Method for producing highly conductive composition after drying and firing

Abstract

A conductive composition according to the present invention comprises: (A) 1.005-1.74 mass% of a bisphenol-type epoxy resin; (B) not less than 0.015 mass% but less than 0.08 mass% of a (meth)acrylic resin that has a weight-average molecular weight of 1000-400,000; (C) 0.5-0.86 mass% of polymer particles that contain a polybutadiene rubber; (D) 5-95 mass% of copper particles that have an average particle diameter of 2-500 nm; (E) 0.9-4.8 mass% of silver particles that have an average particle diameter of 2-500 nm; (F) 0.001-20 mass% of a phosphorus-containing compound; (G) 0.0001-10 mass% of CuH; and (H) 0.1-90 mass% of a solvent.

Description

Formulation for producing a highly conductive composition after drying and firing

[0001] The present invention relates to a formulation for producing a highly conductive composition after drying and firing.

[0002] A method for forming a conductive pattern on a substrate by printing a conductive composition on the substrate is known. For example, Patent Document 1 discloses a conductive composition used in such printing that contains copper nanoparticles, a phosphorus-containing compound, and copper hydride (CuH).

[0003] However, such conductive compositions have room for improvement in terms of adhesion to substrates, particularly adhesion to flexible printed circuit boards (FPCs), and conductivity.

[0004] Patent No. 6959977

[0005] The present invention has been made in view of the above, and an object of the present invention is to provide a conductive composition that has both excellent conductivity and adhesion.

[0006] The present invention includes the following embodiments: [1] A conductive composition comprising: (A) 1.005 to 1.74 mass% of a bisphenol-type epoxy resin; (B) 0.015 mass% or more and less than 0.08 mass% of a (meth)acrylic resin having a weight-average molecular weight of 1,000 to 400,000; (C) 0.5 to 0.86 mass% of polymer particles containing polybutadiene rubber; (D) 5 to 95 mass% of copper particles having an average particle diameter of 2 to 500 nm; (E) 0.9 to 4.8 mass% of silver particles having an average particle diameter of 2 to 500 nm; (F) 0.001 to 20 mass% of a phosphorus-containing compound; (G) 0.0001 to 10 mass% of CuH; and (H) 0.1 to 90 mass% of a solvent. [2] The conductive composition according to [1], wherein the polymer particles (C) have a core-shell structure including a core layer and a shell layer, the core layer includes polybutadiene rubber, and the shell layer is composed of a polymer of a vinyl-based monomer. [3] The conductive composition according to [1] or [2], wherein the content ratio of the copper particles (D) to the silver particles (E) ((D) / (E)) is 15.0 to 45.0 by mass. [4] The conductive composition according to any one of [1] to [3], wherein the total content ratio of the copper particles (D) and the silver particles (E) is 11.6 to 83.8 by mass.

[0007] The conductive composition according to the present invention provides excellent conductivity and adhesion.

[0008] FIG. 1 is a schematic diagram of a sample used in evaluating the conductivity of the examples.

[0009] Hereinafter, the embodiments of the present invention will be described in more detail.

[0010] The conductive composition according to this embodiment contains (A) 1.005 to 1.74% by mass of a bisphenol-type epoxy resin, (B) 0.015% by mass or more and less than 0.08% by mass of a (meth)acrylic resin having a weight-average molecular weight of 1,000 to 400,000, (C) 0.5 to 0.86% by mass of polymer particles containing polybutadiene rubber, (D) 5 to 95% by mass of copper particles having an average particle diameter of 2 to 500 nm, (E) 0.9 to 4.8% by mass of silver particles having an average particle diameter of 2 to 500 nm, (F) 0.001 to 20% by mass of a phosphorus-containing compound, (G) 0.0001 to 10% by mass of CuH, and (H) 0.1 to 90% by mass of a solvent.

[0011] In this specification, the "weight average molecular weight" can be measured by gel permeation chromatography (GPC), using a refractive index detector (RI) as a detector, a "TSKgel G4000HXL" column manufactured by Tosoh Corporation as a column, tetrahydrofuran as a mobile phase, a measurement temperature of 40°C, a flow rate of 1.0 mL / min, an injection amount of 50 μL, and a value calculated using a calibration curve converted into polystyrene using commercially available standard polystyrene.

[0012] Examples of the bisphenol-type epoxy resin (A) include bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, bisphenol S-type epoxy resin, etc. These resins may be used alone or in combination.

[0013] The epoxy equivalent of the bisphenol-type epoxy resin (A) is not particularly limited, but is preferably 200 to 350 g / eq, more preferably 230 to 330 g / eq, and even more preferably 240 to 320 g / eq. When the epoxy equivalent is 200 g / eq or more, cracks are less likely to occur after printing on a substrate. When the epoxy equivalent is 350 g / eq or less, adhesion to the substrate is improved, and long-term reliability of adhesion and conductivity is likely to be improved.

[0014] The content of the bisphenol type epoxy resin (A) is 1.005 to 1.74 mass%, preferably 1.131 to 1.678 mass%, and more preferably 1.257 to 1.616 mass%.

[0015] The (meth)acrylic resin (B) is a polymer containing at least an acrylic acid ester and / or a methacrylic acid ester as a constituent monomer. For example, a polymer containing at least one constituent monomer selected from the group consisting of methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate can be used. The constituent monomer may include a monomer other than an acrylic acid ester or a methacrylic acid ester, as long as it does not deviate from the objectives of the present invention. When two or more types of monomers are contained, the resin may be an alternating copolymer, a random copolymer, a block copolymer, or a graft copolymer. Here, "(meth)acrylic resin" is a general term for "acrylic resin" and "methacrylic resin."

[0016] The weight average molecular weight of the (meth)acrylic resin (B) is 1,000 or more, preferably 5,000 or more, more preferably 7,000 or more, and even more preferably 10,000 or more. Also, it is 400,000 or less, preferably 200,000 or less, more preferably 150,000 or less, and even more preferably 50,000 or less.

[0017] Examples of such (meth)acrylic resins (B) that can be used include those described in JP 2016-155920 A, JP 2015-59196 A, JP 2016-196606 A, and WO 2016 / 132814. Commercially available (meth)acrylic resins can also be used, such as "KC-1100" and "KC-1700P" manufactured by Kyoeisha Chemical Co., Ltd.

[0018] The content of the (meth)acrylic resin (B) is 0.015% by mass or more and less than 0.08% by mass, preferably 0.015 to 0.075% by mass, and more preferably 0.02 to 0.075% by mass.

[0019] The polymer particles (C) may be any particles containing polybutadiene rubber. Preferably, the polymer particles (C) have a core-shell structure consisting of a core layer and a shell layer, the core layer containing polybutadiene rubber, and the shell layer being composed of a polymer of a vinyl monomer. Examples of the vinyl monomer include styrene-based monomers such as styrene, α-methylstyrene, monochlorostyrene, and dichlorostyrene; (meth)acrylic acid-based monomers such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and n-butyl methacrylate; and unsaturated nitrile-based monomers such as acrylonitrile and methacrylonitrile.

[0020] The polymer constituting the shell layer is preferably grafted onto the core layer.

[0021] The content of the polymer particles (C) is from 0.5 to 0.86% by mass, preferably from 0.557 to 0.827% by mass, and more preferably from 0.619 to 0.796% by mass.

[0022] The average particle size of the polymer particles (C) is not particularly limited, but is preferably 30 to 500 nm, and more preferably 50 to 300 nm. The "average particle size" of the polymer particles (C) refers to the number-based average particle size D50 (median size) measured by dispersing the polymer particles (C) in pure water using a laser diffraction / scattering particle size distribution measuring device "MT3000II" manufactured by Microtrac-Bell Co., Ltd.

[0023] The content of copper particles (D) having an average particle diameter of 2 to 500 nm is 5 to 95 mass%, preferably 40 to 79 mass%, more preferably 60 to 79 mass%, and even more preferably 65 to 75 mass%.

[0024] The copper particles (D) preferably have an average particle diameter of 10 to 500 nm, more preferably 20 to 400 nm. In this specification, the "average particle diameter" of the metal particles refers to the number-based average particle diameter D50 (median diameter) measured using a laser diffraction / scattering particle size distribution analyzer "MT3000II" manufactured by Microtrac-Bell Co., Ltd., after adding butyl carbitol to the metal particles and dispersing them with an ultrasonic vibrator for 10 minutes.

[0025] The shape of the copper particles (D) is not particularly limited, and spherical, flaky (scale-like), dendritic, or fibrous particles can be used, with spherical or flaky (scale-like) particles being preferred. Note that "spherical" metal particles include not only nearly spherical particles (atomized powder) but also nearly polyhedral spheres (reduced powder) and irregularly shaped particles (electrolytic powder).

[0026] The content of silver particles (E) having an average particle size of 2 to 500 nm is 0.9 to 4.8 mass%, preferably 1.69 to 4.5 mass%, and more preferably 1.69 to 4.2 mass%.

[0027] The average particle size of the silver particles (E) is preferably 30 to 400 nm, and more preferably 60 to 300 nm.

[0028] The shape of the silver particles (E) is not particularly limited, and spherical, flaky (scale-like), dendritic, or fibrous particles can be used, with spherical or flaky (scale-like) particles being preferred. Note that "spherical" metal particles include not only nearly perfect spheres (atomized powder) but also nearly polyhedral spheres (reduced powder) and irregularly shaped particles (electrolytic powder).

[0029] The content ratio of the copper particles (D) to the silver particles (E) ((D) / (E)) is not particularly limited, but is preferably 15.0 to 45.0 by mass, and more preferably 16.0 to 42.0 by mass.

[0030] The total content of the copper particles (D) and silver particles (E) is not particularly limited, but is preferably 11.6 to 83.8% by mass, more preferably 42 to 80% by mass, more preferably 62 to 78% by mass, and even more preferably 67 to 75% by mass.

[0031] The content of the phosphorus-containing compound (F) is 0.001 to 20 mass%, preferably 0.003 to 20 mass%, more preferably 0.005 to 15 mass%, more preferably 1 to 14 mass%, more preferably 3 to 13 mass%, and even more preferably 5 to 12 mass%.

[0032] The phosphorus-containing compound (F) acts as a copper-oxidizing agent, converting at least a portion of the copper (Cu) into cuprous ions (Cu ＋ ), thereby forming copper hydride (CuH). Although CuH can be formed as nanoparticles or flakes comprising substantially pure CuH, most of the CuH forms on copper (Cu) nanoparticles, i.e., as a continuous coating layer of CuH, or as CuH domains (i.e., a discontinuous coating) on ​​at least a portion of the copper particles.

[0033] In some embodiments, the phosphorus-containing compound is hypophosphorous acid, phosphorous acid, phosphoric acid, pyrophosphate (H ４ P ２ O ７ ), tripolyphosphate (H ５ P ３ O １０ ), tetrapolyphosphate (H ６ P ４ O ３ ), trimetaphosphate (H ３ P ３ O ９ ), phosphoric anhydride (P ４ O １０ ), polyphosphate, hypophosphate (H ４ P ２ O ６ ), pyrophosphorous acid (H ４ P ２ O ５ ), and metaphosphorous acid (HPO ２ ), and mixtures thereof.

[0034] In other embodiments, the phosphorus-containing compound has the formula HOP(O)H ２ and hypophosphorous acid (HPA, also known as phosphinic acid), having the formula:

[0035] In some embodiments, the ratio between the phosphorus-containing compound and the copper particles is preferably 0.001 to 0.2 by mass (phosphorus-containing compound / copper particles), i.e., 0.1 to 20% by mass of the phosphorus-containing compound per part by mass of the copper particles.

[0036] Regardless of the form, the content of copper hydride (G) is 0.0001 to 10 mass%, preferably 0.0003 to 8 mass%, more preferably 1 to 7 mass%, and even more preferably 3 to 6 mass%.

[0037] Without wishing to be bound by theory, CuH may act as a protective layer against oxidation of copper to copper oxide. Additionally, once applied to a substrate and heated, CuH decomposes to form H ２ An atmosphere is provided which prevents the formation of copper oxide and allows for sintering of the copper particles through metal-metal interactions.

[0038] In some embodiments, the CuH can be crystalline or amorphous. In some other embodiments, the CuH can be amorphous (e.g., characterized by the absence of distinct peaks in an XRD analysis).

[0039] Because the conductive composition of the present invention is subjected to various thermal processes, it is desirable to select the solvent (H) to have a boiling point that allows its evaporation upon exposure to the thermal process. In some embodiments, the solvent (H) can be selected to have a different evaporation rate and / or boiling point than the phosphorus-containing compound. For example, the solvent (H) may have a higher boiling point and / or a lower evaporation rate than the phosphorus-containing compound. In other embodiments, if the presence of a phosphorus-containing compound is desired in the dried pattern, the solvent (H) may be selected to have a lower boiling point and / or a higher evaporation rate than the phosphorus-containing compound. Specifically, the solvent (H) may be water; alcohols such as terpineol and propylene glycol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, ethylene glycol monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monohexyl ether, dipropylene glycol methyl ether, and tripropylene glycol methyl ether;Ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monoisopropyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl ether acetate, ethylene glycol monobenzyl ether acetate, ethylene glycol monohexyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol mono-n-butyl ether acetate, diethylene glycol monohexyl ether acetate, diethylene glycol-n-butyl ether acetate, 1-methoxymethyl acetate, 3-methoxypropyl glycol ether acetates (preferably alkoxyalkyl acetates), such as propyl acetate, 3-ethoxypropyl acetate, 2-methoxypropyl acetate, 2-ethoxypropyl acetate, 2-methoxybutyl acetate, 2-ethoxybutyl acetate, 3-methoxybutyl acetate, 3-ethoxybutyl acetate, 4-methoxybutyl acetate, 4-ethoxybutyl acetate, 2-methoxypentyl acetate, 2-ethoxypentyl acetate, 3-methoxypentyl acetate, 3-ethoxypentyl acetate, 4-methoxypentyl acetate, 4-ethoxypentyl acetate, 5-methoxypentyl acetate, 5-ethoxypentyl acetate, 3-methoxy-3-methylbutyl acetate, and mixtures thereof;

[0040] The content of the solvent (H) is 0.1 to 90 mass%, preferably 5 to 80 mass%, more preferably 7 to 35 mass%, and even more preferably 10 to 30 mass%. In one embodiment, the content of the solvent (H) may be 10 to 90 mass%.

[0041] The conductive composition of the present invention can be obtained by blending and thoroughly mixing the above-mentioned components in predetermined amounts.

[0042] The conductive composition of the present invention may contain additives that have been conventionally added to conductive compositions of the same type, provided that the additives do not depart from the object of the present invention. Examples of such additives include curing catalysts, antifoaming agents, thickeners, tackifiers, fillers, anti-settling agents, colorants, antioxidants, plasticizers, ultraviolet absorbers, and flame retardants.

[0043] The viscosity of the conductive composition of the present invention is not particularly limited and may be adjusted appropriately depending on the application method and the device used therefor. As a guideline, the viscosity at a liquid temperature of 25°C is preferably 500 to 2500 dPa·s, and more preferably 1000 to 2000 dPa·s.

[0044] In this specification, the "viscosity of the conductive composition" means the viscosity measured using a VISCOMETER TVB-10 (manufactured by Toki Sangyo Co., Ltd.) with a spindle No. 7 at a rotation speed of 10 rpm.

[0045] The conductive composition of the present invention can be applied onto a substrate by any suitable application method, such as inkjet printing, screen printing, spin coating, roll coating, spray coating, dip coating, flow coating, doctor blade coating, dispensing, offset printing, pad printing, gravure printing, flexography, stencil printing, imprinting, xerography, lithography, stamping, or any other suitable application method.

[0046] The conductive pattern formed on the substrate can be formed on any suitable substrate. The substrate may be flexible or rigid, stretchable or bendable, absorbent or non-absorbent, conductive or non-conductive, colored or transparent, and may be substantially two-dimensional (thin, flat substrate), three-dimensionally curved (non-flat), uniform or uneven, etc. The surface of the substrate may be any smooth surface. Most commonly, the substrate may be a solid material such as metal, glass, paper, semiconductor, polymer material, or ceramic surface, or a hybrid substrate containing several different materials. In particular, the adhesiveness-improving effect of the conductive composition of the present invention is easily achieved when polymer materials used in flexible printed circuit boards (FPCs) (e.g., polyimide resin, polyester resin, polyamide resin, polyamideimide resin, etc.) are used as the substrate. The material constituting the surface of the substrate to which the conductive composition is applied does not necessarily have to be the same material as the majority of the substrate. In some embodiments, the surface is substantially two-dimensional. In other embodiments, the surface is the surface of a three-dimensional object or article.

[0047] The substrate can have a uniform surface, i.e., a substantially uniform surface roughness and / or a uniform thickness, made of a single material (or single composition). However, it should be noted that in the context of the present disclosure, the surface may be non-uniform. That is, the surface of the substrate may include at least two sections, each of which may differ in at least one of roughness, height, thickness, material, or composition. These at least two sections may be integral with each other or may have a gap therebetween (i.e., the respective sections of the substrate may be continuously associated). For example, one section of the substrate may be a tube, and the other section of the substrate may be a cap that connects to the tube, so that a small gap is formed between the tube and the cap. Thus, the method of the present disclosure can be applied to continuous printing on a substrate having multiple sections.

[0048] A "surface" can refer to the entire surface or any region thereof. A "region" can be of any size and configuration. These regions can be continuous, integral with one another, or composed of several discontinuously spaced regions. In some embodiments, the regions are integral with one another. These "regions" can also refer to a plurality of regions, where at least two regions of the plurality differ from one another in at least one property (i.e., composition, texture, thickness, etc.). Thus, the term is meant to encompass a plurality of regions that differ from other regions by said property, all regions formed on a surface or a portion thereof.

[0049] The conductive composition of the present invention is patterned on a substrate and then subjected to a thermal process, during which CuH is decomposed and Cu nanoparticles are sintered together to obtain a conductive pattern.

[0050] The term sintering refers to the formation of a continuous matrix of individual granular materials through a thermal process. Heating the granular material promotes diffusivity of metal atoms between adjacent contacting particles, thereby forming a continuous metal matrix with reduced porosity. Sintering transforms the non-conductive pattern of copper nanoparticles into a continuous, conductive copper matrix (or grid).

[0051] A method for obtaining a conductive pattern on a substrate using the conductive composition of the present invention includes Step 1: printing the conductive composition of the present invention onto at least a surface region of the substrate to obtain a pattern-bearing substrate; and Step 2: exposing the pattern-bearing substrate to conditions that allow decomposition of CuH and sintering of copper and silver, for a period of about 0.01 to 600 seconds, thereby obtaining a conductive pattern.

[0052] In some embodiments, the conditions that allow for decomposition of CuH and sintering of copper and silver can include exposing the pattern-bearing substrate to a temperature of 125° C. or greater. In other embodiments, the substrate can be exposed to a temperature between about 125° C. and 500° C. Sintering at temperatures above 500° C. or below 125° C. (e.g., between about 50-125° C.) is also contemplated.

[0053] In some other embodiments, the pattern-bearing substrate is exposed to an elevated temperature (at least 125°C) for a period of between about 0.01 and 600 seconds. Without wishing to be bound by theory, the higher the sintering temperature, the shorter the period of exposure of the pattern-bearing substrate to such temperature. As will be understood by those skilled in the art, the pattern may be exposed to a single (i.e., uniform) temperature throughout the sintering temperature range, or to a varying temperature profile. For example, the sintering process may include two or more steps performed at different temperatures for different exposure periods. The temperature change may be gradual (i.e., the temperature may be increased or decreased at various rates) or abrupt (a sudden increase or decrease in temperature).

[0054] The decomposition of CuH and sintering of copper and silver can be carried out in an air atmosphere or in a localized reducing atmosphere, i.e., an atmosphere of gaseous reducing species. The reducing atmosphere can be achieved in situ by the decomposition of CuH and phosphorus-containing compounds to form gaseous reducing agents (e.g., hydrogen as a decomposition product). Alternatively, the reducing atmosphere can be achieved by introducing gaseous reducing species during sintering.

[0055] It should be noted that the decomposition of CuH and sintering can occur immediately after application of the formulation or at any time thereafter. The sintering process can involve heating the pattern-bearing surface by any suitable means, such as a lamp flash from a heat lamp (xenon, NIR, etc.), a UV lamp, a laser, hot air, an oven, or any other heat treatment unit.

[0056] The sintering may be selective. Selective sintering refers to the sintering of a selected portion or portions of a pattern, such that desired portions of the pattern are sintered and other portions are not. Such selective sintering can be obtained, for example, by exposing the printed pattern to a radiation source (e.g., infrared or near-infrared) through a suitable blocking mask. The mask may be removably placed on the printed pattern before exposure to the radiation source, or may be placed between the radiation source and the patterned surface. Selective sintering can also be obtained by other suitable means, such as laser scanning.

[0057] As described above, during the sintering process, the printed pattern is heated to high temperatures for a predetermined period of time, during which one or more processes occur: the increased temperature can cause decomposition of CuH, increase the reactivity of copper with the phosphorus-containing compound (thus forming additional CuH), and / or decompose the phosphorus-containing compound. These processes are highly exothermic, causing extreme and rapid localized temperature increases within the printed pattern.

[0058] Additionally, due to exothermic effects and localized heating as a result of the chemical reaction, it is contemplated that sintering may be carried out at lower temperatures, i.e., lower sintering temperature ranges than those described herein.

[0059] Examples of the present invention will be described below, but the present invention is not limited to these examples. In the following, the blending ratios and the like are based on mass unless otherwise specified.

[0060] Conductive compositions were prepared by mixing the components so as to have the compositions (contents, mass %) shown in Tables 1 to 3 below.

[0061] Bisphenol-type epoxy resin (A1): bisphenol A-type epoxy resin, epoxy equivalent = 270 g / eq Bisphenol-type epoxy resin (A2): bisphenol F-type epoxy resin, epoxy equivalent = 226 g / eq Glycidylamine-based epoxy resin: glycidylamine-based epoxy resin, epoxy equivalent = 124 g / eq (meth)acrylic resin (B): weight-average molecular weight = 17,000, polymer of isobutyl methacrylate Polymer particles (C1): butadiene rubber polymer particles having an average particle size = 100 nm and a core-shell structure (core layer: polybutadiene rubber, shell layer: polymer of vinyl-based monomer) Polymer particles (C2): styrene-butadiene rubber polymer particles having an average particle size = 100 nm and a core-shell structure (core layer: styrene-butadiene rubber, shell layer: polymer of vinyl-based monomer) Copper particles (D): average particle size = 100 nm Silver particles (E): average particle size = 150 nm, spherical Phosphorus-containing compound (F): hypophosphorous acid Copper hydride (G): CuH Solvent (H1): 3-methoxy-3-methylbutyl acetate Solvent (H2): diethylene glycol monobutyl ether

[0062] The resulting conductive compositions were evaluated for conductivity and adhesion, and the results are shown in Tables 1 to 3. The evaluation methods are as follows.

[0063] <Conductivity> The conductive compositions according to each Example and Comparative Example were applied to a prepared polyimide film 10 measuring 100 mm in length, 65 mm in width, and 50 μm in thickness using a 420-mesh Tetron plate and a urethane squeegee, as shown in FIG. 1 . After drying in an air oven at 85°C for 2 minutes, the film was pressed at a surface pressure of 1 MPa and a temperature of 200°C for 1 minute, yielding five samples of cured products 11 measuring 70 mm in length and 2 mm in width. The resistance values ​​(R, Ω) of the cured products 11 were measured using a precision tester, and the average value was calculated. The thickness of the cured products 11 was also measured using a micrometer, and the cross-sectional area of ​​the sample (S, cm ２ The volume resistivity (Ω cm) was calculated from the sample length (L, cm) using the following formula (1). －５ A sample having a volume resistivity of Ω·cm or less was evaluated as having excellent conductivity. Volume resistivity=(sample cross-sectional area (S) / sample length (L))×resistance value (R) (1)

[0064] <Adhesion: Cross-Cut Test> The conductive compositions according to each Example and Comparative Example were applied to a 60 mm long x 60 mm wide polyimide film measuring 100 mm long x 65 mm wide x 50 μm thick using a 420 mesh Tetron plate and a urethane squeegee. After drying for 2 minutes at 85°C in an air oven, the film was pressed at a surface pressure of 1 MPa and a temperature of 200°C for 1 minute to obtain a sample in which the conductive composition was cured. The obtained samples were evaluated by a cross-cut test in accordance with ASTM D 3359. The samples were also evaluated for chipping, with those without chipping marked "P" and those with chipping marked "F." A sample without chipping and rated 4B or higher in accordance with ASTM D 3359 was deemed to have excellent adhesion.

[0065]

[0066]

[0067]

[0068] From the results shown in Tables 1 to 3, it was found that Examples 1 to 7 all had excellent conductivity and adhesion.

[0069] Comparative Example 1 is an example that does not contain polymer particles (C) containing bisphenol-type epoxy resin (A) and polybutadiene rubber, and Comparative Example 2 is an example that the content ratio of these is below the lower limit value, and the adhesion was poor.

[0070] Comparative Example 3 is an example in which the content of the bisphenol type epoxy resin (A) was less than the lower limit, and the adhesion was poor.

[0071] Comparative Example 4 is an example that does not contain the (meth)acrylic resin (B), and the adhesion was poor.

[0072] Comparative Examples 5 and 6 are examples in which the content of the polymer particles (C) containing polybutadiene rubber exceeded the upper limit, and the electrical conductivity was poor.

[0073] Comparative Example 7 is an example in which polymer particles containing styrene-butadiene rubber were used instead of the polymer particles (C) containing polybutadiene rubber, and the adhesiveness was poor.

[0074] Comparative Example 8 is an example in which the content of silver particles (E) was less than the lower limit, and the adhesion was poor.

[0075] Comparative Example 9 is an example in which a glycidylamine-based epoxy resin was blended in place of the bisphenol-type epoxy resin (A) and no polymer particles (C) containing polybutadiene rubber were contained, and the electrical conductivity was poor.

[0076] Comparative Example 10 is an example in which the content of silver particles (E) and the content of (meth)acrylic resin (B) exceeded the upper limit, and the adhesion was poor.

[0077] Comparative Example 11 is an example that does not contain the components (A), (B), (C), and (E), and the adhesion was poor.

[0078] 10... Polyimide film 11... Cured product of conductive composition

Claims

1. A conductive composition comprising: (A) 1.005 to 1.74 mass% of a bisphenol type epoxy resin; (B) 0.015 mass% or more and less than 0.08 mass% of a (meth)acrylic resin having a weight average molecular weight of 1,000 to 400,000; (C) 0.5 to 0.86 mass% of polymer particles containing polybutadiene rubber; (D) 5 to 95 mass% of copper particles having an average particle diameter of 2 to 500 nm; (E) 0.9 to 4.8 mass% of silver particles having an average particle diameter of 2 to 500 nm; (F) 0.001 to 20 mass% of a phosphorus-containing compound; (G) 0.0001 to 10 mass% of CuH; and (H) 0.1 to 90 mass% of a solvent.

2. The conductive composition according to claim 1, wherein the polymer particles (C) have a core-shell structure including a core layer and a shell layer, the core layer includes polybutadiene rubber, and the shell layer is composed of a polymer of a vinyl monomer.

3. The conductive composition according to claim 1 or 2, wherein a content ratio of the copper particles (D) to the silver particles (E) ((D) / (E)) is 15.0 to 45.0 by mass.

4. The conductive composition according to any one of claims 1 to 3, wherein a total content of the copper particles (D) and the silver particles (E) is 11.6 to 83.8 mass%.

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