Adhesive sheet peeling method

Abstract

The present invention provides a method for peeling an adhesive sheet from an adherend, which can effectively reduce the load on the adherend when the adhesive sheet is peeled. The present invention provides a method for peeling an adhesive sheet comprising an adhesive layer constituting an adhesive surface from an adherend to which the adhesive sheet is bonded. The peeling method comprises applying a first peeling force reducing means to the adhesive sheet, and applying a second peeling force reducing means to the adhesive sheet.

Description

Technical Field

[0001] This invention relates to a method for peeling adhesive sheets from an adhered object. Background Technology

[0002] In the manufacturing process of semiconductor devices, for processes such as grinding and cutting of semiconductor wafers that have formed circuits, in order to protect and fix the semiconductor wafer, the process is usually performed with an adhesive sheet (semiconductor processing adhesive sheet) attached to the circuit forming side of the semiconductor wafer (the object to be bonded). For example, when grinding the back side of a semiconductor wafer (backgrind), backgrind tape is used to protect the circuit forming side (front side) of the semiconductor wafer and to hold (fix) the semiconductor wafer (for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-212441

[0006] Patent Document 2: Japanese Patent Application Publication No. 2014-003199 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] For adhesive sheets used in the manufacturing process of in-process products, such as the aforementioned semiconductor processing adhesive sheets, which are temporarily attached to the substrate, they are peeled off from the substrate at a desired time after achieving their intended purpose. At this time, depending on the degree of peeling force applied when peeling the adhesive sheet from the substrate, the substrate may be easily damaged due to the load applied during peeling. Therefore, this damage may lead to a decrease in yield, or a decrease in productivity due to careful peeling operations (e.g., slowing down the stretching speed).

[0009] For example, with the miniaturization, thinning, and high integration of semiconductor devices in recent years, the demand for thinning has increased even for semiconductor wafers after back-grinding. As a result, if back-grinding is performed until the semiconductor wafer is further thinned, the semiconductor wafer is easily damaged due to the load when peeling off the back-grinding tape. In particular, for semiconductor wafers that have been back-grinded with the inner side of the annular protrusion becoming a concave portion as described in Patent Document 2 (so-called TAIKO (registered trademark) wafers), if the semiconductor wafer is fixed by adsorbing the annular protrusion, the back side becomes unsupported in the concave portion. Therefore, damage during the peeling off of the back-grinding tape is particularly likely to occur in the concave portion.

[0010] The present invention was made in view of the above circumstances, and its object is to provide an adhesive peeling method that can effectively reduce the load on the adherend when peeling the adhesive sheet from the adherend. A related object is to provide a method for manufacturing semiconductor devices using the above-described peeling method.

[0011] Methods for solving problems

[0012] This specification provides a method for peeling an adhesive sheet comprising an adhesive layer constituting an adhesive surface from an adherend to which the adhesive sheet is bonded. The peeling method includes: applying a first peel force reduction means to the adhesive sheet; and applying a second peel force reduction means to the adhesive sheet. In a preferred embodiment, the adhesive surface is a surface (first surface) of the adhesive sheet, which is attached to the adherend. By applying the first and second peel force reduction means, the peel force of the first surface against the adherend is progressively reduced, thereby peeling the adhesive sheet from the adherend.

[0013] By applying the first peel force reduction means to the adhesive sheet bonded to the adhered object, the peel force required to peel the adhesive sheet from the adhered object can be reduced. Furthermore, by applying the second peel force reduction means to the adhesive sheet bonded to the adhered object, the peel force required to peel the adhesive sheet from the adhered object can be reduced. By applying both the first and second peel force reduction means, the peel force (final peel force) required to peel the adhesive sheet from the adhered object can be significantly reduced, for example, compared to the peel force (initial peel force) required to peel the adhesive sheet from the adhered object before applying these peel force reduction means. Therefore, according to the peeling method disclosed in this specification, by applying the first and second peel force reduction means, the load on the adhered object can be effectively reduced when peeling the adhesive sheet.

[0014] In some preferred embodiments, the second peel force reduction method is applied after the first peel force reduction method described above. As described above, depending on the phased application of the first and second peel force reduction methods, for example, after applying the first peel force reduction method, the adhered object may be moved, processed, handled, inspected, or stored as desired, and then the second peel force reduction method may be applied to peel off the adhesive sheet. This becomes advantageous from the viewpoint of flexibility in process design incorporating the peeling method disclosed in this specification.

[0015] In some preferred embodiments, an aqueous release solution is supplied as a second peel force reduction measure. This further reduces the peel force of the adhesive sheet after the first peel force reduction measure has been applied, thereby reducing the load on the adhered material during peeling.

[0016] In some preferred embodiments, as the first means of reducing peel force, irradiation with active energy rays (e.g., ultraviolet light) or heating is performed, thereby curing the adhesive layer. When the supply of the aqueous release liquid is used as the second means of reducing peel force, irradiation with active energy rays as the first means of reducing peel force is particularly meaningful. By applying these means of reducing peel force, the peel force can be effectively reduced, and the load on the adhered material during peeling can be significantly reduced.

[0017] The peeling method disclosed in this specification is preferably used as a method for peeling an adhesive sheet with an initial peel force F0 of 0.30 N / 20 mm or more from an adhered object. That is, the adhesive sheet peeled using the peeling method disclosed in this specification can be an adhesive sheet exhibiting the aforementioned initial peel force F0. Here, the initial peel force F0 of the adhesive sheet can be measured using the following method:

[0018] After the above adhesive surface is attached to the silicon wafer, the peel strength is measured under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees.

[0019] Generally, adhesive sheets with high peel strength exhibit good bonding reliability relative to the adherend; however, they tend to have a greater load on the adherend during peeling. Therefore, according to the peeling method disclosed in this specification, the peel strength can be effectively reduced by applying the first and second peel strength reduction methods described above. Thus, adhesive sheets exhibiting the aforementioned initial peel strength F0 are suitable as the peeling targets for the peeling method disclosed in this specification.

[0020] The peeling method disclosed in this specification is preferably used to reduce the UV-induced water peeling force Fw. U2 A method for peeling adhesive sheets with a strength of less than 0.10 N / 20 mm from the adherend is employed. Here, the UV-cured water peel strength Fw of the adhesive sheet is... U2 The following methods can be used to determine:

[0021] The aforementioned adhesive surface was attached to a silicon wafer, and the cumulative light intensity was 1000 mJ / cm. 2 After ultraviolet irradiation treatment, water is supplied to the peeling front of the adhesive sheet that is peeled from the silicon wafer, and the peel strength is measured under the conditions of a tensile speed of 300 mm / min and a peeling angle of 180 degrees.

[0022] The above-mentioned UV-treated water stripping force Fw is shown. U2 The sheet material can be peeled using the peeling method disclosed in this specification, preferably by irradiating with active energy rays as a first peeling force reduction method and supplying an aqueous peeling liquid as a second peeling force reduction method, thereby highly suppressing the load on the adhered material during peeling.

[0023] The peeling method disclosed in this specification is preferably used as a method to apply the conventional peeling force Fd after UV treatment. U1 [N / 20mm] represents the post-UV water stripping force Fw. U2 The adhesive sheet is more than 2.0 times larger than [N / 20mm] (i.e., meets Fd). U1 / Fw U2 A method for peeling an adhesive sheet (≥2.0) from the adherend is employed. Here, the UV-cured water peel strength Fw of the adhesive sheet is... U2 The above method can be used to determine the conventional peel force Fd after UV treatment. U1 The following methods can be used to determine:

[0024] The aforementioned adhesive surface was attached to a silicon wafer, and the cumulative light intensity was 1000 mJ / cm. 2 After ultraviolet irradiation treatment, water is supplied to the peeling front of the adhesive sheet that is peeled from the silicon wafer, and the peel strength is measured under the conditions of a tensile speed of 300 mm / min and a peeling angle of 180 degrees.

[0025] For satisfying Fd U1 / Fw U2 For adhesive sheets with a thickness of ≥2.0, by applying the second peel force reduction means, the peel force after applying the first peel force reduction means can be further reduced to less than half, and therefore, it is suitable as a peeling object of the peeling method disclosed in this specification.

[0026] According to this specification, an adhesive sheet comprising an adhesive layer constituting an adhesive surface can be provided and can be used in any of the peeling methods disclosed in this specification. With respect to the aforementioned adhesive sheet, by utilizing the peeling methods disclosed in this specification, peeling can be performed while suppressing the load on the adhered object during peeling; therefore, it is preferably used, for example, as an adhesive sheet for semiconductor processing.

[0027] According to this specification, a method for manufacturing a semiconductor device can be provided. This method includes the following steps:

[0028] Step (1) involves attaching the adhesive surface of an adhesive sheet containing an adhesive layer constituting an adhesive surface to a semiconductor wafer.

[0029] Step (2) involves processing the semiconductor wafer to which the aforementioned adhesive sheet has been bonded from the side opposite to the adhesive sheet; and

[0030] Step (3) involves peeling the adhesive sheet from the processed semiconductor wafer using any of the peeling methods disclosed in this specification.

[0031] According to the manufacturing method described above, since the adhesive sheet is peeled off from the processed semiconductor wafer using the aforementioned peeling method, damage to the processed semiconductor wafer can be prevented. This can contribute to improving yield and productivity.

[0032] It should be noted that the scope of the invention for which this patent application seeks patent protection may also include solutions that appropriately combine the above-mentioned elements. Attached Figure Description

[0033] [ Figure 1 This is a cross-sectional view schematically illustrating a structural example of an adhesive sheet.

[0034] [ Figure 2 This is a cross-sectional view schematically illustrating another structural example of an adhesive sheet.

[0035] [ Figure 3 This is a cross-sectional view schematically illustrating another structural example of an adhesive sheet.

[0036] [ Figure 4 This is a cross-sectional view schematically illustrating another structural example of an adhesive sheet.

[0037] [ Figure 5 This is a cross-sectional view schematically illustrating another structural example of an adhesive sheet.

[0038] [ Figure 6 This is a cross-sectional view schematically illustrating another structural example of an adhesive sheet.

[0039] [ Figure 7 This is a flowchart illustrating a stripping method according to one implementation.

[0040] Explanation of reference numerals in the attached figures

[0041] 1, 2, 3, 4, 5, 6 Adhesive sheets

[0042] 10 Substrate

[0043] 10A First Page

[0044] 10B Second Page

[0045] 21, 22 Adhesive layers

[0046] 21A First adhesive surface

[0047] 21B Second Adhesive Surface

[0048] 31, 32 Peeling off the gasket Detailed Implementation

[0049] The preferred embodiments of the present invention will be described below. It should be noted that matters necessary for the implementation of the present invention, other than those specifically described in this specification, can be understood by those skilled in the art based on the teachings on implementing the invention as described in this specification and common technical knowledge at the time of application. The present invention can be implemented based on the disclosure in this specification and common technical knowledge in the field. Furthermore, in the following drawings, sometimes the same reference numerals are used to describe components or parts that perform the same function, and sometimes repeated descriptions are omitted or simplified. Also, the embodiments described in the drawings are schematic for the purpose of clearly illustrating the present invention and do not necessarily accurately represent the dimensions or proportions of the actual provided article.

[0050] In this specification, the method of peeling adhesive sheets from a substrate using an aqueous stripping liquid such as water (typically, the method of peeling by supplying an aqueous stripping liquid to the peeling front from the substrate) is sometimes referred to as "water stripping" or "water stripping method".

[0051] In this specification, the term "polymer backbone" refers to the chain-like structure that forms the polymer's skeleton. Conversely, the term "polymer side chain" refers to the molecular chain of groups (pendants) bonded to the aforementioned backbone, which can be considered as side groups.

[0052] In this specification, the term "acrylic polymer" refers to a polymer derived from a monomeric 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 aforementioned acrylic monomer refers to a monomer having at least one (meth)acryloyl group in one molecule. Furthermore, in this specification, the term "(meth)acryloyl" means including both acryloyl and methacryloyl groups. Similarly, the term "(meth)acrylate" means including both acrylate and methacrylate, and the term "(meth)propylene-" means including both propylene- and methpropylene-.

[0053] In addition, in this specification, the term "active energy rays" refers to the concept of 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.

[0054] <Adhesive Sheet Peeling Method>

[0055] In the adhesive sheet peeling method disclosed in this specification, a first peel force reduction means and a second peel force reduction means are applied to the adhesive sheet bonded to the adhered objects. From the viewpoint of efficiently reducing peel force, it is preferable to use different types of peel force reduction means as the first and second peel force reduction means. The first and second peel force reduction means can be applied simultaneously or at different times. Here, "simultaneously" means applying the first and second peel force reduction means together to the same area in the top view of the adhesive sheet. Therefore, for example, the following application method is distinguished from the application method of simultaneously applying the first and second peel force reduction means to the adhesive sheet: the area where the first peel force reduction means is applied is moved sequentially from one end to the other end in the top view of the adhesive sheet, and before that area reaches the other end of the adhesive sheet, the application of the second peel force reduction means begins from the end of the adhesive sheet to which the first peel force reduction means has been applied.

[0056] Reference Figure 7 This specification describes one embodiment of the adhesive sheet peeling method disclosed herein, but it is not intended to limit the invention. In this embodiment, when peeling the adhesive sheet from the adhered object (the adhered object with the adhesive sheet), a first peel force reduction means is first applied, followed by a second peel force reduction means. The peeling of the adhesive sheet from the adhered object can be performed after the application of the second peel force reduction means, or simultaneously with the application of the second peel force reduction means.

[0057] In some of the peeling methods disclosed in this specification, the first peel force reduction means may be a treatment that cures the adhesive layer of the adhesive sheet bonded to the adhered object (e.g., increases the storage modulus of the adhesive layer). The curing treatment of the adhesive layer can be performed using known means such as irradiation with active energy rays (e.g., ultraviolet light) or heating (e.g., heating to the extent that thermosetting functional groups such as carbon-carbon double bonds contained in the adhesive layer can react to form a cross-linked structure). Irradiation with active energy rays and heating can be performed sequentially or simultaneously. When the above curing treatment is performed, the adhesive sheet preferably has an adhesive layer having curability (active energy ray curability, thermosetting property, etc.) corresponding to the applied curing treatment. Hereinafter, an adhesive layer constructed by curing through at least one of active energy ray irradiation treatment and heating treatment is sometimes referred to as a "curable adhesive layer".

[0058] As another example of the first peel force reduction method described above, a process can be given to roughen the adhesive surface of the adhesive sheet bonded to the adherend (i.e., increase the degree of roughness). The heating used for roughening can also be used as the heating used for the curing process of the adhesive layer.

[0059] Regarding the peeling method disclosed in this specification, as the second means of reducing peeling force, it is preferable to implement it by supplying an aqueous peeling solution. The aqueous peeling solution can be a liquid obtained by adding a small amount of additives to water or a mixed solvent with water as the main component, as needed. As a solvent other than water constituting the mixed solvent, a lower alcohol (e.g., ethanol), a lower ketone (e.g., acetone), etc., that can be uniformly mixed with water can be used. As the additives, known surfactants, pH adjusters, etc., can be used. From the viewpoint of avoiding contamination by the adhered material, in some methods, it is preferable to use an aqueous peeling solution that does not substantially contain additives. From the viewpoint of environmental hygiene, water is particularly preferred as the aqueous peeling solution. There are no particular limitations on the water used; considering the purity required for the application, ease of access, etc., distilled water, ion-exchanged water, tap water, etc., can be used, for example.

[0060] When implementing the peeling method disclosed in this specification by supplying an aqueous peeling liquid as a second peeling force reduction measure, it is preferable to supply the aqueous peeling liquid to the peeling front of the adhesive sheet as it peels from the adhered object. Here, in this specification, the peeling front refers to the position where the adhesive surface of the adhesive sheet begins to separate from the adhered object when peeling the adhesive sheet from the adhered object. Furthermore, the peeling after applying the second peeling force reduction measure is preferably performed in the following manner: with the aqueous peeling liquid present at the interface between the adhered object and the adhesive sheet at the peeling front of the adhesive sheet as it peels from the adhered object, the aqueous peeling liquid is introduced into the interface while following the movement of the peeling front, and the adhesive sheet is peeled from the adhered object.

[0061] In some methods, peeling when a water-based peeling liquid is supplied as a second means of reducing peeling force can preferably be performed by including the following steps: forcibly lifting the adhesive sheet from the adhered object at one end of its outer edge, thereby forming an initial peeling front; supplying the water-based peeling liquid to the peeling front; and peeling the adhesive sheet from the adhered object while the water-based peeling liquid enters the interface between the adhesive sheet and the adhered object following the movement of the peeling front. The initial peeling front can be formed, for example, by inserting the tip of a tool such as a cutter or needle into the interface between the adhesive sheet and the adhered object; grasping and lifting the adhesive sheet with a hook or claw; attaching a strong adhesive tape or suction cup to the back of the adhesive sheet and lifting the end of the adhesive sheet; etc. After forming the initial peeling front as described above, water-based peeling liquid is supplied to the peeling front to begin water peeling, thereby enabling efficient supply of the water-based peeling liquid to the peeling front. Furthermore, in the above-described peeling method and the adhesive sheet used in the peeling method, it is ideal to simultaneously achieve: good water-repellent properties after the start of peeling is achieved by performing an operation to forcibly form an initial peeling front; and high water resistance reliability without performing the operation.

[0062] In some methods, when supplying an aqueous stripper as a second means of reducing peeling force, the peeling can preferably be performed by supplying the aqueous stripper to the initial peeling front (i.e., after supplying the aqueous stripper at the start of the aqueous peeling), and then peeling the adhesive sheet without supplying new aqueous stripper. Alternatively, if the aqueous stripper that follows the movement of the peeling front to the interface between the adhesive sheet and the adhered object dries up or becomes insufficient during the aqueous peeling process, the aqueous stripper can be supplied intermittently or continuously after the start of the aqueous peeling. For example, in cases where the length of the peeling front increases as the peeling progresses (e.g., in cases where aqueous peeling is performed radially from one end of the outer edge of the disc-shaped adhered object), or where aqueous stripper tends to remain on the surface of the adhered object, it is preferable to supply the aqueous stripper after the start of the aqueous peeling. Furthermore, the aqueous stripper can be supplied at one location or at multiple locations. When additional aqueous stripping fluid is supplied after the start of aqueous stripping, the number of locations where aqueous stripping fluid is supplied after the start of aqueous stripping can be increased or decreased.

[0063] When an aqueous stripper is supplied as a second means of reducing peel force, irradiation with active energy rays as a first means of reducing peel force can particularly effectively reduce the peel force from the adhered material. The reason for this, while not a particularly limiting explanation, can be considered as follows: When an active energy ray-cured adhesive layer already adhered to the adhered material is irradiated with active energy rays, the rapid curing shrinkage of the adhesive layer causes slight floating from the adhered material or strain accumulation within the adhesive layer. If an aqueous stripper is supplied in this state, the aqueous stripper rapidly penetrates into the interface between the adhesive layer and the adhered material, effectively reducing the peel force. For adhesive sheets constructed by curing the adhesive layer through irradiation with active energy rays, thereby reducing peel force, after irradiation with active energy rays, peeling is performed using a water-based stripping method. Thus, through the synergistic effect of the reduction in peel force due to the curing of the adhesive layer and the reduction in water-based peel force due to the aforementioned rapid curing shrinkage, a particularly significant light peeling effect can be achieved.

[0064] <Example of adhesive sheet structure>

[0065] In the adhesive sheet peeling method disclosed in this specification, the adhesive sheet is peeled off from the adhered object to which it is attached (i.e., to which the adhesive sheet is bonded). The adhesive sheet to be peeled off has an adhesive layer constituting the adhesive surface (the surface to which it is attached to the adhered object). Typically, this adhesive layer constitutes at least one surface of the adhesive sheet. The adhesive sheet may be a substrate-supported adhesive sheet having an adhesive layer on one or both sides of a substrate (support), or it may be an adhesive sheet without a substrate (a substrate-free adhesive sheet).

[0066] The concept of adhesive sheet as used herein can include products referred to as adhesive tape, adhesive label, adhesive film, etc. Furthermore, the adhesive layer described above is typically formed continuously, but is not limited to the aforementioned form; for example, it can be an adhesive layer formed as regular or irregular patterns such as dots or stripes. Additionally, the adhesive sheet provided in this specification can be in roll form or as a single sheet. Alternatively, it can be an adhesive sheet that has been further processed into various shapes.

[0067] In some of the peeling methods disclosed in this specification, the adhesive sheet used in the peeling method (i.e., the adhesive sheet that can be peeled off by the peeling method disclosed in this specification) may, for example, have a [missing information - likely referring to a specific feature or characteristic] before being attached to the substrate. Figures 1-6 The cross-sectional structure of the adhesive sheet is schematically shown in the diagram. Among them, Figure 1 , Figure 2 This is a structural example of a single-sided adhesive sheet with a substrate (a single-sided adhesive sheet with a substrate). Figure 1The adhesive sheet 1 shown has an adhesive layer 21 provided on one side 10A (non-peelable) of the substrate 10, and the surface (adhesive surface) 21A of the adhesive layer 21 is protected by a release liner 31 that at least the adhesive layer side becomes the release surface. Figure 2 The adhesive sheet 2 shown has a structure in which an adhesive layer 21 is provided on one side 10A (non-peelable) of the substrate 10. For this adhesive sheet 2, the other side 10B of the substrate 10 becomes the peeling side. If the adhesive sheet 2 is rolled up, the adhesive layer 21 abuts against the other side 10B, and the surface (adhesive side) 21A of the adhesive layer will be protected by the other side 10B of the substrate 10.

[0068] Figure 3 , Figure 4 This is a structural example of a double-sided adhesive sheet with a substrate (a double-sided adhesive sheet with a substrate). Figure 3 The adhesive sheet 3 shown has the following structure: an adhesive layer (first adhesive layer) 21 and an adhesive layer (second adhesive layer) 22 are respectively provided on the first surface 10A and the second surface 10B (both non-peelable) of the substrate 10. The surface of the first adhesive layer 21 (first adhesive surface) and the surface of the second adhesive layer 22 (second adhesive surface) are respectively protected by release liner 31 and 32, which at least the adhesive layer side serves as the release surface. Figure 4 The adhesive sheet 4 shown has the following structure: a first adhesive layer 21 and a second adhesive layer 22 are respectively provided on the first surface 10A and the second surface 10B (both non-peelable) of the substrate 10. The surface of the first adhesive layer 21 (first adhesive surface) is protected by a release liner 31, which has two sides that are peelable surfaces. For the adhesive sheet 4, by winding the adhesive sheet 4 so that the surface of the second adhesive layer 22 (second adhesive surface) abuts against the back of the release liner 31, a structure can be formed in which the second adhesive surface is also protected by the release liner 31.

[0069] Figure 5 , Figure 6 This is a structural example of a substrate-free double-sided adhesive sheet (substrate-free double-sided adhesive sheet). Figure 5 The adhesive sheet 5 shown has a structure in which one surface (first adhesive surface) 21A and the other surface (second adhesive surface) 21B of the substrate-free adhesive layer 21 are respectively protected by release liner 31, 32 which at least the adhesive layer side serves as the release surface. Figure 6 The adhesive sheet 6 shown has a structure in which one surface (first adhesive surface) 21A of the adhesive layer 21 is protected by a release liner 31 on both sides, which are called release surfaces. If it is wound up, the other surface (second adhesive surface) 21B of the adhesive layer 21 abuts against the back of the release liner 31, thereby forming a structure in which the other side 21B is also protected by the release liner 31.

[0070] For double-sided adhesive sheets with or without a substrate, a single-sided adhesive sheet with a substrate can be formed by bonding a non-peelable substrate to one of the adhesive surfaces.

[0071] The adhesive sheet before being attached to the object can be, for example, such as... Figures 1-6 The adhesive sheet shown is in the form of a release liner with an adhesive surface protected by a release liner. There are no particular limitations on the release liner; for example, a release liner whose surface has been treated with a release agent, such as a resin film or paper liner substrate, or a release liner made of a low-adhesion material such as a fluoropolymer (polytetrafluoroethylene, etc.) or a polyolefin resin (polyethylene, polypropylene, etc.) can be used. In the aforementioned release treatment, for example, a release agent based on silicone or long-chain alkyl groups can be used. In some embodiments, a resin film that has undergone release treatment is preferably used as the release liner.

[0072] In some of the peeling methods disclosed in this specification, when the adhesive sheet used in the peeling method 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) can have the same composition or different compositions. For example, a double-sided adhesive sheet without a substrate where the first adhesive surface and the second adhesive surface have different compositions can be achieved by directly (without a substrate) laminating two or more adhesive layers with different compositions into a multilayer adhesive layer structure.

[0073] In some embodiments of the peeling methods disclosed in this specification, the adhesive sheet used in the peeling method preferably has an adhesive surface composed of an adhesive layer having active energy radiation curable properties (active energy radiation curable adhesive layer). In the case of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, it is preferable that at least one adhesive surface is an adhesive surface composed of an active energy radiation curable adhesive layer. The other adhesive surface may be an adhesive surface composed of an active energy radiation curable adhesive layer or an adhesive surface composed of an adhesive layer that does not have active energy radiation curable properties (non-active energy radiation curable adhesive layer). The peeling method disclosed in this specification can preferably be carried out by peeling a single-sided adhesive sheet with a substrate having an adhesive surface composed of an active energy radiation curable adhesive layer from the adherend. The aforementioned active energy radiation curable adhesive layer preferably contains compound A, which will be described later.

[0074] <Adhesive layer>

[0075] The adhesive layer (preferably a UV-curable adhesive layer) constituting the adhesive surface of the adhesive sheet used in the peeling method disclosed in this specification may be an adhesive layer comprising one or more adhesives selected from a variety of known adhesives, including acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, mixtures thereof, etc.), polysiloxane adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, and fluorinated adhesives. Here, "acrylic adhesive" refers to an adhesive based on an acrylic polymer. The same meaning applies to other adhesives such as rubber adhesives.

[0076] It should be noted that, in this specification, the term "base polymer" in the adhesive refers to the main component of the polymer contained in the adhesive. Furthermore, unless otherwise specified, the term "main component" in this specification refers to the component contained in an amount exceeding 50% by weight.

[0077] (Acrylic adhesive layer)

[0078] In some embodiments, the adhesive layer may be an acrylic adhesive layer containing an acrylic adhesive as the main component. The peeling method disclosed in this specification is preferably applied to the peeling of an adhesive sheet having an acrylic adhesive layer from an adherend, thereby enabling the peeling of the adhesive sheet with good bonding reliability relative to the adherend during use (before the application of the first and second peel force reduction means) while highly suppressing the load on the adherend. The acrylic adhesive layer is also preferred from the viewpoint of easily imparting the active energy radiation curing properties described later.

[0079] As an acrylic adhesive, a polymer containing a monomer raw material comprising an alkyl (meth)acrylate or an acrylic polymer modified by chemical modification is preferred as the base polymer. As a component of the aforementioned monomer raw material, an alkyl (meth)acrylate having a straight-chain or branched alkyl group having 1 or more and 20 or fewer carbon atoms at the ester terminus is preferred. Hereinafter, an alkyl (meth)acrylate having an alkyl group having X or more and Y or fewer carbon atoms at the ester terminus will sometimes be referred to as "(meth)acrylate C". X-Y Alkyl ester. Considering the ease of obtaining adhesive properties suitable for semiconductor processing applications, (meth)acrylic acid C... 1-20 Alkyl ester, preferably (meth)acrylic acid C 1-14 (e.g., C) 1-12 Alkyl esters. Additionally, as acrylic acid C... 1-20 Alkyl ester, preferably C14 acrylic acid 1-20 (e.g., C) 1-14 Typically C 1-12 Alkyl esters.

[0080] As (meth)acrylic acid C 1-20 Non-limiting specific examples of alkyl esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, pentyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isooctyl methacrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecanyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate, nonadecanyl methacrylate, eicosyl methacrylate, etc. These alkyl (meth)acrylates can be used alone or in combination of two or more. 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 raw material preferably contains at least one of EA, BA, 2EHA, and LA; more preferably, it contains at least one of EA, BA, and 2EHA; and even more preferably, it contains at least one of BA and 2EHA.

[0081] Considering the ease of obtaining a balance of properties, in some methods, (meth)acrylic acid C 1-20 The proportion of alkyl esters in the aforementioned monomer raw materials is typically suitable to be 40% by weight or more, preferably more than 50% by weight, for example, it can be 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 (meth)acrylic acid C in the aforementioned monomer raw materials... 1-20 The proportion of alkyl esters is typically suitable to be 99.9% by weight or less, and can be 99% by weight or less, or 98% by weight or less. From the viewpoint of easily forming adhesive sheets suitable for lightly peeling based on supplying an aqueous release agent to the peel front from the adherend, in some embodiments, the (meth)acrylic acid C in the aforementioned monomer raw materials... 1-20 The proportion of alkyl esters can be, for example, less than 95% by weight, less than 85% by weight, less than 80% by weight, less than 70% by weight, or less than 65% by weight.

[0082] In some preferred embodiments, the above-mentioned alkyl (meth)acrylate comprises an alkyl (meth)acrylate A1 having an alkyl group having 9 or fewer carbon atoms at the ester terminus (i.e., (meth)acrylate C... 1-9 Alkyl esters). Alkyl esters (meth)acrylate A1 can be used alone or in combination of two or more. By limiting the length of the side chain alkyl groups as described above, there is a tendency to obtain high cohesiveness (which can highly prevent adhesive residue). For example, in a structure where the side chain (typically, at the end of the side chain) of the polymer has carbon-carbon double bonds, the length of the side chain alkyl groups is limited, so that, for example, in the manner of performing a curing treatment of the adhesive layer as a first peel force reduction method, the reaction of the carbon-carbon double bonds can proceed smoothly during the above-mentioned curing treatment. In addition, since the length of the side chain alkyl groups is limited, for adhesive sheets having an adhesive layer containing a polymer obtained from this monomer, they can be efficiently peeled from the adhesive by supplying an aqueous peeling liquid such as water (preferably supplying an aqueous peeling liquid to the peel front from which the adhesive is peeled off) as a second peel force reduction method.

[0083] The proportion of alkyl methacrylate A1 in the total monomer raw material is preferably about 30% by weight or more, and more preferably about 40% by weight or more, and more preferably about 55% by weight or more, from the viewpoint of better presenting the effect of alkyl methacrylate A1. In some embodiments, the proportion of alkyl methacrylate 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 other embodiments, the proportion of alkyl methacrylate A1 may be, for example, about 85% by weight or more, about 90% by weight or more, or about 95% by weight or more. There is no particular upper limit to the proportion of alkyl methacrylate A1 in the monomer raw material, but it is generally suitable to be 99.5% by weight or less, for example, 99% by weight or less. In some ways, for example from the viewpoint that the effect of the carbon-carbon double bond is well presented in the adhesive layer containing the polymer having carbon-carbon double bonds, the proportion of the alkyl methacrylate A1 in the total monomer raw material is preferably about 95% by weight or less, more preferably about 90% by weight or less, can be about 85% by weight or less, can be about 75% by weight or less, or can be about 70% by weight or less.

[0084] The proportion of alkyl methacrylate A1 in the total alkyl methacrylate is preferably about 50% by weight or more. From the viewpoint of effectively exhibiting the function of alkyl methacrylate A1, it is preferably about 70% by weight or more, more preferably about 80% by weight or more, and can be about 90% by weight or more, about 95% by weight or more, or about 99% by weight or more. The upper limit of the proportion of alkyl methacrylate A1 in the total alkyl methacrylate is 100% by weight.

[0085] In some embodiments, the aforementioned alkyl methacrylate A1 may contain one or more alkyl methacrylates A3 having alkyl groups with fewer than 7 carbon atoms at the ester terminus. Adhesives comprising polymers obtained from monomeric raw materials containing alkyl methacrylate A3 readily provide adhesive sheets that can be efficiently peeled using a peeling method that includes a step of supplying an aqueous peeling liquid such as water as a means of reducing peel force. Furthermore, for active energy radiation-curable adhesives comprising polymers obtained from monomeric raw materials containing alkyl methacrylate A3, the curing reaction based on irradiation by active energy radiation can proceed well. From this viewpoint, the number of carbon atoms in the alkyl methacrylate A3 is preferably 6 or less, more preferably 4 or less, and can be 3 or less or 2 or less. Additionally, the number of carbon atoms in the alkyl methacrylate A3 can be 1 or more, and from the viewpoint of adhesion to the adhered objects, it is preferably 2 or more.

[0086] In the manner in which the aforementioned monomer raw material comprises alkyl methacrylate A3, the proportion of alkyl methacrylate A3 in the total monomer raw material can be, for example, about 1% by weight or more, typically, about 5% by weight or more, and from the viewpoint of effectively exhibiting the function of alkyl methacrylate A3, preferably about 20% by weight or more, more preferably about 30% by weight or more, further preferably about 40% by weight or more, particularly preferably about 50% by weight or more, for example, about 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 methacrylate A3 in the total monomer raw material, but typically, it is suitable to be about 99% by weight or less, for example, about 90% by weight or less. In some methods, for example from the viewpoint of effectively presenting the role of the carbon-carbon double bonds in an adhesive layer comprising a polymer having carbon-carbon double bonds, the proportion of (meth)acrylate alkyl ester A3 in the total 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. This method may, for example, involve introducing reactive groups for curing treatment, or functional groups that become crosslinking points, into the polymer.

[0087] The proportion of alkyl methacrylate A3 in the total alkyl methacrylate is preferably about 5% by weight or more. From the viewpoint of effectively exhibiting the function of alkyl methacrylate 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, particularly preferably about 55% by weight or more, for example, it can be 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 above-mentioned proportion of alkyl methacrylate A3 in the total alkyl methacrylate is 100% by weight, for example, it can be about 98% by weight or less. In some methods, such as when using alkyl methacrylate A2 (described later) in combination with alkyl methacrylate A3, from the viewpoint of best demonstrating its effect, the proportion of alkyl methacrylate A3 in the total alkyl methacrylate may, for example, be 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. Alkyl methacrylate A3 may also be omitted.

[0088] In some embodiments, the aforementioned alkyl methacrylate may include alkyl methacrylate A2 having an alkyl group at the ester terminus having 7 or more carbon atoms, as alkyl methacrylate A1, or as a monomer different from alkyl methacrylate A1. Using alkyl methacrylate A2 can be advantageous, for example, from the viewpoint of adhesion to the adhered material. The alkyl group in alkyl methacrylate A2 preferably has 8 or more carbon atoms, and can be 9 or more. Furthermore, from the viewpoint of adhesive properties such as adhesive strength, the alkyl group in alkyl methacrylate A2 preferably has 14 or fewer carbon atoms, more preferably 12 or fewer, even more preferably 10 or fewer, for example 9 or fewer, and can be less than 9.

[0089] In the manner in which the aforementioned monomer raw material comprises alkyl methacrylate A2, the proportion of alkyl methacrylate A2 in the total monomer raw material can be, for example, about 1% by weight or more, typically, preferably about 5% by weight or more, and from the viewpoint of better exhibiting the effect of alkyl methacrylate A2, preferably about 20% by weight or more, more preferably about 30% by weight or more, further preferably about 40% by weight or more, particularly preferably about 50% by weight or more, for example, about 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 methacrylate A2 in the total monomer raw material, but typically, it is preferably about 99.5% by weight or less, for example, about 99% by weight or less. In some ways, for example from the viewpoint that the effect of the carbon-carbon double bond is well presented in the adhesive layer containing the polymer having carbon-carbon double bonds, the proportion of the alkyl methacrylate A2 in the total monomer raw material is preferably about 95% by weight or less, can be about 90% by weight or less, can be about 85% by weight or less, can be about 75% by weight or less, or can be about 70% by weight or less.

[0090] The proportion of alkyl methacrylate A2 in the total alkyl methacrylate contained in the above-mentioned monomer raw materials is preferably about 5% by weight or more. From the viewpoint of effectively exhibiting the function of alkyl methacrylate 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, it can be 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 methacrylate A2 in the total alkyl methacrylate is 100% by weight. In some methods, such as when using (meth)acrylate A3 in combination with (meth)acrylate A2, from the viewpoint of best demonstrating its effect, the proportion of (meth)acrylate A2 in the total (meth)acrylate may, for example, be less than about 95% by weight, less than about 90% by weight, less than about 80% by weight, less than about 70% by weight, less than about 60% by weight, less than about 45% by weight, less than about 30% by weight, less than about 20% by weight, less than about 10% by weight, or less than about 5% by weight. Alternatively, (meth)acrylate A2 may not be used.

[0091] The monomer raw materials used in the synthesis of acrylic polymers may also include copolymerizable by alkyl methacrylates as described above. These auxomonomers can help introduce crosslinking points into the acrylic polymers or improve their cohesiveness. Furthermore, for example, in the synthesis of polymers containing carbon-carbon double bonds, monomers having functional groups (hereinafter also referred to as "functional group A") capable of reacting with the functional groups of monomers containing carbon-carbon double bonds described later (hereinafter also referred to as "functional group B") are preferably used as auxomonomers.

[0092] As a secondary monomer, one or more monomers containing functional groups can be used alone or in combination, such as the following.

[0093] Monomers containing hydroxyl groups: such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, methyl methacrylate (4-hydroxymethylcyclohexyl) ester, etc. (meth)acrylate hydroxyalkyl esters; unsaturated alcohols such as vinyl alcohol and allyl alcohol; ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, etc.

[0094] Monomers containing carboxyl groups: for example, olefinic unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), crotonic acid, and isocrotonic acid; olefinic unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and citraconic acid.

[0095] Monomers containing anhydride groups: for example, maleic anhydride and itaconic anhydride.

[0096] Monomers having a ring containing a nitrogen atom: for example, N-vinyl-2-pyrrolidone, methyl-N-vinylpyrrolidone, vinylpyridine, vinylpyrazine, vinylpyrimidine, N-vinylpiperidone, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazolium, 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, etc.

[0097] Monomers containing an amide group: for example, (meth)acrylamide; 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, N,N-di(tert-butyl)(meth)acrylamide, etc.; N-alkyl(meth)acrylamides such as N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, N-n-butyl(meth)acrylamide; N-vinylcarboxylic acid amides such as N-vinylacetamide; monomers having both hydroxyl and amide groups, for example, N-(2-hydroxyethyl)(methyl)acrylamide. Acrylamide, N-(2-hydroxypropyl)(methyl)acrylamide, N-(1-hydroxypropyl)(methyl)acrylamide, N-(3-hydroxypropyl)(methyl)acrylamide, N-(2-hydroxybutyl)(methyl)acrylamide, N-(3-hydroxybutyl)(methyl)acrylamide, N-(4-hydroxybutyl)(methyl)acrylamide, and other N-hydroxyalkyl(methyl)acrylamides; monomers having alkoxy and amide groups, such as N-alkoxyalkyl(methyl)acrylamide, N-methoxyethyl(methyl)acrylamide, N-butoxymethyl(methyl)acrylamide, and other N-alkoxyalkyl(methyl)acrylamides; N,N-dialkylaminoalkyl(methyl)acrylamides, such as N,N-dimethylaminopropyl(methyl)acrylamide, etc.

[0098] Monomers containing amino groups: for example, aminoethyl methacrylate, N,N-dimethylaminoethyl methacrylate, and tert-butylaminoethyl methacrylate.

[0099] Monomers having a succinimide backbone: for example, N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, N-(meth)acryloyl-8-oxyhexamethylenesuccinimide, etc.

[0100] Maleimides: For example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, etc.

[0101] Itaconimides: For example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide, etc.

[0102] Monomers containing epoxy groups: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

[0103] Monomers containing cyano groups: such as acrylonitrile and methacrylonitrile.

[0104] Monomers containing ketone groups: such as diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, and vinyl acetoacetate.

[0105] Monomers containing alkoxysilyl groups: such as 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, etc., as well as vinyl compounds containing alkoxysilyl groups such as (meth)acrylates, vinyltrimethoxysilane, vinyltriethoxysilane, etc.

[0106] Monomers containing amino groups: for example, aminoethyl methacrylate, N,N-dimethylaminoethyl methacrylate, and tert-butylaminoethyl methacrylate.

[0107] Monomers with epoxy groups: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

[0108] Monomers containing sulfonic acid or phosphoric acid groups: for example, styrene sulfonic acid, allyl sulfonic acid, sodium vinyl sulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, (meth)acrylate sulfopropyl ester, (meth)acryloyloxynaphthalene sulfonic acid, acryloyl phosphate 2-hydroxyethyl ester, etc.

[0109] Monomers containing isocyanate groups: for example, ethyl (meth)acrylate, methacryloyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate.

[0110] The amount of the aforementioned monomers containing functional groups can be appropriately selected in a way that achieves the desired cohesiveness, without particular limitation. Generally, from the viewpoint of achieving good balance between cohesiveness and other properties (e.g., adhesiveness), the amount of monomers containing functional groups (the total amount when using two or more monomers containing functional groups) is preferably 0.1% by weight or more of the total monomer raw material, preferably 0.3% by weight or more, for example, 1% by weight or more. Alternatively, the amount of monomers containing functional groups can be, for example, 50% by weight or less of the total monomer raw material, preferably 40% by weight or less, for example, 35% by weight or less, 30% by weight or less, 25% by weight or less, or 20% by weight or less.

[0111] In some embodiments, the aforementioned monomer raw material may include a monomer containing hydroxyl groups as the monomer containing the aforementioned functional group. There is no particular limitation on the amount of hydroxyl-containing monomer used; for example, it may be 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 total monomer raw material. In some embodiments, the amount of hydroxyl-containing monomer used may be, for example, less than 50% by weight of the total monomer raw material. From the viewpoint of suppressing water absorption of the adhesive, it is generally suitable to be less than 40% by weight, less than 30% by weight, less than 25% by weight, or less than 20% by weight. Furthermore, in some embodiments, the amount of hydroxyl-containing monomer used may be less than 15% by weight, less than 10% by weight, or less than 5% by weight of the total monomer raw material. Alternatively, hydroxyl-containing monomers may not be used.

[0112] In some embodiments, the aforementioned monomer raw materials may include monomers containing carboxyl groups as the aforementioned monomers containing functional groups. The proportion of carboxyl-containing monomers in the total monomer raw materials usable in the synthesis of acrylic polymers may, for example, be 15% by weight or less, or 10% by weight or less. From the viewpoint of suppressing water absorption in the adhesive layer during semiconductor processing, it is preferably 7% by weight or less, or 5% by weight or less, or 3% by weight or less, or 2% by weight or less, or 1% by weight or less, or 0.5% by weight or less, or less than 0.1% by weight. The aforementioned monomer raw materials may substantially not contain monomers containing carboxyl groups. Here, "substantially not containing monomers containing carboxyl groups" means that monomers containing carboxyl groups are at least not intentionally used. For example, it is preferable to adopt a configuration in which the proportion of carboxyl-containing monomers is limited as described above in the monomer raw materials usable in the preparation of polymers having carbon-carbon double bonds in the side chains.

[0113] In some embodiments, the monomer raw materials may include monomers having nitrogen atoms as the aforementioned monomers containing functional groups. By using monomers having nitrogen atoms, a suitable degree of polarity can be imparted to the adhesive. This can be advantageous for achieving a lightly peelable adhesive sheet suitable for supplying aqueous release liquids such as water. As a preferred example of a monomer having nitrogen atoms, a monomer having a ring containing nitrogen atoms can be cited. From the viewpoint of compatibility, N-vinyl-2-pyrrolidone and other N-vinyl-type compounds (such as N-vinyl cyclic amides), and N-(meth)acryloylmorpholine and other N-(meth)acryloyl-type compounds are preferred as monomers having a ring containing nitrogen atoms.

[0114] There is no particular limitation on the amount of monomers containing nitrogen atoms (e.g., monomers with a ring containing nitrogen atoms) used, for example, it can be 1% or more, 2% or more, 3% or more, 5% or more, or 7% or more of the total monomer raw material. From the viewpoint of obtaining higher performance, in some embodiments, the amount of monomers containing nitrogen atoms used can be 10% or more, 15% or more, or 20% or more of the total monomer raw material. Furthermore, from the viewpoint of easily achieving a balance of properties, the amount of monomers containing nitrogen atoms used is generally suitable to be, for example, 40% or less, 35% or less, 30% or less, or 25% or less of the total monomer raw material. In some embodiments, the amount of monomers containing nitrogen atoms used can be, for example, 20% or less, 15% or less, 10% or less, or 5% or less of the total monomer raw material. Alternatively, monomers containing nitrogen atoms may not be used.

[0115] When the aforementioned monomer raw materials are used in the preparation of polymers having carbon-carbon double bonds, monomers containing functional groups, specifically functional groups (functional group A) that can react with the functional groups (functional group B) of compounds having carbon-carbon double bonds described later, are preferably used as co-monomers. In this case, the type of monomer containing the functional group can be determined based on the type of compound described above. For example, monomers containing hydroxyl groups, carboxyl groups, epoxy groups, and isocyanate groups are preferred as co-monomers, with monomers containing hydroxyl groups being particularly preferred. By using a monomer containing hydroxyl groups as a co-monomer, the acrylic polymer acquires hydroxyl groups. Conversely, by using a monomer containing isocyanate groups as a compound having carbon-carbon double bonds, the hydroxyl groups (functional group A) of the acrylic polymer react with the isocyanate groups (functional group B) of the compound, thereby introducing carbon-carbon double bonds from the compound into the acrylic polymer.

[0116] Furthermore, when using a secondary monomer for the purpose of reacting with compounds having carbon-carbon double bonds, from the viewpoint of easily obtaining an adhesive layer suitable for water peeling, the amount of the aforementioned secondary monomer (preferably a monomer containing hydroxyl groups) is preferably about 1% by weight or more of the total monomer raw material, 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. Additionally, from the viewpoint of maintaining adhesive properties such as tackiness well, the amount of the aforementioned secondary monomer is preferably about 40% by weight or less of the total monomer raw material, preferably about 30% by weight or less, more preferably about 20% by weight or less, for example, about 15% by weight or less.

[0117] For the monomer raw materials that can be used in the preparation of acrylic polymers, in order to improve the cohesiveness of the acrylic polymer, other than the monomers containing functional groups mentioned above (hereinafter also referred to as comonomers) may be included.

[0118] As a specific, non-limiting example of the aforementioned copolymerizable monomers, the following examples can be cited.

[0119] Monomers containing alkoxy groups: for example, alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, and 2-ethoxyethyl (meth)acrylate (alkoxyalkyl meth)acrylates; alkoxy(poly)alkylene glycol (meth)acrylates such as methoxy polyethylene glycol (meth)acrylate, methoxy polyethylene glycol (meth)acrylate, and methoxy polypropylene glycol (meth)acrylate.

[0120] Vinyl esters: such as vinyl acetate, vinyl propionate, etc.

[0121] Vinyl ethers: For example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.

[0122] Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene, etc.

[0123] Olefins: such as ethylene, butadiene, isoprene, isobutene, etc.

[0124] (Meth)acrylates containing alicyclic hydrocarbon groups: for example, cyclopentyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, dicyclopentanyl(meth)acrylate, adamantyl methacrylate, and other (meth)acrylates containing alicyclic hydrocarbon groups.

[0125] (Meth)acrylates containing an aromatic ring: for example, aryl methacrylates such as phenyl methacrylate, aryl methacrylates such as phenoxyethyl methacrylate, and aryl methacrylates such as benzyl methacrylate.

[0126] In addition, (meth)acrylates containing heterocyclic rings such as tetrahydrofurfuryl methacrylate, monomers containing halogen atoms such as vinyl chloride and (meth)acrylates containing fluorine atoms, monomers containing organosiloxane chains such as polysiloxane (meth)acrylates, and (meth)acrylates obtained from terpene compound derivative alcohols, etc.

[0127] Such comonomers can be used alone or in combination of two or more. There are no particular restrictions on the amount of the other comonomers mentioned above, and they can be selected appropriately according to the purpose and use. For example, it is preferred to be less than 20% by weight of all monomer raw materials of acrylic polymers (e.g., 2 to 20% by weight, typically 3 to 10% by weight).

[0128] In a preferred embodiment, from the viewpoint of inhibiting gelation, the total proportion of alkoxyalkyl methacrylate and alkoxypolyalkylene glycol (meth)acrylate in the monomer raw material is preferably limited to less than 20% by weight. More preferably, the total proportion of alkoxyalkyl methacrylate and alkoxypolyalkylene glycol (meth)acrylate is less than 10% by weight, further preferably less than 3% by weight, and particularly preferably less than 1% by weight. In one embodiment, the monomer raw material substantially does not contain alkoxyalkyl methacrylate and alkoxypolyalkylene glycol (meth)acrylate (in a content of 0-0.3% by weight).

[0129] Similarly, in one embodiment, the monomer raw material may contain alkoxy-containing monomers in a proportion of less than 20% by weight, or may not contain alkoxy-containing monomers. The amount of alkoxy-containing monomers in the monomer raw material is preferably less than 10% by weight, more preferably less than 3% by weight, even more preferably less than 1% by weight, and in a particularly preferred embodiment, the monomer raw material substantially does not contain alkoxy-containing monomers (in a content of 0 to 0.3% by weight).

[0130] There are no particular limitations on the method for polymerizing the monomer feedstock, 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 used. For example, solution polymerization is preferred. As for the monomer supply method during solution polymerization, appropriate methods such as simultaneous charging of all monomer feedstocks, continuous supply (droplet addition), and batch supply (droplet addition) can be used. The solvent (polymerization solvent) used in solution polymerization can be appropriately selected from existing known organic solvents. For example, any one solvent or a mixture of two or more solvents 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; haloalkanes such as 1,2-dichloroethane; lower alcohols such as isopropanol (e.g., monohydric alcohols with 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc. can be used. The polymerization temperature can be appropriately selected according to the type of monomer and solvent used, the type of polymerization initiator, etc., for example, it can be around 20℃ to 120℃ (typically, 40℃ to 80℃). Through solution polymerization, a polymerization reaction solution in which the polymer of the monomer raw material is dissolved in the polymerization solvent can be obtained. The adhesive composition used to form the adhesive layer can preferably be manufactured using the above-mentioned polymerization reaction solution. The method for manufacturing the adhesive composition using the above-mentioned polymerization reaction solution may include, for example, a step of chemical modification such as introducing carbon-carbon double bonds into the polymer contained in the above-mentioned polymerization reaction solution.

[0131] During polymerization, known or conventional thermal polymerization initiators and photopolymerization initiators can be used, depending on the polymerization method and polymerization mode. Examples of thermal polymerization initiators include azo-based initiators, peroxide-based initiators, redox initiators based on combinations of peroxides and reducing agents, and substituted ethane initiators. Examples of photopolymerization initiators include α-ketool-based photoinitiators, acetophenone-based photoinitiators, benzoin ether-based photoinitiators, ketal-based photoinitiators, aromatic sulfonyl chloride-based photoinitiators, photoactive oxime-based photoinitiators, benzophenone-based photoinitiators, thioxanone-based photoinitiators, and acylphosphine oxide-based photoinitiators. One polymerization initiator can be used alone or in appropriate combinations of two or more.

[0132] The amount of polymerization initiator used is the usual amount, for example, it can be selected from about 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) relative to 100 parts by weight of all monomer raw materials. In addition, if the polymerization initiator is also used as a photoinitiator, this situation can be taken into account when setting the amount of polymerization initiator used.

[0133] In the above polymerization, various known chain transfer agents (which can also be understood as molecular weight regulators or degree of polymerization regulators) can be used as needed. Thiols such as n-dodecyl mercaptan, tert-dodecyl mercaptan, mercaptoacetic acid, and α-thioglycerol can be used as chain transfer agents. Alternatively, chain transfer agents that do not contain sulfur atoms (non-sulfur chain transfer agents) can 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; styrene compounds such as α-methylstyrene and α-methylstyrene dimer; compounds containing benzylidene groups such as dibenzylideneacetone, cinnamyl alcohol, and cinnamaldehyde; hydroquinones such as hydroquinone and naphthol; quinones such as benzoquinone and naphthoquinone; alkenes such as 2,3-dimethyl-2-butene and 1,5-cyclooctadiene; alcohols such as phenol, benzyl alcohol, and allyl alcohol; benzyl hydrogen compounds such as diphenylbenzene and triphenylbenzene; and so on.

[0134] Chain transfer agents can be used alone or in combination of two or more. When using chain transfer agents, the amount used can be, for example, about 0.01 to 1 part by weight relative to 100 parts by weight of the monomer raw material. The technology disclosed in this specification can also preferably be implemented without the use of chain transfer agents.

[0135] There are no particular limitations on the molecular weight of acrylic polymers; it can be set to an appropriate range according to the required performance. The weight-average molecular weight (Mw) of acrylic polymers is typically about 10 × 10⁻⁶. 4 Above (e.g., 20×10) 4 From the perspective of achieving both good balance and cohesion, a value greater than 30 × 10 is suitable (as mentioned above). 4 Preferably about 40×10 4 The above can be approximately 50×10 4 The above can be approximately 55 × 10 4 That's all. There is no particular upper limit to the Mw of acrylic polymers. From the viewpoint of the coatability of the adhesive composition, the Mw of acrylic polymers is generally suitable to be about 500 × 10⁻⁶. 4 For example, it could be approximately 150×10 4 The following can be approximately 75×10 4 The above Mw can be the Mw of an acrylic polymer in either the adhesive composition or the adhesive layer.

[0136] The term Mw here refers to the value obtained using gel permeation chromatography (GPC) converted to standard polystyrene. For example, a GPC apparatus such as the "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used. The same applies to the examples described later.

[0137] The acrylic adhesive layer may, as needed, further include polymers other than acrylic polymers as by-polymers. Examples of such by-polymers include polymers other than acrylic polymers from various polymers that can be included in the adhesive layer. When the adhesive layer disclosed in this specification is an acrylic adhesive layer that includes not only an acrylic polymer but also by-polymers, the content of the by-polymer is preferably 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 by-polymer may be 5 parts by weight or less, or even 1 part by weight or less, relative to 100 parts by weight of the acrylic polymer. The technology disclosed in this specification can preferably be implemented, for example, by having 99.5% to 100% by weight of the polymer included in the adhesive layer be an acrylic polymer.

[0138] (Adhesive layers other than acrylic)

[0139] The adhesive layer constituting the adhesive surface in the adhesive sheet used in the peeling method disclosed in this specification can be an adhesive layer with a polymer other than an acrylic polymer as the base polymer, i.e., an adhesive layer other than an acrylic polymer. For adhesive layers other than acrylic polymers, in addition to the base polymer, secondary polymers other than the base polymer may be further included as needed. In this case, the content of secondary polymers in the adhesive layer other than acrylic polymers can be selected from the contents exemplified above as the content of secondary polymers in acrylic adhesive layers. The adhesive layer other than acrylic polymers can be an adhesive layer containing an acrylic polymer as a secondary polymer.

[0140] (Glass transition temperature)

[0141] The glass transition temperature (Tg) of the base polymer (e.g., an acrylic polymer) constituting the adhesive layer is preferably about 15°C or lower. In some embodiments, considering the adhesion to the adhered objects (e.g., the ability to follow the surface shape of the adhered objects), the aforementioned Tg is preferably 10°C or lower, preferably 0°C or lower, and can be -10°C or lower or -20°C or lower. Furthermore, considering the cohesiveness of the adhesive and the ease of light peeling based on water stripping, the Tg of the base polymer can 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 can be -45°C or higher, or -40°C or higher.

[0142] Here, in this specification, the glass transition temperature (Tg) of a polymer refers to the glass transition temperature calculated using the Fox formula based on the composition of the monomer raw materials constituting the polymer. The aforementioned Fox formula, as shown below, is a formula relating the Tg of the copolymer to the glass transition temperature (Tgi) of the homopolymer obtained by homopolymerizing the monomers constituting the copolymer.

[0143] 1 / Tg=Σ(Wi / Tgi)

[0144] It should be noted that in the above Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (weight-based copolymerization ratio), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K).

[0145] The glass transition temperature of the homopolymer used in the calculation of Tg is the value recorded in known sources. For example, for the monomers listed below, the following values ​​are used as the glass transition temperatures of the homopolymers of those monomers.

[0146] 2-Ethylhexyl acrylate -70℃

[0147] n-Butyl acrylate -55℃

[0148] Isostearyl acrylate -18℃

[0149] Methyl methacrylate 105℃

[0150] Methyl acrylate 8℃

[0151] Ethyl acrylate -22℃

[0152] N-Vinyl-2-pyrrolidone 54℃

[0153] N-Acryloylmorpholine 145℃

[0154] 2-Hydroxyethyl Acrylate -15℃

[0155] 4-Hydroxybutyl acrylate -40℃

[0156] Acrylic acid 106℃

[0157] Methacrylic acid 228℃

[0158] For the glass transition temperatures of homopolymers of monomers other than those listed above, the values ​​described in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) are used. In cases where multiple values ​​are described in this literature, the highest value is adopted.

[0159] Regarding the monomer whose glass transition temperature of the homopolymer is not recorded in the aforementioned Polymer Handbook, the value obtained using the following determination method was used (see Japanese Patent Application Publication No. 2007-51271). Specifically, 100 parts by weight of monomer, 0.2 parts by weight of azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as the polymerization solvent were added to a reactor equipped with a thermometer, stirrer, nitrogen inlet pipe, and reflux condenser, and stirred for 1 hour while passing nitrogen gas through. The oxygen in the polymerization system was removed by operating as described above, and then the temperature was raised to 63°C and the reaction was carried out for 10 hours. Next, it was cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by weight. Next, the homopolymer solution was cast onto a release liner, dried, and a test sample (sheet-shaped homopolymer) with a thickness of approximately 2 mm was prepared. The test sample was punched into a disc shape with a diameter of 7.9 mm, clamped with parallel plates, and viscoelasticity was measured in shear mode using a viscoelasticity testing machine (ARES, manufactured by Rheometrics Inc.) while providing shear strain at a frequency of 1 Hz, under conditions of -70 to 150 °C and a heating rate of 5 °C / min. The peak temperature of tanδ was taken as the Tg of the homopolymer.

[0160] (Compound A)

[0161] The adhesive layer (which may be a curable adhesive layer, preferably an active energy radiation-curable adhesive layer) may contain a water-based stripping additive as needed. As the water-based stripping additive, at least one compound A selected from the group consisting of surfactants and compounds having a polyoxyalkylene backbone can be used. By containing the water-based stripping additive in the adhesive layer, the effect of reducing the peel force resulting from supplying an aqueous stripping liquid as a second means of reducing peel force can be suitably achieved. The rationale, while not particularly limiting, can be considered as follows: surfactants and compounds having a polyoxyalkylene backbone both have hydrophilic regions, thus exhibiting a moderate tendency to be present on the surface of the adhesive layer, effectively reducing the peel force upon contact with the aqueous stripping liquid.

[0162] As surfactants and compounds having a polyoxyalkylene backbone, one or more known surfactants and compounds having a polyoxyalkylene backbone can be used without particular limitation. Compound A is typically preferably contained in the adhesive layer in a free form. It should be noted that the above-mentioned surfactants include compounds having a polyoxyalkylene backbone, which is self-evident, and vice versa.

[0163] As a surfactant that can be used as compound A, known nonionic surfactants, anionic surfactants, cationic surfactants, etc., can be used. Among them, nonionic surfactants are preferred. One surfactant can be used alone or two or more surfactants can be used in combination.

[0164] Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; polyoxyethylene alkylphenyl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether; polyoxyethylene fatty acid esters such as polyoxyethylene monolaurate, polyoxyethylene monostearate, and polyoxyethylene monooleate; and sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, and sorbitan monostearate. Sorbitan fatty acid esters such as sorbitan monooleate; polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan triisostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, etc.; polyoxyethylene glycerol ether fatty acid esters; polyoxyethylene-polyoxypropylene block copolymers; etc. Nonionic surfactants can be reactive surfactants with free radical polymerizable functional groups such as propenyl, (meth)allyl, vinyl, and (meth)acryloyl groups (e.g., nonionic reactive surfactants such as polyoxyethylene nonylpropenyl phenyl ether). These nonionic surfactants can be used alone or in combination of two or more. From the viewpoint of properly leveraging the effect of compound A being moderately predominantly present on the surface of the adhesive layer and improving the performance stability of the adhesive sheet, it is preferable to use a (non-reactive) nonionic surfactant that does not have such free radical polymerizable functional groups as described above.

[0165] Examples of anionic surfactants include alkylbenzene sulfonates such as nonylbenzene sulfonate and dodecylbenzene sulfonate (e.g., sodium dodecylbenzene sulfonate); alkyl sulfates such as lauryl sulfate (e.g., sodium lauryl sulfate, ammonium lauryl sulfate), and octadecyl sulfate; fatty acid salts; polyoxyethylene alkyl ether sulfates such as polyoxyethylene octadecyl ether sulfate and polyoxyethylene lauryl ether sulfate (e.g., sodium polyoxyethylene alkyl ether sulfate), and polyoxyethylene alkylphenyl ether sulfates such as polyoxyethylene lauryl ether sulfate (e.g., sodium polyoxyethylene alkyl ether sulfate), and polyoxyethylene alkylphenyl ether sulfate (e.g., sodium polyoxyethylene alkyl ether sulfate). Polyoxyethylene alkylphenyl ether ammonium sulfate, polyoxyethylene alkylphenyl ether sodium sulfate, etc.; polyoxyethylene styrene phenyl ether sulfate and other polyether sulfates; polyoxyethylene stearyl ether phosphate, polyoxyethylene lauryl ether phosphate and other polyoxyethylene alkyl ether phosphates; sodium salts, potassium salts and other polyoxyethylene alkyl ether phosphate salts of the above polyoxyethylene alkyl ether phosphates; lauryl sulfosuccinate, polyoxyethylene lauryl sulfosuccinate (e.g., sodium polyoxyethylene alkyl sulfosuccinate) and other sulfosuccinates; polyoxyethylene alkyl ether acetates; etc. When anionic surfactants form salts, the salts can be, for example, metal salts (preferably monovalent metal salts) such as sodium salts, potassium salts, calcium salts, magnesium salts, ammonium salts, amine salts, etc. Anionic surfactants can be used alone or in combination of two or more. From the same viewpoint as nonionic surfactants, non-reactive anionic surfactants are preferred.

[0166] Examples of cationic surfactants include polyoxyethylene laurylamine and polyoxyethylene stearylamine, among other polyether amines. Cationic surfactants can be used alone or in combination of two or more.

[0167] Compounds with a polyoxyalkylene backbone that can be used as compound A include, for example, polyethylene glycol (PEG), polypropylene glycol (PPG), and other polyalkylene glycols; polyethers containing polyoxyethylene units, polyethers containing polyoxypropylene units, compounds containing oxyethylene units and oxypropylene units (these units can be arranged randomly or in a block configuration); their derivatives; and so on. Additionally, compounds with a polyoxyalkylene backbone from the aforementioned nonionic, anionic, and cationic surfactants can also be used. They can be used alone or in combination of two or more. Among these, compounds containing a polyoxyethylene backbone (also called polyoxyethylene segments) are preferred, and PEG is more preferred.

[0168] There is no particular limitation on the molecular weight (chemical weight) of compounds having a polyoxyalkylene backbone (e.g., polyethylene glycol). From the viewpoint of uniform mixing, it is suitable, for example, to be less than 1000, preferably about 600 or less (e.g., 500 or less). There is no particular limitation on the lower limit of the molecular weight of compounds having a polyoxyalkylene backbone (e.g., polyethylene glycol), but compounds with a molecular weight of about 100 or more (e.g., about 200 or more, and further about 300 or more) are preferred.

[0169] An adhesive layer containing compound A can typically be formed from an adhesive composition containing compound A. The adhesive composition containing compound A is preferably prepared by a method including adding compound A in a solvent-free form or in the form of an organic solvent solution. The term "solvent-free form" refers to a form that is not diluted by an organic solvent or water that does not form an adhesive layer, such as a form formed from compound A. The organic solvent used in the preparation of the organic solvent solution can be appropriately selected from existing known organic solvents. Specific examples of the organic solvent mentioned above include the same solvent used in the solution polymerization described later. Preferred examples include ethyl acetate, mixed solvents containing ethyl acetate (which may be a mixture of ethyl acetate and toluene), toluene, and mixed solvents containing toluene. For example, ethyl acetate or a mixed solvent with ethyl acetate as the main component is preferably used. For solvent-based or active energy ray-cured adhesive compositions, from the viewpoint of preventing the introduction of water into the adhesive composition, in some ways, it is preferable to add compound A in the form of a substantially water-free organic solvent solution (e.g., the water content is less than 10 parts by weight, less than 5 parts by weight, or less than 1 part by weight relative to 100 parts by weight of compound A). This results in the formation of an adhesive layer with higher uniformity.

[0170] In some approaches, nonionic compounds, such as compound A, are preferred for their ease of uniform incorporation into the adhesive composition. With an adhesive composition incorporating compound A in good uniformity, there is a tendency to form an adhesive layer in which compound A is uniformly present on the surface. This is preferable from the viewpoint of facilitating smoother peeling of the adhesive sheet from the adhered object and reducing the load on the adhered object caused by variations in peel force (e.g., vibrations or impacts accompanying such variations).

[0171] There are no particular limitations on the HLB of compound A. The HLB of compound A can be, for example, 1 or more, or 3 or more. The HLB of compound A is preferably 5 or more, and can be 6 or more, 8 or more, or 9 or more. This tends to result in suitable water-stripping properties. The HLB of compound A is more preferably 10 or more, further preferably 11 or more, even more preferably 12 or more, particularly preferably 13 or more, can be 14 or more, 15 or more, and even more than 16. With compound A having an HLB within the above range, light water-stripping properties can be more effectively exhibited. The upper limit of the above HLB is 20 or less, for example, 18 or less. In some embodiments, for example from a compatibility viewpoint, the HLB of compound A can be 16 or less, for example, 15 or less.

[0172] It should be noted that HLB in this specification refers to the hydrophilic-lipophilic balance (HLB) proposed by Griffin, which is a value representing the degree of affinity of a surfactant for water and oil, expressed as a ratio of hydrophilicity to lipophilicity between 0 and 20. The definition of HLB is as described in W.G. Griffin: J. Soc. Cosmetic Chemists, 1, 311 (1949), and in "Surfactant Handbook," 3rd edition, published by Kogaku Toshosha, November 25, 1972, pp. 179-182, co-authored by Takahashi Koshimitsu, Naniwa Yoshiro, Koike Motoo, and Kobayashi Masao. Compound A having the above HLB can be selected based on the above references and the technical knowledge of those skilled in the art.

[0173] In some embodiments, compound A, from the viewpoint of affinity with aqueous stripping liquid, is preferably a compound having two or more hydroxyl groups per molecule, and more preferably a compound having three or more hydroxyl groups per molecule. Examples of compound A having two or three or more hydroxyl groups per molecule include sorbitan monoester, polyoxyalkylene sorbitan monoester, polyoxyalkylene glycerol ether, polyoxyalkylene diglycerol ether, and polyoxyalkylene glycerol ether monoester. There is no particular upper limit to the number of hydroxyl groups in compound A per molecule. From the viewpoint of solubility in organic solvents and ease of preparation of the adhesive composition, it is generally suitable to have 10 or less, preferably 8 or less, 6 or less, or 4 or less.

[0174] In some approaches, from the viewpoint of solubility in organic solvents (e.g., esters such as ethyl acetate), a nonionic compound having a fatty acid ester structure is preferred as compound A. Compound A having a fatty acid ester structure also becomes advantageous in terms of compatibility within the adhesive layer. For example, as compound A contained in an acrylic adhesive layer, compound A having a fatty acid ester structure is preferred. Examples of nonionic compounds having a fatty acid ester structure include sorbitan fatty acid esters, polyoxyalkylene fatty acid esters, and polyoxyalkylene fatty acid monoesters.

[0175] In some methods, as compound A, from the viewpoint of ease of preparation of organic solvent solution, it is preferred that it be in liquid state at room temperature (25°C) in the form of 100% solid component.

[0176] In some methods, compound A is preferably a compound that dissolves without phase separation in Test II below, and more preferably a compound that dissolves without phase separation in Test I below. It should be noted that in Tests I and II below, compound A is used in 100% solid form and is carried out at room temperature (23-25°C).

[0177] [Experiment I]

[0178] Place 90g of ethyl acetate and 10g of compound A into a 200ml container, stir with a glass rod for 1 minute, then let stand. After 5 minutes, observe visually whether phase separation has occurred.

[0179] [Experiment II]

[0180] 90g of ethyl acetate and 10g of compound A were placed in a 200mL container and stirred with a glass rod for 1 minute. Then, the mixture was treated with an ultrasonic disperser at 35kHz for 10 minutes, stirred with a glass rod for another minute, and then allowed to stand. After 5 minutes, the presence or absence of phase separation was observed visually.

[0181] It should be noted that, as an ultrasonic dispersion device, the "ULTRASONIC CLEANER" machine model manufactured by AS ONE or an equivalent device can be used.

[0182] There is no particular limitation on the amount of compound A used, and it can be set in a way that effectively results in a decrease in peel strength due to the supply of the aqueous stripper. In some cases, the amount of compound A used, relative to 100 parts by weight of the base polymer, can be, for example, about 5 parts by weight or less. From the viewpoint of bonding reliability and water resistance reliability of the adherends in the undesirable peeling stage, it is suitable to be 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. For compound A with a high HLB (e.g., 5 or more, preferably 10 or more), even a small amount tends to easily exhibit good water-peelability. Furthermore, the amount of compound A relative to 100 parts by weight of the base polymer can be, for example, 0.001 parts by weight or more. From the viewpoint of ensuring that compound A is uniformly present on the surface of the adhesive layer and that the adhesive sheet can be peeled off from the adhered object more smoothly, it is generally suitable to be 0.01 parts by weight or more, preferably 0.03 parts by weight or more (e.g., 0.1 parts by weight or more). In compositions where water-repellent properties are important, the amount of compound A relative to 100 parts by weight of the base polymer can be 0.3 parts by weight or more (e.g., 0.5 parts by weight or more).

[0183] (Cross-linking agent)

[0184] In the adhesive layer (which may be a curable adhesive layer, preferably an active energy radiation-curable adhesive layer), a crosslinking agent may be used as needed for purposes such as adjusting cohesion. In adhesive sheets that can be peeled using the peeling method disclosed in this specification, the crosslinking agent may be included in the adhesive layer in either its post-crosslinking form or its pre-crosslinking form before the application of the first peel force reduction means. There are no particular limitations on the type of crosslinking agent; for example, it may be selected from known crosslinking agents according to the composition of the adhesive composition and in a manner that allows the crosslinking agent to perform an appropriate crosslinking function within the adhesive layer. Examples of usable crosslinking agents 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. One type may be used alone, or two or more may be used in combination. In some preferred embodiments, at least an isocyanate-based crosslinking agent is used as the crosslinking agent. The isocyanate-based crosslinking agent can be used in combination with other crosslinking agents (e.g., epoxy-based crosslinking agents).

[0185] As isocyanate-based crosslinking agents, multifunctional isocyanate compounds with two or more functions can be used. Examples include aromatic isocyanates such as toluene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris(p-isocyanatophenyl) thiophosphate, and diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as 1,6-hexanediisocyanate; etc. Commercially available examples include trimethylolpropane / toluene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), trimethylolpropane / 1,6-hexanediisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate HL"), and isocyanurate derivatives of 1,6-hexanediisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX"), etc.

[0186] As epoxy crosslinking agents, epoxy crosslinking agents having two or more epoxy groups per molecule can be used without particular limitation. Epoxy crosslinking agents having three to five epoxy groups per molecule are preferred. Specific examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-phenylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether. Commercially available epoxy crosslinking agents include those manufactured by Mitsubishi Gas Chemical Co., Ltd. under the trade names "TETRAD-X" and "TETRAD-C", manufactured by DIC under the trade name "EPICLON CR-5L", manufactured by Nagase ChemteX Corporation under the trade name "Denacol EX-512", and manufactured by Nissan Chemical Industries Co., Ltd. under the trade name "TEPIC-G".

[0187] As an oxazoline crosslinking agent, oxazoline crosslinking agents having more than one oxazoline group per molecule can be used without particular restrictions.

[0188] Examples of aziridine-based crosslinking agents include trimethylolpropane tris[3-(1-aziridine)propionate] and trimethylolpropane tris[3-(1-(2-methyl)aziridine propionate)].

[0189] As a carbodiimide-based crosslinking agent, low-molecular-weight compounds or high-molecular-weight compounds having two or more carbodiimide groups can be used.

[0190] Metal chelate crosslinking agents are typically substances having a structure formed by covalent or coordinate bonding of a multivalent metal with an organic compound. Examples of such multivalent metal atoms include Al, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Ba, Mo, La, Sn, and Ti. Al, Zr, and Ti are preferred. Examples of such organic compounds include alkyl esters, alcohols, carboxylic acids, ethers, and ketones. Metal chelate crosslinking agents are typically compounds in which the oxygen atom of the organic compound is bonded (covalently or coordinately) to the aforementioned multivalent metal.

[0191] In some methods, peroxides can be used as crosslinking agents. Examples of peroxides include di(2-ethylhexyl) peroxydicarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, disec-butyl peroxydicarbonate, tert-butyl peroxyneodecanate, tert-hexyl peroxyneopentate, tert-butyl peroxyneopentate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxyisobutyrate, and benzoyl peroxide. Among these, di(4-tert-butylcyclohexyl) peroxydicarbonate, dilauroyl peroxide, and benzoyl peroxide are examples of peroxides with particularly excellent crosslinking reaction efficiency. It should be noted that when using peroxides as the above-mentioned polymerization initiators, the peroxide residues that were not used in the polymerization reaction can also be used in the crosslinking reaction. In this case, the residual amount of peroxide is quantified, and if the proportion of peroxide does not meet the specified amount, peroxide is added as needed to reach the specified amount. The quantification of peroxides can be performed using the method described in Japanese Patent No. 4971517.

[0192] There is no particular limitation on the amount of crosslinking agent used (the total amount of two or more crosslinking agents used). It can be set appropriately in a way that achieves the desired effect.

[0193] From the viewpoint of adhesion and bonding reliability of the adherend before applying the first peel force reduction method, the amount of crosslinking agent used relative to 100 parts by weight of the base polymer (e.g., acrylic polymer) is generally suitable to be 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 can 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 the case of compound A containing a certain amount (e.g., more than 0.2 parts by weight relative to 100 parts by weight of the base polymer), it is also advantageous from the viewpoint of avoiding contamination of the adherend due to excessive presence of compound A on the surface of the adhesive layer, provided that the amount of crosslinking agent used is not excessive.

[0194] Furthermore, for example, in the case of an adhesive sheet having an adhesive surface composed of an active energy ray-curable adhesive layer, from the viewpoint of exhibiting adequate cohesiveness before curing treatment based on active energy ray irradiation (which can be a first peel force reduction means), the amount of crosslinking agent used relative to 100 parts by weight of the base polymer (e.g., an acrylic polymer) is generally suitable to be about 0.005 parts by weight or more, preferably about 0.01 parts by weight or more, and can be about 0.05 parts by weight or more, about 0.1 parts by weight or more, or about 0.2 parts by weight or more. In some embodiments, the amount of crosslinking agent used relative to 100 parts by weight of the base polymer is preferably greater than 0.3 parts by weight, more preferably greater than 0.5 parts by weight, and can be greater than 1.0 parts by weight, greater than 1.5 parts by weight, greater than 2.0 parts by weight, greater than 3.0 parts by weight, or greater than 4.0 parts by weight. For adhesive sheets that can be peeled off by a peeling method that includes the step of irradiating active energy rays as a first means of reducing peeling force and the step of supplying an aqueous peeling liquid as a second means of reducing peeling force, when the amount of crosslinking agent used increases, the strain caused by curing shrinkage will be more easily maintained until the supply of the aqueous peeling liquid, and the light peeling effect brought about by the application of the water peeling method can be better utilized.

[0195] In the use of isocyanate-based crosslinking agents, from the viewpoint of exhibiting appropriate cohesiveness before curing, the amount of isocyanate-based crosslinking agent used relative to 100 parts by weight of the base polymer is typically suitable to be about 0.005 parts by weight or more, preferably about 0.01 parts by weight or more, and can be about 0.05 parts by weight or more, about 0.1 parts by weight or more, about 0.2 parts by weight or more, greater than 0.3 parts by weight, greater than 0.5 parts by weight, greater than 1.0 parts by weight, greater than 1.5 parts by weight, greater than 2.0 parts by weight, greater than 3.0 parts by weight, or greater than 4.0 parts by weight. For adhesive sheets that can be peeled by a peeling method including the step of irradiating with active energy rays as a first peeling force reduction means and the step of supplying an aqueous peeling liquid as a second peeling force reduction means, increasing the amount of isocyanate-based crosslinking agent used can better exert the light peeling effect brought about by the application of the water peeling method.

[0196] Furthermore, the amount of isocyanate-based crosslinking agent used relative to 100 parts by weight of the base polymer is generally suitable to be about 15 parts by weight or less. From the viewpoint of adhesion and bonding reliability to the adherend before applying the first peel force reduction method, it is preferably about 12 parts by weight or less, more preferably about 10 parts by weight or less, and can 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 the case of compound A containing a certain amount (for example, more than 0.2 parts by weight relative to 100 parts by weight of the base polymer), it is also advantageous from the viewpoint of avoiding contamination of the adherend due to excessive presence of compound A on the surface of the adhesive layer, provided that the amount of isocyanate-based crosslinking agent used is not excessive.

[0197] To make the crosslinking reaction proceed more efficiently, a crosslinking catalyst can be used. Examples of crosslinking catalysts include tetrabutyl titanate, tetraisopropyl titanate, iron acetylacetone, butyltin oxide, and dioctyltin dilaurate, among other metal-based crosslinking catalysts. Tin-based crosslinking catalysts, such as dioctyltin dilaurate, are preferred. There is no particular limitation on the amount of crosslinking catalyst used. The amount of crosslinking catalyst used relative to 100 parts by weight of the base polymer can be, for example, about 0.0001 parts by weight or more and 1 part by weight, 0.001 parts by weight or more and 0.1 parts by weight, or 0.005 parts by weight or more and 0.5 parts by weight or less.

[0198] (Multifunctional monomer)

[0199] In the adhesive layer, multifunctional monomers may be used as needed. Multifunctional monomers, used in place of or in combination with crosslinking agents, can function to adjust cohesiveness and other purposes. Compounds having two or more carbon-carbon double bonds (e.g., olefinic unsaturated groups such as (meth)acryloyl groups) can be used as multifunctional monomers. Multifunctional monomers can be included in the adhesive layer in an unreacted form or in a reacted (crosslinked) form. An adhesive layer containing unreacted multifunctional monomers can be a radioactive ray-cured adhesive layer: by irradiating the adhesive layer with radioactive rays such as ultraviolet light, the multifunctional monomers react, thereby forming a crosslinked structure. Alternatively, an adhesive layer containing unreacted multifunctional monomers can be a thermosetting adhesive layer: by heating the adhesive layer, the multifunctional monomers react, thereby forming a crosslinked structure.

[0200] Examples of multifunctional 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 methacrylate, ethylene methacrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butanediol (meth)acrylate, and hexanediol di(meth)acrylate. Among them, trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate may be used appropriately. One multifunctional monomer may be used alone or in combination of two or more.

[0201] The appropriate amount of multifunctional monomer used varies depending on its molecular weight, number of functional groups, etc., but is generally suitable in the range of about 0.01 parts by weight to 3.0 parts by weight relative to 100 parts by weight of the base polymer (e.g., acrylic polymers). In some cases, the amount of multifunctional monomer used relative to 100 parts by weight of the base polymer can 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 multifunctional monomer used, there is a tendency to obtain higher cohesive strength. On the other hand, from the viewpoint of avoiding a decrease in the adhesion to the adhered material and a decrease in the storage stability of the adhesive sheet due to excessive increase in cohesive strength, the amount of multifunctional monomer used relative to 100 parts by weight of the base polymer can 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, multifunctional monomers may not be used. For example, an adhesive layer comprising a polymer having a structure that undergoes a cross-linking reaction upon irradiation by active energy rays (carbon-carbon double bonds, benzophenone structures, etc.) can be an adhesive layer that substantially does not contain unreacted polyfunctional monomers, or an adhesive layer formed from an adhesive composition that substantially does not contain polyfunctional monomers. Here, "the adhesive composition substantially does not contain polyfunctional monomers" means that the amount of polyfunctional monomers is less than 0.05 parts by weight (e.g., less than 0.01 parts by weight) relative to 100 parts by weight of the base polymer.

[0202] (Other optional ingredients)

[0203] The adhesive layer (which can be a curable adhesive layer, preferably an active energy radiation-curable adhesive layer) may, as needed, contain tackifying resins (e.g., tackifying resins based on rosin, petroleum, terpenes, phenols, ketones, etc.), viscosity modifiers (e.g., tackifiers), leveling agents, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, antioxidants, anti-aging agents, and various other additives conventional in the field of adhesives as optional components. Such additives can be obtained using conventional methods with existing known additives; detailed descriptions are omitted as these are not substances that particularly characterize the present invention.

[0204] From the viewpoint of simultaneously achieving a good balance between the adhesion to the adherend before applying the first peel force reduction method and the excellent peelability resulting from applying the peeling method disclosed in this specification (e.g., peelability in a peeling method where an aqueous peeling liquid is supplied as a second peel force reduction method), in some embodiments, the content of the tackifying resin in the adhesive layer is, for example, less than 5 parts by weight, and further 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. It can be an adhesive layer that substantially does not contain tackifying resin (e.g., 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 tackifying resin as described above can also become advantageous, for example, from the viewpoint of improving the curability of the active energy ray-curable adhesive layer.

[0205] In some preferred embodiments, the adhesive layer may contain a polymer (typically a base polymer) comprising about 80% by weight or more of the total weight of the adhesive layer. This ideally achieves the effect of reduced peel force when water is applied for peeling (a gentler peeling effect). From this perspective, the polymer content is preferably about 85% by weight or more of the total weight of the adhesive layer, more preferably about 90% by weight or more, about 92% by weight or more, or about 95% by weight or more.

[0206] (Active energy radiation curable adhesive layer)

[0207] In some of the peeling methods disclosed in this specification, the adhesive layer constituting at least one adhesive surface of the adhesive sheet used in the peeling method is preferably an adhesive layer composed of an active energy radiation-curable adhesive (active energy radiation-curable adhesive layer). Preferably, the active energy radiation-curable adhesive layer is configured such that it is cured by irradiating the adherend with active energy radiation after attachment, thereby reducing the peeling force from the adherend compared to before irradiation. For adhesive sheets having such an active energy radiation-curable adhesive layer, the bonding reliability with respect to the adherend is good before irradiation with active energy radiation, and the peeling force from the adherend decreases rapidly after irradiation with active energy radiation (preferably followed by the supply of an aqueous peeling liquid). Therefore, for adhesive sheets having adhesive surfaces composed of an active energy radiation-curable adhesive layer, a peeling method that cures the adhesive layer by applying irradiation with active energy radiation as a first peeling force reduction means, and then supplies an aqueous peeling liquid as a second peeling force reduction means for peeling, can particularly effectively reduce the peeling force from the adherend.

[0208] A preferred example of an active energy ray-curable adhesive layer is one in which curing properties are achieved by including carbon-carbon double bonds within the adhesive layer. Carbon-carbon double bonds are chemically stable and do not react with moisture or acidity in the air under typical storage conditions suitable for industrial applications. On the other hand, when free radicals are generated by irradiation with active energy rays, reactions (e.g., polymerization, crosslinking) occur, resulting in curing. From the viewpoint of ease of handling, light (e.g., ultraviolet light) is a preferred active energy ray.

[0209] In an adhesive layer that achieves curability by incorporating carbon-carbon double bonds, the form in which the carbon-carbon double bonds exist is not particularly limited. These carbon-carbon double bonds can be incorporated into the adhesive layer, for example, in the form of polymers (e.g., base polymers) or monomers (e.g., unreacted multifunctional monomers as described above). They can be used individually or in combination of two or more.

[0210] There are no particular restrictions on the form of carbon-carbon double bonds in polymers or monomers. For example, carbon-carbon double bonds can exist in polymers or monomers as olefinic unsaturated groups. Examples of olefinic unsaturated groups include (meth)acryloyl, vinyl, allyl, and methanallyl. From a reactivity point of view, (meth)acryloyl is preferred.

[0211] (Polymers with carbon-carbon double bonds)

[0212] In some embodiments, the active energy radiation-curable adhesive layer preferably comprises a polymer having carbon-carbon double bonds. Hereinafter, polymers having carbon-carbon double bonds will also be referred to as "polymers (PD)". For example, polymers (PD) having carbon-carbon double bonds in the form of olefinic unsaturated groups are preferred. In some preferred embodiments, the polymer (PD) may be included in the active energy radiation-curable adhesive layer as the base polymer of the adhesive layer. In other embodiments, the polymer (PD) may be included in the active energy radiation-curable adhesive layer as a by-product, used in addition to a base polymer that does not contain carbon-carbon double bonds. An active energy radiation-curable adhesive layer may contain a polymer (PD) as the base polymer and subsequently a monomer having carbon-carbon double bonds (e.g., an unreacted polyfunctional monomer) as a by-product.

[0213] There are no particular limitations on the morphology of the carbon-carbon double bonds in the polymer (PD). The polymer (PD) can be a polymer with carbon-carbon double bonds in its side chains or a polymer with carbon-carbon double bonds in its main chain. Here, "having carbon-carbon double bonds in the main chain" includes the presence of carbon-carbon double bonds in the main chain backbone of the polymer (PD) or at the ends of the main chain. From the viewpoint of the reactivity of carbon-carbon double bonds, polymers (PDs) with carbon-carbon double bonds in their side chains are preferred. There are no particular limitations on the method of incorporating carbon-carbon double bonds into the polymer (PD), and appropriate methods can be selected from those known to those skilled in the art.

[0214] There are no particular limitations on the polymer (PD), and an appropriate polymer can be selected based on factors such as the properties of the adhesive layer. As a polymer (PD), a polymer (secondary polymer) obtained by introducing carbon-carbon double bonds into a primary polymer (which does not contain carbon-carbon double bonds or has a lower content of carbon-carbon double bonds than the target material) through chemical modification or other methods is preferred.

[0215] As a specific example of a method for introducing carbon-carbon double bonds into a primary polymer, the following method can be cited: A primary polymer obtained by copolymerizing a monomer having a functional group (functional group A) is prepared, and the primary polymer is reacted with a compound (hereinafter also referred to as "an unsaturated compound containing functional group B") having a functional group (functional group B) capable of reacting with functional group A and a carbon-carbon double bond within one molecule, in a manner that the carbon-carbon double bond is not lost. The reaction between functional group A and functional group B is preferably a condensation reaction, addition reaction, or other reaction that does not involve the generation of free radicals.

[0216] Examples of combinations of functional groups A and B include combinations of carboxyl and epoxy groups, combinations of carboxyl and aziridinyl groups, and combinations of hydroxyl and isocyanate groups. From the viewpoint of reaction traceability, the combination of hydroxyl and isocyanate groups is preferred. Furthermore, any combination of functional groups A and B that yields a polymer with a carbon-carbon double bond is acceptable. One functional group in the combination can be functional group A, and the other functional group can be functional group B, or one functional group can be functional group B, and the other functional group can be functional group A. For example, if we use the combination of hydroxyl and isocyanate groups, functional group A can be either hydroxyl (in which case, functional group B becomes an isocyanate group) or an isocyanate group (in which case, functional group B becomes a hydroxyl group). Preferably, the primary polymer has a hydroxyl group and the compound has an isocyanate group. This combination is particularly preferred when the primary polymer is an acrylic polymer.

[0217] Another preferred example of a method for obtaining a polymer having carbon-carbon double bonds is the following method: using a vinyl alcohol-based polymer (typically polyvinyl alcohol) as the primary polymer, the vinyl alcohol-based polymer (typically a vinyl alcohol-based polymer without carbon-carbon double bonds) is reacted with vinyl halides such as vinyl bromide and allyl halides such as allyl bromide. In this method, the reaction can be carried out under appropriate alkaline conditions, and through this reaction, a vinyl alcohol-based polymer containing vinyl groups in its side chains can be obtained. Alternatively, for example, a method for preparing a polymer having carbon-carbon double bonds can be used, employing polymer-producing microorganisms as disclosed in Japanese Patent No. 4502363. Various conditions in this method, such as the type of microorganism and the microbial culture conditions, can be set using the conditions described in the aforementioned patent publication, or appropriately modified within the scope of the technical knowledge of those skilled in the art.

[0218] For the molar (M) of the aforementioned functional group A A ) and the molar of functional group B (M B molar ratio (M) A / M B From the perspective of the reactivity of both, a molar ratio of 0.2 or higher is generally suitable, but can be 0.5 or higher, 0.7 or higher, or 1.0 or higher. In some methods, the molar ratio (M... A / M B The molar ratio (M) can be greater than 1.0, greater than 1.5, or greater than 2.0. For example, when functional group A is applied to other reactions (such as crosslinking reactions with crosslinking agents), it is preferable to make the molar ratio (M) greater than 1.0, greater than 1.5, or greater than 2.0. A / M B The molar ratio (M) is greater than 1.0. A / M B For example, it can be below 20. In some approaches, from the viewpoint of simultaneously achieving good balance between the adhesion to the substrate before light irradiation and the peelability from the substrate after light irradiation (e.g., peelability based on water peeling), the molar ratio (M) A / M B The value is preferably below 10, but can be below 5.0, below 2.5, below 1.8, below 1.5, or below 1.3.

[0219] Regarding the amount of compound containing functional group B and carbon-carbon double bonds (hereinafter also referred to as "unsaturated compound containing functional group B") used, in accordance with the above molar ratio (M... A / M BWithin the range of [specific range], relative to 100 parts by weight of the primary polymer having functional group A, the amount can be, for example, 1.0 parts 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. From the viewpoint of simultaneously achieving a higher level of adhesion before light irradiation and peelability after light irradiation (e.g., peelability based on water peeling), in some methods, the amount of the unsaturated compound containing functional group B 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, 12 parts by weight or more, 14 parts by weight or more, or 16 parts by weight or more. Furthermore, the amount of the unsaturated compound containing functional group B used relative to 100 parts by weight of the primary polymer can, for example, be less than 40 parts by weight, typically less than 35 parts by weight, preferably less than 30 parts by weight, less than 25 parts by weight, or less than 20 parts by weight. In some methods, the amount of the unsaturated compound containing functional group B used relative to 100 parts by weight of the primary polymer may 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.

[0220] As a preferred example of a polymer having carbon-carbon double bonds, an acrylic polymer having (meth)acryloyl groups introduced into its side chain can be cited. Such an acrylic polymer can be obtained, for example, by reacting an acrylic primary polymer having hydroxyl groups (functional group A) introduced through copolymerization with a compound having carbon-carbon double bonds and isocyanate groups (functional group B) in a manner that does not cause the carbon-carbon double bonds to disappear.

[0221] Additionally, polymers having carbon-carbon double bonds can be diene polymers (typically, conjugated diene polymers). Diene polymers (typically, conjugated diene polymers) are polymers obtained by polymerizing or copolymerizing dienes (typically, conjugated dienes). Examples of diene polymers (typically, conjugated diene polymers) include butadiene polymers such as polybutadiene and styrene-butadiene copolymers; isoprene polymers such as polyisoprene and styrene-isoprene copolymers; chloroprene polymers such as polychloroprene; and so on.

[0222] Other examples of ray-curable adhesive layers include adhesive layers comprising polymers having structures other than carbon-carbon double bonds that are crosslinked by irradiation with ray-cured materials. For example, adhesives comprising polymers having a benzophenone structure in their side chains can exhibit ray-curability by photocrosslinking using the aforementioned benzophenone structure. Acrylic polymers having a benzophenone structure in their side chains are preferably preferred as polymers.

[0223] (Photoinitiator)

[0224] When using ultraviolet light as the active energy ray for curing the active energy ray-curable adhesive layer, from the viewpoint of promoting reaction or improving the utilization efficiency of light energy, it is preferable to contain a photoinitiator in the adhesive layer.

[0225] Examples of photoinitiators include benzoin ether-based photoinitiators, acetophenone-based photoinitiators, α-hydroxyketone-based photoinitiators, aromatic sulfonyl chloride-based photoinitiators, photoactive oxime-based photoinitiators, benzoin-based photoinitiators, benzoyl-based photoinitiators, benzophenone-based photoinitiators, ketal-based photoinitiators, thioxanone-based photoinitiators, α-aminoketone-based photoinitiators, and acylphosphine oxide-based photoinitiators. A single photoinitiator can be used alone, or two or more can be used in combination.

[0226] Examples of benzoin ether-based 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-based photoinitiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxy-cyclohexyl-phenyl ketone, 4-phenoxydichloroacetophenone, and 4-tert-butyl-dichloroacetophenone. Examples of α-hydroxyketone-based photoinitiators include 2-hydroxy-2-methyl-1-phenyl-propane-1-one and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one. Examples of aromatic sulfonyl chloride-based photoinitiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime photoinitiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of benzoin-based photoinitiators include benzoin. Examples of benzoyl-based photoinitiators include benzoyl. Examples of benzophenone-based photoinitiators include benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. Examples of ketal-based photoinitiators include benzoyldimethyl ketal. Examples of thioxanthone-based photoinitiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. Examples of α-aminoketone-based photoinitiators include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone. Examples of acylphosphine oxide-based photoinitiators include 2,4,6-trimethylbenzoyl diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

[0227] Commercially available products can be used as photoinitiators. Examples include those manufactured by IGM Regins under the trade names "Omnirad 651", "Omnirad 184", "Omnirad 2959", "Omnirad 907", "Omnirad 369", "Omnirad 1173", and "Omnirad TPO".

[0228] In some methods, photoinitiators that are not easily decomposed or generate free radicals upon heating are preferred. For example, a photoinitiator with a heat resistance of 10% by weight at a reduction temperature of 200°C or higher can be used. By using such a heat-resistant photoinitiator, the reduction in peel strength resulting from curing based on active energy rays is less likely to be impaired even when exposed to high temperatures before curing. It should be noted that the 10% by weight reduction in temperature refers to the ambient temperature at which the weight of the photoinitiator decreases by 10% by weight relative to its weight before heating (i.e., the weight of the photoinitiator becomes 90% by weight relative to its weight before heating) when the ambient temperature is increased from 23°C to 300°C at a heating rate of 2°C / min under a nitrogen atmosphere. The 10% by weight reduction temperature of the photoinitiator is more preferably 210°C or higher, and even more preferably 220°C or higher. Examples of photoinitiators that reduce the temperature range by 10% by weight include, for example, those manufactured by IGM Regins under the trade names “Omnirad 369”, “Omnirad 127”, “Omnirad 379”, and “Omnirad 819”; those manufactured by BASF Japan under the trade name “IrgacureOXE02”; those manufactured by Lamberti under the trade names “Esacur one” and “Esacur 1001m”; and those manufactured by Asahi Denka Kogyo under the trade names “ADEKA OPTOMER N-1414”, “ADEKA OPTOMER N-1606”, and “ADEKA OPTOMER N-1717”.

[0229] An adhesive layer containing a photoinitiator can be formed using an adhesive composition containing the photoinitiator. There are no particular limitations on the method of including the photoinitiator in the adhesive composition. For example, a photoinitiator can be added to an adhesive composition, typically a liquid containing a polymer (a polymerized polymer), and the mixture can be stirred. In this method, the photoinitiator can be added to the composition along with other additives (e.g., crosslinking agents). Another method is to add a polymerization initiator that functions as a photoinitiator during polymer polymerization. In this method, the polymerization initiator can be added in such a way that a predetermined amount remains after polymerization. The residual amount of the polymerization initiator (the amount of photoinitiator present) can be adjusted not only by the amount of polymerization initiator added, but also by the polymer polymerization conditions, the drying conditions during adhesive layer formation, the curing conditions, etc.

[0230] When the adhesive layer contains a photoinitiator, the content of the photoinitiator in the adhesive layer is not particularly limited and can be set in a way that appropriately achieves the desired effect. In some embodiments, the content of the photoinitiator, relative to 100 parts by weight of the base polymer of the adhesive layer, can 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. By increasing the content of the photoinitiator, there is a tendency to improve the curability of the adhesive layer to active energy rays. In some embodiments, the content of the photoinitiator, relative to 100 parts by weight of the base polymer, can be, for example, about 0.8 parts by weight or more, about 2.0 parts by weight or more, or 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, typically, preferably about 10 parts by weight or less, preferably about 8 parts by weight or less, about 6 parts by weight or less, or about 4 parts by weight or less. When the content of photoinitiator is not excessive, it is preferable from the viewpoint of the preservation stability of the adhesive layer (e.g., the ability to suppress performance changes caused by the preservation of the adhesive layer before it is attached to the substrate).

[0231] (irradiation conditions)

[0232] There are no particular restrictions on the irradiation conditions of the active energy rays; they can be set in a manner that allows the adhesive layer to cure properly. Those skilled in the art can set appropriate irradiation conditions without undue burden based on common technical knowledge in the field, therefore detailed descriptions are omitted. As an example, when using UV as the active energy ray, for example, the cumulative light intensity can be set to approximately 50 mJ / cm². 2 ~5000mJ / cm 2 The range is approximately 50 mJ / cm. 2 ~2000mJ / cm 2 The range, or approximately 100 mJ / cm 2 ~2000mJ / cm 2 The range allows for irradiation times ranging from approximately 1 second to 30 minutes.

[0233] (Thermosetting adhesive layer)

[0234] The peeling method disclosed in this specification can also be implemented by peeling an adhesive sheet, whose adhesive layer constituting the bonding surface (adhesive surface) to the adhered object is a thermosetting adhesive layer, from the adhered object. In the above method, as a means of reducing peeling force, a heat treatment is preferably performed to cure the thermosetting adhesive layer constituting the adhesive surface by heating. This heat treatment can be implemented as a first means of reducing peeling force or as a second means of reducing peeling force. As one embodiment of the peeling method disclosed in this specification, an example is performing a heat treatment as a first means of reducing peeling force and supplying an aqueous peeling liquid as a second means of reducing peeling force (water peeling of the adhesive sheet).

[0235] Thermosetting adhesive layers are typically cured by heating to react the thermosetting functional groups, thereby forming a cross-linked structure. To promote the reaction of these thermosetting functional groups, a curing catalyst may be included in the thermosetting adhesive layer as needed. For example, for thermosetting adhesive layers containing carbon-carbon double bonds (such as olefinic unsaturated groups) as thermosetting functional groups, known thermal polymerization initiators such as azo polymer initiators and peroxide polymer initiators may be included as the curing catalyst. The composition of the thermosetting adhesive layer and the conditions of the heat treatment as a means of reducing peel strength can be selected in a way that appropriately exerts the peel strength reduction effect based on the heat treatment.

[0236] (An adhesive layer that can have its bonding surface textured by heating)

[0237] The peeling method disclosed in this specification can also be implemented by peeling an adhesive layer having an adhesive layer that can be made uneven by heating from the adherend. In the above method, as a means of reducing peel force, a heat treatment that makes the adhesive surface uneven is preferred. This heat treatment can be implemented as a first means of reducing peel force or as a second means of reducing peel force. The unevenness of the adhesive surface can be achieved, for example, by containing known thermally expandable microspheres in the adhesive layer and expanding these microspheres by heating. A foaming agent can be used instead of the thermally expandable microspheres, or they can be used together. As one method of the peeling method disclosed in this specification, an example is to perform active energy ray irradiation treatment as a first means of reducing peel force and a heat treatment that makes the adhesive surface uneven as a second means of reducing peel force. The composition of the adhesive layer that can make the adhesive surface uneven by heating and the conditions of the heat treatment as a means of reducing peel force can be selected in a way that appropriately exerts the peel force reduction effect based on the heat treatment.

[0238] <Formation of Adhesive Layer>

[0239] The adhesive layer of the adhesive sheet used in the peeling method disclosed in this specification (which may be a curable adhesive layer, preferably an active energy radiation-curable adhesive layer) may be an adhesive layer formed from an adhesive composition comprising a base polymer (e.g., an acrylic polymer) and, if necessary, other optional components. The adhesive composition may be in various forms, including: a solvent-based adhesive composition containing the adhesive (adhesive component) in an organic solvent; an active energy radiation-curable adhesive composition prepared by curing with active energy rays such as ultraviolet light or radiation to form an adhesive; an aqueous dispersion adhesive composition in which the adhesive is dispersed in water; a hot-melt adhesive composition that is applied in a molten state and forms an adhesive upon cooling to near room temperature; and so on. It should be noted that the aforementioned active energy radiation-curable adhesive composition is typically a liquid composition that exhibits a degree of fluidity suitable for application at room temperature (approximately 0°C to 40°C, for example, around 25°C) and is cured by irradiation with active energy rays to form an adhesive (viscoelastic).

[0240] Some methods involve adhesive sheets that have an adhesive layer formed using a solvent-based adhesive composition or an active energy ray curable adhesive composition. From the viewpoint of ease of controlling the curability of the active energy ray curable adhesive layer, a solvent-based adhesive composition is preferred as the adhesive composition used to form the active energy ray curable adhesive layer.

[0241] The adhesive layer of the adhesive sheet used in the peeling method disclosed in this specification can be formed by applying an adhesive composition to a suitable surface (e.g., coating) and then appropriately performing a curing treatment (drying, crosslinking, polymerization, etc.). If two or more curing treatments are performed, they can be performed simultaneously or in multiple steps. Multilayer adhesive layers with two or more layers can be fabricated by bonding pre-formed adhesive layers together. Alternatively, an adhesive composition can be applied to a pre-formed first adhesive layer and cured to form a second adhesive layer.

[0242] The coating of the adhesive composition can be carried out using conventional coating machines such as gravure roller coaters, reverse roller coaters, kiss roller coaters, dip roller coaters, bar coaters, doctor blade coaters, and spray coaters. For adhesive sheets having a support structure, as a method for forming an adhesive layer on the support, a direct method can be used to directly apply the adhesive composition to the support to form the adhesive layer, or a transfer method can be used to transfer the adhesive layer formed on the release surface to the support.

[0243] In the peeling method disclosed in this specification, the thickness of the adhesive layer in the adhesive sheet is not particularly limited and can be appropriately selected according to the purpose. Generally, a thickness of about 5 to 200 μm is suitable. From the viewpoint of adhesion, it is preferably about 10 μm or more (e.g., 15 μm or more), and can be 25 μm or more. In addition, it 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). It can be 35 μm or less or less than 30 μm. In the case of a double-sided adhesive sheet in which adhesive layers are provided on both sides of a substrate, the thickness of each adhesive layer can be the same or different.

[0244] <Additional adhesive layer>

[0245] In some of the peeling methods disclosed in this specification, the adhesive sheet used in the peeling method can be a structure formed by laminating an additional adhesive layer on the back side (the side opposite to the adhesive surface) of the adhesive layer constituting the adhesive surface. The adhesive layer constituting the adhesive surface and the additional adhesive layer are preferably laminated in direct contact. That is, it is preferable that there is no separator layer (e.g., a resin film such as a polyester film) completely separating the two adhesive layers between the adhesive layer constituting the adhesive surface and the additional adhesive layer. The additional adhesive layer can be, for example, an adhesive layer comprising one or more adhesives selected from various known adhesives such as acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, and mixtures thereof), polysiloxane adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, and fluorinated adhesives. From the viewpoint of transparency and weather resistance, in some embodiments, acrylic adhesives are preferably used as the constituent material of the additional adhesive layer. Regarding other matters concerning the additional adhesive layer, the same configuration as the adhesive layer described above may be adopted, or an appropriate configuration may be adopted based on known or conventional techniques and common technical knowledge, depending on the application and purpose. Therefore, detailed descriptions are omitted here.

[0246] <Substrate>

[0247] In single-sided or double-sided adhesive sheets with a substrate, the substrate serving as the supporting (lining) adhesive layer can be various sheet-like substrates such as resin film, paper, cloth, rubber sheet, foam sheet, metal foil, or composites thereof. The aforementioned substrate can be a single layer or a laminate of the same or different substrates. It should be noted that, in this specification, a single layer refers to a layer formed from the same composition, including layers formed by stacking multiple layers of the same composition.

[0248] In a preferred embodiment, a substrate (resin film substrate) primarily composed of resin sheets can be used. Examples of resins constituting the substrate include, for instance, low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolymer polypropylene, polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ion-crosslinked polymers, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid (random, alternating) copolymers, ethylene-butene copolymers, ethylene-hexene copolymers, and other polyolefin resins; polyurethanes; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonate; polyimide; polyetheretherketone; polyetherimide; aromatic polyamides, fully aromatic polyamides, and other polyamides; polyphenylene sulfide; fluoropolymers; polyvinyl chloride; polyvinylidene chloride; cellulose resins; polysiloxane resins; and so on. The aforementioned resins can be used alone or in combination of two or more for the formation of the entire substrate or a portion thereof (e.g., any layer of a substrate with two or more laminated structures). When the adhesive layer constituting the bonding surface is an active energy radiation-curable adhesive layer, the substrate preferably has active energy radiation transmittance. In some embodiments, a substrate with an ultraviolet transmittance of 40% to 100% (more preferably 60% to 100%) at a wavelength of 365 nm is preferred. Using a substrate with high transmittance allows the adhesive layer to cure more easily.

[0249] Depending on the requirements, various additives such as fillers (inorganic fillers, organic fillers, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, and colorants (pigments, dyes, etc.) can be added to the substrate.

[0250] The aforementioned substrate can be manufactured using any suitable method. For example, it can be manufactured using known methods such as calendering, casting, expansion extrusion, and T-die extrusion. Additionally, it can be manufactured by stretching treatment as needed.

[0251] To improve adhesion to and retention of the adhesive layer, physical treatments such as corona discharge, plasma treatment, sanding, ozone exposure, flame exposure, high-voltage electric shock exposure, and ionized radiation treatment can be applied to the adhesive layer side surface of the substrate; chemical treatments such as acid treatment, alkali treatment, and chromic acid treatment can be applied; and known or conventional surface treatments such as easy-to-bond treatment based on the coating agent (primer) can be used. Additionally, to impart antistatic properties, a conductive vapor-deposited layer containing metals, alloys, or their oxides can be formed on the substrate surface.

[0252] In some preferred embodiments, a primer layer may be provided on the adhesive layer side surface of the substrate. In other words, a primer layer may be disposed between the substrate and the adhesive layer. There are no particular limitations on the primer layer forming material; one or more of the following can be used: urethane (polyisocyanate) resins, polyester resins, acrylic resins, polyamide resins, melamine resins, olefin resins, polystyrene resins, epoxy resins, phenolic resins, isocyanurate resins, and polyvinyl acetate resins. When an acrylic or other adhesive layer is provided on a resin film substrate through a primer layer, polyester, urethane, or acrylic primer layers are preferred. When an acrylic adhesive layer is provided on a polyester substrate such as a PET film through a primer layer, a polyester primer layer is particularly preferred. The thickness of the primer layer is not particularly limited and is typically in the range of about 0.1 μm to 10 μm (e.g., 0.1 μm to 3 μm, typically 0.1 μm to 1 μm). The base coating can be formed using known or conventional coating machines such as gravure roller coating machines and reverse roller coating machines.

[0253] In the case where the adhesive sheet used in the peeling method disclosed in this specification is a single-sided adhesive sheet with an adhesive layer provided on one side of the substrate, a peeling treatment agent (back side treatment agent) can be used to peel off the non-adhesive layer forming side (back side) of the substrate. There are no particular limitations on the back side treatment agent that can be used to form the back side treatment layer; known or conventional treatment agents such as polysiloxane-based back side treatment agents, fluorine-based back side treatment agents, and long-chain alkyl-based back side treatment agents can be used depending on the purpose and application.

[0254] The thickness of the substrate is not particularly limited and can be appropriately selected depending on the purpose; typically, it can be around 3μm to 800μm. From the viewpoint of the processability and operability of the adhesive sheet (e.g., ease of application and peeling from the adherend), a substrate thickness of 5μm or more is suitable, preferably 10μm or more. From the viewpoint of improving the protection of the adherend, 20μm or more is preferred, but 30μm or more, or 40μm or more, is also acceptable. In some cases where greater emphasis is placed on protection, the substrate thickness can be, for example, 55μm or more, 75μm or more, or 90μm or more. Furthermore, from the viewpoint of reducing the load on the adherend during peeling, a substrate thickness of 300μm is generally suitable, preferably 200μm or less, but can be 150μm or less, 125μm or less, 80μm or less, or 60μm or less.

[0255] The total thickness of the adhesive sheet (which may include an adhesive layer and a substrate, but not a release liner) used in the peeling method disclosed in this specification is not particularly limited, but is suitable in the range of about 10 μm to 1000 μm. Considering adhesion and operability, the total thickness of the adhesive sheet is preferably in the range of about 15 μm to 300 μm, more preferably in the range of about 20 μm to 300 μm, and can be in the range of 20 μm to 200 μm. Furthermore, from the viewpoint of improving the protection of the adhered object, a total thickness of about 30 μm or more is advantageous, preferably about 40 μm or more, and more preferably about 50 μm or more (e.g., 60 μm or more). In some embodiments where greater emphasis is placed on protection, the total thickness of the adhesive sheet can be greater than 65 μm, greater than 80 μm, or greater than 100 μm.

[0256] <Adhesive Sheet>

[0257] (Initial peel force Fd0)

[0258] In some of the peeling methods disclosed in this specification, the initial peeling force Fd0 of the adhesive sheet used in the peeling method is preferably 0.10 N / 20 mm or more, more preferably 0.20 N / 20 mm or more, and even more preferably 0.30 N / 20 mm or more. For adhesive sheets exhibiting such characteristics, the adhesion reliability to the adhered object is good before the application of the first peeling force reduction means. The above-mentioned adhesive sheet can be preferably used, for example, as a semiconductor processing adhesive sheet (back grinding tape, cutting tape, etc.) for temporary attachment to the adhered object during the manufacturing process of semiconductor devices, which can help improve processability. For example, in the back grinding process of semiconductor wafers, when the adhesive sheet disclosed in this specification is used as a back grinding tape to protect the circuit forming surface of the semiconductor wafer (adhesive object), peeling of the adhesive sheet and damage to the semiconductor wafer during back grinding can be prevented.

[0259] The initial peel force Fd0 can be determined using the method described above, and more specifically, using the following method. Specifically, the adhesive sheet to be tested is cut into strips with a width of 20 mm to prepare test pieces. At 23°C and 50% RH, the adhesive surface of the test piece is pressed against the mirror surface of a 6-inch silicon wafer (manufactured by Shin-Etsu Chemical Co., Ltd., 6-inch N<100>-100) using a hand roller, and left for 30 minutes to prepare an evaluation sample.

[0260] Then, at 23°C and 50% RH, a cutter was inserted into the interface between the test piece and the substrate of the above-mentioned evaluation sample, and one end of the test piece in the longitudinal direction was peeled from the substrate. The peel strength was determined according to JIS Z0237:2009, "10.4.1 Method 1: Peel adhesion force relative to a test plate at 180°", specifically, at a test temperature of 23°C, using a tensile testing machine at a tensile speed of 300 mm / min and a peel angle of 180 degrees. The peel strength was determined by peeling the test piece attached to the substrate from bottom to top. Three measurements were performed, and their average value was taken as the initial peel force Fd0 [N / 20 mm].

[0261] From the viewpoint of improving the adhesion and protection relative to the adhered object, in some methods, the initial peel force Fd0 can be, for example, 0.50 N / 20 mm or more, 1.00 N / 20 mm or more, 2.00 N / 20 mm or more, 3.00 N / 20 mm or more, 4.00 N / 20 mm or more, 5.00 N / 20 mm or more, or 5.50 N / 20 mm or more. Using the peeling method disclosed in this specification, even adhesive sheets exhibiting such an initial peel force Fd0 can be peeled well from the adhered object while suppressing the load on the adhered object. There is no particular upper limit to the initial peel force Fd0. From the viewpoint of easily further reducing the peel force after applying the first and second peel force reduction methods, in some methods, the initial peel force Fd0 can be, for example, less than 10.0 N / 20 mm, less than 8.00 N / 20 mm, less than 5.00 N / 20 mm, less than 3.50 N / 20 mm, less than 2.50 N / 20 mm, less than 2.00 N / 20 mm, less than 1.50 N / 20 mm, less than 1.00 N / 20 mm, or less than 0.50 N / 20 mm. The initial peel force Fd0 can be adjusted by the selection of the base polymer, the type and amount of compound A when using compound A, and the type and amount of crosslinking agent when using crosslinking agent.

[0262] (UV-treated conventional peel force Fd) U1 )

[0263] In some of the peeling methods disclosed in this specification, the adhesive sheet used in the peeling method has a UV-cured conventional peel force Fd. U1Preferably, the force is 0.10 N / 20 mm or less. Adhesive sheets exhibiting such characteristics demonstrate excellent light peeling properties, for example, in peeling methods where active energy ray (preferably ultraviolet) irradiation is used as a first means of reducing peeling force, thus reducing the load imposed on the adherend during peeling. Therefore, for example, for adhesive sheets that can be used as back-grinding tapes, not only can damage to semiconductor wafers that have been thinned by back-grinding be avoided, but the adhesive sheets can also be efficiently peeled from the semiconductor wafer.

[0264] Post-UV standard peel force Fd U1 The above method, and more specifically, the following method, can be used for measurement. Specifically, at 23°C and 50% RH, UV light is applied to the evaluation sample, prepared in the same manner as the initial peel strength Fd0 measurement, from the substrate side of the adhesive sheet (the side opposite to the adhesive surface being measured; hereinafter, also referred to as the "back side") under UV irradiation conditions A. Then, at 23°C and 50% RH, a cutter is inserted into the interface between the test piece and the adherend of the evaluation sample, and one end of the test piece in the longitudinal direction is peeled from the adherend. The peel strength is measured in the same manner as the initial peel strength Fd0 measurement. Three measurements are performed, and their average value is taken as the post-UV conventional peel strength Fd. U1 [N / 20mm].

[0265] [UV Irradiation Condition A]

[0266] UV irradiation machine: manufactured by Nitto Seiki Co., Ltd., product name "NEL SYSTEM UM810" (high-pressure mercury lamp light source).

[0267] Irradiation dose: 60 mW / cm² 2 The cumulative light intensity is 1000 mJ / cm². 2

[0268] In some methods, the conventional peel force Fd after UV treatment is... U1 For example, it can be below 0.080 N / 20 mm, below 0.060 N / 20 mm, below 0.040 N / 20 mm, below 0.030 N / 20 mm, or below 0.020 N / 20 mm. For the conventional peel force Fd after UV treatment... U1 For low-adhesion sheets, in a peeling method where active energy irradiation is used as the first means of reducing peeling force, the peeling force can be further reduced by applying a second means of reducing peeling force (e.g., supplying an aqueous peeling solution), which is therefore preferred. The conventional peeling force Fd after UV treatment... U1There is no particular limitation on the lower limit. From the viewpoint of avoiding the adhesive sheet accidentally (unintentionally) peeling off from the substrate after the application of the first peel force reduction method and before the application of the second peel force reduction method, in some methods, the conventional peel force Fd after UV treatment is... U1 For example, it can be above 0.001N / 20mm, above 0.005N / 20mm, above 0.010N / 20mm, or above 0.020N / 20mm. The standard peel force Fd after UV treatment. U1 The selection of the base polymer, the type and amount of compound A when using compound A, and the type and amount of crosslinking agent when using crosslinking agent can be adjusted.

[0269] (UV-treated water stripping force Fw) U2 )

[0270] The UV-cured water peel strength Fw of the adhesive sheet disclosed in this specification is... U2 Preferably less than 0.10 N / 20 mm. Adhesive sheets exhibiting such characteristics demonstrate excellent easy peeling properties in peeling methods where active energy ray (preferably ultraviolet) irradiation is used as a first peeling force reduction method, and the supply of an aqueous peeling liquid is used as a second peeling force reduction method, reducing the load imposed on the adherend during peeling. Therefore, for example, for adhesive sheets that can be used as back-grinding tapes, not only can damage to semiconductor wafers that have been thinned by back-grinding be avoided, but the adhesive sheets can also be efficiently peeled from the semiconductor wafer.

[0271] Post-UV water stripping force Fw U2 The above method, and more specifically, the following method, can be used to determine the peel force Fd after UV treatment. U1 In the test, 20 μL of distilled water was supplied to the point where the test piece began to separate from the adhered material (the peeling front) midway through the peeling process, and the peel strength after the supply of distilled water was measured. For the test, each peel strength was measured sequentially (i.e., three times), and their average value was taken as the post-UV water peel force Fw. U2 [N / 20mm].

[0272] In some methods, the post-UV water stripping force Fw U2 Preferably less than 0.050 N / 20 mm, more preferably less than 0.020 N / 20 mm, and can be less than 0.010 N / 20 mm, less than 0.009 N / 20 mm, less than 0.007 N / 20 mm, or less than 0.005 N / 20 mm. Water peeling force Fw after UV treatment. U2There is no particular limitation on the lower limit; from the viewpoint of reducing the load on the adhered material, the smaller the value, the more advantageous it is. On the other hand, from the viewpoint of achieving a balance between adhesion to the adhered material and protection during processing, in some methods, the post-UV water peel force Fw... U2 For example, it can be above 0.0005 N / 20 mm, or above 0.001 N / 20 mm. Water peel strength Fw after UV treatment. U2 The selection of the base polymer, the type and amount of compound A when using compound A, and the type and amount of crosslinking agent when using crosslinking agent can be adjusted.

[0273] (Initial water stripping force Fw0)

[0274] In some of the peeling methods disclosed in this specification, the initial water peeling force Fw0 of the adhesive sheet used in the peeling method is preferably greater than 0.10 N / 20 mm (preferably greater than 0.20 N / 20 mm, more preferably greater than 0.25 N / 20 mm, for example greater than 0.30 N / 20 mm). Thus, the adhesive sheet exhibits good water resistance before the application of the first peeling force reduction means, and can be preferably used, for example, as an adhesive sheet for semiconductor processing (back-grinding tape, cutting tape, etc.).

[0275] The initial water peel strength Fw0 can be determined using the following method. Specifically, during the determination of the initial peel strength Fw0, 20 μL of distilled water is supplied to the point where the test piece begins to separate from the adhered material (the peel front) midway through the peeling process, and the peel strength after the supply of distilled water is measured. For the measurement, each peel strength is measured sequentially (i.e., three times), and their average value is taken as the initial water peel strength Fw0 [N / 20 mm].

[0276] There is no particular upper limit to the initial water peel force Fw0. In some methods, the initial water peel force Fw0 can be, for example, below 5.00 N / 20 mm, below 3.00 N / 20 mm, or below 1.00 N / 20 mm. The initial water peel force Fw0 can be adjusted by the selection of the base polymer, the type and amount of compound A, and the type and amount of crosslinking agent used.

[0277] The tensile testing machine used for measuring the aforementioned peel forces can be the Shimadzu Autograph EZ-S precision universal testing machine or an equivalent device. During the test, if necessary, a suitable lining material (e.g., a PET film with a thickness of approximately 25 μm) can be attached to the adhesive sheet being tested to reinforce it.

[0278] In some of the peeling methods disclosed in this specification, the adhesive sheet used in the peeling method has the aforementioned post-UV conventional peel force Fd. U1 [N / 20mm] is preferably the above-mentioned post-UV water stripping force Fw. U2 More than 2.0 times [N / 20mm]. As mentioned above, for the ratio (Fd) U1 / Fw U2 For adhesive sheets with a peel force of 2.0 or higher, by applying the second peel force reduction method, the peel force after applying the first peel force reduction method can be further reduced to less than half. Therefore, it is suitable as a peeling target for the peeling method disclosed in this specification. Furthermore, for such adhesive sheets, for example, it is preferable to use them in a manner where the adhered object is moved, processed, handled, inspected, or stored after the application of the first peel force reduction method and before the application of the second peel force reduction method, thus preventing unintended peeling of the adhesive sheet before the application of the second peel force reduction method. From the viewpoint of better simultaneously achieving prevention of unintended peeling before the application of the second peel force reduction method and easy peeling after the application of the second peel force reduction method, the ratio (Fd) is... U1 / Fw U2 The ratio (Fd) can be 2.5 or higher, 3.0 or higher, 4.0 or higher, or 5.0 or higher. U1 / Fw U2 There is no particular upper limit to the value of Fw, which is easy to achieve after UV exposure. U2 From another perspective, it could be below 50, below 25, or below 10.

[0279] In some of the peeling methods disclosed in this specification, the adhesive sheet used in the peeling method has the aforementioned UV-cured water peeling force Fw. U2 Preferably, it is less than 0.9% of the initial peel force Fd0 mentioned above. As described above, for the ratio (Fw) U2 For adhesive sheets with an initial peel force (Fd0) of less than 0.9%, the application of the first and second peel force reduction methods can significantly reduce the initial peel force (Fd0) to a lower peel strength, making them suitable as the target for the peeling method disclosed in this specification. From the viewpoint of simultaneously achieving better bonding reliability before applying the first and second peel force reduction methods and better peel strength after applying the first and second peel force reduction methods, the ratio (Fw) is... U2 / Fd0) can be below 0.8%, below 0.6%, below 0.5%, or below 0.3%. The ratio (Fw) U2 There is no particular limitation on the lower limit of / Fd0), but from the point of view of reducing the load on the adhered object during peeling, the smaller the value, the better. From a practical point of view, it can be greater than 0.0%.

[0280] <Uses>

[0281] The peeling method disclosed in this specification is preferably used as a method for peeling adhesive sheets (e.g., adhesive sheets for semiconductor processing) from various semiconductor wafers (attached objects). The semiconductor wafers mentioned above can be, for example, silicon wafers, silicon carbide (SiC) wafers, nitride semiconductor wafers (silicon nitride (SiN), gallium nitride (GaN), etc.), gallium arsenide wafers, and other compound semiconductor wafers. In the process of manufacturing semiconductor devices (e.g., semiconductor chips) from such semiconductor wafers, the peeling method disclosed in this specification is typically preferred as a method for peeling adhesive sheets, which have been bonded to the semiconductor wafer through previous processes to form circuits, from the semiconductor wafer after processing. Examples of processing that can be performed on the semiconductor wafer include back-grinding and dicing, but are not limited to these. It should be noted that in this specification, when the shape of the semiconductor wafer to be processed changes due to processing (e.g., overall or partial thinning based on back-grinding, single-wafer obtained by dicing, etc.), the processed article is sometimes still referred to as a semiconductor wafer.

[0282] The bonding of the adhesive sheet peeled using the peeling method disclosed in this specification to the semiconductor wafer can be performed using any suitable method. The temperature for bonding the adhesive sheet can be around room temperature (e.g., 10°C to 35°C) or a temperature higher than room temperature (e.g., higher than 35°C, preferably 60°C to 90°C). Bonding the adhesive sheet at a temperature higher than room temperature is advantageous from the viewpoint of improving the adhesion between the adhesive sheet and the semiconductor wafer. After bonding the adhesive sheet at room temperature, a heat-pressurization treatment can be performed, applying a temperature higher than room temperature (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). There is no particular limitation on the time for performing the above heat-pressurization treatment, and it can be set in a way that yields a suitable treatment effect. In some methods, considering the stability of the treatment effect and the balance of productivity, the time for performing the above heat-pressurization treatment can be set to 3 minutes to 1 hour (e.g., 5 minutes to 30 minutes).

[0283] The peeling method disclosed in this specification, by applying first and second peeling force reduction means, can peel the adhesive sheet from the adhered object while highly suppressing the load on the adhered object. Therefore, it is suitable as a method for peeling the adhesive sheet from the hard and brittle thin portion (e.g., a portion of 150 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less) of an adhered object having a thin portion (hereinafter also referred to as a hard and brittle thin portion) made of a hard and brittle material (e.g., the constituent material of the semiconductor wafer mentioned above, various ceramic materials such as sapphire, glass, etc.). The peeling method disclosed in this specification can preferably be used as a method for peeling the adhesive sheet temporarily attached to such an adhered object from the adhered object, and can prevent cracking or damage to the hard and brittle thin portion due to the load during peeling of the adhesive sheet. It should be noted that the hard and brittle thin portion may be a portion formed by processing the adhered object after the adhesive sheet is attached to it.

[0284] <Semiconductor Device Manufacturing Methods>

[0285] The following describes one embodiment of a semiconductor device manufacturing method using the adhesive sheet disclosed in this specification. The semiconductor device manufacturing method of this embodiment includes the following steps: step (1), attaching the adhesive surface of the semiconductor processing adhesive sheet to the circuit forming surface side of a semiconductor wafer having a circuit forming surface; step (2), processing the semiconductor wafer with the adhesive sheet attached from the side opposite to the adhesive sheet; and step (3), peeling the adhesive sheet from the processed semiconductor wafer.

[0286] The above-described step (3) is preferably performed by supplying an aqueous stripping solution to the peeling front of the adhesive sheet as it is peeled from the processed semiconductor wafer (adhesive). This allows for gentle peeling of the adhesive sheet, thereby suppressing residual adhesive and reducing the load on the adhesive (processed semiconductor wafer). In some embodiments, the above-described step (3) may preferably be performed using the adhesive sheet peeling method described later.

[0287] Preferably, the high-temperature process described above is performed after step (1) and before step (3). Furthermore, it is preferable to irradiate the adhesive sheet with active energy rays during or before step (3). Typically, the peeling force of the adhesive sheet is reduced by the irradiation treatment. The irradiation treatment can be performed during step (3), or before step (3) and before the high-temperature process. By peeling the adhesive sheet after the irradiation treatment (preferably with water), the load imposed on the adherend (processed semiconductor wafer) during peeling can be effectively reduced. From the viewpoint of simultaneously achieving adhesion reliability relative to the adherend in step (2) and light peeling in step (3), the irradiation treatment is preferably performed after step (2).

[0288] In some embodiments, step (2) can be a back-side grinding process. In this case, the adhesive sheet can be used as a back-side grinding tape. The back-side grinding process can be performed by any suitable method. The back-side grinding process can be the following process: thinning the semiconductor wafer with the adhesive sheet attached until the thickness of the semiconductor wafer becomes, for example, 150 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. As described above, in the thinning process, the effect of water stripping the adhesive sheet in step (3) can be appropriately utilized. It should be noted that the back-side grinding process can be performed in such a way that the inner side of the annular protrusion becomes a concave portion (i.e., in such a way that a TAIKO (registered trademark) wafer can be 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 back-side grinding can be, for example, about 500 μm to 1000 μm.

[0289] The semiconductor device manufacturing method disclosed in this specification may further include any suitable steps. Examples of such arbitrary steps include, but are not limited to, etching, photolithography, ion implantation, dicing, die bonding, wire bonding, and packaging. The steps listed above may be performed in step (2) above, after step (2) above, before step (3) above, or after step (3) above.

[0290] It should be noted that the matters disclosed in this application include the following schemes.

[0291] [1] An adhesive sheet peeling method, which is a method for peeling an adhesive sheet comprising an adhesive layer constituting an adhesive surface from an object bonded by the adhesive sheet, the method comprising:

[0292] Apply a first peel force reduction method to the aforementioned adhesive sheet, and

[0293] A second peel force reduction method is applied to the aforementioned adhesive sheet.

[0294] [2] The method described in [1] above, wherein, after applying the first peeling force reduction means, the second peeling force reduction means is applied.

[0295] [3] As described in [1] or [2] above, wherein, as the second peeling force reduction means, an aqueous peeling liquid is supplied to the peeling front of the adhesive sheet as it peels off from the adhered object.

[0296] [4] The method as described in any one of [1] to [3] above, wherein, as the first means of reducing peeling force, the adhesive layer is cured by irradiation or heating with active energy rays.

[0297] [5] The method as described in any one of [1] to [4] above, wherein the initial peel force F0 of the adhesive sheet is 0.30 N / 20 mm or more.

[0298] The initial peel force F0 was determined using the following method:

[0299] After the above adhesive surface is attached to the silicon wafer, the peel strength is measured under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees.

[0300] [6] The method as described in any one of [1] to [5] above, wherein the UV-cured water peel strength Fw of the adhesive sheet is... U2 Less than 0.10N / 20mm,

[0301] The UV-induced water stripping force Fw U2 The following methods were used to determine:

[0302] The aforementioned adhesive surface was attached to a silicon wafer, and the cumulative light intensity was 1000 mJ / cm. 2 After ultraviolet irradiation treatment, water is supplied to the peeling front of the adhesive sheet that is peeled from the silicon wafer, and the peel strength is measured under the conditions of a tensile speed of 300 mm / min and a peeling angle of 180 degrees.

[0303] [7] The method as described in any one of [1] to [6] above, wherein the post-UV conventional peel force Fd of the adhesive sheet is... U1 [N / 20mm] represents the post-UV water stripping force Fw. U2 More than 2.0 times that of [N / 20mm]

[0304] The post-UV conventional peel force Fd U1 [N / 20mm] was determined using the following method:

[0305] The aforementioned adhesive surface was attached to a silicon wafer, and the cumulative light intensity was 1000 mJ / cm. 2 After UV irradiation treatment, the peel strength was measured under the conditions of tensile speed of 300 mm / min and peel angle of 180 degrees.

[0306] The UV-induced water stripping force Fw U2 [N / 20mm] was determined using the following method:

[0307] The aforementioned adhesive surface was attached to a silicon wafer, and the cumulative light intensity was 1000 mJ / cm. 2After ultraviolet irradiation treatment, water is supplied to the peeling front of the adhesive sheet that is peeled from the silicon wafer, and the peel strength is measured under the conditions of a tensile speed of 300 mm / min and a peeling angle of 180 degrees.

[0308] [8] The method as described in any one of [1] to [7] above, wherein the adhesive surface, which is the first side of the adhesive sheet, is attached to the substrate, and the adhesive sheet is peeled off from the substrate by applying the first peel force reduction means and the second peel force reduction means.

[0309] [9] An adhesive sheet, which is an adhesive sheet containing an adhesive layer constituting an adhesive surface, said adhesive sheet being used in any of the peeling methods described in any one of [1] to [8] above.

[0310]

[10] A method for manufacturing a semiconductor device, comprising the following steps:

[0311] Step (1) involves attaching the adhesive surface of an adhesive sheet containing an adhesive layer constituting an adhesive surface to a semiconductor wafer.

[0312] Step (2) involves processing the semiconductor wafer to which the aforementioned adhesive sheet has been bonded from the side opposite to the adhesive sheet; and

[0313] In step (3), the adhesive sheet is peeled off from the processed semiconductor wafer using any one of the peeling methods described in [1] to [8].

[0314] Example

[0315] The following describes some embodiments of the present invention, but it is not intended to limit the invention to the contents shown in the embodiments. It should be noted that, unless otherwise specified, "parts" and "%" in the following description are based on weight.

[0316] <Example 1>

[0317] (Preparation of test samples)

[0318] A test sample was prepared by bonding the adhesive strip (test piece) with a width of 20 mm, which was made by cutting the adhesive strip shown in Table 1 (i.e., adhesive strip A), to the silicon wafer as the substrate. More specifically, the adhesive surface of the test piece was pressed against the mirror surface of a 6-inch silicon wafer (manufactured by Shin-Etsu Chemical Co., Ltd., 6-inch N<100>-100) as the substrate with a hand roller at 23°C and 50% RH for 30 minutes to prepare the test sample.

[0319] (Peeling off the adhesive sheet)

[0320] Under conditions of 23°C and 50% RH, a cutter was inserted into the interface between the test piece and the substrate of the above-mentioned test sample, and one end of the test piece along its length was peeled from the substrate. The peel strength was determined according to JIS Z0237:2009, "10.4.1 Method 1: Peel Adhesion Force at 180° Relative to the Test Plate." Specifically, at a test temperature of 23°C, a tensile testing machine (Shimadzu Autograph EZ-S precision universal testing machine) was used at a tensile speed of 300 mm / min and a peel angle of 180 degrees. The peel strength was measured by peeling the test piece attached to the substrate from bottom to top. Three measurements were performed, and their average value was taken as the initial peel force Fd0 [N / 20 mm]. The results are shown in Table 1.

[0321] In this example of the peeling method, no peeling force reduction measures are applied. Therefore, the initial peeling force Fd0 mentioned above is consistent with the final peeling force obtained through the peeling method in this example.

[0322] <Example 2>

[0323] The peeling method described in this example was implemented using test samples prepared in the same manner as in Example 1.

[0324] Specifically, in the determination of the initial peel force Fd0, as a means of reducing peel force, 20 μL of distilled water was supplied to the position where the test piece began to separate from the adhered material (the peel front) during the peeling process, and the peel strength after the distilled water supply was measured. For the measurement, each peel strength was measured sequentially (i.e., three times), and their average value was taken as the final peel force obtained by the peeling method in this example. The results are shown in Table 1.

[0325] It should be noted that the same adhesive sheet as in Example 1 is used in the peeling method of this example. Therefore, the initial peel force Fd0 obtained by the peeling method of this example is the same as the initial peel force Fd0 in Example 1.

[0326] <Example 3>

[0327] The peeling method described in this example was implemented using test samples prepared in the same manner as in Example 1.

[0328] Specifically, for the test samples mentioned above, in an environment of 23°C and 50% RH, as a means of reducing peel strength, UV irradiation conditions A (high-pressure mercury lamp light source, illuminance of 60 mW / cm²) were applied from the substrate side (back side) of the adhesive sheet using the aforementioned conditions. 2 The cumulative light intensity is 1000 mJ / cm². 2The sample was irradiated with ultraviolet light. Then, at 23°C and 50% RH, a cutter was inserted into the interface between the test piece and the adherend, and one end of the test piece in the longitudinal direction was peeled from the adherend. The peel strength was measured in the same manner as the initial peel force Fd0 measured above. Three measurements were performed, and their average value was taken as the final peel force in this example peeling method. The results are shown in Table 1.

[0329] <Example 4>

[0330] The peeling method described in this example was implemented using test samples prepared in the same manner as in Example 1.

[0331] Specifically, for the test sample mentioned above, in an environment of 23°C and 50%RH, as a first means of reducing peel force, ultraviolet light was irradiated from the back side of the adhesive sheet using the aforementioned UV irradiation condition A.

[0332] Then, at 23°C and 50% RH, a cutter was inserted into the interface between the test piece of the above-mentioned evaluation sample and the adherend, and one end of the test piece in the longitudinal direction was peeled from the adherend. The peel strength was measured in the same manner as the initial peel force Fd0 measured above. Three measurements were performed, and their average value was taken as the intermediate peel force (normal peel force after UV) in the peeling method of this example.

[0333] In the above-mentioned intermediate peel strength determination, as a second peel strength reduction measure, 20 μL of distilled water was supplied to the position where the test piece began to separate from the adhered material (peel front) as the test piece began to peel from the adhered material, and the peel strength after the distilled water supply was measured. For the measurement, each peel strength was measured successively (i.e., 3 times), and their average value was taken as the final peel strength obtained by the peeling method of this example.

[0334] The results are shown in Table 1.

[0335] <Examples 5~9>

[0336] Except for using adhesive sheets B to F shown in Table 1, the test samples involved in Examples 5 to 9 were prepared in the same manner as in Example 1. The initial peel force Fd0 [N / 20mm] of these test samples was measured in the same manner as in Example 1.

[0337] For the test samples described above, as a first means of reducing peel force, they were irradiated with ultraviolet light in the same manner as in Example 4. Then, the intermediate peel force (normal peel force after UV irradiation) was measured in the same manner as in Example 4.

[0338] In the aforementioned intermediate peel strength determination, as a second peel strength reduction measure, 20 μL of distilled water was supplied to the position where the test piece began to separate from the adhered material (peel front) as part of the process of peeling the test piece from the adhered material, and the peel strength after the distilled water supply was measured. For the measurement, each peel strength was measured sequentially (i.e., three times), and their average value was taken as the final peel strength obtained by the measurement method described in each example.

[0339] The results are shown in Table 1.

[0340] [Table 1]

[0341] Table 1

[0342]

[0343] NA: Not applicable, U: Irradiate with ultraviolet light, W: Supply aqueous stripping solution

[0344] As shown in Table 1, the peeling methods of Examples 4 to 9, which apply the first and second peeling force reduction methods, can peel with a final peeling force that is significantly reduced compared to the initial peeling force, and can greatly reduce the load on the adhered object during peeling.

[0345] It should be noted that in Examples 1 to 9 above, the adhesive sheets A to F used in the preparation of the test samples were prepared in the following manner.

[0346] <Adhesive Sheet A>

[0347] A monomer composition was prepared by mixing 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 with 0.3 parts of benzoyl peroxide (BPO) as a polymerization initiator and toluene as a polymerization solvent.

[0348] The above monomer composition was placed into a polymerization apparatus consisting of a 1L round-bottom detachable flask equipped with a detachable cap, a separatory funnel, a thermometer, a nitrogen inlet tube, a Liebig condenser, a vacuum seal, a stir bar, and stirring blades. The mixture was stirred while being purged with nitrogen at room temperature for 6 hours. Then, under a nitrogen flow, polymerization was carried out at 60°C for 6 hours with stirring, followed by a period at 78°C for 1 hour, yielding a solution of polymer Q1 (Mw approximately 500,000). The Tg calculated using the Fox equation based on the composition of the above monomer raw materials was -37.2°C.

[0349] After cooling the above polymer Q1 solution to room temperature, 43.6 parts of ethyl 2-isocyanate methacrylate (manufactured by Showa Denko Co., Ltd., trade name "Karenz MOI") were added, followed by 0.2 parts of dibutyltin dilaurate (IV) (manufactured by Wako Pure Chemical Industries Co., Ltd.). The mixture was stirred at 50°C for 24 hours in an air atmosphere, thereby causing the above polymer Q1 to undergo an addition reaction with MOI to obtain a solution of polymer P1 with carbon-carbon double bonds.

[0350] It should be noted that the above-mentioned MOI usage is based on the molar amount (M) of hydroxyl groups (functional group A) contained in the HEA used in the synthesis of polymer Q1. A ), and the molar ratio (M) of isocyanate groups (functional group B) contained in the above MOI. B The ratio of (M) A / M B It becomes approximately 1.2.

[0351] To a solution of the polymer P1 described above, 1.0 part of isocyanate-based crosslinking agent X1 (trimethylolpropane / toluene diisocyanate trimer adduct, manufactured by Tosoh Corporation, trade name "Coronate L", solid content concentration of 75% by weight) was added relative to 100 parts of polymer P1 in the solution, based on the solid content. Then, 1.0 part of photoinitiator H1 (manufactured by IGM Regins, trade name "Omnirad 369") was added, and the mixture was mixed to prepare adhesive composition C1.

[0352] Adhesive composition C1 was applied to the release surface of a 38 μm thick release film R1 (Mitsubishi Resin Co., Ltd., MRF38) with one side being a polysiloxane-treated release surface. The film was dried at 140°C for 2 minutes to form an adhesive layer with a thickness of 20 μm. This adhesive layer was then bonded to the easy-to-bond surface of an easy-to-bond treated PET film (50 μm thick) as a substrate, and then aged at 50°C for 2 days to obtain adhesive sheet A.

[0353] <Adhesive Sheet B>

[0354] To the solution of polymer P1, relative to 100 parts of polymer P1 in the solution, 0.50 parts of nonionic surfactant A1 (polyoxyethylene sorbitan monolaurate, sorbitan fatty acid ester manufactured by Kao Corporation, trade name "Rheodol TW-L120", ethylene oxide addition molar number of 20, HLB of 16.7) which is soluble in ethyl acetate and does not undergo phase separation in the above-described test I, are added. Except as described above, adhesive composition C2 is prepared in the same manner as adhesive composition C1. It should be noted that the nonionic surfactant A1 is used in the form of an ethyl acetate solution and in the amount described above based on the solid component. The same applies to the preparation of adhesive composition C6 described below.

[0355] Except that adhesive composition C2 is used instead of adhesive composition C1, adhesive sheet B is obtained in the same manner as adhesive sheet A.

[0356] <Adhesive Sheet C>

[0357] Except that the amount of isocyanate-based crosslinking agent X1 used relative to 100 parts of polymer P1 is changed to 5.0 parts, adhesive composition C3 is prepared in the same manner as adhesive composition C1. Adhesive sheet C is obtained in the same manner as adhesive sheet A, except that adhesive composition C3 is used.

[0358] <Adhesive Sheet D>

[0359] A monomer composition was prepared by mixing 100 parts of 2-ethylhexyl acrylate (2EHA), 25.5 parts of N-acryloylmorpholine (ACMO), and 18.5 parts of HEA as monomer raw materials with 0.3 parts of BPO and toluene as a polymerization solvent.

[0360] The above monomer composition was placed into a polymerization apparatus consisting of a 1-liter round-bottom detachable flask equipped with a detachable cap, separatory funnel, thermometer, nitrogen inlet tube, Liebig condenser, vacuum seal, stir bar, and stirring blades. The mixture was stirred while being purged with nitrogen at room temperature for 6 hours. Then, polymerization was carried out under a nitrogen flow, with stirring, at 60°C for 8 hours to obtain a solution of polymer Q2. The weight-average molecular weight (Mw) of polymer Q2 was approximately 900,000. The Tg calculated using the Fox equation based on the composition of the above monomer raw materials was -42.7°C.

[0361] After cooling the above polymer Q2 solution to room temperature, 12.3 parts of ethyl 2-isocyanate methacrylate (manufactured by Showa Denko Co., Ltd., trade name "Karenz MOI") were added, and 0.1 parts of dibutyltin dilaurate (IV) (manufactured by Wako Pure Chemical Industries Co., Ltd.) were further added. The mixture was stirred at 50°C for 24 hours under air atmosphere, thereby causing the above polymer Q2 to undergo an addition reaction with MOI to obtain a solution of polymer P2 with carbon-carbon double bonds.

[0362] It should be noted that the above-mentioned MOI usage is based on the molar amount (M) of hydroxyl groups (functional group A) contained in the HEA used in the synthesis of polymer Q2. A ), and the molar ratio (M) of isocyanate groups (functional group B) contained in the above MOI. B The ratio of (M) A / M B It becomes approximately 2.0.

[0363] To a solution of polymer P2, 5.0 parts of isocyanate-based crosslinking agent X1 (based on solid content) were added relative to 100 parts of polymer P2 in the solution, followed by 1.0 part of photoinitiator H1. The mixture was then stirred to prepare adhesive composition C4. Adhesive sheet D was obtained in the same manner as adhesive sheet A, except that adhesive composition C4 was used.

[0364] <Adhesive Sheet E>

[0365] (Preparation of the adhesive composition)

[0366] The amount of ethyl 2-isocyanate methacrylate (manufactured by Showa Denko Co., Ltd., trade name "Karenz MOI") added to the solution of polymer Q2 was changed to 22.5 parts. Otherwise, a solution of polymer P3 having carbon-carbon double bonds was obtained by following the same method as the synthesis of polymer P2.

[0367] It should be noted that the above-mentioned MOI usage is based on the molar amount (M) of hydroxyl groups (functional group A) contained in the HEA used in the synthesis of polymer Q2. A ), and the molar ratio (M) of isocyanate groups (functional group B) contained in the above MOI. B The ratio of (M) A / M B It becomes approximately 1.1.

[0368] To a solution of polymer P3, 5.0 parts of isocyanate-based crosslinking agent X1 (based on solid content) were added relative to 100 parts of polymer P3 in the solution, followed by 1.0 part of photoinitiator H1. The mixture was then stirred to prepare adhesive composition C5. Adhesive sheet E was obtained by using adhesive composition C5 in the same manner as adhesive sheet A.

[0369] <Adhesive Sheet F>

[0370] To the solution of polymer P3, 0.50 parts of nonionic surfactant A1 are added, relative to 100 parts of polymer P3 in the solution. Except as described above, adhesive composition C6 is prepared in the same manner as adhesive composition C1. In addition to using adhesive composition C6, adhesive sheet F is obtained in the same manner as adhesive sheet A.

[0371] The above description details specific examples of the present invention, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes technologies modified or altered from the specific examples illustrated above.

Claims

1. An adhesive sheet peeling method which is a method of peeling an adhesive sheet including an adhesive layer constituting an adhesive surface from an adherend to which the adhesive sheet is bonded, the method comprising: applying a first peeling force reducing means to the adhesive sheet; and applying a second peeling force reducing means to the adhesive sheet, in the adhesive layer, at least one compound A selected from the group consisting of a surfactant and a compound having a polyoxyalkylene skeleton is contained as a water peeling additive, as the first peeling force reducing means, at least one of a process of curing the adhesive layer of the adhesive sheet bonded to the adherend and a process of embossing the adhesive surface of the adhesive sheet bonded to the adherend is performed, as the second peeling force reducing means, at an end of an outer edge of the adhesive sheet attached to the adherend, the adhesive sheet is lifted from the adherend, thereby forming an initial peeling front, and an aqueous peeling solution is supplied to the peeling front of the adhesive sheet peeled from the adherend. the second peeling force reducing means is applied after the first peeling force reducing means is applied.

2. The method of claim 1, wherein, as the first peeling force reducing means, irradiation of active energy rays or heating is performed, thereby curing the adhesive layer.

3. The method of claim 1 or 2, wherein, an initial peeling force F0 of the adhesive sheet is 0.30 N / 20 mm or more, 4. The method of claim 1 or 2, wherein, the initial peeling force F0 is measured by attaching the adhesive surface to a silicon wafer and measuring a peeling strength under conditions of a tensile speed of 300 mm / minute and a peeling angle of 180 degrees. the adhesive surface of a first surface of the adhesive sheet is attached to the adherend, and by applying the first peeling force reducing means and the second peeling force reducing means, the peeling force of the first surface against the adherend is gradually reduced, and the adhesive sheet is peeled from the adherend.

5. The method of claim 1 or 2, wherein, The UV after water peel strength Fw of the adhesive sheet U2 less than 0.10 N / 20 mm, The UV post-water peel force Fw U2 The UV post-water peel force Fw was measured by the following method: the adhesive surface was attached to a silicon wafer, UV irradiation treatment was performed at a cumulative light amount of 1000 mJ / cm 2 After the treatment, water was supplied to the peel front of the adhesive sheet peeled from the silicon wafer, and the peel strength was measured at a stretching speed of 300 mm / min and a peel angle of 180 degrees.

6. The method of claim 1 or 2, wherein, The UV post-conventional peel force Fd of the adhesive sheet U1 [N / 20mm] is the UV post-water peel force Fw U2 2.0 times or more of [N / 20mm] the UV post-conventional peel force Fd U1 [N / 20 mm] measured by the following method: the adhesive surface was attached to a silicon wafer, and after ultraviolet irradiation treatment with a cumulative light amount of 1000 mJ / cm 2 at a tensile speed of 300 mm / min and a peel angle of 180 degrees the UV post-water peel force Fw U2 [N / 20 mm] The following method was used: the adhesive surface was attached to a silicon wafer, and after ultraviolet irradiation treatment with a cumulative light amount of 1000 mJ / cm 2 2, the peel strength was measured at a stretching speed of 300 mm / min and a peel angle of 180 degrees.

7. The method of claim 1 or 2, wherein, 8. An adhesive sheet which is an adhesive sheet including an adhesive layer constituting an adhesive surface, the adhesive sheet is used in the peeling method according to any one of claims 1 to 7.

9. A semiconductor element manufacturing method including the following steps: a step (1) of attaching the adhesive surface of an adhesive sheet including an adhesive layer constituting an adhesive surface to a semiconductor wafer; a step (2) of performing processing on the semiconductor wafer to which the adhesive sheet is attached from a side opposite to the adhesive sheet; and a step (3) of peeling the adhesive sheet from the processed semiconductor wafer using the peeling method according to any one of claims 1 to 7. ​

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