JP7729201B2 - Adhesive composition, adhesive film for circuit connection, connection structure, and method for producing the connection structure - Google Patents

Description

The present invention relates to an adhesive composition, an adhesive film for circuit connection, a connection structure, and a method for manufacturing a connection structure.

Adhesive films for circuit connection, which consist of epoxy or acrylic adhesives with conductive particles dispersed in them, are known as circuit connection materials that electrically connect electrodes in the direction of pressure when opposing circuits are heated and pressurized. Adhesive films for circuit connection are used, for example, to electrically connect a TCP (Tape Carrier Package) or COF (Chip On Flex) equipped with a semiconductor that drives a liquid crystal display (LCD) to an LCD panel, or between a TCP or COF and a printed wiring board.

In recent years, in order to improve manufacturing efficiency, adhesives that use curing agents (polymerization initiators) that can be cured at low temperatures and in a short time have been investigated. For example, Patent Document 1 describes an adhesive composition that can be cured at relatively low temperatures (e.g., 150 to 170°C) and in a short time (e.g., within 10 seconds) by using a specific onium salt.

JP 2017-214472 A

However, when a curing agent that can cure at low temperatures and in a short time is used in an adhesive composition, the adhesive composition's ability to adhere to circuit components can decrease during storage, or the adhesive composition can stick to the release layer (e.g., substrate), leaving room for improvement.

The adhesive composition is also required to exhibit excellent resistance (connection resistance) even when the circuit connection structure is exposed to a high-temperature, high-humidity environment (e.g., 85°C, 85% RH) for an extended period (e.g., 250 hours) after connecting the circuit components.

The present invention therefore aims to provide an adhesive composition that maintains excellent adhesion to circuit components and easy peelability from the release layer even after storage (e.g., storage for 12 hours at 40°C), and that can ensure connection reliability between opposing electrodes even when the circuit connection structure is exposed to a high-temperature, high-humidity environment (e.g., 85°C, 85% RH) for an extended period of time after connecting the circuit components. Another object of the present invention is to provide an adhesive film for circuit connection, a connection structure, and a method for manufacturing a connection structure that use the adhesive composition.

One aspect of the present invention is an adhesive composition comprising a pyridinium salt represented by the following general formula (1), a cationically polymerizable compound, and a polymerization initiator, wherein the polymerization initiator contains an onium salt other than the pyridinium salt represented by the general formula (1):

[In formula (1), ^R1 represents a hydrogen atom or a substituted or unsubstituted alkyl group, ^R2 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, ^R3 represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, R represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group located at any of the 3-, 4-, and 5-positions, n represents an integer of 0 to 3, and ^X- represents a counter anion.]

The adhesive composition of one aspect of the present invention maintains excellent adhesion to circuit components and easy peelability from the release layer, even after storage (e.g., storage for 12 hours at 40°C). Furthermore, the adhesive composition of one aspect of the present invention can ensure connection reliability between opposing electrodes even when the circuit connection structure is exposed to a high-temperature, high-humidity environment (e.g., 85°C, 85% RH) for an extended period of time after connecting the circuit components.

R ¹ in the above general formula (1) may be a hydrogen atom.

In the above general formula (1), ^R2 and ^R3 may both be a substituted or unsubstituted alkyl group.

In the general formula (1), ^R2 and ^R3 may both be a methyl group.

The pyridinium salt may include 2,6-dimethylpyridinium p-toluenesulfonate or 2,4,6-trimethylpyridinium p-toluenesulfonate.

The above-mentioned cationically polymerizable compound may include an epoxy compound.

The polymerization initiator may contain a sulfonium salt or a pyridinium salt other than the pyridinium salt represented by general formula (1) above.

Another aspect of the present invention is an adhesive film for circuit connection, which contains the above-mentioned adhesive composition and conductive particles.

The above-mentioned adhesive film for circuit connection comprises a first adhesive layer and a second adhesive layer laminated on the first adhesive layer, and the first adhesive layer may contain the pyridinium salt represented by the above-mentioned general formula (1), the above-mentioned cationic polymerizable compound, the above-mentioned polymerization initiator, and the above-mentioned conductive particles.

Another aspect of the present invention is a connection structure comprising a first circuit member having a first electrode, a second circuit member having a second electrode, and a connection portion disposed between the first circuit member and the second circuit member and electrically connecting the first electrode and the second electrode to each other, the connection portion including a cured product of the above-described circuit connection adhesive film.

Another aspect of the present invention is a method for manufacturing a connection structure, comprising the steps of interposing the above-described circuit connection adhesive film between a first circuit member having a first electrode and a second circuit member having a second electrode, and thermocompression bonding the first circuit member and the second circuit member to electrically connect the first electrode and the second electrode to each other.

According to the present invention, even after storage (e.g., storage for 12 hours at 40°C), the adhesive composition maintains excellent adhesion to circuit components and easy peelability from the release layer. Furthermore, even after connecting the circuit components, the circuit connection structure can maintain connection reliability between opposing electrodes even when exposed to a high-temperature, high-humidity environment (e.g., 85°C, 85% RH) for an extended period of time.

1 is a schematic cross-sectional view showing one embodiment of an adhesive film for circuit connection. 1 is a schematic cross-sectional view showing one embodiment of an adhesive film for circuit connection. 1 is a schematic cross-sectional view showing one embodiment of a connection structure. 4A to 4C are schematic cross-sectional views showing a method for manufacturing the connection structure of FIG. 3.

Embodiments of the present invention are described in detail below. Note that the present invention is not limited to the following embodiments.

<Adhesive Composition>
Another embodiment of the present invention is an adhesive composition containing a pyridinium salt represented by the following general formula (1), a cationically polymerizable compound, and a polymerization initiator, wherein the polymerization initiator contains an onium salt other than the pyridinium salt represented by general formula (1). Hereinafter, the pyridinium salt represented by general formula (1) will be referred to as "pyridinium salt A."

[In formula (1), ^R1 represents a hydrogen atom or a substituted or unsubstituted alkyl group, ^R2 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, ^R3 represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, R represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group located at any of the 3-, 4-, and 5-positions, n represents an integer of 0 to 3, and ^X- represents a counter anion.]

Pyridinium salt A may be a stabilizer (polymerization inhibitor). By including pyridinium salt A in the adhesive composition, the adhesive composition maintains excellent adhesion to circuit components and easy peelability from the release layer, even after storage (e.g., storage for 12 hours at 40°C). Furthermore, by including pyridinium salt A in the adhesive composition, connection reliability between opposing electrodes can be ensured even when the circuit connection structure is exposed to a high-temperature, high-humidity environment (e.g., 85°C, 85% RH) for an extended period of time after connecting the circuit components.

R ¹ in general formula (1) may be a hydrogen atom or a methyl group, from the viewpoint of easily obtaining good storage stability, or may be a hydrogen atom.

At least one of ^R2 and ^R3 in general formula (1) may be a substituted or unsubstituted alkyl group, or both may be substituted or unsubstituted alkyl groups, or both may be unsubstituted alkyl groups. The number of carbon atoms in the alkyl group may be 1 to 4, 1 to 3, or 1 to 2. At least one of ^R2 and ^R3 in general formula (1) may be a methyl group, or both may be methyl groups.

R in general formula (1) may be a substituted or unsubstituted alkyl group from the viewpoint of easily achieving connection reliability between electrodes. The number of carbon atoms in the alkyl group may be 1 to 4, 1 to 3, or 1 to 2. R in general formula (1) may be a methyl group. R in general formula (1) may be located at at least the 3-position. n in general formula (1) may be 0 to 2, or 0 to 1.

Examples of the pyridinium cation of pyridinium salt A include 2,6-dimethylpyridinium cation, 2,6-diethylpyridinium cation, 2-methyl-6-ethylpyridinium cation, 2-ethyl-6-methylpyridinium cation, 2,4,6-trimethylpyridinium cation, 2,4,6-triethylpyridinium cation, and 2,4-dimethyl-6-ethylpyridinium cation. From the viewpoints of easily achieving excellent adhesion to circuit components, excellent peelability of the release layer, and excellent connection reliability, the pyridinium cation of pyridinium salt A may be 2,6-dimethylpyridinium cation or 2,4,6-trimethylpyridinium cation.

Examples of the anion of pyridinium salt A include p-toluenesulfonate, SbF ₆ ⁻ , PF ₆ ⁻ , PF _X (CF ₃ ) _6-X ⁻ (where X is an integer of 1 to 5), BF ₄ ⁻ , B(C ₆ F ₅ ) ₄ ⁻ , RSO ₃ ⁻ (where R is an alkyl group having 1 to 3 carbon atoms, or a substituted or unsubstituted aryl group), C(SO ₂ CF ₃ ) ₃ ⁻ , etc. The anion of pyridinium salt A may be p-toluenesulfonate from the viewpoints of excellent storage stability and ease of obtaining excellent connection reliability.

Pyridinium salt A may be a compound combining the above-mentioned pyridinium cation and the above-mentioned anion. From the viewpoint of easily achieving excellent adhesion to circuit components, excellent peelability of the release layer, and excellent connection reliability, pyridinium salt A may contain 2,6-dimethylpyridinium p-toluenesulfonate or 2,4,6-trimethylpyridinium p-toluenesulfonate.

From the viewpoint of easily achieving excellent adhesion to circuit components, excellent releasability of the release layer, and excellent connection reliability, the content of pyridinium salt A may be 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.02% by mass or more, or 0.025% by mass or more, based on the total mass of the adhesive composition. From the viewpoint of easily achieving excellent adhesion to circuit components, excellent releasability of the release layer, and excellent connection reliability, the content of pyridinium salt A may be 10% by mass or less, 5% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.15% by mass or less, based on the total mass of the adhesive composition. From these viewpoints, the content of pyridinium salt A may be 0.001 to 10% by mass or 0.01 to 1% by mass, based on the total mass of the adhesive composition.

From the viewpoint of easily achieving excellent adhesion to circuit components, excellent releasability of the release layer, and excellent connection reliability, the content of pyridinium salt A may be 0.005% by mass or more, 0.01% by mass or more, 0.02% by mass or more, 0.03% by mass or more, or 0.035% by mass or more, based on the total mass of the adhesive composition excluding the conductive particles. From the viewpoint of easily achieving excellent adhesion to circuit components, excellent releasability of the release layer, and excellent connection reliability, the content of pyridinium salt A may be 10% by mass or less, 5% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.15% by mass or less, based on the total mass of the adhesive composition excluding the conductive particles. From these viewpoints, the content of pyridinium salt A may be 0.005 to 10% by mass or 0.02 to 1% by mass, based on the total mass of the adhesive composition excluding the conductive particles.

From the viewpoint of easily achieving excellent adhesion to circuit components, excellent releasability of the release layer, and excellent connection reliability, the content of pyridinium salt A may be 0.01% by mass or more, 0.02% by mass or more, 0.03% by mass or more, or 0.04% by mass or more, based on the total mass of the adhesive composition excluding the conductive particles and filler. From the viewpoint of easily achieving excellent adhesion to circuit components, excellent releasability of the release layer, and excellent connection reliability, the content of pyridinium salt A may be 10% by mass or less, 5% by mass or less, 1% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.2% by mass or less, based on the total mass of the adhesive composition excluding the conductive particles and filler. From these viewpoints, the content of pyridinium salt A may be 0.01 to 10% by mass or 0.03 to 1% by mass, based on the total mass of the adhesive composition excluding the conductive particles and filler.

The cationically polymerizable compound may be, for example, a compound that reacts with a polymerization initiator by heating to form crosslinks. Examples of the cationically polymerizable compound include epoxy compounds and vinyl ether compounds. The cationically polymerizable compound may contain an epoxy compound. One type of cationically polymerizable compound may be used alone, or two or more types may be used in combination.

Examples of epoxy compounds include bisphenol A epoxy resins, bisphenol S epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, bisphenol F novolac epoxy resins, tetramethylbisphenol epoxy resins, 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bi-7-oxabicyclo[4,1,0]heptane), 3,4-epoxycyclohexylmethyl (meth)acrylate, (3,3',4,4'-diepoxy)bicyclohexyl, dicyclopentadiene dimethanol diglycidyl ether, and xylene novolac glycidyl ether. The epoxy compound may be at least one selected from the group consisting of bisphenol A epoxy resins, tetramethylbisphenol epoxy resins, dicyclopentadiene dimethanol diglycidyl ether, and xylene novolac glycidyl ether.

The content of the cationically polymerizable compound may be 20% by mass or more, 30% by mass or more, or 45% by mass or more, based on the total mass of the adhesive composition, from the viewpoint of ensuring the curability of the adhesive composition. The content of the cationically polymerizable compound may be 80% by mass or less, 70% by mass or less, or 65% by mass or less, based on the total mass of the adhesive composition, from the viewpoint of ensuring the formability of the adhesive composition. From these viewpoints, the content of the cationically polymerizable compound may be 20 to 80% by mass, based on the total mass of the adhesive composition.

The mass ratio of the content of the cationically polymerizable compound to the content of pyridinium salt A (content of cationically polymerizable compound/content of pyridinium salt A) may be 100 or more, 200 or more, or 300 or more from the viewpoint of ensuring the curability of the adhesive composition, and may be 2500 or less, 1500 or less, or 1300 or less from the viewpoint of easily achieving excellent adhesion to circuit components, excellent releasability of the release layer, and excellent connection reliability. From these viewpoints, the mass ratio of the content of the cationically polymerizable compound to the content of pyridinium salt A may be 100 to 2500.

The polymerization initiator includes an onium salt (hereinafter also simply referred to as an onium salt) other than the pyridinium salt represented by general formula (1) (pyridinium salt A). The onium salt may be a compound that generates an acid or the like upon heating to initiate polymerization. The polymerization initiator may be an onium salt such as a ^sulfonium _salt , a _{pyridinium salt} ^other than pyridinium salt A, a phosphonium salt, an ammonium salt, a diazonium salt, an iodonium salt, or an anilinium salt having an anion such as SbF ₆ ⁻ , PF ₆ ⁻ , PF _X (CF ₃ ) _6-X ⁻ (where X is an integer of 1 to 5), BF 4 ⁻ , B(C ₆ F ₅ ) ₄ ⁻ , RSO ₃ − (where R is an alkyl group having _{1 to} 3 carbon atoms or a substituted or unsubstituted aryl group), or C(SO 2 CF 3 ) 3 − . These may be used alone or in combination of two or more. The polymerization initiator may contain a sulfonium salt or a pyridinium salt other than the pyridinium salt A as the onium salt.

From the viewpoint of rapid curing, the polymerization initiator may be an onium salt having an anion containing boron as a constituent element. Examples of such onium salts include onium salts having BF ₄ ^- or BR ₄ ^- (R represents a phenyl group substituted with two or more fluorine atoms or two or more trifluoromethyl groups) as the anion. The anion containing boron as a constituent element may be BR ₄ ^- or tetrakis(pentafluorophenyl)borate.

Polymerization initiators include sulfonium salts such as 4-hydroxyphenylnaphthylmethylmethylsulfonium salt, 4-hydroxyphenylnaphthylmethyldimethylsulfonium salt, 3-methyl-2-butenyldimethylsulfonium salt, 3-methyl-2-butenyltetramethylenesulfonium salt, cinnamyldimethylsulfonium salt, and cinnamyltetramethylenesulfonium salt; and pyridinium salts such as 2-cyano-1-(4-methoxybenzyl)pyridinium salt, 2-chloro-1-(4-methoxybenzyl)pyridinium salt, 2-cyano-1-(2,4,6-trimethylbenzyl)pyridinium salt, and 2-chloro-1-(2,4,6-trimethylbenzyl)pyridinium salt. The polymerization initiator may be 4-hydroxyphenylnaphthylmethyldimethylsulfonium tetrakis(pentafluorophenyl)borate or 2-cyano-1-(2,4,6-trimethylbenzyl)pyridinium tetrakis(pentafluorophenyl)borate.

The content of the polymerization initiator may be 0.5% by mass or more, 1% by mass or more, or 3% by mass or more, based on the total mass of the adhesive composition, from the viewpoint of sufficiently promoting the curing reaction. The content of the polymerization initiator may be 25% by mass or less, 20% by mass or less, or 15% by mass or less, based on the total mass of the adhesive composition, from the viewpoint of improving the physical properties of the cured product. From these viewpoints, the content of the polymerization initiator may be 0.5 to 25% by mass, or 3 to 15% by mass, based on the total mass of the adhesive composition.

The mass ratio of the polymerization initiator content to the pyridinium salt A content (polymerization initiator content/pyridinium salt A content) may be 30 or more, 50 or more, or 80 or more from the viewpoint of sufficiently promoting the curing reaction, and may be 500 or less, 300 or less, or 200 or less from the viewpoint of easily achieving excellent adhesion to circuit components, excellent releasability of the release layer, and excellent connection reliability. From these viewpoints, the mass ratio of the polymerization initiator content to the pyridinium salt A content may be 30 to 500.

The content of the polymerization initiator may be 1 part by mass or more, 3 parts by mass or more, or 5 parts by mass or more, based on 100 parts by mass of the cationically polymerizable compound, from the viewpoint of sufficiently promoting the curing reaction. The content of the polymerization initiator may be 50 parts by mass or less, 40 parts by mass or less, or 30 parts by mass or less, based on 100 parts by mass of the cationically polymerizable compound, from the viewpoint of improving the physical properties of the cured product. From these viewpoints, the content of the polymerization initiator may be 1 to 50 parts by mass, or 5 to 30 parts by mass, based on 100 parts by mass of the cationically polymerizable compound.

The adhesive composition may contain conductive particles. The conductive particles are not particularly limited as long as they are conductive, and examples include metal particles made of metals such as gold, silver, palladium, nickel, copper, and solder; conductive carbon particles made of conductive carbon; and coated conductive particles having a core containing non-conductive glass, ceramic, plastic (polystyrene, etc.), and a coating layer containing the above metal or conductive carbon that coats the core. The conductive particles may be coated conductive particles because they can be easily deformed by heating and/or pressure, and can increase the contact area between the electrodes and the conductive particles when electrically connecting the electrodes, thereby further improving the conductivity between the electrodes.

The average particle diameter of the conductive particles may be 1 μm or more, 2 μm or more, or 2.5 μm or more, from the viewpoint of excellent dispersibility and conductivity. The average particle diameter of the conductive particles may be 20 μm or less, 15 μm or less, 10 μm or less, 8 μm or less, 6 μm or less, 5.5 μm or less, or 5 μm or less, from the viewpoint of ensuring insulation between adjacent electrodes. From these viewpoints, the average particle diameter of the conductive particles may be 1 to 20 μm, 1 to 15 μm, 1 to 10 μm, 1 to 8 μm, or 1 to 6 μm.

The average particle diameter of the conductive particles is determined by observing 300 conductive particles contained in the adhesive composition using a scanning electron microscope (SEM), measuring the particle diameter of each conductive particle, and averaging the particle diameters of the 300 conductive particles. Note that if the conductive particles are not spherical, the particle diameter of the conductive particles is the diameter of the circle circumscribing the conductive particles in the SEM observation image.

The particle density of the conductive particles in the adhesive composition may be 100 particles/ ^mm2 or more, 1000 particles/ ^mm2 or more, or 3000 particles/ ^mm2 or more, from the viewpoint of obtaining stable connection resistance. The particle density of the conductive particles in the adhesive composition may be 100,000 particles/mm2 or ^less , 50,000 particles/ ^mm2 or less, or 30,000 particles/ ^mm2 or less, from the viewpoint of ensuring insulation between adjacent electrodes. From these viewpoints, the particle density of the conductive particles in the adhesive composition may be 100 to 100,000 particles/ ^mm2 , 1000 to 50,000 particles/ ^mm2 , or 3000 to 30,000 particles/ ^mm2 .

The content of the conductive particles may be 10% by mass or more, 15% by mass or more, 20% by mass or more, or 25% by mass or more, based on the total mass of the adhesive composition. The content of the conductive particles may be 50% by mass or less, 40% by mass or less, or 30% by mass or less, based on the total mass of the adhesive composition. From these perspectives, the content of the conductive particles may be 10 to 50% by mass, based on the total mass of the adhesive composition.

The content of the conductive particles may be 10 parts by mass or more, 35 parts by mass or more, 60 parts by mass or more, or 90 parts by mass or more, based on 100 parts by mass of the cationically polymerizable compound. The content of the conductive particles may be 200 parts by mass or less, 150 parts by mass or less, 120 parts by mass or less, or 100 parts by mass or less, based on 100 parts by mass of the cationically polymerizable compound. From these perspectives, the content of the conductive particles may be 10 to 200 parts by mass, based on 100 parts by mass of the cationically polymerizable compound.

The adhesive composition may further contain a thermoplastic resin. The inclusion of a thermoplastic resin makes the adhesive composition easier to form into a film. Examples of thermoplastic resins include phenoxy resin, polyester resin, polyamide resin, polyurethane resin, polyester urethane resin, and acrylic rubber. These may be used alone or in combination of two or more.

The weight average molecular weight (Mw) of the thermoplastic resin may be, for example, 5,000 or more, 10,000 or more, 20,000 or more, or 40,000 or more, and may be 200,000 or less, 100,000 or less, 80,000 or less, or 60,000 or less. The weight average molecular weight of the thermoplastic resin is a value measured by gel permeation chromatography (GPC) and converted using a calibration curve based on standard polystyrene. From these perspectives, the weight average molecular weight (Mw) of the thermoplastic resin may be 5,000 to 200,000.

The content of the thermoplastic resin may be 1% by mass or more, 5% by mass or more, 10% by mass or more, or 15% by mass or more, based on the total mass of the adhesive composition. The content of the thermoplastic resin may be 40% by mass or less, 30% by mass or less, or 20% by mass or less, based on the total mass of the adhesive composition. From these perspectives, the content of the thermoplastic resin may be 1 to 40% by mass, based on the total mass of the adhesive composition.

The content of the thermoplastic resin may be 10 parts by mass or more, 30 parts by mass or more, or 60 parts by mass or more, based on 100 parts by mass of the cationically polymerizable compound. The content of the thermoplastic resin may be 150 parts by mass or less, 100 parts by mass or less, or 70 parts by mass or less, based on 100 parts by mass of the cationically polymerizable compound. From these perspectives, the content of the thermoplastic resin may be 10 to 150 parts by mass, based on 100 parts by mass of the cationically polymerizable compound.

The adhesive composition may further contain a coupling agent. By including a coupling agent, the adhesive composition can further improve its adhesive properties. The coupling agent may be a silane coupling agent, such as vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, and condensates thereof. These may be used alone or in combination.

The coupling agent content may be 0.5% by mass or more, 1% by mass or more, or 1.5% by mass or more, based on the total mass of the adhesive composition. The coupling agent content may be 15% by mass or less, 10% by mass or less, or 5% by mass or less, based on the total mass of the adhesive composition.

The amount of coupling agent may be 1 part by mass or more, 2 parts by mass or more, or 4 parts by mass or more, based on 100 parts by mass of the cationically polymerizable compound. The amount of coupling agent may be 30 parts by mass or less, 20 parts by mass or less, 10 parts by mass or less, or 6 parts by mass or less, based on 100 parts by mass of the cationically polymerizable compound.

The adhesive composition may further contain a filler. By including a filler, the adhesive composition can further improve connection reliability. Examples of fillers include non-conductive fillers (e.g., non-conductive particles). The filler may be either an inorganic filler or an organic filler.

Inorganic fillers include metal oxide particles such as silica particles, alumina particles, silica-alumina particles, titania particles, and zirconia particles; metal nitride particles, etc. These may be used alone or in combination of two or more types.

Examples of organic fillers include silicone particles, methacrylate-butadiene-styrene particles, acrylic-silicone particles, polyamide particles, and polyimide particles. These may be used alone or in combination of two or more.

From the viewpoint of improving film formability and the reliability of the connection structure, the filler may be an inorganic filler or silica particles. The silica particles may be crystalline silica particles or amorphous silica particles, and these silica particles may be synthetic products. The silica may be synthesized by a dry method or a wet method. The silica particles may include at least one type selected from the group consisting of fumed silica particles and sol-gel silica particles.

The silica particles may be surface-treated to improve dispersibility in the adhesive component. Surface-treated silica particles are, for example, silica particles in which the hydroxyl groups on the surface of the silica particles have been hydrophobized with a silane compound or a silane coupling agent. The surface-treated silica particles may be, for example, silica particles surface-treated with a silane compound such as an alkoxysilane compound, a disilazane compound, or a siloxane compound, or silica particles surface-treated with a silane coupling agent.

Examples of alkoxysilane compounds include methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, dimethoxydiphenylsilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, and 3,3,3-trifluoropropyltrimethoxysilane.

Examples of disilazane compounds include 1,1,1,3,3,3-hexamethyldisilazane, 1,3-diphenyltetramethyldisilazane, 1,3-bis(3,3,3-trifluoropropyl)-1,1,3,3-tetramethyldisilazane, and 1,3-divinyl-1,1,3,3-tetramethyldisilazane.

Siloxane compounds include tetradecamethylcycloheptasiloxane, decamethylcyclopentasiloxane, hexaphenylcyclosiloxane, octadecamethylcyclononasiloxane, hexadecamethylcyclooctasiloxane, dodecamethylcyclohexasiloxane, octaphenylcyclotetrasiloxane, hexamethylcyclotrisiloxane, heptaphenyldisiloxane, tetradecamethylhexasiloxane, dodecamethylpentasiloxane, hexamethyl Tyldisiloxane, decamethyltetrasiloxane, hexamethoxydisiloxane, octamethyltrisiloxane, octamethylcyclotetrasiloxane, 1,3-vinyltetramethyldisiloxane, 2,4,6-trimethyl-2,4,6-trivinylcyclotrisiloxane, 1,3-dimethoxy-1,1,3,3-tetraphenyldisiloxane, 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane, 1,3-dimethyl-1,3-diphenyl-1,3- Divinyldisiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 1,1,1,3,5,5,5,-heptamethyl-3-(3-glycidyloxypropyl)trisiloxane, 1,3,5-tris(3,3,3-trifluoropropyl)-1,3,5-trimethylcyclotrisiloxane, 1,1,1,3,5,5,5,-heptamethyl-3-[(trimethylsilyl)oxy]trisiloxane, 1,3-bis[2-(7 -oxabicyclo[4.1.0]heptan-3-yl)ethyl]-1,1,3,3-tetramethyldisiloxane, 1,1,1,5,5,5-hexamethyl-3-[(trimethylsilyl)oxy]-3-vinyltrisiloxane, 3-[[dimethyl(vinyl)silyl]oxy]-1,1,5,5-tetramethyl-3-phenyl-1,5-vinyltrisiloxane, octavinyloctasilsesquioxane, and octaphenyloctasilasilsesquioxane.

Silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(amino Examples of suitable silanes include N-(2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-ureidopropyltrialkoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-trimethoxysilylpropylsuccinic anhydride.

Silica particles that have been surface-treated with a silane compound or silane coupling agent may be further surface-treated with a silane compound such as 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, or trimethoxyphenylsilane to further hydrophobize the hydroxyl group residues on the surface of the silica particles.

The surface-treated silica particles may contain at least one selected from the group consisting of a reaction product (hydrolysis product) of silica and trimethoxyoctylsilane, a reaction product of silica and dimethylsiloxane, a reaction product of silicon dioxide or silica and dichloro(dimethyl)silane, a reaction product (hydrolysis product) of silica and bis(trimethylsilyl)amine, and a reaction product of silica and hexamethyldisilazane, or may contain at least one selected from the group consisting of a reaction product of silica and trimethoxyoctylsilane and a reaction product of silica and bis(trimethylsilyl)amine, from the viewpoint of easily controlling fluidity when the adhesive composition is used as an adhesive film for circuit connection and improving the mechanical properties and water resistance of the connection structure after compression.

The filler content may be 1% by mass or more, 5% by mass or more, or 10% by mass or more, based on the total mass of the adhesive composition. The filler content may be 50% by mass or less, 30% by mass or less, or 20% by mass or less, based on the total mass of the adhesive composition.

The filler content may be 10 parts by mass or more, 20 parts by mass or more, or 25 parts by mass or more, based on 100 parts by mass of the cationically polymerizable compound. The filler content may be 100 parts by mass or less, 60 parts by mass or less, or 40 parts by mass or less, based on 100 parts by mass of the cationically polymerizable compound.

The adhesive composition may further contain other components in addition to the components described above. Examples of other components include colorants and antioxidants.

<Adhesive film for circuit connection>
Another embodiment of the present disclosure is an adhesive film for circuit connection, which contains the above adhesive composition and conductive particles.

The content range of each component in the adhesive film for circuit connection may be the same as the content of each component based on the total mass of the adhesive composition. The content range of each component in the adhesive film for circuit connection based on 100 parts by mass of the cationically polymerizable compound may be the same as the content of each component based on 100 parts by mass of the cationically polymerizable compound in the adhesive composition.

Figure 1 is a schematic cross-sectional view showing an adhesive film for circuit connection according to one embodiment. As shown in Figure 1, in one embodiment, adhesive film for circuit connection 1 is composed of a single layer consisting of adhesive component 2 and conductive particles 3 dispersed in adhesive component 2. In one embodiment, adhesive component 2 contains at least a polymerization initiator, a cationically polymerizable compound, and pyridinium salt A. Adhesive film for circuit connection 1 may be in an uncured state or in a partially cured state.

The thickness of the circuit-connecting adhesive film may be, for example, 3 μm or more or 10 μm or more, and 30 μm or less or 20 μm or less.

The adhesive film for circuit connection may be a single layer, or may have a multilayer structure in which multiple layers are laminated. When the adhesive film for circuit connection has a multilayer structure, it may, for example, comprise a first adhesive layer and a second adhesive layer laminated on the first adhesive layer, and the first adhesive layer may contain a polymerization initiator, a cationically polymerizable compound, pyridinium salt A, and conductive particles. The second adhesive layer may contain a polymerization initiator, a cationically polymerizable compound, and pyridinium salt A. When the adhesive film for circuit connection has a multilayer structure, the content of each component in each layer may be within the content range based on the total mass of the adhesive composition described above, based on the total mass of each layer.

The adhesive film for circuit connection may have multiple regions with different types and contents of components. The adhesive film for circuit connection may, for example, have a first region and a second region disposed on the first region, and the first region may contain pyridinium salt A, a cationic polymerizable compound, a polymerization initiator, and conductive particles. That is, the adhesive film for circuit connection may have a first region formed from a first adhesive composition containing pyridinium salt A, a cationic polymerizable compound, a polymerization initiator, and conductive particles, and a second region formed from a second adhesive composition disposed on the first region. When the adhesive film for circuit connection has multiple regions, the content of each of the above components in each region may be within a range based on the total mass of the region and the total mass of the adhesive composition.

FIG. 2 is a schematic cross-sectional view showing one embodiment of an adhesive film for circuit connection having two or more layers. The adhesive film for circuit connection 1 has a two-layer structure comprising a layer 1A containing conductive particles 3A (a first adhesive layer consisting of adhesive component 2A and conductive particles 3A dispersed in adhesive component 2A) and a layer 1B not containing conductive particles (a second adhesive layer consisting of adhesive component 2B). The first adhesive layer 1A may be a layer consisting of an adhesive composition (first adhesive composition) containing pyridinium salt A, a cationic polymerizable compound, a polymerization initiator, and conductive particles. The second adhesive layer 1B may be a layer consisting of an adhesive composition (second adhesive composition) containing pyridinium salt A, a cationic polymerizable compound, and a polymerization initiator. The types, contents, etc. of the components contained in the second adhesive layer 1B may be the same as or different from those in the first adhesive layer 1A. The first adhesive layer 1A and second adhesive layer 1B of the circuit connection adhesive film 1 may each be in an uncured state or in a partially cured state.

The thickness of the first adhesive layer 1A may be, for example, 3 μm or more or 5 μm or more, and 15 μm or less or 10 μm or less. The thickness of the second adhesive layer 1B may be, for example, 3 μm or more or 10 μm or more, and 20 μm or less or 15 μm or less. The thickness of the first adhesive layer 1A may be the same as or different from the thickness of the second adhesive layer 1B. The ratio of the thickness of the first adhesive layer 1A to the thickness of the second adhesive layer 1B (thickness of the first adhesive layer 1A/thickness of the second adhesive layer 1B) may be 0.1 or more or 0.3 or more, and 1.5 or less or 0.5 or less.

The adhesive film for circuit connection may be provided on a substrate (e.g., a PET film). A substrate-attached adhesive film for circuit connection can be produced, for example, by applying an adhesive composition containing conductive particles onto a substrate using a knife coater, roll coater, applicator, comma coater, die coater, or the like.

The above-mentioned adhesive film for circuit connection may be an adhesive film with anisotropic conductivity (anisotropic conductive film), or it may be an adhesive film without anisotropic conductivity.

<Connection structure>
Another embodiment of the present disclosure is a connection structure comprising: a first circuit member having a first electrode; a second circuit member having a second electrode; and a connection portion disposed between the first circuit member and the second circuit member and electrically connecting the first electrode and the second electrode to each other, wherein the connection portion comprises a cured product of the above-described adhesive film for circuit connection.

Figure 3 is a schematic cross-sectional view showing one embodiment of a connection structure. As shown in Figure 3, the structure 10 includes a first circuit member 4 and a second circuit member 5 facing each other, and a connection portion 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 includes a first circuit board 41 and a first electrode 42 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 electrode 52 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; and printed wiring boards, and a combination of these may also be used.

The connection portion 6 contains a cured product of the circuit connection adhesive film 1, an insulating material 7 which is a cured product of the adhesive component 2, and conductive particles 3. The conductive particles 3 may be disposed not only between the opposing first electrode 42 and second 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 30, the first electrode 42 and the second electrode 52 are electrically connected via the conductive particles 3. That is, the conductive particles 3 are in contact with both the first electrode 42 and the second electrode 52.

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

<Method of manufacturing connection structure>
Another embodiment of the present disclosure is a method for manufacturing a connection structure, comprising the steps of interposing the above-mentioned adhesive film for circuit connection between a first circuit member having a first electrode and a second circuit member having a second electrode, and thermocompression bonding the first circuit member and the second circuit member to electrically connect the first electrode and the second electrode to each other.

Figure 4 is a schematic cross-sectional view showing one embodiment of a method for manufacturing a connection structure. As shown in Figure 4(a), first, a first circuit member 4 and an adhesive film for circuit connection 1 are prepared. Next, the adhesive film for circuit connection 1 is placed on the main surface 41a of the first circuit member 4. If the adhesive film for circuit connection 1 is laminated on a substrate (not shown), the laminate is placed on the first circuit member 4 with the adhesive film for circuit connection 1 side of the substrate facing the first circuit member 4. If the adhesive film for circuit connection 1 has a first adhesive layer 1A and a second adhesive layer 1B as shown in Figure 2, the first adhesive layer side may be placed in contact with the main surface 41a of the first circuit member 4 to increase the number of conductive particles captured between the opposing electrodes.

Then, the adhesive film 1 for circuit connection is pressed in the directions of arrows A and B in Figure 4(a) to temporarily connect the adhesive film 1 for circuit connection to the first circuit member 4 (see Figure 4(b)). At this time, heat may be applied in addition to the pressure.

Next, as shown in FIG. 4(c), a second circuit member 5 is placed on the circuit connection adhesive film 1 placed on the first circuit member 4, with the second electrode 52 facing the first circuit member 4 (i.e., the first electrode 42 and the second electrode 52 are arranged opposite each other, and the circuit connection adhesive film 1 is interposed between the first circuit member 4 and the second circuit member 5). If the circuit connection adhesive film 1 is laminated on a substrate (not shown), the substrate is peeled off and then the second circuit member 5 is placed on the circuit connection adhesive film 1.

Then, the circuit connection adhesive film 1 is thermocompressed in the directions of arrows A and B in Figure 4(c). This hardens the circuit connection adhesive film 1, completing the electrical connection between the first electrode 42 and the second electrode 52. As a result, a structure 10 like the one shown in Figure 3 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 electrode 42 and second electrode 52, thereby sufficiently reducing the connection resistance between the first electrode 42 and the second electrode 52.

By applying pressure to the circuit connection adhesive film 1 while heating it, the adhesive component 2 hardens and becomes an insulating material 7 while the distance between the first electrode 42 and the second electrode 52 is kept sufficiently small, firmly connecting the first circuit member 4 and the second circuit member 5 via the connection portion 6. Furthermore, the structure 10 maintains a sufficiently high adhesive strength for an extended period of time. Therefore, the structure 10 sufficiently suppresses changes in the distance between the first electrode 42 and the second electrode 52 over time, resulting in excellent long-term reliability of the electrical properties between the first electrode 42 and the second electrode 52.

The present invention will be explained in detail below using examples. However, the present invention is not limited to the following examples.

<Preparation of conductive particles>
A nickel layer was formed on the surface of the cross-linked polystyrene particles to a thickness of 0.15 μm, thereby obtaining conductive particles with an average particle size of 3.3 μm, a maximum particle size of 3.5 μm, and a specific gravity of 2.7.

<Synthesis of phenoxy resin a>
In a 3000 mL three-neck flask equipped with a Dimroth condenser, a calcium chloride tube, and a Teflon (registered trademark) stirring rod connected to a stirring motor, 45 g of 4,4'-(9-fluorenylidene)-diphenol (Sigma-Aldrich Japan Co., Ltd.) and 50 g of 3,3',5,5'-tetramethylbiphenol diglycidyl ether (trade name: YX-4000H, Mitsubishi Chemical Corporation) were dissolved in 1000 mL of N-methylpyrrolidone to form a reaction solution. 21 g of potassium carbonate was added to this reaction solution, and the mixture was stirred for 3 hours while heated to 110°C using a mantle heater. The stirred reaction solution was added dropwise to a beaker containing 1000 mL of methanol, and the resulting precipitate was collected by suction filtration. The collected precipitate was further washed three times with 300 mL of methanol to obtain 75 g of phenoxy resin a. The molecular weight of the obtained phenoxy resin a was measured using a high performance liquid chromatograph (GP8020 manufactured by Tosoh Corporation, column: Gelpack GL-A150S and GLA160S manufactured by Hitachi Chemical Co., Ltd., eluent: tetrahydrofuran, flow rate: 1.0 mL/min), and the values were Mn=15769, Mw=38045, and Mw/Mn=2.413, calculated in terms of polystyrene.

<Synthesis of polymerization initiator a>
100 mL of acetonitrile and a stirrer tip were placed in a 300 mL Erlenmeyer flask and placed on a magnetic stirrer. 12.5 g of 2-cyanopyridine (120 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.), 16.8 g of 2,4,6-trimethylbenzyl chloride (100 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.), and 17.8 g of sodium iodide (119 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.) were added to the acetonitrile in the 300 mL Erlenmeyer flask, and the mixture was allowed to react at room temperature (25°C) for 24 hours to obtain crystals. The resulting crystals were filtered through a glass filter, and the crystals on the glass filter were washed with acetone and distilled water and then vacuum-dried to obtain 29.1 g of 2-cyano-1-(2,4,6-trimethylbenzyl)pyridinium iodide (yield 80%).
200 mL of dichloromethane and a stirrer tip were placed in a 500 mL Erlenmeyer flask and placed on a magnetic stirrer. 3.6 g (10 mmol) of the obtained 2-cyano-1-(2,4,6-trimethylbenzyl)pyridinium iodide was added to a 500 mL Erlenmeyer flask and suspended in dichloromethane in the 500 mL Erlenmeyer flask. 72 g (10.2 mmol) of an aqueous sodium tetrakis(pentafluorophenyl)borate solution (solid content 10%), manufactured by Nippon Shokubai Co., Ltd., and 50 mL of distilled water were added to the 500 mL Erlenmeyer flask and stirred at room temperature (25°C) for 3 hours to carry out a salt exchange reaction. After stirring, the organic layer was washed with distilled water, concentrated, and vacuum dried to obtain 8.0 g of compound (yield 88%). The resulting compound was designated polymerization initiator a.

The resulting compound was measured by nuclear magnetic resonance spectroscopy ( ¹ H-NMR, JNM-ECX400II, manufactured by JEOL Ltd.), and the following spectral data was obtained. From the ¹ H-NMR measurement, it was confirmed that the resulting compound was 2-cyano-1-(2,4,6-trimethylbenzyl)pyridinium tetrakis(pentafluorophenyl)borate having the following structure:
^1H -NMR (400MHz, _CD3 OD), δ: 2.26 (s, 6H), 2.32 (s, 3H), 6.10 (s, 2H), 7.08 (s, 2H), 8.25 (td, 1H, J = 3.2, 6.4Hz) 8.43 (d, 1H, J = 6.4Hz) 8.77-8.82 (m, 2H)

<Preparation of Adhesive Film for Circuit Connection>
A first adhesive composition for forming a first adhesive layer and a second adhesive composition for forming a second adhesive layer were prepared by mixing the components in the amounts (unit: parts by mass) shown in Tables 1 and 2. Details of each component in Tables 1 and 2 are as follows, and the amount of each component in the tables represents the amount of non-volatile content.
Polymerization initiator A1: aromatic sulfonium salt (product name: SI-60L, manufactured by Sanshin Chemical Industry Co., Ltd.)
A2: Polymerization initiator a prepared above
Stabilizers B1: 2,6-dimethylpyridinium p-toluenesulfonate B2: 2,4,6-trimethylpyridinium p-toluenesulfonate B3: Pyridinium p-toluenesulfonate B4: 4-hydroxyphenyldimethylsulfonium methylsulfate Cationic polymerizable compound C1: Dicyclopentadiene dimethanol diglycidyl ether (trade name: EP-4088S, manufactured by ADEKA Corporation)
C2: Bisphenol A epoxy resin (product name: YL980, manufactured by Mitsubishi Chemical Corporation)
C3: Tetramethylbiphenol type epoxy resin (product name: YX4000, manufactured by Mitsubishi Chemical Corporation)
C4: Xylene-novolac glycidyl ether (product name: YX7700, manufactured by Mitsubishi Chemical Corporation)
C5: Bisphenol A solid epoxy resin (product name: jER1010, manufactured by Mitsubishi Chemical Corporation)
Thermoplastic resin D: Phenoxy resin a prepared above
Conductive particles E: Conductive particles prepared as above Coupling agent F: 3-glycidoxypropyltrimethoxysilane (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.)
Filler G1: Surface-treated silica fine particles (hydrolysis product of trimethoxyoctylsilane and silica, trade name: Aerosil R805, manufactured by Evonik Industries AG, diluted with an organic solvent to a non-volatile content of 10% by mass)
G2: Surface-treated silica particles (hydrolysis product of silica and bis(trimethylsilyl)amine)

The second adhesive composition was applied onto a substrate (PET film) to form a second adhesive layer on the substrate. The first adhesive composition was then applied onto the second adhesive layer to form a first adhesive layer, producing an adhesive film for circuit connection in which the first adhesive layer, second adhesive layer, and substrate were laminated in this order. The thickness of the first adhesive layer in each of the adhesive films for circuit connection in Examples 1 to 4 and Comparative Examples 1 to 7 was 7 μm, and the thickness of the second adhesive layer was 11 μm.

<Production of connection structure>
As a first circuit member, an alkali-free glass substrate (OA-11, manufactured by Nippon Electric Glass Co., Ltd., outer dimensions: 38 mm × 28 mm, thickness: 0.3 mm) on the surface of which an AlNd (100 nm) / Mo (50 nm) / ITO (100 nm) wiring pattern (pattern width: 19 μm, inter-electrode space: 5 μm) was formed was prepared. As a second circuit member, an IC chip (outer dimensions: 0.9 mm × 20.3 mm, thickness: 0.3 mm, bump electrode size: 70 μm × 12 μm, inter-electrode space: 12 μm, bump electrode thickness: 8 μm) in which bump electrodes were arranged in two rows in a staggered pattern was prepared.

<ACF adhesion>
Connection structures were produced using the adhesive films for circuit connection of Examples 1 to 4 and Comparative Examples 1 to 7. A first adhesive layer of a 1.5 mm x 25 mm adhesive film for circuit connection was placed on a first circuit member. Using a thermocompression bonding device (LD-06, manufactured by Ohashi Manufacturing Co., Ltd.) consisting of a ceramic heater stage and a tool (8 mm x 50 mm), heating and pressure were applied for 2 seconds at 30°C and 0.98 MPa (10 kgf/cm ² ) to attach the anisotropic conductive film to the first circuit member. At this time, adhesion was evaluated as 'good' when the adhesive film for circuit connection adhered to the first circuit member, and 'bad' when it did not adhere. Next, for those films for which adhesion was evaluated as 'good', the substrate on the side of the adhesive film for circuit connection opposite the first circuit member was peeled off with tweezers. At this time, the peelability was evaluated as ◯ when the adhesive film for circuit connection peeled from the substrate but not from the first circuit member, and x when the adhesive film for circuit connection did not peel from the substrate but peeled from the first circuit member. The evaluation results are shown in Tables 3 and 4. In addition, a life test was performed by storing the adhesive film for circuit connection in a thermostatic chamber at 40°C for 12 hours, and the adhesion and peelability of the adhesive film for circuit connection after the life test were evaluated using the same methods. The evaluation results are shown in Tables 3 and 4.

<Evaluation of connection resistance>
For those whose adhesion was evaluated as good, the bump electrodes of the first circuit member and the circuit electrodes of the second circuit member were aligned. Next, using a heat tool (8 mm x 45 mm), the second adhesive layer of the circuit connection adhesive film was attached to the second circuit member via a 50 μm thick PTFE sheet as a buffer material by heating and pressing at 120°C for 5 seconds at 60 MPa on a base heated to 80°C, thereby producing a connection structure. The temperature was the maximum measured temperature of the circuit connection adhesive film, and the pressure was a value calculated relative to the total area of the surface of the bump electrodes of the second circuit member facing the first circuit member.

The connection resistance of the connection structure was measured at 14 locations using the four-probe measurement method immediately after fabrication (initial) and after a high-temperature, high-humidity test, and evaluated as the maximum connection resistance value (maximum resistance value). The high-temperature, high-humidity test was conducted by storing the connection structure in a high-temperature, high-humidity chamber at a temperature of 85°C and a humidity of 85% RH for 100 hours. A multimeter (MLR21, manufactured by ETAC) was used to measure the connection resistance. In addition, a life test was conducted by storing the circuit connection adhesive film in a constant-temperature chamber at a temperature of 40°C for 12 hours, and a connection structure was fabricated using the circuit connection adhesive film that had been subjected to the life test. The connection resistance of the connection structure fabricated using the circuit connection adhesive film that had been subjected to the life test immediately after fabrication (initial) and the connection resistance of the connection structure fabricated using the circuit connection adhesive film that had been subjected to the life test after the high-temperature, high-humidity test were measured using the same method. The measurement results are shown in Tables 3 and 4.

1...adhesive film for circuit connection, 1A...first adhesive layer, 1B...second adhesive layer, 2, 2A, 2B...adhesive component, 3, 3A...conductive particles, 4...first circuit member, 5...second circuit member, 6...connection portion, 7...insulating material, 10...structure, 41...first circuit board, 42...first electrode, 51...second circuit board, 52...second electrode.

Claims (10)

The composition contains a pyridinium salt represented by the following general formula (1), a cationic polymerizable compound, and a polymerization initiator,
the pyridinium salt comprises 2,6-dimethylpyridinium p-toluenesulfonate or 2,4,6-trimethylpyridinium p-toluenesulfonate;
The adhesive composition, wherein the polymerization initiator contains an onium salt other than the pyridinium salt represented by the general formula (1).

[In formula (1), ^R1 represents a hydrogen atom or a substituted or unsubstituted alkyl group, ^R2 represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, ^R3 represents a hydrogen atom, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, R represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group located at any of the 3-, 4-, and 5-positions, n represents an integer of 0 to 3, and ^X- represents a counter anion.] The adhesive composition according to claim 1 , wherein R ¹ in the general formula (1) is a hydrogen atom. The adhesive composition according to claim 1 or 2, wherein ^R2 and ^R3 in the general formula (1) are both substituted or unsubstituted alkyl groups. The adhesive composition according to any one of claims 1 to 3, wherein R ² and R ³ in the general formula (1) are both methyl groups. The adhesive composition according to any one of claims 1 to 4 , wherein the cationically polymerizable compound comprises an epoxy compound. The adhesive composition according to any one of claims 1 to 5 , wherein the polymerization initiator comprises a sulfonium salt or a pyridinium salt other than the pyridinium salt represented by general formula (1). An adhesive film for circuit connection, comprising the adhesive composition according to any one of claims 1 to 6 and conductive particles. a first adhesive layer and a second adhesive layer laminated on the first adhesive layer;
8. The adhesive film for circuit connection according to claim 7 , wherein the first adhesive layer contains the pyridinium salt represented by general formula (1), the cationically polymerizable compound, the polymerization initiator, and the conductive particles. a first circuit member having a first electrode;
a second circuit member having a second electrode;
a connection portion disposed between the first circuit member and the second circuit member, electrically connecting the first electrode and the second electrode to each other;
A connection structure, wherein the connection portion comprises a cured product of the adhesive film for circuit connection according to claim 7 or 8 . 9. A method for manufacturing a connection structure, comprising the steps of: interposing the adhesive film for circuit connection according to claim 7 or 8 between a first circuit member having a first electrode and a second circuit member having a second electrode; and thermocompression bonding the first circuit member and the second circuit member together to electrically connect the first electrode and the second electrode to each other.