conductive paste

Abstract

To provide a low-viscosity resin composition that comprises a flexible epoxy resin in combination with a diluent and yields a cured product with high conductivity.SOLUTION: A flexible epoxy resin is combined with a reactive diluent that features the structure (Gly-O-R-O-Gly), where two glycidyl ether groups (-O-Gly) are bound to a divalent aliphatic hydrocarbon group (R), and exhibits a viscosity of 500 mPa s or less at 25°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a conductive paste. [Background technology]

[0002] Conventionally, it has been known to use a thermosetting conductive paste containing silver particles as an alternative connection method to solder for assembling electronic components and connecting them to substrates (Patent Document 1). Conductive pastes are sometimes used to electrically connect multiple components and to form wiring and electrodes in the manufacture of electronic devices such as camera modules and printed wiring boards. In order to achieve finer connections and form finer wiring and electrodes, it may be necessary to reduce the viscosity of the conductive paste. For example, a low-viscosity diluent is known as a means for reducing the viscosity of the conductive paste. Furthermore, when used in electronic devices, printed wiring boards, etc., the cured product of the conductive paste may be required to have impact resistance. For example, an epoxy resin with a flexible structure (flexible epoxy resin) is known as a means for imparting impact resistance to the cured product (Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2015-42696 [Patent Document 2] Patent No. 5786418 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a flexible epoxy resin is used in a conductive paste, the viscosity of the conductive paste also increases due to the high viscosity of the flexible epoxy resin. In this case, using a diluent to reduce the viscosity is considered, but using too much tends to reduce the physical properties of the cured product, such as the mechanical strength. If the amount used is limited, depending on the type of diluent, the viscosity of the conductive paste may not be reduced sufficiently. Furthermore, depending on the type of diluent, problems such as reduced conductivity (higher resistance) of the cured product may occur.

[0005] An object of the present invention is to provide a low-viscosity resin composition that uses a flexible epoxy resin and a diluent in combination to produce a cured product with high electrical conductivity. [Means for solving the problem]

[0006] The present inventors have discovered that when a flexible epoxy resin is used in combination with a reactive diluent having a specific structure, it is possible to maintain an appropriate viscosity as a paste and also to suppress a decrease in the electrical conductivity of the cured product, and have completed the present invention.

[0007] That is, the present invention includes the following aspects. [1] (A) a flexible epoxy resin containing a linear hydrocarbon structural unit having 4 to 20 carbon atoms and / or a polyalkylene ether structural unit having 3 to 20 ether oxygen atoms, (B) a reactive diluent having a structure (Gly-ORO-Gly) in which two glycidyl ether groups (-O-Gly) are bonded to a divalent aliphatic hydrocarbon group (R), and having a viscosity of 500 mPa s or less at 25°C; (C) an epoxy resin curing agent; (D) silver particles; A resin composition comprising: [2] The resin composition according to [1] above, wherein the aliphatic hydrocarbon group (R) is a saturated aliphatic hydrocarbon group. [3] The resin composition according to [1] or [2] above, wherein the aliphatic hydrocarbon group (R) is a non-alicyclic aliphatic hydrocarbon group. [4] The resin composition according to any one of the above [1] to [3], wherein the aliphatic hydrocarbon group (R) has 3 or more and 6 or less carbon atoms. [5] The resin composition according to [4] above, wherein the aliphatic hydrocarbon group (R) has 4 or 5 carbon atoms. [6] The resin composition according to any one of [1] to [5], wherein the viscosity of the reactive diluent (B) at 25° C. is 100 mPa·s or less. [7] The resin composition according to any one of the above [1] to [6], wherein the flexible epoxy resin (A) further contains a bisphenol-type structural unit. [8] The resin composition according to any one of [1] to [7], wherein the epoxy resin curing agent (C) is at least one selected from the group consisting of a tertiary amino group-containing modified polyamine, a urea bond-containing modified polyamine, and an imidazole-containing modified polyamine. [9] The resin composition according to any one of the above [1] to [8], further comprising (E) an epoxy resin (excluding the flexible epoxy resin (A)).

[10] The resin composition according to any one of [1] to [9], which contains 0.1 to 40 mass % of the flexible epoxy resin (A) relative to the total mass of the resin composition.

[11] The resin composition according to any one of [1] to

[10] above, which contains 0.1 to 30 mass % of the reactive diluent (B) relative to the total mass of the resin composition.

[12] The resin composition according to any one of [1] to

[11] , which contains 2 to 40 parts by weight of the epoxy resin curing agent (C) relative to 100 parts by weight of the epoxy resin contained in the resin composition.

[13] The resin composition according to any one of [1] to

[12] above, comprising 30 to 95 mass% of the silver particles (D) relative to the total mass of the resin composition.

[14] A cured product of the resin composition according to any one of [1] to

[13] above. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a low-viscosity resin composition that uses a flexible epoxy resin and a diluent in combination and that produces a cured product with high electrical conductivity. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 shows a test sample for contact resistance measurement. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention relates to a resin composition containing: (A) a flexible epoxy resin containing linear hydrocarbon structural units having from 4 to 20 carbon atoms and / or polyalkylene ether structural units having from 3 to 20 ether oxygen atoms; (B) a reactive diluent having a structure (Gly-ORO-Gly) in which two glycidyl ether groups (-O-Gly) are bonded to a divalent aliphatic hydrocarbon group (R) and having a viscosity of 500 mPa s or less at 25°C; (C) an epoxy resin curing agent; and (D) silver particles.

[0011] (A) Flexible epoxy resin The flexible epoxy resin used in the present invention contains linear hydrocarbon structural units having 4 to 20 carbon atoms and / or polyalkylene ether structural units having 3 to 20 ether oxygen atoms.

[0012] The linear hydrocarbon structural unit contained in flexible epoxy resins is -(CH2) x -, where x is 4 or more and 20 or less. x is preferably 4 or more and 10 or less. In place of the hydrogen atoms, a substituent such as a hydroxyl group may be present, and further, at least one of the hydrogen atoms may be substituted with a hydrocarbon group, an alkoxyl group, an aryl group, an aryloxy group, or the like. The hydrocarbon or alkoxyl group as the substituent preferably has 4 or less carbon atoms, and the aryl group of the aryl group or aryloxy group is preferably a phenyl group. These substituents can be present within a range that does not impair the flexibility of the structural unit.

[0013] The polyalkylene ether structural unit contained in the flexible epoxy resin has 3 to 20 ether oxygen atoms, preferably 3 to 10. Specific examples include structural units derived from a polymer of one or more alkylene oxides selected from ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, neopentylene oxide, tetramethylene oxide, etc. Also included are those in which one or more hydrogen atoms of the alkylene oxide are substituted with, for example, a hydroxyl group, an alkoxyl group, an aryl group, an aryloxy group, or a hydrocarbon group. The hydrocarbon or alkoxyl group as the substituent preferably has 4 or fewer carbon atoms, and the aryl group of the aryl group or aryloxy group is preferably a phenyl group. These substituents can be present within a range that does not impair the flexibility of the structural unit.

[0014] The linear hydrocarbon structural unit having 4 to 20 carbon atoms improves the heat resistance of the cured product, and the polyalkylene ether structural unit improves the adhesion and bonding properties to, for example, metal substrates. By appropriately selecting these structural units, it is possible to accommodate a variety of substrates, manufacturing processes, and required performance.

[0015] The flexible epoxy resin preferably contains a bisphenol structural unit in addition to the linear hydrocarbon structural unit and / or polyalkylene ether structural unit. Examples of the bisphenol structural unit include structural units derived from bisphenol A, bisphenol F, and bisphenol S. Specific examples include units derived from these compounds with the OH groups removed from their terminals and units represented by the following general formula (1), and the rings may be hydrogenated. Furthermore, these rings may have a substituent such as a hydrocarbon group, an alkoxyl group, an aryl group, an aryloxy group, or a hydroxyl group.

[0016] JPEG0007828541000001.jpg37170

[0017] When the flexible epoxy resin contains bisphenol structural units, the molar ratio of the linear hydrocarbon structural units and / or polyalkylene ether structural units to the bisphenol structural units is preferably 1:10 to 5:1, more preferably 1:5 to 3:1. If the amount of bisphenol structural units is greater than this range, the cured product will not have sufficient flexibility. If the amount of bisphenol structural units is less than the above range, the Tg of the cured product will be lowered, resulting in reduced heat resistance.

[0018] Specifically, the flexible epoxy resin containing a bisphenol structural unit preferably has one or more structures shown in the following structural formulas (2-i) to (2-iv): Furthermore, multiple hydroxyl groups in the structural formulas shown below may undergo a crosslinking reaction, and the oxygen atoms of the hydroxyl groups may form nodes in an unspecified structure.

[0019] JPEG0007828541000002.jpg103170

[0020] In structural formulas (2-i) to (2-iv), Ar 1 , Ar 2 are bisphenol structural units which may be the same or different and may be hydrogenated or have a substituent, and X is a linear hydrocarbon group having from 4 to 20 carbon atoms and / or a polyalkylene ether structure having from 1 to 18 ether oxygen atoms. When X is a linear hydrocarbon group having from 4 to 20 carbon atoms, X is a linear hydrocarbon structural unit, and when X is a polyalkylene ether structure having from 1 to 18 ether oxygen atoms, -OXO- is a polyalkylene ether structural unit. Furthermore, n is the average value of the repeating units and is 1 to 30.

[0021] Examples of flexible epoxy resins containing bisphenol structural units include "EPICLON EXA4816" and "EPICLON EXA4822" (both manufactured by DIC Corporation), "YL7175-500" and "YL7175-1000" (both manufactured by Mitsubishi Chemical Corporation), and the like.

[0022] The content of the flexible epoxy resin is preferably 0.1 to 40 mass% of the total mass of the resin composition, more preferably 0.2 to 35 mass%, and even more preferably 0.5 to 30 mass%, and may be, for example, 0.8 to 20 mass%, 1 to 10 mass%, or 1.5 to 6 mass%. When the amount of the flexible epoxy resin is within the above range, it is possible to improve the impact resistance and adhesiveness of the cured product while suppressing an increase in the viscosity of the resin composition.

[0023] (B) Reactive diluent The reactive diluent used in the present invention has a structure (Gly-ORO-Gly) in which two glycidyl ether groups (-O-Gly) are bonded to a divalent aliphatic hydrocarbon group (R), and has a viscosity at 25°C of 500 mPa s or less.

[0024] The aliphatic hydrocarbon group (R) may be unsaturated or saturated, and may be alicyclic or acyclic. From the viewpoint of obtaining a cured product having good impact resistance and electrical conductivity while reducing the viscosity of the resin composition, the aliphatic hydrocarbon group (R) is preferably saturated and preferably acyclic. The number of carbon atoms in the aliphatic hydrocarbon group (R) is preferably 6 or less, more preferably 5 or less, and is preferably 3 or more, more preferably 4 or more.

[0025] The reactive diluent has a viscosity of 500 mPa·s or less at 25°C. Flexible epoxy resin (A) usually has a high viscosity, greater than 500 mPa·s at 25°C (for example, a viscosity of more than 100 Pa·s at 25°C). Therefore, a diluent having a viscosity of 500 mPa·s or less can reduce the viscosity of a resin composition containing the flexible epoxy resin. The reactive diluent preferably has a viscosity of 100 mPa·s or less at 25°C, more preferably 75 mPa·s or less, even more preferably 50 mPa·s or less, and preferably 1 mPa·s or more, more preferably 3 mPa·s or more, and even more preferably 5 mPa·s or more. A low viscosity of 500 mPa·s or less can be measured, for example, by placing 1.2 ml of a sample in an E-type viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) and measuring the viscosity after 2 minutes at 25°C, 5 rpm, and a 1.34°×R24 rotor according to JIS-K7117-2. A viscosity of more than 1 Pa·s can be measured, for example, by placing 0.22 ml of a sample in an E-type viscometer (RE-80U manufactured by Toki Sangyo Co., Ltd.) and measuring the viscosity after 2 minutes at 25°C, 20 rpm, and a 3°×R9.7 rotor according to JIS-K7117-2.

[0026] Examples of reactive diluents include "ED-523L" and "ED-503G" (both manufactured by ADEKA Corporation), "BD(D)" (manufactured by Yokkaichi Chemical Co., Ltd.), and "ZX-1658GS" (manufactured by Nippon Steel Chemical Co., Ltd.).

[0027] The content of the reactive diluent is preferably 0.1 to 30 mass% of the total mass of the resin composition, more preferably 0.2 to 25 mass%, and even more preferably 0.5 to 20 mass%, and may be, for example, 1 to 15 mass%, 1.5 to 12.5 mass%, or 2 to 10 mass%. When the amount of the reactive diluent is within the above range, it is possible to obtain a cured product having good electrical conductivity while reducing the viscosity of the resin composition.

[0028] (C) Epoxy resin hardener As the epoxy resin curing agent in the present invention, any known epoxy resin curing agent can be used without any particular limitation.

[0029] From the viewpoint of handling of the resin composition, the epoxy resin curing agent is preferably a latent curing agent. In this specification, a latent curing agent refers to a compound that is blended into a resin composition for the purpose of curing the epoxy resin, and that does not react with functional groups such as epoxy groups under normal storage conditions of the resin composition (e.g., room temperature, visible light, etc.), but exhibits reactive activity toward functional groups in the presence of heat or light, thereby curing the resin composition. These may be used alone or in combination of two or more.

[0030] From the viewpoints of the viscosity of the resin composition and the electrical conductivity and adhesiveness of the cured product, the epoxy resin curing agent is preferably one or more selected from the group consisting of a tertiary amino group-containing modified polyamine, a urea bond-containing modified polyamine, and an imidazole-containing modified polyamine, and from the viewpoint of adhesiveness, it is more preferable to use a urea bond-containing modified polyamine and an imidazole-containing modified polyamine in combination.

[0031] In this specification, the term "tertiary amino group-containing modified polyamine" refers to a compound that has a polymer structure containing an aliphatic tertiary amine other than imidazole, in which the active amine forms a stabilized structure with an epoxy resin and / or a phenolic resin, and can be used as a latent curing agent. Examples of tertiary amino group-containing modified polyamines include EH4380S, EH3616S, EH5001P, and EH4357S manufactured by ADEKA Corporation.

[0032] Imidazole group-containing modified polyamines are compounds that have a polymer structure containing imidazole, in which active amines form a stabilized structure with epoxy resins and / or phenolic resins, and can be used as latent curing agents. Examples of imidazole group-containing modified polyamines include PN-23, PN-H, and PN-40 manufactured by Ajinomoto Fine-Techno Co., Ltd., EH4346S manufactured by ADEKA Corporation, FXR-1121 manufactured by T&K TOKA Corporation, and Sanmide LH210 manufactured by Air Products Japan Co., Ltd.

[0033] Urea bond-containing modified polyamines are compounds in which an active amine forms a stabilized structure through the urea bond formed with an isocyanate resin, and can be used as latent curing agents. Examples of urea bond-containing modified polyamines include FXR-1020 and FXR-1081 manufactured by T&K TOKA Corporation.

[0034] The epoxy resin curing agent is preferably used in an amount of 1 to 50 parts by weight relative to 100 parts by weight of the epoxy resin contained in the resin composition. In consideration of the curing rate of the epoxy resin, sufficient crosslinking formation, viscosity of the resin composition, and coatability, the amount is more preferably 2 to 40 parts by weight, and even more preferably 5 to 35 parts by weight, relative to 100 parts by weight of the epoxy resin contained in the resin composition, and may be, for example, 10 to 30 parts by weight, 15 to 28 parts by weight, or 20 to 27 parts by weight.

[0035] (D) Silver particles The resin composition of the present invention contains silver particles to impart electrical conductivity. The shape of the silver particles used in the present invention is not particularly limited, and known shapes such as spherical, flake, and needle shapes can be used, but flake shapes are preferred from the viewpoint of obtaining good electrical conductivity in the cured product. The flake shape refers to a plate-like shape (see JIS Z2500:2000), and is also called scale-like because it is thin and plate-like.

[0036] The average particle size of the silver particles used in the present invention is preferably 1 to 15 μm. Considering the ease of handling of the resin composition (appropriate viscosity) and the occurrence of nozzle clogging when applying with a dispenser, 1.5 to 12.5 μm is more preferable, and 2 to 10 μm is even more preferable. In this specification, the average particle size is measured using a laser diffraction particle size distribution analyzer as the particle size (median diameter) at which the relative particle amount is 50% (50% of the total particle amount, the particle size at the midpoint of the particle amount when the total particle amount and particle size are graphed).

[0037] When using flake silver particles, the specific surface area must be 0.1 to 1.5 m 2 From the viewpoint of the electrical conductivity of the cured product or the dispensability of the resin composition (in this specification, dispensability means application performance such as ease of application when filling a resin composition into a syringe and applying it with a dispenser), it is preferable to set the viscosity to 0.15 to 1.0 m / g. 2 / g is more preferable, and 0.2 to 0.9m 2 / g is more preferable. The specific surface area is measured by the BET (Brunauer, Emmett, and Teller) single-point method using a specific surface area measurement device.

[0038] The content of silver particles is preferably 30 to 95 mass% of the total mass of the resin composition, and from the viewpoints of the conductivity of the cured product and the viscosity of the resin composition, is more preferably 40 to 80 mass%, and may be, for example, 50 to 80 mass%, or 60 to 75 mass%.

[0039] (E) Epoxy resin (excluding flexible epoxy resin (A)) The resin composition of the present invention may optionally contain an epoxy resin different from the flexible epoxy resin (A) to impart high adhesiveness. The epoxy resin (E) may be solid or liquid at 25°C. If it is liquid, it preferably has a viscosity of greater than 500 mPa·s at 25°C. The viscosity at 25°C is preferably 750 mPa·s or greater, more preferably 1000 mPa·s or greater, and preferably 20000 mPa·s or less, more preferably 10000 mPa·s or less, for example, 5000 mPa·s or less, or 4000 mPa·s or less. The viscosity of the epoxy resin (E) at 25°C can be measured, for example, by placing a 0.22 ml sample in an E-type viscometer (RE-80U manufactured by Toki Sangyo Co., Ltd.) and measuring the viscosity at 25°C, 20 rpm, or 2 minutes after the measurement, according to JIS-K7117-2, using a 3° × R9.7 rotor.

[0040] The epoxy resin (E) is not particularly limited, but is preferably one having an average of two or more epoxy groups per molecule. Examples of epoxy resins include bisphenol A epoxy resins, biphenyl epoxy resins, biphenyl aralkyl epoxy resins, phenol aralkyl epoxy resins, naphthol epoxy resins, naphthalene epoxy resins, bisphenol F epoxy resins, phosphorus-containing epoxy resins, bisphenol S epoxy resins, aromatic glycidylamine epoxy resins (e.g., tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, diglycidyl toluidine, diglycidyl aniline, etc.), alicyclic epoxy resins, aliphatic linear epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, epoxy resins having a butadiene structure, epoxy resins having a dicyclopentadiene structure, diglycidyl ethers of bisphenols, diglycidyl ethers of naphthalene diols, glycidyl ethers of phenols, and diglycidyl ethers of alcohols, as well as alkyl-substituted, halides, and hydrogenated versions of these epoxy resins. One or more of these may be used. Among these, it is preferable to use a bisphenol type epoxy resin, which has low viscosity and good stability, and it is more preferable to use a bisphenol A type epoxy resin or a bisphenol F type resin, and it is preferable to use a mixture of a bisphenol A type epoxy resin and a bisphenol F type resin.

[0041] Available bisphenol-type epoxy resins include, for example, RE-310S, RE-304S, and RE-404S manufactured by Nippon Kayaku Co., Ltd., and YD-115, YD-115G, YD-115CA, YD-118P, YD-127, YD-128, YD-128G, YD-128S, YD-128CA, YD-134, and YD-134P manufactured by Nippon Steel Chemical Co., Ltd. N, YD-011, YD-012, YD-013, YD-014, YD-017, YD-019, YD-020, YD-8125, YD-7011R, YD-7014R , YD-7017, YD-7019, YD-7020, YD-900, YD-901, YD-902, YD-903, YD-904, YD-907, YD-909, YD- 927H, ZX-1059, YDF-8170, YDF-170, YDF-175S, YDF-2001, YDF-2004, Epicron series 840, 840S, 850, 850S, 850CRP, 855, 857, D-515, 860, 900-IM, 1050, 1055, 2055, 3050, 40 manufactured by Dainippon Ink and Chemicals, Inc. Examples of such resins include 50, 4055, 7050, 9055, 830, 830S, 830LVP, 835, 835LV, EXA-1514, EXA-4004, 828, 828EL, 827, 806, 807, YL980, and YL983 manufactured by Mitsubishi Chemical Corporation, and EP-4100, EP-4500, and EP-4901 from the Adeka Resin series manufactured by ADEKA Corporation.

[0042] The epoxy resin (E) can be blended in the resin composition of the present invention in an amount of preferably 0.5% by mass to 50% by mass, more preferably 1% by mass to 40% by mass, for example, 5% by mass to 30% by mass, or 10 to 20% by mass.

[0043] <(F) Metal powders other than silver particles (D)> The resin composition of the present invention may contain a metal powder other than silver particles (D) to suppress an increase in contact resistance of the cured product under high temperature and high humidity conditions. Examples of metal powders other than silver particles (D) include tin powder, zinc powder, and aluminum powder. The shape of the metal powder (F) is not particularly limited, and known shapes such as spherical, flake, and needle shapes can be used. However, spherical shapes are preferred from the viewpoint of the viscosity of the resin composition.

[0044] The particle size of the metal powder (F) is preferably 1 to 15 μm, more preferably 1 to 10 μm, taking into consideration the ease of handling of the resin composition and the occurrence of nozzle clogging when applying with a dispenser.

[0045] The specific surface area of ​​the metal powder (F) is preferably 0.1 to 1.5 m from the viewpoints of the conductivity of the cured product, the dispensability of the resin composition, etc. 2 / g, more preferably 0.1 to 1.0 m 2 / g.

[0046] From the viewpoint of suppressing contact resistance of the cured product under high temperature and high humidity conditions, the content of the metal powder (F) is preferably 3% by mass or more, more preferably 5% by mass or more, and preferably 20% by mass or less, and more preferably 15% by mass or less, based on 100% by mass of the nonvolatile components in the resin composition. In one embodiment of the present invention, the content of the metal powder (F) is preferably 3% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less, based on 100% by mass of the nonvolatile components in the resin composition.

[0047] (G) Core-shell polymer The resin composition of the present invention can contain a core-shell polymer to improve adhesion and provide stress relaxation. The core-shell polymer is a polymer having a core and a shell, and is obtained by polymerizing a relatively soft core prepared from a rubber elastomer prepared from a diene monomer, a (meth)acrylic acid ester monomer and / or a vinyl monomer, a polysiloxane rubber elastomer, or a mixture thereof, with a relatively hard shell layer prepared from a (meth)acrylic acid ester, an aromatic vinyl, a vinyl cyanide, an epoxy alkyl vinyl ether, an unsaturated acid derivative, a (meth)acrylamide derivative and / or a maleimide derivative. Available core-shell polymers include MX-120, MX-125, MX-130, MX-135, MX-960, and MX-965 from Kaneka Corporation, RKB-3040 and RKB-1133 from Resinous Chemicals, JF-001 and JF-003 from Mitsubishi Rayon Co., Ltd., and F351G from Ganz Chemicals. Known core-shell polymers can be used, such as those in the form of a powder or dispersed in an epoxy resin. These may be used alone or in combination as a powder and dispersed in an epoxy resin. The content of the core-shell polymer is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, of the total mass of the resin composition, and may be, for example, 0.5 to 5% by mass or 1 to 3% by mass.

[0048] The resin composition of the present invention is a liquid resin composition that has fluidity at 25°C. Taking into consideration applications in which the resin composition penetrates into gaps in adherends for bonding, the viscosity at 25°C is preferably less than 20 Pa·s, more preferably 10 Pa·s or less, preferably 1 Pa·s or more, and more preferably 5 Pa·s or more. In one embodiment of the present invention, the viscosity of the resin composition at 25°C is preferably 1 Pa·s or more but less than 20 Pa·s, more preferably 5 Pa·s or more but less than 15 Pa·s, and even more preferably 5 Pa·s or more but less than 10 Pa·s. In the present invention, the viscosity of the resin composition at 25°C can be measured, for example, by placing a 0.22 ml sample in an E-type viscometer (RE-80U manufactured by Toki Sangyo Co., Ltd.) and measuring the viscosity at 25°C, 20 rpm, and the value after 2 minutes using a 3° × R9.7 rotor according to JIS-K7117-2.

[0049] Other additives that may be added to the resin composition of the present invention include a silane coupling agent from the viewpoint of improving the adhesion of the resin composition to the substrate, a corrosion inhibitor such as benzimidazole from the viewpoint of protecting the connection terminals, and a thixotropic agent such as a boric acid ester or aerosil.

[0050] The resin composition of the present invention is produced by mixing the above-mentioned components in a conventional manner and dispersing them uniformly using a planetary mixer, a roll mill or the like to form a paste.

[0051] The present invention further relates to a cured product of the resin composition. The resin composition of the present invention, which uses a flexible epoxy resin in combination with a reactive diluent having a specific structure, can provide a cured product with excellent impact resistance and electrical conductivity. The cured product of the present invention also exhibits good electrical conductivity (contact resistance value) and adhesive strength even under high temperature and high humidity conditions. Heating is a preferred curing method, and heating conditions can be adjusted appropriately. For example, the resin composition may be cured by maintaining it at a temperature of 60 to 100°C, preferably 70 to 90°C, for 20 minutes to 3 hours, preferably 40 minutes to 2 hours.

[0052] The resin composition of the present invention can be used as a conductive adhesive for use in assembling electronic components, connecting them to substrates, and mounting chip components on substrates. [Example]

[0053] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0054] A resin composition was prepared according to the formulation shown in Table 1. All components except for components (E) and (F) were mixed for 30 minutes in a planetary mixer (5DMV-01-r, manufactured by Dalton Co., Ltd.). Then, components (E) and (F) were added and mixed for 20 minutes, and then degassed and mixed for 30 minutes in the planetary mixer to prepare the resin composition. The materials used are as follows:

[0055] EXA-4816: DIC Corporation, modified epoxy resin (flexible and tough), 100 Pa·s or more ZX-1059: Nippon Steel Chemical Co., Ltd., 1:1 mixture of bisphenol A resin and bisphenol F resin, viscosity 2500 mPa·s YDF-8170: Nippon Steel Chemical Co., Ltd., bisphenol F resin, viscosity 1300 mPa·s RKB-3040: Resinous Chemical Co., Ltd., product name: Resinous Bond, core-shell polymer-containing epoxy resin, 30% by weight of core-shell polymer, 70% by weight of bisphenol A resin and bisphenol F resin (viscosity measurement of the epoxy resin component is not possible due to the mixture) ED-523L: ADEKA Corporation, neopentyl glycol diglycidyl ether, viscosity 8 mPa·s BD(D): Yokkaichi Chemical Co., Ltd., product name "Epogosey", 1,4-butanediol diglycidyl ether, 8 mPa·s ED-503G: ADEKA Corporation, 1,6-hexanediol diglycidyl ether, viscosity 24 mPa·s ZX-1658GS: Nippon Steel Chemical Co., Ltd., 1,4-cyclohexanedimethanol diglycidyl ether, viscosity 32 mPa·s EX-201: Nagase ChemteX Corporation, resorcinol diglycidyl ether, viscosity 350 mPa·s Epolite 200P(N): Kyoeisha Chemical Co., Ltd., tripropylene glycol diglycidyl ether, viscosity 30 mPa·s EX-830: Nagase ChemteX Corporation, polyethylene glycol diglycidyl ether, viscosity 70 mPa·s EX-841: Nagase ChemteX Corporation, polyethylene glycol diglycidyl ether, viscosity 110 mPa·s ZX-1542: Nippon Steel Chemical Co., Ltd., trimethylolpropane triglycidyl ether, viscosity 61 mPa·s PN-H: Ajinomoto Fine-Techno Co., Inc., product name "Amicure", imidazole group-containing modified polyamine FXR-1081: T&K TOKA, product name "Fujicure", urea-containing modified polyamine Silver particles: manufactured by Metallo, trade name EA-0101, average particle diameter 6.8μm, specific surface area 0.28m 2 / g, flakes Zinc particles: Manufactured by Hakusui Tech Co., Ltd., product name Zinc Powder R Powder, average particle diameter 5.2 μm, specific surface area 0.25 m 2 / g, spherical JF-003: Mitsubishi Rayon Co., Ltd., product name: pregelling agent, core-shell polymer

[0056] The viscosity of the resin compositions of the examples and comparative examples, and the resistivity, tensile shear adhesive strength, and increase in contact resistance under high temperature and high humidity of the cured products were measured by the following methods. The results are shown in Table 1.

[0057] (1) Viscosity measurement (25°C) 0.22 ml of the resin composition was added, and the viscosity was measured using an E-type viscometer (RE-80U manufactured by Toki Sangyo Co., Ltd.) at 20 rpm and 2 minutes later using a 3°×R9.7 rotor according to the procedure in accordance with JIS-K7117-2.

[0058] (2) Conductivity (resistivity) measurement A 120 mm line with a width of 2 mm and a thickness of approximately 80 μm was bar-coated on an FR-4 substrate with the resin compositions of the Examples and Comparative Examples, and cured at 80°C for 60 minutes in a heat circulation oven (DF-610, manufactured by Yamato Scientific Co., Ltd.) to prepare a test sample for measuring resistivity. The resistance of the cured product was measured in four-terminal mode at a distance of 100 mm using a digital multimeter (R6552, manufactured by Advantest Corporation), and the resistivity was calculated.

[0059] (3) Measurement of tensile shear bond strength Adhesion test specimens were prepared from nickel-plated stainless steel (100mm x 25mm x 1.5mm) according to the procedure specified in JIS-K6850 and cured at 80°C for 60 minutes. The tensile shear adhesive strength was measured according to the procedure specified in JIS-K6850 using a universal tensile testing machine (TSE AC-50kN).

[0060] (4) Increase in contact resistance under high temperature and humidity As shown in Figure 1, a conductor wire 2 was fixed across a nickel-plated 100 mm x 25 mm x 1.5 mm stainless steel plate 4. A resin composition 3 was applied to the conductor wire 2 so that it was in contact with the nickel surface, with a diameter of 1 mm. The resin composition 3 was then cured in a heat-circulating oven at 80°C for 60 minutes to prepare a test sample for contact resistance measurement. The resistance between the conductor wire 2 and the nickel-plated surface was measured using a digital multimeter 1 (R6552, manufactured by Advantest Corporation), and this was taken as the contact resistance between the resin composition 3 and nickel. The reliability retention time was the time required for the contact resistance to exceed 10 times its initial value after exposure to a temperature of 85°C and humidity of 85%.

[0061] The resin compositions or cured products of the examples and comparative examples were evaluated for viscosity, resistivity, adhesiveness, and reliability under high temperature and humidity conditions according to the following criteria.

[0062] (1) Viscosity ○: Viscosity (Pa s) less than 10 ×: Viscosity (Pa s) is 10 or more

[0063] (2) Specific resistance ◎: 4.0 x 10 -3 Less than Ω·cm ○:4.0×10 -3 Ω cm or more, 5.0×10 -3 Less than Ω·cm △:5.0×10 -3 Ω cm or more, 7.0×10 -3 Less than Ω·cm ×:7.0×10 -3 Ω cm or more

[0064] (3) Adhesiveness ○: Tensile shear adhesive strength (N / mm 2 ) is 8 or more △: Tensile shear adhesive strength (N / mm 2 ) is 6 or more and less than 8 ×: Tensile shear adhesive strength (N / mm 2 ) is less than 6

[0065] (4) Reliability retention time under high temperature and humidity conditions ◎: Retention time is 300 hours or more ○: Retention time is 200 hours or more and less than 300 hours ×: Retention time is less than 200 hours

[0066] [Table 1]

[0067] When a diluent containing an aromatic ring (Comparative Example 2) or a diluent having three glycidyl ether groups (Comparative Example 6) was used, the viscosity of the resin composition was not sufficiently reduced compared to when no diluent was used (Comparative Example 1). Furthermore, when a diluent having an aromatic ring (Comparative Example 2) or a polyether structure (Comparative Examples 3 to 5) was used, even though it was a low-viscosity diluent having two glycidyl ether groups, the resistivity increased significantly compared to when no diluent was used (Comparative Example 1).

[0068] On the other hand, in Examples 1 to 4, which used the reactive diluent of the present invention, both low viscosity of the resin composition and high conductivity of the cured product were achieved, and both adhesion and reliability under high temperature and high humidity were also good. Furthermore, among these, Examples 1 to 3, which used a diluent having a non-alicyclic aliphatic hydrocarbon group as the aliphatic hydrocarbon group (R), showed higher conductivity, and further, Examples 1 and 2, which used a diluent whose aliphatic hydrocarbon group (R) had 4 or 5 carbon atoms, demonstrated high reliability under high temperature and high humidity.

Claims

1. (A) a flexible epoxy resin containing linear hydrocarbon structural units having from 4 to 20 carbon atoms and / or polyalkylene ether structural units having from 3 to 20 ether oxygen atoms, and having a viscosity of more than 500 mPa s at 25°C; (B) a reactive diluent having a structure (Gly-O-R-O-Gly) in which two glycidyl ether groups (-O-Gly) are bonded to a divalent aliphatic hydrocarbon group (R), and having a viscosity at 25°C of 500 mPa s or less; (C) an epoxy resin curing agent; (D) silver particles; A resin composition comprising: the aliphatic hydrocarbon group (R) is a non-alicyclic aliphatic hydrocarbon group and / or the number of carbon atoms in the aliphatic hydrocarbon group (R) is 3 or more and 6 or less, the epoxy resin curing agent (C) is at least one selected from the group consisting of a tertiary amino group-containing modified polyamine, a urea bond-containing modified polyamine, and an imidazole-containing modified polyamine, the silver particles (D) are contained in an amount of 30 to 80% by mass, relative to the total mass of the resin composition; A resin composition having a viscosity at 25°C of less than 10 Pa·s.

2. The resin composition according to claim 1 , wherein the aliphatic hydrocarbon group (R) is a saturated aliphatic hydrocarbon group.

3. The resin composition according to claim 1, wherein the aliphatic hydrocarbon group (R) has 4 or 5 carbon atoms.

4. The resin composition according to claim 1, wherein the viscosity of the reactive diluent (B) at 25°C is 100 mPa·s or less.

5. The resin composition according to claim 1, wherein the flexible epoxy resin (A) further contains a bisphenol-type structural unit.

6. The resin composition according to claim 1, further comprising (E) an epoxy resin (excluding the flexible epoxy resin (A)).

7. The resin composition according to claim 1, comprising 0.1 to 40% by mass of the flexible epoxy resin (A) relative to the total mass of the resin composition.

8. The resin composition according to claim 1, comprising 0.1 to 30 mass% of the reactive diluent (B) relative to the total mass of the resin composition.

9. 2. The resin composition according to claim 1, comprising 2 to 40 parts by weight of the epoxy resin curing agent (C) relative to 100 parts by weight of the epoxy resin contained in the resin composition.

10. 2. The resin composition according to claim 1, comprising 40 to 80% by mass of the silver particles (D), relative to the total mass of the resin composition.

11. The resin composition of claim 1 , which is solvent-free.

12. A cured product of the resin composition according to any one of claims 1 to 11.

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