Conductive composition

Abstract

To provide a conductive composition which can form a cured film with suppressed bubble formation during screen printing and having superior initial conductivity and stability of conductivity under conditions of high temperature and high humidity.SOLUTION: A conductive composition comprises (A) 40 to 90 mass% of conductive particles, (B) 1 to 30 mass% of a resol-type phenol resin, (C) 0.05 to 5 mass% of an amine compound having an ethylenediamine skeleton, (D) 0.01 to 5 mass% of polybutadiene, and (E) 1 to 30 mass% of a terpenoid alcohol.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrically conductive composition, and in particular to an electrically conductive composition that is applied to screen printing.

[0002] BACKGROUND ART In the field of electronic materials, conductive compositions have been used for applications such as through-hole bonding materials for printed circuit boards, materials for forming lead wiring for touch panels, and signal materials for membrane switches.

[0003] Conductive compositions typically contain metal particles such as silver or copper as the main component, along with a binder resin and a dispersant. A pattern is drawn on the conductive composition using screen printing or other methods, and the conductive composition is cured by applying light or heat to form a conductive cured product (conductive cured film). However, when the conductive composition is screen-printed, differences in the wettability and viscosity of the conductive composition can cause bubbles to form in the printed cured film, leading to problems such as oxidation of the metal particles, increased surface irregularities in the cured film, and the generation of voids.

[0004] Furthermore, conductive cured films are intended for long-term use, and therefore require not only good initial conductivity but also stable conductivity. In recent years, demand for electronic materials has been increasing in Southeast Asia, a region experiencing rapid economic growth. However, because silver, which is a metal particle used in conductive compositions, is prone to migration, and copper, which is prone to oxidation, there are concerns about deterioration of conductivity due to migration and oxidation in the high-temperature, high-humidity environments of Southeast Asia. Therefore, there is a growing demand for stable conductivity under high-temperature, high-humidity conditions.

[0005] For example, Patent Document 1 discloses a conductive composition containing water, conductive particles, a styrene / (meth)acrylic copolymer, an anionic surfactant, and an antifoaming agent. This conductive composition can suppress bubbles during printing by using the antifoaming agent. However, because silver is used as the conductive particles, there are concerns about the low stability of conductivity under high temperature and high humidity conditions.

[0006] Furthermore, Patent Document 2 discloses a conductive composition comprising copper powder, a thermosetting resin, a fatty acid, an amine or amine compound, and a wetting and dispersing agent having a decomposition temperature of 250°C or less. The wetting and dispersing agent improves the conductivity stability of this conductive composition under high temperature and high humidity conditions. However, the conductive composition has a high viscosity, which raises concerns about the generation of bubbles during screen printing. Furthermore, under more severe conditions, the wetting and dispersing agent is likely to decompose, reducing the stability of the conductivity under high temperature and high humidity conditions. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-72914 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-141332 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in view of the above-mentioned conventional techniques, and an object of the present invention is to provide a conductive composition that can suppress the generation of bubbles during screen printing and can form a cured film that has excellent initial conductivity and excellent stability of conductivity under high temperature and high humidity conditions. [Means for solving the problem]

[0009] As a result of various investigations aimed at solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved simultaneously by combining conductive particles, a resol-type phenolic resin, an amine compound having an ethylenediamine skeleton, polybutadiene, and a terpenoid alcohol in a specific ratio range, thereby achieving the present invention. That is, the present invention relates to the following [1] and [2].

[0010] [1] (A) Conductive particles 40~90% by mass (B) Resol-type phenolic resin 1 to 30% by mass (C) Amine compound having an ethylenediamine skeleton: 0.05 to 5% by mass (D) Polybutadiene 0.01 to 5% by mass (E) Terpenoid alcohol 1 to 30% by mass 1. A conductive composition comprising:

[0011] [2] The conductive composition according to [1] above, wherein the (C) amine compound having an ethylenediamine skeleton is at least one selected from the group consisting of an amine represented by the following formula (1), an amine represented by the following formula (2), and a polyethyleneimine having a molecular weight of 100 to 10,000.

[0012] [ka]

[0013] (In formula (1), the degree of polymerization n is a number from 1 to 5.)

[0014] [ka]

[0015] (In formula (2), R 1 is a hydrocarbon group having 1 to 3 carbon atoms, and R 2 is a hydrocarbon group having 1 to 5 carbon atoms. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a conductive composition that can suppress the generation of bubbles during screen printing and form a cured film that has excellent initial conductivity and excellent stability of conductivity under high temperature and high humidity conditions. DETAILED DESCRIPTION OF THE INVENTION

[0017] In this specification, numerical ranges defined using the symbol "to" are inclusive of both the upper and lower limits of the symbol. For example, "2 to 5" means 2 or more and 5 or less. Furthermore, when a concentration or amount is specified, any higher concentration or amount can be associated with any lower concentration or amount. For example, the descriptions "2 to 10% by mass" and "preferably 4 to 8% by mass" also encompass the descriptions "2 to 4% by mass," "2 to 8% by mass," "4 to 10% by mass," and "8 to 10% by mass."

[0018] The conductive composition according to an embodiment of the present invention contains (A) 40 to 90% by mass of conductive particles, (B) 1 to 30% by mass of a resol-type phenolic resin, (C) 0.05 to 5% by mass of an amine compound having an ethylenediamine skeleton, (D) 0.01 to 5% by mass of polybutadiene, and (E) 1 to 30% by mass of a terpenoid alcohol. Each component contained in the conductive composition will be described below.

[0019] <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.

[0020] 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 (3).

[0021] [ka]

[0022] (In formula (3), m is an integer of 0 to 3, n is an integer of 0 to 2, and when n=0, m is an integer of 0 to 3, and when n=1 or n=2, m is an integer of 1 to 3.)

[0023] 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 (3) 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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).

[0029] 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.).

[0030] 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.

[0031] The content of component (A) is 40 to 90% by mass. The lower limit of the content of component (A) is preferably 50% by mass, more preferably 55% by mass. If the content of component (A) is less than 40% by mass, it becomes difficult for the conductive particles to come into contact with each other during curing, and a cured film exhibiting excellent conductivity may not be obtained. Furthermore, from the viewpoint of conductivity, the upper limit of the content of component (A) is preferably 80% by mass.

[0032] <(B) Resol-type phenolic resin> Component (B) used in an embodiment of the present invention is a resol-type phenolic resin. Resole-type phenolic resins are obtained by reacting a compound containing a phenolic hydroxyl group with an aldehyde such as formaldehyde in the presence of an alkaline catalyst. Resol-type phenolic resins are also commercially available. Examples of phenolic compounds that serve as raw materials for resol-type phenolic resins include phenol, cresol, p-tert-butylphenol, 2,3-xylenol, bisphenol A, and bisphenol F. From the viewpoints of curability and conductivity, phenol is preferred. Examples of formaldehydes include formaldehyde, paraformaldehyde, and trioxane, and these may be used alone or in combination. Of these, those with a weight-average molecular weight of 500 to 5,000 are preferred from the viewpoint of conductivity. Examples of commercially available resol phenolic resins include RESITOP (registered trademark) PL-5208, PL-2211, and PL-6220 (Gunei Chemical Industry Co., Ltd.).

[0033] The content of component (B) is 1 to 30% by mass. The content of component (B) is preferably 5 to 25% by mass, more preferably 5 to 20% by mass. When the content of component (B) is 1% by mass or more, the adhesion between copper particles is good and the conductive composition has sufficient fluidity when printed. When the content of component (B) is 30% by mass or less, the reducing property of (B) makes it easy to obtain a cured copper film with a low resistance value. When a solvent component is included, the content is calculated based on the solid content.

[0034] <Component (C) Amine Compound Having an Ethylenediamine Skeleton> Component (C) used in the embodiment of the present invention is an amine compound having an ethylenediamine skeleton. Among the amine compounds having an ethylenediamine skeleton, at least one selected from the group consisting of amines represented by the following formula (1), amines represented by the following formula (2), and polyethyleneimines having a weight-average molecular weight of 100 to 10,000 is more preferred.

[0035] [ka]

[0036] (In formula (1), the degree of polymerization n is a number from 1 to 5.)

[0037] [ka]

[0038] (In formula (2), R 1 is a hydrocarbon group having 1 to 3 carbon atoms, and R 2 is a hydrocarbon group having 1 to 5 carbon atoms.

[0039] The amine represented by formula (1) is not particularly limited as long as it has a linear ethylenediamine skeleton and the degree of polymerization n is a number from 1 to 5, but from the viewpoint of electrical conductivity, those in which n is 1 to 3 are preferred.

[0040] Specific examples of the amine represented by formula (1) include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and hexaethyleneheptamine. These may be used alone or in combination of two or more.

[0041] The amine represented by formula (2) is not particularly limited as long as it has a cyclic ethylenediamine skeleton represented by formula (2), and R 1 is a hydrocarbon group having 1 to 3 carbon atoms, and R 2 However, a hydrocarbon group having 1 to 5 carbon atoms can be appropriately selected and used. From the viewpoint of achieving better conductivity and better suppressing bleeding at the edges of the cured film, R 1 is a hydrocarbon group having 1 to 2 carbon atoms, and R 2 R is more preferably a hydrocarbon group having 1 to 2 carbon atoms. 1 The hydrocarbon group constituting R is preferably a divalent saturated aliphatic hydrocarbon group, and when it has 3 carbon atoms, its structure may be linear or branched, but linear is preferred. 2 The hydrocarbon group constituting the formula (I) is also preferably a divalent saturated aliphatic hydrocarbon group, and when it has 3 to 5 carbon atoms, the structure may be either linear or branched, but linear is preferred.

[0042] Specific examples of the amine represented by formula (2) include 2-aminoethylimidazolidine, aminomethylpiperazine, 2-aminoethylpiperazine, 3-aminopropylpiperazine, 4-aminobutylpiperazine, 5-aminopentylpiperazine, and 2-aminoethylhomopiperazine.

[0043] The amine represented by formula (2) may be used alone or in combination of two or more kinds.

[0044] Polyethyleneimine is a polymer having -(CH2-CH2-NH)- as a repeating unit, and is an amine compound having an ethylenediamine skeleton. The structure of polyethyleneimine may be linear or branched, but from the viewpoints of better electrical conductivity and reduced surface irregularities of the cured film, those having branches containing primary, secondary, and tertiary amines are preferred. The weight-average molecular weight of polyethyleneimine is preferably 100 to 10,000. Of these, those having a weight-average molecular weight of 100 to 1,000 tend to be preferred from the viewpoint of reduced surface irregularities of the cured film. From the viewpoint of electrical conductivity, those having a weight-average molecular weight of 100 to 5,000 tend to be preferred.

[0045] 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.

[0046] The polyethyleneimine may be used alone or in combination of two or more kinds.

[0047] The component (C) is preferably selected from one or more of the amines represented by the formula (1), the amines represented by the formula (2), and the specified polyethyleneimines described above. However, by combining amine compounds with different properties, better conductivity can be imparted. When two or more amine compounds having an ethylenediamine skeleton are combined, for example, two or more selected from the amines represented by the formula (1), the amines represented by the formula (2), and polyethyleneimines are preferred. For example, it is preferred to use a combination of the amines represented by the formula (1) and / or the formula (2) with polyethyleneimines, and the mixing ratio is preferably 50 to 80% by mass of the amines represented by the formula (1) and / or the formula (2), and 20 to 50% by mass of the polyethyleneimines. Specifically, the component (C) may be selected from the amines represented by the formula (1) having a degree of polymerization n of 1 to 2 and / or the hydrocarbon group R having 1 to 2 carbon atoms. 1 and R2 and the like, for example, a combination of an amine represented by formula (2) with a polyethyleneimine having a weight-average molecular weight of 100 to 1,000 and a branched structure. In particular, a combination of diethylenetriamine and / or 2-aminoethylpiperazine with a polyethyleneimine having a weight-average molecular weight of 300 and a branched structure (for example, Epomin (registered trademark) SP-003, manufactured by Nippon Shokubai Co., Ltd.) is preferred.

[0048] The content of component (C) is 0.05 to 5 mass%, preferably 0.3 to 3.5 mass%. If the content of component (C) is less than 0.05 mass% or more than 5 mass%, the volume resistivity of the cured film obtained using the conductive composition may increase.

[0049] <Component (D) Polybutadiene> Component (D) used in an embodiment of the present invention is polybutadiene. Among polybutadienes, those with a weight-average molecular weight of 1,000 to 50,000 are preferred. From the viewpoints of conductivity and viscosity, a weight-average molecular weight of 5,000 to 30,000 is preferred, and a weight-average molecular weight of 10,000 to 20,000 is even more preferred. Furthermore, the SP value is preferably 7.0 to 12.0. From the viewpoints of defoaming properties and stability of conductivity under high temperature and humidity, an SP value of 8.0 to 10.0 is preferred, an SP value of 8.5 to 9.5 is preferred, and an SP value of 8.5 to 8.8 is even more preferred. The SP value is an abbreviation for Solubility Parameter and is a measure of solubility. A larger SP value indicates higher polarity, and a smaller SP value indicates lower polarity. The SP value can be calculated by the method proposed by Fedors et al. (Fedors method). Specifically, it can be determined by referring to "POLYMER ENGINEERING AND SCIENCE, February 1974, Vol. 14, No. 2, ROBEAT F. FEDORS. (pp. 147-154)."

[0050] Specific examples of polybutadiene include FLORENE AC-1190, FLORENE AC-1190HF, FLORENE AC-2000, and FLORENE AC-2000HF manufactured by Kyoeisha Chemical Co., Ltd.

[0051] The content of component (D) is 0.01 to 5% by mass, preferably 0.01 to 3% by mass, and more preferably 0.01 to 1.0% by mass. If the content of component (D) is less than 0.01% by mass, sufficient defoaming properties and stable conductivity under high temperature and high humidity conditions cannot be obtained. If the content is more than 5% by mass, the volume resistivity of the cured film obtained using the conductive composition may increase. Note that when a solvent component is included, the content is calculated based on the solid content.

[0052] <Component (E) Terpenoid Alcohol> Component (E) used in an embodiment of the present invention is a terpenoid alcohol. Terpenoid alcohols are compounds in which a hydroxy group has been introduced into a linear or cyclic terpene in which a plurality of isoprene units (having 5 carbon atoms) are bonded, and the number of isoprene units contained in the compound is not particularly limited as long as it is 2 or more (having 10 carbon atoms). The skeletal structure of carbon atoms contained in the terpenoid alcohol is not particularly limited, and may be a linear structure or may contain a cyclic structure, and may or may not have an unsaturated bond. The number of cyclic structures may be one (monocyclic) or two or more (polycyclic). Of the terpenoid alcohols used as component (E), monoterpenoid alcohols consisting of two isoprene units are preferred. Of these, monocyclic monoterpenoid alcohols are more preferred from the viewpoints of compatibility with the conductive composition and viscosity, and monocyclic monoterpenoid alcohols having an unsaturated bond are particularly preferred.

[0053] Specific examples of terpenoid alcohols include α-terpineol, β-terpineol, γ-terpineol, and dihydroterpineol.

[0054] Component (E) can be used alone or in combination of two or more types. When two or more types are used in combination, the mixing ratio is not particularly limited.

[0055] The content of component (E) is 1 to 30% by mass, preferably 5 to 25% by mass, and more preferably 10 to 25% by mass. If the content of component (E) is less than 1% by mass, printing defects such as blurring may occur during screen printing. If the content is more than 30% by mass, the volume resistivity of the cured film obtained using the conductive composition may increase.

[0056] <Other ingredients> In addition to the above-described components (A) to (E), the conductive composition according to the embodiment may contain various additives, such as antioxidants, lubricants, dispersants, curing agents, curing accelerators, viscosity modifiers, antifoaming agents, and solvents, as needed, provided that the effects of the 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 50% by mass, and preferably up to 30% by mass.

[0057] (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-phenylenediamine. Examples of antioxidants include, but are not limited to, aromatic diamines such as amine, 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.

[0058] 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.

[0059] When the conductive composition according to the embodiment contains an antioxidant, the content of the antioxidant is preferably 0.01 to 10 mass %, and more preferably 0.1 to 8 mass %.

[0060] (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; and polyethers such as polyethylene glycol, polypropylene glycol, and modified versions thereof. One type of lubricant 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.

[0061] 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 magnesium stearate and lauric acid.

[0062] When the conductive composition according to the embodiment contains a lubricant, the content of the lubricant is preferably 0.01% to 10% by mass, more preferably 0.1 to 5% by mass, and even more preferably 0.2 to 3% by mass.

[0063] (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.

[0064] Among these dispersants, it is preferable to use one or more selected from sarcosine compounds, and it is more preferable to use oleoyl sarcosine.

[0065] When the conductive composition according to the embodiment contains a dispersant, the content of the dispersant is preferably 0.01 to 10 mass %, more preferably 0.2 to 5 mass %, and even more preferably 0.3 to 3 mass %.

[0066] The conductive composition described above can be obtained by mixing and kneading the aforementioned components according to a standard method. The form of the conductive composition can be determined appropriately depending on the application, etc., and a liquid form is preferable, especially when using a high-mesh screen (high-mesh screen). Furthermore, a conductive cured film (metal film) can be obtained by heating a coating film formed using the conductive composition according to a standard method. The coating film can be formed using a known coating machine, and conductive circuits can be easily patterned using various coating machines such as die coaters, inkjet printers, screen printers, gravure offset printers, and pad printers. Screen printers, in particular, are capable of printing thick films of 10 μm or more and are suitable as coating machines when highly conductive circuits are required. When applied by screen printing, the viscosity at 25°C is preferably 500 mPa·s or more and 300 Pa·s or less. A liquid and homogeneous state at 25°C is preferred.

[0067] The conductive composition described above has the effect of suppressing air bubbles on the surface of the printed film, even when the printed material is formed by screen printing, and the resulting cured film has good conductivity. It is believed that the inclusion of components (A) to (E) within the specified ranges suppresses air bubbles and unevenness caused by air bubbles in the cured film, thereby providing a cured film with excellent conductivity and excellent conductivity stability under high temperature and high humidity. The presence or absence of air bubbles in the conductive composition printed film, the conductivity of the cured film obtained by curing the printed film, and the conductivity stability of the cured film under high temperature and high humidity can be evaluated, for example, using the method described in the Examples section below. [Example]

[0068] Hereinafter, the embodiments of the present invention will be described more specifically with reference to examples and comparative examples.

[0069] [Synthesis Example 1] (Production of Copper Particles (1): 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 [Mitsui Mining & Smelting Co., Ltd. "1400YP"; particle size (D50) 6 μm, BET specific surface area 0.60 m] 2 50 g of [1 / g, shape: plate-like] was added to an aqueous ammonium chloride solution and stirred at 30°C for 60 minutes under nitrogen bubbling. Stirring was carried out using a mechanical stirrer at a rotation speed of 150 rpm. Subsequent stirring was carried out using the same stirring device at the same rotation speed. 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)).

[0070] [Synthesis Example 2] (Copper particles (2): Production of surface-coated copper particles (2)) Copper particles a were replaced with copper particles b ["1200Y" manufactured by Mitsui Mining & Smelting Co., Ltd.; particle size (D50) 2 μm, BET specific surface area 0.40 m 2 / g, shape: spherical], surface-coated copper particles (2) (copper particles (2)) were obtained in the same manner as in Synthesis Example 1.

[0071] Example 1 32.5 g of the surface-coated copper particles (copper particles (1)) obtained in Synthesis Example 1 as component (A), 7.5 g of a resol-type phenolic resin (Gun-ei Chemical Industry Co., Ltd., Resitop PL-5208) as component (B), 0.4 g of diethylenetriamine as component (C), 0.05 g of polybutadiene (Kyoeisha Chemical Co., Ltd., Florene AC-1190HF) as component (D), 7.05 g of a terpenoid alcohol (Nippon Terpene Chemical Co., Ltd., Terpineol C) as component (E), 0.5 g of lauric acid as a lubricant, and 2.0 g of hydroquinone as an antioxidant were mixed. Next, the mixture was subjected to primary kneading using a planetary mixer (ARV-310, Thinky Corporation) at room temperature at 2000 rpm for 60 seconds. Next, a secondary mixing was performed using a three-roll mill [EXAKT-M80S, manufactured by Nagase Screen Printing Laboratory Co., Ltd.] by passing the mixture five times at room temperature with a roll distance of 5 μm. The mixture obtained in the secondary mixing was then mixed and degassed using a planetary mixer [ARV-310, manufactured by Thinky Corporation] at room temperature under vacuum conditions at a rotation speed of 1000 rpm for 90 seconds to produce a conductive composition. The compounding ratio of the conductive composition is shown in Table 1.

[0072] [Evaluation of electrical conductivity (volume resistivity)] (Formation of hardened film) The resulting conductive composition was printed onto a PET film using a screen printer (MT-320T, manufactured by Micro-Tec Corporation) and a screen plate to obtain a screen-printed product. The printed pattern was a thin line measuring 2.0 mm wide x 150 mm long x 20 μm thick. The PET film on which the conductive composition had been printed was heated in a convection oven at 150°C for 15 minutes to obtain a cured film of the screen-printed product. (Method for evaluating volume resistivity) The thickness of the resulting cured film was measured at three points using a micro-profiler (ET4000A, manufactured by Kosaka Laboratory Co., Ltd.) and the average value was calculated. The resistance value was measured by pressing the measurement probe of a digital multimeter (87V, manufactured by Fluke) against both ends (150 mm long) of the resulting cured film. The volume resistivity of the cured film was calculated using the following formula from the average thickness and resistance values ​​measured by the above method. Volume resistivity (μΩ·cm) = {Average film thickness (μm) × Resistance value (Ω) × Width 2.0 (mm) × 100 / Length 150 (mm)}

[0073] The 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 conductivity. Volume resistivities of ⊚, ◯, and △ were considered to be acceptable. ◎: The volume resistivity is less than 30 μΩ·cm. Good: The volume resistivity is 30 μΩ·cm or more and less than 70 μΩ·cm. △: Volume resistivity value is 70 μΩ·cm or more and less than 100 μΩ·cm. ×: The volume resistivity is 100 μΩ·cm or more.

[0074] The conductivity evaluated in this manner is defined as the initial conductivity.

[0075] [Evaluation of conductivity stability (rate of change in resistivity) under high temperature and humidity conditions] The cured film with the fine line pattern used in the above conductivity evaluation was used as a measurement sample for the high-temperature, high-humidity test. The measurement sample was placed in a pressure cooker tester (PC-304R8, manufactured by Hirayama Manufacturing Co., Ltd.) and stored at 105°C and 95% RH for 150 hours, after which the measurement sample was removed.

[0076] The resistance value after the high-temperature, high-humidity test was evaluated using the following method. The resistance value was measured by pressing the measuring probes of a digital multimeter (87V, manufactured by Fluke) against both ends (150 mm long) of the cured film, and the rate of change in resistance value was calculated using the following formula. The resistance value before the test was the value obtained in the "Evaluation of conductivity" section above. Resistance change rate (%) = (resistance after test) / (resistance before test) x 100 - 100

[0077] The conductivity stability of the cured film under high temperature and high humidity conditions was evaluated according to the following evaluation criteria. The smaller the rate of change in resistance value, the smaller the change in resistance value, indicating excellent conductivity stability under high temperature and high humidity conditions. A rate of change in resistance value of ◎, ○, or △ was considered to be acceptable. ◎: The rate of change in resistance value is less than 10%. Good: The resistance change rate is 10% or more and less than 30%. △: The rate of change in resistance is 30% or more and less than 50%. ×: The rate of change in resistance value is 50% or more.

[0078] [Evaluation of defoaming properties (presence or absence of bubbles on the surface of the printed film)] A screen print (printed film) was obtained in the same manner as in "Evaluation of Electrical Conductivity (Volume Resistivity)." Air bubbles on the surface of the printed film were visually checked.

[0079] The defoaming ability was evaluated according to the following evaluation criteria. If bubbles were found on the surface of the printed film, it indicates that the surface of the cured film would become uneven and that voids would be present in the cured film as traces of bubbles, leading to a decrease in conductivity. A rating of ◯ for the presence or absence of bubbles on the surface of the printed film was considered to be acceptable. ◯: No bubbles were generated on the surface of the printed film. ×: Bubbles occurred on the surface of the printed film.

[0080] [Examples 2 to 21, Comparative Examples 1 to 5] Conductive compositions were produced in the same manner as in Example 1, except that the blending ratios were as shown in Tables 1 to 3. Using the obtained conductive compositions, various evaluations were carried out in the same manner as in Example 1. The results are shown in Tables 1 to 3.

[0081] Components (A), (B), (C), (D), (D'), (E), and (E') in Tables 1 to 3 are as follows: (A) Conductive composition ·Copper particles (1): Synthesis example 1 ·Copper particles (2): Synthesis example 2 (B) Resol-type phenolic resin PL-5208: Gun-ei Chemical Industry Co., Ltd., Resitop PL-5208, solid content 60% by mass (C) Amine compound having an ethylenediamine skeleton Diethylenetriamine (amine represented by formula (1)) 2-aminoethylpiperazine (amine represented by formula (2)) Epomin SP-003: Nippon Shokubai Co., Ltd., Epomin (registered trademark) SP-003, weight average molecular weight 300, branched polyethyleneimine (D) Polybutadiene D-1 Kyoeisha Chemical Co., Ltd., FLOLENE AC-1190HF, weight average molecular weight 12,000, SP value 8.8, solid content 30% by mass D-2 Kyoeisha Chemical Co., Ltd., FLOLENE AC-2000HF, weight average molecular weight 12,000, SP value 8.9, solid content 35% by mass (D') Polymers other than polybutadiene D'-1 Kyoeisha Chemical Co., Ltd., FLOLENE AC-326F, polyvinyl ether, weight average molecular weight 25,000, SP value 8.5, solid content 98% by mass D'-2 Kyoeisha Chemical Co., Ltd., FLOLENE AC-2200HF, polyolefin, weight average molecular weight 5,000, SP value 8.5, solid content 50% by mass D'-3 BYK, BYK1799, polysiloxane (E) Terpenoid alcohol E-1 Terpineol C, a mixture of α-, β-, and γ-terpineol isomers, manufactured by Nippon Terpene Chemical Co., Ltd. E-2 Manufactured by Nippon Terpene Chemical Co., Ltd., a mixture of dihydroterpineol, p-menthan-1-ol and p-menthan-8-ol, with no unsaturated bonds (E') Alcohols other than terpenoid alcohols E'-1 Diethylene glycol monoethyl ether

[0082] [Table 1]

[0083] [Table 2]

[0084] [Table 3]

[0085] In Examples 1 to 21, the volume resistivity was a maximum of 95 μΩ cm, indicating good conductivity (initial conductivity), the rate of change in resistance was a maximum of 48%, indicating good stability of conductivity under high temperature and high humidity conditions, and no bubbles were generated on the surface of the printed film, indicating good defoaming properties.

[0086] In Comparative Example 1, in which a conductive composition was prepared without blending components (D) and (D'), the volume resistivity was 70 μΩ·cm, which was excellent in conductivity (initial conductivity). However, the rate of change in resistance was 100%, and copper oxidation occurred under high temperature and high humidity conditions, indicating insufficient stability. In Comparative Examples 2 to 4, in which conductive compositions were prepared using polymers other than component (D), the volume resistivity was extremely high, the rate of change in resistance was large, or bubbles were observed on the surface of the printed film. None of the comparative examples achieved practical levels of conductivity, stability of conductivity under high temperature and high humidity, and defoaming properties. In Comparative Example 5, in which a conductive composition was prepared using an alcohol other than component (E), the volume resistivity deteriorated, the rate of change in resistance was large, and bubbles were observed on the surface of the printed film, resulting in poor evaluations in all categories.

[0087] As described above, it is clear that a conductive composition containing the predetermined components (A) to (E) in a predetermined ratio is less likely to generate bubbles on the surface and inside of a printed film formed by, for example, screen printing, and the cured printed film has good conductivity (initial conductivity) and excellent conductivity stability under high temperature and high humidity. Therefore, it is clear that the conductive composition is suitable for electronic materials, particularly materials for forming printed films by screen printing or the like.

Claims

1. (A) Conductive particles 40-90% by mass (B) Resol-type phenolic resin: 1 to 30% by mass (C) Amine compound having an ethylenediamine skeleton: 0.05 to 5% by mass (D) Polybutadiene 0.01 to 5% by mass (E) Terpenoid alcohol 1 to 30% by mass 1. A conductive composition comprising:

2. 2. The conductive composition according to claim 1, wherein the amine compound (C) having an ethylenediamine skeleton is at least one selected from the group consisting of an amine represented by the following formula (1), an amine represented by the following formula (2), and a polyethyleneimine having a weight-average molecular weight of 100 to 10,000: 【Chemical 1】 (In formula (1), the degree of polymerization n is a number from 1 to 5.) 【Chemistry 2】 (In formula (2), R １ is a hydrocarbon group having 1 to 3 carbon atoms, and R ２ is a hydrocarbon group having 1 to 5 carbon atoms.

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