Adhesive composition, adhesive sheet and joined body

Abstract

The present invention relates to an adhesive composition comprising a polymer, an ionic liquid and an orientation material, and an adhesive sheet having an adhesive layer formed of the adhesive composition.

Description

Technical Field

[0001] The present invention relates to an adhesive composition, an adhesive sheet including an adhesive layer formed from the adhesive composition, and a joint of the adhesive sheet and an adherend. Background Art

[0002] In the process of manufacturing electronic components, there is an increasing demand for reprocessing (rework) to improve the yield rate, and recycling in which components are disassembled and recovered after use. In order to meet such demands, double-sided adhesive sheets with a certain degree of adhesiveness and a certain degree of peelability are sometimes used when joining components in the process of manufacturing electronic components. In addition, with the miniaturization of electronic devices, adhesive sheets with a certain degree of adhesiveness and a certain degree of peelability are sometimes used in the placement and fixation of fine components based on transfer.

[0003] As a double-sided PSA sheet that achieves both adhesive strength and releasability, there is known a PSA sheet that uses an ionic liquid containing cations and anions as a component forming the PSA composition and is releasable by applying a voltage to the PSA layer (electrically releasable PSA sheet) (Patent Documents 1 to 3).

[0004] It is believed that in the electro-peelable pressure-sensitive adhesive sheets of Patent Documents 1 to 3, the cations of the ionic liquid migrate to the cathode side and are reduced, and the anions of the ionic liquid migrate to the anode side and are oxidized by application of voltage, thereby weakening the adhesive strength of the adhesive interface and facilitating peeling.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2010-037354

[0008] Patent Document 2: Japanese Patent No. 6097112

[0009] Patent Document 3: Japanese Patent No. 4139851 Summary of the invention

[0010] Problems to be solved by the invention

[0011] The electrically removable adhesive sheet preferably firmly joins the components when no voltage is applied and can be peeled off with a small force when a voltage is applied. However, in the conventional electrically removable adhesive sheet using an ionic liquid, there are the following problems: if the adhesive force after the voltage is applied is reduced, the initial adhesive force when no voltage is applied cannot be fully obtained, and if the initial adhesive force when no voltage is applied is increased, the adhesive force after the voltage is applied is not sufficiently reduced.

[0012] The present invention has been completed in view of the above situation, and its purpose is to provide an adhesive composition and an adhesive sheet having an adhesive layer formed from the adhesive composition, wherein the adhesive composition can form an adhesive layer having excellent adhesive strength when no voltage is applied and the adhesive strength is sufficiently reduced by the application of voltage.

[0013] Means for solving problems

[0014] The inventors of the present application have conducted intensive studies to achieve the above-mentioned object, and as a result, have found that the above-mentioned problems in the prior art can be solved by adding an orientation material to an adhesive composition, thereby completing the present invention. That is, the present invention is as follows.

[0015] [1]

[0016] An adhesive composition comprises a polymer, an ionic liquid and an orientation material.

[0017] [2]

[0018] The adhesive composition according to [1], wherein the adhesive layer formed using the adhesive composition is bonded to an adherend and a voltage of 10 V is applied for 10 seconds, thereby being cleaved and peeled from the adherend.

[0019] 〔3〕

[0020] The adhesive composition as described in [2], wherein the cleavage peeling is natural peeling.

[0021] [4]

[0022] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the ionic liquid is contained in an amount of 4 parts by mass or more based on 100 parts by mass of the polymer.

[0023] 〔5〕

[0024] The adhesive composition according to any one of [1] to [4], wherein the polymer includes at least one selected from the group consisting of polyester polymers, urethane polymers, and acrylic polymers.

[0025] [6]

[0026] The pressure-sensitive adhesive composition according to [5], wherein the acrylic polymer comprises a unit derived from a polar group-containing monomer having a carboxyl group, an alkoxy group, a hydroxyl group and / or an amide bond.

[0027] 〔7〕

[0028] The pressure-sensitive adhesive composition according to [6], wherein the ratio of the polar group-containing monomer to the total monomer components constituting the acrylic polymer is 0.1 to 35% by mass.

[0029] [8]

[0030] The adhesive composition according to any one of [1] to [7], which is used for electrical stripping.

[0031] 〔9〕

[0032] A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of [1] to [8].

[0033] 〔10〕

[0034] A joined body comprising an adherend having a metal adherend surface and the adhesive sheet according to [9], wherein the adhesive layer of the adhesive sheet is bonded to the metal adherend surface.

[0035] Effects of the Invention

[0036] The adhesive composition of the present invention can form an adhesive layer having excellent adhesive strength when no voltage is applied and whose adhesive strength is sufficiently reduced by application of voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] [ Figure 1 ] is a schematic cross-sectional view showing an example of the adhesive sheet of the present invention.

[0038] [ Figure 2 ] is a schematic cross-sectional view showing an example of the layered structure of the adhesive sheet of the present invention.

[0039] [ Figure 3 ] is a schematic cross-sectional view showing another example of the laminated structure of the adhesive sheet of the present invention.

[0040] [ Figure 4 ] is a cross-sectional view showing an overview of the method of the 180° tear test in the embodiment.

[0041] [ Figure 5 ] is a simplified three-dimensional diagram showing a test joint body used in the cleavage peeling test in the embodiment. DETAILED DESCRIPTION

[0042] Hereinafter, this specific embodiment will be described in detail. It should be noted that the present invention is not limited to the embodiment described below.

[0043] [Adhesive composition]

[0044] The adhesive composition according to the embodiment of the present invention is an adhesive composition including a polymer, an ionic liquid, and an orientation material.

[0045] With regard to the adhesive layer formed by the adhesive composition involved in the embodiment of the present invention, it has excellent adhesive force (initial adhesive force) when no voltage is applied, and the adhesive force will be fully reduced due to the application of voltage, so it can also be used in the manufacturing process of electronic equipment, etc. In addition, the adhesive force will be fully reduced due to the application of voltage, so it can be split and peeled. In addition, preferably, with regard to the adhesive layer formed by the adhesive composition, it is attached to the adherend and a voltage of 10V is applied for 10 seconds, thereby splitting and peeling from the adherend.

[0046] Here, the so-called split peeling refers to peeling along the interface between the adhesive layer and the adherend. By split peeling, the entire interface between the adhesive layer and the adherend can be easily peeled off, and there is no need to apply a large stress to a part of the interface between the adhesive layer and the adherend by peeling, etc., so it has the advantages of not deforming the adherend.

[0047] In the embodiment of the present invention, the cleavage peeling may be natural peeling or not, but is preferably natural peeling.

[0048] In addition, the so-called natural peeling refers to peeling (cracking) along the interface between the adherend and the adhesive layer, and natural peeling without applying stress to a part of the interface between the adhesive layer and the adherend. Natural peeling also includes the case where peeling occurs in a static state, the case where peeling occurs naturally when moving to the next process, the case where the adherend and the adhesive layer peel due to the weight of the adherend or the adhesive layer itself, etc.

[0049] Examples of cleavage peeling other than natural peeling include a case where a slight stress is applied to a portion of the interface between the PSA layer and the adherend, thereby causing the PSA layer to peel from one end of the adherend without causing deformation or damage to the PSA layer and the adherend.

[0050] The adhesive composition to which the embodiment of the present invention is related comprises a polymer, an ionic liquid and an orientation material. By making the adhesive composition comprise a polymer, an ionic liquid and an orientation material, there is excellent adhesion when no voltage is applied, and the adhesion can be fully reduced due to the application of voltage. It is believed that this is because the orientation material undergoes dielectric polarization due to the application of voltage, thereby increasing the mobility of the ionic liquid.

[0051] The adhesive layer formed using the adhesive composition according to the embodiment of the present invention has excellent adhesive strength when no voltage is applied, and the adhesive strength is sufficiently reduced by application of voltage to enable cleavage peeling. The adhesive composition is suitable as an adhesive composition for electrical peeling.

[0052] These adhesive compositions are described below.

[0053] In addition, in this specification, the adhesive force when no voltage is applied may be referred to as "initial adhesive force".

[0054] In addition, the property that the adhesive force decreases due to voltage application is sometimes referred to as "electrical peeling property", and the case where the rate of decrease in adhesive force due to voltage application is large is sometimes referred to as "excellent electric peeling property".

[0055] <Ingredients of Adhesive Composition>

[0056] (polymer)

[0057] The adhesive composition according to the embodiment of the present invention contains a polymer. In the present 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 can be one monomer or a mixture of two or more monomers. It should be noted that 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.

[0058] The polymer in the embodiment of the present invention is not particularly limited as long as it is generally used as an adhesive and has adhesive properties, and examples thereof include acrylic polymers, rubber polymers, vinyl alkyl ether polymers, silicone polymers, polyester polymers, polyamide polymers, urethane polymers, fluorine polymers, and epoxy polymers, etc. The polymers may be used alone or in combination of two or more.

[0059] In order to obtain an adhesive layer having excellent adhesion when no voltage is applied and whose adhesion is sufficiently reduced by the application of voltage, it is preferred that the polymer has a large relative dielectric constant. From this point of view, it is particularly preferred that the polymer in this embodiment contains at least one selected from the group consisting of polyester polymers, urethane polymers and acrylic polymers.

[0060] The acrylic polymer preferably contains a unit derived from a polar group-containing monomer having a carboxyl group, an alkoxy group, a hydroxyl group and / or an amide bond. Polyester polymers and urethane polymers have a hydroxyl group that is easily polarized at the end, and the carboxyl group, alkoxy group, hydroxyl group and / or amide bond of the acrylic polymer having a carboxyl group, an alkoxy group, a hydroxyl group and / or an amide bond are easily polarized. Therefore, by using these polymers, a polymer that can form an adhesive layer having excellent adhesive strength when no voltage is applied and whose adhesive strength is sufficiently reduced by the application of a voltage can be obtained.

[0061] The total content of the polyester polymer, the urethane polymer, and the acrylic polymer in the polymer of the present embodiment is preferably 60% by mass or more, more preferably 80% by mass or more.

[0062] In addition, in particular, in order to reduce costs, improve productivity, and increase initial adhesive strength, the polymer in this embodiment is preferably an acrylic polymer.

[0063] That is, the pressure-sensitive adhesive composition according to the embodiment of the present invention is preferably an acrylic pressure-sensitive adhesive composition containing an acrylic polymer as a polymer.

[0064] 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 large initial adhesive force. In addition, in order to improve the electrical peeling property, the alkyl group R in the following formula (1) b The smaller the number of carbon atoms, the better. It is particularly preferably 8 or less, and more preferably 4 or less.

[0065] CH 2 =C(R a )COOR b (1)

[0066] [R in formula (1) a is a hydrogen atom or a methyl group, R b is an alkyl group having 1 to 14 carbon atoms]

[0067] Examples of the alkyl (meth)acrylate having an alkyl group having 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 (meth)acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms can be used alone or in combination of two or more.

[0068] 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% by mass) constituting the acrylic polymer is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 85% by mass or more. If the ratio of the (meth)acrylic acid alkyl ester having an alkyl group with 1 to 14 carbon atoms is 70% by mass or more, a large initial adhesive force is easily obtained.

[0069] As an acrylic polymer, for the purpose of improving cohesive force, heat resistance, crosslinking property, etc., it is preferred to contain a monomer unit derived from a polar group-containing monomer copolymerizable therewith in addition to a monomer unit derived from an alkyl (meth)acrylate having an alkyl group with 1 to 14 carbon atoms. The monomer unit can provide a crosslinking point and is suitable for obtaining a large initial adhesive force.

[0070] As the polar group-containing monomer, for example, carboxyl-containing monomers, alkoxy-containing monomers, hydroxyl-containing monomers, cyano-containing monomers, vinyl-containing monomers, aromatic vinyl monomers, amide-containing monomers, imide-containing monomers, amino-containing monomers, epoxy-containing monomers, vinyl ether monomers, N-acryloylmorpholine, sulfonic acid-containing monomers, phosphoric acid-containing monomers, and anhydride-containing monomers can be cited. Among them, from the aspect of excellent cohesion, carboxyl-containing monomers, alkoxy-containing monomers, hydroxyl-containing monomers, and amide-containing monomers are preferred, and carboxyl-containing monomers are particularly preferred. Carboxyl-containing monomers are particularly suitable for obtaining large initial adhesion. Polar group-containing monomers can be used alone or in combination of two or more.

[0071] 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 isocrotonic acid. Acrylic acid is particularly preferred. The carboxyl-containing monomers may be used alone or in combination of two or more.

[0072] Examples of the alkoxy group-containing monomer include methoxy group-containing monomers and ethoxy group-containing monomers. Examples of the methoxy group-containing monomer include 2-methoxyethyl acrylate.

[0073] As the hydroxyl-containing monomer, for example, 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 can be mentioned. 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are particularly preferred. The hydroxyl-containing monomer can be used alone or in combination of two or more.

[0074] 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.

[0075] Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

[0076] 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.

[0077] Examples of the aromatic vinyl monomer include styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes.

[0078] Examples of the imide group-containing monomer include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

[0079] Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

[0080] Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

[0081] Examples of the vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether.

[0082] The ratio of the polar group-containing monomer relative to the total monomer components (100 mass %) constituting the acrylic polymer is preferably 0.1 mass % or more and 35 mass % or less. The upper limit of the ratio of the polar group-containing monomer is more preferably 25 mass %, more preferably 20 mass %, and the lower limit is more preferably 0.5 mass %, more preferably 1 mass %, and particularly preferably 2 mass %. If the ratio of the polar group-containing monomer is more than 0.1 mass %, it is easy to obtain cohesive force, therefore, it is not easy to produce residual glue on the adherend surface after peeling the adhesive layer, and electrical stripping is improved. In addition, if the ratio of the polar group-containing monomer is less than 35 mass %, it is easy to prevent the adhesive layer from being excessively close to the adherend and re-stripping. Especially if it is more than 2 mass % and less than 20 mass %, it is easy to realize the consideration of the peelability relative to the adherend and the adhesion of the adhesive layer and other layers.

[0083] Furthermore, as a monomer component constituting the acrylic polymer, a polyfunctional monomer may be contained in order to introduce a cross-linked structure into the acrylic polymer and to facilitate obtaining necessary cohesive force.

[0084] Examples of the multifunctional monomer include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, divinylbenzene, and N,N'-methylenebisacrylamide. The multifunctional monomer may be used alone or in combination of two or more.

[0085] The content of the multifunctional monomer relative to the total monomer components (100% by mass) constituting the acrylic polymer is preferably 0.1% by mass or more and 15% by mass or less. The upper limit of the content of the multifunctional monomer is more preferably 10% by mass, and the lower limit is more preferably 3% by mass. If the content of the multifunctional monomer is more than 0.1% by mass, the flexibility and adhesion of the adhesive layer are easily improved, so it is preferred. If the content of the multifunctional monomer is less than 15% by mass, the cohesive force will not be excessively increased, and it is easy to obtain appropriate adhesion.

[0086] Typically, polyester polymers are polymers having a structure formed by condensation of polycarboxylic acids such as dicarboxylic acids and their derivatives (hereinafter also referred to as “polycarboxylic acid monomers”) and polyols such as diols and their derivatives (hereinafter referred to as “polyol monomers”).

[0087] 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, citraconic acid, and derivatives thereof can be used.

[0088] The polyvalent carboxylic acid monomers can be used alone or in combination of two or more.

[0089] 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.

[0090] The polyol monomers can be used alone or in combination of two or more.

[0091] In addition, the polymer of the present embodiment may include an ionic polymer. An ionic polymer is a polymer having an ionic functional group. By making the polymer include an ionic polymer, the electrical stripping property 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.

[0092] In the present embodiment, the polymer can be obtained by (co)polymerizing the monomer components. As the polymerization method, it is not particularly limited, and solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, photopolymerization (active energy ray polymerization) method, etc. can be cited. In particular, from the viewpoint of cost and productivity, solution polymerization is preferably used. In the case of copolymerization, the polymer can be any polymer in a random copolymer, a block copolymer, an alternating copolymer, a graft copolymer, etc.

[0093] The solution polymerization method is not particularly limited, and examples thereof include a method in which monomer components, a polymerization initiator, and the like are dissolved in a solvent, and the mixture is heated to perform polymerization to obtain a polymer solution containing a polymer.

[0094] As a solvent that can be used for the solution polymerization method, various common solvents can be used. As such a solvent (polymerization solvent), for example, 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 can be cited. The solvent can be used alone or in combination of two or more.

[0095] 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.

[0096] The polymerization initiator that can be used in the solution polymerization method is not particularly limited, and examples thereof include peroxide-based polymerization initiators and azo-based polymerization initiators.

[0097] 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. More specifically, examples thereof include benzoyl peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, tert-butyl perbenzoate, diisopropylbenzene peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-bis(tert-butylperoxy)cyclododecane.

[0098] The azo 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, etc. The polymerization initiator can be used alone or in combination of two or more.

[0099] The amount of the polymerization initiator used is not particularly limited, but is preferably 0.01 to 5 parts by mass 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.

[0100] The heating temperature during polymerization by heating in the solution polymerization method is not particularly limited, and is, for example, 50° C. to 80° C. The heating time is not particularly limited, and is, for example, 1 hour to 24 hours.

[0101] The weight average molecular weight of the polymer is not particularly limited, but is preferably 100,000 to 5,000,000. The upper limit of the weight average molecular weight is more preferably 4,000,000, more preferably 3,000,000, and the lower limit is more preferably 200,000, more preferably 300,000. If the weight average molecular weight is 100,000 to 5,000,000, sufficient adhesion can be obtained.

[0102] The weight average molecular weight is measured by gel permeation chromatography (GPC). More specifically, for example, the weight average molecular weight can be calculated from a value converted to standard polystyrene using a GPC measuring apparatus having a trade name of "HLC-8220GPC" (manufactured by TOSOH Corporation) under the following conditions.

[0103] (Weight average molecular weight measurement conditions)

[0104] Sample concentration: 0.2 mass% (tetrahydrofuran solution)

[0105] Sample injection volume: 10μL

[0106] Sample column: TSK guard column SuperHZ-H (1 column) + TSKgel SuperHZM-H (2 columns)

[0107] Reference column: TSKgel SuperH-RC (1 column)

[0108] ·Eluent: Tetrahydrofuran (THF)

[0109] Flow rate: 0.6mL / min

[0110] Detector: Differential Refractometer (RI)

[0111] Column temperature (measurement temperature): 40°C

[0112] 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. In addition, it is particularly preferred that it is -40°C or lower because the rate of decrease in adhesive force due to voltage application becomes particularly large, and most preferably -50°C or lower.

[0113] The glass transition temperature (Tg) can be calculated based on, for example, the following formula (Y) (Fox equation).

[0114] 1 / Tg=W1 / Tg1+W2 / Tg2+……+Wn / Tgn(Y)

[0115] [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]

[0116] The above formula (Y) is a calculation formula when a polymer is composed of n types of monomer components, namely, monomer 1, monomer 2, ..., monomer n.

[0117] It should be noted that the glass transition temperature when a homopolymer is formed refers to the glass transition temperature of the homopolymer of the monomer, and 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, numerical values ​​are listed in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc, 1989). It should be noted that the glass transition temperature (Tg) of the homopolymer not recorded in the document refers to a value obtained, for example, by the following determination method. That is, 100 parts by mass of monomer X, 0.2 parts by mass of 2,2'-azobisisobutyronitrile and 200 parts by mass of ethyl acetate as a polymerization solvent are 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 in the polymerization system as described above, the temperature is raised to 63 ° C and the reaction is carried out for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution having a solid content concentration of 33% by mass. Next, the homopolymer solution is cast on a release liner and dried to prepare a test sample (sheet-shaped homopolymer) with a thickness of about 2 mm. Then, about 1 to 2 mg of the test sample is weighed into an open aluminum dish (open cell), and a temperature-modulated DSC (trade name "Q-2000" manufactured by TA Instruments, Inc.) is used to obtain the reversing heat flow (Reversing Heat Flow) (specific heat component) behavior of the homopolymer at a heating rate of 5°C / min under a nitrogen atmosphere of 50 ml / min. Referring to JIS-K-7121, the temperature of the point where a straight line that is equidistant from the baseline on the low temperature side of the obtained reversing heat flow and the straight line obtained by extending the baseline on the high temperature side in the longitudinal direction intersects with the curve of the step-shaped change part of the glass transition is taken as the glass transition temperature (Tg) when the homopolymer is made.

[0118] Relative to the total amount of the adhesive composition (100 mass %), the content of the polymer in the adhesive composition of this embodiment is preferably greater than 50 mass % and less than 99.9 mass %, the upper limit is more preferably 99.5 mass %, and further preferably 99 mass %, and the lower limit is more preferably 60 mass %, and further preferably 70 mass %.

[0119] (Ionic Liquids)

[0120] The ionic liquid in the present embodiment is not particularly limited as long as it is a molten salt (normal temperature molten salt) composed of a pair of anions and cations and is liquid at 25° C. Examples of anions and cations are given below, and among the ionic substances obtained by combining them, the substance that is liquid at 25° C. is an ionic liquid, and the substance that is solid at 25° C. is not an ionic liquid, but an ionic solid described later.

[0121] 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 anion, from the viewpoint of being chemically stable and suitable for improving the electrical stripping property, (FSO 2 ) 2 N - [bis(fluorosulfonyl)imide anion], and (CF 3 SO 2 ) 2 N - [Bis(trifluoromethanesulfonyl)imide anion] Anion of a sulfonyl imide compound such as the like.

[0122] From the viewpoint of being chemically stable and suitable for improving the electrical peeling property, the cation in the ionic liquid is preferably a nitrogen-containing onium, sulfur-containing onium, or phosphorus-containing onium cation, and more preferably an imidazolium, ammonium, pyrrolidinium, or pyridinium cation.

[0123] 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. onium cation, 1-tridecyl-3-methylimidazolium cation, 1-tetradecyl-3-methylimidazolium cation, 1-pentadecyl-3-methylimidazolium cation, 1-hexadecyl-3-methylimidazolium cation, 1-heptadecyl-3-methylimidazolium cation, 1-octadecyl-3-methylimidazolium cation, 1-undecyl-3-methylimidazolium cation, 1-benzyl-3-methylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, and 1,3-bis(dodecyl)imidazolium cation.

[0124] 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.

[0125] Examples of the pyrrolidinium cation include 1-ethyl-1-methylpyrrolidinium cation and 1-butyl-1-methylpyrrolidinium cation.

[0126] Examples of the ammonium cation include a tetraethylammonium cation, a tetrabutylammonium cation, a methyltrioctylammonium cation, a tetradecyltrihexylammonium cation, a glycidyltrimethylammonium cation, and a trimethylaminoethyl acrylate cation.

[0127] As the ionic liquid, from the viewpoint of increasing the rate of decrease in adhesive force when a voltage is applied, it is preferred to select a cation having a molecular weight of 160 or less as the cation constituting the ionic liquid, and it is particularly preferred to include the above-mentioned (FSO 2 ) 2 N - [bis(fluorosulfonyl)imide anion] or (CF 3 SO 2 ) 2 N -[bis(trifluoromethanesulfonyl)imide anion] and an ionic liquid of a cation having a molecular weight of 160 or less. Examples of the cation having a molecular weight of 160 or less include 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, 1-ethyl-1-methylpyrrolidinium cation, 1-butyl-1-methylpyrrolidinium cation, tetraethylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethyl acrylate cation.

[0128] In addition, as the cation of the ionic liquid, cations represented by the following formulae (2-A) to (2-D) are also preferred.

[0129] [Chemical formula 1]

[0130]

[0131] R in formula (2-A) 1 represents a hydrocarbon group having 4 to 10 carbon atoms (preferably a hydrocarbon group having 4 to 8 carbon atoms, more preferably a hydrocarbon group having 4 to 6 carbon atoms), which may contain a heteroatom, and R 2 and R 3 are the same or different and represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms (preferably a hydrocarbon group having 1 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms, and further preferably a hydrocarbon group having 2 to 4 carbon atoms), and may also contain a heteroatom. In the case where the nitrogen atom forms a double bond with the adjacent carbon atom, R 3 .

[0132] R in formula (2-B) 4 represents a hydrocarbon group having 2 to 10 carbon atoms (preferably a hydrocarbon group having 2 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms), which may contain a heteroatom, and R 5 , R 6 and R 7 The same or different radicals represent a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms (preferably a hydrocarbon group having 1 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms, and further preferably a hydrocarbon group having 2 to 4 carbon atoms), and may contain a heteroatom.

[0133] R in formula (2-C) 8 represents a hydrocarbon group having 2 to 10 carbon atoms (preferably a hydrocarbon group having 2 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms), which may contain a heteroatom, and R 9 , R 10and R 11 The same or different radicals represent a hydrogen atom or a hydrocarbon group having 1 to 16 carbon atoms (preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 8 carbon atoms), and may contain a heteroatom.

[0134] In formula (2-D), X represents a nitrogen, sulfur or phosphorus atom, and R 12 , R 13 , R 14 and R 15 are the same or different and represent a hydrocarbon group having 1 to 16 carbon atoms (preferably a hydrocarbon group having 1 to 14 carbon atoms, more preferably a hydrocarbon group having 1 to 10 carbon atoms, further preferably a hydrocarbon group having 1 to 8 carbon atoms, and particularly preferably a hydrocarbon group having 1 to 6 carbon atoms), and may also contain a heteroatom. In the case where X is a sulfur atom, R is absent. 12 .

[0135] The molecular weight of the cation in the ionic liquid is, for example, less than 500, preferably less than 400, more preferably less than 300, further preferably less than 250, particularly preferably less than 200, and most preferably less than 160. In addition, it is usually more than 50. It is believed that the cation in the ionic liquid has the following properties: in the adhesive layer, it moves to the cathode side when a voltage is applied, and is concentrated near the interface between the adhesive layer and the adherend. In the present invention, for this reason, the adhesive force during voltage application is lower than the initial adhesive force, resulting in electrical peeling. Cations with a molecular weight of less than 500 are suitable from the following aspects: the movement of the cation to the cathode side in the adhesive layer becomes easier, increasing the rate of reduction of the adhesive force when a voltage is applied.

[0136] As commercially available products of ionic liquids, for example, there can be mentioned "ELEXCEL AS-210", "ELEXCEL AS-110", "ELEXCEL MP-442", "ELEXCEL IL-210", "ELEXCEL MP-471", "ELEXCEL MP-456", "ELEXCEL AS-804" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., "HMI-FSI" manufactured by Mitsubishi Materials Co., Ltd., "CIL-312" and "CIL-313" manufactured by Japan Carlit Co., Ltd., and the like.

[0137] The ionic conductivity of the ionic liquid is preferably 0.1mS / cm or more and 10mS / cm or less. The upper limit of the ionic conductivity is more preferably 5mS / cm, more preferably 3mS / cm, and the lower limit is more preferably 0.3mS / cm, more preferably 0.5mS / cm. By having an ionic conductivity in this range, even at low voltage, the adhesive force is fully reduced. It should be noted that the ionic conductivity can be measured by AC impedance method using, for example, a 1260 frequency response analyzer manufactured by Solartron.

[0138] About the content (compounding amount) of the ionic liquid in the adhesive composition of the present embodiment, relative to 100 parts by mass of the polymer, it is preferably more than 4 parts by mass from the viewpoint of reducing the adhesive force in voltage application, and preferably less than 50 parts by mass from the viewpoint of improving the initial adhesive force. From the same viewpoint, it is more preferably less than 40 parts by mass, further preferably less than 30 parts by mass, particularly preferably less than 25 parts by mass, and most preferably less than 20 parts by mass. In addition, it is more preferably more than 8 parts by mass, further preferably more than 10 parts by mass, particularly preferably more than 12 parts by mass, and most preferably more than 15 parts by mass.

[0139] (Oriented Materials)

[0140] The adhesive composition according to the embodiment of the present invention contains an orientation material in addition to the polymer and the ionic liquid.

[0141] The so-called oriented material refers to a material that is easily oriented in a specific direction by dielectric polarization caused by an electric field.

[0142] Examples of the orientation material used in the embodiment of the present invention include liquid crystal monomers and liquid crystal polymers, and liquid crystal monomers are preferred.

[0143] As the liquid crystalline monomer, any monomer of lyotropic and thermotropic liquid crystalline monomers can be used. From the aspect of workability, thermotropic liquid crystalline monomers are preferred. For example, monomers having biphenyl derivatives, phenyl benzoate derivatives, stilbene derivatives, dicyclohexyl derivatives and the like introduced with functional groups such as acryloyl, vinyl and epoxy groups as basic skeletons can be cited.

[0144] For such a liquid crystalline monomer, for example, the following method is preferably adopted: orienting it by appropriately using known methods such as methods based on heat or light, methods of adding an orientation aid, and then, while maintaining the orientation, crosslinking and polymerization are carried out using light, heat, electron beams, etc., thereby fixing the orientation.

[0145] Liquid crystal monomers have the property of exhibiting ion conductivity and may be non-polymerizable, in other words, may not have a polymerizable functional group, or may be liquid crystal molecules without a polymerizable functional group. Liquid crystal molecules are low molecular weight liquid crystal compounds having a molecular weight of less than 10,000, preferably less than 1,000.

[0146] The liquid crystal monomer is not limited to molecules that exhibit liquid crystallinity at room temperature (25° C.), and molecules that exhibit liquid crystallinity at a higher temperature may be used.

[0147] Even if a molecule exhibits liquid crystallinity at a temperature exceeding 40° C. in the case of a single body, the lower limit of the temperature at which it exhibits liquid crystallinity may be lowered to below 40° C. by mixing with other liquid crystal molecules.

[0148] As liquid crystal monomers showing liquid crystal properties below 40°C, cyanobiphenyl liquid crystals such as 4'-pentylbiphenyl-4-carbonitrile, 4'-hexylbiphenyl-4-carbonitrile, and 4'-heptylbiphenyl-4-carbonitrile, benzoic acid cyanophenyl ester liquid crystals such as 4-butylbenzoic acid-4-cyanophenyl ester, pyrimidine liquid crystals such as 5-n-heptyl-2-[4-(n-hexyloxy)phenyl]pyrimidine, 5-n-octyl-2-[4-(n-octyloxy)phenyl]pyrimidine, 1-(4-ethylphenyl)-2-(4-methoxyphenyl)acetylene, 1-(4-n-butylphenyl)-2-(4-methoxyphenyl)acetylene, etc. can be cited, but they are not limited to these. All the liquid crystal molecules exemplified above are non-polymerizable liquid crystal molecules.

[0149] The liquid crystal molecules are not limited to two types, and three or more types may be mixed.

[0150] As liquid crystalline polymers, for example, various liquid crystalline polymers of main chain type and side chain type obtained by introducing conjugated linear atomic groups (mesogens) imparting liquid crystal orientation into the main chain and side chain of polymers can be cited. As a specific example of liquid crystalline polymers of main chain type, a polyester liquid crystalline polymer, a discotic polymer, a cholesteric polymer, etc., which have a structure of a mesogen group bonded to the spacer group part imparting bending, for example, a nematic orientation, can be cited. As a specific example of liquid crystalline polymers of side chain type, a liquid crystalline polymer having a mesogen part formed by a para-substituted cyclic compound unit imparting nematic orientation as a side chain, etc., can be cited using polysiloxane, polyacrylate, polymethacrylate or polymalonate as the main chain skeleton, separated by a spacer group part formed by a conjugated atomic group.

[0151] Regarding the content (compounding amount) of the orientation material in the adhesive composition of the present embodiment, relative to 100 parts by mass of the polymer, it is preferably 0.05 parts by mass or more from the viewpoint of reducing the adhesive force when applying a voltage, and it is preferably 30 parts by mass or less from the viewpoint of improving the initial adhesive force. From the same viewpoint, it is more preferably 20 parts by mass or less, further preferably 10 parts by mass or less, particularly preferably 8 parts by mass or less, and most preferably 5 parts by mass or less. In addition, it is more preferably 0.1 parts by mass or more, further preferably 0.5 parts by mass or more, particularly preferably 1 parts by mass or more, and most preferably 1.5 parts by mass or more.

[0152] (Other ingredients)

[0153] The adhesive composition of the present embodiment may contain one or more components other than the polymer, ionic liquid and orientation material (hereinafter sometimes referred to as "other components") as needed within the range that does not impair the effects of the present invention. Other components that may be contained in the adhesive composition of the present embodiment are described below.

[0154] The adhesive composition of this embodiment may contain an ionic additive for the purpose of providing excellent adhesive force (initial adhesive force) when no voltage is applied and sufficiently reducing the adhesive force by application of voltage. As the ionic additive, for example, an ionic solid can be used.

[0155] 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 substance among ionic substances obtained by combining the anions and cations exemplified in the description column of the ionic liquid can be used. When the adhesive composition contains an ionic solid, the content of the ionic solid is preferably 0.5 parts by mass or more, 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.

[0156] For the purpose of improving creep and shear properties by crosslinking the polymer, the adhesive composition of the present embodiment may contain a crosslinking agent as needed. As a crosslinking agent, for example, an isocyanate crosslinking agent, a carbodiimide crosslinking agent, an epoxy crosslinking agent, a melamine crosslinking agent, a peroxide crosslinking agent, a urea crosslinking agent, a metal alkoxide crosslinking agent, a metal chelate crosslinking agent, a metal salt crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, and an amine crosslinking agent, etc., can be cited. As an isocyanate crosslinking agent, for example, toluene diisocyanate and methylene diisocyanate phenyl ester, etc., can be cited. As an epoxy crosslinking agent, for example, N, N, N', N'-tetraglycidyl-m-xylene diamine, diglycidyl aniline, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane and 1,6-hexanediol diglycidyl ether, etc., can be cited. The content of the crosslinking agent when contained is preferably 0.1 parts by mass or more, more preferably 0.7 parts by mass or more, relative to 100 parts by mass of the polymer, 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. It should be noted that the crosslinking agent can be used alone or in combination of two or more.

[0157] For the purpose of helping the movement of the ionic liquid when a voltage is applied, the adhesive composition of the present embodiment may contain polyethylene glycol and tetraethylene glycol dimethyl ether as needed. As polyethylene glycol and tetraethylene glycol dimethyl ether, substances with a number average molecular weight of 100 to 6000 can be used. The content of these components when contained relative to 100 parts by mass of the polymer 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 preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 15 parts by mass or less.

[0158] For the purpose of imparting conductivity to the adhesive composition, the adhesive composition of the present embodiment may contain a conductive filler as required. The conductive filler is not particularly limited, and generally known or commonly used conductive fillers may be used, for example, graphite, carbon black, carbon fiber, metal powders such as silver and copper may be used. The content of the conductive filler when contained is preferably 0.1 to 200 parts by mass relative to 100 parts by mass of the polymer.

[0159] For the purpose of inhibiting corrosion of metal adherends, the adhesive composition of the present embodiment may contain an anticorrosive agent as required. The anticorrosive agent is not particularly limited, and generally known or commonly used anticorrosive agents may be used, for example, carbodiimide compounds, adsorption inhibitors, chelate-forming metal passivators, etc. may be used.

[0160] As the carbodiimide compound, for example, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, N,N'-dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, 1-ethyl-3-tert-butylcarbodiimide, N-cyclohexyl-N'-(2-morpholinoethyl)carbodiimide, N,N'-di-tert-butylcarbodiimide, 1,3-bis(p-tolyl)carbodiimide, and polycarbodiimide resins using them as monomers can be cited. These carbodiimide compounds can be used alone or in combination of two or more. Relative to 100 parts by mass of the polymer, the content when the carbodiimide compound is contained in the adhesive composition of the present embodiment is preferably 0.01 parts by mass or more and 10 parts by mass or less.

[0161] As adsorption type inhibitors, for example, alkylamines, carboxylates, carboxylic acid derivatives, alkyl phosphates, etc. can be cited. The adsorption type inhibitor can be used alone or in combination of two or more. The content of alkylamine as an adsorption type inhibitor in the adhesive composition of the present embodiment is preferably 0.01 to 20 parts by mass relative to 100 parts by mass of the polymer. The content of carboxylate as an adsorption type inhibitor in the adhesive composition of the present embodiment is preferably 0.01 to 10 parts by mass relative to 100 parts by mass of the polymer. The content of carboxylate as an adsorption type inhibitor in the adhesive composition of the present embodiment is preferably 0.01 to 10 parts by mass relative to 100 parts by mass of the polymer. The content of carboxylic acid derivative as an adsorption type inhibitor in the adhesive composition of the present embodiment is preferably 0.01 to 10 parts by mass relative to 100 parts by mass of the polymer. The content of alkyl phosphate as an adsorption type inhibitor in the adhesive composition of the present embodiment is preferably 0.01 to 10 parts by mass relative to 100 parts by mass of the polymer.

[0162] As a chelate-forming metal deactivator, for example, a triazole-containing compound or a benzotriazole-containing compound can be used. They have a high effect of passivating the surface of metals such as aluminum, and even if they are included in the adhesive component, they are not easy to affect the adhesion, which is preferred from the above aspects. The chelate-forming metal deactivator can be used alone or in combination of two or more. Relative to 100 parts by mass of the polymer, the content when the chelate-forming metal deactivator is contained in the adhesive composition of the present embodiment is preferably 0.01 parts by mass or more and 20 parts by mass or less.

[0163] The total content (amount of the anticorrosive) is preferably 0.01 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of the polymer.

[0164] In addition, 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 (leveling agents), rust inhibitors, adhesion imparting resins, and antistatic agents. The total content of these components is not particularly limited as long as the effect of the present invention is achieved, and is preferably 0.01 to 20 parts by mass, 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.

[0165] Examples of the filler include silicon dioxide, iron oxide, zinc oxide, aluminum oxide, titanium oxide, barium oxide, magnesium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, pyrophyllite clay, kaolinite clay, and calcined clay.

[0166] Plasticizers that can be used are known and commonly used plasticizers used in general resin compositions, for example, oils such as paraffin oil and process oil, liquid rubbers such as liquid polyisoprene, liquid polybutadiene, and liquid ethylene-propylene rubber, tetrahydrophthalic acid, azelaic acid, benzoic acid, phthalic acid, trimellitic acid, pyrophthalic acid, adipic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, citric acid, and their derivatives, dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diisononyl adipate (DINA), and isodecyl succinate, etc. can be used.

[0167] Examples of the antioxidant include hindered phenol-based compounds and aliphatic and aromatic hindered amine-based compounds.

[0168] Examples of the antioxidant include butylhydroxytoluene (BHT) and butylhydroxyanisole (BHA).

[0169] Examples of the pigment include inorganic pigments such as titanium dioxide, zinc oxide, ultramarine blue, red iron oxide, lithopone, lead, cadmium, iron, cobalt, aluminum, hydrochloride, and sulfate; organic pigments such as azo pigments and copper phthalocyanine pigments; and the like.

[0170] Examples of the rust preventive include zinc phosphate, tannic acid derivatives, phosphoric acid esters, basic sulfonates, and various rust preventive pigments.

[0171] Examples of the adhesion-imparting agent include a titanium coupling agent and a zirconium coupling agent.

[0172] Examples of the antistatic agent generally include quaternary ammonium salts, or hydrophilic compounds such as polyglycolic acid and ethylene oxide derivatives.

[0173] As the tackifier resin, for example, in addition to rosin-based tackifier resins, terpene-based tackifier resins, phenol-based tackifier resins, hydrocarbon-based tackifier resins, and ketone-based tackifier resins, polyamide-based tackifier resins, epoxy-based tackifier resins, and elastic-based tackifier resins can also be cited. It should be noted that the tackifier resin can be used alone or in combination of two or more.

[0174] <Method for producing adhesive composition>

[0175] The adhesive composition of the present invention is not particularly limited and can be produced by appropriately stirring and mixing a polymer, an ionic liquid, an orientation material, and additives, a crosslinking agent, polyethylene glycol, a conductive filler, and the like as needed.

[0176] [Adhesive sheet]

[0177] (Composition of adhesive sheet)

[0178] The adhesive sheet of the present embodiment has no particular restrictions as long as it has at least one adhesive layer formed by the adhesive composition of the present embodiment described above (hereinafter also referred to as "electrically peelable adhesive layer"). The adhesive sheet of the present embodiment may also have an adhesive layer other than the electrically peelable adhesive layer that does not contain an ionic liquid (hereinafter sometimes referred to as "other adhesive layer"). The adhesive sheet of the present embodiment may also have a substrate, a conductive layer, a substrate for conducting electricity, an intermediate layer, and a primer layer, etc. in addition to the above. The adhesive sheet of the present embodiment can be, for example, in a form wound into a roll or in a sheet-like form. It should be noted that "adhesive sheet" also includes the meaning of "adhesive tape". That is, the adhesive sheet of the present embodiment can also be an adhesive tape having a strip-like form.

[0179] The adhesive sheet of the present embodiment may also be formed only by the electrical stripping adhesive layer without a substrate, that is, a double-sided adhesive sheet (without substrate) without a substrate layer. The adhesive sheet of the present embodiment may also be a double-sided adhesive sheet having a substrate and both sides of the substrate as an adhesive layer (electrical stripping adhesive layer, or other adhesive layers). In addition, the adhesive sheet of the present embodiment may also be a single-sided adhesive sheet having a substrate and only one side of the substrate as an adhesive layer (electrical stripping adhesive layer, or other adhesive layers). It should be noted that the adhesive sheet of the present embodiment may also have a separator (peeling liner) for the purpose of protecting the surface of the adhesive layer, but the separator is not included in the adhesive sheet of the present embodiment.

[0180] The structure of the pressure-sensitive adhesive sheet of the present embodiment is not particularly limited, but preferably includes: Figure 1 The adhesive sheet X1 shown, Figure 2 The laminated structure of the adhesive sheet X2 is shown in FIG. Figure 3An adhesive sheet X3 having a laminated structure is shown in the figure. Adhesive sheet X1 is a double-sided adhesive sheet without a substrate formed only by an electrically peelable adhesive layer 1. Adhesive sheet X2 is a double-sided adhesive sheet with a substrate 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. Adhesive sheet X3 is a double-sided adhesive sheet with a substrate having a layer structure of an adhesive layer 2, an electrically conductive substrate 5 (substrate 3 and conductive layer 4), an electrically peelable adhesive layer 1, an electrically conductive substrate 5 (substrate 3 and conductive layer 4), and an adhesive layer 2. In Figure 2 and 3 In the conductive substrate 5 of the adhesive sheets X2 and X3 shown in the drawings, the substrate 3 is not essential and only the conductive layer 4 may be used. Figure 2 The PSA sheet X2 may be a single-sided PSA sheet without the PSA layer 2 .

[0181] The substrate 3 is not particularly limited, and may include paper substrates such as paper, fiber substrates such as cloth and nonwoven fabrics, plastic substrates such as films and sheets formed by various plastics (polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, acrylic resins such as polymethyl methacrylate, etc.), and laminates thereof. The substrate may have a single-layer form or a multi-layer form. It should be noted that the substrate may also be subjected to various treatments such as back treatment, antistatic treatment, and primer treatment as required.

[0182] The conductive layer 4 can be any layer with conductivity without any particular limitation, and may be a metal substrate such as metal (e.g., aluminum, magnesium, copper, iron, tin, gold, etc.) foil, a metal plate (e.g., aluminum, magnesium, copper, iron, tin, silver, etc.), a conductive polymer, etc. In addition, it may also be a metal vapor-deposited film provided on the substrate 3, etc.

[0183] The conducting substrate 5 is not particularly limited as long as it is a substrate having a conductive layer (conducting electricity), and examples thereof include a substrate having a metal layer formed on the surface of the substrate, for example, a substrate having a metal layer formed on the surface of the substrate exemplified above by plating, chemical vapor deposition, sputtering, etc. Examples thereof include the metals, metal plates, conductive polymers, etc. exemplified above.

[0184] In the pressure-sensitive adhesive sheet X1, the adherends on both sides are preferably adherends having metal adherend surfaces. In the pressure-sensitive adhesive sheet X2, the adherend on the side of the electrically removable pressure-sensitive adhesive layer 1 is preferably an adherend having a metal adherend surface.

[0185] As the metal adherend surface, there can be cited a conductive surface formed by a metal having aluminum, copper, iron, magnesium, tin, gold, silver, lead, etc. as the main component, among which a surface formed by a metal containing aluminum is preferred. As the adherend having a metal adherend surface, for example, sheets, parts, and plates formed by metal having aluminum, copper, iron, magnesium, tin, gold, silver, lead, etc. as the main component can be cited. As adherends other than the adherend having a metal adherend surface, there is no particular limitation, and fiber sheets such as paper, cloth, and nonwoven fabrics, and films and sheets of various plastics can be cited.

[0186] From the viewpoint of initial adhesive force, the thickness of the electrically peelable adhesive layer 1 is preferably 1 μm or more and 1000 μm or less. The upper limit of the thickness of the electrically 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. It should be noted that the adhesive sheet is a double-sided adhesive sheet ( Figure 1 In the case of the pressure-sensitive adhesive sheet X1) shown in the figure, the thickness of the electrically removable pressure-sensitive adhesive layer is equal to the thickness of the pressure-sensitive adhesive sheet.

[0187] From the viewpoint of adhesive strength, the thickness of the adhesive layer 2 is preferably 1 μm to 2000 μm. The upper limit of the thickness of the adhesive layer 2 is more preferably 1000 μm, further preferably 500 μm, particularly preferably 100 μm, and the lower limit is more preferably 3 μm, further preferably 5 μm, particularly preferably 8 μm.

[0188] 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.

[0189] The thickness of the conductive layer 4 is preferably 0.001 μm to 1000 μm. The upper limit 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.

[0190] The thickness of the current-carrying 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.

[0191] The surface of the electrically peelable adhesive layer and other adhesive layers of the adhesive sheet of this embodiment can be protected by a separator (peeling liner). The separator is not particularly limited, and examples thereof include: a peeling liner obtained by treating the surface of a substrate (liner substrate) such as paper or plastic film with silicone; a peeling liner obtained by laminating the surface of a substrate (liner substrate) such as paper or plastic film with a polyolefin resin, etc. The thickness of the separator is not particularly limited, and is preferably 10 μm to 100 μm.

[0192] The thickness of the pressure-sensitive adhesive sheet of the present embodiment is preferably 20 μm to 3000 μm. 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.

[0193] Especially for Figure 2 In the case of the pressure-sensitive adhesive sheet X2 shown, the thickness of the pressure-sensitive adhesive sheet is preferably 50 μm or more and 2000 μm or less. The upper limit of the thickness is more preferably 1000 μm, and further preferably 200 μm, and the lower limit is more preferably 80 μm, and further preferably 100 μm.

[0194] Especially for Figure 3 In the case of the adhesive sheet X3 shown, 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.

[0195] (Method for producing adhesive sheet)

[0196] The manufacturing method of the adhesive sheet of the present embodiment can adopt a known or commonly used manufacturing method. For the electro-peelable adhesive layer in the adhesive sheet of the present embodiment, the following methods can be cited: a solution obtained by dissolving the adhesive composition of the present embodiment in a solvent as needed is applied on the separator, and the solution is dried and / or cured. In addition, for other adhesive layers, the following methods can be cited: a solution obtained by dissolving an adhesive composition that does not contain an ionic liquid, an oriented material, and an additive in a solvent as needed is applied on the separator, and the solution is dried and / or cured. It should be noted that the solvent and the separator can use the solvents and separators listed above.

[0197] In coating, a commonly used coater (for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a rod coater, a knife coater, a spray roll coater, etc.) can be used.

[0198] The above method can be used to manufacture the electrically peelable adhesive layer and other adhesive layers, and the adhesive sheet of the present embodiment can be manufactured by appropriately stacking the electrically peelable adhesive layer and other adhesive layers on the substrate, the conductive layer, and the conductive substrate. It should be noted that the adhesive sheet can also be manufactured by using the substrate, the conductive layer, and the conductive substrate instead of the separator and applying the adhesive composition.

[0199] (Electro-stripping method of adhesive sheet)

[0200] The adhesive sheet of the present embodiment can be peeled off from the adherend in the following manner: by applying a voltage to the electrically peelable adhesive layer, thereby generating a potential difference in the thickness direction of the electrically peelable adhesive layer. For example, in the case where the two sides of the adhesive sheet X1 are adherends with metal adhered surfaces, the metal adhered surfaces of the two sides can be energized, and a voltage is applied to the electrically peelable adhesive layer, thereby peeling off. In the case where the electrically peelable adhesive layer side of the adhesive sheet X2 is an adherend with a metal adhered surface, the conductive adherend and the conductive layer 4 can be energized, and a voltage is applied to the electrically peelable adhesive layer, thereby peeling off. In the case of the adhesive sheet X3, the conductive layer 4 on both sides can be energized, and a voltage is applied to the electrically peelable adhesive layer, thereby peeling off. The energization is preferably carried out by connecting terminals at one end and the other end of the adhesive sheet in a manner that a voltage is applied to the entire electrically peelable adhesive layer. It should be noted that, in the case where the adherend has a metal adhered surface, the above-mentioned one end and the other end can be a part of the adherend with a metal adhered surface. In addition, during the peeling, water may be added to the interface between the metal adherend surface and the electro-peelable pressure-sensitive adhesive layer and then a voltage may be applied.

[0201] The applied voltage and voltage application time during the electrical peeling are not particularly limited as long as the adhesive layer or the adhesive sheet can be peeled from the adherend. The preferred ranges of these are shown below.

[0202] 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.

[0203] The voltage application time is preferably less than 60 seconds, more preferably less than 40 seconds, further preferably less than 20 seconds, and particularly preferably less than 10 seconds. In such a case, workability is excellent. In addition, the application time is as short as possible, but is usually more than 1 second.

[0204] (Application of adhesive sheet)

[0205] As a previous re-peeling technique, there is an adhesive layer that is cured and peeled by irradiating ultraviolet rays (UV), and an adhesive layer that is peeled by heat. The adhesive sheet using such an adhesive layer cannot be used in the case where it is difficult to irradiate ultraviolet rays (UV), or the member as the adherend is damaged due to heat. The adhesive sheet of the present embodiment with the above-mentioned electrical peeling type adhesive layer does not use ultraviolet rays or heat, so it will not damage the member as the adherend, and can be easily split and peeled by applying voltage. Therefore, the adhesive sheet of the present embodiment is suitable for the use of the secondary battery (such as lithium ion battery pack) used by mobile terminals such as smart phones, mobile phones, notebook computers, video cameras, digital cameras, etc. to fix the housing.

[0206] In addition, as for the rigid components to be bonded using the adhesive sheet of the present embodiment, for example, silicon substrates for semiconductor wafers, sapphire substrates, SiC substrates and metal base substrates for LEDs, TFT substrates and color filter substrates for displays, and base substrates for organic EL panels can be cited. As for the fragile components to be bonded using the double-sided adhesive sheet, for example, semiconductor substrates such as compound semiconductor substrates, silicon substrates for MEMS devices, passive matrix substrates, surface cover glass for smartphones, OGS (One Glass Solution) substrates formed by attaching touch panel sensors to the cover glass, organic substrates and organic-inorganic hybrid substrates using silsesquioxane as the main component, flexible glass substrates for flexible displays, and graphene sheets can be cited.

[0207] [Joint body]

[0208] The bonded body of this embodiment has a laminated structure, which includes: an adherend having a metal adherend surface, and an adhesive sheet in which the electro-peelable adhesive layer is bonded to the metal adherend surface. As the adherend having a metal adherend surface, for example, an adherend formed of a metal having aluminum, copper, iron, magnesium, tin, gold, silver, lead, etc. as a main component can be cited, among which a metal containing aluminum is preferred.

[0209] As the joined body of this embodiment, for example, there can be mentioned: a joined body having an adherend having a metal adhered surface on both sides of an electrically peelable adhesive layer 1, namely an adhesive sheet X1; a joined body having an adherend having a metal adhered surface on the electrically peelable adhesive layer 1 side and an adherend on the adhesive layer 2 side, namely an adhesive sheet X2; a joined body having an adherend on both sides of an adhesive layer 2, namely an adhesive sheet X3; and the like.

[0210] Example

[0211] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. The weight average molecular weight described below is measured by the method described above using gel permeation chromatography (GPC).

[0212] [Examples 1 to 4 and Comparative Examples 1 to 3]

[0213] <Preparation of polymer solution>

[0214] (Preparation of Acrylic Polymer 1 Solution)

[0215] 95 parts by mass of n-butyl acrylate (BA) as a monomer component, 5 parts by mass of acrylic acid (AA), and 250 parts by mass of ethyl acetate as a polymerization solvent were placed in a separable flask and stirred for 1 hour while introducing nitrogen. After removing oxygen from the polymerization system as described above, 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. Then, ethyl acetate was added to obtain an acrylic polymer 1 solution (BA / AA (95 / 5)) with a solid content concentration of 28.6% by mass.

[0216] <Preparation of Adhesive Composition>

[0217] The acrylic polymer 1 solution obtained above, the ionic liquid shown below, the orientation material, and the crosslinking agent were added, stirred, and mixed to obtain the adhesive compositions of Examples 1 to 4 and Comparative Examples 1 to 3. Table 1 shows the blending amount (parts by mass) of each component.

[0218] In addition, the value of each component in Table 1 means mass part.

[0219] The abbreviations of the polymer, ionic liquid, orientation material, and crosslinking agent in Table 1 are as follows.

[0220] (Ionic Liquids)

[0221] AS110: Cation: 1-ethyl-3-methylimidazolium cation, anion: bis(fluorosulfonyl)imide anion, trade name "ELEXCEL AS-110", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0222] (Oriented Materials)

[0223] 4-Butylbenzoate-4-cyanophenyl ester: manufactured by Wako Pure Chemical Industries, Ltd.

[0224] (Trans, trans)-4-butyl-4'-vinylbicyclohexane: manufactured by Tokyo Chemical Industry Co., Ltd.

[0225] 4-Cyano-4'-heptylbiphenyl: manufactured by Tokyo Chemical Industry Co., Ltd.

[0226] (Crosslinking agent)

[0227] V-05: Polycarbodiimide resin, trade name "Carbodilite V-05", manufactured by Nisshinbo Chemical Inc.

[0228] <Evaluation>

[0229] (Initial Adhesion)

[0230] The adhesive composition of each example was applied to a release-treated surface of a polyethylene terephthalate separator (trade name "MRF38", manufactured by Mitsubishi Plastics Co., Ltd.) using an applicator to a uniform thickness. Then, the adhesive composition was dried by heating at 130° C. for 3 minutes to obtain an electrically removable adhesive layer (adhesive sheet) with a thickness of 30 μm.

[0231] Next, the obtained electrically peelable adhesive layer (adhesive sheet) is 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) is bonded to the side without the separator to prepare a single-sided adhesive sheet with a substrate. The separator of the single-sided adhesive sheet with a substrate is peeled off, and a stainless steel plate (SUS304BA, Φ120 mm, thickness 1.5 mm) as an adherend is attached to the peeled side in a manner that one end of the adhesive sheet protrudes from the adherend by about 2 mm. The sheet is pressed with a 2 kg roller moving back and forth once, and the sheet is left in an environment of 23°C for 30 minutes to obtain a joint body formed by a stainless steel plate 6 / 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 Then, using a peel tester (trade name "variable angle tear tester YSP", manufactured by Asahi Seiko Co., Ltd.), press Figure 4 The film was torn in the direction of the arrow in the figure, and the adhesive strength in a 180° tear test (tensile speed: 300 mm / min, peeling temperature: 23° C.) was measured. The measurement results are shown in Table 1.

[0232] (Adhesion strength after voltage application)

[0233] After pressing with a 2 kg roller once, the bonded body was left in an environment of 22°C and 20% RH for 3 days, and before tearing, the bonded body was Figure 4The negative and positive electrodes of the DC current machine were respectively installed at the α and β positions, and a voltage of 10 V was applied for 10 seconds before being torn off. Except for the above two points, the same operation as the above initial adhesive strength measurement was performed to measure the adhesive strength during voltage application. The measurement results are shown in Table 1.

[0234] (Crack peel strength)

[0235] Using an applicator, the adhesive composition of each example was applied to a release-treated surface of a polyethylene terephthalate separator (trade name "MRF38", manufactured by Mitsubishi Plastics Co., Ltd.) to a uniform thickness. Subsequently, the adhesive composition was dried by heating at 130° C. for 3 minutes to obtain an electrically removable adhesive layer (adhesive sheet) with a thickness of 30 μm.

[0236] Next, the obtained electro-peelable adhesive layer (adhesive sheet) was made into a sheet with a size of 25 mm × 30 mm, and a stainless steel plate (SUS304BA, 50 mm × 60 mm) was attached to the side without the separator. The separator of the adhesive sheet was peeled off, and a round bar (SUS304, Φ12.7 mm × 38 mm) used in the round bar tensile peel strength test method described in JIS K6849 was attached to the peeled side, pressed with 5 kg for 10 seconds, and left at 23°C for 30 minutes to obtain the following. Figure 5 The bonded structure for the cleavage peeling test is composed of SUS304BA plate 10 / electrically peelable adhesive layer (adhesive sheet) 1 / round bar 15 as shown.

[0237] Then, the round bar was pulled while pressing the SUS304BA plate using a peel tester (trade name "Small Table Tester EZ-SX", manufactured by Shimadzu Corporation), and the adhesive strength in the cleavage peel test (tensile speed: 10 mm / min, peeling temperature 23° C.) was measured as the cleavage peel strength. The measurement results are shown in Table 1.

[0238] (Cracking electrical peeling force)

[0239] After 10 seconds of crimping with 5 kg, the samples were placed in an environment of 23°C and 50% RH for 48 hours. Before peeling, the positive electrode was attached to the SUS304BA plate of the bonded body and the negative electrode was attached to the round bar. After applying a voltage of 10 V for 10 seconds, the samples were measured under the voltage applied. Except for the above two points, the cleavage electrical peeling force was measured in the same manner as the above cleavage peeling force measurement. When the samples can be peeled under the condition of 25 N / 12.7 mmΦ or less, the cleavage peeling can be performed by applying a voltage. The measurement results are shown in Table 1.

[0240] [Table 1]

[0241]

[0242] As shown in Table 1, the adhesive layers formed using the adhesive compositions of Examples 1 to 4 have excellent adhesive strength (initial adhesive strength) before voltage is applied, and the adhesive strength is sufficiently reduced by the application of voltage. In addition, since the adhesive strength is sufficiently reduced by the application of voltage, cleavage peeling can be performed.

[0243] On the other hand, in Comparative Examples 1 to 3 containing no orientation material, the initial adhesive force was lower than that of the examples, and even when a voltage was applied, the adhesive force was not sufficiently reduced.

[0244] As mentioned above, although the preferred embodiment of the present invention has been described, the present invention is not limited to the above embodiment, and various modifications and substitutions can be added to the above embodiment within the scope not departing from the scope of the present invention.

[0245] It should be noted that the present application is based on the Japanese patent application (Japanese Patent Application No. 2020-060439) filed on March 30, 2020, and the contents thereof are incorporated herein by reference.

[0246] Description of Reference Numerals

[0247] X1, X2, X3 adhesive sheet

[0248] 1 Electro-peelable adhesive layer

[0249] 2 Adhesive layer

[0250] 3. Substrate

[0251] 4 Conductive layer

[0252] 5. Electrically conductive substrate

[0253] 6 Stainless steel plate

[0254] 10 SUS304BA plate

[0255] 15 Round rod

Claims

1. An adhesive composition comprising a polymer, an ionic liquid and an oriented material, The polymer includes at least one selected from the group consisting of polyester polymers, urethane polymers, and acrylic polymers, The acrylic polymer comprises a monomer unit derived from an alkyl (meth)acrylate represented by the following formula (1): CH 2 =C(R a )COOR b (1) In formula (1), R a is a hydrogen atom or a methyl group, R b is an alkyl group having 1 to 14 carbon atoms, The alignment material is a liquid crystal monomer that exhibits liquid crystallinity at 40° C. or less, and the adhesive composition contains 0.5 to 10 parts by mass of the liquid crystal monomer relative to 100 parts by mass of the polymer. The ionic liquid is a molten salt composed of a pair of anions and cations and is liquid at 25° C. The binder composition contains 4 parts by mass or more of the ionic liquid based on 100 parts by mass of the polymer.

2. The adhesive composition according to claim 1, in, The pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition was attached to an adherend and a voltage of 10 V was applied for 10 seconds, thereby being cleaved and peeled from the adherend.

3. The adhesive composition according to claim 2, in, The splitting and peeling is natural peeling.

4. The adhesive composition according to any one of claims 1 to 3, in, The acrylic polymer further includes a unit derived from a polar group-containing monomer having a carboxyl group, an alkoxy group, a hydroxyl group and / or an amide bond.

5. The adhesive composition according to claim 4, in, The ratio of the polar group-containing monomer to the total monomer components constituting the acrylic polymer is 0.1 to 35% by mass.

6. Use of the adhesive composition according to any one of claims 1 to 5 for electrical stripping. 7 . A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to claim 1 .

8. A joined body comprising an adherend having a metal adherend surface, and the adhesive sheet according to claim 7, wherein the adhesive layer of the adhesive sheet is joined to the metal adherend surface.

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