JP4196350B2 - Method for producing flaky silver powder - Google Patents
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- JP4196350B2 JP4196350B2 JP2004273032A JP2004273032A JP4196350B2 JP 4196350 B2 JP4196350 B2 JP 4196350B2 JP 2004273032 A JP2004273032 A JP 2004273032A JP 2004273032 A JP2004273032 A JP 2004273032A JP 4196350 B2 JP4196350 B2 JP 4196350B2
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本発明は銀粉末の製造方法に関し、特にエレクトロニクス用の導体ペースト、導電性塗料、導電性接着剤等の導電性フィラーとして有用な、フレーク形状の銀粉末の製造方法に関するものである。 The present invention relates to a method for producing silver powder, and more particularly to a method for producing flake-shaped silver powder useful as a conductive filler such as a conductor paste for electronics, a conductive paint, and a conductive adhesive.
銀粉末は、導電性が高く優れた特性を有するため、エレクトロニクス分野において、導体回路や、電子部品の電極を形成するための厚膜導体ペースト、導電性塗料、導電性インク、あるいは導電性接着剤等（以下、総称して「導体ペースト」と言う。）の導電性フィラーとして広く用いられている。このような用途においては、主として球状銀粉末、粒状銀粉末、樹枝状銀粉末、あるいはリン片状、板状、扁平状等の形状を有するフレーク状の銀粉末が、用途や目的に応じて使用される。 Silver powder is highly conductive and has excellent characteristics, so in the electronics field, it is a thick film conductor paste, conductive paint, conductive ink, or conductive adhesive for forming conductor circuits and electrodes of electronic components. Etc. (hereinafter collectively referred to as “conductor paste”). In such applications, spherical silver powder, granular silver powder, dendritic silver powder, or flake-shaped silver powder having shapes such as flakes, plates, and flats are used depending on the application and purpose. Is done.
このうちフレーク状銀粉末は、導体ペーストの塗布適性や塗布形状の調整、導電性や焼結性の制御等に重要な役割を果たすことが知られている。近年の急速な電子部品の小型化、高性能化に伴い、高精細な導体パターンや薄く緻密な電極を精度良く形成する技術が要望されており、このため微細なフレーク状銀粉末、特に平均粒径が１０μｍ以下で、大きさや粒子形状の揃った高品質のフレーク状銀粉末が要求されている。 Among these, the flaky silver powder is known to play an important role in the application suitability of the conductor paste, the adjustment of the application shape, the control of conductivity and sinterability, and the like. Along with the rapid miniaturization and high performance of electronic components in recent years, there is a demand for technology for accurately forming high-definition conductor patterns and thin and dense electrodes. For this reason, fine flaky silver powder, especially average grains There is a demand for high-quality flaky silver powder having a diameter of 10 μm or less and having a uniform size and particle shape.
フレーク状銀粉末は、一般的には液相還元法やアトマイズ法によって得られる球状や粒状の銀粉末をボールミル、スタンプミルなどを用いて粉砕処理し、機械的応力により磨砕、扁平化する方法で製造されている。この方法は容易であるが、原料粉末が凝集していたり、また粉砕時に銀粒子同士が合着したりするために粗大になり易く、また厚みや大きさが不揃いになる。また未粉砕粒子が残り易い。このため粒子形状や粒径がばらつき、導体ペーストの特性に影響を及ぼす。さらにジルコニアボールやステンレスボールなど粉砕メディアの材料が、不純物として混入し易い問題がある。さらに球状や粒状の銀粉末を製造する工程とこれを偏平化する工程の２つの工程が必要となり、工程数が多い上に、各工程において銀粉の未回収分が生じて収率が減少するために、コスト的に不利である。 Flaky silver powder is generally obtained by grinding spherical or granular silver powder obtained by a liquid phase reduction method or atomizing method using a ball mill, stamp mill, etc., and grinding and flattening with mechanical stress. Manufactured by. This method is easy, but the raw material powder is agglomerated, and the silver particles are coalesced at the time of pulverization, so that it tends to be coarse, and the thickness and size are not uniform. Moreover, unpulverized particles tend to remain. For this reason, the particle shape and particle size vary, which affects the properties of the conductor paste. Furthermore, there is a problem that the material of the grinding media such as zirconia balls and stainless balls is likely to be mixed as impurities. In addition, two processes are required: a process for producing spherical and granular silver powder and a process for flattening this, and the number of processes is large, and unrecovered silver powder is produced in each process, resulting in a decrease in yield. However, it is disadvantageous in terms of cost.
このため、湿式の化学還元法で直接フレーク状銀粉末を製造することも検討されている（特許文献１参照）。特許文献１においては、硝酸銀水溶液とＬ−アスコルビン酸を混合して銀粒子を析出する際に、ポリアクリル酸アンモニウムを添加することにより、粒状銀粉末を機械的に偏平化する工程を必要とせず、１工程にてフレーク状銀粉末を得ることが開示されている。 For this reason, production of flaky silver powder directly by a wet chemical reduction method has also been studied (see Patent Document 1). In patent document 1, when mixing silver nitrate aqueous solution and L-ascorbic acid and depositing silver particles, the process of mechanically flattening granular silver powder is not required by adding ammonium polyacrylate. It is disclosed to obtain flaky silver powder in one step.
しかしながら、特許文献１の方法で生成するフレーク状銀粉末は、平均粒径が１０μｍを超える比較的大きいものであり、またポリアクリル酸アンモニウムの分子量の分布幅により厚みや大きさのばらつきが大きくなる。さらに、生成する銀粉末の表面に高分子量のポリアクリル酸アンモニウムが付着しており、洗浄によっても完全には除去しにくいため、粉末表面に有機物が多量に残存することになる。このため、導体ペースト等に配合したとき、銀粉末同士の接触が阻害されて高導電性が得られなかったり、ペーストの焼成時に多量のガスを発生したり、カーボンが残留したりし、導体膜の緻密性や電子部品の特性を損なう恐れがある。 However, the flaky silver powder produced by the method of Patent Document 1 has a relatively large average particle diameter exceeding 10 μm, and the variation in thickness and size increases due to the molecular weight distribution width of ammonium polyacrylate. . Furthermore, since a high molecular weight ammonium polyacrylate is attached to the surface of the silver powder to be produced, and it is difficult to completely remove it by washing, a large amount of organic matter remains on the powder surface. For this reason, when blended in a conductor paste or the like, contact between silver powders is hindered and high conductivity cannot be obtained, or a large amount of gas is generated during firing of the paste, carbon remains, and the conductor film There is a risk of damaging the density and the characteristics of electronic components.
本発明は、このような問題を解決し、微細で形状や大きさの揃ったフレーク状銀粉末を、粉砕工程を経ない湿式還元法により容易に得ることを目的とする。また、とりわけ粉末表面の有機物の付着が少なく、かつ平均粒径が１０μｍ以下の分散性のよい微細なフレーク状銀粉末を、安定して製造し得る方法を提供することを目的とする。 An object of the present invention is to solve such a problem and to easily obtain a flaky silver powder having a fine shape and a uniform size by a wet reduction method without passing through a pulverization step. Another object of the present invention is to provide a method capable of stably producing a fine flaky silver powder having a good dispersibility, in particular, having less adhesion of organic substances on the powder surface and an average particle size of 10 μm or less.
本発明者は鋭意研究を重ねた結果、硝酸銀溶液と還元剤溶液を反応させて銀粒子を析出させる際に、下記の２種の添加剤（Ａ）、（Ｂ）を存在させることにより、厚みや大きさが均一で、微細なフレーク状銀粉末が得られることを知見し、本発明に到達したものである。 As a result of intensive studies, the present inventor made the following two types of additives (A) and (B) present when the silver nitrate solution and the reducing agent solution were reacted to precipitate silver particles. It has been found that fine flaky silver powder having a uniform size can be obtained, and the present invention has been achieved.
すなわち、本発明に係るフレーク状銀粉末の製造方法は、硝酸銀溶液と還元剤溶液とを、（Ａ）エチレンジアミン四酢酸および／またはその塩、および（Ｂ）カルボン酸、カルボン酸金属塩、カルボン酸無水物およびカルボン酸アミドからなる群より選ばれる少なくとも１種の化合物の存在下で反応させることを特徴とするものである。 That is, the method for producing a flaky silver powder according to the present invention comprises: (A) ethylenediaminetetraacetic acid and / or a salt thereof; and (B) a carboxylic acid, a carboxylic acid metal salt, or a carboxylic acid. The reaction is carried out in the presence of at least one compound selected from the group consisting of an anhydride and a carboxylic acid amide.
還元剤は、Ｌ−アスコルビン酸、Ｄ−エリソルビン酸またはこれらの塩であることが好ましい。 The reducing agent is preferably L-ascorbic acid, D-erythorbic acid or a salt thereof.
添加剤（Ｂ）は、総炭素数が５〜３０の脂肪酸または総炭素数が５〜３０の脂肪酸アミドであることが好ましく、総炭素数が５〜２０の三級脂肪酸であることがさらに好ましい。 The additive (B) is preferably a fatty acid having 5 to 30 carbon atoms or a fatty acid amide having 5 to 30 carbon atoms, and more preferably a tertiary fatty acid having 5 to 20 carbon atoms. .
本発明の方法によれば、導体ペースト等に用いるのに適した、厚みや大きさの揃った微細なフレーク状銀粉末を、簡単な方法で製造することができる。特に、電子顕微鏡観察による平均粒径が１０μｍ以下の微細なフレーク状粉末を容易に得ることができる。なお、本発明においてフレーク状粉末の粒径は、特に断らない限り長径を意味するものとする。 According to the method of the present invention, a fine flaky silver powder having a uniform thickness and size suitable for use in a conductor paste or the like can be produced by a simple method. In particular, it is possible to easily obtain a fine flaky powder having an average particle diameter of 10 μm or less as observed by an electron microscope. In the present invention, the particle diameter of the flaky powder means a long diameter unless otherwise specified.
また粉砕工程を経ずにフレーク状粉末が得られるので、工程数が少なく、また不純物の混入が少ない。 In addition, since a flaky powder can be obtained without going through a pulverization step, the number of steps is small and impurities are hardly mixed.
さらに本発明で用いる添加剤は、低分子量で、かつ粉末製造後に洗浄除去しやすいので、粉末表面に残留する有機物量を少なくすることができる。なお、添加剤を完全に除去せず粉末表面に適度に残すことにより、製造されたフレーク状銀粉末の二次凝集を防止することができ、また導体ペースト等に配合したとき、分散性、リーフィング性を向上させることもできる。この場合も、本発明で用いる添加剤は低分子量で熱分解性が良好なので、ペーストの焼成時に容易に分解され、形成された導体の特性を損なうことがない。 Furthermore, since the additive used in the present invention has a low molecular weight and is easy to wash and remove after the powder production, the amount of organic matter remaining on the powder surface can be reduced. In addition, it is possible to prevent secondary agglomeration of the manufactured flaky silver powder by leaving the additive properly on the powder surface without completely removing the additive. It can also improve the performance. Also in this case, since the additive used in the present invention has a low molecular weight and good thermal decomposability, it is easily decomposed when the paste is fired, and does not impair the properties of the formed conductor.
本発明で用いられる硝酸銀溶液としては、硝酸銀を水および／またはアルコールに溶解したものが好適に用いられる。 As the silver nitrate solution used in the present invention, a solution in which silver nitrate is dissolved in water and / or alcohol is preferably used.
還元剤溶液としては、前記硝酸銀溶液と混合することにより硝酸銀を還元して、銀粉末を析出させるものである。還元剤としては限定されず、Ｌ−アスコルビン酸、Ｄ−エリソルビン酸、ヒドラジン、ヒドラジン化合物、ホルムアルデヒド、蟻酸、グルコース、ハイドロキノン等の硝酸銀の還元剤として公知のものを用いることができる。特に、Ｌ−アスコルビン酸および／またはＤ−エリソルビン酸を用いた場合、結晶性の良いフレーク状銀粉末を得ることができるので好ましい。またＬ−アスコルビン酸、Ｄ−エリソルビン酸のアルカリ金属塩等の塩類を用いても、同様の効果が得られる。溶媒としては、水および／またはアルコールを好適に用いることができる。 As the reducing agent solution, silver nitrate is reduced by mixing with the silver nitrate solution to precipitate silver powder. It does not limit as a reducing agent, A well-known thing can be used as reducing agents of silver nitrate, such as L-ascorbic acid, D-erythorbic acid, hydrazine, a hydrazine compound, formaldehyde, formic acid, glucose, hydroquinone. In particular, when L-ascorbic acid and / or D-erythorbic acid is used, flaky silver powder having good crystallinity can be obtained, which is preferable. The same effect can be obtained by using salts such as alkali metal salts of L-ascorbic acid and D-erythorbic acid. As the solvent, water and / or alcohol can be preferably used.
添加剤（Ａ）としては、エチレンジアミン四酢酸のほか、エチレンジアミン四酢酸のアルカリ金属塩、アンモニウム塩などの塩類が使用される。（以下これらをまとめて「エチレンジアミン四酢酸」ということもある。）エチレンジアミン四酢酸の添加量は、硝酸銀溶液に含まれる銀量（金属銀換算）１００重量部に対して、０．０５重量部〜１重量部であることが望ましい。０．０５重量部よりも添加量が少ない場合、フレーク状粉末が得られ難くなる。また１重量部よりも添加量が多い場合、フレーク状銀粉末は得られるが、銀粉末上に残存する有機物量が多くなるため導体ペーストの特性に悪影響を及ぼす場合があり、またコストも増加するので好ましくない。 As the additive (A), in addition to ethylenediaminetetraacetic acid, salts such as alkali metal salts and ammonium salts of ethylenediaminetetraacetic acid are used. (Hereinafter, these may be collectively referred to as “ethylenediaminetetraacetic acid.”) The amount of ethylenediaminetetraacetic acid added is 0.05 parts by weight to 100 parts by weight of silver (in terms of metallic silver) contained in the silver nitrate solution. 1 part by weight is desirable. When the addition amount is less than 0.05 parts by weight, it becomes difficult to obtain a flaky powder. If the amount added is greater than 1 part by weight, flaky silver powder can be obtained, but the amount of organic matter remaining on the silver powder increases, which may adversely affect the properties of the conductor paste, and the cost also increases. Therefore, it is not preferable.
添加剤（Ｂ）として使用されるカルボン酸、カルボン酸金属塩、カルボン酸無水物、カルボン酸アミド（以下これらをまとめて「カルボン酸類」ということもある。）は、限定されないが、例えばピバリン酸、ネオヘプタン酸、ネオノナン酸、ネオデカン酸等の３級カルボン酸、酢酸、オクチル酸、カプリン酸、ラウリン酸、ミリスチン酸、パルミチン酸、ステアリン酸等の飽和脂肪酸、アクリル酸、メタクリル酸、オレイン酸、リノール酸、リノレン酸等の不飽和脂肪酸、マロン酸、コハク酸、アジピン酸、ピメリン酸、マレイン酸、アルキル置換コハク酸、水素添加フタル酸等の多価カルボン酸、またはこれらの金属塩、これらの酸の無水物、これらの酸から誘導される酸アミド等が例示される。 The carboxylic acid, carboxylic acid metal salt, carboxylic acid anhydride, and carboxylic acid amide (hereinafter sometimes collectively referred to as “carboxylic acids”) used as the additive (B) are not limited, but, for example, pivalic acid , Tertiary carboxylic acids such as neoheptanoic acid, neononanoic acid, neodecanoic acid, saturated fatty acids such as acetic acid, octylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, acrylic acid, methacrylic acid, oleic acid, linol Acid, unsaturated fatty acid such as linolenic acid, malonic acid, succinic acid, adipic acid, pimelic acid, maleic acid, alkyl-substituted succinic acid, polyvalent carboxylic acid such as hydrogenated phthalic acid, or metal salts thereof, these acids And anhydrides, acid amides derived from these acids, and the like.
これらの中でも、特に総炭素数が５〜３０の脂肪酸およびそのアミドが好ましく使用される。また水またはアルコールに溶解するもので、かつフレーク状銀粉末の滑剤、分散剤としての作用を有するものを選択して用いることにより、凝集が抑制されて分散性の良いフレーク状銀粉末が得られ易く、また導体ペーストに使用する際付着させたまま用いることもできるので好ましい。とりわけネオノナン酸、ネオデカン酸等の総炭素数が５〜２０の三級脂肪酸は、粒子形状、粒径のコントロールが容易にでき、また熱分解性が高いので、粉末表面に残ってもペーストの加熱工程で容易に除去されるので好ましい。 Among these, fatty acids having 5 to 30 total carbon atoms and amides thereof are particularly preferably used. Also, by selecting and using a substance that dissolves in water or alcohol and that acts as a lubricant or dispersant for flaky silver powder, agglomeration is suppressed and flaky silver powder with good dispersibility is obtained. It is preferable because it is easy to use and can be used while attached to a conductor paste. In particular, tertiary fatty acids such as neononanoic acid and neodecanoic acid having a total carbon number of 5 to 20 can easily control the particle shape and particle size and have high thermal decomposability. This is preferable because it is easily removed in the process.
カルボン酸類の添加量は、硝酸銀溶液に含まれる銀量（金属銀換算）１００重量部に対して、０．５重量部〜１０重量部であることが望ましい。０．５重量部よりも添加量が少ない場合、フレーク状粉末が得られ難くなる。１重量部よりも添加量が多くなると、銀粉末上に付着する有機物量が多くなるためペースト特性に悪影響を及ぼす場合があり、またコストも増加するので好ましくない。 The addition amount of the carboxylic acids is desirably 0.5 to 10 parts by weight with respect to 100 parts by weight of silver (converted to metallic silver) contained in the silver nitrate solution. When the addition amount is less than 0.5 parts by weight, it becomes difficult to obtain a flaky powder. If the amount added is greater than 1 part by weight, the amount of organic matter adhering to the silver powder increases, which may adversely affect paste properties and increase costs, which is not preferable.
本発明においては、（Ａ）、（Ｂ）の存在下で硝酸銀溶液と還元剤溶液を混合することにより、硝酸銀を還元し、銀粉末を生成させる。このとき添加剤（Ａ）、（Ｂ）が存在しないと、生成銀粉末は粒状の不定形粉末になり易いが、（Ａ）、（Ｂ）を反応溶液に添加することにより、粒度の揃った微細なフレーク状銀粉末が生成する。（Ａ）、（Ｂ）はそれぞれ単独で添加しても、本発明のフレーク状銀粉末は得られない。これら個々の化合物の作用は明確ではないが、両者の複合作用により、フレーク状に銀粒子を成長させると推察される。なお、本発明において「フレーク状」とは、リン片状、板状、扁平状等の形状を有するものを含むものである。 In the present invention, by mixing a silver nitrate solution and a reducing agent solution in the presence of (A) and (B), silver nitrate is reduced to produce silver powder. At this time, if the additives (A) and (B) are not present, the resulting silver powder is likely to be a granular amorphous powder, but by adding (A) and (B) to the reaction solution, the particle size is uniform. Fine flaky silver powder is produced. Even if (A) and (B) are added alone, the flaky silver powder of the present invention cannot be obtained. Although the action of these individual compounds is not clear, it is presumed that silver particles are grown in the form of flakes by the combined action of both. In the present invention, the “flakes” include those having a shape such as a flake shape, a plate shape, and a flat shape.
硝酸銀溶液と還元剤溶液の混合方法は、特に限定されず、硝酸銀溶液と還元剤溶液とを同時に反応容器に添加する方法、硝酸銀溶液を母液とし、これに還元剤溶液を添加する方法、逆に還元剤溶液に硝酸銀溶液を添加する方法のいずれの方法でもよいが、硝酸銀溶液と還元剤溶液を同時に反応容器に添加する場合、大きさと厚みの揃ったフレーク状銀粉末がより得られ易い。 The mixing method of the silver nitrate solution and the reducing agent solution is not particularly limited. The method of adding the silver nitrate solution and the reducing agent solution to the reaction vessel at the same time, the method of using the silver nitrate solution as the mother liquor, and adding the reducing agent solution thereto, conversely Any method of adding the silver nitrate solution to the reducing agent solution may be used, but when the silver nitrate solution and the reducing agent solution are added to the reaction vessel at the same time, a flaky silver powder having a uniform size and thickness is more easily obtained.
添加剤（Ａ）、（Ｂ）は、硝酸銀溶液と還元剤溶液を混合する前に、どちらか一方の溶液に予め添加、溶解しておく方法と、硝酸銀溶液と還元剤溶液を混合する際に、同時に添加する方法とがあり、いずれでもよい。前者では、例えば（Ａ）、（Ｂ）の一方を硝酸銀溶液に添加しておき、他方を還元剤溶液に添加しておいてもよい。また、後者の方法では、（Ａ）、（Ｂ）を予め混合しておいたものを添加してもよい。いずれにしても硝酸銀溶液と還元剤溶液を混合する際、（Ａ）、（Ｂ）がともに存在している必要がある。反応開始時に(Ａ)および／または（Ｂ）が存在していないと、フレーク状銀粉末が安定して生成しにくい。このように反応開始時に、（Ａ）および（Ｂ）の両方を存在させることによりフレーク状銀粉末が生成する機構は必ずしも明らかではないが、銀粒子の成長に際し、（Ａ）、（Ｂ）が特定の結晶面と協調的に相互作用することによって、異方的な結晶成長が有利になり、板状に粒子が成長し易くなると考えられる。 Additives (A) and (B) are added to and dissolved in either solution before mixing the silver nitrate solution and the reducing agent solution, and when the silver nitrate solution and the reducing agent solution are mixed. There are methods of adding them at the same time. In the former, for example, one of (A) and (B) may be added to the silver nitrate solution, and the other may be added to the reducing agent solution. Moreover, in the latter method, what mixed (A) and (B) previously may be added. In any case, both (A) and (B) must be present when the silver nitrate solution and the reducing agent solution are mixed. If (A) and / or (B) is not present at the start of the reaction, the flaky silver powder is not easily formed stably. Thus, at the start of the reaction, the mechanism by which flaky silver powder is produced by the presence of both (A) and (B) is not necessarily clear, but during the growth of silver particles, (A) and (B) By interacting with a specific crystal plane in a coordinated manner, anisotropic crystal growth is advantageous, and it is considered that particles are likely to grow in a plate shape.
反応溶液中で生成したフレーク状銀粉末は、ろ過等により反応溶液中から分離され、水やアルコール等で洗浄された後、乾燥される。 The flaky silver powder produced in the reaction solution is separated from the reaction solution by filtration or the like, washed with water or alcohol, and then dried.
本発明によって得られるフレーク状銀粉末は、導体ペーストのようなエレクトロニクス用の他、装飾用や、抗菌剤、触媒等にも好ましく用いられる。 The flaky silver powder obtained by the present invention is preferably used not only for electronics such as conductor paste, but also for decoration, antibacterial agent, catalyst and the like.
以下に実施例および比較例を示し、より具体的に説明するが、本発明はこれに限定されるものではない。 Examples and Comparative Examples are shown below and will be described more specifically, but the present invention is not limited to these.
[実施例１]
硝酸銀溶液として、硝酸銀３５．０ｇを純水に溶解し、全量を２５０．０ｇとしたものを用意した。一方、還元剤溶液としてＬ−アスコルビン酸１８．５ｇを純水・エタノール混合溶媒（体積比１：１）に溶解し、全量を５００．０ｇとしたものを用意した。この還元剤溶液に、エチレンジアミン四酢酸０．１ｇと、ネオデカン酸１．０ｇを加えて溶解させた。前記硝酸銀溶液と、前記還元剤溶液を１Ｌビーカーに同時に添加し、３００ｒｐｍにて３分間攪拌して反応させた。得られた沈殿をろ過し、洗浄した後、４０℃で３時間乾燥して、粉末を得た。
[Example 1]
As the silver nitrate solution, 35.0 g of silver nitrate was dissolved in pure water to prepare a total amount of 250.0 g. On the other hand, 18.5 g of L-ascorbic acid as a reducing agent solution was dissolved in a pure water / ethanol mixed solvent (volume ratio 1: 1) to prepare a total amount of 500.0 g. To this reducing agent solution, 0.1 g of ethylenediaminetetraacetic acid and 1.0 g of neodecanoic acid were added and dissolved. The silver nitrate solution and the reducing agent solution were simultaneously added to a 1 L beaker and reacted by stirring at 300 rpm for 3 minutes. The obtained precipitate was filtered and washed, and then dried at 40 ° C. for 3 hours to obtain a powder.
Ｘ線回折装置（理学電機株式会社製）を用いて、得られた粉末のＸ線回折パターンを観察したところ、金属銀と同一のパターンが得られたことから、銀粉末が得られたことを確認した。また走査型電子顕微鏡（ＳＥＭ、株式会社日立製作所製）を用いて得られた粉末を観察し、平均粒径約６．８μｍ、平均厚みが約０．２μｍの、大きさの揃ったフレーク状銀粉末であることを確認した。ＳＥＭ像を図１に示す。 When the X-ray diffraction pattern of the obtained powder was observed using an X-ray diffractometer (manufactured by Rigaku Denki Co., Ltd.), the same pattern as metallic silver was obtained. confirmed. In addition, the powder obtained using a scanning electron microscope (SEM, manufactured by Hitachi, Ltd.) was observed, and flaky silver with a uniform size having an average particle diameter of about 6.8 μm and an average thickness of about 0.2 μm. The powder was confirmed. An SEM image is shown in FIG.
[比較例１]
実施例１において、エチレンジアミン四酢酸とネオデカン酸をともに加えなかった以外は、実施例１と同様にして粉末を製造した。Ｘ線回折パターンとＳＥＭ像から、得られた粉末は花弁状にフレークが集合したような形状の粒状の銀粉末であることを確認した。図２にＳＥＭ像を示す。
[Comparative Example 1]
A powder was produced in the same manner as in Example 1 except that neither ethylenediaminetetraacetic acid nor neodecanoic acid was added. From the X-ray diffraction pattern and SEM image, it was confirmed that the obtained powder was a granular silver powder having a shape in which flakes gathered in a petal shape. FIG. 2 shows an SEM image.
この例から明らかなように、硝酸銀水溶液とＬ−アスコルビン酸水溶液の反応において、エチレンジアミン四酢酸およびカルボン酸類のいずれも添加しない場合には、フレーク粉末は得られなかった。 As apparent from this example, in the reaction of the aqueous silver nitrate solution and the L-ascorbic acid aqueous solution, when neither ethylenediaminetetraacetic acid nor carboxylic acids were added, flake powder was not obtained.
[比較例２]
実施例１において、ネオデカン酸を加えない以外は同様にして粉末を製造した。Ｘ線回折パターンとＳＥＭ像から、得られた粉末は粒状の凝集した銀粉末であることを確認した。ＳＥＭ像を図３に示す。
[Comparative Example 2]
A powder was produced in the same manner as in Example 1 except that neodecanoic acid was not added. From the X-ray diffraction pattern and the SEM image, it was confirmed that the obtained powder was granular aggregated silver powder. An SEM image is shown in FIG.
[比較例３]
実施例１において、エチレンジアミン四酢酸を加えない以外は同様にして、粉末を製造した。Ｘ線回折パターンとＳＥＭ観察から、得られた粉末は粒状の銀粉末であることを確認した。ＳＥＭ像を図４に示す。
[Comparative Example 3]
A powder was produced in the same manner as in Example 1 except that ethylenediaminetetraacetic acid was not added. From the X-ray diffraction pattern and SEM observation, it was confirmed that the obtained powder was a granular silver powder. An SEM image is shown in FIG.
比較例２、３の結果から、硝酸銀水溶液と、Ｌ−アスコルビン酸水溶液の反応において、エチレンジアミン四酢酸、またはカルボン酸の一方のみを添加した場合には、フレーク状銀粉末が得られないことがわかる。 From the results of Comparative Examples 2 and 3, it is understood that when only one of ethylenediaminetetraacetic acid or carboxylic acid is added in the reaction of the aqueous silver nitrate solution and the aqueous L-ascorbic acid solution, flaky silver powder cannot be obtained. .
[実施例２]
Ｌ−アスコルビン酸に代えて、Ｄ−エリソルビン酸を用いる以外は実施例１と同様にして、粉末を得た。Ｘ線回折パターンとＳＥＭ観察から、得られた粉末は平均粒径約３．６μｍ、平均厚みが約０．２μｍのフレーク状の銀粉末であることを確認した。
[Example 2]
A powder was obtained in the same manner as in Example 1 except that D-erythorbic acid was used instead of L-ascorbic acid. From the X-ray diffraction pattern and SEM observation, it was confirmed that the obtained powder was a flaky silver powder having an average particle diameter of about 3.6 μm and an average thickness of about 0.2 μm.
[実施例３]
ネオデカン酸に代えて、ステアリン酸を用いる以外は実施例１と同様にして、粉末を得た。Ｘ線回折パターンとＳＥＭ観察から、得られた粉末は平均粒径約８．６μｍ、平均厚みが約０．０５μｍのフレーク状の銀粉末であることを確認した。
[Example 3]
A powder was obtained in the same manner as in Example 1 except that stearic acid was used instead of neodecanoic acid. From the X-ray diffraction pattern and SEM observation, it was confirmed that the obtained powder was a flaky silver powder having an average particle diameter of about 8.6 μm and an average thickness of about 0.05 μm.
[実施例４]
ネオデカン酸に代えて、ステアリン酸アミドを用いる以外は実施例１と同様にして、粉末を得た。Ｘ線回折パターンとＳＥＭ観察から、得られた粉末は平均粒径約７．５μｍ、平均厚みが約０．０５μｍのフレーク状の銀粉末であることを確認した。
[Example 4]
A powder was obtained in the same manner as in Example 1 except that stearamide was used instead of neodecanoic acid. From the X-ray diffraction pattern and SEM observation, it was confirmed that the obtained powder was a flaky silver powder having an average particle diameter of about 7.5 μm and an average thickness of about 0.05 μm.
[実施例５]
ネオデカン酸に代えて、オレイン酸を用いる以外は実施例１と同様にして、粉末を得た。Ｘ線回折パターンとＳＥＭ観察から、得られた粉末は平均粒径約８．０μｍ、平均厚みが約０．１μｍのフレーク状の銀粉末であることを確認した。
[Example 5]
A powder was obtained in the same manner as in Example 1 except that oleic acid was used instead of neodecanoic acid. From the X-ray diffraction pattern and SEM observation, it was confirmed that the obtained powder was a flaky silver powder having an average particle diameter of about 8.0 μm and an average thickness of about 0.1 μm.
Claims (4)
The method for producing flaky silver powder according to any one of claims 1 to 3, wherein (B) is a tertiary fatty acid having 5 to 20 carbon atoms in total.
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