JP7739173B2 - Adhesive film for circuit connection, method for manufacturing circuit connection structure, and adhesive film storage set - Google Patents

Description

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

Conventionally, various adhesive materials have been used to make circuit connections. For example, anisotropically conductive circuit connection adhesive films with conductive particles dispersed in the adhesive have been used as adhesive materials for connecting liquid crystal displays and tape carrier packages (TCPs), flexible printed circuit boards (FPCs) and TCPs, or FPCs and printed wiring boards. Specifically, circuit components are bonded together by the circuit connection portion formed by the circuit connection adhesive film, and electrodes on the circuit components are electrically connected together via the conductive particles in the circuit connection portion, resulting in a circuit connection structure.

Adhesive films for circuit connection contain, for example, an adhesive component containing a thermosetting resin or the like, and optionally conductive particles, and are formed as an adhesive layer on a substrate such as a polyethylene terephthalate (PET) film. Furthermore, adhesive films may be used in the form of a reel, where the original film is cut into tapes of a width appropriate for the application, and the tapes are wound around a core to form a wound body (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2003-34468

When connecting a driver IC or the like to an LCD module using an adhesive film, the adhesive film was traditionally first transferred to the glass panel. However, in recent years, due to factors such as a movement to reduce the amount of adhesive film used in order to cut LCD manufacturing costs and the demand for narrow-frame panel designs, a manufacturing method has been adopted in which the adhesive film is first attached to a flexible substrate such as COF or FPC.

However, when using conventional adhesive films, it was difficult to efficiently capture conductive particles between circuit electrodes, resulting in problems such as a deterioration in conductivity reliability and an increased risk of short circuits due to the accumulation of conductive particles that were not captured between the circuits.

The present invention has been made to solve the above-mentioned problems, and aims to provide an adhesive film for circuit connection that can obtain a circuit connection structure with excellent connection reliability between opposing circuit components, even when the film is first attached to a flexible substrate to make the circuit connection, as well as a method for manufacturing a circuit connection structure using the same, and an adhesive film storage set.

One aspect of the present invention is an adhesive film for circuit connection comprising a peelable support film, a first adhesive layer containing conductive particles provided on the support film, and a second adhesive layer laminated on the first adhesive layer, wherein the thickness of the first adhesive layer is 0.1 to 1.0 times the average particle size of the conductive particles.

This adhesive film for circuit connection allows for a circuit connection structure with excellent connection reliability between opposing circuit components, even when the film is first attached to a flexible substrate for circuit connection. It is preferable that 90% or more of the conductive particles in the first adhesive layer are separated from other conductive particles.

The first adhesive layer may consist of a cured product of a first curable composition, and the first curable composition may contain a radically polymerizable compound having a radically polymerizable group.

The second adhesive layer may comprise a second curable composition, which may contain a radically polymerizable compound having a radically polymerizable group.

A method for manufacturing a circuit connection structure according to one aspect of the present invention includes the steps of interposing the first adhesive layer and the second adhesive layer of 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 thermocompressing the first circuit member and the second circuit member to electrically connect the first electrode and the second electrode to each other.

This method makes it possible to obtain a circuit connection structure with excellent connection reliability between opposing circuit components, even when the circuit connection is made by first attaching the circuit connection adhesive film to the flexible substrate.

That is, the method for manufacturing a circuit connection structure according to the present invention may include a step in which the first circuit member has a flexible substrate and the circuit connection adhesive film is attached to the first circuit member so that the second adhesive layer contacts the first circuit member.

An adhesive film storage set according to one aspect of the present invention comprises the above-described circuit connection adhesive film and a storage member for storing the adhesive film, wherein the storage member has a visible portion that allows the interior of the storage member to be viewed from the outside, and the transmittance of light at a wavelength of 365 nm at the visible portion is 10% or less.

The present invention provides an adhesive film for circuit connection that can obtain a circuit connection structure with excellent connection reliability between opposing circuit components, even when the film is first attached to a flexible substrate to make the circuit connection, as well as a method for manufacturing a circuit connection structure using the same, and an adhesive film storage set.

1 is a schematic cross-sectional view showing one embodiment of an adhesive film for circuit connection according to the present invention. 3A to 3C are schematic cross-sectional views showing steps in a method for manufacturing a circuit connection structure. FIG. 3 is a schematic cross-sectional view showing a laminate obtained through the steps of FIG. 2 . 3 is a schematic cross-sectional view showing a step subsequent to that shown in FIG. 2. FIG. FIG. 5 is a schematic cross-sectional view showing a circuit connection structure obtained through the steps of FIG. 4. 2 is a schematic diagram showing a manufacturing process of the adhesive film for circuit connection shown in FIG. 1. FIG. 10 is a schematic diagram showing a magnetic field application step. FIG. 2 is a schematic cross-sectional view showing the state of the adhesive film for circuit connection after undergoing a magnetic field application step and a drying step. FIG. 8 is a schematic cross-sectional view showing a lamination step subsequent to FIG. 7. 1 is a perspective view showing an embodiment of an adhesive film storage set according to the present invention.

Embodiments of the present invention will be described in detail below, with reference to the drawings where necessary. Note that the upper and lower limits individually stated in this specification can be combined in any way. Furthermore, in this specification, "(meth)acrylate" means at least one of an acrylate and its corresponding methacrylate. The same applies to other similar expressions such as "(meth)acryloyl."

<Adhesive film for circuit connection>
Fig. 1 is a schematic cross-sectional view showing an adhesive film for circuit connection according to one embodiment. As shown in Fig. 1, the adhesive film for circuit connection 11 (hereinafter also referred to simply as "adhesive film 11") comprises a peelable support film 12, a first adhesive layer 13 provided on the support film 12, and a second adhesive layer 14 laminated on the first adhesive layer 13. The first adhesive layer 13 contains conductive particles P.

In the adhesive film 11, conductive particles P are dispersed in the first adhesive layer 13. Therefore, the adhesive film 11 is an anisotropically conductive adhesive film with anisotropic conductivity. The adhesive film 11 is used to electrically connect the first electrode and the second electrode to each other by interposing the first adhesive layer and the second adhesive layer between a first circuit member having a first electrode and a second circuit member having a second electrode, and thermocompressing the first circuit member and the second circuit member.

Furthermore, when the circuit component to be connected has a flexible substrate, the circuit connection adhesive film 11 can be attached to the first circuit component so that the second adhesive layer contacts the first circuit component.

In this embodiment, the thickness of the first adhesive layer 13 may be 0.1 to 1.0 times, and more preferably 0.1 to 0.7 times, the average particle size of the conductive particles P. Furthermore, in the first adhesive layer 13, 90% or more of the conductive particles P may be separated from other conductive particles.

In addition, in this embodiment, the ratio (X/Y) of the melt viscosity X of the first adhesive layer 13 at the temperature Ty at which the second adhesive layer 14 exhibits the minimum melt viscosity Y to the minimum melt viscosity Y of the second adhesive layer 14 may be 10 or more.

From the viewpoint of improving adhesion to circuit components, the melt viscosity ratio (X/Y) is preferably 10 or greater, more preferably 20 or greater, even more preferably 50 or greater, and particularly preferably 100 or greater. From the viewpoint of wettability to circuit components, the melt viscosity ratio (X/Y) may be 10,000 or less, 5,000 or less, or 1,000 or less. From these viewpoints, the melt viscosity ratio (X/Y) may be 10 to 10,000, 20 to 5,000, 50 to 5,000, or 100 to 1,000. The melt viscosity X and minimum melt viscosity Y can be confirmed by first measuring the melt viscosity of the second adhesive layer to determine the minimum melt viscosity Y of the second adhesive layer (and the temperature Ty at which the second adhesive layer exhibits the minimum melt viscosity Y), and then measuring the melt viscosity of the first adhesive layer to determine the melt viscosity X of the first adhesive layer at temperature Ty. Note that the melt viscosity measurement can also be performed after obtaining the adhesive film.

(Support film)
The support film 12 is formed of, for example, polyethylene terephthalate (PET), polyethylene, polypropylene, or the like. The support film 12 may contain any filler. The surface of the support film 12 may be subjected to a release treatment, a plasma treatment, or the like. The support film 12 can be peeled off after the first adhesive layer and the second adhesive layer are transferred to the circuit member.

(First adhesive layer)
The first adhesive layer may be, for example, a cured product of a first curable composition. The first curable composition may be a photocurable composition, a thermosetting composition, or a mixture of a photocurable composition and a thermosetting composition. The first curable composition may contain, for example, (A) a polymerizable compound (hereinafter also referred to as "component (A)"), (B) a polymerization initiator (hereinafter also referred to as "component (B)"), and (C) conductive particles (hereinafter also referred to as "component (C)"). When the first curable composition is a photocurable composition, the first curable composition contains a photopolymerization initiator as component (B). When the first curable composition is a thermosetting composition, the first curable composition contains a thermal polymerization initiator as component (B). Such a first adhesive layer can be obtained, for example, by irradiating or heating a layer made of the first curable composition with light to polymerize component (A) and thereby curing the first curable composition. That is, the first adhesive layer may be composed of conductive particles and an adhesive component obtained by photocuring a first curable composition. The first adhesive layer may be a cured product obtained by completely curing the first curable composition, or a cured product obtained by partially curing the first curable composition. That is, when the first curable composition contains components (A) and (B), the adhesive component may or may not contain unreacted components (A) and (B). The first adhesive layer may be composed of a resin composition other than the cured product of the curable composition. For example, the first adhesive layer may be composed of a resin composition containing a resin component such as a phenoxy resin such as PKHC, a polyester urethane resin, a polyurethane resin, or an acrylic rubber. By using such a resin component, the melt viscosity of the second adhesive layer at the temperature at which it exhibits the minimum melt viscosity (e.g., 100°C) can be adjusted to approximately 100,000 to 10,000,000 Pa·s, and the melt viscosity ratio (X/Y) can be set to 10 or more.

[Component (A): Polymerizable compound]
The component (A) is a compound that polymerizes, for example, by radicals, cations, or anions generated by a polymerization initiator (a photopolymerization initiator or a thermal polymerization initiator) upon irradiation with light (e.g., ultraviolet light) or heating. The component (A) may be a monomer, oligomer, or polymer. As the component (A), one type of compound may be used alone, or multiple types of compounds may be used in combination.

Component (A) has at least one polymerizable group. The polymerizable group is, for example, a group containing a polymerizable unsaturated double bond (ethylenically unsaturated bond). The polymerizable group is preferably a radically polymerizable group that reacts with radicals, from the viewpoints of easily achieving the desired melt viscosity, reducing peeling between the circuit component and the circuit connection in high-temperature, high-humidity environments, and further improving the effect of reducing connection resistance and providing superior connection reliability. That is, component (A) is preferably a radically polymerizable compound. Examples of radically polymerizable groups include vinyl groups, allyl groups, styryl groups, alkenyl groups, alkenylene groups, (meth)acryloyl groups, and maleimide groups. The number of polymerizable groups in component (A) may be two or more, from the viewpoints of easily achieving the desired melt viscosity after polymerization and easily controlling the physical properties of the cured resin, and may be ten or less, from the viewpoint of suppressing cure shrinkage during polymerization. In order to balance the crosslink density and cure shrinkage, a polymerizable compound having a number of polymerizable groups within the above range may be used, and then a polymerizable compound having a number outside the above range may be additionally used.

Specific examples of component (A) include (meth)acrylate compounds, maleimide compounds, vinyl ether compounds, allyl compounds, styrene derivatives, acrylamide derivatives, nadimide derivatives, natural rubber, isoprene rubber, butyl rubber, nitrile rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, and carboxylated nitrile rubber.

(Meth)acrylate compounds include epoxy (meth)acrylate, (poly)urethane (meth)acrylate, methyl (meth)acrylate, polyether (meth)acrylate, polyester (meth)acrylate, polybutadiene (meth)acrylate, silicone acrylate, ethyl (meth)acrylate, 2-cyanoethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, isopropyl (meth)acrylate, hydroxypropyl (meth)acrylate, isobutyl (meth)acrylate, isobornyl (meth)acrylate, isodecyl (meth)acrylate, isooctyl (meth)acrylate, n-lauryl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-(meth)acryloyloxyethyl phosphate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl propyl (meth)acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, polyethylene glycol di(meth)acrylate, polyalkylene glycol di(meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol (meth)acrylate, dipentaerythritol Examples of the copolymer include lithritol hexa(meth)acrylate, isocyanuric acid-modified bifunctional (meth)acrylate, isocyanuric acid-modified trifunctional (meth)acrylate, tricyclodecanyl acrylate, dimethylol-tricyclodecane diacrylate, 2-hydroxy-1,3-diacryloxypropane, 2,2-bis[4-(acryloxymethoxy)phenyl]propane, 2,2-bis[4-(acryloxypolyethoxy)phenyl]propane, 2,2-di(meth)acryloyloxydiethyl phosphate, and 2-(meth)acryloyloxyethyl acid phosphate.

Examples of maleimide compounds include 1-methyl-2,4-bismaleimidebenzene, N,N'-m-phenylene bismaleimide, N,N'-p-phenylene bismaleimide, N,N'-m-toluylene bismaleimide, N,N'-4,4-biphenylene bismaleimide, N,N'-4,4-(3,3'-dimethyl-biphenylene) bismaleimide, N,N'-4,4-(3,3'-dimethyldiphenylmethane) bismaleimide, N,N'-4,4-(3,3'-diethyldiphenylmethane) bismaleimide, N,N'-4,4-diphenylmethane bismaleimide, and N,N'-4,4-diphenylpropane. propane bismaleimide, N,N'-4,4-diphenylether bismaleimide, N,N'-3,3-diphenylsulfone bismaleimide, 2,2-bis(4-(4-maleimidophenoxy)phenyl)propane, 2,2-bis(3-s-butyl-4-8(4-maleimidophenoxy)phenyl)propane, 1,1-bis(4-(4-maleimidophenoxy)phenyl)decane, 4,4'-cyclohexylidene-bis(1-(4maleimidophenoxy)-2-cyclohexylbenzene), 2,2'-bis(4-(4-maleimidophenoxy)phenyl)hexafluoropropane, and the like.

Examples of vinyl ether compounds include diethylene glycol divinyl ether, dipropylene glycol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylolpropane trivinyl ether.

Allyl compounds include 1,3-diallyl phthalate, 1,2-diallyl phthalate, triallyl isocyanurate, etc.

Component (A) is preferably a (meth)acrylate compound, from the viewpoints of ease of obtaining the desired melt viscosity, the availability of compounds with various structures, and ease of availability. Component (A) may be a (poly)urethane (meth)acrylate compound (urethane (meth)acrylate compound or polyurethane (meth)acrylate compound), from the viewpoint of obtaining even more excellent adhesive properties. Furthermore, component (A) may be a (meth)acrylate compound having a high Tg skeleton, such as a dicyclopentadiene skeleton, from the viewpoint of obtaining even more excellent adhesive properties.

Component (A) may be a compound (e.g., polyurethane (meth)acrylate) in which a polymerizable group such as a vinyl group, allyl group, or (meth)acryloyl group has been introduced into the terminal or side chain of a thermoplastic resin such as an acrylic resin, phenoxy resin, or polyurethane resin, from the viewpoints of easily achieving the desired melt viscosity, balancing crosslink density and cure shrinkage, further reducing connection resistance, and improving connection reliability. In this case, the weight-average molecular weight of component (A) may be 3,000 or more, 5,000 or more, or 10,000 or more, from the viewpoint of achieving an excellent balance between crosslink density and cure shrinkage. Furthermore, the weight-average molecular weight of component (A) may be 1,000,000 or less, 500,000 or less, or 250,000 or less, from the viewpoint of achieving excellent compatibility with other components. The weight-average molecular weight refers to a value measured by gel permeation chromatography (GPC) using a calibration curve based on standard polystyrene under the conditions described in the examples.

The component (A) preferably contains, as a (meth)acrylate compound, a radically polymerizable compound having a phosphate ester structure represented by the following general formula (1): In this case, the adhesive strength to the surface of an inorganic material (such as a metal) is improved, making it suitable for bonding electrodes (e.g., circuit electrodes), for example.
[In the formula, n represents an integer of 1 to 3, and R represents a hydrogen atom or a methyl group.]

The radically polymerizable compound having the above phosphate ester structure can be obtained, for example, by reacting phosphoric anhydride with 2-hydroxyethyl (meth)acrylate. Specific examples of radically polymerizable compounds having a phosphate ester structure include mono(2-(meth)acryloyloxyethyl) acid phosphate and di(2-(meth)acryloyloxyethyl) acid phosphate.

The content of component (A), based on the total mass of the first curable composition, may be 5% by mass or more, 10% by mass or more, or 20% by mass or more, from the viewpoint of easily obtaining the desired melt viscosity and the desired physical properties of the cured product. The content of component (A), based on the total mass of the first curable composition, may be 90% by mass or less, 80% by mass or less, or 70% by mass or less, from the viewpoint of suppressing cure shrinkage during polymerization.

[Component (B): Polymerization initiator]
Component (B) may be a photopolymerization initiator (photoradical polymerization initiator, photocationic polymerization initiator, or photoanionic polymerization initiator) that generates radicals, cations, or anions upon irradiation with light having a wavelength in the range of 150 to 750 nm, preferably light having a wavelength in the range of 254 to 405 nm, and more preferably light having a wavelength of 365 nm (e.g., ultraviolet light), or a thermal polymerization initiator (thermal radical polymerization initiator, thermal cationic polymerization initiator, or thermal anionic polymerization initiator) that generates radicals, cations, or anions upon heat. Component (B) is preferably a radical polymerization initiator (photoradical polymerization initiator or thermal radical polymerization initiator) from the viewpoints of easily achieving a desired melt viscosity, further improving the effect of reducing connection resistance and providing better connection reliability, and facilitating curing at low temperatures and in a short time. As component (B), a single compound may be used alone, or multiple compounds may be used in combination. For example, the first curable composition may contain both a photopolymerization initiator and a thermal polymerization initiator as component (B).

Photoradical polymerization initiators decompose when exposed to light, generating free radicals. In other words, photoradical polymerization initiators are compounds that generate radicals when exposed to external light energy. Examples of photoradical polymerization initiators include compounds having an oxime ester structure, a bisimidazole structure, an acridine structure, an α-aminoalkylphenone structure, an aminobenzophenone structure, an N-phenylglycine structure, an acylphosphine oxide structure, a benzyl dimethyl ketal structure, an α-hydroxyalkylphenone structure, and the like. From the perspectives of easily achieving the desired melt viscosity and achieving a superior effect in reducing connection resistance, it is preferable that the photoradical polymerization initiator have at least one structure selected from the group consisting of an oxime ester structure, an α-aminoalkylphenone structure, and an acylphosphine oxide structure.

Specific examples of compounds having an oxime ester structure include 1-phenyl-1,2-butanedione-2-(o-methoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-(o-methoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-(o-ethoxycarbonyl)oxime, 1-phenyl-1,2-propanedione-2-o-benzoyloxime, 1,3-diphenylpropanetrione-2-(o-ethoxycarbonyl)oxime, 1-phenyl-3-ethoxypropanetrione-2-(o-benzoyl)oxime, 1,2-octanedione, 1-[4-(phenylthio)phenyl-, 2-(o-benzoyloxime)], ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(o-acetyloxime), etc.

Specific examples of compounds having an α-aminoalkylphenone structure include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-morpholinophenyl)-butanone-1, etc.

Specific examples of compounds having an acylphosphine oxide structure include bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide.

A thermal radical polymerization initiator decomposes when exposed to heat, generating free radicals. In other words, a thermal radical polymerization initiator is a compound that generates radicals when exposed to external thermal energy. Thermal radical polymerization initiators can be selected from conventionally known organic peroxides and azo compounds. From the standpoints of stability, reactivity, and compatibility, organic peroxides with a one-minute half-life temperature of 90 to 175°C and a weight-average molecular weight of 180 to 1,000 are preferably used as thermal radical polymerization initiators. Having a one-minute half-life temperature within this range ensures excellent storage stability, sufficiently high radical polymerization properties, and rapid curing.

Specific examples of organic peroxides include 1,1,3,3-tetramethylbutyl peroxyneodecanoate, di(4-t-butylcyclohexyl) peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, cumyl peroxyneodecanoate, dilauroyl peroxide, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyneoheptanoate, t-amylperoxy-2-ethylhexanoate, di-t-butylperoxyhexahydroterephthalate, t-amylperoxy-3,5,5-trimethylhexanoate peroxide, 3-hydroxy-1,1-dimethylbutylperoxyneodecanoate, t-amylperoxyneodecanoate, t-amylperoxy-2-ethylhexanoate, di(3-methylbenzoyl) peroxide, dibenzoyl peroxide, di(4-methylbenzoyl) peroxide, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate peroxybenzoate, 2,5-dimethyl-2,5-di(3-methylbenzoylperoxy)hexane, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butyl peroxybenzoate, dibutyl peroxytrimethyl adipate, t-amyl peroxy normal octoate, t-amyl peroxy isononanoate, and t-amyl peroxybenzoate.

Specific examples of azo compounds include 2,2'-azobis-2,4-dimethylvaleronitrile, 1,1'-azobis(1-acetoxy-1-phenylethane), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 4,4'-azobis(4-cyanovaleric acid), and 1,1'-azobis(1-cyclohexanecarbonitrile).

The content of component (B) may be 0.1% by mass or more, or 0.5% by mass or more, based on the total mass of the first curable composition, from the viewpoint of achieving excellent rapid curing properties and an excellent effect of reducing connection resistance. The content of component (B) may be 15% by mass or less, or 10% by mass or less, or 5% by mass or less, based on the total mass of the first curable composition, from the viewpoint of improving storage stability and an excellent effect of reducing connection resistance.

The first curable composition preferably contains at least one of a photopolymerization initiator and a thermal polymerization initiator as component (B) in order to easily obtain the desired viscosity, and it is more preferable that it contains a photopolymerization initiator in order to facilitate the production of an adhesive film for circuit connection.

[(C) Component: Conductive particles]
The component (C) is not particularly limited as long as it is a conductive particle, and may be, for example, a metal particle made of a metal such as Au, Ag, Ni, Cu, or solder, or a conductive carbon particle made of conductive carbon. The component (C) may also be a coated conductive particle having a core containing non-conductive glass, ceramic, or plastic (such as polystyrene), and a coating layer containing the metal or conductive carbon that coats the core. Among these, metal particles formed of a heat-fusible metal or coated conductive particles having a core containing plastic and a coating layer containing a metal or conductive carbon that coats the core are preferred. In this case, the cured product of the first curable composition can be easily deformed by heating or pressure, which increases the contact area between the electrodes and the component (C) when electrically connecting the electrodes, thereby further improving the conductivity between the electrodes.

Component (C) may be an insulating-coated conductive particle comprising the above-mentioned metal particles, conductive carbon particles, or coated conductive particles, and an insulating layer containing an insulating material such as resin that coats the surface of the particles. When component (C) is an insulating-coated conductive particle, even if the content of component (C) is high, the particle surface is coated with resin, which can suppress the occurrence of short circuits due to contact between components (C), and can also improve the insulation between adjacent electrode circuits. Component (C) can be one type of the various conductive particles described above, or a combination of two or more types.

The maximum particle size of component (C) must be smaller than the minimum electrode spacing (the shortest distance between adjacent electrodes). From the viewpoint of excellent dispersibility and conductivity, the maximum particle size of component (C) may be 1.0 μm or more, 2.0 μm or more, or 2.5 μm or more. From the viewpoint of excellent dispersibility and conductivity, the maximum particle size of component (C) may be 50 μm or less, 30 μm or less, or 20 μm or less. In this specification, the particle size of 300 random conductive particles (pcs) is measured by observation using a scanning electron microscope (SEM), and the largest value obtained is defined as the maximum particle size of component (C). Note that if component (C) has protrusions or is not spherical, the particle size of component (C) is defined as the diameter of a circle circumscribing the conductive particle in the SEM image.

From the viewpoint of excellent dispersibility and conductivity, the average particle size of component (C) may be 1.0 μm or more, 2.0 μm or more, or 2.5 μm or more. From the viewpoint of excellent dispersibility and conductivity, the average particle size of component (C) may be 50 μm or less, 30 μm or less, or 20 μm or less. In this specification, the particle size of 300 random conductive particles (pcs) is measured by observation using a scanning electron microscope (SEM), and the average value of the obtained particle sizes is defined as the average particle size.

In the first adhesive layer, the component (C) is preferably uniformly dispersed. From the viewpoint of obtaining stable connection resistance, the particle density of the component (C) in the first adhesive layer may be 100 pcs/ ^mm2 or more, 1000 pcs/ ^mm2 or more, or 2000 pcs/ ^mm2 or more. From the viewpoint of improving insulation between adjacent electrodes, the particle density of the component (C) in the first adhesive layer may be 100,000 pcs/ ^mm2 or less, 50,000 pcs/ ^mm2 or less, or 10,000 pcs/ ^mm2 or less.

The content of component (C) may be 0.1 vol.% or more, 1 vol.% or more, or 5 vol.% or more, based on the total volume of the first adhesive layer, from the viewpoint of further improving conductivity. The content of component (C) may be 50 vol.% or less, 30 vol.% or less, or 20 vol.% or less, based on the total volume of the first adhesive layer, from the viewpoint of easily suppressing short circuits. The content of component (C) in the first curable composition (based on the total volume of the first curable composition) may be the same as the above range.

[Other ingredients]
The first curable composition may further contain components other than the components (A), (B), and (C). Examples of the other components include a thermoplastic resin, a coupling agent, and a filler. These components may be contained in the first adhesive layer.

Examples of thermoplastic resins include phenoxy resin, polyester resin, polyamide resin, polyurethane resin, polyester urethane resin, and acrylic rubber. When the first curable composition contains a thermoplastic resin, the first adhesive layer can be easily formed. Furthermore, when the first curable composition contains a thermoplastic resin, stress in the first adhesive layer that occurs when the first curable composition cures can be alleviated. Furthermore, when the thermoplastic resin has a functional group such as a hydroxyl group, the adhesion of the first adhesive layer is likely to be improved. The content of the thermoplastic resin may be, for example, 5% by mass or more and 80% by mass or less, based on the total mass of the first curable composition.

Examples of coupling agents include silane coupling agents having organic functional groups such as (meth)acryloyl groups, mercapto groups, amino groups, imidazole groups, and epoxy groups; silane compounds such as tetraalkoxysilanes; tetraalkoxytitanate derivatives; and polydialkyltitanate derivatives. When the first curable composition contains a coupling agent, adhesion can be further improved. The content of the coupling agent may be, for example, 0.1% by mass or more and 20% by mass or less, based on the total mass of the first curable composition.

Examples of fillers include non-conductive fillers (e.g., non-conductive particles). When the first curable composition contains a filler, improved connection reliability can be expected. The filler may be either an inorganic or organic filler. Examples of inorganic fillers include inorganic fine particles such as metal oxide fine particles, such as silica fine particles, alumina fine particles, silica-alumina fine particles, titania fine particles, and zirconia fine particles; and nitride fine particles. Examples of organic fillers include organic fine particles, such as silicone fine particles, methacrylate-butadiene-styrene fine particles, acrylic-silicone fine particles, polyamide fine particles, and polyimide fine particles. These fine particles may have a uniform structure or a core-shell structure. The maximum diameter of the filler is preferably less than the minimum diameter of the conductive particles. The content of the filler may be, for example, 0.1% by volume or more and 50% by volume or less, based on the total volume of the first curable composition.

The first curable composition may contain other additives such as softeners, accelerators, anti-degradants, colorants, flame retardants, and thixotropic agents. The content of these additives may be, for example, 0.1 to 10% by mass based on the total mass of the first curable composition. These additives may also be contained in the first adhesive layer.

The first curable composition may contain a thermosetting resin instead of or in addition to components (A) and (B). A thermosetting resin is a resin that cures when heated and has at least one thermosetting group. A thermosetting resin is, for example, a compound that crosslinks when reacted with a curing agent when heated. A single compound may be used as the thermosetting resin, or multiple compounds may be used in combination.

The thermosetting group may be, for example, an epoxy group, an oxetane group, an isocyanate group, etc., from the viewpoint of easily achieving the desired melt viscosity, further improving the effect of reducing connection resistance, and achieving better connection reliability.

Specific examples of thermosetting resins include epoxy resins such as bisphenol-type epoxy resins, which are reaction products of epichlorohydrin with bisphenol A, F, AD, etc.; epoxy novolac resins, which are reaction products of epichlorohydrin with phenol novolac, cresol novolac, etc.; naphthalene-based epoxy resins with a skeleton containing a naphthalene ring; and various epoxy compounds with two or more glycidyl groups per molecule, such as glycidyl amine and glycidyl ether.

When a thermosetting resin is used instead of components (A) and (B), the content of the thermosetting resin in the first curable composition may be, for example, 20% by mass or more and 80% by mass or less, based on the total mass of the first curable composition. When a thermosetting resin is used in addition to components (A) and (B), the content of the thermosetting resin in the first curable composition may be, for example, 30% by mass or more and 70% by mass or less, based on the total mass of the first curable composition.

When the first curable composition contains a thermosetting resin, the first curable composition may contain a curing agent for the thermosetting resin described above. Examples of curing agents for thermosetting resins include thermal radical generators, thermal cation generators, and thermal anion generators. The content of the curing agent may be, for example, 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the thermosetting resin.

The first adhesive layer may contain components derived from the first curable composition, such as unreacted (A) and (B) components. When the adhesive film of this embodiment is stored and transported in a conventional container, residual unreacted (B) component in the first adhesive layer may cause a portion of the second curable composition in the second adhesive layer to harden during storage and transport, potentially resulting in problems such as increased peeling between the circuit component and the circuit connection in high-temperature, high-humidity environments and a reduced effect of reducing the connection resistance of the adhesive film. Therefore, to prevent these problems, the content of (B) component in the first adhesive layer 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 first adhesive layer. The content of (B) component in the first adhesive layer may be 0.1% by mass or more, based on the total mass of the first adhesive layer. When the first adhesive layer contains a photopolymerization initiator as the component (B), the occurrence of the above-mentioned problems can be suppressed by storing the adhesive film in a storage member described below.

The melt viscosity X of the first adhesive layer at the temperature Ty at which the second adhesive layer exhibits the minimum melt viscosity Y may be 1,000 Pa·s or more, 10,000 Pa·s or more, or 50,000 Pa·s or more, from the viewpoint of reducing the likelihood of peeling. The melt viscosity X may be 10,000,000 Pa·s or less, 1,000,000 Pa·s or less, or 500,000 Pa·s or less, from the viewpoint of achieving excellent wettability to the substrate. The melt viscosity X can be adjusted by changing the composition of the first curable composition, changing the curing conditions of the first curable composition, or the like.

The thickness of the first adhesive layer may be 0.1 times or more, 0.2 times or more, or 0.3 times or more the average particle size of the conductive particles, from the viewpoint of making it easier for the conductive particles to be trapped between electrodes and further reducing connection resistance. The thickness of the first adhesive layer 2 may be 1.0 times or less, 0.8 times or less, or 0.7 times or less the average particle size of the conductive particles, from the viewpoint of making it easier for the conductive particles to be crushed when sandwiched between opposing electrodes during thermocompression bonding and further reducing connection resistance. From these viewpoints, the thickness of the first adhesive layer may be 0.1 to 0.7 times, 0.2 to 0.8 times, or 0.3 to 0.7 times the average particle size of the conductive particles. Note that the thickness of the adhesive layer refers to the thickness of the adhesive layer located between adjacent conductive particles. When the thickness of the first adhesive layer and the average particle size of the conductive particles satisfy the above-mentioned relationship, for example, as shown in Fig. 1, some of the conductive particles P in the first adhesive layer 13 may protrude from the first adhesive layer 13 toward the second adhesive layer 14. In this case, the boundary S between the first adhesive layer 13 and the second adhesive layer 14 is located in the space between adjacent conductive particles P. The conductive particles P are not exposed on the surface of the first adhesive layer 13 opposite the second adhesive layer 14 side, and the opposite surface may be flat.

The thickness of the first adhesive layer may be appropriately set depending on the height of the electrodes of the circuit components to be bonded. The thickness of the first adhesive layer may be, for example, 0.5 μm or more and 20 μm or less. Note that, if a portion of the conductive particles is exposed from the surface of the first adhesive layer (e.g., protruding toward the second adhesive layer), the thickness of the first adhesive layer is the distance from the surface of the first adhesive layer opposite the second adhesive layer to the boundary S between the first and second adhesive layers, which is located between adjacent conductive particles, and the exposed portion of the conductive particles is not included in the thickness of the first adhesive layer. The length of the exposed portion of the conductive particles may be, for example, 0.1 μm or more and 20 μm or less. The thickness of the adhesive layer can be measured by the following method.
The adhesive film was sandwiched between two pieces of glass (thickness: approximately 1 mm) and a resin composition consisting of 100 g of bisphenol A type epoxy resin (trade name: JER811, manufactured by Mitsubishi Chemical Corporation) and 10 g of a curing agent (trade name: Epomount Curing Agent, manufactured by Refine Tech Co., Ltd.) was poured into a mold. The cross section was then polished using a polishing machine, and the thickness of each adhesive layer was measured using a scanning electron microscope (SEM, trade name: SE-8020, manufactured by Hitachi High-Tech Science Corporation).

(Second adhesive layer)
The second adhesive layer is made of, for example, a second curable composition. The second curable composition contains, for example, (a) a polymerizable compound (hereinafter also referred to as component (a)) and (b) a polymerization initiator (hereinafter also referred to as component (b)). The second curable composition may be a thermosetting composition containing a thermal polymerization initiator as component (b), a photocurable composition containing a photopolymerization initiator as component (b), or a mixture of a thermosetting composition and a photocurable composition. The second curable composition constituting the second adhesive layer is an uncured curable composition that is flowable when a circuit is connected, for example, an uncured curable composition.

[Component (a): Polymerizable compound]
Component (a) is, for example, a compound that polymerizes by radicals, cations, or anions generated by a polymerization initiator (photopolymerization initiator or thermal polymerization initiator) upon irradiation with light (e.g., ultraviolet light) or heating. The compounds exemplified as component (A) can be used as component (a). From the viewpoints of facilitating connection at low temperatures and in a short time, making it easier to obtain a desired melt viscosity, and further improving the effect of reducing connection resistance and providing superior connection reliability, component (a) is preferably a radically polymerizable compound having a radically polymerizable group that reacts with radicals. Examples of preferred radically polymerizable compounds and combinations of preferred radically polymerizable compounds for component (a) are the same as those for component (A). When component (a) is a radically polymerizable compound and component (B) in the first adhesive layer is a photoradical polymerization initiator, storing the adhesive film in a storage member described below tends to significantly suppress curing of the second curable composition during storage or transportation of the adhesive film.

Component (a) may be a monomer, oligomer, or polymer. As component (a), a single compound may be used alone, or multiple compounds may be used in combination. Component (a) may be the same as or different from component (A).

The content of component (a) may be 10% by mass or more, 20% by mass or more, or 30% by mass or more, based on the total mass of the second curable composition, from the viewpoint of easily achieving the crosslink density required to reduce connection resistance and improve connection reliability. The content of component (a) may be 90% by mass or less, 80% by mass or less, or 70% by mass or less, based on the total mass of the second curable composition, from the viewpoint of suppressing cure shrinkage during polymerization and achieving good reliability.

[Component (b): Polymerization initiator]
As the component (b), a polymerization initiator similar to the polymerization initiator exemplified as the component (B) can be used. The component (b) is preferably a radical polymerization initiator. Examples of preferred radical polymerization initiators for the component (b) are the same as those for the component (B). As the component (b), one type of compound may be used alone, or multiple types of compounds may be used in combination.

The content of component (b) may be 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more, based on the total mass of the second curable composition, from the viewpoint of facilitating connection at low temperatures in a short time and achieving better connection reliability. From the viewpoint of pot life, the content of component (b) may be 30% by mass or less, 20% by mass or less, or 10% by mass or less, based on the total mass of the second curable composition.

[Other ingredients]
The second curable composition may further contain other components in addition to the components (a) and (b). Examples of the other components include a thermoplastic resin, a coupling agent, a filler, a softener, an accelerator, an anti-degradant, a colorant, a flame retardant, a thixotropic agent, etc. Details of the other components are the same as those of the other components in the first adhesive layer.

The second curable composition may contain a thermosetting resin instead of or in addition to components (a) and (b). When the second curable composition contains a thermosetting resin, the second curable composition may contain a curing agent used to cure the thermosetting resin. The thermosetting resin and curing agent may be the same as the thermosetting resin and curing agent exemplified as other components in the first curable composition. When a thermosetting resin is used instead of components (a) and (b), the content of the thermosetting resin in the second curable composition may be, for example, 20% by mass or more and 80% by mass or less, based on the total mass of the second curable composition. When a thermosetting resin is used in addition to the components (a) and (b), the content of the thermosetting resin in the second curable composition may be, for example, 20 mass% or more and 80 mass% or less, based on the total mass of the second curable composition. The content of the curing agent may be in the same range as the content of the curing agent in the first curable composition.

The content of conductive particles in the second adhesive layer may be, for example, 1% by mass or less, or even 0% by mass, based on the total mass of the second adhesive layer. It is preferable that the second adhesive layer does not contain conductive particles.

The minimum melt viscosity Y of the second adhesive layer may be 50 Pa·s or more, 100 Pa·s or more, or 300 Pa·s or more, from the viewpoint of obtaining excellent blocking resistance. The minimum melt viscosity Y may be 100,000 Pa·s or less, 10,000 Pa·s or less, or 5,000 Pa·s or less, from the viewpoint of obtaining excellent filling properties (resin filling properties) between electrodes. The minimum melt viscosity Y can be adjusted by, for example, changing the composition of the second curable composition.

The thickness of the second adhesive layer may be set appropriately depending on the height of the electrodes of the circuit components to be bonded, etc. The thickness of the second adhesive layer may be 5 μm or more and 200 μm or less, from the viewpoint of being able to sufficiently fill the space between the electrodes and seal the electrodes, thereby achieving better reliability. Note that if some of the conductive particles are exposed from the surface of the first adhesive layer (e.g., protruding toward the second adhesive layer), the thickness of the second adhesive layer is the distance from the surface of the second adhesive layer opposite the first adhesive layer to the boundary S between the first adhesive layer and the second adhesive layer, which is located in the space between adjacent conductive particles.

The ratio of the thickness of the first adhesive layer 2 to the thickness of the second adhesive layer (thickness of the first adhesive layer/thickness of the second adhesive layer) may be 1 or more and 1000 or less, from the viewpoint of being able to sufficiently fill the space between the electrodes and seal the electrodes, thereby obtaining better reliability.

The thickness of the adhesive film (the sum of the thicknesses of all layers that make up the adhesive film) may be, for example, 5 μm or more and 200 μm or less.

The above-mentioned adhesive film for circuit connection comprises a peelable support film and an adhesive layer provided on the support film, the adhesive layer containing an adhesive component and conductive particles. The conductive particles are unevenly distributed on the support film side and dispersed in a direction perpendicular to the thickness direction of the adhesive layer. The adhesive layer may have, from the support film side in the thickness direction of the adhesive layer, a first region containing a cured product of the above-mentioned first curable composition and a second region containing the above-mentioned second curable composition. The ranges of the first and second regions in the thickness direction of the adhesive layer can be set in the same way as the thicknesses of the above-mentioned first adhesive layer and second adhesive layer, respectively. The conductive particles can also be set in the same way as the conditions described above.

The above describes the adhesive film for circuit connection of this embodiment, but the present invention is not limited to the above embodiment.

[Method of manufacturing a circuit connection structure]
The method for manufacturing a circuit connection structure of this embodiment is a method for manufacturing a circuit connection structure in which a first circuit member provided with a first circuit electrode and a second circuit member provided with a second circuit electrode corresponding to the first circuit electrode are connected via the adhesive film for circuit connection of this embodiment described above.

The method of the present embodiment includes, for example, a preparation step of preparing the adhesive film for circuit connection of the present embodiment described above;
a laminating step of laminating the adhesive film for circuit connection onto the first circuit member such that the second adhesive layer side of the adhesive film for circuit connection faces the surface of the first circuit member on which the circuit electrodes are provided;
a heating and pressurizing step of placing a second circuit member on a first circuit member laminated with an adhesive film for circuit connection so that the first circuit electrode and the second circuit electrode face each other, and pressing the first circuit member and the second circuit member in a direction in which the first circuit electrode and the second circuit electrode face each other while heating the adhesive film for circuit connection;
Equipped with.

(preparation process)
In this step, the adhesive film for circuit connection of the present embodiment described above can be produced.
The method for producing an adhesive film for circuit connection of this embodiment may, for example, comprise a preparation step (first preparation step) of the above-described first adhesive layer, and a lamination step of laminating the above-described second adhesive layer on the first adhesive layer. The method for producing an adhesive film for circuit connection may further comprise a preparation step (second preparation step) of the second adhesive layer.

In the first preparation step, the first adhesive layer is prepared, for example, by forming a first adhesive layer on a support film to obtain a first adhesive film. Specifically, first, components (A), (B), and (C), as well as other components added as needed, are added to an organic solvent and dissolved or dispersed by stirring, mixing, kneading, or the like to prepare a varnish composition. The varnish composition is then applied to a release-treated substrate using a knife coater, roll coater, applicator, comma coater, die coater, or the like, and the organic solvent is then volatilized by heating to form a layer of the first curable composition on the substrate. Subsequently, the layer of the first curable composition is cured by irradiating or heating the first curable composition, forming a first adhesive layer on the substrate (curing step). This results in a first adhesive film.

The organic solvent used in preparing the varnish composition is preferably one that can uniformly dissolve or disperse each component, such as toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, and butyl acetate. These organic solvents can be used alone or in combination of two or more. Stirring, mixing, and kneading during preparation of the varnish composition can be performed using, for example, a mixer, a kneading mill, a three-roll mill, a ball mill, a bead mill, or a homodisper.

The support film is not particularly limited as long as it has heat resistance sufficient to withstand the heating conditions used to volatilize the organic solvent when the first curable composition is cured by light. When the first curable composition is cured by heat, the support film is not particularly limited as long as it has heat resistance sufficient to withstand the heating conditions used to volatilize the organic solvent and the heating conditions used to cure the first curable composition. Examples of support films that can be used include substrates (e.g., films) made of oriented polypropylene (OPP), polyethylene terephthalate (PET), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, polyimide, cellulose, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, liquid crystal polymer, and the like. From the perspective of high versatility, polyethylene terephthalate is preferred.

When volatilizing the organic solvent from the varnish composition applied to the support film, the heating conditions are preferably such that the organic solvent is sufficiently volatilized. For example, the heating conditions may be 40°C or higher and 120°C or lower for 0.1 minutes or higher and 10 minutes or lower.

For the light irradiation in the curing step, it is preferable to use irradiation light (e.g., ultraviolet light) having a wavelength in the range of 150 to 750 nm. Light irradiation can be carried out using, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, a metal halide lamp, or the like. The amount of light irradiation may be adjusted so that the melt viscosity ratio (X/Y) is 10 or more. The amount of light irradiation may be, for example, an integrated light amount of light with a wavelength of 365 nm, such as 100 mJ/ ^cm2 or more, 200 mJ/ ^cm2 or more, or 300 mJ/ ^cm2 or more. The amount of light irradiation may be, for example, an integrated light amount of light with a wavelength of 365 nm, such as 10,000 mJ/cm2 or ^less , 5,000 mJ/ ^cm2 or less, or 3,000 mJ/ ^cm2 or less. The greater the amount of light irradiation (integrated amount of light), the greater the melt viscosity X tends to be, and the greater the melt viscosity ratio (X/Y) tends to be.

The heating conditions in the curing process may be adjusted so that the melt viscosity ratio (X/Y) is 10 or greater. The heating conditions may be, for example, 30°C to 300°C for 0.1 to 5,000 minutes, or 50°C to 150°C for 0.1 to 3,000 minutes. The higher the heating temperature, the greater the melt viscosity X tends to be, and the greater the melt viscosity ratio (X/Y). Furthermore, the longer the heating time, the greater the melt viscosity X tends to be, and the greater the melt viscosity ratio (X/Y).

In the second preparation step, the second adhesive layer is prepared by forming a second adhesive layer on a substrate to obtain a second adhesive film, in the same manner as in the first preparation step, except that components (a) and (b) and other components added as needed are used, and a curing step is not performed (light irradiation and heating are not performed). The substrate can be the same as the support film described above.

In the lamination process, the first adhesive film and the second adhesive film may be bonded together to laminate the second adhesive layer onto the first adhesive layer, or the second adhesive layer may be laminated onto the first adhesive layer by applying a varnish composition obtained using components (a) and (b), as well as other components added as necessary, onto the first adhesive layer and volatilizing the organic solvent.

Methods for bonding the first adhesive film and the second adhesive film include, for example, heat pressing, roll lamination, and vacuum lamination. Lamination may be performed under heating conditions of, for example, 0 to 80°C.

Furthermore, in this embodiment, when a circuit-connecting adhesive film is used in which 90% or more of the conductive particles P are separated from other conductive particles in the first adhesive layer, such a dispersed state can be achieved by the magnetic field application process described below. In this case, nickel-containing particles are preferably used as the conductive particles P from the perspective of implementing dispersion through the magnetic field application process. Generally, iron, cobalt, and nickel are ferromagnetic materials and are known to be magnetized by an external magnetic field. However, the use of nickel is advantageous in that it can achieve both conductivity and dispersibility through the application of a magnetic field. Furthermore, to ensure storage stability of the conductive particles P, the surface layer of the conductive particles P may be made of a platinum group precious metal such as gold or silver instead of nickel. The surface of nickel may also be coated with a precious metal such as Au. Furthermore, non-conductive glass, ceramic, plastic, etc. coated with a conductive material such as the above metals may also be used, and in this case, a nickel layer may also be added to form a multilayer structure.

In addition, because the magnetism of nickel is affected by the phosphorus concentration in the nickel plating, it is preferable to adjust the magnetism required for dispersing the conductive particles P using a magnetic field as needed. The magnetism of the conductive particles P can be measured, for example, by saturation magnetization using a vibrating sample magnetometer (VSM). To disperse the conductive particles P using an external magnetic field, it is preferable that the saturation magnetization measured with the VSM be in the range of 5.0 emu/g to 50 emu/g. A value of 5.0 emu/g or higher facilitates sufficient dispersion of the conductive particles P. On the other hand, a value of 50 emu/g or lower prevents the magnetization of the conductive particles P from becoming too large, suppressing bonding of the conductive particles P in the thickness direction of the first adhesive layer 13 and tending to increase the dispersibility of the conductive particles P.

The average particle size of the conductive particles P is preferably 1.0 μm or more and 10.0 μm or less. When the average particle size of the conductive particles P is 1.0 μm or more, the coating accuracy onto the support film is high, making it easier to disperse the conductive particles P well in the first adhesive layer. When the average particle size of the conductive particles P is 10.0 μm or less, good insulation between adjacent circuit electrodes of the connection structure tends to be obtained. To obtain good dispersibility of the conductive particles P, the average particle size of the conductive particles P is more preferably 2.0 μm or more, and even more preferably 2.5 μm or more. On the other hand, from the perspective of ensuring insulation between adjacent circuit electrodes of the connection structure, the average particle size of the conductive particles P is more preferably 8.5 μm or less, even more preferably 7 μm or less, and even more preferably 6.0 μm or less.

The amount of conductive particles P is preferably 1 to 100 parts by volume per 100 parts by volume of the components other than the conductive particles P in the first adhesive layer. From the viewpoint of preventing short-circuiting between adjacent circuit electrodes due to the presence of excessive conductive particles P, the amount of conductive particles P is more preferably 10 to 50 parts by volume. Furthermore, when the average particle size of the conductive particles is in the range of 1.0 μm to 10.0 μm, the particle density of the conductive particles is preferably 1,000 particles/ ^mm² to 50,000 particles/ ^mm² . In this case, both the dispersibility of the conductive particles P and the insulation between adjacent circuit electrodes can be more suitably achieved.

(Lamination process)
2 is a schematic cross-sectional view showing the laminating step in the manufacturing method of the connection structure of this embodiment. In this step, as shown in the figure, the adhesive film for circuit connection 11 is laminated onto the first circuit member 2 so that the second adhesive layer 14 side of the adhesive film for circuit connection 11 faces the surface of the first circuit member 2 on which the first circuit electrodes 6 are provided. If the adhesive film for circuit connection 11 has a release film provided on the second adhesive layer 14, the second adhesive layer 14 can be laminated onto the first circuit member 2 after or while peeling off the release film so that the second adhesive layer 14 is in close contact with the first circuit member 2.

The first circuit member 2 has a circuit electrode 6 on the mounting surface 5a side of the main body 5. Examples of the first circuit member 2 include a member having a flexible substrate such as COP, FCP, or polyimide. Examples of the circuit electrode 6 include copper plated with a metal such as tin. Note that an insulating layer may be formed on the mounting surface 5a in areas where the circuit electrode 6 is not formed.

A known laminator can be used as a laminating means. The laminating conditions can be set appropriately.

Figure 3 is a schematic cross-sectional view showing the laminate obtained through the lamination process.

(Heat and pressure process)
4 is a schematic cross-sectional view showing the heat and pressure application step in the manufacturing method of the connection structure of this embodiment. In this step, as shown in the figure, the second circuit member 3 is placed on the first circuit member 2 laminated with the circuit connection adhesive film (second adhesive layer 14 and first adhesive layer 13) so that the first circuit electrode 6 and the second circuit electrode 8 face each other, and while heating the circuit connection adhesive film (second adhesive layer 14 and first adhesive layer 13), the first circuit member 2 and the second circuit member 3 are pressed in a direction so that the first circuit electrode 6 and the second circuit electrode 8 face each other.

The second circuit member 3 is, for example, a glass substrate or plastic substrate on which a circuit is formed using ITO, IZO, or metal, which are used in liquid crystal displays, or a ceramic wiring board. As shown in Figure 4, the second circuit member 3 has second circuit electrodes 8 corresponding to the first circuit electrodes 6 on the mounting surface 7a of the main body 7.

The circuit electrode 8 has, for example, a rectangular shape in a plan view and a thickness of, for example, approximately 100 nm to 1000 nm. The surface of the circuit electrode 8 is made of one or more materials selected from, for example, gold, silver, copper, tin, ruthenium, rhodium, palladium, osmium, iridium, platinum, indium tin oxide (ITO), and indium zinc oxide (IZO). An insulating layer may also be formed on the mounting surface 7a in areas where the circuit electrode 8 is not formed.

A known thermocompression bonding device can be used as the heating means. The heating temperature of the circuit-connecting adhesive film (second adhesive layer 14 and first adhesive layer 13) is preferably equal to or higher than the temperature at which active polymerization species are generated in the curing agent and polymerization of the polymerization monomer is initiated. This heating temperature is, for example, 80°C to 200°C, and preferably 100°C to 180°C. The heating time is, for example, 0.1 seconds to 30 seconds, and preferably 1 second to 20 seconds. A heating temperature of 80°C or higher facilitates a sufficient curing rate, while a heating temperature of 200°C or lower reduces the risk of undesired side reactions. A heating time of 0.1 seconds or longer facilitates sufficient curing reaction, while a heating time of 30 seconds or shorter makes it easier to maintain productivity of the cured product and also reduces the risk of undesired side reactions.

A known thermocompression device can be used as the pressure application means. The pressure and time for application can be set as appropriate.

Figure 5 is a schematic cross-sectional view showing a circuit connection structure obtained through a heating and pressurizing process. During the heating and pressurizing process, the adhesive components of the circuit connection adhesive film (second adhesive layer 14 and first adhesive layer 13) flow, reducing the distance between the first circuit electrode 6 and the second circuit electrode 8 and causing the conductive particles P to interlock, and then the second adhesive layer and the first adhesive layer harden. The hardening of the second adhesive layer and the first adhesive layer electrically connects the first circuit electrode 6 and the second circuit electrode 8, and forms a cured product 4 of the circuit connection adhesive film (second adhesive layer 14 and first adhesive layer 13) in a state in which adjacent circuit electrodes 6, 6 are electrically connected to each other and adjacent circuit electrodes 8, 8 are electrically insulated from each other, thereby obtaining the circuit connection structure 1 shown in Figure 5. In the obtained circuit connection structure 1, the cured product 4 of the circuit connection adhesive film (second adhesive layer 14 and first adhesive layer 13) sufficiently prevents the distance between the first circuit electrode 6 and the second circuit electrode 8 from changing over time, and also ensures long-term reliability of the electrical properties.

The cured product 4 of the circuit-connecting adhesive film (second adhesive layer 14 and first adhesive layer 13) has a first region 9 formed by curing the first adhesive layer 13 and a second region 10 formed by curing the second adhesive layer 14. In this embodiment, the first region 9 is located on the second circuit member 3 side, and the second region 10 is located on the first circuit member 2 side.

The conductive particles P are interposed between the first circuit electrode 6 and the second circuit electrode 8 in a state where they have been slightly flattened by the pressure bonding. This allows for electrical connection between the first circuit electrode 6 and the second circuit electrode 8. Furthermore, the conductive particles P are spaced apart between adjacent first circuit electrodes 6, 6 and between adjacent second circuit electrodes 8, 8, allowing for electrical insulation between adjacent first circuit electrodes 6, 6 and adjacent second circuit electrodes 8, 8.

[Method of manufacturing an adhesive film for circuit connection]
6 is a schematic diagram showing the manufacturing process of the adhesive film for circuit connection shown in FIG. 1. In the example shown in the figure, a long support film 12 is transported at a predetermined speed by a payout roller 21 and a take-up roller 22. A coater 23 is disposed on the transport path of the support film 12 to apply an adhesive paste W, which is the material for forming the first adhesive layer 13. The coater 23 applies the adhesive paste W, in which conductive particles P are dispersed, onto the support film 12 (application process). The thickness of the adhesive paste W applied onto the support film 12 by the coater 23 varies depending on the proportion of solvent contained in the resin composition, but is preferably less than 1.6 times the average particle size of the conductive particles P.

The viscosity of the adhesive paste W can be varied depending on the application and application method, but is typically preferably between 10 mPa·s and 10,000 mPa·s. From the perspective of suppressing separation of the components in the adhesive paste W and improving compatibility, a viscosity of 50 mPa·s to 5,000 mPa·s is more preferable. Furthermore, to improve the appearance of the circuit-connecting adhesive film 11, a viscosity of 100 mPa·s to 3,000 mPa·s is preferable. If the viscosity is 10,000 mPa·s or less, it will be difficult to suppress the dispersion of the conductive particles P in the subsequent magnetic field application process, and if the viscosity is 10 mPa·s or more, separation of the components in the adhesive paste W will be less likely to occur.

The method for applying the adhesive paste W is not limited to the above, and known methods can be used. Examples include spin coating, roller coating, bar coating, dip coating, microgravure coating, curtain coating, die coating, spray coating, doctor coating, kneader coating, flow coating, screen printing, and casting. Bar coating, die coating, and microgravure coating are suitable for producing the circuit-connecting adhesive film 11, with microgravure coating being particularly suitable from the standpoint of film thickness accuracy.

A pair of magnets 24, 25 are arranged facing each other above and below the coater 23, sandwiching the support film 12. In this embodiment, as shown in Figure 7, the upper magnet 24 has a north pole and the lower magnet 25 has a south pole, creating a magnetic field in a substantially vertical direction from magnet 24 to magnet 25. Therefore, when the support film 12 is transported between the magnets 24, 25, the conductive particles P in the adhesive paste W are magnetized, and a repulsive force causes the conductive particles P, P to be spaced apart in the in-plane direction of the adhesive paste W (magnetic field application process).

To maintain the spacing of the conductive particles P during the magnetic field application process, the adhesive paste W is dried using hot air or the like while the support film 12 passes between the magnets 24 and 25 (drying process). This increases the viscosity of the adhesive paste W, resulting in the formation of a first adhesive layer 13 on the support film 12 in which 70% or more, preferably 90% or more, of the conductive particles P are spaced apart from adjacent conductive particles P, as shown in Figure 8. The thickness of the adhesive paste W also decreases during the drying process. As described above, by setting the thickness of the adhesive paste W to less than 1.6 times the average particle size of the conductive particles P, it becomes easy to set the thickness of the first adhesive layer 13 to between 0.6 and 1.0 times the average particle size of the conductive particles P. Furthermore, by using an adhesive paste (varnish) diluted with an organic solvent (e.g., methyl ethyl ketone), it is possible to reduce the thickness of the adhesive layer to approximately 0.1 times the average particle size of the conductive particles P. There are no particular restrictions on the amount of organic solvent used for dilution, but it is preferable to add 50 to 500 parts by mass per 100 parts by mass of the adhesive component.

The drying temperature of the adhesive paste W is preferably, for example, 20°C to 80°C. The conveying speed of the support film 12 is preferably, for example, 30 mm/s to 160 mm/s. The thickness of the adhesive paste W is preferably, for example, 5 μm to 10 μm when using conductive particles P with an average particle size of 3 μm. When the conveying speed of the support film 12 is 30 mm/s or higher, the adhesive paste W dries with the conductive particles P sufficiently spaced apart, tending to provide sufficient dispersion. When the conveying speed of the support film 12 is 160 mm/s or lower, the application of the magnetic field tends to cease after drying, preventing re-aggregation of the conductive particles P. When the thickness of the adhesive paste W is 5 μm or higher, the gap of the coater 23 can be prevented from becoming insufficient, and the number of conductive particles P in the first adhesive layer 13 can be prevented from becoming insufficient. When the thickness of the adhesive paste W is 10 μm or less, the gap of the coater 23 can be prevented from becoming excessive, and the number of conductive particles P in the first adhesive layer 13 can be prevented from becoming excessive.

After the first adhesive layer 13 is formed, as shown in Figure 9, a second adhesive layer 14 formed separately on a release film 15 is laminated onto the first adhesive layer 13 (lamination process). This results in the circuit connection adhesive film 11 shown in Figure 2. Note that a hot roll laminator, for example, can be used to laminate the second adhesive layer 14. Furthermore, instead of being limited to lamination, an adhesive paste, which is the material for the second adhesive layer 14, can also be applied and dried onto the first adhesive layer 13.

As described above, in the adhesive film for circuit connection 11, 70% or more, preferably 90% or more, of the conductive particles P in the first adhesive layer 13 can be separated from adjacent conductive particles P. In this case, aggregation of adjacent conductive particles P is suppressed when connecting the first circuit member 2 and the second circuit member 3, thereby ensuring good insulation between adjacent first circuit electrodes 6 and 6 and between adjacent second circuit electrodes 8 and 8. Furthermore, in this adhesive film for circuit connection 11, the thickness of the first adhesive layer 13 can be set to 0.1 to 1.0 times, 0.1 to 0.7 times, or 0.6 to less than 1.0 times the average particle size of the conductive particles P. In this case, the flow of the conductive particles P during compression bonding is suppressed, improving the capture efficiency of the conductive particles P between the first circuit electrode 6 and the second circuit electrode 8. Therefore, the connection reliability between the first circuit member 2 and the second circuit member 3 can be ensured.

<Adhesive film storage set>
Fig. 10 is a perspective view showing an adhesive film storage set according to one embodiment. As shown in Fig. 10, the adhesive film storage set 120 includes an adhesive film 11 for circuit connection, a reel 121 around which the adhesive film 11 is wound, and a storage member 122 that stores the adhesive film 11 and the reel 121.

As shown in Figure 10, the adhesive film 11 is, for example, in the form of a tape. The tape-shaped adhesive film 11 is produced, for example, by cutting a sheet-shaped raw material into a long piece with a width appropriate for the intended use. The adhesive film 11 may have a support film 12 on the first adhesive layer side. The support film 12 can be a substrate such as the PET film described above.

The reel 121 comprises a first side plate 124 having a winding core 123 on which the adhesive film 11 is wound, and a second side plate 125 arranged opposite the first side plate 124 across the winding core 123.

The first side plate 124 is a circular plate made of, for example, plastic, and has an opening with a circular cross-section in the central portion of the first side plate 124.

The winding core 123 of the first side plate 124 is the portion around which the adhesive film 11 is wound. The winding core 123 is made of, for example, plastic, and is annular in shape with a thickness similar to the width of the adhesive film 11. The winding core 123 is fixed to the inner surface of the first side plate 124 so as to surround the opening of the first side plate 124. In addition, a shaft hole 126 is provided in the center of the reel 121, into which the rotating shaft of a winding device or unwinding device (not shown) is inserted. When the rotating shaft of the winding device or unwinding device is inserted into this shaft hole 126 and the rotating shaft is driven, the reel 121 rotates without spinning freely. A desiccant container containing a desiccant may be fitted into the shaft hole 126.

The second side plate 125, like the first side plate 124, is a circular plate made of, for example, plastic, and has an opening in the center of the second side plate 125 that has a circular cross-section and the same diameter as the opening in the first side plate 124.

The storage member 122 is, for example, bag-shaped and stores the adhesive film 11 and the reel 121. The storage member 122 has an insertion opening 127 for storing (inserting) the adhesive film 11 and the reel 121 inside the storage member 122.

The storage member 122 has a viewing portion 128 that allows the interior of the storage member 122 to be viewed from the outside. The storage member 122 shown in Figure 10 is configured so that the entire storage member 122 forms the viewing portion 128.

The visible portion 128 is transparent to visible light. For example, when the light transmittance of the visible portion 128 is measured in the wavelength range of 450 to 750 nm, there is at least one region between 450 and 750 nm with a wavelength width of 50 nm, where the average light transmittance is 30% or higher. The light transmittance of the visible portion 128 can be obtained by cutting the visible portion 128 to a predetermined size to prepare a sample and measuring the light transmittance of the sample with an ultraviolet-visible spectrophotometer. Because the storage member 122 has such a visible portion 128, various information inside the storage member 122, such as the product name, lot number, and expiration date affixed to the reel 121, can be confirmed from outside the storage member 122. This is expected to prevent the mixing of incorrect products and improve the efficiency of sorting operations.

The transmittance of light with a wavelength of 365 nm through the viewing portion 128 is 10% or less. Because the transmittance of light with a wavelength of 365 nm through the viewing portion 128 is 10% or less, when a photopolymerization initiator is used as component (B), it is possible to suppress the curing of the second curable composition caused by light entering the housing member 122 from the outside to the inside and the photopolymerization initiator remaining in the first adhesive layer. From the viewpoint of further suppressing the generation of active species (e.g., radicals) from the photopolymerization initiator, the transmittance of light with a wavelength of 365 nm through the viewing portion 128 is preferably 10% or less, more preferably 5% or less, even more preferably 1% or less, and particularly preferably 0.1% or less.

From a similar perspective, the maximum transmittance of light in the wavelength region in which radicals, cations, or anions can be generated from the above-mentioned photopolymerization initiator (component (B)) in the visible portion 128 is preferably 10% or less, more preferably 5% or less, even more preferably 1% or less, and particularly preferably 0.1% or less. Specifically, the maximum transmittance of light in the wavelength region of 254 to 405 nm in the visible portion 128 is preferably 10% or less, more preferably 5% or less, even more preferably 1% or less, and particularly preferably 0.1% or less.

The viewing portion 128 (housing member 122) is formed from a sheet, for example, 10 to 5000 μm thick. The sheet is made of a material that has a transmittance of 10% or less for light with a wavelength of 365 nm in the viewing portion 128. Such a material may consist of a single component or multiple components. Examples of such materials include low-density polyethylene, linear low-density polyethylene, polycarbonate, polyester, acrylic resin, polyamide, and glass. These materials may also contain ultraviolet absorbers. The viewing portion 128 may have a layered structure formed by stacking multiple layers with different light transmittances. In this case, each layer constituting the viewing portion 128 may be made of the materials described above.

The insertion opening 127 may be sealed, for example, by closing it with a sealing machine, to prevent air from entering from the outside during storage. In this case, it is preferable to remove the air from inside the storage member 122 by suction before closing the insertion opening 127. This is expected to reduce humidity inside the storage member 122 from the initial stage of storage and prevent air from entering from the outside. Furthermore, by closely contacting the inner surface of the storage member 122 with the surface of the reel 121, it is possible to prevent foreign matter from rubbing against the inner surface of the storage member 122 and the surface of the reel 121 due to vibration during transport, and to prevent damage to the outer surfaces of the side panels 124 and 125 of the reel 121.

In the above embodiment, the storage member was configured so that the entire storage member was the visible portion. However, in another embodiment, the storage member may have a visible portion in only a portion of the storage member. For example, the storage member may have a rectangular visible portion approximately in the center of the side of the storage member. In this case, the portion of the storage member other than the visible portion may be black, for example, to prevent ultraviolet light and visible light from passing through.

In addition, in the above embodiment, the storage member is bag-shaped, but the storage member may also be box-shaped, for example. It is preferable that the storage member has a notch for easy opening. In this case, opening the storage member when in use becomes easier.

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

<Method for preparing polyester urethane resin>
48 parts by mass of isophthalic acid and 37 parts by mass of neopentyl glycol were added to a stainless steel autoclave equipped with a stirrer, a thermometer, a condenser, a vacuum generator, and a nitrogen gas inlet tube, and 0.02 parts by mass of tetrabutoxy titanate as a catalyst was added. Then, the temperature was raised to 220 ° C. under a nitrogen stream and stirred for 8 hours. After that, the pressure was reduced to atmospheric pressure (760 mmHg), and the mixture was cooled to room temperature. The white precipitate was removed, washed with water, and vacuum dried to obtain a polyester polyol.

The polyester polyol obtained by the reaction of the dicarboxylic acid and diol described above was thoroughly dried, then dissolved in MEK and placed in a four-neck flask equipped with a stirrer, dropping funnel, reflux condenser, and nitrogen gas inlet tube. Additionally, dibutyltin laurate was added as a catalyst in an amount of 0.05 parts by weight per 100 parts by weight of polyester polyol, and 4,4'-diphenylmethane diisocyanate dissolved in MEK was added via a dropping funnel in an amount of 50 parts by weight per 100 parts by weight of polyester polyol. The mixture was stirred at 80°C for 4 hours to obtain the desired polyester urethane resin.

<Synthesis of polyurethane acrylate (UA1)>
2500 parts by mass (2.50 mol) of poly(1,6-hexanediol carbonate) (trade name: Duranol T5652, manufactured by Asahi Kasei Chemicals Corporation, number average molecular weight 1000) and 666 parts by mass (3.00 mol) of isophorone diisocyanate (manufactured by Sigma-Aldrich Co.) were uniformly added dropwise over 3 hours to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser with a calcium chloride drying tube, and a nitrogen gas inlet tube. Next, nitrogen gas was sufficiently introduced into the reaction vessel, and the reaction vessel was then heated to 70 to 75°C to allow the mixture to react. Next, 0.53 parts by mass (4.3 mmol) of hydroquinone monomethyl ether (Sigma-Aldrich) and 5.53 parts by mass (8.8 mmol) of dibutyltin dilaurate (Sigma-Aldrich) were added to the reaction vessel, followed by the addition of 238 parts by mass (2.05 mol) of 2-hydroxyethyl acrylate (Sigma-Aldrich), and the mixture was allowed to react for 6 hours at 70°C in an air atmosphere. This yielded polyurethane acrylate (UA1). The weight-average molecular weight of polyurethane acrylate (UA1) was 15,000. The weight-average molecular weight was measured by gel permeation chromatography (GPC) using a calibration curve based on standard polystyrene under the following conditions.
(Measurement conditions)
Apparatus: GPC-8020 manufactured by Tosoh Corporation
Detector: Tosoh Corporation RI-8020
Column: Gelpack GLA160S + GLA150S manufactured by Hitachi Chemical Co., Ltd.
Sample concentration: 120mg/3mL
Solvent: tetrahydrofuran Injection volume: 60 μL
Pressure: 2.94×10 ⁶ Pa (30 kgf/cm ² )
Flow rate: 1.00mL/min

<Preparation of conductive particles>
A nickel layer was formed on the surface of the polystyrene particles to a thickness of 0.2 μm, thereby obtaining conductive particles with an average particle size of 4 μm, a maximum particle size of 4.5 μm, and a specific gravity of 2.5.

<Preparation of Varnish (Varnish Composition) for Conductive Particle-Containing Layer>
The components shown below were mixed in the amounts (parts by mass) shown in Table 1 to prepare a varnish of photocurable composition 1. The content (volume %) of conductive particles and the content (volume %) of filler shown in Table 1 are based on the total volume of the photocurable composition.
(Polymerizable compound)
A1: Dicyclopentadiene diacrylate (trade name: DCP-A, manufactured by Toagosei Co., Ltd.)
A2: Polyurethane acrylate (UA1) synthesized as described above
A3: 2-methacryloyloxyethyl acid phosphate (trade name: Light Ester P-2M, manufactured by Kyoeisha Chemical Co., Ltd.)
(Photopolymerization initiator)
B1: B1: 1,2-octanedione, 1-[4-(phenylthio)phenyl-, 2-(O-benzoyloxime)] (trade name: Irgacure (registered trademark) OXE01, manufactured by BASF)
(Thermal polymerization initiator)
C1: Benzoyl peroxide (product name: Niper BMT-K40, manufactured by NOF Corporation)
(Conductive particles)
D1: Conductive particles (thermoplastic resin) prepared as described above
E1: Polyester urethane resin (coupling agent) synthesized above
F1: 3-methacryloxypropyltrimethoxysilane (trade name: KBM503, manufactured by Shin-Etsu Chemical Co., Ltd.)
(filling material)
G1: Silica fine particles (product name: R104, manufactured by Nippon Aerosil Co., Ltd., average particle size (primary particle size): 12 nm)
(solvent)
H1: Methyl ethyl ketone

<Preparation of Thermosetting Varnish (Varnish Composition)>
The polymerizable compounds a1 to a3, thermoplastic resin e1, coupling agent f1, filler g1, and solvent h1 were the same as the polymerizable compounds A1 to A3, thermoplastic resin E1, coupling agent F1, filler G1, and solvent H1 in the photocurable composition, and these components and the thermal polymerization initiator shown below were mixed in the amounts (parts by mass) shown in Table 2 to prepare a varnish of thermosetting composition 1. The filler content (vol %) shown in Table 2 is the content based on the total volume of the thermosetting composition.
(Thermal polymerization initiator)
c1: Benzoyl peroxide (trade name: Niper BMT-K40, manufactured by NOF Corporation)

Example 1
[Preparation of First Adhesive Film]
A varnish of photocurable composition 1 was applied to a 50 μm-thick PET film using a coating device. Next, hot air drying was performed at 70°C for 3 minutes, and a magnetic field was simultaneously applied to form a layer of photocurable composition 1 with a thickness (thickness after drying) of 4 μm on the PET film. The thickness was measured using a contact thickness meter. Note that the use of a contact thickness meter reflects the size of the conductive particles, and the thickness of the region where the conductive particles are present is measured. Therefore, after laminating the second adhesive layer to prepare a two-layer circuit connection adhesive film, the thickness of the first adhesive layer located in the space between adjacent conductive particles was measured using the method described below.
Next, the layer made of photocurable composition 1 was irradiated with light using a metal halide lamp so that the cumulative light dose was 1500 mJ/ ^cm² , polymerizing the polymerizable compound. This cured the photocurable composition 1, forming a first adhesive layer. Through the above operations, a first adhesive film was obtained, comprising a first adhesive layer having a thickness of 4 µm (the thickness of the region where the conductive particles were present) on the PET film. The conductive particle density at this time was approximately 7000 pcs/ ^mm² .

[Evaluation of Monodispersion Ratio of Conductive Particles]
The monodispersity of the conductive particles (the ratio of conductive particles separated from adjacent conductive particles (monodispersed state)) of the first adhesive film was evaluated, and the monodispersity was 70% or more.
The monodispersity ratio was calculated using the formula: Monodispersity ratio (%) = (number of monodispersed conductive particles in 2500 ^μm2 /number of conductive particles in 2500 ^μm2 ) × 100. The conductive particles were observed at a magnification of 200 times using a metallurgical microscope.

[Preparation of second adhesive film]
The varnish of thermosetting composition 1 was applied onto a 50 μm thick PET film using a coating device. Next, hot air drying was performed at 70°C for 3 minutes to form a second adhesive layer (a layer made of thermosetting composition 1) with a thickness of 8 μm on the PET film. Through the above operations, a second adhesive film having a second adhesive layer on the PET film was obtained.

[Preparation of adhesive film for circuit connection]
The first adhesive film and the second adhesive film were laminated together with the PET film substrate using a roll laminator while being heated at 40°C. At this time, the PET film on the second adhesive film side was peeled off. This produced an adhesive film for circuit connection having a laminated structure in which the PET film, the first adhesive layer, and the second adhesive layer were laminated in this order.
The thickness of the first adhesive layer of the prepared adhesive film for circuit connection was measured by the method described above. Specifically, it was measured by the following method. The adhesive film for circuit connection was sandwiched between two sheets of glass (thickness: approximately 1 mm) and a resin composition consisting of 100 g of bisphenol A type epoxy resin (trade name: JER811, manufactured by Mitsubishi Chemical Corporation) and 10 g of a curing agent (trade name: Epomount Curing Agent, manufactured by Refine Tech Co., Ltd.) was poured into a mold. The cross section was polished using a polishing machine, and the thickness of the first adhesive layer located in the space between adjacent conductive particles was measured using a scanning electron microscope (SEM, trade name: SE-8020, manufactured by Hitachi High-Tech Science Corporation). The thickness of the first adhesive layer was 2 μm.

[Fabrication of circuit connection structure]
A 25 μm pitch COF (manufactured by FLEXSEED) and a glass substrate (manufactured by Geomatec Co., Ltd.) with thin-film electrodes (height: 1200 Å) made of amorphous indium tin oxide (ITO) on the glass substrate were connected over a width of 1 mm using a thermocompression bonding device (heating method: constant heat type, manufactured by Taiyo Kikai Seisakusho Co., Ltd.) under conditions of 170°C, 6 MPa, and 4 seconds to produce a circuit connection structure (connection structure). Note that, during connection, the adhesive film for circuit connection was first attached to the COF substrate from the second adhesive layer side, and after peeling off the separator, the substrate was placed facing the glass substrate and heated and pressurized.

[Evaluation of Circuit Connection Structure]
The connection resistance between the opposing electrodes of the resulting circuit connection structure was measured with a multimeter immediately after connection, and the connection resistance was calculated as the average value of 16 resistance points between the opposing electrodes.
Next, the number of captured particles in an area of 10 μm×200 μm (=2000 μm ² ) on each electrode was counted, and the average value for 20 lines was calculated. The results are shown in Table 3.
The particle dispersion after mounting was also observed under a microscope and was evaluated as follows: 1 indicates that the state before mounting was maintained, 3 indicates that the state before mounting was not maintained at all, and 2 indicates that the state before mounting was not maintained at all.
1 and 2 are at levels that pose no practical problems.

(Reference example 1)
Evaluation was performed in the same manner as in Example 1, except that an adhesive film for circuit connection having a laminated structure in which the first adhesive layer, the second adhesive layer, and the PET film were laminated in this order was produced by laminating the first adhesive layer and the second adhesive layer and then peeling off the PET film on the first adhesive layer side. When connecting, the adhesive film for circuit connection was first attached to the COF substrate from the first adhesive layer side, and after peeling off the separator, it was placed opposite the glass substrate and heated and pressurized. The results are shown in Table 3.

Examples 2 and 3
Adhesive films for circuit connection and circuit connection structures were prepared in the same manner as in Example 1, except that the thickness of the first adhesive layer was changed to 1.5 μm and 3.0 μm. The prepared circuit connection structures were evaluated in the same manner as in Example 1. The results are shown in Table 3. The monodispersity rates of the conductive particles in the first adhesive layer were 70% or higher.

When the circuit connection adhesive film obtained in Example 1 was first attached to a COF substrate and then mounted, it was found that the number of conductive particles captured was greater than in Reference Example 1, and the fluidity of the particles was also suppressed.

1...circuit connection structure, 2...first circuit member, 3...second circuit member, 6...first circuit electrode, 8...second circuit electrode, 11...circuit connection adhesive film, 12, 15...support film (release film), 13...first adhesive layer, 14...second adhesive layer, P...conductive particles, W...adhesive paste.

Claims (8)

The adhesive tape comprises a peelable support film, a first adhesive layer containing conductive particles provided on the support film, and an uncured second adhesive layer laminated on the first adhesive layer,
the first adhesive layer is made of a photocured product of a first curable composition containing the conductive particles, a polymerizable compound, and a photopolymerization initiator;
an adhesive film for circuit connection, wherein the thickness of the first adhesive layer is 0.1 to 1.0 times the average particle size of the conductive particles. The adhesive film for circuit connection according to claim 1, wherein the first curable composition contains, as the polymerizable compound, a radically polymerizable compound having a radically polymerizable group. the second adhesive layer comprises a second curable composition;
3. The adhesive film for circuit connection according to claim 1, wherein the second curable composition contains a radically polymerizable compound having a radically polymerizable group. The adhesive film for circuit connection according to any one of claims 1 to 3, wherein the ratio of the melt viscosity of the first adhesive layer at the temperature at which the second adhesive layer exhibits its minimum melt viscosity to the minimum melt viscosity of the second adhesive layer is 20 or greater. The adhesive film for circuit connection according to any one of claims 1 to 4, wherein the melt viscosity of the first adhesive layer at the temperature at which the second adhesive layer exhibits its minimum melt viscosity is 10,000 Pa·s or more. A method for manufacturing a circuit connection structure, comprising the steps of: interposing the first adhesive layer and the second adhesive layer of the circuit connection adhesive film described in any one of claims 1 to 3 between a first circuit member having a first circuit electrode and a second circuit member having a second circuit electrode; and thermocompression bonding the first circuit member and the second circuit member to electrically connect the first circuit electrode and the second circuit electrode to each other. the first circuit member has a flexible substrate;
a laminating step of attaching the adhesive film for circuit connection to the first circuit member so that the second adhesive layer is in contact with the first circuit member;
7. The method for manufacturing a circuit connection structure according to claim 6, further comprising the steps of: after the laminating step, placing the second circuit member on the first circuit member on which the second adhesive layer and the first adhesive layer have been laminated so that the first circuit electrode and the second circuit electrode face each other; and thermocompression bonding the first circuit member and the second circuit member together. An adhesive film for circuit connection according to any one of claims 1 to 5, and a housing member for housing the adhesive film,
the storage member has a visual confirmation portion that allows the inside of the storage member to be visually confirmed from the outside,
The adhesive film storage set has a transmittance of 10% or less for light with a wavelength of 365 nm in the visible portion.