Electrically peelable adhesive sheet and conjugate

Abstract

To provide an electrically peelable adhesive sheet and a conjugate, capable of preventing a conductive layer from peeling off from a support base material under a high-temperature high-humidity environment.SOLUTION: An electrically peelable adhesive sheet includes: a conductive base material including a support base material and a conductive layer; and an electrically peelable adhesive layer with an adhesive force to be reduced by application of voltage, in this order. The support base material and the conductive layer are abutted. A surface roughness Sa of the support base material on a face at the conductive layer side is less than 6.2 μm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electrically peelable adhesive sheet and a bonded body.

Background Art

[0002] In the manufacturing process of electronic components and the like, there is an increasing demand for rework to improve the yield, recycling to disassemble and recover components after use, and the like. In order to meet such demands, a double-sided electrically peelable adhesive sheet having a certain adhesiveness and a certain peelability may be used when joining members in the electronic component manufacturing process and the like.

[0003] As a double-sided electrically peelable adhesive sheet that realizes the above adhesiveness and peelability, an electrically peelable adhesive sheet (electrically peelable adhesive sheet) that uses an ionic liquid composed of a cation and an anion as a component for forming an adhesive composition and peels by applying a voltage to the adhesive layer is known (Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] It is preferable that the electrically peelable adhesive sheet firmly joins the members when no voltage is applied and can be peeled with a small force when a voltage is applied.

[0006] However, in the prior art, in a bonded body where an electrically peelable adhesive sheet is attached to a conductive adherend, in a high temperature and high humidity environment, when attempting electrical peeling, the conductive layer peels off from the support substrate, and there is a risk that the electrically peelable adhesive sheet will not function, leading to contamination of the adherend, etc. The present invention has been completed in view of the above, and an object thereof is to provide an electrically peelable adhesive sheet and a bonded body that suppress peeling of the conductive layer from the support substrate in a high temperature and high humidity environment.

Means for Solving the Problems

[0007] As a result of repeated studies by the present inventors, in a conductive substrate in which a support substrate and a conductive layer are in contact, by setting the surface roughness Sa of the support substrate on the surface of the conductive layer side within a specific range, it was found that peeling of the conductive layer from the support substrate in a high temperature and high humidity environment can be suppressed.

[0008] The means for solving the above problems are as follows. [1] A conductive substrate including a support substrate and a conductive layer, and an electrically peelable adhesive layer whose adhesive force decreases upon application of a voltage, provided in this order, wherein the support substrate and the conductive layer are in contact, An electrically peelable adhesive sheet, wherein the surface roughness Sa of the support substrate on the surface on the conductive layer side is less than 6.2 μm. [2] The electrically peelable adhesive sheet according to [1], wherein the electrically peelable adhesive layer contains a polymer and an electrolyte. [3] The electrically peelable adhesive sheet according to [2], wherein the content of the electrolyte is 0.5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the polymer.

[0009] [4] The electrolyte is an ionic liquid, and the anion of the ionic liquid is at least one selected from the group consisting of bis(fluorosulfonyl)imide anion and bis(trifluoromethanesulfonyl)imide anion. The electrically peelable pressure-sensitive adhesive sheet according to [2]. [5] The electrolyte is an ionic liquid, and the cation of the ionic liquid is at least one selected from the group consisting of nitrogen-containing onium cations, sulfur-containing onium cations, and phosphorus-containing onium cations. The electrically peelable pressure-sensitive adhesive sheet according to [2]. [6] A coat layer is formed on the surface of the electrically peelable pressure-sensitive adhesive layer on the side of the conductive substrate. The electrically peelable pressure-sensitive adhesive sheet according to [1]. [7] The coat layer contains at least one resin selected from polyester resins, acrylic resins, epoxy resins, and urethane resins, or at least one inorganic substance selected from SiNx, SiOx, Al2O3, Ni, and NiCr. The electrically peelable pressure-sensitive adhesive sheet according to [6].

[0010] [8] Furthermore, it is provided with another pressure-sensitive adhesive layer, The other pressure-sensitive adhesive layer is formed on the surface of the support substrate on the side opposite to the conductive layer. The electrically peelable pressure-sensitive adhesive sheet according to [1]. [9] Furthermore, it is provided with another pressure-sensitive adhesive layer, a second conductive layer, and a second other pressure-sensitive adhesive layer, The other pressure-sensitive adhesive layer is formed on the surface of the support substrate on the side opposite to the conductive layer, On the surface of the electrically peelable pressure-sensitive adhesive layer on the side opposite to the conductive layer, the second conductive layer and the second other pressure-sensitive adhesive layer are formed in this order. The electrically peelable pressure-sensitive adhesive sheet according to [1].

[0011]

[10] An electrically peelable pressure-sensitive adhesive sheet according to any one of [1] to [8], and a conductive material are provided, A joined body in which the electrically peelable pressure-sensitive adhesive layer is adhered to the conductive material.

[11] comprises the electrically releasable pressure-sensitive adhesive sheet described in [9] and an adherend material; A joined body in which the other pressure-sensitive adhesive layer is adhered to the adherend material. [Advantages of the Invention]

[0012] The electrically releasable pressure-sensitive adhesive sheet of the present invention can suppress peeling of the conductive layer from the support substrate in a high-temperature and high-humidity environment. [Brief Description of the Drawings]

[0013]

Figure 1

Figure 2

Figure 3

[0014] Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that the present invention is not limited to the embodiments described below.

[0015] [Electrically Releasable Pressure-Sensitive Adhesive Sheet] (Configuration of Electrically Releasable Pressure-Sensitive Adhesive Sheet) The electrically releasable pressure-sensitive adhesive sheet according to an embodiment of the present invention includes a conductive substrate including a support substrate and a conductive layer, and an electrically releasable pressure-sensitive adhesive layer whose adhesive force decreases when a voltage is applied, in this order. The support substrate and the conductive layer are in contact with each other, and the surface roughness Sa of the support substrate on the surface on the conductive layer side is less than 6.2 μm.

[0016] In the conductive base material where the support base material and the conductive layer are in contact, the surface roughness Sa of the support base material on the surface side of the conductive layer is set within a specific range in the electric peelable adhesive sheet according to an embodiment of the present invention, so that there is an effect of suppressing the peeling of the conductive layer from the support base material in a high temperature and high humidity environment. As a reason for obtaining such an effect, the present inventors presume as follows.

[0017] In a conventional electric peelable adhesive sheet including a conductive base material including a support base material and a conductive layer, and an electric peelable adhesive layer whose adhesive force decreases when a voltage is applied, it is considered that the constituent components of the electric peelable adhesive layer pass through the conductive layer. As a result of the constituent components of the electric peelable adhesive layer moving between the support base material and the conductive layer, the adhesion between the two layers decreases, and it is considered that peeling of the conductive layer from the support base material occurs in a high temperature and high humidity environment. On the other hand, in the electric peelable adhesive sheet of the present embodiment, since the surface roughness Sa of the support base material on the surface side of the conductive layer is small, cracks (cracks, holes, grooves, etc.) in the conductive layer are less likely to occur, and it is considered that the constituent components of the electric peelable adhesive layer passing through the conductive layer are suppressed. And thereby, it is considered that peeling of the conductive layer from the support base material in a high temperature and high humidity environment is less likely to occur.

[0018] The electric peelable adhesive sheet of the present embodiment may have a plurality of conductive base materials each including a support base material and a conductive layer, and an electric peelable adhesive layer, and in addition to the conductive base material including the support base material and the conductive layer, and the electric peelable adhesive layer, it may have a coat layer, an adhesive layer, an intermediate layer, and an undercoat layer, etc. The electric peelable adhesive sheet of the present embodiment may be, for example, in a form wound in a roll shape or in a sheet shape. Note that the "electric peelable adhesive sheet" also includes the meaning of "adhesive tape". That is, the electric peelable adhesive sheet of the present embodiment may be an adhesive tape having a tape shape.

[0019] The electric peelable adhesive sheet of the present embodiment may be a single-sided electric peelable adhesive sheet having a conductive base material and provided with an electric peelable adhesive layer only on one side of the conductive base material. The electrically peelable pressure-sensitive adhesive sheet of the present embodiment may further include other pressure-sensitive adhesive layers that do not have electrical peelability, and may further include other pressure-sensitive adhesive layers on the surface of the electrically peelable pressure-sensitive adhesive sheet on the side of the support substrate. Further, the electrically peelable pressure-sensitive adhesive sheet of the present embodiment may be a double-sided electrically peelable pressure-sensitive adhesive sheet in which the conductive substrate has conductive layers on both sides of the support substrate, and the electrically peelable pressure-sensitive adhesive layers are provided on the respective conductive layers. Note that the electrically peelable pressure-sensitive adhesive sheet of the present embodiment may have a separator (release liner) for the purpose of protecting the surfaces of the electrically peelable pressure-sensitive adhesive layer and other pressure-sensitive adhesive layers, but the separator is not included in the electrically peelable pressure-sensitive adhesive sheet of the present embodiment.

[0020] The electrically peelable pressure-sensitive adhesive sheet according to the embodiment of the present invention further includes other pressure-sensitive adhesive layers, and it is also preferable that the other pressure-sensitive adhesive layer is formed on the surface of the support substrate opposite to the conductive layer.

[0021] Further, the electrically peelable pressure-sensitive adhesive sheet according to the embodiment of the present invention further includes other pressure-sensitive adhesive layers, a second conductive layer, and a second other pressure-sensitive adhesive layer, the other pressure-sensitive adhesive layer is formed on the surface of the support substrate opposite to the conductive layer, and it is preferable that the second conductive layer and the second other pressure-sensitive adhesive layer are formed in this order on the surface of the electrically peelable pressure-sensitive adhesive layer opposite to the conductive layer.

[0022] The structure of the electrically peelable pressure-sensitive adhesive sheet according to the embodiment of the present invention is not particularly limited, but preferably includes the electrically peelable pressure-sensitive adhesive sheet X1 shown in FIG. 1, the electrically peelable pressure-sensitive adhesive sheet X2 shown in FIG. 2, and the electrically peelable pressure-sensitive adhesive sheet X3 shown in FIG. 3.

[0023] The electrically peelable pressure-sensitive adhesive sheet X1 shown in FIG. 1 is an electrically peelable pressure-sensitive adhesive sheet having a layer structure of an electrically peelable pressure-sensitive adhesive layer 1 and a conductive substrate 5 (conductive layer 3 and support substrate 4).

[0024] The electrically peelable adhesive sheet X2 shown in FIG. 2 is an electrically peelable adhesive sheet having a layer structure of another adhesive layer 6, a conductive base material 5 (support base material 4 and conductive layer 3), and an electrically peelable adhesive layer 1.

[0025] The electrically peelable adhesive sheet X3 shown in FIG. 3 is an electrically peelable adhesive sheet having a layer structure including another adhesive layer 6, a conductive base material 5 (support base material 4, conductive layer 3), an electrically peelable adhesive layer 1, a conductive base material 5 (conductive layer 3, support base material 4), and another adhesive layer 6 in this order. That is, the electrically peelable adhesive layer 1 in the electrically peelable adhesive sheet X3 shown in FIG. 3 is a double-sided electrically peelable adhesive sheet having a conductive layer 3, a support base material 4, and another adhesive layer 6 in this order on both of its surfaces.

[0026] The conductive layer 3 is not particularly limited as long as it is a layer having conductivity, and may be, for example, a metal-based substrate such as a metal (e.g., aluminum, magnesium, copper, iron, tin, gold, etc.) foil or a metal plate (e.g., aluminum, magnesium, copper, iron, tin, silver, etc.), a conductive polymer, etc., or may be a metal vapor deposition film provided on the support base material 4.

[0027] The thickness of the conductive layer 3 is preferably 0.001 μm or more and 1000 μm or less. The upper limit of the thickness is more preferably 500 μm, still more preferably 300 μm, still more preferably 100 μm, still more preferably 50 μm, still more preferably 10 μm, still more preferably 5 μm, still more preferably 1 μm, still more preferably 0.5 μm, and the lower limit is more preferably 0.01 μm, still more preferably 0.02 μm, still more preferably 0.03 μm, still more preferably 0.04 μm, still more preferably 0.05 μm.

[0028] The support substrate 4 is included in the conductive substrate 5 together with the conductive layer 3. Further, the support substrate 4 is in contact with the conductive layer 3. The surface roughness Sa of the support substrate 4 on the surface side of the conductive layer 3 is less than 6.2 μm, preferably 4 μm or less, more preferably 2 μm or less, and even more preferably 1 μm or less. Also, the smaller the surface roughness Sa of the support substrate 4 on the surface side of the conductive layer 3, the better. Generally, it is 0 μm or more, and can be 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more. When the surface roughness Sa of the support substrate 4 on the surface side of the conductive layer 3 becomes 6.2 μm or more, there is a possibility that the conductive layer 3 may peel off from the support substrate 4 in a high-temperature and high-humidity environment. This is presumably due to the components of the electrically peelable adhesive layer 1 moving between the support substrate 4 and the conductive layer 3, resulting in a decrease in the adhesion between the two layers.

[0029] In this specification, the surface roughness Sa can be measured, for example, by a laser microscope in accordance with the method defined in ISO25178.

[0030] There is no particular limitation on the water contact angle of the surface of the support substrate 4 on the surface side of the conductive layer 3, but it is preferably greater than 60°, more preferably 62° or more, even more preferably 64° or more, and particularly preferably 66° or more. Also, the larger the water contact angle of the surface of the support substrate 4 on the surface side of the conductive layer 3, the better. Generally, it is 80° or less, and can be 78° or less, or 76° or less. When the water contact angle of the surface of the support substrate 4 on the surface side of the conductive layer 3 is greater than 60°, it is preferable because peeling of the conductive layer 3 from the support substrate 4 in a high-temperature and high-humidity environment is further prevented.

[0031] The water contact angle can be measured, for example, by a contact angle meter. The larger the water contact angle, the smaller the polarity and the more hydrophobic it becomes, and the smaller the water contact angle, the larger the polarity and the more hydrophilic it becomes.

[0032] The water contact angle of the surface of the support substrate 4 on the surface side of the conductive layer 3 can be increased, for example, by plasma treatment or corona treatment.

[0033] The supporting substrate 4 is not particularly limited as long as it satisfies the surface roughness Sa on the surface on the conductive layer 3 side, and examples thereof include paper-based substrates such as paper, fiber-based substrates such as cloth and nonwoven fabric, plastic-based substrates such as films and sheets made of various plastics (polyolefin-based resins such as polyethylene and polypropylene, polyester-based resins such as polyethylene terephthalate, acrylic resins such as polymethyl methacrylate, etc.), and laminates thereof. The substrate may have a single layer form or a multilayer form. The substrate may be subjected to various treatments such as back surface treatment, antistatic treatment, and undercoat treatment as necessary.

[0034] The thickness of the supporting substrate 4 is preferably 10 μm or more and 1000 μm or less. The upper limit of the thickness is more preferably 500 μm, further preferably 300 μm, further preferably 100 μm, further preferably 70 μm, further preferably 50 μm, further preferably 40 μm, and the lower limit is more preferably 12 μm, further preferably 25 μm.

[0035] The conductive substrate 5 is not particularly limited as long as it includes a supporting substrate 4 and a conductive layer 3. For example, the conductive substrate 5 may be one in which the above-mentioned conductive layer is formed on the surface of the supporting substrate exemplified above by a plating method, a chemical vapor deposition method, a sputtering method, or the like.

[0036] The thickness of the conductive substrate 5 is preferably 10 μm or more and 1000 μm or less. The upper limit of the thickness is more preferably 500 μm, further preferably 300 μm, further preferably 100 μm, further preferably 70 μm, further preferably 50 μm, further preferably 40 μm, and the lower limit is more preferably 12 μm, further preferably 25 μm.

[0037] The electrically peelable pressure-sensitive adhesive sheet according to an embodiment of the present invention may further comprise a coating layer 2, and it is preferable that the coating layer 2 is formed on the surface of the electrically peelable pressure-sensitive adhesive layer 1 that faces the conductive substrate 5.

[0038] The coating layer 2 is a layer mainly composed of a resin or an inorganic substance, and can be formed by a resin composition mainly composed of a resin component or a composition mainly composed of an inorganic substance. The coating layer 2 preferably contains at least one resin selected from polyester resins, acrylic resins, epoxy resins, and urethane resins, or at least one inorganic substance selected from SiNx, SiOx, Al2O3, Ni, and NiCr.

[0039] The electrically releasable pressure-sensitive adhesive sheet can be attached to a conductive material to form a bonded body. Examples of the conductive material include adherends such as metal-coated surfaces. Examples of the metal-coated surface include surfaces made of metals mainly composed of aluminum, copper, iron, magnesium, tin, gold, silver, lead, etc. Among them, a surface made of a metal containing aluminum is preferred. Examples of the adherend having a metal-coated surface include sheets, parts, and plates made of metals mainly composed of aluminum, copper, iron, magnesium, tin, gold, silver, lead, etc. The adherend other than the adherend having a metal-coated surface is not particularly limited, and examples thereof include fiber sheets such as paper, cloth, and non-woven fabric, and various plastic films and sheets.

[0040] The electrically releasable pressure-sensitive adhesive layer 1 according to the embodiment of the present invention is a pressure-sensitive adhesive layer having the property that the adhesive force decreases when a voltage is applied. The electrically releasable pressure-sensitive adhesive layer can contain a polymer and an electrolyte. The polymer has a function as a pressure-sensitive adhesive. The electrolyte contained in the electrically releasable pressure-sensitive adhesive layer is a substance that can be ionized into anions and cations. Examples of such electrolytes include ionic liquids, alkali metal salts, and alkaline earth metal salts. From the viewpoint of realizing good electrical releasability in the electrically releasable pressure-sensitive adhesive layer, the electrolyte contained in the electrically releasable pressure-sensitive adhesive layer is preferably an ionic liquid. An ionic liquid is a salt that is liquid at room temperature (about 25°C) and contains anions and cations. That is, the electrically releasable pressure-sensitive adhesive layer preferably contains a polymer and an ionic liquid.

[0041] In the pressure-sensitive adhesive composition according to the present embodiment, the content (blending amount) of the electrolyte is preferably 0.5 parts by mass or more with respect to 100 parts by mass of the polymer from the viewpoint of reducing the adhesive force during voltage application, and preferably 30 parts by mass or less from the viewpoint of increasing the initial adhesive force. From the same viewpoint, it is more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less, particularly preferably 10 parts by mass or less, and most preferably 5 parts by mass or less. Further, it is more preferably 0.6 parts by mass or more, still more preferably 0.8 parts by mass or more, particularly preferably 1.0 parts by mass or more, and most preferably 1.5 parts by mass or more.

[0042] The electrically releasable pressure-sensitive adhesive layer 1 can be formed of a pressure-sensitive adhesive composition containing a polymer and an ionic liquid. Hereinafter, the pressure-sensitive adhesive composition of the present embodiment will be described. In this specification, the adhesive force when no voltage is applied may be referred to as "initial adhesive force". In addition, the composition composed of components other than the ionic liquid among the components contained in the pressure-sensitive adhesive composition may be referred to as "ionic liquid-free pressure-sensitive adhesive composition". In addition, the pressure-sensitive adhesive layer formed of the ionic liquid-free pressure-sensitive adhesive composition may be referred to as "ionic liquid-free pressure-sensitive adhesive layer". In addition, the property that the adhesive force decreases due to voltage application is referred to as "electrical releasability", and the fact that the rate of decrease in adhesive force due to voltage application is large is referred to as "excellent electrical releasability".

[0043] <Components of the pressure-sensitive adhesive composition> (Polymer) The pressure-sensitive adhesive composition of the present embodiment contains a polymer. In the present embodiment, the polymer is not particularly limited as long as it is a general organic polymer compound, and is, for example, a polymer or a partial polymer of a monomer. The monomer may be one kind of monomer or a mixture of two or more kinds of monomers. The partial polymer means a polymer in which at least a part of the monomer or the monomer mixture is partially polymerized.

[0044] The polymer in this embodiment is usually used as an adhesive and is not particularly limited as long as it has adhesiveness. For example, it can be an acrylic polymer, a rubber polymer, a vinyl alkyl ether polymer, a silicone polymer, a polyester polymer, a polyamide polymer, a urethane polymer, a fluorine polymer, an epoxy polymer, etc. The polymers can be used alone or in combination of two or more. In order to increase the relative dielectric constant of the components other than the ionic liquid in the obtained electrically peelable adhesive layer and improve the electrical peelability, it is preferable that the polymer has a large relative dielectric constant. From this viewpoint, particularly in this embodiment, the polymer preferably contains at least one selected from the group consisting of a polyester polymer and an acrylic polymer having a carboxyl group and / or a hydroxyl group. Since the polyester polymer has a hydroxyl group that is likely to be polarized at the terminal, and since the acrylic polymer having a carboxyl group and / or a hydroxyl group has a carboxyl group and / or a hydroxyl group that is likely to be polarized, by using these polymers, a polymer having a relatively large relative dielectric constant can be obtained. The total content of the polyester polymer and the acrylic polymer having a carboxyl group and / or a hydroxyl group in the polymer of this embodiment is preferably 60% by mass or more, and more preferably 80% by mass or more. Further, particularly in order to increase the cost, productivity, and initial adhesive strength, the polymer in this embodiment is preferably an acrylic polymer. That is, the adhesive composition of this embodiment is preferably an acrylic adhesive composition containing an acrylic polymer as the polymer.

[0045] The acrylic polymer preferably contains monomer units derived from an alkyl (meth)acrylate having an alkyl group with 1 to 14 carbon atoms (the following formula (1)). Such monomer units are suitable for obtaining a large initial adhesive force. In addition, in order to increase the relative permittivity of the components other than the ionic liquid in the electrically peelable adhesive layer and improve the electrical peelability, the alkyl group R in the following formula (1) b preferably has a small number of carbon atoms, particularly preferably 8 or less, and more preferably 4 or less. CH2=C(R a )COOR b (1) [In formula (1), R a is a hydrogen atom or a methyl group, and R b is an alkyl group with 1 to 14 carbon atoms which may have a substituent]

[0046] Examples of the alkyl (meth)acrylate having an alkyl group with 1 to 14 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, 1,3-dimethylbutyl acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, and 2-methoxyethyl acrylate. Among them, n-butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, and 2-methoxyethyl acrylate are preferred. The alkyl (meth)acrylate having an alkyl group with 1 to 14 carbon atoms can be used alone or in combination of two or more.

[0047] The ratio of the alkyl (meth)acrylate having an alkyl group with 1 to 14 carbon atoms to all the monomer components (100% by mass) constituting the acrylic polymer is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 85% by mass or more. When the ratio of the alkyl (meth)acrylate having an alkyl group with 1 to 14 carbon atoms is 70% by mass or more, it is easy to obtain a large initial adhesive force.

[0048] As the acrylic polymer, for the purpose of modifying cohesion, heat resistance, crosslinkability, etc., in addition to the monomer unit derived from the alkyl (meth)acrylate having an alkyl group with 1 to 14 carbon atoms, it is preferable to contain the monomer unit derived from the polar group-containing monomer copolymerizable therewith. The monomer unit can impart a crosslinking point and is suitable for obtaining a large initial adhesive force. Also, from the viewpoint of increasing the relative dielectric constant of the components other than the ionic liquid in the electrically peelable adhesive layer and improving the electrical peelability, it is preferable to contain the monomer unit derived from the polar group-containing monomer.

[0049] Examples of the polar group-containing monomer include carboxyl group-containing monomers, hydroxyl group-containing monomers, cyano group-containing monomers, vinyl group-containing monomers, aromatic vinyl monomers, amide group-containing monomers, imide group-containing monomers, amino group-containing monomers, epoxy group-containing monomers, vinyl ether monomers, N-acryloylmorpholine, sulfo group-containing monomers, phosphate group-containing monomers, and acid anhydride group-containing monomers. Among them, carboxyl group-containing monomers, hydroxyl group-containing monomers, and amide group-containing monomers are preferable from the viewpoint of excellent cohesiveness, and particularly, carboxyl group-containing monomers are preferable. The carboxyl group-containing monomer is particularly suitable for obtaining a large initial adhesive force. The polar group-containing monomers can be used alone or in combination of two or more.

[0050] Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. In particular, acrylic acid is preferable. The carboxyl group-containing monomer can be used alone or in combination of two or more kinds.

[0051] Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl (meth)acrylate, N-methylol (meth)acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. In particular, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferable. The hydroxyl group-containing monomer can be used alone or in combination of two or more kinds.

[0052] Examples of the amide group-containing monomer include acrylamide, methacrylamide, N-vinylpyrrolidone, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N'-methylenebisacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, and diacetoneacrylamide. The amide group-containing monomer can be used alone or in combination of two or more kinds.

[0053] Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

[0054] Examples of the vinyl group-containing monomer include vinyl esters such as vinyl acetate, vinyl propionate, and vinyl laurate, and vinyl acetate is particularly preferred.

[0055] Examples of the aromatic vinyl monomer include styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes.

[0056] Examples of the imide group-containing monomer include cyclohexyl maleimide, isopropyl maleimide, N-cyclohexyl maleimide, and itaconic imide.

[0057] Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

[0058] Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

[0059] Examples of the vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether.

[0060] The proportion of the polar group-containing monomer with respect to all the monomer components (100% by mass) constituting the acrylic polymer is preferably 0.1% by mass or more and 35% by mass or less. The upper limit of the proportion of the polar group-containing monomer is more preferably 25% by mass, still more preferably 20% by mass, the lower limit is more preferably 0.5% by mass, still more preferably 1% by mass, and particularly preferably 2% by mass. When the proportion of the polar group-containing monomer is 0.1% by mass or more, cohesive force is easily obtained, so that glue residue hardly occurs on the surface of the adherend after peeling the electrically peelable pressure-sensitive adhesive layer, and the electrical peelability is improved. Further, when the proportion of the polar group-containing monomer is 35% by mass or less, it becomes easy to prevent the electrically peelable pressure-sensitive adhesive layer from adhering excessively to the adherend and causing re-peeling. In particular, when it is 2% by mass or more and 20% by mass or less, it becomes easy to achieve both peelability with respect to the adherend and adhesion between the electrically peelable pressure-sensitive adhesive layer and other layers.

[0061] Further, as the monomer component constituting the acrylic polymer, a polyfunctional monomer may be included in order to introduce a crosslinked structure into the acrylic polymer and easily obtain the necessary cohesive force.

[0062] Examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, divinylbenzene, and N,N'-methylenebisacrylamide. The polyfunctional monomer can be used alone or in combination of two or more.

[0063] The content of the polyfunctional monomer with respect to all the monomer components (100% by mass) constituting the acrylic polymer is preferably 0.1% by mass or more and 15% by mass or less. The upper limit of the content of the polyfunctional monomer is more preferably 10% by mass, and the lower limit is more preferably 3% by mass. When the content of the polyfunctional monomer is 0.1% by mass or more, the flexibility and adhesiveness of the electrically releasable pressure-sensitive adhesive layer are likely to be improved, which is preferable. When the content of the polyfunctional monomer is 15% by mass or less, the cohesive force does not become too high, and appropriate adhesiveness is easily obtained.

[0064] The polyester-based polymer is typically a polymer having a structure in which a polyvalent carboxylic acid such as dicarboxylic acid and its derivatives (hereinafter also referred to as "polyvalent carboxylic acid monomer") and a polyhydric alcohol such as diol and its derivatives (hereinafter referred to as "polyhydric alcohol monomer") are condensed.

[0065] The polyvalent carboxylic acid monomer is not particularly limited, and for example, adipic acid, azelaic acid, dimer acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, dodecenyl succinic anhydride, fumaric acid, succinic acid, dodecanedioic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, etc., maleic acid, maleic anhydride, itaconic acid, citraconic acid, and derivatives thereof can be used. The polyvalent carboxylic acid monomer can be used alone or in combination of two or more.

[0066] The polyhydric alcohol monomer is not particularly limited, and examples thereof include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,5-pentanediol, 2-ethyl-2-butylpropanediol, 1,9-nonanediol, 2-methyloctanediol, 1,10-decanediol, and derivatives thereof. The polyhydric alcohol monomer can be used alone or in combination of two or more.

[0067] In addition, the polymer of the present embodiment may contain an ionic polymer. The ionic polymer is a polymer having an ionic functional group. By including an ionic polymer in the polymer, the relative permittivity of the polymer increases and the electrical peelability is improved. When the polymer contains an ionic polymer, the content of the ionic polymer is preferably 0.05 parts by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the polymer.

[0068] In the present embodiment, the polymer can be obtained by (co)polymerizing monomer components. The polymerization method is not particularly limited, and examples thereof include solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, photopolymerization (active energy ray polymerization) method, and the like. In particular, from the viewpoints of cost and productivity, the solution polymerization method is preferred. When the polymer is copolymerized, it may be any of a random copolymer, a block copolymer, an alternating copolymer, a graft copolymer, and the like.

[0069] The solution polymerization method is not particularly limited, and examples thereof include a method of dissolving monomer components, a polymerization initiator, etc. in a solvent, heating and polymerizing to obtain a polymer solution containing the polymer.

[0070] As the solvent used in the solution polymerization method, various common solvents can be used. Examples of such solvents (polymerization solvents) include aromatic hydrocarbons such as toluene, benzene, and xylene; esters such as ethyl acetate and n-butyl acetate; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone. The solvents can be used alone or in combination of two or more.

[0071] The amount of the solvent used is not particularly limited, but it is preferably 10 parts by mass or more and 1000 parts by mass or less with respect to all the monomer components (100 parts by mass) constituting the polymer. The upper limit of the amount of the solvent used is more preferably 500 parts by mass, and the lower limit is more preferably 50 parts by mass.

[0072] The polymerization initiator used in the solution polymerization method is not particularly limited, and examples thereof include peroxide-based polymerization initiators and azo-based polymerization initiators. Examples of the peroxide-based polymerization initiators include, but are not particularly limited to, peroxicarbonates, ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, and peroxy esters. More specifically, examples include benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-bis(t-butylperoxy)cyclododecane. Examples of the azo-based polymerization initiators include, but are not particularly limited to, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylpropionic acid) dimethyl, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4,4-trimethylpentane), 4,4'-azobis-4-cyanovaleric acid, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine) hydrochloride, and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate. The polymerization initiator can be used alone or in combination of two or more.

[0073] The amount of the polymerization initiator used is not particularly limited, but is preferably 0.01 part by mass or more and 5 parts by mass or less with respect to all the monomer components (100 parts by mass) constituting the polymer. The upper limit of the amount of the polymerization initiator used is more preferably 3 parts by mass, and the lower limit is more preferably 0.05 part by mass.

[0074] In the solution polymerization method, the heating temperature during heating and polymerization is not particularly limited, but is, for example, 50°C or higher and 80°C or lower. The heating time is not particularly limited, but is, for example, 1 hour or longer and 24 hours or shorter.

[0075] The weight average molecular weight of the polymer is not particularly limited, but is preferably 100,000 or more and 5,000,000 or less. The upper limit of the weight average molecular weight is more preferably 4,000,000, still more preferably 3,000,000, the lower limit is more preferably 200,000, and still more preferably 300,000. When the weight average molecular weight is 100,000 or more, the cohesive force becomes small, and the problem of glue residue on the surface of the adherend after peeling the electro-strippable adhesive layer can be effectively suppressed. Further, when the weight average molecular weight is 5,000,000 or less, the problem of insufficient wettability of the surface of the adherend after peeling the electro-strippable adhesive layer can be effectively suppressed.

[0076] The weight average molecular weight is obtained by measurement by the gel permeation chromatography (GPC) method. More specifically, for example, as a GPC measuring device, using the trade name "HLC-8220GPC" (manufactured by Tosoh Corporation), it can be measured under the following conditions and calculated by the standard polystyrene conversion value. (Weight average molecular weight measurement conditions) · Sample concentration: 0.2 mass% (tetrahydrofuran solution) · Sample injection volume: 10 μL · Sample column: TSKguardcolumn SuperHZ-H (1 piece) + TSKgel SuperHZM-H (2 pieces) · Reference column: TSKgel SuperH-RC (1 piece) · Eluent: Tetrahydrofuran (THF) · Flow rate: 0.6 mL / min · Detector: Differential refractometer (RI) · Column temperature (measurement temperature): 40°C

[0077] The glass transition temperature (Tg) of the polymer is not particularly limited, but it is preferably 0 °C or lower, more preferably -10 °C or lower, and even more preferably -20 °C or lower, because the decrease in the initial adhesion can be suppressed. Further, it is particularly preferably -40 °C or lower, and most preferably -50 °C or lower, because the rate of decrease in adhesion due to voltage application becomes particularly large at -40 °C or lower.

[0078] The glass transition temperature (Tg) can be calculated, for example, based on the following formula (Y) (Fox formula). 1 / Tg = W1 / Tg1 + W2 / Tg2 + ··· + Wn / Tgn (Y) [In formula (Y), Tg is the glass transition temperature of the polymer (unit: K), Tgi (i = 1, 2, ··· n) is the glass transition temperature (unit: K) when monomer i forms a homopolymer, and Wi (i = 1, 2, ··· n) represents the mass fraction of monomer i in all monomer components.] The above formula (Y) is a calculation formula when the polymer is composed of n types of monomer components of monomer 1, monomer 2, ···, monomer n.

[0079] Note that the glass transition temperature when forming a homopolymer means the glass transition temperature of the homopolymer of the monomer, that is, the glass transition temperature (Tg) of a polymer formed with only a certain monomer (which may be referred to as "monomer X") as the monomer component. Specifically, numerical values are listed in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc, 1989). The glass transition temperature (Tg) of a homopolymer not described in the literature refers to a value obtained by, for example, the following measurement method. That is, 100 parts by mass of monomer X, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 200 parts by mass of ethyl acetate as a polymerization solvent are charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and stirred for 1 hour while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 °C and reacted for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by mass. Next, this homopolymer solution is cast and coated on a release liner and dried to produce a test sample (sheet-like homopolymer) with a thickness of about 2 mm. Then, about 1 to 2 mg of this test sample is weighed into an aluminum open cell, and the behavior of the Reversing Heat Flow (specific heat component) of the homopolymer is obtained at a heating rate of 5 °C / min under a nitrogen atmosphere of 50 ml / min using temperature-modulated DSC (trade name "Q-2000", manufactured by TA Instruments). Referring to JIS-K-7121, the temperature at the point where a straight line equidistant from the vertical axis direction from the straight line extending the baseline on the low-temperature side and the baseline on the high-temperature side of the obtained Reversing Heat Flow intersects with the curve of the step-like change part of the glass transition is defined as the glass transition temperature (Tg) of the homopolymer.

[0080] In the pressure-sensitive adhesive composition of this embodiment, the content of the polymer is preferably 50% by mass or more and 99.9% by mass or less, more preferably 99.5% by mass, still more preferably 99% by mass, and the upper limit is preferably 60% by mass, still more preferably 70% by mass, based on the total amount (100% by mass) of the pressure-sensitive adhesive composition.

[0081] (Ionic liquid) The ionic liquid in this embodiment is composed of a pair of anions and cations, and is not particularly limited as long as it is a molten salt (room temperature molten salt) that is liquid at 25°C. Examples of anions and cations are given below. Among the ionic substances obtained by combining these, those that are liquid at 25°C are ionic liquids, and those that are solid at 25°C are not ionic liquids but are ionic solids as described later.

[0082] Examples of the anion of the ionic liquid include (FSO2)2N - , (CF3SO2)2N - , (CF3CF2SO2)2N - , (CF3SO2)3C - , Br - , AlCl4 - , Al2Cl7 - , NO3 - , BF4 - , PF6 - , CH3COO - , CF3COO - , CF3CF2CF2COO - , CF3SO3 - , CF3(CF2)3SO3 - , AsF6 - , SbF6 - , and F(HF) n - and so on. Among them, as the anion, (FSO2)2N - [bis(fluorosulfonyl)imide anion], and anions of sulfonylimide-based compounds such as (CF3SO2)2N - [bis(trifluoromethanesulfonyl)imide anion] are preferred because they are chemically stable and suitable for improving the electrical stripping property. That is, the anion of the ionic liquid is preferably at least one selected from the group consisting of bis(fluorosulfonyl)imide anion and bis(trifluoromethanesulfonyl)imide anion.

[0083] The cation in the ionic liquid is preferably at least one selected from the group consisting of nitrogen-containing onium cations, sulfur-containing onium cations, and phosphorus-containing onium cations, because it is chemically stable and suitable for improving electric dissociability. Imidazolium-based, ammonium-based, pyrrolidinium-based, and pyridinium-based cations are more preferred.

[0084] Examples of imidazolium-based cations include 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-heptyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-nonyl-3-methylimidazolium cation, 1-undecyl-3-methylimidazolium cation, 1-dodecyl-3-methylimidazolium cation, 1-tridecyl-3-methylimidazolium cation, 1-tetradecyl-3-methylimidazolium cation, 1-pentadecyl-3-methylimidazolium cation, 1-hexadecyl-3-methylimidazolium cation, 1-heptadecyl-3-methylimidazolium cation, 1-octadecyl-3-methylimidazolium cation, 1-undecyl-3-methylimidazolium cation, 1-benzyl-3-methylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, 1,3-bis(dodecyl)imidazolium cation, and the like.

[0085] Examples of pyridinium-based cations include 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, 1-octyl-4-methylpyridinium cation, and the like.

[0086] Examples of the pyrrolidinium cation include 1-ethyl-1-methylpyrrolidinium cation and 1-butyl-1-methylpyrrolidinium cation.

[0087] Examples of the ammonium cation include tetraethylammonium cation, tetrabutylammonium cation, methyltrioctylammonium cation, tetradecyltrihexylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethyl acrylate cation.

[0088] From the viewpoint of increasing the reduction rate of the adhesive force upon voltage application, it is preferable to select a cation having a molecular weight of 160 or less as the cation constituting the ionic liquid. The above (FSO2)2N - [bis(fluorosulfonyl)imide anion] or (CF3SO2)2N - [bis(trifluoromethanesulfonyl)imide anion] and an ionic liquid containing a cation having a molecular weight of 160 or less are particularly preferable. Examples of the cation having a molecular weight of 160 or less include 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, 1-ethyl-1-methylpyrrolidinium cation, 1-butyl-1-methylpyrrolidinium cation, tetraethylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethyl acrylate cation.

[0089] In addition, as the cation of the ionic liquid, cations represented by the following formulas (2-A) to (2-D) are also preferable.

[0090]

Chemical formula

[0091] R in formula (2-A) 1 represents a hydrocarbon group having 4 to 10 carbon atoms (preferably a hydrocarbon group having 4 to 8 carbon atoms, more preferably a hydrocarbon group having 4 to 6 carbon atoms), and may contain a heteroatom. R 2 and R 3 are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms (preferably a hydrocarbon group having 1 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms, still more preferably a hydrocarbon group having 2 to 4 carbon atoms), and may contain a heteroatom. However, when a nitrogen atom forms a double bond with an adjacent carbon atom, R 3 does not exist.

[0092] R in formula (2-B) 4 represents a hydrocarbon group having 2 to 10 carbon atoms (preferably a hydrocarbon group having 2 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms), and may contain a heteroatom. R 5 , R 6 , and R 7 are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms (preferably a hydrocarbon group having 1 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms, still more preferably a hydrocarbon group having 2 to 4 carbon atoms), and may contain a heteroatom.

[0093] R in formula (2-C) 8 represents a hydrocarbon group having 2 to 10 carbon atoms (preferably a hydrocarbon group having 2 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms), and may contain a heteroatom. R 9 , R 10 , and R 11 are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 16 carbon atoms (preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 8 carbon atoms), and may contain a heteroatom.

[0094] X in formula (2-D) represents a nitrogen, sulfur, or phosphorus atom, and R 12 , R 13 , R 14 , and R15 is the same or different and represents a hydrocarbon group having 1 to 16 carbon atoms (preferably a hydrocarbon group having 1 to 14 carbon atoms, more preferably a hydrocarbon group having 1 to 10 carbon atoms, still more preferably a hydrocarbon group having 1 to 8 carbon atoms, particularly preferably a hydrocarbon group having 1 to 6 carbon atoms), and may contain a heteroatom. However, when X is a sulfur atom, R 12 does not exist.

[0095] The molecular weight of the cation in the ionic liquid is, for example, 500 or less, preferably 400 or less, more preferably 300 or less, still more preferably 250 or less, particularly preferably 200 or less, and most preferably 160 or less. Usually, it is 50 or more. The cation in the ionic liquid is considered to have the property of moving to the cathode side when a voltage is applied in the electrostripping pressure-sensitive adhesive layer and being biased near the interface between the electrostripping pressure-sensitive adhesive layer and the adherend. In the present invention, for this reason, the adhesive force during voltage application decreases with respect to the initial adhesive force, and electrostripping property occurs. A cation having a small molecular weight such as 500 or less is suitable for increasing the rate of decrease in the adhesive force during voltage application because the movement of the cation to the cathode side in the electrostripping pressure-sensitive adhesive layer becomes easier.

[0096] Examples of commercially available ionic liquids include "Electrel AS-110", "Electrel MP-442", "Electrel IL-210", "Electrel MP-471", "Electrel MP-456", "Electrel AS-804" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., "HMI-FSI" manufactured by Mitsubishi Materials Corporation, "CIL-312", and "CIL-313" manufactured by Nippon Carlit Co., Ltd.

[0097] The ionic conductivity is preferably 0.1 mS / cm or more and 10 mS / cm or less. The upper limit of the ionic conductivity is more preferably 5 mS / cm, still more preferably 3 mS / cm. The lower limit is more preferably 0.3 mS / cm, still more preferably 0.5 mS / cm. By having the ionic conductivity within this range, the adhesive strength decreases sufficiently even at a low voltage. The ionic conductivity can be measured, for example, by the AC impedance method using a 1260 Frequency Response Analyzer manufactured by Solartron.

[0098] The content (blending amount) of the ionic liquid in the adhesive composition of the present embodiment is preferably 0.5 parts by mass or more with respect to 100 parts by mass of the polymer from the viewpoint of reducing the adhesive strength during voltage application, and preferably 30 parts by mass or less from the viewpoint of increasing the initial adhesive strength. From the same viewpoint, it is more preferably 20 parts by mass or less, still more preferably 15 parts by mass or less, particularly preferably 10 parts by mass or less, and most preferably 5 parts by mass or less. Also, it is more preferably 0.6 parts by mass or more, still more preferably 0.8 parts by mass or more, particularly preferably 1.0 parts by mass or more, and most preferably 1.5 parts by mass or more.

[0099] (Other components) The adhesive composition of the present embodiment may contain one or more components other than the polymer and the ionic liquid (hereinafter sometimes referred to as "other components") as long as the effects of the present invention are not impaired. Hereinafter, the other components that can be contained in the adhesive composition of the present embodiment will be described.

[0100] The adhesive composition of the present embodiment may contain an ionic additive. As the ionic additive, for example, an ionic solid can be used.

[0101] An ionic solid is an ionic substance that is solid at 25°C. The ionic solid is not particularly limited, and for example, among the ionic substances obtained by combining the anions and cations exemplified in the column of the description of the aforementioned ionic liquid, those that are solid can be used. When the adhesive composition contains an ionic solid, the content of the ionic solid is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the polymer.

[0102] The adhesive composition of this embodiment may contain a crosslinking agent as necessary for the purpose of improving creep properties and shear properties by crosslinking the polymer. Examples of the crosslinking agent include isocyanate-based crosslinking agents, carbodiimide-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and amine-based crosslinking agents. Examples of the isocyanate-based crosslinking agent include toluene diisocyanate and methylene bisphenyl isocyanate. Examples of the epoxy-based crosslinking agent include N,N,N´,N´-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and 1,6-hexanediol diglycidyl ether. When containing a crosslinking agent, the content is preferably 0.1 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the polymer. The crosslinking agent can be used alone or in combination of two or more.

[0103] The adhesive composition of this embodiment may contain polyethylene glycol as necessary for the purpose of assisting the movement of the ionic liquid when a voltage is applied. As the polyethylene glycol, those having a number average molecular weight of 200 to 6000 can be used. When containing polyethylene glycol, the content is preferably 0.1 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the polymer.

[0104] The pressure-sensitive adhesive composition of this embodiment may contain a conductive filler as necessary for the purpose of imparting conductivity to the pressure-sensitive adhesive composition. The conductive filler is not particularly limited, and general known or commonly used conductive fillers can be used. For example, graphite, carbon black, carbon fiber, metal powders such as silver and copper, etc. can be used. When containing a conductive filler, the content is preferably 0.1 part by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the polymer.

[0105] The pressure-sensitive adhesive composition of this embodiment may also contain various additives such as fillers, plasticizers, anti-aging agents, antioxidants, pigments (dyes), flame retardants, solvents, surfactants (leveling agents), rust preventives, adhesion-imparting resins, corrosion inhibitors, and antistatic agents. The total content of these components is not particularly limited as long as the effects of the present invention are achieved, but it is preferably 0.01 part by mass or more and 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less with respect to 100 parts by mass of the polymer.

[0106] Examples of the filler include silica, iron oxide, zinc oxide, aluminum oxide, titanium oxide, barium oxide, magnesium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, wax stone clay, kaolin clay, and fired clay. As the plasticizer, known and commonly used plasticizers used in general resin compositions and the like can be used. For example, oils such as paraffin oil and process oil, liquid rubbers such as liquid polyisoprene, liquid polybutadiene, and liquid ethylene-propylene rubber, tetrahydrophthalic acid, azelaic acid, benzoic acid, phthalic acid, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, citric acid, and their derivatives, dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diisononyl adipate (DINA), and isodecyl succinate can be used. Examples of the anti-aging agent include compounds such as hindered phenol-based, aliphatic and aromatic hindered amine-based compounds. Examples of the antioxidant include butylhydroxytoluene (BHT), butylhydroxyanisole (BHA), and the like. Examples of the pigment include inorganic pigments such as titanium dioxide, zinc oxide, ultramarine, red iron oxide, lithopone, lead, cadmium, iron, cobalt, aluminum, hydrochloride, sulfate, etc., azo pigments, and organic pigments such as copper phthalocyanine pigments. Examples of the rust inhibitor include zinc phosphate, tannic acid derivatives, phosphate esters, basic sulfonates, and various rust-inhibiting pigments. Examples of the adhesion promoter include titanium coupling agents, zirconium coupling agents, and the like. Examples of the antistatic agent generally include quaternary ammonium salts or hydrophilic compounds such as polyglycolic acid and ethylene oxide derivatives. Examples of the tackifying resin include rosin-based tackifying resins, terpene-based tackifying resins, phenol-based tackifying resins, hydrocarbon-based tackifying resins, ketone-based tackifying resins, polyamide-based tackifying resins, epoxy-based tackifying resins, and elastomer-based tackifying resins. The tackifying resin can be used alone or in combination of two or more. Examples of the corrosion inhibitor include carbodiimide compounds, adsorption-type inhibitors, and chelate-forming metal deactivators. For example, those described in JP-A-2019-059908 can be used.

[0107] <Initial adhesive strength, rate of decrease in adhesive strength due to voltage application> The adhesive strength of the electrically peelable adhesive layer of this embodiment can be evaluated by various methods. For example, it can be evaluated by the 180° peel test described in the column of the examples.

[0108] The electrically releasable pressure-sensitive adhesive layer of this embodiment preferably has an initial adhesive strength of 2.0 N / cm or more, more preferably 2.5 N / cm or more, and most preferably 3.0 N / cm or more, as measured by forming an electrically releasable pressure-sensitive adhesive sheet as described in the Examples section and performing a 180° peel test. When the initial adhesive strength is 2.0 N / cm or more, the adhesion to the adherend is sufficient, and the adherend is less likely to peel off or shift.

[0109] The applied voltage is preferably 1 V or more, preferably 3 V or more, more preferably 5 V or more, more preferably 6 V or more, and even more preferably 10 V or more. Also, it is preferably 500 V or less, more preferably 300 V or less, even more preferably 100 V or less, and particularly preferably 50 V or less. The voltage application time is preferably 300 seconds or less, more preferably 180 seconds or less, even more preferably 120 seconds or less, even more preferably 60 seconds or less, and particularly preferably 30 seconds or less. In such cases, the workability is excellent. Also, the shorter the application time, the better, but it is usually 1 second or more.

[0110] The pressure-sensitive adhesive composition according to the embodiment of the present invention is not particularly limited, but can be produced by appropriately stirring and mixing a polymer, an ionic liquid, an additive, and, if necessary, a crosslinking agent, polyethylene glycol, a conductive filler, etc.

[0111] The thickness of the electrically releasable pressure-sensitive adhesive layer 1 is preferably 1 μm or more and 1000 μm or less from the viewpoint of initial adhesive strength. The upper limit of the thickness of the electrically releasable pressure-sensitive adhesive layer 1 is more preferably 500 μm, still more preferably 300 μm, still more preferably 200 μm, still more preferably 150 μm, still more preferably 100 μm, still more preferably 80 μm, still more preferably 70 μm, still more preferably 60 μm, still more preferably 50 μm, and the lower limit is more preferably 5 μm, still more preferably 10 μm, still more preferably 20 μm, still more preferably 30 μm.

[0112] The thickness of the electrically releasable pressure-sensitive adhesive sheet of the present embodiment is preferably 20 μm or more and 3000 μm or less. The upper limit of the thickness is more preferably 1000 μm, still more preferably 500 μm, still more preferably 300 μm, still more preferably 250 μm, still more preferably 200 μm, still more preferably 150 μm, still more preferably 100 μm, and the lower limit is more preferably 30 μm, still more preferably 50 μm.

[0113] In particular, in the case of the electrically releasable pressure-sensitive adhesive sheets X1 and X2 shown in FIGS. 1 and 2, the thickness of the electrically releasable pressure-sensitive adhesive sheet is preferably 20 μm or more and 2000 μm or less. The upper limit of the thickness is more preferably 1000 μm, still more preferably 500 μm, still more preferably 300 μm, still more preferably 250 μm, still more preferably 200 μm, still more preferably 150 μm, and the lower limit is more preferably 30 μm, still more preferably 50 μm, still more preferably 100 μm.

[0114] In particular, in the case of the electrically releasable pressure-sensitive adhesive sheet X3 shown in FIG. 3, the thickness of the electrically releasable pressure-sensitive adhesive sheet is preferably 50 μm or more and 3000 μm or less. The upper limit of the thickness is more preferably 1000 μm, still more preferably 500 μm, and the lower limit is more preferably 50 μm, still more preferably 100 μm, still more preferably 200 μm.

[0115] When the pressure-sensitive adhesive layer of the electrically peelable pressure-sensitive adhesive sheet of the present embodiment and the pressure-sensitive adhesive layer in the case of having other pressure-sensitive adhesive layers are provided, the surface of the pressure-sensitive adhesive layer may be protected by a separator (release liner). The separator is not particularly limited, and examples thereof include a release liner in which the surface of a base material (liner base material) such as paper or a plastic film is silicone-treated, and a release liner in which the surface of a base material (liner base material) such as paper or a plastic film is laminated with a polyolefin-based resin. The thickness of the separator is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 30 μm or more, preferably 100 μm or less, more preferably 80 μm or less, and still more preferably 50 μm or less.

[0116] (Method for manufacturing an electrically peelable pressure-sensitive adhesive sheet) As the method for manufacturing the electrically peelable pressure-sensitive adhesive sheet of the present embodiment, known or conventional manufacturing methods can be used. The electrically peelable pressure-sensitive adhesive layer in the electrically peelable pressure-sensitive adhesive sheet of the present embodiment can be formed by applying a solution obtained by dissolving the pressure-sensitive adhesive composition of the present embodiment in a solvent, if necessary, onto a separator, and then drying and / or curing it. When providing other pressure-sensitive adhesive layers, examples of the method for forming the other pressure-sensitive adhesive layers include applying a solution obtained by dissolving a pressure-sensitive adhesive composition that does not contain an ionic liquid and an additive in a solvent, if necessary, onto a separator, and then drying and / or curing it. Note that the solvents and separators described above can be used.

[0117] When applying, a conventional coater (for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray roll coater, etc.) can be used.

[0118] By the above method, an electrically peelable pressure-sensitive adhesive layer and other pressure-sensitive adhesive layers can be manufactured. Appropriately, by laminating a conductive substrate, an electrically peelable pressure-sensitive adhesive layer, and, if necessary, a coating layer or other pressure-sensitive adhesive layers, the electrically peelable pressure-sensitive adhesive sheet of the present embodiment can be manufactured. Note that instead of a separator, a coating layer may be used to apply an adhesive composition to form an electrically peelable pressure-sensitive adhesive layer.

[0119] (Method for electrically peeling an electrically peelable pressure-sensitive adhesive sheet) The peeling of the electrically peelable pressure-sensitive adhesive sheet of the present embodiment from the adherend can be performed by applying a voltage to the electrically peelable pressure-sensitive adhesive layer to generate a potential difference in the thickness direction of the electrically peelable pressure-sensitive adhesive layer. For example, a bonded body obtained by attaching the electrically peelable pressure-sensitive adhesive sheet X1 or X2 to a conductive adherend can be peeled by energizing the conductive adherend and applying a voltage to the electrically peelable pressure-sensitive adhesive layer. For example, in the case of the electrically peelable pressure-sensitive adhesive sheets X3 to X5, both conductive layers can be energized and a voltage can be applied to the electrically peelable pressure-sensitive adhesive layer to peel it from the adherend. It is preferable to perform energization by connecting terminals to one end and the other end of the electrically peelable pressure-sensitive adhesive sheet so that a voltage is applied to the entire electrically peelable pressure-sensitive adhesive layer. Note that the above one end and the other end may be a part of the adherend having a metal adherend surface when the adherend has a metal adherend surface. Note that water may be added to the interface between the adherend surface of the conductive adherend and the electrically peelable pressure-sensitive adhesive layer before applying a voltage during peeling.

[0120] (Applications of the electrically peelable pressure-sensitive adhesive sheet) As conventional re-peeling technologies, there are adhesive layers that are cured by ultraviolet (UV) irradiation for peeling and adhesive layers that are peeled by heat. In an electrically peelable adhesive sheet using such an adhesive layer, it cannot be used when UV irradiation is difficult or when damage is caused to a member that is an adherend by heat. The electrically peelable adhesive sheet of the present embodiment provided with the above electrically peelable adhesive layer does not use ultraviolet rays or heat, so it can be easily peeled by applying a voltage without damaging the member that is the adherend. Therefore, the electrically peelable adhesive sheet of the present embodiment is suitable for fixing to the housing of a secondary battery (for example, a lithium ion battery pack) used in mobile terminals such as smartphones, mobile phones, notebook computers, video cameras, and digital cameras, and for fixing between the display panel and the housing of those devices.

[0121] In addition, examples of the rigid member as the object to be joined by the electrically peelable adhesive sheet of the present embodiment include a silicon substrate for semiconductor wafer applications, a sapphire substrate for LEDs, a SiC substrate and a metal base substrate, a TFT substrate for displays and a color filter substrate, and a base substrate for organic EL panels. Examples of the fragile member as the object to be joined by the double-sided electrically peelable adhesive sheet include semiconductor substrates such as compound semiconductor substrates, silicon substrates for MEMS device applications, passive matrix substrates, surface cover glass for smartphones, OGS (One Glass Solution) substrates in which a touch panel sensor is attached to the cover glass, organic substrates and organic-inorganic hybrid substrates mainly composed of silsesquioxane, flexible glass substrates for flexible displays, and graphene sheets.

[0122] [Joined body] The joined body according to the embodiment of the present invention includes the electrically peelable adhesive sheet according to the embodiment of the present invention and a conductive material, and is a joined body in which the electrically peelable adhesive layer in the electrically peelable adhesive sheet is adhered to the conductive material. The conductive material is preferably an adherend having a metal-coated surface. Examples of the adherend having a metal-coated surface include those made of metals mainly composed of aluminum, copper, iron, magnesium, tin, gold, silver, lead, etc., and among them, metals containing aluminum are preferred.

[0123] Examples of the bonded body of the present embodiment include a bonded body in which an electrically peelable adhesive sheet X1 and the side of the electrically peelable adhesive layer 1 of the electrically peelable adhesive sheet X1 are adhered to a conductive adherend having, for example, a metal-coated surface.

[0124] When the electrically peelable adhesive sheet according to the embodiment of the present invention further includes another adhesive layer, a second conductive layer, and a second other adhesive layer, and the other adhesive layer is formed on the surface of the support substrate opposite to the conductive layer, and the second conductive layer and the second other adhesive layer are formed in this order on the surface of the electrically peelable adhesive layer opposite to the conductive layer, another aspect of the bonded body according to the embodiment of the present invention includes the electrically peelable adhesive sheet according to the embodiment of the present invention and an adherend material, and the other adhesive layer is a bonded body adhered to the adherend material. The adherend material is selected from a conductive material and a non-conductive material.

[0125] Examples of the bonded body of the present embodiment include a bonded body in which the other adhesive layers 6 on both sides of the electrically peelable adhesive sheet X3 are adhered to a conductive material having, for example, a metal-coated surface, and a bonded body in which any one of the other adhesive layers 6 in the electrically peelable adhesive sheet X3 is adhered to a non-conductive material.

[0126] As described above, the following matters are disclosed in this specification. <1> A conductive substrate including a support substrate and a conductive layer, An electrically peelable adhesive layer whose adhesive force decreases when a voltage is applied, provided in this order, The support substrate and the conductive layer are in contact with each other, An electrically peelable pressure-sensitive adhesive sheet in which the surface roughness Sa of the support substrate on the surface side of the conductive layer is less than 6.2 μm. <2> The electrically peelable pressure-sensitive adhesive sheet according to <1>, wherein the electrically peelable pressure-sensitive adhesive layer contains a polymer and an electrolyte. [3] The electrically peelable pressure-sensitive adhesive sheet according to <2>, wherein the content of the electrolyte is 0.5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the polymer.

[0127] <4> The electrolyte is an ionic liquid, and the anion of the ionic liquid is at least one selected from the group consisting of bis(fluorosulfonyl)imide anion and bis(trifluoromethanesulfonyl)imide anion. The electrically peelable pressure-sensitive adhesive sheet according to <2> or <3>. <5> The electrolyte is an ionic liquid, and the cation of the ionic liquid is at least one selected from the group consisting of nitrogen-containing onium cations, sulfur-containing onium cations, and phosphorus-containing onium cations. The electrically peelable pressure-sensitive adhesive sheet according to any one of <2> to <4>. <6> The electrically peelable pressure-sensitive adhesive sheet according to any one of <1> to <5>, wherein a coating layer is formed on the surface of the electrically peelable pressure-sensitive adhesive layer on the side of the conductive substrate. <7> The coating layer contains at least one resin selected from polyester resins, acrylic resins, epoxy resins, and urethane resins, or at least one inorganic substance selected from SiNx, SiOx, Al2O3, Ni, and NiCr. The electrically peelable pressure-sensitive adhesive sheet according to <6>.

[0128] <8> Furthermore, it is provided with another pressure-sensitive adhesive layer, The electrically peelable pressure-sensitive adhesive sheet according to any one of <1> to <7>, wherein the other pressure-sensitive adhesive layer is formed on the surface of the support substrate on the side opposite to the conductive layer. <9> Further comprising another adhesive layer, a second conductive layer, and a second other adhesive layer, The other adhesive layer is formed on the surface of the support substrate opposite to the conductive layer, On the surface of the electrically peelable adhesive layer opposite to the conductive layer, the second conductive layer and the second other adhesive layer are formed in this order. The electrically peelable adhesive sheet according to any one of <1> to <6>.

[0129] <10> Comprising the electrically peelable adhesive sheet according to any one of <1> to <8> and a conductive material, A joined body in which the electrically peelable adhesive layer is adhered to the conductive material. <11> Comprising the electrically peelable adhesive sheet according to <9> and an adherend material, A joined body in which the other adhesive layer is adhered to the adherend material.

Example

[0130] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. The following weight average molecular weight was measured by the gel permeation chromatography (GPC) method according to the method described above.

[0131] (Preparation of acrylic polymer solution) As monomer components, 87 parts by mass of n-butyl acrylate (BA), 10 parts by mass of 2-methoxyethyl acrylate (MEA), 3 parts by mass of acrylic acid (AA), and 150 parts by mass of ethyl acetate as a polymerization solvent were charged into a separable flask and stirred for 1 hour while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.2 part by mass of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and the temperature was raised to 63°C and reacted for 6 hours. Then, ethyl acetate was added to obtain an acrylic polymer solution with a solid content concentration of 30% by mass. The weight average molecular weight of the obtained acrylic polymer was 700,000.

[0132] [Example 1] (Preparation of Electrically Peeling Adhesive Layer) The acrylic polymer (solution) obtained above, a crosslinking agent, an ionic liquid, an additive (corrosion inhibitor), and ethyl acetate were added and stirred and mixed to obtain each electrically peeling adhesive composition (solution) adjusted to a solid content concentration of 25% by mass.

[0133] The blending amounts of the respective components are shown in Table 1. Note that the values of the respective components in Table 1 below mean parts by mass. The obtained electrically peeling adhesive composition (solution) was applied onto the peeling-treated surface of a polyethylene terephthalate separator (trade name "MRF38", manufactured by Mitsubishi Rayon Co., Ltd.) using an applicator so as to have a uniform thickness. Next, heat drying was performed at 150 °C for 3 minutes, and the peeling-treated surface of a polyethylene terephthalate separator (trade name "MRE38", manufactured by Mitsubishi Rayon Co., Ltd.) was laminated onto the adhesive using a hand roller to obtain an electrically peeling adhesive layer having a thickness of 50 μm.

[0134] The abbreviations of the ionic liquid, corrosion inhibitor, and crosslinking agent in Table 1 are as follows.

[0135] (Ionic Liquid) AS-110: Cation: 1-ethyl-3-methylimidazolium cation, Anion: bis(fluorosulfonyl)imide anion, Trade name "Electrel AS-110", Manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (Crosslinking Agent) V-05: Polycarbodiimide resin, Trade name "Carbodilite V-05", Manufactured by Nisshinbo Chemical Inc. (Corrosion Inhibitor) AMINE O: 2-(8-heptadecen-1-yl)-4,5-dihydro-1H-imidazole-1-ethanol, Trade name "AMINE O", Manufactured by BASF Japan Ltd. Irgacor DSSG: Sodium sebacate, Trade name "Irgacor DSSG", Manufactured by BASF Japan Ltd. (Chelating Metal Inactivator) Irgamet 30: N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine, trade name "Irgamet 30", manufactured by BASF Japan Ltd.

[0136] (Preparation of Samples) On a support substrate T912E75 (polyethylene terephthalate, surface roughness Sa 0.7 μm, manufactured by Mitsubishi Chemical Corporation), an aluminum vapor deposition layer with a thickness of 40 nm was formed using a vacuum vapor deposition apparatus (EX-550, manufactured by ULVAC, Inc.). The aluminum vapor deposition surface of the aluminum vapor deposited support substrate was bonded to the electrically peelable pressure-sensitive adhesive layer obtained above to obtain the electrically peelable pressure-sensitive adhesive sheet of Example 1. The obtained electrically peelable pressure-sensitive adhesive sheet was cut into 2 cm × 2 cm sizes to obtain small pieces of the electrically peelable pressure-sensitive adhesive sheet.

[0137] Note that, including Comparative Example 1 described later, the surface roughness Sa of the support substrate was measured in accordance with the method defined by ISO25178. Specifically, using a 3D laser measurement microscope (trade name: LEXT OSL5500, manufactured by Olympus Corporation), the measurement was performed with an objective lens magnification of 20 times and a measurement area of 600 μm × 600 μm.

[0138] [Comparative Example 1] An electrically peelable pressure-sensitive adhesive sheet and small pieces of the electrically peelable pressure-sensitive adhesive sheet of Comparative Example 1 were obtained in the same manner as in Example 1, except that T134E125 (polyethylene terephthalate, surface roughness Sa 6.2 μm, manufactured by Mitsubishi Chemical Corporation) was used as the support substrate.

[0139] (Aluminum Peeling Test after Damp Heat Test) For each of the small pieces of the electrically peelable pressure-sensitive adhesive sheets of Example 1 and Comparative Example 1, an aluminum peeling test after a damp heat test was carried out according to the following procedure. The test sample was left standing in a thermo-hygrostat at 85°C and 85% RH for 4 hours. Immediately after taking it out, the polyethylene terephthalate separator of the electrically peelable adhesive sheet was peeled off, and a polyethylene terephthalate film (trade name: Lumirror S10, manufactured by Toray Industries, Inc.) was attached to the exposed surface, and the aluminum peel test samples of Example 1 and Comparative Example 1 were obtained respectively. Then, the polyethylene terephthalate film was peeled off by hand in the 180° direction, and the peeled area of aluminum was confirmed at that time.

[0140] The determination of the above test was carried out as follows. 〇 (Good): The area where aluminum was peeled off was less than 5% of the area of the support substrate. × (Bad): The area where aluminum was peeled off was 5% or more of the area of the support substrate.

[0141] The obtained results are shown in Table 1.

[0142]

Table 1

[0143] From the results in Table 1, it was shown that the aluminum peel test sample of Example 1 containing an electrically peelable adhesive sheet with a surface roughness Sa of the support substrate on the surface of the conductive layer side less than 6.2 μm suppressed the peeling of the conductive layer from the support substrate in a high-temperature and high-humidity environment. On the other hand, it was shown that the aluminum peel test sample of Comparative Example 1 had significant peeling of the conductive layer from the support substrate in a high-temperature and high-humidity environment.

[0144] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Industrial Applicability

[0145] The electrically peelable adhesive sheet according to the present invention can be used, for example, for fixing a secondary battery (e.g., a lithium-ion battery pack) to a housing of a mobile terminal such as a smartphone, a mobile phone, a notebook computer, a video camera, a digital camera, etc., or for fixing a display panel and a housing of those devices.

Explanation of Signs

[0146] X1, X2, X3 Electrically peelable adhesive sheet 1 Electrically peelable adhesive layer 3 Conductive layer 4 Support substrate 5 Conductive substrate 6 Other adhesive layer

Claims

1. A conductive substrate including a support substrate and a conductive layer, and an electrically peelable pressure-sensitive adhesive layer whose adhesive force decreases upon application of voltage, provided in this order, wherein the support substrate and the conductive layer are in contact with each other, and an electrically peelable pressure-sensitive adhesive sheet in which a surface roughness Sa of the support substrate on the surface on the conductive layer side is less than 6.2 μm.

2. The electrically peelable pressure-sensitive adhesive sheet according to claim 1, wherein the electrically peelable pressure-sensitive adhesive layer contains a polymer and an electrolyte.

3. The electrically peelable pressure-sensitive adhesive sheet according to claim 2, wherein a content of the electrolyte is 0.5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the polymer.

4. The electrically peelable pressure-sensitive adhesive sheet according to claim 2, wherein the electrolyte is an ionic liquid, and an anion of the ionic liquid is at least one selected from the group consisting of a bis(fluorosulfonyl)imide anion and a bis(trifluoromethanesulfonyl)imide anion.

5. The electrically peelable pressure-sensitive adhesive sheet according to claim 2, wherein the electrolyte is an ionic liquid, and a cation of the ionic liquid is at least one selected from the group consisting of a nitrogen-containing onium cation, a sulfur-containing onium cation, and a phosphorus-containing onium cation.

6. The electrically peelable pressure-sensitive adhesive sheet according to claim 1, wherein a coating layer is formed on a surface of the electrically peelable pressure-sensitive adhesive layer on the conductive substrate side.

7. The coat layer contains at least one resin selected from polyester resins, acrylic resins, epoxy resins, and urethane resins, or at least one inorganic substance selected from SiNx, SiOx, Al ２ O ３ , Ni, and NiCr. The electrically peelable pressure-sensitive adhesive sheet according to claim 6.

8. Further comprising another pressure-sensitive adhesive layer, and the other pressure-sensitive adhesive layer is formed on a surface of the support substrate on the side opposite to the conductive layer, the electrically peelable pressure-sensitive adhesive sheet according to claim 1.

9. Further comprising another pressure-sensitive adhesive layer, a second conductive layer, and a second other pressure-sensitive adhesive layer, wherein the other pressure-sensitive adhesive layer is formed on a surface of the support substrate on the side opposite to the conductive layer, and the second conductive layer and the second other pressure-sensitive adhesive layer are formed in this order on a surface of the electrically peelable pressure-sensitive adhesive layer on the side opposite to the conductive layer, the electrically peelable pressure-sensitive adhesive sheet according to claim 1.

10. An electrically peelable pressure-sensitive adhesive sheet according to any one of claims 1 to 8, and a conductive material, and a joined body in which the electrically peelable pressure-sensitive adhesive layer is adhered to the conductive material.

11. An electrically peelable pressure-sensitive adhesive sheet according to claim 9, and an adherend material, and a joined body in which the other pressure-sensitive adhesive layer is adhered to the adherend material.

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