Adhesive sheet and joined body

Abstract

Provided is an adhesive sheet comprising a substrate and an adhesive layer, wherein the adhesive layer contains a polymer having a radical-reactive carbon-carbon double bond in a side chain, the tensile elastic modulus at 23°C after curing of the adhesive layer is 9-1000 MPa, and the peeling force of the adhesive sheet at 23°C before curing of the adhesive layer on a silicon wafer is 0.001-3.0 N / 20 mm when the adhesive sheet is peeled at 180° at a tensile speed of 300 mm / min.

Description

Adhesive sheets and joints

[0001] The present invention relates to an adhesive sheet and a bonded body of the adhesive sheet and a two-dimensional material.

[0002] In recent years, adhesive sheets that can be removably attached to an adherend (removable adhesive sheets) have been used in various technical fields. Removable adhesive sheets have an adhesive layer that forms an adhesive surface that can be peeled off from the adherend after being attached to the adherend. Such removable adhesive sheets are used as protective films to protect the surface of the adherend, for example, during the production and processing of various optical materials such as polarizing films, retardation films, and anti-reflection films, and during the manufacturing and transportation of furniture. During the production and processing of various optical materials, specifically, removable adhesive sheets are attached to the surface of the optical material for purposes such as preventing scratches and stains on the optical material surface and suppressing cracks during cutting and processing of the optical material. The removable adhesive sheet is then peeled off from the optical material at a predetermined point in the production and processing of the optical material or before use of the optical material. Removable adhesive sheets are described, for example, in Patent Document 1 below.

[0003] Furthermore, two-dimensional materials such as two-dimensional carbon materials are expected to have various applications, such as wiring materials and transparent electrodes, due to their excellent electrical and optical properties. ２ Graphene, a conductive planar crystal composed of bonded carbon atoms, has high optical transmittance and electrical conductivity, and is expected to be used in transparent conductive films, transparent electrodes, transistors, etc. Graphene is typically produced by chemical vapor deposition (CVD) on the surface of a catalytic metal. However, when graphene is used in a device, a process is required to transfer the graphene formed on the surface of the catalytic metal to the surface of a substrate.

[0004] For example, Patent Document 2 describes an adhesive agent for temporarily fixing fragile members, which contains as a main component a polyurethane resin obtained by curing an adhesive composition containing a polyol and a polyfunctional isocyanate compound, and is used for temporarily fixing fragile members such as graphene.

[0005] Japanese Unexamined Patent Publication No. 11-000961 Japanese Unexamined Patent Publication No. 2014-172989

[0006] A removable adhesive sheet is required to have low contamination, i.e., to prevent contamination such as adhesive residue from occurring on an adherend when the adhesive sheet is peeled from the adherend. Furthermore, an adhesive sheet used for transferring two-dimensional materials is desired to achieve a high transfer rate of the two-dimensional material. According to the findings of the present inventors, the technology described in Patent Document 2 leaves room for further improvement in terms of low contamination.

[0007] In view of the above, an object of the present disclosure is to provide a pressure-sensitive adhesive sheet that can achieve a high transfer rate of two-dimensional materials and also has excellent low contamination properties.

[0008] A pressure-sensitive adhesive sheet according to one aspect of the present disclosure is a pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer comprises a polymer having a radically reactive carbon-carbon double bond in a side chain, and wherein the pressure-sensitive adhesive layer has a tensile modulus of 9 to 1000 MPa at 23°C after curing, measured under the following measurement conditions: the pressure-sensitive adhesive sheet exhibits a peel force of 0.001 to 3.0 N / 20 mm at 23°C before curing when peeled at 180° at a pulling rate of 300 mm / min from a silicon wafer. (Measurement conditions for the tensile modulus of the pressure-sensitive adhesive layer after curing) ２ A cylindrical sample was irradiated with ultraviolet light and rolled to a length of 30 mm and a diameter of 1 mm, and chucked at 10 mm above and below the length. The sample was pulled at a speed of 50 mm / min. The initial tensile modulus was calculated from the slope at the point where the slope of the stress versus strain is maximum between 10% strain and 100% strain, and this was used as the tensile modulus of the pressure-sensitive adhesive layer after curing.

[0009] Also, a pressure-sensitive adhesive sheet according to another aspect of the present disclosure is a pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer contains a polymer having a radically reactive carbon-carbon double bond in a side chain, and the pressure-sensitive adhesive sheet is subjected to a 180° peel at a tensile speed of 300 mm / min, and the peel force x (N / 20 mm) of the pressure-sensitive adhesive layer at 23°C before curing from a silicon wafer and the HSP polarity term y (MPa ０．５) satisfy at least one of the following relationships of formula 1 and formula 2: y−0.52x−4.7≧0 (formula 1) y+0.50x−4.8≦0 (formula 2)

[0010] A bonded structure according to one embodiment of the present disclosure is a bonded structure in which the pressure-sensitive adhesive layer of any one of the pressure-sensitive adhesive sheets described above is attached to a two-dimensional material.

[0011] The pressure-sensitive adhesive sheet of the present disclosure can achieve a high transfer rate of two-dimensional materials and also has excellent low contamination properties.

[0012] FIG. 1 is a schematic cross-sectional view showing a laminate (first laminate) having a two-dimensional material on a first substrate. FIG. 2 is a schematic cross-sectional view showing a state (second laminate) in which an adhesive sheet is attached to the two-dimensional material on the first substrate. FIG. 3 is a schematic cross-sectional view showing a state in which air bubbles are formed between the first substrate and the two-dimensional material. FIG. 4 is a schematic cross-sectional view of a laminate (third laminate) including an adhesive sheet and a two-dimensional material. FIG. 5 is a schematic cross-sectional view showing a state (fourth laminate) in which a laminate (third laminate) including an adhesive sheet and a two-dimensional material is placed on a second substrate so that the surface of the laminate facing the two-dimensional material contacts the second substrate. FIG. 6 is a schematic cross-sectional view showing a process of obtaining a two-dimensional material laminate including a second substrate and a two-dimensional material by peeling the adhesive sheet from the fourth laminate. Figure 7 is a graph plotting the relationship between the peel strength (N / 20 mm) from a silicon wafer before UV irradiation and the tensile modulus (MPa) of the adhesive layer after UV irradiation for the pressure-sensitive adhesive sheets of each Example and Comparative Example. However, the pressure-sensitive adhesive sheet of Comparative Example 2 was not subjected to UV irradiation. Figure 8 is a graph plotting the relationship between the peel strength (N / 20 mm) from a silicon wafer before UV irradiation and the HSP polarity term (MPa) of the polymer for the pressure-sensitive adhesive sheets of each Example and Comparative Example. ０．５ ) is a graph plotting the relationship between

[0013] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to such embodiments. In the following drawings, components and parts that perform the same function may be described using the same reference numerals, and duplicate descriptions may be omitted or simplified. The embodiments shown in the drawings are schematic to clearly explain the present invention, and do not necessarily accurately represent the size or scale of the actual product. In addition, when the expression "~" is used in this specification, it is used as an expression that includes the numerical values ​​or physical property values ​​before and after it.

[0014] [Adhesive Sheet] An adhesive sheet according to one aspect (first aspect) of the present embodiment is an adhesive sheet comprising a substrate and an adhesive layer, wherein the adhesive layer comprises a polymer having a radically reactive carbon-carbon double bond in a side chain, wherein the adhesive layer has a tensile modulus of elasticity at 23°C after curing measured under the following measurement conditions of 9 to 1000 MPa, and wherein the adhesive sheet exhibits a peel force of 0.001 to 3.0 N / 20 mm at 23°C before curing when subjected to a 180° peel at a pulling rate of 300 mm / min on a silicon wafer. (Conditions for measuring the tensile modulus of elasticity after curing of the adhesive layer) The adhesive layer is exposed to an integrated light dose of 450 mJ / cm ２ A cylindrical sample was irradiated with ultraviolet light and rolled to a length of 30 mm and a diameter of 1 mm, and chucked at 10 mm above and below the length. The sample was pulled at a speed of 50 mm / min. The initial tensile modulus was calculated from the slope at the point where the slope of the stress versus strain is maximum between 10% strain and 100% strain, and this was used as the tensile modulus of the pressure-sensitive adhesive layer after curing.

[0015] Furthermore, a pressure-sensitive adhesive sheet according to another aspect (second aspect) of the present embodiment is a pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer contains a polymer having a radically reactive carbon-carbon double bond in a side chain, and the pressure-sensitive adhesive sheet is subjected to a 180° peel at a tensile speed of 300 mm / min, and the peel force x (N / 20 mm) of the pressure-sensitive adhesive layer at 23°C before curing from a silicon wafer and the HSP polarity term y (MPa ０．５) satisfy at least one of the following relationships of formula 1 and formula 2: y−0.52x−4.7≧0 (formula 1) y+0.50x−4.8≦0 (formula 2)

[0016] Hereinafter, the pressure-sensitive adhesive sheet according to the first aspect and the pressure-sensitive adhesive sheet according to the second aspect may be collectively referred to as the pressure-sensitive adhesive sheet of the present embodiment.

[0017] The pressure-sensitive adhesive sheet of this embodiment is a pressure-sensitive adhesive sheet with a substrate, which comprises a pressure-sensitive adhesive layer and a substrate. Among these, from the viewpoint of ease of handling, a pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet) having a pressure-sensitive adhesive layer on one side of a substrate is preferred. The concept of pressure-sensitive adhesive sheet here may include those called pressure-sensitive adhesive tape, pressure-sensitive adhesive film, pressure-sensitive adhesive label, etc.

[0018] Furthermore, the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of this embodiment contains a polymer having a radical-reactive carbon-carbon double bond in its side chain. Because the pressure-sensitive adhesive layer contains a polymer having a radical-reactive carbon-carbon double bond in its side chain, it cures when exposed to active energy rays such as ultraviolet light. Therefore, when the pressure-sensitive adhesive layer of this embodiment is attached to an adherend, irradiated with active energy rays such as ultraviolet light, and then peeled from the adherend, contamination such as adhesive residue on the adherend is effectively suppressed or prevented, demonstrating excellent low-contamination properties. Therefore, the pressure-sensitive adhesive sheet of this embodiment has good removability. Examples of active energy rays supplied to cure the pressure-sensitive adhesive layer include ionizing radiation such as α-rays, β-rays, γ-rays, X-rays, neutron beams, and electron beams, as well as ultraviolet light and visible light. From the viewpoints of versatility in consideration of the scale of the equipment and reduction of damage to materials, radiation such as electron beams, ultraviolet light, α-rays, β-rays, γ-rays, and X-rays is preferred, with ultraviolet light being particularly preferred. The method for generating ultraviolet light is not particularly limited, and well-known and commonly used generation methods can be used, such as a discharge lamp method (arc lamp), a flash method, a laser method, and a UV-LED method. In the present invention, the use of a discharge lamp method (arc lamp) or a UV-LED method is preferred because of their excellent industrial productivity. Among these, the use of an irradiation method using a high-pressure mercury lamp, a metal halide lamp, or a UV-LED is preferred because of their excellent irradiation efficiency. The wavelength of the ultraviolet light can be any wavelength in the ultraviolet region without particular limitation, but it is preferable to use a wavelength of about 250 to 440 nm, which is used in general photopolymerization and is used in the ultraviolet light generation method. In this specification, removability refers to the property of being able to easily peel an article from an adherend when peeling the article from the adherend.

[0019] In the pressure-sensitive adhesive sheet of the first embodiment, the peel strength of the pressure-sensitive adhesive layer at 23°C before curing from a silicon wafer (180° peel strength from a silicon wafer) is 0.001 to 3.0 N / 20 mm when a 180° peel is performed at a tensile speed of 300 mm / min. From the viewpoint of handleability, the peel strength is 0.001 N / 20 mm or more, preferably 0.01 N / 20 mm or more, more preferably 0.03 N / 20 mm or more, and even more preferably 0.05 N / 20 mm or more. Furthermore, from the viewpoint of transferring two-dimensional materials at a high transfer rate, the peel strength is 3.0 N / 20 mm or less, preferably 2.5 N / 20 mm or less, more preferably 2.0 N / 20 mm or less, and even more preferably 1.5 N / 20 mm or less. The peel strength of the pressure-sensitive adhesive layer at 23°C before curing from a silicon wafer (180° peel strength from a silicon wafer) can be calculated using the method described in the Examples.

[0020] Furthermore, in the pressure-sensitive adhesive sheet of the second aspect, for the same reasons as above, the peel strength of the pressure-sensitive adhesive sheet from a silicon wafer at 23°C before curing of the pressure-sensitive adhesive layer (180° peel strength from silicon wafer) is preferably 0.001 to 3.0 N / 20 mm when 180° peeling is performed at a pulling rate of 300 mm / min.

[0021] In the pressure-sensitive adhesive sheet of the first embodiment, the pressure-sensitive adhesive layer has a tensile modulus at 23°C after curing of 9 to 1000 MPa. Here, the tensile modulus of the pressure-sensitive adhesive layer is 9 MPa or more, preferably 10 MPa or more, more preferably 20 MPa or more, and even more preferably 100 MPa or more, from the viewpoint of suppressing damage to the two-dimensional material due to deformation and transferring the two-dimensional material at a high transfer rate. Furthermore, the tensile modulus of the pressure-sensitive adhesive layer is 1000 MPa or less, preferably 200 MPa or less, and more preferably 150 MPa or less. When the tensile modulus of the pressure-sensitive adhesive layer is 1000 MPa or less, large bending stress is unlikely to be applied when peeling between the first substrate and the two-dimensional material, and stable peeling can be achieved.

[0022] Specifically, the tensile modulus of the pressure-sensitive adhesive layer after curing can be calculated as follows: ２A cylindrical sample is irradiated with ultraviolet light and rolled to a length of 30 mm and a diameter of 1 mm, and chucked at 10 mm above and below the length, and pulled at a rate of 50 mm / min. The initial tensile modulus is calculated from the slope of the stress versus strain gradient at the maximum point between 10% strain and 100% strain, and measured using a tensile tester. This is the tensile modulus of the adhesive layer after curing. If the adhesive after ultraviolet irradiation is brittle and easily breaks when rolled to a length of 30 mm and a diameter of 1 mm, it can be wound without breakage by masking 5% or less of the winding direction at the start of winding to prevent ultraviolet irradiation.

[0023] In the pressure-sensitive adhesive sheet of the second embodiment, for the same reasons as above, the pressure-sensitive adhesive layer preferably has a tensile modulus at 23° C. after curing of 9 to 1000 MPa.

[0024] Furthermore, the adhesive sheet of the second aspect exhibited a peel strength x (N / 20 mm) at 23°C before curing of the adhesive layer from a silicon wafer when subjected to a 180° peel at a tensile speed of 300 mm / min, and a HSP polarity term y (MPa ０．５ ) satisfy at least one of the following relationships of formula 1 and formula 2: y−0.52x−4.7≧0 (formula 1) y+0.50x−4.8≦0 (formula 2)

[0025] The inventors focused on the adhesion and interaction between the two-dimensional material and the adhesive. If the peel strength of the adhesive layer of the adhesive sheet before curing is too high, the two-dimensional material and the adhesive will adhere too closely, and even if the peel strength becomes lighter after curing, the two-dimensional material will be damaged during release. Furthermore, if the HSP polarity term of the polymer is too low, the interaction between the two-dimensional material and the adhesive will be low, and the two-dimensional material will be damaged during separation from the first substrate. Furthermore, as shown in the examples and comparative examples described below, it has been experimentally discovered that when an adhesive sheet satisfies the relationship of Formula 1 above, it is possible to achieve both excellent low-contamination properties and a high transfer rate when used to transfer two-dimensional materials.

[0026] On the other hand, even if the HSP polarity term of the polymer is low, it is believed that the interaction between the two-dimensional material and the adhesive can be maintained as long as the peel strength before hardening of the adhesive layer of the adhesive sheet is within a certain range. Furthermore, as shown in the examples and comparative examples described below, even when the adhesive sheet satisfies the relationship of the above formula 2, it has been experimentally found that excellent low-contamination properties and a high transfer rate when used to transfer two-dimensional materials can be achieved at the same time.

[0027] The pressure-sensitive adhesive sheet of the second embodiment may satisfy at least one of the relationships of the above formula 1 and formula 2, and may also satisfy both relationships. The pressure-sensitive adhesive sheet of the second embodiment preferably satisfies the relationship of either the above formula 1 or formula 2. Depending on the two-dimensional material to be transferred using the pressure-sensitive adhesive sheet, it can be selected whether the pressure-sensitive adhesive sheet of the second embodiment satisfies formula 1 or formula 2.

[0028] For the same reasons as above, the adhesive sheet of the first aspect is obtained by subjecting the adhesive layer to a silicon wafer at 23°C before curing to a peel force x (N / 20 mm) when peeled at 180° at a tensile speed of 300 mm / min, and the HSP polarity term y (MPa ０．５ ) preferably satisfies at least one of the relationships of formula 1 and formula 2 above.

[0029] Furthermore, in the pressure-sensitive adhesive sheet of this embodiment, the peel strength (180° peel strength from silicon wafer) at 23°C after curing of the pressure-sensitive adhesive layer from a silicon wafer is preferably 1.0 N / 20 mm or less, more preferably 0.5 N / 20 mm or less, and even more preferably 0.1 N / 20 mm or less, from the viewpoint of re-peelability when 180° peeling is performed at a tensile speed of 300 mm / min. Furthermore, the peel strength is, for example, 0.001 N / 20 mm or more. Note that when measuring the peel strength, a pressure of 450 mJ / cm is applied from the substrate side of the pressure-sensitive adhesive sheet, similar to the conditions described in the Examples section. ２ The measurement shall be made after irradiating with ultraviolet light at a dose of 1000 kJ / s.

[0030] In the pressure-sensitive adhesive sheet of the present embodiment, the HSP polarity parameter of the polymer having a radical reactive carbon-carbon double bond in the side chain contained in the pressure-sensitive adhesive layer is 0 to 15 MPa. ０．５From the viewpoint of adhesive force development due to polar interactions, the HSP polar term is preferably 2 MPa. ０．５ It is preferable that the pressure is 3 MPa or more. ０．５ More preferably, 4 MPa or more ０．５ From the viewpoint of maintaining the flexibility of the adhesive, the HSP polarity term is more preferably 15 MPa. ０．５ It is preferable that the pressure is 10 MPa or less. ０．５ More preferably, it is 9 MPa or less. ０．５ More preferably, 8 MPa or less ０．５ The following is particularly preferred: The HSP polarity term can be calculated by the method described in the Examples.

[0031] A preferred embodiment of the pressure-sensitive adhesive composition that forms the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of this embodiment will be described below.

[0032] In the present embodiment, the pressure-sensitive adhesive composition is an active energy ray-curable pressure-sensitive adhesive composition containing a polymer having a radical-reactive carbon-carbon double bond (hereinafter also referred to as a carbon-carbon unsaturated double bond) in a side chain as a base polymer. The base polymer may be a polymer having a carbon-carbon unsaturated double bond only in the side chain, or a polymer having a carbon-carbon unsaturated double bond in the side chain and at a terminal.

[0033] Examples of base polymers include (meth)acrylic polymers, vinyl alkyl ether polymers, silicone polymers, polyester polymers, polyamide polymers, urethane polymers, and styrene-diene block copolymers, with (meth)acrylic polymers being preferred. The use of a (meth)acrylic polymer makes it easy to adjust the storage modulus and tensile modulus of the pressure-sensitive adhesive layer, and also makes it possible to obtain a pressure-sensitive adhesive composition that has an excellent balance between adhesive strength and releasability. Furthermore, contamination of the adherend by components derived from the pressure-sensitive adhesive can be reduced. Note that "(meth)acrylic" refers to acrylic and / or methacrylic.

[0034] The weight-average molecular weight of the base polymer is preferably 300,000 or more, more preferably 400,000 or more, and even more preferably 600,000 to 1,000,000. Within these ranges, bleeding of low molecular weight components can be prevented, and a low-staining PSA composition can be obtained. The molecular weight distribution (weight-average molecular weight / number-average molecular weight) of the base polymer is preferably 1 to 20, and more preferably 3 to 10. By using a base polymer with a narrow molecular weight distribution, bleeding of low molecular weight components can be prevented, and a low-staining PSA composition can be obtained. The weight-average molecular weight and number-average molecular weight can be determined by gel permeation chromatography (solvent: tetrahydrofuran, polystyrene equivalent).

[0035] One aspect of the pressure-sensitive adhesive composition used in the pressure-sensitive adhesive sheet of this embodiment includes a base polymer and a photopolymerization initiator. This base polymer is, for example, a polymer obtained by reacting a monomer composition including a polymer and a monomer having a carbon-carbon unsaturated double bond. In this example, appropriate components are appropriately selected so that the carbon-carbon unsaturated double bond is introduced into the side chain of the polymer. In this specification, the monomer composition may be a composition containing only a monomer, or may be a composition containing a monomer and any other components such as an oligomer and a polymer.

[0036] The base polymer can be obtained, for example, by reacting a polymer having a hydroxyl group with a monomer composition (hereinafter also referred to as base polymer monomer composition 1) containing a monomer having an isocyanate group and a functional group containing a carbon-carbon unsaturated double bond. By reacting base polymer monomer composition 1, the polymer having a hydroxyl group can undergo an addition reaction with the monomer having an isocyanate group and a functional group containing a carbon-carbon unsaturated double bond. As a result, a polymer having structural units derived from the monomer having an isocyanate group and a functional group containing a carbon-carbon unsaturated double bond is obtained.

[0037] The polymer having a hydroxyl group can be any suitable polymer having a hydroxyl group introduced into the side chain thereof. Examples include (meth)acrylic polymers, vinyl alkyl ether polymers, silicone polymers, polyester polymers, polyamide polymers, urethane polymers, and styrene-diene block copolymers, each having a hydroxyl group introduced into the side chain thereof. Preferably, a (meth)acrylic polymer having a hydroxyl group introduced into the side chain thereof is used.

[0038] The (meth)acrylic polymer having a hydroxyl group can be obtained, for example, by polymerizing a monomer composition containing any suitable acrylic or methacrylic acid ester having a linear or branched alkyl group and a monomer having a hydroxyl group. The acrylic or methacrylic acid ester having a linear or branched alkyl group may be used alone or in combination of two or more.

[0039] The linear or branched alkyl group is preferably an alkyl group having 30 or less carbon atoms, more preferably an alkyl group having 1 to 20 carbon atoms, and even more preferably an alkyl group having 4 to 18 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a t-butyl group, an isobutyl group, an amyl group, an isoamyl group, a hexyl group, a heptyl group, a cyclohexyl group, a 2-ethylhexyl group, an octyl group, an isooctyl group, a nonyl group, an isononyl group, a decyl group, an isodecyl group, an undecyl group, a lauryl group, a tridecyl group, a tetradecyl group, a stearyl group, an octadecyl group, and a dodecyl group.

[0040] Any appropriate monomer can be used as the hydroxyl group-containing monomer. Examples include 2-hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxymethyl methacrylate, 2-hydroxyethyl methacrylate, and N-(2-hydroxyethyl)acrylamide. Preferably, 2-hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxymethyl methacrylate, and 2-hydroxyethyl methacrylate are used. These monomers may be used alone or in combination of two or more.

[0041] The hydroxyl group-containing monomer preferably accounts for 5 mol% to 40 mol%, more preferably 15 mol% to 30 mol%, and even more preferably 20 mol% to 25 mol%, based on 100 mol% of all monomer components in the monomer composition used in the polymerization of the hydroxyl group-containing polymer. Polymerization of a monomer composition containing a hydroxyl group-containing monomer produces a polymer containing hydroxyl groups. This hydroxyl group can serve as the introduction point for a structural unit derived from a monomer having a functional group containing a carbon-carbon unsaturated double bond and an isocyanate group. For example, a base polymer having a carbon-carbon unsaturated double bond can be obtained by reacting a polymer (prepolymer) containing hydroxyl groups with a monomer having a functional group containing a carbon-carbon unsaturated double bond and an isocyanate group.

[0042] For the purpose of modifying cohesive strength, heat resistance, crosslinkability, etc., other monomer components copolymerizable with the above-mentioned (meth)acrylic acid alkyl ester may be further used as necessary. Examples of such monomer components include carboxyl group-containing monomers such as acrylic acid and methacrylic acid; acid anhydride monomers such as maleic anhydride and itaconic anhydride; sulfonic acid group-containing monomers such as styrenesulfonic acid and allylsulfonic acid; (N-substituted) amide monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and acryloylmorpholine; aminoalkyl (meth)acrylate monomers such as aminoethyl (meth)acrylate; alkoxyalkyl (meth)acrylate monomers such as methoxyethyl (meth)acrylate; maleimide monomers such as N-cyclohexylmaleimide and N-isopropylmaleimide; itaconimide monomers such as N-methylitaconimide and N-ethylitaconimide; succinimide vinyl monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, and methylvinylpyrrolidone; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; glycol-based acrylic ester monomers such as polyethylene glycol (meth)acrylate and polypropylene glycol (meth)acrylate; acrylic ester monomers having a heterocycle, halogen atom, silicon atom, or the like, such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, and silicone (meth)acrylate; olefin-based monomers such as isoprene, butadiene, and isobutylene; and vinyl ether-based monomers such as vinyl ether. These monomer components may be used alone or in combination of two or more.

[0043] The content of the other monomer component copolymerizable with the (meth)acrylic acid alkyl ester in the monomer composition can be any appropriate amount. Specifically, the other monomer component copolymerizable with the (meth)acrylic acid alkyl ester is used so that the total of the (meth)acrylic acid alkyl ester, the hydroxyl group-containing monomer, and any other monomer component copolymerizable with the (meth)acrylic acid alkyl ester is 100 mol %.

[0044] The polymer having a hydroxyl group can be obtained by any suitable method. For example, a (meth)acrylic polymer having a hydroxyl group can be obtained by polymerizing a monomer composition containing a (meth)acrylic acid alkyl ester, a hydroxyl group-containing monomer, and any other monomer component copolymerizable with the (meth)acrylic acid alkyl ester by any suitable polymerization method.

[0045] As described above, the base polymer of the pressure-sensitive adhesive composition is a polymer obtainable, for example, by reacting the above-mentioned hydroxyl-containing polymer with a monomer composition containing a monomer having an isocyanate group and a functional group containing a carbon-carbon unsaturated double bond. The reaction of the hydroxyl group of the hydroxyl-containing polymer with the isocyanate group of the monomer having an isocyanate group and a functional group containing a carbon-carbon unsaturated double bond results in a base polymer having an introduced carbon-carbon unsaturated double bond. The use of this base polymer makes it possible to provide a pressure-sensitive adhesive composition that has excellent irregularity-filling properties and adhesive properties, and that can prevent adhesive residue on the adherend upon peeling.

[0046] Examples of monomers having a functional group containing a carbon-carbon unsaturated double bond and an isocyanate group include monomers having an acryloyl group or a methacryloyl group and an isocyanate group, such as 2-(2-methacryloyloxyethyloxy)ethyl isocyanate, 2-isocyanate ethyl acrylate (2-acryloyloxyethyl isocyanate), 2-isocyanate ethyl methacrylate (2-methacryloyloxyethyl isocyanate), methacryloyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate. These may be used alone or in combination of two or more.

[0047] The amount of the monomer having a carbon-carbon unsaturated double bond and an isocyanate group added relative to the number of moles of hydroxyl groups in the hydroxyl group-containing polymer is preferably 10 mol% to 90 mol%, more preferably 30 mol% to 85 mol%, and even more preferably 50 mol% to 80 mol%. When the amount of the monomer having a carbon-carbon unsaturated double bond and an isocyanate group added is within the above range, the pressure-sensitive adhesive composition can be well cured by irradiation with active energy rays, and a pressure-sensitive adhesive composition with excellent releasability can be provided. When the amount of the monomer having a carbon-carbon unsaturated double bond and an isocyanate group added exceeds 90 mol%, the number of reaction sites with the crosslinking agent decreases, and a sufficient crosslinking effect may not be obtained.

[0048] Furthermore, for example, the monomers constituting the (meth)acrylic polymer can be roughly divided into hydrophilic monomers, hydrophobic monomers, and monomers other than the hydrophilic and hydrophobic monomers.

[0049] As the hydrophilic monomer, any appropriate monomer having a polar group can be used. Specifically, carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride monomers such as maleic anhydride and itanoic anhydride; 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and 1-hydroxypropyl (meth)acrylate; Hydroxyl group-containing monomers such as 0-hydroxydecyl, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl methacrylate; sulfonic acid group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate; (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylolpropane (meth)acrylamide, and acryloylmorpholine; (meth)acrylic acid aminoalkyl monomers such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; and (meth)methoxy acrylate. alkoxyalkyl (meth)acrylate monomers such as ethyl, and ethoxyethyl (meth)acrylate; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide;succinimide-based monomers such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, and N-(meth)acryloyl-8-oxyoctamethylene succinimide; vinyl-based monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinylcarboxylic acid amides, styrene, α-methylstyrene, and N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, and the like. p) Glycol-based acrylic ester monomers such as methoxyethylene glycol acrylate and methoxypolypropylene glycol (meth)acrylate; acrylic ester-based monomers having heterocycles, halogen atoms, silicon atoms, etc., such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, and silicon (meth)acrylate; and polyfunctional monomers such as hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate. Hydrophilic monomers that can be used include hydroxyl group-containing monomers and / or (N-substituted) amide-based monomers. Only one hydrophilic monomer may be used, or two or more may be used in combination. ;

[0050] The hydrophobic monomer may be any suitable monomer as long as it has hydrophobicity. Specific examples include vinyl alkyl or aryl ethers having an alkyl group having 9 to 30 carbon atoms, such as vinyl 2-ethylhexanoate, vinyl laurate, vinyl stearate, and stearyl vinyl ether; hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl acrylate, isononyl acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, lauryl (meth)acrylate, oleyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate; unsaturated vinyl esters of (meth)acrylic acid derived from fatty acids and aliphatic alcohols; monomers derived from cholesterol; and olefin monomers such as 1-butene, 2-butene, 1-pentene, 1-hexene, 1-octene, isobutylene, and isoprene. The hydrophobic monomer may be used alone or in combination of two or more. The hydrophobic monomer used in the present invention refers to a monomer having a solubility of 0.02 g or less in 100 g of water.

[0051] The base polymer may further contain a monomer component other than the hydrophilic monomer and the hydrophobic monomer. Examples of the other monomer component include alkyl acrylates such as butyl acrylate and ethyl acrylate. The other monomer components may be used alone or in combination of two or more.

[0052] When a hydroxyl group-containing polymer is used, the ratio of the hydrophilic monomer other than the hydroxyl group-containing monomer to the total amount of monomer components other than the hydroxyl group-containing monomer (100 mol%) is preferably 0 to 50 mol%, more preferably 0 to 45 mol%, and even more preferably 0 to 40 mol%. Furthermore, by setting the ratio of the hydrophilic monomer other than the hydroxyl group-containing monomer to 50 mol% or less to the total amount of monomer components other than the hydroxyl group-containing monomer (100 mol%), the polarity of the adhesive is not too high, thereby maintaining water resistance and moisture resistance, and the cohesive strength is not too high, thereby maintaining adhesive strength. The lower the ratio, the better; however, the ratio may be, for example, 5 mol% or more, 15 mol% or more, or 25 mol% or more.

[0053] The above description has focused on the case where a base polymer is obtained by reacting a monomer composition (base polymer monomer composition 1) containing a polymer having a hydroxyl group with a monomer having a carbon-carbon unsaturated double bond and an isocyanate group. However, the base polymer is not limited to this. That is, the base polymer can be prepared, for example, by reacting a polymer having a reactive functional group (first functional group) with a compound having a functional group (second functional group) capable of reacting with the first functional group to form a bond and a functional group containing a carbon-carbon unsaturated double bond, while maintaining the radiation polymerizability of the carbon-carbon unsaturated double bond. For this reason, the base polymer preferably contains a structural portion derived from the polymer having the first functional group and a structural portion derived from the compound having the second functional group and a carbon-carbon unsaturated double bond. In addition to acryloyl and methacryloyl groups, examples of functional groups containing a carbon-carbon unsaturated bond include vinyl, propenyl, and isopropenyl groups.

[0054] Examples of combinations of the first functional group and the second functional group include a carboxy group and an epoxy group, an epoxy group and a carboxy group, a carboxy group and an aziridyl group, an aziridyl group and a carboxy group, a hydroxy group and an isocyanate group, and an isocyanate group and a hydroxy group. Among these, from the viewpoint of ease of reaction tracking, a combination of a hydroxy group and an isocyanate group, and a combination of an isocyanate group and a hydroxy group are preferred. The above combinations may be one type only, or two or more types.

[0055] The base polymer can be prepared, for example, by polymerizing (copolymerizing) raw material monomers containing a monomer component having a first functional group to obtain a polymer having the first functional group, and then subjecting a compound having the second functional group and a carbon-carbon unsaturated double bond to a condensation reaction or addition reaction with the polymer while maintaining the radiation polymerizability of the carbon-carbon unsaturated double bond.

[0056] Various common solvents may be used during polymerization of the monomer components. Examples of such solvents include organic solvents such as esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. One or more of the above solvents may be used.

[0057] The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization of the monomer components are not particularly limited and can be appropriately selected and used. The weight-average molecular weight of the polymer can be controlled by the amounts of the polymerization initiator and chain transfer agent used and the reaction conditions, and the amounts used are appropriately adjusted depending on the types of these.

[0058] As the polymerization initiator used for polymerizing the monomer components, a thermal polymerization initiator, a photopolymerization initiator (photoinitiator), etc. can be used depending on the type of polymerization reaction. Only one type of the polymerization initiator may be used, or two or more types may be used.

[0059] The thermal polymerization initiator is not particularly limited, and examples thereof include azo-based polymerization initiators, peroxide-based polymerization initiators, redox-based polymerization initiators, etc. The amount of the thermal polymerization initiator used is preferably 1 part by mass or less, more preferably 0.005 to 1 part by mass, and even more preferably 0.02 to 0.5 parts by mass, relative to 100 parts by mass of the total amount of all monomer components constituting the polymer having the first functional group.

[0060] As the photopolymerization initiator used for polymerizing the monomer components, any of the photopolymerization initiators exemplified below as the photopolymerization initiator contained in the pressure-sensitive adhesive composition can be used as appropriate.

[0061] The reaction between the polymer having the first functional group and the compound having the second functional group and a functional group containing a carbon-carbon unsaturated double bond can be carried out, for example, by stirring in a solvent in the presence of a catalyst. Examples of the solvent include those described above. The catalyst is appropriately selected depending on the combination of the first functional group and the second functional group. The reaction temperature in the reaction is, for example, 5 to 100°C, and the reaction time is, for example, 1 to 36 hours.

[0062] The pressure-sensitive adhesive composition of this embodiment also contains a photopolymerization initiator in addition to the base polymer. Any appropriate initiator can be used as the photopolymerization initiator that can be contained in the pressure-sensitive adhesive composition. Examples of the photopolymerization initiator include acylphosphine oxide photoinitiators such as ethyl 2,4,6-trimethylbenzylphenylphosphinate and (2,4,6-trimethylbenzoyl)phenylphosphine oxide; α-ketol compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and 1-hydroxycyclohexylphenyl ketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether; and benzyl dimethyl ketal. aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; benzophenone compounds such as benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone; camphorquinone; halogenated ketones; acylphosphonates; and α-hydroxyacetophenones such as 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropane-1. Preferably, 2,2-dimethoxy-2-phenylacetophenone and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropane-1 can be used.The photopolymerization initiator may be used alone or in combination of two or more.

[0063] As the photopolymerization initiator, commercially available products may be used, for example, Omnirad 127D and Omnirad 651, both of which are trade names of IGM Resins.

[0064] The photopolymerization initiator can be used in any appropriate amount. The content of the photopolymerization initiator is preferably 0.5 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, relative to 100 parts by mass of the base polymer. If the content of the photopolymerization initiator is less than 0.5 parts by mass, there is a risk that the composition will not cure sufficiently when irradiated with active energy rays. If the content of the photopolymerization initiator exceeds 20 parts by mass, there is a risk that the storage stability of the pressure-sensitive adhesive composition will decrease.

[0065] The PSA composition may further contain any appropriate additives, such as a crosslinking agent, a catalyst (e.g., a platinum catalyst), a tackifier, a plasticizer, a pigment, a dye, a filler, an antioxidant, a conductive material, an ultraviolet absorber, a light stabilizer, a release modifier, a softener, a surfactant, a flame retardant, and a solvent.

[0066] The pressure-sensitive adhesive composition preferably further contains a crosslinking agent. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and chelate-based crosslinking agents. The content of the crosslinking agent can be adjusted to any appropriate amount, but is preferably 0.5 to 20 parts by mass, more preferably 4 to 15 parts by mass, and even more preferably 6 to 12 parts by mass, relative to 100 parts by mass of the base polymer. The flexibility of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition can be controlled by the content of the crosslinking agent. A content of 0.5 parts by mass or more is preferable because it provides an appropriate cohesive strength. A content of 20 parts by mass or less is preferable because it provides an appropriate adhesive strength.

[0067] As the crosslinking agent, an isocyanate-based crosslinking agent is preferably used. Isocyanate-based crosslinking agents are preferred because they can react with various functional groups. Particularly preferably, a crosslinking agent having three or more isocyanate groups is used. By using an isocyanate-based crosslinking agent as the crosslinking agent and setting the content of the crosslinking agent within the above range, it is possible to form a pressure-sensitive adhesive layer that has excellent releasability and significantly less adhesive residue even after heating.

[0068] The pressure-sensitive adhesive layer may also contain a thermoplastic resin. Examples of thermoplastic resins include natural or synthetic rubbers such as natural rubber, polyisobutylene, polyisoprene, chloroprene rubber, butyl rubber, and nitrile butyl rubber; olefin elastomers such as ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, polybutene, and chlorinated polyethylene; styrene elastomers such as styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, and hydrogenated products thereof; polyester elastomers; polyamide elastomers; and various thermoplastic elastomers such as polyurethane elastomers. These rubber components or thermoplastic elastomer components may be used alone or in combination of two or more.

[0069] The pressure-sensitive adhesive layer can be produced, for example, by applying a pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer onto a release liner and drying the resulting pressure-sensitive adhesive composition layer, or by applying the pressure-sensitive adhesive composition onto a release liner. If necessary, the applied layer may be further dried by heating.

[0070] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but from the viewpoint of exhibiting good adhesion to two-dimensional materials, it is preferably 2 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, and from the viewpoint of forming a smooth pressure-sensitive adhesive layer, it is preferably 500 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less.

[0071] Examples of substrates constituting the pressure-sensitive adhesive sheet include those made of resin, nonwoven fabric, woven fabric, metal foil, paper, etc. Among these, substrates made of resin (resin substrates) are preferred from the viewpoints of smoothness, ease of handling, cost, etc.

[0072] Specific examples of resins constituting the substrate include polyester-based resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polybutylene naphthalate (PBN), polyolefin-based resins such as ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer, polyethylene, polypropylene, and ethylene-propylene copolymer, polyurethane-based resins, polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyamide, polyimide, celluloses, fluorine-based resins, polyethers, polystyrene-based resins such as polystyrene, polycarbonate, and polyethersulfone. Among these, from the viewpoint of tensile modulus that provides flexibility, ethylene-vinyl acetate copolymer (EVA), polyolefin-based resins, and polyurethane-based resins are preferred, and ethylene-vinyl acetate copolymer (EVA) is particularly preferred.

[0073] The thickness of the substrate can be set to any appropriate value. The thickness of the substrate is preferably 10 μm to 300 μm, more preferably 50 μm to 150 μm. The substrate may be an unstretched film, or may be one that has been subjected to uniaxial or biaxial stretching treatment as necessary. In addition, the substrate preferably has the property of transmitting active energy rays such as ultraviolet rays.

[0074] The tensile modulus of the substrate is preferably 10 MPa to 4000 MPa. Here, from the viewpoint of ease of handling of the pressure-sensitive adhesive tape, the tensile modulus of the substrate is preferably 10 MPa or more, more preferably 30 MPa or more, and even more preferably 50 MPa or more. Furthermore, the tensile modulus of the substrate is preferably 4000 MPa or less, more preferably 1000 MPa or less, and even more preferably 100 MPa or less. When the tensile modulus of the substrate is 4000 MPa or less, large bending stress is unlikely to be applied when peeling between the first substrate and the two-dimensional material, and stable peeling can be achieved. Note that the tensile modulus of the substrate is the tensile modulus at 23°C.

[0075] The tensile modulus of the substrate can be calculated specifically as follows. A sample of the substrate with a width of 10 mm and a length of 20 mm is prepared, chucked at 5 mm above and below the longitudinal direction with a chuck distance of 10 mm, and pulled at a speed of 50 mm / min. The initial tensile modulus is calculated from the slope at the point where the slope of the stress versus strain is maximum between 10% strain and 100% strain, and measured using a tensile tester. This is the tensile modulus of the substrate. When the tensile modulus has anisotropy that varies depending on the pulling direction, the average of the tensile modulus when pulled in at least two orthogonal directions in the plane is used. For example, the average of the values ​​measured in two orthogonal directions in the plane (MD and TD) is used as the long side direction (length direction).

[0076] (Method for producing pressure-sensitive adhesive sheet) The pressure-sensitive adhesive sheet can be produced by any appropriate method. In one embodiment, the pressure-sensitive adhesive sheet can be produced by forming a pressure-sensitive adhesive layer on a substrate. The pressure-sensitive adhesive layer may be formed by coating the substrate with the composition that forms the pressure-sensitive adhesive layer, or the pressure-sensitive adhesive layer may be formed on any appropriate release liner and then transferred to the substrate. As the coating method, various methods can be used, such as bar coater coating, air knife coating, gravure coating, gravure reverse coating, reverse roll coating, lip coating, die coating, dip coating, offset printing, flexographic printing, and screen printing.

[0077] [Method for transferring two-dimensional materials] The pressure-sensitive adhesive sheet of this embodiment can achieve a high transfer rate of two-dimensional materials and is also excellent in low contamination. Therefore, it is suitable for use in applications such as transferring two-dimensional materials. Below, an example of a method for transferring two-dimensional materials using the pressure-sensitive adhesive sheet of this embodiment will be described as a method for manufacturing a laminate or a method for manufacturing a two-dimensional material laminate.

[0078] First, an example of a method for manufacturing a laminate will be described.

[0079] 1 is a schematic cross-sectional view showing a stack 101 having a two-dimensional material 30 on a first substrate 21. The stack 101 may be referred to as a first stack. In the method for manufacturing the stack of this example, as a preliminary step, first, the two-dimensional material 30 is formed on the first substrate 21.

[0080] The first substrate 21 is not particularly limited and may be a metal substrate, ceramic substrate, silicon substrate, resin substrate, etc. Examples of the first substrate 21 include metal substrates made of transition metals such as copper, nickel, cobalt, iron, chromium, gold, platinum, molybdenum, and tungsten; alloy metal substrates of these metals; single crystal substrates such as sapphire, magnesia, spinel, mica, SiC, SiN, and Si, and single crystal substrates whose surfaces have been oxidized; quartz substrates; substrates for forming two-dimensional materials on the surfaces of these substrates, on which thin films of the transition metals listed above are formed, and substrates on which two-dimensional materials are formed on the aforementioned substrates. The first substrate 21 is preferably a substrate for forming two-dimensional materials.

[0081] The method for forming the two-dimensional material on the metal substrate for film formation is not particularly limited, and a CVD method is preferably used. Examples of the film formation method include a thermal CVD method in which a raw material gas is introduced in the presence of a catalytic metal and processed by thermal decomposition of the raw material gas, and a surface wave microwave plasma chemical vapor deposition (CVD) method in which microwave plasma is used for processing. However, any method may be used as long as the two-dimensional material 30 can be formed on the first substrate 21.

[0082] The two-dimensional material 30 is a material having a two-dimensional layered structure made of a single element or two or more elements, and having an extremely thin sheet structure. Graphene, a two-dimensional sheet made only of carbon, is a typical example. The two-dimensional material 30 may also be a ribbon-like film having a width in the nanometer range. Examples of the two-dimensional material 30 include two-dimensional carbon materials, transition metal chalcogenides, molybdenum disulfide, tungsten disulfide, hexagonal boron nitride (h-BN), black phosphorus, and derivatives thereof. Two-dimensional carbon materials, molybdenum disulfide, tungsten disulfide, or hexagonal boron nitride are preferred. Graphene or graphene derivatives are preferred as the two-dimensional carbon material. Graphene is a two-dimensional carbon material consisting of sp ２ It is a film formed by bonded carbon atoms, forming a hexagonal lattice structure made of carbon atoms and their bonds. In this specification, multi-layer graphene, in which these films are stacked in 2 to 100 layers, is also referred to as "graphene." Furthermore, the two-dimensional material 30 may be composed of a single layer or multiple layers. When the two-dimensional material is composed of multiple layers, each layer may be composed of the same material or different materials.

[0083] Examples of graphene derivatives include graphene oxide, sulfonated graphene oxide, graphene hydroxide, graphene carbonate, and graphene nitride, and graphene oxide is preferred.

[0084] The laminate 101 may be subjected to a pretreatment process of immersion in water. For example, when the two-dimensional material is graphene and the graphene film-forming catalyst of the laminate 101 is Cu, the laminate 101 is immersed in water at 4 to 100°C for 4 to 72 hours. This treatment causes water to intercalate at the interface between the graphene and Cu, oxidizing the Cu surface. During immersion, the water may be left standing or stirred. Stirring the water makes the Cu surface more likely to oxidize. Other methods include adding a metal salt such as potassium chloride or sodium chloride to water to promote Cu oxidation, or contacting the water with water vapor to oxidize Cu. In either case, water intercalates at the interface between the graphene and Cu, oxidizing the Cu surface. This oxidation weakens the interaction between the graphene and Cu, allowing the graphene to be effectively transferred to the adhesive sheet 10 in the subsequent process.

[0085] (Adhesive Sheet Adhesion Process) FIG. 2 is a schematic cross-sectional view showing a state in which an adhesive sheet 10 is attached to a two-dimensional material 30 on a first substrate 21. Here, a laminate formed by adhering an adhesive sheet 10 to a two-dimensional material 30 on a first substrate 21 is referred to as a laminate 102. Furthermore, a laminate 102 in which the first substrate 21, the two-dimensional material 30, and the adhesive sheet 10 are laminated in this order may be referred to as a second laminate. Note that FIG. 2 shows an embodiment in which an adhesive sheet having an adhesive layer 12 on one side of a base material 11 is used as the adhesive sheet 10. In the laminate manufacturing method of this example, an adhesive sheet 10 is attached to a two-dimensional material 30 on a first substrate 21.

[0086] By placing the adhesive sheet 10 on the two-dimensional material 30 side of the laminate 101 of the first substrate 21 and the two-dimensional material 30, the adhesive sheet 10 can be attached to the two-dimensional material 30. This results in a laminate 102. Here, when attaching the adhesive sheet 10 to the two-dimensional material 30, for example, a roller or the like may be used to press the two-dimensional material 30 and the adhesive sheet 10 together.

[0087] After obtaining the laminate 102, autoclave treatment may be performed as necessary. The conditions for the autoclave treatment are not particularly limited, but for example, the temperature is preferably 20 to 300°C, more preferably 30 to 70°C. The pressure is preferably 1.1 to 20 atmospheres, more preferably 2 to 10 atmospheres. The treatment time is preferably 1 to 120 minutes, more preferably 10 to 60 minutes.

[0088] (Pre-curing step) The method for producing a laminate in this example may include a pre-curing step after the pressure-sensitive adhesive sheet attachment step and before the bubble-forming step described below. It is possible to appropriately select whether to perform the pre-curing step or the post-curing step described below. Hereinafter, the pre-curing step refers to a step of curing a pressure-sensitive adhesive layer when a pressure-sensitive adhesive sheet 10 having a pressure-sensitive adhesive layer that cures upon receiving active energy rays is used. Hereinafter, a pressure-sensitive adhesive layer that cures upon receiving active energy rays may be referred to as an active energy ray-curable pressure-sensitive adhesive layer. Furthermore, a pressure-sensitive adhesive sheet having an active energy ray-curable pressure-sensitive adhesive layer may be referred to as an active energy ray-curable pressure-sensitive adhesive sheet.

[0089] Because the pressure-sensitive adhesive sheet of this embodiment is an active energy ray-curable pressure-sensitive adhesive sheet, in the above-described pressure-sensitive adhesive sheet attachment process, the pressure-sensitive adhesive layer 12 of the pressure-sensitive adhesive sheet 10 easily conforms to the shape of the two-dimensional material. Furthermore, by undergoing a curing process before the bubble-forming process and separation process described below, the pressure-sensitive adhesive sheet 10 becomes hard enough to suppress deformation of the two-dimensional material 30 when a laminate including the pressure-sensitive adhesive sheet 10 and the two-dimensional material 30 is separated from the first substrate 21 in the separation process. Therefore, the two-dimensional material 30 can be separated from the first substrate 21 over a large area and with little or no damage. As a result, a two-dimensional material with a high transfer rate is easily obtained. In one aspect, when the two-dimensional material is graphene, graphene with a high transfer rate and high mobility is easily obtained.

[0090] (Bubble Formation Process) FIG. 3 is a schematic cross-sectional view showing a state in which bubbles B have been formed between the first substrate 21 and the two-dimensional material 30. FIG. 3 also shows how the laminate 103, which includes the pressure-sensitive adhesive sheet 10 and the two-dimensional material 30, has been separated from the first substrate 21 due to the formation of bubbles in the bubble formation process. In the laminate manufacturing method of this embodiment, bubbles B are then formed between the first substrate 21 and the two-dimensional material 30. Here, a bubble forming unit 260 is used to form bubbles B between the first substrate 21 and the two-dimensional material 30. The bubble forming unit 260 includes at least a solution 261, a potential source 262 (e.g., a power source or battery) having a positive lead 262P and a negative lead 262N, and an anode 263 located in the solution 261 and electrically connected to the positive lead 262P.

[0091] The laminate (second laminate) 102 is immersed in the solution 261 of the bubble forming unit 260. With the laminate (second laminate) 102 immersed in the solution 261, the negative lead 262N is electrically connected to the first substrate 21 in the solution 261. Therefore, the first substrate 21 functions as the cathode of the bubble forming unit 260.

[0092] That is, the formation of bubbles B between the first substrate 21 and the two-dimensional material 30 is performed by, for example, an electrochemical reaction in the bubble formation unit 260. As an example, the electrochemical reaction is the release of hydrogen due to electrolysis of water in the solution 261, and bubbles B are formed by the electrochemical reaction.

[0093] More specifically, when a potential is applied to the solution 261, a reduction reaction occurs on the negatively charged first substrate 21 (cathode), hydrogen gas is formed from the first substrate 21, and hydrogen bubbles B are formed on the conductive surface of the first substrate 21. As a result, bubbles B are formed between the first substrate 21 and the two-dimensional material 30. Here, in the bubble forming unit 260, the arrangement of the anode 263 is adjusted so that bubbles B are formed in a concentrated manner between the first substrate 21 and the two-dimensional material 30.

[0094] The solution 261 contains water and at least one electrolyte, preferably 0.01 to 10 moles of electrolyte per liter of water. The electrolyte is not particularly limited and may be a single type or a combination of two or more types. Examples of the electrolyte include sodium hydroxide, potassium hydroxide, sulfuric acid, sodium chloride, and any suitable combination thereof.

[0095] Instead of the bubble forming step and the separation step described below, a peeling step in which peeling is performed in an appropriate liquid such as water may be employed.

[0096] (Separation Process) The laminate manufacturing method of this example includes a process of separating the laminate 103 including the adhesive sheet 10 and the two-dimensional material 30 from the first substrate 21. FIG. 4 shows a schematic cross-sectional view of the laminate 103 including the adhesive sheet 10 and the two-dimensional material 30. The laminate 103 may also be referred to as a third laminate. Here, the separation of the laminate 103 including the adhesive sheet 10 and the two-dimensional material 30 from the first substrate 21 may occur due to the formation of bubbles in the bubble formation process described above, as shown in FIG. 3. In this case, it can be said that the bubble formation process and the separation process are performed simultaneously. Alternatively, the separation of the laminate 103 including the adhesive sheet 10 and the two-dimensional material 30 from the first substrate 21 may be performed by pulling at least one of the adhesive sheet 10 and the first substrate 21 after the bubble formation process described above.

[0097] The laminate 103 separated from the first substrate 21 may be washed with an appropriate cleaning liquid such as ion-exchanged water, pure water such as distilled water, ultrapure water, or alcohol such as ethanol or isopropyl alcohol, if necessary.

[0098] Furthermore, when separating the laminate 103 from the first substrate 21 by pulling at least one of the pressure-sensitive adhesive sheet 10 and the first substrate 21 after the bubble formation process, the peel angle is not particularly limited and is typically 180 degrees or less. However, a small peel angle can prevent defects such as tears and cracks in the two-dimensional material 30 due to changes in the shape of the laminate 103. For this reason, a small peel angle is preferable, preferably 150 degrees or less, and more preferably 120 degrees or less. Furthermore, from the perspective of increasing the size of the peeling device itself, the peel angle is preferably 0 degrees or more. The peel angle refers to the angle between the first substrate 21 and the peeled portion of the laminate 103 when separating the laminate 103 from the first substrate 21.

[0099] The peeling speed when separating the laminate 103 from the first substrate 21 is not particularly limited, but a fast peeling speed shortens the time it takes for the shape of the laminate 103 to change, thereby preventing defects such as tears and cracks from occurring in the two-dimensional material 30. For this reason, the peeling speed is typically 1 mm / min or higher, but a fast peeling speed is preferable, preferably 10 mm / min or higher, and more preferably 100 mm / min or higher. Furthermore, from the viewpoint of stable operation of the device, the peeling speed is preferably 100,000 mm / min or lower, and more preferably 90,000 mm / min or lower. The peeling speed refers to the length of the laminate 103 peeled from the laminate 102 per unit time when separating the laminate 103 from the laminate 102.

[0100] According to the laminate manufacturing method of this example, bubbles that release the interaction between the first substrate 21 and the two-dimensional material 30 with a gentle force can be efficiently formed, so that the two-dimensional material 30 can be separated without tearing or scratching even if the two-dimensional material 30 has a large area. As a result, even if the two-dimensional material 30 has a large area, it is possible to manufacture a laminate 103 that can efficiently transfer the two-dimensional material 30 at a high transfer rate. Note that a large area is, for example, 100 mm ２ Although the area is as described above, the manufacturing method of the laminate of this example is of course applicable to cases where the area of ​​the two-dimensional material is relatively small, and it is easily understood that such cases are also included.

[0101] Next, an example of a method for manufacturing a two-dimensional material laminate will be described.

[0102] (Placement Step) In the method for manufacturing a two-dimensional material stack of this example, first, the stack obtained by the above-described method for manufacturing a stack is placed on a second substrate so that the surface of the stack on the two-dimensional material side is in contact with the second substrate. Figure 5 is a schematic cross-sectional view showing the step (placing step) of placing the stack 103 on the second substrate 40 so that the surface of the stack 103 on the two-dimensional material 30 side is in contact with the second substrate 40. By the placing step, a stack 104 is obtained in which the second substrate 40 and the stack 103 are stacked.

[0103] Here, when placing the laminate 103 on the second substrate 40, the laminate 103 may be wetted with an appropriate liquid such as water or alcohol, placed on the second substrate (liquid application), and then left to stand or dried, as necessary. This can increase the adhesion of the laminate 103 to the second substrate 40. Furthermore, when placing the laminate 103 on the second substrate 40, the laminate 103 and the second substrate 40 may be pressed together using, for example, a roller or the like. Furthermore, the laminate 103 may be cut to an appropriate size and placed at any desired location on the second substrate 40. This allows the two-dimensional material to be placed at any desired location on the second substrate.

[0104] (Post-curing process) The method for producing a two-dimensional material laminate of this example may include a post-curing process after the placing process and before the transfer process described below. It is possible to arbitrarily select whether to perform the pre-curing process or the post-curing process. Here, the post-curing process is a process for curing the pressure-sensitive adhesive layer 12 of the pressure-sensitive adhesive sheet 10 by irradiating it with active energy rays. However, the post-curing process is performed after the bubble-incorporating process in the method for producing a laminate described above, and is distinct from the pre-curing process performed before the bubble-incorporating process.

[0105] Because the pressure-sensitive adhesive sheet of the present embodiment is an active energy ray-curable pressure-sensitive adhesive sheet, in the above-described pressure-sensitive adhesive sheet attachment step, the pressure-sensitive adhesive layer 12 of the pressure-sensitive adhesive sheet 10 easily conforms to the shape of the two-dimensional material 30. Furthermore, by performing a post-curing step before the transfer step described below, the adhesive strength of the pressure-sensitive adhesive layer 12 of the pressure-sensitive adhesive sheet 10 decreases, making it easier to peel the pressure-sensitive adhesive sheet 10 from the two-dimensional material 30 in the transfer step. As a result, a high transfer rate is easily obtained. In one aspect, when the two-dimensional material is graphene, graphene having a high transfer rate and high mobility is easily obtained.

[0106] In this example, either the pre-curing step or the post-curing step may be performed, but from the viewpoint of easily obtaining a higher transfer rate and mobility, it is preferable to perform the pre-curing treatment.

[0107] (Transfer Process) In the manufacturing method of the two-dimensional material laminate of this example, the two-dimensional material is subsequently transferred onto a second substrate by peeling off the adhesive sheet, thereby obtaining a two-dimensional material laminate including the second substrate and the two-dimensional material. Figure 6 is a schematic cross-sectional view showing the process of transferring the two-dimensional material 30 onto the second substrate 40 by peeling off the adhesive sheet 10. By peeling off the adhesive sheet 10 of the laminate 104, the two-dimensional material 30 is transferred onto the second substrate 40, thereby obtaining a laminate 105 including the second substrate 40 and the two-dimensional material 30. This laminate 105 including the second substrate 40 and the two-dimensional material 30 is sometimes referred to as a two-dimensional material laminate.

[0108] The peel angle when peeling the adhesive sheet 10 from the laminate 104 is not particularly limited and is usually 180 degrees or less. However, if the peel angle is large, stress is concentrated at the peel tip of the adhesive sheet 10, reducing the peel force at the interface between the adhesive sheet 10 and the two-dimensional material 30, preventing defects such as tears and cracks from occurring in the two-dimensional material 30. For this reason, the peel angle is preferably large, preferably 90 degrees or more, and more preferably 120 degrees or more. Furthermore, from the perspective of the peeling mechanism, the peel angle is preferably 180 degrees or less. The peel angle refers to the angle between the two-dimensional material 30 and the peeled portion of the adhesive sheet 10 when peeling the adhesive sheet 10 from the laminate 104.

[0109] The peeling speed when peeling the adhesive sheet 10 from the laminate 104 is not particularly limited, but if the peeling speed is slow, the elastic properties of the adhesive sheet 10 will be reduced, thereby reducing the peel force at the interface between the adhesive sheet 10 and the two-dimensional material 30, thereby preventing defects such as tearing and cracking in the two-dimensional material 30. For this reason, although the peeling speed is typically 1000 mm / min or less, a slower peeling speed is preferred, preferably 600 mm / min or less, and more preferably 300 mm / min or less. Furthermore, from the viewpoint of stable operation of the device, the peeling speed is preferably 3 mm / min or more, and more preferably 10 mm / min or more. The peeling speed refers to the length of the adhesive sheet 10 peeled from the laminate 104 per unit time when peeling the adhesive sheet 10 from the laminate 104.

[0110] The second substrate 40 is a material onto which the two-dimensional material is transferred. The second substrate 40 is preferably a substrate in which the adhesive strength between its transfer surface and the two-dimensional material 30 is stronger than the adhesive strength between the pressure-sensitive adhesive layer 12 and the two-dimensional material 30 after the application of active energy rays. Such a second substrate 40 may have a strong interacting force by itself, or may have an interacting force imparted by surface processing. Examples of surface processing include, but are not limited to, applying a curable resin, melting the surface, forming a microstructure, and chemically modifying the surface.

[0111] The second substrate 40 is not particularly limited, and may be any of a metal substrate, a ceramic substrate, a silicon substrate, a resin substrate, etc. The second substrate 40 may be, for example, a SiO ２ / Si substrate, quartz substrate, glass substrate, PET substrate, sapphire substrate, ITO substrate, substrate with two-dimensional material laminated thereon are preferred, SiO ２A / Si substrate is more preferred. Furthermore, the second substrate 40 may be a substrate in which a film made of copper, nickel, iron, or a mixed oxide containing at least one of these is partially formed on the surface of an appropriate base substrate such as a metal substrate, ceramic substrate, silicon substrate, or resin substrate. Here, the area occupied by the film in the area of ​​the surface of the base substrate is preferably 80% or less, and more preferably 70% or less. Furthermore, the area occupied by the film in the area of ​​the surface of the base substrate is preferably 5% or more, and more preferably 15% or more.

[0112] The thickness of the second substrate 40 is not particularly limited and can be selected appropriately, but is preferably 1 μm or more, more preferably 10 μm or more, and even more preferably 100 μm or more, and from the viewpoint of handling, is preferably 100 mm or less, more preferably 20 mm or less, and even more preferably 5 mm or less.

[0113] Furthermore, in the above example, a method for manufacturing a laminate was described that includes a step of forming bubbles between the first substrate and the two-dimensional material, and a step of separating the laminate including the adhesive sheet and the two-dimensional material from the first substrate by forming the bubbles or by pulling at least one of the adhesive sheet and the first substrate after forming the bubbles. However, in other examples of the method for manufacturing a laminate, instead of these steps, a step of peeling and separating the laminate including the adhesive sheet and the two-dimensional material from the first substrate may be included.

[0114] The two-dimensional material laminate obtained by the above-described method for producing a two-dimensional material laminate can be applied to transparent conductive films for touch panels, etc., semiconductor devices or electronic devices such as transistors and integrated circuits, transparent electrodes and electrochemical electrodes that require a large area, etc.

[0115] In addition to applications for transferring two-dimensional materials, the pressure-sensitive adhesive sheet of this embodiment can also be suitably used for applications requiring removability and low contamination, such as protective films for protecting the surfaces of various adherends.

[0116] [Joint] The joined body of the present embodiment is a joined body in which the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present embodiment is attached to a two-dimensional material. The joined body is, for example, a laminate 103 including the pressure-sensitive adhesive sheet 10 and the two-dimensional material 30, obtained by the separation step in the above-described method for producing a laminate.

[0117] As explained above, the present specification describes the following: (1) A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer contains a polymer having a radically reactive carbon-carbon double bond in a side chain, and wherein the pressure-sensitive adhesive layer has a tensile modulus of 9 to 1000 MPa at 23°C after curing, measured under the following measurement conditions: The pressure-sensitive adhesive sheet has a peel force of 0.001 to 3.0 N / 20 mm at 23°C before curing, when the pressure-sensitive adhesive sheet is subjected to a 180° peel at a pulling rate of 300 mm / min. (Measurement conditions for the tensile modulus of the pressure-sensitive adhesive layer after curing): The pressure-sensitive adhesive layer is subjected to a 180° peel at a pulling rate of 300 mm / min. ２ (2) A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer contains a polymer having a radical-reactive carbon-carbon double bond in its side chain, and wherein the peel force x (N / 20 mm) at 23°C before curing of the pressure-sensitive adhesive layer and the HSP polarity term y (MPa) of the polymer are calculated from the initial tensile modulus of the pressure-sensitive adhesive layer when the pressure-sensitive adhesive sheet is irradiated with ultraviolet light of 100 nm and rolled to a length of 30 mm and a diameter of 1 mm, and the sample is chucked at 10 mm above and below in the longitudinal direction and pulled at a speed of 50 mm / min. ０．５ ) satisfies at least one of the relationships of the following formula 1 and formula 2. y - 0.52x - 4.7 ≧ 0 (formula 1) y + 0.50x - 4.8 ≦ 0 (formula 2) (3) When the pressure-sensitive adhesive sheet is subjected to a 180° peel at a tensile speed of 300 mm / min, the peel force x (N / 20 mm) at 23°C before curing of the pressure-sensitive adhesive layer from a silicon wafer and the HSP polarity term y (MPa ０．５) satisfies at least one of the relationships of the following formula 1 and formula 2. y - 0.52x - 4.7 ≧ 0 (Formula 1) y + 0.50x - 4.8 ≦ 0 (Formula 2) (4) The pressure-sensitive adhesive sheet according to any one of (1) to (3), wherein the tensile modulus of the substrate at 23°C is 10 to 4000 MPa under the following measurement conditions. (Measurement conditions for tensile modulus of substrate) A sample of the substrate having a width of 10 mm and a length of 20 mm is chucked at 5 mm above and below in the longitudinal direction, and pulled at a rate of 50 mm / min. The initial tensile modulus is calculated from the slope at the point where the slope of stress with respect to strain is maximum between 10% strain and 100% strain, and is taken as the tensile modulus of the substrate. (5) The pressure-sensitive adhesive sheet according to any one of (1) to (4), which is for two-dimensional material transfer. (6) A bonded body in which the adhesive layer of the adhesive sheet according to any one of (1) to (5) is attached to a two-dimensional material.

[0118] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples in any way.

[0119] Example 1 A monomer composition (solid concentration: 40%) was prepared by mixing three types of monomers: 71.2 g of 2-ethylhexyl acrylate (2EHA) (60 mol % of the total amount of monomers not containing a hydroxyl group), 36.4 g of acryloylmorpholine (ACMO) (40 mol % of the total amount of monomers not containing a hydroxyl group), and 20.4 g of 4-hydroxybutyl acrylate (4HBA) (amount equivalent to 22 mol % when the total amount of monomers not containing a hydroxyl group was taken as 100 mol %), 0.3 mass % of a polymerization initiator (manufactured by NOF Corporation, trade name: Nyper (registered trademark) BW) relative to the total mass of the monomers, and a solvent (ethyl acetate). The monomer composition was placed in a 1 L round-bottom separable flask equipped with a separable cover, a separatory funnel, a thermometer, a nitrogen inlet tube, a Liebig condenser, a vacuum seal, a stirring rod, and a stirring blade. The mixture was then purged with nitrogen at room temperature for 2 hours while stirring. The mixture was then polymerized at 61°C for 8 hours under a nitrogen inflow to obtain a resin solution. To the resulting resin solution was added 12.0 g (equivalent to 12 mol% when the total amount of hydroxyl-free monomers was taken as 100 mol%) of a compound (manufactured by Showa Denko K.K., trade name "Karenz MOI") that introduces a carbon-carbon unsaturated double bond. Furthermore, 0.063 parts by mass of dibutyltin IV dilaurate (manufactured by Wako Pure Chemical Industries, Ltd.) was added per 100 parts by mass of resin solids, and a solvent (ethyl acetate) was added as appropriate to adjust the solids concentration to 15%. The mixture was then stirred at 50°C for 24 hours in an air atmosphere to obtain a pressure-sensitive adhesive solution A (pressure-sensitive adhesive composition) containing the acrylic polymer A. Next, 12 parts by mass of a polyisocyanate compound (crosslinking agent, trade name "Takenate D-101E", manufactured by Mitsui Chemicals, Inc.) and 4 parts by mass of a photopolymerization initiator (trade name "Omnirad 651", manufactured by IGM Resins) were added to the pressure-sensitive adhesive solution A, relative to 100 parts by mass of the acrylic polymer A, to prepare a pressure-sensitive adhesive solution A'. The pressure-sensitive adhesive solution A' prepared above was applied to the silicone-treated surface of a PET release liner and heated at 120°C for 2 minutes to crosslink the adhesive, thereby forming a pressure-sensitive adhesive layer with a thickness of 15 μm. Next, a 115 μm-thick ethylene-vinyl acetate copolymer (EVA) film was laminated to the pressure-sensitive adhesive layer surface. The sheet was then stored at 50°C for 24 hours, and the resulting sheet was used as the pressure-sensitive adhesive sheet of Example 1.

[0120] An adhesive sheet of Example 2 was produced in the same manner as in Example 1, except that Karenz MOI was used in an amount equivalent to 21 mol % when the total amount of hydroxyl group-free monomers was taken as 100 mol %, Omnirad 651 was used in 2 parts by mass, and Takenate D-101E was used in 6 parts by mass. The acrylic polymer contained in the adhesive solution obtained in Example 2 was referred to as acrylic polymer B.

[0121] An adhesive sheet of Example 3 was produced in the same manner as in Example 1, except that Karenz MOI was changed to an amount equivalent to 9 mol % when the total amount of hydroxyl group-free monomers was taken as 100 mol %, Omnirad 651 was changed to 1 part by mass, and Takenate D-101E was changed to 10 parts by mass in Example 1. The acrylic polymer contained in the adhesive solution obtained in Example 3 was referred to as acrylic polymer C.

[0122] Example 4 An adhesive sheet of Example 4 was produced in the same manner as in Example 1, except that in Example 1, 2EHA was changed to 90 mol% of the total amount of hydroxyl-free monomers, ACMO was changed to 10 mol% of the total amount of hydroxyl-free monomers, KarenzMOI was changed to an amount equivalent to 18 mol% when the total amount of hydroxyl-free monomers was taken as 100 mol%, and Omnirad 651 was changed to 6 parts by mass. The acrylic polymer contained in the adhesive solution obtained in Example 4 was designated as acrylic polymer D.

[0123] Examples 5 and 6 The pressure-sensitive adhesive sheets of Examples 5 and 6 were prepared in the same manner as in Example 1, except that in Example 1, 2EHA was used in an amount of 75 mol% of the total amount of monomers not containing a hydroxyl group, ACMO was used in an amount of 25 mol% of the total amount of monomers not containing a hydroxyl group, KarenzMOI was used in an amount equivalent to 11 mol% when the total amount of monomers not containing a hydroxyl group was taken as 100 mol%, Omnirad 651 was used in an amount of 3 parts by mass, and Takenate D-101E was used in an amount of 4 parts by mass. The acrylic polymer contained in the pressure-sensitive adhesive solution obtained in Examples 5 and 6 was referred to as acrylic polymer E.

[0124] Comparative Example 1 An adhesive sheet of Comparative Example 1 was produced in the same manner as in Example 1, except that in Example 1, 2EHA was changed to 90 mol% of the total amount of monomers not containing a hydroxyl group, ACMO was changed to 10 mol% of the total amount of monomers not containing a hydroxyl group, KarenzMOI was changed to an amount equivalent to 15 mol% when the total amount of monomers not containing a hydroxyl group was taken as 100 mol%, Omnirad 651 was changed to 5 parts by mass, and Takenate D-101E was changed to 2 parts by mass. The acrylic polymer contained in the adhesive solution obtained in Comparative Example 1 was designated as acrylic polymer F.

[0125] Comparative Example 2 A monomer composition (solids concentration: 40%) was prepared by mixing two types of monomers, 130.0 g of n-butyl acrylate (BA) and 2.6 g of acrylic acid (AA), 0.3 mass% of a polymerization initiator (manufactured by NOF Corporation, trade name: Nyper (registered trademark) BW) based on the total mass of the monomers, and a solvent (ethyl acetate). The monomer composition was placed in a 1 L round-bottom separable flask and placed in a polymerization experimental apparatus equipped with a separable cover, a separatory funnel, a thermometer, a nitrogen inlet tube, a Liebig condenser, a vacuum seal, a stirring rod, and a stirring blade. The atmosphere was replaced with nitrogen at room temperature for 2 hours while stirring. Thereafter, the mixture was polymerized by maintaining the temperature at 61°C for 8 hours while stirring under a nitrogen inflow, to obtain a pressure-sensitive adhesive solution G (pressure-sensitive adhesive composition) containing an acrylic polymer G. Next, 3 parts by mass of an epoxy-based crosslinking agent (trade name "Tetrad C", manufactured by Mitsubishi Gas Chemical Company, Inc.) was added to 100 parts by mass of acrylic polymer G to prepare adhesive solution G'. The adhesive solution G' prepared above was applied to the silicone-treated surface of a PET release liner and crosslinked by heating at 120°C for 2 minutes to form an adhesive layer with a thickness of 15 μm. Next, an EVA film with a thickness of 115 μm was laminated to the adhesive layer surface. After storage at 50°C for 24 hours, the resulting sheet was used as the adhesive sheet of Comparative Example 2. Comparative Example 3 A monomer composition (solids concentration: 40%) was prepared by mixing 60.0 g of 2-ethylhexyl acrylate (2EHA), 65.4 g of methyl acrylate (MA), 6.3 g of acrylic acid (AA), 0.3 wt% of a polymerization initiator (manufactured by NOF Corporation, trade name: Nyper (registered trademark) BW) based on the total mass of the monomers, and a solvent (ethyl acetate). The monomer composition was placed in a 1 L round-bottom separable flask and placed in a polymerization experimental apparatus equipped with a separable cover, a separatory funnel, a thermometer, a nitrogen inlet tube, a Liebig condenser, a vacuum seal, a stirring rod, and a stirring blade. The atmosphere was replaced with nitrogen at room temperature for 2 hours while stirring. Thereafter, the mixture was polymerized at 61°C for 8 hours while stirring under a nitrogen inflow, to obtain a pressure-sensitive adhesive solution H (pressure-sensitive adhesive composition) containing an acrylic polymer H.Next, to 100 parts by mass of acrylic polymer H, 100 parts by weight of dipentaerythritol hexaacrylate (polyfunctional low molecular weight, manufactured by Nippon Kayaku Co., Ltd.: DPHA), 3 parts by mass of a polyisocyanate compound (trade name "Takenate D-101E", manufactured by Mitsui Chemicals, Inc.), and 3 parts by mass of a photopolymerization initiator (trade name "Omnirad 651", manufactured by IGM Resins) were added to prepare adhesive solution H'. The adhesive solution H' prepared above was applied to the silicone-treated surface of a PET release liner and heated at 120 ° C. for 2 minutes to crosslink, forming a 30 μm thick adhesive layer. Next, a 115 μm thick EVA film was bonded to the adhesive layer surface. After that, the sheet was stored at 50 ° C. for 24 hours, and the resulting sheet was used as the adhesive sheet of Comparative Example 3.

[0126] Example 7 An adhesive sheet of Example 7 was produced in the same manner as in Example 1, except that in Example 1, 2EHA was changed to 100 mol% of the total amount of monomers not containing a hydroxyl group, ACMO was changed to 0 mol% of the total amount of monomers not containing a hydroxyl group, KarenzMOI was changed to an amount equivalent to 16 mol% when the total amount of monomers not containing a hydroxyl group was taken as 100 mol%, Omnirad 651 was changed to 3 parts by mass, and Takenate D-101E was changed to 4 parts by mass. The acrylic polymer contained in the adhesive solution obtained in Example 7 was referred to as acrylic polymer I.

[0127] <Polymer HSP Polarity Term> For each of the acrylic polymers A to I in Examples 1 to 7 and Comparative Examples 1 to 3, the value of the polar term in the HSP was calculated as follows. The Hansen solubility parameter (HSP) value of each polymer was obtained by creating a Smiles notation for the polymer unit obtained by polymerizing each of the monomers used, calculating the HSP dispersion term, polar term, and hydrogen bond term using the Windows (registered trademark) software "HSPiP ver. 5," and for copolymers, adding up the results multiplied by the molar fraction. When expressing a polymer unit obtained by polymerizing a monomer using Smiles notation, for example, a polymer unit obtained by polymerizing styrene is expressed as X on both sides of the main chain, such as XCC (C1=CC=CC=C1)X. The molar ratio of the copolymerization composition of a carrier containing a polymerized high-molecular-weight reactive polymer can also be determined as follows. First, the monomer composition of the carrier containing the polymerized high molecular weight reactive polymer is estimated using pyrolysis GC / MS. A polymer containing that monomer is then separately synthesized. If the same peak is detected in the same analysis, it is considered that the monomer is contained in the copolymer reactive polymer. In this case, pyrolysis GC / MS measurements are performed on approximately 100 μg of sample. The pyrolysis GC / MS equipment used is a Frontier Labs PY-2020iD heating device, an Agilent Technologies 7890A GC, and an Agilent Technologies 5975C MS. The pyrolysis temperature condition is 550 °C. The GC conditions were as follows: column: HP-5MS UI 30 m x 0.25 mm id x 0.25 μm film thickness; carrier gas: He 3.0 mL / min (constant flow mode); column temperature: 40 ° C (5 min) → +10 ° C / min → 300 ° C (9 min); inlet: split mode (50:1); inlet temperature: 250 ° C; detector: MS. The MS conditions were as follows: ionization method: EI; emission current: 35 μA; electron energy: 70 eV; E.M. voltage: 1718 V; source temperature: 230 ° C; Q-pole temperature: 150 ° C; interface temperature: 300 ° C. Next, once the monomers contained have been identified, their quantitative ratio (wt% or mol%) can be quantified using pyrolysis GC / MS, thereby determining the molar ratio of the copolymerization reactive polymer composition.The numerical value of the polarity term of the HSP of each polymer used in the adhesive, calculated using the Windows (registered trademark) software "HSPiP ver. 5.2", was taken as the polymer HSP polarity term.

[0128] <Formation of an epitaxial metal film on the surface of a single crystal substrate by sputtering> Sapphire (α-Al) purchased from Adamant Namiki Precision Jewel Co., Ltd. was used as a single crystal substrate. ２ O ３ The c-plane (0001) of the single crystal substrate was used. The single crystal substrate was placed in the chamber of an RF magnetron sputtering device (Shibaura Mechatronics CFS-4ES), and Cu metal was sputtered onto the entire surface of the single crystal substrate (Ar atmosphere, standard vacuum of 0.6 Pa). This resulted in the epitaxial deposition of a Cu film with a thickness of 1000 nm, yielding a Cu / sapphire substrate.

[0129] <Graphene CVD Deposition> The Cu / sapphire substrate described above was placed inside a quartz tube (inner diameter 26 mm) set in a ceramic tubular furnace manufactured by Asahi Rika Seisakusho, as a substrate for graphene deposition. The Cu / sapphire substrate had a substrate size of 10 mm x 20 mm. The temperature was then raised to a predetermined temperature (1000-1075°C) under atmospheric pressure while flowing argon and hydrogen. After reaching the predetermined temperature, the temperature was maintained under the same conditions for 0-3 hours to reduce and smooth the Cu surface. Then, 10-200 ppm of methane was added, and a chemical vapor reaction was carried out for 90 minutes. After the reaction, the substrate was cooled to room temperature (23°C), and the Cu / sapphire substrate (first laminate) on which single-layer graphene had been formed was removed from the quartz tube. This reaction resulted in the formation and synthesis of a continuous single-layer graphene film covering the entire Cu surface. Furthermore, 90% or more of the area of ​​the graphene formed is a single layer.

[0130] <MoS ２ CVD deposition of molybdenum disulfide (MoS), a type of transition metal chalcogenide, was placed inside a quartz tube (inner diameter 26 mm) set in a ceramic tube furnace at Asahi Rika Seisakusho. ２) A sapphire substrate (c-plane, manufactured by Kyocera Corporation) was placed as the film-forming substrate. Furthermore, a crucible containing molybdenum trioxide powder, the raw material, was placed in the upstream region of the gas flow relative to the film-forming substrate inside the quartz tube, and a crucible containing sulfur powder was placed further upstream. The sapphire substrates used were 10 mm x 20 mm in size, and 10 to 50 mg of molybdenum trioxide and 50 to 200 mg of sulfur were used. The distance between the sapphire substrate and each crucible was such that the sapphire substrate requiring the highest reaction temperature was placed at the center of the tubular furnace, the molybdenum trioxide crucible was placed 10 to 20 cm away from it, and the sulfur crucible was placed 15 to 25 cm away from the molybdenum trioxide crucible. Then, under atmospheric pressure, the sapphire substrate and each crucible were heated to a predetermined temperature (substrate: 850-950°C, molybdenum trioxide: 580-600°C, sulfur: 100-200°C) while argon was flowing, and a chemical vapor reaction was carried out for 1 hour. After the reaction, the substrate was cooled to room temperature (23°C), and then MoS ２ The sapphire substrate on which MoS was formed was removed from the quartz tube. ２ was formed on the surface of a sapphire substrate, and a laminate A (first laminate, MoS ２ / sapphire substrate) was obtained.

[0131] <Transfer of graphene using adhesive sheet> The following experiment was carried out using each of the adhesive sheets of Examples 1 to 5 and Comparative Examples 1 to 3. However, when the adhesive sheet of Comparative Example 2 was used, UV treatment using a UV irradiator was not carried out. The adhesive sheet was attached to the graphene side of the first laminate using a roller (pressure of 2 kg / 10 mm), autoclaved at 50°C and 5 atmospheres for 30 minutes, and left to stand at room temperature and normal pressure for 30 minutes to form a second laminate. A portion of the adhesive sheet in the outer periphery of the substrate of the second laminate was trimmed with a cutter knife to remove a 5 mm ２ A Cu / graphene surface exposed portion of about 450 mJ / cm was prepared from the substrate side of the adhesive sheet using a UV irradiator (UM-810 manufactured by Nitto Seiki Co., Ltd.). ２The UV treatment was performed with an irradiation dose of 1000 kJ / cm. The exposed Cu / graphene surface of the second laminate (substrate / graphene / adhesive sheet) was clamped with an electrode clip to form a working electrode, a Pt electrode as a counter electrode, and an Ag / AgCl electrode as a reference electrode. Each was immersed in an acrylic water tank filled with 1 M aqueous sodium hydroxide solution, and a DC voltage of 4 V was applied using a potentiostat (Vertex 10A manufactured by IVIUM). After voltage application, gas (bubbles) were generated by electrolysis at the interface between the Cu surface and the graphene, and the graphene / adhesive sheet laminate (third laminate) was separated from the Cu / sapphire substrate. The graphene / adhesive sheet laminate (third laminate) was immersed in ion-exchanged water for cleaning, and then attached to a silicon substrate with an oxide film (manufactured by SUMCO Corporation, silicon (crystal plane (100)), surface thermally oxidized, oxide film thickness 300 nm, hereinafter simply referred to as "silicon substrate") using a roller (pressure of 2 kg / 10 mm) with water, left to stand at room temperature for 24 hours, and then heat-treated at 90°C for 3 hours to obtain a fourth laminate. Note that the graphene was attached to the oxide film (SiO ２ ) side. The silicon substrate in the fourth laminate was fixed, and the adhesive sheet was peeled off at a peel angle of 180 degrees and a peel speed of 300 mm / min using a tensile tester (VPA-H200F, manufactured by Kyowa Interface Science Co., Ltd.), thereby transferring graphene to the silicon substrate, and a laminate of the silicon substrate and graphene in Example 1 (fifth laminate) was obtained. The fifth laminate is also referred to as a two-dimensional material laminate.

[0132] <MoS with adhesive sheet ２ The following experiment was carried out using the pressure-sensitive adhesive sheets of Examples 6 and 7. ２ The pressure-sensitive adhesive sheet of Example 6 or 7 was attached to the surface of the adhesive sheet with a roller (pressure of 2 kg / 10 mm), and the adhesive sheet was autoclaved at 50°C and 5 atmospheres for 30 minutes, and then left to stand at room temperature and normal pressure for 30 minutes. A UV irradiator (UM-810 manufactured by Nitto Seiki Co., Ltd.) was used to irradiate the adhesive sheet from the substrate side at 450 mJ / cm. ２ After that, the laminate B (second laminate, adhesive sheet / MoS ２The MoS film was then immersed in water and peeled at a peeling angle of 120° and a peeling speed of 30 mm / min in water at room temperature, and the MoS film was then attached to the adhesive sheet. ２ The laminate C (third laminate, adhesive sheet / MoS ２ ) was obtained. Then, the stack C was ２ The laminate was placed so that the side surface was in contact with a silicon substrate with an oxide film (SUMCO silicon (crystal plane (100)), surface thermal oxidation - oxide film thickness 300 nm), and attached with a roller (pressure of 2 kg / 10 mm) to form laminate D (fourth laminate, adhesive sheet / MoS ２ After leaving the laminate D at room temperature and normal pressure for 30 minutes, the pressure-sensitive adhesive sheet of Example 6 or 7 was peeled off at a peel angle of 180° and a peel speed of 300 mm / min, and the MoS ２ The silicon substrate and MoS ２ A laminate E (fifth laminate, two-dimensional material laminate) was obtained.

[0133] <Tensile modulus of adhesive layer after curing> The tensile modulus of the adhesive layer after curing was measured by applying an integrated light dose of 450 mJ / cm to the adhesive layer before bonding to the substrate, which was obtained during the production of each adhesive sheet. ２ A cylindrical sample was irradiated with ultraviolet light and rolled to a length of 30 mm and a diameter of 1 mm. The sample was chucked at the top and bottom 10 mm apart with a chuck distance of 10 mm, and pulled at a rate of 50 mm / min. The initial tensile modulus was calculated from the slope at the point where the slope of the stress versus strain was maximum between 10% strain and 100% strain, and was measured using a tensile tester (AUTOGRAPH AGS-X, manufactured by Shimadzu Corporation). This was used as the tensile modulus after curing of the adhesive layer. However, the adhesive sheet of Comparative Example 2 was not subjected to UV treatment. Note that each tensile modulus was a value measured at 23°C.

[0134] <Tensile modulus of substrate> The tensile modulus of the substrate was measured and calculated in the same manner as above for a 115 μm thick ethylene-vinyl acetate copolymer (EVA) film used in each of the Examples and Comparative Examples, using a 10 mm wide × 20 mm long sample with chucks at 5 mm above and below in the length direction, and was found to be 55 MPa.

[0135] <Peel strength of pressure-sensitive adhesive sheets> The pressure-sensitive adhesive sheets of Examples 1 to 7 and Comparative Examples 1 to 3 were each cut to a width of 20 mm and a length of 10 cm, and the release liners were peeled off. Subsequently, the pressure-sensitive adhesive sheet of each example was attached to a silicon wafer (4-inch silicon mirror wafer) by pressing it back and forth once with a 2 kg roller, and allowed to stand for 30 minutes. Using a tensile tester (VPA-H200F, manufactured by Kyowa Interface Science Co., Ltd.), the peel strength (180° peel strength from silicon wafer) (N / 20 mm) was measured when peeled at a peel angle of 180° and a peel speed of 300 mm / min. The measurement temperature was 23°C. Furthermore, in the same manner as above, 450 mJ / cm was applied to the pressure-sensitive adhesive layer from the substrate side of the pressure-sensitive adhesive sheet of each example attached to the silicon wafer. ２ After irradiating with ultraviolet light at an exposure dose of 1000 nm, the peel force (180° peel force from silicon wafer) (N / 20 mm) was measured using a tensile tester (VPA-H200F, manufactured by Kyowa Interface Science Co., Ltd.) when peeled at a peel angle of 180° and a peel speed of 300 mm / min. The measurement temperature was 23°C. However, since the pressure-sensitive adhesive sheet of Comparative Example 2 was not subjected to UV treatment, the above-mentioned peel force measurement was not performed, and this is indicated by "-" in Table 1.

[0136] <Transfer Rate> The pressure-sensitive adhesive sheets of Examples 1 to 7 and Comparative Examples 1 to 3 were used to transfer graphene or MoS ２ The silicon substrate and the graphene or MoS obtained by transferring ２ The laminate (fifth laminate) of the transferred material (oxide film (SiO ２ Graphene or MoS remaining on the surface of the ２ The image was obtained as a digital image using an optical microscope (VHX-8000, manufactured by Keyence Corporation). The digital image was an observation image at 500x magnification using an objective lens, and was a 10 mm long x 20 mm wide laminate of graphene or MoS. ２Images were acquired from nine locations on the side surface. Specifically, the center of the substrate was designated as point E, and two points 6.5 mm away from point E on the left and right were designated as points D and F, respectively. Furthermore, points 2.5 mm away from point D on the top and bottom were designated as points A and G, respectively. Similarly, points 2.5 mm away from point E on the top and bottom were designated as points B and H, respectively, and points 2.5 mm away from point F on the top and bottom were designated as points C and I, respectively. From the digital images acquired for each of points A to I, RGB separation and binarization analysis of each component image were performed using the software "imageJ" using a 500 μm × 300 μm range, and the amount of graphene or MoS present in the corresponding digital image was analyzed. ２ The area ratio of graphene or MoS in the digital images of nine points A to I was calculated as a percentage. ２ The average value of the area ratio was taken as the transfer rate (%).

[0137] <Low Contamination (Amount of Contamination)> The pressure-sensitive adhesive sheets of Examples 1 to 7 and Comparative Examples 1 to 3 were used to measure graphene or MoS ２ The silicon substrate and the graphene or MoS obtained by transferring ２ The carbon element amount (atomic %) calculated by ESCA analysis was compared with that of graphene or MoS on the Cu surface before transfer. ２The amount of contamination was determined as the increase in the carbon element amount (atomic %) of the laminate measured in the same manner. The carbon amount was determined as the elemental ratio (atomic %) of carbon to the total amount of the five elements by narrow scan analysis of the five elements carbon, oxygen, nitrogen, silicon, and copper using X-ray photoelectron spectroscopy (ESCA) on the surface of the target substrate. The analytical device used was a "Quantum 2000" manufactured by ULVAC PHI. The analytical device and measurement conditions used to measure the carbon amount are shown below. Equipment: Quantum 2000, manufactured by ULVAC PHI; X-ray source: Monochrome AlKα; X-ray setting: 200 μmφ [15 kV, 30 W]; Bond energy correction: Peak due to C-C bonds corrected to 285.0 eV; Charge neutralization conditions: Neutralization gun and Ar ion gun (neutralization mode) used in combination. A contamination level of -30% or more and 10% or less was evaluated as low-contamination. The contamination level can be negative because pre-transfer residue may be removed during the transfer process. If the contamination level of the two-dimensional material falls below -30%, the quality of the two-dimensional material before transfer deteriorates due to excessive pre-transfer residue. If the contamination level of the two-dimensional material exceeds 10%, the performance of the two-dimensional material after transfer deteriorates due to excessive post-transfer residue.

[0138] The pressure-sensitive adhesive sheets of Examples 1 to 7 and Comparative Examples 1 to 3 are summarized in Table 1 below, along with the respective measurement results. FIG. 7 shows a plot of the relationship between the peel force (N / 20 mm) from a silicon wafer before UV irradiation and the tensile modulus (MPa) of the pressure-sensitive adhesive layer after UV irradiation for the pressure-sensitive adhesive sheets of Examples 1 to 7 and Comparative Examples 1 to 3. However, since the pressure-sensitive adhesive sheet of Comparative Example 2 was not subjected to UV irradiation, the relationship between the peel force (N / 20 mm) from a silicon wafer without UV irradiation and the tensile modulus (MPa) of the pressure-sensitive adhesive layer without UV irradiation is plotted. FIG. 8 also shows a plot of the relationship between the peel force (N / 20 mm) from a silicon wafer before UV irradiation and the HSP polarity term of the polymer for the pressure-sensitive adhesive sheets of Examples 1 to 7 and Comparative Examples 1 to 3. In FIG. 8, the gray area indicates the peel force x (N / 20 mm) at 23° C. before UV irradiation on the silicon wafer when 180° peeling was performed at a pulling speed of 300 mm / min, and the HSP polar term y (MPa ０．５ ) satisfies at least one of the relationships of the following formula 1 and formula 2: y−0.52x−4.7≧0 (formula 1) y+0.50x−4.8≦0 (formula 2)

[0139]

[0140] The pressure-sensitive adhesive sheets of Examples 1 to 7 had a tensile modulus of elasticity of the pressure-sensitive adhesive layer after UV irradiation in the range of 9 to 1000 MPa. Furthermore, the peel strength from the silicon wafer before UV irradiation was in the range of 0.001 to 3.0 N / 20 mm. Additionally, the peel strength (N / 20 mm) from the silicon wafer before UV irradiation and the HSP polarity term of the polymer satisfied the relationship of at least one of the following formulas 1 and 2. The pressure-sensitive adhesive sheets of Examples 1 to 7 had excellent low-contamination properties and were able to transfer two-dimensional materials at a high transfer rate. y - 0.52x - 4.7 ≧ 0 (Formula 1) y + 0.50x - 4.8 ≦ 0 (Formula 2)

[0141] The pressure-sensitive adhesive sheet of Comparative Example 1 had a tensile modulus of elasticity of the pressure-sensitive adhesive layer after UV irradiation of less than 9 MPa. Furthermore, the peel strength from the silicon wafer before UV irradiation and the HSP polarity term of the polymer did not satisfy either the relationship of Equation 1 or Equation 2. The pressure-sensitive adhesive sheet of Comparative Example 1 had a poor graphene transfer rate.

[0142] The pressure-sensitive adhesive sheet of Comparative Example 2 used a pressure-sensitive adhesive layer that did not contain a polymer having a radically reactive carbon-carbon double bond in its side chain. Furthermore, the peel strength from the silicon wafer before UV irradiation and the HSP polarity term of the polymer did not satisfy the relationship expressed by either Equation 1 or Equation 2. Therefore, the pressure-sensitive adhesive sheet of Comparative Example 2 did not achieve good low-staining properties.

[0143] The pressure-sensitive adhesive sheet of Comparative Example 3 used a pressure-sensitive adhesive layer that contained a small molecule containing a radical-reactive carbon-carbon double bond but did not contain a polymer having a radical-reactive carbon-carbon double bond in its side chain. Furthermore, the peel strength from the silicon wafer before UV irradiation and the HSP polarity term of the polymer did not satisfy the relationship expressed by either Equation 1 or Equation 2. Therefore, the pressure-sensitive adhesive sheet of Comparative Example 3 did not achieve good low-staining properties.

[0144] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2023-223308) filed on December 28, 2023, the entirety of which is incorporated by reference.

[0145] 10: Adhesive sheet 11: Base material 12: Adhesive layer 21: First substrate 30: Two-dimensional material 40: Second substrate 101: Laminate (first laminate) 102: Laminate (second laminate) 103: Laminate (third laminate) 104: Laminate (fourth laminate) 105: Two-dimensional material laminate (fifth laminate)

Claims

1. An adhesive sheet comprising a base material and an adhesive layer, wherein the adhesive layer contains a polymer having a radical-reactive carbon-carbon double bond in the side chain, the tensile elastic modulus of the adhesive layer at 23 °C after curing under the following measurement conditions is 9 to 1000 MPa, and the peel force of the adhesive layer on the silicon wafer at 23 °C before curing when a 180° peel is performed at a tensile speed of 300 mm / min of the adhesive sheet is 0.001 to 3.0 N / 20 mm. (Measurement conditions for the tensile elastic modulus of the adhesive layer after curing) Ultraviolet rays with an integrated light amount of 450 mJ / cm ２ are irradiated, and a sample in the form of a cylinder rolled to a length of 30 mm and a diameter of 1 mm is used. The upper and lower 10 mm in the length direction are chucked and pulled at a speed of 50 mm / min. The initial tensile elastic modulus calculated from the slope at the point where the slope of the stress with respect to the strain is maximized between 10% strain and 100% strain is taken as the tensile elastic modulus of the adhesive layer after curing.

2. An adhesive sheet comprising a base material and an adhesive layer, wherein the adhesive layer contains a polymer having a radical-reactive carbon-carbon double bond in a side chain, and the peel strength x (N / 20 mm) of the adhesive layer before curing at 23°C with respect to a silicon wafer when a 180° peel is performed on the adhesive sheet at a tensile speed of 300 mm / min, and the HSP polar term y (MPa ０．５ of the polymer) satisfy at least one of the following relationships of Formula 1 and Formula 2. y - 0.52x - 4.7 ≥ 0 (Formula 1) y + 0.50x - 4.8 ≤ 0 (Formula 2) 3. The peel strength x (N / 20 mm) at 23°C before curing of the pressure-sensitive adhesive layer with respect to the silicon wafer when performing a 180° peel on the pressure-sensitive adhesive sheet at a tensile speed of 300 mm / min, and the HSP polar term y (MPa ０．５ ) of the polymer satisfy at least one of the following relationships of Formula 1 and Formula 2: The pressure-sensitive adhesive sheet according to claim 1. y - 0.52x - 4.7 ≥ 0 (Formula 1) y + 0.50x - 4.8 ≤ 0 (Formula 2) 4. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the tensile elastic modulus of the base material at 23°C under the following measurement conditions is 10 to 4000 MPa. (Measurement conditions for the tensile elastic modulus of the base material) Using a sample of the base material with a width of 10 mm and a length of 20 mm, chucking 5 mm above and below in the length direction and pulling at a speed of 50 mm / min, the initial tensile elastic modulus calculated from the slope at the point where the slope of the stress with respect to the strain is maximized between 10% strain and 100% strain is taken as the tensile elastic modulus of the base material.

5. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, which is for two-dimensional material transfer.

6. A bonded body in which the adhesive layer of the pressure-sensitive adhesive sheet according to any one of claims 1 to 3 is adhered to a two-dimensional material.

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