Composite fine particle

Abstract

In one embodiment, the present invention relates to a composite fine particle in which a part of the surface of a copper fine particle is coated with a vinyl-based polymer P, wherein the primary particle diameter of the composite fine particle is 50-300 nm and the ratio (carbon content / BET specific surface area) of the carbon content (mass%) of the composite fine particle to the BET specific surface area (m2 / g) of the composite fine particle is 0.020-0.060. In another embodiment, the present invention relates to a composite fine particle dispersion containing the composite fine particle. In another embodiment, the present invention relates to a wiring pattern or a bonding layer, which is a heat-treated product of the composite fine particle dispersion.

Description

composite fine particles

[0001] The present invention relates to composite microparticles, a composite microparticle dispersion containing the composite microparticles, and a wiring pattern and a bonding layer formed using the composite microparticle dispersion.

[0002] Because copper has excellent electrical and thermal conductivity, it is widely used as a material for conductive wiring, heat transfer, heat exchange, and heat dissipation, as well as a joining material for joining objects. When used as a conductive wiring material, a copper nanoparticle dispersion, in which copper nanoparticles are dispersed, is applied to the object in any shape using various coating methods and then fired to form a conductive wiring pattern. When used as a joining material, various techniques have been proposed in which a copper nanoparticle dispersion, in which copper nanoparticles are dispersed, is applied to the object using various coating methods and then fired to join the objects.

[0003] For example, Japanese Patent Publication No. 2024-8681 (Patent Document 1) contains the BET specific surface area (m²). 2 A copper powder is disclosed in which the ratio of carbon content (mass%) to carbon ( / g) (C / SSA) is 0.07 or less, and in the C1s spectrum obtained by X-ray photoelectron spectroscopy, the peak area ratio (A2 / A1) of the peak area A2 having a peak top in the range of 288 eV to 289.2 eV to the peak area A1 having a peak top in the range of 284 eV to 285 eV is 0.5 or more. Furthermore, International Publication No. 2023 / 013034 (Patent Document 2) discloses a copper nanoparticle dispersion containing copper nanoparticles A dispersed in polymer B and a dispersion medium C, wherein polymer B includes structural units derived from monomer (b-1) having a carboxyl group and structural units derived from monomer (b-2) having a polyalkylene glycol segment, the content of polyalkylene glycol segments in polymer B is 55% by mass or more and 97% by mass or less, the acid value of polymer B is 20 mg KOH / g or more and 250 mg KOH / g or less, and the dispersion medium C includes at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivatives, terpene alcohols, glycerin and glycerin derivatives.

[0004] The present inventors have found that copper fine particles are coated with a vinyl polymer P, and the primary particle size and BET specific surface area (m²) are such that copper fine particles are coated with a vinyl polymer P. 2 We have found that composite microparticles in which the ratio of carbon content (mass%) to ( / g) is within a specific range can solve the above problems. The present invention relates to the following [1] to [6]. [1] A composite microparticle in which a part of the surface of copper microparticles is coated with a vinyl polymer P, the primary particle diameter of the composite microparticle is 50 nm or more and 300 nm or less, and the BET specific surface area (m²) of the composite microparticle 2 [1] A composite fine particle having a ratio of carbon content (mass%) of the composite fine particle to (g) (carbon content / BET specific surface area) of 0.020 or more and 0.060 or less. [2] A method for producing composite fine particles as described in [1], comprising the following steps (1) to (3): Step (1): A step of preparing a mixed solution containing copper oxide, a vinyl polymer P, and a dispersion medium. Step (2): A step of reducing copper oxide with a reducing agent. Step (3): A step of separating composite fine particles from the dispersion of composite fine particles obtained in step (2), which contains copper fine particles and a vinyl polymer P that covers a part of its surface. [3] A composite fine particle dispersion containing the composite fine particles described in [1]. [4] A wiring pattern which is a heat-treated product of the composite fine particle dispersion described in [3]. [5] A bonding layer which is a heat-treated product of the composite fine particle dispersion described in [3]. [6] Use of the composite fine particle dispersion described in [3] as a bonding material for bonding objects to be bonded together.

[0005] In this invention, "composite fine particles in which a portion of the surface of copper fine particles is coated with a vinyl polymer P" is synonymous with "composite fine particles containing copper fine particles and a vinyl polymer that coats a portion of the surface of copper fine particles." "Heat-treated product" refers to a product obtained by heat-treating a composite fine particle dispersion to volatilize volatile components such as the dispersion medium and sinter the composite fine particles.

[0006] When forming conductive wiring, the heat resistance of the object to be printed is low, so after applying the copper microparticle dispersion, it is necessary to sinter it at a low temperature of 230°C or less and for a short time. Furthermore, when used as a bonding material, from the viewpoint of production process and environmental impact, it is required that the copper microparticle dispersion be sintered at a low temperature and for a short time to obtain a strong bonding layer. As described above, there is a need for improved low-temperature sintering speed for copper microparticles, specifically sintering at a low temperature of 230°C or less and for a short time. In the copper powder disclosed in Patent Document 1, the low-temperature sinterability has been studied, but there were issues with the sintering speed. Similarly, in the copper microparticle dispersion disclosed in Patent Document 2, the bonding strength when used as a bonding material has been studied, but there were issues with low-temperature sinterability and low-temperature sintering speed. The present invention relates to composite microparticles that have excellent low-temperature sintering speed, a composite microparticle dispersion containing said composite microparticles, and a wiring pattern and bonding layer formed using said composite microparticle dispersion.

[0007] [Composite Fine Particles] The composite fine particles of the present invention comprise copper fine particles and a vinyl polymer P that coats a portion of the surface of the copper fine particles, wherein the primary particle diameter of the composite fine particles is 50 nm or more and 300 nm or less, and the BET specific surface area (m²) of the composite fine particles is 2 The ratio of the carbon content (mass%) of composite fine particles to the total mass ( / g) (carbon content / BET specific surface area) is 0.020 or more and 0.060 or less.

[0008] The composite microparticles of the present invention exhibit excellent low-temperature sintering speed. The reason for this is not entirely clear, but it is thought to be as follows. The composite microparticles of the present invention have a structure that includes copper microparticles and a vinyl polymer P that coats a portion of the surface of the copper microparticles. Therefore, when the composite microparticles of the present invention are dispersed in various dispersion media, aggregation of the copper microparticles is suppressed, and the copper microparticles are stably dispersed. As a result, the composite microparticle dispersion containing the composite microparticles of the present invention can be coated in a close-packed state, so when sintered, a strong sintered body can be formed in a short time, and the low-temperature sintering speed is improved. Furthermore, the composite microparticles of the present invention have a BET specific surface area (m²). 2The ratio of carbon content (mass%) to copper (carbon content / BET specific surface area) is 0.020 or higher, thus containing a sufficient amount of vinyl polymer P to improve the dispersibility of copper nanoparticles. Therefore, when composite nanoparticles containing copper nanoparticles are sintered, a strong copper sintered body can be formed in a short time, improving the low-temperature sintering rate. Furthermore, in the composite nanoparticles of the present invention, the ratio (carbon content / BET specific surface area) is 0.060 or lower, so the copper surface of the copper nanoparticles is adequately exposed, and the proportion of organic compounds in the composite nanoparticles is not too high. Therefore, the low-temperature sinterability of the composite nanoparticles containing copper nanoparticles is improved, and the low-temperature sintering rate is improved. Moreover, in the composite nanoparticles of the present invention, its BET specific surface area (m²) 2 The ratio of carbon content (mass%) to total material ( / g) (carbon content / BET specific surface area) is within the above range, and the primary particle size is 50 nm or larger, which suppresses the oxidation of copper nanoparticles that cause a decrease in sintering rate, thus improving the low-temperature sintering rate. Furthermore, the primary particle size of the composite nanoparticles is 300 nm or smaller, which facilitates the melting of copper nanoparticles when sintering the composite nanoparticles containing copper nanoparticles, thus improving low-temperature sinterability and improving the low-temperature sintering rate.

[0009] According to the present invention, it is possible to provide composite microparticles that exhibit excellent low-temperature sintering speed, a composite microparticle dispersion containing the composite microparticles, and a wiring pattern and bonding layer formed using the composite microparticle dispersion.

[0010] The primary particle diameter of the composite microparticles of the present invention is 50 nm or more, preferably 80 nm or more, more preferably 100 nm or more, even more preferably 120 nm or more, still more preferably 150 nm or more, from the viewpoint of improving the sinterability at low temperature and the low-temperature sintering rate. And from the viewpoint of improving the meltability during sintering, improving the sinterability at low temperature, and improving the low-temperature sintering rate, it is 300 nm or less, preferably 280 nm or less, more preferably 260 nm or less, even more preferably 240 nm or less, still more preferably 230 nm or less. The primary particle diameter of the composite microparticles is measured by the method described in the examples. The primary particle diameter of the composite microparticles can be adjusted by the production conditions of the composite microparticles such as the reduced metal ratio, the type and amount of the reducing agent, the type and amount of the vinyl-based polymer P, the reduction temperature, and the reduction time.

[0011] In the composite microparticles of the present invention, the ratio of the carbon content (mass%) to the BET specific surface area (m 2 / g) (carbon content / BET specific surface area) is 0.020 or more, preferably 0.025 or more, more preferably 0.030 or more, still more preferably 0.035 or more, even more preferably 0.038 or more, still more preferably 0.040 or more, from the viewpoint of improving the sinterability at low temperature and the low-temperature sintering rate. And from the viewpoint of improving the sinterability at low temperature and the low-temperature sintering rate, it is 0.060 or less, preferably 0.058 or less, more preferably 0.055 or less, still more preferably 0.053 or less, even more preferably 0.052 or less, still more preferably 0.045 or less. The ratio (carbon content / BET specific surface area) can be determined by the method described in the examples.

[0012] In the composite microparticles of the present invention, the BET specific surface area (m 2 / g) is preferably 1.0 m 2 / g or more, more preferably 1.2 m 2 / g or more, still more preferably 1.5 m 2 / g or more, even more preferably 1.7 m 2The value should be 5.0 m or more, and from the viewpoint of improving sinterability at low temperatures and improving the low-temperature sintering rate, it is preferable. 2 / g or less, more preferably 3.5m 2 / g or less, more preferably 3.2m 2 / g or less, more preferably 3.0m 2 It is less than or equal to / g. The BET specific surface area of ​​the composite fine particles is measured by the method described in the examples. The BET specific surface area of ​​the composite fine particles can be adjusted by the reducing metal ratio, the type and amount of reducing agent, the type and amount of vinyl polymer P, and the manufacturing conditions of the copper fine particles, such as the reduction temperature and reduction time.

[0013] The content of vinyl polymer P in the composite fine particles of the present invention is preferably greater than 0.05% by mass, more preferably 0.10% by mass or more, even more preferably 0.15% by mass or more, and from the viewpoint of improving the dispersibility of the composite fine particles, improving sinterability at low temperatures, and improving the sintering rate, when the composite fine particles of the present invention are considered to be 100% by mass. From the same viewpoint, it is preferably 0.40% by mass or less, more preferably 0.30% by mass or less, and even more preferably 0.25% by mass or less. The content of vinyl polymer P in the composite fine particles can be calculated from the amount of carbon measured by high-frequency induction heating furnace combustion-infrared absorption method and the structure and composition of the monomer of vinyl polymer P.

[0014] The copper fine particle content in the composite fine particles of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and preferably 99.9% by mass or less, from the viewpoint of improving the dispersibility of the composite fine particles, improving sinterability at low temperatures, and improving the sintering rate, when the composite fine particles of the present invention are considered to be 100% by mass. The copper fine particle content in the composite fine particles can be calculated by thermogravimetric analysis from the ratio of the weight loss to the remaining weight when heated from room temperature to 550°C at a heating rate of 10°C / min.

[0015] The mass ratio of vinyl polymer P to copper nanoparticles in the composite fine particles of the present invention (vinyl polymer P / copper nanoparticles) is preferably 0.001 or higher, more preferably 0.002 or higher, from the viewpoint of improving the dispersibility of the composite fine particles, improving sinterability at low temperatures, and improving the sintering rate, and similarly, preferably 0.003 or lower, more preferably 0.002 or lower.

[0016] The composite fine particles of the present invention may contain a small amount of solvent (hereinafter also referred to as dispersion medium) used to disperse the vinyl polymer P and the copper raw material compound. From the viewpoint of obtaining a composite fine particle dispersion with stable performance, the content of the dispersion medium in the composite fine particles of the present invention is preferably 1% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less.

[0017] <Vinyl Polymer P> In the composite fine particles of the present invention, a portion of the surface of the copper fine particles is coated with a vinyl polymer P. Since the composite fine particles of the present invention consist of copper fine particles and a vinyl polymer P that coats a portion of the surface of the copper particles, they exhibit excellent dispersibility in the dispersion medium C described later and excellent low-temperature sintering speed. A vinyl polymer refers to a polymer obtained by addition polymerization of monomers having vinyl groups. Examples of vinyl polymers P in the present invention include acrylic resins, styrene resins, styrene-acrylic resins, and acrylic silicone resins.

[0018] In the present invention, the vinyl polymer P preferably comprises at least one selected from a monomer having a carboxyl group (p-1), a monomer having a polyalkylene glycol segment (p-2), and a monomer having a hydrophobic monomer (p-3), from the viewpoint of improving the dispersibility of composite fine particles, improving sinterability at low temperatures, and improving the low-temperature sintering rate. More preferably comprises at least two selected from a monomer having a carboxyl group (p-1), a monomer having a polyalkylene glycol segment (p-2), and a monomer having a hydrophobic monomer (p-3). Even more preferably comprises a monomer having a carboxyl group (p-1), a monomer having a polyalkylene glycol segment (p-2), and at least one selected from a monomer having a hydrophobic monomer (p-3). Even more preferably comprises a monomer having a carboxyl group (p-1) and a monomer having a polyalkylene glycol segment (p-2).

[0019] (Carboxyloid group-containing monomer (p-1)) Examples of monomer (p-1) having a carboxyloid group (hereinafter also referred to as "monomer (p-1)") include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and 2-methacryloyloxymethyl succinic acid; and unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, and citraconic acid. The unsaturated dicarboxylic acid may also be an anhydride. Monomer (p-1) may be used alone or in combination of two or more. From the viewpoint of improving the dispersibility of composite fine particles containing copper fine particles, improving sinterability at low temperatures, and improving the low-temperature sintering rate, monomer (p-1) is preferably at least one selected from (meth)acrylic acid and maleic acid, more preferably (meth)acrylic acid, and even more preferably methacrylic acid. In this specification, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid. The same applies to "(meth)acrylic acid" below.

[0020] (Monomers (p-2) having polyalkylene glycol segments) Examples of monomers (p-2) having polyalkylene glycol segments (hereinafter also referred to as "monomers (p-2)") include polyalkylene glycol (meth)acrylate, alkoxy polyalkylene glycol (meth)acrylate, phenoxy polyalkylene glycol (meth)acrylate, etc. Monomers (p-2) may be used individually or in combination of two or more. In this specification, "(meth)acrylate" refers to at least one selected from acrylate and methacrylate. The same applies to "(meth)acrylate" below.

[0021] From the viewpoint of improving the dispersibility of composite fine particles containing copper fine particles, improving sinterability at low temperatures, and improving the low-temperature sintering rate, the monomer (p-2) is preferably at least one selected from polyalkylene glycol (meth)acrylate and alkoxy polyalkylene glycol (meth)acrylate, more preferably alkoxy polyalkylene glycol (meth)acrylate, and even more preferably alkoxy polyalkylene glycol methacrylate.

[0022] The number of carbon atoms in the alkoxy group of alkoxy polyalkylene glycol (meth)acrylate is preferably 1 to 18, more preferably 1 to 14, and even more preferably 1 to 12, from the viewpoint of improving the dispersibility of composite fine particles containing copper fine particles, improving sinterability at low temperatures, and improving the low-temperature sintering rate. Examples of alkoxy polyalkylene glycol (meth)acrylate include methoxy polyalkylene glycol (meth)acrylate, ethoxy polyalkylene glycol (meth)acrylate, propoxy polyalkylene glycol (meth)acrylate, butoxy polyalkylene glycol (meth)acrylate, octoxy polyalkylene glycol (meth)acrylate, and lauroxy polyalkylene glycol (meth)acrylate. Among these, methoxy polyalkylene glycol (meth)acrylate is preferred, and methoxy polyalkylene glycol methacrylate is preferred.

[0023] The monomer (p-2) polyalkylene glycol segment preferably contains units derived from alkylene oxide having 2 to 4 carbon atoms, from the viewpoint of improving the dispersibility of composite fine particles containing copper fine particles, improving sinterability at low temperatures, and improving the low-temperature sintering rate. Examples of alkylene oxides include ethylene oxide, propylene oxide, and butylene oxide, and preferably at least one selected from ethylene oxide and propylene oxide, and more preferably ethylene oxide. The number of alkylene oxide-derived units in the polyalkylene glycol segment is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, and preferably 100 or less, more preferably 70 or less, even more preferably 50 or less, even more preferably 40 or less, even more preferably 35 or less, and even more preferably 23 or less, from the viewpoint of improving the dispersibility of composite fine particles containing copper fine particles, improving sinterability at low temperatures, and improving the low-temperature sintering rate. The polyalkylene glycol segment may also be a copolymer containing units derived from ethylene oxide and units derived from propylene oxide, from the viewpoint of improving the dispersibility of composite fine particles containing copper fine particles, improving sinterability at low temperatures, and improving the low-temperature sintering rate. The copolymer containing units derived from ethylene oxide and units derived from propylene oxide may be a block copolymer, a random copolymer, or an alternating copolymer.

[0024] Specific examples of commercially available monomers (p-2) include NK ester AM-90G, AM-130G, AM-230G, AMP-20GY, M-20G, M-40G, M-90G, M-230G, etc., manufactured by Shin Nakamura Chemical Industry Co., Ltd.; and Bremmer PE-90, PE-200, PE-350, PME-100, P, etc., manufactured by NOF Corporation. Examples include ME-200, PME-400, PME-1000, PME-4000, PP-500, PP-500D, PP-800, PP-1000, PP-2000D, AP-150, AP-400, AP-550, 50PEP-300, 50POEP-800B, 43PAPE-600B, PLE-1300, and others.

[0025] (Hydrophobic monomer (p-3)) In this specification, "hydrophobic monomer" means a monomer in which the amount dissolved when dissolved in 100 g of ion-exchanged water at 25°C until saturated is less than 10 g. The amount of monomer (p-3) dissolved is preferably 5 g or less, more preferably 1 g or less, from the viewpoint of improving sinterability at low temperatures and improving the low-temperature sintering rate. The monomer (p-3) is preferably at least one selected from aromatic group-containing monomers and (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols.

[0026] The aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group with 6 to 22 carbon atoms, which may have substituents containing heteroatoms, from the viewpoint of improving the dispersibility of composite fine particles containing copper fine particles, improving sinterability at low temperatures, and improving the low-temperature sintering rate. More preferably, it is at least one selected from styrene monomers and aromatic group-containing (meth)acrylates. The molecular weight of the aromatic group-containing monomer is preferably less than 500. Examples of styrene monomers include styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), and divinylbenzene. Examples of aromatic group-containing (meth)acrylates include phenyl (meth)acrylate, benzyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

[0027] (Meth)acrylates having hydrocarbon groups derived from aliphatic alcohols are preferably those having hydrocarbon groups derived from aliphatic alcohols having 1 to 22 carbon atoms, more preferably those having hydrocarbon groups derived from aliphatic alcohols having 1 to 12 carbon atoms, even more preferably those having hydrocarbon groups derived from aliphatic alcohols having 1 to 8 carbon atoms, and even more preferably those having hydrocarbon groups derived from aliphatic alcohols having 1 to 4 carbon atoms. Examples of (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols include (meth)acrylates having linear alkyl groups, (meth)acrylates having branched alkyl groups, and (meth)acrylates having alicyclic alkyl groups. Examples of (meth)acrylates having a linear alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. Examples of (meth)acrylates having a branched alkyl group include isopropyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isopentyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, isododecyl (meth)acrylate, isostearyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of (meth)acrylates having an alicyclic alkyl group include cyclohexyl (meth)acrylate. The monomer (p-3) may be used alone or in combination of two or more types.

[0028] The monomer (p-3) is preferably at least one selected from an aromatic group-containing monomer and a (meth)acrylate having a linear alkyl group from the viewpoint of improving the dispersibility of the composite fine particles containing copper fine particles, improving the sinterability at low temperature, and improving the low-temperature sintering rate. More preferably, it is at least one selected from a styrene-based monomer and a (meth)acrylate having a linear alkyl group with 1 to 4 carbon atoms. Even more preferably, it is at least one selected from styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate. Even more preferably, it is at least one selected from styrene and methyl (meth)acrylate. Even more preferably, it is at least one selected from methyl (meth)acrylate. Even more preferably, it is methyl methacrylate.

[0029] When the vinyl polymer P contains a structural unit derived from the monomer (p-1), the content of the monomer (p-1) in the raw material monomer during the production of the vinyl polymer P or the content of the structural unit derived from the monomer (p-1) in the vinyl polymer P is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 2.5% by mass or more, even more preferably 3% by mass or more, even more preferably 4% by mass or more, even more preferably 5% by mass or more from the viewpoint of improving the dispersibility of the composite fine particles containing copper fine particles, improving the sinterability at low temperature, and improving the low-temperature sintering rate. And preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, even more preferably 15% by mass or less, even more preferably 10% by mass or less, even more preferably 7% by mass or less.

[0030] When the vinyl polymer P contains constituent units derived from monomer (p-2), the content of monomer (p-2) in the raw material monomer during the production of the vinyl polymer P, or the content of constituent units derived from monomer (p-2) in the vinyl polymer P, is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 85% by mass or more, and preferably 99% by mass or less, more preferably 98% by mass or less, even more preferably 97% by mass or less, even more preferably 96% by mass or less, and even more preferably 95% by mass or less.

[0031] When the vinyl polymer P contains constituent units derived from monomer (p-3), the content of monomer (p-3) in the raw material monomer during the production of the vinyl polymer P, or the content of constituent units derived from monomer (p-3) in the vinyl polymer P, is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 1.5% by mass or more, even more preferably 2% by mass or more, even more preferably 2.5% by mass or more, even more preferably 3% by mass or more, and preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, even more preferably 15% by mass or less, even more preferably 10% by mass or less, and even more preferably 3.5% by mass or less.

[0032] When the vinyl polymer P contains a structural unit derived from monomer (p-1) and a structural unit derived from monomer (p-2), the total content of monomer (p-1) and monomer (p-2) in the raw material monomers during the production of the vinyl polymer P, or the total content of the structural unit derived from monomer (p-1) and the structural unit derived from monomer (p-2) in the vinyl polymer P, from the viewpoint of improving the dispersibility of the composite fine particles containing copper fine particles, improving the sintering property at low temperature, and improving the low-temperature sintering rate, is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably substantially 100% by mass. Examples of the components contained unintentionally include monomers other than monomer (b-1) and monomer (b-2) contained in the raw material monomers (b-1) and (b-2).

[0033] When the vinyl polymer P contains a structural unit derived from monomer (p-2), the content of the polyalkylene glycol segment in the vinyl polymer P, from the viewpoint of improving the dispersibility of the composite fine particles containing copper fine particles, improving the sintering property at low temperature, and improving the low-temperature sintering rate, is preferably 55% by mass or more, more preferably 60% by mass or more, still more preferably 63% by mass or more, even more preferably 65% by mass or more, and even more preferably 69% by mass or more, and is preferably 97% by mass or less, more preferably 96% by mass or less, still more preferably 95% by mass or less, even more preferably 94% by mass or less, even more preferably 93% by mass or less, even more preferably 92% by mass or less, and even more preferably 88% by mass or less.

[0034] The number-average molecular weight Mn of the vinyl polymer P is preferably 2,000 or more, more preferably 4,000 or more, even more preferably 6,000 or more, even more preferably 7,000 or more, and even more preferably 8,100 or more, from the viewpoint of improving the dispersibility of composite fine particles containing copper fine particles, improving sinterability at low temperatures, and improving the low-temperature sintering rate. Furthermore, from the viewpoint of improving the thermal decomposition properties of the vinyl polymer P, improving sinterability at low temperatures, and improving the low-temperature sintering rate, it is preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, even more preferably 10,000 or less, and even more preferably 8,600 or less. The number-average molecular weight Mn of the vinyl polymer P is measured by the method described in the examples.

[0035] The acid value of the vinyl polymer P is preferably 4 mg KOH / g or more, more preferably 6 mg KOH / g or more, even more preferably 8 mg KOH / g or more, even more preferably 10 mg KOH / g or more, even more preferably 12 mg KOH / g or more, even more preferably 15 mg KOH / g or more, and preferably 250 mg KOH / g or less, more preferably 200 mg KOH / g or less, even more preferably 120 mg KOH / g or less, even more preferably 80 mg KOH / g or less, even more preferably 40 mg KOH / g or less, and even more preferably 28 mg KOH / g or less, from the viewpoint of improving the dispersibility of composite fine particles containing copper fine particles, improving sinterability at low temperatures, and improving the low-temperature sintering rate.

[0036] (Method for producing composite microparticles) Composite microparticles can be produced by preparing a mixed solution containing a copper raw material compound, a vinyl polymer P, and a dispersion medium, reducing the copper raw material compound with a reducing agent in this mixed solution to obtain copper microparticles, obtaining a dispersion of composite microparticles containing the copper microparticles and a vinyl polymer P that coats a part of their surface, and separating the composite particles from this dispersion. In the method for producing composite microparticles, a solvent for dispersing the copper raw material compound and the reducing agent, a complexing agent, etc., may be further added to the mixed solution as needed. In a preferred embodiment, the method for producing composite microparticles of the present invention is a method for producing composite microparticles in which a part of the surface of copper microparticles is coated with a vinyl polymer P, and comprises the following steps (1) to (3). Step (1): A step of preparing a mixed solution containing copper oxide, a vinyl polymer P, and a dispersion medium. Step (2): A step of reducing the copper oxide with a reducing agent. Step (3): A step of separating the composite microparticles from the dispersion of composite microparticles obtained in step (2), which contains copper microparticles and a vinyl polymer P that coats a part of their surface.

[0037] (Step (1)) In Step (1), for example, copper oxide, vinyl polymer P, and dispersion medium are added to the reaction vessel and stirred to prepare a mixture containing copper oxide, vinyl polymer P, and dispersion medium. The copper oxide is preferably copper oxide from the viewpoint of obtaining composite fine particles with excellent low-temperature sintering speed. The copper oxide is preferably cupric oxide and / or cuprous oxide, more preferably cupric oxide, from the viewpoint of obtaining composite fine particles with excellent low-temperature sintering speed. Examples of dispersion mediums include water, methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol. Among these, ethanol is preferably used as the solvent.

[0038] In step (1) above, the amount of copper oxide added is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 9% by mass or more, relative to the mixed liquid obtained in step (1), from the viewpoint of improving the dispersibility of the composite fine particles, improving sinterability at low temperatures, and improving the sintering rate. Similarly, from the same viewpoint, it is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 20% by mass or less.

[0039] In step (1) described above, the mass ratio of the amount of vinyl polymer P added to the amount of copper oxide added (vinyl polymer P / copper oxide) is preferably 0.001 or more, more preferably 0.002 or more, even more preferably 0.005 or more, from the viewpoint of improving the dispersibility of composite fine particles, improving sinterability at low temperatures, and improving the sintering rate, and from the same viewpoint, preferably 0.03 or less, more preferably less than 0.016, and even more preferably 0.01 or less.

[0040] In step (1) described above, the mass ratio of the amount of dispersion medium added to the amount of copper oxide added (dispersion medium / copper oxide) is preferably 1 or more, more preferably 1.5 or more, and even more preferably 2.5 or more, from the viewpoint of improving the dispersibility of composite fine particles, improving sinterability at low temperatures, and improving the sintering rate, and from the same viewpoint, preferably 100 or less, more preferably 20 or less, and even more preferably 10 or less.

[0041] (Step (2)) The reducing agent can be added in step (1) or step (2). From the viewpoint of efficiently obtaining composite fine particles, it is preferable to add the reducing agent in step (2) while raising the temperature of the mixture. Examples of the reducing agent include hydrazine compounds, boron compounds, inorganic salts, etc. Examples of hydrazine compounds include hydrazine, hydrazine hydrochloride, hydrazine sulfate, hydrated hydrazine (hydrazine monohydrate), etc. Examples of boron compounds include sodium borohydride, etc. Examples of inorganic salts include sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium nitrite, sodium hyponitrite, phosphorous acid, sodium phosphite, hypophosphorous acid, sodium hypophosphite, etc. Among these, from the viewpoint of obtaining composite fine particles with excellent low-temperature sintering speed, the reducing agent is preferably one or more selected from the group consisting of hydrazine compounds, more preferably hydrazine and hydrated hydrazine, and even more preferably hydrated hydrazine (hydrazine monohydrate). The reducing agent may be used individually or in combination of two or more types.

[0042] In step (2), the reduction of copper oxide with a reducing agent is preferably carried out by raising the temperature of the mixture obtained in step (1), from the viewpoint of obtaining composite fine particles with excellent low-temperature sintering speed. In step (2), the temperature of the mixture after raising the temperature is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher, from the viewpoint of reducing and making the particle size of the composite fine particles uniform, and preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower, from the viewpoint of obtaining composite fine particles stably. In step (2), the temperature of the mixture after raising the temperature is preferably maintained for 1 hour or more, more preferably 1.5 hours or more, even more preferably 2 hours or more, and similarly preferably 24 hours or less, more preferably 5 hours or less, and even more preferably 3 hours or less, from the viewpoint of obtaining composite fine particles with excellent low-temperature sintering speed. Step (2) may be carried out in an air atmosphere or in an inert gas atmosphere such as nitrogen gas.

[0043] In step (2) above, the molar ratio of the amount of reducing agent added to the amount of copper oxide added (reducing agent / copper oxide) is preferably 1.0 or higher, more preferably 1.2 or higher, and even more preferably 1.5 or higher, from the viewpoint of improving the dispersibility of composite fine particles, improving sinterability at low temperatures, and improving the sintering rate, and from the same viewpoint, preferably 5.0 or lower, more preferably 4.0 or lower, and even more preferably 3.0 or lower.

[0044] (Step (3)) Step (3) preferably includes a step of membrane treatment such as dialysis, vacuum filtration, pressure filtration, or ultrafiltration of the mixture obtained in step (2) and / or a step of centrifugal separation of the mixture obtained in step (2) from unreacted reducing agents, excess polymer P and other impurities and dispersion medium in the mixture obtained in step (2). Furthermore, from the viewpoint of obtaining composite fine particles with a low dispersion medium content, step (3) preferably further includes a vacuum drying step, more preferably a freeze-drying step.

[0045] <Applications of Composite Microparticles> The composite microparticles of the present invention have excellent low-temperature sinterability and low-temperature sintering speed, and can therefore be used to form conductive members for various electronic and electrical devices. Examples of such conductive members include those conventionally formed using conductive bonding agents such as solder. Furthermore, the composite microparticles of the present invention can be used to form conductive members that constitute antennas such as RFID (radio frequency identifier) ​​tags; capacitors such as MLCCs (multilayer ceramic capacitors); electronic paper; image display devices such as liquid crystal displays and organic EL displays; organic EL elements; organic transistors; wiring boards such as printed circuit boards and flexible circuit boards; organic solar cells; sensors such as flexible sensors, etc. Among these, the composite microparticles of the present invention are preferably used as a raw material for conductive bonding agents and preferably as a material for forming wiring boards such as printed circuit boards and flexible circuit boards.

[0046] [Composite Microparticle Dispersion] The composite microparticle dispersion of the present invention is prepared using the composite microparticles of the present invention as described above. That is, the composite microparticle dispersion of the present invention contains the composite microparticles of the present invention as described above. Because the composite microparticle dispersion of the present invention contains the composite microparticles described above, it exhibits excellent sinterability at low temperatures and excellent low-temperature sintering rate.

[0047] The composite microparticle dispersion of the present invention preferably contains a dispersion medium C, which is a solvent for dispersing the composite microparticles. That is, the composite microparticle dispersant of the present invention preferably contains the composite microparticles of the present invention and the dispersion medium C described above. As the dispersion medium C, from the viewpoint of improving sinterability at low temperatures and improving the low-temperature sintering rate, it preferably includes at least one selected from aliphatic monohydric alcohols, (poly)alkylene glycols, (poly)alkylene glycol derivatives, glycerin, and glycerin derivatives.

[0048] Examples of aliphatic monohydric alcohols include allyl alcohol, n-heptanol, n-octanol, 2-ethylhexanol, n-nonanol, and terpene alcohols. Preferred terpene alcohols include monoterpene alcohols such as α-terpineol, linalool, geraniol, and citronellol.

[0049] In this specification, "(poly)alkylene glycol" means at least one selected from alkylene glycols and polyalkylene glycols. Examples of alkylene glycols include ethylene glycol, propylene glycol, and butylene glycol (1,3-butanediol). Examples of polyalkylene glycols include diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, and polytetramethylene glycol. The number-average molecular weight of polyethylene glycol is preferably 70 to 1000, more preferably 80 to 500, and even more preferably 90 to 200, from the viewpoint of improving sinterability at low temperatures and improving the low-temperature sintering rate. The number-average molecular weight of polypropylene glycol is preferably 100 to 1000, more preferably 110 to 600, and even more preferably 120 to 500, from the viewpoint of improving sinterability at low temperatures and improving the low-temperature sintering rate. Among these, from the viewpoint of improving sinterability at low temperatures and increasing the low-temperature sintering rate, at least one selected from diethylene glycol and dipropylene glycol is preferred.

[0050] Examples of (poly)alkylene glycol derivatives include the following (poly)alkylene glycol alkyl ethers and (poly)alkylene glycol monoalkyl ether acetates, which are compounds in which the terminal hydroxyl groups of the (poly)alkylene glycol are etherified or esterified.

[0051] In this specification, "(poly)alkylene glycol alkyl ether" means at least one selected from alkylene glycol alkyl ethers and polyalkylene glycol alkyl ethers. Examples of alkylene glycol alkyl ethers include ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, and propylene glycol monobutyl ether. Examples of polyalkylene glycol alkyl ethers include diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and dipropylene glycol monomethyl ether.

[0052] In this specification, "(poly)alkylene glycol monoalkyl ether acetate" means at least one selected from alkylene glycol monoalkyl ether acetate and polyalkylene glycol monoalkyl ether acetate. Examples of alkylene glycol monoalkyl ether acetate include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate. Examples of polyalkylene glycol monoalkyl ether acetate include diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.

[0053] There are no particular restrictions on the glycerin derivative as long as it is a solvent containing a structure derived from glycerin. Examples include glycerin ether derivatives, glycerin ester derivatives, polyglycerin, and glycerin alkylene oxide adducts (e.g., ethylene oxide adducts and propylene oxide adducts). Preferred polyglycerins include, for example, diglycerin and triglycerin. Commercially available polyglycerins include, for example, polyglycerin #310, polyglycerin #500, and polyglycerin #750 manufactured by Sakamoto Pharmaceutical Co., Ltd. A preferred glycerin ether derivative is, for example, 3-(2-ethylhexyloxy)-1,2-propanediol. A preferred glycerin ester derivative is, for example, glyceryl triplylate (tributyline).

[0054] The dispersion medium C preferably contains (poly)alkylene glycol, and more preferably contains at least one selected from diethylene glycol and dipropylene glycol, from the viewpoint of improving sinterability at low temperatures and improving the low-temperature sintering rate.

[0055] In the composite fine particle dispersion of the present invention, the content of the dispersion medium C is preferably 3% by mass or more, more preferably 4% by mass or more, even more preferably 5% by mass or more, and even more preferably 6% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less, from the viewpoint of improving sinterability at low temperatures and improving the low-temperature sintering rate.

[0056] In the composite fine particle dispersion of the present invention, the content of composite fine particles is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 85% by mass or more, and preferably 97% by mass or less, more preferably 96% by mass or less, even more preferably 95% by mass or less, and even more preferably 94% by mass or less, from the viewpoint of improving sinterability at low temperatures and improving the low-temperature sintering rate.

[0057] (Production of Composite Microparticle Dispersion) The composite microparticle dispersion of the present invention is obtained by mixing the composite microparticles and dispersion medium C described above. The composite microparticle dispersion of the present invention can be produced by adding and mixing pre-prepared composite microparticles, dispersion medium C, and various additives as needed. Known methods can be used for mixing, and from the viewpoint of better dispersing the composite microparticles in the dispersion medium C, it is preferable to pre-mix the composite microparticles and dispersion medium C using an agate mortar and pestle or the like, and then further mix the resulting mixture using a stirring device such as a rotation-orbit stirring device. Alternatively, the composite microparticle dispersion can also be produced by adding the dispersion medium C and various additives as needed to a dispersion containing the composite microparticles obtained in the production of composite microparticles, and then vaporizing the liquid components other than the dispersion medium C and various additives at a predetermined temperature while stirring.

[0058] <Applications of the Composite Microparticle Dispersion> The composite microparticle dispersion of the present invention has excellent low-temperature sinterability and low-temperature sintering speed, and can therefore be used to form conductive members for various electronic and electrical devices. Examples of such conductive members include those conventionally formed using conductive bonding agents such as solder. Furthermore, the composite microparticle dispersion of the present invention is preferably used to form conductive members that constitute antennas such as RFID (radio frequency identifier) ​​tags; capacitors such as MLCCs (multilayer ceramic capacitors); electronic paper; image display devices such as liquid crystal displays and organic EL displays; organic EL elements; organic transistors; wiring boards such as printed circuit boards and flexible circuit boards; organic solar cells; and sensors such as flexible sensors. Among these, the composite microparticle dispersion of the present invention is preferably used as a conductive bonding agent and preferably as a material for forming wiring boards such as printed circuit boards and flexible circuit boards.

[0059] (Wiring Pattern) The wiring pattern of the present invention is a heat-treated product of the composite fine particle dispersion of the present invention described above. Because the composite fine particle dispersion of the present invention has the above-described characteristics, it has excellent low-temperature sinterability and low-temperature sintering speed, so the wiring pattern of the present invention can be formed at a low temperature of 230°C or less and in a short time. As a result, the wiring pattern of the present invention can be formed on a substrate with low high-temperature resistance, such as plastic. Because the wiring pattern of the present invention has the above characteristics, it is preferably used for forming wiring boards such as printed circuit boards and flexible circuit boards, which are substrates with low high-temperature resistance.

[0060] (Bonding Layer) The bonding layer of the present invention is a heat-treated product of the composite fine particle dispersion of the present invention described above. Because the composite fine particle dispersion of the present invention has the above-described characteristics, it has excellent low-temperature sinterability and low-temperature sintering speed, so the bonding layer of the present invention can be formed at a low temperature of 250°C or less and in a short time. As a result, the bonding layer of the present invention can be used for bonding materials with low high-temperature resistance, such as plastics, and for bonding members made of multiple different raw materials, such as metals and plastics. Because the bonding layer of the present invention has the above-described characteristics, it is preferably used for bonding materials with low high-temperature resistance.

[0061] This application further discloses the following inventions.

[0062] <1> A composite microparticle in which a portion of the surface of copper microparticles is coated with a vinyl polymer P, the primary particle diameter of the composite microparticle is 50 nm or more and 300 nm or less, and the BET specific surface area (m²) of the composite microparticle 2<1> A composite fine particle in which the ratio of the carbon content (mass%) of the composite fine particle to ( / g) (carbon content / BET specific surface area) is 0.020 or more and 0.060 or less. <2> The composite fine particle according to <1>, wherein the primary particle diameter of the composite fine particle is preferably 80 nm or more, more preferably 100 nm or more, even more preferably 120 nm or more, even more preferably 150 nm or more, and preferably 280 nm or less, even more preferably 260 nm or less, even more preferably 240 nm or less, and even more preferably 230 nm or less. <3> The composite fine particles according to <1> or <2> above, wherein the ratio (carbon content / BET specific surface area) is preferably 0.025 or more, more preferably 0.030 or more, even more preferably 0.035 or more, even more preferably 0.038 or more, even more preferably 0.040 or more, and preferably 0.058 or less, more preferably 0.055 or less, even more preferably 0.053 or less, even more preferably 0.052 or less, and even more preferably 0.045 or less. <4> The BET specific surface area is preferably 1.0 m 2 / g or more, more preferably 1.2m 2 / g or more, more preferably 1.5m 2 / g or more, more preferably 1.7m 2 It is 1 / g or more, and preferably 5.0 m 2 / g or less, more preferably 3.5m 2 / g or less, more preferably 3.2m 2 / g or less, more preferably 3.0m 2A composite fine particle according to any one of <1> to <3> above, wherein the density is less than or equal to / g. <5> A composite fine particle according to any one of <1> to <4> above, wherein the vinyl polymer P comprises at least one selected from a monomer having a carboxyl group (p-1), a monomer having a polyalkylene glycol segment (p-2), and a constituent unit having a hydrophobic monomer (p-3), and more preferably comprises at least two selected from a monomer having a carboxyl group (p-1), a monomer having a polyalkylene glycol segment (p-2), and a constituent unit having a hydrophobic monomer (p-3). <6> A composite fine particle according to any one of <1> to <5> above, wherein the vinyl polymer P comprises at least one selected from a monomer having a polyalkylene glycol segment (p-2) and a constituent unit having a hydrophobic monomer (p-3), and a constituent unit having a carboxyl group (p-1). <7> The composite microparticle according to any one of <1> to <6>, wherein the vinyl polymer P comprises a constituent unit derived from a monomer having a carboxyl group (p-1) and a constituent unit derived from a monomer having a polyalkylene glycol segment (p-2). <8> The composite microparticle according to any one of <5> to <7>, wherein the monomer having a carboxyl group (p-1) is one or more selected from (meth)acrylic acid, crotonic acid, 2-methacryloyloxymethyl succinic acid, maleic acid, itaconic acid, fumaric acid, and citraconic acid. <9> The composite microparticle according to any one of <5> to <7>, wherein the monomer having a polyalkylene glycol segment (p-2) is one or more selected from polyalkylene glycol (meth)acrylate, alkoxy polyalkylene glycol (meth)acrylate, and phenoxy polyalkylene glycol (meth)acrylate. <10> The composite fine particles according to <5> or <6>, wherein the hydrophobic monomer (p-3) is preferably at least one selected from aromatic group-containing monomers and (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols.<11> The composite fine particles according to any one of <5> to <8> above, wherein the content of monomers having a carboxyl group (p-1) in the raw material monomers during the production of vinyl polymer P, or the content of constituent units derived from monomers having a carboxyl group (p-1) in vinyl polymer P is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 2.5% by mass or more, even more preferably 3% by mass or more, even more preferably 4% by mass or more, even more preferably 5% by mass or more, and preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, even more preferably 15% by mass or less, even more preferably 10% by mass or less, and even more preferably 7% by mass or less. <12> The composite fine particles according to any one of <5> to <7> or <9> above, wherein the content of monomers (p-2) having polyalkylene glycol segments in the raw material monomers during the production of the vinyl polymer P, or the content of constituent units derived from monomers (p-2) having polyalkylene glycol segments in the vinyl polymer P, is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 85% by mass or more, and preferably 99% by mass or less, more preferably 98% by mass or less, even more preferably 97% by mass or less, even more preferably 96% by mass or less, and even more preferably 95% by mass or less. <13> The composite fine particles according to any one of <5>, <6>, or <10>, wherein the content of hydrophobic monomer (p-3) in the raw material monomer during the production of vinyl polymer P, or the content of constituent units derived from hydrophobic monomer (p-3) in vinyl polymer P, is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 1.5% by mass or more, even more preferably 2% by mass or more, even more preferably 2.5% by mass or more, even more preferably 3% by mass or more, and preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, even more preferably 15% by mass or less, even more preferably 10% by mass or less, and even more preferably 3.5% by mass or less.<14> The composite fine particles according to any one of <5> to <7>, <8> and <9> above, wherein the total content of monomers having carboxyl groups (p-1) and monomers having polyalkylene glycol segments (p-2) in the raw material monomers during the production of the vinyl polymer P, or the total content of constituent units derived from monomers having carboxyl groups (p-1) and constituent units derived from monomers having polyalkylene glycol segments (p-2) in the vinyl polymer P, is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably substantially 100% by mass. <15> The composite fine particles according to any one of <5> to <7> or <9> above, wherein the content of polyalkylene glycol segments in the vinyl polymer P is preferably 55% by mass or more, more preferably 60% by mass or more, even more preferably 63% by mass or more, even more preferably 65% ​​by mass or more, even more preferably 69% by mass or more, and preferably 97% by mass or less, more preferably 96% by mass or less, even more preferably 95% by mass or less, even more preferably 94% by mass or less, even more preferably 93% by mass or less, even more preferably 92% by mass or less, and even more preferably 88% by mass or less. <16> The composite fine particles according to any one of <1> to <15> above, wherein the number average molecular weight of the vinyl polymer P is preferably 2,000 or more, more preferably 4,000 or more, even more preferably 6,000 or more, even more preferably 7,000 or more, even more preferably 8,100 or more, and preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, even more preferably 10,000 or less, and even more preferably 8,600 or less.<17> The composite fine particles according to any one of <1> to <16> above, wherein the acid value of the vinyl polymer P is preferably 4 mg KOH / g or more, more preferably 6 mg KOH / g or more, even more preferably 8 mg KOH / g or more, even more preferably 10 mg KOH / g or more, even more preferably 12 mg KOH / g or more, even more preferably 15 mg KOH / g or more, and preferably 250 mg KOH / g or less, more preferably 200 mg KOH / g or less, even more preferably 120 mg KOH / g or less, even more preferably 80 mg KOH / g or less, even more preferably 40 mg KOH / g or less, and even more preferably 28 mg KOH / g or less. <18> The composite fine particles according to any one of <1> to <17>, wherein the content of vinyl polymer P in the composite fine particles is preferably more than 0.05% by mass, more preferably 0.10% by mass or more, even more preferably 0.15% by mass or more, and preferably 0.40% by mass or less, more preferably 0.30% by mass or less, and even more preferably 0.25% by mass or less, based on 100% by mass of the composite fine particles. <19> The composite fine particles according to any one of <1> to <18>, wherein the content of copper fine particles in the composite fine particles is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and preferably 99.9% by mass or less, based on 100% by mass of the composite fine particles. <20> The composite fine particles according to any one of <1> to <19>, wherein the mass ratio of vinyl polymer P to copper fine particles in the composite fine particles (vinyl polymer P / copper fine particles) is preferably 0.001 or more, more preferably 0.002 or more, and preferably 0.003 or less, more preferably 0.002 or less. <21> A method for producing composite fine particles in which a part of the surface of copper fine particles is coated with vinyl polymer P, comprising: preparing a mixed solution containing copper raw material compound powder, a reducing agent, and vinyl polymer P; reducing the copper raw material compound powder with the reducing agent to obtain copper fine particles; obtaining a dispersion of composite fine particles containing copper fine particles and vinyl polymer P that coats a part of the surface thereof; and drying the composite fine particles.<22> The method for producing composite fine particles according to <21>, wherein the temperature of the reduction reaction is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 30°C or higher, even more preferably 50°C or higher, and preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower. <23> A composite fine particle dispersion comprising the composite fine particles according to any one of <1> to <20>. <24> The composite fine particle dispersion according to <23>, wherein the composite fine particle dispersion contains a dispersion medium C which is a solvent for dispersing the composite fine particles, and the dispersion medium C comprises at least one selected from an aliphatic monohydric alcohol, a (poly)alkylene glycol, a (poly)alkylene glycol derivative, glycerin, and a glycerin derivative. <25> The composite fine particle dispersion according to <24>, wherein the content of the dispersion medium C is preferably 3% by mass or more, more preferably 4% by mass or more, even more preferably 5% by mass or more, even more preferably 6% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less. <26> The composite fine particle dispersion according to any one of <23> to <25>, wherein the content of the composite fine particles is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 85% by mass or more, and preferably 97% by mass or less, more preferably 96% by mass or less, even more preferably 95% by mass or less, and even more preferably 94% by mass or less. <27> A wiring pattern which is a heat-treated composite fine particle dispersion according to any one of <23> to <26>. <28> A bonding layer which is a heat-treated composite fine particle dispersion according to any one of <23> to <26>. <29> Use of the composite fine particle dispersion described in any of <23> to <26> as a bonding material for bonding objects to be bonded together.

[0063] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to these examples. In the following manufacturing examples, examples, and comparative examples, "parts" and "%" refer to "parts by mass" and "mass%" unless otherwise specified. Various physical properties were measured or calculated by the following methods.

[0064] <Primary Particle Size of Composite Microparticles> Scanning electron microscope (SEM) images of composite microparticles were taken using a scanning electron microscope (Hitachi High-Technologies Corporation, electrolytic emission scanning electron microscope: S-4800). The magnification was determined according to the primary particle size of the composite microparticles, and images were taken in the range of 5,000x to 150,000x. The SEM images were analyzed using the image analysis software ImageJ (obtained from the National Institutes of Health, United States), and the particle size was determined for more than 200 primary particles per sample. The arithmetic mean of these particles was taken as the average primary particle size of the composite microparticles.

[0065] <BET Specific Surface Area of ​​Composite Microparticles> The BET specific surface area was measured using a BET specific surface area analyzer (Macsorb, Mountech) under the following conditions: (Measurement conditions) - Sample pretreatment: Heat at 100°C for 10 minutes and dry - Cooling: 10 minutes at room temperature - Adsorption gas: N2 gas, flow rate 25 mL / min

[0066] <BET specific surface area (m²) of composite microparticles 2 The ratio of carbon content (mass%) to total carbon ( / g) (carbon content / BET specific surface area) > The BET specific surface area of ​​composite microparticles was measured by the method described above. The carbon content of composite microparticles was determined by combustion of composite microparticles at 500°C using a high-frequency induction heating furnace combustion-infrared absorption method (device: LECO RC612), detection of the generated carbon dioxide by infrared absorption, conversion of the detected carbon dioxide amount to carbon dioxide amount, and measurement of the carbon content derived from the vinyl polymer coated with copper microparticles. From the measured BET specific surface area and carbon content of the composite microparticles, the BET specific surface area (m²) of the composite microparticles was calculated using the following formula. 2 The ratio of carbon content (mass%) to total surface area (m²) was calculated. [Ratio (carbon content / BET specific surface area)] = carbon content (mass%) / BET specific surface area (m²) 2 / g)

[0067] <Number-average molecular weight Mn of vinyl polymer P> The number-average molecular weight of vinyl polymer P was determined by gel permeation chromatography under the following measurement conditions. The sample was prepared by mixing 0.1 g of vinyl polymer P with 10 mL of eluent in a glass vial, stirring with a magnetic stirrer at 25°C for 10 hours, and filtering through a syringe filter (DISMIC-13HP PTFE 0.2 μm, manufactured by Advantec Toyo Co., Ltd.) to obtain the filtrate. (Measurement conditions) GPC instrument: Tosoh Corporation "HLC-8320GPC" Column: Tosoh Corporation "TSKgel Super AWM-H, TSKgel Super AW3000, TSKgel guardcolumn Super AW-H" Eluent: N,N-dimethylformamide in which phosphoric acid and lithium bromide are dissolved at concentrations of 60 mmol / L and 50 mmol / L, respectively Flow rate: 0.5 mL / min Standard substance: Monodisperse polystyrene kit Tosoh Corporation "PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500)"

[0068] <Acid Value of Vinyl Polymer P> The acid value of vinyl polymer P was measured in accordance with JIS K 0070-1992 (potentiometric titration method). Only the measurement solvent was changed from the mixed solution of ethanol and ether specified in JIS K 0070 to a mixed solvent of acetone and toluene (acetone:toluene = 4:6 (volume ratio)).

[0069] <Polyalkylene glycol segment content in vinyl polymer P> The polyalkylene glycol segment content of vinyl polymer P was determined by multiplying the composition (parts by mass) of each monomer in vinyl polymer P by the polyalkylene glycol segment ratio in each monomer.

[0070] [Production of vinyl polymer P] Production example 1 (Production of vinyl polymer P1) (1) 20.0 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) was placed in a 1000 mL four-necked round-bottom flask equipped with a thermometer, two 100 mL dropping funnels with nitrogen bypass, and a reflux apparatus. The internal temperature of the flask was heated to 80°C in an oil bath, and then nitrogen bubbling was performed for 10 minutes. (2) Separately, 7.0 g of methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 93.0 g of methoxypolyethylene glycol (EO 23 mol) methacrylate (manufactured by NOF Corporation, "PME-1000", polyalkylene glycol segment ratio: 93.8%), 1.0 g of mercaptopropanediol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), and 28.7 g of ethanol were dissolved in a polybeaker and placed in dropping funnel (A). (3) Separately, 51.3 g of ethanol and 1.3 g of 2,2'-azobis(isobutyrate)dimethyl (V-601, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., polymerization initiator) were dissolved and placed in a dropping funnel (B). (4) The contents of the dropping funnel (A) from (2) and the contents of the dropping funnel (B) from (3) were simultaneously added dropwise to the contents of the four-necked round-bottom flask from (1) while stirring, over a period of 90 minutes. (5) After the operation in (4), the internal temperature of the four-necked round-bottom flask was raised to 90°C, and the mixture was stirred for another hour to allow the reaction to proceed. (6) After the reaction in (5) was completed, the obtained polymer solution was freeze-dried using a freeze-dryer (Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., model: DRC-1000) to obtain vinyl polymer P1 (methacrylic acid / methoxypolyethylene glycol (EO 23 mol) methacrylate polymer, Mn: 8600, acid value: 28 mg KOH / g, polyalkylene glycol segment content: 87.2%). Freeze-drying was carried out by freezing at -25°C for 1 hour, then drying under reduced pressure at -10°C for 9 hours at 5 Pa, and then drying under reduced pressure at 25°C for 5 hours at 5 Pa. The physical properties of vinyl polymer P1 are shown in Table 1.

[0071] Production Example 2 (Production of Vinyl Polymer P2) In the procedure of (2) of Production Example 1, 3.5 g of methacrylic acid, 3.5 g of methyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 93.0 g of methoxypolyethylene glycol (EO 23 mol) methacrylate, 1.0 g of mercaptopropanediol, and 28.7 g of ethanol were dissolved in a polybeaker and placed in a dropping funnel (A). Except for this, the vinyl polymer P2 (methacrylic acid / methoxypolyethylene glycol (EO 23 mol) methacrylate / methyl methacrylate polymer, Mn: 8400, acid value: 15 mg KOH / g, polyalkylene glycol segment content: 87.2%) was obtained in the same manner as in Production Example 1. The physical properties of vinyl polymer P2 are shown in Table 1.

[0072] Production Example 3 (Production of Vinyl Polymer P3) Vinyl polymer P3 (methacrylic acid / methoxypolyethylene glycol (EO 4 mol) methacrylate polymer, Mn: 8100, acid value: 28 mg KOH / g, polyalkylene glycol segment content: 69.8%) was obtained in the same manner as in Production Example 1, except that in the operation of Production Example 1 (2), 7.0 g of methacrylic acid, 93.0 g of methoxypolyethylene glycol (EO 4 mol) methacrylate (manufactured by NOF Corporation, "PME-200", polyalkylene glycol segment ratio: 75.0%), 1.0 g of mercaptopropanediol, and 28.7 g of ethanol were dissolved and placed in a dropping funnel (A). The physical properties of vinyl polymer P3 are shown in Table 1.

[0073] Manufacturing Example 4 (Manufacturing of vinyl polymer P11) In the operation of Production Example 1 (2), 30.0 g of methacrylic acid, 70.0 g of methoxypolyethylene glycol (EO 4 mol) methacrylate, 1.0 g of 3-mercaptopropionic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), and 28.7 g of ethanol were dissolved and placed in a dropping funnel (A), and in the operation of Production Example 1 (3), 51.3 g of ethanol and 1.3 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., "V-65", polymerization initiator) were dissolved and placed in a dropping funnel (B), otherwise vinyl polymer P11 (methacrylic acid / methoxypolyethylene glycol (EO 4 mol) methacrylate polymer, Mn: 8000, acid value: 190 mg KOH / g, polyalkylene glycol segment content: 52.5%) were obtained in the same manner as in Production Example 1. The physical properties of vinyl polymer P11 are shown in Table 1.

[0074] Production Example 5 (Production of Vinyl Polymer P4) (1) Add ethanol (50 parts), methacrylic acid (7 parts), and 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid (3.3 parts) to a reactor equipped with a dropping funnel, reflux condenser, and thermometer, and after bubbling with nitrogen for 10 minutes, raise the temperature to 75°C under a nitrogen atmosphere. Next, add a solution of 2,2'-azobis(isobutyrate)dimethyl (0.2 parts) in ethanol (10 parts) to the reactor and carry out the polymerization reaction for 3 hours while maintaining the temperature at 75-80°C. (2) Next, a solution consisting of 50 parts ethanol, 93 parts methoxypolyethylene glycol (EO 23 mol) methacrylate, and 0.8 parts 2,2'-azobis(isobutyrate)dimethyl is prepared. Immediately before adding the solution dropwise, nitrogen is bubbling for 10 minutes, and then the solution is added dropwise to the reactor over approximately 10 minutes. The polymerization reaction is carried out for 3 hours while maintaining the temperature at 75-80°C. (3) After the reaction, the obtained solution is added to 1000 parts n-hexane, and the supernatant is removed by decantation. Further, 500 parts n-hexane is added to the residue and stirred, then allowed to stand, and the supernatant is removed twice. Finally, the mixture is dried under reduced pressure at 50°C to obtain a viscous oil. The vinyl polymer P4 (block copolymer) of Production Example 5 described in Table 2 is obtained by the above procedure.

[0075]

[0076] Details of each monomer in Table 1 are as follows: (Monomer (p-1)) MAA: Methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) (Monomer (p-2)) PEG(4)MA: Methoxypolyethylene glycol (EO 4 mol) methacrylate (manufactured by NOF Corporation, "PME-200", polyalkylene glycol segment ratio: 75.0%) PEG(23)MA: Methoxypolyethylene glycol (EO 23 mol) methacrylate (manufactured by NOF Corporation, "PME-1000", polyalkylene glycol segment ratio: 93.8%) (Monomer (p-3)) MMA: Methyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent)

[0077]

[0078] [Production of Composite Microparticles] Example 1 (Production of Composite Microparticle 1) (1) 50.0 g of copper raw material compound powder (manufactured by Nisshin Chemco Co., Ltd., N-120, cupric oxide), 0.4 g of vinyl polymer P1, 0.3 g of levulinic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 500 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., first-grade reagent) were added to a 2 L beaker and stirred for 15 minutes to obtain a mixture. During stirring, an oil bath was used to control the temperature of the reaction solution to 70°C. (2) 63.0 g of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) in a 50 mL dropping funnel was added dropwise to the mixture from (1) over 20 minutes. (3) After the operation in (2) above, the reaction solution was stirred in an oil bath for 1 hour while controlling the temperature to 70°C, and then air-cooled to obtain a reddish-brown dispersion containing composite fine particles consisting of copper fine particles and vinyl polymer P1 that coats a portion of the surface of the copper fine particles. The entire amount of this dispersion was placed in a 500PA centrifugal sedimentation tube bottle manufactured by Hitachi Koki Co., Ltd., using a cooling centrifuge "himacCR22G" and rotor (R12A, radius 15.1 cm), and centrifuged for 15 minutes at 3000 rpm and a centrifugal acceleration of 675 G. (4) After the operation in (3) above, 300 g of ethanol was added to the precipitate separated by centrifugation, stirred for 15 minutes to redisperse, and then centrifuged again under the same conditions as in (3) above. This operation was performed a total of two times. (5) The precipitate of the purified composite fine particles was freeze-dried using a freeze-dryer (Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., model: DRC-1000) to obtain 36.5 g of composite fine particles 1 (dried powder). Freeze-drying was performed by freezing at -25°C for 1 hour, then drying under reduced pressure at -10°C for 9 hours at 5 Pa, and then drying under reduced pressure at 25°C for 5 hours at 5 Pa. The physical properties of composite fine particles 1 are shown in Table 3.

[0079] Example 2 (Production of Composite Fine Particles 2) Composite fine particles 2 (dried powder) were obtained in the same manner as in Example 1, except that the amount of vinyl polymer P1 added was changed to 0.3 g in the operation of (1) of Example 1. The physical properties of composite fine particles 2 are shown in Table 3.

[0080] Example 3 (Production of composite fine particles 3) Composite fine particles 3 (dried powder) were obtained in the same manner as in Example 1, except that 0.4 g of vinyl polymer P2 was added instead of 0.4 g of vinyl polymer P1 in the operation of (1) of Example 1. The physical properties of composite fine particles 3 are shown in Table 3.

[0081] Example 4 (Production of composite fine particles 4) Composite fine particles 4 (dried powder) were obtained in the same manner as in Example 1, except that 0.4 g of vinyl polymer P3 was added instead of 0.4 g of vinyl polymer P1 in the operation of (1) of Example 1. The physical properties of composite fine particles 4 are shown in Table 3.

[0082] Comparative Example 1 (Production of Composite Fine Particles 11) Composite fine particles 11 were obtained in the same manner as in Example 1, except that the amount of vinyl polymer P1 added was changed to 0.8 g in the operation of (1) of Example 1. The physical properties of the composite fine particles 11 are shown in Table 3.

[0083] Comparative Example 2 (Production of Composite Fine Particles 12) Composite fine particles 12 were obtained in the same manner as in Example 1, except that the amount of vinyl polymer P1 added was changed to 0.1 g in the operation of (1) of Example 1. The physical properties of the composite fine particles 12 are shown in Table 3. In Comparative Example 2, the composite fine particles 12 could not be dispersed in the dispersion medium in the production of the composite fine particle dispersion described later, and therefore a composite fine particle dispersion could not be obtained.

[0084] Comparative Example 3 (Production of Composite Fine Particles 13) (1) 88.4 g of copper raw material compound powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent, copper sulfate pentahydrate), 0.7 g of vinyl polymer P11, and 1000 g of ion-exchanged water were added to a 2 L beaker, and the mixture was stirred at 40°C using a magnetic stirrer until it became visually clear to obtain a mixed solution. (2) 17.8 g of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) in a 50 mL dropping funnel was added dropwise to the mixed solution from (1) over 60 minutes. (3) After the operation in (2), the reaction solution was stirred for 5 hours in an oil bath while controlling the temperature to 40°C, and then air-cooled to obtain a reddish-brown dispersion containing composite fine particles consisting of copper fine particles and vinyl polymer P1 that coats a part of the surface of the copper fine particles. The entire volume of this dispersion was placed into a dialysis tube (manufactured by REPLIGEN, product name: Spectra / Pore 6, dialysis membrane: regenerated cellulose, molecular weight cutoff (MWCO) = 50K), and the top and bottom of the tube were sealed with a closeer. This tube was immersed in 5 L of deionized water in a 5 L glass beaker, and the water temperature was maintained at 20-25°C and stirred for 1 hour to perform dialysis. (4) The operation in (3) above was repeated, with the entire volume of deionized water being replaced every hour. A sample was taken before replacing the deionized water, and the dialysis treatment was terminated when the conductivity of the dispersion of composite microparticles became 7 mS / m or less, and the dispersion of composite microparticles was obtained. The conductivity was measured after diluting the dispersion of composite microparticles with deionized water to adjust the copper concentration to 1%. (5) The precipitate of the purified composite fine particles was freeze-dried using a freeze-dryer (Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., model: DRC-1000) to obtain 20.8 g of composite fine particles 13 (dried powder). Freeze-drying was performed by freezing at -25°C for 1 hour, then drying under reduced pressure at -10°C for 9 hours at 5 Pa, and then drying under reduced pressure at 25°C for 5 hours at 5 Pa. The physical properties of the composite fine particles 13 are shown in Table 3.

[0085] Comparative Example 4 (Production of Composite Fine Particles 14) (1) 240 g of copper sulfate pentahydrate (powder), 3 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 99.5% by weight), and 870 mL of pure water were added to a 5 L beaker to obtain an aqueous solution of copper sulfate pentahydrate / citric acid. 670 mL of an aqueous solution containing 54 g of sodium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 14.4 g of hydrazine monohydrate was added all at once and mixed to obtain a slurry containing cuprous oxide particles. (2) The slurry from (1) was heated to 60°C, and 450 mL of an aqueous solution containing 7.2 g of hydrazine monohydrate and 25.2 g of sodium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) was added dropwise over 90 minutes. Further sodium hydroxide was added to adjust the pH to 12.5. (3) After the operation in (2) above, 130 mL of an aqueous solution containing 11.5 g of hydrazine monohydrate was added dropwise over 30 minutes, and stirring was continued in a nitrogen atmosphere for 6 hours to reduce cuprous oxide to metallic copper, obtaining a dispersion of composite microparticles consisting of copper microparticles and citric acid that coats part of the surface of the copper microparticles. (4) The dispersion of composite microparticles from (3) above was decanted five times and washed with water. (5) The precipitate of the washed composite microparticles was freeze-dried using a freeze-dryer (Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., model: DRC-1000) to obtain 20.8 g of composite microparticles 14. Freeze-drying was performed by freezing at -25°C for 1 hour, then drying under reduced pressure at -10°C for 9 hours at 5 Pa, and then drying under reduced pressure at 25°C for 5 hours at 5 Pa. The physical properties of the composite fine particles 14 of Comparative Example 4 are shown in Table 3.

[0086] (Production of composite fine particles using vinyl polymer P4) By carrying out the same method as in Example 1, except that vinyl polymer P4 is used instead of vinyl polymer P1, composite fine particles containing copper fine particles and vinyl polymer P4 that coats a part of their surface can be produced.

[0087] [Evaluation of Composite Microparticles] <Production of Composite Microparticle Dispersion> 6.0 parts by mass of diethylene glycol, 5.0 parts by mass of dipropylene glycol, and 89 parts by mass of composite microparticles obtained in the examples and comparative examples were added to an agate mortar and kneaded until no dry powder was visible to the naked eye, and a mixture was obtained. The obtained mixture was transferred to a plastic bottle and sealed tightly, and the plastic bottle was stirred for 2000 mins using a rotation-and-revolution type stirring device (Sinky Co., Ltd., Planetary Vacuum Mixer ARV-310) -1 The mixture was stirred at 2000 revolutions per minute for 5 minutes. Then, it was passed through a three-roll mill (AIMEX Co., Ltd., BV 100) with a gap adjusted to 0.2 mm five times to obtain the composite fine particle dispersions of each example and comparative example.

[0088] <Evaluation of Low-Temperature Sintering Properties> A stainless steel metal mask (thickness: 50 μm) with an 11 mm x 11 mm square opening was placed on a glass slide, and a composite microparticle dispersion was applied to the glass slide by stencil printing using a metal squeegee. Then, the glass slide coated with the composite microparticle dispersion was placed on a hot plate heated to 200°C, covered with a two-port separable cover, and nitrogen was circulated through one of the ports to start firing. After firing for 1 hour, the glass slide was removed, and the volume resistivity of the heat-treated composite microparticle dispersion was measured using a Loresta GP RSH-40N (manufactured by Nitto Seikou Analytech Co., Ltd., resistance measuring device) and an MCP-1610PSP probe. A smaller volume resistivity after firing at 200°C for 1 hour indicates better low-temperature sintering properties.

[0089] <Evaluation of Low-Temperature Sintering Speed> A stainless steel metal mask (thickness: 50 μm) with an 11 mm x 11 mm square opening was placed on a glass slide, and a copper microparticle dispersion was applied to the glass slide using stencil printing with a metal squeegee. Eighteen slides coated with the composite microparticle dispersion were prepared in this manner. Then, the eighteen glass slides coated with the composite microparticle dispersion were placed on a hot plate heated to 200°C, covered with a two-port separable cover, and nitrogen was circulated through one of the ports to start firing. One glass slide was removed every 10 minutes, and the volume resistivity of the heat-treated composite microparticle dispersion was measured using a Loresta GP RSH-40N (manufactured by Nitto Seikou Analytech Co., Ltd., resistance measuring device) and an MCP-1610PSP probe, and the time until the volume resistivity became 10 μΩ·cm or less was measured. A shorter time until the volume resistivity became 10 μΩ·cm or less during firing at 200°C indicates a superior low-temperature sintering speed.

[0090]

[0091] As shown in Table 3, the composite microparticles include copper nanoparticles and a vinyl polymer P that coats a portion of the surface of the copper nanoparticles, the primary particle diameter is 50 nm to 300 nm, and the BET specific surface area (m²) of the composite microparticles is 2The composite fine particles of Examples 1 to 4, in which the ratio of the carbon content (mass%) of the composite fine particles to the total material ( / g) (carbon content / BET specific surface area) is 0.020 or more and 0.060 or less, exhibit excellent low-temperature sintering speed. Similarly, it is presumed that the composite fine particles containing copper fine particles and a vinyl polymer P4 coating a portion of their surface will also exhibit excellent low-temperature sintering speed. On the other hand, the composite fine particles of Comparative Example 1 had a ratio (carbon content / BET specific surface area) exceeding 0.060, so they could not be sufficiently sintered at low temperatures, resulting in a poor low-temperature sintering speed. Furthermore, the composite fine particles of Comparative Example 2 had a ratio (carbon content / BET specific surface area) less than 0.020, so a dispersion of the composite fine particles could not be obtained, and a sintered body could not be formed. Furthermore, the composite fine particles of Comparative Example 3 had a ratio (carbon content / BET specific surface area) exceeding 0.060, so they could not be sufficiently sintered at low temperatures, resulting in a poor low-temperature sintering speed. Furthermore, the composite fine particles of Comparative Example 4 were not coated with a vinyl polymer P, and their ratio (carbon content / BET specific surface area) exceeded 0.060, resulting in poor dispersibility of the composite fine particles and insufficient sintering at low temperatures, leading to a poor low-temperature sintering rate.

[0092] According to the present invention, it is possible to provide composite fine particles, a composite fine particle dispersion containing composite fine particles, and a wiring pattern and bonding layer formed using the composite fine particle dispersion, all of which exhibit excellent low-temperature sintering speed.

Claims

1. A composite microparticle in which a portion of the surface of copper microparticles is coated with a vinyl polymer P, the primary particle diameter of the composite microparticle is 50 nm or more and 300 nm or less, and the BET specific surface area (m²) of the composite microparticle 2 Composite fine particles having a ratio of carbon content (mass%) of the composite fine particles to ( / g) (carbon content / BET specific surface area) of 0.020 or more and 0.060 or less.

2. BET specific surface area is 1.0 m² 2 / g or more 5.0m 2 The composite fine particles according to claim 1, wherein the amount is less than or equal to / g.

3. The composite fine particles according to claim 1 or 2, wherein the vinyl polymer P comprises at least one selected from a monomer having a carboxyl group (p-1), a monomer having a polyalkylene glycol segment (p-2), and a hydrophobic monomer (p-3).

4. The composite fine particles according to any one of claims 1 to 3, wherein the vinyl polymer P comprises at least one selected from constituent units of a monomer (p-2) having a polyalkylene glycol segment and constituent units of a hydrophobic monomer (p-3), and a constituent unit of a monomer (p-1) having a carboxyl group.

5. The composite fine particles according to any one of claims 1 to 4, wherein the vinyl polymer P comprises a constituent unit of a monomer having a carboxyl group (p-1) and a constituent unit of a monomer having a polyalkylene glycol segment (p-2).

6. The composite fine particles according to claim 3, wherein the content of polyalkylene glycol segments in the vinyl polymer P is 55% by mass or more and 97% by mass or less.

7. The composite fine particles according to any one of claims 1 to 6, wherein the number average molecular weight of the vinyl polymer P is 2,000 or more and 50,000 or less.

8. The composite fine particles according to any one of claims 1 to 7, wherein the acid value of the vinyl polymer P is 4 mg KOH / g or more and 250 mg KOH / g or less.

9. The composite fine particles according to any one of claims 1 to 8, wherein the content of vinyl polymer P in the composite fine particles is greater than 0.05% by mass and less than or equal to 0.40% by mass.

10. The composite fine particles according to any one of claims 1 to 9, wherein the content of copper fine particles in the copper fine particles is 80% by mass or more and 99.9% by mass or less.

11. The composite fine particles according to any one of claims 1 to 10, wherein the mass ratio of vinyl polymer P to copper fine particles in the composite fine particles is 0.001 or more and 0.003 or less.

12. A method for producing composite fine particles according to any one of claims 1 to 11, comprising the following steps (1) to (3): Step (1): A step of preparing a mixed solution containing copper oxide, a vinyl polymer P, and a dispersion medium. Step (2): A step of reducing copper oxide with a reducing agent. Step (3): A step of separating composite fine particles from a dispersion of composite fine particles obtained in step (2), which contains copper fine particles and a vinyl polymer P that coats a part of its surface.

13. A composite particle dispersion comprising composite particles according to any one of claims 1 to 11.

14. A wiring pattern which is a heat-treated composite fine particle dispersion according to claim 13.

15. A bonding layer which is a heat-treated composite fine particle dispersion according to claim 13.

16. Use of the composite fine particle dispersion according to claim 13 as a bonding material for joining objects to be joined together.

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