JP2008169474A - Copper powder having excellent dispersibility in liquid and corrosion resistance, and method for producing the same - Google Patents
Copper powder having excellent dispersibility in liquid and corrosion resistance, and method for producing the same Download PDFInfo
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本発明は、微細な銅粒子からなる銅粉であって、特に水や有機溶媒に対する分散性および耐食性に優れ、微細な回路パターンや電極を形成するための導電性ペーストや導電性インクのフィラーに好適な銅粉、およびその製造法に関する。 The present invention is a copper powder comprising fine copper particles, and is particularly excellent in dispersibility and corrosion resistance to water and organic solvents, and is used as a filler for conductive pastes and conductive inks for forming fine circuit patterns and electrodes. It is related with suitable copper powder and its manufacturing method.
配線や電極形成方法として、生産性の良いスクリーン印刷法が広く利用されている。しかし、近年の電子機器の軽薄短小化に伴い、それらを構成する部品の電子配線や電極等についても微細化が要求され、電子配線や電極の形成方法としても、インクジェット法等新たな技術の検討がなされている。それらに用いられるペーストやインク用のフィラーについても同様で、より微細、かつ上記新たな技術に適した特性を有するものが求められるようになってきている。 As a wiring and electrode forming method, a screen printing method with high productivity is widely used. However, as electronic devices have become smaller and lighter in recent years, miniaturization is required for electronic wiring and electrodes of the components that compose them, and new techniques such as inkjet methods are being considered as methods for forming electronic wiring and electrodes. Has been made. The same applies to pastes and ink fillers used for these, and finer ones having characteristics suitable for the new technology have been demanded.
これまで広く利用されてきた導電性ペースト用フィラーは、μｍオーダーの粒径のものがほとんどであった。しかし、インクジェット法等の新しく検討されている配線・電極の形成方法では、インク内の粒子沈降やインクの粘度上昇を抑えるために、数ｎｍ〜約２００ｎｍオーダーの分散性の良い微粒子が求められる。 Most of the fillers for conductive pastes that have been widely used so far have a particle size on the order of μm. However, the newly studied wiring / electrode forming methods such as the ink jet method require fine particles having good dispersibility on the order of several nm to about 200 nm in order to suppress the sedimentation of particles in the ink and the increase in the viscosity of the ink.
一般に、固体物質が数ｎｍ〜約２００ｎｍオーダーの超微粒子（以下「ナノ粒子」と呼ぶ）になると比表面積が非常に大きくなるために、固体でありながら気体や液体との界面が極端に大きくなり、その表面の特性が固体物質の性質を大きく左右するようになる。 In general, when the solid substance becomes ultrafine particles (hereinafter referred to as “nanoparticles”) on the order of several nanometers to about 200 nm, the specific surface area becomes very large, so that the interface with gas or liquid becomes extremely large while being solid. The properties of the surface greatly influence the properties of the solid material.
金属ナノ粒子の場合は、バルク状態のものに比べ融点が劇的に低下することが知られている。そのため、従来のμｍオーダーの粒子に比べ、微細な配線が描画できるという特徴以外にも、低温焼結が可能になるなどの特徴が発現するようになり、その特徴を活かした新しい用途が開拓される可能性を秘めている。 In the case of metal nanoparticles, it is known that the melting point is drastically lowered as compared with those in the bulk state. Therefore, in addition to the feature that fine wiring can be drawn, features such as enabling low-temperature sintering have been developed, and new applications that take advantage of this feature have been developed. It has the potential to
金属ナノ粒子の中では、銀のナノ粒子が低抵抗、高い耐候性を有するといった点で期待されているが、その一方でエレクトロマイグレーションを起こしやすく、貴金属であるため比較的高価であるといった問題もある。そのため、より安価な部材が要求される用途や、エレクトロマイグレーションが敬遠される用途によっては、銅のナノ粒子が望まれている。 Among metal nanoparticles, silver nanoparticles are expected in terms of low resistance and high weather resistance, but on the other hand, they tend to cause electromigration and are relatively expensive because they are noble metals. is there. For this reason, copper nanoparticles are desired depending on applications where a cheaper member is required or where electromigration is avoided.
金属ナノ粒子の製造方法としては大別して気相法と液相法が知られている。気相法ではガス中での蒸着法が一般的であり、例えば特許文献１にはヘリウム等の不活性ガス雰囲気でかつ０.５Ｔｏｒｒ程度の低圧中で金属を蒸発させることによって銀含有超微粒子を製造する方法が記載されている。液相法に関しては、銅の微粒子を製造する技術がいくつか開示されている。例えば特許文献２には硫黄化合物と保護コロイド存在下で銅酸化物を還元する方法が、特許文献３にはベンゾトリアゾール存在下の水溶液中で硫酸銅を中和・還元する方法が、特許文献４には高分子量顔料分散剤の存在下で塩化銅を水素化ホウ素化合物により還元する方法が記載されている。 As manufacturing methods of metal nanoparticles, a gas phase method and a liquid phase method are roughly classified. In the vapor phase method, a vapor deposition method in a gas is generally used. For example, in Patent Document 1, silver-containing ultrafine particles are obtained by evaporating a metal in an inert gas atmosphere such as helium and a low pressure of about 0.5 Torr. A method of manufacturing is described. As for the liquid phase method, several techniques for producing copper fine particles have been disclosed. For example, Patent Document 2 discloses a method of reducing copper oxide in the presence of a sulfur compound and a protective colloid, and Patent Document 3 discloses a method of neutralizing and reducing copper sulfate in an aqueous solution in the presence of benzotriazole. Describes a method of reducing copper chloride with a borohydride compound in the presence of a high molecular weight pigment dispersant.
特許文献１の気相法では、原料に金属を用いているため還元力について配慮する必要がなく、ナノ粒子の凝集抑制に集中すればよいため、比較的容易に分散性の良好なナノ粒子を得ることができる。しかし、この技術は特別な装置が必要であるため、銅ナノ粒子を工業的に大量に合成するには難がある。 In the gas phase method of Patent Document 1, since metal is used as a raw material, it is not necessary to consider the reducing power, and it is only necessary to concentrate on the suppression of aggregation of nanoparticles. Obtainable. However, since this technique requires a special apparatus, it is difficult to industrially synthesize copper nanoparticles in large quantities.
これに対して液相法は、基本的に大量合成に適した方法である。しかし、液中では金属ナノ粒子は極めて凝集性が高いので単分散したナノ粒子粉末を得難いという問題がある。一般に、金属ナノ粒子を製造するためには分散剤としてクエン酸を用いる例が多く、また液中の金属イオン濃度も１０ｍｍｏｌ／Ｌ（＝０.０１ｍｏｌ／Ｌ）以下と極めて低いのが通常である。また、銅は金や銀等の貴金属に比較し還元されにくい。このようなことから、金属銅までの還元とナノ粒子の分散性確保との両立が難しく、これが液相法による銅ナノ粒子の実用化にとって大きな障壁の一つとなっている。 In contrast, the liquid phase method is basically a method suitable for mass synthesis. However, there is a problem in that it is difficult to obtain monodispersed nanoparticle powder because the metal nanoparticles are extremely cohesive in the liquid. In general, in order to produce metal nanoparticles, there are many examples in which citric acid is used as a dispersing agent, and the metal ion concentration in the liquid is usually very low as 10 mmol / L (= 0.01 mol / L) or less. . Also, copper is less likely to be reduced than noble metals such as gold and silver. For this reason, it is difficult to achieve both reduction to metallic copper and ensuring the dispersibility of nanoparticles, which is one of the major obstacles to the practical application of copper nanoparticles by the liquid phase method.
特許文献２では、ナノ粒子の分散性の改善を図るために、銅ナノ粒子との結合力が強いチオール系界面活性剤を保護剤として使用し、分散性の向上を図っている。しかしながら、チオール系界面活性剤には、硫黄（Ｓ）が含まれており、この硫黄分は配線やその他電子部品を腐食させる原因となるため、配線形成用途に使用するには問題がある。 In Patent Document 2, in order to improve the dispersibility of the nanoparticles, a thiol surfactant having a strong binding force with the copper nanoparticles is used as a protective agent to improve the dispersibility. However, the thiol-based surfactant contains sulfur (S), and this sulfur content corrodes the wiring and other electronic components, so that there is a problem in using it for wiring formation applications.
特許文献３についても同様である。原材料に硫酸銅および苛性ソーダを用いているため、硫黄成分やアルカリ金属成分が粒子内に不純物として残留し、配線やその他電子部品の腐食を起こす原因になると懸念される。また、水溶液中での急激な反応を用いているため、その制御性についても問題があると言える。 The same applies to Patent Document 3. Since copper sulfate and caustic soda are used as raw materials, there is a concern that sulfur components and alkali metal components remain as impurities in the particles and cause corrosion of wiring and other electronic components. Moreover, since the rapid reaction in aqueous solution is used, it can be said that the controllability is also problematic.
本発明はこのような問題点を解決し、配線や電子部品用途に適用可能な、極めて腐食しにくい、すなわち表面酸化が極めて起こりにくい銅粒子の合成を目的とする。 The present invention is intended to solve such problems and to synthesize copper particles that can be applied to wiring and electronic component applications and are extremely resistant to corrosion, that is, surface oxidation is unlikely to occur.
発明者らは詳細な検討の結果、上記のような腐食しにくい銅粒子は、銅化合物を、アルコール溶媒中で、アルコールおよび水に可溶な有機ポリマーの共存下において、８０℃以上かつ溶媒の沸点以下の温度域で還元処理することによって合成できることを見出した。 As a result of detailed investigations, the inventors have found that the copper particles that do not corrode as described above have a copper compound in an alcohol solvent in the presence of an alcohol and water-soluble organic polymer at 80 ° C. or higher. It has been found that the synthesis can be carried out by reduction treatment in a temperature range below the boiling point.
この手法によれば、アルコールおよび水に可溶な有機ポリマーが金属銅相表面に付着している平均粒径２００ｎｍ以下の銅粒子からなる液中分散性および耐食性に優れた銅粉が提供される。前記有機ポリマーは、例えば１−ビニル−２−ピロリドンのポリマーである。 According to this method, a copper powder having excellent dispersibility in liquid and corrosion resistance, comprising copper particles having an average particle size of 200 nm or less, in which an alcohol and water-soluble organic polymer is attached to the surface of the metallic copper phase, is provided. . The organic polymer is, for example, a polymer of 1-vinyl-2-pyrrolidone.
この粉末の具体的な製造法として、銅化合物を、アルコール溶媒中で、アルコールおよび水に可溶な有機ポリマーの共存下において、８０℃以上かつ溶媒の沸点以下の温度域で還元処理することにより、前記ポリマー中に銅粒子が分散して存在する「ポリマー／銅粒子複合体」を形成させ、その後、「ポリマー／銅粒子複合体」を含むスラリーを固液分離することにより「ポリマー／銅粒子複合体」を固形分として回収する操作を少なくとも１回行う銅粉の製造法が提供される。 As a specific method for producing this powder, a copper compound is reduced in an alcohol solvent in the presence of an alcohol and water-soluble organic polymer in a temperature range of 80 ° C. or more and the boiling point of the solvent or less. By forming a “polymer / copper particle composite” in which copper particles are dispersed in the polymer, and then solid-liquid separating the slurry containing the “polymer / copper particle composite”, the “polymer / copper particles” A method for producing copper powder is provided in which the operation of recovering the “composite” as a solid content is performed at least once.
本発明によれば、ポリマーが表面に付着している耐食性に優れた銅ナノ粒子の粉末が提供された。この銅粉は、種々の液中で良好な分散性を呈する。また、分散液を乾燥して得た膜中においても、銅の酸化による劣化や腐食が極めて起こりにくい。さらに、この銅粉は液相法によって比較的容易に製造でき、工業生産にも適している。したがって、本発明は配線材料に好適な銅粉の実用化に寄与するものである。 ADVANTAGE OF THE INVENTION According to this invention, the powder of the copper nanoparticle excellent in the corrosion resistance which the polymer has adhered to the surface was provided. This copper powder exhibits good dispersibility in various liquids. Further, even in a film obtained by drying the dispersion, deterioration or corrosion due to copper oxidation is extremely difficult to occur. Furthermore, this copper powder can be manufactured relatively easily by the liquid phase method and is suitable for industrial production. Therefore, the present invention contributes to the practical use of copper powder suitable for wiring materials.
本発明の銅粉は、銅化合物をアルコール溶媒中で、そのアルコールによって還元する手法を利用して得ることができる。その際、アルコール溶媒中には保護剤となる有機ポリマーを共存させておく。アルコールによって還元されて生成した金属銅の粒子は、周囲の有機ポリマーに取り囲まれ、その後、固液分離工程を経て分散液として保存した場合や、乾燥させた場合にも、銅粒子は表面が有機ポリマーで覆われた形で存在する。このため、そのような銅粒子からなる本発明の銅粉は、極めて耐食性が良好で、かつ、各種の液に対する分散性に優れる。
この銅粉は以下のようにして製造できる。
The copper powder of the present invention can be obtained by utilizing a technique of reducing a copper compound with an alcohol in an alcohol solvent. At that time, an organic polymer serving as a protective agent is allowed to coexist in the alcohol solvent. The copper particles produced by reduction with alcohol are surrounded by the surrounding organic polymer and then stored as a dispersion through a solid-liquid separation process, or when dried, the copper particles have an organic surface. Present in polymer-covered form. For this reason, the copper powder of this invention which consists of such a copper particle is very good in corrosion resistance, and is excellent in the dispersibility with respect to various liquids.
This copper powder can be manufactured as follows.
〔銅化合物〕
出発原料である銅化合物は、アルコールに可溶の物質である必要がある。そのような物質として各種銅塩や酸化銅があるが、例えば安価でかつ工業的に安定した供給が可能な銅塩として、塩化銅ＣｕＣｌ2が好適な対象となる。硫酸銅はアルコールへの溶解性があまり良好ではなく、また電子部品の腐食の原因となりうる硫黄を含むことから本発明の原料としては利用しにくい。
[Copper compound]
The copper compound as a starting material needs to be a substance soluble in alcohol. Examples of such a substance include various copper salts and copper oxides. For example, copper chloride CuCl 2 is a suitable target as a copper salt that can be supplied inexpensively and industrially stably. Copper sulfate is not very good as a raw material of the present invention because it has poor solubility in alcohol and contains sulfur which can cause corrosion of electronic components.
〔アルコール〕
アルコールは、銅化合物の溶媒であるとともに、還元剤として機能する。沸点が８０〜２００℃程度のアルコールであれば特に制限はないが、イソブタノール、１−ヘプタノール、２−オクタノールが好適に使用できる。これらを単独で使用するか、２種以上混合して使用すればよい。
〔alcohol〕
Alcohol is a solvent for the copper compound and functions as a reducing agent. Although there will be no restriction | limiting in particular if it is alcohol with a boiling point of about 80-200 degreeC, Isobutanol, 1-heptanol, and 2-octanol can use it conveniently. These may be used alone or in combination of two or more.
〔有機ポリマー〕
保護剤である有機ポリマーは、溶媒のアルコールに可溶の物質であることが必要である。また、このポリマーは生成した銅粒子を取り囲むようにして保護し、その後も銅粒子に付着した状態をとる。すなわちこの有機ポリマーは本発明の銅粉に付随して存在し、銅粉の液中分散性と耐食性を維持する機能を担う。水系の種々の液に対する分散性を確保するために、このポリマーは水にも可溶な物質であることが重要である。また、非イオン性であることが望ましい。
[Organic polymer]
The organic polymer that is a protective agent needs to be a substance that is soluble in a solvent alcohol. Moreover, this polymer protects so that the produced | generated copper particle may be surrounded, and will take the state adhered to the copper particle after that. That is, this organic polymer is present accompanying the copper powder of the present invention, and has a function of maintaining the dispersibility and corrosion resistance of the copper powder in the liquid. In order to ensure dispersibility of various aqueous liquids, it is important that the polymer is a substance that is also soluble in water. Moreover, it is desirable that it is nonionic.
好適な有機ポリマーとして、１−ビニル−２−ピロリドンのポリマーを挙げることができる。この物質は分散剤として工業的に普及しており、入手が容易であると共に、各種ペーストやインクの構成材料としても実績があるため、本発明の銅粉の実用化を妨げる要因になりにくい。 Suitable organic polymers include 1-vinyl-2-pyrrolidone polymers. This substance is widely used industrially as a dispersing agent, is easily available, and has a track record as a constituent material for various pastes and inks. Therefore, it is unlikely to hinder the practical application of the copper powder of the present invention.
発明者らの研究によれば、有機ポリマーの分子量（重合度）が、銅粒子を生成させる際の還元速度に大きく関わってくることがわかった。これは、金属銅に対する有機ポリマーの凝集抑制力は、有機ポリマーの分子量が大きくなると増大し、小さくなると低減することに起因するものと考えられる。このような凝集抑制力の差を利用し、銅の還元速度の制御、すなわち粒径制御を行うことができる。種々検討の結果、１−ビニル−２−ピロリドンのポリマーの場合、数平均分子量が５，０００〜５００，０００程度のポリマーを使用することにより、平均粒径２００ｎｍ以下の銅粒子を合成することができ、特に５，０００〜１００，０００程度のものが好適に使用できる。有機ポリマーの分子量が小さすぎると、有機ポリマーが銅粒子の表面から物理的に剥離しやすく、したがって銅粒子の表面が酸化されやすい状態となり、高耐食性が維持されにくい。逆に有機ポリマーの分子量が大きすぎると、還元反応後の固液分離操作を行うことが困難になり、工業プロセスに適さない。 According to the inventors' research, it has been found that the molecular weight (degree of polymerization) of the organic polymer is greatly related to the reduction rate when the copper particles are produced. This is considered to be due to the fact that the aggregation suppressing power of the organic polymer with respect to copper metal increases as the molecular weight of the organic polymer increases and decreases as the molecular weight of the organic polymer decreases. By utilizing such a difference in agglomeration inhibiting power, the reduction rate of copper, that is, the particle size can be controlled. As a result of various studies, in the case of a polymer of 1-vinyl-2-pyrrolidone, it is possible to synthesize copper particles having an average particle size of 200 nm or less by using a polymer having a number average molecular weight of about 5,000 to 500,000. In particular, those of about 5,000 to 100,000 can be preferably used. If the molecular weight of the organic polymer is too small, the organic polymer is likely to be physically peeled from the surface of the copper particles, and thus the surface of the copper particles is likely to be oxidized, and high corrosion resistance is difficult to be maintained. Conversely, if the molecular weight of the organic polymer is too large, it becomes difficult to perform a solid-liquid separation operation after the reduction reaction, which is not suitable for an industrial process.
〔還元処理〕
溶媒であるアルコール中に、出発物質である銅化合物と保護剤である有機ポリマーを入れて充分に溶解させる。銅化合物の仕込み濃度（溶液１リットル当たりに存在する銅原子のモル数）は３０ｍｍｏｌ／Ｌ以上とすれば良く、３０〜８０ｍｍｏｌ／Ｌ程度とすることが好ましい。有機ポリマーと銅化合物の量比は、１−ビニル−２−ピロリドンのポリマーを使用する場合、［ビニルピロリドン基の数］／［銅化合物中の銅原子の数］の比で、約１〜２０程度とすることができ、３〜１４の範囲がより好ましい。銅化合物と有機ポリマーが溶媒中に溶解した後、還元電位を上げるために苛性ソーダ等のアルカリを添加することができる。
[Reduction treatment]
In the alcohol which is a solvent, a copper compound which is a starting material and an organic polymer which is a protective agent are put and sufficiently dissolved. The preparation concentration of copper compound (the number of moles of copper atoms present per liter of solution) may be 30 mmol / L or more, and is preferably about 30 to 80 mmol / L. When the polymer of 1-vinyl-2-pyrrolidone is used, the ratio of the organic polymer to the copper compound is about 1 to 20 in the ratio of [number of vinyl pyrrolidone groups] / [number of copper atoms in the copper compound]. The range of 3-14 is more preferable. After the copper compound and the organic polymer are dissolved in the solvent, an alkali such as caustic soda can be added to increase the reduction potential.
この溶液を昇温して、８０℃以上〜沸点以下の温度に維持し、撹拌することにより、銅化合物をアルコールによって還元する。還流器を備えた容器を用いて、蒸発したアルコールを液相中に戻しながら反応を行わせることが好ましい。撹拌には窒素等の不活性ガスによるバブリングや、機械撹拌を利用することができる。還元反応の進行に伴って液がスラリー状になる。通常、３０〜１５０ｍｉｎ程度で還元反応が終了する。得られたスラリーは、生成した銅粒子が保護剤であるポリマーに取り囲まれるようにポリマー中に分散して存在する「ポリマー／銅粒子複合体」が澱物として形成されたものである。 The temperature of the solution is raised, maintained at a temperature of 80 ° C. or higher and a boiling point or lower, and stirred to reduce the copper compound with alcohol. It is preferable to carry out the reaction while returning the evaporated alcohol to the liquid phase using a container equipped with a refluxing device. For the stirring, bubbling with an inert gas such as nitrogen or mechanical stirring can be used. As the reduction reaction proceeds, the liquid becomes a slurry. Usually, the reduction reaction is completed in about 30 to 150 minutes. The obtained slurry is a “polymer / copper particle composite” formed as a starch dispersed in the polymer so that the produced copper particles are surrounded by the polymer as the protective agent.
〔固液分離〕
得られたスラリーを固液分離することにより「ポリマー／銅粒子複合体」を固形分として回収する。次いで、この固形分に洗浄液を加え、超音波分散機などを用いて洗浄することが望ましい。洗浄後には再度、固液分離することによりポリマー／銅粒子複合体を固形分として回収する。固液分離には遠心分離機を使用することができる。このような「洗浄→固液分離」の操作を複数回繰り返すことが好ましい。洗浄液にはアセトンやメチルアルコールが使用できるが、最終的に回収されたポリマー／銅粒子複合体を水系の溶媒に分散させて保存する場合は、少なくとも最終の洗浄を水によって行うことが好ましい。この操作により、ポリマー／銅粒子複合体中に含まれるＮａＣｌを除去することができる。
(Solid-liquid separation)
The resulting slurry is subjected to solid-liquid separation to recover the “polymer / copper particle composite” as a solid content. Next, it is desirable to add a cleaning liquid to the solid content and perform cleaning using an ultrasonic disperser or the like. After washing, the polymer / copper particle composite is recovered as a solid content again by solid-liquid separation. A centrifuge can be used for solid-liquid separation. Such an operation of “washing → solid-liquid separation” is preferably repeated a plurality of times. Acetone or methyl alcohol can be used as the cleaning liquid. However, when the finally recovered polymer / copper particle composite is dispersed in an aqueous solvent and stored, it is preferable to perform at least the final cleaning with water. By this operation, NaCl contained in the polymer / copper particle composite can be removed.
本発明の銅粉は、このようにして分離回収されたポリマー／銅粒子複合体の中に存在する銅粒子によって構成される。このポリマー／銅粒子複合体は、すぐに溶媒を揮発させて乾燥状態として種々の用途に供することもできるが、以下のような液状媒体中で保存することもできる。 The copper powder of the present invention is constituted by the copper particles present in the polymer / copper particle composite thus separated and recovered. The polymer / copper particle composite can be used for various purposes as a dry state by immediately evaporating the solvent, but can also be stored in the following liquid medium.
〔非極性または極性の小さい液状媒体〕
高濃度インクを作成する場合など、銅粉の液中分散性を重視する場合には、本発明の銅粉を非極性または極性の小さい液状媒体に分散させることが有利である。「非極性または極性の小さい」というのは２５℃での比誘電率が１５以下であることを意味する。比誘電率がこれより大きいと、銅粒子の分散性が悪化し沈降することがあり、好ましくない。２５℃での比誘電率が５以下の液状媒体を使用することがより好ましい。
[Nonpolar or small liquid medium]
When emphasizing the dispersibility of the copper powder in the liquid, such as when creating a high-density ink, it is advantageous to disperse the copper powder of the present invention in a non-polar or low-polarity liquid medium. “Nonpolar or low polarity” means that the relative dielectric constant at 25 ° C. is 15 or less. If the relative dielectric constant is larger than this, the dispersibility of the copper particles may deteriorate and settle, which is not preferable. It is more preferable to use a liquid medium having a relative dielectric constant of 5 or less at 25 ° C.
非極性または極性の小さい液状媒体としては、用途に応じて沸点が６０〜３００℃の種々のものが使用できるが、炭化水素系が特に好適であり、なかでも、イソオクタン、ｎ−デカン、イソドデカン、イソヘキサン、ｎ−ウンデカン、ｎ−テトラデカン、ｎ−ドデカン、トリデカン、ヘキサン、ヘプタン等の脂肪族炭化水素、ベンゼン、トルエン、キシレン、エチルベンゼン、デカリン、テトラリン等の芳香族炭化水素等が好適な対象として挙げられる。これらの液状有機媒体は１種類を単独で使用することができ、また２種類以上混合したものを使用することもできる。ケロシンのような混合物であっても良い。 As the non-polar or low-polarity liquid medium, various media having a boiling point of 60 to 300 ° C. can be used depending on the application, and hydrocarbon systems are particularly preferable, among which isooctane, n-decane, isododecane, Examples of suitable targets include aliphatic hydrocarbons such as isohexane, n-undecane, n-tetradecane, n-dodecane, tridecane, hexane, and heptane, and aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, decalin, and tetralin. It is done. These liquid organic media can be used individually by 1 type, and can also use what mixed 2 or more types. A mixture such as kerosene may also be used.
〔極性の大きい液状媒体〕
極性の大きい液状媒体は表面張力が大きいので、使用時に液だれを防止したい場合などに有利である。透明電磁波シールド材の製造のように、スピンコート法でインク溶媒を塗布し乾燥させる操作を繰り返すことにより層を積んでいく場合には、極性の大きい液状媒体のうち沸点の低いものを用いると、乾燥時間が短縮でき効率的である。「極性の大きい」というのは２５℃での比誘電率が１５を超えることを意味する。本発明の銅粉は保護剤として付着している有機ポリマーの働きで極めて分散性が良く、このような極性の大きい液状媒体中でも良好な分散性を示す。極性の大きい液状媒体の代表的なものとして、アセトン、メチルアルコール、水が挙げられる。これらは、ハンドリングも比較的容易である。
[Liquid medium with large polarity]
Since a liquid medium having a large polarity has a large surface tension, it is advantageous when it is desired to prevent dripping during use. When the layers are stacked by repeating the operation of applying and drying the ink solvent by spin coating as in the production of a transparent electromagnetic shielding material, using a low-polarity liquid medium having a high polarity, The drying time is shortened and efficient. “Large polarity” means that the relative dielectric constant at 25 ° C. exceeds 15. The copper powder of the present invention has extremely good dispersibility due to the action of the organic polymer attached as a protective agent, and exhibits good dispersibility even in such a liquid medium having a large polarity. Typical examples of the liquid medium having a large polarity include acetone, methyl alcohol, and water. These are also relatively easy to handle.
《実施例１》
溶媒兼還元剤であるアルコールとしてイソヘプタノール（和光純薬株式会社製の特級）２００ｍＬ、出発原料である銅化合物として無水塩化銅（ＣｕＣｌ2）１.０ｇ、保護剤である有機ポリマーとして１−ビニル−２−ピロリドンのポリマー（和光純薬株式会社製、ＰＶＰ Ｋ３０、数平均分子量４００００）８.４８ｇをそれぞれ用意した。上記イソヘプタノールに、上記無水塩化銅と１−ビニル−２−ピロリドンのポリマーを添加し、マグネットスターラーにより撹拌して室温で溶解させた。この場合、銅化合物の仕込み濃度（溶液１リットル当たりに存在する銅原子のモル数）は３５ｍｍｏｌ／Ｌとなる。また、有機ポリマーと銅化合物の量比は、［ビニルピロリドン基の数］／［銅化合物中の銅原子の数］の比で１０となる。
Example 1
200 mL of isoheptanol (special grade manufactured by Wako Pure Chemical Industries, Ltd.) as an alcohol as a solvent and reducing agent, 1.0 g of anhydrous copper chloride (CuCl 2 ) as a copper compound as a starting material, and 1-as an organic polymer as a protective agent 8.48 g of a polymer of vinyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd., PVP K30, number average molecular weight 40000) was prepared. To the isoheptanol, the polymer of anhydrous copper chloride and 1-vinyl-2-pyrrolidone was added and stirred with a magnetic stirrer and dissolved at room temperature. In this case, the preparation concentration of the copper compound (the number of moles of copper atoms present per liter of solution) is 35 mmol / L. The amount ratio of the organic polymer to the copper compound is 10 in the ratio of [number of vinyl pyrrolidone groups] / [number of copper atoms in the copper compound].
その後、還元電位を制御するため苛性ソーダ顆粒（和光純薬株式会社製）１.７５ｇを添加し、マグネットスターラーで溶解させた。この溶液を還流器のついた容器に移してオイルバスに載せ、溶液中に窒素ガスを４００ｍＬ／ｍｉｎの流量で吹き込みながら、該溶液をマグネットスターラーにより２００ｒｐｍの回転速度で撹拌しつつ加熱し、１７６℃の沸騰状態で１ｈの還流を行うことにより還元反応を終えた。１７６℃に至るまでの昇温速度は１０℃／ｍｉｎとした。 Thereafter, 1.75 g of caustic soda granule (manufactured by Wako Pure Chemical Industries, Ltd.) was added to control the reduction potential and dissolved with a magnetic stirrer. The solution was transferred to a container equipped with a refluxer and placed on an oil bath. While nitrogen gas was blown into the solution at a flow rate of 400 mL / min, the solution was heated while stirring at a rotation speed of 200 rpm with a magnetic stirrer. The reduction reaction was completed by refluxing for 1 h in a boiling state at ° C. The heating rate up to 176 ° C. was 10 ° C./min.
反応終了後のスラリーを以下の手順で処理した。
１.反応後のスラリー５ｍＬに、アセトン（和光純薬株式会社製）２５ｍＬを添加し、超音波分散機に１０ｍｉｎかけて分散させる。
２.この分散液を日立工機（株）製の遠心分離機ＣＦ７Ｄ２を用いて３０００ｒｐｍで２０ｍｉｎ処理することにより固液分離し、固形分を回収する。上澄みは廃棄する。
３.前記の１〜２の工程を繰返す。
４.得られたスラリーに水を８ｍＬ、アセトン３２ｍＬを添加し、超音波分散機に１０ｍｉｎかけて分散させる。
５.次に上記遠心分離機を用いて３０００ｒｐｍで２０ｍｉｎ処理することにより固液分離し、固形分を回収する。上澄みは廃棄する。
６.回収されたペースト状の固形分にメタノールを添加して分散液とし、その分散液を上記遠心分離機にかけることにより粗粒子および凝集粒子を分離除去した分散液を得る。
７.上記５で得た分散液を無反射板に塗布し、室温で乾燥させることにより、溶媒を揮発させた乾燥膜を得る。
その後、以下のようにしてＴＥＭ粒径ＤTEM、そのＣＶ値、およびＸ線回折パターンを求めた。
The slurry after the reaction was processed in the following procedure.
1. To 5 mL of the slurry after the reaction, 25 mL of acetone (manufactured by Wako Pure Chemical Industries, Ltd.) is added and dispersed in an ultrasonic disperser over 10 min.
2. This dispersion is subjected to solid-liquid separation by treating it for 20 minutes at 3000 rpm using a centrifugal separator CF7D2 manufactured by Hitachi Koki Co., Ltd., and the solid content is recovered. Discard the supernatant.
3. Repeat steps 1 and 2 above.
4. 8 mL of water and 32 mL of acetone are added to the obtained slurry and dispersed in an ultrasonic disperser over 10 min.
5. Next, solid-liquid separation is performed by treating at 3000 rpm for 20 minutes using the above centrifugal separator, and the solid content is recovered. Discard the supernatant.
6. Methanol is added to the recovered pasty solid to form a dispersion, and the dispersion is subjected to the above-mentioned centrifuge to obtain a dispersion from which coarse particles and aggregated particles are separated and removed.
7. The dispersion obtained in 5 above is applied to a non-reflective plate and dried at room temperature to obtain a dry film in which the solvent is volatilized.
Thereafter, the TEM particle size D TEM , its CV value, and X-ray diffraction pattern were determined as follows.
〔ＴＥＭ粒径ＤTEM〕
前記６で得た分散液を対象に、ＴＥＭ（透過電子顕微鏡）観察を行った。６０万倍に拡大した画像から重なっていない独立した銅粒子３００個を無作為に選んでその径を測定し、その平均値をＤTEMとした。銅粒子は球状であるが、個々の粒子の「径」の値は画像上で粒子の最も長い部分の直径を測定して求めた。また、個々の粒子の粒子径の測定値からＤTEMの標準偏差σDを求め、下記（１）式によりＣＶ値を算出した。
ＣＶ値（％）＝σD／ＤTEM×１００ ……（１）
ＣＶ値が小さいほど銅粒子の粒径は均一化されていることになる。このＣＶ値が５０％以下であれば、導電性ペーストや導電性インクのフィラー用として充分に均一化された粒度分布を有していると評価される。
[TEM particle size D TEM ]
TEM (transmission electron microscope) observation was performed on the dispersion obtained in 6 above. 300 independent copper particles that were not overlapped from the image magnified 600,000 times were randomly selected and their diameters were measured, and the average value was defined as DTEM . Although the copper particles are spherical, the “diameter” value of each particle was determined by measuring the diameter of the longest part of the particle on the image. Further, the standard deviation σ D of D TEM was obtained from the measured value of the particle diameter of each particle, and the CV value was calculated by the following formula (1).
CV value (%) = σ D / D TEM × 100 (1)
The smaller the CV value, the more uniform the particle size of the copper particles. If this CV value is 50% or less, it is evaluated that it has a sufficiently uniform particle size distribution as a filler for conductive paste and conductive ink.
〔Ｘ線回折パターン〕
前記７で得られた乾燥膜について、理学電気社製のＲＡＤ−ｒＢを用いてＸ線回折を行いＸ線回折パターンを得た。ＣｕＫα線を使用し、管電圧５０ｋＶ、管電流１００ｍＡとし、回折角２θが３０〜９０°の範囲を３０００ステップに分割し、１ステップ０.６ｓｅｃで試料を走査する方法で測定した。
[X-ray diffraction pattern]
The dry film obtained in 7 was subjected to X-ray diffraction using RAD-rB manufactured by Rigaku Corporation, and an X-ray diffraction pattern was obtained. A CuKα ray was used, the tube voltage was 50 kV, the tube current was 100 mA, the range of the diffraction angle 2θ of 30 to 90 ° was divided into 3000 steps, and the measurement was performed by scanning the sample in 1 step 0.6 sec.
これらの測定の結果、得られた銅粉のＴＥＭ平均粒径ＤTEMは７９ｎｍ、そのＣＶ値は１４.１％であった。この銅粉はポリマー／銅粒子複合体の中に存在する銅粒子によって構成されており、液中への分散性も極めて良好であった（例えば上記６の分散液）。また、乾燥膜のＸ線回折では、金属Ｃｕ相を示すピークしか検出されなかった。すなわち、上記１〜５、７の処理を経ても、銅粒子表面が酸化されておらず、極めて優れた耐食性を呈することが確かめられた。 The results of these measurements, the obtained TEM average particle diameter D TEM of a copper powder 79 nm, the CV value was 14.1%. This copper powder was composed of copper particles present in the polymer / copper particle composite, and the dispersibility in the liquid was extremely good (for example, the above-mentioned dispersion 6). Moreover, in the X-ray diffraction of the dry film, only a peak indicating a metallic Cu phase was detected. That is, it was confirmed that even after the treatments 1 to 5 and 7 described above, the surface of the copper particles was not oxidized and exhibited extremely excellent corrosion resistance.
《実施例２》
保護剤である有機ポリマーとして１−ビニル−２−ピロリドンのポリマー（純正化学株式会社製、ＰＶＰ−Ｋ１５、数平均分子量１０，０００）８.４８ｇを用いた以外、実施例１と同様の条件で実験を行った。この場合も、銅化合物の仕込み濃度、および有機ポリマーと銅化合物の量比は実施例１と同じになる。
Example 2
Under the same conditions as in Example 1, except that 8.48 g of a polymer of 1-vinyl-2-pyrrolidone (manufactured by Junsei Co., Ltd., PVP-K15, number average molecular weight 10,000) was used as the protective organic polymer. The experiment was conducted. Also in this case, the preparation concentration of the copper compound and the amount ratio of the organic polymer and the copper compound are the same as those in Example 1.
測定の結果、得られた銅粉のＴＥＭ平均粒径ＤTEMは１５０ｎｍ、そのＣＶ値は４７.１％であった。液中への分散性も極めて良好であった（例えば上記６の分散液）。また、乾燥膜のＸ線回折では、金属Ｃｕ相を示すピークしか検出されずなかった。すなわち、この銅粉は実施例１と同様、極めて優れた耐食性を呈することが確かめられた。 As a result of the measurement, the obtained copper powder had a TEM average particle diameter DTEM of 150 nm and a CV value of 47.1%. The dispersibility in the liquid was also very good (for example, the above dispersion 6). Further, in the X-ray diffraction of the dried film, only a peak indicating a metallic Cu phase was detected. That is, it was confirmed that this copper powder exhibited extremely excellent corrosion resistance as in Example 1.
《比較例１》
有機ポリマーの替わりに１−ビニル−２−ピロリドンのモノマー（和光純薬株式会社製、分子量１１１.１１）８.４８ｇを用いた以外、実施例１と同様の条件で実験を行った（ただしＴＥＭ観察は未実施）。
<< Comparative Example 1 >>
An experiment was performed under the same conditions as in Example 1 except that 8.48 g of a monomer of 1-vinyl-2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 111.11) was used instead of the organic polymer (however, TEM Observation not conducted).
乾燥膜のＸ線回折の結果、Ｘ線回折パターンには金属Ｃｕ相を示すピークの他、ＣｕＯ、Ｃｕ（ＯＨ）2を示すピークが検出された。保護剤として用いた１−ビニル−２−ピロリドンの分子量が小さすぎたことにより、生成した銅粒子表面から保護剤が剥離し、充分な耐食性が得られなかったものと考えられる。 As a result of X-ray diffraction of the dried film, peaks indicating CuO and Cu (OH) 2 were detected in the X-ray diffraction pattern in addition to peaks indicating a metal Cu phase. It is considered that the protective agent was peeled off from the surface of the produced copper particles and sufficient corrosion resistance was not obtained because the molecular weight of 1-vinyl-2-pyrrolidone used as the protective agent was too small.
《比較例２》
保護剤である有機ポリマーとして１−ビニル−２−ピロリドンのポリマー（Ａｌｄｒｉｃｈ社製、数平均分子量１３０００００）８.４８ｇを用いた以外、実施例１と同様の条件での実験を試みた。しかしながら、有機ポリマーの分子量が大きすぎたことにより、還元反応後の有機溶媒が常温で固化し、固液分離の操作ができなかった。
<< Comparative Example 2 >>
An experiment under the same conditions as in Example 1 was tried except that 8.48 g of a polymer of 1-vinyl-2-pyrrolidone (manufactured by Aldrich, number average molecular weight 1300000) was used as the organic polymer as a protective agent. However, since the molecular weight of the organic polymer was too large, the organic solvent after the reduction reaction was solidified at room temperature, and solid-liquid separation operation could not be performed.
《実施例３》
溶媒兼還元剤であるアルコールとして１−ヘプタノール（和光純薬株式会社製の特級）１００ｍＬ、出発原料である銅化合物として酸化銅（ＣｕＯ）０.５ｇ、保護剤である有機ポリマーとして１−ビニル−２−ピロリドンのポリマー（和光純薬株式会社製、ＰＶＰ Ｋ３０、数平均分子量４００００）１.５６ｇをそれぞれ用意した。上記１−ヘプタノールに、上記酸化銅と１−ビニル−２−ピロリドンのポリマーを添加し、マグネットスターラーにより撹拌して室温で溶解させた。有機ポリマーと銅化合物の量比は、［ビニルピロリドン基の数］／［銅化合物中の銅原子の数］の比で３.８となる。
Example 3
100 mL of 1-heptanol (special grade manufactured by Wako Pure Chemical Industries, Ltd.) as an alcohol as a solvent and reducing agent, 0.5 g of copper oxide (CuO) as a copper compound as a starting material, and 1-vinyl- as an organic polymer as a protective agent 1.56-g each of 2-pyrrolidone polymers (Wako Pure Chemical Industries, PVP K30, number average molecular weight 40000) were prepared. To the 1-heptanol, the polymer of copper oxide and 1-vinyl-2-pyrrolidone was added and stirred at room temperature by a magnetic stirrer. The amount ratio between the organic polymer and the copper compound is 3.8 in the ratio of [number of vinyl pyrrolidone groups] / [number of copper atoms in the copper compound].
その後、還元電位を制御するため苛性ソーダ顆粒（和光純薬株式会社製）０.１ｇ（０.００２５ｍｏｌ）を添加し、マグネットスターラーで溶解させた。この溶液を還流器のついた容器に移してオイルバスに載せ、溶液中に窒素ガスを４００ｍＬ／ｍｉｎの流量で吹き込みながら、該溶液をマグネットスターラーにより２００ｒｐｍの回転速度で撹拌しつつ加熱し、１７６℃の沸騰状態で２ｈの還流を行うことにより還元反応を終えた。１７６℃に至るまでの昇温速度は１０℃／ｍｉｎとした。 Thereafter, 0.1 g (0.0025 mol) of caustic soda granules (manufactured by Wako Pure Chemical Industries, Ltd.) was added to control the reduction potential, and dissolved with a magnetic stirrer. The solution was transferred to a vessel equipped with a refluxer and placed on an oil bath. While blowing nitrogen gas into the solution at a flow rate of 400 mL / min, the solution was heated while being stirred by a magnetic stirrer at a rotation speed of 200 rpm. The reductive reaction was completed by refluxing for 2 hours in a boiling state of ° C. The heating rate up to 176 ° C. was 10 ° C./min.
反応終了後のスラリーを実施例１で示した手順１〜７にしたがって処理した。得られた物質について実施例１と同様にＸ線回折パターンを求めた。その結果を図１中に例示する（以下の実施例、比較例において同じ）。図１からわかるように、金属Ｃｕに対応する回折パターンが観測され、銅粉が得られたことが確認された。この銅粉はポリマー／銅粒子複合体の中に存在する銅粒子によって構成されており、液中への分散性も極めて良好であった（例えば上記６の分散液）。すなわち、上記１〜５、７の処理を経ても、銅粒子表面が酸化されておらず、極めて優れた耐食性を呈することが確かめられた。 The slurry after completion of the reaction was treated according to procedures 1 to 7 shown in Example 1. The X-ray diffraction pattern was determined for the obtained substance in the same manner as in Example 1. The results are illustrated in FIG. 1 (same in the following examples and comparative examples). As can be seen from FIG. 1, a diffraction pattern corresponding to the metal Cu was observed, and it was confirmed that copper powder was obtained. This copper powder was composed of copper particles present in the polymer / copper particle composite, and the dispersibility in the liquid was very good (for example, the above-mentioned dispersion 6). That is, it was confirmed that even after the treatments 1 to 5 and 7 described above, the surface of the copper particles was not oxidized and exhibited extremely excellent corrosion resistance.
図２（ａ）にこの銅粉のＳＥＭ写真を例示する。この写真から、銅粒子の平均粒子径は２００ｎｍ以下であることが明らかである。 FIG. 2A illustrates an SEM photograph of this copper powder. From this photograph, it is clear that the average particle diameter of the copper particles is 200 nm or less.
《実施例４》
苛性ソーダの添加量を０.２ｇ（０.００５ｍｏｌ）に増量して還元電位をさらに高めたことを除き、実施例３と同様の実験を行った。図１中に示すように金属Ｃｕに対応する回折パターンが観測され、銅粉が得られたことが確認された。この銅粉はポリマー／銅粒子複合体の中に存在する銅粒子によって構成されており、液中への分散性も極めて良好であった（例えば上記６の分散液）。すなわち、上記１〜５、７の処理を経ても、銅粒子表面が酸化されておらず、極めて優れた耐食性を呈することが確かめられた。
Example 4
The same experiment as in Example 3 was performed except that the reduction potential was further increased by increasing the amount of caustic soda added to 0.2 g (0.005 mol). As shown in FIG. 1, a diffraction pattern corresponding to metal Cu was observed, and it was confirmed that copper powder was obtained. This copper powder was composed of copper particles present in the polymer / copper particle composite, and the dispersibility in the liquid was extremely good (for example, the above-mentioned dispersion 6). That is, it was confirmed that even after the treatments 1 to 5 and 7 described above, the surface of the copper particles was not oxidized and exhibited extremely excellent corrosion resistance.
図２（ｂ）にこの銅粉のＳＥＭ写真を例示する。この写真から、銅粒子の平均粒子径は２００ｎｍ以下であることが明らかである。 FIG. 2B illustrates an SEM photograph of this copper powder. From this photograph, it is clear that the average particle diameter of the copper particles is 200 nm or less.
《実施例５》
苛性ソーダの添加量を０.４ｇ（０.０１ｍｏｌ）に増量して還元電位をさらに高めたことを除き、実施例３と同様の実験を行った。図１中に示すように金属Ｃｕに対応する回折パターンが観測され、銅粉が得られたことが確認された。この銅粉はポリマー／銅粒子複合体の中に存在する銅粒子によって構成されており、液中への分散性も極めて良好であった（例えば上記６の分散液）。すなわち、上記１〜５、７の処理を経ても、銅粒子表面が酸化されておらず、極めて優れた耐食性を呈することが確かめられた。
Example 5
The same experiment as in Example 3 was performed except that the reduction potential was further increased by increasing the amount of caustic soda added to 0.4 g (0.01 mol). As shown in FIG. 1, a diffraction pattern corresponding to metal Cu was observed, and it was confirmed that copper powder was obtained. This copper powder was composed of copper particles present in the polymer / copper particle composite, and the dispersibility in the liquid was extremely good (for example, the above-mentioned dispersion 6). That is, it was confirmed that even after the treatments 1 to 5 and 7 described above, the surface of the copper particles was not oxidized and exhibited extremely excellent corrosion resistance.
図２（ｃ）にこの銅粉のＳＥＭ写真を例示する。この写真から、銅粒子の平均粒子径は２００ｎｍ以下であることが明らかである。 FIG. 2C illustrates an SEM photograph of this copper powder. From this photograph, it is clear that the average particle diameter of the copper particles is 200 nm or less.
この実施例５における上記７の処理によって得られた乾燥膜について、さらに６０℃のオーブン中で２４時間乾燥させる実験を行った。６０℃オーブン乾燥後の試料について上記と同様の方法でＸ線回折パターンを測定した。その結果を図３の最上段に示す。この場合も金属Ｃｕに対応するＸ線回折パターンが得られた。すなわち、この銅粉は極めて優れた耐酸化性を呈することが確かめられた。 The dried film obtained by the process 7 in Example 5 was further dried for 24 hours in an oven at 60 ° C. The X-ray diffraction pattern of the sample after oven drying at 60 ° C. was measured by the same method as described above. The result is shown in the uppermost part of FIG. Also in this case, an X-ray diffraction pattern corresponding to the metal Cu was obtained. That is, it was confirmed that this copper powder exhibits extremely excellent oxidation resistance.
《実施例６》
苛性ソーダの添加量を０.８ｇ（０.０２ｍｏｌ）に増量して還元電位をさらに高めたことを除き、実施例３と同様の実験を行った。図１中に示すように金属Ｃｕに対応する回折パターンが観測され、銅粉が得られたことが確認された。この銅粉はポリマー／銅粒子複合体の中に存在する銅粒子によって構成されており、液中への分散性も極めて良好であった（例えば上記６の分散液）。すなわち、上記１〜５、７の処理を経ても、銅粒子表面が酸化されておらず、極めて優れた耐食性を呈することが確かめられた。
Example 6
The same experiment as in Example 3 was performed except that the reduction potential was further increased by increasing the amount of caustic soda added to 0.8 g (0.02 mol). As shown in FIG. 1, a diffraction pattern corresponding to metal Cu was observed, and it was confirmed that copper powder was obtained. This copper powder was composed of copper particles present in the polymer / copper particle composite, and the dispersibility in the liquid was extremely good (for example, the above-mentioned dispersion 6). That is, it was confirmed that even after the treatments 1 to 5 and 7 described above, the surface of the copper particles was not oxidized and exhibited extremely excellent corrosion resistance.
図２（ｄ）にこの銅粉のＳＥＭ写真を例示する。この写真から、銅粒子の平均粒子径は２００ｎｍ以下であることが明らかである。アルカリの添加量を増大させて還元電位を高めると銅粒子が粗大化する傾向が見られる。すなわちアルカリの添加量によって、銅粒子の粒径をコントロールすることができる。 FIG. 2D illustrates an SEM photograph of this copper powder. From this photograph, it is clear that the average particle diameter of the copper particles is 200 nm or less. When the addition amount of alkali is increased to increase the reduction potential, the copper particles tend to be coarsened. That is, the particle size of the copper particles can be controlled by the amount of alkali added.
《比較例３》
苛性ソーダを添加しなかったことを除き、実施例３と同様の条件で実験を行った。この場合も、銅化合物の仕込み濃度、および有機ポリマーと銅化合物の量比は実施例３と同じになる。
<< Comparative Example 3 >>
The experiment was conducted under the same conditions as in Example 3 except that no caustic soda was added. Also in this case, the preparation concentration of the copper compound and the amount ratio of the organic polymer to the copper compound are the same as in Example 3.
図１中のＸ線回折パターンからわかるように、粒子は原料のＣｕＯのままであった。アルカリを添加しなかったことにより還元電位が低すぎ、結果的に還元反応がほとんど進行しなかった。 As can be seen from the X-ray diffraction pattern in FIG. 1, the particles remained as raw material CuO. The reduction potential was too low because no alkali was added, and as a result, the reduction reaction hardly proceeded.
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