JP7167909B2 - Conductive paste, stretchable wiring using the same, clothing-type electronic device having stretchable wiring - Google Patents

Description

TECHNICAL FIELD The present invention relates to a conductive paste comprising a conductive filler and a binder resin, and more particularly to a conductive paste capable of forming a conductive film having stretchability. In addition, the present invention relates to a conductive material used in a clothing-type wearable electronic device that incorporates electronic or electrical functions into clothing, and includes clothing that has stretchable electrical wiring and that is comfortable to wear. related to type electronics.

2. Description of the Related Art Recently, wearable electronic devices have been developed that are intended to be used in close proximity to or in close contact with the body, electronic devices having input/output, arithmetic, and communication functions. As wearable electronic devices, there are known accessories-shaped devices such as wristwatches, eyeglasses, and earphones, and textile-integrated devices in which electronic functions are incorporated into clothes. An example of such a textile integrated device is disclosed in US Pat.

Electronic devices require electrical wiring for power supply and signal transmission. In particular, in textile-integrated wearable electronic devices, electrical wiring is required to be stretchable to match stretchable clothing. Normally, electrical wiring made of metal wires and metal foils does not inherently have practical elasticity, so metal wires and metal foils are arranged in a wavy or repeated horseshoe shape to give them a pseudo-stretch function. method is used.
In the case of a metal wire, wiring can be formed by treating the metal wire as an embroidery thread and sewing it onto clothes. However, it is self-evident that such a technique is not suitable for mass production.
A method of forming wiring by etching a metal foil is generally used as a method of manufacturing a printed wiring board. A technique is known in which a metal foil is attached to a stretchable resin sheet to form a wavy wiring in the same manner as a printed wiring board, thereby forming a pseudo-stretchable wiring. (See Non-Patent Literature 1) This method gives a pseudo elastic property by twisting the wavy wiring portion. When it was used, it gave a very uncomfortable wearing feeling, which was not preferable. In addition, when subjected to excessive deformation such as during washing, the metal foil undergoes permanent plastic deformation, and there is also a problem in the durability of the wiring.

As a technique for realizing stretchable conductor wiring, a method using a special conductive paste has been proposed. Conductive particles such as silver particles, carbon particles, carbon nanotubes, elastic elastomers such as urethane resin, natural rubber, synthetic rubber, solvents, etc. are kneaded to form a paste, which can be applied directly to clothing or as a stretchable film base. Wiring is printed and drawn in combination with materials.
A conductive composition comprising conductive particles and a stretchable binder resin can macroscopically realize a stretchable conductor. Microscopically, the conductive composition obtained from such a paste deforms the resin binder portion when subjected to an external force, and maintains conductivity to the extent that the electrical chain of the conductive particles is not interrupted. is. The macroscopically observed specific resistance is higher than that of metal wires and metal foils, but since the composition itself has elasticity, there is no need to adopt a shape such as a wavy wire, and the width and thickness of the wire can be reduced. Since it has a high degree of freedom, it is practically possible to realize a wiring with a lower resistance than a metal wire.

Patent Literature 2 discloses a technique for suppressing a decrease in electrical conductivity during elongation by combining silver particles and silicone rubber and further coating the conductive film on the silicone rubber substrate with silicone rubber. Patent Document 3 discloses a combination of silver particles and a polyurethane emulsion, which is said to yield a conductive film with high conductivity and high elongation. Furthermore, many examples have been proposed in which conductive particles with a high aspect ratio, such as carbon nanotubes and silver fillers, are combined to try to improve characteristics.

Patent Literature 4 discloses a technique for directly forming electrical wiring on clothing using a printing method.

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

Noble metals such as silver are often used as conductive particles, but these noble metals are expensive and account for most of the chemical cost of pastes and conductive coatings produced using them. On the other hand, in order to reduce the cost of fillers, attempts have long been made to coat non-conductive particles or inexpensive metal particles with noble metals and use them as fillers for conductive coatings.
Such metal-coated particles are highly dispersed with a surface treatment agent in order to prevent aggregation during the manufacturing process. , it is difficult to maintain the conductive network during coating elongation, and it is necessary to increase the compounding ratio of the conductive particles in the coating. However, when the compounding ratio of the conductive particles in the coating is increased, the binder component ratio is decreased, resulting in the problem of deterioration in durability during expansion and contraction.
The present inventors have studied the application of silver-coated particles in a conductive paste for forming a stretchable conductive film. It is rare that silver-coated particles have been considered for stretchable conductive coatings.

The inventor of the present invention has conducted intensive research in order to develop a conductive paste for obtaining a stretchable conductive film that is low in cost and has high durability. Furthermore, by combining specific additives, it was found that high conductivity can be obtained during film elongation, and the following inventions were achieved.

That is, the present invention has the following configurations.
[1] It contains at least a conductive filler made of metal-coated particles having a metal layer on the surface of a non-conductive core particle, a binder resin made of an elastomer, and an organic solvent, and the surface of the conductive filler is not previously surface-treated. A 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 urethane resin.
[3] The conductive material according to [1] or [2], characterized by containing 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] The additives of [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. Conductive paste according to any one.
[5] The conductive paste according to any one of [1] to [4], wherein the additive has a surface free energy of 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 on at least one end.
[7] Contains at least a conductive filler made of metal-coated particles having a metal layer on the surface of a non-conductive core particle, a binder resin made of an elastomer, and an organic solvent, and the surface of the conductive filler is not surface-treated in advance. A stretchable conductive coating characterized by:
[8] The conductive film according to [7], wherein the binder resin is a nitrile group-containing elastomer or urethane resin.
[9] The conductive material according to [7] or [8], characterized by containing 0.1 to 3.0% by mass of a treating agent having a surface free energy of 30 mJ/m ² or less based on the conductive filler. sexual membrane.
[10] The additives of [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 one end. The conductive film according to any one of the above.
[11] The conductive film according to any one of [7] to [10], wherein the additive has a surface free energy of 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 on at least one terminal.
[13] The stretchability according to any one of [7] to [12], wherein the conductive film has a specific resistance when stretched by 100% within 20 times the resistivity when not stretched. A conductive coating having
[14] The stretchable conductive film according to any one of [7] to [12], wherein the conductive film maintains its conductivity after 1000 cycles of 20% repeated stretching.
[15] A clothing-type electronic device having electrical wiring made of the stretchable conductive film according to any one of [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 the ratio of the major axis to the minor axis, of 1.5 or less. , a metal-coated particle having a metal layer on the surface of a 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 an aspect ratio that is the ratio of the major axis to the minor axis is 5 or more, is a metal-coated particle having a metal layer on the surface of a 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 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 of [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 a conductive film having at least a conductive filler and a binder resin as constituent components, at least two types of conductive filler A and conductive filler B are contained as conductive fillers, and the conductive filler A has a major axis to minor axis ratio of It is a metal-coated particle having an aspect ratio of 1.5 or less and a metal layer on the surface of a non-conductive core particle, and has a median particle diameter D of 0.5 μm or more and 15 μm or less, and the conductive filler B is , an aspect ratio, which is the ratio of the major axis to the minor axis, of 5 or more, a metal-coated particle having a metal layer on the surface of a non-conductive core particle, an average length L of the major axis of 10 μm or more and 30 μm or less, and a conductive A stretchable conductive film characterized in that the ratio of the conductive filler B to the total amount of fillers 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 coating has a specific resistance at 100% elongation within 10 times the specific resistance at non-elongation. A conductive coating having
[24] The stretchable conductive film according to any one of [20] to [23], wherein the conductive film maintains its conductivity after 1000 cycles of 20% repeated stretching.
[25] The conductive film has a specific resistance of the sheet after repeating the twist cycle of the following twist test 100 times is within 3.0 times the initial specific resistance [20] to [24] ] The conductive film according to any one of the above.
[Twisting test: sample: width 10 mm, length 100 mm (fixing one end of the sample in the longitudinal direction, twisting by rotating the other end)
Twist cycle: 10 twists in positive direction (3600°), return to initial state, 10 twists in negative direction (−3600°), return to initial state]
[26] A stretchable electronic component having electrical wiring made of the conductive film according to any one of [20] to [25].
[27] A clothing-type electronic device having electrical wiring made of the conductive film according to any one of [20] to [25].

Further, the present invention preferably has the following configuration.
[28] It contains at least a conductive filler made of metal-coated particles having a metal layer on the surface of a non-conductive core particle, a binder resin made of an elastomer, and an organic solvent, and the surface of the conductive filler has a carbon number of 3 or more. 28 or less mono- or polyvalent carboxylic acids having 0 to 3 double bonds in the molecule, fatty amines having 3 to 24 carbon atoms and 0 to 2 double bonds in the molecule A conductive paste used for forming stretchable wiring characterized by not being surface-treated with at least one selected surface-treating agent.
[29] Mono- or polyvalent carboxylic acids having 3 to 28 carbon atoms and 0 to 3 double bonds in the molecule, and 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 1 to 2 fatty amines is 3% by mass or less.
[30] It contains at least a conductive filler composed of metal-coated particles having a metal layer on the surface of a non-conductive core particle, a binder resin composed of an elastomer, and an organic solvent, and the surface of the conductive filler has a carbon number of 3 in advance. mono- or polyvalent carboxylic acids having 0 to 3 double bonds in the molecule, and fatty amines having 3 to 24 carbon atoms and 0 to 2 double bonds in the molecule. A stretchable conductive film characterized by not being surface-treated with at least one surface treatment agent selected from:
[31] A mono- or polyvalent carboxylic acid having 3 to 28 carbon atoms and 0 to 3 double bonds in the molecule, and 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 1 to 2 fatty amines is 5% by mass or less.
[32] A clothing-type electronic device having the electrical wiring according to [15], which is made of the stretchable conductive film according to [30] or [31].

The conductive paste of the present invention is characterized by using metal-coated particles and an elastomer whose surfaces have not undergone surface treatment such as high dispersion treatment in advance.
Here, as a surface treatment agent such as high dispersion treatment, a mono- or polyvalent carboxylic acid having 3 to 28 carbon atoms and 0 to 3 double bonds in the molecule, and/or 3 or more carbon atoms Fatty amines having 24 or less and 0 to 2 double bonds in the molecule, or derivatives thereof can be exemplified. Since the metal-coated particles are not treated to improve dispersibility, which is the case with these surface treatment agents, aggregation of particles tends to occur during coating film formation, and even with a low conductive particle blending ratio, the particles are conductive. Since a network is easily formed, durability during expansion and contraction is maintained.
Furthermore, by using an additive having a surface free energy of 30 mJ/m ² or less, the particles are more easily agglomerated, and the durability during expansion and contraction is further enhanced.
In addition, since the conductive particles obtained by coating the particle surfaces with a metal have the advantage that the raw material cost is lower than that of the metal particles, the stretchable conductive paste can be produced at a lower cost.

The conductive paste of the present invention is characterized by blending the conductive fillers A and B into the elastomer so that the proportion of the conductive filler B to the total conductive fillers is 25 to 60% by mass. By combining two types of conductive fillers with different aspect ratios, it becomes easier to form a conductive network, so the durability against repeated expansion and contraction is improved. In addition, since the conductive particles obtained by coating the particle surfaces with a metal have the advantage that the raw material cost is lower than that of the metal particles, the stretchable conductive paste can be produced at a lower cost.

FIG. 1 is a SEM image (magnification: 5,000 times) of particles that are silver-coated particles of the present invention and that are an example of conductive filler A. FIG. 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 stretch recovery rate. FIG. 4 is a schematic process diagram showing a method of forming electrodes and electric wiring using a transfer method in the present invention. FIG. 5 shows an example of electrode wiring produced using the conductive paste of the present invention. FIG. 6 is a schematic diagram showing the arrangement of electrode wiring in FIG. 5 of the present invention.

The conductive paste in the present invention comprises a conductive filler having a metal layer on the surface of non-conductive core particles, a binder, and an organic solvent.
The conductive filler of the present invention is a metal-coated particle that has not been previously subjected to a high-dispersion treatment with a mono- or polycarboxylic acid or the like and has a surface metal layer with a specific resistance of 1×10 ⁻² Ω·cm or less. Preferably, the median particle size 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 substances having a resistivity 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 non-conductive core particles can be used as the conductive filler A.
In addition, the conductive filler B is made of a substance whose surface metal layer has a specific resistance of 1×10 ⁻² Ωcm or less, and has an aspect ratio, which is the ratio of the major axis to the minor axis, of 5 or more, preferably 4 or more, more preferably 4 or more. It is 20 or more, more preferably 30 or more, and the average length L of the major axis is 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 preferably 25 to 60% by mass. If the weight ratio is small, the effect of maintaining the conductive network during elongation due to the high aspect ratio conductive filler is small. strength becomes smaller.

In the present invention, as a surface treatment agent such as high dispersion treatment, a mono- or polyvalent carboxylic acid having 3 to 28 carbon atoms and 0 to 3 double bonds in the molecule, and 3 to 24 carbon atoms The following fatty amines having 0 to 2 double bonds in the molecule, or derivatives thereof can be exemplified. In the present invention, the phrase "no high-dispersion treatment with a mono- or polyvalent carboxylic acid or the like" means that no surface treatment with these surface-treating agents has been performed.
More specifically, the content of these surface treatment agents in the entire paste is 5000 ppm or less, preferably 2000 ppm or less, and more preferably 1200 ppm or less.
Although it is effective to pre-treat the raw material metal filler with these surface-treating agents, effects can also be obtained by adding them during paste mixing and kneading. include.

Examples of 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, pentadecyl acid, palmitic acid, palmitoleic acid, margaric acid, stearic acid, oleic acid, vaccenic acid, linoleic acid, (9,12,15)-linolenic acid, (6,9,12)-linolene acids, dihomo-γ-linolenic acid, eleostearic acid, tubercrostearic acid, arachidic acid (eicosanoic acid), 8,11-eicosadienoic acid, 5,8,11-eicosatrienoic acid, arachidonic acid, behenic acid, Aromatic dicarboxylic acids such as lignoceric acid, nervonic acid, elaidic acid, erucic acid, docosahexaenoic acid, eicosapentaenoic acid, stearidonic acid, terephthalic acid, isophthalic acid, orthophthalic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, dicarboxylic acids such as adipic acid, sebacic acid, dodecanedicarboxylic acid and azelaic acid; dibasic acids having 12 to 28 carbon atoms such as maleic acid and dimer acid; 1,4-cyclohexanedicarboxylic acid; 1,2-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, 2-methylhexahydrophthalic anhydride, dicarboxyhydrogenated bisphenol A, dicarboxyhydrogenated bisphenol S, dimer Acids, hydrogenated dimer acids, hydrogenated naphthalenedicarboxylic acids, alicyclic dicarboxylic acids such as tricyclodecanedicarboxylic acid, hydroxybenzoic acid, hydroxycarboxylic acids such as lactic acid can be mentioned. 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 can also be exemplified.

In the present invention, the aliphatic amine having 3 to 24 carbon atoms and 0 to 2 double bonds in the molecule includes capryylamine, laurylamine, myristylamine, pentadecylamine, and palmitic amine. luamine, palmitoleylamine, margaliylamine, stearylamine, oleylamine, vacceylamine, linoleylamine, (9,12,15)-linoleylamine, (6,9,12)-linoleylamine, dihomo- gamma-linoleylamine, eleosestearylamine, tubercosterylamine, arachidiylamine (eicosylamine), 8,11-eicosadienylamine, 5,8,11-eicosatrienylamine, arachidonylamine, Examples include behenylamine, lignoceriylamine, nervonylamine, elaidinylamine, elkylamine, docosahexaenylamine, eicosapentaenylamine, stearidonyylamine, and the like.

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 desirably 0.1 to 3.0% by mass, more desirably 1.0 to 2.0% by mass, based on the conductive filler. Surface treatment agents not intended for high dispersion include antioxidants, reducing agents, adhesion promoters, 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.
Structures exhibiting low surface free energy include polydimethylsiloxane and fluorine-containing groups. Moreover, the functional group includes an amino group, a carboxyl group, a glycidyl group, and the like, and the carboxyl group is more preferable.

Preferably, the additive in the present invention is liquid at room temperature.
The surface free energy of the additive in the present invention is preferably 30 mJ/m ² or less, more preferably 26 mJ/m ² or less, still more preferably 24 mJ/m ² or less, and 20 mJ/m 2 or less. It is even more preferable to have
The amount of the additive compounded is preferably 0.1 to 3.0% by mass, more preferably 0.12 to 2.0% by mass, based on the conductive filler.

As an additive preferably used in the present invention, dimethylsiloxane having a molecular weight in the range of 300 or more and 8000 or less and having one end carboxy-modified can be exemplified.
Examples of additives preferably used in the present invention include fluoromonocarboxylic acids having a molecular weight in the range of 100 or more and 1000 or less. As the fluorinated additive, fully fluorinated, partially fluorinated, or fluoromonocarboxylic acid is preferable.

The present invention may contain non-conductive particles having an average particle size of 0.3 μm or more and 10 μm or less. The non-conductive particles in the present invention are mainly particles of metal oxides, such as silicon oxide, titanium oxide, magnesium oxide, calcium oxide, aluminum oxide, iron oxide, metal sulfates, metal carbonates, metal oxides. Titanates and the like can be used. Among such non-conductive particles, barium sulfate particles are preferably used in the present invention.

The binder resin used in the stretchable conductor layer of the present invention preferably has a stretch recovery rate of 99% or more after 20% stretch, more preferably 99.5% or more, and still more preferably 99.85%. It is preferable that it is above. The stretch recovery rate of the binder resin is measured under an environment of 25±3° C. by molding the binder resin into 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 increase the stretch recovery rate of the stretchable conductor layer to a predetermined range or more. Furthermore, if the stretch recovery rate of the binder resin is less than this range, the repeated stretchability and twist resistance of the conductive paste are lowered.

The stretch recovery rate in the present invention means that the _stretchable conductive sheet is suspended as shown in FIG. When the length when stretched by 20% or a predetermined % is L ₁ and the length when the extension load is removed is L ₂ ,
(Number 1)
Stretch recovery rate = ((L ₁ -L ₂ )/(L ₁ -L ₀ )) x 100 [%]
(Number 2)
Permanent strain rate = ((L2 _{- L0} )/ _L0 ) x 100 [%]
L ₀ initial length L ₃ elongation = L ₁ - L ₀
L ₄ recovery length = L ₁ - L _2
L5 residual strain ₌ L2 - _L0
and define. A similar measurement method is specified in JIS L 1096 Woven and Knitted Fabric Test Methods, but it is not the recovery rate after stretching under a constant load, but the recovery rate when stretched to a certain length. different. Since the load applied to the stretchable conductor layer in actual use is often repeatedly stretched to a predetermined length regardless of the load, the stretch recovery rate according to the constant load method cannot express practical performance. The stretch recovery rate is evaluated under an environment of 25°C ± 3°C unless otherwise specified.

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 preferably has a glass transition temperature of -60°C to 0°C. Examples include rigid rubber and natural rubber. Rubber, polyurethane resin, and polyester resin are preferable in order to develop stretchability of the coating film (sheet). Examples of rubber include urethane rubber, acrylic rubber, silicone rubber, butadiene rubber, nitrile group-containing rubber such as nitrile rubber and hydrogenated nitrile rubber, isoprene rubber, vulcanized rubber, styrene-butadiene rubber, butyl rubber, chlorosulfonated polyethylene rubber, and ethylene propylene. rubber, vinylidene fluoride copolymers, and the like. Among these, nitrile group-containing rubber, chloroprene rubber, chlorosulfonated polyethylene rubber, and styrene-butadiene rubber are preferred, and nitrile group-containing rubber is particularly preferred.

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, even 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 composed of polyether-, polyester-, or polycarbonate-based polyol or the like with a hard segment composed of diisocyanate or the like. As the soft segment component, polyester polyol is more preferable in view of the degree of freedom in molecular design.

Polyether polyols in the present invention include, for example, polyethylene glycol, polypropylene glycol, polypropylene triol, polypropylene tetraol, polytetramethylene glycol, polytetramethylene triol, and monomer materials such as cyclic ethers for synthesizing them. polyalkylene glycols such as copolymers obtained by the above-mentioned methods, derivatives obtained by introducing side chains or branched structures into these, modified products, mixtures thereof, and the like. Among these, polytetramethylene glycol is preferred. The reason is that the mechanical properties are excellent.

Aromatic polyester polyols, aromatic/aliphatic copolyester polyols, aliphatic polyester polyols, and alicyclic polyester polyols can be used as polyester polyols in the present invention. As the polyester polyol in the present invention, either a saturated type or an unsaturated type may be used. Among 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 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 Co., Ltd.) and the like.

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

Examples of commercially available polycarbonate diol compounds that can be used in the present invention include Kuraray Polyol C series manufactured by Kuraray Co., Ltd., Duranol series manufactured by Asahi Kasei Chemicals Corporation, 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- T5650E, DURANOL-T5651, DURANOL-T5652 and the like can be mentioned.

The diisocyanate compound in the present invention includes 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'-diisocyanatodiphenyl ether, 1,5- Aromatic diisocyanates such as naphthalene diisocyanate and m-xylylene diisocyanate, or aliphatic 1,6-hexane diisocyanate, isophorone diisocyanate, 4,4′-diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate (ortho, meta, para) , and alicyclic diisocyanates. Among these, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and isophorone diisocyanate are preferred. In addition, if necessary, the above isocyanates may be used in combination, or tri- or higher-functional polyisocyanate compounds may be used in combination.

The polyurethane resin of the present invention may optionally be copolymerized with a diol compound generally called a chain extender.

Examples of diol compounds used as chain extenders include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propanediol and 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, neopentyl glycol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5- Aliphatic glycols such as hexanediol, 1,8-octanediol, 2-methyl-1,8-octanediol and 1,9-nonanediol are included. 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 preferred.

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. If the glass transition temperature exceeds 0° C., the elongation of the produced conductive coating film becomes small, and the increase in resistance during elongation may become poor. If the temperature is less than -60°C, blocking may occur in the produced conductive coating film. In addition, the reduced viscosity is 0.2 dl/g or more and 3.0 dl/g or less, preferably 0.3 dl/g or more and 2.5 dl/g or less, more preferably 0.4 dl/g or more and 2.0 dl/g or less. is. If it is less than 0.2 dl/g, the conductive coating film may become brittle and the resistance increase during elongation may deteriorate. On the other hand, when it exceeds 3.0 dl/g, the solution viscosity of the polyurethane resin composition becomes high, which may make handling difficult.

When producing a polyurethane resin, stannous octoate, dibutyltin dilaurate, triethylamine, bismuth metal, etc. may be used as a catalyst.

The nitrile group-containing rubber is not particularly limited as long as it is a nitrile group-containing rubber or elastomer, but nitrile rubber and hydrogenated nitrile rubber are preferred. Nitrile rubber is a copolymer of butadiene and acrylonitrile, and when the amount of bound acrylonitrile is large, the affinity with metals increases, but rubber elasticity, which contributes to stretchability, decreases. Therefore, the amount of bound acrylonitrile is preferably 18 to 50% by mass, more preferably 30 to 50% by mass, more preferably 40 to 50% by mass, based on 100% by mass of nitrile-containing rubber (eg, acrylonitrile-butadiene copolymer rubber). % by weight is particularly preferred.

The glass transition temperature of such a binder resin is preferably 0° C. or lower, more preferably -8° C. or lower, still more preferably -16° C. or lower, and even more preferably -24° C. or lower. If the glass transition temperature exceeds this range, it becomes difficult to develop the stretch recovery property.
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, there is a concern that the solvent will volatilize during the paste production process or paste use, and the component ratios constituting the conductive paste will easily change. On the other hand, if the boiling point of the organic solvent is too high, a large amount of the solvent may remain in the coating film when a low-temperature drying process is required (for example, 150 ° C. or less), causing a decrease in the reliability of the coating film. I have concerns.

Such high-boiling solvents include cyclohexanone, toluene, isophorone, γ-butyrolactone, benzyl alcohol, Solvesso 100, 150, 200 manufactured by Exxon Chemical Co., Ltd., propylene glycol monomethyl ether acetate, terpineol, butyl glycol acetate, diamylbenzene ( boiling point: 260-280°C), triamylbenzene (boiling point: 300-320°C), n-dodecanol (boiling point: 255-29°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 (boiling 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), triethylene glycol monoethyl ether (boiling point: 256°C), triethylene glycol monobutyl ether (boiling point: 271°C) ° 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.). In addition, as petroleum 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 Co., Ltd. , No. 7 (boiling point: 259 to 282° C.), and No. 0 Solvent H (boiling point: 245 to 265° C.), etc., and two or more thereof may be included as necessary. Such an organic solvent is appropriately contained so that the conductive silver paste has a viscosity suitable for printing.

In the conductive paste of the present invention, the total conductive filler to binder ratio is preferably 25-50% by volume:50-75% by volume, more preferably 30-40% by volume:60-70% 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 using a dispersing machine such as a dissolver, three-roll mill, rotation-revolution mixer, attritor, ball mill, and sand mill.

The conductive paste of the present invention contains a thixotropic agent, an antifoaming agent, a flame retardant, a tackifier, a hydrolysis inhibitor, a leveling agent, a plasticizer, an antioxidant, an ultraviolet Contributing agents such as absorbers, pigments, dyes, etc. can be incorporated.

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 filler.

The conductive paste thus obtained can be coated or printed on a substrate, and then the organic solvent can be evaporated and dried to form a conductive coating film. Although the range of film thickness is not particularly limited, it is preferably 1 μm to 1 mm. If the thickness is less than 1 μm, coating film defects such as pinholes are likely to occur, which may pose a problem. If it exceeds 1 mm, the organic solvent tends to remain inside the coating film, and the reproducibility of the physical properties of the coating film may be poor.

The base material to which the conductive silver paste is applied is not particularly limited, but a flexible or stretchable base material is preferable. Examples of flexible substrates include paper, cloth, polyethylene terephthalate, polyvinyl chloride, polyethylene, polyimide, and the like. Stretchable substrates include polyurethane, polydimethylsiloxane (PDMS), nitrile rubber, butadiene rubber, SBS elastomer, SEBS elastomer, and the like. These substrates are preferably creasable and stretchable in the plane direction. From this point of view, a base material made of rubber or elastomer is preferable.

After the coating film of the conductive silver paste is peeled off from the base material and the wiring, electrodes, and sheets are formed with only the coating film, it is preferable to select a base material having excellent releasability when carrying out transfer or the like. Specific examples include a silicon sheet, a Teflon (registered trademark) sheet, and the like, and the conductive coating film can be easily peeled off.

The step of applying the conductive silver paste onto the substrate is not particularly limited, but can be performed by, for example, a coating method, a printing method, or the like. The printing method includes screen printing, lithographic offset printing, inkjet, flexographic printing, gravure printing, gravure offset printing, stamping, dispensing, and squeegee printing.
The conductive paste of the present invention can be processed into a sheet by a coating method, then processed into a predetermined shape by a method such as punching, punching, laser cutting, or cutting, and laminated on a substrate.

The step of heating the base material coated with the conductive silver paste can be performed under air, vacuum atmosphere, inert gas atmosphere, reducing gas atmosphere, or the like. The heating temperature is in the range of 20 to 200.degree. The organic solvent is volatilized, and in some cases, the curing reaction proceeds under heating, and the conductivity, adhesion, and surface hardness of the conductive film after drying are improved. If the temperature is less than 20°C, the solvent may remain in the coating film, failing to obtain electrical conductivity. If treated for a long time, it develops conductivity, but the specific resistance may be significantly deteriorated. A preferred heating temperature is 70 to 180°C. If the temperature is less than 70°C, the heat shrinkage of the coating film becomes small, and a conductive network of the silver powder in the coating film cannot be sufficiently formed, which may increase the specific resistance. Due to the denseness of the coating film, the elongation rate and repeated stretchability may also deteriorate. If the temperature exceeds 180° C., the base material is limited due to heat resistance, and if treated for a long period of time, the base material may be thermally deteriorated, and the elongation rate and repeated stretchability may be deteriorated.

It is preferable that the conductive paste of the present invention can form 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, it can be used in flexible wiring, flexible antenna, When designing stretchable electrodes, constraints such as coating film thickness, wiring length, wiring width, etc. arise, and it may not be possible to adapt.

Furthermore, the conductive paste of the present invention has a breaking elongation of more than 35% and can form a coating film that does not break even after repeated stretching of 50 times or more when repeated stretchability evaluation is performed at an elongation rate of 20%. is preferred. The breaking elongation of the coating film is more preferably 60% or more in consideration of application to the human body or the joints of robots, and more preferably 100% or more from the viewpoint of reliability. In addition, when evaluating the repeated stretchability of the coating film at an elongation rate of 20%, it is more preferable that no breakage occurs after repeated stretching of 100 times or more, and long-term reliability is required instead of disposable applications. It is more preferable that no breakage occurs even after repeated expansion and contraction of 1000 times or more.

EXAMPLES Hereinafter, the present invention will be described in more detail and specifically by showing examples. The evaluation results and the like in the examples were measured by the following methods. "Parts" in the examples means "parts by weight".

<Surface energy>
A silver-plated specular metal plate, a polyethylene terephthalate film, and a fluororesin plate were used as solid materials. DM-501 of Kyowa Interface Science Co., Ltd. was used to measure the contact angle, and the surface roughness of the solid material was polished with emery paper so that the center line average roughness was 0.10 μm or more and 0.20 μm or less. The droplet size was approximately 1 μL. The measurement environment was set at 25°C.

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

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

<Glass transition temperature>
5 mg of the sample resin was placed in an aluminum sample pan, sealed, and heated to 100 ° C. at a rate of 20 ° C./min using a differential scanning calorimeter (DSC) DSC-7020 manufactured by Seiko Instruments Inc. It was measured as the temperature at the intersection of the extension of the baseline below the glass transition temperature and the tangent line showing the maximum slope at the transition.

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

<Urethane group concentration>
The urethane group concentration is calculated by the following formula: Urethane group concentration (eq/t) = (W/(X/Y))/Z x ¹⁰⁶
W: Weight of isocyanate constituting polyurethane resin X: Molecular weight of isocyanate Y: Number of isocyanate per molecule of isocyanate Z: Total weight of raw materials constituting polyurethane resin

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

<Evaluation of resistivity>
The sheet resistance and film thickness of the conductive coating film in the natural state (0% elongation) were measured, and the specific resistance was calculated. Thickness gauge SMD-565L (manufactured by TECLOCK) was used for film thickness, and sheet resistance was measured for four test pieces using Loresta-GP MCP-T610 (manufactured by Mitsubishi Chemical Analytic Tech), and the average value was used. .
Then, in the same manner as in the natural state (elongation rate 0%), the following 4. and measured the specific resistance at an elongation rate of 100%. The specific resistance during elongation was read 30 seconds after reaching a predetermined degree of elongation. The specific resistance was calculated by the following formula.
Specific resistance (Ω cm) = Rs (Ω _/ ) × t (cm)
Here, Rs is the sheet resistance measured under each condition, and t is the film thickness measured under each condition.

<Evaluation of repeated stretchability>
Using a cyclic endurance tester (TIQ-100, manufactured by Lesca), the sample film is repeatedly stretched by 20% of its original length and then returned to its original length Repeatedly at an elongation rate of 20% The specific resistance was measured in the state of returning to the original length (elongation rate 0%) after repeating the return and contraction 1000 times. Both the elongation speed and the speed of returning to the original length were set to 10 mm/sec. As an index of repeated stretchability, a value obtained by dividing the specific resistance after repeated stretching 1000 times by the initial specific resistance was used.

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

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

<Resin Production Example 1>
100 parts of ODX-2044 (polyester diol manufactured by DIC), 33 parts of P-2010 (polyester diol manufactured by Kuraray), and 1,6-hexanediol as a chain extender were placed in a 1 L four-necked flask for synthesis of polyurethane resin composition (A). (manufactured by Ube Industries) was put into 125 parts of diethylene glycol monoethyl ether acetate and set on a mantle heater. A stirring rod fitted with a stirring seal, a reflux condenser, a temperature detector, and a ball stopper were set in the flask, and the mixture was stirred at 50° C. for 30 minutes to dissolve. 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 heat of reaction settled down, the mixture was heated to 90° C. and reacted for 4 hours to obtain a polyurethane resin composition (A). Table 1 shows the properties of the obtained resin.

<Resin Production Example 2>
Synthesis of Polyurethane Resin Composition (B) In a 1 L four-necked flask, 100 parts of ODX-2044 (polyester diol manufactured by DIC) and 33 parts of 1,6-hexanediol (manufactured by Ube Industries) as a chain extender were added to diethylene glycol monoethyl ether. It was placed in 100 parts of acetate and set on a heating mantle. A stirring rod fitted with a stirring seal, a reflux condenser, a temperature detector, and a ball stopper were set in the flask, and the mixture was stirred at 50° C. for 30 minutes to dissolve. 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 the heat of reaction settled down, the mixture was heated to 90° C. and reacted for 4 hours to obtain a polyurethane resin composition (B). Table 1 shows the properties of the obtained resin.

<Preparation and Evaluation of Conductive Paste>
First, the binder resin is dissolved in a solvent that is half the predetermined amount of solvent, the metal particles, the processing agent, and the remaining solvent are added to the resulting solution, premixed, and then dispersed using a three-roll mill. to obtain conductive pastes of Examples 1 to 8 and Comparative Examples 1 and 2 shown in Tables 2 and 3. Tables 2 and 3 show the evaluation results of the obtained conductive pastes.

In Tables 2 and 3, conductive filler 1: Mitsubishi Materials Corporation silver-coated powder general-purpose type (average particle size 2 μm)
Conductive filler 2: Mitsubishi Materials Corporation silver coated powder general-purpose type (average particle size 1.2 μm)
Binder resin 1: JSR Corporation extra 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: Shin-Etsu Chemical Co., Ltd. Reactive silicone oil single-end type (average single-end carboxyl-modified) (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 conductive filler 1 and binder resin 1 were used, and 0.1% by weight of additive 1 was added to the conductive filler to prepare a paste. The initial resistivity is 5.9×10 ⁻⁴ (Ω・cm), the resistivity at 100% elongation is 86×10 ⁻⁴ (Ω・cm), and the resistivity after 1000 cycles of 20% repeated stretching is 5000×10. ⁻⁴ (Ω·cm), which was good.

Example 2 in Table 2 is an example in which conductive filler 1 and binder resin 1 were used, and 1% by weight of additive 1 was added to the conductive filler to prepare a paste. The initial resistivity is 5.4×10 ⁻⁴ (Ω・cm), the resistivity at 100% elongation is 52×10 ⁻⁴ (Ω・cm), and the resistivity after 1000 cycles of 20% repeated stretching is 1300×10 ⁻⁴ (Ω·cm), which was extremely good.

Example 3 in Table 2 is an example in which conductive filler 1 and binder resin 1 were used, and 2% by weight of additive 1 was added to the conductive filler to prepare a paste. The initial resistivity is 6.4×10 ⁻⁴ (Ω・cm), the resistivity at 100% elongation is 83×10 ⁻⁴ (Ω・cm), and the resistivity after 1000 cycles of 20% repeated stretching is 1100×10 ⁻⁴ (Ω·cm), which was extremely good.

Example 4 in Table 2 is an example in which conductive filler 2 and binder resin 1 were used, and 1% by weight of additive 1 was added to the conductive filler to prepare a paste. The initial resistivity is 3.5×10 ⁻⁴ (Ω・cm), the resistivity at 100% elongation is 30×10 ⁻⁴ (Ω・cm), and the resistivity after 1000 cycles of 20% repeated stretching is 790×10. ⁻⁴ (Ω·cm), which was extremely good.

Example 5 in Table 2 is an example in which conductive filler 1 and binder resin 1 were used, and 1% by weight of additive 2 was added to the conductive filler to prepare a paste. The initial resistivity is 36.6×10 ⁻⁴ (Ω・cm), the resistivity at 100% elongation is 93×10 ⁻⁴ (Ω・cm), and the resistivity after 1000 cycles of 20% repeated stretching is 1600×10 ⁻⁴ (Ω·cm), which was extremely good.

Example 6 in Table 2 is an example in which a paste was prepared using conductive filler 1 and binder resin 1 without adding additives. The initial resistivity is 7.6×10 ⁻⁴ (Ω·cm), the resistivity at 100% elongation is 110×10 ⁻⁴ (Ω·cm), and the resistivity after 1000 cycles of 20% repeated stretching is 6800×10. ⁻⁴ (Ω·cm), which was good.

Example 7 in Table 2 is an example in which conductive filler 1 and binder resin 2 were used, and 1% by weight of additive 1 was added to the conductive filler to prepare a paste. The initial resistivity is 5.1×10 ⁻⁴ (Ω・cm), the resistivity at 100% elongation is 39×10 ⁻⁴ (Ω・cm), and the resistivity after 1000 cycles of 20% repeated stretching is 1250×10. ⁻⁴ (Ω·cm), which was extremely good.

Example 8 in Table 2 is an example in which conductive filler 1 and binder resin 3 were used, and 1% by weight of additive 1 was added to the conductive filler to prepare a paste. The initial resistivity is 5.2×10 ⁻⁴ (Ω・cm), the resistivity at 100% elongation is 54×10 ⁻⁴ (Ω・cm), and the resistivity after 1000 cycles of 20% repeated stretching is 1000×10. ⁻⁴ (Ω·cm), which was extremely good.

Comparative Example 1 in Table 2 is an example in which conductive filler 1 and binder resin 1 were used, and 5.0% by weight of additive 1 was added to the conductive filler to prepare a paste. The initial resistivity was 7.2×10 ⁻⁴ (Ω·cm), the resistivity at 100% elongation was 125×10 ⁻⁴ (Ω·cm), and after 1000 cycles of 20% repeated stretching, the electrical continuity disappeared.

Comparative Example 2 in Table 2 is an example in which conductive filler 1 and binder resin 1 were used, and 1.0% by weight of additive 3 was added to the conductive filler to prepare a paste. The initial specific resistance was 21×10 ⁻⁴ (Ω·cm), and the conductivity was lost after 1000 cycles of 20% repetitive expansion and contraction at 100% elongation.

[Application Example 1]
The conductive film obtained from the conductive paste obtained in Example 1 was used as the elastic conductor layer, and the elastic insulating polymer layer was an elastomer sheet with a hot melt layer "Mobilon" manufactured by Nisshinbo Co., Ltd., and the electrode surface A sports shirt with electrodes and wiring was obtained by a method of cutting out each sheet into a predetermined shape, omitting the layers, and laminating the sheets.
The resulting sports shirt with electrodes and wiring has circular electrodes with a diameter of 50 mm at the intersection of the left and right posterior axillary lines and the 7th rib, and a striped stretchable conductor composition from the circular electrodes to the center of the chest. Electrical wiring is formed inside. The wiring extending from the left and right electrodes to the center of the back surface of the neck is rectangular with a side of 20 mm on the center side of the chest.

Next, stainless steel hooks are attached to the front side of the pair of electrodes on the central side of the chest, and a stretchable conductor is used to secure electrical continuity with the wiring section on the back side using a conductive thread twisted with thin metal wires. An electrical connection was made between the composition layer and the stainless steel hook.
The heart rate sensor WHS-2 made by Union Tool is connected via a stainless steel hook, and the heart rate data is received by an Apple smartphone that incorporates the dedicated application "myBeat" for the same heart rate sensor WHS-2 and displayed on the screen. set to be displayed. As described above, a sports shirt incorporating a heart rate measurement function was produced.

Subjects were made to wear this shirt and electrocardiographic data was obtained while driving. The electrocardiographic data obtained has little noise and high resolution, and has the quality that can be analyzed from changes in heartbeat intervals, electrocardiographic waveforms, etc., such as mental state, physical condition, fatigue, drowsiness, and tension as an electrocardiogram. rice field. 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, according to the composition ratio shown in Table 4, a conductive paste was produced. A binder resin is dissolved in a solvent that is half the amount of a predetermined solvent, metal particles are added to the resulting solution, premixed, and then dispersed with a three-roll mill to obtain a conductive paste D11 shown in Table 1. 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: Mitsubishi Materials Corporation silver-coated powder general-purpose type (average particle size 1.2 μm)
Conductive filler B: YCC techno powder silver-coated potassium titanate fiber YTA-1575 manufactured by Yokozawa Metal Industry Co., Ltd.
Binder resin 11: Ultra high nitrile type N215SL manufactured by JSR Corporation
Stretch recovery rate of 99.9% or more Binder resin 12: Polyurethane resin composition (B)
Stretch recovery rate 99.9% or more Solvent 1: isophorone Solvent 3: ethylene glycol monoethyl ether acetate.

<Preparation of conductive film>
The obtained conductive paste D11 was applied with an applicator onto a stretchable urethane sheet with a thickness of 1 mm and dried at 120° C. for 20 minutes to prepare a sheet having a conductive film with a thickness of about 80 μm. The conductive film formed on the urethane sheet and the urethane sheet were evaluated using a strip-shaped slit having a width of 10 mm as required. Table 4 shows the evaluation results.

<Examples 12 to 15, Comparative Examples 11 to 14>
Thereafter, according to the composition ratio in Table 4, the same operation as in Example 11 was performed to obtain conductive pastes D12 to D19. 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 clothing-type electronic device for electrocardiogram measurement having electrical wiring by the transfer method shown in FIG. 4 was manufactured.
First, a carbon paste to be an electrode surface layer was screen-printed in a predetermined pattern on a release PET film having a thickness of 125 μm, and dried and cured. Next, an insulating paste to be an insulating cover layer was screen-printed in a predetermined pattern, dried and cured. The electrode surface layer for electrocardiographic measurement is circular 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 part, and the wiring part extending from the electrode has a width of 14 mm. A circular electrode is similarly printed with carbon paste. The dry film thickness of the carbon paste layer is 25 μm, and the thickness of the insulating cover layer is 15 μm. Then, the electrode portion and the wiring portion are screen-printed using the conductive paste D11, which will be the conductor layer, and dried under predetermined conditions. Cured. The electrode portion was circular with a diameter of 32 mm, the wiring portion was 10 mm wide, and the dry thickness on the insulating cover layer was adjusted to 30 μm. Further, the base layer is screen-printed using the same insulating paste as the insulating cover layer, adjusted to a dry thickness of 20 μm, and dried. The remaining 25% by mass of the tackiness on the surface was left, and a printed electric wiring with transferability was obtained.
Next, the transferable printed electric wiring obtained by the above steps is overlaid on a predetermined portion of a sports shirt made of a knitted fabric turned inside out, pressed at room temperature to temporarily adhere the printed electric wiring to the back side of the sports shirt, and released from the mold. After removing the PET film, the sports shirt was hung on a hanger and 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 circular electrodes with a diameter of 30 mm at the intersection of the left and right posterior axillary lines and the 7th rib. Electrical wiring is formed inside. The wiring extending from the left and right electrodes to the center of the posterior 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 back neck, and a conductive thread twisted with a thin metal wire is used to ensure electrical continuity with the wiring part on the back side. and stainless steel hooks were electrically connected.
The heart rate sensor WHS-2 made by Union Tool is connected via a stainless steel hook, and the heart rate data is received by an Apple smartphone that incorporates the dedicated application "myBeat" for the same heart rate sensor WHS-2 and displayed on the screen. set to be displayed. As described above, a sports shirt incorporating a heart rate measurement function was produced.

This shirt was put on by the subject, and radio exercise 1 and radio exercise 2 were performed continuously, and electrocardiographic data was obtained during that period. The electrocardiographic data obtained has little noise and high resolution, and has the quality that can be analyzed from changes in heartbeat intervals, electrocardiographic waveforms, etc., such as mental state, physical condition, fatigue, drowsiness, and tension as an electrocardiogram. rice field. 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 field of application

As described above, the conductive paste and the conductive film obtained from the conductive paste in the present invention can be produced at low cost, and have elasticity, so that the conductive film obtained from the paste can be repeatedly bent. It is excellent in flexibility, repetitive twistability, and repetitive extensibility, and also causes less discomfort when worn.
By using the stretchable conductive film of the present invention in wearable smart devices, it is possible to obtain information possessed by the human body, i.e. biopotentials such as myoelectric potential and cardiac potential, and biometric information such as body temperature, pulse, and blood pressure. Wearable devices for detection, or clothing incorporating electrical heating devices, wearable devices incorporating sensors for measuring clothing pressure, clothing that measures body size using clothing pressure, soles Sock-type devices for measuring pressure, clothing with flexible solar cell modules integrated into textiles, wiring parts for tents, bags, etc., low-frequency therapy equipment with joints, wiring parts for heat treatment equipment, etc. It can be applied to a sensing part or the like. Such wearable devices can be applied not only to the human body, but also to animals such as pets and livestock, or to mechanical devices having stretchable or flexible parts. It can also be used as electrical wiring for systems that are used by connecting. It can also be applied as a wiring material for implant devices that are embedded in the body, patchable devices that are used by being attached to the surface of the body or mucous membranes, or edible devices that measure biological information in the digestive tract.

1. Base material (fabric)
2. Insulating base layer3. Elastic conductor composition layer (elastic conductor layer)
4. Elastic cover layer (insulating cover layer)
5. Elastic carbon layer (electrode surface layer)
6. Adhesive layer (insulating base layer)
10. Temporary support (release indicator)

Claims (25)

It contains at least a conductive filler made of metal-coated particles having a metal layer on the surface of a non-conductive core particle, a binder resin made of an elastomer, an organic solvent and an additive, and the surface of the conductive filler is not previously surface-treated. , said additive is polydimethylsiloxane or pentadecafluorooctanoic acid having at least one functional group selected from an amino group, a carboxyl group, and a glycidyl group, at least one end thereof. Conductive paste used for forming. 2. The conductive paste according to claim 1, wherein said binder resin is a nitrile group-containing elastomer or urethane resin. Claim 1 or Claim 2, wherein the surface free energy of the additive is 30 mJ/m ² or less, and the additive is contained in an amount of 0.1 to 3.0% by mass with respect to the conductive filler. The conductive paste described in . The conductive paste according to any one of claims 1 to 3 , wherein the additive has a surface free energy of 25 mJ/ ^m2 or less. 5. The conductive paste according to any one of claims 1 to 4 , wherein the additive is polydimethylsiloxane having a carboxyl group at least on one end. At least, it contains a conductive filler made of metal-coated particles having a metal layer on the surface of a non-conductive core particle, a binder resin made of an elastomer, an organic solvent and additives, and the surface of the conductive filler is previously surface- treated . First, the additive is polydimethylsiloxane or pentadecafluorooctanoic acid having at least one functional group selected from an amino group, a carboxyl group, and a glycidyl group on at least one terminal. conductive coating. 7. The conductive film according to claim 6 , wherein the binder resin is a nitrile group-containing elastomer or urethane resin. Claim 6 or Claim 7 , wherein the surface free energy of the additive is 30 mJ/ ^m2 or less, and the additive is contained in an amount of 0.1 to 3.0% by mass with respect to the conductive filler. The conductive coating according to . 9. The conductive film according to any one of claims 6 to 8 , wherein the additive has a surface free energy of 25 mJ/ ^m2 or less. 10. The conductive film according to any one of claims 6 to 9 , wherein the additive is polydimethylsiloxane having a carboxyl group at least on one end. 11. The elastic conductive material according to any one of claims 6 to 10 , wherein the conductive film has a specific resistance when stretched by 100% within 20 times the specific resistance when stretched. sexual capsule. 11. The stretchable conductive coating according to claim 6 , wherein the conductive coating retains its conductivity after 1000 cycles of 20 % repeated stretching. A clothing-type electronic device having electrical wiring made of the stretchable conductive film according to any one of claims 6 to 12 . 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 the ratio of the major axis to the minor axis, of 1.5 or less, and is non-conductive. The conductive filler B is a metal-coated particle having a metal layer on the surface of a core particle having a diameter of 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. It is a metal-coated particle having a metal layer on the surface of a 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 60% by mass. The conductive paste according to claim 1, characterized in that 15. The conductive paste according to claim 14 , wherein the elastomer used as the binder resin is a non-crosslinked elastomer. 16. The conductive paste according to claim 14 or 15 , wherein the binder resin is a nitrile group-containing elastomer. 16. The conductive paste according to claim 14 , wherein said binder resin is urethane resin. In a conductive film containing at least a conductive filler, a binder resin, and an additive as constituent components, at least two types of conductive filler A and conductive filler B are contained as conductive fillers, and the conductive filler A has a major axis to minor axis ratio of It is a metal-coated particle having an aspect ratio of 1.5 or less and a metal layer on the surface of a non-conductive core particle, and has a median particle diameter D of 0.5 μm or more and 15 μm or less, and the conductive filler B is , an aspect ratio, which is the ratio of the major axis to the minor axis, of 5 or more, a metal-coated particle having a metal layer on the surface of a non-conductive core particle, an average length L of the major axis of 10 μm or more and 30 μm or less, and a conductive The ratio of the conductive filler B to the total filler is 25 to 60% by mass, the binder resin is an elastomer, and the additive has at least one terminal selected from an amino group, a carboxyl group, and a glycidyl group. A stretchable conductive film characterized by being polydimethylsiloxane or pentadecafluorooctanoic acid having a functional group of 19. The conductive coating according to claim 18 , wherein said binder resin is a nitrile group-containing elastomer. 19. The conductive film according to claim 18 , wherein said binder resin is a urethane resin. 21. The elastic conductive material according to any one of claims 18 to 20 , wherein the conductive film has a specific resistance at 100% elongation within 10 times the specific resistance at non-elongation. sexual capsule. 22. The stretchable conductive coating according to any one of claims 18 to 21 , wherein the conductive coating maintains its conductivity after 1000 cycles of 20% repeated stretching. Claims 18 to 22 , wherein 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. Conductive coating according to any one of.
[Torsion test:
Sample: Width 10 mm, length 100 mm (one end of the sample fixed in the longitudinal direction, twisted by rotating the other end)
Twist cycle: 10 twists in positive direction (3600°), return to initial state, 10 twists in negative direction (−3600°), return to initial state] A stretchable electronic component having electrical wiring comprising the conductive film according to any one of claims 18 to 23 . A clothing-type electronic device having electrical wiring made of the conductive film according to any one of claims 18 to 23 .

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