Method for producing copper particle dispersion

Abstract

The present invention has a step of mixing copper nanoparticles A, copper microparticles B, and a dispersion medium C, wherein the copper nanoparticles A contain copper particles a and a coating agent D, the average particle size of the copper nanoparticles A is 50 nm or more and 300 nm or less, the copper microparticles B contain copper particles b and a coating agent E, or contain the copper particles b and do not contain the coating agent E, the average particle size of the copper microparticles B is 0.5 μm or more and 10 μm or less, and the distance Ra (A-B) is 9.0 MPa 1 / 2 or less, and relates to a method for producing a copper particle dispersion excellent in the retention of bonding strength after storage.

Description

Technical Field

[0001] The present invention relates to a method for producing a copper particle dispersion.

Background Art

[0002] Since copper is excellent in electrical conductivity and thermal conductivity, it is widely used as, for example, a conductor wiring material, a heat transfer material, a heat exchange material, a heat dissipation material, etc. Since copper is excellent in thermal conductivity, it may also be used as an alternative material for solder for joining an object to be joined.

[0003] In recent years, semiconductor devices called power devices have been increasingly used as power conversion and control devices such as inverters. Unlike integrated circuits such as memories and microprocessors, power devices are for controlling high currents, and the amount of heat generated during operation becomes large. Therefore, the solder used for mounting a power device is required to have heat resistance in addition to joining strength. However, the lead-free solder widely used recently has a drawback of low heat resistance. Therefore, various techniques have been proposed in which a metal fine particle dispersion is used instead of solder, and this is applied to an object by various coating means and fired to join the object to be joined. The metal species of the metal fine particle dispersion used for mounting is mainly silver or copper. Silver does not have an oxide film at room temperature (25°C). Therefore, the silver fine particle dispersion is fired without a reducing agent to form a continuous body of silver and join the object to be joined. On the other hand, since copper is stable in an oxidized state at room temperature (25°C), it contains copper atoms in an oxidized state. Therefore, in order to join an object to be joined with a copper particle dispersion, it is necessary to reduce the copper atoms in the oxidized state and fire them to form a continuous body of copper.

[0004] WO2023 / 013034 (Patent Document 1) aims to provide a copper particle dispersion with high bonding strength to a bonded object even after being stored at room temperature for one month. The copper particle dispersion contains copper powder and a liquid medium, and is a copper particle dispersion containing copper nanoparticles A dispersed by polymer B and a dispersion medium C. The polymer B contains a structural unit derived from monomer (b-1) having a carboxyl group and a structural unit derived from monomer (b-2) having a polyalkylene glycol segment. The content of the polyalkylene glycol segment in the polymer B is 55% by mass or more and 97% by mass or less, the acid value of the polymer B is 20 mgKOH / g or more and 250 mgKOH / g or less, and the dispersion medium C contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative. A copper particle dispersion is described.

Summary of the Invention

[0005] The present invention relates to a method for producing a copper particle dispersion, which has a step of mixing copper nanoparticles A, copper microparticles B, and a dispersion medium C. The copper nanoparticles A contain copper particles a and a coating agent D, the average particle size of the copper nanoparticles A is 50 nm or more and 300 nm or less, the copper microparticles B contain copper particles b, the average particle size of the copper microparticles B is 0.5 μm or more and 10 μm or less, and the distance Ra of the Hansen solubility parameters between the copper nanoparticles A and the copper microparticles B, which is obtained by the following formula (1) (A-B) is 9.0 MPa 1 / 2 or less. Ra (A-B) ={(4×(δD A -δD B ) 2 +(δP A -δP B ) 2 +(δH A -δH B ) 2 ) 1 / 2 (1) (However, in the above formula (1), δD A , δP A , and δH Arepresents the dispersion force term, polar term, and hydrogen bonding term of the Hansen solubility parameter of copper nanoparticles A, respectively, where δD B , δP B , and δH B represent the dispersion force term, polar term, and hydrogen bonding term of the Hansen solubility parameter of copper microparticles B, respectively. The Hansen solubility parameters of copper nanoparticles A and copper microparticles B are the values obtained from the HSPiP program.)

Embodiments for Carrying Out the Invention

[0006] Although metal particle dispersions that have been proposed so far as solder replacement joining materials have higher heat resistance than solder, there is still room for improvement in terms of the joining strength with the object to be joined. In addition, the driving temperature of recent power devices has been on the rise and is said to reach 250°C. Depending on the storage period, the joining property of conventional copper particle dispersions may deteriorate, and defects may occur in the joining strength of the obtained joined bodies.) When a joined body was produced after storing the copper microparticle dispersion of Patent Document 1 at room temperature for three months, defects were found in the joining strength of the obtained joined body, and a decrease in the joining property of the copper particle dispersion was observed. This is considered to be because the copper nanoparticles A in the copper microparticle dispersion of Patent Document 1 were separated from other components.) Therefore, further improvement in the joining strength retention rate after storage of the copper particle dispersion is required.) The present invention relates to a method for producing a copper particle dispersion having an excellent joining strength retention rate after storage.)

[0007] The present inventors have found that a copper particle dispersion having an excellent joining strength retention rate after storage can be obtained when the distance between the Hansen solubility parameters of copper nanoparticles A and copper microparticles B is equal to or less than a certain value.) That is, the present invention relates to the following [1]. [1] A method for producing a copper particle dispersion, comprising a step of mixing copper nanoparticles A, copper microparticles B, and a dispersion medium C, wherein the copper nanoparticles A contain copper particles a and a coating agent D, the average particle diameter of the copper nanoparticles A is 50 nm or more and 300 nm or less, the copper microparticles B contain copper particles b, the average particle diameter of the copper microparticles B is 0.5 μm or more and 10 μm or less, and the distance Ra of the Hansen solubility parameters between the copper nanoparticles A and the copper microparticles B, which is determined by the following formula (1) (A-B) is 9.0 MPa 1 / 2 or less. Ra (A-B) = {(4 × (δD A - δD B ) 2 + (δP A - δP B ) 2 + (δH A - δH B ) 2 ) 1 / 2 (1) (However, in the formula (1), δD A , δP A , and δH A represent the dispersion force term, the polar term, and the hydrogen bond term of the Hansen solubility parameter of the copper nanoparticles A, respectively, δD B , δP B , and δH B represent the dispersion force term, the polar term, and the hydrogen bond term of the Hansen solubility parameter of the copper microparticles B, respectively, and the Hansen solubility parameters of the copper nanoparticles A and the copper microparticles B are values obtained from the HSPiP program.)

[0008] According to the present invention, a method for producing a copper particle dispersion excellent in the joint strength retention rate after storage can be provided. Further, according to the present invention, a method for producing a copper particle dispersion excellent in the heat resistance of the joined body even when used for the joined body after long-term storage can be provided.

[0009] [Method for producing copper particle dispersion] The method for producing a copper particle dispersion of the present invention (hereinafter, also simply referred to as "the production method of the present invention") includes a step of mixing copper nanoparticles A, copper microparticles B, and a dispersion medium C, wherein the copper nanoparticles A contain copper particles a and a coating agent D, the average particle size of the copper nanoparticles A is 50 nm or more and 300 nm or less, the copper microparticles B contain copper particles b, the average particle size of the copper microparticles B is 0.5 μm or more and 10 μm or less, and the distance Ra of the Hansen solubility parameters between the copper nanoparticles A and the copper microparticles B, which is obtained by the following formula (1) (A-B) is 9.0 MPa 1 / 2 or less. Ra (A-B) ={(4×(δD A -δD B ) 2 +(δP A -δP B ) 2 +(δH A -δH B ) 2 ) 1 / 2 (1) (However, in the formula (1), δD A , δP A , and δH A respectively represent the dispersion force term, the polar term, and the hydrogen bond term of the Hansen solubility parameter of the copper nanoparticles A, δD B , δP B , and δH B respectively represent the dispersion force term, the polar term, and the hydrogen bond term of the Hansen solubility parameter of the copper microparticles B, and the Hansen solubility parameters of the copper nanoparticles A and the copper microparticles B are values obtained from the HSPiP program.)

[0010] In this specification, the "Hansen solubility parameter" uses a value obtained using the software HSPiP program of Charles Hansen Consulting, Inc. (Horsholm, Denmark, hansen-solubility.com). In the present invention, the Hansen solubility parameters of copper nanoparticles A and copper microparticles B are determined by the method described in the examples. Also, in the present invention, for organic solvents such as dispersion medium C, regarding solvents registered in the database of version 5.4.01 of the HSPiP program (refer to the literature for various Hansen solubility parameters), the values thereof are used, and for solvents not in the database, values estimated by the HSPiP program are used.

[0011] Also, in this specification, the bondability after storing the copper particle dispersion at 25°C and 50% humidity for three months is referred to as "bondability after storage", and the higher the ratio (bond strength retention rate) of the bond strength after storage under the above conditions to the bond strength of the bonded body using the copper particle dispersion before storage under the above conditions, the better the bond strength retention rate after storage is determined to be. Also, the bondability after subjecting the bonded body obtained by firing the copper particle dispersion to 1000 cycles of 15 minutes each at -55°C and 200°C is also referred to as "thermal resistance to temperature cycling". Also, the bondability after storing the bonded body obtained by firing the copper particle dispersion at 250°C for 1000 h is also referred to as "thermal resistance at 250°C".

[0012] According to the present invention, a copper particle dispersion excellent in the bond strength retention rate after storage and further excellent in the heat resistance of the bonded body can be obtained. The reason is not clear, but it is considered as follows. The production method of the present invention is such that the distance Ra between the Hansen solubility parameters of copper nanoparticles A and copper microparticles B (A-B) is 9.0 MPa 1 / 2 or less. As a result, in the obtained copper particle dispersion, since the affinity of each copper particle is high, aggregation is less likely to occur and separation is less likely to occur. As a result, it is considered that the copper particle dispersion obtained in the present invention is excellent in storage stability and has a good bond strength retention rate even after long-term storage. Also, since the copper particle dispersion obtained in the present invention contains copper nanoparticles A and copper microparticles B having the above configuration, it is considered that the thermal resistance to temperature cycling and the thermal resistance at 250°C can be improved by using it for the bonded body.

[0013] In the present invention, the distance Ra of the Hansen solubility parameters between the copper nanoparticles A and the copper microparticles B (A-B) is 9.0 MPa or less, preferably 8.0 MPa or less, more preferably 6.0 MPa or less, from the viewpoint of improving the dispersibility of the copper nanoparticles A and the copper microparticles B and improving the bonding strength retention rate after storage of the copper particle dispersion. 1 / 2 is 8.0 MPa or less, preferably 1 / 2 is 6.0 MPa or less, more preferably 1 / 2 is 6.0 MPa or less.

[0014] In the present invention, the distance Ra of the Hansen solubility parameters between the copper nanoparticles A and the dispersion medium C, which is obtained by the following formula (2) (A-C) is preferably 20.0 MPa or less, more preferably 15.0 MPa or less, still more preferably 10.0 MPa or less, even more preferably 8.0 MPa or less, from the viewpoint of improving the dispersibility of the copper nanoparticles A and improving the bonding strength retention rate after storage of the copper particle dispersion. 1 / 2 is 15.0 MPa or less, more preferably 1 / 2 is 10.0 MPa or less, still more preferably 1 / 2 is 8.0 MPa or less, even more preferably 1 / 2 is 8.0 MPa or less.

[0015] Ra (A-C) ={(4×(δD A -δD C ) 2 +(δP A -δP C ) 2 +(δH A -δH C ) 2 ) 1 / 2 (2) However, in the formula (2), δD A , δP A , and δH A respectively represent the dispersion force term, the polar term, and the hydrogen bond term of the Hansen solubility parameter of the copper nanoparticles A, and δD C , δP C , and δH Crespectively represent the dispersion force term, polar term, and hydrogen bonding term of the Hansen solubility parameter of the dispersion medium C. The Hansen solubility parameter of the dispersion medium C is a value obtained by weighted average weighted by the content (volume basis) of each dispersion medium based on the value obtained by the HSPiP program. In addition, the δD A , δP A , and δH A are the same as in the case of the formula (1).

[0016] In the present invention, the distance Ra (B-C) between the copper microparticles B and the dispersion medium C, which is obtained by the following formula (3), is preferably 15.0 MPa 1 / 2 or less, more preferably 12.0 MPa 1 / 2 or less, still more preferably 8.0 MPa 1 / 2 or less, and even more preferably 6.0 MPa 1 / 2 or less from the viewpoint of improving the dispersibility of the copper microparticles B and improving the bonding property after storage of the copper particle dispersion. Ra (B-C) ={(4×(δD B -δD C ) 2 +(δP B -δP C ) 2 +(δH B -δH C ) 2 ) 1 / 2 (3) However, in the formula (3), δD B , δP B , and δH B respectively represent the dispersion force term, polar term, and hydrogen bonding term of the Hansen solubility parameter of the copper microparticles B, and δD C , δP C , and δH C respectively represent the dispersion force term, polar term, and hydrogen bonding term of the Hansen solubility parameter of the dispersion medium C. The Hansen solubility parameter of the dispersion medium C is a value obtained by weighted average weighted by the content (volume basis) of each dispersion medium based on the value obtained by the HSPiP program. In addition, the δD B , δPB and δH B is the same as in the case of the above formula (1), and δD C , δP C and δH C is the same as in the case of the above formula (2).

[0017] In the present invention, among the Hansen solubility parameters of the copper nanoparticles A, δP A (polar term) of the copper nanoparticles A is preferably 1.0 MPa 1 / 2 or more, more preferably 3.0 MPa 1 / 2 or more, still more preferably 5.0 MPa 1 / 2 or more, even more preferably 7.0 MPa 1 / 2 or more.

[0018] In the present invention, among the Hansen solubility parameters of the copper microparticles B, δP B (polar term) of the copper microparticles B is preferably 1.0 MPa 1 / 2 or more, more preferably 3.0 MPa 1 / 2 or more, still more preferably 5.0 MPa 1 / 2 or more, even more preferably 7.0 MPa 1 / 2 or more.

[0019] The manufacturing method of the present invention includes a step of mixing copper nanoparticles A, copper microparticles B, and a dispersion medium C. The manufacturing method of the copper particle dispersion of the present invention is a method of adding and mixing the pre-prepared copper nanoparticles A, the pre-prepared copper microparticles B, the dispersion medium C, and various additives as required; a method of mixing a copper raw material compound, a reducing agent, a coating agent D, and a solvent for dispersing the copper raw material compound and the reducing agent as required to reduce the copper raw material compound to obtain a dispersion liquid of copper nanoparticles A, and then adding and mixing the pre-prepared copper microparticles B, the dispersion medium C, and various additives as required. Among them, from the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion, a method of adding and mixing the pre-prepared copper nanoparticles A, the pre-prepared copper microparticles B, the dispersion medium C, and various additives as required is preferable.

[0020] <Copper nanoparticles A> The copper nanoparticles A in the present invention contain copper particles a and a coating agent D, and the average particle size of the copper nanoparticles A is 50 nm or more and 300 nm or less. In the copper nanoparticles A, the coating agent D functions as a dispersant for the copper nanoparticles A.

[0021] From the viewpoints of improving the dispersibility of the copper nanoparticles A and suppressing oxidation during storage, the average particle size of the copper nanoparticles A is 50 nm or more, preferably 75 nm or more, more preferably 100 nm or more, still more preferably 125 nm or more. And from the viewpoint of improving the joint property after storage of the copper particle dispersion, it is 300 nm or less, preferably 250 nm or less, more preferably 230 nm or less, and even more preferably 200 nm or less. The average particle size of the copper nanoparticles A is measured by the method described in the examples. The average particle size of the copper nanoparticles A can be adjusted by the types and amounts of the reducing agent and the coating agent D, temperature conditions, etc. in the production of the copper nanoparticles A.

[0022] In the present invention, from the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion, the blending amount of the copper nanoparticles A is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, and even more preferably 40% by mass or more. And, from the viewpoint of suppressing shrinkage due to sintering when the copper particle dispersion is used for a joined body and improving the joint strength of the joined body, it is preferably 90% by mass or less, more preferably 80% by mass or less, still more preferably 70% by mass or less, and even more preferably 60% by mass or less.

[0023] (Copper particles a) From the viewpoints of improving the dispersibility of the copper nanoparticles A and suppressing oxidation during storage, the average particle diameter of the copper particles a is preferably 50 nm or more, more preferably 75 nm or more, still more preferably 100 nm or more, and even more preferably 125 nm or more. And, from the viewpoint of improving the joinability after storage of the copper particle dispersion, it is preferably 400 nm or less, more preferably 300 nm or less, still more preferably 250 nm or less, and even more preferably 200 nm or less. In the production of the copper nanoparticles A, the average particle diameter of the copper particles a can be adjusted by the types and amounts of the reducing agent and the coating agent D, temperature conditions, and the like.

[0024] (Coating agent D) The copper nanoparticles A in the present invention include the copper particles a and the coating agent D, so that the dispersibility is improved, the storage stability of the copper particle dispersion is improved, and the joint strength retention rate after storage of the copper particle dispersion is improved. In the present invention, from the viewpoints of improving the dispersibility of the copper nanoparticles A and improving the joint strength retention rate after storage of the copper particle dispersion, the coating agent D is preferably at least one selected from the group consisting of aliphatic carboxylic acids and polymers containing hydrophilic groups.

[0025] [Aliphatic carboxylic acid] From the perspective of improving the dispersibility of copper nanoparticles A and from the perspective of improving the joint strength retention rate after storage of the copper particle dispersion, the number of carbon atoms of the aliphatic carboxylic acid is preferably 1 or more and 24 or less, more preferably 2 or more and 20 or less, still more preferably 4 or more and 16 or less, and even more preferably 6 or more and 12 or less. Specific examples of the aliphatic carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, linderic acid, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, etc. Among these, as the aliphatic carboxylic acid, preferably one or more selected from the group consisting of hexanoic acid, octanoic acid, decanoic acid, and lauric acid, and more preferably lauric acid.

[0026] 〔Polymer containing a hydrophilic group〕 From the perspective of improving the dispersibility of copper nanoparticles A and from the perspective of improving the joint strength retention rate after storage of the copper particle dispersion, the polymer containing a hydrophilic group is preferably a polymer having one or more selected from the group consisting of a nonionic group, a cationic group, and an anionic group. It is more preferable that the hydrophilic group is present in the side chain of the polymer. Examples of the hydrophilic group include nonionic groups such as a hydroxy group, an amide group, and an oxyalkylene group; cationic groups such as an amino group; and anionic groups such as a carboxy group, a sulfonic acid group, and a phosphoric acid group. Examples of the polymer having a nonionic group include polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, etc. Examples of the polymer having a cationic group include polyallylamine, polyethyleneimine, etc. As the polymer having an anionic group, those having a carboxy group are preferable. Examples of the basic structure of the polymer having a carboxy group include vinyl polymers such as acrylic resins, styrene resins, styrene-acrylic resins, and acrylic-silicone resins; and condensation polymers such as polyesters and polyurethanes. As the polymer containing a hydrophilic group, those synthesized as appropriate may be used, or commercially available products may be used.

[0027] Among these, from the viewpoints of improving the dispersibility of the copper nanoparticles A and improving the joint strength retention rate after storage of the copper particle dispersion, the polymer containing a hydrophilic group is preferably a vinyl polymer P containing a structural unit derived from a monomer (p-1) having a carboxy group and a structural unit derived from a monomer (p-2) having a polyalkylene glycol segment. The vinyl polymer P may be any of a random copolymer, a block copolymer, and an alternating copolymer.

[0028] ≪Monomer (p-1) having a carboxy group≫ Examples of the monomer (p-1) having a carboxy group (hereinafter also referred to as "monomer (p-1)") preferably 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 be an anhydride. The monomer (p-1) may be used alone or in combination of two or more. From the viewpoints of improving the dispersibility of the copper nanoparticles A and improving the joint strength retention rate after storage of the copper particle dispersion, the monomer (p-1) is preferably at least one selected from the group consisting of (meth)acrylic acid and maleic acid, more preferably (meth)acrylic acid, and still more preferably methacrylic acid. In this specification, "(meth)acrylic acid" means at least one selected from the group consisting of acrylic acid and methacrylic acid.

[0029] ≪Monomer (p-2) having a polyalkylene glycol segment≫ Examples of the monomer (p-2) having a polyalkylene glycol segment (hereinafter also referred to as "monomer (p-2)") include polyalkylene glycol (meth)acrylate, alkoxypolyalkylene glycol (meth)acrylate, phenoxypolyalkylene glycol (meth)acrylate, and the like. The monomer (p-2) may be used alone or in combination of two or more. In this specification, "(meth)acrylate" means one or more selected from the group consisting of acrylate and methacrylate.

[0030] From the viewpoint of improving the dispersibility of the copper nanoparticles A and from the viewpoint of improving the retention rate of the bonding strength after storage of the copper particle dispersion, the monomer (p-2) is preferably one or more selected from the group consisting of polyalkylene glycol (meth)acrylate and alkoxypolyalkylene glycol (meth)acrylate, and more preferably alkoxypolyalkylene glycol (meth)acrylate. From the same viewpoint as described above, the number of carbon atoms of the alkoxy group of the alkoxypolyalkylene glycol (meth)acrylate is preferably 18 or less, more preferably 14 or less, and still more preferably 12 or less. Examples of the alkoxypolyalkylene glycol (meth)acrylate 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 them, methoxypolyalkylene glycol (meth)acrylate is more preferable.

[0031] The polyalkylene glycol segment of monomer (p-2) preferably contains units derived from an alkylene oxide having 2 to 4 carbon atoms from the viewpoint of improving the dispersibility of copper nanoparticles A and from the viewpoint of improving the bonding property after storage of the copper particle dispersion. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, etc., preferably one or more selected from the group consisting of ethylene oxide and propylene oxide, and more preferably ethylene oxide. From the viewpoint of improving the dispersibility of copper nanoparticles A and from the viewpoint of improving the bonding strength retention rate after storage of the copper particle dispersion, the number of units derived from alkylene oxide in the polyalkylene glycol segment is preferably 2 or more, more preferably 3 or more, still more preferably 4 or more, and preferably 100 or less, more preferably 70 or less, still more preferably 50 or less, even more preferably 40 or less, and even more preferably 35 or less. From the viewpoint of improving the dispersibility of copper nanoparticles A and from the viewpoint of improving the bonding strength retention rate after storage of the copper particle dispersion, the polyalkylene glycol segment may be a copolymer containing units derived from ethylene oxide and units derived from propylene oxide. The copolymer containing units derived from ethylene oxide and units derived from propylene oxide may be any of a random copolymer, a block copolymer, and an alternating copolymer.

[0032] Specific examples of commercially available monomer (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 Co., Ltd.; Brenmer PE-90, PE-200, PE-350, PME-100, PME-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, etc. manufactured by NOF Corporation.

[0033] 〔Hydrophobic monomer (p-3)〕 From the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion, the vinyl polymer P may further contain a structural unit derived from a hydrophobic monomer (p-3) (hereinafter also referred to as "monomer (p-3)"). In this specification, the "hydrophobic monomer" means that when the monomer is dissolved until saturated in 100 g of ion-exchanged water at 25°C, the dissolved amount is less than 10 g. From the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion, the dissolved amount of the hydrophobic monomer (p-3) is preferably 5 g or less, more preferably 1 g or less. The monomer (p-3) is preferably at least one selected from the group consisting of aromatic group-containing monomers and (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol.

[0034] From the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion, the aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group with 6 to 22 carbon atoms which may have a substituent containing a hetero atom, more preferably at least one selected from the group consisting of styrene-based monomers and aromatic group-containing (meth)acrylates, and still more preferably a styrene-based monomer. The molecular weight of the aromatic group-containing monomer is preferably less than 500. Examples of the styrene-based monomer include styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), and divinylbenzene. From the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion, styrene and α-methylstyrene are more preferred, and styrene is still more preferred. From the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion, examples of the aromatic group-containing (meth)acrylate include phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, etc., and benzyl (meth)acrylate is more preferred.

[0035] (Meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol preferably has a hydrocarbon group derived from an aliphatic alcohol having 22 or less carbon atoms, more preferably has a hydrocarbon group derived from an aliphatic alcohol having 12 or less carbon atoms, still more preferably has a hydrocarbon group derived from an aliphatic alcohol having 8 or less carbon atoms, and even more preferably has a hydrocarbon group derived from an aliphatic alcohol having 4 or less carbon atoms, from the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion. Examples thereof include (meth)acrylate having a linear alkyl group, (meth)acrylate having a branched alkyl group, and (meth)acrylate having an alicyclic alkyl group. Examples of the (meth)acrylate having a linear alkyl group preferably 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. Among them, methyl (meth)acrylate is more preferable, and methyl methacrylate is more preferable. Examples of the (meth)acrylate having a branched alkyl group preferably 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 the (meth)acrylate having an alicyclic alkyl group preferably include cyclohexyl (meth)acrylate. The monomer (p-3) may be used alone or in combination of two or more.

[0036] Monomer (p-3) is preferably at least one selected from the group consisting of aromatic group-containing monomers and (meth) acrylates having a linear alkyl group, more preferably at least one selected from the group consisting of styrene-based monomers and (meth) acrylates having a linear alkyl group with 1 to 4 carbon atoms, still more preferably at least one selected from the group consisting of 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 the group consisting of styrene, α-methylstyrene and methyl (meth) acrylate, and even more preferably at least one selected from the group consisting of styrene and methyl (meth) acrylate.

[0037] The number average molecular weight Mn of the vinyl polymer P is preferably 4,000 or more, more preferably 6,000 or more, still more preferably 7,000 or more, and preferably 50,000 or less, more preferably 30,000 or less, still more preferably 20,000 or less, even more preferably 15,000 or less, and even more preferably 10,000 or less, from the viewpoints of improving the dispersibility of the copper nanoparticles A and improving the joint strength retention rate after storage of the copper particle dispersion. The number average molecular weight Mn is measured by the method described in the examples.

[0038] The acid value of the vinyl polymer P is preferably 20 mgKOH / g or more, more preferably 25 mgKOH / g or more, still more preferably 30 mgKOH / g or more, even more preferably 35 mgKOH / g or more, and even more preferably 40 mgKOH / g or more, and preferably 250 mgKOH / g or less, more preferably 200 mgKOH / g or less, still more preferably 150 mgKOH / g or less, even more preferably 130 mgKOH / g or less, and even more preferably 110 mgKOH / g or less, from the viewpoints of improving the dispersibility of the copper nanoparticles A and improving the joint strength retention rate after storage of the copper particle dispersion. The acid value of the vinyl polymer P can be measured by the method described in the examples, but can also be calculated from the mass ratio of the monomers constituting it.

[0039] In the present invention, from the viewpoint of improving the dispersibility of the copper nanoparticles A and from the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion, the content of the coating agent D coated on the copper particles a in the copper nanoparticles A is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.6% by mass or more, even more preferably 0.8% by mass or more, and even more preferably 1.0% by mass or more, and is preferably 2.5% by mass or less, more preferably 2.0% by mass or less, still more preferably 1.8% by mass or less, and even more preferably 1.6% by mass or less. The content of the coating agent D is calculated from the content of the copper particles a and the content of the coating agent D in the copper particle dispersion measured by the method described in the examples using a differential thermal thermogravimetric simultaneous measurement device (TG / DTA).

[0040] (Production of Copper Nanoparticles A) In the present invention, the copper nanoparticles A are obtained by mixing a copper raw material compound, a reducing agent, and a coating agent D, and coating the copper particles a obtained by reducing the copper raw material compound with the reducing agent with the coating agent D. Further, after the copper nanoparticles A are obtained as a dispersion liquid by the above method, the dispersion liquid of the copper nanoparticles A can be dried by freeze-drying or the like to obtain a dry powder of the copper nanoparticles A.

[0041] The copper raw material compound is not particularly limited as long as it is a compound containing copper. Examples of the copper raw material compound include copper sulfate, copper nitrate, cupric oxide, cuprous oxide, copper formate, copper acetate, copper oxalate, etc. Among these, the copper raw material compound is preferably cupric oxide. The copper raw material compound may be used alone or in combination of two or more.

[0042] The reducing agent is not particularly limited as long as it is a compound capable of reducing the copper raw material compound. Examples of the reducing agent include hydrazine compounds, boron compounds, inorganic acid salts, and the like. Examples of the hydrazine compounds include hydrazine, hydrazine hydrochloride, hydrazine sulfate, hydrazine hydrate (hydrazine monohydrate), and the like. Examples of the boron compounds include sodium borohydride and the like. Examples of the inorganic acid salts include sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium nitrite, sodium hyponitrite, phosphorous acid, sodium phosphite, hypophosphorous acid, sodium hypophosphite, and the like. Among these, as the reducing agent, a hydrazine compound is preferable, one or more selected from the group consisting of hydrazine and hydrazine hydrate are more preferable, and hydrazine hydrate (hydrazine monohydrate) is still more preferable. The reducing agent may be used alone or in combination of two or more.

[0043] Examples of the solvent for dispersing the copper raw material compound and the reducing agent include water, methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and the like. Among these, ethanol is preferable as the solvent. The solvent may be used alone or in combination of two or more.

[0044] From the viewpoint of reducing the particle size and making the particle size of copper nanoparticles A uniform, the temperature of the reduction reaction is preferably 5°C or higher, more preferably 10°C or higher, still more preferably 20°C or higher, still more preferably 30°C or higher, and from the viewpoint of stably producing copper nanoparticles A, it is preferably in the range of 100°C or lower, more preferably 90°C or lower, still more preferably 80°C or lower, still more preferably 75°C or lower. The reduction reaction may be carried out in an air atmosphere or in an inert gas atmosphere such as nitrogen gas.

[0045] In the production of copper nanoparticles A, from the viewpoint of removing impurities such as unreacted reducing agent and excess coating agent D that did not participate in the coating of copper particles a, after obtaining a dispersion of copper nanoparticles A, before performing freeze-drying or the like, the dispersion of copper nanoparticles A may be purified. The method for purifying the dispersion of copper nanoparticles A is not particularly limited, and examples thereof include membrane treatment such as dialysis and ultrafiltration; and methods such as centrifugation treatment. Among them, centrifugation treatment is preferable from the viewpoint of efficiently removing impurities. From the viewpoint of efficiently removing impurities, the molecular weight cut-off of the dialysis membrane is preferably 1,000 or more, more preferably 5,000 or more, still more preferably 10,000 or more, and preferably 100,000 or less, more preferably 70,000 or less.

[0046] <Copper microparticles B> The copper microparticles B in the present invention contain copper particles b, and the average particle diameter of the copper microparticles B is 0.5 μm or more and 10 μm or less.

[0047] The average particle diameter of the copper microparticles B is 0.5 μm or more from the viewpoint of suppressing shrinkage due to sintering when the copper particle dispersion is used for the joined body and improving the joint strength retention rate after storage of the copper particle dispersion, preferably 0.8 μm or more, more preferably 2.0 μm or more, still more preferably 3.0 μm or more, and is 10 μm or less, preferably 8.0 μm or less, more preferably 7.0 μm or less, still more preferably 6.0 μm or less from the viewpoint of increasing the surface energy of the copper particles and improving the joint strength retention rate after storage of the copper particle dispersion. The average particle diameter of the copper microparticles B is measured by the method described in the examples. The average particle diameter of the copper microparticles B can be adjusted by the type and amount of the reducing agent and the coating agent E described below, temperature conditions, etc. in the production of the copper microparticles B.

[0048] In the present invention, the blending amount of the copper microparticles B is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and even more preferably 35% by mass or more from the viewpoint of suppressing shrinkage due to sintering when the copper particle dispersion is used for the joined body and improving the joining strength of the joined body. And from the viewpoint of improving the joining strength retention rate after storage of the copper particle dispersion, it is preferably 70% by mass or less, more preferably 60% by mass or less, still more preferably 55% by mass or less, and even more preferably 50% by mass or less.

[0049] (Copper particles b) The average particle size of the copper particles b is preferably 0.5 μm or more, more preferably 0.8 μm or more, still more preferably 2.0 μm or more, and even more preferably 3.0 μm or more from the viewpoint of suppressing shrinkage due to sintering when the copper particle dispersion is used for the joined body and improving the joining strength retention rate after storage of the copper particle dispersion. And from the viewpoint of increasing the surface energy of the copper particles and improving the joining strength retention rate after storage of the copper particle dispersion, it is preferably 10 μm or less, more preferably 8.0 μm or less, still more preferably 7.0 μm or less, and even more preferably 6.0 μm or less. The average particle size of the copper particles b can be adjusted by the type and amount of the reducing agent and the coating agent E described later, temperature conditions, etc. in the production of the copper microparticles B.

[0050] (Coating agent E) The copper microparticles B in the present invention may further contain the coating agent E or may not contain the coating agent E. That is, the copper microparticles B in the present invention preferably contain the copper particles b and the coating agent E. Further, the copper microparticles B in the present invention preferably consist of the copper particles b. In the present invention, when the copper microparticles B contain the copper particles b and the coating agent E, the dispersibility of the copper microparticles B can be further improved by containing the coating agent E. On the other hand, when the copper microparticles B consist of the copper particles b, shrinkage due to sintering when the copper particle dispersion of the copper microparticles B is used for the joined body can be further suppressed, and the joining strength retention rate after storage of the copper particle dispersion can be further improved. From the above viewpoints, the copper microparticles B in the present invention preferably consist of copper particles b.

[0051] From the viewpoint of improving the bondability after storage of the copper particle dispersion, the boiling point of the coating agent E is preferably 350 °C or lower, more preferably 320 °C or lower, still more preferably 300 °C or lower.

[0052] As the coating agent E, those similar to the coating agent D in the above-mentioned copper nanoparticles A can be preferably used. Among these, as the coating agent E, from the viewpoint of suppressing the shrinkage due to sintering when the copper particle dispersion is used for the joined body and improving the retention rate of the bond strength after storage of the copper particle dispersion, it is preferably an aliphatic carboxylic acid, more preferably one or more selected from the group consisting of hexanoic acid, octanoic acid, decanoic acid, and lauric acid. Also, the coating agent E is preferably the same as the coating agent D from the viewpoint of suppressing the shrinkage due to sintering when the copper particle dispersion is used for the joined body and improving the retention rate of the bond strength after storage of the copper particle dispersion.

[0053] In the present invention, from the viewpoint of suppressing the shrinkage due to sintering when the copper particle dispersion is used for the joined body and improving the retention rate of the bond strength after storage of the copper particle dispersion, the content of the coating agent E coated on the copper particles b in the copper microparticles B is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, even more preferably 0.1% by mass or less, and is 0% by mass. The coating agent mass ratio is calculated from the content of the copper particles a and the content of the coating agent D in the copper particle dispersion measured by the method described in the examples using a differential thermal thermogravimetric simultaneous measurement device (TG / DTA).

[0054] (Production of Copper Microparticles B) In the present invention, when the copper microparticles B contain copper particles b and the coating agent E, the copper microparticles B are obtained by mixing a copper raw material compound, a reducing agent, and the coating agent E, and coating the copper particles b obtained by reducing the copper raw material compound with the reducing agent with the coating agent E. In addition, when the copper microparticles B contain copper particles b and a coating agent E, the copper microparticles B can be obtained as a dry powder of the copper microparticles B by drying the dispersion of the copper microparticles B by freeze-drying or the like after the copper microparticles B are obtained as a dispersion by the above method. When the copper microparticles B contain copper particles b and a coating agent E, in the production of the copper microparticles B, as aspects of the copper raw material compound, the reducing agent, and the conditions and steps, etc., those similar to the aspects of the production of the above copper nanoparticles A are preferably mentioned.

[0055] In the present invention, when the copper microparticles B consist of copper particles b, the copper microparticles are obtained by removing the coating agent E from the copper microparticles B containing the copper particles b and the coating agent E after obtaining the copper microparticles B containing the copper particles b and the coating agent E by the above method. In addition, when the copper microparticles B consist of copper particles b, as a method for removing the coating agent E from the copper microparticles B containing the copper particles b and the coating agent E in the production of the copper microparticles B, it is preferable to perform centrifugation after dispersing the copper microparticles B containing the copper particles b and the coating agent E in a solvent. The solvent for dispersing the copper microparticles B containing the copper particles b and the coating agent E is preferably alcohol, more preferably ethanol. The time for the centrifugation treatment is preferably 10 minutes or more, more preferably 15 minutes or more, and still more preferably 20 minutes or more. In addition, when the copper microparticles B consist of copper particles b, the copper microparticles B can be obtained as a dry powder of the copper microparticles B by drying the dispersion of the copper microparticles B by freeze-drying or the like after the copper microparticles B are obtained as a dispersion by the above method.

[0056] In addition, as another production method of the copper microparticles B consisting of copper particles b, an atomization method can be mentioned. Examples of the copper microparticles B obtained by the atomization method preferably include Cu-HWQ (Fukuda Metal Foil Powder Industry Co., Ltd.), MA-C02 (Mitsui Mining & Smelting Co., Ltd.), and MA-C03 (Mitsui Mining & Smelting Co., Ltd.).

[0057] In the present invention, the total blending amount of copper nanoparticles A and copper microparticles B in the copper particle dispersion is preferably 97% by mass or less, more preferably 96% by mass or less, still more preferably 95% by mass or less, and even more preferably 94% by mass or less, from the viewpoint of improving the bonding strength retention rate after storage of the copper particle dispersion, and is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0058] The blending mass ratio [copper nanoparticles A / copper microparticles B] of the copper nanoparticles A and the copper microparticles B suppresses shrinkage due to sintering when the copper particle dispersion is used for a bonded body, and from the viewpoint of improving the bonding strength retention rate after storage of the copper particle dispersion, is preferably 0.30 or more, more preferably 0.50 or more, still more preferably 0.80 or more, and even more preferably 1.00 or more, and is preferably 3.00 or less, more preferably 2.50 or less, still more preferably 2.00 or less, and even more preferably 1.50 or less.

[0059] <Dispersion medium C> In the production method of the present invention, dispersion medium C is mixed as a dispersion medium for dispersing copper nanoparticles A and copper microparticles B. As the dispersion medium C, from the viewpoint of improving the bonding strength retention rate after storage of the copper particle dispersion, it preferably contains one or more selected from the group consisting of aliphatic monohydric alcohols, (poly)alkylene glycols, (poly)alkylene glycol derivatives, glycerin, and glycerin derivatives.

[0060] Examples of the aliphatic monohydric alcohol include allyl alcohol (boiling point: 97 °C, molecular weight: 58), n-heptanol (boiling point: 176 °C, molecular weight: 116), n-octanol (boiling point: 195 °C, molecular weight: 130), 2-ethylhexanol (boiling point: 183 °C, molecular weight: 130), n-nonanol (boiling point: 214 °C, molecular weight: 144), and terpene alcohol. Among these, terpene alcohol is preferred as the aliphatic monohydric alcohol. Examples of terpene alcohols include preferably monoterpene alcohols such as α-terpineol (boiling point: 219°C, molecular weight: 154), linalool (boiling point: 198°C, molecular weight: 154), geraniol (boiling point: 229°C, molecular weight: 154), citronellol (boiling point: 225°C, molecular weight: 156), etc. Among them, α-terpineol is more preferable.

[0061] As used herein, “(poly)alkylene glycol” means one or more selected from the group consisting of alkylene glycol and polyalkylene glycol. Examples of alkylene glycol include, for example, ethylene glycol (boiling point: 197°C, molecular weight: 62), propylene glycol (boiling point: 188°C, molecular weight: 76), butylene glycol (1,3-butanediol, boiling point: 209°C, molecular weight: 90), etc. Examples of polyalkylene glycol include, for example, diethylene glycol (boiling point: 244°C, molecular weight: 106), triethylene glycol (boiling point: 287°C, molecular weight: 150), tetraethylene glycol (boiling point: 328°C, molecular weight: 194), polyethylene glycol, dipropylene glycol (boiling point: 232°C, molecular weight: 134), tripropylene glycol (boiling point: 273°C, molecular weight: 192), tetrapropylene glycol (boiling point: 300°C or higher, molecular weight: 250), polypropylene glycol, polytetramethylene glycol, etc. The number average molecular weight of polyethylene glycol is preferably 200 or more and 1000 or less, more preferably 250 or more and 600 or less, still more preferably 300 or more and 500 or less. Also, the number average molecular weight of polypropylene glycol is 260 or more and 1000 or less, more preferably 300 or more and 600 or less, still more preferably 350 or more and 500 or less. Among these, preferably one or more selected from diethylene glycol and tetraethylene glycol.

[0062] Examples of the (poly)alkylene glycol derivative include compounds in which the hydroxy group at the terminal of the (poly)alkylene glycol is etherified or esterified. Specifically, the (poly)alkylene glycol derivative is preferably at least one selected from the group consisting of (poly)alkylene glycol alkyl ethers and (poly)alkylene glycol monoalkyl ether acetates.

[0063] As used herein, the term "(poly)alkylene glycol alkyl ether" means at least one selected from the group consisting of alkylene glycol alkyl ethers and polyalkylene glycol alkyl ethers. Examples of the alkylene glycol alkyl ether include ethylene glycol monomethyl ether (boiling point: 124 °C, molecular weight: 76), ethylene glycol monobutyl ether (boiling point: 171 °C, molecular weight: 118), propylene glycol monomethyl ether (boiling point: 120 °C, molecular weight: 90), propylene glycol monobutyl ether (boiling point: 170 °C, molecular weight: 132), and the like. Examples of the polyalkylene glycol alkyl ether include diethylene glycol monomethyl ether (boiling point 194 °C, molecular weight: 120), diethylene glycol monoethyl ether (boiling point: 202 °C, molecular weight: 134), diethylene glycol monobutyl ether (boiling point: 231 °C, molecular weight: 162), triethylene glycol monobutyl ether (boiling point 276 °C, molecular weight: 206), dipropylene glycol monomethyl ether (boiling point 190 °C, molecular weight: 148), and the like.

[0064] As used herein, the term "(poly)alkylene glycol monoalkyl ether acetate" means at least one selected from the group consisting of alkylene glycol monoalkyl ether acetates and polyalkylene glycol monoalkyl ether acetates. Examples of the alkylene glycol monoalkyl ether acetate include ethylene glycol monomethyl ether acetate (boiling point: 143°C, molecular weight: 118), ethylene glycol monoethyl ether acetate (boiling point: 156°C, molecular weight: 132), ethylene glycol monobutyl ether acetate (boiling point: 192°C, molecular weight: 160), propylene glycol monomethyl ether acetate (boiling point: 146°C, molecular weight: 132), propylene glycol monoethyl ether acetate (boiling point: 145°C, molecular weight: 132), and the like. Examples of the polyalkylene glycol monoalkyl ether acetate include diethylene glycol monomethyl ether acetate (boiling point: 218°C, molecular weight: 176), diethylene glycol monoethyl ether acetate (boiling point: 217°C, molecular weight: 176), diethylene glycol monobutyl ether acetate (boiling point: 247°C, molecular weight: 204), and the like.

[0065] The glycerin derivative is not particularly limited as long as it is a solvent containing a structure derived from glycerin, and examples thereof include ether derivatives of glycerin, ester derivatives of glycerin, polyglycerin, and alkylene oxide adducts of glycerin (for example, ethylene oxide adducts and propylene oxide adducts). Examples of the polyglycerin preferably include diglycerin and triglycerin, and commercially available polyglycerins preferably include polyglycerin #310, polyglycerin #500, and polyglycerin #750 manufactured by Sakamoto Yakuhin Kogyo Co., Ltd. Examples of the ether derivative of glycerin preferably include 3-(2-ethylhexyloxy)-1,2-propanediol (boiling point: 325°C, molecular weight: 204). Examples of the ester derivative of glycerin preferably include glyceryl tributyrate (tributyrin, boiling point: 305°C, molecular weight: 302). Among these, as the glycerin derivative, glyceryl tributyrate (tributyrin) is preferred.

[0066] From the perspective of improving the joint strength retention rate after storage of the copper particle dispersion, the dispersion medium C preferably contains at least one selected from the group consisting of aliphatic monohydric alcohols, (poly)alkylene glycols, and glycerin derivatives, more preferably contains at least one selected from the group consisting of terpene alcohols, (poly)alkylene glycols, and glycerin derivatives, still more preferably contains at least one selected from the group consisting of α-terpineol, diethylene glycol, tetraethylene glycol, and glycerol tributyrate, and even more preferably contains two or more selected from the group consisting of α-terpineol, diethylene glycol, tetraethylene glycol, and glycerol tributyrate.

[0067] From the perspective of improving the joint strength retention rate after storage of the copper particle dispersion, the boiling point of the dispersion medium C at 1 atm is preferably 180 °C or higher, more preferably 200 °C or higher, still more preferably 210 °C or higher, and even more preferably 215 °C or higher, and is preferably 400 °C or lower, more preferably 360 °C or lower, still more preferably 330 °C or lower, and even more preferably 300 °C or lower. When two or more dispersion media C are used in combination, the boiling point of the dispersion medium C is the weighted average value weighted by the content (mass%) of each dispersion medium.

[0068] From the perspective of improving the joint strength retention rate after storage of the copper particle dispersion, the molecular weight of the dispersion medium C is preferably 60 or higher, more preferably 80 or higher, still more preferably 100 or higher, and even more preferably 120 or higher, and is preferably 450 or lower, more preferably 400 or lower, still more preferably 350 or lower, and even more preferably 300 or lower. When two or more dispersion media C are used in combination, the molecular weight of the dispersion medium C is the weighted average value weighted by the content (mass%) of each dispersion medium.

[0069] In the present invention, the blending amount of the dispersion medium C is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 5% by mass or more, even more preferably 6% by mass or more, from the viewpoint of improving the bonding strength retention rate after storage of the copper particle dispersion, and is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less, even more preferably 10% by mass or less.

[0070] In the present invention, in addition to the above-described copper nanoparticles A, the above-described copper microparticles B, and the above-described dispersion medium C, various additives may be blended as necessary. Examples of the additives include metal particles other than the copper nanoparticles A and the copper microparticles, sintering accelerators such as glass frit, antioxidants, viscosity modifiers, pH adjusters, buffers, defoamers, leveling agents, volatility inhibitors, and the like. Examples of the metal particles other than the copper nanoparticles A and the copper microparticles include metal particles such as zinc, nickel, silver, gold, palladium, and platinum. In the copper particle dispersion of the present invention, the blending amount of the additive in the copper particle dispersion is preferably 1% by mass or less.

[0071] [Copper particle dispersion] The copper particle dispersion of the present invention can be obtained by the method for producing the copper particle dispersion of the present invention described above. That is, the copper particle dispersion of the present invention contains the above-described copper nanoparticles A, the above-described copper microparticles B, and the above-described dispersion medium C, and the distance Ra of the Hansen solubility parameters between the copper nanoparticles A and the copper microparticles B, which is obtained by the above formula (1) (A-B) is 9.0 MPa 1 / 2 or less.

[0072] In the copper particle dispersion of the present invention, the distance Ra of the Hansen solubility parameters between the copper nanoparticles A and the copper microparticles B (A-B) improves the dispersibility of the copper nanoparticles A and the copper microparticles B, and is 9.0 MPa 1 / 2 or less, preferably 8.0 MPa 1 / 2 or less, more preferably 6.0 MPa 1 / 2 or less, from the viewpoint of improving the bonding strength retention rate after storage of the copper particle dispersion.

[0073] In the copper particle dispersion of the present invention, the distance Ra between the Hansen solubility parameter of the copper nanoparticles A and the dispersion medium C, which is obtained by the above formula (2) (A-C) is preferably 20.0 MPa or less, more preferably 15.0 MPa or less, still more preferably 10.0 MPa or less, and even more preferably 8.0 MPa or less from the viewpoint of improving the dispersibility of the copper nanoparticles A and improving the joint strength retention rate after storage of the copper particle dispersion. 1 / 2 is preferably 15.0 MPa or less, more preferably 12.0 MPa or less, still more preferably 8.0 MPa or less, and even more preferably 6.0 MPa or less from the viewpoint of improving the dispersibility of the copper microparticles B and improving the joint strength retention rate after storage of the copper particle dispersion. 1 / 2 is preferably 10.0 MPa or less, more preferably 8.0 MPa or less, still more preferably 6.0 MPa or less, and even more preferably 4.0 MPa or less from the viewpoint of improving the dispersibility of the copper microparticles B and improving the joint strength retention rate after storage of the copper particle dispersion. 1 / 2 is preferably 8.0 MPa or less, more preferably 6.0 MPa or less, still more preferably 4.0 MPa or less, and even more preferably 2.0 MPa or less from the viewpoint of improving the dispersibility of the copper microparticles B and improving the joint strength retention rate after storage of the copper particle dispersion. 1 / 2 is as follows.

[0074] In the copper particle dispersion of the present invention, the distance Ra between the Hansen solubility parameter of the copper microparticles B and the dispersion medium C, which is obtained by the above formula (3) (B-C) is preferably 15.0 MPa or less, more preferably 12.0 MPa or less, still more preferably 8.0 MPa or less, and even more preferably 6.0 MPa or less from the viewpoint of improving the dispersibility of the copper microparticles B and improving the joint strength retention rate after storage of the copper particle dispersion. 1 / 2 is preferably 12.0 MPa or less, more preferably 10.0 MPa or less, still more preferably 6.0 MPa or less, and even more preferably 4.0 MPa or less from the viewpoint of improving the dispersibility of the copper microparticles B and improving the joint strength retention rate after storage of the copper particle dispersion. 1 / 2 is preferably 8.0 MPa or less, more preferably 6.0 MPa or less, still more preferably 4.0 MPa or less, and even more preferably 2.0 MPa or less from the viewpoint of improving the dispersibility of the copper microparticles B and improving the joint strength retention rate after storage of the copper particle dispersion. 1 / 2 is preferably 6.0 MPa or less, more preferably 4.0 MPa or less, still more preferably 2.0 MPa or less, and even more preferably 1.0 MPa or less from the viewpoint of improving the dispersibility of the copper microparticles B and improving the joint strength retention rate after storage of the copper particle dispersion. 1 / 2 is as follows.

[0075] In the copper particle dispersion of the present invention, the content of the copper nanoparticles A in the copper particle dispersion is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, and even more preferably 40% by mass or more from the viewpoint of improving the joint property after storage of the copper particle dispersion. And, from the viewpoint of suppressing the shrinkage due to sintering when the copper particle dispersion is used for a joined body and improving the joint strength of the joined body, it is preferably 90% by mass or less, more preferably 80% by mass or less, still more preferably 70% by mass or less, and even more preferably 60% by mass or less.

[0076] In the copper particle dispersion of the present invention, the content of the coating agent D in the copper particle dispersion is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, even more preferably 0.4% by mass or more, even more preferably 0.5% by mass or more, from the viewpoint of improving the dispersibility of the copper nanoparticles A and from the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion, and is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, even more preferably 1.5% by mass or less, even more preferably 1% by mass or less.

[0077] In the copper particle dispersion of the present invention, the content of the copper microparticles B in the copper particle dispersion is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, even more preferably 35% by mass or more, from the viewpoint of suppressing shrinkage due to sintering when the copper particle dispersion is used as a joined body and improving the joint strength of the joined body, and is preferably 70% by mass or less, more preferably 60% by mass or less, still more preferably 55% by mass or less, even more preferably 50% by mass or less, from the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion.

[0078] In the copper particle dispersion of the present invention, when the copper microparticles B contain copper particles b and a dispersant E, the content of the coating agent E in the copper particle dispersion is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, still more preferably 0.2% by mass or less, even more preferably 0.1% by mass or less, even more preferably 0.05% by mass or less, and even more preferably 0% by mass, from the viewpoint of suppressing shrinkage due to sintering when the copper particle dispersion is used as a joined body and from the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion.

[0079] In the copper particle dispersion of the present invention, the total content of copper nanoparticles A and copper microparticles B in the copper particle dispersion is preferably 97% by mass or less, more preferably 96% by mass or less, still more preferably 95% by mass or less, and even more preferably 94% by mass or less, from the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion, and is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0080] In the copper particle dispersion of the present invention, the content of the dispersion medium C in the copper particle dispersion is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 5% by mass or more, and even more preferably 6% by mass or more, from the viewpoint of improving the joint strength retention rate after storage of the copper particle dispersion, and is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0081] The copper particle dispersion of the present invention may contain various additives as required, in addition to the above-mentioned copper nanoparticles A, the above-mentioned copper microparticles B, and the above-mentioned dispersion medium C. Examples of the additive include metal particles other than copper nanoparticles A and copper microparticles, sintering accelerators such as glass frit, antioxidants, viscosity modifiers, pH adjusters, buffers, defoamers, leveling agents, volatilization inhibitors, and the like. Examples of the metal particles other than copper nanoparticles A and copper microparticles include metal particles such as zinc, nickel, silver, gold, palladium, and platinum. In the copper particle dispersion of the present invention, the content of the additive in the copper particle dispersion is preferably 1% by mass or less.

[0082] (Use) The copper particle dispersion obtained by the production method of the present invention is excellent in the joint strength retention rate after storage of the copper particle dispersion, and thus can be used for forming conductive members of various electronic and electrical devices. The conductive member can preferably be used for bonding agents such as solder; antennas such as RFID (radio frequency identifier) tags; capacitors such as MLCC (multi-layer 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 wiring boards and flexible wiring boards; organic solar cells; sensors such as flexible sensors, etc. Among these, since the copper particle dispersion according to the present invention is excellent in the joint strength retention rate after storage of the copper particle dispersion, it is preferably used for bonding a plurality of metal members.

[0083] The present invention further discloses the following aspects. <1> A method for producing a copper particle dispersion, comprising a step of mixing copper nanoparticles A, copper microparticles B, and a dispersion medium C, wherein the copper nanoparticles A contain copper particles a and a coating agent D, the average particle size of the copper nanoparticles A is 50 nm or more and 300 nm or less, the copper microparticles B contain copper particles b, the average particle size of the copper microparticles B is 0.5 μm or more and 10 μm or less, and the distance Ra(A - B) of the Hansen solubility parameters between the copper nanoparticles A and the copper microparticles B, which is obtained by the following formula (1), is 9.0 MPa 1 / 2 or less, which is a method for producing a copper particle dispersion. Ra (A-B) ={(4×(δD A -δD B ) 2 +(δP A -δP B ) 2 +(δH A -δH B ) 2 ) 1 / 2 (1) (However, in the above formula (1), δD A , δP A , and δH A respectively represent the dispersion force term, the polar term, and the hydrogen bond term of the Hansen solubility parameter of the copper nanoparticles A, and δD B , δP B , and δHB represents the dispersion force term, polar term, and hydrogen bonding term of the Hansen solubility parameter of copper microparticles B, respectively. The Hansen solubility parameters of copper nanoparticles A and copper microparticles B are the values obtained from the HSPiP program. <2> Distance Ra between the Hansen solubility parameters of copper nanoparticles A and copper microparticles B (A-B) is preferably 8.0 MPa 1 / 2 or less, more preferably 6.0 MPa 1 / 2 or less, for the method for producing a copper particle dispersion according to <1>. <3> Distance Ra between the Hansen solubility parameters of copper nanoparticles A and dispersion medium C, obtained by the following formula (2) (A-C) is preferably 20.0 MPa 1 / 2 or less, more preferably 15.0 MPa 1 / 2 or less, still more preferably 10.0 MPa 1 / 2 or less, even more preferably 8.0 MPa 1 / 2 or less, for the method for producing a copper particle dispersion according to <1> or <2>. Ra (A-C) = {(4 × (δD A - δD C ) 2 + (δP A - δP C ) 2 + (δH A - δH C ) 2 ) 1 / 2 (2) (However, in the above formula (2), δD A , δP A , and δH A represent the dispersion force term, polar term, and hydrogen bonding term of the Hansen solubility parameter of copper nanoparticles A, respectively. δD C , δP C , and δH C represent the dispersion force term, polar term, and hydrogen bonding term of the Hansen solubility parameter of dispersion medium C, respectively. The Hansen solubility parameter of dispersion medium C is the value obtained by weighted average weighted by the content (volume basis) of each dispersion medium based on the value obtained by the HSPiP program. <4> The distance Ra between the Hansen solubility parameters of the copper microparticles B and the dispersion medium C, which is obtained by the following formula (3) (B-C) is preferably 15.0 MPa 1 / 2 or less, more preferably 12.0 MPa 1 / 2 or less, still more preferably 8.0 MPa 1 / 2 or less, even more preferably 6.0 MPa 1 / 2 or less, which is the method for producing a copper particle dispersion according to any one of <1> to <3>. Ra (B-C) = {(4 × (δD B - δD C )) 2 + (δP B - δP C )) 2 + (δH B - δH C )) 2 ) 1 / 2 (3) (However, in the formula (3), δD B , δP B , and δH B respectively represent the dispersion force term, the polar term, and the hydrogen bond term of the Hansen solubility parameter of the copper microparticles B, and δD C , δP C , and δH C respectively represent the dispersion force term, the polar term, and the hydrogen bond term of the Hansen solubility parameter of the dispersion medium C. The Hansen solubility parameter of the dispersion medium C is a value obtained by weighted average weighted by the content (volume basis) of each dispersion medium based on the value obtained by the HSPiP program.) <5> Among the Hansen solubility parameters of the copper nanoparticles A, the δP A (polar term) of the copper nanoparticles A is preferably 1.0 MPa 1 / 2 or more, more preferably 3.0 MPa 1 / 2 or more, still more preferably 5.0 MPa 1 / 2 or more, even more preferably 7.0 MPa 1 / 2 or more, which is the method for producing a copper particle dispersion according to any one of <1> to <4>. <6> Among the Hansen solubility parameters of the copper microparticles B, the δP B(Polar term) is preferably 1.0 MPa 1 / 2 or more, more preferably 3.0 MPa 1 / 2 or more, still more preferably 5.0 MPa 1 / 2 or more, even more preferably 7.0 MPa 1 / 2 or more, the method for producing a copper particle dispersion according to any one of <1> to <5>. <7> The average particle diameter of copper nanoparticles A is preferably 75 nm or more, more preferably 100 nm or more, still more preferably 125 nm or more, and preferably 250 nm or less, still more preferably 230 nm or less, even more preferably 200 nm or less, the method for producing a copper particle dispersion according to any one of <1> to <6>. <8> The compounding amount of copper nanoparticles A is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, even more preferably 40% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less, still more preferably 70% by mass or less, even more preferably 60% by mass or less, the method for producing a copper particle dispersion according to any one of <1> to <7>. <9> The average particle diameter of copper particles a is preferably 50 nm or more, more preferably 75 nm or more, still more preferably 100 nm or more, even more preferably 125 nm or more, and preferably 400 nm or less, more preferably 300 nm or less, still more preferably 250 nm or less, even more preferably 200 nm or less, the method for producing a copper particle dispersion according to any one of <1> to <8>. <10> The coating agent D is preferably at least one selected from the group consisting of aliphatic carboxylic acids and polymers containing a hydrophilic group, the method for producing a copper particle dispersion according to any one of <1> to <9>. <11> The number of carbon atoms of the aliphatic carboxylic acid is preferably 1 or more and 24 or less, more preferably 2 or more and 20 or less, still more preferably 4 or more and 16 or less, even more preferably 6 or more and 12 or less, the method for producing a copper particle dispersion according to <10>. <12> The method for producing a copper particle dispersion according to <10> or <11>, wherein the polymer containing a hydrophilic group is a vinyl polymer P containing a structural unit derived from a monomer (p-1) having a carboxy group and a structural unit derived from a monomer (p-2) having a polyalkylene glycol segment. <13> The method for producing a copper particle dispersion according to <12>, wherein the vinyl polymer P is at least one of a random copolymer, a block copolymer, and an alternating copolymer. <14> The method for producing a copper particle dispersion according to <12> or <13>, wherein the monomer (p-1) is preferably at least one selected from the group consisting of (meth)acrylic acid and maleic acid, more preferably (meth)acrylic acid, and still more preferably methacrylic acid. <15> The method for producing a copper particle dispersion according to any one of <12> to <14>, wherein the monomer (p-2) is preferably at least one selected from the group consisting of polyalkylene glycol (meth)acrylate and alkoxypolyalkylene glycol (meth)acrylate, and more preferably alkoxypolyalkylene glycol (meth)acrylate. <16> The method for producing a copper particle dispersion according to <15>, wherein the carbon number of the alkoxy group of the alkoxypolyalkylene glycol (meth)acrylate is preferably 18 or less, more preferably 14 or less, and still more preferably 12 or less. <17> The method for producing a copper particle dispersion according to any one of <12> to <16>, wherein the polyalkylene glycol segment of the monomer (p-2) preferably contains units derived from an alkylene oxide having 2 to 4 carbon atoms. <18> The method for producing a copper particle dispersion according to <17>, wherein the alkylene oxide of the unit derived from an alkylene oxide having 2 to 4 carbon atoms is preferably at least one selected from the group consisting of ethylene oxide and propylene oxide, and more preferably ethylene oxide. <19> The number of units derived from alkylene oxide in the polyalkylene glycol segment is preferably 2 or more, more preferably 3 or more, still more preferably 4 or more, and preferably 100 or less, more preferably 70 or less, still more preferably 50 or less, even more preferably 40 or less, and even more preferably 35 or less. The method for producing a copper particle dispersion according to any one of <12> to <18>. <20> The vinyl polymer P further contains a structural unit derived from a hydrophobic monomer (p-3). The method for producing a copper particle dispersion according to any one of <12> to <19>. <21> The monomer (p-3) is preferably at least one selected from the group consisting of an aromatic group-containing monomer and a (meth) acrylate having a hydrocarbon group derived from an aliphatic alcohol. The method for producing a copper particle dispersion according to <20>. <22> The aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group having 6 to 22 carbon atoms, which may have a substituent containing a hetero atom, more preferably at least one selected from the group consisting of a styrene-based monomer and an aromatic group-containing (meth) acrylate, and still more preferably a styrene-based monomer. The method for producing a copper particle dispersion according to <21>. <23> The (meth) acrylate having a hydrocarbon group derived from an aliphatic alcohol preferably has a hydrocarbon group derived from an aliphatic alcohol having 22 or less carbon atoms, more preferably a hydrocarbon group derived from an aliphatic alcohol having 12 or less carbon atoms, still more preferably a hydrocarbon group derived from an aliphatic alcohol having 8 or less carbon atoms, and even more preferably a hydrocarbon group derived from an aliphatic alcohol having 4 or less carbon atoms. The method for producing a copper particle dispersion according to any one of <21> or <22>. <24> The monomer (p-3) is preferably at least one selected from the group consisting of aromatic group-containing monomers and (meth)acrylates having a linear alkyl group, more preferably at least one selected from the group consisting of styrene-based monomers and (meth)acrylates having a linear alkyl group with 1 to 4 carbon atoms, still more preferably at least one selected from the group consisting of 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 the group consisting of styrene, α-methylstyrene, and methyl (meth)acrylate, and even more preferably at least one selected from the group consisting of styrene and methyl (meth)acrylate, the method for producing a copper particle dispersion according to any one of <20> to <23>. <25> The number average molecular weight Mn of the vinyl polymer P is preferably 4,000 or more, more preferably 6,000 or more, still more preferably 7,000 or more, and preferably 50,000 or less, more preferably 30,000 or less, still more preferably 20,000 or less, even more preferably 15,000 or less, and even more preferably 10,000 or less, the method for producing a copper particle dispersion according to any one of <12> to <24>. <26> The acid value of the vinyl polymer P is preferably 20 mgKOH / g or more, more preferably 25 mgKOH / g or more, still more preferably 30 mgKOH / g or more, even more preferably 35 mgKOH / g or more, and even more preferably 40 mgKOH / g or more, and preferably 250 mgKOH / g or less, more preferably 200 mgKOH / g or less, still more preferably 150 mgKOH / g or less, even more preferably 130 mgKOH / g or less, and even more preferably 110 mgKOH / g or less, the method for producing a copper particle dispersion according to any one of <12> to <25>. <27> In the copper nanoparticles A, the content of the coating agent D coated on the copper particles a is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.6% by mass or more, even more preferably 0.8% by mass or more, and even more preferably 1.0% by mass or more, and is preferably 2.5% by mass or less, more preferably 2.0% by mass or less, still more preferably 1.8% by mass or less, and even more preferably 1.6% by mass or less. The method for producing a copper particle dispersion according to any one of <1> to <26>. <28> The copper nanoparticles A are obtained by mixing a copper raw material compound, a reducing agent, and a coating agent D, and coating the copper particles a obtained by reducing the copper raw material compound with the reducing agent with the coating agent D. The method for producing a copper particle dispersion according to any one of claims <1> to <27>. <29> The copper raw material compound is one or more selected from the group consisting of copper sulfate, copper nitrate, cupric oxide, cuprous oxide, copper formate, copper acetate, and copper oxalate. The method for producing a copper particle dispersion according to <28>. <30> The reducing agent is one or more selected from the group consisting of hydrazine compounds, boron compounds, and inorganic acid salts. The method for producing a copper particle dispersion according to <28> or <29>. <31> The hydrazine compound is one or more selected from the group consisting of, for example, hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrazine hydrate. The method for producing a copper particle dispersion according to <30>. <32> The boron compound is one or more selected from the group consisting of sodium borohydride. The method for producing a copper particle dispersion according to <30> or <31>. <33> The inorganic acid salt is one or more selected from the group consisting of sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium nitrite, sodium hyponitrite, phosphorous acid, sodium phosphite, hypophosphorous acid, and sodium hypophosphite. The method for producing a copper particle dispersion according to any one of <30> to <32>. <34> The method for producing a copper particle dispersion according to any one of <28> to <33>, wherein the solvent for dispersing the copper raw material compound and the reducing agent is at least one selected from the group consisting of water, methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol. <35> The method for producing a copper particle dispersion according to any one of <28> to <34>, wherein the temperature of the reduction reaction is preferably 5°C or higher, more preferably 10°C or higher, still more preferably 20°C or higher, still more preferably 30°C or higher, and preferably 100°C or lower, more preferably 90°C or lower, still more preferably 80°C or lower, still more preferably 75°C or lower. <36> The method for producing a copper particle dispersion according to any one of <1> to <35>, wherein the average particle diameter of the copper microparticles B is preferably 0.8 μm or more, more preferably 2.0 μm or more, still more preferably 3.0 μm or more, and preferably 8.0 μm or less, more preferably 7.0 μm or less, still more preferably 6.0 μm or less. <37> The method for producing a copper particle dispersion according to any one of <1> to <36>, wherein the blending amount of the copper microparticles B is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, even more preferably 35% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less, still more preferably 55% by mass or less, even more preferably 50% by mass or less. <38> The method for producing a copper particle dispersion according to any one of <1> to <37>, wherein the average particle diameter of the copper particles b is preferably 0.5 μm or more, more preferably 0.8 μm or more, still more preferably 2.0 μm or more, even more preferably 3.0 μm or more, and preferably 10 μm or less, more preferably 8.0 μm or less, still more preferably 7.0 μm or less, even more preferably 6.0 μm or less. <39> The method for producing a copper particle dispersion according to any one of <1> to <37>, wherein the copper microparticles B contain the copper particles b and the coating agent E. <40>The method for producing the copper particle dispersion according to <39>, wherein the boiling point of the coating agent E is preferably 350 ° C or lower, more preferably 320 ° C or lower, still more preferably 300 ° C or lower. <41>The method for producing the copper particle dispersion according to <39> or <40>, wherein the coating agent E is preferably an aliphatic carboxylic acid, more preferably at least one selected from the group consisting of hexanoic acid, octanoic acid, decanoic acid, and lauric acid. <42>The method for producing the copper particle dispersion according to any one of <39> to <41>, wherein the coating agent E is the same as the coating agent D. <43>The method for producing the copper particle dispersion according to any one of <39> to <42>, wherein the content of the coating agent E coated on the copper particles b in the copper microparticles B is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less, and is 0% by mass. <44>The method for producing the copper particle dispersion according to any one of <1> to <38>, wherein the copper microparticles B are composed of copper particles b. <45>The method for producing the copper particle dispersion according to any one of <1> to <44>, wherein the total blending amount of the copper nanoparticles A and the copper microparticles B in the copper particle dispersion 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, and is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, and even more preferably 90% by mass or more. <46>The method for producing the copper particle dispersion according to any one of <1> to <45>, wherein the blending mass ratio [copper nanoparticles A / copper microparticles B] of the copper nanoparticles A and the copper microparticles B is preferably 0.30 or more, more preferably 0.50 or more, still more preferably 0.80 or more, even more preferably 1.00 or more, and is preferably 3.00 or less, more preferably 2.50 or less, still more preferably 2.00 or less, and even more preferably 1.50 or less. <47> The method for producing a copper particle dispersion according to any one of <1> to <46>, wherein the dispersion medium C contains one or more selected from the group consisting of aliphatic monohydric alcohols, (poly)alkylene glycols, (poly)alkylene glycol derivatives, glycerin, and glycerin derivatives. <48> The method for producing a copper particle dispersion according to <47>, wherein the aliphatic monohydric alcohol is preferably one or more selected from the group consisting of allyl alcohol, n-heptanol, n-octanol, 2-ethylhexanol, n-nonanol, and terpene alcohol, and more preferably terpene alcohol. <49> The method for producing a copper particle dispersion according to <47> or <48>, wherein the (poly)alkylene glycol is one or more selected from ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, and polytetramethylene glycol. <50> The method for producing a copper particle dispersion according to any one of <47> to <49>, wherein the (poly)alkylene glycol derivative is one or more selected from the group consisting of (poly)alkylene glycol alkyl ethers and (poly)alkylene glycol monoalkyl ether acetates. <51> The method for producing a copper particle dispersion according to <50>, wherein the (poly)alkylene glycol alkyl ether is one or more selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and dipropylene glycol monomethyl ether. <52> The (poly)alkylene glycol monoalkyl ether acetate is at least one selected from the group consisting of ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate, and is the method for producing a copper particle dispersion according to <50> or <51>. <53> The glycerin derivative is at least one selected from the group consisting of 3-(2-ethylhexyloxy)-1,2-propanediol and glyceryl tributyrate, and is the method for producing a copper particle dispersion according to any one of <47> to <52>. <54> The dispersion medium C preferably contains at least one selected from the group consisting of aliphatic monohydric alcohols, (poly)alkylene glycols, and glycerin derivatives, more preferably contains at least one selected from the group consisting of terpene alcohols, (poly)alkylene glycols, and glycerin derivatives, still more preferably contains at least one selected from the group consisting of α-terpineol, diethylene glycol, tetraethylene glycol, and glyceryl tributyrate, and even more preferably contains two or more selected from the group consisting of α-terpineol, diethylene glycol, tetraethylene glycol, and glyceryl tributyrate, and is the method for producing a copper particle dispersion according to any one of <1> to <53>. <55> The boiling point of the dispersion medium C at 1 atm is preferably 180 °C or higher, more preferably 200 °C or higher, still more preferably 210 °C or higher, and even more preferably 215 °C or higher, and is preferably 400 °C or lower, more preferably 360 °C or lower, still more preferably 330 °C or lower, and even more preferably 300 °C or lower, and is the method for producing a copper particle dispersion according to any one of <1> to <54>. <56> The molecular weight of dispersion medium C is preferably 60 or more, more preferably 80 or more, still more preferably 100 or more, even more preferably 120 or more, and is preferably 450 or less, more preferably 400 or less, still more preferably 350 or less, even more preferably 300 or less. The method for producing a copper particle dispersion according to any one of <1> to <55>. <57> The blending amount of dispersion medium C is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 5% by mass or more, even more preferably 6% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less, even more preferably 10% by mass or less. The method for producing a copper particle dispersion according to any one of <1> to <56>. <58> It contains copper nanoparticles A, copper microparticles B, and dispersion medium C, contains copper particles a and coating agent D, the average particle size of the copper nanoparticles A is 50 nm or more and 300 nm or less, the copper microparticles B contain copper particles b, the average particle size of the copper microparticles B is 0.5 μm or more and 10 μm or less, and the distance Ra(A - B) of the Hansen solubility parameters between the copper nanoparticles A and the copper microparticles B obtained by the following formula (1) is 9.0 MPa 1 / 2 The following is a copper particle dispersion. Ra (A-B) ={(4×(δD A -δD B ) 2 +(δP A -δP B ) 2 +(δH A -δH B ) 2 ) 1 / 2 (1) (However, in the above formula (1), δD A , δP A , and δH A respectively represent the dispersion force term, polar term, and hydrogen bond term of the Hansen solubility parameter of copper nanoparticles A, and δD B , δP B , and δH Brespectively represent the dispersion force term, polar term, and hydrogen bonding term of the Hansen solubility parameter of copper microparticles B. The Hansen solubility parameters of copper nanoparticles A and copper microparticles B are the values obtained from the HSPiP program. <59> Distance Ra between the Hansen solubility parameters of copper nanoparticles A and copper microparticles B (A-B) is preferably 8.0 MPa 1 / 2 or less, more preferably 6.0 MPa 1 / 2 or less. The copper particle dispersion according to <58>. <60> Distance Ra between the Hansen solubility parameters of copper nanoparticles A and dispersion medium C, obtained by the following formula (2) (A-C) is preferably 20.0 MPa 1 / 2 or less, more preferably 15.0 MPa 1 / 2 or less, still more preferably 10.0 MPa 1 / 2 or less, even more preferably 8.0 MPa 1 / 2 or less. The copper particle dispersion according to <58> or <59>. Ra (A-C) ={(4 × (δD A - δD C ) 2 + (δP A - δP C ) 2 + (δH A - δH C ) 2 ) 1 / 2 (2) (However, in the above formula (2), δD A , δP A , and δH A respectively represent the dispersion force term, polar term, and hydrogen bonding term of the Hansen solubility parameter of copper nanoparticles A. δD C , δP C , and δH C respectively represent the dispersion force term, polar term, and hydrogen bonding term of the Hansen solubility parameter of dispersion medium C. The Hansen solubility parameter of dispersion medium C is a value obtained by weighted average weighted by the content (volume basis) of each dispersion medium based on the value obtained by the HSPiP program. <61> The distance Ra between the Hansen solubility parameters of the copper microparticles B and the dispersion medium C, which is obtained by the following formula (3) (B-C) is preferably 15.0 MPa 1 / 2 or less, more preferably 12.0 MPa 1 / 2 or less, still more preferably 8.0 MPa 1 / 2 or less, even more preferably 6.0 MPa 1 / 2 or less, and is the copper particle dispersion according to any one of <58> to <60>. Ra (B-C) = {(4 × (δD B - δD C ) 2 + (δP B - δP C ) 2 + (δH B - δH C ) 2 ) 1 / 2 (3) (However, in the formula (3), δD B , δP B , and δH B respectively represent the dispersion force term, the polar term, and the hydrogen bond term of the Hansen solubility parameter of the copper microparticles B, and δD C , δP C , and δH C respectively represent the dispersion force term, the polar term, and the hydrogen bond term of the Hansen solubility parameter of the dispersion medium C. The Hansen solubility parameter of the dispersion medium C is a value obtained by weighted average weighted by the content (volume basis) of each dispersion medium based on the value obtained by the HSPiP program.) <62> The content of the copper nanoparticles A in the copper particle dispersion is preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, even more preferably 40% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less, still more preferably 70% by mass or less, even more preferably 60% by mass or less, and is the copper particle dispersion according to any one of <58> to <61>. <63> The content of coating agent D in the copper particle dispersion is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, even more preferably 0.4% by mass or more, even more preferably 0.5% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, even more preferably 1.5% by mass or less, even more preferably 1% by mass or less, the copper particle dispersion according to any one of <58> to <62>. <64> The content of copper microparticles B in the copper particle dispersion is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, even more preferably 35% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less, still more preferably 55% by mass or less, even more preferably 50% by mass or less, the copper particle dispersion according to any one of <58> to <63>. <65> The content of coating agent E in the copper particle dispersion is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, still more preferably 0.2% by mass or less, even more preferably 0.1% by mass or less, even more preferably 0.05% by mass or less, and even more preferably 0% by mass, the copper particle dispersion according to any one of <58> to <64>. <66> The total content of copper nanoparticles A and copper microparticles B in the copper particle dispersion 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, and preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, even more preferably 90% by mass or more, the copper particle dispersion according to any one of <58> to <65>. <67> The content of dispersion medium C in the copper particle dispersion is preferably 3% by mass or more, more preferably 4% by mass or more, still 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, still more preferably 20% by mass or less, even more preferably 10% by mass or less, the copper particle dispersion according to any one of <58> to <66>.

Examples

[0084] Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. In the following production examples, examples and comparative examples, "parts" and "%" are "parts by mass" and "mass%" unless otherwise specified. Various physical properties were measured or calculated by the following methods.

[0085] <Average particle sizes of copper nanoparticles A and copper microparticles B> Using a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, field emission scanning electron microscope: S-4800), scanning electron microscope (SEM) images of copper nanoparticles A and copper microparticles B were taken. The magnification was determined according to the particle size of the particles, and imaging was performed in the range of 5000 times to 150000 times. The SEM images were analyzed using image analysis software ImageJ (National Institutes of Health, USA). The particle sizes were determined for 100 or more particles per sample, and the arithmetic mean value thereof was taken as the average particle size of copper nanoparticles A and copper microparticles B.

[0086] [Content (mass %) of coating agent D coated on copper particles a in copper nanoparticles A] Using a differential thermal thermogravimetric simultaneous measurement device (TG / DTA) (manufactured by Hitachi High-Technologies Science Corporation, trade name: STA7200RV), 10 mg of copper nanoparticles A was weighed into an aluminum pan cell, and the temperature was raised from 35°C to 550°C at a heating rate of 10°C / min under a nitrogen flow of 50 mL / min, and the mass reduction amount was measured. Taking the mass reduction amount from 35°C to 550°C as the mass of the coating agent D and the remaining mass at 550°C as the mass of the copper particles a, the content (mass %) of the coating agent D coated on the copper particles a in the copper nanoparticles A was calculated by the following formula. Content (mass %) of coating agent D coated on copper particles a in copper nanoparticles A = (Content of coating agent D (g)) / (Content of coating agent D (g) + Content of copper particles a (g)) × 100 = (Mass reduction amount from 35°C to 550°C) / {(Mass reduction amount from 35°C to 550°C) + (Remaining mass at 550°C)} × 100

[0087] <Content (mass %) of coating agent E coated on copper particles b in copper microparticles B> Using a differential thermal thermogravimetric simultaneous measurement device (TG / DTA) (manufactured by Hitachi High-Tech Science Corporation, product name: STA7200RV), 10 mg of copper microparticles B was weighed into an aluminum pan cell, and the temperature was raised from 35 °C to 550 °C at a heating rate of 10 °C / min under a nitrogen flow of 50 mL / min, and the mass reduction amount was measured. Regarding the mass reduction amount from 35 °C to 550 °C as the mass of coating agent E and the remaining mass at 550 °C as the mass of copper particles b, the content (mass %) of coating agent E coated on copper particles b in copper microparticles B was calculated by the following formula. Content (mass %) of coating agent E coated on copper particles b in copper microparticles B = (Content of coating agent E (g)) / (Content of coating agent E (g) + Content of copper particles b (g)) × 100 = (Mass reduction amount from 35 °C to 550 °C) / {(Mass reduction amount from 35 °C to 550 °C) + (Remaining mass at 550 °C)} × 100

[0088] <Number average molecular weight Mn of polymer P> It was determined by gel permeation chromatography. The measurement sample was prepared by mixing 0.1 g of the polymer with 10 mL of the eluent in a glass vial, stirring at 25 °C for 10 hours with a magnetic stirrer, and filtering with a syringe filter (DISMIC-13HP PTFE 0.2 μm, manufactured by Advantec Toyo Co., Ltd.). The measurement conditions are shown below. GPC device: "HLC-8320GPC" manufactured by Tosoh Corporation Column: "TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guardcolumn Super AW-H" manufactured by Tosoh Corporation 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: 0.5 mL / min Standard substance: Monodisperse polystyrene kit "PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500)" manufactured by Tosoh Corporation

[0089] <Acid value of polymer P> The acid value of polymer P was measured in accordance with JIS K0070-1992 (Potentiometric titration method). However, the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K 0070 to a mixed solvent of acetone and toluene (acetone:toluene = 4:6 (volume ratio)).

[0090] [Production of polymer P] Production Example 1 (Production of polymer P1) Into a 1000 mL four-necked round-bottom flask equipped with a thermometer, two dropping funnels with 100 mL nitrogen bypass, and a reflux device, 20.0 g of ethanol (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) was placed. After heating the internal temperature of the flask to 80 °C in an oil bath, nitrogen bubbling was carried out for 10 minutes. Next, 15.3 g of methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent), 7.2 g of methyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent), 10.0 g of styrene (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent), 67.5 g of methoxypolyethylene glycol (EO 23 mol) methacrylate (「PME-1000」manufactured by NOF Corporation), 1.0 g of 3-mercaptopropionic acid (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent), and 28.7 g of ethanol were dissolved in a poly beaker and placed in dropping funnel (1). Separately, 51.3 g of ethanol and 1.3 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (「V-65」manufactured by Fujifilm Wako Pure Chemical Corporation, polymerization initiator) were dissolved in a poly beaker and placed in dropping funnel (2). Then, while facing the above flask, the mixtures in dropping funnel (1) and dropping funnel (2) were simultaneously added dropwise over 90 minutes each. After that, after raising the internal temperature in the flask to 90 °C, stirring was continued for another 1 hour to complete the reaction. The resin solution was freeze-dried using a freeze dryer (manufactured by Tokyo Rikakikai Co., Ltd., model: FDU-2110) attached with a dry chamber (manufactured by Tokyo Rikakikai Co., Ltd., model: DRC-1000) under drying conditions (-25 °C for 1 hour freezing, -10 °C for 9 hours under reduced pressure, 25 °C for 5 hours under reduced pressure. Degree of reduced pressure: 5 Pa) to obtain completely dried polymer P1 (methacrylic acid / methyl methacrylate / styrene / methoxypolyethylene glycol (EO 23 mol) methacrylate polymer, acid value: 100 mg KOH / g, Mn: 8,300). The results are shown in Table 1.

[0091] Production Example 2 (Production of Polymer P2) It was produced by the same production method as in Production Example 1 except that the monomer composition shown in Table 1 was changed, and polymer P2 (methacrylic acid / methoxypolyethylene glycol (EO 23 mol) methacrylate polymer, acid value: 46 mg KOH / g, Mn: 9,000) was obtained. The results are shown in Table 1.

[0092]

Table 1

[0093] Details of each monomer in Table 1 are as follows. (Monomer (p-1)) · MAA: Methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) (Monomer (p-2)) · PEGMA(23)MA: Methoxypolyethylene glycol (EO 23 mol) methacrylate (「PME-1000」manufactured by NOF Corporation) (Monomer (p-3)) · MMA: Methyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) · St: Styrene (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent)

[0094] [Synthesis of Copper Nanoparticles A] Synthesis Example 1-1 (Production of Copper Nanoparticles A-1) Into a 2 L beaker, 50.0 g of copper oxide (manufactured by Nisshin Chemco Co., Ltd., N-120 (cupric oxide)) as a copper raw material compound, 4.40 g of lauric acid (manufactured by Fujifilm Wako Pure Chemical Corporation, primary reagent, boiling point: 298 °C) as a coating agent D, and 500 g of ethanol (95) (manufactured by Fujifilm Wako Pure Chemical Corporation, primary reagent) were added and stirred for 15 minutes. During stirring, the temperature of the reaction solution was controlled at 70 °C in an oil bath. Next, 63.0 g of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) placed in a 50 mL dropping funnel was added dropwise to the above mixture at 25 °C over 20 minutes. Then, the reaction solution was stirred for 1 hour while controlling the temperature of the reaction solution at 70 °C in an oil bath, and then air-cooled to obtain a reddish-brown dispersion containing a precursor of copper nanoparticles A-1. The entire amount of the obtained dispersion was placed in a 500 PA bottle of a centrifugal sedimentation tube manufactured by Hitachi Koki Co., Ltd., using a cooling centrifuge "himac CR22G" and a rotor (R12A, radius 15.1 cm) manufactured by the same company, and centrifuged at 3000 revolutions per minute with a centrifugal acceleration of 675 G, and held in this state for 30 minutes. 300 g of ethanol (95) (manufactured by Fujifilm Wako Pure Chemical Corporation, primary reagent) was added to the precipitate separated by centrifugation, and it was stirred for 15 minutes for redispersion. Again, the entire amount of the redispersion was centrifuged under the same conditions, and the precipitate was separated. This operation was performed 3 times. The precipitate of the purified copper nanoparticles A-1 was freeze-dried using a freeze dryer (manufactured by Tokyo Rika Kikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (manufactured by Tokyo Rika Kikai Co., Ltd., model: DRC-1000) to obtain 38.0 g of copper nanoparticles A-1. Freeze-drying was carried out by freezing at -25°C for 1 hour, followed by vacuum drying at -10°C and 5 Pa for 9 hours, and further vacuum drying at 25°C and 5 Pa for 5 hours. The obtained copper nanoparticles A-1 had an average particle size of 187 nm and a lauric acid (coating agent D) content of 1.3 mass%. The results are shown in Table 2.

[0095] Synthesis Example 1-2 (Production of Copper Nanoparticles A-2) In Synthesis Example 1-1, except that 4.40 g of lauric acid as the coating agent D was changed to 0.8 g of polymer P1, a dry powder of copper nanoparticles A-2 was obtained in the same manner as in Synthesis Example 1-1. The results are shown in Table 2.

[0096] Synthesis Example 1-3 (Production of Copper Nanoparticles A-3) In Synthesis Example 1-1, except that 4.40 g of lauric acid as the coating agent D was changed to 1.2 g of polymer P2, a dry powder of copper nanoparticles A-3 was obtained in the same manner as in Synthesis Example 1-1. The results are shown in Table 2.

[0097]

Table 2

[0098] [Synthesis of Copper Micro-Particles B] Synthesis Example 2-1 (Production of Copper Micro-Particles B-1) Into a 2 L beaker, 50.0 g of copper oxide (manufactured by Nisshin Chemical Co., Ltd., N-120 (cupric oxide)), 1.0 g of octanoic acid (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent, boiling point: 238 °C) as coating agent E, and 500 g of ethanol (95) (manufactured by Fujifilm Wako Pure Chemical Corporation, first grade reagent) were added and stirred for 15 minutes. During the stirring, the temperature of the reaction solution was controlled at 70 °C with an oil bath. Next, 63.0 g of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Corporation, special grade reagent) placed in a 50 mL dropping funnel was added dropwise to the above mixture at 25 °C over 20 minutes. Then, while controlling the temperature of the reaction solution at 70 °C with an oil bath, it was stirred for 1 hour, and then air-cooled to obtain a reddish-brown dispersion containing a precursor of copper microparticles B-1. The entire amount of the obtained dispersion was placed in a 500 PA bottle of the centrifugal sedimentation tube manufactured by the same company using a cooling centrifuge "himac CR22G" and a rotor (R12A, radius 15.1 cm) manufactured by Hitachi Koki Co., Ltd., and centrifuged at 3000 revolutions / minute with a centrifugal acceleration of 675 G and held in this state for 30 minutes. 300 g of ethanol (95) (manufactured by Fujifilm Wako Pure Chemical Corporation, first grade reagent) was added to the precipitate separated by centrifugation and stirred for 15 minutes for redispersion. Again, the entire amount of the redispersion was centrifuged under the same conditions, and the precipitate was separated. This operation was performed 3 times. The purified precipitate of copper microparticles B-1 was freeze-dried using a freeze dryer (manufactured by Tokyo Rika Kikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (manufactured by Tokyo Rika Kikai Co., Ltd., model: DRC-1000) to obtain 38.2 g of copper microparticles B-1. The freeze-drying was carried out by freezing at -25 °C for 1 hour, followed by vacuum drying at -10 °C and 5 Pa for 9 hours, and further vacuum drying at 25 °C and 5 Pa for 5 hours. The obtained copper microparticles B-1 had an average particle size of 0.79 μm and a content of octanoic acid (coating agent E) of 0.43 mass%. The results are shown in Table 3.

[0099] Synthesis Example 2-2 (Production of copper microparticles B-2) In Synthesis Example 2-1, except that 1.0 g of octanoic acid as the coating agent E was changed to 0.4 g of decanoic acid (Fuji Film Wako Pure Chemical Industries, Ltd., special grade reagent, boiling point: 270 °C), dry powder of copper microparticles B-2 was obtained in the same manner as in Synthesis Example 2-1. The results are shown in Table 3.

[0100] Synthesis Example 2-3 (Production of Copper Microparticles B-3) In Synthesis Example 2-1, except that 1.0 g of octanoic acid as the coating agent E was changed to 0.3 g of hexanoic acid (Fuji Film Wako Pure Chemical Industries, Ltd., special grade reagent, boiling point: 205 °C), dry powder of copper microparticles B-3 was obtained in the same manner as in Synthesis Example 2-1. The results are shown in Table 3.

[0101] Synthesis Example 2-4 (Production of Copper Microparticles B-4) In Synthesis Example 2-1, except that 1.0 g of octanoic acid as the coating agent E was changed to 0.3 g of lauric acid, dry powder of copper microparticles B-4 was obtained in the same manner as in Synthesis Example 2-1. The results are shown in Table 3.

[0102] Synthesis Example 2-5 (Production of Copper Microparticles B-5) In Synthesis Example 2-1, except that the input amount of octanoic acid as the coating agent E was changed from 1.0 g to 0.2 g, dry powder of copper microparticles B-5 was obtained in the same manner as in Synthesis Example 2-1. The results are shown in Table 3.

[0103] Synthesis Example 2-6 (Production of Copper Microparticles B-6) In Synthesis Example 2-1, except that the input amount of octanoic acid as the coating agent E was changed from 1.0 g to 0.05 g, dry powder of copper microparticles B-6 was obtained in the same manner as in Synthesis Example 2-1. The results are shown in Table 3.

[0104] Synthesis Example 2-7 (Production of Copper Microparticles B-7) 10 g of the copper microparticles B-1 obtained in Synthesis Example 2-1 was added to 50 mL of nitric acid adjusted to 0.01 mol / L, and the mixture was stirred for 5 minutes using a magnetic stirrer. Then, using a centrifuge, it was placed in a 500 PA bottle for a centrifuge sedimentation tube, and centrifuged at 3000 revolutions per minute with a centrifugal acceleration of 675 G, and held in this state for 30 minutes. 300 g of ethanol (95) (manufactured by Fujifilm Wako Pure Chemical Corporation, first-grade reagent) was added to the precipitate separated by centrifugation, and the mixture was stirred for 15 minutes for redispersion. Again, the entire amount of the redispersion liquid was centrifuged under the same conditions, and the precipitate was separated. This operation was performed 3 times. The precipitate of the purified copper particles 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), whereby 9.3 g of copper microparticles B-7 was obtained. Freeze-drying was carried out by freezing at -25°C for 1 hour, followed by vacuum drying at -10°C and 5 Pa for 9 hours, and further vacuum drying at 25°C and 5 Pa for 5 hours. The obtained copper microparticles B-7 had an average particle size of 0.65 μm and the content of coating agent E was 0 mass%. The results are shown in Table 3.

[0105] Synthesis Example 2-8 (Production of copper microparticles B-8) In Synthesis Example 2-7, except that the raw material copper microparticles B were changed from the copper microparticles B-1 to B-4 obtained in Synthesis Example 2-1, a dry powder of copper microparticles B-8 was obtained in the same manner as in Synthesis Example 2-7. The content of coating agent E was 0 mass%. The results are shown in Table 3.

[0106] Synthesis Example 2-9 (Production of copper microparticles B-9) In Synthesis Example 2-7, except that the raw material copper microparticles B were changed from the copper microparticles B-1 to B-5 obtained in Synthesis Example 2-1, a dry powder of copper microparticles B-9 was obtained in the same manner as in Synthesis Example 2-7. The content of coating agent E was 0 mass%. The results are shown in Table 3.

[0107]

Table 3

[0108] [Calculation of Hansen Solubility Parameters of Copper Nanoparticles A and Copper Micro-Particles B] Weigh 9 g of copper nanoparticles A or copper micro-particles B obtained in each of the above production examples and 1 g of 1,7-heptanediol, add them to an agate mortar, knead for 15 minutes to obtain a mixed solution. Transfer the obtained mixed solution to a 10 mL ointment bottle (Plastic Ointment Bottle manufactured by KM Chemical Co., Ltd.), seal it, and use a planetary vacuum mixer (Planetary Vacuum Mixer ARV-310 manufactured by Shinki Co., Ltd.) to stir at 2000 revolutions per minute for 5 minutes to prepare a sample for evaluating the dispersion state. For this sample, tilt the container and observe the contents at the bottom of the container, and evaluate the dispersion state according to the following evaluation criteria. Change 1,7-heptanediol to the following solvents for evaluation and perform the same operations. Also evaluate the dispersion state for each solvent for evaluation in the same way. Based on the evaluation results of the dispersion state, input into the computer software HSPiP (manufactured by (LCC) pirika) to to calculate the Hansen solubility parameters of each copper nanoparticle A and copper micro-particle B. The evaluation results of the dispersion state and the Hansen solubility parameters of each copper nanoparticle A and copper micro-particle B are shown in Table 4. (Evaluation Criteria) A (Good dispersion): No particles remained at the bottom of the container, and it became a smooth paste B (Poor dispersion): Some or all of the particles were not dispersed and remained at the bottom

[0109] (Solvents for Evaluation) · 1,7-Heptanediol (Tokyo Chemical Industry Co., Ltd., purity (test method): >98.0% (GC)) · Diethylene glycol monobutyl ether (Tokyo Chemical Industry Co., Ltd., purity (test method): >99.0% (GC)) · Propylene glycol monophenyl ether (Tokyo Chemical Industry Co., Ltd., purity (test method): >96.0% (GC)) · Diethylene glycol (FUJIFILM Wako Pure Chemical Corporation, special grade reagent) · Tetraethylene glycol dimethyl ether (Tokyo Chemical Industry Co., Ltd., purity (test method): >98.0% (GC)) · α - Terpineol (FUJIFILM Wako Pure Chemical Corporation, special grade reagent) · Tributyrin (Glyceryl tributyrate) (FUJIFILM Wako Pure Chemical Corporation, special grade reagent) · 1 - Methyl - 2 - pyrrolidone (FUJIFILM Wako Pure Chemical Corporation, special grade reagent) · Ethylene glycol (FUJIFILM Wako Pure Chemical Corporation, special grade reagent) · γ - Butyrolactone (FUJIFILM Wako Pure Chemical Corporation, special grade reagent) · Dodecane (FUJIFILM Wako Pure Chemical Corporation, special grade reagent)

[0110]

Table 4

[0111] [Production of copper particle dispersion] Example 1 As the dispersion medium C, 4.0 parts by mass of α - terpineol, 3.0 parts by mass of tributyrin, 50 parts by mass of the dry powder of copper nanoparticles A - 1, and 43 parts by mass of the dry powder of copper microparticles B - 1 were added to an agate mortar and kneaded until the dry powder was no longer visible to the naked eye. The obtained mixed solution was transferred to a plastic bottle. The sealed plastic bottle was stirred at 2000 revolutions per minute for 5 minutes using a planetary - type stirring device (manufactured by Shinki Co., Ltd., Planetary Vacuum Mixer ARV - 310). Then, it was passed through three rolls (manufactured by Aimex Co., Ltd., BV 100) with the gap adjusted to 0.2 mm to obtain the copper particle dispersion of Example 1. For the obtained copper particle dispersion, the distance Ra of each solubility parameter was calculated as described below. The results are shown in Table 5.

[0112] Examples 2 to 14, Comparative Examples 1 to 4 The copper particle dispersions of Examples 2 to 14 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1, except that the composition of the copper particle dispersion was changed to the composition shown in Table 5. For the obtained copper particle dispersions, the distance Ra of each Hansen solubility parameter was calculated as described below. The results are shown in Table 5.

[0113] [Distance Ra between Hansen solubility parameters of copper nanoparticles A and copper microparticles B (A-B) Calculation of From the values of the Hansen solubility parameters of copper nanoparticles A and copper microparticles B shown in Table 4, the distance Ra between the Hansen solubility parameters of copper nanoparticles A and copper microparticles B contained in each copper particle dispersion of the examples and comparative examples was calculated by the following formula (1). (A-B) was calculated. Ra (A-B) ={(4×(δD A -δD B ) 2 +(δP A -δP B ) 2 +(δH A -δH B ) 2 ) 1 / 2 (1)

[0114] [Distance Ra between Hansen solubility parameters of copper nanoparticles A and dispersion medium C (A-C) Calculation of From the value of the Hansen solubility parameter of copper nanoparticles A shown in Table 4 and the value of the Hansen solubility parameter of dispersion medium C, the distance Ra between the Hansen solubility parameters of copper nanoparticles A and dispersion medium C contained in each copper particle dispersion of the examples and comparative examples was calculated by the following formula (2). (B-C) was calculated. When the dispersion medium C is a mixed dispersion medium, the Hansen solubility parameter of the dispersion medium C is a value obtained by weighted average based on the value obtained by the HSPiP program. Specifically, the value obtained by calculating the solubility parameter of the mixed dispersion medium described below was used. The value of the Hansen solubility parameter of the dispersion medium C is shown in Table 5. Ra (A-C) ={(4×(δD A -δD C )2 +(δP A -δP C ) 2 +(δH A -δH C ) 2 ) 1 / 2 (2)

[0115] [Calculation of the distance Ra between the Hansen solubility parameters of copper microparticle B and dispersion medium C (B-C) of] Based on the values of the Hansen solubility parameters of copper microparticle B and the values of the Hansen solubility parameters of dispersion medium C shown in Table 4, the distance Ra between the Hansen solubility parameters of copper microparticle B and dispersion medium C contained in each copper particle dispersion of the examples and comparative examples was calculated by the following formula (3). (B-C) was calculated. When the dispersion medium C is a mixed dispersion medium, the Hansen solubility parameter of the dispersion medium C is a value obtained by weighted average based on the value obtained by the HSPiP program, and specifically, the value obtained by the calculation of the solubility parameter of the mixed dispersion medium described later was used. The value of the Hansen solubility parameter of the dispersion medium C is shown in Table 5. Ra (B-C) ={(4×(δD B -δD C ) 2 +(δP B -δP C ) 2 +(δH B -δH C ) 2 ) 1 / 2 (3)

[0116] (Calculation of the solubility parameter of dispersion medium C (mixed dispersion medium)) When the dispersion medium C is a mixed dispersion medium in which two kinds of dispersion media are mixed, using the Hansen solubility parameters of each dispersion medium described in the database of the computer software HSPiP, the dispersion force term, polar term, and hydrogen bond term of the Hansen solubility parameter of each dispersion medium C were obtained by weighted average weighted by the content (volume basis) of each dispersion medium as shown in the following formulas (4-1) to (4-3). δD C(Dispersion term of dispersion medium C (mixed dispersion medium)) = (V1 × δD C1 + V2 × δD C2 ) / (V1 + V2) (4-1) δP C (Polar term of dispersion medium C (mixed dispersion medium)) = (V1 × δP C1 + V2 × δP C2 ) / (V1 + V2) (4-2) δH C (Hydrogen bond term of dispersion medium C (mixed dispersion medium)) = (V1 × δH C1 + V2 × δH C2 ) / (V1 + V2) (4-3) In the above formulas (4-1) to (4-3), δD C1 , δP C1 , δH C1 represent the dispersion force term, polar term, and hydrogen bond term of the first solvent, V1 represents the volume of the first solvent, δD C2 , δP C2 , δH C2 represent the dispersion force term, polar term, and hydrogen bond term of the second solvent, and V2 represents the volume of the second solvent.

[0117] [Evaluation] <Method for producing a bonded body> Using each of the copper particle dispersions obtained in the examples and comparative examples, a bonded body was created according to the following method. First, a stainless steel metal mask (thickness: 100 μm) having three rows of 6 mm × 6 mm square openings was placed on a 30 mm × 30 mm copper plate (total thickness: 1 mm), and the copper particle dispersion was applied onto the copper plate by stencil printing using a metal squeegee. Then, it was dried at 120°C for 10 minutes on an atmospheric pressure chamal hot plate (manufactured by AS ONE Corporation, HHP-441). Then, a silicon chip (thickness: 400 μm) of 5 mm × 5 mm was prepared, and a silicon chip sputter-treated with titanium, nickel, and gold in this order was placed on the applied copper particle dispersion such that gold was in contact with the copper particle dispersion. Thus, a laminate in which a copper plate, a copper particle dispersion, and a silicon chip were laminated in this order was obtained. The obtained laminate was fired by the following method to obtain a bonded body. First, the laminate was set in a pressure firing machine (manufactured by Meisho Kiko Co., Ltd., HTM-1000), and nitrogen was flowed into the furnace at 500 mL / min to replace the air in the furnace with nitrogen. Then, while pressing the laminate at 10 MPa with the upper and lower heating heads, the temperature of the heating heads was raised to 260°C over 3 minutes. After the temperature rise, it was held at 260°C for 500 seconds for sintering treatment to obtain a bonded body. After sintering, the heating heads were water-cooled at -60°C / min, and the bonded body was taken out into the air at 100°C or lower.

[0118] <Evaluation of Initial Bonding Strength> Immediately after manufacturing the copper particle dispersions obtained in the examples and comparative examples, bonded bodies were produced by the above-described method for producing a bonded body. Using a universal bond tester (manufactured by Nordson Advanced Technology Co., Ltd., Prospector), while the test speed was 5 mm / min and the shear height was 50 μm, the silicon chip of the bonded body was pushed horizontally, and the die shear strength of the bonded body was measured. This was performed for each of three bonded bodies, and the average value of the values obtained by measuring the three bonded bodies was taken as the bonding strength of the bonded body.

[0119] <Evaluation of Bonding Strength after Storage> The copper particle dispersions obtained in the examples and comparative examples were stored under the conditions of 25°C and 50% humidity for 3 months, and then bonded bodies were produced by the above-described method for producing a bonded body. For the obtained bonded bodies, measurements were performed in the same manner as the above evaluation of the initial bonding strength, and the bonding strength after storage was measured.

[0120] <Evaluation of Bonding Strength Retention Rate> The bonding strength retention rate was determined from the following calculation formula. The higher the bonding strength retention rate, the higher the retention rate of the bonding strength after storage of the copper particle dispersion. Bonding strength retention rate (%) = Bonding strength after storage (MPa) / Initial bonding strength (MPa) × 100

[0121]

Table 5

[0122] From Table 5, the copper particle dispersions obtained in Examples 1 to 14 had a better joint strength retention rate of the resulting joints even after being stored for 3 months compared to the copper particle dispersions of Comparative Examples 1 to 4. That is, it was found that the copper particle dispersions obtained in Examples 1 to 14 were excellent in storage stability and excellent in the joint strength retention rate after storage.

[0123] <Evaluation of Thermal Resistance to Temperature Cycling> The copper particle dispersion of Example 10 was stored for 3 months under the conditions of 25°C and 50% humidity, and then a joint was prepared by the above-described method for preparing a joint. Thereafter, a temperature cycle test was performed under the conditions of -55°C and 200°C for 15 minutes each for 1000 cycles in the atmosphere using a small thermal shock apparatus (ESPEC CORPORATION, TSE-12-A), and the joint strength of the joint was measured in the same manner as the evaluation of the initial joint strength described above. As a result, the joint force after the temperature cycle test was 60 MPa, and it only slightly decreased compared to the joint force of 62 MPa before the test. Therefore, it was found that the joint obtained using the copper particle dispersion of Example 10 after long-term storage also had good thermal resistance to temperature cycling.

[0124] <Evaluation of Thermal Resistance at 250°C> The copper particle dispersion of Example 10 was stored for 3 months under the conditions of 25°C and 50% humidity, and then a joint was prepared by the above-described method for preparing a joint. The obtained joint was subjected to a 250°C heat resistance test under the conditions of 250°C and 1000 hours under atmospheric pressure, and measurement was performed in the same manner as the evaluation of the initial joint strength described above, and the joint strength of the joint was measured. As a result, the joint force after the 250°C heat resistance test was 59 MPa, and it only slightly decreased compared to the joint force of 62 MPa before the test. Therefore, it was found that the joint obtained using the copper particle dispersion of Example 10 after long-term storage also had good thermal resistance at 250°C.

[0125] From the evaluation of the temperature cycle heat resistance and 250°C heat resistance of the bonded body using the copper particle dispersion of Example 10 described above, it was found that the copper particle dispersion of the present invention is excellent in the heat resistance of the bonded body even when used for the bonded body after long-term storage.

Industrial Applicability

[0126] According to the present invention, it is possible to provide a method for producing a copper particle dispersion excellent in the retention rate of the bonding strength after storage.

Claims

1. The process includes a step of mixing copper nanoparticles A, copper microparticles B, and dispersion medium C. The copper nanoparticle A comprises copper particles a and a coating agent D, and the average particle size of the copper nanoparticle A is 50 nm or more and 300 nm or less. The copper microparticles B contain copper particles b, and the average particle size of the copper microparticles B is 0.5 μm or more and 10 μm or less. The distance Ra of the Hansen solubility parameter between the copper nanoparticle A and the copper microparticle B is calculated using the following formula (1) （Ａ－Ｂ） 9.0 MPa １／２ The following is a method for producing a copper particle dispersion. Ra （Ａ－Ｂ） ={(4×(δD Ａ -δD Ｂ ) ２ +(δP Ａ -δP Ｂ ) ２ +(δH Ａ -δH Ｂ ) ２ ) １／２ (1) (However, in formula (1) above, δD Ａ δP Ａ , and δH Ａ These terms represent the dispersion force term, polarity term, and hydrogen bonding term of the Hansen solubility parameter of copper nanoparticle A, respectively, and δD Ｂ δP Ｂ , and δH Ｂ The terms shown represent the dispersion force, polarity, and hydrogen bonding components of the Hansen solubility parameters for copper microparticle B, respectively. The Hansen solubility parameters for copper nanoparticles A and copper microparticle B were obtained using the HSPiP program.

2. The method for producing a copper particle dispersion according to claim 1, wherein the content of the coating agent D applied to the copper particles a in the copper nanoparticles A is 0.3% by mass or more.

3. A method for producing a copper particle dispersion according to claim 1 or 2, wherein the copper microparticles B include copper particles b and a coating agent E.

4. The method for producing a copper particle dispersion according to claim 3, wherein the coating agent E is the same as the coating agent D.

5. The method for producing a copper particle dispersion according to claim 3, wherein the content of the coating agent E applied to the copper particles b in the copper microparticles B is 1.0% by mass or less.

6. A method for producing a copper particle dispersion according to claim 1 or 2, wherein the copper microparticles B consist of the copper particles b.

7. The distance Ra of the Hansen solubility parameter between the copper nanoparticles A and the dispersion medium C is calculated using the following formula (2). （Ａ－Ｃ） 20.0 MPa １／２ The method for producing a copper particle dispersion according to claim 1 or 2, which is as follows: Ra （Ａ－Ｃ） ={(4×(δD Ａ -δD Ｃ ) ２ +(δP Ａ -δP Ｃ ) ２ +(δH Ａ -δH Ｃ ) ２ ) １／２ (2) (However, in formula (2) above, δD Ａ δP Ａ , and δH Ａ These represent the Hansen solubility parameters of copper nanoparticles A, respectively, and are the same as in formula (1) above, δD Ｃ δP Ｃ , and δH Ｃ These terms represent the dispersion force term, polarity term, and hydrogen bonding term of the Hansen solubility parameter of dispersion medium C, respectively. The Hansen solubility parameter of dispersion medium C is a weighted average obtained by weighting the content (by volume) of each dispersion medium based on values ​​obtained by the HSPiP program.

8. Of the Hansen solubility parameters of the copper nanoparticles A, the δP of the copper nanoparticles A Ａ (Polarity term) is 1.0 MPa １／２ The method for producing a copper particle dispersion according to claim 1 or 2.

9. The method for producing a copper particle dispersion according to claim 1 or 2, wherein the coating agent D is one or more selected from the group consisting of aliphatic carboxylic acids and polymers containing hydrophilic groups.

10. The method for producing a copper particle dispersion according to claim 9, wherein the polymer containing the hydrophilic group is a vinyl polymer P containing a constituent unit derived from a monomer (p-1) having a carboxyl group and a constituent unit derived from a monomer (p-2) having a polyalkylene glycol segment.

11. A method for producing a copper particle dispersion according to claim 1 or 2, wherein the dispersion medium C comprises one or more selected from the group consisting of aliphatic monohydric alcohols, (poly)alkylene glycols, (poly)alkylene glycol derivatives, glycerin, and glycerin derivatives.

12. A method for producing a copper particle dispersion according to claim 1 or 2, wherein the blending mass ratio [copper nanoparticle A / copper microparticle B] of the copper nanoparticles A and the copper microparticles B is 0.30 or more and 3.00 or less.