Adhesive composition, adhesive sheet, and bonded body

Abstract

This invention provides an adhesive composition capable of forming an adhesive layer with excellent adhesive properties and impact resistance, and capable of inhibiting metal corrosion; an adhesive sheet having an adhesive layer formed from the adhesive composition; and a bonding body between the adhesive sheet and an adherend. This invention relates to an adhesive composition containing an emulsion-type acrylic polymer (A), said emulsion-type acrylic polymer (A) comprising monomer units derived from amide-containing monomers.

Description

Technical Field

[0001] The present invention relates to an adhesive composition, an adhesive sheet comprising an adhesive layer formed from the adhesive composition, and a bonding body between the adhesive sheet and an object to be bonded. Background Technology

[0002] In recent years, adhesive sheets with adhesive layers have been used in various technical fields. For example, in electronic component manufacturing processes, there is an increasing demand for rework to improve yield and recycling to disassemble and recover components after use. To meet these demands, double-sided adhesive sheets that have both adhesive strength and peelability are sometimes used when joining components in electronic component manufacturing processes.

[0003] On the other hand, when metal is present in the adhered material such as metal electrodes used in electronic components, corrosion of the metal can sometimes occur due to acidic components such as polymers with acidic sites or electrolytes contained in the adhesive layer or adhesive sheet. Conventionally, corrosion inhibitors have been added to the adhesive composition forming the adhesive layer to suppress such metal corrosion.

[0004] For example, Patent Document 1 describes an acrylic adhesive composition comprising an acrylic copolymer, an antistatic agent, and a corrosion inhibitor.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2015-014011 Summary of the Invention

[0006] The problem that the invention aims to solve However, if a corrosion inhibitor is added separately from the acrylic copolymer, as in the adhesive composition described in Patent Document 1, although the corrosion of the metal can be inhibited, the adhesive properties such as adhesion strength and creep resistance will be reduced accordingly, since the corrosion inhibitor itself is a component that does not contribute to the adhesive properties.

[0007] The present invention was made in view of the above circumstances, and its object is to provide an adhesive composition that can form an adhesive layer with excellent adhesive properties such as adhesive strength and creep resistance, and can inhibit the corrosion of metals, an adhesive sheet having an adhesive layer formed from the adhesive composition, and a joint between the adhesive sheet and the adhered object.

[0008] Methods for solving problems The inventors of this application conducted repeated research and discovered that by using an adhesive composition containing an emulsion-type acrylic polymer (A) comprising monomer units derived from amide-containing monomers, it is possible to form an adhesive layer with excellent adhesive properties and the ability to inhibit metal corrosion. Furthermore, it was found that the adhesive layer formed using this adhesive composition also exhibits excellent impact resistance.

[0009] Here, monomer unit refers to the structural unit in the polymer that originates from the monomer.

[0010] The methods used to solve the aforementioned problems are as follows.

[0011] [1] An adhesive composition comprising an emulsion acrylic polymer (A) containing monomer units derived from amide-containing monomers.

[0012] [2] The adhesive composition as described in [1], wherein the content of the amide-containing monomer in all monomer components constituting the emulsion-type acrylic polymer (A) is 0.1 to 50.0% by mass.

[0013] [3] The adhesive composition as described in [1], wherein the amide-containing monomer comprises at least one selected from the group consisting of N-isopropylacrylamide and N,N-dimethylacrylamide.

[0014] [4] The adhesive composition as described in [1], wherein the emulsion acrylic polymer (A) further comprises monomer units derived from carboxyl-containing monomers, wherein the content of the carboxyl-containing monomers in all monomer components constituting the emulsion acrylic polymer (A) is 2.5 to 6.0 by mass.

[0015] [5] The adhesive composition as described in [1] further comprises a crosslinking agent.

[0016] [6] The adhesive composition as described in [1] further comprises an electrolyte (B).

[0017] [7] The adhesive composition as described in [6], wherein the electrolyte (B) is an ionic substance.

[0018] [8] The adhesive composition as described in [7], wherein the ionic substance is an ionic liquid, and the anion of the ionic liquid comprises at least one selected from the group consisting of bis(fluorosulfonyl)imide anion and bis(trifluoromethanesulfonyl)imide anion.

[0019] [9] The adhesive composition as described in [8] further comprises a tackifier (C). The content of the tackifier (C) is 0.01 to 10 parts by mass relative to 100 parts by mass of the emulsion-type acrylic polymer (A).

[0020]

[10] The adhesive composition as described in [9], wherein the tackifier (C) comprises at least one selected from the group consisting of urethane associative tackifiers, alkali-swellable tackifiers and cellulose tackifiers.

[0021]

[11] The adhesive composition as described in [1] is used for electro-peeling.

[0022]

[12] An adhesive sheet having an adhesive layer formed from any one of the adhesive compositions described in [1] to

[11] .

[0023]

[13] A bonding body having an adherend and an adhesive sheet as described in

[12] , wherein the adhesive layer is adhered to the adherend.

[0024] Invention Effects The adhesive composition of the present invention can form an adhesive layer with excellent adhesive properties and impact resistance, and can inhibit metal corrosion. Attached Figure Description

[0025] [ Figure 1 [A cross-sectional view showing an example of the adhesive sheet of the present invention.]

[0026] [ Figure 2 This is a cross-sectional view illustrating an example of the laminated structure of the adhesive sheet of the present invention.

[0027] [ Figure 3 [A cross-sectional view illustrating another example of the laminated structure of the adhesive sheet of the present invention.]

[0028] [ Figure 4 [A cross-sectional view showing the general outline of the 180° peel test method in the embodiment.] Detailed Implementation

[0029] The following describes in detail the embodiments for carrying out the present invention. It should be noted that the present invention is not limited to the embodiments described below.

[0030] [Adhesive Composition] The adhesive composition according to embodiments of the present invention contains an emulsion acrylic polymer (A), said emulsion acrylic polymer (A) comprising monomer units derived from amide-containing monomers.

[0031] The adhesive composition according to embodiments of the present invention is preferably used for electro-stripping.

[0032] The adhesive composition will now be described.

[0033] It should be noted that in this instruction manual, the adhesive force when no voltage is applied is sometimes referred to as the "initial adhesive force".

[0034] In addition, the property that adhesive strength decreases due to voltage application is sometimes called "electrope release property," and the case of a large rate of decrease in adhesive strength caused by voltage application is called "excellent electrope release property," etc.

[0035] [Components of the adhesive composition] <Emulsion-type acrylic polymer (A)> The adhesive composition according to embodiments of the present invention contains an emulsion-type acrylic polymer (A), which comprises monomer units derived from amide-containing monomers. Using an emulsion-type acrylic polymer offers excellent cost and productivity, and typically increases peel strength. Impact resistance can also be improved. The reason for improving the impact resistance of the resulting adhesive layer by using an emulsion-type adhesive composition is uncertain, but one possible reason is the interfacial energy dissipation of the emulsion particles formed using the emulsion-type acrylic polymer (A).

[0036] Furthermore, by including monomer units derived from amide-containing monomers, metal corrosion can be suppressed. This is presumably because a particle interface exists in emulsion-type acrylic polymers, and when a highly hydrophilic acrylamide monomer is copolymerized, it can be tightly adsorbed onto the metal substrate by being located on the outer side of the particle interface. Moreover, the inventors of this application speculate that this is because when the adhesive layer formed using the adhesive composition according to embodiments of the present invention is bonded to the metal substrate, the amide groups adsorb onto the surface of the metal substrate, forming a film of the emulsion-type acrylic polymer (A) on the substrate surface. Furthermore, it is believed that due to the excellent cohesive force of the amide-containing monomers, adhesive properties such as adhesion and creep resistance are also improved.

[0037] On the other hand, when using solvent-based acrylic polymers, a uniform coating is usually formed. Therefore, in order to improve corrosion resistance by adhering tightly to the metal substrate, it is necessary to increase the amount of amide-containing monomers. However, in this case, it is believed that there is a trade-off between the deterioration of the adhesion properties (strong adhesion).

[0038] By using an adhesive composition comprising an emulsion-type acrylic polymer dispersed in an aqueous medium (hereinafter also referred to as an emulsion-based adhesive composition), compared to using an adhesive composition comprising a solvent-based polymer dissolved in an organic solvent (hereinafter also referred to as a solvent-based adhesive composition), the amount of organic solvent used can be reduced, thereby reducing the environmental impact. Furthermore, in the case where a highly hydrophilic acrylamide monomer is copolymerized in the emulsion-type acrylic polymer, the structural units derived from the acrylamide monomer are biased towards the outer side of the particle interface, thereby enabling them to adhere tightly to the metal substrate and function as a protective layer on the surface of the metal substrate, thus presumably resulting in excellent corrosion resistance.

[0039] In the embodiments of the present invention, the total content of emulsion-type acrylic polymer (A) in all polymers contained in the adhesive composition is preferably 60% by mass or more, and more preferably 80% by mass or more.

[0040] In the adhesive composition of the embodiments of the present invention, the emulsion-type acrylic polymer (A) comprises monomer units derived from amide-containing monomers.

[0041] Examples of amide-containing monomers include acrylamide, methacrylamide, N-vinylpyrrolidone (NVP), N,N-dimethylacrylamide (DMAA), N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N-isopropylacrylamide (NIAA), N,N'-methylenebisacrylamide, N,N-dimethylaminopropylacrylamide (DMAPAA), N,N-dimethylaminopropylmethacrylamide, N-propylacrylamide, N-propylmethacrylamide, N-benzylacrylamide, N-benzylmethacrylamide, N-dodecylacrylamide, N-dodecylmethylacrylamide, acryloylmorpholine (ACMO), and diacetoneacrylamide. Amide-containing monomers can be used alone or in combination of two or more.

[0042] From the perspective of improving the corrosion inhibition effect of metals, the amide-containing monomer preferably includes at least one selected from the group consisting of N-isopropylacrylamide and N,N-dimethylacrylamide.

[0043] Regarding the content of amide-containing monomers, 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 3% by mass or more, is preferably the total monomer content (100% by mass) constituting the emulsion-type acrylic polymer (A). As an upper limit, 50.0% by mass or less is preferred, more preferably 20% by mass or less, and even more preferably 10% by mass or less. By setting the amide-containing monomer content to 0.1% by mass or more, it is easy to obtain corrosion inhibition effect on metals and improved adhesion properties. In addition, by setting it to 50.0% by mass or less, in applications for electro-peeling, it is easy to prevent the adhesive layer from becoming overly adhered to the adhered object and thus re-peeling.

[0044] Regarding the content of amide-containing monomers, the total monomer components (100% by mass) constituting the emulsion-type acrylic polymer (A) are preferably 0.1 to 50.0% by mass, more preferably 0.5 to 10% by mass.

[0045] The emulsion-type acrylic polymer (A) preferably contains monomer units derived from alkyl (meth)acrylates having alkyl groups having 1 to 14 carbon atoms (hereinafter, formula (1)). Such monomer units are suitable for obtaining high general peel strength. Furthermore, in order to improve the adhesion and electro-peelability of the resulting adhesive layer without applied voltage, the alkyl group R in formula (1) is... b It is preferred to have a small number of carbon atoms, especially 8 or less, and more preferably 4 or less.

[0046] CH2=C(R) a COOR b (1) R in equation (1) a R is a hydrogen atom or a methyl group. b [Alkyl groups having 1 to 14 carbon atoms] Examples of alkyl (meth)acrylates having alkyl groups 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, pentyl (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 these, n-butyl acrylate, 2-ethylhexyl acrylate, and isononyl acrylate are preferred. Alkyl (meth)acrylates having alkyl groups having 1 to 14 carbon atoms can be used alone or in combination of two or more.

[0047] Of all the monomer components constituting the emulsion-type acrylic polymer (A), the content of alkyl (meth)acrylates having alkyl groups with 1 to 14 carbon atoms is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more. If the content of alkyl (meth)acrylates having alkyl groups with 1 to 14 carbon atoms is 70% by mass or more, it is easy to obtain a large general peel strength.

[0048] As an emulsion-type acrylic polymer (A), for the purpose of modifying cohesion, heat resistance, crosslinking, etc., monomer units are preferably derived from monomer units derived from amide-containing monomers and monomer units derived from alkyl (meth)acrylates having 1 to 14 carbon atoms, as well as monomer units derived from polar monomers containing polar groups other than amide groups (hereinafter, sometimes simply referred to as polar monomers). Monomer units derived from polar monomers can impart crosslinking points, making them suitable for obtaining large general peel strength. Furthermore, from the viewpoint of improving adhesion and electro-peelability without applied voltage, monomer units derived from polar monomers are also preferred.

[0049] Examples of monomers containing polar groups include, for example, carboxyl-containing monomers, alkoxy-containing monomers, hydroxyl-containing monomers, cyano-containing monomers, vinyl-containing monomers, aromatic vinyl monomers, imide-containing monomers, amino-containing monomers, epoxy-containing monomers, vinyl ether monomers, sulfonyl-containing monomers, phosphate-containing monomers, and anhydride-containing monomers. Among these, carboxyl-containing monomers, alkoxy-containing monomers, and hydroxyl-containing monomers are preferred from the perspective of excellent cohesiveness, with carboxyl-containing monomers being particularly preferred. Carboxyl-containing monomers are especially suitable for obtaining high general peel strength.

[0050] Furthermore, forming a protective layer on the surface of emulsion particles made from emulsion-type acrylic polymers can prevent shear failure of the particles and improve creep resistance. This effect is further enhanced by neutralizing carboxyl groups with alkali.

[0051] Monomers containing polar groups can be used alone or in combination of two or more.

[0052] Examples of carboxyl-containing monomers include acrylic acid, methacrylic acid, carboxyethyl methacrylate, carboxypentyl methacrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Acrylic acid is particularly preferred. Carboxyl-containing monomers can be used alone or in combination of two or more.

[0053] Examples of alkoxy-containing monomers include methoxy-containing monomers and ethoxy-containing monomers. For example, 2-methoxyethyl acrylate is an example of a methoxy-containing monomer.

[0054] Examples of hydroxyl-containing monomers include, 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, methyl (4-hydroxymethylcyclohexyl)methacrylate, 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. Hydroxyl-containing monomers can be used alone or in combination of two or more.

[0055] Examples of cyano-containing monomers include acrylonitrile and methacrylonitrile.

[0056] Examples of vinyl monomers include vinyl esters such as vinyl acetate, vinyl propionate, and vinyl laurate, with vinyl acetate being particularly preferred.

[0057] Examples of aromatic vinyl monomers include styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrene.

[0058] Examples of monomers containing an imide group include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconitumide.

[0059] Examples of amino-containing monomers include aminoethyl methacrylate, N,N-dimethylaminoethyl methacrylate, and N,N-dimethylaminopropyl methacrylate.

[0060] Examples of epoxy-containing monomers include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

[0061] Examples of vinyl ether monomers include, for example, methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether.

[0062] The content of polar monomers in all monomer components constituting the emulsion-type acrylic polymer (A) is preferably 0.1% by mass or more and 35% by mass or less, more preferably 2.5% by mass or more and 6.0% by mass or less. The upper limit of the content of polar monomers is more preferably 25% by mass, further preferably 20% by mass, even more preferably 6.0% by mass, even more preferably 5.5% by mass, particularly preferably 5.0% by mass, most preferably 4.5% by mass, and the lower limit is more preferably 0.5% by mass, further preferably 1% by mass, even more preferably 2% by mass, even more preferably 2.5% by mass, particularly preferably 3.0% by mass, and most preferably 3.5% by mass. If the content of polar monomers is 0.1% by mass or more, cohesive strength is easily obtained, therefore, it is less likely to leave adhesive residue on the surface of the adhered object after the adhesive layer is peeled off, and the electro-peelability is improved. Furthermore, if the content of polar monomers is 35% by mass or less, it is easier to prevent the adhesive layer from becoming overly adhered to the adhered object and thus re-peeling. In particular, if the content is between 2% and 20% by mass, it is easy to achieve a balance between the peelability of the adhered object and the adhesion between the adhesive layer and other layers.

[0063] In the adhesive composition of the embodiments of the present invention, the emulsion acrylic polymer (A) further comprises a carboxyl-containing monomer, and the content of the carboxyl-containing monomer in all monomer components constituting the emulsion acrylic polymer (A) is preferably 2.5 to 6.0 by mass.

[0064] Of all the monomer components constituting the emulsion-type acrylic polymer (A), the upper limit of the content of carboxyl-containing monomers is more preferably 5.5% by mass, further preferably 5.0% by mass, particularly preferably 4.5% by mass, and the lower limit is more preferably 3.0% by mass, further preferably 3.5% by mass. If the content of carboxyl-containing monomers is 2.5% by mass or more, the peel strength is generally improved. In addition, if the content of carboxyl-containing monomers is 6.0% by mass or less, it is preferred from the viewpoint of inhibiting metal corrosion. In particular, if it is 3.0% by mass or more and 4.5% by mass or less, it is easy to achieve a balance between general peel strength and metal corrosion inhibition.

[0065] In addition, as a monomer component constituting the emulsion-type acrylic polymer (A), it may also contain multifunctional monomers in order to easily obtain the necessary cohesive force by introducing cross-linking structures into the emulsion-type acrylic polymer (A).

[0066] Examples of multifunctional monomers 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. Multifunctional monomers can be used alone or in combination of two or more.

[0067] The content of polyfunctional monomers in all monomer components (100% by mass) constituting the emulsion-type acrylic polymer (A) is preferably 0.1% by mass to 15% by mass. The upper limit of the polyfunctional monomer content is more preferably 10% by mass, and the lower limit is more preferably 3% by mass. If the content of polyfunctional monomers is 0.1% by mass or more, the flexibility and adhesion of the adhesive layer are easily improved, which is therefore preferred. If the content of polyfunctional monomers is 15% by mass or less, the cohesive force will not increase excessively, and moderate adhesion is easily obtained.

[0068] The glass transition temperature (Tg) of the emulsion-type acrylic polymer (A) is not particularly limited, but it is preferred to be below 0°C, as it can suppress the decrease in normal peel strength. More preferably, it is below -10°C, and even more preferably below -20°C. In addition, it is particularly preferred to be below -40°C, as the rate of decrease in adhesive strength caused by voltage application becomes particularly large. Most preferably, it is below -50°C.

[0069] The glass transition temperature (Tg) can be calculated, for example, based on the following equation (Y) (Fox equation).

[0070] 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 of monomer i when it forms a homopolymer (unit: K), and Wi (i = 1, 2, ..., n) represents the mass fraction of monomer i in the total monomer composition.] The above formula (Y) is a calculation formula for a polymer composed of n monomer components: monomer 1, monomer 2, ..., monomer n.

[0071] It should be noted that the glass transition temperature (Tg) at which a homopolymer is formed refers to the glass transition temperature of the homopolymer of that monomer, specifically the glass transition temperature (Tg) of the polymer formed using only one monomer (sometimes referred to as "monomer X"). Specifically, values ​​are listed in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). It should be noted that the glass transition temperature (Tg) of the homopolymer not described in this literature refers to values ​​obtained, for example, by the following determination method: 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 the polymerization solvent are added to a reactor equipped with a thermometer, stirrer, nitrogen inlet, and reflux condenser. Nitrogen gas is introduced while stirring for 1 hour. After removing oxygen from the polymer system as described above, the temperature is raised to 63°C and the reaction is carried out for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution with a solids content of 33% by mass. Next, the homopolymer solution was cast onto a release liner and dried to prepare a test sample (sheet-like homopolymer) with a thickness of approximately 2 mm. Then, approximately 1–2 mg of this test sample was weighed into an aluminum open cell, and the reversing heat flow (specific heat component) behavior of the homopolymer was obtained using a temperature-modulated DSC (trade name "Q-2000" manufactured by TA Instruments, Inc.) at a heating rate of 5 °C / min under a nitrogen atmosphere at a rate of 50 ml / min. Referring to JIS-K-7121, the temperature at which the straight line equidistant from the baselines of the low-temperature and high-temperature sides of the obtained reversible heat flow intersects the curve of the step-like change in glass transition is taken as the glass transition temperature (Tg) at which the homopolymer is formed.

[0072] In embodiments of the present invention, the emulsion-type acrylic polymer (A) can be obtained by emulsion polymerization of a monomer component containing an amide-containing monomer using an emulsifier and a polymerization initiator.

[0073] As emulsifiers for emulsion polymerization of emulsion-type acrylic polymers, reactive emulsifiers (reactive emulsifiers containing free radical polymerizable functional groups) obtained by introducing free radical polymerizable functional groups into the molecule are preferred. These emulsifiers can be used alone or in combination with two or more.

[0074] (Emulsifier) Examples of emulsifiers include anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers, amphoteric emulsifiers, and polymeric emulsifiers.

[0075] Examples of anionic emulsifiers mentioned above include sodium polyoxyethylene lauryl sulfate, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkylphenyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, and sodium polyoxyethylene alkyl sulfosuccinate.

[0076] Examples of nonionic emulsifiers mentioned above include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, and polyoxyethylene polyoxypropylene block polymers.

[0077] Examples of cationic emulsifiers mentioned above include dodecyl ammonium chloride, lauryl trimethyl ammonium chloride, and lauryl dimethyl ethyl ammonium ethyl sulfate.

[0078] Examples of amphoteric emulsifiers include, for instance, betaine ester-type emulsifiers.

[0079] Examples of the aforementioned polymeric emulsifiers include, for example, poly(meth)acrylates such as sodium polyacrylate, polyvinyl alcohol, polyvinylpyrrolidone, polyhydroxyethyl acrylate, copolymers in which one or more of the monomers constituting polyhydroxyethyl acrylate are copolymer components, styrene-maleic acid copolymer ammonium salt, sodium carboxymethyl cellulose, etc.

[0080] Alternatively, a reactive emulsifier having polymerizable groups (hereinafter referred to as "reactive emulsifier") can be used as the aforementioned emulsifier. By using a reactive emulsifier, the emulsifier is introduced into the polymer, reducing contamination from the emulsifier, and is therefore preferred.

[0081] As a reactive emulsifier, examples include emulsifiers obtained by introducing free radical polymerizable functional groups such as vinyl, propylene, isopropylene, vinyl ether, and allyl ether groups into the aforementioned anionic, nonionic, and cationic emulsifiers. Specifically, examples include ammonium polyoxyethylene styrene-propylene phenyl ether sulfate, ammonium polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate, polyoxyethylene styrene-propylene phenyl ether, polyoxyethylene-1-(allyloxymethyl)alkyl ether, and ammonium-α-sulfonate-ω-1-(allyloxymethyl)alkyloxypolyoxyethylene. When a reactive emulsifier is used, the acrylic polymer, as a water-dispersible polymer obtained by emulsification polymerization, contains monomer units derived from the reactive emulsifier.

[0082] As reactive emulsifiers, commercially available products under trade names such as "ADEKA REASOAP SE-10N" (manufactured by ADEKA Co., Ltd.), "Aqualon HS-10" (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), "Aqualon HS-05" (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), "Aqualon HS-1025" (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), "Aqualon KH-1025" (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), and "Aqualon AR-10" (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) can also be used.

[0083] Furthermore, especially in cases where the presence of impurity ions becomes problematic, it is desirable to remove these impurity ions using SO4. 2- Emulsifiers with anion concentration of 100 μg / g or less are preferred. Furthermore, in the case of anionic emulsifiers, ammonium salt emulsifiers are desirable. As methods for removing impurities from emulsifiers, suitable methods such as ion exchange resin methods, membrane separation methods, and precipitation filtration methods using alcohol impurities can be used.

[0084] Regarding the amount of the aforementioned reactive emulsifier used, it is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 6 parts by mass, and even more preferably 1 to 4 parts by mass, relative to 100 parts by mass of the total amount of raw material monomers constituting the emulsion-type acrylic polymer (A). Setting the amount to 0.1 parts by mass or more ensures stable emulsification, and is therefore preferred. On the other hand, setting the amount to 10 parts by mass or less increases the cohesive strength of the adhesive (adhesive layer), suppresses contamination of the adhered material, and also suppresses contamination caused by the emulsifier, and is therefore preferred.

[0085] (pH buffer) Furthermore, when using emulsifiers to perform emulsion polymerization on monomer mixtures, pH buffers can be used as needed to adjust the pH. As a pH buffer, any material with pH buffering properties is acceptable, and there are no particular limitations. Examples include sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate, sodium acetate, ammonium acetate, sodium formate, and ammonium formate.

[0086] (Polymerization initiator) The emulsion-type acrylic polymer (A) is preferably a polymer obtained by polymerization using a polymerization initiator. There are no particular limitations on the polymerization initiator used for the emulsion polymerization of the acrylic emulsion polymer of the present invention described above. For example, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinylpropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropanediamine) disulfide, 2,2'-azobis(N,N'-dimethyleneisobutyronitrile), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropanediamine] disulfide, and other similar initiators may be used. Azo polymerization initiators such as amidine hydrate; persulfates such as potassium persulfate and ammonium persulfate; peroxide polymerization initiators such as benzoyl peroxide, tert-butyl hydroperoxide, and hydrogen peroxide; redox initiators based on combinations of peroxides and reducing agents, such as redox polymerization initiators based on combinations of peroxides and ascorbic acid (combinations of aqueous hydrogen peroxide solution and ascorbic acid, etc.), combinations of peroxides and iron(II) salts (combinations of aqueous hydrogen peroxide solution and iron(II) salts, etc.), and combinations of persulfates and sodium bisulfite, etc.

[0087] The amount of the aforementioned polymerization initiator can be appropriately determined based on the type of polymerization initiator and raw material monomers, and is not particularly limited. However, relative to 100 parts by mass of the total amount of raw material monomers constituting the emulsion-type acrylic polymer (A), it is preferably 0.01 to 1 part by mass, more preferably 0.02 to 0.5 parts by mass. It should be noted that regarding the addition (dropleting) of the polymerization initiator, methods such as adding the entire total amount at once and two-step polymerization by adding it in two separate drops can be cited. The former method makes it easier to control the particle size of the emulsion and has an advantageous effect on antistatic properties, therefore it is the preferred method.

[0088] (Chain transfer agent) Furthermore, the emulsion-type acrylic polymer (A) is preferably a polymer obtained by polymerization using a chain transfer agent. For example, terpene compounds such as α-pinene, β-pinene, limonene, and terpinene are preferably used as the aforementioned chain transfer agent. Compounds having thiol or hydroxyl groups are also commonly known.

[0089] Examples of compounds containing a thiol group include, for example, thiols such as lauryl thiol, 2-mercaptoethanol, tert-dodecyl thiol, and mercaptosuccinic acid; alkyl mercaptopropionic acid esters such as n-butyl mercaptopropionate and octyl mercaptopropionate; and alkyl mercaptopropionic acid methoxybutyl mercaptopropionate. Examples of compounds containing a hydroxyl group include, for example, alcohols such as methanol, n-propanol, isopropanol (IPA), tert-butanol, and benzyl alcohol.

[0090] The amount of the aforementioned chain transfer agent used is preferably 0 to 1 part by mass relative to 100 parts by mass of the total monomer mixture used for emulsification polymerization. By setting it to less than 1 part by mass, it is possible to prevent the reduction in water resistance, heat resistance, etc., caused by the decrease in molecular weight, thereby preventing the problem of guide roller contamination, and therefore it is preferred.

[0091] Emulsion polymerization of the emulsion-type acrylic polymer (A) can be carried out using conventional methods by emulsifying the monomer components in an aqueous medium followed by emulsion polymerization. This allows the preparation of an aqueous dispersion (polymer emulsion) containing the emulsion-type acrylic polymer (A). The method of emulsion polymerization is not particularly limited; for example, known emulsion polymerization methods such as one-time addition (one-time polymerization), monomer drop addition, and monomer emulsion drop addition can be used. It should be noted that in the monomer drop addition method and monomer emulsion drop addition method, continuous drop addition (total drop addition) or segmented drop addition (including two-step drop addition. It should be noted that segmented drop addition refers to dividing the polymerization process by changing the drop addition rate and amount, such as slowing down the first drop addition or accelerating the second drop addition) can be appropriately selected. Continuous drop addition (total drop addition) is particularly preferred. By using continuous drop addition (total drop addition), the average particle size of the emulsion particles of the emulsion-type acrylic polymer (A) used in this invention can be adjusted to the desired range, which is a preferred method. It should be noted that polymerization through two-step dropwise addition is sometimes referred to as two-step (dropwise) polymerization.

[0092] Regarding the aforementioned total addition polymerization, in the case of total addition polymerization, since there is no sufficient emulsifier to form micelles in the reaction system (the aqueous solution containing the polymerization initiator) at the initial stage of addition, no reaction occurs (because emulsion addition polymerization occurs within the emulsifier micelles). When a certain amount of monomer emulsion is added and the concentration required to form micelles (critical micelle concentration) is reached, large particle sizes are formed during the reaction due to the large amount of monomer present in the system. Therefore, considering the critical micelle concentration of the emulsifier, the average particle size can be adjusted to the desired range by controlling the initial dosage of emulsifier. These methods can be appropriately combined. Reaction conditions can be appropriately selected; for example, the polymerization temperature is preferably around 40–95°C, and the polymerization time is preferably around 30 minutes to 24 hours. In addition, the average particle size of the emulsion particles can also be adjusted by increasing the dropping rate of the monomer emulsion or increasing the polymerization temperature.

[0093] (Average particle size of emulsion particles) The average particle size of the emulsion particles of the emulsion-type acrylic polymer (A) used in this invention is preferably 100 nm to 500 nm.

[0094] Furthermore, the particle size distribution of the emulsion particles is preferably 1.0 to 4.0.

[0095] Regarding the average particle size of the emulsion particles, in addition to using polymerization conditions such as polymerization initiator, the method of adding raw monomers, polymerization temperature, and polymerization time as described above, it can be controlled by the type and concentration of emulsifier added during polymerization, and the concentration of polymerization initiator. Here, the average particle size of the emulsion particles is based on the median particle size of the volume standard obtained by measuring using a laser diffraction / scattering particle size distribution measuring device.

[0096] Regarding the solvent insoluble content (the proportion of solvent-insoluble components, sometimes referred to as "gel fraction") of the emulsion-type acrylic polymer (A), from the viewpoint of low contamination and appropriate peel strength (adhesion), it is preferably 40% (mass%) or more, more preferably 50% (mass%) or more, and even more preferably 60% (mass%) or more. When the solvent insoluble content is less than 40% (mass%), the emulsion-type acrylic polymer (A) contains a large amount of low molecular weight components. Therefore, the low molecular weight components in the adhesive layer cannot be sufficiently reduced by the crosslinking effect alone, resulting in contamination from adhered materials such as low molecular weight components, or excessively high peel strength (adhesion). The aforementioned solvent insoluble content can be controlled by the polymerization initiator, reaction temperature, emulsifier, type of raw material monomer, etc. The upper limit of the aforementioned solvent insoluble content is not particularly limited, for example, it is 99% (mass%). It should be noted that in this invention, the solvent insoluble content of the emulsion-type acrylic polymer (A) is a value calculated by the following "method for determining solvent insoluble content".

[0097] • Determination of solvent insoluble content Emulsion-type acrylic polymer (A): Approximately 0.1 g was collected, wrapped in a porous tetrafluoroethylene sheet (trade name "NTF1122", manufactured by Nitto Denko Corporation) with an average pore size of 0.2 μm, and then tied with kite string. The weight at this point was measured and used as the weight before impregnation. It should be noted that this weight before impregnation is the total weight of the emulsion-type acrylic polymer (A) (collected above), the tetrafluoroethylene sheet, and the kite string. In addition, the combined weight of the tetrafluoroethylene sheet and the kite string was also measured beforehand and used as the bag weight.

[0098] Next, the object (referred to as the "sample"), which was wrapped with a tetrafluoroethylene sheet and tied with kite string, was placed in a 50 ml container filled with ethyl acetate and left to stand at 23°C for 7 days. Then, the sample (after ethyl acetate treatment) was removed from the container, transferred to an aluminum cup, and dried in a desiccator at 130°C for 2 hours to remove the ethyl acetate. The weight was then measured and taken as the weight after impregnation. The solvent-insoluble amount was calculated according to the following formula.

[0099] Solvent insoluble amount (wt%) = (ab) / (cb) × 100 (2) (In formula (2), a is the weight after soaking, b is the weight of the bag, and c is the weight before soaking.) The weight-average molecular weight (Mw) of the solvent-soluble portion (sometimes referred to as "sol") of the emulsion-type acrylic polymer (A) is preferably 40,000 to 200,000, more preferably 50,000 to 150,000, and even more preferably 60,000 to 100,000. By making the weight-average molecular weight of the solvent-soluble portion of the emulsion-type acrylic polymer (A) 40,000 or more, the wettability of the adhesive composition on the adhered object is improved, and the adhesion to the adhered object is improved. In addition, by making the weight-average molecular weight of the solvent-soluble portion of the emulsion-type acrylic polymer (A) 200,000 or less, the residue of the adhesive composition on the adhered object is reduced, and the low-contamination of the adhered object is improved. The weight-average molecular weight of the solvent-soluble portion of the above-mentioned acrylic emulsion polymer can be determined by the following method: the ethyl acetate-treated solution (ethyl acetate solution) obtained in the determination of the solvent insoluble amount of the emulsion-type acrylic polymer (A) is air-dried at room temperature, and the resulting sample (solvent-soluble portion of the acrylic emulsion polymer) is determined by GPC (gel permeation chromatography). Specific determination methods are given below.

[0100] Methods for determining weight-average molecular weight GPC determination was performed using a TOSOH HLC-8220GPC apparatus, and the molecular weight was determined based on the polystyrene conversion value. The determination conditions are as follows.

[0101] Sample concentration: 0.2% by weight (THF solution) Sample injection volume: 10 μl Elution buffer: THF Flow rate: 0.6 ml / min Measurement temperature: 40℃ column: Sample columns: 1 TSK SuperHZ-H guard column + 2 TSKgel SuperHZM-H guard columns Reference column: 1 TSKgel SuperH-RC column Detector: Differential refractometer The content of the emulsion-type acrylic polymer (A) in the adhesive composition according to the embodiments of the present invention is preferably 50% by mass or more and 99.9% by mass or less relative to the total solid components (100% by mass) of the adhesive composition, with an upper limit of more preferably 99.5% by mass, further preferably 99% by mass, and a lower limit of more preferably 60% by mass, further preferably 70% by mass.

[0102] It should be noted that, in this specification, the solid component of the adhesive composition refers to the components other than water and other dispersion media, and the solid component concentration refers to the mass percentage of the components other than water and other dispersion media relative to the total mass of the adhesive composition.

[0103] <Electrolyte (B)> The adhesive compositions according to embodiments of the present invention preferably contain an electrolyte, particularly for applications involving electro-removal. An electrolyte is a substance capable of ionizing into anions and cations; preferably, it is an ionic substance. Ionic substances refer to substances that exist in a state other than gas at room temperature (25°C) and consist of at least one pair of anions and cations. Ionic substances at room temperature (25°C) can be solid, liquid, or an intermediate state between solid and liquid (e.g., liquid crystals, viscous crystals, viscous solids, viscous liquids). The state of an ionic substance at room temperature (25°C) varies depending on its molecular structure. Examples of ionic substances include ionic liquids, viscous ionic crystals, ionic surfactants, alkali metal salts, alkaline earth metal salts, and organic quaternary ammonium salts. From the viewpoint of achieving good electro-removal properties, an ionic liquid is more preferably the electrolyte contained in the adhesive composition.

[0104] (Ionic liquid) Regarding ionic liquids, there are no particular limitations as long as they are molten salts composed of a pair of anions and cations and are liquid at 25°C (room temperature molten salts). The following examples of anions and cations illustrate this; among the ionic substances obtained by combining them, those that are liquid at 25°C are ionic liquids, while those that are solid at 25°C are not ionic liquids, but rather ionic solids, as described later.

[0105] As for ionic liquids, they have high ionic conductivity and high thermal stability among ionic substances, and thus can exist in a wide temperature range as liquids. Therefore, the effects of the technology disclosed here tend to be ideally realized.

[0106] Examples of anions in ionic liquids include (FSO₂)₂N. - (CF3SO2)2N - (CF3CF2SO2)2N - (CF3SO2)3C - ,Br - AlCl4 - Al2Cl7 - NO3 - BF4 - PF6 - CH3COO - CF3COO- CF3CF2CF2COO - CF3SO3 - CF3(CF2)3SO3 - AsF6 - SbF6 - and F (HF) n - Among these, (FSO2)2N is preferred as an anion, considering its chemical stability and suitability for achieving good electrostripping properties. - [bis(fluorosulfonyl)imide anion], and (CF3SO2)2N - [bis(trifluoromethanesulfonyl)imide anion] and other sulfonylimide compounds. That is, the anion of the ionic liquid preferably includes at least one selected from the group consisting of bis(fluoromethanesulfonyl)imide anion and bis(trifluoromethanesulfonyl)imide anion.

[0107] From the perspective of chemical stability and suitability for good electrostripping properties, the cations in the ionic liquid are preferably nitrogen-containing, sulfur-containing, and phosphorus-containing cations, and more preferably imidazolium-based, ammonium-based, pyrrolidine-based, and pyridinium-based cations.

[0108] Examples of imidazolium cations include, for example, 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-heptyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-nonyl-3-methylimidazolium cation, 1-undecyl-3-methylimidazolium cation, and 1-dodecyl-3-methylimidazolium cation. Onion cations, 1-tridecyl-3-methylimidazolium cation, 1-tetradecyl-3-methylimidazolium cation, 1-pentadecanyl-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, etc.

[0109] Examples of pyridinium cations include 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, and 1-octyl-4-methylpyridinium cation.

[0110] Examples of pyrrolidine-onium cations include, for example, 1-ethyl-1-methylpyrrolidine-onium cation and 1-butyl-1-methylpyrrolidine-onium cation.

[0111] Examples of ammonium cations include tetraethylammonium cation, tetrabutylammonium cation, methyltrioctylammonium cation, tetradecyltrihexylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethyl acrylate cation.

[0112] From the viewpoint of increasing the rate of decrease in adhesive force when voltage is applied, it is preferable to select cations with a molecular weight of 160 or less as constituent cations for ionic liquids, and particularly preferred to include (FSO2)2N as described above. - [bis(fluorosulfonyl)imide anion] or (CF3SO2)2N - Ionic liquids containing bis(trifluoromethanesulfonyl)imide anions and cations with a molecular weight of 160 or less. Examples of cations with a molecular weight of 160 or less include 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, 1-ethyl-1-methylpyrrolidineium cation, 1-butyl-1-methylpyrrolidineium cation, tetraethylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethyl acrylate cation.

[0113] In addition, the cations represented by the following formulas (2-A) to (2-D) are also preferred as cations for ionic liquids.

[0114] [Chemical Formula 1] R in equation (2-A) 1 The R group represents a hydrocarbon group with 4 to 10 carbon atoms (preferably a hydrocarbon group with 4 to 8 carbon atoms, more preferably a hydrocarbon group with 4 to 6 carbon atoms), and may also contain heteroatoms. 2 and R 3 Whether the groups are the same or different, they represent hydrogen atoms or hydrocarbon groups with 1 to 12 carbon atoms (preferably hydrocarbon groups with 1 to 8 carbon atoms, more preferably hydrocarbon groups with 2 to 6 carbon atoms, and even more preferably hydrocarbon groups with 2 to 4 carbon atoms), and may also include heteroatoms. Wherein, if a nitrogen atom forms a double bond with an adjacent carbon atom, R 3 It does not exist.

[0115] R in equation (2-B) 4The R group represents a hydrocarbon group having 2 to 10 carbon atoms (preferably a hydrocarbon group having 2 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms), and may also contain heteroatoms. 5 R 6 and R 7 Whether the groups are the same or different, they may represent hydrocarbon groups with 1 to 12 carbon atoms (preferably hydrocarbon groups with 1 to 8 carbon atoms, more preferably hydrocarbon groups with 2 to 6 carbon atoms, and even more preferably hydrocarbon groups with 2 to 4 carbon atoms), and may also contain heteroatoms.

[0116] R in equation (2-C) 8 The R group represents a hydrocarbon group having 2 to 10 carbon atoms (preferably a hydrocarbon group having 2 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms), and may also contain heteroatoms. 9 R 10 and R 11 Whether the groups are the same or different, they represent hydrocarbon groups with 1 to 16 carbon atoms (preferably hydrocarbon groups with 1 to 10 carbon atoms, more preferably hydrocarbon groups with 1 to 8 carbon atoms), and may also contain heteroatoms.

[0117] In formula (2-D), X represents a nitrogen, sulfur, or phosphorus atom, and R... 12 R 13 R 14 and R 15 Whether the groups are the same or different, they represent hydrocarbon groups with 1 to 16 carbon atoms (preferably hydrocarbon groups with 1 to 14 carbon atoms, more preferably hydrocarbon groups with 1 to 10 carbon atoms, even more preferably hydrocarbon groups with 1 to 8 carbon atoms, and particularly preferably hydrocarbon groups with 1 to 6 carbon atoms), and may also include heteroatoms. Where X is a sulfur atom, R... 12 It does not exist.

[0118] In embodiments of the present invention, the cation of the ionic liquid preferably includes at least one selected from the group consisting of nitrogen-containing cations, sulfur-containing cations, and phosphorus-containing cations.

[0119] Commercially available ionic liquids include, for example, “E1452”, “E0599”, “M2098”, “M2980”, “M2981”, and “M2998” manufactured by Tokyo Chemical Industry Co., Ltd., “HMI-FSI” manufactured by Mitsubishi Materials Co., Ltd., and “CIL-312” and “CIL-313” manufactured by Japan Carlit Co., Ltd.

[0120] (Flexible ionic crystal) Flexible ionic crystals refer to substances that have a pair of anions and cations, are composed of a regularly arranged three-dimensional lattice, and exhibit disorder at the ionic level, such as localized orientation and rotational disturbances.

[0121] Compared to ionic solids, viscous ionic crystals have high plasticity and excellent electrochemical stability and heat resistance among ionic substances. Therefore, they tend to achieve the desired effects of the technology disclosed herein.

[0122] Examples of anions in viscous ionic crystals include (FSO2)2N. - (CF3SO2)2N - (CF3CF2SO2)2N - (FSO2)(CF3SO2)N - ,Br - BF4 - PF6 - N(CN)2 - and F (HF) n - Among these, (FSO2)2N is preferred as an anion, considering its chemical stability and suitability for achieving good electrostripping properties. - [bis(fluorosulfonyl)imide anion], and (CF3SO2)2N - [Bis(trifluoromethanesulfonyl)imide anion] and other sulfonamide compounds. That is, the anion of the viscous ionic crystal preferably includes at least one selected from the group consisting of bis(fluorosulfonyl)imide anion and bis(trifluoromethanesulfonyl)imide anion.

[0123] Examples of cations in flexible ionic crystals include imidazolium, ammonium, pyrrolidineonium, and phosphorusonium cations. Among these, imidazolium and pyrrolidineonium cations are preferred for their chemical stability and suitability for achieving good electrostripping properties.

[0124] Examples of imidazolium cations include, for example, 1-ethyl-3-methylimidazolium cation and 1-butyl-3-methylimidazolium cation. Examples of pyrrolidine-onium cations include, for example, 1-ethyl-1-methylpyrrolidine-onium cation and 1-butyl-1-methylpyrrolidine-onium cation.

[0125] As a flexible ionic crystal, from the viewpoint of increasing the rate of decrease in adhesive force when voltage is applied, it is preferable to select a cation with a molecular weight of 160 or less as the constituting cation, and particularly preferably (FSO2)2N as described above. - [bis(fluorosulfonyl)imide anion] or (CF3SO2)2N- A flexible ionic crystal containing [bis(trifluoromethanesulfonyl)imide anion] and cations with a molecular weight of 160 or less. Examples of cations with a molecular weight of 160 or less include 1-ethyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-ethyl-1-methylpyrrolidineonium cation, and 1-butyl-1-methylpyrrolidineonium cation.

[0126] Commercially available examples of flexible ionic crystals include, for instance, "ETHYLMETHYLPYRROLIDINIUM BIS (FLUOROSULFONYL)IMIDE" manufactured by Boron Molecular Inc.

[0127] (Ionic surfactants) Examples of ionic surfactants include anionic surfactants and cationic surfactants, such as sodium polyoxyethylene lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, lauryl trimethyl ammonium chloride, and polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium, etc.

[0128] (Alkali metal salts) Examples of alkali metal salts include LiCl, Li₂SO₄, LiBF₄, LiPF₆, LiClO₄, LiAsF₆, LiCF₃SO₃, LiN(SO₂CF₃)₂, LiN(SO₂C₂F₅)₂, and LiC(SO₂CF₃)₃. It should be noted that while these are lithium salts, they could also be sodium or potassium salts.

[0129] (Alkaline earth metal salts) Examples of alkaline earth metal salts include, for example, calcium salts, magnesium salts, barium salts, cesium salts and their halides.

[0130] (Organic quaternary ammonium salt) Examples of organic quaternary ammonium salts include tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide, tetramethylammonium hydroxide, and tetramethylammonium fluoride tetrahydrate.

[0131] The molecular weight of the cation in the ionic substance 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. It is also generally 50 or more. The cation in the ionic substance is considered to have the property that, in the adhesive layer, it migrates to the cathode side when a voltage is applied, concentrating near the interface between the adhesive layer and the adhered object. In this invention, for this reason, the applied voltage reduces the adhesive force compared to the usual peel force, resulting in electro-peelability. A cation with a small molecular weight such as 500 or less is suitable from the viewpoint that the migration of the cation to the cathode side in the adhesive layer becomes easier, increasing the rate of reduction in adhesive force when a voltage is applied.

[0132] The ionic conductivity of the ionic material is preferably 0.1 mS / cm or higher. More preferably, it is 1 mS / cm or higher, even more preferably 3 mS / cm or higher, even more preferably 5 mS / cm or higher, even more preferably 10 mS / cm or higher, particularly preferably 15 mS / cm or higher, and most preferably 20 mS / cm or higher. The upper limit is not particularly limited; by having the above-mentioned ionic conductivity, the adhesive force will be sufficiently reduced even at low voltages. It should be noted that the ionic conductivity can be measured, for example, using a Solartron 1260 frequency response analyzer via AC impedance spectroscopy.

[0133] Regarding the content (combining amount) of electrolyte (B) in the adhesive composition according to embodiments of the present invention, relative to 100 parts by weight of emulsion-type acrylic polymer (A), it is preferably 0.5 parts by weight or more from the viewpoint of reducing adhesive force during voltage application, and preferably 30 parts by weight or less from the viewpoint of improving general peel strength and inhibiting metal corrosion. From the same viewpoint, it is more preferably 20 parts by weight or less, further preferably 15 parts by weight or less, particularly preferably 10 parts by weight or less, and most preferably 5 parts by weight or less. Furthermore, it is more preferably 0.6 parts by weight or more, further preferably 0.8 parts by weight or more, particularly preferably 1.0 parts by weight or more, and most preferably 1.5 parts by weight or more.

[0134] <Tackifier (C)> In the case of the adhesive composition according to embodiments of the present invention, for the purpose of improving adhesive properties, impact resistance, and electro-removal properties in electro-removal applications, it is preferable to further contain a tackifier (C).

[0135] Examples of tackifiers (C) include, for example, urethane-associated tackifiers, alkali-swellable tackifiers, cellulose-based tackifiers, and natural polymer-based tackifiers.

[0136] Carbamate associative tackifiers are, for example, carbamate compounds having carbamate bonds and polyether chains in their molecules. Examples of carbamate compounds that can exhibit tackifying effects by associating with each other in water through carbamate bonds are exemplified.

[0137] As a urethane-associated tackifier, it can be a tackifier obtained by reacting isocyanate compounds with polyol compounds, for example, depending on the type of polyol, ester-based, ether-based, carbonate-based, etc.

[0138] Examples of alkali-swellable tackifiers include, for instance, polyacrylic acid-based tackifiers.

[0139] Examples of polyacrylic acid-based tackifiers include polyacrylic acid and polyacrylic acid-poly(meth)acrylate copolymers (acrylic copolymers). Additionally, examples of polyacrylic acid-based tackifiers include the neutralized product obtained by pre-neutralizing the aforementioned polyacrylic acid, namely polyacrylates. Examples of polyacrylates include sodium polyacrylate and potassium polyacrylate. Furthermore, examples of polyacrylic acid-based tackifiers include hydrophobic polyacrylic acid obtained by modifying a portion of the carboxyl group with hydrophobic groups such as styrene or alkyl groups.

[0140] The acid value of the polyacrylic acid tackifier is, for example, 30 to 300 mg / KOH, preferably 80 to 280 mg / KOH.

[0141] Examples of cellulose-based thickeners include methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, and carboxymethylcellulose.

[0142] Examples of natural polymeric thickeners include xanthan gum, gellan gum, guar gum, sodium alginate, carrageenan, and pectin.

[0143] Other examples of tackifiers include polyethylene oxide and polyvinyl alcohol.

[0144] These tackifiers can be used alone or in combination of two or more.

[0145] The tackifier (C) preferably comprises at least one selected from the group consisting of urethane-associated tackifiers, alkali-swellable tackifiers, and cellulose-based tackifiers.

[0146] These tackifiers (C) can be commercially available products. Specifically, examples of urethane-associated tackifiers include, for instance, ADEKA NOL UH-462, ADEKA NOL UH-752, ADEKA NOL UH-140S, ADEKA NOL UH-420, ADEKA NOL UH-438, ADEKA NOL UH-472, ADEKA NOL UH-450, ADEKA NOL UH-450VF, ADEKA NOL UH-540, ADEKA NOL UH-550, ADEKA NOL UH-541VF, ADEKA NOL UH-526, and ADEKA NOL. UH-530 (all manufactured by ADEKA), RHEOLATE266, RHEOLATE288, RHEOLATE244, RHEOLATE255, RHEOLATE278 (all manufactured by RHEOX), SN Thickener A-803, SN Thickener A-804, SN Thickener A-807, SN Thickener A-812, SN Thickener A-814 (all manufactured by SAN NOPCO), etc.

[0147] Examples of alkali-swellable thickeners include PRIMAL ASE-60, PRIMAL TT-615, PRIMAL ASE-75, PRIMAL ASE-95, PRIMAL ASE-108, PRIMAL RM-5 (all manufactured by Rohm and Haas), Zogen100, Zogen 150, Zogen 200, Zogen 250, Zogen 350 (all manufactured by RHEOX), SN Thickener A-815, SN Thickener A-818, SN Thickener A-850 (all manufactured by SAN NOPCO), RHEOVIS CR (manufactured by Ichika Oils & Fats Co., Ltd.), Aron B-300K, Aron B-500 (acrylic copolymer), Aron A-7070 (manufactured by Toa Synthetic Co., Ltd.), Chikuzol K-150B (manufactured by Kyoei-sha Oils & Fats Chemical Co., Ltd.), ACRISET WR-503, and ACRISET... WR-650 (manufactured by Nippon Shokubai Co., Ltd.) and others. Additionally, SN Thickener 640 (hydrophobic modified polyacrylic acid, manufactured by SAN NOPCO) and others can also be cited.

[0148] Examples of cellulose-based thickeners include RHEOCRYSTA I-2SX (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), RHEOCRYSTA I-2AX (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), and RHEOCRYSTA I-2SXS (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.).

[0149] In addition, the aforementioned thickeners can be prepared in forms such as powder (particle) type, aqueous solution type, emulsion type, etc.

[0150] In addition, the thickener (C) is prepared in the form of a 1% by mass aqueous solution, and the turbidity at pH 8 is, for example, 100 NTU or less, preferably 50 NTU or less, more preferably 20 NTU or less, and usually 0.1 NTU or more.

[0151] To adjust the pH of a 1% by mass aqueous solution to 8, for example, an alkaline aqueous solution such as an ammonia solution with a concentration of 5-15% by mass is added to the 1% by mass aqueous solution of the thickener. The amount of alkaline aqueous solution added is adjusted in such a way that the concentration of the thickener is reduced by, for example, less than 1%.

[0152] In addition, turbidity is measured using a turbidimeter. NTU is the unit of turbidity (nephelometric turbidity unit).

[0153] By setting the turbidity of a 1% by mass aqueous solution of the pH-adjusted thickener to the range mentioned above, the insoluble matter (particles) of the thickener remain, and the thickener exists as larger particles in the adhesive layer as is, which makes it less likely for turbidity caused by reduced transparency of the adhesive layer to occur.

[0154] The molecular weight of the thickener (C) is preferably 5,000 to 2,000,000, based on weight-average molecular weight.

[0155] In the embodiments of the present invention, the content of the tackifier (C) in the adhesive composition is preferably 0.01 parts by weight or more, more preferably 0.05 parts by weight or more, relative to 100 parts by weight of the above-mentioned emulsion-type acrylic polymer (A). Furthermore, as an upper limit, it is preferably 15 parts by weight or less, more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less.

[0156] The adhesive composition according to the embodiments of the present invention further includes a tackifier (C), the content of which is preferably 0.01 to 15 parts by weight, more preferably 0.01 to 10 parts by weight, further preferably 0.01 to 7 parts by weight, and even more preferably 0.05 to 5 parts by weight, relative to 100 parts by weight of the above-mentioned emulsion-type acrylic polymer (A).

[0157] It should be noted that the content of tackifier (C) indicates the content as a solid component.

[0158] <Other Ingredients> The adhesive compositions according to embodiments of the present invention may contain one or more other components (hereinafter sometimes referred to as "other components") other than the emulsion-type acrylic polymer (A), electrolyte (B), and tackifier (C), as needed and without impairing the effects of the present invention. The other components that may be contained in the adhesive compositions according to embodiments of the present invention will be described below.

[0159] The adhesive composition according to embodiments of the present invention may contain ionic additives for the purpose of controlling electro-peeling force. For example, ionic solids may be used as ionic additives.

[0160] Ionic solids are ionic substances that are solid at 25°C. There is no particular limitation on ionic solids; for example, solid substances obtained by combining anions and cations exemplified in the description of the aforementioned ionic liquids can be used. When the adhesive composition contains ionic solids, the content of ionic solids is preferably 0.5 parts by mass or more, more preferably 1% by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 2.5 parts by mass or less, relative to 100 parts by mass of the emulsion-type acrylic polymer (A).

[0161] For the purpose of improving creep and shear properties by crosslinking the emulsion-type acrylic polymer (A), the adhesive composition according to embodiments of the present invention may contain a crosslinking agent as needed. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, carbodiimide-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and amine-based crosslinking agents.

[0162] Examples of isocyanate-based crosslinking agents include toluene diisocyanate and phenyl methylene diisocyanate.

[0163] Examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-phenylenediamine, diglycidyl aniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and 1,6-hexanediol diglycidyl ether.

[0164] Examples of carbodiimide-based crosslinking agents include low-molecular-weight compounds or high-molecular-weight compounds having two or more carbodiimide groups.

[0165] Low molecular weight compounds having a carbodiimide group are represented, for example, by the following general formula.

[0166] R 1 -N=C=NR 2 -N=C=NR 3 (In the general formula, R) 1 R 2 and R 3 The differences between them indicate hydrocarbon groups. Polycarbodiimide is a polymeric compound containing a carbodiimide group, and preferably a polymeric compound having a site with excellent affinity for water, specifically an oxidized olefin (-CH2-CH2-O-) site.

[0167] As a polymeric compound containing a carbodiimide group, commercially available products can be used. Specifically, examples include the "CARBODILITE" series manufactured by Nisshinbo Chemical Inc. Examples of this series include water-soluble (e.g., grade names "V-04", "V-02", "V-02-L2"), emulsion (e.g., "E-02", "E-05"), solvent-based (e.g., "V-03", "V-07", "V-09"), and solvent-free (e.g., "V-05").

[0168] The content of the crosslinking agent relative to 100 parts by weight of the emulsion-type acrylic polymer (A) is preferably 0.1 parts by weight or more, more preferably 0.7 parts by weight or more, and preferably 50 parts by weight or less, more preferably 10 parts by weight or less, and even more preferably 7 parts by weight or less. It should be noted that the crosslinking agent can be used alone or in combination of two or more types.

[0169] For the purpose of facilitating the movement of the electrolyte (B) when voltage is applied, the adhesive composition according to embodiments of the present invention may contain polyethylene glycol or tetraethylene glycol dimethyl ether as needed. As polyethylene glycol or tetraethylene glycol dimethyl ether, substances having a number average molecular weight of 100 to 6000 can be used. The content of these components relative to 100 parts by weight of the emulsion-type acrylic polymer (A) is preferably 30 parts by weight or less, more preferably 20 parts by weight or less, and even more preferably 15 parts by weight or less.

[0170] From the viewpoint of suppressing the deterioration of adhesive properties and impact resistance, it is preferable that the adhesive composition involved in the embodiments of the present invention does not contain these components.

[0171] For the purpose of imparting conductivity to the adhesive composition, the adhesive composition according to embodiments of the present invention may contain conductive fillers as needed. There are no particular limitations on the conductive filler; commonly known or frequently used conductive fillers may be used, such as metal powders like graphite, carbon black, carbon fiber, silver, and copper. The content of the conductive filler is preferably 0.1 parts by weight or more and 200 parts by weight or less relative to 100 parts by weight of the emulsion-type acrylic polymer (A).

[0172] For the purpose of inhibiting corrosion of the metal adhered to the substrate, the adhesive composition according to embodiments of the present invention may further contain a corrosion inhibitor without impairing the effects of the present invention. There are no particular limitations on the corrosion inhibitor; commonly known or frequently used corrosion inhibitors may be used, such as carbodiimide compounds, adsorption inhibitors, chelate-forming metal passivators, etc.

[0173] Examples of carbodiimide compounds include, 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'-ditert-butylcarbodiimide, 1,3-bis(p-tolyl)carbodiimide, and polycarbodiimide resins using these compounds as monomers. These carbodiimide compounds can be used alone or in combination of two or more.

[0174] Examples of adsorption inhibitors include alkylamines, carboxylates, carboxylic acid derivatives, and alkyl phosphates. Adsorption inhibitors can be used alone or in combination of two or more.

[0175] As chelate-forming metal passivating agents, for example, triazole-containing compounds or benzotriazole-containing compounds can be used. They are preferred because they provide high passivation effects on the surfaces of metals such as stainless steel and aluminum, and do not easily affect adhesion even when included in adhesive components. Chelate-forming metal passivating agents can be used alone or in combination of two or more.

[0176] The total content (compound amount) of corrosion inhibitor is preferably less than 5 parts by mass relative to 100 parts by mass of emulsion-type acrylic polymer (A), and from the viewpoint of improving adhesive properties, it is preferable that it does not contain corrosion inhibitor.

[0177] In addition, the adhesive composition according to embodiments of the present invention may also contain various additives such as tackifying resin, filler, plasticizer, anti-aging agent, antioxidant, pigment (dye), flame retardant, surfactant (leveling agent), rust inhibitor, adhesion promoter, and antistatic agent. There are no particular limitations on the total content of these components, as long as the effects of the present invention are achieved. Preferably, it is 0.01 parts by weight or more and 20 parts by weight or less, more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less, relative to 100 parts by weight of the emulsion-type acrylic polymer (A).

[0178] Examples of tackifying resins include rosin-based resins, rosin-derived resins, petroleum-based resins, terpene-based resins, phenolic resins, ketone-based resins, and other tackifying resins. Rosin-based resins and terpene-based resins are preferred examples.

[0179] The content of the tackifying resin relative to 100 parts by weight of the water-dispersible polymer is, for example, 5 parts by weight or more, preferably 15 parts by weight or more, more preferably 25 parts by weight or more, and even more preferably 33 parts by weight or more. In addition, it is, for example, 50 parts by weight or less, preferably 45 parts by weight or less, and more preferably 38 parts by weight or less.

[0180] 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, kaolinite clay, and calcined clay.

[0181] Plasticizers can be commonly used in general resin compositions, such as paraffin oil, processing oil, liquid rubbers such as liquid isoprene, liquid butadiene, and liquid ethylene-propylene rubber, tetrahydrophthalic acid, azelaic acid, benzoic acid, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, citric acid and their derivatives, dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diisononyl adipate (DINA), and isodecanyl succinate, etc.

[0182] Examples of anti-aging agents include hindered phenolic compounds, aliphatic compounds, and aromatic hindered amine compounds.

[0183] Examples of antioxidants include butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA).

[0184] Examples of pigments include inorganic pigments such as titanium dioxide, zinc oxide, ultramarine, iron oxide red, zinc barium white, lead, cadmium, iron, cobalt, aluminum, hydrochloride, and sulfate, as well as organic pigments such as azo pigments and copper phthalocyanine pigments.

[0185] Examples of rust inhibitors include zinc phosphate, tannic acid derivatives, phosphate esters, basic sulfonates, and various rust-inhibiting pigments.

[0186] Examples of adhesive agents include titanium coupling agents and zirconium coupling agents.

[0187] As antistatic agents, examples generally include quaternary ammonium salts or hydrophilic compounds such as polyglycolic acid and ethylene oxide derivatives.

[0188] [Standard peel force and electro-peel force] The adhesive strength of the adhesive composition according to the embodiments of the present invention can be evaluated using various methods, such as the 180° peel force test described in Example 1.

[0189] Regarding the adhesive composition according to embodiments of the present invention, the typical peel strength measured by forming an adhesive sheet and performing a 180° peel test as described in Example 1 is preferably 4.0 N / cm or more, more preferably 4.5 N / cm or more, further preferably 5.0 N / cm or more, particularly preferably 5.5 N / cm or more, and most preferably 6.0 N / cm or more. If the typical peel strength is 4.0 N / cm or more, the adhesion to the adhered object is sufficient, and the adhered object is not easily peeled off or shifted.

[0190] Furthermore, regarding the adhesive composition according to embodiments of the present invention, in applications involving electro-peeling, it is preferable that the adhesive sheet formed as described in Example 1, and the adhesive force, i.e., the electro-peeling force, measured by a 180° peel test after applying a voltage of 30V for 30 seconds, is sufficiently small compared to the ordinary peeling force.

[0191] Regarding the adhesive composition according to embodiments of the present invention, in applications involving electro-peeling, the electro-peeling force, as described in Example 1, formed into an adhesive sheet and measured by a 180° peel test after applying a voltage of 30V for 30 seconds, is preferably less than 2.0 N / cm, more preferably less than 0.5 N / cm, further preferably less than 0.3 N / cm, particularly preferably less than 0.1 N / cm, and most preferably less than 0.01 N / cm. If the electro-peeling force is less than 2.0 N / cm, the electro-peeling properties are excellent; therefore, even easily damaged adhered materials can be reprocessed without damage.

[0192] It should be noted that the applied voltage and voltage application time during electro-peeling are not limited to those described above, as long as the adhesive sheet can be peeled off; there are no particular limitations. Preferred ranges for these parameters are as follows.

[0193] The applied voltage is preferably 1V or higher, more preferably 3V or higher, and even more preferably 6V or higher. Additionally, it is preferably 100V or lower, more preferably 50V or lower, even more preferably 30V or lower, and particularly preferably 15V or lower.

[0194] The voltage application time is preferably 60 seconds or less, more preferably 40 seconds or less, even more preferably 20 seconds or less, and particularly preferably 10 seconds or less. Under these conditions, workability is excellent. Furthermore, the shorter the application time, the better, but it is typically 1 second or more.

[0195] [Uses of Adhesive Compositions] The uses of the adhesive compositions according to embodiments of the present invention are not particularly limited, but they are preferably used as adhesive compositions for fixing components including metal parts. In particular, they are preferably used as adhesive compositions for electro-removal applications and / or for fixing components in electrical and electronic equipment. The specific methods of application to such applications are the same as those described below for applications involving adhesive sheets.

[0196] [Method for manufacturing adhesive composition] Regarding the adhesive composition according to embodiments of the present invention, there are no particular limitations, and it can be manufactured by appropriately stirring and mixing an emulsion-type acrylic polymer (A) with an electrolyte (B), a tackifier (C), a crosslinking agent, etc., as needed. Regarding the emulsion-type acrylic polymer (A), it is preferable to directly combine the acrylic polymer solution obtained during polymerization.

[0197] The concentration of solid components in the adhesive composition according to the embodiments of the present invention is not particularly limited, for example, it can be set to 20 to 60% by mass, and from the viewpoint of coatability, it can be set to 40 to 55% by mass, for example.

[0198] As mentioned above, the solids concentration of an adhesive composition refers to the mass percentage of the components other than water and other dispersion media relative to the total mass of the adhesive composition.

[0199] In the adhesive composition according to the embodiments of the present invention, the mass of water is preferably 50 to 100% by mass, more preferably 95% to 100% by mass, relative to the total mass of water and other dispersion media.

[0200] [Adhesive sheet] [Composition of adhesive sheet] The adhesive sheet according to embodiments of the present invention is not particularly limited as long as it has an adhesive layer formed from the adhesive composition according to embodiments of the present invention described above. The adhesive layer formed from the adhesive composition according to embodiments of the present invention is preferably an electro-removable adhesive layer containing an electrolyte (B). The adhesive sheet according to embodiments of the present invention may also have an adhesive layer that does not contain an electrolyte (B), other than an electro-removable adhesive layer (hereinafter sometimes referred to as "other adhesive layers"). The adhesive sheet according to embodiments of the present invention may also have a substrate, a conductive layer, an electrical substrate, an intermediate layer, and a base layer, in addition to the above-described components. The adhesive sheet according to embodiments of the present invention may, for example, be in the form of a roll or a sheet. It should be noted that "adhesive sheet" also includes the meaning of "adhesive tape." That is, the adhesive sheet according to embodiments of the present invention may also be an adhesive tape in the form of a strip.

[0201] The adhesive sheet according to embodiments of the present invention may also be formed solely of an electrically removable adhesive layer without a substrate, i.e., a double-sided adhesive sheet without a substrate layer (substrate-free). The adhesive sheet according to embodiments of the present invention may also be a double-sided adhesive sheet having a substrate on both sides of which are adhesive layers (electrically removable adhesive layers or other adhesive layers). Furthermore, the adhesive sheet according to embodiments of the present invention may also be a single-sided adhesive sheet having a substrate on only one side of which is an adhesive layer (electrically removable adhesive layer or other adhesive layer). It should be noted that the adhesive sheet according to embodiments of the present invention may also have a release liner for protecting the surface of the adhesive layer, but this release liner is not included in the adhesive sheet according to embodiments of the present invention.

[0202] The structure of the adhesive sheet according to embodiments of the present invention is not particularly limited, but preferred examples can be given. Figure 1 The adhesive sheet X1 shown Figure 2 The adhesive sheet X2 with a stacked structure is shown in the figure. Figure 3 The image shows a laminated adhesive sheet X3. Adhesive sheet X1 is a substrate-free double-sided adhesive sheet formed solely of an electrically removable adhesive layer 1. Adhesive sheet X2 is a substrate-bearing double-sided adhesive sheet consisting of an adhesive layer 2, an electrically conductive substrate 5 (substrate 3 and conductive layer 4), and an electrically removable adhesive layer 1. Adhesive sheet X3 is a substrate-bearing double-sided adhesive sheet consisting of an adhesive layer 2, an electrically conductive substrate 5 (substrate 3 and conductive layer 4), an electrically removable adhesive layer 1, an electrically conductive substrate 5 (substrate 3 and conductive layer 4), and an adhesive layer 2. Figure 2 and 3 In the conductive substrate 5 of the adhesive sheets X2 and X3 shown, substrate 3 is not necessary; it can be simply the conductive layer 4. Furthermore, in Figure 2 In the adhesive sheet X2, it can also be a single-sided adhesive sheet without adhesive layer 2.

[0203] As for substrate 3, there are no particular limitations, and examples include paper-based substrates such as paper, fiber-based substrates such as cloth and non-woven fabrics, plastic-based substrates such as films and sheets formed from various plastics (polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, acrylic resins such as polymethyl methacrylate, etc.), and their laminates. The substrate can be single-layered or multi-layered. It should be noted that various treatments such as back-side treatment, antistatic treatment, and primer treatment can be applied to the substrate as needed.

[0204] As the conductive layer 4, any conductive layer is acceptable and there are no particular limitations. It can be a metal (e.g., aluminum, magnesium, copper, iron, tin, gold, etc.) foil, a metal plate (e.g., aluminum, magnesium, copper, iron, tin, silver, etc.) or a conductive polymer, etc. Alternatively, it can be a metal vapor-deposited film disposed on the substrate 3.

[0205] As for the substrate 5 for conducting electricity, any substrate having a conductive layer (conducting electricity) is acceptable, and there are no particular limitations. Examples include substrates obtained by forming a metal layer on the surface of a substrate. For instance, substrates obtained by forming a metal layer on the surface of the substrates exemplified above using methods such as plating, chemical vapor deposition, or sputtering are examples. Examples of metal layers include metals, metal plates, and conductive polymers exemplified above.

[0206] In adhesive sheet X1, the adhered materials on both sides are preferably adhered materials with a metal adhered surface. In adhesive sheet X2, the adhered material on the side of the electro-peelable adhesive layer 1 is preferably an adhered material with a metal adhered surface.

[0207] Examples of metal-coated surfaces include conductive surfaces formed from metals such as aluminum, copper, iron, magnesium, tin, gold, silver, and lead, with surfaces formed from metals containing iron or aluminum (e.g., stainless steel) being preferred. Examples of adhered objects with metal-coated surfaces include sheets, components, and plates formed from metals such as aluminum, copper, iron, magnesium, tin, gold, silver, and lead. Other than adhered objects with metal-coated surfaces, there are no particular limitations; examples include fibrous sheets such as paper, cloth, and non-woven fabrics, and films and sheets of various plastics.

[0208] From the viewpoint of general adhesive strength, the thickness of the electro-removable adhesive layer 1 is preferably 1 μm to 1000 μm. The upper limit of the thickness of the electro-removable adhesive layer 1 is more preferably 500 μm, further preferably 300 μm, even more preferably 200 μm, particularly preferably 150 μm, even more preferably 100 μm, even more preferably 80 μm, even more preferably 70 μm, very preferably 60 μm, most preferably 50 μm, and the lower limit is more preferably 5 μm, further preferably 10 μm, even more preferably 20 μm, and particularly preferably 30 μm.

[0209] The thickness of the electrically peelable adhesive sheet in 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 500 μm, even more preferably 300 μm, particularly preferably 250 μm, even more preferably 200 μm, even more preferably 150 μm, even more preferably 100 μm, and the lower limit is more preferably 30 μm, even more preferably 50 μm.

[0210] 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, particularly preferably 100 μm, and the lower limit is more preferably 3 μm, further preferably 5 μm, and particularly preferably 8 μm.

[0211] The thickness of the substrate 3 is preferably 10 μm to 1000 μm. The upper limit of the thickness is more preferably 500 μm, further preferably 300 μm, particularly preferably 100 μm, and the lower limit is more preferably 12 μm, further preferably 25 μm.

[0212] The thickness of the conductive layer 4 is preferably 0.001 μm to 1000 μm. The upper limit of the thickness is more preferably 500 μm, further preferably 300 μm, particularly preferably 50 μm, most preferably 10 μm, and the lower limit is more preferably 0.01 μm, further preferably 0.03 μm, and particularly preferably 0.05 μm.

[0213] The thickness of the conductive substrate 5 is preferably 10 μm to 1000 μm. The upper limit of the thickness is more preferably 500 μm, further preferably 300 μm, particularly preferably 100 μm, and the lower limit is more preferably 12 μm, further preferably 25 μm.

[0214] In embodiments of the present invention, the surfaces of the electro-release adhesive layer and other adhesive layers of the adhesive sheet can be protected using a release liner. The release liner is not particularly limited, and examples include: release liners obtained by treating the surface of a substrate (liner substrate) such as paper or plastic film with silicone; and release liners obtained by laminating the surface of a substrate (liner substrate) such as paper or plastic film with a polyolefin resin. The thickness of the release liner is not particularly limited, but is preferably 10 μm to 100 μm.

[0215] The thickness of the adhesive sheet according to the embodiments of the present invention is preferably 5 μm or more and 3000 μm or less. The upper limit of the thickness is more preferably 1000 μm, further preferably 500 μm, even more preferably 300 μm, particularly preferably 250 μm, even more preferably 200 μm, even more preferably 150 μm, even more preferably 100 μm, and the lower limit is more preferably 20 μm, further preferably 35 μm, and even more preferably 50 μm.

[0216] Especially in Figure 2 In the case of the two adhesive sheets shown, the thickness of the adhesive sheets is preferably 15 μm or more and 2000 μm or less. The upper limit of the thickness is more preferably 1000 μm, further preferably 500 μm, even more preferably 300 μm, particularly preferably 250 μm, even more preferably 200 μm, even more preferably 150 μm, and the lower limit is more preferably 35 μm, further preferably 50 μm, even more preferably 80 μm, and particularly preferably 100 μm.

[0217] Especially in Figure 3 In the case of the adhesive sheet X3 shown, the thickness of the adhesive sheet is preferably 25 μm or more and 3000 μm or less. The upper limit of the thickness is more preferably 1000 μm, further preferably 500 μm, even more preferably 300 μm, particularly preferably 250 μm, even more preferably 200 μm, even more preferably 150 μm, and the lower limit is more preferably 50 μm, further preferably 80 μm, and even more preferably 100 μm.

[0218] The adhesive sheet according to embodiments of the present invention may further include a coating. The coating is preferably disposed between the electrically peelable adhesive layer and the conductive layer.

[0219] In the case of the electrically peelable adhesive sheet of this embodiment, by also having a coating, the electrolyte (B) contained in the electrically peelable adhesive layer is prevented from penetrating the conductive layer due to voltage application, thereby achieving the effect of preventing the conductive layer from peeling off from the substrate.

[0220] In addition, since the coating is in contact with the electro-removable adhesive layer, the adhesion between the electro-removable adhesive layer and the conductive layer is improved, thereby preventing the electro-removable adhesive layer from being degraded and peeled off within the electro-removable adhesive sheet due to the thermal curing of the electro-removable adhesive layer exposed to high temperature environments, which would reduce the interfacial adhesion between the electro-removable adhesive layer and the conductive material (such as the adherend).

[0221] A coating is a layer with resin or inorganic material as the main component. It can be formed using a resin composition with resin as the main component or a composition with inorganic material as the main component.

[0222] The coating preferably comprises at least one resin selected from polyester resin, acrylic resin, epoxy resin, and urethane resin, or at least one inorganic substance selected from SiNx, SiOx, Al2O3, Ni, and NiCr.

[0223] [Manufacturing method of adhesive sheet] The manufacturing method of the adhesive sheet according to the embodiments of the present invention can employ known or commonly used manufacturing methods. Regarding the adhesive layer in the adhesive sheet according to the embodiments of the present invention, methods such as applying the adhesive composition (a solution obtained by dissolving in a solvent as needed) according to the embodiments of the present invention onto a release liner, followed by drying and / or curing.

[0224] Regarding the electro-release adhesive layer in the adhesive sheet according to embodiments of the present invention, methods such as coating an adhesive composition according to embodiments of the present invention (a solution obtained by dissolving an electrolyte (B) in a solvent as needed) onto a release liner, followed by drying and / or curing. Alternatively, regarding other adhesive layers, methods such as coating an adhesive composition (a solution obtained by dissolving an electrolyte (B) and additives) onto a release liner, followed by drying and / or curing. It should be noted that the solvent and release liner can be any of the solvents and release liners listed above.

[0225] During coating, commonly used coating machines can be used (e.g., gravure roller coating machine, reverse roller coating machine, kiss roller coating machine, dip roller coating machine, bar coating machine, doctor blade coating machine, spray roller coating machine, etc.).

[0226] The electrically release adhesive layer and other adhesive layers can be manufactured using the methods described above, and the adhesive sheet according to embodiments of the present invention can be manufactured by appropriately laminating the electrically release adhesive layer and other adhesive layers onto a substrate, a conductive layer, and an electrically conductive substrate. It should be noted that the substrate, conductive layer, and electrically conductive substrate can also be used instead of the release liner, and the adhesive composition can be applied to manufacture the adhesive sheet.

[0227] [Electrolytic stripping method for adhesive sheets] The peeling of the adhesive sheet from the adhered object according to the embodiments of the present invention can be performed 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.

[0228] For example, in the case of a bond obtained by attaching the adhesive sheet X1 to a conductive substrate, an electric current can be applied to the conductive substrate to apply a voltage to the electrically peelable adhesive layer, thereby peeling it off.

[0229] When the adhesive layer side of the adhesive sheet X2 is a substrate with a metal adhesive surface, an electric current can be applied to the conductive substrate and the conductive layer 4 to apply a voltage to the adhesive layer, thereby performing peeling.

[0230] In the case of adhesive sheet X3, current can be applied to the conductive layers 4 on both sides to apply voltage to the electrically peelable adhesive layer, thereby peeling it off.

[0231] The energizing is preferably performed by connecting terminals to one and the other ends of the adhesive sheet, thereby applying voltage to the entire electro-peelable adhesive layer. It should be noted that if the adhered object has a metallic adhesive surface, the aforementioned one and the other ends can be a portion of the adhered object with a metallic adhesive surface. It should also be noted that during peeling, water can be added to the interface between the metallic adhesive surface and the electro-peelable adhesive layer before applying voltage.

[0232] [Uses of adhesive sheets] Conventional peeling techniques include adhesive layers that are cured by ultraviolet (UV) irradiation and then peeled off, and adhesive layers that are peeled off by heat. Adhesive sheets using such adhesive layers are unusable in situations where UV irradiation is difficult or where heat could damage the adhered components. The adhesive sheet according to embodiments of the present invention, which incorporates the aforementioned electrically peelable adhesive layer, does not use ultraviolet light or heat; therefore, it does not damage the adhered components and can be easily peeled off by applying voltage. Therefore, the adhesive sheet according to embodiments of the present invention is suitable for fixing secondary batteries (e.g., lithium-ion battery packs) used in mobile terminals such as smartphones, mobile phones, laptops, camcorders, and digital cameras to their housings, and for fixing the display panels of these devices to their housings.

[0233] Furthermore, examples of rigid components that can be bonded using the adhesive sheet according to embodiments of the present invention include silicon substrates for semiconductor wafers, sapphire substrates for LEDs, SiC substrates and metal substrates, TFT substrates and color filter substrates for displays, display units, display unit protection components, housings included in mobile devices, and substrates for organic EL panels. Examples of fragile components that can be bonded using double-sided adhesive sheets include semiconductor substrates such as compound semiconductor substrates, silicon substrates for MEMS devices, passive matrix substrates, surface cover glass for smartphones, OGS (One Glass Solution) substrates formed by attaching touch panel sensors to the cover glass, organic substrates and organic-inorganic hybrid substrates with silsesquioxanes as main components, flexible glass substrates for flexible displays, and graphene sheets.

[0234] [Assembly] The bonding body according to embodiments of the present invention is a bonding body having an adhesive sheet according to embodiments of the present invention and a conductive material, wherein the aforementioned adhesive layer is adhered to the aforementioned conductive material. More specifically, it is a bonding body having an adhesive sheet according to embodiments of the present invention and a conductive material, wherein an electrically peelable adhesive layer in the adhesive sheet is adhered to the conductive material.

[0235] The conductive material is preferably an adhesive having a metallic adhesive surface. Examples of adhesives having a metallic adhesive surface include adhesives formed of metals such as aluminum, copper, iron, magnesium, tin, gold, silver and lead as main components, with metals containing aluminum being the most preferred.

[0236] As a bonding body in this embodiment, an example is a bonding body obtained by attaching the adhesive sheet X2, i.e., the side of the electrically peelable adhesive layer 1 of the adhesive sheet X2, to an adhesive object having conductivity such as a metal adhesive surface.

[0237] Examples of the bonding bodies in this embodiment include bonding bodies obtained by attaching other adhesive layers 2 on both sides of the adhesive sheet X3 to a conductive material having a metal bonding surface, and bonding bodies obtained by attaching any one of the other adhesive layers 2 of the adhesive sheet X3 to a non-conductive material.

[0238] Examples of the bonding bodies according to embodiments of the present invention include: an adhesive sheet X1, a bonding body having an adhesive object having a metal adhesive surface on both sides of the electrically peelable adhesive layer 1; an adhesive sheet X2, a bonding body having an adhesive object having a metal adhesive surface on the side of the electrically peelable adhesive layer 1 and an adhesive object on the side of the adhesive layer 2; an adhesive sheet X3, a bonding body having an adhesive object on both sides of the adhesive layer 2; and so on.

[0239] As stated above, the following matters are disclosed in this specification.

[0240] [1] An adhesive composition comprising an emulsion acrylic polymer (A) containing monomer units derived from amide-containing monomers.

[0241] [2] The adhesive composition as described in [1], wherein the content of the amide-containing monomer in all monomer components constituting the emulsion-type acrylic polymer (A) is 0.1 to 50.0% by mass.

[0242] [3] The adhesive composition as described in [1] or [2], wherein the amide-containing monomer comprises at least one selected from the group consisting of N-isopropylacrylamide and N,N-dimethylacrylamide.

[0243] [4] The adhesive composition as described in any one of [1] to [3], wherein the emulsion acrylic polymer (A) further comprises monomer units derived from carboxyl-containing monomers, wherein the content of the carboxyl-containing monomers in all monomer components constituting the emulsion acrylic polymer (A) is 2.5 to 6.0 by mass.

[0244] [5] The adhesive composition as described in any one of [1] to [4] further comprises a crosslinking agent.

[0245] [6] The adhesive composition as described in any one of [1] to [5] further comprises an electrolyte (B).

[0246] [7] The adhesive composition as described in [6], wherein the electrolyte (B) is an ionic substance.

[0247] [8] The adhesive composition as described in [7], wherein the ionic substance is an ionic liquid, and the anion of the ionic liquid comprises at least one selected from the group consisting of bis(fluorosulfonyl)imide anion and bis(trifluoromethanesulfonyl)imide anion.

[0248] [9] The adhesive composition as described in any one of [1] to [8] further comprises a tackifier (C). The content of the tackifier (C) is 0.01 to 10 parts by mass relative to 100 parts by mass of the emulsion-type acrylic polymer (A).

[0249]

[10] The adhesive composition as described in [9], wherein the tackifier (C) comprises at least one selected from the group consisting of urethane associative tackifiers, alkali-swellable tackifiers and cellulose tackifiers.

[0250]

[11] The adhesive composition as described in any one of [1] to

[10] is used for electro-peeling.

[0251]

[12] An adhesive sheet having an adhesive layer formed from any one of the adhesive compositions described in [1] to

[11] .

[0252]

[13] A bonding body comprising a conductive material and an adhesive sheet as described in

[12] , wherein the adhesive layer is adhered to the conductive material.

[0253] Example The present invention will be described in more detail below using examples, but the invention is not limited to these examples. The weight-average molecular weights described below were determined using gel permeation chromatography (GPC).

[0254] <Preparation of Emulsion-type Acrylic Polymer (A)> (Preparation of Em-based acrylic polymer 1) In a container, 93 parts by weight of n-butyl acrylate (BA), 4 parts by weight of acrylic acid (AA), 3 parts by weight of N,N-dimethylacrylamide (DMAA), 0.05 parts by weight of n-dodecyl mercaptan (chain transfer agent), 2.70 parts by weight of Aqualon KH-1025 (emulsifier), and 53 parts by weight of distilled water are mixed and stirred to prepare a monomer emulsion.

[0255] Next, 0.3 parts by weight of Aqualon KH-1025 (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., emulsifier) ​​and 50 parts by weight of distilled water were added to a reaction vessel equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser. The mixture was stirred while being purged with nitrogen at room temperature (25°C) for 1 hour. Then, 0.1 parts by weight of VA-057 (manufactured by Fujifilm and Kogyo Pure Chemicals, polymerization initiator) were added, and the mixture was heated to 60°C.

[0256] Next, the monomer emulsion was added dropwise to the reaction vessel over 4 hours, and polymerization was carried out while maintaining the liquid temperature in the reaction vessel at around 60°C and stirring. Then, it was cooled to room temperature, and the pH was adjusted to 6 using 10% ammonia water, thereby obtaining a solution of Em-based acrylic polymer 1 with a solid content concentration of 50% by mass.

[0257] (Preparation of Em-based acrylic polymers 2-8) The monomer composition was changed to the monomer types and amounts shown in Tables 1 to 3. Otherwise, solutions of Em-based acrylic polymers 2 to 8 with a solid content of 50% by mass were obtained by the same method as Em-based acrylic polymer 1 above.

[0258] It should be noted that in Tables 1 to 3, NIAA represents N-isopropylacrylamide, NVP represents N-vinylpyrrolidone, ACMO represents acrylomorpholine, DMAPAA represents N,N-dimethylaminopropylacrylamide, and MMA represents methyl methacrylate. Furthermore, Em-based acrylic polymers 1 to 6 correspond to the emulsion-type acrylic polymer (A) according to the embodiments of the present invention.

[0259] (Preparation of solvent-based acrylic polymer 9) 93 parts by mass of n-butyl acrylate (BA), 4 parts by mass of acrylic acid (AA), 3 parts by mass of N-isopropylacrylamide (NIAA), and 150 parts by mass of ethyl acetate (ethyl acetate) as the polymerization solvent were added to a separable flask, and the mixture was stirred for 1 hour while introducing nitrogen gas. After removing oxygen from the polymerization system as described above, 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as the polymerization initiator were added, and the mixture was heated to 63°C and reacted for 6 hours. Then, ethyl acetate was added to obtain a solvent-based acrylic polymer 9 solution with a solid content concentration of 50% by mass. The weight-average molecular weight of the obtained solvent-based acrylic polymer 9 was 750,000.

[0260] (Preparation of solvent-based acrylic polymer 10) The monomer composition was changed to the monomer types and amounts shown in Tables 1 to 3. Otherwise, a solvent-based acrylic polymer 10 solution with a solid content of 50% by mass was obtained by the same method as the solvent-based acrylic polymer 9 described above.

[0261] [Examples 1-14, Comparative Examples 1-5] <Preparation of Adhesive Compositions> As described in Tables 1-3, the emulsion-type acrylic polymer or solvent-based acrylic polymer solution obtained above, electrolyte (B), crosslinking agent, tackifier (C), and corrosion inhibitor are stirred and mixed to obtain various electro-stripping adhesive compositions (solutions) with a solid component concentration of 40% by mass. The proportions of each component are shown in Tables 1-3.

[0262] It should be noted that the values ​​of each component in Tables 1 to 3 below refer to parts by mass. Additionally, the amount of acrylic polymer (parts by mass) indicates the amount (parts by mass) of the solid component in the acrylic polymer solution.

[0263] Regarding the adjustment of the concentration of solid components, distilled water was used in Examples 1-14, Comparative Examples 1, 2 and 5, and ethyl acetate was used in Comparative Examples 3 and 4.

[0264] <Preparation of the electro-peelable adhesive layer> Using an applicator, the electro-peel adhesive composition (solution) obtained above is applied to the peel-treated surface of a peel-treated polyethylene terephthalate (PET) release liner (trade name "MRF38", manufactured by Mitsubishi Chemical Corporation) to achieve a uniform thickness. Next, the surface is heated and dried at 150°C for 3 minutes. Using a hand roller, the peel-treated surface of the PET release liner (trade name "MRE38", manufactured by Mitsubishi Chemical Corporation) is pressed onto the adhesive to obtain an electro-peel adhesive layer (adhesive sheet) with a thickness of 60 μm.

[0265] <Fabrication of Single-Sided Adhesive Sheets with Substrate> The obtained electro-peelable adhesive layer (adhesive sheet) is made into a sheet with a size of 10mm×80mm. The release liner (MRE38) is peeled off, and the metal layer side of the film with the metal layer (trade name "1005CR", manufactured by Toray Industries, Inc., with a thickness of 122μm and a size of 10mm×100mm) is attached to the exposed electro-peelable adhesive layer to make a single-sided adhesive sheet with a substrate.

[0266] <Construction of the Joint> Peel off the release liner (MRF38) of the single-sided adhesive sheet with a substrate. Attach the stainless steel sheet (the substrate) to the peeled surface with one end of the adhesive sheet protruding approximately 20 mm from the substrate. Press the sheet back and forth once using a 2 kg roller. Leave the surface at 23°C for 72 hours to obtain a bond consisting of a stainless steel sheet 6, an electrically peelable adhesive layer (adhesive sheet 1'), and a film with a metal layer (electrically conductive substrate) 5'. An outline of this bond is shown below. Figure 4 .

[0267] <Evaluation> (180° peel force) A 180° peel force test was conducted on the joints of the examples and comparative examples.

[0268] Using a peel testing machine (trade name "YSP Variable Angle Peel Testing Machine", manufactured by Asahi Seiko Co., Ltd.), along... Figure 4Peeling is performed in the direction of the arrow in the diagram, and the adhesive force in a 180° peel test (tensile speed: 300 mm / min, peel temperature: 23°C) is measured to determine the 180° peel force, which is then used as the normal peel force. Furthermore, judgments and evaluations are based on the following criteria.

[0269] 5.0 [N / cm] or above: ○ 4.0 [N / cm] and above to less than 5.0 [N / cm]: △ Less than 4.0 [N / cm]: × (Electro-peeling force) The electro-peeling force was measured using the joints from the examples and comparative examples. Figure 4 The positive and negative electrodes of a DC current meter are installed at the α and β locations. Immediately after applying a 30V voltage for 30 seconds, peeling is performed in the same manner as the 180° peel force test described above. The adhesive force immediately after the voltage is applied is measured and taken as the electro-peel force. Furthermore, judgment and evaluation are based on the following criteria.

[0270] Less than 0.01 [N / cm]: ○ 0.01 N / cm or more to less than 2.0 N / cm: △ 2.0 [N / cm] or above: × (Creep resistance) The electro-peelable adhesive layers (adhesive sheets) of each embodiment and comparative example were cut into 25mm × 25mm sizes to prepare samples. The release liner (MRE38) was peeled off from the sample, and the exposed electro-peelable adhesive layer was adhered to the front end of a stainless steel plate (SUS316, size: 30mm × 120mm) serving as the first adherend. Next, the release liner (MRF38) of the other embodiment was peeled off, and the front end of a stainless steel plate (SUS316, size: 30mm × 120mm) serving as the second adherend was brought into contact with the exposed electro-peelable adhesive layer, thereby obtaining a laminate with two adherends (first adherend / electro-peelable adhesive layer (adhesive sheet) / second adherend). The laminate was then pressed back and forth once using a 2kg roller and placed at 23°C for 72 hours (hr). The attachment position of the laminate at the 72-hr placement time was taken as the initial attachment position.

[0271] Then, a 5 kg load was applied to one end of the laminate, and it was placed at 23°C for 168 hours (1 week). The offset (mm) of the laminate from its initial attachment position at the 168-hour placement time was measured (test time 72 hours). If the laminate peeled off and fell off in less than 168 hours (1 week), it was recorded as "falling". In addition, judgment and evaluation were performed based on the following criteria.

[0272] Offset less than 10mm: ○ Offset of 10mm or more: △ Falling: × (Impact resistance) Two strips (5mm wide × 20mm long) of the electro-peelable adhesive layer (adhesive sheet) of each embodiment and comparative example were cut as evaluation samples. The evaluation samples were placed on opposite sides of a square stainless steel plate (2mm thick, 50mm × 50mm in shape) with a 20mm x 20mm hole in the center. A square stainless steel plate (30mm outer diameter, 3mm thickness) was placed on top of the plate. The plates were then pressed together (70N × 15s) with uniform force applied in the direction of gravity. After standing at 50°C for 3 hours, the evaluation samples were removed and returned to 23°C. Next, a testing platform was set on the base of a DuPont impact testing machine (manufactured by Toyo Seiki Co., Ltd.), and the evaluation samples were placed on it with the square stainless steel plate as the underside. Next, a stainless steel impact core with a front radius of 3.1 mm was placed on the evaluation sample, and the weight of the falling weight and the falling height were varied in the following order to gradually increase the energy until peeling occurred: 50 g, 50 mm to 500 mm increments; 100 g, 50 mm to 500 mm increments; 150 g, 350 mm to 500 mm increments; 200 g, 400 mm to 500 mm increments; 300 g, 350 mm to 500 mm increments. At this point, no test was conducted on the evaluated energy; instead, the load and height were set in a non-repeatable manner. The energy up to peeling was then calculated as load × height. Furthermore, judgment and evaluation were performed based on the following criteria.

[0273] Above 0.30J: ○ Above 0.20J and below 0.30J: △ Less than 0.20J: × (Corrosion resistance) (60℃ / 90%RH 168hr) The aforementioned joint was stored in a constant temperature and humidity apparatus at 60°C and 90%RH for 168 hours. After removal, it was allowed to stand at 22°C and 50%RH for 30 minutes to cool down. Then, the corrosion appearance and the same electro-peeling force as described above were measured.

[0274] The appearance of corrosion is evaluated in the table below.

[0275] The film with a metal layer (for electrical conduction) shows no corrosion under visual inspection: ○ The film with a metal layer (for electrical conduction) shows corrosion under visual conditions: × Furthermore, regarding the electro-peeling force, the following criteria are used for judgment. In addition, the situation where vapor deposition peeling occurs due to residual metal layers that have peeled off from the electro-peeling adhesive layer and the support substrate on the adherend is described as "vapor deposition peeling".

[0276] Less than 0.01 [N / cm]: ○ 0.01 N / cm or more to less than 2.0 N / cm: △ 2.0 [N / cm] or above: × The measurement results are shown in Tables 1 to 3.

[0277] [Table 1] [Table 2] [Table 3] The abbreviations for electrolytes (B), crosslinking agents, thickeners (C), and corrosion inhibitors in Tables 1 to 3 are as follows.

[0278] (Electrolyte (B)) Ionic Liquid 1: Cation: 1-Ethyl-3-methylimidazolium cation; Anion: Bis(fluorosulfonyl)imide anion; Trade name "E1452", manufactured by Tokyo Chemical Industry Co., Ltd. Flexible Ionic Crystal 1: Cation: 1-Ethyl-1-methylpyrrolidone onion cation, Anion: Bis(fluorosulfonyl)imide anion, Trade name "ETHYLMETHYLPYRROLIDINIUM BIS(FLUOROSULFONYL)IMIDE", Boron Molecular Inc. (Cross-linking agent) V-05: Polycarbodiimide resin, trade name "CARBODILITE V-05", manufactured by Nisshinbo Chemical Inc. E-02: Polycarbodiimide resin, trade name "CARBODILITE E-02", manufactured by Nisshinbo Chemical Inc. (Tackifier (C)) · Carbamate-associated UH-450VF: Trade name "ADEKA NOL UH-450VF", manufactured by ADEKA Co., Ltd. Alkali-swellable type B-500: Acrylic tackifier, trade name "Aron B-500", manufactured by Toa Synthetic Co., Ltd. Cellulose type RHEOCRYSTA: Trade name "RHEOCRYSTA I-2SX", manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd. (Corrosion inhibitor) AMINE O: 2-(8-heptadecen-1-yl)-4,5-dihydro-1H-imidazol-1-ethanol, trade name "AMINE O", manufactured by BASF Japan Ltd. The adhesive layers formed using the adhesive compositions of Examples 1-14 exhibit excellent adhesion properties (generally peel force and creep resistance) without applied voltage, and successfully inhibit metal corrosion.

[0279] Furthermore, the adhesive strength is significantly reduced by the application of voltage, and even after storage at 60°C and 90%RH for 72 hours, no vapor deposition peeling due to metal corrosion occurs, and the adhesive strength is also significantly reduced by the application of voltage. In addition, it exhibits excellent impact resistance.

[0280] This invention is not limited to the foregoing embodiments, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of this invention.

[0281] Various embodiments have been described above with reference to the accompanying drawings; however, it goes without saying that the present invention is not limited to the examples described. Those skilled in the art will obviously conceive of various modifications or alterations within the scope of the claims, and these will also fall within the technical scope of the present invention. Furthermore, the constituent elements in the above embodiments can be arbitrarily combined without departing from the spirit of the invention.

[0282] Industrial availability The adhesive composition of the present invention can form an adhesive layer with excellent adhesive properties, impact resistance, and the ability to inhibit metal corrosion.

[0283] The present invention has been described in detail with reference to specific embodiments, but it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

[0284] This application is based on Japanese Patent Application No. 2023-185743, filed on October 30, 2023, the contents of which are incorporated herein by reference.

[0285] Explanation of reference numerals in the attached figures X1, X2, X3 adhesive sheets 1. Electro-peelable adhesive layer 2 Adhesive layer 3. Substrate 4. Conductive layer 5. Substrate for electrical conduction.

Claims

1. An adhesive composition comprising an emulsion acrylic polymer (A), said emulsion acrylic polymer (A) comprising monomer units derived from amide-containing monomers.

2. The adhesive composition of claim 1, wherein, Of all the monomer components constituting the emulsion-type acrylic polymer (A), the content of the amide-containing monomer is 0.1 to 50.0% by mass.

3. The adhesive composition of claim 1, wherein, The amide-containing monomer comprises at least one selected from the group consisting of N-isopropylacrylamide and N,N-dimethylacrylamide.

4. The adhesive composition of claim 1, wherein, The emulsion-type acrylic polymer (A) further comprises monomer units derived from carboxyl-containing monomers, and the content of the carboxyl-containing monomers in all monomer components constituting the emulsion-type acrylic polymer (A) is 2.5 to 6.0% by mass.

5. The adhesive composition of claim 1, further comprising a crosslinking agent.

6. The adhesive composition of claim 1, further comprising an electrolyte (B).

7. The adhesive composition of claim 6, wherein, The electrolyte (B) is an ionic substance.

8. The adhesive composition of claim 7, wherein, The ionic substance is an ionic liquid, and the anion of the ionic liquid includes at least one selected from the group consisting of bis(fluorosulfonyl)imide anion and bis(trifluoromethanesulfonyl)imide anion.

9. The adhesive composition of claim 8, further comprising a tackifier (C). in, The content of the tackifier (C) is 0.01 to 10 parts by weight relative to 100 parts by weight of the emulsion-type acrylic polymer (A).

10. The adhesive composition of claim 9, wherein, The tackifier (C) comprises at least one selected from the group consisting of urethane-associated tackifiers, alkali-swellable tackifiers, and cellulose-based tackifiers.

11. The adhesive composition of claim 1, for use in electro-peeling.

12. An adhesive sheet having an adhesive layer formed from the adhesive composition according to any one of claims 1 to 11.

13. A bonding body comprising a conductive material and an adhesive sheet as claimed in claim 12, wherein the adhesive layer is adhered to the conductive material.

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