Method for producing copper particle dispersion

Abstract

The present invention relates to a method for producing a copper particle dispersion that has excellent bond strength retention after storage, said method comprising a step for 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 50-300 nm; the copper microparticles B either contain copper particles b and a coating agent E, or contain the copper particles b but do not contain the coating agent E; the average particle size of the copper microparticles B is 0.5-10 μm; and the distance Ra(A-B) of the Hansen solubility parameters of the copper nanoparticles A and the copper microparticles B is not more than 9.0 MPa1 / 2.

Description

Method for producing copper particle dispersion

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

[0002] Copper has excellent electrical and thermal conductivity, and is therefore widely used, for example, as a conductor wiring material, a heat transfer material, a heat exchange material, a heat dissipation material, etc. Because copper has excellent thermal conductivity, it is sometimes used as an alternative material to solder for joining objects to be joined.

[0003] In recent years, semiconductor devices known as power devices have become increasingly popular as power conversion and control devices, such as inverters. Unlike integrated circuits such as memory and microprocessors, power devices are designed to control high currents and generate a large amount of heat during operation. Therefore, solder used to mount power devices requires not only high bonding strength but also heat resistance. However, lead-free solder, which is widely used these days, has the disadvantage of low heat resistance. Therefore, various techniques have been proposed to bond objects by using metal particle dispersions instead of solder, which are applied to objects by various coating methods and then fired. The metal species of metal particle dispersions used for mounting are mainly silver or copper. Silver does not have an oxide film at room temperature (25°C). Therefore, silver particle dispersions are fired without a reducing agent to form a silver continuum, which is then used to bond objects. On the other hand, copper contains oxidized copper atoms because its oxidation state is stable at room temperature (25°C). Therefore, to bond objects using copper particle dispersions, it is necessary to reduce the oxidized copper atoms and fire them to form a copper continuum.

[0004] WO 2023 / 013034 (Patent Document 1) describes a copper particle dispersion containing copper powder and a liquid medium, with the aim of providing a copper particle dispersion that exhibits high bonding strength with respect to the bonded object by low-temperature firing even after storage at room temperature for one month. The copper particle dispersion contains copper nanoparticles A dispersed in a polymer B, and a dispersion medium C, wherein the polymer B contains structural units derived from a monomer (b-1) having a carboxy group and structural units derived from a 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 mg KOH / g or more and 250 mg KOH / g or less, and the dispersion medium C contains at least one selected from the group consisting of (poly)alkylene glycol, (poly)alkylene glycol derivative, terpene alcohol, glycerin, and glycerin derivative.

[0005] The present invention provides a method for producing a dispersion medium comprising a step of mixing copper nanoparticles A, copper microparticles B, and a dispersion medium C, wherein the copper nanoparticles A comprise copper particles a and a coating agent D, the copper nanoparticles A have an average particle size of 50 nm or more and 300 nm or less, the copper microparticles B comprise copper particles b, the copper microparticles B have an average particle size of 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 is calculated by the following formula (1): （Ａ－Ｂ） is 9.0 MPa １／２ The present invention relates to a method for producing a copper particle dispersion, which is as follows: （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 represent the dispersion term, polar term, and hydrogen bond term of the Hansen solubility parameter of copper nanoparticle A, respectively, and δD Ｂ , δP Ｂ, and δH Ｂ indicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of copper microparticles B, respectively, and the Hansen solubility parameters of copper nanoparticles A and copper microparticles B are values ​​calculated using the HSPiP program.

[0006] Metal particle dispersions proposed as solder replacement bonding materials have higher heat resistance than solder, but still have room for improvement in terms of bonding strength with the bonded objects. Furthermore, the operating temperatures of power devices have been increasing in recent years and are said to reach 250°C. Conventional copper particle dispersions have sometimes exhibited reduced bonding strength depending on the storage period, resulting in poor bonding strength of the resulting bonded body. When a bonded body was produced using the copper particle dispersion of Patent Document 1 after storage at room temperature for three months, poor bonding strength was observed in the resulting bonded body, and the bonding strength of the copper particle dispersion was observed to be reduced. This is believed to be due to separation of copper nanoparticles A in the copper particle dispersion of Patent Document 1 from other components. Therefore, further improvement in the bonding strength retention rate of copper particle dispersions after storage is desired. The present invention relates to a method for producing a copper particle dispersion that exhibits excellent bonding strength retention rate after storage.

[0007] The present inventors have found that a copper particle dispersion having excellent bonding strength retention after storage can be obtained when the Hansen solubility parameter distance between copper nanoparticles A and copper microparticles B is a certain value or less. That is, the present invention relates to the following [1]. [1] 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 copper nanoparticles A have an average particle size of 50 nm to 300 nm, the copper microparticles B contain copper particles b, and the copper microparticles B have an average particle size of 0.5 μm to 10 μm, and the Hansen solubility parameter distance Ra between the copper nanoparticles A and the copper microparticles B is calculated by the following formula (1): （Ａ－Ｂ） is 9.0 MPa １／２ A method for producing a copper particle dispersion, Ra （Ａ－Ｂ） = {(4 × (δD Ａ -δD Ｂ ) ２ + (δP Ａ -δPＢ ) ２ + (δH Ａ -δH Ｂ ) ２ ) １／２ (1) (However, in the above formula (1), δD Ａ , δP Ａ , and δH Ａ represent the dispersion term, polar term, and hydrogen bond term of the Hansen solubility parameter of copper nanoparticle A, respectively, and δD Ｂ , δP Ｂ , and δH Ｂ indicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of copper microparticles B, respectively, and the Hansen solubility parameters of copper nanoparticles A and copper microparticles B are values ​​calculated using the HSPiP program.

[0008] According to the present invention, there is provided a method for producing a copper particle dispersion that has excellent bonding strength retention after storage. Furthermore, according to the present invention, there is provided a method for producing a copper particle dispersion that has excellent heat resistance of a bonded body even when used in a bonded body after long-term storage.

[0009] [Method for producing copper particle dispersion] A 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 copper nanoparticles A have an average particle size of 50 nm or more and 300 nm or less, the copper microparticles B contain copper particles b, the copper microparticles B have an average particle size of 0.5 μm or more and 10 μm or less, and a distance Ra of the Hansen solubility parameters between the copper nanoparticles A and the copper microparticles B calculated by the following formula (1) is （Ａ－Ｂ） is 9.0 MPa １／２ The following is true: （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 , δPＡ , and δH Ａ represent the dispersion term, polar term, and hydrogen bond term of the Hansen solubility parameter of copper nanoparticle A, respectively, and δD Ｂ , δP Ｂ , and δH Ｂ indicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of copper microparticles B, respectively, and the Hansen solubility parameters of copper nanoparticles A and copper microparticles B are values ​​calculated using the HSPiP program.

[0010] As used herein, "Hansen solubility parameter" refers to a value determined using the HSPiP program software from 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. In addition, in the present invention, the Hansen solubility parameters of organic solvents such as dispersion medium C are determined using values ​​registered in the database of HSPiP program version 5.4.01 for solvents (see literature on various Hansen solubility parameters). For solvents not included in the database, values ​​estimated by the HSPiP program are used.

[0011] In this specification, the bondability after storing a copper particle dispersion for three months under conditions of 25°C and 50% humidity is referred to as "bondability after storage," and the greater the ratio (bonding strength retention) of the bond strength after storage under these conditions to the bond strength of a bonded body using the copper particle dispersion before storage under these conditions, the better the bond strength retention after storage is considered to be. Furthermore, the bondability after subjecting a bonded body obtained by firing a copper particle dispersion to 1000 cycles of temperatures of -55°C and 200°C for 15 minutes each is also referred to as "temperature cycle heat resistance." Furthermore, the bondability after storing a bonded body obtained by firing a copper particle dispersion under conditions of 250°C for 1000 hours is also referred to as "250°C heat resistance."

[0012] According to the present invention, it is possible to obtain a copper particle dispersion that has excellent bonding strength retention after storage and also has excellent heat resistance of the bonded body. The reason for this is unclear, but is thought to be as follows. The manufacturing method of the present invention is such that the distance Ra of the Hansen solubility parameters of copper nanoparticles A and copper microparticles B is （Ａ－Ｂ） is 9.0 MPa １／２ When the copper particle dispersion obtained is below this range, the affinity between the copper particles is high, making it difficult for aggregation to occur and separation to occur. As a result, the copper particle dispersion obtained by the present invention is thought to have excellent storage stability and to have a good bonding strength retention rate even after long-term storage. Furthermore, since the copper particle dispersion obtained by the present invention contains copper nanoparticles A and copper microparticles B having the above-mentioned configuration, it is thought that using it in a bonded body can improve temperature cycle heat resistance and 250°C heat resistance.

[0013] In the present invention, the distance Ra between the Hansen solubility parameters of copper nanoparticles A and copper microparticles B （Ａ－Ｂ） is 9.0 MPa 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 preferably 8.0 MPa or less. １／２ Not more than 6.0 MPa, more preferably １／２ The following is the result.

[0014] In the present invention, the distance Ra of the Hansen solubility parameter between copper nanoparticles A and dispersion medium C is calculated by the following formula (2): （Ａ－Ｃ） is preferably 20.0 MPa 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 Not more than 15.0 MPa, more preferably １／２ More preferably, 10.0 MPa or less １／２ More preferably, 8.0 MPa or less １／２ The following is the result.

[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 above formula (2), δD Ａ , δP Ａ , and δH Ａ represent the dispersion term, polar term, and hydrogen bond term of the Hansen solubility parameter of copper nanoparticle A, respectively, and δD Ｃ , δP Ｃ , and δH Ｃ indicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of the dispersion medium C, respectively, and the Hansen solubility parameter of the dispersion medium C is a value calculated by a weighted average weighted by the content (volume basis) of each dispersion medium based on the value calculated by the HSPiP program. Ａ , δP Ａ , and δH Ａ is the same as in the case of the above formula (1).

[0016] In the present invention, the distance Ra of the Hansen solubility parameters between the copper microparticles B and the dispersion medium C is calculated by the following formula (3): （Ｂ－Ｃ） is preferably 15.0 MPa from the viewpoint of improving the dispersibility of the copper microparticles B and improving the bonding property of the copper particle dispersion after storage. １／２ or less, more preferably 12.0 MPa １／２ More preferably, 8.0 MPa or less １／２ More preferably, 6.0 MPa or less １／２ The following is true: （Ｂ－Ｃ） = {(4 × (δD Ｂ -δD Ｃ ) ２ + (δP Ｂ -δP Ｃ ) ２ + (δH Ｂ -δH Ｃ ) ２ ) １／２ (3) However, in the above formula (3), δD Ｂ , δP Ｂ , and δH Ｂ represent the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of copper microparticle B, respectively, and δDＣ , δP Ｃ , and δH Ｃ indicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of the dispersion medium C, respectively, and the Hansen solubility parameter of the dispersion medium C is a value calculated by a weighted average weighted by the content (volume basis) of each dispersion medium based on the value calculated by the HSPiP program. Ｂ , δP Ｂ , 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 copper nanoparticles A, δP of copper nanoparticles A Ａ (polarity term) is preferably 1.0 MPa from the viewpoint of improving the bonding strength before storage of the copper particle dispersion and the bonding strength retention rate after storage. １／２ More preferably, 3.0 MPa １／２ More preferably, 5.0 MPa １／２ More preferably, 7.0 MPa or more １／２ That's all.

[0018] In the present invention, the δP of the copper microparticles B among the Hansen solubility parameters of the copper microparticles B Ｂ (polarity term) is preferably 1.0 MPa from the viewpoint of improving the bonding strength before storage of the copper particle dispersion and improving the bonding strength retention rate after storage. １／２ More preferably, 3.0 MPa １／２ More preferably, 5.0 MPa １／２ More preferably, 7.0 MPa or more １／２ That's all.

[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 includes a method of adding and mixing pre-prepared copper nanoparticles A, pre-prepared copper microparticles B, and a dispersion medium C, and, if necessary, various additives; a method of mixing a copper raw compound, a reducing agent, and a coating agent D, and, if necessary, a solvent for dispersing the copper raw compound and the reducing agent, and reducing the copper raw compound to obtain a dispersion of copper nanoparticles A, and then adding and mixing pre-prepared copper microparticles B, a dispersion medium C, and, if necessary, various additives, etc. It can be obtained by, for example. Among these, from the viewpoint of improving the bonding strength retention rate after storage of the copper particle dispersion, a method of adding and mixing pre-prepared copper nanoparticles A, pre-prepared copper microparticles B, and a dispersion medium C, and, if necessary, various additives, is preferred.

[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] 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, and even more preferably 125 nm or more, from the viewpoint of improving the dispersibility of the copper nanoparticles A and suppressing oxidation during storage. From the viewpoint of improving the bonding property of the copper particle dispersion after storage, the average particle size of the copper nanoparticles A 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 type and amount of the reducing agent and coating agent D, temperature conditions, etc., during the production of the copper nanoparticles A.

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

[0023] (Copper particles a) The average particle size of the copper particles a is preferably 50 nm or more, more preferably 75 nm or more, even more preferably 100 nm or more, and even more preferably 125 nm or more from the viewpoint of improving the dispersibility of the copper nanoparticles A and suppressing oxidation during storage, and is preferably 400 nm or less, more preferably 300 nm or less, even more preferably 250 nm or less, and even more preferably 200 nm or less from the viewpoint of improving the bonding property of the copper particle dispersion after storage. The average particle size of the copper particles a can be adjusted by the type and amount of the reducing agent and coating agent D, temperature conditions, etc. in the production of the copper nanoparticles A.

[0024] (Coating Agent D) The copper nanoparticles A in the present invention contain copper particles a and coating agent D, which improves dispersibility, thereby improving the storage stability of the copper particle dispersion and improving the bonding strength retention rate of the copper particle dispersion after storage. In the present invention, coating agent D is preferably one or more selected from the group consisting of aliphatic carboxylic acids and polymers containing hydrophilic groups, from the viewpoint of improving the dispersibility of the copper nanoparticles A and improving the bonding strength retention rate of the copper particle dispersion after storage.

[0025] [Aliphatic Carboxylic Acid] The number of carbon atoms of the aliphatic carboxylic acid is preferably 1 to 24, more preferably 2 to 20, even more preferably 4 to 16, and even more preferably 6 to 12, from the viewpoint of improving the dispersibility of copper nanoparticles A and improving the bonding strength retention rate after storage of the copper particle dispersion. Specific examples of aliphatic carboxylic acids 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, Lindelic acid, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, etc. Among these, the aliphatic carboxylic acid is preferably one or more selected from the group consisting of hexanoic acid, octanoic acid, decanoic acid, and lauric acid, more preferably lauric acid.

[0026] [Polymer Containing Hydrophilic Groups] The polymer containing hydrophilic groups is preferably a polymer having one or more groups selected from the group consisting of nonionic groups, cationic groups, and anionic groups, from the viewpoint of improving the dispersibility of copper nanoparticles A and improving the bonding strength retention rate of the copper particle dispersion after storage. It is more preferable that the hydrophilic group is present on the side chain of the polymer. Examples of hydrophilic groups include nonionic groups such as hydroxy groups, amide groups, and oxyalkylene groups; cationic groups such as amino groups; and anionic groups such as carboxy groups, sulfonic acid groups, and phosphate groups. Examples of polymers having nonionic groups include polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylamide. Examples of polymers having cationic groups include polyallylamine and polyethyleneimine. Examples of polymers having anionic groups are preferably those having carboxy groups. Examples of the basic structure of polymers having carboxy groups include vinyl polymers such as acrylic resins, styrene resins, styrene-acrylic resins, and acrylic silicone resins; and condensation polymers such as polyesters and polyurethanes. The polymer containing a hydrophilic group may be suitably synthesized or may be a commercially available product.

[0027] Among these, 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, 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. The vinyl polymer P may be a random copolymer, a block copolymer, or an alternating copolymer.

[0028] <<Monomer (p-1) Having a Carboxy Group>> Preferred examples of the monomer (p-1) having a carboxy group (hereinafter also referred to as "monomer (p-1)") include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and 2-methacryloyloxymethylsuccinic acid; and unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, and citraconic acid. The unsaturated dicarboxylic acid may be an anhydride. Monomer (p-1) may be used alone or in combination of two or more. From the viewpoint of improving the dispersibility of copper nanoparticles A and improving the bonding strength retention rate after storage of the copper particle dispersion, monomer (p-1) is preferably one or more selected from the group consisting of (meth)acrylic acid and maleic acid, more preferably (meth)acrylic acid, and even more preferably methacrylic acid. In this specification, "(meth)acrylic acid" means one or more 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, alkoxy polyalkylene glycol (meth)acrylate, and phenoxy polyalkylene glycol (meth)acrylate. The monomer (p-2) may be used alone or in combination of two or more. In this specification, "(meth)acrylate" refers to one or more selected from the group consisting of acrylates and methacrylates.

[0030] From the viewpoint of improving the dispersibility of copper nanoparticles A and improving the bonding strength retention rate after storage of the copper particle dispersion, monomer (p-2) is preferably one or more selected from the group consisting of polyalkylene glycol (meth)acrylate and alkoxy polyalkylene glycol (meth)acrylate, more preferably alkoxy polyalkylene glycol (meth)acrylate. From the same viewpoint as above, the number of carbon atoms in the alkoxy group of the alkoxy polyalkylene glycol (meth)acrylate is preferably 18 or less, more preferably 14 or less, and even more preferably 12 or less. Preferred examples of the alkoxy polyalkylene glycol (meth)acrylate include methoxy polyalkylene glycol (meth)acrylate, ethoxy polyalkylene glycol (meth)acrylate, propoxy polyalkylene glycol (meth)acrylate, butoxy polyalkylene glycol (meth)acrylate, octoxy polyalkylene glycol (meth)acrylate, and lauroxy polyalkylene glycol (meth)acrylate. Among these, methoxypolyalkylene glycol (meth)acrylate is more preferred.

[0031] The polyalkylene glycol segment of monomer (p-2) preferably contains units derived from alkylene oxide having 2 to 4 carbon atoms, from the viewpoint of improving the dispersibility of copper nanoparticles A and improving the bonding strength retention of the copper particle dispersion after storage. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, etc., and are preferably at least one selected from the group consisting of ethylene oxide and propylene oxide, more preferably ethylene oxide. The number of alkylene oxide-derived units in the polyalkylene glycol segment is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, from the viewpoint of improving the dispersibility of copper nanoparticles A and improving the bonding strength retention rate of the copper particle dispersion after storage, and is preferably 100 or less, more preferably 70 or less, even more preferably 50 or less, even more preferably 40 or less, and even more preferably 35 or less. The polyalkylene glycol segment may be a copolymer containing units derived from ethylene oxide and units derived from propylene oxide, from the viewpoint of improving the dispersibility of copper nanoparticles A and improving the bonding strength retention rate of the copper particle dispersion after storage. 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, and M-230G, manufactured by Shin-Nakamura Chemical Co., Ltd.; and Blenmar PE-90, PE-200, PE-350, PME-100, and PME-230G, manufactured by NOF Corporation. Examples of such polyether esters include ME-200, PME-400, PME-1000, PME-4000, PP-500, PP-500D, PP-800, PP-1000, PP-2000D, AP-150, AP-400, AP-550, 50PEP-300, 50POEP-800B, 43PAPE-600B, and PLE-1300.

[0033] [Hydrophobic Monomer (p-3)] From the viewpoint of improving the bonding strength retention rate of the copper particle dispersion after storage, 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)"). As used herein, "hydrophobic monomer" refers to a monomer that dissolves in an amount of less than 10 g when dissolved in 100 g of ion-exchanged water at 25°C until saturation occurs. From the viewpoint of improving the bonding strength retention rate of the copper particle dispersion after storage, the amount of hydrophobic monomer (p-3) that dissolves is preferably 5 g or less, more preferably 1 g or less. 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 bond strength retention rate of the copper particle dispersion after storage, the aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group having from 6 to 22 carbon atoms, which may have a heteroatom-containing substituent, more preferably at least one selected from the group consisting of styrene-based monomers and aromatic group-containing (meth)acrylates, and even more preferably a styrene-based monomer. The molecular weight of the aromatic group-containing monomer is preferably less than 500. Preferred examples of the styrene-based monomer include styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), and divinylbenzene. From the viewpoint of improving the bond strength retention rate of the copper particle dispersion after storage, styrene and α-methylstyrene are more preferred, and styrene is even more preferred. From the viewpoint of improving the bond strength retention rate of the copper particle dispersion after storage, preferred examples of the aromatic group-containing (meth)acrylate include phenyl (meth)acrylate, benzyl (meth)acrylate, and phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate is more preferred.

[0035] From the viewpoint of improving the bonding strength retention rate of the copper particle dispersion after storage, 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 has a hydrocarbon group derived from an aliphatic alcohol having 12 or less carbon atoms, even 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. Examples of the (meth)acrylate having a linear alkyl group include (meth)acrylates having a branched alkyl group, and (meth)acrylates having an alicyclic alkyl group. Preferred examples of the (meth)acrylate having a linear alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate. Among these, methyl (meth)acrylate is more preferred, and methyl methacrylate is even more preferred. Preferred examples of (meth)acrylates having a branched alkyl group include isopropyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isopentyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, isododecyl (meth)acrylate, isostearyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Preferred examples of (meth)acrylates having an alicyclic alkyl group include cyclohexyl (meth)acrylate. Monomer (p-3) may be used alone or in combination of two or more.

[0036] From the viewpoint of improving the bonding strength retention rate of the copper particle dispersion after storage, 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 linear alkyl group, more preferably at least one selected from the group consisting of a styrene-based monomer and a (meth)acrylate having a linear alkyl group having from 1 to 4 carbon atoms, even 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, still 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, even more preferably 7,000 or more, 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, and is preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, even more preferably 15,000 or less, and even more preferably 10,000 or less. 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 mg KOH / g or more, more preferably 25 mg KOH / g or more, even more preferably 30 mg KOH / g or more, even more preferably 35 mg KOH / g or more, even more preferably 40 mg KOH / g or more, 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, and is preferably 250 mg KOH / g or less, more preferably 200 mg KOH / g or less, even more preferably 150 mg KOH / g or less, even more preferably 130 mg KOH / g or less, even more preferably 110 mg KOH / g or less. The acid value of the vinyl polymer P can be measured by the method described in the examples, but it can also be calculated from the mass ratio of the constituent monomers.

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

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

[0041] The copper source compound is not particularly limited as long as it is a compound containing copper. Examples of the copper source compound include copper sulfate, copper nitrate, cupric oxide, cuprous oxide, copper formate, copper acetate, and copper oxalate. Among these, the copper source compound is preferably cupric oxide. The copper source 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, and inorganic acid salts. Examples of hydrazine compounds include hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrazine hydrate (hydrazine monohydrate). Examples of boron compounds include sodium borohydride. Examples of inorganic acid salts include sodium sulfite, sodium bisulfite, sodium thiosulfate, sodium nitrite, sodium hyponitrite, phosphorous acid, sodium phosphite, hypophosphorous acid, and sodium hypophosphite. Among these, the reducing agent is preferably a hydrazine compound, more preferably one or more selected from the group consisting of hydrazine and hydrazine hydrate, and even more preferably hydrazine hydrate (hydrazine monohydrate). The reducing agents may be used alone or in combination of two or more.

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

[0044] The temperature of the reduction reaction is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, even more preferably 20 ° C. or higher, and even more preferably 30 ° C. or higher from the viewpoint of reducing and uniformly dispersing the particle size of the copper nanoparticles A, and from the viewpoint of stably producing the copper nanoparticles A, it is preferably carried out at a temperature of 100 ° C. or lower, more preferably 90 ° C. or lower, even more preferably 80 ° C. or lower, and even more preferably 75 ° C. or lower. The reduction reaction may be carried out in an air atmosphere or 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 was not involved in coating the copper particles a, after obtaining the dispersion of copper nanoparticles A, the dispersion of copper nanoparticles A may be purified before freeze-drying or the like. The method for purifying the dispersion of copper nanoparticles A is not particularly limited, and includes methods such as membrane treatments such as dialysis and ultrafiltration; and centrifugation. Among these, centrifugation is preferred from the viewpoint of efficiently removing impurities. The molecular weight cutoff of the dialysis membrane is preferably 1,000 or more, more preferably 5,000 or more, even more preferably 10,000 or more, and preferably 100,000 or less, more preferably 70,000 or less, from the viewpoint of efficiently removing impurities.

[0046] <Copper Microparticles B> The copper microparticles B in the present invention 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.

[0047] The average particle size of the copper microparticles B is 0.5 μm or more, preferably 0.8 μm or more, 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 in a bonded body and improving the bond strength retention rate of the copper particle dispersion after storage. Furthermore, from the viewpoint of increasing the surface energy of the copper particles and improving the bond strength retention rate of the copper particle dispersion after storage, the average particle size of the copper microparticles B is 10 μm or less, preferably 8.0 μm or less, more preferably 7.0 μm or less, and even more preferably 6.0 μm or less. The average particle size of the copper microparticles B is measured by the method described in the Examples. The average particle size of the copper microparticles B can be adjusted in the production of the copper microparticles B by the type and amount of the reducing agent and the coating agent E described below, the temperature conditions, etc.

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

[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, even 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 in a bonded body and improving the bonding strength retention rate of the copper particle dispersion after storage. Furthermore, from the viewpoint of increasing the surface energy of the copper particles and improving the bonding strength retention rate of the copper particle dispersion after storage, the average particle size of the copper particles b is preferably 10 μm or less, more preferably 8.0 μm or less, even 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 in the production of the copper microparticles B by the type and amount of the reducing agent and the coating agent E described below, the temperature conditions, etc.

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

[0051] The boiling point of the coating agent E is preferably 350° C. or lower, more preferably 320° C. or lower, and even more preferably 300° C. or lower, from the viewpoint of improving the bonding property of the copper particle dispersion after storage.

[0052] As the coating agent E, the same coating agent D as in the above-mentioned copper nanoparticles A can be preferably used. Among these, the coating agent E 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, from the viewpoint of suppressing shrinkage due to sintering when the copper particle dispersion is used in a bonded body and improving the bonding strength retention rate of the copper particle dispersion after storage. Furthermore, the coating agent E is preferably the same as the coating agent D, from the viewpoint of suppressing shrinkage due to sintering when the copper particle dispersion is used in a bonded body and improving the bonding strength retention rate of the copper particle dispersion after storage.

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

[0054] (Production of Copper Microparticles B) In the present invention, when copper microparticles B contain copper particles b and coating agent E, copper microparticles B are obtained by mixing a copper source compound, a reducing agent, and coating agent E, and then reducing the copper source compound with the reducing agent to obtain copper particles b, which are then coated with coating agent E. Furthermore, when copper microparticles B contain copper particles b and coating agent E, copper microparticles B are obtained as a dispersion by the above-mentioned method, and then the dispersion of copper microparticles B is dried by freeze-drying or the like to obtain a dry powder of copper microparticles B. When copper microparticles B contain copper particles b and coating agent E, the copper source compound, reducing agent, conditions, steps, and the like in the production of copper microparticles B are preferably the same as those in the production of copper nanoparticles A described above.

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

[0056] Another method for producing copper microparticles B made of copper particles B is atomization. Preferred examples of copper microparticles B obtained by atomization include Cu-HWQ (Fukuda Metal Foil & Powder Co., Ltd.), MA-C02 (Mitsui Mining & Smelting Co., Ltd.), and MA-C03 (Mitsui Mining & Smelting Co., Ltd.).

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

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

[0059] <Dispersion medium C> In the production method of the present invention, a dispersion medium C is mixed as a dispersion medium for dispersing copper nanoparticles A and copper microparticles B. From the viewpoint of improving the bonding strength retention rate after storage of the copper particle dispersion, the dispersion medium C 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 aliphatic monohydric alcohols 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 alcohols. Among these, terpene alcohols are preferred as aliphatic monohydric alcohols. Preferred examples of terpene alcohols include 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), and citronellol (boiling point: 225°C, molecular weight: 156). Of these, α-terpineol is more preferred.

[0061] As used herein, the term "(poly)alkylene glycol" refers to one or more selected from the group consisting of alkylene glycols and polyalkylene glycols. Examples of alkylene glycols include ethylene glycol (boiling point: 197°C, molecular weight: 62), propylene glycol (boiling point: 188°C, molecular weight: 76), and butylene glycol (1,3-butanediol, boiling point: 209°C, molecular weight: 90). Examples of polyalkylene glycols include 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, and polytetramethylene glycol. The number average molecular weight of polyethylene glycol is preferably 200 or more and 1,000 or less, more preferably 250 or more and 600 or less, and even more preferably 300 or more and 500 or less. The number average molecular weight of polypropylene glycol is 260 or more and 1,000 or less, more preferably 300 or more and 600 or less, and even more preferably 350 or more and 500 or less. Among these, one or more selected from diethylene glycol and tetraethylene glycol are preferred.

[0062] Examples of the (poly)alkylene glycol derivative include compounds in which the terminal hydroxy groups of the (poly)alkylene glycol are 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" refers to one or more alkylene glycol alkyl ethers selected from the group consisting of alkylene glycol alkyl ethers and polyalkylene glycol alkyl ethers. Examples of alkylene glycol alkyl ethers 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), and propylene glycol monobutyl ether (boiling point: 170°C, molecular weight: 132). Examples of polyalkylene glycol alkyl ethers 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), and dipropylene glycol monomethyl ether (boiling point: 190°C, molecular weight: 148).

[0064] As used herein, the term "(poly)alkylene glycol monoalkyl ether acetate" refers to one or more alkylene glycol monoalkyl ether acetates selected from the group consisting of alkylene glycol monoalkyl ether acetates and polyalkylene glycol monoalkyl ether acetates. Examples of alkylene glycol monoalkyl ether acetates 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), and propylene glycol monoethyl ether acetate (boiling point: 145°C, molecular weight: 132). Examples of polyalkylene glycol monoalkyl ether acetates 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), and diethylene glycol monobutyl ether acetate (boiling point: 247°C, molecular weight: 204).

[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 (e.g., ethylene oxide adducts and propylene oxide adducts). Preferred examples of polyglycerin include diglycerin and triglycerin, and commercially available polyglycerin products such as Polyglycerin #310, Polyglycerin #500, and Polyglycerin #750 manufactured by Sakamoto Pharmaceutical Co., Ltd. are preferred. Preferred examples of ether derivatives of glycerin include 3-(2-ethylhexyloxy)-1,2-propanediol (boiling point: 325°C, molecular weight: 204). Preferred examples of ester derivatives of glycerin include glyceryl tributyrate (tributyrin, boiling point: 305°C, molecular weight: 302). Among these, glycerol tributyrate (tributyrin) is preferred as the glycerin derivative.

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

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

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

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

[0070] In the present invention, in addition to the above-mentioned copper nanoparticles A, the above-mentioned copper microparticles B, and the above-mentioned dispersion medium C, various additives may be blended as necessary. Examples of additives include metal particles other than copper nanoparticles A and copper microparticles, sintering accelerators such as glass frit, antioxidants, viscosity modifiers, pH adjusters, buffers, antifoaming agents, leveling agents, and volatilization inhibitors. Examples of 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 amount of additives blended 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 copper nanoparticles A described above, the copper microparticles B described above, and the dispersion medium C described above, and the distance Ra of the Hansen solubility parameters between the copper nanoparticles A and the copper microparticles B calculated by the above formula (1) （Ａ－Ｂ） is 9.0 MPa １／２ The following is the result.

[0072] In the copper particle dispersion of the present invention, the distance Ra between the Hansen solubility parameters of copper nanoparticles A and copper microparticles B is （Ａ－Ｂ） is 9.0 MPa from the viewpoint of improving the dispersibility of copper nanoparticles A and copper microparticles B and improving the bonding strength retention rate after storage of the copper particle dispersion. １／２ is preferably 8.0 MPa or less. １／２ Not more than 6.0 MPa, more preferably １／２ The following is the result.

[0073] In the copper particle dispersion of the present invention, the distance Ra of the Hansen solubility parameters between the copper nanoparticles A and the dispersion medium C calculated by the above formula (2) （Ａ－Ｃ） is preferably 20.0 MPa 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 Not more than 15.0 MPa, more preferably １／２ More preferably, 10.0 MPa or less １／２ More preferably, 8.0 MPa or less １／２ The following is the result.

[0074] In the copper particle dispersion of the present invention, the distance Ra of the Hansen solubility parameters between the copper microparticles B and the dispersion medium C calculated by the above formula (3) （Ｂ－Ｃ） is preferably 15.0 MPa from the viewpoint of improving the dispersibility of the copper microparticles B and improving the bonding strength retention rate after storage of the copper particle dispersion. １／２ or less, more preferably 12.0 MPa １／２ More preferably, 8.0 MPa or less １／２ More preferably, 6.0 MPa or less １／２ The following is the result.

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

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

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

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

[0079] In the copper particle dispersion of the present invention, from the viewpoint of improving the bonding strength retention rate of the copper particle dispersion after storage, 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, even more preferably 95% by mass or less, still more preferably 94% by mass or less, and is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and still 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, from the viewpoint of improving the bonding strength retention rate after storage of the copper particle dispersion, preferably 3% by mass or more, more preferably 4% by mass or more, even more preferably 5% by mass or more, still more preferably 6% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and still more preferably 10% by mass or less.

[0081] The copper particle dispersion of the present invention may contain various additives as needed, in addition to the above-mentioned copper nanoparticles A, copper microparticles B, and dispersion medium C. Examples of additives include metal particles other than copper nanoparticles A and copper microparticles, sintering accelerators such as glass frit, antioxidants, viscosity adjusters, pH adjusters, buffers, antifoaming agents, leveling agents, and volatilization inhibitors. Examples of 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 additives in the copper particle dispersion is preferably 1% by mass or less.

[0082] (Uses) The copper particle dispersion obtained by the production method of the present invention has excellent bonding strength retention after storage, and therefore can be used to form conductive members for various electronic and electrical devices. The conductive members are preferably used for bonding agents such as solder; antennas such as RFID (radio frequency identifier) ​​tags; capacitors such as MLCCs (multilayer ceramic capacitors); electronic paper; image display devices such as liquid crystal displays and organic EL displays; organic EL elements; organic transistors; wiring boards such as printed wiring boards and flexible wiring boards; organic solar cells; sensors such as flexible sensors, and the like. Among these, the copper particle dispersion according to the present invention has excellent bonding strength retention after storage, and therefore is preferably used for bonding multiple metal members.

[0083] The present invention further discloses the following aspects: <1> A method for producing a dispersion medium 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 copper nanoparticles A have an average particle size of 50 nm to 300 nm, the copper microparticles B contain copper particles b, the copper microparticles B have an average particle size of 0.5 μm to 10 μm, and the distance Ra(A−B) of the Hansen solubility parameters between the copper nanoparticles A and the copper microparticles B calculated by the following formula (1) is 9.0 MPa: １／２ 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 represent the dispersion term, polar term, and hydrogen bond term of the Hansen solubility parameter of copper nanoparticle A, respectively, and δD Ｂ , δP Ｂ , and δH Ｂindicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of copper microparticles B, respectively, and the Hansen solubility parameters of copper nanoparticles A and copper microparticles B are values ​​calculated using the HSPiP program.) <2> Distance Ra of the Hansen solubility parameters of copper nanoparticles A and copper microparticles B （Ａ－Ｂ） However, preferably 8.0 MPa １／２ Not more than 6.0 MPa, more preferably １／２ <3> The method for producing a copper particle dispersion according to <1>, wherein the distance Ra of the Hansen solubility parameters between copper nanoparticles A and a dispersion medium C is calculated by the following formula (2): （Ａ－Ｃ） However, preferably 20.0 MPa １／２ Not more than 15.0 MPa, more preferably １／２ More preferably, 10.0 MPa or less １／２ More preferably, 8.0 MPa or less １／２ The method for producing a copper particle dispersion according to <1> or <2>, wherein Ra is: （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 term, polar term, and hydrogen bond term of the Hansen solubility parameter of copper nanoparticle A, respectively, and δD Ｃ , δP Ｃ , and δH Ｃ indicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of the dispersion medium C, respectively, and the Hansen solubility parameter of the dispersion medium C is a value calculated by a weighted average weighted by the content (volume basis) of each dispersion medium based on the value calculated by the HSPiP program.) <4> The distance Ra of the Hansen solubility parameter between the copper microparticles B and the dispersion medium C calculated by the following formula (3) （Ｂ－Ｃ） However, preferably 15.0 MPa １／２or less, more preferably 12.0 MPa １／２ More preferably, 8.0 MPa or less １／２ More preferably, 6.0 MPa or less １／２ The method for producing a copper particle dispersion according to any one of <1> to <3>, wherein 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 above formula (3), δD Ｂ , δP Ｂ , and δH Ｂ represent the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of copper microparticle B, respectively, and δD Ｃ , δP Ｃ , and δH Ｃ indicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of dispersion medium C, respectively, and the Hansen solubility parameter of dispersion medium C is a value calculated by a weighted average weighted by the content (volume basis) of each dispersion medium based on the value calculated by the HSPiP program.) <5> Of the Hansen solubility parameters of copper nanoparticles A, δP of copper nanoparticles A Ａ (polar term) is preferably 1.0 MPa １／２ More preferably, 3.0 MPa １／２ More preferably, 5.0 MPa １／２ More preferably, 7.0 MPa or more １／２ <6> The method for producing a copper particle dispersion according to any one of <1> to <4>, wherein the δP of the copper microparticles B is Ｂ (polar term) is preferably 1.0 MPa １／２ More preferably, 3.0 MPa １／２ More preferably, 5.0 MPa １／２ More preferably, 7.0 MPa or more １／２<7> The method for producing a copper particle dispersion according to any one of <1> to <5>, wherein the average particle size of the copper nanoparticles A is preferably 75 nm or more, more preferably 100 nm or more, even more preferably 125 nm or more, and preferably 250 nm or less, even more preferably 230 nm or less, and still more preferably 200 nm or less. <8> The method for producing a copper particle dispersion according to any one of <1> to <7>, wherein the blending amount of the copper nanoparticles A is preferably 25 mass% or more, more preferably 30 mass% or more, even more preferably 35 mass% or more, still more preferably 40 mass% or more, and preferably 90 mass% or less, more preferably 80 mass% or less, even more preferably 70 mass% or less, and still more preferably 60 mass% or less. <9> The method for producing a copper particle dispersion according to any one of <1> to <8>, wherein the copper particles a have an average particle size of preferably 50 nm or more, more preferably 75 nm or more, even more preferably 100 nm or more, still more preferably 125 nm or more, and preferably 400 nm or less, more preferably 300 nm or less, even more preferably 250 nm or less, and still more preferably 200 nm or less. <10> The method for producing a copper particle dispersion according to any one of <1> to <9>, wherein the coating agent D is preferably one or more selected from the group consisting of aliphatic carboxylic acids and polymers containing a hydrophilic group. <11> The method for producing a copper particle dispersion according to <10>, wherein the aliphatic carboxylic acid has preferably 1 to 24 carbon atoms, more preferably 2 to 20 carbon atoms, even more preferably 4 to 16 carbon atoms, and still more preferably 6 to 12 carbon atoms. <12> The method for producing a copper particle dispersion according to <10> or <11>, wherein the polymer having 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 even 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)acrylates and alkoxypolyalkylene glycol (meth)acrylates, more preferably alkoxypolyalkylene glycol (meth)acrylate. <16> The method for producing a copper particle dispersion according to <15>, wherein the alkoxy group of the alkoxypolyalkylene glycol (meth)acrylate has preferably 18 or less carbon atoms, more preferably 14 or less, and even more preferably 12 or less carbon atoms. <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 a unit derived from an alkylene oxide having from 2 to 4 carbon atoms. <18> The method for producing a copper particle dispersion according to <17>, wherein the alkylene oxide in the unit derived from an alkylene oxide having from 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 method for producing a copper particle dispersion according to any one of <12> to <18>, wherein the number of alkylene oxide-derived units in the polyalkylene glycol segment is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, and is preferably 100 or less, more preferably 70 or less, even more preferably 50 or less, still more preferably 40 or less, and still more preferably 35 or less. <20> The method for producing a copper particle dispersion according to any one of <12> to <19>, wherein the vinyl polymer P further contains a structural unit derived from a hydrophobic monomer (p-3). <21> The method for producing a copper particle dispersion according to <20>, wherein 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.<22> The method for producing a copper particle dispersion according to <21>, wherein the aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group of 6 to 22 carbon atoms, which may have a substituent containing a heteroatom, more preferably at least one selected from the group consisting of a styrene-based monomer and an aromatic group-containing (meth)acrylate, and even more preferably a styrene-based monomer. <23> The method for producing a copper particle dispersion according to either <21> or <22>, wherein the (meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol is preferably one having a hydrocarbon group derived from an aliphatic alcohol having 22 or less carbon atoms, more preferably one having a hydrocarbon group derived from an aliphatic alcohol having 12 or less carbon atoms, even more preferably one having a hydrocarbon group derived from an aliphatic alcohol having 8 or less carbon atoms, and still more preferably one having a hydrocarbon group derived from an aliphatic alcohol having 4 or less carbon atoms. <24> The method for producing a copper particle dispersion according to any one of <20> to <23>, wherein 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 linear alkyl group, more preferably at least one selected from the group consisting of a styrene-based monomer and a (meth)acrylate having a linear alkyl group having from 1 to 4 carbon atoms, even 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, still more preferably at least one selected from the group consisting of styrene, α-methylstyrene, and methyl (meth)acrylate, and still more preferably at least one selected from the group consisting of styrene and methyl (meth)acrylate. <25> The method for producing a copper particle dispersion according to any one of <12> to <24>, wherein the number average molecular weight Mn of the vinyl polymer P is preferably 4,000 or more, more preferably 6,000 or more, even more preferably 7,000 or more, and preferably 50,000 or less, more preferably 30,000 or less, even more preferably 20,000 or less, still more preferably 15,000 or less, and still more preferably 10,000 or less.<26> The method for producing a copper particle dispersion according to any one of <12> to <25>, wherein the acid value of the vinyl polymer P is preferably 20 mgKOH / g or more, more preferably 25 mgKOH / g or more, even more preferably 30 mgKOH / g or more, still more preferably 35 mgKOH / g or more, still more preferably 40 mgKOH / g or more, and is preferably 250 mgKOH / g or less, more preferably 200 mgKOH / g or less, even more preferably 150 mgKOH / g or less, still more preferably 130 mgKOH / g or less, and still more preferably 110 mgKOH / g or less. <27> The method for producing a copper particle dispersion according to any one of <1> to <26>, wherein the content of the coating agent D coating 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, even more preferably 0.6% by mass or more, still more preferably 0.8% by mass or more, still more preferably 1.0% by mass or more, and preferably 2.5% by mass or less, more preferably 2.0% by mass or less, even more preferably 1.8% by mass or less, and still more preferably 1.6% by mass or less. <28> The method for producing a copper particle dispersion according to any one of <1> to <27>, wherein the copper nanoparticles A are obtained by mixing a copper source compound, a reducing agent, and the coating agent D, and reducing the copper source compound with the reducing agent to obtain copper particles a, and coating the copper particles a with the coating agent D. <29> The method for producing a copper particle dispersion according to <28>, wherein the copper source 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. <30> The method for producing a copper particle dispersion according to <28> or <29>, wherein the reducing agent is one or more selected from the group consisting of a hydrazine-based compound, a boron compound, and an inorganic acid salt. <31> The method for producing a copper particle dispersion according to <30>, wherein the hydrazine-based compound is, for example, one or more selected from the group consisting of hydrazine, hydrazine hydrochloride, hydrazine sulfate, and hydrazine hydrate. <32> The method for producing a copper particle dispersion according to <30> or <31>, wherein the boron compound is one or more selected from the group consisting of sodium borohydride.<33> The method for producing a copper particle dispersion according to any one of <30> to <32>, wherein 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. <34> The method for producing a copper particle dispersion according to any one of <28> to <33>, wherein the solvent for dispersing the copper source compound and the reducing agent is one or more 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, even more preferably 20°C or higher, and even more preferably 30°C or higher, and preferably 100°C or lower, more preferably 90°C or lower, even more preferably 80°C or lower, and even 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 size of the copper microparticles B is preferably 0.8 μm or more, more preferably 2.0 μm or more, even more preferably 3.0 μm or more, and preferably 8.0 μm or less, more preferably 7.0 μm or less, and even 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, even more preferably 30% by mass or more, still more preferably 35% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 55% by mass or less, and still 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 size of the copper particles b is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 2.0 μm or more, still more preferably 3.0 μm or more, and preferably 10 μm or less, more preferably 8.0 μm or less, even more preferably 7.0 μm or less, and still 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 copper particles b and a coating agent E. <40> The method for producing a copper particle dispersion according to <39>, wherein the boiling point of the coating agent E is preferably 350°C or less, more preferably 320°C or less, and even more preferably 300°C or less. <41> The method for producing a copper particle dispersion according to <39> or <40>, wherein the coating agent E 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. <42> The method for producing a 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 a copper particle dispersion according to any one of <39> to <42>, wherein the content of coating agent E coating copper particles b in copper microparticles B is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, even 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, and is 0% by mass. <44> The method for producing a copper particle dispersion according to any one of <1> to <38>, wherein copper microparticles B consist of copper particles b. <45> The method for producing a copper particle dispersion according to any one of <1> to <44>, wherein the total 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, even more preferably 95% by mass or less, still more preferably 94% by mass or less, and preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and still more preferably 90% by mass or more. <46> The method for producing a copper particle dispersion according to any one of <1> to <45>, wherein the blending mass ratio of copper nanoparticles A to copper microparticles B [copper nanoparticles A / copper microparticles B] is preferably 0.30 or more, more preferably 0.50 or more, even more preferably 0.80 or more, still more preferably 1.00 or more, and preferably 3.00 or less, more preferably 2.50 or less, even more preferably 2.00 or less, and still 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 an aliphatic monohydric alcohol, a (poly)alkylene glycol, a (poly)alkylene glycol derivative, glycerin, and a glycerin derivative. <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 a terpene alcohol, more preferably a 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 the group consisting of 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 at least one 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 at least one 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 method for producing a copper particle dispersion according to <50> or <51>, wherein the (poly)alkylene glycol monoalkyl ether acetate is one or more 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. <53> The method for producing a copper particle dispersion according to any one of <47> to <52>, wherein the glycerin derivative is one or more selected from the group consisting of 3-(2-ethylhexyloxy)-1,2-propanediol and glyceryl tributyrate. <54> The method for producing a copper particle dispersion according to any one of <1> to <53>, wherein the dispersion medium C preferably contains one or more selected from the group consisting of aliphatic monohydric alcohols, (poly)alkylene glycols, and glycerin derivatives, more preferably contains one or more selected from the group consisting of terpene alcohols, (poly)alkylene glycols, and glycerin derivatives, even more preferably contains one or more selected from the group consisting of α-terpineol, diethylene glycol, tetraethylene glycol, and glycerol tributyrate, and still more preferably contains two or more selected from the group consisting of α-terpineol, diethylene glycol, tetraethylene glycol, and glycerol tributyrate. <55> The method for producing a copper particle dispersion according to any one of <1> to <54>, wherein the boiling point of the dispersion medium C at 1 atmosphere is preferably 180°C or higher, more preferably 200°C or higher, even more preferably 210°C or higher, still more preferably 215°C or higher, and preferably 400°C or lower, more preferably 360°C or lower, even more preferably 330°C or lower, and still more preferably 300°C or lower.<56> The method for producing a copper particle dispersion according to any one of <1> to <55>, wherein the molecular weight of the dispersion medium C is preferably 60 or more, more preferably 80 or more, even more preferably 100 or more, still more preferably 120 or more, and preferably 450 or less, more preferably 400 or less, even more preferably 350 or less, and still more preferably 300 or less. <57> The method for producing a copper particle dispersion according to any one of <1> to <56>, wherein the blending amount of the dispersion medium C is preferably 3% by mass or more, more preferably 4% by mass or more, even more preferably 5% by mass or more, still more preferably 6% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and still more preferably 10% by mass or less. <58> A dispersion medium C containing copper nanoparticles A, copper microparticles B, and a dispersion medium C, and containing copper particles a and a coating agent D, wherein the copper nanoparticles A have an average particle size of 50 nm or more and 300 nm or less, the copper microparticles B contain copper particles b, and the copper microparticles B have an average particle size of 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 calculated by the following formula (1) is 9.0 MPa: １／２ A copper particle dispersion having a Ra of: （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 represent the dispersion term, polar term, and hydrogen bond term of the Hansen solubility parameter of copper nanoparticle A, respectively, and δD Ｂ , δP Ｂ , and δH Ｂindicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of copper microparticles B, respectively, and the Hansen solubility parameters of copper nanoparticles A and copper microparticles B are values ​​calculated using the HSPiP program.) <59> Distance Ra of the Hansen solubility parameters between copper nanoparticles A and copper microparticles B （Ａ－Ｂ） However, preferably 8.0 MPa １／２ Not more than 6.0 MPa, more preferably １／２ <60> The copper particle dispersion according to <58>, wherein the distance Ra of the Hansen solubility parameters between copper nanoparticles A and a dispersion medium C is calculated by the following formula (2): （Ａ－Ｃ） However, preferably 20.0 MPa １／２ Not more than 15.0 MPa, more preferably １／２ More preferably, 10.0 MPa or less １／２ More preferably, 8.0 MPa or less １／２ The copper particle dispersion according to <58> or <59>, wherein Ra is: （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 term, polar term, and hydrogen bond term of the Hansen solubility parameter of copper nanoparticle A, respectively, and δD Ｃ , δP Ｃ , and δH Ｃ indicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of the dispersion medium C, respectively, and the Hansen solubility parameter of the dispersion medium C is a value calculated by a weighted average weighted by the content (volume basis) of each dispersion medium based on the value calculated by the HSPiP program.) <61> The distance Ra of the Hansen solubility parameter between the copper microparticles B and the dispersion medium C calculated by the following formula (3) （Ｂ－Ｃ） is preferably 15.0 MPa １／２or less, more preferably 12.0 MPa １／２ More preferably, 8.0 MPa or less １／２ More preferably, 6.0 MPa or less １／２ The copper particle dispersion according to any one of <58> to <60>, wherein Ra is: （Ｂ－Ｃ） = {(4 × (δD Ｂ -δD Ｃ ) ２ + (δP Ｂ -δP Ｃ ) ２ + (δH Ｂ -δH Ｃ ) ２ ) １／２ (3) (However, in the above formula (3), δD Ｂ , δP Ｂ , and δH Ｂ represent the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of copper microparticle B, respectively, and δD Ｃ , δP Ｃ , and δH Ｃindicate the dispersing force term, polarity term, and hydrogen bonding term of the Hansen solubility parameter of dispersion medium C, respectively, and the Hansen solubility parameter of dispersion medium C is a value calculated by a weighted average weighted by the content (volume basis) of each dispersion medium based on the value calculated by the HSPiP program.) <62> The copper particle dispersion according to any one of <58> to <61>, wherein the content of copper nanoparticles A in the copper particle dispersion is preferably 25% by mass or more, more preferably 30% by mass or more, even more preferably 35% by mass or more, still more preferably 40% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and still more preferably 60% by mass or less. <63> The copper particle dispersion according to any one of <58> to <62>, wherein 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, even more preferably 0.3% by mass or more, still more preferably 0.4% by mass or more, still more preferably 0.5% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, still more preferably 1.5% by mass or less, and still more preferably 1% by mass or less. <64> The copper particle dispersion according to any one of <58> to <63>, wherein 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, even more preferably 30% by mass or more, still more preferably 35% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 55% by mass or less, and still more preferably 50% by mass or less. <65> The copper particle dispersion according to any one of <58> to <64>, wherein 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, even more preferably 0.2% by mass or less, still more preferably 0.1% by mass or less, still more preferably 0.05% by mass or less, and still more preferably 0% by mass.<66> The copper particle dispersion according to any one of <58> to <65>, wherein 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, even more preferably 95% by mass or less, still more preferably 94% by mass or less, and preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and still more preferably 90% by mass or more. <67> The copper particle dispersion according to any one of <58> to <66>, wherein 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, even more preferably 5% by mass or more, still more preferably 6% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and still more preferably 10% by mass or less.

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

[0085] <Average particle size of copper nanoparticles A and copper microparticles B> Scanning electron microscope (SEM) images of copper nanoparticles A and copper microparticles B were taken using a scanning electron microscope (Hitachi High-Tech Corporation, field emission scanning electron microscope: S-4800). The magnification was determined according to the particle size of the particles, and images were taken in the range of 5,000 to 150,000 times. The SEM images were analyzed using image analysis software ImageJ (National Institutes of Health), and the particle sizes of 100 or more particles per sample were determined. The arithmetic average value was used 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 simultaneous differential thermal thermogravimetry analyzer (TG / DTA) (Hitachi High-Tech Science Corporation, product name: STA7200RV), 10 mg of copper nanoparticles A was weighed into an aluminum pan, and the temperature was increased 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 loss was measured. The mass loss from 35 ° C. to 550 ° C. was taken as the mass of coating agent D, and the remaining mass at 550 ° C. was taken as the mass of copper particles a. The content (mass%) of coating agent D coated on copper particles a in copper nanoparticles A was calculated using the following formula. Content (mass%) of coating agent D coating copper particles a in copper nanoparticles A = (content (g) of coating agent D) / (content (g) of coating agent D + content (g) of copper particles a) × 100 = (mass loss from 35°C to 550°C) / {(mass loss 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 simultaneous differential thermal thermogravimetry analyzer (TG / DTA) (Hitachi High-Tech Science Corporation, trade name: STA7200RV), 10 mg of copper microparticles B was weighed into an aluminum pan, heated 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 loss was measured. The mass loss from 35 ° C. to 550 ° C. was the mass of coating agent E, and the remaining mass at 550 ° C. was the mass of copper particles b. The content (mass%) of coating agent E coated on copper particles b in copper microparticles B was calculated using the following formula. Content (mass%) of coating agent E coated on copper particles b in copper microparticles B = (content (g) of coating agent E) / (content (g) of coating agent E + content (g) of copper particles b) × 100 = (mass loss from 35°C to 550°C) / {(mass loss from 35°C to 550°C) + (remaining mass at 550°C)} × 100

[0088] <Number average molecular weight Mn of polymer P> This was determined by gel permeation chromatography. The measurement sample was prepared by mixing 0.1 g of polymer with 10 mL of eluent in a glass vial, stirring with a magnetic stirrer at 25°C for 10 hours, 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 apparatus: "HLC-8320GPC" manufactured by Tosoh Corporation Column: "TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guard column Super AW-H" manufactured by Tosoh Corporation Eluent: N,N-dimethylformamide dissolved with phosphoric acid and lithium bromide to concentrations of 60 mmol / L and 50 mmol / L, respectively Flow rate: 0.5 mL / min Standard substance: Monodisperse polystyrene kit manufactured by Tosoh Corporation "PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500)"

[0089] <Acid Value of Polymer P> The acid value of Polymer P was measured in accordance with JIS K0070-1992 (potentiometric titration method), except that the measurement solvent was changed from the ethanol and ether mixed solvent specified in JIS K0070 to an acetone and toluene mixed solvent (acetone:toluene=4:6 (volume ratio)).

[0090] [Production of Polymer P] Production Example 1 (Production of Polymer P1) 20.0 g of ethanol (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was placed in a 1000 mL four-necked round-bottom flask equipped with a thermometer, two 100 mL nitrogen-bypass-equipped dropping funnels, and a reflux apparatus, and the internal temperature of the flask was heated to 80°C in an oil bath, followed by bubbling with nitrogen for 10 minutes. Next, 15.3 g of methacrylic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., special grade reagent), 7.2 g of methyl methacrylate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., special grade reagent), 10.0 g of styrene (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., special grade reagent), 67.5 g of methoxypolyethylene glycol (EO 23 mol) methacrylate (NOF Corporation, "PME-1000"), 1.0 g of 3-mercaptopropionic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., special grade reagent), and 28.7 g of ethanol were dissolved in a polybeaker and placed in the dropping funnel (1). Separately, 51.3 g of ethanol and 1.3 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., "V-65", polymerization initiator) were dissolved in a polybeaker and placed in the dropping funnel (2). Next, the mixtures in the dropping funnels (1) and (2) were simultaneously added dropwise to the flask over 90 minutes. The internal temperature of the flask was then raised to 90°C, and stirring was continued for another hour to terminate the reaction. The resin solution was freeze-dried using a freeze dryer (Tokyo Rikakikai Co., Ltd., Model: FDU-2110) equipped with a dry chamber (Tokyo Rikakikai Co., Ltd., Model: DRC-1000) under drying conditions (-25°C 1 hour freezing, -10°C 9 hours reduced pressure, 25°C 5 hours reduced pressure, vacuum degree 5 Pa) to obtain bone-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) Polymer P2 (methacrylic acid / methoxypolyethylene glycol (EO 23 mol) methacrylate polymer, acid value: 46 mg KOH / g, Mn: 9,000) was obtained by the same production method as in Production Example 1, except that the monomer composition was changed to that shown in Table 1. The results are shown in Table 1.

[0092]

[0093] Details of each monomer in Table 1 are as follows: (Monomer (p-1)) MAA: methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) (Monomer (p-2)) PEGMA (23) MA: methoxypolyethylene glycol (EO 23 mol) methacrylate (manufactured by NOF Corporation, "PME-1000") (Monomer (p-3)) MMA: methyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) St: styrene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent)

[0094] [Synthesis of Copper Nanoparticles A] Synthesis Example 1-1 (Production of Copper Nanoparticles A-1) In 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 (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent, boiling point: 298 ° C.) as a coating agent D, and 500 g of ethanol (95) (Fujifilm Wako Pure Chemical Industries, Ltd., first-class 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 Industries, Ltd., special grade reagent) placed in a 50 mL dropping funnel was added dropwise to the mixed solution at 25 ° C. over 20 minutes. Thereafter, the reaction solution was stirred for 1 hour while controlling the temperature at 70 ° C. in an oil bath, and then air-cooled to obtain a reddish-brown dispersion containing the precursor of copper nanoparticles A-1. The entire amount of the obtained dispersion was placed in a Hitachi Koki Co., Ltd. refrigerated centrifuge "himacCR22G" and rotor (R12A, radius 15.1 cm) in a centrifugal sedimentation tube 500PA bottle, and centrifuged at 3000 rpm with a centrifugal acceleration of 675 G. This state was maintained for 30 minutes. 300 g of ethanol (95) (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent) was added to the precipitate separated by centrifugation, and the mixture was re-dispersed by stirring for 15 minutes. The entire amount of the re-dispersion was centrifuged again under the same conditions, and the precipitate was separated. This operation was performed three times. The precipitate of purified copper nanoparticles A-1 was freeze-dried using a freeze dryer (manufactured by Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (manufactured by Tokyo Rikakikai Co., Ltd., model: DRC-1000) to obtain 38.0 g of copper nanoparticles A-1. Freeze-drying was performed by freezing at -25 ° C. for 1 hour, drying under reduced pressure at -10 ° C. and 5 Pa for 9 hours, and further drying under reduced pressure 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% by mass. The results are shown in Table 2.

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

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

[0097]

[0098] [Synthesis of copper microparticles B] Synthesis Example 2-1 (production of copper microparticles B-1) In 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, 1.0 g of octanoic acid (FUJIFILM Wako Pure Chemical Industries, Ltd., special grade reagent, boiling point: 238 ° C.) as a coating agent E, 500 g of ethanol (95) (FUJIFILM Wako Pure Chemical Industries, Ltd., first-class reagent) was added and stirred for 15 minutes. During stirring, the temperature of the reaction solution was controlled to 70 ° C. in an oil bath. Next, 63.0 g of hydrazine monohydrate (FUJIFILM Wako Pure Chemical Industries, Ltd., special grade reagent) placed in a 50 mL dropping funnel was added dropwise to the mixture at 25 ° C. over 20 minutes. Thereafter, the reaction solution was stirred for 1 hour while controlling the temperature at 70 ° C. in an oil bath, and then air-cooled to obtain a reddish-brown dispersion containing the precursor of copper microparticles B-1. The entire amount of the obtained dispersion was placed in a Hitachi Koki Co., Ltd. refrigerated centrifuge "himacCR22G" and rotor (R12A, radius 15.1 cm) in a centrifugal sedimentation tube 500PA bottle, and centrifuged at 3000 rpm with a centrifugal acceleration of 675 G. The mixture was maintained in this state for 30 minutes. 300 g of ethanol (95) (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent) was added to the precipitate separated by centrifugation, and the mixture was re-dispersed by stirring for 15 minutes. The entire amount of the re-dispersion was centrifuged again under the same conditions, and the precipitate was separated. This operation was performed three times. The precipitate of purified copper microparticles B-1 was freeze-dried using a freeze dryer (manufactured by Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (manufactured by Tokyo Rikakikai Co., Ltd., model: DRC-1000), to obtain 38.2 g of copper microparticles B-1. The freeze-drying was performed by freezing at -25°C for 1 hour, followed by drying under reduced pressure at -10°C and 5 Pa for 9 hours, and then further drying under reduced pressure 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 an octanoic acid (coating agent E) content of 0.43% by mass. The results are shown in Table 3.

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

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

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

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

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

[0104] Synthesis Example 2-7 (Production of Copper Microparticles B-7) 10 g of 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 stirred for 5 minutes with a magnetic stirrer. Thereafter, using a centrifuge, the mixture was placed in a centrifugal sedimentation tube 500 PA bottle, and centrifuged at 3000 rpm with a centrifugal acceleration of 675 G. This state was maintained for 30 minutes. 300 g of ethanol (95) (Fujifilm Wako Pure Chemical Industries, Ltd., first-class reagent) was added to the precipitate separated by centrifugation, and the mixture was redispersed by stirring for 15 minutes. The entire redispersion liquid was centrifuged again under the same conditions, and the precipitate was separated. This operation was performed three times. The purified copper particle precipitate was freeze-dried using a freeze dryer (manufactured by Tokyo Rikakikai Co., Ltd., model: FDU-2110) equipped with a dry chamber (manufactured by Tokyo Rikakikai Co., Ltd., model: DRC-1000) to obtain 9.3 g of copper microparticles B-7. The freeze-drying was performed by freezing at -25°C for 1 hour, followed by drying under reduced pressure at -10°C and 5 Pa for 9 hours, and then further drying under reduced pressure 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 a coating agent E content of 0% by mass. The results are shown in Table 3.

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

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

[0107]

[0108] [Calculation of Hansen Solubility Parameters of Copper Nanoparticles A and Copper Microparticles B] 9 g of copper nanoparticles A or copper microparticles B obtained in each of the above production examples and 1 g of 1,7-heptanediol were weighed and added to an agate mortar and kneaded for 15 minutes to obtain a mixed solution. The resulting mixed solution was transferred to a 10 mL ointment bottle (Platsubo ointment bottle manufactured by KM Chemical Co., Ltd.), sealed, and stirred at 2000 rpm for 5 minutes using a rotation-revolution type stirring device (Thinky Corporation, Planetary Vacuum Mixer ARV-310) to prepare a sample for dispersion state evaluation. For this sample, the container was tilted, and the contents at the bottom of the container were observed. The dispersion state was evaluated according to the following evaluation criteria. The same operation was performed except that 1,7-heptanediol was replaced with the evaluation solvent below, and the dispersion state was similarly evaluated for each evaluation solvent. Based on the evaluation results of the dispersion state, "0" was entered in the designated input field of the computer software HSPiP (manufactured by (LCC) Pirika) if the evaluation was "A" and "1" if the evaluation was "B," and the Hansen solubility parameter of each copper nanoparticle A and copper microparticle B was calculated. The evaluation results of the dispersion state and the Hansen solubility parameters of each copper nanoparticle A and copper microparticle B are shown in Table 4. (Evaluation criteria) A (good dispersion): Particles did not remain at the bottom of the container and formed a smooth paste. B (poor dispersion): Some or all of the particles did not disperse 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 Industries Co., Ltd., special grade reagent) Tetraethylene glycol dimethyl ether (Tokyo Chemical Industry Co., Ltd., purity (test method): >98.0% (GC)) α-Terpineol (Fujifilm Wako Pure Chemical Industries Co., Ltd., special grade reagent) Tributyrin (glyceryl tributyrate) (Fujifilm Wako Pure Chemical Industries Co., Ltd., special grade reagent) 1-methyl-2-pyrrolidone (Fujifilm Wako Pure Chemical Industries Co., Ltd., special grade reagent)・Ethylene glycol (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) ・γ-butyrolactone (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) ・Dodecane (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent)

[0110]

[0111] [Production of Copper Particle Dispersion] Example 1 4.0 parts by mass of α-terpineol and 3.0 parts by mass of tributyrin as dispersion medium C, 50 parts by mass of dried powder of copper nanoparticles A-1, and 43 parts by mass of dried powder of copper microparticles B-1 were added to an agate mortar and kneaded until the dried powder was no longer visible. The resulting mixture was transferred to a plastic bottle. The sealed plastic bottle was stirred at 2000 rpm for 5 minutes using a planetary vacuum mixer (Thinky Corporation, Planetary Vacuum Mixer ARV-310). The mixture was then passed three times through a three-roll mill (Imex Co., Ltd., BV 100) with a gap adjusted to 0.2 mm, to obtain the copper particle dispersion of Example 1. The distance Ra of the solubility parameter of each of the resulting copper particle dispersions was calculated as described below. The results are shown in Table 5.

[0112] Examples 2 to 14 and Comparative Examples 1 to 4 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 each of the obtained copper particle dispersions, the Hansen solubility parameter distance Ra was calculated as described below. The results are shown in Table 5.

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

[0114] [The distance Ra between the Hansen solubility parameters of copper nanoparticles A and dispersion medium C （Ａ－Ｃ） From the Hansen solubility parameter values ​​of copper nanoparticles A and dispersion medium C shown in Table 4, the distance Ra of the Hansen solubility parameters between copper nanoparticles A and dispersion medium C contained in each copper particle dispersion of the Examples and Comparative Examples was calculated using the following formula (2). （Ｂ－Ｃ） When dispersion medium C is a mixed dispersion medium, the Hansen solubility parameter of dispersion medium C is a value calculated by weighted averaging based on the values ​​calculated using the HSPiP program, and specifically, the value calculated by calculating the solubility parameter of the mixed dispersion medium described below was used. The Hansen solubility parameter values ​​of dispersion medium C are 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] [The distance Ra between the Hansen solubility parameters of copper microparticles B and dispersion medium C （Ｂ－Ｃ） From the Hansen solubility parameter values ​​of copper microparticles B and dispersion medium C shown in Table 4, the distance Ra of the Hansen solubility parameters between copper microparticles B and dispersion medium C contained in each copper particle dispersion of the Examples and Comparative Examples was calculated using the following formula (3): （Ｂ－Ｃ） When dispersion medium C is a mixed dispersion medium, the Hansen solubility parameter of dispersion medium C is a value calculated by weighted averaging based on the values ​​calculated using the HSPiP program, and specifically, the value calculated by calculating the solubility parameter of the mixed dispersion medium described below was used. The Hansen solubility parameter values ​​of dispersion medium C are 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 solubility parameter of dispersion medium C (mixed dispersion medium)) When dispersion medium C is a mixed dispersion medium obtained by mixing two types of dispersion mediums, the Hansen solubility parameters of each dispersion medium listed in the database of the computer software HSPiP were used to calculate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of each dispersion medium C by weighting 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)) = (V １ ×δD Ｃ１ +V ２ ×δD Ｃ２ ) / (V １ +V ２ ) (4-1) δP Ｃ(Polar term of dispersion medium C (mixed dispersion medium)) = (V １ ×δP Ｃ１ +V ２ ×δP Ｃ２ ) / (V １ +V ２ ) (4-2) δH Ｃ (Hydrogen bond term of dispersion medium C (mixed dispersion medium)) = (V １ ×δH Ｃ１ +V ２ ×δH Ｃ２ ) / (V １ +V ２ ) (4-3) In the above formulas (4-1) to (4-3), δD Ｃ１ , δP Ｃ１ , δH Ｃ１ indicates the dispersion force term, polarity term, and hydrogen bond term of the first solvent, and V １ indicates the volume of the first solvent, and δD Ｃ２ , δP Ｃ２ , δH Ｃ２ represents the dispersion force term, polarity term, and hydrogen bond term of the second solvent, and V ２ indicates the volume of the second solvent.

[0117] [Evaluation] <Method for Producing Bonded Structure> Bonded structures were produced using the copper particle dispersions obtained in the Examples and Comparative Examples 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 to the copper plate by stencil printing using a metal squeegee. The copper plate was then dried at 120°C for 10 minutes in air on a Shamal hot plate (HHP-441, manufactured by AS ONE Corporation). A 5 mm × 5 mm silicon chip (thickness: 400 μm) was then prepared by sputtering titanium, nickel, and gold in this order onto the silicon chip. The silicon chip was then placed on the applied copper particle dispersion so that the gold was in contact with the copper particle dispersion. This resulted in a laminate comprising a copper plate, a copper particle dispersion, and a silicon chip stacked in this order. The resulting laminate was fired by the following method to produce a bonded structure. First, the laminate was placed in a pressure firing machine (HTM-1000, manufactured by Meisho Kiko Co., Ltd.), and nitrogen was flowed into the furnace at 500 mL / min to replace the air in the furnace with nitrogen. Then, the temperature of the heating heads was raised to 260°C over 3 minutes while pressurizing the laminate at 10 MPa using the upper and lower heating heads. After the temperature increase, the laminate was sintered by holding at 260°C for 500 seconds 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 air at 100°C or below.

[0118] <Evaluation of Initial Bond Strength> The copper particle dispersions obtained in the Examples and Comparative Examples were used immediately after production to produce bonded bodies using the above-mentioned bonded body production method. Using a universal bond tester (Prospector, manufactured by Nordson Advanced Technologies Co., Ltd.), the silicon chip of the bonded body was pressed horizontally at a test speed of 5 mm / min and a shear height of 50 μm to measure the die shear strength of the bonded body. Three bonded bodies were tested, and the average of the values ​​measured for the three bonded bodies was taken as the bond 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 for 3 months under conditions of 25°C and 50% humidity, and then bonded bodies were produced by the above-mentioned bonded body production method. The obtained bonded bodies were measured in the same manner as in the evaluation of the initial bonding strength described above, and the bonding strength after storage was measured.

[0120] <Evaluation of Bonding Strength Retention Rate> The bonding strength retention rate was calculated using the following formula. A higher bonding strength retention rate indicates a higher bonding strength retention rate of the copper particle dispersion after storage. Bonding strength retention rate (%) = bonding strength after storage (MPa) / initial bonding strength (MPa) × 100

[0121]

[0122] As can be seen from Table 5, the copper particle dispersions obtained in Examples 1 to 14 had better retention of bonding strength of the resulting bonded bodies even after storage for 3 months than 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 had excellent storage stability and excellent retention of bonding strength after storage.

[0123] <Evaluation of Temperature Cycle Heat Resistance> The copper particle dispersion of Example 10 was stored for 3 months under conditions of 25°C and 50% humidity, and then a bonded body was produced using the above-mentioned bonded body production method. Thereafter, a temperature cycle test was performed using a small thermal shock device (Espec Corporation, TSE-12-A) under atmospheric conditions of -55°C and 200°C for 15 minutes each, for 1000 cycles, and the bond strength of the bonded body was measured in the same manner as in the evaluation of the initial bond strength described above. As a result, the bond strength after the temperature cycle test was 60 MPa, which was only slightly lower than the bond strength of 62 MPa before the test. Therefore, it was found that the bonded body obtained using the copper particle dispersion of Example 10 after long-term storage also had good temperature cycle heat resistance.

[0124] <Evaluation of Heat Resistance at 250°C> The copper particle dispersion of Example 10 was stored for 3 months under conditions of 25°C and 50% humidity, and then a bonded body was produced by the above-mentioned bonded body production method. The obtained bonded body was subjected to a 250°C heat resistance test under conditions of atmospheric pressure, 250°C, and 1000 hours, and measurements were performed in the same manner as in the evaluation of the initial bond strength described above to measure the bond strength of the bonded body. As a result, the bond strength after the 250°C heat resistance test was 59 MPa, which was only slightly lower than the bond strength of 62 MPa before the test. Therefore, it was found that the bonded body obtained using the copper particle dispersion of Example 10 after long-term storage also had good heat resistance at 250°C.

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

[0126] According to the present invention, a method for producing a copper particle dispersion having excellent bonding strength retention after storage can be provided.

Claims

1. A method for producing a dispersion medium comprising a step of mixing copper nanoparticles A, copper microparticles B, and a dispersion medium C, wherein the copper nanoparticles A comprise copper particles a and a coating agent D, and the copper nanoparticles A have an average particle size of 50 nm or more and 300 nm or less, the copper microparticles B comprise copper particles b, and the copper microparticles B have an average particle size of 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 is calculated by the following formula (1): （Ａ－Ｂ） is 9.0 MPa １／２ 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 represent the dispersion term, polar term, and hydrogen bond term of the Hansen solubility parameter of copper nanoparticle A, respectively, and δD Ｂ , δP Ｂ , and δH Ｂ indicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of copper microparticles B, respectively, and the Hansen solubility parameters of copper nanoparticles A and copper microparticles B are values ​​calculated 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 coated on the copper particles a in the copper nanoparticles A is 0.3 mass% or more.

3. The method for producing a copper particle dispersion according to claim 1 or 2, wherein the copper microparticles B comprise 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. A method for producing a copper particle dispersion as described in claim 3 or 4, wherein the content of coating agent E coated on copper particles B in the copper microparticles B is 1.0 mass% or less.

6. The 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 between the Hansen solubility parameters of the copper nanoparticles A and the dispersion medium C is calculated by the following formula (2): （Ａ－Ｃ） is 20.0 MPa １／２ The method for producing a copper particle dispersion according to any one of claims 1 to 6, wherein Ra is below 0.

05. （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 Hansen solubility parameters of copper nanoparticles A, which are the same as those of the formula (1), and δD Ｃ , δP Ｃ , and δH Ｃ indicate the dispersion force term, polarity term, and hydrogen bond term of the Hansen solubility parameter of dispersion medium C, respectively, and the Hansen solubility parameter of dispersion medium C is a value calculated by a weighted average weighted by the content (volume basis) of each dispersion medium based on the value calculated by the HSPiP program.

8. The δP of the Hansen solubility parameters of the copper nanoparticles A Ａ (polar term) is 1.0 MPa １／２ The method for producing a copper particle dispersion according to any one of claims 1 to 7, wherein the copper particle dispersion is a copper particle dispersion having a diameter of 100 mm or less.

9. The method for producing a copper particle dispersion according to any one of claims 1 to 8, wherein the coating agent D is at least one 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 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.

11. The method for producing a copper particle dispersion according to any one of claims 1 to 10, wherein the dispersion medium C contains at least one selected from the group consisting of aliphatic monohydric alcohols, (poly)alkylene glycols, (poly)alkylene glycol derivatives, glycerin, and glycerin derivatives.

12. The method for producing a copper particle dispersion according to any one of claims 1 to 11, wherein the blending mass ratio of the copper nanoparticles A to the copper microparticles B [copper nanoparticles A / copper microparticles B] is 0.30 or more and 3.00 or less.

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