Electrically peelable adhesive composition, electrically peelable adhesive layer, adhesive sheet, and joined body

Abstract

The present invention provides an electrically peelable adhesive composition which can form an adhesive layer, an adhesive sheet, and a joined body that have excellent impact resistance and allow the adhesive force to be lowered by applying voltage. The present invention relates an electrically peelable adhesive composition containing a (meth)acrylic polymer having a glass transition temperature (Tg) of -45°C to 25°C and an ionic substance. The (meth)acrylic polymer includes a unit derived from a monomer containing a cyclic hydrocarbon group and a unit derived from a monomer containing an oxyalkylene group.

Description

Electrolytically removable adhesive composition, electrolytically removable adhesive layer, adhesive sheet, and bond

[0001] The present invention relates to an electropenetrating adhesive composition, an electropenetrating adhesive layer, an adhesive sheet, and a bonded structure.

[0002] In recent years, with the increasing sophistication of various performance aspects of mobile devices such as mobile phones, digital cameras, and PDAs (Personal Digital Assistants), there has been a growing demand for improved performance in the various components used in these devices. In mobile devices, double-sided adhesive tape is sometimes used to join components such as the casing. Depending on how they are used, mobile devices are at risk of being dropped. Therefore, there is a need for mobile devices with high impact resistance and / or initial adhesive strength. To improve the impact resistance and / or initial adhesive strength of mobile devices, impact-absorbing members may be provided on the outside of the casing and / or the surface of the casing may be treated to facilitate adhesion before the adhesive tape is applied to the casing. However, such methods may increase the size of the mobile device, impair its design, and increase the cycle time (the time required to manufacture). Therefore, it is desirable that the double-sided adhesive tape used inside mobile devices has impact resistance and / or high initial adhesive strength so that it is less likely to be damaged or detached from components due to the impact of the mobile device being dropped.

[0003] On the other hand, in the manufacturing process of electronic components, there is a growing demand for rework to improve yield and for recycling, which involves disassembling and recovering components after use. To meet these demands, double-sided adhesive sheets that possess both a certain level of adhesive strength and a certain level of release properties are sometimes used to join materials together in the manufacturing process of electronic components.

[0004] As an adhesive sheet that achieves the above-mentioned adhesive strength and peelability, an adhesive sheet is known that uses an ionic substance such as an ionic liquid consisting of cations and anions as a component forming the adhesive composition, and is peeled off by applying a voltage to the adhesive layer (electropeelable adhesive sheet). For example, Patent Document 1 discloses that a composite adhesive exhibiting electropeelability, good impact resistance, and good shear resistance can be obtained by an adhesive composite composition containing an ionic liquid and a polymer derived from a (meth)acrylate monomer with a Tg above room temperature.

[0005] International Publication No. 2023 / 175424

[0006] Electropeelable adhesive sheets are preferable because they firmly bond components and can be peeled off with little force when voltage is applied. Therefore, it is preferable for electropeelable adhesive sheets to have a large rate of decrease in adhesive strength due to voltage application. However, in conventional adhesive compositions used in mobile devices, external impacts such as dropping or falling could unintentionally cause delamination at the interface between the adhesive layer and the adherend.

[0007] The present invention has been completed in view of the above, and aims to provide an electro-removable adhesive composition capable of forming an electro-removable adhesive layer with excellent impact resistance and electro-removable properties that can reduce adhesive strength by applying voltage, an adhesive sheet comprising an electro-removable adhesive layer formed from the electro-removable adhesive composition, and a bonded body.

[0008] As a result of extensive research by the present inventors, it has been found that the above problem can be solved by providing an electrolytic adhesive composition that has a glass transition temperature (Tg) of -45°C to 25°C and includes a (meth)acrylic polymer containing units derived from monomers containing cyclic hydrocarbon groups and units derived from monomers containing oxyalkylene groups, as well as an ionic substance.

[0009] The means for solving the above problems are as follows: [1] An electrolytic adhesive composition comprising an (meth)acrylic polymer having a glass transition temperature (Tg) of -45°C or higher and 25°C or lower, and an ionic substance, wherein the (meth)acrylic polymer comprises units derived from monomers containing cyclic hydrocarbon groups and units derived from monomers containing oxyalkylene groups. [2] The electrolytic adhesive composition according to [1], wherein the proportion of monomers containing cyclic hydrocarbon groups to the total monomer components constituting the (meth)acrylic polymer is 10% by mass or more. [3] The electrolytic adhesive composition according to [1], wherein the cyclic hydrocarbon group is a polycyclic aliphatic hydrocarbon group. [4] The electrolytic adhesive composition according to [1], wherein the proportion of monomers containing cyclic hydrocarbon groups to the total monomer components constituting the (meth)acrylic polymer is 10% by mass or higher and 45% by mass or less, and the proportion of monomers containing oxyalkylene groups is 5% by mass or higher and 30% by mass or less. [5] The electro-removable adhesive composition according to [1], wherein the ionic substance is an ionic liquid. [6] The electro-removable adhesive composition according to [1], for electro-removal and / or for fixing components in electrical and electronic equipment. [7] An electro-removable adhesive layer formed from the electro-removable adhesive composition according to any one of [1] to [6]. [8] An adhesive sheet comprising an electro-removable adhesive layer formed from the electro-removable adhesive composition according to any one of [1] to [6]. [9] A bond comprising the adhesive sheet according to [8] and a conductive material, wherein the electro-removable adhesive layer is attached to the conductive material.

[0010] The electropenetrating adhesive composition of the present invention can form electropenetrating adhesive layers, adhesive sheets, and bonded bodies that have excellent impact resistance and can be peeled off from the adherend with little force when a predetermined voltage is applied.

[0011] Figure 1 is a cross-sectional view showing an example of an adhesive sheet according to an embodiment of the present invention. Figure 2 is a cross-sectional view showing an example of a laminated structure of a bond according to an embodiment of the present invention. Figure 3 is a cross-sectional view showing an example of a laminated structure of a bond according to an embodiment of the present invention. Figure 4 is a cross-sectional view showing an example of a laminated structure of a bond according to an embodiment of the present invention. Figure 5 is a cross-sectional view showing an example of a laminated structure of a bond according to an embodiment of the present invention. Figure 6 is a cross-sectional view showing an example of a laminated structure of a bond according to an embodiment of the present invention. Figure 7 is a cross-sectional view showing an example of a laminated structure of a bond according to an embodiment of the present invention. Figure 8 is a cross-sectional view showing an overview of the 180° peel test method in the example.

[0012] The embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below. In this specification, "adhesive" is used to mean a tackling agent (also called a "pressure-sensitive adhesive").

[0013] [Electrolytic Adhesive Composition] An electrolytic adhesive composition according to an embodiment of the present invention is an electrolytic adhesive composition containing an (meth)acrylic polymer having a glass transition temperature (Tg) of -45°C or higher and 25°C or lower, and an ionic substance, wherein the (meth)acrylic polymer includes units derived from monomers containing cyclic hydrocarbon groups and units derived from monomers containing oxyalkylene groups.

[0014] The mechanism by which the above problems are solved by the (meth)acrylic polymer contained in the electro-peelable adhesive composition according to the embodiment of the present invention contains units derived from monomers containing cyclic hydrocarbon groups and units derived from monomers containing oxyalkylene groups is not clear, but the inventors speculate as follows. The (meth)acrylic polymer contained in the electro-peelable adhesive composition according to the embodiment of the present invention has a glass transition temperature (Tg) of -45°C or higher and 25°C or lower, and is a (meth)acrylic polymer containing units derived from monomers containing cyclic hydrocarbon groups and units derived from monomers containing oxyalkylene groups (hereinafter sometimes referred to as "specific (meth)acrylic polymer"). When the specific (meth)acrylic polymer contains units derived from monomers containing cyclic hydrocarbon groups, these units have significant steric hindrance due to their structure, and therefore act as stress-relieving units in the (meth)acrylic polymer where entanglement is suppressed, resulting in an adhesive composition that is difficult to peel off when impact is applied. On the other hand, if the specific (meth)acrylic polymer contains units derived from monomers containing oxyalkylene groups, the highly flexible structure can improve conformability to the adherend and stress relaxation. Furthermore, the inclusion of oxyalkylene groups with high polarity and hydrophilicity can improve interfacial adhesion and electrolysis. As described above, by including both units derived from monomers containing cyclic hydrocarbon groups and units derived from monomers containing oxyalkylene groups in the specific (meth)acrylic polymer, the adhesive layer can be given excellent impact resistance and electrolysis. The electrolysis adhesive composition (hereinafter also referred to as the adhesive composition of this embodiment) will now be described.

[0015] In this specification, the adhesive strength when no voltage is applied is sometimes referred to as "initial adhesive strength." Furthermore, the property of adhesive strength decreasing upon the application of voltage is called "electropenetration," and a large decrease in adhesive strength due to voltage application is sometimes described as "excellent electropenetration."

[0016] The electropenetrating adhesive layer formed by the electropenetrating adhesive composition according to the embodiment of the present invention is an adhesive layer having the property of decreasing adhesive strength when a voltage is applied. Furthermore, it is preferable that the ionic substance is an ionic liquid. Furthermore, it is preferable that the electropenetrating adhesive layer is for electropenetration and / or for fixing components in electrical and electronic equipment.

[0017] <Components of the electrolytic adhesive composition> ((meth)acrylic polymer having a glass transition temperature (Tg) of -45°C or higher and 25°C or lower) The electrolytic adhesive composition according to the embodiment of the present invention contains a (meth)acrylic polymer having a glass transition temperature (Tg) of -45°C or higher and 25°C or lower, comprising monomer units derived from monomers containing cyclic hydrocarbon groups and units derived from monomers containing oxyalkylene groups.

[0018] If the glass transition temperature (Tg) of the specific (meth)acrylic polymer contained in the electropenetrating adhesive composition according to the embodiment of the present invention is 25°C or lower, it is advantageous from the viewpoint of increasing the flexibility of the adhesive in the room temperature range (e.g., 25°C) and making it easier to adhere to the adherend. In addition, the rate of decrease in adhesive strength due to voltage application becomes larger, making it easier to achieve both electropenetration and impact resistance. The glass transition temperature (Tg) is preferably 23°C or lower, more preferably 20°C or lower, more preferably 10°C or lower, and may also be 5°C or lower, 3°C or lower, 0°C or lower, or -5°C or lower. Furthermore, if the glass transition temperature (Tg) of the specific (meth)acrylic polymer contained in the electropenetrating adhesive composition according to the embodiment of the present invention is -45°C or higher, it is advantageous from the viewpoint of ensuring the cohesive force of the electropenetrating adhesive layer and obtaining high impact resistance and / or retention force. The glass transition temperature (Tg) is preferably -40°C or higher, more preferably -35°C or higher, even more preferably -30°C or higher, still more preferably -25°C or higher, and most preferably -20°C or higher.

[0019] The glass transition temperature (Tg) of a specific (meth)acrylic polymer contained in an electrolytic adhesive composition can be adjusted by setting the type and content of monomers within the preferred range described below. More specifically, the glass transition temperature (Tg) of a specific (meth)acrylic polymer contained in an electrolytic adhesive composition tends to increase, for example, by selecting monomers with high homopolymer glass transition temperatures and / or increasing their content.

[0020] The glass transition temperature (Tg) of a polymer can be calculated, for example, based on the following equation (Y) (Fox equation): 1 / Tg = W1 / Tg1 + W2 / Tg2 + ... + Wn / Tgn (Y) [In equation (Y), Tg is the glass transition temperature of the polymer (unit: K), Tgi (i = 1, 2, ..., n) is the glass transition temperature when monomer i forms a homopolymer (unit: K), and Wi (i = 1, 2, ..., n) represents the mass fraction of monomer i in the total monomer components]. The above equation (Y) is the calculation formula when the polymer is composed of n types of monomer components: monomer 1, monomer 2, ..., monomer n.

[0021] The glass transition temperature when forming a homopolymer refers to the glass transition temperature of the homopolymer of the monomer in question, and specifically refers to the glass transition temperature (Tg) of a polymer formed using only one monomer (sometimes referred to as "monomer X") as the monomer component. Specifically, the values ​​listed in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. For monomers for which multiple values ​​are listed in this document, the highest value shall be adopted. For monomers for which the glass transition temperature of homopolymers is not listed in the above document, the value obtained by the measurement method described in International Publication No. 2017 / 064918 shall be used.

[0022] The glass transition temperature (Tg) of a specific (meth)acrylic polymer contained in an electrolytic adhesive composition according to an embodiment of the present invention refers to a value obtained, for example, by the following measurement method. That is, when preparing a test sample by solution polymerization, 100 parts by mass of a mixture of monomers in a predetermined proportion, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 200 parts by mass of ethyl acetate as a polymerization solvent are added to a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, and the mixture is stirred for 1 hour while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, the temperature is raised to 63°C and the reaction is carried out for 10 hours. Then, it is cooled to room temperature to obtain a polymer solution with a solid content of 33% by mass. Next, this polymer solution is cast onto a release liner and dried to prepare a test sample (sheet-like polymer) with a thickness of approximately 2 mm. When preparing a test sample using ultraviolet polymerization, a type of photopolymerization method, 100 parts by mass of a monomer mixture in a predetermined ratio, along with 0.05 parts by mass of Omnirad 184 and 0.05 parts by mass of Omnirad 651 as photoinitiators, are placed in a separateable flask and stirred for 15 minutes while introducing nitrogen gas. After removing oxygen from the polymerization system in this manner, ultraviolet light is irradiated until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reaches approximately 20 Pa·s to obtain a prepolymer composition (polymerization rate 5%) in which a portion of the above monomer components have polymerized. Next, this prepolymer composition is cast onto a release liner to a thickness of 200 μm after the coating layer is formed, and then the release liner is bonded to the surface of the coating layer. Subsequently, a black light is used as the light source, and the integrated light intensity is 2000 mJ / cm². ２Under these conditions, ultraviolet light is irradiated to photocur the coated layer and a test sample (sheet-like polymer) is prepared. Then, approximately 1-2 mg of this test sample is weighed into an aluminum open cell, and the reversing heat flow (specific heat component) behavior of the polymer is obtained using a temperature-modulated DSC (product name "Q-2000", manufactured by T.A. Instruments Co., Ltd.) at a heating rate of 5°C / min under a nitrogen atmosphere of 50 ml / min. Referring to JIS-K-7121, the temperature at which a line equidistant in the vertical axis direction from the line extending from the low-temperature baseline and high-temperature baseline of the obtained reversing heat flow intersects with the curve of the step-like change portion of the glass transition is defined as the glass transition temperature (Tg) of the polymer.

[0023] The specific (meth)acrylic polymer according to the embodiment of the present invention is not particularly limited as long as it has a glass transition temperature (Tg) of -45°C or higher and 25°C or lower, and contains units derived from monomers containing cyclic hydrocarbon groups and units derived from monomers containing oxyalkylene groups. For example, it may be a monomer polymer or a partially polymerized polymer (prepolymer). The monomer may be a single monomer or a mixture of two or more monomers. A partially polymerized polymer means a polymer in which at least a portion of the monomer or monomer mixture is partially polymerized.

[0024] The specific (meth)acrylic polymer contained in the electrolytic adhesive composition according to the embodiment of the present invention contains monomer units containing cyclic hydrocarbon groups, which makes it easier to set the glass transition temperature (Tg) of the acrylic polymer to -45°C or higher and 25°C or lower. Furthermore, due to steric hindrance between the monomer units containing the cyclic hydrocarbon groups, stress relaxation occurs, resulting in an improved impact resistance.

[0025] The cyclic hydrocarbon group in a monomer containing a cyclic hydrocarbon group may be either a monocyclic or polycyclic hydrocarbon group. Furthermore, the hydrocarbon group may be either an aliphatic or aromatic hydrocarbon group, with an aliphatic hydrocarbon group being preferable.

[0026] As monocyclic aliphatic hydrocarbon groups, for example, monocycloalkyl groups having 3 to 30 carbon atoms are preferred, and examples of monocycloalkyl groups include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group, and cyclododecyl group.

[0027] Examples of polycyclic aliphatic hydrocarbon groups include adamantyl group, norbornyl group, isobornyl group, and tricyclo[5.2.1.0 ２，６ It may be a polycycloalkyl group having a crosslinked ring polycyclic skeleton such as a decyl group or a tetracyclododecyl group, or it may be a polycycloalkyl group having a condensed ring polycyclic skeleton such as a dicyclopentanyl group, a dicyclo[4.3.0]nonyl group, a tricyclopentanyl group or a dodecahydroacenaphthylene group, or it may be a polycycloalkyl group having a spirocyclic polycyclic skeleton.

[0028] Examples of monocyclic aromatic hydrocarbon groups include the benzyl group and the phenoxyethyl group.

[0029] Examples of polycyclic aromatic hydrocarbon groups include biphenyl groups, naphthyl groups, naphthylmethyl groups, and anthracenyl groups.

[0030] Among the cyclic hydrocarbon groups mentioned above, cyclohexyl groups, dicyclopentanyl groups, isobornyl groups, adamantyl groups, etc., are preferred from the viewpoint of being able to form an electrolytic adhesive composition with excellent impact resistance.

[0031] The monomer containing a cyclic hydrocarbon group is preferably an alkyl (meth)acrylate containing a cyclic hydrocarbon group. That is, the specific (meth)acrylic polymer contained in the electrolytic adhesive composition according to the embodiment of the present invention preferably contains monomer units derived from alkyl (meth)acrylate containing a cyclic hydrocarbon group, and more preferably contains monomer units derived from the following formula (1-1).

[0032] A monomer unit derived from a (meth)acrylic acid alkyl ester containing a cyclic hydrocarbon group facilitates adjusting the glass transition temperature (Tg) of the acrylic polymer to −45° C. or higher and 25° C. or lower, and is suitable for obtaining an impact resistance effect. CH ２ =C(R ａ )COOR ｂ１ (1-1) [In formula (1-1), R ａ is a hydrogen atom or a methyl group, and R ｂ１ is an optionally substituted cyclic hydrocarbon group]

[0033] R ｂ１ is an optionally substituted cyclic hydrocarbon group, and for example, the cyclic hydrocarbon groups listed above may be mentioned, and preferred examples are also the same. R ｂ１ Examples of the substituent that may be possessed by include a cyclohexyl group, an adamantyl group, an isobornyl group, and a dicyclopentanyl group.

[0034] The monomer containing a cyclic hydrocarbon group is preferably an alkyl (meth)acrylate containing a cyclic hydrocarbon group. Examples of alkyl (meth)acrylates containing a cyclic hydrocarbon group include cyclohexyl acrylate (Tg: 15°C), cyclohexyl methacrylate (Tg: 104°C), dicyclopentanyl methacrylate (Tg: 175°C), dicyclopentanyl acrylate (Tg: 120°C), isobornyl methacrylate (Tg: 173°C), and isobornyl acrylate (Tg: 97°C). (°C), 1-adamantyl methacrylate (Tg: 250°C), 1-adamantyl acrylate (Tg: 153°C), dodecahydroacenaphthyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyl oxyethyl (meth)acrylate ) Acrylate, dicyclopentanyloxyethyl (meth)acrylate, dicyclopentanyl methacrylate, biphenyl (meth)acrylate, phenylphenoxyethyl (meth)acrylate, o-biphenyloxyethyl (meth)acrylate, o-biphenyloxyethoxyethyl (meth)acrylate, m-biphenyloxyethyl acrylate, p-biphenyloxyethyl (meth)acrylate, o-biphenyloxy-2-hydroxypropyl (meth)acrylate, p-biphenyloxy-2-hydroxypropyl Examples include biphenyl group-containing monomers such as pyr (meth)acrylate, m-biphenyloxy-2-hydroxypropyl (meth)acrylate, N-(meth)acryloyloxyethyl-o-biphenyl=carbamate, N-(meth)acryloyloxyethyl-p-biphenyl=carbamate, N-(meth)acryloyloxyethyl-m-biphenyl=carbamate, o-phenylphenol glycidyl ether acrylate, terphenyl (meth)acrylate, and o-terphenyloxyethyl (meth)acrylate.Preferably, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, and dodecahydroacenaphthyl (meth)acrylate are used. By using these monomers, polymers with high glass transition temperatures can be obtained.

[0035] In embodiments of the present invention, it is preferable to use at least one monomer selected from the above, specifically cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, and dodecahydroacenaphthyl (meth)acrylate, as the monomer containing a cyclic hydrocarbon group.

[0036] Monomers containing cyclic hydrocarbon groups can be used alone or in combination of two or more.

[0037] The proportion of monomers containing cyclic hydrocarbon groups relative to the total monomer components (100% by mass) constituting the specific (meth)acrylic polymer is not particularly limited and may be, for example, 1% by mass or more, 3% by mass or more, or 6% by mass or more. In some embodiments, from the viewpoint of impact resistance and / or retention, 10% by mass or more is preferred, more preferably 15% by mass or more, and even more preferably 20% by mass or more. When the proportion of monomers containing cyclic hydrocarbon groups is 10% by mass or more, an electropenetrating adhesive layer with good impact resistance and / or retention is easily obtained. In some embodiments where impact resistance and / or retention is given greater importance, the proportion of monomers containing cyclic hydrocarbon groups may be 25% by mass or more, 30% by mass or more, or 35% by mass or more. The upper limit of the proportion of monomers containing cyclic hydrocarbon groups is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less, from the viewpoint of electropenetration. In some embodiments where electropenetration is given greater importance, the proportion of monomers containing cyclic hydrocarbon groups may be 30% by mass or less, or 25% by mass or less. The content of monomers containing cyclic hydrocarbon groups relative to the total monomer components (100% by mass) constituting the acrylic polymer is preferably 10% by mass or more and 45% by mass or less, preferably 15% by mass or more and 40% by mass or less, and preferably 20% by mass or more and 35% by mass or less.

[0038] The specific (meth)acrylic polymer contained in the electrolytic adhesive composition according to the embodiment of the present invention contains units derived from monomers containing oxyalkylene groups, which are not units derived from monomers containing the cyclic hydrocarbon group described above. The specific (meth)acrylic polymer further contains monomer units containing oxyalkylene groups, thereby enhancing the stress relaxation properties of the units derived from the monomers containing the cyclic hydrocarbon group and improving impact resistance. The monomer units containing oxyalkylene groups preferably include monomer units derived from the following formula (1-2): CH ２ = C(R ａ ) COO(R ｂ２ O)nRｃ２ (1-2) [R in equation (1-2) ａ R is a hydrogen atom or a methyl group, ｂ２ R is an alkylene group having 1 to 14 carbon atoms, which may have substituents. ｃ２ [where n is an alkyl group having 1 to 14 carbon atoms, which may have substituents, and n is an integer from 1 to 15.]

[0039] R ｂ２ R is an alkylene group having 1 to 14 carbon atoms, which is not a cyclic hydrocarbon group, and is preferably a chain-like alkylene group. ｃ２ is an alkyl group having 1 to 14 carbon atoms, which is not a cyclic hydrocarbon group, and is preferably a chain-like alkyl group. n represents the number of repeating units of the oxyalkylene group.

[0040] Examples of monomers containing an oxyalkylene group include methoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, and ethoxypolypropylene glycol (meth)acrylate. These monomers can be those commercially available under product names such as "Acrylics C-1" (manufactured by Toagosei Co., Ltd.), "Viscote #190" (manufactured by Osaka Organic Chemical Industry Co., Ltd.), "Bremmer PME200", "Bremmer PME400", "Bremmer AME400" (manufactured by NOF Corporation), "NK Ester AM-30G", "NK Ester AM-90G", "NK Ester AM-130G", "NK Ester AM-30PG", "NK Ester M-40G", "NK Ester M-90G", "NK Ester M-130G" (manufactured by Shin Nakamura Chemical Industry Co., Ltd.), "Light Acrylate MTG-A", "Light Acrylate 130A", and "Light Ester 130MA" (manufactured by Kyoeisha Chemical Co., Ltd.).

[0041] In embodiments of the present invention, it is preferable to use at least one monomer selected from methoxyethyl (meth)acrylate and ethoxyethoxyethyl (meth)acrylate as the monomer containing an oxyalkylene group, from the viewpoint of impact resistance and retention.

[0042] Monomers containing an oxyalkylene group can be used alone or in combination of two or more.

[0043] The proportion of monomers containing oxyalkylene groups relative to the total monomer components (100% by mass) constituting the specific (meth)acrylic polymer is not particularly limited and may be, for example, 1% by mass or more, or 3% by mass or more. In some embodiments, 5% by mass or more is preferred and 10% by mass or more is more preferred from the viewpoint of impact resistance. When the proportion of monomers containing oxyalkylene groups is 5% by mass or more, an electro-peelable adhesive layer with good impact resistance is easily obtained. The upper limit of the proportion of monomers containing oxyalkylene groups is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, even more preferably 25% by mass or less, and most preferably 20% by mass or less from the viewpoint of impact resistance. The content of monomers containing oxyalkylene groups relative to the total monomer components (100% by mass) constituting the (meth)acrylic polymer is preferably 5% by mass or more and 30% by mass or less, more preferably 10% by mass or more and 25% by mass or less, and most preferably 10% by mass or more and 20% by mass or less. Furthermore, an embodiment in which the proportion of monomers containing cyclic hydrocarbon groups to the total monomer components constituting the (meth)acrylic polymer is 10% by mass or more and 45% by mass or less, and the proportion of monomers containing oxyalkylene groups is 5% by mass or more and 30% by mass or less, is also preferred. From the viewpoint of more favorably achieving both impact resistance and electropeelability and / or retention, it is even more preferred that the proportion of monomers containing cyclic hydrocarbon groups is 10% by mass or more and 30% by mass or less, and the proportion of monomers containing oxyalkylene groups is 10% by mass or more and 30% by mass or less, and more preferably that the proportion of monomers containing cyclic hydrocarbon groups is 10% by mass or more and 25% by mass or less, and the proportion of monomers containing oxyalkylene groups is 10% by mass or more and 30% by mass or less.

[0044] Furthermore, it is preferable that the specific (meth)acrylic polymer includes monomer units derived from alkyl (meth)acrylate esters having an alkyl group with 1 to 14 carbon atoms (formula (1-3) below), which do not fall under the units derived from monomers containing the above-mentioned cyclic hydrocarbon group or units derived from monomers containing an oxyalkylene group. Such monomer units are suitable for obtaining a large initial adhesive strength. In addition, to increase the dielectric constant of components other than ionic substances in the electropenetrating adhesive layer and improve electropenetration, the alkyl group R in formula (1-3) below is preferable. ｂ３ The number of carbon atoms is preferably small, particularly preferably 8 or less, and more preferably 4 or less. ２ = C(R ａ ) COOR ｂ３ (1-3) [R in equation (1-3) ａ R is a hydrogen atom or a methyl group, ｂ３ This is an alkyl group having 1 to 14 carbon atoms, which may have substituents.

[0045] R ｂ３The alkyl group is not a cyclic hydrocarbon group, but an alkyl group having 1 to 14 carbon atoms, and is preferably a chain-like alkyl group. Examples of alkyl (meth)acrylate esters having an alkyl group with 1 to 14 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, 1,3-dimethylbutyl acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, and 2-ethylbutyl Examples include methyl acrylate, heptyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate, isononyl acrylate, n-decyl acrylate, isodecyl acrylate, n-dodecyl acrylate, n-tridecyl acrylate, and n-tetradecyl acrylate. Among these, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate are preferred. Alkyl esters of (meth)acrylate having an alkyl group with 1 to 14 carbon atoms can be used alone or in combination of two or more.

[0046] The proportion of the alkyl (meth)acrylate ester having a C1-C14 alkyl group to the total monomer components (100% by mass) constituting the specific (meth)acrylic polymer is not particularly limited and can be set according to the purpose. In some embodiments, the proportion of the alkyl (meth)acrylate ester having a C1-C14 alkyl group may be 25% by mass or more from the viewpoint of imparting flexibility to the electropenetrating adhesive layer. In some embodiments, it is preferably 30% by mass or more, and more preferably 35% by mass or more, from the viewpoint of easily obtaining high initial adhesion and good electropenetration. In some embodiments, it is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and even more preferably 70% by mass or less, from the viewpoint of easily obtaining high impact resistance and / or retention force. When the proportion of the alkyl (meth)acrylate ester having a C1-C14 alkyl group is 25% by mass or more, the flexibility of the electropenetrating adhesive layer can be increased and adhesion to the adherend can be improved.

[0047] As a specific (meth)acrylic polymer, it is preferable to include monomer units derived from alkyl (meth)acrylate esters having alkyl groups with 1 to 14 carbon atoms, as well as monomer units derived from polar group-containing monomers copolymerizable thereto, for the purpose of modifying properties such as cohesive strength, heat resistance, and crosslinkability. Monomer units derived from polar group-containing monomers are suitable for obtaining high initial adhesion strength because they undergo chemical interactions with the adherend.

[0048] Examples of polar group-containing monomers include carboxyl group-containing monomers, hydroxyl group-containing monomers, cyano group-containing monomers, vinyl group-containing monomers, aromatic vinyl monomers, amide group-containing monomers, imide group-containing monomers, amino group-containing monomers, heterocyclic monomers such as N-acryloylmorpholine, epoxy group-containing monomers, vinyl ether monomers, sulfo group-containing monomers, phosphate group-containing monomers, and acid anhydride group-containing monomers. Among these, carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, and heterocyclic monomers are preferred due to their excellent cohesiveness, and are particularly preferred. Carboxyl group-containing monomers, amide group-containing monomers, and heterocyclic monomers are especially suitable for obtaining high initial adhesion. Polar group-containing monomers can be used alone or in combination of two or more.

[0049] Examples of carboxyl group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Acrylic acid is particularly preferred. Carboxyl group-containing monomers can be used alone or in combination of two or more.

[0050] Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl (meth)acrylate, N-methylol (meth)acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. In particular, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred. Hydroxyl group-containing monomers can be used alone or in combination of two or more.

[0051] Examples of amide group-containing monomers include acrylamide, methacrylamide, N-vinylpyrrolidone, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N'-methylenebisacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, and diacetoneacrylamide. Amide group-containing monomers can be used alone or in combination of two or more.

[0052] Examples of cyano group-containing monomers include acrylonitrile and methacrylonitrile.

[0053] Examples of vinyl group-containing monomers include vinyl acetate, vinyl propionate, and vinyl esters such as vinyl laurate, with vinyl acetate being particularly preferred.

[0054] Examples of aromatic vinyl monomers include styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrenes.

[0055] Examples of imide group-containing monomers include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

[0056] Examples of amino group-containing monomers include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

[0057] Examples of epoxy group-containing monomers include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, and allyl glycidyl ether.

[0058] Examples of vinyl ether monomers include methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether.

[0059] Examples of heterocyclic monomers include N-acryloylmorpholine and N-vinylpyrrolidone.

[0060] The proportion of polar group-containing monomers to the total monomer components (100% by mass) constituting the specific (meth)acrylic polymer is preferably 0.1% by mass or more and 35% by mass or less. The upper limit of the proportion of polar group-containing monomers is more preferably 25% by mass, even more preferably 20% by mass, the lower limit is more preferably 0.5% by mass, even more preferably 1% by mass, and particularly preferably 2% by mass. When the proportion of polar group-containing monomers is 0.1% by mass or more, cohesive force is easily obtained, so that adhesive residue is less likely to occur on the surface of the adherend after the electrorelease adhesive layer is peeled off, and electrorelease properties are improved. Furthermore, when the proportion of polar group-containing monomers is 35% by mass or less, it is easier to prevent the electrorelease adhesive layer from adhering excessively to the adherend and causing excessive peeling. In particular, when it is 2% by mass or more and 20% by mass or less, it is easier to achieve both peelability to the adherend and adhesion between the electrorelease adhesive layer and other layers.

[0061] Furthermore, the monomer components constituting the specific (meth)acrylic polymer may include polyfunctional monomers in order to introduce a cross-linked structure into the acrylic polymer and facilitate obtaining the necessary cohesive force.

[0062] Polyfunctional monomers are monomers having at least two polymerizable functional groups having unsaturated double bonds, such as (meth)acryloyl groups or vinyl groups. Examples include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate. Examples include polyfunctional monomers such as tetramethylolmethane tri(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, hexyl di(meth)acrylate, and N,N'-methylenebisacrylamide. Polyfunctional monomers can be used alone or in combination of two or more.

[0063] The content of polyfunctional monomers relative to the total monomer components (100% by mass) constituting the specific (meth)acrylic polymer is preferably 0.01% by mass or more and 15% by mass or less. The upper limit of the polyfunctional monomer content is more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 3% by mass or less, even more preferably 1% by mass or less, and most preferably 0.5% by mass or less. The lower limit is more preferably 0.03% by mass or more, even more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more. A polyfunctional monomer content of 0.01% by mass or more is preferable because it tends to improve the holding power of the adhesive layer. A polyfunctional monomer content of 15% by mass or less prevents excessive cohesive force and makes it easier to obtain appropriate adhesion and electrorelease properties. A polyfunctional monomer content of 0.01% by mass or more and 1% by mass or less is most preferable, as it yields an adhesive layer with excellent electrorelease properties and holding power.

[0064] The electrolytic adhesive composition according to the embodiment of the present invention may further contain other polymers besides the specified (meth)acrylic polymer described above. The other polymers are not particularly limited as long as they are commonly used as adhesives and have adhesive properties, but examples include (meth)acrylic polymers other than the specified (meth)acrylic polymer, rubber polymers, vinyl alkyl ether polymers, silicone polymers, polyester polymers, polyamide polymers, urethane polymers, fluorine polymers, and epoxy polymers. The other polymers can be used alone or in combination of two or more.

[0065] In order to increase the dielectric constant of components other than ionic substances in the resulting electropenetrating adhesive layer and improve its electropenetration properties, it is preferable that the polymer contained in the electropenetrating adhesive composition has a high dielectric constant. From this viewpoint, it is particularly preferable that the polymer contained in the electropenetrating adhesive composition according to the embodiment of the present invention contains a polyester polymer. Since polyester polymers have hydroxyl groups that are easily polarized at their ends, using a polyester polymer makes it possible to obtain an electropenetrating adhesive layer with a relatively high dielectric constant. The total content of polyester polymers and specific (meth)acrylic polymers in the polymer contained in the electropenetrating adhesive composition according to the embodiment of the present invention is preferably 60% by mass or more, and more preferably 80% by mass or more.

[0066] Polyester polymers are typically polymers having a structure in which polycarboxylic acids such as dicarboxylic acids or their derivatives (hereinafter also referred to as "polycarboxylic acid monomers") and polyhydric alcohols such as diols or their derivatives (hereinafter referred to as "polyhydric alcohol monomers") are condensed together.

[0067] The polycarboxylic acid monomers are not particularly limited, but examples include adipic acid, azelaic acid, dimer acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, dodecenyl succinic anhydride, fumaric acid, succinic acid, dodecanediic acid, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, maleic acid, maleic anhydride, itaconic acid, citraconic acid, isophthalic acid, terephthalic acid, orthophthalic acid, benzylmalonic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-dicarboxydiphenyl ether, naphthalenedicarboxylic acid, and derivatives thereof. The polycarboxylic acid monomers can be used alone or in combination of two or more.

[0068] The polyhydric alcohol monomer is not particularly limited, but examples include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,5-pentanediol, 2-ethyl-2-butylpropanediol, 1,9-nonanediol, 2-methyloctanediol, 1,10-decanediol, and derivatives thereof. The polyhydric alcohol monomer can be used alone or in combination of two or more.

[0069] Furthermore, the electrolytic adhesive composition according to the embodiment of the present invention may further contain an ionic polymer. An ionic polymer is a polymer having an ionic functional group. Including an ionic polymer increases the dielectric constant of the polymer and improves the electrolytic properties. When the electrolytic adhesive composition contains an ionic polymer, the content of the ionic polymer is preferably 0.05 parts by mass or more and 2 parts by mass or less, based on 100 parts by mass of the total polymer contained in the electrolytic adhesive composition.

[0070] In this embodiment, the specific (meth)acrylic polymer can be obtained by (co)polymerizing the monomer components. The polymerization method is not particularly limited, but examples include solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization (active energy ray polymerization). Photopolymerization is particularly preferred from the viewpoint of thick-film coating properties, cost, and productivity. When copolymerized, the specific (meth)acrylic polymer may be a random copolymer, block copolymer, alternating copolymer, graft copolymer, etc. A solvent may be used for polymerization.

[0071] Photopolymerization methods include UV polymerization, which is carried out by irradiation with light such as ultraviolet (UV) rays (typically carried out in the presence of a photopolymerization initiator), and radiation polymerization, which is carried out by irradiation with radiation such as beta rays and gamma rays. From the viewpoint of productivity, UV polymerization is preferred. UV polymerization will be described below.

[0072] When performing UV polymerization, it is preferable to include a photopolymerization initiator in the monomer component due to the advantage of being able to shorten the polymerization time. In this embodiment, the specific (meth)acrylic polymer can also be prepared as a partially polymerized monomer (prepolymer) by irradiating a mixture of the monomer component and the photopolymerization initiator with UV light. An electrolytic adhesive composition can also be prepared by mixing the prepolymer with an ionic substance described later, and optionally with a polyfunctional monomer, other additives, etc., and this electrolytic adhesive composition can be applied to a predetermined substrate and the polymerization can be completed by irradiating with UV light.

[0073] While not particularly limited, the following can be used as photopolymerization initiators: benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, etc. The polymerization initiators can be used alone or in combination of two or more. Specifically, examples of benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one (trade name "Omnirad 651," manufactured by IGM Resins B.V.), anisoin methyl ether, etc. Examples of acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone (trade name "Omnirad 184", manufactured by IGM Resins B.V.), 4-phenoxydichloroacetophenone, and 4-t-butyldichloroacetophenone. Examples of α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-hydroxy-2-methylpropan-1-one. Examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,2-propanedione-2-(O-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzyl-based photopolymerization initiators include benzyl. Benzophenone-based photopolymerization initiators include, for example, benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. Ketal-based photopolymerization initiators include benzyldimethyl ketal.Thioxanthone-based photopolymerization initiators include, for example, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. Acylphosphine oxide-based photopolymerization initiators include, for example, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

[0074] The amount of polymerization initiator used is not particularly limited, but it is preferably 0.01 parts by mass or more and 5 parts by mass or less relative to the total monomer components (100 parts by mass) constituting the acrylic polymer. The upper limit of the amount of polymerization initiator used is more preferably 3 parts by mass, and the lower limit is more preferably 0.05 parts by mass.

[0075] The polymerization rate of the prepolymer is not particularly limited, but from the viewpoint of achieving a viscosity suitable for application to a substrate, 3 to 50% by mass is preferred, and 5 to 40% by mass is more preferred. The polymerization rate of the prepolymer can be adjusted to a desired range by adjusting the type and amount of polymerization initiator used, the irradiation intensity and irradiation time of active light such as UV light, etc. The polymerization rate of the prepolymer is calculated from the mass before and after heating at 130°C for 3 hours using the following formula. The polymerization rate of the electrorelease adhesive layer is calculated using the same method. The polymerization rate of the electrorelease adhesive layer is not particularly limited, but from the viewpoint of reducing monomer odor, 80 to 100% by mass is preferred, 90 to 100% by mass is more preferred, and 95 to 100% by mass is most preferred. The polymerization rate of the electrorelease adhesive layer can be adjusted to a desired range by adjusting the type and amount of polymerization initiator used, the irradiation intensity and irradiation time of active light such as UV light, etc. Polymerization rate (%) = Mass after drying / Mass before drying × 100

[0076] Solution polymerization methods are not particularly limited, but include methods in which monomer components, polymerization initiators, etc., are dissolved in a solvent, heated to polymerize, and a polymer solution containing an acrylic polymer is obtained.

[0077] Various common solvents can be used as solvents for polymerization. Examples of such solvents (polymerization solvents) include aromatic hydrocarbons such as toluene, benzene, and xylene; esters such as ethyl acetate and n-butyl acetate; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone. Solvents can be used individually or in combination of two or more.

[0078] The amount of solvent used is not particularly limited, but is preferably 10 parts by mass or more and 1000 parts by mass or less, relative to the total monomer components (100 parts by mass) constituting the specific (meth)acrylic polymer. The upper limit of the amount of solvent used is more preferably 500 parts by mass, and the lower limit is more preferably 50 parts by mass.

[0079] During polymerization, known or conventional thermal polymerization initiators or photopolymerization initiators may be used depending on the polymerization method and polymerization mode. Polymerization initiators can be used individually or in appropriate combinations of two or more types.

[0080] Polymerization initiators are not particularly limited, but include peroxide-based polymerization initiators and azo-based polymerization initiators. Peroxide-based polymerization initiators are not particularly limited, but include peroxycarbonates, ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, and peroxyesters. More specifically, examples include benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-bis(t-butylperoxy)cyclododecane. The azo polymerization initiators are not particularly limited, but include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylpropionic acid)dimethyl, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitride), 2,2'-azobis(2,4,4-trimethylpentane), and 4,4'-azobis Examples include -4-cyanovaleric acid, 2,2'-azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidine)disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine)hydrochloride, and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate. Polymerization initiators can be used alone or in combination of two or more.

[0081] The amount of polymerization initiator used is not particularly limited, but it is preferably 0.01 parts by mass or more and 5 parts by mass or less relative to the total monomer components (100 parts by mass) constituting the acrylic polymer. The upper limit of the amount of polymerization initiator used is more preferably 3 parts by mass, and the lower limit is more preferably 0.05 parts by mass.

[0082] The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the polymerization method, the type of polymerization initiator, etc. A polymerization temperature of 20°C or higher is appropriate, preferably 40°C or higher, more preferably 50°C or higher, and may also be 60°C or higher, 65°C or higher, and even 70°C or higher. Furthermore, a polymerization temperature of 170°C or lower (typically 140°C or lower) is appropriate, preferably 95°C or lower (for example, 85°C or lower). In solution polymerization, the heating temperature during polymerization is not particularly limited, but for example, it is between 50°C and 80°C. The heating time is not particularly limited, but for example, it is between 1 hour and 24 hours.

[0083] The weight-average molecular weight of the specific (meth)acrylic polymer is not particularly limited, but is preferably between 100,000 and 10,000,000. The upper limit of the weight-average molecular weight is more preferably 7,500,000, even more preferably 5,000,000, and the lower limit is more preferably 200,000, even more preferably 300,000. When the weight-average molecular weight is 100,000 or more, the cohesive force increases, effectively suppressing the problem of adhesive residue remaining on the adherend surface after the electro-release adhesive layer is peeled off. Furthermore, when the weight-average molecular weight is 10,000,000 or less, effectively suppressing the problem of insufficient adhesive strength of the electro-release adhesive layer.

[0084] The weight-average molecular weight was obtained by measuring using gel permeation chromatography (GPC). More specifically, for example, using a GPC measuring device such as the "HLC-8220GPC" (manufactured by Tosoh Corporation), the measurement was performed under the following conditions, and the value was calculated using the standard polystyrene equivalent. (Weight-average molecular weight measurement conditions) ・Sample concentration: 0.2% by mass (tetrahydrofuran solution) ・Sample injection volume: 10 μL ・Sample column: TSKguardcolumn SuperHZ-H (1 tube) + TSKgel SuperHZM-H (2 tubes) ・Reference column: TSKgel SuperH-RC (1 tube) ・Eluent: Tetrahydrofuran (THF) ・Flow rate: 0.6 mL / min ・Detector: Differential refractometer (RI) ・Column temperature (measurement temperature): 40°C

[0085] The content of the specific (meth)acrylic polymer in the electrolytic adhesive composition according to the embodiment of the present invention is preferably 50% by mass or more and 99.9% by mass or less, based on the total amount (100% by mass) of the electrolytic adhesive composition, with the upper limit being more preferably 99.5% by mass, even more preferably 99% by mass, and the lower limit being more preferably 60% by mass, even more preferably 70% by mass.

[0086] (Ionic Substances) The electrolytic adhesive composition according to the embodiment of the present invention contains an ionic substance. Ionic substances are a general term for substances composed of at least one pair of anions and cations. Regardless of their form, they refer to substances that ionize in a polymer, in a solution, in a liquid state, or in a solid state and exhibit electrical conductivity. At room temperature (25°C), the ionic substance can be in any state other than gas. That is, at room temperature (25°C), the ionic substance may be a solid, a liquid, or in an intermediate state between solid and liquid (for example, a liquid crystal, a flexible crystal, a viscous solid, or a viscous liquid). The state in which an ionic substance is at room temperature (25°C) depends on its molecular structure. For example, an ionic liquid is a compound composed of a cation and anion that has a melting point below room temperature (25°C) and has liquid properties at room temperature, such as 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide. Furthermore, ionic solids include substances with a melting point higher than 25°C and possessing ionic properties, such as metal salts (e.g., sodium chloride and copper sulfate) and high-melting-point organic ionic solids (e.g., 1-ethyl-3-methylimidazolium bromide and 1-ethyl-1-methylpiperidinium iodide). From the viewpoint of achieving good electropenetration properties, ionic liquids are preferred as ionic substances contained in electropenetrating adhesive compositions.

[0087] Anions in ionic substances are, for example, (FSO ２ ) ２ N － (CF ３ SO ２ ) ２ N － (CF ３ CF ２ SO２ ) ２ N － (CF ３ SO ２ ) ３ C － , Br － AlCl ４ － Al ２ Cl ７ － NO ３ － BF ４ － , PF ６ － ,CH ３ COO － CF ３ COO － CF ３ CF ２ CF ２ COO － CF ３ SO ３ － CF ３ (CF ２ ) ３ SO ３ － AsF ６ － SbF ６ － , and F (HF) ｎ － These are some examples. Among them, as anions, (FSO ２ ) ２ N － [Bis(fluorosulfonyl)imide anion] and (CF ３ SO ２ ) ２ N － Anions of sulfonylime compounds such as [bis(trifluoromethanesulfonyl)imide anion] are preferred because they are chemically stable and suitable for improving electrolysis properties. In other words, the anion of the ionic substance is preferably at least one selected from the group consisting of bis(fluorosulfonyl)imide anion and / or bis(trifluoromethanesulfonyl)imide anion.

[0088] In ionic materials, the cation is preferably at least one selected from the group consisting of nitrogen-containing onium cations, sulfur-containing onium cations, and phosphorus-containing onium cations, as this is chemically stable and suitable for improving electrolysis properties. Imidazolium-based, ammonium-based, pyrrolidinium-based, and pyridinium-based cations are more preferred.

[0089] Examples of imidazolium-based cations include 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-heptyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-nonyl-3-methylimidazolium cation, 1-undecyl-3-methylimidazolium cation, and 1-dodecyl-3-methylimidazolium cation. Examples include mucation, 1-tridecyl-3-methylimidazolium cation, 1-tetradecyl-3-methylimidazolium cation, 1-pentadecyl-3-methylimidazolium cation, 1-hexadecyl-3-methylimidazolium cation, 1-heptadecyl-3-methylimidazolium cation, 1-octadecyl-3-methylimidazolium cation, 1-undecyl-3-methylimidazolium cation, 1-benzyl-3-methylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, and 1,3-bis(dodecyl)imidazolium cation.

[0090] Examples of pyridinium-based cations include 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, and 1-octyl-4-methylpyridinium cation.

[0091] Examples of pyrrolidinium-based cations include 1-ethyl-1-methylpyrrolidinium cation and 1-butyl-1-methylpyrrolidinium cation.

[0092] Examples of ammonium-based cations include tetraethylammonium cation, tetrabutylammonium cation, methyltrioctylammonium cation, tetradecyltrihexylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethyl acrylate cation.

[0093] As the ionic substance, from the viewpoint of increasing the reduction rate of adhesive strength upon voltage application, it is preferable to select a cation having a molecular weight of 160 or less as the constituent cation. The above-mentioned (FSO ２ ) ２ N － [bis(fluorosulfonyl)imide anion] or (CF ３ SO ２ ) ２ N － [bis(trifluoromethanesulfonyl)imide anion] and an ionic substance containing a cation having a molecular weight of 160 or less is particularly preferable. Examples of the cation having a molecular weight of 160 or less include 1-methylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-propyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-pentyl-3-methylimidazolium cation, 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, 1-ethyl-1-methylpyrrolidinium cation, 1-butyl-1-methylpyrrolidinium cation, tetraethylammonium cation, glycidyltrimethylammonium cation, and trimethylaminoethyl acrylate cation.

[0094] Further, as the cation of the ionic substance, cations represented by the following formulas (2-A) to (2-D) are also preferable.

[0095]

[0096] R in formula (2-A) １represents a hydrocarbon group having 4 to 10 carbon atoms (preferably a hydrocarbon group having 4 to 8 carbon atoms, more preferably a hydrocarbon group having 4 to 6 carbon atoms), which may contain a hetero atom, and R ２ and R ３ are the same or different, each represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms (preferably a hydrocarbon group having 1 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms, still more preferably a hydrocarbon group having 2 to 4 carbon atoms), which may contain a hetero atom. Provided that when a nitrogen atom forms a double bond with an adjacent carbon atom, R ３ does not exist.

[0097] In formula (2-B), R ４ represents a hydrocarbon group having 2 to 10 carbon atoms (preferably a hydrocarbon group having 2 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms), which may contain a hetero atom, and R ５ , R ６ , and R ７ are the same or different, each represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms (preferably a hydrocarbon group having 1 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms, still more preferably a hydrocarbon group having 2 to 4 carbon atoms), which may contain a hetero atom.

[0098] In formula (2-C), R ８ represents a hydrocarbon group having 2 to 10 carbon atoms (preferably a hydrocarbon group having 2 to 8 carbon atoms, more preferably a hydrocarbon group having 2 to 6 carbon atoms), which may contain a hetero atom, and R ９ , R １０ , and R １１ are the same or different, each represents a hydrogen atom or a hydrocarbon group having 1 to 16 carbon atoms (preferably a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 8 carbon atoms), which may contain a hetero atom.

[0099] In formula (2-D), X represents a nitrogen, sulfur, or phosphorus atom, and R １２ , R １３ , R １４ , and R １５R represents a hydrocarbon group having 1 to 16 carbon atoms, either identical or different, (preferably a hydrocarbon group having 1 to 14 carbon atoms, more preferably a hydrocarbon group having 1 to 10 carbon atoms, even more preferably a hydrocarbon group having 1 to 8 carbon atoms, and particularly preferably a hydrocarbon group having 1 to 6 carbon atoms), and may contain heteroatoms. However, if X is a sulfur atom, R １２ It does not exist.

[0100] The molecular weight of cations in ionic materials is, for example, 500 or less, preferably 400 or less, more preferably 300 or less, even more preferably 250 or less, particularly preferably 200 or less, and most preferably 160 or less. It is also usually 50 or more. It is believed that cations in ionic materials have the property of moving towards the cathode side when a voltage is applied within the electropenetrating adhesive layer, and becoming concentrated near the interface between the electropenetrating adhesive layer and the adherend (more specifically, the conductive layer in the adherend), or near the interface between the electropenetrating adhesive layer and the conductive material. In the present invention, this results in a decrease in adhesive strength when a voltage is applied compared to the initial adhesive strength, causing electropenetration. Cationic materials with a small molecular weight, such as 500 or less, are preferable because the movement of cations towards the cathode side within the electropenetrating adhesive layer is easier, and this is beneficial for increasing the rate of decrease in adhesive strength when a voltage is applied.

[0101] Examples of commercially available ionic substances include "Elexel AS-110" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "D5237", "E0599", "M2981", and "B5763" manufactured by Tokyo Kasei Kogyo Co., Ltd., and "BM1697" manufactured by Boron Molecular Inc.

[0102] The ionic conductivity of the ionic material is preferably between 0.0001 mS / cm and 20 mS / cm. The upper limit of the ionic conductivity can be, for example, 15 mS / cm or 10 mS / cm. The lower limit of the ionic conductivity is more preferably 0.1 mS / cm, and even more preferably 0.3 mS / cm. An ionic conductivity of 0.0001 mS / cm or higher is preferable because it sufficiently reduces the adhesive strength after voltage is applied. Furthermore, an ionic conductivity of 20 mS / cm or lower is preferable because it suppresses the influence of weak external currents, and electrolysis can only occur when voltage is intentionally applied. Having an ionic conductivity within this range allows for sufficient reduction of adhesive strength even at low voltages. The ionic conductivity can be measured, for example, by the AC impedance method using a Solartron 1260 frequency response analyzer.

[0103] In the electro-peelable adhesive composition according to the embodiment of the present invention, the content (amount blended) of the ionic substance is preferably 0.5 parts by mass or more per 100 parts by mass of polymer, from the viewpoint of increasing the rate of decrease in adhesive strength due to voltage application, and preferably 30 parts by mass or less, from the viewpoint of increasing the initial adhesive strength. From the same viewpoint, it is more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, particularly preferably 10 parts by mass or less, and most preferably 5 parts by mass or less. Furthermore, it is more preferably 0.6 parts by mass or more, even more preferably 0.8 parts by mass or more, particularly preferably 1.0 part by mass or more, and most preferably 1.5 parts by mass or more. In some embodiments, considering the balance between the initial adhesive strength and the rate of decrease in adhesive strength due to voltage application, the content of the ionic substance may be, for example, 2.0 parts by mass or more, 2.5 parts by mass or more, 3.0 parts by mass or more, 3.5 parts by mass or more, or 4.0 parts by mass or more. The ionic substance can be used alone or in combination of two or more types.

[0104] (Other Components) The electrolytic adhesive composition according to the embodiment of the present invention may contain one or more components other than polymers and ionic substances (hereinafter sometimes referred to as "other components"), as necessary, to the extent that they do not impair the effects of the present invention. The other components that may be contained in the electrolytic adhesive composition according to the embodiment of the present invention will be described below.

[0105] The electrolytic adhesive composition according to the embodiment of the present invention may optionally contain a crosslinking agent for the purpose of improving creep and shear properties by crosslinking the polymer. Examples of crosslinking agents include isocyanate-based crosslinking agents, carbodiimide-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and amine-based crosslinking agents. Examples of isocyanate-based crosslinking agents include toluene diisocyanate and methylene bisphenyl isocyanate. Examples of epoxy-based crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane and 1,6-hexanediol diglycidyl ether.

[0106] When a crosslinking agent is included, its content is preferably 0.01 parts by mass or more and 30 parts by mass or less per 100 parts by mass of (meth)acrylic polymer. The lower limit is more preferably 0.1 parts by mass or more. A crosslinking agent content of 0.01 parts by mass or more is preferable from the viewpoint of imparting appropriate cohesiveness to the electro-release adhesive layer and increasing the holding power of the electro-release adhesive layer. From the viewpoint of improving adhesion to the adherend, in some embodiments, the content of the crosslinking agent can be, for example, 0.01 parts by mass or more, or 1.0 part by mass or more. The crosslinking agent can be used alone or in combination of two or more types.

[0107] The electrolytic adhesive composition according to the embodiment of the present invention preferably contains 0.01 parts by mass or more and 1 part by mass or less of a crosslinking agent or polyfunctional monomer per 100 parts by mass of a (meth)acrylic polymer.

[0108] The electrolytic adhesive composition according to the embodiment of the present invention may optionally contain polyethylene glycol for the purpose of assisting the movement of ionic substances when voltage is applied. Polyethylene glycol having a number average molecular weight of 200 to 6000 can be used. When these components are included, the content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of (meth)acrylic polymer.

[0109] The electrolytic adhesive composition according to the embodiment of the present invention may optionally contain a conductive filler for the purpose of imparting conductivity to the electrolytic adhesive composition. The conductive filler is not particularly limited, and general known or conventional conductive fillers can be used, such as graphite, carbon black, carbon fiber, or metal powders such as silver or copper. When a conductive filler is included, the content is preferably 0.01 parts by mass or more and 200 parts by mass or less per 100 parts by mass of (meth)acrylic polymer.

[0110] The electrolytic adhesive composition according to the embodiment of the present invention may optionally contain a corrosion inhibitor for the purpose of suppressing corrosion of the adherend. The corrosion inhibitor is not particularly limited, and general known or conventional corrosion inhibitors can be used, such as carbodiimide compounds, adsorption inhibitors, chelate-forming metal deactivators, etc.

[0111] Examples of carbodiimide compounds include 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, N,N'-dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, 1-ethyl-3-tert-butylcarbodiimide, N-cyclohexyl-N'-(2-morpholinoethyl)carbodiimide, N,N'-di-tert-butylcarbodiimide, and 1,3-bis(p-tolyl)carbodiimide. These carbodiimide compounds can be used alone or in combination of two or more. When an electrolytic adhesive composition according to an embodiment of the present invention contains a carbodiimide compound, the content is preferably 0.01 parts by mass or more and 10 parts by mass or less per 100 parts by mass of (meth)acrylic polymer.

[0112] Examples of adsorbent inhibitors include alkylamines such as 1,1'-(cyclohexyl hyimino)bis(2-propanol) (product name: Sanhibiter No. 70, manufactured by Sanyo Chemical Industries, Ltd.) and dilauryl monomethylamine (product name: Farmin M2-2095, manufactured by Kao Corporation), carboxylate salts such as a salt of 1,1'-(cyclohexyl hyimino)bis(2-propanol) and a carboxylic acid, carboxylate salts such as a salt of 1,1'-(cyclohexyl hyimino)bis(2-propanol) and sebaciate, carboxylic acid derivatives, and alkyl phosphates. Adsorbent inhibitors can be used alone or in combination of two or more. When an alkylamine is included as an adsorbent inhibitor in the electrolytic adhesive composition according to the embodiment of the present invention, the content is preferably 0.01 parts by mass or more and 20 parts by mass or less per 100 parts by mass of polymer, and is preferably a tertiary amine. When a carboxylate is included as an adsorbent inhibitor in the electro-peelable adhesive composition according to an embodiment of the present invention, the content is preferably 0.01 parts by mass or more and 10 parts by mass or less per 100 parts by mass of (meth)acrylic polymer. When a carboxylic acid derivative is included as an adsorbent inhibitor in the electro-peelable adhesive composition according to an embodiment of the present invention, the content is preferably 0.01 parts by mass or more and 10 parts by mass or less per 100 parts by mass of (meth)acrylic polymer. When an alkyl phosphate is included as an adsorbent inhibitor in the electro-peelable adhesive composition according to an embodiment of the present invention, the content is preferably 0.01 parts by mass or more and 10 parts by mass or less per 100 parts by mass of (meth)acrylic polymer.

[0113] As chelate-forming metal deactivators, for example, triazole group-containing compounds or benzotriazole group-containing compounds can be used. These are preferred because they have a high deactivating effect on the surface of metals such as stainless steel and aluminum, and do not significantly affect adhesion when included in adhesive components. Chelate-forming metal deactivators can be used alone or in combination of two or more. When a chelate-forming metal deactivator is included in the electrolytic adhesive composition according to the embodiment of the present invention, the content is preferably 0.01 parts by mass or more and 20 parts by mass or less per 100 parts by mass of (meth)acrylic polymer. The total content (amount blended) of the corrosion inhibitor is preferably 0.01 parts by mass or more and 30 parts by mass or less per 100 parts by mass of (meth)acrylic polymer.

[0114] The electrolytic adhesive composition according to the embodiment of the present invention may also contain various additives such as fillers, plasticizers, antioxidants, pigments (dyes), flame retardants, solvents, water, surfactants (leveling agents), rust inhibitors, tackifying resins, and antistatic agents. The total content of these components is not particularly limited as long as the effects of the present invention are achieved, but is preferably 0.01 parts by mass to 20 parts by mass, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of (meth)acrylic polymer.

[0115] Examples of fillers include silica, iron oxide, zinc oxide, aluminum oxide, titanium oxide, barium oxide, magnesium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, pyrophyllite clay, kaolin clay, and calcined clay. For plasticizers, commonly known and conventional plasticizers used in general resin compositions can be used, such as oils like paraffin oil and process oil; liquid rubbers like liquid polyisoprene, liquid polybutadiene, and liquid ethylene-propylene rubber; tetrahydrophthalic acid, azelaic acid, benzoic acid, phthalic acid, trimellitic acid, pyromellitic acid, adipic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, citric acid, and their derivatives; dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl adipate, diisononyl adipate (DINA), and isodecyl succinate. Examples of anti-aging agents include hindered phenol compounds, aliphatic and aromatic hindered amine compounds, etc. Examples of antioxidants include butylhydroxytoluene (BHT) and butylhydroxyanisole (BHA), etc. Examples of pigments include inorganic pigments such as titanium dioxide, zinc oxide, ultramarine, red iron oxide, lithopone, lead, cadmium, iron, cobalt, aluminum, hydrochloride salts, sulfates, azo pigments, and organic pigments such as copper phthalocyanine pigments, etc. Examples of rust inhibitors include zinc phosphate, tannic acid derivatives, phosphate esters, basic sulfonates, and various rust-inhibiting pigments, etc. Examples of antistatic agents include quaternary ammonium salts, or hydrophilic compounds such as polyglycolic acid and ethylene oxide derivatives, etc.

[0116] For example, tackifying resins are used as tackifiers. Specific examples of tackifying resins include phenolic tackifying resins, terpene tackifying resins, rosin tackifying resins, hydrocarbon tackifying resins, epoxy tackifying resins, polyamide tackifying resins, elastomer tackifying resins, and ketone tackifying resins.

[0117] Phenolic tackifying resins include, for example, terpene phenol resins, hydrogenated terpene phenol resins, alkylphenol resins, rosin phenol resins, and xylene formaldehyde resins. Terpene phenol resins refer to polymers containing terpene residues and phenol residues, and are a concept that encompasses both copolymers of terpenes and phenol compounds (terpene-phenol copolymer resins) and homopolymers or copolymers of terpenes modified with phenol (phenol-modified terpene resins). Examples of terpenes that constitute such terpene phenol resins include monoterpenes such as α-pinene, β-pinene, and limonene (including d-isomers, l-isomers, and d / l-isomers (dipentene)). Hydrogenated terpene phenol resins are hydrogenated terpene phenol resins having a structure obtained by hydrogenating such terpene phenol resins, and are sometimes called hydrogenated terpene phenol resins. Alkylphenol resins are resins (oil-based phenol resins) obtained from alkylphenols and formaldehyde. Examples of alkylphenol resins include novolac type and resol type. Examples of rosinphenol resins include phenol-modified products of rosins or various rosin derivatives (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters). Examples of rosinphenol resins include rosinphenol resins obtained by methods such as adding phenol to rosins or various rosin derivatives with an acid catalyst and then thermal polymerization.

[0118] Examples of terpene-based tackifying resins include terpene resins, terpene phenol resins, styrene-modified terpene resins, aromatic-modified terpene resins, and hydrogenated terpene resins. Examples of terpene resins include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. Examples of single-molecule polymers of terpenes include α-pinene polymers, β-pinene polymers, and dipentene polymers.

[0119] The concept of rosin-based tackifying resins encompasses both rosins and rosin derivative resins. Examples of rosins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; and modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins) obtained by hydrogenation, disproportionation, polymerization, etc.

[0120] Examples of rosin derivative resins include rosin esters such as unmodified rosin esters (esters of unmodified rosin and alcohols) and modified rosin esters (esters of modified rosin and alcohols); unsaturated fatty acid modified rosins obtained by modifying rosins with unsaturated fatty acids; unsaturated fatty acid modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl groups of rosins or rosin derivative resins (rosin esters, unsaturated fatty acid modified rosins, unsaturated fatty acid modified rosin esters, etc.); rosin phenols; and metal salts thereof. Examples of rosin esters include methyl esters, triethylene glycol esters, glycerin esters, pentaerythritol esters, and maleic acid esters of unmodified rosin or modified rosin (e.g., hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.).

[0121] Examples of hydrocarbon-based tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins (e.g., styrene-based resins, xylene-based resins, etc.), aliphatic cyclic hydrocarbon resins, aliphatic-aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, and coumarone-indene-based resins.

[0122] Examples of acrylic tackifiers include acrylic oligomers.

[0123] Other tackifiers include, for example, epoxy oligomers and styrene oligomers.

[0124] The content of the tackifier in the electro-peelable adhesive composition according to the embodiment of the present invention is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, more preferably 7.5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the polymer. By setting the tackifier content to 3 parts by mass or more, the tackifier addition effect, that is, the effect of achieving both initial adhesive strength and electro-peelability, is easily obtained. Furthermore, the upper limit is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, even more preferably 40 parts by mass or less, and most preferably 30 parts by mass or less. By setting the tackifier content to 50 parts by mass or less, the dispersibility of the tackifier in the resin can be maintained, and initial adhesive strength is easily obtained.

[0125] Examples of adhesion promoters include titanium coupling agents and zirconium coupling agents.

[0126] The electrolytic adhesive composition according to the embodiment of the present invention is not particularly limited, but can be produced by appropriately stirring and mixing a specific (meth)acrylic polymer and, if necessary, a polymer, an ionic substance, an additive, a crosslinking agent, polyethylene glycol, a conductive filler, etc.

[0127] <Impact Resistance> The impact resistance of the electrolytic adhesive composition according to the embodiment of the present invention can be evaluated by various methods, but for example, it can be evaluated by testing using the impact testing machine described in the Examples section.

[0128] The reason why the impact resistance of the electrolytic adhesive composition according to the embodiment of the present invention is improved by containing a specific (meth)acrylic polymer is not entirely clear, but the following reasons are considered: When the specific (meth)acrylic polymer contains monomer units containing cyclic hydrocarbon groups and monomer units containing oxyalkylene groups, stress relaxation is thought to occur. As a result, impact resistance is thought to be improved.

[0129] Furthermore, the inclusion of a specific (meth)acrylic polymer is preferable because it not only improves impact resistance but also enhances electropenetration. The reason why the inclusion of a specific (meth)acrylic polymer enhances electropenetration is not entirely clear, but the following reasons are considered: When a specific (meth)acrylic polymer is included, the entanglement between polymers weakens, and it is thought that ionic substances can be effectively bleed out by applying a voltage. As a result, it is thought that electropenetration is enhanced.

[0130] <Initial Adhesion and Electropeel Strength> The adhesion strength of the electropeelable adhesive composition according to the embodiment of the present invention can be evaluated by various methods, but for example, it can be evaluated by the 180° peel test described in the Examples section.

[0131] The adhesive composition according to the embodiment of the present invention preferably has an initial adhesive strength of 4.0 N / cm or more, more preferably 5.0 N / cm or more, even more preferably 6.0 N / cm or more, and most preferably 7.0 N / cm or more, as measured by forming an adhesive sheet as described in the Examples section and performing a 180° peel test. In embodiments where initial adhesive strength is given greater emphasis, the initial adhesive strength may be, for example, 10.0 N / cm or more, 15.0 N / cm or more, or 20.0 N / cm or more. When the initial adhesive strength is 4.0 N / cm or more, the adhesion to the adherend is sufficient, and the adherend is less likely to peel off or shift.

[0132] Furthermore, it is preferable that the adhesive composition for electropenetration according to the embodiment of the present invention, when an adhesive sheet is formed as described in the Examples section, and the adhesive strength measured in a 180° peel test immediately after applying a voltage of 30V for 180 seconds, is sufficiently small compared to the initial adhesive strength.

[0133] In the embodiment of the present invention, the electropenetrating adhesive composition is preferably 10.0 N / cm or less, more preferably 5.0 N / cm or less, even more preferably 3.0 N / cm or less, particularly preferably 1.0 N / cm or less, and most preferably 0.5 N / cm or less, when an adhesive sheet is formed as described in the Examples section and an electropenetrating adhesive sheet is applied with a voltage of 30 V for 180 seconds, and measured in a 180° peel test. When the electropenetrating adhesive composition is 1.0 N / cm or less, the electropenetrating properties are excellent, making it possible to rework even fragile adherends non-destructively.

[0134] The electrolytic adhesive composition according to the embodiment of the present invention achieves both the initial adhesive strength and the electrolytic peeling strength. Therefore, the peeling strength change rate calculated by the following formula is preferably 50% or more, more preferably 70% or more, and even more preferably 90% or more. The formula is expressed as follows: [(Initial Adhesion Strength) - (Electrolytic Peeling Strength)] × 100 / Initial Adhesion Strength = Peeling Strength Change Rate (%)

[0135] The applied voltage and voltage application time during electrolysis are not limited to those described above and are not particularly limited as long as the adhesive sheet can be peeled off. Preferred ranges are shown below. The applied voltage is preferably 1V or more, more preferably 3V or more, and even more preferably 6V or more. It is also preferably 100V or less, more preferably 50V or less, even more preferably 30V or less, and may be 15V or less. The voltage application time is preferably 300 seconds or less, more preferably 250 seconds or less, even more preferably 200 seconds or less, and may be 100 seconds or less. In such cases, workability is excellent. The shorter the application time, the better, but it is usually 1 second or more.

[0136] <Holding Force> The holding force of the electrolytic adhesive composition according to the embodiment of the present invention can be evaluated by various methods, but for example, it can be evaluated by the holding force of a 3 kg load at 22°C and 50% RH as described in the Examples section.

[0137] The reason why the adhesive composition for electrolytic release according to the embodiment of the present invention has improved retention due to the inclusion of a specific (meth)acrylic polymer is not entirely clear, but the following reasons are considered: It is thought that if the glass transition temperature (Tg) of the specific (meth)acrylic polymer is -45°C or higher, an appropriate cohesive force is maintained. As a result, it is thought that the retention force is improved.

[0138] In the embodiment of the present invention, the adhesive composition for electrolytic release is formed by creating an adhesive sheet as described in the Examples section, and bonding a laminate formed by overlapping a portion of the first adherend and the second adherend. When a load of 3 kg is suspended at 22°C and 50% RH, the displacement of the second adherend from its initial position is preferably 5 mm or less, more preferably 4 mm or less, even more preferably 3 mm or less, particularly preferably 2 mm or less, even more preferably 1 mm or less, and most preferably 0 mm. When the above displacement is 5 mm or less, for example, a member having a precise and / or fine structure with a width of 5 mm or less or 5 mm ２ Even when the electrolytic adhesive composition of the present invention is used on members having the following bonding areas, unintended peeling can be suppressed.

[0139] The holding power of the electrolytic adhesive composition according to the embodiment of the present invention can be adjusted by setting the type and content of monomers, additives, and reaction time to the preferred range described below. More specifically, the holding power of the electrolytic adhesive composition according to the embodiment of the present invention tends to increase by, for example, selecting monomers with a high glass transition temperature of homopolymer and / or increasing their content, increasing the glass transition temperature, average molecular weight, and gel fraction of a specific (meth)acrylic polymer, narrowing the molecular weight distribution of the specific (meth)acrylic polymer and / or removing unreacted residual monomers, selecting a suitable polymerization initiator and / or decreasing its content, lengthening the reaction time of the specific (meth)acrylic polymer, including and / or increasing the amount of crosslinking agents and polyfunctional monomers, and including rigid materials.

[0140] <Gel Fraction> From the viewpoint of having excellent holding power, the electrolytic adhesive composition according to the embodiment of the present invention preferably has a gel fraction of 80% or more, more preferably 84% or more, and even more preferably 88% or more.

[0141] The gel fraction of the electrolytic adhesive composition according to the embodiment of the present invention can be adjusted by setting the amount of crosslinking agent, the amount of polyfunctional monomer, the amount of polymerization initiator, and the type and content of monomers within the preferred range described above. More specifically, the gel fraction of the electrolytic adhesive composition according to the embodiment of the present invention tends to increase by, for example, including and / or increasing the content of crosslinking agents and polyfunctional monomers, and / or removing unreacted residual monomers, selecting a suitable polymerization initiator, and / or decreasing its content.

[0142] <Uses of the electrolytic adhesive composition> The uses of the electrolytic adhesive composition according to the embodiment of the present invention are not particularly limited, but it can be preferably used as an electrolytic adhesive composition for electrolytic removal and / or for fixing components in electrical and electronic equipment. The specific aspects of its application in such uses are the same as those described later for the uses of adhesive sheets.

[0143] <Method for Manufacturing an Electrolytic Adhesive Composition> The electrolytic adhesive composition according to the embodiment of the present invention is not particularly limited, but can be manufactured by appropriately stirring and mixing the above-mentioned polymer, ionic substance, additive, and, if necessary, a crosslinking agent, polyethylene glycol, conductive filler, etc.

[0144] [Electrorelease Adhesive Layer and Adhesive Sheet] The electrorelease adhesive layer according to the embodiment of the present invention is formed from the electrorelease adhesive composition according to the embodiment of the present invention described above. The structure of the adhesive sheet according to the embodiment of the present invention is not particularly limited, but the adhesive sheet 10 shown in Figure 1 is preferred. The adhesive sheet 10 is a substrate-less double-sided adhesive sheet consisting only of the electrorelease adhesive layer 1.

[0145] The adhesive sheet according to the embodiment of the present invention is not particularly limited as long as it comprises an electrorelease adhesive layer formed from the electrorelease adhesive composition according to the embodiment of the present invention described above. The adhesive sheet according to the embodiment of the present invention may also have other adhesive layers (hereinafter sometimes referred to as "other adhesive layers") other than the electrorelease adhesive layer according to the embodiment of the present invention.

[0146] The adhesive sheet according to the embodiment of the present invention may have, in addition to the above, a base material (for example, an electrically conductive base material), a conductive layer, an intermediate layer, and a primer layer. The adhesive sheet according to the embodiment of the present invention may be in the form of a roll wound up or in the form of a sheet. The term "adhesive sheet" also includes the meaning of "adhesive tape." That is, the adhesive sheet according to the embodiment of the present invention may be an adhesive tape having a tape-like form.

[0147] An adhesive sheet according to an embodiment of the present invention may consist only of an electro-release adhesive layer without a substrate, i.e., a substrate-less double-sided adhesive sheet. An adhesive sheet according to an embodiment of the present invention may be a double-sided adhesive sheet having a substrate, wherein both sides of the substrate are electro-release adhesive layers, or a double-sided adhesive sheet where one side of the substrate is an electro-release adhesive layer and the other side is another adhesive layer. Furthermore, an adhesive sheet according to an embodiment of the present invention may be a single-sided adhesive sheet having a substrate, wherein only one side of the substrate is an electro-release adhesive layer. An adhesive sheet according to an embodiment of the present invention may have a release liner for the purpose of protecting the surface of the electro-release adhesive layer, but such release liner is not included in the adhesive sheet according to the embodiment of the present invention.

[0148] The conductive substrate is not particularly limited as long as it has conductivity on at least one surface. For example, it may be a conductive substrate with a laminated structure including a non-conductive substrate and a conductive layer, or it may be a conductive substrate with a single-phase structure consisting only of a conductive layer.

[0149] The conductive layer is not particularly limited as long as it is a conductive layer, but may be a metal-based substrate such as metal foil (e.g., aluminum, magnesium, copper, iron, tin, gold, etc.), metal plate (e.g., aluminum, magnesium, copper, iron, tin, silver, etc.), a conductive polymer, or a metal vapor-deposited film provided on the substrate.

[0150] The non-conductive substrate is not particularly limited, but examples include paper-based substrates such as paper, fibrous substrates such as cloth and nonwoven fabric, plastic substrates such as films and sheets made of various plastics (polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, acrylic resins such as polymethyl methacrylate, etc.), and laminates thereof. The substrate may be in the form of a single layer or a multi-layer structure. The substrate may be subjected to various treatments as needed, such as back treatment, antistatic treatment, and primer treatment.

[0151] Generally, from the viewpoint of initial adhesive strength, the thickness of the electropenetrating adhesive layer is preferably 1 μm or more and 1000 μm or less. The upper limit of the thickness of the electropenetrating adhesive layer is more preferably 500 μm, even more preferably 400 μm, and even more preferably 300 μm. In some embodiments, the thickness of the electropenetrating adhesive layer may be 250 μm or less, 200 μm or less, 150 μm or less, 125 μm or less, 100 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, or 50 μm or less. Furthermore, from the viewpoint of achieving both adhesive properties and high impact resistance, the lower limit of the thickness of the electropenetrating adhesive layer is more preferably 5 μm, even more preferably 10 μm, even more preferably 20 μm, and particularly preferably 30 μm. Furthermore, from the viewpoint of achieving both adhesive properties, holding power, and high impact resistance, the thickness of the electro-peelable adhesive layer is preferably 50 μm or more, more preferably 75 μm or more, even more preferably 100 μm or more, and particularly preferably 150 μm or more.

[0152] The preferred range for the thickness of the electrorelease adhesive layer can be appropriately set depending on the purpose and the form of the double-sided adhesive sheet. For example, in the case of the adhesive sheet 10 shown in Figure 1, i.e., a substrate-less double-sided adhesive sheet, the thickness of the electrorelease adhesive layer is preferably 20 μm or more and 3000 μm or less. A thickness of 20 μm or more is preferable because it improves impact resistance and / or initial adhesive strength. A thickness of 3000 μm or less is preferable because it improves electrorelease properties. In the case of a substrate-less double-sided adhesive sheet, the upper limit of the thickness of the electrorelease adhesive layer is more preferably 1000 μm, even more preferably 500 μm, and even more preferably 300 μm. In some embodiments, the thickness of the electropenetrating adhesive layer may be 250 μm or less, 200 μm or less, 150 μm or less, 125 μm or less, 100 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, or 50 μm or less. The lower limit is more preferably 30 μm, even more preferably 40 μm, even more preferably 50 μm, and particularly preferably 60 μm. Furthermore, from the viewpoint of achieving both adhesive properties, holding power, and high impact resistance, the thickness of the electropenetrating adhesive layer is preferably 50 μm or more, more preferably 75 μm or more, even more preferably 100 μm or more, and particularly preferably 150 μm or more.

[0153] <Method for Manufacturing Adhesive Sheets> The method for manufacturing adhesive sheets according to the embodiments of the present invention can be a known or conventional manufacturing method. For the electropenetrating adhesive layer in the adhesive sheet according to the embodiments of the present invention, one method is to apply a solution of the electropenetrating adhesive composition according to the embodiments of the present invention dissolved in a solvent as needed onto a release liner, and then dry and / or cure it. For other adhesive layers, one method is to apply a solution of another electropenetrating adhesive composition dissolved in a solvent as needed onto a release liner, and then dry and / or cure it. The solvent and release liner can be those listed above.

[0154] Conventional coaters (e.g., gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, spray roll coaters, etc.) can be used for application.

[0155] When the electro-peelable adhesive composition is an ultraviolet-curable adhesive composition, and an electro-peelable adhesive layer is formed by irradiating a coating film formed from the ultraviolet-curable adhesive composition with ultraviolet light, it is preferable to attach a cover sheet to the surface of the coating film and irradiate the electro-peelable adhesive composition between the two sheets with ultraviolet light to prevent polymerization inhibition by oxygen. Any suitable substrate can be used as the substrate and cover sheet used to form the adhesive sheet. The substrate and cover sheet may also be a release liner having a release treatment layer on the contact surface with the adhesive sheet. The light source for ultraviolet irradiation is not particularly limited as long as it can irradiate light in the wavelength range to which the photopolymerization initiator contained in the electro-peelable adhesive composition is sensitive, and black light lamps, LED light sources, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, etc., are preferably used.

[0156] The irradiation intensity of the ultraviolet light is 3 mW / cm². ２ The above is preferable. The irradiance of the ultraviolet light is 3 mW / cm². ２ If the UV intensity is below this level, the polymerization reaction time will be longer, which may result in lower productivity. The UV intensity in question is 200 mW / cm². ２ The following is preferable: The irradiance of the ultraviolet light is 200 mW / cm². ２ If the UV light intensity exceeds 100 mJ / cm², the photopolymerization initiator is rapidly consumed, leading to a decrease in the molecular weight of the polymer, which can reduce its retention capacity, especially at high temperatures. ２ ~5000mJ / cm ２ It is preferable that this is the case. By irradiating the electro-peelable adhesive composition applied to the substrate with ultraviolet light, unreacted monomer components and polyfunctional monomers in the prepolymer composition react to obtain a polymer in which a cross-linked structure is introduced into the acrylic polymer chain.

[0157] By the above method, an electrorelease adhesive layer and other adhesive layers can be manufactured, and by laminating the electrorelease adhesive layer and other adhesive layers on a substrate, a conductive layer, and an electrically conductive substrate as appropriate, an adhesive sheet according to the embodiment of the present invention can be manufactured. Alternatively, instead of a release liner, an adhesive sheet may be manufactured by applying an electrorelease adhesive composition to a substrate, a conductive layer, and an electrically conductive substrate.

[0158] <Applications of the Adhesive Sheet> The adhesive sheet according to the embodiment of the present invention is suitable for fixing secondary batteries (e.g., lithium-ion battery packs) used in mobile terminals such as smartphones, mobile phones, laptop computers, video cameras, and digital cameras to their casings, and for fixing the display panel of these devices to their casings.

[0159] Furthermore, examples of materials to be bonded by the adhesive sheet according to the embodiment of the present invention include silicon substrates for semiconductor wafer applications, sapphire substrates, SiC substrates and metal base substrates for LEDs, TFT substrates and color filter substrates for displays, display units, display unit protective members and housings included in mobile devices, and base substrates for organic EL panels. Examples of fragile members to be bonded by the double-sided adhesive sheet include semiconductor substrates such as compound semiconductor substrates, silicon substrates for MEMS devices, passive matrix substrates, surface cover glass for smartphones, OGS (One Glass Solution) substrates in which a touch panel sensor is attached to the cover glass, organic substrates mainly composed of silsesquioxane and organic-inorganic hybrid substrates, flexible glass substrates for flexible displays, and graphene sheets.

[0160] [Bonded Body] A bonded body according to an embodiment of the present invention comprises an adhesive sheet according to an embodiment of the present invention and a conductive material, wherein the electrorelease adhesive layer is attached to the conductive material. More specifically, a bonded body comprises an adhesive sheet according to an embodiment of the present invention and a conductive material, wherein the electrorelease adhesive layer of the adhesive sheet is attached to the conductive material. The surface resistance value of the conductive material to which the adhesive layer is attached is, for example, 1.0 × 10⁻⁶.４ Ω / □ or less, preferably 1.0 × 10 ３ The surface resistance is less than or equal to Ω / □. The surface resistance can be calculated by dividing the resistivity measured by the four-terminal method by the thickness of the conductive material, in accordance with JIS K 7194 (1994). Furthermore, the surface resistance of the conductive material can be selected according to the intended use and conditions, i.e., the applied voltage conditions for stripping (whether high voltage or low voltage is desired). Lowering the surface resistance of the conductive material tends to lower the voltage required for stripping. For example, the surface resistance is 5.0 × 10⁻⁶. ２ It can also be less than or equal to Ω / □, and 1.0 × 10 ２ It may be less than or equal to Ω / □, less than or equal to 50Ω / □, less than or equal to 40Ω / □, or less than or equal to 30Ω / □.

[0161] Examples of conductive materials that serve as the adherend for the adhesive sheet according to the embodiment of the present invention include conductive substrates and substrates having a conductive layer.

[0162] The conductive substrate may be a single layer or a laminate of a conductive material. Examples of conductive materials include metallic materials such as aluminum, magnesium, copper, iron, tin, silver, gold, lead, or alloys thereof; inorganic materials such as conductive metal oxides (e.g., ITO) or carbon (e.g., graphene); and resin materials such as conductive polymers (e.g., a composite made of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid). Among these, metallic materials containing aluminum are preferred.

[0163] Examples of substrates having a conductive layer include a substrate laminated with a conductive layer formed from the conductive materials exemplified above or a composite containing such materials. Examples of composites include a conductive composition in which the conductive materials exemplified above are dispersed in a resin (for example, a conductive composition in which particles made of a metal material are dispersed in an epoxy resin). The substrate having a conductive layer may be a conductive substrate or a non-conductive substrate.

[0164] The non-conductive substrate of the adherend is not particularly limited, but examples include paper-based substrates such as paper, fiber-based substrates such as cloth and nonwoven fabric, plastic-based substrates such as films, sheets, and housings made of various plastics (polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate, acrylic resins such as polymethyl methacrylate, and polyimide resins), glass substrates, metal substrates, and laminates thereof. The substrate may be in the form of a single layer or a multi-layer structure. The substrate may be subjected to various treatments as needed, such as rust prevention treatment, back treatment, antistatic treatment, and primer treatment.

[0165] [Structure of the bonded body] The bonded body according to the embodiment of the present invention comprises an adhesive sheet having an electrorelease adhesive layer formed from an electrorelease adhesive composition according to the embodiment of the present invention, and a conductive material, wherein the electrorelease adhesive layer is attached to the conductive material.

[0166] The above description can be applied directly to electrolytically removable adhesive compositions, electrolytically removable adhesive layers, adhesive sheets, and conductive materials.

[0167] Examples of the structures of the bonded bodies according to the embodiments of the present invention include the structures shown in Figures 2 to 7. In all cases, the conductive materials are bonded by an electropenetrating adhesive layer 1. Examples of the bonded bodies according to the embodiments of the present invention include: Bonded body X1 in Figure 2, in which a conductive substrate 2 is bonded to both sides of the electropenetrating adhesive layer 1; Bonded body X2 in Figure 3, in which a conductive substrate 2 is bonded to one side of the electropenetrating adhesive layer 1, and the conductive layer side of a conductive substrate 2 having a conductive layer 5 is bonded to the other side; Bonded body X3 in Figure 4, in which the conductive layer side of a non-conductive substrate 3 having a conductive layer 5 is bonded to both sides of the electropenetrating adhesive layer 1. Also, Bonded body X4 in Figure 5, in which the conductive substrate 7 and the non-conductive substrate 3 are bonded via other adhesive layers 6, in which the conductive substrate 7 and the non-conductive substrate 3 are bonded to the conductive layer side of a single-sided adhesive sheet 11 having an electropenetrating adhesive layer 1 on one side of the conductive substrate 7.

[0168] Furthermore, examples include the assembled body X5 in Figure 6, in which conductive substrates 2 are bonded to both sides of a double-sided adhesive sheet 21, where both sides of the conductive substrate 7 are electropenetrating adhesive layers 1; and the assembled body X6 in Figure 7, in which a conductive substrate 2 is bonded to one side of a double-sided adhesive sheet 21, where both sides of the conductive substrate 7 are electropenetrating adhesive layers 1, and a non-conductive substrate 3 is bonded to the other side.

[0169] [Method for separating a bonded body] A method for separating a bonded body according to an embodiment of the present invention comprises an adhesive sheet having an electro-removable adhesive layer formed by an electro-removable adhesive composition according to an embodiment of the present invention, and a conductive material, wherein the adhesive layer is attached to the conductive material, and the method for separating a bonded body involves applying a voltage to the electro-removable adhesive layer to separate the adhesive sheet and the conductive material.

[0170] In the bonded structure, the electropenetrating adhesive layer is attached to a conductive substrate, the conductive layer side of a conductive material, or an electrically conductive substrate. The bonded structure is separated by applying a voltage to the electropenetrating adhesive layer via the conductive substrate, conductive layer, or electrically conductive substrate. In other words, the separation of the bonded structure according to the embodiment of the present invention can be achieved by applying a voltage to the electropenetrating adhesive layer, thereby generating a potential difference in the thickness direction of the electropenetrating adhesive layer.

[0171] For example, if the bonded body has a laminated structure similar to bonded body X1 shown in Figure 2, it can be separated by applying current to the conductive substrates 2 bonded to both sides of the electropenetrating adhesive layer 1 and applying a voltage to the electropenetrating adhesive layer. If the bonded body has a laminated structure similar to bonded body X2 shown in Figure 3, it can be separated by applying current to the conductive layer 5 bonded to one side of the electropenetrating adhesive layer 1 and the conductive substrate 2 bonded to the other side of the electropenetrating adhesive layer 1 and applying a voltage to the electropenetrating adhesive layer 1. If the bonded body has a laminated structure similar to bonded body X3 shown in Figure 4, it can be separated by applying current to the conductive layers 5 bonded to both sides of the electropenetrating adhesive layer 1 and applying a voltage to the electropenetrating adhesive layer 1. If the bonded body has a laminated structure similar to bonded body X4 shown in Figure 5, it can be separated by applying current to the conductive layer 5 and the conductive substrate 7 and applying a voltage to the electropenetrating adhesive layer 1.

[0172] It is preferable to apply current by connecting terminals to one end and the other end of the bond so that a voltage is applied to the entire electro-peelable adhesive layer. The aforementioned one end and the other end may be part of the conductive substrate, conductive layer, and current-carrying substrate. When separating, water may be added to the interface between the conductive layer and the electro-peelable adhesive layer, or the interface between the conductive material and the electro-peelable adhesive layer, before applying the voltage. Depending on the adhesive interface to be separated, conductive materials can be selected to connect the cathode and anode.

[0173] As described above, the following matters are disclosed in this specification: <1> An electrolytic adhesive composition comprising an (meth)acrylic polymer having a glass transition temperature (Tg) of -45°C or higher and 25°C or lower, and an ionic substance, wherein the (meth)acrylic polymer comprises units derived from monomers containing cyclic hydrocarbon groups and units derived from monomers containing oxyalkylene groups. <2> The electrolytic adhesive composition according to <1>, wherein the proportion of monomers containing cyclic hydrocarbon groups to the total monomer components constituting the (meth)acrylic polymer is 10% by mass or more. <3> The electrolytic adhesive composition according to <1> or <2>, wherein the cyclic hydrocarbon group is a polycyclic aliphatic hydrocarbon group. <4> The electrolytic adhesive composition according to any one of <1> to <3>, wherein the proportion of monomers containing cyclic hydrocarbon groups to the total monomer components constituting the (meth)acrylic polymer is 10% by mass or higher and 45% by mass or less, and the proportion of monomers containing oxyalkylene groups is 5% by mass or higher and 30% by mass or less. <5> An electrolytic adhesive composition according to any one of <1> to <4>, wherein the ionic substance is an ionic liquid. <6> An electrolytic adhesive composition according to any one of <1> to <5>, for electrolytic release and / or for fixing components in electrical and electronic equipment. <7> An electrolytic adhesive layer formed from an electrolytic adhesive composition according to any one of <1> to <6>. <8> An adhesive sheet comprising an electrolytic adhesive layer formed from an electrolytic adhesive composition according to any one of <1> to <6>. <9> A bond comprising the adhesive sheet according to <8> and a conductive material, wherein the electrolytic adhesive layer is attached to the conductive material.

[0174] The present invention will be described more specifically below with reference to examples, but the present invention is not limited to these examples.

[0175] (Preparation of Acrylic Prepolymer Composition 1) As monomer components, 77 parts by mass of n-butyl acrylate (BA), 10 parts by mass of dicyclopentanyl acrylate (DCPA), 10 parts by mass of 2-methoxyethyl acrylate (MEA), 3 parts by mass of acrylic acid (AA), and as photoinitiators, 0.05 parts by mass of Omnirad 184 and 0.05 parts by mass of Omnirad 651 were placed in a separable flask and stirred for 15 minutes while introducing nitrogen gas. After removing oxygen from the polymerization system in this manner, ultraviolet light was irradiated until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) was approximately 20 Pa·s, thereby obtaining acrylic prepolymer composition 1 (polymerization rate 5%) in which a portion of the above monomer components had polymerized.

[0176] The obtained acrylic prepolymer composition 1 (polymer 1) was applied to the peeled surface of a polyethylene terephthalate peel liner (product name "MRF38", manufactured by Mitsubishi Chemical Corporation) so that the thickness of the coated layer after formation was 200 μm. Next, the peeled surface of the polyethylene terephthalate peel liner (product name "MRE38", manufactured by Mitsubishi Chemical Corporation) was bonded to the surface of the coated layer. After that, a black light was used as the light source, and the integrated light intensity was 2000 mJ / cm². ２ The coated layer was photocured by irradiating it with ultraviolet light under the specified conditions, and the glass transition temperature (Tg) of the obtained acrylic polymer 1 was measured and is shown in Table 1. The integrated amount of ultraviolet light was measured using an industrial UV checker UVR-T2 (manufactured by Topcon Techno House Co., Ltd.). Approximately 1 to 2 mg of the obtained acrylic polymer 1 was weighed into an aluminum open cell, and the reversing heat flow (specific heat component) behavior of the polymer was obtained using a temperature-modulated DSC (product name "Q-2000" manufactured by T.A. Instruments Inc.) at a heating rate of 5°C / min under a nitrogen atmosphere of 50 ml / min. Referring to JIS-K-7121, the temperature at the point where a line equidistant in the vertical axis direction from the line extending from the low-temperature baseline and high-temperature baseline of the obtained reversing heat flow intersects with the curve of the step-like change portion of the glass transition was defined as the glass transition temperature (Tg) of the polymer.

[0177] (Preparation of Acrylic Prepolymer Compositions 2-11) Acrylic prepolymer compositions 2-11 (polymers 2-11) were obtained in the same manner as the preparation of acrylic prepolymer composition 1, except that the monomer components and blending ratios were changed as shown in Table 3. Acrylic polymers 2-11 were prepared using the obtained acrylic prepolymer compositions 2-11 in the same manner as acrylic polymer 1, and the glass transition temperature (Tg) was measured and is shown in Tables 1 and 2, respectively.

[0178] [Example 1] (Preparation of electropenetrating adhesive layer) To 100 parts by mass of the acrylic prepolymer composition 1 (polymer 1) obtained above, 0.16 parts by mass of NDDA as a polyfunctional monomer and 4 parts by mass of AS-110 as an ionic substance were added, and the mixture was stirred and mixed to obtain the electropenetrating adhesive composition of Example 1. The obtained electropenetrating adhesive composition was applied to the peeled surface of a polyethylene terephthalate peel liner (product name "MRF38", manufactured by Mitsubishi Chemical Corporation) whose surface had been peeled, so that the thickness of the adhesive layer after formation was 200 μm. Then, the peeled surface of the polyethylene terephthalate peel liner (product name "MRE38", manufactured by Mitsubishi Chemical Corporation) whose surface had been peeled was bonded to the surface of the adhesive composition layer. After that, an integrated light intensity of 2000 mJ / cm was applied. ２ The adhesive composition was photocured by irradiating it with ultraviolet light under these conditions to obtain an electro-peelable adhesive layer with a polymerization rate of 99.5%.

[0179] The abbreviations for monomers, ionic substances, and polyfunctional monomers in Tables 1 to 3 are as follows:

[0180] (Monomers) BA: n-butyl acrylate, manufactured by Nippon Shokubai Co., Ltd. (Tg: -40°C) MA: methyl acrylate, manufactured by Toagosei Co., Ltd. (Tg: 5°C) MEA: 2-methoxyethyl acrylate, manufactured by Toagosei Co., Ltd. (Tg: -50°C) AA: acrylic acid, manufactured by Toagosei Co., Ltd. (Tg: 106°C) DCPA: dicyclopentanyl acrylate, manufactured by Resonac Co., Ltd. (Tg: 120°C) IBXA: isobornyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd. (Tg: 97°C) NK Ester AM-90G: methoxypolyethylene glycol acrylate, trade name "NK Ester AM-90G", manufactured by Shin Nakamura Chemical Industry Co., Ltd. (Tg: -71°C) (Ionic substances) AS-110: Cation: 1-ethyl-3-methylimidazolium cation, Anion: bis(fluorosulfonyl)imide anion, Ionic liquid, Trade name "Elexel AS-110", Manufactured by Daiichi Kogyo Seiyaku Co., Ltd. (Polyfunctional monomer) NDDA: 1,9-nonanediol diacrylate, Trade name "Viscote #260", Manufactured by Osaka Organic Chemical Industry Co., Ltd.

[0181] [Examples 2-9] Except that acrylic prepolymer composition 1 was replaced with acrylic prepolymer compositions 2-8 and 11 (polymers 2-8 and 11), electropenetrating adhesive layers of Examples 2-9 were obtained in the same manner as in Example 1.

[0182] [Comparative Examples 1-2] Except that acrylic prepolymer composition 1 was replaced with acrylic prepolymer compositions 9-10, electropenetrating adhesive layers of Comparative Examples 1-2 were obtained in the same manner as in Example 1.

[0183] <Preparation of single-sided adhesive sheet with substrate> The obtained electro-peelable adhesive layer (adhesive sheet) was made into a sheet with a size of 10 mm x 80 mm, the release liner (product name "MRE38", manufactured by Mitsubishi Chemical Corporation) was peeled off, and the metal layer side of a metal-layered film (product name "1005CR", manufactured by Toray Industries, Inc., thickness 12 μm, size 10 mm x 100 mm) was bonded to the exposed electro-peelable adhesive layer surface to create a single-sided adhesive sheet with a substrate.

[0184] <Preparation of the bonded body> The release liner (product name "MRF38", manufactured by Mitsubishi Chemical Corporation) of the single-sided adhesive sheet with a base material was peeled off, and a stainless steel plate was attached to the peeled surface so that one end of the adhesive sheet protruded from the adherend by about 2 mm. The sheet was then pressed back and forth once with a 2 kg roller to obtain a bonded body (Figure 8) consisting of a stainless steel plate 3' (product name "SUS316", manufactured by Standard Test Piece Co., Ltd.) / electropenetrating adhesive layer 4' (adhesive sheet) / metal layered film 5' (electrical conductive base material).

[0185] The electropenetrating adhesive layers of Examples 1 to 9 and Comparative Examples 1 to 2 were evaluated.

[0186] (Gel fraction) Approximately 0.1 g of the electropenetrating adhesive layer obtained in the examples and comparative examples was taken, wrapped in a porous tetrafluoroethylene sheet with an average pore size of 0.2 μm (product name "NTF1122", manufactured by Nitto Denko Corporation), tied with kite string, and the mass at that time was measured and this mass was taken as the mass before immersion (Z). The mass before immersion is the total mass of the electropenetrating adhesive layer (the electropenetrating adhesive layer taken above), the tetrafluoroethylene sheet, and the kite string. The total mass of the tetrafluoroethylene sheet and the kite string was also measured and this mass was taken as the package mass (Y). Next, the electropenetrating adhesive layer wrapped in a tetrafluoroethylene sheet and tied with kite string (referred to as "sample") was placed in a 50 ml container filled with ethyl acetate and left to stand at 23°C for 7 days. Subsequently, the sample (after ethyl acetate treatment) was removed from the container, transferred to an aluminum cup, and dried in a drying oven at 130°C for 2 hours to remove the ethyl acetate. The mass was then measured and designated as the mass after immersion (X). The gel fraction was then calculated using the following formula: Gel fraction [% (mass%)] = (X - Y) / (Z - Y) × 100

[0187] (Initial Adhesion (22°C / 50%RH 72hr)) The bonded material prepared as described above was left to stand at 22°C / 50%RH for 72 hours, and then the adhesion strength (22°C / 50%RH 72hr) in a 180° peel test (tensile speed: 300 mm / min, peel temperature 22°C, humidity 50%RH) was measured using a peel tester (product name "Variable Angle Peel Tester YSP", manufactured by Asahi Seiko Co., Ltd.). The initial adhesion strength was calculated according to the measurement method 1 for 180° peel adhesion described in JIS Z 0237:2009.

[0188] (Electrolytic peeling force (22°C / 50%RH 72hr)) Before peeling, the positive and negative electrodes of a DC current machine were attached to locations α and β in Figure 8 of the bonded body, respectively. A voltage of 30V was applied for 180 seconds, and the electrolytic peeling force (22°C / 50%RH 72hr) was measured in the same manner as the initial adhesion force measurement described above, except for the point where peeling occurred immediately after the application of the voltage was stopped.

[0189] (Evaluation Criteria for Change in Peeling Force Rate) The change in peeling force rate was calculated from the initial adhesive strength and electropeeling force mentioned above, and the electropeelability was determined. The calculation formula is as follows: [(Initial Adhesion) - (Electropeeling Force)] × 100 / Initial Adhesion = Change in Peeling Force Rate (%)

[0190] (Evaluation criteria for peeling force change rate) A: Peeling force change rate is 90% or more. B: Peeling force change rate is 50% or more but less than 90%. C: Peeling force change rate is less than 50%. If the electropeelability is judged as "A" or "B", it is considered to be acceptable for practical use.

[0191] (Impact Resistance) Two pieces of adhesive sheet measuring 5 mm in width and 20 mm in length were cut from each example and comparative example. A stainless steel plate was prepared with a thickness of 2 mm and an outer diameter of 50 mm x 50 mm, with a square hole measuring 20 mm vertically and 20 mm horizontally in the center of the square. One of the adhesive sheets cut as described above was positioned so that one side of the square hole and one side of the adhesive sheet in the longitudinal direction were aligned, and the other adhesive sheet was similarly positioned on the side of the square hole opposite to the aforementioned side. A square stainless steel plate (thickness 3 mm, outer diameter 30 mm x 30 mm) was placed on the stainless steel plate with the square hole so as to sandwich the adhesive sheet and so that the centers of gravity of the two stainless steel plates coincided, and this was used as the evaluation sample. The evaluation sample was pressed (70 N x 15 s) so that force was applied uniformly to the adhesive sheet, and then left to stand at 50°C for 3 hours with the force released. Subsequently, the evaluation sample was removed and returned to 22°C and 50% RH. Next, a measuring platform was placed on the base of a DuPont impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the evaluation sample was placed on the measuring platform so that the stainless steel plate with the square-shaped hole was facing upwards. Then, a stainless steel impact pin with a tip radius of 3.1 mm was placed in the center of the square-shaped hole, and the impact resistance was measured by changing the mass of the drop weight and the drop height in the following order. The impact resistance measurement was carried out so that the amount of energy increased until peeling occurred.

[0192] (1) The drop weight was 50g and varied in 50mm increments from 50mm to 500mm. (2) The drop weight was 100g and varied in 50mm increments from 50mm to 500mm. (3) The drop weight was 150g and varied in 50mm increments from 350mm to 500mm. (4) The drop weight was 200g and varied in 50mm increments from 400mm to 500mm. (5) The drop weight was 300g and varied in 50mm increments from 350mm to 500mm.

[0193] In this process, tests were not conducted on energy quantities that had already been evaluated, and the load and height were set so that the energy quantities would not overlap. The energy quantity (J) used in the test conducted immediately before peeling was calculated by multiplying the load by the height, and this was used as the evaluation of impact resistance.

[0194] (Impact Resistance Evaluation Criteria) Impact resistance was judged according to the following evaluation criteria: A: 0.23 J or more. B: 0.21 J or more and less than 0.23 J. C: 0.19 J or more and less than 0.21 J. D: 0.17 J or more and less than 0.19 J. E: Less than 0.17 J. If the impact resistance judgment was "A", "B", or "C", it was considered that there would be no problem in actual use.

[0195] (3kg load holding capacity under a 22°C 50% RH environment) The adhesive sheets of each example and comparative example were cut to a size of 15 x 25 mm to create samples. The release liner (MRE38) was peeled off from these samples, and the exposed electro-peelable adhesive layer surface was attached to the lower end of the first adherend, a stainless steel plate (SUS316, size: 30 mm x 120 mm), so that the long side direction of the adhesive layer and the stainless steel plate were horizontal. Next, the other release liner (MRF38) was peeled off, and the upper end of the second adherend, a stainless steel plate (SUS316, size: 30 mm x 120 mm), was brought into contact with the exposed electro-peelable adhesive layer surface, thereby obtaining a laminate (first adherend / electro-peelable adhesive layer (adhesive sheet) / second adherend) in which the lower end of the first adherend and the upper end of the second adherend overlapped by 30 mm x 15 mm. Next, the laminate was pressed with a 2 kg roller for one back-and-forth motion, and a test specimen was obtained by leaving it in an environment of 22°C and 50% RH for 72 hours (hr). After that, in an environment of 22°C and 50% RH, the upper end of the test specimen in the longitudinal direction (upper end of the first adherend) was suspended from a stand, and a load of 3 kg was applied to the lower end of the test specimen in the longitudinal direction (lower end of the second adherend). After 168 hours (hr), the amount of displacement of the second adherend from its initial position was measured, and this value was defined as the holding force.

[0196] (Holding Force Assessment) The holding force for a 3kg load under a 22°C 50% RH environment was assessed according to the following evaluation criteria: A: Displacement is 0mm. B: Displacement is greater than 0mm but 3mm or less. C: Displacement is greater than 3mm but 5mm or less. D: Displacement exceeds 5mm, or the device falls. If the holding force assessment is "A", "B", or "C", it is considered acceptable for practical use.

[0197] The above examples, comparative examples, and measurement results are shown in Tables 1 and 2. Tables 1 and 2 also show the amounts of each component used in the above examples and comparative examples, and the glass transition temperature (Tg) of the polymer. Table 3 shows the polymer composition used in the above examples and comparative examples. Note that the values ​​for each component in Tables 1 and 2 below represent parts by mass.

[0198]

[0199]

[0200]

[0201] The adhesive sheets using the electro-peelable adhesive layers of Examples 1 to 9 were found to have excellent impact resistance. It was also found that the adhesive strength could be reduced by applying voltage. The acrylic polymer contained in the electro-peelable adhesive layer of Comparative Example 1 had a glass transition temperature of -45°C to 25°C, but did not contain units derived from monomers containing oxyalkylene groups. The acrylic polymer contained in the electro-peelable adhesive layer of Comparative Example 2 did not contain units derived from monomers containing cyclic hydrocarbon groups. The adhesive sheets of Comparative Examples 1 and 2 using such electro-peelable adhesive layers had low impact resistance. In contrast to the adhesive sheets of Comparative Examples 1 and 2, the acrylic polymer contained in the electro-peelable adhesive layer of Example 2 had a glass transition temperature of -45°C to 25°C, and contained units derived from monomers containing cyclic hydrocarbon groups and units derived from monomers containing oxyalkylene groups. The impact resistance of the adhesive sheet of Example 2 using such an electro-peelable adhesive layer was 0.23 J, which was higher than the impact resistance of the adhesive sheet of Comparative Example 1 (where the glass transition temperature of the acrylic polymer contained in the electro-peelable adhesive layer was similar to that of Example 2).

[0202] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of the present invention. This application is based on Japanese Patent Application No. 2025-056526 filed on 28 March 2025, the contents of which are incorporated herein by reference.

[0203] 1, 4' Electropeelable adhesive layer 2 Conductive substrate 3 Non-conductive substrate 3' Stainless steel plate 5' Film with metal layer 5 Conductive layer 6 Other adhesive layers 7 Conductive substrate 10 Adhesive sheet 11 Single-sided adhesive sheet 21 Double-sided adhesive sheet X1-X6 Joint

Claims

1. An electrolytic adhesive composition comprising a (meth)acrylic polymer having a glass transition temperature (Tg) of -45°C or higher and 25°C or lower, and an ionic substance, wherein the (meth)acrylic polymer comprises units derived from monomers containing cyclic hydrocarbon groups and units derived from monomers containing oxyalkylene groups.

2. The electrolytic adhesive composition according to claim 1, wherein the proportion of monomers containing the cyclic hydrocarbon group to the total monomer components constituting the (meth)acrylic polymer is 10% by mass or more.

3. The electrolytic adhesive composition according to claim 1, wherein the cyclic hydrocarbon group is a polycyclic aliphatic hydrocarbon group.

4. The electrolytic adhesive composition according to claim 1, wherein the proportion of monomers containing the cyclic hydrocarbon group to the total monomer components constituting the (meth)acrylic polymer is 10% by mass or more and 45% by mass or less, and the proportion of monomers containing the oxyalkylene group is 5% by mass or more and 30% by mass or less.

5. The electrolytic adhesive composition according to claim 1, wherein the ionic substance is an ionic liquid.

6. The electrolytic adhesive composition according to claim 1, which is for electrolytic stripping and / or for fixing components in electrical and electronic equipment.

7. An electropenetrating adhesive layer formed by the electropenetrating adhesive composition according to any one of claims 1 to 6.

8. An adhesive sheet comprising an electropenetrating adhesive layer formed from the electropenetrating adhesive composition according to any one of claims 1 to 6.

9. A bond comprising the adhesive sheet described in claim 8 and a conductive material, wherein the electropenetrating adhesive layer is attached to the conductive material.

Images