Electrically releasable pressure-sensitive adhesive composition, electrically releasable pressure-sensitive adhesive sheet, and method for using the electrically releasable pressure-sensitive adhesive sheet

Abstract

To provide an electric peelable adhesive composition that enables adhesiveness to be efficiently reduced by voltage application, regardless of the type of an adherend.SOLUTION: An electric peelable adhesive composition contains a base polymer (A), an ionic compound (B), and a polypropyleneglycol with a number average molecular weight of 200-3500 (C).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an electrically peelable pressure-sensitive adhesive composition, an electrically peelable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the electrically peelable pressure-sensitive adhesive composition, and a method for using the electrically peelable pressure-sensitive adhesive sheet.

Background Art

[0002] As one of the characteristics of a pressure-sensitive adhesive sheet, for example, in applications such as temporary fixing tapes, surface protection films, painting or decorative masking tapes, re-peelable memos, etc., re-peelability may be required. In the case of a re-peelable pressure-sensitive adhesive sheet, when attached to an adherend, it is required to have an adhesive force such that it does not peel from the adherend during transportation, storage, processing, etc., while after fulfilling its function, it is required to have re-peelability that can be easily removed.

[0003] By the way, as an adhesive used for such a re-peelable pressure-sensitive adhesive sheet, an adhesive whose adhesive force decreases by applying a voltage is known. For example, Patent Document 1 discloses an electrically peelable composition containing an ionic liquid as an adhesive that can be easily peeled from an adherend after use.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, an electrically peelable pressure-sensitive adhesive composition with improved efficiency of reducing adhesiveness by applying a voltage is required regardless of the type of adherend.

Means for Solving the Problems

[0006] The present invention provides an electrically peelable pressure-sensitive adhesive composition obtained by blending a base polymer, an ionic compound, and a polypropylene glycol having a predetermined number-average molecular weight, an electrically peelable pressure-sensitive adhesive sheet having an adhesive layer formed from the electrically peelable pressure-sensitive adhesive composition, and a method for using the electrically peelable pressure-sensitive adhesive sheet. Specific embodiments of the present invention are as follows [1] to

[15] . [1] An electrically peelable pressure-sensitive adhesive composition obtained by blending a base polymer (A), an ionic compound (B), and a polypropylene glycol (C) having a number-average molecular weight of 200 to 3500. [2] The electrically peelable pressure-sensitive adhesive composition according to [1] above, wherein the blending ratio of component (B) is 1.0 part by mass or more with respect to 100 parts by mass of the total amount of component (A). [3] The electrically peelable pressure-sensitive adhesive composition according to [1] or [2] above, wherein the blending ratio of component (C) is 0.1 part by mass or more with respect to 100 parts by mass of the total amount of component (A). [4] The electrically peelable pressure-sensitive adhesive composition according to any one of [1] to [3] above, wherein the blending amount ratio [(C) / (B)] of component (C) to component (B) is 0.01 to 10.0 in terms of mass ratio. [5] The electrically peelable pressure-sensitive adhesive composition according to any one of [1] to [4] above, wherein the ionic compound (B) contains one or more selected from an alkali metal salt (B1), an organic quaternary ammonium salt (B2), and an ionic liquid (B3). [6] The electrically peelable pressure-sensitive adhesive composition according to any one of [1] to [5] above, further blended with a crosslinking agent (E). [7] The electrically peelable pressure-sensitive adhesive composition according to [6] above, wherein the blending ratio of component (E) is 0.01 part by mass or more with respect to 100 parts by mass of the total amount of component (A). [8] The electrically peelable pressure-sensitive adhesive composition according to any one of [1] to [7] above, wherein the content of the active ingredient that is liquid at 25°C is 1 to 50% by mass with respect to the total amount of the active ingredients in the pressure-sensitive adhesive composition. [9] An electrically peelable pressure-sensitive adhesive sheet having an adhesive layer formed from the electrically peelable pressure-sensitive adhesive composition according to any one of [1] to [8] above.

[10] The electric peelable pressure-sensitive adhesive sheet according to [9] above, wherein the thickness of the pressure-sensitive adhesive layer is 40 μm or less.

[11] The electric peelable pressure-sensitive adhesive sheet according to [9] or

[10] above, having a conductive substrate and having the pressure-sensitive adhesive layer on at least one surface side of the conductive substrate.

[12] The electric peelable pressure-sensitive adhesive sheet according to any one of [9] to

[11] above, which peels off on the cathode side when a voltage is applied to the pressure-sensitive adhesive layer.

[13] The electric peelable pressure-sensitive adhesive sheet according to any one of [9] to

[12] above, which satisfies the following requirement (I). · Requirement (I): The adhesion reduction rate calculated from the following formula (i), which shows the change in adhesion before and after voltage application for 60 seconds at 10 V, is 50% or more. Formula (i): [Adhesion reduction rate (%)] = 100 - [Adhesion after voltage application] / [Adhesion before voltage application] × 100

[14] A method of using an electric peelable pressure-sensitive adhesive sheet, wherein the electric peelable pressure-sensitive adhesive sheet according to any one of [9] to

[13] above is attached to an adherend having conductivity.

[15] The method of using an electric peelable pressure-sensitive adhesive sheet according to

[14] above, wherein after the electric peelable pressure-sensitive adhesive sheet is attached to an adherend having conductivity, a voltage is applied to the pressure-sensitive adhesive layer to peel it off from the adherend.

Advantages of the Invention

[0007] The electric peelable pressure-sensitive adhesive composition according to a preferred embodiment of the present invention has high adhesiveness before voltage application regardless of the type of adherend, and is excellent in the efficiency of reducing adhesiveness by voltage application.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0009] The numerical ranges described in this specification can be arbitrarily combined with upper and lower limit values. For example, when described as "preferably 20 to 120, more preferably 40 to 90" as a numerical range, ranges such as "20 to 90" and "40 to 120" are also included in the numerical ranges described in this specification. Also, for example, when described as "preferably 20 or more, more preferably 40 or more, and preferably 120 or less, more preferably 90 or less" as a numerical range, ranges such as "20 to 90" and "40 to 120" are also included in the numerical ranges described in this specification. In addition, as the numerical range described in this specification, for example, the description "60 to 100" means a range of "60 or more and 100 or less".

[0010] In this specification, for example, "(meth)acrylate" is used as a term indicating both "acrylate" and "methacrylate", and the same applies to other similar terms. Also, the "active ingredient" of the electrically releasable pressure-sensitive adhesive composition means the components among the components contained in the electrically releasable pressure-sensitive adhesive composition excluding the diluting solvents such as water and organic solvents.

[0011] In this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are values in terms of polystyrene measured by the gel permeation chromatography (GPC) method, and specifically are values measured based on the method described in the examples.

[0012] 〔Electrically Releasable Pressure-Sensitive Adhesive Composition〕 The electro-releasable pressure-sensitive adhesive composition of the present invention (hereinafter, also simply referred to as "pressure-sensitive adhesive composition") is prepared by blending a base polymer (A) (hereinafter, also referred to as "component (A)"), an ionic compound (B) (hereinafter, also referred to as "component (B)"), and a polypropylene glycol (C) having a number average molecular weight of 200 to 3500 (hereinafter, also referred to as "component (C)"). In this specification, for example, the phrase "a pressure-sensitive adhesive composition prepared by blending component (A), component (B), and component (C)" means that component (A), component (B), and component (C) are used as raw materials for the pressure-sensitive adhesive composition. Therefore, for example, a mode in which component (B) is ionized into cations and anions in the pressure-sensitive adhesive composition is also included.

[0013] In general electro-releasable pressure-sensitive adhesive compositions, an ionic compound is blended with a base polymer to impart the property of reducing adhesiveness upon application of electric power. However, an electro-releasable pressure-sensitive adhesive composition containing an ionic compound has insufficient adhesiveness before application of voltage as compared with a pressure-sensitive adhesive composition not containing an ionic compound. In particular, when a stainless steel plate is the adherend, improvement in adhesiveness before application of voltage is required. In addition, there is room for improvement in the efficiency of reducing the adhesive force by application of voltage in an electro-releasable pressure-sensitive adhesive sheet having an adhesive layer formed from the above electro-releasable pressure-sensitive adhesive composition. According to the study by the present inventors, it has been found that, in particular, when the adherend is a stainless steel plate or when the thickness of the adhesive layer is relatively thin, the reduction in adhesive force by application of voltage becomes insufficient. When the reduction in adhesive force by application of voltage is insufficient, it is necessary to apply a high voltage or to increase the voltage application time during voltage application. However, increasing the voltage causes problems with the safety of the operator, and increasing the voltage application time causes problems with work efficiency. Therefore, there is a need for a pressure-sensitive adhesive composition with improved efficiency of reducing adhesiveness by application of voltage. In view of such problems, the inventors of the present invention conducted various studies and found that, by using an adhesive composition containing polypropylene glycol having a number average molecular weight of 200 to 3500 together with a base polymer and an ionic compound, it is possible to have high adhesiveness before voltage application while significantly improving the efficiency of reducing adhesiveness by voltage application. It was found that this property is sufficiently exhibited even when the adherend is a stainless steel plate or when the thickness of the adhesive layer formed from the adhesive composition is reduced. The adhesive composition according to one aspect of the present invention has been completed based on this finding.

[0014] From the viewpoint of obtaining an adhesive composition that has high adhesiveness before voltage application and further improves the efficiency of reducing adhesiveness by voltage application, it is preferable that the adhesive composition according to one aspect of the present invention further contains a rosin-containing diol (D) (hereinafter also referred to as "component (D)"). Also, from the same viewpoint as above, it is preferable that the adhesive composition according to one aspect of the present invention further contains a crosslinking agent (E) (hereinafter also referred to as "component (E)"). Furthermore, the adhesive composition according to one aspect of the present invention may be an adhesive composition containing other additives in addition to components (A) to (E).

[0015] In the adhesive composition according to one aspect of the present invention, from the viewpoint of obtaining an adhesive composition that has high adhesiveness before voltage application and further improves the efficiency of reducing adhesiveness by voltage application, the total blending amount of component (A), component (B), and component (C) is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 55% by mass or more, further preferably 60% by mass or more, even more preferably 65% by mass or more, particularly preferably 70% by mass or more, with respect to the total amount (100% by mass) of the active ingredients of the adhesive composition, and may also be 100% by mass or less, 95% by mass or less, 90% by mass or less, 85% by mass or less, or 80% by mass or less.

[0016] From the same perspective as above, in the pressure-sensitive adhesive composition of one embodiment of the present invention, the total blending amount of component (A), component (B), component (C), component (D), and component (E) is preferably 70% by mass or more, more preferably 75% by mass or more, still more preferably 80% by mass or more, further preferably 85% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, with respect to the total amount (100% by mass) of the active ingredients of the pressure-sensitive adhesive composition. It may also be 100% by mass or less, 99.5% by mass or less, 99.0% by mass or less, 98.0% by mass or less, or 97.0% by mass or less.

[0017] In the pressure-sensitive adhesive composition of one embodiment of the present invention, the content of the active ingredient that is liquid at 25°C (hereinafter also referred to as "liquid component") is preferably 1.0% by mass or more, more preferably 3.0% by mass or more, still more preferably 5.0% by mass or more, even more preferably 7.0% by mass or more, particularly preferably 10.0% by mass or more, from the perspective of obtaining a pressure-sensitive adhesive composition with improved efficiency of reducing adhesiveness by voltage application, with respect to the total amount (100% by mass) of the active ingredients in the pressure-sensitive adhesive composition. Also, from the perspective of obtaining a pressure-sensitive adhesive composition with high adhesiveness before voltage application, it is preferably 50% by mass or less, more preferably 45% by mass or less, still more preferably 40% by mass or less, further preferably 35% by mass or less, even more preferably 30% by mass or less, particularly preferably 25% by mass or less. Note that the above "liquid component" is an active ingredient that is liquid at 25°C other than the solvent, and specifically includes the ionic liquid (B3) used as component (B), component (C), etc.

[0018] Hereinafter, each component included in the pressure-sensitive adhesive composition of one embodiment of the present invention will be described.

[0019] <Component (A): Base Polymer> The base polymer (A) used in one embodiment of the present invention may be any polymer having adhesiveness. Examples include acrylic polymers, urethane polymers, rubber polymers, olefin polymers, silicone polymers, and curable polymers having polymerizable functional groups in these polymers. These base polymers (A) may be used alone or in combination of two or more. Further, the base polymer (A) used in one embodiment of the present invention may be an emulsion type polymer or a non-emulsion type polymer.

[0020] From the viewpoint of obtaining a pressure-sensitive adhesive composition having high tack before voltage application, the mass average molecular weight (Mw) of the base polymer (A) used in one embodiment of the present invention is preferably from 10,000 to 2,000,000, more preferably from 20,000 to 1,800,000, still more preferably from 30,000 to 1,500,000.

[0021] Among these, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high tack before voltage application and further improving the efficiency of reducing tack by voltage application, the base polymer (A) used in one embodiment of the present invention preferably contains an acrylic polymer (A1). From the above viewpoints, in the pressure-sensitive adhesive composition of one embodiment of the present invention, the content ratio of the acrylic polymer (A1) in the component (A) is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, still more preferably 70 to 100% by mass, further preferably 80 to 100% by mass, still further preferably 90 to 100% by mass, particularly preferably 95 to 100% by mass, based on the total amount (100% by mass) of the component (A) contained in the pressure-sensitive adhesive composition.

[0022] Examples of the acrylic polymer (A1) used in one embodiment of the present invention include polymers having a structural unit (a1) derived from an alkyl (meth) acrylate (hereinafter also referred to as "monomer (a1')"). From the viewpoint of obtaining a pressure-sensitive adhesive composition having high tack before voltage application and further improving the efficiency of reducing tack by voltage application, it is preferably a copolymer having a structural unit (a2) derived from a functional group-containing monomer (hereinafter also referred to as "monomer (a2')") together with the structural unit (a1).

[0023] When the acrylic polymer (A1) is a copolymer, there are no particular restrictions on the form of copolymerization, and it may be any of a random copolymer, a block copolymer, and a graft copolymer. The acrylic polymer (A1) used in one aspect of the present invention may be used alone or in combination of two or more.

[0024] From the viewpoint of obtaining a pressure-sensitive adhesive composition having high tack before voltage application, the mass average molecular weight (Mw) of the acrylic polymer (A1) is preferably 50,000 to 2,000,000, more preferably 100,000 to 1,500,000, still more preferably 200,000 to 1,200,000, even more preferably 300,000 to 1,000,000, and particularly preferably 400,000 to 700,000.

[0025] The acrylic polymer (A1) used in one aspect of the present invention may be a copolymer having a structural unit (a3) derived from a monomer other than the monomers (a1') and (a2') (hereinafter also referred to as "monomer (a3')").

[0026] In the acrylic polymer (A1) used in one aspect of the present invention, the content ratio of the structural units (a1) and (a2) may be 55% by mass or more, 60% by mass or more, 65% by mass or more, 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more, and may also be 100% by mass or less, 99% by mass or less, 98% by mass or less, 97% by mass or less, or 96% by mass or less, based on the total amount (100% by mass) of the structural units of the acrylic polymer (A1). Hereinafter, the monomers and structural units constituting the acrylic polymer (A1) will be described.

[0027] [Monomer (a1'), Structural unit (a1)] The number of carbon atoms of the alkyl group of the monomer (a1') is preferably 1 to 30, more preferably 1 to 20, still more preferably 1 to 16, even more preferably 1 to 12, particularly preferably 1 to 8, and especially preferably 4 to 8. The alkyl group of monomer (a1') may be a linear alkyl group or a branched alkyl group.

[0028] Specific examples of monomer (a1') include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate (n-propyl (meth)acrylate, i-propyl (meth)acrylate), butyl (meth)acrylate (n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate), pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, and the like. These monomers (a1') may be used alone or in combination of two or more. Among these, monomer (a1') preferably contains at least an alkyl (meth)acrylate having an alkyl group with 4 to 8 carbon atoms, more preferably contains at least one selected from butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, still more preferably contains at least butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate, and even more preferably contains at least butyl (meth)acrylate.

[0029] The acrylic polymer (A1) used in one aspect of the present invention preferably has a structural unit (a1-1) derived from an alkyl (meth)acrylate having an alkyl group with 4 to 8 carbon atoms as the structural unit (a1), and may also have a structural unit (a1-2) derived from an alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms together with the structural unit (a1-1). In the acrylic polymer (A1) used in one aspect of the present invention, the content ratio of the structural unit (a1-1) is preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 60% by mass or more, even more preferably 65% by mass or more, particularly preferably 70% by mass or more, and also 100% by mass or less, 99% by mass or less, 98% by mass or less, 95% by mass or less, 90% by mass or less, 85% by mass or less, or 80% by mass or less, based on the total amount (100% by mass) of the structural units (a1) that the acrylic polymer (A1) has.

[0030] In the acrylic polymer (A1) used in one aspect of the present invention, as the content ratio of the structural unit (a1), from the viewpoint of making the pressure-sensitive adhesive composition have better tack before voltage application, it is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, even more preferably 60% by mass or more, particularly preferably 70% by mass or more, based on the total amount (100% by mass) of the structural units of the acrylic polymer (A1). Also, from the viewpoint of making the pressure-sensitive adhesive composition capable of ensuring the content ratio of the above-mentioned structural unit (a2) and further improving the cohesive force, it is preferably 99.99% by mass or less, more preferably 99.90% by mass or less, still more preferably 99.0% by mass or less, even more preferably 97.0% by mass or less, particularly preferably 96.0% by mass or less, and further, it may be 95.0% by mass or less, 90.0% by mass or less, or 85.0% by mass or less.

[0031] [Monomer (a2’), Structural unit (a2)] Examples of the monomer (a2’) include hydroxy group-containing monomers, carboxy group-containing monomers, epoxy group-containing monomers, and the like. These monomers (a2’) may be used alone or in combination of two or more.

[0032] Examples of the hydroxy group-containing monomers include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol, and the like. The number of carbon atoms of the alkyl group in the hydroxyalkyl (meth) acrylates is preferably 1 to 10, more preferably 1 to 8, still more preferably 1 to 6, and even more preferably 2 to 4. The alkyl group may be a linear alkyl group or a branched alkyl group.

[0033] Examples of the carboxy group-containing monomers include ethylenically unsaturated monocarboxylic acids such as (meth) acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid, and citraconic acid; 2-carboxyethyl (meth) acrylate, and the like.

[0034] Examples of the epoxy group-containing monomers include epoxy group-containing (meth) acrylic acid esters such as glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, (3,4-epoxycyclohexyl) methyl (meth) acrylate, and 3-epoxycyclo-2-hydroxypropyl (meth) acrylate; glycidyl crotonate, allyl glycidyl ether, and the like.

[0035] Among these, the acrylic polymer (A1) used in one embodiment of the present invention is preferably a copolymer having a structural unit (a2-1) derived from a hydroxy group-containing monomer as the structural unit (a2).

[0036] From the above viewpoints, in the acrylic polymer (A1) used in one embodiment of the present invention, the content ratio of the structural unit (a2-1) is preferably 60 to 100% by mass, more preferably 70 to 100% by mass, still more preferably 80 to 100% by mass, even more preferably 90 to 100% by mass, particularly preferably 95 to 100% by mass, based on the total amount (100% by mass) of the structural units (a2) contained in the acrylic polymer (A1).

[0037] In the acrylic polymer (A1) used in one embodiment of the present invention, from the viewpoint of obtaining an adhesive composition capable of further improving cohesion, the content ratio of the structural unit (a2) is preferably 0.01% by mass or more, more preferably 0.10% by mass or more, still more preferably 1.0% by mass or more, even more preferably 3.0% by mass or more, particularly preferably 4.0% by mass or more, based on the total amount (100% by mass) of the structural units of the acrylic polymer (A1). Further, it may be 5.0% by mass or more, 7.0% by mass or more, 10.0% by mass or more, 12.0% by mass or more, or 15.0% by mass or more. Also, from the viewpoint of ensuring the content of the structural unit (a1) and obtaining an adhesive composition with better tack before voltage application, it is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less, even more preferably 30% by mass or less, particularly preferably 25% by mass or less.

[0038] [Monomer (a3’), Structural unit (a3)] The monomers (a3’) other than the monomers (a1’) and (a2’) are not particularly limited. Examples thereof include olefins such as ethylene, propylene, and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; diene monomers such as butadiene, isoprene, and chloroprene; styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, (meth)acrylamide, (meth)acrylonitrile, (meth)acryloylmorpholine, N-vinylpyrrolidone, and the like. These monomers (a3’) may be used alone or in combination of two or more.

[0039] In the acrylic polymer (A1) used in one aspect of the present invention, the content ratio of the constitutional unit (a3) may be 0% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more, or 4% by mass or more with respect to the total amount (100% by mass) of the constitutional units of the acrylic polymer (A1), and may also be 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, or 5% by mass or less.

[0040] In the pressure-sensitive adhesive composition of one aspect of the present invention, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high adhesiveness before voltage application and further improving the efficiency of reducing adhesiveness by voltage application, the blending amount (content) of component (A) is preferably 25% by mass or more, more preferably 30% by mass or more, more preferably 35% by mass or more, still more preferably 40% by mass or more, still more preferably 45% by mass or more, even more preferably 50% by mass or more, particularly preferably 55% by mass or more, and preferably 98% by mass or less, more preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 87% by mass or less, still more preferably 85% by mass or less, even more preferably 80% by mass or less, particularly preferably 75% by mass or less, with respect to the total amount (100% by mass) of the active ingredients of the pressure-sensitive adhesive composition. Further, it may be 70% by mass or less, 67% by mass or less, or 65% by mass or less.

[0041] <Component (B): Ionic compound> Examples of the ionic compound (B) used in one aspect of the present invention include one or more selected from alkali metal salts (B1), organic quaternary ammonium salts (B2), and ionic liquids (B3).

[0042] Among these, the component (B) used in one aspect of the present invention preferably contains one or more selected from alkali metal salts (B1) and ionic liquids (B3). Further, as the component (B) used in one aspect of the present invention, it is preferable to use an alkali metal salt (B1) or an ionic liquid (B3) as the main component. In addition, in this specification, the above "main component" means the component with the highest content among the components constituting component (B).

[0043] When the main component of component (B) is an alkali metal salt (B1), the content of component (B) other than the alkali metal salt (B1) may be less than 100 parts by mass, 0 to 90 parts by mass, 0 to 50 parts by mass, 0 to 30 parts by mass, 0 to 20 parts by mass, 0 to 10 parts by mass, 0 to 5 parts by mass, 0 to 1 part by mass, 0 to 0.1 part by mass, 0 to 0.01 part by mass, 0 to 0.001 part by mass, or 0 to 0.0001 part by mass with respect to 100 parts by mass of the total amount of the alkali metal salt (B1).

[0044] When the main component of component (B) is an ionic liquid (B3), the content of component (B) other than the ionic liquid (B3) may be less than 100 parts by mass, 0 to 90 parts by mass, 0 to 50 parts by mass, 0 to 30 parts by mass, 0 to 20 parts by mass, 0 to 10 parts by mass, 0 to 5 parts by mass, 0 to 1 part by mass, 0 to 0.1 part by mass, 0 to 0.01 part by mass, 0 to 0.001 part by mass, or 0 to 0.0001 part by mass with respect to the total amount of 100 parts by mass of the ionic liquid (B3).

[0045] In the pressure-sensitive adhesive composition of one aspect of the present invention, from the viewpoint of obtaining a pressure-sensitive adhesive composition with a more improved efficiency of reducing adhesiveness by voltage application, the blending ratio of component (B) with respect to 100 parts by mass of the total amount of component (A) is preferably 1.0 part by mass or more, more preferably 3.0 parts by mass or more, still more preferably 5.0 parts by mass or more, further preferably 7.0 parts by mass or more, even more preferably 9.0 parts by mass or more, particularly preferably 11.0 parts by mass or more, and further, it may be 13.0 parts by mass or more, or 15.0 parts by mass or more. Also, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high adhesiveness before voltage application, it is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, still more preferably 160 parts by mass or less, further preferably 150 parts by mass or less, even more preferably 130 parts by mass or less, particularly preferably 120 parts by mass or less, and further, it may be 100 parts by mass or less, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, 45 parts by mass or less, 40 parts by mass or less, 35 parts by mass or less, or 30 parts by mass or less.

[0046] In the pressure-sensitive adhesive composition according to one aspect of the present invention, from the viewpoint of obtaining a pressure-sensitive adhesive composition with improved efficiency of reducing adhesiveness by voltage application, the blending amount (content) of component (B) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1.0% by mass or more, further preferably 3.0% by mass or more, still further preferably 5.0% by mass or more, particularly preferably 7.0% by mass or more, based on the total amount (100% by mass) of the active ingredients of the pressure-sensitive adhesive composition. Also, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high adhesiveness before voltage application, it is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, further preferably 25% by mass or less, still further preferably 20% by mass or less, particularly preferably 15% by mass or less.

[0047] ≪Component (B1): Alkali metal salt≫ The alkali metal salt (B1) used in one aspect of the present invention may be a compound that is solid at normal temperature (25°C) but ionizes into cations (alkali metal ions) and anions in a liquid. Specific examples of the alkali metal salt (B1) include, for example, MCl, MBr, MI, MAlCl4, MAl2Cl7, MBF4, MPF6, MSCN, MClO4, MNO3, CH3COOM, C9H 19 COOM, CF3COOM, C3F7COOM, MCH3SO3, MCF3SO3, MC4F9SO3, MC2H5OSO3, MC6H 13 OSO3, MC8H 17 OSO3, M(CF3SO2)2N, M(C2F5SO2)2N, M(C3F7SO2)2N, M(C4F9SO2)2N, M(CF3SO2)3C, MAsF6, MSbF6, MNbF6, MTaF6, M(CN)2N, M(CF3SO2)(CF3CO)N, M(CH3)2PO4, M(C2H5)2PO4, MCH3(OC2H4)2OSO3, MC6H4(CH3)SO3, M(C2F5)3PF3, CH3CH(OH)COOM, M(FSO2)2N, etc. (where M is an alkali metal atom). M is preferably Li, Na, or K, more preferably Na or K, and still more preferably Na. These alkali metal salts (B1) may be used alone or in combination of two or more thereof.

[0048] Among these, the alkali metal salt (B1) used as the component (B) in one aspect of the present invention preferably contains an alkali metal salt (B11) represented by the following general formula (b-1).

Chemical formula

[0049] In the above formula (b-1), R F is each independently a fluorine atom or a fluorinated alkyl group. The number of carbon atoms of the fluorinated alkyl group is preferably 1 to 10, more preferably 1 to 8, still more preferably 1 to 4, even more preferably 1 to 3, and particularly preferably 1 to 2. In the present specification, the "fluorinated alkyl group" means a group in which at least one hydrogen atom of the alkyl group is substituted with a fluorine atom, and may be linear or branched. Among the fluorinated alkyl groups, a perfluoroalkyl group in which all hydrogen atoms of the alkyl group are substituted with fluorine atoms is preferred. The preferred range of the number of carbon atoms of the perfluoroalkyl group is the same as the preferred range of the number of carbon atoms of the above-mentioned fluorinated alkyl group. In one aspect of the present invention, R F is preferably a fluorine atom or a perfluoroalkyl group, more preferably a fluorine atom, -CF3, -C2F5, -C3F7, or -C4F9, and still more preferably a fluorine atom or -CF3.

[0050] M is an alkali metal atom (lithium atom (Li), sodium atom (Na), potassium atom (K), rubidium atom (Rb), cesium atom (Cs), francium atom (Fr)), but is preferably Li, Na or K, more preferably Na or K, and still more preferably Na.

[0051] <<Component (B2): Organic quaternary ammonium salt>> As the organic quaternary ammonium salt (B2) used in one aspect of the present invention, it may be a compound represented by the following general formula (b-2) and is solid at normal temperature (25 °C). The organic quaternary ammonium salt (B2) may be used alone or in combination of two or more. [Chemical formula]

[0052] In the above general formula (b-2), R 11 ~R 14 are each independently an alkyl group having 1 to 4 carbon atoms. X is F, Cl, Br, I, ClO4, BF4, PF6, or [(R 15 )4N]2SO4 (R 15 are each independently an alkyl group having 1 to 4 carbon atoms).

[0053] Specific examples of the organic quaternary ammonium salt (B2) include ammonium bromide or ammonium chloride such as tetrabutyl, tetrapropyl, tetraethyl, tetramethyl, triethylbutyl, triethylpropyl, triethylmethyl, etc.; ammonium tetrafluoroborate such as tetrabutyl, tetrapropyl, tetraethyl, tetramethyl, triethylbutyl, triethylpropyl, triethylmethyl, etc.; ammonium hexafluorophosphate such as tetrabutyl, tetrapropyl, tetraethyl, tetramethyl, triethylbutyl, triethylpropyl, triethylmethyl, etc.; ammonium perchlorate such as tetrabutyl, tetrapropyl, tetraethyl, tetramethyl, triethylbutyl, triethylpropyl, triethylmethyl, etc.; ammonium sulfate such as tetrabutyl, tetrapropyl, tetraethyl, tetramethyl, triethylbutyl, triethylpropyl, triethylmethyl, etc.; and the like.

[0054] <<Component (B3): Ionic liquid>> As the ionic liquid (B3) used in one aspect of the present invention, it may be a molten salt that is liquid at room temperature (25°C), and may be a compound composed of an organic cation and an anion that is its counter ion. Examples of the organic cation constituting the ionic liquid (B3) include cations represented by any of the following general formulas (b-3-i) to (b-3-viii). Among these, the organic cation constituting the ionic liquid (B3) is preferably a cation represented by the following general formula (b-3-ii).

Chemical formula

[0055] In the above formulas (b-3-i) to (b-3-iv), R a is each independently an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 1 to 20 carbon atoms. Further, in the above formulas (b-3-v) to (b-3-viii), R b is each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, -(C2H4O) n -R c group represented by (n is an integer of 1 to 20, R c is an alkyl group having 1 to 20 carbon atoms), or an amino group.

[0056] R a 、R b and R c As the alkyl group that can be selected, examples include a methyl group, an ethyl group, a propyl group (n-propyl group, i-propyl group), a butyl group (n-butyl group, i-butyl group, s-butyl group, t-butyl group), a pentyl group (n-pentyl group, i-pentyl group, neopentyl group), a hexyl group, a heptyl group, an octyl group, 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, etc. The alkyl group may be a linear alkyl group or a branched-chain alkyl group.

[0057] Ra and R b Examples of the alkenyl group that can be selected as said alkenyl group include an ethenyl group (vinyl group), a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, a hexadecenyl group, an octadecenyl group, and the like. The alkenyl group may be a linear alkyl group or a branched alkyl group.

[0058] In addition, at least one hydrogen atom bonded to the carbon atom of the cation represented by any of the general formulas (b-3-i) to (b-3-ii) may be substituted with an alkyl group having 1 to 20 carbon atoms. Specific examples of the alkyl group are as described above.

[0059] Examples of the cation represented by the general formula (b-3-i) and the cation in which at least one hydrogen atom of the cation is substituted with the alkyl group include cations represented by any of the following formulas (b-3-i-1) to (b-3-i-11).

Chemical formula

[0060] Examples of the cation represented by the general formula (b-3-ii) and the cation in which at least one hydrogen atom of the cation is substituted with the alkyl group include cations represented by any of the following formulas (b-3-ii-1) to (b-3-ii-26). Among them, cations represented by any of the following formulas (b-3-ii-1) to (b-3-ii-15) are preferred, cations represented by any of the following formulas (b-3-ii-1) to (b-3-ii-3) and (b-3-ii-9) to (b-3-ii-10) are more preferred, cations represented by any of the following formulas (b-3-ii-1) to (b-3-ii-3) are still more preferred, and the cation represented by the following formula (b-3-ii-2) is even more preferred.

Chemical formula

[0061] Examples of the cation represented by the general formula (b-3-iii) include cations represented by any of the following formulas (b-3-iii-1) to (b-3-iii-6).

Chemical formula

[0062] Examples of the cation represented by the general formula (b-3-iv) include cations represented by any of the following formulas (b-3-iv-1) to (b-3-iv-6).

Chemical formula

[0063] Examples of the cation represented by any of the general formulas (b-3-v) to (b-3-viii) include cations represented by any of the following formulas.

Chemical formula

[0064] Examples of the anion constituting the ionic liquid (B3) include Cl - , Br - , I - , AlCl4 - , Al2Cl7 - , BF4 - , PF6 - , SCN - , ClO4 - , NO3 - , CH3COO - , CF3COO - , CH3SO3 - , CF3SO3 - , C4F9SO3 - , (CF3SO2)2N - , (C2F5SO2)2N - , (C3F7SO2)2N - , (C4F9SO2)2N- 、(CF3SO2)3C - 、AsF6 - 、SbF6 - 、NbF6 - 、TaF6 - 、(CN)2N - 、C4F9SO3 - 、(C2F5SO2)2N - 、C3F7COO - 、(CF3SO2)(CF3CO)N - 、C9H 19 COO - 、(CH3)2PO4 - 、(C2H5)2PO4 - 、CH3OSO3 - 、C2H5OSO3 - 、C4H9OSO3 - 、C6H 13 OSO3 - 、C8H 17 OSO3 - 、CH3(OC2H4)2OSO3 - 、C6H4(CH3)SO3 - 、(C2F5)3PF3 - 、CH3CH(OH)COO - 、(FSO2)2N - 、B(CN)4 - 、C(CN)3 - 、N(CN)2 - 、Examples include p-toluenesulfonate anion, 2-(2-methoxyethyl)ethyl sulfate anion, etc. Among these, as the anion constituting the ionic liquid (B3) used in one aspect of the present invention, (CF3SO2)2N - or (FSO2)2N - is preferred.

[0065] <Component (C): Polypropylene glycol> The pressure-sensitive adhesive composition of one aspect of the present invention contains polypropylene glycol (C) having a number average molecular weight of 200 to 3500. Since the pressure-sensitive adhesive composition according to one aspect of the present invention contains component (C), it has high adhesiveness before voltage application, while the efficiency of reducing adhesiveness by voltage application can be significantly improved. In particular, even when the adherend is a stainless steel plate or when the thickness of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is reduced, these properties can be fully exhibited.

[0066] Among the above viewpoints, the number average molecular weight (Mn) of the polypropylene glycol (C) used in one aspect of the present invention is, in particular, from the viewpoint of obtaining a pressure-sensitive adhesive composition that can significantly improve the efficiency of reducing adhesiveness by voltage application, 200 or more, preferably 250 or more, more preferably 270 or more, still more preferably 300 or more, even more preferably 320 or more, particularly preferably 350 or more. Also, among the above viewpoints, in particular, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high adhesiveness before voltage application, it is 3500 or less, preferably 3300 or less, more preferably 3100 or less, more preferably 3000 or less, more preferably 2700 or less, still more preferably 2500 or less, still more preferably 2300 or less, still more preferably 2000 or less, even more preferably 1700 or less, particularly preferably 1500 or less. Further, it may be 1300 or less, 1200 or less, 1100 or less, 1000 or less, 900 or less, 800 or less, 700 or less, or 600 or less.

[0067] The polypropylene glycol (C) used in one aspect of the present invention may be a polymer having a structural unit (c1) represented by the following general formula (c-1) as a main structural unit, and may have other structural units other than the structural unit (c1) in a proportion less than the content ratio of the structural unit (c1) as long as the effects of the present invention are not impaired. Note that the polypropylene glycol (C) used in one aspect of the present invention preferably has hydroxyl groups at both ends.

Chemical formula

[0068] However, from the perspective of obtaining a pressure-sensitive adhesive composition that has high adhesiveness before voltage application and yet more improved efficiency of reducing adhesiveness upon voltage application, in the polypropylene glycol (C) used in one aspect of the present invention, it is preferable that the content ratio of other constituent units than the constituent unit (c1) is as small as possible. From the above perspective, in the polypropylene glycol (C) used in one aspect of the present invention, the content ratio of the constituent unit (c1) is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, still more preferably 80 to 100% by mass, further preferably 90 to 100% by mass, still further preferably 95 to 100% by mass, even more preferably 98 to 100% by mass, and particularly preferably 100% by mass, based on the total amount (100% by mass) of the constituent units of the polypropylene glycol (C).

[0069] That is, from the above perspective, the polypropylene glycol (C) used in one aspect of the present invention is preferably a homopolymer composed only of the constituent unit (c1) represented by the general formula (c-1) as a constituent unit, and more preferably a compound represented by the following formula (c-2).

Chemical formula

[0070] In the pressure-sensitive adhesive composition according to one aspect of the present invention, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high adhesiveness before voltage application and further improving the efficiency of reducing adhesiveness by voltage application, the blending ratio of component (C) with respect to 100 parts by mass of the total amount of component (A) is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, still more preferably 1.0 part by mass or more, still more preferably 1.2 part by mass or more, further preferably 1.5 part by mass or more, further preferably 1.7 part by mass or more, further preferably 2.0 part by mass or more, even more preferably 2.2 part by mass or more, particularly preferably 2.5 part by mass or more, and further may be 2.7 part by mass or more, 3.0 part by mass or more, 3.2 part by mass or more, 3.5 part by mass or more, or 3.7 part by mass or more. Also, it is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 60 parts by mass or less, still more preferably 50 parts by mass or less, further preferably 40 parts by mass or less, further preferably 30 parts by mass or less, further preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, particularly preferably 15 parts by mass or less, and further may be 13 parts by mass or less, 12 parts by mass or less, 11 parts by mass or less, 10 parts by mass or less, 9.5 parts by mass or less, 9.0 parts by mass or less, 8.5 parts by mass or less, 8.0 parts by mass or less, 7.5 parts by mass or less, or 7.0 parts by mass or less.

[0071] In the pressure-sensitive adhesive composition of one aspect of the present invention, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high adhesiveness before voltage application and further improving the efficiency of reducing adhesiveness by voltage application, the blending amount (content) of component (C) is preferably 0.5% by mass or more, more preferably 0.7% by mass or more, more preferably 1.0% by mass or more, more preferably 1.2% by mass or more, still more preferably 1.5% by mass or more, still more preferably 1.7% by mass or more, still more preferably 2.0% by mass or more, even more preferably 2.2% by mass or more, particularly preferably 2.5% by mass or more, based on 100% by mass of the total amount of the active ingredients of the pressure-sensitive adhesive composition. Also, it is preferably 30% by mass or less, more preferably 20% by mass or less, more preferably 18% by mass or less, more preferably 15% by mass or less, still more preferably 12% by mass or less, still more preferably 11% by mass or less, still more preferably 10% by mass or less, even more preferably 8.0% by mass or less, particularly preferably 6.5% by mass or less, and further, it may be 6.0% by mass or less, 5.5% by mass or less, 5.0% by mass or less, 4.5% by mass or less, 4.0% by mass or less, or 3.5% by mass or less.

[0072] In the pressure-sensitive adhesive composition of one aspect of the present invention, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high adhesiveness before voltage application and further improving the efficiency of reducing adhesiveness by voltage application, the blending amount ratio [(C) / (B)] of component (C) to component (B) is preferably 0.01 or more, more preferably 0.05 or more, more preferably 0.07 or more, more preferably 0.10 or more, still more preferably 0.12 or more, still more preferably 0.15 or more, still more preferably 0.17 or more, even more preferably 0.20 or more, particularly preferably 0.22 or more, in terms of mass ratio. Also, it is preferably 10.0 or less, more preferably 8.0 or less, more preferably 6.0 or less, more preferably 5.0 or less, still more preferably 4.0 or less, still more preferably 3.0 or less, still more preferably 2.0 or less, even more preferably 1.5 or less, particularly preferably 1.0 or less, and further, it may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, or 0.40 or less.

[0073] <Other polyalkylene glycol> The pressure-sensitive adhesive composition of one embodiment of the present invention may contain other polyalkylene glycols other than polypropylene glycol as long as the effects of the present invention are not impaired. Examples of such other polyalkylene glycols include polyethylene glycol, polybutylene glycol, polyethylene glycol-polybutylene glycol, and the like.

[0074] However, from the viewpoint of obtaining a pressure-sensitive adhesive composition that has high adhesiveness before voltage application and further improved efficiency of reducing adhesiveness by voltage application, it is preferable that the content of other polyalkylene glycols is as small as possible. The specific content of other polyalkylene glycols is preferably less than 10 parts by mass, more preferably less than 5 parts by mass, still more preferably less than 1 part by mass, even more preferably less than 0.1 part by mass, and particularly preferably less than 0.01 part by mass, based on 100 parts by mass of the total amount of component (C) contained in the pressure-sensitive adhesive composition.

[0075] <Component (D): Rosin-containing diol> The pressure-sensitive adhesive composition of one embodiment of the present invention is preferably a pressure-sensitive adhesive composition further containing a rosin-containing diol (D). The rosin-containing diol (D) has excellent compatibility with the ionic compound (B) (particularly, an ionic liquid). Therefore, by forming a pressure-sensitive adhesive composition containing the rosin-containing diol (D) together with the base polymer (A) and the ionic compound (B), it is possible to have high adhesiveness before voltage application and further improve the efficiency of reducing adhesiveness by voltage application. In addition, even when the content of the liquid component contained in the pressure-sensitive adhesive composition of one embodiment of the present invention is large, by blending the rosin-containing diol (D) having good compatibility with the liquid component, it is possible to obtain a pressure-sensitive adhesive composition with further improved adhesiveness.

[0076] The rosin-containing diol (D) used in one embodiment of the present invention may be any diol having a rosin-derived skeleton, and examples thereof include a reaction product of rosin and an epoxy compound. The rosin-containing diol (D) may be used alone or in combination of two or more thereof.

[0077] The rosin constituting the rosin-containing diol (D) means the residual resin obtained by using the resin oil obtained from coniferous plants as a raw material and distilling off volatile substances such as essential oils. The residual resin is usually a mixture containing resin acids mainly composed of abietic acid and its analogs and a small amount of neutral components. Examples of the resin acids include abietic acid, dehydroabietic acid, dihydroabietic acid, tetrahydroabietic acid, diabietic acid, neoabietic acid, levopimaric acid, hydrogenated rosins obtained by hydrogenating these, disproportionated rosins obtained by disproportionating these, and the like.

[0078] Examples of the epoxy compound include acyclic aliphatic diglycidyl ethers such as ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether; aromatic diglycidyl ethers or cycloaliphatic diglycidyl ethers such as 2,2-bis(4-hydroxyphenyl)propane diglycidyl ether, bis(4-hydroxyphenyl)methane diglycidyl ether, 1,1-bis(4-hydroxyphenyl)ethane diglycidyl ether, 2,2-bis(4-hydroxycyclohexyl)propane diglycidyl ether, 3,3’,5,5’-tetramethyl-4,4’-dihydroxybiphenyl diglycidyl ether, 2,2’-bis(4-(β-hydroxypropoxy)phenyl)propane diglycidyl ether; cycloaliphatic cyclic oxiranes such as 3,4-epoxycyclohexylmethyl, 3,4-epoxycyclohexanecarboxylate, vinylcyclohexene dioxide; and the like. These epoxy compounds may be used alone or in combination of two or more thereof.

[0079] The rosin-containing diol (D) used in one embodiment of the present invention is preferably a compound having two rosin-derived skeletons and two hydroxyl groups in the molecule.

[0080] From the viewpoint of obtaining a pressure-sensitive adhesive composition having high tackiness before voltage application and further improving the efficiency of reducing tackiness by voltage application by improving the compatibility with components (A), (B) and (C) (particularly the compatibility with components (B) and (C)), the softening point of the rosin-containing diol (D) used in one embodiment of the present invention is preferably 60°C or higher, more preferably 65°C or higher, still more preferably 70°C or higher, even more preferably 75°C or higher, particularly preferably 80°C or higher, and is preferably 160°C or lower, more preferably 150°C or lower, still more preferably 140°C or lower, further more preferably 130°C or lower, still further more preferably 120°C or lower, even further more preferably 110°C or lower, particularly preferably 104°C or lower. In the present specification, the softening point means a value measured in accordance with the ring and ball method defined in JIS K5902.

[0081] From the viewpoint of obtaining a pressure-sensitive adhesive composition having high tackiness before voltage application and further improving the efficiency of reducing tackiness by voltage application by improving the compatibility with components (A), (B) and (C) (particularly the compatibility with components (B) and (C)), the acid value of the rosin-containing diol (D) used in one embodiment of the present invention is preferably 0 to 10.0 mgKOH / g, more preferably 0 to 4.9 mgKOH / g, still more preferably 0 to 1.9 mgKOH / g, even more preferably 0 to 1.4 mgKOH / g, particularly preferably 0 to 1.1 mgKOH / g. In addition, from the perspective of obtaining a pressure-sensitive adhesive composition that has high adhesiveness before voltage application and yet has improved efficiency of reducing adhesiveness upon voltage application by ensuring good compatibility with components (A), (B), and (C) (particularly with components (B) and (C)), the hydroxyl value of the rosin-containing diol (D) used in one embodiment of the present invention is preferably 30 mgKOH / g or more, more preferably 50 mgKOH / g or more, still more preferably 70 mgKOH / g or more, even more preferably 80 mgKOH / g or more, particularly preferably 90 mgKOH / g or more, and is preferably 300 mgKOH / g or less, more preferably 250 mgKOH / g or less, still more preferably 200 mgKOH / g or less, even more preferably 180 mgKOH / g or less, particularly preferably 150 mgKOH / g or less. In the present specification, the acid value and the hydroxyl value mean the values measured in accordance with the potentiometric titration method defined in JIS K0070.

[0082] In the pressure-sensitive adhesive composition of one embodiment of the present invention, from the perspective of obtaining a pressure-sensitive adhesive composition that has high adhesiveness before voltage application and yet has improved efficiency of reducing adhesiveness upon voltage application, the blending ratio of component (D) relative to 100 parts by mass of the total amount of component (A) is preferably 2.0 parts by mass or more, more preferably 5.0 parts by mass or more, still more preferably 8.0 parts by mass or more, even more preferably 12.0 parts by mass or more, particularly preferably 18.0 parts by mass or more, and may further be 25.0 parts by mass or more, or 30.0 parts by mass or more. Also, it is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, still more preferably 150 parts by mass or less, even more preferably 130 parts by mass or less, particularly preferably 110 parts by mass or less, and may further be 100 parts by mass or less, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, or 50 parts by mass or less.

[0083] In the pressure-sensitive adhesive composition according to one aspect of the present invention, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high adhesiveness before voltage application and further improving the efficiency of reducing adhesiveness by voltage application, the blending amount (content) of component (D) is preferably 0.2% by mass or more, more preferably 1.2% by mass or more, more preferably 3.0% by mass or more, more preferably 5.0% by mass or more, still more preferably 7.0% by mass or more, still more preferably 9.0% by mass or more, even more preferably 11.0% by mass or more, particularly preferably 16.0% by mass or more, based on 100% by mass of the total amount of the active ingredients of the pressure-sensitive adhesive composition. Also, it is preferably 60% by mass or less, more preferably 55% by mass or less, more preferably 50% by mass or less, still more preferably 45% by mass or less, even more preferably 40% by mass or less, particularly preferably 35% by mass or less.

[0084] In the pressure-sensitive adhesive composition according to one aspect of the present invention, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high adhesiveness before voltage application and further improving the efficiency of reducing adhesiveness by voltage application, the blending ratio [(D) / (B)] of component (D) to component (B) is preferably 0.10 or more, more preferably 0.30 or more, more preferably 0.50 or more, still more preferably 0.80 or more, still more preferably 1.00 or more, even more preferably 1.20 or more, particularly preferably 1.50 or more, in terms of mass ratio. Also, it is preferably 20.0 or less, more preferably 15.0 or less, more preferably 10.0 or less, still more preferably 8.0 or less, still more preferably 6.0 or less, even more preferably 5.0 or less, particularly preferably 4.0 or less.

[0085] <Other tackifiers> The pressure-sensitive adhesive composition according to one aspect of the present invention may contain other tackifiers other than component (D) as long as the effects of the present invention are not impaired. Examples of such other tackifiers include rosin resins other than component (D); hydrogenated rosin resins obtained by hydrogenating rosin resins other than component (D); terpene resins such as terpene resins, terpene phenol resins, and aromatic modified terpene resins; hydrogenated terpene resins obtained by hydrogenating these terpene resins; C5 petroleum resins obtained by copolymerizing C5 fractions such as pentene, isoprene, piperene, and 1,3-pentadiene produced by thermal decomposition of petroleum naphtha, and hydrogenated petroleum resins of these C5 petroleum resins; C9 petroleum resins obtained by copolymerizing C9 fractions such as indene, vinyltoluene, α-methylstyrene, and β-methylstyrene produced by thermal decomposition of petroleum naphtha, and hydrogenated petroleum resins of these C9 petroleum resins; and the like. These other tackifiers may be used alone or in combination of two or more.

[0086] However, from the viewpoint of obtaining a pressure-sensitive adhesive composition that has high tack before voltage application and more improved efficiency of reducing tack by voltage application, it is preferable that the content of other tackifiers other than component (D) contained in the pressure-sensitive adhesive composition of one aspect of the present invention is as small as possible. Specifically, the content of other tackifiers other than component (D) is preferably less than 10 parts by mass, more preferably less than 5 parts by mass, still more preferably less than 1 part by mass, even more preferably less than 0.1 part by mass, and particularly preferably less than 0.01 part by mass with respect to 100 parts by mass of the total amount of component (D) contained in the pressure-sensitive adhesive composition.

[0087] <Component (E): Crosslinking agent> The pressure-sensitive adhesive composition of one aspect of the present invention is preferably a pressure-sensitive adhesive composition further containing a crosslinking agent (E). By blending the crosslinking agent (E), it becomes easier to prepare a pressure-sensitive adhesive composition that has high tack before voltage application and more improved efficiency of reducing tack by voltage application. Note that the crosslinking agent (E) may be used alone or in combination of two or more.

[0088] Examples of the crosslinking agent (E) used in one aspect of the present invention include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, imine-based crosslinking agents, and metal chelate-based crosslinking agents.

[0089] Examples of the isocyanate crosslinking agent include tolylene diisocyanate compounds such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate; xylylene diisocyanate compounds such as 1,3-xylylene diisocyanate and 1,4-xylylene diisocyanate; diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, lysine isocyanate, and the like. In addition, trimers of these organic polyisocyanate compounds, and terminal isocyanate urethane prepolymers obtained by reacting these organic polyisocyanate compounds with polyol compounds can also be used.

[0090] Examples of the epoxy crosslinking agent include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, 1,3-bis(N,N-diglycidylaminomethyl)toluene, N,N,N',N'-tetraglycidyl-4,4-diaminodiphenylmethane, and the like.

[0091] Examples of the imine crosslinking agent include N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate, N,N'-toluene-2,4-bis(1-aziridinecarboxamide)triethylenemelamine, and the like.

[0092] Examples of the metal chelate crosslinking agent include coordination compounds of polyvalent metals such as aluminum chelate compounds such as trisethylacetoacetate aluminum, aluminum diisopropylate ethylacetoacetate, and trisacetylacetonate aluminum.

[0093] In the pressure-sensitive adhesive composition of one embodiment of the present invention, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high adhesiveness before voltage application and further improving the efficiency of reducing adhesiveness by voltage application, the blending ratio of component (E) with respect to 100 parts by mass of the total amount of component (A) is preferably 0.01 part by mass or more, more preferably 0.05 part by mass or more, still more preferably 0.10 part by mass or more, still more preferably 0.20 part by mass or more, still more preferably 0.30 part by mass or more, still more preferably 0.40 part by mass or more, still more preferably 0.50 part by mass or more, even more preferably 0.55 part by mass or more, particularly preferably 0.60 part by mass or more, and further may be 0.65 part by mass or more, 0.70 part by mass or more, 0.75 part by mass or more, 0.80 part by mass or more, or 0.85 part by mass or more. Also, it is preferably 10.0 parts by mass or less, more preferably 7.0 parts by mass or less, still more preferably 5.0 parts by mass or less, still more preferably 4.0 parts by mass or less, still more preferably 3.5 parts by mass or less, still more preferably 3.0 parts by mass or less, still more preferably 2.5 parts by mass or less, even more preferably 2.0 parts by mass or less, particularly preferably 1.5 parts by mass or less.

[0094] In the pressure-sensitive adhesive composition of one embodiment of the present invention, from the viewpoint of obtaining a pressure-sensitive adhesive composition having high adhesiveness before voltage application and further improving the efficiency of reducing adhesiveness by voltage application, the blending amount (content) of component (E) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.10% by mass or more, still more preferably 0.20% by mass or more, still more preferably 0.30% by mass or more, even more preferably 0.35% by mass or more, particularly preferably 0.40% by mass or more, and also preferably 7.0% by mass or less, more preferably 5.0% by mass or less, still more preferably 4.0% by mass or less, still more preferably 3.0% by mass or less, still more preferably 2.5% by mass or less, even more preferably 2.0% by mass or less, particularly preferably 1.5% by mass or less.

[0095] <Other additives> The pressure-sensitive adhesive composition of one embodiment of the present invention may contain other additives other than components (A) to (E). Such other additives are appropriately selected according to the use of the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition. Examples thereof include compatibilizers, wetting agents, thickeners, defoaming agents, antioxidants, ultraviolet absorbers, softeners (plasticizers), fillers, rust preventives, pigments, dyes, and the like. As these other additives, additives used in general pressure-sensitive adhesive compositions can be used. Each additive may be used alone or in combination of two or more.

[0096] The blending amount of each of these other additives is appropriately set according to the type of the additive. Preferably, it is 0.01 to 50 parts by mass, more preferably 0.05 to 40 parts by mass, still more preferably 0.1 to 30 parts by mass, and even more preferably 0.2 to 20 parts by mass with respect to 100 parts by mass of the total amount of component (A).

[0097] From the viewpoint of facilitating coating on a base material or the like described later and improving workability, the pressure-sensitive adhesive composition according to one embodiment of the present invention may be further diluted with an organic solvent to be in the form of a solution. Examples of the organic solvent include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, isopropanol, and the like. Note that as these organic solvents, the organic solvent used during the synthesis of component (A) may be used as it is, or one or more organic solvents other than the organic solvent used during the synthesis of component (A) may be added.

[0098] 〔Electrically releasable pressure-sensitive adhesive sheet〕 The electrically releasable pressure-sensitive adhesive sheet of the present invention (hereinafter, also simply referred to as "pressure-sensitive adhesive sheet") has a pressure-sensitive adhesive layer formed from the above-described electrically releasable pressure-sensitive adhesive composition of the present invention. The pressure-sensitive adhesive sheet according to one embodiment of the present invention is not particularly limited as long as it has a configuration having the pressure-sensitive adhesive layer. For example, it may be a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on at least one side of a base material, or a pressure-sensitive adhesive sheet having a configuration in which the pressure-sensitive adhesive layer is sandwiched between two release sheets.

[0099] FIG. 1 is a schematic cross-sectional view of an electrically peelable pressure-sensitive adhesive sheet according to an aspect of the present invention, showing an example of the configuration of the pressure-sensitive adhesive sheet. As a specific configuration of the pressure-sensitive adhesive sheet according to an aspect of the present invention, for example, there is an electrically peelable pressure-sensitive adhesive sheet 1a with a substrate, which has a pressure-sensitive adhesive layer 3 on one surface side of the substrate 2 as shown in FIG. 1(a). Further, a configuration such as an electrically peelable pressure-sensitive adhesive sheet 1b with a substrate, which has a pressure-sensitive adhesive layer 3 and a pressure-sensitive adhesive layer 3' on both surface sides of the substrate 2, respectively, as shown in FIG. 1(b) may also be used. In addition, in the pressure-sensitive adhesive sheet according to an aspect of the present invention, the substrate 2 and the pressure-sensitive adhesive layer 3 may be directly laminated as in the electrically peelable pressure-sensitive adhesive sheet 1a shown in FIG. 1(a), or a configuration having another layer between the substrate 2 and the pressure-sensitive adhesive layer 3 may also be used. This also applies to the substrate 2 and the pressure-sensitive adhesive layer 3, and the substrate 2 and the pressure-sensitive adhesive layer 3' in the electrically peelable pressure-sensitive adhesive sheet 1b shown in FIG. 1(b).

[0100] Further, the pressure-sensitive adhesive sheet according to an aspect of the present invention may have a configuration such as an electrically peelable pressure-sensitive adhesive sheet 1c with a substrate, in which a release sheet 4 is further laminated on the adhesive surface of the pressure-sensitive adhesive layer 3 as shown in FIG. 1(c). Similarly, in the electrically peelable pressure-sensitive adhesive sheet 1b, a configuration in which release sheets are laminated on the adhesive surfaces of the pressure-sensitive adhesive layer 3 and the pressure-sensitive adhesive layer 3', respectively, can also be used.

[0101] As another aspect, the pressure-sensitive adhesive sheet according to an aspect of the present invention may have a configuration such as a substrate-free electrically peelable pressure-sensitive adhesive sheet 1d, which has a configuration in which the pressure-sensitive adhesive layer 3 is sandwiched between two release sheets 4 and 4' without using a substrate, as shown in FIG. 1(d). The materials of the release sheets 4 and 4' of this electrically peelable pressure-sensitive adhesive sheet 1d may be the same or different, but it is preferable that the materials are adjusted so that the peeling forces between the release sheet 4 and the release sheet 4' are different. In addition, there are also examples such as an electrically peelable pressure-sensitive adhesive sheet having a configuration in which a pressure-sensitive adhesive layer is provided on one side of a release sheet whose surface has been subjected to a peeling treatment and is wound into a roll shape.

[0102] Hereinafter, the details of the pressure-sensitive adhesive layer, base material, and release sheet constituting the pressure-sensitive adhesive sheet of one embodiment of the present invention will be described.

[0103] <Pressure-sensitive adhesive layer> The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is a layer formed from the above-described electro-releasable pressure-sensitive adhesive composition of the present invention and has the property that the adhesive force can be reduced by applying a voltage. The thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of one embodiment of the present invention is appropriately adjusted according to the use and the like, but is preferably 0.5 to 120 μm, more preferably 1 to 100 μm, still more preferably 3 to 80 μm, even more preferably 5 to 80 μm, and particularly preferably 10 to 60 μm. If the thickness of the pressure-sensitive adhesive layer is 0.5 μm or more, good adhesive force can be exhibited regardless of the type of adherend. On the other hand, if the thickness of the pressure-sensitive adhesive layer is 120 μm or less, there are advantages in terms of productivity, and an electro-releasable pressure-sensitive adhesive sheet with good handleability can be obtained.

[0104] The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of one embodiment of the present invention is a layer formed from the pressure-sensitive adhesive composition of one embodiment of the present invention described above. Therefore, the thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of one embodiment of the present invention can be 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, or 30 μm or less. Even if the thickness of the pressure-sensitive adhesive layer is made relatively thin in this way, it has a high adhesive force before voltage application, and the reduction efficiency of the adhesive force due to voltage application can be favorably maintained.

[0105] <Base material> As the base material of the pressure-sensitive adhesive sheet of one embodiment of the present invention, from the viewpoint of applying a voltage to the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet when it is desired to peel from the adherend, a conductive base material is preferable. That is, the pressure-sensitive adhesive sheet of one embodiment of the present invention preferably has a conductive base material and has a pressure-sensitive adhesive layer on at least one surface side of the conductive base material. Examples of the material constituting the conductive base material include metals such as aluminum, tin-doped indium oxide, copper, iron, silver, platinum, and gold, and alloys of these metals. Alternatively, a metal vapor deposition body formed by vapor-depositing the above metal on a resin film such as polyethylene terephthalate may be used as a base material. When vapor-depositing a metal on a resin film, it is preferable to vapor-deposit the metal on the surface of the resin film that contacts the adhesive layer.

[0106] The thickness of the base material is preferably 5 to 300 μm, more preferably 10 to 150 μm, and still more preferably 20 to 100 μm.

[0107] <Release Sheet> The release sheet included in the pressure-sensitive adhesive sheet according to one aspect of the present invention can be obtained by applying a release agent to one or both surfaces of a base material for the release sheet. Examples of the base material for the release sheet include resin films such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and other polyesters, polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymers, polyurethanes, ethylene-vinyl acetate copolymers, ionomer resins, ethylene (meth)acrylic acid copolymers, polystyrene, polycarbonate, fluororesins, low-density polyethylene, linear low-density polyethylene, and triacetyl cellulose; paper base materials such as fine paper, coated paper, and glassine paper; and laminated papers obtained by laminating a thermoplastic resin such as polyethylene on these paper base materials.

[0108] Examples of the release agent used in one aspect of the present invention include silicone resins, olefin resins, long-chain alkyl resins, alkyd resins, fluororesins, and rubber elastomers such as isoprene resins and butadiene resins.

[0109] The thickness of the release sheet is not particularly limited, but is preferably 5 to 300 μm, more preferably 10 to 200 μm. When using a polyester film as the base material for the release sheet, it is preferably 10 to 100 μm.

[0110] 〔Method for Manufacturing Electrically Peeling Pressure-Sensitive Adhesive Sheet〕 As a method for manufacturing the electrically peelable pressure-sensitive adhesive sheet of the present invention, there is no particular limitation, and the pressure-sensitive adhesive composition of one embodiment of the present invention prepared by the above method can be applied onto the above-described base material or release sheet by a known coating method to manufacture it. From the viewpoint of improving the coatability with respect to the base material or the release sheet, the pressure-sensitive adhesive composition of one embodiment of the present invention is preferably diluted with an organic solvent and used in the form of a solution.

[0111] Examples of the method for applying the pressure-sensitive adhesive composition onto the base material or the release sheet include a spin coating method, a spray coating method, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, and the like.

[0112] After applying the pressure-sensitive adhesive composition onto the base material or the release sheet to form a coating film, it is preferable to perform a drying treatment. As the drying conditions for the formed coating film, it is preferable to heat and dry at a temperature of 80°C to 150°C for 30 seconds to 5 minutes (preferably 40 seconds to 3 minutes, more preferably 45 seconds to 2 minutes). Through this drying step, a pressure-sensitive adhesive layer can be formed on the base material or the release sheet. In addition, when a crosslinking agent is blended in the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer, it is preferable to undergo a seasoning step of holding for a certain period (for example, about 1 day to 14 days) in order to complete the crosslinking. On the other hand, when a crosslinking agent is not blended in the used pressure-sensitive adhesive composition, there is no need to perform the seasoning step.

[0113] As a specific manufacturing method according to the configuration of the electrically peelable pressure-sensitive adhesive sheet, the following methods can be mentioned. First, an electrically peelable pressure-sensitive adhesive sheet 1a having a pressure-sensitive adhesive layer 3 on one side of a base material 2 as shown in Fig. 1(a) can be produced, for example, by directly applying a solution of the above-described pressure-sensitive adhesive composition onto one surface of the base material 2 to form the pressure-sensitive adhesive layer 3. Alternatively, after directly applying a solution of the above-described pressure-sensitive adhesive composition onto the release treatment surface of the release sheet to form a pressure-sensitive adhesive layer 3, the pressure-sensitive adhesive layer 3 and the base material 2 may be bonded together and the release sheet may be removed for production.

[0114] The electrically peelable pressure-sensitive adhesive sheet 1b having pressure-sensitive adhesive layers 3 and 3' on both sides of the base material 2 as shown in Fig. 1(b) can be produced, for example, by directly applying a solution of the above-described pressure-sensitive adhesive composition to both sides of the base material 2 to form the pressure-sensitive adhesive layers 3 and 3'. Alternatively, two sheets each having a pressure-sensitive adhesive layer formed by directly applying a solution of the above-described pressure-sensitive adhesive composition to the peel surface of the release sheet may be prepared, and the respective pressure-sensitive adhesive layers may be bonded to both sides of the base material 2, followed by removing the release sheet.

[0115] The electrically peelable pressure-sensitive adhesive sheet 1c having the pressure-sensitive adhesive layer 3 and the release sheet 4 on the base material 2 in this order as shown in Fig. 1(c) can be produced, for example, by laminating the release sheet 4 on the surface of the pressure-sensitive adhesive layer 3 of the electrically peelable pressure-sensitive adhesive sheet 1a obtained as described above. Alternatively, after directly applying a solution of the above-described pressure-sensitive adhesive composition to the peel surface of the release sheet 4 to form the pressure-sensitive adhesive layer 3, the pressure-sensitive adhesive layer 3 and the base material 2 may be bonded together.

[0116] The electrically peelable pressure-sensitive adhesive sheet 1d having a structure in which the pressure-sensitive adhesive layer 3 is sandwiched between two release sheets 4 and 4' without using a base material as shown in Fig. 1(d) can be produced, for example, by directly applying a solution of the above-described pressure-sensitive adhesive composition to the peel surface of the release sheet 4 to form the pressure-sensitive adhesive layer 3, and then laminating another release sheet 4' on the surface of this pressure-sensitive adhesive layer 3. As described above, it is preferable that the release force of the release sheet 4 and the release sheet 4' be adjusted to be different.

[0117] 〔Properties of Electrically Peelable Pressure-Sensitive Adhesive Sheet〕 The pressure-sensitive adhesive sheet according to one embodiment of the present invention has a property of peeling on the cathode side when a voltage is applied to the pressure-sensitive adhesive layer. That is, peeling occurs between the adhesive surface of the pressure-sensitive adhesive layer connected to the cathode side and the adherend or base material attached to the adhesive surface. For example, consider a case where the electrically peelable pressure-sensitive adhesive sheet 1a of one aspect of the present invention is to be peeled from the adherend 11 as shown in FIG. 2(a). In FIG. 2(a), the pressure-sensitive adhesive layer 3 is sandwiched between the adherend 11 and the base material 2a. By connecting the anode terminal 51 of the voltage application device 50 to the base material 2a and the cathode terminal 52 to the adherend 11, a voltage can be applied between the two surfaces of the pressure-sensitive adhesive layer 3. When using the base material-free electrically peelable pressure-sensitive adhesive sheet 1d as shown in FIG. 1(d), the configuration of the "base material 2a" in FIG. 2 becomes another "adherend", and the pressure-sensitive adhesive layer 3 is sandwiched between two adherends. By connecting the anode terminal 51 and the cathode terminal 52 of the voltage application device 50 to the respective adherends, a voltage can be applied between the surfaces on both sides of the pressure-sensitive adhesive layer 3. When a voltage is applied in the state shown in FIG. 2(a), as shown in FIG. 2(b), the adhesive force decreases between the adhesive surface 3a of the pressure-sensitive adhesive layer connected to the cathode side and the adherend 11 adhered to the adhesive surface 3a, and the electrically peelable pressure-sensitive adhesive sheet 1a can be easily peeled from the adherend.

[0118] Conversely, as shown in FIG. 3(a), when the cathode terminal and the anode terminal are connected in reverse compared to FIG. 2, the adhesive force decreases between the adhesive surface 3a' of the pressure-sensitive adhesive layer connected to the cathode side and the base material 2a adhered to the adhesive surface 3a of the pressure-sensitive adhesive layer connected to the cathode side, and the base material 2a is peeled from the pressure-sensitive adhesive layer 3.

[0119] The applied voltage (applied voltage) is preferably 1 to 200 V, more preferably 3 to 140 V, and still more preferably 6 to 120 V. The time for applying the voltage within this range (application time) is preferably 1 to 180 seconds, more preferably 5 to 120 seconds, and still more preferably 10 to 90 seconds.

[0120] When the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to one aspect of the present invention is attached to a stainless steel plate as an adherend, the adhesive force before voltage application is preferably 20.0 N / 25 mm or more, more preferably 22.0 N / 25 mm or more, still more preferably 23.0 N / 25 mm or more, further preferably 24.0 N / 25 mm or more, still further preferably 24.5 N / 25 mm or more, even more preferably 26.0 N / 25 mm or more, and particularly preferably 29.0 N / 25 mm or more. In addition, when the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to one aspect of the present invention is attached to a stainless steel plate as an adherend and a voltage is applied at 10 V for 60 seconds, the adhesive force after the voltage application is preferably 2.0 N / 25 mm or less, more preferably 1.6 N / 25 mm or less, still more preferably 1.4 N / 25 mm or less, further preferably 1.3 N / 25 mm or less, still further preferably 1.2 N / 25 mm or less, and particularly preferably 1.0 N / 25 mm or less.

[0121] When the pressure-sensitive adhesive sheet according to one aspect of the present invention is attached to an adherend and a voltage of 10 V is applied for 60 seconds, the following formula (i) before and after the voltage application · Formula (i): [Adhesive force reduction rate (%)] = 100 - [Adhesive force of the test sheet after voltage application] / [Adhesive force of the test sheet before voltage application] × 100 The calculated adhesive force reduction rate is preferably 92.0% or more, more preferably 94.0% or more, still more preferably 95.0% or more, further preferably 96.0% or more, still further preferably 97.0% or more. In addition, in this specification, the method for measuring the adhesive force of the pressure-sensitive adhesive sheet before and after voltage application is based on the method described in the following examples.

[0122] 〔Method for using the electrically peelable pressure-sensitive adhesive sheet〕 The electrically peelable pressure-sensitive adhesive sheet according to one aspect of the present invention can be used by being attached to an arbitrary adherend. The adherend is not particularly limited and may or may not have conductivity. However, from the viewpoint of easily applying a voltage to the pressure-sensitive adhesive layer, it is preferable that the adherend has conductivity so that the adherend itself serves as an electrode. Examples of the adherend having conductivity include metals such as aluminum, tin-doped indium oxide, copper, iron, silver, platinum, and gold, and alloys of these metals (e.g., stainless steel). In particular, for the electrically peelable adhesive sheet according to one aspect of the present invention, even when the adherend is stainless steel, where it is difficult to sufficiently exhibit the adhesive force before voltage application and the reduction efficiency of the adhesive force due to voltage application, it has a high adhesive force before voltage application, while being able to significantly improve the reduction efficiency of the adhesive force due to voltage application. Therefore, the electrically peelable adhesive sheet according to one aspect of the present invention is preferably used for applications where stainless steel is the adherend.

[0123] From the above, the present invention also provides the following method of use described in [i]. [i] A method of using an electrically peelable adhesive sheet, which comprises attaching the electrically peelable adhesive sheet according to one aspect of the present invention to an adherend having conductivity. In the method of use described in the above [i], after attaching the electrically peelable adhesive sheet to an adherend having conductivity, when it is desired to peel off the adhesive sheet, voltage is applied to the adhesive layer, whereby it can be peeled off from the adherend. When applying voltage to the adhesive layer, voltage is applied while connecting such that the side of the adherend from which the adhesive sheet is to be peeled becomes the cathode. Also, as described above, the adhesive sheet has a high adhesive force before voltage application, while being able to significantly improve the reduction efficiency of the adhesive force due to voltage application, even when the adherend is stainless steel. Therefore, the adherend is preferably stainless steel.

Examples

[0124] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples at all. Also, each physical property value is a value measured by the method shown below.

[0125] (1) Weight average molecular weight (Mw) and number average molecular weight (Mn) Using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8020"), measurements were taken under the following conditions, and values measured in terms of standard polystyrene were used. (Measurement conditions) · Column: A series of columns connected in sequence: "TSK guard column HXL-L", "TSK gel G2500HXL", "TSK gel G2000HXL", and "TSK gel G1000HXL" (all manufactured by Tosoh Corporation) · Column temperature: 40 °C · Developing solvent: Tetrahydrofuran · Flow rate: 1.0 mL / min (2) Softening point Measured in accordance with the ring and ball method specified in JIS K5902. (3) Acid value, hydroxyl value Measured in accordance with the potentiometric titration method specified in JIS K0070.

[0126] Examples 1 - 6, Comparative Examples 1 - 2 (1) Preparation of the adhesive composition Each component was added in the types and amounts shown in Table 1, and diluted with ethyl acetate as the diluting solvent to prepare the adhesive composition. Details of each component used in the preparation of the adhesive compositions of the examples and comparative examples described in Table 1 are as follows. <Component (A): Base polymer> · "Acrylic polymer": A copolymer having structural units derived from n-butyl acrylate (BA), methyl acrylate (MA), and 2-hydroxyethyl acrylate (2-HEA) (structural unit ratio: BA / MA / 2-HEA = 60 / 20 / 20 (mass ratio)), Mw = 600,000. <Component (B): Ionic compound> · "Ionic liquid": Manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name "AS-210", 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, an ionic liquid that is liquid at room temperature (25 °C). <Component (C): Polypropylene glycol> · "PPG400": Polypropylene glycol with Mn = 400, a homopolymer consisting only of the structural unit (c1) represented by the general formula (c-1) (the compound represented by the general formula (c-2)), liquid at room temperature (25°C). · "PPG1000": Polypropylene glycol with Mn = 1000, a homopolymer consisting only of the structural unit (c1) represented by the general formula (c-1) (the compound represented by the general formula (c-2)), liquid at room temperature (25°C). · "PPG3000": Polypropylene glycol with Mn = 3000, a homopolymer consisting only of the structural unit (c1) represented by the general formula (c-1) (the compound represented by the general formula (c-2)), liquid at room temperature (25°C). <PAG: Polyalkylene glycol> · "PEG400": Polyethylene glycol with Mn = 400, a homopolymer consisting only of the structural units derived from ethylene oxide, liquid at room temperature (25°C). <Component (D): Rosin-containing diol> · "Rosin-containing diol": Manufactured by Arakawa Chemical Industries, Ltd., product name "Pink Crystal D-6011", rosin-containing diol, softening point = 84 - 99°C, acid value = 1 mgKOH / g or less, hydroxyl value = 110 - 125 mgKOH / g. <Component (E): Crosslinking agent> · "Isocyanate-based crosslinking agent": Manufactured by Tosoh Corporation, product name "Coronate L", isocyanate-based crosslinking agent.

[0127] (2) Preparation of the pressure-sensitive adhesive sheet On the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031", thickness: 38 μm, a polyethylene terephthalate (PET) film with a silicone release treatment on the surface), the pressure-sensitive adhesive composition prepared in the examples was applied to form a coating film so that the thickness after drying would be 30 μm, and the coating film was dried at 100°C for 2 minutes to form a pressure-sensitive adhesive layer on the release sheet. Then, the exposed surface of the formed adhesive layer was attached to the aluminum foil side of a PET film with aluminum foil as the base material (manufactured by Asia Aluminum Co., Ltd., thickness: 23 μm, a conductive base material in which a PET film, an adhesive layer, and an aluminum foil were laminated in this order), and a pressure-sensitive adhesive sheet with a base material having the same configuration as the electrical peelable pressure-sensitive adhesive sheet 1c shown in Fig. 1(c) was produced.

[0128] Using the produced pressure-sensitive adhesive sheet, based on the following method, the adhesive strength of the test sheet before and after applying power was measured, and the adhesive strength reduction rate was calculated. These results are shown in Table 1.

[0129] [Adhesive strength of the test sheet before voltage application] The produced pressure-sensitive adhesive sheet with a base material was cut into a size of 25 mm × 75 mm and used as a test sheet. In an environment of 23°C and 50% RH (relative humidity), the release sheet of the test sheet was removed, and it was attached to a stainless steel plate (SUS304, #360 polishing) as the adherend on the adhesive surface of the exposed adhesive layer. When attaching, a roller with a weight of 2 kg was used, and it was reciprocated once to crimp it to the adherend. The sample left standing for 30 minutes after attachment in an environment of 23°C and 50% RH (relative humidity) was used as a sample for measuring the adhesive strength. Then, in an environment of 23°C and 50% RH (relative humidity), using a tensile testing machine (manufactured by Orientec Co., Ltd., product name "Tensilon"), the value measured when peeling the test sheet of the sample for measuring the adhesive strength under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180° (unit: N / 25 mm) was taken as the adhesive strength of the test sheet before voltage application.

[0130] [Adhesive strength of the test sheet after voltage application] As shown in Fig. 2(a), the above sample for measuring the adhesive strength was used with a voltage application device 50 (manufactured by Takasago Seisakusho Co., Ltd., product name "KH-100H"). The anode terminal 51 was connected to the aluminum foil base material 2a, and the cathode terminal 52 was connected to the adherend 11, and a voltage of 10 V was applied for 60 seconds. After applying the voltage and leaving it for 1 minute, in an environment of 23°C and 50% RH (relative humidity), using a tensile testing machine (manufactured by Orientec Co., Ltd., trade name "Tensilon"), under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180°, the value measured (unit: N / 25 mm) when peeling the test sheet of the sample for measuring the adhesive force was taken as the adhesive force of the test sheet after applying the voltage. Then, from the adhesive force values of the test sheets before and after applying the voltage, the adhesive force reduction rate was calculated according to the following formula. · [Adhesive force reduction rate (%)] = 100 - [Adhesive force of the test sheet after applying the voltage] / [Adhesive force of the test sheet before applying the voltage] × 100 In addition, when the value of the adhesive force reduction rate becomes negative, it indicates that the adhesive force has increased due to the application of the voltage.

[0131]

Table 1

[0132] From Table 1, for the pressure-sensitive adhesive sheets prepared in Examples 1 to 6, even though the adhesive layer was as thin as 30 μm and the adherend was a stainless steel plate, the adhesive force before applying the voltage was as high as 20 N / 25 mm or more, while the adhesive force reduction rate due to applying the voltage was as high as 92% or more, resulting in an efficient reduction in the adhesive force. On the other hand, for the pressure-sensitive adhesive sheets prepared in Comparative Examples 1 to 2, compared with the pressure-sensitive adhesive sheets of the examples, both the adhesive force before applying the voltage and the adhesive force reduction rate due to applying the voltage were inferior.

Explanation of symbols

[0133] 1a, 1b, 1c, 1d Electrically peelable pressure-sensitive adhesive sheet 2, 2a Substrate 3, 3’ Adhesive layer 3a, 3a’ Adhesive surface 4, 4’ Release sheet 11 Adherend 50 Voltage application device 51 Anode terminal 52 Cathode terminal

Claims

1. An electrically peelable pressure-sensitive adhesive composition comprising a base polymer (A), an ionic compound (B), and a polypropylene glycol (C) having a number-average molecular weight of 200 to 3500, wherein the base polymer (A) contains an acrylic polymer (A1), the ionic compound (B) contains an ionic liquid (B3), an electrically peelable pressure-sensitive adhesive composition.

2. The electrically peelable pressure-sensitive adhesive composition according to claim 1, wherein the blending ratio of the component (B) is 1.0 part by mass or more with respect to 100 parts by mass of the total amount of the component (A).

3. The electrically peelable pressure-sensitive adhesive composition according to claim 1 or 2, wherein the blending ratio of the component (C) is 0.1 part by mass or more with respect to 100 parts by mass of the total amount of the component (A).

4. The electrically peelable pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the blending amount ratio [(C) / (B)] of the component (C) to the component (B) is 0.01 to 10.0 in terms of mass ratio.

5. The electrically peelable pressure-sensitive adhesive composition according to any one of claims 1 to 4, further comprising a crosslinking agent (E).

6. The electrically peelable pressure-sensitive adhesive composition according to claim 5, wherein the blending ratio of the component (E) is 0.01 part by mass or more with respect to 100 parts by mass of the total amount of the component (A).

7. The electrically peelable pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the content of the active ingredient that is liquid at 25°C is 1 to 50% by mass with respect to the total amount of the active ingredient in the pressure-sensitive adhesive composition.

8. An electrically peelable pressure-sensitive adhesive sheet having an adhesive layer formed from the electrically peelable pressure-sensitive adhesive composition according to any one of claims 1 to 7.

9. The electrically peelable pressure-sensitive adhesive sheet according to claim 8, wherein the thickness of the adhesive layer is 40 μm or less.

10. The electrically peelable pressure-sensitive adhesive sheet according to claim 8 or 9, having a conductive substrate and having the adhesive layer on at least one surface side of the conductive substrate.

11. The electrically peelable pressure-sensitive adhesive sheet according to any one of claims 8 to 10, which peels off on the cathode side when a voltage is applied to the adhesive layer.

12. The electrically peelable pressure-sensitive adhesive sheet according to any one of claims 8 to 11, satisfying the following requirement (I). - Requirement (I): The adhesive force reduction rate calculated from the following formula (i), which shows the change in the adhesive force before and after the voltage application for 60 seconds at 10 V, is 50% or more. Formula (i): [Adhesive force reduction rate (%)] = 100 - [Adhesive force after voltage application] / [Adhesive force before voltage application] × 100

13. A method of using an electrically peelable adhesive sheet according to any one of claims 8 to 12, wherein the electrically peelable adhesive sheet is attached to an adherend having conductivity.

14. The method of using an electrically peelable adhesive sheet according to claim 13, wherein after the electrically peelable adhesive sheet is attached to an adherend having conductivity, a voltage is applied to the adhesive layer to peel the sheet from the adherend.

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