Electrically releasable adhesive sheet and method for producing the same

Abstract

The present invention addresses the problem of providing an electrically removable pressure-sensitive adhesive sheet which is thin and is easy to apply to adherends. The electrically removable pressure-sensitive adhesive sheet comprises a flat core and a pressure-sensitive adhesive layer comprising an electrically removable pressure-sensitive adhesive composition, wherein the core has a basis weight of 10.0 g / m2 or less and a thickness of 10-35 μm and the electrically removable pressure-sensitive adhesive composition comprises an acrylic polymer and an ionic liquid, the pressure sensitive adhesive sheet being a double-sided pressure-sensitive adhesive sheet.

Description

Technical Field

[0001] The present invention relates to an electrically releasable pressure-sensitive adhesive sheet. The present invention relates to a method for manufacturing an electrically releasable pressure-sensitive adhesive sheet.

Background Art

[0002] Adhesives and adhesive sheets having adhesiveness to an adherend and peelability from the adherend are used in various applications (for example, surface protection films, masking tapes for painting, removable notes, etc.). As methods for peeling an adhesive from an adherend, in addition to physical methods, methods of peeling by stimulation with light, heat, vibration, or energization are known. For example, Patent Document 1 describes that an adhesive (electrically releasable adhesive) that can be peeled from an adherend by applying a voltage can be provided by using a polymer and an ionic liquid in the adhesive. Further, Patent Document 2 describes that an electrically releasable adhesive without adhesive residue can be provided by examining conditions such as a migration promoter used together with a polymer or an ionic liquid even when a low voltage is applied.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to achieve good electrical peelability of an adhesive sheet having electrical peelability, it is necessary to select the material of the core material. For example, films such as polyethylene terephthalate (PET) used in general adhesive tapes are insulators, so a double-sided tape using PET as the core material does not exhibit electrical peelability. Therefore, for adhesive sheets such as double-sided tapes having electrical peelability, it was necessary to use a porous material such as non-woven fabric as the core material. However, in a conventional electrical peelable adhesive sheet using non-woven fabric, it is necessary to increase the thickness of the adhesive layer in order to achieve electrical peeling, resulting in an increase in the thickness of the adhesive sheet. In addition, an electrical peelable adhesive without a core material has a shape of the adhesive surface that easily changes and is difficult to attach to an adherend. For this reason, there has been a demand for an electrical peelable adhesive sheet that is thin and easy to attach to an adherend.

Means for Solving the Problems

[0005] The inventors of the present invention have found that by using a core material having a basis weight of 10.0 g / m 2 or less and a thickness of 10 μm to 35 μm, it is possible to provide an electrical peelable adhesive sheet that is thin and easy to attach to an adherend without affecting the electrical peelability, and thus arrived at the present invention. Thus, the present invention is an electrical peelable adhesive sheet including a planar core material and an adhesive layer containing an electrical peelable adhesive composition, wherein the core material has a basis weight of 10.0 g / m 2 or less and a thickness of 10 μm to 35 μm, the electrical peelable adhesive composition is a composition containing an acrylic polymer and an ionic liquid, and the adhesive sheet is a double-sided adhesive sheet.

[0006] Furthermore, according to the present invention, there is provided a method for manufacturing an electrical peelable adhesive sheet, including a step of bringing an electrical peelable adhesive composition containing an acrylic polymer and an ionic liquid into contact with a planar core material having a basis weight of 10.0 g / m 2 or less and a thickness of 10 μm to 35 μm to form an adhesive layer.

Effects of the Invention

[0007] According to the present invention, there is provided an electrically peelable adhesive sheet that does not affect the electrical peelability, is thin, and is easily attachable to an adherend.

Brief Description of the Drawings

[0008]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 6A

Figure 6B

Best Mode for Carrying Out the Invention

[0009] In this specification, "x to y" (where x and y are specific values) means x or more and y or less, unless otherwise specified.

[0010] [Electrically Peeling Adhesive Sheet] The electrically peeling adhesive sheet of this embodiment (hereinafter, also simply referred to as "adhesive sheet") includes an adhesive layer containing a planar core material and an electrically peeling adhesive composition (hereinafter, also simply referred to as "composition"), and a part or all of each of the two sides of the sheet has adhesiveness. That is, the adhesive sheet of the present invention is, for example, in the form of a double-sided sheet or double-sided tape. Further, the adhesive sheet of this embodiment has electrical peelability. This electrical peelability means that an adherend or a fixed object described later can be adhered and fixed using the adhesive sheet, and the voltage is applied to reduce the adhesiveness of the adhesive sheet, so that the adherend or the fixed object can be detached. It is preferable that the adhesive sheet has an adhesive force of 10 N / 25 mm or more before the application of voltage.

[0011] The thickness of the adhesive sheet is not particularly limited, but is preferably 1 to 200 μm, more preferably 1 to 100 μm, still more preferably 1 to 80 μm, still more preferably more than 1 μm and less than 80 μm, still more preferably 5 to 60 μm, still more preferably 5 to 50 μm, and still more preferably 10 to 50 μm. The upper limit of the thickness of the adhesive sheet is, for example, 200, 150, 100, 90, 80, 79, 75, 70, 65, 60, 55, 50 μm. The lower limit of the thickness of the adhesive sheet is, for example, 1, 3, 5, 10, 15, 20, 25, 29, 30 μm.

[0012] The thickness of the adhesive sheet and the core material can be measured using a known thickness measuring instrument. Examples of the thickness measuring instrument include a Peacock precision measuring instrument. The thickness here refers to the average value obtained by measuring at least five randomly selected points or more from the measurement object using the thickness measuring instrument.

[0013] (Core material) The core material in this embodiment refers to a planar object that can form an adhesive layer together with the electro-releasable adhesive composition described later. The core material does not have to be completely flat, and a part or all of it may have unevenness. Further, the core material may have at least one through hole. The core material is not particularly limited as long as it allows the adhesive layer to conduct ions when a voltage is applied to the adhesive sheet and can satisfy the following properties (thickness, basis weight).

[0014] In order for the adhesive layer of the adhesive sheet to exhibit ion conductivity, for example, the core material is composed of fibers, and this can be achieved by allowing the composition to penetrate into the gaps between the fibers.

[0015] The material of the core material is not particularly limited as long as it can satisfy the following properties (thickness, basis weight). Examples of the core material include fibers such as plant fibers and inorganic / chemical fibers, and porous films. Among these, it is preferably composed of fibers, and more preferably composed of plant fibers. Examples of the core material composed of plant fibers include woodfree paper and Japanese paper. Examples of the core material composed of inorganic / chemical fibers include non-woven fabrics and woven fabrics such as polyester (particularly non-woven fabrics made of polyethylene terephthalate), carbon fibers, and glass fibers. Examples of the porous film include films made of polyimide and polyester. Since the core material is composed of fibers, the composition can penetrate into the gaps between the fibers and exhibit ion conductivity when a voltage is applied. The core material is preferably an insulator, and more preferably fibers made of an insulator. Examples of the fibers made of an insulator include plant fibers and polyester fibers.

[0016] The thickness of the core material is 10 to 35 μm, preferably 10 to 30 μm. The upper limit of the thickness of the core material is, for example, 35, 34, 33, 32, 31, 30 μm. The lower limit of the thickness of the core material is, for example, 10, 11, 12, 13, 14 μm.

[0017] The basis weight of the core material is 10.0 g / m 2is as follows, 2.0 to 10.0 g / m 2 is preferably, 2.0 to 9.0 g / m 2 is more preferably, 2.0 to 8.0 g / m 2 is more preferable. The upper limit of the basis weight is, for example, 10.0, 9.5, 9.0, 8.5, 8.4, 8.3, 8.2, 8.1, 8.0 g / m 2 is. The lower limit of the basis weight is, for example, 2.0, 2.3, 2.5, 2.7, 2.9, 3.0, 3.2, 3.5, 3.8, 3.9, 4.0 g / m 2 is.

[0018] When the core material is thicker than 35 μm, the thickness of the adhesive sheet becomes thicker. Further, when the fiber used for the core material is a non-conductive fiber and the basis weight of the core material is greater than 10.0 g / m 2 In the case of being larger, since it is difficult for the composition to penetrate into the gaps between the fibers, the adhesive sheet to be manufactured may not have a decrease in adhesive force even when a voltage is applied. The core material has a basis weight of 10.0 g / m 2 or less and a thickness of 10 μm to 35 μm, it does not affect the electrical peelability and can be made into a thin adhesive sheet.

[0019] The adhesive layer may consist only of the electro-strippable adhesive composition that has penetrated into the core material, or an electro-strippable adhesive composition layer may be formed by the electro-strippable adhesive composition contacting each of one or both sides of the core material. In this case, the electro-strippable adhesive composition layer is also referred to as an electro-strippable adhesive layer. When the adhesive layer consists only of the composition that has penetrated into the core material, both sides of the core material are in a state of having adhesiveness due to the composition.

[0020] The electro-strippable adhesive sheet of the present invention may be defined by density. That is, the electro-strippable adhesive sheet of the present invention is an electro-strippable adhesive sheet including a planar core material and an adhesive layer containing an electro-strippable adhesive composition, wherein the core material is 2.0 g / cm 3Also provided is an electrically peelable pressure-sensitive adhesive sheet having the following density and a thickness of 10 μm to 35 μm, wherein the electrically peelable pressure-sensitive adhesive composition is a composition containing an acrylic polymer and an ionic liquid, and the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet.

[0021] The density of the core material is 2.0 g / cm 3 is as follows, 0.1 to 1.5 g / cm 3 is preferably, 0.1 to 1.0 g / cm 3 is more preferably, 0.1 to 0.8 g / cm 3 is more preferably, 0.1 to 0.6 g / cm 3 is more preferably, 0.1 to 0.5 g / cm 3 is more preferably. The upper limit of the density is, for example, 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5 g / cm 3 is. The lower limit of the density is, for example, 0.1, 0.15, 0.2 g / cm 3 is.

[0022] [Electrically Peelable Pressure-Sensitive Adhesive Composition] The electrically peelable pressure-sensitive adhesive composition of this embodiment contains at least an acrylic polymer and an ionic liquid. (Acrylic Polymer) The acrylic polymer of this embodiment can be obtained by polymerizing an acrylic monomer in the presence of an arbitrary polymerization initiator. Any polymer can be used as long as the acrylic polymer can adhere to a conductive object. A conductive object refers to a conductive adherend, a conductive auxiliary material, a conductive core material, or a conductive object to be fixed (these definitions will be described later). From the viewpoint of adhesiveness, the weight average molecular weight of the acrylic polymer is preferably 10 to 5 million, more preferably 20 to 4 million, and even more preferably 30 to 3 million. Here, the weight average molecular weight refers to the weight average molecular weight in terms of polystyrene. Specifically, it may be the weight average molecular weight in terms of polystyrene calculated using GPC (System21) of Shodex with tetrahydrofuran as the mobile phase.

[0023] The glass transition temperature (Tg) of the acrylic polymer is preferably 0 °C or lower, more preferably -20 °C or lower, and even more preferably -40 °C or lower. The above Tg can be calculated, for example, based on the Fox equation of the following formula. 1 / Tg = (W1 / Tg1) + (W2 / Tg2) + ····· + (Wn / Tgn) The glass transition temperature can be measured, for example, by differential thermal analysis (DTA).

[0024] The acrylic polymer may be crosslinked by the action of a crosslinking agent. Examples of the crosslinking agent include isocyanate-based crosslinking agents such as toluene diisocyanate and methylene bisphenyl isocyanate. The amount of the crosslinking agent is preferably 1 to 10 parts by weight or less, more preferably 3 to 10 parts by weight, and even more preferably 5 to 10 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. By crosslinking the acrylic polymer, when the composition is formed as a layer on the core material, the creep resistance and / or shear resistance of the layer can be improved.

[0025] The above acrylic polymer more preferably contains a copolymer of an alkyl (meth)acrylate having an alkyl group with 1 to 8 carbon atoms, a carboxyl group-containing acrylic monomer, and / or a hydroxyl group-containing acrylic monomer. By the acrylic polymer containing these copolymers, a composition excellent in adhesive strength is obtained.

[0026] (Acrylic monomer) The acrylic monomer preferably contains an alkyl (meth)acrylate having an alkyl group with 1 to 14 carbon atoms as a main component (50% by weight or more). Note that (meth)acrylate means methacrylate or acrylate.

[0027] Examples of the alkyl (meth)acrylate having an alkyl group with 1 to 14 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, dodecyl (meth)acrylate, and the like. These alkyl (meth)acrylates may be used alone or in combination of two or more. Among these alkyl (meth)acrylates, alkyl (meth)acrylates having an alkyl group with 1 to 8 carbon atoms are preferred, alkyl (meth)acrylates having an alkyl group with 1 to 4 carbon atoms are more preferred, n-butyl (meth)acrylate is more preferred, and n-butyl acrylate is more preferred.

[0028] Examples of other acrylic monomers include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, and carboxyethyl acrylate, and hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. These other acrylic monomers may be used alone or in combination of two or more. As other acrylic monomers, it is preferable that either a carboxyl group-containing monomer or a hydroxyl group-containing monomer, or both are included.

[0029] The acrylic monomer may consist only of alkyl (meth)acrylate without using the above-mentioned other acrylic monomers. Further, from the viewpoint of easily obtaining a composition having desired performance, it is preferable that other acrylic monomers are contained in an amount of 1% by weight or more and less than 50% by weight, more preferably 5 to 30% by weight, and even more preferably 5 to 15% by weight.

[0030] Also, when either a carboxyl group-containing monomer or a hydroxyl group-containing monomer, or both are included, the total content of these two monomers is not particularly limited, but when the total monomer amount is 100 parts by weight, it is preferably 1 to 20 parts by weight. By using these two monomers within this range, the adhesive properties can be improved. Furthermore, the total content of the two monomers is more preferably 1 to 10 parts by weight.

[0031] Furthermore, a vinyl monomer may be added to the (meth)acrylate as needed. Examples of the vinyl monomer include itaconic acid, maleic acid, crotonic acid, maleic anhydride, itaconic anhydride, vinyl acetate, N-vinylpyrrolidone, N-vinyl carboxamides, styrene, and N-vinylcaprolactam. These vinyl monomers may be used alone or in combination of two or more. (Polymerization initiator) Examples of the polymerization initiator that can be arbitrarily used include azo polymerization initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylpropionamidine) disulfide, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4,4-trimethylpentane), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis[2-methyl-N-(phenylmethyl)-propionamidine] dihydrochloride, 2,2'-azobis[2-(3,4,5,6-tetrahydropyrimidin-2-yl)propane] dihydrochloride, and 2,2'-azobis[2-(2-imidazolin-2-yl)propane]; persulfate-based polymerization initiators such as potassium persulfate and ammonium persulfate; peroxide-based polymerization initiators such as benzoyl peroxide, hydrogen peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy) cyclododecane, 3,3,5-trimethylcyclohexanoyl peroxide, and t-butyl peroxy pivalate; redox-based polymerization initiators composed of persulfate and sodium bisulfite, etc. These polymerization initiators may be used alone or in combination of two or more. Also, ultraviolet irradiation or radiation irradiation may be performed. The polymerization initiator is preferably used in an amount of 0.005 parts by weight or more and 1 part by weight or less based on 100 parts by weight of the acrylic monomer. By using the polymerization initiator within this range, an acrylic polymer excellent in adhesive properties can be formed.

[0032] (Ionic liquid) An ionic liquid is a combination of a cation and an anion that is liquid at room temperature and is also called a room-temperature molten salt. Ionic liquids have properties such as non-flammability, non-volatility, and chemical stability. When a voltage is applied to an ionic liquid, anions move to the anode side and cations move to the cathode side. It is considered that the adhesion of the composition weakens due to the movement of anions and cations near the electrodes or the redox reaction of anions or cations at the interface between the electrodes and the composition, and as a result, the peelability is improved.

[0033] The ionic conductivity of the ionic liquid is not particularly limited, but it preferably has an ionic conductivity of 10 -7 S / cm or more, more preferably has an ionic conductivity of 10 -6 ~10 -1 S / cm, and even more preferably has an ionic conductivity of 10 -4 ~10 -2 S / cm, and even more preferably has an ionic conductivity of 10 -3 ~10 -2 S / cm. The ionic conductivity can be measured, for example, by the AC impedance method. The measurement of the ionic conductivity of an ionic liquid by the AC impedance method can be performed, for example, as follows.

[0034] At room temperature, using a two-electrode cell, place the ionic liquid on stainless steel, and then place another stainless steel plate on top of the ionic liquid to sandwich the ionic liquid between the stainless steel plates. Control it into a disk shape with a certain area and thickness using a spacer to obtain a sample. Apply a voltage to this sample, and determine the bulk resistance (Ω) by curve fitting the Cole-Cole plot obtained when changing the frequency that defines the amplitude using an equivalent circuit. By substituting the area A of the sample, the thickness L of the sample, and the bulk resistance Rb into the following formula, the ionic conductivity δ of the ionic liquid can be calculated. δ = L / (Rb × A) [δ: ionic conductivity, Rb: bulk resistance, L: thickness of the sample (cm), A: area of the sample (cm 2 )]

[0035] Examples of the ionic liquid include a combination of a cyclic cation represented by the following formula (1) and an anion.

[0036] [Chemical formula] [In the formula, R 1 is a divalent hydrocarbon group having 2 to 8 carbon atoms which may contain a hetero atom, and forms a ring together with N + in the formula, and R 2 and R 3 are the same or different and are a hydrogen atom or an alkyl group having 1 to 6 carbon atoms (however, when the nitrogen atom forms a double bond with an adjacent carbon atom, R 3 does not exist), X - is Cl - , Br - , I - , AlCl4 - , Al2Cl7 - , NO3 - , BF4 - , PF6 - , ClO4 - , CH3COO - , CF3COO - , CF3SO3 - , (CF3SO2)2N - , (FSO2)2N - , (CF3SO2)3C - , AsF6 - , SbF6 - , NbF6-, F(HF) n - , B(C6H5)4 - , C4F9SO3 - , CF3(CF2)3SO3 - , (CF3CF2SO2)2N - and CF3CF2COO - which is an anion selected from]

[0037] In the above formula, R 1 and N +The ring composed of the following contains a ring in which at least one carbon atom constituting a hydrocarbon ring such as a saturated alicyclic hydrocarbon like cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane and cyclooctane, or an unsaturated cyclic hydrocarbon like cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclopentadiene and benzene, etc. is replaced by a nitrogen atom. Examples of heteroatoms include N, O, S, P, etc., and preferably N.

[0038] Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group, etc. The alkyl group having 3 to 8 carbon atoms includes structural isomers.

[0039] Another example of the ionic liquid includes, for example, a combination of a cation and an anion represented by the following formula (2) or (3).

[0040]

Chemical formula

[0041] [Chemical formula] [In the formula, R 8 ~ R 10 are the same or different and are a hydrogen atom (provided that not all of R 8 ~ R 10 are hydrogen atoms) or a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, which may have a substituent, and the substituent is selected from the group consisting of a halogen atom, a hydroxy group, a nitro group, and a cyano group, X - is Cl - 、Br - 、I - 、AlCl4 - 、Al2Cl7-, NO3 - 、BF4 - 、PF6 - 、ClO4 - 、CH3COO - 、CF3COO - 、CF3SO3 - 、(CF3SO2)2N - 、(FSO2)2N - 、(CF3SO2)3C - 、AsF6 - 、SbF6 - 、NbF6-, F(HF) n - 、B(C6H5)4 - 、C4F9SO3 - 、CF3(CF2)3SO3- 、(CF3CF2SO2)2N - and CF3CF2COO - is an anion selected from]

[0042] The cation in the ionic liquid preferably has a weight average molecular weight of 700 or less, more preferably has a weight average molecular weight of 50 to 600, still more preferably has a weight average molecular weight of 50 to 500, and still more preferably has a weight average molecular weight of 50 to 400. The upper limit of the weight average molecular weight of the cation in the ionic liquid is, for example, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 200, 150. The lower limit of the weight average molecular weight of the cation in the ionic liquid is, for example, 30, 40, 50, 60, 70, 80, 90, 99, 100. The weight average molecular weight referred to here means the weight average molecular weight in terms of polystyrene.

[0043] The ionic liquid is preferably a combination of a cyclic cation represented by the formula (1) and an anion, and a cation selected from pyridinium-based cations, cyclic aliphatic ammonium cations and imidazolium-based cations, and (FSO2)2N - , (CF3SO2)2N - and BF4 - and an anion selected from, and a combination of a cation selected from imidazolium-based cations and an anion selected from (FSO2)2N-, (CF3SO2)2N- and BF4- is more preferable from the viewpoint of improving the peelability after application of voltage.

[0044] Ionic liquids are available from Daiichi Sankyo, Kanto Chemical, Hiroei Chemical Industry Co., Ltd., etc. For example, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMI-FSI) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI-TFSI) from Daiichi Sankyo, 1-hexylpyridinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide and 1-ethyl-3-methylimidazolium tetrafluoroborate from Kanto Chemical, 1-ethyl-3-methylimidazolium hexafluorophosphate (IL-C3), 1-butylpyridinium tetrafluoroborate (IL-P10) and 1-hexylpyridinium bis(trifluoromethanesulfonyl)imide (IL-P14) from Hiroei Chemical Industry Co., Ltd. can be obtained. The combinations of cations and anions contained in EMI-FSI and EMI-TFSI are as follows.

[0045] [Chemical formula]

[0046] [Chemical formula]

[0047] The amount of the ionic liquid contained in the composition is not particularly limited, but it is preferably 1 to 90 parts by weight, more preferably 5 to 80 parts by weight, more preferably 5 to 60 parts by weight, more preferably 5 to 50 parts by weight, more preferably 5 to 40 parts by weight, and more preferably 5 to 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. The upper limit of the amount of the ionic liquid contained in the composition is, for example, 90 parts by weight, 85 parts by weight, 80 parts by weight, 70 parts by weight, 60 parts by weight, 50 parts by weight, 45 parts by weight, 40 parts by weight, 35 parts by weight, 33 parts by weight, 32 parts by weight, 31 parts by weight, 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. The lower limit of the amount of the ionic liquid contained in the composition is, for example, 1 part by weight, 3 parts by weight, 5 parts by weight, 7 parts by weight, 9 parts by weight, 10 parts by weight, 12 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight with respect to 100 parts by weight of the acrylic polymer. The ionic liquid may be a combination of one cation and one anion, or a combination of a plurality of types of cations and anions.

[0048] (Migration promoter) In this embodiment, the composition may contain a migration promoter that assists the migration of ions when a voltage is applied. Examples of the migration promoter include polyethylene glycol, alkyl ethers of polyethylene glycol, etc., and alkyl ethers of polyethylene glycol are preferred.

[0049] The molecular weight of the migration promoter is not particularly limited, but preferably has a weight average molecular weight of 120 to 600, more preferably has a weight average molecular weight of 120 to 550, still more preferably has a weight average molecular weight of 120 to 500, and even more preferably has a weight average molecular weight of 120 to 360. The upper limit of the weight average molecular weight of the migration promoter is, for example, 600, 590, 580, 570, 560, 550, 540, 530, 520, 510, 500, 490, 480, 470, 460, 450, 440, 430, 420, 410, 400, 390, 380, 370, 360, 355, 350, 340. The lower limit of the weight average molecular weight of the migration promoter is, for example, 120, 125, 130, 135, 140, 145, 150, 155, 160, 170. The weight average molecular weight referred to here means the weight average molecular weight in terms of polystyrene.

[0050] Examples of the alkyl ether of polyethylene glycol include polyethylene glycol mono(di)methyl ether, polyethylene glycol mono(di)ethyl ether, polyethylene glycol mono(di)propyl ether, polyethylene glycol mono(di)isopropyl ether, polyethylene glycol mono(di)butyl ether, polyethylene glycol mono(di)isobutyl ether, polyethylene glycol mono(di)methyl ether, and polyethylene glycol mono(di)pentyl ether. Among these, the alkyl ether of polyethylene glycol having a weight average molecular weight of 120 to 360 is preferred, the polyethylene glycol mono(di)methyl ether having a weight average molecular weight of 120 to 360 is more preferred, and it is more preferably selected from tetraethylene glycol dimethyl ether (dimethyltetraglycol), diethylene glycol dibutyl ether, triethylene glycol butyl methyl ether, dimethyltriglycol, and triethylene glycol monomethyl ether, and even more preferably tetraethylene glycol dimethyl ether. The alkyl ether of polyethylene glycol is available from Nippon Emulsifier, Toho Chemical Industry, etc. The alkyl ether of polyethylene glycol used may be used alone or in combination of two or more.

[0051] The amount of the migration promoter contained in the composition is not particularly limited. For example, it may be 1 to 90 parts by weight, 5 to 80 parts by weight, 5 to 50 parts by weight, 5 to 40 parts by weight, or 5 to 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. The upper limit of the migration promoter contained in the composition is, for example, 90 parts by weight, 80 parts by weight, 70 parts by weight, 60 parts by weight, 50 parts by weight, 40 parts by weight, or 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. The lower limit of the migration promoter contained in the composition is, for example, 1 part by weight, 3 parts by weight, 5 parts by weight, 7 parts by weight, 9 parts by weight, 10 parts by weight, 12 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, or 20 parts by weight with respect to 100 parts by weight of the acrylic polymer.

[0052] (Organic solvent) The composition may contain an organic solvent. The organic solvent is not particularly limited, and examples thereof include known organic solvents that can be used in adhesives. As the organic solvent, either a hydrophilic organic solvent or a hydrophobic organic solvent may be used. Examples of the hydrophilic organic solvent include methanol, ethanol, 1-propanol, 2-propanol, n-butyl alcohol, sec-butyl alcohol, isobutanol, tert-butyl alcohol, acetonitrile, acetone, dimethylformamide, and the like. Examples of the hydrophobic organic solvent include aliphatic hydrocarbons such as hexane, heptane, and isooctane; esters such as methyl acetate, ethyl acetate, and propyl acetate; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; halogenated hydrocarbons such as dichloromethane, 1,2-dichloroethane, chloroform, 1-chlorobutane, and chlorobenzene; ethers such as diethyl ether and t-butyl methyl ether; ketones such as methyl ethyl ketone and methyl isobutyl ketone. These organic solvents may be used alone or in combination of two or more. When using an organic solvent, it is preferable to adjust the usage ratio so that the solid content consisting of the acrylic polymer is 10% by weight or more. More preferably, the usage ratio is adjusted so that the solid content is 20% by weight or more and 50% by weight or less.

[0053] (Additive) In addition to the above components, the composition of this embodiment may contain additives such as a conductive material, a filler, a plasticizer, an antioxidant, a flame retardant, a colorant, a surfactant, or an adhesive other than the above acrylic polymer.

[0054] As conductive materials, there are mainly carbon-based conductive materials and metal-based conductive materials. Examples of carbon-based conductive materials include nanocarbon or carbon fibers [such as vapor-grown carbon fibers (VGCF) or carbon nanofibers], and more specifically, natural graphite, artificial graphite, acetylene black, ketjen black, furnace black, etc. Examples of metal-based conductive materials include metals such as Cu, Ni, Al, Ag, Au, Pt, Zn, or Mn, or alloys thereof. The conductive materials may be used alone or in combination of multiple types.

[0055] Examples of fillers include silica, diatomaceous earth, alumina, zinc oxide, magnesium oxide, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, calcium silicate, talc, mica, bentonite, activated clay, glass fiber, aluminum nitride, etc. The fillers may be used alone or in combination of multiple types.

[0056] Examples of plasticizers include polyols such as glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, polyethylene glycol, etc., aliphatic polycarboxylic acid esters such as adipic acid ester, citric acid ester, sebacic acid ester, azelaic acid ester, maleic acid ester, etc., aromatic polycarboxylic acid esters such as terephthalic acid ester, isophthalic acid ester, phthalic acid ester, trimellitic acid ester, benzoic acid ester, etc., and polyesters. The plasticizers may be used alone or in combination of multiple types.

[0057] Examples of antioxidants include phenolic antioxidants, amine antioxidants, lactone antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. The antioxidants may be used alone or in combination of multiple types.

[0058] Examples of flame retardants include addition and reaction type flame retardants such as phosphorus and halogen-containing organic compounds, bromine or chlorine-containing organic compounds, ammonium polyphosphate, aluminum hydroxide, antimony oxide, etc. The flame retardant may be used alone or in combination of multiple types.

[0059] Examples of colorants include inorganic pigments such as carbon black, titanium oxide, zinc oxide, iron oxide, mica, etc., and organic pigments such as coupling azo-based, condensed azo-based, anthraquinone-based, thioindigo-based, dioxazone-based, phthalocyanine-based, etc. The colorant may be used alone or in combination of multiple types.

[0060] Examples of surfactants include anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, cationic surfactants such as amine salts (alkylamine salts, imidazoline, etc.), quaternary ammonium salts (dialkyldimethylammonium salts, alkylbenzyldimethylammonium salts, pyridinium salts, benzethonium chloride, etc.), and nonionic surfactants such as sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, monoglyceride stearate, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecyl ether, etc. The surfactant may be used alone or in combination of multiple types.

[0061] Examples of the adhesive other than the above acrylic polymer include silicone adhesives, polyester adhesives, urethane adhesives, rubber adhesives, etc. Examples of the silicone adhesive include dimethylsiloxane-based and diphenylsiloxane-based ones. Examples of the polyester adhesive include polyesters obtained by polycondensing a carboxylic acid component and a diol component having two or more functional groups. Examples of the urethane adhesive include urethane polymers obtained by reacting a polyol and a polyisocyanate compound. Examples of the rubber adhesive include synthetic rubbers such as styrene-isoprene block copolymers, styrene-butadiene-styrene block copolymers, styrene-butadiene rubbers, polyisoprene rubbers, polyisobutylene, and butyl rubber, and natural rubbers.

[0062] The amount of these adhesives other than the above acrylic polymer is less than 100 parts by weight, preferably 90 parts by weight or less, more preferably 80 parts by weight or less, more preferably 70 parts by weight or less, more preferably 60 parts by weight or less, more preferably 50 parts by weight or less, more preferably 40 parts by weight or less, more preferably 30 parts by weight or less, more preferably 20 parts by weight or less, more preferably 10 parts by weight or less, more preferably 5 parts by weight or less, more preferably 3 parts by weight or less, and more preferably no adhesive other than the acrylic polymer is included, based on 100 parts by weight of the acrylic polymer.

[0063] The amount of these additives (excluding the adhesive other than the above acrylic polymer) contained in the composition is not particularly limited, but can be, for example, 0.1 to 200 parts by weight, and can be 1 to 100 parts by weight, based on 100 parts by weight of the acrylic polymer.

[0064] The method for forming the adhesive layer or the electrically peelable adhesive layer is not particularly limited. For example, it can be formed by applying a composition to a film of polyethylene terephthalate (release film) that has been subjected to a release treatment (release film), etc., and laminating a core material thereto. After applying the composition to the release film, the composition may be heated to dry the composition. As another example of forming the adhesive layer or the electrically peelable adhesive layer, it can be formed by applying the composition to the core material. The application method of these compositions is not particularly limited, but examples include directly applying with a brush or the like, or using an application device used in the production of adhesive tapes. As the application device, a spin coater, a gravure coater, an applicator, a multi-coater, a die coater, a bar coater, a roll coater, a blade coater, or a knife coater, etc. can be used. The thickness of the electrically peelable adhesive layer is not particularly limited, but it is preferably 1 to 100 μm, more preferably 1 to 50 μm, and even more preferably 5 to 30 μm. When the electrically peelable adhesive layers are formed on both sides of the adhesive layer, the two electrically peelable adhesive layers may have the same thickness or different thicknesses respectively.

[0065] The adhesive sheet of this embodiment functions as a substance for fixing an object (referred to as a fixing target object) to be fixed to an adherend by the adhesive sheet to the adherend. The use surface of the adhesive sheet may be protected by a release film, release paper, etc. until use.

[0066] The adherend of this embodiment refers to an object that provides a place where the fixing target object is fixed via the adhesive sheet of this embodiment. Here, there are direct fixing and indirect fixing. Direct fixing refers to a state where the adherend and the fixing target object are in direct contact with the adhesive sheet, and indirect fixing refers to a state where the adherend and / or the fixing target object do not directly touch the adhesive sheet and are in contact via a conductive auxiliary material. As long as the fixing target object can be fixed to the adherend, the fixing method may be direct fixing or indirect fixing.

[0067] The adherend may be a conductive adherend (conductive adherend) or a non-conductive adherend (non-conductive adherend). When the adherend is a conductive adherend, the adhesive sheet may be directly attached to the adherend. When the adherend is a non-conductive adherend, it is essential to attach a conductive auxiliary material to the non-conductive adherend. When attaching the conductive auxiliary material, any adhesive such as a commercially available adhesive can be used.

[0068] Examples of the conductive adherend include a metal plate, a metal product, or a metal workbench made of a metal such as iron, aluminum, copper, silver, gold, or an alloy of these metals. Examples of the non-conductive adherend include a wooden plywood, a plastic product, or a non-metal workbench.

[0069] The object to be fixed in this embodiment is not particularly limited. However, if the object to be fixed has conductivity, the object to be fixed may be directly attached to the adhesive sheet. When the object to be fixed is non-conductive, similar to the case of the non-conductive adherend, it is essential to attach a conductive auxiliary material to the object to be fixed and then attach it to the adhesive sheet.

[0070] Examples of the conductive object to be fixed include a metal such as iron, aluminum, copper, silver, gold, or a foil (less than 100 μm thick), a plate (100 μm or more thick) made of an alloy of these metals, a mesh or cloth containing fibers mixed or coated with these metals or alloys, a resin sheet containing these metals or alloys, a resin plate provided with a layer containing these metals, alloys, or conductive metal oxides, etc. Examples of the non-conductive object to be fixed include resin, wood, or a plastic plate.

[0071] The conductive auxiliary material is not particularly limited as long as it has conductivity. For example, metals such as aluminum, copper, silver, and gold, alloys of these metals, or films deposited with conductive metal oxides (indium tin oxide: ITO, etc.), cloth containing fibers mixed or coated with these metals or alloys, resin sheets containing these metals or alloys, and resin plates provided with layers containing these metals, alloys, or conductive metal oxides can be mentioned.

[0072] FIG. 1A shows an example of a cross-section of an adhesive sheet having an electrically peelable adhesive layer formed thereon (a cross-section when a tape attached to a horizontal plane is cut in the vertical direction. The same applies hereinafter). FIG. 1B shows an example of a cross-section of an adhesive sheet composed of a core material penetrated by an electrically peelable adhesive composition. FIGS. 2A to 5B show circuit examples when a voltage is applied to the electrically peelable adhesive layer of the adhesive sheet having the electrically peelable adhesive layer formed thereon via a conductive object and examples of peeling after the voltage application. FIGS. 6A and 6B show circuit examples when a voltage is applied to each of both sides of the adhesive layer of the adhesive sheet composed of a core material penetrated by an electrically peelable adhesive composition via a conductive object and examples of peeling after the voltage application. The usage form of the adhesive sheet of the present invention is not limited to the following circuit examples and peeling examples. In the following peeling examples, it is described that the adhesive sheet remains on the adherend side, but by arranging the positive and negative directions of the DC power supply in each example in reverse, peeling can be performed so that the adhesive sheet remains on the object to be fixed. Note that which side of the power supply the adhesive sheet remains on depends on the composition of the adhesive sheet and is not particularly limited.

[0073] In each drawing, 1 represents an electrically peelable adhesive layer, 2 represents a core material, 3 represents a conductive adherend, 4 represents a DC power source, 5 represents a conductive object to be fixed, 6 represents a non-conductive object to be fixed, 7 represents an arbitrary adhesive, 8 represents a conductive auxiliary material, 9 represents a non-conductive adherend, and 10 represents an adhesive layer. In Fig. 1A, an electrically peelable adhesive layer 1 is formed on each of both sides of the core material 2, and an adhesive layer 10 is formed by the core material 2 and the electrically peelable adhesive layer 1 (the same applies to the examples shown in Figs. 2A to 5B). In Fig. 1B, the electrically peelable adhesive composition has penetrated into the core material 2, and the core material 2 itself forms the adhesive layer 10 (the same applies to the examples shown in Figs. 6A and B). Note that in Figs. 1A and 1B, the adhesive layer 10 is also the adhesive sheet itself.

[0074] Fig. 2A shows an example of a cross-section in which a conductive object 5 to be fixed is adhered to a conductive adherend 3 using an adhesive sheet and a voltage is applied. As shown in Fig. 2A, terminals are connected to the conductive object 5 to be fixed and the conductive adherend 3 to form a circuit with the DC power source 4, thereby applying a voltage to the electrically peelable adhesive layer 1, and the adhered conductive object 5 can be peeled from the conductive adherend 3 as shown in Fig. 2B.

[0075] Fig. 3A shows an example of a cross-section in which a non-conductive object 6 to be fixed is adhered to a conductive adherend 3 using an adhesive sheet and a voltage is applied. As shown in Fig. 3A, an aluminum plate is attached to the non-conductive object 6 to be fixed as a conductive auxiliary material 8 using an arbitrary adhesive 7, and the non-conductive object 6 and the conductive auxiliary material 8 and the conductive adherend 3 are adhered using an adhesive sheet. Terminals are connected to the conductive auxiliary material 8 and the conductive adherend 3 to form a circuit with the DC power source 4, thereby applying a voltage to the electrically peelable adhesive layer 1, and the adhered non-conductive object 6 can be peeled from the conductive adherend 3 as shown in Fig. 3B. In this case, the conductive auxiliary material 8 attached to the non-conductive object 6 remains on the non-conductive object 6.

[0076] Fig. 4A shows an example of a cross-section in which a conductive object to be fixed 5 is adhered to a non-conductive adherend 9 using an adhesive sheet and a voltage is applied. As shown in Fig. 4A, an aluminum plate is attached to the non-conductive adherend 9 as a conductive auxiliary material 8 using an arbitrary adhesive 7, and the conductive object to be fixed 5, the conductive auxiliary material 8, and the non-conductive adherend 9 are adhered using an adhesive sheet. Terminals are connected to the conductive object to be fixed 5 and the conductive auxiliary material 8 to form a circuit with a DC power source 4, thereby applying a voltage to the electro-strippable adhesive layer 1, and the conductive object to be fixed 5 adhered as shown in Fig. 4B can be peeled from the non-conductive adherend 9.

[0077] Fig. 5A shows an example of a cross-section in which a non-conductive object to be fixed 6 is adhered to a non-conductive adherend 9 using an adhesive sheet and a voltage is applied. As shown in Fig. 5A, an aluminum plate is attached to each of the non-conductive object to be fixed 6 and the non-conductive adherend 9 as a conductive auxiliary material 8 using an arbitrary adhesive 7, and the conductive auxiliary material 8 to which the non-conductive object to be fixed 6 is adhered and the conductive auxiliary material 8 to which the non-conductive adherend 9 is adhered are adhered using an adhesive sheet. Terminals are connected to each conductive auxiliary material 8 to form a circuit with a DC power source 4, thereby applying a voltage to the electro-strippable adhesive layer 1, and the non-conductive object to be fixed 6 adhered as shown in Fig. 5B can be peeled from the non-conductive adherend 9. In this case, the conductive auxiliary material 8 attached to the non-conductive object to be fixed 6 remains on the non-conductive object to be fixed 6.

[0078] Fig. 6A shows an example of a cross-section in which a conductive object to be fixed 5 is adhered to a conductive adherend 3 using an adhesive sheet made of a core material penetrated by an electro-strippable adhesive composition and a voltage is applied. As shown in Fig. 6A, terminals are connected to the conductive object to be fixed 5 and the conductive adherend 3 to form a circuit with a DC power source 4, thereby applying a voltage to the core material 2 (adhesive layer 10), and the conductive object to be fixed 5 adhered as shown in Fig. 6B can be peeled from the conductive adherend 3.

[0079] (Applications of the electro-strippable adhesive sheet) The electrically peelable pressure-sensitive adhesive sheet of the present embodiment can easily peel the pressure-sensitive adhesive sheet from a conductive object by applying a low voltage of 30 V or less without performing UV irradiation or heat treatment. Therefore, the pressure-sensitive adhesive sheet can be suitably used for pressure-sensitive adhesion to non-transparent members that cannot be irradiated with UV or members that are vulnerable to heat. In addition, since the composition of the present invention is also excellent in the pressure-sensitive adhesiveness to a conductive object, it can be suitably used for fixing members that require high processing accuracy or fixing members that are difficult to physically fix, such as thin metal plates and substrates. For example, the composition can be used for temporarily fixing components in the electronic component manufacturing process (for example, temporarily fixing a wafer during dicing of an LSI chip), and the temporary fixing of the components can be easily released by applying a voltage. Further, the electrically peelable pressure-sensitive adhesive sheet of the present embodiment is thin and can be easily attached to an adherend uniformly. Therefore, even when fixing components by a flow operation, the work can be carried out efficiently.

[0080] (Method for manufacturing an electrically peelable pressure-sensitive adhesive composition) The electrically peelable pressure-sensitive adhesive composition of the present embodiment can be manufactured by stirring and mixing an acrylic polymer, an ionic liquid, and optionally a migration promoter, a crosslinking agent, etc. The stirring method is not particularly limited, and a known mixing method can be used. Specifically, for example, an acrylic polymer, an ionic liquid, and optionally a migration promoter, a crosslinking agent, etc. can be stirred by a V-type mixer or a mixer (dissolver, homomixer, planetary mixer, etc.). Additives as described above may be added during stirring.

[0081] (Method for manufacturing an electrically peelable pressure-sensitive adhesive sheet) One embodiment of the present invention is a method for manufacturing an electrically peelable pressure-sensitive adhesive sheet. The electrically peelable pressure-sensitive adhesive sheet can be manufactured by bringing an electrically peelable pressure-sensitive adhesive composition containing an acrylic polymer and an ionic liquid into contact with a planar core material having a basis weight of 10.0 g / m 2 or less and a thickness of 10 μm to 35 μm to form an adhesive layer. The electrically peelable pressure-sensitive adhesive composition, the core material, and the electrically peelable pressure-sensitive adhesive sheet are as described above.

[0082] Contacting the core material with the electrically releasable pressure-sensitive adhesive composition includes, for example, permeating the electrically releasable pressure-sensitive adhesive composition into the core material, or contacting the electrically releasable pressure-sensitive adhesive composition with each of both sides of the core material to form a layer of the electrically releasable pressure-sensitive adhesive composition.

[0083] Permeating the electrically releasable pressure-sensitive adhesive composition into the core material, or contacting the electrically releasable pressure-sensitive adhesive composition with each of both sides of the core material to form a layer of the electrically releasable pressure-sensitive adhesive composition can be achieved, for example, by applying the electrically releasable pressure-sensitive adhesive composition on a release film and attaching the core material thereto. A release film similarly coated with the electrically releasable pressure-sensitive adhesive composition may be attached to the side of the core material where the release film is not laminated. When the core material is composed of fibers or has pores, the laminated electrically releasable pressure-sensitive adhesive composition penetrates into the fibers or pores. At this time, pressure may be applied to the attached core material. Applying pressure makes it easier for the electrically releasable pressure-sensitive adhesive composition to penetrate into the core material. The pressure may be applied from only one side of the core material or to both sides. The electrically releasable pressure-sensitive adhesive composition may be completely contained in the core material by penetrating into the core material. At that time, the adhesive sheet becomes an adhesive sheet composed of the core material into which the electrically releasable pressure-sensitive adhesive composition has penetrated. The electrically releasable pressure-sensitive adhesive composition may form a layer of the electrically releasable pressure-sensitive adhesive composition while penetrating into the core material. In the above-described method, a film coated with the electrically releasable pressure-sensitive adhesive composition is attached to the core material, but the electrically releasable pressure-sensitive adhesive composition may be directly applied to the core material. The application method of the electrically releasable pressure-sensitive adhesive composition is as described above.

[0084] (Release method) The adhesive sheet of the present embodiment can be peeled off from the conductive object to which the adhesive sheet is attached by applying a voltage after attaching the adhesive sheet on the conductive object.

[0085] As a peeling method, for example, if the object to be fixed and the adherend have conductivity, the adhesive sheet can be peeled from the object to be fixed or the adherend by connecting terminals to the object to be fixed and the adherend and applying a voltage between the terminals. If the object to be fixed and / or the adherend does not have conductivity, even if it is non-conductive, the fixing and peeling operations can be performed by adhering an aluminum plate or the like as a conductive auxiliary material. These fixing and peeling operations are shown in the peeling examples of the above adhesive sheet.

[0086] The voltage to be applied is not particularly limited as long as the adhesive sheet can be peeled off. However, considering the scale of the voltage application device, the influence on the object to be fixed, and the risk to the human body due to accidents during work, a low voltage is preferable. The range of the voltage to be applied can be, for example, selecting the upper limit from voltages of 690V, 650V, 600V, 550V, 500V, 480V, 450V, 415V, 400V, 380V, 350V, 347V, 300V, 250V, 240V, 230V, 220V, 210V, 208V, 200V, 180V, 160V, 150V, 130V, 125V, 120V, 115V, 110V, 105V, 100V, 90V, 80V, 70V, 60V, 50V, 40V and 30V, and selecting the lower limit from voltages of 0.5V, 1V, 2V, 3V, 4V, 5V, 6V, 7V, 8V, 9V and 10V and combining them. Among these, it is particularly preferable to work at a voltage of 1 to 30V because the application device can be small, and it is preferable in terms of safety and the influence on the object to be fixed.

[0087] The adhesive sheet of this embodiment can be peeled from a conductive object even when the applied voltage is a relatively low voltage of several volts. Therefore, even if the power source is, for example, a commercially available dry battery, the peeling operation can be performed. This shows that according to this embodiment, the peeling operation can be performed by a simple application device that is excellent in the safety of the operator and can be carried around.

[0088] The voltage application time is not particularly limited as long as the adhesive sheet can be peeled off. However, considering the influence on the object to be fixed, it is preferably within 10 minutes, more preferably within 5 minutes, even more preferably within 3 minutes, and still more preferably within 1 minute.

[0089] The temperature at the time of peeling is not particularly defined, but it is preferably carried out at room temperature. Since the adhesive sheet of the present embodiment can be peeled off from a conductive object with a low voltage and in a short time as described above, the influence of heat on the object to be fixed can be extremely reduced.

[0090] The electro-peelable adhesive sheet of the present embodiment includes a core material having a basis weight of 10.0 g / m 2 or less and a thickness of 10 μm to 35 μm, which facilitates the handling of the adhesive sheet. Specifically, when using the adhesive sheet of the present embodiment, when the release films attached to both sides are peeled off, the shape of the adhesive sheet does not break or stretch, and it is easy to stick. When using the composition, if the base material (core material) is not used, when peeling off the release film attached to the adhesive layer, the shape of the adhesive layer is likely to change, making it difficult to stick. If a core material having a basis weight of 10.0 g / m 2 or less and a core material with a thickness exceeding 35 μm, for example, a thick core material that does not satisfy 10 μm to 35 μm is used, although it becomes easier to stick, it becomes a thick adhesive sheet, or the electro-peelability decreases, and it becomes difficult to easily peel off the adhesive sheet after applying the voltage. Whether the adhesive sheet can be easily peeled off after applying the voltage can be determined that the adhesive sheet is an adhesive sheet that can be easily peeled off after applying the voltage if the adhesion reduction rate calculated by the following formula (4) is 70% or more. The reduction rate is preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, and still more preferably 90% or more. By using a core material having a basis weight of 10.0 g / m 2 or less and a thickness of 10 μm to 35 μm, an electro-peelable adhesive sheet that is easy to stick can be obtained.

[0091]

Number

[0092] One embodiment of the present invention includes the use of a core material having a basis weight of 10.0 g / m 2 or less and a thickness of 10 μm to 35 μm for the production of an electrically peelable pressure-sensitive adhesive sheet. By using a core material having a basis weight of 10.0 g / m 2 or less and a thickness of 10 μm to 35 μm, an electrically peelable pressure-sensitive adhesive sheet excellent in electrical peelability and workability can be produced. The electrically peelable pressure-sensitive adhesive sheet and the core material are as described above.

Examples

[0093] Hereinafter, the present invention will be described more specifically by way of examples and comparative examples, but the present invention is not limited thereto.

[0094] (Production 1 of the electrically peelable pressure-sensitive adhesive composition) An electrically peelable pressure-sensitive adhesive composition was prepared as follows using an acrylic polymer, an ionic liquid, and a migration promoter.

[0095] 1. Preparation of acrylic polymer A monomer mixture consisting of 91 parts by weight of n-butyl acrylate (Mitsubishi Chemical Corporation), 8 parts by weight of acrylic acid (Mitsubishi Chemical Corporation), and 1 part by weight of 2-hydroxyethyl methacrylate (Nippon Shokubai Co., Ltd.) and 186 parts by weight of a polymerization solvent (ethyl acetate:toluene (weight ratio) = 9:1) were charged into a glass flask, replaced with nitrogen gas, and then 0.2 parts by weight of azobisisobutyronitrile (AIBN, Junsei Chemical Co., Ltd.) as a polymerization initiator was added. The temperature was raised to 85°C and a polymerization reaction was carried out for 5 hours to obtain an acrylic pressure-sensitive adhesive. The obtained acrylic pressure-sensitive adhesive contained 35% by weight of an acrylic polymer (weight-average molecular weight of about 800,000, Tg -46°C) and had a viscosity of 7,000 mPa·s.

[0096] 2. Preparation of Electrically Peeling Pressure-Sensitive Adhesive Composition To 100 parts by weight of the above acrylic pressure-sensitive adhesive (including 35 parts by weight as an acrylic polymer), 3.85 parts by weight of Coronate (registered trademark) L-55E (Tosoh Corporation) as an isocyanate-based crosslinking agent, 7.0 parts by weight of Excel (registered trademark) AS-110 (EMI-FSI: Daiichi Kogyo Seiyaku Co., Ltd.) as an ionic liquid, and 7.0 parts by weight of dimethyltetraglycol (Nippon Emulsion Co., Ltd.: molecular weight of about 220) as a migration promoter were added, and the mixture was stirred with a dissolver at room temperature for 10 minutes and then allowed to stand for defoaming to obtain an electrically peeling pressure-sensitive adhesive composition A (Composition A).

[0097] (Manufacture of Electrically Peeling Pressure-Sensitive Adhesive Composition 2) Using an acrylic polymer and an ionic liquid, a composition was prepared as follows. As the acrylic polymer, the acrylic polymer prepared in the above "1. Preparation of Acrylic Polymer" was used. To 100 parts by weight of an acrylic pressure-sensitive adhesive (including 35 parts by weight as an acrylic polymer), 3.85 parts by weight of Coronate L-55E (Tosoh Corporation) as an isocyanate-based crosslinking agent and 14.0 parts by weight of EMI-FSI as an ionic liquid were added, and the mixture was stirred with a dissolver at room temperature for 10 minutes and then allowed to stand for defoaming to obtain an electrically peeling pressure-sensitive adhesive composition B (Composition B).

[0098] (Example 1) Manufacture of Electrically Peeling Adhesive Sheet 1 Using Composition A, an electrically peeling adhesive sheet in the form of a double-sided adhesive sheet (hereinafter, also simply referred to as a double-sided sheet) was manufactured. As the core material of the double-sided sheet, Japanese paper with a basis weight of 5.0 g / m 2 and a thickness of 30 μm (manufactured by Hidaka Washi Co., Ltd.) was used. Composition A was applied to a polyethylene terephthalate film whose surface was silicone-treated (hereinafter, also referred to as a release film) in an amount such that the thickness after drying of Composition A would be 22 μm, and dried at 100 °C for 5 minutes. The coated surface of the composition on the dried film was attached to one side of the Japanese paper. Similarly, Composition A was applied to the release film to prepare a film in which the thickness after drying of Composition A was 22 μm, and this film was attached to the side of the Japanese paper to which the film was not attached. Thereafter, the double-sided sheet of Example 1 was manufactured by allowing it to stand at 40 °C for 3 days.

[0099] (Example 2) Manufacture of Electrically Peeling Adhesive Sheet 2 The double-sided sheet of Example 2 was manufactured in the same manner as in the manufacture of the electrically peeling adhesive sheet 1, except that an amount such that the thickness after drying of Composition A would be 12 μm was applied to each surface of the release film.

[0100] (Example 3) Manufacture of Electrically Peeling Adhesive Sheet 3 The double-sided sheet of Example 3 was manufactured in the same manner as in the manufacture of the electrically peeling adhesive sheet 1, except that Composition B was used instead of Composition A.

[0101] (Example 4) Manufacture of Electrically Peeling Adhesive Sheet 4 As the core material, a polyester nonwoven fabric with a basis weight of 8.0 g / m 2 and a thickness of 14 μm (UT-PET(A)8S: manufactured by Nippon Paper Papiria Co., Ltd.) was used, and the double-sided sheet of Example 4 was manufactured in the same manner as in the manufacture of the electrically peeling adhesive sheet 1.

[0102] (Example 5) Manufacture of Electrically Peeling Adhesive Sheet 5 As the core material, paper with a basis weight of 6.0 g / m 2 and a thickness of 17 μm (thin-mouth base paper: manufactured by Nippon Paper Papiria Co., Ltd.) was used, and a double-sided sheet of Example 5 was manufactured in the same manner as in the production 1 of the electrically peelable adhesive sheet, except for this.

[0103] (Example 6) Production 6 of the electrically peelable adhesive sheet As the core material, paper with a basis weight of 6.0 g / m 2 and a thickness of 17 μm (thin-mouth base paper: manufactured by Nippon Paper Papiria Co., Ltd.) was used, and an amount such that the dried thickness of Composition A becomes 12 μm was applied to each surface of the release film, and a double-sided sheet of Example 6 was manufactured in the same manner as in the production 1 of the electrically peelable adhesive sheet, except for this.

[0104] (Comparative Example 1) As the core material, a polyester nonwoven fabric with a basis weight of 8.0 g / m 2 and a thickness of 40 μm [Miraif (registered trademark) TY0503FE (ENEOS Techno Materials Co., Ltd.)] was used, and an amount such that the dried thickness of Composition A becomes 30 μm was applied to each surface of the release film, and a double-sided sheet of Comparative Example 1 was manufactured in the same manner as in the production 1 of the electrically peelable adhesive sheet, except for this.

[0105] (Comparative Example 2) As the core material, a polyester nonwoven fabric with a basis weight of 8.0 g / m 2 and a thickness of 40 μm [Miraif (registered trademark) TY0503FE] was used, and an amount such that the dried thickness of Composition A becomes 20 μm was applied to each surface of the release film, and a double-sided sheet of Comparative Example 2 was manufactured in the same manner as in the production 1 of the electrically peelable adhesive sheet, except for this.

[0106] (Comparative Example 3) As the core material, a polyester nonwoven fabric with a basis weight of 8.0 g / m 2 and a thickness of 40 μm [Miraif (registered trademark) TY0503FE] was used, and an amount such that the dried thickness of Composition A becomes 15 μm was applied to each surface of the release film, and a double-sided sheet of Comparative Example 3 was manufactured in the same manner as in the production 1 of the electrically peelable adhesive sheet, except for this.

[0107] (Comparative Example 4) Composition A was applied onto a film of polyethylene terephthalate with a silicone-treated surface so that the dried thickness became 50 μm, and a release film was attached to the applied surface to produce a double-sided sheet of Comparative Example 4.

[0108] (Comparative Example 5) Composition A was applied onto a film of polyethylene terephthalate with a silicone-treated surface so that the dried thickness became 30 μm, and a release film was attached to the applied surface to produce a double-sided sheet of Comparative Example 5.

[0109] (Comparative Example 6) As the core material, a polyester film (E5007: manufactured by Toyobo Co., Ltd.: PET film) with a basis weight of 35.0 g / m 2 and a thickness of 25 μm was used. A double-sided sheet of Comparative Example 6 was produced in the same manner as in the production of the electrically releasable pressure-sensitive adhesive sheet 1, except that an amount such that the dried thickness of Composition A became 12 μm was applied to each surface of the release film. This PET film is a non-fibrous film without pores, different from the polyester non-woven fabric used in Example 4.

[0110] (Comparative Example 7) As the core material, a non-woven fabric (manufactured by Daio Paper Corporation) with a basis weight of 23.0 g / m 2 and a thickness of 40 μm was used. A double-sided sheet of Comparative Example 7 was produced in the same manner as in the production of the electrically releasable pressure-sensitive adhesive sheet 1, except that an amount such that the dried thickness of Composition A became 10 μm was applied to each surface of the release film.

[0111] (Comparative Example 8) As the core material, rayon (manufactured by Nippon Paper Papiria Co., Ltd.) with a basis weight of 14.0 g / m 2 and a thickness of 40 μm was used. A double-sided sheet of Comparative Example 8 was produced in the same manner as in the production of the electrically releasable pressure-sensitive adhesive sheet 1, except that an amount such that the dried thickness of Composition A became 15 μm was applied to each surface of the release film.

[0112] (Evaluation of the double-sided sheet) The thickness, workability, adhesiveness, and electrical peelability of the fabricated double-sided sheet were evaluated. Note that the core materials used in each example and comparative example all have no conductivity. Each procedure will be described below.

[0113] (Measurement of thickness) For the measurement of the thickness of the double-sided sheet, a Peacock precision measuring instrument was used. The measurement was carried out at 5 locations on the double-sided sheet, and the average of each measurement result was taken as the thickness of the double-sided sheet. If the thickness of the double-sided sheet was 50 μm or less, it was evaluated as a thin sheet, and if it was greater than 50 μm, it was evaluated as a thick double-sided sheet.

[0114] (Evaluation of workability) For the evaluation of the workability of the double-sided sheet, when the polyethylene terephthalate film attached to both sides of the double-sided sheet was peeled off, if the shape of the double-sided sheet did not break or stretch and it was easy to attach, the double-sided sheet was evaluated as having excellent workability. If the shape of the double-sided sheet broke or stretched when the release film was peeled off and it was difficult to attach, the double-sided sheet was evaluated as having poor workability.

[0115] (Evaluation of adhesiveness) The release film on one side of each double-sided sheet of Examples 1 to 6 and Comparative Examples 1, 5 to 8 was peeled off, and an aluminum foil (object to be fixed) with a thickness of 50 μm was attached. After attaching the aluminum foil, the double-sided sheet was cut out together with the aluminum foil so as to have a length of 250 mm × 25 mm (3 pieces for each double-sided sheet. Hereinafter, this is referred to as a double-sided tape). The release film on the other side of each cut double-sided tape was peeled off and attached to a polished stainless steel plate (conductive adherend: 125 mm × 50 mm) for 100 mm × 25 mm. On the contrary, by using a 2 kg rubber roller and reciprocating once in the long side direction of the sample piece at a speed of 300 mm / min, the adherend, the adhesive product, and the object to be fixed were pressure-bonded to obtain an evaluation sample. 30 minutes after pressure-bonding the adherend, the double-sided tape, and the object to be fixed, each evaluation sample was evaluated using an autograph (registered trademark) AGS-H manufactured by Shimadzu Corporation, in accordance with JIS Z-0237 (2009), and the force (adhesive force: N / 25 mm) required to peel the double-sided tape in the evaluation sample from the adherend at an angle of 180° (180° peel) at a tensile speed of 300 mm / min was measured, and the average value of the measured values for each evaluation sample was taken as the measured value.

[0116] From each double-sided sheet of Examples 1 to 6 and Comparative Examples 1, 5 to 8, 3 evaluation samples were prepared for each double-sided sheet in the same manner as above. Electrodes were attached so that the conductive adherend side of each evaluation sample was the negative electrode and the object to be fixed side was the positive electrode. Using a DC power supply and adjusting the voltage using a transformer, a voltage of 10 V was applied to the evaluation sample for 10 seconds. After applying the voltage, the force required to peel the adhesive tape from the adherend at 180° was measured in the same manner as above.

[0117] The degree of decrease (decrease rate) in the adhesive force of the double-sided tape after voltage application was evaluated. The decrease rate was calculated by the following formula (5). When the decrease rate is 70% or more, peeling due to voltage application is easy. When it is less than 70%, peeling is difficult.

[0118]

Equation

[0119] The configurations, tape thicknesses, thickness evaluations, and adhesiveness evaluations of the double-sided tapes of Examples 1 to 6 and Comparative Examples 1 to 8 are shown in Tables 1 and 2 below, respectively. In the tables, A in the column of the composition indicates Composition A, B indicates Composition B, and the composition thickness indicates the thickness of the composition after drying on one side (for Comparative Examples 4 and 5, it is the total amount).

[0120]

Table 1

[0121]

Table 2

[0122] As in Examples 1 to 6, the double-sided tape using a core material with a small basis weight and a thin thickness became a thin double-sided tape with excellent workability and excellent electrical peelability. In Examples 1 to 6 and Comparative Examples 1, 2, 6 to 8, the final thickness of the double-sided tape is smaller than the sum of the thickness of the core material and the thickness of the composition after drying. This is because part of the composition penetrated into the gaps of the core material when applied. As in Comparative Examples 1 to 3 and 6 to 8, the double-sided tapes using a core material with a large basis weight or a thick thickness became thick double-sided tapes. Regarding Comparative Examples 2 to 4, although the adhesive strength was not measured, the double-sided tapes of Comparative Examples 2 and 3 were very uneven on the coating surface of the composition and had uneven thickness, so they were unsuitable as double-sided tapes and the adhesive strength could not be correctly evaluated, so it was not measured. Regarding Comparative Example 4, the inventors consider that the same results as the test of Comparative Example 5 without using a core material will be obtained. As in Comparative Examples 4 and 5, the double-sided tape without a core material became a thin double-sided tape, but since there was no core material, the shape of the tape was lost when the release film was peeled off, and the workability was poor. As in Comparative Example 6, in the core material without conductivity and without the composition penetrating into the core material, even when a voltage was applied, the movement of the ionic liquid could not be caused and the adhesiveness did not decrease. As in Comparative Examples 7 and 8, when the core material was too thick, sufficient electrical peelability could not be obtained even if a thin double-sided tape was formed.

[0123] From the above experimental results, it was shown that by using a core material that is thin and has a small basis weight, an electrically peelable adhesive sheet that is thin, has excellent workability, and also has excellent electrical peelability can be obtained.

Explanation of Reference Signs

[0124] 1 Electrically peelable adhesive layer 2 Core material 3 Conductive adherend 4 DC power supply 5 Conductive object to be fixed 6 Non-conductive object to be fixed 7 Arbitrary adhesive 8 Conductive auxiliary material 9 Non-conductive adherend 10 Adhesive layer

Claims

1. An electrically releasable pressure-sensitive adhesive sheet comprising a planar core material and a pressure-sensitive adhesive layer containing an electrically releasable pressure-sensitive adhesive composition, The core material has a basis weight of 10.0 g / m 2 as follows and a thickness of 10 μm to 35 μm, and is penetrated by the electrically peelable pressure-sensitive adhesive composition, wherein the electrically releasable pressure-sensitive adhesive composition is a composition containing an acrylic polymer and an ionic liquid, the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, and the thickness of the pressure-sensitive adhesive sheet is 10 to 50 μm. Electrically releasable pressure-sensitive adhesive sheet.

2. The pressure-sensitive adhesive sheet according to claim 1, wherein in the pressure-sensitive adhesive layer, the electrically releasable pressure-sensitive adhesive composition is in contact with each of both surfaces of the core material.

3. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the core material is composed of fibers.

4. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the core material has at least one through-hole.

5. The pressure-sensitive adhesive sheet according to claim 1 or 3, wherein the pressure-sensitive adhesive sheet is composed of the core material penetrated by the electrically releasable pressure-sensitive adhesive composition.

6. The basis weight of the core material is 2.0 to 8.0 g / m 2 The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the basis weight is as defined above.

7. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the thickness of the pressure-sensitive adhesive sheet is 15 to 50 μm.

8. The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the electrically releasable pressure-sensitive adhesive composition contains a migration promoter.

9. The pressure-sensitive adhesive sheet according to claim 8, wherein the migration promoter is an alkyl ether of polyethylene glycol.

10. The pressure-sensitive adhesive sheet according to claim 9, wherein the alkyl ether of polyethylene glycol is polyethylene glycol mono(di)methyl ether having a weight average molecular weight of 120 to 360.

11. The pressure-sensitive adhesive sheet according to any one of claims 8 to 10, wherein the content of the migration promoter is 5 to 30 parts by weight with respect to 100 parts by weight of the acrylic polymer.

12. The ionic conductivity of the ionic liquid is 10 -4 to 10 -2 S / cm, and the pressure-sensitive adhesive sheet according to any one of claims 1 to 11.

13. The pressure-sensitive adhesive sheet according to any one of claims 1 to 12, wherein the ionic liquid is represented by the following formula (1). 【Chemical 1】 (wherein R 1 is a divalent hydrocarbon group having 2 to 8 carbon atoms which may contain a hetero atom, and N in the formula + forms a ring together with R 2 and R 3 are the same or different and are a hydrogen atom or an alkyl group having 1 to 6 carbon atoms (however, when the nitrogen atom forms a double bond with an adjacent carbon atom, R 3 does not exist), X - is Cl - 、Br - 、I - 、AlCl 4 - 、Al 2 Cl 7 - 、NO 3 - 、BF 4 - 、PF 6 - 、ClO 4 - 、CH 3 COO - 、CF 3 COO - 、CF 3 SO 3 - 、(CF 3 SO 2 ) 2 N - 、(FSO 2 ) 2 N - 、(CF 3 SO 2 ) 3 C - 、AsF 6 - 、SbF 6 - 、NbF 6 - 、F(HF) n - 、B(C 6 H 5 ) 4 - 、C 4 F 9 SO 3 - 、CF 3 (CF 2 ) 3 SO 3 - 、(CF 3 CF 2 SO 2 ) 2 N - and CF 3 CF 2 COO - is an anion selected from)

14. The ionic liquid is a salt of a cation selected from a pyridinium-based cation, a cycloaliphatic ammonium cation, and an imidazolium-based cation, and an anion selected from (FSO 2 ) 2 N - , (CF 3 SO 2 ) 2 N - and BF 4 - The pressure-sensitive adhesive sheet according to any one of claims 1 to 13.

15. The pressure-sensitive adhesive sheet according to any one of claims 1 to 14, wherein the content of the ionic liquid is 5 to 60 parts by weight with respect to 100 parts by weight of the acrylic polymer.

16. The pressure-sensitive adhesive sheet according to any one of claims 1 to 15, wherein the acrylic polymer includes a copolymer of an alkyl (meth)acrylate having an alkyl group with 1 to 8 carbon atoms, a carboxyl group-containing acrylic monomer, and / or a hydroxyl group-containing acrylic monomer.

17. The pressure-sensitive adhesive sheet according to any one of claims 1 to 16, further comprising a peelable release film, wherein the release film is attached to both sides of the pressure-sensitive adhesive layer.

18. The pressure-sensitive adhesive sheet according to any one of claims 1 to 17, wherein the rate of decrease in adhesive strength calculated by the following formula (2) is 70% or more. 【Number 1】 (In the formula, the adhesive strength of the pressure-sensitive adhesive sheet before application refers to the adhesive strength measured in accordance with JIS-Z-0237 (2009) after the pressure-sensitive adhesive sheet has fixed a conductive adherend and a conductive object to be fixed. The adhesive strength of the pressure-sensitive adhesive sheet after the application treatment refers to the adhesive strength measured in accordance with JIS-Z-0237 (2009) after applying a voltage of 10 V for 10 seconds after the pressure-sensitive adhesive sheet has fixed a conductive adherend and a conductive object to be fixed.)

19. The basis weight is 10.0 g / m 2 a step of forming an adhesive layer by bringing an electrically peelable pressure-sensitive adhesive composition containing an acrylic polymer and an ionic liquid into contact with both surfaces of a planar core material having a basis weight of 10.0 g / m or less and a thickness of 10 μm to 35 μm is included, The total thickness of the core material and the pressure-sensitive adhesive layers formed on both sides of the core material is 10 to 50 μm. The contact is to penetrate the electro-releasable pressure-sensitive adhesive composition into the core material. A method for manufacturing an electro-releasable pressure-sensitive adhesive sheet.

20. The manufacturing method according to claim 19, wherein the contact is to bring the electro-releasable pressure-sensitive adhesive composition into contact with each of both sides of the core material to form a layer of the electro-releasable pressure-sensitive adhesive composition.

21. The manufacturing method according to claim 19 or 20, wherein the electro-releasable pressure-sensitive adhesive composition further contains a migration promoter.

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