TWI844802B - Adhesive composition and connecting structure - Google Patents

Abstract

The adhesive composition of the present invention contains (a) a thermoplastic resin, (b) a radical polymerizable compound, (c) a radical polymerization initiator, and (d) a boron-containing salt, wherein the boron-containing salt (d) is a compound represented by the following general formula (A). [In formula (A), R ¹ , R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and R ² , R ³ and R ⁴ each independently represent an aryl group]

Description

Adhesive composition and connecting structure

The present invention relates to an adhesive composition and a connecting structure.

In semiconductor components and liquid crystal display components, various adhesives have been used in the past to combine various components in the components. The requirements for adhesives are represented by adhesiveness, and cover many aspects such as heat resistance and reliability under high temperature and high humidity conditions. The adhesive is used for connecting liquid crystal display components to tape carrier packages (TCP) (chip on film (COF)), connecting flexible printed circuits (FPC) to TCP (COF), connecting TCP (COF) to printed wiring boards, and connecting FPC to printed wiring boards. In addition, the adhesive can also be used when mounting semiconductor components on substrates.

As for the adherends used for bonding, the typical examples are printed wiring boards or organic substrates such as polyimide, polyethylene terephthalate (PET), polycarbonate (PC), and polyethylene naphthalate (PEN). Metals such as copper and aluminum, or substrates with various surface conditions such as ITO (Indium Tin Oxide, a composite oxide of indium and tin), IZO (Indium Zinc Oxide, a composite of indium oxide and zinc oxide), AZO (Aluminum-doped Zinc Oxide, zinc and aluminum oxide), SiN (silicon nitride), and SiO ₂ (silicon dioxide) can be used. Therefore, the molecular design of the adhesive composition must be carried out according to each adherend.

Recently, with the high integration of semiconductor components and the high precision of liquid crystal display components, the pitch between components and the pitch between wirings have been miniaturized. In addition, semiconductor components, liquid crystal display components, or touch panels using organic substrates with low heat resistance such as PET, PC, and PEN are gradually being used. If the heating temperature during the curing of the adhesive composition used in such semiconductor components is high and the curing speed is slow, there is a tendency that not only the required connection parts but also the peripheral components are overheated, causing damage to the peripheral components, etc., so the adhesive composition is required to be bonded during low-temperature curing.

Conventionally, as an adhesive for the semiconductor element or liquid crystal display element, a thermosetting resin using an epoxy resin that exhibits high adhesion and high reliability has been used (see, for example, Patent Document 1 below). The resin components generally include an epoxy resin, a hardener such as a phenol resin that is reactive with the epoxy resin, and a thermolatent catalyst that promotes the reaction between the epoxy resin and the hardener. The thermolatent catalyst is a substance that does not react at storage temperatures such as room temperature but exhibits high reactivity when heated, and is an important factor in determining the curing temperature and curing speed. Various compounds are used from the viewpoints of the storage stability of the adhesive at room temperature and the curing speed when heated. In the actual process, the desired bonding is achieved by curing at a temperature of 170°C to 250°C for 1 to 3 hours. However, in order to cure the adhesive at a low temperature, a thermal latent catalyst with low activation energy is required, which is difficult to achieve storage stability.

In recent years, free radical curing adhesives that use free radical polymerizable compounds such as acrylate derivatives or methacrylate derivatives together with peroxides as free radical polymerization initiators have attracted attention. Free radical curing can be cured in a short time because free radicals as reactive species are highly reactive (for example, see Patent Document 2 below). Regarding such free radical curing adhesives, a method of using benzoyl peroxide (BPO), amine compounds, organic boron compounds, etc. as free radical polymerization initiators has been proposed (for example, see Patent Document 3 below).

[Prior art literature] [Patent document 1] Japanese Patent Publication No. 1-113480 [Patent document 2] International Publication No. 98/44067 [Patent document 3] Japanese Patent Publication No. 2000-290121

In order to make the radical curing adhesive harden at low temperature, a radical polymerization initiator needs to be used. For the existing radical curing adhesive, it is difficult to have both low temperature curability and storage stability. For example, when using benzoyl peroxide (BPO), amine compounds, organic boron compounds, etc. as radical polymerization initiators for radical polymerizable compounds such as acrylate derivatives or methacrylate derivatives, the curing reaction also proceeds at room temperature (25°C, the same below), so the storage stability may be reduced.

Therefore, the object of the present invention is to provide an adhesive composition having excellent low temperature curing property and storage stability. In addition, the object of the present invention is to provide a connection structure using the adhesive composition.

The inventors of the present invention have conducted intensive research to solve the above-mentioned problems and have found that excellent low-temperature hardening and storage stability can be obtained by using a specific boron compound as a constituent component of the adhesive composition, thereby completing the present invention.

That is, the adhesive composition of the present invention contains (a) a thermoplastic resin, (b) a radical polymerizable compound, (c) a radical polymerization initiator, and (d) a boron-containing salt, wherein the boron-containing salt (d) is a compound represented by the following general formula (A). [Chemical 1] [In formula (A), R ¹ , R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and R ² , R ³ and R ⁴ each independently represent an aryl group]

In the present invention, the adhesive composition contains (d) a boron-containing salt, which can promote the decomposition of (c) a radical polymerization initiator at low temperatures (e.g., 80°C to 120°C), so that the adhesive composition has excellent low-temperature curing properties. In addition, in the present invention, the boron-containing salt (d) is a compound represented by the general formula (A), so that the adhesive composition has excellent storage stability (e.g., storage stability near room temperature (e.g., -20°C to 25°C)), and even when the adhesive composition is stored for a long time, excellent bonding strength and connection resistance (e.g., bonding strength and connection resistance of a connection structure of a circuit component or a solar cell module) can be obtained. As described above, the adhesive composition of the present invention has excellent low-temperature curing property and storage stability.

Furthermore, in the present invention, whether or not the adhesive composition is stored for a long time, excellent bonding strength and connection resistance can be obtained. In addition, in the present invention, whether or not the adhesive composition is stored for a long time, stable performance (bonding strength and connection resistance) can be maintained even after a long-term reliability test (high temperature and high humidity test).

In addition, in the adhesive composition of the present invention, (b) the radical polymerizable compound may also include a vinyl compound having a phosphate group and a radical polymerizable compound other than the vinyl compound. In this case, bonding becomes easier during low temperature curing, and the bonding strength with the substrate having the connection terminal can be further improved.

In addition, the melting point of the boron-containing salt (d) may be 60° C. to 300° C. In this case, the stability (for example, the stability at around room temperature) is further improved, and the storage stability is further improved.

In addition, the (a) thermoplastic resin may include at least one selected from the group consisting of phenoxy resins, polyurethane resins, polyesterurethane resins, butyral resins, acrylic resins, polyimide resins, polyamide resins, and copolymers having vinyl acetate as a structural unit. In this case, heat resistance and adhesion are further improved, and these excellent properties can be easily maintained even after a long-term reliability test (high temperature and high humidity test).

In addition, the adhesive composition of the present invention may further contain (e) conductive particles. In this case, the adhesive composition can be given good conductivity or anisotropic conductivity, so it can be more preferably used for connecting circuit components with connection terminals or solar battery modules. In addition, the connection resistance of the connection structure obtained by electrical connection through the adhesive composition can be more fully reduced.

In addition, the inventors have found that the adhesive composition is useful for connecting components having connection terminals. The adhesive composition of the present invention can be used to electrically connect a first connection terminal disposed on the main surface of a first substrate with a second connection terminal disposed on the main surface of a second substrate, and can also be used to electrically connect a connection terminal of a solar cell having a connection terminal disposed on the main surface of a substrate with a wiring component.

The connection structure of one side of the present invention comprises: a first circuit member having a first substrate and a first connection terminal arranged on the main surface of the first substrate, a second circuit member having a second substrate and a second connection terminal arranged on the main surface of the second substrate, and a connection member arranged between the first circuit member and the second circuit member, and the connection member contains a cured product of the adhesive composition, and the first connection terminal and the second connection terminal are electrically connected. In the connection structure of one side of the present invention, the connection member contains the cured product of the adhesive composition, thereby improving the connection resistance and bonding strength of the connection structure.

In the connection structure of one aspect of the present invention, at least one of the first substrate and the second substrate may be formed of a base material containing a thermoplastic resin having a glass transition temperature of 200° C. or less. In this case, the bonding strength of the connection structure using the adhesive composition can be further improved.

In the connection structure of one side of the present invention, at least one of the first substrate and the second substrate can be composed of a base material containing at least one selected from the group consisting of polyethylene terephthalate, polycarbonate and polyethylene naphthalate. In this case, even if the first circuit component or the second circuit component having a substrate composed of the specific material (material with low heat resistance) is used, it can be cured at a low temperature by using the adhesive composition of the present invention, so that thermal damage to the first circuit component or the second circuit component can be reduced. In addition, the wettability of the substrate composed of the specific material and the adhesive composition is improved, and the bonding strength can be further improved. Thereby, when the substrate composed of the specific material is used, excellent connection reliability can be obtained.

In the connection structure on one side of the present invention, the following aspect may be adopted: the first substrate is composed of a base material containing at least one selected from the group consisting of polyethylene terephthalate, polycarbonate and polyethylene naphthalate, and the second substrate is composed of a base material containing at least one selected from the group consisting of polyimide resin and polyethylene terephthalate. In this case, even when the first circuit component or the second circuit component having a substrate composed of the specific material is used, it can be cured at a low temperature by using the adhesive composition of the present invention, thereby reducing heat damage to the first circuit component or the second circuit component. In addition, the wettability of the substrate composed of the specific material and the adhesive composition is improved, and the bonding strength can be further improved. Thereby, when a substrate made of the specific material is used, excellent connection reliability can be obtained.

The connection structure of the other side of the present invention comprises: a solar cell having a substrate and a connection terminal arranged on the main surface of the substrate, a wiring member, and a connection member arranged between the solar cell and the wiring member, and the connection member contains a cured product of the adhesive composition, and the connection terminal and the wiring member are electrically connected. In the connection structure of the other side of the present invention, the connection member contains the cured product of the adhesive composition, thereby improving the connection resistance and bonding strength of the connection structure.

According to the present invention, an adhesive composition having excellent low-temperature curing property and storage stability can be provided. This adhesive composition can improve storage stability compared to the case of using an alkyl boron compound as described in the aforementioned patent document 3. In addition, the adhesive composition of the present invention has an excellent balance between low-temperature curing property and storage stability. Since the adhesive composition of the present invention has excellent storage stability, excellent bonding strength and connection resistance can be obtained even when the adhesive composition is stored for a long time. Furthermore, for the adhesive composition of the present invention, excellent bonding strength and connection resistance can be obtained regardless of whether the adhesive composition is stored for a long time. In addition, the adhesive composition of the present invention can maintain stable performance (bonding strength and connection resistance) even after a long-term reliability test (high temperature and high humidity test) regardless of whether the adhesive composition is stored for a long time. The present invention can provide a connection structure using the adhesive composition.

The preferred embodiments of the present invention are described in detail below. In addition, in this specification, the term "(meth)acrylic acid" refers to acrylic acid and its corresponding methacrylic acid; the term "(meth)acrylate" refers to acrylate and its corresponding methacrylate; the term "(meth)acryloyl" refers to acryl and methacryloyl; the term "(meth)acryloyloxy" refers to acryloxy and its corresponding methacryloyloxy.

In this specification, the so-called "melting point" refers to the temperature obtained by the method described in JIS standard K0064, or the temperature of the endothermic peak measured by weighing 5.0 mg of a sample in a non-sealed sample pan and using a differential scanning calorimeter (DSC7, manufactured by PERKIN ELMER) under nitrogen at a heating rate of 10°C/min.

In addition, in this specification, the so-called "weight average molecular weight" refers to the value measured by gel permeation chromatograph (GPC) using a calibration curve of standard polystyrene according to the conditions shown below. (Measurement conditions) Apparatus: GPC-8020 manufactured by Tosoh Co., Ltd. Detector: RI-8020 manufactured by Tosoh Co., Ltd. Column: Gelpack GL-A-160-S+Gelpack GL-A150 manufactured by Hitachi Chemical Co., Ltd. Sample concentration: 120 mg/3 ml Solvent: Tetrahydrofuran Injection volume: 60 μl Pressure: 30 kgf/cm ² Flow rate: 1.00 ml/min

The adhesive composition of this embodiment contains (a) a thermoplastic resin, (b) a radical polymerizable compound, (c) a radical polymerization initiator, and (d) a boron-containing salt.

(a) Thermoplastic resins (a) Thermoplastic resins refer to resins (polymers) having the following properties: when heated, they become a high-viscosity liquid state and can be deformed freely by external force. When cooled and the external force is removed, they maintain the shape and become hard, and this process can be repeated. In addition, (a) thermoplastic resins may also be resins (polymers) having the above properties and containing reactive functional groups. The glass transition temperature (Tg) of (a) thermoplastic resins is preferably not less than -30°C and not more than 190°C, more preferably not less than -25°C and not more than 170°C, and even more preferably not less than -20°C and not more than 150°C.

(a) Thermoplastic resins may contain, for example, at least one selected from the group consisting of phenoxy resins, polyurethane resins, polyesterurethane resins, butyraldehyde resins (e.g., polyvinylbutyraldehyde resins), acrylic resins, polyimide resins, polyamide resins, and copolymers having vinyl acetate as a structural unit (vinyl acetate copolymers, e.g., ethylene-vinyl acetate copolymers). These resins may be used alone or in combination of two or more. Furthermore, these (a) thermoplastic resins may contain siloxane bonds or fluorine substituents. These resins are preferably in a state where the mixed resins are completely compatible with each other, or in a state where microphase separation occurs and the resins are turbid.

When the adhesive composition is made into a film, the larger the weight average molecular weight of the (a) thermoplastic resin, the easier it is to obtain good film forming properties, and the melt viscosity that affects the fluidity of the film-like adhesive composition can be set to a wide range. The weight average molecular weight of the (a) thermoplastic resin is preferably 5,000 or more, more preferably 7,000 or more, and further preferably 10,000 or more. If the weight average molecular weight of the (a) thermoplastic resin is 5,000 or more, there is a tendency to easily obtain good film forming properties. The weight average molecular weight of the (a) thermoplastic resin is preferably 150,000 or less, more preferably 100,000 or less, and further preferably 80,000 or less. When the weight average molecular weight of the thermoplastic resin (a) is 150,000 or less, good compatibility with other components tends to be easily obtained.

The amount of the (a) thermoplastic resin in the adhesive composition is preferably 5% by mass or more, more preferably 15% by mass or more, based on the total mass of the adhesive component (the components excluding the conductive particles in the adhesive composition). If the amount of the (a) thermoplastic resin is 5% by mass or more, when the adhesive composition is used in the form of a film, good film-forming properties tend to be easily obtained. The amount of the (a) thermoplastic resin in the adhesive composition is preferably 80% by mass or less, more preferably 70% by mass or less, based on the total mass of the adhesive component (the components excluding the conductive particles in the adhesive composition). When the amount of the thermoplastic resin (a) blended is 80% by mass or less, good fluidity of the adhesive composition tends to be easily obtained.

((b) Radical polymerizable compounds) (b) Radical polymerizable compounds refer to compounds that undergo free radical polymerization by the action of a free radical polymerization initiator, and may also be compounds that generate free radicals by themselves by applying activation energy such as light or heat. (b) Radical polymerizable compounds preferably include compounds having functional groups that undergo polymerization by active free radicals, such as vinyl, (meth)acryl, allyl, and maleimide groups.

(b) The free radical polymerizable compounds include: epoxy (meth)acrylate oligomers, urethane (meth)acrylate oligomers, polyether (meth)acrylate oligomers, polyester (meth)acrylate oligomers, etc.; trihydroxymethylpropane tri(meth)acrylate, polyethylene glycol di(meth)acrylate, polyalkylene glycol di(meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, neopentyl glycol di(meth)acrylate, dipentylethylene glycol di(meth)acrylate, Tetraol hexa(meth)acrylate, isocyanuric acid-modified difunctional (meth)acrylate, isocyanuric acid-modified trifunctional (meth)acrylate, bisphenoxyethanol fluoride acrylate, epoxy (meth)acrylate obtained by adding (meth)acrylic acid to the glycidyl group of bisphenol fluoride diglycidyl ether, a compound obtained by introducing a (meth)acryloyloxy group into a compound obtained by adding ethylene glycol or propylene glycol to the glycidyl group of bisphenol fluoride diglycidyl ether, a compound represented by the following general formula (B) or general formula (C), etc.

[Chemistry 2] [In formula (B), ^R9 and ^R10 each independently represent a hydrogen atom or a methyl group, and a and b each independently represent an integer of 1 to 8]

[Chemistry 3] [In formula (C), R ¹¹ and R ¹² each independently represent a hydrogen atom or a methyl group, and c and d each independently represent an integer of 0 to 8]

In addition, the (b) radical polymerizable compound may be a compound that is in a solid state such as wax, crystalline, glassy, or powdery state when left alone at 30°C and has no fluidity, and may be used without particular limitation. Specific examples of such (b) radical polymerizable compounds include: N,N'-methylenebisacrylamide, diacetone acrylamide, acrylamide), N-hydroxymethyl acrylamide, N-phenylmethacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, tris(2-acryloxyethyl)isocyanurate, N-phenylmaleimide, N-(o-methylphenyl)maleimide, N-(m-methylphenyl)maleimide, N-(p-methylphenyl)maleimide, N-(o-methoxyphenyl)maleimide, N-(m-methoxyphenyl)maleimide imide, N-(p-methoxyphenyl) maleimide, N-methyl maleimide, N-ethyl maleimide, N-octyl maleimide, 4,4'-diphenylmethane dimaleimide, m-phenylene dimaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane dimaleimide, 4-methyl-1,3-phenylene dimaleimide, N-methylacryloyloxy maleimide, N-acryloyl Enyloxymaleimide, 1,6-bismaleimide-(2,2,4-trimethyl)hexane, N-methylacryloyloxysuccinimide, N-acryloyloxysuccinimide, 2-naphthyl methacrylate, 2-naphthyl acrylate, pentaerythritol tetraacrylate, divinyl ethyl urea, divinyl propyl urea, 2-polystyryl ethyl methacrylate, N-phenyl-N'-(3-methacryloyloxy-2-hydroxy The invention also includes the following compounds: N-(2-(4-(6-propyl)-p-phenylenediamine, N-phenyl-N'-(3-acryloxy-2-hydroxypropyl)-p-phenylenediamine, tetramethylpiperidinyl methacrylate, tetramethylpiperidinyl acrylate, pentamethylpiperidinyl methacrylate, pentamethylpiperidinyl acrylate, octadecyl acrylate, N-tert-butylacrylamide, diacetoneacrylamide, N-(hydroxymethyl)acrylamide, and compounds represented by the following general formulas (D) to (M).

[Chemistry 4] [In formula (D), e represents an integer from 1 to 10]

[Chemistry 5]

[Chemistry 6] [In formula (F), R ¹³ and R ¹⁴ each independently represent a hydrogen atom or a methyl group, and f represents an integer of 15 to 30]

[Chemistry 7] [In formula (G), R ¹⁵ and R ¹⁶ each independently represent a hydrogen atom or a methyl group, and g represents an integer of 15 to 30]

[Chemistry 8] [In formula (H), R ¹⁷ represents a hydrogen atom or a methyl group]

[Chemistry 9] [In formula (I), R ¹⁸ represents a hydrogen atom or a methyl group, and h represents an integer from 1 to 10]

[Chemistry 10] [In formula (J), R ¹⁹ represents a hydrogen atom or an organic group represented by the following general formula (i) or general formula (ii), and i represents an integer from 1 to 10]

[Chemistry 11] [Chemistry 12]

[Chemistry 13] [In formula (K), ^R20 represents a hydrogen atom or an organic group represented by the following general formula (iii) or general formula (iv), and j represents an integer of 1 to 10]

[Chemistry 14] [Chemistry 15]

[Chemistry 16] [In formula (L), ^R21 represents a hydrogen atom or a methyl group]

[Chemistry 17] [In formula (M), ^R22 represents a hydrogen atom or a methyl group]

In addition, urethane acrylate can be used as the (b) radical polymerizable compound. Urethane acrylate can be used alone or in combination with a (b) radical polymerizable compound other than urethane acrylate. By using urethane acrylate alone or in combination with a (b) radical polymerizable compound other than urethane acrylate, flexibility is improved and bonding strength can be further improved.

The urethane acrylate is not particularly limited, but is preferably an urethane acrylate represented by the following general formula (N). Here, the urethane acrylate represented by the following general formula (N) can be obtained by a condensation reaction of an aliphatic diisocyanate or an alicyclic diisocyanate with at least one selected from the group consisting of an aliphatic ester diol and an alicyclic ester diol, and an aliphatic carbonate diol and an alicyclic carbonate diol.

[Chemistry 18] [In formula (N), R ²³ and R ²⁴ each independently represent a hydrogen atom or a methyl group, R ²⁵ represents an ethyl group or a propyl group, R ²⁶ represents a saturated aliphatic group or a saturated alicyclic group, R ²⁷ represents a saturated aliphatic group or a saturated alicyclic group containing an ester group, or a saturated aliphatic group or a saturated alicyclic group containing a carbonate group, and k represents an integer of 1 to 40. In formula (N), R ²⁵ and R ²⁶ may be the same or different from each other]

The aliphatic diisocyanate or alicyclic diisocyanate constituting the acrylic urethane may be selected from the following diisocyanates: tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, 2,2,4-trimethylhexamethylene-1,6-diisocyanate, 2,4,4-trimethylhexamethylene-1,6-diisocyanate, isophorone diisocyanate, cyclohexyl diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated trimethylxylene diisocyanate, etc.

In addition, the aliphatic ester diol or alicyclic ester diol constituting the urethane acrylate may be selected from the following diols: ethylene glycol, propylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, neopentyl glycol, 1,2-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,4-di ... 1,2-Hexanediol, 1,5-Hexanediol, 1,6-Hexanediol, 2,5-Hexanediol, 2-Ethyl-1,3-Hexanediol, 2,5-Dimethyl-2,5-Hexanediol, 1,2-Octanediol, 1,8-Octanediol, 1,7-Heptanediol, 1,9-Nonanediol, 1,2-Decanediol, 1,10-Decanediol, 1,12-Dodecanediol, Dodecanediol alcohol, pinacol, 1,4-butynediol, triethylene glycol, diethylene glycol, dipropylene glycol, cyclohexanedimethanol, 1,4-cyclohexanedimethanol and other saturated low molecular weight glycols; adipic acid, 3-methyladipic acid, 2,2,5,5-tetramethyladipic acid, maleic acid, fumaric acid, succinic acid, 2,2-dimethylsuccinic acid, 2-ethyl-2-methylsuccinic acid, 2,3-dimethylsuccinic acid, oxalic acid, malonic acid, methylmalonic acid Polyester diols obtained by dehydration condensation of dibasic acids such as ethylmalonic acid, butylmalonic acid, dimethylmalonic acid, glutaric acid, 2-methylglutaric acid, 3-methylglutaric acid, 2,2-dimethylglutaric acid, 3,3-dimethylglutaric acid, 2,4-dimethylglutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid or the acid anhydrides corresponding to these acids; polyester diols obtained by ring-opening polymerization of cyclic ester compounds such as ε-caprolactone. The aliphatic ester diols and alicyclic ester diols can be used alone or in combination of two or more.

In addition, the aliphatic carbonate diol or alicyclic carbonate diol constituting the urethane acrylate may be selected from polycarbonate diols obtained by reacting at least one of the diols with phosgene. The polycarbonate diol obtained by reacting the diols with phosgene may be used alone or in combination of two or more.

From the viewpoint of further improving the bonding strength, the urethane acrylate can be preferably used by freely adjusting the weight average molecular weight within the range of 5000 to less than 30000. If the weight average molecular weight of the urethane acrylate is within the range, both flexibility and cohesion can be sufficiently obtained, the bonding strength with organic substrates such as PET, PC, and PEN can be further improved, and better connection reliability can be obtained. In addition, from the viewpoint of more fully obtaining this effect, the weight average molecular weight of the urethane acrylate is more preferably 8000 to less than 25000, and further preferably 10000 to less than 20000. In addition, from the viewpoint of more fully obtaining this effect, the weight average molecular weight of the urethane acrylate is preferably 10000 to less than 25000. If the weight average molecular weight is 5,000 or more, sufficient flexibility tends to be easily obtained, while if the weight average molecular weight is less than 30,000, the fluidity of the adhesive composition tends to be suppressed from decreasing.

In addition, based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the blending amount of the acrylic urethane is preferably 5 mass% or more, more preferably 10 mass% or more, and further preferably 15 mass% or more. If the blending amount is 5 mass% or more, sufficient heat resistance tends to be easily obtained after curing. In addition, based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the blending amount of the acrylic urethane is preferably 95 mass% or less, more preferably 80 mass% or less, and further preferably 70 mass% or less. If the blending amount is 95 mass% or less, when the adhesive composition is used as a film-like adhesive, good film forming properties tend to be easily obtained.

(b) The radical polymerizable compound may also include one or more vinyl compounds containing a phosphoric acid group (vinyl compounds having a phosphoric acid group), and radical polymerizable compounds other than the vinyl compounds containing a phosphoric acid group. (b) The radical polymerizable compound may also include one or more N-vinyl compounds selected from the group consisting of N-vinyl compounds and N,N-dialkyl vinyl compounds, and radical polymerizable compounds other than the N-vinyl compounds. By using a vinyl compound containing a phosphoric acid group in combination, the adhesion of the adhesive composition to the substrate having a connection terminal can be further improved. In addition, by using an N-vinyl compound in combination, the crosslinking rate of the adhesive composition can be increased.

The phosphoric acid group-containing vinyl compound is not particularly limited as long as it has a phosphoric acid group and a vinyl group, but is preferably a compound represented by the following general formula (O) to general formula (Q).

[Chemistry 19] [In formula (O), R ²⁸ represents a (meth)acryloyloxy group, R ²⁹ represents a hydrogen atom or a methyl group, and l and m each independently represent an integer of 1 to 8. In formula (O), R ²⁸ , R ²⁹ , l and m may be the same or different from each other]

[Chemistry 20] [In formula (P), R ³⁰ represents a (meth)acryloyloxy group, and n, o, and p each independently represent an integer of 1 to 8. In formula (P), R ³⁰ , n, o, and p may be the same or different from each other]

[Chemistry 21] [In formula (Q), R ³¹ represents a (meth)acryloxy group, R ³² represents a hydrogen atom or a methyl group, and q and r each independently represent an integer of 1 to 8]

The vinyl compounds containing phosphoric acid groups specifically include: acid phosphatidyl ethyl methacrylate, acid phosphatidyl ethyl acrylate, acid phosphatidyl propyl methacrylate, acid phosphatidyl polyoxyethylene glycol monomethacrylate, acid phosphatidyl polyoxypropylene glycol monomethacrylate, 2,2'-di(meth)acryloyloxydiethyl phosphate, ethylene oxide (EO) modified phosphoric acid dimethacrylate, phosphoric acid modified epoxy acrylate, 2-(meth)acryloyloxyethyl phosphate, vinyl phosphate, etc.

Specific examples of N-vinyl compounds include N-vinylimidazole, N-vinylpyridine, N-vinylpyrrolidone, N-vinylformamide, N-vinylcaprolactam, 4,4'-vinylidenebis(N,N-dimethylaniline), N-vinylacetamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, and the like.

The amount of each of the phosphate-containing vinyl compound and the N-vinyl compound is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, and further preferably 0.5% by mass or more, independently of the amount of the free radical polymerizable compound other than the phosphate-containing vinyl compound and the N-vinyl compound, based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition). If the amount is 0.2% by mass or more, it is easy to obtain high bonding strength. Based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the amount of each of the phosphate-containing vinyl compound and the N-vinyl compound is preferably 15% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less. If the blending amount is 15 mass % or less, the physical properties of the adhesive composition after curing are unlikely to deteriorate, and reliability tends to be easily ensured.

In addition, based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the amount of the (b) radical polymerizable compound excluding the phosphate group-containing vinyl compound and the N-vinyl compound is preferably 5 mass% or more, more preferably 10 mass% or more, and further preferably 15 mass% or more. If the amount is 5 mass% or more, sufficient heat resistance tends to be easily obtained after curing. Based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the amount of the (b) radical polymerizable compound excluding the phosphate group-containing vinyl compound and the N-vinyl compound is preferably 95 mass% or less, more preferably 80 mass% or less, and further preferably 70 mass% or less. When the amount is 95% by mass or less, when the adhesive composition is used as a film-like adhesive, good film-forming properties tend to be easily obtained.

((c) Radical polymerization initiator) (c) Radical polymerization initiator may be a compound that generates free radicals by energy imparted from the outside, such as organic peroxides and azo compounds, which are known in the past. From the viewpoint of stability, reactivity, and compatibility, (c) radical polymerization initiator is preferably an organic peroxide having a one-minute half-life temperature of 90°C to 175°C and a weight average molecular weight of 180 to 1000. When the one-minute half-life temperature is within this range, the storage stability is better, the radical polymerization is sufficiently high, and hardening can be achieved in a short time.

(c) The free radical polymerization initiator may specifically include: 1,1,3,3-tetramethylbutyl peroxyneodecanoate, di(4-tert-butylcyclohexyl) peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, cumyl peroxyneodecanoate, dilauryl peroxide, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, tert-hexyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, tert-butyl peroxytrimethylacetate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, 2,5-dioctyl peroxide, Methyl-2,5-di(2-ethylhexanoylperoxy)hexane, tert-hexyl peroxy-2-ethylhexanoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy-neoheptanoate, tert-pentyl peroxy-2-ethylhexanoate, di-tert-butyl peroxy-hexahydrophthalate, tert-pentyl peroxy-3,5,5-trimethylhexanoate, 3-hydroxy-1,1-dimethylbutyl peroxy-neodecanoate, tert-pentyl peroxy-2-ethylhexanoate, di(3-methylbenzoyl)peroxide ), dibenzoyl peroxide, di(4-methylbenzoyl peroxide), tert-butyl peroxyisopropyl monocarbonate, tert-butyl peroxymaleate, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxylaurate, 2,5-dimethyl-2,5-di(3-methylbenzoylperoxy)hexane, tert-butyl peroxy-2-ethylhexyl monocarbonate, tert-butyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butyl peroxybenzoate, tri-butyl peroxide Organic peroxides such as dibutyl methyl adipate, tert-pentyl peroxyoctanoate, tert-pentyl peroxyisononanoate, and tert-pentyl peroxybenzoate; azo compounds such as 2,2'-azobis-2,4-dimethylvaleronitrile, 1,1'-azobis(1-acetyloxy-1-phenylethane), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), dimethyl-2,2'-azobisisobutyronitrile, 4,4'-azobis(4-cyanovaleric acid), and 1,1'-azobis(1-cyclohexanecarbonitrile). These compounds may be used alone or in combination of two or more.

In addition, (c) free radical polymerization initiators may be compounds that generate free radicals by irradiation with light of 150 nm to 750 nm. Such compounds are highly sensitive to light irradiation, and examples thereof include α-aminoacetophenone derivatives and phosphine oxide derivatives described in "Photoinitiation, Photopolymerization, and Photocuring" (J.-P. Fouassier, Hanser Publishers (1995, p17-p35)). In addition to using one of these compounds alone, these compounds may also be used in combination with the above-mentioned organic peroxides or azo compounds.

Based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the amount of the (c) radical polymerization initiator is preferably 0.5 mass% or more, more preferably 1 mass% or more, and further preferably 2 mass% or more. If the amount is 0.5 mass% or more, the adhesive composition tends to be easily and sufficiently hardened. Based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the amount of the (c) radical polymerization initiator is preferably 40 mass% or less, more preferably 30 mass% or less, and further preferably 20 mass% or less. If the amount is 40 mass% or less, the storage stability tends to be less likely to decrease.

((d) Boron-containing salt) (d) Boron-containing salt (hereinafter referred to as "component (d)") is a compound represented by the following general formula (A). Component (d) contains a borate compound and an ammonium compound as a counter cation of the borate compound. [Chemistry 22] [In formula (A), R ¹ , R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and R ² , R ³ and R ⁴ each independently represent an aryl group. R ¹ , R ⁵ , R ⁶ , R ⁷ and R ⁸ may be the same or different from each other. R ² , R ³ and R ⁴ may be the same or different from each other]

The borate compound contained in the component (d) may include alkyl triaryl borate, triaryl borate, etc. From the viewpoint of better low temperature curing property and storage stability, the borate compound is preferably an alkyl triaryl borate. The borate compound may also be a compound having a plurality of these compounds in the molecule, or a compound having the above compounds on the main chain and/or side chain of the polymer.

The alkyl group bonded to the boron atom in the borate compound may be a straight chain, branched chain or cyclic alkyl group. Specific examples of the alkyl group having 1 to 18 carbon atoms include: methyl, trifluoromethyl, ethyl, n-butyl, hexyl, octyl, 2-ethylhexyl, decyl, dodecyl, octadecyl, propyl, isopropyl, isobutyl, sec-butyl, t-butyl, pentyl, 1-ethylpentyl, cyclopentyl, cyclohexyl, isopentyl, heptyl, nonyl, undecyl, t-octyl, etc. Among these groups, n-butyl is preferred from the viewpoint of better low-temperature curability and storage stability. From the viewpoint of better low-temperature curability and storage stability, the carbon number of the alkyl group is preferably 1 to 12, and more preferably 1 to 6.

Specific examples of the aromatic group bonded to the boron atom in the borate compound include phenyl, p-tolyl, m-tolyl, mesityl, xylyl, p-tert-butylphenyl (4-tert-butylphenyl), p-methoxyphenyl, biphenyl, naphthyl, 4-methylnaphthyl, etc. Among these groups, phenyl, p-tert-butylphenyl, and 4-methylnaphthyl are preferred from the viewpoint of better low-temperature curing property and storage stability, and phenyl is more preferred. The aromatic groups bonded to the boron atom in the borate compound may be the same or different from each other.

The ammonium compound used as the component (d) to counteract cations may include tetraalkylammonium, trialkylammonium, dialkylammonium, monoalkylammonium, etc. Among these compounds, tetraalkylammonium is preferred from the viewpoint of superior low-temperature curing property and storage stability. The ammonium compound may be a compound having a plurality of these compounds in the molecule, or a compound having the above-mentioned compound on the main chain and/or side chain of the polymer.

Among the ammonium compounds, tetraalkylammonium is preferred from the viewpoint of better low-temperature curing property and storage stability, and tetraalkylammonium having an alkyl group with a carbon number of 6 or less bonded to a nitrogen atom is more preferred, and tetraalkylammonium having four alkyl groups with a carbon number of 6 or less bonded to a nitrogen atom (i.e., tetraalkylammonium in which ^R5 , ^R6 , ^R7 , and ^R8 are alkyl groups with a carbon number of 1 to 6) is further preferred. In this case, the solubility in thermoplastic resins, free radical polymerizable compounds, and solvents is improved, and the low-temperature curing property can be further improved.

The alkyl group bonded to the nitrogen atom in the ammonium compound may be a straight chain, branched chain or cyclic alkyl group. Specific examples of the alkyl group having 1 to 18 carbon atoms include: methyl, trifluoromethyl, ethyl, n-butyl, hexyl, octyl, 2-ethylhexyl, decyl, dodecyl, octadecyl, propyl, isopropyl, isobutyl, sec-butyl, t-butyl, pentyl, 1-ethylpentyl, cyclopentyl, cyclohexyl, isopentyl, heptyl, nonyl, undecyl, t-octyl, etc. Among these groups, n-butyl is preferred from the viewpoint of better low-temperature curability and storage stability. From the viewpoint of better low-temperature curability and storage stability, the carbon number of the alkyl group is preferably 1 to 12, and more preferably 1 to 6.

From the viewpoint of better low-temperature curing property and storage stability, specific examples of the compound represented by the general formula (A) are preferably tetra-n-butylammonium-n-butyltri(4-tert-butylphenyl)borate (TBA-BPB), tetra-n-butylammonium-n-butyltri(4-methyl-1-naphthyl)borate (TBA-MNB), and tetra-n-butylammonium-n-butyltriphenylborate (TBA-PB).

The component (d) is preferably a combination of an alkyl triaryl borate and tetraalkyl ammonium. When the component (d) is a salt composed of the alkyl triaryl borate and tetraalkyl ammonium, the low temperature curability and storage stability of the adhesive composition can be improved with a better balance.

Specifically, the component (d) may be a salt obtained by a conventional synthesis method. For example, in the case of obtaining an alkyl triaryl borate-ammonium salt, an alkali metal or alkali earth metal, an aryl halide, triethyl borate and an alkyl alkali metal or alkyl halide may be reacted, and then an aqueous solution of an alkyl ammonium halide may be added dropwise to obtain an alkyl triaryl borate-ammonium salt.

The salts obtained from these compounds may be used alone or in combination of two or more.

From the viewpoint of further improving storage stability, the melting point of the component (d) is preferably 60°C or higher, more preferably 70°C or higher, and further preferably 80°C or higher. From the viewpoint of better low-temperature curability, the melting point of the component (d) is preferably 300°C or lower, more preferably 270°C or lower, and further preferably 250°C or lower. When the adhesive composition contains a plurality of components (d), it is preferred that the melting point of at least one salt satisfies the above range, and it is more preferred that the melting points of all the salts satisfy the above range.

Based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the amount of component (d) is preferably 0.1 mass % or more, more preferably 0.5 mass % or more. If the amount of component (d) is 0.1 mass % or more, the effect of promoting the reactivity of the radical polymerization initiator tends to be easily obtained. Based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the amount of component (d) is preferably 20 mass % or less, more preferably 15 mass % or less, and further preferably 10 mass % or less. If the amount of component (d) is 20 mass % or less, the storage stability of the adhesive composition tends to be less likely to decrease.

((e) Conductive particles) (e) Conductive particles may be particles that are conductive in their entirety or on their surfaces. When used to connect components having connection terminals, particles having an average particle size that is smaller than the distance between the connection terminals are preferred.

(e) Conductive particles include metal particles made of metals such as Au, Ag, Ni, Cu, Pd or solder, and particles made of carbon. In addition, (e) conductive particles may be particles having a non-conductive glass, ceramic or plastic as a core and the core coated with the metal, metal particles or carbon. As (e) conductive particles, particles formed by coating the metal, metal particles or carbon on a plastic core and hot-melt metal particles are preferably deformable by heating and pressurizing, so the contact area with the electrode during connection is increased and reliability is improved. (e) Conductive particles may also be particles formed by coating silver on metal particles containing copper. In addition, as the (e) conductive particles, metal powder having a shape in which a large number of fine metal particles are linked in a chain as described in Japanese Patent Application Laid-Open No. 2005-116291 may be used.

In addition, by using microparticles obtained by further coating the surfaces of these (e) conductive particles with a polymer resin or the like, or by using particles having an insulating layer containing an insulating material on the surface of the (e) conductive particles by a method such as hybridization, when the amount of conductive particles formulated is increased, short circuits caused by contact between particles are suppressed, and the insulation between electrode circuits is improved. Therefore, the particles can be appropriately used alone or mixed with the (e) conductive particles.

In terms of dispersibility and conductivity, the average particle size of the (e) conductive particles is preferably 1 μm to 18 μm, for example. When such (e) conductive particles are contained, the adhesive composition can be preferably used as an anisotropic conductive adhesive. The average particle size of the (e) conductive particles can be measured using a laser diffraction particle size distribution measuring device (e.g., laser diffraction SALD-2100 manufactured by Shimadzu Corporation).

The amount of (e) conductive particles is not particularly limited, but is preferably 0.1% by volume or more, more preferably 0.2% by volume or more, based on the total volume of the adhesive component (the component excluding the conductive particles in the adhesive composition). If the amount is 0.1% by volume or more, the decrease in conductivity tends to be suppressed. The amount of (e) conductive particles is preferably 30% by volume or less, more preferably 10% by volume or less, based on the total volume of the adhesive component (the component excluding the conductive particles in the adhesive composition). If the amount is 30% by volume or less, short circuits in the circuit tend to be less likely to occur. In addition, "volume %" is determined based on the volume of each component before curing at 23°C, and the volume of each component can be converted from weight to volume using specific gravity. In addition, instead of dissolving or swelling the component in a measuring cylinder, the component can be put into a container with a suitable solvent (water, alcohol, etc.) that can fully wet the component, and the increased volume can be calculated as the volume of the component.

(Other components) In order to control the curing speed and further improve the storage stability, a stabilizer can be added to the adhesive composition of this embodiment. Such stabilizers are not particularly limited, and known compounds can be used, preferably quinone derivatives such as benzoquinone and hydroquinone; phenol derivatives such as 4-methoxyphenol and 4-tert-butyl o-catechol; aminooxy derivatives such as 2,2,6,6-tetramethylpiperidin-1-oxy and 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxy; hindered amine derivatives such as tetramethylpiperidinyl methacrylate, etc. The stabilizer can be used alone or in combination of two or more.

Based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the amount of the stabilizer is preferably 0.005 mass% or more, more preferably 0.01 mass% or more, and further preferably 0.02 mass% or more. If the amount is 0.005 mass% or more, the curing rate tends to be easily controlled and the storage stability tends to be easily improved. Based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the amount of the stabilizer is preferably 10 mass% or less, more preferably 8 mass% or less, and further preferably 5 mass% or less. If the amount is 10 mass% or less, the compatibility with other components tends to be less likely to decrease.

In addition, the adhesive composition of the present embodiment may also be appropriately added with an adhesive aid such as a coupling agent represented by an alkoxysilane derivative and a silazane derivative, an adhesion improver, and a leveler. Specifically, the coupling agent is preferably a compound represented by the following general formula (R). The coupling agent may be used alone or in combination of two or more.

[Chemistry 23] [In formula (R), R ³³ , R ³⁴ and R ³⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an alkoxycarbonyl group having 1 to 5 carbon atoms or an aryl group; R ³⁶ represents a (meth)acryl group, a vinyl group, an isocyanato group, an imidazolyl group, an amine group, a methylamino group, a dimethylamino group, a benzylamino group, a phenylamino group, a cyclohexylamino group, a morpholinyl group, a piperazinyl group, a ureido group or a glycidyl group; and s represents an integer from 1 to 10]

The adhesive composition of this embodiment may also contain a rubber component in order to relieve stress and improve adhesion. The so-called rubber component refers to a component that exhibits rubber elasticity (JIS K6200) while maintaining its original state or a component that exhibits rubber elasticity through reaction. The rubber component may be solid or liquid at room temperature (25°C), and is preferably liquid from the perspective of improving fluidity. The rubber component is preferably a compound having a polybutadiene skeleton. The rubber component may also have a cyano group, a carboxyl group, a hydroxyl group, a (meth)acryloyl group or a morpholine group. In addition, from the perspective of improving adhesion, a rubber component containing a cyano group or a carboxyl group as a highly polar group in the side chain or at the end is preferred. Furthermore, even if they have a polybutadiene skeleton, they are classified as (a) thermoplastic resins when they exhibit thermoplasticity, and they are classified as (b) radical polymerizable compounds when they exhibit radical polymerizability.

The rubber component may specifically include: polyisoprene, polybutadiene, carboxyl-terminated polybutadiene, hydroxyl-terminated polybutadiene, 1,2-polybutadiene, carboxyl-terminated 1,2-polybutadiene, hydroxyl-terminated 1,2-polybutadiene, acrylic rubber, styrene-butadiene rubber, hydroxyl-terminated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene rubber containing a carboxyl group, a hydroxyl group, a (meth)acryl group or a morpholine group at the polymer terminal, carboxylated nitrile rubber, hydroxyl-terminated poly(oxypropylene), alkoxysilyl-terminated poly(oxypropylene), poly(oxytetramethylene) glycol, polyolefin glycol, and the like.

In addition, the rubber component having a highly polar group and being liquid at room temperature can be specifically exemplified by: liquid acrylonitrile-butadiene rubber, liquid acrylonitrile-butadiene rubber containing a carboxyl group, a hydroxyl group, a (meth)acryl group or a morpholine group at the polymer terminal, liquid carboxylated nitrile rubber, etc., wherein the blending amount of acrylonitrile as a polar group is preferably 10 mass % to 60 mass %.

These rubber components may be used alone or in combination of two or more.

In addition, in the adhesive composition of the present embodiment, organic microparticles may be added to relieve stress and improve adhesion. The average particle size of the organic microparticles is preferably 0.05 μm to 1.0 μm, for example. Furthermore, when the organic microparticles contain the rubber component, they are not classified as organic microparticles but are classified as rubber components. When the organic microparticles contain the (a) thermoplastic resin, they are not classified as organic microparticles but are classified as (a) thermoplastic resins.

Specific examples of organic microparticles include organic microparticles containing the following substances: polyisoprene, polybutadiene, carboxyl-terminated polybutadiene, hydroxyl-terminated polybutadiene, 1,2-polybutadiene, carboxyl-terminated 1,2-polybutadiene, acrylic rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene rubber containing a carboxyl group, a hydroxyl group, a (meth)acryl group or a morpholine group at the polymer terminal, carboxylated nitrile rubber, hydroxyl-terminated poly(oxypropylene), alkoxysilyl-terminated poly(oxypropylene), poly(oxytetramethylene) glycol, polyalkylene glycol (meth)acrylate-butadiene-styrene copolymer, (meth)acrylate-silicone copolymer or silicone-(meth)acrylic copolymer, or a composite of these substances.

In addition, the adhesive composition used in the connection structure in which the substrate described later is composed of a base material containing at least one selected from the group consisting of polyethylene terephthalate, polycarbonate, and polyethylene naphthalate may also contain silicone fine particles.

Since the adhesive composition used in the connection structure composed of a substrate containing at least one selected from the group consisting of polyethylene terephthalate, polycarbonate and polyethylene naphthalate contains silicone particles, internal stress can be fully relieved, so the bonding strength to polyethylene terephthalate, polycarbonate and polyethylene naphthalate can be further improved, and the bonding strength to the component having the connection terminal can be further improved. In addition, stable performance can be further maintained after a long-term reliability test.

Regarding the silicone microparticles, microparticles of polyorganosilsesquioxane resins having rubber elasticity are known, and spherical or amorphous silicone microparticles can be used. In addition, from the viewpoint of dispersibility and internal stress relief, it is preferred that the silicone microparticles have a weight average molecular weight of more than 1 million. In addition, the silicone microparticles preferably have a three-dimensional cross-linked structure. Such silicone microparticles have high dispersibility in the resin and better stress relief after curing. Silicone microparticles with a weight average molecular weight of more than 1 million and/or silicone microparticles with a three-dimensional cross-linked structure have low solubility in polymers, monomers, and solvents such as thermoplastic resins, so the above effect can be more significantly achieved. Here, "having a three-dimensional cross-linked structure" means that the polymer chain has a three-dimensional network structure. In addition, the glass transition temperature of the silicone microparticles is preferably above -130°C and below -20°C, and more preferably above -120°C and below -40°C. Such silicone microparticles can fully alleviate the internal stress of the adhesive composition used as a circuit connection material.

Silicone particles having such a structure can be specifically used: silicone particles obtained by reacting an organic polysiloxane containing at least two vinyl groups, an organic hydrogenated polysiloxane having at least two hydrogen atoms bonded to silicon atoms, and a platinum catalyst (for example, Japanese Patent Laid-Open No. 62-257939); silicone particles obtained by using an organic polysiloxane having an alkenyl group, an organic polysiloxane having a hydrosilyl group, and a platinum catalyst (for example, Japanese Patent Publication No. 63-77942); silicone particles obtained by using diorganosiloxane, monoorganosilsesquioxane, triorganosiloxane and platinum catalyst (for example, Japanese Patent Publication No. 62-270660); silicone particles obtained by adding a water/alcohol solution of methylsilanetriol and/or its partial condensate to an alkaline aqueous solution for polycondensation (for example, Japanese Patent Publication No. 3970453), etc. In addition, in order to improve dispersibility and adhesion to the substrate, silicone particles added or copolymerized with epoxy compounds (for example, Japanese Patent Publication No. 3-167228), silicone particles added or copolymerized with acrylate compounds, etc. can also be used.

In order to further improve dispersibility, it is preferred to use silicone microparticles having a core-shell structure. The core-shell structure has a structure in which a surface layer (shell layer) having a glass transition temperature higher than the glass transition temperature of the surface of the core material (core layer) is formed, and a structure in which a graft layer (shell layer) is formed on the outside of the core material (core layer). Silicone microparticles having different compositions in the core layer and the shell layer can be used. Specifically, it is also possible to use: core-shell silicone microparticles formed by adding alkaline substances or alkaline aqueous solutions and organic trialkoxysilane to the aqueous dispersion of silicone rubber spherical microparticles to carry out hydrolysis and condensation reactions (for example, Japanese Patent No. 2832143); core-shell silicone microparticles described in WO2009/051067. In addition, silicone microparticles containing functional groups such as hydroxyl, epoxy, ketimino, carboxyl, and hydroxyl groups at the molecular end or in the inner side chain of the molecule can be used. Such silicone microparticles are more preferred because of their improved dispersibility in film-forming components and free radical polymerizable substances.

The average particle size of the silicone microparticles is preferably 0.05 μm to 25 μm, more preferably 0.1 μm to 20 μm. If the average particle size is 0.05 μm or more, the decrease in fluidity of the adhesive composition due to the increase in surface area tends to be suppressed. On the other hand, if the average particle size is 25 μm or less, the internal stress relaxation tends to be easily exerted.

Based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the blending amount of the silicone microparticles is preferably 3 mass % or more, and more preferably 5 mass % or more. If the blending amount of the silicone microparticles is 3 mass % or more, the internal stress tends to be easily and sufficiently relieved. Based on the total mass of the adhesive component (the component excluding the conductive particles in the adhesive composition), the blending amount of the silicone microparticles is preferably 40 mass % or less, and more preferably 30 mass % or less. If the blending amount of the silicone microparticles is 40 mass % or less, the decrease in the flexibility (elastic modulus, elongation) of the adhesive composition is suppressed, and the bonding strength tends to be less likely to decrease.

The silicone fine particles may be used alone or in combination of two or more.

The adhesive composition of this embodiment can be used in a paste form when the adhesive composition is liquid at room temperature. When the adhesive composition is solid at room temperature, in addition to heating it for use, it can also be made into a paste using a solvent. The solvent that can be used is preferably a solvent that is non-reactive with the adhesive composition and the additive and shows sufficient solubility, and preferably has a boiling point of 50°C to 150°C at normal pressure. If the boiling point is above 50°C, the volatility becomes less when it is left at room temperature, and there is a tendency to be easy to use in an open system. In addition, if the boiling point is below 150°C, the solvent is easy to volatilize, and there is a tendency that the reliability after bonding is not easily reduced.

In addition, the adhesive composition of this embodiment can also be formed into a film and used in the form of a film-like adhesive. The film-like adhesive of this embodiment contains the adhesive composition. After the solution obtained by adding a solvent to the adhesive composition as needed is applied to a releasable substrate such as a fluororesin film, a polyethylene terephthalate film, or a release paper, or after the substrate such as a non-woven fabric is impregnated with the solution and placed on the releasable substrate, the solvent is removed and used in the form of a film. If used in the shape of a film, it is more convenient in terms of operability and the like. According to this embodiment, a bonding sheet having a substrate and a film-like adhesive can be provided. In the bonding sheet, the film-like adhesive is arranged on the substrate, for example, to form an adhesive layer.

The adhesive composition of this embodiment can be bonded by heating and pressurizing. The heating temperature is preferably 100°C to 200°C. The pressure is preferably within a range that does not damage the bonded body, and is generally preferably 0.1 MPa to 10 MPa. The heating and pressurizing are preferably performed within a range of 0.5 seconds to 120 seconds, and heating at 120°C to 190°C, 3 MPa, and 10 seconds is also possible.

The adhesive composition of this embodiment can be used to electrically connect a first connection terminal disposed on the main surface of a first substrate and a second connection terminal disposed on the main surface of a second substrate. In addition, the adhesive composition of this embodiment can be used to electrically connect a connection terminal of a solar cell having a connection terminal disposed on the main surface of a substrate and a wiring member.

The adhesive composition of the present embodiment can be used as an adhesive for the same type of adherends, and can be used as an adhesive for different types of adherends with different thermal expansion coefficients. Specifically, the adhesive composition of the present embodiment can be used as circuit connection materials represented by anisotropic conductive adhesives, silver pastes, silver films, etc., and semiconductor component bonding materials represented by elastomers for chip scale packages (CSP), bottom filling materials for CSP, lead on chip (LOC) tapes, etc.

For example, by using the adhesive composition of the present embodiment, a first circuit component having a first circuit substrate and a first connection terminal disposed on the main surface of the first circuit substrate, and a second circuit component having a second circuit substrate and a second connection terminal disposed on the main surface of the second circuit substrate are disposed in a state where the first connection terminal and the second connection terminal face each other and are electrically connected, thereby forming a connection structure of the circuit components. In this case, the adhesive composition of the present embodiment is useful as an adhesive for circuit connection.

(Connection structure) Next, a connection structure using the adhesive composition and a method for manufacturing the same are described. According to the present embodiment, a method for manufacturing a connection structure is provided, wherein the adhesive composition is interposed between a first circuit component having a first substrate and a first connection terminal disposed on a main surface of the first substrate, and a second circuit component having a second substrate and a second connection terminal disposed on a main surface of the second substrate, and the adhesive composition is hardened, thereby connecting the first circuit component and the second circuit component in a state where the first connection terminal and the second connection terminal are electrically connected. In addition, according to the present embodiment, a method for manufacturing a connection structure is provided, wherein the adhesive composition is placed between a solar cell having a substrate and a connection terminal arranged on a main surface of the substrate and a wiring member, and the adhesive composition is hardened, thereby connecting the solar cell and the wiring member in a state where the connection terminal and the wiring member are electrically connected.

Fig. 1 is a schematic cross-sectional view showing a connection structure of a first embodiment. Fig. 2 is a schematic cross-sectional view showing a method for manufacturing the connection structure shown in Fig. 1. The circuit component connection structure 100 shown in Fig. 1 is obtained by using an adhesive composition that does not contain (e) conductive particles.

The circuit component connection structure 100 shown in FIG1 includes a circuit component (first circuit component) 10, a circuit component (second circuit component) 20, and a connection component 30. The circuit component 10 includes a circuit substrate (first substrate) 12, and a connection terminal (first connection terminal) 14 disposed on a main surface 12a of the circuit substrate 12. The circuit component 20 includes a circuit substrate (second substrate) 22, and a connection terminal (second connection terminal) 24 disposed on a main surface 22a of the circuit substrate 22.

The connection member 30 is disposed between the circuit member 10 and the circuit member 20. The connection member 30 connects the circuit member 10 and the circuit member 20 in a manner that the main surface 12a and the main surface 22a face each other substantially in parallel. In the connection structure 100, the connection terminal 14 and the connection terminal 24 are disposed facing each other and in contact with each other, thereby being electrically connected. The connection member 30 includes a cured product of an adhesive composition 30a described later.

The connection structure 100 can be manufactured, for example, as follows. First, as shown in FIG. 2 , a circuit component 10, a circuit component 20, and an adhesive composition 30a including the adhesive composition are prepared. The adhesive composition 30a is formed into a film, for example. Then, the adhesive composition 30a is placed on the main surface 22a of the circuit component 20 on which the connection terminal 24 is formed. Then, the circuit component 10 is placed on the adhesive composition 30a in a manner that the connection terminal 14 and the connection terminal 24 face each other. Then, the adhesive composition 30a is hardened while being heated through the circuit components 10 and 20, and pressure is applied in a direction perpendicular to the main surfaces 12a and 22a to form the connection component 30 between the circuit components 10 and 20. Thus, the connection structure 100 is obtained.

When the adhesive composition contains conductive particles, the anisotropic conductive film made using the adhesive composition is placed between opposing connection terminals and heated and pressurized, thereby electrically connecting the connection terminals to each other through the conductive particles and connecting the circuit components to each other, thereby obtaining a connection structure of the circuit components. FIG. 3 is a schematic cross-sectional view of the connection structure of the second embodiment. FIG. 4 is a schematic cross-sectional view of a method for manufacturing the connection structure shown in FIG. 3 . The connection structure 200 of the circuit component shown in FIG. 3 is obtained by using an adhesive composition containing (e) conductive particles.

The circuit component connection structure 200 shown in Fig. 3 includes the circuit components 10 and 20, which are the same as the connection structure 100, and the connection component 40. In the connection structure 200, the connection terminals 14 and 24 are arranged to face each other in a state of being spaced apart from each other.

The connection member 40 is disposed between the circuit member 10 and the circuit member 20. The connection member 40 includes a cured product of an adhesive composition 40a described later, and has an adhesive component 42 and conductive particles 44 dispersed in the adhesive component 42. The adhesive component 42 includes a cured product of an adhesive component 42a described later. In the connection structure 200, the conductive particles 44 are in contact with the connection terminals 14 and 24 between the opposing connection terminals 14 and 24, thereby electrically connecting the connection terminals 14 and 24 to each other through the conductive particles 44.

The connection structure 200 can be manufactured, for example, as follows. First, as shown in FIG. 4 , a circuit component 10, a circuit component 20, and a bonding agent composition 40a including the bonding agent composition are prepared. The bonding agent composition 40a is formed into a film, for example. The bonding agent composition 40a has a bonding agent component 42a and conductive particles 44 dispersed in the bonding agent component 42a. Thereafter, the circuit component 10 and the circuit component 20 are connected via the bonding agent composition 40a by the same method as the method for obtaining the connection structure 100 of the circuit component. In this way, the connection structure 200 can be obtained.

At least one of the circuit substrate 12 and the circuit substrate 22 in the connection structure 100 and the connection structure 200 of the circuit component may also be composed of a base material containing a thermoplastic resin having a glass transition temperature of 200°C or less. For example, at least one of the circuit substrate 12 and the circuit substrate 22 may also be composed of an organic base material containing at least one selected from the group consisting of polyethylene terephthalate, polycarbonate, and polyethylene naphthalate. Thus, when an organic base material such as polyethylene terephthalate, polycarbonate, or polyethylene naphthalate is used, the wettability of the circuit substrate with the adhesive composition is improved, thereby obtaining excellent bonding strength even under low-temperature curing conditions. Therefore, even after a long reliability test (high temperature and high humidity test), stable performance (bonding strength and connection resistance) can be maintained, and excellent connection reliability can be obtained.

In addition, when one of the circuit substrates 12 and 22 is composed of a base material containing at least one selected from the group consisting of polyethylene terephthalate, polycarbonate, and polyethylene naphthalate, the other of the circuit substrates 12 and 22 may also be composed of a base material containing at least one selected from the group consisting of polyimide and polyethylene terephthalate. In this way, the wettability and bonding strength of the circuit substrate with the adhesive composition are further improved, and better connection reliability can be obtained.

Furthermore, the circuit substrate 12 and the circuit substrate 22 may also be formed of a substrate containing the following materials: inorganic materials such as semiconductors, glass or ceramics; organic materials such as polyethylene terephthalate, polyethylene naphthalate, polyimide or polycarbonate; composite materials of these materials such as glass/epoxy. In addition, the circuit substrate 12 and the circuit substrate 22 may also be a flexible substrate.

Fig. 5 is a schematic cross-sectional view showing a connection structure according to the third embodiment. The solar cell module 300 shown in Fig. 5 includes a solar cell 310a, a solar cell 310b, a wiring member 320, and a connection member 330.

The solar cell 310a and the solar cell 310b have a substrate 312, a surface electrode (connection terminal) 314 disposed on the surface (main surface) 312a of the substrate 312, and a back electrode (connection terminal) 316 disposed on the back (main surface) 312b of the substrate 312. The substrate 312 may be made of, for example, a semiconductor, an inorganic material such as glass or ceramic, or a composite material such as glass/epoxide. In addition, the substrate 312 may also be a flexible substrate. The surface 312a is a light-receiving surface.

The wiring member 320 is used to electrically connect the solar cell 310a with other components, for example, to electrically connect one solar cell with another solar cell. In FIG5 , the wiring member 320 electrically connects the surface electrode 314 of the solar cell 310a with the back electrode 316 of the solar cell 310b.

The connecting member 330 is respectively arranged between the solar cell 310a and the wiring member 320, and between the solar cell 310b and the wiring member 320, to connect the solar cell 310a, the solar cell 310b and the wiring member 320. The connecting member 330 contains a hardened material of the adhesive composition and contains an insulating material. The connecting member 330 may further contain conductive particles or may not contain conductive particles. When the connecting member 330 contains conductive particles, the surface electrode 314 of the solar cell 310a and the wiring member 320 can be electrically connected via the conductive particles. In addition, the back electrode 316 of the solar cell 310b and the wiring member 320 can also be electrically connected via conductive particles. When the connecting member 330 does not contain conductive particles, for example, the surface electrode 314 of the solar cell 310a and/or the back electrode 316 of the solar cell 310b can also contact the wiring member 320.

In the solar cell module 300, the connection member 330 is formed by the hardened material of the adhesive composition. As a result, the bonding strength of the connection member 330 between the solar cell 310a and the wiring member 320 and between the solar cell 310b and the wiring member 320 is sufficiently increased, and the connection resistance between the solar cell 310a and the wiring member 320 is sufficiently reduced. In addition, even when placed in a high temperature and high humidity environment for a long time, the decrease in bonding strength and the increase in connection resistance can be fully suppressed. Furthermore, the connection member 330 can be formed by a low temperature and short time heating treatment. Therefore, the solar cell module shown in FIG. 5 can be manufactured without deteriorating the solar cell 310a and the solar cell 310b during connection, and can have higher reliability than before.

The solar cell module 300 can be manufactured by using the same method as the method for manufacturing the connection structure, using the solar cell 310a, the solar cell 310b and the wiring member 320 instead of the circuit member 10 and the circuit member 20 in the method for manufacturing the connection structure 100 and the connection structure 200.

Furthermore, in the connection structure 100, the connection structure 200 and the solar cell module 300, the adhesive composition used as the connection member does not need to be completely hardened (the highest degree of hardening that can be achieved under given hardening conditions), and can also be in a partially hardened state as long as the above characteristics are produced. [Example]

Hereinafter, the present invention will be specifically described based on embodiments, but the present invention is not limited thereto.

<Thermoplastic resin> (Preparation of polyester urethane resin) Polyester urethane resin (manufactured by Toyobo Co., Ltd., UR-4800 (trade name), weight average molecular weight: 32000, glass transition temperature: 106°C) was dissolved in a 1:1 mixed solvent of methyl ethyl ketone and toluene to prepare a mixed solvent solution containing 30% by mass of the resin component.

(Preparation of phenoxy resin) 40 parts by mass of phenoxy resin (trade name: YP-50 (manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd.), weight average molecular weight: 60,000, glass transition temperature: 80°C) was dissolved in 60 parts by mass of methyl ethyl ketone to prepare a solution having a solid content of 40% by mass.

<Free Radical Polymerizable Compound> (Synthesis of Urethane Acrylate (UA1)) In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser with a calcium chloride drying tube, and a nitrogen inlet tube, 2500 parts by mass (2.50 mol) of poly(1,6-hexanediol carbonate) with a number average molecular weight of 1000 (trade name: Duranol T5652, manufactured by Asahi Kasei Chemicals Co., Ltd.) and 666 parts by mass (3.00 mol) of isophorone diisocyanate (manufactured by Sigma-Aldrich) were uniformly added dropwise over 3 hours. After nitrogen was fully introduced into the reaction vessel, the reaction was heated to 70°C to 75°C. After adding 0.53 parts by mass of hydroquinone monomethyl ether (manufactured by Sigma-Aldrich) and 5.53 parts by mass of dibutyltin dilaurate (manufactured by Sigma-Aldrich) to a reaction container, 238 parts by mass (2.05 mol) of 2-hydroxyethyl acrylate (manufactured by Sigma-Aldrich) was added, and the mixture was reacted at 70°C for 6 hours in an air environment to obtain urethane acrylate (UA1). The weight average molecular weight of urethane acrylate was 15,000.

(Preparation of vinyl compound (P-2M) having a phosphate group) 2-(Meth)acryloyloxyethyl phosphate (trade name: Light Ester P-2M, manufactured by Kyoeisha Chemical Co., Ltd.) was prepared as a vinyl compound having a phosphate group.

<Preparation of boron compounds> (Synthesis of tetra-n-butylammonium-n-butyltri(4-tert-butylphenyl)borate (TBA-BPB)) To a solution prepared by dissolving 4.38 g (30.0 mmol) of triethyl borate in 20 ml of tetrahydrofuran, 18.8 ml (30.0 mmol) of a 1.59 M hexane solution of n-butyl lithium was added at -78°C to -70°C in a nitrogen atmosphere, and the mixture was stirred at room temperature for 2 hours. 3.00 g (123 mmol) of metallic magnesium and 30 mg of iodine were added to the reaction solution, and a solution obtained by dissolving 21.1 g (100 mmol) of 1-bromo-4-tert-butylbenzene in 60 ml of tetrahydrofuran was added dropwise in a nitrogen atmosphere at a reaction temperature of 67°C to 72°C, and then stirred at 30°C to 50°C for 2 hours to complete the reaction. After the reaction solution was cooled to room temperature, 600 ml of diethyl ether was added, and then 150 ml of water was added in small amounts. The reaction solution was transferred to a separatory funnel, washed with 240 ml of water, 180 ml of a 0.2 M aqueous solution of tetra-n-butylammonium bromide, and 240 ml of water in that order, and then concentrated. 600 ml of diethyl ether was added to the residue, and the precipitated solid was filtered to obtain 17.7 g of the target product (TBA-BPB, melting point 190° C.) as a white solid (yield 83%).

(Synthesis of tetra-n-butylammonium-n-butyltri(4-methyl-1-naphthyl)borate (TBA-MNB)) 10 mg of iodine and 10 ml of tetrahydrofuran were added to 1.00 g (41.1 mmol) of metallic magnesium, and a solution prepared by dissolving 4.11 g (30 mmol) of n-butyl bromide in 20 ml of tetrahydrofuran was added dropwise in a nitrogen atmosphere so that the reaction temperature became 67°C to 72°C, and then stirred at room temperature for 2 hours. 4.38 g (30.0 mmol) of triethyl borate was added at -78°C to -70°C, and then stirred at room temperature for 2 hours. 3.00 g (123 mmol) of metallic magnesium and 30 mg of iodine were added to the reaction solution, and a solution obtained by dissolving 22.1 g (100 mmol) of 1-bromo-4-methylnaphthalene in 60 ml of tetrahydrofuran was added dropwise in a nitrogen atmosphere at a reaction temperature of 67 to 72°C, and then stirred at 30 to 50°C for 2 hours to complete the reaction. After the reaction solution was cooled to room temperature, 600 ml of ethyl acetate was added, followed by adding 150 ml of water in small amounts. The reaction solution was transferred to a separatory funnel, washed with 240 ml of water, 180 ml of a 0.2 M aqueous solution of tetra-n-butylammonium bromide, and 240 ml of water in that order, and then concentrated. 600 ml of diethyl ether was added to the residue, and the precipitated solid was filtered to obtain 17.0 g of the target product (TBA-MNB, melting point 175° C.) as a white solid (yield 77%).

(Synthesis of tetra-n-butylammonium-n-butyltriphenylborate (TBA-PB)) To a solution prepared by dissolving 4.38 g (30.0 mmol) of triethyl borate in 20 ml of tetrahydrofuran, 18.8 ml (30.0 mmol) of a 1.59 M hexane solution of n-butyl lithium was added at -78°C to -70°C in a nitrogen atmosphere, and the mixture was stirred at room temperature for 2 hours. 3.00 g (123 mmol) of metallic magnesium and 30 mg of iodine were added to the reaction solution, and a solution obtained by dissolving 15.7 g (100 mmol) of 1-bromobenzene in 60 ml of tetrahydrofuran was added dropwise in a nitrogen atmosphere at a reaction temperature of 67°C to 72°C, and then stirred at 30°C to 50°C for 2 hours to complete the reaction. After the reaction solution was cooled to room temperature, 600 ml of diethyl ether was added, followed by adding 150 ml of water in small amounts. The reaction solution was transferred to a separatory funnel, washed with 240 ml of water, 180 ml of a 0.2 M aqueous solution of tetra-n-butylammonium bromide, and 240 ml of water in that order, and then concentrated. 600 ml of diethyl ether was added to the residue, and the precipitated solid was filtered to obtain 14.9 g of the target product (TBA-PB, melting point 142° C.) as a white solid (yield 89%).

<Preparation of amine compound> N,N-dimethylaniline (abbreviated as DMA, manufactured by Aldrich) was prepared as an amine compound.

<Free radical polymerization initiator> Prepare dilauryl peroxide (trade name: Peroyl L, manufactured by NOF Corporation).

<Conductive particles> (Production of conductive particles) After providing a 0.2 μm thick nickel layer on the surface of particles with polystyrene as the core, a 0.02 μm thick gold layer was provided on the outer side of the nickel layer to produce conductive particles with an average particle size of 10 μm and a specific gravity of 2.5.

<Example 1 to Example 6 and Comparative Example 1 to Comparative Example 4> (Preparation of adhesive for circuit connection) A thermoplastic resin, a radical polymerizable compound and a radical polymerization initiator, and a boron compound or an amine compound were prepared in a manner as shown in Table 1 in terms of solid mass ratio, and 1.5 volume % of conductive particles were dispersed based on the total volume of adhesive components (components in the adhesive for circuit connection excluding conductive particles) to obtain an adhesive for circuit connection. The obtained circuit connecting adhesive was applied onto a fluororesin film having a thickness of 80 μm using a coating device, and dried by hot air at 70°C for 10 minutes to obtain a circuit connecting adhesive film having an adhesive layer thickness of 20 μm.

[Table 1] UR-4800 YP-50 UA1 P-2M TBA-BPB TBA-MNB TBA-PB DMA Paroi L Embodiment 1 50 - 50 3 3 - - - 8 Embodiment 2 50 - 50 3 - 3 - - 8 Embodiment 3 50 - 50 3 - - 3 - 8 Embodiment 4 50 - 50 3 2 - - - 8 Embodiment 5 - 50 50 3 - 2 - - 8 Embodiment 6 - 50 50 3 - - 2 - 8 Comparison Example 1 50 - 50 3 - - - 3 8 Comparison Example 2 50 - 50 3 - - - 2 8 Comparison Example 3 - 50 50 3 - - - 3 8 Comparison Example 4 - 50 50 3 - - - 2 8

(Measurement of connection resistance and bonding strength) The film-shaped circuit connection adhesive of Examples 1 to 6 and Comparative Examples 1 to 4 was placed between a flexible circuit board (FPC) having 500 copper circuits with a line width of 25 μm, a pitch of 50 μm, and a thickness of 8 μm on a polyimide film and a 1.1 mm thick glass (ITO, surface resistance 20 Ω/□) formed with a 0.2 μm ITO thin layer. A heat press device (heating method: constant temperature type, manufactured by Toray Engineering) was used to heat and press at 120°C and 2 MPa for 10 seconds to connect with a width of 2 mm to produce a connection structure A (FPC/ITO). Immediately after connection and after being kept in a constant temperature and humidity chamber at 85°C and 85%RH for 240 hours (after high temperature and high humidity test), a multimeter was used to measure the resistance between adjacent circuits of the connection structure A. The resistance value is expressed as the average value of the resistance at 37 points between adjacent circuits.

In addition, the bonding strength of the connection structure A was measured using the 90-degree peeling method according to JIS-Z0237 immediately after connection and after the high temperature and high humidity test. Here, the bonding strength measuring device used was Tensilon UTM-4 manufactured by Toyo Holding Co., Ltd. (peeling speed 50 mm/min, 25°C).

The film-shaped circuit connection adhesive of Examples 1 to 6 and Comparative Examples 1 to 4 was placed between a flexible circuit board (FPC) having 80 copper circuits with a line width of 150 μm, a pitch of 300 μm, and a thickness of 8 μm on a polyimide film (Tg of 350°C) and a PET substrate (Ag) with a thickness of 0.1 μm on which a thin layer of Ag paste with a thickness of 5 μm was formed. The connection was made with a heat press device (heating method: constant temperature type, manufactured by Toray Engineering) at 120°C and 2 MPa for 20 seconds to heat and press them with a width of 2 mm to produce a connection structure B (FPC/Ag). The resistance between adjacent circuits of the connection structure B consisting of FPC and PET substrate with a thin layer of Ag paste was measured using a multimeter immediately after connection and after being kept in a constant temperature and humidity chamber at 85°C and 85%RH for 240 hours (after high temperature and high humidity test). The resistance value is expressed as the average value of the resistance at 37 points between adjacent circuits.

In addition, the bonding strength of the connection structure B was measured and evaluated under the same conditions as the connection structure A just after connection and after the high temperature and high humidity test.

The measurement results of the connection resistance and the bonding strength (bonding force) of the connection structure A and the connection structure B measured as described above are shown in Table 2 below.

[Table 2] Connection resistance (Ω) Adhesion force (N/m) FPC/ITO FPC/Ag FPC/ITO FPC/Ag After connection 240 hours later After connection 240 hours later After connection 240 hours later After connection 240 hours later Embodiment 1 2 3.4 0.5 1.1 680 610 690 630 Embodiment 2 1.9 3.5 0.4 0.9 650 610 670 600 Embodiment 3 2.1 3.2 0.5 0.8 680 600 630 640 Embodiment 4 2.2 3.1 0.5 1.2 670 680 610 650 Embodiment 5 2.3 3.4 0.6 1.1 660 680 640 640 Embodiment 6 2.4 3.5 0.6 0.9 640 630 670 630 Comparison Example 1 2.2 3.6 0.5 0.9 700 640 640 600 Comparison Example 2 2.1 3.9 0.8 1.2 630 610 620 580 Comparison Example 3 2.7 15.2 0.9 3.3 700 580 590 570 Comparison Example 4 3.3 19.9 1.0 5.5 630 580 600 540

(Storage stability test) The film-shaped circuit connection adhesive of Example 1 to Example 2 and Comparative Example 1 to Comparative Example 2 was placed in a gas-tight container (manufactured by Asahi Kasei Pax Co., Ltd., trade name: Polyflex bag Feilong, model: N-9, material: nylon·thickness 15 μm/PE·thickness 60 μm, size: 200 mm×300 mm), the air in the gas-tight container was removed, and then sealed with a heat sealer, and then placed in a 40°C environment for 48 hours. By placing it in the above environment, it is equivalent to placing it in a -10°C environment for 5 months. Then, the film-shaped circuit connection adhesive of Examples 1 and 2 and Comparative Examples 1 and 2 was placed between the same FPC and glass formed with an ITO thin layer, and between the FPC and a PET substrate formed with an Ag paste thin layer, respectively. They were heated and pressed using the same method and conditions as in the measurement of the connection resistance and bonding strength to produce a connection structure. The connection resistance and bonding strength of the connection structure were measured using the same method as described above.

The measurement results of the connection resistance and adhesion strength of the connection structure measured as described above are shown in Table 3 below.

[table 3] Connection resistance (Ω) Adhesion force (N/m) FPC/ITO FPC/Ag FPC/ITO FPC/Ag After connection 240 hours later After connection 240 hours later After connection 240 hours later After connection 240 hours later Embodiment 1 2.4 3.6 0.4 1.5 670 640 610 650 Embodiment 2 2.5 3.7 0.5 1.2 650 660 640 590 Comparison Example 1 5.8 18.8 2.8 6.8 400 320 390 290 Comparison Example 2 7.6 20.4 5.3 8.7 450 360 420 390

In addition, the same tests as in Examples 1 and 2 were conducted on connection structures using the film-like circuit connection adhesives obtained in Examples 3 to 6. The results were similar to those in Examples 1 and 2, and the low-temperature curing properties and storage stability were good.

The FPC/ITO connection structure A using the circuit connection adhesive obtained in Examples 1 to 6 showed a good connection resistance of 3.7 Ω or less and a good bonding strength of 600 N/m or more at a heating temperature of 120°C and after being kept in a constant temperature and humidity bath at 85°C and 85%RH for 240 hours (after the high temperature and humidity test), regardless of whether the storage stability test was performed or not. In addition, the FPC/Ag connection structure B also showed a good connection resistance of 1.5 Ω or less and a good bonding strength of 590 N/m or more at a heating temperature of 120°C and after being kept in a constant temperature and humidity bath at 85°C and 85%RH for 240 hours (after the high temperature and humidity test). It was confirmed that the circuit connection adhesives obtained in Examples 1 to 6 were excellent in low-temperature curing property and storage stability.

In contrast, regarding the connection structure using the circuit connection adhesive obtained in Comparative Examples 1 and 2, good connection characteristics can be obtained when the circuit connection adhesive before the storage stability test is used. However, since the circuit connection adhesive does not contain (d) a boron-containing salt, when the circuit connection adhesive after the storage stability test is used, an increase in connection resistance is observed after being kept in a constant temperature and humidity bath for 240 hours (after the high temperature and high humidity test). In addition, regarding the connection structure using the circuit connection adhesive obtained in Comparative Examples 3 to 4, since the circuit connection adhesive does not contain (d) a boron-containing salt, even if the storage stability test is not performed, it is confirmed that the connection resistance increases after being kept in a constant temperature and humidity bath for 240 hours (after the high temperature and high humidity test).

10: Circuit component (first circuit component) 12: Circuit substrate (first substrate) 12a, 22a: Main surface 14: Connecting terminal (first connecting terminal) 20: Circuit component (second circuit component) 22: Circuit substrate (second substrate) 24: Connecting terminal (second connecting terminal) 30, 40, 330: Connecting component 30a, 40a: Adhesive composition 42, 42a: Adhesive component 44: Conductive particles 100, 200: Connection structure of circuit components 300: Solar cell module (connection structure) 310a, 310b: Solar cell unit 312: Substrate 312a: Surface (main surface) 312b: Back (main surface) 314: Surface electrode 316: Back electrode 320: Wiring component

FIG1 is a schematic cross-sectional view showing a connection structure of the first embodiment of the present invention. FIG2 is a schematic cross-sectional view showing a method for manufacturing the connection structure shown in FIG1. FIG3 is a schematic cross-sectional view showing a connection structure of the second embodiment of the present invention. FIG4 is a schematic cross-sectional view showing a method for manufacturing the connection structure shown in FIG3. FIG5 is a schematic cross-sectional view showing a connection structure of the third embodiment of the present invention.

Claims (16)

An adhesive composition for circuit connection, comprising (a) a thermoplastic resin, (b) a radical polymerizable compound, (c) a radical polymerization initiator, (d) a boron-containing salt, and (e) conductive particles, wherein the boron-containing salt (d) is a compound represented by the following general formula (A), and the amount of the conductive particles (e) is not less than 0.1 volume % and not more than 30 volume % based on the total volume of the adhesive components (components in the adhesive composition excluding the conductive particles).

In formula (A), R ¹ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent an alkyl group having 1 to 18 carbon atoms, and R ² , R ³ and R ⁴ each independently represent an aryl group. The adhesive composition as claimed in claim 1, wherein R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent an alkyl group having 1 to 12 carbon atoms. The adhesive composition as claimed in claim 1, wherein R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent an alkyl group having 1 to 6 carbon atoms. The adhesive composition as described in any one of items 1 to 3 of the patent application scope, wherein the (b) radical polymerizable compound contains a vinyl compound having a phosphate group and a radical polymerizable compound other than the vinyl compound. The adhesive composition as described in any one of items 1 to 3 of the patent application scope, wherein the melting point of the boron-containing salt (d) is above 60°C and below 300°C. The adhesive composition as described in any one of items 1 to 3 of the patent application scope, wherein the (a) thermoplastic resin contains at least one selected from the group consisting of phenoxy resins, polyurethane resins, butyraldehyde resins, acrylic resins, polyimide resins and polyamide resins, and copolymers having vinyl acetate as structural units. The adhesive composition as described in any one of items 1 to 3 of the patent application scope, wherein the (a) thermoplastic resin contains a polyester urethane resin. The adhesive composition as described in any one of items 1 to 3 of the patent application scope is used to electrically connect the first connecting terminal arranged on the main surface of the first substrate and the second connecting terminal arranged on the main surface of the second substrate. The adhesive composition as described in any one of items 1 to 3 of the patent application scope is used to electrically connect the connection terminal of a solar cell having a connection terminal arranged on the main surface of a substrate to a wiring component. In the adhesive composition described in any one of items 1 to 3 of the patent application scope, the amount of the (c) free radical polymerization initiator is 0.5 mass % or more and 40 mass % or less based on the total mass of the adhesive components (components in the adhesive composition excluding the conductive particles). In the adhesive composition described in any one of items 1 to 3 of the patent application scope, the amount of the boron-containing salt (d) is not less than 0.1% by mass and not more than 20% by mass based on the total mass of the adhesive components. A connection structure, comprising: a first circuit component having a first substrate and a first connection terminal arranged on the main surface of the first substrate, a second circuit component having a second substrate and a second connection terminal arranged on the main surface of the second substrate, and a connection component arranged between the first circuit component and the second circuit component, wherein the connection component contains a cured product of the adhesive composition described in any one of items 1 to 7 of the patent application scope, and the first connection terminal and the second connection terminal are electrically connected. As described in item 12 of the patent application, at least one of the first substrate and the second substrate is composed of a base material containing a thermoplastic resin with a glass transition temperature of 200°C or less. As described in item 12 or 13 of the patent application, at least one of the first substrate and the second substrate is composed of a base material containing at least one selected from the group consisting of polyethylene terephthalate, polycarbonate and polyethylene naphthalate. The connection structure as described in item 12 or 13 of the patent application, wherein the first substrate is composed of a substrate containing at least one selected from the group consisting of polyethylene terephthalate, polycarbonate and polyethylene naphthalate, and the second substrate is composed of a substrate containing at least one selected from the group consisting of polyimide resin and polyethylene terephthalate. A connection structure comprises: a solar cell having a substrate and a connection terminal arranged on the main surface of the substrate, a wiring component, and a connection component arranged between the solar cell and the wiring component, wherein the connection component contains a cured product of the adhesive composition described in any one of items 1 to 7 of the patent application scope, and the connection terminal and the wiring component are electrically connected.