JP2004256857A - Copper fine particles and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide copper fine particles containing few agglomerated particles, which specifically have an average primary particle diameter (D) measured with an electron microscope in the range of 0.05 to 1.0 μm, an average secondary particle diameter (d) measured with a laser diffraction type particle size distribution measurement instrument in the range of 0.1 to 2.0 μm, and d/D in a range of 1 to 3. <P>SOLUTION: This method for manufacturing the copper fine particles comprises reacting copper oxide with a reducing agent such as hydrazine, in a medium which contains a sulfur compound such as mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol and cysteine, and a protective colloid such as gelatin, gum arabic, polyvinyl alcohol, polyvinylpyrrolidone, and polyethylene glycol. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２７】
評価２：粒子形状の確認
実施例１〜４、比較例１、２で得られた試料Ａ〜Ｆを１８０００倍で電子顕微鏡写真を撮影した。その結果を図１〜６に示す。本発明により得られた銅微粒子は、真球にほぼ近似した整った粒子形状を有することが判る。
【００２８】
【発明の効果】
本発明により、分散性に優れ凝集粒子をほとんど含まず、真球状に近似した整った粒子形状の銅微粒子が得られる。このものは、電子機器の電極材料等として有用であり、この銅微粒子を銅ペーストにして、例えば、積層セラミックスコンデンサーの内部電極、プリント配線基板の回路、その他の電極等に用いると、薄膜で高密度の電極等が得られる。
【図面の簡単な説明】
【図１】図１は実施例１で得られた銅微粒子（試料Ａ）の電子顕微鏡写真（倍率１８０００倍）である。
【図２】図２は実施例２で得られた銅微粒子（試料Ｂ）の電子顕微鏡写真（倍率１８０００倍）である。
【図３】図３は実施例３で得られた銅微粒子（試料Ｃ）の電子顕微鏡写真（倍率１８０００倍）である。
【図４】図４は実施例４で得られた銅微粒子（試料Ｄ）の電子顕微鏡写真（倍率１８０００倍）である。
【図５】図５は比較例１で得られた銅微粒子（試料Ｅ）の電子顕微鏡写真（倍率１８０００倍）である。
【図６】図６は比較例２で得られた銅微粒子（試料Ｆ）の電子顕微鏡写真（倍率１８０００倍）である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to copper fine particles and a method for producing the same, and more particularly to copper fine particles suitable for an internal electrode of a multilayer ceramic capacitor and a method for producing the same.
[0002]
[Prior art]
Copper fine particles are inexpensive materials with good electrical conductivity, and are widely used as materials to ensure electrical continuity of printed circuit board circuit forming members, various electrical contact members, external electrode members such as capacitors, etc. It has been. In recent years, it has begun to be used for internal electrodes of multilayer ceramic capacitors. Multilayer ceramic capacitors are rapidly spreading because they are easy to obtain a large capacity compared to other types of capacitors such as electrolytic capacitors and film capacitors, are excellent in mountability, and have high safety and stability. With the recent miniaturization of electronic equipment, multilayer ceramic capacitors are also in the direction of miniaturization, but in order to maintain a large capacity, it is necessary to miniaturize without reducing the number of laminated ceramic sheets. However, since there is a limit to thinning the sheet, the miniaturization of the multilayer ceramic capacitor is realized by thinning the internal electrode using fine metal particles such as palladium, nickel and copper.
[0003]
As a method for producing such copper fine particles, a method of reducing copper oxide with a hydrazine-based reducing agent in an aqueous medium containing a protective colloid such as gum arabic (see, for example, Patent Document 1), or a pH of 12 or more. There is known a method of reducing cuprous oxide with a hydrazine reducing agent at a temperature of 50 ° C. or higher after reducing copper hydroxide with reducing sugar to produce cuprous oxide (see, for example, Patent Document 2).
[0004]
[Patent Document 1]
Japanese Patent Publication No. 61-55562 [Patent Document 2]
Japanese Patent No. 2638271
[Problems to be solved by the invention]
The copper fine particles obtained by the above method are mixed with a binder such as an epoxy resin to form a paste or paint, and this copper paste / paint is, for example, a printed wiring board, after screen printing on a substrate, In the case of a multilayer ceramic capacitor, it is applied onto a thin ceramic sheet, the sheets are laminated, and then heated and fired to form an electric circuit, an electrode, and the like. In order to ensure electrical continuity, it is necessary that the obtained electric circuit and electrode have a high density with few defects. For this reason, it is preferable to use copper fine particles that have good filling properties in pastes and paints. If the particles have an ordered particle shape close to a true sphere and contain almost no aggregated particles, the bulk density is small and the dispersibility is low. Therefore, the filling property to paste and paint is improved, and high conductivity can be obtained even if the layer is made thin like the internal electrode of the multilayer ceramic capacitor. However, although the above-mentioned prior art method can obtain fine primary particles, the particles are generated in a significantly aggregated state, and the shape of the secondary particles is agglomerated, so that the filling property and dispersibility are insufficient. Therefore, it is difficult to obtain sufficient characteristics for internal electrodes. Therefore, the present invention overcomes the above-mentioned problems of the prior art, and provides copper fine particles having almost no aggregated particles, excellent dispersibility, and a well-shaped particle shape, and a method for producing the same.
[0006]
[Means for Solving the Problems]
As a result of earnest research to solve these problems, the present inventor made a protective colloid and a sulfur compound exist in a method of producing copper fine particles by reacting copper oxide and a reducing agent, By carrying out the above reaction, it was found that fine copper particles having excellent dispersibility and almost no aggregated particles and having a substantially spherical shape were obtained, and the present invention was completed.
[0007]
That is, the present invention is a method for producing copper fine particles characterized by reacting a copper oxide and a reducing agent in the presence of a sulfur compound and a protective colloid. Moreover, the average primary particle diameter (D) measured with the electron microscope obtained by this method is in the range of 0.05 to 1.0 μm, and the average secondary particle diameter (measured with a laser diffraction particle size distribution analyzer) ( d) is in the range of 0.1 to 2.0 μm, and d / D is in the range of 1 to 3.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, copper oxide and a reducing agent are reacted in the presence of a sulfur compound and a protective colloid to produce copper fine particles. According to the present invention, copper particles having almost no agglomerated particles and excellent dispersibility and a uniform particle shape can be obtained because the sulfur compound suppresses the reaction rate between the copper oxide and the reducing agent, and the copper particles gradually It is presumed that it is generated. Therefore, when a sulfur compound is not used, the reaction ends instantaneously and copper agglomerated particles are generated.
[0009]
The reaction is carried out in a medium, for example, in an aqueous medium or an organic solvent medium such as alcohol, preferably in an aqueous medium. If a sulfur compound and a protective colloid are present during the reaction between the copper oxide and the reducing agent, the order of addition of the respective raw materials is not limited. For example, copper oxide is added to the liquid medium containing the sulfur compound and the protective colloid. However, it is preferable to add a reducing agent to a liquid medium containing a sulfur compound, a protective colloid, and a copper oxide because the reaction can be easily controlled. The reaction temperature is preferably in the range of 10 ° C. to the boiling point of the liquid medium used, since the reaction is easy to proceed, and more preferably in the range of 40 to 95 ° C. It is preferable to adjust the pH of the reaction solution in the range of 3 to 12 in advance with an acid or an alkali, since the precipitation of copper oxide can be prevented and the reaction can be performed uniformly.
[0010]
The “copper oxide” of the present invention is used in the sense of including a copper hydrated oxide and a copper hydroxide in addition to a normal copper oxide. As the copper oxide, cuprous oxide ( Alternatively, cuprous oxide), copper oxide (or cupric oxide), or the like can be used. There is no particular limitation on the method for producing the oxide, and for example, an electrolytically produced method, a chemical conversion method, a heat oxidation method, a thermal decomposition method, an indirect wet method, or the like can be used. Since it is considered that the particle diameter is related to the particle diameter of the copper fine particles to be generated, the copper oxide particle diameter can be appropriately set to obtain copper fine particles having a target particle diameter. .
[0011]
The “sulfur compound” of the present invention includes thiones, thiocarbonates, thioureas, in addition to thiol compounds and derivatives thereof, which are organic compounds RSH (R is a hydrocarbon group such as an alkyl group) having a mercapto group —SH. And sulfur compounds such as hydrogen sulfide and derivatives thereof, such as mercaptopropionic acid, mercaptoacetic acid, thiodipropionic acid, mercaptosuccinic acid, thioacetic acid thiols, methyl mercaptan, Aliphatic thiols such as ethyl mercaptan, propyl mercaptan, isopropyl mercaptan, n-butyl mercaptan, allyl mercaptan, dimethyl mercaptan, mercaptoethanol, aminoethyl mercaptan, thiodiethylamine, cysteine, alicyclic thiols such as cyclohexylthiol, thiophene Thiols such as aromatic thiols such as thiols, thioglycols such as thiodiethylene glycol, thiodiglycolic acid, ethylenethioglycol, thioamides such as thioformamide, dithiols, thiones, polythiols, thiocarbonates, Examples thereof include sulfur compounds such as thioureas and hydrogen sulfide, and derivatives thereof, and one or more of these may be used. Among them, mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol, and cysteine are preferable because of their high effects. The amount of the sulfur compound used can be appropriately set. At least, it is preferably set in the range of 0.5 to 50 parts by weight with respect to 1000 parts by weight of the copper oxide because the effects of the present invention can be easily obtained. A range of parts by weight is more preferred.
[0012]
The protective colloid acts as a dispersion stabilizer for the produced copper fine particles. When the amount used is in the range of 1 to 100 parts by weight with respect to 100 parts by weight of the copper oxide, the produced copper fine particles are dispersed and stabilized. Since it is easy, it is preferable, and the range of 2-50 weight part is further more preferable. In the present invention, known colloids can be used, such as gelatin, gum arabic, casein, sodium caseinate, ammonium caseinate, and other natural polymers such as starch, dextrin, agar, sodium alginate, and the like. , Celluloses such as hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, vinyls such as polyvinyl alcohol and polyvinylpyrrolidone, acrylic acids such as sodium polyacrylate and ammonium polyacrylate, higher fatty acids such as stearic acid, polyethylene glycol, etc. Synthetic polymers, polyvalent carboxylic acids such as citric acid, aniline or derivatives thereof, and the like may be used alone or in combination. Since the protective colloid of a polymer has a high effect of dispersion stabilization, it is preferable to use this, and when reacting in an aqueous medium, it is preferable to use a water-soluble one, particularly gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, Polyethylene glycol is preferred.
[0013]
The amount of the reducing agent used can be appropriately set as long as it is an amount capable of producing copper fine particles from the copper oxide, and is in the range of 0.2 to 5 mol with respect to 1 mol of copper contained in the copper oxide. Is preferred. If the reducing agent is less than the above range, the reaction is difficult to proceed, and copper fine particles are not sufficiently formed. If the amount is more than the above range, the reaction proceeds excessively and it is difficult to obtain desired copper fine particles, which is not preferable. Furthermore, the usage-amount of a preferable reducing agent is the range of 0.3-2 mol. As the reducing agent, known ones can be used. For example, hydrazine reducing agents such as hydrazine, hydrazine hydrochloride, hydrazine sulfate, hydrazine hydrate and the like, sodium borohydride, sodium sulfite, sodium bisulfite, thiol Sodium sulfate, sodium nitrite, sodium hyponitrite, phosphorous acid and metal salts thereof such as sodium phosphite, metal salts such as hypophosphorous acid and sodium hypophosphite, aldehydes, alcohols, amines , Saccharides and the like, and one or more of these may be used. In particular, hydrazine-based reducing agents are preferred because of their strong reducing power.
[0014]
In the present invention, the primary particle diameter can be controlled by controlling the particle diameter, reduction rate, reduction temperature, and the like of the copper oxide used. For example, the average particle diameter of the primary particles is 0.05 to 1.0 μm. The range can be fine. Moreover, the secondary particle diameter can be controlled by appropriately setting the type and amount of the sulfur compound and protective colloid, and the average particle diameter of the secondary particles is preferably in the range of 0.1 to 2.0 μm. Can be in the range of 0.1 to 1.0 μm.
[0015]
After the copper fine particles are formed, they are filtered, washed and dried by ordinary methods. Drying is preferably performed in an atmosphere of an inert gas such as nitrogen or argon so that the copper fine particles are not oxidized. After drying, you may grind | pulverize as needed.
[0016]
The copper fine particles obtained by the present invention contain almost no agglomerated particles and have a fine shape with almost perfect spheres. Aggregated particles are secondary particles in which primary particles of copper fine particles are aggregated and aggregated. The copper fine particles have an average primary particle diameter (D) in the range of 0.05 to 1.0 μm and an average secondary particle diameter (d) in the range of 0.1 to 2.0 μm, preferably 0.1 to 0.1 μm. It is in the range of 1.0 μm. The average particle diameter (D) of the primary particles is expressed as a cumulative 50% diameter measured by electron microscopy, and the average particle diameter (d) of the secondary particles is expressed as a cumulative 50% diameter measured by the laser scattering method. The The smaller the ratio of the average particle diameter (d) of the secondary particles to the average particle diameter (D) of the primary particles, the smaller the aggregated particles, and the d / D is preferably in the range of 1 to 3, The range is more preferable, and the range of 1 to 1.5 is more preferable. Moreover, the preferable copper fine particle of this invention has the regular particle shape approximated in the perfect spherical shape, and such a particle shape can be observed with an electron microscope.
[0017]
The copper fine particles of the present invention can be used for various conventional applications. In particular, the copper fine particles are useful as an electrode material for electronic equipment, and the copper fine particles are mixed with a resin such as an epoxy resin to obtain a copper paste or When a copper paint is used, for example, for an internal electrode of a multilayer ceramic capacitor, a circuit of a printed wiring board, other electrodes, etc., a thin film and a high density electrode can be obtained.
[0018]
【Example】
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
[0019]
Example 1
30 g of industrial cuprous oxide (NC-102: manufactured by NC Tech), 0.085 g of 3-mercaptopropionic acid as a sulfur compound and 5 g of gelatin as a protective colloid are added to 400 ml of pure water, mixed, and 10% sulfuric acid Was used to adjust the pH of the mixture to 7, and the temperature was raised from room temperature to 90 ° C. over 20 minutes. After the temperature rise, 80% hydrazine monohydrate was added with stirring and reacted with cuprous oxide over 2 hours to produce copper fine particles. Thereafter, the filtrate was washed by filtration until the filtrate specific resistance reached 100 μS / cm or less, and dried for 10 hours at a temperature of 60 ° C. in an atmosphere of nitrogen gas to obtain the copper fine particles (sample A) of the present invention.
[0020]
Example 2
Example 1 except that the amount of 3-mercaptopropionic acid used was 0.065 g, the amount of gelatin used was 1.5 g, and the pH of the mixed solution was adjusted to 10.5 using 15% aqueous ammonia. Thus, copper fine particles (sample B) of the present invention were obtained.
[0021]
Example 3
The same procedure as in Example 1 was conducted except that the amount of 3-mercaptopropionic acid used was 0.085 g, the amount of gelatin used was 3 g, and the pH of the mixed solution was adjusted to 11.8 using 15% aqueous ammonia. Copper fine particles (sample C) of the present invention were obtained.
[0022]
Example 4
24 g of industrial copper oxide (N-120: manufactured by NC Tech), 0.065 g of 3-mercaptopropionic acid as a sulfur compound, and 3.8 g of gelatin as a protective colloid are added to 400 ml of pure water, mixed, and 10% After adjusting the pH of the mixed solution to 4 using sulfuric acid, the temperature was raised from room temperature to 90 ° C. over 20 minutes. After the temperature rise, 80% hydrazine monohydrate was added with stirring and reacted with copper oxide over 2 hours to produce copper fine particles. Thereafter, the filtrate was washed by filtration until the filtrate specific resistance was 100 μS / cm or less, and dried for 10 hours at a temperature of 60 ° C. in an atmosphere of nitrogen gas to obtain the copper fine particles (sample D) of the present invention.
[0023]
Comparative Example 1
Copper fine particles (sample E) were obtained in the same manner as in Example 2 except that 3-mercaptopropionic acid was not used.
[0024]
Comparative Example 2
Copper fine particles (sample F) were obtained in the same manner as in Example 4 except that 3-mercaptopropionic acid was not used.
[0025]
Evaluation 1: Measurement of average particle diameter and tap density of primary particles and secondary particles The average particle diameter of primary particles of Samples A to F obtained in Examples 1 to 4 and Comparative Examples 1 and 2 was measured by electron microscopy. The average particle size of the secondary particles was measured using a laser diffraction particle size distribution analyzer (Microtrac UPA type: manufactured by Nikkiso Co., Ltd.). For the measurement of secondary particles, an aqueous slurry was used in which the sample was sufficiently dispersed in water using an ultrasonic disperser and the concentration was adjusted so that the laser signal intensity was 0.6 to 0.8.
Further, 50 g of a sample was taken into a 100 ml measuring cylinder and tapped 100 times to measure the tap density. The greater the tap density, the better the fillability. The results are shown in Table 1. It can be seen that the copper fine particles obtained from the present invention are fine in primary particles and secondary particles, and have excellent filling properties.
[0026]
[Table 1]

[0027]
Evaluation 2: Confirmation of particle shape Electron micrographs were taken at 18000 times the samples A to F obtained in Examples 1 to 4 and Comparative Examples 1 and 2. The results are shown in FIGS. It can be seen that the copper fine particles obtained by the present invention have a well-defined particle shape that is approximately approximate to a true sphere.
[0028]
【The invention's effect】
According to the present invention, it is possible to obtain copper fine particles having excellent dispersibility and containing almost no agglomerated particles and having a well-shaped particle shape close to a true sphere. This is useful as an electrode material for electronic equipment, etc. The copper fine particles are made into a copper paste, and are used in, for example, an internal electrode of a multilayer ceramic capacitor, a circuit of a printed wiring board, and other electrodes. Density electrodes and the like are obtained.
[Brief description of the drawings]
1 is an electron micrograph (magnification: 18000 times) of the copper fine particles (sample A) obtained in Example 1. FIG.
FIG. 2 is an electron micrograph (magnification: 18000 times) of the copper fine particles (sample B) obtained in Example 2.
FIG. 3 is an electron micrograph (magnification: 18000 times) of the copper fine particles (sample C) obtained in Example 3.
FIG. 4 is an electron micrograph (magnification: 18000 times) of the copper fine particles (sample D) obtained in Example 4.
FIG. 5 is an electron micrograph (magnification: 18000 times) of the copper fine particles (sample E) obtained in Comparative Example 1.
6 is an electron micrograph (magnification: 18000 times) of the copper fine particles (sample F) obtained in Comparative Example 2. FIG.

Claims (5)

A method for producing copper fine particles, comprising reacting a copper oxide and a reducing agent in the presence of a sulfur compound and a protective colloid. The method for producing copper fine particles according to claim 1, wherein the sulfur compound is at least one selected from mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol, and cysteine. 2. The method for producing copper fine particles according to claim 1, wherein a sulfur compound in a range of 0.5 to 50 parts by weight is used with respect to 1000 parts by weight of the copper oxide. The method for producing copper fine particles according to claim 1, wherein the reducing agent is a hydrazine-based reducing agent. Copper fine particles obtained by the production method according to any one of claims 1 to 4, wherein the average primary particle diameter (D) measured with an electron microscope is in the range of 0.05 to 1.0 µm, Copper having an average secondary particle diameter (d) measured by a laser diffraction particle size distribution measuring device in the range of 0.1 to 2.0 μm and d / D in the range of 1 to 3 Fine particles.

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