JP2004111106A

JP2004111106A - Conductive powder and manufacturing method of the same, and conductive paint and conductive coating film using the same

Info

Publication number: JP2004111106A
Application number: JP2002269084A
Authority: JP
Inventors: Takeaki Fujino; 藤野　剛聡; Tatsumi Inamura; 稲村　辰美; Yoshifumi Horikawa; 堀川　義史
Original assignee: Dowa Mining Co Ltd
Current assignee: Dowa Holdings Co Ltd
Priority date: 2002-09-13
Filing date: 2002-09-13
Publication date: 2004-04-08
Anticipated expiration: 2022-09-13
Also published as: JP4134314B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide conductive powder which can be painted at low cost, composed of Indium oxide containing Sn having excellent conductivity and transmissivity, and to provide a transparent conductive coating film. <P>SOLUTION: The conductive powder is obtained by heating hydroxide of In containing trivalent element and Sn obtained by neutralizing an acidic solution containing In and Sn, and a solution containing three valent element except In, by an alkali, at 300-1,000°C. The shape of the powdered particle is of a stick or needle-shape with a length of 500 nm or less and a width of 100 nm or less with the ratio of the lengths of 1.5 to 10, or of a ball or a grain-shape with a diameter of 200 nm or less. The coating film using the above has excellent conductivity and transmissivity. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、錫含有インジウム酸化物（Ｓｎ含有Ｉｎ酸化物と表す、また、ＩＴＯということがある。）及びその製造方法並びにそれを用いた導電性塗料及び導電性塗膜に関するものである。
【０００２】
【従来の技術】
Ｓｎ含有Ｉｎ酸化物は、可視光に対する透過性と高い導電性を示すことから各種表示デバイスや太陽電池などの導電性膜として用いられている。
従来、これらの導電性膜の製法としては、１）スパッタ法によるもの、２）ＩＴＯ粒子を塗布するもの、３）金属とＩＴＯの混合粒子を塗布するもの、などが挙げられる。
【０００３】
これらのうち、導電性塗膜については、ＩＴＯ粒子同士の接触により導電経路が形成されるため、この導電経路が得られやすい粒子の形状として、フレーク状、棒状、針状、板状等の粒子を用いることによって導電性を向上させることができるものであり、これらの種々の粒子形状を得る試みはこれまでもなされている（例えば、特許文献１、特許文献２、特許文献３、特許文献４参照。）。
【０００４】
【特許文献１】
特開平７−２３２９２０号公報
【特許文献２】
特開平７−２３５２１４号公報
【特許文献３】
特開平８−２１７４４６号公報
【特許文献４】
特開平６−８０４２２号公報
【０００５】
【発明が解決しようとする課題】
しかしながら、上記の１）のスパッタ法によるものは導電性や透過率等の特性に優れているが、製造において真空装置等の高価な設備を必要としてコスト高となり、２）の粒子塗布法では導電性、透過率等の特性の改善は必ずしも十分ではなく、３）の混合粒子塗布法も上記特性が必ずしも十分ではなかった。
また、一般的に、上記の２）及び３）による導電性塗膜はブラウン管の電磁波シールド膜に利用されているが、上記の１）のスパッタ法による膜に比べてまだ導電性が低く、用途に限定があるのが実情である。
【０００６】
さらに、導電性粉末粒子の形状のみの改善では、導電性は改善されるものの透過率等の光学特性を達成できず、特に散乱光が多く発生し、塗膜のヘイズ（直接透過光に対する拡散透過光の割合）が大きいという問題、あるいは逆に、透過率が十分であっても、導電性において不十分で電磁波シールド性に欠けるなどの問題があった。
【０００７】
従って、本発明の目的とするところは、低コストの塗布型であって優れた導電性及び透過特性を有するＳｎ含有Ｉｎ酸化物からなる導電性粉末及びその製造方法並びにそれを用いた導電性塗料及び導電性塗膜を提供することにある。
【０００８】
【課題を解決するための手段】
上記の目的に対し、本発明者等は、鋭意研究の結果、Ｉｎ以外にも原子価が３価の元素を添加した錫含有インジウム水酸化物（Ｓｎ含有Ｉｎ水酸化物と表す。）を弱還元雰囲気で加熱処理（焼成ということがある。）したＩＴＯ粒子によって、導電性及び透過特性を向上でき、上記の目的を達成できることを見出した。
【０００９】
すなわち、本発明は、第１に、Ｓｎ含有Ｉｎ酸化物中にＩｎ以外の原子価３価の元素（３価元素という。）を含有することを特徴とする導電性粉末；第２に、前記導電性粉末が、ＣＩＥ　１９７６　Ｌ＊ａ＊ｂ＊色空間において明度指数Ｌ＊値が２５〜８５であり、クロマティクネス指数ａ＊値及びｂ＊値がいずれも−１．０〜−４０．０である青系色調を有する、第１記載の導電性粉末；第３に、前記３価元素が、Ａｌ、Ｇａ、Ｔｌ、Ａｕ、Ｂｉ、Ｆｅ、Ｙ、Ｌａ、Ｎｄ、Ｅｕ、Ｇｄ、Ｄｙ、Ｈｏ、Ｅｒ及びＹｂからなる群から選ばれる１種以上の元素である、第１または２に記載の導電性粉末；第４に、前記３価元素として、Ａｌ、Ｆｅのうちの１種以上の元素を含有する、第３記載の導電性粉末；第５に、長軸径が５００ｎｍ以下、短軸径が１００ｎｍ以下、軸比が１．５〜１０である棒状または針状の形状を有する、第１〜４のいずれかに記載の導電性粉末；第６に、径が２００ｎｍ以下である球状または粒状の形状を有する、第１〜４のいずれかに記載の導電性粉末；第７に、第１〜６のいずれかに記載の導電性粉末粒子を導電材として含有することを特徴とする導電性塗料；第８に、第１〜６のいずれかに記載の導電性粉末粒子を導電材として含有することを特徴とする導電性塗膜；第９に、Ｉｎ、Ｓｎ及び前記３価元素を含有する酸性溶液にアルカリを添加して予備中和し、該予備中和された液にさらにアルカリを添加して中和することにより得られた沈殿を加熱処理することを特徴とする、第１〜５のいずれかに記載の導電性粉末の製造方法；第１０に、ＩｎとＳｎを含有する酸性溶液にアルカリを添加して予備中和し、該予備中和された液にさらに前記３価元素とアルカリを添加して中和することにより得られた沈殿を加熱処理することを特徴とする、第１〜５のいずれかに記載の導電性粉末の製造方法；第１１に、前記予備中和時の液温が４５℃以下であり、前記中和時の液温が５０℃以上である、第９または１０に記載の導電性粉末の製造方法；第１２に、前記予備中和後液のｐＨが２〜３であり、前記中和後液のｐＨが７〜１２である、第９〜１１のいずれかに記載の導電性粉末の製造方法；第１３に、アルカリに前記３価元素含有溶液及びＩｎとＳｎを含有する酸性溶液を添加して中和することにより得られた沈殿を加熱処理することを特徴とする、第１、２、３、４または６に記載の導電性粉末の製造方法；第１４に、前記中和時の液温が１０〜９０℃であり、前記中和後液のｐＨが６〜１２である、第１３記載の導電性粉末の製造方法；第１５に、前記加熱処理温度が３００〜１０００℃である、第９〜１４のいずれかに記載の導電性粉末の製造方法を提供するものである。
【００１０】
【発明の実施の形態】
本発明に係る導電性粉末は、Ｉｎ、Ｓｎさらには３価元素を含有するものであって、これらのＩｎ、Ｓｎ及び３価元素の総モル数に対してＳｎが好ましくは０．５〜１５モル％、更に好ましくは０．８〜１０モル％含有される。Ｓｎの含有量が０．５モル％未満では導電性が低下し、一方、１５モル％を超えるとやはり導電性が低下するからである。また、Ｉｎ、Ｓｎ及び３価元素の総モル数に対して３価元素が、元素の種類によってより好ましい範囲は異なるが、好ましくは０．０１〜１５モル％含有される。３価元素の含有量が０．０１モル％未満では導電性が低下し、一方、１５モル％を超えるとやはり導電性が低下するからである。ここで、本発明で用いられる３価元素としては、Ｉｎと同族のＡｌ、Ｇａ、Ｔｌ等でもよいし、希土類のＹ、Ｌａ、Ｎｄ、Ｅｕ、Ｇｄ、Ｄｙ、Ｈｏ、Ｅｒ、Ｙｂ等でも良いし、さらにはＦｅ、ＢｉやＡｕ等でもよい。ただし、上記の３価元素を添加することで低抵抗化することや、元素の種類によって最適となるより好ましい添加範囲が異なること等の作用原理は今のところ不明である。
【００１１】
本発明に係る導電性粉末の青系色調については、ＣＩＥ（国際照明委員会）１９７６制定Ｌ＊ａ＊ｂ＊色空間（測定用光源Ｃ：色温度６７７４Ｋ）において明度指数Ｌ＊値が好ましくは２５〜８５であり、更に好ましくは３０〜８０である。Ｌ＊値が２５未満では色が暗すぎ、一方、８５を超えても不具合はないが事実上本発明の製造方法では実現できないからである。また、上記におけるクロマティクネス指数ａ＊値　、ｂ＊値は好ましくはいずれも−１．０〜−４０．０であり、更に好ましくはいずれも−２．５〜−３０．０である。クロマティクネス指数ａ＊値　、ｂ＊値が−１．０未満ではくすんだ色となり鮮やかさに欠けるからであり、一方、−４０．０を超えても不具合はないが事実上本発明の製造方法では実現できないからである。
【００１２】
なお、ＣＩＥ　１９７６　Ｌ＊ａ＊ｂ＊色空間とは、国際照明委員会（ＣＩＥ）が１９７６年にＣＩＥ　ＸＹＺ表色系を変換し、表色系内の一定距離がどの色の領域でもほぼ知覚的に等歩度の差をもつように定めた色空間である。また、明度指数Ｌ＊値、クロマティクネス指数ａ＊値　、ｂ＊値は、ＣＩＥ　１９７６　Ｌ＊ａ＊ｂ＊色空間内の直交座標系で定められる量であり、次の式（Ａ）〜（Ｃ）で表される。
Ｌ＊＝１１６（Ｙ／Ｙ_０）^１／３−１６　　　　　　　　　・・・（Ａ）
ａ＊＝５００［（Ｘ／Ｘ_０）^１／３−（Ｙ／Ｙ_０）^１／３　］　　・・・（Ｂ）
ｂ＊＝２００［（Ｙ／Ｙ_０）^１／３−（Ｚ／Ｚ_０）^１／３　］　・・・（Ｃ）
但し、Ｘ／Ｘ_０、Ｙ／Ｙ_０、Ｚ／Ｚ_０＞０．００８８５６であり、Ｘ、Ｙ、Ｚは物体色の三刺激値であり、Ｘ_０、Ｙ_０、Ｚ_０は物体色を照明する光源の三刺激値でＹ_０＝１００に基準化されている。
【００１３】
本発明の特徴的な導電性を有するＩＴＯ粉は、３価元素とＳｎを含有するＩｎ塩酸（硝酸、硫酸等でもよい。）溶液を出発溶液とし、これにＮａＯＨ、ＫＯＨ、ＮＨ_４ＯＨ、またはＮＨ_４ＨＣＯ_３等のアルカリ液によって４５℃以下の液温での予備中和を経て５０℃以上まで昇温した後に時間をかけた中和処理を行い、Ｓｎと３価元素とを含有するＩｎ水酸化物の沈殿を得て、この沈殿を大気中等で３００℃以下の温度で予備焼成を行った後、または予備焼成を行うことなく、３００〜１０００℃の温度で加熱処理を行うことにより得ることができる。また、３価元素を最初から添加しておくことなく、例えば昇温後にアルカリ溶液と一緒に添加しても良い。あるいはまた、前記酸性溶液のアルカリ溶液による中和処理ではなく、アルカリ溶液に対して、３価元素を含有する溶液およびＳｎを含有するＩｎ酸性溶液を、中間において特に昇温することなく１０〜９０℃の温度で添加する短時間の逆中和処理によってもよい。
【００１４】
予備中和処理は反応液を４５℃以下、好ましくは１５〜４５℃、さらに好ましくは１５〜２５℃のほぼ一定の温度に保持して行う。その反応後液は好ましくはｐＨ２〜３とする。この予備中和処理は、微粒子核を生成させることを目的としている。これに引き続く中和処理は、３０分〜２時間で前記反応後液を昇温して５０℃以上、好ましくは８０〜９５℃になるように昇温して行い、前記の微粒子核を成長させて、棒状、針状または板状の水酸化物を生成させる。中和後液は好ましくはｐＨ７〜１２とする。予備中和の中和率（全Ｉｎ量を１とした場合の予備中和で沈殿するＩｎ量の比率をいう。）、温度、ｐＨ等の条件により粒子形状を制御でき、また、予備中和時と中和時の温度域を調整することにより、所望の粒径、形状の水酸化物粒子を比較的均一に生成することができる。
【００１５】
中和処理は予備中和処理より高温浴で行い、中和操作のみで５０分以上、昇温時間を含むと２〜３時間を要するが、棒状、針状、または板状の粒子からなる水酸化物粉が得られ、これを焼成して導電性に優れた棒状、針状等の酸化物粒子が得られる。アルカリ液に酸性溶液を添加する中和法では中和時間は０．５〜１５分の短時間で済むが、結晶粉は球状または粒状の粉体粒子となる。
【００１６】
得られた３価元素とＳｎとを含有するＩｎ水酸化物を焼成し、脱水分解、焼結を行うことによって、粒状、球状、棒状、針状またはこれらに類似した形状の酸化物粉末粒子を得ることができる。焼成雰囲気は、水蒸気を含有する不活性ガスまたは、水蒸気とアンモニア等還元性ガスを含有する不活性ガスによる弱還元性雰囲気とする。すなわち、水酸化物の脱水分解後の粒子は結晶性が悪く、結晶成長させないと導電性が低くなる。焼結を促進させるため、焼成雰囲気に水蒸気を添加すると共に導電性を高めるために還元性のアンモニアや水素ガスを含有させるのが望ましい。
【００１７】
加熱処理温度は、水酸化物粒子のサイズ、形状、焼成雰囲気ガスに合わせて設定するが、加熱処理温度が高いほど、水蒸気が多い程、還元性が強い程、焼結が進み、得られる酸化物粒子の形状異方性が低くなる。焼成温度は３００〜１０００℃が好ましく、３００〜７００℃がさらに好ましい。上記の温度、雰囲気での焼成により水酸化物粒子の結晶化を進めて形状異方性を維持し、目的の酸化物粒子を得ることができる。ただし、３００℃未満の温度では水酸化物の分解が不十分であり、１０００℃を超えると水酸化物粒子の形状異方性を維持することが困難になると共に粒子間焼結による凝集が多くなり、分散性が低下する。
【００１８】
焼成して得られる３価元素とＳｎを含有するＩｎ酸化物粉末粒子は、好ましくは、長軸径が５００ｎｍ以下、更に好ましくは２００ｎｍ以下、短軸径が１００ｎｍ以下、更に好ましくは５０ｎｍ以下であって、針状、棒状または板状の形状を有する酸化物粉末粒子であり、長軸径／短軸径の軸比は１．５〜１０が好ましく、３〜１０がさらに好ましい。
また、球状ないし粒状の３価元素とＳｎを含有するＩｎ酸化物粉末にあっては、粒径が２００ｎｍ以下であることが好ましく、１００ｎｍ以下が更に好ましい。
【００１９】
３価元素とＳｎとを含有するＩｎ酸化物粉末粒子の長軸径は、５００ｎｍを超えると、可視光の散乱が発生し、透過率等の光学特性が低下する。特に長軸径が２００ｎｍ以下では可視光の散乱が一層抑制される。また、短軸径は１００ｎｍを超えると、粒子同士の接触度が低く、塗膜導電性が低くなるので１００ｎｍ以下とする。特に、短軸径５０ｎｍ以下では塗膜導電性が一層向上する。長軸径と短軸径との軸比が１．５〜１０の範囲を外れると導電性、分散性、粒子内結晶性が低下する。球状ないし粒状の３価元素とＳｎを含有するＩｎ酸化物粉末粒子にあっては、粒子同士の接触度の点から抵抗値が増すおそれがあり、特に径は２００ｎｍ以下とし、好ましくは１００ｎｍ以下とする。Ｘ線回折による（２２２）面の半価幅より算出した好ましい結晶子径Ｄｘ　は導電性の点から、１５０Å以上であることが好ましい。
【００２０】
上記の３価元素とＳｎとを含有するＩｎ酸化物粉を溶媒中に分散させて塗料化し、塗布後に溶媒を揮発させて膜を固定することにより、透過性の高い、導電性の塗膜を得ることができる。塗料化の方法は、公知の方法を使用することができ、溶媒としては、アルコール、ケトン、エーテル等の有機溶媒、分散剤として界面活性剤、カップリング剤等を添加し、ビーズミル等の分散装置を用いて分散させる。また、バインダーとなる結合剤を添加するか、塗布成膜後にバインダーを成膜して固定してもよい。
【００２１】
【実施例】
以下に実施例によって本発明をさらに詳細に説明するが、本発明の技術的範囲はこれらの記載に限定されないことはいうまでもない。
【００２２】
〔実施例１〕　Ｉｎを１８ｗｔ％含む塩酸溶液２００ｇを純水で２．９Ｌとし、さらに塩化第２錫５．４ｇ、および硝酸アルミニウム・９水和物１．５ｇを混合溶液として出発溶液の酸性溶液としガラスビーカーに仕込んだ。４８％ＮａＯＨ溶液１０８．２ｇを純水８９０ｇで希釈し、このアルカリ溶液を上記酸性溶液に添加する。まず、はじめに液温２０℃の酸性溶液にアルカリ溶液を１５分間添加してｐＨ３に予備中和する。ついで液温を９０℃まで昇温し残りのアルカリ溶液を４０分間かけて添加する。最終のｐＨは１０．０であった。これをろ過、脱水、乾燥してＳｎ、Ａｌ含有Ｉｎ水酸化物の沈殿を得た。このＳｎ、Ａｌ含有Ｉｎ水酸化物の透過型電子顕微鏡写真（ＴＥＭ写真という。）を図−１に示す。この水酸化物粉末粒子の長軸径は１８１．４２ｎｍ、短軸径は３３．７３ｎｍ、長軸径／短軸径の比は５．４であった。
【００２３】
次いで、このＳｎ、Ａｌ含有Ｉｎ水酸化物を管状炉に入れ、１．５ｖｏｌ．％の水蒸気と０．０５ｖｏｌ．％のＮＨ_３ガスとを含有するＮ_２ガスの雰囲気中で６００℃にて２時間焼成した。この得られたＳｎ、Ａｌ含有Ｉｎ酸化物粉末粒子は、図−２のＴＥＭ写真に示されるものであって、長軸径は１５０．１６ｎｍ、短軸径は３３．３６ｎｍ、長軸径／短軸径の比は４．５０の棒状粒子であった。なお、長軸径、短軸径の求め方としては、ＴＥＭ写真中の５０個の粒子の長軸径、短軸径をノギスで実測して、倍率換算しその平均値を求めた。更に軸比は前記の長軸径と短軸径の比率より算出した。この得られたＳｎ、Ａｌ含有Ｉｎ酸化物粒子は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が７２．９３、クロマティクネス指数ａ＊値が−８．４６およびｂ＊値が−９．６７の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２２．５ｍ^２／ｇであった。また結晶子径Ｄ_ｘは１８０Åであった。
【００２４】
この粉末６ｇと溶剤（エタノール）１８ｇ及び分散剤としてアニオン系界面活性剤０．３ｇを遊星ボールミル（フリッチェ製Ｐ−５型、容器容量８０ｍＬ、ＰＳＺ０．３ｍｍボール）に入れ、回転数３００ｒｐｍで３０分間回転させて、この分散液にコロイダルシリカとエタノールを加えて、ＩＴＯ粉末の含有量が２％、シリカ含有量が２％、残部がエタノールである塗料を作成し、ガラス板にスピンコートした後、２００℃で３０分間乾燥し、膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値が１．４０ｋΩ／□であった。また分光光度計にて透過率を測定したところ透過率は９８．９％であり、良好な透明導電性膜が得られた。
【００２５】
〔実施例２〕　２５％アンモニア水５５０ｇを純水１７９０ｇで希釈して出発溶液のアルカリ溶液とし、ガラスビーカーに仕込んだ。Ｉｎを１８ｗｔ％含む塩酸溶液８００ｇを純水で１．５Ｌとし、さらにＳｎＣｌ_４・５Ｈ_２Ｏ　２１．１９ｇ、および塩化金酸・四水和物　０．７０７７５ｇを混合溶液として、５０℃に温度調節したこの酸性溶液を５０℃に温度調節した上記アルカリ性溶液に添加した。最終のｐＨは９．０であった。これを濾過、脱水、乾燥してＡｕ、Ｓｎ含有Ｉｎ水酸化物の沈殿を得た。
【００２６】
次いで、このＡｕ、Ｓｎ含有Ｉｎ水酸化物を管状炉に入れ、１．５ｖｏｌ．％水蒸気と０．０５ｖｏｌ．％のＮＨ_３ガスとを含有するＮ_２ガスの雰囲気中で６００℃にて２時間焼成した。この得られた平均径４５ｎｍの球状のＡｕ、Ｓｎ含有Ｉｎ酸化物粒子は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が５９．６７、クロマティクネス指数ａ＊値が−２．９４およびｂ＊値が−１２．５３の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２６．０ｍ^２／ｇであった。また結晶子径Ｄｘは２４０Åであった。
【００２７】
この粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値は１．５９ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９７．２９％であり、良好な透明導電性膜が得られた。
【００２８】
〔実施例３〕　塩化金酸に代えて酸化ビスマス３．５ｇを添加した以外は実施例２と同様の条件で処理してＢｉ、Ｓｎ含有Ｉｎ水酸化物を得た。次いで、実施例２と同様の焼成を行ってＢｉ、Ｓｎ含有Ｉｎ酸化物粉を得た。得られたＢｉ、Ｓｎ含有Ｉｎ酸化物粉は平均粒径が４５ｎｍの粒状粉であった。この得られた粒状のＢｉ、Ｓｎ含有Ｉｎ酸化物粒子は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が６３．５４、クロマティクネス指数ａ＊値が−７．５９およびｂ＊値が−７．２１の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２７．５ｍ^２／ｇであった。また結晶子径Ｄｘは２２１Åであった。
【００２９】
この粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗を測定したところ、抵抗値は２．４３ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９６．２８％であり、良好な透明導電性膜が得られた。
【００３０】
〔実施例４〕　硝酸アルミニウムに代えて酸化鉄（Ｆｅ_２Ｏ_３）０．１４ｇを添加した以外は実施例１と同様の条件で処理してＳｎ、Ｆｅ含有Ｉｎ水酸化物を得た。次いで、実施例１と同様の焼成を行ってＳｎ、Ｆｅ含有Ｉｎ酸化物粉を得た。この得られたＳｎ、Ｆｅ含有Ｉｎ酸化物粉末粒子は長軸径が１４１．６ｎｍ、短軸径は３２．０７ｎｍ、長軸径／短軸径の比は４．４２の棒状粒子であり、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が６９．８５、クロマティクネス指数ａ＊値が−４．４２およびｂ＊値が−８．１６の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２０．３ｍ^２／ｇであった。また結晶子径Ｄｘは２０５Åであった。
【００３１】
この粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値は１．７０ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９３．２９％であり、良好な透明導電性膜が得られた。
【００３２】
〔実施例５〕　塩化インジウム溶液に代えて１００ｇ／Ｌのインジウムを含む硝酸インジウム溶液４００ｍＬを使用し、硝酸アルミニウムに代えて酸化タリウム０．４５ｇを添加した以外は実施例１と同様の条件で処理してＳｎ、Ｔｌ含有Ｉｎ水酸化物を得た。次いで、実施例１と同様の焼成を行ってＳｎ、Ｔｌ含有Ｉｎ酸化物粉を得た。この得られたＳｎ、Ｔｌ含有Ｉｎ酸化物粉末粒子は長軸径が２３２．２３ｎｍ、短軸径は５９．０５ｎｍ、長軸径／短軸径の比は３．９３の棒状粒子であった。この粒子は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が６６．０２、クロマティクネス指数ａ＊値が−６．９６およびｂ＊値が−７．１１の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ１８．７ｍ^２／ｇであった。また結晶子径Ｄｘは１６２Åであった。
【００３３】
この粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値は１．８３ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９２．０９％であり、良好な透明導電性膜が得られた。
【００３４】
〔実施例６〕　硝酸アルミニウムに代えて酸化ネオジム０．２ｇを添加した以外は実施例１と同様の条件で処理してＳｎ、Ｎｄ含有Ｉｎ水酸化物を得た。次いで、実施例１と同様の焼成を行ってＳｎ、Ｎｄ含有Ｉｎ酸化物粉を得た。この得られたＳｎ、Ｎｄ含有Ｉｎ酸化物粉末粒子は長軸径が１１７．７ｎｍ、短軸径は３６．９１ｎｍ、長軸径／短軸径の比は３．１９の棒状粒子であった。この粒子は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が７２．２９、クロマティクネス指数ａ＊値が−７．６４およびｂ＊値が−９．９２の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２３．２ｍ^２／ｇであった。また結晶子径Ｄｘは１８１Åであった。
【００３５】
この粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値は１．９９ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９８．２５％であり、良好な透明導電性膜が得られた。
【００３６】
〔実施例７〕　硝酸アルミニウムを０．６５ｇに減らす代わりに酸化鉄を０．１５ｇ添加した以外は実施例１と同様の条件で処理してＡｌ、Ｆｅ、Ｓｎ含有Ｉｎ水酸化物を得た。次いで、実施例１と同様の焼成を行ってＡｌ、Ｆｅ、Ｓｎ含有Ｉｎ酸化物粉を得た。この得られたＳｎ、Ａｌ、Ｆｅ含有Ｉｎ酸化物粉末粒子は長軸径が１４５．８８ｎｍ、短軸径は３２．７２ｎｍ、長軸径／短軸径の比は４．４５の棒状粒子であった。この粒子は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が７２．８０、クロマティクネス指数ａ＊値が−４．３２およびｂ＊値が−６．６９の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２４．５ｍ^２／ｇであった。また結晶子径Ｄｘは１７２Åであった。
【００３７】
この粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値は１．５９ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９６．０１％であり、良好な透明導電性膜が得られた。
【００３８】
〔実施例８〕　硝酸アルミニウムの代わりにアルミン酸ナトリウムを用い、アルミン酸ナトリウムを溶かしたアルカリ溶液により中和した以外は実施例１と同様の条件で処理してＳｎ、Ａｌ含有Ｉｎ水酸化物を得た。次いで、実施例１と同様の焼成を行ってＳｎ、Ａｌ含有Ｉｎ酸化物粉を得た。この得られたＳｎ、Ａｌ含有Ｉｎ酸化物粉末粒子については長軸径が１４３．０７ｎｍ、短軸径が３７．２０ｎｍ、長軸径／短軸径の比が３．８５の棒状粒子であった。この粒子については、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が７０．４１、クロマティクネス指数ａ＊値が−８．０５およびｂ＊値が−１１．７５の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２１．９３ｍ^２／ｇであった。また結晶子径Ｄｘは１９０Åであった。
【００３９】
この粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値は１．７８ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９５．２７％であり、良好な透明導電性膜が得られた。
【００４０】
〔実施例９〕　硝酸アルミニウムに代えて塩化イットリウム６水和物０．５５ｇを添加した以外は実施例１と同様の条件で処理してＳｎ、Ｙ含有Ｉｎ水酸化物を得た。次いで、実施例１と同様の焼成を行ってＳｎ、Ｙ含有Ｉｎ酸化物粉を得た。この得られたＳｎ、Ｙ含有Ｉｎ酸化物粉末粒子は長軸径が１３３．４１ｎｍ、短軸径は３２．２８ｎｍ、長軸径／短軸径の比は４．１３の棒状粒子であった。この粒子は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が７５．２２、クロマティクネス指数ａ＊値が−７．５３およびｂ＊値が−７．１７の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２３．５６ｍ^２／ｇであった。また結晶子径Ｄｘは１９８Åであった。
【００４１】
この粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値は１．８３ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９８．２３％であり、良好な透明導電性膜が得られた。
【００４２】
〔実施例１０〕　塩化金酸に代えて硝酸アルミニウム・９水和物２．７ｇを添加した以外は実施例２と同様の条件で処理してＳｎ、Ａｌ含有Ｉｎ水酸化物を得た。次いで、実施例２と同様の焼成を行ってＳｎ、Ａｌ含有Ｉｎ酸化物粉を得た。得られたＳｎ、Ａｌ含有Ｉｎ酸化物粉は平均粒径が４５ｎｍの粒状粉であった。この粒子は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が６６．５９、クロマティクネス指数ａ＊値が−８．８７およびｂ＊値が−１１．８９の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２９．０ｍ^２／ｇであった。また結晶子径Ｄｘは２０７Åであった。
【００４３】
この粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値は２．３８ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９６．４１％であり、良好な透明導電性膜が得られた。
【００４４】
〔比較例１〕　Ｉｎ以外の３価元素を添加しない以外は、実施例１と同様の条件で、塩酸酸性溶液を用意し、この塩酸酸性溶液にアルカリ溶液を添加し予備中和後、液温をあげて中和を行い、濾過、脱水、乾燥してＳｎ含有Ｉｎ水酸化物を得た。このＳｎ含有Ｉｎ水酸化物のＴＥＭ写真を図３に示した。
【００４５】
次いで、実施例１と同様の条件で、このＳｎ含有Ｉｎ水酸化物を焼成し、Ｓｎ含有Ｉｎ酸化物を得た。このＳｎ含有Ｉｎ酸化物のＴＥＭ写真を図４に示した。
このＳｎ含有Ｉｎ酸化物は長軸径が１５６．６６ｎｍ、短軸径が４０．７０ｎｍ、軸比が３．８５の針状粒子であった。この粒子は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が７６．８２、クロマティクネス指数ａ＊値が−８．２７およびｂ＊値が−４．０５の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２３．７ｍ^２／ｇであった。また結晶子径Ｄｘは２１４Åであった。
【００４６】
この粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値は３．６７ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９７．２０％であった。このＩｎ以外の３価元素の添加がないこの比較例１のＳｎ含有Ｉｎ酸化物粉の場合の塗膜では顕著に高い抵抗値を示した。
【００４７】
〔比較例２〕　硝酸アルミニウムに代えて塩化パラジウム０．３５ｇを添加した以外は、実施例１と同様の条件で、塩酸酸性溶液を用意し、この塩酸酸性溶液にアルカリ溶液を添加し予備中和後、液温をあげて中和を行い、濾過、脱水、乾燥してＰｄ、Ｓｎ含有Ｉｎ水酸化物を得た。このＰｄ、Ｓｎ含有Ｉｎ水酸化物のＴＥＭ写真を図５に示した。
【００４８】
次いで、実施例１と同様の条件で、このＰｄ、Ｓｎ含有Ｉｎ水酸化物を焼成し、Ｐｄ、Ｓｎ含有Ｉｎ酸化物を得た。このＰｄ、Ｓｎ含有Ｉｎ酸化物のＴＥＭ写真を図６に示した。
このＰｄ、Ｓｎ含有Ｉｎ酸化物粉末粒子は水酸化物の針状を保持せず長軸径が４５．９９ｎｍ、短軸径が３０．７７ｎｍ、軸比が１．４９の粒状であった。この粒子は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が５３．６０、クロマティクネス指数ａ＊値が−３．５８およびｂ＊値が−５．６２の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２０．５ｍ^２／ｇであった。また結晶子径Ｄｘは２３２Åであった。
【００４９】
このＰｄ、Ｓｎ含有Ｉｎ酸化物粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値は６．４３ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９２．２３％であった。このＩｎ以外の３価元素の添加がなく、２価であるパラジウムを添加したこの比較例２のＰｄ、Ｓｎ含有Ｉｎ酸化物粉の場合の塗膜では顕著に高い抵抗値を示した。
【００５０】
〔比較例３〕　Ｉｎ以外の３価元素を添加しない以外は実施例２と同様の条件で処理してＳｎ含有Ｉｎ水酸化物を得た。次いで、実施例２と同様の焼成を行ってＳｎ含有Ｉｎ酸化物粉を得た。得られたＳｎ含有Ｉｎ酸化物粉末粒子は平均粒径が４５ｎｍの粒状であった。この粒子は、ＣＩＥ制定（１９７６）のＬ＊ａ＊ｂ＊色空間で明度指数Ｌ＊値が６６．５３、クロマティクネス指数ａ＊値が−７．４３およびｂ＊値が−１１．８の青系色調を有していた。得られた粉体の比表面積をＢＥＴ１点法にて測定したところ２８．０ｍ^２／ｇであった。また結晶子径Ｄｘは２４０Åであった。
【００５１】
この粉末を用いて実施例１と同様にして膜厚０．３μｍの透明導電性膜を作成した。作成した膜の抵抗値を測定したところ、抵抗値は４．８１ｋΩ／□であった。また分光光度計にて透過率を測定したところ、透過率は９７．０２％であった。このＩｎ以外の３価元素を含有しないこの比較例３のＳｎ含有Ｉｎ酸化物粉の場合の塗膜では顕著に高い抵抗値を示した。
【００５２】
【発明の効果】
本発明によれば、Ｉｎ以外の３価元素を含有するＳｎ含有Ｉｎ水酸化物を弱還元雰囲気等で焼成を行うという効率的な製法により、抵抗値が低く透過率に優れた、３価元素を含有するＳｎ含有Ｉｎ酸化物粉末（ＩＴＯ粉末）並びに導電性塗料及び導電性塗膜を得ることができるという効果を奏する。
【図面の簡単な説明】
【図１】実施例１におけるＡｌ、Ｓｎ含有Ｉｎ水酸化物粉のＴＥＭ写真である。
【図２】図１のＡｌ、Ｓｎ含有Ｉｎ水酸化物粉を焼成して得られたＡｌ、Ｓｎ含有Ｉｎ酸化物粉のＴＥＭ写真である。
【図３】比較例１におけるＳｎ含有Ｉｎ水酸化物粉のＴＥＭ写真である。
【図４】図３のＳｎ含有Ｉｎ水酸化物粉を焼成して得られたＳｎ含有Ｉｎ酸化物粉のＴＥＭ写真である。
【図５】比較例２におけるＰｄ、Ｓｎ含有Ｉｎ水酸化物粉のＴＥＭ写真である。
【図６】図５のＰｄ、Ｓｎ含有Ｉｎ水酸化物粉を焼成して得られたＰｄ、Ｓｎ含有Ｉｎ酸化物粉のＴＥＭ写真である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a tin-containing indium oxide (expressed as Sn-containing In oxide, and sometimes referred to as ITO), a method for producing the same, and a conductive paint and a conductive coating film using the same.
[0002]
[Prior art]
BACKGROUND ART Sn-containing In oxides have been used as conductive films for various display devices, solar cells, and the like because of their transparency to visible light and high conductivity.
Conventionally, methods for manufacturing these conductive films include 1) a method using a sputtering method, 2) a method using ITO particles, and 3) a method using a mixture of metal and ITO.
[0003]
Among these, as for the conductive coating film, since the conductive path is formed by the contact between the ITO particles, the shape of the particle in which the conductive path is easily obtained includes particles such as flake, rod, needle, and plate. Can be used to improve conductivity, and attempts to obtain these various particle shapes have been made (for example, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4). reference.).
[0004]
[Patent Document 1]
JP-A-7-232920
[Patent Document 2]
JP-A-7-235214
[Patent Document 3]
JP-A-8-217446
[Patent Document 4]
JP-A-6-80422
[0005]
[Problems to be solved by the invention]
However, although the sputtering method 1) is excellent in properties such as conductivity and transmittance, it requires expensive equipment such as a vacuum apparatus in manufacturing, and the cost is high. Improvements in properties such as properties and transmittance were not always sufficient, and the above-mentioned properties were not necessarily sufficient in the mixed particle coating method of 3).
In general, the conductive coatings according to the above 2) and 3) are used for the electromagnetic wave shielding film of the cathode ray tube. However, the conductivity is still lower than that of the film formed by the sputtering method 1). The fact is that there is a limit.
[0006]
In addition, when only the shape of the conductive powder particles is improved, the conductivity is improved, but optical characteristics such as transmittance cannot be achieved. In particular, a large amount of scattered light is generated, and the haze of the coating film (diffuse transmission to direct transmitted light) (Ratio of light) is large, or conversely, even if the transmittance is sufficient, there is a problem that the conductivity is insufficient and the electromagnetic wave shielding property is lacking.
[0007]
Accordingly, it is an object of the present invention to provide a conductive powder composed of a Sn-containing In oxide which is a low-cost coating type and has excellent conductivity and transmission properties, a method for producing the same, and a conductive paint using the same. And a conductive coating film.
[0008]
[Means for Solving the Problems]
For the above purpose, the present inventors have made intensive studies and found that tin-containing indium hydroxide (expressed as Sn-containing In hydroxide) to which an element having a valency of 3 has been added in addition to In. It has been found that the conductivity and transmission characteristics can be improved and the above-mentioned object can be achieved by the ITO particles subjected to the heat treatment (sometimes called baking) in a reducing atmosphere.
[0009]
That is, the present invention firstly provides a conductive powder characterized in that a Sn-containing In oxide contains a trivalent element other than In (referred to as trivalent element) other than In; The conductive powder has a lightness index L * value of 25 to 85 in the CIE 1976 L * a * b * color space, and both a * value and b * value of the chromaticness index are -1.0 to -40.0. Third, the trivalent element is Al, Ga, Tl, Au, Bi, Fe, Y, La, Nd, Eu, Gd, Dy, or the like. The conductive powder according to 1 or 2, which is one or more elements selected from the group consisting of Ho, Er, and Yb; fourth, one or more of Al and Fe as the trivalent element. The conductive powder according to the third aspect, containing an element; fifthly, the major axis diameter is 500 nm or less, and the minor axis is The conductive powder according to any one of the first to fourth aspects, which has a rod-like or needle-like shape having a diameter of 100 nm or less and an axial ratio of 1.5 to 10; sixth, a spherical or granular shape having a diameter of 200 nm or less. 7. The conductive powder according to any one of the first to fourth aspects, wherein the conductive powder contains the conductive powder particles according to any one of the first to sixth aspects as a conductive material. Eighth, a conductive coating film comprising the conductive powder particles according to any one of the first to sixth aspects as a conductive material; ninth, containing In, Sn and the trivalent element Preliminary neutralization by adding an alkali to the acidic solution to be performed, wherein the precipitate obtained by adding an alkali to the preneutralized solution and neutralizing the solution is heat-treated, 5. The method for producing a conductive powder according to any one of 5 .; The alkali obtained is preliminarily neutralized by adding an alkali to the contained acidic solution, and the precipitate obtained by adding the trivalent element and the alkali to the preneutralized solution for neutralization is heat-treated. Eleventh, the liquid temperature during the preliminary neutralization is 45 ° C. or lower, and the liquid temperature during the neutralization is 50 ° C. or higher. Twelfth, the method of producing a conductive powder according to ninth or tenth, wherein the pH of the pre-neutralized solution is 2 to 3 and the pH of the post-neutralized solution is 7 to 12, The method for producing a conductive powder according to any one of the ninth to eleventh aspects; thirteenth, the method is obtained by adding the trivalent element-containing solution and the acidic solution containing In and Sn to an alkali to neutralize the same. 7. The conductive powder according to the first, second, third, fourth or sixth aspect, wherein the precipitate is subjected to a heat treatment. 14. A method for producing a conductive powder according to the thirteenth aspect, wherein the liquid temperature during the neutralization is 10 to 90 ° C. and the pH of the neutralized liquid is 6 to 12; 15. The method for producing a conductive powder according to any one of ninth to fourteenth, wherein the heat treatment temperature is 300 to 1000 ° C.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The conductive powder according to the present invention contains In, Sn and further a trivalent element, and Sn is preferably 0.5 to 15 with respect to the total number of moles of In, Sn and the trivalent element. Mol%, more preferably 0.8 to 10 mol%. If the Sn content is less than 0.5 mol%, the conductivity will be reduced, while if it exceeds 15 mol%, the conductivity will also be reduced. The preferable range of the trivalent element with respect to the total number of moles of In, Sn and the trivalent element varies depending on the kind of the element, but is preferably 0.01 to 15 mol%. If the content of the trivalent element is less than 0.01% by mole, the conductivity is reduced, while if it exceeds 15% by mole, the conductivity is also lowered. Here, the trivalent element used in the present invention may be Al, Ga, Tl, or the like, which is the same as In, or may be rare earth Y, La, Nd, Eu, Gd, Dy, Ho, Er, Yb, or the like. Alternatively, Fe, Bi, Au or the like may be used. However, the principle of action such as lowering the resistance by adding the above-mentioned trivalent element and changing the more preferable addition range which is optimal depending on the type of element is unknown at present.
[0011]
Regarding the bluish hue of the conductive powder according to the present invention, the lightness index L * value in the L * a * b * color space (light source C for measurement: color temperature 6774 K) established by the CIE (International Commission on Illumination) 1976 is preferable. It is 25-85, More preferably, it is 30-80. If the L * value is less than 25, the color is too dark. On the other hand, if it exceeds 85, there is no problem, but it cannot be realized by the production method of the present invention. Further, the chromaticness index a * value and b * value in the above are preferably both -1.0 to -40.0, and more preferably both are -2.5 to -30.0. When the chromaticness index a * value and b * value are less than -1.0, the color becomes dull and lacks vividness. On the other hand, when the value exceeds -40.0, there is no problem, but the production method of the present invention is practically used. This is because it cannot be realized.
[0012]
The CIE 1976 L * a * b * color space is defined by the International Commission on Illumination (CIE) converting the CIE XYZ color system in 1976, and a certain distance within the color system is almost perceived in any color region. This is a color space defined so as to have a constant equal rate difference. Further, the lightness index L * value, the chromaticness index a * value, and the b * value are quantities determined in a rectangular coordinate system in the CIE 1976 L * a * b * color space, and are expressed by the following equations (A) to (A). C).
L * = 116 (Y / Y ₀ ) ^1/3 -16 (A)
a * = 500 [(X / X ₀ ) ^1/3 − (Y / Y ₀ ) ^1/3 ] (B)
b * = 200 [(Y / Y ₀ ) ^1/3 − (Z / Z ₀ ) ^1/3 ] (C)
However, X / X ₀ , Y / Y ₀ , Z / Z ₀ Where X, Y, and Z are the tristimulus values of the object color. ₀ , Y ₀ , Z ₀ Is the tristimulus value of the light source that illuminates the object color, Y ₀ = 100.
[0013]
The ITO powder having a characteristic conductivity according to the present invention is obtained by using an In hydrochloric acid (which may be nitric acid, sulfuric acid or the like) solution containing a trivalent element and Sn as a starting solution, and adding NaOH, KOH, NH ₄ OH or NH ₄ HCO ₃ After pre-neutralization at a liquid temperature of 45 ° C. or lower with an alkaline liquid such as the above, the temperature is raised to 50 ° C. or higher, and then a time-consuming neutralization treatment is performed to obtain an In hydroxide containing Sn and a trivalent element. A precipitate can be obtained by preliminarily sintering the precipitate at a temperature of 300 ° C. or lower in the atmosphere or the like, or by performing a heat treatment at a temperature of 300 to 1000 ° C. without preliminarily sintering. Further, the trivalent element may not be added from the beginning, but may be added together with the alkali solution after the temperature is raised, for example. Alternatively, instead of the neutralization treatment of the acidic solution with an alkali solution, a solution containing a trivalent element and an In acidic solution containing Sn with respect to the alkali solution may be added in a range of 10 to 90 without particularly increasing the temperature in the middle. A short period of reverse neutralization treatment at a temperature of ° C may be used.
[0014]
The pre-neutralization treatment is performed while maintaining the reaction solution at a substantially constant temperature of 45 ° C or lower, preferably 15 to 45 ° C, and more preferably 15 to 25 ° C. The solution after the reaction is preferably adjusted to pH 2-3. This pre-neutralization treatment aims at generating fine particle nuclei. Subsequent neutralization treatment is performed by raising the temperature of the solution after the reaction in 30 minutes to 2 hours to 50 ° C. or higher, preferably 80 to 95 ° C., to grow the fine particle nuclei. To form a rod-like, needle-like or plate-like hydroxide. The pH of the solution after neutralization is preferably 7 to 12. The particle shape can be controlled by conditions such as the neutralization rate of pre-neutralization (the ratio of the amount of In precipitated by pre-neutralization when the total In amount is 1), temperature, pH, etc. By adjusting the temperature range between the time and the time of neutralization, hydroxide particles having a desired particle size and shape can be generated relatively uniformly.
[0015]
The neutralization treatment is performed in a higher temperature bath than the pre-neutralization treatment, and it takes 50 minutes or more for the neutralization operation alone, and it takes 2 to 3 hours when the temperature is raised, but water consisting of rod-like, needle-like, or plate-like particles is required. An oxide powder is obtained, which is fired to obtain rod-shaped or needle-shaped oxide particles having excellent conductivity. In the neutralization method in which an acidic solution is added to an alkaline solution, the neutralization time can be as short as 0.5 to 15 minutes, but the crystal powder becomes spherical or granular powder particles.
[0016]
The obtained In hydroxide containing trivalent element and Sn is calcined, dehydrated, decomposed, and sintered to obtain oxide powder particles having a granular, spherical, rod, needle, or similar shape. Obtainable. The firing atmosphere is an inert gas containing steam or a weak reducing atmosphere containing an inert gas containing steam and a reducing gas such as ammonia. That is, the particles after dehydration and decomposition of the hydroxide have poor crystallinity, and if the crystal is not grown, the conductivity becomes low. In order to promote sintering, it is desirable to add water vapor to the firing atmosphere and to contain reducing ammonia or hydrogen gas in order to increase conductivity.
[0017]
The heat treatment temperature is set in accordance with the size, shape, and firing atmosphere gas of the hydroxide particles. However, the higher the heat treatment temperature, the more the steam, and the stronger the reducing property, the more the sintering proceeds, and the resulting oxidation Shape anisotropy of material particles is reduced. The firing temperature is preferably from 300 to 1000C, more preferably from 300 to 700C. By baking at the above-mentioned temperature and atmosphere, crystallization of the hydroxide particles is promoted to maintain the shape anisotropy, and the desired oxide particles can be obtained. However, when the temperature is lower than 300 ° C., the decomposition of the hydroxide is insufficient, and when the temperature is higher than 1000 ° C., it becomes difficult to maintain the shape anisotropy of the hydroxide particles, and the agglomeration due to the inter-particle sintering often occurs. And the dispersibility decreases.
[0018]
The In oxide powder particles containing a trivalent element and Sn obtained by firing preferably have a major axis diameter of 500 nm or less, more preferably 200 nm or less, and a minor axis diameter of 100 nm or less, and more preferably 50 nm or less. The oxide powder particles have a needle-like, rod-like, or plate-like shape, and the ratio of the major axis diameter to the minor axis diameter is preferably 1.5 to 10, and more preferably 3 to 10.
Further, in the case of an In oxide powder containing a spherical or granular trivalent element and Sn, the particle diameter is preferably 200 nm or less, more preferably 100 nm or less.
[0019]
If the major axis diameter of the In oxide powder particles containing a trivalent element and Sn exceeds 500 nm, scattering of visible light occurs, and optical characteristics such as transmittance deteriorate. In particular, when the major axis diameter is 200 nm or less, scattering of visible light is further suppressed. When the minor axis diameter exceeds 100 nm, the degree of contact between the particles is low and the conductivity of the coating film is low. In particular, when the short axis diameter is 50 nm or less, the conductivity of the coating film is further improved. When the axis ratio between the major axis diameter and the minor axis diameter is out of the range of 1.5 to 10, the conductivity, dispersibility, and crystallinity within the particles are reduced. In the case of the spherical or granular In oxide powder particles containing a trivalent element and Sn, the resistance value may increase in terms of the degree of contact between the particles, and the diameter is particularly 200 nm or less, preferably 100 nm or less. I do. The preferred crystallite diameter Dx calculated from the half width of the (222) plane by X-ray diffraction is preferably 150 ° or more from the viewpoint of conductivity.
[0020]
The above-described trivalent element and In oxide powder containing Sn are dispersed in a solvent to form a coating, and after coating, the solvent is volatilized to fix the film, thereby forming a highly permeable, conductive coating film. Obtainable. A known method can be used for the method of forming a coating. As a solvent, an organic solvent such as alcohol, ketone or ether, a surfactant as a dispersant, a coupling agent, etc. are added, and a dispersing device such as a bead mill is added. Disperse using. Further, a binder serving as a binder may be added, or the binder may be formed into a film after coating to form a film.
[0021]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the technical scope of the present invention is not limited to these descriptions.
[0022]
Example 1 200 g of a hydrochloric acid solution containing 18% by weight of In was made up to 2.9 L with pure water, and 5.4 g of stannic chloride and 1.5 g of aluminum nitrate / 9 hydrate were used as a mixed solution to obtain an acidic solution of the starting solution. The solution was charged into a glass beaker. 108.2 g of a 48% NaOH solution is diluted with 890 g of pure water, and this alkali solution is added to the acidic solution. First, an alkaline solution is added to an acidic solution at a liquid temperature of 20 ° C. for 15 minutes to preliminarily neutralize to pH3. Next, the liquid temperature is raised to 90 ° C., and the remaining alkaline solution is added over 40 minutes. The final pH was 10.0. This was filtered, dehydrated and dried to obtain a precipitate of Sn and Al-containing In hydroxide. FIG. 1 shows a transmission electron micrograph (hereinafter, referred to as a TEM photograph) of the Sn and Al-containing In hydroxide. The major axis diameter of the hydroxide powder particles was 181.42 nm, the minor axis diameter was 33.73 nm, and the ratio of the major axis diameter / minor axis diameter was 5.4.
[0023]
Next, this Sn and Al-containing In hydroxide was put into a tube furnace, and 1.5 vol. % Steam and 0.05 vol. % NH ₃ N containing gas ₂ Baking was performed at 600 ° C. for 2 hours in a gas atmosphere. The obtained Sn and Al-containing In oxide powder particles are those shown in the TEM photograph of FIG. 2, and have a major axis diameter of 150.16 nm, a minor axis diameter of 33.36 nm, and a major axis diameter / short axis. The rod-shaped particles had a shaft diameter ratio of 4.50. The major axis diameter and the minor axis diameter were determined by measuring the major axis diameter and the minor axis diameter of 50 particles in a TEM photograph with calipers, converting the magnification, and calculating the average value. Further, the axial ratio was calculated from the ratio between the major axis diameter and the minor axis diameter. The obtained Sn and Al-containing In oxide particles have a lightness index L * value of 72.93 and a chromaticness index a * value of -8.46 in an L * a * b * color space established by CIE (1976). And a b * value of −9.67. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 22.5 m. ² / G. Also, the crystallite diameter D _x Was 180 °.
[0024]
6 g of this powder, 18 g of a solvent (ethanol) and 0.3 g of an anionic surfactant as a dispersant are put into a planetary ball mill (P-5 type, manufactured by Fritsch, container capacity 80 mL, PSZ 0.3 mm ball), and rotated at 300 rpm for 30 minutes. After rotation, colloidal silica and ethanol are added to the dispersion to prepare a paint having an ITO powder content of 2%, a silica content of 2%, and the balance ethanol, and spin-coating on a glass plate. After drying at 200 ° C. for 30 minutes, a transparent conductive film having a thickness of 0.3 μm was formed. When the resistance value of the formed film was measured, the resistance value was 1.40 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 98.9%, and a good transparent conductive film was obtained.
[0025]
Example 2 550 g of 25% aqueous ammonia was diluted with 1790 g of pure water to obtain an alkaline solution of a starting solution, and the solution was charged into a glass beaker. 800 g of a hydrochloric acid solution containing 18 wt% of In was adjusted to 1.5 L with pure water, and SnCl was further added. ₄ ・ 5H ₂ 21.19 g of O and 0.70775 g of chloroauric acid tetrahydrate were added as a mixed solution, and this acidic solution whose temperature was adjusted to 50 ° C was added to the alkaline solution whose temperature was adjusted to 50 ° C. The final pH was 9.0. This was filtered, dehydrated and dried to obtain a precipitate of Au and Sn-containing In hydroxide.
[0026]
Next, this Au and Sn-containing In hydroxide was put into a tube furnace, and 1.5 vol. % Steam and 0.05 vol. % NH ₃ N containing gas ₂ Baking was performed at 600 ° C. for 2 hours in a gas atmosphere. The obtained Au and Sn-containing In oxide particles having an average diameter of 45 nm have a lightness index L * value of 59.67 and a chromaticness index a * in an L * a * b * color space established by CIE (1976). It had a bluish hue with a value of -2.94 and a b * value of -12.53. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 26.0 m. ² / G. The crystallite diameter Dx was 240 °.
[0027]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance value of the formed film was measured, the resistance value was 1.59 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 97.29%, and a good transparent conductive film was obtained.
[0028]
Example 3 Bi and Sn-containing In hydroxides were obtained by treating under the same conditions as in Example 2 except that 3.5 g of bismuth oxide was added instead of chloroauric acid. Next, the same baking as in Example 2 was performed to obtain a Bi- and Sn-containing In oxide powder. The obtained Bi and Sn-containing In oxide powder was a granular powder having an average particle size of 45 nm. The obtained granular Bi and Sn-containing In oxide particles have a lightness index L * value of 63.54 and a chromaticness index a * value of -7 in the L * a * b * color space established by CIE (1976). It had a bluish hue of .59 and a b * value of -7.21. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 27.5 m. ² / G. The crystallite diameter Dx was 221 °.
[0029]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance of the formed film was measured, the resistance was 2.43 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 96.28%, and a good transparent conductive film was obtained.
[0030]
[Example 4] Instead of aluminum nitrate, iron oxide (Fe ₂ O ₃ ) A treatment was performed under the same conditions as in Example 1 except that 0.14 g was added to obtain an Sn- and Fe-containing In hydroxide. Next, the same sintering as in Example 1 was performed to obtain Sn and Fe-containing In oxide powder. The obtained Sn and Fe-containing In oxide powder particles are rod-shaped particles having a major axis diameter of 141.6 nm, a minor axis diameter of 32.07 nm, and a ratio of major axis diameter / minor axis diameter of 4.42, and CIE. In the L * a * b * color space enacted (1976), it has a bluish color tone with a lightness index L * value of 69.85, a chromaticness index a * value of -4.42 and a b * value of -8.16. Was. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 20.3 m. ² / G. The crystallite diameter Dx was 205 °.
[0031]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance value of the formed film was measured, the resistance value was 1.70 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 93.29%, and a good transparent conductive film was obtained.
[0032]
Example 5 Treatment was performed under the same conditions as in Example 1 except that 400 mL of an indium nitrate solution containing 100 g / L of indium was used instead of the indium chloride solution, and 0.45 g of thallium oxide was added instead of aluminum nitrate. Thus, an Sn and Tl-containing In hydroxide was obtained. Next, the same sintering as in Example 1 was performed to obtain an Sn and Tl-containing In oxide powder. The obtained Sn and Tl-containing In oxide powder particles were rod-shaped particles having a major axis diameter of 232.23 nm, a minor axis diameter of 59.05 nm, and a major axis diameter / minor axis diameter ratio of 3.93. The particles have a lightness index L * value of 66.02, a chromaticness index a * value of -6.96 and a b * value of -7.11 in the LIE color space defined by CIE (1976). It had a bluish hue. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 18.7 m. ² / G. The crystallite diameter Dx was 162 °.
[0033]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance value of the formed film was measured, the resistance value was 1.83 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 92.09%, and a good transparent conductive film was obtained.
[0034]
Example 6 The same treatment as in Example 1 was carried out except that 0.2 g of neodymium oxide was added instead of aluminum nitrate to obtain an Sn- and Nd-containing In hydroxide. Next, the same sintering as in Example 1 was performed to obtain Sn and Nd-containing In oxide powder. The obtained Sn and Nd-containing In oxide powder particles were rod-shaped particles having a major axis diameter of 117.7 nm, a minor axis diameter of 36.91 nm, and a ratio of major axis diameter / minor axis diameter of 3.19. These particles have a lightness index L * value of 72.29, a chromaticness index a * value of -7.64 and a b * value of -9.92 in the L * a * b * color space established by CIE (1976). It had a bluish hue. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 23.2 m. ² / G. The crystallite diameter Dx was 181 °.
[0035]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance value of the formed film was measured, the resistance value was 1.99 kΩ / □. When the transmittance was measured with a spectrophotometer, the transmittance was 98.25%, and a good transparent conductive film was obtained.
[0036]
Example 7 An Al, Fe, and Sn-containing In hydroxide was obtained under the same conditions as in Example 1 except that 0.15 g of iron oxide was added instead of reducing aluminum nitrate to 0.65 g. Next, the same baking was performed as in Example 1 to obtain an Al, Fe, and Sn-containing In oxide powder. The obtained Sn, Al, and Fe-containing In oxide powder particles were rod-shaped particles having a major axis diameter of 145.88 nm, a minor axis diameter of 32.72 nm, and a major axis diameter / minor axis diameter ratio of 4.45. Was. These particles have a lightness index L * value of 72.80, a chromaticness index a * value of -4.32 and a b * value of -6.69 in the LIE color space defined by CIE (1976). It had a bluish hue. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 24.5 m. ² / G. The crystallite diameter Dx was 172 °.
[0037]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance value of the formed film was measured, the resistance value was 1.59 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 96.01%, and a favorable transparent conductive film was obtained.
[0038]
[Example 8] Sn and Al-containing In hydroxide were treated under the same conditions as in Example 1 except that sodium aluminate was used instead of aluminum nitrate and neutralization was performed with an alkali solution in which sodium aluminate was dissolved. Obtained. Next, the same sintering as in Example 1 was performed to obtain Sn and Al-containing In oxide powder. The obtained Sn and Al-containing In oxide powder particles were rod-shaped particles having a major axis diameter of 143.07 nm, a minor axis diameter of 37.20 nm, and a ratio of major axis diameter / minor axis diameter of 3.85. . These particles have a lightness index L * value of 70.41, a chromaticness index a * value of -8.05 and a b * value of -11.75 in the L * a * b * color space established by CIE (1976). Blue tones. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 21.93 m. ² / G. The crystallite diameter Dx was 190 °.
[0039]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance value of the formed film was measured, the resistance value was 1.78 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 95.27%, and a good transparent conductive film was obtained.
[0040]
Example 9 The same treatment as in Example 1 was carried out except that 0.55 g of yttrium chloride hexahydrate was added instead of aluminum nitrate to obtain a Sn, Y-containing In hydroxide. Next, the same sintering as in Example 1 was performed to obtain a Sn and Y-containing In oxide powder. The obtained Sn and Y-containing In oxide powder particles were rod-shaped particles having a major axis diameter of 133.41 nm, a minor axis diameter of 32.28 nm, and a ratio of major axis diameter / minor axis diameter of 4.13. This particle has a lightness index L * value of 75.22, a chromaticness index a * value of -7.53 and a b * value of -7.17 in the L * a * b * color space defined by CIE (1976). It had a bluish hue. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 23.56 m. ² / G. The crystallite diameter Dx was 198 °.
[0041]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance value of the formed film was measured, the resistance value was 1.83 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 98.23%, and a good transparent conductive film was obtained.
[0042]
Example 10 The procedure of Example 2 was repeated, except that 2.7 g of aluminum nitrate 9-hydrate was added instead of chloroauric acid to obtain an Sn- and Al-containing In hydroxide. Next, the same baking as in Example 2 was performed to obtain Sn and Al-containing In oxide powder. The obtained Sn and Al-containing In oxide powder was a granular powder having an average particle size of 45 nm. This particle has a lightness index L * value of 66.59, a chromaticness index a * value of -8.87 and a b * value of -11.89 in the L * a * b * color space established by CIE (1976). It had a bluish hue. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 29.0 m. ² / G. The crystallite diameter Dx was 207 °.
[0043]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance value of the formed film was measured, the resistance value was 2.38 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 96.41%, and a good transparent conductive film was obtained.
[0044]
[Comparative Example 1] A hydrochloric acid acidic solution was prepared under the same conditions as in Example 1 except that a trivalent element other than In was not added. And then neutralized, filtered, dehydrated and dried to obtain a Sn-containing In hydroxide. FIG. 3 shows a TEM photograph of the Sn-containing In hydroxide.
[0045]
Next, the Sn-containing In hydroxide was fired under the same conditions as in Example 1 to obtain a Sn-containing In oxide. FIG. 4 shows a TEM photograph of the Sn-containing In oxide.
This Sn-containing In oxide was needle-like particles having a major axis diameter of 156.66 nm, a minor axis diameter of 40.70 nm, and an axial ratio of 3.85. These particles have a lightness index L * value of 76.82, a chromaticness index a * value of -8.27 and a b * value of -4.05 in the L * a * b * color space defined by CIE (1976). It had a bluish hue. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 23.7 m. ² / G. The crystallite diameter Dx was 214 °.
[0046]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance value of the formed film was measured, the resistance value was 3.67 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 97.20%. The coating film of the Sn-containing In oxide powder of Comparative Example 1 in which no trivalent element other than In was added showed a remarkably high resistance value.
[0047]
[Comparative Example 2] An acid solution of hydrochloric acid was prepared under the same conditions as in Example 1 except that 0.35 g of palladium chloride was added instead of aluminum nitrate, and an alkaline solution was added to this acid solution of hydrochloric acid for preliminary neutralization. Thereafter, the liquid temperature was increased to perform neutralization, followed by filtration, dehydration and drying to obtain Pd and Sn-containing In hydroxide. FIG. 5 shows a TEM photograph of the Pd and Sn-containing In hydroxide.
[0048]
Next, the Pd and Sn-containing In hydroxide was fired under the same conditions as in Example 1 to obtain a Pd and Sn-containing In oxide. FIG. 6 shows a TEM photograph of the Pd and Sn-containing In oxide.
The Pd and Sn-containing In oxide powder particles did not retain the needle shape of the hydroxide, and were granular with a major axis diameter of 45.99 nm, a minor axis diameter of 30.77 nm, and an axial ratio of 1.49. These particles have a lightness index L * value of 53.60, a chromaticness index a * value of -3.58 and a b * value of -5.62 in the L * a * b * color space defined by CIE (1976). It had a bluish hue. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 20.5 m. ² / G. The crystallite diameter Dx was 232 °.
[0049]
Using this Pd and Sn-containing In oxide powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance value of the formed film was measured, the resistance value was 6.43 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 92.23%. The coating film of the Pd / Sn-containing In oxide powder of Comparative Example 2 to which divalent palladium was added without adding any trivalent element other than In showed a remarkably high resistance value.
[0050]
Comparative Example 3 An Sn-containing In hydroxide was obtained by treating under the same conditions as in Example 2 except that no trivalent element other than In was added. Next, the same firing as in Example 2 was performed to obtain a Sn-containing In oxide powder. The obtained Sn-containing In oxide powder particles were granular with an average particle size of 45 nm. The particles have a lightness index L * value of 66.53, a chromaticness index a * value of -7.43 and a b * value of -11.8 in the LIE color space defined by CIE (1976). It had a bluish hue. When the specific surface area of the obtained powder was measured by the BET one-point method, it was 28.0 m. ² / G. The crystallite diameter Dx was 240 °.
[0051]
Using this powder, a transparent conductive film having a thickness of 0.3 μm was formed in the same manner as in Example 1. When the resistance value of the formed film was measured, the resistance value was 4.81 kΩ / □. When the transmittance was measured by a spectrophotometer, the transmittance was 97.02%. The coating film of the Sn-containing In oxide powder of Comparative Example 3 containing no trivalent element other than In showed a remarkably high resistance value.
[0052]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the trivalent element which is low in resistance value and excellent in the transmittance | permeability by the efficient manufacturing method of baking the Sn containing In hydroxide containing a trivalent element other than In in a weak reducing atmosphere etc. And a conductive paint and a conductive coating film having an Sn-containing In oxide powder (ITO powder).
[Brief description of the drawings]
FIG. 1 is a TEM photograph of an Al and Sn-containing In hydroxide powder in Example 1.
FIG. 2 is a TEM photograph of the Al and Sn-containing In oxide powder obtained by firing the Al and Sn-containing In hydroxide powder of FIG.
FIG. 3 is a TEM photograph of Sn-containing In hydroxide powder in Comparative Example 1.
FIG. 4 is a TEM photograph of the Sn-containing In oxide powder obtained by firing the Sn-containing In hydroxide powder of FIG.
FIG. 5 is a TEM photograph of a Pd and Sn-containing In hydroxide powder in Comparative Example 2.
6 is a TEM photograph of the Pd and Sn-containing In oxide powder obtained by firing the Pd and Sn-containing In hydroxide powder of FIG.

Claims

A conductive powder comprising a Sn-containing In oxide containing a trivalent element other than In.

The conductive powder has a lightness index L * value of 25 to 85 in the CIE {1976} L * a * b * color space, and has a chromaticness index a * value and b * value of -1.0 to -40. The conductive powder according to claim 1, which has a bluish tone of 0.

The said trivalent element is at least one element selected from the group consisting of Al, Ga, Tl, Au, Bi, Fe, Y, La, Nd, Eu, Gd, Dy, Ho, Er and Yb. Item 3. The conductive powder according to item 1 or 2.

4. The conductive powder according to claim 3, wherein the trivalent element contains at least one of Al and Fe.

The conductive powder according to any one of claims 1 to 4, having a rod-like or needle-like shape having a major axis diameter of 500 nm or less, a minor axis diameter of 100 nm or less, and an axial ratio of 1.5 to 10.

The conductive powder according to any one of claims 1 to 4, which has a spherical or granular shape having a diameter of 200 nm or less.

A conductive paint comprising the conductive powder particles according to claim 1 as a conductive material.

A conductive coating film comprising the conductive powder particles according to claim 1 as a conductive material.

An alkali is added to the acidic solution containing In, Sn and the trivalent element for pre-neutralization, and the pre-neutralized solution is further alkali-added and neutralized to obtain a precipitate. The method for producing a conductive powder according to any one of claims 1 to 5, wherein the method comprises:

A pre-neutralization is performed by adding an alkali to the acidic solution containing In and Sn, and the precipitate obtained by adding the trivalent element and the alkali to the pre-neutralized solution to neutralize the precipitate is subjected to heat treatment. The method for producing a conductive powder according to any one of claims 1 to 5, wherein the method comprises:

The method for producing a conductive powder according to claim 9, wherein a liquid temperature during the preliminary neutralization is 45 ° C. or lower, and a liquid temperature during the neutralization is 50 ° C. or higher.

The method for producing a conductive powder according to any one of claims 9 to 11, wherein the pH of the pre-neutralized solution is 2 to 3, and the pH of the post-neutralized solution is 7 to 12.

The precipitate obtained by adding and neutralizing the trivalent element-containing solution and the acidic solution containing In and Sn to an alkali is subjected to heat treatment, wherein the precipitate is heated. 7. The method for producing a conductive powder according to item 6.

The method for producing a conductive powder according to claim 13, wherein the liquid temperature during the neutralization is 10 to 90C, and the pH of the neutralized liquid is 6 to 12.

The method for producing a conductive powder according to claim 9, wherein the heat treatment temperature is 300 to 1000 ° C. 15.