KR102403998B1 - Copper particles and their manufacturing method - Google Patents

Abstract

The copper particle of this invention has a core part containing copper, and _the copper oxide layer containing CuO and Cu2O formed in the surface of this core part. When the content rate (mass %) of oxygen contained in a copper particle is X and the crystallite size (nm) _of Cu2O contained in a copper oxide layer is made into Y, the condition of Y≥36X-18 is satisfy|filled. D _C /D which is the ratio of the crystallite size D _C (μm) of metallic copper contained in the core part to the volume cumulative particle size D ₅₀ (μm) in the cumulative volume 50 volume % by the laser diffraction scattering particle size distribution measurement method It is also suitable that the value of ₅₀ is 0.10 or more and 0.40 or less. Moreover, it is also suitable that the content rate of oxygen is 0.80 mass % or more and 1.80 mass % or less.

Description

Copper particles and their manufacturing method

This invention relates to a copper particle and its manufacturing method.

Copper has a specific resistance value similar to that of silver, and is used suitably as a raw material for conductive pastes used for formation of printed wiring boards, electric circuits, and electrodes, since the material cost is lower than that of silver. In recent years, in the field|area, such as an electric circuit, fine-pitch formation and coexistence of favorable sintering property are calculated|required with fine-pitch formation and thinning of an electrode advancing the fine particle|grains of the copper particle for electrically conductive pastes. On the other hand, since the surface area of the fine copper is very large, the surface oxidation of particle|grains becomes remarkable at the time of manufacture of an electrically conductive paste, and electroconductivity may fall.

Patent Document 1 proposes a method for producing copper powder by a physical vapor deposition method (PVD method) using direct current thermal plasma for the purpose of fine-graining copper powder and ensuring electrical conductivity.

International Publication No. 2015/122251 pamphlet

The fine copper particles produced by the PVD method or the like have a very large surface area, and the particles tend to aggregate. Therefore, in the wet dispersion process etc. which are a commercialization process after copper particle manufacture, surface treatment which mixes a copper particle and surface treatment agents, such as a fatty acid, makes it difficult for particle|grains to occur aggregation is generally performed. However, in such a copper particle, even if surface treatment is made|formed, primary particle|grains may aggregate again (henceforth re-aggregation).

Moreover, in addition to the thing which particle|grains tend to aggregate, the copper particle manufactured by the PVD method etc. has many coarse particle|grains. Therefore, when an electrically conductive paste is produced using such a copper particle, this paste is apply|coated to a base material and it bakes, favorable surface smoothness is hard to be acquired for the electrically conductive film obtained by baking. Then, when producing an electrically conductive paste using the copper particle manufactured by PVD method etc. as a raw material, it is necessary to remove a flock|aggregate and coarse particle beforehand using a filter. However, the conventional copper particle is a flock|aggregate and coarse particle. Due to the large number of particles, the number of particles removed by the filter may increase and the yield may become low.

Therefore, this invention exists in improvement of a copper particle and its manufacturing method, Specifically, in the wet dispersion process which is a commercialization process after copper particle manufacture. It relates to a manufacturing method thereof.

As a result of the inventors earnestly examining in order to solve the above-mentioned subject, the degree of re-aggregation of particle|grains is after surface treatment for copper particles which satisfy the specific relationship between the oxygen content rate and the crystallite size of Cu ₂ O. found to be lowered. The present invention has been completed based on this knowledge.

That is, this invention provides the copper particle which has a core part containing copper, and _the copper oxide layer containing CuO and Cu2O formed on the surface of this core part, and satisfy|fills the relationship of following formula (1).

In formula, X is the content rate (mass %) of the oxygen contained in a copper particle, Y is a crystallite size (nm) of Cu ₂ O contained in a copper oxide layer.

Moreover, this invention is a suitable manufacturing method of said copper particle,

Raw material powder containing copper element is introduced into a plasma flame to make copper in a gaseous state,

Exposing the produced copper particles to an oxygen-containing atmosphere while producing copper particles by cooling the copper in the gas phase;

It is to provide the manufacturing method of the copper particle which has the process of oxidizing the surface of the said copper particle after exposure to oxygen _- containing atmosphere, and producing|generating the copper oxide layer containing CuO and Cu2O.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one Embodiment of the apparatus for manufacturing the copper particle of this invention.
It is a graph which shows the relationship between the crystallite size _of Cu2O in the copper particle obtained by the Example and the comparative example, and the content rate of oxygen.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated based on the preferable embodiment. The copper particle of this invention has a core part containing copper, and _the copper oxide layer containing CuO and Cu2O formed in the surface of a core part. A core part is located in the center area|region in the copper particle of this invention, and is a site|part which occupies most of the mass in the copper particle of this invention. On the other hand, a copper oxide layer is located in the surface area|region in the copper particle of this invention, and comprises the outermost surface of the copper particle of this invention. It is preferable that the copper oxide layer covers the entire surface of the core part, but as long as the effects of the present invention are not impaired, the copper oxide layer may cover the surface of the core part so that a part of the surface of the core part is exposed to the outside world. In the copper particle of this invention, the layer containing a metal element does not exist outside a copper oxide layer. However, it is permissible for a layer made of an organic compound to exist outside the copper oxide layer.

There is no restriction|limiting in particular in the shape, The copper particle of this invention can employ|adopt various shapes according to a specific use. For example, copper particles having various shapes, such as spherical shape, flake shape, plate shape, and resin shape, may be used.

The copper particles of the present invention preferably have a volume cumulative particle diameter D ₅₀ of 0.2 μm or more and 0.6 μm or less in a cumulative volume of 50% by volume according to a laser diffraction scattering type particle size distribution measurement method, even when the shape is any of the above-mentioned shapes, It is more preferable that they are 0.2 micrometer or more and 0.5 micrometer or less. When the particle size of the copper particles is within this range, a conductive composition such as an electrically conductive paste is prepared from the copper particles and a conductive film is formed using the conductive composition, the conductive film is dense and the conductivity is high. . In order to obtain the copper particle of the particle diameter of this range, what is necessary is just to employ|adopt a wet reduction method, a PVD method, etc. and to manufacture a copper particle, for example. In addition, the measurement of the volume accumulation particle _diameter D50 can be performed by the method described in the Example mentioned later.

The core part in the copper particle of this invention is comprised including copper. That the core part contains copper includes (a) the case where the core part consists substantially of copper, and (b) the case where the core part consists of copper and other elements. In the case of (a), it is preferable that the ratio of copper to a core part is 99 mass % or more, It is more preferable that it is 99.5 mass % or more, It is still more preferable that the core part consists only of copper and an unavoidable impurity.

In any case of said (a) and (b), as above-mentioned, a core part is a site|part which occupies most of the mass in the copper particle of this invention. It is preferable that they are 1 nm or more and 100 nm or less, and, as for the thickness of a copper oxide layer, it is more preferable that they are 1 nm or more and 55 nm or less. When a copper oxide layer exists in this thickness range, the electroconductivity of the copper particle of this invention can be made high enough. The ratio of the core part to the copper particle of this invention performs line analysis of the copper particle surface part by STEM-EDS (Scanning Transmission Electron Microscope-Energy-Dispersive X-ray Spectroscopy), for example, The line profile of oxygen (O-K line) The thickness of the copper oxide layer can be measured from

The copper oxide layer located on the surface of the core part contains CuO and Cu ₂ O as described above. The copper oxide layer is made of only copper oxide containing (c) CuO and Cu ₂ O, or (d) copper oxide containing CuO and Cu ₂ O, and other materials are also included. . In the case of (c), it is preferable that the copper oxide layer consists only of the oxide _of copper containing CuO and Cu2O, and an unavoidable impurity.

In any case of said (c) and (d), there is no restriction|limiting in particular in the presence state _of CuO and Cu2O in a copper oxide layer. For example, _the state in which CuO and Cu2O were arbitrarily mixed may be sufficient, or the site|part which consists of CuO and the site|part which consists _of Cu2O may exist separately, respectively. When a site made of CuO and a site made of Cu ₂ O exist separately, for example, a site made of Cu ₂ O is present on the surface of the core part, and a site made of CuO is present on the surface of the site can be heard

As a particularly preferable embodiment of the copper particle of the present invention, for example, an embodiment in which the core part consists only of copper and unavoidable impurities and the copper oxide layer consists only of the oxide and unavoidable impurities of copper containing CuO and Cu ₂ O and unavoidable impurities. have.

As a result of examination of this inventor, if the content rate of oxygen in the copper particle of this invention, and the crystallite size _of Cu2O in the copper oxide layer of a copper particle have a specific relationship, the dispersibility of the copper particle after the surface treatment in a commercialization process This was found to be improved. When the content rate (unit: mass %) of oxygen in a copper particle is specifically, let X and the crystallite size (unit: nm) of Cu ₂ O in a copper oxide layer be Y, the relationship of following formula (1) It became clear that re-aggregation did not occur easily in the copper particle after the surface treatment in a commercialization process, and dispersibility improved especially when this was satisfied.

If the relationship of Formula (1) is satisfied, although the reason that the dispersibility of the copper particle after surface treatment in a commercialization process improves especially is not clear, the present inventors guess as follows. As for the copper particle produced|generated by the wet reduction method, the PVD method, etc., the degree _of exposure of Cu2O in the particle|grain surface increases. When such copper particles are mixed with a surface treatment agent such as a fatty acid in a commercialization step such as a wet dispersion step, Cu ₂ O is dissolved by the reaction between the fatty acid and Cu ₂ O, and metallic copper contained in the core portion of the copper particle. is exposed to the outside world. Since the copper particle of the state to which metallic copper was exposed to the outside is easy to couple|bond with the copper particle which is in the same state, re-aggregation of particle|grains occurs easily. On the other hand, the copper particle which satisfy|fills Formula (1) originates in the _high crystallinity of Cu2O contained in a copper oxide layer, and thinks that CuO is produced|generated uniformly on the outermost surface of a copper particle. Since CuO is more stable _than Cu2O, it is hard to react with surface treatment agents, such as a fatty acid, and it is hard to melt|dissolve _than Cu2O. Therefore, it becomes difficult for the metallic copper contained in a core part to be exposed to the outside of a copper particle. As a result, it becomes difficult for copper particles to re-agglomerate.

On condition that the relationship of the said Formula (1) is satisfied, it is preferable that the content rates of oxygen in the copper particle of this invention are 0.8 mass % or more and 1.80 mass % or less, and it is further that they are 0.8 mass % or more and 1.6 mass % or less. It is preferable, and it is still more preferable that they are 0.8 mass % or more and 1.5 mass % or less. When the content rate of oxygen exists in this range, it will become difficult for copper particles to re-aggregate after the surface treatment in a commercialization process. The content rate of oxygen in the copper particle of this invention can be measured by the method as described in the Example mentioned later, for example.

Similarly, on condition that the relationship of the formula (1) is satisfied, the copper particles of the present invention preferably have a crystallite size of Cu ₂ O contained in the copper oxide layer of 15 nm or more and 60 nm or less, 20 nm or more and 60 It is more preferable that they are nm or less, and it is still more preferable that they are 20 nm or more and 55 nm or less. When the crystallite size _of Cu2O exists in this range, it will become difficult for copper particles to re-aggregate after the surface treatment in a commercialization process. The crystallite size of Cu ₂ O is calculated by Scherrer's formula from a diffraction peak obtained by powder X-ray diffraction. The measurement by powder X-ray diffraction can be performed by the method described in Examples to be described later.

In order for the copper particle of this invention to satisfy|fill the conditions of Formula (1), what is necessary is just to manufacture a copper particle by the method mentioned later, for example.

In the above description, although mention was made about the crystallite size of Cu ₂ O in the copper particle of the present invention, in addition to this crystallite size, in the copper particle of the present invention, the crystallite size D _C of metallic copper contained in the core part is It is preferable that they are 0.060 micrometers or more and 0.090 micrometers or less, It is more preferable that they are 0.065 micrometers or more and 0.085 micrometers or less, It is still more preferable that they are 0.070 micrometers or more and 0.085 micrometers or less. When the crystallite size D _C of the metallic copper is in this range, the crystallite size of Cu ₂ O can also be increased, and CuO can be uniformly generated on the outermost surface of the copper oxide layer. The crystallite size of metallic copper is calculated by Scherrer's formula from a diffraction peak obtained by powder X-ray diffraction. The measurement by powder X-ray diffraction can be performed by the method described in Examples to be described later.

From the viewpoint of more effectively preventing re-aggregation of copper particles, the copper particles of the present invention are in the core part with respect to the volume cumulative particle diameter D ₅₀ (μm) in the cumulative volume 50 volume % by the laser diffraction scattering particle size distribution measurement method. The value of _DC / _{D 50} , which is the ratio of the crystallite size DC (μm) of metallic copper, is preferably 0.10 or more and 0.40 or less, more preferably 0.10 or more and 0.30 or less, and still more preferably 0.20 or more and 0.30 or less. In order for the value of _DC / _D50 to satisfy this range, what is necessary is just to manufacture a copper particle by the method mentioned later, for example.

As mentioned above, the copper particle of this invention contains the metallic copper which is zero-valent copper, Cu2O which is monovalent copper, and CuO which is _divalent copper. The abundance ratio of these three characters on the surface of a copper particle can be measured using an X-ray photoelectron spectroscopy apparatus (XPS). According to XPS measurement, the X-ray photoelectron spectroscopy spectrum of various elements can be acquired, and quantitative analysis can be performed about the element component of the depth from the surface of a copper particle to about 10 nm. In the X-ray photoelectron spectral spectrum obtained by measuring the surface state of the copper particles of the present invention by XPS, the peak area P1 of Cu(I) which is monovalent copper and the peak area P0 of Cu(0) which is zero-valent copper , it is preferable that the value of P2/(P1+P0) which is the ratio of the peak area P2 of Cu(II) which is divalent copper is 0.30 or more and 2.50 or less, and it is still more preferable that they are 0.40 or more and 2.50 or less. When the copper particle of the present invention satisfies 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 particle to suppress re-aggregation of copper particles can be set appropriately. Measurement using XPS can be carried out by the method described in Examples to be described later.

Below, the suitable manufacturing method of the copper particle of this invention is demonstrated.

<Step 1. Synthesis of copper particles>

As a manufacturing method of the copper particle known heretofore, generally a wet reduction method, an atomization method, the physical vapor deposition method (PVD method), etc. are mentioned. Among these manufacturing methods, the PVD method is employed so that the oxygen content in the copper particles, the crystallite size of Cu ₂ O and metallic copper, and the D ₅₀ of the copper particles easily satisfy the above-mentioned ranges. It is preferred to produce copper particles. Then, the manufacturing method of the copper particle using PVD method is demonstrated below.

1 shows a thermal plasma generating apparatus 1 suitably used for the production of copper particles by the PVD method. The thermal plasma generator 1 includes a raw powder supply device 2 , a raw powder supply path 3 , a plasma flame generator 4 , a plasma gas supply device 5 , a chamber 6 , and a recovery port 7 . , an oxygen supply device 8 , a pressure regulating device 9 , and an exhaust device 10 .

The raw material powder containing the copper element (hereinafter, 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 path 3 . In the plasma flame generation part 4, a plasma flame generate|occur|produces by supplying a plasma gas from the plasma gas supply apparatus 5. As shown in FIG. The raw material powder introduced into the plasma flame is evaporated to form copper in a gaseous state, and then discharged into the chamber 6 existing on the terminal side of the plasma flame. Copper in a gaseous state cools as it moves away from the plasma flame, goes through nucleation and grain growth, and copper particles are produced. The produced copper particles are exposed to the atmosphere in the chamber 6 . Copper particles after being exposed to the atmosphere in the chamber 6 adhere to the wall surface inside the chamber 6 or accumulate in the recovery port 7 . The inside of the chamber 6 is controlled such that a negative pressure is maintained relative to that of the raw material powder supply path 3 by the pressure regulating device 9 and the exhaust device 10, and a plasma flame is stably generated and the raw material powder is converted into a plasma. It has a structure that can be introduced into the flame generating unit 4 . Details of the atmosphere in the chamber 6 will be described later.

There is no restriction|limiting in particular in the particle size of the raw material powder used for manufacture of the copper particle of this invention. From the viewpoint of supply efficiency to the thermal plasma generating device, it is preferable that the volume cumulative particle diameter D ₅₀ of the raw material powder is 3 µm or more and 30 µm or less. In addition, the shape of the particles of the raw material powder is not particularly limited, and various shapes such as a spherical shape, a flake shape, a plate shape, and a resin shape may be used. The oxidation state in particular of the copper element of a raw material powder is not restrict|limited, For example, metal copper powder, copper oxide powder (for example, CuO or Cu2O), or _a mixture thereof, etc. can be used. There is no restriction|limiting in particular also in the manufacturing method of raw material powder.

In the present manufacturing method, from the viewpoint of stably manufacturing 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.

As the plasma gas for generating the plasma flame, it is preferable to use a mixed gas of argon and nitrogen. By using this mixed gas, a large energy can be imparted by the raw material powder, thereby obtaining copper particles having a particle size and crystallite size (Cu ₂ O and metallic copper) suitable for exhibiting the effects of the present invention. can In particular, from the viewpoint of obtaining spherical or substantially spherical copper particles, in addition to using a mixed gas of argon and nitrogen as the plasma gas, it is preferable to adjust the plasma flame so that it is thick and long in a laminar flow state. The "approximately spherical shape" refers to a shape that is not a perfect spherical shape, but can be recognized as a sphere. 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 observed from the side where the width of the plasma flame is observed to be the thickest. When the ratio of the length of the plasma flame to the width of the plasma flame is 3 or more, it is considered a laminar flow, and when the ratio of the length of the plasma flame to the width of the plasma flame is less than 3, it can be judged as a turbulent flow.

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, and more preferably 5 L/min or more and 30 L/min or less. By adopting the gas flow rate in this range, the generated particles come into contact with an oxygen-containing atmosphere in the chamber 6 to be described later while maintaining an appropriate temperature. _As a result, the copper oxide layer containing CuO and Cu2O made into the objective can be formed smoothly on the surface of a core part. It is preferable that they are 2 kW or more and 50 kW or less, and, as for the plasma output of a thermal plasma generating apparatus, it is more preferable that they are 5 kW or more and 35 kW or less. From the same viewpoint, 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, more preferably 95:5 to 70:30. desirable.

In this manufacturing method, it is preferable that the atmosphere in the chamber 6 is an oxygen containing atmosphere. When copper in the gas phase is cooled and exposed to an oxygen-containing atmosphere in the process of producing copper particles, while maintaining the oxygen content in the copper particles in the above range, the surface of the core part contains Cu ₂ O with high crystallinity. This is because a copper oxide layer can be formed. At this time, by setting the produced|generated core part to an appropriate temperature, the copper oxide layer containing Cu2O with _high crystallinity can be formed easily. The setting of the temperature can be controlled, for example, by adjusting the gas flow rate of the plasma gas or adjusting the flow rate of oxygen supplied into the chamber 6 (this will be described later) as described above. As the oxygen-containing atmosphere, oxygen gas itself, a mixed gas of oxygen gas and another gas, or the like can be used. When using a mixed gas, various inert gases including argon and nitrogen can be used as another gas, for example. In addition, in the embodiment shown in Fig. 1, the oxygen supply device 8 is connected to the side surface of the chamber and oxygen is supplied to the chamber, but the connection position of the oxygen supply device is a position where oxygen can be stably supplied into the chamber 6 If it is a position, it will not specifically limit.

From the viewpoint of stably exposing copper particles produced from copper in the gas phase to an oxygen-containing atmosphere, the flow rate of oxygen supplied into the chamber 6 is preferably 0.002 L/min or more and 0.75 L/min or less, and 0.004 L/min. It is more preferable that they are 0.70 L/min or more and 0.70 L/min or less. Moreover, from a viewpoint _of forming the copper oxide layer containing Cu2O with high crystallinity, it is preferable that they are 100 ppm or more and 2000 ppm or less, and, as for oxygen concentration in a chamber, it is more preferable that they are 200 ppm or more and 1000 ppm or less.

<Step 2. Oxidation Treatment>

It is preferable that the copper particle produced|generated by the said <process 1> is further oxidized. By performing this step, Cu ₂ O on the surface of the copper particles, which was unreacted in <Step 1>, is gently oxidized to CuO, and a thicker copper oxide layer containing Cu ₂ O and CuO is produced without gaps on the entire surface. It can make it, and after surface treatment, the copper particle which is more difficult to re-agglomerate can be obtained.

Oxidation in this step is performed as follows. After the supply of the raw material powder and the generation of the plasma flame are stopped and the inside of the chamber 6 is returned to normal pressure, the copper particles generated in the <Step 1> are accumulated in the recovery port 7 and then recovered, and the copper particles are recovered. is placed under an atmospheric atmosphere, and Cu ₂ O on the surface of the copper particles is oxidized to CuO to form a copper oxide layer.

When this process puts a copper particle in atmospheric atmosphere and performs it, the rapid oxidation reaction of a copper particle does not generate|occur|produce but a copper oxide layer can be produced|generated. However, from a viewpoint of industrial productivity, it is preferable to put the produced|generated copper particle in atmospheric atmosphere, using a sieve etc. to pulverize the aggregated particle|grains.

From a viewpoint of the uniformity of the oxidation treatment of a copper particle, in this process, it is preferable that a relative humidity is 30 % or more and 60 % or less, and temperature puts a copper particle in the atmospheric atmosphere of 15 degreeC or more and 30 degrees C or less. By performing the oxidation reaction under this condition, Cu ₂ O of the copper oxide layer can be gently oxidized to CuO by the moisture contained in the air atmosphere, and a stable copper oxide layer can be formed on the surface.

In addition, the processing time of this process is 5 minutes or more and 60 minutes or less, on the condition that the conditions of the atmospheric atmosphere are in the above-mentioned range from the viewpoint of preventing the rapid oxidation reaction at the time of collection|recovery of copper particles, It is preferable, It is more preferable that they are 5 minutes or more and 30 minutes or less.

With the above manufacturing method, the copper particle of this invention can be manufactured smoothly. Thus, for the purpose of maintaining the oxidation state of the copper particle surface, it is preferable to seal the copper particle obtained in this way in the container of a moisture impermeable material, and to preserve|save at the temperature of room temperature (25 degreeC) or less.

Moreover, in the wet dispersion process which is a commercialization process after copper particle manufacture, the copper particle of this invention manufactured by the manufacturing method mentioned above WHEREIN: When a surface treating agent is used, compared with the conventional copper particle, it becomes difficult to reaggregate. Moreover, conductive compositions, such as an electrically conductive paste, can be manufactured by using the copper particle of this invention, without impairing the sinterability in low temperature.

Example

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 these examples. Unless otherwise specified, "%" means "mass %".

[Example 1]

On the following manufacturing conditions, the <process 1> and <process 2> mentioned above were performed, and the copper particle was manufactured.

<Process 1>

Copper particles (particle diameter D ₅₀ : 12 μm, particle shape: spherical) that become raw powder produced by the atomization method are introduced into the plasma flame of the thermal plasma generator shown in FIG. 1 at a supply amount of 5 g/min, It was set as the copper of a weather condition. As a condition for generating a plasma flame, a mixed gas of argon and nitrogen is used as the plasma gas, the flow rate of the plasma gas is 19.0 L/min, and the flow rate (L/min) ratio of argon and nitrogen in the plasma gas is 82:18 , the plasma output was set to 19 kW.

The copper particles were exposed to an oxygen-containing atmosphere while producing copper particles by cooling the vapor phase copper in the chamber to form copper particles having a core portion and a copper oxide layer. The flow rate of the oxygen-nitrogen mixed gas (containing 5 vol% of oxygen) into the chamber was 0.20 L/min (the flow rate of oxygen was 0.01 L/min), and the oxygen concentration in the chamber was 440 ppm. After that, generation of plasma flame is stopped while copper particles are present in the chamber, nitrogen gas is supplied into the chamber at negative pressure (-0.05 MPa) at a flow rate of 30 L/min, and it takes 15 minutes from the negative pressure to normal pressure returned to

<Process 2>

After performing <Process 1>, the copper particle was collect|recovered. A copper oxide layer was produced|generated on the surface of a copper particle, a relative humidity being 50 %, and disintegrating the particle|grains by a sieve in the atmospheric atmosphere whose temperature is 25 degreeC for the copper particle. The time left in the atmospheric atmosphere was set to 30 minutes.

After adding 2-propanol so that the obtained copper particle might become 30 mass %, 5 mass % of lauric acid was added with respect to a copper particle as a dispersing agent, and the slurry was prepared. This slurry was pulverized (disintegration conditions: 50 MPa, 5 passes) with Nanoizer mark II (wet pulverizer, Yoshida Kikai Kogyo Co., Ltd. product name: NM2-2000AR). The pulverized slurry was filtered with a filter (ROKI TECHNO Co., LTD. product name: SBP010) having an eye size of 1 μm, the supernatant of the filtrate was removed, and the remaining solid content was dried in a vacuum dryer (manufactured by ADVANTEC) at 40° C. dried in Then, under a nitrogen atmosphere, the sieve was performed with a 150 micrometers sieve and copper particle was obtained.

[Example 2]

In Example 1, the same operation as in Example 1 was performed except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.29 L/min (the flow rate of oxygen was 0.0145 L/min) and the oxygen concentration in the chamber was 640 ppm. It carried out and manufactured the copper particle.

[Example 3]

In Example 1, the same operation as in Example 1 was performed except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.11 L/min (the flow rate of oxygen was 0.0055 L/min) and the oxygen concentration in the chamber was 240 ppm. Copper particles were prepared.

[Example 4]

In Example 1, the same operation as in Example 1 was performed except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.34 L/min (the flow rate of oxygen was 0.017 L/min) and the oxygen concentration in the chamber was 750 ppm. It carried out and manufactured the copper particle.

[Example 5]

In Example 1, the same operation as in Example 1 was performed except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.09 L/min (the flow rate of oxygen was 0.0045 L/min) and the oxygen concentration in the chamber was 200 ppm. It carried out and manufactured the copper particle.

[Example 6]

In Example 1, the same operation as in Example 1 was performed except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.39 L/min (the flow rate of oxygen was 0.0195 L/min) and the oxygen concentration in the chamber was 850 ppm. It carried out and manufactured the copper particle.

[Example 7]

In Example 1, the same operation as in Example 1 was performed except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.33 L/min (the flow rate of oxygen was 0.0165 L/min) and the oxygen concentration in the chamber was 730 ppm. It carried out and manufactured the copper particle.

[Example 8]

In Example 1, the same operation as in Example 1 was performed except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.18 L/min (the flow rate of oxygen was 0.009 L/min) and the oxygen concentration in the chamber was 400 ppm. It carried out and manufactured the copper particle.

[Example 9]

In Example 1, the same operation as in Example 1 was performed except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.26 L/min (the flow rate of oxygen was 0.013 L/min) and the oxygen concentration in the chamber was 570 ppm. It carried out and manufactured the copper particle.

[Example 10]

In Example 1, the same operation as in Example 1 was performed except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.24 L/min (the flow rate of oxygen was 0.012 L/min) and the oxygen concentration in the chamber was 540 ppm. It carried out and manufactured the copper particle.

[Comparative Example 1]

In Example 1, the flow rate of the plasma gas was 36 L/min, the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.74 L/min (the flow rate of oxygen was 0.037 L/min), and the oxygen concentration in the chamber was 860 ppm. Except that, operation similar to Example 1 was performed and the copper particle was manufactured.

[Comparative Example 2]

In Example 1, the flow rate of the plasma gas was 36 L/min, the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.35 L/min (the flow rate of oxygen was 0.0175 L/min), and the oxygen concentration in the chamber was 410 ppm. Except that, operation similar to Example 1 was performed and the copper particle was manufactured.

[Comparative Example 3]

In Example 1, the flow rate of the plasma gas was 36 L/min, the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.79 L/min (the flow rate of oxygen was 0.0395 L/min), and the oxygen concentration in the chamber was 910 ppm. Except that, operation similar to Example 1 was performed and the copper particle was manufactured.

[Comparative Example 4]

In Example 1, the flow rate of the plasma gas was 36 L/min, and except not having introduce|transduced oxygen-nitrogen mixed gas in the chamber, operation similar to Example 1 was performed and the copper particle was manufactured.

[Comparative Example 5]

In Example 1, the flow rate of the plasma gas is 36 L/min, the flow rate of the oxygen-nitrogen mixed gas into the chamber is 0.44 L/min (the flow rate of oxygen is 0.022 L/min), and the oxygen concentration in the chamber is 510 ppm, Except not having performed <process 2>, operation similar to Example 1 was performed and the copper particle was manufactured.

〔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 with the following method. And when the content rate (unit: mass %) of oxygen in copper particles is X and the crystallite size (unit: nm) of Cu ₂ O contained in the copper oxide layer is Y, in each Example and Comparative Example It was confirmed whether the relationship of the said Formula (1) was satisfied. The results are shown in Table 1. In addition, the graph of the relationship between X and Y is shown in FIG. 2 .

Moreover, about the copper particle obtained by the Example and the comparative example, the volume cumulative particle _diameter D50 and the crystallite size _DC of metallic copper were measured with the following method. And the value of _DC / _D50 was computed by dividing the crystallite size _DC of metallic copper by the volume cumulative particle _diameter D50 of copper particles. Their results are shown in Table 1.

Moreover, about the copper particle obtained by the Example and the comparative example, the abundance-ratio of copper of each valence was measured with the following method by XPS. The results are shown in Table 1.

Moreover, for the purpose of evaluating the degree of aggregation of the copper particle obtained by the Example and the comparative example, the recovery rate of the copper particle by filter filtration, and the surface roughness of the coating film of the composition containing copper particle were measured with the following method. Their results are shown in Table 1.

[Method for measuring oxygen content]

LECO Japan Kodo Co., Ltd. oxygen/nitrogen analyzer TC-500 was used. After measuring 0.05 g of a measurement sample and putting it into a nickel capsule, it heats in a graphite crucible. During heating, carbon monoxide and carbon dioxide produced by the reaction of oxygen in the sample with the crucible were detected by an infrared absorption method, and the oxygen content (% by mass) was calculated.

[Measurement of the crystallite size of Cu ₂ O]

The crystallite size of Cu ₂ O contained in the copper oxide layer of copper particles was measured using CuKα1 ray in SmartLab manufactured by Rigaku Co., Ltd., X-ray diffraction intensity of copper particles in the measurement range 2θ = 20° to 100° From the integral width of the X-ray diffraction peak in the crystal plane 111 of Cu ₂ O at the time of measurement, it was computed by the following Scherrer's formula.

Scherer's equation: 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 Volume Cumulative Particle Size D ₅₀ of Copper Particles]

To a 0.1 g measurement sample, a few drops of an aqueous solution of polyoxyethylene (10) octylphenyl ether (manufactured by Wako Junyaku Kogyo Co., Ltd.) at a concentration of 0.1% was added with a dropper to familiarize them with an anionic surfactant (Sannofuco) It was mixed with 80 ml of a 0.1% aqueous solution of SN Dispersant 5468) and dispersed for 5 minutes with an ultrasonic homogenizer (US-300T manufactured by Nippon Seiki Seisakusho). Then, the volume cumulative particle _diameter D50 was measured using the laser diffraction scattering type particle size distribution analyzer and Microtrac HRA manufactured by Microtrac Bell Corporation.

[Measurement of crystallite size of metallic copper]

The crystallite size of metallic copper contained in the core portion of the copper particles was determined by measuring the X-ray diffraction intensity of the copper particles in the measurement range 2θ = 20° to 100° using CuKα1 ray in SmartLab manufactured by Rigaku Co., Ltd. From the integral width of the X-ray diffraction peak in the crystal plane 200 of metallic copper at the time, it was computed by the following Scherer's formula.

Scherer's equation: 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 the abundance ratio of copper of each valence by XPS]

VersaProbeII manufactured by ULVAC PAI Co., Ltd. was used. The measurement conditions are as follows.

X-ray source: Mg-Kα ray (1253.6 eV)

Condition of X-ray source: 400W

Pass Energy: 23eV

Energy step: 0.1 eV

Detector and sample stand angle: 90°

Charge neutralization: using slow-speed ions and electrons

For the analysis, analysis software of MultiPak 9.0 manufactured by ULVAC PAI Corporation was used. The peak separation uses the Curve Fit of MultiPak 9.0, and the main peak of Cu 2p3/2 is a peak that appears between 930eV and 940eV. The background mode used is Shirley. Charge correction made the binding energy of C1s to 234.8 eV.

The above-mentioned peak areas P0, P1 and P2 were calculated from the peak area ratio by performing waveform separation of the Cu 2p3/2 peak in the range of Cu [930.0 eV or more and 933.0 eV or less for Cu(I)).

[Recovery rate of copper particles by filter filtration]

In the production of the copper particles obtained in each Example and Comparative Example, the filter having an eye size of 1 μm after filtering the slurry containing the copper particles was dried at 40° C. in a vacuum dryer (manufactured by ADVANTEC), and remained on the filter The mass of one copper particle and the filter was measured. The mass of the copper particle which remained on the filter was computed by subtracting the mass of the filter before filtration from this measured mass. Moreover, the mass of the copper particle manufactured by the method of each Example and a comparative example was measured. From these masses, the ratio of the mass of the produced copper particles to the total amount of the mass of the copper particles remaining on the filter and the mass of the produced copper particles (mass of the produced copper particles / (of the copper particles remaining on the filter) Mass + mass of the produced copper particle) x100) was computed, and this value was made into recovery (%). The case where the recovery rate was 60% or more was referred to as "○", and the case where the recovery rate was less than 60% was referred to as "x".

[Surface Roughness of Coating Film of Composition Containing Copper Particles]

10 g of the copper particles obtained in each Example and Comparative Example and 1.5 g of a vehicle 1.5 g of tapineol (manufactured by Yasuhara Chemical Co., Ltd.) containing 10 mass % of thermoplastic cellulose ether (The Dow Chemical Company product name: ETHOCEL STD100) After weighing and pre-kneading with a spatula, agitation mode (1000 rpm × 1 minute) and defoaming mode (2000 rpm × 30 seconds) were set as 1 cycle using a rotating/revolving vacuum mixer ARE-500 manufactured by Thinky Co., Ltd. The treatment was performed for 2 cycles to form a paste. This paste was further dispersed and mixed by processing 5 times in total using a 3-axis roll mill to prepare a paste. The paste thus prepared was applied on a glass slide substrate with a gap of 35 µm using a doctor blade. Then, using nitrogen oven, it heat-dried at 150 degreeC for 10 minute(s), and produced the coating film. About this coating film, the surface roughness was measured using the surface roughness meter (SURFCOM 480B-12 made from TOKYO SEIMITSU).

It turns out that the filter recovery rate of the copper particle of a comparative example is low, whereas the copper particle of each Example has a high filter recovery rate so that it may become clear from the result shown in Table 1. This reason is because the copper particle of an Example was suppressed from the reaggregation of particle|grains.

Moreover, it turns out that the surface roughness of the coating film obtained from the copper particle of each Example with a high recovery rate is equal to the surface roughness of the coating film obtained from the copper particle of a comparative example even though the filter recovery rate increased. This reason is also because the aggregation of particle|grains was suppressed as for the copper particle of an Example.

ADVANTAGE OF THE INVENTION According to this invention, when a surface treating agent is used in the wet dispersion process which is a commercialization process after copper particle manufacture, the copper particle which particle|grains are hard to reaggregate is provided.

Claims (6)

The copper particle which has the core part containing copper, and _the copper oxide layer containing CuO and Cu2O formed in the surface of this core part, and satisfy|fills the relationship of following formula (1).

In the formula, X is the oxygen content (mass%) contained in the copper particles, has a value of 0.80 mass% or more and 1.80 mass% or less, and Y is the crystallite size (nm) of Cu ₂ O contained in the copper oxide layer . The crystallite size D _C (μm) of metallic copper contained in the core portion with respect to the volume cumulative particle diameter D ₅₀ (μm) in the cumulative volume 50 vol% according to the laser diffraction scattering particle size distribution measurement method The value of DC / _{D 50} which is a ratio of 0.10 or more and 0.40 or less, copper particles. delete The Cu(II) according to claim 1 or 2, with respect to the peak area P1 of Cu(I) and the peak area P0 of Cu(0) in the X-ray photoelectron spectral spectrum obtained by measuring the surface of the copper particle. The copper particle whose value of P2/(P1+P0) which is the ratio of the peak area P2 of ) is 0.30 or more and 2.50 or less. As a manufacturing method of the copper particle of Claim 1 or 2,
Raw material powder containing copper element is introduced into a plasma flame to make copper in a gaseous state,
exposing the produced copper particles to an oxygen-containing atmosphere while producing copper particles by cooling the copper in the gaseous state;
The manufacturing method of the copper particle which has the process of oxidizing the surface of the said copper particle after exposure to oxygen _- containing atmosphere, and producing|generating the copper oxide layer containing CuO and Cu2O. The copper particles according to claim 5, wherein the copper particles after exposure to an oxygen-containing atmosphere are placed in an atmospheric atmosphere with a relative humidity of 30% or more and 60% or less and 15°C or more and 30°C or less for 5 minutes or more and 60 minutes or less, A method for producing copper particles, wherein the surface of the particles is oxidized to form the copper oxide layer.

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