JP2011236453A - Silver particulate and method for producing the same, conductive paste containing the silver particulates, conductive film, and electronic device - Google Patents
Silver particulate and method for producing the same, conductive paste containing the silver particulates, conductive film, and electronic device Download PDFInfo
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本発明は、低温焼成が可能な導電性組成物の原料用として好適な、平均粒子径３０〜１００ｎｍの銀微粒子とその製造法並びに該銀微粒子を含有する導電性ペースト、導電性膜及び電子デバイスに関する。 The present invention relates to silver fine particles having an average particle size of 30 to 100 nm, a method for producing the same, and a conductive paste, conductive film, and electronic device suitable for use as a raw material for a conductive composition capable of low-temperature firing. About.
電子デバイスの電極や回路パターンの形成は、金属粒子を含む導電性ペーストを用いて基板上に電極や回路パターンを印刷した後、加熱焼成して導電性ペーストに含まれる金属粒子を焼結させることにより行われているが、近年、その加熱焼成温度は低温化する傾向にある。 The electrodes and circuit patterns of electronic devices are formed by printing electrodes and circuit patterns on a substrate using a conductive paste containing metal particles, and then baking by heating and sintering the metal particles contained in the conductive paste. However, in recent years, the heating and baking temperature tends to be lowered.
例えば、電子デバイスの実装基板としては、一般に、３００℃程度までの加熱が可能であるためポリイミド製フレキシブル基板が用いられているが、耐熱性に優れるものの高価であるため、最近では、より安価なＰＥＴ（ポリエチレンテレフタレート）基板やＰＥＮ（ポリエチレンナフタレート）基板が代替材料として検討されている。しかしながら、ＰＥＴ基板やＰＥＮ基板はポリイミド製フレキシブル基板と比較して耐熱性が低く、加熱焼成を２００℃以下で行う必要がある。 For example, as a mounting substrate for an electronic device, a polyimide flexible substrate is generally used because it can be heated up to about 300 ° C. However, since it is excellent in heat resistance but is expensive, recently, it is more inexpensive. A PET (polyethylene terephthalate) substrate and a PEN (polyethylene naphthalate) substrate have been studied as alternative materials. However, PET substrates and PEN substrates have lower heat resistance than polyimide flexible substrates, and it is necessary to carry out heating and baking at 200 ° C. or lower.
また、加熱焼成を２００℃より更に低い温度で行うことができれば、ポリカーボネートや紙等の基板への電極や回路パターンの形成も可能となり、各種電極材等の用途が広がることが期待される。 Moreover, if heating and baking can be performed at a temperature lower than 200 ° C., it becomes possible to form electrodes and circuit patterns on a substrate such as polycarbonate and paper, and it is expected that applications of various electrode materials and the like will be expanded.
このような低温焼成が可能な導電性ペーストの原料となる金属粒子として、ナノメートルオーダーの銀微粒子が期待されている。その理由として、金属粒子の大きさがナノメートルオーダーになると表面活性が高くなり、融点が金属のバルクのものよりもはるかに低下するため、低い温度で焼結させることが可能になるためである。また、金属粒子の中でも銀微粒子は低抵抗であり、価格も他の貴金属と比較して安価であることが挙げられる。 Nanometer-order silver fine particles are expected as metal particles that can be used as a raw material for conductive paste that can be fired at such a low temperature. The reason for this is that when the size of the metal particles is on the order of nanometers, the surface activity becomes high and the melting point is much lower than that of the bulk metal, so that it can be sintered at a low temperature. . Among metal particles, silver fine particles have low resistance, and the price is low compared with other noble metals.
また、ナノメートルオーダーの銀微粒子は低温で焼結が可能であると共に、一度焼結すると耐熱性が維持されるという、従来のはんだにはない性質を利用した鉛フリーのはんだ代替材料としても期待されている。 In addition, nanometer-order silver fine particles can be sintered at low temperatures, and heat resistance is maintained once sintered, which is also expected as a lead-free solder replacement material using a property not found in conventional solder. Has been.
これまでに、低温焼成が可能な銀微粒子として、サブミクロン以下の銀微粒子が提案されており、炭素数６〜１２の１級アミンで構成される有機保護材によって被覆された平均粒子径（ＤＴＥＭ）３〜２０ｎｍの銀微粉（特許文献１及び特許文献２）、粒子表面に有機物の低温度有機物成分飛散定数が５６〜１８０である有機物が付着している平均粒子径が２０〜１００ｎｍである銀微粒子（特許文献３）、粒子表面に硝酸銀のアンミン錯体及びアミンが１ｗｔ％以下付着している平均粒子径が２０〜１００ｎｍである銀微粒子（特許文献４）、アルキルアミンでキャッピングされた金属ナノ粒子（特許文献５）、平均粒子径が４０〜１００ｎｍであり、単結晶化度（ＤＴＥＭ／ＤＸ）が１〜５である銀微粒子（特許文献６）等が知られている。 Until now, silver fine particles of submicron or less have been proposed as silver fine particles that can be fired at a low temperature, and an average particle diameter (D) coated with an organic protective material composed of primary amines having 6 to 12 carbon atoms. TEM ) Silver fine powder of 3 to 20 nm (Patent Document 1 and Patent Document 2), organic particles having a low-temperature organic compound scattering constant of 56 to 180 on the surface of the particles is an average particle diameter of 20 to 100 nm Silver fine particles (Patent Document 3), silver nitrate ammine complexes and amines adhering to 1 wt% or less on the surface of the particles, silver fine particles having an average particle diameter of 20 to 100 nm (Patent Document 4), metal nanoparticles capped with alkylamine particles (Patent Document 5), an average particle diameter of 40 to 100 nm, the fine silver particles (Patent Document 6), and single crystallinity (D TEM / D X) is 1 to 5 are known There.
銀微粒子が低温で焼結するためには、銀微粒子が活性であることが必要であるが、前出特許文献１及び特許文献２に開示されているような平均粒子サイズが２０ｎｍ以下の銀微粒子の場合、活性が高すぎて不安定であるため多量の有機物で被覆する必要がある。また、特許文献１及び特許文献２では銀微粒子を製造する上で６０〜１００℃の温度をかけているので、銀微粒子の結晶子径は大きくなる傾向にあるため銀微粒子内部の反応性としては低いものとなり、低温焼結には不利となる。 In order for the silver fine particles to sinter at a low temperature, the silver fine particles need to be active, but the silver fine particles having an average particle size of 20 nm or less as disclosed in the aforementioned Patent Document 1 and Patent Document 2 are used. In this case, since the activity is too high and unstable, it is necessary to coat with a large amount of organic matter. Moreover, in patent document 1 and patent document 2, since the temperature of 60-100 degreeC is applied when manufacturing silver fine particles, since the crystallite diameter of silver fine particles tends to become large, as the reactivity inside silver fine particles, It is low and disadvantageous for low temperature sintering.
また、前出特許文献３及び特許文献４には、粒子表面に有機物もしくは硝酸銀のアンミン錯体及びアミンが付着している平均粒子径が２０〜１００ｎｍの銀微粒子が記載されているが、還元反応における反応温度については考慮なされておらず、また、乾燥時に４０℃の温度をかけているために結晶粒径が大きくなる傾向にあるため、銀微粒子内部の反応性としては低いものとなり、低温焼結には不利となる。 In addition, in the above-mentioned Patent Document 3 and Patent Document 4, silver fine particles having an average particle diameter of 20 to 100 nm in which an organic substance or an ammine complex of silver nitrate and an amine are attached to the particle surface are described. The reaction temperature is not taken into consideration, and since the crystal grain size tends to increase because a temperature of 40 ° C. is applied at the time of drying, the reactivity inside the silver fine particles is low and low temperature sintering is performed. Is disadvantageous.
また、前出特許文献５には、アルキルアミンでキャッピングされた金属ナノ粒子が記載されているが、銀微粒子を製造する上で８０℃の温度をかけているので、銀微粒子の結晶子径は大きくなる傾向にあるため、銀微粒子内部の反応性としては低いものとなり、低温焼結には不利となる。また、キャッピング分子の含有量は５〜３０重量％であり、たとえ比較的沸点が低い被覆物質を選択したとしても多量に付着している被覆物を完全に除去することは困難である。 Further, in Patent Document 5 described above, metal nanoparticles capped with alkylamine are described, but since a temperature of 80 ° C. is applied to produce silver fine particles, the crystallite diameter of the silver fine particles is Since it tends to be large, the reactivity inside the silver fine particles is low, which is disadvantageous for low-temperature sintering. Further, the content of capping molecules is 5 to 30% by weight, and even if a coating material having a relatively low boiling point is selected, it is difficult to completely remove the coating material adhering to a large amount.
また、前出特許文献６には、平均粒子径が４０〜１００ｎｍであり、単結晶化度（ＤＴＥＭ／ＤＸ）が１〜５である銀微粒子が記載されているが、銀微粒子を製造する上で４０℃前後の温度をかけているので、銀微粒子の結晶子径は大きくなる傾向にある。そのため銀微粒子内部の反応性としては低いものとなり、低温焼結には不利となる。また、反応に用いている脂肪族第一級アミンはいずれも沸点が１１０℃以上と高いものであり、この点においても低温焼結には不利である。 Further, in the aforementioned Patent Document 6, silver fine particles having an average particle diameter of 40 to 100 nm and a single crystallinity (D TEM / D X ) of 1 to 5 are described. In this case, since a temperature of about 40 ° C. is applied, the crystallite diameter of the silver fine particles tends to increase. Therefore, the reactivity inside the silver fine particles is low, which is disadvantageous for low-temperature sintering. In addition, all of the aliphatic primary amines used in the reaction have a boiling point as high as 110 ° C. or higher, which is disadvantageous for low-temperature sintering.
そこで、本発明は、低温焼成が可能な導電性ペーストの原料用として好適な、平均粒子径３０〜１００ｎｍであって粒子表面に炭素数２〜４の脂肪族アミン及び硝酸銀のアミン錯体が存在する銀微粒子を提供することを技術的課題とする。 Therefore, the present invention is suitable for use as a raw material for conductive paste that can be fired at low temperature, and has an average particle diameter of 30 to 100 nm and an amine complex of an aliphatic amine having 2 to 4 carbon atoms and silver nitrate on the particle surface. It is a technical problem to provide silver fine particles.
前記技術的課題は、次の通りの本発明によって達成できる。 The technical problem can be achieved by the present invention as follows.
即ち、本発明は、平均粒子径（ＤＳＥＭ）が３０〜１００ｎｍであって、粒子表面に炭素数２〜４の脂肪族アミン及び硝酸銀のアミン錯体が存在する銀微粒子であり、ＤＴＡ（示差熱分析）曲線のピークが１００〜１４０℃の間にあることを特徴とする銀微粒子である（本発明１）。 That is, the present invention is a silver fine particle having an average particle diameter (D SEM ) of 30 to 100 nm and having an amine complex of an aliphatic amine having 2 to 4 carbon atoms and silver nitrate on the particle surface. Analysis) Silver fine particles characterized in that the peak of the curve is between 100 and 140 ° C. (Invention 1).
また、本発明は、ＴＧ（熱重量測定）による加熱減量が３％以下であることを特徴とする本発明１記載の銀微粒子である（本発明２）。 The present invention also provides the silver fine particles according to the first aspect of the present invention, wherein the loss on heating by TG (thermogravimetry) is 3% or less (the second aspect of the invention).
また、本発明は、ＢＥＴ比表面積値（ＳＳＡ）（ｍ２／ｇ）が下記式（１）で表されることを特徴とする本発明１又は本発明２の銀微粒子である（本発明３）。
ＳＳＡ（ｍ２／ｇ）≧−０．０５×ＤＳＥＭ＋７．４ （１）
Further, the present invention is the silver fine particles of the present invention 1 or the present invention 2, wherein the BET specific surface area value (SSA) (m 2 / g) is represented by the following formula (1) (the present invention 3): ).
SSA (m 2 /g)≧−0.05×D SEM +7.4 (1)
また、本発明は、硝酸銀と、水溶性あるいは水可溶性であって炭素数２〜４の脂肪族アミン１種類以上とを用いて調製した硝酸銀のアミン錯体のアルコール溶液を、アスコルビン酸又はエリソルビン酸を溶解させた水−アルコール混合溶媒中に添加して還元析出させ、得られた銀微粒子を分離・洗浄した後、温度３０℃以下で真空乾燥により銀微粒子を乾燥させることを特徴とする本発明１乃至本発明３いずれかに記載の銀微粒子の製造方法である（本発明４）。 In addition, the present invention provides an alcohol solution of an amine complex of silver nitrate prepared using silver nitrate and one or more water-soluble or water-soluble aliphatic amines having 2 to 4 carbon atoms, ascorbic acid or erythorbic acid. The present invention is characterized in that it is added to a dissolved water-alcohol mixed solvent for reduction precipitation, and the resulting silver fine particles are separated and washed, and then the silver fine particles are dried by vacuum drying at a temperature of 30 ° C. or lower. Thru | or the manufacturing method of the silver fine particle in any one of this invention 3 (this invention 4).
また、本発明は、本発明１乃至本発明３いずれかに記載の銀微粒子を含有する導電性ペーストである（本発明５）。 Further, the present invention is a conductive paste containing the silver fine particles according to any one of the present invention 1 to the present invention 3 (the present invention 5).
また、本発明は、本発明５の導電性ペーストを用いて形成された導電性膜である（本発明６）。 Moreover, this invention is a conductive film formed using the electrically conductive paste of this invention 5 (this invention 6).
また、本発明は、本発明６の導電性膜を有する電子デバイスである（本発明７）。 Moreover, this invention is an electronic device which has the electroconductive film of this invention 6 (this invention 7).
本発明に係る銀微粒子は、平均粒子径３０〜１００ｎｍであるため、平均粒子径が１〜２０ｎｍ程度のシングルナノオーダーの銀微粒子のように多量の有機物で表面を被覆する必要がなく、また、銀微粒子の粒子表面に存在する有機物も１００〜１４０℃の温度範囲で飛散してしまうと共に、多結晶化度が２．０以上であることから粒子内部の活性が高いため、低温においても銀微粒子同士の焼結が進行するので、低温焼成が可能な導電性ペースト等の原料として好適である。 Since the silver fine particles according to the present invention have an average particle diameter of 30 to 100 nm, it is not necessary to coat the surface with a large amount of organic matter like single nano-order silver fine particles having an average particle diameter of about 1 to 20 nm. The organic matter present on the surface of the silver fine particles is also scattered in the temperature range of 100 to 140 ° C., and since the polycrystallinity is 2.0 or more, the activity inside the particles is high, so the silver fine particles even at low temperatures Since the sintering of each other proceeds, it is suitable as a raw material for a conductive paste or the like that can be fired at a low temperature.
本発明の構成をより詳しく説明すれば、次の通りである。 The configuration of the present invention will be described in more detail as follows.
先ず、本発明に係る銀微粒子について述べる。 First, the silver fine particles according to the present invention will be described.
本発明に係る銀微粒子は、平均粒子径（ＤＳＥＭ）が３０〜１００ｎｍであって、粒子表面に炭素数２〜４の脂肪族アミン及び硝酸銀のアミン錯体が存在する銀微粒子であり、ＤＴＡ曲線のピークが１００〜１４０℃の間にあることを特徴とする銀微粒子である。 The silver fine particles according to the present invention are silver fine particles having an average particle diameter (D SEM ) of 30 to 100 nm and having an amine complex of an aliphatic amine having 2 to 4 carbon atoms and silver nitrate on the particle surface, and a DTA curve. The silver fine particles are characterized by having a peak of 100 to 140 ° C.
本発明に係る銀微粒子の平均粒子径（ＤＳＥＭ）は３０〜１００ｎｍであり、好ましくは４０〜１００ｎｍ、より好ましくは５０〜１００ｎｍである。平均粒子径（ＤＳＥＭ）が３０ｎｍ未満の場合には、銀微粒子の持つ表面活性が高くなり、その微細な粒子径を安定に維持するために多量の有機物等を付着させる必要があるため好ましくない。また、平均粒子径（ＤＳＥＭ）が１００ｎｍを超える場合には、銀微粒子の持つ表面活性が低くなり、低温焼結性が損なわれてしまうため好ましくない。 The average particle diameter (D SEM ) of the silver fine particles according to the present invention is 30 to 100 nm, preferably 40 to 100 nm, more preferably 50 to 100 nm. When the average particle size (D SEM ) is less than 30 nm, the surface activity of the silver fine particles increases, and it is not preferable because a large amount of organic matter or the like needs to be adhered in order to stably maintain the fine particle size. . Moreover, when the average particle diameter (D SEM ) exceeds 100 nm, the surface activity of the silver fine particles is lowered, and the low-temperature sinterability is impaired.
本発明に係る銀微粒子は、粒子表面に炭素数２〜４の脂肪族アミン及び硝酸銀のアミン錯体が存在している。炭素数２〜４の脂肪族アミンとしては、具体的にはエチルアミン、ｎ−プロピルアミン、ｉｓｏ−プロピルアミン、ｎ−ブチルアミン、ｉｓｏ−ブチルアミン等を用いることができるが、銀微粒子の低温焼結性及びハンドリング性を考慮すれば、ｎ−プロピルアミン及びｎ−ブチルアミンが好ましい。また、硝酸銀のアミン錯体は、硝酸銀と前述の炭素数２〜４の脂肪族アミンからなるアミン錯体である。 Silver fine particles according to the present invention have an amine complex of an aliphatic amine having 2 to 4 carbon atoms and silver nitrate on the particle surface. Specific examples of the aliphatic amine having 2 to 4 carbon atoms include ethylamine, n-propylamine, iso-propylamine, n-butylamine, iso-butylamine, and the like. And if handling property is considered, n-propylamine and n-butylamine are preferable. The amine complex of silver nitrate is an amine complex composed of silver nitrate and the above-described aliphatic amine having 2 to 4 carbon atoms.
本発明に係る銀微粒子は、１００〜１４０℃の間にＤＴＡ（示差熱分析）曲線のピークを有する。１００〜１４０℃の温度範囲にあるＤＴＡ曲線のピークは、前述の炭素数２〜４の脂肪族アミン及び硝酸銀のアミン錯体に由来するものと考えられる。従って、ＤＴＡ曲線のピークがこの温度範囲内であることにより、低温焼結性に優れた銀微粒子を得ることが可能となる。ＤＴＡ曲線のピークが１００℃未満の温度範囲にある場合には、銀微粒子の保存安定性が低下するため好ましくない。また、ＤＴＡ曲線のピークが１４０℃を超える温度範囲にある場合には、銀微粒子の粒子表面に存在する有機物を除去するために１４０℃を超える温度をかける必要があり、低温焼結性を有するとはいいがたいものである。好ましくは、１００〜１３５℃であり、より好ましくは１００〜１３０℃の温度範囲である。 The silver fine particles according to the present invention have a peak of a DTA (differential thermal analysis) curve between 100 and 140 ° C. It is considered that the peak of the DTA curve in the temperature range of 100 to 140 ° C. is derived from the aforementioned amine complex of an aliphatic amine having 2 to 4 carbon atoms and silver nitrate. Therefore, when the peak of the DTA curve is within this temperature range, it is possible to obtain silver fine particles having excellent low-temperature sinterability. When the peak of the DTA curve is in a temperature range of less than 100 ° C., the storage stability of the silver fine particles is lowered, which is not preferable. Further, when the peak of the DTA curve is in a temperature range exceeding 140 ° C., it is necessary to apply a temperature exceeding 140 ° C. in order to remove organic substances present on the surface of the silver fine particles, and low temperature sinterability is obtained. That's not good. Preferably, it is 100-135 degreeC, More preferably, it is a temperature range of 100-130 degreeC.
本発明に係る銀微粒子は、ＴＧ（熱重量測定）による加熱減量が３％以下であることが好ましく、より好ましくは２．５％以下、更により好ましくは２．０％以下である。３％を超える場合には、粒子表面に存在する有機物が多すぎるため、低温焼結には不利となる。また、ＴＧ（熱重量測定）による加熱減量の下限値は０．１重量％であることが好ましく、より好ましくは０．２％である。 The silver fine particles according to the present invention preferably have a loss on heating by TG (thermogravimetry) of 3% or less, more preferably 2.5% or less, and even more preferably 2.0% or less. If it exceeds 3%, too much organic matter is present on the particle surface, which is disadvantageous for low-temperature sintering. Further, the lower limit of the loss on heating by TG (thermogravimetry) is preferably 0.1% by weight, more preferably 0.2%.
本発明に係る銀微粒子のＢＥＴ比表面積値（ＳＳＡ）は、下記式（１）で表される範囲にある。ＢＥＴ比表面積値（ＳＳＡ）が下記式（１）の範囲よりも小さい場合には、銀微粒子表面に多量の有機物が処理されていたりすることで表面活性が低下していると考えられるため、良好な低温焼結性を得ることが困難である。
ＳＳＡ（ｍ２／ｇ）≧−０．０５×ＤＳＥＭ＋７．４ （１）
The BET specific surface area value (SSA) of the silver fine particles according to the present invention is in the range represented by the following formula (1). In the case where the BET specific surface area value (SSA) is smaller than the range of the following formula (1), the surface activity is considered to be reduced because a large amount of organic matter is treated on the surface of the silver fine particles. It is difficult to obtain a low sinterability.
SSA (m 2 /g)≧−0.05×D SEM +7.4 (1)
本発明に係る銀微粒子の多結晶化度［平均粒子径（ＤＳＥＭ）と結晶子径（ＤＸ）の比（ＤＳＥＭ／ＤＸ）］は２．０以上であり、より好ましくは２．１以上、更により好ましくは２．２以上である。多結晶化度が２．０未満の場合には、銀微粒子中の結晶子径が大きくなり単結晶に近づくため銀微粒子中の反応性が低下し、低温焼結性が損なわれてしまうため好ましくない。 The polycrystallinity of the silver fine particles according to the present invention [ratio of average particle diameter (D SEM ) to crystallite diameter (D X ) (D SEM / D X )] is 2.0 or more, more preferably 2. 1 or more, still more preferably 2.2 or more. When the degree of polycrystallinity is less than 2.0, the crystallite size in the silver fine particles becomes large and approaches a single crystal, so the reactivity in the silver fine particles is lowered and the low-temperature sinterability is impaired. Absent.
本発明に係る銀微粒子の粒子形状は、球状もしくは粒状が好ましい。 The particle shape of the silver fine particles according to the present invention is preferably spherical or granular.
次に、本発明に係る銀微粒子の製造方法について述べる。 Next, a method for producing silver fine particles according to the present invention will be described.
本発明に係る銀微粒子は、硝酸銀と、水溶性あるいは水可溶性であって炭素数２〜４の脂肪族級アミンの１種類以上とを用いて調製した硝酸銀のアミン錯体のアルコール溶液を、アスコルビン酸又はエリソルビン酸を溶解させた水−アルコール混合溶媒中に添加して還元析出させ、得られた銀微粒子を分離・洗浄した後、温度３０℃以下で真空乾燥により銀微粒子を乾燥させることで得ることができる。 The silver fine particles according to the present invention comprise an alcohol solution of an amine complex of silver nitrate prepared using silver nitrate and one or more of water-soluble or water-soluble aliphatic class amines having 2 to 4 carbon atoms. Alternatively, it can be obtained by adding it to a water-alcohol mixed solvent in which erythorbic acid is dissolved and reducing and depositing it, separating and washing the obtained silver fine particles, and then drying the silver fine particles by vacuum drying at a temperature of 30 ° C. or lower. Can do.
本発明における炭素数２〜４の脂肪族アミンとしては、水溶性あるいは水可溶性のものを用いることが肝要であり、具体的には、エチルアミン、ｎ−プロピルアミン、ｉｓｏ−プロピルアミン、ｎ−ブチルアミン、ｉｓｏ−ブチルアミン、等を用いることができるが、銀微粒子の低温焼結性及びハンドリング性を考慮すれば、ｎ−プロピルアミン及びｎ−ブチルアミンが好ましい。また、硝酸銀のアミン錯体は、前述の炭素数２〜４の脂肪族アミンからなるアミン錯体である。 In the present invention, it is important to use a water-soluble or water-soluble aliphatic amine having 2 to 4 carbon atoms, specifically, ethylamine, n-propylamine, iso-propylamine, n-butylamine. , Iso-butylamine, and the like can be used, but n-propylamine and n-butylamine are preferable in consideration of the low-temperature sintering property and handling property of the silver fine particles. The amine complex of silver nitrate is an amine complex composed of the above-mentioned aliphatic amine having 2 to 4 carbon atoms.
本発明におけるアルコールとしては、水と相溶性のあるものを用いることができる。具体的には、メタノール、エタノール、プロパノール及びイソプロパノール等を用いることができ、好ましくはメタノール及びエタノールである。これらアルコールは単独でも混合して用いてもよい。 As alcohol in this invention, what is compatible with water can be used. Specifically, methanol, ethanol, propanol, isopropanol, and the like can be used, and methanol and ethanol are preferable. These alcohols may be used alone or in combination.
以下、炭素数２〜４の脂肪族アミンの代表としてｎ−ブチルアミンを用いた例について記述するが、その他の炭素数２〜４の脂肪族アミンでも同様に調製が可能である。 Hereinafter, an example using n-butylamine as a representative of an aliphatic amine having 2 to 4 carbon atoms will be described, but other aliphatic amines having 2 to 4 carbon atoms can be similarly prepared.
また、上述した硝酸銀と炭素数２〜４の脂肪族アミンを１種類以上用いて調製した硝酸銀のアミン錯体のアルコール溶液を、水−アルコール混合溶媒中においてアスコルビン酸またはエリソルビン酸により還元することを特徴とする基本的な概念が同様であれば、以下の条件に限定されるものではない。例えば、メタノールの量や水の量は、用いるアミンの溶液への溶解性、反応容器と攪拌機構によりその最適な体積比率は変化する。 In addition, an alcohol solution of an amine complex of silver nitrate prepared using one or more of the above-described silver nitrate and an aliphatic amine having 2 to 4 carbon atoms is reduced with ascorbic acid or erythorbic acid in a water-alcohol mixed solvent. As long as the basic concept is the same, it is not limited to the following conditions. For example, the optimal volume ratio of the amount of methanol and the amount of water varies depending on the solubility of the amine used in the solution, the reaction vessel and the stirring mechanism.
まず、硝酸銀とｎ−ブチルアミンにより硝酸銀のアミン錯体をアルコール溶媒中で形成させる。ｎ−ブチルアミンは硝酸銀に対して２．０〜２．５当量が好ましく、より好ましくは２．０〜２．３当量である。ｎ−ブチルアミンの量が硝酸銀に対して２．０当量未満の場合には、大きな粒子が生成しやすい傾向がある。 First, an amine complex of silver nitrate is formed in an alcohol solvent with silver nitrate and n-butylamine. n-Butylamine is preferably 2.0 to 2.5 equivalents, more preferably 2.0 to 2.3 equivalents, relative to silver nitrate. When the amount of n-butylamine is less than 2.0 equivalents with respect to silver nitrate, large particles tend to be generated.
次に、還元剤であるアスコルビン酸又はエリソルビン酸を水中に溶解させた後、アルコールを添加し混合する。アスコルビン酸又はエリソルビン酸は硝酸銀に対して１．０〜２．０当量が好ましく、より好ましくは１．０〜１．８当量である。アスコルビン酸又はエリソルビン酸が２．０当量を超える場合には、生成した銀微粒子同士が凝集する傾向があるため好ましくない。 Next, ascorbic acid or erythorbic acid as a reducing agent is dissolved in water, and then alcohol is added and mixed. Ascorbic acid or erythorbic acid is preferably 1.0 to 2.0 equivalents, more preferably 1.0 to 1.8 equivalents with respect to silver nitrate. When ascorbic acid or erythorbic acid exceeds 2.0 equivalents, the resulting silver fine particles tend to aggregate, which is not preferable.
続いて、硝酸銀のアミン錯体を形成させたアルコール溶液を、アスコルビン酸またはエリソルビン酸を溶解させた水−アルコール溶液中に滴下し、還元反応を行うことにより銀微粒子を析出させる。還元反応における反応温度は１５〜３０℃の範囲であり、より好ましくは１８〜３０℃である。反応温度が３０℃を超える場合、結晶子径が大きくなり、得られる銀微粒子は単結晶に近づくため好ましくない。 Subsequently, an alcohol solution in which an amine complex of silver nitrate is formed is dropped into a water-alcohol solution in which ascorbic acid or erythorbic acid is dissolved, and silver fine particles are precipitated by performing a reduction reaction. The reaction temperature in the reduction reaction is in the range of 15 to 30 ° C, more preferably 18 to 30 ° C. When the reaction temperature exceeds 30 ° C., the crystallite size becomes large, and the resulting silver fine particles are close to a single crystal, which is not preferable.
滴下終了後、１時間以上攪拌を続けた後、静置することにより銀微粒子を沈降させ、上澄み液をデカンテーションにより取り除いた後、アルコール及び水を用いて余分な還元剤、ｎ−ブチルアミン、硝酸銀等を洗浄する。 After the completion of dropping, stirring is continued for 1 hour or more, and then the mixture is allowed to stand to precipitate silver fine particles. After removing the supernatant by decantation, an excess reducing agent, n-butylamine, silver nitrate is used with alcohol and water. Wash etc.
洗浄した銀微粒子を、温度３０℃以下で真空乾燥後、常法により粉砕することによって本発明の銀微粒子を得ることができる。乾燥温度が３０℃を超える場合には結晶子径が大きくなり、得られる銀微粒子は単結晶に近づくため好ましくない。 The silver fine particles of the present invention can be obtained by vacuum-drying the washed silver fine particles at a temperature of 30 ° C. or lower and then pulverizing them by a conventional method. When the drying temperature exceeds 30 ° C., the crystallite size becomes large, and the resulting silver fine particles are not preferable because they approach single crystals.
次に、本発明に係る銀微粒子を含む導電性ペーストについて述べる。 Next, the conductive paste containing silver fine particles according to the present invention will be described.
本発明に係る導電性ペーストは、本発明に係る銀微粒子及び溶剤からなり、必要に応じて、バインダ樹脂、硬化剤、分散剤、レオロジー調整剤等の他の成分を配合してもよい。 The conductive paste according to the present invention is composed of the silver fine particles according to the present invention and a solvent, and may contain other components such as a binder resin, a curing agent, a dispersant, and a rheology modifier as necessary.
バインダ樹脂としては、当該分野において公知のものを使用することができ、例えば、エチルセルロース、ニトロセルロース等のセルロース系樹脂、ポリエステル樹脂、ウレタン変性ポリエステル樹脂、エポキシ変性ポリエステル樹脂、アクリル変性ポリエステル等の各種変性ポリエステル樹脂、ポリウレタン樹脂、塩化ビニル・酢酸ビニル共重合体、アクリル樹脂、エポキシ樹脂、フェノール樹脂、アルキド樹脂、ブチラール樹脂、ポリビニルアルコール、ポリイミド、ポリアミドイミド等が挙げられる。これらバインダ樹脂は、単独又は２種類以上を併用することもできる。 As the binder resin, those known in the art can be used. For example, cellulose resins such as ethyl cellulose and nitrocellulose, various modified resins such as polyester resins, urethane-modified polyester resins, epoxy-modified polyester resins, and acrylic-modified polyesters. Examples include polyester resin, polyurethane resin, vinyl chloride / vinyl acetate copolymer, acrylic resin, epoxy resin, phenol resin, alkyd resin, butyral resin, polyvinyl alcohol, polyimide, and polyamideimide. These binder resins can be used alone or in combination of two or more.
溶剤としては、当該分野において公知のものを使用することができ、例えば、テトラデカン、トルエン、キシレン、エチルベンゼン、ジエチルベンゼン、イソプロピルベンゼン、アミルベンゼン、ｐ−シメン、テトラリン及び石油系芳香族炭化水素混合物等の炭化水素系溶剤；エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、プロピレングリコールモノメチルエーテル、プロピレングリコールモノエチルエーテル、プロピレングリコールモノ−ｎ−ブチルエーテル、プロピレングリコールモノ−t−ブチルエーテル、ジエチレングリコールモノエチルエーテル、ジエチレングリコ−ルモノブチルエーテル、ジプロピレングリコールモノメチルエーテル、ジプロピレングリコールモノブチルエーテル、トリプロピレングリコールモノメチルエーテル等のエーテル又はグリコールエーテル系溶剤；エチレングリコールモノメチルエーテルアセテート、エチレングリコールモノエチルエーテルアセテート、エチレングリコールモノブチルエーテルアセテート、プロピレングリコールモノメチルエーテルアセテート、プロピレングリコールモノエチルエーテルアセテート等のグリコールエステル系溶剤；メチルイソブチルケトン、シクロヘキサノン等のケトン系溶剤；テルピネオール、リナロール、ゲラニオール、シトロネロール等のテルペンアルコール；ｎ−ブタノール、ｓ−ブタノール、ｔ−ブタノール等のアルコール系溶剤；エチレングリコール、ジエチレングリコール等のグリコール系溶剤；γ−ブチロラクトン及び水等が挙げられる。溶剤は、単独又は２種類以上を併用することもできる。 As the solvent, those known in the art can be used, for example, tetradecane, toluene, xylene, ethylbenzene, diethylbenzene, isopropylbenzene, amylbenzene, p-cymene, tetralin and petroleum aromatic hydrocarbon mixtures. Hydrocarbon solvents: ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-t-butyl ether, diethylene glycol monoethyl ether, diethylene glyco- Monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, tripro Ether or glycol ether solvents such as pyrene glycol monomethyl ether; glycol ester solvents such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate Ketone solvents such as methyl isobutyl ketone and cyclohexanone; terpene alcohols such as terpineol, linalool, geraniol and citronellol; alcohol solvents such as n-butanol, s-butanol and t-butanol; glycol solvents such as ethylene glycol and diethylene glycol; Γ-butyrolactone and water. The solvent can be used alone or in combination of two or more.
導電性ペースト中の銀微粒子の含有量は用途に応じて様々であるが、例えば配線形成用途の場合などは可能な限り１００重量％に近いことが好ましい。 Although the content of silver fine particles in the conductive paste varies depending on the application, it is preferably as close to 100% by weight as possible, for example, in the case of wiring formation.
本発明に係る導電性ペーストは、各成分を、ライカイ機、ポットミル、三本ロールミル、回転式混合機、二軸ミキサー等の各種混練機、分散機を用いて、混合・分散させることにより得ることができる。 The conductive paste according to the present invention is obtained by mixing and dispersing each component using various kneaders and dispersers such as a laika machine, a pot mill, a three roll mill, a rotary mixer, a twin screw mixer, and the like. Can do.
本発明に係る導電性ペーストは、スクリーン印刷、インクジェット法、グラビア印刷、転写印刷、ロールコート、フローコート、スプレー塗装、スピンコート、ディッピング、ブレードコート、めっき等各種塗布方法に適用可能である。 The conductive paste according to the present invention can be applied to various coating methods such as screen printing, inkjet method, gravure printing, transfer printing, roll coating, flow coating, spray coating, spin coating, dipping, blade coating, and plating.
また、本発明に係る導電性ペーストは、ＦＰＤ（フラットパネルディスプレイ）、太陽電池、有機ＥＬ等の電極形成やＬＳＩ基板の配線形成、更には微細なトレンチ、ビアホール、コンタクトホールの埋め込み等の配線形成材料として用いることができる。また、積層セラミックコンデンサや積層インダクタの内部電極形成用等の高温での焼成用途はもちろん、低温焼成が可能であることからフレキシブル基板やＩＣカード、その他の基板上への配線形成材料及び電極形成材料として好適である。また、導電性被膜として電磁波シールド膜や赤外線反射シールド等にも用いることができる。エレクトロニクス実装においては部品実装用接合材として用いることもできる。 In addition, the conductive paste according to the present invention is used for forming electrodes such as FPD (flat panel display), solar cell, organic EL, wiring for LSI substrates, and wiring for filling fine trenches, via holes, contact holes, etc. It can be used as a material. In addition to firing applications at high temperatures, such as for the formation of internal electrodes for multilayer ceramic capacitors and multilayer inductors, as well as low temperature firing, it is possible to form wiring and materials for wiring on flexible substrates, IC cards, and other substrates. It is suitable as. Moreover, it can also be used for an electromagnetic wave shielding film, an infrared reflection shield, etc. as a conductive film. In electronics mounting, it can also be used as a bonding material for component mounting.
＜作用＞
本発明において重要な点は、平均粒子径（ＤＳＥＭ）が３０〜１００ｎｍであり、ＤＴＡ（示差熱分析）曲線のピークが１００〜１４０℃の間にある銀微粒子は、低温焼成が可能であるという事実である。
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The important point in the present invention is that silver fine particles having an average particle diameter (D SEM ) of 30 to 100 nm and a peak of a DTA (differential thermal analysis) curve between 100 to 140 ° C. can be fired at a low temperature. That is the fact.
本発明に係る銀微粒子が低温焼結性に優れている理由について、本発明者は次のように考えている。 The present inventor considers the reason why the silver fine particles according to the present invention are excellent in low temperature sinterability as follows.
即ち、銀微粒子が低温で焼結するためには、銀微粒子が活性であることが必要であるが、平均粒子径が２０ｎｍ以下では活性が高すぎて不安定あるため、通常多量の有機物で被覆する必要があり、その被覆物は通常高分子であり低温では除去できないため、焼成温度を下げることは困難であった。また、多量の有機物でコートする必要がなく、できる限り表面活性が高い粒子サイズとしては３０〜１００ｎｍが考えられるが、従来あるこの粒子サイズの銀微粒子の場合、低温で焼結するための表面活性エネルギーとしては不十分であり、低温焼成が困難であった。本発明に係る銀微粒子の場合、粒子内部、即ち、銀微粒子が単結晶ではなく多結晶体で構成されることにより、粒子内部のエネルギーが高くなり、そのため、低温焼成が可能となったと考えている。 That is, in order for the silver fine particles to sinter at low temperature, the silver fine particles need to be active. However, when the average particle size is 20 nm or less, the activity is too high and unstable, and therefore, usually coated with a large amount of organic matter. Since the coating is usually a polymer and cannot be removed at low temperatures, it has been difficult to lower the firing temperature. In addition, it is not necessary to coat with a large amount of organic substance, and the particle size having as high a surface activity as possible is considered to be 30 to 100 nm. However, in the case of conventional silver fine particles of this particle size, the surface activity for sintering at low temperature The energy was insufficient, and low-temperature firing was difficult. In the case of the silver fine particles according to the present invention, it is considered that the internal energy of the particles, that is, the silver fine particles are composed of a polycrystal rather than a single crystal, so that the energy inside the particles is increased, and therefore, low-temperature firing is possible. Yes.
また、本発明に係る銀微粒子は上述の通り分子量の大きい有機物を粒子表面に多量に存在させる必要がないため、沸点が低く、揮散しやすい炭素数２〜４の脂肪族アミンを有機保護材として用いることができたためと考えている。更に、反応温度及び乾燥温度を３０℃以下とすることにより、銀微粒子と反応系で用いられる有機物との間の不揮発性もしくは揮発温度の高い物質の生成が抑制されたためと考えている。 In addition, since the silver fine particles according to the present invention do not need to have a large amount of organic substances having a large molecular weight on the particle surface as described above, an aliphatic amine having 2 to 4 carbon atoms having a low boiling point and being easily volatilized is used as an organic protective material. I think it was because I was able to use it. Furthermore, the reaction temperature and the drying temperature are set to 30 ° C. or less, which is considered to suppress the generation of a non-volatile or high volatilization substance between the silver fine particles and the organic substance used in the reaction system.
以下に、本発明における実施例を示し、本発明を具体的に説明する。 Examples of the present invention are shown below, and the present invention will be specifically described.
銀微粒子の平均粒子径は、走査型電子顕微鏡写真「Ｓ−４８００」（ＨＩＴＡＣＨＩ製）を用いて粒子の写真を撮影し、該写真を用いて粒子１００個以上について粒子径を測定し、その平均値を算出し、平均粒子径（ＤＳＥＭ）とした。 The average particle diameter of the silver fine particles was obtained by taking a photograph of the particles using a scanning electron micrograph “S-4800” (manufactured by HITACHI), measuring the particle diameter of 100 or more particles using the photograph, The value was calculated and taken as the average particle size (D SEM ).
銀微粒子の比表面積は、「モノソーブＭＳ−１１」（カンタクロム株式会社製）を用いて、ＢＥＴ法により測定した値で示した。 The specific surface area of the silver fine particles was shown as a value measured by BET method using “Monosorb MS-11” (manufactured by Kantachrome Co., Ltd.).
ＤＴＡ曲線におけるピークは、熱分析装置（Ｓｅｉｋｏ Ｉｎｓｔｒｕｍｅｎｔｓ
Ｉｎｃ． 製 ＥＸＳＴＡＲ ６０００ ＴＧ／ＤＴＡ６３００）を用い、乾燥空気を３００ｍｌ／ｍｉｎフローし、室温（３０℃）から５５０℃まで１０℃／ｍｉｎで昇温加熱した条件下、測定を行った。
The peak in the DTA curve is a thermal analyzer (Seiko Instruments).
Inc. EXSTAR 6000 TG / DTA6300) was used, and measurement was performed under a condition where dry air was flowed at 300 ml / min and heated from room temperature (30 ° C.) to 550 ° C. at a rate of 10 ° C./min.
ＴＧ
ＴＧによる加熱減量は、前述の熱分析装置（Ｓｅｉｋｏ Ｉｎｓｔｒｕｍｅｎｔｓ Ｉｎｃ． 製 ＥＸＳＴＡＲ ６０００ ＴＧ／ＤＴＡ６３００）を用い、乾燥空気を３００ｍｌ／ｍｉｎフローした条件下、室温（３０℃）から５５０℃まで１０℃／ｍｉｎで昇温加熱し、加熱始め（３０℃）のサンプル量から減量が終了した時点（銀微粒子の酸化開始時点（サンプルによって異なるが、２５０〜３００℃））までのサンプル量を差し引いた量で示した。
TG
The heat loss by TG is 10 ° C./min from room temperature (30 ° C.) to 550 ° C. under the condition that dry air is flowed at 300 ml / min using the above-mentioned thermal analyzer (EXSTAR 6000 TG / DTA6300 manufactured by Seiko Instruments Inc.). The amount of the sample is subtracted from the sample amount at the beginning of heating (30 ° C) to the point when the weight reduction is completed (at the start of oxidation of silver fine particles (depending on the sample, 250 to 300 ° C)). It was.
銀微粒子の結晶子径（ＤＸ）は、Ｘ線回折装置「ＲＩＮＴ２５００」（株式会社リガク製）を用いて、ＣｕのＫα線を線源とした面指数（１，１，１）面ピークの半値幅を求め、Ｓｃｈｅｒｒｅｒの式より結晶子径を計算した。 The crystallite diameter (D X ) of the silver fine particles is a surface index (1,1,1) plane peak using an X-ray diffractometer “RINT 2500” (manufactured by Rigaku Corporation) as a source of Cu Kα rays. The full width at half maximum was determined, and the crystallite diameter was calculated from the Scherrer equation.
銀微粒子の多結晶化度は、平均粒子径（ＤＳＥＭ）と結晶子径（ＤＸ）の比（ＤＳＥＭ／ＤＸ）で示した。 The degree of polycrystallinity of the silver fine particles was indicated by the ratio (D SEM / D X ) between the average particle diameter (D SEM ) and the crystallite diameter (D X ).
導電性塗膜の比抵抗は、後述する導電性ペーストをポリエステルフィルム上に塗布し、１２０℃で予備乾燥した後、１５０℃で３０分間加熱硬化さることにより得られた導電性膜について、４端子電気抵抗測定装置「ロレスタＧＰ／ＭＣＰ−Ｔ６１０」（株式会社ダイアインスツルメンツ製）を用いて測定し、シート抵抗と膜厚より比抵抗を算出した。 The specific resistance of the conductive coating film is 4 terminals for a conductive film obtained by applying a conductive paste described later on a polyester film, preliminarily drying at 120 ° C., and then heat-curing at 150 ° C. for 30 minutes. It measured using the electrical resistance measuring apparatus "Loresta GP / MCP-T610" (made by Dia Instruments Co., Ltd.), and calculated the specific resistance from the sheet resistance and the film thickness.
＜銀微粒子の製造＞
実施例１−１
５００ｍＬのビーカーに硝酸銀４０ｇとメタノール２００ｍＬを加えた後、２２℃となるように水浴にて冷却しながらｎ−ブチルアミン３７．９ｇを添加・攪拌してＡ液を調製した。別に２Ｌのビーカーにエリソルビン酸６２．２ｇを量り取り、水４００ｍＬを加え攪拌して溶解した後、メタノール２００ｍＬを加えてＢ液を調製した。
<Manufacture of silver fine particles>
Example 1-1
After adding 40 g of silver nitrate and 200 mL of methanol to a 500 mL beaker, 37.9 g of n-butylamine was added and stirred while cooling in a water bath to 22 ° C. to prepare solution A. Separately, 62.2 g of erythorbic acid was weighed into a 2 L beaker, 400 mL of water was added and dissolved by stirring, and then 200 mL of methanol was added to prepare solution B.
次いで、反応系を２２℃に維持しつつ、Ｂ液を攪拌しながらＡ液をＢ液に１時間２０分かけて滴下した。滴下終了後、１４時間攪拌した後、３０分間静置して固形物を沈降させた。上澄み液をデカンテーションにより取り除いた後、ろ紙を用いて吸引ろ過し、続いて、メタノールと純水を用いて洗浄・ろ過した。得られた銀微粒子の固形物を真空乾燥機中３０℃で６時間乾燥した後、常法により粉砕して実施例１−１の銀微粒子を得た。 Next, while maintaining the reaction system at 22 ° C., the liquid A was added dropwise to the liquid B over 1 hour and 20 minutes while stirring the liquid B. After the completion of dropping, the mixture was stirred for 14 hours and then allowed to stand for 30 minutes to precipitate a solid. After removing the supernatant liquid by decantation, suction filtration was performed using a filter paper, followed by washing and filtration using methanol and pure water. The obtained solid matter of silver fine particles was dried in a vacuum dryer at 30 ° C. for 6 hours and then pulverized by a conventional method to obtain silver fine particles of Example 1-1.
得られた銀微粒子の平均粒子径（ＤＳＥＭ）は８０．４ｎｍ、結晶子径（ＤＸ）は２０．１ｎｍ、多結晶化度（ＤＳＥＭ／ＤＸ）は４．０、ＢＥＴ比表面積値は５．６ｍ２／ｇであった。また、ＤＴＡ曲線のピークは１２５℃であり、ＴＧによる加熱減量は０．３８％であった。 The obtained silver fine particles had an average particle size (D SEM ) of 80.4 nm, a crystallite size (D X ) of 20.1 nm, a polycrystallinity (D SEM / D X ) of 4.0, and a BET specific surface area value. Was 5.6 m 2 / g. Moreover, the peak of the DTA curve was 125 ° C., and the loss on heating by TG was 0.38%.
前記実施例１−１に従って銀微粒子を作製した。各製造条件及び得られた銀微粒子末の諸特性を示す。 Silver fine particles were prepared according to Example 1-1. Various characteristics of each production condition and the obtained silver fine particles are shown.
実施例１−２〜１−４及び比較例１−１〜１−４：
銀微粒子の生成条件を種々変更することにより、銀微粒子得た。
Examples 1-2 to 1-4 and Comparative Examples 1-1 to 1-4:
Silver fine particles were obtained by variously changing the production conditions of the silver fine particles.
比較例１−５（特開２００６−１８３０７２号公報 実施例１２の追試実験）：
１０Ｌのガラス製反応容器に３−メトキシプロピルアミン３．０ｋｇ（３３．７ｍｏｌ）を入れた。撹拌しながら、反応温度を４５℃以下に保持しつつ、酢酸銀５．０ｋｇ（３０．０ｍｏｌ）を添加した。次いで、９５重量％のアスコルビン酸３．７ｋｇ（２１．０ｍｏｌ）を、反応温度を３０〜４５℃に保持しつつ６時間かけて全量を滴下した後、反応を終了させた。反応混合物を４０℃で静置し、上澄み液をデカンテーションにより取り除いた後、ろ紙を用いて吸引ろ過し、続いて、メタノールと純水を用いて洗浄・ろ過した。得られた銀微粒子の固形物を真空乾燥機中３０℃で６時間乾燥した後、常法により粉砕して比較例１−５の銀微粒子を得た。得られた比較例１−５の銀微粒子の諸特性を表２に示す。
Comparative Example 1-5 (Japanese Unexamined Patent Application Publication No. 2006-183072 Example 12 follow-up experiment):
In a 10 L glass reaction vessel, 3.0 kg (33.7 mol) of 3-methoxypropylamine was placed. While stirring, the reaction temperature was kept at 45 ° C. or lower, and 5.0 kg (30.0 mol) of silver acetate was added. Next, 95 kg of ascorbic acid (3.7 kg, 21.0 mol) was added dropwise over 6 hours while maintaining the reaction temperature at 30 to 45 ° C., and then the reaction was terminated. The reaction mixture was allowed to stand at 40 ° C., and the supernatant liquid was removed by decantation, followed by suction filtration using filter paper, followed by washing and filtration using methanol and pure water. The obtained solid particles of silver fine particles were dried in a vacuum dryer at 30 ° C. for 6 hours and then pulverized by a conventional method to obtain silver fine particles of Comparative Example 1-5. Table 2 shows the various characteristics of the obtained silver fine particles of Comparative Example 1-5.
このときの製造条件を表１に、得られた銀微粒子の諸特性を表２に示す。 The production conditions at this time are shown in Table 1, and the characteristics of the obtained silver fine particles are shown in Table 2.
＜導電性ペーストの製造＞
実施例２−１
本発明の銀微粒子１００重量部に対してポリエステル樹脂１１．０重量部及び硬化剤１．４重量部と、導電性ペーストにおける銀微粒子の含有量が７０ｗｔ％となるようにジエチレングリコールモノエチルエーテルを加え、プレミックスを行った後、３本ロールを用いて均一に混練・分散処理を行い、導電性ペーストを得た。
<Manufacture of conductive paste>
Example 2-1
Add 11.0 parts by weight of polyester resin and 1.4 parts by weight of curing agent to 100 parts by weight of silver fine particles of the present invention, and add diethylene glycol monoethyl ether so that the content of silver fine particles in the conductive paste is 70 wt%. After premixing, the mixture was uniformly kneaded and dispersed using three rolls to obtain a conductive paste.
得られた導電性塗膜の比抵抗は３．７×１０−５Ω・ｃｍであった。 The specific resistance of the obtained conductive coating film was 3.7 × 10 −5 Ω · cm.
実施例２−２〜２−４及び比較例２−１〜２−５：
銀微粒子の種類を種々変化させた以外は、前記実施例２−１の導電性ペーストの作製方法に従って、導電性ペースト及び導電性膜を製造した。
Examples 2-2 to 2-4 and comparative examples 2-1 to 2-5:
A conductive paste and a conductive film were produced according to the method for producing a conductive paste of Example 2-1 except that the type of silver fine particles was variously changed.
このときの製造条件及び得られた導電性塗膜の諸特性を表３に示す。 Table 3 shows the production conditions at this time and various characteristics of the obtained conductive coating film.
本発明に係る銀微粒子は、平均粒子径３０〜１００ｎｍであるため、平均粒子径が１〜２０ｎｍ程度のシングルナノオーダーの銀微粒子のように多量の有機物で表面を被覆する必要がなく、また銀微粒子の粒子表面に存在する有機物も１００〜１４０℃の温度範囲で飛散してしまうと共に、多結晶化度が２．０以上であることから粒子内部の活性が高いため、低温においても銀微粒子同士の焼結が進行するので、低温焼成が可能な導電性ペースト等の原料として好適である。 Since the silver fine particles according to the present invention have an average particle diameter of 30 to 100 nm, it is not necessary to coat the surface with a large amount of organic matter unlike single nano-order silver fine particles having an average particle diameter of about 1 to 20 nm. The organic matter present on the particle surface of the fine particles also scatters in the temperature range of 100 to 140 ° C., and since the polycrystallinity is 2.0 or more, the activity inside the particles is high. Therefore, it is suitable as a raw material for a conductive paste that can be fired at a low temperature.
Claims (7)
ＳＳＡ（ｍ２／ｇ）≧−０．０５×ＤＳＥＭ＋７．４ （１） The silver fine particles according to claim 1 or 2, wherein a BET specific surface area value (SSA) (m 2 / g) is represented by the following formula (1).
SSA (m 2 /g)≧−0.05×D SEM +7.4 (1)
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