TWI803486B - Copper particle and its manufacturing method - Google Patents

Abstract

The copper particle of this invention has the core part containing copper, and the copper oxide layer formed in the surface of this core part and containing CuO and _Cu2O . When X is the content ratio (mass %) of oxygen contained in the copper particles and Y is the crystallite size (nm) of Cu ₂ O contained in the copper oxide layer, Y≧36X-18 is satisfied. condition. It is also suitable that the crystallite size D _C (μm) of the metallic copper contained in the core part is relative to the cumulative volume particle diameter D 50 at ₅₀ volume % of the cumulative volume measured by the laser diffraction scattering particle size distribution measurement method The ratio of (μm), that is, the value of D _C /D ₅₀ is not less than 0.10 and not more than 0.40. Moreover, it is also preferable that the content ratio of oxygen is 0.80 mass % or more and 1.80 mass % or less.

Description

Copper particle and its manufacturing method

The present invention relates to a copper particle and its manufacturing method.

Copper has the same specific resistance value as silver, and is also cheaper in material cost than silver, so it can be suitably used as a raw material for printed circuit boards, conductive pastes used for forming circuits, and electrodes. In recent years, in the field of circuits and the like, with the continuous development of fine pitch and thinner electrodes, the industry requires both finer copper particles for conductive paste and good sinterability. On the other hand, micronized copper has a very large surface area, so when producing conductive paste, the surface oxidation of the particles becomes remarkable, and the conductivity may be poor. Patent Document 1 proposes a method for producing copper powder using a physical vapor deposition method (PVD method) using DC thermal plasma in order to ensure micronization and electrical conductivity of copper powder. [Prior Art Document] [Patent Document] Patent Document 1: Specification of International Publication No. 2015/122251

Copper particles of fine particles produced by the PVD method etc. have a very large surface area, and the particles tend to aggregate with each other. Therefore, in the wet dispersion process etc. which are a manufacturing process after copper particle manufacture, the surface treatment which mixes copper particle and a surface treatment agent, such as a fatty acid, so that aggregation of particle|grains is hard to generate|occur|produces normally is performed. However, such copper particles may re-aggregate (hereinafter also referred to as re-aggregation) even if surface treatment is performed. Furthermore, the copper particle manufactured by PVD method etc. is not only easy to agglomerate particle|grains, but also has many coarse grains. Therefore, when such copper particles are used to prepare a conductive paste, and the paste is applied to a base material and fired, it is difficult to obtain good surface smoothness of the conductive film obtained by firing. Therefore, when using copper particles produced by the PVD method as a raw material to produce conductive paste, it is necessary to use a filter to remove aggregated particles or coarse particles in advance, but the conventional copper particles have many aggregated particles and coarse particles. There are cases where the number of particles removed by the filter increases, resulting in a decrease in yield. Therefore, the present invention is an improvement of copper particles and a method for producing the same. Specifically, the present invention relates to a wet dispersion step as a productization step after producing copper particles. Copper particles not easily re-agglomerated and method for producing the same. The inventors of the present invention conducted diligent research to solve the above-mentioned problems, and as a result, found that the degree of re-agglomeration of the particles is reduced after surface treatment of copper particles having a specific relationship between the oxygen content ratio and the crystallite size of Cu ₂ O. This invention was completed based on this knowledge. That is, this invention provides the copper particle which has the core part which consists of copper, and the copper oxide layer which consists of CuO and _Cu2O formed in the surface of this core part, and satisfies the relationship of following formula (1). Y≧36X－18 (1) In the formula, X is the content ratio (mass %) of oxygen contained in the copper particles, and Y is the crystallite size (nm) of Cu ₂ O contained in the copper oxide layer. In addition, the present invention provides a method for producing copper particles as a suitable method for producing the above-mentioned copper particles, which has the following steps: introducing raw material powder containing copper element into a plasma flame to form copper in a gas phase state, Copper particles are generated by cooling the above-mentioned copper in the gas phase state, and the generated copper particles are exposed to an oxygen-containing atmosphere, and the surface of the above-mentioned copper particles after being exposed to an oxygen-containing atmosphere is oxidized to generate a copper particle containing CuO and Copper oxide layer of Cu ₂ O.

根據表1所示之結果明確可知，各實施例之銅粒子之過濾器回收率增高，相對於此，比較例之銅粒子之過濾器回收率變低。其原因在於，實施例之銅粒子之粒子彼此之再凝聚被抑制。 又，可知，關於由回收率較高之各實施例之銅粒子獲得之塗膜之表面粗糙度，過濾器回收率雖然增大，但成為與由比較例之銅粒子獲得之塗膜之表面粗糙度同等。其原因亦在於，實施例之銅粒子之粒子彼此之凝聚被抑制。 [產業上之可利用性] 根據本發明，提供一種於製造銅粒子後之作為製品化步驟之濕式分散步驟中，於使用表面處理劑之情形時，粒子彼此不易再凝聚之銅粒子。Hereinafter, the present invention will be described based on its preferred embodiments. The copper particle of this invention has the core part containing copper, and the copper oxide layer formed in the surface of the core part and containing CuO and _Cu2O . The core part is located in the central region of the copper particle of the present invention, and is a part that accounts for most of the mass of the copper particle of the present invention. On the other hand, the copper oxide layer is located in the surface region of the copper particle of the present invention, and constitutes the outermost surface of the copper particle of the present invention. The copper oxide layer preferably covers the entire surface of the core, but as long as the effect of the present invention is not impaired, the copper oxide layer can cover the surface of the core with a part of the surface of the core exposed to the outside. In the copper particles of the present invention, a layer containing a metal element does not exist on the outside of the copper oxide layer. However, it is allowed to exist a layer containing an organic compound on the outer side than the copper oxide layer. The shape of the copper particles of the present invention is not particularly limited, and various shapes can be adopted according to specific uses. For example, copper particles having various shapes such as spherical shape, flake shape, plate shape, and dendritic shape can be used. Regarding the copper particle of the present invention, when its shape is any of the above-mentioned situations, the volume cumulative particle diameter _D50 measured under the cumulative volume of 50% by volume as measured by the laser diffraction scattering particle size distribution measurement method is preferably 0.2 μm or more and 0.6 μm or less, more preferably 0.2 μm or more and 0.5 μm or less. When the particle size of the copper particles is within this range, when using the copper particles to prepare a conductive composition such as a conductive paste, and using the conductive composition to form a conductive film, the conductive film becomes dense and more conductive. taller. In order to obtain the copper particle of the particle diameter of this range, what is necessary is just to manufacture copper particle by the wet reduction method, PVD method, etc., for example. Moreover, the measurement of the volume cumulative particle diameter _D50 can be performed by the method described in the following Example. The core part in the copper particle of this invention is comprised containing copper. Containing copper in the core part includes (A) the case where the core part is substantially composed of copper, and (B) the case where the core part contains copper and other elements. In the case of (A), the ratio of copper in the core portion is preferably at least 99% by mass, more preferably at least 99.5% by mass, and even more preferably the core portion contains only copper and unavoidable impurities. In any one of the situations of said (A) and (B), as mentioned above, a core part is a site which accounts for most of the mass of the copper particle of this invention. The thickness of the copper oxide layer is preferably not less than 1 nm and not more than 100 nm, more preferably not less than 1 nm and not more than 55 nm. When the copper oxide layer exists in this thickness range, the electroconductivity of the copper particle of this invention can fully be improved. The ratio of the core portion in the copper particles of the present invention can be determined by STEM-EDS (Scanning Transmission Electron Microscope-Energy-Dispersive X-ray Spectroscopy, Scanning Transmission Electron Microscope-Energy Dispersive X-ray Analyzer) for example. Line analysis of the particle surface, and measure the thickness of the copper oxide layer according to the line profile of oxygen (OK ray). The copper oxide layer located on the surface of the core part contains CuO and _Cu2O as mentioned above. The copper oxide layer system (C) contains only the oxide of copper containing CuO and _Cu2O , or (D) contains the oxide of copper containing CuO and _Cu2O , and contains other substances in addition to these. In the case of (C), it is preferable that the copper oxide layer contains only copper oxide including CuO and Cu ₂ O and unavoidable impurities. In either case of the above (C) and (D), the existence state of CuO and Cu ₂ O in the copper oxide layer is not particularly limited. For example, CuO and Cu ₂ O may be present in a mixed state arbitrarily, or a site containing CuO and a site containing Cu ₂ O may exist independently. When a site containing CuO and a site containing Cu2O exist independently, for example, a form in which a site containing _Cu2O exists on the surface of the core part and a site containing CuO exists on the surface of _the site . As a particularly preferable embodiment of the copper particles of the present invention, for example, the following embodiment can be cited: the core part contains only copper and unavoidable impurities, and the copper oxide layer contains only copper oxide containing CuO and _Cu2O and impermeable impurities. Avoid impurities. The inventors of the present invention conducted research and found out that if the content ratio of oxygen in the copper particles of the present invention and the crystallite size of Cu ₂ O in the copper oxide layer of the copper particles are in a specific relationship, the surface in the manufacturing process will be The dispersibility of the treated copper particles is improved. Specifically, it was found that when the oxygen content ratio (unit: mass %) in the copper particles is X and the crystallite size (unit: nm) of Cu ₂ O in the copper oxide layer is Y, if According to the relationship of the following formula (1), the surface-treated copper particles in the productization step are less likely to re-agglomerate, and the dispersibility is particularly improved. Y≧36X-18 (1) If the relationship of the formula (1) is satisfied, the reason why the dispersibility of the surface-treated copper particles in the manufacturing step is particularly improved is not clear, but the inventors of the present invention presume as follows. The degree of exposure of Cu ₂ O on the surface of the copper particles produced by the wet reduction method or PVD method increases. If a surface treatment agent such as fatty acid is mixed with such copper particles in a wet dispersion process, etc., the Cu ₂ O is dissolved due to the reaction between the fatty acid and Cu ₂ O, and the metallic copper contained in the core of the copper particles will be exposed. to the outside world. Copper particles in a state in which metallic copper is exposed to the outside easily bond to copper particles in the same state, and re-agglomeration of the particles tends to occur. On the other hand, in the copper particle satisfy|filling Formula (1), since the crystallinity of _Cu2O contained in a copper oxide layer is high, it thinks that CuO is uniformly produced in the outermost surface of a copper particle. Since CuO is more stable than Cu ₂ O, it is less likely to react with surface treatment agents such as fatty acids, and it is more difficult to dissolve than Cu ₂ O. Therefore, metallic copper contained in the core part is less likely to be exposed to the outside of the copper particles. As a result, copper particles are less likely to re-agglomerate. On the condition that the relationship of the above formula (1) is satisfied, the content ratio of oxygen in the copper particles of the present invention is preferably from 0.8 mass % to 1.80 mass %, more preferably from 0.8 mass % to 1.6 mass %, Furthermore, it is more preferable that it is 0.8 mass % or more and 1.5 mass % or less. When the content ratio of oxygen exists in this range, copper particles are less likely to re-agglomerate after the surface treatment in the manufacturing process. The content rate of the oxygen in the copper particle of this invention can be measured by the method described in the following Example, for example. Similarly, on the condition that the relationship of the above formula (1) is satisfied, in the copper particles of the present invention, the crystallite size of Cu ₂ O contained in the copper oxide layer is preferably 15 nm or more and 60 nm or less, and more preferably 20 nm or more. nm or more and 60 nm or less, more preferably 20 nm or more and 55 nm or less. When the crystallite size of Cu ₂ O is within this range, the copper particles are less likely to re-agglomerate after the surface treatment in the manufacturing step. The crystallite size of Cu ₂ O was calculated by the Scherrer formula from the diffraction peak obtained by powder X-ray diffraction. The measurement by powder X-ray diffraction can be performed by the method described in the following Examples. In order to make the copper particle of this invention satisfy the condition of formula (1), what is necessary is just to manufacture copper particle by the following method, for example. In the above description, the crystallite size of _Cu2O in the copper particle of the present invention has been described. In addition to the crystallite size, in the copper particle of the present invention, the crystallite of metallic copper contained in the core portion The dimension D _C is preferably from 0.060 μm to 0.090 μm, more preferably from 0.065 μm to 0.085 μm, still more preferably from 0.070 μm to 0.085 μm. When the crystallite size D _C of metallic copper is in this range, the crystallite size of Cu ₂ O can also be increased, and CuO can be uniformly formed on the outermost surface of the copper oxide layer. The crystallite size of metallic copper was calculated by Scherrer's formula from the diffraction peak obtained by powder X-ray diffraction. The measurement by powder X-ray diffraction can be performed by the method described in the following Examples. From the viewpoint of more effectively preventing the re-agglomeration of copper particles, regarding the copper particles of the present invention, the crystallite size D _C (μm) of metallic copper in the core part is compared with that measured by laser diffraction scattering particle size distribution. The ratio of the volume cumulative particle diameter D ₅₀ (μm) at 50 volume % of the cumulative volume measured by the method, that is, the value of D _C /D ₅₀ is preferably 0.10 or more and 0.40 or less, more preferably 0.10 or more and 0.30 or less, and further More preferably, it is 0.20 or more and 0.30 or less. In order to make the value of _DC /D ₅₀ satisfy this range, it is only necessary to manufacture copper particles by the following method, for example. As mentioned above, the copper particle of this invention contains metal copper which is zero-valent copper, _Cu2O which is monovalent copper, and CuO which is divalent copper. The abundance ratios of these three on the surface of copper particles can be measured using X-ray photoelectron spectroscopy (XPS). According to the XPS measurement, the X-ray photoelectron spectroscopy of various elements can be obtained, and the element composition can be quantitatively analyzed from the surface of the copper particle to a depth of about ten nm. In the X-ray photoelectron spectroscopy spectrum obtained by measuring the surface state of the copper particles of the present invention by XPS, the peak area P2 of Cu(II) as divalent copper is relative to the peak area of Cu(I) as monovalent copper The value of P2/(P1+P0), which is the ratio of the peak area P0 of P1 and Cu(0) which is zero-valent copper, is preferably from 0.30 to 2.50, more preferably from 0.40 to 2.50. When the copper particles of the present invention satisfy this ratio range, the total amount of Cu(0) and Cu(I) and the amount of Cu(II) present on the surface of the copper particles can be appropriately set so as to suppress re-aggregation of the copper particles. Measurement using XPS can be performed by the method described in the following Examples. Hereinafter, the suitable manufacturing method of the copper particle of this invention is demonstrated. <Procedure 1. Synthesis of copper particles> As a conventionally known method for producing copper particles, generally, a wet reduction method, an atomization method, and a physical vapor deposition method (PVD method) etc. are mentioned. Among these production methods, in order to easily satisfy the above-mentioned ranges such as the content ratio of oxygen in copper particles, the crystallite size of Cu ₂ O and metallic copper, and the D ₅₀ of copper particles, it is preferable to produce copper by PVD method. particle. Therefore, the manufacturing method of the copper particle using the PVD method is demonstrated below. FIG. 1 shows a thermal plasma generator 1 that can be suitably used for producing copper particles by the PVD method. The thermoplasma generating device 1 includes a raw material powder supply device 2, a raw material powder supply pipeline 3, a plasma flame generating part 4, a plasma gas supply device 5, a chamber 6, a recovery tank 7, an oxygen supply device 8, and a pressure regulating device 9 and exhaust device 10 to form. Raw material powder containing copper element (hereinafter also simply referred to as raw material powder) is introduced into the plasma flame generating unit 4 from the raw material powder supply device 2 through the raw material powder supply line 3 . In the plasma flame generating unit 4 , a plasma flame is generated by supplying plasma gas from the plasma gas supply device 5 . The raw material powder introduced into the plasma flame is released into the chamber 6 present at the end portion side of the plasma flame after being evaporated and vaporized into copper in a gaseous state. The copper in the gas phase cools as it moves away from the plasma flame, and produces copper particles through nucleation and grain growth. The resulting copper particles are exposed to the atmosphere inside the chamber 6 . The copper particles exposed to the atmosphere in the chamber 6 adhere to the wall inside the chamber 6 or accumulate in the recovery tank 7 . The inside of the chamber 6 is controlled by means of a pressure regulator 9 and an exhaust device 10 to maintain a negative pressure relative to the raw material powder supply line 3, so that the plasma flame can be stably generated and the raw material powder can be introduced into the The structure in the plasma flame generating part 4. The details of the atmosphere in the chamber 6 will be described below. The particle diameter of the raw material powder used for manufacture of the copper particle of this invention is not specifically limited. From the viewpoint of supply efficiency to the thermal plasma generator, the cumulative volume particle diameter D ₅₀ of the raw material powder is preferably not less than 3 μm and not more than 30 μm. Also, the particle shape of the raw material powder is not particularly limited, and various shapes such as spherical shape, flake shape, plate shape, and dendritic shape can be used. The oxidation state of the copper element in the raw material powder is not particularly limited, for example, metal copper powder, copper oxide powder (such as CuO or Cu ₂ O) or a mixture thereof can be used. The production method of the raw material powder is also not particularly limited. In this production method, from the viewpoint of stably producing copper particles having a large crystallite size of metallic copper, the supply amount of the raw material powder is preferably 0.1 g/min or more and 100 g/min or less. The plasma gas for generating the plasma flame is preferably a mixed gas of argon and nitrogen. By using this mixed gas, greater energy can be imparted to the raw material powder, and therefore, copper particles having suitable particle diameters and crystallite sizes (Cu ₂ O and metallic copper) can be obtained for exhibiting the effect of the present invention. In particular, from the viewpoint of obtaining spherical or substantially spherical copper particles, it is preferable to use a mixed gas of argon and nitrogen as the plasma gas, and to use a method in which the plasma flame becomes thicker and longer in a laminar flow state. be adjusted. The so-called "approximately spherical shape" refers to a shape that can be recognized as a ball although it is not a perfect spherical shape. Whether the plasma flame is in a laminar flow state can be judged according to the ratio of the length of the plasma flame to the width of the plasma flame when viewed from the side where the width of the plasma flame is the thickest. When the ratio of the length of the plasma flame to the width of the plasma flame is 3 or more, it can be judged as a laminar flow state, and when the ratio of the length of the plasma flame to the width of the plasma flame is less than 3 , can be judged as a turbulent state. From the viewpoint of stably maintaining the laminar flow state of the plasma flame, the gas flow rate of the plasma gas is preferably 1 L/min or more and 35 L/min at room temperature, more preferably 5 L/min or more and Below 30 L/min. By adopting the gas flow rate in this range, the generated particles are brought into contact with the oxygen-containing atmosphere in the chamber 6 described below while maintaining an appropriate temperature. As a result, a target copper oxide layer containing CuO and Cu ₂ O can be smoothly formed on the surface of the core portion. The plasma output of the thermal plasma generator is preferably not less than 2 kW and not more than 50 kW, more preferably not less than 5 kW and not more than 35 kW. From the same point of view, the flow rate (L/min) ratio of argon and nitrogen in the plasma gas is preferably argon: nitrogen = 99:1 to 10:90 at room temperature, and more preferably 95: 5～70:30. In this manufacturing method, the atmosphere in the chamber 6 is preferably an oxygen-containing atmosphere. The reason is that by being exposed to an oxygen-containing atmosphere during the process of cooling the copper in the gaseous state to form copper particles, the content ratio of oxygen in the copper particles can be kept within the above-mentioned range, and the oxygen content on the surface of the core part A copper oxide layer containing Cu ₂ O with higher crystallinity is formed. At this time, the copper oxide layer containing _Cu2O with high crystallinity can be easily formed by setting the core part which was formed at an appropriate temperature. The setting of the temperature can be controlled by, for example, adjusting the gas flow rate of the plasma gas as described above, or adjusting the oxygen flow rate supplied into the chamber 6 (which will be described later). As the oxygen-containing atmosphere, oxygen itself, a mixed gas of oxygen and other gases, or the like can be used. In the case of using a mixed gas, various inert gases such as argon or nitrogen can be used as other gases. Furthermore, in the embodiment shown in FIG. 1 , the oxygen supply device 8 is connected to the side of the chamber to supply oxygen into the chamber, but as long as the connection position of the oxygen supply device is such that oxygen can be stably supplied to the chamber 6 The location is not particularly limited. From the viewpoint of stably exposing the copper particles generated from copper in the gaseous state to an oxygen-containing atmosphere, the flow rate of oxygen supplied to the chamber 6 is preferably not less than 0.002 L/min and not more than 0.75 L/min, and more preferably Preferably, it is not less than 0.004 L/min and not more than 0.70 L/min. Also, from the viewpoint of forming a copper oxide layer containing highly crystalline Cu ₂ O, the oxygen concentration in the chamber is preferably 100 ppm or more and 2000 ppm or less, more preferably 200 ppm or more and 1000 ppm or less. <Step 2. Oxidation Treatment> It is preferable that the copper particles generated in the above <Step 1> are further subjected to oxidation treatment. By performing this step, Cu ₂ O on the surface of unreacted copper particles in <Step 1> can be slowly oxidized to CuO, and a copper oxide layer containing Cu ₂ O and CuO can be formed thicker and without gaps on the entire surface , and after surface treatment, copper particles that are less likely to re-agglomerate can be obtained. Oxidation in this step is carried out as follows. Stop the supply of raw material powder and the generation of plasma flame, and return the inside of the chamber 6 to normal pressure, store the copper particles generated in the above <step 1> in the recovery tank 7 and recover them, and place the copper particles in the Under the air atmosphere, Cu ₂ O on the surface of the copper particles was oxidized to CuO to form a copper oxide layer. If the copper particles are placed in the atmosphere for this step, the copper oxide layer can be formed without a rapid oxidation reaction of the copper particles. However, from the viewpoint of industrial productivity, it is preferable to crush the agglomerated particles using a screen or the like for the produced copper particles, and to leave them under the air atmosphere. From the viewpoint of the uniformity of oxidation treatment of copper particles, in this step, it is preferable to place the copper in an atmosphere with a relative humidity of 30% to 60% and a temperature of 15°C to 30°C. particle. By carrying out the oxidation reaction under this condition, the Cu ₂ O in the copper oxide layer can be slowly oxidized to CuO by using the moisture contained in the atmosphere, and a stable copper oxide layer can be formed on the surface. Also, the processing time of this step is from the viewpoint of preventing a rapid oxidation reaction at the time of recovery of copper particles, the condition of the air atmosphere being within the above range, preferably 5 minutes or more and 60 minutes or less, more preferably 5 minutes or more and 30 minutes or less. The copper particle of this invention can be manufactured smoothly by the above manufacturing method. In order to maintain the oxidized state of the surface of the copper particles, the copper particles obtained in the above manner are preferably sealed in a container of non-moisture-permeable material, and stored at a temperature below room temperature (25° C.). In addition, the copper particles of the present invention produced by the above-mentioned production method are less likely to be regenerated when a surface treatment agent is used in the wet dispersion step as a commercialization step after the production of the copper particles, compared with the conventional copper particles. aggregator. Also, by using the copper particles of the present invention, conductive compositions such as conductive paste can be produced without impairing sinterability at low temperatures. [Examples] Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited to this embodiment. Unless otherwise specified, "%" means "mass %". EXAMPLE 1 Under the following manufacturing conditions, said <step 1> and <step 2> were performed, and copper particle was manufactured. <Step 1> Introduce the copper particles (particle size D ₅₀ : 12 μm, particle shape: spherical) produced by the atomization method as the raw material powder into the thermoelectric device shown in Fig. 1 at a supply rate of 5 g/min In the plasma flame of the plasma generating device, the copper in the gas phase state is produced. As the conditions for plasma flame generation, a mixed gas of argon and nitrogen is used as the plasma gas, the flow rate of the plasma gas is set to 19.0 L/min, and the flow rate of the argon and nitrogen in the plasma gas (L/min ) ratio is set to 82:18, and the plasma output is set to 19 kW. Copper particles in the gaseous state are generated in the chamber by cooling, and the copper particles are exposed to an oxygen-containing atmosphere to form copper particles with a core portion and a copper oxide layer. The flow rate of oxygen-nitrogen mixed gas (containing 5% oxygen by volume) into the chamber was set at 0.20 L/min (the oxygen flow rate was 0.01 L/min), and the oxygen concentration in the chamber was set at 440 ppm. Thereafter, the generation of the plasma flame was stopped under the condition that there were copper particles in the chamber, and nitrogen gas was supplied to the chamber at a flow rate of 30 L/min to become a negative pressure (-0.05 MPa), and the negative pressure lasted for 15 minutes. Return to normal pressure. <Step 2> After carrying out <Step 1>, recover copper particles. While crushing the copper particles with a sieve in an atmosphere with a relative humidity of 50% and a temperature of 25°C, a copper oxide layer was formed on the surface of the copper particles. The time for standing in the air atmosphere was set at 30 minutes. After adding 2-propanol so that the obtained copper particle might become 30 mass %, 5 mass % of lauric acid was added as a dispersing agent to copper particle, and the slurry was prepared. The slurry was crushed using a Nanomizer mark II (wet crushing device, Yoshida Machinery Industrial Co., Ltd. product name: NM2-2000AR) (crushing conditions: 50 MPa, 5 strokes). After filtering the crushed slurry with a filter with a mesh size of 1 μm (trade name: SBP010 manufactured by ROKI TECHNO Co., LTD.), the supernatant of the filtrate was removed, and dried at 40° C. using a vacuum dryer (manufactured by ADVANTEC). Dry the remaining solids. Then, it sieved by the sieve of 150 micrometers of openings in nitrogen atmosphere, and obtained copper particle. [Example 2] In Example 1, the flow rate of the oxygen-nitrogen mixed gas in the chamber is set to 0.29 L/min (the oxygen flow rate is 0.0145 L/min), and the oxygen concentration in the chamber is set to 640 ppm , except that, the operation similar to Example 1 was performed, and the copper particle was manufactured. [Example 3] In Example 1, the oxygen-nitrogen mixed gas flow into the chamber is set to 0.11 L/min (the oxygen flow rate is 0.0055 L/min), and the oxygen concentration in the chamber is set to 240 ppm, Except for that, the same operation as in Example 1 was performed to manufacture copper particles. [Example 4] In Example 1, the flow rate of the oxygen-nitrogen mixed gas in the chamber is set to 0.34 L/min (the oxygen flow rate is 0.017 L/min), and the oxygen concentration in the chamber is set to 750 ppm , except that, the operation similar to Example 1 was performed, and the copper particle was manufactured. [Example 5] In Example 1, the flow rate of the oxygen-nitrogen mixed gas in the chamber is set to 0.09 L/min (the oxygen flow rate is 0.0045 L/min), and the oxygen concentration in the chamber is set to 200 ppm , except that, the operation similar to Example 1 was performed, and the copper particle was manufactured. [Example 6] In Example 1, the flow rate of the oxygen-nitrogen mixed gas in the chamber is set to 0.39 L/min (the oxygen flow rate is 0.0195 L/min), and the oxygen concentration in the chamber is set to 850 ppm , except that, the operation similar to Example 1 was performed, and the copper particle was manufactured. [Example 7] In Example 1, the flow rate of the oxygen-nitrogen mixed gas in the chamber is set to 0.33 L/min (the oxygen flow rate is 0.0165 L/min), and the oxygen concentration in the chamber is set to 730 ppm , except that, the operation similar to Example 1 was performed, and the copper particle was manufactured. [Example 8] In Example 1, the flow rate of the oxygen-nitrogen mixed gas in the chamber is set to 0.18 L/min (the oxygen flow rate is 0.009 L/min), and the oxygen concentration in the chamber is set to 400 ppm , except that, the operation similar to Example 1 was performed, and the copper particle was manufactured. [Example 9] In Example 1, the flow rate of the oxygen-nitrogen mixed gas in the chamber is set to 0.26 L/min (the oxygen flow rate is 0.013 L/min), and the oxygen concentration in the chamber is set to 570 ppm , except that, the operation similar to Example 1 was performed, and the copper particle was manufactured. [Example 10] In Example 1, the flow rate of the oxygen-nitrogen mixed gas in the chamber is set to 0.24 L/min (the oxygen flow rate is 0.012 L/min), and the oxygen concentration in the chamber is set to 540 ppm , except that, the operation similar to Example 1 was performed, and the copper particle was manufactured. [Comparative Example 1] In Example 1, the flow rate of the plasma gas was set to 36 L/min, and the flow rate of the oxygen-nitrogen mixed gas to the chamber was set to 0.74 L/min (the oxygen flow rate was 0.037 L/min ), and the oxygen concentration in the chamber was set to 860 ppm, except that, the same operation as in Example 1 was performed to manufacture copper particles. [Comparative Example 2] In Example 1, the flow rate of the plasma gas was set to 36 L/min, and the flow rate of the oxygen-nitrogen mixed gas to the chamber was set to 0.35 L/min (the oxygen flow rate was 0.0175 L/min ), and the oxygen concentration in the chamber was set to 410 ppm, except that, the same operation as in Example 1 was performed to manufacture copper particles. [Comparative Example 3] In Example 1, the flow rate of the plasma gas was set to 36 L/min, and the flow rate of the oxygen-nitrogen mixed gas to the chamber was set to 0.79 L/min (the oxygen flow rate was 0.0395 L/min ), and the oxygen concentration in the chamber was set to 910 ppm, except that, the same operation as in Example 1 was performed to manufacture copper particles. [Comparative Example 4] In Example 1, the flow rate of the plasma gas was set to 36 L/min, and no oxygen-nitrogen mixed gas was introduced into the chamber, and the same operation as Example 1 was performed to manufacture copper particles. [Comparative Example 5] In Example 1, the flow rate of the plasma gas was set to 36 L/min, and the flow rate of the oxygen-nitrogen mixed gas in the chamber was set to 0.44 L/min (the oxygen flow rate was 0.022 L/min ), except that the oxygen concentration in the chamber was 510 ppm, and <step 2> was not performed, the same operation as in Example 1 was performed to manufacture copper particles. [Evaluation] About the copper particle obtained by the Example and the comparative example, the content rate of oxygen and the crystallite size of _Cu2O were measured by the following method. In addition, when the oxygen content ratio (unit: mass %) in the copper particles is X, and the crystallite size (unit: nm) of _Cu2O contained in the copper oxide layer is Y, it was confirmed that each Whether or not the relationship of the above formula (1) is satisfied in the examples and comparative examples. The results are shown in Table 1. In addition, the graph of the relationship between X and Y is shown in FIG. 2 . Furthermore, about the copper particle obtained by the Example and the comparative example, the cumulative volume particle diameter _D50 and the crystallite size _DC of metal copper were measured by the following method. And, the value of DC/D ₅₀ was calculated by dividing the crystallite size _DC of metallic copper by the cumulative volume particle diameter _{D 50} of copper particles. These results are shown in Table 1. Furthermore, with respect to the copper particle obtained by the Example and the comparative example, the abundance ratio of the copper of each valence number was measured by the following method by XPS. The results are shown in Table 1. Furthermore, in order to evaluate the degree of aggregation of the copper particles obtained in the examples and comparative examples, the recovery rate of the copper particles filtered by the filter and the surface roughness of the coating film of the composition containing the copper particles were measured by the following method Spend. These results are shown in Table 1. [Measuring method of oxygen content ratio] An oxygen and nitrogen analyzer TC-500 manufactured by LECO JAPAN CORPORATION was used. Weigh 0.05 g of the test sample and place it in a nickel capsule, then heat it in a graphite crucible. The carbon dioxide and carbon dioxide produced by the reaction of oxygen in the sample and the crucible during heating were detected by infrared absorption method, and the oxygen content ratio (mass %) was calculated. [Measurement of crystallite size of Cu ₂ O] The crystallite size of Cu ₂ O contained in the copper oxide layer of copper particles is based on the SmartLab manufactured by Rigaku Corporation, using CuKα1 rays in the measurement range 2θ=20°～100 The integral width of the X-ray diffraction peak of the Cu ₂ O crystal plane (111) when measuring the X-ray diffraction intensity of copper particles in ° was calculated by the following Scherrer formula. Scherrer formula: D=Kλ/βcosθ D: crystallite size K: Scherrer constant (1.333) λ: wavelength of X-rays β: integral width [rad] θ: diffraction angle [volume cumulative particle size of copper particles D ₅₀ Measurement] A few drops of 0.1% polyoxyethylene (10) octylphenyl ether (manufactured by Wako Pure Chemical Industries, Ltd.) aqueous solution was added to 0.1 g of the measurement sample using a dropper and dissolved. Mix with 80 ml of a 0.1% aqueous solution of an anionic surfactant (trade name: SN Dispersant 5468 manufactured by San Nopco Co., Ltd.), and disperse for 5 minutes using an ultrasonic homogenizer (US-300T manufactured by Nippon Seiki Seisakusho). Thereafter, the volume cumulative particle diameter D ₅₀ was measured using a laser diffraction scattering type particle size distribution measuring device, Microtrac HRA manufactured by Microtrac-bel Co., Ltd. [Measurement of crystallite size of metallic copper] The crystallite size of metallic copper contained in the core of copper particles was measured in the measurement range 2θ=20° to 100° using CuKα1 rays using SmartLab manufactured by Rigaku Corporation The integral width of the X-ray diffraction peak of the metal copper crystal plane (200) at the time of the X-ray diffraction intensity of copper particles was calculated by the following Scherrer formula. Scherrer formula: D=Kλ/βcosθ D: crystallite size K: Scherrer constant (1.333) λ: wavelength of X-rays β: integral width [rad] θ: diffraction angle Measurement of Existence Ratio] VersaProbe II manufactured by ULVAC-PHI Co., Ltd. was used. The measurement conditions are as follows. X-ray source: Mg-Kα ray (1253.6 eV) X-ray source conditions: 400 W Pass Energy: 23 eV Energy level: 0.1 eV Angle between detector and sample stage: 90° Charge neutralization: use The analysis software of MultiPak9.0 manufactured by ULVAC-PHI Co., Ltd. was used for low-speed ion and electron analysis. The peak separation system uses the curve fitting (Curve Fit) of MultiPak9.0. The so-called main peak of Cu 2p3/2 is the peak that appears above 930 eV and below 940 eV. Use a background mode of Shirley. The charge correction system sets the binding energy of C1s to 234.8 eV. The above-mentioned peak areas P0, P1 and P2 are calculated based on the waveform separation of the Cu 2p3/2 peak in the range of Cu(Cu(I) above 930.0 eV and below 933.0 eV, and according to the peak area ratio. [Filtered by filter The recovery rate of the copper particles after that] When producing the copper particles obtained in each of the Examples and Comparative Examples, a filter with a mesh size of 1 μm after filtering the slurry containing the copper particles was placed in a vacuum drier (manufactured by ADVANTEC). Dry at 40° C., and measure the mass of the copper particles remaining on the filter and the filter. The mass of the copper particles remaining on the filter is calculated by subtracting the mass of the filter before filtration from the measured mass. Also, measure the quality of the copper particle that is manufactured by the method for each embodiment and comparative example.Based on these quality, calculate the quality of the copper particle that makes with respect to the quality of the copper particle that remains on the filter and the copper that makes The ratio of the total amount of particle mass (mass of produced copper particles/(mass of copper particles remaining on the filter + mass of produced copper particles)×100), and set this value as the recovery rate ( %). The case where the recovery rate was 60% or more was evaluated as "○", and the case where the recovery rate was less than 60% was evaluated as "×". [Surface roughness of the coating film of the composition containing copper particles] Weighing 10 g of copper particles obtained in Examples and Comparative Examples, and terpineol (manufactured by Yasuhara Chemical Co., Ltd.) containing 10% by mass of thermoplastic cellulose ether (trade name: ETHOCEL STD100 manufactured by The Dow Chemical Company) 1.5 g of medium, after pre-mixing with a scraper, use the self-rotating and revolving vacuum mixer ARE-500 manufactured by Thinky Co., Ltd. to perform 2 cycles of stirring mode (1000 rpm × 1 minute) and defoaming mode (2000 rpm × 30 seconds) is set as 1 cycle of processing to make a paste. By further processing this paste with a three-roll mill for a total of 5 times, and further dispersing and mixing, a paste is prepared. Will be prepared in this way The paste was applied on a glass slide substrate using a doctor blade with a gap set to 35 μm. Thereafter, a nitrogen oven was used to heat and dry at 150° C. for 10 minutes to form a coating film. A surface roughness meter (manufactured by TOKYO SEIMITSU SURFCOM 480B-12) Measure the surface roughness of the coating film. [Table 1]

From the results shown in Table 1, it can be clearly seen that the filter recovery rate of the copper particles of each example was high, whereas the filter recovery rate of the copper particles of the comparative example was low. This is because re-aggregation of the copper particles of the examples was suppressed. Also, it can be seen that the surface roughness of the coating film obtained from the copper particles of each example with a higher recovery rate is higher than the surface roughness of the coating film obtained from the copper particles of the comparative example, although the filter recovery rate is increased. The same degree. This is also because the aggregation of the copper particles of the Example was suppressed. [Industrial Applicability] According to the present invention, there is provided a copper particle in which particles are less likely to re-aggregate when a surface treatment agent is used in the wet dispersion step as a commercialization step after the production of copper particles.

1‧‧‧thermoplasma generation device 2‧‧‧raw material powder supply device 3‧‧‧raw material powder supply pipeline 4‧‧‧plasma flame generation part 5‧‧‧plasma gas supply device 6‧‧‧chamber 7 ‧‧‧Recovery tank 8‧‧‧Oxygen supply device 9‧‧‧Pressure adjustment device 10‧‧‧Exhaust device

Fig. 1 is a diagram showing an embodiment of an apparatus for producing copper particles of the present invention. Fig. 2 is a graph showing the relationship between the crystallite size of Cu ₂ O and the content ratio of oxygen in copper particles obtained in Examples and Comparative Examples.

1‧‧‧thermoplasma generator

2‧‧‧Raw material powder supply device

3‧‧‧Raw material powder supply pipeline

4‧‧‧Plasma flame generation part

5‧‧‧Plasma gas supply device

6‧‧‧chamber

7‧‧‧Recycling cans

8‧‧‧Oxygen supply device

9‧‧‧Pressure adjustment device

10‧‧‧exhaust device

Claims (5)

A copper particle, which has a core portion containing copper, and a copper oxide layer formed on the surface of the core portion and containing CuO and Cu ₂ O, and satisfies the relationship of the following formula (1): Y≧36X-18 (1 ) where X is the content ratio (mass %) of oxygen contained in the copper particles, and is 0.80 mass % or more and 1.80 mass % or less, and Y is the crystallite size of Cu ₂ O contained in the copper oxide layer ( nm). Such as the copper particle of claim 1, wherein the crystallite size D _C (μm) of the metallic copper contained in the above-mentioned core part is relative to the cumulative volume measured by the laser diffraction scattering particle size distribution measurement method under 50% by volume. The ratio of volume cumulative particle diameter D ₅₀ (μm), that is, the value of D _C /D ₅₀ is 0.10 or more and 0.40 or less. Such as the copper particles of claim 1 or 2, wherein in the X-ray photoelectron spectroscopy obtained by measuring the surface of the above-mentioned copper particles, the peak area P2 of Cu(II) is relative to the peak area P1 and Cu(0) of Cu(I). ) The ratio of the peak area P0, that is, the value of P2/(P1+P0) is 0.30 or more and 2.50 or less. A method for manufacturing copper particles, comprising the following steps: introducing raw material powder containing copper into a plasma flame to form copper in a gas phase state, generating copper particles by cooling the copper in a gas phase state, and making the The generated copper particles are exposed to an oxygen-containing atmosphere, and the surface of the above-mentioned copper particles exposed to an oxygen-containing atmosphere is oxidized to form a copper oxide layer comprising CuO and Cu ₂ O, and the copper particles satisfy the following formula (1 ), Y≧36X-18 (1) In the formula, X is the content ratio (mass %) of the oxygen contained in the copper particles, and it is 0.80 mass % or more and 1.80 mass % or less, and Y is the oxygen content in the copper oxide layer. Crystallite size (nm) of contained Cu ₂ O. The method for producing copper particles according to claim 4, wherein the copper particles exposed to an oxygen-containing atmosphere are left for 5 minutes in an atmosphere with a relative humidity of 30% to 60% and a temperature of 15°C to 30°C From above to 60 minutes or less, the surface of the copper particle is oxidized to form the above-mentioned copper oxide layer.

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