Adhesive sheet

Abstract

To provide an adhesive sheet which can be easily peeled from an adherend by coming into contact with water.SOLUTION: An adhesive sheet 10 includes an adhesive layer (X)2 formed of an acrylic adhesive composition containing an acrylic polymer (A) having a carboxy group, a neutralizer (B) and a crosslinking agent (C), and recesses 1 are present on at least one surface of the adhesive layer (X)2. The adhesive sheet 10 is formed using the acrylic adhesive composition in which: the component (B) is an amine compound; and the component (A) contains 0.1-20 mass% of a constituent unit (a2) derived from a monomer (am2) containing a carboxy group in all the constituent units of the component (A).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet, more specifically to a pressure-sensitive adhesive sheet that exhibits self-releasability upon contact with water. [Background technology]

[0002] Adhesive sheets are not only used to semi-permanently fix components, but may also be used to temporarily fix components such as building materials, interior materials, and electronic components when processing or inspecting them. As an example, in the manufacturing process of a semiconductor device, when processing a semiconductor wafer or using materials for electronic devices such as semiconductor chips, a pressure-sensitive adhesive sheet is used as a temporary fixing sheet. In this way, when the pressure-sensitive adhesive sheet is attached to an adherend such as an electronic device material and then peeled off after use, it is desirable to be able to do so without applying an excessive load to the adherend. Similarly, the pressure-sensitive adhesive sheet can also be used as, for example, a protective material such as a protective film, wallpaper, various label applications, etc. If it becomes possible to peel the pressure-sensitive adhesive sheet attached to the adherend from the adherend without applying a load to the adherend, it is expected that defects such as contamination, deformation, and breakage of the adherend caused by the pressure-sensitive adhesive sheet can be reduced and prevented. In this way, when a pressure-sensitive adhesive sheet is used by temporarily attaching it to an adherend, the pressure-sensitive adhesive sheet is required to exhibit sufficient adhesive strength when attached and to have excellent releasability when removed.

[0003] For example, Patent Document 1 discloses a temporary fixing adhesive composition that contains a (meth)acrylate and an alicyclic (meth)acrylate, each of which has a homopolymer glass transition temperature that falls within a specific range, and a photopolymerization initiator; and a method for temporarily fixing a member, which comprises using the temporary fixing adhesive composition to temporarily fix a member, immersing the processed member in an organic solvent, and removing the cured body of the composition. Furthermore, for example, Patent Document 2 discloses a processing method for brittle materials that includes a step of forming a unit in which a brittle material is fixed to a hard plate via a double-sided adhesive sheet having adhesive layers on both sides, and peeling the brittle material from the hard plate, characterized in that the unit is immersed in a liquid that is insoluble or poorly soluble in the adhesive, allowing the liquid to penetrate into the interface between the double-sided adhesive sheet and the brittle material, or the interface between the double-sided adhesive sheet and the hard plate, and then peeling the brittle material from an end of the unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-108044 A [Patent Document 2] JP 2003-338475 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in recent years, when adhesive sheets such as those disclosed in Patent Documents 1 and 2 are used in the manufacturing processes of various products, there has been a demand, from the standpoint of improving productivity, for shortening the time required for the adhesive sheet to be peeled off from the adherend after being immersed in a solvent or the like. Furthermore, even in the case of pressure-sensitive adhesive sheets used in processes other than the production process as described above, there is a demand for shortening the peeling process time from the viewpoint of improving workability during peeling. In the method of peeling off the pressure-sensitive adhesive sheet by immersion in a solvent or the like, it is desirable to use a safer solvent from the standpoint of environmental considerations and workability. From this perspective, an object of the present invention is to provide a pressure-sensitive adhesive sheet that can be easily peeled off from an adherend by contacting it with water. [Means for solving the problem]

[0006] The present inventors have found that by forming a pressure-sensitive adhesive layer from a specific acrylic pressure-sensitive adhesive composition and providing a recess on at least one surface of the pressure-sensitive adhesive layer, a pressure-sensitive adhesive sheet having the specific pressure-sensitive adhesive layer can solve the above-mentioned problems, and have completed the present invention. That is, the present invention provides the following [1] to

[11] . [1] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer (X) formed from an acrylic pressure-sensitive adhesive composition comprising an acrylic polymer (A) having a carboxy group, a neutralizing agent (B), and a crosslinking agent (C), wherein a recess is present on at least one surface of the pressure-sensitive adhesive layer (X). [2] The pressure-sensitive adhesive sheet according to [1] above, wherein component (B) is an amine compound. [3] The pressure-sensitive adhesive sheet according to [1] or [2] above, wherein component (A) contains 0.1 to 20 mass% of structural units (a2) derived from monomer (am2) containing a carboxy group, relative to 100 mass% of all structural units constituting component (A). [4] The pressure-sensitive adhesive sheet according to any one of [1] to [3] above, wherein the content of component (A) in the acrylic pressure-sensitive adhesive composition is 75 to 95 mass% of the total amount of the acrylic pressure-sensitive adhesive composition (100 mass% of active ingredient). [5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein the content of component (B) in the acrylic pressure-sensitive adhesive composition is 0.05 to 10 parts by mass relative to the total amount of component (A) (100 parts by mass of active ingredient). [6] The pressure-sensitive adhesive sheet according to any one of the above [1] to [5], wherein the component (C) is at least one selected from the group consisting of epoxy-based crosslinking agents and metal chelate-based crosslinking agents. [7] The pressure-sensitive adhesive sheet according to any one of [1] to [6], wherein the content of component (C) in the acrylic pressure-sensitive adhesive composition is 0.05 to 10 parts by mass relative to the total amount of component (A) (100 parts by mass of active ingredient). [8] The pressure-sensitive adhesive sheet according to any one of [1] to [7] above, wherein the height difference of the recesses is 0.5 μm or more. [9] The pressure-sensitive adhesive sheet according to any one of [1] to [8], wherein, when the pressure-sensitive adhesive layer (X) is viewed in plan, the recesses are present and are continuously connected from one point to another point on the contour of the surface of the pressure-sensitive adhesive layer (X).

[10] The pressure-sensitive adhesive sheet according to any one of the above [1] to [9], wherein the pressure-sensitive adhesive layer (X) has an adhesive strength of a surface on which the recesses are present of 0.20 to 10.00 N / 25 mm.

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

[10] , which has a substrate. Effect of the Invention

[0007] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that can be easily peeled off from an adherend by contacting it with water. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic cross-sectional view showing one example of the configuration of the pressure-sensitive adhesive sheet of the present invention, taken along a plane that allows the depressions present on the surface of the pressure-sensitive adhesive layer (X) to be discerned. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing one example of the configuration of the pressure-sensitive adhesive sheet of the present invention, taken along a plane that allows the depressions present on the surface of the pressure-sensitive adhesive layer (X) to be discerned. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing one example of the configuration of the pressure-sensitive adhesive sheet of the present invention, taken along a plane that allows the depressions present on the surface of the pressure-sensitive adhesive layer (X) to be discerned. [Figure 4] FIG. 2 is a schematic cross-sectional view showing one example of the configuration of the pressure-sensitive adhesive sheet of the present invention, taken along a plane that allows the depressions present on the surface of the pressure-sensitive adhesive layer (X) to be discerned. [Diagram 5] FIG. 2 is a schematic cross-sectional view of a sample for evaluating the water contact peelability of a pressure-sensitive adhesive sheet in an example, cut along a plane that allows the depressions present on the surface of the pressure-sensitive adhesive layer (X) to be discerned. [Figure 6] 1 is a schematic plan view illustrating an example of a pressure-sensitive adhesive sheet of the present invention. [Figure 7] 1 is a schematic plan view illustrating an example of a pressure-sensitive adhesive sheet of the present invention. [Figure 8] This is a schematic cross-sectional view showing an example of the configuration of a release material that may be possessed by the adhesive sheet of the present invention, and is a schematic cross-sectional view of a release material cut on a plane that allows the convex portions present on the surface of the release material to be identified. [Figure 9] 1 is an example of a scanning electron microscope (SEM) image when confirming the height difference and width of recesses in the pressure-sensitive adhesive sheet produced in Example 1, which is an example of this embodiment. [Figure 10] 1 is an example of a scanning electron microscope (SEM) image of the height difference and width of the convex portions of the release material 1 used in producing the adhesive sheet produced in Example 1, which is an example of this embodiment. [Figure 11] 1 is an example of a scanning electron microscope (SEM) digital microscope image obtained when confirming the pattern shape of recesses in the pressure-sensitive adhesive sheet produced in Example 1, which is an example of this embodiment. [Figure 12] 1 is an example of a scanning electron microscope (SEM) image for confirming the pattern shape of the convex portions of a release material 1 used in producing the adhesive sheet produced in Example 1, which is an example of this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Adhesive sheet] The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer (X) formed from an acrylic pressure-sensitive adhesive composition containing an acrylic polymer (A) having a carboxy group, a neutralizing agent (B), and a crosslinking agent (C), and has recesses on at least one surface of the pressure-sensitive adhesive layer (X).

[0010] An example of a pressure-sensitive adhesive sheet according to an embodiment of the present invention will be described below with reference to the accompanying drawings. However, the pressure-sensitive adhesive sheet of the present invention is not limited to the following example as long as the effects of the present invention are exhibited. Figures 1 to 4 are schematic cross-sectional views of adhesive sheets 10, 20, 30 and 40, respectively, showing an example of the configuration of the adhesive sheet of the present invention, and are schematic cross-sectional views of an adhesive layer (X) (hereinafter also simply referred to as "layer (X)") 2 having a recess 1 present on at least one surface, cut along a plane where the recess 1 can be identified. For example, when adhesive sheet 70, which is one example of the configuration of the adhesive sheet of the present invention shown in the schematic plan view of FIG. 7, is cut along line AA, schematic cross-sectional views such as those shown in FIGS. 1 to 4 are obtained.

[0011] One embodiment of the pressure-sensitive adhesive sheet of the present invention is, for example, a pressure-sensitive adhesive sheet consisting of a single layer of layer (X) 2, such as pressure-sensitive adhesive sheet 10 shown in Fig. 1. In the case of the pressure-sensitive adhesive sheet shown in Fig. 1, an adherend to be peeled off when layer (X) 2 is brought into contact with water can be attached to the surface having recesses 1. In addition, the pressure-sensitive adhesive sheet 10 shown in Fig. 1 may have recesses 1 on both surfaces of layer (X) 2 (not shown), or a release material may be provided on one exposed surface and both exposed surfaces of layer (X) 2 (not shown).

[0012] One embodiment of the pressure-sensitive adhesive sheet of the present invention includes a structure in which a base material 3 and a layer (X) 2 are laminated in this order, such as the pressure-sensitive adhesive sheet 20 shown in Fig. 2. Providing the layer (X) 2 on the base material 3 can improve the shape stability of the pressure-sensitive adhesive sheet and impart stiffness to the pressure-sensitive adhesive sheet, which is preferable from the viewpoint of improving the workability when removing the release material from the layer (X) 2 and when peeling the pressure-sensitive adhesive sheet from the adherend. In the adhesive sheet 20 shown in FIG. 2, the adhesive sheet may have a recess 1 on the surface side of the layer (X) 2 that contacts the substrate 3 (not shown), or the adhesive sheet may have a recess 1 on both the surface of the layer (X) 2 facing the substrate 3 and the surface opposite the substrate 3 (not shown), or a release material may be provided on the surface of the layer (X) 2 opposite the substrate 3 and / or the surface of the substrate 3 opposite the layer (X) 2 (not shown).

[0013] One embodiment of the pressure-sensitive adhesive sheet of the present invention is, for example, a double-sided pressure-sensitive adhesive sheet having a multilayer structure in which layers (X) 2 are laminated on both sides of a substrate 3, as in the pressure-sensitive adhesive sheet 30 shown in Fig. 3. In the pressure-sensitive adhesive sheet 30 shown in Fig. 3, the two layers (X) 2 may be the same layer (X) 2 or different layers (X) 2. Also, the pressure-sensitive adhesive sheet 30 shown in Fig. 3 may be a pressure-sensitive adhesive sheet in which a recess 1 is present on the surface of the layer (X) 2 that contacts the substrate 3 (not shown), or a pressure-sensitive adhesive sheet in which a recess 1 is present on both the surface of the layer (X) 2 on the substrate 3 side and the surface opposite to the substrate 3 (not shown). In addition, in the adhesive sheet 30 shown in FIG. 3, one of the two layers (X) 2 may be an adhesive layer other than the layer (X) 2 that does not have recesses 1 on its surface (not shown).

[0014] In addition, as one embodiment of the adhesive sheet of the present invention, for example, as in adhesive sheet 40 shown in FIG. 4, in adhesive sheet 30 shown in FIG. 3, release material 4-1 and release material 4-2 may be provided on the surface (exposed surface) of layer (X) 2 opposite to substrate 3. In FIG. 4, the release material 4-1 is a release material having a convex portion 4a that pairs with the concave portion 1 of the layer (X) 2, and the release material 4-2 is a release material having no convex portion. In the adhesive sheet 40 shown in FIG. 4, the release material 4-1 may be used for both of the release materials, or the release material 4-2 may be used for both of the release materials. However, from the viewpoint of easily maintaining the shape of the concave portion 1 on the layer (X) 2 during storage and / or transportation of the adhesive sheet 40, and also from the viewpoint of easily forming the concave portion 1 as described later in the manufacturing method of the adhesive sheet, which is one embodiment of the present invention, it is preferable to provide the release material 4-1 having the convex portion 4a that pairs with the concave portion 1 of the layer (X) 2 on the surface having the concave portion 1 of the layer (X) 2. The same applies when a release material is provided in the adhesive sheets 10, 20, and 30 shown in FIG. 1 to FIG. 3.

[0015] Fig. 5 shows a schematic cross-sectional view of a sample 100 for evaluating the water contact peelability of a pressure-sensitive adhesive sheet in an example of the present application. The pressure-sensitive adhesive sheet 50 shown in Fig. 5 is a double-sided pressure-sensitive adhesive sheet having a multilayer structure in which a pressure-sensitive adhesive layer (X) 2, a substrate 3, and a pressure-sensitive adhesive layer (Z) (hereinafter also simply referred to as "layer (Z)") 5 which is a pressure-sensitive adhesive layer other than the pressure-sensitive adhesive layer (X) are laminated in this order. In the adhesive sheet 50 shown in FIG. 5, the recess 1 of the layer (X) 2 does not come into contact with the adherend (glass plate) 101 even when it comes into contact with the adherend 101, and water penetrates along the recess 1. Therefore, it is considered that the time for water to penetrate into the interface between the layer (X) 2 and the adherend 101 and the time for the layer (X) 2 to swell with water can be shortened, compared to, for example, a layer (Z) that does not have the recess 1.

[0016] In addition, in the pressure-sensitive adhesive sheet 20 shown in Fig. 2, the base material 3 and the layer (X) 2 may be directly laminated as shown in Fig. 2, or another layer may be interposed between the base material 3 and the layer (X) 2. Here, "directly laminated" refers to a configuration in which, for example, in the case of the pressure-sensitive adhesive sheet 20 shown in Fig. 2, the base material 3 and the layer (X) 2 are in direct contact with each other without there being another layer between them. In the pressure-sensitive adhesive sheets 30 and 40 shown in Figures 3 and 4, the base material 3 and the layer (X) 2 may be laminated directly to each other as three layers as shown in each figure, or another layer may be laminated between the base material 3 and either one of the layers (X) 2, or between the base material 3 and both layers (X) 2, via another layer. In addition, in the adhesive sheet 50 shown in FIG. 5, the layer (X) 2, the base material 3, and the layer (Z) 5 may be laminated directly as shown in FIG. 5, or another layer may be interposed between the layer (X) 2 and the base material 3, and / or between the base material 3 and the layer (Z) 5. Furthermore, for example, as shown in FIGS. 1 to 5, a portion where no recess 1 exists relative to the recess 1 of the layer (X) 2 may be referred to as a protrusion 2a of the layer (X) 2.

[0017] The pressure-sensitive adhesive sheet according to one embodiment of the present invention is a pressure-sensitive adhesive sheet that exhibits self-peeling properties upon contact with water. In addition, it is preferable that the pressure-sensitive adhesive sheet according to one embodiment of the present invention can be self-peeled from an adherend by attaching a surface having recesses of the pressure-sensitive adhesive layer (X) of the pressure-sensitive adhesive sheet to the adherend and then contacting the pressure-sensitive adhesive layer (X) with water. In this specification, "self-peeling" refers to the state in which the adhesive sheet is peeled off or falls off from the adherend without the application of a force to pull the adhesive sheet off, and such a property is referred to as "self-peeling properties." In this specification, the self-peeling that occurs when the PSA sheet comes into contact with water is referred to as "peeling upon contact with water," and such a property is referred to as "peeling property upon contact with water." Here, the "water" also includes the form of an "aqueous solution" in which a liquid or solid other than water is dissolved, so long as the effects of the present application are achieved. The "water" can be appropriately selected depending on the application of the pressure-sensitive adhesive sheet, and preferably includes tap water, pure water such as ion-exchanged water, RO water, and distilled water, and ultrapure water, and more preferably includes one or more types selected from the group consisting of pure water and ultrapure water.

[0018] When the layer (X) used in the present invention comes into contact with water, it is believed that self-peeling occurs due to a combined effect of water penetration into the interface between the layer (X) and the adherend due to the hydrophilicity of the layer (X) and water penetration into the interface between the layer (X) and the adherend due to the layer (X) itself absorbing water and swelling (hereinafter also referred to as "water swelling"). Since the layer (X) used in the present invention has the recesses, water penetrates along the recesses, and when the pressure-sensitive adhesive sheet is viewed in plan, water can easily penetrate into the interface between the layer (X) and the adherend not only from the outer edge of the pressure-sensitive adhesive sheet but also from the location where the recesses are present. In addition, the time required for the layer (X) to swell with water is shortened by the penetration of water from the recesses. As a result, the time required for water to penetrate into the interface between the layer (X) and the adherend to the extent that the pressure-sensitive adhesive sheet can be self-peeled from the adherend is significantly shortened, and it is considered that the water contact peelability is significantly improved. From this viewpoint, the method of bringing the layer (X) into contact with water is preferably to immerse the layer (X) in water so that the interface between the layer (X) and the adherend is located below the water surface, more preferably to immerse the layer (X) in water so that at least the recesses located on the outer periphery of the layer (X) when the layer (X) is viewed in a plan view are immersed in water, and further preferably to immerse the layer (X) in water so that the entire layer (X) is immersed in water.

[0019] The temperature of the water is not particularly limited as long as it does not impair the effects of the present invention, but is preferably more than 0° C. and less than 100° C., more preferably 4° C. or more and less than 50° C., and even more preferably 5° C. or more and 40° C. or less. The pressure-sensitive adhesive sheet according to one embodiment of the present invention can be sufficiently effective even when treated with water at room temperature (25° C.). That is, even if the water that is brought into contact with the pressure-sensitive adhesive sheet is not particularly subjected to treatment such as heating or cooling, the pressure-sensitive adhesive sheet can exhibit water-contact releasability, and therefore the pressure-sensitive adhesive sheet is excellent in workability and economy when used (during the peeling treatment).

[0020] Furthermore, in a water contact peelability evaluation performed by the method described in the Examples below, the time required for the pressure-sensitive adhesive sheet of one embodiment of the present invention to self-peel from an adherend when immersed in water is preferably 10 minutes or less, more preferably 5 minutes or less, even more preferably 1 minute or less, and still more preferably less than 1 minute.

[0021] In addition, in this specification, the lower limit and the upper limit described in stages for the preferred numerical range (for example, the range of the content, etc.) can be combined independently. For example, from the description "preferably 10 or more, more preferably 30 or more, and preferably 90 or less, more preferably 60 or less", the "preferable lower limit (10)" and the "more preferable upper limit (60)" can be combined to make the preferred range "10 or more, 60 or less". Similarly, from the description "preferably 10 to 90, more preferably 30 to 60", it can be made "10 to 60". In addition, unless otherwise specified, when the preferred numerical range is simply described as "10 to 90", it represents a range of 10 to 90. In addition, in this specification, for example, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid", and the same applies to other similar terms. In addition, in this specification, the "active ingredient" in the pressure-sensitive adhesive composition refers to, among the components contained in the pressure-sensitive adhesive composition, components that are liquid at room temperature (25°C) excluding solvents (water and organic solvents) that are not directly involved in the reaction, and components that are solid at room temperature (25°C). The pressure-sensitive adhesive sheet of the present invention will be described in more detail below, but the aspects of the present invention are not limited thereto.

[0022] <Adhesive layer (X)> The pressure-sensitive adhesive layer (X) is a layer formed from an acrylic pressure-sensitive adhesive composition (hereinafter also referred to as "pressure-sensitive adhesive composition") containing an acrylic polymer (A) having a carboxy group (hereinafter also referred to as "component (A)"), a neutralizing agent (B) (hereinafter also referred to as "component (B)"), and a crosslinking agent (C) (hereinafter also referred to as "component (C)"), and has recesses on at least one surface. Each component contained in the pressure-sensitive adhesive composition will now be described.

[0023] (Component (A): Acrylic polymer having a carboxy group (A)) If the pressure-sensitive adhesive composition does not contain the acrylic polymer (A) having a carboxy group, the resulting pressure-sensitive adhesive sheet will have poor water contact peelability, presumably because the layer (X) will not have sufficient hydrophilicity and water swelling properties, and water will not penetrate sufficiently into the interface between the layer (X) and the adherend.

[0024] Component (A) has a structural unit (a1) (hereinafter also referred to as "structural unit (a1)") derived from an alkyl (meth)acrylate (am1) (hereinafter also referred to as "monomer (am1)"). The number of carbon atoms in the alkyl group of the monomer (am1) is preferably 1 to 24, more preferably 1 to 12, even more preferably 2 to 10, and still more preferably 4 to 8, from the viewpoint of improving adhesive properties. The alkyl group contained in the monomer (am1) may be a linear alkyl group or a branched alkyl group.

[0025] Examples of the monomer (am1) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, and stearyl (meth)acrylate. As the monomer (am1), one or more selected from the group consisting of ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isooctyl (meth)acrylate are preferable, one or more selected from the group consisting of n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are more preferable, and n-butyl (meth)acrylate is even more preferable. These monomers (am1) may be used alone or in combination of two or more kinds.

[0026] The content of the structural unit (a1) is preferably 45 to 99 mass%, more preferably 55 to 98 mass%, even more preferably 65 to 96 mass%, still more preferably 75 to 94 mass%, and even more preferably 80 to 90 mass%, of all the structural units constituting component (A) (100 mass%). The content of the structural unit (a1) can also be calculated as the content of the monomer (am1) in 100% by mass of all the monomers used when polymerizing component (A).

[0027] Furthermore, component (A) is preferably an acrylic polymer having a structural unit (a2) (hereinafter also referred to as "structural unit (a2)") derived from a monomer (am2) (hereinafter also referred to as "monomer (am2)") containing a carboxy group.

[0028] Examples of the monomer (am2) include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids and anhydrides thereof such as fumaric acid, itaconic acid, maleic acid and citraconic acid; 2-(acryloyloxy)ethyl succinate, 2-carboxyethyl (meth)acrylate, and the like. The monomer (am2) also includes the anhydrides of the ethylenically unsaturated dicarboxylic acids and derivatives of the ethylenically unsaturated dicarboxylic acids. This is because it is possible to generate carboxyl groups by hydrolyzing the groups derived from the unsaturated carboxylic anhydrides in the component (A). Examples of the unsaturated carboxylic anhydrides include the anhydrides of the above-mentioned unsaturated polyvalent carboxylic acids, such as maleic anhydride, citraconic anhydride, and nadic anhydride. The monomer (am2) is preferably one or more selected from an ethylenically unsaturated monocarboxylic acid and an ethylenically unsaturated dicarboxylic acid, more preferably an ethylenically unsaturated monocarboxylic acid, even more preferably one or more selected from the group consisting of (meth)acrylic acid, and even more preferably acrylic acid. These monomers (am2) may be used alone or in combination of two or more kinds.

[0029] Component (A) more preferably contains 0.1 to 20 mass % of the structural unit (a2) relative to 100 mass % of all monomers constituting component (A). The content of the structural unit (a2) in 100% by mass of all structural units constituting component (A) is preferably 0.1% by mass or more, since the water contact peelability of the resulting pressure-sensitive adhesive sheet is improved. The content of the structural unit (a2) in 100% by mass of all structural units constituting component (A) is preferably 20% by mass or less, since the glass transition temperature can be set low and the adhesive strength can be improved. From this viewpoint, the content of the structural unit (a2) in 100% by mass of all structural units constituting component (A) is more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and more preferably 15% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less. The content of the structural unit (a2) can also be calculated as the content of the monomer (am2) in 100% by mass of all the monomers used when polymerizing component (A).

[0030] Furthermore, component (A) is preferably an acrylic polymer having a structural unit (a3) ​​(hereinafter also referred to as "structural unit (a3)") derived from a monomer (am3) (hereinafter also referred to as "monomer (am3)") that contains a hydroxy group.

[0031] Examples of the monomer (am3) include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and unsaturated alcohols such as vinyl alcohol and allyl alcohol. The monomer (am3) is preferably a hydroxyalkyl (meth)acrylate, more preferably one or more selected from the group consisting of 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, and further preferably 2-hydroxyethyl (meth)acrylate. These monomers (am3) may be used alone or in combination of two or more kinds.

[0032] Component (A) more preferably contains 1 to 30 mass % of the structural unit (a3), relative to 100 mass % of all monomers constituting component (A). The content of the structural unit (a3) ​​in 100% by mass of all structural units constituting component (A) is preferably 1% by mass or more, since the water contact peelability of the resulting pressure-sensitive adhesive sheet is improved. The content of the structural unit (a3) ​​in 100% by mass of all structural units constituting component (A) is preferably 30% by mass or less, since the glass transition temperature can be set low and the adhesive strength can be improved. From this viewpoint, the content of the structural unit (a3) ​​in 100% by mass of all structural units constituting component (A) is more preferably 3% by mass or more, even more preferably 6% by mass or more, even more preferably 9% by mass or more, and more preferably 25% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less. The content of the structural unit (a3) ​​can also be calculated as the content of the monomer (am3) in 100% by mass of all the monomers used when polymerizing component (A).

[0033] In component (A), the total content of the structural units (a1), (a2), and (a3) ​​is preferably 80 to 100 mass%, more preferably 85 to 100 mass%, even more preferably 90 to 100 mass%, still more preferably 95 to 100 mass%, and even more preferably 98 to 100 mass%, based on 100 mass% of all structural units constituting component (A). The total content of the structural units (a1), (a2), and (a3) ​​can also be calculated as the total content of the monomers (am1), (am2), and (am3) in 100% by mass of all the monomers used when polymerizing component (A).

[0034] Component (A) may have a structural unit (a4) (hereinafter also referred to as "structural unit (a4)") derived from a monomer (am4) (hereinafter also referred to as "monomer (am4)") other than the above-mentioned monomers (am1) to (am3).

[0035] Examples of the monomer (am4) include functional group-containing monomers other than the monomers (am2) and (am3), such as amino group-containing monomers, substituted amino group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, and alkoxysilyl group-containing monomers; olefins such as ethylene, propylene, and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; diene monomers such as butadiene, isoprene, and chloroprene; cyclohexyl (meth)acrylate, benzyl (meth)acrylate, Examples of the monomer (am4) include isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, imide (meth)acrylate, and other (meth)acrylates having a cyclic structure; styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, (meth)acrylamide, (meth)acrylonitrile, (meth)acryloylmorpholine, and N-vinylpyrrolidone. When these monomers (am4) are used, they may be used alone or in combination of two or more.

[0036] Examples of the amino group or substituted amino group-containing monomer include 2-aminoethyl(meth)acrylate, 2-aminoethyl(meth)acrylamide, N-methylaminoethyl(meth)acrylate, and N-methylaminoethyl(meth)acrylamide.

[0037] Examples of epoxy group-containing monomers include epoxy group-containing (meth)acrylic acid esters and non-acrylic epoxy group-containing monomers. Examples of epoxy group-containing (meth)acrylic acid esters include glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, (3,4-epoxycyclohexyl)methyl (meth)acrylate, 3-epoxycyclo-2-hydroxypropyl (meth)acrylate, etc. Examples of non-acrylic epoxy group-containing monomers include glycidyl crotonate, allyl glycidyl ether, etc.

[0038] As a method for introducing a carboxy group into component (A) other than the method using the monomer (am2), a method can be used in which a homopolymer of the monomer (am1) or a copolymer with a monomer other than the monomer (am1) is polymerized, and then the homopolymer or copolymer is partially saponified to introduce a carboxy group into component (A). In this case, it is preferable to adjust the content of the structural unit (a1) that remains unsaponified in component (A) to the content of the structural unit (a1) described above, and the preferred content is also the same.

[0039] Component (A) can be produced by using a known polymerization method such as bulk polymerization, solution polymerization, or emulsion polymerization. When the component (A) is a copolymer having two or more types of structural units, the copolymer may be in the form of a block copolymer, a random copolymer, or a graft copolymer.

[0040] The mass average molecular weight (Mw) of component (A) is not particularly limited as long as the effects of the present invention are manifested, but from the viewpoint of making it easier for the obtained pressure-sensitive adhesive sheet to manifest sufficient adhesion before contact with water and better releasability upon contact with water, it is preferably from 100,000 to 3,000,000, more preferably from 200,000 to 2,000,000, and even more preferably from 300,000 to 1,000,000. The value of the weight average molecular weight (Mw) is a value calculated in terms of standard polystyrene measured by gel permeation chromatography (GPC), specifically, a value measured based on the method described in the examples.

[0041] From the viewpoint of enabling the resulting pressure-sensitive adhesive sheet to easily exhibit sufficient adhesion before contact with water and better releasability upon contact with water, the content of component (A) in the pressure-sensitive adhesive composition is preferably 75 to 95 mass%, more preferably 80 to 92 mass%, and even more preferably 85 to 90 mass%, of the total amount of the pressure-sensitive adhesive composition (100 mass% active ingredient). The content of component (A) can also be calculated as the amount of component (A) in 100% by mass of all components blended when preparing the pressure-sensitive adhesive composition. The same applies to the contents of components (B), (C) and other components contained in the pressure-sensitive adhesive composition.

[0042] (Component (B): Neutralizer) If the pressure-sensitive adhesive composition does not contain the neutralizing agent (B), the water-swelling properties of the layer (X) will be insufficient, and the resulting pressure-sensitive adhesive sheet will have poor peelability when contacted with water. It is believed that the neutralizing agent (B) reacts with some or all of the carboxy groups of the component (A), and the reaction sites partially form salt-like sites (hereinafter also referred to as "salt sites").The salt sites formed by the carboxy groups of the component (A) and the component (B), and the crosslinked structure formed by the component (A) and the crosslinking agent (C) described below, improve the hydrophilicity and water swelling of the layer (X), and the layer (X) exhibits excellent water-contact peelability.

[0043] As the component (B), various basic compounds can be used as long as the effects of the present invention are exhibited, and preferred examples include amine compounds. Examples of the amine compound include organic amino compounds exhibiting alkalinity, such as ammonia, ammonium salts exhibiting alkalinity, primary amine compounds such as monoethylamine and monoethanolamine, secondary amine compounds such as diethylamine and diethanolamine, tertiary amine compounds such as triethylamine, triethanolamine, N,N-dimethylformamide diethylacetal, N,N,N-trimethylethylenediamine, N-methyldiethanolamine, N,N-diethylhydroxylamine and N,N-diethylethanolamine, amino compounds having multiple nitrogen atoms in one molecule such as diamine and polyethyleneimine, and cyclic amino compounds such as pyridine. The amine compound is preferably a tertiary amine compound.

[0044] In addition, as described above, it is considered that the component (B) can provide better hydrophilicity when it forms a salt moiety with the carboxyl group in the component (A), so among the amine compounds, a hydroxyl group-containing amine compound is more preferred. When the component (B) is a hydroxyl group-containing amine compound, it is considered that the hydroxyl group derived from the component (B) makes it easier for the layer (X) to take up water, and the water swelling property of the layer (X) is further improved. From this viewpoint, the component (B) is more preferably a hydroxyl group-containing tertiary amine compound, and even more preferably triethanolamine. These neutralizing agents (B) may be used alone or in combination of two or more kinds.

[0045] From the viewpoint of making it easier for the resulting pressure-sensitive adhesive sheet to exhibit good water-contact peelability, the content of component (B) in the pressure-sensitive adhesive composition is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 9 parts by mass, even more preferably 1 to 8 parts by mass, still more preferably 4 to 8 parts by mass, and even more preferably 6 to 8 parts by mass, relative to the total amount of component (A) (100 parts by mass of active ingredient).

[0046] (Component (C): Crosslinking agent) If the pressure-sensitive adhesive composition does not contain the crosslinking agent (C), the layer (X) will not have sufficient water-swelling properties. Component (C) is a compound that reacts with component (A) to form a crosslinked structure, and is preferably a compound that reacts with some or all of the carboxy groups in component (A) to crosslink component (A). As described above, it is believed that the excellent water-contact peelability of the pressure-sensitive adhesive layer (X) is exhibited by the pressure-sensitive adhesive layer (X) being a layer having a crosslinked structure derived from component (A) and component (C) and a salt-like moiety derived from component (A) and component (B).

[0047] Examples of the component (C) include epoxy-based crosslinking agents, methylol-based crosslinking agents, metal chelate-based crosslinking agents, aziridine-based crosslinking agents, etc. Among these, one or more types selected from epoxy-based crosslinking agents and metal chelate-based crosslinking agents are preferred, and epoxy-based crosslinking agents are more preferred.

[0048] Examples of the epoxy crosslinking agent include neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, phthalic acid diglycidyl ester, dimer acid diglycidyl ether, diglycerol triglycidyl ether, sorbitol tetraglycidyl ether, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, N,N,N',N'-tetraglycidyldiaminodiphenylmethane, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, diglycidylamine, etc. These may be used alone or in combination of two or more.

[0049] Examples of the metal chelate crosslinking agent include metal chelate compounds in which acetylacetone, ethyl acetoacetate, tris(2,4-pentanedionate), etc. are coordinated to polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, zirconium, etc. These may be used alone or in combination of two or more. These crosslinking agents (C) may be used alone or in combination of two or more kinds.

[0050] The content of component (C) in the pressure-sensitive adhesive composition is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 9 parts by mass, even more preferably 1 to 8 parts by mass, still more preferably 4 to 8 parts by mass, and even more preferably 6 to 8 parts by mass, relative to the total amount of component (A) (100 parts by mass of active ingredient), from the viewpoint of making it easier for the obtained pressure-sensitive adhesive sheet to exhibit sufficient adhesion before contact with water and better releasability upon contact with water.

[0051] (Other additives) The pressure-sensitive adhesive composition may contain other additives in addition to the above-mentioned components (A) to (C) as long as the effects of the present invention are not impaired. Examples of other additives include resin components other than component (A), surfactants, antioxidants, ultraviolet absorbers, light stabilizers, flame retardants, conductive agents, antistatic agents, slip agents, antiblocking agents, colorants, plasticizers, and the like. When these additives are contained, the content of each is preferably 0.01 to 20 mass%, more preferably 0.01 to 10 mass%, even more preferably 0.01 to 5 mass%, and even more preferably 0.01 to 2 mass%, relative to 100 mass% of the pressure-sensitive adhesive composition. Examples of resin components other than component (A) include polyolefin resins such as polyethylene and polypropylene; polyester resins; and the like.

[0052] (recess) The "recesses" of the layer (X) refer to depressions that are intentionally provided so that the layer (X) does not come into contact with an adherend when the surface of the layer (X) having the recesses is attached to the adherend. The shape of the recesses when the layer (X) is viewed from above can be appropriately selected depending on the application of the pressure-sensitive adhesive sheet, and may be either regular or irregular. When the shape of the recess in the plan view of the layer (X) is a fixed shape, examples of the shape include polygons such as triangles, quadrilaterals (including rectangles, squares, and trapezoids), pentagons, and hexagons; shapes in which some or all of the corners of the polygon are slightly rounded (also referred to as "rounded corners (R)"); circles such as perfect circles and ellipses; semicircles such as semicircles, semiellipses, and U-shapes; and shapes represented by closed areas surrounded by at least three lines (including straight lines and curves), as well as one or more shapes selected from figures combining these (hereinafter also referred to as "independent recess shapes").

[0053] Furthermore, the shape of the recesses when the layer (X) is viewed in a plane is preferably such that the recesses are in contact with the contour of the surface of the layer (X) having the recesses, more preferably such that the recesses are continuously connected from any one point on the contour of the surface of the layer (X) having the recesses to other points (not limited to the contour, any point on the plane where the recesses of the layer (X) exist) (hereinafter also referred to as a "continuous recess shape"), further preferably such that the recesses are continuously connected from any one point on the contour of the surface of the layer (X) having the recesses to other points on the contour, and still further preferably such that the recesses are continuously connected from any one side of the surface of the layer (X) having the recesses to another side. When the recesses have a continuous recess shape, water can more easily penetrate from the outer edge (contour) of layer (X) toward the center when layer (X) is viewed in a plane, which is preferable because it further improves the water-contact releasability of the pressure-sensitive adhesive sheet.

[0054] For this reason, for example, when the layer (X) is viewed in a plane, it is preferable that at least a part of the continuous recesses is present on the line segment (including the center of gravity) on the center of gravity side when the shortest straight line (hereinafter also referred to as the "shortest distance to the center of gravity") connecting the center of gravity of a figure drawn by the contour of the surface having the recesses of the layer (X) is bisected, it is more preferable that at least a part of the continuous recesses is present on the line segment (including the center of gravity) closest to the center of gravity side when the shortest distance to the center of gravity is divided into thirds, and it is even more preferable that at least a part of the continuous recesses is present on the line segment (including the center of gravity) closest to the center of gravity side when the shortest distance to the center of gravity is divided into fifths. Furthermore, when the layer (X) is viewed in a plane, it is preferable that at least a part of the continuous recesses is present on the line segment (including the center of gravity) on the center of gravity side when the longest straight line (hereinafter also referred to as the "longest distance to the center of gravity") connecting the center of gravity of a figure drawn by the contour of the surface having the recesses of the layer (X) and any one point on the contour is divided into two equal parts; it is more preferable that at least a part of the continuous recesses is present on the line segment (including the center of gravity) closest to the center of gravity side when the longest distance to the center of gravity is divided into thirds; and it is even more preferable that at least a part of the continuous recesses is present on the line segment (including the center of gravity) closest to the center of gravity side when the longest distance to the center of gravity is divided into fifths.

[0055] Further, it is more preferable that the layer (X) has both continuous recesses at least a part of which is present at a preferred position on the shortest distance to the center of gravity, and continuous recesses at least a part of which is present at a preferred position on the longest distance to the center of gravity. In this case, the preferred position where the part of the continuous recesses is present on the shortest distance to the center of gravity and the preferred position where the part of the continuous recesses is present on the longest distance to the center of gravity can be combined independently. For example, the continuous recesses may have at least a part of the recesses present on the line segment (including the center of gravity) closest to the center of gravity when the shortest distance to the center of gravity is divided into two equal parts, and the continuous recesses may have at least a part of the recesses present on the line segment (including the center of gravity) closest to the center of gravity when the longest distance to the center of gravity is divided into five equal parts. Among them, it is more preferable to combine the above-mentioned recesses in the more preferable modes. That is, it is more preferable to combine the modes in which at least a part of the continuous recesses is present at a position closer to the center of gravity.

[0056] Examples of the continuous recess shape include linear shapes such as straight lines, curved lines, zigzags, and wavy lines connecting any one point on the surface of the layer (X) having recesses to one or more other points. Among these, a shape composed of straight lines is preferable, and examples of such shapes include striped and lattice-shaped recesses described below. On the layer (X), at least one selected from these continuous recess shapes can be arranged at a predetermined interval so as not to intersect, or to intersect with each other, to provide recesses in the form of, for example, striped shapes as shown in FIG. 6, lattice shapes as shown in FIG. 7, or other geometric patterns. In this case, a region 6 surrounded by recesses 1 may be formed, as in the lattice shape shown in FIG. 7, and examples of the shape of the region 6 include shapes similar to those described for the independent recess shapes described above. The region 6 is also the protrusion 2a. On the surface of the layer (X), a discontinuous shape may exist due to a part of the continuous recessed shape being missing, or a continuous recessed shape and an independent recessed shape may exist together. Each shape that can be taken by the recesses when the layer (X) is viewed in a plane may be present regularly or irregularly, but it is preferable that they are present regularly in a pattern as shown in Figure 6 or 7. In the case of a lattice pattern as shown in FIG. 7, identical recess shapes (straight lines) intersect with each other to form one recess, and since there are no discontinuous portions, the recess shapes can be regarded as a single recess shape.

[0057] In addition, the cross-sectional shape of the recess when the layer (X) is cut in the thickness direction may vary depending on the cut surface and cannot be generally specified, but examples thereof include polygons such as triangles, quadrilaterals (including rectangles, squares, and trapezoids), pentagons, and hexagons; shapes in which some or all of the corners of the polygons are slightly rounded (also referred to as "rounded corners (R)"); semicircular shapes such as semicircles, semiellipses, and U-shapes; and the like.

[0058] The height difference of the recesses is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 0.5 μm or more, more preferably 1.0 μm or more, even more preferably 3.0 μm or more, and is preferably 50.0 μm or less, more preferably 30.0 μm or less, even more preferably 25.0 μm or less, and even more preferably 20.0 μm or less. The width of the recess is preferably 150 μm or less, more preferably 100 μm or less, even more preferably 75.0 μm or less, still more preferably 50.0 μm or less, and still more preferably 35.0 μm or less. There is no particular lower limit to the width of the recess, but it is preferably 1.0 μm, more preferably 3.0 μm, and still more preferably 5.0 μm. The height difference and width of the recess are values ​​measured using the method described in the Examples. Regarding the values ​​described as the preferred ranges, for example, when "the height difference of the recess is 0.5 μm or more," it is sufficient that a portion having a height difference of 0.5 μm or more exists in any portion of the recess, and it is not necessary that the entire region of the recess has a height difference of 0.5 μm or more. Similarly, even if there are multiple recesses with different shapes on layer (X), it is sufficient that any of the recesses has a portion having a height difference of 0.5 μm or more, and it is not necessary that all of the recesses have a height difference of 0.5 μm or more. The height difference and width of the recess are values ​​measured using the method described in the Examples. For example, the distance 1h shown in Fig. 1 corresponds to the height difference of the recess. Also, the distance 1w shown in Figs. 1, 6, and 7 corresponds to the width of the recess. As an example, if we use the cross-sectional image of the recess shown in Fig. 9, which is a scanning electron microscope (SEM) image taken using the method described in the Examples, the distance 1h in Fig. 9 corresponds to the height difference of the recess, and the distance 1w corresponds to the width of the recess.

[0059] The shape of the recesses can be formed, for example, by applying the pressure-sensitive adhesive composition onto a release material having protrusions that correspond to the recesses, as described below, and drying the composition to transfer the shape of the protrusions on the surface of the release material to the surface of layer (X).

[0060] When a plurality of recesses are present on the layer (X), the shapes of the plurality of recesses may be the same or different, and in that case, the height difference and width of the recesses may be independently the same or different.

[0061] The distance between the edges of the recesses is preferably 50.0 μm or more, more preferably 100 μm or more, even more preferably 150 μm or more, and even more preferably 200 μm or more. And, it is preferably 2,000 μm or less, more preferably 1,500 μm or less, and even more preferably 1,000 μm or less. For example, in the case of Figure 6 where there are multiple recesses, the distance between the edges of the recesses refers to the shortest distance between the edge of any one recess and the edge of the other recess that is closest to that recess, which refers to distance 7f in Figure 6. Furthermore, for example, in the case of the lattice-shaped recess shown in FIG. 7, the edge-to-edge distance of the recess refers to the shortest distance between the edge of any one side of the recess forming the lattice and the edge of the side opposite to that side, and refers to distance 7f in FIG. 7. The shortest pitch between the recesses is preferably 50.0 μm or more, more preferably 100 μm or more, even more preferably 150 μm or more, and even more preferably 200 μm or more, and is preferably 2,000 μm or less, more preferably 1,500 μm or less, and even more preferably 1,000 μm or less. For example, in the case of Figure 6 where there are multiple recesses, the shortest pitch of the recesses refers to the shortest distance from the midpoint of the shortest distance between the edges of any one recess to the midpoint of the shortest distance between the edges of another recess that is closest to the recess in question, and refers to distance 7p in Figure 6. Also, for example, in the case of the lattice-shaped recesses shown in Figure 7, the shortest pitch of the recesses refers to the shortest distance from the midpoint of the shortest distance between the edges of a recess portion forming one side of the lattice to the midpoint of the shortest distance between the edges of another recess portion forming a side opposite to the one side, and refers to distance 7p in Figure 7.

[0062] The adhesive strength of the surface of layer (X) where the recesses are present is appropriately set depending on the application of the adhesive sheet, but is preferably 0.20 to 10.00 N / 25 mm, more preferably 0.30 to 8.00 N / 25 mm, and even more preferably 0.40 to 4.0 N / 25 mm. In this specification, the adhesive strength of the pressure-sensitive adhesive layer refers to the adhesive strength before the layer (X) comes into contact with water, specifically, the value measured by the method described in the Examples.

[0063] The thickness of the layer (X) is preferably 5 to 150 μm, more preferably 8 to 100 μm, even more preferably 12 to 70 μm, and even more preferably 15 to 50 μm, although the thickness of the layer (X) is preferably thicker than the height difference of the recesses. When the thickness of the layer (X) is 5 μm or more, sufficient adhesive strength is easily obtained, and unintended peeling from the adherend during temporary fixing, displacement of the adherend, etc. are easily suppressed. On the other hand, when the thickness of the layer (X) is 150 μm or less, the adhesive sheet is easily handled.

[0064] <Base material> Examples of materials for forming the substrate that can be used in one embodiment of the present invention include resins, metals, and paper materials, and can be appropriately selected depending on the application of the pressure-sensitive adhesive sheet.

[0065] Examples of resins used for the substrate include polyolefin resins such as polyethylene and polypropylene; vinyl resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol copolymer; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polystyrene; acrylonitrile-butadiene-styrene copolymer; cellulose triacetate; polycarbonate; urethane resins such as polyurethane and acrylic-modified polyurethane; polymethylpentene; polysulfone; polyether ether ketone; polyether sulfone; polyphenylene sulfide; polyimide resins such as polyetherimide and polyimide; polyamide resins; acrylic resins; and fluorine-based resins. Among these, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are preferred. Examples of the substrate using the resin as a forming material include a resin film or a resin sheet containing the resin. Examples of the metal include aluminum, tin, chromium, and titanium. Examples of the paper material include thin paper, medium-quality paper, fine paper, impregnated paper, coated paper, art paper, parchment paper, glassine paper, and dust-free paper.

[0066] These forming materials may be used alone or in combination of two or more kinds. Examples of substrates that combine two or more forming materials include paper laminated with a thermoplastic resin such as polyethylene, and resin-containing resin films or sheets having a metal layer formed on the surface thereof. Examples of methods for forming the metal layer include a method of depositing a metal by a PVD method such as vacuum deposition, sputtering, or ion plating, and a method of attaching a metal foil with a general adhesive.

[0067] Among these substrates, a resin film or sheet is preferred, a film or sheet made of a polyester-based resin is more preferred, and a film or sheet made of polyethylene terephthalate (PET) is even more preferred.

[0068] In addition, from the viewpoint of improving interlayer adhesion with other layers laminated on the substrate, one or both surfaces of the substrate may be subjected to a surface treatment such as an oxidation method or a roughening method. Examples of the oxidation method include corona discharge treatment, plasma treatment, chromic acid oxidation (wet), flame treatment, hot air treatment, ozone irradiation treatment, ultraviolet irradiation treatment, ultraviolet-ozone treatment, etc. Examples of the roughening method include sandblasting, solvent treatment, etc.

[0069] Furthermore, a primer layer, a filling layer, etc. may be provided on one or both surfaces of the substrate, if necessary. Examples of components constituting the primer layer include polyester-based resins, urethane-based resins, polyester urethane-based resins, acrylic resins, etc., and these resins may be used alone or in combination of two or more kinds. The filling layer is provided to further improve the adhesion between the substrate and a layer adjacent to the substrate, or to impart rigidity to the substrate when the substrate is too soft, such as a paper substrate. The filling layer is not particularly limited, and examples thereof include layers composed of a styrene-butadiene copolymer, an acrylic resin, a polyester resin, a polyurethane resin, a polystyrene resin, or the like as the main component, to which a filler such as clay, silica, calcium carbonate, titanium oxide, or zinc oxide is added as necessary. When these other layers are present, their thicknesses are each independently preferably 0.05 to 30 μm, more preferably 0.1 to 5 μm, even more preferably 0.1 to 1 μm, and still more preferably 0.1 to 0.5 μm. The substrate that can be used in the present invention may contain, as desired, additives for the substrate, such as an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a slip agent, an antiblocking agent, a colorant, etc., within the scope that does not impair the effects of the present invention.

[0070] The thickness of the substrate is appropriately set depending on the application of the pressure-sensitive adhesive sheet, but from the standpoint of ease of handling and economic efficiency, it is preferably 5 to 250 μm, more preferably 10 to 200 μm, and even more preferably 25 to 150 μm.

[0071] <Removal material> Examples of the release material that can be used in one embodiment of the present invention include a release sheet that has been treated for release on both sides and a release sheet that has been treated for release on one side, and examples of such a release material include a release agent applied to a substrate for the release material. Examples of the substrate for the release material include plastic films such as polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, and polyolefin resin films such as polypropylene resin and polyethylene resin. Examples of the release agent include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, and butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, and fluorine-based resins.

[0072] As described above, for the purpose of forming recesses on the pressure-sensitive adhesive layer (X), a release material in which a convex shape is formed on the release treatment surface (hereinafter also referred to as a "release material having convex portions") is preferred, and from the viewpoint of making it easier to maintain the recess shape of the layer (X) during storage of the pressure-sensitive adhesive sheet, a release material in which convex portions that pair with the recesses of the layer (X) are formed on the release treatment surface is more preferred. In addition, the term "protrusion" as defined in this specification refers to a protruding portion having a difference in height. The shape of the convex portions can be formed, for example, by transferring a shape engraved on the peripheral surface of an embossing roll onto the release surface by embossing. Moreover, for example, the convex portions can be formed by utilizing a printing technique such as a screen printing method.

[0073] In addition, examples of the shape of the convex portion include a shape that pairs with a concave portion of the layer (X). A preferred embodiment of the convex portion is a shape that pairs with the concave portion described as a preferred embodiment in the description of the concave portion of the layer (X), and therefore detailed description thereof will be omitted here. Furthermore, for example, preferred aspects of “the cross-sectional shape of the recess when the layer (X) is cut in the thickness direction” and “the shape of the recess when the layer (X) is viewed in plan” are similar to preferred aspects of “the cross-sectional shape of the convex portion when the release material is cut in the thickness direction” and “the shape of the convex portion when the release material is viewed in plan”.

[0074] Furthermore, the preferred range of the "height difference and width of convex portions" present on the surface of the release material can also be referred to as the height difference and width of convex portions that can form the "height difference and width of concave portions" present on the surface of the layer (X) described above. Similarly, the preferred range of the "base-to-base distance and shortest pitch of convex portions" present on the surface of the release material can also be referred to as the base-to-base distance and shortest pitch of convex portions that can form the "edge-to-edge distance and shortest pitch of concave portions" present on the surface of the layer (X) described above. Therefore, the preferred ranges of the "height difference and width of the convex portion" and the "distance between the bases of the convex portions and the shortest pitch" are not particularly limited as long as they do not impair the effects of the present invention, and may be, for example, the ranges shown below.

[0075] The height difference of the convex portions is preferably 0.5 μm or more, more preferably 1.0 μm or more, even more preferably 3.0 μm or more, and is preferably 50.0 μm or less, more preferably 30.0 μm or less, even more preferably 25.0 μm or less, and even more preferably 20.0 μm or less. Similarly, the width of the convex portion is preferably 150 μm or less, more preferably 100 μm or less, even more preferably 75.0 μm or less, still more preferably 50.0 μm or less, still more preferably 35.0 μm or less, and still more preferably 30.0 μm or less. There is no particular lower limit to the width of the concave portion, but it is preferably 1.0 μm, more preferably 3.0 μm, and still more preferably 5.0 μm. The height difference and width of the convex portion are values ​​measured using the method described in the Examples. For example, distance 4h shown in Fig. 8 corresponds to the height difference of convex portion 4a. Distance 4w shown in Fig. 8 corresponds to the width of the convex portion. As an example, if we use the cross-sectional image of convex portion 4a shown in Fig. 10, which is a scanning electron microscope (SEM) image taken using the method described in the Examples, distance 4h in Fig. 10 corresponds to the height difference of the convex portion, and distance 4w corresponds to the width of the convex portion.

[0076] The distance between the bases of the convex portions is preferably 50.0 μm or more, more preferably 100 μm or more, even more preferably 150 μm or more, and even more preferably 200 μm or more. It is preferably 2,000 μm or less, more preferably 1,500 μm or less, and even more preferably 1,000 μm or less. For example, if the concave portions in Figure 6 are replaced with convex portions (assuming that Figure 6 is a surface having convex portions of a release material), the distance between the bases of the convex portions refers to the shortest distance between the base of any convex portion and the base of the convex portion closest to that convex portion, which refers to distance 7f in Figure 6. Furthermore, for example, if the lattice-like concave portions shown in Figure 7 are replaced with convex portions (assuming Figure 7 is a surface having convex portions of a release material), the distance between the bases of the convex portions refers to the shortest distance between the base of any one side of the convex portions forming the lattice and the base of the side opposite that side, and refers to distance 7f in Figure 7. The shortest pitch between the convex portions is preferably 50.0 μm or more, more preferably 100 μm or more, even more preferably 150 μm or more, and even more preferably 200 μm or more, and is preferably 2,000 μm or less, more preferably 1,500 μm or less, and even more preferably 1,000 μm or less. For example, if the concave portions in Figure 6 are replaced with convex portions (if Figure 6 is assumed to be a surface having convex portions of a release material), the shortest pitch of the convex portions refers to the shortest distance from the midpoint of the shortest distance between the bases of any one convex portion to the midpoint of the shortest distance between the bases of another convex portion that is closest to the convex portion in question, and refers to distance 7p in Figure 6. Furthermore, for example, if the lattice-like concave portions shown in Figure 7 are replaced with convex portions (assuming Figure 7 is a surface having convex portions of a release material), the shortest pitch of the convex portions refers to the shortest distance from the midpoint of the shortest distance between the bases of convex portions forming one side of the lattice to the midpoint of the shortest distance between the bases of other convex portions forming the side opposite to the one side, and refers to distance 7p in Figure 7. As an example, if we use a planar image of the convex portion 4a shown in Figure 12, which is a scanning electron microscope (SEM) image taken using the method described in the examples, the distance 4p in Figure 12 corresponds to the shortest pitch of the convex portions, and the distance 4w corresponds to the width of the convex portions.

[0077] The thickness of the release material is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 5 to 250 μm, more preferably 30 to 200 μm, and even more preferably 50 to 150 μm.

[0078] The total thickness of the adhesive sheet (the total thickness of each layer, excluding the release material) is set appropriately depending on the application of the adhesive sheet, but is preferably 30 μm or more, more preferably 70 μm or more, even more preferably 95 μm or more, and is preferably 300 μm or less, more preferably 200 μm or less, even more preferably 170 μm or less, and even more preferably 150 μm or less.

[0079] <Other adhesive layers (Z)> The pressure-sensitive adhesive sheet according to one embodiment of the present invention may have a pressure-sensitive adhesive layer (Z) other than the above-mentioned layer (X) as long as the effects of the present invention are not impaired. An example of the pressure-sensitive adhesive sheet is, as described above, a pressure-sensitive adhesive sheet 30 shown in Fig. 3 in which one of the two layers (X) 2 is a pressure-sensitive adhesive layer (Z) other than the layer (X) 2 that does not have a recess 1 on its surface. Another example is a pressure-sensitive adhesive sheet 50 shown in Fig. 5. The pressure-sensitive adhesive layer (Z) other than the layer (X) can be appropriately selected according to the use of the pressure-sensitive adhesive sheet, and is not particularly limited as long as it does not impair the effects of the present invention. Examples of the pressure-sensitive adhesive resin contained in the other pressure-sensitive adhesive layer include rubber-based resins such as acrylic resins, urethane resins, and polyisobutylene resins, polyester resins, olefin resins, silicone resins, and polyvinyl ether resins. These adhesive resins may be used alone or in combination of two or more kinds. Furthermore, when these adhesive resins are copolymers having two or more types of constitutional units, the copolymer may be in the form of any one of a block copolymer, a random copolymer, and a graft copolymer. Furthermore, when the pressure-sensitive adhesive sheet according to one embodiment of the present invention has a pressure-sensitive adhesive layer (Z), the aforementioned release material may be provided on the exposed surface of the pressure-sensitive adhesive layer (Z).

[0080] [Method of manufacturing adhesive sheet] The method for producing the pressure-sensitive adhesive sheet is not particularly limited as long as it is capable of forming a pressure-sensitive adhesive layer (X) having recesses on at least one surface. Preferably, the method includes a production method having at least the following steps (1) and (2): Step (1): A step of applying an acrylic pressure-sensitive adhesive composition containing an acrylic polymer (A) having a carboxy group, a neutralizing agent (B), and a crosslinking agent (C) onto the surface of a release material having convex portions, where the convex portions are present, to form a coating film. Step (2): A step of drying the coating film formed in step (1) to form a pressure-sensitive adhesive layer (X) having recesses on the surface on the release material side, thereby obtaining a pressure-sensitive adhesive sheet.

[0081] In the following explanation, the aspects of the pressure-sensitive adhesive layer (X), the release material and the substrate, the aspect of the acrylic pressure-sensitive adhesive composition forming the layer (X), and the aspect of the obtained pressure-sensitive adhesive sheet are the same as those explained in the section on the pressure-sensitive adhesive sheet, and preferred aspects thereof are also the same, so detailed explanations are omitted.

[0082] By using a release material having convex portions in step (1), the shape of the convex portions can be transferred onto the surface of layer (X) to form concave portions in layer (X) during the process in which the coating film made of the acrylic pressure-sensitive adhesive composition is dried to form the pressure-sensitive adhesive layer (X) in step (2). When the pressure-sensitive adhesive composition is applied onto a release material having convex portions, the pressure-sensitive adhesive composition may be further diluted with an organic solvent and used in the form of a solution of the pressure-sensitive adhesive composition. Examples of the organic solvent to be used include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol. As for these organic solvents, the organic solvents used in producing each component contained in the pressure-sensitive adhesive composition may be used as they are, or one or more other organic solvents may be added thereto.

[0083] The solution of the pressure-sensitive adhesive composition can be applied onto the release material by a known application method to form a coating film. Examples of the coating method include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0084] In step (2), the coating film formed in step (1) is dried. As described above, the coating film is dried to form the pressure-sensitive adhesive layer (X), and recesses in the layer (X) are formed. The drying temperature in step (2) is not particularly limited as long as the layer (X) can be formed, but is preferably 80 to 150° C., more preferably 90 to 140° C., and even more preferably 95 to 130° C. The drying time is not particularly limited as long as the layer (X) can be formed, but is preferably 30 seconds to 5 minutes, and more preferably 1 minute to 3 minutes.

[0085] [Uses of adhesive sheets] The pressure-sensitive adhesive sheet of one embodiment of the present invention has sufficient adhesive strength when applied to an adherend, but when peeled off from the adherend, it can be peeled off by itself in a short time by contacting it with water, and therefore can be used for any purpose as long as the adherend used is one that can come into contact with water. The adherend is not particularly limited, but from the viewpoint that the pressure-sensitive adhesive sheet has self-peeling properties and can reduce the load on the adherend, a suitable embodiment of the adherend is a brittle material, and a suitable example of the brittle material is a wafer for an electronic device, as described below. In addition, from the viewpoint that the pressure-sensitive adhesive sheet has self-peelability and is expected to suppress or prevent defects such as contamination, deformation, and damage of the adherend caused by the pressure-sensitive adhesive sheet, an example of a suitable embodiment of the adherend is a material for electronic devices. Examples of the electronic device material include chips for electronic devices such as semiconductor chips, wafers for electronic devices such as semiconductor wafers, compound semiconductors, packages for electronic devices such as semiconductor packages, electronic components, sapphire substrates, displays, substrates for panels, etc. Among these, wafers for electronic devices are more preferred.

[0086] In addition, the pressure-sensitive adhesive sheet according to one embodiment of the present invention can be used as a temporary fixing sheet in, for example, the manufacturing process of electronic device materials as described above.Specific examples of the pressure-sensitive adhesive sheet in such a usage mode include a dicing sheet used when dicing an adherend such as an electronic device wafer, a backgrind sheet used in the process of grinding an adherend such as an electronic device wafer, a temporary fixing sheet used to temporarily fix a support for supporting a backgrind sheet to which an adherend such as an electronic device wafer is attached, an expand tape used to expand the distance between adherends such as electronic device chips that have been singulated by dicing, a transfer tape used to invert the front and back of an adherend such as an electronic device chip, and a temporary fixing sheet for inspecting an object to be inspected. Therefore, the pressure-sensitive adhesive sheet according to one embodiment of the present invention can be suitably used as a temporary fixing pressure-sensitive adhesive sheet for use in processing and / or inspection of materials for electronic devices.

[0087] In addition, since the pressure-sensitive adhesive sheet according to one embodiment of the present invention is capable of self-peeling, it is expected to suppress and prevent defects such as contamination, deformation, and damage of the adherend caused by the pressure-sensitive adhesive sheet. Therefore, the pressure-sensitive adhesive sheet according to one embodiment of the present invention can be used in a variety of applications other than electronic device materials, including, for example, protective film applications such as window films, protective and design-imparting applications such as wallpaper and wrapping films, various label applications such as returnable labels, and use in attaching temporary notices and the like. Furthermore, when the pressure-sensitive adhesive sheet according to one embodiment of the present invention is a pressure-sensitive adhesive sheet having the layer (X) having the above-mentioned continuous recessed shape, it can be suitably used in applications requiring air release properties and appearance when attached to an adherend, such as identification, decoration, paint masking, and surface protection of metal plates, etc. More specifically, it can be suitably used, for example, as a paint replacement tape; a marking film; and a tape for attachment to a vehicle (for example, a decorative tape for decorating the exterior and interior of an automobile, a blackout tape, etc.).

[0088] In addition, when the pressure-sensitive adhesive sheet according to one embodiment of the present invention is used as a double-sided pressure-sensitive adhesive sheet, for example, when the pressure-sensitive adhesive sheet is composed of only a single pressure-sensitive adhesive layer and the recesses are present only on one surface of the layer (X), or when the pressure-sensitive adhesive sheet has two pressure-sensitive adhesive layers and the layer (X) has recesses only on one surface, it is possible to appropriately select which of the adherends the surface having the recesses is to be attached to. For example, the layer (X) may be attached to the side of the adherend from which it is desired to peel the layer with a lower load, or, for example, when the other pressure-sensitive adhesive layer is another pressure-sensitive adhesive layer provided for a purpose other than the layer (X) (for example, when it is a pressure-sensitive adhesive layer with lower staining properties), the attachment surface for each adherend may be selected according to the effect of each layer.

[0089] For example, when the pressure-sensitive adhesive sheet according to one embodiment of the present invention is used as a double-sided pressure-sensitive adhesive sheet for processing and inspection of an adherend, from the viewpoint of improving the processability and inspectability of the adherend, the adherend can be attached to either one of the pressure-sensitive adhesive layers on both sides, and a support can be attached to either one of the pressure-sensitive adhesive layers. In this case, as described above, it is sufficient to use layer (X) as either one of the pressure-sensitive adhesive layers, and both pressure-sensitive adhesive layers may be layers (X). Fixing the adherend to the support via the adhesive sheet is preferable because it suppresses vibration and displacement of the adherend, and damage when the adherend is a fragile material such as a brittle material, when the adherend is subjected to one or more of processing and inspection, thereby improving processing accuracy and processing speed as well as inspection accuracy and inspection speed. In this case, when using a double-sided adhesive having only one of the adhesive layers as layer (X), depending on the type of adherend to be processed and / or inspected and the type of processing and / or inspection method, the adherend to be processed and / or inspected may be affixed to layer (X) and the support may be affixed to the other adhesive layer, or the support may be affixed to layer (X) and the adherend to be processed and / or inspected may be affixed to the other adhesive layer. Similarly, when using a double-sided pressure-sensitive adhesive sheet having different layers (X) on both sides, either layer (X) may be attached to an adherend that is to be processed and / or inspected.

[0090] As described above, the adherend to be processed and / or inspected is preferably a material for an electronic device. Therefore, for example, when the pressure-sensitive adhesive sheet according to one embodiment of the present invention is used as a double-sided pressure-sensitive adhesive sheet for processing and / or inspecting the material for an electronic device, it can be suitably used for temporarily fixing the material for an electronic device to a support. The material of the support may be appropriately selected taking into consideration the required properties such as mechanical strength and heat resistance depending on the type of adherend to be processed and / or inspected, the type of processing and / or inspection method, etc. For example, when the adhesive sheet of one embodiment of the present invention is used as a double-sided adhesive sheet for processing and / or inspecting the electronic device material, examples of the material for the support include metal materials such as SUS; non-metallic inorganic materials such as glass and silicon wafers; resin materials such as epoxy resin, ABS resin, acrylic resin, engineering plastic, super engineering plastic, polyimide resin, polyamideimide resin; and composite materials such as glass epoxy resin. Of these, SUS, glass, and silicon wafers are preferred. Examples of the engineering plastics include nylon, polycarbonate (PC), and polyethylene terephthalate (PET). Examples of the super engineering plastics include polyphenylene sulfide (PPS), polyethersulfone (PES), and polyetheretherketone (PEEK).

[0091] In addition, when the pressure-sensitive adhesive sheet according to one embodiment of the present invention is used as a double-sided pressure-sensitive adhesive sheet for processing and / or inspecting the electronic device material, the support is preferably attached to the entire adhesive surface of the pressure-sensitive adhesive layer to be attached. Therefore, the surface area of ​​the support on the side attached to the adhesive surface of the pressure-sensitive adhesive layer is preferably equal to or larger than the surface area of ​​the adhesive surface of the pressure-sensitive adhesive layer. In addition, the surface of the support on the side attached to the adhesive surface of the pressure-sensitive adhesive layer is preferably flat. The shape of the support is not particularly limited, but is preferably a plate shape. The thickness of the support may be appropriately selected in consideration of the required characteristics, but is preferably from 20 μm to 50 mm, more preferably from 60 μm to 20 mm. EXAMPLES

[0092] The present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples. Note that the physical properties in the following examples were measured by the following methods.

[0093] <Mass average molecular weight (Mw)> Measurements were carried out using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8020") under the conditions below, and values ​​measured in terms of standard polystyrene were used. (Measurement conditions) Column: "TSK guard column HXL-L", "TSK gel G2500HXL", "TSK gel G2000HXL", and "TSK gel G1000HXL" (all manufactured by Tosoh Corporation) connected in series Column temperature: 40℃ Developing solvent: Tetrahydrofuran ·Flow rate: 1.0mL / min

[0094] <Thickness of the base layer and release layer> The measurements were made using a constant pressure thickness gauge (manufactured by Techclock Corporation, model number: "PG-02J", standard specifications: compliant with JIS K6783-1994, Z1702-1994, Z1709-1995). The thickness of the embossed release material is the distance from the smooth surface of the release material to the point where the protrusions on the embossed surface are formed. For example, the distance 4t shown in Figure 8 corresponds to the thickness of the release material.

[0095] <Thickness of each layer in the adhesive sheet> Cross sections in the thickness direction of the adhesive layer (X1) and the adhesive layer (X2) of the adhesive sheets produced in the Examples and Comparative Examples, cut perpendicularly to a plane parallel to the surface of the base layer (corresponding to a portion where no recesses are formed), were observed using a scanning electron microscope (manufactured by Hitachi, Ltd., product name "S-4700"), and the thicknesses of the adhesive layer (X1) and the adhesive layer (X2) were measured. The thickness of the pressure-sensitive adhesive layer (X) was determined as the distance from the surface of the pressure-sensitive adhesive layer in contact with the substrate to a location on the surface opposite the substrate where no recesses were formed. For example, the distance 2t shown in FIG. 1 corresponds to the thickness of the layer (X). The thickness of the pressure-sensitive adhesive layer (Z), which will be described later, was also measured in the same manner.

[0096] <Height difference, width and minimum pitch of recesses in layer (X)> The height difference and width of the recesses present on the surface opposite the substrate of the pressure-sensitive adhesive layer (X) (layer (X1) and layer (X2)) of the pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples were measured by observing the cross section of the pressure-sensitive adhesive sheet using a scanning electron microscope (manufactured by Hitachi, Ltd., product name "S-4700") and utilizing the measurement function of image analysis software for scanning electron microscopes. 9 shows an SEM image of the measurement of the height difference of the recesses on the layer (X1) in Example 1. In the case of Example 1, the height difference and width values ​​correspond to the distances 1h and 1w shown in FIG. Moreover, Fig. 11 shows an SEM image when the shortest pitch of the recesses on the layer (X1) was measured in Example 1. In the case of Example 1, the value of the shortest pitch corresponds to the distance 7p shown in Fig. 11. Note that 1w shown in Fig. 11 corresponds to the width of the recesses.

[0097] <Height difference, width and minimum pitch of the convex parts of the release material> The height difference, width and shortest pitch of the convex portions present on the adhesive layer side of the release material used in the examples were measured by observing the cross section with a scanning electron microscope (manufactured by Hitachi, Ltd., product name "S-4700") and using the measurement function of image analysis software for scanning electron microscopes. 10 shows an SEM image obtained when measuring the height difference and the like of the convex portions of the release material 1. The height difference and width values ​​of the convex portions of the release material 1 correspond to the distances 4h and 4w shown in FIG. Moreover, Fig. 12 shows an SEM image obtained when measuring the shortest pitch of the convex portions of the release material 1. The value of the shortest pitch of the convex portions of the release material 1 corresponds to the distance 4p shown in Fig. 12. Note that 4w shown in Fig. 12 corresponds to the width of the convex portions.

[0098] <Evaluation of water contact peelability of adhesive sheets> In the pressure-sensitive adhesive sheets prepared in each of the Examples and Comparative Examples described below, each double-sided pressure-sensitive adhesive sheet was prepared for evaluating water contact peelability by replacing the pressure-sensitive adhesive layer (X2) with a pressure-sensitive adhesive layer (Z) having no recesses formed as follows. Specifically, an acrylic copolymer (mass average molecular weight = 500,000) obtained by copolymerizing 77 parts by mass of n-butyl acrylate, 20 parts by mass of methyl methacrylate, and 3 parts by mass of 2-hydroxyethyl acrylate was prepared as the acrylic polymer for the adhesive layer (Z). Next, 5 parts by mass (active ingredient ratio) of trimethylolpropane adduct tolylene diisocyanate (manufactured by Tosoh Corporation, product name "Coronate (registered trademark) L") as a crosslinking agent was added to 100 parts by mass of the acrylic copolymer to prepare an acrylic pressure-sensitive adhesive composition, which was then diluted with toluene and stirred for 30 minutes to prepare a solution of the acrylic pressure-sensitive adhesive composition. Next, the solution of the acrylic adhesive composition was applied onto the embossed surface of the release material 4 described below using an applicator, and dried at a drying temperature of 100°C for 2 minutes to form an adhesive layer (Z) having no recesses to a thickness of 20 μm. Then, the exposed surface of the pressure-sensitive adhesive layer (Z) was bonded to the exposed surface of the PET substrate of a laminate consisting of a pressure-sensitive adhesive layer (X1) and a PET substrate, which was prepared in the same manner as in each of the Examples and Comparative Examples described below, to prepare a double-sided pressure-sensitive adhesive sheet for evaluating water contact peelability. Each of the prepared double-sided PSA sheets for evaluating water contact peelability was cut into test pieces measuring 50 mm in length (MD) × 50 mm in width (TD). In addition, two glass plates (manufactured by Corning Corporation, product name "Eagle XG (registered trademark)", size: length 50 mm × width 50 mm × thickness 2 mm) were prepared. Then, only the release material on the adhesive layer (X1) side was removed, and one of the glass plates was bonded to the exposed surface of the adhesive layer (X1) by pressure bonding using a tabletop laminator (manufactured by Fujipla Inc., product name "LPD3212") at 23°C and a lamination speed of 300 mm / min. Next, the release material 4 on the adhesive layer (Z) side was also removed, and the remaining glass plate was bonded to the exposed surface of the adhesive layer (Z) by pressure bonding using a vacuum laminator (manufactured by Nikko Materials Co., Ltd., product name "V-130") under conditions of 60°C, 0.2 MPa, and 30 seconds, to prepare a sample for evaluating water contact peelability. The obtained water contact peelability evaluation sample was immersed in a water tank of pure water at 25°C with the layer (X1) side facing up, and the time until the entire surface of the glass plate attached to the layer (X1) side peeled off by itself was measured. Even if the evaluation sample was placed flat in the water tank, water penetrated between the peeled glass plate and the layer (X1), causing a difference in refractive index between the peeled and unpeeled parts of the evaluation sample, so that it was possible to visually check whether or not peeling had occurred even from outside the water tank. Here, MD in MD direction is an abbreviation of Machine Direction, and MD direction means the longitudinal direction when the pressure-sensitive adhesive sheet is molded. Also, TD in TD direction is an abbreviation of Transverse Direction, and TD direction means the width direction when the pressure-sensitive adhesive sheet is molded. Here, the "MD direction" of the pressure-sensitive adhesive sheet refers to the direction in which the pressure-sensitive adhesive composition is applied when forming the pressure-sensitive adhesive layer (X1).

[0099] <Adhesive strength of adhesive layer (X1)> In the same manner as the pressure-sensitive adhesive sheets prepared in the Examples and Comparative Examples, single-sided pressure-sensitive adhesive sheets not forming a pressure-sensitive adhesive layer (X2) were prepared as samples for evaluating adhesive strength. Each evaluation sample was cut into test pieces measuring 300 mm in length (MD) × 25 mm in width (TD). Then, the release material on the adhesive layer (X1) was removed, and the exposed surface of the adhesive layer (X1) was attached to the mirror surface of a silicon mirror wafer using a 2 kg rubber roller in accordance with JIS Z0237:2000. After that, after leaving it to stand for 20 minutes in an environment of 23°C and 50% RH (relative humidity), the adhesive layer (X1) was peeled off from the silicon mirror wafer at a tensile speed of 300 mm / min by the 180° peeling method based on JIS Z0237:2000, and the adhesive strength of the adhesive layer (X1) was measured.

[0100] [Manufacturing of adhesive sheets]

[0101] (Preparation of Acrylic Pressure-Sensitive Adhesive Composition) Manufacturing Example 1 An acrylic pressure-sensitive adhesive composition was prepared by blending 100 parts by mass (effective component ratio) of an acrylic copolymer (an acrylic copolymer having structural units derived from raw material monomers consisting of n-butyl acrylate (BA) / 2-hydroxyethyl acrylate (2HEA) / acrylic acid (AAc) = 85 / 12 / 3 (mass ratio), mass average molecular weight (Mw): 400,000) which is an acrylic polymer (A) having a carboxy group, with 7 parts by mass of triethanolamine as a neutralizing agent (B) and 7 parts by mass (effective component ratio) of an epoxy crosslinking agent (manufactured by Nagase ChemteX Corporation, product name "Denacol (registered trademark) EX-810") as a crosslinking agent (C). The mixture was then diluted with toluene and stirred uniformly to prepare a solution of the acrylic pressure-sensitive adhesive composition.

[0102] Manufacturing Example 2 A solution of an acrylic pressure-sensitive adhesive composition was prepared in the same manner as in Production Example 1, except that triethanolamine was not added.

[0103] (Substrate and release material) The abbreviations shown below respectively represent the following materials. PET substrate: polyethylene terephthalate film, manufactured by Toyobo Co., Ltd., product name "Cosmoshine (registered trademark)", product number "A4300", thickness 50 μm Release material 1: Film with silicone release treatment on the embossed surface, thickness 139μm (including convex height), embossed pattern diagonal lattice, minimum pattern pitch 250μm, convex cross-sectional shape V-shaped, convex height 9μm, convex width 20μm Release material 2: Release paper having a resin layer with a silicone release treatment on the embossed surface, thickness 143 μm (including the height of the convex part), embossing pattern parallel oblique lines, minimum pattern pitch 700 μm, cross-sectional shape of the convex part U-shaped, convex part height 23 μm, convex part width 71 μm Release material 3: Release paper having a resin layer with a silicone release treatment on the embossed surface, thickness 142 μm (including the height of the convex part), embossing pattern wavy line, cross-sectional shape of the convex part U-shaped, convex part height 22 μm, convex part width 98 μm Release material 4: Polyethylene terephthalate film with silicone release treatment on one side, product name "SP-PET381031", thickness 38μm, not embossed.

[0104] (Creating adhesive sheets) Example 1 The solution of the acrylic adhesive composition prepared in Production Example 1 was applied onto the embossed surface of the release material 1 using an applicator, and dried for 2 minutes at a drying temperature of 100° C. to form a first adhesive layer (X1). Furthermore, the PET substrate was laminated onto the exposed surface of the adhesive layer (X1). Separately, a second pressure-sensitive adhesive layer (X2) was formed on the embossed surface of the release material 1 prepared above in the same manner as above, using the solution of the acrylic pressure-sensitive adhesive composition prepared in Production Example 1. Then, the exposed surface of the pressure-sensitive adhesive layer (X2) was laminated onto the exposed surface of the PET substrate laminated to the pressure-sensitive adhesive layer (X1), to obtain a pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers (X) on both sides.

[0105] Examples 2 and 3, and Comparative Example 1 Each pressure-sensitive adhesive sheet shown in Table 1 below was obtained in the same manner as in Example 1, except that the release material shown in Table 1 below was used as the release material and the thickness of each of the pressure-sensitive adhesive layers (X1) and (X2) was changed.

[0106] Comparative Example 2 An adhesive sheet was obtained in the same manner as in Example 1, except that the adhesive composition prepared in Production Example 2 was used as the adhesive composition forming the adhesive layers (X1) and (X2).

[0107] The pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples were evaluated using the evaluation methods described above, and the results are shown in Table 1 below.

[0108] [Table 1]

[0109] It was confirmed from Table 1 that the pressure-sensitive adhesive sheets of Examples 1 to 3 had excellent releasability when contacted with water, and the time it took for the pressure-sensitive adhesive sheets to self-peel from the adherend after immersion in water was significantly shorter than that of the pressure-sensitive adhesive sheets of Comparative Examples 1 and 2. It was also confirmed that the pressure-sensitive adhesive sheets had sufficient adhesive strength to hold the adherend in place before immersion in water. The pressure-sensitive adhesive sheets of Examples 1 to 3 have recesses on the surface of the pressure-sensitive adhesive layer (X) (layer (X1) and layer (X2)) that is attached to the adherend, and therefore when the pressure-sensitive adhesive sheet is viewed in plan, water can easily penetrate from the outer edge of the pressure-sensitive adhesive sheet to the center of the pressure-sensitive adhesive sheet along the recesses when immersed in water. As a result, it is believed that the time until water-contact peeling is significantly shortened. On the other hand, in Comparative Example 1, since there are no recesses on the attachment surfaces of the pressure-sensitive adhesive layers (layer (X1) and layer (X2)), after the pressure-sensitive adhesive sheet is immersed in water, water can only penetrate into the interface between each pressure-sensitive adhesive layer and the adherend from the outer edge of the pressure-sensitive adhesive sheet. Therefore, it is believed that it took a long time for water to penetrate into the interface between each pressure-sensitive adhesive layer and the adherend to the extent that the pressure-sensitive adhesive sheet becomes self-peelable from the adherend. In addition, in Comparative Example 2, recesses were present on the application surface of the pressure-sensitive adhesive layer (layer (X1) and layer (X2)), but the pressure-sensitive adhesive composition forming each pressure-sensitive adhesive layer did not contain neutralizing agent (B), resulting in a longer time until water-contact peeling compared to the pressure-sensitive adhesive sheets of Examples 1 to 3. This result is believed to indicate that the pressure-sensitive adhesive layer (X) of the pressure-sensitive adhesive sheets of Examples 1 to 3 is a layer formed from a pressure-sensitive adhesive composition containing components (A) to (C), thereby improving the water-swellability of the pressure-sensitive adhesive layer (X), making it easier for water to penetrate into the interface between the layer (X) and the adherend, and improving the water-contact releasability. It was also confirmed that the shortest pitch of the recesses formed on the surface of the adhesive layer (X) of the adhesive sheet of Example 1 was 250 μm, and the shortest pitch of the recesses formed on the surface of the adhesive layer (X) of the adhesive sheet of Example 2 was 700 μm. In addition, for the pressure-sensitive adhesive sheets of Examples 1 to 3, before the evaluation samples prepared in the water contact peelability evaluation were immersed in a water tank, the surfaces of the pressure-sensitive adhesive layers (X1) and (X2) were viewed in plan (magnification: 100 times) using an optical digital microscope (manufactured by Keyence Corporation, product name "Digital Microscope VHX-5000"). As a result, it was confirmed that both of the pressure-sensitive adhesive layers (X1) and (X2) of the pressure-sensitive adhesive sheets of Examples 1 to 3 have a plurality of the recesses continuously bonded from any one point on the contour of the surface to another point on the contour. It was also confirmed that the continuously bonded recesses form recesses continuously bonded from any one side to any other side of the surface of the pressure-sensitive adhesive layer (X). [Industrial Applicability]

[0110] The pressure-sensitive adhesive sheet of one embodiment of the present invention has sufficient adhesive strength when applied to an adherend, but when peeled off from the adherend, it can be peeled off by itself in a short time by contacting it with water, and therefore can be used for any purpose as long as the adherend used is one that can come into contact with water. For example, it can be used as various temporary fixing sheets used in the manufacturing process of materials for electronic devices as described above. In addition to electronic device applications, the pressure-sensitive adhesive sheet of one embodiment of the present invention can be used in a variety of applications, including, for example, protective film applications such as the window film described above, protective and decorative applications such as wallpaper and wrapping films, various label applications such as returnable labels, and use for attaching temporary notices, etc. Furthermore, when the pressure-sensitive adhesive sheet of one embodiment of the present invention is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer (X) having the above-mentioned continuous recessed shape, it can also be suitably used for, for example, the above-mentioned identification, decoration, paint masking, surface protection of metal plates, etc. [Explanation of symbols]

[0111] 10, 20, 30, 40, 50, 60, 70 Adhesive Sheet 100 Water contact peelability evaluation sample of the pressure sensitive adhesive sheet in the present embodiment 101 Adherend (glass plate) 1. A recess on the surface of the adhesive layer (X) 1h Height difference of depressions on the surface of the adhesive layer (X) 1w: Width of the recess on the surface of the adhesive layer (X) 2 Adhesive layer (X) 2a Convex portion of adhesive layer (X) 2t Thickness of adhesive layer (X) 3 Base material 4 Release material 4-1 First release material 4-2 Second release material 4a: A convex portion of the release material that is paired with a concave portion of the adhesive layer (X) 4h Height difference of the convex part of the release material 4w Width of the convex part of the release material 4p The shortest pitch of the convex parts of the release material 4t Thickness of the peeling material 5. Adhesive layer (Z) other than adhesive layer (X) 6 Area surrounded by recess 1 7f Distance between edges of recess 1 7p Shortest pitch of recess 1

Claims

1. A pressure-sensitive adhesive sheet comprising: a pressure-sensitive adhesive layer (X) formed from an acrylic pressure-sensitive adhesive composition comprising an acrylic polymer (A) having a carboxy group, a neutralizing agent (B) and a crosslinking agent (C), wherein recesses are present on at least one surface of the pressure-sensitive adhesive layer (X), and the shape of the recesses when the pressure-sensitive adhesive layer (X) is viewed in plan is a stripe shape, a lattice shape or a wavy line shape, and the component (B) is a hydroxy group-containing amine compound.

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the component (B) is a hydroxy group-containing tertiary amine compound.

3. 3. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein component (A) contains 0.1 to 20 mass% of a structural unit (a2) derived from a monomer (am2) containing a carboxy group, relative to 100 mass% of all structural units constituting component (A).

4. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the content of component (A) in the acrylic pressure-sensitive adhesive composition is 75 to 95 mass% in the total amount of the acrylic pressure-sensitive adhesive composition (100 mass% of active ingredient).

5. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the content of component (B) in the acrylic pressure-sensitive adhesive composition is 0.05 to 10 parts by mass relative to the total amount of component (A) (100 parts by mass of active ingredient).

6. 6. The pressure-sensitive adhesive sheet according to claim 1, wherein the component (C) is at least one selected from the group consisting of epoxy-based crosslinking agents and metal chelate-based crosslinking agents.

7. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the content of component (C) in the acrylic pressure-sensitive adhesive composition is 0.05 to 10 parts by mass relative to the total amount of component (A) (100 parts by mass of active ingredient).

8. The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the height difference of the recesses is 0.5 µm or more.

9. The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein, when the pressure-sensitive adhesive layer (X) is viewed in plan, the recesses are present and are continuously connected from one point to another point on the contour of the surface of the pressure-sensitive adhesive layer (X).

10. The pressure-sensitive adhesive sheet according to any one of claims 1 to 9, wherein the pressure-sensitive adhesive layer (X) has an adhesive strength of a surface on which the recesses are present, of 0.20 to 10.00 N / 25 mm.

11. The pressure-sensitive adhesive sheet according to any one of claims 1 to 10, which has a substrate.

12. The pressure-sensitive adhesive sheet according to any one of claims 1 to 11, further comprising a release material on a surface of the pressure-sensitive adhesive layer (X) having recesses, the release material having protrusions that form pairs with the recesses of the pressure-sensitive adhesive layer (X).

Images