【発明の詳細な説明】
【０００１】
【産業上の利用分野】本発明は、湿式法による銅微粉末
の製造方法に関し、特に粒度分布幅が狭く、良好な粒径
に制御された球状の銅微粉末を製造する方法に係る。
【０００２】
【従来の技術およびその問題点】従来、銅微粉末を得る
方法としては、種々の方法が提案されている。本発明に
関連する粒径範囲約１０μｍ以下の平均粒径を持つ銅微
粉を製造する方法としては、溶融銅を霧化させるアトマ
イズ法、陰極上への電解析出法、及び銅を機械的に粉砕
する方法等がある。しかしながら、これらの従来法はい
ずれも平均粒径が通常１０μｍ以上と大きく、製造後に
なんらかの分級操作を加えて初めて１０μｍ以下の微粉
末が得られ、それも粒度分布が広く、しかも粒径制御が
困難であるという問題がある。
【０００３】また、不活性ガス中で銅を強制蒸発させる
所謂ガス中蒸発法、プラズマ炎中に銅粗粉を吹き込んで
揮発凝集させるプラズマ炎法、水素富化ガス中でアーク
プラズマにより製造する所謂水素プラズマ法、及び銅イ
オン溶液に水素化ホウ素ナトリウムを加えて銅超微粉末
を還元析出させる方法（特開昭５８−２２４１０３）等
の従来法は、平均粒径が通常０．１μｍ以下と小さく、
嵩高で比表面積が大きくて酸化しやすく、しかも設備が
高価で量産性に乏しいという欠点がある。
【０００４】一方、銅イオンをヒドラジンあるいはヒド
ラジン化合物で還元し、金属銅として析出させることは
公知であるが（新実験化学講座８「無機化合物の合成
（１）」東京化学同人発行）、これらのヒドラジン（化
合物）による銅イオンの還元方法によると、微細な銅粉
末も得られるが、粒度分布が広く、形状も不規則であ
り、しかも粒径の制御が困難で一定品質の銅粉末が得ら
れにくいという欠点がある。
【０００５】その中で、炭酸銅の溶液からヒドラジンに
より還元析出させる方法（特公昭５９−１２７２３）で
は、球状の銅粉は得られるが、凝集のため、粒度分布が
広いという欠点がある。また、硫酸銅の溶液に界面活性
剤も添加してヒドラジンで還元析出させ、単分散させた
銅微粉を得る方法がある（特開昭６２−７７４０７
他）。しかし、界面活性剤は析出銅粉の成長を阻害する
ため、粒径の大きい銅粉を得るのは困難で、平均粒径２
μｍ以上の銅粉を得るには界面活性剤の添加量を抑える
必要があり、その結果、ある程度の凝集は避けられず、
粒度分布もかなり広くなるという欠点がある。
【０００６】本発明は、上記した従来法の問題点を解消
し、約１〜１０μｍの適度の粒径に容易に制御できると
ともに粒度分布幅が小さく、球状の銅微粉末を製造し得
る方法を提供することを目的とする。
【０００７】
【問題点を解決するための手段】本発明方法は特許請求
の範囲に規定したとおり、酢酸を含む水溶液中で懸濁状
の銅化合物をヒドラジンで還元するものであり、これに
より前記した問題点を解決したものである。
【０００８】本発明における還元反応のプロセスは、明
確には解明されていないが、本発明者らは、酢酸が一種
の界面活性剤的な働きをすると同時に、銅表面に銅錯化
合物が析出、還元することにより、球状で単分散された
銅粉末が得られるものと推測している。なお、銅粉末の
粒径は還元温度、ヒドラジン添加量等を調整し制御する
ことができる。
【０００９】銅化合物としては、酸化銅、亜酸化銅、炭
酸銅、酢酸銅、硫酸銅、硝酸銅等のいずれをも使用でき
るが、硫酸銅、硝酸銅等、強酸との塩を使用したものは
酸化銅、亜酸化銅、炭酸銅、酢酸銅を使ったものと比べ
て還元時のＰＨが低くなり、還元反応が遅くなり、粒径
が大きい銅粉となる。また、ヒドラジンとしては、抱水
ヒドラジン、無水ヒドラジン、硫酸ヒドラジン等が挙げ
られ、これらヒドラジンは酢酸を含む水溶液中に通常、
銅粉生成に必要な理論量の１〜３倍当量程度添加する。
反応は通常、４０〜９０℃の還元温度で、１〜４８時間
とする。
【００１０】かくして本発明により、粒度分布幅が小さ
く、球状の単分散された平均粒径１〜１０μｍの銅粉末
が得られる。なお、銅粉末の粒径が１μｍより小さい
と、ペーストにした時、凝集が激しくなりスクリーンの
目詰りを生じ、さらにはちくそ性が大となり、レベリン
グが悪くなって印刷面が平滑にならなくなる。逆に１０
μｍより大きくなると、緻密な膜ができず、導電回路と
して不安定になる。
【００１１】
【実施例１】水４ｌ、酢酸５００ｇに酸化銅６００ｇを
懸濁し、抱水ヒドラジン３００ｇを添加し、９０℃で４
時間反応させた。この結果、平均粒径が２．４μｍで、
粒径分布が１〜１０μｍに１００％が入る粒度分布幅の
小さい球状の銅粉末が得られた。
【００１２】
【実施例２】水４ｌ、酢酸５００ｇに酸化銅５４０ｇを
懸濁し、抱水ヒドラジン２８０ｇを添加し、９０℃で８
時間反応させた。この結果、平均粒径が２．９μｍで、
粒径分布が１〜１０μｍに１００％が入る粒度分布幅の
小さい球状の銅粉末が得られた。
【００１３】
【実施例３】水４ｌ、酢酸５００ｇに炭酸銅９３０ｇを
懸濁し、抱水ヒドラジン３００ｇを添加し、９０℃で４
時間反応させた。この結果、平均粒径が２．３μｍで、
粒径分布が１〜１０μｍに１００％が入る粒度分布幅の
小さい球状の銅粉末が得られた。
【００１４】
【実施例４】水２．５ｌ、酢酸５００ｇに硫酸銅５水和
物２ｋｇを懸濁し、抱水ヒドラジン３５０ｇを添加し、
９０℃で４８時間反応させた。この結果、平均粒径が
６．３μｍで、粒径分布が１〜１０μｍに９０％が入る
粒度分布幅の小さい球状の銅粉末が得られた。
【００１５】
【比較例１】水５ｌに硫酸銅５水和物２ｋｇを溶解し
た。次に抱水ヒドラジン３５０ｇを添加し、９０℃で４
８時間反応させた。この結果、平均粒径８．５μｍで粒
度分布が１〜１０μｍに３０％が入る粒度分布幅の大き
い銅粉末が得られた。
【００１６】
【比較例２】水４ｌに、炭酸銅１３５０ｇを懸濁し、抱
水ヒドラジン３００ｇを添加し、９０℃で４時間反応さ
せた。この結果、平均粒径が２．８μｍで、粒径分布が
１〜１０μｍに４０％が入る粒度分布幅の大きい銅粉末
が得られた。
【００１７】
【比較例３】水５ｌに硫酸銅５水和物２ｋｇを溶解し、
硫酸銅水溶液とした。この硫酸銅水溶液に界面活性剤Ｃ
10Ｈ21ＮＨＣＨ2ＣＯＯＮａを２．０ｇ添加した。次に
抱水ヒドラジン３５０ｇを添加し、９０℃で４８時間反
応させた。この結果、平均粒径２．６μｍで粒度分布が
１〜１０μｍに７０％が入る粒度分布幅の大きい銅粉末
が得られた。
【００１８】
【比較例４】水５ｌに硫酸銅５水和物２ｋｇを溶解し、
水酸化ホウ素ナトリウム１３０ｇを添加し、９０℃で４
時間反応させた。この結果、得られた銅粉の粒径は０．
１μｍ以下であった。
【００１９】
【発明の効果】以上説明したように、本発明によれば、
約１〜１０μｍの適度の粒径に容易に制御できるととも
に、生成する球状銅微粒子の粒度分布が１〜１０μｍの
範囲に９０％以上が含まれている極めて小さい球状の銅
微粉末が得られ、スクリーン印刷等をはじめとして各種
用途に広範囲に使用し得る銅微粉末が安価に製造し得
る。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing copper fine powder by a wet method, and more particularly to a method for producing spherical copper having a narrow particle size distribution width and a good particle size. The present invention relates to a method for producing fine powder. 2. Description of the Related Art Conventionally, various methods have been proposed for obtaining copper fine powder. As a method for producing copper fine powder having an average particle diameter of about 10 μm or less in the particle diameter range related to the present invention, an atomizing method for atomizing molten copper, an electrolytic deposition method on a cathode, and There is a pulverizing method and the like. However, all of these conventional methods have a large average particle size of usually 10 μm or more, and a fine powder of 10 μm or less can be obtained only by performing some classification operation after the production, which also has a wide particle size distribution and is difficult to control the particle size. There is a problem that is. Further, a so-called gas evaporation method in which copper is forcibly evaporated in an inert gas, a plasma flame method in which copper coarse powder is blown into a plasma flame to volatilize and coagulate, and a so-called arc plasma production in a hydrogen-enriched gas. Conventional methods such as a hydrogen plasma method and a method in which sodium borohydride is added to a copper ion solution to reduce and precipitate a copper ultrafine powder (JP-A-58-224103) have a small average particle diameter of usually 0.1 μm or less. ,
It is bulky, has a large specific surface area, is easily oxidized, and has the drawback of expensive equipment and poor mass productivity. [0004] On the other hand, it is known that copper ions are reduced with hydrazine or a hydrazine compound and are precipitated as metallic copper (New Experimental Chemistry Course 8 "Synthesis of Inorganic Compounds (1)" published by Tokyo Chemical Dojin). According to the method of reducing copper ions with hydrazine (compound), fine copper powder can be obtained, but the particle size distribution is wide, the shape is irregular, and it is difficult to control the particle size. There is a disadvantage that it is difficult. [0005] Among them, a method of reducing and precipitating from a copper carbonate solution with hydrazine (Japanese Patent Publication No. 59-12723) can obtain spherical copper powder, but has a disadvantage that the particle size distribution is wide due to aggregation. Further, there is a method of obtaining a monodispersed copper fine powder by adding a surfactant to a solution of copper sulfate and performing reductive precipitation with hydrazine (Japanese Patent Application Laid-Open No. Sho 62-77407).
other). However, the surfactant inhibits the growth of the precipitated copper powder, so that it is difficult to obtain a copper powder having a large particle diameter.
In order to obtain copper powder of μm or more, it is necessary to reduce the amount of surfactant added, and as a result, some aggregation is inevitable,
There is the disadvantage that the particle size distribution is also quite wide. The present invention solves the above-mentioned problems of the conventional method, and provides a method capable of easily controlling an appropriate particle size of about 1 to 10 μm, having a small particle size distribution width, and producing a spherical copper fine powder. The purpose is to provide. According to the method of the present invention, a copper compound in a suspension in an aqueous solution containing acetic acid is reduced with hydrazine, as defined in the claims. This is a solution to the problem that has been solved. Although the process of the reduction reaction in the present invention has not been clearly elucidated, the present inventors have found that while acetic acid acts as a kind of surfactant, a copper complex compound precipitates on the copper surface. It is presumed that spherical monodispersed copper powder is obtained by reduction. The particle size of the copper powder can be controlled by adjusting the reduction temperature, the amount of hydrazine added, and the like. As the copper compound, any of copper oxide, cuprous oxide, copper carbonate, copper acetate, copper sulfate, copper nitrate and the like can be used, but a compound using a salt with a strong acid such as copper sulfate and copper nitrate can be used. As compared with those using copper oxide, cuprous oxide, copper carbonate, or copper acetate, PH at the time of reduction becomes lower, the reduction reaction becomes slower, and copper powder having a large particle size is obtained. Examples of hydrazine include hydrazine hydrate, anhydrous hydrazine, hydrazine sulfate, and the like.These hydrazines are usually contained in an aqueous solution containing acetic acid.
Add about 1 to 3 equivalents of the theoretical amount required for copper powder generation.
The reaction is usually performed at a reduction temperature of 40 to 90 ° C. for 1 to 48 hours. Thus, according to the present invention, spherical monodispersed copper powder having a small particle size distribution width and an average particle size of 1 to 10 μm can be obtained. If the particle size of the copper powder is smaller than 1 μm, when the paste is formed into a paste, agglomeration becomes severe and clogging of the screen occurs, and further, the brittleness increases, leveling is deteriorated, and the printed surface is not smooth. Conversely 10
If it is larger than μm, a dense film cannot be formed and the conductive circuit becomes unstable. EXAMPLE 1 600 g of copper oxide was suspended in 4 l of water and 500 g of acetic acid, and 300 g of hydrazine hydrate was added.
Allowed to react for hours. As a result, the average particle size was 2.4 μm,
Spherical copper powder having a small particle size distribution width having a particle size distribution of 100% within 1 to 10 μm was obtained. Example 2 540 g of copper oxide was suspended in 4 l of water and 500 g of acetic acid, and 280 g of hydrazine hydrate was added.
Allowed to react for hours. As a result, the average particle size was 2.9 μm,
Spherical copper powder having a small particle size distribution width having a particle size distribution of 100% within 1 to 10 μm was obtained. EXAMPLE 3 930 g of copper carbonate was suspended in 4 l of water and 500 g of acetic acid, and 300 g of hydrazine hydrate was added.
Allowed to react for hours. As a result, the average particle size was 2.3 μm,
Spherical copper powder having a small particle size distribution width having a particle size distribution of 100% within 1 to 10 μm was obtained. EXAMPLE 4 2 kg of copper sulfate pentahydrate was suspended in 2.5 l of water and 500 g of acetic acid, and 350 g of hydrazine hydrate was added.
The reaction was performed at 90 ° C. for 48 hours. As a result, a spherical copper powder having an average particle size of 6.3 μm and a particle size distribution of 90% in 1 to 10 μm and a small particle size distribution width was obtained. Comparative Example 1 2 kg of copper sulfate pentahydrate was dissolved in 5 l of water. Next, 350 g of hydrazine hydrate was added.
The reaction was performed for 8 hours. As a result, a copper powder having an average particle size of 8.5 μm and a particle size distribution of 1% to 10 μm and having a large particle size distribution width of 30% included in 1 to 10 μm was obtained. Comparative Example 2 1350 g of copper carbonate was suspended in 4 l of water, 300 g of hydrazine hydrate was added, and the mixture was reacted at 90 ° C. for 4 hours. As a result, a copper powder having an average particle size of 2.8 μm and a large particle size distribution width in which the particle size distribution is 40% in 1 to 10 μm was obtained. Comparative Example 3 2 kg of copper sulfate pentahydrate was dissolved in 5 l of water,
An aqueous copper sulfate solution was used. Surfactant C is added to this copper sulfate aqueous solution.
2.0 g of 10 H 21 NHCH 2 COONa was added. Next, 350 g of hydrazine hydrate was added and reacted at 90 ° C. for 48 hours. As a result, a copper powder having an average particle size of 2.6 μm and a particle size distribution of 1% to 10 μm and having a large particle size distribution width of 70% was obtained. Comparative Example 4 2 kg of copper sulfate pentahydrate was dissolved in 5 l of water.
Add 130 g of sodium borohydride, and add 4 g at 90 ° C.
Allowed to react for hours. As a result, the particle size of the obtained copper powder was 0.1.
It was 1 μm or less. As described above, according to the present invention,
An extremely small spherical copper fine powder which can be easily controlled to an appropriate particle size of about 1 to 10 μm and has a particle size distribution of 90% or more in the range of 1 to 10 μm, and Copper fine powder which can be widely used for various uses such as screen printing can be produced at low cost.
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(72)発明者 納 武士
埼玉県上尾市原市1380−１ 三井金属社
宅Ａ−104
(72)発明者 牛島 昭夫
山口県下関市彦島西山町２−８−２
(56)参考文献 特開 昭64−15309（ＪＰ，Ａ)
特開 昭63−186807（ＪＰ，Ａ)
特開 昭62−77407（ＪＰ，Ａ)
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Continuation of front page
(72) Inventor Takeshi Nori
1380-1 Hara-shi, Ageo-shi, Saitama Mitsui Kinzoku Company
House A-104
(72) Inventor Akio Ushijima
2-8-2 Nishiyamacho, Hikoshima, Shimonoseki City, Yamaguchi Prefecture
(56) References JP-A-64-15309 (JP, A)
JP-A-63-186807 (JP, A)
JP-A-62-77407 (JP, A)