JP7367586B2 - Conductive paste, conductive film, laminate and electronic device - Google Patents

Description

The present invention relates to a conductive paste for producing a conductive film that has high heat and humidity resistance and is suitable for expandable and contractible electrodes and wiring. Furthermore, the present invention relates to a conductive film, a laminate, and an electronic device formed from the conductive paste.

BACKGROUND OF THE INVENTION Conductive materials are used in various industrial fields, and various proposals have been made to further improve the functionality of these materials. Particularly in recent years, the development of flexible and stretchable conductive films has progressed, and proposals have been made for use in actuators and wearable sensors.
Patent Document 1 discloses a conductive paste for obtaining a stretchable conductive film that is low cost and has high durability. It is disclosed that by using silver-coated particles that have not been surface-treated and further combining specific additives, high conductivity can be obtained during film extension.
Patent Document 2 discloses a conductive composition that can obtain a conductor with significantly improved stretchability by combining a block copolymer and a specific silver powder.
Patent Document 3 discloses an excellent conductive paste that can be coated or printed, is stretchable, and can realize a conductive film with high conductivity. The conductive film formed by this conductive paste is highly conductive to form an effective conductive network and is also conductive when stretched due to the high aspect ratio of the conductive material (metal nanowires). Since the conductive network does not break, its high conductivity can be maintained even during elongation.

International Publication No. 2018/159374 International Publication No. 2017/026130 Patent No. 6319085

BACKGROUND OF THE INVENTION With advances in the fields of healthcare devices such as biosensing, wearable devices, and robotics, conductive materials with excellent stretchability are required. In these applications, in addition to the conventionally required conductivity, elasticity that can follow curved surfaces and movable parts during processing and/or use is required.

Further, when a conductive material is used for the curved surface portion or the movable portion, there is a problem that cracks are likely to occur in the resin itself due to structural destruction of the resin due to repeated expansion and contraction. In particular, in the case of conductive materials, in most cases, a conductive material is added, and the conductive material peels off from the resin during deformation due to expansion and contraction, creating voids in the resin, and cracks occur from these voids. It becomes easier. As a result, there is a problem in that the conductivity decreases with each expansion and contraction.
Furthermore, in fields such as healthcare equipment, wearable equipment, and robotics, equipment must continue to operate even in harsh environments such as high temperature and high humidity, but the coating film structure tends to change in high temperature and high humidity environments. There is also the problem of reduced conductivity.

The present invention has been made in view of the above background, and provides a conductive paste that has excellent stretchability, can effectively suppress the occurrence of cracks during stretching, and maintains conductivity even under high temperature and high humidity environments, and a conductive paste as described above. An object of the present invention is to provide a conductive film formed from a paste, a laminate, and an electronic device including this conductive film.

As a result of extensive studies, the inventors of the present invention have found that the problems of the present invention can be solved in the following embodiments, and have completed the present invention.
That is, the first invention of the present invention is a conductive paste containing an elastomer (A) having a thiol group and silver particles or silver-coated particles (B), wherein the solid content of the elastomer (A) is The present invention relates to a conductive paste having a thiol group concentration of 0.001 to 0.250 mmol/g.

Further, a second invention relates to the conductive paste of the first invention, wherein the elastomer (A) has a number average molecular weight of 10,000 to 500,000.

Further, a third invention relates to the conductive paste of the first or second invention, wherein the elastomer (A) is an elastomer (A1) having a thiol group in the terminal region.

Further, a fourth invention is the first to third inventions characterized in that the elastomer (A) has one or more glass transition temperatures in a temperature range of 20°C or higher and one or more in a temperature range of lower than 20°C. The present invention relates to a conductive paste according to any one of the inventions.

Further, a fifth invention is the first to fourth invention, wherein the silver particles or silver-coated particles (B) are chain silver powder and have a tap density of 2.0 g/cm ³ or less. The present invention relates to a conductive paste according to any one of the inventions.

Further, a sixth invention relates to the conductive paste according to any one of the first to fifth inventions, characterized in that the conductive paste further contains a solvent having a boiling point of 180° C. or higher and 270° C. or lower.

Furthermore, a seventh invention relates to a conductive film characterized in that it is formed from the conductive paste according to any one of the first to sixth inventions.

Moreover, an eighth invention relates to a laminate comprising the conductive film of the seventh invention on a base material.

Further, a ninth invention relates to an eighth laminate, wherein the base material is a stretchable base material.

Furthermore, a tenth invention relates to an electronic device having the conductive film according to the seventh aspect.

According to the present invention, a conductive paste that has excellent stretchability, can effectively suppress the occurrence of cracks during stretching, and maintains conductivity even under high temperature and high humidity environments, a conductive film formed from the conductive paste, This has the excellent effect of providing a laminate and an electronic device including the conductive film.

Hereinafter, an example of an embodiment of a method for manufacturing a conductive paste, a conductive film, a laminate, and an electronic device to which the present invention is applied will be described in detail. Numerical values specified in this specification are values determined by the methods disclosed in the embodiments or examples. Note that other embodiments are also included within the scope of the present invention as long as they meet the spirit of the present invention. Moreover, the film of the present invention has the same meaning as a sheet, tape, and label. Moreover, unless otherwise mentioned, various components can be used independently or in combination of two or more kinds.

<Conductive paste>
The conductive paste of the present invention contains an elastomer (A) having a thiol group and silver particles or silver-coated particles (B), and the thiol group concentration in the solid content of the elastomer (A) having a thiol group is , 0.001 to 0.250 mmol/g. Furthermore, a solvent may be added to the conductive paste of the present invention. It is characterized in that silver particles or silver-coated particles (B) are dispersed throughout the elastomer (A) and/or the solvent (S).

<Elastomer (A) having thiol group>
The type of elastomer (A) having a thiol group used in the present invention is not particularly limited as long as the thiol group concentration in the solid content of the elastomer (A) is 0.001 to 0.25 mmol/g. For example, hydrocarbon elastomers such as natural rubber, isoprene rubber, nitrile rubber (NBR), ethylene propylene rubber (EPDM), styrene-butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), and their water. Examples include additive elastomers, silicone elastomers, fluorine elastomers, urethane elastomers, acrylic elastomers, polyester elastomers, polyamide elastomers, and polyimide elastomers. These may be used alone or in combination of two or more. Alternatively, it may be a composite elastomer in which two or more types of elastomers are chemically bonded.
Among these, silicone elastomers, urethane elastomers, and acrylic elastomers are preferred from the viewpoint of stretchability, and urethane elastomers and acrylic elastomers are further preferred from the viewpoint of adhesion to the base material.
The term elastomer referred to here refers to a highly elastic polymeric material, which is a material that quickly stretches when subjected to tension without generating heat due to energy dissipation, and returns to its original length when the tension is removed. It is about.

The urethane elastomer (A) has an amino group of a compound having a thiol group and an amino group, or a thiol group and a hydroxyl group, relative to the terminal isocyanate group of the resin obtained by reacting at least a polyol component and an isocyanate component. It can be synthesized by reacting the hydroxyl group of a compound.
Examples of compounds having a thiol group and an amino group include cysteamine, cysteine, 11-amino-1-undecanethiol, 8-amino-1-octanethiol, and 6-amino-1-hexanethiol. Examples of compounds having this include mercaptoethanol, 1-thioglycerol, 2-thioglycerol, and the like.

Examples of urethane elastomers include olefin urethane elastomers containing olefin polyols as the polyol component, ester urethane elastomers containing ester polyols as the polyol component, ether urethane elastomers containing ether polyols as the polyol component, and carbonate polyols. Examples include carbonate-based urethane elastomers having a polyol component, castor oil-based urethane elastomers having a castor oil-based polyol as a polyol component, and the like. These may be used alone or in combination of two or more.
Further, the urethane elastomer may be a combination of two or more of the polyol components.

Examples of the polyol component include:
Olefin polyols such as Epol (manufactured by Idemitsu Kosan);
Ester polyols such as the Polylite series (manufactured by DIC Corporation) such as Polylite RX-4800, and the Kuraray Polyol series (manufactured by Kuraray Corporation) such as P-1010, P-2050, and F-2010;
ADEKA polyethers (manufactured by ADEKA) such as P series, G series, and EDP series, PTG and PTG-L series (manufactured by Hodogaya Chemical Industry Co., Ltd.), Preminol series and Preminol S series (manufactured by Asahi Glass Co., Ltd.), etc. Ether polyol;
Carbonate polyols such as Beneviol series (manufactured by Mitsubishi Chemical Corporation) and Kuraray Polyol C series;
Examples include castor oil-based polyols such as various URIC series and POLYCASTOR series.

As the isocyanate component, for example,
1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanate (hereinafter sometimes abbreviated as TDI), crude TDI, 2,4'- and 4,4' -Diphenylmethane diisocyanate (hereinafter sometimes abbreviated as MDI), polymethylene polyphenylene polyisocyanate (crude MDI), naphthylene-1,5-diisocyanate, triphenylmethane-4,4',4''-triisocyanate, etc. aromatic polyisocyanate;
Linear or branched aliphatic polyisocyanates such as 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and lysine diisocyanate; isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate and cycloaliphatic polyisocyanates such as norbornane diisocyanate;
Aroaliphatic polyisocyanates such as xylylene diisocyanate and α, α, α', α'-tetramethylxylylene diisocyanate;
Examples include modified products of the isocyanate component containing a urethane group, a carbodiimide group, an allophanate group, a urea group, a biuret group, an isocyanurate group, and an oxazolidone group.
One type of isocyanate component may be used, or two or more types may be used in combination.

The acrylic elastomer is a polymer obtained by polymerizing an ethylenically unsaturated monomer with a thermal polymerization initiator, and a thiol group can be introduced, for example, by the following two methods.

The first is that the amino group of a compound having a thiol group and an amino group, or the thiol group An acrylic elastomer containing a thiol group can be synthesized by reacting the hydroxyl group of a compound having a hydroxyl group.

The second method is to form an acrylic elastomer containing a thiol group by reacting an amine with the xanthate group in the polymer obtained by polymerizing an ethylenically unsaturated monomer containing a xanthate ester. Can be synthesized.

Examples of the ethylenically unsaturated monomer containing an isocyanate group include 2-isocyanatoethyl (meth)acrylate, 2-(2-methacryloyloxyethyloxy)ethyl isocyanate, and the like. Here, (meth)acrylate means methacrylate or acrylate.
As the compound having a thiol group and an amino group and the compound having a thiol group and a hydroxyl group, the same compounds as mentioned above can be used.

Examples of the ethylenically unsaturated monomer containing a xanthate ester include O-ethyl-S-(meth)acryloyloxyethylcarbodithioate, O-ethyl-S-acryloyloxyethylcarbodithioate, etc. . Here, (meth)acryloyl means methacryloyl or acryloyl.

Examples of amines that act on the xanthate groups in the polymer include triethylamine, diazabicycloundecene, tributylamine, dimethylbenzylamine, diethylamine, and phenethylamine.

The ethylenically unsaturated monomer containing an isocyanate group or the ethylenically unsaturated monomer containing a xanthate ester may be polymerized alone or copolymerized with other ethylenically unsaturated monomers. It's okay.
Examples of copolymerizable ethylenically unsaturated monomers include:
Methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2- Alkyl (meth)acrylates such as ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate;
Aromatic (meth)acrylates such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate;
Carboxyl group-containing (meth)acrylates such as (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid;
2-Hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 2-hydroxybutyl ( Hydroxyl group-containing (meth)acrylates such as meth)acrylate, ethyl-α-(hydroxymethyl)acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and 1,4-cyclohexanedimethanol mono(meth)acrylate;
Heterocyclic (meth)acrylates such as glycidyl (meth)acrylate, oxetane (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate;
Alkoxypolyalkylene glycol (meth)acrylates such as methoxypolypropylene glycol (meth)acrylate and ethoxypolyethylene glycol (meth)acrylate;
Amino group-containing (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate and N,N-diethylaminoethyl (meth)acrylate;
(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, isobutyl(meth)acrylamide, t-butyl (meth)acrylamide, and N-substituted (meth)acrylamides such as t-octyl (meth)acrylamide, diacetone (meth)acrylamide, and acryloylmorpholine;
N-methyleneallylamine, N-(2,2-dimethylpropylidene)allylamine, N-(2-furylmethylene)allylamine, N-benzylideneallylamine, N-(4-methylbenzylidene)allylamine, N-(4-chlorobenzylidene) ) N-alkyleneallylamine such as allylamine;
Nitriles such as (meth)acrylonitrile; and
Examples include polymerizable oligomers such as polymethyl methacrylate oligomers having one end methacryloylated, polystyrene oligomers having one end methacryloylated, and polyethylene glycol having one end methacryloylated.

Furthermore, styrenes such as styrene, α-methylstyrene, p-hydroxystyrene, chloromethylstyrene, vinyltoluene, and indene, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, and 2-hydroxyethyl. Examples include vinyl ethers such as vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether, and fatty acid vinyls such as vinyl acetate and vinyl propionate.

During polymerization, 0.001 to 5 parts by weight of a polymerization initiator can be optionally used per 100 parts by weight of the ethylenically unsaturated monomer (f). As the polymerization initiator, an azo compound and an organic peroxide can be used.
Furthermore, an acrylic elastomer may be obtained by living polymerization for the purpose of improving the molecular weight distribution and synthesizing a block copolymer. Examples of living polymerization include atom transfer radical living polymerization, reversible addition-fragmentation chain transfer living polymerization, living polymerization using an organic tellurium compound, and living radical polymerization using an organic catalyst such as an iodine compound.
By using living polymerization, it is possible to synthesize block copolymers, star-shaped polymers, comb-shaped polymers, etc. with controlled primary structures.

In the case of solution polymerization, the polymerization solvent includes ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, xylene, acetone, hexane, methyl ethyl ketone, cyclohexanone, propylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol diethyl ether, Diethylene glycol methyl ethyl ether, diethylene glycol monoethyl ether acetate, tetraethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol dimethyl ether, diacetone alcohol, cyclohexanone, isophorone and the like are used, but are not particularly limited thereto. Although two or more of these polymerization solvents may be used as a mixture, it is preferable to use a solvent for final use.

The number average molecular weight Mn of the elastomer (A) used in the present invention is a value determined by the method described in the Examples below. Mn is preferably 10,000 to 500,000. By setting it as this range, when elastomer (A) is shape|molded into a film, for example, elasticity and strength can be made compatible. The preferred range of Mn is 10,000 to 400,000, and the more preferred range is 30,000 to 300,000.

The elastomer (A) used in the present invention has one or more glass transition temperatures Tg in the temperature range of 20°C or higher and one or more in the temperature range of lower than 20°C, so that it has excellent elasticity and prevents the occurrence of cracks during elongation. This is preferable because it can be effectively suppressed.
More preferably, there is one Tg in the temperature range of 60°C or more and 180°C or less and -70°C or more and 0°C or less, and even more preferably 90°C or more and 180°C or less and -60°C or more - Preferably, there is one in each temperature range of 30° C. or lower.

The elastomer used in the present invention may contain additives such as plasticizers, antioxidants, anti-aging agents, and colorants.

The thiol group concentration in the solid content of the elastomer (A) used in the present invention is 0.001 to 0.250 mmol/g. If the thiol group concentration is less than 0.001 mmol/g, wet heat resistance cannot be obtained, and if it is greater than 0.250 mmol/g, silver dispersibility deteriorates and the odor becomes worse. More preferably, it is 0.015 to 0.100 mmol/g.

The thiol groups in elastomer (A) are preferably located in the terminal regions of the elastomer's chemical structure. The presence of the thiol group in the terminal region may improve the elasticity of the conductive coating. The terminal region here means a region within 30 atoms from the terminal element.

<Silver particles or silver coated particles (B)>
Next, the silver particles or silver-coated particles (B) used in the present invention will be explained. The silver particles or silver-coated particles (B) may be particulate matter made of silver or conductive particles or non-conductive particles coated with silver.
Examples of the conductive particles include:
Metals such as gold, platinum, copper, palladium, cobalt, nickel, aluminum, zinc, lead, tin; alloys such as brass, bronze, cupronickel, solder;
Conductive carbon such as carbon, graphite, graphene, carbon nanotubes;
Conductive ceramic fillers such as ITO and IZO;
Examples include conductive polymers such as polyacetylene, polythiophene, poly(3,4-ethylenedioxythiophene), and polyaniline.
Examples of the non-conductive particles include plastic particles such as acrylic, polyester, polyurethane, polyimide, and polyamide, and they may be soft or hard and deformable like rubber.
Silver-coated particles can be obtained by coating or plating these conductive particles or non-conductive particles with silver.

The shape of the silver particles or silver-coated particles (B) used in the present invention is not particularly limited, and examples thereof include spherical, chain/spherical, flake, dendrite, coiled (helical, spiral) shape. (including shape). Dendritic refers to a shape in which branched branches extend in two or three dimensions from a rod-shaped main branch. The shape of the conductive particles is preferably a chain of flakes and/or spherical particles from the viewpoint of ease of contact between the conductive particles.

The tap density of the silver particles or silver-coated particles (B) used in the present invention is preferably 2.0 g/cm ³ or less. When the tap density is 2.0 g/cm ³ or less, the volume occupied by the silver powder in the conductive film becomes large, so the number of points of contact between the silver particles or silver-coated particles (B) increases, and conduction becomes easier.

The average particle diameter D50 of the silver particles or silver-coated particles (B) used in the present invention can be, for example, about 0.5 to 50 μm. From the viewpoint of ease of contact between conductive particles, the thickness is preferably 1 to 12 μm, and from the viewpoint of reducing the thickness of the film, the thickness is preferably 1 to 6 μm.

In addition to the silver particles or silver-coated particles (B), the conductive paste of the present invention may further contain conductive particles, such as gold, platinum, copper, palladium, cobalt, nickel, aluminum, zinc, and lead. , metals such as tin;
Alloys such as brass, bronze, cupronickel, and solder;
Conductive carbon such as carbon, graphite, graphene, carbon nanotubes;
Conductive ceramic fillers such as ITO and IZO;
Examples include conductive polymers such as polyacetylene, polythiophene, poly(3,4-ethylenedioxythiophene), and polyaniline.

The silver particles or silver-coated particles (B), and the conductive particles that may be added may be used alone or in combination of two or more.

The conductive paste used in the present invention can contain a solvent in order to impart printing suitability according to a desired printing method.
Examples of the solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, xylene, acetone, hexane, methyl ethyl ketone, cyclohexanone, propylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, Examples include, but are not limited to, diethylene glycol monoethyl ether acetate, tetraethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol dimethyl ether, diacetone alcohol, cyclohexanone, and isophorone. Two or more of these solvents may be used in combination.
Above all, in order to make a paste suitable for silk screen printing, it is necessary to use a solvent with a boiling point of 180°C or higher and 270°C or lower to prevent it from drying inside the mesh of the printing plate and clogging the mesh. is preferred.

The conductive paste of the present invention may further contain other components as necessary. Such other components include crosslinking agents, dispersants, friction improvers, infrared absorbers, ultraviolet absorbers, fragrances, antioxidants, organic pigments, inorganic pigments, antifoaming agents, silane coupling agents, Examples include plasticizers, flame retardants, humectants, and the like.

The crosslinking agent is used to crosslink the elastomer (A), and is selected from among those having two or more reactive functional groups in one molecule that can form a crosslink with the thiol group of the elastomer (A). It can be used selectively. Examples of such reactive functional groups include epoxy groups, isocyanate groups, blocked isocyanate groups, (meth)acryloyl groups, and the like.
When using a crosslinking agent, it is preferably used in an amount of 0.05 parts by mass or more and 30 parts by mass or less, and more preferably 1 part by mass or more and 25 parts by mass or less, based on 100 parts by mass of the elastomer (A).

The method for producing the conductive paste of the present invention may be a method in which the elastomer (A), silver particles or silver-coated particles (B), and other components used as necessary are mixed or dispersed in a solvent. It can be manufactured by mixing using a known mixing means.

<Conductive film, laminate, electronic device>
The conductive film of the present invention is formed from the conductive paste of the present invention, and specifically, it can be formed by applying the conductive paste on a base material and drying it as necessary. can.
The method of applying the conductive paste is not particularly limited, and printing methods such as screen printing, offset printing, inkjet printing, flexographic printing, gravure printing, and coating methods may be used.Drying may be performed using a known dryer such as a hot air oven or an infrared heater. can be used.

The base material to which the conductive paste is applied is not particularly limited, and includes, for example, thermoplastic elastomer, plastic, fiber, nonwoven fabric, silicone rubber, fluororubber, nitrile rubber, acrylic rubber, styrene rubber, styrene-butadiene rubber, and chloropyrene rubber. , urethane rubber, butyl rubber, ethylene rubber, propylene rubber, ethylene propylene rubber, epoxy rubber, butadiene rubber, and natural rubber.

Examples of the thermoplastic elastomer include polyurethane-based, polyester-based, polyolefin-based, polyamide-based, polyimide-based, polyester-based, vinyl chloride-based, styrene-based block polymers, and acrylic-based block polymers.

Examples of the plastic include polyolefins such as polyvinyl alcohol, triacetylcellulose, polypropylene, polyethylene, polycycloolefin, and ethylene-vinyl acetate copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polycarbonate, Includes polynorbornene, polyarylate, polyacrylic, polyphenylene sulfide, polystyrene, epoxy resin, polyamide, and polyimide.

As the base material, a stretchable base material may be used to take advantage of the stretchability of the conductive film. Examples of the stretchable base material include stretchable plastic films and stretchable fibers, and the stretchable fibers may be textile fabrics.

Further, the laminate in the present invention includes the conductive film on a base material, and also includes a structure in which the conductive film is embedded in a recess provided in a support. In this specification, when a stretchable base material is used as a base material, the laminate may be referred to as a stretchable conductor.

Since the conductive film of the present invention has excellent stretchability, it is suitable for use as stretchable wiring and stretchable electrodes, for example. Further, the conductive film can be used for films such as a stretchable electromagnetic shielding layer and a stretchable heat dissipation layer, as well as molded bodies having desired shapes and having conductivity.
Furthermore, in the laminate of the present invention, a shield electrode layer for removing crosstalk noise is formed on the opposite side (front side) of the conductive film base material to cover the detection part via an insulating layer (dielectric layer). It's okay. Further, the outermost layer may include an overcoat layer for protecting the electrode layer (the front electrode layer, the back electrode layer, and the shield electrode layer).

The electronic device of the present invention has a conductive film. By using the conductive film of the present invention which has excellent stretchability, flexibility, flexibility, and stretchability can be imparted to the conductive portion. Therefore, the conductive film of the present invention is suitable for use in general electronic devices in which conductive parts are required to have bendability, flexibility, and/or stretchability, such as sensors attached to the body or robots, and internally attached to clothing. Suitable for wearable sensors and biological information acquisition devices.

Further, the conductive film of the present invention is suitable for use in flexible displays, flexible wiring boards, flexible transducers, and flexible mobile devices in the electronics field. Further, it is applicable to motors and actuators driven by electromagnetism, speakers using piezoelectric effects, vibrators, ultrasonic generators, etc.

A conductive film in an electronic device can be used without limitation for members that require conductivity. For example, it is used for wiring, electrodes, conductive adhesives, vias, electromagnetic shielding films, and thermally conductive films.

Conventionally, electrodes made of metal layers have excellent conductivity, but their use has been limited due to their lack of elasticity. On the other hand, by using a stretchable conductive film as a conductor, stretchability can be significantly improved. Furthermore, it has the advantage of being flexible and easily adapting to the movements of the human body.

Note that in electronic devices, adhesive layers, protective layers, etc. that require stretchability, bendability, and/or flexibility may be used.

EXAMPLES The present invention will be specifically explained below using Examples, but the present invention is not limited thereto. In the following description, unless otherwise specified, "part" means "part by mass" and "%" means "% by mass." In addition, values other than the solvent are non-volatile content equivalent values.

[Number average molecular weight (Mn)]
Using GPC (product name: GPCV-2000, manufactured by Nippon Waters Co., Ltd., column: TSKgel, α-3000, mobile phase: 10mM triethylamine/dimethylformamide solution), polystyrene (molecular weight 427,000, 190,000, 96 , 400, 37,400, 10,200, 2,630, 440, 92) to create a calibration curve and measure the number average molecular weight (Mn).

[Measurement of glass transition temperature]
The glass transition temperature is measured in accordance with JIS K 7121 (2012) plastic transition temperature measurement method, and the glass transition temperature is determined by the extrapolated glass transition initiation temperature (Tig) described in JIS 9.3. I asked for it. A differential scanning calorimeter (manufactured by TA Instruments, DSC Q2000) was used for the measurement.

[Measurement of thiol group concentration]
Approximately 1 g of dried and solidified resin was accurately weighed in advance, and a mixed solution of 100 ml of a 1.2 wt% potassium iodide aqueous solution in which the resin was dissolved, 400 ml of toluene, and 600 ml of pyridine was added to a 0.05 N iodine solution in toluene. Titration was performed. The end point was when the solution turned yellow, and the thiol group concentration was determined using the following formula.
Thiol group concentration (mmol/g) = 0.05 x (titration amount) x (factor of iodine toluene solution) / sample weight (g)

[Measurement of tap density]
The tap density refers to the mass per volume after a certain amount of powder is placed in a certain container while being shaken up and down, and was measured based on the JIS Z 2512:2006 method. Specifically, conductive fine particles (powder amount 100 g) were collected in a graduated glass container (capacity 100 ml), and tapped with a predetermined tapping device under the conditions of a tap stroke of 3 mm and a number of taps of 100 times/min. .

<Manufacture of elastomer>
(Elastomer production example 1)
783 parts of polytetramethylene ether glycol (molecular weight 1,000) and 200 parts of isophorone diisocyanate (IPDI) were charged into a 4-necked flask equipped with a stirrer, a reflux condenser, a gas introduction pipe, a thermometer, and a dropping funnel, and gradually The temperature was raised to 90° C. and the reaction was continued for 6 hours. Thereafter, after cooling to 50°C, 17 parts of cysteamine and 333 parts of methyl isobutyl ketone (boiling point 116°C) were added, and the reaction was carried out at ⁵⁰ °C for 1 hour. confirmed. By adding methyl isobutyl ketone so that the solid content is 30%, thiol is added only to the terminal region with a number average molecular weight of 45,000, a thiol group concentration of 0.22 mmol/g, and a glass transition temperature of -55°C. An elastomer (A1) having groups was obtained.

(Elastomer production example 2)
692 parts of polytetramethylene ether glycol (molecular weight 1,000) and 231 parts of isophorone diisocyanate (IPDI) were charged into a four-necked flask equipped with a stirrer, a reflux condenser, a gas introduction pipe, a thermometer, and a dropping funnel, and gradually The temperature was raised to 90° C. and the reaction was continued for 6 hours. After cooling to 50°C, 15 parts of cysteamine, 63 parts of dibutylamine, and 333 parts of methyl isobutyl ketone (boiling point 116°C) were added and reacted at 50°C for 1 hour. The disappearance of the peak at 2270 cm ⁻¹ was confirmed. By adding methyl isobutyl ketone so that the solid content is 30%, thiol is added only to the terminal region with a number average molecular weight of 9,300, a thiol group concentration of 0.19 mmol/g, and a glass transition temperature of -57°C. An elastomer (A2) having groups was obtained.

(Elastomer production example 3)
In a 4-necked flask equipped with a stirrer, reflux condenser, gas inlet tube, thermometer, and dropping funnel, 690 parts of polytetramethylene ether glycol (molecular weight 1,000), 11 parts of butanol, and 97 parts of isophorone diisocyanate (IPDI) were added. 194 parts of isocyanurate trimer of IPDI, and 1000 parts of cyclohexanone (boiling point 156°C) were charged, the temperature was gradually raised, and the mixture was reacted at 90°C for 10 hours. After cooling to 50°C, 11 parts of cysteamine and 200 parts of cyclohexanone (boiling point 156°C) were added and reacted at 50°C for 1 hour, and disappearance of the peak at 2270 cm ^-1 based on isocyanate groups was confirmed by IR. . By adding cyclohexanone so that the solid content is 30%, thiol groups are added only to the terminal region with a number average molecular weight of 50,000, a thiol group concentration of 0.11 mmol/g, and a glass transition temperature of -10°C. An elastomer (A3) having the following properties was obtained.

(Elastomer production example 4)
In a 4-necked flask equipped with a stirrer, reflux condenser, gas inlet tube, thermometer, and dropping funnel, 854 parts of polycarbonate diol C2090 (manufactured by Kuraray), 7 parts of 1,4-butanediol, and 135 parts of diphenylmethane diisocyanate were added. Then, 1000 parts of cyclohexanone were charged, the temperature was gradually raised, and the reaction was carried out at 90°C for 8 hours. After cooling to 50° C., 4 parts of cysteamine and 200 parts of cyclohexanone were added, and the mixture was allowed to react at 50° C. for 1 hour, and disappearance of the peak at 2270 cm ⁻¹ based on isocyanate groups was confirmed by IR. By adding cyclohexanone so that the solid content is 30%, it has a number average molecular weight of 40,000, a thiol group concentration of 0.05 mmol/g, and a thiol group only in the terminal region with a glass transition temperature of 30 ° C. An elastomer (A4) was obtained.

(Elastomer production example 5)
A four-necked flask equipped with a stirrer, a reflux condenser, a gas introduction tube, a thermometer, and a dropping funnel was charged with 2,000 parts of acetone (boiling point 56°C), and the temperature was gradually raised to start refluxing at 56°C. About 3 parts of a mixed solution of 837 parts of butyl acrylate (BA), 127 parts of methyl methacrylate (MMA), 36 parts of 2-isocyanatoethyl methacrylate (MOI), and 2 parts of azoisobutyronitrile (AIBN) was added thereto. It dripped over time. 1 part of AIBN was added 1 hour after the completion of the dropwise addition, and then 1 part of AIBN was added three times every hour, and the reaction was further carried out at the reflux temperature of acetone for 3 hours. After cooling to 50° C., 16 parts of cysteamine and 300 parts of cyclohexanone were added, and the mixture was reacted at 50° C. for 1 hour, and the disappearance of the peak at 2270 cm ⁻¹ based on isocyanate groups was confirmed by IR. By adding cyclohexanone so that the solid content is 30%, an elastomer (A5) having a number average molecular weight of 150,000, a thiol group concentration of 0.21 mmol/g, and a glass transition temperature of -40°C. ) was obtained.

(Elastomer production example 6)
A four-necked flask equipped with a stirrer, a reflux condenser, a gas introduction tube, a thermometer, and a dropping funnel was charged with 2,000 parts of acetone (boiling point 56°C), and the temperature was gradually raised to start refluxing at 56°C. A mixed solution of 837 parts of BA, 144 parts of MMA, 12 parts of MOI, and 2 parts of AIBN was dropped therein over about 3 hours. 1 part of AIBN was added 1 hour after the completion of the dropwise addition, and then 1 part of AIBN was added 3 times every hour, and the reaction was further carried out at the reflux temperature of acetone for 3 hours. After cooling to 50° C., 5 parts of cysteamine and 300 parts of cyclohexanone were added, and the mixture was reacted at 50° C. for 1 hour, and the disappearance of the peak at 2270 cm ⁻¹ based on isocyanate groups was confirmed by IR. By adding cyclohexanone so that the solid content is 30%, an elastomer (A6 ) was obtained.

(Elastomer production example 7)
A four-necked flask equipped with a stirrer, a reflux condenser, a gas introduction tube, a thermometer, and a dropping funnel was charged with 2,000 parts of acetone (boiling point 56°C), and the temperature was gradually raised until reflux started at 56°C. A mixed solution of 706 parts of BA, 229 parts of MMA, 36 parts of MOI, and 2 parts of AIBN was added dropwise thereto over about 3 hours. 1 part of AIBN was added 1 hour after the completion of the dropwise addition, and then 1 part of AIBN was added 3 times every hour, and the reaction was further carried out at the reflux temperature of acetone for 3 hours. After cooling to 50° C., 16 parts of cysteamine and 300 parts of cyclohexanone were added, and the mixture was reacted at 50° C. for 1 hour, and the disappearance of the peak at 2270 cm ⁻¹ based on isocyanate groups was confirmed by IR. By adding cyclohexanone so that the solid content is 30%, an elastomer (A7) having a number average molecular weight of 145,000, a thiol group concentration of 0.21 mmol/g, and a glass transition temperature of -20°C ) was obtained.

(Elastomer production example 8)
In a 4-necked flask equipped with a stirrer, reflux condenser, gas inlet tube, thermometer, and dropping funnel, 1.6 parts of methyl 4-cyano-4-(dodecylthiocarbonothioylthio)pentanoate was added as a RAFT initiator. , 1 part of AIBN, 52 parts of MMA, and 100 parts of diethylene glycol monoethyl ether acetate (boiling point 218°C) were charged and reacted at 80°C for 8 hours. Furthermore, 0.15 parts of AIBN, 146 parts of BA, and 150 parts of diethylene glycol monobutyl ether (boiling point 247°C) were added, and the mixture was reacted at 80°C for 12 hours.
Then, after cooling to 50°C, the RAFT initiator residue was converted to a thiol group by adding 2 parts of dibutylamine, resulting in a number average molecular weight of 15,000 and a thiol group concentration of 0.01 mmol/g. An elastomer (A8) having a thiol group only in the terminal region and having two glass transition temperatures of -57°C and 102°C was obtained.

(Elastomer production example 9)
1000 parts of diethylene glycol monoethyl ether acetate (boiling point 218°C) was charged into a 4-necked flask equipped with a stirrer, a reflux condenser, a gas introduction pipe, a thermometer, and a dropping funnel, and the temperature was gradually raised to 80°C. A mixed solution of 454 parts of BA, 319 parts of MMA, 10 parts of MOI, 212 parts of polystyrene macromer having a molecular weight of 6,000 (manufactured by Toagosei Co., Ltd.), and 2 parts of AIBN was added dropwise thereto over about 3 hours. 1 part of AIBN was added 1 hour after the completion of the dropwise addition, and then 1 part of AIBN was added three times every hour, followed by reaction at 80°C for 3 hours, and further reaction at 110°C for 2 hours. After cooling to 50° C., 5 parts of cysteamine and 300 parts of diethylene glycol monoethyl ether acetate were added and reacted at 50° C. for 1 hour, and the disappearance of the peak at 2270 cm ⁻¹ based on isocyanate groups was confirmed by IR. By adding diethylene glycol monoethyl ether acetate so that the solid content is 30%, the number average molecular weight is 80,000, the thiol group concentration is 0.06 mmol/g, and the glass transition temperature is -5°C and 105°C. An elastomer (A9) having two thiol groups was obtained.

(Elastomer production example 10)
In a 4-necked flask equipped with a stirrer, a reflux condenser, a gas inlet tube, a thermometer, and a dropping funnel, 150 parts of acid-modified polyolefin (Aurelen 550S, manufactured by Nippon Paper Industries) and 679 parts of isophorone (boiling point 215°C) were added. , 170 parts of methyl ethyl ketone (MEK, boiling point 79°C) were charged, and the acid-modified polyolefin was dissolved by stirring at 70°C for 2 hours. Thereafter, after cooling to 50°C, 2 parts of cysteamine and 10 parts of MEK were added, and the mixture was reacted at 50°C for 1 hour, and the disappearance of the peak at 1780 cm ^-1 based on the acid anhydride group was confirmed by IR. By adding MEK so that the solid content is 15%, an elastomer (A10) having a number average molecular weight of 86,000, a thiol group concentration of 0.09 mmol/g, and a glass transition temperature of 5°C. Obtained.

(Elastomer production example 11)
In a 4-necked flask equipped with a stirrer, a reflux condenser, a gas inlet tube, a thermometer, and a dropping funnel, 408 parts of Pripol 1009 (dimer acid manufactured by Croda), 25 parts of adipic acid, and Priamine 1074 (dimer acid manufactured by Croda) were placed. diamine) for 12 hours at 180°C. Thereafter, 500 parts of diethylene glycol monoethyl ether acetate was added and then cooled to 100°C, 23 parts of IPDI was added, and the mixture was reacted at 100°C for 3 hours. After further cooling to 50°C, 8 parts of cysteamine and 500 parts of diethylene glycol monoethyl ether acetate were added and reacted at 50°C for 1 hour, and the disappearance of the peak at 2270 cm ^-1 based on isocyanate groups was confirmed by IR. By adding diethylene glycol monoethyl ether acetate so that the solid content is 30%, the terminal region has a number average molecular weight of 8,200, a thiol group concentration of 0.10 mmol/g, and a glass transition temperature of -15°C. An elastomer (A11) having only thiol groups was obtained.

(Elastomer production example 12)
783 parts of polytetramethylene ether glycol (molecular weight 1,000) and 200 parts of IPDI were charged into a 4-necked flask equipped with a stirrer, a reflux condenser, a gas introduction pipe, a thermometer, and a dropping funnel, and the temperature was gradually raised. , and reacted at 90°C for 6 hours. Thereafter, methyl isobutyl ketone was added so that the solid content was 30%, thereby obtaining an elastomer (A12) having no thiol group and having a number average molecular weight of 43,000 and a glass transition temperature of -59°C. .

(Elastomer production example 13)
In a 4-neck flask equipped with a stirrer, reflux condenser, gas inlet tube, thermometer, and dropping funnel, 581 parts of polytetramethylene ether glycol (molecular weight 1,000), 19 parts of butanol, and 97 parts of isophorone diisocyanate (IPDI) were added. 194 parts of isocyanurate trimer of IPDI, and 1000 parts of cyclohexanone were charged, the temperature was gradually raised, and the mixture was reacted at 90° C. for 10 hours. After cooling to 50°C, 25 parts of cysteamine and 200 parts of cyclohexanone were added, and the mixture was allowed to react at 50°C for 1 hour, and disappearance of the peak at 2270 cm ^-1 based on isocyanate groups was confirmed by IR. By adding cyclohexanone so that the solid content is 30%, thiol groups are added only to the terminal region with a number average molecular weight of 43,000, a thiol group concentration of 0.36 mmol/g, and a glass transition temperature of -5°C. An elastomer (A13) having the following properties was obtained.

(Elastomer production example 14)
A four-necked flask equipped with a stirrer, a reflux condenser, a gas introduction tube, a thermometer, and a dropping funnel was charged with 2,000 parts of acetone (boiling point 56°C), and the temperature was gradually raised until reflux started at 56°C. Add about 3 parts of a mixed solution of 813 parts of butyl acrylate (BA), 127 parts of methyl methacrylate (MMA), 60 parts of 2-isocyanatoethyl methacrylate (MOI), and 2 parts of azoisobutyronitrile (AIBN) to it. It dripped over time. 1 part of AIBN was added 1 hour after the completion of the dropwise addition, and then 1 part of AIBN was added 3 times every hour, and the reaction was further carried out at the reflux temperature of acetone for 3 hours. After cooling to 50° C., 28 parts of butylamine and 300 parts of cyclohexanone were added, and the mixture was allowed to react at 50° C. for 1 hour, and the disappearance of the peak at 2270 cm ⁻¹ based on isocyanate groups was confirmed by IR. By adding cyclohexanone so that the solid content was 30%, an elastomer (A14) having no thiol group and having a number average molecular weight of 146,000 and a glass transition temperature of -35°C was obtained.

(Elastomer production example 15)
1000 parts of diethylene glycol monoethyl ether acetate was charged into a four-neck flask equipped with a stirrer, a reflux condenser, a gas inlet tube, a thermometer, and a dropping funnel, and the temperature was gradually raised to 80°C. A mixed solution of 454 parts of BA, 291 parts of MMA, 50 parts of MOI, 212 parts of polystyrene macromer having a molecular weight of 6,000 (manufactured by Toagosei Co., Ltd.), and 2 parts of AIBN was added dropwise thereto over about 3 hours. 1 part of AIBN was added 1 hour after the completion of the dropwise addition, and then 1 part of AIBN was added three times every hour, followed by reaction at 80°C for 3 hours, and further reaction at 110°C for 2 hours. After cooling to 50° C., 25 parts of cysteamine and 300 parts of diethylene glycol monoethyl ether acetate were added and reacted at 50° C. for 1 hour, and the disappearance of the peak at 2270 cm ⁻¹ based on isocyanate groups was confirmed by IR. By adding diethylene glycol monoethyl ether acetate so that the solid content is 30%, the number average molecular weight is 78,000, the thiol group concentration is 0.32 mmol/g, and the glass transition temperature is -7°C and 102°C. An elastomer (A15) having two thiol groups was obtained.

(Elastomer production example 16)
In a 4-necked flask equipped with a stirrer, a reflux condenser, a gas inlet tube, a thermometer, and a dropping funnel, 150 parts of acid-modified polyolefin (Aurelen 550S, manufactured by Nippon Paper Industries) and 679 parts of isophorone (boiling point 215°C) were added. , 170 parts of methyl ethyl ketone (MEK, boiling point 79°C) were charged, and the acid-modified polyolefin was dissolved by stirring at 70°C for 2 hours. Thereafter, by adding MEK so that the solid content was 15%, an elastomer (A16) having a number average molecular weight of 85,000 and a glass transition temperature of 5° C. and having no thiol group was obtained.

(Elastomer production example 17)
Into a 4-necked flask equipped with a stirrer, reflux condenser, gas inlet tube, thermometer, and dropping funnel, 150 parts of Thiokol LP-2 (manufactured by Toray Fine Chemical Co., Ltd.) and 350 parts of diethylene glycol monoethyl ether acetate were charged. By stirring at ℃ for 1 hour, a thiol group-containing elastomer (A17) with a solid content of 30%, a number average molecular weight of 4,000, a thiol group concentration of 0.50 mmol/g, and a glass transition temperature of -61 ℃ was obtained. Obtained.

<Manufacture of conductive paste>
(Example 1)
The conductive paste of Example 1 was obtained by thoroughly mixing 2.25 parts of an elastomer (A1) with a solid content of 30% and 2.7 parts of silver particles or silver-coated particles (B1).

(Examples 2 to 16 and Comparative Examples 1 to 8)
A conductive paste was obtained in the same manner as in Example 1 except for the conductive paste formulation shown in Table 1.

<Evaluation of conductive paste>
The following evaluations were performed using the obtained conductive paste. The results are shown in Tables 1 and 2.

(Storage stability of conductive paste)
The fluidity of the obtained conductive paste after being stored at 40° C. for 3 days was checked.
・Liquidity evaluation criteria:
+: No change in fluidity, screen printing is possible even after storage at 40℃ for 3 days NG: Fluidity decreases, screen printing is not possible after storage at 40℃ for 3 days

<Production of laminate including conductive film>
The obtained conductive paste was applied by screen printing onto the following base material C1 or base material C2, and heat treated at 80° C. for 30 minutes to produce a laminate having a conductive film with a thickness of 25 μm.
Stretchable base material C1: stretchable urethane film (Tough Grace film manufactured by Takeda Sangyo Co., Ltd., thickness 80 μm)
Base material C2: PET film (Toyobo Co., Ltd. Cosmoshine A4100, thickness 100 μm)

(Odor evaluation)
The odor of the obtained laminate was sensory evaluated using the following criteria.
++: No odor +: Slight odor NG: Strong odor

(Initial volume resistivity)
A test piece was prepared by cutting the laminate to a width of 10 mm and a length of 140 mm. Using a surface resistance measuring device (product number: Loresta AP MCP-T400, probe: ASP probe (4-probe probe, manufactured by Mitsubishi Chemical Corporation), in an atmosphere with a temperature of 25°C and a relative humidity of 50%, in accordance with JIS K7194 The initial volume resistivity of the test piece was measured and evaluated according to the following criteria.
+++: less than 2.0×10 ⁻⁴ Ω・cm ++: 2.0×10 ⁻⁴ Ω・cm or more, less than 9.9×10 ⁻⁴ Ω・cm +: 9.9×10 ⁻⁴ Ω・cm or more, less than 9.9×10 ^-3 Ω・cm NG: 9.9×10 ⁻³ Ω・cm or more

(Change rate of volume resistivity under humid heat environment)
Using the laminate, the volume resistivity after 10 days (after moist heat) in a moist heat environment of 85 ° C. and 85% relative humidity was measured in the same manner as the initial stage, and the rate of change from the initial stage was calculated. Evaluation was made based on the following criteria.
[Rate of change(%)]
= [(Initial volume resistivity) - (Volume resistivity after moist heat)] ÷ [(Initial volume resistivity)]
+++: Rate of change is 20% or less ++: Rate of change is more than 20% and less than 50% +: Rate of change is more than 50% and less than 100% NG: Rate of change is more than 100%

(Change rate of volume resistivity and appearance evaluation after expansion/contraction test)
A laminate using the stretchable base material C1 was cut into a sample of 20 mm x 60 mm, the end of which was fixed in a Tensilon tensile tester, and tested at 25° C., relative humidity 50%, and a speed of 4 mm/s for 50 minutes. %, then held for 2 seconds, and then unloaded at a speed of 4 mm/s and held for 2 seconds, after which the volume resistivity was measured 1000 times in the same manner as the initial one. The rate of change in volume resistivity before and after the stretching cycle was calculated using the following formula, and evaluated using the following criteria.
[Change rate (%)] = [(R1000) - (R0)] ÷ [(R0)] x 100
(Here, R1000 indicates the volume resistivity immediately after the expansion/contraction cycle, and R0 indicates the volume resistivity using the same laminate before the expansion/contraction cycle.)
+++: Rate of change is 20% or less ++: Rate of change is more than 20% and less than 50% +: Rate of change is more than 50% and less than 100% NG: Rate of change is more than 100%

Further, the appearance of the laminate after shrinking 1000 times was compared with the state before the test and evaluated based on the following criteria.
++: No change in appearance +: Slight cracks or other cracks have occurred on the appearance NG: Cracks or cracks have completely formed on the appearance

The silver particles or silver-coated particles used in Tables 1 and 2 are as follows.
Silver particles or silver-coated particles (B1): chain silver with a tap density of 1.4 g/cm ³ (manufactured by Fukuda Metal Foil & Powder Co., Ltd., AgC-G)
Silver particles or silver-coated particles (B2): flaky silver with a tap density of 3.3 g/cm ³ (manufactured by Fukuda Metal Foil & Powder Co., Ltd., AgC-A)
Silver particles or silver-coated particles (B3): foil-like silver with a tap density of 1.1 g/cm ³ (manufactured by Fukuda Metal Foil & Powder Co., Ltd., Ag-XF301S)
Silver particles or silver-coated particles (B4): flake powder with a tap density of 3.3 g/cm ³ (manufactured by Mitsui Mining & Smelting Co., Ltd., 1000YP)

As shown in Table 1, the conductive pastes of Examples 1 to 19 prepared using the conductive paste of the present invention have excellent storage stability, and the laminates comprising conductive films formed from the conductive pastes have good conductivity and elasticity. In contrast, Comparative Examples 1 to 8 in Table 2 had one of the defects and all of them were good. was not obtained. As described above, the conductive pastes of Examples 1 to 19 and the conductive films and laminates obtained from the conductive pastes were found to be useful.

Claims (10)

A conductive paste containing an elastomer (A) having a thiol group and silver particles or silver-coated particles (B),
A conductive paste characterized in that the thiol group concentration in the solid content of the elastomer (A) is 0.001 to 0.250 mmol/g. The conductive paste according to claim 1, wherein the elastomer (A) has a number average molecular weight of 10,000 to 500,000. 3. The conductive paste according to claim 1, wherein the elastomer (A) is an elastomer (A1) having a thiol group in its terminal region. The conductive paste according to any one of claims 1 to 3, wherein the elastomer (A) has one or more glass transition temperatures in a temperature range of 20°C or higher and one or more in a temperature range of lower than 20°C. The conductive paste according to any one of claims 1 to 4, wherein the silver particles or silver-coated particles (B) are chain silver powder and have a tap density of 2.0 g/cm ³ or less. The conductive paste according to any one of claims 1 to 5, characterized in that the conductive paste further contains a solvent having a boiling point of 180°C or more and 270°C or less. A conductive film formed from the conductive paste according to any one of claims 1 to 6. A laminate comprising the conductive film according to claim 7 on a base material. The laminate according to claim 8, wherein the base material is a stretchable base material. An electronic device comprising the conductive film according to claim 7.