Adhesive composition, adhesive film, laminate, and method for producing circuit connection structure

Abstract

An adhesive composition comprising: a radically polymerizable compound; a radical polymerization initiator; and an acrylic resin that has at least one epoxy group per molecule and that has a weight-average molecular weight of not less than 5,000.

Description

Adhesive composition, adhesive film, laminate, and method for producing circuit connection structure

[0001] The present disclosure relates to adhesive compositions, adhesive films, laminates, and methods for producing circuit connection structures.

[0002] Conventionally, various adhesive materials have been used for circuit connection. For example, an adhesive film (film-like adhesive) for circuit connection, which has anisotropic conductivity and contains conductive particles dispersed in the adhesive, has been used as an adhesive material for connecting a liquid crystal display and a tape carrier package (TCP), for connecting a flexible printed circuit board (FPC) and a TCP, or for connecting an FPC and a printed wiring board (see, for example, Patent Document 1).

[0003] WO 2005 / 054388

[0004] Generally, an adhesive film for circuit connection is placed on a substrate and cut into a tape before use. In this case, a technique called "half-cutting" is sometimes used, in which only the adhesive film for circuit connection is cut, without cutting the substrate itself. However, conventional adhesive films for circuit connection do not have sufficient half-cutting properties. That is, with conventional adhesive films for circuit connection, when only one side of an adhesive film cut by half-cutting is used, the adhesive film may reattach at the cut surface, causing the other adhesive film to peel off at the same time, even though only one side of the adhesive film needs to be peeled off.

[0005] Therefore, some aspects of the present disclosure aim to provide an adhesive film with excellent half-cutting properties, an adhesive composition capable of forming the adhesive film, a laminate having the adhesive film on a substrate, and a method for manufacturing a circuit connection structure using the laminate.

[0006] Some aspects of the present disclosure provide the following [1] to

[10] .

[0007] [1] An adhesive composition comprising a radically polymerizable compound, a radical polymerization initiator, and an acrylic resin having at least one epoxy group in the molecule and a weight average molecular weight of 5,000 or more.

[0008] [2] The adhesive composition according to [1], wherein the content of the acrylic resin is 1 to 15 mass% based on the total amount of solids contained in the adhesive composition.

[0009] [3] The adhesive composition according to [1] or [2], wherein the acrylic resin has an epoxy equivalent of 1000 g / eq or less.

[0010] [4] The adhesive composition according to any one of [1] to [3], wherein the radical polymerizable compound includes a (meth)acrylate compound having at least one phosphate group in the molecule.

[0011] [5] The adhesive composition according to any one of [1] to [4], further comprising at least one thermoplastic resin selected from the group consisting of a phenoxy resin, a polyester resin, a polyurethane resin, a polyester urethane resin, a butyral resin, an acrylic resin, and a polyimide resin.

[0012] [6] The adhesive composition according to any one of [1] to [5], further comprising conductive particles.

[0013] [7] An adhesive film comprising a first adhesive layer made of the adhesive composition according to any one of [1] to [6].

[0014] [8] The adhesive film according to [7], further comprising a second adhesive layer laminated on the first adhesive layer, wherein at least one of the first adhesive layer and the second adhesive layer contains conductive particles.

[0015] [9] A laminate comprising a substrate and the adhesive film according to [7] or [8] provided on the substrate.

[0016]

[10] A method for manufacturing a circuit connection structure, comprising: a half-cutting step of cutting the adhesive film of the laminate described in [9] along an outline line forming the outline of the adhesive film piece; a step of peeling the adhesive film piece formed by the half-cutting step from the base material; and a step of interposing the adhesive film piece between a first circuit member having a first electrode and a second circuit member having a second electrode, and thermocompression-bonding the first circuit member and the second circuit member to electrically connect the first electrode and the second electrode to each other.

[0017] According to some aspects of the present disclosure, it is possible to provide an adhesive film with excellent half-cutting properties, an adhesive composition capable of forming the adhesive film, a laminate having the adhesive film on a substrate, and a method for manufacturing a circuit connection structure using the laminate.

[0018] Fig. 1 is a cross-sectional view showing an adhesive film according to an embodiment of the present disclosure. Fig. 2 is a perspective view illustrating a manufacturing process for a circuit connection structure according to an embodiment of the present disclosure. Fig. 3 is a cross-sectional view illustrating a manufacturing process for a circuit connection structure according to an embodiment of the present disclosure. Fig. 4 is a schematic view illustrating a method for evaluating half-cut properties.

[0019] Hereinafter, embodiments of the present disclosure will be described in detail, possibly with reference to the drawings. In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values ​​before and after "to" are the same. Furthermore, individually stated upper and lower limit values ​​can be arbitrarily combined. Furthermore, in this specification, "(meth)acrylate" means at least one of acrylate and its corresponding methacrylate. The same applies to other similar expressions such as "(meth)acryloyl." Furthermore, "(poly)" refers to both cases with and without the "poly" prefix.

[0020] <Adhesive Composition> One embodiment of the present disclosure is an adhesive composition containing a radically polymerizable compound, a radical polymerization initiator, and an acrylic resin having at least one epoxy group in the molecule and having a weight average molecular weight of 5000 or more (hereinafter also referred to as an "epoxy group-containing acrylic resin").

[0021] The adhesive composition having the above characteristics can form an adhesive film with excellent half-cutting properties (i.e., excellent handling properties when peeling the adhesive film after half-cutting). Therefore, it is particularly suitable for use in producing adhesive films that require half-cutting properties. While the reason for this effect is unclear, it is presumed that the epoxy group-containing acrylic resin tends to be crystalline, and thus the adhesive composition containing the epoxy group-containing acrylic resin reduces the stress at break of the adhesive film, thereby achieving the above effect. Furthermore, radical-curing adhesives generally generate fewer intermolecular bonds during the curing reaction than non-radical-curing adhesives, which tends to reduce the stress at break of the adhesive film. Therefore, it is presumed that the fact that the adhesive composition is radical-curing is one of the reasons for the above effect.

[0022] Furthermore, the adhesive composition having the above-described characteristics is suitable for circuit connection, and the adhesive composition makes it possible to easily obtain a circuit connection structure that has sufficiently high adhesive strength and sufficiently low connection resistance between opposing electrodes.

[0023] The adhesive composition of this embodiment may be insulating or conductive. That is, the adhesive composition may be used to form an insulating adhesive film or a conductive adhesive film. A conductive adhesive composition may contain conductive particles.

[0024] The adhesive composition of the present embodiment may be used to form an adhesive film consisting of an insulating adhesive layer or a conductive adhesive layer, or may be used to form at least one of the insulating adhesive layer and the conductive adhesive layer of an adhesive film comprising an insulating adhesive layer and a conductive adhesive layer.

[0025] The adhesive composition of the present embodiment may further contain a thermoplastic resin. Note that the epoxy group-containing acrylic resin may be a thermoplastic resin, but even if the epoxy group-containing acrylic resin is a thermoplastic resin, the adhesive composition may further contain a thermoplastic resin other than the epoxy group-containing acrylic resin.

[0026] The components that can be contained in the adhesive composition are described below.

[0027] (Radical Polymerizable Compound) The radical polymerizable compound is a compound that is polymerized by radicals generated by a radical polymerization initiator, for example. The polymerizable compound may be any of a monomer, an oligomer, or a polymer.

[0028] The radical polymerizable compound has at least one radical polymerizable group, such as a vinyl group, an allyl group, a styryl group, an alkenyl group, an alkenylene group, a (meth)acryloyl group, or a maleimide group.

[0029] Specific examples of the radical polymerizable compound include (meth)acrylate compounds, maleimide compounds, vinyl ether compounds, allyl compounds, styrene, 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.

[0030] Examples of the (meth)acrylate compound 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, and n-hexyl (meth)acrylate. 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-dimethyl methylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (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, neo Pentyl glycol di(meth)acrylate, pentaerythritol (meth)acrylate, dipentaerythritol 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,Examples include 2-di(meth)acryloyloxydiethyl phosphate and 2-(meth)acryloyloxyethyl acid phosphate.

[0031] Examples of the maleimide compound 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. Examples of such bismaleimide include panbismaleimide, N,N'-4,4-diphenyletherbismaleimide, N,N'-3,3-diphenylsulfonebismaleimide, 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-cyclohexyl)benzene, and 2,2'-bis(4-(4-maleimidophenoxy)phenyl)hexafluoropropane.

[0032] Examples of the vinyl ether compound include diethylene glycol divinyl ether, dipropylene glycol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylolpropane trivinyl ether.

[0033] Examples of the allyl compound include 1,3-diallyl phthalate, 1,2-diallyl phthalate, and triallyl isocyanurate.

[0034] Examples of styrene derivatives include polymerizable compounds in which a hydrogen atom at the α-position or on the aromatic ring of styrene, such as vinyltoluene and α-methylstyrene, is substituted.

[0035] As the radical polymerizable compound, one type of compound may be used alone, or multiple types of compounds may be used in combination. From the viewpoint of further suppressing peeling under high-temperature and high-humidity environments and obtaining a better resistance value, it is preferable to use a (meth)acrylate compound. By using a (meth)acrylate compound, there is a tendency for a good balance between the curing reaction rate and the physical properties after curing to be achieved.

[0036] From the viewpoint of further suppressing peeling under high-temperature and high-humidity environments and obtaining even better resistance values, the content of the (meth)acrylate compound may be 5% by mass or more, 10% by mass or more, 20% by mass or more, 40% by mass or more, 60% by mass or more, or 80% by mass or more, based on the total mass of the radical polymerizable compounds. The content of the (meth)acrylate compound may be 100% by mass. That is, the content of the (meth)acrylate compound may be 5 to 100% by mass, 10 to 100% by mass, 20 to 100% by mass, 40 to 100% by mass, 60 to 100% by mass, or 80 to 100% by mass.

[0037] From the viewpoint of balancing the crosslink density and the cure shrinkage, further reducing the connection resistance, and further improving the connection reliability, it is preferable to use a compound in which a radical polymerizable group is introduced into the end or side chain of a thermoplastic resin (thermoplastic polymer) as the radical polymerizable compound. Examples of the thermoplastic resin include acrylic resin, phenoxy resin, polyurethane resin, etc. Examples of the radical polymerizable group include vinyl group, allyl group, (meth)acryloyl group, etc.

[0038] As a compound in which a radical polymerizable group is introduced into the end or side chain of a thermoplastic resin, a (poly)urethane (meth)acrylate compound is preferred from the viewpoint of achieving both cohesive strength for reducing connection resistance and elongation for improving adhesive strength, thereby obtaining better adhesive properties.

[0039] The (poly)urethane (meth)acrylate compound preferably has an alicyclic ring and / or an aromatic ring. Examples of the alicyclic ring that the (poly)urethane (meth)acrylate compound may have include a cyclopentane ring, a cyclohexane ring, a dicyclopentane ring, an adamantane ring, and a norbornane ring. Examples of the aromatic ring that the (poly)urethane (meth)acrylate compound may have include a benzene ring, a naphthalene ring, and a phenanthrene ring.

[0040] The weight average molecular weight of a compound having a radical polymerizable group introduced into the end or side chain of a thermoplastic resin 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. The weight average molecular weight of a compound having a radical polymerizable group introduced into the end or side chain of a thermoplastic resin may be 1,000,000 or less, 500,000 or less, 250,000 or less, or 50,000 or less, from the viewpoint of achieving excellent compatibility with other components (e.g., other radical polymerizable compounds). From these viewpoints, the weight average molecular weight may be 3,000 to 1,000,000, 5,000 to 500,000, 10,000 to 250,000, or 10,000 to 50,000. The weight average molecular weight in this specification is a value measured by gel permeation chromatography (GPC) using a calibration curve with standard polystyrene.

[0041] The content of the compound having a radical polymerizable group introduced into the terminal or side chain of the thermoplastic resin may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more, based on the total mass of the radical polymerizable compounds, from the viewpoint of further reducing connection resistance and further improving connection reliability. The content of the compound having a radical polymerizable group introduced into the terminal or side chain of the thermoplastic resin may be 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less, based on the total mass of the radical polymerizable compounds, from the viewpoint of suppressing cure shrinkage during polymerization. From these viewpoints, the content may be 10 to 90% by mass, 20 to 80% by mass, 30 to 70% by mass, or 40 to 60% by mass, based on the total mass of the radical polymerizable compounds. In one embodiment, the content of the compound having a radical polymerizable group introduced into the terminal or side chain of the thermoplastic resin, based on the total mass of the (meth)acrylate compounds, may be in the above-mentioned range.

[0042] From the viewpoint of obtaining even better adhesive properties, the content of the (poly)urethane (meth)acrylate compound may be 30% by mass or more, 40% by mass or more, or 50% by mass or more, based on the total mass of the (meth)acrylate compounds. From the viewpoint of improving cohesive strength and improving reliability, the content of the (poly)urethane (meth)acrylate compound may be 80% by mass or less, 70% by mass or less, or 60% by mass or less, based on the total mass of the (meth)acrylate compounds. From these viewpoints, the content may be 30 to 80% by mass, 40 to 70% by mass, 40 to 60% by mass, or 50 to 60% by mass, based on the total mass of the (meth)acrylate compounds. In one embodiment, the content of the (poly)urethane (meth)acrylate compound, based on the total mass of the radically polymerizable compounds, may be in the above-mentioned range.

[0043] From the viewpoint of improving cohesive strength and further reducing connection resistance, it is preferable to use a (meth)acrylate compound having a high Tg skeleton (for example, a (meth)acrylate compound having a tricyclodecane skeleton) as the radical polymerizable compound. From the viewpoint of further reducing connection resistance, the (meth)acrylate compound having a high Tg skeleton preferably has two methacryloyloxy groups (i.e., is a di(meth)acrylate compound). Examples of such compounds include dicyclopentadiene diacrylate.

[0044] The content of the (meth)acrylate compound having a high Tg skeleton may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more, based on the total mass of the (meth)acrylate compounds, from the viewpoint of further improving cohesive strength and further reducing connection resistance. The content of the (meth)acrylate compound having a high Tg skeleton may be 60% by mass or less, 50% by mass or less, or 40% by mass or less, based on the total mass of the (meth)acrylate compounds, from the viewpoint of suppressing cure shrinkage during polymerization. From these viewpoints, the content may be 10 to 60% by mass, 20 to 50% by mass, 30 to 40% by mass, or 40 to 60% by mass, based on the total mass of the (meth)acrylate compounds. In one embodiment, the content of the (meth)acrylate compound having a high Tg skeleton, based on the total mass of the radically polymerizable compounds, may be in the above-mentioned range. The "content of the (meth)acrylate compound having a high Tg skeleton" may be interpreted as the content of the (meth)acrylate compound having a tricyclodecane skeleton or the content of the dicyclopentadiene diacrylate. That is, the content of the (meth)acrylate compound having a tricyclodecane skeleton and the content of the dicyclopentadiene diacrylate based on the total mass of the (meth)acrylate compounds may be within the above-mentioned ranges, and the content of the (meth)acrylate compound having a tricyclodecane skeleton and the content of the dicyclopentadiene diacrylate based on the total mass of the radical polymerizable compounds may be within the above-mentioned ranges.

[0045] From the viewpoint of further improving the adhesive strength to the surface of an inorganic material (such as a metal) and further improving the adhesive strength between electrodes (for example, between circuit electrodes), it is preferable to use a (meth)acrylate compound having at least one phosphate group in the molecule as the radical polymerizable compound. Examples of the (meth)acrylate compound having at least one phosphate group in the molecule include (meth)acrylate compounds represented by the following formula (1):

[0046] In formula (1), n ​​represents an integer of 1 to 3, and R １ represents a hydrogen atom or a methyl group.

[0047] The (meth)acrylate compound represented by the formula (1) can be obtained, for example, by reacting phosphoric anhydride with 2-hydroxyethyl (meth)acrylate. Specific examples of the (meth)acrylate compound represented by the formula (1) include mono(2-(meth)acryloyloxyethyl) acid phosphate and di(2-(meth)acryloyloxyethyl) acid phosphate.

[0048] The content of the (meth)acrylate compound represented by Formula (1) may be 0.5% by mass or more, 1.5% by mass or more, 3% by mass or more, or 5% by mass or more, based on the total mass of the (meth)acrylate compounds, from the viewpoint of further improving the adhesive strength to the surface of an inorganic material (such as a metal) and further improving the adhesive strength between electrodes (for example, between circuit electrodes). From the viewpoint of pot life, the content of the (meth)acrylate compound represented by Formula (1) may be 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less, based on the total mass of the (meth)acrylate compounds. From these viewpoints, the content may be 0.5 to 30% by mass, 1.5 to 20% by mass, 3 to 10% by mass, 5 to 10% by mass, or 1.5 to 5% by mass, based on the total mass of the (meth)acrylate compounds. In one embodiment, the content of the (meth)acrylate compound represented by Formula (1), based on the total mass of the radically polymerizable compounds, may be within the above-mentioned range. The "content of the (meth)acrylate compound represented by formula (1)" may be interpreted as the content of the (meth)acrylate compound having at least one phosphoric acid group in the molecule. That is, the content of the (meth)acrylate compound having at least one phosphoric acid group in the molecule based on the total mass of the (meth)acrylate compounds may be in the above-mentioned range, and the content of the (meth)acrylate compound having at least one phosphoric acid group in the molecule based on the total mass of the radical polymerizable compounds may be in the above-mentioned range.

[0049] The content of the radical polymerizable compound may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more, based on the total mass of the adhesive composition, from the viewpoint of easily achieving the crosslink density required to reduce connection resistance and improve connection reliability. The content of the radical polymerizable compound may be 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less, based on the total mass of the adhesive composition, from the viewpoint of suppressing cure shrinkage during polymerization and achieving good reliability. From these viewpoints, the content of the radical polymerizable compound may be 10 to 90% by mass, 20 to 80% by mass, 30 to 70% by mass, or 40 to 60% by mass, based on the total mass of the adhesive composition. In one embodiment, the content of the radical polymerizable compound based on the total solid content contained in the adhesive composition may be within the above range. Note that the total solid content refers to the amount obtained by excluding the amount of solvent from the total amount of the adhesive composition. If the adhesive composition does not contain a solvent, it refers to the total amount of the adhesive composition. However, the solid content does not include conductive particles.

[0050] (Radical polymerization initiator) The radical polymerization initiator is a compound that generates radicals by heat, light, or the like. The radical polymerization initiator may be a thermal radical polymerization initiator or a photoradical polymerization initiator, but from the viewpoint of further improving the effect of reducing connection resistance and achieving more excellent connection reliability, it is preferable that the radical polymerization initiator is a compound that generates radicals by heat (thermal radical polymerization initiator). As the radical polymerization initiator, one type of compound may be used alone, or multiple types of compounds may be used in combination.

[0051] A thermal radical polymerization initiator decomposes due to heat to generate free radicals. In other words, a thermal radical polymerization initiator is a compound that generates radicals when external thermal energy is applied. The thermal radical polymerization initiator can be arbitrarily selected from conventionally known organic peroxides and azo compounds. As the thermal radical polymerization initiator, an organic peroxide is preferred from the viewpoint of further improving the effect of suppressing the flow and peeling of the conductive particles. From the viewpoints of stability, reactivity, and compatibility, an organic peroxide having a one-minute half-life temperature of 90 to 175°C and a weight-average molecular weight of 180 to 1,000 is more preferred. Having a one-minute half-life temperature within this range results in even better storage stability, sufficiently high radical polymerizability, and short curing time.

[0052] Specific examples of the thermal radical polymerization initiator 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, and t-butyl peroxyneodecanoate. Oxypivalate, 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, 3-hydroxy-1,1-dimethylbutylperoxyneodecanoate, t-amylperoxyneodecanoate, di(3-methylbenzoyl) peroxide, dibenzoyl peroxide, di(4-methylbenzoyl) peroxide, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2 organic peroxides such as 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;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);

[0053] The photoradical polymerization initiator is a polymerization initiator that generates radicals 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). The photopolymerization initiator is preferably a photoradical polymerization initiator from the viewpoint of facilitating curing at low temperatures in a short time. Examples of the photoradical polymerization initiator include photopolymerization initiators having a structure such as 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, or an α-hydroxyalkylphenone structure.

[0054] Specific examples of the compound 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), and the like.

[0055] Examples of compounds having a bisimidazole structure include 2,4,5-triarylimidazole dimers such as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(m-methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-phenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer, 2,4-di(p-methoxyphenyl)-5-phenylimidazole dimer, and 2-(2,4-dimethoxyphenyl)-4,5-diphenylimidazole dimer.

[0056] Examples of compounds having an acridine structure include 9-phenylacridine and 1,7-bis(9,9'-acridinyl)heptane.

[0057] The radical polymerization initiator may be a thermal radical polymerization initiator, from the viewpoint of further improving the effect of reducing connection resistance and achieving more excellent connection reliability. Among the thermal radical polymerization initiators, when an organic peroxide is used, the above-mentioned effect is more likely to be obtained significantly.

[0058] The content of the radical polymerization initiator 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 adhesive composition, from the viewpoint of further improving the effect of reducing connection resistance and achieving more excellent connection reliability. From the viewpoint of pot life, the content of the radical polymerization initiator may be 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less, based on the total mass of the adhesive composition. From these viewpoints, the content of the radical polymerization initiator may be 0.1 to 30% by mass, 0.5 to 20% by mass, 1 to 10% by mass, or 1 to 5% by mass, based on the total mass of the adhesive composition. In one embodiment, the content of the radical polymerization initiator, based on the total amount of solids contained in the adhesive composition, may be in the above-mentioned range.

[0059] <Epoxy Group-Containing Acrylic Resin> The epoxy group-containing acrylic resin is an acrylic resin having at least one epoxy group in the molecule. Here, the acrylic resin refers to a polymer containing a monomer unit derived from a (meth)acrylate compound. The epoxy group-containing acrylic resin may be a polymer containing only a monomer unit derived from a (meth)acrylate compound, or may be a polymer containing a monomer unit derived from a (meth)acrylate compound and a monomer unit derived from a polymerizable compound other than a (meth)acrylate compound.

[0060] Examples of the (meth)acrylate compound contained as a monomer unit in the epoxy group-containing acrylic resin include the (meth)acrylate compounds exemplified above as the radical polymerizable compound.

[0061] Examples of polymerizable compounds other than (meth)acrylate compounds that can be contained as monomer units in the epoxy group-containing acrylic resin include compounds other than the (meth)acrylate compounds exemplified above as the radically polymerizable compounds (maleimide compounds, vinyl ether compounds, allyl compounds, styrene, styrene derivatives, acrylamide derivatives, nadimide derivatives, natural rubber, isoprene rubber, butyl rubber, nitrile rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, carboxylated nitrile rubber, etc.). Among these, styrene and styrene derivatives are preferably used.

[0062] The epoxy group-containing acrylic resin may be solid at 25° C. The shape of the epoxy group-containing acrylic resin is not particularly limited, and may be, for example, powder, flake, or the like.

[0063] The weight-average molecular weight of the epoxy group-containing acrylic resin is 5,000 or more, and may be 7,500 or more, 10,000 or more, 15,000 or more, or 20,000 or more. When the weight-average molecular weight of the epoxy group-containing acrylic resin is 5,000 or more, not only is excellent half-cutting property obtained, but film formability is improved and good toughness tends to be obtained. The weight-average molecular weight of the epoxy group-containing acrylic resin may be 30,000 or less, 20,000 or less, 15,000 or less, or 10,000 or less, from the viewpoint of obtaining good fluidity during mounting and better connection resistance. In particular, when the weight-average molecular weight of the epoxy group-containing acrylic resin is 15,000 or less, better adhesive strength is likely to be obtained. From these viewpoints, the weight average molecular weight of the epoxy group-containing acrylic resin may be 5,000 to 30,000, 7,500 to 20,000, 7,500 to 15,000, 7,500 to 10,000, 10,000 to 30,000, 15,000 to 30,000, or 20,000 to 30,000.

[0064] The epoxy equivalent (unit: g / eq) of the epoxy group-containing acrylic resin may be 100 or more, 200 or more, or 300 or more, from the viewpoint of excellent storage stability. The epoxy equivalent (unit: g / eq) of the epoxy group-containing acrylic resin is preferably 1000 or less, from the viewpoint of suppressing warping of the cured product due to an increased cure shrinkage rate, and may be 500 or less, 350 or less, or 200 or less. In particular, when the epoxy equivalent (unit: g / eq) of the epoxy group-containing acrylic resin is 200 or less, better adhesive strength is likely to be obtained. From these viewpoints, the epoxy equivalent (unit: g / eq) of the epoxy group-containing acrylic resin may be 100 to 1000, 200 to 500, 300 to 500, 100 to 350, or 100 to 200. Here, the epoxy equivalent is the number of grams (g / eq) of a resin containing 1 gram equivalent of epoxy groups, and is measured according to the method specified in JIS K-7236.

[0065] The glass transition temperature (Tg) of the epoxy group-containing acrylic resin may be 25°C or higher, 35°C or higher, or 45°C or higher, from the viewpoint of improving reliability and stability against external stress. The glass transition temperature (Tg) of the epoxy group-containing acrylic resin may be 100°C or lower, 80°C or lower, 60°C or lower, or 50°C or lower, from the viewpoint of preventing peeling after curing. In particular, when the glass transition temperature (Tg) of the epoxy group-containing acrylic resin is 60°C or lower, better adhesive strength is likely to be obtained. From these viewpoints, the glass transition temperature (Tg) of the epoxy group-containing acrylic resin may be 25 to 100°C, 35 to 80°C, 45 to 60°C, 25 to 60°C, or 25 to 50°C. Here, the glass transition temperature is a value measured by differential scanning calorimetry.

[0066] The content of the epoxy group-containing acrylic resin may be 1% by mass or more, 5% by mass or more, or 10% by mass or more, based on the total solid content of the adhesive composition, from the viewpoint of further improving half-cutting properties. The content of the epoxy group-containing acrylic resin may be 15% by mass or less, 10% by mass or less, or 5% by mass or less, based on the total solid content of the adhesive composition, from the viewpoint of easily obtaining a homogeneous composition by mixing the epoxy group-containing acrylic resin well with other components (e.g., radically polymerizable compounds) in the composition. From these viewpoints, the content of the epoxy group-containing acrylic resin may be 1 to 15% by mass, 5 to 15% by mass, or 10 to 15% by mass, based on the total solid content of the adhesive composition. Note that, when the adhesive composition contains a solvent, the total solid content refers to the amount obtained by excluding the solvent from the total amount of the adhesive composition. When the adhesive composition does not contain a solvent, the total solid content refers to the total amount of the adhesive composition. However, the solid content does not include conductive particles.

[0067] <Conductive Particles> The conductive particles are not particularly limited as long as they are conductive particles, and may be metal particles made of metals such as Au, Ag, Ni, Cu, or solder, or conductive carbon particles made of conductive carbon. The conductive particles may also be coated conductive particles having a core containing non-conductive glass, ceramic, plastic (polystyrene, etc.), or the like, 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 metal or conductive carbon that coats the core are preferably used. In this case, the cured product of the adhesive composition can be easily deformed by heating or pressure, which increases the contact area between the electrodes and the conductive particles when electrically connecting the electrodes, thereby further improving the conductivity between the electrodes.

[0068] The conductive particles may be insulating coated conductive particles comprising the above-mentioned metal particles, conductive carbon particles, or coated conductive particles, and an insulating layer containing an insulating material such as resin and coating the surfaces of the particles. When the conductive particles are insulating coated conductive particles, even if the content of the conductive particles is high, the surfaces of the particles are coated with resin, which can suppress the occurrence of short circuits due to contact between the conductive particles, and can also improve the insulation between adjacent electrode circuits. The conductive particles may be one of the above-mentioned various conductive particles, or a combination of two or more of them.

[0069] The maximum particle size of the conductive particles must be smaller than the minimum spacing between the electrodes (the shortest distance between adjacent electrodes). From the viewpoint of excellent dispersibility and conductivity, the maximum particle size of the conductive particles 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 the conductive particles may be 50 μm or less, 30 μm or less, or 20 μm or less. From these viewpoints, the maximum particle size of the conductive particles may be 1.0 to 50 μm, 2.0 to 30 μm, or 2.5 to 20 μm. 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 the conductive particles. Note that if the conductive particles are not spherical, e.g., have protrusions, the particle size of the conductive particles is defined as the diameter of a circle circumscribing the conductive particles in an SEM image.

[0070] The average particle size of the conductive particles 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 the conductive particles may be 50 μm or less, 30 μm or less, or 20 μm or less, from the viewpoint of excellent dispersibility and conductivity. From these viewpoints, the average particle size of the conductive particles may be 1.0 to 50 μm, 2.0 to 30 μm, or 2.5 to 20 μm. 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.

[0071] When the adhesive composition is a composition used to form an insulating adhesive layer of an adhesive film, the content of conductive particles is preferably less than 0.1% by volume, and more preferably 0% by volume, based on the total volume of the adhesive composition.

[0072] When the adhesive composition is a composition used to form a conductive adhesive layer, the content of the conductive particles may be 0.1 vol% or more, 1 vol% or more, or 5 vol% or more, and may be 50 vol% or less, 30 vol% or less, or 20 vol% or less, or may be 0.1 to 50 vol%, 1 to 30 vol%, or 5 to 20 vol%, based on the total volume of the adhesive composition. When the content of the conductive particles is equal to or greater than the above-mentioned lower limit, conductivity can be further improved. When the content of the conductive particles is equal to or less than the above-mentioned upper limit, short circuits can be easily suppressed.

[0073] <Thermoplastic Resin> Examples of thermoplastic resins include phenoxy resin, polyester resin, polyurethane resin, polyesterurethane resin, butyral resin, acrylic resin (acrylic rubber, etc., excluding resins that fall under the category of epoxy group-containing acrylic resin), polyimide resin, polyamide resin, etc. When the adhesive composition contains a thermoplastic resin, the adhesive composition can be easily formed into a film. Furthermore, when the adhesive composition contains a thermoplastic resin, stress in the adhesive film that occurs during curing can be alleviated. Furthermore, when the thermoplastic resin has a functional group such as a hydroxyl group, the adhesiveness of the adhesive film is likely to be improved. From these perspectives, it is preferable to use at least one thermoplastic resin selected from the group consisting of phenoxy resin, polyester resin, polyurethane resin, polyesterurethane resin, butyral resin, acrylic resin, and polyimide resin, and it is more preferable to use a phenoxy resin.

[0074] The content of the thermoplastic resin may be 5% by mass or more, 15% by mass or more, or 30% by mass or more, and may be 80% by mass or less, 65% by mass or less, or 50% by mass or less, or may be 5 to 80% by mass, 15 to 65% by mass, or 30 to 50% by mass, based on the total mass of the solids contained in the adhesive composition. In one embodiment, the content of the thermoplastic resin based on the total mass of solids contained in the adhesive composition may be in the above range.

[0075] <Other Components> The adhesive composition may further contain components (other components) other than the components described above. Examples of other components include coupling agents, fillers, softeners, accelerators, anti-degradants, colorants, flame retardants, thixotropic agents, etc.

[0076] (Coupling Agent) Examples of the coupling agent include silane coupling agents having an organic functional group such as a (meth)acryloyl group, a mercapto group, an amino group, an imidazole group, or an epoxy group; silane compounds such as tetraalkoxysilane; tetraalkoxytitanate derivatives; and polydialkyltitanate derivatives. When the adhesive 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, 20% by mass or less, or 0.1 to 20% by mass, based on the total mass of the adhesive composition. In one embodiment, the content of the coupling agent based on the total solid content of the adhesive composition may be within the above range. Note that, in this specification, silane coupling agents having a radically polymerizable group such as a (meth)acryloyl group are not considered to be included in the radically polymerizable compound.

[0077] (Filler) Examples of the filler include non-conductive fillers (e.g., non-conductive particles). When the adhesive composition contains a filler, further improvement in connection reliability can be expected. The filler may be either an inorganic filler or an 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 content of the filler may be, for example, 1% by volume or more, 30% by volume or less, or 1 to 30% by volume, based on the total volume of the adhesive composition.

[0078] <Adhesive Film> Another embodiment of the present disclosure is an adhesive film (film-like adhesive) including a first adhesive layer made of the adhesive composition of the above embodiment.

[0079] The adhesive film of this embodiment has excellent half-cutting properties because it includes a first adhesive layer made of the adhesive composition of the above embodiment. Furthermore, the adhesive film of this embodiment is suitable for circuit connection, and the adhesive film can easily provide a circuit connection structure that has sufficiently high adhesive strength and sufficiently low connection resistance between opposing electrodes.

[0080] The adhesive film may be a single-layer adhesive film consisting of only a first adhesive layer, or may be a multi-layer adhesive film further including a second adhesive layer laminated on the first adhesive layer.The adhesive film may also be composed of three or more layers, including a layer other than the first and second adhesive layers (e.g., a third adhesive layer).

[0081] The adhesive film may be an adhesive film containing conductive particles. When the adhesive film is a multilayer adhesive film, any layer may contain conductive particles, but from the viewpoint of achieving better half-cutting properties, it is preferable that the first adhesive layer is substantially free of conductive particles. Here, "substantially free of conductive particles" means that the content of conductive particles based on the total volume of the adhesive layer is less than 0.1 volume %.

[0082] The adhesive film containing conductive particles may be, for example, an adhesive film consisting of a first adhesive layer containing conductive particles, or may be an adhesive film including a first adhesive layer and a second adhesive layer, at least one of which contains conductive particles. The adhesive film containing conductive particles may or may not have anisotropic conductivity.

[0083] The adhesive film may be insulating or conductive. The adhesive film may be an adhesive film consisting of an insulating adhesive layer or a conductive adhesive layer, or may be an adhesive film including an insulating adhesive layer and a conductive adhesive layer. When the adhesive film includes an insulating adhesive layer and a conductive adhesive layer, one of the first adhesive layer and the second adhesive layer may be an insulating adhesive layer, and the other may be a conductive adhesive layer. The conductive adhesive layer and the insulating adhesive layer may be distinguished by the content of the conductive particles described above. That is, the insulating adhesive layer may be, for example, an adhesive layer in which the content of conductive particles is less than 0.1 vol% based on the total volume of the adhesive layer. Furthermore, the conductive adhesive layer may be, for example, an adhesive layer in which the content of conductive particles is 0.1 vol% or more based on the total volume of the adhesive layer.

[0084] In order to suppress the flow of conductive particles that occurs during the production of a circuit connection structure, the adhesive film may include a layer made of a cured product of a photo- and thermosetting composition containing conductive particles (e.g., a composition containing a polymerizable compound, a photopolymerization initiator, a thermal polymerization initiator, and conductive particles) as a second adhesive layer. An adhesive film including such a second adhesive layer can suppress the occurrence of short circuits due to the aggregation of conductive particles between electrodes, as well as the deterioration of insulating properties and the occurrence of variations in connection resistance values ​​due to the distribution of conductive particle density associated with the flow of conductive particles. Examples of the polymerizable compound, photopolymerization initiator, and thermal polymerization initiator that can be used include the radical polymerizable compounds, photoradical polymerization initiators, and thermal radical polymerization initiators described above.

[0085] The adhesive film of this embodiment will be described in detail below, taking a two-layer adhesive film for circuit connection as an example.

[0086] Figure 1 is a schematic cross-sectional view showing an adhesive film for circuit connection of one embodiment. The adhesive film for circuit connection 1 (hereinafter also simply referred to as "adhesive film 1") shown in Figure 1 comprises a first adhesive layer 2 and a second adhesive layer 3 laminated on the first adhesive layer 2. At least one of the first adhesive layer 2 and the second adhesive layer 3 is made of the adhesive composition of the above embodiment. Hereinafter, the adhesive composition constituting the first adhesive layer 2 will sometimes be referred to as the "first adhesive composition," and the adhesive composition constituting the second adhesive layer will sometimes be referred to as the "second adhesive composition."

[0087] (First adhesive layer) The first adhesive layer 2 is an insulating adhesive layer. The content of conductive particles in the first adhesive layer 2 is, for example, less than 0.1% by volume based on the total volume of the first adhesive layer 2. The first adhesive layer 2 does not necessarily contain conductive particles.

[0088] The thickness d1 of the first adhesive layer 2 may be set appropriately depending on the height of the electrodes of the circuit components to be bonded, etc. The thickness d1 of the first adhesive layer 2 may be 5 μm or more, 200 μm or less, or may be 5 to 200 μm, from the viewpoint of being able to sufficiently fill the space between the electrodes and seal the electrodes, thereby obtaining better connection reliability. As will be described later, when a portion of the conductive particles 4 is exposed from the surface of the second adhesive layer 3 (e.g., protruding toward the first adhesive layer 2), the thickness of the first adhesive layer 2 is the distance (d1 in FIG. 1 ) from the surface 2a of the first adhesive layer 2 opposite the second adhesive layer 3 to the boundary S between the first adhesive layer 2 and the second adhesive layer 3, which is located in the space between adjacent conductive particles 4, 4.

[0089] The thickness of the adhesive layer can be measured by the following method. First, the adhesive film 1 is sandwiched between two pieces of glass (thickness: approximately 1 mm). Next, 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.) is cast. Thereafter, the cross section is polished using a polishing machine, and the thickness of each adhesive layer is measured using a scanning electron microscope (SEM, trade name: SE-8020, manufactured by Hitachi High-Tech Science Corporation).

[0090] (Second Adhesive Layer) The second adhesive layer 3 is a conductive adhesive layer. The second adhesive layer 3 contains conductive particles 4 and an adhesive component 5. From the viewpoint of further improving conductivity, the content of the conductive particles 4 in the second adhesive layer 3 may be 0.1 vol% or more, 1 vol% or more, or 5 vol% or more, based on the total volume of the second adhesive layer 3. From the viewpoint of easily suppressing short circuits, the content of the conductive particles 4 in the second adhesive layer 3 may be 50 vol% or less, 30 vol% or less, or 20 vol% or less, based on the total volume of the second adhesive layer 3. From these viewpoints, the content of the conductive particles 4 in the second adhesive layer 3 may be 0.1 to 50 vol%, 1 to 30 vol%, or 5 to 20 vol%, based on the total volume of the second adhesive layer 3.

[0091] The thickness d2 of the second adhesive layer 3 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 4, from the viewpoint of making it easier for the conductive particles 4 to be trapped between opposing electrodes and further reducing connection resistance. The thickness d2 of the second adhesive layer 3 may be 0.8 times or less, or 0.7 times or less the average particle size of the conductive particles 4, from the viewpoint of making it easier for the conductive particles 4 to be crushed when sandwiched between opposing electrodes during thermocompression bonding and further reducing connection resistance. From these viewpoints, the thickness d2 of the second adhesive layer 3 may be 0.1 to 0.8 times, 0.2 to 0.8 times, or 0.3 to 0.7 times the average particle size of the conductive particles 4. The thickness d2 of the second adhesive layer 3 refers to the thickness of the second adhesive layer located in the space between adjacent conductive particles 4, 4.

[0092] When the thickness d2 of the second adhesive layer 3 and the average particle size of the conductive particles 4 satisfy the above-described relationship, for example, as shown in FIG. 1 , some of the conductive particles 4 in the second adhesive layer 3 may protrude from the second adhesive layer 3 toward the first adhesive layer 2. In this case, the boundary S between the second adhesive layer 3 and the first adhesive layer 2 is located in the space between adjacent conductive particles 4. By having the boundary S on the conductive particles 4 along the surface of the conductive particles 4, the conductive particles 4 in the second adhesive layer 3 may not protrude from the second adhesive layer 3 toward the first adhesive layer 2, and the above-described relationship may be satisfied. The conductive particles 4 may not be exposed on the surface 3 a of the second adhesive layer 3 opposite the first adhesive layer 2, and the opposite surface 3 a may be flat.

[0093] The relationship between the thickness d2 of the second adhesive layer 3 and the maximum particle size of the conductive particles 4 may be the same as above. For example, the thickness d2 of the second adhesive layer 3 may be 0.1 to 0.8 times, 0.2 to 0.8 times, or 0.3 to 0.7 times the maximum particle size of the conductive particles 4.

[0094] The thickness d2 of the second adhesive layer 3 may be, for example, 0.5 μm or more, 20 μm or less, or 0.5 to 20 μm. When a portion of the conductive particles 4 is exposed from the surface of the second adhesive layer 3 (e.g., protruding toward the first adhesive layer 2), the shortest distance (d2 in FIG. 1 ) from the surface 3 a of the second adhesive layer 3 opposite the first adhesive layer 2 to the boundary S between the second adhesive layer 3 and the first adhesive layer 2, which is located between adjacent conductive particles 4, 4, is the thickness of the second adhesive layer 3, and the exposed portions of the conductive particles 4 are not included in the thickness of the second adhesive layer 3. The length of the exposed portions of the conductive particles 4 may be, for example, 0.1 μm or more, 20 μm or less, or 0.1 to 20 μm.

[0095] The ratio of the thickness d2 of the second adhesive layer 3 to the thickness d1 of the first adhesive layer 2 (thickness d2 of the second adhesive layer 3 / thickness d1 of the first adhesive layer 2) may be 1 or more and 100 or less, from the viewpoint of being able to sufficiently fill the space between the electrodes and seal the electrodes, thereby obtaining better reliability.

[0096] The thickness of the adhesive film 1 (the total thickness of all layers constituting the adhesive film 1) may be, for example, 5 μm or more, 200 μm or less, or may be 5 to 200 μm.

[0097] In the adhesive film 1, conductive particles 4 are dispersed in the second adhesive layer 3. Therefore, the adhesive film 1 is an anisotropically conductive adhesive film having anisotropic conductivity. The adhesive film 1 is interposed between a first circuit member having a first electrode and a second circuit member having a second electrode, and is used to electrically connect the first electrode and the second electrode to each other by thermocompression bonding the first circuit member and the second circuit member.

[0098] Either the first adhesive layer 2 or the second adhesive layer 3 may be made of an adhesive composition that does not contain an epoxy group-containing acrylic resin. The adhesive composition may contain components that can be contained in the adhesive composition of the above embodiment (components other than the epoxy group-containing acrylic resin), and may be, for example, a composition that contains a radical polymerizable compound and a radical polymerization initiator.

[0099] The second adhesive layer 3 may be a layer made of a cured product of the photo- and thermosetting composition containing the conductive particles described above. In this case, the first adhesive layer 2 is made of the adhesive composition of the above embodiment.

[0100] The adhesive film 1 can be manufactured, for example, by a method including a step of preparing a first adhesive layer 2 (first preparation step), a step of preparing a second adhesive layer 3 (second preparation step), and a step of laminating the first adhesive layer 2 and the second adhesive layer 3 (lamination step).

[0101] (First Preparation Step) In the first preparation step, for example, a first adhesive layer 2 is formed on a substrate. Specifically, for example, each component contained in the first adhesive composition is added to a solvent (organic solvent) and dissolved or dispersed by stirring, mixing, kneading, or the like to prepare a varnish composition (varnish-like first adhesive composition). Thereafter, the varnish composition is applied to a release-treated substrate using a knife coater, roll coater, applicator, comma coater, die coater, or the like, and the solvent is volatilized by heating to form a first adhesive layer 2 made of the first adhesive composition.

[0102] The solvent used in preparing the varnish composition is preferably one that has the property of being able to uniformly dissolve or disperse each component, and examples thereof include toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, butyl acetate, etc. These solvents can be used alone or in combination of two or more. The stirring, mixing, and kneading in preparing the varnish composition can be carried out using, for example, a stirrer, a kneading machine, a three-roll mill, a ball mill, a bead mill, or a homodisper.

[0103] The substrate is not particularly limited as long as it has heat resistance sufficient to withstand the heating conditions when volatilizing the solvent, and for example, 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, etc. can be used.

[0104] The heating conditions (drying conditions) for volatilizing the solvent from the varnish composition applied to the substrate are preferably conditions that allow the solvent to volatilize sufficiently, such as a temperature of 40°C or higher and 120°C or lower for 0.1 minutes or longer and 10 minutes or shorter.

[0105] A portion of the solvent may remain unremoved in the first adhesive layer 2. The content of the solvent in the first adhesive layer 2 may be, for example, 10 mass % or less based on the total mass of the first adhesive layer 2.

[0106] (Second Preparation Step) In the second preparation step, for example, a second adhesive layer 3 is formed on a substrate. Specifically, for example, a layer made of the second adhesive composition is formed on the substrate in the same manner as in the first preparation step. The types of solvents that can be used, the types of substrates, and drying conditions are the same as those for the first adhesive layer. Next, when the second adhesive composition is a photo- and thermosetting composition, the layer made of the second adhesive composition is irradiated with light to cure (photo-cure) the second adhesive composition, thereby forming a second adhesive layer 3 on the substrate.

[0107] A portion of the solvent may remain unremoved in the second adhesive layer 3. The content of the solvent in the second adhesive layer 3 may be, for example, 10 mass % or less based on the total mass of the second adhesive layer 3.

[0108] For the light irradiation, it is preferable to use irradiation light (e.g., ultraviolet light) having a wavelength in the range of 150 to 750 nm. The 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, an LED light source, or the like. The amount of light irradiation is not particularly limited, and for example, the integrated light amount of light with a wavelength of 365 nm is 100 mJ / cm. ２ or more, and 200 mJ / cm ２ or more, and 300 mJ / cm ２ The amount of light irradiation may be, for example, 10,000 mJ / cm in terms of the integrated light amount of light with a wavelength of 365 nm. ２ or less, and ２ or less, and ２ It may be the following:

[0109] (Lamination Step) In the lamination step, the first adhesive layer 2 and the second adhesive layer 3 are laminated by bonding the first adhesive layer 2 and the second adhesive layer 3. Examples of methods for bonding the first adhesive layer 2 and the second adhesive layer 3 include hot pressing, roll lamination, and vacuum lamination. Lamination may be performed, for example, under temperature conditions of 0 to 80°C.

[0110] Although the method for producing the adhesive film for circuit connection 1 has been described above, the method for producing the adhesive film for circuit connection 1 is not limited to the above embodiment.

[0111] For example, the adhesive film for circuit connection 1 may be obtained by preparing a second adhesive layer 3 in the second preparation step, and then forming a first adhesive layer 2 directly on the second adhesive layer 3 in the same manner as in the first preparation step. The order in which the first and second preparation steps are performed is not limited. Either the first preparation step or the second preparation step may be performed first. Furthermore, for example, when the second adhesive composition is a photocurable and thermosetting composition, the adhesive film for circuit connection 1 may be obtained by preparing a laminate including a layer made of the second adhesive composition and a layer made of the first adhesive composition, and then irradiating the laminate with light to cure the second adhesive composition.

[0112] <Laminate> Another embodiment of this embodiment is a laminate comprising a substrate and the adhesive film of the above embodiment provided on the substrate. As the substrate, those exemplified as the substrates used in producing the adhesive film 1 can be used.

[0113] <Method for manufacturing circuit connection structure> Another embodiment of this embodiment is a method for manufacturing a circuit connection structure, comprising: a half-cutting step of cutting the adhesive film of the laminate of the above embodiment along an outline line that forms the outline of the adhesive film piece; a step of peeling the adhesive film piece formed by the half-cutting step from the substrate; and a step of interposing the adhesive film piece between a first circuit member having a first electrode and a second circuit member having a second electrode, and thermocompression-bonding the first circuit member and the second circuit member to electrically connect the first electrode and the second electrode to each other.

[0114] Hereinafter, the method for producing the circuit connection structure of this embodiment will be described, taking as an example a method using a laminate including the adhesive film 1 described above.

[0115] 2 and 3 are schematic cross-sectional views showing a method for manufacturing the circuit connection structure 10 of one embodiment.

[0116] In the method for manufacturing the circuit connection structure 10, first, a laminate 7 including a substrate 6 and an adhesive film 1 provided on the substrate 6 is prepared, and then a half-cutting process is performed on the laminate 7 (see FIGS. 2(a) and 2(b)). In the half-cutting process, the adhesive film 1 of the laminate 7 is cut along the outline 8a that forms the outline of the adhesive film piece 8. At this time, the cut is made from the adhesive film 1 side to the surface of the substrate 6 so as not to cut the substrate 6. The half-cutting process can be performed using a known half-cutting blade.

[0117] Next, the adhesive film piece 8 formed by the half-cutting step is peeled off from the substrate 6 (see FIG. 2(c)). In this case, since the adhesive film 1 is used in this embodiment, the adhesive is less likely to reattach at the cut portion, and the adhesive film piece 8 can be easily peeled off from the substrate 6.

[0118] Next, a first circuit board 11 and a first circuit member 13 having a first electrode 12 formed on the main surface 11a of the first circuit board 11, and a second circuit board 14 and a second circuit member 16 having a second electrode 15 formed on the main surface 14a of the second circuit board 14 are prepared, and the first circuit member 13 and the second circuit member 16 are arranged so that the first electrode 12 and the second electrode 15 face each other, and an adhesive film piece 8 is placed between the first circuit member 13 and the second circuit member 16 (see (a) of Figure 3).

[0119] The first circuit member 13 and the second circuit member 16 may be the same or different. The first circuit member 13 and the second circuit member 16 may be a glass or plastic substrate on which electrodes are formed, a printed wiring board, a ceramic wiring board, a flexible wiring board, a semiconductor silicon IC chip, or the like. The first circuit board 11 and the second circuit board 14 may be formed of an inorganic material such as a semiconductor, glass, or ceramic, an organic material such as polyimide or polycarbonate, or a composite material such as glass / epoxy. The first electrode 12 and the second electrode 15 may be formed of gold, silver, tin, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, aluminum, molybdenum, titanium, indium tin oxide (ITO), indium zinc oxide (IZO), indium gallium zinc oxide (IGZO), or the like. The first electrode 12 and the second electrode 15 may be circuit electrodes or bump electrodes. At least one of the first electrode 12 and the second electrode 15 may be a bump electrode. In Fig. 3, the second electrode 15 is a bump electrode.

[0120] There are no particular limitations on the order in which the first circuit member 13, the second circuit member 16, and the adhesive film piece 8 are arranged. For example, the adhesive film piece 8 may be laminated onto the first circuit member 13 so that the second adhesive layer 3 faces the mounting surface 11 a of the first circuit member 13, and then the second circuit member 16 may be arranged on the first circuit member 13 to which the adhesive film piece 8 has been laminated so that the first electrode 12 on the first circuit board 11 and the second electrode 15 on the second circuit board 14 face each other.

[0121] Next, the first circuit member 13, the adhesive film piece 8, and the second circuit member 16 are heated while the first circuit member 13 and the second circuit member 16 are pressed together in the thickness direction, thereby thermocompression-bonding the first circuit member 13 and the second circuit member 16 to each other (see FIG. 3( b)). At this time, as indicated by the arrows in FIG. 3( b), the first adhesive layer 2 is made of a flowable uncured thermosetting composition (first adhesive composition), so it flows to fill the gaps between the second electrodes 15, 15 and is cured by the heating. As a result, the first electrode 12 and the second electrode 15 are electrically connected to each other via the conductive particles 4, and the first circuit member 13 and the second circuit member 16 are bonded to each other by the cured product 17 of the adhesive film piece 8, thereby obtaining the circuit connection structure 10 shown in FIG. 3( c). The cured product 17 of the adhesive film piece 8 is composed of a first region 18 located on the second circuit member 16 side in the direction in which the first circuit member 13 and the second circuit member 16 face each other (hereinafter referred to as the "facing direction") and consisting of a cured product of the above-mentioned first adhesive composition, a second region 19 located on the first circuit member 13 side in the facing direction and consisting of a cured product of components other than the conductive particles 4 of the above-mentioned second adhesive composition, and conductive particles 4 interposed at least between the first electrode 12 and the second electrode 15 and electrically connecting the first electrode 12 and the second electrode 15 to each other.

[0122] In the manufacturing method of the circuit connection structure 10, the second adhesive layer 3 is a pre-cured layer, so the conductive particles 4 hardly flow during the thermocompression bonding and are efficiently captured between the opposing electrodes, thereby reducing the connection resistance between the opposing electrodes 12 and 15. As a result, a circuit connection structure with excellent connection reliability can be obtained.

[0123] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0124] <Synthesis of polyurethane acrylate (UA1)> 2,500 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 1,000) 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 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: RI-8020 manufactured by Tosoh Corporation Column: Gelpack GLA160S+GLA150S manufactured by Hitachi Chemical Co., Ltd. Sample concentration: 120 mg / 3 mL Solvent: tetrahydrofuran Injection volume: 60 μL Pressure: 2.94×10 ６ Pa (30kgf / cm ２ ) Flow rate: 1.00mL / min

[0125] <Preparation of Conductive Particles> A nickel layer was formed on the surface of 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.

[0126] Examples 1 to 4 and Comparative Example 1 Preparation of Varnish-like Adhesive Compositions (Varnish Compositions) The components shown below were mixed together with a solvent (methyl ethyl ketone) to prepare Varnish Compositions 1 to 6. The amount (parts by mass) of each component is shown in Table 1. The amount of A1 is the solids content of the thermoplastic resin solution. The amount of solvent was adjusted so that the solids content of the varnish composition was 50% by mass.

[0127] [Thermoplastic resin solution] A1: A solution having a solid content concentration of 40% by mass prepared by dissolving 40 g of bisphenol A-type phenoxy resin (trade name: PKHC, manufactured by Union Carbide Corporation) in 60 g of methyl ethyl ketone.

[0128] [Radical polymerizable compounds] B1: polyurethane acrylate (UA1) synthesized as described above B2: diacrylate having a tricyclodecane skeleton (trade name: DCP-A, manufactured by Toagosei Co., Ltd.) B3: 2-methacryloyloxyethyl acid phosphate (trade name: Light Ester P-2M, manufactured by Kyoeisha Chemical Co., Ltd.)

[0129] [Epoxy group-containing acrylic resins] C1: Acrylic resin having at least one epoxy group in the molecule (trade name: Marproof G-01100, manufactured by NOF Corporation, weight average molecular weight: 10,000, epoxy equivalent: 170 g / eq, Tg: 47°C) C2: Acrylic resin having at least one epoxy group in the molecule (trade name: Marproof G-0150M, manufactured by NOF Corporation, weight average molecular weight: 10,000, epoxy equivalent: 310 g / eq, Tg: 71°C) C3: Acrylic resin having at least one epoxy group in the molecule (trade name: Marproof G-0250SP, manufactured by NOF Corporation, weight average molecular weight: 20,000, epoxy equivalent: 310 g / eq, Tg: 74°C)

[0130] [Conductive particles] D1: Conductive particles prepared as described above

[0131] (Thermal radical polymerization initiator) E1: Benzoyl peroxide (trade name: Niper BMT-K40, manufactured by NOF Corporation)

[0132]

[0133] (Preparation of First Laminate) In Example 1, a first laminate was prepared using varnish composition 1. Specifically, varnish composition 1 was first applied to a 50 μm-thick PET film using a coating device. Next, hot air drying was performed at 70° C. for 3 minutes to form an 8 μm-thick insulating adhesive layer (insulating adhesive film) on the PET film. Through the above operations, a first laminate (laminate 1) comprising an insulating adhesive layer (insulating adhesive film) on a PET film was obtained.

[0134] In Examples 2 to 4 and Comparative Example 1, first laminates (Laminates 2 to 5) each comprising an insulating adhesive layer (insulating adhesive film) on a PET film were prepared in the same manner as above, except that varnish compositions 2 to 5 were used instead of varnish composition 1. Varnish composition 2 corresponds to laminate 2, varnish composition 3 corresponds to laminate 3, varnish composition 4 corresponds to laminate 4, and varnish composition 5 corresponds to laminate 5.

[0135] (Preparation of Second Laminate) A second laminate was prepared using varnish composition 6. Specifically, varnish composition 6 was first applied to 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 having a thickness (thickness after drying) of 4 μm on the PET film. Through the above operations, a second laminate (laminate 6) was obtained that had a conductive adhesive layer (conductive adhesive film) on the PET film. The conductive particle density at this time was approximately 7000 pcs / mm ２ The thickness of the region where the conductive particles were present, measured using a contact thickness meter, was 4 μm. Note that if the thickness of the conductive adhesive layer is smaller than the thickness (diameter) of the conductive particles, measuring the layer thickness using a contact thickness meter will reflect the thickness of the conductive particles, and the thickness of the region where the conductive particles were present will be measured. Therefore, the thickness of the conductive adhesive layer was determined by producing the adhesive film for circuit connection described below and then measuring the thickness of the conductive adhesive layer located in the spaced apart portion between adjacent conductive particles.

[0136] (Preparation of Laminates Comprising an Adhesive Film for Circuit Connection) The first laminate and the second laminate were arranged with their adhesive layers facing each other, and were laminated together with the PET film substrate using a roll laminator while being heated at 40° C. In this way, laminates of Examples 1 to 4 and Comparative Example 1 each comprising a substrate and an adhesive film for circuit connection (a two-layer adhesive film) provided on the substrate were prepared.

[0137] The thickness of the conductive adhesive layer of the prepared adhesive film for circuit connection was measured by the following method. First, 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 (product name: JER811, manufactured by Mitsubishi Chemical Corporation) and 10 g of a curing agent (product 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 the conductive adhesive layer located between adjacent conductive particles was measured using a scanning electron microscope (SEM, product name: SE-8020, manufactured by Hitachi High-Tech Science Corporation). The thickness of the conductive adhesive layer was 2 μm.

[0138] (Half-cut property evaluation) The half-cut property of the adhesive film for circuit connection obtained above was evaluated using a thermocompression bonding device LD-06 manufactured by Ohashi Manufacturing Co., Ltd. A specific evaluation method will be explained with reference to Figure 4. In Figure 4, 21 is the laminate obtained above, 22 is the substrate, and 23 is the adhesive film for circuit connection (adhesive film with a two-layer configuration).

[0139] First, a half-cut blade was collided with the laminate 21 obtained above to cut only the adhesive film 23. At this time, the contact position of the half-cut blade on the surface of the substrate 22 was used as the cutting reference position, and the blade depth (cut depth from the cutting reference position) was 5 μm. Next, using adhesive tape 24, the substrate 22 side of the laminate 21 after half-cutting was fixed to a flat plate 25, and one of the adhesive films (adhesive film piece 23 a) divided based on the cut surface 26 was pinched and lifted up and peeled down to the cut surface 26. At this time, the degree of lifting of the other adhesive film (adhesive film piece 23 b) divided based on the cut surface was confirmed. The above operation was performed at five locations, and a state in which no lifting occurred was designated A; a state in which the adhesive film lifted at least once or to some extent was designated B; and a state in which the adhesive film lifted at least once or significantly or peeled off together with the adhesive film piece 23 a was designated C.

[0140] (Evaluation of circuit connection structure) A 25 μm pitch COF (manufactured by FLEXSEED Co., Ltd.) 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 circuit connection adhesive film was placed on the glass substrate so that the adhesive layer side of the circuit connection adhesive film faced the glass substrate.

[0141] [Measurement of Connection Resistance Value] The connection resistance value between the opposing electrodes of the circuit connection structure obtained above was measured using a multimeter. The connection resistance value was calculated as the average value of 16 resistance points between the opposing electrodes. The results are shown in Table 2.

[0142] [Measurement of Adhesion Strength] The adhesion strength of the circuit connection structure obtained above was measured by the 90-degree peel method in accordance with JIS-Z0237. The adhesion strength measuring device used was Tensilon UTM-4 (trade name, manufactured by Toyo Baldwin Co., Ltd., peel strength 50 mm / min, 25°C). The results are shown in Table 2.

[0143] 1...adhesive film for circuit connection, 2...first adhesive layer, 3...second adhesive layer, 4...conductive particles, 6...substrate, 7...laminate, 8...adhesive film piece, 8a...outline, 10...circuit connection structure, 12...circuit electrode (first electrode), 13...first circuit member, 15...bump electrode (second electrode), 16...second circuit member.

Claims

1. An adhesive composition comprising a radically polymerizable compound, a radical polymerization initiator, and an acrylic resin having at least one epoxy group in the molecule and a weight average molecular weight of 5,000 or more.

2. The adhesive composition according to claim 1, wherein the content of the acrylic resin is 1 to 15 mass % based on the total amount of solids contained in the adhesive composition.

3. The adhesive composition according to claim 1 or 2, wherein the acrylic resin has an epoxy equivalent of 1000 g / eq or less.

4. The adhesive composition according to any one of claims 1 to 3, wherein the radically polymerizable compound comprises a (meth)acrylate compound having at least one phosphoric acid group in the molecule.

5. The adhesive composition according to any one of claims 1 to 4, further comprising at least one thermoplastic resin selected from the group consisting of a phenoxy resin, a polyester resin, a polyurethane resin, a polyester urethane resin, a butyral resin, an acrylic resin, and a polyimide resin.

6. The adhesive composition according to any one of claims 1 to 5, further comprising conductive particles.

7. An adhesive film comprising a first adhesive layer comprising the adhesive composition according to any one of claims 1 to 6.

8. The adhesive film of claim 7, further comprising a second adhesive layer laminated onto the first adhesive layer, and at least one of the first adhesive layer and the second adhesive layer contains conductive particles.

9. A laminate comprising a substrate and the adhesive film according to claim 7 or 8 provided on the substrate.

10. A method for manufacturing a circuit connection structure, comprising: a half-cutting step of cutting the adhesive film of the laminate described in claim 9 along an outline line forming the outline of the adhesive film piece; a step of peeling the adhesive film piece formed by the half-cutting step from the substrate; and a step of interposing the adhesive film piece 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.

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