Conductive composition

Abstract

This conductive composition contains (A) an epoxy resin, (B) a polyol, (C) a cationic polymerization initiator, and (D) conductive particles. (A-1) an alicyclic epoxy resin and (A-2) a rubber-modified epoxy resin are contained as the epoxy resin (A). A polyol that has a molecular weight of 200 or more is contained as the polyol (B).

Description

conductive composition CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2023-205871, the disclosure of which is incorporated herein by reference.

[0002] The present invention relates to an electrically conductive composition.

[0003] Conventionally, printed wiring boards have been produced by etching copper-clad laminates, which are made by laminating copper foil on an electrically insulating substrate, and then soldering electronic elements such as LSIs and capacitors to the printed wiring board to produce printed circuit boards. Examples of printed wiring boards used in this type of printed circuit board include rigid boards, which have a substrate made of glass cloth impregnated with epoxy resin, as well as flexible boards and film boards, which have a substrate made of polyimide film or polyethylene terephthalate resin film. Other known types of printed wiring boards include single-sided boards, in which wiring is provided on only one side of the substrate; double-sided boards, in which wiring is provided on both sides of the substrate; and multilayer boards, in which multiple substrates are alternately laminated with wiring. Among these, double-sided boards and multilayer boards often have through-holes that penetrate the substrate in the thickness direction, allowing electrical connections between layers to be made through the through-holes.

[0004] Recently, there has been an increase in the use of printing methods that use conductive compositions instead of copper foil to form wiring on substrates, and in the use of conductive compositions instead of soldering to electrically connect electronic elements to wiring. Known conductive compositions of this type include those containing conductive particles, such as silver particles, and a curable resin. When used as a wiring agent, such conductive compositions do not require complex processes such as etching copper foil, and when used as a conductive adhesive, they do not require high-temperature processes such as soldering, making them highly convenient.

[0005] It is desirable that the conductive composition be able to exhibit excellent conductivity even when cured at low temperatures. From this perspective, Patent Documents 1 and 2 propose conductive compositions containing an alicyclic epoxy resin, conductive particles, and a cationic polymerization initiator. Patent Document 1 shows that the combination of an alicyclic epoxy resin and a cationic polymerization initiator can exhibit the above-mentioned performance even when cured at low temperatures.

[0006] International Publication No. 2019 / 159566 Japanese Patent No. 7249473

[0007] However, it cannot be said that sufficient research has been done on conductive compositions that can be cured at low temperatures, and there is room for improvement, particularly in terms of conductivity.

[0008] Furthermore, in printed wiring boards on which electronic elements are mounted, the electronic elements become a heat source. Furthermore, the wiring itself may generate heat due to Joule heat, and the degree of heat generation depends on the magnitude of the current flowing through the wiring. Therefore, a heat cycle, which is a phenomenon in which low-temperature and high-temperature states are repeatedly switched, may occur in printed circuit boards. This heat cycle may cause a change in the conductivity of the cured product of the conductive composition, potentially reducing the reliability of the printed circuit board. The heat cycle does not occur only when the conductive composition is used in printed circuit boards; that is, stable conductivity is required for applications other than those described above.

[0009] In view of the above circumstances, an object of the present invention is to provide a conductive composition that can form a cured product that has excellent conductivity and in which changes in conductivity due to heat cycles are suppressed.

[0010] The conductive composition according to the present invention comprises: (A) an epoxy resin; (B) a polyol; (C) a cationic polymerization initiator; and (D) conductive particles; the (A) epoxy resin comprises (A-1) an alicyclic epoxy resin and (A-2) a rubber-modified epoxy resin; and the (B) polyol comprises a polyol having a molecular weight of 200 or more.

[0011] In the conductive composition according to one aspect of the present invention, the alicyclic epoxy resin (A-1) has an epoxycycloalkyl group.

[0012] In a conductive composition according to one aspect of the present invention, the content of the (A-1) alicyclic epoxy resin is 20% by mass or more and 90% by mass or less, based on the total mass of the (A) epoxy resin, and the content of the (A-2) rubber-modified epoxy resin is 2% by mass or more and 10% by mass or less, based on the total mass of the (A) epoxy resin.

[0013] The conductive composition according to one aspect of the present invention includes, as the polyol (B), a polyalkylene glycol (B-1) or a polyester polyol (B-2).

[0014] The conductive composition according to one aspect of the present invention includes the polyalkylene glycol (B-1), and the content of the polyalkylene glycol (B-1) is 1 part by mass or more and 12 parts by mass or less per 100 parts by mass of the epoxy resin (A).

[0015] As described above, according to the present invention, it is possible to provide a conductive composition capable of forming a cured product that has excellent conductivity and in which changes in conductivity due to heat cycles are suppressed.

[0016] Hereinafter, the conductive composition according to an embodiment of the present invention will be described.

[0017] The conductive composition according to the embodiment includes a curable resin composition including (A) an epoxy resin, (B) a polyol, and (C) a cationic polymerization initiator, and (D) conductive particles. The curable resin composition may optionally include (E) a solvent and (F) an additive.

[0018] The curable resin composition may be reactively curable and thermosetting. The conductive composition is liquid when the curable resin composition is in an uncured state. In this specification, the term "liquid" does not only mean a low-viscosity composition that exhibits fluidity under the action of gravity at room temperature, but also includes a semi-solid state such as a paste state.

[0019] The curable resin composition may contain an alicyclic epoxy resin (A-1) as the epoxy resin (A). The alicyclic epoxy resin (A-1) preferably has an epoxycycloalkyl group such as an epoxycyclopentyl group or an epoxycyclohexyl group. The alicyclic epoxy resin (A-1) preferably has 2 or more and 4 or less epoxycycloalkyl groups.

[0020] The alicyclic epoxy resin (A-1) may be an ester-type alicyclic epoxy resin in which two epoxy cycloalkyl groups are linked via an ester bond, such as 3,4-epoxycyclohexylmethyl(3,4-epoxy)cyclohexanecarboxylate.

[0021] The alicyclic epoxy resin (A-1) may be a fused-ring alicyclic epoxy resin consisting of two or more fused rings having epoxy groups. The fused-ring alicyclic epoxy resin may be one in which the fused rings having epoxy groups share one carbon-carbon bond. Examples of such fused-ring alicyclic epoxy resins include tetrahydroindene diepoxide (more specifically, 3,4:7,8-diepoxybicyclo[4,3,0]nonane) in which the diene of tetrahydroindene is epoxidized. The fused-ring alicyclic epoxy resin may also be one in which the fused rings having epoxy groups are connected via one or more fused rings not having epoxy groups. Examples of such fused-ring alicyclic epoxy resins include tetracyclotetradegadiene diepoxide in which the diene of tetracyclotetradegadiene is epoxidized, and 5,12-dioxahexacyclo[7.6.1.0(2,8).0(4,6). 0(10,15).0(11,13)]hexadecane, and 5,12-dioxaheptacyclo[7.6.1.1(3,7).0(2,8).0(4,6).0(10,15).0(11,13)]heptadecane.

[0022] The alicyclic epoxy resin (A-1) may be a bicycloaliphatic epoxy resin in which two epoxycycloalkyl groups are linked via a carbon-carbon covalent bond (single bond). An example of the bicycloaliphatic epoxy resin is (3,3',4,4'-diepoxy)bicyclohexyl.

[0023] The alicyclic epoxy resin (A-1) may be a cyclic siloxane-type alicyclic epoxy resin in which 3 to 4 epoxycycloalkyl groups are linked via a trimeric to tetrameric cyclic siloxane. Examples of the cyclic siloxane-type alicyclic epoxy resin include 2,4,6,8-tetrakis(2-(3,4-epoxycyclohexyl)ethyl)-2,4,6,8-tetramethylcyclotetrasiloxane).

[0024] The curable resin composition may contain one or more of the above-mentioned (A-1) alicyclic epoxy resins.

[0025] The epoxy equivalent of the alicyclic epoxy resin (A-1) is preferably 100 to 300 g / eq, and more preferably 100 to 200 g / eq.

[0026] The content of the (A-1) alicyclic epoxy resin is preferably 80% by mass or more and 95% by mass or less, more preferably 80% by mass or more and 90% by mass or less, and even more preferably 80% by mass or more and 87% by mass or less, relative to the total mass of the (A) epoxy resin that can be contained in the curable resin composition.

[0027] The curable resin composition also includes a rubber-modified epoxy resin (A-2) as the epoxy resin (A). The rubber-modified epoxy resin (A-2) is a reaction product of an epoxy resin and rubber. Examples of the rubber-modified epoxy resin (A-2) include an NBR-modified epoxy resin, which is a reaction product of an epoxy resin and acrylonitrile butadiene rubber (NBR), a CTBN-modified epoxy resin, which is a reaction product of an epoxy resin and a carboxyl-terminated acrylonitrile butadiene rubber, and an ATBN-modified epoxy resin, which is a reaction product of an epoxy resin and an amino-terminated acrylonitrile butadiene rubber. The inclusion of the rubber-modified epoxy resin (A-2) in the curable resin composition can reduce the initial resistance value.

[0028] Examples of epoxy resins to be reacted with the rubber include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, tetrabromobisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and bisphenol S-type epoxy resins; glycidyl ether-type epoxy resins such as tris(glycidyloxyphenyl)methane and tetrakis(glycidyloxyphenyl)ethane; glycidylamine-type epoxy resins such as N,N-diglycidyl-4-glycidyloxyaniline and 4,4'-methylenebis(N,N-diglycidylaniline); and novolac-type epoxy resins such as cresol novolac-type epoxy resins, phenol novolac-type epoxy resins, α-naphthol novolac-type epoxy resins, and brominated phenol novolac-type epoxy resins.

[0029] The content of the (A-2) rubber-modified epoxy resin is typically less than 50% by mass, based on the total mass of the (A) epoxy resin that can be contained in the curable resin composition. The content here is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 10% by mass or less, even more preferably 2% by mass or more and 8% by mass or less, and even more preferably 5% by mass or more and 8% by mass or less. In particular, a content of 2% by mass or more results in favorable volume resistivity and resistance values ​​for the cured product. Furthermore, a content of 10% by mass or less ensures that the (A-2) rubber-modified epoxy resin is sufficiently dispersed in the curable resin composition, suppressing an increase in the viscosity of the conductive composition, making it easier to apply the conductive composition to an adherend in a desired thickness and shape.

[0030] The curable resin composition may contain (A-3) an optional epoxy resin other than those described above. Examples of the optional epoxy resin (A-3) include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, tetrabromobisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and bisphenol S-type epoxy resins; glycidyl ether-type epoxy resins such as tris(glycidyloxyphenyl)methane and tetrakis(glycidyloxyphenyl)ethane; glycidylamine-type epoxy resins such as N,N-diglycidyl-4-glycidyloxyaniline and 4,4'-methylenebis(N,N-diglycidylaniline); and novolac-type epoxy resins such as cresol novolac-type epoxy resins, phenol novolac-type epoxy resins, α-naphthol novolac-type epoxy resins, and brominated phenol novolac-type epoxy resins. The curable resin composition may also contain an epoxy resin as a reactive diluent that is liquid at room temperature (25°C), such as butyl glycidyl ether, 2-ethylhexyl glycidyl ether, or 1,6-hexanediol diglycidyl ether. The content of these optional epoxy resins (A-3) is preferably 1% by mass or more and 12% by mass or less, based on the total mass of the epoxy resins (A) that may be contained in the curable resin composition. For example, when the optional epoxy resin (A-3) is a bisphenol epoxy resin, the content is preferably 7% by mass or more and 12% by mass or less. The curable resin composition may also contain a resin other than the epoxy resin (A), but the content of the epoxy resin (A) is preferably 90% by mass or more, and more preferably 95% by mass or more, based on the total mass of the resins that may be contained in the curable resin composition.

[0031] The conductive composition contains a (B-1) polyalkylene glycol or a (B-2) polyester polyol having a molecular weight of 200 to 2,000. When the curable resin composition contains a (B-1) polyalkylene glycol or a (B-2) polyester polyol, the heat cycle resistance can be improved. More specifically, the combination of the rubber-modified epoxy resin (A-2) with the (B-1) polyalkylene glycol or the (B-2) polyester polyol provides heat cycle resistance at a low resistance value. In this specification, the molecular weight of the (B) polyol refers to the weight average molecular weight, which can be determined by comparison with a polystyrene standard by gel permeation chromatography (GPC).

[0032] The polyalkylene glycol (B-1) preferably has a repeating unit represented by the following chemical formula (1): R １ is preferably an alkylene structure having 2 to 5 carbon atoms. The alkylene structure is preferably linear and unbranched. Examples of such polyalkylene glycols include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, a copolymer of oxyethylene and oxypropylene, polybutylene glycol, and polypentylene glycol.

[0033] The molecular weight of the polyalkylene glycol (B-1) is more preferably 200 or more and 1,000 or less, and even more preferably 200 or more and 500 or less.

[0034] The hydroxyl group equivalent of the polyalkylene glycol (B-1) is preferably 100 to 1000 g / eq.

[0035] When the curable resin composition contains the polyalkylene glycol (B-1), the content of the polyalkylene glycol (B-1) is preferably 1 part by mass or more and 12 parts by mass or less, and more preferably 2 parts by mass or more and 12 parts by mass or less, relative to 100 parts by mass of the epoxy resin (A) contained in the curable resin composition.

[0036] Next, the polyester polyol (B-2) preferably has a repeating unit represented by the following chemical formula (2): R ２ is preferably an alkylene structure having 2 to 5 carbon atoms. In addition, the alkylene structure is preferably linear and unbranched.

[0037] The (B-2) polyester polyol is preferably a lactone-based polyester polyol. The lactone-based polyester polyol is preferably a reaction product of a lactone having 3 to 6 carbon atoms in the lactone ring with a lower alcohol having 5 or less carbon atoms and 2 to 5 hydroxyl groups. Examples of the lactone include β-propiolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone. Examples of the lower alcohol include ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, propanetriol, butanetriol, pentanetriol, butanetetraol, and pentanetetraol. The lactone-based polyester polyol is preferably polycaprolactone glycol, polycaprolactone triol, or polycaprolactone tetraol.

[0038] The molecular weight of the polyester polyol (B-2) is more preferably 300 or more and 2,000 or less, and even more preferably 500 or more and 2,000 or less.

[0039] The hydroxyl group equivalent of the polyester polyol (B-2) is preferably 100 to 1000 g / eq.

[0040] When the curable resin composition contains the polyester polyol (B-2), the content of the polyester polyol (B-2) is preferably 1 part by mass or more and 15 parts by mass or less, and more preferably 10 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the epoxy resin (A) contained in the curable resin composition.

[0041] The cationic polymerization initiator (C) generates a strong acid when heated, and this strong acid initiates the polymerization reaction of the epoxy resin (A). The cationic polymerization initiator (C) is preferably a salt of an aromatic sulfonium and an anion. Examples of the aromatic sulfonium include benzyl(4-hydroxyphenyl)methylsulfonium, (4-acetoxyphenyl)dimethylsulfonium, (4-hydroxyphenyl)dimethylsulfonium, (2-methylbenzyl)(4-hydroxyphenyl)methylsulfonium, (4-acetoxyphenyl)(2-methylbenzyl)methylsulfonium, (1-naphthylmethyl)(4-hydroxyphenyl)methylsulfonium, and benzyl(4-acetoxyphenyl)methylsulfonium. Examples of the anion include tris(pentafluoroethyl)trifluorophosphate, hexafluorophosphate, tetrafluoroborate, tetrakis(pentafluorophenyl)borate, hexafluoroantimonate, p-toluenesulfonate, dodecylbenzenesulfonate, trifluoromethanesulfonate, and perfluorobutanesulfonate.

[0042] The content of the (C) cationic polymerization initiator is preferably 0.1 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the (A) epoxy resin contained in the curable resin composition.

[0043] The content of the (C) cationic polymerization initiator is preferably 0.5 parts by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 9 parts by mass or less, relative to 100 parts by mass of the (A) epoxy resin contained in the curable resin composition.

[0044] Examples of the (D) conductive particles include copper particles, silver particles, nickel particles, silver-coated copper particles, gold-coated copper particles, silver-coated nickel particles, gold-coated nickel particles, and solder particles (including not only those made of an alloy primarily composed of lead and tin, but also those made of so-called lead-free solder). The shape of the (D) conductive particles is not particularly limited, and examples include spherical, flake, and dendritic shapes. The average particle size of the (D) conductive particles is preferably 0.5 to 30 μm. The average particle size of the (D) conductive particles can be determined from a volume-based particle size distribution measured by a laser diffraction / scattering particle size distribution measurement method.

[0045] The content of the (D) conductive particles is preferably 250 parts by mass or more and 1,500 parts by mass or less, more preferably 300 parts by mass or more and 1,000 parts by mass or less, and even more preferably 300 parts by mass or more and 800 parts by mass or less, relative to 100 parts by mass of the (A) epoxy resin contained in the curable resin composition.

[0046] The (E) solvent preferably has a boiling point of about 150 to 250° C., and examples thereof include esters such as γ-butyrolactone and propylene carbonate, and ether alcohols such as butyl carbitol. The curable resin composition may contain only one type of solvent, or may contain multiple types of solvents.

[0047] The content of the (E) solvent is preferably 10 parts by mass or less relative to 100 parts by mass of the (A) epoxy resin contained in the curable resin composition.

[0048] Examples of the additive (F) include a colorant such as a pigment, a plasticizer, a flame retardant, an antioxidant, an antifoaming agent, an adhesion promoter, a leveling agent, a rheology control agent, a filler, etc. The content of the additive (F) is, for example, 0.5 to 20 parts by mass relative to 100 parts by mass of the epoxy resin (A) contained in the curable resin composition.

[0049] The viscosity of the conductive composition is preferably 80 Pa·s or less, more preferably 50 Pa·s or less, and even more preferably 40 Pa·s or less, as measured using a cone-plate viscometer at 25°C and a shear rate of 10 (1 / sec).

[0050] The curable resin composition is applied to an adherend in an uncured state and then cured to form a cured product with excellent conductivity. The adherend can be coated by printing, transfer, spraying, or the like, or spot-applied using a dispenser or the like. The curable resin composition can be used to form wiring for electrical and electronic circuits using a cured product. In this case, examples of adherends to which the curable resin composition can be applied include metal materials such as copper foil; and insulating materials (electrical insulating sheets) such as epoxy resin-impregnated glass sheets, polyimide resin sheets, polyethylene terephthalate resin sheets, and ceramic sheets. When used as a constituent material for circuit boards, the curable resin composition can be used as a wiring material, a bonding material for electrically connecting wiring and electronic elements instead of soldering, a filler for filling through holes, and the like.

[0051] The curable resin composition can be cured at a temperature lower than the melting point of solder (for example, 180°C or lower). The curable resin composition can be particularly useful in situations where the adherend is a polyethylene terephthalate resin sheet, which has a lower softening temperature than a polyimide resin sheet or the like. Polyethylene terephthalate resin has a high affinity with epoxy resins and exhibits good wettability with the curable resin composition. Therefore, the adherend to which the curable composition is attached may have at least the adherend surface to which the curable composition is attached composed of a resin composition containing polyethylene terephthalate resin.

[0052] The surface of the adherend may be subjected to a surface treatment such as a mechanical surface treatment to enhance the anchoring effect, such as a hairline finish or a matte finish, an electrical surface treatment to increase the number of functional groups such as hydroxyl groups on the surface, such as a plasma treatment or a corona treatment, or a coating with a primer or a coupling agent.

[0053] The curable resin composition can also be used as a conductive adhesive for purposes other than circuit formation, and can also be used as a thermally conductive adhesive primarily intended for heat dissipation.

[0054] The conductive composition is a combination of (A-1) an alicyclic epoxy resin and (A-2) a rubber-modified epoxy resin with (B-1) a polyalkylene glycol or (B-2) a polyester polyol having a molecular weight of 200 to 2000, and can form a cured product with excellent conductivity by heating at a low temperature of 150° C. or less, more preferably 120° C. or less, and even more preferably 100° C. or less. Such a cured product is suitable for forming circuits in printed wiring boards, filling vias, bonding substrates to electronic elements, etc.

[0055] Although one embodiment has been shown above as an example, the conductive composition according to the present invention is not limited to the configuration of the above embodiment. Furthermore, the conductive composition according to the present invention is not limited by the above-mentioned effects. The conductive composition according to the present invention can be modified in various ways without departing from the gist of the present invention.

[0056] The present disclosure includes the following: [1] A conductive composition comprising: (A) an epoxy resin; (B) a polyol; (C) a cationic polymerization initiator; and (D) conductive particles, wherein the (A) epoxy resin comprises an (A-1) alicyclic epoxy resin and an (A-2) rubber-modified epoxy resin, and the (B) polyol comprises a polyol having a molecular weight of 200 or more.

[0057] By including a polyol having a molecular weight of 200 or more in the conductive composition of the present invention, the cured product formed from the conductive composition of the present invention has excellent conductivity and is suppressed from changing in conductivity due to heat cycles.

[0058] [2] The conductive composition according to the above [1], wherein the (A-1) alicyclic epoxy resin has an epoxycycloalkyl group.

[0059] A cured product formed from the conductive composition of this embodiment will have superior properties as described above.

[0060] [3] The conductive composition according to the above [1] or [2], wherein the content of the (A-1) alicyclic epoxy resin is 20% by mass or more and 90% by mass or less, based on the total mass of the (A) epoxy resin, and the content of the (A-2) rubber-modified epoxy resin is 2% by mass or more and 10% by mass or less, based on the total mass of the (A) epoxy resin.

[0061] A cured product formed from the conductive composition of this embodiment is further suppressed in change in conductivity due to heat cycles.

[0062] [4] The conductive composition according to any one of [1] to [3] above, wherein the polyol (B) comprises a polyalkylene glycol (B-1) or a polyester polyol (B-2).

[0063] A cured product formed from the conductive composition of this embodiment will have superior properties as described above.

[0064] [5] The conductive composition according to [4] above, which contains the polyalkylene glycol (B-1), and the content of the polyalkylene glycol (B-1) is 1 part by mass or more and 12 parts by mass or less per 100 parts by mass of the epoxy resin (A).

[0065] A cured product formed from the conductive composition of this embodiment is further suppressed in change in conductivity due to heat cycles.

[0066] The present invention will be further explained below with reference to examples, but the present invention is not limited to these examples.

[0067] [Raw materials used] (A-1) Alicyclic epoxy resin 1 (ester type alicyclic epoxy resin): 3,4-epoxycyclohexylmethyl (3,4-epoxy) cyclohexanecarboxylate (manufactured by Daicel Corporation, CELLOXIDE (registered trademark) 2021P) (A-1) Alicyclic epoxy resin 2 (cyclic siloxane type alicyclic epoxy resin): 2,4,6,8-tetrakis(2-(3,4-epoxycyclohexyl)ethyl)-2,4,6,8-tetramethylcyclotetrasiloxane) (A-1) Alicyclic epoxy resin 3 (condensed ring type alicyclic epoxy resin): tetrahydroindene diepoxide (A-1) Alicyclic epoxy resin 4 (condensed ring type alicyclic epoxy resin): tetracyclotetradecadiene diepoxy (A-1) Alicyclic epoxy resin 5 (bicyclo type alicyclic epoxy resin): (3,3',4,4'-diepoxy)bicyclohexyl (A-2) Rubber-modified epoxy resin: NBR-modified epoxy resin which is a reaction product of bisphenol A type epoxy resin and acrylonitrile butadiene rubber (manufactured by ADEKA Corporation, ADEKA RESIN (registered trademark) EPR-4030, NBR-modified epoxy resin 40 mass%, (A-3) bisphenol A type epoxy resin 60 mass%) (B-1) Polyalkylene glycol 1: Polyethylene glycol (molecular weight 200, hydroxyl group equivalent 100 g / eq): Polyethylene glycol 200, manufactured by Wako Pure Chemical Industries, Ltd. (B-1) Polyalkylene glycol 2: Polyethylene glycol (molecular weight 400, hydroxyl group equivalent 200 g / eq): Polyethylene glycol 400, manufactured by Wako Pure Chemical Industries, Ltd. (B-2) Polyester polyol 1: Polycaprolactone polyol (molecular weight 550, hydroxyl group equivalent 167 g / eq), PCL305, manufactured by Daicel Chemical Industries, Ltd. (B-2) Polyester polyol 2: Polycaprolactone polyol (molecular weight 2000, hydroxyl equivalent 667 g / eq), PCL320, Daicel Chemical Industries, Ltd. (B-2) Polyester polyol 3: Polycaprolactone polyol (molecular weight 2000, hydroxyl equivalent 1000 g / eq): PCL L220AL, Daicel Chemical Industries, Ltd. Diethylene glycol (molecular weight 106, hydroxyl equivalent 53 g / eq): Wako Pure Chemical Industries, Ltd. Hydrogenated polybutadiene with hydroxyl groups at both ends (number average molecular weight 1500, hydroxyl equivalent 750 g / eq): GI-1000, Nippon Soda Co., Ltd. (C) Cationic polymerization initiator 1: Salt of aromatic sulfonium and hexafluoroantimonate, Sanshin Chemical Industry Co., Ltd., San-Aid (registered trademark) SI-100 (C) Cationic polymerization initiator 2: 1-naphthylmethylmethyl p-hydroxyphenylsulfonium hexafluorophosphate, manufactured by Sanshin Chemical Industry Co., Ltd., San-Aid (registered trademark) SI-360 (D) Conductive particles: silver powder, flake-shaped, average particle diameter 6 μm (E) Solvent: γ-butyl lactone,

[0068] [Measurement of Molecular Weight of Polyol] Apparatus: Alliance GPC System Column: KF-802 + KF-803 connected column Exclusion limit molecular weight: 2,000,000 Column packing: styrene divinylbenzene copolymer (particle diameter: 6 μm) Column size: 8 mm I.D. × 300 mL Apparatus settings: detector wavelength (2D) 254 nm, detector temperature 40°C, oven temperature 40°C, solution flow rate 1 mL / min, solvent THF, injection amount 0.01 mL Sample preparation: A sample was dissolved in THF to a concentration of 1% by mass, and filtered using a syringe filter (made of PTFE, diameter 25 mm, pore size 0.45 μm).

[0069] [Production Examples] Conductive compositions were prepared by blending the components in the blending ratios shown in Tables 1 to 4.

[0070] [Evaluation 1: Initial Conductivity] The conductivity was evaluated by measuring the volume resistivity of a cured product formed using the prepared conductive composition. Specifically, the conductive composition was line-printed using a metal plate on a 100 mm x 65 mm glass epoxy substrate (length 60 mm, width 1 mm, thickness approximately 100 μm, 5 lines per substrate). Next, the conductive composition was cured by heat treatment at 120°C for 30 minutes in a hot air drying oven to prepare a measurement sample. The resistance value (Ω) at both ends of this measurement sample was measured using a four-terminal electrical resistance measuring device (Tables 1 to 4). Next, the thickness of the cured conductive composition was measured using a micrometer. The resistance value (Ω) and cross-sectional area (cm) of the cured conductive composition were measured. ２ The volume resistivity (Ω cm) was calculated from the thickness (cm) and length (cm) and evaluated according to the following evaluation criteria. The results are shown in Tables 1 to 3. (Evaluation criteria) ○: Volume resistivity is 1.5E-04 Ω cm or less ×: Volume resistivity exceeds 1.5E-04 Ω cm

[0071] [Evaluation 2: Conductivity after heat cycle (HC) test] Apparatus: Air-chamber temperature cycle tester (ETAC WINTECH NEO NT1050A, manufactured by Kusumoto Chemicals Co., Ltd.) Evaluation method: The initial conductivity evaluation measurement sample used in Evaluation 1 was subjected to 300 heat cycles of 30 minutes at -40°C and 30 minutes at 85°C. The resistance values ​​of the samples after the heat cycle test were measured and the average value was calculated (Tables 1 to 4), and the rate of change relative to the initial resistance value obtained in Evaluation 1 was determined and evaluated according to the following evaluation criteria. The results are as shown in Tables 1 to 3. (Evaluation criteria) ○: Rate of change in resistivity is within -30% to 10% ×: Rate of change in resistivity exceeds -30% to 10%

[0072] [Evaluation 3: Adhesion Strength] A conductive composition was applied to the copper foil surface of a 70 mm square glass epoxy copper-clad laminate. A 2 mm square silicon die was then placed on the applied portion. The conductive composition was then cured by heating at 120°C for 30 minutes in a hot air drying oven to prepare a measurement sample. The measurement sample was then fixed to a Bond Tester 4000 Plus (manufactured by Nordson Dage) equipped with a cartridge S200KG (manufactured by Nordson Dage). After adjusting one surface of the silicon die to be parallel to the tool surface of the device, adhesion strength was measured at a height of 0.1 mm relative to the copper foil surface of the glass epoxy copper-clad laminate, at a movement speed of 0.3 mm / s. The results are shown in Tables 1 and 2.

[0073]

[0074]

[0075]

[0076]

Claims

1. A conductive composition comprising: (A) an epoxy resin; (B) a polyol; (C) a cationic polymerization initiator; and (D) conductive particles; the epoxy resin (A) comprises: (A-1) an alicyclic epoxy resin and (A-2) a rubber-modified epoxy resin; and the polyol (B) comprises: a polyol having a molecular weight of 200 or more.

2. The conductive composition according to claim 1, wherein the alicyclic epoxy resin (A-1) has an epoxycycloalkyl group.

3. The conductive composition according to claim 1 or 2, wherein the content of the (A-1) alicyclic epoxy resin is 20 mass% or more and 90 mass% or less based on the total mass of the (A) epoxy resin, and the content of the (A-2) rubber-modified epoxy resin is 2 mass% or more and 10 mass% or less based on the total mass of the (A) epoxy resin.

4. The conductive composition according to claim 1 or 2, wherein the polyol (B) comprises a polyalkylene glycol (B-1) or a polyester polyol (B-2).

5. The conductive composition according to claim 4, comprising the polyalkylene glycol (B-1), the content of the polyalkylene glycol (B-1) being 1 part by mass or more and 12 parts by mass or less per 100 parts by mass of the epoxy resin (A).

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