Adhesive composition and adhesive tape

Abstract

To provide an adhesive composition having excellent heat resistance and electrolyte resistance.SOLUTION: There is provided an adhesive composition which comprises a crosslinked polymer obtained by reacting a base polymer with a crosslinking agent, wherein the base polymer is a copolymer obtained by copolymerizing a constituent monomer including a low Tg (meth)acrylic acid alkyl ester monomer having a Tg of 20°C or less and a carboxyl group-containing monomer, the content of the low Tg (meth)acrylic acid alkyl ester monomer having an alkyl moiety having 5 or more carbon atoms in the constituent monomer is 30 mass% or more based on the total amount of the constituent monomers, the content of the low Tg (meth)acrylic acid alkyl ester monomer having an alkyl moiety having less than 5 carbon atoms in the constituent monomer is 10 mass% or less based on the total amount of the constituent monomers, the crosslinking agent includes an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent and when the amount of the base polymer is defined as 100 pts.mass, the amount ME of the epoxy-based crosslinking agent is less than 0.10 pt.mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to adhesive compositions and adhesive tapes, and more particularly to adhesive compositions and adhesive tapes suitable for fixing electronic components and the like. [Background technology]

[0002] Capacitor elements are manufactured by winding anode foil and cathode foil via a separator and inserting them into a cylindrical housing. The wound anode, cathode, and separator (capacitor element) may also be secured (wound) with adhesive tape.

[0003] The adhesive tape used to secure the winding of capacitor elements is required to have the following properties: [1] sufficient winding performance even after solder reflow (heat resistance), and [2] sufficient winding performance even when in contact with the electrolyte filling inside the capacitor (electrolyte resistance). Meeting these properties prevents the adhesive tape from loosening due to heat during reflow or contact with the electrolyte, allowing the capacitor to perform to its full potential.

[0004] Patent Document 1 discloses an adhesive tape suitable for winding capacitor elements. Specifically, Patent Document 1 discloses an adhesive tape comprising a base material and an adhesive layer disposed on at least one side of the base material, wherein the adhesive layer contains a base polymer and the acid value of the base polymer is 45 mg KOH / g to 150 mg KOH / g. Patent Document 1 discloses that such an adhesive tape has excellent heat resistance and can reliably wind capacitor elements even at high temperatures. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-125026 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the adhesive tape described in Patent Document 1 above sometimes lacked sufficient heat resistance and electrolyte resistance.

[0007] Therefore, the object of the present invention is to provide an adhesive composition having excellent heat resistance and electrolyte resistance. [Means for solving the problem]

[0008] Through diligent research, the present invention was completed by discovering that the above problems can be solved by using an adhesive composition containing specific components.

[0009] The present invention An adhesive composition comprising a crosslinked polymer obtained by reacting a base polymer with a crosslinking agent, The base polymer is a copolymer obtained by copolymerizing a low-Tg alkyl ester monomer having a Tg of 20°C or less with constituent monomers containing a carboxyl group. The content of the low-Tg (meth)acrylate alkyl ester monomer in the constituent monomer, in which the alkyl portion has 5 or more carbon atoms, is 30% by mass or more based on the total amount of the constituent monomer. The content of the low-Tg (meth)acrylate alkyl ester monomer in the constituent monomer, in which the alkyl portion has fewer than 5 carbon atoms, is 10% by mass or less based on the total amount of the constituent monomer. The aforementioned crosslinking agent includes an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent. When the amount of the base polymer is 100 parts by mass, the amount of the epoxy crosslinking agent M E This is an adhesive composition in which the amount is less than 0.10 parts by mass.

[0010] Furthermore, the present invention relates to an adhesive tape comprising a base material and an adhesive layer provided on at least one side of the base material, wherein the adhesive layer contains the adhesive composition. The adhesive tape may be used in environments with a temperature of 80°C or higher. The adhesive tape may be used for fixing electronic components or electronic component constituent materials. The adhesive tape may be for winding a capacitor element.

Advantages of the Invention

[0011] According to the present invention, an adhesive composition having excellent heat resistance and electrolytic solution resistance 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 for Carrying Out the Invention

[0012] Hereinafter, the adhesive composition, the adhesive tape containing the adhesive composition, and the capacitor element to which the adhesive tape is applied will be described in detail, but the present invention is not limited to the following.

[0013] Further, the present invention may be a raw material composition for producing an adhesive composition. The raw material composition may contain all the raw materials of the adhesive composition or may contain some of the raw materials. In that case, the raw materials contained in the raw material composition can be appropriately selected, and the blending amount, use, production method, etc. in that case shall conform to the description of the adhesive composition.

[0014] In this specification, when a plurality of upper limit values and a plurality of lower limit values are separately described, it should be understood that all numerical ranges that can be freely combined and set by these upper limit values and lower limit values are described in this specification.

[0015] When isomers exist in the compounds disclosed in this specification, unless otherwise specified, all possible isomers can be used in the present invention.

[0016] In this specification, unless otherwise specified, the amounts described for the content, blending amount, etc. indicate the amounts of components (solid components) excluding volatile components. Also, in this specification, "amount", "content", "blending amount", etc. can be appropriately read mutually within a non-contradictory range.

[0017] In this specification, the Tg (glass transition temperature) of each monomer refers to the Tg when each monomer is formed into a homopolymer. Tg is a conventionally known physical property and can be measured, for example, by performing differential scanning calorimetry (DSC) on each homopolymer.

[0018] Each component classified herein may be used alone or in combination of two or more, unless otherwise specified.

[0019] Electronic components are not limited to any part used in electrical products. Specific examples of electronic components include capacitors, coils, transformers, batteries, and lead wires. Electronic component materials are the materials that make up these electronic components.

[0020] <<<<<Adhesive composition>>>>> <<<<Ingredients>>>> The adhesive composition contains a crosslinked polymer. The adhesive composition may also contain other components.

[0021] <<<Cross-linked polymer>>> Crosslinked polymers are obtained by crosslinking a base polymer; in other words, they are obtained by reacting a base polymer with a crosslinking agent.

[0022] <<Crosslinking agent>> The crosslinking agent preferably includes both an epoxy crosslinking agent and an isocyanate crosslinking agent. By using both an epoxy crosslinking agent and an isocyanate crosslinking agent in combination, it becomes possible to control the crosslinking reaction to occur over a multi-stage temperature range. More specifically, by combining an epoxy crosslinking agent and an isocyanate crosslinking agent, it becomes easier to appropriately control the crosslinking state of the adhesive tape before and after heat treatment (such as reflow treatment) when used as a tape for securing electronic components, such as capacitor elements. As a result, it is considered easier to appropriately control the properties of the adhesive tape required at each temperature stage. The adhesive composition may also contain unreacted crosslinking agents.

[0023] <Epoxy-based crosslinking agent> As an epoxy crosslinking agent, a compound having two or more epoxy groups (preferably 2 to 5, more preferably 2 to 4) in one molecule can be used.

[0024] Examples of epoxy crosslinking agents include glycerin polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycidylaniline, N,N,N',N'-tetraglycidyl-m-xylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

[0025] The epoxy crosslinking agent may be a commercially available product such as "Tetrad X" manufactured by Mitsubishi Gas Chemical Company.

[0026] Amount of epoxy crosslinking agent M when the amount of base polymer is 100 parts by mass. E The amount of epoxy crosslinking agent M is preferably greater than 0.001 parts by mass, greater than 0.01 parts by mass, 0.02 parts by mass or more, or 0.05 parts by mass or more. E Preferably, the amount is less than 1.0 part by mass, less than 0.10 parts by mass, or less than 0.08 parts by mass.

[0027] Amount of epoxy crosslinking agent M E By setting the range to this extent, it is possible to improve the heat resistance and electrolyte resistance of the adhesive composition.

[0028] Using an isocyanate-based crosslinking agent, along with the amount M of epoxy-based crosslinking agent... E By keeping the amount below 0.10 parts by mass, the heat resistance and electrolyte resistance of the adhesive tape can be particularly enhanced.

[0029] Using an isocyanate-based crosslinking agent, along with the amount M of epoxy-based crosslinking agent... E By setting the amount to more than 0.01 parts by mass, it is possible to improve the heat shrinkage resistance of the adhesive tape in particular while balancing the heat resistance and electrolyte resistance.

[0030] <Isocyanate crosslinking agent> As the isocyanate crosslinking agent, a compound having two or more isocyanate groups (preferably 2 to 5, more preferably 2 to 4) in one molecule can be used.

[0031] Specific examples of the isocyanate crosslinking agent include aromatic crosslinking agents such as toluene diisocyanate (TDI), phenylene diisocyanate, diphenylmethane diisocyanate (MDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), and hydrogenated products thereof; alicyclic crosslinking agents such as cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate; alkylene crosslinking agents such as hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, lysine diisocyanate; and the like. [[ID=id18]]

[0032] The isocyanate crosslinking agent may be a commercially available product such as "Coronate L" manufactured by Tosoh Corporation and "Takenate D-101E" manufactured by Mitsui Chemicals, Inc.

[0033] The amount M of the isocyanate crosslinking agent when the amount of the base polymer is 100 parts by mass I is preferably 0.01 part by mass or more, 0.05 part by mass or more, 0.10 part by mass or more, 0.5 part by mass or more, or 1.0 part by mass or more. Also, the amount M of the isocyanate crosslinking agent I 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.

[0034] The amount M of the isocyanate crosslinking agent I By setting the amount M within such a range, it becomes easier to appropriately control the crosslinked state of the adhesive tape before and after heat treatment (reflow treatment, etc.), and it is possible to enhance the heat resistance and electrolyte resistance of the adhesive composition.

[0035] Amount of isocyanate crosslinking agent M I By setting the amount to 0.10 parts by mass or more, the heat shrinkage resistance of the adhesive tape can be particularly enhanced.

[0036] M I / M E It is preferable that it is greater than 1, 2 or more, 5 or more, 10 or more, 20 or more, or 25 or more. Also, M I / M E It is preferable that the value is 500 or less, 200 or less, 100 or less, 75 or less, or 50 or less.

[0037] M I / M E By setting the range to this extent, it is possible to improve the heat resistance and electrolyte resistance of the adhesive composition.

[0038] <Other crosslinking agents> The crosslinking agent may include crosslinking agents other than epoxy crosslinking agents and isocyanate crosslinking agents (for example, known crosslinking agents such as polyvalent metal crosslinking agents, polyol crosslinking agents, and polyamine crosslinking agents), as long as they do not impair the effects of the present invention.

[0039] When the amount of the base polymer is 100 parts by mass, the amount of other crosslinking agents is preferably 10 parts by mass or less, 5 parts by mass or less, 2 parts by mass or less, 1 part by mass or less, or 0.1 parts by mass or less.

[0040] <<Base Polymer>> The base polymer can be one that has crosslinkable functional groups (for example, functional groups containing unsaturated carbon bonds such as acryloyl groups).

[0041] The following describes preferred base polymers.

[0042] The base polymer is preferably a copolymer obtained by copolymerizing multiple copolymerizable monomers (referred to as constituent monomers).

[0043] <Constituent monomers> The constituent monomers preferably include low-Tg (meth)acrylate alkyl ester monomers. Furthermore, the constituent monomers preferably include carboxyl group-containing monomers. By using such monomers as constituent monomers, it is possible to improve the heat resistance and electrolyte resistance of the adhesive composition in a well-balanced manner.

[0044] The constituent monomers may also include other monomers.

[0045] (Low Tg (meth)acrylate alkyl monomer) Low-Tg alkyl methacrylates have a Tg of less than 20°C when homopolymerized, preferably less than 0°C, less than -20°C, or less than -50°C. The lower limit of Tg is not particularly limited, but for example, it is -90°C or -80°C.

[0046] Examples of low-Tg (Tg) alkyl ester monomers include 2-ethylhexyl acrylate (2EHA, Tg: -70°C, 8 carbon atoms in the alkyl portion), isononyl acrylate (INA, Tg: -58°C, 9 carbon atoms in the alkyl portion), butyl acrylate (BA, Tg: -55°C, 4 carbon atoms in the alkyl portion), lauryl acrylate (LA, Tg: -23°C, 12 carbon atoms in the alkyl portion), lauryl methacrylate (LMA, Tg: -65°C, 12 carbon atoms in the alkyl portion), and isostearyl acrylate (ISA, Tg: -18°C, 18 carbon atoms in the alkyl portion).

[0047] The constituent monomers preferably include low-Tg (meth)acrylate alkyl ester monomers with 5 or more, 6 or more, or 8 or more carbon atoms in the alkyl portion. While there is no particular upper limit to the number of carbon atoms, for example, it may be 30, 25, or 20.

[0048] The content of low-Tg (meth)acrylate alkyl ester monomers with 5 or more carbon atoms in the alkyl portion of the constituent monomer is preferably 30% by mass or more, 45% by mass or more, or 60% by mass or more, based on the total amount of constituent monomers.

[0049] By setting the content of low-Tg (meth)acrylate alkyl ester monomers with 5 or more carbon atoms in the alkyl portion within this range, it is possible to improve the heat resistance and electrolyte resistance of the adhesive composition in a well-balanced manner.

[0050] The constituent monomers may include low-Tg (meth)acrylate alkyl ester monomers in which the alkyl portion has fewer than 5 carbon atoms.

[0051] The content of low-Tg (meth)acrylate alkyl ester monomers, in which the alkyl portion has fewer than 5 carbon atoms, is preferably 15% by mass or less, 10% by mass or less, 5% by mass or less, 2% by mass or less, less than 1% by mass, or less than 0.1% by mass, based on the total amount of constituent monomers.

[0052] By setting the content of low-Tg (meth)acrylate alkyl ester monomers with fewer than 5 carbon atoms in the alkyl portion within this range, it is possible to improve the heat resistance and electrolyte resistance of the adhesive composition in a well-balanced manner.

[0053] (carboxyl group-containing monomer) Carboxyl group-containing monomers have a carboxyl group and a functional group (a functional group having an unsaturated carbon bond, such as a vinyl group) for copolymerization with other constituent monomers. Typically, carboxyl group-containing monomers have one carboxyl group and one functional group having an unsaturated carbon bond.

[0054] Examples of carboxyl group-containing monomers 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, and 2-acryloyloxyethyl phthalic acid.

[0055] In the constituent monomers, the content of carboxyl group-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, based on the total amount of constituent monomers, and preferably 15% by mass or less, 10% by mass or less, 8% by mass or less, or 7% by mass or less.

[0056] By setting the content of carboxyl group-containing monomers within this range, it is possible to improve the probe tack, heat resistance, electrolyte resistance, etc., of the adhesive composition.

[0057] (Other monomers) The constituent monomers may include one or more selected from high-Tg alkyl (meth)acrylates, alicyclic group-containing (meth)acrylates with a Tg of -20°C or higher, and (meth)acrylamide derivatives.

[0058] High-Tg alkyl methacrylates are monomers whose Tg is 20°C or higher or 50°C or higher. The upper limit of Tg is not particularly limited, but examples include 200°C, 190°C, or 180°C.

[0059] High-Tg alkyl (meth)acrylates and alicyclic group-containing (meth)acrylates with a Tg of -20°C or higher are preferably those in which the alkyl moiety or alicyclic group has 5 or more carbon atoms, 6 or more carbon atoms, or 8 or more carbon atoms. The upper limit of this carbon number is not particularly limited, but examples include 30, 25, or 20. The alicyclic group may be monocyclic or polycyclic.

[0060] Examples of high-Tg (meth)acrylate alkyl esters include isobornyl acrylate (IBOA, Tg: 97°C, number of carbon atoms in the alkyl portion: 10) and isobornyl methacrylate (IBOMA, Tg: 180°C, number of carbon atoms in the alkyl portion: 10).

[0061] Examples of alicyclic group-containing (meth)acrylic acid esters with a Tg of -20°C or higher include cyclohexyl acrylate (CHA, Tg: 15°C, number of carbon atoms in the alicyclic group: 6), cyclohexyl methacrylate (CHMA, Tg: 66°C, number of carbon atoms in the alicyclic group: 6), dicyclopentanyl acrylate (Tg: 120°C, number of carbon atoms in the alicyclic group: 10), and dicyclopentanyl methacrylate (Tg: 175°C, number of carbon atoms in the alicyclic group: 10).

[0062] (Meth)acrylamide derivatives are compounds in which the terminal hydrogen atoms of (meth)acrylamide are substituted with other substituents.

[0063] Examples of (meth)acrylamide derivatives include acryloylmorpholine (ACMO, Tg: 145°C, acrylamide derivative), diethylacrylamide (DEAA, Tg: 81°C, acrylamide derivative), dimethylacrylamide (DMAA, Tg: 119°C, acrylamide derivative), isopropylacrylamide (NIPAM, Tg: 134°C, acrylamide derivative), and dimethylaminopropylacrylamide (DMAPAA, Tg: 134°C, acrylamide derivative).

[0064] The content of high-Tg alkyl (meth)acrylates, alicyclic group-containing (meth)acrylates with a Tg of -20°C or higher, and (meth)acrylamide derivatives may be 1% by mass or more, 5% by mass or more, 10% by mass or more, or 30% by mass or less, or 25% by mass or less, based on the total amount of constituent monomers.

[0065] The constituent monomer may further contain other monomers. In that case, the content of the other monomer is preferably 10% by mass or less, 5% by mass or less, or 1% by mass or less, based on the total amount of the constituent monomers.

[0066] <Weight-average molecular weight of the base polymer> The weight-average molecular weight of the base polymer is preferably 100,000 or more, 200,000 or more, 300,000 or more, or 500,000 or more, and also preferably 3,000,000 or less, 2,000,000 or less, 1,500,000 or less, or 1,000,000 or less.

[0067] The weight-average molecular weight of the base polymer was determined from the polystyrene-equivalent molecular weight measured by gel permeation chromatography (GPC).

[0068] <Tg of base polymer> The Tg of the base polymer is preferably -10°C or lower, -20°C or lower, or -30°C or lower, and more preferably -80°C or higher, -70°C or higher, -60°C or higher, or -50°C or higher.

[0069] The Tg of the base polymer may be measured using a differential scanning calorimeter (DSC), or a theoretical value may be calculated from the types and proportions of constituent monomers.

[0070] <<<Gel fraction of cross-linked polymers>>> The gel fraction of the crosslinked polymer can typically be 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more.

[0071] Here, when the adhesive composition and adhesive tape are used for fastening electronic components (particularly for winding capacitor elements) and are subjected to heat treatment (e.g., reflow treatment), the gel fraction may change before and after the heat treatment. In particular, by including both an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent, a relatively low gel fraction can be maintained before heat treatment (e.g., reflow treatment), while a relatively high gel fraction can be achieved after heat treatment (reflow treatment). Thus, the preferred gel fraction of the crosslinked polymer may differ depending on whether the adhesive composition, adhesive tape, or capacitor element according to this embodiment is before or after heat treatment.

[0072] 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 also preferably 95% by mass or less, 90% by mass or less, or 85% by mass or less.

[0073] In adhesive compositions in which sufficient crosslinking has been completed by heat treatment (for example, adhesive compositions in capacitor elements assembled on a substrate by reflow treatment), the gel fraction of the crosslinked 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. The upper limit of this gel fraction is not particularly limited, but it can be 98% by mass or 99% by mass.

[0074] More specifically, when the adhesive composition is subjected to heat treatment, if Gf1 is the gel fraction of the crosslinked polymer in the adhesive composition, and Gf2 is the gel fraction of the crosslinked polymer in the adhesive composition after heating at 200°C for 1 hour, it is preferable that Gf1 is 50% by mass or more, 60% by mass or more, or 70% by mass or more, 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 is greater than 1.00, 1.05 or more, 1.10 or more, 1.15 or more, or 1.20 or more. By setting the ratio within this range, an adhesive composition particularly suitable for adhesive tapes used to fasten electronic components subjected to heat treatment (e.g., reflow treatment) can be obtained.

[0075] By setting the gel fraction of the cross-linked polymer within this range, it is possible to improve the heat resistance and electrolyte resistance of the adhesive composition in a well-balanced manner.

[0076] The gel fraction can be adjusted by the type of monomer, the type and amount of crosslinking agent, the temperature and time of the heat treatment, etc.

[0077] <<<Other ingredients>>> The adhesive composition may contain other components as long as they do not impair the effects of the present invention. Other components include known additives such as fillers (e.g., calcium carbonate, talc, silica, carbon black, etc.), surfactants, organic pigments, inorganic pigments, stabilizers, silane coupling agents, spacer particles, tackifiers, and plasticizers.

[0078] Furthermore, solvents and other substances may be added during the manufacture of the adhesive composition to improve workability. Such solvents and other substances that may be added during manufacture may remain in the adhesive composition, but it is preferable that the solvents are removed.

[0079] <<<<<Adhesive Tape>>>>>> The adhesive tape comprises a base material and an adhesive layer provided on at least one side of the base material.

[0080] The width of the adhesive tape should be adjusted as appropriate, taking into account the size of the object to which it is applied (e.g., electronic components).

[0081] The adhesive tape may be provided, for example, in the form of a long length and wound onto a core as needed, or it may be provided as a film before being cut into tape.

[0082] The adhesive tape may also be a double-sided tape having adhesive layers on both sides of the base material.

[0083] <<<<Adhesive layer>>>> The adhesive layer consists of the aforementioned adhesive composition.

[0084] The thickness of the adhesive layer is not particularly limited, but can be, for example, 2 to 100 μm, 5 to 50 μm, 10 to 40 μm, or 12 to 35 μm.

[0085] <<<<Base material>>>> The base material can be appropriately selected within a range that does not hinder the effects of the present invention, but it is preferable that it consists 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.

[0086] When adhesive tape is used for aluminum electrolytic capacitors, etc., it is preferable that the base material be made of polypropylene (PP) and / or polyphenylene sulfide (PPS) from the viewpoint of hydrolysis resistance.

[0087] Polyethylene terephthalate (PET), polypropylene (PP), polyphenylene sulfide (PPS), polyimide (PI), and polyetherimide (PEI) may be synthetic resin films or synthetic resin fibers.

[0088] If the base material consists of synthetic resin fibers and plant fibers, it may be formed by papermaking.

[0089] Furthermore, when the base material is made of a synthetic resin film, it is preferable that it be a stretched film (for example, a uniaxially oriented film or a biaxially oriented film) from the viewpoint of improving heat resistance.

[0090] The thickness of the substrate is not particularly limited, but can be, for example, 5 to 100 μm or 9 to 50 μm.

[0091] The surface of the substrate layer may be subjected to appropriate surface treatment. Examples of surface treatments include corona treatment to improve adhesion with the adhesive layer, and peeling treatment performed on the surface of the substrate that does not come into contact with the adhesive layer.

[0092] <<<<Other layers>>>>> The adhesive tape may include other conventionally known layers. Examples of these other layers include a primer layer that enhances the adhesion between the substrate and the adhesive layer, and a separator layer that is provided in contact with the adhesive layer and is removed during use. However, considering productivity and environmental impact, direct winding (non-separator) is preferable.

[0093] <<<<<<Method for manufacturing adhesive composition and adhesive tape>>>>> Adhesive compositions and adhesive tapes can be manufactured according to conventionally known methods.

[0094] The adhesive composition can be manufactured by the following procedure. First, a raw material composition is prepared that includes a base polymer and a crosslinking agent, and optionally other additives and solvents (raw material preparation step). Next, the raw material composition is heated to remove the solvent and crosslink the base polymer to obtain an adhesive composition (crosslinking step).

[0095] Furthermore, adhesive tape can be manufactured by following the procedure below. First, a raw material composition is prepared that includes a base polymer and a crosslinking agent, and optionally other additives and solvents (raw material preparation step). Next, the raw material composition is applied to the substrate (coating process). Next, the raw material composition is heated to remove the solvent and crosslink the base polymer, thereby obtaining an adhesive tape (crosslinking step). Additionally, cutting and winding are performed as needed (processing steps).

[0096] Adhesive tape may also be manufactured by laminating an adhesive layer, which has been formed in advance in the form of a film or the like, onto a substrate.

[0097] The solvent that the raw material composition can contain is not particularly limited, and conventionally known solvents can be used.

[0098] Here, as mentioned above, it is preferable to stop the crosslinking reaction in the crosslinking step at a temperature and time at which unreacted crosslinking agent remains in the adhesive composition, and to react the remaining unreacted crosslinking agent in a heat treatment after the adhesive tape is applied for fastening electronic components. 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.

[0099] The crosslinking process may be carried out under temperature conditions such that no unreacted crosslinking agent remains in the adhesive composition. In this case, the heating conditions in the crosslinking process can be, for example, 80°C or higher, 100°C or higher, 120°C or higher, 150°C or higher, or 200°C or higher, or 200 to 280°C. The heating time can be, for example, 1 to 60 minutes.

[0100] In the crosslinking process, solvent removal and crosslinking may be performed simultaneously, or solvent removal and crosslinking may be performed separately.

[0101] <<<<Usage>>>> The adhesive composition and adhesive tape according to this embodiment can be used for various purposes, but are preferably used for fastening electronic components (for fixing electronic components or components).

[0102] The adhesive composition and adhesive tape according to this embodiment are particularly suitable for use in securing capacitor windings (especially for securing aluminum capacitor windings) because they possess sufficient heat resistance and electrolyte resistance even after contact with an electrolyte or exposure to a high-temperature environment.

[0103] More specifically, the capacitor element (particularly an aluminum electrolytic capacitor element) can include a winding body formed by winding multiple thin-film electrodes (anode foil and cathode foil) via separators or electrolytic paper as needed, an adhesive tape for securing the winding body (attached to the outer circumference of the winding body to fix the thin-film electrodes), and an electrolyte.

[0104] In this case, after the capacitor element is mounted on a substrate or the like, a heat treatment (such as reflow soldering or heat treatment to cure conductive adhesive) may be performed. During this process, the capacitor element is also exposed to the heated environment. The capacitor element according to this embodiment may be either a capacitor element that has not undergone such a heat treatment, or a capacitor element that has undergone such a heat treatment.

[0105] As mentioned above, when such heat treatment is performed, the preferred gel fraction of the adhesive composition before heat treatment may differ from the preferred gel fraction of the adhesive composition after heat treatment. Specifically, in a capacitor element before heat treatment, if the gel fraction of the crosslinked polymer in the adhesive composition is Gf3 and the gel fraction of the crosslinked polymer in the adhesive composition after heat treatment is Gf4, then it is preferable that Gf3 is 50% by mass or more, 60% by mass or more, or 70% by mass or more, and that Gf4 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 that Gf4 / Gf3 is greater than 1.00, 1.05 or more, 1.10 or more, 1.15 or more, or 1.20 or more.

[0106] The heating temperature in such a heat treatment varies depending on components other than the capacitor element (e.g., solder), but can be, for example, 80°C or higher, 120°C or higher, 150°C or higher, or 200°C or higher. In other words, the adhesive composition and adhesive tape according to this embodiment are suitable for use in environments of 80°C or higher, 120°C or higher, 150°C or higher, or 200°C or higher.

[0107] The heating time in such a heat treatment can be, for example, 5 minutes or more, 10 minutes or more, 30 minutes or more, or 1 hour or more.

[0108] Other applications of the adhesive composition and adhesive tape according to this embodiment include their excellent heat resistance and electrolyte resistance, making them suitable for use as electrode insulation in lithium-ion secondary batteries, among others.

[0109] Furthermore, electronic components other than capacitor elements are also exposed to the high-temperature environment of reflow and may be exposed to electrolytes seeping from the capacitor elements. Therefore, the adhesive composition and adhesive tape according to this embodiment can be preferably used for applications other than winding capacitor elements, within the scope of electronic component fastening (for fixing electronic components or electronic component components).

[0110] Furthermore, when the adhesive composition and adhesive tape are used to secure capacitor elements, the smaller the diameter, the greater the influence of the substrate's repulsive force on terminal peeling. Therefore, smaller diameter capacitors require higher adhesive performance. The adhesive composition and adhesive tape according to this embodiment have excellent adhesive properties and can be used for small diameter capacitor elements (for example, capacitor elements with a diameter of 4-20 mm).

[0111] <<<<<Preferred Embodiment of the Invention>>>>> Preferred embodiments of the present invention will be described in detail below.

[0112] <<<<Form 1>>>> Embodiment 1 is an adhesive composition comprising a crosslinked polymer obtained by reacting a base polymer with a crosslinking agent, The base polymer is a copolymer obtained by copolymerizing a low-Tg alkyl ester monomer having a Tg of 20°C or less with constituent monomers containing a carboxyl group. The content of the low-Tg (meth)acrylate alkyl ester monomer in the constituent monomer, in which the alkyl portion has 5 or more carbon atoms, is 30% by mass or more based on the total amount of the constituent monomer. The content of the low-Tg (meth)acrylate alkyl ester monomer in the constituent monomer, in which the alkyl portion has fewer than 5 carbon atoms, is 10% by mass or less based on the total amount of the constituent monomer. The aforementioned crosslinking agent includes an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent. When the amount of the base polymer is 100 parts by mass, the amount of the epoxy crosslinking agent M E is less than 0.10 parts by mass. This is an adhesive composition characterized by the following features.

[0113] Furthermore, Embodiment 1 is an adhesive tape comprising a base material and an adhesive layer provided on at least one side of the base material, wherein the adhesive layer contains the adhesive composition. The adhesive tape may be used in environments with a temperature of 80°C or higher. The adhesive tape may be used to fix electronic components or components of electronic components. The adhesive tape may also be used to secure the capacitor element.

[0114] According to this embodiment 1, an adhesive composition having excellent heat resistance and electrolyte resistance is provided. An adhesive tape obtained using such an adhesive composition can be used to properly fix electronic components, including capacitor elements.

[0115] <<<<Form 2>>>> This second form is, An adhesive tape comprising a base material and an adhesive layer provided on at least one side of the base material, The adhesive layer comprises an adhesive composition containing a crosslinked polymer obtained by reacting a base polymer with a crosslinking agent, The aforementioned crosslinking agent includes an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent. When the amount of the base polymer is 100 parts by mass, the amount of the epoxy crosslinking agent M E The amount is greater than 0.01 parts by mass and less than 0.10 parts by mass. When the amount of the base polymer is 100 parts by mass, the amount of the isocyanate-based crosslinking agent M I This is an adhesive tape containing 0.10 parts by mass or more.

[0116] The gel fraction of the crosslinked polymer may be 60-90%. The base polymer may be a copolymer obtained by copolymerizing a low-Tg alkyl ester monomer having a Tg of 20°C or less with constituent monomers containing a carboxyl group. The content of the low-Tg (meth)acrylate alkyl ester monomer in the constituent monomer, in which the alkyl portion has 5 or more carbon atoms, may be 30% by mass or more based on the total amount of the constituent monomer. The content of the low-Tg (meth)acrylate alkyl ester monomer in the constituent monomer, in which the alkyl portion has fewer than 5 carbon atoms, may be 10% by mass or less based on the total amount of the constituent monomer. The adhesive tape may be used to fix electronic components or electronic component materials that are subjected to heat treatment at 80°C or higher.

[0117] According to this embodiment 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 fix electronic components, including capacitor elements.

[0118] <<<<Form 3>>>> This form 3 is, A capacitor element comprising a winding body formed by winding multiple thin film electrodes, an adhesive tape for securing the winding body, and an electrolyte, The adhesive tape comprises a base material and an adhesive layer provided on at least one side of the base material. The adhesive layer comprises an adhesive composition containing a crosslinked polymer obtained by reacting a base polymer with a crosslinking agent, The capacitor element comprises an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent.

[0119] The base polymer may be a copolymer obtained by copolymerizing a low-Tg alkyl ester monomer having a Tg of 20°C or less with constituent monomers containing a carboxyl group. The content of the low-Tg (meth)acrylate alkyl ester monomer in the constituent monomer, in which the alkyl portion has 5 or more carbon atoms, may be 30% by mass or more based on the total amount of the constituent monomer. The content of the low-Tg (meth)acrylate alkyl ester monomer in the constituent monomer, in which the alkyl portion has fewer than 5 carbon atoms, may be 10% by mass or less based on the total amount of the constituent monomer. The gel fraction of the crosslinked polymer may be 85% or more. The aforementioned capacitor element may be an aluminum electrolytic capacitor.

[0120] According to this embodiment 3, it is possible to provide a capacitor element with improved winding resistance. [Examples]

[0121] The present invention will be described in more detail below, but it is not limited to these descriptions.

[0122] <<<<Manufacturing of adhesive tape>>>> The adhesive tape was manufactured according to the following procedure. A biaxially oriented polyphenylene sulfide film [product name "Torelina 3040" (thickness: 16 μm), manufactured by Toray Industries, Inc., double-sided corona treated] was used as the substrate. If necessary, a primer was applied to one side of the substrate and allowed to dry. A long-chain alkyl-based release agent was applied to the other surface and dried (coating amount after drying: 5 mg / m²). 2 ). Next, a raw material composition containing a base polymer, a crosslinking agent, and a solvent was applied to the primer-coated surface of the substrate, heated at 100°C for 3 minutes to remove the solvent, and an adhesive layer consisting of an adhesive composition of a predetermined thickness was formed. For the crosslinking process, the base polymer was heated at 50°C for 72 hours to complete the crosslinking.

[0123] Each example is an adhesive tape in which the adhesive composition used has been changed. The table shows the types of constituent monomers and crosslinking agents used in each example, as well as their respective amounts (parts by mass of solids).

[0124] For some adhesive tapes, primer was not applied to the substrate.

[0125] In the table, Tetrad® X is an epoxy crosslinking agent manufactured by Mitsubishi Gas Chemical Company, Narsem® Al is a metal crosslinking agent manufactured by Nippon Chemical Industrial Co., Ltd., and Coronate® L is a polyisocyanate crosslinking agent manufactured by Tosoh Corporation.

[0126] The Tg values ​​shown in the table are conventionally known physical properties and can be measured, for example, by performing differential scanning calorimetry (DSC) on each homopolymer. The carbon numbers shown in the table indicate the number of carbon atoms in the side chains.

[0127] <<<Gel fraction>>> The adhesive was dissolved in THF and allowed to stand at room temperature for 24 hours. The gel was then separated using a 200-mesh metal mesh. The separated gel was dried and its mass was measured. The gel fraction was determined by dividing the obtained value by the mass of the adhesive initially dissolved in THF.

[0128] <<<Gel fraction after heating>>> Except for using an adhesive that had been heated at 200°C for 1 hour, the evaluation was performed in the same manner as the gel fraction evaluation method.

[0129] <<<Weight average molecular weight>>> The samples were evaluated using a Shimadzu Corporation GPC instrument (LC-20) with a sample concentration of 0.2 wt% (THF solution), a sample injection volume of 100 μl, THF as the eluent, a flow rate of 1.0 ml / min, two TOSOH TSK-GMHXL columns, and a differential refractometer (RI) detector. Molecular weight was calculated using polystyrene equivalent values.

[0130] <<<<Rating>>>>> For each example and comparative example, the adhesive tapes were evaluated for probe tack, end peeling, and heat shrinkage rate. The evaluation results are shown in Table 1-4, and the evaluation criteria for each evaluation are shown in Table 5.

[0131] <<<Probe Tack>>> Using an NS probe tack tester (manufactured by Nichiban Co., Ltd.) in accordance with ASTM D2979, the cylindrical contact (probe) was measured with a diameter of 5 mm and a pressure of 100 gf / cm². 2 The test was conducted under the following conditions: contact time; 1 second, peeling speed; 10 mm / sec.

[0132] <<<Device peeling rating: 1>>> <<Evaluation Method>> A sample for evaluation was prepared by wrapping a 50mm length of adhesive tape (5mm wide) around a 2mm diameter stainless steel rod under a 5°C atmosphere. The sample was immersed in γ-butyllactone at 23°C for 12 hours, and the length of the peeled-off end of the adhesive tape was confirmed. γ-butyllactone is a solvent commonly used as an electrolyte.

[0133] <<<Device peeling evaluation 2>>> <<Evaluation Method>> A sample for evaluation was prepared by wrapping a 50mm length of adhesive tape (5mm wide) around a 2mm diameter stainless steel rod in an atmosphere of 5℃. The sample was immersed in γ-butyllactone at 105℃ for 12 hours, and the length of the peeled-off end of the adhesive tape was confirmed. γ-butyllactone is a solvent commonly used as an electrolyte.

[0134] <<<Heat shrinkage rate evaluation>>> <<Evaluation Method>> An evaluation sample was prepared by attaching a 50mm length of evaluation adhesive tape (5mm wide) to the back of an adhesive tape attached to an aluminum panel. The evaluation sample was heated in an oven at 260°C for 1 hour, and the shrinkage rate of the adhesive tape was calculated based on the following formula. Shrinkage rate (%) = (1 - Tape length after heating / Tape length before heating) × 100

[0135] [Table 1]

[0136] [Table 2]

[0137] [Table 3]

[0138] [Table 4]

[0139] [Table 5]

[0140] As can be seen from the table, Examples 1-21, 23-31, and 33-41, which are adhesive compositions or adhesive tapes according to Form 1, have both terminal peeling at 23°C and terminal peeling at 105°C rated C or higher, and at least one of the terminal peeling at 23°C and 105°C rated B or higher, indicating that they have excellent heat resistance and electrolyte resistance.

[0141] Furthermore, as can be seen from the table, examples 1-27, 29-32, and 34-41, which are adhesive tapes relating to Form 2, do not have a D rating, indicating that they have an excellent balance of heat resistance, electrolyte resistance, and heat shrinkage resistance.

[0142] Furthermore, as can be seen from the table, Example 1-41 shows no D ratings for terminal peeling at 23°C and 105°C, indicating an excellent balance of heat resistance and electrolyte resistance. In other words, it is understood that the capacitor elements in Form 3 to which these adhesive tapes are applied have high winding retention (high reliability).

Claims

[Claim 1] An adhesive tape comprising a base material and an adhesive layer provided on at least one side of the base material, The adhesive layer comprises an adhesive composition containing a crosslinked polymer obtained by reacting a base polymer with a crosslinking agent, The base polymer is a copolymer obtained by copolymerizing a low-Tg alkyl ester monomer having a Tg of 20°C or less with constituent monomers containing a carboxyl group. The content of the low-Tg (meth)acrylate alkyl ester monomer in the constituent monomer, in which the alkyl portion has 5 or more carbon atoms, is 30% by mass or more based on the total amount of the constituent monomer. The content of the low-Tg (meth)acrylate alkyl ester monomer in the constituent monomer, in which the alkyl portion has fewer than 5 carbon atoms, is 10% by mass or less based on the total amount of the constituent monomer. The aforementioned crosslinking agent includes an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent. When the amount of the base polymer is 100 parts by mass, the amount of the epoxy crosslinking agent M Ｅ The amount is greater than 0.001 parts by mass and less than 0.10 parts by mass, An adhesive tape characterized by its use in securing capacitor elements.

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