Conductive paint and circuit forming body

Abstract

The conductive paint of the present invention comprises a silicone resin (A) and a conductive powder (B) in a specific mass ratio, wherein the conductive powder (B) comprises a flake-shaped conductive powder (B1) having an average particle size of 1 to 7 μm and an irregularly shaped conductive powder (B2) having an average particle size of 1 to 6 μm in a specific mass ratio, and satisfies the following equation (1). 100 ≤ X1 + X2 ≤ 260 ··· (1) X1 = (average particle size of conductive powder (B1) / tap density of conductive powder (B1)) × (content of conductive powder (B1) relative to the total mass of conductive powder (B)) X2 = (average particle size of conductive powder (B2) / tap density of conductive powder (B2)) × (content of conductive powder (B2) relative to the total mass of conductive powder (B))

Description

Technology Field

[0001] The present invention relates to a conductive paint and a circuit forming body.

[0002] The present application claims priority based on Japanese Patent Application No. 2022-073168 filed in Japan on April 27, 2022, and incorporates the contents thereof herein. Background Technology

[0003] Recently, efforts to promote the widespread adoption of devices requiring flexibility or stretchability, such as wearable devices, flexible printed circuit boards, and displays, have been active. These devices are typically formed by applying a conductive coating containing conductive particles and a binder resin onto a substrate that is flexible or stretchable, but there are cases where the coating film formed by the conductive coating also requires stretchability.

[0004] As a conductive member having flexible wiring, for example, Patent Document 1 discloses a conductive member having wiring formed by drying a conductive paste of a polyurethane dispersion and conductive particles, and a plastic substrate. Prior art literature

[0005] Japanese Patent Publication No. 2012-54192 The problem to be solved

[0006] However, coating films formed with conventional conductive paints have a problem with electrical resistance stability because they become disconnected or their resistance increases when repeatedly stretched.

[0007] The objective of the present invention is to provide a conductive paint capable of forming a film with excellent durability even when subjected to repeated stretching and a small rate of change in resistance value. means of solving the problem

[0008] The present invention has the following aspects.

[0009] [1] Includes silicone resin (A) and conductive powder (B),

[0010] The mass ratio (A / B) of the above silicone resin (A) and the above conductive powder (B) is 10 / 90 to 35 / 65, and

[0011] The conductive powder (B) comprises a flake-shaped conductive powder (B1) having an average particle size of 1 to 7 μm and an irregularly shaped conductive powder (B2) having an average particle size of 1 to 6 μm.

[0012] The mass ratio (B1 / B2) of the conductive powder (B1) and the conductive powder (B2) is 40 / 60 to 90 / 10, and

[0013] A conductive paint satisfying the following formula (1).

[0014] 100≤X1+X2≤260 ···(1)

[0015] X1 = (average particle size of conductive powder (B1) / tap density of conductive powder (B1)) × (content of conductive powder (B1) relative to the total mass of conductive powder (B))

[0016] X2 = (average particle size of conductive powder (B2) / tap density of conductive powder (B2)) × (content of conductive powder (B2) relative to the total mass of conductive powder (B))

[0017] [2] The above silicone resin (A) comprises a curable silicone resin, preferably comprising at least one of an addition reaction curable silicone resin and a condensation reaction curable silicone resin, the conductive paint of [1].

[0018] [3] The above silicone resin (A) comprises the above addition reaction curing silicone resin, and

[0019] The conductive paint of [2] further comprises one or more catalysts selected from platinum-based metal catalysts, rhodium-based metal catalysts, palladium-based metal catalysts, cobalt-based metal catalysts, nickel-based metal catalysts and iron-based metal catalysts.

[0020] [4] A conductive paint of any one of [1] to [3], wherein each of the conductive powder (B1) and the conductive powder (B2) comprises one or more selected from gold, silver, copper, platinum, nickel, graphite and two or more elements (e.g., alloys, metals, or resins coated with metal).

[0021] [5] A conductive paint of any one of [1] to [4], wherein the average particle size of the conductive powder (B1) is 1.5 to 6.7 μm, more preferably 2 to 6.5 μm, and more preferably 2 to 5 μm.

[0022] [6] A conductive paint of any one of [1] to [5], wherein the average particle size of the conductive powder (B2) is 1.5 to 5.5 μm, more preferably 2 to 5.5 μm, and more preferably 2.5 to 5 μm.

[0023] [7] A conductive paint of any one of [1] to [6], wherein the mass ratio (A / B) of the silicone resin (A) and the conductive powder (B) is 15 / 85 to 30 / 70, and more preferably 15 / 85 to 25 / 75.

[0024] [8] A conductive paint of any one of [1] to [7], wherein the sum of the contents of the silicone resin (A) and the conductive powder (B) is 70 mass% or more, more preferably 80 mass% or more, more preferably 90 mass% or more, and particularly preferably 100 mass% with respect to the total mass of the conductive paint.

[0025] [9] A conductive paint of any one of [1] to [8], wherein the mass ratio (B1 / B2) is 45 / 55 to 85 / 15, and more preferably 45 / 55 to 80 / 20.

[0026]

[10] A conductive paint of any one of [1] to [9], wherein the sum of the contents of the conductive powder (B1) and the conductive powder (B2) is 80 mass% or more, more preferably 90 mass% or more, more preferably 95 mass% or more, and particularly preferably 100 mass% with respect to the total mass of the conductive powder (B).

[0027]

[11] A conductive paint of any one of [1] to

[10] , wherein X1 + X2 is 120 to 250, more preferably 130 to 210.

[0028]

[12] A circuit formed by forming a circuit on a substrate using a film obtained by using any one of the conductive paints [1] to

[11] . Effects of the invention

[0029] According to the present invention, a conductive paint can be provided that can form a film having excellent durability even when subjected to repeated stretching and a small rate of change in resistance value. Brief explanation of the drawing

[0030] FIG. 1 is a perspective view schematically showing a circuit forming body according to one embodiment of the present invention. Specific details for implementing the invention

[0031] The following definitions of terms apply throughout this specification and claims.

[0032] "Conductivity" is a term distinct from "insulation" in the general sense, and for circuit patterns, it preferably means that the electrical resistance value is less than 150Ω.

[0033] "Coating film" refers to a coating film formed by the conductive paint of the present invention.

[0034] The "~" indicating a numerical range means that the values ​​listed before and after it are included as lower and upper limits.

[0035] The numerical ranges of content, various physical properties, and characteristic values ​​disclosed in this specification may be changed to new numerical ranges by arbitrarily combining their lower and upper limits.

[0036] [Conductive paint]

[0037] A conductive paint according to one embodiment of the present invention comprises a silicone resin (A) and a conductive powder (B) as shown below.

[0038] The conductive paint may additionally include components other than the silicone resin (A) and the conductive powder (B) as needed (hereinafter also referred to as “optional components”), provided that such components do not impede the effects of the present invention.

[0039] <Silicone Resin (A)>

[0040] Silicone resin (A) is a resin with excellent durability and flexibility. Among silicone resins (A), a curable silicone resin is preferred.

[0041] Examples of curable silicone resins include addition reaction curable silicone resins, condensation reaction curable silicone resins, radical reaction curable silicone resins, and ultraviolet or electron beam curable silicone resins. Among these, addition reaction curable silicone resins and condensation reaction curable silicone resins are preferred, and addition reaction curable silicone resins are more preferred, as they can form not only thin films but also thick films, making it easy to adjust the film thickness according to the required application.

[0042] Silicone resin (A) may be used as a single type or in combination with two or more types.

[0043] The addition reaction curing type silicone resin is composed of functional groups in two types of organopolysiloxanes that are combined by an addition reaction and cross-linked.

[0044] The condensation reaction curing type silicone resin is composed of functional groups in two types of organopolysiloxane, or functional groups in organopolysiloxane and silicon compounds such as silica or silane, which are combined by a condensation reaction and cross-linked.

[0045] As for the silicone resin (A), commercially available products can be used.

[0046] Examples of commercially available addition reaction curing silicone resins include, for instance, “KE-1820” and “KE-1823” manufactured by Shin-Etsu Chemical Co., Ltd.; “TSE-3221”, “TSE-3250” and “TSE-3251” manufactured by Momentive Performance Materials Japan Joint Company; “SE-1750” and “SE-4450” manufactured by Dow Toray Corporation; and “SEMICOSIL 987 GR”, “SEMICOSIL 988 / 1 K GRAY” and “SEMICOSIL 989 / 1 K” manufactured by Asahi Kasei Wacker Silicon Co., Ltd.

[0047] Examples of commercially available condensation reaction curing silicone resins include, for instance, “KE-441,” “KE-471,” and “KE-47” manufactured by Shin-Etsu Chemical Co., Ltd.; “TSE-387” and “TSE-397” manufactured by Momentive Performance Materials Japan Joint Company; and “SE-917G,” “SE-9186,” and “SE-9184” manufactured by Dow Toray Corporation.

[0048] When using an addition reaction curing type silicone resin as the silicone resin (A), it is desirable to also use a catalyst to promote the addition reaction.

[0049] Examples of catalysts include platinum-based metal catalysts, rhodium-based metal catalysts, palladium-based metal catalysts, cobalt-based metal catalysts, nickel-based metal catalysts, and iron-based metal catalysts. Among these, platinum-based metal catalysts are preferred because they are the most widely used and facilitate the improvement of the addition reaction rate.

[0050] One type of catalyst may be used alone, or two or more types may be used in combination.

[0051] <conductive powder (B)>

[0052] The conductive powder (B) includes a flake-shaped conductive powder (B1) with an average particle size of 1 to 7 μm and an irregularly shaped conductive powder (B2) with an average particle size of 1 to 6 μm. By including the flake-shaped conductive powder (B1) and the irregularly shaped conductive powder (B2) in the conductive powder (B), a coating film can be formed that has excellent durability even when stretched repeatedly and has a small rate of change in resistance value.

[0053] If the conductive powder (B) is within a range that does not impede the effects of the present invention, it may additionally include a conductive powder other than the conductive powder (B1) and the conductive powder (B2) (hereinafter also referred to as "conductive powder (B3)") as needed.

[0054] (conductive powder (B1))

[0055] The conductive powder (B1) is a flake-shaped conductive powder with an average particle size of 1 to 7 μm. The average thickness of the flake shape is typically 1 / 10 to 1 / 2 of the average particle size.

[0056] The conductive powder (B1) imparts conductivity to the coating film.

[0057] As for the conductive powder (B1), it is not particularly limited as long as it is used in conductive paint, but examples include metals such as gold, silver, copper, platinum, and nickel; graphite, etc. Among these, silver is preferred from the view that it has excellent conductivity and is resistant to oxidation.

[0058] In addition, the conductive powder (B1) may be composed of two or more types of elements, and, for example, may be an alloy, metal, or resin coated with the metal listed above. Among these, it is preferable to coat a metal or resin other than silver with silver, from the perspective of having excellent conductivity and being resistant to oxidation.

[0059] Conductive powder (B1) may be used as a single type or in combination with two or more types.

[0060] In addition, in the present invention, "flake shape" can be replaced with scale-like, flat, plate-like, or thin-flaked shapes.

[0061] The average particle size of the conductive powder (B1) is 1 to 7 μm, preferably 1.5 to 6.7 μm, more preferably 2 to 6.5 μm, and more preferably 2 to 5 μm. If the average particle size of the conductive powder (B1) is greater than or equal to the lower limit value, good conductivity can be maintained. If the average particle size of the conductive powder (B1) is less than or equal to the upper limit value, the durability of the coating film is excellent even when repeated stretching.

[0062] The average particle size of the conductive powder (B1) is a value measured as follows. That is, the arithmetic mean diameter calculated from the volume distribution measured by the laser diffraction scattering particle size distribution measurement method is taken as the average particle size of the conductive powder (B1). In addition, if a catalog value exists, the catalog value may be adopted as the average particle size of the conductive powder (B1) as a simple measurement value.

[0063] (conductive powder (B2))

[0064] The conductive powder (B2) is an irregularly shaped conductive powder with a diameter of 1 to 6 μm.

[0065] The conductive powder (B2) imparts conductivity to the coating film.

[0066] As for the conductive powder (B2), it is not particularly limited as long as it is used in conductive paint, but examples include metals such as gold, silver, copper, platinum, and nickel; graphite, etc. Among these, silver is preferred from the view that it has excellent conductivity and is resistant to oxidation.

[0067] In addition, the conductive powder (B2) may be composed of two or more types of elements, and, for example, may be an alloy, metal, or resin coated with the metal listed above. Among these, it is preferable to coat a metal or resin other than silver with silver from the viewpoint that it has excellent conductivity and is resistant to oxidation.

[0068] Conductive powder (B2) may be used as a single type or in combination with two or more types.

[0069] In addition, in the present invention, "irregular shape" means a shape other than a flake shape, and a shape in which two or more types of various shapes such as spherical, cubical, needle-shaped, bead-shaped, or star-shaped with protrusions on the surface are mixed together so that the shape cannot be limited; and means an aggregate of primary particles aggregated by including one or more shapes selected from spherical, cubical, needle-shaped, bead-shaped, or star-shaped with protrusions on the surface.

[0070] The average particle size of the conductive powder (B2) is 1 to 6 μm, preferably 1.5 to 5.5 μm, more preferably 2 to 5.5 μm, and more preferably 2.5 to 5 μm. If the average particle size of the conductive powder (B2) is greater than or equal to the lower limit value above, good conductivity can be maintained. Additionally, the durability of the coating film is excellent even when subjected to repeated stretching. If the average particle size of the conductive powder (B2) is less than or equal to the upper limit value above, the durability of the coating film is excellent even when subjected to repeated stretching.

[0071] The average particle size of the conductive powder (B2) is a value measured as follows. That is, the arithmetic mean diameter calculated from the volume distribution measured by the laser diffraction scattering particle size distribution measurement method is taken as the average particle size of the conductive powder (B2). In addition, if a catalog value exists, the catalog value may be adopted as the average particle size of the conductive powder (B2) as a simple measurement value.

[0072] (conductive powder (B3))

[0073] The conductive powder (B3) is a conductive powder other than the conductive powder (B1) and the conductive powder (B2).

[0074] Examples of conductive powders (B3) include flake-shaped conductive powder with an average particle size of more than 7 μm, irregularly shaped conductive powder with an average particle size of more than 6 μm, and spherical conductive powder.

[0075] The conductive powder (B3) imparts conductivity to the coating film.

[0076] As for the conductive powder (B3), it is not particularly limited as long as it is used in conductive paint, but examples include metals such as gold, silver, copper, platinum, and nickel; graphite, etc. Among these, silver is preferred from the view that it has excellent conductivity and is resistant to oxidation.

[0077] In addition, the conductive powder (B3) may be composed of two or more types of elements, and, for example, may be an alloy, metal, or resin coated with the metal listed above. Among these, it is preferable to coat a metal or resin other than silver with silver, from the perspective of having excellent conductivity and being resistant to oxidation.

[0078] Conductive powder (B3) may be used as a single type or in combination with two or more types.

[0079] <Optional Components>

[0080] Optional components include components that can be used in conventionally known conductive paints, such as organic solvents, binder resins other than silicone resin (A), dispersants, surface modifiers, thixotropic agents, adhesion promoters, resin modifiers, etc.

[0081] Optional ingredients may be used as a single type or in combination of two or more types.

[0082] However, among the above optional components, it is preferable not to include insulating components that remain as solids when formed into a coating film, as this lowers the conductivity performance of the coating film. Also, when the conductive paint includes an addition-reaction type silicone resin as the silicone resin (A), it is preferable not to substantially include impurities that act as curing inhibitors, such as sulfur.

[0083] Here, "substantially not containing" means not actively incorporating insulating components or impurities that act as curing inhibitors, such as sulfur, except for those unintentionally contained.

[0084] If the conductive paint contains an organic solvent, the viscosity can be easily adjusted.

[0085] As for the organic solvent, it is preferable that it be capable of dissolving the silicone resin (A), and for example, a mixture such as a petroleum-based aliphatic hydrocarbon solvent or a petroleum-based aromatic solvent, or a single substance such as toluene, diethylbenzene, decalin, or dodecane can be used.

[0086] Organic solvents may be used alone or in combination of two or more types.

[0087] Examples of binder resins other than silicone resin (A) (hereinafter also referred to as “other binder resins”) include polyester resin, phenoxy resin, polyamide resin, polyamideimide resin, polyimide resin, polyurethane resin, acrylic resin, polystyrene, styrene-acrylic resin, styrene-butadiene copolymer, epoxy resin, phenolic resin, polyether resin, polycarbonate resin, alkyd resin, polysulfone resin, polyethersulfone resin, vinyl chloride-vinyl acetate copolymer resin, ethylene-vinyl acetate copolymer, fluorine resin, and resins obtained by silicone modification of these resins.

[0088] Other binder resins may be used as a single type or in combination of two or more types.

[0089] <Content / Mass Ratio>

[0090] The mass ratio (A / B) of the silicone resin (A) and the conductive powder (B) is 10 / 90 to 35 / 65, preferably 15 / 85 to 30 / 70, and more preferably 15 / 85 to 25 / 75. If the mass ratio (A / B) is 10 / 90 or higher, the durability of the coating film is excellent even with repeated stretching. If the mass ratio (A / B) is 35 / 65 or lower, good conductivity can be maintained. Additionally, the durability of the coating film is excellent even with repeated stretching.

[0091] In addition, when an addition reaction curable silicone resin is used as the silicone resin (A) and the addition reaction curable silicone resin and a catalyst are used together, the mass of the silicone resin (A) used to calculate the mass ratio (A / B) and the content of the silicone resin (A) below also include the mass of the catalyst. In addition, when the addition reaction curable silicone resin and a catalyst are used together, the content of the catalyst is preferably 0.01 to 5 parts by mass and more preferably 0.1 to 3 parts by mass per 100 parts by mass of the addition reaction curable silicone resin.

[0092] The total content of the silicone resin (A) and the conductive powder (B) is preferably 70 mass% or more, more preferably 80 mass% or more, more preferably 90 mass% or more, and may be 100 mass% with respect to the total mass of the conductive paint. That is, the conductive paint may consist only of the silicone resin (A) and the conductive powder (B).

[0093] The mass ratio (B1 / B2) of the conductive powder (B1) and the conductive powder (B2) is 40 / 60 to 90 / 10, 45 / 55 to 85 / 15 is preferred, and 45 / 55 to 80 / 20 is more preferred. If the mass ratio (B1 / B2) is 40 / 60 or higher, the durability of the coating film is excellent even when repeated stretching and contraction, and the rate of change of the resistance value of the coating film is small. If the mass ratio (B1 / B2) is 90 / 10 or lower, the durability of the coating film is excellent even when repeated stretching and contraction.

[0094] The sum of the contents of the conductive powder (B1) and the conductive powder (B2) is preferably 80 mass% or more, more preferably 90 mass% or more, more preferably 95 mass% or more, and may be 100 mass% with respect to the total mass of the conductive powder (B). That is, the conductive powder (B) may consist only of the conductive powder (B1) and the conductive powder (B2).

[0095] <Equation (1)>

[0096] The conductive paint satisfies the following formula (1).

[0097] 100≤X1+X2≤260 ···(1)

[0098] X1 = (average particle size of conductive powder (B1) / tap density of conductive powder (B1)) × (content of conductive powder (B1) relative to the total mass of conductive powder (B))

[0099] X2 = (average particle size of conductive powder (B2) / tap density of conductive powder (B2)) × (content of conductive powder (B2) relative to the total mass of conductive powder (B))

[0100] X1 + X2 is 100 to 260, preferably 120 to 250, and more preferably 130 to 210. If X1 + X2 is greater than or equal to the lower limit value above, the durability of the coating film is excellent even when repeated expansion and contraction, and the rate of change of the resistance value of the coating film is small. If X1 + X2 is less than or equal to the upper limit value above, the durability of the coating film is excellent even when repeated expansion and contraction, and the rate of change of the resistance value of the coating film is small.

[0101] The tap density of the conductive powder (B1) and the conductive powder (B2) is measured by a method in accordance with JIS Z 2512:2012. In addition, if a catalog value exists, the catalog value may be adopted as the tap density of the conductive powder (B1) or the conductive powder (B2) as a simple measurement value.

[0102] <Manufacturing Method>

[0103] A conductive paint is obtained by mixing the above-described silicone resin (A) and conductive powder (B) with optional components as needed.

[0104] For mixing, mixers such as roll mills and planetary mixers can be used.

[0105] <Effects of Action>

[0106] The conductive paint of the present embodiment described above satisfies the above formula (1), and furthermore contains a silicone resin (A) and a conductive powder (B) in a specific ratio, and the conductive powder (B) contains a flake-shaped conductive powder (B1) with a specific average particle size and an irregularly shaped conductive powder (B2) in a specific ratio, so that a coating film with excellent durability and a small rate of change in resistance value can be formed even when repeated stretching.

[0107] <Uses>

[0108] Applications of the conductive paint of the present embodiment include circuits for electronic components. Specifically, applications include touch panel circuits, flexible substrates, and wearable devices. The conductive paint of the present embodiment is particularly suitable for flexible substrates and wearable devices that require flexibility or elasticity, as it is a conductive paint capable of forming a film with excellent durability even when subjected to repeated stretching and a small rate of change in resistance value.

[0109] [Circuit assembly]

[0110] A circuit forming body according to one embodiment of the present invention is formed by forming a circuit on a substrate using a coating film (hereinafter also referred to as a "conductive coating film") obtained by using the conductive paint of the present invention described above. That is, the circuit forming body has a substrate and a circuit formed on the substrate, and the circuit is formed using the conductive paint of the present invention.

[0111] FIG. 1 shows an example of a circuit forming body according to the present embodiment. The circuit forming body (10) shown in FIG. 1 has a substrate (11) and a circuit (12) formed on the substrate (11).

[0112] As for the substrate (11), conventional known materials used as wiring boards may be used, such as a substrate made of inorganic materials such as a glass substrate, a ceramic substrate, or a silicon substrate; a substrate made of organic materials, etc.

[0113] Examples of organic materials include polyesters such as polyethylene terephthalate and polyethylene naphthalate; silicones such as polydimethylsiloxane, polydiphenylpolysiloxane, and polyfluorosiloxane; urethanes such as thermoplastic polyurethane elastomers; polyimide; polyphenylene sulfide; polyolefins such as polyethylene and polypropylene; polyamide; polystyrene; acrylic; polyvinyl alcohol; ethylene propylene diene; and epoxy. Among these, a substrate formed of silicone (silicon substrate) is preferred because it exhibits good adhesion to the silicone resin in the conductive paint.

[0114] The thickness of the substrate (11) can be appropriately set according to the use of the circuit forming body (10), for example, 20 to 600 μm is preferred. If the thickness of the substrate (11) is within the above range, it is easy to make the circuit forming body (10) with good flexibility and durability.

[0115] The method of forming the circuit (12) on the substrate (11) is not particularly limited, but for example, a method of forming the circuit (12) formed by applying the conductive paint of the present invention onto the substrate (11) to form a desired circuit pattern and drying it can be given.

[0116] That is, as one embodiment of the method for manufacturing a circuit forming body (10), there is a pattern forming process of forming a circuit pattern by applying a conductive paint of the present invention onto a substrate (11) and a drying process of drying the circuit pattern.

[0117] Examples of methods for applying conductive paint include screen printing, gravure printing, offset printing, roll coating, bar coating, dispensing, dipping, transfer, inkjet, aerosol jet, etc.

[0118] The drying temperature is preferably, for example, 70 to 160°C.

[0119] The drying time is preferably, for example, 2 to 60 minutes.

[0120] The circuit forming body of the present embodiment described above has a circuit formed by a coating film obtained using the conductive paint of the present invention described above, so it has excellent durability even when stretched repeatedly and has a small rate of change in resistance value. Therefore, the circuit forming body of the present embodiment is particularly suitable for flexible substrate applications and wearable device applications where flexibility or elasticity is required.

[0121] Examples

[0122] The present invention will be described in detail below by way of examples, but the present invention is not limited to these.

[0123] In addition, the following Examples 2 to 8, 10, 14, 16 to 19, 22 to 27 are examples, and Examples 1, 9, 11 to 13, 15, 20, 21, 28, and 29 are comparative examples.

[0124] The materials used in each example are as follows.

[0125] [ingredient]

[0126] · A-1: ​​Addition reaction curing type silicone resin (manufactured by Asahi Kasei Wacker Silicone Co., Ltd., product name “SEMICOSIL 989 / 1K”, containing platinum catalyst).

[0127] · B1-1: Flake-shaped silver powder (Manufactured by Tokuriki Chemical Research Institute, Inc., Product name "TC-20V", Average particle size: 3.6 μm, Tap density: 3 g / cm³ 3 ).

[0128] · B1-2: Flake-shaped silver powder (Manufactured by Ames Goldsmith, Trade name "SF70M", average particle size: 2.1 μm, tap density: 3.15 g / cm³ 3 ).

[0129] · B1-3: Flake-shaped silver powder (Manufactured by Tokuriki Chemical Research Institute, Inc., Product name "TC-506", Average particle size: 6.7 μm, Tap density: 5.5 g / cm³ 3 ).

[0130] · B1-4: Flake-shaped silver powder (Manufactured by Tokuriki Chemical Research Institute, Inc., Product name "TC-25 A", Average particle size: 7.7 μm, Tap density: 3.5 g / cm³ 3 ).

[0131] · B2-1: Irregular silver powder (Manufactured by Yokosawa Chemical Co., Ltd., Trade name "Y-AF-K", Average particle size: 3μm, Tap density: 1.15g / cm³) 3 ).

[0132] · B2-2: Irregular silver powder (aggregate) (Manufactured by Ames Goldsmith, Trade name "SPK-1", average particle size: 3μm, tap density: 0.75g / cm³) 3 ).

[0133] · B2-3: Irregular silver powder (Manufactured by Ames Goldsmith, Trade name "SPG", average particle size: 5.36 μm, tap density: 1 g / cm³) 3 ).

[0134] · B2-4: Irregular silver powder (aggregate) (Manufactured by Ames Goldsmith, Trade name "SPI", average particle size: 4.54 μm, tap density: 1.1 g / cm³ 3 ).

[0135] · B2-5: Irregular silver powder (Manufactured by Tokuriki Chemical Research Institute, Inc., Trade name "C-34", average particle size: 0.34 μm, tap density: 2.25 g / cm³) 3 ).

[0136] · B2-6: Irregular silver powder (aggregate) (Manufactured by Tokuriki Chemical Research Institute, Inc., Trade name "E-20", Average particle size: 10.8 μm, Tap density: 2 g / cm³) 3 ).

[0137] · B2-7: Irregular silver powder (Manufactured by Yokosawa Chemical Co., Ltd., Trade name "Y-AE-K", Average particle size: 2 μm, Tap density: 1.3 g / cm³ 3 ).

[0138] · B2-8: Irregular silver powder (manufactured by Mitsui Metal Mining Co., Ltd., trade name "SPN10JS", average particle size: 2μm, tap density: 5.3g / cm³)3 ).

[0139] · B3-1: Spherical silver powder (Manufactured by DOWA Electronics Co., Ltd., average particle size: 1.6 μm, tap density: 3.8 g / cm³) 3 ).

[0140] [Examples 1–29]

[0141] According to the formulations shown in Tables 1 to 3, a total of 100 parts by mass of silicone resin (A) and conductive powder (B) were mixed and dispersed in 11 parts by mass of solvent (dodecane) to obtain a conductive paint with a solid content concentration of 90% by mass. Additionally, blank spaces in Tables 1 to 3 indicate that the component was not included.

[0142] A conductive paint was applied to a substrate made of silicone rubber material with a width of 15 mm, a length of 70 mm, and a thickness of 100 μm by screen printing to form a pattern with a width of 1 mm, a length of 50 mm, and a thickness of 20 μm. After that, the substrate was dried and cured at 160°C for 60 minutes to produce a test specimen with a circuit pattern formed on it.

[0143] For the obtained test specimens, conductivity, rate of change of resistance value, and durability were evaluated as follows. The results are shown in Tables 1 to 3.

[0144] (1) Evaluation of challenge

[0145] The electrical resistance value between the two ends in the longitudinal direction of the circuit pattern was measured using a digital multimeter (manufactured by ADC Co., Ltd.), and the conductivity was evaluated according to the following evaluation criteria.

[0146] A: The electrical resistance value is less than 10Ω.

[0147] B: The electrical resistance value is 10Ω or more and less than 150Ω.

[0148] C: The electrical resistance value is 150Ω or higher.

[0149] (2) Evaluation of the rate of change of resistance value

[0150] A circuit pattern with an initial length of 50 mm was stretched to 60 mm and then returned to its initial length of 50 mm. This stretching was repeated 100 times at a stretching speed of 500 mm / min to perform a resistance value change test. Afterward, the electrical resistance value between the two ends in the longitudinal direction of the circuit pattern was measured, the rate of change of resistance value (([electrical resistance value at the 100th stretching cycle] - [electrical resistance value before the test]) / [electrical resistance value before the test] × 100 (%)) was calculated, and conductivity was evaluated according to the following evaluation criteria.

[0151] A: The rate of change is less than 2000%.

[0152] B: The rate of change is 2000% or more and less than 4000%.

[0153] C: The rate of change is 4000% or more.

[0154] (3) Evaluation of durability

[0155] A resistance value change test was performed in the same manner as (2). The difference between the rate of change of the resistance value at the 10th expansion cycle and the rate of change of the resistance value at the 100th expansion cycle ([rate of change of the resistance value at the 100th expansion cycle] - [rate of change of the resistance value at the 10th expansion cycle] (%)) was calculated, and the conductivity was evaluated according to the following evaluation criteria.

[0156] A: The difference in the rate of change is less than 20%.

[0157] B: The difference in the rate of change is 20% or more and less than 40%.

[0158] C: The difference in the rate of change is 40% or more.

[0159]

[0160]

[0161]

[0162] The conductive paints obtained in Examples 2–8, 10, 14, 16–19, and 22–27 were able to form a film with excellent conductivity, excellent durability even when subjected to repeated stretching, and a small rate of change in resistance value.

[0163] In contrast, the coating film formed by the conductive paint of Example 1, in which the mass ratio (B1 / B2) of the conductive powder (B1) and the conductive powder (B2) is 95 / 5, had poor durability.

[0164] The coating film formed by the conductive paint of Example 9, which contains flake-shaped silver powder with an average particle size of 7.7 μm and does not contain flake-shaped conductive powder (B1) with an average particle size of 1 to 7 μm, had poor durability.

[0165] The coating film formed with the conductive paint of Example 11, where X1+X2 is 281, showed a large change in resistance value as it was repeatedly stretched and contracted. In addition, its durability was poor.

[0166] A coating film formed by the conductive paint of Example 12, which contains irregular silver powder with an average particle size of 0.34 μm and does not contain irregular conductive powder (B2) with an average particle size of 1 to 6 μm, had poor conductivity and durability.

[0167] The coating film formed by the conductive paint of Example 13, which contains irregular silver powder with an average particle size of 10.8 μm and does not contain irregular conductive powder (B2) with an average particle size of 1 to 6 μm, had poor durability.

[0168] The coating film formed with the conductive paint of Example 15, where X1+X2 is 92.82, showed a large change in resistance value as it was repeatedly stretched and contracted. In addition, its durability was poor.

[0169] A coating film formed by the conductive paint of Example 20, in which the mass ratio (B1 / B2) of the conductive powder (B1) and the conductive powder (B2) is 35 / 65, showed a significant change in resistance value as it was repeatedly stretched. In addition, its durability was poor.

[0170] The coating film formed by the conductive paint of Example 21, in which the mass ratio (A / B) of silicone resin (A) and conductive powder (B) is 8 / 92, had poor durability.

[0171] A coating film formed by the conductive paint of Example 28, in which the mass ratio (A / B) of silicone resin (A) and conductive powder (B) is 40 / 60, had poor conductivity and durability.

[0172] A coating film formed by the conductive paint of Example 29, which contains spherical conductive powder (B3) with an average particle size of 1.6 μm instead of irregular conductive powder (B2) with an average particle size of 1 to 6 μm, showed a large change in resistance value when repeatedly stretched and contracted. In addition, the durability was poor. Industrial applicability

[0173] The conductive paint of the present invention is useful as a paint for forming circuits of electronic components such as touch panel circuits, flexible substrates, and wearable devices, because it can form a film with excellent durability even when stretched and contracted repeatedly and with a small rate of change in resistance value. Explanation of the symbols

[0174] 10: Circuit assembly 11: Substrate 12: Circuit

Claims

Claim 1 A conductive paint comprising a silicone resin (A) and a conductive powder (B), wherein the mass ratio (A / B) of the silicone resin (A) and the conductive powder (B) is 10 / 90 to 35 / 65, and the conductive powder (B) comprises flake-shaped conductive powder (B1) having an average particle size of 1 to 7 μm and irregularly shaped conductive powder (B2) having an average particle size of 1 to 6 μm, wherein the mass ratio (B1 / B2) of the conductive powder (B1) and the conductive powder (B2) is 40 / 60 to 90 / 10, and satisfies the following equation (1). 100 ≤ X1 + X2 ≤ 260 ···(1) X1 = (average particle size of conductive powder (B1) / tap density of conductive powder (B1)) × (content of conductive powder (B1) relative to the total mass of conductive powder (B)) X2 = (conductive Average particle size of powder (B2) / Tap density of conductive powder (B2) × (Content of conductive powder (B2) relative to the total mass of conductive powder (B)) Claim 2 A circuit forming body formed by forming a circuit on a substrate using a coating film obtained by using the conductive paint described in claim 1.

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