Adhesive sheet and peeling method

Abstract

An adhesive sheet comprising an adhesive layer for holding an object, the adhesive layer having an uneven surface, and a base portion configured in the thickness direction of the adhesive layer from a depression where the adhesive layer has the smallest thickness to a surface opposite the uneven surface, the sheet comprising a first portion provided to have a first height on the base portion, and a second portion provided to have a second height on the base portion different from the first height.

Description

[Technical field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet and a peeling method. [Background technology]

[0002] Adhesive sheets that temporarily hold an object are known. Such adhesive sheets can be used to transfer an object to a desired location.

[0003] Pressure-sensitive adhesive sheets come in various shapes depending on their applications. For example, Patent Document 1 discloses a technology that enables a functional pressure-sensitive adhesive sheet to be firmly attached to an adherend, while also enabling the pressure-sensitive adhesive sheet to be temporarily attached. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP2004-115766A Summary of the Invention [Problem to be solved by the invention]

[0005] A pressure-sensitive adhesive sheet that temporarily holds an object is required to have a certain degree of ability to hold the object, as well as to be able to easily remove the object.

[0006] An object of the present invention is to provide a pressure-sensitive adhesive sheet having a structure that allows the held object to be peeled off while maintaining a certain degree of ability to hold the object. [Means for solving the problem]

[0007] As a result of extensive research, the inventors have found that by providing the surface of the adhesive layer with unevenness having protrusions of different heights, the adhesive sheet can retain a certain degree of ability to hold an object while making it easier to peel off the held object, thereby solving the above-mentioned problems. After further research, they have completed the present invention.

[0008] That is, the present invention relates to the following [1] to

[13] . [1] An adhesive sheet having an adhesive layer for holding an object, The adhesive layer has an uneven surface, a base portion including a portion from a concave portion where the thickness of the adhesive layer is smallest to a surface opposite to the surface having the concaves and convexes in a thickness direction of the adhesive layer; a first portion provided on the base portion to have a first height; a second portion provided on the base portion so as to have a second height different from the first height; An adhesive sheet comprising: [2] The pressure-sensitive adhesive sheet according to [1], wherein the difference between the first height and the second height is 1 μm or more and 40 μm or less. [3] The first portion is a first convex portion provided on the base portion, The pressure-sensitive adhesive sheet according to [1] or [2], wherein the second portion is a second convex portion provided on the base portion and different from the first convex portion. [4] the first height is greater than the second height; The pressure-sensitive adhesive sheet according to any one of [1] to [3], wherein the number of the first convex portions is smaller than the number of the second convex portions. [5] the first height is greater than the second height; The pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein an area of ​​the pressure-sensitive adhesive layer occupied by the first convex portions is smaller than an area of ​​the pressure-sensitive adhesive layer occupied by the second convex portions. [6] The pressure-sensitive adhesive sheet according to any one of [1] to [5], wherein the base portion is integral with the first portion and the second portion. [7] The pressure-sensitive adhesive sheet according to any one of [1] to [6], further comprising a substrate supporting the pressure-sensitive adhesive layer. [8] The pressure-sensitive adhesive sheet described in [7], wherein the tensile modulus of the substrate is 2500 MPa or less. [9] The adhesive sheet described in any one of [1] to [8], characterized in that the adhesive sheet is expandable in a planar direction, and the planar peelability of an object on the adhesive sheet after expansion is improved compared to before expansion.

[10] A method for peeling an object from an adhesive sheet, comprising: an expansion step of expanding, in a planar direction, the adhesive sheet according to any one of [1] to [9], which holds an object on an adhesive layer; and a peeling step of peeling the object from the adhesive layer of the adhesive sheet expanded in the planar direction.

[11] The peeling method according to any one of [1] to

[10] , wherein in the expanding step, the object is peeled off from the second portion of the adhesive sheet while remaining in contact with the first portion of the adhesive sheet. Effect of the Invention

[0009] It is possible to provide a pressure-sensitive adhesive sheet having a certain degree of ability to hold an object, while having a structure that allows the held object to be peeled off.

[0010] Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which the same reference numerals are used to designate the same or similar components throughout the drawings. [Brief description of the drawings]

[0011] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. [Figure 1] FIG. 2 is a cross-sectional view of a pressure-sensitive adhesive sheet according to an embodiment. [Figure 2A] 1A to 1C are diagrams showing a method for holding and peeling an object using an adhesive sheet. [Figure 2B] 1A to 1C are diagrams showing a method for holding and peeling an object using an adhesive sheet. [Figure 2C] 1A to 1C are diagrams showing a method for holding and peeling an object using an adhesive sheet. [Figure 2D] 1A to 1C are diagrams showing a method for holding and peeling an object using an adhesive sheet. [Figure 3A] FIG. 4 is a cross-sectional view showing an example of projections and recesses on a pressure-sensitive adhesive sheet. [Figure 3B] FIG. 4 is a cross-sectional view showing an example of projections and recesses on a pressure-sensitive adhesive sheet. [Figure 4] FIG. 2 is a plan view of a pressure-sensitive adhesive sheet according to an embodiment. [Figure 5A] FIG. 4 is a plan view showing an example of projections and recesses on an adhesive sheet. [Figure 5B] FIG. 4 is a plan view showing an example of projections and recesses on an adhesive sheet. [Figure 5C] FIG. 4 is a plan view showing an example of projections and recesses on an adhesive sheet. [Figure 5D] FIG. 4 is a plan view showing an example of projections and recesses on an adhesive sheet. [Figure 6] 4 is a flowchart of a peeling method according to an embodiment. [Figure 7A] Schematic diagram of an adhesive sheet placed in an expanding device. [Figure 7B] Schematic diagram of an adhesive sheet placed in an expanding device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more features among the multiple features described in the embodiments may be arbitrarily combined. In addition, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0013] (definition) In this specification, the mass average molecular weight (Mw) and the number average molecular weight (Mn) are values ​​calculated in terms of standard polystyrene measured by size exclusion chromatography, specifically, values ​​measured based on JIS K7252-1: 2016. In addition, in this specification, "(meth)acrylic acid" is a term that refers to both "acrylic acid" and "methacrylic acid", and the same applies to other similar terms.

[0014] In the present specification, when one or more lower limit values ​​and one or more upper limit values ​​of a numerical range (e.g., a range of content, etc.) are described, it can be understood that any combination of the lower limit value and the upper limit value therein is described. For example, the description that it is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and preferably 9 or less, more preferably 8 or less, even more preferably 7 or less clearly means that the numerical range may be any of 1 or more to 9 or less, 1 or more to 8 or less, 1 or more to 7 or less, 2 or more to 9 or less, 2 or more to 8 or less, 2 or more to 7 or less, 3 or more to 9 or less, 3 or more to 8 or less, and 3 or more to 7 or less.

[0015] (Structure of adhesive sheet) An adhesive sheet according to one embodiment of the present invention includes an adhesive layer 1 for holding an object. For example, the adhesive sheet may include an adhesive layer 1 and a substrate 2 supporting the adhesive layer 1. Hereinafter, the configuration of such an adhesive sheet will be described with reference to FIG. 1, which is a schematic diagram of an adhesive sheet according to one embodiment.

[0016] (base material) The adhesive layer 1 may be provided on a substrate 2. For example, as shown in FIG. 1, an adhesive sheet including an adhesive layer 1 and a substrate 2 can be used. However, it is not essential that the adhesive sheet has a substrate 2. For example, the adhesive sheet may be composed of only the adhesive layer 1. In this case, an adhesive layer 1 having high support can be used.

[0017] The substrate 2 functions as a support for supporting the adhesive layer 1. The substrate 2 is located on the surface F1 opposite to the surface having the unevenness 1a of the adhesive layer 1. The type of the substrate 2 is not particularly limited, and may be a hard substrate or a flexible substrate. From the viewpoint of improving cushioning when holding the object 4, facilitating attachment to the object 4, improving peelability, facilitating lamination, or enabling the substrate 2 to be in a roll form, the substrate 2 is preferably a flexible substrate. For example, a resin film can be used as the substrate 2.

[0018] The resin film is a film in which a resin-based material is used as a main material, and may be made of a resin material or may contain an additive in addition to the resin material. The resin film may be laser beam transmissive.

[0019] Specific examples of the resin film include polyethylene films such as low-density polyethylene film, linear low-density polyethylene film, and high-density polyethylene film, polyolefin films such as polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, ethylene-norbornene copolymer film, and norbornene resin film; ethylene copolymer films such as ethylene-vinyl acetate copolymer film, ethylene-(meth)acrylic acid copolymer film, and ethylene-(meth)acrylic acid ester copolymer film; polyvinyl chloride films such as polyvinyl chloride film and vinyl chloride copolymer film; polyester films such as polyethylene terephthalate film and polybutylene terephthalate film; polyurethane film; polyimide film; polystyrene film; polycarbonate film; and fluororesin film. In addition, films containing a mixture of two or more materials, crosslinked films in which the resins forming these films are crosslinked, and modified films such as ionomer films may be used. In addition, the substrate 2 may be a laminated film in which two or more resin films are laminated.

[0020] From the viewpoints of versatility, relatively high strength making it easy to prevent warping, and heat resistance, the resin film is preferably a monolayer film selected from the group consisting of polyethylene films, polyester films, and polypropylene films, or a laminate film in which two or more types of films selected from this group are laminated.

[0021] The thickness of the substrate 2 is not particularly limited, but from the viewpoint of achieving both supportability and roll winding properties, it is preferably in the range of 10 μm to 500 μm, more preferably 25 μm to 200 μm, and even more preferably 40 μm to 90 μm.

[0022] In one embodiment, the adhesive sheet is expanded when peeled off from the object 4. To facilitate expansion of the adhesive sheet, the tensile modulus of the substrate 2 is preferably 50 MPa or more, more preferably 80 MPa or more, even more preferably 120 MPa or more, and is preferably 2500 MPa or less, more preferably 1000 MPa or less, even more preferably 200 MPa or less. In this specification, the tensile modulus means a value measured by the method described in the examples.

[0023] Similarly, in order to facilitate expansion of the pressure-sensitive adhesive sheet, the breaking elongation of the substrate 2 is preferably 105% or more, more preferably 110% or more, and even more preferably 115% or more. The breaking elongation is measured in accordance with JIS C2151:2019.

[0024] From the viewpoint of facilitating the expansion of the pressure-sensitive adhesive sheet, the base material 2 is preferably a polyolefin film or a vinyl chloride copolymer film. Examples of polyolefin films include polyethylene films, polypropylene films, and ethylene copolymers including ethylene-methacrylic acid copolymers. Examples of vinyl chloride copolymer films include vinyl chloride-vinylidene chloride copolymer films, vinyl chloride-vinyl acetate copolymer films, and vinyl chloride-ethylene copolymer films.

[0025] (Adhesive layer) The adhesive layer 1 is a layer having adhesiveness and may contain a resin. As described below, the adhesive layer 1 has irregularities 1a on its surface. The adhesive sheet may have two or more adhesive layers 1. For example, the adhesive sheet may have a laminate of one type or two or more types of adhesive layers 1.

[0026] (Composition of adhesive layer) Examples of the resin contained in the adhesive layer 1 include rubber-based resins such as polyisobutylene-based resins, polybutadiene-based resins, and styrene-butadiene-based resins, acrylic resins, urethane-based resins, polyester-based resins, olefin-based resins, silicone-based resins, and polyvinyl ether-based resins. The adhesive layer may have heat resistance, and examples of the material of the adhesive layer 1 having such heat resistance include polyimide-based resins and silicone-based resins. The adhesive layer 1 may contain a copolymer having two or more types of constitutional units. The form of such a copolymer is not particularly limited, and may be any of a block copolymer, a random copolymer, an alternating copolymer, and a graft copolymer.

[0027] The resin contained in the adhesive layer 1 is preferably an adhesive resin having adhesiveness by itself. The resin is preferably a polymer having a mass average molecular weight (Mw) of 10,000 or more. From the viewpoint of improving the retention, the mass average molecular weight (Mw) of the resin is preferably 10,000 or more, more preferably 70,000 or more, and even more preferably 140,000 or more. From the viewpoint of suppressing the shear storage modulus to a predetermined value or less, it is preferably 2 million or less, more preferably 1.2 million or less, and even more preferably 900,000 or less. From the viewpoint of improving the retention, the number average molecular weight (Mn) of the resin is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more. From the viewpoint of suppressing the shear storage modulus to a predetermined value or less, it is preferably 2 million or less, more preferably 1 million or less, and even more preferably 700,000 or less. In addition, when the adhesive layer 1 contains a resin derived from an energy reactive resin as described later, the mass average molecular weight (Mw) and the number average molecular weight (Mn) refer to the mass average molecular weight (Mw) and the number average molecular weight (Mn) before the crosslinking reaction by the application of energy. The glass transition temperature (Tg) of the resin is preferably −75° C. or higher, more preferably −70° C. or higher, and preferably 5° C. or lower, more preferably −20° C. or lower. When Tg is within this range, the retention and shear storage modulus of the obtained adhesive layer 1 can be easily set within the ranges described below.

[0028] The amount of resin contained in adhesive layer 1 relative to the total amount of components constituting adhesive layer 1 can be set appropriately depending on the desired retention and shear storage modulus of adhesive layer 1, but is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 55% by mass or more, even more preferably 60% by mass or more, and is preferably 99.99% by mass or less, more preferably 99.95% by mass or less, even more preferably 99.90% by mass or less, even more preferably 99.80% by mass or less, and even more preferably 99.50% by mass or less.

[0029] The shear storage modulus of the adhesive layer 1 is preferably 0.001 MPa or more, more preferably 0.01 MPa or more, even more preferably 0.05 MPa or more, and even more preferably 0.1 MPa or more, from the viewpoint of the morphological stability of the uneven shape of the surface of the adhesive layer 1. On the other hand, a low shear storage modulus of the adhesive layer 1 is preferable in that it can suppress positional deviation when holding an object. From this viewpoint, the shear storage modulus of the adhesive layer 1 is preferably 100 MPa or less, more preferably 10 MPa or less, even more preferably 5 MPa or less, even more preferably 2 MPa or less, even more preferably 1 MPa or less, and even more preferably 0.5 MPa or less. In this specification, the shear storage modulus means a value measured by the method described in the Examples.

[0030] In one embodiment, the resin contained in the adhesive composition forming the adhesive layer 1 may include a thermoplastic resin. That is, the adhesive layer 1 can be formed from a thermoplastic resin. When a thermoplastic resin is used, it becomes easy to form the unevenness 1a in the adhesive layer 1 by heating the resin to soften it, and it becomes easy to maintain the uneven shape formed by cooling the resin. Examples of the thermoplastic resin include rubber-based resins, acrylic-based resins, urethane-based resins, and olefin-based resins. Examples include polybutadiene-based thermoplastic elastomers using butadiene as a monomer, styrene-based thermoplastic elastomers using styrene as a monomer, and acrylic-based thermoplastic elastomers using (meth)acrylic acid esters as monomers.

[0031] The resin contained in the adhesive layer 1 is preferably derived from an energy reactive resin. The energy reactive resin refers to a resin whose elastic modulus is improved by applying energy. Examples of the energy reactive resin include an energy ray reactive resin and a heat reactive resin. The energy ray reactive resin refers to a resin whose elastic modulus is improved by irradiating it with an energy ray. The heat reactive resin refers to a resin whose elastic modulus is improved by heating it. The resin contained in the adhesive layer 1 is more preferably derived from a thermoplastic energy reactive resin, and even more preferably derived from a thermoplastic energy ray reactive resin. The type of energy ray is not particularly limited, and examples thereof include ultraviolet rays, electron beams, and ionizing radiation. The energy ray is preferably ultraviolet rays, that is, the resin is preferably an ultraviolet-reactive resin.

[0032] A thermoplastic energy reactive resin refers to an energy reactive resin that has thermoplasticity at least before energy is applied. Also, a resin derived from an energy reactive resin means that the resin is obtained from an energy reactive resin. For example, a resin derived from an energy reactive resin is a crosslinked energy reactive resin.

[0033] When such an energy reactive resin is used, it becomes easy to maintain the formed uneven shape by imparting energy (for example, irradiating with energy rays) after forming the unevenness 1a in the resin.

[0034] As such an energy reactive resin, a polymer having a polymerizable functional group can be used. The polymerizable functional group is a functional group that is crosslinked by the application of energy (for example, irradiation with energy rays). Examples of the polymerizable functional group include alkenyl groups such as vinyl groups and allyl groups, (meth)acryloyl groups, oxetanyl groups, and epoxy groups.

[0035] For example, diene rubber composed of a polymer having a polymerizable functional group at the main chain end and / or side chain can be used as the energy reactive resin. Diene rubber refers to a rubbery polymer having a double bond in the polymer main chain. Specific examples of diene rubber include polymers using butadiene or isoprene as a monomer (i.e., having butenediyl or pentenediyl groups as a constituent unit). Preferred examples of the energy reactive resin include polybutadiene resin (PB resin), styrene-butadiene-styrene block copolymer (SBS resin), and styrene-isoprene-styrene block copolymer. These resins can be used as ultraviolet reactive resins.

[0036] The average number of polymerizable functional groups per molecule in these energy reactive resins is preferably 1.5 or more, more preferably 2 or more, from the viewpoint of easily maintaining the uneven shape of the adhesive layer 1. On the other hand, from the viewpoint of enhancing the adhesiveness and flexibility of the adhesive layer 1, this average number is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less.

[0037] The adhesive layer 1 may contain one type of resin, or may contain two or more types of resin. The adhesive layer 1 according to one embodiment contains a resin derived from a liquid resin or an energy-reactive liquid resin, in addition to a resin derived from a thermoplastic resin or a thermoplastic energy-reactive resin. The liquid resin refers to a resin that is liquid at room temperature (25°C) before mixing. The energy-reactive liquid resin refers to an energy-reactive resin that is liquid at room temperature (25°C) before mixing and before energy is applied. By adding the liquid resin in this way, it becomes easy to control the retention and shear storage modulus of the adhesive layer 1.

[0038] It is preferable that the adhesive layer 1 according to an embodiment contains a resin derived from an energy reactive liquid resin, since it is easy to maintain the uneven shape of the adhesive layer 1. An example of such a liquid resin is a diene rubber, and a specific example is a polybutadiene resin in which butadiene is used as a monomer.

[0039] The adhesive layer 1 according to one embodiment contains a combination of a resin derived from a thermoplastic energy reactive resin and a resin derived from an energy reactive liquid resin. Preferably, the adhesive layer 1 contains a combination of a resin derived from an energy ray reactive styrene-based thermoplastic elastomer and a resin derived from a diene rubber, which is an energy ray reactive liquid resin.

[0040] A preferred example of the thermoplastic energy ray reactive resin is a resin in which styrene and butadiene are used as monomers, and a particularly preferred example is SBS resin. The resin in which styrene and butadiene are used as monomers includes not only a resin in which only styrene and butadiene are used as monomers, but also a resin in which a monomer other than styrene and butadiene is further used. The mass average molecular weight (Mw) of such a resin is preferably 10,000 or more, more preferably 50,000 or more, even more preferably 100,000 or more, and even more preferably 150,000 or more, from the viewpoint of improving the adhesiveness of the adhesive layer 1. The mass average molecular weight (Mw) of such a resin is preferably 2 million or less, more preferably 1 million or less, and even more preferably 200,000 or less, from the viewpoint of reducing the shear storage modulus of the adhesive layer 1 to an appropriate range. For the same reasons, the number average molecular weight (Mn) of such a resin is preferably 10,000 or more, more preferably 30,000 or more, even more preferably 70,000 or more, and even more preferably 130,000 or more, while it is preferably 2 million or less, more preferably 1 million or less, and even more preferably 200,000 or less.

[0041] A preferred example of the energy ray reactive liquid resin is a resin using butadiene as a monomer, and a particularly preferred example is PB resin. The resin using butadiene as a monomer includes not only a resin using only butadiene as a monomer, but also a resin using a monomer other than butadiene. The mass average molecular weight (Mw) of such a resin is preferably 500 or more, more preferably 1000 or more, even more preferably 2000 or more, and even more preferably 3000 or more, from the viewpoint of increasing the shear storage modulus of the adhesive layer 1. The mass average molecular weight (Mw) of such a resin is preferably 500,000 or less, more preferably 100,000 or less, and even more preferably 10,000 or less, from the viewpoint of decreasing the shear storage modulus of the adhesive layer 1. For the same reason, the number average molecular weight (Mn) of such a resin is preferably 500 or more, more preferably 1000 or more, even more preferably 3000 or more, and even more preferably 120,000 or more, while it is preferably 500,000 or less, more preferably 100,000 or less, and even more preferably 10,000 or less.

[0042] The ratio of the resin derived from the thermoplastic energy reactive resin and the resin derived from the energy reactive liquid resin contained in the adhesive layer 1 can be selected according to the required retention and shear storage modulus of the adhesive layer 1. For example, the amount of the resin derived from the energy reactive liquid resin relative to 100 parts by mass of the resin derived from the thermoplastic energy reactive resin may be 10 parts by mass or more, or 30 parts by mass or more, or even 40 parts by mass or more from the viewpoint of improving the retention, while it may be 500 parts by mass or less, or 200 parts by mass or less, or even 150 parts by mass or less from the viewpoint of improving the shear storage modulus.

[0043] The ratio of the total amount of the resin derived from the thermoplastic energy reactive resin and the resin derived from the energy reactive liquid resin to the total amount of the components constituting the adhesive layer 1 can be selected according to the desired retention and shear storage modulus of the adhesive layer 1. For example, this ratio is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 55% by mass or more, even more preferably 60% by mass or more, and is preferably 99.99% by mass or less, more preferably 99.95% by mass or less, even more preferably 99.90% by mass or less, even more preferably 99.80% by mass or less, and even more preferably 99.50% by mass or less.

[0044] The adhesive layer 1 may contain components other than resin, for example, the adhesive layer 1 may contain one or more of a tackifier, a polymerization initiator, an ultraviolet absorbing agent, and other additives.

[0045] The polymerization initiator is a component that initiates a crosslinking reaction in response to the application of energy (e.g., irradiation with energy rays). When the adhesive layer 1 contains an energy reactive resin, the adhesive layer 1 further contains a polymerization initiator, so that the crosslinking reaction proceeds even when a relatively low amount of energy is applied.

[0046] As the polymerization initiator, for example, a photopolymerization initiator can be used. Examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0047] The adhesive layer 1 may contain one type of polymerization initiator or may contain two or more types of polymerization initiators. When the adhesive layer 1 contains a polymerization initiator, the content of the polymerization initiator in the adhesive layer 1 is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more, from the viewpoint of proceeding with the crosslinking reaction at an appropriate rate, and is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less.

[0048] Examples of the ultraviolet absorbent include benzotriazole compounds, oxazolic acid amide compounds, and benzophenone compounds.

[0049] Other additives that may be contained in the adhesive layer 1 are not particularly limited, but include, for example, hindered amine-based, benzophenone-based, or benzotriazole-based light stabilizers, phenol-based antioxidants such as hindered phenol-based compounds, aromatic amine-based antioxidants, sulfur-based antioxidants, or phosphorus-based antioxidants such as phosphate ester-based compounds, resin stabilizers such as imidazole-based resin stabilizers, dithiocarbamate-based resin stabilizers, phosphorus-based resin stabilizers, or sulfur ester-based resin stabilizers, fillers, pigments, extenders, and softeners.

[0050] When the adhesive layer 1 contains these additives, the content of the additives in the adhesive layer 1 is preferably 0.0001 mass% or more, more preferably 0.01 mass% or more, particularly preferably 0.1 mass% or more, even more preferably 1 mass% or more, and preferably 20 mass% or less, more preferably 10 mass% or less, even more preferably 5 mass% or less.

[0051] (Shape of adhesive layer) FIG. 1 shows a cross-sectional view of an adhesive layer 1 according to an embodiment, passing through a protrusion 10a and perpendicular to the surface of the adhesive layer 1. The adhesive layer 1 has an irregularity 1a on its surface. The adhesive layer 1 also has a base portion 1b that is configured from a recess 10b, where the thickness of the adhesive layer 1 is the smallest, to a surface F1 on the opposite side to the surface having the irregularity 1a in the thickness direction of the adhesive layer 1. In FIG. 1, the base portion 1b is integrally formed with the irregularity 1a and is in contact with the substrate 2. The irregularity 1a has a protrusion 10a and a recess 10b. In FIG. 1, the recess 10b is located between the protrusions 10a. The protrusion 10a includes a first protrusion 110 provided on the base portion 1b to have a first height H1, and a second protrusion 120 provided on the base portion 1b to have a second height H2 smaller than the first protrusion 110. The first height H1 and the second height H2 refer to the height in the vertical direction from the upper surface F2 of the base portion 1b to the top of the protrusion 10a. The first height H1 and the second height H2 correspond to the height difference between the tops of the first protrusion 110 and the second protrusion 120 and the surface of the recess 10b in the thickness direction of the adhesive sheet.

[0052] 2A to 2D show an example of a state in which the adhesive sheet of FIG. 1 holds the object 4 and the object 4 is peeled off from the adhesive sheet. FIG. 2A shows an example of a state in which the object 4 approaches the adhesive sheet. The type of the object 4 is not particularly limited. The object 4 may be, for example, an element, a wafer, a panel, or a substrate. When the object 4 approaches the adhesive layer 1, the gas between the adhesive layer 1 and the object 4 is compressed. At this time, the compressed gas is likely to escape to the outside from between the adhesive layer 1 and the object 4 through the recess 10b. Therefore, when the surface of the adhesive layer 1 has the unevenness 1a, it is easy to suppress the holding position of the object 4 from being shifted due to the pressure of the compressed gas.

[0053] 2B and 2C show an example of the state when the object 4 is held by the adhesive sheet. As shown in FIG. 2B, when the object 4 approaches the adhesive sheet, the object 4 first comes into contact with the first convex portion 110. After that, the first convex portion 110 deforms and the object 4 approaches the second convex portion 120, and as shown in FIG. 2C, the object 4 also comes into contact with the second convex portion 120. In the example of FIG. 2C, the object 4 is held by both the first convex portion 110 and the second convex portion 120. In this way, since the object 4 comes into contact with the first convex portion 110 in the initial stage of holding, the repulsive force exerted by the adhesive sheet on the object 4 becomes smaller. Then, in the subsequent stage, the force of the object 4 coming into contact with the adhesive sheet, the weight of the object 4 or the weight of the adhesive sheet itself, or an external force is applied, the object 4 comes into contact with the second convex portion 120 in addition to the first convex portion 110, and the holding ability of the object 4 by the adhesive sheet becomes greater. In this way, the adhesive sheet according to one embodiment can suppress the displacement of the held position of the object 4 while maintaining a certain degree of holding ability of the object 4.

[0054] FIG. 2D shows an example of a state in which the adhesive sheet is peeled off from the object 4. In one embodiment, the adhesive sheet is expanded in the planar direction for peeling. For example, the adhesive sheet can be expanded by pulling it with an external force. At this time, a shear force acts on the adhesive surface between the object 4 and the adhesive sheet. Here, the height H1 of the first convex portion 110 is greater than the height H2 of the second convex portion 120. Therefore, the second convex portion 120 is more likely to peel off from the object 4 than the first convex portion 110. Also, the first convex portion 110 is more likely to deform to follow the expansion than the second convex portion 120. As a result, as shown in FIG. 2D, by expanding the adhesive sheet in the planar direction, the second convex portion 120 is separated from the object 4. In the example of FIG. 2D, after the expansion of the adhesive sheet, the object 4 is held by the first convex portion 110. In this way, the contact area between the adhesive sheet and the object 4 can be reduced by the expansion. Therefore, the adhesive sheet is less able to hold the object 4, making it easier to peel off. In this manner, the adhesive layer 1 has the unevenness 1a on its surface, and the protrusions 10a have portions of different heights, which makes it easier to peel the object 4 from the adhesive sheet.

[0055] In FIG. 1, an example of the rectangular irregularities 1a like a square wave is shown, but the specific shape of the surface irregularities 1a is not particularly limited. For example, in a cross-sectional view perpendicular to the surface of the adhesive layer 1 passing through the protrusions 10a, the surface irregularities 1a may be an acute-angled shape like a sawtooth wave, a stepped shape like a step wave, a continuous hemispherical shape like a full-wave rectified wave, or a spaced hemispherical shape like a half-wave rectified wave. The surface irregularities 1a may also have a shape that combines these shapes.

[0056] 3A and 3B show cross-sectional views of the adhesive layer 1 according to another embodiment, which are perpendicular to the surface of the adhesive layer 1 and pass through the convex portion 10a'. For example, as shown in FIG. 3A, the surface irregularities 1a' may have a curved shape such as a sine wave. Also, as shown in FIG. 3B, the surface irregularities 1a' may have an acute shape such as a triangular wave. As shown in FIG. 3A and FIG. 3B, the surface irregularities 1a' have a tip portion 110' of the convex portion 10a' that is provided to have a first height H1 on the base portion 1b. Also, the irregularities 1a' have an inclined portion 120' of the convex portion 10a' that is provided to have a second height H2 on the base portion 1b. Also, in the thickness direction of the adhesive sheet, the first height H1 is greater than the second height H2.

[0057] The adhesive layer 1 shown in FIG. 3A and FIG. 3B, like the adhesive layer 1 shown in FIG. 2A to FIG. 2D, can allow the gas compressed between the object 4 and the object 4 to escape to the outside through the recess 10b' when the object 4 approaches. Therefore, this adhesive sheet can also suppress the displacement of the holding position of the object 4 due to the compressed gas. Also, like the adhesive layer 1 shown in FIG. 2A to FIG. 2D, when the object 4 approaches, the object 4 first comes into contact with the tip portion 110', and then the inclined portion 120' also comes into contact with the object 4. In this way, the repulsive force exerted by the adhesive sheet on the object 4 is also smaller in this adhesive sheet. Therefore, the adhesive sheet can suppress the displacement of the holding position of the object 4 while maintaining a certain holding ability of the object 4. When the adhesive sheet is peeled off from the object 4, the adhesive layer 1 is expanded in the surface direction. In this case, like the adhesive layer 1 shown in FIG. 2A to FIG. 2D, the inclined portion 120' can be separated from the object 4. Therefore, the contact area between the convex portion 10a' and the object 4 can be reduced, making peeling easier. In this way, the adhesive layer 1 has an uneven surface 1a', and the convex portion 10' has an inclined portion 120' in addition to a tip portion 110', so that the adhesive sheet has a certain degree of retention of the object 4 while making it easy to peel the object 4 from the adhesive sheet.

[0058] From the viewpoint of improving the releasability of the object 4, the difference between the first height H1 and the second height H2 is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. On the other hand, from the viewpoint of maintaining adhesiveness, the difference is preferably 120 μm or less, more preferably 80 μm or less, and even more preferably 40 μm or less.

[0059] FIG. 4 shows an example of a plan view of an adhesive sheet. The adhesive layer 1 has a first convex portion 110 and a second convex portion 120 on its surface, which are separated from each other via a concave portion 10b. The first convex portion 110 and the second convex portion 120 may be separated by a concave portion 10b that is continuous throughout the entire adhesive layer 1. By providing the concave portion 10b between the first convex portion 110 and the second convex portion 120, gas between the adhesive sheet and the object 4 is easily released to the outside when the object is held. In addition, gas is easily introduced between the adhesive layer 1 and the object 4 through the concave portion 10b during peeling, so that the adhesive sheet can be easily peeled off from the object 4. In addition, in one embodiment, the concave portions 10b located around each of the first convex portion 110 and the second convex portion 120 may be continuous to the end of the adhesive layer 1. In this way, by providing the concave portion 10b that is continuous to the end of the adhesive layer 1, gas is more easily introduced between the object 4 and the adhesive layer 1. Furthermore, according to these configurations, the gas compressed between the object 4 and the adhesive layer 1 can be efficiently released to the outside from between the object 4 and the adhesive layer 1, so that the holding position can be prevented from shifting.

[0060] In FIG. 4, the first convex portion 110 and the second convex portion 120 are the same size and arranged alternately, but the present invention is not limited to this. The first convex portion 110 and the second convex portion 120 may be formed to have different sizes. The arrangement method may also be adjusted appropriately. Here, the size means the area of ​​the first convex portion 110 and the second convex portion 120 protruding in a plan view of the adhesive layer 1. An example is shown in FIG. 5A to FIG. 5D. FIG. 5A to FIG. 5D are diagrams showing an example of a plan view of the adhesive layer. For example, as shown in FIG. 5A, the size of the first convex portion 110 may be smaller than the size of the second convex portion. For example, even if the first convex portion 110 and the second convex portion 120 are not arranged alternately as in FIG. 5A, the area of ​​the first convex portion 120 per unit area of ​​the adhesive sheet may be adjusted to be smaller than the area of ​​the second convex portion 120. By making the size of the first protrusions 110 smaller than the size of the second protrusions 120, the adhesive sheet can reduce the contact area with the object 4 in the initial stage of holding. Even if the sizes of the first protrusions 110 and the second protrusions 120 are the same as in Fig. 5B, by making the number of first protrusions 110 smaller than the number of second protrusions 120, the same effect as in Fig. 5A can be obtained.

[0061] 5A and 5B show an example in which the first convex portion 110 and the second convex portion 120 are arranged at equal intervals, but this is not limited thereto. The first convex portion 110 and the second convex portion 120 may be arranged so that the interval between them varies. For example, as shown in FIG. 5C, the interval between the second convex portions 120 may be short, and an arrangement in which the first convex portions 110 are grouped together may be adopted. Also, the interval between the first convex portions 110 located around the second convex portion 120 may be long. In this way, by adjusting the interval between the first convex portion 110 and the second convex portion 120, the opening portion in the surface direction of the adhesive sheet surface can be made wide. This makes it easier for gas to escape to the outside when holding an object. Also, gas is more likely to enter during peeling, improving peelability.

[0062] Fig. 5D is a top view showing another shape of the adhesive layer 1. As shown in Fig. 5D, the surface of the adhesive layer 1 may be provided with stripe-shaped convex portions 10a of different heights. In Fig. 5D, linear first convex portions 110 and second convex portions 120 having a certain width are arranged at a certain interval. On the other hand, the width or interval of the linear first convex portions 110 and second convex portions 120 may vary regularly, or the linear first convex portions 110 and second convex portions 120 may be arranged irregularly.

[0063] The convex portions (first convex portion 110, second convex portion 120, and convex portion 10a') preferably have the configuration shown below. For example, it is preferable that one first convex portion 110, one second convex portion 120, and one convex portion included in convex portion 10a' and having a tip portion 110' and an inclined portion 120' each independently have the configuration shown below. The convex portions having the configuration shown below means that 90% or more or all of the convex portions located in the portion of the adhesive sheet that holds an object have the configuration shown below.

[0064] The area of ​​each protrusion is set to 10 μm in order to maintain the retention. 2 It is preferable that the thickness is 20 μm or more. 2 More preferably, it is 30 μm or more. 2 On the other hand, from the viewpoint of enhancing the releasability from the object 4, the area of ​​one protrusion is preferably 30000 μm or more. 2 It is preferable that the thickness is less than 3000 μm. 2 More preferably, it is 500 μm or less. 2 It is even more preferable that:

[0065] From the viewpoint of maintaining the holding property, the width or diameter of one convex portion is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 4 μm or more, and even more preferably 7 μm or more. On the other hand, from the viewpoint of enhancing the peelability of the object, the width or diameter of each of the convex portions is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, and even more preferably 20 μm or less. Here, the width and diameter of each of the convex portions means the minimum distance and maximum distance between two parallel lines that contact both sides of the convex portion on the surface of the concave portion 10b, 10b' (represented by the diameter T1 or T2 in FIG. 4).

[0066] From the viewpoint of increasing the ease of peeling between the object 4 and the adhesive sheet or the ease of gas escape, the pitch P of the protrusions 10a is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and even more preferably 15 μm or more. On the other hand, from the viewpoint of stably holding the object 4, this pitch is preferably 300 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, even more preferably 35 μm or less, and particularly preferably 25 μm or less.

[0067] Here, the pitch of the convex portions 10a means the distance between the center point of one arbitrarily selected convex portion and the center point of another convex portion closest to that convex portion. For example, in the case of Fig. 4, the pitch of the convex portions 10a represents the distance between the center point of one convex portion on a line on which the convex portions (e.g., the first convex portion 110 and the second convex portion 120) are arranged at regular intervals and the center point of another convex portion closest to that convex portion. When the convex portions are arranged on multiple lines, the pitch represents the distance between the center points of the convex portions on the line on which they are arranged at the shortest pitch.

[0068] The number of individual convex portions per unit area of ​​the adhesive layer 1 (for example, the total number of the first convex portions 110 and the second convex portions 120, or the number of each convex portion included in the convex portion 10a′ and having a tip portion 110′ and an inclined portion 120′) is set to 3 / mm from the viewpoint of stably holding the object 1. 2 It is preferable that the number of pieces is 30 pieces / mm or more. 2 More preferably, 300 pieces / mm 2 More preferably, it is 1000 pieces / mm 2 On the other hand, from the viewpoint of the stability of the uneven shape, it is more preferable that the number of particles is 10,000 / mm 2 It is preferable that:

[0069] From the viewpoint of improving releasability, the ratio of the total area of ​​the first protrusions 110 to the total area of ​​the second protrusions 120 in the adhesive sheet is preferably 70% or less, more preferably 50% or less, and even more preferably 40% or less. Here, the areas of the first protrusions 110 and the second protrusions 120 refer to the areas of the portions protruding from the surface of the adhesive layer 1 (the area of ​​a circle with diameter T1 or T2 in the case of FIG. 4).

[0070] From the viewpoint of improving releasability, the ratio of the number of first protrusions 110 to the number of second protrusions 120 in the area of ​​the adhesive sheet is preferably 70% or less, more preferably 50% or less, and even more preferably 40% or less. Here, the number of first protrusions 110 and second protrusions 120 in the area of ​​the adhesive sheet means the number protruding from the surface of the adhesive layer 1.

[0071] Moreover, the ratio of the area occupied by the protrusions 10a, 10a' to the area of ​​the adhesive layer 1 is preferably 1% or more, more preferably 5% or more, even more preferably 10% or more, even more preferably 18% or more, and even more preferably 40% or more, from the viewpoint of maintaining the holding ability to the object 4. On the other hand, the area of ​​the protrusions 10a, 10a' is preferably 95% or less, more preferably 75% or less, and even more preferably 60% or less, from the viewpoint of improving the releasability.

[0072] The unevenness 1a, 1a' of the adhesive layer 1 may be designed according to the shape of the object 4. For example, the ratio of the holding area of ​​the adhesive layer 1 and one object 4 to the area of ​​one object 4 is preferably 1% or more, more preferably 2% or more, more preferably 3% or more, more preferably 4% or more, more preferably 5% or more, more preferably 7% or more, and more preferably 10% or more, from the viewpoint of maintaining the holding property. On the other hand, the area of ​​the protrusion 10a is preferably 95% or less, more preferably 70% or less, more preferably 50% or less, and more preferably 30% or less, from the viewpoint of improving the peelability from the object 4. In the case of FIG. 4, the holding area corresponds to the area of ​​the circle with the diameter T1, T2. Note that when the position of the object 4 on the adhesive layer 1 is shifted, the holding area may change. In this case, it is preferable that the ratio of the holding area falls within the above range regardless of the position of the object 4.

[0073] (Other layers) The above-mentioned adhesive sheet may have a layer other than the substrate and the adhesive layer. For example, an additional adhesive layer may be provided on the surface of the substrate opposite to the adhesive layer. The adhesive sheet can be attached to another object via such an adhesive layer. The type of the additional adhesive layer is not particularly limited, and for example, the additional adhesive layer can be formed using a general adhesive.

[0074] (Method of manufacturing adhesive layer and adhesive sheet) There is no particular limitation on the manufacturing method of the adhesive layer and the adhesive sheet. For example, an adhesive sheet having an adhesive layer provided on a substrate can be prepared as follows. First, an organic solvent is added to a raw material composition containing each component of the adhesive layer described above to prepare a solution of the raw material composition. Then, the solution is applied to a substrate to form a coating film, and then the coating film is dried to provide an adhesive layer on the substrate. Furthermore, a treatment is performed to provide irregularities on the surface of the adhesive layer to form an adhesive layer having irregularities.

[0075] Examples of organic solvents used to prepare the solution of the raw material composition include toluene, ethyl acetate, and methyl ethyl ketone, etc. Examples of the solution application method include spin coating, spray coating, bar coating, knife coating, roll coating, roll knife coating, blade coating, die coating, gravure coating, and printing methods (e.g., screen printing and inkjet printing).

[0076] There is no particular limitation on the treatment for providing unevenness on the surface of the adhesive layer. For example, unevenness can be provided on the surface of the adhesive layer using an imprinting method. In the imprinting method, a mold having a shape complementary to the unevenness to be provided on the surface can be used. Specifically, unevenness can be provided on the surface of the adhesive layer by heating the adhesive layer while pressing the adhesive layer provided on the substrate with a mold. As a more specific method, the adhesive layer can be pressed with a mold, heated and maintained for a predetermined time, and then cooled and the mold can be removed. When heating the adhesive layer, for example, the adhesive layer can be heated to a temperature higher than the softening point of the adhesive layer. In addition, the time for maintaining the adhesive layer in a heated state is not particularly limited, but may be maintained for 10 seconds or more, or may be maintained for 10 minutes or less. A specific method for heating the adhesive layer while pressing the adhesive layer with a mold includes a method of vacuum laminating the adhesive layer and the mold provided on the substrate. Instead of carrying out the two-stage process of forming an adhesive layer and then forming projections and recesses, an adhesive layer having projections and recesses on its surface may be formed on a substrate in a single-stage process.

[0077] Alternatively, a solution of the raw material composition can be sprayed to provide an adhesive layer having a rough surface. Furthermore, a filler can be added to the solution of the raw material composition, and the solution can be applied to provide an adhesive layer having a rough or fibrous surface. As another method, a printing method such as an inkjet method can be used to apply the solution of the raw material composition according to a desired pattern to provide an adhesive layer having a concave-convex shape directly on the substrate.

[0078] In addition, the adhesive sheet without a substrate can be produced by forming a composition containing each component of the adhesive layer into a sheet. Furthermore, the adhesive layer can be formed by applying a liquid adhesive containing each component of the adhesive layer to any object. In these cases, after forming the adhesive layer, a treatment to provide irregularities on the surface of the adhesive layer can be performed, or the adhesive layer can be formed by a method that forms irregularities on the surface.

[0079] (How to use the adhesive sheet) The adhesive sheet according to the present embodiment is used to hold an object, particularly to temporarily hold an object. For example, the adhesive sheet according to the present embodiment can be used to transfer an object. As a specific example, the adhesive sheet according to the present embodiment can be used to transfer a semiconductor chip obtained by dicing to a desired position. Thus, in one embodiment, the adhesive sheet according to the present embodiment is used as a transfer sheet.

[0080] For example, the adhesive sheet can be brought into contact with an object attached to a holding substrate, and the adhesive force between the holding substrate and the object can be reduced by physical stimulation or the like, thereby holding the object on the adhesive sheet. As another method, the object can be separated from the holding substrate and captured by the adhesive sheet, thereby holding the object on the adhesive sheet. As described above, by using the adhesive sheet according to one embodiment, positional deviation when capturing the object can be suppressed. As a method for separating the object from the holding substrate, a laser lift-off method in which a laser is irradiated on the holding substrate can also be used.

[0081] Thereafter, the object is separated from the adhesive sheet. Before separating the object from the adhesive sheet, the object may be treated or processed. An example of a method for separating an object from an adhesive sheet is described below with reference to FIG. 6. In S61, the adhesive sheet holding the object on the adhesive layer is expanded in the surface direction. The expansion rate of the adhesive sheet may be 1% or more, or 5% or more, and may be 20% or less, or 15% or less. The adhesive sheet may be expanded in one direction, two or more directions, or all directions. As a method for expanding the adhesive sheet in all directions, a method using a stage (e.g., a circular stage) and a frame (e.g., a circular frame) larger than the stage can be mentioned. In this case, the adhesive sheet can be fixed to the frame. Then, the frame can be pressed down while the adhesive sheet is placed on the stage. By such a method, the adhesive sheet is expanded in all directions.

[0082] (How to expand the adhesive sheet) An example of a specific method for expanding an adhesive sheet will be described with reference to Figs. 7A and 7B. Figs. 7A and 7B show an expanding device 300 used for expanding an adhesive sheet including an adhesive layer 1 and a base material 2 in a planar direction. Fig. 7A shows a state in which an adhesive sheet placed on a base 310 of the expanding device 300 holds objects 4a to 4d. The expanding device 300 includes a base 310 for holding an adhesive sheet as the above-mentioned stage. The base 310 may be, for example, mesh-shaped or may be ring-shaped with an opening. The expanding device 300 also includes a ring frame 320 for supporting the outer periphery of the adhesive sheet as the above-mentioned frame. The ring frame 320 may support, for example, a part of the outer periphery of the adhesive sheet, or may support the entire outer periphery of the adhesive sheet. Fig. 7B shows a state in which the adhesive sheet is expanded by displacing the ring frame 320 downward. The ring frame 320 may displace, for example, at a speed of 0.1 mm / sec or more, or may displace at a speed of 1 mm / sec or more. Furthermore, the amount of displacement of the ring frame 320, i.e., the amount of pulling down, may be, for example, 1 mm or more, or 5 mm or more. In the state shown in Fig. 7B, the needle 330 is used to push up the objects 4a-4d held on the adhesive sheet to apply a physical stimulus. This allows the objects 4a-4d to be peeled off from the expanded adhesive sheet. Furthermore, the method of expanding the adhesive sheet is not limited to this, and may be performed by displacing the ring frame 320 in the surface direction of the adhesive sheet, for example.

[0083] Next, in S62, the object is peeled off from the adhesive layer of the adhesive sheet expanded in the surface direction. The peeling method is not particularly limited. For example, a method of applying a physical stimulus (e.g., piercing with a needle) to the back surface of the adhesive sheet (the surface opposite to the surface holding the object) can be mentioned. Another method of irradiating the adhesive sheet with an energy ray (e.g., laser light) can also be mentioned. The object peeled off in this manner can be lifted up using a holding device such as a vacuum chuck and a collet. As described above, the expansion of the adhesive sheet reduces the holding ability of the object by the adhesive sheet. That is, the surface peelability of the object on the adhesive sheet after expansion is improved compared to before expansion. This makes it easier to peel off the object from the adhesive sheet. In one embodiment, the object is lifted off from the adhesive sheet without applying a physical stimulus to the back surface of the adhesive sheet and irradiating it with an energy ray. EXAMPLES

[0084] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples. Parts and % in each example are by weight unless otherwise specified.

[0085] The following compounds were used in the examples and comparative examples. <Component (A)> Energy ray curable resin (A1): SBS having a vinyl group in the side chain (styrene-butadiene-styrene block copolymer (SBS) having a 1,2-vinyl group in the side chain [having a branched structure and a radial structure with a branch point as the central nucleus, number average molecular weight (Mn) 160,000, mass average molecular weight (Mw) 180,000, styrene block content 20 mass%, butadiene block content 80 mass%, content of structural units having a 1,2-vinyl group in the side chain among all structural units constituting the butadiene block is 42 mol%, melt flow rate measured under the conditions of temperature 200°C and load 5 kg is 5 g / 10 min]) Energy ray curable resin (A2): PB with vinyl groups on the side chains (polybutadiene copolymer with 1,2-vinyl groups on the side chains [mass average molecular weight (Mw) 5,500, glass transition temperature -49°C, liquid at room temperature]) <(C) component> Photopolymerization initiator (C1): Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide <(E) Antioxidants> Antioxidant (E1) A mixture of a hindered phenol-based antioxidant and a phosphorus-based antioxidant in a mass ratio of 1:1

[0086] Example 1 An adhesive composition was prepared by dissolving 100 parts by mass of energy ray curable resin (A1), 50 parts by mass of energy ray curable resin (A2), 3 parts by mass of photopolymerization initiator (C1), and 3 parts by mass of antioxidant (E1) in toluene. This adhesive composition was applied onto the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name: SP-PET381130, a polyethylene terephthalate film laminated with a silicone-based release agent, thickness 38 μm), and the resulting coating was dried at 100 ° C for 2 minutes to form an adhesive layer with a thickness of 25 μm. A non-embossed surface of an EMAA substrate (ethylene-methacrylic acid copolymer film, acid content 9% by mass, one surface of which was embossed to give a matte finish, thickness: 80 μm, breaking elongation 490%) was attached onto this adhesive layer to prepare an adhesive sheet.

[0087] After the release sheet was peeled off, the adhesive layer of the adhesive sheet was attached to a replica mold in which a concave shape had been formed in advance, and vacuum laminated at 60° C. for 300 seconds. Next, an ultraviolet irradiator (Heraeus) was used to irradiate the adhesive layer with an illuminance of 200 mW / cm 2 . 2 , light intensity 800mJ / cm 2 By irradiating the sheet with ultraviolet light at 400 rpm, a pressure-sensitive adhesive sheet having an uneven surface was produced.

[0088] The surface of the adhesive layer of the adhesive sheet is formed with unevenness having convex portions of different heights, as in FIG. 1. The convex portions of different heights were cylindrical as shown in FIG. 4, and were arranged in a lattice pattern with concave portions interposed therebetween. The convex portions of different heights function as holding portions. In the adhesive sheet produced in Example 1, the convex portions were composed of first convex portions having a first height H1 of 8 μm and second convex portions having a second height H2 of 4 μm. The pitch (P) between the first convex portions and the second convex portions in the adhesive sheet was 20 μm. The diameters of the first convex portions and the second convex portions (T1 and T2 shown in FIG. 1) were 8 μm. The ratio of the total area of ​​the first convex portions to the total area of ​​the second convex portions was 100%, and the ratio of the number of the first convex portions to the number of the second convex portions was 100%.

[0089] When the pitch between each protrusion is 20 μm, the ratio of the area of ​​the holding portion between the adhesive layer and the object to be held (i.e., the area of ​​the tip surface of each protrusion) to the area of ​​the adhesive sheet is approximately 12.6%.

[0090] Example 2 An adhesive sheet was produced in the same manner as in Example 1, except that a replica mold in which a concave shape different from that in Example 1 was formed was used.

[0091] The surface of the adhesive layer of the adhesive sheet is formed with unevenness having convex portions of different heights, as in FIG. 1. The convex portions of different heights were cylindrical as shown in FIG. 5B, and were arranged in a lattice pattern via concave portions. The convex portions of different heights function as holding portions. In the adhesive sheet produced in Example 2, the convex portions were composed of a first convex portion having a first height H1 of 8 μm and a second convex portion having a second height H2 of 4 μm. The pitch (P) between the first convex portion and the second convex portion in the adhesive sheet was 20 μm. The diameters of the first convex portion and the second convex portion (T1 and T2 shown in FIG. 1) were 8 μm. The ratio of the total area of ​​the first convex portions to the total area of ​​the second convex portions was 11.1%, and the ratio of the number of the first convex portions to the number of the second convex portions was 11.1%.

[0092] Comparative Example 1 Except for not bonding the replica mold and the adhesive layer, an adhesive sheet was produced in the same manner as in Example 1. In the comparative example, no irregularities were formed on the adhesive layer.

[0093] (Tensile modulus of base material) The substrate used in the examples was cut to 150 mm in MD × 15 mm in TD to prepare a test sample. The tensile modulus of the test sample was measured under an environment of 23°C and 50% RH (relative humidity) in accordance with JIS K 7161-1:2014 and JIS K 7127:1999.

[0094] Specifically, the above test sample was subjected to a tensile test at a speed of 200 mm / min using a tensile testing machine (manufactured by Shimadzu Corporation, product name "Autograph (registered trademark) AG-IS 500N") with the chuck distance set to 100 mm, and the tensile modulus (MPa) in the MD direction of the support was measured.

[0095] In addition, MD in MD direction is an abbreviation of Machine Direction, and for example, the MD direction of a substrate means the longitudinal direction when the substrate is manufactured, and TD in TD direction is an abbreviation of Transverse Direction, and for example, the TD direction of a substrate means the width direction when the substrate is manufactured.

[0096] (Shear storage modulus of adhesive layer) An adhesive layer was formed from the adhesive composition obtained in the examples and comparative examples, and exposed to an ultraviolet irradiator (manufactured by Heraeus) with an illumination intensity of 200 mW / cm 2 , light intensity 800mJ / cm 2 A 1 mm thick adhesive layer was prepared by irradiating ultraviolet light at 1000 rpm. The obtained adhesive layer was punched out into a cylindrical shape with a diameter of 8 mm, and the shear storage modulus of the adhesive layer at 23°C was measured by a torsional shear method using a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR302") under the conditions of a test start temperature of -60°C, a test end temperature of 150°C, a heating rate of 3.5°C / min, and a frequency of 1 Hz.

[0097] (Preparation of samples for evaluating surface peelability) The adhesive layer of the adhesive sheet obtained in the example was attached to a ring frame (made of stainless steel), and the adhesive sheet was cut to fit the outer diameter of the ring frame.

[0098] A wafer substrate (mirror silicon wafer, 6 inches, 150 μm thick) was fixed to a separately prepared dicing tape and diced into 15 mm × 15 mm squares to obtain a plurality of elements (silicon chips, element size 10 mm × 10 mm × 150 μm). The obtained plurality of elements were attached to the center part inside the ring frame of the adhesive layer of the adhesive sheet, and the dicing tape was peeled off to transfer the elements from the dicing tape to the adhesive sheet. At this time, the surface was adjusted so that the mirror surface of the silicon chip was attached to the adhesive layer of the adhesive sheet, and the attachment was performed by laminating at room temperature (23 ° C.), thereby preparing a surface peelability evaluation sample consisting of an adhesive sheet on which elements were placed and supported by a ring frame.

[0099] (Surface peelability before stretching) The obtained sample for evaluating surface peelability was evaluated by poking the element with a needle through the adhesive sheet 10 times, and the number of times the silicon chip was peeled off without being destroyed was counted, and the surface peelability was evaluated according to the following criteria.

[0100] A: The silicon chip was successfully peeled off more than nine times.

[0101] B: The silicon chip was successfully peeled off five or more times.

[0102] F: The silicon chip was successfully peeled off four times or less.

[0103] (Surface peelability after stretching) The obtained sample for evaluating surface peelability was placed in an expanding device having the mechanism shown in Figures 7A and 7B, and with the element supported by a mesh-like base through the adhesive sheet, the ring frame was pressed down at a speed of 1 mm / sec and a drop of 5 mm. After pressing down, the element was pushed up through the adhesive sheet with a needle 10 times, and the number of times that the silicon chip could be peeled off without breaking was counted, and the surface peelability was evaluated according to the following criteria.

[0104] A: The silicon chip was successfully peeled off more than nine times.

[0105] B: The silicon chip was successfully peeled off five or more times.

[0106] F: The silicon chip was successfully peeled off four times or less.

[0107] [Table 1]

[0108] When the adhesive layer was not provided with unevenness having convex portions of different heights as in Comparative Example 1, the adhesive sheet failed to peel off from the object. On the other hand, it was confirmed that by forming unevenness having convex portions of different heights on the adhesive layer as in Examples 1 and 2, the object was more likely to be successfully peeled off from the adhesive sheet. This is thought to be because the contact area between the adhesive layer and the object during expansion was reduced by providing unevenness having convex portions of different heights on the surface of the adhesive layer, which made it easier for the adhesive layer to retain the object.

[0109] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention.

[0110] This application claims priority based on Japanese Patent Application No. 2023-058461, filed on March 31, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. An expanding step of expanding an adhesive sheet holding an object on an adhesive layer in a planar direction; A peeling step of peeling the object from the adhesive layer of the adhesive sheet expanded in a planar direction, The pressure-sensitive adhesive sheet is The adhesive layer has an uneven surface, a base portion including a portion from a concave portion where the thickness of the adhesive layer is smallest to a surface opposite to the surface having the concaves and convexes in a thickness direction of the adhesive layer; a first portion provided on the base portion to have a first height; a second portion provided on the base portion to have a second height different from the first height; A peeling method comprising the steps of:

2. The peeling method according to claim 1 , wherein in the expanding step, the object is peeled off from the second portion of the adhesive sheet while remaining in contact with the first portion of the adhesive sheet.

3. The peeling method according to claim 1 , wherein a difference between the first height and the second height is 1 μm or more and 40 μm or less.

4. the first portion is a first convex portion provided on the base portion, The peeling method according to claim 1 , wherein the second portion is a second convex portion provided on the base portion and different from the first convex portion.

5. the first height is greater than the second height; The peeling method according to claim 4 , wherein the number of the first convex portions is smaller than the number of the second convex portions.

6. the first height is greater than the second height; The peeling method according to claim 4 , wherein an area of ​​the adhesive layer occupied by the first convex portion is smaller than an area of ​​the adhesive layer occupied by the second convex portion.

7. The peeling method according to claim 1 or 2, wherein the base portion is integral with the first portion and the second portion.

8. The peeling method according to claim 1 or 2, further comprising a substrate supporting the adhesive layer.

9. The peeling method according to claim 8 , wherein the substrate has a tensile modulus of elasticity of 2500 MPa or less.

10. The peeling method according to claim 1 or 2, characterized in that the adhesive sheet is expandable in a planar direction, and the planar peelability of an object on the adhesive sheet after expansion is improved compared to before expansion.

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