Composite microparticles

Abstract

To provide composite microparticles with excellent low-temperature sintering speed, a composite microparticle dispersion containing the composite microparticles, and a wiring pattern and bonding layer which are heat-treated products of the composite microparticle dispersion. [Solution] In one embodiment, the present invention provides composite microparticles in which a portion of the surface of copper microparticles is coated with a vinyl polymer P, the primary particle diameter of the composite microparticles is 50 nm or more and 300 nm or less, and the BET specific surface area (m²) of the composite microparticles. 2 The present invention relates to composite fine particles in which the ratio of the carbon content (mass%) of the composite fine particles to (carbon content / BET specific surface area) is 0.020 or more and 0.060 or less. In another embodiment, the present invention relates to a composite fine particle dispersion containing the composite fine particles. In another embodiment, the present invention relates to a wiring pattern or bonding layer which is a heat-treated product of the composite fine particle dispersion.

Description

[Technical Field]

[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. [Background technology]

[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, Patent Document 1 describes the BET specific surface area (m²). 2 A copper powder is disclosed in which the ratio of carbon content (mass%) to (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, 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 constituent units derived from monomer (b-1) having a carboxyl group and constituent 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 contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivatives, terpene alcohols, glycerin and glycerin derivatives. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2024-8681 [Patent Document 2] International Publication No. 2023 / 013034 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] When forming conductive wiring, the low heat resistance of the object to be printed on necessitates coating the copper nanoparticle dispersion and then sintering it at a low temperature of 230°C or lower for a short time. Furthermore, when used as a bonding material, from the perspective of production processes and environmental impact, it is required to sinter the copper nanoparticle dispersion at a low temperature and for a short time to obtain a strong bonding layer. As described above, there is a need to improve the low-temperature sintering rate of copper nanoparticles, specifically by sintering them at a low temperature of 230°C or lower and in a short amount of time. While the copper powder disclosed in Patent Document 1 has been studied for its sinterability at low temperatures, there were issues with the sintering rate. Similarly, while the copper fine particle dispersion disclosed in Patent Document 2 has been studied for its bonding strength when used as a bonding material, there were issues with its low-temperature sinterability and low-temperature sintering rate. The present invention relates to composite microparticles exhibiting 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. [Means for solving the problem]

[0006] The 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 determined. 2 We found that composite microparticles in which the ratio of carbon content (mass%) to ( / g) is within a specific range can solve the above problem. The present invention relates to the following [1] to [4]. [1] Composite fine particles in which a portion of the surface of copper fine particles is coated with a vinyl polymer P, 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 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] A method for producing composite fine particles as described in [1] above, comprising the following steps (1) to (3). Step (1): Step of preparing a mixture containing copper oxide, vinyl polymer P, and 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 portion of its surface. [3] A composite particle dispersion containing the composite particle described in [1] above. [4] A wiring pattern which is a heat-treated composite fine particle dispersion as described in [3] above. [5] A bonding layer which is a heat-treated composite fine particle dispersion described in [3] above. [6] Use of the composite fine particle dispersion described in [3] above as a bonding material for joining objects to be joined together. 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 subjecting a composite microparticle dispersion to heat treatment, thereby volatilizing volatile components such as the dispersion medium and sintering the composite microparticles. [Effects of the Invention]

[0007] 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. [Modes for carrying out the invention]

[0008] [Composite fine particles] The composite microparticles of the present invention comprise copper microparticles and a vinyl polymer P that coats a portion of the surface of the copper microparticles, the primary particle diameter of the composite microparticles is 50 nm or more and 300 nm or less, and the BET specific surface area (m²) of the composite microparticles is 2 The ratio of the carbon content (mass%) of composite fine particles to the total carbon content (carbon content / BET specific surface area) is between 0.020 and 0.060.

[0009] The composite microparticles of the present invention exhibit excellent low-temperature sintering rates. 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 rate is improved. Furthermore, in the composite fine particles of the present invention, the ratio (carbon content / BET specific surface area) of the carbon content (mass%) to the BET specific surface area (m 2 / g) is 0.020 or more, so that it contains a sufficient amount of the vinyl polymer P for improving the dispersibility of the copper fine particles. Therefore, when the composite fine particles containing the copper fine particles are sintered, a strong copper sintered body can be formed in a short time, and the low-temperature sintering rate is improved. Also, in the composite fine particles of the present invention, since the ratio (carbon content / BET specific surface area) is 0.060 or less, the copper surface of the copper fine particles is appropriately exposed, and the proportion of the organic compound in the composite fine particles is not too high. Therefore, the sinterability at low temperature of the composite fine particles containing the copper fine particles is improved, and the low-temperature sintering rate is improved. Furthermore, in the composite fine particles of the present invention, the ratio (carbon content / BET specific surface area) of the carbon content (mass%) to the BET specific surface area (m 2 / g) is within the above range, and the primary particle size thereof is 50 nm or more, so that the oxidation of the copper fine particles, which causes a decrease in the sintering rate, is suppressed. Therefore, the low-temperature sintering rate is improved. Also, since the primary particle size of the composite fine particles is 300 nm or less, when the composite fine particles containing the copper fine particles are sintered, the melting of the copper fine particles becomes easy, so that the sinterability at low temperature is improved and the low-temperature sintering rate is improved.

[0010] From the viewpoint of improving the sinterability at low temperature and improving the low-temperature sintering rate, the primary particle size of the composite fine particles 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, even more preferably 150 nm or more, 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, even more preferably 230 nm or less. The primary particle size of the composite fine particles is measured by the method described in the examples. The primary particle diameter of the composite microparticles can be adjusted according to the production conditions of the composite microparticles such as the reduction metal ratio, the type and amount of the reducing agent, the type and amount of the vinyl polymer P, and the reduction temperature and 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, even more preferably 0.040 or more from the viewpoint of improving the sinterability at low temperature and improving the low-temperature sintering rate, and 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, even more preferably 0.045 or less from the viewpoint of improving the sinterability at low temperature and improving the low-temperature sintering rate. 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 2 / g or more from the viewpoint of improving the sinterability at low temperature and improving the low-temperature sintering rate, and is preferably 5.0 m 2 / g or less, more preferably 3.5 m 2 / g or less, still more preferably 3.2 m 2 / g or less, even more preferably 3.0 m 2 / g or less from the viewpoint of improving the sinterability at low temperature and improving the low-temperature sintering rate. The BET specific surface area of the composite microparticles is measured by the method described in the examples. The BET specific surface area of ​​composite microparticles 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 microparticles, 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 more 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. Similarly, the content 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 contained 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 monomers of vinyl polymer P.

[0014] The copper fine particles contained in the composite fine particles of the present invention, when the composite fine particles of the present invention are considered to be 100% by mass, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, from the viewpoint of improving the dispersibility of the composite fine particles, improving sinterability at low temperatures, and improving the sintering rate, and from the same viewpoint, preferably 99.9% by mass or less. The copper content of the composite microparticles 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 microparticles of the present invention, a portion of the surface of the copper microparticles is coated with a vinyl polymer P. Since the composite microparticles of the present invention consist of copper microparticles 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 have excellent low-temperature sintering speed. Vinyl polymers refer to polymers obtained by addition polymerization of monomers having vinyl groups. Examples of vinyl polymers P in this 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, it 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, it 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, it comprises a monomer having a carboxyl group (p-1) and a monomer having a polyalkylene glycol segment (p-2).

[0019] (Carboxylated monomer (p-1)) Examples of monomers (p-1) having a carboxyl group (hereinafter also referred to as "monomer (p-1)") include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and 2-methacryloyloxymethylsuccinic acid; and unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, and citraconic acid. The aforementioned unsaturated dicarboxylic acids may also be anhydrides. The monomer (p-1) may be used alone or in combination of two or more types. 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" hereafter.

[0020] (Monomer having a polyalkylene glycol segment (p-2)) Examples of monomers (p-2) having a polyalkylene glycol segment (hereinafter also referred to as "monomer (p-2)") include polyalkylene glycol (meth)acrylate, alkoxy polyalkylene glycol (meth)acrylate, and phenoxy polyalkylene glycol (meth)acrylate. Monomers (p-2) may be used individually or in combination of two or more. In this specification, "(meth)acrylate" means at least one selected from acrylates and methacrylates. 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 the 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 alkoxypolyalkylene glycol (meth)acrylates include methoxypolyalkylene glycol (meth)acrylate, ethoxypolyalkylene glycol (meth)acrylate, propoxypolyalkylene glycol (meth)acrylate, butoxypolyalkylene glycol (meth)acrylate, octoxypolyalkylene glycol (meth)acrylate, and lauroxypolyalkylene glycol (meth)acrylate. Among these, methoxypolyalkylene glycol (meth)acrylate is preferred, and methoxypolyalkylene glycol methacrylate is more preferred.

[0023] The monomer (p-2) polyalkylene glycol segment preferably contains units derived from an 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 including copper fine particles, improving sinterability at low temperatures, and improving the low-temperature sintering rate. The polyalkylene glycol segment may be a copolymer containing ethylene oxide-derived units and propylene oxide-derived units, 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, and PLE-1300.

[0025] (Hydrophobic monomer (p-3)) In this specification, "hydrophobic monomer" means a monomer in which the amount dissolved when dissolved in 100 g of deionized 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 branched alkyl groups 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] 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-3) is preferably at least one selected from aromatic group-containing monomers and (meth)acrylates having a linear alkyl group, more preferably at least one selected from styrene monomers and (meth)acrylates having a linear alkyl group with 1 to 4 carbon atoms, even more preferably 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 at least one selected from styrene and methyl (meth)acrylate, even more preferably at least one selected from methyl (meth)acrylate, and even more preferably methyl methacrylate.

[0029] When the vinyl polymer P contains constituent units derived from monomer (p-1), the content of monomer (p-1) in the raw material monomer during the production of the vinyl polymer P, or the content of constituent units derived from 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, 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.

[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 constituent units derived from monomer (p-1) and monomer (p-2), the total content of monomer (p-1) and monomer (p-2) in the raw material monomer during the production of the vinyl polymer P, or the total content of constituent units derived from monomer (p-1) and monomer (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, 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 unintentionally included components include monomers other than monomer (b-1) and monomer (b-2) contained in the raw material monomer (b-1) and monomer (b-2).

[0033] When the vinyl polymer P contains constituent units derived from monomer (p-2), 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.

[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. The acid value of the vinyl polymer P is measured by the method described in the examples.

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

[0037] (Process (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 rate. 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 rate. Examples of dispersion media include water, methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol. Among these, ethanol is preferred as the solvent.

[0038] In step (1), 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 similarly, preferably 0.03 or less, more preferably less than 0.016, and even more preferably 0.01 or less.

[0040] In step (1) 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] (Process (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, and hydrazine monohydrate. Examples of boron compounds include sodium borohydride. Examples of inorganic acid salts include sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium nitrite, sodium hyponitrite, phosphorous acid, sodium phosphite, hypophosphorous acid, and sodium hypophosphite. Among these, 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), from the viewpoint of obtaining composite fine particles with excellent low-temperature sintering speed. 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 rate. 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. From the viewpoint of obtaining composite fine particles with excellent low-temperature sintering rate, the temperature of the mixed liquid in step (2) after heating is preferably maintained for 1 hour or more, more preferably 1.5 hours or more, even more preferably 2 hours or more, and from the same viewpoint, preferably 24 hours or less, more preferably 5 hours or less, and even more preferably 3 hours or less. The above 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, from the viewpoint of separating composite fine particles from unreacted reducing agents, excess polymer P and other impurities and dispersion medium in the mixture obtained in step (2), a membrane treatment step such as dialysis, vacuum filtration, pressure filtration, or ultrafiltration of the mixture obtained in step (2) and / or a centrifugal treatment step of 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 comprises a vacuum drying step, and more preferably a freeze-drying step.

[0045] <Applications of composite microparticles> The composite microparticles of the present invention exhibit 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; and sensors such as flexible sensors. Among these, the composite fine particles of the present invention are preferably used as a raw material for conductive bonding agents and are preferably used as a material for forming wiring boards such as printed circuit boards and flexible circuit boards.

[0046] [Composite fine particle 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 above-mentioned composite microparticles, it exhibits excellent sinterability at low temperatures and a high 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 described above and the dispersion medium C. The dispersion medium C preferably includes at least one selected from aliphatic monohydric alcohols, (poly)alkylene glycols, (poly)alkylene glycol derivatives, glycerin, and glycerin derivatives, from the viewpoint of improving sinterability at low temperatures and improving the low-temperature sintering rate.

[0048] Examples of aliphatic monohydric alcohols include allyl alcohol, n-heptanol, n-octanol, 2-ethylhexanol, n-nonanol, and terpene alcohols. Examples of 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 (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 acetates 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 acetates include diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.

[0053] There are no particular restrictions on glycerin derivatives as long as they are solvents containing a structure derived from glycerin. Examples include glycerin ether derivatives, glycerin ester derivatives, polyglycerins, 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 ether derivative of glycerin is, for example, 3-(2-ethylhexyloxy)-1,2-propanediol. As an ester derivative of glycerin, glyceryl tributyrate (tributyline) is a preferred example.

[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] (Manufacturing of composite microparticle dispersions) The composite microparticle dispersion of the present invention is obtained by mixing the composite microparticles of the present invention described above with the dispersion medium C. The present invention provides a method for producing a composite particle dispersion, which can be obtained by adding and mixing pre-prepared composite fine particles, a dispersion medium C, and various additives as needed. As for the mixing method, known methods can be used, and from the viewpoint of better dispersing the composite fine particles in the dispersion medium C, it is preferable to pre-mix the composite fine particles and the dispersion medium C using an agate mortar or the like, and then further mix the resulting mixture using a stirring device such as a rotational stirring device. Furthermore, a composite microparticle dispersion can also be produced by adding dispersion medium C and various additives as needed to a dispersion containing composite microparticles obtained in the production of composite microparticles, and then vaporizing the liquid components other than dispersion medium C and various additives at a predetermined temperature while stirring.

[0058] <Applications of composite particulate dispersions> The composite microparticle dispersion of the present invention exhibits 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 fine particle 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 exhibits excellent low-temperature sinterability and low-temperature sintering speed, allowing the wiring pattern of the present invention to be formed at a low temperature of 230°C or lower and in a short time. As a result, the wiring pattern of the present invention can be formed on substrates with low high-temperature resistance, such as plastics. Because the wiring pattern of the present invention has the above-mentioned characteristics, it is preferably used for forming wiring boards such as printed circuit boards and flexible circuit boards, which have low high-temperature resistance of the substrate.

[0060] (Joining 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 exhibits excellent low-temperature sinterability and low-temperature sintering speed, and therefore the bonding layer of the present invention can be formed at a low temperature of 250°C or below 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 components 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 objects that have low high-temperature resistance. [Examples]

[0061] 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 using the following methods.

[0062] <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.

[0063] <BET specific surface area of ​​composite microparticles> The BET specific surface area was measured using a Macsorb measuring device (Mountech Corporation) under the following measurement conditions. (Measurement conditions) Sample pretreatment: Heat at 100°C for 10 minutes and dry. • Cooling: 10 minutes at room temperature • Adsorbent gas: N2 gas, flow rate 25 mL / min

[0064] <BET specific surface area of ​​composite microparticles (m²) 2 Ratio of carbon content (mass%) to g (carbon content / BET specific surface area) > The BET specific surface area of ​​the composite microparticles was measured using the method described above. The carbon content of the composite microparticles was determined by combustion in a high-frequency induction heating furnace using infrared absorption spectroscopy (device: LECO RC612). The composite microparticles were burned at 500°C, and the generated carbon dioxide was detected by infrared absorption spectroscopy. The detected amount of carbon dioxide was converted to the amount of carbon atoms, and the carbon content derived from the vinyl polymer coated with copper microparticles was measured. From the measured BET specific surface area and carbon content of the composite microparticles, the BET specific surface area (m²) of the composite microparticles can be calculated using the following formula. 2 The ratio of carbon content (mass%) to the total surface area ( / g) was calculated (carbon content / BET specific surface area). [Ratio (carbon content / BET specific surface area)] = Carbon content (mass%) / BET specific surface area (m 2 / g)

[0065] <Number-average molecular weight Mn of vinyl polymer P> The number-average molecular weight of the 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.). (Measurement conditions) GPC device: Tosoh Corporation "HLC-8320GPC" Columns: Tosoh Corporation products "TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guardcolumn Super AW-H" Eluent: A solution prepared by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively. Flow rate: 0.5mL / min Standard material: Monodisperse polystyrene kit manufactured by 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)"

[0066] <Acid value of vinyl polymer P> The acid value of vinyl polymer P was measured according to JIS K 0070-1992 (potentiometric titration method). However, the measurement solvent was changed from the ethanol and ether mixture specified in JIS K 0070 to an acetone and toluene mixture (acetone:toluene = 4:6 (volume ratio)).

[0067] <Content of polyalkylene glycol segment 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 ratio of polyalkylene glycol segments in each monomer.

[0068] [Manufacturing of vinyl polymer P] Manufacturing Example 1 (Manufacturing of vinyl polymer P1) (1) 20.0 g of ethanol (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was placed in a 1000 mL four-necked round-bottom flask equipped with a thermometer, two 100 mL dropping funnels with nitrogen bypasses, and a reflux apparatus. The internal temperature of the flask was then raised to 80°C using an oil bath, and 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 poly beaker and placed in a 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 four-necked round-bottom flask of (1) were simultaneously added dropwise over a period of 90 minutes, while stirring, with the contents of the dropping funnel (A) of (2) and the contents of the dropping funnel (B) of (3). (5) After the operation in (4) above, the internal temperature of the four-necked round-bottom flask was raised to 90°C and 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 (EO23 mol) methacrylate polymer, Mn: 8600, acid value: 28 mg KOH / g, polyalkylene glycol segment content: 87.2%). Freeze-drying was performed by freezing at -25°C for 1 hour, then drying under reduced pressure at 5 Pa at -10°C for 9 hours, and then drying under reduced pressure at 5 Pa at 25°C for 5 hours. The physical properties of vinyl polymer P1 are shown in Table 1.

[0069] Manufacturing Example 2 (Manufacturing of vinyl polymer P2) In the procedure of (2) in 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 (EO23 mol) methacrylate, 1.0 g of mercaptopropanediol, and 28.7 g of ethanol were dissolved in a polybeaker and placed into a dropping funnel (A). Except for these steps, vinyl polymer P2 (methacrylic acid / methoxypolyethylene glycol (EO23 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.

[0070] Manufacturing Example 3 (Manufacturing of vinyl polymer P3) In the procedure of (2) in Production Example 1, 7.0 g of methacrylic acid, 93.0 g of methoxypolyethylene glycol (EO 4 mol) methacrylate (NOF Co., Ltd. "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). Except for these steps, 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. The physical properties of vinyl polymer P3 are shown in Table 1.

[0071] Manufacturing Example 4 (Manufacturing of vinyl polymer P11) In the procedure 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). In the procedure 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). Except for these differences, 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. Table 1 shows the physical properties of vinyl polymer P11.

[0072] Manufacturing Example 5 (Manufacturing 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, prepare a solution consisting of 50 parts ethanol, 93 parts methoxypolyethylene glycol (EO 23 mol) methacrylate, and 0.8 parts 2,2'-azobis(isobutyrate)dimethyl, and after bubbling with nitrogen for 10 minutes immediately before adding it dropwise, add it dropwise to the reactor over approximately 10 minutes and carry out the polymerization reaction for 3 hours while maintaining the temperature at 75-80°C. (3) After the reaction, the resulting solution is added to 1000 parts n-hexane, and the supernatant is removed by decantation. Then, 500 parts n-hexane is added to the residue and stirred, and after standing, the supernatant is removed twice, and the mixture is dried under reduced pressure at 50°C to obtain a viscous oil. Based on the above, it is considered that the vinyl polymer P4 (block copolymer) of Production Example 5 described in Table 2 can be obtained.

[0073] [Table 1]

[0074] 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)) • PEGMA(4)MA: Methoxypolyethylene glycol (EO4 mol) methacrylate (NOF Co., Ltd. "PME-200", polyalkylene glycol segment ratio: 75.0%) • PEGMA(23)MA: Methoxypolyethylene glycol (EO23 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)

[0075] [Table 2]

[0076] [Manufacturing of composite microparticles] Example 1 (Production of composite microparticles 1) (1) In a 2L beaker, 50.0g of copper raw material compound powder (N-120, cupric oxide, manufactured by Nisshin Chemco Co., Ltd.), 0.4g of vinyl polymer P1, 0.3g of levulinic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 500g of ethanol (first-grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added 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), placed in a 50 mL dropping funnel, was added dropwise to the mixture from (1) over a period of 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, and the mixture was stirred for 15 minutes to redisperse it. Then, the centrifugation treatment was performed 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 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 36.5 g of composite microparticle 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 microparticle 1 are shown in Table 3.

[0077] Example 2 (Production of composite microparticles 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.

[0078] Example 3 (Production of composite microparticles 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.

[0079] Example 4 (Production of composite microparticles 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.

[0080] Comparative Example 1 (Manufacturing of Composite Microparticles 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.

[0081] Comparative Example 2 (Manufacturing of Composite Microparticles 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 composite fine particles 12 are shown in Table 3. Note that the composite fine particles 12 of Comparative Example 2 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.

[0082] Comparative Example 3 (Manufacturing of Composite Microparticles 13) (1) In a 2L beaker, 88.4g of copper raw material compound powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent, copper sulfate pentahydrate), 0.7g of vinyl polymer P11, and 1000g of deionized water were added, 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), placed in a 50 mL dropping funnel, was added dropwise to the mixture from (1) over a period of 60 minutes. (3) After the operation in (2) above, the reaction solution was stirred in an oil bath for 5 hours 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 part of the surface of the copper fine particles. The entire volume of this dispersion was placed into a dialysis tube (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 closer. 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, to obtain the dispersion of composite microparticles. 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 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 13 (dried powder). Freeze-drying was performed by freezing at -25°C for 1 hour, then drying under reduced pressure at 5 Pa at -10°C for 9 hours, and then drying under reduced pressure at 5 Pa at 25°C for 5 hours. The physical properties of composite microparticles 13 are shown in Table 3.

[0083] Comparative Example 4 (Manufacturing of Composite Microparticles 14) (1) In a 5L beaker, 240g of copper sulfate pentahydrate (powder), 3g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 99.5% by weight), and 870mL of pure water were added to obtain an aqueous solution of copper sulfate pentahydrate / citric acid. To the obtained aqueous solution of copper sulfate pentahydrate / citric acid, 670mL of an aqueous solution containing 54g of sodium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 14.4g of hydrazine monohydrate was added all at once and mixed to obtain a slurry containing cuprous oxide particles. (2) The slurry from (1) above 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, and 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 fine particles consisting of copper fine particles and citric acid that coats a portion of the surface of the copper fine particles. (4) The dispersion of composite microparticles described in (3) was decanted five times and washed with water. (5) The precipitate of the washed composite microparticles was freeze-dried using a freeze-dryer (manufactured by Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (manufactured by 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 5 Pa at -10°C for 9 hours, and then drying under reduced pressure at 5 Pa at 25°C for 5 hours. The physical properties of the composite fine particles 14 in Comparative Example 4 are shown in Table 3.

[0084] (Manufacturing of composite microparticles using vinyl polymer P4) By following 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 portion of their surface can be produced.

[0085] [Evaluation of composite microparticles] <Manufacturing of composite microparticle dispersions> 6.0 parts by mass of diethylene glycol, 5.0 parts by mass of dipropylene glycol, and 89 parts by mass of composite fine particles 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, to obtain a mixed liquid. The resulting mixture is transferred to a plastic bottle, sealed tightly, and then stirred for 2000 minutes using a rotation-and-revolving 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 for each example and comparative example.

[0086] <Evaluation of low-temperature sinterability> 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 using stencil printing with 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 port 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. The smaller the volume resistivity after firing at 200°C for 1 hour, the better the low-temperature sinterability.

[0087] <Evaluation of low-temperature sintering rate> 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 such glass slides coated with the composite microparticle dispersion were prepared. Then, the 18 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 port 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. The shorter the time it takes for the volume resistivity to become 10 μΩ·cm or less during firing at 200°C, the better the low-temperature sintering rate.

[0088] [Table 3]

[0089] 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, with a primary particle diameter of 50 nm to 300 nm, and the BET specific surface area (m²) of the composite microparticles. 2 The 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 surface area ( / 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 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, which prevented them from being sufficiently sintered at low temperatures, resulting in a poor low-temperature sintering rate. Furthermore, in Comparative Example 2, the composite fine particles had a ratio (carbon content / BET specific surface area) of less than 0.020, making it impossible to obtain a dispersion of the composite fine particles and thus impossible to form a sintered body. Furthermore, the composite fine particles of Comparative Example 3 had a ratio (carbon content / BET specific surface area) exceeding 0.060, which prevented them from being sufficiently sintered at low temperatures, resulting in a poor low-temperature sintering rate. 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. [Industrial applicability]

[0090] 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. These are composite microparticles in which a portion of the surface of copper microparticles is coated with a vinyl polymer P. The primary particle diameter of the composite fine particles is 50 nm or more and 300 nm or less. The BET specific surface area (m²) of the composite fine particles 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, 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 claim 1, 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 claim 1, wherein the vinyl polymer P comprises a constituent unit of a monomer (p-1) having a carboxyl group and a constituent unit of a monomer (p-2) having a polyalkylene glycol segment.

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 claim 1, 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 claim 1, 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 claim 1, wherein the content of vinyl polymer P in the composite fine particles is more than 0.05% by mass and 0.40% by mass or less.

10. The composite fine particles according to claim 1, 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 claim 1, 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 mixture containing copper oxide, 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 portion 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. The composite fine particle dispersion described in claim 13 is used as a bonding material for joining objects to be joined together.

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