TWI761533B - Conductive composition and conductor and laminated structure using the same - Google Patents

Abstract

An object of the present invention is to provide a conductive composition capable of obtaining a conductor having excellent electrical resistance stability even when expansion and contraction are repeated or when the expansion is increased. The means of the present invention is a conductive composition comprising an elastomer and silver powder, characterized in that the silver powder is surface-treated, the average primary particle size of the silver powder is 1.0 μm or less and the apparent porosity is 50-95% , In the conductive composition, the cumulative 95% particle size (D95 particle size) in the particle size distribution of the secondary particles of the silver powder is 3.0 to 25.0 μm.

Description

Conductive composition and conductor and laminated structure using the same

The present invention relates to a conductive composition, a conductor for curing the conductive composition, a laminate structure having a layer of the conductor, and an electronic component including the conductor or the laminate structure.

As a material for forming patterned conductors such as electrodes of printed wiring boards, etc., a paste-like conductive composition in which metal powder is mixed with an organic binder is used. A desired conductor can be formed by applying a conventional conductive composition in a pattern and then curing it, but the resulting conductor generally has high hardness. Therefore, in a flexible printed wiring board, the hardened conductor is required to have an electroconductive composition which is resistant to bending.

On the other hand, with the recent growth in the field of wearable devices, it is also required to impart stretchability to conductors. In particular, a wearable device with a higher degree of adhesion to the body requires a higher degree of stretchability.

In response to such a demand, for example, as an organic binder containing a metal powder, there has been proposed a conductive composition using an elastomer and having not only flexibility but also stretchability in the conductor (refer to Patent Document 1, etc.). [Prior Art Literature]

[Patent Document] [Patent Document 1] International Publication No. 2015/005204 Pamphlet

[Problems to be solved by the invention]

However, even if it is a conductor using the above-mentioned conductive composition, the resistance value increases rapidly due to repeated expansion and contraction, or if the conductor is stretched to a certain extent, or the wire may be disconnected depending on the situation. Even when expansion and contraction are repeated or stretched, a conductive composition of a conductor excellent in electrical resistance stability can be obtained.

Therefore, an object of the present invention is to provide an electroconductive composition capable of obtaining a conductor having excellent electrical resistance stability even when expansion and contraction are repeated or when the expansion and contraction are increased.

Another object of the present invention is to provide a conductor in which such a conductive composition is cured, a laminate structure having a layer of the conductor, and an electronic component including the conductor or the laminate structure. [Means to solve the problem]

The inventors of the present invention have obtained the following knowledge and insight: as the conductive metal powder blended with the elastomer, the surface-treated silver powder having a specific average primary particle size is brought into a specific agglomerated state in the composition, It is possible to realize an electroconductive composition which can obtain a conductor having excellent electrical resistance stability even when repeatedly stretched or stretched, for example, when it is stretched to 400% or more. The present invention is based on this knowledge.

That is, the conductive composition of the present invention is a conductive composition comprising an elastomer and a silver powder, the silver powder is surface-treated, and the silver powder has an average primary particle size of 1.0 μm or less and an apparent porosity of 50 to 95 %, In the conductive composition, the cumulative 95% particle size (D95 particle size) in the particle size distribution of the secondary particles of the silver powder is 3.0 to 25.0 μm.

In the embodiment of this invention, the said silver powder is 60-95 mass % in solid content with respect to the whole electroconductive composition.

Moreover, the electroconductive system which concerns on another embodiment of this invention hardens the said electroconductive composition.

Moreover, the laminated structure system which concerns on another embodiment of this invention has the layer of the said conductor on a base material.

Moreover, the electronic component which concerns on another embodiment of this invention is provided with the layer of the said conductor or the said laminated structure. [Effect of invention]

According to the conductive composition of the present invention, as the conductive metal powder mixed with the elastomer, the surface-treated silver powder having a specific average primary particle size is brought into a specific agglomerated state in the composition. Even when the expansion and contraction are repeated or the expansion is increased, a conductor having excellent electrical resistance stability is obtained.

[The form of carrying out the invention]

The conductive composition of the present invention contains an elastomer and a silver powder, and by blending a specific silver powder with the elastomer, a conductor with excellent resistance stability can be obtained not only when it is bent, but also when stretched or stretched. Wait. As a result, the conductive composition of the present invention can utilize such characteristics and is suitable for the formation of conductors for wearable devices such as in vitro devices, body surface devices, electronic skin devices, and in vivo devices. Hereinafter, each component contained in the conductive composition of the present invention will be described in detail.

<Silver powder> The silver powder constituting the conductive composition of the present invention is surface-treated, and its average primary particle size is 1.0 μm or less, preferably 0.1 to 1.0 μm, and the apparent porosity is 50 to 95%, preferably The best is 60 to 95%. By using such a silver powder, since the particle size distribution of the secondary particles serving as the silver powder in the composition is in an agglomerated state in the range described later, stability of electrical resistance can be maintained even when expansion and contraction are repeated or increased. Furthermore, in the present invention, the average primary particle size of the silver powder means that the silver powder in the powder state is observed with a scanning electron microscope at a magnification of 10,000 times, 10 primary particles are randomly extracted, and the particle size is measured. , the average of their particle sizes. In addition, the apparent porosity of the silver powder is an index indicating the state of an aggregated structure (secondary particle) in which the primary particles of the silver powder are connected and appropriate voids exist, and can be measured as follows. That is, when the density of silver is regarded as ρ ₀ (g/cm ³ ), and the volume of silver powder when a load of 1 kg is applied to the silver powder of mass M (g) is regarded as V (cm ³ ), the apparent density ρ (g/cm ³ ) is defined as: ρ=M/V The apparent porosity (P) can be calculated from the apparent density by the following formula. P=(1-ρ/ρ ₀ )×100 Furthermore, the density ρ ₀ of silver is 10.49 g/cm ³ , and the silver powder volume V under a heavy load of 1 kg is the silver powder volume after 1 hour after additional loading.

The said apparent porosity P is an index which shows the aggregation state of the primary particle of the silver powder before mixing with an elastomer in this invention. When a certain load is applied to the silver powder, the filled silver powder is compressed. At this time, when the silver powder is not in an aggregated state but in a state in which primary particles are separated from each other, the apparent porosity after compression becomes small. On the other hand, when the silver powder is in an agglomerated state, the apparent porosity increases due to the voids inside the agglomeration. Thereby, the aggregated state of the primary particles of the silver powder can be evaluated as the apparent porosity.

In addition, in the present invention, the shape of the primary particles of the silver powder is preferably slightly spherical, and the slightly spherical primary particles exist in the conductive composition in the form of three-dimensional and randomly connected secondary particles, such as As described above, even when the cured product of the conductive composition is greatly stretched, the contact points of the primary particles are not reduced, and the silver powder can follow the stretching deformation of the elastomer in the cured product of the conductive composition.

In addition, the shape of the primary particles of the silver powder is not limited to the slightly spherical shape, and it is of course also possible to include silver powder with shapes other than the slightly spherical shape within the range that does not impair the effect of the present invention.

The silver powder with the average primary particle size and apparent porosity in the above-mentioned ranges can be used commercially. In addition, commercially available silver powder can be classified into a specific average primary particle size and apparent porosity using a classifier, etc. of silver powder.

The average secondary particle size of the silver powder used in the present invention (that is, the silver powder before preparation as a conductive composition) is preferably 5.0 to 40.0 μm, more preferably more than 10.0 to 40.0 μm, particularly preferably more than 15.0 to 40.0 μm μm. Since the average secondary particle size is in the above-mentioned range, when the silver powder is dispersed in the composition, it is easy to adjust the particle size to the specific range described later. In addition, the average secondary particle size of the silver powder before preparation as the conductive composition means the average value (D50) of the particle size of the silver powder in the powder state measured by the laser diffraction scattering particle size distribution measurement method. .

In addition, the silver powder used in the present invention (silver powder before preparation as a conductive composition) is preferably 30 to 200 ml/100 g of DBP oil absorption measured in accordance with JIS K 6217-4 (2017). The DBP oil absorption of silver powder refers to the value of measuring the amount of dibutyl phthalate absorbed by 100 g of silver powder according to JIS K 6217-4, and in the present invention, indicates the degree of bonding of primary particles of silver powder or an indicator of the degree of agglutination. Since the silver powder whose DBP oil absorption is in the above-mentioned range is used, when the silver powder is dispersed in the composition, it is easy to adjust the particle size to the specific range described later.

In the conductive composition of the present invention, when the above-mentioned silver powder is used and dispersed in an elastomer, the cumulative 95% particle size (D95 particle size) of the secondary particles of the silver powder in the conductive composition is 3.0 to 25.0 range of μm. In the present invention, the surface-treated silver powder having a specific average primary particle size as described later, and preferably a silver powder having a specific DBP oil absorption in a specific agglomerated state (that is, a specific apparent porosity), When it is blended into an elastomer to form a composition, the conductive composition is improved by controlling the aggregation state of the silver powder in the composition (that is, making the cumulative 95% particle size in the particle size distribution of the secondary particles within a specific range). The electrical conductivity of the cured cured product can be used as a conductor with excellent resistance stability even when the expansion and contraction are repeated or the expansion is increased.

It is considered that even when the silver powder constituting the conductive composition of the present invention is mixed or kneaded with the elastomer, it is dispersed in the conductive composition while maintaining a constant aggregation state in which a plurality of primary particles are three-dimensionally and randomly connected. middle. That is, when silver powder having a specific apparent porosity is mixed or kneaded into an elastomer, among the secondary particles aggregated by the primary particles of the silver powder, the secondary particles with larger particle diameters disintegrate, and to some extent the secondary particles are disintegrated. become smaller. By adjusting so that the cumulative 95% particle size in the particle size distribution of the secondary particles at that time becomes 3.0 to 25.0 μm, the apparent voids remain moderately in the secondary particles of the silver powder, and since the elastomer enters the voids, It is considered that the effects peculiar to the present invention are easily exhibited.

Although the detailed mechanism which achieves this effect peculiar to this invention is not clear, it is judged as follows. That is, it is considered that the silver powder having an average primary particle size of 1.0 μm or less after surface treatment, an apparent void ratio of 50 to 95%, and a preferable DBP oil absorption in the above-mentioned range, as described later, is blended into the elastic powder. When the composition is prepared by dispersing it in the body, the agglomeration of the silver powder is appropriately disintegrated, and the composition is stirred or kneaded so that the D95 particle size becomes 3.0 to 25.0 μm. There are moderate voids, and since the elastomer sufficiently enters the voids, even when the cured product of the conductive composition is greatly stretched, the contact points of the primary particles are not reduced, and the silver powder can follow the stretch deformation of the elastomer.

In the conductive composition, the cumulative 95% particle size (D95 particle size) in the particle size distribution of the secondary particles of the silver powder can be determined by mixing or kneading the silver powder and the elastomer by the laser diffraction scattering particle size distribution measurement method. The obtained conductive composition. Specifically, propylene glycol monomethyl ether acetate was used as the measurement solvent, and the conductive composition was diluted with the measurement solvent (propylene glycol monomethyl ether acetate) so that the conductive composition became 3000% by mass, and the secondary In a way that the particles do not disintegrate, after moderate stirring with a spatula, etc., the particle size distribution is quickly measured in the measurement range of 0.020 μm to 1000.00 μm, taking the refractive index of the particles as 1.33 and the refractive index of the solvent as 1.40. The value calculated as the particle size of the cumulative 95% of the particle size distribution is defined as the D95 particle size.

In this way, according to the conductive composition of the present invention, since the surface-treated silver powder is dispersed in the conductive composition so that the D95 particle size falls within the above-mentioned range, it is judged that even if the conductive composition is composed of Even when the cured product repeats the expansion and contraction or expands greatly, a conductor with excellent resistance stability can be obtained.

If the general silver powder is dispersed in the elastomer, the agglomerated state of the silver powder in the conductive composition disintegrates excessively, and when the cured product of the conductive composition is greatly stretched, the contact points of the primary particles of the silver powder This stretching deformation is reduced. In this regard, if it is structured according to the features of the present invention as described above, in the secondary particles of the silver powder in the conductive composition, the apparent voids are appropriately present, and the elastic body sufficiently enters the voids. It is judged that even when the cured product composed of such a conductive composition is largely stretched, the contact points of the primary particles are not reduced, and the silver powder can follow the stretch deformation of the elastic body.

In the conductive composition of the present invention, in order for the silver powder to exist in the above-mentioned form, it is necessary that the silver powder has a high affinity with the elastomer by the surface treatment, and the primary particles of the silver powder are connected to each other, and it is necessary to have agglomeration in which the voids are appropriately present. Construct (secondary particles).

Therefore, in the present invention, in order to adjust the above-mentioned DBP oil absorption, silver powder, and affinity with the elastomer, surface-treated silver powder is used. The surface treatment of the silver powder includes a wet method in which the silver powder is put into a solution containing the dispersion liquid and stirred, or a dry method in which the solution containing the dispersion liquid is sprayed while stirring the silver powder. Furthermore, a surfactant may be used in combination to perform surface treatment.

As the dispersing agent used in such surface treatment, for example, protective colloids such as fatty acids, organometallics, and gelatin can be used, but in consideration of the possibility of contamination of impurities or the improvement of adsorption properties with hydrophobic groups, fatty acids or their salts are preferred. . Moreover, as this dispersing agent, what emulsified the fatty acid or its salt with a surfactant is preferable. A preferred dispersant is a fatty acid having 6 to 24 carbon atoms, and more preferably, stearic acid, oleic acid, myristic acid, palmitic acid, linoleic acid, lauric acid, hypolinoleic acid and the like can be used. It is considered that these fatty acids have little adverse effect on wiring layers and electrodes using the conductive composition. The above-mentioned fatty acids may be used alone or in combination.

The silver powder described above is adjusted to the range of 3.0 to 25.0 μm for the D95 particle size of the secondary particles of the silver powder by blending, stirring, or kneading the below-described elastomer and optionally a solvent. For example, a mixer such as a dissolver or a disc mixer, or a kneader such as a roll mill or a bead mill can be used for stirring or kneading. It can be adjusted according to various conditions such as the shape of the blade or the kneading device, the stirring or kneading time, the temperature during stirring or kneading, the bead filling rate or the roll interval.

The blending amount of the silver powder in the conductive composition is preferably 60 to 95% by mass based on the total solid content contained in the conductive composition. If it is 60 mass % or more, a conductor with a low resistance value can be easily obtained. When it is 95 mass % or less, it becomes less likely that disconnection will occur at the time of expansion and contraction. Furthermore, in the conductive composition of the present invention, other conductive powders such as carbon other than silver powder may be used in combination within a range that does not impair the effects of the present invention.

<Elastomer> The elastomer contained in the conductive composition of the present invention can be used without particular limitation as long as it has rubber elasticity at room temperature. For example, rubber, thermoplastic elastomer, functional based elastomers, block copolymers, etc.

As the rubber, either a diene-based rubber or a non-diene-based rubber may be used, and a known and customary one may be used alone or in a mixture of two or more.

Further, as the thermoplastic elastomer, styrene-based elastomers, olefin-based elastomers, urethane-based elastomers, polyester-based elastomers, polyamide-based elastomers, acrylic-based elastomers, and polysilicon Oxygen-based elastomers and the like can be used alone or in combination of two or more.

As the functional group-containing elastomer, from the viewpoint of stretchability, urethane-based and olefin-based elastomers are preferred, and from the viewpoint of solvent resistance, those having a (meth)acryloyl group or Functional groups such as acid anhydride group, carboxyl group, epoxy group, etc.

As a block copolymer, the block copolymer of a hard segment and a soft segment can be used, and it can use individually or in mixture of 2 or more types.

Among the above elastomers, the block copolymer has low crystallinity and weak intermolecular force, so the glass transition point (hereinafter referred to as Tg) is lower than that of other rubbers. When mixed with silver powder, it is soft and has good elongation and is suitable. . Therefore, block copolymers are suitable for the formation of electrical conductors for wearable devices. In particular, a block copolymer of a hard segment with a Tg of less than 150°C and a soft segment with a Tg of less than 0°C is more suitable. In addition, the glass transition point Tg is measured by differential scanning calorimetry (DSC).

The ratio of the hard segment to the soft segment in such a block copolymer is preferably in the range of 20:80 to 50:50. Within this range, the conductive system in which the conductive composition has been cured is less likely to be disconnected during elongation, which is preferable. More preferably, it is 25:75-40:60.

Here, as a hard segment in a block copolymer, a methyl (meth)acrylate unit, a styrene unit, etc. are mentioned. Moreover, as a soft segment unit, n-butyl acrylate, a butadiene unit, etc. are mentioned. The block copolymer is preferably a triblock copolymer of poly(methyl)acrylate/poly(n-butyl(meth)acrylate/poly(meth)acrylate). A block copolymer system may be used individually by 1 type, and may be used in combination of 2 or more types. In addition, the so-called (meth)acrylate in the specification of this case is a term collectively referring to acrylate and methacrylate, and other similar expressions are also the same.

The block copolymer can be a commercially available product. An example of a commercial product is an acrylic triblock copolymer manufactured by using living polymerization, manufactured by ARKEMA. Specifically, SBM types represented by polystyrene-polybutadiene-polymethyl methacrylate, and SBM types represented by polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate can be used. MAM type, and MAM N type or MAM A type modified with carboxylic acid or hydrophilic group. Examples of SBM types are E41, E40, E21 and E20. Examples of MAM types are M51, M52, M53 and M22. Examples of MAM N types are 52N and 22N. An example of MAM A type is SM4032XM10. Another example of a commercially available product is Clarity manufactured by KURARAY. The Clarity is a block copolymer derived from methyl methacrylate and butyl acrylate.

The block copolymer containing the (meth)acrylate polymer block as described above can be obtained, for example, by the method described in JP 2007-516326 A or JP 2005-515281 A.

The weight average molecular weight of the block copolymer is preferably 20,000 to 400,000, more preferably 50,000 to 300,000. Since the weight average molecular weight is 20,000 or more, the desired effects of toughness and flexibility can be obtained, and excellent adhesiveness can be obtained when the conductive composition is formed into a thin film and dried, or when it is coated on a substrate and dried. Moreover, since the weight average molecular weight is 400,000 or less, the conductive composition has good viscosity, and can achieve higher printability and processability. In addition, when the weight average molecular weight is 50,000 or more, an excellent effect is obtained in the alleviation of impact from the outside.

The tensile elongation at break of the block copolymer is preferably 100 to 600% as measured by the measurement method of the international standard ISO 37 of the International Organization for Standardization. When the tensile elongation at break is 100 to 600%, the stretchability of the conductor and the stability of electrical resistance are more excellent. More preferably, it is 300 to 600%. Tensile elongation at break (%) = (elongation at break point (mm) - initial size mm) / (initial size mm) × 100

Among the rubbers or functional group-containing elastomers, sulfur-based vulcanizing agents or non-sulfur-based vulcanizing agents are generally used. In the conductive composition comprising the silver powder and the elastomer according to the present invention, there is a risk that the silver powder in the wiring is oxidized or vulcanized due to sulfur contained in the vulcanizing agent in the elastomer and corroded. In the present invention, it is preferable not to contain a sulfur-based vulcanizing agent.

The conductive composition of the present invention may contain a certain amount of sulfur compounds within a range not adversely affecting the conductivity (in a range not impairing the specific effects of the present invention).

Moreover, well-known additives, such as a softener and a plasticizer, may be contained in an elastomer. Examples of the softener include mineral oil-based softeners and vegetable oil-based softeners, and examples of mineral oil-based softeners include various oils such as paraffin-based processing oils, naphthenic-based processing oils, and aromatic-based processing oils. Examples of vegetable oil-based softeners include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, groundnut oil, pine oil, tall oil, and the like. Use alone or in combination of two or more. The desired rubber elasticity or extensibility can be adjusted by the amount of softener added.

The elastomers described above are preferably blended in a ratio of 5 to 40% by mass, more preferably 14 to 28% by mass, based on the total solid content contained in the conductive composition. In particular, when the above-mentioned block copolymers are contained, the blending amount of these block copolymers is preferably 85 to 100% by mass relative to the entire elastomer including other elastomers. When the blending amount is within the above range, the stretchability of the formed coating film will be improved. Furthermore, within the range that does not impair the effects of the present invention, other organic binders such as thermoplastic resins other than elastomers may be used in combination with the conductive composition of the present invention.

The conductive composition of the present invention can use an organic solvent for adjustment of the composition or adjustment of the viscosity of the coating on a substrate.

Examples of such organic solvents include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, and petroleum-based solvents. More specifically, ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; cellosolve, methyl cellosolve, butyl cellosolve, Glycol ethers such as carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, triethylene glycol monoethyl ether, etc. ; Ethyl acetate, butyl acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol butyl ether Esters such as acetate; alcohols such as ethanol, propanol, ethylene glycol, propylene glycol, etc.; aliphatic hydrocarbons such as octane and decane; petroleum systems such as petroleum ether, naphtha, hydrogenated naphtha, mineral spirits, etc. solvent, etc. Such an organic solvent system can be used individually or as a mixture of 2 or more types. Among them, from the viewpoint of coatability, diethylene glycol monoethyl ether acetate is preferred.

The conductive composition of the present invention may further contain a thermosetting component. Examples of thermosetting components include polyester resins (urethane-modified, epoxy-modified, acrylic-modified, etc.), epoxy Resins, urethane resins, phenolic resins, melamine resins, vinyl resins and silicone resins.

The conductive composition of the present invention may contain other components within a range that does not impair the effects of the present invention. For example, additives such as a coupling agent and a photopolymerization initiator may be contained.

The conductive composition of the present invention can be produced, for example, by kneading an elastomer dissolved in a solvent and the above-mentioned silver powder. As a kneading method, the method of using a stirring mixing apparatus, such as a roll mill, is mentioned, for example. Specifically, a resin solution having a solid content of 50% by mass of an elastomer dissolved in an organic solvent is prepared, silver powder is mixed with the resin solution, and after preliminarily stirring and mixing with a mixer, it is kneaded with a three-roll mill to obtain a conductive sexual composition. Depending on the type of the elastomer to be used and the blending ratio of the organic solvent, a liquid conductive composition or a paste (semi-solid) conductive composition can be obtained.

In the present invention, the conductive composition as described above can be formed as a conductor by, for example, pattern coating on a base material and heat treatment. As this heat treatment, drying treatment, thermosetting treatment, etc. are mentioned.

In this way, the conductive composition of the present invention can provide a conductor excellent in stretchability and resistance stability. Moreover, by using the above-mentioned silver powder, coating suitability also improves.

<Conductor layer and its use> The above-mentioned conductive composition can be cured to become a conductor. For example, a coating film composed of a conductive composition can be formed, dried and cured to form a conductive layer. Curing of the conductive composition can be performed by drying or heat-treating the conductive composition. An example of the heat treatment is hot air drying or thermal hardening. Forming may also be performed before heat treatment. For example, the layer of the conductor can be obtained by applying the above-described conductive composition on the base material to obtain a desired shape, and then curing the conductor to obtain the layer of the conductor. The layers of electrical conductors can be of various shapes in accordance with the application being used. For example, it can be applied to conductor circuits, wirings, and the like.

When manufacturing a conductor circuit, a pattern forming step of printing or coating the above-mentioned conductive composition on a substrate to form a coating film pattern, and a step of curing the patterned coating film are included. In the formation of the coating film pattern, a masking method, a method using a resist, or the like can be used.

As a pattern formation process, a printing method and a distribution method are mentioned. As a printing method, for example, gravure printing, offset printing, screen printing, etc. are mentioned, When a fine circuit is formed, screen printing is preferable. In addition, as a coating method for a large area, gravure printing and lithographic printing are suitable. The so-called dispensing method is a method of controlling the coating amount of the conductive composition and extruding it from a needle to form a pattern.

As the base material to which the conductive composition is applied, it can be used without any particular limitation as long as it is electrically insulating, and examples include the use of paper-phenol resin, paper-epoxy resin, glass cloth-epoxy resin, glass- Polyimide, glass cloth/non-woven fabric-epoxy resin, glass cloth/paper-epoxy resin, synthetic fiber-epoxy resin, fluororesin・polyethylene・polyphenylene ether, polyphenylene ether・cyanate ester, etc. All grades of composite materials (FR-4, etc.) copper clad laminates, polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, etc. Sheets or films composed of plastics such as ester, polyimide, polyphenylene sulfide, polyamide, etc., and sheets composed of cross-linked rubber such as urethane, silicone rubber, acrylic rubber, butadiene rubber, etc. Or films, sheets or films made of thermoplastic elastomers such as polyester-based, polyurethane-based, polyolefin-based, and styrene-based block copolymers. Among them, by using not only a material having flexibility but also a material having stretchability (for example, rubber or thermoplastic elastomer) as a base material, the conductor can be applied to the application described later. As the material having stretchability, the same thing as the above-mentioned elastomer component can be used.

The conductor layer of the present invention is excellent in resistance stability even when the expansion and contraction are repeated or stretched as described above, so it can be applied to external devices, body surface devices, electronic skin devices, other than conductor circuits and wirings. Formation of conductors for wearable devices such as in-vivo devices. Moreover, the layer of a conductor can also be used for the electrode of a flexible printed circuit board. Furthermore, the conductive composition of the present invention is also suitable for forming layers of conductors such as actuator electrodes. Moreover, it is also suitable for the formation of the conductor of the design which conventionally lacked the stability of elasticity and resistance, and was difficult to implement. For example, the following are mentioned.

<Wearable biosensor> The conductor of the present invention can be used as a wiring material for wearable biosensors worn on the body in order to acquire/transmit active potential/biological information generated from animals and plants including humans . The installation place of the sensor must be close to or close to the surface tissue of animals and plants including humans, but the surface tissue is stretched. Conventional rigid substrates or flexible substrates have no followability to the expansion and contraction installation places, and the installation places of the sensors are also limited, resulting in limited biological information obtained. According to the conductor of the present invention, since the wiring material for sensors can be applied even to the surface tissues of animals and plants including humans, it can be used as a wearable biosensor that can be installed even in places where expansion and contraction occur.

Since the wiring used in the wearable biosensor can be formed by screen printing or distribution, it is possible to miniaturize the signal wiring, which is considered to contribute to the miniaturization of the sensor device.

<Wiring material for smart textiles> In recent years, the field of so-called "smart textiles" using grey fabrics as sensors has been expanding. Using the conductor of the present invention, a wiring board or a sensor formed by wiring on a substrate that has flexibility and can be thermocompressed, etc., is excellent in resistance stability during expansion and contraction. It is possible to develop a fabric with the functions of electronic products and devices, that is, the development of smart textiles. As a smart textile, functions such as pressure sensors, touch sensors, and antenna wiring can be imparted to the fabric.

<Wiring for 3D Molded Products> In the conventional plastic molding products for electronic equipment housings, etc. by the FIM (Film-Insert-Molding) method, a plastic film such as polycarbonate is used as the base. The substrate, after the design and printing, is processed by hot pressing. The conductor wiring composed of the laminated structure in which the conductor of the present invention is provided on a stretchable base material has the property of suppressing the change in resistance value without disconnection during extension, so it can be used in the design and printing of plastic molded products. , to form conductor wiring, and to perform subsequent hot pressing (partial elongation) molding process, it is possible to realize electronic products and devices with built-in 3D-shaped wiring.

In addition, by using a stretchable base material such as the above-mentioned elastic body to perform hot pressing, it is possible to realize electronic products and devices that can be stretched and deformed with flexible wiring in a flexible casing. Suitable for use as a pressure sensor, a touch sensor, or an antenna wiring.

<Stretchable and Deformable Wiring Sheet or Wiring Board> A conductor wiring comprising a laminated structure in which a layer of the conductor of the present invention is provided on a stretchable base material can be used as a stretchable and deformable wiring board sheet. For example, such a conductor wiring can be attached to the object while being stretched or deformed on the surface of an object having a three-dimensional shape such as a molded product without breaking the wiring. Therefore, a laminated structure in which a layer of the conductor of the present invention is provided on a stretchable base material can be suitably used as a pressure sensor, a touch sensor, or an antenna wiring.

<Flexible Wiring Sheet or Wiring Board> In the conventional flexible wiring sheet or wiring board using conductive paste, when extreme bending of the claws is performed, the wiring may be disconnected. This point is that when the conductor of the present invention is used, since it is a conductive material with elongation properties, it can cope with the bending properties in the range that the conventional conductive paste cannot handle, and it can be realized that there is no occurrence even when the claws are folded. Flexible wiring sheet or wiring board for wire breakage.

[Example]

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Preparation of silver powder> As the silver powder for preparing the conductive composition, the following three types of silver powder were prepared. Silver powder A: silver powder with an average primary particle size of 0.3 μm and an apparent porosity of 92%, which has been surface-treated with secondary linoleic acid. Silver powder B: silver powder with an average primary particle size of 0.5 μm and an apparent void ratio of 63%, which has been surface-treated with secondary linoleic acid. Silver powder C: silver powder with an average primary particle size of 1.3 μm and an apparent porosity of 44%, which has been surface-treated with secondary linoleic acid.

Furthermore, the average primary particle size of the silver powder was measured using a scanning electron microscope (manufactured by Nippon Electronics Co., Ltd., JSM-6360L), and the silver powder was observed at 10,000 times. average value. In addition, the apparent porosity P of each silver powder was calculated as follows. That is, a cylindrical container is filled with silver powder, the container is vibrated several times, and the silver powder is replenished until the upper surface of the silver powder becomes a certain height. A cylinder with an inner diameter and an outer diameter is applied with a load of 1 kg on the silver powder, and the volume of the silver powder after being left for 1 hour (the product of the bottom area of the cylindrical container and the height from the bottom of the container to the top of the silver powder) is regarded as V(cm ³ ), the apparent density ρ (g/cm ³ ) defined by ρ=M/V is calculated, and the following formula is calculated using the true density ρ ₀ (10.49 g/cm ³ ) of silver: P=(1 The apparent porosity P (%) of the silver powder represented by -ρ/ρ ₀ )×100.

<Preparation of the conductive composition> As the elastomer for preparing the conductive composition, the following two types were prepared.・Elastomer A (manufactured by KURARAY Co., Ltd., LA2330) ・Elastomer B (manufactured by KURARAY Co., Ltd., LA2250) ・Polyester C (manufactured by Toyobo Co., Ltd., Vylon 290) The elastomer was dissolved in diethylene glycol monoethyl ether acetate, and a resin solution was prepared so that the solid content would be 50% by mass. Moreover, about polyester C, it melt|dissolved in diethylene glycol monoethyl ether acetate, and it prepared a resin solution so that it might become 30 mass % of solid content.

According to the composition shown in the following Table 1, the above-mentioned silver powder and the resin solution of elastomer or polyester were mixed, and after preliminary stirring and mixing with a mixer, a three-roll mill (manufactured by EXAKT Corporation, EXAKT50) was used to change the three-roll mill. The kneading was carried out under the conditions of the number of times of kneading of the machine, the rotational speed, the interval between the rolls, and the like, and the conductive composition of the embodiment was obtained. In addition, in Table 1, the numerical value of the compounding quantity of elastomer or polyester and silver powder shows mass parts.

The secondary particle D95 particle size of the silver powder contained in the obtained conductive composition was measured. D95 particle size is performed as follows. First, the conductive composition was diluted with 3000 mass % of propylene glycol monomethyl ether acetate to prepare a solution. This solution was measured in the range of 0.020 μm to 1000.00 μm using a laser diffraction scattering particle size distribution analyzer (TM3000, manufactured by MicrotracBEL Corporation), with the refractive index of the particles being 1.33 and the refractive index of the solvent being 1.40 Among them, the particle size distribution was measured, and the cumulative 95% particle size was obtained from the particle size distribution, which was regarded as the D95 particle size.

<Evaluation of the conductive composition> (1) Measurement of specific resistance Each conductive composition was applied to a substrate by screen printing, and heat-treated at 80°C for 30 minutes to obtain a conductor. As the base material, a PET film was used. The resistance value at both ends of the obtained conductor was measured by the 4-terminal method, and the line width, line length, and thickness were further measured, and the specific resistance (volume resistivity) was obtained. The results are shown in Table 1.

(2) Determination of the maximum resistance value of the 20% expansion and contraction test Using screen printing, each conductive composition was coated on the substrate, and heat-treated at 80°C for 30 minutes to form a line width of 1 mm, a thickness of 20 μm, Conductor with a length of 40mm. As a base material, a urethane film (Takeda Sangyo Co., Ltd. make, TG88-I, thickness 70 micrometers) was used. The resistance value of the conductor was measured while repeating 100 reciprocations for 250 seconds from a state of expansion and contraction of 2.5% (state without deflection) to expansion and contraction of 20%. The maximum resistance values during the period are shown in Table 1.

(3) The presence or absence of wire breakage in the 50% expansion and contraction test was screen-printed, each conductive composition was coated on a substrate, and heat-treated at 80°C for 30 minutes to form a line width of 1 mm, a thickness of 20 μm, and a length of 40 mm on the substrate. the conductor. As a base material, a urethane film (Takeda Sangyo Co., Ltd. make, TG88-I, thickness 70 micrometers) was used. From the non-stretching state of 0% to the expansion and contraction of 50%, it takes 700 seconds and 100 reciprocating repetitions to evaluate whether there is a disconnection. The measurement results are shown in Table 1.

(4) The resistance value at 400% elongation was screen-printed, each conductive composition was coated on the substrate, and heat-treated at 80°C for 30 minutes to form a line width of 1 mm, thickness of 20 μm, and length of 40 mm on the substrate. conductor. As a base material, a urethane film (Takeda Sangyo Co., Ltd. make, TG88-I, thickness 70 micrometers) was used. After stretching 25% at a speed of 5 mm/sec, it was held for 15 seconds, and the presence or absence of thread breakage was evaluated. This operation is repeated until the conductor is elongated by 400%. The evaluation results are shown in Table 1.

As is clear from the results shown in Table 1, using silver powder and an elastomer having an average primary particle size of 1.0 μm or less and an apparent void ratio of 50 to 95%, stirring or mixing so that the D95 particle size becomes 3.0 to 25 μm The smelted conductive compositions (Examples 1 to 4) were able to obtain conductors with excellent electrical resistance stability and no disconnection even when the expansion and contraction were repeated or stretched.

On the other hand, even when silver powder and an elastomer having an average primary particle size of 1.0 μm or less and an apparent porosity of 50 to 95% were used, the D95 particle size of the conductive composition was not in the range of 3.0 to 25 μm (Comparative Example 2 ), although the initial electrical conductivity was good, it was found that the electrical conductivity dropped sharply when the expansion and contraction were repeated or stretched. In addition, when using silver powder with an average primary particle size of not less than 1.0 μm and an apparent porosity of not in the range of 50 to 95% (Comparative Examples 1 and 3), it was found that the electrical conductivity at the initial stage was also insufficient, and the repetition of expansion and contraction or Upon elongation, the conductivity decreases sharply.

Claims (5)

A conductive composition, which is a conductive composition comprising elastomer and silver powder, characterized in that the aforementioned silver powder is surface-treated, the shape of the primary particles of the aforementioned silver powder is slightly spherical, and the aforementioned silver powder is the average primary particle of the aforementioned silver powder. The diameter is 1.0 μm or less and the apparent porosity is 50 to 95%. In the conductive composition, the cumulative 95% particle size (D95 particle size) of the secondary particles of the silver powder in the particle size distribution is 3.0 to 25.0 μm. The conductive composition according to claim 1, wherein the silver powder is contained in an amount of 60 to 95 mass % in terms of solid content with respect to the entire conductive composition. A conductor characterized by curing the conductive composition according to claim 1 or 2. A laminated structure characterized by providing a layer of the conductor as claimed in claim 3 on a base material. An electronic component comprising a layer of a conductor as claimed in claim 3 or a laminated structure as claimed in claim 4.