JP7729360B2 - adhesive composition - Google Patents

Description

The present invention relates to an adhesive composition and a film-like adhesive composition.

In recent years, various adhesives have been used in fields such as semiconductors and liquid crystal displays to secure electronic components and connect circuits. These applications have become increasingly dense and precise, requiring adhesives with high adhesive strength and reliability.

In particular, anisotropic conductive adhesives, which have conductive particles dispersed in the adhesive, are used as circuit connection materials for connecting liquid crystal displays and TCPs (Tape Carrier Packages), FPCs (Flexible Printed Circuits) and TCPs, or FPCs and printed wiring boards. Furthermore, recently, even when mounting semiconductor silicon chips to substrates, rather than using the conventional wire bonding method, a method known as COG (Chip On Glass) is being used in which the semiconductor silicon chip is directly mounted to the substrate, and anisotropic conductive adhesives are also used here.

Furthermore, in recent years, the field of precision electronic devices has seen an increase in circuit density, resulting in extremely narrow electrode widths and electrode spacing. For this reason, the connection conditions for conventional circuit connection adhesives using epoxy resins can lead to problems such as circuit (wiring) falling off, peeling, and misalignment, while COG can cause warping due to differences in thermal expansion between the chip and the substrate. Furthermore, improving throughput is necessary to reduce costs, and there is a demand for adhesives that can be cured at relatively low temperatures (e.g., 150-170°C) and in a short time (e.g., within 10 seconds) (low-temperature, fast-curing adhesives).

To meet these demands, it is known to use, for example, onium salts containing sulfonium cations with specific structures as polymerization initiators in adhesives (see Patent Documents 1 and 2 below).

Patent No. 2706833 Japanese Patent Application Publication No. 6-345726

However, when the polymerization initiators described in Patent Documents 1 and 2 are used, polymerization may begin even at temperatures of around 40 to 60°C, which could lead to the adhesive curing progressing during storage. On the other hand, when a polymerization initiator with lower reactivity than the polymerization initiators described in Patent Documents 1 and 2 (such as an iodonium salt compound) is used, storage stability is ensured, but it is difficult to cure the adhesive at a relatively low temperature (e.g., 150 to 170°C) in a short time (e.g., within 10 seconds).

The present invention therefore aims to provide an adhesive composition and a film-like adhesive composition that have excellent storage stability and can be cured at relatively low temperatures (e.g., 150 to 170°C) in a short time (e.g., within 10 seconds).

In order to achieve the above objective, the inventors conducted extensive research and discovered that by using an onium salt containing a specific nitrogen onium cation and counter anion, it is possible to achieve both storage stability and curing ability at relatively low temperatures in a short period of time, thereby completing the present invention.

That is, the present invention provides an adhesive composition containing an onium salt represented by the following general formula (1) and a cationically polymerizable substance.

[In formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkoxyl group, a substituted or unsubstituted aryloxy group, or a substituted or unsubstituted heterocyclic oxy group; R ¹ , R ² , R ³ and R ⁴ may be bonded to each other to form a ring structure; and X ⁻ represents SbF ₆ ⁻ , PF ₆ ⁻ , B(C ₆ F ₅ ) ₄ ⁻ , Ga(C ₆ F ₅ ) ₄ ⁻ , Ga(C ₆ F ₅ ) ₂ F ₂ ⁻ , Ga(C ₆ F ₅ )F ₃ ⁻ or C(CF ₃ SO ₂ ) ₃ ⁻ .] ］

The adhesive composition of the present invention has excellent storage stability and can be cured at relatively low temperatures (e.g., 150 to 170°C) in a short time (e.g., within 10 seconds). Such an adhesive composition can be suitably used as an adhesive composition for connecting circuits.

The onium salt is preferably at least one selected from the group consisting of anilinium salts and pyridinium salts.

In general formula (1), any one of R ¹ , R ² , R ³ and R ⁴ is preferably a substituted or unsubstituted benzyl group, a substituted or unsubstituted naphthylmethyl group, or a substituted or unsubstituted cinnamyl group.

The cationically polymerizable substance may be at least one selected from the group consisting of epoxy compounds, oxetane compounds, and vinyl ether compounds.

The adhesive composition may further contain a film-forming polymer. The adhesive composition may further contain conductive particles.

The adhesive composition may have anisotropic conductivity. The adhesive composition may be for circuit connection.

The present invention also provides a film-like adhesive composition obtained by forming the adhesive composition into a film.

The present invention provides an adhesive composition and a film-like adhesive composition that have excellent storage stability and can be cured at relatively low temperatures (e.g., 150 to 170°C) in a short time (e.g., within 10 seconds).

1 is a schematic cross-sectional view showing one embodiment of a film-like adhesive composition having anisotropic conductivity. FIG. 1 is a schematic cross-sectional view showing one embodiment of a structure. 3A to 3C are schematic cross-sectional views showing a method for manufacturing the structure of FIG. 2.

Embodiments of the present invention are described in detail below. In this specification, when the composition contains multiple substances corresponding to each component, the content of each component in the composition refers to the total amount of those multiple substances present in the composition, unless otherwise specified.

The adhesive composition according to this embodiment contains (A) an onium salt (onium salt compound; hereinafter also referred to as "component (A)") represented by the following general formula (1), and (B) a cationically polymerizable substance (hereinafter also referred to as "component (B)").

[In formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkoxyl group, a substituted or unsubstituted aryloxy group, or a substituted or unsubstituted heterocyclic oxy group; R ¹ , R ² , R ³ and R ⁴ may be bonded to each other to form a ring structure; and X ⁻ represents SbF ₆ ⁻ , PF ₆ ⁻ , B(C ₆ F ₅ ) ₄ ⁻ , Ga(C ₆ F ₅ ) ₄ ⁻ , Ga(C ₆ F ₅ ) ₂ F ₂ ⁻ , Ga(C ₆ F ₅ )F ₃ ⁻ or C(CF ₃ SO ₂ ) ₃ ⁻ .] ］

Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, n-pentyl, n-hexyl, n-heptyl, and aralkyl groups. Examples of aralkyl groups include benzyl, naphthylmethyl, and cinnamyl groups. These alkyl groups may have a substituent.

Examples of the aryl group include a phenyl group, a naphthyl group, and a biphenyl group. These aryl groups may have a substituent.

Examples of the alkenyl group include propenyl, 2-butenyl, 2-pentanyl, and 2-hexanyl groups. Examples of the heterocyclic group include pyridinyl groups. Examples of the alkoxyl group include methoxy, ethoxy, propoxy, and butoxy groups. Examples of the aryloxy group include 4-phenylmethoxy, 4-phenylethoxy, and 4-phenyloxycarbonylmethyl groups. Examples of the heterocyclic oxy group include 4-cyclohexaneoxide. These groups may have a substituent.

Substituents for the above alkyl, aryl, and other groups include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, and hexyl; aryl groups such as phenyl and naphthyl; alkoxy groups such as methoxy, ethoxy, propoxy, and butoxy; alkoxycarbonyl groups such as acetoxy, propionyloxy, decylcarbonyloxy, and dodecylcarbonyloxy; ester groups such as methoxycarbonyl, ethoxycarbonyl, and benzoyloxy; phenylthio; halogen atoms such as fluorine, chlorine, bromine, and iodine; cyano; nitro; and hydroxy. The substitution positions of these substituents are not particularly limited and may be any position.

^X- in formula (1) represents a counter anion of the nitrogen onium cation. Examples of ^X- include _SbF6- ^, _PF6- , B( _C6F5 ) ^4- , ^Ga ( _C6F5 ) _4- , ^Ga(C6F5)2F2- _, ^Ga ( _{C6F5 )F3- ,} and _{C ( CF3SO2 ) 3-} ^{. SbF6-} , _{( C6F5 ) 4B- ,} ^and ₍ ^CF3SO2 _{) 3C-} are preferred because better curability can be obtained when the ^{nucleophilicity} _{of the anion} is low.

From the viewpoint of lowering the decomposition temperature of the initiator and further improving the curability, it is preferable that any one of R ¹ , R ² , R ³ and R ⁴ (only one of R ¹ , R ² , R ³ and R ⁴ ) is a substituted or unsubstituted benzyl group, a substituted or unsubstituted naphthylmethyl group, or a substituted or unsubstituted cinnamyl group.

R ¹ , R ² , R ³ and R ⁴ may be bonded to each other to form a ring structure, for example, adjacent groups among R ¹ , R ² , R ³ and R ⁴ are bonded to each other to form a ring structure. Examples of nitrogen onium cations having a ring structure include cations represented by the following general formula (2). Examples of the ring structure Q include heterocycles, aromatic rings, heteroaromatic rings (pyridinium rings, etc.), alicyclic rings, etc. Furthermore, the ring structure Q is, for example, a multi-membered ring such as a four-membered ring, a five-membered ring, a six-membered ring, or a seven-membered ring. The ring structure Q may be unsubstituted or may have a substituent. Examples of the substituent include the substituents described above for each group such as an alkyl group or an aryl group. m represents 1 or 2. R ⁵ is a group equivalent to R ¹ , R ² , R ³ and R ⁴ .

From the perspective of achieving even better storage stability, component (A) is preferably a compound that exhibits activity at temperatures between 80 and 250°C, and more specifically, at least one selected from the group consisting of anilinium salts (anilinium salt compounds) and pyridinium salts (pyridinium salt compounds) is more preferred.

As the anilinium salt, from the viewpoint of lowering the decomposition temperature and further improving the curability, N-alkylanilinium salts, N,N-dialkylanilinium salts and N,N,N-trialkylanilinium salts are preferred. Specific examples of the anilinium salt include N-benzyl-N,N-dimethylanilinium antimony hexafluoride, N-(4-nitrobenzyl)-N,N-dimethylanilinium antimony hexafluoride, N-(4-methoxybenzyl)-N,N-dimethylanilinium antimony hexafluoride, N-(α-phenylbenzyl)-N,N-dimethylanilinium antimony hexafluoride, N-(α-methylbenzyl)-N,N-dimethylanilinium antimony hexafluoride, N-(1-naphthylmethyl)-N,N-dimethylanilinium antimony hexafluoride, N-cinnamyl-N,N-dimethylanilinium antimony hexafluoride, onium salts having a substituted benzylanilinium cation (e.g., K-PURE CXC-1612 (manufactured by KING Industries, counter anion: SbF ₆ ), K-PURE Examples of anilinium salts include CXC-1738 (manufactured by KING Industries, counter anion: PF ₆ ), K-PURE CXC-1740 (manufactured by KING Industries, counter anion: SbF ₆ ), K-PURE CXC-1741 (manufactured by KING Industries, counter anion: SbF ₆ ), and K-PURE CXC-1821 (manufactured by KING Industries, counter anion: B(C ₆ F ₅ ) ₄ ). In these compounds, the aromatic ring bonded to the nitrogen atom may be unsubstituted or may have a substituent. Examples of anilinium salts in which the aromatic ring has a substituent include N-(1-naphthylmethyl)-N,N-dimethyl(4-bromophenyl)anilinium antimony hexafluoride.

As the anilinium salt, from the viewpoints of lowering the decomposition temperature and further improving the curability, N-benzyl-N,N-dialkylanilinium salt and N-naphthylmethyl-N,N-dialkylanilinium salt are preferred, and N-benzyl-N,N-dimethylanilinium salt and N-naphthylmethyl-N,N-dimethylanilinium salt are more preferred. As the counter anion of these anilinium salts, SbF ₆ ^- is preferred from the viewpoints of increasing the reaction rate of the cationic polymerization reaction and further improving the curability.

As the pyridinium salt, from the viewpoint of lowering the decomposition temperature and further improving the curability, N-benzylpyridinium salt, N-naphthylmethylpyridinium salt, and N-cinnamylpyridinium salt are preferred. As the counter anion of these pyridinium salts, SbF ₆ ^- is preferred from the viewpoint of improving the reaction rate of the cationic polymerization reaction and further improving the curability. Specific examples of pyridinium salts include N-benzylpyridinium antimony hexafluoride, N-(4-nitrobenzyl)pyridinium antimony hexafluoride, N-(4-methoxybenzyl)pyridinium antimony hexafluoride, N-(α-phenylbenzyl)pyridinium antimony hexafluoride, N-(α-methylbenzyl)pyridinium antimony hexafluoride, N-(1-naphthylmethyl)pyridinium antimony hexafluoride, and N-cinnamylpyridinium antimony hexafluoride. The pyridinium ring in these compounds may be unsubstituted or may have a substituent. Examples of pyridinium salts having a substituted pyridinium ring include N-(α-phenylbenzyl)-4-cyanopyridinium antimony hexafluoride, naphthylmethyl-2-cyanopyridinium antimony hexafluoride, and cinnamyl-2-cyanopyridinium antimony hexafluoride.

The content of component (A) is preferably 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more, per 100 parts by mass of component (B), from the viewpoint that the adhesive composition tends to cure sufficiently easily. The content of component (A) is preferably 30 parts by mass or less, and more preferably 15 parts by mass or less, per 100 parts by mass of component (B), from the viewpoint that compatibility tends to be improved.

Component (A) may be used alone or in combination with multiple types. Furthermore, to increase the cation generation efficiency of component (A) and the reaction rate of component (B), a chain transfer agent may be used as appropriate in addition to components (A) and (B). There are no particular restrictions on the chain transfer agent as long as it is a protic compound, and known compounds can be used. Examples of chain transfer agents that can be used include alcohols such as cyclohexene diol, 2,3-butane diol, ethylene glycol, diethylene glycol, and triethylene glycol, as well as derivatives of these.

The (B) cationically polymerizable substance is a substance having a cationically polymerizable substituent. Examples of the cationically polymerizable substituent include an epoxy group, an oxetanyl group, and a vinyl ether group. Examples of the (B) component include an epoxy compound, an oxetane compound, and a vinyl ether compound. Examples of the epoxy compound include a glycidyl ether epoxy compound and an alicyclic epoxy compound. The (B) component may be used alone or in combination.

The glycidyl ether-type epoxy compound, component (B), is a compound containing a glycidyl ether group in the molecule that cures upon exposure to actinic rays or heating in the presence or absence of a curing agent, and any known compound can be used. Among these, glycidyl ether-type epoxy compounds containing two or more epoxy groups per molecule are preferred because they increase crosslink density upon curing. Examples of glycidyl ether-type epoxy compounds include bisphenol-type epoxy resins derived from epichlorohydrin and bisphenol compounds (such as bisphenol A and bisphenol F); polyglycidyl ethers; novolac-type epoxy compounds such as cresol novolac-type epoxy resins and phenol novolac-type epoxy resins; biphenyl diglycidyl ether, glycidyl alkyl isocyanurate, polyglycidyl methacrylate, and copolymers of glycidyl methacrylate and a vinyl monomer copolymerizable therewith. Glycidyl ether-type epoxy compounds may be used alone or in combination.

The alicyclic epoxy compound (B), component (B), is a compound that contains an epoxy group in the molecule and that cures upon exposure to actinic rays or heating in the presence or absence of a curing agent, and any known compound can be used. Alicyclic epoxy compounds containing two or more epoxy groups per molecule are preferred because they increase the crosslink density upon curing. Examples of alicyclic epoxy compounds that can be used include cyclohexene oxide- or cyclopentene oxide-containing compounds obtained by oxidizing a cyclohexene ring-containing compound or a cyclopentene ring-containing compound. Examples of the alicyclic epoxy compounds include 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-metadioxane, 3,4-epoxy-1-methylcyclohexyl-3,4-epoxy-1-methylhexanecarboxylate, 3,4-epoxy-3-methylcyclohexylmethyl-3,4-epoxy-3-methylcyclohexanecarboxylate, 3,4-epoxy-5-methylcyclohexylmethyl-3,4-epoxy-5-methylcyclohexanecarboxylate, 3, Examples of alicyclic epoxy compounds include 4-epoxy-6-methylcyclohexylcarboxylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 6-methyl-3,4-epoxycyclohexylmethyl-6-methyl-3,4-epoxycyclohexanecarboxylate, ethylene bis(3,4-epoxycyclohexanecarboxylate), dicyclopentadiene diepoxide, bis(3,4-epoxycyclohexylmethyl)adipate, and methylene bis(3,4-epoxycyclohexane). Alicyclic epoxy compounds can be used alone or in combination.

The oxetane compound of component (B) may be any oxetane compound having an oxetanyl group in the molecule that can be cured by exposure to actinic rays or heating in the presence or absence of a curing agent. Among these, oxetane compounds having two or more oxetanyl groups are preferred because they increase the crosslink density when cured. From the perspective of achieving even better curability, aliphatic or alicyclic compounds having 2 to 6 oxetanyl groups and 1 to 6 hydroxyl groups in the molecule are particularly preferred. One type of oxetane compound may be used alone, or multiple types can be used in combination.

Specific examples of the oxetane compound include compounds represented by the following general formula (3).

In formula (3), ^R11 represents a hydrogen atom, a fluorine atom, or a monovalent hydrocarbon group, ^R12 represents a hydrogen atom or an n-valent hydrocarbon group, and n represents an integer of 1 or more. When ^R12 represents a monovalent hydrocarbon group, examples of the hydrocarbon group include an alkyl group and an aryl group. When ^R12 is a hydrogen atom, n is 1. When n is an integer of 2 or more, multiple oxygen atoms bonded to ^R12 may be bonded to the same carbon atom of ^R12 or may be bonded to different carbon atoms of ^R12 . Note that n is, for example, an integer of 4 or less.

Examples of oxetane compounds include 1,4-di[(3-oxetanyl-n-butoxy)methyl]benzene, 4,4'-bis[(3-oxetanyl-n-butoxy)methyl]biphenyl, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, 3-ethyl-3-hydroxymethyloxetane, and 2-ethylhexyloxetane.

The vinyl ether compound of component (B) is a compound that has a vinyl ether group in its molecule and that cures upon exposure to actinic rays or heating in the presence or absence of a curing agent. Vinyl ether compounds that have two or more vinyl ether groups in one molecule are preferred because they increase the crosslink density upon curing. Vinyl ether compounds may be used alone or in combination.

Specific examples of the vinyl ether compound include compounds represented by the following general formula (4).

In formula (4), ^R13 represents a p-valent hydrocarbon group, where p is an integer of 1 or greater. When ^R13 represents a monovalent hydrocarbon group, examples of the hydrocarbon group include an alkyl group and an aryl group. When p is an integer of 2 or greater, multiple oxygen atoms bonded to ^R13 may be bonded to the same carbon atom of ^R13 or may be bonded to different carbon atoms of ^R13 . Note that p is, for example, an integer of 4 or less.

Examples of vinyl ether compounds include 1,4-butanediol divinyl ether, cyclohexanedimethanol divinyl ether, diethylene glycol divinyl ether, and triethylene glycol divinyl ether.

The cationically polymerizable substituent equivalent of component (B) is preferably 43 to 1,000 g/mol, more preferably 50 to 800 g/mol, and even more preferably 73 to 600 g/mol. A cationically polymerizable substituent equivalent of 43 g/mol or more or 1,000 g/mol or less ensures sufficient adhesive strength when connecting electrodes, as described below.

From the viewpoint of corrosion prevention, it is preferable to use a high-purity product as component (B) in which impurity ions (Na ⁺ , Cl ⁻ , etc.), hydrolyzable chlorine, etc. have been reduced to 300 ppm or less.

The content of component (B) is preferably 10% by mass or more, and more preferably 25% by mass or more, based on the total amount of the adhesive composition, from the viewpoint of obtaining even better physical properties (glass transition temperature, elastic modulus, etc.) of the cured product of the adhesive composition. The content of component (B) is preferably 90% by mass or less, and more preferably 75% by mass or less, based on the total amount of the adhesive composition, from the viewpoint of suppressing shrinkage of the adhesive composition during curing and maintaining adhesive strength.

The adhesive composition according to this embodiment may further contain a film-forming polymer (C) (hereinafter also referred to as "component (C)"), which is a component different from components (A) and (B) for the purpose of thickening or improving film-forming properties. Any known polymer may be used as component (C) as long as it does not inhibit the curing of component (B). Examples of such polymers include polyimide, polyamide, phenoxy resin, polymethacrylate, polyacrylate, polyurethane, polyester, polyesterurethane, polyvinyl butyral, SBS (styrene-butadiene-styrene copolymer) and its epoxy-modified derivatives, SEBS (styrene-ethylene-butylene-styrene copolymer) and its modified derivatives, and NBR (acrylonitrile-butadiene copolymer) and its hydrogenated derivatives. Component (C) may be used alone or in combination. These polymers may contain siloxane bonds or fluorine substituents. Such polymers can be suitably used as adhesive compositions if the resins to be mixed are completely compatible with each other, or if microphase separation occurs and the mixture becomes cloudy.

The weight-average molecular weight of component (C) is not particularly limited, but is preferably in the following range. From the viewpoint of easily improving film-forming properties and enabling the melt viscosity, which affects the fluidity of the adhesive composition, to be set over a wide range, the weight-average molecular weight of component (C) is preferably 5,000 or more, more preferably 10,000 or more. From the viewpoint of ensuring sufficient compatibility between component (C) and other components, the weight-average molecular weight of component (C) is preferably 150,000 or less, more preferably 80,000 or less. The weight-average molecular weight of component (C) can be calculated using gel permeation chromatography (GPC) by conversion from a calibration curve using standard polystyrene. Measurement conditions that can be used include, for example, the following conditions.
(Measurement conditions)
Apparatus: GPC-8020 manufactured by Tosoh Corporation
Detector: Tosoh Corporation RI-8020
Column: Gelpack GL-A-160-S + GL-A150 manufactured by Hitachi Chemical Co., Ltd.
Sample concentration: 120mg/3ml
Solvent: tetrahydrofuran Injection volume: 60 μl
Pressure: 30 kgf/ ^cm2
Flow rate: 1.00ml/min

The content of component (C) is preferably 20 to 320 parts by mass per 100 parts by mass of component (B). A content within this range tends to ensure sufficient fluidity and adhesiveness of the adhesive composition.

The adhesive composition according to this embodiment may further contain (D) conductive particles. Examples of (D) conductive particles include particles of metals such as Au, Ag, Ni, Cu, solder, and carbon. The (D) conductive particles may be particles in which a non-conductive core of glass, ceramic, plastic, or the like is coated with the above metal or carbon. Conductive particles in which a plastic core is coated with the above metal or carbon, or heat-fusible metal particles, are preferred because they deform when heated and pressurized, increasing the contact area between the conductive particles and the electrodes during connection and improving connection reliability. The (D) conductive particles may also be coated particles in which the surfaces of the above conductive particles are further coated with a polymer resin or the like. The coated particles can suppress short circuits caused by contact between particles when the particle content is increased and improve insulation between electrode circuits. The coated particles may be used alone or in combination with conductive particles that are not coated with a polymer resin or the like. The (D) conductive particles may be used alone or in combination.

The average particle size of the (D) conductive particles is preferably 1 to 18 μm from the viewpoint of excellent dispersibility and conductivity. The content of the (D) conductive particles is not particularly limited, but is preferably 0.1 to 30 vol%, and more preferably 0.1 to 10 vol%, of the total amount of the adhesive composition. A content of 0.1 vol% or more tends to improve conductivity, while a content of 30 vol% or less tends to sufficiently suppress short circuits. The above content (vol%) is determined based on the volume of each component of the adhesive composition at 23°C before curing. The volume of each component can be converted from mass to volume using specific gravity. The volume of each component can also be determined as the increase in volume when the component is placed in a measuring cylinder or the like containing a solvent (water, alcohol, etc.) that thoroughly wets the component without dissolving or swelling it.

The adhesive composition according to this embodiment may further contain at least one metal hydroxide or metal oxide for the purpose of preventing corrosion of the adherend. Specifically, the metal hydroxide is preferably at least one metal selected from the group consisting of aluminum hydroxide, magnesium hydroxide, and calcium hydroxide. Specifically, the metal oxide is preferably at least one metal selected from the group consisting of silicon oxide, aluminum oxide, magnesium oxide, antimony oxide, tin oxide, titanium oxide, manganese oxide, and zirconium oxide. From the viewpoints of excellent dispersibility in the adhesive composition, adhesive strength to the adherend, and corrosion prevention ability for the adherend, these metal hydroxides or metal oxides are preferably in the form of particles with a particle size of 10 μm or less.

The total content of the metal hydroxide and metal oxide is preferably 0.1 to 60 parts by mass, and more preferably 1 to 30 parts by mass, per 100 parts by mass of component (B). A content of 0.1 part by mass or more provides sufficient corrosion prevention, while a content of 60 parts by mass or less ensures sufficient dispersibility in the adhesive composition.

The adhesive composition according to this embodiment may further contain at least one compound selected from the group consisting of linear ether compounds and cyclic ether compounds as a component different from components (A) to (C) for the purpose of controlling the curing behavior of component (B). There are no particular restrictions on the linear ether compound or cyclic ether compound, as long as it has two or more ether groups per molecule, and known compounds can be used. Examples of linear ether compounds include polyethylene glycols such as diethylene glycol, triethylene glycol, and tetraethylene glycol; derivatives of these polyethylene glycols in which the terminal hydroxyl groups are functionalized with ether or ester bonds; monofunctional epoxy polymers such as ethylene oxide, propylene oxide, and cyclohexene oxide; crosslinked polyfunctional epoxies; monofunctional or polyfunctional oxetane polymers; and monofunctional or polyfunctional tetrahydrofuran polymers. Examples of cyclic ether compounds include cyclic ether compounds such as 12-crown-4-ether, 14-crown-4-ether, 15-crown-5-ether, 18-crown-6-ether, 21-crown-7-ether, 24-crown-8-ether, 30-crown-7-ether, benzo-18-crown-6-ether, dibenzo-18-crown-6-ether, and tribenzo-18-crown-6-ether; cyclized polyethylene glycol; and cyclized monofunctional epoxy polymers such as ethylene oxide, propylene oxide, and cyclohexene oxide. The chain ether compounds and cyclic ether compounds may be used alone or in combination.

Of the chain ether compounds and cyclic ether compounds, cyclic ether compounds are preferred from the viewpoint of excellent reaction control ability, and 12-crown-4-ether, 14-crown-4-ether, 15-crown-5-ether, 18-crown-6-ether, 21-crown-7-ether, 24-crown-8-ether, 30-crown-7-ether, benzo-18-crown-6-ether, dibenzo-18-crown-6-ether, and tribenzo-18-crown-6-ether are more preferred.

The total content of the chain ether compound and cyclic ether compound relative to component (A) is preferably 0.05 to 20 chemical equivalents, and more preferably 0.1 to 10 chemical equivalents. A content of 0.05 chemical equivalents or more makes it easier to achieve high adhesive strength, while a content of 20 chemical equivalents or less makes it easier to achieve favorable curing, resulting in a high crosslink density.

The adhesive composition according to this embodiment may further contain various known additives, provided that the effects of the invention are not impaired. Examples of additives include inorganic fillers; reinforcing agents; colorants; stabilizers (thermal stabilizers, weather resistance improvers, etc.); extenders; viscosity modifiers; tackifiers such as terpene-phenol copolymers, terpene resins, rosin derivatives, and alicyclic hydrocarbon resins; flame retardants; ultraviolet absorbers; antioxidants; discoloration inhibitors; antibacterial agents; antifungal agents; antioxidants; antistatic agents; plasticizers; lubricants; foaming agents; and mold release agents.

Colorants include dyes such as direct dyes, acid dyes, basic dyes, and metal complex dyes; inorganic pigments such as carbon black and mica; and organic pigments such as coupling azo, condensed azo, anthraquinone, thioindigo, dioxazone, and phthalocyanine. Stabilizers include compounds such as hindered phenols, hydrazines, phosphorus, benzophenones, benzotriazoles, and oxalic acid anilides. Examples of inorganic fillers include inorganic fibers such as glass fiber, asbestos fiber, carbon fiber, silica fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, basic magnesium sulfate fiber, boron fiber, stainless steel fiber, aluminum fiber, titanium fiber, copper fiber, brass fiber, and magnesium fiber; metal powders such as copper, iron, nickel, zinc, tin, lead, stainless steel, aluminum, gold, and silver; wood flour; salts such as aluminum silicate, carbonates, sulfates, phosphates, borates, borosilicates, aluminosilicates, and titanates; basic salts such as basic sulfates and basic carbonates; glass materials such as hollow glass spheres and glass flakes; silicon carbide; aluminum nitride; and minerals such as talc, clay, mullite, and cordierite.

If the adhesive composition according to this embodiment is liquid at room temperature (25°C; the same applies below), it can be used in a paste form. If the adhesive composition according to this embodiment is solid at room temperature, it may be used in a paste form by heating or using a solvent. There are no particular restrictions on the solvent, as long as it is non-reactive with the adhesive composition and exhibits sufficient solubility, but solvents with a boiling point of 50 to 150°C at atmospheric pressure are preferred. If the boiling point is 50°C or higher, evaporation at room temperature can be suppressed, making them suitable for use in open systems. If the boiling point is 150°C or lower, the solvent can be easily evaporated, ensuring sufficient reliability after bonding.

The adhesive composition according to this embodiment can be suitably used as a film-like adhesive composition. The film-like adhesive composition is obtained by forming the adhesive composition according to this embodiment into a film. The film-like adhesive composition can be obtained, for example, by applying a paste-like adhesive composition onto a resin film such as a PET (polyethylene terephthalate) film and drying it.

The adhesive composition according to this embodiment can be cured, for example, by heat treatment. The heating temperature is preferably 40°C to 250°C, more preferably 40°C to 180°C, and even more preferably 50°C to 150°C. A heating temperature of 40°C or higher makes it easier to ensure a sufficient curing rate, while a heating temperature of 250°C or lower can suppress undesired side reactions. The heating time is preferably 0.1 seconds to 10 hours, and more preferably 1 second to 1 hour. A heating time of 0.1 seconds or longer allows the curing reaction to proceed smoothly, while a heating time of 10 hours or less can improve the productivity of the cured product and suppress undesired side reactions.

The adhesive composition according to this embodiment can be bonded to an adherend by applying heat and pressure in combination. The heating temperature is not particularly limited, but a temperature of 50 to 190°C is preferred. The pressure is not particularly limited as long as it does not damage the adherend, but a pressure of 0.1 to 30 MPa is generally preferred. The heating and pressure are preferably applied for a period of 0.5 to 120 seconds.

The adhesive composition according to this embodiment can be used as an adhesive for bonding adherends of the same type together, and can also be used as an adhesive for bonding adherends of different types (for example, adherends with different thermal expansion coefficients) together. Specifically, the adhesive composition according to this embodiment can be used as an anisotropic conductive adhesive; an adhesive for circuit connection, typified by silver paste and silver film; an elastomer for CSP, an underfill material for CSP, an adhesive for semiconductor elements, typified by LOC tape, etc.

The adhesive composition according to this embodiment may have anisotropic conductivity. An adhesive composition having anisotropic conductivity (anisotropically conductive adhesive) contains, for example, (D) conductive particles. An adhesive composition having anisotropic conductivity may be an anisotropically conductive adhesive film (a film-like adhesive composition having anisotropic conductivity).

Figure 1 is a schematic cross-sectional view showing one embodiment of an anisotropically conductive adhesive film. As shown in Figure 1, the anisotropically conductive adhesive film 1 comprises a film-like adhesive component 2 and a plurality of conductive particles 3 disposed within the adhesive component 2.

The thickness of the anisotropically conductive adhesive film 1 is preferably 10 to 50 μm. If the thickness of the anisotropically conductive adhesive film 1 is 10 μm or more, when used as a circuit connecting material, the circuit connecting material will be sufficiently filled between the circuit electrodes. If the thickness of the anisotropically conductive adhesive film 1 is 50 μm or less, when used as a circuit connecting material, the circuit connecting material can be prevented from leaking out from between the circuit electrodes.

The adhesive composition according to this embodiment is suitable for use in circuit connections (circuit connection materials). Below, we will explain an example of a structure (connector, circuit connection structure, etc.) using an anisotropic conductive adhesive film 1 containing conductive particles 3, and a method for manufacturing such a structure.

Figure 2 is a schematic cross-sectional view showing one embodiment of a structure. As shown in Figure 2, the structure 10 includes a first circuit member 4 and a second circuit member 5 facing each other, and a circuit connecting member 6 that connects the first circuit member 4 and the second circuit member 5 between the first circuit member 4 and the second circuit member 5.

The first circuit member 4 comprises a first circuit board 41 and a first circuit electrode 42 formed on the main surface 41a of the first circuit board 41. In some cases, an insulating layer (not shown) may be formed on the main surface 41a of the first circuit board 41.

The second circuit member 5 includes a second circuit board 51 and a second circuit electrode 52 formed on the main surface 51a of the second circuit board 51. In addition, an insulating layer (not shown) may optionally be formed on the main surface 51a of the second circuit board 51.

There are no particular restrictions on the first circuit member 4 and the second circuit member 5, as long as they are members on which electrodes that require electrical connection are formed. Examples of members on which electrodes are formed (circuit members, etc.) include inorganic substrates such as semiconductors, glass, and ceramics; polyimide substrates such as TCP, FPC, and COF; substrates on which electrodes are formed on films such as polycarbonate, polyester, and polyethersulfone; printed wiring boards, and combinations of these may also be used.

The circuit connection member 6 is formed from the cured product of the anisotropic conductive adhesive film 1 and contains an insulating material 7, which is the cured product of the adhesive component 2, and conductive particles 3. The conductive particles 3 may be disposed not only between the opposing first circuit electrode 42 and second circuit electrode 52, but also between the main surface 41a of the first circuit board 41 and the main surface 51a of the second circuit board 51. In the structure 10, the first circuit electrode 42 and the second circuit electrode 52 are electrically connected via the conductive particles 3. That is, the conductive particles 3 are in contact with both the first circuit electrode 42 and the second circuit electrode 52.

As described above, in the structure 10, the opposing first circuit electrode 42 and second circuit electrode 52 are electrically connected via the conductive particles 3. This sufficiently reduces the connection resistance between the first circuit electrode 42 and the second circuit electrode 52. This allows for smooth current flow between the first circuit electrode 42 and the second circuit electrode 52, allowing the functions of the first circuit member 4 and the second circuit member 5 to be fully realized.

A method for manufacturing a structure according to this embodiment includes, for example, a step of placing the electrodes of two substrates, each having an electrode formed thereon, opposite each other, and a compression step of applying heat and pressure to an anisotropically conductive adhesive film disposed between the opposing electrodes of the two substrates. In the compression step, the anisotropically conductive adhesive film is connected to the electrodes, thereby electrically connecting the electrodes via the conductive particles in the anisotropically conductive adhesive film and bonding the substrates together via the anisotropically conductive adhesive film.

Next, the method for manufacturing the structure will be described in detail using Figure 3. Figure 3 is a schematic cross-sectional view showing one embodiment of the method for manufacturing the structure.

First, prepare the first circuit member 4 and the anisotropic conductive adhesive film 1 (see Figure 3(a)).

Next, the anisotropically conductive adhesive film 1 is placed on the main surface 41a of the first circuit member 4. If the anisotropically conductive adhesive film 1 is laminated on a support (not shown), the laminate is placed on the first circuit member 4 with the anisotropically conductive adhesive film 1 side of the laminate facing the first circuit member 4.

Then, the anisotropically conductive adhesive film 1 is pressed in the directions of arrows A and B in Figure 3(a) to temporarily connect the anisotropically conductive adhesive film 1 to the first circuit member 4 (see Figure 3(b)). At this time, heating may be performed in addition to the pressure application.

Next, as shown in FIG. 3(c), a second circuit member 5 is further placed on the anisotropically conductive adhesive film 1 placed on the first circuit member 4, with the second circuit electrode 52 facing the first circuit member 4 (i.e., with the first circuit electrode 42 and the second circuit electrode 52 facing each other). If the anisotropically conductive adhesive film 1 is laminated on a support (not shown), the support is peeled off and then the second circuit member 5 is placed on the anisotropically conductive adhesive film 1.

Then, while heating the anisotropically conductive adhesive film 1, it is pressed in the directions of arrows A and B in Figure 3(c). This hardens the anisotropically conductive adhesive film 1, completing the permanent connection. As a result, a structure 10 like the one shown in Figure 2 is obtained.

In the structure 10 obtained as described above, it is possible to bring the conductive particles 3 into contact with both the opposing first circuit electrode 42 and second circuit electrode 52, thereby sufficiently reducing the connection resistance between the first circuit electrode 42 and the second circuit electrode 52.

Furthermore, by applying pressure to the anisotropically conductive adhesive film 1 while heating, the adhesive component 2 hardens to form the insulating material 7 while the distance between the first circuit electrode 42 and the second circuit electrode 52 is sufficiently reduced, firmly connecting the first circuit member 4 and the second circuit member 5 via the circuit connecting member 6. In other words, in the structure 10, the circuit connecting member 6 is composed of a cured product of the circuit connecting material, which is the adhesive composition, and therefore the adhesive strength of the circuit connecting member 6 to the first circuit member 4 and the second circuit member 5 is sufficiently high, particularly under high-temperature and high-humidity conditions. Furthermore, in the structure 10, the sufficiently high adhesive strength is maintained for an extended period of time. Therefore, in the structure 10, changes in the distance between the first circuit electrode 42 and the second circuit electrode 52 over time are sufficiently suppressed, resulting in excellent long-term reliability of the electrical properties between the first circuit electrode 42 and the second circuit electrode 52.

In the above embodiment, the structure 10 is manufactured using an anisotropically conductive adhesive film 1, which is easy to handle. Therefore, the anisotropically conductive adhesive film 1 can be easily interposed between the first circuit member 4 and the second circuit member 5, facilitating connection between the first circuit member 4 and the second circuit member 5. However, an adhesive composition that is not in film form may be used instead of the anisotropically conductive adhesive film 1. Even in this case, the adhesive composition can be interposed between the first circuit member 4 and the second circuit member 5 by applying a solution obtained by dissolving the adhesive composition in a solvent to either the first circuit member 4 or the second circuit member 5 and drying it.

This embodiment provides the application of the adhesive composition to circuit connection. This embodiment provides the application of the adhesive composition for the manufacture of an adhesive for circuit connection. This embodiment provides the application of the adhesive composition for the manufacture of a structure.

The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples.

[Preparation of film-like adhesive composition]
Example 1
N-(α-phenylbenzyl)-4-cyanopyridinium antimony hexafluoride was mixed as component (A), an alicyclic epoxy compound (product name GT401, manufactured by Daicel Corporation) as component (B), and a phenoxy resin (product name YP-70, manufactured by Tohto Kasei Co., Ltd.) as component (C). The mixing ratios of the components are shown in Table 1. Furthermore, conductive particles were dispersed at 8 volume % to obtain an adhesive composition. The conductive particles used were polystyrene-based particles with an average particle size of 3 μm and a specific gravity of 2.5, each having a 0.2 μm-thick nickel layer on the surface and a 0.02 μm-thick metal layer on the outer surface of the nickel layer. The adhesive composition was then applied to a 40 μm-thick PET (polyethylene terephthalate) film using a coating device, and the resulting film-like adhesive composition had an adhesive layer thickness of 20 μm after hot air drying at 70°C for 5 minutes.

Example 2
A film-like adhesive composition was obtained in the same manner as in Example 1, except that naphthylmethyl-2-cyanopyridinium antimony hexafluoride was used as component (A). The mixing ratios of the components are shown in Table 1.

Example 3
A film-like adhesive composition was obtained in the same manner as in Example 1, except that cinnamyl-2-cyanopyridinium hexafluoride was used as component (A). The mixing ratios of the components are shown in Table 1.

Example 4
A film-like adhesive composition was obtained in the same manner as in Example 1, except that naphthylmethyldimethyl(4-bromophenyl)anilinium antimony hexafluoride was used as component (A). The mixing ratios of the components are shown in Table 1.

Example 5
A film-like adhesive composition was obtained in the same manner as in Example 1, except that benzyldimethylphenylammonium antimony hexafluoride synthesized according to the method described below was used as component (A). The mixing ratios of the components are shown in Table 1.
<Synthesis of benzyldimethylphenylammonium antimony hexafluoride>
A 10% aqueous solution of benzyldimethylphenylammonium chloride (6.19 g (25 mmol), manufactured by Tokyo Chemical Industry Co., Ltd.) and sodium hexafluoroantimonate (7.11 g (27.5 mmol), manufactured by Wako Pure Chemical Industries, Ltd.) was mixed and stirred for 1 hour. The solvent was removed under reduced pressure to obtain a precipitate. A small amount of water was added to the precipitate, and the mixture was filtered under reduced pressure. The collected filter cake was dried to obtain a solid. The obtained solid was confirmed to be benzyldimethylphenylammonium antimony hexafluoride by ¹ H-NMR spectrum and ¹⁹ F-NMR spectrum.

Example 6
A film-like adhesive composition was obtained in the same manner as in Example 1, except that benzyldimethylphenylammonium tetrakis(pentafluorophenyl)borate (BABF), synthesized according to the method described below, was used as component (A). The mixing ratios of each component are shown in Table 1.
<Synthesis of benzyldimethylphenylammonium tetrakis(pentafluorophenyl)borate (BABF)>
Benzyldimethylphenylammonium chloride (6.19 g (25 mmol), manufactured by Tokyo Chemical Industry Co., Ltd.) and a 10% aqueous solution of sodium tetrakis(pentafluorophenyl)borate (193.19 g (27.5 mmol), manufactured by Nippon Shokubai Co., Ltd.) were mixed and stirred for 1 hour. The solvent was removed under reduced pressure to obtain a precipitate. A small amount of water was added to the precipitate, which was then filtered under reduced pressure. The collected residue was dried to obtain a solid. The resulting solid was confirmed to be benzyldimethylphenylammonium tetrakis(pentafluorophenyl)borate (BABF) by ¹ H-NMR and ¹⁹ F-NMR spectroscopy.

Example 7
A film-like adhesive composition was obtained in the same manner as in Example 6, except that an oxetane compound (product name OXT-121, manufactured by Toagosei Co., Ltd.) was used as component (B). The mixing ratios of the components are shown in Table 1.

(Example 8)
A film-like adhesive composition was obtained in the same manner as in Example 6, except that an alicyclic epoxy compound (product name GT401, manufactured by Daicel Corporation) and an oxetane compound (product name OXT-121, manufactured by Toagosei Co., Ltd.) were used as component (B). The mixing ratios of the components are shown in Table 1.

(Comparative Example 1)
A film-like adhesive composition was obtained in the same manner as in Example 1, except that a sulfonium salt compound (product name: San-Aid SI-60, manufactured by Sanshin Chemical Industry Co., Ltd.) was used as component (A'). The mixing ratios of each component are shown in Table 2.

(Comparative Example 2)
A film-like adhesive composition was obtained in the same manner as in Comparative Example 1, except that an oxetane compound (product name OXT-121, manufactured by Toagosei Co., Ltd.) was used as component (B). The mixing ratios of the components are shown in Table 2.

(Comparative Example 3)
A film-like adhesive composition was obtained in the same manner as in Comparative Example 1, except that an alicyclic epoxy compound (product name GT401, manufactured by Daicel Corporation) and an oxetane compound (product name OXT-121, manufactured by Toagosei Co., Ltd.) were used as component (B). The mixing ratios of the components are shown in Table 2.

(Comparative Example 4)
A film-like adhesive composition was obtained in the same manner as in Comparative Example 1, except that a sulfonium salt compound (product name: San-Aid SI-80, manufactured by Sanshin Chemical Industry Co., Ltd.) was used as component (A'). The mixing ratios of each component are shown in Table 2.

(Comparative Example 5)
A film-like adhesive composition was obtained in the same manner as in Comparative Example 2, except that a sulfonium salt compound (product name: San-Aid SI-80, manufactured by Sanshin Chemical Industry Co., Ltd.) was used as component (A'). The mixing ratios of each component are shown in Table 2.

(Comparative Example 6)
A film-like adhesive composition was obtained in the same manner as in Comparative Example 3, except that a sulfonium salt compound (product name: San-Aid SI-80, manufactured by Sanshin Chemical Industry Co., Ltd.) was used as component (A'). The mixing ratios of each component are shown in Table 2.

[DSC Measurement]
Using an electronic balance (product name HR202, manufactured by A&D Co., Ltd.), 3.0±0.2 mg of the film-like adhesive composition obtained in each Example and Comparative Example was weighed out and used as a measurement sample. Using a differential scanning calorimetry (DSC) device (product name DSC7, manufactured by Perkin Elmer), measurements were carried out under a nitrogen gas flow at a measurement temperature range of 30°C to 250°C and a heating rate of 10°C/min, and the exothermic peak temperature (curing temperature) was calculated. The results are shown in Tables 1 and 2.

The above DSC measurement results show that in all cases of Examples 1 to 8 and Comparative Examples 1 to 6, the exothermic peak was 150°C or less, indicating that the adhesive composition cures at a relatively low temperature. In particular, in Examples 5, 6, and 8, which used CXC-1612 or CXC1821 as component (A) and the alicyclic epoxy compound GT401 as component (B), the exothermic peak was approximately 100°C, indicating that the adhesive composition cures at a relatively low temperature. It is also clear that the exothermic peaks of Examples 5, 6, and 8 are equivalent to those of Comparative Examples 1, 3, 4, and 6, which used a sulfonium salt compound as component (A') and the alicyclic epoxy compound GT401 as component (B).

[Evaluation of storage stability]
The infrared absorption spectrum of the film-like adhesive composition obtained in each Example and Comparative Example was measured, and the ratio R0 (functional group of component (B)/aromatic group) of the total peak area derived from the functional groups of component (B) (epoxy group (789 cm ^-1 ) and oxetanyl group (979 cm ^-1 )) to the total peak area derived from the aromatic group (1610 cm ^-1 ) was calculated. In addition, the film-like adhesive compositions obtained in each Example and Comparative Example were left in a thermostatic chamber at 40°C for 1 day. For these film-like adhesive compositions after leaving them at 40°C, the peak area ratio Rx (functional group of component (B)/aromatic group) in the infrared absorption spectrum was calculated in the same manner as above. The cure rate of the film-like adhesive composition was calculated using the following formula (I). The results are shown in Tables 1 and 2.
Curing rate (%) = (1-Rx/R0) x 100...(I)

The above evaluation of storage stability shows that in Examples 1 to 8, which used component (A), curing hardly progressed, and storage stability was good. On the other hand, when SI-60 or SI-80 was used as the sulfonium salt compound, as in Comparative Examples 1 to 6, curing progressed rapidly, and storage stability was poor in all cases.

[Production of connector]
The film-like adhesive compositions obtained in each Example and Comparative Example were transferred from a PET film to a glass substrate (Corning #1737, outer dimensions 38 mm x 28 mm, thickness 0.5 mm, having an ITO (indium tin oxide) wiring pattern (pattern width 50 μm, pitch 50 μm) on the surface) in a size of 2 × 20 mm. Under the mounting conditions (temperature and time) shown in Tables 3 and 4, a load of 80 MPa (equivalent to the bump area) was applied and heat and pressure were applied, and an IC chip (outer dimensions 1.7 mm x 17.2 mm, thickness 0.55 mm, bump size 50 μm x 50 μm, bump pitch 50 μm) was mounted. Furthermore, similar mounting was performed using the film-like adhesive compositions after evaluation of storage stability.

[Connection Resistance Measurement]
The resistance between adjacent circuits of the resulting connection body (the maximum value among the 14 terminals measured) was measured. The results are shown in Tables 3 and 4.

For all of Examples 1 to 8, when the connection resistance was measured after connection at 150°C for 5 seconds, good values of 10 Ω or less were observed both before and after the storage stability evaluation. Furthermore, for Examples 5, 6, and 8, when the connection resistance was measured after connection at 130°C for 5 seconds, good values of 10 Ω or less were observed both before and after the storage stability evaluation. On the other hand, for Comparative Examples 1 to 6, which used sulfonium salt compounds, no connection could be made after the storage stability evaluation.

1...anisotropic conductive adhesive film, 2...adhesive component, 3...conductive particles, 4...first circuit member, 5...second circuit member, 6...circuit connecting member, 7...insulating material, 10...structure, 41...first circuit board, 42...first circuit electrode, 51...second circuit board, 52...second circuit electrode.

Claims (11)

The composition contains an onium salt represented by the following general formula (1) and a cationically polymerizable substance,
the cationically polymerizable material comprises an alicyclic epoxy compound;
The adhesive composition, wherein the cationically polymerizable substance does not contain an oxetane compound.

[In formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted alkoxyl group, a substituted or unsubstituted aryloxy group, or a substituted or unsubstituted heterocyclic oxy group; R ¹ , R ² , R ³ and R ⁴ do not bond to each other to form a ring structure; and X ⁻ represents PF ₆ ⁻ , B(C ₆ F ₅ ) ₄ ⁻ , Ga(C ₆ F ₅ ) ₄ ⁻ , Ga(C ₆ F ₅ ) ₂ F ₂ ⁻ , Ga(C ₆ F ₅ )F ₃ ⁻ or C(CF ₃ SO ₂ ) ₃ ⁻ .] The adhesive composition of claim 1, wherein the onium salt is an anilinium salt. 3. The adhesive composition according to claim 1, wherein any one of R ¹ , R ² , R ³ and R ⁴ in general formula (1) is a substituted or unsubstituted benzyl group, a substituted or unsubstituted naphthylmethyl group, or a substituted or unsubstituted cinnamyl group. The adhesive composition according to any one of claims 1 to 3 , further comprising a film-forming polymer. The adhesive composition according to any one of claims 1 to 4 , further comprising conductive particles. The adhesive composition according to any one of claims 1 to 5 , which has anisotropic conductivity. The adhesive composition according to any one of claims 1 to 6 , which is used for connecting circuits. The adhesive composition according to any one of claims 1 to 6 , which is used as an adhesive for semiconductor elements. The adhesive composition according to any one of claims 1 to 8 , which is in the form of a paste. A film-like adhesive composition obtained by forming the adhesive composition according to any one of claims 1 to 9 into a film. A method for bonding adherends together using the adhesive composition according to any one of claims 1 to 9 or the film-like adhesive composition according to claim 10 .