Adhesive composiiton, adhesive tape and capacitor element

Abstract

This invention provides adhesive compositions, adhesive tapes, and capacitor elements with excellent performance. One aspect of this invention is an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent; wherein the matrix polymer is a copolymer obtained by copolymerizing structural monomers, the structural monomers comprising low-Tg (meth)acrylate monomers with a Tg of 20°C or less and carboxyl-containing monomers; wherein, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate monomers with 5 or more carbon atoms in the alkyl portion is 30% by mass or more, and the content of the aforementioned low-Tg (meth)acrylate monomers with fewer than 5 carbon atoms in the alkyl portion, based on the total amount of the aforementioned structural monomers, is 10% by mass or less; the crosslinking agent comprises an epoxy crosslinking agent and an isocyanate crosslinking agent, the amount of the aforementioned epoxy crosslinking agent being less than 0.10 parts by mass.

Description

Technical Field

[0001] The present invention relates to an adhesive composition, an adhesive tape, and a capacitor element. For example, it relates to an adhesive composition and an adhesive tape suitable for fixing electronic parts and the like. Prior Art

[0002] A capacitor element is manufactured by winding an anode foil and a cathode foil with a separator interposed therebetween and inserting them into a cylindrical casing. Further, the wound anode, cathode, and separator (capacitor element) may be fixed (wound and fixed) with an adhesive tape.

[0003] For an adhesive tape used for winding and fixing a capacitor element, the following are required: [1] to exhibit sufficient winding and fixing performance (heat resistance) even after solder reflow, and [2] to exhibit sufficient winding and fixing performance (electrolyte resistance) even in a state of contact with an electrolyte filled in the capacitor. By satisfying these performances, it is possible to prevent the adhesive tape from loosening due to heat during reflow or contact with an electrolyte, and to fully exhibit the performance of the capacitor.

[0004] Patent Document 1 discloses an adhesive tape suitable for winding and fixing a capacitor element. Specifically, Patent Document 1 discloses an adhesive tape having a base material and an adhesive layer disposed on at least one side of the base material, the adhesive layer containing a matrix polymer having an acid value of 45 mgKOH / g to 150 mgKOH / g. The adhesive tape disclosed in Patent Document 1 has excellent heat resistance and can wind and fix a capacitor element well even at a high temperature. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-125026 Summary of the Invention Problems to be Solved by the Invention

[0006] However, the adhesive tape described in Patent Document 1 above has insufficient performance in terms of heat resistance and electrolyte resistance.

[0007] Therefore, an object of the present invention is to provide an adhesive composition having excellent performance. Means for Solving the Problems

[0008] The present invention is based on detailed research that found that the above-mentioned problems can be solved by using an adhesive composition containing specific ingredients, thereby completing the present invention.

[0009] The present invention, type (1), is an adhesive composition comprising an adhesive composition containing a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent, wherein, The aforementioned matrix polymer is a copolymer obtained by copolymerizing structural monomers, wherein the structural monomers include low-Tg (meth)acrylate monomers with a Tg below 20°C and carboxyl-containing monomers. Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate alkyl monomers with 5 or more carbon atoms in the alkyl moiety is 30% by mass or more. Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate monomers with fewer than 5 carbon atoms in the alkyl moiety is less than 10% by mass. The aforementioned crosslinking agents include epoxy-based crosslinking agents and isocyanate-based crosslinking agents. When the amount of the aforementioned matrix polymer is set to 100 parts by mass, the amount of the aforementioned epoxy crosslinking agent ME is less than 0.10 parts by mass.

[0010] Furthermore, the present invention, type (2), is an adhesive tape having a substrate and an adhesive layer disposed on at least one side of the substrate, wherein, The aforementioned adhesive layer comprises an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The aforementioned crosslinking agents include epoxy-based crosslinking agents and isocyanate-based crosslinking agents. When the amount of the aforementioned matrix polymer is set to 100 parts by mass, the amount of the aforementioned epoxy crosslinking agent ME exceeds 0.01 parts by mass but does not reach 0.10 parts by mass. When the amount of the aforementioned matrix polymer is set to 100 parts by mass, the amount MI of the aforementioned isocyanate-based crosslinking agent is 0.10 parts by mass or more. MI / ME>1; The aforementioned matrix polymer is a copolymer obtained by copolymerizing structural monomers, wherein the structural monomers include low-Tg (meth)acrylate monomers with a Tg below 20°C and carboxyl-containing monomers. Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate alkyl monomers with 5 or more carbon atoms in the alkyl moiety is 30% by mass or more. Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate monomers with fewer than 5 carbon atoms in the alkyl moiety is less than 10% by mass. This adhesive tape is used to secure electronic components or materials that are subjected to heat treatment at temperatures above 80°C. However, the adhesive tape excludes those in which the adhesive layer is only deposited on the inner side of the substrate at least 0.5 mm from both ends of the substrate, and those in which the adhesive resin is contained in an amount of more than 10 parts by weight relative to 100 parts by weight of acrylic polymer.

[0011] The present invention, type (3), is an adhesive tape having a substrate and an adhesive layer disposed on at least one side of the substrate; wherein, The aforementioned adhesive layer comprises an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The aforementioned crosslinking agents include epoxy-based crosslinking agents and isocyanate-based crosslinking agents. When the amount of the aforementioned matrix polymer is set to 100 parts by mass, the amount of the aforementioned epoxy crosslinking agent ME exceeds 0.01 parts by mass but does not reach 0.10 parts by mass. When the amount of the aforementioned matrix polymer is set to 100 parts by mass, the amount MI of the aforementioned isocyanate-based crosslinking agent is 0.10 parts by mass or more. MI / ME>1, The aforementioned matrix polymer is a copolymer obtained by copolymerizing structural monomers, wherein the structural monomers include low-Tg (meth)acrylate monomers with a Tg below 20°C and carboxyl-containing monomers. Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate alkyl monomers with 5 or more carbon atoms in the alkyl moiety is 30% by mass or more. Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate monomers with fewer than 5 carbon atoms in the alkyl moiety is less than 10% by mass. This adhesive tape is used to wrap and fix the capacitor element; However, the adhesive tape excludes those in which the adhesive layer is only deposited on the inner side of the substrate at least 0.5 mm from both ends of the substrate, and those in which the adhesive resin is contained in an amount of more than 10 parts by weight relative to 100 parts by weight of acrylic polymer.

[0012] The gel fraction of the aforementioned crosslinked polymer is preferably 60 to 90%. The weight average molecular weight of the aforementioned matrix polymer is preferably between 500,000 and 1,500,000.

[0013] The present invention, type (4), is a capacitor element comprising: a wound body formed by winding a plurality of thin-film electrodes, an adhesive tape for winding and fixing the wound body, and an electrolyte, wherein, The aforementioned adhesive tape has a substrate and an adhesive layer disposed on at least one side of the aforementioned substrate. The aforementioned adhesive layer comprises an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The aforementioned crosslinking agents include epoxy-based crosslinking agents and isocyanate-based crosslinking agents. This capacitor element is intended for use in assembly onto a substrate via reflow soldering.

[0014] The present invention, type (5), is a capacitor element comprising: a wound body formed by winding a plurality of thin-film electrodes, an adhesive tape for winding and fixing the wound body, and an electrolyte, wherein, The aforementioned adhesive tape has a substrate and an adhesive layer disposed on at least one side of the aforementioned substrate. The aforementioned adhesive layer comprises an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The aforementioned crosslinking agents include epoxy-based crosslinking agents and isocyanate-based crosslinking agents. The aforementioned substrate is polyphenylene sulfide.

[0015] The present invention, type (6), is a capacitor element comprising: a wound body formed by winding a plurality of thin-film electrodes, an adhesive tape for winding and fixing the wound body, and an electrolyte, wherein, The aforementioned adhesive tape has a substrate and an adhesive layer disposed on at least one side of the aforementioned substrate. The aforementioned adhesive layer comprises an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The aforementioned crosslinking agents include epoxy-based crosslinking agents and isocyanate-based crosslinking agents. The aforementioned matrix polymers have a weight-average molecular weight of 500,000 to 1,500,000.

[0016] The aforementioned matrix polymer is a copolymer obtained by copolymerizing structural monomers, wherein the structural monomers include low-Tg (meth)acrylate monomers with a Tg below 20°C and carboxyl-containing monomers. Preferably, in the above structural monomer, based on the total amount of the above structural monomer, the content of the above low-Tg (meth)acrylic acid alkyl ester monomer having 5 or more carbon atoms in the alkyl part is 30% by mass or more. In the above structural monomer, based on the total amount of the above structural monomer, the content of the above low-Tg (meth)acrylic acid alkyl ester monomer having less than 5 carbon atoms in the alkyl part is 10% by mass or less.

[0017] The gel fraction of the above crosslinked polymer is preferably 85% or more.

[0018] The above capacitor element is preferably an aluminum electrolytic capacitor.

[0019] Aspect (7) of the present invention is a heat treatment method for a capacitor element, which includes: After assembling a capacitor element including an electrolytic solution, a wound body formed by winding a plurality of thin film electrodes, and an adhesive tape for winding and fixing the above wound body to a substrate, a step of heat-treating the above capacitor element; wherein, The above adhesive tape has a base material and an adhesive layer provided on at least one side of the above base material. The above adhesive layer includes an adhesive composition, and the adhesive composition includes a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The above crosslinking agent includes an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent. When setting the gel fraction of the above crosslinked polymer in the above capacitor element before performing the above heat treatment as Gf3, and setting the gel fraction of the above crosslinked polymer after performing the above heat treatment as Gf4, The above Gf3 is 50% by mass or more. The above Gf4 is 70% by mass or more. [Gf4 / Gf3] is 1.05 or more.

[0020] The heating temperature in the above heat treatment is preferably 120°C or more.

[0021] The above heat treatment is preferably a reflow treatment. Advantages of the Invention

[0022] According to the present invention, an adhesive composition having excellent performance can be provided. According to the adhesive tape obtained by using such an adhesive composition, electronic components including capacitor elements can be appropriately fixed. Embodiments

[0023] The following details adhesive compositions, adhesive tapes containing adhesive compositions, and capacitor elements using adhesive tapes, but the present invention is not limited by the following description.

[0024] Furthermore, the present invention can also be a raw material composition for manufacturing adhesive compositions. The raw material composition may contain all or some of the raw materials of the adhesive composition. In this case, the raw materials contained in the raw material composition can be appropriately selected, and the mixing amount, uses, and manufacturing methods are based on relevant descriptions of adhesive compositions.

[0025] In this specification, the individual description of multiple upper limit values ​​and multiple lower limit values ​​should be understood as describing all numerical ranges that can be set by freely combining these upper limit values ​​and lower limit values.

[0026] Unless otherwise specified, all isomers of the compounds disclosed in this specification may be used in this invention.

[0027] Unless otherwise specified, the descriptions of content and blending amount in this instruction manual refer to the amount of the component (solid component) after deducting volatile components. Furthermore, in this instruction manual, the terms "amount," "content," and "blending amount" can be appropriately substituted for each other without causing contradiction.

[0028] In this specification, the Tg (glass transition temperature) of each monomer represents the Tg when the monomer is used as a homopolymer. Tg is a conventional property that can be measured, for example, by performing differential scanning calorimetry (DSC) on each homopolymer.

[0029] Unless otherwise specified, each component classified in this instruction manual may be used alone or in combination of two or more.

[0030] The term "electronic component" is not specifically limited to any part that can be used in electrical products. Specific examples of electronic components include: capacitors, coils, transformers, batteries, and leads. The materials used to construct electronic components are the materials that make up these electronic components.

[0031] <<<<<Adhesive Composition>>>>> <<<<Ingredients>>>> The adhesive composition contains a cross-linked polymer. Furthermore, the adhesive composition may also contain other components.

[0032] <<<Crosslinked Polymers>>> Crosslinked polymers are obtained by crosslinking a matrix polymer; in other words, they are obtained by reacting a matrix polymer with a crosslinking agent.

[0033] <<Crossing Agents>> The crosslinking agent preferably includes both epoxy-based and isocyanate-based crosslinking agents. By using both epoxy-based and isocyanate-based crosslinking agents, it is possible to control the crosslinking reaction to occur across a multi-stage temperature range. More specifically, particularly by combining epoxy-based and isocyanate-based crosslinking agents, when used as tapes for securing electronic components, primarily capacitors, it becomes easier to appropriately control the crosslinking state of the adhesive tape before and after heat treatment (such as reflow soldering). This results in easier and more appropriate control of the adhesive tape properties required at each temperature stage. The adhesive composition may also contain unreacted crosslinking agents.

[0034] <Epoxy Crosslinking Agent> As an epoxy crosslinking agent, it can be used in compounds having two or more epoxy groups in one molecule (preferably two to five, more preferably two to four).

[0035] Specific examples of epoxy crosslinking agents include: glycerol polyglycidyl ether, sorbitol polyglycidyl ether, neopentyl tertrol polyglycidyl ether, diglycidyl aniline, N,N,N',N'-tetraglycidyl-m-xylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

[0036] Epoxy crosslinking agents can also be commercially available products such as "TETRAD X" manufactured by Mitsubishi Gas Chemical Co., Ltd.

[0037] When the amount of matrix polymer is set to 100 parts by mass, the amount of epoxy crosslinking agent ME is preferably more than 0.001 parts by mass, more than 0.01 parts by mass, more than 0.02 parts by mass, or more than 0.05 parts by mass. Furthermore, the amount of epoxy crosslinking agent ME is preferably less than 1.0 parts by mass, less than 0.10 parts by mass, or less than 0.08 parts by mass.

[0038] By keeping the amount of epoxy crosslinking agent ME within such a range, the heat resistance and electrolyte resistance of the adhesive composition can be improved.

[0039] By using isocyanate-based crosslinking agents and setting the amount of epoxy-based crosslinking agent ME to less than 0.10 parts by weight, the heat resistance and electrolyte resistance of adhesive tapes can be significantly improved.

[0040] By using isocyanate-based crosslinking agents and setting the amount of epoxy-based crosslinking agent ME to more than 0.01 parts by mass, heat resistance and electrolyte resistance can be improved in a balanced way, and the heat shrinkage resistance of adhesive tape can be particularly improved.

[0041] <Isocyanate-based crosslinking agents> As an isocyanate-based crosslinking agent, a compound having two or more (preferably two to five, more preferably two to four) isocyanate groups in one molecule can be used.

[0042] Specific examples of isocyanate-based crosslinking agents include: Aromatic crosslinking agents such as toluene diisocyanate (TDI), phenyl diisocyanate, diphenylmethane diisocyanate (MDI), phenyl dimethyl diisocyanate (XDI), tetramethylxylyl diisocyanate (TMXDI), and their hydrides; Alicyclic crosslinking agents such as cyclohexane diisocyanate, isoflavone diisocyanate, dicyclohexylmethane diisocyanate, and methylcyclohexane diisocyanate; Crosslinking agents based on alkyl groups, such as hexamethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, and lysine diisocyanate.

[0043] Isocyanate-based crosslinking agents can also be commercially available products such as "Coronate L" manufactured by Tosoh Co., Ltd., and "Takenate D-101E" manufactured by Mitsui Chemicals Co., Ltd.

[0044] When the amount of matrix polymer is set to 100 parts by mass, the amount MI of the isocyanate-based crosslinking agent is preferably 0.01 parts by mass or more, 0.05 parts by mass or more, 0.10 parts by mass or more, 0.5 parts by mass or more, or 1.0 parts by mass or more. Furthermore, the amount MI of the isocyanate-based crosslinking agent is preferably 25 parts by mass or less, 15 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 3 parts by mass or less.

[0045] By keeping the amount of isocyanate-based crosslinking agent MI within such a range, the crosslinking state of the adhesive tape before and after heat treatment (such as reflow treatment) can be easily and appropriately controlled, and the heat resistance and electrolyte resistance of the adhesive composition can be improved.

[0046] By setting the amount (MI) of the isocyanate-based crosslinking agent to 0.10 parts by mass or more, the heat shrinkage resistance of adhesive tape can be significantly improved.

[0047] The preferred MI / ME is above 1, above 2, above 5, above 10, above 20, or above 25. Alternatively, the preferred MI / ME is below 500, below 200, below 100, below 75, or below 50.

[0048] By keeping the MI / ME within this range, the heat resistance and electrolyte resistance of the adhesive composition can be improved.

[0049] <Other crosslinking agents> Without hindering the effects of the present invention, the crosslinking agent may also include crosslinking agents other than epoxy crosslinking agents and isocyanate crosslinking agents (such as conventional crosslinking agents such as polyvalent metal crosslinking agents, polyol crosslinking agents, and polyamine crosslinking agents).

[0050] When the amount of matrix polymer is set to 100 parts by mass, the amount of other crosslinking agents is preferably less than 10 parts by mass, less than 5 parts by mass, less than 2 parts by mass, less than 1 part by mass, or less than 0.1 parts by mass.

[0051] <<Matrix Polymers>> The matrix polymer can be one with crosslinking functional groups (such as acrylonitrile or other functional groups containing unsaturated carbon bonds).

[0052] The following describes preferred matrix polymers.

[0053] The matrix polymer is preferably a copolymer obtained by copolymerizing a plurality of copolymerizable monomers (as structural monomers).

[0054] <Structural Monomer> The structural monomer preferably comprises a low-Tg (meth)acrylate monomer. Furthermore, the structural monomer preferably comprises a carboxyl-containing monomer. By using such a monomer as the structural monomer, the heat resistance and electrolyte resistance of the adhesive composition can be effectively improved in a balanced manner.

[0055] Structural monomers may also contain other monomers.

[0056] (Low Tg (meth)acrylate monomer) Low Tg (meth)acrylates, when used as homopolymers, have a Tg of less than 20°C, preferably less than 0°C, less than -20°C, or less than -50°C. The lower limit of Tg is not particularly limited, but may be, for example, -90°C or -80°C.

[0057] Examples of low-Tg (meth)acrylate monomers include: 2-ethylhexyl acrylate (2EHA, Tg: -70℃, 8 carbons in the alkyl group), isononyl acrylate (INA, Tg: -58℃, 9 carbons in the alkyl group), butyl acrylate (BA, Tg: -55℃, 4 carbons in the alkyl group), lauryl acrylate (LA, Tg: -23℃, 12 carbons in the alkyl group), lauryl methacrylate (LMA, Tg: -65℃, 12 carbons in the alkyl group), and isostearyl acrylate (ISA, Tg: -18℃, 18 carbons in the alkyl group), etc.

[0058] The structural monomer is preferably a low-Tg (meth)acrylate alkyl monomer containing an alkyl moiety with 5 or more, 6 or more, or 8 or more carbon atoms. Furthermore, there is no particular upper limit to this number of carbon atoms; it can be, for example, 30, 25, or 20.

[0059] Of the structural monomers, based on the total amount of structural monomers, the content of low Tg (meth)acrylate monomers with 5 or more carbon atoms in the alkyl part is preferably 30% by mass or more, 45% by mass or more, or 60% by mass or more.

[0060] By keeping the content of low-Tg (meth)acrylate monomers with alkyl moieties having 5 or more carbon atoms within such a range, the heat resistance and electrolyte resistance of the adhesive composition can be improved in a balanced way.

[0061] The structural monomer may also include low Tg (meth)acrylate monomers with fewer than 5 carbon atoms in the alkyl moiety.

[0062] Among the structural monomers, based on the total amount of structural monomers, the content of low Tg (meth)acrylate monomers with less than 5 carbon atoms in the alkyl part is preferably 15% by mass or less, 10% by mass or less, 5% by mass or less, 2% by mass or less than 1% by mass or less than 0.1% by mass.

[0063] By keeping the content of low-Tg (meth)acrylate monomers with less than 5 carbon atoms in the alkyl moiety within such a range, the heat resistance and electrolyte resistance of the adhesive composition can be improved in a balanced way.

[0064] (Monomers containing carboxyl groups) A carboxyl-containing monomer has a carboxyl group and a functional group (a functional group with an unsaturated carbon bond, such as vinyl groups) for copolymerization with other structural monomers. Typically, a carboxyl-containing monomer has one carboxyl group and one functional group with an unsaturated carbon bond.

[0065] Monomers containing carboxyl groups include: (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, ω-carboxy-polycaprolactone (n≒2) monoacrylate, 2-acryloyloxyethyl-succinic acid, 2-acryloyloxyethyl-hexahydrophthalic acid, 2-acryloyloxyethyl-phthalic acid, etc.

[0066] In the structural monomers, based on the total amount of structural monomers, the content of carboxyl-containing monomers is preferably 0.5% by mass or more, 1% by mass or more, 2% by mass or more, or 3% by mass or more, and preferably 15% by mass or less, 10% by mass or less, 8% by mass or less, or 7% by mass or less.

[0067] By keeping the content of carboxyl-containing monomers within this range, the probe tack, heat resistance, and electrolyte resistance of the adhesive composition can be improved.

[0068] (Other monomers) The structural monomer may also include one or more selected from high Tg (meth)acrylates, (meth)acrylates containing alicyclic groups with a Tg of -20°C or higher, and (meth)acrylamide derivatives.

[0069] High Tg (meth)acrylate alkyl groups are monomers with a Tg of 20°C or 50°C or higher. There is no particular upper limit to the Tg value, such as 200°C, 190°C or 180°C.

[0070] In high-Tg (meth)acrylates and (meth)acrylates containing alicyclic groups with a Tg of -20°C or higher, the alkyl portion or alicyclic group preferably has 5 or more, 6 or more, or 8 or more carbon atoms. However, there is no particular upper limit to this number of carbon atoms; for example, it can be 30, 25, or 20. The alicyclic group can be a monocyclic or polycyclic structure.

[0071] Examples of high Tg (meth)acrylate alkyl esters include: isoborneol acrylate (IBOA, Tg: 97℃, alkyl moiety carbon number: 10), isoborneol methacrylate (IBOMA, Tg: 180℃, alkyl moiety carbon number: 10), etc.

[0072] Examples of (meth)acrylates containing alicyclic groups with a Tg of -20℃ or higher include: cyclohexyl acrylate (CHA, Tg: 15℃, number of carbons in the alicyclic group: 6), cyclohexyl methacrylate (CHMA, Tg: 66℃, number of carbons in the alicyclic group: 6), dicyclopentyl acrylate (Tg: 120℃, number of carbons in the alicyclic group: 10), and dicyclopentyl methacrylate (Tg: 175℃, number of carbons in the alicyclic group: 10), etc.

[0073] (Meth)acrylamide derivatives are compounds formed by replacing the terminal hydrogen atom of (meth)acrylamide with other substituents.

[0074] Examples of (meth)acrylamide derivatives include: acrylamide morpholine (ACMO, Tg: 145℃, acrylamide derivative), diethylacrylamide (DEAA, Tg: 81℃, acrylamide derivative), dimethylacrylamide (DMAA, Tg: 119℃, acrylamide derivative), isopropylacrylamide (NIPAM, Tg: 134℃, acrylamide derivative), and dimethylaminopropylacrylamide (DMAPAA, Tg: 134℃, acrylamide derivative), etc.

[0075] Based on the total amount of structural monomers, the content of high Tg (meth)acrylate, (meth)acrylate with alicyclic group containing Tg above -20℃ and (meth)acrylamide derivatives can be above 1% by mass, above 5% by mass, above 10% by mass, and can be below 30% by mass or below 25% by mass.

[0076] The structural monomer may further include other monomers. In this case, based on the total amount of the structural monomer, the content of other monomers is preferably less than 10% by mass, less than 5% by mass, or less than 1% by mass.

[0077] <Weight average molecular weight of matrix polymer> The weight average molecular weight of the matrix polymer is preferably 100,000 or more, 200,000 or more, 300,000 or more, or 500,000 or more, and more preferably 3,000,000 or less, 2,000,000 or less, 1,500,000 or less, or 1,000,000 or less.

[0078] The weight-average molecular weight of the matrix polymer was determined by gel permeation chromatography (GPC) and calculated from the molecular weight of polystyrene.

[0079] <Tg of matrix polymers> The Tg of the matrix polymer is preferably below -10℃, below -20℃, or below -30℃, and more preferably above -80℃, above -70℃, above -60℃, or above -50℃.

[0080] The Tg system of matrix polymers can be determined using a differential scanning calorimeter (DSC), or theoretical values ​​can be calculated from the types and proportions of structural monomers.

[0081] <<<Gel fraction of cross-linked polymers>>> The gel fraction of cross-linked polymers can typically be 30% or more by mass, 40% or more by mass, 50% or more by mass, 60% or more by mass, 70% or more by mass, 80% or more by mass, 85% or more by mass, 90% or more by mass, or 95% or more by mass.

[0082] In this case, when the adhesive composition and adhesive tape are used to fix electronic components (especially for wrapping and fixing capacitor elements) and are then subjected to heat treatment (e.g., reflow soldering), the gel content may change before and after the heat treatment. In particular, because the crosslinking agent includes epoxy-based and isocyanate-based crosslinking agents, a lower gel content can be maintained before heat treatment (e.g., reflow soldering), while the gel content increases after heat treatment (reflow soldering). Therefore, in this embodiment, the optimal gel content of the crosslinked polymer in the adhesive composition, adhesive tape, or capacitor element may differ depending on whether the heat treatment is performed before or after heat treatment.

[0083] When the adhesive composition is subjected to heat treatment, the gel fraction of the crosslinked polymer is preferably 50% by mass or more, 60% by mass or more, or 70% by mass or more, and more preferably 95% by mass or less, 90% by mass or less, or 85% by mass or less.

[0084] In adhesive components that have undergone sufficient cross-linking through heat treatment (e.g., adhesive components in capacitor elements assembled onto a substrate through reflow soldering), the gel fraction of the cross-linked polymer is preferably 70% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass. There is no particular upper limit to this gel fraction; it can be set to 98% by mass or 99% by mass.

[0085] More specifically, when the adhesive composition is subjected to heat treatment, and the gel fraction of the crosslinked polymer in the adhesive composition is set as Gf1, and the gel fraction of the crosslinked polymer in the adhesive composition after heating at 200°C for 1 hour is set as Gf2, it is preferable that Gf1 is 50% by mass or more, 60% by mass or more, or 70% by mass or more, and Gf2 is 70% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass, and Gf2 / Gf1 exceeds 1.00, 1.05 or more, 1.10 or more, 1.15 or more, or 1.20 or more. By achieving such a range, an adhesive composition particularly suitable for use in adhesive tapes for fixing electronic components subjected to heat treatment (e.g., reflow soldering) can be formed.

[0086] By setting the gel fraction of the crosslinked polymer within such a range, the heat resistance and electrolyte resistance of the adhesive composition can be improved in a balanced way.

[0087] The gel fraction can be adjusted according to the type of monomer, the type and amount of crosslinking agent, the temperature and time of heat treatment, etc.

[0088] <<<Other Ingredients>>> Other components may be included in the adhesive composition without hindering the effects of the present invention. Examples of other components include: fillers (e.g., calcium carbonate, talc, silica, carbon black, etc.), surfactants, organic pigments, inorganic pigments, stabilizers, silane coupling agents, spacer particles, tackifiers, plasticizers, and other known additives.

[0089] Furthermore, solvents are sometimes added during the manufacturing of adhesive compositions to improve workability. While such solvents, which can be prepared during manufacturing, may remain in the adhesive composition, it is preferable to remove them.

[0090] <<<<<Adhesive Tape>>>>> The adhesive tape has a substrate and an adhesive layer disposed on at least one side of the substrate.

[0091] The width of the adhesive tape can be adjusted appropriately by taking into account the size of the object being applied (such as electronic components).

[0092] Adhesive tapes can be formed into strips and provided as needed, wound around a core, or provided as a thin film before being cut into strips.

[0093] Adhesive tape can be a double-sided tape with adhesive layers on both sides of a substrate.

[0094] <<<<Adhesive Layer>>>> The adhesive layer is composed of the aforementioned adhesive components.

[0095] The thickness of the adhesive layer is not particularly limited, for example it can be 2 to 100 μm, 5 to 50 μm, 10 to 40 μm or 12 to 35 μm.

[0096] <<<<Substrate>>>> The substrate may be appropriately selected within the scope of not hindering the effects of the present invention, but it is preferably composed of at least one selected from the group consisting of polyethylene terephthalate (PET), polypropylene (PP), polyphenylene sulfide (PPS), polyimide (PI), polyetherimide (PEI) and plant fibers.

[0097] When adhesive tape is used for applications such as aluminum electrolytic capacitors, from the viewpoint of hydrolysis resistance, the substrate is preferably composed of polypropylene (PP) and / or polyphenylene sulfide (PPS).

[0098] Polyethylene terephthalate (PET), polypropylene (PP), polyphenylene sulfide (PPS), polyimide (PI), and polyetherimide (PEI) can be used to make synthetic resin films or synthetic resin fibers.

[0099] When the substrate is composed of synthetic resin fibers and plant fibers, it can also be formed by papermaking.

[0100] Furthermore, when the substrate is made of a synthetic resin film, from the viewpoint of improving heat resistance, a stretched film (e.g., a uniaxial stretched film or a biaxial stretched film) is preferred.

[0101] The thickness of the substrate is not particularly limited; for example, it can be 5 to 100 μm or 9 to 50 μm.

[0102] The surface of the substrate layer can also be subjected to appropriate surface treatments. Examples of surface treatments include: corona treatment to improve adhesion to the adhesive layer, and peeling treatment for surfaces of the substrate that are not in contact with the adhesive layer.

[0103] <<<<Other Layers>>>> Adhesive tape may also include other layers as commonly known. Other layers may include, for example, a primer layer that improves the adhesion between the substrate and the adhesive layer, and a spacer layer that is applied in contact with the adhesive layer and removed during use. Alternatively, direct winding (without spacers) is preferable when considering productivity and environmental impact.

[0104] <<<<<Adhesive Compositions and Manufacturing Methods of Adhesive Tapes>>>>> Adhesive components and adhesive tapes can be manufactured using conventional methods.

[0105] The adhesive composition can be manufactured using the following procedure. First, a raw material composition is prepared, comprising a matrix polymer and a crosslinking agent, and, if necessary, other additives and solvents (raw material preparation step). Then, the raw material composition is heated to remove the solvent and crosslink the matrix polymer to obtain the adhesive composition (crosslinking step).

[0106] Furthermore, adhesive tape can be manufactured using the following process. First, a raw material composition is prepared, comprising a matrix polymer and a crosslinking agent, and, if necessary, other additives and solvents (raw material preparation step). Then, the raw material composition is applied to the substrate (coating step). Then, the adhesive tape is obtained by heating the raw material composition to remove the solvent and crosslinking the matrix polymer (crosslinking step). Furthermore, cutting and winding may be performed as needed (processing steps).

[0107] Adhesive tape can also be manufactured by laminating a pre-formed film-like adhesive onto a substrate.

[0108] There are no particular restrictions on the solvents that may be contained in the raw material components; conventionally known solvents may be used.

[0109] As previously described, a preferred method is to stop the crosslinking reaction at a specific temperature and time during the crosslinking step, where unreacted crosslinking agent remains in the adhesive composition, and then heat-treat the adhesive tape after it has been used to fix electronic components, thereby re-reacting the remaining unreacted crosslinking agent. In this case, the heating conditions in the crosslinking step can be, for example, heating below 80°C, or heating between 30 and 60°C. The heating time can be, for example, 24 to 168 hours.

[0110] The crosslinking step can also be carried out at temperatures where no unreacted crosslinking agent remains in the adhesive composition. In this case, the heating conditions in the crosslinking step can be, for example, above 80°C, above 100°C, above 120°C, above 150°C, or above 200°C, or heating from 200 to 280°C. The heating time can be, for example, from 1 to 60 minutes.

[0111] In the crosslinking step, solvent removal and crosslinking can be carried out simultaneously, or solvent removal and crosslinking can be carried out separately.

[0112] <<<<Uses>>>> The adhesive composition and adhesive tape of this embodiment can be used for various purposes, but are preferably used for fixing electronic components (to fix electronic components or electronic component constituent materials).

[0113] The adhesive composition and adhesive tape of this embodiment are particularly suitable for use as capacitor winding and fixing (especially for aluminum capacitor winding and fixing) because they "have sufficient heat resistance and electrolyte resistance even when in contact with electrolyte and exposed to high heat environments".

[0114] More specifically, a capacitor element (especially an aluminum electrolytic capacitor element) can be formed, comprising: a wound body consisting of a plurality of thin-film electrodes (anode foil and cathode foil) wound with spacers or electrolytic paper as required, an adhesive tape for winding and fixing the wound body (attached to the periphery of the wound body to fix the thin-film electrodes), and an electrolyte.

[0115] Here, there are cases where, after the capacitor element is mounted on a substrate, heat treatment (reflow treatment and heat treatment to harden the conductive adhesive) is performed. At this time, the capacitor element is also exposed to a heated environment. The capacitor element in this embodiment can be either a capacitor element that has not undergone such heat treatment or a capacitor element that has undergone such heat treatment.

[0116] As described above, when performing such heat treatment, there may be a difference between the preferred gel fraction of the adhesive composition before heat treatment and the preferred gel fraction of the adhesive composition after heat treatment. Specifically, when the gel fraction of the crosslinked polymer in the adhesive composition of the capacitor element before heat treatment is set as Gf3, and the gel fraction of the crosslinked polymer in the adhesive composition after heat treatment is set as Gf4, Gf3 is preferably 50% by mass or more, 60% by mass or more, or 70% by mass or more; Gf4 is preferably 70% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass; and the Gf4 / Gf3 ratio is preferably greater than 1.00, 1.05 or more, 1.10 or more, 1.15 or more, or 1.20 or more.

[0117] The heating temperature during such heat treatment may vary depending on components other than capacitor elements (such as solder), and may be above 80°C, 120°C, 150°C, or 200°C. In other words, the adhesive composition and adhesive tape of this embodiment are suitable for use in environments with temperatures above 80°C, 120°C, 150°C, or 200°C.

[0118] The heating time in such a heat treatment can be, for example, more than 5 minutes, more than 10 minutes, more than 30 minutes, or more than 1 hour.

[0119] Other uses of the adhesive composition and adhesive tape of this embodiment, from the viewpoint of excellent heat resistance and electrolyte resistance, include electrode insulation for Li-ion secondary batteries.

[0120] Furthermore, electronic components other than capacitor elements may be exposed to the high-heat environment of reflow soldering and may be exposed to electrolyte seeping from capacitor elements. Therefore, the adhesive composition and adhesive tape of this embodiment can also be better used in applications other than wrapping and fixing capacitor elements within the scope of electronic component fixing (for fixing electronic components or electronic component constituent materials).

[0121] Furthermore, when using adhesive compositions and adhesive tapes to wrap and fix capacitor elements, the smaller the diameter, the greater the impact on end-peeling caused by the rebound force of the substrate. Therefore, capacitors with smaller diameters require higher adhesive performance. The adhesive composition and adhesive tape of this embodiment have excellent adhesion and can therefore be used for small-diameter capacitor elements (e.g., capacitor elements with diameters of 4-20 mm).

[0122] <<<<<Preferred Embodiment of the Invention>>>>> The preferred embodiment of the present invention will be described in detail below.

[0123] <<<<Type 1>>>> Type 1 is an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent, wherein... The aforementioned matrix polymer is a copolymer obtained by copolymerizing structural monomers, wherein the structural monomers comprise low-Tg (meth)acrylate monomers with a Tg below 20°C and carboxyl-containing monomers. Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low Tg (meth)acrylate alkyl monomers with 5 or more carbon atoms in the alkyl portion is 30% by mass or more; Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate monomers with fewer than 5 carbon atoms in the alkyl moiety is less than 10% by mass. The aforementioned crosslinking agents include epoxy-based crosslinking agents and isocyanate-based crosslinking agents. When the amount of the aforementioned matrix polymer is set to 100 parts by mass, the amount of the aforementioned epoxy crosslinking agent ME is less than 0.10 parts by mass.

[0124] Furthermore, this type 1 is an adhesive tape having a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer comprising the aforementioned adhesive composition. The aforementioned adhesive tape can be used in environments above 80°C. The aforementioned adhesive tape can be used to fix electronic components or the materials that make up electronic components. The aforementioned adhesive tape can be used to wrap and fix capacitor components.

[0125] According to this type 1, an adhesive composition with excellent heat resistance and electrolyte resistance can be provided. Adhesive tapes obtained using such an adhesive composition can appropriately fix electronic components, including capacitor elements.

[0126] <<<<Type 2>>>> This type 2 is an adhesive tape, which has a substrate and an adhesive layer disposed on at least one side of the substrate, wherein, The aforementioned adhesive layer comprises an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The aforementioned crosslinking agents include epoxy-based crosslinking agents and isocyanate-based crosslinking agents. When the amount of the aforementioned matrix polymer is set to 100 parts by mass, the amount of the aforementioned epoxy crosslinking agent ME exceeds 0.01 parts by mass but does not reach 0.10 parts by mass. When the amount of the aforementioned matrix polymer is set to 100 parts by mass, the amount of the aforementioned isocyanate-based crosslinking agent MI is 0.10 parts by mass or more.

[0127] The gel fraction of the aforementioned cross-linked polymer can also be 60 to 90%. The aforementioned matrix polymer can also be a copolymer obtained by copolymerizing structural monomers, wherein the structural monomers include low Tg (meth)acrylate monomers with a Tg below 20°C and carboxyl-containing monomers. In the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low Tg (meth)acrylate alkyl monomers with 5 or more carbon atoms in the alkyl portion may also be 30% by mass or more. Among the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low Tg (meth)acrylate monomers with less than 5 carbon atoms in the alkyl portion can also be less than 10% by mass. The aforementioned adhesive tape can also be used to fix electronic components or electronic component materials subjected to heat treatment at temperatures above 80°C.

[0128] According to this type 2, an adhesive tape with sufficient heat resistance, electrolyte resistance, and heat shrinkage resistance can be provided. Such an adhesive tape can be used to properly secure electronic components, including capacitor elements.

[0129] Here, the aforementioned adhesive tape preferably excludes those in which the adhesive layer is only deposited on the inner side of the substrate at least 0.5 mm from both ends of the substrate. Furthermore, the aforementioned adhesive tape preferably excludes those containing an adhesive resin in an amount exceeding 10 parts by weight relative to 100 parts by weight of acrylic polymer.

[0130] <<<<Type 3>>>> This type 3 is a capacitor element, comprising: a wound body formed by winding a plurality of thin-film electrodes, an adhesive tape for winding and fixing the wound body, and an electrolyte, wherein... The aforementioned adhesive tape has a substrate and an adhesive layer disposed on at least one side of the aforementioned substrate. The aforementioned adhesive layer comprises an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The aforementioned crosslinking agents include epoxy-based crosslinking agents and isocyanate-based crosslinking agents.

[0131] The aforementioned matrix polymer can also be a copolymer obtained by copolymerizing structural monomers, wherein the structural monomers include low Tg (meth)acrylate monomers with a Tg below 20°C and structural monomers containing carboxyl groups. In the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low Tg (meth)acrylate alkyl monomers with 5 or more carbon atoms in the alkyl portion may also be 30% by mass or more. Among the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low Tg (meth)acrylate monomers with less than 5 carbon atoms in the alkyl portion can also be less than 10% by mass. The gel fraction of the aforementioned cross-linked polymer can also be above 85%. The aforementioned capacitor element can also be an aluminum electrolytic capacitor. The aforementioned capacitor elements can also be used for applications where they are assembled onto a substrate via reflow soldering. The aforementioned substrate can also be polyphenylene sulfide. The weight average molecular weight of the aforementioned matrix polymer can also be between 500,000 and 1,500,000.

[0132] According to this type 3, a capacitor element with improved winding and fixing performance can be provided. [Example]

[0133] The present invention will now be described in more detail, but the invention is not limited thereto by such description.

[0134] <<<<Making Adhesive Tape>>>> Make adhesive tape according to the following procedure. Biaxially stretched polyphenylene sulfide film [trade name "Torelina 3040" (thickness: 16μm), manufactured by Toray Industries, Inc., double-sided corona treatment] was used as the substrate. Apply a primer to one side of the substrate as needed and allow it to dry. Apply a long-chain alkyl stripping agent to the other side and allow it to dry (the amount of coating after drying is 5 mg / m2). Next, a raw material composition comprising a matrix polymer, a crosslinking agent and a solvent is coated onto the primer coating surface of the substrate, and heated at 100°C for 3 minutes to remove the solvent, forming an adhesive layer of a predetermined thickness composed of an adhesive composition. In addition, during crosslinking, the matrix polymer is heated at 50°C for 72 hours to complete the crosslinking.

[0135] Each example is an adhesive tape made by changing the composition of the adhesive used. The table shows the types of structural monomers and crosslinking agents of the matrix polymers used in each example, as well as the amounts of these (parts by mass of solid components).

[0136] Some adhesive tapes were not primed onto the substrate; instead, the raw material composition was applied directly to the substrate and then dried.

[0137] In the table, TETRAD (registered trademark) X is an epoxy-based crosslinking agent manufactured by Mitsubishi Gas Chemical Co., Ltd., NACEM (registered trademark) A1 is a metal-based crosslinking agent manufactured by Nippon Chemical Industry Co., Ltd., and Coronate (registered trademark) L is a polyisocyanate-based crosslinking agent manufactured by Tosoh Co., Ltd.

[0138] The Tg values ​​shown in the table are conventional physical properties, which can be measured by differential scanning calorimetry (DSC) for each homopolymer. The carbon number shown in the table represents the carbon number of the side chain.

[0139] <<<Gel Fraction>>> The adhesive was dissolved in THF and allowed to stand at room temperature for 24 hours. The gel components were then separated using a 200-mesh metal sieve. The separated gel components were dried and their mass was measured. The resulting value was divided by the mass of the adhesive initially dissolved in THF, and the result was taken as the gel fraction.

[0140] <<<Gel fraction after heating>>> The adhesive was heated at 200°C for 1 hour to serve as an adhesive, and otherwise evaluated in the same manner as the gel fraction evaluation method.

[0141] <<<Weight Average Molecular Weight>>> The evaluation was conducted using a Shimadzu Corporation GPC apparatus (LC-20) with the following conditions: sample concentration of 0.2 wt% (THF solution), sample injection volume of 100 μl, THF as the precipitate, flow rate of 1.0 ml / min, two Tosoh TSK-GMHXL columns, and a differential refractometer (RI) as the detector. The molecular weight is a polystyrene equivalent.

[0142] <<<<Evaluation>>>> For the adhesive tapes of each embodiment and comparative example, probe adhesion, end peeling, and heat shrinkage were evaluated. The evaluation results are shown in Tables 1 to 4, and the evaluation criteria for each evaluation are shown in Table 5.

[0143] <<<Probe viscosity>>> The test was conducted according to ASTM D2979 using an NS probe adhesion tester (manufactured by NICHIBAN Inc.) with a cylindrical contact element (probe) diameter of 5 mm, a pressing pressure of 100 gf / cm2, a contact time of 1 second, and a peeling speed of 10 mm / second.

[0144] <<<End-of-tear peeling assessment 1>>> <<Evaluation Methods>> In a gas environment at 5°C, a 50mm thick adhesive tape (5mm wide) is wound around a 2mm thick layer. A stainless steel (SUS) rod was used to prepare an evaluation sample. This sample was immersed in γ-butyl lactone at 23°C for 12 hours, and the peel length of the adhesive tape ends was confirmed. Furthermore, γ-butyl lactone is frequently used as a solvent in electrolytes.

[0145] <<<End-of-Terminal Stripping Assessment 2>>> <<Evaluation Methods>> Wrap a 50mm thick adhesive tape (5mm wide) around a 2mm thick layer in a gas environment at 5℃. Evaluation samples were prepared on stainless steel rods. These samples were then immersed in γ-butyl lactone at 105°C for 12 hours to confirm the peel length at the ends of the adhesive tape. Furthermore, γ-butyl lactone is frequently used as a solvent in electrolytes.

[0146] <<<Evaluation of Heat Shrinkage Rate>>> <<Evaluation Methods>> A 50mm thick evaluation adhesive tape (5mm wide) was attached to the back of the adhesive tape already attached to the aluminum plate to prepare an evaluation sample. The evaluation sample was heated in an oven at 260°C for 1 hour, and the shrinkage rate of the adhesive tape was calculated using the following formula. Shrinkage rate (%) = (1 - length of tape after heating / length of tape before heating) × 100

[0147] [Table 1]

[0148] [Table 2]

[0149] [Table 3]

[0150] [Table 4]

[0151] [Table 5]

[0152] As can be understood from the table, Examples 1 to 21, 23 to 31, and 33 to 41 of the adhesive composition or adhesive tape of type 1, which are rated as C or above in both end peel at 23°C and end peel at 105°C, and at least one of the end peel at 23°C and end peel at 105°C is rated as B or above, can be understood as having excellent heat resistance and electrolyte resistance.

[0153] Furthermore, as can be understood from the table, Examples 1 to 27, 29 to 32, and 34 to 41 of Type 2 adhesive tape were not evaluated as D, and therefore can be understood as having an excellent balance of heat resistance, electrolyte resistance, and heat shrinkage resistance.

[0154] Furthermore, as can be seen from the table, the end-peeling tests at 23°C and 105°C in Examples 1 to 41 were not evaluated as D. Therefore, it can be understood that the balance between heat resistance and electrolyte resistance is excellent. In other words, it can be understood that the capacitor element of Type 3 using these adhesive tapes has high winding and fixing properties (high reliability).

Claims

1. An adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent, wherein, The aforementioned matrix polymer is a copolymer obtained by copolymerizing structural monomers. The structural monomers include low-Tg (meth)acrylate monomers with a Tg of less than 20°C and carboxyl-containing monomers. The aforementioned structural monomers further include (meth)acrylate monomers with 5 or more carbon atoms in the alkyl portion and a Tg of more than 20°C, or (meth)acrylate monomers with 5 or more carbon atoms in the alicyclic group and a Tg of more than -20°C. Among the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate monomers with 5 or more carbon atoms in the alkyl portion is more than 30% by mass. Among the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate monomers with less than 5 carbon atoms in the alkyl portion is less than 10% by mass. The aforementioned crosslinking agent includes epoxy crosslinking agent and isocyanate crosslinking agent. When the amount of the aforementioned matrix polymer is set to 100 parts by mass, the amount of the aforementioned epoxy crosslinking agent ME is less than 0.10 parts by mass.

2. An adhesive tape having a substrate and an adhesive layer disposed on at least one side of the substrate, wherein, The aforementioned adhesive layer comprises an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The crosslinking agent comprises an epoxy crosslinking agent and an isocyanate crosslinking agent. When the amount of the matrix polymer is set to 100 parts by mass, the amount of the epoxy crosslinking agent (ME) exceeds 0.01 parts by mass but does not reach 0.10 parts by mass. When the amount of the matrix polymer is set to 100 parts by mass, the amount of the isocyanate crosslinking agent (MI) is 0.10 parts by mass or more, and MI / ME > 1. The aforementioned matrix polymer is a copolymer obtained by copolymerizing structural monomers. The structural monomers comprise low-Tg (meth)acrylate monomers with a Tg of 20°C or less and carboxyl-containing monomers. The aforementioned structural monomers further comprise (meth)acrylate monomers with 5 or more carbon atoms in the alkyl portion and a Tg of 20°C or more, or (meth)acrylates containing alicyclic groups with 5 or more carbon atoms in the alicyclic group and a Tg of -20°C or more. Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low Tg (meth)acrylate alkyl monomers with 5 or more carbon atoms in the alkyl portion is 30% by mass or more; of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low Tg (meth)acrylate alkyl monomers with less than 5 carbon atoms in the alkyl portion is 10% by mass or less. This adhesive tape is used to fix electronic components or electronic component constituent materials subjected to heat treatment at 80°C or above; however, this adhesive tape excludes those in which the adhesive layer is only deposited on the inner side of the substrate within 0.5 mm or more from both ends of the substrate, and those in which the adhesive resin is contained in an amount exceeding 10 parts by mass relative to 100 parts by mass of acrylic polymer.

3. An adhesive tape having a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer comprising an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent, the crosslinking agent comprising an epoxy crosslinking agent and an isocyanate crosslinking agent, wherein when the amount of the matrix polymer is set to 100 parts by mass, the amount of the epoxy crosslinking agent ME is more than 0.01 parts by mass and less than 0.10 parts by mass, and when the amount of the matrix polymer is set to 100 parts by mass, the amount of the isocyanate crosslinking agent MI is 0.10 parts by mass or more, MI / ME > 1, the matrix polymer being a copolymer obtained by copolymerizing structural monomers, the structural monomers comprising a low Tg (meth)acrylate monomer with a Tg of less than 20°C and a carboxyl-containing monomer. Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate alkyl monomers with 5 or more carbon atoms in the alkyl portion is 30% by mass or more. The aforementioned structural monomers further include (meth)acrylate alkyl monomers with 5 or more carbon atoms in the alkyl portion and a Tg of 20°C or more, or (meth)acrylates containing alicyclic groups with 5 or more carbon atoms in the alicyclic group and a Tg of -20°C or more. Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low-Tg (meth)acrylate alkyl monomers with less than 5 carbon atoms in the alkyl portion is 10% by mass or less. This adhesive tape is used to wrap and fix capacitor elements. However, this adhesive tape excludes those where the adhesive layer is only deposited on the inner side of the substrate within 0.5 mm or more from both ends of the substrate and those containing an adhesive resin in an amount exceeding 10 parts by mass relative to 100 parts by mass of acrylic polymer.

4. The adhesive tape as described in claim 2 or 3, wherein, The gel fraction of the aforementioned cross-linked polymer is 60 to 90%.

5. The adhesive tape as described in claim 2 or 3, wherein, The aforementioned matrix polymers have a weight-average molecular weight of 500,000 to 1,500,000.

6. A capacitor element comprising: a wound body formed by winding a plurality of thin-film electrodes, an adhesive tape for winding and fixing the wound body, and an electrolyte, wherein, The aforementioned adhesive tape has a substrate and an adhesive layer disposed on at least one side of the aforementioned substrate. The aforementioned adhesive layer contains an adhesive composition, which includes a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The aforementioned crosslinking agent includes an epoxy crosslinking agent and an isocyanate crosslinking agent. The aforementioned matrix polymer is a copolymer obtained by copolymerizing structural monomers. The structural monomers include a low-Tg (meth)acrylate monomer with a Tg of less than 20°C and a carboxyl-containing monomer. The aforementioned structural monomers further contain a (meth)acrylate monomer with 5 or more carbon atoms in the alkyl portion and a Tg of more than 20°C, or a (meth)acrylate containing an alicyclic group with 5 or more carbon atoms in the alicyclic group and a Tg of more than -20°C. The capacitor element is used for assembly onto a substrate by reflow soldering.

7. A capacitor element comprising: a wound body formed by winding a plurality of thin-film electrodes, an adhesive tape for winding and fixing the wound body, and an electrolyte, wherein, The aforementioned adhesive tape has a substrate and an adhesive layer disposed on at least one side of the aforementioned substrate. The aforementioned adhesive layer contains an adhesive composition, which contains a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The aforementioned matrix polymer is a copolymer obtained by copolymerizing structural monomers. The structural monomers contain low-Tg (meth)acrylate monomers with a Tg of less than 20°C and carboxyl-containing monomers. The aforementioned structural monomers further contain (meth)acrylate monomers with 5 or more carbon atoms in the alkyl portion and a Tg of more than 20°C, or (meth)acrylates containing alicyclic groups with 5 or more carbon atoms in the alicyclic group and a Tg of more than -20°C. The aforementioned crosslinking agent includes epoxy crosslinking agents and isocyanate crosslinking agents. The aforementioned substrate is polyphenylene sulfide.

8. A capacitor element comprising: a wound body formed by winding a plurality of thin-film electrodes, an adhesive tape for winding and fixing the wound body, and an electrolyte, wherein, The aforementioned adhesive tape has a substrate and an adhesive layer disposed on at least one side of the aforementioned substrate. The aforementioned adhesive layer contains an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The aforementioned matrix polymer is a copolymer obtained by copolymerizing structural monomers. The structural monomers comprise a low-Tg (meth)acrylate monomer with a Tg of 20°C or less and a carboxyl-containing monomer. The aforementioned structural monomers further comprise (meth)acrylate monomers with 5 or more carbon atoms in the alkyl portion and a Tg of 20°C or more, or (meth)acrylates containing alicyclic groups with 5 or more carbon atoms in the alicyclic group and a Tg of -20°C or more. The aforementioned crosslinking agent comprises an epoxy crosslinking agent and an isocyanate crosslinking agent. The aforementioned matrix polymer has a weight average molecular weight of 500,000 or more and 1,500,000 or less.

9. The capacitor element as described in any one of claims 6 to 8, wherein, Of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low Tg (meth)acrylate alkyl monomers with 5 or more carbon atoms in the alkyl portion is 30% by mass or more; of the aforementioned structural monomers, based on the total amount of the aforementioned structural monomers, the content of the aforementioned low Tg (meth)acrylate alkyl monomers with less than 5 carbon atoms in the alkyl portion is 10% by mass or less.

10. The capacitor element as described in any one of claims 6 to 8, wherein, The gel fraction of the aforementioned cross-linked polymer is over 85%.

11. The capacitor element described in any one of claims 6 to 8 is an aluminum electrolytic capacitor.

12. A method for heat-treating a capacitor element, comprising: assembling a capacitor element comprising an electrolyte and a plurality of thin-film electrodes, and an adhesive tape wrapped around and fixing the aforementioned capacitor element, onto a substrate, and then subjecting the aforementioned capacitor element to heat treatment; wherein, The aforementioned adhesive tape has a substrate and an adhesive layer disposed on at least one side of the aforementioned substrate. The aforementioned adhesive layer comprises an adhesive composition comprising a crosslinked polymer obtained by reacting a matrix polymer with a crosslinking agent. The aforementioned matrix polymer is a copolymer obtained by copolymerizing structural monomers. The structural monomers comprise low-Tg (meth)acrylate monomers with a Tg of 20°C or less and carboxyl-containing monomers. The aforementioned structural monomers further comprise (meth)acrylate monomers with 5 or more carbon atoms in the alkyl portion and a Tg of 20°C or more, or (meth)acrylates containing alicyclic groups with 5 or more carbon atoms in the alicyclic group and a Tg of -20°C or more. The aforementioned crosslinking agent comprises an epoxy crosslinking agent and an isocyanate crosslinking agent. When the gel fraction of the aforementioned crosslinked polymer in the aforementioned capacitor element before the aforementioned heat treatment is set as Gf3, and the gel fraction of the aforementioned crosslinked polymer after the aforementioned heat treatment is set as Gf4, the aforementioned Gf3 is 50% by mass or more, and the aforementioned Gf4 is 70% by mass or more. [Gf4 / Gf3] is 1.05 or higher.

13. The method for heat treatment of a capacitor element as described in claim 12, wherein, The heating temperature in the aforementioned heat treatment is above 120°C.

14. A method for heat-treating a capacitor element as described in claim 12 or 13, wherein, The aforementioned heat treatment is a reflow process.