Method for producing copper particles

Abstract

The present application provides a method for producing copper particles having an average particle diameter within the range of 1 nm to 1,000 nm, the method being characterized by comprising a step of mixing at least a first fluid and a second fluid to precipitate copper particles, wherein one of the first fluid and the second fluid is a copper raw material solution containing a raw material of the copper particles, the other of the first fluid and the second fluid is a reducing agent solution containing at least one kind of reducing agent, the copper raw material solution contains monovalent copper ions and / or divalent copper ions, and the oxidation-reduction potential of the copper raw material solution is set so that the average particle diameter is achieved. According to this production method, copper particles having a controlled average particle diameter can be supplied easily and stably by using a method suitable for large-scale production without requiring a complex chemical reaction or a heat treatment.

Description

Method for producing copper particles

[0001] The present invention relates to a method for producing copper particles. More specifically, the present invention relates to a method for producing copper particles having an average particle size controlled within a range of 1 nm to 1000 nm, and a method for controlling the average particle size of copper particles within a range of 1 nm to 1000 nm.

[0002] In recent years, conductive pastes containing dispersed metal particles have been used as materials for forming wiring and electrodes on substrates for electronic devices. Silver, which exhibits high conductivity, is the most commonly used metal particle, but it is expensive and has migration issues. Therefore, the use of copper has been widely considered, but the problem of copper particles being susceptible to oxidation is raised by the increased surface area relative to the mass due to atomization.

[0003] Wiring and electrodes require metal particles of various particle sizes depending on the electronic device and the formation method used. Furthermore, when applying metal particles using screen printing, inkjet printing, dispensers, etc., if there is a distribution in the particle size of the metal particles used, not only can clogging occur, but wettability with the substrate can also deteriorate, potentially resulting in defects during printing. Therefore, uniform particle size is required.

[0004] Patent Document 1 describes a method for producing copper microparticles by adding a reducing agent to a solvent containing copper oxide as a raw material, a complexing agent, and a protective agent. Impurity ions are removed by subjecting gelatin used as a protective agent to an enhanced desalting treatment, and the enhanced desalting gelatin controls particle shape and prevents particle aggregation. However, the desalting treatment requires several treatments using ion exchange membranes, which makes the process complicated and increases production costs.

[0005] Patent Document 2 describes a method for producing copper powder that is granular in shape and has a particle size of 0.1 μm to 3.0 μm. After mixing with a dispersant solution, a reducing agent solution is added at a temperature in the range of 50°C to 90°C to produce particles with high oxidation resistance. It also states that if the average particle size is less than 0.1 μm, the particles tend to aggregate easily and are difficult to form into a paste.

[0006] Patent Document 3 describes a method for synthesizing copper nanoparticles in an aqueous solution to form low wiring resistance. It states that using ascorbic acid as a reducing agent and antioxidant causes the OH groups of ascorbic acid to adhere to the copper particle surface, thereby inhibiting copper oxidation. Although it is stated that a reducing agent other than ascorbic acid may be used in combination, a follow-up experiment found that when hydrazine monohydrate was used as the reducing agent and ascorbic acid as the antioxidant, an oxide layer was observed on the surface of the resulting copper particles when the amount of hydrazine monohydrate added was 10% by weight or more relative to the ascorbic acid. Essentially, the antioxidant effect of copper particles was confirmed only when copper ions were reduced with ascorbic acid. When ascorbic acid is used as a reducing agent, its reducing power is lower than that of hydrazine monohydrate, making it difficult to produce copper particles with a particle size of, for example, 50 nm or less.

[0007] JP 2012-241213 A, JP 2017-137530 A, JP 2017-71816 A

[0008] Recent demands have created a need for precise control of the average particle size of copper particles and for easy and stable production. However, as described above, it has been difficult to satisfactorily meet these requirements with conventional techniques. In view of the above circumstances, the object of the present invention is to provide a production method that does not require complex chemical reactions or heat treatments and that can easily and stably produce copper particles with a controlled average particle size, using a method suitable for mass production.

[0009] As a result of intensive research to solve the above problems, the present inventors discovered that the average particle size can be controlled by adjusting the oxidation-reduction potential of a copper raw material solution containing raw materials for the copper particles, and that copper particles with a controlled average particle size can be continuously and stably obtained, thereby completing the present invention.

[0010] [1] A method for producing copper particles having an average particle size within a range of 1 nm to 1000 nm, comprising: a step of mixing at least a first fluid and a second fluid to precipitate copper particles; one of the first fluid and the second fluid is a copper raw material solution containing a raw material for the copper particles; and the other of the first fluid and the second fluid is a reducing agent solution containing at least one reducing agent, the copper raw material solution containing at least monovalent copper ions and / or divalent copper ions; and the potential difference between the oxidation-reduction potential of the copper raw material solution and the oxidation-reduction potential of the reducing agent solution is set so as to achieve the average particle size.

[0011] [2] The molar concentration ratio of monovalent copper ions to the total copper ions in the copper raw material solution ([Cu ＋ ] / ([Cu ＋ ]+[Cu ２＋ [3] The manufacturing method according to [1] or [2], wherein the ligand coordinated to the copper ion in the copper source solution is at least one selected from water, hydroxide ion, ammonia, halide ion, amino acid, phosphine, carboxylic acid, thiol, cyanide ion, thiocyanide ion, nitrile, amine, and ethylenediaminetetraacetic acid, and the oxidation-reduction potential of the copper source solution is set by selecting the ligand.

[0012] [4] The manufacturing method according to any one of [1] to [3], wherein the reducing agent is at least one selected from ascorbic acid salts, ferrous sulfate, sulfites, hydroxylamine, formic acid, hydroquinone, reducing sugars, aldehydes, tetrahydroboric acids, hydrazine, and hydrazine compounds, and the oxidation-reduction potential of the reducing agent solution is set by selecting the reducing agent. [5] The manufacturing method according to any one of [1] to [4], wherein the mixed solution obtained by mixing the first fluid and the second fluid contains oxidized ascorbic acid. [6] The manufacturing method according to any one of [1] to [5], wherein the oxide layer on the surface of the copper particles has a thickness of 4 nm or less.

[0013] [7] The manufacturing method according to any one of [1] to [6], wherein at least two fluids to be treated, including the copper raw solution and the reducing agent solution, are continuously introduced between processing surfaces disposed opposite to each other and rotating toward or away from each other, copper particles are precipitated by mixing the at least two fluids to be treated between the processing surfaces disposed opposite to each other and rotating toward or away from each other, and copper particles are continuously manufactured by discharging the mixed fluid containing the precipitated copper particles from between the processing surfaces. [8] The manufacturing method according to [7], wherein one of the copper raw solution and the reducing agent solution passes between the processing surfaces while forming a thin film fluid, and the other of the copper raw solution and the reducing agent solution is introduced between the processing surfaces through another introduction path independent of the flow path introduced between the processing surfaces and from an opening formed in at least one of the processing surfaces, and the copper raw solution and the reducing agent solution are mixed between the processing surfaces.

[0014] [9] A method for controlling the average particle size of copper particles within a range of 1 nm to 1000 nm, comprising: a step of mixing at least a first fluid and a second fluid to precipitate copper particles; one of the first fluid and the second fluid is a copper raw material solution containing a raw material of the copper particles; and the other of the first fluid and the second fluid is a reducing agent solution containing at least one reducing agent, the copper raw material solution containing at least monovalent copper ions and / or divalent copper ions; and the control method is characterized by changing a potential difference between an oxidation-reduction potential of the copper raw material solution and an oxidation-reduction potential of the reducing agent solution.

[0015] The manufacturing method of the present invention makes it possible to easily and stably produce copper particles with a controlled average particle size in a manner suitable for mass production without requiring complex chemical reactions or heat treatments.

[0016] Fig. 2 is a schematic cross-sectional view of a fluid treatment device according to an embodiment of the present invention. Fig. 3 is a schematic plan view of a first processing surface of the fluid treatment device shown in Fig. 1. Fig. 4 is a TEM photograph of copper particles obtained in Example 1 of the present invention. Fig. 5 is a TEM photograph of copper particles obtained in Example 9 of the present invention.

[0017] The following describes one embodiment of the present invention. 1. Manufacturing Method of Copper Particles The manufacturing method of copper particles of the present invention is a method for manufacturing copper particles having an average particle size in the range of 1 nm to 1000 nm, comprising a step of mixing at least a first fluid and a second fluid to precipitate copper particles, wherein one of the first fluid and the second fluid is a copper raw material solution containing a raw material for the copper particles, and the other of the first fluid and the second fluid is a reducing agent solution containing at least one reducing agent, the copper raw material solution containing at least monovalent copper ions and / or divalent copper ions, and the potential difference between the oxidation-reduction potential of the copper raw material solution and the oxidation-reduction potential of the reducing agent solution is set so as to achieve the average particle size.

[0018] (Preparation of copper particle raw material and copper raw material solution) The raw material of the copper particles used in the production method of the present invention is not particularly limited as long as it can supply monovalent copper ions or divalent copper ions in the solution, and examples thereof include copper simple substance, oxide, hydroxide, salt, etc. These copper particle raw materials may be used alone or in combination.

[0019] Examples of raw materials for copper particles that supply monovalent copper ions include copper(I) chloride, copper(I) sulfide, copper(I) oxide, etc. Examples of raw materials for copper particles that supply divalent copper ions include copper(II) oxide, copper(II) chloride, copper(II) sulfate, copper(II) nitrate, copper(II) acetate, copper(II) citrate, copper(II) hydroxide, copper(II) carbonate, copper(II) sulfide, etc.

[0020] A copper source solution can also be prepared by adding an oxidizing agent or a reducing agent to monovalent copper ions and / or divalent copper ions to oxidize or reduce the copper ions. That is, by adding a required amount of an oxidizing agent to a solution in which monovalent copper ions have been dissolved, some of the monovalent copper ions can be oxidized and converted to divalent copper ions. By adding a required amount of a reducing agent to a solution in which divalent copper ions have been dissolved, some of the divalent copper ions can be reduced and converted to monovalent copper ions.

[0021] Examples of the ligand that coordinates with the copper ions in the copper source solution include at least one selected from water, hydroxide ions, ammonia, halide ions, amino acids, phosphines, carboxylic acids, thiols, cyanide ions, thiocyanide ions, nitriles, amines, and ethylenediaminetetraacetic acid. To coordinate the ligand, a raw material containing the ligand can be added to the copper source solution. For example, when coordinating chloride ions, examples of the raw material containing the ligand include chloride ion-containing substances such as hydrochloric acid and salts with chloride ions as the anion, such as sodium chloride. The redox potential of the copper source solution can be changed by changing the type and concentration of the ligand.

[0022] In the production method of the present invention, the copper source solution can be prepared by mixing at least the raw materials for the copper particles and the raw materials for the ligand in a solvent to dissolve or molecularly disperse them.

[0023] (Preparation of Reducing Agent and Reducing Agent Solution) Examples of reducing agents used in the production method of the present invention include ascorbic acid salts, ferrous sulfate, sulfite salts, hydroxylamine, formic acid, hydroquinone, reducing sugars, aldehydes, tetrahydroboric acids (sodium borohydride, potassium borohydride, etc.), hydrazine, hydrazine compounds, etc., with ascorbic acid salts, hydrazine, and hydrazine compounds being preferred. These may be used alone or in combination. In the present invention, a reducing agent solution can be prepared by dissolving or molecularly dispersing at least the reducing agent in a solvent. Since the reduction reaction of many reducing agents proceeds well under alkaline conditions, a basic substance can be mixed into the reducing agent solution. Examples of basic substances include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, metal alkoxides, quaternary ammonium salts such as tetramethylammonium hydroxide, ammonia, amines, etc.

[0024] (Solvent) The solvent is not particularly limited as long as it can dissolve or molecularly disperse the copper particle raw material and the reducing agent, etc., and examples thereof include water, organic solvents, and mixtures thereof. Examples of water include tap water, ion-exchanged water, pure water, ultrapure water, RO water, etc. Examples of organic solvents include alcohol solvents such as ethanol, ethylene glycol, and glycerin; ketone solvents such as acetone and 2-butanone; ether solvents such as diethyl ether and tetrahydrofuran; aromatic solvents such as toluene and xylene; amine solvents such as triethylamine and ethylenediamine; amide solvents such as N,N-dimethylformamide; aliphatic hydrocarbon solvents such as hexane and liquid paraffin; nitrile solvents such as acetonitrile; sulfoxide solvents such as dimethyl sulfoxide; halogenated solvents such as dichloromethane; ester solvents such as ethyl acetate and ethylene glycol monoethyl ether acetate; carboxylic acid solvents such as acetic acid and propionic acid; aprotic polar solvents such as carbon disulfide and N-methyl-2-pyrrolidone; ionic liquids; sulfonic acid compounds; and the like. Each solvent may be used alone or in combination. From the viewpoint of the solubility of the copper particle raw material and the reducing agent, it is preferable to prepare the copper raw material solution and the reducing agent solution using an alcohol solvent or a mixed solvent of water and an alcohol solvent.

[0025] Additives such as oxidizing agents or reducing agents for changing the valence of copper ions in the copper source solution, acidic or basic substances or their salts for adjusting the pH or ion concentration, surface protective agents for preventing particle aggregation, surfactants, dispersants, etc., may be added to the solvent as needed. Examples of acidic substances include inorganic acids such as aqua regia, hydrochloric acid, nitric acid, fuming nitric acid, sulfuric acid, and fuming sulfuric acid, and organic acids such as formic acid, acetic acid, chloroacetic acid, dichloroacetic acid, oxalic acid, trifluoroacetic acid, and trichloroacetic acid. Surface protective agents, surfactants, and dispersants include various commonly used commercial products, products, and newly synthesized products. Examples include anionic surfactants, cationic surfactants, nonionic surfactants, and dispersants such as various polymers. These may be used alone or in combination. The surface protective agents, surfactants, and dispersants may be contained in either the copper source solution or the reducing agent solution, or both.

[0026] (Preparation Apparatus) In the production method of the present invention, the apparatus for preparing the copper raw material solution or the reducing agent solution is preferably an apparatus that realizes homogeneous mixing by applying shear force to the fluid, such as an apparatus that rotates stirrers of various shapes such as rod-shaped, plate-shaped, or propeller-shaped in a tank, or an apparatus equipped with a screen that rotates relative to the stirrers. As a preferred example of a rotary disperser, the stirrer disclosed in Japanese Patent No. 5147091 can be applied.

[0027] The rotary disperser may be a batch type or a continuous type. In the case of a continuous type device, the fluid may be continuously supplied to and discharged from a stirring tank, or a continuous mixer may be used without using a stirring tank, and the stirring energy can be appropriately controlled using a known stirrer or stirring means. The stirring energy is described in detail in JP-A-4-114725 filed by the applicant of the present application. The stirring method in the present invention is not particularly limited, and can be carried out using various shear type, friction type, high-pressure jet type, ultrasonic type stirrers, dissolvers, emulsifiers, dispersers, homogenizers, etc. Examples include continuous emulsifiers such as Ultra Turrax (manufactured by IKA), Polytron (manufactured by Kinematica), TK Homomixer (manufactured by Primix), Ebara Milder (manufactured by Ebara Corporation), TK Homomic Lineflow (manufactured by Primix), Colloid Mill (manufactured by Kobelco Pantech), Slasher (manufactured by Nippon Coke Engineering Co., Ltd.), Trigonal Wet Mill (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.), Cavitron (manufactured by Eurotech), and Fine Flow Mill (manufactured by Pacific Machinery Co., Ltd.), as well as batch or continuous dual-use emulsifiers such as Clearmix (manufactured by M Technique), Clearmix Dissolver (manufactured by M Technique), and Filmix (manufactured by Primix). In particular, it is desirable to prepare the copper raw material solution or copper precipitation solution using a stirrer equipped with rotating stirring blades, particularly the Clearmix (manufactured by M Technique) or Clearmix Dissolver (manufactured by M Technique).

[0028] (Production Method: Apparatus) In the production method of the present invention, the copper raw material solution and the reducing agent solution can be mixed by known methods, such as a batch method in a beaker or tank, or a continuous method in which the reaction is carried out in a tubular reactor or a microreactor. Among these, it is preferable to use a fluid treatment device similar to the forced thin film microreactor ULREA manufactured by M Technique Co., Ltd., which is described in JP 2011-189348 A shown in FIGS. 1 and 2 and which is capable of contacting and mixing at least two types of fluids to be treated between at least two treatment surfaces, at least one of which rotates relative to the other. Specifically, it is preferable to use a device similar to the forced thin film microreactor ULREA manufactured by M Technique Co., Ltd. In the example shown in FIG. 1, the number of types of fluids to be treated and the number of flow paths for the fluid treatment device are two, but may be three or more. Furthermore, the shape, size, and number of introduction openings provided in each treatment unit are not particularly limited and can be modified as appropriate. 1, the shape of the opening d20 may be a concentric annular shape surrounding the central opening of the ring-shaped disk processing surface 2, and the annular opening may be continuous or discontinuous. Also, an introduction opening may be provided immediately before or further upstream of the first and second processing surfaces 1 and 2.

[0029] (Average particle size) The average particle size of the copper particles produced by the production method of the present invention can be controlled by setting the oxidation-reduction potential of the copper raw material solution. In addition, the molar concentration ratio of monovalent copper ions to total copper ions in the copper raw material solution ([Cu ＋ ] / ([Cu ＋ ]+[Cu ２＋ The oxidation-reduction potential of the copper raw solution can be changed by changing the ratio of the cations of the copper ions to the total cations of the copper raw solution or by selecting the ligands that coordinate to the copper ions in the copper raw solution. One of the reasons for the change in average particle size is thought to be due to the free energy and reaction rate of each copper ion. The relationship between the potential difference E in the oxidation-reduction potential in the reaction and the difference in the standard free energy of formation ΔG is expressed by the following formula. Here, E is calculated as a value relative to the standard hydrogen electrode. ΔG = -nFE n: number of electrons involved in the reaction F: Faraday constant

[0030] As shown in the above formula, the free energy of each copper ion correlates with the redox potential. However, the free energy in an actual reaction system varies not only with the valence of the ion but also with the ligand, the concentration in the solution, and other coexisting compounds. When a copper source solution and a reducing agent solution are mixed, the greater the potential difference between the redox potential of the copper source solution and the redox potential of the reducing agent solution, the greater the driving force of the reduction reaction, so the reaction rate increases, and many crystal nuclei of copper particles are generated, which reduces the copper source concentration near the crystal nuclei and produces trace amounts of copper particles. Using literature values ​​for the redox potential, in the presence of chloride ions, Cu ２＋ / Cu ＋ The potential difference between Cu and Cu is +0.56 V in terms of the standard hydrogen electrode potential. ＋ The potential difference between Cu and Cu is +0.12 V, and the particle size is smaller when copper particles are prepared from a Cu(II) solution.

[0031] On the other hand, since copper ions in a solution are partially coordinated with solvent molecules due to solvation or the like, it can be difficult to determine all the redox potentials of a prepared copper raw material solution from literature values. If literature data is not available, they can be calculated from the standard free energy of formation of each ion. Following this concept, for example, in the case of a Cu ammine complex coordinated with an ammonia molecule, Cu(NH ３ ) ４ ２＋ ions and Cu(NH ３ ) ２＋ The redox potentials calculated from the standard free energy of formation of each ion are -0.028 V and -0.100 V, respectively. ３ ) ４ ２＋Since the copper ions have a more noble redox potential, it was expected that the copper particles from the Cu(II) ammine complex would be smaller. However, the particle sizes obtained in the examples conducted this time were 185.3 nm and 59.6 nm, respectively, which is contrary to expectations. One reason for this is that the standard free energy of formation values ​​in the literature are values ​​in aqueous solution, and the examples use a mixed solvent of ethylene glycol and water, so the coordination state of the copper ions differs from that in water alone. Accordingly, it is believed that the standard free energy of formation in pure water changes to the standard free energy of formation in ethylene glycol and pure water, which is presumably why the redox potential differs from that in aqueous solution. In the examples, the potential measured by the ORP meter, which reflects the redox potential of the copper source solution, is more noble than that of the Cu(I) ammine complex. Therefore, it is expected that the driving force for the reduction reaction to copper particles would be greater when using a Cu(I) ammine complex than when using a Cu(II) ammine complex, and experimental results actually support this. For these reasons, it is believed that the potential of the ORP meter, which reflects the oxidation-reduction potential of the copper raw material solution, substitutes for the oxidation-reduction potential of the copper raw material solution being used, and therefore, in the present invention as well, copper particle size control can be performed based on the potential of the copper raw material solution measured by the ORP meter.

[0032] The reference electrode of the ORP meter is an Ag / AgCl (KCl saturated) electrode, and the electrode potential is +0.199 V nobler than the standard hydrogen electrode often used in literature, so conversion is necessary when comparing with literature values.

[0033] (pH Adjustment) In the production method of the present invention, the pH during the reaction can be adjusted by controlling the concentrations of the copper particle raw material, basic substance, acidic substance, etc. contained in the copper raw material solution and the reducing agent solution, and the introduction flow rates of the copper raw material solution and the reducing agent solution. Since the reduction reaction of many reducing agents proceeds well under alkaline conditions, the pH during the reaction is preferably 7 to 14, more preferably 8 to 13.

[0034] (Reducing Agent) In order to set the potential difference between the oxidation-reduction potential of the copper raw material solution and the oxidation-reduction potential of the reducing agent solution, the oxidation-reduction potential of the reducing agent solution can be changed by selecting a reducing agent. The molar concentration ratio of the electron donating amount of the reducing agent in the reducing agent solution to the amount of electrons required to reduce copper ions in the copper raw material solution to metallic copper ([e － ] / ([Cu ＋ ]+2×[Cu ２＋ ])) is preferably 1 or more and 100 or less, and more preferably 1.5 or more and 50 or less. If it is 1 or less, oxides will be mixed in, and if it is 100 or more, the amount of raw material used will increase, which is not preferable as it increases the production cost. － ] / ([Cu ＋ ]+2×[Cu ２＋ ]) increases the reaction rate, reduces the particle size, and － ] / ([Cu ＋ ]+2×[Cu ２＋ ]) is lowered, the particle size becomes larger.

[0035] (Anti-oxidation) The presence of oxidized ascorbic acid in the solution obtained after mixing the copper raw material solution and the reducing agent solution can prevent oxidation of the resulting copper particles. Oxidized ascorbic acid is generated by the oxidation of ascorbic acid when copper ions are reduced using ascorbic acids as a reducing agent. In addition, when other reducing agents are used and oxidized ascorbic acid is not generated, oxidized ascorbic acid can be added to the copper raw material solution and / or the reducing agent solution in advance to make it present in the system. FT-IR confirmed that oxidized ascorbic acid such as dehydroascorbic acid was bound to copper on the surface of the particles obtained under the above conditions. Even when stored under atmospheric conditions, oxidation hardly progresses, allowing for stable storage.

[0036] (Washing of Particles) The copper particles produced by the production method of the present invention can be washed as needed. There are no particular limitations on the washing method, and various known methods such as decantation, centrifugation, and filtration can be used. As the washing solvent, any solvent capable of dissolving the inorganic salt by-product can be used, and examples thereof include alcohols such as methanol, pure water, and ion-exchanged water. From the viewpoint of preventing oxidation of the copper particles, alcohols are preferred, and deoxygenated alcohols are more preferred.

[0037] In the production method of the present invention, it is preferable that at least one selected from the group consisting of the temperature of the first fluid, the temperature of the second fluid, and the temperature of the mixed fluid obtained by mixing the first fluid and the second fluid is 100° C. or higher. This at least one temperature is more preferably 110 to 250° C., and even more preferably 120 to 200° C. By setting the temperature to 100° C. or higher, the crystallinity of the copper particles is increased, and the higher the temperature, the faster the reaction rate, so the particle size tends to be smaller.

[0038] The manufacturing method of the present invention makes it possible to manufacture copper particles with a controlled particle size in a simple and stable manner, using a method suitable for mass production.

[0039] 2. Method for Controlling the Average Particle Size of Copper Particles The method for controlling the average particle size of copper particles of the present invention is a method for controlling the average particle size of copper particles within a range of 1 nm to 1000 nm, comprising the step of mixing at least a first fluid and a second fluid to precipitate copper particles, wherein one of the first fluid and the second fluid is a copper raw material solution containing a raw material for the copper particles, and the other of the first fluid and the second fluid is a reducing agent solution containing at least one reducing agent, the copper raw material solution contains at least monovalent copper ions and / or divalent copper ions, and the oxidation-reduction potential of the copper raw material solution is changed. The method for controlling the average particle size of copper particles can be carried out with reference to the description of the method for producing copper particles described above.

[0040] The present invention will be described below using examples, but the present invention is not limited to these examples. In the following examples and comparative examples, liquid A refers to the first treated fluid introduced from the first introduction part d1 of the apparatus shown in Figure 1, and liquid B refers to the second treated fluid introduced from the second introduction part d2 of the apparatus.

[0041] Example 1 A copper raw material solution and a reducing agent solution were prepared using a Clearmix (product name: CLM-0.8S, manufactured by M Technique), a high-speed rotary dispersion and emulsification device. Specifically, argon was flowed into the solvent and bubbling was performed for 1 hour in advance to deoxygenate the solvent. Based on the formulation of the copper raw material solution shown in Example 1 in Table 1, a copper particle raw material, a solvent, and an additive were mixed, and the mixture was homogeneously mixed by stirring for 30 minutes at a rotor speed of 20,000 rpm using a Clearmix under an argon atmosphere at a preparation temperature of 50°C, thereby dissolving the copper particle raw material and additive in the solvent, thereby preparing a copper raw material solution. Furthermore, based on the formulation of the reducing agent solution shown in Example 1 in Table 1, a reducing agent, a basic substance, and a solvent were mixed, and the mixture was homogeneously mixed by stirring for 30 minutes at a rotor speed of 15,000 rpm using a Clearmix under an argon atmosphere at a preparation temperature of 45°C, thereby preparing a reducing agent solution.

[0042] Next, the prepared copper raw material solution and reducing agent solution were mixed in the fluid treatment device shown in Figure 1 under the treatment conditions shown in Table 1. Specifically, the copper raw material solution was introduced as the first fluid to be treated (liquid A) between the treatment surfaces from the first inlet d1 of the fluid treatment device shown in Figure 1, and while the processing unit 10 was operating at a rotation speed of 2000 rpm, the reducing agent solution was introduced as the second fluid to be treated (liquid B) between the treatment surfaces 1 and 2 from the second inlet d2 of the fluid treatment device shown in Figure 1, and mixed in the thin film fluid. Copper particles were precipitated between the treatment surfaces 1 and 2, and a discharge liquid containing the copper particles was discharged from between the treatment surfaces 1 and 2 of the fluid treatment device. The discharge liquid containing the copper particles was recovered in a beaker b via a vessel v.

[0043] The introduction temperatures (liquid delivery temperatures) of liquid A and liquid B were measured using a thermometer installed in the sealed introduction path (first introduction part d1 and second introduction part d2) connecting between the processing surfaces 1 and 2. The introduction temperature of liquid A shown in Table 1 is the actual temperature of liquid A in the first introduction part d1, and the introduction temperature of liquid B is the actual temperature of liquid B in the second introduction part d2.

[0044] A pH meter, model D-51, manufactured by HORIBA was used for pH measurement. An ORP meter, model RM-30P, manufactured by DKK-TOA was used for ORP measurement. Before introducing the first and second treated fluids into the fluid treatment device, the pH of the treated fluids and the temperature at the time of pH measurement were measured. In addition, since it is difficult to measure the pH and ORP of the mixed fluid immediately after mixing the copper raw material solution and the reducing agent solution, the copper particle dispersion discharged from the device and recovered in beaker b was measured at room temperature.

[0045] A dry powder and a wet cake sample were prepared from the discharged liquid containing copper particles collected in beaker b. The preparation method was performed according to a known method. Specifically, the discharged liquid containing copper particles was collected by centrifugation, the copper particles were allowed to settle, and the supernatant was removed. The copper particles were then washed by repeating washing and settling twice with methanol deoxygenated by argon flow. A portion of the finally obtained copper particle wet cake was dried to prepare a dry powder. The other was used as the wet cake sample.

[0046] (Preparation of Sample for TEM Observation) A portion of the wet cake sample of copper particles after the washing treatment obtained in Example 1 was dispersed in methanol. The obtained dispersion was dropped onto a grid with a support film and dried to prepare a sample for TEM observation.

[0047] (Transmission Electron Microscope) A transmission electron microscope, JEM-2100 (manufactured by JEOL) was used for the transmission electron microscope (TEM) observation. The observation conditions were an acceleration voltage of 200 kV and an observation magnification of 10,000 to 500,000 times. The average particle diameter (D) is the average value of the primary particle diameters, and is the average value of the results of measuring the particle diameters of 100 particles by TEM observation. In addition, the thickness of the oxide layer on the particle surface was measured under the condition of an observation magnification of 500,000 times.

[0048] (X-ray Diffraction Measurement) X-ray diffraction (XRD) measurement was performed using an EMPYREAN powder X-ray diffractometer (manufactured by Malvern Panalytical). The measurement conditions were: measurement range: 10 to 100 [°2 Theta], Cu anticathode, tube voltage: 45 kV, tube current: 40 mA, and scan rate: 0.3° / min.

[0049] In Examples 2 to 13, similarly to Example 1, a copper source solution and a reducing agent solution were mixed according to the formulations and treatment conditions shown in Table 1, and particles were precipitated between the treatment surfaces 1 and 2. A discharged liquid containing copper particles was discharged from the fluid treatment device and recovered in a beaker b via a vessel v. A dry powder and a wet cake sample were prepared from the discharged liquid, and TEM observation and XRD measurement were performed in the same manner as in Example 1.

[0050] The measurement results of Examples 1 to 13 are shown in Tables 1 and 2. TEM photographs of the copper particles obtained in Examples 1 and 9 are shown in Figs.

[0051] As shown in Tables 1 and 2 and FIGS. 3 and 4 , by changing the molar ratio of monovalent copper ions to all copper ions in the raw material in the copper raw material solution and the ligand, the oxidation-reduction potential of the copper raw material solution could be changed, and the average particle size could be controlled.

[0052] Comparative Example 1 In Comparative Example 1, except that sodium ascorbate was omitted from the reducing agent solution, a copper source solution and a reducing agent solution were mixed using the formulations and treatment conditions shown in Table 6 in the same manner as in Example 1, and particles were precipitated between the treatment surfaces 1 and 2. A discharged liquid containing copper particles was discharged from the fluid treatment device and recovered in a beaker b via a vessel v. A dry powder and a wet cake sample were prepared from the discharged liquid, and TEM observation and XRD measurement were performed in the same manner as in Example 1.

[0053] The measurement results for Comparative Example 1 are shown in Table 2. In the comparative example, the thickness of the oxide layer on the particle surface was 5.6 nm. Furthermore, XRD measurement confirmed the copper diffraction pattern and the cuprous oxide diffraction pattern, confirming that the particles were partially oxidized.

[0054]

[0055]

[0056] As can be seen from the Examples and Comparative Examples, copper particles with a controlled average particle size could be easily produced by the production method of the present invention.

[0057] The manufacturing method of the present invention makes it possible to easily and stably produce copper particles with a controlled average particle size in a manner suitable for mass production without requiring complex chemical reactions or heat treatments.

[0058] 1 First processing surface 2 Second processing surface 10 First processing member 11 First holder 20 Second processing member 21 Second holder d1 First introduction part d2 Second introduction part d20 Opening

Claims

1. A method for producing copper particles having an average particle size in the range of 1 nm to 1000 nm, The method includes a step of mixing at least a first fluid and a second fluid to precipitate copper particles, one of the first fluid and the second fluid is a copper source solution containing a source of copper particles; the other of the first fluid and the second fluid is a reducing agent solution containing at least one reducing agent; the copper source solution contains at least monovalent copper ions and / or divalent copper ions, a potential difference between the oxidation-reduction potential of the copper raw material solution and the oxidation-reduction potential of the reducing agent solution is set so as to achieve the average particle diameter.

2. The molar concentration ratio of monovalent copper ions to the total copper ions in the copper raw material solution ([Cu + ] / ([Cu + ]+[Cu 2+ 2. The method according to claim 1, wherein the oxidation-reduction potential of the copper raw material solution is set by adjusting the amount of the copper raw material solution.

3. a ligand coordinated to copper ions in the copper source solution is at least one selected from water, hydroxide ions, ammonia, halide ions, amino acids, phosphines, carboxylic acids, thiols, cyanide ions, thiocyanide ions, nitriles, amines, and ethylenediaminetetraacetic acid; The method according to claim 1 , wherein the oxidation-reduction potential of the copper source solution is set by selecting the ligand.

4. the reducing agent is at least one selected from ascorbic acid salts, ferrous sulfate, sulfites, hydroxylamine, formic acid, hydroquinone, reducing sugars, aldehydes, tetrahydroboric acids, hydrazine, and hydrazine compounds; The method of claim 1 , wherein the oxidation-reduction potential of the reducing agent solution is set by selecting the reducing agent.

5. The method according to claim 1 , wherein the mixed solution obtained by mixing the first fluid and the second fluid contains oxidized ascorbic acid.

6. The method according to claim 1, wherein the oxide layer on the surface of the copper particles has a thickness of 4 nm or less.

7. continuously introducing at least two fluids to be treated, including the copper source solution and the reducing agent solution, between processing surfaces disposed opposite to each other and rotating relatively so as to be approachable and separable from each other; mixing the at least two fluids to be treated between processing surfaces that are disposed opposite to each other and rotate relatively toward and away from each other, thereby precipitating copper particles; The method according to any one of claims 1 to 6, wherein the mixed fluid containing the precipitated copper particles is discharged from between the processing surfaces to continuously produce copper particles.

8. one of the copper source solution and the reducing agent solution passes between the processing surfaces while forming a thin film fluid; the other of the copper raw material solution and the reducing agent solution is introduced into the space between the processing surfaces through another introduction path independent of the flow path introduced into the space between the processing surfaces, and from an opening formed in at least one of the processing surfaces; The manufacturing method according to claim 7 , wherein the copper source solution and the reducing agent solution are mixed between the processing surfaces.

9. A method for controlling the average particle size of copper particles within a range of 1 nm to 1000 nm, comprising: The method includes a step of mixing at least a first fluid and a second fluid to precipitate copper particles, one of the first fluid and the second fluid is a copper source solution containing a source of copper particles; the other of the first fluid and the second fluid is a reducing agent solution containing at least one reducing agent; the copper source solution contains at least monovalent copper ions and / or divalent copper ions, A control method comprising changing a potential difference between an oxidation-reduction potential of the copper raw material solution and an oxidation-reduction potential of the reducing agent solution.

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