KR20190132351A - Copper particle and its manufacturing method - Google Patents

Abstract

Copper particles of the present invention, the core portion comprising copper, and has a layer of copper oxide containing CuO and Cu ₂ O formed in the surface of the core. When the content ratio (mass%) of oxygen contained in the copper particles is X and the crystallite size (nm) of Cu ₂ O contained in the copper oxide layer is Y, the condition of Y ≧ 36X-18 is satisfied. D _C / D which is the ratio of the crystallite size D _C (μm) of the metal copper contained in the core portion to the volume cumulative particle size D ₅₀ (μm) in the cumulative volume 50 vol% 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 particle and its manufacturing method

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

Copper has a specific resistance value similar to that of silver, but has a low material cost compared to silver, and therefore copper is suitably used as a raw material such as a conductive paste used for forming printed wiring boards, electrical circuits, and electrodes. In recent years, in the field of electrical circuits and the like, fine pitching and electrode thinning have been progressed, and both fine particle formation of copper paste for conductive paste and good sintering properties are required. On the other hand, since fine particle | grains copper have a very large surface area, the surface oxidation of particle | grains becomes remarkable at the time of manufacture of an electrically conductive paste, and electrical conductivity may fall.

In patent document 1, the manufacturing method of the copper powder by the physical vapor deposition method (PVD method) using the direct current thermal plasma is proposed for the purpose of microparticles | fine-particles of copper powder and ensuring of electroconductivity.

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 together. Therefore, in the wet dispersion process etc. which are the manufacturing processes after copper particle manufacture, surface treatment which mixes copper particle and surface treating agents, such as a fatty acid, and makes it hard to produce aggregation of particle | grains is generally performed. However, even if such a copper particle is surface-treated, primary particles may aggregate again (henceforth a reaggregation).

Moreover, the copper particle manufactured by PVD method etc. have many coarse particles in addition to the particle | grains which are easy to aggregate. Therefore, when an electrically conductive paste is produced using such a copper particle, and this paste is apply | coated to a base material and baked, the electrically conductive film obtained by baking hardly obtains the favorable surface smoothness. Therefore, when producing a conductive paste using copper particles produced by the PVD method or the like as a raw material, it is necessary to remove agglomerated particles and coarse particles in advance using a filter, but conventional copper particles are agglomerated particles and coarse particles. Due to the large number of particles, the number of particles removed by the filter increases, resulting in a lower yield.

Therefore, this invention is an improvement of a copper particle and its manufacturing method, Specifically, in the wet dispersion process which is a commercialization process after copper particle manufacture, when using a surface treating agent, a copper particle which particle | grains are hard to reaggregate, and The manufacturing method is related.

The present inventors have made intensive studies to solve the above problems result, copper particles that have a crystallite size in a content ratio of the oxygen and Cu ₂ O satisfy a particular relationship, in after the surface treatment, the degree of re-agglomeration of the particles Found out. This invention is completed based on this knowledge.

That is, the present invention, and comprising a copper core, having a layer of copper oxide containing CuO and Cu ₂ O formed in the surface of the core portion, to to provide a copper particles satisfies the relationship of formula (1).

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

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

Raw powder containing elemental copper is introduced into the plasma flame to make copper in the gas phase,

By cooling the said copper in a gaseous state, the said copper particle produced | generated is exposed to oxygen containing atmosphere, generating a copper particle,

After exposure to the oxygen-containing atmosphere having a process to produce a copper oxide layer by oxidizing the surface of the copper particles include CuO and Cu ₂ O, to provide a method for producing copper particles.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one Embodiment of the apparatus which manufactures the copper particle of this invention.
Figure 2 is a graph showing the relationship between the content of the crystallite size and the oxygen in the Cu ₂ O in the copper particles obtained in Examples and Comparative Examples.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated based on the preferable embodiment. Copper particles of the present invention, the core portion comprising copper, and has a layer of copper oxide containing CuO and Cu ₂ O formed in the core surface portion. A core part is located in the center 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. The copper oxide layer preferably covers the entire surface of the core portion. However, as long as the effect of the present invention is not impaired, the copper oxide layer may cover the surface of the core portion so that a part of the surface of the core portion is exposed to the outside world. In the copper particle of this invention, the layer containing a metal element does not exist outside the copper oxide layer. However, it is permissible that a layer made of an organic compound exists outside the copper oxide layer.

The copper particle of this invention does not have a restriction | limiting in particular in the shape, Various shapes can be employ | adopted according to a specific use. For example, copper particles of various shapes such as spherical, flake, plate and resin can be used.

Even if the shape of the copper particle of this invention is any of the above-mentioned, it is preferable that the volume cumulative particle diameter D50 in ₅₀ volume% of cumulative volume by a laser diffraction scattering type particle size distribution measuring method is 0.2 micrometer or more and 0.6 micrometer or less, It is more preferable that they are 0.2 micrometer or more and 0.5 micrometer or less. When the particle diameter of a copper particle exists in this range, when the electrically conductive composition, such as an electrically conductive paste, is prepared from this copper particle, and a electrically conductive film is formed using the said electrically conductive composition, this electrically conductive film becomes dense and electroconductivity becomes high. . In order to obtain copper particle of the particle diameter of this range, what is necessary is just to employ | adopt a wet reduction method, PVD method, etc., and to manufacture copper particle, for example. In addition, measurement of the volume cumulative particle diameter D ₅₀ may be carried out by the method described in Examples described later.

The core part in the copper particle of this invention is comprised including copper. The core part containing copper includes the case where (a) the core part consists essentially of copper and (b) 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 further more preferable that a core part consists only of copper and an unavoidable impurity.

In any of the cases (a) and (b) described above, as described above, the core portion is a portion that occupies most of the mass in the copper particles of the present 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. Since 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 the line analysis of the copper particle surface part by STEM-EDS (Scanning Transmission Electron Microscope-Energy-Dispersive X-ray Spectroscopy), for example, and the line profile of oxygen (OK line) From this, the thickness of the copper oxide layer can be measured.

The copper oxide layer located on the surface of the core portion contains CuO and Cu ₂ O as described above. The copper oxide layer consists only of oxides of copper containing (C) CuO and Cu ₂ O, or (D) contains oxides of copper containing CuO and Cu ₂ O, and also contains other materials. . In the case of (C), the copper oxide layer is preferably made of only an oxide of copper containing CuO and Cu ₂ O and unavoidable impurities.

In any of the above (C) and (D), there are no particular restrictions on the presence state of CuO and Cu ₂ O in the copper oxide layer. For example, the CuO and Cu ₂ O and even a randomly mixed state, or is a region composed of a part made of CuO and Cu ₂ O may be present separately. If the region comprising the site and the Cu ₂ O consisting of CuO, which are present separately, for example, a form of the region made of a Cu ₂ O present in the core portion surface, and the portion made of CuO on the surface of the area Can be mentioned.

As a particularly preferred embodiment of the copper particles of the present invention, for example, the core portion is made of copper and only unavoidable impurities, the copper oxide layer be an embodiment containing only unavoidable impurities and oxides of copper containing CuO and Cu ₂ O have.

Review of the present inventors, is in the content of the oxygen in the copper particles of the present invention, the crystallite size of the copper particles, Cu ₂ O in the copper oxide layer of a certain relationship, the dispersibility of the copper particles after the surface treatment of the commercialized process This proved to be improved. Specifically, when the content ratio (unit: mass%) of oxygen in the copper particles is X and the crystallite size (unit: nm) of Cu ₂ O in the copper oxide layer is Y, the relationship of the following formula (1) When was satisfied, it was found that the copper particles after the surface treatment in the commercialization step hardly reaggregate, and the dispersibility is particularly improved.

When the relationship of Formula (1) is satisfied, the reason why the dispersibility of the copper particle after the surface treatment in a manufacturing process improves especially is not clear, but the present inventors guess as follows. Copper particles produced by a wet reduction method or a PVD method, there is a degree of the Cu ₂ O is exposed to a lot of the particle surface. When the copper particles are mixed with a surface treating agent such as a fatty acid in a commercialization step such as a wet dispersion step, Cu ₂ O is dissolved by the reaction of the fatty acid with Cu ₂ O, and the metallic copper contained in the core portion of the copper particles. Is exposed to extraterrestrial. Since the copper particle of the state in which the metallic copper was exposed to the external field is easy to combine with the copper particle which is in the same state, reaggregation of particle | grains tends to occur easily. On the other hand, copper particles that satisfy formula (1), due to high crystallinity of the Cu ₂ O contained in the layer of copper oxide, and think that CuO is uniformly generated on the outermost surface of the copper particles. Since CuO is more stable than Cu ₂ O, it is less likely to react with surface treatment agents such as fatty acids, and more difficult to dissolve than Cu ₂ O. Therefore, the metallic copper contained in a core part becomes difficult to be exposed to the external system of copper particle. As a result, it becomes difficult for copper particles to reaggregate.

It is preferable that the content rate of oxygen in the copper particle of this invention is 0.8 mass% or more and 1.80 mass% or less, provided that it satisfy | fills the relationship of said Formula (1), and it is 0.8 mass% or more and 1.6 mass% or less further. 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 ratio of oxygen is in this range, it becomes difficult for copper particles to reaggregate 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, the condition that satisfies the relationship of formula (1), the copper particles of the present invention, 20㎚ than 60 preferably less than the crystallite size of the Cu ₂ O 15㎚ 60㎚, and contained in the copper oxide layer It is more preferable that it is 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 Cu ₂ O is in this range, it becomes difficult for the copper particles to reaggregate after the surface treatment in the commercialization step. The crystallite size of Cu ₂ O is calculated by the Scherrer equation from the diffraction peaks obtained by powder X-ray diffraction. The measurement by powder X-ray diffraction can be performed by the method as described in the Example mentioned later.

In order to make the copper particle of this invention satisfy | fill the conditions of Formula (1), you may manufacture copper particle by the method mentioned later, for example.

In the above description, although reference may be made to the crystallite size of the Cu ₂ O in the copper particles of the present invention, in the copper particles of the invention in addition to the crystallite size and the crystallite size D _C of the metal copper it contained in the core portion is It is preferable that they are 0.060 micrometer or more and 0.090 micrometer or less, It is more preferable that they are 0.065 micrometer or more and 0.085 micrometer or less, It is further more preferable that they are 0.070 micrometer or more and 0.085 micrometer or less. When the crystallite size D _C of the metallic copper is in this range, the crystallite size of Cu ₂ O can be increased, and CuO can be uniformly generated on the outermost surface of the copper oxide layer. The crystallite size of the metal copper is calculated by the Scherrer equation from the diffraction peak obtained by powder X-ray diffraction. The measurement by powder X-ray diffraction can be performed by the method as described in the Example mentioned later.

From the viewpoint of preventing the reaggregation of the copper particles more effectively, the copper particles of the present invention are contained in the core portion with respect to the volume cumulative particle diameter D ₅₀ (µm) at a cumulative volume of 50% by volume by the laser diffraction scattering particle size distribution measurement method. of metallic copper crystallite size D _C (㎛) ratio of D _C / D over ₅₀ value of 0.10 0.40 or less is preferred, and 0.10 or more 0.30 or less of it is more preferable, and still more preferably not more than 0.20 not more than 0.30. In order to to the value of the D _C / D ₅₀ satisfies the range, for example, when manufacturing the copper particles in the following manner.

Copper particles of the present invention, includes a zero-valent copper metal and copper, monovalent copper of Cu ₂ O and CuO in the divalent copper as described above. The abundance ratio of these three in the surface of a copper particle can be measured using an X-ray photoelectron spectroscopy apparatus (XPS). According to the XPS measurement, X-ray photoelectron spectroscopy spectra of various elements can be obtained, and quantitative analysis can be performed on element components having a depth of up to about 10 nm from the surface of the copper particles. 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 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 bivalent copper is 0.30 or more and 2.50 or less, and it is further more preferable that it is 0.40 or more and 2.50 or less. 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 are controlled so as to suppress reaggregation between the copper particles. Can be set appropriately. The measurement using XPS can be performed by the method described in Examples 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 currently known, the wet reduction method, the atomization method, the physical vapor-phase growth method (PVD method), etc. are mentioned generally. Of these production methods, in order to make the content ratio of oxygen in the copper particles, crystallite sizes of Cu ₂ O and metal copper, D ₅₀ of the copper particles, and the like easily satisfy the above-mentioned range, the PVD method is employed. It is preferable to produce copper particles. Therefore, the manufacturing method of the copper particle using the 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 material powder supply device 2, a raw material powder supply path 3, a plasma flame generating unit 4, a plasma gas supply device 5, a chamber 6, and a recovery port 7. , The oxygen supply device 8, the pressure regulator 9, and the exhaust device 10 are configured.

Raw material powder containing copper element (henceforth simply called raw material powder) is introduce | transduced into the plasma flame generating part 4 from the raw material powder supply apparatus 2 through the raw material powder supply path 3. In the plasma flame generating unit 4, 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 evaporated and vaporized into copper in a gaseous state, and then discharged into the chamber 6 existing on the end side of the plasma flame. The copper in the gaseous state is cooled as it is spaced apart from the plasma flame and undergoes nucleation and grain growth, thereby producing copper particles. The resulting copper particles are exposed to the atmosphere in the chamber 6. The 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 chamber 6 is controlled by the pressure adjusting device 9 and the exhaust device 10 so as to maintain a negative pressure relative to the raw material powder supply path 3, and stably generates a plasma flame and stably feeds the raw powder into plasma. It is a structure that can be introduced into the flame generating section 4. The detail of the atmosphere in the chamber 6 is mentioned 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 generator, 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. Moreover, the shape of the particle | grains of a raw material powder is not restrict | limited, Various things, such as spherical shape, a flake shape, a plate shape, resin shape, can be used. Oxidation state of the copper element of the raw material powder is not particularly limited, for example, metal copper powder, copper powder oxide and the like can be used (e.g., CuO or Cu ₂ O) or mixtures thereof. There is no restriction | limiting in particular also in the manufacturing method of a raw material powder.

In the present 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.

It is preferable to use a mixed gas of argon and nitrogen as the plasma gas generating the plasma flame. 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 metal copper) suitable for achieving the effect of the present invention. Can be. 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 to be thick and long in a laminar flow state. The term "approximately spherical shape" is not a perfect spherical shape but refers to a shape recognizable as a sphere. Whether the plasma flame is in the 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 in which the width of the plasma flame is observed to be the thickest. If the ratio of the length of the plasma flame to the width of the plasma flame is 3 or more, it can be judged to be a laminar flow state, and if the ratio of the length of the plasma flame to the width of the plasma flame is less than 3, it can be determined to be 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, and more preferably 5 L / min or more and 30 L / min or less at room temperature. By employing the gas flow rate in this range, the produced particles come into contact with the oxygen-containing atmosphere in the chamber 6, which will be described later, while maintaining an appropriate temperature. As a result, a layer of copper oxide containing CuO and Cu ₂ O for the purpose, can be formed favorably on the surface of the core. It is preferable that it is 2 kW or more and 50 kW or less, and, as for the plasma output of a thermal plasma generator, it is more preferable that they are 5 kW or more and 35 kW or less. From the same point of view, the ratio of the flow rate (L / min) 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. The copper in the gaseous state is exposed to an oxygen-containing atmosphere in the course of cooling to produce copper particles, thereby containing Cu ₂ O having high crystallinity on the surface of the core part while maintaining the content ratio of oxygen in the copper particles in the above-described range. This is because the copper oxide layer can be formed. At this time, by setting the generated core part at an appropriate temperature, the copper oxide layer containing Cu ₂ O with high crystallinity can be easily formed. As described above, the temperature can be controlled by adjusting the gas flow rate of the plasma gas or by adjusting the flow rate of oxygen supplied into the chamber 6 (which will be described later). 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, as other gas, various inert gases including argon and nitrogen can be used, for example. In addition, in the embodiment shown in FIG. 1, although the oxygen supply apparatus 8 is connected to the side surface of the chamber, and oxygen is supplied in the chamber, the connection position of the oxygen supply apparatus can supply oxygen to the chamber 6 stably. The position is not particularly limited.

From the viewpoint of stably exposing the copper particles generated from the copper in the gaseous state 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 it is more than 0.70 L / min. From the viewpoint of forming a copper oxide layer containing Cu ₂ O having high crystallinity, the oxygen concentration in the chamber is preferably 100 ppm or more and 2000 ppm or less, and more preferably 200 ppm or more and 1000 ppm or less.

<Step 2. Oxidation treatment>

It is preferable that the copper particle produced | generated at said <process 1> is further oxidized. By carrying out this step, Cu ₂ O on the surface of the copper particles which were not reacted in <Step 1> is gently oxidized with CuO, and a copper oxide layer containing Cu ₂ O and CuO is formed thicker and without gaps throughout the surface. The copper particle which can be made to be hard to reaggregate further after surface treatment can be obtained.

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

When this step is performed while leaving the copper particles in an air atmosphere, a sudden oxidation reaction of the copper particles does not occur, and the copper oxide layer can be generated. However, from the viewpoint of industrial productivity, it is preferable to place the produced copper particles in an atmospheric atmosphere while pulverizing the aggregated particles using a sieve or the like.

In view of the uniformity of the oxidation treatment of the copper particles, in this step, it is preferable to place the copper particles under an atmospheric atmosphere having a relative humidity of 30% or more and 60% or less and a temperature of 15 ° C or more and 30 ° C or less. By performing the oxidation reaction under these conditions, Cu ₂ O of the copper oxide layer can be gently oxidized to CuO by moisture contained in the atmospheric atmosphere, and a stable copper oxide layer can be formed on the surface.

Moreover, it is preferable that the processing time of this process is 5 minutes or more and 60 minutes or less on the conditions that the conditions of an atmospheric atmosphere are in the above-mentioned range from a viewpoint of preventing the rapid oxidation reaction at the time of collect | recovering a copper particle, It is more preferable that they are 5 minutes or more and 30 minutes or less.

By the above manufacturing method, the copper particle of this invention can be manufactured smoothly. Thus, the obtained copper particle is sealed in the container of a non-moisture-proof material for the purpose of maintaining the oxidation state of the surface of a copper particle, and it is preferable to store it at the temperature below room temperature (25 degreeC).

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

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to this embodiment. Unless otherwise stated, "%" means "mass%."

EXAMPLE 1

Under the following manufacturing conditions, the above-mentioned <step 1> and <step 2> were performed, and copper particle was manufactured.

<Step 1>

Copper particles (particle size D ₅₀ : 12 μm, particle shape: spherical shape) to be raw material powders produced by the atomizing method were 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 copper of a gaseous state. As a condition for plasma flame generation, a mixture gas of argon and nitrogen was used as the plasma gas, and the flow rate of plasma gas was 19.0 L / min, and the flow rate (L / min) ratio of argon and nitrogen in the plasma gas was 82:18. The plasma output was set to 19 Hz.

While the copper in the gaseous state was produced in the chamber by cooling the copper particles, the copper particles were exposed to an oxygen-containing atmosphere, and copper particles having a core portion and a copper oxide layer were formed. The flow rate of the oxygen-nitrogen mixed gas (containing 5% by volume 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. Thereafter, the generation of plasma flame is stopped while copper particles are present in the chamber, and nitrogen gas is supplied at a flow rate of 30 L / min into the chamber at a negative pressure (−0.05 MPa), and the atmospheric pressure takes 15 minutes from the negative pressure. Returned to.

<Step 2>

After performing <Step 1>, copper particle was collect | recovered. The copper oxide was produced on the surface of the copper particle while disintegrating the particle by a sieve in an atmospheric atmosphere having a relative humidity of 50% and a temperature of 25 ° C. The time to place in an atmospheric atmosphere was 30 minutes.

After 2-propanol was added so that the obtained copper particle might be 30 mass%, 5 mass% of lauric acid was added with respect to the copper particle as a dispersing agent, and the slurry was prepared. This slurry was pulverized (disintegration condition: 50 MPa, 5 passes) by Nanomizer mark II (wet disintegrating apparatus, product name: NM2-2000AR made from Kikai Kogyo Co., Ltd.). The pulverized slurry was filtered through a filter having an eye size of 1 μm (ROK TECHNO Co., LTD. Product name: SBP010), the supernatant of the filtrate was removed, and the remaining solid was 40 ° C. in a vacuum dryer (ADVANTEC). Dried in. Thereafter, in a nitrogen atmosphere, sifting was performed using a sieve having an eye size of 150 µm to obtain copper particles.

EXAMPLE 2

The same operation as in Example 1 was carried out except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.29 L / min (the oxygen flow rate was 0.0145 L / min) and the oxygen concentration in the chamber was 640 ppm. Copper particles were produced.

EXAMPLE 3

The same operation as in Example 1 was carried out 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

The same operation as in Example 1 was carried out except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.34 L / min (the oxygen flow rate was 0.017 L / min) and the oxygen concentration in the chamber was 750 ppm. Copper particles were produced.

[Example 5]

The same operation as in Example 1 was carried out except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.09 L / min (the oxygen flow rate was 0.0045 L / min) and the oxygen concentration in the chamber was 200 ppm. Copper particles were produced.

EXAMPLE 6

The same operation as in Example 1 was carried out 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. Copper particles were produced.

EXAMPLE 7

The same operation as in Example 1 was carried out except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.33 L / min (the oxygen flow rate was 0.0165 L / min) and the oxygen concentration in the chamber was 730 ppm. Copper particles were produced.

EXAMPLE 8

The same operation as in Example 1 was carried out 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. Copper particles were produced.

EXAMPLE 9

The same operation as in Example 1 was carried out except that the flow rate of the oxygen-nitrogen mixed gas into the chamber was 0.26 L / min (the oxygen flow rate was 0.013 L / min) and the oxygen concentration in the chamber was 570 ppm. Copper particles were produced.

EXAMPLE 10

The same operation as in Example 1 was carried out 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. Copper particles were produced.

[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 oxygen flow rate was 0.037 L / min), and the oxygen concentration in the chamber was 860 ppm. Copper particles were produced in the same manner as in Example 1 except for the above.

[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 oxygen flow rate was 0.0175 L / min), and the oxygen concentration in the chamber was 410 ppm. Copper particles were produced in the same manner as in Example 1 except for the above.

(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 oxygen flow rate was 0.0395 L / min), and the oxygen concentration in the chamber was 910 ppm. Copper particles were produced in the same manner as in Example 1 except for the above.

(Comparative Example 4)

A copper particle was produced in the same manner as in Example 1 except that the flow rate of the plasma gas was 36 L / min and no oxygen-nitrogen mixed gas was introduced into the chamber.

(Comparative Example 5)

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 0.44 L / min (the oxygen flow rate was 0.022 L / min), and the oxygen concentration in the chamber was 510 ppm. And copper particle | grains were manufactured similarly to Example 1 except having not performed <process 2>.

〔evaluation〕

Carried out on examples and comparative copper particles obtained in Examples were measured for a crystallite size in a content ratio of the oxygen and Cu ₂ O in the following manner. Then, the content of the oxygen in the copper particles (unit: mass%) as X a, and the crystallite size of the Cu ₂ O is contained in the copper oxide layer: When called (in ㎚) Y, in the respective examples and comparative examples In the above, it was confirmed whether or not the relationship of formula (1) was satisfied. The results are shown in Table 1. In addition, graphing the relationship between X and Y is shown in FIG.

In addition, with respect to the copper particles obtained in Examples and Comparative Examples were measured in the volume cumulative particle diameter D and a crystallite size D _C of _50, and metallic copper by the following method. Then, the calculated values of _C D / D ₅₀ by dividing the crystallite size D _C of the metallic copper, the volume cumulative particle diameter D ₅₀ of the 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 the copper of each valence was measured by the following method by XPS. The results are shown in Table 1.

In addition, in order to evaluate 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 a copper particle were measured with the following method. Their results are shown in Table 1.

[Measurement method of oxygen content rate]

The oxygen and nitrogen analyzer TC-500 made from LECO Japan Altitude Company was used. 0.05 g of the measurement sample is weighed and placed in a nickel capsule, followed by heating in a graphite crucible. At the time of heating, carbon monoxide and carbon dioxide produced by reacting oxygen in the sample with the crucible were detected by an infrared absorption method to calculate the oxygen content ratio (mass%).

[Measurement of the crystallite size of Cu ₂ O]

The crystallite size of Cu ₂ O contained in the copper oxide layer of the copper particles is determined by using a KKα1 line in SmartLab, manufactured by Rigaku Corporation, to measure the X-ray diffraction intensity of the copper particles in the measurement range 2θ = 20 ° to 100 °. from X-ray diffraction peak of the integral width of the crystal plane (111) of the Cu ₂ O, as measured, it was calculated by the Scherer equation.

Scherrer's equation: D = Kλ / βcosθ

D: crystallite size

K: Scherrer constant (1.333)

λ: wavelength of X-ray

β: integral width [rad]

θ: diffraction angle

[Measurement of Volume Cumulative Particle Size D ₅₀ of Copper Particles]

After 0.1 g of the sample of polyoxyethylene (10) octylphenyl ether (manufactured by Wako Junyaku Kogyo Co., Ltd.) at 0.1% concentration was added dropwise with a dropper to become familiar, anionic surfactants (Sannofuco It was mixed with 80 ml of 0.1% aqueous solution of the product name: SN Dispersant 5468 by the company, and it disperse | distributed for 5 minutes in the ultrasonic homogenizer (US-300T by Nippon Seiki Seisakusho). Thereafter, the volume cumulative particle diameter D ₅₀ was measured using a laser diffraction scattering particle size distribution analyzer and a microtrack HRA manufactured by Microtrack Bell Co., Ltd.

[Measurement of Crystalline Size of Metallic Copper]

The crystallite size of the metallic copper contained in the core part of the copper particle measured the X-ray diffraction intensity of the copper particle in the measurement range 2θ = 20 ° to 100 ° using CuKα1 line in SmartLab manufactured by Rigaku Corporation. From the integral width of the X-ray-diffraction peak in the crystal surface 200 of the metallic copper at the time, it computed by the following Scherrer formula.

Scherrer's equation: D = Kλ / βcosθ

D: crystallite size

K: Scherrer constant (1.333)

λ: wavelength of X-ray

β: integral width [rad]

θ: diffraction angle

[Measurement of abundance ratio of copper of each valence by XPS]

VersaProbe II manufactured by Albak Pi Co., Ltd. was used. Measurement conditions are as follows.

X-ray source: Mg-Kα (1253.6 eV)

Condition of X-ray source: 400 W

Pass Energy: 23eV

Energy Step: 0.1eV

Detector and sample stand angle: 90 °

Charge neutralization: using slow ions and electrons

The analysis used the analysis software of MultiPak 9.0 by Albakk Pie Co., Ltd. The peak separation is a peak appearing at 930 eV or more and 940 eV or less, using the curve fit of MultiPak 9.0, and the main peak of Cu 2p3 / 2. The background mode used is Shirley. The charge correction made the binding energy of C1s 2323 eV.

The peak areas P0, P1 and P2 described above were subjected to waveform separation of Cu 2p3 / 2 peaks in the range of Cu (930.0 eV or more and 933.0 eV or less for Cu (I)) and were calculated from the peak area ratios.

[Recovery rate of copper particles by filter filtration]

At the time of manufacture of the copper particle obtained by each Example and the comparative example, the filter of 1 micrometer of eye size after filtering the slurry containing copper particle is dried at 40 degreeC with a vacuum dryer (made by ADVANTEC), and it remains on a filter. The mass of one copper particle and a 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 copper particles remaining on the filter and the mass of the produced copper particles (mass of manufactured copper particles / (of copper particles remaining on the filter) Mass + mass of produced copper particles) x 100) was calculated, and the value was referred to as a recovery rate (%). The case where the recovery rate was 60% or more was called "(circle)", and the case where the recovery rate was less than 60% was called "x".

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

10 g of copper particles obtained in each Example and Comparative Example, and 1.5 g of tapineol (manufactured by Yashara Chemical Co., Ltd.) vehicle containing 10% by mass of thermoplastic cellulose ether (product name: ETHOCEL STD100 manufactured by The Dow Chemical Company) After weighing and preliminarily kneading with a spatula, using a rotating / revolving vacuum mixer ARE-500 manufactured by Sinkie Co., Ltd., the stirring mode (1000 rpm x 1 minute) and the defoaming mode (2000 rpm x 30 seconds) were used as one cycle. The treatment was carried out for two cycles to form a paste. This paste was further processed 5 times in total using a triaxial roll mill, and dispersion | distribution mixing was further performed and the paste was prepared. The paste thus prepared was applied onto the slide glass substrate by setting the gap to 35 μm using a doctor blade. Then, it heated and dried at 150 degreeC for 10 minutes using the nitrogen oven, and produced the coating film. About this coating film, surface roughness was measured using the surface roughness meter (SURFCOM 480B-12 by TOKYO SEIMITSU).

As is clear from the results shown in Table 1, it can be seen that the copper particles of the comparative examples have a low filter recovery rate, while the copper particles of each example have a high filter recovery rate. This reason is because the copper particle of an Example suppressed 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 high recovery rate is equivalent to the surface roughness of the coating film obtained from the copper particle of the comparative example, although the filter recovery rate was increased. This reason is also because the copper particle of an Example suppressed aggregation of particle | grains.

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

Claims (6)

Copper particle which has a core part containing copper and a copper oxide layer containing CuO and Cu ₂ O formed on the surface of this core part, and satisfy | fills the relationship of following formula (1).

In the formula, X is the content ratio (mass%) of oxygen contained in the copper particles, Y is a crystallite size (㎚) of Cu ₂ O contained in the copper oxide layer. The crystallite size D _C of the metal copper contained in the said core part with respect to the volume cumulative particle diameter D50 (micrometer) in ₅₀ volume% of cumulative volume by a laser diffraction scattering particle size distribution measuring method of Claim 1 the ratio of D _C / D ₅₀ value of 0.10 or more 0.40 or less, the copper particles. The copper particle of Claim 1 or 2 whose content rate of oxygen is 0.80 mass% or more and 1.80 mass% or less. The X-ray photoelectron spectroscopy spectrum obtained by measuring the surface of the said copper particle WHEREIN: The peak area P1 of Cu (I) and the peak area P0 of Cu (0) in any one of Claims 1-3. The copper particle whose value of P2 / (P1 + P0) which is the ratio of the peak area P2 of Cu (II) is 0.30 or more and 2.50 or less. Raw powder containing elemental copper is introduced into the plasma flame to make copper in the gas phase,
The copper particles produced are exposed to an oxygen-containing atmosphere while the copper particles are produced by cooling the copper in the gaseous state.
The method of after exposure to an oxygen-containing atmosphere having a process to produce a copper oxide layer by oxidizing the surface containing CuO and Cu ₂ O on the copper particles, copper particles. The said copper particle after exposure to an oxygen containing atmosphere is set to 5 minutes or more and 60 minutes or less in the atmospheric atmosphere whose relative humidity is 30% or more and 60% or less, and 15 degreeC or more and 30 degrees C or less, The said copper particle The surface of the particle is oxidized to produce the copper oxide layer.

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