WO2023152913A1

WO2023152913A1 - Electrically removable pressure-sensitive adhesive sheet and production method therefor

Info

Publication number: WO2023152913A1
Application number: PCT/JP2022/005473
Authority: WO
Inventors: 孝浩青木; 陸史共田
Original assignee: ビッグテクノス株式会社
Priority date: 2022-02-10
Filing date: 2022-02-10
Publication date: 2023-08-17
Also published as: JPWO2023152913A1

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

Electro-peelable pressure-sensitive adhesive sheet and its manufacturing method

The present invention relates to an electrically peelable pressure-sensitive adhesive sheet. TECHNICAL FIELD The present invention relates to a method for producing an electrically peelable pressure-sensitive adhesive sheet.

Adhesives and adhesive sheets that have adhesiveness to adherends and releasability from adherends are used in various applications (for example, surface protection films, masking tapes for painting, peelable memos, etc.). . As a method for peeling the pressure-sensitive adhesive from the adherend, other than the physical method, there is known a method of peeling by stimulus such as light, heat, vibration or electric current. For example, Patent Document 1 describes that by using a polymer and an ionic liquid as an adhesive, it is possible to provide an adhesive that can be peeled off from an adherend by applying a voltage (electro-peeling adhesive). . In addition, Patent Document 2 describes that it is possible to provide an electro-peelable pressure-sensitive adhesive that leaves no adhesive residue even when a low voltage is applied by studying conditions such as a migration promoter used together with a polymer or an ionic liquid.

JP 2010-037354 A U.S. Patent Application No. 17/602,212

In order to achieve good electrical detachability of the adhesive sheet with electrical detachment, it is necessary to select the material of the core material. For example, films such as polyethylene terephthalate (PET), which are used in general adhesive tapes, are insulators, so double-sided tapes using PET as a core material do not exhibit electrical exfoliation. Therefore, it has been necessary to use a porous material such as a non-woven fabric as a core material for adhesive sheets such as double-sided tapes having electrical exfoliation properties. However, conventional electro-peelable pressure-sensitive adhesive sheets using non-woven fabric require a thick adhesive layer in order to achieve electro-peeling, resulting in increased thickness of the pressure-sensitive adhesive sheet. In addition, the electro-peelable pressure-sensitive adhesive without a core material is likely to change the shape of the pressure-sensitive adhesive surface, making it difficult to apply to the adherend. Therefore, there has been a demand for an electrically peelable pressure-sensitive adhesive sheet that is thin and can be easily attached to an adherend.

The present inventors have found that by using a core material with a basis weight of 10.0 g/m ² or less and a thickness of 10 μm to 35 μm, it is thin and easy to attach to the adherend without affecting the electropeeling property. The inventors have found that an electrically peelable pressure-sensitive adhesive sheet can be provided, and have arrived at the present invention.
Thus, the present invention provides an electro-peeling pressure-sensitive adhesive sheet comprising a planar core material and an adhesive layer containing an electro-peeling pressure-sensitive adhesive composition, wherein the core material has a basis weight of 10.0 g/m ² or less and a weight of 10 μm or less. Provided is an electrically exfoliating pressure-sensitive adhesive sheet having a thickness of 35 μm, wherein the electrically exfoliating 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.

Furthermore, according to the present invention, 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 is brought into contact with an electro-peeling adhesive composition containing an acrylic polymer and an ionic liquid. Provided is a method for producing an electrically peelable pressure-sensitive adhesive sheet, comprising the step of forming a pressure-sensitive adhesive layer.

According to the present invention, there is provided an electrically exfoliating pressure-sensitive adhesive sheet that does not affect the electrically exfoliating property, is thin and can be easily attached to an adherend.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the cross section of the electrical peeling adhesive sheet in which the electrical peeling adhesive layer was formed. 1 is a diagram showing an example of a cross-section of an electro-peeling adhesive sheet comprising a core material impregnated with an electro-peeling adhesive composition. FIG. FIG. 2 is a diagram showing an example of a circuit for applying a voltage to a conductive adherend and a conductive fixed object, and peeling the conductive fixed object from the electrically exfoliating pressure-sensitive adhesive sheet. FIG. 10 is a diagram showing an example in which a voltage is applied and a conductive fixed object is peeled off; FIG. 3 is a diagram showing an example of a circuit for applying a voltage to a conductive adherend and a conductive auxiliary material to peel off a non-conductive fixed object from an electrically exfoliating pressure-sensitive adhesive sheet. FIG. 10 is a diagram showing an example in which a voltage is applied to peel off a non-conductive fixed object; FIG. 2 is a diagram showing an example of a circuit for applying a voltage to a conductive auxiliary material and a conductive fixed object to separate the conductive fixed object from the electrical peeling pressure-sensitive adhesive sheet. FIG. 10 is a diagram showing an example in which a voltage is applied and a conductive fixed object is peeled off; A voltage is applied to the conductive auxiliary material adhered to the non-conductive adherend and the conductive auxiliary material adhered to the non-conductive fixed object, and the electrically peelable adhesive sheet is applied to the non-conductive fixed object. It is a figure which shows an example of the circuit which peels. FIG. 10 is a diagram showing an example in which a voltage is applied to peel off a non-conductive fixed object; FIG. 2 is a diagram showing an example of a circuit for applying a voltage to a conductive adherend and a conductive fixed object, and peeling the conductive fixed object from the electrically exfoliating pressure-sensitive adhesive sheet. FIG. 10 is a diagram showing an example in which a voltage is applied and a conductive fixed object is peeled off;

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

[Electro-peeling adhesive sheet]
The electro-peeling pressure-sensitive adhesive sheet (hereinafter also simply referred to as "adhesive sheet") of the present embodiment comprises an adhesive layer containing a planar core material and an electro-peeling pressure-sensitive adhesive composition (hereinafter also simply referred to as composition). Both sides of the sheet are partly or wholly tacky. That is, the pressure-sensitive adhesive sheet of the present invention is, for example, in the form of a double-sided sheet or double-sided tape. In addition, the pressure-sensitive adhesive sheet of the present embodiment has electrical releasability. This electro-releasing property means that the adherend or the object to be fixed is adhered and fixed using an adhesive sheet, and a voltage is applied to reduce the adhesiveness of the adhesive sheet, thereby removing the adherend or the object to be fixed. It refers to being able to unfix something. The adhesive sheet preferably has an adhesive strength of 10 N/25 mm or more before voltage application.

Although the thickness of the adhesive sheet is not particularly limited, it is preferably 1 to 200 μm, more preferably 1 to 100 μm, more preferably 1 to 80 μm, more preferably 1 μm or more and less than 80 μm. It is more preferably 5-60 μm, more preferably 5-50 μm, more preferably 10-50 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.

The thickness of the adhesive sheet and core material can be measured using a known thickness measuring machine. Examples of the thickness measuring instrument include a Peacock precision measuring instrument. Here, the thickness refers to the average value obtained by measuring at least five locations randomly selected from the object to be measured using a thickness gauge.

(core material)
The core material of the present embodiment refers to a planar object that can form an adhesive layer together with the electro-peeling adhesive composition described below. The core may not be completely planar, and may have unevenness on part or all. Also, the core material may have at least one through hole. The core material is not particularly limited as long as the adhesive layer conducts ion conduction when a voltage is applied to the adhesive sheet, and the following properties (thickness, basis weight) can be satisfied.

In order for the adhesive layer of the adhesive sheet to exhibit ionic conductivity, for example, the core material is composed of fibers, and this can be achieved by permeating the composition into the gaps between the fibers.

The material of the core material is not particularly limited as long as it satisfies the following properties (thickness, basis weight). Examples of the core material include fibers such as vegetable fibers, inorganic and 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 Western paper and Japanese paper. Examples of the core material composed of inorganic or chemical fibers include nonwoven fabrics and woven fabrics such as polyester (especially, nonwoven fabrics made of polyethylene terephthalate), carbon fibers, glass fibers, and the like. Examples of porous films include polyimide and polyester films. Since the core material is composed of fibers, the composition can permeate the interstices of the fibers and exhibit ionic conductivity when a voltage is applied. The core material is preferably an insulator, and more preferably a fiber made of the insulator. Fibers composed of insulators include, for example, vegetable fibers and polyester fibers.

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

The basis weight of the core material is 10.0 g/m ² or less, preferably 2.0 to 10.0 g/m ² , more preferably 2.0 to 9.0 g/m ² , and 2.0 to 8.0 g/m ² . is more preferable. The upper limit of 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 . The lower limit of 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 .

When the core material is thicker than 35 μm, the thickness of the pressure-sensitive adhesive sheet is increased. In addition, when the fiber used for the core material is a non-conductive fiber and the basis weight of the core material is more than 10.0 g/m ² , the composition does not easily penetrate into the gaps between the fibers, so the pressure-sensitive adhesive sheet produced is There is a possibility that the adhesive strength will not decrease even if a voltage is applied. When the core material has a basis weight of 10.0 g/m ² or less and a thickness of 10 μm to 35 μm, a thin pressure-sensitive adhesive sheet can be obtained without affecting the electrical exfoliation properties.

The adhesive layer may be composed only of the core material in which the electro-peelable adhesive composition has permeated, or the electro-peelable adhesive composition may be in contact with one side or both sides of the core material. A layer of the adhesive composition may be formed. In this case, the layer of the electro-peeling adhesive composition is also called an electro-peeling adhesive layer. When the adhesive layer consists only of the core material in which the composition has permeated, both sides of the core material are in a state of being adhesive due to the composition.

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

The density of the core material is 2.0 g/cm ³ or less, preferably 0.1 to 1.5 g/cm ³ , more preferably 0.1 to 1.0 g/cm ³ , and 0.1 to 0.8 g/cm ³ . more preferably 0.1 to 0.6 g/cm ³ , more preferably 0.1 to 0.5 g/cm ³ . The upper density limit 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 . The lower limits of density are, for example, 0.1, 0.15, 0.2 g/cm ³ .

[Electro-peeling adhesive composition]
The electro-peelable pressure-sensitive adhesive composition of this embodiment contains at least an acrylic polymer and an ionic liquid.
(acrylic polymer)
The acrylic polymer of the present embodiment can be obtained by polymerizing an acrylic monomer in the presence of any polymerization initiator. Any acrylic polymer can be used as long as it 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 fixing object (definition of these will be described later). The weight average molecular weight of the acrylic polymer is preferably 100,000 to 5,000,000, more preferably 200,000 to 4,000,000, and more preferably 300,000 to 3,000,000 from the viewpoint of adhesiveness. Here, the weight average molecular weight refers to the weight average molecular weight in terms of polystyrene. Specifically, it may be a polystyrene-equivalent weight-average molecular weight calculated using Shodex's GPC (System 21) and using tetrahydrofuran as a mobile phase.

The glass transition temperature (Tg) of the acrylic polymer is preferably 0°C or lower, more preferably -20°C or lower, and more preferably -40°C or lower. The above Tg can be calculated, for example, based on the following Fox formula.

1/Tg=(W1/Tg1)+(W2/Tg2)+・・・・+(Wn/Tgn)

The glass transition temperature can be measured, for example, by differential thermal analysis (DTA).

The acrylic polymer may be crosslinked by using a crosslinking agent. Examples of cross-linking agents include isocyanate-based cross-linking agents such as toluene diisocyanate and methylenebisphenyl isocyanate. The amount of the cross-linking agent is preferably 1 to 10 parts by weight or less, more preferably 3 to 10 parts by weight, and 5 to 10 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. is more preferable. Crosslinking the acrylic polymer can improve the creep resistance and/or shear resistance of the layer when the composition is formed as a layer on a core.

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

(acrylic monomer)
The acrylic monomer preferably contains an alkyl (meth)acrylate having an alkyl group of 1 to 14 carbon atoms as a main component (50% by weight or more). (Meth)acrylate means methacrylate or acrylate.

Examples of alkyl (meth)acrylates having an alkyl group having 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 and 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 having 1 to 8 carbon atoms are preferred, alkyl (meth)acrylates having an alkyl group having 1 to 4 carbon atoms are more preferred, and n-butyl (Meth)acrylates are more preferred, and n-butyl acrylate is more preferred.

Other acrylic monomers include acrylic acid, methacrylic acid, carboxyl group-containing monomers such as carboxyethyl acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate. , 6-hydroxyhexyl (meth)acrylate and (4-hydroxymethylcyclohexyl)-methylacrylate. These other acrylic monomers may be used alone or in combination of two or more. Other acrylic monomers preferably contain either carboxyl group-containing monomers or hydroxyl group-containing monomers, or both.

The acrylic monomer may consist only of alkyl (meth)acrylate without using the other acrylic monomers described above. In addition, from the viewpoint of easily obtaining a composition with the desired performance, it is preferable that the other acrylic monomer is contained in an amount of 1% by weight or more and less than 50% by weight, and more preferably 5 to 30% by weight. Preferably, it is contained in an amount of 5 to 15% by weight.

In addition, 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 the total amount of monomers is 100 wt. When expressed as parts, it is preferably 1 to 20 parts by weight. By using both monomers in this range, adhesive properties can be improved. Furthermore, the total content of both monomers is more preferably 1 to 10 parts by weight.

Furthermore, a vinyl-based monomer may be added to the (meth)acrylate, if necessary. Examples of vinyl monomers include itaconic acid, maleic acid, crotonic acid, maleic anhydride, itaconic anhydride, vinyl acetate, N-vinylpyrrolidone, N-vinylcarboxylic acid amides, styrene and N-vinylcaprolactam. be done. These vinyl-based monomers may be used alone or in combination of two or more.
(polymerization initiator)
Examples of optionally used polymerization initiators include 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 Azo polymerization initiators such as ,2'-azobis[2-(2-imidazolin-2-yl)propane]; persulfate polymerization initiators such as potassium persulfate and ammonium persulfate; 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, Peroxide initiators such as 1,1-bis(t-butylperoxy)cyclododecane, 3,3,5-trimethylcyclohexanoyl peroxide and t-butylperoxypivalate; persulfates and sulfites and a redox polymerization initiator composed of sodium hydrogen. These polymerization initiators may be used alone or in combination of two or more. Alternatively, 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 with respect to 100 parts by weight of the acrylic monomer. By using the polymerization initiator within this range, an acrylic polymer having excellent adhesive properties can be formed.

(ionic liquid)
Ionic liquids are combinations of cations and anions that are liquid at room temperature, and are also called room temperature molten salts. Ionic liquids have properties such as non-flammability, non-volatility and chemical stability. When a voltage is applied to the ionic liquid, anions move to the anode side and cations move to the cathode side. It is believed that the migration of anions and cations to the vicinity of the electrodes or the redox reaction of the anions or cations at the interface between the electrodes and the composition weakens the adhesive strength of the composition, resulting in improved peelability. .

Although the ionic conductivity of the ionic liquid is not particularly limited, it preferably has an ionic conductivity of 10 ^-7 S/cm or more, and preferably has an ionic conductivity of 10 ^-6 to 10 ^-1 S/cm. , more preferably 10 ⁻⁴ to 10 ⁻² S/cm, more preferably 10 ⁻³ to 10 ⁻² S/cm. Ionic conductivity can be measured, for example, by an AC impedance method. The ionic conductivity of an ionic liquid can be measured by the AC impedance method, for example, as follows.

At room temperature, the ionic liquid is placed on stainless steel using a bipolar cell, and another stainless steel plate is placed on the ionic liquid to sandwich the ionic liquid between the stainless steel plates. A sample is obtained by controlling the disk shape of Bulk resistance (Ω) is obtained by applying a voltage to this sample and 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: sample thickness (cm), A: sample area (cm ² )]

Examples of ionic liquids include combinations of cyclic cations and anions represented by the following formula (1).

[In the formula, R ¹ is a divalent hydrocarbon group having 2 to 8 carbon atoms which may contain a heteroatom, forms a ring together with N ⁺ in the formula, and R ² and R ³ are the same or different is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms (however, when the nitrogen atom forms a double bond with the adjacent carbon atom, R ³ does not exist),
^X- _is ^Cl- , Br- _, ^I- , ^AlCl4- ^, _Al2Cl7- ^, ^NO3- _, ^BF4- _, ^PF6- ^, _ClO4- ^, _CH3COO- _, _CF3COO- ^, CF _3SO3- ^, ₍ _CF3SO2 ₎ _2N- ^, ( _FSO2 ) _2N- , ( _CF3SO2 ) ^3C- ^, _AsF6- _, _SbF6- ^, _NbF6- , _F (HF ⁾ _n ^- _, _B ⁽ _C6H5 ₎ _4- ^, _C4F9SO3- _, _CF3 ₍ _CF2 ₎ _3SO3- ^, ⁽ _CF3CF2SO2 ₎ _2N- ^and _CF3CF2COO- is the anion of choice]

In the above formula, the ring composed of R ¹ and N ⁺ includes saturated alicyclic hydrocarbons such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane and cyclooctane, cyclopropene, cyclobutene, cyclopentene and cyclohexene. , cycloheptene, cyclooctene, cyclopentadiene, and unsaturated cyclic hydrocarbons such as benzene. Heteroatoms include N, O, S, P and the like, preferably N.

Examples of alkyl groups having 1 to 6 carbon atoms include methyl group, ethyl group, propyl group, butyl group, pentyl group and hexyl group. Alkyl groups having 3 to 8 carbon atoms include structural isomers.

Another example of an ionic liquid is a combination of a cation and an anion represented by the following formula (2) or (3).

[Wherein Y is N or P, and R ⁴ to R ⁷ are the same or different, and are hydrogen atoms (provided that all of R ⁴ to R ⁷ are not hydrogen atoms) or having 1 to 20 carbon atoms, a linear, branched or cyclic alkyl group which may have a substituent (provided that when the nitrogen atom forms a double bond with the adjacent carbon atom, R ⁷ does not exist); 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- ^, _CF _3SO3- ^, ₍ _CF3SO2 ₎ _2N- ^, ( _FSO2 ) _2N- , ( _CF3SO2 ) ^3C- ^, _AsF6- _, _SbF6- ^, _NbF6- , _F (HF ⁾ _n ^- _, _B ⁽ _C6H5 ₎ _4- ^, _C4F9SO3- _, _CF3 ₍ _CF2 ₎ _3SO3- ^, ⁽ _CF3CF2SO2 ₎ _2N- ^and _CF3CF2COO- is the anion of choice]

[In the formula, R ⁸ to R ¹⁰ may be the same or different and may have a hydrogen atom (provided that not all of R ⁸ to R ¹⁰ are hydrogen atoms) or a substituent having 1 to 20 carbon atoms. a linear, branched or cyclic alkyl group, wherein 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- ^, _CF _3SO3- ^, ₍ _CF3SO2 ₎ _2N- ^, ( _FSO2 ) _2N- , ( _CF3SO2 ) ^3C- ^, _AsF6- _, _SbF6- ^, _NbF6- , _F (HF ⁾ _n ^- _, _B ⁽ _C6H5 ₎ _4- ^, _C4F9SO3- _, _CF3 ₍ _CF2 ₎ _3SO3- ^, ⁽ _CF3CF2SO2 ₎ _2N- ^and _CF3CF2COO- is the anion of choice]

Cations in the ionic liquid preferably have a weight average molecular weight of 700 or less, more preferably have a weight average molecular weight of 50 to 600, and have a weight average molecular weight of 50 to 500. More preferably, it has a weight average molecular weight of 50-400. The upper limits of the weight average molecular weight of cations in the ionic liquid are, for example, 700, 650, 600, 550, 500, 450, 400, 350, 300, 250, 200, 150. The lower limits of the weight average molecular weight of cations in the ionic liquid are, for example, 30, 40, 50, 60, 70, 80, 90, 99, and 100. The weight average molecular weight referred to here refers to the weight average molecular weight in terms of polystyrene.

The ionic liquid is preferably a combination of a cyclic cation and an anion represented by formula (1), and a cation selected from pyridinium cations, cycloaliphatic ammonium cations and imidazolium cations, and (FSO ₂ ⁾ more preferably in combination with an anion selected from _2N- , ( _CF3SO2 ) _2N- ^and _BF4- , a cation selected from imidazolium cations and ⁽ _FSO2 ₎ ₂ A combination with an anion selected from N-, (CF ₃ SO ₂ ) ₂ N- and BF ₄ - is more preferable from the viewpoint of improving peelability after voltage application.

The ionic liquid is available from Daiichi Kogyo Seiyaku, Kanto Chemical, Koei Chemical Industry, etc. For example, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMI-FSI) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI-TFSI) from Daiichi Kogyo Seiyaku, 1-hexylpyridinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide and 1-ethyl-3-methylimidazolium tetrafluoroborate from Kanto Kagaku, Koei Chemical Industry Obtain 1-ethyl-3-methylimidazolium hexafluorophosphate (IL-C3), 1-butylpyridinium tetrafluoroborate (IL-P10) and 1-hexylpyridinium bis(trifluoromethanesulfonyl)imide (IL-P14) be able to. The combinations of cations and anions included in EMI-FSI and EMI-TFSI are as follows.

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, with respect to 100 parts by weight of the acrylic polymer. It is more preferably 60 parts by weight, more preferably 5 to 50 parts by weight, more preferably 5 to 40 parts by weight, more preferably 5 to 30 parts by weight. 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, and 45 parts by weight with respect to 100 parts by weight of the acrylic polymer. , 40 parts by weight, 35 parts by weight, 33 parts by weight, 32 parts by weight, 31 parts by weight, and 30 parts by weight. 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 with respect to 100 parts by weight of the acrylic polymer. , 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, and 20 parts by weight. The ionic liquid may be a combination of one cation and one anion, or a combination of multiple types of cations and anions.

(migration promoter)
In this embodiment, the composition may contain a migration enhancer that aids in the migration of ions upon application of a voltage. Examples of the transfer accelerator include polyethylene glycol, alkyl ether of polyethylene glycol, and the like, and alkyl ether of polyethylene glycol is preferable.

Although the molecular weight of the migration promoter is not particularly limited, it preferably has a weight average molecular weight of 120 to 600, more preferably 120 to 550, and a weight average molecular weight of 120 to 500. It more preferably has a molecular weight, more preferably a weight average molecular weight of 120-360. The upper limit of the weight average molecular weight of the migration enhancer is, for example, , 410, 400, 390, 380, 370, 360, 355, 350, 340. The lower limit of the weight average molecular weight of the migration enhancer is 120, 125, 130, 135, 140, 145, 150, 155, 160, 170, for example. The weight average molecular weight referred to here refers to the weight average molecular weight in terms of polystyrene.

Alkyl ethers of polyethylene glycol include, for example, 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, polyethylene glycol mono(di)pentyl ether and the like. Among them, alkyl ether of polyethylene glycol having a weight average molecular weight of 120 to 360 is preferred, and polyethylene glycol mono(dimethyl) ether having a weight average molecular weight of 120 to 360 is more preferred. 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, more preferably tetraethylene glycol dimethyl ether. Alkyl ethers of polyethylene glycol are available from Nihon Nyukazai, Toho Chemical Industry and the like. The alkyl ether of polyethylene glycol to be used may be used alone or in combination of two or more.

The amount of migration promoter contained in the composition is not particularly limited, but may be, for example, 1 to 90 parts by weight or 5 to 80 parts by weight with respect to 100 parts by weight of the acrylic polymer. , 5 to 50 parts by weight, 5 to 40 parts by weight, or 5 to 30 parts by weight. 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, and 30 parts by weight, relative to 100 parts by weight of the acrylic polymer. Department. 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 with respect to 100 parts by weight of the acrylic polymer. , 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, and 20 parts by weight.

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

(Additive)
In addition to the above components, the composition of the present embodiment contains additives such as conductive materials, fillers, plasticizers, antioxidants, flame retardants, colorants, surfactants, and adhesives other than the above acrylic polymers. may be included.

There are mainly carbon-based conductive materials and metal-based conductive materials as conductive materials. Carbon-based conductive materials include, for example, nanocarbon or carbon fiber [eg, vapor grown carbon fiber (VGCF) or carbon nanofiber], more specifically natural graphite, artificial graphite, acetylene black, and ketjen black. , furnace black and the like. Examples of metal-based conductive materials include metals such as Cu, Ni, Al, Ag, Au, Pt, Zn, and Mn, and alloys thereof. A single conductive material may be used, or a plurality of types may be used in combination.

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, and aluminum nitride. mentioned. The filler may be used alone or in combination of multiple types.

Examples of plasticizers include polyols such as glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol and polyethylene glycol; Aromatic polycarboxylic acid esters such as polycarboxylic acid esters, terephthalic acid esters, isophthalic acid esters, phthalic acid esters, trimellitic acid esters, and benzoic acid esters, and polyesters. The plasticizer may be used alone or in combination of multiple types.

Examples of antioxidants include phenol-based antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. Antioxidants may be used alone or in combination of multiple types.

Examples of flame retardants include phosphorus- and halogen-containing organic compounds, bromine- or chlorine-containing organic compounds, ammonium polyphosphate, aluminum hydroxide, antimony oxide, and other additive and reactive flame retardants. A flame retardant may be used independently and may be used in combination of multiple types.

Examples of colorants include inorganic pigments such as carbon black, titanium oxide, zinc oxide, iron oxide and mica, and organic pigments such as coupling azo, condensed azo, anthraquinone, thioindigo, dioxazone and phthalocyanine pigments. A pigment etc. are mentioned. Colorants may be used alone or in combination of multiple types.

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

Examples of adhesives other than the above acrylic polymers include silicone-based adhesives, polyester-based adhesives, urethane-based adhesives, and rubber-based adhesives. Examples of silicone-based adhesives include dimethylsiloxane-based and diphenylsiloxane-based adhesives. Examples of the polyester pressure-sensitive adhesive include polyester obtained by polycondensation of a carboxylic acid component having two or more functional groups and a diol component. Urethane-based adhesives include, for example, urethane-based polymers obtained by reacting polyols with polyisocyanate compounds. Examples of rubber adhesives include synthetic rubbers such as styrene-isoprene block copolymers, styrene-butadiene-styrene block copolymers, styrene-butadiene rubbers, polyisoprene rubbers, polyisobutylenes, and butyl rubbers, and natural rubbers. .

The amount of these adhesives other than the acrylic polymer is less than 100 parts by weight, preferably 90 parts by weight or less, more preferably 80 parts by weight or less, relative to 100 parts by weight of the acrylic polymer. Preferably, it is 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, and 30 parts by weight or less. is 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 , it is more preferable that no pressure-sensitive adhesive other than the acrylic polymer is contained.

The amount of these additives (excluding pressure-sensitive adhesives other than the acrylic polymer) contained in the composition is not particularly limited, but can be, for example, 0.1 to 200 parts by weight based on 100 parts by weight of the acrylic polymer. , 1 to 100 parts by weight.

The method of forming the adhesive layer or the electrically peelable adhesive layer is not particularly limited, and for example, it is formed by applying the composition to a release-treated polyethylene terephthalate film (release film) or the like and bonding a core material to this. can. After applying the composition to the release film, the composition may be dried by heating the composition. Another formation example of the adhesive layer and the electrically peelable adhesive layer can be formed by applying the composition to the core material. The method of applying these compositions is not particularly limited, but examples include direct application with a brush or the like, and use of an application device used in the production of pressure-sensitive adhesive tapes. A spin coater, gravure coater, applicator, multi coater, die coater, bar coater, roll coater, blade coater, knife coater, or the like can be used as the coating device. The thickness of the electrically peelable pressure-sensitive adhesive layer is not particularly limited, but it is preferably 1 to 100 μm, more preferably 1 to 50 μm, even more preferably 5 to 30 μm. In the case where the adhesive layer is formed with an electro-peeling adhesive layer on both sides, the two electro-peeling adhesive layers may have the same thickness or may have different thicknesses.

The pressure-sensitive adhesive sheet of this embodiment functions as a substance that fixes a substance to be fixed to an adherend by the pressure-sensitive adhesive sheet (referred to as a fixed object) to the adherend. The surface of the pressure-sensitive adhesive sheet to be used may be protected with a release film, release paper, or the like until use.

The adherend in this embodiment refers to an object that provides a place to which an object to be fixed is fixed via the pressure-sensitive adhesive sheet of this embodiment. Here, fixing includes direct fixing and indirect fixing, and direct fixing refers to a state in which the adherend and the object to be fixed are in direct contact with the adhesive sheet. The term refers to a state in which the adherend and/or the object to be fixed are not in direct contact with the pressure-sensitive adhesive sheet but are in contact with each other via the conductive auxiliary material. As long as the object to be fixed can be fixed to the adherend, the fixing method may be direct fixing or indirect fixing.

The adherend may be an adherend having conductivity (conductive adherend) or an adherend having no conductivity (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 the conductive auxiliary material to the non-conductive adherend. Any adhesive such as a commercially available adhesive is used to attach the conductive auxiliary material.

Examples of conductive adherends include metals such as iron, aluminum, copper, silver, and gold, metal plates made of alloys of these metals, metal products, and metal workbenches. Non-conductive adherends include, for example, wooden plywood, plastic products, non-metallic workbenches, and the like.

The object to be fixed in this embodiment is not particularly limited, but 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, it is essential to attach the electrically conductive auxiliary material to the object to be fixed and then to the adhesive sheet, as in the case of non-conductive adherends.

Examples of conductive fixed objects include foils (thickness less than 100 μm) and plates (thickness 100 μm or more) made of metals such as iron, aluminum, copper, silver, and gold, or alloys of these metals. Mesh or cloth containing fibers mixed or coated with metals or alloys, resin sheets containing these metals or alloys, resin plates with layers containing these metals, alloys or conductive metal oxides, etc. be done. Examples of non-conductive fixed objects include resin, wood, plastic plates, and the like.

The conductive auxiliary material is not particularly limited as long as it has conductivity. Examples include metals such as aluminum, copper, silver, and gold, alloys of these metals, or conductive metal oxides (indium tin oxide: ITO, etc.) vapor-deposited films, cloth containing fibers mixed or coated with these metals or alloys, resin sheets containing these metals or alloys, these metals, alloys or conductive metal oxides A resin plate having a layer containing

FIG. 1A shows an example of a cross section of the pressure-sensitive adhesive sheet on which an electrically exfoliating pressure-sensitive adhesive layer is formed (a cross section when a tape attached to a horizontal surface is cut in the vertical direction; the same applies hereinafter). FIG. 1B shows an example of a cross-section of a pressure-sensitive adhesive sheet comprising a core material impregnated with an electro-releasable pressure-sensitive adhesive composition. 2A to 5B show an example of a circuit when voltage is applied to the electro-peelable pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet formed with the electro-peeling pressure-sensitive adhesive layer via a conductive object, and the peeling after voltage application. Give an example. 6A and 6B show circuit examples and voltages when voltage is applied via a conductive object to both sides of the adhesive layer of the adhesive sheet, which consists of a core material in which the electro-peelable adhesive composition permeates. shows an example of peeling after application of . The form of use of the pressure-sensitive adhesive sheet of the present invention is not limited to the following circuit examples and peeling examples. In the peeling examples below, the adhesive sheet remains on the adherend side. Detachment can be performed as follows. The side of the power supply on which the adhesive sheet remains depends on the composition of the adhesive sheet and is not particularly limited.

In each drawing, 1 is an electro-peeling adhesive layer, 2 is a core material, 3 is a conductive adherend, 4 is a DC power supply, 5 is a conductive fixing object, and 6 is a non-conductive fixing object. , 7 means an optional adhesive, 8 means a conductive auxiliary material, 9 means a non-conductive adherend, and 10 means an adhesive layer. In FIG. 1A, the adhesive sheet has an electro-releasing adhesive layer 1 formed on both sides of a core material 2, and an adhesive layer 10 is formed by the core material 2 and the electro-releasing adhesive layer 1 (see FIG. 1A). The same applies to the examples shown in FIGS. 2A to 5B). In FIG. 1B, the electro-peeling adhesive composition permeates 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 6B). 1A and 1B, the adhesive layer 10 is also the adhesive sheet itself.

FIG. 2A shows an example of a cross section in which a conductive fixing target 5 is adhered to a conductive adherend 3 using an adhesive sheet and a voltage is applied. As shown in FIG. 2A, a terminal is connected to a conductive fixing object 5 and a conductive adherend 3, and a voltage is applied to the electro-peeling adhesive layer 1 by forming a circuit with a DC power source 4. The adhered conductive fixing object 5 can be separated from the conductive adherend 3 as shown in 2B.

FIG. 3A shows an example of a cross section in which a non-conductive fixed object 6 is adhered to a conductive adherend 3 using an adhesive sheet and a voltage is applied. As shown in FIG. 3A, an aluminum plate as a conductive auxiliary material 8 is attached to a non-conductive fixed object 6 using an arbitrary adhesive agent 7, and the non-conductive fixed object 6 and the conductive auxiliary are attached. The material 8 and the conductive adherend 3 are adhered using an adhesive sheet. A terminal was 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 electro-peeling adhesive layer 1 and sticking it as shown in FIG. 3B. The non-conductive fixing object 6 can be peeled off from the conductive adherend 3 . In this case, the conductive auxiliary material 8 attached to the non-conductive fixing object 6 remains on the non-conductive fixing object 6 .

FIG. 4A shows an example of a cross section in which a conductive fixing target 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 as a conductive auxiliary material 8 is attached to a non-conductive adherend 9 using an arbitrary adhesive agent 7, and a conductive fixed object 5 and a conductive auxiliary are attached. The material 8 and the non-conductive adherend 9 are adhered using an adhesive sheet. Terminals were connected to the conductive fixing object 5 and the conductive auxiliary material 8 to form a circuit with the DC power source 4, thereby applying a voltage to the electro-peeling adhesive layer 1 and sticking it as shown in FIG. 4B. A conductive fixed object 5 can be separated from a non-conductive adherend 9 .

FIG. 5A shows an example of a cross section in which a non-conductive fixed object 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 as a conductive auxiliary material 8 is attached to each of the non-conductive fixing object 6 and the non-conductive adherend 9 using an arbitrary pressure-sensitive adhesive 7. A conductive auxiliary material 8 to which a non-conductive object 6 is adhered and a conductive auxiliary material 8 to which a non-conductive adherend 9 is adhered are adhered using an adhesive sheet. Terminals are connected to each of the conductive auxiliary materials 8, a voltage is applied to the electrically peeling adhesive layer 1 by forming a circuit with the DC power supply 4, and a non-conductive fixed object is adhered as shown in FIG. 5B. 6 can be peeled from the non-conductive adherend 9 . In this case, the conductive auxiliary material 8 attached to the non-conductive fixing object 6 remains on the non-conductive fixing object 6 .

FIG. 6A shows an example of a cross section of a conductive fixing object 5 adhered to a conductive adherend 3 using an adhesive sheet consisting of a core material impregnated with an electro-peelable adhesive composition, and voltage is applied. is shown. As shown in FIG. 6A, a terminal is connected to a conductive fixing object 5 and a conductive adherend 3, and a voltage is applied to the core material 2 (adhesive layer 10) by forming a circuit with a DC power supply 4, As shown in FIG. 6B, the adhered conductive fixing object 5 can be peeled off from the conductive adherend 3 .

(Uses of electro-releasable adhesive sheets)
The electrically peelable pressure-sensitive adhesive sheet of this embodiment can be easily peeled from a conductive object by applying a low voltage such as 30 V or less without UV irradiation or heat treatment. Therefore, the adhesive sheet can be suitably used for adhesively fixing non-transparent members that cannot be irradiated with UV rays, members that are vulnerable to heat, and the like. In addition, since the composition of the present invention is excellent in adhesive fixation of conductive objects, it is used for fixing members that require high processing accuracy, and for fixing members that are difficult to physically fix such as thin metal plates and substrates. It can be suitably used for For example, the composition can be used for temporary fixing of parts in the electronic part manufacturing process (for example, temporary fixing of wafers during dicing of LSI chips), and the temporary fixing of parts can be easily released by applying a voltage. In addition, the electrically exfoliating pressure-sensitive adhesive sheet of the present embodiment is thin and can be easily and evenly attached to an adherend. Therefore, it is possible to work efficiently even when fixing parts in an assembly line.

(Method for producing an electro-peelable pressure-sensitive adhesive composition)
The electro-peelable pressure-sensitive adhesive composition of the present embodiment can be produced by stirring and mixing an acrylic polymer, an ionic liquid, and optionally a transfer accelerator, a cross-linking agent, and the like. 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 accelerator, a cross-linking agent, and the like may be stirred using a V-type mixer or mixer (dissolver, homomixer, planetary mixer, etc.). During stirring, the above additives may be added.

(Method for producing an electrically peelable pressure-sensitive adhesive sheet)
One embodiment of the present invention is a method for producing an electrically peelable pressure-sensitive adhesive sheet. The electro-peeling pressure-sensitive adhesive sheet is produced by contacting 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 with an electro-peeling adhesive composition containing an acrylic polymer and an ionic liquid. can be manufactured by forming an adhesive layer with The electro-peeling adhesive composition, the core material, and the electro-peeling adhesive sheet are as described above.

Bringing the electro-peeling adhesive composition into contact with the core material can be achieved, for example, by permeating the electro-peeling adhesive composition into the core material, or by bringing the electro-peeling adhesive composition into contact with both sides of the core material. forming a layer of the electro-releasable pressure-sensitive adhesive composition.

For example, impregnation of the electro-peeling adhesive composition into the core material, or contacting the electro-peeling adhesive composition on both sides of the core material to form a layer of the electro-peeling adhesive composition is, for example, It can be obtained by applying an electrically peelable pressure-sensitive adhesive composition on a peeling film and attaching a core material to this. A release film coated with an electrically peelable pressure-sensitive adhesive composition may be attached to the side of the core material to which the release film is not attached. When the core material is composed of fibers or has pores, the adhered electro-peeling adhesive composition permeates into the fibers and pores. At this time, pressure may be applied to the pasted core material. By applying pressure, it becomes easier for the electro-peelable pressure-sensitive adhesive composition to permeate the core material. The pressure may be applied from only one side of the core material, or may be applied from both sides. The electro-peelable pressure-sensitive adhesive composition may be completely contained in the core material by permeating the core material. At that time, the pressure-sensitive adhesive sheet becomes a pressure-sensitive adhesive sheet comprising a core material impregnated with the electro-releasable pressure-sensitive adhesive composition. The electro-peelable pressure-sensitive adhesive composition may form a layer of the electro-peeling pressure-sensitive adhesive composition while permeating the core material. In the method described above, the film coated with the electro-peeling adhesive composition is attached to the core material, but the electro-peeling adhesive composition may be applied directly to the core material. The method for applying the electrically peelable pressure-sensitive adhesive composition is as described above.

(Peeling method)
The pressure-sensitive adhesive sheet of this embodiment can be peeled off from the conductive object to which the pressure-sensitive adhesive sheet is pasted by applying a voltage after the pressure-sensitive adhesive sheet is pasted on the conductive object.

As a peeling method, for example, if the object to be fixed and the adherend are conductive, terminals are connected to the object to be fixed and the adherend, and a voltage is applied between the terminals to remove the adhesive sheet from the object to be fixed. Can be peeled off from objects or adherends. If the object to be fixed and/or the adherend is not conductive, fixing and peeling operations can be performed even if it is non-conductive by adhering an aluminum plate or the like as a conductive auxiliary material. These fixing and peeling operations are shown in the peeling example of the pressure-sensitive adhesive sheet described above.

The voltage to be applied is not particularly limited as long as the adhesive sheet can be peeled off, but considering the scale of the voltage application device, the impact on fixed objects, and the risk to the human body due to accidents during work, a low voltage is preferable. The applied voltage range is, for example, 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 up to 0.5V, 1V, 2V, 3V, 4V, 5V , 6V, 7V, 8V, 9V and 10V voltages can be selected and combined with lower limits. Among these, working with a voltage of 1 to 30 V is particularly preferable from the standpoints of small size of the application device, safety, and impact on fixed objects.

The pressure-sensitive adhesive sheet of this embodiment can be peeled off from a conductive object even when the applied voltage is as low as several volts. This indicates that according to this embodiment, the peeling operation can be performed with a simple application device that is excellent in safety for the operator and can be carried around.

The voltage application time is not particularly limited as long as the pressure-sensitive adhesive sheet can be peeled off, but considering the effect on the fixed object, it is preferably within 10 minutes, more preferably within 5 minutes, and within 3 minutes. It is more preferable that the time is within 1 minute.

Although the temperature at which peeling is performed is not particularly specified, it is preferable to perform at room temperature. As described above, the pressure-sensitive adhesive sheet of the present embodiment can be peeled off from a conductive object at a low voltage in a short period of time.

Since the electro-peeling adhesive sheet of the present embodiment contains a core material having a basis weight of 10.0 g/m ² or less and a thickness of 10 μm to 35 μm, the handling of the adhesive sheet is facilitated. Specifically, when the adhesive sheet of the present embodiment is used, when the release films attached to both sides are peeled off, the shape of the adhesive sheet does not break or stretch, making it easy to apply. When the composition is used without using a base material (core material), the shape of the pressure-sensitive adhesive layer tends to change when the release film attached to the pressure-sensitive adhesive layer is peeled off, making it difficult to apply. If a core material with a basis weight of 10.0 g/m ² or less and a thickness of 10 μm to 35 μm is not satisfied, for example, if a thick core material exceeding 35 μm is used, it will be easier to apply, but the adhesive sheet will be thicker, or the electrical peeling property will be reduced. However, the adhesive sheet cannot be easily peeled off after the voltage is applied. Whether the adhesive sheet can be easily peeled off after voltage application is determined by the adhesive sheet that can be easily peeled off after voltage application if the rate of decrease in adhesive strength calculated by the following formula (4) is 70% or more. can be determined to be The reduction rate is preferably 75% or more, more preferably 80% or more, more preferably 85% or more, and 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, it is possible to obtain an electro-peelable pressure-sensitive adhesive sheet that is easy to apply.

(In the formula, the adhesive force of the adhesive sheet not applied is measured in accordance with JIS-Z-0237 (2009) after fixing the adhesive sheet to a conductive adherend and a conductive fixing object. refers to stickiness,
The adhesive strength of the adhesive sheet after application treatment is determined by JIS-Z-0237 (2009 ) refers to the adhesive strength measured in accordance with

One embodiment of the present invention involves the use of a core material with a basis weight of 10.0 g/m ² or less and a thickness of 10 μm to 35 μm for the manufacture of an electro-peeling 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, it is possible to produce an electro-peeling pressure-sensitive adhesive sheet having excellent electro-peeling properties and workability. The electrically peelable pressure-sensitive adhesive sheet and the core material are as described above.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited by these.

(Production of Electro-Peeling Adhesive Composition 1)
Using an acrylic polymer, an ionic liquid, and a transfer accelerator, an electro-peeling adhesive composition was prepared as follows.

1. Preparation of acrylic polymer A monomer mixture consisting of 91 parts by weight of n-butyl acrylate (Mitsubishi Chemical Co., Ltd.), 8 parts by weight of acrylic acid (Mitsubishi Chemical Co., Ltd.), and 1 part by weight of 2-hydroxyethyl methacrylate (Nippon Shokubai Co., Ltd.), 186 parts by weight of the polymerization solvent (ethyl acetate:toluene (weight ratio) = 9:1) was put into a glass flask, and after purging with nitrogen gas, azobisisobutyronitrile (AIBN, Junsei Chemical Company) was added, and the temperature was raised to 85° C. and polymerized 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.

2. Preparation of Electro-Peelable Adhesive Composition 100 parts by weight of the above acrylic adhesive (including 35 parts by weight of the acrylic polymer) was added with Coronate (registered trademark) L-55E (Tosoh Corporation) as an isocyanate cross-linking agent. ) 3.85 parts by weight, 7.0 parts by weight of ELEXCEL (registered trademark) AS-110 (EMI-FSI: Daiichi Kogyo Seiyaku Co., Ltd.) as an ionic liquid, and 7.0 parts by weight of dimethyl tetraglycol (Nippon Nyukazai Co., Ltd.: molecular weight: about 220) as a migration promoter. parts by weight were added, stirred at room temperature for 10 minutes with a dissolver, and degassed by standing to obtain an electrically peelable pressure-sensitive adhesive composition A (composition A).

(Production of Electro-Peeling Adhesive Composition 2)
A composition was prepared as follows using an acrylic polymer and an ionic liquid. As the acrylic polymer, the acrylic polymer prepared in the above "1. Preparation of acrylic polymer" was used.
100 parts by weight of acrylic adhesive (including 35 parts by weight of acrylic polymer), 3.85 parts by weight of Coronate L-55E (Tosoh Corporation) as an isocyanate cross-linking agent, and 14.0 parts by weight of EMI-FSI as an ionic liquid. was added, stirred at room temperature for 10 minutes with a dissolver, and degassed by standing to obtain an electrically peelable pressure-sensitive adhesive composition B (composition B).

(Example 1)
Production of electro-peelable adhesive sheet 1
Composition A was used to produce an electropeelable pressure-sensitive adhesive sheet in the form of a double-sided pressure-sensitive adhesive sheet (hereinafter also simply referred to as a double-sided sheet). Japanese paper (manufactured by Hidaka Washi Co., Ltd.) having a basis weight of 5.0 g/m ² and a thickness of 30 μm was used as the core material of the double-sided sheet.
Composition A was applied to a polyethylene terephthalate film (hereinafter also referred to as release film) having a surface treated with silicone in such an amount that the thickness of composition A after drying would be 22 μm, and dried at 100° C. for 5 minutes. The composition-applied surface of the dried film was attached to one side of Japanese paper. Similarly, Composition A was applied to a release film in such an amount that the composition A had a thickness of 22 μm after drying, followed by drying to prepare a film, which was attached to the surface of Japanese paper to which no film had been attached. After that, the double-faced sheet of Example 1 was produced by standing at 40° C. for 3 days.

(Example 2)
Production of electro-peelable adhesive sheet 2
A double-faced sheet of Example 2 was produced in the same manner as in Production of Electro-Releasable Adhesive Sheet 1, except that composition A was applied to each side of the release film in such an amount that the thickness after drying was 12 μm. .

(Example 3)
Production of electro-peelable adhesive sheet 3
A double-faced sheet of Example 3 was produced in the same manner as in the production of the electrically peelable adhesive sheet 1, except that the composition B was used instead of the composition A.

(Example 4)
Production of electro-peelable adhesive sheet 4
Same as Manufacture of Electro-Releasable Adhesive Sheet 1, except that polyester-based nonwoven fabric (UT-PET (A) 8S: manufactured by Nippon Paper Papylia Co., Ltd.) with a basis weight of 8.0 g/m ² and a thickness of 14 μm is used as the core material. A double-faced sheet of Example 4 was produced.

(Example 5)
Manufacture of electro-peelable adhesive sheets5
A double-faced sheet of Example 5 was produced in the same manner as in Production of Electro-Releasable Adhesive Sheet 1, except that paper having a basis weight of 6.0 g/m ² and a thickness of 17 μm (thin base paper: manufactured by Nippon Paper Papylia Co., Ltd.) was used as the core material. manufactured.

(Example 6)
Manufacture of electro-peelable adhesive sheets6
Paper with a basis weight of 6.0 g/m ² and a thickness of 17 μm (thin base paper: manufactured by Nippon Paper Papylia Co., Ltd.) was used as the core material, and the composition A was applied to each surface of the release film so that the thickness after drying was 12 μm. A double-faced sheet of Example 6 was produced in the same manner as in the production of the electro-peeling pressure-sensitive adhesive sheet 1, except that the respective amounts were applied.

(Comparative example 1)
As a core material, a polyester-based nonwoven fabric [MILIFE (registered trademark) TY0503FE (ENEOS Techno Material Co., Ltd.)] having a basis weight of 8.0 g/m ² and a thickness of 40 μm was used, and composition A was applied to each surface of the release film. A double-faced sheet of Comparative Example 1 was produced in the same manner as in Production of Electro-Removable Adhesive Sheet 1, except that each coating was applied in such an amount that the thickness after drying was 30 μm.

(Comparative example 2)
As a core material, a polyester-based nonwoven fabric [Milife (registered trademark) TY0503FE] having a basis weight of 8.0 g/m ² and a thickness of 40 μm was used, and the thickness of the composition A after drying was 20 μm on each surface of the release film. A double-faced sheet of Comparative Example 2 was produced in the same manner as in the production of the electrically peelable pressure-sensitive adhesive sheet 1, except that each coating was applied in the amount of

(Comparative Example 3)
As a core material, a polyester-based nonwoven fabric [Milife (registered trademark) TY0503FE] having a basis weight of 8.0 g/m ² and a thickness of 40 μm was used, and the composition A was applied to each surface of the release film so that the thickness after drying was 15 μm. A double-faced sheet of Comparative Example 3 was produced in the same manner as in Production of Electro-Peelable Adhesive Sheet 1, except that each coating was applied in an amount of

(Comparative Example 4)
A double-faced sheet of Comparative Example 4 was produced by coating composition A on a polyethylene terephthalate film having a silicone-treated surface to a thickness of 50 μm after drying, and attaching a release film to the coated surface.

(Comparative Example 5)
A double-faced sheet of Comparative Example 5 was produced by coating composition A on a polyethylene terephthalate film having a silicone-treated surface so that the thickness after drying was 30 μm, and attaching a release film to the coated surface.

(Comparative Example 6)
As a 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, and the thickness of the composition A after drying was applied to each surface of the release film. A double-faced sheet of Comparative Example 6 was produced in the same manner as in the production of the electro-peeling adhesive sheet 1, except that each coating was applied in such an amount that the thickness was 12 μm. Unlike the polyester-based nonwoven fabric used in Example 4, this PET film is non-fiber and has no pores.

(Comparative Example 7)
As a core material, a non-woven fabric (manufactured by Daio Paper Co., Ltd.) having a basis weight of 23.0 g/m ² and a thickness of 40 μm was used, and an amount of composition A was applied to each surface of the release film so that the thickness after drying was 10 μm. A double-faced sheet of Comparative Example 7 was produced in the same manner as in Production 1 of Electro-Peelable Adhesive Sheet except for the coating.

(Comparative Example 8)
Rayon (manufactured by Nippon Paper Papylia Co., Ltd.) with a basis weight of 14.0 g/m ² and a thickness of 40 μm was used as the core material, and the composition A was added to each surface of the release film so that the thickness after drying was 15 μm. A double-faced sheet of Comparative Example 8 was produced in the same manner as in Production 1 of Electro-Peelable Adhesive Sheet except that each coating was applied.

(Evaluation of double-sided sheet)
The thickness, workability, adhesive strength, and electrical releasability of the produced double-faced sheet were evaluated. It should be noted that none of the core materials used in the examples and comparative examples has electrical conductivity. Each procedure is described below.

(Thickness measurement)
A Peacock precision measuring instrument was used to measure the thickness of the double-sided sheet. The measurement was performed at 5 points on the double-sided sheet, and the average of the measurement results 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.

(Evaluation of workability)
Evaluating the workability of the double-sided sheet, when the polyethylene terephthalate film pasted on both sides of the double-sided sheet is peeled off, the double-sided sheet does not tear or stretch, and if it is easy to apply, the double-sided sheet is workable. It was evaluated as having excellent performance. When the release film was peeled off, the shape of the double-sided sheet was cut or stretched, and if it was difficult to stick, the double-sided sheet was evaluated as inferior in workability.

(Adhesive evaluation)
The release film on one side of each of the double-sided sheets of Examples 1 to 6 and Comparative Examples 1 and 5 to 8 was peeled off, and a 50 μm thick aluminum foil (an object to be fixed) was attached. After attaching the aluminum foil, the double-sided sheet was cut out together with the aluminum foil to a length of 250 mm x 25 mm (three pieces for each double-sided sheet, hereinafter referred to as double-sided tape). The release film on the other side of each cut double-sided tape was peeled off, and a 100 mm x 25 mm portion was attached to a polished stainless steel plate (conductive adherend: 125 mm x 50 mm). On the other hand, a rubber roller weighing 2 kg was reciprocated once in the longitudinal direction of the sample piece at a speed of 300 mm/min to press the adherend, the adhesive product, and the object to be fixed to obtain an evaluation sample. After 30 minutes from crimping the adherend, double-sided tape and fixed object, each evaluation sample was subjected to tension using Autograph (registered trademark) AGS-H manufactured by Shimadzu Corporation in accordance with JIS Z-0237 (2009). Measure the force (adhesive strength: N/25mm) required to peel off the double-sided tape in the evaluation sample from the adherend at an angle of 180° (peel 180°) at a speed of 300mm/min. The average value of the measured values was taken as the measured value.

From each double-sided sheet of Examples 1 to 6 and Comparative Examples 1 and 5 to 8, three evaluation samples were prepared for each double-sided sheet in the same manner as above. Attach the electrodes so that the conductive adherend side of each evaluation sample is the negative electrode, and the fixed object side is the positive electrode. seconds. After voltage application, the force required to peel the adhesive tape from the adherend by 180° was measured in the same manner as described above.

The degree of decrease (decrease rate) in the adhesive strength 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 by voltage application is easy. When it is lower than 70%, peeling is difficult.

The structure, tape thickness, evaluation of thickness, and evaluation of adhesiveness of each double-sided tape of Examples 1 to 6 and Comparative Examples 1 to 8 are shown in Tables 1 and 2 below, respectively. In the table, A in the composition column indicates the composition A, B indicates the composition B, and the composition thickness indicates the thickness of the composition after drying on one side (comparative examples 4 and 5 are the total amount).

As in Examples 1 to 6, the double-sided tape having a small basis weight and using a thin core material turned out to be a thin double-sided tape with excellent workability, and a double-sided tape with excellent electrical peeling properties. In Examples 1 to 6 and Comparative Examples 1, 2, and 6 to 8, the thickness of the final double-sided tape was 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 permeated into the interstices of the core material when applied. As in Comparative Examples 1 to 3 and 6 to 8, the double-sided tape with a large basis weight or using a thick core material became a thick double-sided tape. In Comparative Examples 2 to 4, the adhesive force was not measured, but the double-sided tapes of Comparative Examples 2 and 3 had very uneven surfaces on which the composition was applied, and the thickness was uneven. It is not suitable for this, and the adhesive strength cannot be evaluated correctly, so it is not measured. For Comparative Example 4, the inventors believe that the same results as the test of Comparative Example 5, which does not use the core material, are obtained. As in Comparative Examples 4 and 5, the double-faced tapes without a core material were thin, but the shape of the tape was lost when the release film was peeled off due to the absence of a core material, resulting in poor workability. As in Comparative Example 6, when the core material had no electrical conductivity and the composition did not penetrate into the core material, the ionic liquid did not move even when a voltage was applied, and the adhesiveness did not decrease. As in Comparative Examples 7 and 8, if the core material was too thick, even if a thin double-faced tape was formed, sufficient electropeeling properties could not be obtained.

From the above experimental results, it was shown that by using a core material that is thin and has a small basis weight, it is possible to obtain an electro-peeling adhesive sheet that is thin, has excellent workability, and has excellent electro-peeling properties.

Reference Signs List 1 Electro-peeling 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 Optional adhesive 8 Conductive auxiliary material 9 Non-conducting Adherent 10 Adhesive layer

Claims

An electro-peeling adhesive sheet comprising a planar core material and an adhesive layer containing an electro-peeling adhesive composition,
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 electro-peelable 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,
Electro-peeling adhesive sheet.
The pressure-sensitive adhesive sheet according to claim 1, wherein in the pressure-sensitive adhesive layer, both sides of the core material are in contact with the electro-releasable pressure-sensitive adhesive composition.
The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the electro-peelable pressure-sensitive adhesive composition permeates the core material in the pressure-sensitive adhesive layer.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the core material is composed of fibers.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the core material has at least one through hole.
The pressure-sensitive adhesive sheet according to claim 3 or 4, wherein the pressure-sensitive adhesive sheet comprises the core material permeated with the electro-releasable pressure-sensitive adhesive composition.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the core material has a basis weight of 2.0 to 8.0 g/m 2 .
The adhesive sheet according to any one of claims 1 to 7, wherein the adhesive sheet has a thickness of 10 to 50 µm.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the electro-peeling pressure-sensitive adhesive composition contains a transfer accelerator.
The pressure-sensitive adhesive sheet according to claim 9, wherein the transfer promoter is an alkyl ether of polyethylene glycol.
The adhesive sheet according to claim 10, wherein the alkyl ether of polyethylene glycol is polyethylene glycol mono(dimethyl)ether having a weight average molecular weight of 120-360.
The pressure-sensitive adhesive sheet according to any one of claims 9 to 11, wherein the content of said transfer promoter is 5 to 30 parts by weight with respect to 100 parts by weight of said acrylic polymer.
The adhesive sheet according to any one of claims 1 to 12, wherein the ionic liquid has an ionic conductivity of 10 -4 to 10 -2 S/cm.
The adhesive sheet according to any one of claims 1 to 13, wherein the ionic liquid is represented by the following formula (1).

(Wherein, R 1 is a divalent hydrocarbon group having 2 to 8 carbon atoms which may contain a heteroatom, and forms a ring together with N + in the formula,
R 2 and R 3 are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms (provided that when the nitrogen atom forms a double bond with the adjacent carbon atom, R 3 does not exist),
X- is Cl- , Br- , I- , AlCl4- , Al2Cl7- , NO3- , BF4- , PF6- , ClO4- , CH3COO- , CF3COO- , CF 3SO3- , ( CF3SO2 ) 2N- , ( FSO2 ) 2N- , ( CF3SO2 ) 3C- , AsF6- , SbF6- , NbF6- , F (HF ) n - , B ( C6H5 ) 4- , C4F9SO3- , CF3 ( CF2 ) 3SO3- , ( CF3CF2SO2 ) 2N- and CF3CF2COO- anion of choice)
The ionic liquid is selected from cations selected from pyridinium-based cations, cycloaliphatic ammonium cations and imidazolium-based cations, and (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 14, which is a salt with an anion to be used.
The adhesive sheet according to any one of claims 1 to 15, wherein the content of said ionic liquid is 5 to 60 parts by weight with respect to 100 parts by weight of said acrylic polymer.
Claims 1 to 16, wherein the acrylic polymer comprises an alkyl (meth)acrylate having an alkyl group of 1 to 8 carbon atoms, a carboxyl group-containing acrylic monomer and/or a copolymer with a hydroxyl group-containing acrylic monomer. The pressure-sensitive adhesive sheet according to any one of the above.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 17, further comprising a peelable release film, wherein the release films are attached to both sides of the pressure-sensitive adhesive layer.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 18, wherein the pressure-sensitive adhesive strength reduction rate calculated by the following formula (2) is 70% or more.

(In the formula, the adhesive force of the adhesive sheet not applied is measured in accordance with JIS-Z-0237 (2009) after fixing the adhesive sheet to a conductive adherend and a conductive fixing object. refers to the adhesive strength
The adhesive strength of the pressure-sensitive adhesive sheet after application treatment is determined by JIS-Z-0237 ( 2009))
A step of contacting a flat core material having a basis weight of 10.0 g/m 2 or less and a thickness of 10 μm to 35 μm with an electro-releasable adhesive composition containing an acrylic polymer and an ionic liquid to form an adhesive layer. A method for producing an electrically peelable pressure-sensitive adhesive sheet.
The manufacturing method according to claim 20, wherein said contact is permeation of said electro-peeling adhesive composition into said core material.
21. The manufacturing method according to claim 20, wherein the contacting is to bring the electro-peeling adhesive composition into contact with both sides of the core material to form a layer of the electro-peeling adhesive composition.
The manufacturing method according to any one of claims 20 to 22, wherein the electro-peeling adhesive composition further contains a transfer accelerator.