WO2018159374A1

WO2018159374A1 - Electrically conductive paste, flexible wiring obtained using same, and garment-type electronic device having flexible wiring

Info

Publication number: WO2018159374A1
Application number: PCT/JP2018/005896
Authority: WO
Inventors: 桂也 ▲徳▼田; 達彦入江; 佑子中尾
Original assignee: 東洋紡株式会社
Priority date: 2017-03-02
Filing date: 2018-02-20
Publication date: 2018-09-07
Also published as: JPWO2018159374A1; JP7167909B2; TW201839779A; TWI758423B

Abstract

[Problem] To realize a flexible electrically conductive coating film that is inexpensive and has high durability, and to provide a wearable device using such coating film as wiring. [Solution] An electrically conductive paste is obtained by blending and kneading at least: an electrically conductive filler which comprises metal-coated particles having a non-surface-treated metal layer on the surface of electrically non-conductive core particles; a binder resin comprising an elastomer; and an organic solvent. By further adding an additive having a surface of free energy of 30 mJ/m2 or less, repetition durability is improved. An electrically conductive coating film obtained from the electrically conductive paste exhibits high durability to repeated expansion and contraction, is suitable for use in wearable applications requiring flexibility, and is inexpensive.

Description

Conductive paste, elastic wiring using the same, and clothes-type electronic device having elastic wiring

The present invention relates to a conductive paste composed of a conductive filler and a binder resin, and particularly relates to a conductive paste capable of forming a conductive film having stretch properties. The present invention also relates to a conductive material used in a clothes-type wearable electronic device in which an electronic function or an electric function is incorporated in a garment, and a stretchable electrical wiring is formed, and the garment has a natural feeling of wear. Type electronic equipment.

Recently, wearable electronic devices intended to use electronic devices having input / output, arithmetic and communication functions in close proximity to or close to the body have been developed. As wearable electronic devices, devices having an accessory-type outer shape such as a wristwatch, glasses, and earphones, and textile integrated devices in which electronic functions are incorporated into clothes are known. An example of such a textile integrated device is disclosed in Patent Document 1.

Electronic equipment requires electrical wiring for power supply and signal transmission. In particular, in textile-integrated wearable electronic devices, the electrical wiring is required to be stretchable in accordance with the stretchable clothes. Usually, electrical wiring made of metal wires or metal foils is not practically elastic, so the metal wires or metal foils are placed in a corrugated or repeated horseshoe shape to give a pseudo expansion / contraction function. The method is used.
In the case of a metal wire, wiring can be formed by regarding the metal wire as an embroidery thread and sewing it onto clothes. However, it is obvious that this method is not suitable for mass production.
A method of forming a wiring by etching a metal foil is a general method for producing a printed wiring board. A technique is known in which a metal foil is bonded to a stretchable resin sheet, and corrugated wiring is formed by a technique similar to that of a printed wiring board to make a pseudo stretchable wiring. (Refer to Non-Patent Document 1) Such a technique is to give a pseudo expansion / contraction characteristic by torsional deformation of the corrugated wiring portion. However, since the metal foil is also deformed in the thickness direction by torsional deformation, When used, it was very uncomfortable and unpleasant. In addition, when subjected to excessive deformation as in washing, permanent plastic deformation occurs in the metal foil, and there is a problem in the durability of the wiring.

As a technique for realizing a stretchable conductor wiring, a method using a special conductive paste has been proposed. Conductive particles such as silver particles, carbon particles, carbon nanotubes and elastomers such as stretchable urethane resin, natural rubber, synthetic rubber, solvent, etc. are kneaded to form a paste, directly on clothes or stretchable film base The wiring is printed and drawn in combination with a material.
Macroscopically, a conductive composition composed of conductive particles and a stretchable binder resin can realize a stretchable conductor. When viewed microscopically, the conductive composition obtained from such a paste maintains its conductivity within a range in which the resin binder portion is deformed when external force is applied and the electrical chain of the conductive particles is not interrupted. It is. The specific resistance observed macroscopically is higher than that of metal wires and metal foils, but because the composition itself has elasticity, there is no need to adopt a shape such as corrugated wiring, and the wiring width and thickness. Since there is a high degree of freedom, it is practically possible to realize a low resistance wiring compared to a metal wire.

Patent Document 2 discloses a technique for suppressing a decrease in conductivity at the time of elongation by combining silver particles and silicone rubber and further coating a conductive film on a silicone rubber substrate with silicone rubber. Patent Document 3 discloses a combination of silver particles and a polyurethane emulsion, and it is said that a conductive film having high conductivity and high elongation can be obtained. Further, many examples have been proposed in which characteristics are improved by combining high aspect ratio conductive particles such as carbon nanotubes and silver fillers.

Patent Document 4 discloses a technique for directly forming electrical wiring on clothes using a printing method.

JP-A-2-234901 JP 2007-173226 A JP 2012-54192 A Japanese Patent No. 3723565

Although noble metals such as silver are frequently used as the conductive particles, these noble metals are expensive and occupy most of the chemical cost of pastes and conductive films produced using these noble metals. On the other hand, for the purpose of reducing the cost of fillers, attempts have been made for a long time to use non-conductive particles or inexpensive metal particles as a filler for conductive films by coating noble metals.
These metal-coated particles are subjected to high dispersion treatment with a surface treatment agent in order to prevent agglomeration during the manufacturing process. However, when the highly dispersed particles are used as conductive fillers, aggregation of fillers is inhibited. It is difficult to maintain the conductive network when the coating is elongated, and it is necessary to increase the compounding ratio of the conductive particles in the coating. However, when the blending ratio of the conductive particles in the coating is increased, there is a problem that the binder component ratio is decreased and durability during expansion and contraction is deteriorated.
The inventors have studied the application of silver-coated particles in a conductive paste for forming a stretchable conductive film. Silver coated particles have rarely been investigated for use in stretchable conductive films.

As a result of intensive research to develop a conductive paste for obtaining a stretchable conductive film having low durability at a low cost, the present inventors have used silver-coated particles that have not been subjected to surface treatment. Furthermore, it discovered that high electroconductivity was acquired at the time of film expansion | extension by combining a specific additive, and reached the following invention.

That is, the present invention has the following configuration.
[1] At least a conductive filler composed of metal-coated particles having a metal layer on the surface of non-conductive core particles, a binder resin composed of an elastomer, and an organic solvent, and the surface of the conductive filler is not previously surface-treated. Conductive paste used for forming stretchable wiring characterized by
[2] The conductive paste according to [1], wherein the binder resin is a nitrile group-containing elastomer or a urethane resin.
[3] The conductive material according to [1] or [2], which contains 0.1 to 3.0% by mass of an additive having a surface free energy of 30 mJ / m ² or less based on the conductive filler. Sex paste.
[4] From [1] to [3], wherein the additive is polydimethylsiloxane having at least one functional group selected from an amino group, a carboxyl group, and a glycidyl group at least at one end. The electrically conductive paste in any one.
[5] The conductive paste according to any one of [1] to [4], wherein a surface free energy of the additive is 25 mJ / m ² or less.
[6] The conductive paste according to any one of [1] to [5], wherein the additive is polydimethylsiloxane having a carboxyl group at least at one end.
[7] At least a conductive filler composed of metal-coated particles having a metal layer on the surface of non-conductive core particles, a binder resin composed of an elastomer, and an organic solvent, and the surface of the conductive filler is not surface-treated in advance. An electrically conductive film that can be stretched.
[8] The conductive film according to [7], wherein the binder resin is a nitrile group-containing elastomer or a urethane resin.
[9] The conductive material according to [7] or [8], which contains 0.1 to 3.0% by mass of a treatment agent having a surface free energy of 30 mJ / m ² or less based on the conductive filler. Film.
[10] From [7] to [9], wherein the additive is polydimethylsiloxane having at least one functional group selected from an amino group, a carboxyl group, and a glycidyl group at least at one end. The conductive film in any one.
[11] The conductive film according to any one of [7] to [10], wherein a surface free energy of the additive is 25 mJ / m ² or less.
[12] The conductive film according to any one of [7] to [11], wherein the additive is polydimethylsiloxane having a carboxyl group at least at one end.
[13] The stretchability according to any one of [7] to [12], wherein the conductive film has a specific resistance when 100% stretched within 20 times of a specific resistance when not stretched. A conductive coating having
[14] The conductive film having stretchability according to [7] to [12], wherein the conductivity of the conductive film after 1000 times of 20% repeated stretch is maintained.
[15] A clothes-type electronic device having an electrical wiring made of the conductive film having elasticity described in [7] to [14].
[16] The conductive filler composed of the metal-coated particles contains at least two types of conductive filler A and conductive filler B, and the conductive filler A has an aspect ratio which is a ratio of a major axis to a minor axis of 1.5 or less. The metal-coated particles having a metal layer on the surface of the non-conductive core particles, the center particle diameter D is not less than 0.5 μm and not more than 15 μm, and the conductive filler B has an aspect ratio that is a ratio of the major axis to the minor axis Is a metal-coated particle having a metal layer on the surface of the non-conductive core particle, the average length L of the major axis is 3 μm or more and 30 μm or less, and the ratio of the conductive filler B to the total conductive filler is 25 to 25 The conductive paste according to [1], which is 60% by mass.
[17] The conductive paste according to [16], wherein the elastomer used as the binder resin is a non-crosslinked elastomer.
[18] The conductive paste according to [16] or [17], wherein the binder resin is a nitrile group-containing elastomer.
[19] The conductive paste according to [16] or [17], wherein the binder resin is a urethane resin.
[20] In the conductive film having at least the conductive filler and the binder resin as the constituent components, the conductive filler contains at least two types of conductive filler A and conductive filler B as the conductive filler, and the conductive filler A has a ratio of the major axis to the minor axis. A certain aspect ratio is 1.5 or less, is a metal-coated particle having a metal layer on the surface of a non-conductive core particle, a center particle diameter D is 0.5 μm or more and 15 μm or less, and the conductive filler B is The ratio of the major axis to the minor axis is a metal-coated particle having an aspect ratio of 5 or more and having a metal layer on the surface of the non-conductive core particle, the average length L of the major axis is 10 μm or more and 30 μm or less. A conductive film having stretchability, characterized in that the ratio of the conductive filler B to the total filler is 25 to 60% by mass, and the binder resin is an elastomer.
[21] The conductive film according to [20], wherein the binder resin is a nitrile group-containing elastomer.
[22] The conductive film according to [20], wherein the binder resin is a urethane resin.
[23] The stretchability according to any one of [20] to [22], wherein the conductive film has a specific resistance when 100% stretched within 10 times of a specific resistance when not stretched. A conductive coating having
[24] The conductive film having stretchability according to any one of [20] to [23], wherein the conductivity of the conductive film after 1000 times of 20% repeated stretch is maintained.
[25] The conductive film has a specific resistance of the sheet after repeating the twist cycle of the following twist test 100 times within 3.0 times the initial specific resistance [20] to [24] ] The electroconductive film in any one of.
[Torsion test: sample: width 10 mm, length 100 mm (fixed at one end in the longitudinal direction of the sample, twisted by rotation of the other end)
Twisting cycle: 10 rotations (3600 °) in the positive direction, return to the initial state, 10 rotations (-3600 °) in the negative direction, return to the initial state]
[26] A stretchable electronic component having an electrical wiring comprising the conductive film according to any one of [20] to [25].
[27] A clothes-type electronic device having an electrical wiring made of the conductive film according to any one of [20] to [25].

The present invention preferably further has the following configuration.
[28] At least a conductive filler composed of metal-coated particles having a metal layer on the surface of non-conductive core particles, a binder resin composed of an elastomer, and an organic solvent, and the surface of the conductive filler has 3 or more carbon atoms in advance. A mono- or polyvalent carboxylic acid having 28 or less and 0 to 3 double bonds in the molecule, an aliphatic amine having 3 to 24 carbon atoms and 0 to 2 double bonds in the molecule A conductive paste used for forming stretchable wiring, characterized in that it is not surface-treated with at least one selected surface treatment agent.
[29] A mono- or polyvalent carboxylic acid having 3 to 28 carbon atoms and 0 to 3 double bonds in the molecule, and having 3 to 24 carbon atoms and 0 double bonds in the molecule The conductive paste according to any one of [1] to [6], wherein the content of at least one surface treatment agent selected from two aliphatic amines is 3% by mass or less.
[30] At least a conductive filler composed of metal-coated particles having a metal layer on the surface of non-conductive core particles, a binder resin composed of an elastomer, and an organic solvent, and the surface of the conductive filler has 3 carbon atoms in advance. Mono- or polyvalent carboxylic acid having 28 to 28 and the number of double bonds in the molecule is 0 to 3, and aliphatic amine having 3 to 24 carbon atoms and the number of the double bond in the molecule is 0 to 2 A stretchable conductive film characterized by being not surface-treated with at least one surface treatment agent selected from
[31] Mono- or polyvalent carboxylic acid having 3 to 28 carbon atoms and 0 to 3 double bonds in the molecule, and having 3 to 24 carbon atoms and 0 double bonds in the molecule The conductive paste according to any one of [7] to [14], wherein the content of at least one surface treatment agent selected from 2 aliphatic amines is 5% by mass or less.
[32] A clothes-type electronic device having the electrical wiring according to [15], comprising the stretchable conductive film according to [30] or [31].

According to the conductive paste of the present invention, metal-coated particles and an elastomer that are not subjected to surface treatment such as high dispersion treatment on the surface in advance are used.
Here, as a surface treatment agent for high dispersion treatment or the like, a mono- or polyvalent carboxylic acid having 3 to 28 carbon atoms and having 0 to 3 double bonds in the molecule, and / or 3 or more carbon atoms. Examples thereof include aliphatic amines having 24 or less and 0 to 2 double bonds in the molecule, or derivatives thereof. The treatment with these surface treatment agents that improves the dispersibility of the metal-coated particles is not performed, so that the particles tend to agglomerate during the preparation of the coating film. Since it is easy to form a network, durability during expansion and contraction is maintained.
Further, by using an additive having a surface free energy of 30 mJ / m ² or less, the particles are more easily aggregated, and durability during expansion and contraction is further increased.
Moreover, since the electroconductive particle formed by coating the particle surface portion with a metal has a merit that the raw material cost is lower than that of the metal particle, a stretchable conductive paste can be produced at a lower cost.

According to the conductive paste of the present invention, the conductive fillers A and B are blended in the elastomer so that the ratio of the conductive filler B to the total conductive filler is 25 to 60% by mass. By combining two kinds of conductive fillers having different aspect ratios, it becomes easy to form a conductive network, and thus durability against repeated expansion and contraction is improved. Moreover, since the electroconductive particle formed by coating the particle surface portion with a metal has a merit that the raw material cost is lower than that of the metal particle, a stretchable conductive paste can be produced at a lower cost.

FIG. 1 is an SEM image (magnification 5000 times) of particles which are silver-coated particles of the present invention and are an example of conductive filler A. FIG. 2 is an SEM image showing an example of the conductive filler B of the present invention. FIG. 3 is a schematic diagram for explaining the extension recovery rate. FIG. 4 is a schematic process diagram showing a method of forming electrodes and electrical wiring using the transfer method in the present invention. FIG. 5 is an example of an electrode wiring manufactured using the conductive paste of the present invention. FIG. 6 is a schematic view showing the arrangement of electrode wirings in FIG. 5 of the present invention.

The electrically conductive paste in this invention is comprised from the electrically conductive filler which has a metal layer on the surface of a nonelectroconductive core particle, a binder, and an organic solvent.
The conductive filler of the present invention is a metal-coated particle made of a material having a specific resistance of the surface metal layer of 1 × 10 ⁻² Ω · cm or less, which has not been previously subjected to high dispersion treatment with mono- or polyvalent carboxylic acid. Preferably, the center particle diameter is 0.5 μm or more and 15 μm or less, more preferably 0.5 μm or more and 3 μm or less, and still more preferably 0.5 μm or more and 2 μm or less. Examples of the material having a specific resistance of 1 × 10 ⁻² Ωcm or less include silver, gold, platinum, palladium, copper, nickel, aluminum, zinc, lead, and tin.

In the present invention, when the conductive filler A and the conductive filler B are mixed and used, a conductive filler having a metal layer on the surface of the nonconductive core particles can be used as the conductive filler A.
The conductive filler B is made of a material having a specific resistance of the surface metal layer of 1 × 10 ⁻² Ωcm or less, and has an aspect ratio of 5 or more, preferably 4 or more, more preferably, a ratio of major axis to minor axis. 20 or more, more preferably 30 or more, and particles having an average length L of the major axis of 3 μm or more and 30 μm or less.

The non-conductive particles in the present invention are particles having a specific resistance of 30 × 10 ¹⁴ Ω · cm or more.

In the present invention, the ratio of the conductive filler B to the total conductive filler is desirably 25 to 60% by mass. When the weight ratio is small, the effect of maintaining the conductive network when stretched by the high aspect ratio conductive filler is small, and when the weight ratio is large, the effect of maintaining the conductive network when stretched is large, but the conductive film is formed by the filler arrangement by coating. The strength of is reduced.

In the present invention, as a surface treatment agent such as a high dispersion treatment, a mono- or polyvalent carboxylic acid having 3 to 28 carbon atoms and 0 to 3 double bonds in the molecule, having 3 to 24 carbon atoms. Examples thereof include aliphatic amines having 0 to 2 double bonds in the molecule and derivatives thereof. In the present invention, the fact that the high dispersion treatment with mono- or polyvalent carboxylic acid or the like has not been performed in advance means that the surface treatment with these surface treatment agents has not been performed.
More specifically, the content of these surface treatment agents with respect to the entire paste is 5000 ppm or less, preferably 2000 ppm or less, and more preferably 1200 ppm or less.
These surface treatment agents are effective to pre-treat the raw material metal filler in advance, but the effect can also be obtained by adding at the time of paste mixing and kneading. include.

Mono- or polyvalent carboxylic acids having 3 to 28 carbon atoms and 0 to 3 double bonds in the molecule include crotonic acid, acrylic acid, methacrylic acid, caprylic acid, pelargonic acid, capric acid, Lauric acid, myristic acid, pentadecylic acid, palmitic acid, palmitoleic acid, margaric acid, stearic acid, oleic acid, vaccenic acid, linoleic acid, (9,12,15) -linolenic acid, (6,9,12) -linolene Acid, dihomo-γ-linolenic acid, eleostearic acid, tuberculostearic acid, arachidic acid (eicosanoic acid), 8,11-eicosadienoic acid, 5,8,11-eicosatrienoic acid, arachidonic acid, behenic acid, Lignoceric acid, nervonic acid, elaidic acid, erucic acid, docosahexaenoic acid, eicosapentaenoic acid, stearidonic acid, Aromatic dicarboxylic acids such as rephthalic acid, isophthalic acid, orthophthalic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, azelaic acid and other dicarboxylic acids, maleic acid, dimer acid Dibasic acids having 12 to 28 carbon atoms such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic anhydride, 3-methylhexahydro Alicyclic rings such as phthalic anhydride, 2-methylhexahydrophthalic anhydride, dicarboxy hydrogenated bisphenol A, dicarboxy hydrogenated bisphenol S, dimer acid, hydrogenated dimer acid, hydrogenated naphthalenedicarboxylic acid, tricyclodecane dicarboxylic acid Group dicarboxylic acid, hydroxybenzoic acid, Mention may be made of hydroxycarboxylic acids such as lactic acid. Examples thereof include trivalent or higher carboxylic acids such as trimellitic anhydride and pyromellitic anhydride, unsaturated dicarboxylic acids such as fumaric acid, and carboxylic acid diols such as dimethylolbutanoic acid and dimethylolpropionic acid.

Examples of the aliphatic amine having 3 to 24 carbon atoms and 0 to 2 double bonds in the molecule include capriylamine, laurylamine, myristylamine, pentadecylamine, palmitic acid. Ruamine, palmitolylamine, margarylylamine, stearylylamine, oleylamine, buxeylamine, linoleylamine, (9,12,15) -linoleylamine, (6,9,12) -linoleylamine, dihomo- γ-linoleylamine, eleostearylamine, tuberculosearylamine, arachidiylamine (eicosylamine), 8,11-eicosadienylamine, 5,8,11-eicosatrienylamine, arachidonylamine, Behenylamine, lignosericylamine, nerbonylua Emissions, Elias isoxazolidinyl amines, exemplified Erukiiruamin, docosahexaenoyl anycast propylamine, eicosapentaenoic anycast propylamine, the steering Lido Niiru amine.

In the present invention, the conductive paste may contain a surface treatment agent that is not intended for high dispersion. The amount of the surface treatment agent not intended for high dispersion is preferably 0.1 to 3.0% by mass, more preferably 1.0 to 2.0% by mass with respect to the conductive filler. The surface treatment agent not intended for high dispersion means an antioxidant, a reducing agent, an adhesion promoter and the like.

The additive in the present invention is a compound having a molecular structure exhibiting low surface free energy and having a functional group at least at one end.
Examples of the structure exhibiting low surface free energy include polydimethylsiloxane and fluorine-containing groups. In addition, examples of the functional group include an amino group, a carboxyl group, and a glycidyl group, and a carboxyl group is more preferable.

The additive in the present invention is preferably a liquid which is liquid at room temperature.
Preferably the surface free energy of the additive in the present invention is less than 30 mJ / ^{m 2,} further preferably 26 mJ / ^{m 2} or less, further preferably 24 mJ / ^{m 2} or less, 20 mJ / m @ 2 or less More preferably it is.
The amount of the additive is preferably 0.1 to 3.0% by mass, more preferably 0.12 to 2.0% by mass with respect to the conductive filler.

As an additive preferably used in the present invention, there can be exemplified dimethylsiloxane having a molecular weight in the range of 300 or more and 8000 or less and carboxy-modified at one end.
Examples of the additive preferably used in the present invention include fluoromonocarboxylic acids having a molecular weight in the range of 100 to 1,000. As the fluorine-based additive, partial fluorine or fluoromonocarboxylic acid which is not completely fluorine is preferable.

In the present invention, non-conductive particles having an average particle size of 0.3 μm or more and 10 μm or less may be included. The non-conductive particles in the present invention are mainly metal oxide particles, such as silicon oxide, titanium oxide, magnesium oxide, calcium oxide, aluminum oxide, iron oxide, metal sulfate, metal carbonate, metal A titanate or the like can be used. In the present invention, it is preferable to use barium sulfate particles among such non-conductive particles.

The binder resin used in the stretchable conductor layer of the present invention preferably has a stretch recovery rate after stretching 20% of 99% or more, more preferably 99.5% or more, and still more 99.85%. The above is preferable. The elongation recovery rate of the binder resin is measured in an environment of 25 ± 3 ° C. by molding the binder resin on a sheet having a thickness of 20 to 200 μm and a film thickness unevenness of 10% or less. If the stretch recovery rate of the binder resin is less than this range, it becomes difficult to make the stretch recovery rate of the stretchable conductor layer above a predetermined range. Further, if the elongation recovery rate of the binder resin is less than this range, the repeated stretchability and torsion resistance of the conductive paste are lowered.

The stretch recovery rate in the present invention means that the initial length is L ₀ , when an elastic conductive sheet is suspended as shown in FIG. When the length when stretched by 20% to a predetermined percentage is L ₁ and the length when the stretch load is removed is L ₂ ,
(Equation 1)
Elongation recovery rate = ((L ₁ −L ₂ ) / (L ₁ −L ₀ )) × 100 [%]
(Equation 2)
Residual strain rate = ((L ₂ −L ₀ ) / L ₀ ) × 100 [%]
L ₀ initial length L ₃ elongation = L ₁ −L ₀
L ₄ recovery length = L _1- L ₂
L ₅ residual strain = L ₂ −L ₀
And define. A similar measurement method is stipulated in the JIS L 1096 woven and knitted fabric test method, but it is not the recovery rate after stretching under a constant load, but the recovery rate when stretched to a certain length. Different. In actual use, the load applied to the stretchable conductor layer is often repeatedly stretched to a predetermined length regardless of the load, so that the practical performance cannot be expressed by the stretch recovery rate by the constant load method. Unless otherwise specified, the extension recovery rate is evaluated under an environment of 25 ° C. ± 3 ° C.

A crosslinked or non-crosslinked elastomer is used as the binder resin in the present invention. In the present invention, it is preferable to use a non-crosslinked elastomer.
The non-crosslinked elastomer preferably has a modulus of elasticity of 3 to 600 MPa, and a thermoplastic elastomer resin having a glass transition temperature in the range of −60 ° C. to 0 ° C. can be preferably used. Examples include rigid rubber and natural rubber. In order to develop the stretchability of the coating film (sheet), rubber, polyurethane resin, and polyester resin are preferable. As rubber, urethane rubber, acrylic rubber, silicone rubber, butadiene rubber, nitrile group-containing rubber such as nitrile rubber and hydrogenated nitrile rubber, isoprene rubber, sulfurized rubber, styrene butadiene rubber, butyl rubber, chlorosulfonated polyethylene rubber, ethylene propylene Examples include rubber and vinylidene fluoride copolymer. Among these, nitrile group-containing rubber, chloroprene rubber, chlorosulfonated polyethylene rubber and styrene butadiene rubber are preferable, and nitrile group-containing rubber is particularly preferable.

The elastic modulus of the flexible resin is preferably 3 to 600 MPa, more preferably 10 to 500 MPa, still more preferably 15 to 300 MPa, still more preferably 20 to 150 MPa, and particularly preferably 25 to 100 MPa.

The urethane resin of the present invention can be obtained by reacting a soft segment made of a polyether, polyester, or polycarbonate polyol with a hard segment made of diisocyanate or the like. As the soft segment component, polyester polyol is more preferable from the viewpoint of molecular design freedom.

Examples of the polyether polyol in the present invention include copolymerization of monomer materials such as polyethylene glycol, polypropylene glycol, polypropylene triol, polypropylene tetraol, polytetramethylene glycol, polytetramethylene triol, and cyclic ether for synthesizing these. Examples thereof include polyalkylene glycols such as copolymers, derivatives obtained by introducing side chains or branched structures, modified products, and mixtures thereof. Of these, polytetramethylene glycol is preferred. The reason is that the mechanical properties are excellent.

As the polyester polyol in the present invention, aromatic polyester polyol, aromatic / aliphatic copolymer polyester polyol, aliphatic polyester polyol, and alicyclic polyester polyol can be used. As the polyester polyol in the present invention, either a saturated type or an unsaturated type may be used. Of these, aliphatic polyester polyols are preferred.

A commercial item can also be used as said aliphatic polyester polyol. Specific examples of commercially available products include, for example, Polylite ODX-688, ODX-2044, ODX-240 (manufactured by DIC), Kuraray polyol P-2010, P-2050, P-1010 (Kuraray), Teslac 2461, 2455, 2469 (manufactured by Hitachi Chemical).

Examples of the polycaprolactone diol in the present invention include polycaprolactone diol compounds obtained by ring-opening addition reaction of lactones such as γ-butyllactone, ε-caprolactone, and δ-valerolactone.

Examples of commercially available polycarbonate diol compounds that can be used in the present invention include Kuraray Kuraray Polyol C Series, Asahi Kasei Chemicals Duranol Series, and the like. For example, Kuraray polyol C-1015N, Kuraray polyol C-1065N, Kuraray polyol C-2015N, Kuraray polyol C2065N, Kuraray polyol C-1050, Kuraray polyol C-1090, Kuraray polyol C-2050, Kuraray polyol C-2090, DURANOL- Examples thereof include T5650E, DURANOL-T5651 and DURANOL-T5652.

Examples of the diisocyanate compound in the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, m-phenylene diisocyanate, 3,3′-dimethoxy-4. , 4′-biphenylene diisocyanate, 2,6-naphthalene diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 4,4′-diphenylene diisocyanate, 4,4′-diisocyanate diphenyl ether, 1,5- Aromatic diisocyanates such as naphthalene diisocyanate and m-xylene diisocyanate, or 1,6-hexane diisocyanate, isophorone diisocyanate, 4,4′-diphenylmethane diisocyanate Over DOO, aliphatic hydrogenated xylylene diisocyanate (ortho, meta, para), and alicyclic diisocyanates. Of these, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and isophorone diisocyanate are preferable. Moreover, you may use together the said isocyanate combined use and the polyfunctional compound more than trifunctional as needed.

The polyurethane resin of the present invention may be copolymerized with a diol compound or the like generally called a chain extender if necessary.

Examples of the diol compound used as a chain extender include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol. 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, 1,2- Butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5- Pentanediol, 2,2,4-trimethyl-1,3-pentanediol, neope Tyl glycol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol, 1,8-octanediol, 2-methyl-1,8-octane Aliphatic glycols such as diols and 1,9-nonanediol. Alternatively, low molecular weight triols such as trimethylolpropane and triethanolamine, diamine compounds such as diethylamine and 4,4'-diaminodiphenylmethane, and trimethylolpropane can be used. Among these, 1,6-hexanediol is particularly preferable.

The glass transition temperature of the polyurethane resin of the present invention is preferably 0 ° C. or lower, more preferably −60 ° C. or higher and −10 ° C. or lower, and most preferably −50 ° C. or higher and −20 ° C. or lower. When the glass transition temperature exceeds 0 ° C., the elongation of the produced conductive coating film becomes small, and there is a possibility that the resistance increase at the time of elongation becomes worse. On the other hand, when the temperature is lower than −60 ° C., the produced conductive coating film may cause blocking. The reduced viscosity is from 0.2 dl / g to 3.0 dl / g, preferably from 0.3 dl / g to 2.5 dl / g, more preferably from 0.4 dl / g to 2.0 dl / g. It is. If it is less than 0.2 dl / g, the conductive coating film becomes brittle and there is a risk that the resistance increase at the time of elongation will worsen. Moreover, when it exceeds 3.0 dl / g, there exists a possibility that the solution viscosity of a polyurethane resin composition may become high and handling may become difficult.

When a polyurethane resin is produced, stannous octylate, dibutyltin dilaurate, triethylamine, bismuth metal, or the like may be used as a catalyst.

The rubber containing a nitrile group is not particularly limited as long as it is a rubber or elastomer containing a nitrile group, but nitrile rubber and hydrogenated nitrile rubber are preferable. Nitrile rubber is a copolymer of butadiene and acrylonitrile. If the amount of bound acrylonitrile is large, the affinity with metal increases, but the rubber elasticity contributing to stretchability decreases conversely. Therefore, the amount of bound acrylonitrile is preferably 18 to 50% by mass, more preferably 30 to 50% by mass, and more preferably 40 to 50% by mass in 100% by mass of nitrile-containing rubber (for example, acrylonitrile butadiene copolymer rubber). It is particularly preferable that the content is% by mass.

The glass transition temperature of such a binder resin is preferably 0 ° C. or lower, more preferably −8 ° C. or lower, even more preferably −16 ° C. or lower, still more preferably −24 ° C. or lower. When the glass transition temperature exceeds this range, the stretch recovery property is hardly exhibited.
The glass transition temperature can be determined by differential scanning calorimetry (DSC) according to a conventional method.

The organic solvent used in the conductive paste of the present invention preferably has a boiling point of 100 ° C. or higher and lower than 300 ° C., more preferably 150 ° C. or higher and lower than 290 ° C. If the boiling point of the organic solvent is too low, the solvent volatilizes during the paste manufacturing process or use of the paste, and there is a concern that the component ratio of the conductive paste is likely to change. On the other hand, if the boiling point of the organic solvent is too high, when a low-temperature drying step is required (for example, 150 ° C. or less), a large amount of the solvent may remain in the coating film, causing a decrease in the reliability of the coating film. There are concerns.

Examples of such high-boiling solvents include cyclohexanone, toluene, isophorone, γ-butyrolactone, benzyl alcohol, Exxon Chemical Solvesso 100, 150, 200, propylene glycol monomethyl ether acetate, terpionol, butyl glycol acetate, diamylbenzene ( Boiling point: 260 to 280 ° C., triamylbenzene (boiling point: 300 to 320 ° C.), n-dodecanol (boiling point: 255 to 29 ° C.), diethylene glycol (boiling point: 245 ° C.), ethylene glycol monoethyl ether acetate (boiling point: 145 ° C), diethylene glycol monoethyl ether acetate (boiling point 217 ° C), diethylene glycol monobutyl ether acetate (boiling point: 247 ° C), diethylene glycol dibutyl ether ( Point: 255 ° C.), diethylene glycol monoacetate (boiling point: 250 ° C.), triethylene glycol diacetate (boiling point: 300 ° C.), triethylene glycol (boiling point: 276 ° C.), triethylene glycol monomethyl ether (boiling point: 249 ° C.), tri Ethylene glycol monoethyl ether (boiling point: 256 ° C.), triethylene glycol monobutyl ether (boiling point: 271 ° C.), tetraethylene glycol (boiling point: 327 ° C.), tetraethylene glycol monobutyl ether (boiling point: 304 ° C.), tripropylene glycol ( Boiling point: 267 ° C.), tripropylene glycol monomethyl ether (boiling point: 243 ° C.), 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (boiling point: 253 ° C.), and the like. As petroleum-based hydrocarbons, AF Solvent No. 4 (boiling point: 240 to 265 ° C.), No. 5 (boiling point: 275 to 306 ° C.), No. 6 (boiling point: 296 to 317 ° C.) manufactured by Nippon Oil Corporation No. 7, (boiling point: 259-282 ° C.), and No. 0 solvent H (boiling point: 245-265 ° C.), etc., and two or more of them may be included if necessary. Such an organic solvent is appropriately contained so that the conductive silver paste has a viscosity suitable for printing or the like.

In the conductive paste of the present invention, the blending ratio of the total conductive filler: binder is preferably 25 to 50% by volume: 50 to 75% by volume, more preferably 30 to 40% by volume: 60 to 70% by volume.

The compounding ratio of the organic solvent in the present invention is 15 to 35% by weight, preferably 20 to 30% by weight, based on the elastomer.

The conductive paste of the present invention can be obtained by mixing and dispersing with a disperser such as a dissolver, a three-roll mill, a self-revolving mixer, an attritor, a ball mill, and a sand mill.

The conductive paste of the present invention includes a thixotropic agent, an antifoaming agent, a flame retardant, a tackifier, a hydrolysis inhibitor, a leveling agent, a plasticizer, an antioxidant, and an ultraviolet ray as long as the content of the invention is not impaired. Addition agents such as an absorbent, a pigment, and a dye can be blended.

The amount of the imparting agent in the present invention is preferably 0.1 to 10% by weight, more preferably 0.3 to 5% by weight, based on the total amount of the conductive fillers.

The conductive paste thus obtained can be applied or printed on a substrate, and then an organic solvent is evaporated and dried to form a conductive coating film. The range of the film thickness is not particularly limited, but 1 μm to 1 mm is preferable. When the thickness is 1 μm or less, coating film defects such as pinholes are likely to occur, which may cause a problem. When it exceeds 1 mm, the organic solvent tends to remain inside the coating film, and the reproducibility of the coating film properties may be inferior.

The substrate to which the conductive silver paste is applied is not particularly limited, but a flexible or stretchable substrate is preferable. 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.

When the conductive silver paste coating film is peeled off from the base material and the wiring, electrodes, and sheets only with the coating film are formed, and then transfer is performed, it is preferable to select a base material having excellent peelability. Specific examples include a silicon sheet and a Teflon (registered trademark) sheet, and the conductive coating film can be easily peeled off.

Although the process of apply | coating an electroconductive silver 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 conductive paste of the present invention can be used by a method of forming a sheet by a coating method, processing the sheet into a predetermined shape by a method such as punching, punching, laser cutting, or cutting and laminating it on a substrate.

The step of heating the substrate coated with the conductive silver 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 organic solvent 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. If it is less than 20 degreeC, a solvent may remain in a coating film and electroconductivity may not be acquired. If treated for a long period of time, conductivity is exhibited, but the specific resistance may be significantly inferior. A preferred heating temperature is 70 to 180 ° C. If it is less than 70 degreeC, the heat shrink of a coating film becomes small, the conductive network of the silver powder in a coating film cannot fully be formed, and a specific resistance may become high. The elongation rate and repeated stretchability may also deteriorate due to the denseness of the coating film. When the temperature exceeds 180 ° C., the base material is limited due to the heat resistance, and when it is treated for a long time, the base material may be thermally deteriorated, and the elongation rate and repeated stretchability may deteriorate.

The conductive paste of the present invention is preferably capable of forming a coating film having a specific resistance of less than 1.0 × 10 ⁻³ (Ω · cm). When the specific resistance is 1.0 × 10 ⁻³ (Ω · cm) or more, the extension wiring, extension antenna, etc. used in the fields of FPC, robot, smart wear, healthcare sensor, display, solar cell, RFID, game machine, etc. In designing the stretchable electrode, restrictions such as the coating thickness, wiring length, wiring width, etc. may arise and may not be applicable.

Furthermore, the conductive paste of the present invention is capable of forming a coating film having a breaking elongation greater than 35% and capable of forming a coating that does not break by repeated stretching and stretching 50 times or more when an elongation rate of 20% is repeatedly evaluated. Is preferred. The breaking elongation of the coating film is more preferably 60% or more in view of adapting to the human body or robot joints, and more preferably 100% or more from the viewpoint of reliability. In addition, when repeated stretch evaluation of the coating film is performed at a coating film elongation rate of 20%, it is more preferable that breakage does not occur due to repeated stretching of 100 times or more. In the case where it is formed, it is more preferable that no breakage occurs due to repeated expansion and contraction 1000 times or more.

Hereinafter, the present invention will be described in more detail and specifically with reference to examples. The evaluation results in the examples were measured by the following methods. In the examples, “parts” means “parts by weight”.

<Surface energy>
As a solid material, a mirror-plated metal plate, a polyethylene terephthalate film, and a fluororesin plate subjected to silver plating were used, and the contact angle between each solid material and the additive was determined and calculated based on the extended Fowkes equation. The contact angle was DM-501 from Kyowa Interface Chemical Co., Ltd., and the surface roughness of the solid material was polished with emery polishing paper so that the center line average roughness was 0.10μ to 0.20μ. The droplet was about 1 μL. The measurement environment was 25 ° C.

<Reducing viscosity, glass transition temperature, sample preparation method for mechanical properties>
A polyurethane resin composition was applied onto a polypropylene film (pyrene OT; 50 μm thickness) manufactured by Toyobo Co., Ltd. using an applicator having a 300 μm gap and a width of 130 mm (applied surface is 130 mm × 200 mm). The coated product was fixed on cardboard, dried using a hot air dryer (DH42 manufactured by Yamato Scientific Co., Ltd.) at 120 ° C. for 30 minutes, and then cooled. Then, it peeled from the polypropylene film and obtained the sample for evaluation.

<Reduced viscosity>
0.1 g of the sample prepared based on the above reduced viscosity sample preparation method is accurately weighed and placed in a 25 ml volumetric flask. About 20 ml of phenol / tetrachloroethane = 6/4 (weight ratio) mixed solvent is added and heated to dissolve the resin. After complete dissolution, a mixed solvent of phenol / tetrachloroethane = 6/4 (weight ratio) is added to a line of 25 ml at 30 ° C. It mixed uniformly and measured at 30 degreeC using the Ubbelohde viscosity tube.

<Glass transition temperature>
5 mg of the sample resin is put in an aluminum sample pan and sealed, and the differential scanning calorimeter (DSC) DSC-7020 manufactured by Seiko Instruments Inc. is used to increase the temperature to 100 ° C. at a temperature rising rate of 20 ° C./min. Measured and determined at the temperature of the intersection of the baseline extension below the glass transition temperature and the tangent indicating the maximum slope at the transition.

<Mechanical properties>
A sample with a sample size of 10 mm x 50 mm is cut out from the sample prepared based on the sample preparation method for measuring mechanical properties, and is clamped and fixed to the sample fixing chuck of a tensile tester (Orientec RTA-100) by 20 mm each, and the distance between chucks The measurement was performed under the conditions of 10 mm, a pulling speed of 20 mm / min, and a temperature of 25 ° C. and 60 RH%, and the elastic modulus and elongation were measured five times and averaged from the SS curve.

<Urethane group concentration>
Urethane group concentration is calculated by the following formula: Urethane group concentration (eq / t) = (W ÷ (X ÷ Y)) ÷ Z × 10 ⁶
W: Weight of isocyanate constituting polyurethane resin X: Molecular weight of isocyanate Y: Number of isocyanates per molecule of isocyanate Z: Total weight of raw materials constituting polyurethane resin

<Preparation of conductive film>
A conductive paste was applied by an applicator on a stretchable urethane sheet having a thickness of 100 μm, and dried at 120 ° C. for 20 minutes to produce a sheet having a conductive film having a thickness of about 80 μm. Specific resistance and repeated stretchability were evaluated together with the urethane sheet on the conductive film formed on the urethane sheet.

<Evaluation of specific resistance>
The sheet resistance and film thickness of the conductive coating film in the natural state (elongation rate 0%) were measured, and the specific resistance was calculated. Thickness gauge SMD-565L (manufactured by TECLOCK) was used for the film thickness, and sheet resistance was measured for four test pieces using Loresta-GP MCP-T610 (manufactured by Mitsubishi Chemical Analytech), and the average value was used. .
In the same manner as in the natural state (elongation rate 0%), the following 4. The specific resistance was measured when the elongation rate was 100%. In addition, the specific resistance at the time of extending | stretching read the value 30 seconds after reaching a predetermined expansion | extension degree. The specific resistance was calculated by the following formula.
Specific resistance (Ω · cm) = Rs (Ω _{/ □} ) × t (cm)
Here, Rs represents the sheet resistance measured under each condition, and t represents the film thickness measured under each condition.

<Repetitive stretch evaluation>
Using a repeated durability tester (TIQ-100, manufactured by Reska Co., Ltd.), the sample film was repeatedly stretched by 20% of its original length and returned to its original length. The specific resistance was measured in a state where the length was returned to the original length after repeating the expansion and contraction 1000 times (elongation rate 0%). The elongation speed and the speed for returning to the original length were both 10 mm / second. As an index of repeated stretchability, a value obtained by dividing the specific resistance after 1000 times stretching by the initial specific resistance was used.

<Evaluation of core particle diameter and aspect ratio>
The average particle diameter of the core particles, the average particle diameter of the silver-coated particles, and the aspect ratio were measured using a scanning electron microscope (model number: S-4500) manufactured by Hitachi High-Technologies Corporation, with software (product name: EMAX). It was determined by measuring 300 core particles at 2000 times.

<Evaluation of torsion>
The specific resistance of the stretchable conductor sheet in the initial state and the specific resistance of the stretchable conductor sheet obtained by repeating the twist cycle of the twist test 100 times were calculated, and the change in specific resistance was calculated by the following formula. Change in specific resistance (times) = specific resistance of stretchable conductor sheet after 100 twist cycles / specific resistance of stretchable conductor sheet in initial state
[Torsion test:
Sample: width 10 mm, test length 100 mm (One end in the longitudinal direction of the sample is fixed and twisted by rotating one end)
Twist cycle: Twist in the positive direction (3600 °), return to the initial state,
Twist in the negative direction (-3600 °) and return to the initial state]

<Resin production example 1>
Synthesis of polyurethane resin composition (A) In a 1 L four-necked flask, 100 parts of ODX-2044 (DIC polyester diol), 33 parts P-2010 (Kuraray polyester diol), 1,6-hexanediol as a chain extender 30% by weight (manufactured by Ube Industries) was put in 125 parts of diethylene glycol monoethyl ether acetate and set in a mantle heater. A stir bar with a stirring seal, a reflux condenser, a temperature detector, and a ball stopper were set in the flask and dissolved by stirring at 50 ° C. for 30 minutes. 70 parts of Desmodur I (manufactured by Bayer, isocyanate) and 1 part of a bismuth metal catalyst were added. When the temperature rise due to the reaction heat settled, the temperature was raised to 90 ° C. and reacted for 4 hours to obtain a polyurethane resin composition (A). The properties of the obtained resin are shown in Table 1.

<Resin production example 2>
Synthesis of polyurethane resin composition (B) In a 1 L four-necked flask, 100 parts of ODX-2044 (DIC polyester diol), 33 parts of 1,6-hexanediol (manufactured by Ube Industries) as a chain extender, diethylene glycol monoethyl ether It put into 100 parts of acetate and set to the mantle heater. A stir bar with a stirring seal, a reflux condenser, a temperature detector, and a ball stopper were set in the flask and dissolved by stirring at 50 ° C. for 30 minutes. 58 parts of T-100 (manufactured by Tosoh, isocyanate) and 0.1 part of dibutyltin dilaurate as a catalyst were added. When the temperature rise due to reaction heat settled, the temperature was raised to 90 ° C. and reacted for 4 hours to obtain a polyurethane resin composition (B). The properties of the obtained resin are shown in Table 1.

<Production and evaluation of conductive paste>
First, dissolve the binder resin in half the amount of the solvent specified, add the metal particles, the treating agent and the remaining solvent to the resulting solution, and after premixing, disperse in a three-roll mill. The conductive pastes of Examples 1 to 8 and Comparative Examples 1 and 2 shown in Tables 2 and 3 were obtained. The evaluation results of the obtained conductive paste are shown in Tables 2 and 3.

In Tables 2 and 3, conductive filler 1: Silver coated powder, general-purpose type (average particle size 2 μm) manufactured by Mitsubishi Materials Corporation
Conductive filler 2: Silver coated powder, general-purpose type (average particle size 1.2μm), manufactured by Mitsubishi Materials Corporation
Binder resin 1: JSR Corporation very high nitrile type N215SL
Binder resin 2: Polyurethane resin composition A obtained in Resin Production Example 1
Binder resin 3: Polyurethane resin composition B obtained in Resin Production Example 2
Additive 1: Pentadecafluorooctanoic acid manufactured by Tokyo Chemical Industry Co., Ltd. (surface free energy: 18 mJ / m ² )
Additive 2: Reactive silicone oil one-end type (average one-terminal carboxyl modification) manufactured by Shin-Etsu Chemical Co., Ltd. (surface free energy: 22 mJ / m ² )
Additive 3: Tokyo Chemical Industry Co., Ltd. Dodecanedioic acid (surface free energy: 31 mJ / m ² )
Solvent 1: Isophorone solvent 2: Diethylene glycol monoethyl ether acetate

Example 1 in Table 2 is an example in which a conductive filler 1 and a binder resin 1 were used, and 0.1 wt% of additive 1 was added to the conductive filler to produce a paste. The initial specific resistance is 5.9 × 10 ⁻⁴ (Ω · cm), the specific resistance at 100% elongation is 86 × 10 ⁻⁴ (Ω · cm), and the specific resistance after 1000% expansion and contraction 20% is 5000 × 10. ^-4 (Ω · cm).

Example 2 in Table 2 is an example in which the conductive filler 1 and the binder resin 1 were used, and 1% by weight of the additive 1 was added to the conductive filler to produce a paste. The initial specific resistance is 5.4 × 10 ⁻⁴ (Ω · cm), the specific resistance at 100% elongation is 52 × 10 ⁻⁴ (Ω · cm), and the specific resistance after 1000% expansion and contraction 20% is 1300 × 10 ^-4 (Ω · cm), which was very good.

Example 3 in Table 2 is an example in which a conductive filler 1 and a binder resin 1 were used and 2% by weight of additive 1 was added to the conductive filler to produce a paste. The initial specific resistance is 6.4 × 10 ⁻⁴ (Ω · cm), the specific resistance at 100% elongation is 83 × 10 ⁻⁴ (Ω · cm), and the specific resistance after 1000% expansion and contraction 20% is 1100 × 10 ^-4 (Ω · cm), which was very good.

Example 4 in Table 2 is an example in which the conductive filler 2 and the binder resin 1 were used, and 1% by weight of the additive 1 was added to the conductive filler to produce a paste. The initial specific resistance is 3.5 × 10 ⁻⁴ (Ω · cm), the specific resistance at 100% elongation is 30 × 10 ⁻⁴ (Ω · cm), and the specific resistance after 1000% expansion and contraction 20% is 790 × 10. ^-4 (Ω · cm), which was very good.

Example 5 in Table 2 is an example in which the conductive filler 1 and the binder resin 1 were used, and 1% by weight of the additive 2 was added to the conductive filler to produce a paste. The initial specific resistance is 36.6 × 10 ⁻⁴ (Ω · cm), the specific resistance at 100% elongation is 93 × 10 ⁻⁴ (Ω · cm), and the specific resistance after 1000% expansion and contraction 20% is 1600 × 10 ^-4 (Ω · cm), which was very good.

Example 6 in Table 2 is an example in which a conductive filler 1 and a binder resin 1 were used and a paste was prepared without adding additives. Initial resistivity is ^{7.6 × 10 -4 (Ω · cm} ), 100% specific resistance at the time of extension ^{110 × 10- 4 (Ω · cm} ), the specific resistance after 20% repeated stretching 1000 times 6800 × 10 ^{- 4 (Ω} · cm) was achieved, good.

Example 7 in Table 2 is an example in which a conductive filler 1 and a binder resin 2 were used, and 1% by weight of additive 1 was added to the conductive filler to produce a paste. The initial specific resistance is 5.1 × 10 ⁻⁴ (Ω · cm), the specific resistance at 100% elongation is 39 × 10 ⁻⁴ (Ω · cm), and the specific resistance after 1000% expansion and contraction 20% is 1250 × 10. ^{It was −4} (Ω · cm), which was very good.

Example 8 in Table 2 is an example in which the conductive filler 1 and the binder resin 3 were used, and 1% by weight of the additive 1 was added to the conductive filler to produce a paste. The initial specific resistance is 5.2 × 10 ⁻⁴ (Ω · cm), the specific resistance at 100% elongation is 54 × 10 ⁻⁴ (Ω · cm), and the specific resistance after 1000 times of 20% repeated expansion and contraction is 1000 × 10 ^{It was −4} (Ω · cm), which was very good.

Comparative Example 1 in Table 2 is an example in which conductive paste 1 and binder resin 1 were used, and 5.0 wt% of additive 1 was added to the conductive filler to produce a paste. The initial specific resistance was 7.2 × 10 ⁻⁴ (Ω · cm), the specific resistance at 100% elongation was 125 × 10 ⁻⁴ (Ω · cm), and conduction was lost after 1000 times of 20% repeated expansion and contraction.

Comparative Example 2 in Table 2 is an example in which conductive paste 1 and binder resin 1 were used, and 1.0 wt% of additive 3 was added to the conductive filler to produce a paste. The initial specific resistance was 21 × 10 ⁻⁴ (Ω · cm), and when 100% stretched, conduction was lost after 20% repeated stretching 1000 times.

[Application Example 1]
The conductive film obtained from the conductive paste obtained in Example 1 was used as a stretchable conductor layer, and the elastic insulating polymer layer used was an elastomer sheet “Mobilon” with a hot melt layer manufactured by Nisshinbo Co., Ltd. The sports shirt with electrodes and wiring was obtained by omitting the layers and cutting each sheet into a predetermined shape and laminating and laminating.
The obtained sports shirt with electrodes and wiring has a circular electrode with a diameter of 50 mm at the intersection of the left and right posterior axillary lines and the seventh rib, and further, by a striped stretchable conductor composition from the circular electrode to the center of the chest Electrical wiring is formed on the inside. Note that the chest central side of the wiring extending from the left and right electrodes to the center of the back of the neck is a rectangle with a side of 20 mm.

Subsequently, a stainless steel hook is attached to the surface side of the pair of electrode parts at the center of the chest, and a stretchable conductor using conductive yarn twisted with a thin metal wire to ensure electrical continuity with the wiring part on the back side. The composition layer and the stainless steel hook were electrically connected.
Connect a heart rate sensor WHS-2 made by Union Tool through a stainless steel hook, and receive heart rate data with an Apple smartphone incorporating the app “myBeat” dedicated to the heart rate sensor WHS-2. Set to display. A sports shirt incorporating a heart rate measurement function was produced as described above.

The electrocardiogram data while driving a car was acquired by wearing this shirt on a subject. The obtained electrocardiogram data has low noise, high resolution, and quality that can be analyzed from the heartbeat interval change, electrocardiogram waveform, etc., as the electrocardiogram mental state, physical condition, fatigue level, sleepiness, tension level, etc. It was. The same shirt was worn by 10 subjects, and the feeling of wearing was evaluated. None of the subjects complained of discomfort or discomfort.

<Example 11>
First, a conductive paste was manufactured according to the composition ratio shown in Table 4. The binder resin is dissolved in half the solvent amount of the predetermined solvent amount, the metal particles are added to the resulting solution, premixed, and then dispersed by a three-roll mill, whereby the conductive paste D11 shown in Table 1 is obtained. Got.

In Table 4, conductive filler A1: Silver coated powder, general-purpose type manufactured by Mitsubishi Materials Corporation (average particle size 2 μm)
Conductive filler A2: Silver coated powder, general-purpose type (average particle size 1.2μm) manufactured by Mitsubishi Materials Corporation
Conductive filler B: YCC techno powder silver coated potassium titanate fiber YTA-1575 manufactured by Yokozawa Metal Industry Co., Ltd.
Binder resin 11: Extremely high nitrile type N215SL made by JSR Corporation
Elongation recovery rate 99.9% or more Binder resin 12: Polyurethane resin composition (B)
Elongation recovery rate 99.9% or more Solvent 1: Isophorone solvent 3: Ethylene glycol monoethyl ether acetate

<Preparation of conductive film>
A conductive paste D11 obtained by an applicator was applied on a stretchable urethane sheet having a thickness of 1 mm, and dried at 120 ° C. for 20 minutes to produce a sheet having a conductive film with a thickness of about 80 μm. The conductive film formed on the urethane sheet was evaluated using a test piece that was slit into a strip shape with a width of 10 mm together with the urethane sheet. The evaluation results are shown in Table 4.

<Examples 12 to 15 and Comparative Examples 11 to 14>
Thereafter, the same operation as in Example 11 was performed according to the composition ratio in Table 4, and conductive pastes D12 to D19 were obtained. The obtained conductive paste was evaluated in the same manner as in Example 11. The results are shown in Table 4. Shown in

[Application Example 2]
A clothes-type electronic device for measuring an electrocardiogram having electrical wiring by the transfer method shown in FIG. 4 was manufactured.
A carbon paste serving as an electrode surface layer was first screen-printed in a predetermined pattern on a release PET film having a thickness of 125 μm, and then dried and cured. Next, an insulating paste serving as an insulating cover layer was screen-printed in a predetermined pattern and dried and cured. The electrode surface layer for electrocardiogram measurement is a circle with a diameter of 30 mm. The insulating cover layer has a donut shape with an inner diameter of 30 mm and an outer diameter of 36 mm at the electrode portion, the wiring portion extending from the electrode has a width of 14 mm, and the end of the wiring portion has a diameter of 10 mm to attach a hook for connection with the sensor. The circular electrodes are similarly printed with carbon paste. The thickness of the carbon paste layer is 25 μm in terms of dry film thickness, and the insulating cover layer is 15 μm. Next, the electrode part and the wiring part are screen-printed using the conductive paste D11 as the conductor layer, and dried under predetermined conditions. Cured. The electrode part was circular with a diameter of 32 mm, the wiring part was 10 mm wide, and the dry thickness on the insulating cover layer was adjusted to 30 μm. Furthermore, the base layer is adjusted to a dry thickness of 20 μm using the same insulating paste as that of the insulating cover layer, screen-printed and dried, and the base layer is printed again under the same conditions, and the drying time is adjusted and the solvent is adjusted. The surface tackiness was left so that 25% by mass remained, and printed electric wiring having transferability was obtained.
Next, the transferable printed electrical wiring obtained by the above process is superimposed on a predetermined part of a sports shirt made of knitted fabric turned upside down, pressed at room temperature to temporarily bond the printed electrical wiring to the backside of the sports shirt, and release The PET film was peeled off, the sports shirt was hung on a hanger, and further dried at 115 ° C. for 30 minutes to obtain a sports shirt with electrical wiring. The wiring pattern is shown in FIG. 5, and the layout of the wiring pattern with respect to the shirt is shown in FIG.
The resulting sports shirt with electrical wiring has a circular electrode with a diameter of 30 mm at the intersection of the left and right posterior axillary lines and the seventh rib, and further with a stretchable conductor with a width of 10 mm from the circular electrode to the center of the posterior neck. Electrical wiring is formed on the inside. The wiring extending from the left and right electrodes to the center of the rear neck has a gap of 5 mm at the center of the neck, and both are not short-circuited.

Subsequently, a stainless steel hook is attached to the surface side of the central end of the rear neck, and a stretchable conductor composition layer using a conductive thread twisted with a thin metal wire to ensure electrical continuity with the wiring part on the back side And a stainless steel hook were electrically connected.
Connect a heart rate sensor WHS-2 made by Union Tool through a stainless steel hook, and receive heart rate data with an Apple smartphone incorporating the app “myBeat” dedicated to the heart rate sensor WHS-2. Set to display. A sports shirt incorporating a heart rate measurement function was produced as described above.

The subject was made to wear this shirt, and radio exercises 1 and 2 were continuously performed, and electrocardiographic data during that time was acquired. The obtained electrocardiogram data has low noise, high resolution, and quality that can be analyzed from the heartbeat interval change, electrocardiogram waveform, etc., as the electrocardiogram mental state, physical condition, fatigue level, sleepiness, tension level, etc. It was. The same shirt was worn by 10 subjects, and the feeling of wearing was evaluated. None of the subjects complained of discomfort or discomfort.

Industrial application fields

As described above, the conductive paste and the conductive film obtained from the conductive paste according to the present invention can be manufactured at low cost, and have elasticity, so that the conductive film obtained from the paste is repeatedly bent. Excellent in twisting, repetitive twisting, and repetitive stretchability, and less uncomfortable when worn.
By using the stretchable conductive film of the present invention in a wearable smart device, information on the human body, that is, a sensor provided with biological information such as bioelectric potential such as myoelectric potential and cardiac potential, body temperature, pulse, blood pressure, etc. Wearable device for detection, or clothing incorporating an electrical heating device, wearable device incorporating a sensor for measuring clothing pressure, clothing for measuring body size using clothing pressure, sole of foot Socks-type devices for measuring pressure, wiring parts such as clothes, tents and bags with flexible solar cell modules integrated in textiles, low-frequency treatment devices with joints, wiring parts such as thermotherapy machines, flexion degree It can be applied to sensing parts. Such wearable devices can be applied not only to the human body but also to animals such as pets and livestock, or mechanical devices having a telescopic part, a bent part, etc. It can also be used as electrical wiring for systems that are connected. It can also be applied as a wiring material for implant devices that are embedded and specified in the body, patchable devices that are used by being attached to the surface of the body or mucous membrane, or edible devices that measure biological information in the digestive tract.

1. Base material (fabric)
2. 2. Insulating underlayer Stretchable conductor composition layer (stretchable conductor layer)
4). Elastic cover layer (insulation cover layer)
5). Stretchable carbon layer (electrode surface layer)
6). Adhesive layer (insulating underlayer)
10. Temporary support (release indicator)

Claims

It is characterized in that it contains at least a conductive filler composed of metal-coated particles having a metal layer on the surface of non-conductive core particles, a binder resin composed of an elastomer, and an organic solvent, and the surface of the conductive filler is not previously surface-treated. Conductive paste used for forming stretchable wiring.
2. The conductive paste according to claim 1, wherein the binder resin is a nitrile group-containing elastomer or a urethane resin.
The conductive paste according to claim 1 or 2, which contains 0.1 to 3.0% by mass of an additive having a surface free energy of 30 mJ / m 2 or less based on the conductive filler.
The additive according to any one of claims 1 to 3, wherein the additive is polydimethylsiloxane having at least one functional group selected from an amino group, a carboxyl group, and a glycidyl group at one terminal. The conductive paste as described.
The conductive paste according to any one of claims 1 to 4, wherein the additive has a surface free energy of 25 mJ / m 2 or less.
The conductive paste according to any one of claims 1 to 5, wherein the additive is polydimethylsiloxane having a carboxyl group at least at one end.
It contains at least a conductive filler composed of metal-coated particles having a metal layer on the surface of non-conductive core particles, a binder resin composed of an elastomer, and an organic solvent, and the surface of the conductive filler is not previously surface-treated. A stretchable conductive coating.
The conductive film according to claim 7, wherein the binder resin is a nitrile group-containing elastomer or a urethane resin.
The conductive film according to claim 7 or 8, comprising a treatment agent having a surface free energy of 30 mJ / m 2 or less in an amount of 0.1 to 3.0 mass% with respect to the conductive filler.
The additive according to any one of claims 7 to 9, wherein the additive is polydimethylsiloxane having at least one functional group selected from an amino group, a carboxyl group, and a glycidyl group at least at one end. The electroconductive film as described.
11. The conductive film according to claim 7, wherein a surface free energy of the additive is 25 mJ / m 2 or less.
The conductive film according to any one of claims 7 to 11, wherein the additive is polydimethylsiloxane having a carboxyl group at least at one end.
The conductive film according to any one of claims 7 to 12, wherein the conductive film has a specific resistance when 100% stretched within 20 times of a specific resistance when not stretched. Coating.
The conductive film having stretchability according to any one of claims 7 to 12, wherein the conductivity of the conductive film after 1000 times of 20% repeated stretch is maintained.
A clothes-type electronic device having an electrical wiring made of the conductive film having elasticity according to claim 7.
The conductive filler composed of the metal-coated particles contains at least two types of conductive filler A and conductive filler B, and the conductive filler A has an aspect ratio which is a ratio of a major axis to a minor axis of 1.5 or less, and is non-conductive. Metal-coated particles having a metal layer on the surface of the conductive core particles, the center particle diameter D is 0.5 μm or more and 15 μm or less, and the conductive filler B has an aspect ratio of 5 or more, which is the ratio of the major axis to the minor axis The metal-coated particles having a metal layer on the surface of the non-conductive core particles, the average length L of the major axis is 3 μm or more and 30 μm or less, and the ratio of the conductive filler B to the total conductive filler is 25 to 60% by mass The conductive paste according to claim 1, wherein:
The conductive paste according to claim 16, wherein the elastomer used as the binder resin is a non-crosslinked elastomer.
The conductive paste according to claim 16 or 17, wherein the binder resin is a nitrile group-containing elastomer.
The conductive paste according to claim 16 or 17, wherein the binder resin is a urethane resin.
In the conductive film containing at least a conductive filler and a binder resin as a constituent component, the conductive filler contains at least two kinds of conductive filler A and conductive filler B as the conductive filler, and the conductive filler A is an aspect ratio that is a ratio of the major axis to the minor axis. Is a metal-coated particle having a metal layer on the surface of the non-conductive core particle, the center particle diameter D is 0.5 μm or more and 15 μm or less, and the conductive filler B has a long diameter and The aspect ratio, which is the ratio of the minor axis, is a metal-coated particle having a metal layer on the surface of the non-conductive core particle, the average length L of the major axis is 10 μm or more and 30 μm or less, and the total conductive filler A stretchable conductive film characterized in that the ratio of the conductive filler B is 25 to 60% by mass and the binder resin is an elastomer.
The conductive film according to claim 20, wherein the binder resin is a nitrile group-containing elastomer.
The conductive film according to claim 20, wherein the binder resin is a urethane resin.
23. The electrically conductive film having stretchability according to any one of claims 20 to 22, wherein the conductive film has a specific resistance at 100% elongation of not more than 10 times the specific resistance at non-elongation. Coating.
25. The conductive film having stretchability according to any one of claims 20 to 23, wherein the conductivity of the conductive film after 1000% stretching and stretching of 20% is maintained.
The specific resistance of the sheet after the twist cycle of the following twist test of the conductive film is repeated 100 times is within 3.0 times the initial specific resistance. The conductive film according to crab.
[Torsion test:
Sample: width 10 mm, length 100 mm (fixed at one end in the longitudinal direction of the sample, twisted by rotation of the other end)
Twisting cycle: 10 rotations (3600 °) in the positive direction, return to the initial state, 10 rotations (-3600 °) in the negative direction, return to the initial state]
A stretchable electronic component having an electrical wiring comprising the conductive coating according to any one of claims 20 to 25.
26. A clothes-type electronic device having an electrical wiring made of the conductive film according to claim 20.