conductive components

Abstract

To provide a conductive composition which is good in both continuous printability in screen printing and cold-heat cycle impact resistance of a cured film formed on a substrate, and is usable as a wiring formation material excellent in conductivity.SOLUTION: A conductive composition contains (a) polyethylene glycol having a weight average molecular weight of 200-2,000, (b) at least one compound selected from a predetermined polyether ester having a weight average molecular weight of 200-1,000 and a predetermined adipic acid ester having a weight average molecular weight of 200-3,000, (c) conductive particles and (d) a binder resin, wherein with respect to 100 mass% of the total of components (a) to (d) based on a solid content, a percentage content of the component (a) is 0.1-5 mass%, a percentage content of the component (b) is 0.01-5 mass%, a percentage content of the component (c) is 60-99 mass%, and a percentage content of the component (d) is 0.5-30 mass%.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, in light of the Sustainable Development Goals (SDGs), there has been a shift in wiring formation methods for electronic components from the conventional wet etching method, which uses large amounts of chemicals, to printing methods using screen printers and the like.

[0003] Among these, the development of wiring formation technology using a screen printer, a general-purpose printing method, is being actively pursued, and the development of conductive paste compositions suitable for screen printing as materials for this method is underway.

[0004] One advantage of forming wiring using screen printing is that it allows continuous printing on film substrates using the roll-to-roll method. Therefore, with the aim of improving productivity, the formation of wiring using screen printing has been widely investigated. However, to ensure stable continuous printing using conductive paste, various properties of the conductive paste, such as viscosity and drying speed, must be optimized to match the screen printing conditions.

[0005] A characteristic required of conductive pastes that is specific to the roll-to-roll method is that the cured film obtained by heating and curing the conductive paste during the roll winding process must be free of cracks, breaks, etc. For example, Patent Document 1 discloses a silver paste composition that can improve the uniformity of printed patterns even when produced at a high viscosity, and can obtain a cured film with improved adhesion to the substrate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special table number 2013-507750 Summary of the Invention [Problem to be solved by the invention]

[0007] However, although the silver paste composition disclosed in Patent Document 1 has excellent initial adhesion to a substrate, it has poor adaptability to deformation of the substrate that occurs when the substrate, on which a cured film has been formed, is stored at low or high temperatures. Therefore, when a laminate of a film and a cured film of the conductive paste is subjected to a thermal shock test in which the laminate is repeatedly stored at low and high temperatures, peeling or cracking of the cured film may occur.

[0008] The problem to be solved by the present invention is to provide a conductive composition that has good continuous printability in screen printing and good resistance to cold and thermal shock of a cured film formed on a substrate, and that can be used as a wiring-forming material with excellent conductivity. [Means for solving the problem]

[0009] As a result of extensive investigations into solving the above problems, the inventors discovered that a conductive composition capable of solving the above problems can be provided by compounding specific components in addition to conductive particles and a binder resin, and thus completed the present invention.

[0010] That is, the present invention relates to a conductive composition containing (a) polyethylene glycol having a weight-average molecular weight of 200 to 2000, (b) at least one compound selected from polyether esters having a weight-average molecular weight of 200 to 1000 and adipic acid esters having a weight-average molecular weight of 200 to 3000, (c) conductive particles, and (d) a binder resin, wherein the content of component (a) is 0.1 to 5 mass%, the content of component (b) is 0.01 to 5 mass%, the content of component (c) is 60 to 99 mass%, and the content of component (d) is 0.5 to 30 mass%, relative to 100 mass% of the total of components (a) to (d), on a solids basis. [Effects of the Invention]

[0011] The conductive composition of the present invention can be used as a wiring-forming material that has good continuous printability in screen printing, and a cured film formed on a film substrate using the conductive composition has high adaptability to deformation of the substrate at low and high temperatures. When subjected to a thermal shock test in which the composition is repeatedly stored at low and high temperatures, the cured film is less likely to peel or crack, resulting in an increase in resistance (i.e., the cured film has good thermal shock resistance), and a wiring pattern that exhibits excellent conductivity can be formed. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described.

[0013] In this specification, numerical ranges defined using the symbol "to" are inclusive of the numerical values ​​at both ends (upper and lower limits) of the symbol "to." For example, "2 to 5" means 2 or more and 5 or less.

[0014] 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."

[0015] A conductive composition according to an embodiment of the present invention contains (a) polyethylene glycol having a weight-average molecular weight of 200 to 2000, (b) at least one compound selected from polyether esters having a weight-average molecular weight of 200 to 1000 and adipic acid esters having a weight-average molecular weight of 200 to 3000, (c) conductive particles, and (d) a binder resin. Based on the solid content, the total content of components (a) to (d) is 100% by mass, with component (a) accounting for 0.1 to 5% by mass, component (b) for 0.01 to 5% by mass, component (c) for 60 to 99% by mass, and component (d) for 0.5 to 30% by mass. Each component will be described below.

[0016] [Component (a): Polyethylene glycol] Component (a) is polyethylene glycol, and its weight-average molecular weight is 200 to 2000, and from the viewpoint of maintaining wettability, it is preferably 400 to 1500, more preferably 500 to 800. These may be used alone or in combination of two or more.

[0017] The weight-average molecular weight of polyethylene glycol can be measured by a method of calculating the weight-average molecular weight based on the hydroxyl value measured in accordance with JIS K1557.

[0018] The content of component (a) is 0.1 to 5 mass% and preferably 0.2 to 3 mass% based on the solid content, relative to 100 mass% of the total of components (a) to (d). If the content of component (a) is too low, the film thickness may be prone to change as the number of successive screen printings increases. If the content of component (a) is too high, the conductivity of the conductive composition may decrease.

[0019] [Component (b)] The content of component (b) is 0.01 to 5 mass% and preferably 0.1 to 3 mass% based on the total mass of components (a) to (d), based on the solid content. If the content of component (b) is too low, when a cured film of the conductive composition is subjected to a thermal shock test, the cured film may be prone to peeling or cracking, resulting in an increase in resistance. If the content of component (b) is too high, the conductivity of the conductive composition may decrease.

[0020] Component (b) is at least one compound selected from a predetermined polyether ester and a predetermined adipic acid ester. The predetermined polyether ester may be a compound having a weight average molecular weight of 200 to 1000, preferably a compound having a weight average molecular weight of 400 to 900.

[0021] The polyetheresters can be produced according to known methods, and examples of commercially available products include Adekacizer RS-700 (weight average molecular weight: 550), Adekacizer RS-735 (weight average molecular weight: 850), Adekacizer RS-966 (weight average molecular weight: 470), and Adekacizer RS-1000 (weight average molecular weight: 550) (all manufactured by ADEKA Corporation).

[0022] The predetermined adipic acid ester may be a compound having a weight-average molecular weight of 200 to 3000, preferably a compound having a weight-average molecular weight of 1000 to 3000, and more preferably a compound having a weight-average molecular weight of 1500 to 2500.

[0023] The above-mentioned adipic acid esters can be produced according to known methods, but are also available as commercial products. Examples of commercially available products include Adeka Cizer PN-150 (weight average molecular weight 1000), Adeka Cizer PN-170 (weight average molecular weight 1100), Adeka Cizer P-200 (weight average molecular weight 2000), Adeka Cizer PN-350 (weight average molecular weight 3000) (all manufactured by ADEKA Corporation), D620 (weight average molecular weight 800), D623 (weight average molecular weight 1800), D643 (weight average molecular weight 1800), D645 (weight average molecular weight 2200), D633 (weight average molecular weight 1800), D620N (weight average molecular weight 800), D623N (weight average molecular weight 1800), D643D (weight average molecular weight 1800), D640A (weight average molecular weight 1200), and D671A (weight average molecular weight 650) (all manufactured by J-Plus Corporation).

[0024] [Component (c): Conductive particles] Component (c) is a conductive particle, and inorganic conductive particles such as copper particles can be used. The copper particles may consist of copper alone, 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.

[0025] 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 (1).

[0026] [ka]

[0027] (In formula (1), m is an integer of 0 to 3, n is an integer of 0 to 2, and when n=0, m is any of 0 to 3, and when n=1 or n=2, m is any of 1 to 3.)

[0028] 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 such as the amine compound represented by the above formula (1) are further coated with an aliphatic monocarboxylic acid.

[0029] As a result, the surfaces of the conductive particles are coated with a first coating layer formed from an amine compound and a second coating layer formed from an aliphatic monocarboxylic acid. Preferably, the first coating layer is formed on the surfaces of the conductive particles, and the second coating layer is formed on the first coating layer.

[0030] 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.

[0031] 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.

[0032] As the aliphatic monocarboxylic acid, one selected from the above compounds may be used alone, or two or more may be used in combination.

[0033] 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, for example, an ammonium chloride aqueous solution, and then the washed conductive particles are added to a solution of an amine compound and heated as needed, and a method in which conductive particles are added to a solution containing, for example, ammonium chloride and an amine compound and heated as needed.

[0034] 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.

[0035] 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 (c) can be printed well by various printing methods such as inkjet printing, screen printing, etc. 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.

[0036] The average particle size (D50) of the conductive particles can be measured using a laser diffraction / scattering particle size distribution measuring device (Microtrac MT3000II, manufactured by Microtrac Bell Co., Ltd.).

[0037] The BET specific surface area of ​​the conductive particles is 0.05 to 400 m 2 / g, and 0.1 to 200m 2 / g is more preferred.

[0038] The BET specific surface area of ​​the conductive particles can be measured by the BET single-point method using a specific surface area measuring device (Monosorb, manufactured by Yuasa Ionics Co., Ltd.).

[0039] 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.

[0040] The content of component (c) is 60 to 99 mass% based on the solid content, relative to 100 mass% of the total of components (a) to (d). The lower limit of the content of component (c) is preferably 70 mass%, more preferably 80 mass%.

[0041] [Component (d): Binder resin] Component (d) is a binder resin, which acts as a binder in the conductive composition.

[0042] As component (d), known binder resins used in conductive compositions, etc. can be used, and examples thereof include thermosetting resins and photocurable resins that are cured by heating or light irradiation, and thermoplastic resins.

[0043] Examples of thermosetting resins include epoxy resins, melamine resins, phenolic resins, silicone resins, polyurethane resins, unsaturated polyester resins, vinyl ester resins, polyvinylphenol resins, xylene resins, acrylic resins, oxetane resins, and diallyl phthalate resins. Examples of photocurable resins include acrylic resins, imide resins, urethane resins, and oxetane resins. Examples of thermoplastic resins include polyolefin resins such as polyamide, polyethylene terephthalate, and polyethylene; and acrylonitrile-butadiene-styrene copolymer resins.

[0044] As the binder resin of component (d), one selected from these resins can be used alone, or two or more can be used in combination.

[0045] In addition, from the viewpoint of curability, it is preferable to use one or more thermosetting resins selected from epoxy resins, phenol resins, and polyvinylphenol resins, and it is more preferable to use one or two selected from epoxy resins and phenol resins.

[0046] The content of component (d) is 0.5 to 30 mass% and preferably 1 to 20 mass% based on the total of components (a) to (d), 100 mass%, on a solids basis. If the content of component (d) is too low, it may be difficult to achieve sufficient fluidity when printing using the conductive composition. If the content of component (d) is too high, it may be difficult for the conductive particles of component (c) in the conductive composition to come into contact with each other, making it difficult to obtain a cured film that exhibits excellent conductivity.

[0047] In addition, the blending ratio of component (d) is preferably adjusted depending on the type of component (b) contained in the conductive composition, in order to improve the adhesion between the cured film obtained from the conductive composition and the substrate.

[0048] When a specific polyether ester is used as component (b), the blending ratio of component (d) binder resin is preferably 5 to 30 mass %, more preferably 5 to 20 mass %, based on the solid content, relative to 100 mass % of the total of components (a) to (d).

[0049] When a predetermined adipic acid ester is used as component (b), the blending ratio of component (d) binder resin is preferably 0.5 to 5 mass %, more preferably 1 to 5 mass %, based on the solid content, relative to 100 mass % of the total of components (a) to (d).

[0050] [Other ingredients] In addition to the above components (a) to (d), the conductive composition may contain various additives, such as solvents, antioxidants, lubricants, leveling agents, dispersants, curing agents, curing accelerators, viscosity modifiers, foaming agents, and antioxidants, 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 total amount may be more than 0 parts by mass and up to 60 parts by mass, preferably up to 30 parts by mass, per 100 parts by mass of the total content of (a) to (d).

[0051] (solvent) The conductive composition may contain a solvent for the purposes of improving the coating properties and adjusting the viscosity.

[0052] Examples of the solvent include ether alcohols such as ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, propylene glycol diacetate, dipropylene glycol monomethyl ether, and ethylene glycol monobutyl ether acetate; non-ether alcohols such as propylene glycol and 1,4-butanediol; esters such as 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.

[0053] Among these solvents, it is preferable to use one or more selected from the above-mentioned ether-based alcohols, esters, and terpenes, and it is more preferable to use one or more selected from the above-mentioned ether-based alcohols and terpenes.

[0054] The type of solvent is not limited to the above, and depending on the application, one selected from various solvents may be used alone or two or more may be mixed and used. When two or more types are mixed, the mixing ratio is not particularly limited.

[0055] When the conductive composition contains a solvent, the content of the solvent is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, per 100 parts by mass of the total content of components (a) to (d).

[0056] (antioxidant) The conductive composition may contain an antioxidant to maintain the performance of each component during storage. Examples of the antioxidant 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, and 1,2-phenylenediamine. Examples of aromatic diamines include diamine, 1,3-phenylenediamine, 1,4-phenylenediamine, 2,5-dimethyl-1,4-phenylenediamine, 2,3,5,6-tetramethyl-1,4-phenylenediamine, N,N-dimethyl-1,4-phenylenediamine, N,N,N'N'-tetramethyl-1,4-phenylenediamine, and N,N'-diphenyl-1,4-phenylenediamine.

[0057] Among these antioxidants, it is preferable to use one or more selected from the group consisting of 2,2-bipyridyl, which is a nitrogen-containing heterocyclic compound, N,N'-bis(salicylidene)ethylenediamine and N,N'-bis(salicylidene)-1,2-propanediamine, which are Schiff bases, and 1,2-phenylenediamine, 1,3-phenylenediamine, and 1,4-phenylenediamine, which are aromatic diamines.

[0058] The type of antioxidant is not limited to the above, and depending on the application, one selected from various solvents may be used alone or two or more may be mixed and used. When two or more types are mixed, the mixing ratio is not particularly limited.

[0059] When the conductive composition contains an antioxidant, the content of the antioxidant is preferably 0.01 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the total content of components (a) to (d).

[0060] (lubricant) A lubricant may be added to the conductive composition as appropriate to adjust the dispersibility of the conductive particles of component (c) in the conductive composition. The type of lubricant and its mixing ratio are not particularly limited, and one type may be used alone or two or more types may be mixed depending on the application.

[0061] Examples of types of lubricants include fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid; fatty acid metal salts formed from metals such as sodium, potassium, barium, magnesium, calcium, aluminum, iron, cobalt, manganese, zinc, and tin and the above-mentioned fatty acids; 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; polysiloxanes such as silicone oil; and fluorine compounds such as fluorine-based oils.

[0062] Among these lubricants, it is preferable to use one or more selected from fatty acids and fatty acid metal salts, and it is more preferable to use at least one selected from lauric acid and magnesium stearate.

[0063] When the conductive composition contains a lubricant, the content of the lubricant is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the total content of components (a) to (d).

[0064] (dispersant) A dispersant may be added to the conductive composition as appropriate to adjust the dispersibility of the conductive particles of component (c) in the conductive composition. The type of dispersant and its mixing ratio are not particularly limited, and one type may be used alone or two or more types may be mixed depending on the application.

[0065] Examples of types of dispersants include sarcosine compounds such as lauroyl sarcosine, myristoyl sarcosine, palmitoyl sarcosine, stearoyl sarcosine, and oleoyl sarcosine; polymeric amine compounds such as Filanol PA-075F, Filanol PA-085C, Filanol PA-107P, Esreem AD-3172M, Esreem AD-374M, and Esreem AD-508E (all manufactured by NOF Corporation, and "Esreem" is a registered trademark); and polymeric polycarboxylic acid compounds such as Marialim AKM-0531, Marialim AFB-1521, Marialim AAB-0851, Marialim AWS-0851, Marialim SC-0505K, Marialim SC-1015F, and Marialim SC-0708A (all manufactured by NOF Corporation).

[0066] Among these dispersants, it is preferable to use one or more sarcosines, and it is more preferable to use at least one selected from lauroyl sarcosine and oleoyl sarcosine.

[0067] When the conductive composition contains a dispersant, the content of the dispersant is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass, per 100 parts by mass of the total content of components (a) to (d). [Example]

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

[0069] The components used in the examples and comparative examples are shown below. The physical properties of each component were measured by the methods described herein.

[0070] [Component (a): Polyethylene glycol] PEG200 (polyethylene glycol with a weight-average molecular weight of 200) PEG600 (polyethylene glycol with a weight-average molecular weight of 600) PEG2000 (polyethylene glycol with a weight-average molecular weight of 2000)

[0071] [Component (a'): Polyethylene glycol with a weight-average molecular weight exceeding 2000] PEG4000 (polyethylene glycol with a weight-average molecular weight of 4000)

[0072] [Component (a'): Polytetramethylene glycol] PTMG2000 (polytetramethylene glycol with an average molecular weight of 2000)

[0073] [Component (b)] (b1): Adeka Cizer RS-1000 (polyether ester, weight average molecular weight 550, manufactured by ADEKA Corporation) (b2): Adeka Cizer P-200 (adipic acid polyester, weight average molecular weight 2000, manufactured by ADEKA Corporation)

[0074] [Component (b')] (b3): ​​Bis(2-ethylhexyl) phthalate

[0075] [Component (c): Conductive particles] Copper particles (1): spherical copper particles [surface-coated copper particles (1), the manufacturing method is shown below.] Copper particles (2): Plate-shaped copper particles [surface-coated copper particles (2), the manufacturing method of which is shown below.]

[0076] [Component (d): Binder resin] Phenolic resin Resole phenolic resin [PL-5208, manufactured by Gun-ei Chemical Industry Co., Ltd., solid content 60.0% by mass, solvent: diethylene glycol monoethyl ether] Epoxy resin Bisphenol F epoxy resin [jER (registered trademark)-806, manufactured by Mitsubishi Chemical Corporation, solid content 100% by mass]

[0077] The following materials were used as other components:

[0078] (antioxidant) N,N'-bis(salicylidene)ethylenediamine (lubricant) Lauric acid (dispersant) Oleoyl Sarcosine (solvent) Terpineol Ethylene glycol monobutyl ether acetate Isobornylcyclohexanol

[0079] [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 [ / g, shape: spherical] 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. Stirring was carried out using the same stirring device at the same rotation speed below. After stirring was completed, the copper particles were filtered out by vacuum filtration using a Kiriyama funnel with 5C filter paper, and then the copper particles were washed twice with 150 g of water on the Kiriyama funnel.

[0080] 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.

[0081] 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.

[0082] 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)).

[0083] [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 1, except that the powder was changed to [0.1g / g, shape: plate-like].

[0084] Example 1 (Production of conductive composition)

[0085] 0.5 g of PEG200 (component (a)), 0.5 g of (b1) Adeka Cizer RS-1000 (component (b)), 65 g of surface-coated copper particles (copper particles (1)) and 28.0 g of surface-coated copper particles (copper particles (2)) (component (c)), 10.0 g (6.0 g as solids) of resol-type phenolic resin (component (d)) [PL-5208, Gun-ei Chemical Industry Co., Ltd., solids content 60% by mass, solvent: diethylene glycol monoethyl ether], 0.5 g of N,N'-bis(salicylidene)ethylenediamine (Salen), and 2.0 g of lauric acid were mixed. Next, the mixture was subjected to primary mixing at room temperature for 60 seconds at 1500 rpm using a planetary mixer [ARV-310, Thinky Corporation].

[0086] Next, a three-roll mill [EXAKT-M80S, manufactured by Nagase Screen Printing Laboratory Co., Ltd.] was used to perform secondary mixing by passing the mixture five times at room temperature with a roll distance of 5 μm. 4.0 g of terpineol (Ter) was added to the mixture obtained in the secondary mixing, and the mixture was degassed and kneaded for 90 seconds at 1000 rpm using a planetary mixer at room temperature under vacuum conditions to produce a conductive composition. The blending ratios of each component of the conductive composition are shown in Table 1.

[0087] <Conductivity evaluation> (Formation of hardened film) The obtained conductive composition was applied to a polyimide film using a metal mask to form a pattern with a width x length x thickness of 1.0 mm x 30 mm x 50 μm. The polyimide film with the conductive composition applied was heated in a convection oven at 170°C for 30 minutes to produce a cured film.

[0088] (Resistance evaluation method) The electrical conductivity of the cured film obtained by the above method was evaluated by measuring the resistance value as follows: A measuring probe was pressed against both ends of the formed pattern, and the resistance value of the cured film was measured using a digital multimeter [PC7000, manufactured by Sanwa Electric Meter Co., Ltd.], and the resistance was evaluated according to the following criteria.

[0089] The lower the resistance value of the cured film, the easier it is for current to flow, indicating superior conductivity. ◎: Resistance value is less than 1.0 Ω. ○: Resistance value is 1.0Ω or more and less than 10.0Ω. △: Resistance value is 10.0Ω or more and less than 50.0Ω. ×: Resistance value is 50.0Ω or more.

[0090] <Evaluation of continuous printing> (Method for evaluating the rate of change in film thickness before and after continuous printing) The obtained conductive composition was printed continuously onto 50 polyethylene terephthalate (PET) films using a screen printing machine [MT-320T, manufactured by Micro-Tec Co., Ltd.].

[0091] The resulting prints were heated in a convection oven at 120°C for 30 minutes to produce cured films. The thicknesses of the cured films on the first and 50th sheets were measured using a stylus film thickness measuring device (DEKTAK XT, manufactured by Bruker), and the film thickness change rate was calculated using the following formula (I) and evaluated according to the following criteria.

[0092] In this test, the closer the film thickness change rate is to 100%, the longer the wettability of the conductive composition is maintained during continuous printing, indicating that wiring patterns can be printed stably.

[0093]

number

[0094] ◎: The rate of change in film thickness is 90% or more and 100% or less. ◯: The rate of change in film thickness is 70% or more and less than 90%. △: The film thickness change rate is 50% or more and less than 70%. ×: The rate of change in film thickness is less than 50%.

[0095] <Evaluation of thermal shock resistance> (Method for evaluating thermal shock resistance) The cured film obtained in the same manner as the cured film used in the conductivity evaluation above was used as a measurement sample for the thermal shock test. The measurement sample was placed in a small thermal shock apparatus (TSE-11, manufactured by Espec Corporation) and subjected to a total of 1,000 cycles, each cycle consisting of holding at -40°C for 1 minute, then raising the temperature to 100°C and holding for 2 minutes.

[0096] After the test, the resistance value was measured by pressing the measuring probes of a digital multimeter [PC7000, manufactured by Sanwa Electric Meter Co., Ltd.] against both ends of the cured film, and the rate of change in resistance value was calculated using the following formula (II) and evaluated according to the following criteria.

[0097] In this test, the closer the resistance change rate is to 100%, the better the thermal shock resistance of the cured film is.

[0098] Resistance change rate (%) = (resistance after test) / (resistance before test) × 100 (II)

[0099] ◎: The rate of change in resistance value is less than 110%. ○: The rate of change in resistance value is 110% or more and less than 150%. △: The resistance change rate is 150% or more and less than 200%. ×: The rate of change in resistance value is 200% or more.

[0100] The evaluation results are shown in Table 1.

[0101] [Examples 2 to 8, Comparative Examples 1 to 5] A conductive composition was produced and a cured film was formed in the same manner as in Example 1, except that the blending ratio of each component was as shown in Table 1. Regarding the formation of the cured film, heating was performed in an air atmosphere in Examples 2 to 4 and Comparative Examples 1 and 5, and heating was performed in a nitrogen atmosphere in Examples 5 to 8 and Comparative Examples 2 to 4.

[0102] Furthermore, the electrical conductivity, continuous printability, and thermal shock resistance of each cured film were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2. The content of the phenolic resin in Tables 1 and 2 is the amount converted to solid content.

[0103] [Table 1]

[0104] [Table 2]

[0105] The following can be seen from Tables 1 and 2. In Examples 1 to 8, the resistance of the cured film was less than 10.0 Ω, the rate of change in resistance before and after the thermal shock test was less than 150%, and the rate of change in film thickness before and after continuous printing was 70% or more. In contrast, in Comparative Example 1, in which the conductive composition was prepared without blending component (a), the rate of change in resistance before and after the thermal shock test was less than 150%, but the resistance of the cured film was high at 10.0 Ω or more, and the rate of change in film thickness before and after continuous printing was low at less than 50%. Furthermore, in Comparative Example 2, in which the conductive composition was prepared without blending component (b), the resistance of the cured film was less than 1.0 Ω, the rate of change in film thickness before and after continuous printing was less than 90%, but the rate of change in resistance before and after the thermal shock test was high at 200% or more. In Comparative Example 3, in which a conductive composition was prepared using PEG4000 instead of component (a), the rate of change in resistance before and after the thermal shock test was less than 150%, but the resistance of the cured film was high at 10.0Ω or more, and the rate of change in film thickness before and after continuous printing was low at less than 70%. In Comparative Example 4, in which a conductive composition was prepared using PTMG2000 instead of component (a), the rate of change in resistance before and after the thermal shock test was less than 150%, but the resistance of the cured film was high at 50.0Ω or more, and the rate of change in film thickness before and after continuous printing was low at less than 50%. In Comparative Example 5, in which a conductive composition was prepared using (b3) bis(2-ethylhexyl) phthalate instead of component (b), the resistance of the cured film was less than 10.0Ω, and the rate of change in film thickness before and after continuous printing was less than 90%, but the rate of change in resistance before and after the thermal shock test was high at 150% or more.

[0106] As described above, a conductive composition containing the specified components (a) to (d) in the specified ratio has good continuous printability, and when formed into a cured film, it also has good resistance to cold and heat shock, and is therefore suitable as a wiring-forming material with excellent conductivity.

Claims

[Claim 1] (a) polyethylene glycol having a weight average molecular weight of 200 to 2000; (b) at least one compound selected from polyether esters having a weight-average molecular weight of 200 to 1,000 and adipic acid esters having a weight-average molecular weight of 200 to 3,000; (c) conductive particles, and (d) containing a binder resin; A conductive composition, in which, based on the solid content, the content of component (a) is 0.1 to 5 mass%, the content of component (b) is 0.01 to 5 mass%, the content of component (c) is 60 to 99 mass%, and the content of component (d) is 0.5 to 30 mass%, relative to 100 mass% of the total of components (a) to (d).

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