JP2015065139A - Conductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste that can be applied or printed and can give a stretchable conductive film having a high conductivity.SOLUTION: The conductive paste includes a conductive filler (B) uniformly dispersed in a resin (A). The resin (A) is a water dispersion (A1) of a conjugate double bond polymer including a polyanion as a dopant derived from sulfonated or sulfated rubber. The conductive filler (B) is a metal power (B1) having an average particle diameter of 0.5 to 10 μm. The compounded amounts of the resin (A) and the conductive filler (B) in a solid content of the conductive paste are 50 to 80 vol% and 20 to 50 vol.%, respectively.

Description

  The present invention relates to a conductive paste for producing a conductive film suitable for stretchable electrodes and wiring.

  Most high-performance electronics are basically rigid and planar, and use single crystal inorganic materials such as silicon and gallium arsenide. On the other hand, when a flexible substrate is used, the wiring must be bent. Furthermore, for applications such as actuator electrodes and skin sensors, a conductive material exhibiting high stretchability is desired. For example, by using a film of a stretchable conductive material, it is possible to develop a device that can be fitted in close contact with a flexible and curved human body. Applications of these devices range from measuring electrophysiological signals to delivering advanced therapies and human-machine interfaces. One solution in the development of stretchable conductive materials is the use of organic conductive materials, but conventional materials are flexible but cannot be stretched and cannot cover curved surfaces. . Therefore, it lacks performance and reliability for integration into a complicated integrated circuit. Other materials, such as films of metal nanowires and carbon nanotubes, are promising to some extent, but are difficult to develop because they are unreliable and expensive.

  Two approaches have been reported as an approach for developing a flexible wiring that can be stretched.

  One is a method of constructing a wave-like structure to give stretchability even to a brittle material (see Non-Patent Document 1). In this method, a metal thin film is formed on silicone rubber by vapor deposition, plating, photoresist treatment, or the like. Although the metal thin film shows only a few percent of expansion / contraction, there are zigzag or continuous horseshoe-like shapes, corrugated metal thin films, or saddle-shaped metal thin films obtained by forming metal thin films on pre-stretched silicone rubber, etc. Shows elasticity. However, in any case, when the elongation is several tens of percent, the conductivity decreases by two orders of magnitude or more. In addition, since silicone rubber has a low surface energy, it has a drawback that it is easily peeled when stretched because the adhesion between the wiring and the substrate is weak. Therefore, with this method, it is difficult to achieve both stable high conductivity and high extensibility. Moreover, there is a problem that the manufacturing cost is high.

  The other is a composite material of a conductive material and an elastomer. The advantage of this material is excellent printability and stretchability. Commercially available silver pastes used for electrodes and wiring have a high elastic modulus binder resin with a high elastic modulus because of high filling and silver powder blended in a high elastic modulus binder resin. When it elongates, cracks are generated and the electrical conductivity is significantly reduced. Therefore, in order to give flexibility, study of rubber and elastomer as binders, silver flakes with high aspect ratio and high conductivity as conductive materials, carbon nanotubes, metal nanowires, etc. to reduce the filling degree of conductive materials Is being studied. Reported is a combination of silver particles and silicone rubber (see Patent Document 1), a combination of silver particles and polyurethane (see Patent Document 2), a combination of carbon nanotubes, ionic liquid, and vinylidene fluoride (see Patent Documents 3 and 4). Has been. However, even in these combinations, it is difficult to achieve both high conductivity and high stretchability. On the other hand, a printable, highly conductive and stretchable composite material has been reported using a combination of micron-sized silver powder, carbon nanotubes surface-modified with self-assembled silver nanoparticles, and polyvinylidene fluoride (non-patented) Reference 2). However, surface modification of carbon nanotubes with silver nanoparticles is not preferable because it is complicated to manufacture and causes cost increase.

JP 2007-173226 A JP 2012-54192 A WO2009 / 102077 JP 2011-216562 A

Jong-Hyun Ahn and Jung Ho Je, “Stretchable electronics: materials, architectures and integrations“ J. Phys. D: Appl. Phys. 45 (2012) 103001 Kyoung-Yong Chun, Youngseok Oh, Jonghyun Rho, Jong-Hyun Ahn, Young-Jin Kim, Hyoung Ryeol Choi and Seunghyun Baik, "Highly conductive, printable and stretchable composite films of carbon nanotubes and silver" Nature Nanotechnology, 5,853 ( 2010)

  The present invention has been made against the background of the problems of the prior art, and the object thereof is excellent in that it can be applied or printed, can be expanded and contracted, and can realize a highly conductive film. It is to provide a conductive paste.

As a result of intensive studies to achieve this object, the present inventor has found that the above-mentioned problems can be solved by the following means, and has reached the present invention.
That is, the present invention comprises the following configurations (1) to (9).
(1) A conductive paste in which a conductive filler (B) is uniformly dispersed in a resin (A), wherein the resin (A) contains a polyanion based on a sulfonated or sulfated rubber as a dopant. It is an aqueous dispersion (A1) of a heavy bond polymer, the conductive filler (B) is a metal powder (B1) having an average particle size of 0.5 to 10 μm, and the resin in the solid content of the conductive paste The electrically conductive paste characterized by each compounding quantity of (A) and an electroconductive filler (B) being 50-80 volume% and 20-50 volume%, respectively.
(2) The conductive material according to (1), further comprising, as the resin (A), an aqueous dispersion (A2) of a conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant. Sex paste.
(3) The conductive paste according to (1) or (2), wherein the metal powder (B1) is flaky metal powder, spherical metal powder or aggregated metal powder.
(4) Conductive material (B2) having a conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant as the conductive filler (B) and having an aspect ratio of 10 to 10,000 The conductive paste according to any one of (1) to (3), further comprising:
(5) The conductive material according to (4), wherein the conductive material (B2) is a carbon nanotube surface-treated with a conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant. Sex paste.
(6) The conductive paste according to (5), wherein the conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant contains a mercapto group or a nitrile group.
(7) The conductive paste according to any one of (1) to (6), further including metal nanoparticles (B3) having an average particle diameter of 2 to 100 nm as a conductive filler.
(8) The conductive paste according to (7), wherein the metal powder (B1) and the metal nanoparticles (B3) contain silver and / or copper as a main component.
(9) A conductive film or a conductive pattern obtained using the conductive paste according to any one of (1) to (8).

  According to the conductive paste of the present invention, the metal powder (B1) and optionally the conductive material (B2) are uniformly dispersed in the stretchable and conductive resin (A). Therefore, the conductive film formed by the conductive paste of the present invention is highly conductive in order to form an effective conductive network, and can maintain the high conductivity even when stretched.

Hereinafter, the conductive paste of the embodiment of the present invention will be described.
The conductive paste of the present invention is a conductive paste in which the conductive filler (B) is uniformly dispersed in the resin (A), and the resin (A) contains a polyanion based on a sulfonated or sulfated rubber. An aqueous dispersion (A1) of a conjugated double bond polymer containing as a dopant and an aqueous dispersion (A2) of a conjugated double bond polymer containing an aromatic group-containing polymer polyanion as a dopant, if desired. Conductor having a conjugated double bond polymer on the surface of which filler (B) contains metal powder (B1) and optionally a polymer polyanion containing an aromatic group as a dopant, and an aspect ratio of 10 to 10,000 It is a material (B2).

  Resin (A) is required to have good affinity with conductive filler (B) (metal powder (B1) and conductive material (B2)) in order to achieve uniform dispersion of conductive filler (B). . Sulfur corresponds to a soft base having a strong orbital interaction, has a good affinity with metals classified as soft acids, and shows a strong affinity. Nitrile groups are also known to have high affinity with metals. The conductive material (B2) itself has strong cohesive force and is difficult to disperse because of its high aspect ratio, but adsorbs a conjugated double bond polymer containing an aromatic group-containing polymer polyanion as a dopant on the surface. Thereby, dispersibility improves. In addition, when a mercapto group or a nitrile group is included, the affinity of the group to the metal is increased, so that the affinity with the metal powder (B1) is increased, and an effective conductive network together with the metal powder (B1). Can be formed. In addition, the resin (A) itself has high extensibility and high conductivity. As a result, the conductive paste of the present invention can retain a certain degree of high conductivity even when stretched due to the high stretchability and conductivity of the resin (A) itself, and the high aspect ratio of the conductive material (B2). . The resin (A) may further contain an aqueous dispersion (A2) of a conjugated double bond polymer containing, as a dopant, a polymer polyanion containing an aromatic group exhibiting high conductivity within a range that does not impair extensibility. it can. The metal powder (B1) has an average particle size of 0.5 μm to 10 μm, and can be selected from flaky metal powder, spherical metal powder or aggregated metal powder. In addition, metal nanoparticles (B3) having an average particle size of 100 nm or less can be further included. Moreover, since the component of the composition of this invention can be melt | dissolved or disperse | distributed to a solvent, a conductive film and a conductive pattern can be formed using processes, such as application | coating and printing.

  In aqueous dispersion (A1) of conjugated double bond polymer containing polyanion based on sulfonated or sulfated rubber as a dopant, the kind of sulfonated or sulfated rubber and conjugated double bond polymer is obtained membrane There is no particular limitation as long as the extensibility and conductivity are satisfied. Examples of the sulfonated or sulfated rubber include sulfonated polystyrene-b- (ethylene-co-butylene) -b-styrene triblock copolymer, sulfonated polystyrene-b-ethylene diblock copolymer, and sulfonated poly. t-butylstyrene-b- (ethylene-co-propylene) -b-styrene triblock copolymer, poly (perfluorosulfonic acid) such as Nafion (manufactured by DuPont), sulfated polybutadiene, sulfated poly (β- Hydroxy ether) and 1,3-bis (4-t-butylphenoxy) -2-polysulfate.

  Examples of the conjugated double bond polymer include polyaniline, polypyrrole, polythiophene, poly (3-hexylthiophene), poly (3,4-ethylenedioxythiophene), and the like. Among these, poly (3,4-ethylenedioxythiophene) is preferable for the expression of high conductivity.

  Examples of the aqueous dispersion (A1) of a conjugated double bond polymer containing a polyanion based on a sulfonated or sulfated rubber as a dopant include polyaniline: sulfated poly (β-hydroxyether), polypyrrole: sulfated poly ( β-hydroxyether), poly (3,4-ethylenedioxythiophene): sulfated poly (β-hydroxyether), poly (3,4-ethylenedioxythiophene): poly (perfluorosulfonic acid), poly ( 3,4-ethylenedioxythiophene): sulfonated polystyrene-b- (ethylene-co-butylene) -b-styrene triblock copolymer, poly (3,4-ethylenedioxythiophene): sulfonated polystyrene-b -Ethylene diblock copolymer, poly (3,4-ethylenedioxythiophene): Such as oxidation polybutadiene.

  As an aqueous dispersion (A2) of a conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant, polyaniline: polystyrene sulfonic acid, polypyrrole: polystyrene sulfonic acid, poly (3-hexylthiophene): polystyrene Examples include sulfonic acid, poly (3,4-ethylenedioxythiophene): polystyrene sulfonic acid (PEDOT: PSS), poly (3,4-ethylenedioxythiophene): sulfate esterified phenoxy resin, and the like. Of these, poly (3,4-ethylenedioxythiophene): polystyrene sulfonic acid (PEDOT: PSS) is preferred because of its high conductivity.

  The aqueous dispersion (A1) or (A2) of the conjugated double bond polymer described above can be synthesized by a conventionally known method. For example, poly (3,4-ethylenedioxythiophene): polystyrenesulfonic acid water In the case of a dispersion, water, 3,4-ethylenedioxythiophene, and polystyrene sulfonic acid are mixed to obtain a monomer dispersion, and then ferric sulfate and ammonium persulfate are added to the monomer dispersion at room temperature. Can be obtained by stirring for several hours.

  In the compounding quantity of resin (A) in an electrically conductive paste, when the volume% in solid content is small, electrical conductivity will become high, but a stretching property will worsen. On the other hand, when the volume% is large, the stretchability is improved, but the conductivity is lowered. Therefore, the compounding amount of the resin (A) in the solid content of the conductive paste is 50 to 80% by volume, and preferably 60 to 75% by volume. In addition, the volume% in this solid content measures the mass of each solid content of each component contained in the paste, and calculates (the mass of each solid content / the specific gravity of each solid content) to calculate the solid content of each component. It can be determined by calculating the volume.

  In addition, other resin may be mix | blended with the electrically conductive paste of this invention in the range which does not impair the performance as a stretchable conductive film, applicability | paintability, or printability.

  The conductive filler (B) is a metal powder (B1) and optionally a conductive material (B2). The compounding quantity of the electroconductive filler (B) in solid content of an electroconductive paste is 20-50 volume%. The metal powder (B1) is used for imparting conductivity in the conductive film or conductive pattern to be formed.

  As the metal powder (B1), noble metal powders such as silver powder, gold powder, platinum powder and palladium powder, and base metal powders such as copper powder, nickel powder, aluminum powder and brass powder are preferable. Further, a plating powder obtained by plating different kinds of particles made of an inorganic material such as a base metal or silica with a noble metal such as silver, a base metal powder obtained by alloying with a noble metal such as silver, or the like can be given. These metal powders may be used alone or in combination. Among these, those containing silver powder and / or copper powder as the main component (50% by weight or more) are particularly preferable from the viewpoint of easily obtaining a coating film exhibiting high conductivity and price.

  Examples of preferable shapes of the metal powder (B1) include known flaky shapes (flaky shapes), spherical shapes, dendritic shapes (dendritic shapes), aggregated shapes (shapes in which spherical primary particles are aggregated three-dimensionally), and the like. Can be mentioned. Of these, flaky, spherical, and aggregated metal powders are preferred.

  The average particle diameter of the metal powder (B1) is 0.5 to 10 μm from the viewpoint of imparting fine pattern properties. When metal powder having an average diameter larger than 10 μm is used, the shape of the formed pattern is poor, and the resolution of the patterned fine line may be reduced. When the average diameter is smaller than 0.5 μm, when blended in a large amount, the cohesive force of the metal powder may increase and printability may be deteriorated, and it is expensive, which is not preferable in terms of cost.

  The amount of the metal powder (B1) in the conductive paste is determined in consideration of conductivity and stretchability. When the volume% in the solid content is large, the electrical conductivity increases, but the amount of rubber decreases and the stretchability deteriorates. When the volume% is small, the stretchability is improved, but it is difficult to form a conductive network and the conductivity is lowered. Therefore, the blending amount of the metal powder (B1) in the solid content of the conductive paste is preferably 19 to 49% by volume, particularly preferably 25 to 40% by volume.

  The conductive material (B2) has on its surface a conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant, and has an aspect ratio of 10 to 10,000. As the conductive material (B2), carbon nanotubes are preferable. Carbon nanotubes having a conjugated double bond polymer having a polymer polyanion containing an aromatic group as a dopant on the surface are produced by surface treatment of the carbon nanotubes. The carbon nanotube to be treated is not particularly limited as long as the aspect ratio in the above range is satisfied.

  The carbon nanotube has a structure in which a two-dimensional graphene sheet is wound in a cylindrical shape, and is divided into a multilayer type, a single layer type, and a horn type depending on the number of layers and the shape of the tip. Also, depending on how the graphene sheet is wound, it can be divided into three types: an armchair structure, a zigzag structure, and a chiral structure. In the present invention, any of a multilayer type, a single layer type, and a horn type can be used, and any layer structure may be used.

  The diameter of the carbon nanotube is preferably 0.5 to 200 nm. When carbon nanotubes are used, the aspect ratio is preferably 20 to 10,000, particularly preferably 50 to 1,000.

  A method for dispersing a compound or polymer having a functional group on the surface of a carbon nanotube has been conventionally known. For example, a method of introducing by covalent bond after reaction, a method of utilizing hydrophobic interaction / hydrogen bond, a method of utilizing π-stacking, and a method of utilizing electrostatic interaction have been reported. Among them, in the method using π-stacking, the aromatic compound selectively adheres to the surface of the carbon nanotube by generating π-stacking with the graphite structure in the carbon nanotube. Therefore, a conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant selectively adheres to the carbon nanotube surface because the aromatic ring effectively π-stacks with the graphite structure of the carbon nanotube surface. In addition, carbon nanotubes are efficiently dispersed in water by repulsion between anions. Poly (3,4-dioxyethylenethiophene): polystyrene sulfonic acid (PEDOT: PSS) has been reported to be effective as a carbon nanotube dispersant in water (Non-patent Document 3). In this way, a carbon nanotube having a conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant can be produced.

  As the conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant, polyaniline: polystyrene sulfonic acid, poly (3-hexylthiophene): polystyrene sulfonic acid, poly (3,4-ethylenedioxythiophene) ): Polystyrene sulfonic acid (PEDOT: PSS), poly (3,4-ethylenedioxythiophene): sulfated phenoxy resin, and the like. Of these, poly (3,4-ethylenedioxythiophene): polystyrene sulfonic acid (PEDOT: PSS) is preferred because of its high conductivity.

  In order to improve the affinity with the metal powder (B1), a conjugated double bond polymer containing a sulfur or nitrile group is used, or a mercapto group in addition to a polymer polyanion containing an aromatic group as a dopant. A sulfonic acid compound containing can be included. Examples of the sulfonic acid compound containing a mercapto group include 3-mercapto-1-propanesulfonic acid and 5-mercapto-1H-tetrazole-1-methanesulfonic acid.

  Specifically, when carbon nanotubes are dispersed using an ultrasonic treatment machine or the like in an aqueous dispersion (A2) of a conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant, A conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant adheres to the surface of the carbon nanotube thus produced, and a desired carbon nanotube dispersion is produced.

  The carbon nanotube (B2) having a conjugated double bond polymer having a polymer polyanion containing an aromatic group as a dopant on its surface becomes a good dispersion by dispersion treatment in water, and becomes a sulfonated or sulfated rubber. By mixing with an aqueous dispersion (A1) of a conjugated double bond polymer containing a polyanion based on it as a dopant, it can be uniformly dispersed in the particles of the aqueous dispersion (A1). Further, by including sulfur or a nitrile group, an effective and highly conductive network is formed together with the metal particles because of good affinity with the metal powder (B1). In addition, even when stretched, high conductivity can be maintained because breakage of the conductive network can be suppressed due to the high aspect ratio.

  The conductive material (B2) having a conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant on the surface and having an aspect ratio of 10 to 10,000 is generally expensive and contains too much. And distributed processing becomes difficult. Therefore, the blending amount of the conductive material (B2) in the solid content in the conductive paste is preferably 1 to 10% by volume, particularly preferably 2 to 5% by volume.

  In the conductive paste of the present invention, metal nanoparticles (B3) can be further blended as a conductive filler for the purpose of improving conductivity and improving printability. Since the metal nanoparticles (B3) have a function of imparting conductivity between the conductive networks, an improvement in conductivity can be expected. Moreover, it can mix | blend also for the purpose of the rheology adjustment of the electrically conductive paste for printability improvement. The average particle diameter of the metal nanoparticles (B3) is preferably 2 to 100 nm. Specific examples include silver, bismuth, platinum, gold, nickel, tin, copper, and zinc. From the viewpoint of conductivity, copper, silver, platinum, and gold are preferable, and silver and / or copper is the main component (50 (% By weight or more) is particularly preferable.

  Since the metal nanoparticles (B3) are also generally expensive, they are preferably as small as possible. As for the compounding quantity of the metal nanoparticle (B3) in solid content of an electrically conductive paste, 0.5-5 volume% is preferable.

  An inorganic substance can be added to the conductive paste of the present invention as long as the conductivity and stretchability are not impaired. Examples of inorganic substances include silicon carbide, boron carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, tantalum carbide, niobium carbide, tungsten carbide, chromium carbide, molybdenum carbide, calcium carbide, diamond carbon lactam, and other carbides; boron nitride Various nitrides such as titanium nitride and zirconium nitride, various borides such as zirconium boride; various oxidations such as titanium oxide (titania), calcium oxide, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, silica and colloidal silica Products: various titanate compounds such as calcium titanate, magnesium titanate, strontium titanate; sulfides such as molybdenum disulfide; various fluorides such as magnesium fluoride and carbon fluoride; aluminum stearate, calcium stearate Um, zinc stearate, various metal soaps such as magnesium stearate and the like; may be used talc, bentonite, talc, calcium carbonate, bentonite, kaolin, glass fiber, mica or the like. By adding these inorganic substances, it may be possible to improve printability and heat resistance, as well as mechanical properties and long-term durability.

  Further, a thixotropic agent, an antifoaming agent, a flame retardant, a tackifier, a hydrolysis inhibitor, a leveling agent, a plasticizer, an antioxidant, an ultraviolet absorber, a flame retardant, a pigment, and a dye can be blended.

  The solvent used in the conductive paste of the present invention is mainly water, but can contain a water-miscible organic solvent as long as the performance of the paste and dry film is not impaired. The content of the solvent containing water is determined by the dispersion method of the metal filler, the viscosity of the conductive paste suitable for the conductive film forming method, the drying method, and the like. The electrically conductive paste of this invention can disperse | distribute a conductive filler uniformly in resin by using the conventionally well-known method to disperse | distribute powder to a liquid. For example, after mixing a metal powder, a dispersion of a conductive material having a high aspect ratio, and a resin solution, it can be uniformly dispersed by an ultrasonic method, a mixer method, a three-roll mill method, a ball mill method, or the like. These means can be used in combination.

  A conductive film or a conductive pattern is formed by applying or printing the conductive paste of the present invention on a substrate to form a coating film, and then volatilizing and drying water and an organic solvent contained in the coating film. be able to.

  The substrate to which the conductive paste is applied is not particularly limited, but a flexible or stretchable substrate is preferable depending on the application in order to make use of the stretchability of the conductive film. Examples of flexible substrates include paper, cloth, polyethylene terephthalate, polyvinyl chloride, polyethylene, polyimide, and the like. Examples of the stretchable base material include polyurethane, polydimethylsiloxane (PDMS), nitrile rubber, butadiene rubber, SBS elastomer, SEBS elastomer, and the like. These base materials can be creased and are preferably stretchable in the surface direction. In this respect, a base material made of rubber or elastomer is preferable.

  Although the process of apply | coating an electrically conductive paste on a base material is not specifically limited, For example, it can carry out by the coating method, the printing method, etc. Examples of the printing method include screen printing method, planographic offset printing method, ink jet method, flexographic printing method, gravure printing method, gravure offset printing method, stamping method, dispensing method, squeegee printing and the like.

  The step of heating the substrate coated with the conductive paste can be performed in the air, in a vacuum atmosphere, in an inert gas atmosphere, in a reducing gas atmosphere, or the like. The heating temperature is in the range of 20 to 200 ° C., and is selected in consideration of the required conductivity and the heat resistance of the substrate. The solvent containing water is volatilized, the curing reaction proceeds under heating in some cases, and the conductivity, adhesion, and surface hardness of the conductive film after drying become good.

  The elongation required for the stretchable conductive film varies depending on the application used and is not particularly limited. For applications such as wiring, antennas, and electrodes in the fields of assumed healthcare, displays, solar cells, PFID, etc., a growth rate of about 5% to 80% is desired. In the stretchable conductive film obtained by applying or printing the conductive paste of the present invention, for example, the specific resistance at 80% elongation is 10 times the specific resistance at the natural state (at 0% elongation). The following is desired, preferably 5 times or less, more preferably 2 times or less. It is also important to change the conductivity when the operation of extending the conductive film by a predetermined ratio and then returning it to the state of zero stress is repeated. For example, the specific resistance after repeating 10% elongation 1000 times is preferably 10 times or less, and particularly preferably 5 times or less, as compared to the specific resistance in the natural state (at 0% elongation).

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[Poly (3,4-ethylenedioxythiophene): Synthesis of sulfated poly (β-hydroxyether) (PEDOT: PA-1)]
2 g of sulfated poly (β-hydroxyether) (obtained from glycidyl ether of bisphenol A and bisphenol A, 100 mol% sulfated, weight average molecular weight 25000) and 100 g of 3,4-ethylenedioxythiophene (EDT) 1 g Of water / methanol (50/50 weight ratio). Subsequently, 0.5 ml of a 40% aqueous solution of ammonium persulfate as an oxidizing agent was dropped, and thereafter dropped in 6 portions at 10 minute intervals, and then stirred for 60 hours at room temperature to perform chemical polymerization to obtain a dispersion. It was.

[Poly (3,4-ethylenedioxythiophene): Synthesis of sulfonated polystyrene-b- (ethylene-co-butylene) -b-styrene triblock copolymer (PEDOT: PA-2)]
PEDOT is used except that a sulfonated polystyrene-b- (ethylene-co-butylene) -b-styrene triblock copolymer (manufactured by DAIS-Analytical Corporation) is used instead of the sulfated poly (β-hydroxy ether). A dispersion was obtained in the same manner as PA-1.

[Poly (3,4-ethylenedioxythiophene): Synthesis of poly (perfluorosulfonic acid) (PEDOT: PA-3)]
A dispersion was obtained in the same manner as PEDOT: PA-1, except that poly (perfluorosulfonic acid (Nafion PFSA D520 manufactured by DuPont)) was used instead of sulfated poly (β-hydroxyether).

[Poly (3,4-ethylenedioxythiophene): Synthesis of polystyrene sulfonic acid (PEDOT: PSS-1)]
10 g of a 20 wt% aqueous solution of polystyrene sulfonic acid (weight average molecular weight: 14000) and 1 g of 3,4-ethylenedioxythiophene (EDT) were added to 100 g of water and stirred for 30 minutes. Subsequently, 0.5 ml of a 40% by weight aqueous solution of ammonium persulfate as an oxidizing agent was dropped, and thereafter dropped 6 times at 10 minute intervals, followed by chemical polymerization by stirring at room temperature for 60 hours. At this time, the solution changed from light yellow to dark blue.

[Poly (3,4-ethylenedioxythiophene): Synthesis of polystyrene sulfonic acid (PEDOT: PSS-2)]
10 g of a 20 wt% aqueous solution of polystyrene sulfonic acid (weight average molecular weight: 14000), 0.5 g of 3-mercapto-1-propanesulfonic acid, and 1 g of 3,4-ethylenedioxythiophene (EDT) were added to 100 g of water and added to 30 g. Stir for minutes. Subsequently, 0.5 ml of a 40% by weight aqueous solution of ammonium persulfate as an oxidizing agent was dropped, and thereafter dropped 6 times at 10 minute intervals, followed by chemical polymerization by stirring at room temperature for 60 hours. At this time, the solution changed from light yellow to dark blue.

[Preparation of dispersion of carbon nanotube A (CNT-A) having a conjugated double bond polymer containing a polymer polyanion containing an aromatic group on the surface as a dopant]
In a 1.2 wt% PEDOT: PSS-1 aqueous dispersion, multi-walled carbon nanotubes (SWENT MW100, manufactured by Southwest Nano Technologies) were added to multi-walled carbon nanotubes: (PEDOT: PSS-1) = 1: 4 (weight ratio). And an aqueous dispersion of multi-walled carbon nanotubes was prepared using an ultrasonic treatment machine.

[Preparation of dispersion of carbon nanotube B (CNT-B) having a conjugated double bond polymer containing a polymer polyanion containing an aromatic group on the surface as a dopant]
Carbon nanotubes having amino groups on the surface were prepared in the same manner as CNT-A, except that the PEDOT: PSS-2 dispersion was used instead of the PEDOT: PSS-1 aqueous dispersion.

Examples 1-12, Comparative Examples 1-4
Surface treatment with silver particles (and silver nanoparticles if necessary) and a conjugated double bond polymer containing PEDOT dispersion and untreated carbon nanotubes (untreated CNT) or a polymer polyanion containing an aromatic group as a dopant A uniform dispersion of carbon nanotubes (CNT-A to B) was blended so that each component was a volume% in the solid content described in Tables 1 and 2, and a rotating / revolving vacuum mixer (manufactured by THYNKY, ARV-310). ) And kneaded at 2000 rpm for 3 minutes under vacuum to obtain a conductive paste. A conductive paste was formed on a glass plate by a drop cast method and dried at 150 ° C. for 30 minutes to produce a sheet-like conductive film having a thickness of 100 μm. The conductive film was evaluated for specific resistance at an elongation rate of 0%, 20%, 50%, and 80% by a method described later. Moreover, the specific resistance change rate of the electroconductive film after repeating 10% elongation 1000 times was evaluated. Tables 1 and 2 show the compositions of the conductive pastes of Examples 1 to 12 and Comparative Examples 1 to 4 and the evaluation results thereof.

Details of 1) to 5) in the table are as follows.
1) Silver particles: Aggregated silver powder G-35 (average particle size 5.9 μm, manufactured by DOWA Electronics Co., Ltd.) 2) Carbon nanotubes having a conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant on the surface A
3) Carbon nanotube B having a conjugated double bond polymer containing a polymer polyanion containing an aromatic group on the surface as a dopant
4) Untreated CNT: SWeNT MW100 (multi-walled carbon nanotube, diameter 6-9 nm, length 5 μm, aspect ratio 556-833, manufactured by Southwest Nano Technologies)
5) Silver nanoparticles: Silver nanoparticle dry powder 2 (average particle size 60 nm, manufactured by DOWA Electronics)

The evaluation methods of the conductive films of Examples 1 to 12 and Comparative Examples 1 to 4 are as follows.
[Evaluation of resistivity]
The sheet resistance and film thickness of the conductive film test piece in the natural state (elongation rate 0%) were measured, and the specific resistance was calculated. The film thickness was measured for four test pieces using a thickness gauge SMD-565L (manufactured by TECLOCK) and the sheet resistance was Loresta-GP MCP-T610 (manufactured by Mitsubishi Chemical Analytech), and the average value was used. .
Then, in the same manner as in the natural state (elongation rate 0%), the specific resistance at the elongation rate of 20%, 50%, and 80% was measured. The elongation rate was calculated by the following formula.
Elongation rate (%) = (ΔL0 / L0) × 100
Here, L0 represents the distance between the marked lines of the test piece, and ΔL0 represents the increment of the marked line Korean distance of the test piece.
Moreover, the specific resistance change rate of the electroconductive film after repeating 10% elongation 1000 times was computed by the following formula | equation.
Specific resistance change rate = (R ₁₀₀₀ −R ₀ ) / R ₀ × 100 (%)
Here, R ₁₀₀₀ represents the specific resistance after 10% repeated elongation (1000 times), and R ₀ represents the specific resistance in the natural state.

  As is clear from the results of Tables 1 and 2, the conductive pastes of Examples 1 to 12 can maintain high conductivity not only in the natural state but also in extension, after repeated expansion and contraction. However, the decrease in conductivity is small. On the other hand, the conductive pastes of Comparative Examples 1 to 4 have higher specific resistance than those of Examples 1 to 12, or have been broken by elongation, and the conductivity is lowered by repeated expansion and contraction.

  Since the conductive paste of the present invention has high conductivity and stretchability, it can be folded using rubber or an elastomer material, a stretchable LED array, a stretchable solar cell, a stretchable antenna, a stretchable battery, an actuator. It can be suitably used for electrodes and wiring of health care devices, medical sensors, wearable computers and the like.

Claims (9)

  A conductive paste in which a conductive filler (B) is uniformly dispersed in a resin (A), wherein the resin (A) includes a conjugated double bond having a polyanion based on a sulfonated or sulfated rubber as a dopant. It is an aqueous dispersion of molecules (A1), and the conductive filler (B) is a metal powder (B1) having an average particle size of 0.5 to 10 μm, and the resin (A) in the solid content of the conductive paste And the conductive filler (B) are blended in amounts of 50 to 80% by volume and 20 to 50% by volume, respectively.   The conductive paste according to claim 1, further comprising an aqueous dispersion (A2) of a conjugated double bond polymer containing, as a dopant, a polymer polyanion containing an aromatic group as a resin (A).   The conductive paste according to claim 1 or 2, wherein the metal powder (B1) is a flaky metal powder, a spherical metal powder or an agglomerated metal powder.   The conductive filler (B) further includes a conductive material (B2) having a conjugated double bond polymer having a polymer polyanion containing an aromatic group as a dopant on the surface and having an aspect ratio of 10 to 10,000. The electrically conductive paste in any one of Claims 1-3 characterized by the above-mentioned.   The conductive paste according to claim 4, wherein the conductive material (B2) is a carbon nanotube surface-treated with a conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant.   6. The conductive paste according to claim 5, wherein the conjugated double bond polymer containing a polymer polyanion containing an aromatic group as a dopant contains a mercapto group or a nitrile group.   The conductive paste according to claim 1, further comprising metal nanoparticles (B3) having an average particle diameter of 2 to 100 nm as the conductive filler.   The conductive paste according to claim 7, wherein the metal powder (B1) and the metal nanoparticles (B3) contain silver and / or copper as a main component.   A conductive film or a conductive pattern obtained by using the conductive paste according to claim 1.