Conductive composition, conductor, laminated structure, electronic component, and method for producing electronic component

Abstract

To suppress linear increase of resistance value relative to the amount of strain and to suppress fluctuation of the resistance value.SOLUTION: A conductive composition including an elastomer, chain-form conductive particles, and an ionic liquid, the ionic liquid being contained in an amount of 0.1 mass% to 10 mass% based on the total mass of the conductive composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a conductive composition, a conductor, a laminate structure, an electronic component, and a method for manufacturing an electronic component. [Background technology]

[0002] Conventionally, printed wiring boards have used paste-like conductive compositions, which are obtained by mixing metal powder with an organic binder, as a material for forming patterned conductors, such as electrodes, on a substrate. The conductive composition can be applied to a substrate in a pattern and then solidified to form a desired conductor on the substrate. However, the formed conductor generally has high hardness. Therefore, it has been difficult to say that such conductive compositions can fully function in wiring boards that require flexibility, such as flexible printed wiring boards. Therefore, there is a need for a conductive composition that can form a conductor suitable for wiring boards that require flexibility, such as flexible printed wiring boards, and that can stably and fully function even when bent together with the wiring board.

[0003] Furthermore, with the recent growth of the wearable device field, there is a demand for imparting stretchability to conductors. In particular, wearable devices that adhere closely to the body require high levels of stretchability. In response to such demands, for example, a conductive composition has been proposed that uses an elastomer as an organic binder to contain metal powder, and can impart not only flexibility but also stretchability to the resulting conductor (for example, Patent Document 1).

[0004] However, for example, when a wearable device is attached to clothing, the pattern and extent of shape change of the wearable device will vary depending on the shape and size of the clothing, the physique of the wearer, and the pattern (tendency) of movement. That is, even when different wearers wear the same clothing and perform the same movement, the pattern and extent of shape change of the clothing will vary greatly depending on the wearer, and the pattern and extent of shape change of a wearable device attached to clothing will also vary greatly depending on the wearer. Thus, depending on the wearer, the wearable device may not be able to stretch sufficiently to adequately follow changes in the shape of the clothing, and as a result, the wearable device may not operate stably.

[0005] Furthermore, Patent Document 2 discloses a conductive elastomer composition having both excellent conductivity and extensibility, which contains a fluorine-based elastomer, a metal filler, an ionic liquid having a predetermined structure, and a crosslinking agent. In particular, Patent Document 2 uses a dendritic metal filler, which is more likely to provide excellent conductivity when stretched. Patent Document 2 also uses a compound composed of an imidazolium ion and a tetrafluoroborate ion as the ionic liquid. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2015 / 005204 [Patent Document 2] Japanese Patent Application Publication No. 2019-56092 Summary of the Invention [Problem to be solved by the invention]

[0007] In the case of the above-mentioned stretchable conductor, when strain occurs, the resistance value increases linearly with the amount of strain, and the greater the strain, the greater the deviation from the initial value. When such a conductor is used in a device, the resistance value differs significantly between the small strain region and the large strain region, or between when the strain is small and when the strain is large, making it difficult to design a device that can operate stably regardless of the amount of strain.

[0008] Therefore, the present disclosure aims to provide a conductive composition, a conductor, a laminated structure, an electronic component, and a method for manufacturing an electronic component that can suppress a linear increase in resistance value with respect to the amount of strain when strain occurs and can suppress the amount of fluctuation in resistance value. [Means for solving the problem]

[0009] The present disclosure, which achieves the above-mentioned objectives, includes the following. <1> A conductive composition comprising an elastomer, chain-like conductive particles, and an ionic liquid, wherein the content of the ionic liquid is 0.1 mass % to 10 mass % relative to the total mass of the conductive composition. <2> Contains solvents, <1> The conductive composition according to claim 1. <3> The 5% weight loss temperature of the ionic liquid is 300°C or less. <1> or <2> The conductive composition according to claim 1. <4> The ionic liquid is a polymeric ionic liquid. <1> ~ <3> The conductive composition according to any one of the above. <5> The ionic liquid has a polymer side chain, and the weight average molecular weight of the polymer side chain is 500 to 1,000,000. <1> ~ <4> The conductive composition according to any one of the above. <6> The elastomer includes a structural unit having at least one selected from the group consisting of a nitrogen atom and a hydroxyl group. <1> ~ <5> The conductive composition according to any one of the above. <7> The elastomer is an elastomer other than a fluorine-containing elastomer. <1> ~ <6> The conductive composition according to any one of the above. <8> Used to form conductors, <1> ~ <7> The conductive composition according to any one of the above. <9> <8> A conductor which is a solidified product of the conductive composition described in 1. <10> a substrate and a film disposed on at least one main surface of the substrate; <9> and a layer of the conductor according to claim 1. <11> <9> or a layer of the conductor according to <10> An electronic component comprising the laminate structure according to claim 1. <12> The layer or the laminated structure includes a portion that deforms with operation. <11> The electronic component according to claim 1. <13> <8> 10. A method for producing an electronic component having a conductor layer, the method comprising the step of forming a conductor layer, which is a solidified product of the conductive composition according to claim 1, on at least one main surface of a substrate. <14> applying the conductive composition to at least one main surface of the substrate; and drying the conductive composition applied to at least one main surface of the substrate to form the conductor layer. <13> 10. A method for manufacturing an electronic component comprising the conductor layer according to claim 1. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a conductive composition, a conductor, a laminate structure, an electronic component, and a method for manufacturing an electronic component that can suppress a linear increase in resistance value with respect to the amount of strain when strain occurs and can suppress the amount of fluctuation in resistance value. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present disclosure will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure. For example, the present disclosure allows addition, omission, substitution, modification, etc. of the number, amount, position, ratio, material, configuration, type, order, etc., within the scope of the spirit of the present disclosure.

[0012] In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple types of corresponding substances. When multiple types of substances corresponding to each component are present in a composition, the content or amount of each component means the total content or amount of the multiple types of substances present in the composition, unless otherwise specified. In the present disclosure, the term "layer" includes cases where the layer is formed over the entire area when the area in which the layer exists is observed, as well as cases where the layer is formed over only a portion of the area.

[0013] [Conductive composition] The conductive composition of the present disclosure is a conductive composition comprising an elastomer, chain-like conductive particles, and an ionic liquid, wherein the content of the ionic liquid is 0.1 mass % to 10 mass % relative to the total mass of the conductive composition.

[0014] The conductive composition of the present disclosure, as will be described in detail later, can be mixed with a solvent to form a paste, which can be applied to a substrate and then dried and solidified to form a conductor. The conductive composition of the present disclosure can form a conductor that can suppress the linear increase in resistance with the amount of strain when strain occurs and can also suppress the amount of fluctuation in resistance. The mechanism behind this is not entirely clear, but is presumed to be as follows.

[0015] The conductive composition of the present disclosure can form a conductor that exhibits a higher resistance in an unstrained state (also referred to as the initial state) than a conductor formed from a composition that does not contain an ionic liquid. In a conductor containing the conductive composition of the present disclosure, the presence of the ionic liquid in the vicinity of the conductive particles moderately inhibits the conductive path maintained by the chain-like contact between the conductive particles, while at the same time forming a conductive path by the ionic liquid. Because the conductive path by the ionic liquid has a lower rate of electron movement than the conductive path between conductive particles, the conductor exhibits a high resistance in an unstrained state.

[0016] Furthermore, in a conductor containing the conductive composition of the present disclosure, when the strain of the conductor is small, the resistance value fluctuates in a direction lower than the initial state, but the resistance value is suppressed from increasing linearly with the amount of strain, and a stable resistance value is exhibited. This is presumably because the presence of the ionic liquid in the vicinity of the conductive particles makes the conductive particles in the conductor in a state where they are easily mobile, and the conductive particles instantly move in response to strain to form new conductive paths, thereby stabilizing the resistance value when strain is generated in the conductor.

[0017] Furthermore, in a conductor containing the conductive composition of the present disclosure, when the strain of the conductor is large, the resistance value increases from when the strain is small, but is suppressed to about the initial resistance value. This is presumably because the conductive path formed by the ionic liquid within the conductor does not collapse even when the conductor is subjected to large strain.

[0018] Thus, in a conductor containing the conductive composition of the present disclosure, the ionic liquid contributes to increasing the resistance value in the initial state, stabilizing the resistance value when strain is small, and suppressing the increase in resistance value when strain is large. Therefore, the conductive composition of the present disclosure can form a conductor with stable resistance value in the initial state, when strain is small, and when strain is large. Therefore, the conductive composition of the present disclosure can form a conductor that suppresses a linear increase in resistance when strain occurs and enables the design of a device that can operate stably both when strain is small and when strain is large.

[0019] Here, "small strain" refers to a state in which the conductor is stretched from the initial, unstrained state by 1% or more, preferably 5% or more, and more preferably 10% or more in length in a given direction, to a state in which the conductor is stretched by 30% or less, preferably 25% or less, and more preferably 20% or less in length in that direction. "Small strain" refers to either or both of the region in which the conductor is stretched within this range and the period during which the conductor is stretched within this range.

[0020] Furthermore, "large strain" refers to a case where the strain is larger than the above-mentioned small strain. Specifically, "large strain" refers to a state where the conductor is elongated in a predetermined direction by more than 20%, preferably more than 25%, and more preferably more than 30% from the initial state without strain. The upper limit of the large strain is the length until the conductor breaks due to elongation, and can be 60% or less, preferably 55% or less, and more preferably 50% or less in the direction.

[0021] By utilizing the above-described properties, the conductive composition of the present disclosure can be suitably used for forming conductors for wearable devices such as clothing devices, external devices, body surface devices, electronic skin devices, and internal devices, as well as for various sensors and actuators, etc. Each component contained in the conductive composition of the present invention will be described in detail below.

[0022] <Elastomer> The conductive composition of the present disclosure contains an elastomer. The elastomer contained in the conductive composition is not particularly limited, and a material having rubber elasticity at room temperature can be used. For example, rubber, thermoplastic elastomer, functional group-containing elastomer, block copolymer, etc. can be suitably used. One type of elastomer may be used alone, or two or more types may be used in combination.

[0023] Any known and commonly used rubber can be used, including, for example, diene rubber and non-diene rubber.

[0024] Any known and commonly used thermoplastic elastomer can be used, such as a styrene-based elastomer, an olefin-based elastomer, a urethane-based elastomer, a polyester-based elastomer, a polyamide-based elastomer, an acrylic-based elastomer, or a silicone-based elastomer. However, from the viewpoint of compatibility with the ionic liquid, polyvinyl alcohol, polyvinyl acetal, polyvinyl butyral, polyvinyl pyrrolidone, or polyethylene oxide is preferred.

[0025] In particular, the elastomer used in the conductive composition of the present disclosure is preferably an elastomer containing a structural unit containing at least one selected from the group consisting of nitrogen atoms and hydroxyl groups. Using an elastomer containing a structural unit containing at least one selected from the group consisting of nitrogen atoms and hydroxyl groups can prevent the formation of conductive paths in the conductor due to the ammonium ions contained in the ionic liquid from being inhibited. Therefore, using an elastomer containing a structural unit containing at least one selected from the group consisting of nitrogen atoms and hydroxyl groups can more effectively suppress the linear increase in resistance value when strain is applied to the conductor, thereby enabling the design of a conductor that can operate more stably both under small and large strains. Furthermore, from the perspective of compatibility with ionic liquids, it is more preferable to use an elastomer containing a structural unit containing nitrogen atoms.

[0026] Any known and commonly used functional group-containing elastomer can be used, but from the viewpoint of stretchability, urethane-based, olefin-based, etc. are preferred, and from the viewpoint of solvent resistance, those having functional groups such as (meth)acryloyl groups, acid anhydride groups, carboxyl groups, epoxy groups, mercapto groups, hydroxy groups, amino groups, glycidyl groups, (meth)acrylic groups, hydrolyzable silyl groups, nitrile groups, isocyanate groups, etc. Furthermore, from the viewpoint of adhesion to the substrate, elastomers other than fluorine-containing elastomers are preferred.

[0027] Any known and commonly used block copolymer can be used, but a block copolymer comprising a hard segment and a soft segment is preferably used.

[0028] Among the elastomers described above, block copolymers have low crystallinity and weak intermolecular forces, resulting in a lower glass transition temperature (Tg) than other rubbers. Therefore, they have high flexibility and good elongation even when mixed with conductive particles. Therefore, block copolymers are suitable for forming conductors for wearable devices and are preferably used as the elastomer in the conductive composition of the present disclosure. Block copolymers preferably have rubber elasticity at room temperature (25°C). Any known or commonly used block copolymer that satisfies the above conditions can be used. Block copolymers composed of hard and soft segments are particularly preferred. Here, a hard segment can be defined as one with a Tg of 30°C or higher. A soft segment can be defined as one with a Tg of 0°C or lower. The Tg is a value measured by the initial point method in accordance with JIS K7121:2012. However, regarding the heating rate and temperature, the Tg observed at 40°C or higher is specifically obtained from a differential scanning calorimetry (DSC) curve stabilized by repeatedly heating approximately 10 mg of a sample from 25°C to 200°C at a rate of 10°C per minute under a nitrogen gas atmosphere using a differential scanning calorimeter (DSC-6100, Hitachi High-Tech Science Corporation). α-Alumina is used as the reference. The Tg observed below 40°C was obtained from a DSC curve stabilized by repeatedly heating approximately 10 mg of a sample from -100°C to 100°C at a rate of 20°C per minute under a nitrogen gas atmosphere using a differential scanning calorimeter (DSC-6100, Hitachi High-Tech Science Corporation). α-Alumina was used as the reference, as above.

[0029] The ratio of the hard segment to the soft segment in the block copolymer (mass of the hard segment: mass of the soft segment) is not particularly limited, but is preferably 10:90 to 70:30, and more preferably 10:90 to 40:60. When the ratio of the hard segment to the soft segment is within the above range, disconnection of the conductor containing the conductive composition when stretched is suppressed, which is preferable.

[0030] When the hard segments are represented as X blocks and X' blocks and the soft segments as Y blocks and Y' blocks, the block copolymers mentioned above include diblock copolymers of X block-Y block type, and triblock copolymers of X block-Y block-X block type, X block-Y block-X' block type, Y block-X block-Y block type, and Y block-X block-Y' block type. However, from the viewpoint of excellent compatibility with other components and flexibility, triblock copolymers of X block-Y block-X block type are preferred.

[0031] The unit structure constituting the hard segment in the block copolymer is not particularly limited and includes, for example, a methyl (meth)acrylate unit, a styrene unit, etc. Furthermore, the unit structure constituting the soft segment is not particularly limited and includes, for example, an n-butyl acrylate unit, a butadiene unit, etc. Furthermore, the unit structure constituting the block copolymer may have a siloxane bond. By using a block copolymer containing a structural unit having a siloxane bond, a conductor formed by solidifying the conductive composition can be firmly adhered to a substrate such as a silicone substrate. As the block copolymer, for example, a triblock copolymer of polymethyl (meth)acrylate / poly n-butyl (meth)acrylate / polymethyl (meth)acrylate can be used. Note that, in this specification, the term "(meth)acrylate" is a general term that refers to acrylate and methacrylate, and the same applies to other similar expressions.

[0032] Commercially available block copolymers can be used. Examples of commercially available block copolymers include acrylic triblock copolymers manufactured by living polymerization, manufactured by Arkema Inc. More specifically, acrylic triblock copolymers such as SBM types (e.g., polystyrene-polybutadiene-polymethyl methacrylate), MAM types (e.g., polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate), and MAM N or MAM A types that have been modified with a carboxylic acid or hydrophilic group can be used. Examples of SBM types include E41, E40, E21, and E20. Examples of MAM types include M51, M52, M53, and M22. Examples of MAM N types include 52N and 22N. Examples of MAM A types include SM4032XM10. Another example of commercially available block copolymers is Kuralyte (registered trademark), an acrylic block copolymer manufactured by Kuraray Co., Ltd. Clarity® is a block copolymer derived from methyl methacrylate and butyl acrylate.

[0033] In addition to the above-mentioned commercially available block copolymers, appropriately prepared synthetic products can also be used. Examples of synthetic block copolymers containing a (meth)acrylate polymer block include block copolymers synthesized by the methods described in JP-A-2007-516326 and JP-A-2005-515281.

[0034] The weight-average molecular weight of the elastomer is preferably 20,000 to 400,000, more preferably 50,000 to 300,000. When the weight-average molecular weight is 20,000 or more, a conductor containing the conductive composition can be imparted with toughness and flexibility, and a conductor formed into a film or formed on a substrate can exhibit excellent tackiness. Furthermore, when the weight-average molecular weight is 400,000 or less, a paste containing the conductive composition has good viscosity, achieving higher printability and processability. Furthermore, when the weight-average molecular weight is 50,000 or more, excellent effects can be obtained in terms of mitigating external impacts.

[0035] In the conductive composition of the present disclosure, the elastomer has a tensile break elongation in the range of 10 to 600% as measured by a method conforming to the International Standard ISO 37:2017 of the International Organization for Standardization. Furthermore, in the conductive composition of the present disclosure, the elastomer preferably has a tensile break elongation in the range of 10 to 300% as measured by the above method. In this case, a conductor containing the conductive composition has superior stretchability and stable electrical resistance. Furthermore, in the conductive composition of the present disclosure, the elastomer more preferably has a tensile break elongation in the range of 10 to 200% as measured by the above method. The tensile break elongation can be calculated according to the following formula: Tensile elongation at break (%) = [(elongation at break (mm) - initial dimension (mm)) / (initial dimension (mm)] × 100

[0036] Furthermore, when the conductive composition of the present disclosure contains rubber or a functional group-containing elastomer as the elastomer, it is preferable that it further contains a sulfur-based vulcanizing agent or a non-sulfur-based vulcanizing agent. However, when the conductive particles contain metal particles, there is a risk that the metal particles may be oxidized or sulfurized by the sulfur-based vulcanizing agent, resulting in corrosion. Therefore, it is preferable that the conductive composition of the present disclosure does not contain a sulfur-based vulcanizing agent, and it is preferable that it contains a non-sulfur-based vulcanizing agent as needed. Furthermore, the conductive composition of the present disclosure may contain a small amount of a sulfur compound.

[0037] Furthermore, the conductive composition of the present disclosure may contain known additives such as softeners and plasticizers. Examples of softeners include mineral oil-based softeners and vegetable oil-based softeners. Examples of mineral oil-based softeners include various oils such as paraffinic process oil, naphthenic process oil, and aromatic process oil. Examples of vegetable oil-based softeners include castor oil, corn kernel oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, pine oil, and tall oil. These softeners may be used alone or in combination of two or more. The rubber elasticity and extensibility of a conductor containing the conductive composition of the present disclosure can be adjusted by adjusting the amount of softener added.

[0038] The content of the elastomer in the conductive composition of the present disclosure is preferably 5% by mass to 40% by mass, and more preferably 14% by mass to 28% by mass, calculated as solid content, based on the total solid content (100% by mass) contained in the conductive composition. Note that the conductive composition of the present disclosure may contain other organic binders such as thermoplastic resins other than the elastomer.

[0039] <Conductive particles> The conductive composition of the present disclosure contains chain-like conductive particles. The conductive particles contained in the conductive composition can be any conventional material known for use in conductive compositions. Examples include carbon particles such as graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; metal particles such as copper powder, nickel powder, and silver powder; metal carbides such as WC, BC, ZrC, NbC, MoC, TiC, and TaC; metal nitrides such as TiN, ZrN, and TaN; and metal silicides such as WSi2 and MoSi2. These conductive particles may be used alone or in combination of two or more. Metal particles are preferred as the conductive particles, as they provide a conductive composition with low electrical resistance, and silver powder is more preferred. Furthermore, in the conductive composition of the present disclosure, the conductive particles are in a chain (aggregated) state (i.e., chain-like conductive particles). Therefore, it is particularly preferred to use chain-like (aggregated) silver powder, i.e., chain-like silver powder, as the conductive particles. The term "chained" refers to a state in which secondary particles formed by aggregation of conductive primary particles are in contact with each other and linked together.

[0040] In the conductive composition of the present disclosure, the conductive particles are not particularly limited, but preferably have a tap density of 2.0 g / cm when measured after 1000 taps in accordance with ISO 3953:2011. 3 or less, more preferably 0.3 g / cm 3 ~1.5g / cm 3 , and more preferably 0.3 g / cm 3 ~1.0g / cm 3 Although the detailed mechanism is not clear, it is believed that when the conductive particles have a tap density in this range, the volume per unit mass of the conductive particles increases, resulting in many contact points between the conductive particles, resulting in high conductivity. As a result, it is believed that a conductor containing the conductive composition of the present disclosure can sufficiently suppress fluctuations in resistance value, whether it is stretched strongly (when strain is large) or weakly (when strain is small).

[0041] The shape of the conductive particles (primary particles) in the conductive composition of the present disclosure is not particularly limited and may be, for example, spherical, approximately spherical, needle-like, oval-spherical, flake-like, scale-like, irregular, etc., with spherical and approximately spherical shapes being preferred. As the conductive particles, one type of particle having the same shape may be used alone, or two or more types of particles having different shapes may be used in combination.

[0042] In the conductive composition of the present disclosure, the conductive particles (primary particles) preferably have an average particle size (average primary particle size) of 0.1 μm to 10 μm, more preferably 0.1 μm to 5 μm. Furthermore, the chain-like conductive particles (secondary particles) preferably have an average particle size (average secondary particle size) of 1 μm to 100 μm, more preferably 10 μm to 50 μm. For example, when the conductive particles are chain-like silver powder, the average primary particle size of the silver powder particles constituting the chain-like silver powder is preferably 1.0 μm or less, more preferably 0.1 μm to 1.0 μm. Furthermore, the average secondary particle size (D50) of the chain-like silver powder is preferably 10 μm or more, more preferably 10 μm to 50 μm. When the average secondary particle size is within this range, the conductive particles in the conductive composition have many contact points with each other, which is thought to result in high conductivity. As a result, it is believed that a conductor containing the conductive composition of the present disclosure can sufficiently suppress fluctuations in resistance value, whether it is stretched strongly (when strain is large) or weakly (when strain is large).

[0043] The average primary particle diameter of the conductive particles can be determined by observing the conductive particles in a powder state under a scanning electron microscope at 10,000x magnification, randomly extracting 10 primary particles, and measuring their particle diameters, and then calculating the average particle diameter of these particles.

[0044] The average secondary particle diameter (D50) of the conductive particles contained in the conductive composition can be measured according to the following procedure. First, the conductive composition is diluted with 3000 mass% propylene glycol monomethyl ether acetate to obtain a solution. The particle size distribution of the obtained solution is measured in reflection mode using a laser diffraction / scattering particle size distribution analyzer (TM3000, manufactured by Microtrack-Bell) with a solvent refractive index of 1.40 and a measurement range of 0.020 μm to 1000.00 μm. From the particle size distribution, the particle diameter at 50% of the cumulative total is determined and used as the average secondary particle diameter (D50) of the conductive particles.

[0045] The apparent porosity of the chain-like conductive particles is preferably 50% to 95%, more preferably 60% to 90%. The apparent porosity of the chain-like conductive particles is an index that indicates the state of the aggregate structure (secondary particles) in which primary particles of the conductive particles are linked together to form an appropriate amount of voids. For example, when the conductive particles are chain-like silver powder, the apparent porosity is preferably 50% to 95%, more preferably 60% to 95%.

[0046] The apparent porosity of the chain-like conductive particles can be measured as follows: The density of the conductive particles is expressed as ρ0 (g / cm 3 ), and the volume of the conductive particle after 1 hour has passed since a load of 1 kg was applied to the conductive particle with a mass of M (g) is V (cm 3 ), the apparent density ρ(g / cm 3 ) is defined as ρ=M / V, and the apparent porosity (P) can be calculated from the apparent density using the following formula: P = (1-ρ / ρ0) × 100 For example, when the conductive particles contained in the conductive composition of the present disclosure are chain-like silver powder, the density ρ0 is 10.49 g / cm 3 is.

[0047] The DBP oil absorption of the chain-like conductive particles measured in accordance with JIS K 6217-4: 2017 is preferably 30 ml / 100 g to 300 ml / 100 g, more preferably 50 ml / 100 g to 200 ml / 100 g. For example, when the conductive particles contained in the conductive composition of the present disclosure are chain-like silver powder, the DBP oil absorption of the chain-like silver powder measured in accordance with JIS K 6217-4: 2017 is preferably 50 ml / 100 g to 150 ml / 100 g.

[0048] The content of the conductive particles in the conductive composition of the present disclosure is 60% to 95% by mass, preferably 65% ​​to 85% by mass, and more preferably 70% to 80% by mass, calculated as solid content, based on the total solid content (100% by mass) contained in the conductive composition. When the content of the conductive particles in the conductive composition is within this range, a conductor containing the conductive composition of the present disclosure can be obtained that has a low initial electrical resistance in an unstrained state (initial state) and a stably low electrical resistance even in a strained state.

[0049] <Ionic liquid> The conductive composition of the present disclosure contains an ionic liquid. The ionic liquid is not particularly limited, and any known or commonly used ionic liquid can be used. That is, examples of cations constituting the ionic liquid include those having a basic skeleton of an imidazolium-based, pyridinium-based, pyrrolidinium-based, piperidinium-based, ammonium-based, and phosphonium-based. More specifically, examples of cationic species constituting the ionic liquid include primary (R1NH3 + ), second class (R1R2NH2 + ), tertiary (R1R2R3NH + ), quaternary (R1R2R3R4N + ) a chain ammonium cation (wherein R1, R2, R3, and R4 each independently represent a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 18 carbon atoms, and having a linear or branched structure, or a hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 18 carbon atoms, and having one or more hydroxyl groups in the side chain, and having a linear or branched structure.)

[0050] Furthermore, cyclic ammonium cations can be used as the cationic species in the ionic liquid. Examples of cyclic ammonium cations include oxazolium, thiazolium, imidazolium, pyrazolium, pyrrolinium, furazanium, triazolium, pyrrolidinium, imidazolidinium, pyrazolidinium, pyrrolinium, imidazolinium, pyrazolinium, pyrazinium, pyrimidinium, pyridazinium, piperidinium, piperazinium, morpholinium, indolium, and carbazolium. Further examples of other cations include chain phosphonium cations, chain sulfonium cations, and cyclic sulfonium cations. Examples of cyclic sulfonium cations include thiophenium, thiazolinium, and thiopyranium.

[0051] Examples of anions in the ionic liquid include halide ions, tetrafluoroborate, hexafluorophosphate, and bis(trifluoromethylsulfonyl)amide. Specific examples of anions include AlCl4 - , NO2 - , NO3 - , I - , BF4 - , PF6 - , AsF6 - , SbF6 - , NbF6 - , TaF6 - , p-CH3PhSO3 - , CH3CO2 - , CF3CO2 - , CH3SO3 - , CF3SO3 - , (CF3SO2)3C - , C3F7CO2 - , C4F9SO3 - , (CF3SO2)2N - , (C2F5SO2)2N - , (CF3SO2)(CF3CO)N - , (CN)2N - etc.

[0052] As the ionic liquid composed of the above-mentioned cations and anions, ionic liquids into which various functional groups have been introduced can also be used. The ionic liquids can be used alone or in combination of two or more.

[0053] The ionic liquid contained in the conductive composition of the present disclosure is preferably one having a 5% weight loss temperature of 300°C or less. The mechanism of the effect achieved when using an ionic liquid having a 5% weight loss temperature of 300°C or less is not entirely clear, but is speculated as follows. When the conductive composition of the present disclosure is mixed with a solvent to form a paste and then solidified to form a conductor, it is believed that the ionic liquid has a 5% weight loss temperature of 300°C or less, and the thermal energy used to volatilize the solvent causes the ionic liquid to decompose appropriately. The decomposition products adhere to the surfaces of the conductive particles, promoting the formation of a conductive path between the conductive particles and the ionic liquid. This is believed to suppress an increase in resistance even when the conductor is significantly deformed. However, this is merely speculation and is not limited to this.

[0054] In particular, it is preferable to use an ionic liquid whose 5% weight loss temperature is preferably 100°C or higher and 300°C or lower, more preferably 200°C or higher and 300°C or lower. By using an ionic liquid within this range, as described above, the ionic liquid can undergo moderate decomposition, more effectively suppressing an increase in resistance value. The 5% weight loss temperature can be measured by thermogravimetry in accordance with JIS K7120:1987. For example, the 5% weight loss temperature can be measured using a TA Instruments GTA-5500 at a heating rate of 10°C / min. The 5% weight loss temperature can also be referred to as the 5% mass loss temperature in SI units.

[0055] The ionic liquid contained in the conductive composition of the present disclosure is preferably a polymeric ionic liquid. Examples of polymeric ionic liquids include ionic liquids having polymeric side chains. The weight-average molecular weight of the polymeric side chains is preferably 500 to 1,000,000, and more preferably 1,000 to 500,000. The weight-average molecular weight is a value measured using gel filtration chromatography (standard substance: polystyrene). Using an ionic liquid having a polymeric side chain within the above weight-average molecular weight range improves compatibility with elastomers, enabling the ionic liquid to form stable conductive paths even when deformed.

[0056] The ionic liquid contained in the conductive composition of the present disclosure preferably has a surface resistivity of 10 7 Ω / □~10 12 Ω / □, more preferably 10 8 Ω / □~10 10 Ω / □, more preferably 10 9 Ω / □~10 10 An ionic liquid with a surface resistivity of Ω / □ is used. By using an ionic liquid with a surface resistivity in this range, it is possible to suppress the linear increase in resistance when strain occurs in the conductor, and form a conductor that enables the design of devices that can operate stably both in cases of small and large strain. Surface resistivity can be measured using the voltmeter-current method in accordance with JIS C2139:2019.

[0057] The content of the ionic liquid in the conductive composition of the present disclosure is 0.1% by mass to 10% by mass, preferably 0.1% by mass to 5% by mass, and more preferably 0.1% by mass to 2.5% by mass, relative to the total mass (100% by mass) of the conductive composition. The ionic liquid content of 0.1% by mass indicates that the ionic liquid is actively contained. If the ionic liquid content exceeds 10% by mass, the resistance of the conductor increases linearly when strain is applied, or devices incorporating the conductor cannot operate stably under either small or large strain.

[0058] <Solvent> The conductive composition of the present invention may contain a solvent. As the solvent, an organic solvent is preferably used from the viewpoints of preparation of the conductive composition and adjustment of viscosity for applying the conductive composition to a substrate or the like.

[0059] Examples of the organic solvent include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, and petroleum-based solvents. More specifically, examples of the solvent include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; glycol ethers such as cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, and triethylene glycol monoethyl ether; esters such as ethyl acetate, butyl acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, and propylene glycol butyl ether acetate; alcohols such as ethanol, propanol, ethylene glycol, propylene glycol, butylene glycol, and terpineol; aliphatic hydrocarbons such as octane and decane; and petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha. The organic solvents may be used alone or in combination of two or more.

[0060] The boiling point of the organic solvent is not particularly limited, but is preferably 150°C or higher, more preferably 200°C or higher. Using an organic solvent with a boiling point in this range can prevent the organic solvent from volatilizing during the device fabrication process, thereby preventing a decrease in the printability and processability of the conductive composition. Furthermore, as described above, when using an ionic liquid whose 10% weight loss temperature is higher than the boiling point of the solvent, an appropriate organic solvent can be selected based on the 10% weight loss temperature of the ionic liquid. Specifically, for example, when using an ionic liquid whose 10% weight loss temperature is 260°C to 320°C, it is preferable to use a solvent with a boiling point below 260°C. Examples of such solvents include, but are not limited to, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (boiling point 253°C) and diethylene glycol monoethyl ether acetate (boiling point 217°C).

[0061] The content of the solvent in the conductive composition of the present disclosure is preferably 1% by mass to 50% by mass, more preferably 10% by mass to 40% by mass, and even more preferably 15% by mass to 30% by mass, relative to the total mass (100% by mass) of the conductive composition.

[0062] <Other ingredients> The conductive composition of the present disclosure may contain other components in addition to the above-described components. As the other components, those typically used in the production of conductive compositions can be used without any particular limitation. Examples of the other components include thermosetting components, additives, pigments, fillers, etc.

[0063] Examples of thermosetting components include polyester resins (urethane-modified, epoxy-modified, acrylic-modified, etc.), epoxy resins, urethane resins, phenolic resins, melamine resins, vinyl resins, silicone resins, and blocked isocyanates, which are capable of forming films by increasing the molecular weight through a curing reaction and by forming crosslinks.

[0064] Examples of additives include coupling agents, photopolymerization initiators, and flame retardants. In particular, fatty acids can be used as additives. It is believed that the inclusion of fatty acids in the conductive composition of the present disclosure promotes dissociation of aggregated conductive particles, and further enables the conductive particles to be stably maintained in a dispersed state. Furthermore, the inclusion of fatty acids in the conductive composition of the present disclosure enables the conductive particles to be stably maintained in a dispersed state, which also has the additional effect of suppressing deterioration of the performance of the conductive composition of the present disclosure over time.

[0065] The type of fatty acid that can be used includes straight-chain fatty acids, branched fatty acids, and cyclic fatty acids, and both saturated and unsaturated fatty acids can be used.

[0066] The number of carbon atoms in the fatty acid is not particularly limited, but is, for example, 10 to 18. From the viewpoint of suppressing adverse effects on wiring layers and electrodes produced using the conductive composition of the present disclosure, particularly preferred fatty acids include stearic acid, oleic acid, myristic acid, palmitic acid, linoleic acid, lauric acid, and linolenic acid. The fatty acids may be used alone or in combination of two or more.

[0067] The content of the fatty acid in the conductive composition of the present disclosure is, in terms of solid content, preferably 0.01% by mass to 10% by mass, more preferably 0.05% by mass to 5% by mass, and even more preferably 0.1% by mass to 1% by mass, based on the total solid content contained in the conductive composition.

[0068] When the conductive composition of the present disclosure contains a filler, examples of the filler include silica, glass frit, ceramic, hollow particles, and the like. In particular, it is believed that the inclusion of silica in the conductive composition of the present disclosure makes it possible to stably maintain the dispersed state of the conductive particles in the conductive composition. Furthermore, since the inclusion of silica in the conductive composition of the present disclosure makes it possible to stably maintain the dispersed state of the conductive particles, it also has the additional effect of suppressing deterioration of the performance of the conductive composition over time. In particular, it is believed that the conductive composition of the present disclosure makes it possible to particularly stably maintain the dissociated and dispersed state of the conductive particles by using the above-mentioned fatty acid and silica in combination.

[0069] Examples of silica that can be used include fused silica, spherical silica, amorphous silica, and crystalline silica. Silica that has undergone various surface treatments can also be used. Silica may be used alone or in combination of two or more types.

[0070] The surface area of ​​the silica is not particularly limited, but the BET specific surface area is preferably 100 m 2 / g~1000m 2 / g, more preferably 100m 2 / g~800m 2 / g, more preferably 100m 2 / g~500m 2 / g. It is believed that the BET specific surface area of ​​silica within this range can stably maintain the dispersion state of silica in the conductive composition of the present disclosure. Furthermore, when silica has a BET specific surface area within the above-mentioned range, the dispersion state of conductive particles by silica suppresses a linear increase in resistance when strain is generated in the conductor, making it suitable for forming a conductor that enables device design that can operate stably both under small and large strains. Furthermore, because the dispersion state of conductive particles can be stably maintained by silica in this way, an additional effect of suppressing deterioration of the performance of the conductive composition of the present disclosure over time is also achieved. The BET specific surface area can be measured by gas adsorption method in accordance with JIS Z8831-3:2010.

[0071] The average secondary particle diameter (D50) of silica is preferably 1 nm to 1000 nm, more preferably 5 nm to 500 nm, and even more preferably 10 nm to 100 nm.

[0072] The content of silica in the conductive composition is, in terms of solid content, preferably 0.01% by mass to 10% by mass, more preferably 0.1% by mass to 5% by mass, and even more preferably 0.5% by mass to 3% by mass, based on the total solid content (100% by mass) contained in the conductive composition.

[0073] <Paste containing conductive composition> The conductive composition of the present disclosure can be made into a paste by, for example, kneading an elastomer dissolved in a solvent with conductive particles. Examples of kneading methods include a method using a stirring and mixing device such as a roll mill. Specifically, an elastomer solution with a solids content of 50% by mass is prepared by dissolving an elastomer in a solvent, conductive particles are added to this elastomer solution, and the mixture is pre-stirred and mixed with a stirrer, followed by kneading with a three-roll mill, thereby obtaining a paste containing the conductive composition of the present disclosure. During production, the paste containing the conductive composition of the present disclosure is preferably kneaded four or more times with a three-roll mill, thereby achieving an appropriate dispersion state of the components that can form a highly stretchable conductor.

[0074] The viscosity of the paste containing the conductive composition of the present invention is not particularly limited, but is preferably adjusted to 100 dPa·s to 5000 dPa·s, and more preferably 200 dPa·s to 1000 dPa·s. By adjusting the viscosity of the paste containing the conductive composition to fall within this range, it is possible to achieve excellent printability and processability, which are required in device fabrication processes.

[0075] A paste containing the conductive composition of the present disclosure can be applied to a substrate in a pattern and then subjected to a heat treatment, such as a drying treatment or a heat curing treatment, to form a conductor.

[0076] [conductor] The paste containing the conductive composition described above can be solidified to form a conductor. For example, a coating film made of the paste containing the conductive composition can be formed, dried, and solidified to form a conductor layer. The paste containing the conductive composition can be solidified by drying or heat-treating the paste containing the conductive composition. Examples of heat treatment include hot air drying and thermal curing. Molding may be performed prior to the heat treatment. For example, a conductor layer can be obtained by applying a paste containing the conductive composition described above to a substrate in a desired shape and then solidifying it. The conductor layer may have various shapes depending on the intended use. For example, it can be suitably applied to conductor circuits, wiring, etc.

[0077] The method for producing a conductor circuit includes a pattern formation step of printing or applying a paste containing the conductive composition onto a substrate to form a coating pattern, and a step of solidifying the patterned coating. The coating pattern can be formed by a masking method, a method using a resist, or the like.

[0078] Examples of the pattern formation process include a printing method and a dispensing method. Examples of printing methods include gravure printing, offset printing, and screen printing, and screen printing is preferred when forming fine circuits. Gravure printing and offset printing are suitable as large-area coating methods. The dispensing method is a method in which a paste containing a conductive composition is extruded from a needle to form a pattern by controlling the amount of paste applied, and is suitable for forming partial patterns such as earth wiring or patterns on uneven areas.

[0079] The substrate on which the paste containing the conductive composition is applied can be any electrically insulating material, including paper-phenolic resin, paper-epoxy resin, glass cloth-epoxy resin, glass-polyimide, glass cloth / nonwoven cloth-epoxy resin, glass cloth / paper-epoxy resin, synthetic fiber-epoxy resin, copper-clad laminates of all grades (e.g., FR-4) made from composites such as fluororesin, polyethylene, polyphenylene ether, and polyphenylene oxide-cyanate ester, sheets or films made from plastics such as polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate, polyimide, polyphenylene sulfide, and polyamide, sheets or films made from crosslinked rubbers such as urethane, silicone rubber, acrylic rubber, and butadiene rubber, and sheets or films made from thermoplastic elastomers such as polyesters, polyurethanes, polyolefins, and styrene-based block copolymers. Among these, flexible and stretchable materials (e.g., rubber, thermoplastic elastomers, and urethane) can be used as substrates to provide conductors for applications described below. As the stretchable material, the same materials as those explained above for the elastomer can be used.

[0080] [Laminated structure] A laminate structure can be formed by using the conductive composition of the present disclosure and disposing the conductor on at least one main surface of the substrate. In particular, the laminate structure of the present disclosure is preferably formed by disposing multiple layers of the conductor on at least one main surface of the substrate. There are no particular limitations on the method for forming the laminate structure. For example, a conductor formed by solidifying a paste containing the conductive composition may be bonded by heat, pressure, or both, or a paste containing the conductive composition may be applied to a conductor and then solidified. The laminate structure may also include layers other than the conductors described above, such as a metal layer, an insulating layer, a protective layer, an adhesive layer, a pressure-sensitive adhesive layer, or a void layer.

[0081] [Electronic Components] An electronic component can be formed using the above-described conductor or laminate structure as a constituent element. There are no particular limitations on the structure, formation method, or use of the electronic component as long as it is an electronic component that uses the above-described conductor or laminate structure as a constituent element, and examples thereof include sensors, actuators, capacitors, inductors, transistors, converters, thermistors, connectors, transformers, capacitors, diodes, regulators, motors, antennas, and switches, and the like, and the electronic component may also have a combination of multiple uses among these.

[0082] For example, an electronic component having a conductive layer can be manufactured by forming a conductive layer, which is a solidified product of the conductive composition of the present disclosure, on at least one main surface of a substrate. Specifically, an electronic component having a conductive layer can be manufactured by applying the conductive composition of the present disclosure to at least one main surface of a substrate and drying the conductive composition applied to at least one main surface of the substrate to form the conductive layer.

[0083] [Uses for conductors, laminated structures and electronic components] A conductor solidified from a paste containing the conductive composition of the present disclosure suppresses a linear increase in resistance when strain is applied to the conductor and is capable of stable operation under both small and large strains. Therefore, in addition to conductor circuits and wiring, the conductor is preferably used in electronic components having a portion that deforms with movement. Here, "deforming with movement" refers to the movement of the wearer of the device including the electronic component. Examples of such electronic components include conductors for wearable devices such as clothing-worn devices, external devices, surface devices, electronic skin devices, and internal devices. Furthermore, a conductor layer can be applied to electrodes of flexible printed circuit boards. Furthermore, the conductive composition of the present disclosure is also suitable for forming a conductor layer, such as an actuator electrode. It is also suitable for forming conductors with designs that have previously been difficult to achieve due to insufficient stretchability or stable electrical resistance. Specific uses of the conductor include, for example, the following:

[0084] <Wearable biosensor> The conductors disclosed herein can be used as wiring materials for wearable biosensors attached to clothing or the body to acquire or transmit action potentials or bioinformation generated by animals and plants, including humans. The sensor is attached in close contact with or close to the surface tissue of animals and plants, including humans, and stretches and contracts in areas that are in close contact with or close to the surface tissue. Furthermore, when attached to clothing, the pattern or extent of the clothing's shape change (stretching and contracting) varies depending on the wearer's physique or movement pattern (tendency). Conventional rigid and flexible substrates lack the ability to conform to the stretching and contracting of the attachment location, limiting the location where the sensor can be attached and resulting in limited bioinformation. In contrast, the conductors disclosed herein suppress the linear increase in resistance when strain occurs and enable stable operation under both small and large strains, enabling wearable biosensors to be attached to clothing or in close contact with or close to the surface tissue of animals and plants, including humans.

[0085] Furthermore, since wiring for wearable biosensors using the conductors disclosed herein can be formed by screen printing or dispensing methods, it is possible to miniaturize signal wiring, which is thought to contribute to the miniaturization of sensor devices.

[0086] <Wiring material for smart textiles> In recent years, the field of so-called "smart textiles," which use woven fabrics as sensors, has been expanding. The conductors disclosed herein can be applied to smart textiles. Circuit boards or sensors formed by forming wiring on a stretchable substrate that can be thermocompression-bonded using the conductors disclosed herein suppress the linear increase in resistance when strain occurs and operate stably under both small and large strains. Therefore, by attaching the circuit board or sensor to the surface of a stretchable woven fabric, the fabric can function as an electronic device, i.e., a smart textile. Examples of smart textiles that use the conductors disclosed herein include those that impart functions such as pressure-sensitive sensors, touch sensors, and antenna wiring to woven fabrics.

[0087] <Wiring for three-dimensional (3D) molded products> The conductors disclosed herein can be applied to wiring for three-dimensional (3D) molded products. Wiring for 3D molded products refers to wiring embedded in molded products, which are three-dimensional objects. An example of a 3D molded product is a plastic molded product for electronic device housings, etc., made using the FIM (film insert molding) method. Such plastic molded products are produced by printing a design onto a plastic film such as polycarbonate, followed by a heat press process. A conductor disclosed herein can be formed as a design print onto the base substrate, followed by a molding process using a heat press (which causes partial elongation). This 3D molded product will incorporate wiring made of the conductor disclosed herein. The conductor disclosed herein suppresses a linear increase in resistance when strain occurs, and operates stably under both small and large strains. Therefore, 3D molded products incorporating the conductor of the present disclosure have excellent properties in that the conductor wiring made of the conductor of the present disclosure, which is disposed on an elastic substrate, does not break when stretched and changes in resistance value are suppressed.

[0088] Furthermore, a 3D-printed article comprising the conductor of the present disclosure may be obtained by forming the conductor of the present disclosure as a design print on a stretchable substrate such as the above-mentioned elastomer, followed by heat pressing. This 3D-printed article becomes a stretchable electronic device that includes wiring made of the conductor of the present disclosure within a stretchable housing. Examples of such stretchable electronic devices include, but are not limited to, pressure-sensitive sensors, touch sensors, and antenna wiring.

[0089] <Stretchable wiring sheet and wiring board> By using a stretchable substrate in the conductor or laminate structure of the present disclosure, it can be used as a wiring board sheet or wiring substrate that can be stretched and deformed. For example, such a wiring board sheet or wiring substrate can be attached to the surface of an object having a three-dimensional shape, such as a molded product, while being stretched and deformed without causing disconnection of the wiring. Therefore, the conductor or laminate structure of the present disclosure using a stretchable substrate can be suitably used for, but is not limited to, pressure-sensitive sensors, touch sensors, and antenna wiring.

[0090] <Flexible wiring sheet and wiring board> In flexible wiring sheets or wiring boards using conventional conductive pastes, when subjected to extreme bending such as bending with a fingernail, wire breakage occurs. In contrast, the flexible wiring sheet or wiring board formed of the conductor or laminate structure of the present disclosure has elongation properties, and therefore can accommodate excellent bending properties, preventing wire breakage even when bent with a fingernail. [Example]

[0091] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, "parts" and "%" are all by mass unless otherwise specified.

[0092] [Preparation of conductive composition] The following materials were prepared as the conductive composition materials. Elastomer A: Polyvinylpyrrolidone (product number K-30, manufactured by Nippon Shokubai Co., Ltd.; contains a structural unit having a nitrogen atom) Elastomer B: Polyvinyl butyral (product number S-LEC SV-12, manufactured by Sekisui Chemical Co., Ltd.) Elastomer C: Acrylic block copolymer (product number Kuralyte (registered trademark) LA2330 (triblock copolymer having hard segments and soft segments), manufactured by Kuraray Co., Ltd.) Solvent A: 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (boiling point 253°C) Solvent B: Diethylene glycol monoethyl ether acetate (boiling point 217°C) Ionic liquid A: AS300 (manufactured by Nippon Nyukazai Co., Ltd., 5% weight loss temperature 253°C) Ionic liquid B: AS400 (manufactured by Nippon Nyukazai Co., Ltd., 5% weight loss temperature 193°C) Ionic liquid C: AS100 (manufactured by Nippon Nyukazai Co., Ltd., 5% weight loss temperature 178°C) Ionic liquid D: 1-Ethyl-3-methylimidazolium Tetrafluoroborate (5% weight loss temperature 327℃) Ionic liquid E: 1-Hexyl-3-methylimidazolium Tetrafluoroborate (5% weight loss temperature 345℃) Conductive particle A (silver powder) Conductive particles B (silver powder) The particle shapes, average secondary particle diameters (D50) and tap densities of the conductive particles A and B are shown in Table 1 below.

[0093] [Table 1]

[0094] The tap density of each conductive particle was measured after 1000 taps in accordance with ISO 3953: 2011. The 5% weight loss temperature of each ionic liquid was measured using a TA Instruments GTA-5500 at a heating rate of 10°C / min using thermogravimetry in accordance with JIS K7120: 1987.

[0095] Each conductive composition was prepared according to the following procedure. First, the elastomer was dissolved in a solvent to prepare an elastomer solution. Next, the conductive particles, elastomer solution, and ionic liquid were mixed to the compositions shown in Table 2 below, and the mixture was pre-mixed with a mixer and then kneaded with a three-roll mill (EXAKT50, manufactured by EXAKT) to obtain the conductive compositions of Examples 1 to 8 and Comparative Examples 1 to 3.

[0096] [Table 2]

[0097] [Evaluation of conductive composition] Immediately after preparation, each conductive composition of the Examples and Comparative Examples was applied to a substrate by screen printing and heat-treated at 120°C for 30 minutes to form a conductor with a line width of 1 mm, a thickness of 20 μm, and a length of 40 mm on the substrate. A urethane film (TG88-I, manufactured by Takeda Sangyo Co., Ltd., thickness 70 μm) was used as the substrate. The conductor was stretched at a rate of 5 mm / sec to a predetermined elongation (10%, 20%, 30%, 40%, 50% elongation), and then held in that state for 30 seconds. The resistance of the conductor was measured, and the conductivity of the conductor during elongation was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 2. ○: The resistance value increased by less than twice the value before stretching, and the conductivity was sufficiently stable. △: The resistance value increased by more than two times but not more than five times compared to before stretching, and the conductivity was stable. ×: The resistance value increased by more than five times compared to before stretching, and the stability of the conductivity was insufficient.

[0098] The evaluation results shown in Table 2 demonstrate that when the conductive compositions of each example were used, stable conductivity was maintained even during each stage of elongation. That is, a conductive composition containing an elastomer, chain-like conductive particles, and an ionic liquid, in which the content of the ionic liquid was 0.1% by mass to 10% by mass relative to the total mass of the conductive composition, was shown to be able to form a stretchable conductor that suppresses a linear increase in resistance when strain is generated in the conductor and enables the design of devices that can operate stably both under small and large strains.

Claims

1. A conductive composition comprising an elastomer, chain-like conductive particles, and an ionic liquid, The conductive composition, wherein the content of the ionic liquid is 0.1% by mass to 10% by mass relative to the total mass of the conductive composition.

2. The conductive composition of claim 1 , comprising a solvent.

3. The conductive composition according to claim 1 , wherein the ionic liquid has a 5% weight loss temperature of 300° C. or lower.

4. The conductive composition according to claim 1 , wherein the ionic liquid is a polymeric ionic liquid.

5. The conductive composition according to claim 1 , wherein the elastomer comprises a structural unit having at least one selected from the group consisting of a nitrogen atom and a hydroxyl group.

6. The conductive composition according to claim 1 , which is used to form a conductor.

7. A conductor which is a solidified product of the conductive composition according to claim 6.

8. A laminated structure comprising a substrate and a layer of the conductor according to claim 7 disposed on at least one main surface of the substrate.

9. An electronic component comprising the conductor layer according to claim 7 or the laminate structure according to claim 8.

10. The electronic component according to claim 9 , comprising the layer or the laminated structure, and a portion that deforms with operation.

11. A method for manufacturing an electronic component having a conductor layer, comprising the step of forming the conductor layer according to claim 7 on at least one main surface of a substrate.

12. 12. The method for manufacturing an electronic component according to claim 11, wherein the steps include: applying a conductive composition to at least one main surface of the substrate; and drying the conductive composition applied to at least one main surface of the substrate to form the conductor layer.

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