TWI867744B - Adhesive composition, adhesive sheet, and bonded body - Google Patents

Abstract

The present invention relates to an adhesive composition, which at least comprises a polymer and an ionic liquid, and an adhesive layer is formed by using a composition containing components other than the ionic liquid. After the adhesive layer is placed in an environment of 22°C and 20%RH for 3 days, the relative dielectric constant of the adhesive layer at a frequency of 100 Hz is greater than 5.

Description

Adhesive composition, adhesive sheet, and bonded body

The present invention relates to an adhesive composition, an adhesive sheet including an adhesive layer formed by the adhesive composition, and a bonded body of the adhesive sheet and an adherend.

In the manufacturing process of electronic parts, there are increasing demands for secondary processing to improve the yield rate or for disassembling and recycling the parts after use. In order to meet such demands, double-sided adhesive sheets with a certain bonding force and a certain release property are used when joining components in the manufacturing process of electronic parts.

As a double-sided adhesive sheet that realizes the above-mentioned adhesion and peeling properties, there is known an adhesive sheet (electro-peeling adhesive sheet) that is peeled by applying a voltage to the adhesive layer using an ionic liquid containing cations and anions in the components forming the adhesive composition (patent documents 1 to 3). Regarding the electro-peeling adhesive sheets of patent documents 1 to 3, it is believed that by applying a voltage, the cations of the ionic liquid move to the cathode side and are reduced, and the anions of the ionic liquid move to the anode side and are oxidized, so that the adhesion of the bonding interface is weakened, making it easy to peel. [Prior art literature] [Patent literature]

Patent document 1: Japanese Patent Publication No. 2010-037354 Patent document 2: Japanese Patent Publication No. 6097112 Patent document 3: Japanese Patent Publication No. 4139851

[The problem the invention is trying to solve]

It is preferred that the peel-off adhesive sheet can firmly bond components when no voltage is applied, and can be peeled off with less force when voltage is applied. Therefore, it is preferred that the rate of decrease in the adhesion force obtained by voltage application is greater in the peel-off adhesive sheet. However, in a low humidity environment such as winter, the decrease in the rate of decrease in the adhesion force obtained by voltage application becomes a problem.

The present invention is completed in view of the above, and its purpose is to provide an adhesive composition that can sufficiently reduce the bonding force by applying a voltage even in a low humidity environment, and an adhesive sheet having an adhesive layer formed by the adhesive composition. [Technical means for solving the problem]

According to the research of the inventors, the decrease in the rate of decrease of the bonding force obtained by applying a voltage in a low humidity environment is caused by the decrease in the water content of the adhesive layer in a low humidity environment, which makes it difficult for the cations and anions of the ionic liquid to move. The inventors further conducted repeated research and obtained the following insights. First, it was found that the relative dielectric constant of the components other than the ionic liquid in the adhesive layer is correlated with the rate of decrease of the bonding force obtained by applying a voltage, and by increasing the relative dielectric constant, the rate of decrease of the bonding force obtained by applying a voltage can be increased. It was also found that when the moisture content of the adhesive layer is reduced in a low humidity environment, if the relative dielectric constant is larger, the electrical exfoliation property is also good, that is, the reduction rate of the bonding force obtained by applying a voltage is larger. Second, it was found that the ionic conductivity of the adhesive layer and the capacitance per unit area of the interface between the adhesive layer and the adherend are correlated with the reduction rate of the bonding force obtained by applying a voltage. By increasing the ionic conductivity and the capacitance per unit area of the interface between the adhesive layer and the adherend, the reduction rate of the bonding force obtained by applying a voltage can be increased. In addition, it was found that when the moisture content of the adhesive layer is reduced in a low humidity environment, if the ionic conductivity and the capacitance per unit area of the interface between the adhesive layer and the adherend are larger, the electrical peeling property is also good, that is, the reduction rate of the bonding force obtained by applying voltage is larger.

An adhesive composition of the present invention completed based on the above-mentioned first insight comprises a polymer and an ionic liquid, and an adhesive layer is formed using a composition comprising components other than the ionic liquid in the adhesive composition, and after the adhesive layer is placed in an environment of 22° C. and 20% RH for 3 days, the relative dielectric constant of the adhesive layer at a frequency of 100 Hz is greater than 5.

Another adhesive composition of the present invention completed based on the above-mentioned second insight comprises a polymer and an ionic liquid, and an adhesive layer is formed by using the adhesive composition and attached to an aluminum plate comprising A5052P H32 in JIS H4000:2014. After being placed in an environment of 22°C and 15%RH for 7 days, the capacitance per unit area of the interface between the adhesive layer and the aluminum plate is greater than 0.9 μF/ ^cm2 , and the ionic conductivity of the adhesive layer is greater than 10 μS/m.

In one embodiment of the adhesive composition of the present invention, an adhesive layer is formed by using the adhesive composition and attached to an aluminum plate including A5052P H32 in JIS H4000:2014. After being placed in an environment of 22°C and 15%RH for 7 days, the capacitance per unit area of the interface between the adhesive layer and the aluminum plate can be greater than 1.2 μF/ ^cm2 , and the ionic conductivity of the adhesive layer can be greater than 20 μS/m.

In one aspect of the adhesive composition of the present invention, the adhesive composition may further include an ionic solid.

In one aspect of the adhesive composition of the present invention, the polymer may include an ionic polymer.

In one aspect of the adhesive composition of the present invention, the polymer may include at least one selected from the group consisting of polyester polymers, urethane polymers, and acrylic polymers having carboxyl groups, alkoxy groups, hydroxyl groups, and/or amide bonds.

In addition, another adhesive composition of the present invention comprises a polymer and an ionic liquid, and comprises 0.5 to 30 parts by mass of the ionic liquid and 0.5 to 10 parts by mass of the ionic solid relative to 100 parts by mass of the polymer.

In addition, another adhesive composition of the present invention comprises a polymer and an ionic liquid, and relative to 100 parts by mass of the polymer, the ionic liquid is contained in an amount of 0.5 to 30 parts by mass, and the polymer comprises 0.05 to 2 parts by mass of the ionic polymer.

In addition, another adhesive composition of the present invention comprises 100 parts by mass of an acrylic polymer and 0.5 to 30 parts by mass of an ionic liquid, and the ratio of the polar group-containing monomer to the total monomer components constituting the acrylic polymer is 0.1 to 35% by mass.

In one aspect of the present invention, the adhesive composition is for electrostripping.

Furthermore, the adhesive sheet of the present invention comprises an adhesive layer formed of the adhesive composition of the present invention.

Furthermore, the bonded body of the present invention comprises: an adherend having a metal adhered surface, and the adhesive sheet of the present invention, and the adhesive layer of the adhesive sheet of the present invention is bonded to the metal adhered surface. [Effects of the invention]

The adhesive composition of the present invention can also substantially reduce the bonding force by applying a voltage in a low humidity environment.

The following describes the embodiments for implementing the present invention in detail. The present invention is not limited to the embodiments described below.

[Adhesive composition] The adhesive compositions of the first and second embodiments of the present invention both contain a polymer and an ionic liquid. An adhesive layer is formed using a composition containing the components contained in the adhesive composition of the first embodiment except the ionic liquid, and the adhesive layer is placed in an environment of 22°C and 20%RH for 3 days. The relative dielectric constant of the adhesive layer at a frequency of 100 Hz is 5 or more. Furthermore, when the adhesive layer is formed by using the adhesive composition of the second embodiment and attached to an aluminum plate including A5052P H32 in JIS H4000:2014, the capacitance per unit area of the interface between the adhesive layer and the aluminum plate after being placed in an environment of 22°C and 15%RH for 7 days is 0.9 μF/ ^cm2 or more, and the ionic conductivity of the adhesive layer is 10 μS/m or more. The adhesive composition has the property of reducing the adhesion force by applying a voltage, and is suitable as an adhesive composition for electrical stripping. Furthermore, the first and second embodiments are not exclusive, and there are adhesive compositions that conform to either of the first and second embodiments, and there are adhesive compositions that conform to only one of the embodiments. As long as the adhesive composition conforms to either of the first or second embodiments, the effect of the present invention is exerted. The adhesive compositions are described below.

Furthermore, in this specification, the first and second embodiments of the present invention are sometimes collectively referred to as the "present embodiment". Furthermore, in this specification, the adhesion force when no voltage is applied is sometimes referred to as the "initial adhesion force". Also, a composition containing components other than the ionic liquid among the components contained in the adhesive composition is sometimes referred to as an "adhesive composition not containing ionic liquid". Also, an adhesive layer formed using an adhesive composition not containing ionic liquid is sometimes referred to as an "adhesive layer not containing ionic liquid". In addition, the property of reducing the adhesion force by applying voltage is sometimes called "electrical peeling separation", and sometimes a larger reduction rate of adhesion force obtained by applying voltage is called "excellent electric peeling separation", etc.

<Ingredients of Adhesive Composition> (Polymer) The adhesive composition of this embodiment contains a polymer. In this embodiment, the polymer is not particularly limited as long as it is a common organic polymer compound, for example, a polymer or a partial polymer of a monomer. The monomer may be one monomer or a mixture of two or more monomers. Furthermore, the so-called partial polymer refers to a polymer in which at least a part of a monomer or a monomer mixture is partially polymerized.

The polymer in this embodiment is usually used as an adhesive, and is not particularly limited as long as it has adhesive properties, such as acrylic polymers, rubber polymers, vinyl alkyl ether polymers, silicone polymers, polyester polymers, polyamide polymers, urethane polymers, fluorine polymers, and epoxy polymers. The polymer can be used alone or in combination of two or more. In order to increase the relative dielectric constant of the components other than the ionic liquid of the obtained adhesive layer, and to increase the ionic conductivity of the obtained adhesive layer and the capacitance per unit area of the interface, and to improve the electrical stripping property, it is preferred that the polymer has a larger relative dielectric constant. From this point of view, it is particularly preferred that the polymer in the present embodiment includes at least one selected from the group consisting of polyester polymers, urethane polymers, and acrylic polymers having carboxyl groups, alkoxy groups, hydroxyl groups and/or amide bonds. Polyester polymers and urethane polymers have easily polarized hydroxyl groups at the ends, and the carboxyl groups, alkoxy groups, hydroxyl groups and/or amide bonds of acrylic polymers having carboxyl groups, alkoxy groups, hydroxyl groups and/or amide bonds are easily polarized, so by using these polymers, a polymer with a relatively large relative dielectric constant can be obtained. The total content of the polyester polymer and the acrylic polymer having carboxyl groups, alkoxy groups, hydroxyl groups and/or amide bonds in the polymer of this embodiment is preferably 60% by mass or more, and more preferably 80% by mass or more. Moreover, in particular for cost or productivity, and to increase initial adhesion, the polymer in this embodiment is preferably an acrylic polymer. That is, the adhesive composition of the present embodiment is preferably an acrylic adhesive composition containing an acrylic polymer as a polymer.

The acrylic polymer preferably contains a monomer unit derived from an alkyl (meth)acrylate having an alkyl group with 1 to 14 carbon atoms (the following formula (1)). Such a monomer unit is suitable for obtaining a larger initial adhesion. Furthermore, in order to increase the relative dielectric constant of the components other than the ionic liquid of the adhesive layer, and to increase the ionic conductivity of the obtained adhesive layer and the capacitance per unit area of the bonding interface, and to improve the electrical exfoliation property, it is preferred that the carbon number of the alkyl group ^Rb in the following formula (1) is smaller, preferably 8 or less, and more preferably 4 or less. _CH2 =C( ^Ra ) ^COORb (1) [ ^Ra in formula (1) is a hydrogen atom or a methyl group, and ^Rb is an alkyl group with 1 to 14 carbon atoms]

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

The ratio of the (meth)acrylic acid alkyl ester having an alkyl group with 1 to 14 carbon atoms to the total monomer components (100 mass %) constituting the acrylic polymer is not particularly limited, but is preferably 70 mass % or more, more preferably 80 mass % or more, and further preferably 85 mass % or more. If the ratio of the acrylic polymer is 70 mass % or more, a greater initial adhesion is easily obtained.

As an acrylic polymer, in order to improve cohesion, heat resistance, crosslinking, etc., it is preferred that, in addition to monomer units derived from (meth)acrylic acid alkyl esters having an alkyl group with 1 to 14 carbon atoms, monomer units derived from monomers containing polar groups copolymerizable therewith are included. The monomer units can provide crosslinking points, which are suitable for obtaining a larger initial adhesion. Furthermore, from the perspective of increasing the relative dielectric constant of the components other than the ionic liquid of the adhesive layer, increasing the ionic conductivity of the obtained adhesive layer and the capacitance per unit area of the bonding interface, and improving the electrical exfoliation, it is also preferred that the monomer units are derived from monomers containing polar groups.

Examples of the polar group-containing monomer include carboxyl group-containing monomers, alkoxy 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-acryloyl phosphonium, sulfonic group-containing monomers, phosphoric acid group-containing monomers, and acid anhydride group-containing monomers. Among them, carboxyl group-containing monomers, alkoxy group-containing monomers, hydroxyl group-containing monomers, and amide group-containing monomers are preferred in terms of excellent cohesiveness, and carboxyl group-containing monomers are particularly preferred. Carboxyl group-containing monomers are particularly suitable for obtaining greater initial adhesion. The polar group-containing monomer may be used alone or in combination of two or more.

Examples of carboxyl-containing monomers include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isomethacrylic acid. Acrylic acid is particularly preferred. Carboxyl-containing monomers may be used alone or in combination of two or more.

As the alkoxy group-containing monomer, for example, a methoxy group-containing monomer or an ethoxy group-containing monomer can be mentioned. As the methoxy group-containing monomer, for example, 2-methoxyethyl acrylate can be mentioned.

Examples of hydroxyl-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-hydroxymethyl (meth)acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. 2-Hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are particularly preferred. The hydroxyl-containing monomers may be used alone or in combination of two or more.

Examples of the amide group-containing monomer include acrylamide, methacrylamide, N-vinyl pyrrolidone, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N'-methylenebisacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, and diacetoneacrylamide. The amide group-containing monomer may be used alone or in combination of two or more.

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

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

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

Examples of the monomer containing an imide group include cyclohexyl cis-butenediamide, isopropyl cis-butenediamide, N-cyclohexyl cis-butenediamide, and iconimide.

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

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

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

The ratio of the monomer containing a polar group to the total monomer components (100% by mass) constituting the acrylic polymer is preferably 0.1% by mass or more and 35% by mass or less. The upper limit of the ratio of the monomer containing a polar group is more preferably 25% by mass, more preferably 20% by mass, and the lower limit is more preferably 0.5% by mass, more preferably 1% by mass, and particularly preferably 2% by mass. If the ratio of the monomer containing a polar group is 0.1% by mass or more, cohesion is easily obtained, so that it is not easy to generate paste residue on the surface of the adherend after peeling off the adhesive layer, and the electrical stripping property is improved. Furthermore, if the ratio of the polar group-containing monomer is 35% by mass or less, it is easy to prevent the adhesive layer from being too closely attached to the adherend and being re-stripped. In particular, if it is 2% by mass or more and 20% by mass or less, it is easy to achieve both the stripping property of the adherend and the close adhesion between the adhesive layer and other layers.

Furthermore, as a monomer component constituting the acrylic polymer, a multifunctional monomer may be contained in order to introduce a cross-linked structure into the acrylic polymer and to easily obtain the desired cohesive force.

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

The content of the multifunctional monomer relative to the total monomer components (100 mass%) constituting the acrylic polymer is preferably 0.1 mass% or more and 15 mass% or less. The upper limit of the content of the multifunctional monomer is more preferably 10 mass%, and the lower limit is more preferably 3 mass%. If the content of the multifunctional monomer is 0.1 mass% or more, the flexibility and adhesion of the adhesive layer are easily improved and preferred. If the content of the multifunctional monomer is 15 mass% or less, the cohesive force will not become too high, and it is easy to obtain moderate adhesion.

The polyester polymer is typically a polymer having a structure in which a polycarboxylic acid such as dicarboxylic acid or a derivative thereof (hereinafter also referred to as a "polycarboxylic acid monomer") is condensed with a polyol such as diol or a derivative thereof (hereinafter referred to as a "polyol monomer").

The polycarboxylic acid monomer is not particularly limited, and for example, adipic acid, azelaic acid, dimer acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, dodecenylsuccinic anhydride, fumaric acid, succinic acid, dodecanedioic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, maleic acid, maleic anhydride, itaconic acid, liconic acid, and derivatives thereof can be used. The polycarboxylic acid monomer can be used alone or in combination of two or more.

The polyol monomer is not particularly limited, and for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,5-pentanediol, 2-ethyl-2-butylpropanediol, 1,9-nonanediol, 2-methyloctanediol, 1,10-decanediol, and derivatives thereof can be used. The polyol monomer can be used alone or in combination of two or more.

In addition, the polymer of this embodiment may include an ionic polymer. An ionic polymer is a polymer having an ionic functional group. By including an ionic polymer, the relative dielectric constant of the polymer increases and the electrical exfoliation ionization is improved. When the polymer includes an ionic polymer, the content of the ionic polymer is preferably 0.05 parts by mass or more and 2 parts by mass or less relative to 100 parts by mass of the polymer.

In this embodiment, the polymer can be obtained by (co)polymerizing the monomer components. The polymerization method is not particularly limited, and examples thereof include solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, photopolymerization (active energy ray polymerization), etc. In particular, solution polymerization is preferred from the perspective of cost or productivity. In the case of copolymerization, the polymer can be any one of a random copolymer, a block copolymer, an alternating copolymer, a graft copolymer, etc.

The solution polymerization method is not particularly limited, and the following methods can be cited: a monomer component, a polymerization initiator, etc. are dissolved in a solvent, and the solution is heated to polymerize to obtain a polymer solution containing a polymer.

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

The amount of the solvent used is not particularly limited, but is preferably 10 parts by mass or more and 1000 parts by mass or less relative to 100 parts by mass of all monomer components constituting the polymer. The upper limit of the amount of the solvent used is more preferably 500 parts by mass, and the lower limit is more preferably 50 parts by mass.

The polymerization initiator used in the solution polymerization method is not particularly limited, and examples thereof include peroxide-based polymerization initiators and azo-based polymerization initiators. The peroxide-based polymerization initiator is not particularly limited, and examples thereof include peroxycarbonate, ketone peroxide, peroxyketal, hydrogen peroxide, dialkyl peroxide, diacyl peroxide, and peroxyester, and more specifically, examples thereof include benzoyl peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, tert-butyl peroxybenzoate, diisopropylbenzene peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-bis(tert-butylperoxy)cyclododecane. The azo-based polymerization initiator is not particularly limited, and examples thereof include: 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylpropionic acid) dimethyl ester, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4,4-trimethylpentane ), 4,4'-azobis-4-cyanovaleric acid, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine) hydrochloride, and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate. The polymerization initiator may be used alone or in combination of two or more.

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

The heating temperature during the polymerization by the solution polymerization method is not particularly limited, and is, for example, 50° C. or higher and 80° C. or lower. The heating time is not particularly limited, and is, for example, 1 hour or higher and 24 hours or lower.

The weight average molecular weight of the polymer is not particularly limited, but is preferably 100,000 or more and 5,000,000 or less. The upper limit of the weight average molecular weight is more preferably 4,000,000, and further preferably 3,000,000, and the lower limit is more preferably 200,000, and further preferably 300,000. If the weight average molecular weight is more than 100,000, it is possible to effectively suppress the undesirable situation that the cohesive force is reduced and the paste residue is generated on the surface of the adherend after the adhesive layer is peeled off. In addition, if the weight average molecular weight is less than 5,000,000, it is possible to effectively suppress the undesirable situation that the wettability of the adherend surface after the adhesive layer is peeled off becomes insufficient.

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

The glass transition temperature (Tg) of the polymer is not particularly limited, but is preferably 0°C or lower because the decrease in initial adhesive force can be suppressed, more preferably -10°C or lower, and further preferably -20°C or lower. Furthermore, if it is -40°C or lower, the decrease rate of adhesive force obtained by voltage application becomes particularly large, and most preferably -50°C or lower.

The glass transition temperature (Tg) can be calculated based on the following formula (Y) (Fox formula), for example. 1/Tg=W1/Tg1+W2/Tg2+・・・+Wn/Tgn(Y) [In formula (Y), Tg represents the glass transition temperature of the polymer (unit: K), Tgi (i=1, 2, ... n) represents 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 all monomer components] The above formula (Y) is a calculation formula for the case where the polymer is composed of n monomer components, namely monomer 1, monomer 2, ..., monomer n.

Furthermore, the glass transition temperature when forming a homopolymer refers to the glass transition temperature of the homopolymer of the monomer, which refers to the glass transition temperature (Tg) of a polymer formed by using only a certain monomer (sometimes referred to as "monomer X") as a monomer component. Specifically, the values are listed in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc, 1989). Furthermore, the glass transition temperature (Tg) of a homopolymer not described in the literature refers to a value obtained by the following measurement method, for example. That is, 100 parts by mass of monomer X, 0.2 parts by mass of 2,2'-azobisisobutyronitrile and 200 parts by mass of ethyl acetate as a polymerization solvent are added to a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, and nitrogen is introduced while stirring for 1 hour. After removing oxygen from the polymerization system, the temperature is raised to 63°C and allowed to react for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by mass. Then, the homopolymer solution is cast on a peeling pad and dried to produce a test sample (sheet-shaped homopolymer) with a thickness of about 2 mm. Then, about 1-2 mg of the test sample was weighed and placed in an open aluminum tank, and a temperature-modulated DSC (Differential Scanning Calorimeter) (trade name "Q-2000" manufactured by TA Instruments) was used to obtain the reversing heat flow (specific heat component) behavior of the homopolymer at a heating rate of 5°C/min in a nitrogen atmosphere of 50 ml/min. Referring to JIS-K-7121, a straight line equidistant from a straight line extending from a baseline on the low temperature side and a baseline on the high temperature side of the obtained reversing heat flow in the longitudinal direction intersected with the curve of the step-shaped change portion of the glass transition, and the temperature of the intersection was set as the glass transition temperature (Tg) when the homopolymer was prepared.

Regarding the content of the polymer in the adhesive composition of the present embodiment, relative to the total amount of the adhesive composition (100 mass %), it is preferably 50 mass % or more and 99.9 mass % or less, the upper limit is more preferably 99.5 mass %, further preferably 99 mass %, and the lower limit is more preferably 60 mass %, further preferably 70 mass %.

(Ionic liquid) The ionic liquid in this embodiment is composed of a pair of anions and cations, and is not particularly limited as long as it is a molten salt (normal temperature molten salt) that is liquid at 25°C. Among the ionic substances obtained by combining the following examples of anions and cations, those that are liquid at 25°C are ionic liquids, and those that are solid at 25°C are the following ionic solids and are not ionic liquids.

Examples of anions of the ionic liquid include (FSO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₂ N ^- , (CF ₃ CF ₂ SO ₂ ) 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 ^- , and F(HF) _n ^- . Among them, as anions, anions of sulfonyl imide compounds such as (FSO ₂ ) _2n ^- [bis(fluorosulfonyl)imide anion] and (CF ₃ SO ₂ ) _2n ^- [bis(trifluoromethanesulfonyl)imide anion] are preferred because they are chemically stable and suitable for improving the electrolytic ionization property.

As cations in the ionic liquid, nitrogen-containing onium, sulfur-containing onium, and phosphorus-containing onium cations are preferred in terms of being chemically stable and suitable for improving electrolytic ionization properties, and imidazolium, ammonium, pyrrolidinium, and pyridinium cations are more preferred.

Examples of the imidazolium cation include 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-heptyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-nonyl-3-methylimidazolium cation, 1-undecyl-3-methylimidazolium cation, 1-dodecyl-3-methylimidazolium cation, and the like. 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.

Examples of the pyridinium cation include 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, and 1-octyl-4-methylpyridinium cation.

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

Examples of the ammonium cation include tetraethylammonium cation, tetrabutylammonium cation, methyltrioctylammonium cation, tetradecyltrihexylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethylacrylate cation.

From the viewpoint of increasing the rate of decrease in adhesion when a voltage is applied, the constituent cations of the ionic liquid are preferably cations having a molecular weight of 160 or less, and an ionic liquid comprising the above-mentioned (FSO ₂ ) ₂ N ^- [bis(fluorosulfonyl)imide anion] or (CF ₃ SO ₂ ) ₂ N ^- [bis(trifluoromethanesulfonyl)imide anion] and cations having a molecular weight of 160 or less is particularly preferred. Examples of cations having a molecular weight of 160 or less include 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-butylpyridinium cation, 1-hexyl-3-methylimidazolium cation, Pyridinium 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, etc.

Furthermore, as the cation of the ionic liquid, the cation represented by the following formula (2-A) to (2-D) is also preferred.

In formula (2-A), ^R1 represents a alkyl group having 4 to 10 carbon atoms (preferably a alkyl group having 4 to 8 carbon atoms, more preferably a alkyl group having 4 to 6 carbon atoms), and may contain heteroatoms. ^R2 and ^R3 are the same or different and represent a hydrogen atom or a alkyl group having 1 to 12 carbon atoms (preferably a alkyl group having 1 to 8 carbon atoms, more preferably a alkyl group having 2 to 6 carbon atoms, and further preferably a alkyl group having 2 to 4 carbon atoms), and may contain heteroatoms. In the case where the nitrogen atom forms a double bond with the adjacent carbon atom, ^R3 does not exist.

In formula (2-B), ^R4 represents a alkyl group having 2 to 10 carbon atoms (preferably a alkyl group having 2 to 8 carbon atoms, more preferably a alkyl group having 2 to 6 carbon atoms), and may also contain heteroatoms. ^R5 , ^R6 , and ^R7 are the same or different and represent a hydrogen atom or a alkyl group having 1 to 12 carbon atoms (preferably a alkyl group having 1 to 8 carbon atoms, more preferably a alkyl group having 2 to 6 carbon atoms, and further preferably a alkyl group having 2 to 4 carbon atoms), and may also contain heteroatoms.

In formula (2-C), ^R8 represents a alkyl group having 2 to 10 carbon atoms (preferably a alkyl group having 2 to 8 carbon atoms, more preferably a alkyl group having 2 to 6 carbon atoms), and may also contain heteroatoms. ^R9 , ^R10 , and ^R11 are the same or different and represent a hydrogen atom or a alkyl group having 1 to 16 carbon atoms (preferably a alkyl group having 1 to 10 carbon atoms, more preferably a alkyl group having 1 to 8 carbon atoms), and may also contain heteroatoms.

In formula (2-D), X represents a nitrogen, sulfur, or phosphorus atom, and ^R12 , ^R13 , ^R14 , and ^R15 are the same or different and represent a alkyl group having 1 to 16 carbon atoms (preferably a alkyl group having 1 to 14 carbon atoms, more preferably a alkyl group having 1 to 10 carbon atoms, further preferably a alkyl group having 1 to 8 carbon atoms, and particularly preferably a alkyl group having 1 to 6 carbon atoms), and may contain heteroatoms. When X is a sulfur atom, ^R12 is absent.

The molecular weight of the cations in the ionic liquid is, for example, 500 or less, preferably 400 or less, more preferably 300 or less, further preferably 250 or less, particularly preferably 200 or less, and most preferably 160 or less. In addition, it is usually 50 or more. It is believed that the cations in the ionic liquid have the property of moving toward the cathode side when voltage is applied in the adhesive layer and deviating to the interface between the adhesive layer and the adherend. Therefore, in the present invention, the bonding force during voltage application is reduced relative to the initial bonding force, resulting in electrical exfoliation. Cations with a molecular weight of 500 or less are more suitable in that the cations move more easily to the cathode side in the adhesive layer and increase the rate of decrease of the adhesion force when a voltage is applied.

Examples of commercially available ionic liquids include "ELEXCEL AS-110", "ELEXCEL MP-442", "ELEXCEL IL-210", "ELEXCEL MP-471", "ELEXCEL MP-456", and "ELEXCEL AS-804" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "HMI-FSI" manufactured by Mitsubishi Materials Co., Ltd., and "CIL-312" and "CIL-313" manufactured by JAPAN CARLIT Co., Ltd.

The ionic conductivity of the ionic liquid is preferably 0.1 mS/cm or more and 10 mS/cm or less. The upper limit of the ionic conductivity is more preferably 5 mS/cm, more preferably 3 mS/cm, and the lower limit is more preferably 0.3 mS/cm, more preferably 0.5 mS/cm. By having an ionic conductivity within this range, the adhesion force is sufficiently reduced even at a relatively low voltage. Furthermore, the ionic conductivity can be measured by an AC (Alternating Current) impedance method using, for example, a 1260 frequency response analyzer manufactured by Solartron.

The content (mixing amount) of the ionic liquid in the adhesive composition of the present embodiment is preferably 0.5 parts by mass or more, relative to 100 parts by mass of the polymer, from the viewpoint of reducing the adhesion during voltage application, and preferably 30 parts by mass or less, from the viewpoint of improving the initial adhesion. From the same viewpoint, it is more preferably 20 parts by mass or less, further preferably 15 parts by mass or less, particularly preferably 10 parts by mass or less, and most preferably 5 parts by mass or less. Furthermore, it is more preferably 0.6 parts by mass or more, further preferably 0.8 parts by mass or more, particularly preferably 1.0 parts by mass or more, and most preferably 1.5 parts by mass or more.

(Other components) The adhesive composition of this embodiment may contain one or more components other than the polymer and the ionic liquid (hereinafter sometimes referred to as "other components") as needed within the scope that does not impair the effects of the present invention. The following describes other components that may be contained in the adhesive composition of this embodiment.

The adhesive composition of the present embodiment may also contain an ionic additive in order to control the relative dielectric constant, ionic conductivity, and capacitance. As the ionic additive, for example, an ionic solid may be used.

The ionic solid is an ionic substance that is solid at 25°C. The ionic solid is not particularly limited, and for example, a solid ionic substance obtained by combining the anions and cations exemplified in the description of the ionic liquid can be used. When the adhesive composition contains the ionic solid, the content of the ionic solid is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and further preferably 2.5 parts by mass or less, relative to 100 parts by mass of the polymer.

The adhesive composition of the present embodiment may contain a crosslinking agent as needed in order to improve creep or shear properties by crosslinking the polymer. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, and amine crosslinking agents. Examples of the isocyanate crosslinking agent include toluene diisocyanate and methylenebis(phenyl isocyanate). Examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and 1,6-hexanediol diglycidyl ether. When a crosslinking agent is contained, the content is preferably 0.1 parts by mass or more, more preferably 0.7 parts by mass or more, and preferably 50 parts by mass or less, more preferably 10 parts by mass or less, and further preferably 3 parts by mass or less, relative to 100 parts by mass of the polymer. The crosslinking agent may be used alone or in combination of two or more.

The adhesive composition of this embodiment may contain polyethylene glycol or tetraethylene glycol dimethyl ether as needed to facilitate the movement of the ionic liquid when a voltage is applied. As polyethylene glycol or tetraethylene glycol dimethyl ether, those having a number average molecular weight of 100 to 6000 may be used. When these components are contained, the content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 1 part by mass or more, and further preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 15 parts by mass or less, relative to 100 parts by mass of the polymer.

In order to impart conductivity to the adhesive composition, the adhesive composition of the present embodiment may contain a conductive filler as needed. The conductive filler is not particularly limited, and commonly known or commonly used conductive fillers may be used, such as graphite, carbon black, carbon fiber, metal powder such as silver or copper, etc. When the conductive filler is contained, the content is preferably 0.1 parts by mass or more and 200 parts by mass or less relative to 100 parts by mass of the polymer.

In order to inhibit corrosion of the metal adherend, the adhesive composition of this embodiment may contain an antiseptic as needed. There is no particular limitation on the antiseptic, and commonly known or commonly used antiseptics can be used, such as carbodiimide compounds, adsorption inhibitors, chelate-forming metal deactivators, etc. Examples of the carbodiimide compound include 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-oxolinylethyl)carbodiimide, N,N'-di-tert-butylcarbodiimide, 1,3-bis(p-tolyl)carbodiimide, and polycarbodiimide resins using these as monomers. These carbodiimide compounds may be used alone or in combination of two or more. When the adhesive composition of the present embodiment contains a carbodiimide compound, the content thereof is preferably 0.01 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the polymer. As adsorption-type inhibitors, for example: alkylamines, carboxylates, carboxylic acid derivatives, alkyl phosphates, etc. can be listed. Adsorption-type inhibitors can be used alone or in combination of two or more. When the adhesive composition of the present embodiment contains an alkylamine as an adsorption-type inhibitor, the content thereof is preferably 0.01 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the polymer. When the adhesive composition of the present embodiment contains a carboxylate as an adsorption inhibitor, the content is preferably 0.01 mass parts or more and 10 mass parts or less relative to 100 mass parts of the polymer. When the adhesive composition of the present embodiment contains a carboxylic acid derivative as an adsorption inhibitor, the content is preferably 0.01 mass parts or more and 10 mass parts or less relative to 100 mass parts of the polymer. When the adhesive composition of the present embodiment contains an alkyl phosphate as an adsorption inhibitor, the content is preferably 0.01 mass parts or more and 10 mass parts or less relative to 100 mass parts of the polymer. As a chelating metal deactivator, for example, a triazole-containing compound or a benzotriazole-containing compound can be used. The surface deactivation effect of such metals as aluminum is higher, and even if it is contained in the adhesive component, it is not easy to affect the adhesion, so it is better. Chelate-forming metal deactivators can be used alone or in combination of two or more. When the adhesive composition of this embodiment contains a chelate-forming metal deactivator, the content is preferably 0.01 mass parts or more and 20 mass parts or less relative to 100 mass parts of the polymer. The total content (mixing amount) of the preservative is preferably 0.01 mass parts or more and 30 mass parts or less relative to 100 mass parts of the polymer.

The adhesive composition of the present embodiment may also contain various additives such as fillers, plasticizers, anti-aging agents, antioxidants, pigments (dyes), flame retardants, solvents, surfactants (levelers), anti-rust agents, resins, and antistatic agents. The total content of these components is not particularly limited as long as the effects of the present invention are exerted, and is preferably 0.01 parts by mass or more and 20 parts by mass or less, more preferably 10 parts by mass or less, and further preferably 5 parts by mass or less, relative to 100 parts by mass of the polymer.

Examples of fillers include: silicon dioxide, iron oxide, zinc oxide, aluminum oxide, titanium oxide, barium oxide, magnesium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, pyrophyllite clay, kaolin clay, and calcined clay, etc. Plasticizers that can be used are commonly known plasticizers used in conventional resin compositions, such as wax oil, processing oil, liquid polyisoprene, liquid polybutadiene, liquid ethylene-propylene rubber, tetrahydrophthalic acid, azelaic acid, benzoic acid, phthalic acid, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid, fumaric acid, citric acid, itaconic acid, citric acid, and their derivatives, dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diisononyl adipate (DINA), and isodecyl succinate, etc. As anti-aging agents, for example, hindered phenol compounds, aliphatic and aromatic hindered amine compounds, etc. can be listed. As antioxidants, for example, butyl hydroxytoluene (BHT) and butyl hydroxyanisole (BHA) can be listed. As pigments, for example, inorganic pigments such as titanium dioxide, zinc oxide, ultramarine, red iron, zinc barium white, lead, cadmium, iron, cobalt, aluminum, hydrochloric acid salts, and sulfates can be listed; organic pigments such as azo pigments and copper phthalocyanine pigments can be listed. As anti-rust agents, for example, zinc phosphate, tannic acid derivatives, phosphate esters, alkaline sulfonic acid salts, and various anti-rust pigments can be listed. Examples of bonding agents include titanium coupling agents and zirconium coupling agents. Antistatic agents generally include quaternary ammonium salts, hydrophilic compounds such as polyglycolic acid or ethylene oxide derivatives, etc. Adhesive resins include rosin-based adhesive resins, terpene-based adhesive resins, phenol-based adhesive resins, hydrocarbon-based adhesive resins, and ketone-based adhesive resins, as well as polyamide-based adhesive resins, epoxy-based adhesive resins, and elastic-based adhesive resins. Furthermore, the adhesive imparting resin may be used alone or in combination of two or more.

<Relative dielectric constant of adhesive layer not containing ionic liquid> An adhesive layer (adhesive layer not containing ionic liquid) is formed using a composition (adhesive composition not containing ionic liquid) containing components other than ionic liquid among the components contained in the adhesive composition of the first embodiment, and the adhesive layer is placed in an environment of 22°C and 20%RH for 3 days. The relative dielectric constant of the adhesive layer at a frequency of 100 Hz is 5 or more.

Furthermore, the relative dielectric constant referred to above refers to the relative dielectric constant measured in the following manner. First, an adhesive composition containing no ionic liquid is uniformly applied on the peeling surface of the spacer that has been subjected to peeling treatment, and heat-dried at 130°C for 3 minutes to obtain an adhesive layer containing no ionic liquid with a thickness of 30 μm. Then, the obtained adhesive layer containing no ionic liquid is placed in an environment of 22°C and 20%RH for 3 days. Thereafter, the relative dielectric constant is measured under the following conditions. (Measurement conditions of relative dielectric constant) Measurement method: Capacitance method (device: using Agilent Technologies 4294A Precision Impedance Analyzer) Electrode composition: 12.1 mmφ, 0.5 mm thick aluminum plate Counter electrode: 60 μm thick aluminum foil Measurement environment: 23±1℃, 52±1%RH

The relative dielectric constant of the adhesive layer that does not contain ionic liquid is related to the ease of movement of the ionic liquid in the adhesive layer formed using the adhesive composition containing ionic liquid. The larger the relative dielectric constant of the adhesive layer that does not contain ionic liquid, the easier it is for the ionic liquid to move in the adhesive layer formed using the adhesive composition containing ionic liquid, so the bonding force is easily reduced when voltage is applied. The adhesive composition of the first embodiment has a relative dielectric constant of 5 or more at a frequency of 100 Hz after the adhesive layer containing no ionic liquid is placed in an environment of 22°C and 20% RH for 3 days. Therefore, even in a low humidity environment, a bond can be formed in which the bonding force is sufficiently reduced by applying a voltage.

The relative dielectric constant of the adhesive layer not containing ionic liquid can be controlled by, for example, appropriately adjusting the polymer component in the adhesive composition, or the type or content of the ionic additive within the above-mentioned appropriate range.

<Ionic conductivity of adhesive layer and capacitance per unit area at the interface between the adhesive layer and the adherend> Regarding the adhesive composition of the second embodiment, an adhesive layer is formed using the adhesive composition and attached to an aluminum plate comprising A5052P H32 in JIS H4000:2014. After being placed in an environment of 22°C and 15%RH for 7 days, the capacitance per unit area at the interface between the adhesive layer and the aluminum plate is greater than 0.9 μF/ ^cm2 , and the ionic conductivity of the adhesive layer is greater than 10 μS/m.

The ionic conductivity of the adhesive layer is related to the ease of movement of the ionic liquid in the adhesive layer. The greater the ionic conductivity, the easier it is for the ionic liquid to move. In addition, the capacitance per unit area of the interface between the adhesive layer and the adherend is related to the ease of existence of the ionic liquid at the interface between the adhesive layer and the adherend. The greater the capacitance, the easier it is for the ionic liquid to exist in large quantities at the interface between the adhesive layer and the adherend. Regarding the adhesive composition of the second embodiment, an adhesive layer is formed by using the adhesive composition and attached to an aluminum plate including A5052P H32 in JIS H4000:2014. After being placed in an environment of 22°C and 15%RH for 7 days, the capacitance per unit area of the interface between the adhesive layer and the aluminum plate is greater than 0.9 μF/ ^cm2 , and the ionic conductivity of the adhesive layer is greater than 10 μS/m. Therefore, a bond in which the bonding force is sufficiently reduced by applying a voltage can be formed even in a low humidity environment. Furthermore, it is more preferred that the capacitance per unit area is 1.2 μF/cm ² or more, and the ionic conductivity of the adhesive layer is 20 μS/m or more.

The above-mentioned ionic conductivity and capacitance can be controlled by, for example, appropriately adjusting the polymer component in the adhesive composition, or the type or content of the ionic liquid, or the type or content of the ionic additive within the above-mentioned appropriate range.

Furthermore, the above-mentioned ionic conductivity and capacitance refer to the ionic conductivity and capacitance measured in the following manner.

(Production of the sample for measurement (composite sample)) First, the adhesive composition is uniformly applied to the aluminum vapor-deposited surface of the aluminum vapor-deposited PET (Polyethylene Terephthalate) film 100 (trade name "Metalumy TS" manufactured by TORAY ADVANCED FILM). Furthermore, at this time, in order to make the electrode contact with the aluminum vapor-deposited surface, a portion not coated with the adhesive composition is locally set. Then, the adhesive layer 200 is formed by heating and drying at 130°C for 3 minutes, and an adhesive sheet sample is obtained. Thereafter, the adhesive surface of the obtained adhesive sheet sample is attached to an aluminum plate 300 (A5052P H32 (JIS H4000: 2014)), and a joint body sample 400 having a shape as shown in FIGS. 5 and 6 is obtained. Furthermore, FIG. 5 is a side view, and FIG. 6 is a top view.

(Measurement of capacitance and ionic conductivity) When measuring capacitance and ionic conductivity, an LCR (Inductance Capacitance Resistance) meter (e.g., IM3533 manufactured by Hioki Electric Co., Ltd.) is used. First, an AC voltage of 0.5 V is applied between the aluminum plate 300 and the aluminum-deposited surface of the aluminum-deposited PET film 100 using the LCR meter, and the frequency is changed from 0.5 Hz to 200 kHz to obtain a cole-cole curve.

Next, the bulk of the adhesive layer 200 is regarded as a parallel circuit of the resistance component R _adh and the electrostatic capacitance component C _adh , and the interface of the adhesive layer 200 is regarded as a parallel circuit of the resistance component R _p and the electrostatic capacitance component C _dl , and the equivalent circuit of the joint sample is set as shown in FIG7, and the obtained Cole-Cole curve is fitted using the following formula (A). In addition, the resistance component R ₀ is the wiring resistance.

[Number 1]

Furthermore, in formula (A), ω is the angular frequency.

By dividing the obtained C _dl by the area A of the adhesive surface of the adhesive layer 200, the capacitance per unit area of the interface between the adhesive layer 200 and the aluminum plate 300 can be calculated.

Next, the bulk resistance component R _adh of the adhesive layer 200 obtained by equation (A) can be used to obtain the ionic conductivity σ of the adhesive layer using the following equation (B).

[Number 2]

Furthermore, in formula (B), l is the thickness of the adhesive layer, and A is the area of the adhesive surface of the adhesive layer 200.

<Initial adhesion force, reduction rate of adhesion force obtained by voltage application> The adhesion force of the adhesive composition of this embodiment can be evaluated by various methods, for example, it can be evaluated by the 180° peeling test described in the column of the embodiment.

The adhesive composition of this embodiment is formed into an adhesive sheet as described in the column of the embodiment, and the initial adhesion force measured by the 180° peeling test is preferably 1.0 N/cm or more, more preferably 1.5 N/cm or more, further preferably 2.0 N/cm or more, particularly preferably 2.5 N/cm or more, and most preferably 3.0 N/cm or more. If the initial adhesion force is 1.0 N/cm or more, the adhesion with the adherend is more sufficient, and the adherend is not easy to peel off or shift.

In addition, the adhesive composition of the present embodiment is preferably formed into an adhesive sheet as described in the column of the embodiment, and placed in a specific temperature and humidity environment for a specific period of time, and the adhesion force measured by a 180° peel test while applying a voltage of 10 V for 30 seconds is sufficiently small relative to the initial adhesion force. That is, based on the adhesion force measured by the above method (expressed simply as "adhesion force during voltage application" in the following formula (C)) and the initial adhesion force, the adhesion force reduction rate calculated by the following formula (C) is preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. The above-mentioned specific temperature and humidity and period are preferably 22℃20%RH3 days, and more preferably 22℃15%RH7 days. Adhesion force reduction rate (%) = {1-(adhesion force during voltage application/initial adhesion force)}×100  (C)

Furthermore, the applied voltage and voltage application time during the electrical stripping are not limited to the above, and there is no particular limitation as long as the adhesive sheet can be stripped. The appropriate range is shown below. The applied voltage is preferably 1 V or more, more preferably 3 V or more, and further preferably 6 V or more. Also, it is preferably 100 V or less, more preferably 50 V or less, further preferably 30 V or less, and particularly preferably 15 V or less. The voltage application time is preferably 60 seconds or less, more preferably 40 seconds or less, further preferably 20 seconds or less, and particularly preferably 10 seconds or less. In this case, the workability is excellent. Also, the shorter the application time, the better, usually 1 second or more.

<Manufacturing method of adhesive composition> The adhesive composition of the present invention is not particularly limited and can be manufactured by appropriately stirring a polymer, an ionic liquid, an additive, and optionally a crosslinking agent, polyethylene glycol, a conductive filler, etc.

[Adhesive sheet] (Composition of adhesive sheet) The adhesive sheet of this embodiment is not particularly limited as long as it has at least one adhesive layer formed by the adhesive composition of the present embodiment (hereinafter also referred to as "electro-peelable adhesive layer"). The adhesive sheet of this embodiment may have an adhesive layer that does not contain an ionic liquid other than the electro-peelable adhesive layer (hereinafter sometimes referred to as "other adhesive layer"). In addition to the above, the adhesive sheet of this embodiment may have a substrate, a conductive layer, a substrate for conducting electricity, an intermediate layer, and a base coating layer. The adhesive sheet of this embodiment may be, for example, in a form wound into a roll or in a sheet form. Furthermore, the term "adhesive sheet" also includes the meaning of "tape". That is, the adhesive sheet of this embodiment may be a tape in the form of a strip.

The adhesive sheet of this embodiment may be a double-sided adhesive sheet without a substrate and only including an electrically peelable adhesive layer, that is, a double-sided adhesive sheet without a substrate layer (substrate-free). The adhesive sheet of this embodiment may be a double-sided adhesive sheet with a substrate and adhesive layers (electrically peelable adhesive layers or other adhesive layers) on both sides of the substrate. In addition, the adhesive sheet of this embodiment may also be a single-sided adhesive sheet with a substrate and adhesive layers (electrically peelable adhesive layers or other adhesive layers) on only one side of the substrate. Furthermore, the adhesive sheet of the present embodiment may have a separator (peeling pad) for the purpose of protecting the surface of the adhesive layer, and the separator is configured not to be contained in the adhesive sheet of the present embodiment.

The structure of the adhesive sheet of this embodiment is not particularly limited, and preferably includes the adhesive sheet X1 shown in FIG1 , the adhesive sheet X2 having a laminated structure shown in FIG2 , and the adhesive sheet X3 having a laminated structure shown in FIG3 . The adhesive sheet X1 is a double-sided adhesive sheet without a substrate and only includes an electrically peelable adhesive layer 1 . The adhesive sheet X2 is a double-sided adhesive sheet with a substrate and having a layer structure of an adhesive layer 2 , an electrically conductive substrate 5 (substrate 3 and conductive layer 4 ), and an electrically peelable adhesive layer 1 . The adhesive sheet X3 is a double-sided adhesive sheet with a substrate, which has an adhesive layer 2, a conductive substrate 5 (substrate 3 and conductive layer 4), an electrical release adhesive layer 1, a conductive substrate 5 (substrate 3 and conductive layer 4), and an adhesive layer 2. In the conductive substrate 5 of the adhesive sheets X2 and X3 shown in FIGS. 2 and 3 , the substrate 3 is not essential, and only the conductive layer 4 may be provided. In addition, in the adhesive sheet X2 of FIG. 2 , a single-sided adhesive sheet without an adhesive layer 2 may be provided.

The substrate 3 is not particularly limited, and examples thereof include: paper-based substrates such as paper, fiber-based substrates such as cloth and nonwoven fabrics, plastic-based substrates such as films or sheets of various plastics (polyolefin-based resins such as polyethylene and polypropylene, polyester-based resins such as polyethylene terephthalate, acrylic-based resins such as polymethyl methacrylate, etc.), laminates thereof, etc. The substrate may have a single-layer form or a multi-layer form. Furthermore, the substrate may be subjected to various treatments such as back surface treatment, antistatic treatment, and primer treatment as needed.

The conductive layer 4 is not particularly limited as long as it is a conductive layer. It can be a metal substrate such as metal (such as aluminum, magnesium, copper, iron, tin, gold, etc.) foil, a metal plate (such as aluminum, magnesium, copper, iron, tin, silver, etc.), a conductive polymer, etc., or a metal vapor-deposited film provided on the substrate 3.

The conducting substrate 5 is not particularly limited as long as it is a substrate having a conductive layer (conducting electricity), and may include a substrate having a metal layer formed on the surface thereof, such as a substrate having a metal layer formed on the surface of the substrate exemplified above by plating, chemical evaporation, sputtering, etc. Examples of the metal layer include the metals exemplified above, metal plates, and conductive polymers.

In the adhesive sheet X1, the adherends on both sides are preferably adherends having metal adhered surfaces. In the adhesive sheet X2, the adherend on the side of the electrolytic peeling adhesive layer 1 is preferably adherends having metal adhered surfaces.

As the metal adhered surface, there can be listed a surface containing a metal having electrical conductivity, such as aluminum, copper, iron, magnesium, tin, gold, silver, and lead as the main component, among which the surface containing a metal containing aluminum is preferred. As the adherend having a metal adhered surface, there can be listed a sheet, a part, and a plate containing a metal having aluminum, copper, iron, magnesium, tin, gold, silver, and lead as the main component. As the adherend other than the adherend having a metal adhered surface, there is no particular limitation, and there can be listed: fiber sheets such as paper, cloth, and non-woven fabrics, and various plastic films or sheets.

From the viewpoint of initial adhesion, it is preferred that the thickness of the peelable adhesive layer 1 is 1 μm or more and 1000 μm or less. The upper limit of the thickness of the peelable adhesive layer 1 is more preferably 500 μm, further preferably 100 μm, and particularly preferably 30 μm, and the lower limit is more preferably 3 μm, further preferably 5 μm, and particularly preferably 8 μm. Furthermore, in the case where the adhesive sheet is a substrate-free double-sided adhesive sheet (adhesive sheet X1 shown in FIG. 1 ) including only one layer of peelable adhesive layer, the thickness of the peelable adhesive layer becomes the thickness of the adhesive sheet.

From the viewpoint of adhesion, the thickness of the adhesive layer 2 is preferably 1 μm or more and 2000 μm or less. The upper limit of the thickness of the adhesive layer 2 is more preferably 1000 μm, further preferably 500 μm, and particularly preferably 100 μm, and the lower limit is more preferably 3 μm, further preferably 5 μm, and particularly preferably 8 μm.

The thickness of the substrate 3 is preferably 10 μm or more and 1000 μm or less. The upper limit of the thickness is more preferably 500 μm, further preferably 300 μm, and particularly preferably 100 μm, and the lower limit is more preferably 12 μm, further preferably 25 μm.

The thickness of the conductive layer 4 is preferably 0.001 μm or more and 1000 μm or less. The upper limit of the thickness is more preferably 500 μm, further preferably 300 μm, further preferably 50 μm, further preferably 10 μm, and the lower limit is more preferably 0.01 μm, further preferably 0.03 μm, further preferably 0.05 μm.

The thickness of the conducting substrate 5 is preferably 10 μm or more and 1000 μm or less. The upper limit of the thickness is more preferably 500 μm, further preferably 300 μm, and particularly preferably 100 μm, and the lower limit is more preferably 12 μm, further preferably 25 μm.

The surface of the electric peelable adhesive layer and other adhesive layers of the adhesive sheet of this embodiment can be protected by a spacer (peeling pad). The spacer is not particularly limited, and examples thereof include: a peeling pad whose surface is treated with polysilicone on a substrate (backing substrate) such as paper or plastic film, a peeling pad formed by laminating a polyolefin resin on the surface of a substrate (backing substrate) such as paper or plastic film, etc. The thickness of the spacer is not particularly limited, and is preferably greater than 10 μm and less than 100 μm.

The thickness of the adhesive sheet of this embodiment is preferably 20 μm or more and 3000 μm or less. The upper limit of the thickness is more preferably 1000 μm, further preferably 300 μm, and particularly preferably 200 μm, and the lower limit is more preferably 30 μm, further preferably 50 μm.

In particular, in the case of the adhesive sheet X2 shown in Fig. 2 , the thickness of the adhesive sheet is preferably 50 μm or more and 2000 μm or less. The upper limit of the thickness is more preferably 1000 μm, further preferably 200 μm, and the lower limit is more preferably 80 μm, further preferably 100 μm.

In particular, in the case of the adhesive sheet X3 shown in Fig. 3 , the thickness of the adhesive sheet is preferably 100 μm or more and 3000 μm or less. The upper limit of the thickness is more preferably 1000 μm, further preferably 300 μm, and the lower limit is more preferably 150 μm, further preferably 200 μm.

(Adhesive sheet manufacturing method) The adhesive sheet of this embodiment can be manufactured by a known or conventional manufacturing method. The electro-peeling adhesive layer in the adhesive sheet of this embodiment can be a method in which a solution obtained by dissolving the adhesive composition of this embodiment in a solvent as needed is applied on a separator, and the solution is dried and/or hardened. In addition, other adhesive layers can be a method in which a solution obtained by dissolving an adhesive composition containing no ionic liquid and additives in a solvent as needed is applied on a separator, and the solution is dried and/or hardened. Furthermore, the solvent and separator can use those listed above.

During coating, a conventional coating machine (such as a gravure roll coater, a reverse roll coater, a contact roll coater, a dip roll coater, a rod coater, a doctor blade coater, a spray roll coater, etc.) may be used.

By the above method, an electrical peelable adhesive layer and other adhesive layers can be manufactured, and by appropriately laminating the electrical peelable adhesive layer and other adhesive layers on a substrate, a conductive layer, and a conductive substrate, an adhesive sheet of the present embodiment can be manufactured. Furthermore, an adhesive sheet can be manufactured by using a substrate, a conductive layer, and a conductive substrate instead of a spacer and applying an adhesive composition.

(Adhesive sheet stripping method) The adhesive sheet of this embodiment can be stripped from the adherend by applying a voltage to the stripping adhesive layer to generate a potential difference in the thickness direction of the stripping adhesive layer. For example, in the case of an adherend having metal adhered surfaces on both sides of the adhesive sheet X1, the stripping can be performed by applying a voltage to the stripping adhesive layer by electrifying the metal adhered surfaces on both sides. In the case of the adhesive sheet X2, when the peelable adhesive layer has a metal adhered surface, the peeling can be performed by applying a voltage to the peelable adhesive layer by electrifying the conductive adherend and the conductive layer 4. In the case of the adhesive sheet X3, the peeling can be performed by electrifying the conductive layers 4 on both sides and applying a voltage to the peelable adhesive layer. It is preferred that the electrification is performed by connecting the terminals to one end and the other end of the adhesive sheet to apply a voltage to the entire peelable adhesive layer. Furthermore, when the adherend has a metal adhered surface, the one end and the other end may also be a part of the adherend having the metal adhered surface. Furthermore, during peeling, water may be added to the interface between the metal adhered surface and the peelable adhesive layer before applying voltage.

(Application of adhesive sheet) As a previous re-peeling technology, there are adhesive layers that are peeled off by curing them by ultraviolet (UV) irradiation, or adhesive layers that are peeled off by heat. Adhesive sheets with such adhesive layers cannot be used in situations where ultraviolet (UV) irradiation is difficult or when the component to be adhered is damaged by heat. The adhesive sheet of this embodiment having the above-mentioned electric peeling adhesive layer does not use ultraviolet rays or heat, so it will not damage the component to be adhered, and can be easily peeled off by applying voltage. Therefore, the adhesive sheet of this embodiment is suitable for fixing the secondary battery (such as lithium-ion battery pack) used in mobile terminals such as smart phones, mobile phones, laptops, video cameras, digital cameras, etc. on the casing.

In addition, regarding the rigid components that are joined to the adhesive sheet of this embodiment, for example, there can be listed: silicon substrates for semiconductor wafers, sapphire substrates, SiC substrates and metal base substrates for LEDs (Light Emitting Diodes), TFT (Thin Film Transistor) substrates and color filter substrates for displays, and base substrates for organic EL (Electroluminescence) panels. Examples of fragile components that can be bonded to double-sided adhesive sheets include semiconductor substrates such as compound semiconductor substrates, silicon substrates for MEMS (Microelectro Mechanical System) devices, passive matrix substrates, cover glass for smartphones, OGS (One Glass Solution) substrates with a touch panel sensor attached to the cover glass, organic substrates and organic-inorganic hybrid substrates with silsesquioxane as the main component, flexible glass substrates for flexible displays, and graphene sheets.

[Joint body] The joint body of the present embodiment has a laminated structure, which includes: an adherend having a metal adhered surface, and an adhesive sheet having an electro-peelable adhesive layer bonded to the metal adhered surface. Examples of the adherend having a metal adhered surface include metals containing aluminum, copper, iron, magnesium, tin, gold, silver, and lead as main components, among which a metal containing aluminum is preferred.

As the bonding body of this embodiment, for example, the following bonding bodies can be listed: in the case of adhesive sheet X1, a bonding body having an adherend having a metal adhered surface on both sides of the peelable adhesive layer 1; in the case of adhesive sheet X2, a bonding body having an adherend having a metal adhered surface on the peelable adhesive layer 1 side and an adherend on the adhesive layer 2 side; in the case of adhesive sheet X3, a bonding body having an adherend on both sides of the adhesive layer 2, etc. [Example]

The present invention will be described in more detail below with reference to the following examples, but the present invention is not limited to these examples. The weight average molecular weight described below is measured by the gel permeation chromatography (GPC) method described above.

[Examples 1-1 to 1-8, Comparative Examples 1-1 to 1-5] <Preparation of polymer solution> (Preparation of acrylic polymer 1 solution) 95 parts by mass of n-butyl acrylate (BA) as monomer components, 5 parts by mass of acrylic acid (AA), and 150 parts by mass of ethyl acetate as polymerization solvent were placed in a separable flask, and stirred for 1 hour while introducing nitrogen. After removing oxygen from the polymerization system, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added, the temperature was raised to 63°C, and the reaction was carried out for 6 hours. Thereafter, ethyl acetate was added to obtain an acrylic polymer 1 solution having a solid content concentration of 40% by mass.

(Preparation of acrylic polymer 2 solution) 90 parts by mass of n-butyl acrylate (BA) as monomer components, 10 parts by mass of 4-hydroxybutyl acrylate (4HBA) as polymerization solvent, and 150 parts by mass of ethyl acetate as polymerization solvent were placed in a separable flask, and stirred for 1 hour while introducing nitrogen. After removing oxygen from the polymerization system, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added, the temperature was raised to 63°C, and the reaction was carried out for 6 hours. Thereafter, ethyl acetate was added to obtain an acrylic polymer 2 solution with a solid content concentration of 30% by mass.

(Preparation of acrylic polymer 3 solution) 67 parts by mass of n-butyl acrylate (BA) as monomer components, 30 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 polymerization solvent were placed in a separable flask, and stirred for 1 hour while introducing nitrogen. After removing oxygen from the polymerization system, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added, the temperature was raised to 63°C, and the reaction was carried out for 6 hours. Thereafter, ethyl acetate was added to obtain an acrylic polymer 3 solution with a solid content concentration of 40% by mass.

(Preparation of acrylic polymer 4 solution) 67 parts by mass of n-butyl acrylate (BA) as monomer components, 33 parts by mass of methyl methacrylate (MMA) as polymerization solvent, and 150 parts by mass of ethyl acetate as polymerization solvent were placed in a separable flask, and stirred for 1 hour while introducing nitrogen. After removing oxygen from the polymerization system, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added, the temperature was raised to 63°C, and the reaction was carried out for 6 hours. Thereafter, ethyl acetate was added to obtain an acrylic polymer 4 solution with a solid content concentration of 40% by mass.

(Preparation of acrylic polymer 5 solution) 87 parts by mass of n-butyl acrylate (BA) as monomer components, 10 parts by mass of 4-hydroxybutyl acrylate (4HBA), 3 parts by mass of acrylic acid (AA), and 150 parts by mass of ethyl acetate as polymerization solvent were placed in a separable flask, and stirred for 1 hour while introducing nitrogen. After removing oxygen from the polymerization system, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added, the temperature was raised to 63°C, and the reaction was carried out for 6 hours. Thereafter, ethyl acetate was added to obtain an acrylic polymer 5 solution with a solid content concentration of 30% by mass.

<Preparation of Adhesive Composition> The acrylic polymer solution obtained above or the polymer, crosslinking agent, ionic liquid, and additive shown below are added, stirred, and mixed to obtain the adhesive composition of Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-5. The amount of each component is shown in Table 1. In addition, the value of each component in Table 1 refers to the mass part. In addition, the amount of polymer (mass part) is the amount of solid components in the polymer solution (mass part). The abbreviations of the polymer, crosslinking agent, ionic liquid, and additive in Table 1 are as follows. (Polymer) Vylon UR-V8700: Urethane-modified polyester resin, trade name "Vylon UR-V8700", manufactured by Toyobo Co., Ltd. Vylon BX1001: Polyester resin, trade name "Vylon BX1001", manufactured by Toyobo Co., Ltd. SOMAREX 530: Anionic polyacrylamide polymer (ionic polymer), trade name "SOMAREX 530", manufactured by SOMAR Co., Ltd. (Ionic liquid) AS-110: Cation: 1-ethyl-3-methylimidazolium cation, anion: bis(fluorosulfonyl)imide anion, trade name "ELEXCEL AS-110", manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd. (Crosslinking agent) V-05: Polycarbodiimide resin, trade name "Carbodilite V-05", manufactured by Nisshinbo Chemical Co., Ltd. Takenate D110: Trimethylolpropane diisocyanate, trade name "Takenate D110N", manufactured by Mitsui Chemicals Co., Ltd. (additive) EMI-nitrate: 1-ethyl-3-methylimidazolium nitrate, manufactured by Tokyo Chemical Industry Co., Ltd. Zn-nitrate: Zinc nitrate hexahydrate, manufactured by Wako Junyaku Industries Co., Ltd. BTC-5B: Barium titanium oxide No.27776: Carbon black

<Determination of relative dielectric constant of adhesive layer without ionic liquid> Except that no ionic liquid was added, the materials were stirred and mixed in the same manner as in the above-mentioned Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-5, and the obtained adhesive composition without ionic liquid was applied to the peeling surface of the polyethylene terephthalate separator (trade name "MRF38", manufactured by Mitsubishi Resin Co., Ltd.) with a uniform thickness using an applicator. Next, heat drying was performed at 130°C for 3 minutes to obtain an adhesive layer without ionic liquid having a thickness of 30 μm. Next, after the obtained adhesive layer without ionic liquid was placed in an environment of 22°C and 20%RH for 3 days, the relative dielectric constant of the adhesive layer at a frequency of 100 kHz was measured under the following conditions according to JIS K6911. (Measurement conditions) Measurement method: Capacitance method (device: using Agilent Technologies 4294A Precision Impedance Analyzer) Electrode composition: 12.1 mmφ, 0.5 mm thick aluminum plate Counter electrode: 3 oz copper plate Measurement environment: 23±1°C, 52±1%RH

<Determination of the moisture content of the electro-peelable adhesive layer> Using the adhesive composition of each example, the electro-peelable adhesive layer obtained in the same manner as above was placed in an environment of 22°C and 20%RH for 3 days, and then the moisture content of the adhesive layer was measured by the Karl Fischer moisture vaporization-coulometric titration method (JIS K0113: 2005). Specifically, the amount of moisture generated by heating vaporization at 200°C for 30 minutes was measured using the Hiranuma trace moisture measuring device AQ-2100 manufactured by Hiranuma Sangyo Co., Ltd., and the ratio relative to the weight of the sample before heating was set as the moisture content. That is, the moisture content was calculated by the following formula. In addition, "-" in Table 1 means not measured. Moisture content (%) = (Kar Fischer moisture content/total weight of sample before measurement) × 100

<Evaluation> (Initial Adhesion) The adhesive composition of each example was applied to the peeling surface of a polyethylene terephthalate separator (trade name "MRF38", manufactured by Mitsubishi Resin Co., Ltd.) using an applicator to a uniform thickness. Then, heat drying was performed at 130°C for 3 minutes to obtain an electro-peelable adhesive layer (adhesive sheet) with a thickness of 30 μm. Next, the obtained electro-peelable adhesive layer (adhesive sheet) was made into a sheet with a size of 10 mm × 80 mm, and the metal layer of a film with a metal layer as a substrate (trade name "BR1075", manufactured by TORAY ADVANCED FILM Co., Ltd., thickness 25 μm, size 10 mm × 100 mm) was bonded to the side without a spacer to produce a single-sided adhesive sheet with a substrate. The single-sided adhesive sheet of the peeling substrate is attached to the peeling surface of the aluminum plate (A5052P H32 (JIS H4000: 2014)) in a manner that one end of the adhesive sheet protrudes from the adherend by about 2 mm. The sheet is pushed back and forth once with a 2 kg roller and placed in an environment of 23°C for 30 minutes to obtain a joint body including an aluminum plate/electrically peelable adhesive layer (adhesive sheet) 1'/film with a metal layer (electrically conductive substrate) 5'. The outline of the joint body is shown in Figure 4. Afterwards, a peeling tester (trade name "variable angle peeling tester YSP", manufactured by Asahi Seiko Co., Ltd.) was used to perform peeling in the direction of the arrow in Figure 4, and the adhesion force in the 180° peeling test (tensile speed: 300 mm/min, peeling temperature 23°C) was measured. The test results are shown in Table 1.

(Adhesion force during voltage application) After pushing back and forth once with a 2 kg roller, place in an environment of 22°C and 20% RH for 3 days, and install the negative and positive electrodes of the DC galvanometer at α and β in Figure 4 of the joint before peeling, apply voltage at 10 V for 30 seconds, and peel while applying voltage. Except for these aspects, the adhesion force during voltage application is measured in the same way as the above-mentioned initial adhesion force measurement. The measurement results are shown in Table 1.

(Adhesion force reduction rate) Using the initial adhesion force and adhesion force during voltage application measured by the above method, the adhesion force reduction rate obtained by voltage application was calculated using the following formula (C). The results are shown in Table 1. Adhesion force reduction rate (%) = {1-(adhesion force during voltage application/initial adhesion force)} × 100  (C)

[Table 1] Embodiment 1-1 Embodiment 1-2 Embodiment 1-3 Comparison Example 1-1 Comparison Example 1-2 Comparison Example 1-3 Embodiment 1-4 Embodiment 1-5 Embodiment 1-6 Embodiment 1-7 Embodiment 1-8 Comparison Example 1-4 Comparison Examples 1-5 Element polymer Acrylic polymer 1 100 100 100 100 100 100 100 Acrylic polymer 2 100 Acrylic polymer 3 100 Acrylic polymer 4 100 Acrylic polymer 5 100 Vylon UR-V8700 100 Vylon BX1001 100 SOMAREX 530 0.2 Ionic liquids AS-110 5 5 5 5 5 5 5 5 5 5 5 5 5 Crosslinking agent V-05 1 1 1 1 1 1 1 0.3 Takenate D110 0.5 0.5 Additives EMI-nitrate 2 Zn-nitrate 2 2 BTC-5B 2 No.27776 2 Physical properties Relative dielectric constant of adhesive layer without ionic liquid (ε') 5.6 5.4 5.5 4.3 4.6 4.7 6.5 5.8 5.1 5.2 6.4 3.9 4.3 Moisture content (%) 0.22 0.27 0.4 - - 0.15 0.35 0.32 0.13 0.23 - 0.11 0.24 Reviews Initial adhesion force (N/cm) 5.55 4.92 6.01 4.65 4.63 5.12 2.59 3.45 3.02 3.72 5.06 5 5.2 Adhesion force during voltage application (N/cm) 0.32 0.06 0.13 2.31 1.96 2.87 0.08 0.05 0.49 0.79 0.65 2.32 2.57 Adhesion force reduction rate (%) 94.2 98.9 97.8 50.4 57.6 43.9 96.9 98.6 83.8 78.8 87.2 53.6 50.6

The adhesive layer is formed by using a composition including components other than the ionic liquid in the adhesive composition, and after the adhesive layer is placed in an environment of 22°C and 20%RH for 3 days, the relative dielectric constant of the adhesive layer at a frequency of 100 Hz is 5 or more. The reduction rate of the adhesive force obtained by applying a voltage of the adhesive compositions of Examples 1-1 to 1-8 is large.

[Example 2-1 to 2-11, Comparative Example 2-1 to 2-3] <Preparation of polymer solution> (Preparation of acrylic polymer 6 solution) 90 parts by mass of n-butyl acrylate (BA) as monomer components, 10 parts by mass of acrylic acid (AA), and 150 parts by mass of ethyl acetate as polymerization solvent were placed in a separable flask, and stirred for 1 hour while introducing nitrogen. After removing oxygen from the polymerization system, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added, the temperature was raised to 63°C, and the reaction was carried out for 6 hours. Thereafter, ethyl acetate was added to obtain an acrylic polymer 6 solution having a solid content concentration of 40% by mass.

(Preparation of acrylic polymer 7 solution) 90 parts by mass of n-butyl acrylate (BA) as monomer components, 7 parts by mass of 4-hydroxybutyl acrylate (4HBA), 3 parts by mass of acrylic acid (AA), and 150 parts by mass of ethyl acetate as polymerization solvent were placed in a separable flask, and stirred for 1 hour while introducing nitrogen. After removing oxygen from the polymerization system, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added, the temperature was raised to 63°C, and the reaction was carried out for 6 hours. Thereafter, ethyl acetate was added to obtain an acrylic polymer 7 solution with a solid content concentration of 30% by mass.

(Preparation of acrylic polymer 8 solution) 94 parts by mass of n-butyl acrylate (BA) as monomer components, 3 parts by mass of 4-hydroxybutyl acrylate (4HBA), 3 parts by mass of acrylic acid (AA), and 150 parts by mass of ethyl acetate as polymerization solvent were placed in a separable flask, and stirred for 1 hour while introducing nitrogen. After removing oxygen from the polymerization system, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added, the temperature was raised to 63°C, and the reaction was carried out for 6 hours. Thereafter, ethyl acetate was added to obtain an acrylic polymer 8 solution with a solid content concentration of 30% by mass.

(Preparation of acrylic polymer 9 solution) 77 parts by mass of n-butyl acrylate (BA) as monomer components, 20 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 polymerization solvent were placed in a separable flask, and stirred for 1 hour while introducing nitrogen. After removing oxygen from the polymerization system, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added, the temperature was raised to 63°C, and the reaction was carried out for 6 hours. Thereafter, ethyl acetate was added to obtain an acrylic polymer 9 solution with a solid content concentration of 40% by mass.

(Preparation of acrylic polymer 10 solution) 87 parts by mass of n-butyl acrylate (BA) as monomer components, 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 polymerization solvent were placed in a separable flask, and stirred for 1 hour while introducing nitrogen. After removing oxygen from the polymerization system, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added, the temperature was raised to 63°C, and the reaction was carried out for 6 hours. Thereafter, ethyl acetate was added to obtain an acrylic polymer 10 solution with a solid content concentration of 40% by mass.

<Preparation of Adhesive Composition> The acrylic polymer solution obtained above or the above polymer, crosslinking agent, ionic liquid, additive, or the following ionic liquid, preservative are added and stirred and mixed to obtain the adhesive compositions of Examples 2-1 to 2-11 and Comparative Examples 2-1 to 2-3. Table 2 shows the blending amount of each component. (Ionic liquid) 1-Hexyl-pyridinium-bis(trifluorosulfonyl)imide (Preservative, additive, crosslinking agent) Irgamet 30: N,N-bis(2-ethylhexyl)-1,2,4-triazol-1-ylmethaneamine, trade name "Irgamet 30", manufactured by BASF Irgacor DSSG: Disodium sebacate, trade name "Irgacor DSSG", manufactured by BASF Amin O: Imidazolinium derivative, trade name "Amin O", manufactured by BASF PEG400: Polyethylene glycol, trade name "PEG400", manufactured by Tokyo Chemical Industry Co., Ltd. Coronate L: Isocyanate compound, trade name "Coronate L", manufactured by Tosoh Co., Ltd.

<Measurement of ionic conductivity of adhesive layer and capacitance per unit area> The adhesive composition of each example was used to prepare a sample for measurement (composite sample) in the following manner, and the capacitance of the bonding interface and the ionic conductivity of the adhesive layer were obtained by the following method. The results are shown in Table 2.

(Production of the sample for measurement (composite sample)) First, the adhesive composition was uniformly applied to the aluminum vapor-coated surface of the aluminum vapor-coated PET film 100 (trade name "Metalumy TS" manufactured by TORAY ADVANCED FILM). Furthermore, at this time, in order to make the electrode contact with the aluminum vapor-coated surface, a portion where the adhesive composition was not applied was partially set. Then, heat drying was performed at 130°C for 3 minutes to form an adhesive layer 200, and an adhesive sheet sample was obtained. Thereafter, the adhesive surface of the obtained adhesive sheet sample is attached to an aluminum plate 300 (A5052P H32 (JIS H4000: 2014)), and a joint body sample 400 having a shape as shown in FIGS. 5 and 6 is obtained. Furthermore, FIG. 5 is a side view, and FIG. 6 is a top view.

(Measurement of capacitance and ionic conductivity) When measuring capacitance and ionic conductivity, an LCR meter (e.g., IM3533 manufactured by Hioki Electric Co., Ltd.) is used. First, an AC voltage of 0.5 V is applied between the aluminum plate 300 and the aluminum-deposited surface of the aluminum-deposited PET film 100 using the LCR meter, and the frequency is changed from 0.5 Hz to 200 kHz to obtain a Cole-Cole curve.

Next, the bulk of the adhesive layer 200 is regarded as a parallel circuit of the resistance component R _adh and the electrostatic capacitance component C _adh , and the interface of the adhesive layer 200 is regarded as a parallel circuit of the resistance component R _p and the electrostatic capacitance component C _dl. The equivalent circuit of the joint sample is set as shown in FIG7, and the obtained Cole-Cole curve is fitted using the following formula (A). Furthermore, the resistance component R ₀ is the wiring resistance. [Figure 3]

Furthermore, in formula (A), ω is the angular frequency.

By dividing the obtained C _dl by the area A of the adhesive surface of the adhesive layer 200, the capacitance per unit area of the interface between the adhesive layer 200 and the aluminum plate 300 is calculated.

Next, using the bulk resistance component R _adh of the adhesive layer 200 obtained by equation (A), the ionic conductivity σ of the adhesive layer is obtained by using the following equation (B).

[Number 4]

Furthermore, in formula (B), l is the thickness of the adhesive layer, and A is the area of the adhesive surface of the adhesive layer 200.

<Evaluation> (Initial Adhesion Strength) For each adhesive composition, an aluminum-evaporated PET film (trade name "Metalumy TS" manufactured by TORAY ADVANCED FILM) was used as a substrate and an adhesive layer was formed on the aluminum-evaporated surface. The initial adhesion strength was measured in the same manner as in Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-5. The measurement results are shown in Table 2.

(Adhesion force during voltage application after storage at 22°C, 20%RH for 3 days) After being pushed back and forth once with a 2 kg roller, the joint was placed at 22°C, 20%RH for 3 days. Before peeling, the negative and positive electrodes of the DC galvanometer were installed at α and β in Figure 4 of the joint, respectively. The voltage was applied for 30 seconds at a voltage of 10 V. In this state, the joint was peeled while the voltage was applied. Except for these aspects, the adhesion force during voltage application was measured in the same way as the above-mentioned initial adhesion force measurement, and the electrical peeling property was evaluated by the following criteria. The measurement results are shown in Table 2. ○: Adhesion force reduction rate is 60% or more. ×: Adhesion force reduction rate is less than 60%.

(Adhesion force during voltage application after storage at 22°C, 15%RH for 7 days) After being pushed back and forth once with a 2 kg roller, the joint was placed at 22°C, 15%RH for 7 days. Before peeling, the negative and positive electrodes of the DC galvanometer were installed at α and β in Figure 4 of the joint, respectively. The voltage was applied for 10 seconds at a voltage of 10 V. In this state, the joint was peeled while the voltage was applied. Except for these aspects, the adhesion force during voltage application was measured in the same way as the above-mentioned initial adhesion force measurement. The measurement results are shown in Table 2.

(Adhesion force reduction rate) Using the initial adhesion force measured by the above method and the adhesion force during voltage application after storage at 22°C and 15%RH for 7 days, the adhesion force reduction rate obtained by voltage application was calculated using the following formula (C). The results are shown in Table 2. Adhesion force reduction rate (%) = {1-(adhesion force during voltage application/initial adhesion force)} × 100  (C)

[Table 2] Example 2-1 Example 2-2 Embodiment 2-3 Embodiment 2-4 Embodiment 2-5 Comparison Example 2-1 Comparison Example 2-2 Comparison Example 2-3 Embodiment 2-6 Embodiment 2-7 Embodiment 2-8 Embodiment 2-9 Embodiment 2-10 Embodiment 2-11 Element polymer Acrylic polymer 1 100 100 100 Acrylic polymer 2 Acrylic polymer 3 100 100 Acrylic polymer 5 100 Acrylic polymer 6 100 100 Acrylic polymer 7 100 Acrylic polymer 8 100 Acrylic polymer 9 100 Acrylic polymer 10 100 Vylon UR-V8700 100 Vylon BX1001 100 SOMAREX 530 0.2 0.2 0.2 0,2 0.2 0.2 Ionic liquids AS-110 5 5 5 5 5 5 5 5 5 5 5 5 1-Hexyl-pyridinium-bis(trifluorosulfonyl)imide 10 10 Preservatives irgamet30 0.8 0.8 0.8 0.8 0.8 0.8 0.8 Irgacor DSSG 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Amin O 3 3 3 3 3 3 Additives PEG400 20 Zn-nitrate 2 2 EMI-nitrate 2 2 2 2 2 2 Crosslinking agent V-05 1 0.3 1 0.5 0.5 0.75 0.8 0.2 0.5 0.5 0.5 0.5 Coronate L 0.25 0.25 0.1 Takenate D110 0.5 Physical properties and evaluation Initial adhesion force [N/cm] 6.75 5.33 4.32 6.12 5.78 2.92 6.77 5.76 5.29 4.47 2.84 2.74 2.77 3.12 After 3 days of storage at 22℃, 20%RH Electrical stripping ○ ○ ○ ○ ○ ○ × × ○ ○ ○ ○ ○ ○ 22℃, 15%RH after 7 days of storage Capacitance (μF/cm ² ) 1.41 0.95 1.04 0.94 0.92 0.81 0.62 0.89 1.30 1.37 1.37 1.30 1.31 1.30 Ionic conductivity (μS/m) 10.2 22.5 16.1 23.5 258.7 258.7 15.4 8.5 10.7 44.9 21.9 47.1 32.5 22.6 Adhesion force during voltage application (N/cm) 0.23 0.67 0.36 0.11 0.12 7.93 4.90 3.41 0.94 0.11 0.09 0.14 0.10 0.12 Adhesion force reduction rate (%) 96.6 87.4 91.7 98.2 97.9 -171.3 27.6 40.8 82.2 97.5 96.8 94.9 96.4 96.1

Regarding the adhesive layer formed by using the adhesive composition and attached to the aluminum plate including A5052P H32 in JIS H4000:2014, after being placed in an environment of 22°C and 15%RH for 7 days, the capacitance per unit area of the interface between the adhesive layer and the aluminum plate was greater than 0.9 μF/ ^cm2 , and the ionic conductivity of the adhesive layer was greater than 10 μS/m. For the adhesive compositions of Examples 2-1 to 2-11, the reduction rate of the adhesive force obtained by applying a voltage was relatively large.

[Examples 3-1 to 3-5] <Preparation of polymer solution> (Preparation of acrylic polymer 11 solution) 2-methoxyethyl acrylate (MEA): 95 mass parts and 4-hydroxybutyl acrylate (4HBA): 5 mass parts as monomer components were added into a separable flask, and nitrogen was introduced while stirring for 1 hour. After removing oxygen from the polymerization system, 2,2'-azobisisobutyronitrile (AIBN): 0.2 mass parts as a polymerization initiator were added, the temperature was raised to 63°C and the reaction was carried out for 6 hours. Thereafter, ethyl acetate was added to obtain an acrylic polymer 11 solution with a solid content concentration of 30 mass%.

<Preparation of Adhesive Composition> The acrylic polymer solution obtained above or the above polymer, crosslinking agent, ionic liquid, additive, or the following additives are added, stirred and mixed to obtain the adhesive composition of Examples 3-1 to 3-5. Table 3 shows the amount of each component. (Additives) ・EMIM-MeSO ₃ : Ionic additive, imidazolium salt, manufactured by Tokyo Chemical Industry Co., Ltd. ・EPOMIN200: Polyethyleneimine, manufactured by Nippon Catalyst.

<Measurement and evaluation of ionic conductivity and capacitance per unit area of adhesive layer> In the same manner as in Examples 2-1 to 2-11 and Comparative Examples 2-1 to 2-3, the initial bonding force, the bonding force during voltage application and the bonding force reduction rate after 3 days of storage in an environment of 22°C 20%RH, and the bonding force during voltage application and the bonding force reduction rate after 7 days of storage in an environment of 22°C 15%RH were measured. In addition, in the same manner as in Examples 2-1 to 2-11 and Comparative Examples 2-1 to 2-3, a sample for measurement (composite sample) was prepared to obtain the capacitance of the bonding interface and the ionic conductivity of the adhesive layer. The results are shown in Table 3.

[Table 3] Example 3-1 Example 3-2 Embodiment 3-3 Embodiment 3-4 Embodiment 3-5 Element polymer Acrylic polymer 10 100 Acrylic polymer 11 100 100 Vylon UR-V8700 100 Vylon BX1001 100 Ionic liquids AS-110 5 5 5 5 5 Preservatives irgamet30 0.8 0.8 0.8 Irgacor DSSG 0.3 0.3 0.3 Amin O 3 3 3 Additives EMI-nitrate 2 2 SOMAREX 530 0.2 0.2 0.2 EMIM-MeSO ₃ 2 EPOMIN200 10 Crosslinking agent V-05 0.3 Takenate D110 0.15 Physical properties and evaluation Initial adhesion force [N/cm] 6.22 6.25 6.22 2.83 1.93 After 3 days of storage at 22℃, 20%RH Adhesion force during voltage application (N/cm) 0.03 0.04 0.03 0.03 0.03 Adhesion force reduction rate (%) 99.5 99.4 99.5 98.9 98.4 After 7 days at 22℃, 15%RH Capacitance (μF/cm ² ) 1.62 1.24 1.20 0.99 1.7 Ionic conductivity (μS/m) 80.0 25.0 20.0 144.0 196 Adhesion force during voltage application (N/cm) 0.07 0.05 0.09 0.13 0.01 Adhesion force reduction rate (%) 98.9 99.2 98.6 95.4 99.5

Regarding the adhesive composition formed by using the adhesive layer and attached to the aluminum plate including A5052P H32 in JIS H4000:2014, after being placed in an environment of 22°C and 15%RH for 7 days, the capacitance per unit area of the interface between the adhesive layer and the aluminum plate was greater than 0.9 μF/ ^cm2 , and the ionic conductivity of the adhesive layer was greater than 10 μS/m. For the adhesive compositions of Examples 3-1 to 3-5, the reduction rate of the adhesive force obtained by applying a voltage was relatively large.

The preferred embodiments of the present invention are described above, but the present invention is not limited to the above embodiments, and various changes and substitutions can be made to the above embodiments without departing from the scope of the present invention. In addition, this application is based on the Japanese patent application filed on September 3, 2018 (Japanese Patent Application No. 2018-164545), the Japanese patent application filed on March 28, 2019 (Japanese Patent Application No. 2019-065065), and the Japanese patent application filed on August 29, 2019 (Japanese Patent Application No. 2019-157325), and the contents thereof are cited as references in this application.

1: Strippable adhesive layer 1': Strippable adhesive layer (adhesive sheet) 2: Adhesive layer 3: Substrate 4: Conductive layer 5: Current-carrying substrate 5': Film with metal layer (current-carrying substrate) 6: Stainless steel plate 100: Aluminum vapor-deposited PET film 200: Adhesive layer 300: Aluminum plate 400: Joint sample _Cadh : Electrostatic capacitance component _Cdl : Electrostatic capacitance component _Radh : Resistance component _Rp : Resistance component _R0 : Resistance component X1: Adhesive sheet X2: Adhesive sheet X3: Adhesive sheet α: Location β: Location

FIG. 1 is a cross-sectional view showing an example of an adhesive sheet of the present invention. FIG. 2 is a cross-sectional view showing an example of a laminated structure of an adhesive sheet of the present invention. FIG. 3 is a cross-sectional view showing another example of a laminated structure of an adhesive sheet of the present invention. FIG. 4 is a cross-sectional view showing an overview of the method of a 180° peeling test in an embodiment. FIG. 5 is a side view of a composite sample for measuring capacitance and ionic conductivity. FIG. 6 is a top view of a composite sample for measuring capacitance and ionic conductivity. FIG. 7 is an equivalent circuit diagram of a composite sample for measuring capacitance and ionic conductivity.

1: Electrolytic peeling adhesive layer

X1: Adhesive sheet

Claims (11)

An adhesive composition comprises a polymer and an ionic liquid, wherein the polymer is an acrylic polymer having an alkoxy group, and the acrylic polymer comprises a monomer unit derived from an alkyl (meth)acrylate (the following formula (1)), _CH2 =C( ^Ra ) ^COORb (1) wherein ^Ra is a hydrogen atom or a methyl group, and ^Rb is an alkyl group having 1 to 8 carbon atoms. An adhesive layer is formed by using a composition comprising the components contained in the adhesive composition except the ionic liquid, and after the adhesive layer is placed in an environment of 22°C and 20%RH for 3 days, the relative dielectric constant of the adhesive layer at a frequency of 100 Hz is greater than 5. An adhesive composition comprises a polymer and an ionic liquid, wherein the polymer is an acrylic polymer having an alkoxy group, and the acrylic polymer comprises a monomer unit derived from an alkyl (meth)acrylate (the following formula (1)), _CH2 =C( ^Ra ) ^COORb (1) wherein ^Ra is a hydrogen atom or a methyl group, ^{and Rb} is an alkyl group having 1 to 8 carbon atoms. An adhesive layer is formed by using the adhesive composition and attached to an aluminum plate comprising A5052P H32 in JIS H4000:2014. After being placed in an environment of 22°C and 15%RH for 7 days, the capacitance per unit area of the interface between the adhesive layer and the aluminum plate is greater than 0.9μF/ ^cm2 , and the ionic conductivity of the adhesive layer is greater than 10μS/m. An adhesive composition as claimed in claim 2, wherein an adhesive layer is formed by using the adhesive composition and attached to an aluminum plate comprising A5052P H32 in JIS H4000:2014, and after being placed in an environment of 22°C and 15%RH for 7 days, the capacitance per unit area of the interface between the adhesive layer and the aluminum plate is greater than 1.2μF/ ^cm2 , and the ionic conductivity of the adhesive layer is greater than 20μS/m. The adhesive composition of any one of claims 1 to 3 further comprises an ionic solid. An adhesive composition as claimed in any one of claims 1 to 3, wherein the polymer comprises an ionic polymer. The adhesive composition of any one of claims 1 to 3, wherein the adhesive composition comprises 0.5 to 30 parts by mass of the ionic liquid and 0.5 to 10 parts by mass of the ionic solid relative to 100 parts by mass of the polymer. The adhesive composition of any one of claims 1 to 3, wherein the ionic liquid is contained in an amount of 0.5 to 30 parts by mass relative to 100 parts by mass of the polymer, and the polymer contains an ionic polymer in an amount of 0.05 to 2 parts by mass. An adhesive composition comprises 100 parts by weight of an acrylic polymer and 0.5 to 30 parts by weight of an ionic liquid, wherein the acrylic polymer comprises monomer units derived from a monomer containing a polar group, wherein the monomer containing a polar group is an alkoxy group-containing monomer, and wherein the acrylic polymer comprises monomer units derived from an alkyl (meth)acrylate (the following formula (1)): _CH2 =C( ^Ra ) ^COORb (1) wherein ^Ra is a hydrogen atom or a methyl group, and ^Rb is an alkyl group having 1 to 8 carbon atoms, and the ratio of the monomer containing a polar group to all monomer components constituting the acrylic polymer is 0.1 to 35% by weight. The adhesive composition of any one of claim 1 to 3 and 8 is for electrostripping. An adhesive sheet having an adhesive layer formed from the adhesive composition of any one of claims 1 to 9. A bonding body, comprising: an adherend having a metal adhered surface, and an adhesive sheet as claimed in claim 10, wherein the adhesive layer of the adhesive sheet is bonded to the metal adhered surface.

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