Conductive composition

Abstract

To provide a conductive composition capable of forming a cured film by heating at a low temperature in a short time and capable of forming a cured film having high adhesion to a substrate, good solder wettability, and high heat resistance without impairing conductivity.SOLUTION: The conductive composition contains (A) 73-92.4 mass% of conductive particles, (B) 1-7.0 mass% of a binder component, (C) 6.5-15 mass% of a polyol having a boiling point of 300°C or lower and having 2-6 hydroxyl groups, and (D) 0.1-5.0 mass% of an amine compound having an ethylenediamine skeleton.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrically conductive composition. [Background technology]

[0002] In recent years, in order to reduce chemical emissions, there has been a trend toward replacing conventional plating methods, which require large amounts of chemicals and many steps, with printing methods using screen printers, etc. In light of this trend, there has been active development of conductive compositions suitable for screen printing methods.

[0003] When forming an electrode using such a conductive composition, the properties of the cured film obtained by heating the conductive composition must be equivalent to those of a metal film obtained by plating. In particular, properties related to bonding to a substrate such as ceramic or ferrite, which serves as the base for forming the electrode, and bonding to wiring and elements are important. Generally, soldering is performed to bond wiring and elements using soldering materials such as solder paste and solder bar. Therefore, cured films of the conductive composition are required to have high adhesion to various substrates and solder wettability.

[0004] Furthermore, with the recent advancement of power electronics, the operating environment of semiconductor substrates has become higher, increasing the demand for solder with a melting point higher than the conventional 200°C. Accordingly, it is desirable for the cured film of the conductive composition to have heat resistance that can withstand high-melting-point soldering.

[0005] In general, adding a coupling agent or resin component to the composition is effective in improving adhesion to the substrate, but the presence of these organic components can lead to a deterioration in solder wettability, which is a problem.

[0006] For example, Patent Documents 1 and 2 describe conductive compositions that exhibit excellent adhesion to substrates and solder wettability. These conductive compositions contain glass frit, an inorganic substance, which fuses to the substrate and conductive particles, resulting in high adhesion. Furthermore, because a cured film is obtained by heating at a high temperature of 500°C or higher for 60 minutes, the cured film contains few organic components and exhibits good solder wettability. Furthermore, the cured film is considered to have high heat resistance at temperatures above 500°C. However, increasing the amount of glass frit to improve adhesion is likely to result in poor solder wettability. Furthermore, because the process for obtaining the cured film requires high temperatures and a long time, a simpler method is needed.

[0007] Patent Document 3 also describes a conductive composition comprising metal particles, a binder component, and a solvent. Because this conductive composition contains a binder component, it is possible to obtain a cured film at low temperatures in a short time. Furthermore, intentionally leaving uncured portions promotes the penetration of flux applied to the cured film before immersion in a solder bath, resulting in high solder wettability. However, incomplete curing can result in poor adhesion to the substrate and reduced conductivity. Therefore, it is difficult to produce a cured film with sufficient adhesion to the substrate, good solder wettability, and heat resistance using a low-temperature curing conductive composition. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2023-93940 A [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-128005 [Patent Document 3] JP 2019-121568 A Summary of the Invention [Problem to be solved by the invention]

[0009] The problem to be solved by the present invention is to provide an electrically conductive composition that can form a cured film by heating at a low temperature for a short time, and that can form a cured film that has high adhesion to a substrate, good solder wettability, and high heat resistance without impairing electrical conductivity. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems, and have found that the above problems can be solved by a conductive composition containing conductive particles, a binder component, a specific polyol, and a specific amine compound in a specific ratio, thereby completing the present invention. That is, the present invention relates to the following [1] to [3].

[0011] [1] (A) Conductive particles 73~92.4% by mass (B) Binder component: 1 to 7.0 mass% (C) 6.5 to 15% by mass of a polyol having a boiling point of 300°C or less and 2 to 6 hydroxyl groups (D) Amine compound having an ethylenediamine skeleton: 0.1 to 5.0% by mass 1. A conductive composition comprising:

[0012] [2] The conductive composition according to [1] above, characterized in that the (C) polyol having a boiling point of 300°C or less and 2 to 6 hydroxyl groups is a combination of the following (C1) and (C2): (C1) At least one member selected from the group consisting of a polyol represented by the following formula (1), a polyol represented by the following formula (2), and glycerin: (C2) At least one polyol selected from the group consisting of polyols represented by the following formula (3):

[0013] [ka]

[0014] (In formula (1), -(OR 1)- represents at least one oxyalkylene group having 2 to 3 carbon atoms, and when two or more oxyalkylene groups are present, -(OR 1 The addition form of n- may be either block or random, and n represents the average number of moles of oxyalkylene groups added and is a number of 1 to 3.

[0015] [ka]

[0016] (In formula (2), R 2 is either a hydrogen atom, a methyl group, an ethyl group, or a hydroxymethyl group.

[0017] [ka]

[0018] (In formula (3), R 3 , R 4 are each independently either a hydrogen atom or a methyl group. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a conductive composition that can form a cured film by heating at a low temperature for a short time, and that can form a cured film that has high adhesion to a substrate, good solder wettability, and high heat resistance without impairing electrical conductivity. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described, but the present invention is not limited thereto.

[0021] The conductive composition according to an embodiment of the present invention contains (A) 73 to 92.4% by mass of conductive particles, (B) 1 to 7.0% by mass of a binder component, (C) 6.5 to 15% by mass of a polyol having a boiling point of 300°C or less and 2 to 6 hydroxyl groups, and (D) 0.1 to 5.0% by mass of an amine compound having an ethylenediamine skeleton. Each component will be described below.

[0022] [Component (A): Conductive particles] Component (A) used in embodiments of the present invention is a conductive particle, and inorganic conductive particles such as silver, nickel, gold, and copper can be used. From the viewpoint of conductivity, silver and copper are preferred, and from the viewpoint of migration resistance and use in high applied voltage ranges such as device operation, copper is preferred. The copper particles may consist only of copper, or may further contain a metal other than copper, such as silver or platinum, a metal oxide, or a metal sulfide. When the copper particles further contain a metal other than copper, a metal oxide, or a metal sulfide, the mass ratio of copper in the copper particles is preferably 50 mass% or more. Furthermore, the copper particles may have a surface layer or protrusions formed thereon.

[0023] Although commercially available conductive particles may be used as they are, it is preferable to use surface-coated conductive particles whose surfaces are coated for the purpose of improving oxidation resistance, etc. Among these, it is preferable to use surface-coated conductive particles whose surfaces are coated with an amine compound, and it is more preferable to use surface-coated conductive particles whose surfaces are coated with an amine compound represented by the following formula (4).

[0024] [ka]

[0025] (In formula (4), x is an integer of 0 to 3, y is an integer of 0 to 2, and when y=0, x is any one of 0 to 3, and when y=1 or y=2, x is any one of 1 to 3.)

[0026] From the viewpoint of obtaining better oxidation resistance, it is preferable that the surface-coated conductive particles whose surfaces are coated with an amine compound or the like represented by the above formula (4) are further coated with an aliphatic monocarboxylic acid. As a result, the surface of the conductive particle is coated with a first coating layer formed with the amine compound and a second coating layer formed with the aliphatic monocarboxylic acid. Preferably, the first coating layer is formed on the surface of the conductive particle, and the second coating layer is formed on the first coating layer.

[0027] The aliphatic monocarboxylic acid forming the second coating layer is preferably an aliphatic monocarboxylic acid having a carbon number of 8 to 24. Examples of the aliphatic monocarboxylic acid include linear saturated aliphatic monocarboxylic acids, linear unsaturated aliphatic monocarboxylic acids, branched saturated aliphatic monocarboxylic acids, and branched unsaturated aliphatic monocarboxylic acids.

[0028] Examples of linear saturated aliphatic monocarboxylic acids having 8 to 24 carbon atoms include caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, and arachidic acid. Examples of linear unsaturated aliphatic monocarboxylic acids having 8 to 24 carbon atoms include myristoleic acid, palmitoleic acid, petroselinic acid, and oleic acid. Examples of branched saturated aliphatic monocarboxylic acids having 8 to 24 carbon atoms include 2-ethylhexanoic acid. As the aliphatic monocarboxylic acids, one selected from the above compounds can be used alone, or two or more can be used in combination.

[0029] The method for producing the surface-coated conductive particles is not particularly limited. Examples of methods for obtaining surface-coated conductive particles whose surfaces are coated with an amine compound include a method in which conductive particles are washed with an ammonium chloride aqueous solution or the like, and then the washed conductive particles are added to a solution of an amine compound and heated as necessary, and a method in which conductive particles are added to a solution containing, for example, ammonium chloride and an amine compound and heated as necessary.

[0030] As a method for producing surface-coated conductive particles coated with a first coating layer formed by an amine compound and a second coating layer formed by an aliphatic monocarboxylic acid, for example, a method of adding surface-coated conductive particles coated with an amine compound to a solution of an aliphatic monocarboxylic acid can be mentioned. After adding to the solution of the aliphatic monocarboxylic acid, heating may be carried out as necessary.

[0031] The average particle size (D50) of the conductive particles is not particularly limited, but it is preferable to control the average particle size (D50) of the conductive particles so that the conductive composition containing the conductive particles as component (A) can be printed well using various printing methods such as dispenser printing and screen printing. Specifically, the average particle size (D50) of the conductive particles is preferably 5 nm to 20 μm, and more preferably 10 nm to 10 μm. The average particle size (D50) of the conductive particles can be measured using a laser diffraction / scattering particle size distribution analyzer (e.g., Microtrac MT3000II, manufactured by Microtrac-Bell Corporation).

[0032] The BET specific surface area of ​​the conductive particles is 0.05 to 400 m 2 / g, and 0.1 to 200m 2 / g The BET specific surface area of ​​the conductive particles can be measured by a BET single-point method using a specific surface area measuring device (for example, Monosorb, manufactured by Yuasa Ionics Co., Ltd.).

[0033] There are no particular limitations on the shape or aspect ratio (ratio of the long axis to the short axis of the particle) of the conductive particles, and various shapes can be used, such as spherical, polyhedral, flat, plate-like, flake-like, thin plate-like, rod-like, dendritic, fibrous, etc. The conductive particles can be used singly or in combination of two or more types selected from those differing in constituent components, average particle size, shape, aspect ratio, etc.

[0034] The content of component (A) is 73 to 92.4% by mass. The lower limit of the content of component (A) is preferably 78% by mass. If the content of component (A) is less than 73% by mass, the proportion of metal on the surface of the cured film is low, and solder may not wet. From the viewpoint of flowability, the upper limit of the content of component (A) is preferably 88% by mass.

[0035] [Component (B): Binder component] The component (B) used in the embodiment of the present invention is a binder component, and for example, a binder component used in circuit formation can be used. Examples of such binder components include thermoplastic resins and thermosetting resins. Among them, thermosetting resins are preferred from the viewpoint of electrical conductivity, and epoxy resins, polyurethane resins, and polyurea resins are more preferred from the viewpoint of solder wettability.

[0036] Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, hydrogenated bisphenol A type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins, biphenyl type epoxy resins, naphthalene type epoxy resins, dicyclopentadiene type epoxy resins, and triphenylmethane type epoxy resins.

[0037] Examples of commercially available epoxy resins include, but are not limited to, jER 828, 806, 807, YX8000, YX8034, and 834 manufactured by Mitsubishi Chemical Corporation; YD-128, YDF-170, YD-8125, ZX-1059, YDF-870GS, and ST-3000 manufactured by Nippon Steel Chemical & Material Co., Ltd.; and EPICLON 840, 830, 850, and N-680 manufactured by DIC Corporation.

[0038] In an embodiment of the present invention, since component (C) contains a polyol having a boiling point of 300°C or less and 2 to 6 hydroxyl groups, and component (D) contains an amine compound having an ethylenediamine skeleton, a polyisocyanate may be used as the binder component. In this case, the polyisocyanate reacts with the polyol of component (C) and the amine compound of component (D) upon heating to form urethane bonds and urea bonds. Examples of polyisocyanates include aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and their adducts, biurets, and isocyanurates. From the viewpoint of electrical conductivity, aliphatic diisocyanates and their adducts, biurets, and isocyanurates are preferred. From the viewpoint of adhesion, isocyanurates of aliphatic diisocyanates are more preferred.

[0039] The polyisocyanate may also be blocked with a blocking agent. Blocking improves printing stability. Any blocking agent containing active hydrogen (hydrogen bonded to oxygen, sulfur, or nitrogen) that reacts with isocyanate and whose product is reversible, i.e., unblocked by heat, may be used. Typical blocking agents include oximes, lactams, phenols, active methylenes, pyrazoles, mercaptans, imidazoles, amines, imines, triazoles, hydroxylamines, and aliphatic, alicyclic, or aromatic alkyl monoalcohols. Pyrazoles, in particular, have a relatively low dissociation temperature and work well on plastic substrates, such as polyethylene terephthalate (PET), which cannot be heated to high temperatures. Examples of pyrazoles include 2,2-dimethylpyrazole and 3,5-dimethylpyrazole. Examples of commercially available polyisocyanates that have an isocyanurate skeleton and three isocyanate groups formed from a skeleton derived from hexamethylene diisocyanate and are blocked with 3,5-dimethylpyrazole include, but are not limited to, Duranate SBN-70D manufactured by Asahi Kasei Corporation.

[0040] The content of component (B) is 1 to 7.0% by mass, preferably 2 to 6% by mass, and more preferably 2.5 to 5% by mass. If the content of component (B) is less than 1% by mass, the conductivity of the cured film obtained using the conductive composition may decrease, while if it is more than 7.0% by mass, the solder wettability may decrease. The content of the binder component is based on the solid content.

[0041] [Component (C): Polyol with a boiling point of 300°C or less and 2 to 6 hydroxyl groups] Component (C) used in embodiments of the present invention is not particularly limited as long as it is a polyol having a boiling point of 300°C or less and 2 to 6 hydroxyl groups. Examples include (C1) at least one selected from a polyol represented by the following formula (1), a polyol represented by the following formula (2), and glycerin, and (C2) at least one selected from a polyol represented by the following formula (3). Component (C) is preferably two or more selected from polyols having a boiling point of 300°C or less and 2 to 6 hydroxyl groups. A preferred combination of polyols for component (C) is, for example, a combination of (C1) at least one selected from a polyol represented by the following formula (1), a polyol represented by the following formula (2), and glycerin, and (C2) at least one selected from a polyol represented by the following formula (3). The inclusion of a polyol represented by the following formula (3) improves the fluidity of the conductive composition, better suppresses blurring during printing, and improves the conductivity of the resulting cured product.

[0042] Furthermore, if the boiling point of the polyol used in the present invention exceeds 300°C, the polyol may remain in the cured film, resulting in reduced solder wettability, adhesion, and heat resistance. The boiling point of the polyol represented by the following formula (1) is preferably 200°C or less from the viewpoint of the solder wettability of the cured film, and more preferably 150°C or less from the viewpoint of the heat resistance of the cured film. There are no particular restrictions on the lower limit of the boiling point, but it is preferably 100°C or more from the viewpoint of handleability when preparing the composition. Note that the boiling point means the boiling point under atmospheric pressure.

[0043] [ka]

[0044] (In formula (1), -(OR 1 )- represents at least one oxyalkylene group having 2 to 3 carbon atoms, and when two or more oxyalkylene groups are present, -(OR 1 The addition form of n- may be either block or random, and n represents the average number of moles of oxyalkylene groups added and is a number of 1 to 3.

[0045] [ka]

[0046] (In formula (2), R 2 is either hydrogen, a methyl group, an ethyl group, or a hydroxymethyl group.

[0047] [ka]

[0048] (In formula (3), R 3 , R 4 are each independently either a hydrogen atom or a methyl group.

[0049] Examples of the polyol represented by formula (1) include -(OR 1 There are no particular limitations on the polyol as long as the average number of moles n of )- added is a number of 1 to 3. Examples of polyols represented by formula (1) include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, tripropylene glycol, and 3-(2-hydroxyethoxy)-1-propanol.

[0050] The polyols represented by formula (2) include trimethylolmethane, trimethylolethane, trimethylolpropane, and pentaerythritol.

[0051] The polyol represented by formula (1), the polyol represented by formula (2), and glycerin may be used alone or in combination of two or more, but it is preferable to use triethylene glycol alone.

[0052] Examples of the polyol represented by formula (3) include hydroquinone, resorcinol, catechol, 2-methylhydroquinone, 2-methylresorcinol, 4-methylresorcinol, 5-methylresorcinol, 3-methylcatechol, 4-methylcatechol, 2,3-dimethylhydroquinone, 2,5-dimethylhydroquinone, 2,6-dimethylhydroquinone, 2,4-dimethylresorcinol, 2,5-dimethylresorcinol, 4,5-dimethylresorcinol, 3,4-dimethylcatechol, 3,5-dimethylcatechol, 3,6-dimethylcatechol, and 4,5-dimethylcatechol.

[0053] The polyol represented by formula (3) may be used alone or in combination of two or more kinds, but it is preferable to use hydroquinone alone.

[0054] When the components (C1) and (C2) are used in combination, the mixing ratio is preferably 20 to 60 mass % of (C1) and 40 to 80 mass % of (C2), assuming that the total of the components (C1) and (C2) is 100 mass %.

[0055] The content of component (C) is 6.5 to 15 mass%, preferably 8 to 13 mass%, and more preferably 9 to 11 mass%. If the content of component (C) is less than 6.5 mass%, the solder wettability of the cured film obtained using the conductive composition may decrease, while if it is more than 15 mass%, the adhesion may decrease.

[0056] [Component (D): Amine compound having an ethylenediamine skeleton] Component (D) used in the embodiment of the present invention may be any amine compound having an ethylenediamine skeleton, but from the viewpoint of the dispersibility of conductive particles and the solder wettability of the cured film, it is preferable that the compound have one or more primary or secondary amine moieties in its structure. Examples of amine compounds having an ethylenediamine skeleton include amine compounds having a linear ethylenediamine skeleton, amine compounds having a branched ethylenediamine skeleton, and amine compounds having a cyclic ethylenediamine skeleton.

[0057] As the amine compound having a linear ethylenediamine skeleton, ethylenediamine and compounds represented by the following formula (5) are preferred.

[0058] [ka]

[0059] (In formula (5), the degree of polymerization m is a number from 0 to 5.)

[0060] The amine having a linear ethylenediamine skeleton represented by formula (5) is not particularly limited as long as the degree of polymerization m is a number from 0 to 5, but from the viewpoint of electrical conductivity, those in which m is a number from 0 to 3 are preferred, and from the viewpoint of heat resistance of the cured film, those in which m is a number from 0 to 1 are more preferred. Examples include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and hexaethyleneheptamine.

[0061] The amine compound having a branched ethylenediamine skeleton is preferably polyethyleneimine. The weight-average molecular weight (Mw) of polyethyleneimine is preferably 100 to 10,000. Among these, from the viewpoints of electrical conductivity and adhesion, the weight-average molecular weight (Mw) is preferably 100 to 1,000.

[0062] Polyethyleneimine may be synthesized according to a standard method, or commercially available polyethyleneimine may be used. Examples of commercially available polyethyleneimine having a branched structure include Epomin (registered trademark) SP-003, SP-006, and SP-012 manufactured by Nippon Shokubai Co., Ltd.

[0063] The amine compound having a cyclic ethylenediamine skeleton is preferably one represented by the following formula (6).

[0064] [ka]

[0065] (In formula (6), R 5 is a hydrocarbon group having 1 to 3 carbon atoms, and R 6 is a hydrocarbon group having 1 to 5 carbon atoms.

[0066] Specific examples of the amine compound represented by formula (6) include, but are not limited to, 2-aminoethylimidazolidine, aminomethylpiperazine, 2-aminoethylpiperazine, 3-aminopropylpiperazine, 4-aminobutylpiperazine, 5-aminopentylpiperazine, and 2-aminoethylhomopiperazine.

[0067] Component (D) may be used alone or in combination of two or more types. Combining amines with different properties can impart excellent conductivity, adhesion, and heat resistance. When two or more types of component (D) are used in combination, for example, two or more types selected from the amine compound represented by the above formula (5) and / or ethylenediamine, polyethyleneimine, and amine compound represented by formula (6) are preferred. For example, it is preferred to use a combination of the amine compound represented by formula (5) and / or formula (6) with polyethyleneimine, and in this case, the mixing ratio is preferably 50 to 80 mass% of the amine compound represented by formula (5) and / or formula (6) and 20 to 50 mass% of the polyethyleneimine. Specifically, an amine compound having a linear ethylenediamine skeleton represented by formula (5) with a degree of polymerization m of 0 to 2 and / or a hydrocarbon group R having 1 to 2 carbon atoms is preferred. 3 and R 4 and the like, for example, a combination of an amine compound having a cyclic ethylenediamine skeleton represented by formula (6) and polyethyleneimine, which is an amine compound having a branched ethylenediamine skeleton and a weight-average molecular weight of 100 to 1,000. In particular, a combination of diethylenetriamine and / or 2-aminoethylpiperazine and polyethyleneimine having a weight-average molecular weight of 300 (for example, Epomin SP-003, manufactured by Nippon Shokubai Co., Ltd.) is preferred.

[0068] The content of component (D) is 0.1 to 5.0% by mass, preferably 0.1 to 3.0% by mass. If the content of component (D) is less than 0.1% by mass, the volume resistivity of the cured film obtained using the conductive composition may increase, and adhesion may decrease. If the content is more than 5.0% by mass, the solder wettability, heat resistance, and adhesion of the cured film obtained using the conductive composition may decrease.

[0069] [Other ingredients] In addition to the above components (A) to (D), the conductive composition according to the embodiment may contain various additives, such as solvents, antioxidants, lubricants, dispersants, curing agents, curing accelerators, viscosity modifiers, foaming agents, and antifoaming agents, as needed, provided that the effects of the present invention are not impaired. The conductive composition may also contain impurities that may be unavoidably mixed in from raw material components and manufacturing equipment. When any of these components is contained, the content thereof may be greater than 0% by mass and up to 19.4% by mass, and preferably up to 5% by mass.

[0070] (solvent) The conductive composition according to the embodiment may contain a solvent for the purpose of improving coating properties, adjusting viscosity, etc. Examples of the solvent include, but are not limited to, esters such as ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether acetate, propylene glycol diacetate, dipropylene glycol monomethyl ether, ethylene glycol monobutyl ether acetate, triethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, cyclohexanol acetate, methyl methoxypropionate, ethyl ethoxypropionate, and 1,6-hexanediol acetate; ketones such as isophorone and cyclohexanone; terpenes such as terpineol, dihydroterpineol, dihydroterpinyl acetate, and isobornylcyclohexanol; and other hydrocarbons such as octane, decane, dodecane, tetradecane, hexadecane, and propylene carbonate. The solvent may be used alone or in combination of two or more kinds, and when two or more kinds are used in combination, the mixing ratio is not particularly limited.

[0071] When the conductive composition according to the embodiment contains a solvent, the content of the solvent is preferably 1 to 19.4 mass %, more preferably 1 to 10 mass %, of the entire conductive composition. When a solvent is contained in a component other than components (A) to (D) and the solvent, the total amount is used as the basis.

[0072] (antioxidant) The conductive composition according to the embodiment may contain an antioxidant to maintain the performance of each component during storage. The type of antioxidant is not particularly limited, and various antioxidants can be used depending on the application. Examples of antioxidants include nitrogen-containing heterocyclic compounds such as 2,2-bipyridyl and 1,10-phenanthroline; Schiff bases such as N,N'-bis(salicylidene)ethylenediamine, N,N'-bis(salicylidene)-1,2-propanediamine, N,N'-bis(salicylidene)-1,3-propanediamine, and N,N'-bis(salicylidene)-1,2-phenylenediamine; 1,2-phenylenediamine, 1,3-phenylenediamine, 1,4-phenylenediamine, 2,5-dimethyl-1,4-phenylenediamine, 2,3,5,6-tetramethyl-1,4-phenylenediamine, and N,N-dimethyl-1,4-phenylene. Examples of antioxidants include, but are not limited to, aromatic diamines such as diamine, N,N,N'N'-tetramethyl-1,4-phenylenediamine, and N,N'-diphenyl-1,4-phenylenediamine; phenols such as p-methoxyphenol, hydroquinone, tert-butylhydroquinone, dibutylhydroxytoluene, catechol, 4-tert-butylcatechol, pyrogallol, eugenol, and propyl gallate; and ascorbic acids such as L-ascorbic acid, 6-O-palmitoyl-L-ascorbic acid, 6-O-stearoyl-L-ascorbic acid, and tetra-2-hexyldecanoate ascorbyl. Antioxidants may be used alone or in combination of two or more. When two or more antioxidants are used in combination, the mixing ratio is not particularly limited.

[0073] Among the specific examples of the antioxidants mentioned above, it is preferable to use one or more selected from 2,2-bipyridyl, N,N'-bis(salicylidene)ethylenediamine, N,N'-bis(salicylidene)-1,2-propanediamine, 1,2-phenylenediamine, 1,3-phenylenediamine, 1,4-phenylenediamine, p-methoxyphenol, hydroquinone, tert-butylhydroquinone, 6-O-palmitoyl-L-ascorbic acid, and 6-O-stearoyl-L-ascorbic acid. When two or more of these antioxidants are mixed, the mixing ratio is not particularly limited.

[0074] When the conductive composition according to the embodiment contains an antioxidant, the content of the antioxidant is preferably 0.01 to 5 mass %, and more preferably 0.1 to 2 mass %.

[0075] (lubricant) A lubricant may be added to the conductive composition according to the embodiment to adjust the dispersibility of the conductive particles (Component (A)). Examples of lubricants include fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid; fatty acid metal salts formed from the fatty acids and metals such as sodium, potassium, barium, magnesium, calcium, aluminum, iron, cobalt, manganese, zinc, and tin; fatty acid amides such as stearic acid amide, oleic acid amide, behenic acid amide, palmitic acid amide, and lauric acid amide; fatty acid esters such as butyl stearate; waxes such as paraffin wax and liquid paraffin; alcohols such as ethylene glycol and stearyl alcohol; polyethers such as polyethylene glycol, polypropylene glycol, and modified versions thereof; polysiloxanes such as silicone oil; and fluorine compounds such as fluorine-based oils. These lubricants may be used singly or in combination. When using two or more types, the mixing ratio is not particularly limited.

[0076] Among these lubricants, it is preferable to use one or more selected from fatty acids and fatty acid metal salts from the viewpoint of dispersibility, and it is more preferable to use at least one selected from lauric acid and magnesium stearate.

[0077] When the conductive composition according to the embodiment contains a lubricant, the content of the lubricant is preferably 0.01 to 5 mass %, and more preferably 0.1 to 3 mass %.

[0078] (dispersant) A dispersant may be added to the conductive composition according to the embodiment to adjust the dispersibility of the conductive particles (component (A)). Examples of dispersants include sarcosine compounds such as lauroyl sarcosine, myristoyl sarcosine, palmitoyl sarcosine, stearoyl sarcosine, and oleoyl sarcosine; polymeric amine compounds; and polymeric polycarboxylic acid compounds. Commercially available polymeric amine compounds include Filanol PA-075F, PA-085C, and PA-107P, and Esreem (registered trademark) AD-3172M, AD-374M, and AD-508E, all manufactured by NOF Corporation. Commercially available polymeric polycarboxylic acid compounds include Marialim AKM-0531, AFB-1521, AAB-0851, AWS-0851, SC-0505K, SC-1015F, and SC-0708A, all manufactured by NOF Corporation. The dispersant may be used alone or in combination of two or more kinds, and when two or more kinds are used, the mixing ratio is not particularly limited.

[0079] Among these dispersants, it is preferable to use one or more selected from sarcosine compounds, and it is more preferable to use oleoyl sarcosine.

[0080] When the conductive composition according to the embodiment contains a dispersant, the content of the dispersant is preferably 0.01 to 5 mass %, and more preferably 0.1 to 3 mass %.

[0081] (hardening agent) A curing agent may be added to the conductive composition according to the present embodiment to improve the curing property of the binder component (B). This is particularly effective when the binder component is, for example, a curable resin. Improved curing property improves the conductivity of the cured film obtained using the conductive composition. The type of curing agent is not particularly limited as long as it can react with the reactive functional group contained in the binder component (B). Examples of reactive functional groups include, but are not limited to, epoxy groups, hydroxyl groups, phenolic hydroxyl groups, carboxyl groups, and amino groups. Examples of curing agents include, but are not limited to, epoxy compounds, isocyanate compounds, polymercaptan compounds, phenols, and acid anhydrides. One type of curing agent may be used alone, or two or more types may be used in combination. When two or more types are used, the mixing ratio is not particularly limited.

[0082] Among these curing agents, when an epoxy resin is used as component (B) the binder component, it is preferable to use an acid anhydride, for example, Rikacid MH-700 manufactured by New Japan Chemical Co., Ltd.

[0083] When the conductive composition according to the embodiment contains a curing agent, the content of the curing agent is preferably 0.5 to 10 mass %, and more preferably 1 to 5 mass %.

[0084] (curing accelerator) A curing accelerator may be added to the conductive composition according to the embodiment in order to accelerate the low-temperature curing of the binder component (B). Examples of the curing accelerator include phosphines, phosphonium salts, diazacycloundecene salts, phenols, and carboxylic acids. One type of curing accelerator may be used alone, or two or more types may be used in combination. When two or more types are used, the mixing ratio is not particularly limited.

[0085] Among these, it is preferable to use one or more selected from diazacycloundecene salts, and it is more preferable to use U-CAT SA102 manufactured by San-Apro Co., Ltd.

[0086] When the conductive composition according to the embodiment contains a curing accelerator, the content of the curing accelerator is preferably 0.01 to 0.1 mass %, and more preferably 0.01 to 0.05 mass %.

[0087] The aforementioned conductive composition can be obtained by blending the aforementioned specified components and kneading them according to a standard method. Furthermore, a printed film can be produced by printing a desired pattern on the surface of a substrate using a specified method, such as screen printing or stamp printing, using the conductive composition. Furthermore, a cured film can be obtained by heat-treating the printed film using a specified method. Because the conductive composition contains the aforementioned components (A) to (D) in a specified ratio, a cured film can be formed by heating at a low temperature for a short period of time. Even when cured at a low temperature for a short period of time, the cured film exhibits good conductivity. Furthermore, the resulting cured film exhibits high adhesion due to the binder component chemically or mechanically bonding with various substrates. Furthermore, even when the binder component is included, the cured film exhibits good solder wettability and excellent heat resistance, allowing soldering using high-melting-point solder. Therefore, the aforementioned conductive composition is suitable for forming electrodes on electronic substrates and as a conductive adhesive, and can also be used as a power electronics material used in high-temperature operating environments. The conductivity (evaluation of volume resistivity), adhesion to the substrate, solder wettability, and heat resistance (evaluation of high-temperature solder wettability) of a cured film using the conductive composition can be evaluated, for example, by the methods described in the Examples section below. [Example]

[0088] The embodiments of the present invention will be described in more detail below with reference to examples and comparative examples.

[0089] [Synthesis Example 1] (Copper particles (1): Production of surface-coated copper particles (1)) An aqueous solution of ammonium chloride was prepared by dissolving 5 g of ammonium chloride in 100 g of water. Copper particles a ["1200Y" manufactured by Mitsui Mining & Smelting Co., Ltd.; particle size (D50) 2 μm, BET specific surface area 0.40 m] 2 50 g of [1 / g, shape: spherical] was added to an aqueous ammonium chloride solution and stirred at 30°C for 60 minutes under nitrogen bubbling. Stirring was performed using a mechanical stirrer at 150 rpm. The following stirring was performed at the same rotation speed using the same stirring device. After stirring was completed, the copper particles were filtered out by vacuum filtration using a Kiriyama funnel with 5C filter paper, and then washed twice with 150 g of water on the Kiriyama funnel. The washed copper particles were added to 250 g of a 40% by mass aqueous solution of diethylenetriamine, and the mixture was heated and stirred at 60° C. for 1 hour while bubbling with nitrogen. After stopping the stirring and leaving it to stand for 5 minutes, about 200 g of the supernatant was removed. Next, 200 g of isopropanol was added to the precipitate as a washing solvent, and the mixture was stirred at 30° C. for 3 minutes. After stopping the stirring and leaving it to stand for 5 minutes, about 200 g of the supernatant was removed. Then, 250 g of a 2% by mass lauric acid isopropanol solution was added, and the mixture was stirred at 30° C. for 30 minutes. After stirring, the copper particles were filtered under reduced pressure using a Kiriyama funnel with 5C filter paper, and the resulting copper particles were dried under reduced pressure at 25°C for 3 hours to obtain surface-coated copper particles (1) (copper particles (1)).

[0090] [Synthesis Example 2] (Copper particles (2): Production of surface-coated copper particles (2)) Copper particles a were replaced with copper particles b [Mitsui Mining & Smelting Co., Ltd., "1400YP"; particle size (D50) 6 μm, BET specific surface area 0.60 m 2 Surface-coated copper particles (2) (copper particles (2)) were obtained in the same manner as in Synthesis Example 2, except that the powder was changed to [0.1g / g, shape: plate-like].

[0091] The components used in the examples and comparative examples described below (see Tables 4, 5 and 6) are as follows: (1) (A) Conductive composition ·Copper particles (1): Synthesis example 1 ·Copper particles (2): Synthesis example 2 Silver particles: Mitsui Mining & Smelting Co., Ltd., spherical silver particles, particle size (D50) 2.0 μm, BET specific surface area 0.4 m 2 / g Silver-coated copper particles: Mitsui Mining & Smelting Co., Ltd., spherical silver-coated copper particles, particle size (D50) 0.9 μm, BET specific surface area 1.1 m 2 / g, copper content 95% by mass

[0092] (2) (B) Binder component SBN-70D: Asahi Kasei Corporation, Duranate SBN-70D, pyrazole-blocked polyisocyanate, solid content 70% by mass, solvent: dipropylene glycol monomethyl ether jER828: Mitsubishi Chemical Corporation, jER (registered trademark) 828, bisphenol A epoxy resin Epogosey PT: Yokkaichi Synthetic Co., Ltd., Epogosey PT, General G, Polytetramethylene glycol diglycidyl ether

[0093] (3) (C) Polyol having a boiling point of 300°C or less and 2 to 6 hydroxyl groups C-1 to C-9, hydroquinone: Table 1, 2 (4) (C') and related substances of (C) ·C'-1~C'-3: Tables 1 and 2 In Table 1, C'-2 is PEG#600 manufactured by NOF Corporation, weight average molecular weight Mw600.

[0094] (5) (D) Amine compounds having an ethylenediamine skeleton ·D-1~D-7:Table 3 In Table 3, D-7 is Epomin (registered trademark) SP-003 manufactured by Nippon Shokubai Co., Ltd., with a weight average molecular weight Mw of 300. (6) (D') Amine compounds other than (D) ·D'-1~D'-3:Table 3

[0095] (7) Antioxidants Schiff bases: N,N'-bis(salicylidene)ethylenediamine (8) Hardener Rikacid MH-700: Manufactured by New Japan Chemical Co., Ltd., Rikacid MH-700, liquid alicyclic acid anhydride (a mixture of 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride)

[0096] [Table 1]

[0097] [Table 2]

[0098] [Table 3]

[0099] Example 1 (Production of conductive composition) As component (A), 7.0 g of the surface-coated copper particles (copper particles (1)) obtained in Synthesis Example 1 and 3.0 g of the surface-coated copper particles (copper particles (2)) obtained in Synthesis Example 2 were used; as component (B), 0.41 g of pyrazole-blocked polyisocyanate [Duranate SBN-70D, manufactured by Asahi Kasei Corporation, solid content 70 mass%, solvent: dipropylene glycol monomethyl ether] was used; as component (C), 0.51 g of triethylene glycol (hydroxyl groups: 2 to 100%) was used; 0.39 g of polyol C-1) having 6 carbon atoms, 0.75 g of hydroquinone, 0.08 g of 1-(2-aminoethyl)piperazine as component (D), 0.02 g of polyethyleneimine [Nippon Shokubai Co., Ltd., Epomin SP-003, weight average molecular weight 300], 0.1 g of lauric acid as a lubricant, and 0.008 g of N,N'-bis(salicylidene)ethylenediamine (a Schiff base) as an antioxidant were mixed. The mixture was then mixed at room temperature for 60 seconds at 2000 rpm using a planetary mixer [ARV-310, Thinky Corporation] for primary mixing. The mixture was then mixed five times using a three-roll mill [EXAKT-M80S, Nagase Screen Printing Laboratory Co., Ltd.] at room temperature with a roll spacing of 5 μm. The kneaded product obtained in the secondary kneading was stirred and degassed for 90 seconds at 1000 rpm under vacuum conditions at room temperature using a planetary mixer [ARV-310, manufactured by Thinky Corporation] to produce a conductive composition. The blending ratio of the conductive composition is shown in Table 4.

[0100] [Evaluation of electrical conductivity (volume resistivity)] (Formation of hardened film) The obtained conductive composition was applied to a glass slide using a metal mask (pattern: width × length × thickness = 1.0 mm × 30 mm × 50 μm). The glass slide to which the conductive composition was applied was heated on a hot plate at 280°C under nitrogen for 15 minutes to produce a cured film. (Method for measuring volume resistivity) The thickness of the obtained cured film was measured at three points using a stylus film thickness meter (DektakXT, manufactured by Bruker) and the average value was calculated. The volume resistivity of the cured film, converted to a film thickness of 30 μm, was measured by pressing the measurement probe of a low resistivity meter (Loresta-GP MCP-T610, manufactured by Nitto Seiko Analytech Co., Ltd.) against the obtained cured film. The volume resistivity of the cured film was calculated using the following formula from the average film thickness and volume resistivity measured by the above method. Volume resistivity (Ω·cm) = Measured volume resistivity (Ω·cm) × {Average film thickness (μm) / 30 (μm)} The electrical conductivity of the cured film was evaluated according to the following evaluation criteria: The smaller the volume resistivity value, the easier it is for current to flow through the cured film, indicating superior electrical conductivity. ◎: The volume resistivity is less than 20 μΩ·cm. Good: The volume resistivity is 20 μΩ·cm or more and less than 40 μΩ·cm. ×: The volume resistivity is 40 μΩ·cm or more.

[0101] [Evaluation of adhesion to substrate] The obtained conductive composition was applied to the entire surface of a ferrite substrate using a metal mask (pattern: width × length × thickness = 5.0 mm × 5.0 mm × 50 μm). The ferrite substrate with the coated conductive composition was heated on a hot plate in a nitrogen gas atmosphere at 280°C for 15 minutes to produce a cured film on the ferrite substrate. An epoxy resin-attached stud pin (P / N: 901106, manufactured by Phototechnica Corporation) was placed in the center of the cured film and heated on a hot plate in a nitrogen gas atmosphere at 150°C for 60 minutes to produce an evaluation sample with the stud pin attached to the cured film. The stud pin portion of the obtained evaluation sample was pinched and placed in a tensile tester (EZ-S, manufactured by Shimadzu Corporation). The stud pin was pulled upward, and the strength (N) was measured when the stud pin peeled off from the ferrite substrate. The adhesion to the substrate was evaluated according to the following evaluation criteria. A higher peel strength value indicates better adhesion to the substrate. A peel strength value of 10 N or more can be evaluated as having high adhesion. ◎: Peel strength is 30N or more. Good: Peel strength is 20N or more and less than 30N. △: Peel strength value is 10N or more and less than 20N. ×: The peel strength value is less than 10N.

[0102] [Solder wettability evaluation] A cured film was prepared on a ferrite substrate using the obtained conductive composition in the same manner as in "Evaluation of adhesion to substrate." Approximately 1.0 mg of flux (ESR-250T4, manufactured by Senju Metal Co., Ltd.) was applied to the entire surface of the obtained cured film. The substrate was immersed, with the cured film side facing up, in a 250°C solder bath (HS-302, manufactured by Hozan Corporation, solder composition: Sn 96.5% / Ag 3% / Cu 0.5%) for 2 seconds. After 2 seconds, the substrate was removed from the solder bath and allowed to cool at room temperature. After cooling, the area of ​​solder covering the cured film surface was visually confirmed. The heat resistance of the cured film was evaluated according to the following evaluation criteria: A larger solder-covered area indicates higher solder wettability. ◎: Solder coverage is 90% or more. Good: Solder coverage area is 70% or more but less than 90% △: Solder coverage is 50% or more but less than 70% ×: The solder covered area is less than 50%.

[0103] [Evaluation of heat resistance (high-temperature solder wettability) of cured film] An evaluation board was prepared using the same method as in the "solder wettability evaluation." The board was immersed with the cured film side up in a 400°C solder bath (HS-302, manufactured by Hozan Corporation, solder composition: Sn 96.5% / Ag 3% / Cu 0.5%) for 2 seconds. After 2 seconds, it was removed from the solder bath and allowed to cool at room temperature. After cooling, the area of ​​solder covering the cured film surface was visually confirmed. The heat resistance of the cured film was evaluated according to the following evaluation criteria: The larger the solder-covered area, the higher the heat resistance of the cured film. ◎: Solder coverage area is 90% or more. Good: Solder coverage is 70% or more and less than 90%. △: Solder coverage area is 50% or more but less than 70%. ×: The solder covered area is less than 50%.

[0104] [Examples 2 to 20, Comparative Examples 1 to 11] Conductive compositions were produced and evaluated in the same manner as in Example 1, except that the blending ratios of each component were as shown in Tables 4, 5, and 6. The evaluation results are shown in Tables 4, 5, and 6.

[0105] [Table 4]

[0106] [Table 5]

[0107] [Table 6]

[0108] In Examples 1 to 22, the volume resistivity was 38 μΩ·cm or less, indicating good conductivity, and the peel strength was 13 N or more, confirming high adhesion to the substrate. Furthermore, when the cured film was immersed in a solder bath at 250°C, the solder coverage area was 70% or more, and in particular, in Examples 3, 4, 14, and 18, the solder coverage area was 90% or more, confirming high solder wettability of the cured film. Furthermore, even when the cured film was immersed in solder at 400°C, the solder coverage area was 50% or more, confirming high heat resistance of the cured film.

[0109] In Comparative Example 1, the boiling point of component (C) was higher than 300°C, so the wettability to solder at a high temperature of 400°C was low, and the heat resistance of the cured film was low. In Comparative Example 2, the boiling point of component (C) was higher than 300°C, so the heat resistance of the cured film was low and the adhesion to the substrate was also insufficient. In Comparative Example 3, the boiling point of component (C) was higher than 300°C, the heat resistance of the cured film was low, and the carbon chain in the side chain of component (C) was long, so the adhesion to the substrate was also low. In Comparative Example 4, component (D) did not have an ethylenediamine skeleton, and therefore the wettability and peel strength to solder at a high temperature of 400°C were low, and the heat resistance and adhesion to the substrate of the cured film were low. In Comparative Example 5, the component (D) did not have an ethylenediamine skeleton, and therefore the adhesion to the substrate was reduced. In Comparative Example 6, component (D) did not have an ethylenediamine skeleton, nor did it have a primary or secondary amine moiety. This not only resulted in a significant increase in volume resistivity and a deterioration in conductivity, but also in solder wettability regardless of the solder temperature, resulting in low solder wettability and heat resistance of the cured film. In Comparative Example 7, the component (C) was not contained, and therefore the electrical conductivity and heat resistance of the cured film were reduced. In Comparative Example 8, the content of component (C) was 18.5% by mass, which was greater than 15% by mass, and therefore the adhesion to the substrate was reduced. Comparative Example 9 did not contain component (D), and therefore the adhesion to the substrate was reduced. In Comparative Example 10, the content of component (D) was 5.2% by mass, which was higher than 5.0% by mass, so the peel strength and wettability to solder at a high temperature of 400°C were low, and the adhesion to the substrate and the heat resistance of the cured film were reduced. Comparative Example 11 had good electrical conductivity and adhesion, but because the content of component (B) was 7.9 mass%, which was higher than 7.0 mass%, the solder did not wet the film regardless of the solder temperature, and the solder wettability and heat resistance of the cured film were low.

[0110] As described above, a conductive composition containing the specified components (A) to (D) in the specified ratios can form a cured film with good conductivity even when heated at low temperature for a short time. Furthermore, it can be seen that a cured film using this conductive composition has high adhesion to the substrate, good solder wettability with solder at 250°C and 400°C, and high heat resistance. Therefore, it can be seen that this conductive composition is suitable for use as an electrode material or conductive adhesive for power electronics used in high-temperature operating environments.

Claims

1. (A) Conductive particles 73-92.4% by mass (B) Binder component: 1 to 7.0 mass% (C) Polyol having a boiling point of 300°C or less and 2 to 6 hydroxyl groups: 6.5 to 15% by mass (D) Amine compound having an ethylenediamine skeleton: 0.1 to 5.0% by mass 1. A conductive composition comprising:

2. The conductive composition according to claim 1, wherein the polyol (C) having a boiling point of 300°C or less and 2 to 6 hydroxyl groups is a combination of the following (C1) and (C2): (C1) At least one selected from the group consisting of a polyol represented by the following formula (1), a polyol represented by the following formula (2), and glycerin: (C2) At least one polyol selected from the group consisting of polyols represented by the following formula (3): 【Chemistry 1】 (In formula (1), -(OR １ )- represents at least one oxyalkylene group having 2 to 3 carbon atoms, and when two or more oxyalkylene groups are present, -(O-R １ The addition form of n- may be either block or random, and n represents the average number of moles of oxyalkylene groups added and is a number from 1 to 3. 【Chemistry 2】 (In formula (2), R ２ is a hydrogen atom, a methyl group, an ethyl group, or a hydroxymethyl group. 【Transformation 3】 (In formula (3), R ３ , R ４ are each independently either a hydrogen atom or a methyl group.

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