Conductive composition

Abstract

To provide a conductive composition which is difficult to be changed in a line width of a wiring pattern and viscosity of a composition before and after restart of printing when printing is restarted after printing has been stopped for a constant time, and is excellent in printability and conductivity.SOLUTION: A conductive composition contains (a) 0.1-5 mass% of polyethylene glycol having an average molecular weight of 200-2,000, (b) 0.1-5 mass% of an aliphatic monocarboxylic acid having 8 to 18 carbon atoms, (c) 60-95 mass% of conductive particles, and (d) 1-30 mass% of a binder resin.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a conductive composition capable of maintaining a wet state for a long time when the composition before heating is allowed to stand, and having excellent printability and conductivity.

Background Art

[0002] In recent years, due to the increasing awareness of safety and environmental protection, there has been a demand to reduce the amount of chemical solutions that affect the human body and the environment. In the wiring formation method of electronic components as well, a replacement from the conventional wet etching method that uses a large amount of chemical solutions to a printing method that uses relatively less chemical solutions has been promoted. Among them, the development of wiring formation technology using a screen printing machine, which is a general-purpose printing method, has been actively carried out, and research and development of a conductive paste suitable for screen printing has been advanced as its material. The conductive paste is required to have various characteristics necessary for the development of the target product, such as its conductivity and adhesion to the substrate to be coated. Among them, printability is a particularly strongly required characteristic from the viewpoint of productivity, and a conductive paste with excellent printability is strongly demanded. For example, Patent Document 1 discloses a conductive paste that is excellent in fine line printability and has a difficult-to-change printed line width.

[0003] In wiring formation using screen printing, a conductive paste capable of continuously printing a wiring pattern with an equivalent line width for a long time is preferable in terms of productivity. However, in the actual manufacturing process, operations such as inspection of the printed pattern and inspection of the printing machine often require stopping the printing for a long time. For example, when screen printing is performed using the conductive paste of Patent Document 1, when the printing is resumed after stopping the printing for a certain period of time, clogging of the mesh caused by drying of the conductive paste on the screen plate, or thickening caused by volatilization of the solvent in the conductive paste may cause defects such as streaks in the wiring pattern after resuming printing, or a large change in the line width of the wiring pattern before and after resuming printing. That is, when screen printing using the above-described conductive paste is stopped for a certain period of time, depending on the length of the stop time, there is a risk of an increase in the resistance value due to variations in the line width of the wiring pattern and disconnection due to chipping.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem to be solved by the present invention is to provide a conductive composition that is excellent in printability and conductivity, and in which the line width of the wiring pattern and the viscosity of the composition are less likely to change before and after resuming printing when printing is resumed after being stopped for a certain period of time.

Means for Solving the Problems

[0006] As a result of repeated studies to solve the above problems, the present inventors have found that, in addition to conductive particles and a binder resin, by blending a specific component having excellent dispersion stability of the conductive particles and a specific component capable of maintaining the wet state of the composition for a long time, a conductive composition capable of solving the above problems can be provided, and the present invention has been completed.

[0007] That is, the present invention is a conductive composition containing (a) 0.1 to 5% by mass of polyethylene glycol having an average molecular weight of 200 to 2,000, (b) 0.1 to 5% by mass of an aliphatic monocarboxylic acid having 8 to 18 carbon atoms, (c) 60 to 95% by mass of conductive particles, and (d) 1 to 30% by mass of a binder resin.

Effects of the Invention

[0008] According to the conductive composition of the present invention, it can be used as a wiring forming material excellent in conductivity and printability. When printing is resumed after stopping printing for a certain period of time, the line width of the wiring pattern and the viscosity of the composition are less likely to change before and after resuming printing. Therefore, it is possible to print a wiring pattern with a low risk of increase in resistance value and disconnection.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described. In this specification, a numerical range defined using the symbol "~" includes the numerical values at both ends (upper limit and lower limit) of "~". For example, "2~5" represents 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, when there are descriptions of "2~10 mass%" and "preferably 4~8 mass%", descriptions of "2~4 mass%", "2~8 mass%", "4~10 mass%", and "8~10 mass%" are also included.

[0010] The conductive composition of the present invention contains (a) polyethylene glycol having an average molecular weight of 200 to 2,000, (b) an aliphatic monocarboxylic acid having 8 to 18 carbon atoms, (c) conductive particles, and (d) a binder resin. Hereinafter, each component will be described. Note that the content of each of the above components (a), (b), (c), and (d) is the ratio (mass%) with respect to the total value of the contents of components (a), (b), (c), and (d).

[0011] 〔Component (a): Polyethylene Glycol〕 Component (a) used in the present invention is polyethylene glycol, and its average molecular weight is 200 to 2,000. From the viewpoint of maintaining wettability, it is preferably 400 to 1,500, more preferably 500 to 800. These can be used alone or in combination of two or more.

[0012] The average molecular weight of polyethylene glycol can be measured by a method of calculating the average molecular weight based on the hydroxyl value measured in accordance with JIS K1557.

[0013] The content of component (a) is 0.1 to 5% by mass. From the viewpoint of maintaining wettability, it is preferably 0.2 to 5% by mass, more preferably 0.3 to 5% by mass, and still more preferably 0.5 to 5% by mass. On the other hand, from the viewpoint of the conductivity of the cured film, it is preferably 0.1 to 4% by mass, more preferably 0.1 to 3% by mass, and still more preferably 0.1 to 2% by mass. If the content of component (a) is too small, it becomes difficult to exhibit good wettability and difficult to maintain wettability for a long time, so the line width of the wiring pattern may easily change before and after resuming printing. On the other hand, if the content of component (a) is too large, the conductivity of the conductive composition may decrease.

[0014] [Component (b): aliphatic monocarboxylic acid] Component (b) used in the present invention is an aliphatic monocarboxylic acid having 8 to 18 carbon atoms. 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. One selected from the above compounds can be used alone, or two or more thereof can be used in combination.

[0015] Examples of the linear saturated aliphatic monocarboxylic acid having 8 to 18 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, and the like. Examples of the linear unsaturated aliphatic monocarboxylic acid having 8 to 18 carbon atoms include myristoleic acid, palmitoleic acid, petroselinic acid, oleic acid, and the like. Examples of the branched saturated aliphatic monocarboxylic acid having 8 to 18 carbon atoms include 2-ethylhexanoic acid and the like.

[0016] As component (b), from the viewpoint of conductivity, a linear saturated aliphatic monocarboxylic acid having 8 to 18 carbon atoms is preferred. Among them, a linear saturated aliphatic monocarboxylic acid having 12 to 18 carbon atoms is more preferred, a linear saturated aliphatic monocarboxylic acid having 12 to 14 carbon atoms is even more preferred, and a linear saturated aliphatic monocarboxylic acid having 12 carbon atoms is particularly preferred.

[0017] The content of component (b) is 0.1 to 5% by mass. From the viewpoint of suppressing viscosity change, it is preferably 0.3 to 5% by mass, more preferably 0.5 to 5% by mass, and even more preferably 1 to 5% by mass. On the other hand, from the viewpoint of the conductivity of the cured film, it is preferably 0.1 to 4% by mass, more preferably 0.1 to 3.5% by mass, and even more preferably 0.1 to 3% by mass. If the content of component (b) is too small, the viscosity of the conductive composition may easily increase. If the content of component (b) is too large, the conductivity of the conductive composition may decrease.

[0018] 〔Component (c): Conductive particles〕 Component (c) used in the present invention is conductive particles. For example, inorganic conductive particles such as copper particles can be used. 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% by mass or more. Further, the copper particles may have a shape in which a surface layer or protrusions are formed.

[0019] Commercially available conductive particles may be used as they are, but it is preferable to use surface-coated conductive particles having their surfaces coated for the purpose of improving oxidation resistance. Among them, it is preferable to use surface-coated conductive particles having their surfaces coated with an amine compound, and it is more preferable to use surface-coated conductive particles having their surfaces coated with an amine compound represented by the following formula (1).

[0020]

Chemical formula

[0021] (In formula (1), m is an integer from 0 to 3, and n is an integer from 0 to 2. When n = 0, m can be any of 0 to 3. When n = 1 or n = 2, m can be any of 1 to 3.)

[0022] The surface-coated conductive particles coated with an amine compound such as the amine compound represented by the above formula (1) are preferably surface-coated conductive particles further coated with an aliphatic monocarboxylic acid from the viewpoint of obtaining better oxidation resistance. Thereby, the surface of the conductive particles is coated with a first coating layer formed by the amine compound and a second coating layer formed by the aliphatic monocarboxylic acid. Preferably, the first coating layer is formed on the surface of the conductive particles, and the second coating layer is formed on the first coating layer.

[0023] As the aliphatic monocarboxylic acid forming the second coating layer, an aliphatic monocarboxylic acid having 8 to 20 carbon atoms is preferable. 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. Examples of the linear saturated aliphatic monocarboxylic acid having 8 to 20 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, arachidic acid, etc. Examples of the linear unsaturated aliphatic monocarboxylic acid having 8 to 20 carbon atoms include myristoleic acid, palmitoleic acid, petroselinic acid, oleic acid, etc. Examples of the branched saturated aliphatic monocarboxylic acid having 8 to 20 carbon atoms include 2-ethylhexanoic acid, etc. As the above aliphatic monocarboxylic acid, one selected from the above compounds can be used alone, or two or more thereof can be used in combination. From the dispersibility of the surface-coated conductive particles, it is preferable to use an aliphatic monocarboxylic acid having the same or similar structure and number of carbon atoms as the component (b) used.

[0024] The method for producing the surface-coated conductive particles is not particularly limited. As a method for obtaining surface-coated conductive particles having a surface coated with an amine compound, for example, there can be mentioned a method in which the conductive particles are washed with an aqueous ammonium chloride solution or the like, and then the washed conductive particles are added to a solution of the amine compound and heated if necessary. As a method for producing surface-coated conductive particles coated with a first coating layer formed of an amine compound and a second coating layer formed of an aliphatic monocarboxylic acid, for example, there can be mentioned a method in which surface-coated conductive particles having a surface coated with an amine compound are added to a solution of the aliphatic monocarboxylic acid. After adding to the solution of the aliphatic monocarboxylic acid, heating may be performed if necessary. Hereinafter, the description of the conductive particles shall include surface-coated conductive particles.

[0025] The average particle diameter (D50) of the conductive particles is not particularly limited, but in order to enable good printing of the conductive composition containing the conductive particles as component (c) by various printing methods such as inkjet printing and screen printing, it is preferable to control the average particle diameter (D50) of the conductive particles. Specifically, the average particle diameter (D50) of the conductive particles is preferably 5 nm to 20 μm, and more preferably 10 nm to 10 μm. The average particle diameter (D50) of the conductive particles can be measured by a laser diffraction / scattering particle size distribution measuring device ("Microtrac MT3000II" manufactured by Microtrac Bell Corporation).

[0026] Further, the BET specific surface area of the conductive particles is preferably 0.05 to 400 m 2 / g, and more preferably 0.1 to 200 m 2 / g. The BET specific surface area of the conductive particles can be measured by the BET one-point method using a specific surface area measuring device ("Monosorb" manufactured by Yuasa Ionics Co., Ltd.).

[0027] There are no particular restrictions on the shape and aspect ratio (the ratio of the major axis to the minor axis of the particles) of the conductive particles, and various shapes such as spherical, polyhedral, flat, plate-like, flake-like, sheet-like, rod-like, dendritic, and fiber-like can be used. The conductive particles can be used alone, one selected from those having different constituent components, average particle diameters, shapes, aspect ratios, etc., or two or more kinds can be used in combination. From the viewpoint of conductivity, it is preferable to use one kind of conductive particle selected from spherical, flat, plate-like, flake-like, sheet-like, and dendritic conductive particles or two or more kinds of conductive particles, and it is more preferable to use one kind of conductive particle selected from spherical, plate-like, and dendritic conductive particles or two kinds of conductive particles. Further, when two kinds of conductive particles are used in combination, it is preferable to use spherical conductive particles and plate-like conductive particles. When two kinds of spherical conductive particles and plate-like conductive particles are used in combination, the mass ratio, from the viewpoint of the conductivity of the cured film obtained by heat-curing the composition, is preferably 1:99 to 99:1 for spherical conductive particles: plate-like conductive particles, more preferably 5:95 to 95:5, and even more preferably 10:90 to 90:10.

[0028] The content of component (c) is 60 to 95% by mass. The lower limit of the content of component (c) is preferably 70% by mass, more preferably 80% by mass. Also, the upper limit of the content of component (c) is preferably 90% by mass.

[0029] [Component (d): Binder resin] Component (d) used in the present invention is a binder resin and is a component that acts as a binder in the conductive composition of the present invention. As component (d), known binder resins used in conductive pastes and the like can be used, and examples thereof include thermosetting resins, photocurable resins, and thermoplastic resins that are cured by heating or light irradiation.

[0030] Examples of the thermosetting resin include epoxy resin, melamine resin, phenol resin, silicone resin, polyurethane resin, unsaturated polyester resin, vinyl ester resin, polyvinylphenol resin, xylene resin, acrylic resin, oxetane resin, diallyl phthalate resin, and the like. Examples of the photocurable resin include acrylic resin, imide resin, urethane resin, and the like. Examples of the thermoplastic resin include polyolefin resins such as polyamide, polyethylene terephthalate, and polyethylene; acrylonitrile-butadiene-styrene copolymer resin, and the like. As the binder resin of component (d), one selected from these resins can be used alone, or two or more thereof can be used in combination.

[0031] Also, from the viewpoint of curability, it is preferable to use one or more selected from epoxy resin, phenol resin, and polyvinylphenol resin, which are thermosetting resins, and it is more preferable to use one or two selected from epoxy resin and phenol resin.

[0032] The content of component (d) is 1 to 30% by mass, preferably 3 to 25% by mass, more preferably 4 to 20% by mass, and still more preferably 5 to 15% by mass. If the content of component (d) is too small, it may be difficult to impart sufficient fluidity when printing using the conductive composition. If the content of component (d) is too large, it may be difficult for the conductive particles of component (c) in the conductive composition to come into contact with each other, and it may be difficult to obtain a cured film exhibiting excellent conductivity.

[0033] In addition, from the viewpoint of curability, when two kinds of epoxy resin and phenol resin are used in combination as component (d), the mass ratio of epoxy resin:phenol resin is preferably 1:99 to 99:1, more preferably 5:95 to 95:5, and still more preferably 10:90 to 90:10.

[0034] 〔Other Components〕 In addition to the above components (a) to (d), the conductive composition of the present invention may contain various additives such as solvents, lubricants, leveling agents, dispersants, curing agents, curing accelerators, plasticizers, viscosity modifiers, foaming agents, etc., as long as the effects of the present invention are not inhibited. Further, the conductive composition of the present invention may contain impurities that may be unavoidably mixed from raw material components, apparatuses in the manufacturing process, etc.

[0035] (Solvent) The conductive composition of the present invention may contain a solvent for the purpose of improving coatability and adjusting viscosity. Examples of the types of solvents 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, ethylene glycol monobutyl ether acetate; non-ether alcohols such as propylene glycol, 1,4-butanediol; esters such as cyclohexanol acetate, methyl methoxypropionate, ethyl ethoxypropionate, 1,6-hexanediol acetate; ketones such as isophorone, cyclohexanone; terpenes such as terpineol, dihydroterpineol, dihydroterpinyl acetate, isobornyl cyclohexanol; and other hydrocarbons such as octane, decane, dodecane, tetradecane, hexadecane, propylene carbonate, etc. Among these solvents, it is preferable to use one or more selected from the above ether alcohols, the above esters, and the above terpenes, and more preferably to use one or more selected from terpenes.

[0036] The type of solvent is not limited to the above, and depending on the application, one selected from various solvents can be used alone, or two or more can be mixed and used. The mixing ratio when mixing two or more is not particularly limited.

[0037] When the conductive composition of the present invention contains a solvent, the content of the solvent is preferably 2 to 20 parts by mass, more preferably 3 to 15 parts by mass, and still more preferably 4 to 10 parts by mass with respect to 100 parts by mass of the total content of components (a) to (d).

[0038] (Lubricant) For the purpose of adjusting the dispersibility of the conductive particles of component (c) in the composition, a lubricant can be appropriately added to the conductive composition used in the present invention. The type of the lubricant and its mixing ratio are not particularly limited, and one kind alone or two or more kinds can be mixed and used according to the application. Examples of the type of the lubricant 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 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; polyethers composed of polyethylene glycol, polypropylene glycol, and modified products thereof; polysiloxanes such as silicone oil; and fluorine compounds such as fluorine-based oils. Among these lubricants, it is preferable to use one or more selected from fatty acids and fatty acid metal salts, and more preferably to use magnesium stearate.

[0039] When the conductive composition of the present invention 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, and still more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the total content of components (a) to (d).

[0040] (Levelling agent) For the conductive composition used in the present invention, a leveling agent can be appropriately added for the purpose of adjusting the surface defects of the coating film obtained from the conductive composition. The type of the leveling agent and its mixing ratio are not particularly limited, and one type can be used alone or two or more types can be mixed and used according to the application. Examples of the type of the leveling agent include acrylic compounds such as BYK-354, BYK-355, BYK-356, BYK-350, BYK-381, BYK-394, BYK-399, BYK-3440, BYK-3441, BYK-358N, BYK-361N (manufactured by BYK-Chemie Japan Co., Ltd., "BYK" is a registered trademark); silicone compounds such as Polyflow KL-400X, Polyflow KL-400HF, Polyflow KL-401, Polyflow KL-402, Polyflow KL-403, Polyflow KL-404, Polyflow KL-406X (manufactured by Kyoeisha Chemical Co., Ltd.); fluorine compounds such as Megafac F410, Megafac F281, Megafac F477, Megafac F510, Megafac F552, Megafac F554, Megafac F556, Megafac F557, Megafac F558, Megafac F559, Megafac F560, Megafac F561, Megafac F563, Megafac F569 (manufactured by DIC Corporation, "Megafac" is a registered trademark). Among these leveling agents, it is preferable to use one or more selected from fluorine compounds, and more preferably to use Megafac F477.

[0041] When the conductive composition of the present invention contains a leveling agent, the content of the leveling agent is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and still more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the total content of components (a) to (d).

[0042] (Dispersant) In the conductive composition used in the present invention, a dispersant can be appropriately added for the purpose of adjusting the dispersibility of the conductive particles of component (c) in the composition. The type of the dispersant and its mixing ratio are not particularly limited, and one type can be used alone or two or more types can be mixed and used according to the application. Examples of the type of the dispersant include sarcosine compounds such as lauroyl sarcosine, myristoyl sarcosine, palmitoyl sarcosine, stearoyl sarcosine, and oleoyl sarcosine; polymer amine compounds such as Philanol PA-075F, Philanol PA-085C, Philanol PA-107P, Esleem AD-3172M, Esleem AD-374M, Esleem AD-508E (the above are manufactured by NOF Corporation, and "Esleem" is a registered trademark); and polymer polycarboxylic acid compounds such as Mariarim AKM-0531, Mariarim AFB-1521, Mariarim AAB-0851, Mariarim AWS-0851, Mariarim SC-0505K, Mariarim SC-1015F, and Mariarim SC-0708A (the above are manufactured by NOF Corporation). Among these dispersants, it is preferable to use one or more selected from sarcosine compounds, and more preferably to use oleoyl sarcosine.

[0043] When the conductive composition of the present invention 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, and still more preferably 0.3 to 3 parts by mass with respect to 100 parts by mass of the total content of components (a) to (d).

Examples

[0044] Hereinafter, production examples and evaluation methods of the conductive composition according to the present invention will be shown. Further, embodiments of the present invention will be described more specifically with reference to examples and comparative examples. Each component used in the examples and comparative examples is shown below. Note that the physical properties of each component are values measured by the methods described in this specification.

[0045] 〔Component (a): polyethylene glycol〕 PEG200 (Polyethylene glycol with an average molecular weight of 200) PEG600 (Polyethylene glycol with an average molecular weight of 600) PEG2000 (Polyethylene glycol with an average molecular weight of 2,000) PEG4000 (Polyethylene glycol with an average molecular weight of 4,000) Glycerin

[0046] [Component (b): Aliphatic monocarboxylic acid] 2-Ethylhexanoic acid (Branched saturated aliphatic monocarboxylic acid with 8 carbon atoms) Lauric acid (Linear saturated aliphatic monocarboxylic acid with 12 carbon atoms) Stearic acid (Linear saturated aliphatic monocarboxylic acid with 18 carbon atoms)

[0047] [Component (c): Conductive particles] Copper particles (1): Spherical copper particles [Surface-coated copper particles (1), the manufacturing method is shown in Synthesis Example 1 below.] Copper particles (2): Dendritic copper particles [FCC-TB, manufactured by Fukuda Metal Foil & Powder Co., Ltd., particle size (D50): 5.5 - 8.0 μm] Copper particles (3): Plate-like copper particles [Surface-coated copper particles (2), the manufacturing method is shown in Synthesis Example 2 below.]

[0048] [Component (d): Binder resin] Resole-type phenol resin [PL-5208, manufactured by Gunei Chemical Industry Co., Ltd., solid content 60.0 mass%, solvent: diethylene glycol monoethyl ether] Bisphenol F-type epoxy resin [jER (registered trademark)-806, manufactured by Mitsubishi Chemical Corporation]

[0049] As other components, the following materials were used. (Lubricant) Magnesium stearate (Dispersant) Oleoylsarcosine (Leveling agent) Fluorine-based compound [Megafac (registered trademark) F-477, manufactured by DIC Corporation] (Solvent) Terpineol Isobornyl cyclohexanol

[0050] [Synthesis Example 1] (Copper particles (1): Production of surface-coated copper particles (1)) An ammonium chloride aqueous solution in which 5 g of ammonium chloride was dissolved in 100 g of water was prepared. 50 g of copper particles a [manufactured by Mitsui Mining & Smelting Co., Ltd., "1200Y"; particle size (D50) 2 μm, BET specific surface area 0.40 m 2 / g, shape: spherical] was added to the ammonium chloride aqueous solution, and the mixture was 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. Hereinafter, stirring was carried out at the same rotation speed using the same stirring device. After completion of stirring, the copper particles were separated 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. The washed copper particles were added to 250 g of a 40 mass% diethylenetriamine aqueous solution, and heated and stirred at 60 °C for 1 hour while bubbling nitrogen.

[0051] After stopping the stirring and allowing to stand for 5 minutes, about 200 g of the supernatant was withdrawn and removed. Subsequently, 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 allowing to stand for 5 minutes, about 200 g of the supernatant was withdrawn and removed, and then 250 g of a 2 mass% isopropanol solution of lauric acid was added, followed by stirring at 30 °C for 30 minutes. After completion of stirring, the copper particles were separated by vacuum filtration using a Kiriyama funnel with 5C filter paper. The obtained copper particles were dried under reduced pressure at 25 °C for 3 hours to obtain surface-coated copper particles (1) (copper particles (1)).

[0052] [Synthesis Example 2] (Copper particles (3): Production of surface-coated copper particles (2)) Copper particles a were replaced with copper particles b [manufactured by Mitsui Mining & Smelting Co., Ltd., "1400YP"; particle size (D50) 6 μm, BET specific surface area 0.60 m 2Except for changing to "[ / g, Shape: plate-like]", surface-coated copper particles (2) (copper particles (3)) were obtained in the same manner as in Synthesis Example 1.

[0053] [Example 1] (Production of Conductive Composition) As component (a), 1.5 g of PEG200, as component (b), 1.5 g of lauric acid, as component (c), 87 g of surface-coated copper particles (1) (copper particles (1)), and as component (d), 16.7 g (10 g as solid content) of a resol-type phenolic resin [PL-5208, manufactured by Gunei Chemical Industry Co., Ltd., solid content 60% by mass, solvent: diethylene glycol monoethyl ether] were mixed. Next, using a planetary mixer [ARV-310, manufactured by Shinki Co., Ltd.], stirring was performed at room temperature at a rotation speed of 1500 rpm for 60 seconds for primary kneading. Next, using a three-roll mill [EXAKT-M80S, manufactured by Nagase Screen Printing Research Institute Co., Ltd.], secondary kneading was performed by passing through five times under the conditions of room temperature and a roll gap of 5 μm. To the kneaded product obtained by secondary kneading, 8 g of terpineol (Ter) was added, and using a planetary mixer, stirring was performed at room temperature under vacuum conditions at a rotation speed of 1000 rpm for 90 seconds for defoaming kneading to produce a conductive composition. The blending ratios of the respective components in the conductive composition are shown in Table 1.

[0054] (Formation of Cured Film) The obtained conductive composition was applied onto a glass substrate using a metal mask to form a pattern with a width × length × thickness = 1.0 mm × 30 mm × 50 μm. The glass substrate coated with the conductive composition was heated in a convection oven at 250 °C for 30 minutes in an air atmosphere to produce a cured film.

[0055] (Evaluation Method of Resistance Value) The conductivity of the cured film obtained by the above method was evaluated by the following resistance value measurement. Measurement probes were 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 Instrument Co., Ltd.], and judged according to the following evaluation criteria. The lower the resistance value of the cured film, the easier it is for current to flow, indicating excellent conductivity. ◎: The resistance value is less than 1.0 Ω. ○: The resistance value is 1.0 Ω or more and less than 10.0 Ω. △: The resistance value is 10.0 Ω or more and less than 50.0 Ω. ×: The resistance value is 50.0 Ω or more.

[0056] (Evaluation method for the viscosity change rate before and after continuous printing) The obtained conductive composition was continuously printed 100 sheets on a PET film using a screen printing machine [MT-320T, manufactured by Micro Tech Co., Ltd.]. Using an E-type viscometer [TV-25, manufactured by Toki Sangyo Co., Ltd.], the viscosity of the conductive composition before and after continuous printing using the screen printing machine was measured, the viscosity change rate was obtained by the following formula (I), and the determination was made according to the following evaluation criteria. In this test, the smaller the value of the viscosity change rate, the less likely the viscosity of the conductive composition is to change during continuous printing, indicating that the printability is stable.

[0057] Viscosity change rate (%) = [(Viscosity of the conductive composition after the continuous printing test) / (Viscosity of the conductive composition before the continuous printing test)] × 100 ··· (I) ◎: The viscosity change rate is less than 110%. ○: The viscosity change rate is 110% or more and less than 150%. △: The viscosity change rate is 150% or more and less than 200%. ×: The viscosity change rate is 200% or more.

[0058] (Evaluation method for the line width maintenance rate before and after intermittent printing) Using a screen printing machine [MT-320T, manufactured by Micro Tech Co., Ltd.], after printing one sheet of the obtained conductive composition on a PET film, the conductive composition was allowed to stand on the screen plate for 60 minutes and then printed on another PET film. Using a laser microscope [VK-9700, manufactured by Keyence Corporation], the line widths before and after printing were measured, the line width retention rate was determined by the following formula (II), and the determination was made according to the following evaluation criteria. In this test, the closer the value of the line width retention rate is to 100%, the longer the wettability of the conductive composition is maintained during intermittent printing, indicating that the wiring pattern can be printed stably.

[0059] Line width retention rate (%) = [(Line width of the wiring pattern printed after standing for 60 minutes) / (Line width of the wiring pattern printed for the first time)] × 100 ··· (II) ◎: The line width retention rate is 90% or more and 100% or less. ○: The line width retention rate is 70% or more and less than 90%. △: The line width retention rate is 50% or more and less than 70%. ×: The line width retention rate is less than 50%.

[0060] [Examples 2 to 11: Comparative Examples 1 to 4] Except that the blending ratios of the respective components were as shown in Tables 1 to 3, the conductive composition was produced and applied to a glass substrate using a metal mask in the same manner as in Example 1. Regarding the formation of the cured film, Examples 2 to 6, 8 to 10 and Comparative Examples 1 to 4 were heated in an air atmosphere, and Examples 7 and 11 were heated in a nitrogen atmosphere. Furthermore, for each cured film, the resistance value, the viscosity change rate before and after continuous printing, and the line width retention rate before and after intermittent printing were evaluated in the same manner as in Example 1. The results of Examples 1 to 6 are shown in Table 1, the results of Examples 7 to 11 are shown in Table 2, and the results of Comparative Examples 1 to 4 are shown in Table 3, respectively. The content of the phenolic resin in Tables 1 to 3 is the amount in terms of solid content.

[0061]

Table 1

[0062]

Table 2

[0063] [Table 3]

[0064] In Examples 1 to 11, the resistance value of the cured film was less than 10.0 Ω, the viscosity change rate before and after continuous printing was less than 150%, and the line width maintenance rate before and after intermittent printing was 70% or more. On the other hand, in Comparative Example 1 in which the conductive composition was prepared without blending component (a), the resistance value of the cured film was as high as 10.0 Ω or more, the viscosity change rate before and after continuous printing was as high as 200% or more, and the line width maintenance rate before and after intermittent printing was as low as less than 70%. In addition, in Comparative Example 2 in which the conductive composition was prepared without blending component (b), the line width maintenance rate before and after intermittent printing was 70%, but the resistance value of the cured film was as high as 50.0 Ω or more, and the viscosity change rate before and after continuous printing was as high as 200% or more. In Comparative Example 3 in which the conductive composition was prepared using PEG4000 instead of component (a), the resistance value of the cured film was less than 10.0 Ω, but the viscosity change rate before and after continuous printing was as high as 200% or more, and the line width maintenance rate before and after intermittent printing was as low as less than 50%. In addition, in Comparative Example 4 in which the conductive composition was prepared using glycerin instead of component (a), the resistance value of the cured film was as high as 85 Ω.

[0065] [Example 12] With the following formulation, the conductive composition was produced and the cured film was formed in the same manner as in Example 1. Further, for each cured film, the resistance value, the viscosity change rate before and after continuous printing, and the line width maintenance rate before and after intermittent printing were evaluated in the same manner as in Example 1.

[0066] Component (a): 1.5 g of PEG200 Component (b): 1.5 g of lauric acid Component (c) Conductive particles: 87 g of surface-coated copper particles (copper particles (1)) Component (d) Binder resin: 16.7 g of resol-type phenol resin (10 g as solid content) Lubricant: 0.3 g of magnesium stearate Leveling agent: 0.3 g of Megafac F-477 Solvent: 8 g of terpineol

[0067] Since the resistance value of the cured film was 2.5 Ω, the evaluation was "○"; since the viscosity change rate before and after continuous printing was 105%, the evaluation was "◎"; since the line width maintenance rate before and after intermittent printing was 85%, the evaluation was determined to be "○".

[0068] 〔Example 13〕 With the following formulation, a conductive composition was produced and a cured film was formed in the same manner as in Example 1. Further, for each cured film, the resistance value, the viscosity change rate before and after continuous printing, and the line width maintenance rate before and after intermittent printing were evaluated in the same manner as in Example 1.

[0069] Component (a): 1.5 g of PEG600 Component (b): 1.5 g of lauric acid Component (c) Conductive particles: 87 g of surface-coated copper particles (copper particles (1)) Component (d) Binder resin: 10 g of resol-type phenol resin (6 g as solid content), 4 g of bisphenol F-type epoxy resin Dispersant: 1 g of oleoyl sarcosine Solvent: 2 g of terpineol, 6 g of isobornyl cyclohexanol

[0070] Since the resistance value of the cured film was 1.2 Ω, the evaluation was "○"; since the viscosity change rate before and after continuous printing was 105%, the evaluation was "◎"; since the line width maintenance rate before and after intermittent printing was 95%, the evaluation was determined to be "◎".

Claims

【Claim 1】 A conductive composition containing (a) 0.1 to 5% by mass of polyethylene glycol having an average molecular weight of 200 to 2,000, (b) 0.1 to 5% by mass of an aliphatic monocarboxylic acid having 8 to 18 carbon atoms, (c) 60 to 95% by mass of conductive particles, and (d) 1 to 30% by mass of a binder resin.

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