appropriately selected depending on the purpose, but generally can be about 3 μm to 800 μm. From the viewpoint of the processability and handling of the pressure-sensitive adhesive sheet (for example, the workability when attaching to the adherend and peeling off), the thickness of the substrate is suitably 5 μm or more, and suitably 10 μm or more, and from the viewpoint of enhancing the protection of the adherend in wafer processing, the thickness is preferably 20 μm or more, may be 30 μm or more, or may be 40 μm or more. In some embodiments where protection is more important, the thickness of the substrate can be, for example, 55 μm or more, 75 μm or more, or 90 μm or more. Also, from the viewpoint of reducing the load on the adherend when peeling off from the adherend, the thickness of the substrate is usually suitably 300 μm or less, preferably 200 μm or less, may be 150 μm or less, may be 125 μm or less, may be 80 μm or less, or may be 60 μm or less.

The total thickness of the adhesive sheet disclosed herein (which may include an adhesive layer and a substrate, but does not include a release liner) is not particularly limited, and is suitably in the range of approximately 10 μm to 1000 μm. In consideration of adhesion and ease of handling, the total thickness of the adhesive sheet is preferably in the range of approximately 15 μm to 300 μm, and more preferably in the range of approximately 20 μm to 200 μm. In addition, from the viewpoint of enhancing the protection of the adherend during wafer processing, the total thickness of the adhesive sheet is advantageously approximately 30 μm or more, preferably approximately 40 μm or more, and more preferably approximately 50 μm or more (for example, 60 μm or more). In some embodiments in which greater importance is placed on protection, the total thickness of the adhesive sheet may be greater than 65 μm, greater than 80 μm, or greater than 100 μm.

<Applications>
The adhesive sheet disclosed herein can be used in the processing of various wafers. For example, the adhesive sheet disclosed herein can be used in the processing of various semiconductor wafers. The semiconductor wafer can be, for example, a silicon wafer, a silicon carbide (SiC) wafer, a nitride semiconductor wafer (silicon nitride (SiN), gallium nitride (GaN), etc.), a compound semiconductor wafer such as a gallium arsenide wafer, etc. The adhesive sheet disclosed herein can be preferably used as a wafer processing adhesive sheet for protecting and/or fixing the semiconductor wafer during processing of the semiconductor wafer, typically in a form that is laminated to the semiconductor wafer on which a circuit is formed by a previous process, during the process of manufacturing a semiconductor element (e.g., a semiconductor chip) from such a semiconductor wafer. After laminating the adhesive sheet disclosed herein, examples of processing that can be performed on the semiconductor wafer before peeling off the adhesive sheet include, but are not limited to, back grinding and dicing. In addition, the adhesive sheet disclosed herein can also be used in the processing of non-semiconductor wafers such as glass and resin. In this specification, even if the shape of the wafer to be processed (typically a semiconductor wafer) is changed by processing (for example, thinning in whole or in part by back-grinding, or dividing into individual pieces by dicing), the processed item may still be referred to as a wafer (typically a semiconductor wafer).

The adhesive sheet disclosed herein may be bonded to a wafer (typically a semiconductor wafer) by any suitable method. The temperature at which the adhesive sheet is bonded may be around room temperature (e.g., 10°C to 35°C) or may be a temperature higher than the room temperature range (e.g., above 35°C, preferably 60°C to 90°C). Bonding the adhesive sheet at a temperature higher than the room temperature range may be advantageous in terms of improving the adhesion of the adhesive sheet to the wafer. After bonding the adhesive sheet at room temperature, a heating and pressurizing treatment may be performed in which a temperature higher than the room temperature range (e.g., 40°C to 90°C, preferably 40°C to 60°C) and a pressure higher than atmospheric pressure (e.g., 1.5 to 10 atm, preferably 3 to 7 atm) are applied. The time for the heating and pressurizing treatment is not particularly limited and can be set so as to obtain an appropriate treatment effect. In some embodiments, the time for the heating and pressurizing treatment may be set to 3 minutes to 1 hour (e.g., 5 minutes to 30 minutes) in consideration of the balance between the stability of the treatment effect and productivity.

When the adhesive layer constituting the adhesive surface of the adhesive sheet disclosed herein is an active energy ray curable adhesive layer, the adhesive sheet can be preferably used in an embodiment in which the adhesive sheet is laminated to an adherend, and then irradiated with active energy rays and peeled off with water. The irradiation conditions of the active energy rays are not particularly limited, and can be set so as to allow the curing of the active energy ray curable adhesive layer to proceed appropriately. Since a person skilled in the art can set appropriate irradiation conditions without excessive burden based on the technical common sense in the field, detailed explanations are omitted. As an example, when ultraviolet rays are used as the active energy rays, the irradiation conditions of the ultraviolet rays can be, for example, an irradiation cumulative light amount in the range of 50 mJ/cm ² to 5000 mJ/cm ² , in the range of about 50 mJ/cm ² to 2000 mJ/cm ² , or in the range of about 100 mJ/cm ² to 2000 mJ/cm ² , and the irradiation time can be in the range of about 1 second to 30 minutes.

<Method for manufacturing semiconductor device>
An embodiment of a method for manufacturing a semiconductor device using the above-mentioned adhesive sheet for wafer processing is described below. The method for manufacturing a semiconductor device of this embodiment includes a step (1) of attaching the adhesive surface of the adhesive sheet for wafer processing to the circuit formation surface side of a semiconductor wafer having a circuit formation surface, a step (2) of processing the semiconductor wafer with the adhesive sheet attached from the opposite side of the adhesive sheet, and a step (3) of peeling the adhesive sheet from the semiconductor wafer after the processing.

Here, the above step (3) is preferably carried out by supplying an aqueous stripping liquid to the front of the peeling of the above adhesive sheet from the processed semiconductor wafer (adherend). This allows the adhesive sheet to be peeled lightly, and the load on the adherend (processed semiconductor wafer) during peeling can be reduced. Therefore, the above adhesive sheet can be peeled efficiently while avoiding damage to the adherend. In some embodiments, the above step (3) can be preferably carried out by the adhesive sheet peeling method described below.

In addition, as the aqueous stripping solution in the technology disclosed in this specification (including the adhesive sheet for wafer processing, the adhesive composition, the semiconductor device manufacturing method, the adhesive sheet peeling method, etc.), water or a mixed solvent mainly composed of water, containing a small amount of additives as necessary, can be used. As the solvent other than water constituting the mixed solvent, lower alcohols (e.g., ethyl alcohol) and lower ketones (e.g., acetone) that can be mixed uniformly with water can be used. As the additives, known surfactants, pH adjusters, etc. can be used. From the viewpoint of avoiding contamination of the adherend, in some embodiments, an aqueous stripping solution that does not substantially contain additives can be preferably used. From the viewpoint of environmental hygiene, it is particularly preferable to use water as the aqueous stripping solution. There are no particular limitations on the water, and in consideration of the purity required depending on the application and ease of availability, for example, distilled water, ion-exchanged water, tap water, etc. can be used.

When the adhesive layer constituting the adhesive surface is an active energy ray-curable adhesive layer, a treatment is performed to cure the active energy ray-curable adhesive layer by irradiating it with active energy rays before peeling off the adhesive sheet. Typically, the above curing treatment reduces the peeling force of the adhesive sheet. By peeling off the adhesive sheet with water after such a curing treatment, the load on the adherend (processed semiconductor wafer) during peeling can be more effectively reduced. From the viewpoint of achieving both adhesion reliability to the adherend in step (2) and easy peelability in step (3), it is preferable to perform the above curing treatment after step (2).

In some embodiments, the above step (2) may be a backgrinding step. In this case, the adhesive sheet for wafer processing is used as a backgrinding tape. The backgrinding step may be performed by any suitable method. The backgrinding step may be a step of thinning the semiconductor wafer to which the adhesive sheet is attached until the thickness of the semiconductor wafer is, for example, 150 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. In such a thinning mode, the effect of applying the technology disclosed herein may be preferably exhibited. The backgrinding step may be performed so that the inside of the annular convex portion becomes a concave portion (i.e., so that a TAIKO (registered trademark) wafer is obtained). In this case, the thickness of the thinned semiconductor wafer refers to the thickness of the concave portion. In addition, although not particularly limited, the thickness of the semiconductor wafer before backgrinding may be, for example, about 500 μm to 1000 μm.

The semiconductor device manufacturing method disclosed herein may further include any appropriate step. Examples of such optional steps include, but are not limited to, an etching step, a photolithography step, an ion implantation step, a dicing step, a die bonding step, a wire bonding step, a packaging step, and the like. Each of the steps exemplified above may be performed in the step (2), after the step (2), before the step (3), or after the step (3).

<How to remove the adhesive sheet>
According to this specification, a method for peeling a pressure-sensitive adhesive sheet attached to an adherend is provided, which peels the pressure-sensitive adhesive sheet from the adherend. The method may include a water peeling step of peeling the pressure-sensitive adhesive sheet from the adherend while advancing the intrusion of the aqueous peeling solution into the interface in accordance with the movement of the peeling front, in a state where an aqueous peeling solution is present at the interface between the adherend and the pressure-sensitive adhesive sheet at the peeling front of the pressure-sensitive adhesive sheet from the adherend. Here, the peeling front refers to the location where the adhesive surface of the pressure-sensitive adhesive sheet begins to separate from the adherend when the peeling of the pressure-sensitive adhesive sheet from the adherend progresses. According to the water peeling step, the aqueous peeling solution can be effectively used to peel the pressure-sensitive adhesive sheet from the adherend. The peeling method may be preferably carried out, for example, in an embodiment in which any of the pressure-sensitive adhesive sheets disclosed herein are peeled from the adherend.

The adherend in the peeling method disclosed herein may be any of the various semiconductor wafers exemplified above. The semiconductor wafer may be a semiconductor wafer on which a circuit is formed. The peeling method disclosed herein may be preferably used as a method for peeling an adhesive sheet attached to a circuit-forming surface of a semiconductor wafer on which a circuit is formed, from the circuit-forming surface.

The adhesive sheet to be peeled off from the adherend by the above peeling method includes an adhesive layer that constitutes an adhesive surface, and the adhesive layer is composed of an adhesive. As the adhesive sheet, any of the adhesive sheets disclosed herein can be preferably used. Therefore, the above peeling method is suitable as a peeling method for any of the adhesive sheets disclosed herein.

In some embodiments, the peeling method may be preferably carried out in an embodiment including forming an initial peeling front by forcibly lifting the adhesive sheet from the adherend at one end of the outer edge of the adhesive sheet attached to the adherend, supplying an aqueous peeling liquid to the peeling front, and peeling the adhesive sheet from the adherend while advancing the infiltration of the aqueous peeling liquid into the interface between the adhesive sheet and the adherend in accordance with the movement of the peeling front. The initial peeling front may be formed, for example, by inserting the tip of a tool such as a cutter knife or needle into the interface between the adhesive sheet and the adherend, scratching and lifting the adhesive sheet with a hook or claw, or attaching a highly adhesive adhesive tape or suction cup to the back surface of the adhesive sheet to lift the edge of the adhesive sheet. By forming an initial peeling front in this way and then supplying an aqueous peeling liquid to the peeling front to start water peeling, the aqueous peeling liquid can be efficiently supplied to the peeling front. Furthermore, this peeling method and the pressure-sensitive adhesive sheet used in this peeling method can advantageously achieve both good water peelability after an operation to forcibly form an initial peel front is performed to trigger peeling, and high water resistance reliability when such an operation is not performed.

In some embodiments, the above peeling method can be preferably carried out in such a manner that after the aqueous stripping liquid is supplied to the initial peeling front (i.e., after the aqueous stripping liquid is supplied at the start of the aqueous stripping), the peeling of the adhesive sheet is progressed without supplying new aqueous stripping liquid. Alternatively, if the aqueous stripping liquid that is to enter the interface between the adhesive sheet and the adherend in accordance with the movement of the peeling front becomes depleted or insufficient during the progress of the aqueous stripping, additional aqueous stripping liquid may be intermittently or continuously supplied after the start of the aqueous stripping. For example, in cases where the length of the peeling front increases with the progress of the peeling (for example, when the aqueous stripping is progressed from one end of the outer edge of the disc-shaped adherend in the radial direction of the circle) or when the aqueous stripping liquid is likely to remain on the adherend surface, an embodiment in which additional aqueous stripping liquid is supplied after the start of the aqueous stripping can be preferably adopted. In addition, the position where the aqueous stripping liquid is supplied may be one or more positions. When additional aqueous stripping liquid is supplied after the start of the aqueous stripping, the number of positions where the aqueous stripping liquid is supplied after the start of the aqueous stripping may be increased or decreased.

Several examples of the present invention are described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

<Measurement of stick-slip degree>
1. Measurement of unirradiated normal peel stick-slip degree SSd0 A test piece is prepared by cutting a non-UV-irradiated pressure-sensitive adhesive sheet to be measured into a strip of 10 mm width. In an environment of 23°C and 50% RH, the adhesive surface of the test piece is attached with a hand roller to the mirror surface of a 6-inch silicon wafer (manufactured by Shin-Etsu Chemical Co., Ltd., 6-inch N<100>-100) as an adherend, and left at room temperature for 30 minutes to prepare a sample for evaluation.
Thereafter, in an environment of 23°C and 50% RH, a cutter knife is inserted into the interface between the test piece of the evaluation sample and the adherend to peel one end of the test piece in the longitudinal direction from the adherend, and according to "10.4.1 Method 1: 180° peel adhesion to test plate" of JIS Z0237:2009, specifically, at a test temperature of 23°C, a tensile tester (apparatus name "tensile compression tester, VPA-3" manufactured by Kyowa Interface Science Co., Ltd.) is used to peel the sample at a peel speed of 300 mm/min and a peel angle of 180° until the peel distance reaches 100 mm, and peel force data is obtained every 0.25 mm of the peel distance. Among the obtained peel forces, the data on the peel force at peel distances of 30 to 70 mm is used to calculate the stick-slip degree of the adhesive sheet. The stick-slip degree is measured three times, and the average value is taken as the unirradiated normal peel stick-slip degree SSd0 [10 ^-3 N/10 mm]. The stick-slip degree is measured by causing the test piece attached to the adherend to peel from bottom to top.

2. Measurement of stick-slip degree SSw0 after unirradiated water peeling For the above-mentioned evaluation sample unirradiated with UV, 20 μL of distilled water is supplied to the location (peeling interface) where the test piece starts to separate from the adherend during peeling from the adherend, and the stick-slip degree after the distilled water supply is measured. The stick-slip degree is measured three times, and the average value is taken as the stick-slip degree SSw0 after unirradiated water peeling [10 ⁻³ N/10 mm].

3. Measurement of post-irradiation normal peel stick-slip degree SSd1 An unirradiated evaluation sample prepared in the same manner as in the measurement of the unirradiated normal peel stick-slip degree SSd0 above was irradiated with ultraviolet light from the substrate side of the pressure-sensitive adhesive sheet (the side opposite the adhesive surface to be measured; hereinafter also referred to as the "back side") under the following conditions in an environment of 23°C and 50% RH, using a UV irradiator manufactured by Nitto Seiki Co., Ltd., product name "NEL SYSTEM UM810" (high-pressure mercury lamp light source) at an illuminance of 60 mW/ ^cm2 and an accumulated light quantity of 500 mJ/ ^cm2 .
Thereafter, in an environment of 23°C and 50% RH, a cutter knife is inserted into the interface between the test piece of the evaluation sample after UV irradiation and the adherend to peel one end of the test piece in the longitudinal direction from the adherend, and the stick-slip degree is measured in the same manner as in the measurement of the unirradiated normal peel stick-slip degree SSd0. The measurement is carried out three times, and the average value thereof is taken as the post-irradiation normal peel stick-slip degree SSd1 [10 ^-3 N/10 mm].

4. Measurement of post-irradiation water peeling stick-slip degree SSw1 In the same manner as the measurement of the post-irradiation normal peeling stick-slip degree SSd1, a sample for evaluation after UV irradiation is prepared. In the above-mentioned evaluation sample after UV irradiation, 20 μL of distilled water is supplied to the location (peeling interface) where the test piece starts to separate from the adherend during the process of peeling the test piece from the adherend, and the stick-slip degree after the distilled water supply is measured. The stick-slip degree is measured three times, and the average value is taken as the post-irradiation water peeling stick-slip degree SSw1 [10 ⁻³ N/10 mm].

<Measurement of peeling force>
1. Measurement of unirradiated normal peel strength Fd0 The unirradiated pressure-sensitive adhesive sheet to be measured is cut into a strip of 10 mm width to prepare a test piece. In an environment of 23°C and 50% RH, the adhesive surface of the test piece is attached to the mirror surface of a 6-inch silicon wafer (manufactured by Shin-Etsu Chemical Co., Ltd., 6-inch N<100>-100) as an adherend using a hand roller, and left at room temperature for 30 minutes to prepare a sample for evaluation.
Thereafter, in an environment of 23°C and 50% RH, a cutter knife is inserted into the interface between the test piece of the evaluation sample and the adherend to peel one end of the test piece in the longitudinal direction from the adherend, and the peel force is measured according to "10.4.1 Method 1: 180° peel adhesion to test plate" of JIS Z0237:2009, specifically, at a test temperature of 23°C using a tensile tester (device name "DT9503-1000N" manufactured by Tansui Co., Ltd.) at a peel speed of 300 mm/min and a peel angle of 180°. The measurement is performed three times, and the average value is taken as the unirradiated normal peel force Fd0 [N/10 mm]. The peel force is measured so that the peel of the test piece attached to the adherend proceeds from bottom to top.

2. Measurement of unirradiated water peeling force Fw0 In the above unirradiated evaluation sample, 20 μL of distilled water is supplied to the location (peeling interface) where the test piece starts to separate from the adherend during peeling from the adherend, and the peeling force after the distilled water supply is measured. The peeling force is measured three times, and the average value is taken as the unirradiated water peeling force Fw0 [N/10 mm].

3. Measurement of post-irradiation normal peel strength Fd1 A UV-unirradiated evaluation sample prepared in the same manner as in the measurement of the unirradiated normal peel strength Fd0 was irradiated with UV light from the substrate side of the adhesive sheet (the side opposite the adhesive surface to be measured; hereinafter also referred to as the "back side") under an environment of 23°C and 50% RH using a UV irradiator manufactured by Nitto Seiki Co., Ltd., product name "NEL SYSTEM UM810" (high pressure mercury lamp light source), under conditions of illuminance of 60 mW/ ^cm2 and cumulative light quantity of 500 mJ/ ^cm2 .
Then, in an environment of 23° C. and 50% RH, a cutter knife is inserted into the interface between the test piece of the evaluation sample after UV irradiation and the adherend to peel one end of the test piece in the longitudinal direction from the adherend, and the peel force is measured in the same manner as in the measurement of the unirradiated normal peel force Fd0. The measurement is carried out three times, and the average value is taken as the normal peel force after irradiation Fd1 [N/10 mm].

4. Measurement of post-irradiation water peeling force Fw1 In the same manner as the measurement of the post-irradiation normal peeling force Fd1, prepare an evaluation sample after UV irradiation. In the evaluation sample after UV irradiation, 20 μL of distilled water is supplied to the location (peeling interface) where the test piece begins to separate from the adherend during the process of peeling the test piece from the adherend, and the peeling force after the distilled water supply is measured. The measurement is performed three times, and the average value is taken as the post-irradiation water peeling force Fw1 [N/10 mm].

<Example 1>
(Preparation of Pressure-Sensitive Adhesive Composition)
A reaction vessel equipped with a Liebig condenser, a nitrogen inlet tube, a thermometer and a stirrer was charged with 100 parts of 2-ethylhexyl acrylate (2EHA), 25.5 parts of acryloylmorpholine (ACMO) and 18.5 parts of 2-hydroxyethyl acrylate (HEA) as monomer raw materials, and toluene as a polymerization solvent, and 0.3 parts of benzoyl peroxide (BPO) as a polymerization initiator was added to carry out solution polymerization under a nitrogen atmosphere to obtain a solution of polymer P1a. The weight average molecular weight (Mw) of polymer P1a was 900,000. The glass transition temperature (Tg) of polymer P1a based on the composition of the above monomer raw materials is -42.7°C.

After cooling the solution of polymer P1a to room temperature, 12.3 parts of 2-isocyanatoethyl methacrylate (manufactured by Showa Denko K.K., product name "Karenz MOI") was added, followed by 0.1 parts of dibutyltin (IV) dilaurate (manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture was stirred at 50°C for 24 hours in an air atmosphere to allow an addition reaction of MOI with polymer P1a, thereby obtaining a solution of polymer P1 having a carbon-carbon double bond.

5 parts by solids of isocyanate-based crosslinking agent A1 (trimethylolpropane/tolylene diisocyanate trimer adduct, manufactured by Tosoh Corporation, product name "Coronate L", solids concentration 75 wt%) was added to the solution of polymer P1 per 100 parts of polymer P1 in the solution, and 1 part of photoinitiator (manufactured by IGM Regins, product name "Omnirad 369") was further added and mixed to prepare adhesive composition C1.

(Preparation of adhesive sheet)
The adhesive composition C1 was applied to the release surface of a 38 μm-thick release film R1 (Mitsubishi Plastics, MRF38) in which one side of a polyethylene terephthalate (PET) film was treated with silicone to form a release surface, and the adhesive composition C1 was dried for 2 minutes at 140° C. to form an adhesive layer having a thickness of 20 μm. The adhesive layer was attached to the easy-adhesion surface of an easy-adhesion treated PET film (thickness 50 μm) as a substrate, and then aged at 50° C. for 2 days to obtain an adhesive sheet according to this example.

<Example 2>
To the solution of polymer P1, 0.5 parts of a surfactant (polyoxyethylene sorbitan monolaurate, sorbitan fatty acid ester manufactured by Kao Corporation, product name "Rheodol TW-L 120", ethylene oxide addition mole number 20, HLB 16.7) was further added per 100 parts of polymer P1 in the solution. Except for the above points, pressure-sensitive adhesive composition C2 was prepared in the same manner as the preparation of pressure-sensitive adhesive composition C1. A pressure-sensitive adhesive sheet of this example was obtained in the same manner as the preparation of the pressure-sensitive adhesive sheet of Example 1, except that this pressure-sensitive adhesive composition C2 was used.
The surfactant was used in the form of an ethyl acetate solution in the amount shown above based on the solid content. Similarly, for PSA compositions C4 and C7, the surfactant was added in the form of an ethyl acetate solution in the following amount based on the solid content to the polymer solution.

<Example 3>
(Preparation of Pressure-Sensitive Adhesive Composition)
In a reaction vessel equipped with a Liebig condenser, a nitrogen inlet tube, a thermometer and a stirrer, 100 parts of n-butyl acrylate (BA), 78 parts of ethyl acrylate (EA) and 40 parts of 2-hydroxyethyl acrylate (HEA) as monomer raw materials, and toluene as a polymerization solvent were charged, and 0.3 parts of benzoyl peroxide (BPO) as a polymerization initiator was added to carry out solution polymerization under a nitrogen atmosphere to obtain a solution of polymer P3a. The weight average molecular weight (Mw) of polymer P3a was 500,000. The glass transition temperature (Tg) of polymer P3a based on the composition of the above monomer raw materials is -37.2°C.

After cooling the solution of polymer P3a to room temperature, 43.6 parts of 2-isocyanatoethyl methacrylate (manufactured by Showa Denko K.K., product name "Karenz MOI") was added, followed by 0.2 parts of dibutyltin (IV) dilaurate (manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture was stirred at 50°C for 24 hours in an air atmosphere to carry out an addition reaction of MOI with polymer P3a, thereby obtaining a solution of polymer P3 having a carbon-carbon double bond.

5 parts of isocyanate-based crosslinking agent A1 (trimethylolpropane/tolylene diisocyanate trimer adduct, Tosoh Corporation, product name "Coronate L", solid content concentration 75 wt%) was added to the solution of polymer P3 above per 100 parts of polymer P3 in the solution, and 1 part of photoinitiator (IGM Regins, product name "Omnirad 369") was further added and mixed to prepare adhesive composition C3. The adhesive sheet of this example was obtained in the same manner as the adhesive sheet of Example 1, except that this adhesive composition C3 was used.

<Example 4>
To the solution of polymer P3, 0.5 parts of a surfactant (polyoxyethylene sorbitan monolaurate, sorbitan fatty acid ester manufactured by Kao Corporation, product name "Rheodol TW-L 120", ethylene oxide addition mole number 20, HLB 16.7) was further added per 100 parts of polymer P3 in the solution. Except for the above points, adhesive composition C4 was prepared in the same manner as the preparation of adhesive composition C3. An adhesive sheet of this example was obtained in the same manner as the preparation of the adhesive sheet of Example 1, except that adhesive composition C4 was used.

<Example 5>
To the solution of the polymer P3, 1 part of an isocyanate-based crosslinking agent A1 (trimethylolpropane/tolylene diisocyanate trimer adduct, manufactured by Tosoh Corporation, trade name "Coronate L", solid content concentration 75 wt%) was added based on solid content per 100 parts of the polymer P3 in the solution, and 1 part of a photoinitiator (manufactured by IGM Regins, trade name "Omnirad 369") was further added and mixed to prepare a pressure-sensitive adhesive composition C5. A pressure-sensitive adhesive sheet according to this example was obtained in the same manner as in the preparation of the pressure-sensitive adhesive sheet according to Example 1, except that this pressure-sensitive adhesive composition C5 was used.

<Example 6>
(Preparation of Pressure-Sensitive Adhesive Composition)
A reaction vessel equipped with a Liebig condenser, a nitrogen inlet tube, a thermometer and a stirrer was charged with 75 parts of 2-ethylhexyl acrylate (2EHA), 25 parts of acryloylmorpholine (ACMO), 3 parts of acrylic acid (AA) and 0.1 parts of 2-hydroxyethyl acrylate (HEA) as monomer raw materials, and ethyl acetate as a polymerization solvent, and 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added to carry out solution polymerization under a nitrogen atmosphere to obtain a solution of polymer P6. The weight average molecular weight (Mw) of polymer P6 was 1.2 million. The glass transition temperature (Tg) of polymer P6 based on the composition of the above monomer raw materials is -37.4 ° C.

2 parts on a solid basis of isocyanate-based crosslinking agent A1 (trimethylolpropane/tolylene diisocyanate trimer adduct, manufactured by Tosoh Corporation, product name "Coronate L", solid content concentration 75 wt%) and 0.7 parts on a solid basis of epoxy-based crosslinking agent A2 (manufactured by Mitsubishi Gas Chemical Company, Inc., product name "Tetrad C") were added to the solution of polymer P6 and mixed per 100 parts of polymer P6 in the solution to prepare adhesive composition C6. Except for using this adhesive composition C6, the adhesive sheet of this example was obtained in the same manner as in the preparation of the adhesive sheet of Example 1.

<Example 7>
To the solution of polymer P6, 0.5 parts of a surfactant (polyoxyethylene sorbitan monolaurate, sorbitan fatty acid ester manufactured by Kao Corporation, product name "Rheodol TW-L 120", ethylene oxide addition mole number 20, HLB 16.7) was further added. Except for the above points, pressure-sensitive adhesive composition C7 was prepared in the same manner as for the preparation of pressure-sensitive adhesive composition C6. A pressure-sensitive adhesive sheet according to this example was obtained in the same manner as for the preparation of the pressure-sensitive adhesive sheet according to Example 1, except that this pressure-sensitive adhesive composition C7 was used.

<Performance evaluation>
For the pressure-sensitive adhesive sheet according to each example, the unirradiated normal peeling stick-slip degree SSd0, the unirradiated water peeling stick-slip degree SSw0, the post-irradiation normal peeling stick-slip degree SSd1, and the post-irradiation water peeling stick-slip degree SSw1 were measured. In addition, for the pressure-sensitive adhesive sheet according to each example, the unirradiated normal peeling force Fd0, the unirradiated water peeling force Fw0, the post-irradiation normal peeling force Fd1, and the post-irradiation water peeling force Fw1 were measured. The results are shown in Table 1.

As shown in Table 1, the stick-slip degree of all of the adhesive sheets of Examples 1 to 5 could be reduced by UV irradiation. Furthermore, the stick-slip degree of all of the adhesive sheets of Examples 1 to 7 could be reduced by water peeling. In particular, the adhesive sheets of Examples 1 to 5 and 7 showed a significant reduction in stick-slip degree by at least one of water peeling and UV irradiation. Furthermore, the adhesive sheets of Examples 1 to 5 showed a particularly significant reduction in stick-slip degree by UV irradiation followed by water peeling.

Furthermore, the peel strength of all the adhesive sheets of Examples 1 to 5 could be significantly reduced by UV irradiation. The peel strength of all the adhesive sheets of Examples 1 to 7 could be reduced by water peeling. In particular, the adhesive sheets of Examples 1 to 5 showed a particularly significant reduction in peel strength when they were subjected to UV irradiation followed by water peeling.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples given above.

1, 2, 3, 4, 5, 6 Adhesive sheet for wafer processing 10 Substrate 10A First surface 10B Second surface 21, 22 Adhesive layer 21A First adhesive surface 21B Second adhesive surface 31, 32 Release liner x Peel distance y Peel force SS Stick-slip degree L Reference length

Claims (7)

An adhesive sheet for wafer processing comprising an adhesive layer constituting an adhesive surface,
The pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer and a crosslinking agent,
The pressure-sensitive adhesive layer contains a surfactant in an amount of 5 parts by weight or less relative to 100 parts by weight of the base polymer, or does not contain a surfactant,
the pressure-sensitive adhesive layer contains a polymer having a carbon-carbon double bond,
A pressure-sensitive adhesive sheet having a stick-slip degree [10-3 N/10 mm] of 30 or less, measured in accordance with "10.4.1 Method 1: 180° peel adhesion to test plate" of JIS Z0237:2009 under conditions of a peel speed of 300 mm/min and a peel angle of 180 degrees, using an evaluation sample prepared by attaching the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet to a silicon wafer as an adherend, according to the following Method A under conditions of 23 ^° C and 50% RH.
Method A: An aqueous stripping liquid is supplied to the interface between the pressure-sensitive adhesive sheet and the adherend in the evaluation sample, and then the stick-slip degree is measured when the pressure-sensitive adhesive sheet is peeled off from the adherend .
Here , the stick-slip degree [10 ⁻³ N/10 mm] is calculated by the following general formula (1) when the peel force curve is expressed as y=f(x) and only a reference length L is extracted from the peel force curve in the direction of the average line.

The pressure-sensitive adhesive sheet according to claim 1 , wherein the peel strength measured using the evaluation sample by at least one of the following methods E, F and G is 0.10 N/10 mm or less.
Method E: An aqueous stripping liquid is supplied to the interface between the pressure-sensitive adhesive sheet and the adherend in the evaluation sample, and then the peel force when peeling the pressure-sensitive adhesive sheet from the adherend is measured.
Method F: The evaluation sample is irradiated with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and then the peel force when peeling the pressure-sensitive adhesive sheet from the adherend is measured.
Method G: The evaluation sample is irradiated with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and an aqueous stripping liquid is supplied to the interface between the pressure-sensitive adhesive sheet and the adherend, and then the peel force when peeling the pressure-sensitive adhesive sheet from the adherend is measured. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the peel force when the pressure-sensitive adhesive sheet is peeled from the adherend using the evaluation sample without irradiating the evaluation sample with active energy rays is 0.20 N/10 mm or more. The adhesive sheet according to any one of claims 1 to 3, wherein the adhesive layer is an active energy ray-curable adhesive layer. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the stick-slip degree [10 ^-3 N/10 mm] measured using the evaluation sample at a peel rate of 300 mm/min by at least one of the following methods B and C is 10 or less.
Method B: The evaluation sample is irradiated with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and then the stick-slip degree is measured when the pressure-sensitive adhesive sheet is peeled off from the adherend.
Method C: The evaluation sample is irradiated with active energy rays from the side of the pressure-sensitive adhesive sheet opposite the adherend, and an aqueous stripping liquid is supplied to the interface between the pressure-sensitive adhesive sheet and the adherend, and then the stick-slip degree is measured when the pressure-sensitive adhesive sheet is peeled off from the adherend. The pressure-sensitive adhesive sheet according to claim 5 , wherein the stick-slip degree [10 ⁻³ N/10 mm] measured using the evaluation sample at a peel rate of 300 mm/min according to the method C is less than 3. The pressure-sensitive adhesive sheet according to claim 2, wherein the peel strength measured by at least one of the methods F and G using the evaluation sample is less than 0.050 N/10 mm.

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