Double-sided pressure-sensitive adhesive sheet, joined body, electrical / electronic appliance, and method for producing pressure-sensitive adhesive sheet

Abstract

Provided is a double-sided pressure-sensitive adhesive sheet which, even when including a substrate having no electrical conductivity, can be separated by voltage application.　A double-sided pressure-sensitive adhesive sheet 1 comprises a substrate 2 having a volume resistivity of 1.0 × 1010 Ω·cm or greater and, formed on a main surface 2a of the substrate 2, an electrically removable pressure-sensitive adhesive layer 3, the adhesive force of which is reduced by voltage application. The double-sided pressure-sensitive adhesive sheet 1 has a tensile elastic modulus E' at 25°C of 120 MPa or less. The substrate 2 is preferably made of a plastic material. The electrically removable pressure-sensitive adhesive layer 3 preferably includes a polymer and an electrolyte.

Description

Double-sided adhesive sheet, bonded structure, electrical and electronic equipment, and method for manufacturing an adhesive sheet

[0001] The present invention relates to a double-sided adhesive sheet, a bonded structure, electrical and electronic equipment, and a method for manufacturing an adhesive sheet. More specifically, the present invention relates to a double-sided adhesive sheet, a bonded structure and electrical and electronic equipment in which the double-sided adhesive sheets are bonded together, and a method for manufacturing an adhesive sheet.

[0002] In recent years, electronic devices such as home appliances, office automation equipment, mobile phones (smartphones, etc.), digital cameras, and PDAs (Personal Digital Assistants) are widely used. For example, mobile phones, a representative portable device, tend to have thinner and larger screens for their main components. Typically, the display part of a portable device consists mainly of an LCD module and a backlight unit, with various sheet-like components layered to exhibit functions such as light emission, reflection, light shielding, and light guidance. Furthermore, recent mobile phones often employ organic electroluminescent displays, which are even more expensive than LCD modules. Adhesive sheets (adhesive tapes) are used for assembling (joining) these components.

[0003] Incidentally, in recent years, in order to achieve the Sustainable Development Goals (SDGs) adopted at the 2015 UN Summit, industrial bonding materials, including adhesive sheets, have been required to be easily disassembled (reworkable) at any time and in any way, in order to increase the recycling and reuse rate of the components being bonded (adhered objects).

[0004] As an adhesive sheet with reworkability, an adhesive sheet (electro-peelable adhesive sheet) is known in which an ionic liquid consisting of cations and anions is used as a component to form the adhesive composition, and the adhesive layer is peeled off by applying a voltage (Patent Document 1). In the electro-peelable adhesive sheet of Patent Document 1, it is thought that when a voltage is applied, the cations of the ionic liquid move on the cathode side, weakening the adhesive force at the adhesive interface and making it easier to peel off.

[0005] International Publication No. 2017 / 064918

[0006] There are cases where an electro-peelable, thick double-sided adhesive sheet is required. Typically, an adhesive layer containing an ionic liquid is formed by applying a solvent-type adhesive composition to a release liner or substrate, and then heating and drying it to evaporate the solvent. However, since adhesive compositions containing ionic liquids generally have a low solid content concentration of 20-30%, it has been difficult to form a thick adhesive layer.

[0007] To obtain a thick double-sided adhesive sheet, in addition to increasing the thickness of the adhesive layer, it is conceivable to interpose a substrate between the two adhesive layers. However, in order to enable conductivity between the two adhesive surfaces of the double-sided adhesive sheet, it is a prerequisite to use a conductive substrate, and conventionally, it has not been possible to use a non-conductive substrate.

[0008] The present invention was conceived under these circumstances, and its purpose is to provide a double-sided adhesive sheet that can be peeled off by applying a voltage even when a non-conductive substrate is used. Furthermore, the invention provides a bonding body and electrical and electronic equipment comprising the above-mentioned double-sided adhesive sheet. It also provides a method for manufacturing an adhesive sheet that can be peeled off by applying a voltage regardless of the conductivity of the substrate.

[0009] As a result of diligent research to achieve the above objective, the inventors of this invention have found that, with a specific double-sided adhesive sheet, peeling by voltage application is possible even when using a non-conductive substrate. This invention was completed based on these findings.

[0010] In other words, the present invention provides a volume resistivity of 1.0 × 10⁻⁶ １０ The present invention provides a double-sided adhesive sheet comprising a substrate with a density of Ω·cm or greater, and an electro-peelable adhesive layer on at least one main surface of the substrate, wherein the adhesive strength decreases when a voltage is applied, and the tensile modulus E' at 25°C is 120 MPa or less.

[0011] The above double-sided adhesive sheet preferably satisfies the following formulas (1) and / or (2): 0.01 ≤ [thickness of the substrate / total thickness of the electropenetrating adhesive layer] < 3 (1) 0.005 ≤ [thickness of the substrate / thickness of the electropenetrating adhesive layer on one main surface] < 6 (2)

[0012] The above-mentioned base material is preferably made of a non-metallic material.

[0013] The above-mentioned base material is preferably made of a plastic material.

[0014] The above-mentioned electropenetrating adhesive layer preferably contains a polymer and an electrolyte.

[0015] The tensile modulus E' is preferably 40 MPa or less.

[0016] The above-mentioned double-sided adhesive sheet is preferably used for fixing components together in electrical and electronic equipment.

[0017] Furthermore, the present invention provides a bonded body comprising the above-mentioned double-sided adhesive sheet and a conductive material, wherein the electropenetrating adhesive layer is attached to the conductive material.

[0018] Furthermore, the present invention provides an electrical and electronic device comprising the above-mentioned double-sided adhesive sheet, wherein the double-sided adhesive sheet fixes components together on both adhesive surfaces.

[0019] Furthermore, the present invention provides a method for manufacturing an adhesive sheet comprising a base material and an adhesive layer provided on at least one main surface of the base material, comprising a bonding step of bonding the base material and the adhesive layer, wherein one of the base material and the adhesive layer to be bonded in the bonding step contains an electrolyte and the other does not contain the electrolyte, and comprising a transfer step of transferring the electrolyte from one to the other in or after the bonding step.

[0020] The double-sided adhesive sheet of the present invention can be peeled off by applying a voltage, even when using a non-conductive substrate. Therefore, it is possible to provide a double-sided adhesive sheet that can be peeled off by applying a voltage, not only when it is thin, but also when it is thick. Furthermore, the bonded body and electrical and electronic equipment of the present invention can peel off the above-mentioned double-sided adhesive sheet by applying a voltage. Moreover, according to the method for manufacturing the adhesive sheet of the present invention, it is possible to obtain an adhesive sheet that can be peeled off by applying a voltage regardless of the conductivity of the substrate.

[0021] This is a cross-sectional view of a double-sided adhesive sheet according to one embodiment of the present invention. This is a front view showing an example of a portable electronic device equipped with the double-sided adhesive sheet of the present invention. This is a schematic diagram showing the setup used when measuring volume resistivity in the example. This is a cross-sectional view showing an overview of the 180° peel test method in the example. This is a graph showing the relationship between the tensile modulus E' and the electropenetration force (300 sec) in the example. This is a graph showing the relationship between [isocyanate component × substrate thickness / total thickness of adhesive layer] and the electropenetration force (300 sec) in the example. This is a graph showing the relationship between [isocyanate component × substrate thickness / thickness of one layer of adhesive layer] and the electropenetration force (300 sec) in the example.

[0022] [Double-Sided Adhesive Sheet] A double-sided adhesive sheet according to one embodiment of the present invention comprises a base material and at least an electro-release adhesive layer provided on at least one surface (main surface) of the base material. The electro-release adhesive layer is an adhesive layer having the property of decreasing adhesive strength (electro-release properties) when a voltage is applied to the adhesive layer.

[0023] The double-sided adhesive sheet of the present invention comprises an electro-release adhesive layer on one main surface of a substrate. The adhesive layer on the other main surface of the substrate may be the electro-release adhesive layer or an adhesive layer that does not have electro-release properties (non-electro-release adhesive layer). Examples of the non-electro-release adhesive layer include adhesive layers similar to those exemplified and described later as electro-release adhesive layers, except that they do not contain an electrolyte. Furthermore, the adhesive layers provided on both main surfaces of the substrate may each be a single layer or a multi-layer. In the case of a multi-layer, the electro-release adhesive layer on one main surface may be a multi-layer of electro-release adhesive layers or a laminate of an electro-release adhesive layer and a non-electro-release adhesive layer. Furthermore, the adhesive layer on the other main surface may be a multi-layer of electro-release adhesive layers, a laminate of an electro-release adhesive layer and a non-electro-release adhesive layer, or a multi-layer of a non-electro-release adhesive layer. In particular, on at least one main surface, it is preferable that the adhesive layer in contact with the substrate is an electrorelease type adhesive layer. Furthermore, it is preferable that the adhesive layer providing at least one adhesive surface of the double-sided adhesive sheet is an electrorelease type adhesive layer.

[0024] Figure 1 is a cross-sectional view showing one embodiment of the double-sided adhesive sheet of the present invention. As shown in Figure 1, the double-sided adhesive sheet 1 comprises a base material 2 and an electro-release adhesive layer 3 and an electro-release adhesive layer 4 provided on both main surfaces of the base material 2, respectively. The base material 2 has a first main surface 2a and a second main surface 2b, the electro-release adhesive layer 3 is provided on the entire surface of the first main surface 2a of the base material 2, and the electro-release adhesive layer 4 is provided on the entire surface of the second main surface 2b of the base material 2. The base material 2 and the electro-release adhesive layer 3 are directly laminated (in contact), and the base material 2 and the electro-release adhesive layer 4 are directly laminated (in contact). Release liners 5 and 6 are provided on both adhesive surfaces of the double-sided adhesive sheet 1 (the adhesive surfaces of the electro-release adhesive layers 3 and 4), respectively. Note that the electro-release adhesive layer 3 and the electro-release adhesive layer 4 do not necessarily have to be provided on the entire surface of the base material 2, but may be provided on at least a part of it. Also, the release liners 5 and 6 are not necessary.

[0025] <Substrate> The above-mentioned substrate is an element that functions as a support in the adhesive sheet. The above-mentioned substrate may be a single layer or a laminate of the same or different types of substrates. The above-mentioned "substrate" refers to the support, and when the double-sided adhesive sheet of the present invention is used (applied) to an adherend, it is the part that is attached to the adherend together with the adhesive layer. The release liner that is peeled off when the adhesive sheet is used (applied) is not included in the above-mentioned substrate. By providing the above-mentioned substrate, it is possible to provide a double-sided adhesive sheet that can be peeled off by voltage application not only when it is thin, but also when it is thick.

[0026] The above substrate has a volume resistivity of 1.0 × 10 １０ It is preferable that the density is Ω·cm or greater, and more preferably 1.0 × 10⁻⁶. １１ Ω·cm or more, more preferably 1.0 × 10⁻⁶ １２ It is greater than Ω·cm. The volume resistivity is 1.0 × 10⁻⁶. １０ Substrates with a resistivity of Ω·cm or higher are presumed to be non-conductive and prone to electrolyte migration in the electropenetrating adhesive layer. The above volume resistivity is, for example, 1.0 × 10⁻⁶. ２０ It is Ω·cm or less. The volume resistivity of the substrate is the volume resistivity of the substrate before the formation of the ionization-peelable adhesive layer, and corresponds to "before use" in the examples. The volume resistivity is a value measured based on the double-ring method of JIS K6271-1, and can be measured specifically as described in the examples.

[0027] The above-mentioned substrate is preferably composed of a nonmetal from the viewpoint of having a high volume resistivity. Examples of such substrates include plastic substrates (e.g., plastic film), porous materials such as paper, cloth, and nonwoven fabric, nets, and foamed sheets. A plastic substrate (particularly plastic film) is preferred as the above-mentioned substrate. Furthermore, it is preferable that the above-mentioned substrate is a non-foamed sheet.

[0028] Examples of resins constituting the above-mentioned plastic substrate include ethylene-vinyl acetate copolymer (EVA), acrylic polymers, polyurethane resins (thermoplastic polyurethane, thermosetting polyurethane, etc.), rubber resins (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester, polycarbonate, polyimide, polyetheretherketone, polyetherimide, polyamide, polyphenyl sulfide, fluororesin, polyvinyl chloride, polyvinylidene chloride, cellulose resin, and silicone resin. One type of resin may be used, or two or more types may be used.

[0029] Among the above resins, polyurethane and acrylic polymers are preferred. Specifically, the above substrate preferably contains one or more selected from the group consisting of polyurethane resins and polyurethane resins, and is particularly preferred to contain one or more selected from the group consisting of thermoplastic polyurethane, thermosetting polyurethane, and acrylic polymers. For this reason, the above substrate is preferably a thermoplastic polyurethane film, a thermosetting polyurethane film, or an acrylic film.

[0030] The polyurethane resin described above consists of a hard phase (hard segment) made of isocyanate components and a soft phase (soft segment) made of polyol components and chain extenders.

[0031] The above polyurethane resins are typically obtained by reacting a polyisoanate with a polyol (long-chain polyol), a chain extender, and, if necessary, other isocyanate-reactive compounds.

[0032] The above polyisocyanates are compounds having two or more isocyanate groups in their molecules. Examples of the above polyisocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and aromatic aliphatic polyisocyanates. Other examples of the above polyisocyanates include dimers, trimers, reaction products, or polymers of the above aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and / or aromatic aliphatic polyisocyanates (for example, dimers and trimers of diphenylmethane diisocyanate, reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, etc.). Only one type of polyisocyanate may be used, or two or more types may be used.

[0033] Examples of the above-mentioned aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; and 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0034] Examples of the above-mentioned alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0035] Examples of the above aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, and 2,2'-diphenylpropane-4,4'-diisocyanate. Examples include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropanediisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0036] Examples of the long-chain polyols mentioned above include polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, and polyacrylic polyols. The number-average molecular weight of the long-chain polyol is usually 500 or more, preferably 500 to 10000, more preferably 600 to 6000, and even more preferably 800 to 4000. One type of long-chain polyol may be used, or two or more types may be used.

[0037] Examples of polyether polyols include polyalkylene ether glycols such as polyethylene ether glycol, polypropylene ether glycol, and polytetramethylene ether glycol (PTMG), as well as copolymers containing multiple alkylene oxides as monomer components, such as ethylene oxide-propylene oxide copolymers (alkylene oxide-other alkylene oxides).

[0038] Examples of polyester polyols include condensation polymers of polyhydric alcohols and polyhydric carboxylic acids; ring-opening polymers of cyclic esters (lactones); and reaction products of three components: polyhydric alcohols, polyhydric carboxylic acids, and cyclic esters. In condensation polymers of polyhydric alcohols and polyhydric carboxylic acids, examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,9-nonanediol, 1,10-decanediol, glycerin, trimethylolpropane, trimethylolethane, cyclohexanediols (such as 1,4-cyclohexanediol), cyclohexanedimethanols (such as 1,4-cyclohexanedimethanol), bisphenols (such as bisphenol A), and sugar alcohols (such as xylitol and sorbitol). Examples of polycarboxylic acids include aliphatic dicarboxylic acids such as malonic acid, maleic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedionic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, paraphenylenedicarboxylic acid, and trimellitic acid. In ring-opening polymerization of cyclic esters, examples of cyclic esters include propiolactone, β-methyl-δ-valerolactone, and ε-caprolactone. In reaction products with three components, the above-mentioned polyhydric alcohols, polycarboxylic acids, and cyclic esters can be used.

[0039] Examples of polycarbonate polyols include reaction products of polyhydric alcohols with phosgene, chloroformate esters, dialkyl carbonates, or diaryl carbonates; and ring-opening polymers of cyclic carbonates (such as alkylene carbonates). Specifically, in reaction products of polyhydric alcohols with phosgene, the polyhydric alcohol can be one of the aforementioned polyhydric alcohols (e.g., ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, etc.). In ring-opening polymers of cyclic carbonates, the alkylene carbonate can be one of one of the following: ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, hexamethylene carbonate, etc. Polycarbonate polyols are any compound having a carbonate bond in the molecule and a hydroxyl group at its terminus, and may also have an ester bond in addition to the carbonate bond. Typical examples of polycarbonate polyols include polyhexamethylene carbonate diols, diols obtained by ring-opening addition polymerization of lactone to polyhexamethylene carbonate diols, and copolymers of polyhexamethylene carbonate diols with polyester diols or polyether diols.

[0040] Polyolefin polyols are polyols that have an olefin as a component of the polymer or copolymer backbone (or main chain) and have at least two hydroxyl groups in the molecule (especially at the ends). The olefin may be an olefin having a carbon-carbon double bond at the end (e.g., α-olefins such as ethylene and propylene), or an olefin having a carbon-carbon double bond at a site other than the end (e.g., isobutene), or even a diene (e.g., butadiene, isoprene). Typical examples of polyolefin polyols include butadiene homopolymer, isoprene homopolymer, butadiene-styrene copolymer, butadiene-isoprene copolymer, butadiene-acrylonitrile copolymer, butadiene-2-ethylhexyl acrylate copolymer, butadiene-n-octadecyl acrylate copolymer, and other butadiene or isoprene-based polymers modified with hydroxyl groups at the ends.

[0041] Polyacrylic polyols are polyols that have (meth)acrylate as a component of the polymer or copolymer backbone (or main chain) and have at least two hydroxyl groups in the molecule (especially at the terminals). Examples of (meth)acrylates include alkyl (meth)acrylates [e.g., C (meth)acrylate]. １－２０ Examples include alkyl esters, etc.

[0042] As the above-mentioned chain extender, chain extenders commonly used in the production of polyurethane resins can be used, such as low molecular weight polyols and polyamines. The molecular weight of the chain extender is usually less than 500, preferably 300 or less. One type of chain extender may be used, or two or more types may be used.

[0043] Examples of the above-mentioned chain extenders include ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,2-pentanediol, 2,3-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and other diols; and diamines such as hexamethylenediamine, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, and 4,4'-methylenebis-2-chloroaniline. Among these, diols are preferred, and 1,4-butanediol is particularly preferred.

[0044] The proportion of the isocyanate component, which is the hard segment in the above urethane resin, is preferably 2 to 50% by mass, and more preferably 5 to 40% by mass, based on 100% by mass of the above urethane resin. The proportion of the long-chain polyol component and chain extender, which are the soft segments in the above urethane resin, is preferably 50 to 98% by mass, and more preferably 60 to 90% by mass, based on 100% by mass of the above urethane resin.

[0045] The above-mentioned substrate may include auxiliary layers. Examples of such auxiliary layers include a colored layer, a reflective layer, an undercoat layer, and an antistatic layer provided on the surface of the substrate. It is preferable that there are no other layers, such as a metal layer, between the substrate and the electropenetrating adhesive layer, from the viewpoint of facilitating the migration of electrolytes to the substrate.

[0046] The surface of the substrate may be subjected to surface treatments such as physical treatments like corona discharge treatment, plasma treatment, sandblasting, ozone exposure treatment, flame exposure treatment, high-voltage electric shock exposure treatment, and ionizing radiation treatment; chemical treatments like chromic acid treatment; and surface treatments such as easy adhesion treatment with a coating agent (primer) in order to improve adhesion and retention with the electropenetrating adhesive layer. It is preferable that the surface treatment to improve adhesion is applied to the entire surface of the substrate.

[0047] The above-mentioned substrate preferably has a tensile modulus E' of 120 MPa or less at 25°C, more preferably 100 MPa or less, even more preferably 80 MPa or less, even more preferably 60 MPa or less, and particularly preferably 40 MPa or less. If the tensile modulus E' is low, it is presumed that the substrate is likely to absorb electrolytes easily, and the adhesive strength will likely decrease significantly when a voltage is applied. The tensile modulus E' may be, for example, 0.1 MPa or more, or 1 MPa or more.

[0048] The thickness of the above substrate is not particularly limited, but is preferably 5 μm or more, and more preferably 10 μm or more. When the above thickness is 5 μm or more, the reworkability is superior. The above thickness is preferably 500 μm or less, more preferably 400 μm or less, and even more preferably 250 μm or less. When the above thickness is 500 μm or less, if the adhesive layers on both main surfaces of the substrate are electrorelease adhesive layers, it is presumed that the conductivity between the electrorelease adhesive layers located on both main surfaces of the substrate tends to be higher, resulting in superior electrorelease properties.

[0049] <Electrorelease Adhesive Layer> The double-sided adhesive sheet of the present invention may have only one electrorelease adhesive layer on one main surface of the substrate, or it may have two or more layers. In the case where the electrorelease adhesive layers on both main surfaces of the substrate of the double-sided adhesive sheet of the present invention are provided, the electrorelease adhesive layers on both main surfaces may be the same adhesive layer, or they may be adhesive layers with different compositions, thicknesses, physical properties, etc.

[0050] (Polymers) The polymers included in the electro-peelable adhesive layer described above can be known or conventional polymers and are not particularly limited, but examples include acrylic polymers, rubber polymers, vinyl alkyl ether polymers, silicone polymers, polyester polymers, polyamide polymers, urethane polymers, fluorine polymers, epoxy polymers, etc. Only one type of polymer may be used, or two or more types may be used.

[0051] The above polymer is preferably a base polymer. In this specification, the base polymer refers to the main component of the polymer component in the adhesive constituting the adhesive layer, for example, the polymer component that is present in more than 50% by mass. The content ratio of the base polymer in the above adhesive layer is preferably 60% by mass or more, and more preferably 70% by mass or more, based on 100% by mass of the total amount of the electro-peelable adhesive layer.

[0052] As for the base polymer mentioned above, it is preferable that the polymer has a high dielectric constant, from the viewpoint of increasing the dielectric constant of components other than the electrolyte in the electrorelease adhesive layer and improving electrorelease properties. From this viewpoint, polyester polymers and acrylic polymers are preferred as the base polymer. In particular, acrylic polymers are preferred in order to increase cost, productivity, and initial adhesive strength.

[0053] The above-mentioned acrylic polymer is a polymer that contains an acrylic monomer (a monomer having a (meth)acryloyl group in its molecule) as a monomer component constituting the polymer. That is, the above-mentioned acrylic polymer contains constituent units derived from an acrylic monomer. Note that only one type of acrylic polymer may be used, or two or more types may be used. Furthermore, the above-mentioned acrylic polymer may contain only one type of acrylic monomer as a monomer component, or it may contain two or more types. In this specification, "(meth)acrylic" refers to "acrylic" and / or "methacrylic" (either one or both of "acrylic" and "methacrylic"), and the same applies to other terms.

[0054] The above acrylic polymer is preferably a polymer that contains the largest mass percentage of constituent units derived from (meth)acrylic acid ester. Examples of the above (meth)acrylic acid ester include hydrocarbon group-containing (meth)acrylic acid esters which may have alkoxy groups. Examples of hydrocarbon group-containing (meth)acrylic acid esters which may have alkoxy groups include alkyl (meth)acrylic acid esters having linear or branched aliphatic hydrocarbon groups, cycloalkyl (meth)acrylic acid esters having alicyclic hydrocarbon groups, and aryl (meth)acrylic acid esters having aromatic hydrocarbon groups. Only one type of hydrocarbon group-containing (meth)acrylic acid ester which may have alkoxy groups may be used, or two or more types may be used.

[0055] Examples of the above alkyl (meth)acrylate esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and methyl (meth)acrylate. Examples include isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (lauryl (meth)acrylate), tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0056] Among the alkyl (meth)acrylate esters mentioned above, alkyl (meth)acrylate esters having linear or branched aliphatic hydrocarbon groups with 1 to 14 carbon atoms (preferably 2 to 8, more preferably 2 to 4) are preferred. When the number of carbon atoms is within the above range, the dielectric constant of components other than the electrolyte in the electropenetrating adhesive layer can be increased, thereby further improving the electropenetrating properties.

[0057] Examples of the above-mentioned cycloalkyl (meth)acrylates include cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate.

[0058] Examples of hydrocarbon group-containing (meth)acrylic acid esters having an alkoxy group include those in which one or more hydrogen atoms in the hydrocarbon group of the above hydrocarbon group-containing (meth)acrylic acid ester are substituted with an alkoxy group, such as 2-methoxymethyl ester, 2-methoxyethyl ester, and 2-methoxybutyl ester of (meth)acrylic acid.

[0059] In order to appropriately exhibit the basic properties such as tackiness of the hydrocarbon group-containing (meth)acrylic acid ester which may have an alkoxy group in an electropenetrating adhesive layer, the proportion of the hydrocarbon group-containing (meth)acrylic acid ester which may have an alkoxy group in all monomer components constituting the acrylic polymer is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, based on the total amount (100% by mass) of all monomer components. Furthermore, from the viewpoint of enabling copolymerization with other monomer components and obtaining the effects of those other monomer components, the above proportion may be 99.9% by mass or less, 98% by mass or less, or 95% by mass or less.

[0060] In this specification, the term "monomer component" in the context of "total amount of monomer components constituting the acrylic polymer" refers to a compound having only one polymerizable functional group, and does not include compounds having two or more polymerizable functional groups, such as polyfunctional (meth)acrylates.

[0061] The above acrylic polymer may contain constituent units derived from other monomer components copolymerizable with the hydrocarbon group-containing (meth)acrylic acid ester, for the purpose of modifying it to improve cohesiveness or introduce crosslinking points. Examples of the above other monomer components include polar group-containing monomers such as 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. Each of the above other monomer components may be used individually or in combination of two or more.

[0062] Among the polar group-containing monomers mentioned above, carboxyl group-containing monomers, hydroxyl group-containing monomers, and amide group-containing monomers are preferred due to their excellent cohesiveness. Furthermore, acrylic polymers having carboxyl and hydroxyl groups are preferred because the carboxyl and hydroxyl groups are easily polarized, allowing for a relatively high dielectric constant of the polymer. In particular, carboxyl group-containing monomers are preferred from the viewpoint of obtaining a large initial adhesive strength.

[0063] Examples of the above-mentioned carboxyl group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0064] Examples of the above-mentioned hydroxyl group-containing monomers 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.

[0065] Examples of the above-mentioned cyano group-containing monomers include acrylonitrile and methacrylonitrile.

[0066] Examples of the vinyl group-containing monomers mentioned above include vinyl esters such as vinyl acetate, vinyl propionate, and vinyl laurate.

[0067] Examples of the above-mentioned aromatic vinyl monomers include styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes.

[0068] Examples of the above-mentioned amide group-containing monomers 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.

[0069] Examples of the above-mentioned imide group-containing monomers include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

[0070] Examples of the above-mentioned amino group-containing monomers include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

[0071] Examples of the epoxy group-containing monomers mentioned above include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, and allyl glycidyl ether.

[0072] Examples of the vinyl ether monomers mentioned above include methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether.

[0073] Examples of the above sulfo group-containing monomers include styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid.

[0074] Examples of the above-mentioned phosphate group-containing monomers include 2-hydroxyethyl acryloyl phosphate.

[0075] Examples of the above-mentioned acid anhydride monomers include maleic anhydride and itaconic anhydride.

[0076] The total proportion of the polar group-containing monomers in the total monomer components (100% by mass) constituting the above acrylic polymer is not particularly limited, but is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and especially preferably 2% by mass or more. Furthermore, from the viewpoint of obtaining an adhesive layer with appropriate flexibility, the total proportion is preferably 35% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. When the proportion is 0.1% by mass or more, cohesive force is easily obtained, so that adhesive residue is less likely to occur on the surface of the adherend after peeling off the electropenetrating adhesive layer, and electropenetration is improved. Furthermore, when the proportion is 35% by mass or less, it is easier to prevent the electropenetrating adhesive layer from adhering excessively to the adherend and causing excessive peeling. In particular, when the proportion is 2 to 20% by mass, the adhesive strength tends to decrease when voltage is applied.

[0077] The monomer components constituting the above-mentioned acrylic polymer may further include other monomers. Examples of these other monomers include aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.), and vinyltoluene; olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; and chlorine-containing monomers such as vinyl chloride and vinylidene chloride.

[0078] The proportion of the other monomers in the total amount of all monomer components constituting the above acrylic polymer (100% by mass) may be, for example, 0.05% by mass or more, or 0.5% by mass or more. The above proportion may also be, for example, 20% by mass or less, 10% by mass or less, or 5% by mass or less, and may be substantially absent.

[0079] The weight-average molecular weight (Mw) of the above acrylic polymer is preferably between 100,000 and 5,000,000. The upper limit of the weight-average molecular weight is more preferably 4,000,000, and even more preferably 3,000,000. The lower limit is more preferably 200,000, and even more preferably 300,000. When the weight-average molecular weight is 100,000 or more, the cohesive force is reduced, which effectively suppresses the problem of adhesive residue remaining on the surface of the adherend after the electrorelease adhesive layer has been removed. Furthermore, when the weight-average molecular weight is 5,000,000 or less, it effectively suppresses the problem of insufficient wettability on the surface of the adherend after the electrorelease adhesive layer has been removed.

[0080] The above weight-average molecular weight was obtained by measurement using gel permeation chromatography (GPC). More specifically, for example, it can be measured using the "HLC-8220GPC" (manufactured by Tosoh Corporation) as a GPC measuring device under the following conditions and calculated using the standard polystyrene equivalent value. (Weight-average molecular weight measurement conditions) ・Sample concentration: 0.2% by mass (tetrahydrofuran solution) ・Sample injection volume: 10 μL ・Sample column: TSKguardcolumn SuperHZ-H (1 tube) + TSKgel SuperHZM-H (2 tubes) ・Reference column: TSKgel SuperH-RC (1 tube) ・Eluent: Tetrahydrofuran (THF) ・Flow rate: 0.6 mL / min ・Detector: Differential refractometer (RI) ・Column temperature (measurement temperature): 40°C

[0081] The glass transition temperature (Tg) of the polymer is not particularly limited, but it is preferably 0°C or lower because it suppresses the decrease in initial adhesive strength, more preferably -10°C or lower, and even more preferably -20°C or lower. Furthermore, it is even more preferable if the temperature is -40°C or lower because the decrease in adhesive strength due to voltage application is particularly large, and especially preferably -50°C or lower.

[0082] The glass transition temperature (Tg) can be calculated, for example, based on the following equation (Y) (Fox equation): 1 / Tg = W1 / Tg1 + W2 / Tg2 + ... + Wn / Tgn (Y) [In equation (Y), Tg is the glass transition temperature of the polymer (unit: K), Tgi (i = 1, 2, ..., n) is the glass transition temperature when monomer i forms a homopolymer (unit: K), and Wi (i = 1, 2, ..., n) represents the mass fraction of monomer i in the total monomer components]. The above equation (Y) is the calculation formula when the polymer is composed of n types of monomer components: monomer 1, monomer 2, ..., monomer n.

[0083] The glass transition temperature when forming a homopolymer refers to the glass transition temperature of the homopolymer of the monomer in question, and specifically refers to the glass transition temperature (Tg) of a polymer formed using only one monomer (sometimes referred to as "monomer X") as the monomer component. The specific values ​​are given in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). Note that the glass transition temperature (Tg) of a homopolymer not listed in the aforementioned literature refers to a value obtained, for example, by the following measurement method: In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 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 added, and the mixture is stirred for 1 hour while introducing nitrogen gas. After removing oxygen from the polymerization system in this manner, the temperature is raised to 63°C and the reaction is carried out for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution with a solid content of 33% by mass. Next, this homopolymer solution is cast onto a release liner and dried to produce a test sample (sheet-like homopolymer) with a thickness of approximately 2 mm. Then, approximately 1-2 mg of this test sample is weighed into an aluminum open cell, and the reversing heat flow (specific heat component) behavior of the homopolymer is obtained using a temperature-modulated DSC (product name "Q-2000", manufactured by T.A. Instruments Corporation) at a heating rate of 5°C / min under a nitrogen atmosphere of 50 ml / min. Referring to JIS-K-7121, the glass transition temperature (Tg) of the homopolymer is defined as the temperature at the point where a line equidistant in the vertical axis direction from the line extending from the low-temperature baseline and the high-temperature baseline of the obtained reversing heat flow intersects with the curve of the step-like change portion of the glass transition.

[0084] The above-mentioned acrylic polymer is obtained by polymerizing a composition containing at least an acrylic monomer. While not particularly limited, these polymerization methods include solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, and polymerization by active energy ray irradiation (active energy ray polymerization). Among these, bulk polymerization, thermal polymerization, and active energy ray polymerization are preferred in terms of transparency of the adhesive layer and cost. Furthermore, the resulting acrylic polymer may be a random copolymer, block copolymer, graft copolymer, or any other type.

[0085] Various common solvents may be used in the polymerization of monomer components. Examples of such solvents include 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 organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone. One or more of these solvents may be used.

[0086] The polymerization initiators, chain transfer agents, emulsifiers, etc., used in the radical polymerization of monomer components are not particularly limited and can be selected and used as appropriate. The weight-average molecular weight of the polymer can be controlled by the amount of polymerization initiator and chain transfer agent used and the reaction conditions, and the appropriate amounts used are adjusted according to the type of agent.

[0087] Depending on the type of polymerization reaction, various polymerization initiators can be used for the polymerization of monomer components, including thermal polymerization initiators and photopolymerization initiators (photoinitiators). One type of polymerization initiator may be used, or two or more types may be used.

[0088] The above-mentioned thermal polymerization initiators are not particularly limited, but examples include azo polymerization initiators, peroxide polymerization initiators (e.g., persulfates such as dibenzoyl peroxide, tert-butyl permaleate, potassium persulfate, benzoyl peroxide, hydrogen peroxide, etc.), substituted ethane initiators such as phenyl-substituted ethane, aromatic carbonyl compounds, redox polymerization initiators, etc. Among these, the azo polymerization initiator disclosed in Japanese Patent Application Publication No. 2002-69411 is preferred. Examples of the above-mentioned azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid)dimethyl, and 4,4'-azobis-4-cyanovaleric acid. The amount of thermal polymerization initiator used can be the usual amount, for example, it can be selected from a range of 0.01 to 5 parts by mass, preferably 0.05 to 3 parts by mass, per 100 parts by mass of monomer component.

[0089] The above-mentioned photopolymerization initiators are not particularly limited, but examples include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators. Other examples include acylphosphine oxide-based photopolymerization initiators and titanocene-based photopolymerization initiators. Examples of the above-mentioned benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, and anisole methyl ether. Examples of the above acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of the above α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of the above aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of the above photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime. Examples of the above benzoin-based photopolymerization initiators include benzoin. Examples of the above benzyl-based photopolymerization initiators include benzyl. Examples of the benzophenone-based photopolymerization initiators mentioned above include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. Examples of the ketal-based photopolymerization initiators mentioned above include benzyldimethyl ketal.Examples of the thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. Examples of the acylphosphine oxide-based photopolymerization initiators include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Examples of the titanocene-based photopolymerization initiators include bis(η. ５ Examples include (-2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium. The amount of photopolymerization initiator used can be the usual amount, for example, it can be selected from a range of 0.01 to 5 parts by mass, preferably 0.05 to 3 parts by mass, per 100 parts by mass of the monomer component.

[0090] The above acrylic polymer may contain structural components derived from a crosslinking agent. That is, the above acrylic polymer may be crosslinked with a crosslinking agent. By using a crosslinking agent, a crosslinked structure can be formed in the acrylic polymer, and the gel fraction can be controlled. When the above crosslinking agent is used, a crosslinked structure of the base polymer is formed in the adhesive layer, improving the cohesive force. Only one type of crosslinking agent may be used, or two or more types may be used.

[0091] The above-mentioned crosslinking agents are not particularly limited, but examples include isocyanate-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, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, amine-based crosslinking agents, hydrazine-based crosslinking agents, silicone-based crosslinking agents, and silane-based crosslinking agents (silane coupling agents).

[0092] As the carbodiimide crosslinking agent, for example, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, N,N'-dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, 1-ethyl-3-tert-butylcarbodiimide, N-cyclohexyl-N'-(2-morpholinoethyl)carbodiimide, N,N'-di-tert-butylcarbodiimide, 1,3-bis(p-tolyl)carbodiimide, and polycarbodiimide resins having these as monomers can be mentioned.

[0093] As commercially available products of the carbodiimide crosslinking agent, for example, trade name "Carbodilite V-03", trade name "Carbodilite V-05", trade name "Carbodilite V-07", trade name "Carbodilite V-09", trade name "Elastostab H01" (manufactured by Nisshinbo Chemical Co., Ltd., etc.) can be mentioned.

[0094] The content of the crosslinking agent is not particularly limited, but is preferably 0.001 to 50 parts by mass, more preferably 0.01 to 30 parts by mass, and particularly preferably 0.2 to 20 parts by mass with respect to 100 parts by mass of the total amount of the monomer components constituting the acrylic polymer.

[0095] (Electrolyte) The electrically peelable adhesive layer preferably contains an electrolyte. The electrolyte is a substance that can be ionized into anions and cations. Examples of the electrolyte include ionic substances, alkali metal salts, alkaline earth metal salts, organic quaternary ammonium salts, etc. From the viewpoint of realizing good electrical peelability, an ionic substance is preferable as the electrolyte. The electrolyte may be used alone or in combination of two or more.

[0096] The anion of the ionic substance is, for example, (FSO ２ [[]] ２ [[]] ２ [[]] ２ [[]] － [[]] ２ [[]] － [[]] ２ [[]] ３ [[]] ３ [[]] [[]]

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[0096] [[]]<000​​​​​​​​​​​​​​​​​​​２ N － (CF ３ SO ２ ) ３ C － , Br － AlCl ４ － Al ２ Cl ７ － NO ３ － BF ４ － , PF ６ － ,CH ３ COO － CF ３ COO － CF ３ CF ２ CF ２ COO － CF ３ SO ３ － CF ３ (CF ２ ) ３ SO ３ － AsF ６ － SbF ６ － , F (HF) ｎ － These are some examples. Among them, as anions, (FSO ２ ) ２ N － [Bis(fluorosulfonyl)imide anion], (CF ３ SO ２ ) ２ N － Anions of sulfonylime compounds such as [bis(trifluoromethanesulfonyl)imide anions] are commonly used because they are chemically stable and preferable for improving electrolysis properties. In other words, the anions of ionic substances are generally selected from the group consisting of bis(fluorosulfonyl)imide anions and bis(trifluoromethanesulfonyl)imide anions.

[0097] In the above-mentioned ionic substances, the cation is generally selected from the group consisting of nitrogen-containing onium cations, sulfur-containing onium cations, and phosphorus-containing onium cations, as this is preferable for chemical stability and good electrolysis properties. Imidazolium-based, ammonium-based, pyrrolidinium-based, and pyridinium-based cations are more commonly used.

[0098] 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, and 1-dodecyl-3-methylimidazolium cation. Examples include lium cations, 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, and 1,3-bis(dodecyl)imidazolium cation.

[0099] Examples of ammonium-based cations include tetraethylammonium cation, tetrabutylammonium cation, methyltrioctylammonium cation, tetradecyltrihexylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethyl acrylate cation.

[0100] Examples of pyrrolidinium-based cations include 1-ethyl-1-methylpyrrolidinium cation and 1-butyl-1-methylpyrrolidinium cation.

[0101] Examples of pyridinium-based cations include 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, and 1-octyl-4-methylpyridinium cation.

[0102] As for the above ionic material, from the viewpoint of significantly reducing the rate of decrease in adhesive strength when voltage is applied, cations with a molecular weight of 160 or less are generally used as constituent cations, and the above (FSO ２ ) ２ N － [Bis(fluorosulfonyl)imide anion] or (CF ３ SO ２ ) ２ N － Ionic substances containing a [bis(trifluoromethanesulfonyl)imide anion] and a cation with a molecular weight of 160 or less are particularly commonly used. Examples of cations with 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.

[0103] Furthermore, cations represented by the following formulas (2-A) to (2-D) are also commonly used as cations of the above-mentioned ionic substances.

[0104]

[0105] R in equation (2-A) １ R 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 heteroatoms. ２ and R ３ R represents the same or different 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, and even more preferably a hydrocarbon group having 2 to 4 carbon atoms), and may also contain heteroatoms. However, if the nitrogen atom forms a double bond with an adjacent carbon atom, ３ It does not exist.

[0106] R in equation (2-B) ４ R 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 heteroatoms. ５ , R ６ , and R ７ These represent, either identically or differently, 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, and even more preferably a hydrocarbon group having 2 to 4 carbon atoms), and may also contain heteroatoms.

[0107] R in equation (2-C) ８ R 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 heteroatoms. ９ , R １０ , and R １１ These represent, either identically or differently, 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 also contain heteroatoms.

[0108] In formula (2-D), X represents a nitrogen, sulfur, or phosphorus atom, and R １２ , R １３ , R １４ , and R １５R represents a hydrocarbon group having 1 to 16 carbon atoms, either identical or different, (preferably a hydrocarbon group having 1 to 14 carbon atoms, more preferably a hydrocarbon group having 1 to 10 carbon atoms, even more preferably a hydrocarbon group having 1 to 8 carbon atoms, and particularly preferably a hydrocarbon group having 1 to 6 carbon atoms), and may contain heteroatoms. However, if X is a sulfur atom, R １２ It does not exist.

[0109] The molecular weight of the cation in the above-mentioned ionic substance is, for example, 500 or less, preferably 400 or less, more preferably 300 or less, even more preferably 250 or less, even more preferably 200 or less, and particularly preferably 160 or less. It is also usually 50 or more. The cation in the ionic substance is thought to have the property of moving towards the cathode side when a voltage is applied in the electropenetrating adhesive layer, and becoming concentrated near the interface between the electropenetrating adhesive layer and the adherend. Therefore, the adhesive strength decreases during voltage application relative to the initial adhesive strength, resulting in electropenetration. Cationic substances with small molecular weights, such as 500 or less, are preferable because the movement of cations towards the cathode side in the electropenetrating adhesive layer is easier, and the rate of decrease in adhesive strength during voltage application is greater.

[0110] Examples of commercially available ionic substances include the product names "E1452", "E0599", "M2098", "M2980", "M2981", and "M2998" (all manufactured by Tokyo Chemical Industry Co., Ltd.), "HMI-FSI" (manufactured by Mitsubishi Materials Corporation), "CIL-312", and "CIL-313" (both manufactured by Nippon Carlit Co., Ltd.).

[0111] The above-mentioned ionic substance preferably comprises an anion and a cation, wherein the cation has a saturated alicyclic structure containing an N element, and the anion preferably contains an ionic substance that does not contain a trifluoromethane group (sometimes referred to as "ionic substance A"). If the anion of the ionic substance contains a trifluoromethane group, it may be subject to regulations as an organofluorine compound (PFAS). For this reason, even if the electropenetrating adhesive layer contains an ionic substance other than ionic substance A, it is preferable that the anion of the ionic substance does not contain a trifluoromethane group.

[0112] As an anion in the ionic substance A, (FSO ２ ) ２ N － , Br － , AlCl ４ － , Al ２ Cl ７ － , NO ３ － , BF ４ － , PF ６ － , CH ３ COO － , AsF ６ － , SbF ６ － , F(HF) ｎ － can be mentioned. Among these, (FSO ２ ) ２ N － is more preferable. Also, as a commercially available product of the ionic substance A containing such an anion, 1-Methyl-1-propylpyrrolidinium Bis(fluorosulfonyl)imide (manufactured by Tokyo Chemical Industry Co., Ltd.) can be mentioned.

[0113] The ionic conductivity of the ionic substance A is preferably 1.0×10 －４ mS / cm or more. The upper limit of the ionic conductivity is preferably 20 mS / cm, more preferably 15 mS / cm, and still more preferably 10 mS / cm. The lower limit of the ionic conductivity is more preferably 1 mS / cm, still more preferably 3 mS / cm, and particularly preferably 5 mS / cm. When the ionic conductivity is 1.0×10 －４ mS / cm or more, it is preferable because the adhesive force sufficiently decreases after voltage application. When the ionic conductivity is 20 mS / cm or less, the influence of a weak current from the outside is suppressed, and electrical peeling can be achieved only when a voltage is intentionally applied, which is preferable.

[0114] When the ionic conductivity is 1.0×10 －４Ionic substances with a molecular weight of mS / cm or higher include imidazolium, pyridinium, pyrrolidinium, piperidinium, or ammonium cations with a molecular weight of 160 or less, and anions (FSO ２ ) ２ N － (CF ３ SO ２ ) ２ N － , Cl － , Br － BF ４ － , or PF ６ － Examples include combinations of the following: Of these, 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide, 1-(2-ethoxymethyl)-1-methylpyrrolidinium bis(fluorosulfonyl)imide, 1-(2-methoxyethyl)-1-methylpyrrolidinium bis(fluorosulfonyl)imide, 1-methyl-1-(2-propen-1-yl)pyrrolidinium bis(fluorosulfonyl)imide, and 1-methyl-1-propylpiperidinium bis(fluorosulfonyl)imide are preferred, and 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide is more preferred. Furthermore, commercially available examples of such ionic substance A include 1-Methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (manufactured by Tokyo Chemical Industry Co., Ltd.) and N-Methyl-N-propylpiperidinium bis(fluorosulfonyl)imide (manufactured by Kanto Chemical Co., Ltd.).

[0115] The above ionic conductivity can be measured, for example, using the AC impedance method with a Solartron 1260 frequency response analyzer.

[0116] The content (amount blended) of the ionic substance A in the electropenetrating adhesive layer is preferably 0.5 parts by mass or more, more preferably 0.6 parts by mass or more, even more preferably 0.8 parts by mass or more, even more preferably 1.0 part by mass or more, and particularly preferably 1.5 parts by mass or more, per 100 parts by mass of the base polymer, from the viewpoint of sufficiently reducing the adhesive force during voltage application. From the viewpoint of further increasing the initial adhesive force, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less.

[0117] As the above-mentioned ionic substance, only one type of ionic substance A may be used, two or more types of ionic substance A may be used in combination, or ionic substance A may be used in combination with other ionic substances other than ionic substance A. When ionic substance A is used in combination with the above-mentioned other ionic substances, from the viewpoint of exhibiting a function in which the adhesive strength is sufficiently reduced by the application of voltage even in a low humidity environment, the total content of the ionic substances per 100 parts by mass of the base polymer is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more. Furthermore, the total content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. When two or more types of ionic substances are used in combination, it is preferable to use 2 to 5 types of ionic substances, including ionic substances other than ionic substance A, more preferably 2 to 3 types of ionic substances, and even more preferably 2 types of ionic substances.

[0118] The electrolyte content (amount blended) in the above electropenetrating adhesive layer is preferably 0.5 parts by mass or more, more preferably 0.6 parts by mass or more, even more preferably 0.8 parts by mass or more, even more preferably 1.0 part by mass or more, and particularly preferably 1.5 parts by mass or more, per 100 parts by mass of the base polymer, from the viewpoint of further reducing the adhesive force during voltage application. From the viewpoint of further increasing the initial adhesive force, the above content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less.

[0119] (Corrosion inhibitor) The above-mentioned electropenetrating adhesive layer preferably contains a corrosion inhibitor. Examples of the above-mentioned corrosion inhibitor include carbodiimide compounds, adsorption-type inhibitors, and chelate-forming metal deactivators. One type of corrosion inhibitor may be used, or two or more types may be used.

[0120] Corrosion of the metal surface is caused by the interaction of carboxyl groups that may be present in the base polymer with cations of ionic substances, resulting in H₂ ＋ One possible cause is that it reacts with the metal, but in the presence of the above carbodiimide compound, the above carboxyl group reacts with the carbodiimide compound and the carboxyl group disappears, H ＋ Since the occurrence of [unclear] is suppressed, corrosion is thought to be suppressed. The above carbodiimide compound also functions as a crosslinking agent, and those exemplified as carbodiimide-based crosslinking agents described above can be used. The content (amount blended) of the above carbodiimide compound is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.2 parts by mass or more, and particularly preferably 0.5 parts by mass or more, per 100 parts by mass of the base polymer. Furthermore, from the viewpoint of achieving higher initial adhesive strength, the above content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, even more preferably 4 parts by mass or less, and particularly preferably 2 parts by mass or less.

[0121] The above-mentioned adsorption-type inhibitor is a compound that physically or chemically adsorbs onto a metal surface to form a protective film and prevent metal corrosion. Examples of the above-mentioned adsorption-type inhibitor include alkylamines, carboxylates, carboxylic acid derivatives, and alkyl phosphates. One type of the above-mentioned adsorption-type inhibitor may be used, or two or more types may be used.

[0122] Examples of alkylamines include primary amines, secondary amines, and tertiary amines. Examples of alkylamines include amines having an alkyl group with 1 to 25 carbon atoms, preferably amines having an alkyl group with 3 to 20 carbon atoms. The alkyl group may have a branched chain or be cyclic, such as a cycloalkyl group, but a linear alkyl group is preferred. The alkyl group may also have substituents, such as a hydroxyl group, a carboxyl group, and an alkoxy group. In particular, it is preferable that the alkyl group does not have substituents. Examples of primary amines include propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, laurylamine, tridecylamine, tetradecylamine, pentadecylamine, stearylamine, heptadecylamine, and octadecylamine. Examples of the above secondary amines include dicyclohexylamine, diethylamine, dipropylamine, dibutylamine, dihexylamine, dilaurylamine, distearylamine, and diethanolamine. Examples of the above tertiary amines include imidazoline derivatives, trimethylamine, triethylamine, tripropylamine, tributylamine, dimethyloctylamine, dimethyldecylamine, dimethyllaurylamine, dimethyloctylamine, dimethylcoconutamine, dimethylmyristylamine, dimethylpalmitylamine, dimethylstearylamine, dimethylbehenylamine, dilaurylmonomethylamine, and N,N,N',N'-tetramethyl-2,2-dimethyl-1,3-propanediamine.

[0123] The amount of alkylamine (blended amount) is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.2 parts by mass or more, even more preferably 0.5 parts by mass or more, and particularly preferably 0.8 parts by mass or more, per 100 parts by mass of the base polymer. From the viewpoint of having high initial adhesive strength and being able to sufficiently reduce adhesive strength when voltage is applied, the above content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

[0124] Examples of the carboxylate salts mentioned above include disodium sebacate and other sodium salts. The content (amount blended) of the carboxylate salt is preferably 0.01 parts by mass or more per 100 parts by mass of the base polymer. From the viewpoint of having high initial adhesive strength and being able to sufficiently reduce adhesive strength when voltage is applied, the content is preferably 10 parts by mass or less.

[0125] Examples of the carboxylic acid derivatives mentioned above include succinic acid derivatives such as alkenyl succinic acid half-esters. The content (amount blended) of the carboxylic acid derivative is preferably 0.01 parts by mass or more per 100 parts by mass of the base polymer. From the viewpoint of having high initial adhesive strength and being able to sufficiently reduce adhesive strength when voltage is applied, the content is preferably 10 parts by mass or less.

[0126] The content (amount blended) of the alkyl phosphate is preferably 0.01 parts by mass or more per 100 parts by mass of the base polymer. From the viewpoint of having high initial adhesive strength and being able to sufficiently reduce adhesive strength when voltage is applied, the content is preferably 10 parts by mass or less.

[0127] The above-mentioned chelate-forming metal deactivators are compounds that prevent metal corrosion by forming a protective film on the metal surface through the formation of complex salts. Examples of the above-mentioned chelate-forming metal deactivators include triazole group-containing compounds and benzotriazole group-containing compounds. These are preferred because they have a high deactivating effect on the surface of metals such as aluminum, and they do not significantly affect the adhesiveness when included in adhesive components.

[0128] Examples of the above triazole group-containing compounds include 1,2,4-triazole, 1,2,3-triazole, 4-amino-1,2,4-triazole, and N,N-bis(2-ethylhexyl)-1,2,4-triazole-1-ylmethaneamine. Examples of the benzotriazole group-containing compounds mentioned above include 1,2,3-benzotriazole, methylbenzotriazole, potassium methylbenzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl)benzotriazole, 3-(N-salicyroyl)amino-1,2,4-triazole, 2,2'-[[(methyl-1H-benzotriazole-1-yl)methyl]imino]bisethanol, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 1-(methoxymethyl)-1H-benzotriazole, 1H-benzotriazole-1-methanol, and 1-(chloromethyl)-1H-benzotriazole.

[0129] The content (amount blended) of the above-mentioned chelate-forming metal deactivator is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.2 parts by mass or more, even more preferably 0.5 parts by mass or more, and particularly preferably 0.8 parts by mass or more, per 100 parts by mass of the base polymer. From the viewpoint of having high initial adhesive strength and being able to sufficiently reduce adhesive strength when voltage is applied, the above content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 9 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less.

[0130] The total content (amount blended) of the above corrosion inhibitor is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.2 parts by mass or more, even more preferably 0.5 parts by mass or more, and particularly preferably 0.8 parts by mass or more, per 100 parts by mass of the base polymer. From the viewpoint of increasing initial adhesive strength, the above content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less.

[0131] The above-mentioned electropenetrating adhesive layer may optionally contain polyethylene glycol to assist in the movement of electrolytes when voltage is applied. Polyethylene glycol with a number-average molecular weight of 200 to 6000 can be used. When polyethylene glycol is included, the content is preferably 0.1 to 30 parts by mass per 100 parts by mass of the base polymer.

[0132] The electropenetrating adhesive layer may optionally contain a conductive filler for the purpose of imparting conductivity to the electropenetrating adhesive layer. The conductive filler is not particularly limited, and general known or conventional conductive fillers can be used, such as graphite, carbon black, carbon fiber, or metal powders such as silver or copper. When the conductive filler is included, the content is preferably 0.1 to 200 parts by mass per 100 parts by mass of the base polymer.

[0133] The above-mentioned electropenetrating adhesive layer may optionally contain additives such as tackifiers, crosslinking accelerators, antioxidants, antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, flame retardants, leveling agents, light stabilizers, ultraviolet absorbers, fillers, polymerization inhibitors, foil-like materials, rust inhibitors, and colorants (dyes, pigments, etc.), to the extent that they do not impair the effects of the present invention. Each of the above additives may be used individually or in combination of two or more. The total content of the above additives is not particularly limited, but is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the base polymer. The total content may also be 0.01 parts by mass or more.

[0134] The thickness of the electropenetrating adhesive layer (the thickness of the electropenetrating adhesive layer on one main surface of a double-sided adhesive sheet) is preferably 1 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, even more preferably 40 μm or more, and particularly preferably 50 μm or more. When the thickness is 1 μm or more, the initial adhesive strength is higher, and the adhesive strength decreases sufficiently when voltage is applied. The thickness is preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 300 μm or less, and particularly preferably 200 μm or less.

[0135] The above-mentioned electropenetrating adhesive layer may be in any form, for example, an emulsion type, a solvent type (solution type), an active energy ray curing type, or a hot melt type. Among these, solvent-type and active energy ray curing types of adhesive layers are preferred because they make it easier to obtain an adhesive layer with excellent productivity.

[0136] Examples of the active energy rays mentioned above include ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams, as well as ultraviolet rays, with ultraviolet rays being particularly preferred. In other words, the active energy ray-curable adhesive layer is preferably an ultraviolet-curable adhesive layer.

[0137] (Double-sided adhesive sheet) The double-sided adhesive sheet of the present invention has a tensile modulus E' of 120 MPa or less at 25°C, preferably 100 MPa or less, more preferably 80 MPa or less, even more preferably 60 MPa or less, and particularly preferably 40 MPa or less. If the above tensile modulus E' is low, it is presumed that the electrolyte in the electropenetrating adhesive layer is likely to migrate into the substrate, and the adhesive strength is likely to decrease sufficiently when a voltage is applied. The above tensile modulus E' may be, for example, 0.1 MPa or more, and may also be 1 MPa or more.

[0138] The double-sided adhesive sheet of the present invention has a volume resistivity of 1.0 × 10⁻¹⁰ after being stored at 80°C for 3 days after manufacturing. ６ It is preferable that the density is Ω·cm or greater, and more preferably 1.0 × 10⁻⁶. ７ Ω·cm or more, more preferably 1.0 × 10⁻⁶ ８ It is greater than Ω·cm. The volume resistivity is 1.0 × 10⁻⁶. ６If the volume resistivity is greater than Ω·cm, the adhesive strength is likely to decrease significantly when voltage is applied. The above volume resistivity is, for example, 1.0 × 10⁻⁶. ２０ It is less than or equal to Ω·cm. Furthermore, it is preferable that the volume resistivity after storage at 80°C for 8 days after preparation is within the above range. The volume resistivity of the above double-sided adhesive sheet is a value measured based on the double-ring method of JIS K6271-1, and can be measured specifically as described in the examples.

[0139] The double-sided adhesive sheet of the present invention preferably satisfies the following formulas (1) and / or (2) from the viewpoint of having high initial adhesive strength and being able to sufficiently reduce adhesive strength by applying voltage: 0.01 ≤ [thickness of substrate / total thickness of electrorelease adhesive layer] < 3 (1) 0.005 ≤ [thickness of substrate / thickness of electrorelease adhesive layer on one main surface] < 6 (2)

[0140] In formula (1) above, the "total thickness of the electropenetrating adhesive layer" is the sum of the thicknesses of the electropenetrating adhesive layers on both main surfaces if they are formed on both main surfaces of the substrate. The above [thickness of the substrate / total thickness of the electropenetrating adhesive layer] is 0.01 or more and less than 3, preferably 0.03 to 2.7.

[0141] In formula (2) above, "thickness of the electrorelease adhesive layer on one main surface" refers to the thickness of the electrorelease adhesive layer formed on one main surface of the substrate (total thickness in the case of multiple layers). If the substrate has electrorelease adhesive layers on both main surfaces, it is sufficient that formula (2) is satisfied for at least one of the two electrorelease adhesive layers formed on both main surfaces of the substrate, or it is acceptable for formula (2) to be satisfied for both electrorelease adhesive layers on both main surfaces.

[0142] In formula (2) above, the [thickness of the substrate / thickness of the electropenetrating adhesive layer on one main surface] is 0.005 or more and less than 6, preferably 0.01 to 5.7, and more preferably 0.1 to 5.3.

[0143] The double-sided adhesive sheet of the present invention preferably satisfies the following formulas (3) and / or (4) from the viewpoint of having high initial adhesive strength and readily reducing adhesive strength upon voltage application. In the following formulas (3) and (4), "W1" represents the ratio [mass%] of the isocyanate component, which is a hard segment, to 100% by mass of the urethane resin in the polyurethane resin that may be contained in the substrate. [W1 × thickness of substrate / total thickness of electro-release adhesive layer] < 84 (3) [W1 × thickness of substrate / thickness of electro-release adhesive layer on one main surface] < 168 (4)

[0144] In formula (3) above, the "total thickness of the electropenetrating adhesive layer" is the sum of the thicknesses of the electropenetrating adhesive layers on both main surfaces if they are formed on both main surfaces of the substrate. The above [W1 × thickness of substrate / total thickness of electropenetrating adhesive layer] is less than 84, preferably 70 or less, more preferably 60 or less, even more preferably 50 or less, and particularly preferably 40 or less. The above [W1 × thickness of substrate / total thickness of electropenetrating adhesive layer] is, for example, 0.1 or more.

[0145] In formula (4) above, "thickness of the electrorelease adhesive layer on one main surface" refers to the thickness of the electrorelease adhesive layer formed on one main surface of the substrate (total thickness in the case of multiple layers). If the substrate has electrorelease adhesive layers on both main surfaces, it is sufficient that formula (4) is satisfied for at least one of the two electrorelease adhesive layers formed on both main surfaces of the substrate, or it is acceptable for formula (4) to be satisfied for both electrorelease adhesive layers on both main surfaces.

[0146] In formula (4) above, the value of [W1 × thickness of the substrate / thickness of the electropenetrating adhesive layer on one main surface] is less than 168, preferably 140 or less, more preferably 120 or less, even more preferably 100 or less, and particularly preferably 80 or less. The value of [W1 × thickness of the substrate / thickness of the electropenetrating adhesive layer on one main surface] is, for example, 0.1 or more.

[0147] The double-sided adhesive sheet of the present invention preferably satisfies the following formulas (5) and / or (6) from the viewpoint of having high initial adhesive strength and readily reducing adhesive strength upon voltage application. In the following formulas (5) and (6), "W2" represents the total ratio of the M component and the L component, which are the hard segment phase, the hard-soft interface, and the soft segment phase, in the polyurethane resin that may be contained in the substrate, as measured by the Solic-echo method using TD-NMR. [Thickness of substrate / Total thickness of electro-peelable adhesive layer / W2] < 4.1 (5) [Thickness of substrate / Thickness of electro-peelable adhesive layer on one main surface / W2] < 8.2 (6)

[0148] In formula (5) above, the "total thickness of the electrorelease adhesive layer" is the sum of the thicknesses of the electrorelease adhesive layers on both main surfaces if they are formed on both main surfaces of the substrate. The above [substrate thickness / total thickness of the electrorelease adhesive layer / W2] is less than 4.1, preferably 4 or less, and more preferably 3 or less. The above [substrate thickness / total thickness of the electrorelease adhesive layer / W2] is, for example, 0.01 or more.

[0149] In formula (6) above, "thickness of the electrorelease adhesive layer on one main surface" refers to the thickness of the electrorelease adhesive layer formed on one main surface of the substrate (total thickness in the case of multiple layers). If the substrate has electrorelease adhesive layers on both main surfaces, it is sufficient that formula (6) is satisfied for at least one of the two electrorelease adhesive layers formed on both main surfaces of the substrate, or it is acceptable for formula (6) to be satisfied for both electrorelease adhesive layers on both main surfaces.

[0150] In formula (6) above, the value of [thickness of the substrate / thickness of the electropenetrating adhesive layer on one main surface / W2] is less than 8.2, preferably 8 or less, more preferably 7 or less, and even more preferably 6 or less. The value of [thickness of the substrate / thickness of the electropenetrating adhesive layer on one main surface / W2] is, for example, 0.01 or more.

[0151] The double-sided adhesive sheet of the present invention preferably has an adhesive strength (normal peel strength) of 0.05 N / mm or more, more preferably 0.1 N / mm or more, and even more preferably 0.5 N / mm or more, in a 180° peel test (tensile speed: 300 mm / min, peel temperature 22°C, humidity 50% RH) against a stainless steel plate (SUS316) on at least one adhesive surface (preferably both adhesive surfaces). When the above normal peel strength is 0.05 N / mm or more, the initial adhesive strength tends to be high. When measuring the above normal peel strength, a plastic film such as a PET film may be backed on the adhesive surface opposite to the side that is bonded to the stainless steel plate. Specifically, the above normal peel strength can be measured by the method described in the examples.

[0152] The double-sided adhesive sheet of the present invention preferably has an adhesive strength (electropeel strength (A)) of 0.5 N / mm or less, more preferably 0.4 N / mm or less, and even more preferably 0.3 N / mm or less, in a 180° peel test (tensile speed: 300 mm / min, peel temperature 22°C, humidity 50% RH) on the stainless steel plate after a conductive member is bonded to one adhesive surface and a stainless steel plate (SUS316) is bonded to the other adhesive surface and a voltage of 30 V is applied for 30 seconds. When the electropeel strength (A) is 0.5 N / mm or less, the electropeelability is superior. Furthermore, it is preferable that the electropeel strength (B) after a voltage of 30 V is applied for 120 seconds, the electropeel strength (C) after a voltage of 30 V is applied for 300 seconds, or the electropeel strength (D) after a voltage of 30 V is applied for 600 seconds is within the above range. Furthermore, if the substrate has electropenetrating adhesive layers on both main surfaces, it is preferable that the electropenetrating force of the electropenetrating adhesive layers on both main surfaces is within the above range. When measuring the electropenetrating force, a plastic film such as a PET film may be backed on the conductive substrate on the side opposite to the side that is bonded to the stainless steel plate, via a non-conductive adhesive sheet. Specifically, the electropenetrating force can be measured by the method described in the examples.

[0153] The double-sided adhesive sheet of the present invention preferably contains 0.1% by mass or more of electrolyte in the substrate after the electrorelease adhesive layer has been removed, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. When the amount of electrolyte is 0.1% by mass or more, the adhesive strength is easily reduced by the application of voltage. Furthermore, it is preferable that the amount of ionic substance is within the above range. The amount of electrolyte can be measured by freeze-pulverizing the substrate after the electrorelease adhesive layer has been removed, immersing it in an organic solvent, extracting the solution, and then applying it to an LC / MS. Specifically, the amount of electrolyte can be measured by the method described in the examples.

[0154] The double-sided adhesive sheet of the present invention preferably contains 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, in the substrate after the electropenetrating adhesive layer has been removed by electrolysis following adhesion to an adherend. When the amount of electrolyte is 0.1% by mass or more, the adhesive strength is easily reduced by voltage application. Furthermore, it is preferable that the amount of ionic substance is within the above range. The amount of electrolyte can be measured by freeze-drying the substrate after the electropenetrating adhesive layer has been removed from the electropenetrating double-sided adhesive sheet, immersing it in an organic solvent, extracting the solution, and then applying it to an LC / MS. Specifically, the amount of electrolyte can be measured by the method described in the examples.

[0155] The thickness of the double-sided adhesive sheet of the present invention is preferably 20 μm or more, more preferably 30 μm or more, even more preferably 50 μm or more, and may be 60 μm or more, 70 μm or more, 80 μm or more, 90 μm or more, or 100 μm or more. The above thickness is preferably 3000 μm or less, more preferably 1000 μm or less, and even more preferably 500 μm or less. The above thickness of the double-sided adhesive sheet refers to the thickness from one adhesive surface to the other adhesive surface, i.e., the thickness of the adhesive, and does not include the release liner.

[0156] The double-sided adhesive sheet of the present invention may have a release liner attached to the surface (adhesive surface) of the electro-peelable adhesive layer until use. Each adhesive surface of the double-sided adhesive sheet may be protected by two release liners, or it may be protected in a roll-like form (winding body) by a single release liner with release surfaces on both sides. The release liner is used as a protective material for the electro-peelable adhesive layer and is peeled off when it is attached to the substrate. Note that the release liner is not necessarily required.

[0157] The above-mentioned release liner can be conventional release paper or the like, and is not particularly limited, but examples include a substrate having a release treatment layer, a low-adhesion substrate made of a fluoropolymer, or a low-adhesion substrate made of a nonpolar polymer. Examples of the substrate having the release treatment layer include plastic films and paper surface-treated with release agents such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide. Examples of fluorine-based polymers in the low-adhesion substrate made of a fluoropolymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorofluoroethylene-vinylidene fluoride copolymer. Examples of the above-mentioned nonpolar polymer include olefin resins (e.g., polyethylene, polypropylene, etc.). The release liner can be formed by known or conventional methods. The thickness of the release liner is also not particularly limited.

[0158] The double-sided adhesive sheet of the present invention can be manufactured by known or conventional manufacturing methods. The double-sided adhesive sheet of the present invention may be obtained by directly forming the electrorelease adhesive layer on the surface of the substrate (direct transfer method), or by first forming the electrorelease adhesive layer on a release liner and then transferring (bonding) it to the substrate to provide the electrorelease adhesive layer on the substrate (transfer method). When forming the electrorelease adhesive layer on the substrate by the transfer method, it is preferable to pressurize and heat the substrate and the electrorelease adhesive layer in a laminated state from the viewpoint of suppressing peeling between the substrate and the electrorelease adhesive layer and exhibiting high initial adhesive strength. Furthermore, the double-sided adhesive sheet of the present invention can also be manufactured by the following manufacturing method of the adhesive sheet of the present invention.

[0159] [Method for Manufacturing an Adhesive Sheet] The present invention relates to a method for manufacturing an adhesive sheet comprising a base material and an adhesive layer provided on at least one main surface of the base material. The manufacturing method comprises a bonding step of bonding the base material and the adhesive layer. In the bonding step, one of the base material and the adhesive layer to be bonded contains an electrolyte, and the other does not contain the electrolyte. That is, in the bonding step, either a base material containing an electrolyte is bonded to an adhesive layer that does not contain the electrolyte, or a base material that does not contain an electrolyte is bonded to an adhesive layer that contains the electrolyte.

[0160] Furthermore, the above manufacturing method includes a transfer step in which the electrolyte is transferred from one of the materials to the other during or after the bonding step. The transfer of the electrolyte proceeds over time by bonding the substrate and the adhesive layer. Therefore, the transfer step does not need to be performed actively. Also, since the transfer step proceeds over time, it can occur during the bonding step, after the bonding step, or both. In the transfer step, the electrolyte is transferred from the substrate containing the electrolyte to the adhesive layer that does not contain the electrolyte, or from the adhesive layer containing the electrolyte to the substrate. In addition, the other of the substrate and the adhesive layer that does not contain the electrolyte may contain an electrolyte other than the electrolyte to be transferred (i.e., the electrolyte contained in one of the materials).

[0161] The substrate used in the above manufacturing method may be a conductive substrate or a non-conductive substrate (for example, the substrate in the double-sided adhesive sheet of the present invention). The substrate may be a single layer or a laminate of the same or different types of substrates. The adhesive layer may be an electropenetrating adhesive layer or an adhesive layer that does not exhibit electropenetration. An example of the adhesive layer that does not exhibit electropenetration is an adhesive layer that does not contain the electrolyte of the electropenetrating adhesive layer.

[0162] The adhesive sheet obtained by the above manufacturing method may be a single-sided adhesive sheet or a double-sided adhesive sheet having adhesive layers on both main surfaces of the base material. In the case of a double-sided adhesive sheet in which the adhesive layer before bonding contains the electrolyte, it is sufficient that at least one of the two adhesive layers contains the electrolyte, or both may contain the electrolyte.

[0163] For example, when manufacturing the double-sided adhesive sheet of the present invention by the above manufacturing method, the electrorelease adhesive layer and the substrate are bonded together. As a result, the electrolyte in the electrorelease adhesive layer migrates into the substrate, and the substrate in the double-sided adhesive sheet contains the electrolyte. Alternatively, an adhesive layer without electrolyte may be formed on both main surfaces of a substrate into which the electrolyte has been injected, and the electrolyte may be migrated from the substrate to the adhesive layer to subsequently form an electrorelease adhesive layer. In this way, a double-sided adhesive sheet is obtained comprising a substrate containing an electrolyte and an electrorelease adhesive layer provided on at least one main surface of the substrate.

[0164] [Removal Method] The double-sided adhesive sheet of the present invention can be removed from an adherend by applying a voltage to the electro-removable adhesive layer, thereby creating a potential difference in the thickness direction of the electro-removable adhesive layer. For example, a joint in which the double-sided adhesive sheet of the present invention is attached to conductive adherends A and B can be removed from the adherends by energizing conductive adherends A and B and applying a voltage to the electro-removable adhesive layer. It is preferable to connect terminals to one end and the other end of the double-sided adhesive sheet so that the voltage is applied to the entire electro-removable adhesive layer. Note that if the adherend has a metal adherend, the one end and the other end may be parts of the adherend having a metal adherend. Note that when removing the adhesive, water may be added to the interface between the adherend surface of the conductive adherend and the electro-removable adhesive layer before applying the voltage.

[0165] Conventional re-peelable technologies include adhesive layers that harden and peel off with ultraviolet (UV) irradiation or adhesive layers that peel off with heat. However, adhesive sheets using such adhesive layers cannot be used when UV irradiation is difficult or when heat would damage the adherend. The double-sided adhesive sheet of the present invention does not use ultraviolet light or heat, and can therefore be easily peeled off by applying voltage without damaging the adherend.

[0166] [Applications] The double-sided adhesive sheet of the present invention is preferably used for attaching electrical and electronic components, by being bonded to components provided in electrical and electronic equipment. The double-sided adhesive sheet is preferably used for bonding components provided in electrical and electronic equipment to both adhesive surfaces, that is, for fixing components together in electrical and electronic equipment. The double-sided adhesive sheet may be used for fixing components together or for temporary fixing. For example, when a double-sided adhesive sheet is used for fixing or temporarily fixing components provided in electrical and electronic equipment, there may be cases where the double-sided adhesive sheet must be peeled off and reworked due to a problem in the application process, or where the double-sided adhesive sheet must be peeled off in order to repair, replace, inspect, or recycle a component to which the double-sided adhesive sheet has been bonded. Thus, when a double-sided adhesive sheet is used, for example, for fixing or temporarily fixing components provided in electrical and electronic equipment, the frequency of removing the double-sided adhesive sheet is particularly high.

[0167] Furthermore, "electrical and electronic equipment" refers to equipment that falls under either the category of electrical equipment or electronic equipment. Examples of such electrical and electronic equipment include image display devices such as liquid crystal displays, electroluminescent displays, and plasma displays, as well as portable electronic devices.

[0168] Examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (e.g., wristwear-type devices worn on the wrist like watches, modular-type devices attached to a part of the body with clips or straps, eyewear-type devices including glasses (monocular and binocular types, including head-mounted types), clothing-type devices attached to shirts, socks, hats, etc. as accessories, earwear-type devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game consoles, electronic dictionaries, electronic organizers, e-books, in-car information systems, portable radios, portable televisions, portable printers, portable scanners, and portable modems. In this specification, "portable" means not merely being able to carry something, but having a level of portability that allows an individual (a typical adult) to carry it relatively easily. The above-mentioned double-sided adhesive sheet is used, for example, so that the electro-peelable adhesive layer adheres closely to the components of the above-mentioned portable electronic device.

[0169] The double-sided adhesive sheet of the present invention is particularly preferred for applications such as fixing secondary batteries (e.g., lithium-ion battery packs) to their casings.

[0170] Figure 2 schematically shows an example of a portable electronic device (smartphone) in which the double-sided adhesive sheet of the present invention is used to bond the battery and the casing. As shown in Figure 2, a battery (heat-generating element) 9 is built into the casing 8 of the portable electronic device 7. The portable electronic device 7 is also constructed with the double-sided adhesive sheet 1, which is the double-sided adhesive sheet of the present invention. In this example, the double-sided adhesive sheet 1 has the form of a double-sided adhesive sheet that fixes the components constituting the portable electronic device 7, specifically the casing 8 and the battery 9. The portable electronic device 7 is equipped with a touch panel 10 in which the display unit also functions as an input unit.

[0171] Furthermore, examples of materials that can be bonded using the double-sided adhesive sheet of the present invention include rigid members such as silicon substrates for semiconductor wafer applications, sapphire substrates, SiC substrates and metal base substrates for LEDs, TFT substrates and color filter substrates for displays, and base substrates for organic EL panels. In addition, examples of materials that can be bonded using the double-sided adhesive sheet of the present invention include semiconductor substrates such as compound semiconductor substrates, silicon substrates for MEMS devices, passive matrix substrates, surface cover glass for smartphones, OGS (One Glass Solution) substrates with touch panel sensors attached to the cover glass, organic substrates mainly composed of silsesquioxane and organic-inorganic hybrid substrates, flexible glass substrates for flexible displays, and fragile members such as graphene sheets.

[0172] [Bonded Body] The double-sided adhesive sheet of the present invention can be bonded to a conductive material to obtain a bonded body. The bonded body comprises the double-sided adhesive sheet of the present invention and a conductive material, wherein the electropenetrating adhesive layer of the double-sided adhesive sheet is bonded to the conductive material. The conductive material is preferably a substrate having a metal adhesion surface. Examples of substrates having a metal adhesion surface include those made of metals mainly composed of aluminum, copper, iron, magnesium, tin, gold, silver, lead, etc. Among these, metals containing aluminum are preferred.

[0173] Examples of the above-mentioned bonded body include a bonded body in which the double-sided adhesive sheet of the present invention and both electro-peelable adhesive layers of the double-sided adhesive sheet are attached to a conductive adherend having, for example, a metal adherend surface.

[0174] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples. The weight-average molecular weights below were measured by the method described above using gel permeation chromatography (GPC).

[0175] Example 1 (Preparation of Acrylic Polymer Solution) 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 placed in a separable flask and stirred for 1 hour while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and the mixture was heated to 63°C and reacted for 6 hours. Then, ethyl acetate was added to obtain an acrylic polymer solution with a solid content of 30% by mass. The weight-average molecular weight of the obtained acrylic polymer was 700,000.

[0176] (Preparation of electropenetrating adhesive layer) To the acrylic polymer solution obtained above, add 0.4 parts by mass of a crosslinking agent (polycarbodiimide resin, trade name "Carbodilite V-05", manufactured by Nisshinbo Chemical Co., Ltd.) per 100 parts by mass of the acrylic polymer, 3 parts by mass of an ionic substance trade name "E1452" (cation: 1-ethyl-3-methylimidazolium cation, anion: bis(fluorosulfonyl)imide anion, manufactured by Tokyo Chemical Industry Co., Ltd., ionic conductivity 16.5 mS / cm), and ETHYLMETHYLPYRROLIDINIUM BIS(FLUOROSULFONYL)IMIDE (cation: 1-ethyl-1-methylpyrrolidinium, anion: bis(fluorosulfonyl)imide anion, manufactured by Boron Molecular Inc., ionic conductivity 1.2 × 10⁻⁶). －３Two parts by mass of (mS / cm), four parts by mass of the additive (corrosion inhibitor) "Amine O" (2-(8-heptadecene-1-yl)-4,5-dihydro-1H-imidazole-1-ethanol, manufactured by BASF Japan Ltd.), 0.1 parts by mass of the additive (corrosion inhibitor) "Irgacor DSSG" (sodium sebacate, manufactured by BASF Japan Ltd.), one part by mass of the additive "Irgamet 30" (N,N-bis(2-ethylhexyl)[(1,2,4-triazole-1-yl)methyl]amine, manufactured by BASF Japan Ltd.), and ethyl acetate were added, stirred, mixed, and adjusted to a solid content concentration of 25% by mass to obtain an electrolytic adhesive composition (solution). The obtained electro-peelable adhesive composition (solution) was applied to the peel-treated surface of a polyethylene terephthalate peel-off liner (product name "MRF38", manufactured by Mitsubishi Chemical Corporation) using an applicator to achieve a uniform thickness. Next, it was heated and dried at 150°C for 3 minutes, and the peel-treated surface of the polyethylene terephthalate peel-off liner (product name "MRE38", manufactured by Mitsubishi Chemical Corporation) was laminated onto the adhesive using a hand roller to obtain an electro-peelable adhesive layer with a thickness of 60 μm.

[0177] (Preparation of double-sided adhesive sheet) One release liner of the electro-peelable adhesive layer obtained above was peeled off, and a 15 μm thick TPU film (composition ratio of diphenylmethane diisocyanate (MDI) 28% by mass, poly(tetramethylene glycol) (PTMG) 2% by mass, 1,4-butanediol (BD) 24% by mass, 1,6-hexanediol (HD) 13% by mass, adipic acid (AD) 33% by mass) was placed on the exposed surface and laminated using a hand roller. Next, another electro-peelable adhesive layer obtained above was prepared, and one release liner was peeled off in the same way, and the exposed surface was placed on the side of the TPU film that was not bonded with the electro-peelable adhesive layer, and laminated using a hand roller. The resulting three-layer adhesive sheet was then heat-pressed twice using a thermal laminator (MRK-650Y model, speed 1.0 m / min, temperature 90°C, pressure 0.5 MPa). Through these steps, the double-sided adhesive sheet of Example 1 was produced.

[0178] Example 2 A double-sided adhesive sheet was prepared in the same manner as in Example 1, except that the thickness of the electropenetrating adhesive layer was changed to 120 μm.

[0179] Example 3 A double-sided adhesive sheet was prepared in the same manner as in Example 1, except that the thickness of the electropenetrating adhesive layer was changed to 25 μm and the thickness of the TPU film was changed to 150 μm.

[0180] Example 4 A double-sided adhesive sheet was prepared in the same manner as in Example 1, except that the thickness of the TPU film was changed to 150 μm.

[0181] Example 5 A double-sided adhesive sheet was prepared in the same manner as in Example 1, except that the thickness of the TPU film was changed to 100 μm.

[0182] Example 6 A double-sided adhesive sheet was prepared in the same manner as in Example 1, except that a 100 μm thick TPU film (composition ratio of diphenylmethane diisocyanate (MDI) 34% by mass, 1,4-butanediol (BD) 33% by mass, and adipic acid (AD) 33% by mass) was used as the substrate.

[0183] Example 7 A double-sided adhesive sheet was prepared in the same manner as in Example 1, except that a 100 μm thick TPU film (composition ratio of diphenylmethane diisocyanate (MDI) 10% by mass, poly(tetramethylene glycol) (PTMG) 90% by mass) was used as the base material.

[0184] Example 8 A double-sided adhesive sheet was prepared in the same manner as in Example 7, except that the thickness of the TPU film was changed to 150 μm.

[0185] Example 9 A double-sided adhesive sheet was prepared in the same manner as in Example 7, except that the thickness of the TPU film was changed to 300 μm.

[0186] Example 10 A double-sided adhesive sheet was prepared in the same manner as in Example 1, except that a 70 μm thick acrylic film (manufactured by Okura Industries Co., Ltd., product number AC-32) was used as the base material.

[0187] Example 11 A double-sided adhesive sheet was prepared in the same manner as in Example 1, except that a 100 μm thick urethane film (manufactured by Toray Industries, Inc., product number STR-1) was used as the base material.

[0188] Comparative Example 1 A double-sided adhesive sheet was prepared in the same manner as in Example 1, except that a 100 μm thick polyethylene (PE) film (made by molding a sheet of the synthetic resin "Sumikasen F213-P" (manufactured by Sumitomo Chemical Co., Ltd.) into an inflation molded form) was used as the base material.

[0189] Comparative Example 2 A double-sided adhesive sheet was prepared in the same manner as in Example 1, except that a 100 μm thick laminated PP / EVA / PP film (manufactured by Kurabo Industries Ltd., product number NK301) was used as the base material.

[0190] <Evaluation> The double-sided adhesive sheets obtained in the examples and comparative examples were evaluated as follows. The results are shown in the table.

[0191] (1) Volume resistivity The evaluation was carried out by referring to the double-ring method of JIS K6271-1. Two 1 mm thick x 100 mm x 200 mm aluminum plates (A1050) were used as electrodes, four wires (alligator clips) were used for connecting the equipment, a compact DC stabilized power supply for voltage application (manufactured by Kikusui Electronics Co., Ltd., part number: PMX35-1A), a digital multimeter (manufactured by GW Instec, part number: GDM-9061) for checking the current value, a 5 kg weight, and a substrate and double-sided adhesive sheet cut to a size of 100 mm x 100 mm were prepared as test pieces. For the double-sided adhesive sheet, it was stored at 80°C for 3 or 8 days after preparation, and the release liner on both sides was peeled off before use. Then, in a 25°C 50% RH environment, as shown in Figure 3, the test piece 11 was sandwiched between two aluminum plates (distance between aluminum plates "t"). A set was assembled by electrically connecting the lower aluminum plate 12, DC stabilized power supply 15, digital multimeter 16, and upper aluminum plate 13 in series. A weight 14 was placed on the upper aluminum plate 13. The DC power supply was set to a voltage of 30V and a conditional current value of 1.0A, and the digital multimeter 16 was set to "DC Current". The DC stabilized power supply 15 was turned ON, and the voltage was applied for 5 minutes until the resistance value stabilized. The current value displayed on the digital multimeter was then recorded. Using the obtained current value, the volume resistivity of the test piece was calculated using the following formula. (Electrode area S = 10 × 10 = 100 cm²) ２ Volume resistivity (Ω·cm) = [Voltage V ÷ Current A] × ["S" electrode area (cm²)] ２ )÷“t” distance between electrodes (cm)]

[0192] (2) Tensile modulus E' The release liners on both sides were peeled off from the double-sided adhesive sheets prepared in the examples and comparative examples, and a sample with a sheet width of 10 mm was prepared. Using the product name "RSA-G2" (TA Instrument Japan Co., Ltd.) as a dynamic viscoelasticity measuring device, the above sample was placed in the measuring device's tensile jig at a measurement interval of 20 mm, and the measurement environment oven was changed to the measurement start temperature. After confirming that the temperature of the measurement environment was stable, the measurement was taken at 25°C. Tensile deformation was applied at a frequency of 1 Hz during measurement, and the amount of deformation strain was controlled in the region in which the sample did not undergo permanent deformation, and the stress generated was calculated as the storage modulus E'.

[0193] (3) The double-sided adhesive sheets prepared in the normal peeling force examples and comparative examples were made into sheets measuring 25 mm x 80 mm. One release liner was peeled off, and a 50 μm thick PET film (manufactured by Toray Industries, Inc., product number: S-10) was bonded to the exposed electro-peelable adhesive layer using a hand roller. The other release liner of the double-sided adhesive sheet was then peeled off, and SUS316 was attached to the peeled surface as an adherend so that one end of the double-sided adhesive sheet protruded from the adherend by about 20 mm. A 2 kg roller was then pressed back and forth once. After that, it was left in an environment of 22°C / 50% RH for 30 minutes to obtain a bonded body consisting of [PET film / electro-peelable adhesive layer / substrate / electro-peelable adhesive layer / SUS316]. The above-mentioned bond was peeled in the 180° direction (direction of the arrow in Figure 4) using a peel tester (product name "Variable Angle Peel Tester YSP", manufactured by Asahi Seiko Co., Ltd.), and the adhesive strength (22°C / 50%RH) in the 180° peel test (tensile speed: 300 mm / min, peel temperature 22°C, humidity 50%RH) at the interface between the double-sided adhesive sheet and SUS316 was measured and defined as the normal peel strength.

[0194] (4) Electropeelability The double-sided adhesive sheets prepared in the examples and comparative examples were made into sheets measuring 25 mm x 80 mm. One release liner was peeled off, and the conductive layer side of the conductive substrate was bonded to the exposed electropeelable adhesive layer to create a single-sided adhesive sheet with a substrate. As the conductive substrate, a substrate-less double-sided adhesive sheet was used, consisting of an adhesive layer prepared in the same manner as the electropeelable adhesive layer in Example 1, except that ionic substances and corrosion inhibitors were not added to the non-conductive side of a metal-layered film (product name "MetalMe 25S", manufactured by Toray Industries, Inc., thickness 25 μm), and a PET film with a thickness of 50 μm (manufactured by Toray Industries, Inc., product number: S-10) was bonded together with a hand roller. The other release liner of the double-sided adhesive sheet was peeled off, and SUS316 was attached to the peeled surface as an adherend so that one end of the double-sided adhesive sheet protruded from the adherend by about 20 mm, and it was pressed back and forth once with a 2 kg roller. Subsequently, the bond was left for 30 minutes in an environment of 22°C / 50%RH to obtain a bond consisting of [conductive substrate / electro-peelable adhesive layer / substrate / electro-peelable adhesive layer / SUS316]. Before peeling, the positive and negative electrodes of a DC stabilizer were attached to the α and β points in Figure 4 of the bond, respectively, and a voltage of 30V was applied for 30 seconds, 120 seconds, 300 seconds, and 600 seconds, respectively. Immediately afterward, the adhesive force was measured in the same manner as the normal peeling force described above, except for the point where the bond was peeled in the direction of the arrow in Figure 4, and this was defined as the electro-peeling force. In Figure 4, 17 is the adherend (SUS316), and 18 is a backing material formed by bonding a conductive substrate and a PET film with a substrate-less double-sided adhesive sheet.

[0195]

[0196] As shown in Table 1, although the volume resistivity of the substrate is high in the double-sided adhesive sheets of the examples, the electropenetrating force after 300 seconds of voltage application is lower than that of the double-sided adhesive sheets of the comparative examples, and it was determined that they could be easily peeled off by the charge of the voltage. In particular, when [substrate thickness / total thickness of adhesive layer], [substrate thickness / thickness of one layer of adhesive layer], [isocyanate component × substrate thickness / total thickness of adhesive layer], and [isocyanate component × substrate thickness / thickness of one layer of adhesive layer] are within a specific range (Examples 1-2, 4-11), the electropenetrating force after 300 seconds of voltage application is especially low, and it was determined that they could be easily peeled off by the charge of the voltage.

[0197] Figure 5 shows a graph illustrating the relationship between the tensile modulus E' and the electropenetrating force (300 sec). From Figure 5, it can be seen that there is a correlation between the tensile modulus E' and the electropenetrating force (300 sec), and that the lower the tensile modulus E', the smaller the electropenetrating force (300 sec).

[0198] Figure 6 shows a graph illustrating the relationship between [isocyanate component × substrate thickness / total thickness of adhesive layer] and the electropenetrating force (300 sec). From Figure 6, it can be seen that there is a correlation between [isocyanate component × substrate thickness / total thickness of adhesive layer] and the electropenetrating force (300 sec), and that the smaller [isocyanate component × substrate thickness / total thickness of adhesive layer], the smaller the electropenetrating force (300 sec).

[0199] Figure 7 shows a graph illustrating the relationship between [isocyanate component × substrate thickness / thickness of one adhesive layer] and the electropenetrating force (300 sec). From Figure 7, it can be seen that there is a correlation between [isocyanate component × substrate thickness / thickness of one adhesive layer] and the electropenetrating force (300 sec), and that the smaller [isocyanate component × substrate thickness / thickness of one adhesive layer], the smaller the electropenetrating force (300 sec).

[0200] (5) Evaluation of the amount of ionic substance transferred to the substrate The amount of ionic substance (ETHYLMETHYLPYRROLIDINIUM BIS (FLUOROSULFONYL)IMIDE) in the substrate was analyzed for the substrate used in Example 5 (TPU(A)), the substrate used in Example 7 (TPU(B)), and the substrate used in Comparative Example 1 (PE) before the formation of the electropenetrating adhesive layer (before use), after the formation of the electropenetrating adhesive layer (after bonding), and after the electropenetrating force measurement (after electropenetration). Since adhesive adheres to the substrate after bonding and electropenetration, it was removed beforehand to obtain only the substrate. The substrate was then freeze-dried and a certain amount was collected, and tetrahydrofuran (THF) was added to extract the ionic substance overnight. A purified water / acetonitrile mixed solution was added to the extracted solution, diluted as appropriate, and the solution obtained by filtering through a membrane filter (pore size 0.20 μm) was measured by LC / MS. The analytical conditions were as follows. The analytical results are shown in Table 2. Instrument: "ACQUITY UPLC Hclass-bio", manufactured by Waters Corporation. Column: Ion exchange column. Eluent composition: Pure water (with ammonium acetate) / acetonitrile gradient. Detector: MS (SRM). Column temperature: 40°C. Injection volume: 2 μL. Ionization method: ESI (Pos.).

[0201]

[0202] As shown in Table 2, the amount of ionic substances detected in the substrate (PE) used in Comparative Example 1 was low before use, after lamination, and after electrolysis. On the other hand, in the substrates used in the Examples (TPU(A), TPU(B)), the amount of ionic substances detected before use was low, but the amount of ionic substances detected after lamination increased compared to before use. This was thought to be because the ionic substances in the electrolyzable adhesive layer migrated into the substrate when the electrolyzable adhesive layer was laminated to the substrate. It was then inferred that this caused conductivity and electrolysis when a voltage was applied to the double-sided adhesive sheet. Furthermore, since the amount of ionic substances detected after electrolysis was slightly higher than after lamination, it was also inferred that ionic substances migrated from the electrolyzable adhesive layer on the positive electrode side when a voltage was applied.

[0203] The following describes variations of the invention relating to this disclosure. [Note 1] Volume resistivity is 1.0 × 10 １０ A double-sided adhesive sheet comprising a substrate with a thickness of Ω·cm or more, and an electro-release adhesive layer on at least one main surface of the substrate, wherein the adhesive strength decreases when a voltage is applied, and the tensile modulus E' at 25°C is 120 MPa or less. [Note 2] The double-sided adhesive sheet according to Note 1, satisfying the following formula (1) and / or formula (2): 0.01 ≤ [thickness of substrate / total thickness of electro-release adhesive layer] < 3 (1) 0.005 ≤ [thickness of substrate / thickness of electro-release adhesive layer on one main surface] < 6 (2) [Note 3] The double-sided adhesive sheet according to Note 1 or 2, wherein the substrate is made of a non-metallic material. [Note 4] The double-sided adhesive sheet according to any one of Notes 1 to 3, wherein the substrate is made of a plastic material. [Note 5] The double-sided adhesive sheet according to any one of Notes 1 to 4, wherein the electro-release adhesive layer contains a polymer and an electrolyte. [Note 6] The double-sided adhesive sheet according to any one of Notes 1 to 5, wherein the tensile modulus E' is 40 MPa or less. [Note 7] The double-sided adhesive sheet according to any one of Notes 1 to 6 for fixing components together in electrical and electronic equipment. [Note 8] A joint comprising the double-sided adhesive sheet according to any one of Notes 1 to 7 and a conductive material, wherein the electropenetrating adhesive layer is attached to the conductive material. [Note 9] Electrical and electronic equipment comprising the double-sided adhesive sheet according to any one of Notes 1 to 7, wherein the double-sided adhesive sheet fixes components together on both adhesive surfaces. [Note 10] A method for manufacturing an adhesive sheet comprising a base material and an adhesive layer provided on at least one main surface of the base material, comprising a bonding step of bonding the base material and the adhesive layer, wherein one of the base material and the adhesive layer to be bonded in the bonding step contains an electrolyte and the other does not contain the electrolyte, and comprising a transfer step of transferring the electrolyte from one to the other in the bonding step or thereafter.

[0204] 1. Double-sided adhesive sheet 2. Substrate 3,4. Electro-peelable adhesive layer 5,6. Release liner 7. Portable electronic device 8. Housing 9. Battery 10. Touch panel 11. Test piece 12,13. Aluminum plate 14. Weight 15. DC regulated power supply 16. Digital multimeter 17. Adhesion surface 18. Backing material

Claims

1. Volume resistivity is 1.0 × 10⁻⁶ １０ A double-sided adhesive sheet comprising a substrate with a density of Ω·cm or greater, and an electro-peelable adhesive layer on at least one main surface of the substrate, wherein the adhesive strength decreases when a voltage is applied, and the tensile modulus E' at 25°C is 120 MPa or less.

2. The double-sided adhesive sheet according to claim 1, satisfying the following formula (1) and / or formula (2): 0.01 ≤ [thickness of the substrate / total thickness of the electropenetrating adhesive layer] < 3 (1) 0.005 ≤ [thickness of the substrate / thickness of the electropenetrating adhesive layer on one main surface] < 6 (2) 3. The double-sided adhesive sheet according to claim 1 or 2, wherein the substrate is made of a non-metallic material.

4. The double-sided adhesive sheet according to claim 1 or 2, wherein the base material is made of a plastic material.

5. The double-sided adhesive sheet according to claim 1 or 2, wherein the electropenetrating adhesive layer comprises a polymer and an electrolyte.

6. The double-sided adhesive sheet according to claim 1 or 2, wherein the tensile modulus E' is 40 MPa or less.

7. The double-sided adhesive sheet according to claim 1 or 2, for fixing components together in electrical and electronic equipment.

8. A bonding body comprising a double-sided adhesive sheet according to claim 1 or 2 and a conductive material, wherein the electropenetrating adhesive layer is attached to the conductive material.

9. An electrical and electronic device comprising a double-sided adhesive sheet as described in claim 7, wherein the double-sided adhesive sheet fixes components together on both adhesive surfaces.

10. A method for manufacturing an adhesive sheet comprising a base material and an adhesive layer provided on at least one main surface of the base material, comprising a bonding step of bonding the base material and the adhesive layer, wherein one of the base material and the adhesive layer to be bonded in the bonding step contains an electrolyte and the other does not contain the electrolyte, and comprising a transfer step of transferring the electrolyte from one to the other in or after the bonding step.

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