JP2020139178A - Silver powder and method for producing the same - Google Patents

Silver powder and method for producing the same Download PDF

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JP2020139178A
JP2020139178A JP2019033551A JP2019033551A JP2020139178A JP 2020139178 A JP2020139178 A JP 2020139178A JP 2019033551 A JP2019033551 A JP 2019033551A JP 2019033551 A JP2019033551 A JP 2019033551A JP 2020139178 A JP2020139178 A JP 2020139178A
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silver
silver powder
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powder
benzoic acid
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将也 大迫
Masaya OSAKO
将也 大迫
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Dowaエレクトロニクス株式会社
Dowa Electronics Materials Co Ltd
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Abstract

To provide siver powder having a grain size equal to that of silver powder produced by the conventional wet reduction method and also capable of forming a conductive film having a low volume resistivity when being used for firing type conductive paste, and a method for producing the same.SOLUTION: A reducer is added to a silver-ammine complex water solution containing benzoic acid of 0.05 to 6 mass%, and silver grains are reductively precipitated to produce silver powder containing benzoic acid of 0.001 to 1 mass% to silver at the inside of the grains, having an average grain diameter D50 by a laser diffraction method of 0.3 to 5 μm, and having a BET specific surface area of 0.1 to 3 m2/g.SELECTED DRAWING: None

Description

本発明は、銀粉およびその製造方法に関し、特に、太陽電池やタッチパネルの基板などの電子部品の電極や回路などを形成する導電性ペーストに使用するのに適した銀粉およびその製造方法に関する。 The present invention relates to silver powder and a method for producing the same, and more particularly to the silver powder suitable for use in a conductive paste for forming electrodes and circuits of electronic components such as a substrate of a solar cell and a touch panel, and a method for producing the same.
従来、電子部品の電極や回路などを形成する方法として、銀粉をガラスフリットとともに有機ビヒクル中に加えて混練することによって製造される焼成型の導電性ペーストを基板上に所定のパターンに形成した後、500℃以上の温度で加熱することによって、有機成分を除去し、銀粒子同士を焼結させて導電膜を形成する方法が広く用いられている。 Conventionally, as a method of forming electrodes and circuits of electronic components, a firing-type conductive paste produced by adding silver powder together with glass frit to an organic vehicle and kneading it is formed on a substrate in a predetermined pattern. , A method of removing organic components by heating at a temperature of 500 ° C. or higher and sintering silver particles with each other to form a conductive film is widely used.
このような方法に使用される導電性ペースト用の銀粉は、電子部品の小型化による導体パターンの高密度化やファインライン化に対応したり、太陽電池の集光面積を増大して発電効率を向上させるためにフィンガー電極のファインライン化に対応するように、粒径が適度に小さく、粒度が揃っていることが要求されている。また、ファインライン化により導電パターンや電極の断面積が減少しても、電気を効率よく流す導電パターンや電極などを形成することができる導電性ペーストに使用するのに適した銀粉が望まれており、そのため、より低い温度で加熱して銀粒子同士を焼結させることができる銀粉が望まれている。 The silver powder for conductive paste used in such a method can be used to increase the density and fine line of the conductor pattern by downsizing the electronic components, and increase the light collecting area of the solar cell to improve the power generation efficiency. In order to improve the quality, it is required that the particle size is appropriately small and the particle size is uniform so as to correspond to the fine line of the finger electrode. Further, even if the cross-sectional area of the conductive pattern or electrode is reduced due to the fine line, silver powder suitable for use in a conductive paste capable of forming a conductive pattern or electrode that efficiently conducts electricity is desired. Therefore, there is a demand for silver powder that can be heated at a lower temperature to sinter silver particles with each other.
このような導電性ペースト用の銀粉を製造する方法として、銀イオンを含有する水性反応系に還元剤を加えることによって銀粉を還元析出させる湿式還元法が知られている(例えば、特許文献1参照)。 As a method for producing silver powder for such a conductive paste, a wet reduction method is known in which silver powder is reduced and precipitated by adding a reducing agent to an aqueous reaction system containing silver ions (see, for example, Patent Document 1). ).
特開平8−176620号公報(段落番号0008−0013)Japanese Unexamined Patent Publication No. 8-176620 (paragraph number 0008-0013)
しかし、従来の湿式還元法により製造した銀粉と同程度の粒径の銀粉を焼成型の導電性ペーストに使用した場合に、体積抵抗率が低い導電膜を形成することができない場合があった。
したがって、本発明は、このような従来の問題点に鑑み、従来の湿式還元法により製造した銀粉と同程度の粒径を有し且つ焼成型の導電性ペーストに使用した場合に体積抵抗率が低い導電膜を形成可能な銀粉およびその製造方法を提供することを目的とする。
However, when silver powder having a particle size similar to that of silver powder produced by a conventional wet reduction method is used for a firing type conductive paste, it may not be possible to form a conductive film having a low volume resistivity.
Therefore, in view of such conventional problems, the present invention has a particle size similar to that of silver powder produced by a conventional wet reduction method and has a volume resistivity when used in a calcined conductive paste. An object of the present invention is to provide a silver powder capable of forming a low conductive film and a method for producing the same.
本発明者らは、上記課題を解決するために鋭意研究した結果、安息香酸を含む銀錯体水溶液に還元剤を添加して、銀粒子を還元析出させることにより、従来の湿式還元法により製造した銀粉と同程度の粒径を有し且つ焼成型の導電性ペーストに使用した場合に体積抵抗率が低い導電膜を形成可能な銀粉を製造することができることを見出し、本発明を完成するに至った。 As a result of diligent research to solve the above problems, the present inventors added a reducing agent to a silver complex aqueous solution containing benzoic acid to reduce and precipitate silver particles, thereby producing the silver particles by a conventional wet reduction method. We have found that it is possible to produce a silver powder having a particle size similar to that of silver powder and capable of forming a conductive film having a low volume resistivity when used in a baking-type conductive paste, and have completed the present invention. It was.
すなわち、本発明による銀粉の製造方法は、安息香酸を含む銀錯体水溶液に還元剤を添加して、銀粒子を還元析出させることを特徴とする。この銀粉の製造方法において、銀錯体水溶液が銀アンミン錯体水溶液であるのが好ましい。この場合、銀アンミン錯体水溶液中の安息香酸の量が銀に対して0.05〜6質量%であるのが好ましい。また、銀粒子を還元析出させた後、表面処理剤を添加するのが好ましい。 That is, the method for producing silver powder according to the present invention is characterized in that a reducing agent is added to an aqueous silver complex solution containing benzoic acid to reduce and precipitate silver particles. In this method for producing silver powder, it is preferable that the silver complex aqueous solution is a silver ammine complex aqueous solution. In this case, the amount of benzoic acid in the silver ammine complex aqueous solution is preferably 0.05 to 6% by mass with respect to silver. Further, it is preferable to add a surface treatment agent after reducing and precipitating the silver particles.
また、本発明による銀粉は、粒子内部に安息香酸を含むことを特徴とする。この銀粉の粒子内部に含まれる安息香酸の量が銀に対して0.001〜1質量%であるのが好ましい。また、銀粉のレーザー回折法による平均粒径D50が0.3〜5μmであるのが好ましく、銀粉のBET比表面積が0.1〜3m/gであるのが好ましい。 Further, the silver powder according to the present invention is characterized by containing benzoic acid inside the particles. The amount of benzoic acid contained inside the particles of the silver powder is preferably 0.001 to 1% by mass with respect to silver. Further, the average particle size D 50 of the silver powder by the laser diffraction method is preferably 0.3 to 5 μm, and the BET specific surface area of the silver powder is preferably 0.1 to 3 m 2 / g.
また、本発明による導電性ペーストは、上記の銀粉と、有機ビヒクルとを含むことを特徴とする。 Further, the conductive paste according to the present invention is characterized by containing the above-mentioned silver powder and an organic vehicle.
なお、本明細書中において、「レーザー回折法による平均粒径D50」とは、レーザー回折式粒度分布装置により測定した体積基準の累積50%粒子径(D50)をいう。 In the present specification, the “average particle size D 50 by laser diffraction method” means the cumulative 50% particle size (D 50 ) based on the volume measured by the laser diffraction type particle size distribution device.
本発明によれば、従来の湿式還元法により製造した銀粉と同程度の粒径を有し且つ焼成型の導電性ペーストに使用した場合に体積抵抗率が低い導電膜を形成可能な銀粉を製造することができる。 According to the present invention, a silver powder having a particle size similar to that of silver powder produced by a conventional wet reduction method and capable of forming a conductive film having a low volume resistivity when used in a firing type conductive paste can be produced. can do.
本発明による銀粉の製造方法の実施の形態では、安息香酸を含む銀錯体水溶液に還元剤を添加して、銀粒子を還元析出させる。 In the embodiment of the method for producing silver powder according to the present invention, a reducing agent is added to an aqueous silver complex solution containing benzoic acid to reduce and precipitate silver particles.
銀錯体水溶液は、硝酸銀水溶液または塩化銀懸濁液にアンモニア水またはアンモニウム塩(アンモニウムイオンNH と塩化物イオンCl、硝酸イオンNO 、硫酸イオンSO 2−などの陰イオンとの塩)を添加することにより得ることができる。これらの銀錯体水溶液の中で、銀粉が適当な粒径(レーザー回折法による平均粒径D50が0.3〜5μm)を有するようにするためには、硝酸銀水溶液にアンモニア水を添加して得られる銀アンミン錯体水溶液(化学式[Ag(NHで表される銀アンミン錯体の水溶液)を使用するのが好ましい。銀錯体水溶液として銀アンミン錯体水溶液を使用する場合、銀アンミン錯体水溶液中の銀濃度が0.1質量%未満であると、1回の反応で製造することができる銀粉の量が少な過ぎ、一方、10質量%を超えると、銀粒子が析出した後の反応液の粘度が上昇して反応液を均一に撹拌することができなくなるおそれがあるので、銀アンミン錯体水溶液中の銀濃度は、0.1〜10質量%であるのが好ましい。また、銀アンミン錯体中におけるアンモニアの配位数は2であるため、銀1モル当たりアンモニア2モル以上(好ましくは3モル以上)を添加する。また、アンモニアの添加量が多過ぎると錯体が安定化し過ぎて還元が進み難くなるので、アンモニアの添加量は銀1モル当たりアンモニア8モル以下であるのが好ましい。なお、還元剤の添加量を多くするなどの調整を行えば、アンモニアの添加量が8モルを超えても適当な粒径(レーザー回折法による平均粒径D50が0.3〜5μm)の銀粉を得ることは可能である。 Silver complex aqueous solution, an aqueous silver nitrate solution or a chloride ion Cl aqueous ammonia or an ammonium salt (ammonium ion NH 4 + and the silver chloride suspension -, nitrate ions NO 3 -, and anions such as 2-sulfate ion SO 4 It can be obtained by adding (salt). In order for the silver powder to have an appropriate particle size (average particle size D 50 by laser diffraction method is 0.3 to 5 μm) among these silver complex aqueous solutions, ammonia water is added to the silver nitrate aqueous solution. It is preferable to use the obtained silver ammine complex aqueous solution (an aqueous solution of the silver ammine complex represented by the chemical formula [Ag (NH 3 ) 2 ] + ). When a silver ammine complex aqueous solution is used as the silver complex aqueous solution, if the silver concentration in the silver ammine complex aqueous solution is less than 0.1% by mass, the amount of silver powder that can be produced in one reaction is too small, while If it exceeds 10% by mass, the viscosity of the reaction solution after the silver particles are precipitated may increase and the reaction solution may not be uniformly agitated. Therefore, the silver concentration in the silver ammine complex aqueous solution is 0. It is preferably 1 to 10% by mass. Further, since the coordination number of ammonia in the silver ammine complex is 2, 2 mol or more (preferably 3 mol or more) of ammonia is added per 1 mol of silver. Further, if the amount of ammonia added is too large, the complex becomes too stable and reduction does not proceed easily. Therefore, the amount of ammonia added is preferably 8 mol or less per 1 mol of silver. If adjustments are made such as increasing the amount of the reducing agent added, the particle size is appropriate even if the amount of ammonia added exceeds 8 mol (the average particle size D50 by the laser diffraction method is 0.3 to 5 μm). It is possible to obtain silver powder.
安息香酸を含む銀錯体水溶液は、安息香酸イオン(CCOO)を含む銀錯体水溶液であればよく、銀錯体水溶液と安息香酸(CCOOH)または安息香酸塩(例えば、安息香酸ナトリウムCCOONaや安息香酸アンモニウムCCOONH)(あるいは安息香酸または安息香酸塩の水溶液)とを混合することにより得ることができる。 The silver complex aqueous solution containing benzoic acid may be any silver complex aqueous solution containing benzoic acid ion (C 6 H 5 COO ), and the silver complex aqueous solution and benzoic acid (C 6 H 5 COOH) or benzoate (for example, for example). It can be obtained by mixing sodium benzoate C 6 H 5 COONa or ammonium benzoate C 6 H 5 COONH 4 ) (or an aqueous solution of benzoic acid or benzoate).
安息香酸を含む銀アンミン錯体水溶液中の安息香酸の量は、銀に対して0.05〜6質量%であるのが好ましく、0.1〜4質量%であるのがさらに好ましく、0.2〜2質量%であるのが最も好ましい。安息香酸を含む銀アンミン錯体水溶液中の安息香酸の量が0.05質量%未満であると、得られた銀粉を含む導電性ペーストを使用して体積抵抗率が十分に低い導電膜を形成することができなくなり、6質量%を超えると、得られた銀粉を含む導電性ペーストの粘度が高くなり過ぎるため、導電性ペーストを希釈する必要があり、導電性ペーストの銀濃度が低くなって、配線として形成される導電膜が断線する場合がある。 The amount of benzoic acid in the aqueous solution of the silver ammine complex containing benzoic acid is preferably 0.05 to 6% by mass, more preferably 0.1 to 4% by mass, and 0.2. Most preferably, it is ~ 2% by mass. When the amount of benzoic acid in the silver ammine complex aqueous solution containing benzoic acid is less than 0.05% by mass, the obtained conductive paste containing silver powder is used to form a conductive film having a sufficiently low volume resistivity. If it exceeds 6% by mass, the viscosity of the obtained conductive paste containing silver powder becomes too high, so that the conductive paste needs to be diluted, and the silver concentration of the conductive paste becomes low. The conductive film formed as wiring may be broken.
また、安息香酸を含む銀アンミン錯体水溶液は、アルカリ性であるのが好ましく(pHが7より高いのが好ましく、8以上であるのがさらに好ましく)、pH調整剤として水酸化ナトリウムなどのアルカリを添加してアルカリ性に調整するのが好ましい。 Further, the silver ammine complex aqueous solution containing benzoic acid is preferably alkaline (pH is preferably higher than 7, more preferably 8 or more), and an alkali such as sodium hydroxide is added as a pH adjuster. It is preferable to adjust the pH to alkaline.
還元剤としては、銀粒子を還元析出させる還元剤であればよく、例えば、アスコルビン酸、過酸化水素水、ギ酸、酒石酸、ヒドロキノン、ピロガロール、ぶどう糖、没食子酸、ホルムアルデヒド、ヒドラジン、ヒドラジン化合物、アルカノールアミンなどの1種以上を使用することができ、ホルムアルデヒド、ヒドラジンまたはヒドラジン化合物を使用するのが好ましい。このような還元剤を使用することにより、適当な粒径(レーザー回折法による平均粒径D50が0.3〜5μm)の銀粉を得ることができる。還元剤の添加量は、銀の収率を高めるために、銀に対して1当量以上であるのが好ましく、還元力が弱い還元剤を使用する場合には、銀に対して2当量以上、例えば、10〜20当量でもよい。 The reducing agent may be any reducing agent that reduces and precipitates silver particles. For example, ascorbic acid, hydrogen peroxide solution, formic acid, tartaric acid, hydroquinone, pyrogallol, glucose, gallic acid, formaldehyde, hydrazine, hydrazine compound, alkanolamine. One or more of them can be used, and it is preferable to use formaldehyde, hydrazine or a hydrazine compound. By using such a reducing agent, silver powder having an appropriate particle size (average particle size D 50 by laser diffraction method is 0.3 to 5 μm) can be obtained. The amount of the reducing agent added is preferably 1 equivalent or more with respect to silver in order to increase the yield of silver, and when a reducing agent having a weak reducing power is used, it is 2 equivalents or more with respect to silver. For example, it may be 10 to 20 equivalents.
還元剤の添加方法については、銀粉の凝集を防ぐために、1当量/分以上の速さで添加するのが好ましい。また、還元の際には、より短時間で反応が終了するように反応液を攪拌するのが好ましい。また、還元反応時の温度は、5〜80℃であるのが好ましく、5〜40℃であるのがさらに好ましい。 Regarding the method of adding the reducing agent, it is preferable to add the reducing agent at a rate of 1 equivalent / min or more in order to prevent aggregation of the silver powder. Further, at the time of reduction, it is preferable to stir the reaction solution so that the reaction is completed in a shorter time. The temperature during the reduction reaction is preferably 5 to 80 ° C, more preferably 5 to 40 ° C.
また、還元剤により銀粒子を還元析出させた後、表面処理剤を添加して、銀粒子の表面に表面処理剤を付着させるのが好ましい。この表面処理剤として、脂肪酸、脂肪酸塩、界面活性剤、有機金属化合物、キレート剤、高分子分散剤などを使用することができる。脂肪酸および脂肪酸塩として、プロピオン酸、カプリル酸、ラウリン酸、ミリスチン酸、パルミチン酸、ステアリン酸、ベヘン酸、アクリル酸、オレイン酸、リノール酸、アラキドン酸、リシノール酸およびこれらの塩やエマルジョンを使用することができる。また、キレート剤として、ベンゾトリアゾールなどのアゾール類またはその塩や、コハク酸、マロン酸、グルタル酸、アジピン酸などを使用することができる。 Further, it is preferable that the silver particles are reduced and precipitated with a reducing agent, and then a surface treatment agent is added to attach the surface treatment agent to the surface of the silver particles. As the surface treatment agent, fatty acids, fatty acid salts, surfactants, organometallic compounds, chelating agents, polymer dispersants and the like can be used. As fatty acids and fatty acid salts, propionic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, bechenic acid, acrylic acid, oleic acid, linoleic acid, arachidonic acid, ricinolic acid and salts and emulsions thereof are used. be able to. Further, as the chelating agent, azoles such as benzotriazole or salts thereof, succinic acid, malonic acid, glutaric acid, adipic acid and the like can be used.
銀粒子を還元析出させることによって得られた銀含有スラリーを固液分離し、得られた固形物を純水で洗浄して、固形物中の不純物を除去するのが好ましい。この洗浄の終点は、洗浄後の水の電気伝導度により判断することができ、この電気伝導度が0.5mS/m以下になるまで洗浄するのが好ましい。 It is preferable that the silver-containing slurry obtained by reducing and precipitating the silver particles is solid-liquid separated, and the obtained solid substance is washed with pure water to remove impurities in the solid substance. The end point of this washing can be determined from the electric conductivity of the water after washing, and it is preferable to wash until the electric conductivity becomes 0.5 mS / m or less.
この洗浄後に得られた塊状のケーキは、多くの水分を含有しているため、真空乾燥機などの乾燥機によって、乾燥した銀粉を得るのが好ましい。この乾燥の温度は、乾燥の時点で銀粉同士が焼結するのを防止するために、100℃以下であるのが好ましい。 Since the lumpy cake obtained after this washing contains a large amount of water, it is preferable to obtain dried silver powder by a dryer such as a vacuum dryer. The drying temperature is preferably 100 ° C. or lower in order to prevent the silver powders from sintering each other at the time of drying.
また、得られた銀粉に乾式解砕処理や分級処理を施してもよい。この解砕の代わりに、粒子を機械的に流動化させることができる装置に銀粉を投入して、銀粉の粒子同士を機械的に衝突させることによって、銀粉の粒子表面の凹凸や角ばった部分を滑らかにする表面平滑化処理を行ってもよい。また、解砕や平滑化処理の後に分級処理を行ってもよい。なお、乾燥、粉砕および分級を行うことができる一体型の装置を用いて乾燥、粉砕および分級を行ってもよい。 Further, the obtained silver powder may be subjected to a dry crushing treatment or a classification treatment. Instead of this crushing, silver powder is put into a device that can mechanically fluidize the particles, and the silver powder particles are mechanically collided with each other to remove irregularities and angular parts on the surface of the silver powder particles. A surface smoothing treatment for smoothing may be performed. Further, the classification treatment may be performed after the crushing or smoothing treatment. In addition, drying, crushing, and classification may be performed using an integrated device capable of drying, crushing, and classifying.
上記の銀粉の製造方法により、本発明による銀粉の実施の形態を製造することができる。本発明による銀粉の実施の形態は、粒子内部に安息香酸を含む。この銀粉の粒子内部に含まれる安息香酸の量は、銀に対して0.001〜1質量%であるのが好ましい。また、銀粉のレーザー回折法による平均粒径(体積基準の累積50%粒子径)D50は、銀粉を導電性ペーストに使用した場合に、電子部品の小型化による導体パターンの高密度化やファインライン化に対応したり、太陽電池の集光面積を増大して発電効率を向上させるためにフィンガー電極のファインライン化に対応するように、0.3〜5μmであるのが好ましく、0.5〜3μmであるのがさらに好ましい。また、銀粉のBET比表面積は、0.1〜3m/gであるのが好ましく、0.2〜2m/gであるのがさらに好ましい。BET比表面積が0.1m/gより小さいと、銀粉の粒径が大きくなり、そのような大きい銀粉を導電性ペーストに使用して配線などを描画すると、微細配線を描画し難くなり、一方、3m/gより大きいと、導電性ペーストの粘度が高くなり過ぎるため、導電性ペーストを希釈する必要があり、導電性ペーストの銀濃度が低くなって、配線として形成される導電膜が断線する場合がある。 By the above-mentioned method for producing silver powder, an embodiment of silver powder according to the present invention can be produced. Embodiments of silver powder according to the present invention contain benzoic acid inside the particles. The amount of benzoic acid contained inside the particles of the silver powder is preferably 0.001 to 1% by mass with respect to silver. The average particle size D 50 (50% cumulative particle diameter on a volume basis) by laser diffraction method of silver powder, when used in the conductive paste silver powder, density and fine conductor pattern by the miniaturization of electronic components The thickness is preferably 0.3 to 5 μm so as to correspond to the line formation or to correspond to the fine line formation of the finger electrodes in order to increase the light collecting area of the solar cell and improve the power generation efficiency. It is more preferably ~ 3 μm. Further, BET specific surface area of silver powder is preferably from 0.1~3m 2 / g, and even more preferably 0.2~2m 2 / g. If the BET specific surface area is smaller than 0.1 m 2 / g, the particle size of the silver powder becomes large, and if such a large silver powder is used for the conductive paste to draw the wiring or the like, it becomes difficult to draw the fine wiring. If it is larger than 3 m 2 / g, the viscosity of the conductive paste becomes too high, so it is necessary to dilute the conductive paste, the silver concentration of the conductive paste becomes low, and the conductive film formed as wiring is broken. May be done.
以下、本発明による銀粉およびその製造方法の実施例について詳細に説明する。 Hereinafter, examples of the silver powder according to the present invention and the method for producing the same will be described in detail.
[実施例1]
銀49gを含有する硝酸銀水溶液3500gに、濃度28質量%の工業用アンモニア水155g(銀1モルに対してアンモニア5.6モル当量)を加えて、銀アンミン錯体水溶液を得た。この銀アンミン錯体水溶液に、濃度20質量%の水酸化ナトリウム水溶液6gと、4.7質量%の安息香酸を含有する安息香酸ナトリウム水溶液5.31g(20質量%の水酸化ナトリウム0.34gを純水4.72gに溶かしたアルカリ水溶液に安息香酸0.25gを加えて超音波により完全に溶解させた安息香酸ナトリウム水溶液(銀に対して0.50質量%の安息香酸))を加え、液温を20℃に調整した後、攪拌しながら(還元剤として)濃度23質量%のホルムアルデヒド水溶液380gを加えて、銀粒子を含むスラリーを得た。このスラリーに、(表面処理剤として)1.6重量%のステアリン酸水溶液6.5gを加えて、十分に撹拌した後、撹拌を止めて、銀粒子を沈降させた。この銀粒子が沈殿した液をろ過し、通水後の液の電気伝導度が0.5mS/m以下になるまで水洗し、乾燥させた後、解砕して、銀粉を得た。なお、ろ過後のろ液のpHは8.5であった。
[Example 1]
To 3500 g of a silver nitrate aqueous solution containing 49 g of silver, 155 g of industrial ammonia water having a concentration of 28% by mass (5.6 mol equivalents of ammonia per 1 mol of silver) was added to obtain a silver ammine complex aqueous solution. In this silver ammine complex aqueous solution, 6 g of a sodium hydroxide aqueous solution having a concentration of 20% by mass and 5.31 g of a sodium benzoate aqueous solution containing 4.7% by mass of benzoic acid (0.34 g of 20% by mass of sodium hydroxide are purely added. 0.25 g of benzoic acid was added to an alkaline aqueous solution dissolved in 4.72 g of water, and an aqueous sodium benzoate solution (0.50 mass% benzoic acid with respect to silver) completely dissolved by ultrasonic waves was added, and the liquid temperature was increased. Was adjusted to 20 ° C., and then 380 g of an aqueous solution of formaldehyde having a concentration of 23% by mass (as a reducing agent) was added with stirring to obtain a slurry containing silver particles. 6.5 g of a 1.6 wt% stearic acid aqueous solution (as a surface treatment agent) was added to this slurry, and the mixture was sufficiently stirred, and then the stirring was stopped to allow the silver particles to settle. The liquid in which the silver particles were precipitated was filtered, washed with water until the electric conductivity of the liquid after passing water became 0.5 mS / m or less, dried, and then crushed to obtain silver powder. The pH of the filtrate after filtration was 8.5.
このようにして得られた銀粉のBET比表面積を、BET比表面積測定装置(株式会社マウンテック製のMacsorb HM−model 1210)を使用して、測定装置内に60℃で10分間(30体積%の窒素を含む)Ne−N混合ガスを流して脱気した後、BET1点法により測定したところ、BET比表面積は0.76m/gであった。 The BET specific surface area of the silver powder thus obtained was measured in a measuring device at 60 ° C. for 10 minutes (30% by volume) using a BET specific surface area measuring device (Macsorb HM-model 1210 manufactured by Mountech Co., Ltd.). After degassing by flowing a Ne-N 2 mixed gas (containing nitrogen), the BET specific surface area was 0.76 m 2 / g as measured by the BET 1-point method.
また、得られた銀粉の粒度分布を、レーザー回折式粒度分布測定装置(日機装株式会社製のマイクロトラックMT3300EXII)により、分散媒としてイソプロパノール(IPA)を使用して測定したところ、体積基準の累積10%粒子径(D10)は1.1μm、累積50%粒子径(D50)は1.6μm、累積90%粒子径(D90)は2.5μmであり、D90/D50比は1.6であった。 Further, the particle size distribution of the obtained silver powder was measured by a laser diffraction type particle size distribution measuring device (Microtrac MT3300EXII manufactured by Nikkiso Co., Ltd.) using isopropanol (IPA) as a dispersion medium. The% particle size (D 10 ) is 1.1 μm, the cumulative 50% particle size (D 50 ) is 1.6 μm, the cumulative 90% particle size (D 90 ) is 2.5 μm, and the D 90 / D 50 ratio is 1. It was 0.6.
また、得られた銀粉1.0gに超純水8mLと硝酸(関東化学株式会社製の精密分析用硝酸(濃度60〜61質量%))4mLを加えて、ウォーターバスにより70℃で加温分解し、さらに超純水10mLと塩酸(関東化学株式会社製の精密分析用塩酸(濃度35〜37質量%))1.5mLを加えて撹拌し、液が透明になったところで、20分間放冷した後、ろ過し、超純水で100mLに定容し、さらに超純水で100倍に希釈して、液体クロマトグラフ質量分析計(LC/MC)(アジレント・テクノロジー株式会社製のAgilent6470トリプル四重極LC/MS)により分析したところ、銀粉の表面と内部に合計0.34質量%の安息香酸が存在していることが確認された。 Further, 8 mL of ultrapure water and 4 mL of nitric acid (nitrite for precision spectrometry (concentration 60 to 61% by mass) manufactured by Kanto Chemical Co., Ltd.) were added to 1.0 g of the obtained silver powder, and the mixture was heated and decomposed at 70 ° C. by a water bath. Then, add 10 mL of ultrapure water and 1.5 mL of hydrochloric acid (hydrogen for precision spectrometry (concentration 35 to 37% by mass) manufactured by Kanto Chemical Co., Ltd.), stir, and allow to cool for 20 minutes when the liquid becomes transparent. After that, it is filtered, the volume is adjusted to 100 mL with ultrapure water, and further diluted 100 times with ultrapure water, and then liquid chromatograph mass spectrometer (LC / MC) (Agilent 6470 Triple 4 manufactured by Azilent Technology Co., Ltd.) As a result of analysis by heavy electrode LC / MS), it was confirmed that a total of 0.34% by mass of benzoic acid was present on the surface and inside of the silver powder.
また、得られた銀粉1gに、塩酸(関東化学株式会社製の精密分析用塩酸(濃度35〜37質量%))と超純水を体積比1:1で混合した塩酸水溶液20mLを加えて、ウォーターバスにより70℃で加温することにより抽出し、20分間放冷した後、ろ過により固液分離し、得られた液を上記の1:1の塩酸水溶液で50mLに定容し、さらに超純水で1000倍に希釈して、上記の液体クロマトグラフ質量分析計(LC/MC)により分析したところ、銀は塩酸に溶解しないことから、銀粉の表面に0.33質量%の安息香酸が存在していることが確認された。 Further, 20 mL of an aqueous hydrochloric acid solution prepared by mixing hydrochloric acid (hydrochloric acid for precision analysis (concentration 35 to 37% by mass) manufactured by Kanto Chemical Co., Ltd.) and ultrapure water at a volume ratio of 1: 1 was added to 1 g of the obtained silver powder. Extraction is performed by heating at 70 ° C. in a water bath, allowed to cool for 20 minutes, then solid-liquid separated by filtration, and the obtained solution is adjusted to 50 mL with the above 1: 1 hydrochloric acid aqueous solution, and further super When it was diluted 1000 times with pure water and analyzed by the above liquid chromatograph mass analyzer (LC / MC), silver was not dissolved in hydrochloric acid, so 0.33% by mass of benzoic acid was found on the surface of the silver powder. It was confirmed that it existed.
また、上記の固液分離により得られた残渣に超純水8mLと硝酸(関東化学株式会社製の精密分析用硝酸(濃度60〜61質量%))4mLを加えて、ウォーターバスにより70℃で加温分解し、得られた溶液に超純水10mLと塩酸1.5mLを加えて撹拌し、液が透明になるまでウォーターバスにより70℃で加温し、20分間放冷した後、ろ過し、超純水で100mLに定容し、さらに超純水で100倍に希釈して、上記の液体クロマトグラフ質量分析計(LC/MC)により分析したところ、銀粉の内部に0.004質量%の安息香酸が含まれていることが確認された。 Further, 8 mL of ultrapure water and 4 mL of nitric acid (nitrite for precision analysis (concentration 60 to 61% by mass) manufactured by Kanto Chemical Co., Ltd.) were added to the residue obtained by the above solid-liquid separation, and the temperature was 70 ° C. by a water bath. After heating and decomposing, add 10 mL of ultrapure water and 1.5 mL of hydrochloric acid to the obtained solution, stir, heat at 70 ° C. with a water bath until the solution becomes transparent, allow to cool for 20 minutes, and then filter. , 100 mL with ultrapure water, diluted 100 times with ultrapure water, and analyzed with the above liquid chromatograph mass analyzer (LC / MC). 0.004 mass% inside the silver powder. It was confirmed that it contained benzoic acid.
また、得られた銀粉27.0gとテキサノール(JNC株式会社製のCS−12)3.3gをプロペラレス自公転式攪拌脱泡装置(株式会社シンキー製のAR250)で混練した後、3本ロール(EXAKT社製の80S)で混練することにより、導電性ペーストを得た。この導電性ペーストを、シリコン基板の表面に、スクリーン印刷機(マイクロテック株式会社製のMT−320T)により、幅250μm×長さ55mmのライン状に印刷し、熱風式乾燥機により200℃で10分間加熱した後、高速焼成IR炉(日本ガイシ株式会社製の高速焼成試験4室炉)でイン−アウト22.9秒間としてピーク温度770℃で焼成した。このようにして得られた導電膜について、表面粗さ・輪郭形状測定機(東京精密株式会社製のサーフコム480B−12)により(長さ方向における一端から他端までの)平均厚さを測定したところ、平均厚さは16.1μmであり、デジタルマルチメーター(株式会社アドバンテスト製のR6551)により抵抗値を測定したところ、抵抗値は0.289Ωであった。また、(この抵抗値と、膜厚、線幅および長さから求めた体積とから)導電膜の体積抵抗率を算出したところ、2.11μΩ・cmであった。 Further, 27.0 g of the obtained silver powder and 3.3 g of texanol (CS-12 manufactured by JNC Corporation) are kneaded with a propellerless self-revolving stirring and defoaming device (AR250 manufactured by Shinky Co., Ltd.), and then three rolls are used. A conductive paste was obtained by kneading with (80S manufactured by EXAKT). This conductive paste is printed on the surface of a silicon substrate in a line shape of width 250 μm × length 55 mm by a screen printing machine (MT-320T manufactured by Microtech Co., Ltd.), and 10 at 200 ° C. by a hot air dryer. After heating for 1 minute, it was fired in a high-speed firing IR furnace (high-speed firing test 4-chamber furnace manufactured by Nippon Gaishi Co., Ltd.) at a peak temperature of 770 ° C. for in-out 22.9 seconds. The average thickness (from one end to the other end in the length direction) of the conductive film thus obtained was measured by a surface roughness / contour shape measuring machine (Surfcom 480B-12 manufactured by Tokyo Seimitsu Co., Ltd.). However, the average thickness was 16.1 μm, and when the resistance value was measured with a digital multimeter (R6551 manufactured by Advantest Co., Ltd.), the resistance value was 0.289 Ω. Further, when the volume resistivity of the conductive film was calculated (from this resistance value and the volume obtained from the film thickness, line width and length), it was 2.11 μΩ · cm.
[比較例1]
安息香酸ナトリウム水溶液に代えて、4.8質量%のベンゾトリアゾールを含有するベンゾトリアゾールナトリウム水溶液5.12g(純水4.51gに40質量%のベンゾトリアゾールナトリウム0.61gを加えて超音波により完全に溶解させたベンゾトリアゾールナトリウム水溶液(銀に対して0.5質量%のベンゾトリアゾール))を使用した以外は、実施例1と同様の方法により、銀粉を得た。
[Comparative Example 1]
In place of the aqueous sodium benzoate solution, 5.12 g of an aqueous solution of benzotriazole containing 4.8% by mass of benzotriazole (4.51 g of pure water plus 0.61 g of 40% by mass of sodium benzotriazole was added and completely ultrasonically. A silver powder was obtained by the same method as in Example 1 except that an aqueous solution of benzotriazole sodium dissolved in (0.5% by mass of silver with respect to silver) was used.
このようにして得られた銀粉について、実施例1と同様の方法により、BET比表面積と粒度分布を測定したところ、BET比表面積は0.56m/g、体積基準の累積10%粒子径(D10)は1.2μm、累積50%粒子径(D50)は2.0μm、累積90%粒子径(D90)は3.3μmであり、D90/D50比は1.7であった。 When the BET specific surface area and the particle size distribution of the silver powder thus obtained were measured by the same method as in Example 1, the BET specific surface area was 0.56 m 2 / g, and the cumulative 10% particle diameter on a volume basis ( D 10 ) is 1.2 μm, cumulative 50% particle size (D 50 ) is 2.0 μm, cumulative 90% particle size (D 90 ) is 3.3 μm, and D 90 / D 50 ratio is 1.7. It was.
また、得られた銀粉を使用して、実施例1と同様の方法により、導電膜を作製し、その平均厚さと抵抗値を測定し、体積抵抗率を算出したところ、平均厚さは17.5μm、抵抗値は0.307Ω、体積抵抗率は2.44μΩ・cmであった。 Further, using the obtained silver powder, a conductive film was prepared by the same method as in Example 1, the average thickness and resistance value thereof were measured, and the volume resistivity was calculated. As a result, the average thickness was 17. It was 5 μm, the resistance value was 0.307 Ω, and the volume resistivity was 2.44 μΩ · cm.
[比較例2]
安息香酸ナトリウム水溶液に代えて、5.3質量%のL−リシンを含有するL−リシン水溶液5.88g(純水5.57gにL−リシン0.31gを加えて超音波により完全に溶解させたL−リシン水溶液(銀に対して0.6質量%のL−リシン))を使用した以外は、実施例1と同様の方法により、銀粉を得た。
[Comparative Example 2]
Instead of the sodium benzoate aqueous solution, 5.88 g of the L-lysine aqueous solution containing 5.3% by mass of L-lysine (5.31 g of L-lysine was added to 5.57 g of pure water and completely dissolved by ultrasonic waves. Silver powder was obtained by the same method as in Example 1 except that an aqueous solution of L-lysine (0.6% by mass based on silver) was used.
このようにして得られた銀粉について、実施例1と同様の方法により、BET比表面積と粒度分布を測定したところ、BET比表面積は0.53m/g、体積基準の累積10%粒子径(D10)は1.2μm、累積50%粒子径(D50)は2.1μm、累積90%粒子径(D90)は3.6μmであり、D90/D50比は1.7であった。 When the BET specific surface area and the particle size distribution of the silver powder thus obtained were measured by the same method as in Example 1, the BET specific surface area was 0.53 m 2 / g, and the cumulative 10% particle size based on the volume (volume-based cumulative 10% particle size). D 10 ) is 1.2 μm, cumulative 50% particle size (D 50 ) is 2.1 μm, cumulative 90% particle size (D 90 ) is 3.6 μm, and D 90 / D 50 ratio is 1.7. It was.
また、得られた銀粉を使用して、実施例1と同様の方法により、導電膜を作製し、その平均厚さと抵抗値を測定し、体積抵抗率を算出したところ、平均厚さは15.9μm、抵抗値は0.321Ω、体積抵抗率は2.32μΩ・cmであった。 Further, using the obtained silver powder, a conductive film was produced by the same method as in Example 1, the average thickness and resistance value thereof were measured, and the volume resistivity was calculated. As a result, the average thickness was 15. It was 9 μm, the resistance value was 0.321 Ω, and the volume resistivity was 2.32 μΩ · cm.
これらの実施例および比較例で得られた銀粉の特性を表1に示す。 The characteristics of the silver powder obtained in these Examples and Comparative Examples are shown in Table 1.
本発明による銀粉は、より低い温度で焼成可能な銀粉として、導電性ペーストの作製に利用することができ、この銀粉を含む導電性ペーストをスクリーン印刷などにより基板上に印刷して、太陽電池、チップ部品、タッチパネルなどの電子部品の電極や回路の他、電磁波シールド材などに使用することができる。 The silver powder according to the present invention can be used for producing a conductive paste as a silver powder that can be fired at a lower temperature, and the conductive paste containing the silver powder is printed on a substrate by screen printing or the like to obtain a solar cell. It can be used for electrodes and circuits of electronic parts such as chip parts and touch panels, as well as electromagnetic wave shielding materials.

Claims (9)

  1. 安息香酸を含む銀錯体水溶液に還元剤を添加して、銀粒子を還元析出させることを特徴とする、銀粉の製造方法。 A method for producing silver powder, which comprises adding a reducing agent to an aqueous silver complex solution containing benzoic acid to reduce and precipitate silver particles.
  2. 前記銀錯体水溶液が銀アンミン錯体水溶液であることを特徴とする、請求項1に記載の銀粉の製造方法。 The method for producing silver powder according to claim 1, wherein the silver complex aqueous solution is a silver ammine complex aqueous solution.
  3. 前記銀アンミン錯体水溶液中の安息香酸の量が銀に対して0.05〜6質量%であることを特徴とする、請求項2に記載の銀粉の製造方法。 The method for producing silver powder according to claim 2, wherein the amount of benzoic acid in the silver ammine complex aqueous solution is 0.05 to 6% by mass with respect to silver.
  4. 前記銀粒子を還元析出させた後、表面処理剤を添加することを特徴とする、請求項1乃至3のいずれかに記載の銀粉の製造方法。 The method for producing silver powder according to any one of claims 1 to 3, wherein a surface treatment agent is added after the silver particles are reduced and precipitated.
  5. 銀粉の粒子内部に安息香酸を含むことを特徴とする、銀粉。 A silver powder characterized by containing benzoic acid inside the particles of the silver powder.
  6. 前記粒子内部に含まれる安息香酸の量が銀に対して0.001〜1質量%であることを特徴とする、請求項5に記載の銀粉。 The silver powder according to claim 5, wherein the amount of benzoic acid contained in the particles is 0.001 to 1% by mass with respect to silver.
  7. 前記銀粉のレーザー回折法による平均粒径D50が0.3〜5μmであることを特徴とする、請求項5または6に記載の銀粉。 The silver powder according to claim 5 or 6, wherein the average particle size D 50 of the silver powder by laser diffraction is 0.3 to 5 μm.
  8. 前記銀粉のBET比表面積が0.1〜3m/gであることを特徴とする、請求項5乃至7のいずれかに記載の銀粉。 The silver powder according to any one of claims 5 to 7, wherein the silver powder has a BET specific surface area of 0.1 to 3 m 2 / g.
  9. 請求項5乃至8のいずれかに記載の銀粉と、有機ビヒクルとを含むことを特徴とする、導電性ペースト。 A conductive paste comprising the silver powder according to any one of claims 5 to 8 and an organic vehicle.
JP2019033551A 2019-02-27 2019-02-27 Silver powder and method for producing the same Pending JP2020139178A (en)

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