Conductive resin composition

Abstract

The present invention provides a conductive resin composition which is capable of obtaining a cured product having excellent adhesive strength and conductivity even when cured at a low temperature of about 80 DEG C. A conductive resin composition containing the following components (A) to (C), the component (C) including (C-1) and (C-2), the component (A) being an epoxy resin, the component (B) being conductive particles, the component (C) being a polyamine-based latent curing agent, (C-1) being a polyamine-based latent curing agent having a softening point of 50 DEG C to 129 DEG C, and (C-2) being a polyamine-based latent curing agent having a softening point of 130 DEG C to 180 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to an electrically conductive resin composition which can be cured at low temperature and which can provide a cured product having excellent adhesion and electrical conductivity. BACKGROUND

[0002] Conventionally, electrically conductive resin compositions have been used for the fixation and grounding of electrical / electronic components of smartphones, mobile electronic devices, and the like. In recent years, with the miniaturization of electronic components, the amount of the applied electrically conductive resin composition has been decreasing, and more excellent adhesion and electrical conductivity are required in order to achieve performance even with a small amount of resin. In addition, in recent years, electronic components have been mostly made of plastic, and thus, curing at low temperatures such as around 80°C is required. As an electrically conductive resin composition that is cured at low temperature, for example, an electrically conductive resin composition disclosed in Japanese Patent Application Publication No. 2000-230112, Japanese Patent Application Publication No. 2017-214548 can be cited. SUMMARY

[0003] However, when cured at low temperatures such as around 80°C, the curing becomes insufficient due to insufficient heat energy required for the reaction, and sometimes the adhesion and electrical conductivity of the cured product deteriorate.

[0004] The present application was achieved in view of the above-described circumstances, and an object thereof is to provide an electrically conductive resin composition which can be cured at low temperature and which can provide a cured product having excellent adhesion and electrical conductivity. In addition, the present application provides a cured product obtained by curing the above-described electrically conductive resin composition. The present inventors and the like have conducted intensive studies in order to achieve the above-described object, and as a result, have found a method relating to an electrically conductive resin composition having excellent adhesion and electrical conductivity at low temperature, thereby completing the present application.

[0005] Hereinafter, the gist of the present application will be described.

[0006] [1] An electrically conductive resin composition comprising the following (A) to (C) components, the (C) component comprising (C-1) and (C-2), (A) component: an epoxy resin, (B) component: an electrically conductive particle, (C) component: a polyamine-based latent curing agent, (C-1): a polyamine-based latent curing agent having a softening point of 50°C to 129°C, (C-2): a polyamine-based latent curing agent having a softening point of 130°C to 180°C.

[0007] [2] The electrically conductive resin composition according to [1] or [2], wherein the (A) component comprises a bisphenol-type epoxy resin.

[0008] [3] The conductive resin composition according to any one of [1] to [3], wherein component (A) comprises an epoxy resin having two or more epoxy groups in one molecule of (A-1) and an epoxy resin having one epoxy group in one molecule of (A-2).

[0009] [4] The conductive resin composition according to any one of [1] to [4], wherein component (B) comprises (B-1) crystalline conductive particles.

[0010] [5] The conductive resin composition according to [4], wherein component (B) comprises (B-1) crystalline conductive particles and (B-2) amorphous conductive particles.

[0011] [6] The conductive resin composition according to any one of [1] to [5], wherein component (C) is an aliphatic polyamine latent curing agent.

[0012] [7] The conductive resin composition according to any one of [1] to [6], wherein component (C) is an adduct-modified polyamine latent curing agent.

[0013] [8] The conductive resin composition according to any one of [1] to [7], wherein component (C) comprises only (C-1) and (C-2).

[0014] [9] The conductive resin composition according to any one of [1] to [8], wherein the mass ratio of (C-1) to (C-2) is 10:90 to 90:10.

[0015]

[10] A cured product obtained by curing the conductive resin composition described in any one of [1] to [9]. Detailed Implementation

[0016] The present invention will now be described in detail. It should be noted that in this specification, "X to Y" is used to mean "above X and below Y" as a lower and upper limit value, encompassing the numerical values ​​(X and Y) described before and after it. Furthermore, in this specification, "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid. Additionally, "A and / or B" refers to both A and B individually and combinations thereof.

[0017] The present invention is a conductive resin composition comprising the following components (A) to (C), wherein component (C) comprises (C-1) and (C-2). (A) Components: Epoxy resin, (B) Components: Conductive particles, (C) Ingredients: Polyamine-based latent curing agent. (C-1): A polyamine-based latent curing agent with a softening point of 50℃~129℃. (C-2): A polyamine-based latent curing agent with a softening point of 130℃~180℃.

[0018] The conductive resin composition of the present invention having such a configuration can produce a cured product with excellent adhesion and conductivity when cured at low temperature.

[0019] <(A) ingredient>

[0020] The component (A) used in this invention is epoxy resin.

[0021] As component (A), any epoxy resin having one or more epoxy groups per molecule can be either a solid or a liquid, without particular limitation. From the perspective of excellent curability and workability, epoxy resins having two or more epoxy groups per molecule are preferred, and liquids are particularly preferred. The upper limit for the number of epoxy groups in an epoxy resin having two or more epoxy groups per molecule is, for example, four or less or three or less. Specific examples of component (A) include, for example, bisphenol-type epoxy resins, hydrogenated bisphenol-type epoxy resins, 1,2-butanediol diglycidyl ether, 1,3-butanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, (poly)ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 2,3-butanediol diglycidyl ether, 1,5-pentanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentanediol diglycidyl ether, 1, Alkylene glycol-type epoxy resins such as 4-cyclohexanediethanol diglycidyl ether; phenolic varnish-type epoxy resins such as phenolic varnish-type epoxy resins and cresolic varnish-type epoxy resins; glycidylamine compounds such as N,N-diglycidyl-4-glycidoxyaniline, 4,4'-methylenebis(N,N-diglycidylaniline), tetraglycidyldiaminodiphenylmethane, and tetraglycidylm-phenylenediamine; and naphthalene-type epoxy resins having four glycidyl groups. These can be used alone or in combination of two or more. From the perspective of excellent conductivity, bisphenol-type epoxy resins are preferred, and bisphenol-type epoxy resins having two or more epoxy groups are even more preferred. Furthermore, the silane coupling agent described later is not treated as component (A), but rather as an optional component.

[0022] The aforementioned bisphenol-type epoxy resins are not particularly limited to any epoxy resin with a bisphenol backbone. Examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AD ​​type epoxy resin, urethane-modified bisphenol-type epoxy resin, rubber-modified bisphenol-type epoxy resin, and polyoxyethylene-modified bisphenol-type epoxy resin. They can be used alone or in combination of two or more. From the perspective of excellent conductivity and operability, the combination of bisphenol A type epoxy resin and bisphenol F type epoxy resin is preferred. A particularly preferred mass ratio of bisphenol A type epoxy resin to bisphenol F type epoxy resin is 25:75~75:25 or 35:65~65:35. The mass of bisphenol A type epoxy resin can be the same as or slightly more than that of bisphenol F type epoxy resin.

[0023] As commercially available epoxy resins, there are no particular limitations. Examples include JER828, 1001, 801, 806, 807, YX4000, YX8000, YX8034 (manufactured by Mitsubishi Chemical Corporation), EPICLON830, 850, EXA-830CRP, EXA-830LVP, EXA-850CRP, EXA-835LV (manufactured by DIC Corporation), ADEKA RESIN EP-4100, EP-4000, EP-4000S, EP-4080, EP-4085, EP-4088, EPU-6, EPU-7N, EPR-4023, EPR-1309, and EP-4920 (ADEKA). The epoxy resin components of various chemical companies, including: TEPIC (Nissan Chemical Industry Co., Ltd.), KF-101, KF-1001, KF-105, X-22-163B, X-22-9002 (Shin-Etsu Chemical Industry Co., Ltd.), DENACOL EX411, 314, 201, 212, 252 (Nagase ChemteX Corporation), DER-331, 332, 334, 431, 542 (The Dow Chemical Company), YH-434, YH-434L, ST-3000 (NIPPON STEEL Chemical & Material Co., Ltd.), RIKARESIN HBE-100 (Shin-Nippon Rika Co., Ltd.), EPOLITE 4000 (Kyoeisha Chemical Co., Ltd.), and CUREDUCT L-07N (Shikoku Kasei Corporation). They can be used individually, or two or more can be used together.

[0024] The above-mentioned component (A) is preferably combined with an epoxy resin having two or more epoxy groups in one molecule (A-1) and an epoxy resin having one epoxy group in one molecule (A-2). Although the reason is not yet clear, by combining (A-1) and (A-2), not only can the viscosity be adjusted, but the connection resistance value can also be reduced. Therefore, a conductive resin composition with low viscosity and good conductivity can be obtained. As for (A-2), there is no particular limitation, but examples include methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, isobutyl glycidyl ether, phenyl glycidyl ether, 2-ethylhexyl glycidyl ether, decyl glycidyl ether, stearyl glycidyl ether, allyl glycidyl ether, 2-methyloctyl glycidyl ether, methoxy polyethylene glycol monoglycidyl ether, ethoxy polyethylene glycol monoglycidyl ether, butoxy polyethylene glycol monoglycidyl ether, phenoxy polyethylene glycol monoglycidyl ether, p-tert-butylphenyl glycidyl ether, sec-butylphenyl glycidyl ether, n-butylphenyl glycidyl ether, phenylphenol glycidyl ether, cresol glycidyl ether, dibromocresol glycidyl ether, and neodecanoic acid glycidyl ester. These can be used alone or in combination of two or more. Furthermore, from the perspective of excellent storage stability and conductivity, p-tert-butylphenyl glycidyl ether and / or neodecanoic acid glycidyl ester are preferred. Furthermore, from the perspective of suppressing the generation of exhaust gas during heating, the boiling point of (A-2) is preferably 290°C or higher. The boiling point of (A-2) can be 450°C or lower, 400°C or lower, 350°C or lower, or 300°C or lower. The boiling point of (A-2) can be 290°C or higher and 450°C or lower.

[0025] Examples of commercially available products under (A-2) include ED-509S (manufactured by ADEKA Corporation), EPIOL (registered trademark) TB (manufactured by Nippon Yu Co., Ltd.), and CARDURA E10P (manufactured by Momentive Performance Materials, Inc.), but are not limited to these.

[0026] When (A-1) and (A-2) are used together, the preferred mass ratio is 99:1 to 50:50, more preferably 95:5 to 60:40, and most preferably 90:10 to 70:30. A conductive resin composition with excellent storage stability and conductivity can be obtained within the range of 99:1 to 50:50.

[0027] <(B) Component>

[0028] The (B) component used in this invention is a conductive particle. The material and shape of the (B) component are not limited as long as it exhibits conductivity. For example, it can be appropriately selected from metal particles composed of one or more metals selected from gold, silver, copper, nickel, palladium, platinum, tin, bismuth, etc., alloy particles composed of multiple combinations thereof, or particles formed by coating the surface with the aforementioned metals. These can be used alone or in combination of two or more. From the perspectives of conductivity and cost, silver particles or particles formed by coating the surface with silver are preferred. Examples of the shape of the (B) component include spherical, amorphous, sheet-like, filamentous (needle-like), and dendritic shapes. These can be used alone or in combination. Furthermore, the (B) component can be surface-treated with a lubricant. As a lubricant, saturated fatty acids and / or unsaturated fatty acids can be used. Examples include decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, linolenic acid, linoleic acid, palmitoleic acid, oleic acid, malonic acid, and hexanoic acid. In terms of superior adhesion and conductivity during low-temperature curing, untreated component (B) and component (B) treated with stearic acid or oleic acid are preferred. They can be used alone or in combination of two or more.

[0029] The aforementioned component (B) preferably includes (B-1) crystalline conductive particles. The crystalline conductive particles are manufactured using known manufacturing methods, such as the reduction method commonly known as shown in Japanese Patent Application Publication No. 2014-196527, which involves growing a single crystal to produce conductive particles. The crystalline conductive particles are thin sheet particles with a generally uniform thickness and a polygonal plate shape (e.g., triangular plate shape), and have a generally smooth surface. Silver particles are preferred due to their excellent conductivity during low-temperature curing.

[0030] As for the commercially available products mentioned above (B-1), there are no special limitations. Examples include N300, M612, M13, M27, and LM1 (manufactured by TOKUSEN KOGYO Co., Ltd.).

[0031] The above-mentioned component (B) preferably combines (B-1) crystalline conductive particles and (B-2) amorphous conductive particles. The weight ratio of (B-1) and (B-2) when combined is preferably 10:90 to 90:10, more preferably 10:90 to 75:25, and most preferably 15:85 to 50:50. By using a ratio in the range of 10:90 to 90:10, a conductive resin composition with excellent conductivity during low-temperature curing can be obtained. The weight ratio of (B-1) and (B-2) when combined can also be 20:80 to 45:55 or 25:75 to 45:55.

[0032] The shape of (B-2) is not particularly limited. As mentioned above, examples include spherical, amorphous, flake-like (scale-like), filamentous (needle-like), and dendritic shapes. These can be used individually or in combination of two or more. From the perspective of excellent conductivity, it is preferable to include flake-like and / or spherical conductive particles. For example, non-crystalline conductive particles refer to flake-like conductive particles obtained in a pulverizing process, or conductive particles obtained by coating the surface of organic or inorganic particles with a conductive metal. From the perspective of excellent conductivity during low-temperature curing, (B-2) is preferably silver particles or particles coated with silver.

[0033] The average particle size of component (B) is preferably in the range of 0.01 to 100 μm, more preferably in the range of 0.1 to 50 μm, even more preferably in the range of 0.1 to 30 μm, and most preferably in the range of 0.3 to 10 μm. Here, the average particle size of component (B) is the particle size (D50) at which the cumulative volume ratio in the particle size distribution is 50%, as determined by laser diffraction scattering.

[0034] From the perspective of excellent conductivity, the average particle size of (B-1) is preferably in the range of 0.01 to 30 μm, more preferably in the range of 0.1 to 20 μm, and most preferably in the range of 0.3 to 10 μm. Here, the average particle size of (B-1) is the particle size (D50) at which the cumulative volume ratio in the particle size distribution is 50% as determined by laser diffraction scattering method.

[0035] The thickness (average thickness, T) of (B-1) is not particularly limited, but from the viewpoint of superior conductivity of the cured material, it is preferably 1 nm or more and less than 1000 nm, more preferably 10 to 200 nm, further preferably 30 to 150 nm, and particularly preferably 60 to 100 nm. The thickness of (B-1) can be confirmed using a scanning electron microscope (SEM). More specifically, the thickness is obtained by randomly selecting 100 plate-shaped silver particles, measuring their individual thicknesses, and calculating their average value.

[0036] The average particle size of (B-2) described above is preferably in the range of 0.1 to 50 μm, more preferably in the range of 0.1 to 30 μm, even more preferably in the range of 0.5 to 20 μm, and most preferably in the range of 0.5 to 10 μm. Each average particle size is the particle size (D50) at which the cumulative volume ratio in the particle size distribution is 50% as determined by laser diffraction scattering method.

[0037] The content of component (B) is preferably 50 to 500 parts by mass relative to 100 parts by mass of component (A), more preferably 100 to 400 parts by mass, and most preferably 150 to 350 parts by mass. When the content is 50 parts by mass or more, excellent conductivity such as low connection resistance and low volume resistivity is achieved; when the content is 500 parts by mass or less, a conductive resin composition with excellent workability can be obtained.

[0038] (B) The component preferably contains 40% to 95% by mass relative to the total conductive resin adhesive, more preferably 50% to 90% by mass, and most preferably 60% to 85% by mass. By achieving the above range, a conductive resin adhesive with excellent workability and conductivity during low-temperature curing can be obtained.

[0039] <(C) Ingredients>

[0040] The component (C) used in this invention is a latent curing agent containing a polyamine-based latent curing agent (C-1) with a softening point of 50°C to 129°C and a polyamine-based latent curing agent (C-2) with a softening point of 130°C to 180°C. The curing agent contained in the conductive resin composition of this invention may also contain curing agents other than component (C). From the viewpoint of conductivity and adhesion, the combined amount of (C-1) and (C-2) is preferably 50% by mass or more, more preferably 80% by mass or more, and most preferably contains only (C-1) and (C-2). It should be noted that the softening point in this invention refers to a value obtained by measurement according to the softening point determination method of JIS K 7234:1986.

[0041] Examples of latent curing agents include adduct-modified latent curing agents. There are no particular limitations on adduct-modified latent curing agents; for example, reaction products obtained by reacting an amine compound with an isocyanate compound or a urea compound (urea adduct-modified latent curing agent), or reaction products of an amine compound with an epoxy compound (epoxyamine adduct-modified latent curing agent), etc. Furthermore, aliphatic polyamines and aromatic polyamines are examples of polyamine structures; from the viewpoint of curability, aliphatic polyamines are preferred. In other words, adduct-modified aliphatic polyamine-based latent curing agents are preferred.

[0042] The aforementioned component (C) can be a liquid or a solid, but from the viewpoint of preservation stability, a solid is preferred, and from the viewpoint of dispersibility, a powder is more preferred. The average particle size of the powder is preferably in the range of 0.1 to 30 μm, more preferably in the range of 0.5 to 20 μm, and most preferably in the range of 1 to 10 μm. Here, the average particle size of component (C) is the particle size (D50) at which the cumulative volume ratio in the particle size distribution is 50%, as determined by laser diffraction scattering.

[0043] The above-mentioned (C-1) is a polyamine-based latent curing agent with a softening point of 50°C to 129°C. From the perspective of excellent low-temperature curing properties, the softening point of the above-mentioned powder (C-1) is preferably below 125°C. From the perspective of excellent storage properties, the softening point of the above-mentioned powder (C-1) is preferably above 50°C, more preferably above 80°C. In other words, the softening point of (C-1) is preferably 50°C to 125°C, and more preferably 80°C to 125°C.

[0044] The above-mentioned (C-2) is a polyamine-based latent curing agent with a softening point of 130°C to 180°C. From the perspective of excellent electrical conductivity, the softening point of the above-mentioned powder (C-2) is preferably above 130°C. From the perspective of excellent low-temperature curing properties, the softening point of the above-mentioned powder (C-2) is preferably below 180°C, more preferably below 150°C. In other words, the softening point of (C-2) is preferably 130°C to 180°C, and more preferably 130°C to 150°C.

[0045] Commercially available products that constitute component (C) above are not particularly limited. Examples of products listed as (C-1) include FUJICURE FXE-1000, FXR-1020, FXR-1081, and 1061 (manufactured by T&K TOKA CO., LTD.). Examples of products listed as (C-2) include FUJICURE FXE-1030 (manufactured by T&K TOKA CO., LTD.). These products can be used individually or in combination of two or more.

[0046] The content of component (C) above, i.e., the total amount of (C-1) and (C-2), is preferably 1 to 100 parts by mass relative to 100 parts by mass of component (A), more preferably 10 to 50 parts by mass, and most preferably 15 to 40 parts by mass. By being 1 part by mass or more, excellent low-temperature curing properties are obtained; by being 100 parts by mass or less, a conductive resin composition with excellent storage stability can be obtained.

[0047] The weight ratio of (C-1) to (C-2) is preferably 10:90 to 90:10, more preferably 15:85 to 85:15, even more preferably 20:80 to 80:20, even more preferably 20:80 to 60:40, and most preferably 20:80 to 50:50. By setting the weight ratio to 10:90 to 90:10, a cured product with excellent electrical conductivity and adhesion can be obtained.

[0048] <Other Ingredients>

[0049] The conductive resin composition of the present invention preferably does not contain organic solvents. When the conductive resin composition contains organic solvents, the organic solvents dissolve the (C) component, leading to a deterioration in storage stability and separation of the organic solvents, thus affecting the physical properties. "Substantially does not contain organic solvents" means that, as a complex of the conductive resin composition, it intentionally does not contain organic solvents. Specifically, the content of organic solvents relative to the entire conductive resin composition is 1% by mass or less, preferably 0.5% by mass or less, and more preferably 0.1% by mass or less. If it is 1% by mass or less, it will not cause a deterioration in storage stability or separation.

[0050] Examples of organic solvents mentioned above include aromatic organic solvents such as toluene and xylene; aliphatic organic solvents such as n-hexane; alicyclic organic solvents such as cyclohexane, methylcyclohexane, and ethylcyclohexane; ketone organic solvents such as acetone and methyl ethyl ketone; alcohol organic solvents such as methanol and ethanol; ester organic solvents such as ethyl acetate and butyl acetate; propylene glycol ether organic solvents such as propylene glycol methyl ether, propylene glycol ethyl ether, and propylene glycol tert-butyl ether; and fluorinated solvents.

[0051] In the conductive resin composition of the present invention, in addition to the above-mentioned components, various additives may be added as optional components without impairing the effects of the present invention. Examples of additives include preservation stabilizers, rubber particles, silane coupling agents, plasticizers, fillers (excluding component (B)), tackifiers, organic or inorganic pigments, rust inhibitors, defoamers, dispersants, surfactants, viscoelastic modifiers, thickeners, and organometallic complexes. For example, the conductive resin composition of the present invention may not contain additives other than preservation stabilizers and plasticizers.

[0052] The conductive resin composition of the present invention may contain a preservation stabilizer. There are no particular limitations on the preservation stabilizer, as long as it improves preservation stability. Examples of preservation stabilizers include borate ester compounds, phosphoric acid, alkyl phosphates, p-toluenesulfonic acid, methyl p-toluenesulfonate, etc. Examples of borate ester compounds include trimethyl borate, triethyl borate, tri-n-propyl borate, triisopropyl borate, tributyl borate, trihexyl borate, tri-n-octyl borate, tri(2-ethylhexyloxy)borane, triphenyl borate, trimethoxycycloboroxane, 2,2'-(carbonyldioxy)bis(1,3,2-dioxane-4,5-dione), etc. Commercially available and / or synthetic products can be used as preservation stabilizers. Examples of commercially available borate ester compounds include the preservation stabilizer component of "CUREDUCT (registered trademark) L-07N" (manufactured by Shikoku Chemical Industry Co., Ltd.). Examples of alkyl phosphate esters that can be used include trimethyl phosphate and tributyl phosphate, but are not limited to these. The preservation stabilizer can be used alone or in combination. Considering preservation stability, phosphoric acid, borate ester compounds, trimethoxycycloborooxane, and methyl p-toluenesulfonate are preferred. Alternatively, a preservation stabilizer dispersed in the epoxy resin or plasticizer can also be used. It should be noted that when adding a preservation stabilizer, if a mixture containing the preservation stabilizer and epoxy resin is added, the epoxy resin is preferably a bisphenol-type epoxy resin, and examples of plasticizers include phenolic resins. Commercially available phenolic resins include, for example, the plasticizer component of CUREDUCT L-07N (manufactured by Shikoku Chemical Industry Co., Ltd.).

[0053] The content of the aforementioned preservation stabilizer is preferably 0.01 to 10 parts by mass relative to 100 parts by mass of component (A), more preferably 0.02 to 7 parts by mass, and even more preferably 0.05 to 5 parts by mass. A content of 0.01 parts by mass or more results in excellent preservation stability, while a content of 10 parts by mass or less does not hinder curing. The content of the aforementioned plasticizer is preferably 0.01 to 10 parts by mass relative to 100 parts by mass of component (A), more preferably 0.02 to 7 parts by mass, and even more preferably 0.05 to 5 parts by mass.

[0054] The conductive resin composition of the present invention may contain a filler material (excluding component (B)). As a filler material, it may be an inorganic filler such as alumina powder, calcium carbonate powder, talc powder, silica powder, or fumed silica powder, or an organic filler such as rubber particles. While the reasons are not yet certain, from the perspective of obtaining a conductive resin composition with excellent conductivity, the presence of rubber particles is preferred.

[0055] The rubber particles referred to in this invention are particles containing a layer exhibiting rubber elasticity. The rubber particles can be particles consisting of only a single layer exhibiting rubber elasticity, or core-shell particles exhibiting rubber elasticity as a multilayer structure; core-shell particles are preferred from the perspective of excellent volume resistivity. Alternatively, rubber particles pre-dispersed in an epoxy resin can also be used. For example, butadiene rubber, acrylic rubber, silicone rubber, butyl rubber, olefin rubber, styrene rubber, NBR, SBR, IR, EPR, etc., can be used. They can be used alone, or two or more can be used in combination.

[0056] The aforementioned core-shell particles refer to microparticles in which the core (nucleus) and shell (wall) portions are composed of polymers with different properties. In the preferred powder particle manufacturing process used in this invention, the core portion is first manufactured by polymerizing a polymerizable monomer. Examples of such polymerizable monomers include (meth)acrylate monomers such as n-propyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and n-decyl methacrylate; aromatic vinyl compounds such as styrene, vinyltoluene, and α-methylstyrene; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; vinylidene dicyandiamide; 2-hydroxyethyl methacrylate; 3-hydroxybutyl methacrylate; 2-hydroxyethyl fumarate; hydroxybutyl vinyl ether; monobutyl maleate; and butoxyethyl methacrylate. Examples of crosslinking monomers with two or more reactive groups include ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, hexanediol tri(meth)acrylate, low-polyethylene di(meth)acrylate, low-polyethylene tri(meth)acrylate, etc.; aromatic divinyl monomers such as divinylbenzene; triallyl benzotriester; and triallyl isocyanurate, etc. One or more different monomers may be used. Next, using the polymer particles thus obtained as a core, a second polymerization is carried out by polymerizing the polymeric monomers to form a shell composed of a polymer having a melting point above room temperature. The polymeric monomers used at this time may be selected from the same monomers used to obtain the aforementioned core. Preferred examples of polymerizable monomers used as shell materials include ethyl methacrylate, n-butyl acrylate, methyl methacrylate, butyl methacrylate, and other alkyl (meth)acrylates having 1 to 4 carbon atoms.

[0057] Core-shell particles can be synthesized as described above, or commercially available products can be used. Commercially available products for core-shell particles are not specifically limited. Examples include PARALOID EXL-2655 (manufactured by Kureha Chemical Industry Co., Ltd.) composed of butadiene-alkyl methacrylate-styrene copolymer; STAPHYLOID AC-3355, STAPHYLOID AC3364, STAPHYLOID TR-2105, STAPHYLOID TR-2102, STAPHYLOID TR-2122, STAPHYLOID IM-101, STAPHYLOID IM-203, STAPHYLOID IM-301, STAPHYLOID IM-401 and STAPHYLOID IM-406 composed of acrylate-acrylonitrile-styrene copolymer; STAPHYLOID IM-601 composed of acrylate-acrylonitrile-styrene copolymer; ZEFIAC F-351G (manufactured by Aica Kogyo Company, Limited) composed of polymethacrylate polymers; and PARALOID... EXL-2314, EXL-2611, EXL-3387 (manufactured by Dow Chemical Japan Limited), etc. They can be used individually or in combination of two or more.

[0058] The particle size of the rubber particles is preferably 0.01 to 10 μm, and particularly preferably 0.05 to 5 μm. By achieving the above range, the increase in viscosity can be suppressed, resulting in a conductive resin composition with excellent conductivity.

[0059] The content of rubber particles relative to 100 parts by weight of component (A) is preferably 0.01 to 20 parts by weight, more preferably 0.03 to 10 parts by weight, and most preferably 0.05 to 5 parts by weight. By achieving the above range, a conductive resin composition with excellent conductivity can be obtained.

[0060] Rubber particles pre-dispersed within the epoxy resin can be, specifically, rubber particles dispersed within the epoxy resin using a mixing device such as a high-efficiency homogenizer, or rubber particles synthesized within the epoxy resin through emulsion polymerization. These can be used individually or in combination of two or more. The epoxy resin from which the rubber particles are dispersed is treated as component (A) above.

[0061] Commercially available rubber-dispersed epoxy resins include KaneAce MX-153, MX-136, MX-257, MX-127, MX-451 (manufactured by KANEKA CORPORATION), ACRYSET BPF-307, and BPA-328 (manufactured by Nippon Shokubai Co., Ltd.). These can be used individually or in combination of two or more.

[0062] The conductive resin composition of the present invention may contain a silane coupling agent. Examples of silane coupling agents include glycidyl groups such as 3-glycidylpropoxypropyltriethoxysilane, 3-glycidylpropoxypropylmethyldimethoxysilane, 3-glycidylpropoxypropyltrimethoxysilane, and 3-glycidylpropoxypropylmethyldiethoxysilane; vinyl groups such as vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, and vinyltrimethoxysilane; and γ-methacryloyloxysilane. Silane coupling agents containing (meth)acryloyl groups, such as propyltrimethoxysilane; amino-containing silane coupling agents, such as N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, and their oligomers; and those containing glycidyl groups are preferred for their superior adhesion. They can be used alone or in combination of two or more.

[0063] There are no particular limitations on commercially available silane coupling agents. Examples include KBM-1003, KBE-1003, KBM-303, KBM-403, KBE-403, KBM-502, KBE-502, KBM-503, KBE-503, KBM-5103, KBM-1403, KBM-602, KBM-603, KBM-903, KBE-903 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.), Z-6610, Z-6044, Z-6825, Z-6033, and Z-6062 (manufactured by Toray-Dow Corning Co., Ltd.).

[0064] <Curing methods and cured products>

[0065] Cured products obtained by curing the conductive resin composition of the present invention are also an aspect of the invention. Furthermore, since the conductive resin composition of the present invention is used in applications involving heat-sensitive plastic components, it can be cured at low temperatures. The curing temperature is not particularly limited, but as heat curing, a low temperature of 25°C to 100°C is preferred, more preferably 50°C to 95°C, and most preferably 70°C to 90°C. The curing time is not particularly limited, but preferably 10 minutes to 180 minutes, more preferably 30 minutes to 120 minutes, and most preferably 40 minutes to 100 minutes.

[0066] <Application>

[0067] The conductive resin composition of the present invention can be cured at low temperatures, and therefore is suitable for use in components made of heat-sensitive plastics. Specifically, examples include liquid crystal display elements, organic EL elements, solar cell elements, camera modules, flexible printed circuit boards, wearable devices, and battery packs. Furthermore, examples of plastics include polypropylene, polyethylene, polyurethane, ABS, phenolic resin, CFRP (carbon fiber reinforced plastic), GFRP (glass fiber reinforced plastic), 6,6-nylon, PPS, and PBT.

[0068] Furthermore, the conductive resin composition of the present invention is preferably used for adherends with a nickel outermost surface. For the conductive resin composition of the present invention having the above-described structure, although the exact reason is unknown, even for adherends with a nickel oxide film forming on the outermost surface, the connection resistance value can be reduced, and excellent storage stability can be maintained, resulting in superior handleability. Here, there is no particular limitation on adherends with a nickel outermost surface; mainly, adherends that have undergone nickel plating are included, such as adherends obtained by electrolytic or non-electrolytic plating of SPCC (cold-rolled steel sheet), stainless steel components, and copper components (wires, printed circuit boards, etc.).

[0069] [Example]

[0070] Next, examples will be provided to illustrate the invention in more detail, but the invention is not limited to these examples. Furthermore, unless otherwise specified, the tests were conducted at 25°C and 55%RH.

[0071] <Examples 1-7 and Comparative Examples 1-5>

[0072] To prepare the conductive resin composition, the following components are prepared. Hereinafter, the conductive resin composition will also be referred to simply as the composition.

[0073] (A) Component: Epoxy resin

[0074] (A-1): Epoxy resin with two or more epoxy groups per molecule

[0075] • EPICLON EXA-835LV (a mixture of difunctional bisphenol A type epoxy resin and difunctional bisphenol F type epoxy resin, mass ratio 50:50, manufactured by DIC Corporation)

[0076] • CUREDUCT L-07N (a mixture of epoxy resin (difunctional bisphenol A type epoxy resin: 91% by mass), phenolic resin (phenolic varnish resin: 4% by mass), and borate ester compound (2,2'-(carbonyldioxy)bis(1,3,2-dioxane-4,5-dione): 5% by mass), manufactured by Shikoku Chemical Industry Co., Ltd.) is an epoxy resin component.

[0077] (A-2): Epoxy resin with one epoxy group per molecule

[0078] ·ED-509S (p-tert-butylphenyl glycidyl ether, boiling point: 294°C, manufactured by ADEKA Corporation)

[0079] •CARDURA E10P (Glycidyl neodecanoate, boiling point: 278℃, manufactured by HEXION INC.)

[0080] (B) Components: Conductive particles

[0081] (B-1): Crystalline conductive particles

[0082] M27 (Crystallic silver particles, flakes, stearic acid treated, average particle size: 4.5 μm, average thickness T: 80 nm, manufactured by TOKUSEN KOGYO Co., Ltd.)

[0083] (B-2): Non-crystalline conductive particles

[0084] •Silbest TC-770 (non-crystalline silver particles, flakes, stearic acid surface treated, average particle size: 3.5μm, manufactured by Tokureki Honten Co., Ltd.)

[0085] (C) Ingredients: Polyamine-based latent curing agent

[0086] (C-1): Polyamine-based latent curing agent with a softening point of 50℃~129℃

[0087] ·FUJICURE FXR-1081 (Adduct-modified aliphatic polyamine latent curing agent, average particle size: 5μm, softening point: 121℃, manufactured by T&K TOKA CO., LTD.)

[0088] ·FUJICURE 1061 (Adduct-modified aliphatic polyamine latent curing agent, average particle size: 5μm, softening point: 98℃, manufactured by T&K TOKA CO., LTD.)

[0089] ·FUJICURE FXR-1020 (Adduct-modified aliphatic polyamine latent curing agent, average particle size: 5μm, softening point: 124℃, manufactured by T&K TOKA CO., LTD.)

[0090] (C-2): Polyamine-based latent curing agent with a softening point of 130℃~180℃

[0091] ·FUJICURE FXR-1030 (Adduct-modified aliphatic polyamine latent curing agent, average particle size: 5μm, softening point: 140℃, manufactured by T&K TOKA CO., LTD.)

[0092] (C') Ingredient: Latent curing agent other than (C) ingredient

[0093] ·FUJICURE FXR-1121 (Imidazole-based latent curing agent, average particle size: 5μm, softening point: 133℃, manufactured by T&KTOKA CO., LTD.)

[0094] Any component

[0095] • CUREDUCT L-07N (a mixture of epoxy resin (difunctional bisphenol A type epoxy resin: 91% by mass), phenolic resin (phenolic varnish resin: 4% by mass), borate ester compound (2,2'-(carbonyldioxy)bis(1,3,2-dioxane-4,5-dione): 5% by mass), and a preservation stabilizer component manufactured by Shikoku Chemical Industry Co., Ltd.

[0096] • CUREDUCT L-07N (a mixture of epoxy resin (difunctional bisphenol A type epoxy resin: 91% by mass), phenolic resin (phenolic varnish resin: 4% by mass), borate ester compound (2,2'-(carbonyldioxy)bis(1,3,2-dioxane-4,5-dione): 5% by mass), plasticizer component manufactured by Shikoku Chemical Industry Co., Ltd.

[0097] The methods for manufacturing the compositions described in Examples 1-7 and Comparative Examples 1-5 are as follows. Component (A), component (B), and any component were weighed and stirred for 30 minutes using a planetary mixer. Next, component (C) and component (C') were weighed and added, and then stirred further using a planetary mixer while vacuum degassing for 30 minutes to obtain a conductive resin composition.

[0098] <Electrical conductivity>

[0099] Five 5mm diameter holes are made at 10mm intervals along the length of a 10mm wide and 100μm thick masking tape. The masking tape is then applied to an electroless nickel-plated board (25mm wide x 100mm long x 1.6mm thick). A composition is then applied to the board using a squeegee. Care is taken not to introduce air bubbles into the composition during application. Next, the masking tape is peeled off, and two... A gold-plated copper chip measuring 1 mm in diameter is used. The composition is then cured by heating at 80°C for 60 or 90 minutes in a hot air drying oven, serving as a test piece. After the test piece cools to room temperature, the needle electrode of a dual-display multimeter is brought into contact with two gold-plated copper chips (located at 10 mm intervals) on adjacent parts of the composition, and the resistance is measured. The obtained resistance value is taken as the "connection resistance value (Ω)". For conductivity stabilization, the connection resistance value is preferably 3.0 Ω or less, more preferably 2.5 Ω or less, and particularly preferably 2.0 Ω or less (lower limit: 0 Ω).

[0100] <Adhesion>

[0101] On an electroless nickel-plated plate with a thickness of 1.6 mm × width of 25 mm × length of 100 mm, masking tape is applied in a manner that results in a width of 5 mm × thickness of 50 μm. The composition is applied using a squeegee to form a uniform coating, and then the masking tape is peeled off. (Make 2) A 1mm ceramic chip is dropped vertically onto the coating from 1cm above it to create test pieces (n=5). These test pieces are then cured in a hot air drying oven at 80°C for 60 or 90 minutes to solidify the composition. After the test pieces cool to room temperature, with the nickel-plated plate fixed, a digital force gauge with a contact is moved at 50mm / min, pushing the chip perpendicular to the long side of the test piece, and the "maximum strength (N)" is measured. The "adhesive force (MPa)" is calculated from the bonded area and judged according to the evaluation criteria below. A strength of 20MPa or higher is preferred to prevent the adhered material from detaching.

[0102] The composition of the compositions of the examples and comparative examples is shown in Table 1 below. It should be noted that blank columns in Table 1 below indicate that the component is not present.

[0103] [Table 1]

[0104] Examples 1 through 7 confirmed that cured products with excellent conductivity and adhesion could be obtained even during curing at low temperatures such as 80°C. In particular, Examples 1 through 3 confirmed that by increasing the proportion of (C-2) in component (C), the conductivity of the cured product was excellent. In contrast, Comparative Examples 1 and 4, which were compositions without (C-2), showed poor conductivity in their cured products. Comparative Example 2, which was a composition without (C-1), showed poor adhesion in its cured product. Furthermore, Comparative Examples 3 and 5, which were compositions in which (C-1) or (C-2) was replaced with component (C'), showed poor conductivity and adhesion.

[0105] Industrial applicability

[0106] The conductive paste of this invention exhibits excellent conductivity and adhesion, making it useful for conductive / adhesive applications in electrical / electronic components aimed at miniaturization in recent years. In particular, it can reduce the resistance of metals such as nickel, whose conductivity tends to deteriorate. Due to these properties, this invention can be used in the assembly of various electrical / electronic components and has the potential to be extended to a wide range of applications.

[0107] This application is based on Japanese Patent Application No. 2023-181725, filed on October 23, 2023, the disclosure of which is referenced and incorporated herein by reference in its entirety.

Claims

1. A conductive resin composition comprising the following components (A) to (C), wherein component (C) comprises (C-1) and (C-2). (A) Components: Epoxy resin, (B) Components: Conductive particles, (C) Ingredients: Polyamine-based latent curing agent. (C-1): A polyamine-based latent curing agent with a softening point of 50℃~129℃. (C-2): A polyamine-based latent curing agent with a softening point of 130℃~180℃.

2. The conductive resin composition according to claim 1, wherein, (A) The ingredients include bisphenol type epoxy resin.

3. The conductive resin composition according to claim 1, wherein, (A) Components include (A-1) an epoxy resin having two or more epoxy groups in one molecule and (A-2) an epoxy resin having one epoxy group in one molecule.

4. The conductive resin composition according to claim 1, wherein, (B) Component contains (B-1) crystalline conductive particles.

5. The conductive resin composition according to claim 4, wherein, (B) Components include (B-1) crystalline conductive particles and (B-2) amorphous conductive particles.

6. The conductive resin composition according to claim 1, wherein, (C) is an aliphatic polyamine latent curing agent.

7. The conductive resin composition according to claim 1, wherein, (C) is an adduct-modified polyamine latent curing agent.

8. The conductive resin composition according to claim 1, wherein, (C) Components contain only (C-1) and (C-2).

9. The conductive resin composition according to claim 1, wherein, The mass ratio of (C-1) to (C-2) is 10:90 to 90:

10.

10. A cured product obtained by curing the conductive resin composition of claim 1.

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