Stretchable conductive paste and film

Abstract

Provided is a conductive paste capable of reducing an increase in electrical resistance due to elongation of wires when the wires of an electric circuit and / or an electronic circuit are formed on the surface of a base material that can be expanded and contracted and can be bent. A stretchable conductive paste contains (A) surface-treated silver particles and (B) a thermoplastic resin, wherein (A) the surface-treated silver particles contain surface-treated layers.

Description

[Technical Field]

[0001] The present invention relates to a stretchable conductive paste capable of forming wiring for electric and / or electronic circuits on the surface of a stretchable and / or bendable substrate, and also to a film containing the stretchable conductive paste. [Background technology]

[0002] BACKGROUND ART In recent years, conductive pastes have been developed for forming thin film conductors such as electrodes on stretchable and bendable substrates.

[0003] For example, Patent Document 1 describes a conductive paste used to form stretchable wiring. Patent Document 1 describes that the conductive paste 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, and an organic solvent. Patent Document 1 also describes that the surface of the conductive filler is not previously surface-treated.

[0004] Patent Document 2 describes a stretchable conductive sheet used for electrical wiring, etc., and a paste for forming the stretchable conductive sheet used in the stretchable conductive sheet. Patent Document 2 describes that the conductive paste contains at least conductive particles, inorganic particles surface-treated with hydroxide and / or oxide of one or both of Al and Si, a flexible resin having a tensile modulus of elasticity of 1 MPa to 1000 MPa, and a solvent. Patent Document 2 also describes that the blending amount of the inorganic particles in the conductive paste is 2.0 to 30 mass% of a total of 100 mass% of the conductive particles and inorganic particles, and that the blending amount of the flexible resin is 7 to 35 mass% of a total of 100 mass% of the conductive particles, inorganic particles, and flexible resin.

[0005] Patent Document 3 describes a resin composition containing (A) conductive particles, (B) a thermoplastic polyurethane resin having a 100% modulus of 7 MPa or more, and (C) a solvent. Patent Document 3 also describes that the resin composition contains (A) conductive particles in a ratio of 90% by weight or more to less than 100% by weight of the total of (A) conductive particles and (B) thermoplastic polyurethane resin.

[0006] Patent Document 4 describes a conductive paste containing a surface-treated silver-coated alloy powder as a material for forming external electrodes of electronic components. Patent Document 4 also describes that the surface-treated silver-coated alloy powder comprises alloy particles, a silver coating layer that coats the alloy particles, and a surface treatment layer that coats the silver-coated alloy particles composed of the alloy particles and the silver coating layer.

[0007] [Patent Document 1] International Publication No. 2018 / 159374 [Patent Document 2] International Publication No. 2017 / 154978 [Patent Document 3] Japanese Patent Application Publication No. 2018-104581 [Patent Document 4] Japanese Patent Application Publication No. 2019-31735 DISCLOSURE OF THE INVENTION

[0008] In recent years, attempts have been made to form wiring for electric and / or electronic circuits on the surface of a stretchable and / or bendable substrate. In the case of wiring formed on such a substrate, the wiring also stretches and / or expands due to the stretching and / or bending of the substrate. As a result, the electrical resistance of the wiring increases significantly, and the electric and / or electronic circuit may no longer function.

[0009] Therefore, an object of the present invention is to provide a conductive paste that can reduce an increase in electrical resistance due to elongation of wiring when wiring for an electric circuit and / or electronic circuit is formed on the surface of a stretchable and / or bendable substrate.Another object of the present invention is to provide a film that can reduce an increase in electrical resistance (sheet resistance) due to elongation when a film is formed using the conductive paste.

[0010] In order to solve the above problems, the present invention has the following configuration.

[0011] (Configuration 1) Configuration 1 of the present invention is a stretchable conductive paste comprising (A) surface-treated silver particles and (B) a thermoplastic resin, wherein the (A) surface-treated silver particles comprise a surface-treatment layer.

[0012] (Configuration 2) A second aspect of the present invention is the stretchable conductive paste of the first aspect, wherein the surface treatment layer is a surface treatment layer made of at least one selected from dodecylbenzenesulfonic acid, dodecanoic acid, and oleic acid.

[0013] (Configuration 3) A third aspect of the present invention is the stretchable conductive paste of the first aspect, wherein the surface treatment layer is a surface treatment layer made of dodecylbenzenesulfonic acid.

[0014] (Configuration 4) A fourth aspect of the present invention is the stretchable conductive paste of any one of the first to third aspects, in which the weight ratio of (A) the surface-treated silver particles to (B) the thermoplastic resin is 50:50 to 99:1.

[0015] (Configuration 5) A fifth aspect of the present invention is the stretchable conductive paste according to any one of the first to fourth aspects, wherein the average particle size of the surface-treated silver particles (A) is 0.1 to 20 μm.

[0016] (Configuration 6) A sixth aspect of the present invention is the stretchable conductive paste according to any one of the first to fifth aspects, wherein the thermoplastic resin (B) is at least one selected from a urethane resin and a polycarbonate resin.

[0017] (Configuration 7) A seventh aspect of the present invention is the stretchable conductive paste of any one of the first to sixth aspects, further comprising (C) a solvent.

[0018] (Configuration 8) An eighth aspect of the present invention is a film comprising the stretchable conductive paste of any one of the first to seventh aspects.

[0019] The present invention provides a conductive paste that can reduce an increase in electrical resistance due to elongation of wiring when wiring for an electric circuit and / or electronic circuit is formed on the surface of a stretchable and / or bendable substrate.Furthermore, the present invention provides a film that can reduce an increase in electrical resistance (sheet resistance) due to elongation when a film is formed using the conductive paste. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a schematic diagram showing an electrical resistance test pattern used in the evaluation of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail. Note that the following embodiments are forms for realizing the present invention, and are not intended to limit the scope of the present embodiments.

[0022] This embodiment is a conductive paste comprising (A) surface-treated silver particles and (B) a thermoplastic resin, wherein the (A) surface-treated silver particles comprise a surface-treatment layer. In the conductive paste of this embodiment, the (A) surface-treated silver particles comprise a surface-treatment layer. When the conductive paste of this embodiment is used to form wiring for electric and / or electronic circuits (also simply referred to as "wiring") on the surface of a stretchable and / or bendable substrate, the increase in electrical resistance due to the elongation of the wiring can be reduced. Therefore, the conductive paste of this embodiment can be used to form wiring for applications such as clothing with wiring (e.g., clothing with built-in biosensors) and flexible hybrid electronics.

[0023] Furthermore, the conductive paste of this embodiment can reduce an increase in electrical resistance due to the extension of wiring. Therefore, even when the wiring is bent (i.e., the wiring is non-uniformly extended), the increase in electrical resistance can be reduced. Therefore, when the conductive paste of this embodiment is used, it can be said that even when wiring for an electric circuit and / or an electronic circuit is formed on the surface of a bendable substrate, the increase in electrical resistance due to the bending of the wiring can be reduced.

[0024] In this specification, a conductive paste that can reduce an increase in electrical resistance due to stretching of wiring when wiring of an electric circuit and / or electronic circuit is formed on the surface of a stretchable and / or bendable substrate is referred to as a "stretchable conductive paste." In other words, a stretchable conductive paste is a conductive paste that can form wiring of an electric circuit and / or electronic circuit that stretches. The conductive paste of this embodiment is a stretchable conductive paste that can form wiring of an electric circuit and / or electronic circuit that stretches. Note that in this specification, the stretchable conductive paste of this embodiment may sometimes be simply referred to as a "conductive paste."

[0025] In this specification, "stretchable and / or bendable substrate" refers to materials that can bend and / or stretch, such as fabrics used to form clothing, resin plates, and flexible substrates such as paper, metal foil, and flexible glass and ceramic. However, substrates on which wiring can be formed using the resin composition of this embodiment are not limited to these, and may be substrates containing other stretchable and / or bendable materials. Note that wiring can also be formed on substrates that are not stretchable and / or bendable using the resin composition of this embodiment.

[0026] Next, each component contained in the stretchable conductive paste of this embodiment will be described.

[0027] The stretchable conductive paste of this embodiment contains surface-treated silver particles as component (A).

[0028] The conductive particles used as the raw material for the surface-treated silver particles contained in the stretchable conductive paste of this embodiment are preferably silver particles. The conductive particles may contain at least one element selected from Au, Cu, Ni, and Ti as a component other than silver, within a weight percentage range that does not significantly degrade the conductive particle properties (for example, less than 50% by weight, preferably 20% by weight or less, more preferably 10% by weight or less). Silver (Ag) has high electrical conductivity. Therefore, the conductive particles are preferably silver particles consisting only of silver. However, in this specification, "silver particles consisting only of silver" means that they may contain impurities that are inevitably mixed in. In this specification, "A particles consisting of metal A" means that A particles may contain impurities that are inevitably contained in addition to metal A. The same applies to components other than metal particles.

[0029] The surface-treated conductive particles (surface-treated silver particles) contained in the stretchable conductive paste of this embodiment include a surface-treated layer.

[0030] The surface treatment layer of the stretchable conductive paste of this embodiment is preferably a surface treatment layer made of at least one selected from dodecylbenzenesulfonic acid, dodecanoic acid, and oleic acid. Among these, the surface treatment layer is more preferably a surface treatment layer made of dodecylbenzenesulfonic acid. By having the surface treatment layer of the surface-treated silver particles made of a predetermined material, when wiring for an electric circuit and / or electronic circuit is formed on the surface of a stretchable and / or bendable substrate using the stretchable conductive paste, it is possible to reliably reduce an increase in electrical resistance due to the extension of the wiring.

[0031] Methods for forming a surface treatment layer on silver particles using dodecylbenzenesulfonic acid, dodecanoic acid, and / or oleic acid are well known to those skilled in the art. Specifically, a surface treatment layer can be formed on the surfaces of silver particles by mixing and stirring raw material silver powder (silver particles) with dodecylbenzenesulfonic acid, dodecanoic acid, and / or oleic acid.

[0032] The particle shape of the surface-treated conductive particles (surface-treated silver particles) can be, for example, spherical or flake-like. The particle size of the surface-treated conductive particles can be determined by the particle size (D50) of 50% of the total particle size. In this specification, D50 is also referred to as the average particle size. The average particle size (D50) can be determined from the results of particle size distribution measurement performed using the Microtrac method (laser diffraction scattering method).

[0033] The average particle diameter (D50) of the surface-treated conductive particles (surface-treated silver particles) is preferably 0.1 to 20 μm, more preferably 0.2 to 15 μm, and even more preferably 0.5 to 10 μm, from the viewpoints of resistance to stretching and / or bending and workability. If the average particle diameter (D50) is larger than the above range, problems such as clogging may occur during screen printing. If the average particle diameter is smaller than the above range, the particles may be excessively sintered during firing, and the increase in electrical resistance associated with the elongation of the formed wiring may not be sufficiently reduced.

[0034] The size of the surface-treated conductive particles (surface-treated silver particles) can be expressed as a BET value (BET specific surface area). The BET value of the conductive particles is preferably 0.1 to 5 m 2 / g, more preferably 0.2 to 4m 2 / g, more preferably 0.5 to 3m 2 / g.

[0035] The stretchable conductive paste of this embodiment contains a thermoplastic resin as component (B).

[0036] In the stretchable conductive paste of this embodiment, the thermoplastic resin is preferably at least one selected from a urethane resin and a polycarbonate resin. By using a urethane resin and / or a polycarbonate resin as the thermoplastic resin, more appropriate stretchability can be imparted to the formed wiring.

[0037] The urethane resin that can be used as the thermoplastic resin is preferably at least one selected from the group consisting of ether-based urethane resins, ester-based urethane resins, adipate-based urethane resins, caprolactone-based urethane resins, and carbonate-based urethane resins. By using such a urethane resin, it is possible to ensure that the formed wiring has more appropriate stretchability.

[0038] The stretchable conductive paste of this embodiment may contain resins other than urethane resin or polycarbonate resin, such as other thermoplastic resins, thermosetting resins, and / or photocurable resins, as long as the effects of this embodiment are not impaired. However, in order to obtain suitable wiring, the resin contained in the stretchable conductive paste of this embodiment is preferably a resin consisting solely of the above-mentioned urethane resin, a resin consisting solely of polycarbonate resin, or a resin consisting solely of a mixture thereof.

[0039] When the stretchable conductive paste of this embodiment contains surface-treated silver particles having a surface treatment layer made of dodecylbenzenesulfonic acid and a thermoplastic resin such as a urethane resin, when the conductive paste is used to form a wiring, the increase in electrical resistance due to the extension of the wiring can be more reliably reduced. This effect is presumed to be a synergistic effect of the above-mentioned component (A) (surface-treated silver particles) and component (B) (thermoplastic resin), but the present invention is not bound by this presumption.

[0040] In the stretchable conductive paste of this embodiment, the weight ratio of the surface-treated silver particles to the thermoplastic resin (surface-treated silver particles:thermoplastic resin) is preferably 50:50 to 99:1, more preferably 60:40 to 98:2, even more preferably 70:30 to 96:4, and particularly preferably 75:25 to 95:5. By ensuring that the weight ratio of the surface-treated silver particles to the thermoplastic resin contained in the conductive paste is within the specified range, it is possible to impart appropriate electrical resistance and stretchability to the formed wiring.

[0041] The stretchable conductive paste of this embodiment may further contain a solvent as component (C).

[0042] The solvent contained in the conductive paste is not particularly limited as long as it can dissolve the predetermined thermoplastic resin. In the conductive paste of this embodiment, the solvent is preferably at least one selected from cyclohexanone, dimethylformamide, dimethylacetamide, benzyl alcohol, dimethylpropanamide, and isophorone. The solvent is more preferably dimethylpropanamide or isophorone. By using a predetermined solvent, it is possible to reliably dissolve the predetermined resin (e.g., urethane resin and polycarbonate resin). As a result, it is possible to facilitate screen printing of the resin composition for forming wiring.

[0043] The amount of solvent added is 20 to 500 parts by weight, preferably 50 to 400 parts by weight, and more preferably 80 to 300 parts by weight, relative to 100 parts by weight of the thermoplastic resin.Usually, by using a solvent in an amount about 1 to 3 times (preferably 2 to 2.5 times) the weight of the thermoplastic resin, the thermoplastic resin can be properly dissolved.

[0044] The solvent can be added to the resin composition as needed to adjust the viscosity of the resin composition.

[0045] The stretchable conductive paste of this embodiment may contain components other than the resin composition described above, to the extent that the effects of this embodiment are not impaired or to improve the effects of this embodiment. For example, the conductive paste of this embodiment may further contain at least one selected from an inorganic pigment, an organic pigment, a silane coupling agent, a leveling agent, a thixotropic agent, and an antifoaming agent.

[0046] This embodiment is a film-shaped cured product of the above-mentioned stretchable conductive paste. In this specification, the film-shaped cured product may be simply referred to as a "film." This embodiment is a film containing the above-mentioned stretchable conductive paste.

[0047] As used herein, the term "film" refers to a pattern that has a flat, plate-like shape and is solidified on the surface of a specific substrate. Examples of films include planar conductive patterns and wiring patterns for electric and / or electronic circuits.

[0048] In this specification, the pattern of the stretchable conductive paste printed in a flat plate shape by means of screen printing or the like may be referred to as a "film-like composition." A cured film can be obtained by heat-treating the film-like composition.

[0049] The stretchable conductive paste of this embodiment can be formed into the shape of an electric circuit and / or electronic circuit wiring by means of screen printing or the like, and then cured. This allows for the formation of electric circuit and / or electronic circuit wiring on the surface of a stretchable and / or flexible substrate, which can reduce the increase in electrical resistance (sheet resistance) due to the extension of the wiring. The temperature and time for curing the conductive paste can be appropriately selected depending on the type of thermoplastic resin contained in the resin composition. The temperature and time for curing the conductive paste can be appropriately adjusted and determined taking into account the heat resistance of the substrate. For example, the temperature and time for curing the conductive paste can be set to 60°C to 180°C for 5 to 60 minutes, preferably 80 to 140°C for 5 to 60 minutes, and more preferably 110 to 130°C for 20 to 40 minutes.

[0050] The stretchable conductive paste of this embodiment can be applied in a predetermined pattern to the surface of the fabric that will be used to make the clothing, and then cured to form wiring on the surface of the clothing. By using the stretchable conductive paste of this embodiment, wiring can be formed as a conductive pattern on clothing that can stretch and / or bend. The stretchable conductive paste of this embodiment can be used to form wiring for clothing with a built-in biosensor, for example.

[0051] By using the stretchable conductive paste of this embodiment, wiring can be formed on the surface of a flexible substrate such as plastic, paper, metal foil, and flexible glass and ceramic, etc. Therefore, the stretchable conductive paste of this embodiment can be used to form wiring for applications such as flexible hybrid electronics.

[0052] When wiring is formed using the stretchable conductive paste of this embodiment, the initial electrical resistance (X) (electrical resistance before stretching) of a wiring 90 mm long, 1 mm wide, and 20 μm thick is preferably 20 Ω or less (specific resistance 444 μΩ·cm or less), more preferably 15 Ω or less (specific resistance 333 μΩ·cm or less), and even more preferably 10 Ω or less (specific resistance 222 μΩ·cm or less). By keeping the initial electrical resistance (X) (and specific resistance) within the specified range, the wiring can be used as wiring for applications such as clothing and flexible hybrid electronics, even when considering the stretching of the wiring.

[0053] When wiring is formed using the stretchable conductive paste of this embodiment, the ratio (electrical resistance change rate (Y / X)) of the electrical resistance (Y) when the wiring is stretched 100% (when the wiring is stretched to twice its initial length) to the initial electrical resistance (X) of the wiring is preferably 1000 or less, more preferably 500 or less, even more preferably 350 or less, and particularly preferably 250 or less. When the electrical resistance change rate (Y / X) is a predetermined ratio or less, it becomes possible to use the paste as wiring for applications such as clothing with wiring and flexible hybrid electronics.

[0054] The stretchable conductive paste of this embodiment can be produced by mixing the above-mentioned (A) surface-treated silver particles and (B) thermoplastic resin, and optionally other components (e.g., (C) solvent), in a mixer such as a meteoric mixer, dissolver, bead mill, Raikai mixer, three-roll mill, rotary mixer, or twin-screw mixer. In this way, a conductive paste suitable for screen printing, dipping, or other desired coating or wiring formation methods can be prepared.

[0055] The viscosity of the stretchable conductive paste of this embodiment can be adjusted to a viscosity that can be appropriately used in a predetermined coating or wiring formation method such as screen printing. The viscosity can be adjusted by appropriately controlling the amount of solvent.

[0056] The viscosity of the stretchable conductive paste of this embodiment is preferably 10 to 800 Pa·sec (measured at 1 rpm), and more preferably 50 to 600 Pa·sec (measured at 1 rpm). Note that "(measured at 1 rpm)" for viscosity indicates that the measurement was carried out at a rotation speed of 1 rpm. In this specification, viscosity is a value measured at 25°C using a Brookfield viscometer: Type B (manufactured by Brookfield).

[0057] By using the stretchable conductive paste of this embodiment, when wiring for an electric circuit and / or an electronic circuit is formed on the surface of a stretchable and / or bendable substrate by means of screen printing or the like, it is possible to provide a conductive paste that can reduce the increase in electrical resistance due to the stretching of the wiring. [Example]

[0058] The stretchable conductive paste of this embodiment will be specifically described below with reference to examples, but this embodiment is not limited to these.

[0059] <Conductive paste materials and preparation ratio> The compositions of the stretchable conductive pastes of the examples and comparative examples are shown in Tables 1 and 2. The conductive pastes of the examples and comparative examples are resin compositions containing silver particles (surface-treated silver particles), a thermoplastic resin, and a solvent.

[0060] (silver particles) Table 3 shows the manufacturer and model number, surface treatment agent for forming the surface treatment layer, average particle diameter (D50), tapped (TAP) density, and specific surface area of ​​silver particles A to E used in the examples and comparative examples. Silver particles A to D were produced in-house as described below. Silver particles A to D are surface-treated silver particles having a surface treatment layer. Silver particles E are silver particles without a surface treatment layer. Silver particles E were purchased from a commercial source. Tapped density is the bulk density obtained after mechanically tapping a container containing a powder sample. Tapped density can be measured according to JIS Z2512:2012 "Metal powders - Tapped density measurement method." Silver particles A to E have a flake-like particle shape.

[0061] (Silver particle A) A mixture of 1000 g of raw material silver powder, 10 g of dodecylbenzenesulfonic acid, 10 g of dodecanoic acid, and 100 g of ethanol was stirred in a pot mill to surface treat the silver powder, thereby producing silver particles A. Silver powder particle shape: flake Average particle size of silver powder (D50): 0.89 μm Tap density of silver powder: 2.29 g / cm 3 BET specific surface area of ​​silver powder: 2.56m 2 / g

[0062] (Silver particle B) A mixture of 1000 g of raw material silver powder, 10 g of dodecylbenzenesulfonic acid, poly(oxyethylene) oleyl ether, and 100 g of ethanol was stirred in a pot mill to surface treat the silver powder, thereby producing silver particles B. Silver powder particle shape: flake Average particle size of silver powder (D50): 0.94 μm Tap density of silver powder: 2.60 g / cm 3 BET specific surface area of ​​silver powder: 2.04m 2 / g

[0063] (Silver particle C) A mixture of 1000 g of raw material silver powder and 20 g of oleic acid was stirred in a pot mill to surface treat the silver powder, thereby producing silver particles C. Silver powder particle shape: flake Average particle size of silver powder (D50): 6.5 μm Tap density of silver powder: 2.70 g / cm 3 BET specific surface area of ​​silver powder: 1.00m 2 / g

[0064] (Silver particle D) A mixture of 1000 g of raw material silver powder and 20 g of oleic acid was stirred in a pot mill to surface treat the silver powder, thereby producing silver particles D. Silver powder particle shape: flake Average particle size of silver powder (D50): 3.7 μm Tap density of silver powder: 3.10 g / cm 3 BET specific surface area of ​​silver powder: 1.55m 2 / g

[0065] The thermoplastic polyurethane resins used in the examples and comparative examples are as follows. Resin A: Ether-based thermoplastic urethane resin T-8195N (manufactured by DIC Covestro Polymer Co., Ltd., 100% modulus = 9.2 MPa) Resin B: Adipate ester urethane resin P-1098 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., 100% modulus = 13 MPa)

[0066] The polyurethane resin used in the examples and comparative examples was prepared as a polyurethane resin solution by dissolving the polyurethane resin in a solvent with a weight 2.3 times that of the polyurethane resin. For example, in the case of Example 1, a polyurethane resin solution was used in which 6 parts by weight of polyurethane resin A was dissolved in 14 parts by weight of solvent (N,N-dimethylacetamide).

[0067] The solvents A and B used in the examples and comparative examples are as follows: Solvents A and B were used to dissolve polyurethane resin. Solvent A: 3-methoxy-N,N-dimethylpropanamide (trade name: KJCMPA (registered trademark)-100, manufactured by KJ Chemicals Co., Ltd.) Solvent B: Isophorone (manufactured by Taishin Chemical Co., Ltd.)

[0068] Next, the materials in the predetermined preparation ratios described above were mixed in a planetary mixer, and then dispersed in a three-roll mill to form a paste, thereby preparing a conductive paste.

[0069] <Viscosity measurement method> The viscosity of the conductive pastes of the Examples and Comparative Examples was measured using a Brookfield viscometer, Model B (manufactured by Brookfield) at a temperature of 25° C. The viscosity was measured at a rotation speed of 1 rpm for each resin composition of the Examples and Comparative Examples.

[0070] <Method for measuring electrical resistance and resistivity> The conductive pastes of the examples and comparative examples were printed on the surface of a polyurethane sheet using a screen printer to form an electrical resistance test pattern 10 (see FIG. 1 ) with a wiring portion 14 width of 1 mm and a length of 90 mm. The printed pattern was then heat-cured in a constant-temperature oven at 120°C for 30 minutes. The resulting cured electrical resistance test patterns 10 (hereinafter simply referred to as "electrical resistance test patterns 10") all had a film thickness of 20 μm. Film thickness measurements were performed using a surface roughness and shape measuring instrument (model: Surfcom 1500SD-2) manufactured by Tokyo Seimitsu Co., Ltd. The electrical resistance value when the electrical resistance test pattern 10 was not stretched was defined as the "initial electrical resistance (X)." The electrical resistance of the wiring portion 14 of the electrical resistance test pattern 10 was measured by measuring the electrical resistance between a pair of electrodes 12 using a digital multimeter (model: 2001) manufactured by TFF Keithley Instruments, Inc. Since the area of ​​the electrode portion 12 is large, the value of the electrical resistance obtained by measurement can be considered to be the electrical resistance of the wiring portion 14. Tables 1 and 2 show the initial electrical resistance (X) of the examples and comparative examples.

[0071] Next, the polyurethane sheet was stretched to stretch the wiring portion 14 of the electrical resistance test pattern 10 by 100% in the longitudinal direction (stretching the wiring portion 14 to a length of 180 mm), and then the electrical resistance (electrical resistance (Y) at 100% stretch) between the pair of electrode portions 12 was measured. An Instron universal testing machine (model number 5566) was used to stretch the polyurethane sheet. From the measurement results, the rate of change in electrical resistance (Y / X), which is the ratio of the electrical resistance (Y) at 100% stretch to the initial electrical resistance (X), was calculated. Tables 1 and 2 show the rate of change in electrical resistance (Y / X) for the examples and comparative examples.

[0072] <Measurement results of Examples and Comparative Examples> The initial resistance (X) of Examples 1 to 13 of this embodiment was low, ranging from 2.3 Ω to 7.15 Ω (specific resistance 51.1 μΩ·cm to 158.9 μΩ·cm), demonstrating their applicability as wiring for electric and / or electronic circuits. Furthermore, the electrical resistance (Y) at 100% elongation of Examples 1 to 13 of this embodiment was 611 Ω to 862 Ω, demonstrating their applicability as wiring for electric and / or electronic circuits even at 100% elongation. Furthermore, the electrical resistance change rate (Y / X) of Examples 1 to 13 of this embodiment was 85 to 304 (times), which was a change rate of approximately 350 times or less. Note that an electrical resistance change rate (Y / X) of 1000 times or less, preferably 500 times or less, is acceptable for wiring.

[0073] The electrical resistance of the electrical resistance test patterns 10 of Examples 1 to 13 of this embodiment was measured after being stretched 100% and then returned to their original lengths. It was confirmed that the electrical resistance was roughly the same as the initial electrical resistance. Specifically, the electrical resistance when stretched and then returned to their original lengths was within 3 to 4 times the initial electrical resistance (for example, initial resistances of 5.19 Ω and 5.56 Ω were 18.71 Ω and 19.15 Ω, respectively, when returned to their original lengths), which were acceptable values ​​for use as wiring in electrical circuits and / or electronic circuits.

[0074] On the other hand, the initial resistance (X) of Comparative Example 1 was a low value of 4.56 Ω (specific resistance 101.3 μΩ·cm), and before elongation, it was usable as wiring for electric circuits and / or electronic circuits. However, the electrical resistance (Y) at 100% elongation of Comparative Example 1 was a high value of 98,567 Ω, and the rate of change in electrical resistance (Y / X) was 21,616 (times). That is, the electrical resistance (Y) and rate of change in electrical resistance (Y / X) at 100% elongation of Comparative Example 1 were about two orders of magnitude higher than those of Examples 1 to 13. Therefore, it was revealed that Comparative Example 1 could not be used as wiring for electric circuits and / or electronic circuits when elongated to 100%.

[0075] From the above, it was revealed that when the stretchable conductive pastes of Examples 1 to 13 of this embodiment were used, a wiring pattern with low resistivity could be obtained, and even when the wiring pattern was stretched, an increase in electrical resistance could be suppressed. Therefore, it can be said that if the stretchable conductive paste of this embodiment is used, when wiring for an electric circuit and / or an electronic circuit is formed on the surface of a stretchable and / or bendable substrate, an increase in electrical resistance due to stretching of the wiring can be reduced.

[0076] [Table 1]

[0077] [Table 2]

[0078] [Table 3] [Explanation of symbols]

[0079] 10 Electrical resistance test pattern 12 Electrode section 14 Wiring section

Claims

1. (A) surface-treated silver particles and (B) a thermoplastic resin, wherein the (A) surface-treated silver particles include a surface treatment layer, A stretchable conductive paste, in which the weight ratio of (A) surface-treated silver particles to (B) thermoplastic resin is 75:25 to 95:

5.

2. 2. The stretchable conductive paste according to claim 1, wherein the surface treatment layer is a surface treatment layer made of at least one selected from dodecylbenzenesulfonic acid, dodecanoic acid, and oleic acid.

3. The stretchable conductive paste according to claim 1 , wherein the surface treatment layer is a surface treatment layer made of dodecylbenzenesulfonic acid.

4. The stretchable conductive paste according to any one of claims 1 to 3, wherein the thermoplastic resin (B) is at least one selected from a urethane resin and a polycarbonate resin.

5. (B) The thermoplastic resin is selected from the group consisting of ether-based urethane resins, ester-based urethane resins, adipate-based urethane resins, caprolactone-based urethane resins, and carbonate-based urethane resins. The stretchable conductive paste according to any one of claims 1 to 3, comprising at least one urethane resin.

6. The stretchable conductive paste according to any one of claims 1 to 5, further comprising (C) a solvent.

7. A film comprising the stretchable conductive paste according to any one of claims 1 to 6.

Images